Jan Feb2008

IETE TECHNICAL REVIEW The Institution of Electronics and Telecommunication Engineers PRESIDENT S Narayana VICE-PRESIDENTS A K Agarwal

P N Chopra

Anita G Dandekar

PUBLICATIONS COMMITTEE Chairman M L Gupta Co-Chairman M C Chandra Mouly Members H O Agrawal

S S Agrawal

Smriti Dagur

M Jagadesh Kumar

Surendra Pal

Giridhar R Joshi

T K De

T S Rathore

S K Kshirsagar

Coopted K M Paul

K S Prakash Rao SPECIAL INVITEE

S C Dutta Roy

P Banerjee EDITORIAL BOARD Chairman Dilip Sahay Members

H O Agrawal

A K Bhatnagar

R G Gupta

S S Motial

Neeru Mohan Biswas

H Kaushal

Secretary General

Dy Managing Editor

V K Panday

A P Sharma

IETE Technical Review is published bimonthly by the Institution of Electronics and Telecommunication Engineers. All rights of publication are reserved by the IETE. Copyright and Reprint permission : Abstracting is permitted with credit to the source. Libraries are permitted to photocopy for private use of readers. Annual Subscription : Subscription and Advertising rates are available on request and also on website: iete.org The IETE Technical Review invite articles preferably readable without mathematical expressions, state-of-the-art review papers on current and futuristic technologies in the areas of electronics, telecommunication, computer science & engineering, information technology (IT) and related disciplines. In addition, informative and general interest articles describing innovative products & applications, analysis of technical events, articles on technology assessment & comparison, new & emerging topics of interest to professionals are also welcome. While all the papers submitted will go through the same detailed review process, short papers and Practical Designs will receive special attention to enable early publication. Manuscripts may please be submitted in triplicate to the Managing Editor along with a soft copy on floppy/CD/ e-mail. Detailed guidelines to authors may be seen on IETE Website : http://www.iete.org under the heading Publications. Address for correspondence : Managing Editor, IETE, 2, Institutional Area, Lodi Road, New Delhi 110 003, Telephone : +91 (11) 43538842-44 Fax : +91 (11) 24649429, email : [email protected]; [email protected], Website : http://www.iete.org; http://www.iete.info FREE TO IETE CORPORATE MEMBERS : (Cost of Production: Rs.19.00)

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IETE TECHNICAL REVIEW Published bimonthly by the Institution of Electronics and Telecommunication Engineers January-February 2008

Vol 25

No 1

CONTENTS

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SCAN

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Dilip Sahay

Gautam A Shah and Tejmal S Rathore

39TH HOMI J BHABHA MEMORIAL LECTURE

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Role of Communications Satellites in National Development G Madhavan Nair

INVITED ARTICLES 39

This is Mobile TV Broadcasting K M Paul

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Is India ready to face 21st Century?

RAM LAL WADHWA GOLD MEDAL LECTURE

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Morphological Algorithms for Image Processing

Design, Development and Applications of PC-based Process Control Trainer for Automation

S K Kshirsagar

Bhabatosh Chanda 19

Challenges in Technology and Reconfiguration of SDR — A Survey V Jeyalakshmi and K Sankaranarayanan

Note : The Institution of Electronics and Telecommunication Engineers assumes no responsibility for the statements and opinions expressed by individual authors.

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SCAN The first issue of the year 2008 of the Technical Review contains six articles including the 39th Homi J Bhabha Memorial Lecture and Ram Lal Wadhwa Gold Medal Lecture. In addition, there are two invited articles in this review. The first article in this review is the 39th Homi J Bhabha Memorial lecture delivered by Dr G Madhavan Nair on the role of communications satellites in National Development on 29 Sep 2007 at Hyderabad. Second article is the Ram Lal Wadhwa Gold Medal lecture delivered by Prof Bhabatosh Chanda on Morphological Algorithms for image process on 30 Sep 2007 at Hyderabad. Third article is by Ms Jeyalakshmi and Sankaranarayanan concerning software defined radio. This article gives some overview regarding the usage of the software defined radio on the various mobile platform and is definitely expected to be very helpful device towards deployment of wireless applications. Fourth article is concerning PC based process control trainer by Gautam Shah and T S Rathore. The article brings out the applications as well as certain design and development activities for PC based process control trainer for automation. It is expected that this PC based process control trainer would provide cost effective, interactive and easy to use way for automation. The next article is an invited article from KM Paul regarding Mobile Television broadcasting. The article deals with specific technology for mobile TV broadcasting as used by Doordarshan presently. The sixth article is also an invited article by Prof Kshirsagar giving an overview of various means of dissemination for distance education. Dilip Sahay Chairman, Editorial Board Vol. 25, No. 1, Jan-Feb’08

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Role of Communications Satellites in National Development G MADHAVAN NAIR ABSTRACT Recognising the immense potential of communications satellites for establishing connectivity to far-flung and remote areas and for using television broadcasting for mass education, India undertook experimental projects to demonstrate the need for having a domestic communications satellite that paved the way for establishing Indian National Satellite (INSAT) system. Starting with multipurpose communications satellites INSAT-1 series combining telecommunications, TV broadcast and meteorological services procured from abroad, ISRO embarked on design, development of more advanced INSAT -2, 3 and 4 series of satellites indigenously. The telecommunications, TV broadcast, radio networking and meteorological services were operationalised with INSAT-1 system in 1983. While providing uninterrupted services to the country in the above areas, ISRO undertook several innovative experiments using communications satellites. Staring with using INSAT satellites for training and developmental communications, societal applications such as tele-education and tele-medicine facilities were established. Use of INSAT satellites for disaster management support has also been established. A new concept namely Village Resource Centres (VRC) combining the services of INSAT satellites and Indian Remote Sensing (IRS) Satellites for providing holistic services at village level has also been operationalised.

1. INTRODUCTION Late Dr Vikram Sarabahi the founding father of Indian Space Program had envisioned that space technology is a powerful tool which can play a vital role in the development of the country and can be used for the benefit of common man The potential of space technology for mass education, especially in terms of omnipotence, visual power and outreach was recognised in the early 1970s. ISRO undertook in 1975-76, the Satellite Instructional Television Experiment (SITE) to telecast educational TV programs on health, hygiene, agriculture, adult education etc., to cover 2500 villages in six states using the US satellite ATS-6. It was the largest sociological experiment ever carried out in the world. The Satellite Telecommunications Experiment Project (STEP) conducted using the FrancoGerman satellite Symphonie during 1977-79 was another major demonstration of long distance satellite telecommunication application of space. The objectives of STEP was to provide a system test of geosynchronous satellite for domestic telecommunications and to enhance the country’s capability in the design, development and Vol. 25, No. 1, Jan-Feb’08

operation of various ground systems required and to acquire competence in the operation of systems for satellite telecommunications. The demonstration of space applications in SITE and STEP for developmental communications, TV broadcast and for domestic long distance telecommunication and the experience gained through design, development and operation of APPLE satellite in 1981 paved the way for establishment of INSAT system.

2. INSAT-1 Satellites The first generation INSAT-1 series of satellites was a unique design combining telecommunications, television broadcasting and meteorological services in a single platform. The involvement of various users like the Department of Telecommunications, Ministry of Information and Broadcasting and India Meteorological Department enabled realization of INSAT system towards identified national needs. INSAT-1 series of satellites were procured from Ford Aerospace Communication Corporation (FACC). Each of the satellites in INSAT-1 series weighed about 1200 kg with about 11.5 sq. m of solar array of five panels, involving multi axial deployment in I E T E

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orbit to provide 900 W at the end of seven years of life. Each INSAT satellite was designed to provide 12 national coverage C band transponders of 36 MHz bandwidth each, 2 high power S band national coverage transponders for TV broadcast and five low level carriers for radio program distribution, disaster warning and dissemination of standard time and frequency signals and VHRR instrument for meteorological imaging in the visible and infrared channels.

2.1. Second Generation INSAT Satellites Second generation three axis stabilized INSAT2 series of satellites, weighing over 1900 kg and having much higher capacity compared to the first generation INSAT’s, were developed indigenously by ISRO. These satellites carried 12 C-band and 6 extended C-band transponders, two high power Sband transponders, a data relay transponder and an improved VHRR with a resolution of 2 km in the visible and 8 km in the infrared bands. INSAT-2E, launched in 1999, incorporated many new technologies in spacecraft design including ASIC based TTC and AOCS systems and shaped beam and dual grid antennas to increase payload capacity. The meteorological payload of INSAT-2E included VHRR with 2 km resolution in visible band and a water vapour channel having 8 km resolution and a Charge Coupled Device (CCD) camera operating in the visible, near infrared and short wave infrared bands with 1 km resolution. The satellite has been operating since its launch with eleven 36 MHz equivalent C-band transponder capacity.

2.2. Third and Fourth Generation INSAT Satellites Rapid expansion of VSAT services and growing demand from communication and broadcasting services necessitated the development of third generation INSAT’s which began with the launching of INSAT-3B which carried 12 extended C-band and 3 Ku band transponders in March 2000. Since then INSAT-3A, 3C and 3E each weighing in excess of 2,700 kg have been launched to provide extensive communication capability in C, extended C and Ku bands and also enhancing the sensitivity of VHRR. As the communication payloads grew in capacity and capabilities, it was decided to Vol. 25, No. 1, Jan-Feb’08

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separate communication and meteorological spacecrafts, to avoid constraints put by one payload on the other. Accordingly a dedicated meteorological, satellite, originally named as Metsat, weighing 1 ton and carrying VHRR payload with water vapour channels and a data collection transponder was launched on September 12, 2002.

3. GSAT SERIES OF COMMUNICATION SATELLITES Indigenously developed communication satellites launched by the Indian Geo-synchronous Satellite Launch Vehicle (GSLV) form the GSAT series of satellites. GSLV MK-1, in its very first developmental test flight on April 18, 2001, succeeded in placing an experimental communication satellite, GSAT-1 weighing 1540 kg, into a Geosynchronous Transfer Orbit (GTO). Subsequently, other satellites in this series, GSAT2 and GSAT-3 (also called as Edusat) were launched. GSAT-2 carries four C-band transponders, two Ku-band transponders and a Mobile Satellite Service (MMS) payload. EDUSAT is India’s first exclusive satellite for serving the educational sector. It is specially configured for audio-visual medium, employing digital interactive classroom and multimedia delivery. EDUSAT was built around a standardized spacecraft bus called I-2K. It has certain new technological elements - a multiple spot beam antenna with 1.2 m reflector to direct precisely the Ku-band sport beams towards their intended region of India, a dual core bent heat pipe for thermal control, high efficiency multi-junction solar cells and an improved thruster configuration for optimized propellant used for orbit and orientation maintenance.

3.1. Telecommunications and Broadcasting Currently about 90 earth stations are operational on INSAT under government owned Bharat Sanchar Nigam Limited (BSNL) network providing 3840 IDR channels, 1582 MCPC channels and 27 SCPC channels. More than 60,000 Very Small Aperture Terminals (VSAT) are operating with 90 hubs in the government and private sectors. I E T E

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Doordarshan, another government owned TV service-provider, is providing about 60 channels for national, regional, Digital Satellite News Gathering (DSNG) and VSAT services through 11 C band transponders in the INSAT system and 2 C band transponders in PAS10. In Ku-band DTH service they transmit 50 TV and 20 Radio Channels through INSAT, NSS-6 and PAS10 satellites. AIR is operating 40 Radio Networking (RN) channels in S-band, 53 RN Channels in C-band and 12 number of DSNG using INSAT S and C band transponders. Doordarshan and All India Radio (AIR) use satellite medium to transmit the signals to their 1406 and 213 terrestrial transmitters, respectively for local rebroadcast. They cover 70% of Indian landmass and 95% of population. In addition the Direct to Home (DTH) satellite broadcast covers almost 100% landmass except islands. More than 8 million households in India are now receiving the DTH satellite TV and radio transmissions from national and private broadcasters.

3.2. Special Applications Meteorology Indian Meteorological Department (IMD) is regularly provided with VHRR imagery through Kalpana-1 satellite. About 22 pictures are taken in a day. Meteorological Data Distribution (MDD) service is up-linked from the earth stations at Secunderabad on round the clock basis. The Data Relay Transponders (DRT) of Kalpana-1 and INSAT 3A are being used by the IMD, Central Water Commission, Narmada Control Authority, Snow & Avalanche Study Establishment, Andhra Pradesh Government and VRCs for hydro meteorological data collection, water management, flood forecasting, snow assessment, etc. for almost two decades now. Over 300 Automatic Weather Stations are using the Kalpana DRT for data collection from remote/unattended platforms.

3.3. Disaster Management Support and Search and Rescue ISRO has been a part of the international satellite-based search and rescue system COSPAS-SARSAT since the early 1990s. This system uses six Low Earth Orbit (LEO) and four Geostationary Equatorial Orbit (GEO) satellites of Vol. 25, No. 1, Jan-Feb’08

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which one GEO satellite is provided by India. ISRO, therefore, has a special status, among 40 member countries, as a geostationary space segment provider, in this system. Two Local User Terminals (LUT) located at Bangalore and Lucknow are connected to the international search and rescue network and support 121.5 MHz, 243 MHz and 406 MHz beacons. These LUT’s are a part of the international maritime organization’s Global Maritime Distress and Safety System (GMDSS) as also the International Civil Aviation Organization (ICAO). India Meteorological Department also uses satellite medium to transmit cyclone warnings in the local language of the coastal area that may get affected due to impending cyclone. These Cyclone Warning Dissemination signals are transmitted from Area Cyclone Warning Centres of IMD at Chennai, Mumbai and Kolkata earth stations.

4. SOCIETAL APPLICATIONS PROGRAM India was amongst the first few countries to explore the use of satellite communication for carrying Education and Development oriented information and services to the rural masses. The applications started with Satellite TV Broadcasting to schools and rural communities in the mid seventies. With the growth of telephone networks, the broadcasting networks were adopted for oneway video two way audio (return audio on phone) networks for Training. The further development in VSAT technologies, let to applications like telemedicine, tele-education and VRC’s.

4.1 Satellite Based Development TV and Training More than 6000 receiving centres so far have been set up across the country under TDCC programme and more than 10 lakh participants/ functionaries of more than 60 departments of various state governments have been trained in these centres.

4.2. Tele-Education In order to bring the modern developments of the satellite based multimedia communications to the education sector in the country, Edusat a satellite dedicated for education-was launched. The launch of this satellite has let to a revolution in the utilization of satcom networks for education. ISRO I E T E

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is supporting the setting up of VSAT networks for education in all the states and union territories of India by providing one hub with teaching end and few interactive terminals for remote classrooms. Under Edusat utilization program, two types of satellite based (Edusat satellite) VSAT networks, interactive networks consisting of Satellite Interactive Terminals (SIT’s) and receive-only networks using Receive-Only-Terminals (ROT’s) are being setup in various states across the country for promoting universal education.

4.3. Tele-Medicine Telemedicine is one of the important applications of space technology for societal development. The tele-medicine facility connects the hospitals & Community Health Centers located at remote locations with super-specialty hospitals for providing expert consultation to the needy and under served population. Tele-medicine system consists of customized medical software integrated with computer hardware along with medical diagnostic instruments. The program was initiated by ISRO in 2001 as a pilot exercise in five locations but is now being rapidly expanded to cover entire country. The telemedicine networks have been able to provide connectivity to the remotest locations in the country like the Andaman and Nicobar Islands, the Lakshwadeep islands, the Northeastern Hilly regions, and the snow covered mountainous regions of Jammu and Kashmir. Mobile telemedicine vans have also been deployed by ISRO for taking the telemedicine facilities to the remote villages where the permanent patient end is not setup. In addition to this, tele-medicine network is also used for providing Continued Medical Education (CME). Several Specialty Hospitals and Medical Colleges are providing CME programs to keep the doctors and health workers informed of the new practices, treatments plans, advances, unique case studies, etc.

4.4. Village Resource Centres Satellite based communication and remote sensing technologies have demonstrated their capabilities to provide services related to education, healthcare, weather, land and water resources management, mitigation and impact of natural disasters, etc. To provide these spacebased services directly to the rural areas, ISRO Vol. 25, No. 1, Jan-Feb’08

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has initiated a program to set up Village Resource Centres (VRC’s) in association with NGO’s and trusts and state and central agencies concerned. VRC’s are envisaged as single window delivery mechanism for a variety of space based products and services, such as tele-education; telemedicine; information on natural resources for planning and development at local level; interactive advisories on agriculture, fisheries, land and water resources management, livestock management, etc; interactive vocational training towards alternative livelihood; e-governance; weather information; etc. VRC’s also address a variety of social aspects locally, and can act as help lines. More than 350 VRC’s have already been setup across the country and the programme, so far, has been a great success. The expansion of the network is planned in a big way in the coming years.

5. EMERGING TRENDS IN SATCOM Globally, today there are more than 6000 transponders in Space. The growth of transponders requirement over next five years is predicted to be only moderate - about 8000. Multi-media, IP-TV, mobile TV and high definition TV are emerging as new application areas. The migration to Ku band for broadband services rather appears to be slow. The spacecraft bus is still hovering around 4T class, though there are few heavier class spacecraft in the range of 5 to 6 Tons. In the next five years, two major developments are expected in the terrestrial communication area. The number of mobile phones with 3G and multimedia capability will increase considerably and Wi-Fi and Wi-Max systems with broadband multimedia delivery capability will be increasingly used for fixed communications. Large-scale penetration of these two technologies in the Indian scenario will have two major implications on satellite communication services. The first, bandwidth in the 430 MHz, 800 MHz, 1800 MHz, 2.1 GHz, 2.3 GHz, 2.5 GHz and 3.4 GHz bands will be taken over substantially by these services and the second, the cost per Hertz for these terrestrial services will be much lower than the satellite bandwidth charges for similar capability. This will mean that the SATCOM bandwidth lease charges will have to be substantially reduced to remain competitive. Use of advanced modulation techniques for increasing the throughput (bits / hertz) will become necessary to remain competitive. Use of satellites will be increasingly I E T E

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made for connectivity to remote and inaccessible places where no other medium is economical. The satellite systems are increasingly being used for disaster recovery of telecom networks. Other emerging fields are digital multi-media broadcast, back haul link for WiFi/Wimax network and mobile communications. The roadmap for the Indian Space Program has been planned considering these emerging trends and to meet the expected demands of satellitebased services within the country.

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FUTURE ROADMAP OF SATELLITE COMMUNICATIONS PROGRAM

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Augmentation of INSAT/GSAT space segment to meet the demand of 500 transponders by end of 2012.

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Development of high power Ka-band satellites and ground systems for point-to-point connectivity.

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Development of cost-effective 4T-12KW bus with capacity of more than 50 transponders and flexible enough to accommodate wide range of payloads.

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New communication services including multimedia broadcast, broadband services, high definition TV, satellite-based tele-surgery and innovative communication media for education and training, and mobile communications.

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R&D in satellite communication technologies such as multiple spot beam communication payloads, multiple beam frequency reuse, reconfigurable beams, onboard data regeneration, etc.,

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Development of low cost indigenous ground systems including hand held communication system for voice and data communications for strategic users, low cost least maintenance tele-medicine equipments and software, ground systems compatible for MEO SAR payloads.

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Institutionalization of ongoing developmental programmes like tele-education, telemedicine, Village Resource Centres (VRC’s) with the involvement of Central Government Ministries / Departments, State Governments and NGO’s self-sustenance and large scale training.

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Communication systems and support for disaster management.

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Progress towards self-sustenance of INSAT/ GSAT systems and enabling private sector role in Indian Satellite Systems.

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AUGMENTATION OF INSAT/GSAT SPACE SEGMENT

The INSAT/GSAT system currently has 199 transponders. Keeping in mind the growing demand and the need to maintain on-orbit spares, it is planned to create transponder capacity of about 500 by end of 2012. In order to meet the above demand, the planned satcom mission comprise of a mix of small, medium and large satellites compatible with GSLV Mk II, Mk III and procured launches. The planning takes into account the continuity of services for Search and Rescue as well as Data Collection system for meteorological services. An advanced meteorological satellite INSAT3D is scheduled for launch in 2008-2009. Digital multimedia and data broadcast satellites with multiple beams in S-band have also been planned. It is also proposed to realize hand-held terminals capable of receiving broadband services. With the INSAT and GSAT missions planned during next 5 years, the total capacity by end of 2012 is expected to reach 500 transponders as shown in Fig 3 in tune with the estimated demand. A multimedia satellite, INSAT-4E/GSAT-6, is being built to provide satellite based multimedia service using high power transponders in S-band and regional beams covering India. This will cater to requirement of the multimedia service requirements of both fixed and mobile consumers including societal, education and strategic needs via fixed, portable and mobile video/audio receivers for vehicles. The satellite will have 5 spot beams in the C×S (BSS) band and a return link capability in S×C (MSS) band facilitating provision of interactive services and mobile communications. The satellite is being built around I-2K Bus. The life of the satellite will be 12 years. To protect, sustain and expand the services for the long term, necessary back up capacity is being planned. Extensive use of the indigenously developed hardware is envisaged for the spacecraft realization including the 5.5 m unfurlable antenna.

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8. CONCLUSION India was among the first few countries to realize the potential of space technology to solve the real problems of man and society and took initiatives to develop the space technology for the benefit of the nation. Over the last four decades, India has achieved a notable progress in the design, development and operation of space systems, as well as, using them for vital services like telecommunication, television broadcasting, meteorology, disaster warning as well as natural resources survey and management. The space programme has become largely self-reliant with

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capability to design and build satellites for providing space services and to launch them using indigenously designed and developed launch vehicles. The Indian Space Program is application driven with emphasis on self- reliance. The overall thrust of the space program during the coming decades will be to sustain and strengthen the already established space based services towards socio-economic development of the country. The program profile will be based on the emerging requirements in the priority areas of national development and security requirements and will take cognizance of the policy framework and global trends.

Author G Madhavan Nair graduated in Engineering from Kerala University in 1966 and underwent training at Bhabha Atomic Research Center (BARC), Bombay. He is associated with the Indian space programme since inception, Joining Thumba Equatorial Rocket Launching Station (TERLS) in 1967. Mr Madhavan Nair has made outstanding contribution particularly in the development of launch vehicles, specifically, as Project Director, he led the development of Polar Satellite Launch Vehicle (PSLV) which has since become the workhorse for launching mainly Indian remote sensing satellites. As Director of ISRO’s largest R&D Centre, Vikram Sarabhai Space Centre, he also saw India’s Geo-synchronous Satellite Launch Vehicle (GSLV) successfully coming to fruition. Further, as Director of the Liquid Propulsion Systems Centre of ISRO, he played a central role in the design and development of the crucial cryogenic engine for GSLV. He is now guiding the launch vehicle technology development with the aim of reducing the cost of access to space. Since taking over as Chairman, ISRO, in 2003, Mr Madhavan Nair has given further fillip to space applications for societal development especially in implementing the EDUSAT programme for tele-educations and expanding the telemedicine network across the country. He has embarked upon setting up the novel Village resources Centres, that facilitate access to spatial information on important aspects like land use/land cover, soil and ground water prospects and enable farmers to take appropriate decisions through interaction with experts. VRCs also enable to provide telemedicine and artisan training programme as well, thus acting as a powerful tool for rural development. Chandrayyan-1, India’s first scientific mission to moon, which is now being pursued under Mr Madhavan Nair’s overall guidance, is a major scientific mission. Besides carrying the primary Indian instruments, the spacecraft will also carry instruments from European Space Agency, Bulgaria and USA thus increasing the scope of the mission to expand scientific knowledge about the origin and evolution of moon, A multi-wave length observatory in space, ASTROSAT, to be launched in the coming two years, is another important initiative to pursue advanced research in astronautics. The conceptual studies for a manned space mission have also been undertaken. Mr Madhavan Nair has nurtured international co-operation having led the Indian delegation to various flora including the United Nations Committee on Peaceful Uses of Outer Space, International Astronautical Federation and Committee on Space Research. He has been awarded honorary doctorate from several Indian Universities. He has been decorated with many prestigious awards from professional bodies from India and abroad. He has been awarded Padma Bhushan by Government of India. Email:

Paper No 144-B; Copyright © 2008 by the IETE.

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Morphological Algorithms for Image Processing BHABATOSH CHANDA ABSTRACT Mathematical morphological operators are based on set theoretic approach and are suitable for extracting shape information. Some important operators are dilation, erosion, opening and closing. Image intensity profile may be viewed as a topographical surface, where pixel co-ordinate stands for the location and the intensity for the altitude. Thus, the surface relief and slope represent different types of object features. Hence, morphological tools are found very effective for image processing. In this paper we discuss various image processing algorithms using morphological tools and the results obtained by applying them on both grayscale as well as colour image.

1. INTRODUCTION Human decision-making system depends on the information acquired from the environment. A major part of such information is visual in nature. Thus majority of automated decision-making or pattern recognition system are usually supported by some image processing techniques [1]. Image processing methodologies even also act as an aid to human expert by improving the quality of the viewed image. In the modern technology driven society, image processing techniques have proved themselves essential in image display, storing, retrieving, knowledge extraction as well as inference drawing. The techniques are, in general, categorized as image compression, quality improvement, segmentation, feature extraction, and scene analysis and understanding. An image processing system acquires information from 3-d objects or scenes, processes the acquired information, and builds knowledge about the viewed object or scene. A typical system acquires data employing suitable sensors, and processes them using standard image processing methodologies. Though the human visual system is more efficient than the computer vision system in terms of precision, speed of operation and accuracy, there are situations, like routine tedious job, hazardous environment, quantification of information etc., where the employment of image processing system is an acceptable solution. Secondly, human vision system depends solely on the eye in visualizing the objects, which is band-limited; on the other hand, computer vision system may employ various sensors (e.g., x-ray, infra-red ray, ultrasonic) with different ranges of visibility. As a result, image Vol. 25, No. 1, Jan-Feb’08

processing techniques have found numerous applications in the area of defense, medical science, remote sensing, natural resources management, disaster management, office automation, industrial automation, criminology, astronomy, and so on. Image processing tools are developed in both spatial domain as well as frequency domain. Frequency domain tools rely on the transformation of image by some orthogonal transformation like Fourier transform, Cosine transform or Wavelet transform and all processing is done in the transform domain. In spatial domain, the image processing tools operate directly on the pixel value in the image. A relatively new kind of spatial domain operators, known as mathematical morphological operators [2], is being widely used in image processing. These operators are defined based on the concept of set theory. The main advantage of mathematical morphology is that it treats an image as a set, unlike the conventional operators including both spatial domain and frequency domain operators that treats an image as two-dimensional signal. Morphological operators, thus, can directly deal with the shape information with the help of a structuring element, which may be viewed as a probe. Morphological algorithms closely resemble the human strategy of image understanding, as both of them are neither fully subjective nor fully objective, but a judicious combination of the two. In mathematical morphology, the operations are precisely defined but the selection of structuring element is an ad-hoc process and depends on the application and the data. In this work we present a generalized mathematical morphological framework for image I E T E

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processing and then show the application of this framework to various image processing problems with the help of suitable tuning. This paper is organized as follows. Section 2 describes the preliminaries of mathematical morphology including multi-scale morphology. Morphological algorithms for various image processing problems and corresponding results are shown in section 3. Finally, a brief discussion and concluding remarks are presented in section 4.

2. MATHEMATICAL MORPHOLOGY Morphological operators are primarily binary operators that are defined on some set or object (an image or a part of it) using another set, called the structuring element. We may classify images into two groups: (i) two-valued or binary images, and (ii) multi-valued images, which includes graylevel and colour images. In binary images the pixel value is either 0 or 1. In graylevel images, the pixel value may be any integer between 0 and some high value, say, L-l inclusive. Colour image is further extension of graylevel image where the value at each pixel is represented by a vector of three elements corresponding to red, green and blue components of colour information. In other words, a colour image is comprised of three graylevel images each corresponds to red, green and blue components respectively. Accordingly, morphological operators may be grouped as binary and grayscale morphology.

2.1. Binary Morphology In case of binary image, the object may be formed as a set of point (Fig 1):

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A = {(r,c) | f (r,c) = l}

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where f (r,c) is the value at pixel (r,c). Most elementary operations are dilation and erosion, which may be defined with the help of more primitive operations union and intersection as Dilation: A⊕B = {a+b | a ∈ A,b ∈ B} = ∪a∈A Ba (2) Erosion: A Θ B = {a | Ba ⊂ A}

(3)

It may be noted that the dilation inflates an object, whereas erosion shrinks the object. In other words, what dilation does to the object erosion does to its complement or background. Two more useful operations, namely Opening and closing, are defined in terms of dilation and erosion as follows: Opening: A ° B = (A Θ B) ⊕ B

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Closing: A • B = (A ⊕ B) Θ B

(5)

Opening retains only those parts of the objects that can fit in the structuring element. That means it removes, from the object(s), small components and isthmuses. Closing fills up small holes and gulfs. Thus they both can extract fine shape features that are narrower than the structuring element.

2.2. Properties of mathematical morphological operators A mathematical operator T on A by B, denoted by T(A, B), may be analyzed in terms of following properties: Increasing: A ⊂ B ⇒ T(A,C) ⊆ T(B,C) Idem potent: T(T(A,B),B) = T(A,B)

0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 1 1 1 1 1 0 0 0 0

0 0 0 1 1 1 1 1 1 0 0 0

0 0 0 1 1 1 1 1 1 1 0 0

0 0 1 1 1 1 1 1 1 1 1 0

0 0 1 1 1 1 1 1 1 1 1 0

0 0 1 1 1 1 0 1 1 1 0 0

0 0 1 1 1 0 0 0 1 1 0 0

0 0 1 1 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0

Fig 1 Binary image and the point set used for morphological treatment Vol. 25, No. 1, Jan-Feb’08

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Associative: T(T(A,B),B) = T(A,T(B,B))

Anti-extensive: T(A,B) ⊆ B

Distributive: T(A⊗B,C) = T(A,C) ⊗ T(B,C), where ⊗ is a binary operator. Hence, we can summarize that dilation is increasing, commutative, associative, distributive over union, and extensive if structuring element contains the origin (0,0). Erosion is increasing, distributive over intersection, and anti-extensive if structuring element contains the origin (0,0). Opening is increasing, idem potent and antiextensive. Closing is increasing, idem potent and extensive. Dilation and erosion are dual. Similarly, opening and closing are dual, and they are filters too.

2.3. Grayscale morphology In grayscale morphology, a graylevel image (Fig 2a) is considered as a topographic surface (Fig 2b). Thus, the object or the set of points may be defined as a set of triples: (6)

So the two-dimensional representation of the binary morphological operators can simply be extended to three-dimension to define the grayscale morphological operators. Thus we have the grayscale morphological operators as (m,n)

Opening : (g ° h)(r, c) = ((g Θ h) ⊕ h)(r,c)

(9)

Closing: (g • h)(r, c) = ((g ⊕ h) Θ h)(r,c)

Commutative: T(A,B) = T (B,A)

Dilation: (g⊕h)(r,c)=max{g(r–m,c–n)+h(m,n)}

(8)

(m,n)

Extensive: T(A,B) ⊇ A

A = {(r, c, f (r, c)}

Erosion: (gΘh)(r,c)=min{g(r+m,c+n)–h(m,n)}

(7)

(10)

where h(r,c) is the structuring element and the corresponding set may be defined as (r,c,h (r,c)). After processing, the graylevel image is generated from the set of points by taking the top surface of it, i.e, in practice, by considering only the third element of the triplets. In many applications h(r,c) is zero for all (r,c). In that case, we can omit h(r,c) from the definition of grayscale morphological operators as well as from the grayscale structuring element. Then the structuring element becomes a two-dimensional one, i.e., only the domain of structuring element is important. So the structuring element is degenerated to B, where h(r,c) = B = {(r,c)} and we have Dilation: (g ⊕ B)(r, c) = max{g(r – m, c – n) | (m, n) ∈ B} (11) Erosion: (g Θ B)(r, c) = min{g(r + m,c + n) | (m, n) ∈ B}(12) Opening : (g ° B)(r, c) = ((g Θ B) ⊕ B)(r,c)

(13)

Closing: (g • B)(r, c) = ((g ⊕ B) Θ B)(r,c)

(14)

This is known as function-and-set processing scheme. As the grayscale morphology is an extension of binary morphology, the corresponding grayscale morphological operators satisfy all the properties stated in section 2.2. Please note that

Fig 2 (a) Graylevel image, and (b) corresponding topographic surface

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opening clips the bright peaks and closing fills the dark pits. This observation is utilized in designing morphological algorithms for image processing.

2.4. Multi-scale morphology So far we have considered only the shape property of the structuring element, say, B. Sometimes we need to use structuring elements of same shape but of different sizes to deal with shape features in an image at different scale. To achieve this we need to incorporate a size parameter n in the representation of structuring element. Suppose, in the continuous domain, B = {(r,c)} is a compact point set of size one. Then nB = {nb | b ∈ B} = {(nr,nc)} is a set of size n > 0. It may be assumed that nB = {(0,0)} when n = 0 . In the discrete domain, simple multiplication of coordinates leads to many holes in nB. So we need to define nB in a slightly different way as follows. If B is a convex compact set, then nB = B ⊕ B ⊕ B ⊕... (n–1) times for n = 1,2,3,... and nB = {(0,0)} if n = 0. Examples of convex structuring elements of different shapes and sizes are shown in Fig 3. Morphological operators defined using structuring elements of variable sizes are termed as multi-scale morphological operators.

. . . . . . n= 1

2

3

4

Fig 3 Family of structuring elements

Most useful operators are multi-scale opening and multi-scale closing-defined as [3]: Multi-scale opening: (g ° nB)(r,c) = ((g Θ nB) ⊕ nB) (r,c) (15) Multi-scale closing: (g • nB)(r,c) =((g ⊕ nB) Θ nB) (r,c) (16) Since opening and closing are increasing and anti-extensive (extensive, respectively), Vol. 25, No. 1, Jan-Feb’08

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corresponding scale specific features may be extracted by means of top-hat transformation. Because of brightness of the extracted features of the image, we define Top-hat (bright) transformation: Fi°(r,c) = (g ° (i –1) B) (r, c)–(g°iB)(r,c) (17) Bottom-hat (bright) transformation: Fic (r, c) = (g • iB) (r, c) – (g • (i – 1)B)(r, c)

(18)

3. MORPHOLOGICAL ALGORITHMS FOR IMAGE PROCESSING A graylevel image can be decomposed into a number of feature images of different scales. Considering top-hat (bright) and bottom-hat (dark) transformations as defined above, a graylevel image can be expressed in terms of its scale specific bright and dark features as 1 g(r,c) = — {(g ° nB) (r, c) + (g • nB) (r, c)} + 2 1 n 1 n ⎯ Σ Fio – ⎯ Σ Fic (19) 2 i=1 2 i=1 The second term of the right hand side represents the bright features and the third term represents the dark features extracted morphologically. First term may be viewed as the background (or bias or local mean level) of the image. To provide a tool to vary the importance of features at various scales, we may represent equation (19) in a more general form: 1 g(r,c) = — {(g ° nB) (r,c) + (g • nB) (r, c)} + 2 1 n 1 n ⎯ Σ ki o F i o – ⎯ Σ k i c F i c (20) 2 i=1 2 i=1 In this section we present various image processing algorithms based on the scale specific features extracted and represented in the form of equation (20). The image processing problems we present and discuss in this paper are

• Noise cleaning • Local contrast enhancement • Image fusion • Segmentation I E T E

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3.1. Noise cleaning

3.2. Local contrast enhancement

Here we assume that the noise component in an image, by and large, changes the pixel value locally. As a result noise dominates at lower scales. Hence, after extracting scale specific features (both bright and dark), if we reconstruct the image using equation (20) with less emphasis given to small scale features, i.e.,

It is well known that if a small object has to draw attention of the viewer it has to be well contrasted against its surrounding. Smaller the object higher must be the contrast to become visible. Size of the object and the contrast has to be directly related. In other words, for better visual clarity small bright objects should be made brighter and small dark objects should be made darker. Hence, after extracting scale specific features (both bright and dark), if we reconstruct the image using equation (20) with more emphasis given to small scale features, i.e.,

k1o < k2o < k3o < ...< kno and k1c < k2c < k3c < ...< kn c then the effect of noise can be reduced. In our experiment we have used [4]: 1 1 1 kno = knc = ⎯ , koi –1 =⎯kio , and k ci –1 = ⎯ kic 4 2 2 for i = n, n – l, ... The result of the algorithm is shown in Fig 4. Figure 4a shows the noisy image containing speckle noise and Fig 4b shows the noise-cleaned image. Quality of the image is measured in terms of signal to noise ratio defined as Σ f 2 (r,c)

(r,c)

SNR = ⎯⎯⎯⎯⎯⎯⎯⎯⎯2 Σ ( f (r,c) – g(r,c))

(21)

(r,c)

where f(r,c) and g(r,c) are noise-free and noisy images, respectively. Accordingly, SNR of Fig 4a is found 17.51, while that of Fig 4b is 101.45. Please note that morphology based noise-cleaning algorithm, unlike mean filter, preserves the edge information quite well.

Fig 4

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k1o >k2o . k3o >...>kno and k1c >k2c > k3c >...>knc then the local contrast can be enhanced. In our experiment we have used [5]: 1 k1 o = k1 c = — , 4

1 1 koi+1 = — kio and kci+1 =— kic 2 2

for i =1, 2, ... The result of the algorithm is shown in Fig 5. Figure 5a shows the orginal low contrasted image and Fig 5b shows the enhanced image after local contrast intensification. In this work quality of the image is measured in terms of average local contrast defined as 1 Cnt = ⎯⎯ MN

Σ Σ d (r,c) r c

(22)

where d(r,c) = max {g(m,n)}– min {g(m,n)} (23) (m,n)∈W(r,c)

(m,n)∈W(r,c)

Results of noise cleaning algothrim (a) Noisy image (b) Noise cleaned image

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(a)

(b)

Fig 5 Result of enhancement algorithm, (a) Original image, (b) Enhanced image

and W(r, c) represents a square window around the candidate pixel (r, c) and Cnt is the desired quality measure. Accordingly, it is found that Cnt of Fig 5a is 24.63, while that of Fig 5b is 120.33. Visual inspection also reveals the efficacy of the method. The above algorithm can be straightaway extended to colour image enhancement. In that case, at first RGB values at each pixel are converted to YIQ and then local contrast enhancement algorithm is applied to Y-plane, which is nothing but the brightness component of the image. Finally, enhanced colour image is reconstructed and displayed by converting back YIQ to RGB. Result is shown in Fig 6. Average contrast of Fig 6b (Y-component only, other two components remain same as they contribute to chrominance value) is much higher than that of Fig 6a.

3.3. Image fusion Often same object or scene may be imaged through different sensors. For example, in biomedical methodologies same organs are imaged through CT and MR. It is well known that certain features are more visible in some image modality than in the others. Thus if the multi-modal images are fused then all the relevant features can be put together leading to better viewing and interpretation. The fusion algorithm described here is based on the assumption that the more visible features, either bright or dark, have higher values in the top-hat image and the bottom-hat image, respectively. Thus, images can be fused by (i) first, decomposing the images by top-hat transformation, (ii) then putting together the features of same scale but present in different images through some non-liner operation, say, Vol. 25, No. 1, Jan-Feb’08

max, and (iii) finally, integrating the combined feature images. Thus the fused image gfuse(r,c) is obtained as [6]: ffuse (r,c) = avg{g1 (r,c),...,gm(r,c)} n

o

n

o + Σ max{Fi1{r,c) ,..., Fim (r,c)} – Σ max i=1 i=1 o o {Fi1(r,c) ,..., Fim (r,c)} (24)

Result of this algorithm is shown in Fig 7. Figures 7a and 7b show CT and MR images of brain are respectively and the fused image is shown in Fig 7c. Performance of image fusion algorithm may be measured quantitatively in terms of cross-correlation. It is verified that correlation between Fig 7a and 7c as well as between Fig 7b and 7c are much higher than that between Fig 7a and 7b. Sometimes same object or scene is imaged through same sensor, say, camera but with different focusing. This is done as the depth-of-field of camera is finite and different objects in the scene lie at different distances. So in a single image all objects may not appear with equal clarity. Thus, in some application, image fusion is necessary to increase the depth-of-field of the camera artificially, i.e., putting all the sharply focused regions in the same image. It is well known that the sharply focused region contains more fine details than other regions. So sharply focused regions can easily be detected from the small-scale feature image obtained through top-hat and bottom-hat transformations. Thus, the fusion algorithm may simply be described as [7]: (i) detect small scale feature image from each of differently focused images, (ii) find the sharply focused image region by spatial clustering of the features, (iii) stitch the sharply focused regions (any tie may be resolved arbitrarily), and (iv) finally, transfer the pixel value from the corresponding I E T E

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(a)

(b)

Fig 6 Result of colour image enhancement algorithm, (a) Original colour image, (b) Enhanced colour image

(b)

(a)

(c)

Fig 7 Result of multi-modal image fusion, (a) CT image showing hard tissues, (b) MR image showing soft tissues, and (c) Fused image showing all the features

image to the fused image. Result is shown in Fig 8. Figs 8a, 8b and 8c show the images with focus on

near, middle and distant objects, respectively. The fused image is shown in Fig 8d.

(a)

(b)

(c)

(d)

Fig 8 Result of multi-focus image fusion, (a) Center focused, (b) Rear focused, (c) Front focused, and (d) Fused image Vol. 25, No. 1, Jan-Feb’08

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3.4 Segmentation

thresholded to get a thick edge or may be thinned by non-maximum suppression to get the sharp boundary [8]. Detection of meaningful edges is based on the assumption that the regions are larger than the minimum feature size, say, mB. Hence

Image region may be segmented in two different ways: (i ) finding edge (or boundary) between two adjacent regions one of which may be the background and the other may be the object or region of interest, and (ii ) extracting the entire region or feature of particular interest.

gd (r,c) = ((g ° mB)⊕S)(r,c)–((g °mB)ΘS)(r, c) (25) where S is a small isotropic structuring element. Result of a simple edge detection algorithm is shown in Fig 9. Figure 9a is the original image and Fig 9b is the corresponding edge image.

In the first approach, a simple difference between dilated and eroded version of the image can produce a gradient image g d (r,c) between two regions. This gradient image is then

(b)

(a)

Fig 9 Result of edge detection algorithm (a) Original image (b) Edge image

ADW

AY

YM

15T

OL

H A VE

6TH

AVE

BRO

PIA WA Y

(a)

(b)

(c)

Fig 10 Result of segmentation algorithm, (a) Original image, (b) Closed image with a structuring element and thresholded bottom-hat image, (c) Opened image with a structuring element and thresholded top-hat image Vol. 25, No. 1, Jan-Feb’08

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In the second approach, the feature image of a particular scale obtained through morphological tophat (or bottom-hat) transformation may be thresholded at zero to extract desired information. That means the segmented image g s (r, c) can be obtained as gs (r,c) = {

x

1

if Fi (r,c) > 0

0

Otherwise

(26)

where x stand for ‘o’ or ‘c’ depending whether we need to extract bright or dark features, respectively. In some cases, noise may be removed by sequential filter consisting of opening and closing. Result is shown in Fig 10. Figure 10a shows the original image. Results of thresholding Fic and Fjo are shown in Fig 10b and 10c, respectively. Quality of segmentation results is usually measured against the labeled groundtruth. However, in this experiment we have adopted subjective evaluation strategy and the results are found quite satisfactory.

4. CONCLUSION In this paper we have presented an image decomposition methodology based on top-hat and bottom-hat transformations. It has become possible because the image features of different scales are exhibited by relief of different slope and base-width in the topographic surface representation of the image. As a result, an image is represented as a combination of scale specific features along with the background (or bias). Scale specific features are then manipulated to design various image processing algorithms. It is interesting to note that noise removal and contrast enhancement have contradicting requirements, which is managed by using different order for the parameter values. On the other hand, two different image fusion methods, one for multi-modal and the other for multi-focus, are designed based on same set of scale specific feature images but utilized in different way. Two different segmentation approach can also be

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handled using similar types of operators but in different order. Results are presented to establish the usefulness of the algorithms. ACKNOWLEDGEMENT

The author is extremely grateful to his students for experimentation and results. He also acknowledges the source of data files used in this work. REFERENCES 1.

B Chanda & D Dutta Majumder, Digital Image Processing and Analysis, Prentice Hall of India, New Delhi, 2000.

2.

J Serra, Image Analysis and Mathematical Morphology, Academic Press, London, 1982.

3.

P Maragos, Pattern spectrum and multiscale representation, IEEE Transaction on Pattern Analysis and Machine Intelligence, vol 1, pp 701716, 1989.

4.

S Mukhopadhyay & B Chanda, An edge preserving noise smoothing technique using multiscale morphology, Signal Processing, vol 82, pp 527-544, 2002.

5.

S Mukhopadhyay & B Chanda, A multiscale morphological approach to local contrast enhancement. Signal Processing, vol 80, pp 685696, 2000.

6.

S Mukhopadhyay & B Chanda, Fusion of 2D grayscale images using multiscale morphology, Pattern Recognition vol 34, pp1939-1949, 2001.

7.

I De, B Chattopadhyay & B Chanda, Enhancing Effective Depth-of-Field by Image Fusion using Mathematical Morphology, Image and Vision Computing, vol 24, pp 278-1287, 2006.

8.

B Chanda, M K Kundu & V Padmaja, A multi-scale morphologic edge detector, Pattern Recognition, vol 31, pp 1469-1478, 1998.

9.

S Mukhopadhyay & B Chanda, Multiscale Morphological Segmentation of Grayscale Images, IEEE Trans on Image Processing, vol 12, pp 533549, 2003.

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RAM LAL WADHWA GOLD MEDAL LECTURE

Author Bhabatosh Chanda born in 1957. Received BE in Electronics and Telecommunication Engineering and PhD in Electrical Engineering from University of Calcutta in 1979 and 1988 respectively. His research interest includes Image Processing, Pattern Recognition, Computer Vision and Mathematical Morphology. He has published more than 100 technical articles in refereed journals and conferences. He has received “Young Scientist Medal’ of Indian National Science Academy in 1989, ‘Computer Engineering Division Medal’ of the Institution of Engineers (India) in 1998 and ‘Vikram Sarabhai Research Award in 2002. He is also recipient of UN fellowship, UNESCO-INRIA fellowship and Diamond Jubilee fellowship of National Academy of Science, India. He worked at Intelligent System lab, University of Washington, Seattle, USA as a visiting faculty from 1995 to 1996. He is currently working as a Professor in Indian Statistical Institute, Calcutta, India. He is fellow of Institute of Electronics and Telecommunication Engineers, of National Academy of Science, India and of Indian National Academy of Engineering. Email:

Paper No 144-A; Copyright © 2008 by the IETE.

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Challenges in Technology and Reconfiguration of SDR — A Survey V JEYALAKSHMI

AND

K SANKARANARAYANAN

ABSTRACT “Life goes wireless”, a motto for the evolving lifestyle of millions of people has pushed the flowering of several wireless standards spanning short to global coverage. The explosive growth of wireless communication has driven to have a quality radio device at an affordable cost. With the ability to reduce installation costs, add flexibility and easier deployment and maintenance, the attractiveness of wireless technologies needs little reinforcement. Recently this reinforcement turns the researchers to the reconfigurable SDR. In this article, we concentrate on the review of the trends in change and challenging technology in reconfigurable SDR. This is the “any one, anywhere any time”, paradigm of intelligent overlay communication establishment that is reconfiguration and re-programmability by software upgrades. The main technical objective of SDR is a versatile reconfiguration platform, which provides interoperability.

1.

INTRODUCTION

Many forces are drawing researchers as well as manufacturers working on technologies. With the recent development of small size tetherless communication/ computing devices and the increasing diversity in their capabilities, automatic ubiquitous communication environments are emerging. In such environment, the execution of complex task does not necessarily make use of preconfigured devices or networks, but requires instead, the selection of suitable computing elements on-the-fly, based on the dynamic reconfiguration. The inter technology roaming of mobile terminals will be based on a reconfigurable software radio concept. The objective of developing SDR technology is to realize plural system standards on a single hardware platform that is implemented mainly with high speed programmable devices. A desired system standard can be selected by choosing a proper software module. The SDR technique includes the design of both hardware and software modules. The hardware module is reconfigured by the software module, which means that a given hardware platform is converted into specific system standard or special purpose communication system depending on the changes in the software module. For a successful communication with different systems, the radio has to communicate and decode the signals of devices using software download. Vol. 25, No. 1, Jan-Feb’08

Different methods for software download concepts can be conceived, (i) Smart card loading (SIM), (ii) ROM/EPROM based reconfiguration (different radio configurations are stored inside the software radio), (iii) service terminal (offline reconfiguration by connecting physically to a service terminal), (iv) air interface download [1] etc. The following section advocates for the different generation of wireless technologies. The basic SDR concepts are introduced in section 3. Section 4 describes the SDR hardware technology and section 5 gives the need for reconfiguration. How the reconfiguration is performed in SDR and need for securities elaborated in section 6, section 7 gives the application of SDR and last section draws the conclusion.

2. HISTORY OF WIRELESS TECHNOLOGY The mobile communication in various generations has traversed a long way through different phases of evolution since its inception early in the 1970s. Analog voice oriented 1G wireless cellular system had many weaknesses, but their importance cannot be overstated [2]. The transition to digital voice and data oriented 2G systems (GSM) in 1991 were a worldwide success and turned the cellular phone into a commodity for the average consumer. New applications require higher data rates that are at the moment provided I E T E

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by 2.5G (like GPRS), an interim step between 2G and 3G. For applications such as wireless gaming and video however, the third generation (3G) systems in 2002, marked the beginning of a truly multimedia era, where more person to machines interactions than person to person interactions are prevalent [3]. Although not rolling out as fast as expected due to the worldwide market downturn, now is the time to think about fourth generation (4G) systems. Designs must be targeted to multimode and reconfigurability, leading to the concept of a “software-defined radio”. A large part of such a radio will be integrated into a complex SoC (System on Chip), where the substrate noise coupling problem must be solved. SiP (System-inPackage), technology adds another degree of freedom and will allow making a better trade-off between passive components. Presently, the wireless communications research community and industry are about to start discussions on standard activities for the fourth generation (4G) of these systems [4]. The evolution of the SWR concept necessitates the need for multimode, multiband terminals. The SDR forum restarted to evolve towards a universal terminal [5]. In 1999 a boom in the field of SDR started in Japan and it will become one of the most important technologies in advanced communication, broadcasting and intelligent transportation systems on the 21st Century. Advances in technology have brought to us a new form of digital radio service called ‘spread spectrum’, which has the advantage of spread spectrum wireless systems over conventional systems having no crosstalk interference, better voice quality/data integrity and less static noise, lowered susceptibility to multipath fading, inherent security, co existence, longer operating distances, hard to detect, use for ranging and radar and more efficient [6]. The goal of SDR is to provide a single radio transceiver capable of functioning like a cordless telephone, cell phone, pager, wireless e-mail system, wireless fax, wireless videoconferencing device, wireless web browser, global positioning system (GPS) unit and similar devices. In a SDR, functions are performed by the software, which controls high speed signal processors, and operate over a broad range of frequencies, bandwidth and transmission standards and output power. The FCC established a Technical logical Advisory council (TAC) in 1998 [7]. Vol. 25, No. 1, Jan-Feb’08

3.

BASIC SOFTWARE RADIO CONCEPT

Rapid development prevails in microelectronic and computer technology areas in recent years. A new term SWR (Software Radio) was coined by Joe Mitola in May 1992 to refer to the class of reprogrammable or reconfigurable radios [8], which defines a radio system which has configurable operating range, bandwidth, level of power, type of modulation, channel coding and so on, by software without changing the hardware. As depicted in Figure 1, SDR has three main sections namely RF section, (an antenna, LNA, programmable Up/Down converters), Baseband section (Channelization, Sample Rate Conversion and Signal processing) and network section (interfacing layer, protocols, different type of network). The main idea of the software radio is to execute most of the functions through software on the condition that the system construction is universal and stable, to update and improve the system conveniently and cheaply, and to let the heterogeneous network interconnect easily and be compatible with each other. Most of the research focuses on the realization of software radios. It would be easy for software on common hardware platform to be compatible with different communication technologies and to use lot of advanced dynamically adjustable techniques so that flexibility, multi band, multimode, multistandard, [9] and service qualities in radio communications are significantly improved and standard migration can be accommodated purely in software. We can construct a mobile system which has more flexibility, more powerful function and is easier to manufacture and more stable using SDK. The key blocks of a reconfigurable terminal are one that supports cellular WLAN and Blue tooth standards with any two of them able to operate concurrently [10]. The software function module mechanism can support many physical implementations such as switching between modules, or downloading new software or extensions to interoperate with different wireless protocols, incorporate new services and upgrade to new standards. Developing common modules is a good way to save the memory space and is easy to be administrated and modified. I E T E

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The SDR includes radio with a limited set of predefined hardware functions such as air interface Application Specific Integrated Circuits (ASICs), among which one may select by software to the degree that the functions may be redefined in software (e.g. by downloads or subscriber identity cards), the radio is a software radio. Usually, however ASIC with limited functions cost less than fully flexible Digital Signal Processing (DSP) or Field Programmable Gate Array (FPGA) implementation. Early SWR research focused on the military’s goal of total flexibility across dozens of radio frequency (RF) bands and air interface modes.

4.

THE SDR HARDWARE TECHNOLOGY

Before describing the reconfigurable software download scheme, we will first briefly review the elements of an SDR system and know which parts are reconfigurable. We focus on signal processing, radio technologies and development of various industries in SDR.

4.1. Processor/architecture Based on the literature survey and experimental results, associated technical challenges are summarized and proposed in the software radio architecture. Integrated and Programmable Communications shall be the precise way toward future communication technology. The receiver

architecture focusing on the four main aspects of self reconfiguration are base band filtering, symbol synchronization, and carrier synchronization and constellation recognition [11]. A high-level architecture of the Software radio’s base station architecture, using GSM enables a low cost platform, while using distributed computing techniques to achieve reliability. The modulation recognition technique is designed for a real time software radio using general purpose processor and is based on a modified pattern recognition and phase classifier approach. Software radios are typically implemented with multiple processors. Separate processors are often used for internetworking, intranetworking, security and modem processing. The ever increasing demand for mobile and portable communication requires high performance systems employing advanced signal processing techniques to allow operation as close as possible to the Shannon information theoretic bound. A set of processing performance requirements that can be hardly achieved for testing are by traditional digital systems based on DSPs. FPGAs are opening a new door in the digital processing environments and are widely used to implement physical layer signal processing functions for SDRs. Ideas relating to platform based design, originally motivated by system on chip ASICs have been increasingly adopted for FPGA design. The combination of both digital signal processing devices (DSPs and FPGAs) [12] can take advantage

Fig 1 Model of an ideal software radio Vol. 25, No. 1, Jan-Feb’08

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of their respective features. FPGA based signal processors provide high performance, while at the same time maintaining flexibility through static RAM configurability. Third and future generation communication infrastructure must support multiple modulation formats and air interface standards. FPGAs provide the reconfigurability [13] and flexibility to achieve this goal, by providing high levels of performance and completely customized. From a processing point of view, the challenge in SWR is to exploit the three basic processor types namely fixed architecture processors, FPGAs, and programmable DSPs/RISCs/CISCs. The front-end of the receiver implemented in hardware represents a novel wideband design that functionally converts wireless signals directly into a Giga sample digital data stream in the receiver. This direct conversion approach shows the greatest promise in realizing the main goal of software radio [14]. CORDIC is a versatile algorithm widely used in digital signal processing applications for direct conversion in VLSI implementation. It is used to implement Direct Digital Synthesizers [15], AM, PM and FM analog modulator and ASK, PSK and FSK modulators, up/ down converters of in phase and quadrature signals, full mixers of complex signals and phase detection for synchronizers [16]. Using embedded microprocessors in an FPGA and combining them with other advanced features of the fabric, allows for a powerful solution on a single, reprogrammable chip to the architecture of a SDR system. A reconfigurable hardware system (SHaRe) is based exclusively on FPGAs which will allow adding quickly and easily, new improvements and functions into commercial mobile terminal by using hardware description languages (e.g. VHDL, Verilog) as a first layer and even C or JAVA languages in higher and mature levels.

4.2. Radio technology Radio technology is undergoing sweeping changes. Many of the earliest radio receivers were built using crystals and fine wire probes that were moved by the listener to form a diode and included a variable inductor with a slider to tune the receiver to a radio station’s frequency so that one could hear music or voice. The need for precise tuning has changed little in the more than 80 years since CW transmitters replaced the very broadband spark gap approach originally used by Marconi. Today, Vol. 25, No. 1, Jan-Feb’08

even with advancements in RF design and the powerful digital processing available, all radio receivers still use analog parts to tune the radio to a specific carrier frequency. The availability of highspeed RF/D converters has made possible the implementation of true software-radio transmitters and receivers that avoid the use of passive components to tune and modulate/ demodulate high-speed wireless signals. These converters using conventional CMOS and advanced semiconductor technologies have been demonstrated to have performance comparable to or better than conventional analog front-end circuits and enable tuner-less architecture of wireless transmitters and receivers. The front end of the terminal imposes strong requirements regarding dynamic range and bandwidth and thus word length and sample rate [17]. The simplest architecture is that of a tuned radio receiver (TRF) which consists of a Tuned filter followed by a detector. A long known architecture due to Armstrong is the super heterodyne receiver, in which frequency conversion is applied to convert the radio signal to a spectrum where selectivity is easier to implement. The Adaptive Low power Front end (ALF) will be able to switch between feedback architecture for high dynamic range operation and a non-feedback setup for a lower dynamic range at the same noise figure. A possible electronically tunable RF filter, using MEMS (Micro Electro mechanical systems) switches are providing the preselect function in an SDR receiver. The quest for new architectures in radio frequency front - ends is a clear consequence of the ever increasing number of different standards and the resulting task to provide a platform which covers as many standards as possible [18]. Technologies for achieving reliable high speed transmission to wide area mobile and portable cellular subscribers with high spectrum efficiency are more and more necessary. One possibility in the radio link design is the combination of multi carrier schemes, both OFDM and FDSS (Frequency Diversity Spread Spectrum) with antenna diversity to overcome the link budget and diverse fading limitation of the cellular mobile radio environment. A novel wireless radio platform suitable for software defined radio and its proposed platform consists of new broadband radio frequency (RF) front end supported by a reconfigurable digital signal processor (DSP) or field programmable gate I E T E

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array (FPGA) technology. 2001 was an important year in this software radio area since many new researchers were added to the team and several new sub areas were launched, notably in areas new to EuroCOM, such as Radio frequency and FPGA system design [19].

4.3. SDR Development The research on SDR was originally started in the 1980s to develop a US military communication system. It has been continuing as the JTRS (Joint Tactical Radio System) project. In the 1990s, it was driven by rapid progress in technologies and costreductions in digital signal processing devices, such as DSPs and FPGAs. The military application of software radio were more fully described in terms of the US Defense Advanced Research Projects Agency’s (DARPA’s) Speakeasy I technology pathfinder in 1995. The speakeasy II program was the catalyst for the Modular Multifunction Information Transfer System (MMITS) forum, founded in March 1996. Now it is named as SDR forum [20]. The SDR architecture and program download schemes have been discussed in the SDR forum and at many conferences [21]. MMITS global participation has included Alcatel, Erricsson, Motorola, Nokia, Orange Personal Communication, Rhode and Schwarz, Samsung Electronics and Siemens among others. The European community has sponsored precompetitive software radio program in its R&D in Advanced Communication in Europe (RACE) and Advanced Communication Technology and Services (ACTS) program. In December 1998, a software radio study group was organized in the Communication Society of the Institute of Electronics, Information, and Communication Engineers (IEICE), Japan. The group has been very active in discussing SDR issues including devices, algorithms, application programming interfaces, operating systems, software downloading, regulations, and so on. In April 2000, the Telecom Engineering Center (TELEC) support from the Ministry of Public Management, Home Affairs, Posts and Telecommunications. (MPHPT, formerly MPT) of Japan started three years of serious discussions towards accepting the SDR concept in the Japanese legal and regulatory environment, and the final report was made in March 2003. In June 2000, Motorola announced that they had started to develop a cellular SDR terminal. In

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September 2001, the US Federal Communications Commission (FCC) adopted rule changes to accommodate the authorization and deployment of SDRs. In Europe, there are many SDR-related coprojects, such as MMR (Multi-mode Multi-protocol Radio), SORT (Software Radio Technology), PROMURA(PROgrammable MUltimode RAdio for multimedia wireless terminals), SLATS (Software Libraries for Advanced Terminal Solutions), and TRUST (Transparently Reconfigurable Ubiquitous Terminal), under ACTS (Advanced Communications Technologies and Services), ESPRIT (European Strategic Program for R&D in Information Technology), and IST (Information Society Technologies) projects. They have mainly been making new concepts for SDR (some projects have already ended). The major technical issues for SDR mobile terminals include developing high-speed and low power consumption programmable devices, and small multiband RF circuits. Some research organizations including NTT have continued to study these technologies. The results of feasibility studies are showing that SDR technology will allow a single mobile terminal to cover second- and thirdgeneration mobile systems, as well as higherspeed and broader-width wireless systems such as wireless LANs [22]. Researchers at the Georgia Institute of Technology have been collaborating in the development of a wireless prototype test system in a program supported by the Georgia Electronics Design Center (GEDC) and the Georgia Research Alliance. The research team has made major advances towards their goal by using a programmable software radio test bed to implement Multiple Input Multiple Output (MIMO) systems employing Orthogonal Frequency Division Multiplexing (OFDM).

5. NEED FOR RECONFIGURATION The increasing demand for wireless connectivity and current crowding of unlicensed spectra has pushed the regulatory agencies to be more aggressive in providing new ways to use spectra. Today’s radios are fixed, hardware solutions. What is needed is a generic, programmable hardware base that would allow software to enable various features, depending on the radio environment in which the useage moves [23]. The evolution of space systems whether for

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environmental monitoring, experimentation, deep space exploration or communication applications has been towards the creation of a reconfigurable and programmable platform that could leverage the initial investment costs of the satellite, by providing the flexibility that renders the satellite more useful and up-to-date with respect to the latest advances in the sciences. As wireless communications become more and more diverse, the need of software radio is getting stronger. We identify a few critical challenges in software radio and briefly introduce possible directions from different aspects which is a greatly worth serious research in the coming years. The reason that wireless devices are so inflexible is that they are generally implemented in hardware. There is a chipset in each device that performs the signal processing to allow the device to communicate with its wireless network. This inflexibility led researchers to consider alternate software based designs namely SDR. It is a wireless communications device in which all of the signal processing is implemented in software. This strategy leads to device flexibility software portability and system upgradeability. Concept of integrated seamless global coverage requires that the radio support two distinct features: first, global roaming or seamless coverage across geographical regions: second, interfacing with different systems and standards to provide seamless services at a fixed location. Frequent redesign is expensive and inconvenient to the end users. So the reconfigurable SDR can be obtained with either a single device capable of delivering various services or with a radio that can communicate with devices providing complementary services [24].

6. SOFTWARE DOWNLOADING IN RECONFIGURABLE SDR In this section we describe some existing reconfiguration methods and software download approaches with need for security in software downloading.

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architectures or SDR systems [25] is also required. This approach is termed reconfigurable SDR, because the hardware itself can be configured for a particular application [26]. Software radio systems are potentially the next main improvement in mobile and wireless communications. Mobile communication providers have led to the planning of a universal connection that adapts itself to different requirements. The software radio terminals must be auto reconfigurable in order to match the different telecommunication standards. The mode switching and software downloading is very important to SDR. Huge manpower is needed for time-consuming work to upgrade or bug-fix the enormous number of cellular base stations. SDR base stations can be remotely bug-fixed quickly by downloading new software via the network [27]. Many researchers concern a need for reconfigurable terminal and projects on SDR are undergoing with the aim of envisaging multistandard, multimode terminal. Reconfiguration through software download over the air (OTA) is the most concerned issue to many researchers since its attractive concept of dynamic reconfiguration of SDR terminal can, not only be user friendly in subscribers point of view, but also cost effective for network providers [28]. An estimate of the size of the market for SDR terminals has been made by the SDR forum as about 9.5 million handheld devices in 2000/1 timeframe rising to about 130 million in 2005 [29].

6.2. Reconfiguration method Reconfiguration, dynamic/ in-call or static/ outcall; partial or complete is an essential part of software radio technology. Lightweight component based approach uses typical software upgrade scenario for bug fixing and device performance enhancement [30]. The reconfigurability is addressed toward two different concepts: (i) changing the radio interface and (ii) changing the services that a customer desires. The configuration module library contains the functions that allow the terminal to reconfigure itself for supporting a specific air interface. A well layered architecture may minimize download time by eliminating extra amount of code that would otherwise have to be transferred. The software download in the mobile terminal must be as fast as possible and easy to perform. The air interface download is the most flexible one,

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but needs a dedicated channel for the download. This implies standardized hardware solutions of resident compilers. The implementation of a JAVA virtual machine is the most promising technology in this field [31]. The SDR forum developed an application Program Interface (API) to support onthe-fly reconfiguration of the mobile terminal. Reconfiguration option discovery must be generic so as to support inter-standard and intra-standard reconfigurations with minimal runtime adjustments.

6.3. Software Download The communication industry is now looking for a way to create radios that can handle multiple frequency bands, understand multiple transmission protocols, be reconfigured on the fly and be easily upgraded all in a single device design via a simple download. The generic hardware is flexible software architecture. Downloading firmware upgrades using physical media (e.g memory stick, smart card, single plug-in/update module) exist. However it would be most convenient and most cost effective. If SDR users could download radio software upgrades, new air interfaces or even custom defined applications through wireless is possible whenever it suits them. This capability is called OTA download. OTA software download is an enabling technology that leverages on the flexibility on radio hardware. To support OTA download scheme, a suitable wireless transport protocol model should be used to overcome the nature of wireless links. TCP/IP protocol suit is widely used over OSI [32].

Flexible radio interface and network architecture focuses on the realization of the multimode capability of user and control planes and the related management of the protocols of a flexible radio interface [33]. They proposed software download for reconfigurable terminal over wireless TCP and suitable TCP mechanism for OTA downloads by downloading appropriate protocol components, switching from one protocol to another is possible. OTA reconfiguration has three major components, the user terminal, and the service provider who provides the access network and software component store. To implement OTA downloading, an OTA download protocol and a download server, based on TCP/IP was developed as shown in Figure 2. It not only downloads the software, but also authenticates and encrypts the data using SSL (secure socket layer). After the OTA download had finished successfully, the prototype was automatically reconfigured by system control program. OTA software download will be a necessary mechanism to support the proliferation of applications and content resulting from new 3rd generation services and is a key enabler for ubiquitous reconfigurable terminals. The most important requirements for software download traffic are error free reception and an acceptable latency. The OTA download process can be made simple and entirely transparent to the user by having a base-station at the service provider to control the complete download process. According to strategy analytics (http://www.strategyanaystics.net). 69 percent of

Fig 2 Principles of OTA downloading

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handsets sold will be OTA enabled by 2009. The proliferation of successful OTA download companies (e.g, Bitfone, Innopath, Redbend software) demonstrates the huge potential of this emerging field. The software and middleware platforms also vary (Java, J2ME, BREW, etc). The goal is to improve the speed and efficiency of the OTA download process when deployed on a larger scale [34]. For the reconfiguration management and software download, security concepts must be enhanced in close collaboration with standardization [35]. Secure software downloading is a critical security issue in the SDR functioning. For secure downloading, it includes four different cryptographic techniques and employment of tamper resistant hardware. The cryptographic techniques by Kocher employed in 1998 are: (a) a secret key encryption technique; (b) a public key encryption technique; (c) a technique for cryptographic hashing and (d) a technique for digital signature. SDR uses the end to end encryption method in which data is encrypted at the source or very close to it and decrypted at the wireless terminal [11]. One of the most pressing issues for the commercial introduction of SDR systems is the authentication and verification of integrity of the software that is downloaded. As a straightforward attempt based on existing security techniques developed for Internet or wireless communications, several methods of secure download have been considered or could be considered. These include SSL based security, WEP (Wired Equivalent Privacy) based security and some dedicated SDR proposals [36]. In theory, the best solution consists in the standardization of a worldwide download channel by which the user terminal may connect to the BS to exchange request information and for downloading the configuration module set to receive a specific transmission standard. The channel bandwidth may vary according to the transmission standard parameters, such as bit rate and modulation scheme. The software download depends strongly on the selected physical link for transmission; the channel conditions and the system load. Fundamentally we need a better understanding for a secured architect system that can embrace the security evolution in a flexible, non intrusive and efficient manner. Reconfigurability and Vol. 25, No. 1, Jan-Feb’08

reconfiguration from one hand make possible to introduce a series of concerns relating to security, safety, reliability to name a few. Reliability may also be achieved with fault tolerance techniques built in [37]. A novel reconfigurability approach called iterative reconfigurability which minimizes the used hardware area and the reconfiguration logic and thus is appropriate for critical implementation constraints as in user mobile terminals.

7. APPLICATION Accurate positioning is an essential element of next generation software defined radio applications such as cognitive radios, telemetric and E-9-1-1, leading to an increased demand for GPS waveforms on SDR platforms [38]. Researchers are currently using software radio based systems to help them work on problems in realms that include radio astronomy, telecommunications and medical imaging. Already a number of commercial products rely on software radio. The USRP (Universal Software Radio Peripheral) acts as an RF front end for a computer running the GNU radio software converting radio waves picked up by an antenna into digital copies that the computer software can handle or conversely, converting a wave synthesized by the computer into radio transmission. The USRP can be used with proprietary software such as Matlab and Labview or with home brewed code. Programs for GNU radio are written using the C++ and python language. Routing between modules is done with Python, so that a developer might write a python program to the source module and sink module [39].

8. CONCLUSION A detailed review has been done in terms of technology and re-configurability of Software Defined Radio using software downloads. Security issues are also one of the impartment in software download concept, which is discussed in this survey. Reconfigurable platforms can be very effective for lowering production cost, because they allow the reuse of architectural resources across a variety of applications. Given this technological backdrop, it can be envisioned that future wireless communication will entail reconfigurable air interfaces running on highly flexible radio hardware, I E T E

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providing true mobility with users to different network type and services, any time and anywhere.

18.

A V Jacob, Part 2 of 3, Software Defined Radio waiting in the wings, Electronics for you, December 2005.

9. REFERENCES

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Danijela Cabric, lan D O’Dannel, Mike shuo-wel Chen & Robert W.Brodersen, Spectrum Sharing Radios, IEEE circuits and system Magazine, 2nd quarter 2006.

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C Bonnet, P A Humblet & R Knopp, Software Radio Platform, Mobile Communication Research Activity Report, 2001.

21.

Software defined radio (SDR) forum: http// www.sdrforum.org.

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Kazuhiro Uehara, Katsuhiko Araki, & Masahiro Umehira, Trends in Research and Development of Software Defined Radio, NTT Technical Review.

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Danijela Cabric, Ian D O’Dannel, Mike shuo-wel Chen & Robert W Brodersen, Spectrum Sharing Radios, IEEE Circuits and Systems Magazine, 2nd quarter 2006.

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M Cummings & S Heath, Mode Switching and Software Download for Software Defined Radio: The SDK Forum Approach, IEEE Communications Magazine, vol 37, Aug’ 99.

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Sayan Kumar Ray, Fourth generation (4G) networks: Road map - Migration to the Future, IETE Technical Review, July-August 2006.

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Savo G Glisic, Advanced Wireless Communications, 4G Technologies, Wiley.

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A H Aghvami, T H Le, & N Olaziregi, Mode Switching and QoS Issues In Software Radio, IEEE Personal Communications, October 2001.

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Alok Shah, Vinainc, An Introduction to software Radio, White paper - 2002.

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Jeffrey H Reed, ‘Software Radio: A Modern Approach to Radio Engineering, Pearson Education.

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Srikathyayani Srikanteswara, Jeffrey Reed, Peter Athanas & Robert Boyle, A Soft Radio Architecture for Reconfigurable Platforms, IEEE Communications Magazine, February, vol. 38, no 2, pp 140-147, 2000.

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Mehul Mechta, Nigel Drew & Christoph Niedormeier, Reconfigurable terminals an overview of architectural solutions, IEEE Communications Magazine, August 2001.

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Christian Prehofer & Bertrand Soulville, Synchronized Reconfiguration of a Group of Mobile Nodes in Mobile Ad Hoc Networks, IEEE 2003.

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Flemming Christensen, A Scalable Software Defined Radio Development System, Embedded Systems, Winter 2004.

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Didier Bourse & Karim el Khazen, Al lee, Dragun Boscovic, Business perspectives of End -End reconfigurability, Motorola, IEEE, June ’06.

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Vangelis Gazis, Nancy Alonistioti & Lazalos merakos, university of Athens, A generic model for reconfigurable protocol stacks in beyond 3G, IEEE wireless Communication, June 2006.

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Benny Bing, Software Defined Radio Basics, IEEE Distributed Systems Online, Oct 2005.

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Rinaldo Castello, Introduction to the special issue on wireless reconfigurable terminals, IEEE Circuits and Systems Magazine, 1st quarter, 2006.

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Henrigue C Miranda, Pedro C Pinto & Sergio B Silva, A self Reconfigurable Receiver Architecture for Software Radio Systems, IEEE, 2003.

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Yasuo Suzuki & Kazathiro Vehara, Software Radio Base and Personal Station Prototypes; IEICE Transactions on Communication, vol E83.B, no 6, June 2000.

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Massimiliano Laddomada, Politecnico di Torino, Fred Daneshgaran & Ronald M Hickling, A PC-Based Software Receiver Using a Novel Front-End Technology, Issue of IEEE. Communications, Aug 2001.

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A Shoari, M Kamarei & A Radmand, Implementation of Costas loop using CORDIC algorithm for SWR applications, IEEE Proceedings Communications, vol 152, no 1, February 2005.

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Javier vails, Trini Sansaloni & Asun Perez-Pascual, The Use of CORDIC in Software Defined Radio: A Tutorial, IEEE Communication Magazine, September 2006.

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Ronald M Hickling, New Technology Facilitates True Software-Defined Radio, www.rfdesign.com, April 2005.

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Hiroyuki Shiba, Yushi Shirato, Hiroshi Yoshika & Inchihiko Toyoda, Software Defined Radio Prototype(I)- System Design And Performance Evaluation, Selected Papers, NTT Network Innovation Lab, vol 1, no 4, July 2003.

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Authors V Jeyalakshmi is working as Senior lecturer in the Department of IT at VLB Janakiammal College of Engineering and Technology, Coimbatore. She completed her BE in ECE and ME in Optical Engineering from Madurai Kamaraj University. At present she is doing her PhD in Anna University, Chennai. Her areas of interest include Mobile Communication, Neural Network, Computer Network, Microprocessor and interfaces, Microcontrollers and their applications, VLSI and Digital Electronics etc. Email: <jpjeya @ gmail.com>

K Sankaranarayanan is working as the professor and Dean of Electrical sciences at VLB Janakiammal College of Engineering and Technology, Coimbatore. He completed his BE in ECE and ME in Applied Electronics from University of Madras. He did his PhD in the area of Biomedical Engineering, Bharathiar University. His areas of interest include Digital Signal Processing, Computer Networking, Mobile Communication, Network Security, Biomedical Electronics, Neural Networks and their applications etc. Email:

Paper No 103-A; Copyright © 2008 by the IETE.

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Design, Development and Applications of PC-based Process Control Trainer for Automation GAUTAM A SHAH

AND

TEJMAL S RATHORE

ABSTRACT Initially, Process Control was typically done in the analog domain using continuous-time signals with analog systems. However, as the complexity of the control function increased, it became very costly, and, at times, unfeasible to use only analog elements. The rapid evolution of digital computers caused a major shift to digital technologies, and led to the control action being done in the digital domain using discrete-time signals with digital systems. The main motive behind designing and developing the PC-Based Process Control Trainer (PCT) for automation is to have a system which is versatile, easy to use, interactive, intelligent, and quickly developed. Physical variables like temperature, fluid flow and levels at various points in the system are monitored and control action is provided to various heaters, stirrers, valves and pumps. One utilizes LABTECH’s LT/CONTROL software package which reads the inputs from the standard data acquisition and control add-on cards. It performs various calculations as per the requirement and the results are used in the control strategy. It provides real-time data logging, data storage and realtime display control panel for the user interface with multiple display screens to view the system. The PCT is built, tested and found to work satisfactorily. About twenty experiments are set up and performed on it. These check various devices in the system, help in studying various types of control actions and automate the trainer for particular processes. The PCT has varied applications for automation. On the educational front, it can be used as a basic control laboratory. New experimental setups can be configured to study open loop and closed loop control systems for temperature, flow and level control. Automation of different processes with a choice of control actions can be done. From the industrial point of view, it provides an insight to industrial control; prototypes of process control systems can be built and used as a stepping stone to change the present manual or semi-automatic control to complete automation.

1.

INTRODUCTION

Automation provides the means for attaining optimal performance, improving productivity, relieving the drudgery of many repetitive manual operations. An analog controller produces continuous time control signals from continuous time input signals. The cost of the controller rises steeply with the increasing complexity of the control function. Digital controllers, on the other hand, offer precise mathematical operations, reproducible results, provide flexibility in reconfiguring the system, make use of programmable or hardwired machines and provide much better control of accuracy requirements. Digital signals are easily stored, transported and can be processed offline [1,2]. The hardware complexity in a measurement system can be reduced by integrating software control of certain operations and/or multiplexing Vol. 25, No. 1, Jan-Feb’08

certain components/blocks through a microprocessor or a microcontroller. In such cases, the basic measurements are made by hardware and the data are stored in the memory. Logic decisions, mathematical operations and their sequence of operations, etc, are performed through software [3]. Earlier the microprocessors and microcontrollers which were confined to simple test and measuring systems have steadily become more powerful and inexpensive; however, on their own, they are not very user friendly. Microprocessor and microcontroller based systems are slightly more time consuming as they require application software to be developed in machine language and interfaces are required for keyboard, printer and display. The need arose for a system which would be versatile, easy to use, intelligent, interactive and quickly developed in the field of Process Control. A PC-Based system was the ideal choice. The I E T E

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applications that can be implemented with PCs in the process control environment are limited only by one’s imagination.

of the IO devices to be used in the systems and hence is fast and cost-effective [6,8]. The PCT is such a system.

However, successful implementation demands a rather thorough systems analysis of the hardware, software requirements, user communication, hardware and software limitations and theory necessary to support the application [4]. Industrial instrumentation and automation are the main areas of real-time applications of PC’s. Optimization of performance of instrumentation systems basically involves the sensing and processing of physical variables such as flow, temperature, level, pressure, velocity, etc. The optimization is not complete until the system is self-sufficient in its characteristics like the intelligence to adapt to an algorithm for useful and accurate measurement. Likewise the efficiency and productivity of an industry depends on the techniques implemented for automation. An appropriate technique for automation improves the quality and productivity of products and results in a cost effective system. Instrumentation and automation therefore require flexibility, programmability and sufficient intelligence with the system, which is easily possible with the incorporation of the PC [5].

Section two of the paper gives a brief review on the fundamental aspects of Process Control Systems and Automation, followed by section three which gives the details regarding design, development and applications of the PCT for automation.

The PC on the other hand is gaining acceptance in the laboratory for measurement, analysis of acquired data, calculations, sequencing, etc, with the major advantage of friendly interaction with the user by way of dialogue menus and interactive displays. In the field of laboratory process control and instrumentation with a PC there is a significant ‘Do It Yourself’ content, for the simple reason that every laboratory activity is unique and requires an individual approach to its solution. The application of computer techniques in the laboratory for measurement and control is best carried out by the users themselves. A number of PC-based instruments have entered the market, thus the same PC can be used with a number of instruments. Even existing equipment can be interfaced to the PC with the help of add-on cards thus converting the PC into a data acquisition, processing and control system. The hardware interfaces for many input-output (IO) devices, disk drives, keyboard, printer and display are built into the PC. Many of the instruments and systems to be used in the laboratory need the above mentioned devices to be integrated in them. Therefore developing systems around the PC saves the need for developing interfaces for many

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2. PROCESS CONTROL SYSTEMS AND AUTOMATION A.

Process Control Systems

A Process may be defined as a natural, progressively continuing operation or development marked by a series of gradual changes that succeed one another in a relatively fixed manner and lead towards a particular result. The word ‘Control’ is usually taken to mean ‘regulate, direct or command’. A system is an arrangement of equipment functioning together in such a manner so as to form an entity, the purpose of which is to perform a particular operation (process). Thus Process Control System (PCS) may be defined as an arrangement of equipment related in such a manner so as to command, direct or regulate itself for the purpose of performing a Process. In a PCS, the input is the stimulus or excitation applied from an external source in order to produce a specified response from the system, and the output is the actual response obtained from it, which may or may not be equal to the specified response implied by the input [9,10]. PCS can be classified into two categories, Open Loop Systems (OLS) and Closed Loop Systems (CLS). OLS is one in which the control action is independent of the output. Figure 1 shows the basic block diagram of an OLS [11].

Input

PCS

Output

Fig 1 Open loop system

Some features of an open loop system are simple construction and ease of maintenance. It is less expensive than a corresponding CLS and has

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no stability problems. Disturbances and changes in calibration result in errors and the output may be different from desired. To maintain the quality of output recalibration is required from time to time. CLS is one in which the control action is somehow dependent on the output. Figure 2 shows the basic block diagram of a CLS.

Reference Input

Primary Feedback Signal

PCS

Controlled Output

Actuating Signal

Feedback Element

Fig 2 Closed loop system

These are usually called feedback control systems. Feedback is the property of a closed loop system which permits the output (or some other controlled variable of the system) to be compared with the input to the system (or an input to some internally situated component or subsystem of the system) so that appropriate control action may be performed as some function of the input and output. A cause and effect relationship exists between the system variables [12]. Some features of a closed loop system are increased accuracy, reduced error, reduced sensitivity, reduced effects of nonlinearity and a tendency towards oscillation and instability.

B.

Automation

Automation relates with feedback control of process variables. Process automation deals with the automatic control of process variables such as flow, temperature, level, pressure, humidity, concentration, etc. The automatic control of the process variables refers to the regulation of these variables in the true sense. This means that any change in the process variable is brought to zero. In other words, the process variable is first sensed or measured and compared with a desired value. The error generated is then processed and fed to the system in such a way that the actual process Vol. 25, No. 1, Jan-Feb’08

variable reaches the desired value. Any change in the actual process variable shall render change in error which will drive the system to compensate for the change. Thus process automation is essentially an error actuating mechanism [13]. Automatic control has played a vital role in the advancement of engineering and science. An automatic controller compares the actual value of the system output with the reference (desired value); it determines the deviation, and produces a control signal that will reduce the deviation to zero or to a small value. The manner in which the automatic controller produces the control signal is called the control action. The basic control actions are: Two position or On-Off control, Two position or On-Off control with differential gap, Proportional Control, Integral Control, Proportional + Integral (PI) Control, Proportional + Derivative (PD) Control and Proportional + Integral + Derivative (PID) Control [14].

3.

PROCESS CONTROL TRAINER

The PCT, a cupboard size laboratory model on a movable trolley is configured as shown in Fig 3. It consists of three chambers and a sump. All the chambers have a level sensor and transmitter, temperature sensor and transmitter, heater and stirrer with a provision for overflow. A pump is connected to propel the fluid from the sump into identical Chambers A and B each of which have an inlet solenoid valve and outlet motorized valve for fluid flow into and out from the chamber respectively. Chamber C has a heat exchanger; fluid flows into the chamber through the outlet motorized valves of Chambers A and B and out of it through an outlet motorized valve to the sump. Temperature and flow is monitored at various points in the system as shown in Fig 3. Chamber A is designed to demonstrate level, temperature and flow control. Chamber B is designed to demonstrate at a glance, the difference between two types of control actions. At the output of the two identical chambers, motorized valves are connected to let out different proportions of fluids from the chambers. To observe the effect of the mix, Chamber C is provided, in which the effect of various combinations of the mix can be observed. A process disturbance loop is introduced in this chamber in the form of a heat exchanger to observe the effect of a process disturbance and the way the control action takes care of the same. A solenoid valve is provided at the process I E T E

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disturbance input, to enable or disable the flow of liquid in the heat exchanger, to provide the required process disturbance. The stirrer in this chamber is provided with variable speed control to study the effect of variation of speed on the heat distribution.

A. Software Support LT/CONTROL is an easy to use, integrated, industrial monitoring and control software system which provides process monitoring, data logging, alarms, process control, real-time operator interface, real-time display and online analysis.

Process monitoring It interfaces to a wide variety of process variable types, such as analog voltages and current, discrete I/O, thermocouples, RTDs, strain gauges, resistance, counter and frequency inputs. Thermocouple, RTD and strain gauge linearization are handled by the software. Other variable types include RS-232 devices, time, replay of stored or theoretical data, and derived or calculated variables. Analog and digital outputs are supported as is the pulse output for controlling devices such as a stepper motor.

Data logging Process data can be monitored on a continual basis. As data is collected, values, tag names, and alarm conditions are time stamped and stored. Data can also be displayed and logged as it is acquired, as a function of time-of-day, or as a result of a decision made by the operator or by the system. Its menu-driven set-ups add flexibility to configuring processes. Variables are assigned meaningful tag names and alarm limits, and can be displayed in engineering units.

Alarms Alarms can be triggered when a variable reaches or passes a predetermined limit or as a result of a calculated variable or operator action. It supports multiple alarm states, hi-hi, high, normal, low and lo-lo, which can be displayed on the computer monitor or logged to disk. The system can be configured so that when an alarm occurs, the operator is notified and must acknowledge the condition. Alarms can also be treated as events whereby the system can take specific actions, modifying its monitoring functions and sending Vol. 25, No. 1, Jan-Feb’08

outputs to various hardware devices.

Process control It provides control functions for both local and remote control between nodes in a network. Alarm and bang-bang control features allow for the turning on and off of equipment for control applications or to indicate alarm conditions. Its PID loops provide closed loop control for constant or variable set points. Set points can be entered through the keyboard, automatically through on-line calculations, or as a preset schedule of values stored on the computer’s disk. It allows tuning of control loops on-line. Control parameters – upper and lower alarm limits, gain, reset, scan rate and set points of the PID algorithm – can be adjusted manually from the keyboard. Once tuning is complete, you can switch from manual to automatic control.

Real-time operator interface Its flexible operator interface allows for the easy configuring of the system using menu driven set-up screens. For process diagram display, it allows drawing real-time graphic displays with the pixel based drawing program. One can animate the control strategy in real-time by graphically creating production flows or physical layouts of the system. One can divide the displayed process into logical segments, and view summary screens showing the complete process, or more detailed screens showing portions of the process. Screen displays can be switched on operator command, or automatically by the system.

Real-time display It allows the display of process data in a variety of formats. They include: trend line (variable versus time), X-Y graph (variable 1 versus variable 2), non-time based trend line (points versus Y), bar graph, digital meter, and control faceplates. In setting up the graphs one can select graph size, units, axis labels, background and trend line colors, line and data point symbols, as well as other display characteristics. It provides online trending facilities, and one can configure multiple trend lines to be displayed on the same screen. In order to visually compare and check process values, data can also be displayed as analog meters (horizontal or vertical bars) or as labeled faceplates. Faceplate displays include tag name, current value, I E T E

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Legend SV- Solenoid Valve MV- Motorized Valve Ovf,- Overflow

T- Temperature sensor & transmitter L- Level sensor & transmitter F- Flow sensor & transmitter

Fig 3 Block diagram of process control trainer

units, set point value, alarm limits, and color coded bars. Digital meters provide the current variables value in the chosen units. Each meter corresponds to an input variable, or a derived value as a function of one or several variables.

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On-line analysis It has a large number of built in functions through which on-line calculations and statistical analyses can be performed and the results I E T E

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displayed and logged in real time. It supports online statistical process control (SPC) charts through its built-in statistical functions, including means, standard deviations, and moving averages. Based on these real-time calculations, it can provide online control charts. Other standard mathematical and trigonometric functions include derivatives and integrals, polynomial transformations, calibration tables, digital filters and FFTs. For additional real time analysis, its multitasking capability allows performing process monitoring and control in the background while running other programs such as spreadsheets or statistical analysis programs in the foreground. Through its Real Time Access module, foreground programs are allowed to have access to real-time process data, to modify the control parameters, or to send data directly to various hardware devices [15].

B. Hardware Support The PC forms the heart of the control hardware. It is interfaced to the process environment with the help of add-on cards. Figure 4 shows the flow of signals from the process environment to the PC and vice-versa.

Add-on Cards The PCL-812 card is used for acquiring data from the process in the analog form. It has 16 single ended input channels out of which 9 are used. 5 are used for taking the data from the temperature sensors and transmitters and 4 for taking the data from the flow sensors and transmitters. It has 2 analog output channels which are used to output the analog voltages to control the stirrer and the pump.

thermocouple whose junction material is made up of Chromel/ Alumel. Cold reference junction compensation is provided and the signal is amplified to give the desired analog value of voltage which serves as a measure of the temperature. The flow sensor and transmitter sense the flow with the help of a turbine type flow meter which uses an optical source and detector. The output of the detector is a train of pulses which is converted into a corresponding analog voltage using a frequency to voltage converter. The level sensor and transmitter sense the level with the help of a conductive type level sensor comprising eight strips of conducting material of different lengths for the measurement of level. The output is an eight bit digital code showing level indications in multiples of 12.5%.

Control units Power control unit controls the power being delivered to the load. The firing angle of the triac circuit is controlled by the analog voltage given as control input to this circuit. A reference input from the mains supply is also given to the unit. As the control voltage is increased the triac is fired earlier delivering more power to the load. Motorized valve control unit senses the position of the valve and controls the same using a bidirectional motor. The desired position of the valve is given as control input, which is compared with the value got from the actual position of the valve to rotate the motor in the desired direction.

C. Experimental Set-ups

The PCL-726 card is used for sending data to the process in analog form. It has 6 independent analog output channels. 3 are used to control the heaters and the other 3 are used to control the motorized valves.

Various experimental set-ups were configured for the trainer and executed. One of the experimental setups is as follows

The PCL-224 is used for optically isolated digital input and output. Digital outputs are used for controlling the solenoid valves and stirrers through relays. The digital inputs are used for taking in the data from the level sensors and transmitters.

Inputs: Keyboard entries for input valve and output valve to be entered in the control panel.

Sensors and Transmitters The temperature sensor and transmitter sense the temperature with the help of a K type Vol. 25, No. 1, Jan-Feb’08

Title: Automation for level control with interaction for single chamber.

The starting positions of these valves are fixed, the input valve is open and the output valve is closed. Keyboard entry ‘0’ closes the valve and ‘1’ opens the valve. These may be changed during the run time. I E T E

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Level Sensor and Transmitter

Flow Sensor and Transmitter

Personal Computer (PC)

Temperature Sensor and Transmitter Measured Inputs

Data Acquisition and Control Add-on Cards

Controlled Outputs Pump

Stirrer

Heater

Solenoid Valve

Motorized Valve

Fig 4 Flow of signals

Output: Digital output for pump. This is a controlled output. It depends on the level of the chamber and the status of the valve. Table 1 gives the possible input conditions and the corresponding action to be taken. Results: Level in the chamber increases, decreases or remains constant depending on the status of the pump and the positions of the input and output valves. The pump is turned off if the level exceeds H.L. or the input valve is closed. It is turned on if the level goes below L.L. and the input valve is open. It remains in its immediately previous state if the level is between H.L. and L.L. and the input valve is open. It turns off the moment the input valve is closed. The positions of the input and output valves are solely governed by the keyboard entries. Remarks: Here it is assumed that the pump can be switched on at any time and that there is always

a sufficient amount of fluid to be pumped at the inlet of the pump. The piping from the pump to the chamber is considered to have a negligible amount of liquid to cause any significant change in the level of the chamber. Display: The process diagram is made using Paintbrush. The display windows are adjusted on this process diagram to give a realistic view. In screen 1 only the windows are used to display the various parameters of interest without any process diagram. This is helpful in diagnosing errors before going for a realistic view in screen 2 as shown in Fig. 5. Various types of traces are used to try and give a realistic view. Horizontal bars are used to indicate the level of the chamber. Vertical bars are used to indicate the position of the valve and status of the pump. Meters are provided to indicate the level of the chamber and status of the pump and valves.

4. CONCLUSION TABLE 1 : Controlled output for pump Input Valve

Level

Pump

Closed

X

Off

Open

Less than L.L.

On

Open

More than H.L.

Off

Open

Between H.L. & L.L.

Previous state

X - Don’t care, LL - Lower limit, HL - Higher limit

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The PCT provides the user with the practical ascent of Process Control, Intelligent Instrumentation, Automation and Interfacing the PC with real-time processes. After deciding its configuration, the add-on cards have been chosen. To get the system up and running in a short span of time, LT/CONTROL has been chosen as the software package as it is made especially for the process control environment. Setups for various

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Legend SV-Solenoid Valve MV-Motorized Valve Ovf-Overflow HL-Higher Limit LL-Lower Limit PL-Present Level

Fig 5 Screen 2 of experimental setup

experiments have been developed using the demoboard which is a software simulation of a hardware data acquisition and control interface. On getting satisfactory results from the demo-board, the addon cards have been installed and tested for their performance. The software has been developed and tested with the add-on cards using dummy inputs, followed by the testing of the hardware modules. Each sensor and transmitter unit has been individually tested and calibrated. They have then been interfaced to the PC with the help of the add-on cards, tested and found to respond fairly well. Finally the mechanical assembly of the various devices on the trainer has been carried out as per the configuration and the entire system has been tested. Experimental setups have been configured on the PCT to observe the various types of control actions and automate processes on the trainer. The PCT has been successfully designed, developed and applied for automation. REFERENCES 1.

R J Bibbero, Microprocessors in Instruments and Control, John Wiley and Sons Inc., 1978.

2.

P C Sharma & P K Chande, “Microcomputer based flow measurement system,” IEEE Trans Industrial Electronics, vol IE-32, no 2, pp 103-107, 1985.

3.

T S Rathore, Digital Measurement Techniques, 2nd ed., Narosa Publishing House, New Delhi, 2004.

4.

J Schoeffler, Minicomputers: Hardware, Software and applications, IEEE Press, 1972.

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5.

G C Barney, Intelligent Instrumentation: Microprocessor applications in measurement and control, Prentice Hall International, Englewood Cliffs, 1995.

6.

S S Lamba & Y P Singh, Distributed Computer Control Systems, Tata McGraw-Hill, New Delhi.

7.

M R Skrokov, Mini and Microcomputer control in industrial control: handbook of systems and application strategies, Van Nostrand Reinhold, New York, 1980.

8.

E A Parr, Industrial Control Handbook, 3rd ed., Industrial Press Inc., 1999.

9.

K Ogata, Modern Control Engineering, 4th ed., Prentice Hall, 2001.

10.

J J Distefano, A R Stubberud & I J Williams, Feedback and Control Systems, McGraw-Hill, 1967.

11.

D Patranabis, Principles of Process Control, McGraw-Hill Education, 1982.

12.

D R Coughanowr, Process Systems Analysis and Control, 2nd ed., McGraw-Hill Higher Education, 1991.

13.

B Kuo & F Golnaraghi, Automatic Control Systems, 8th ed., Wiley, 2002.

14.

P Harriott, Process Control, Krieger Publishing Co., 1983.

15.

LT/CONTROL Reference Manual, Laboratory Technologies Corporation.

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Authors G A Shah received BE from WIT Solapur, ME from SGSITS, Indore, and is pursuing PhD at MPSTME, NMIMS University, Mumbai. He served the Electronics Department of SSVPS, CoE, Dhule from 1990 to 2001 in the capacity of Lecturer and Senior Lecturer before joining the Electronics & Telecommunication Department at SFIT, Borivli, as an Asst. Professor. His areas of teaching and research interest are Analog Signal Processing, Filters, Digital Techniques, Microprocessors and Biomedical Engineering. He is a Graduate Student Member of IEEE, Fellow of IETE, Member of IE & Member of ISTE. E-mail: T S Rathor received BSc, ME and PhD degrees in Electrical Engineering from Indore University, Indore. He served SGSITS, Indore from 1965 to 1978 before joining the EE Department of IIT Bombay from where he retired as a Professor on superannuation in June 2006. From July 2006, he is the Dean (R&D) and Head of Electronics & Telecommunication Department at SFIT, Borivli. He was a post-doctoral fellow at the Concordia University, Montreal, and a visiting researcher at the University of South Australia, Adelaide. He was an ISTE visiting professor. He has published and presented over 182 research papers in various national/international journals and conferences. He has authored the book Digital Measurement Techniques and translated in Russian language in 2004. His areas of teaching and research interest are Analysis and Synthesis of Networks, Electronic Circuit Design, Switched-Capacitor Filters, Electronic-Aided Instrumentation, Hartley Transform & Signal Processing. Prof Rathore is a Senior Member of IEEE, Fellow of IETE, Fellow of IE, Member of ISTE, Member of Instrument Society of India. He was the guest editor of the special issue of Journal of IE in Instrumentation Electronics (1992). He is a member on the editoral boards of ISTE National Journal of Technical Education and IETE Journal of Education. He is a member of the publications and Technical Program Committee of the Council. He has played a very active role as Fellow of IETE and has served its Mumbai Centre as Volunteer member (1997-98), Co-opted member (1998-99), Secretary (1999-2000), Chairman (2001-02), Vice Chairman (2003-06) and currently he has been elected unopposed as the Chairman (2006-08). He has received IETE M N Saha Memorial Award (1995), IEEE Silver Jubilee Medal (2001), ISTE U P Government National Award (2002), ISTE Maharashtra State National Award (2003), IETE BR Batra Memorial Award (2005), and IETE Prof K Sreenivasan Memorial Award (2005). E-mail:

Paper No 102-B; Copyright © 2008 by the IETE.

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This is

Mobile TV Broadcasting K M PAUL ABSTRACT Mobile reception is a new feature evolved in TV broadcasting. Mobile reception requires a robust signal to overcome the complexity of mobile propagation channel. Though DVB-T, primarily intended for fixed terrestrial reception, has limited capacity for mobile TV broadcasting; addition of powerful ‘Forward Error Correction’(MPE-FEC); new operational Mode-‘4K’ and new ‘Time Slicing’ technique for power conservation in the mobile handset, gave birth to a fully enabled mobileTV broadcast standard-DVB-H, as an extension of DVB-T.

WHAT IS MOBILE TV

Can DTT provide Mobile Reception?

So long the Radio Broadcasting was known as the only mobile media, whereas the TV broadcasting was not so. This was an edge of radio over TV; enabling mass communication any time anywhere. Radio can receive anywhere including ‘in motion’. This is a great feature of radio which made it an unique medium of mass communication. However with the evolution of broadcast technology, TV has now overcome that limitation of mobile reception and it is now a mobile medium.

In order to analyse the aspect- whether the existing Digital Terrestrial Television (DTT) can also provide mobile reception; let us take for example the DVB-T system of Europe. Before the mobile reception aspect of DVB-T is examined it will be worthwhile to look at the evolution of DVB technology system as depicted in the tree diagram given below:-

Mobile TV reception means that the TV broadcast signal should enable reception in mobile condition using a pocket size hand-held device like cellular mobile telephone, without any external or directional antenna system. There is however an upper limit of speed of mobility which is a tradeoff among- number of channels broadcast; range of coverage and the spacing between the adjacent carriers, in the multicarrier COFDM modulation system. Being a mobile medium the receiving device must satisfy the requirement of its power supply (battery). That means, it must have sufficient power supply to work for a specified minimum period while the user is outdoor away from home/office. This requirement demands that the receiving device must have a built-in power saving system, so that it can provide uninterrupted mobile service for a reasonably long period before the power supply system is recharged from a stationary charging power source at home or any other place.

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DVB

DVB-T

DVB-C

DVB-S

DVB-H

DVB-S2

DVB-SH

The Digital Video Broadcasting (DVB) system as developed by the European Consortium originally had mainly three standards- DVB-T for terrestrial broadcasting; DVB-S for satellite broadcasting and DVB-C for cable-casting of digital television. DVB-T meant for terrestrial fixed reception has now evolved its mobile version DVB-

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H ( DVB-Handheld ). The DVB-H is basically derived from DVB-T with the addition of technical features required for protection of signal in the mobile propagation channel environments. In the present article we shall primarily discuss these additional technical features which are added to DVB-T technology to enable the intended mobile reception capability of digital TV broadcasting. DVB-S meant for fixed reception of satellite broadcasting evolved two different standards- (i) DVB-S2- a satellite broadcast standard for fixed reception with much higher data throughput, capable of delivering High Definition TV (HDTV), which requires a higher data rate in comparison to the Standard Definition TV (SDTV). (ii) DVB-SH- is a satellite direct broadcast standard for mobile reception of TV signal with handheld devices as in DVB-H. Now coming to mobile reception capability of DVB-T, it can be said that the DVB-T technology in Europe was designed with the prime focus on portable and fixed reception with roof-top antenna. But the standard met much more than the intended design objectives. For example, DVB-T has been used in public transports and later with the receiver developments, it was possible to use DVB-T in cars as well as in high speed trains. But the limitations of DVB-T system in respect of expectations as envisaged in mobile TV are as follows: Firstly, the speed of mobility upto which it can allow desired number of programme channels with acceptable reception quality, is limited. Secondly, the receiving device is not a handheld type with built-in antenna. Rather it needs an external antenna to the receiving device. These are the two serious limitations as far as the spirit of mobile reception of TV signal is concerned.

Birth of Mobile TV – DVB-H DVB-H the terrestrial mobile TV broadcasting was born, which overcomes the above limitations and is capable of providing multiple programmes in high speed mobile receivers in a small handheld receiving device with built-in antenna. The receiver system also has a built-in power saving device to allow outdoor use of the mobile device before it is charged with stationary power sources.

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Hand-held Receiver with Built-in Antenna TV broadcast signal has always been received in nonportable big receiving set and invariably with roof-top antenna or atleast an indoor telescopic ‘V’ antenna. TV reception in a small hand-held device with built-in antenna was a new challenge and required improved receiver design with miniature devices, higher sensitivity and better noise figure. This is an important technological breakthrough enabling reception of TV broadcast signal in a hand-held device for the first time. This development primarily opened the way for TV broadcasting in the field of mobile reception.

Special Features of Mobility In fixed reception the radio wave propagation channel condition more or less remains fixed. It means that the channel is either ‘AWGN’ i.e. direct line-of-sight (LOS) channel or it is a ‘Rayleigh’ channel i.e. only reflected signal or combination of the above two channels, called ‘Rich-Nakagami’ channel- giving both direct ‘LOS’ signal as well as reflected signal components. But in a mobile reception, the channel does not remain fixed. It goes on changing with receiving locations as rapidly as the speed of mobility. Hence the reception has to encounter all types of radio wave propagation channel conditions including the worst one i.e. the ‘Rayleigh’ channel. The second important feature of mobility is the ‘Doppler Frequency Shift’ of the carriers in the COFDM modulated multicarrier RF signal. The Doppler carrier shift with mobility of receiver produces additional ‘Bit Error Ratio’(BER) and hence more noise and signal aberrations. Depending on the receiver characteristics in terms of required C/N, it can tolerate this bit error/ additional noise upto certain extent which limits the maximum speed of the reception. Beyond this speed, the Doppler Frequency Shift of the carriers crosses the safe limit and produces irrecoverable signal aberrations. The third feature of mobility is contained in the fact that the service planning of mobile TV reception is not based on reception with roof-top antanna, as in the case of fixed reception. The receiving device being a hand-set with built-in antenna, the reception is expected anywhere- inside the building,

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building basement, congested urban builtup areas etc. The received signal strength;error-correction coding etc should be strong enough to lay a robust received signal in all such environments.

Finally, while planning the mobile TV service, adequate link margin should be provided for reception inside building, in building basement and congested urban environments.

How Mobile TV Takes Care of Mobile Factors

Power Saving Technique in Mobile Handset

In order to take care of these mobility factors, the mobile TV reception and transmission systems are empowered with additional protective features.

Like cellular mobile handset, the battery life is a critical parameter for mobile TV handset. Users will prefer operating the receiving handset for the whole day and even for several days, without requiring to recharge the device. Power saving in the mobile TV handset is effected by a special technique called ‘Time Slicing’. In this technique, the bunches of data pertaining to a particular service is delivered to the handheld receiver in short duration‘bursts’ at given intervals. Video and audio data (1 to 2 Mbps), generally representing between 1-5 seconds of the content, are contained in the single ‘burst’. When a burst pertaining the service tuned in the receiver arrives, it is received by the ‘active’ tuner of the receiver. When the bursts containing the bunches of data for other services arrive at the receiver successively, the tuner of the receiver goes into ‘sleep mode’ and remains inactive till the time, the last burst of the untuned services arrives at the receiver. Thereafter, the tuner again awakes from sleep and becomes active to receive the next burst of the desired service which is tuned in the receiver.

First of all the receiving device with built-in antenna is made highly sensitive with low Noise Figure (NF). Secondly the transmitted signal is made more robust with additional (additional to that of fixed reception system i. e. DVB-T or DTT) Forward Error Correction (FEC) code. This additional FEC code is added at the Multi-Protocol Encapsulation (MPE) layer and known as MPEFEC. This makes the signal more robust and more error resilient, which in turn enables the signal to encounter the mobile propagation channel and protect the signal from effects of Doppler Frequency Shift, and odd reception environments like- building indoor, building basement and congested urban spots. In order to effectively handle the mobility factor the DVB-H standard incorporates a new mode- ‘4K’ in addition to modes-‘2K’ and ‘8K’ as available in DVB-T standard. In ‘4K’mode the frequency spacing between the two adjacent carriers in the multicarrier COFDM system is larger than that in ‘8K’ mode. Because of this ‘4K’ mode, the system can tolerate more Doppler Frequency Shift before reaching irrecoverable signal errors. In other words the ‘4K’ mode can increase the safe limit of speed of mobility. In fact ‘4K’ mode increases mobility by a factor of ‘Two’ when compared to the ‘8K’ mode. When ‘4K’ increases the speed limit, it reduces the SFN (Single Frequency Network) size w. r. t. that of ‘8K’ mode. In fact change of mode-‘2K’, ‘4K’ and ‘8K’ gives a tradeoff between ‘speed of mobility’ and ‘SFN’ size. When ‘4K’ is compared with ‘2K’ mode, it gives the SFN size as double. So considering the optimization in mobile reception, ‘4K’ mode provides the most optimized ‘speed of mobility’ and SFN size for service planning. However, the ‘4K’ mode cannot be used in combination with an existing DVB-T network.

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This ‘time slicing’ saves power upto 95% , compared to conventional and continuously operating DVB-T tuners. Other parts of the receiver viz. audio and video decoders, display device etc however consume power continuously. DVB-H broadcasts sound, picture and other data using ‘Internet Protocol’(IP), where the content is delivered in the form of data packets using the same distribution technique as used for delivering digital content on the internet. Use of ‘Internet Protocol’ allows DVB-H to broadcast not only the streaming audio and video, but also file delivery. It also allows DVB-H to rely upon standard components and protocols for content manipulation, storage and transmission, which is a step forward towards convergence of technology.

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Author K M Paul is the former Engineer-In-Chief and the Acting Director General of AIR. He served the Public Broadcaster for 35 years in different capacities, responsible for development of broadcasting in India. Some of his significant contributions are- innovative broadcast R&D projects; FM radio expansion; introduction of ‘Narrow- casting’ in AIR; DTH radio service of AIR; setting up ‘AIR RESOURCES’-a revenue earning broadcast cosultancy wing in ‘Prasar Bharati’ etc. He was member of ‘Specialists Group’ of European Broadcasting Union (EBU) on ‘Eureka147 DAB’technology. He participated in the ‘Expert’s Mission’ of the Asia-pacific Telecommunity (APT), in Bangkok and DPR Korea. He actively participated in important Broadcast Projectssponsored by the Asia-Pacific Broadcasting Union (ABU). He served International Telecmmunication Union (ITU) - ‘Study Group 6’ on Broadcasting as Vice-Chairman for two consecutive terms. Mr Paul belongs to the Electronics and Telecommunication Engg. Discipline of Jadavpur University, Kolkata, where he obtained his Bachelor’s degree and Master’s degree in Engg. in 1967 and 1969 respectively. He is member of Programme Advisory Committee (PAC) of the Deptt. of Science and Technology (DST); Life Fellow of IETE and BES(I). Email:

Paper No 153-B; Copyright © 2008 by the IETE.

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Is India ready to face 21st Century? S K KSHIRSAGAR

Distance education is essential for those who have immense desire of learning in spite of their struggle against the odds. It means due to heavy expenses required for education they cannot get formal education by joining schools, colleges which are run as if these are turned into Industry. Industry though appears to be business, it is real fact that educational institution requires lot of money for creating infrastructure e.g. buildings, laboratories, equipments, staff, welfare of the staff etc. To get into this vicious circle, for a young man with moderate income, it is rather impossible to quench the thirst of knowledge.

education to anybody, anywhere at anytime. Because of development in the Information and Communication Technology it has become possible to educate the people at remote places.

EDUSAT PROGRAMME The IETE has accepted the recommendations of the experts hence the learning materials have been sent to Andhra & Gujarat Govt. for transmission through Edusat. They have agreed in principle and modus operandi are being worked out.

In this circumstance we cannot deprive him from his social rights. His desire to acquire knowledge must be fulfilled.

Broadcast of contents by Eklavya Channel

Our whole cultural heritage lays the highest importance on the role of a teacher whose place is next to the mother and father for any individual. The teacher has been given the highest place by our seers, because he gives the right perspective of life to his pupil & prepares him as a useful member of the society.

Eklavya Channel has accepted this recommendation.

In olden days the communication of knowledge was more personal by direct method from Guru to Shishya. Hence four different stratas known as ‘Varnas’ evolved. But even Bhagawat Gita has declared.

^^pkrqoZ.;± e;k l`"Va xq.kdeZ foHkkx'k%A And not “tUeKkfr

foHkkx…k% ”

This can even in modern times, apply to any society. Our seers say that our main aim is to achieve a social order.

lgukoorq lg ukS HkquDrqA Science and Technology are changing at a very fast pace. We can utilize them for spreading

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For all these, content creation in simple language must be undertaken by experts and dedicated teachers. It may be simple video graphing of the Lecture in classroom using chalk and blackboard the usual method. This recording needs modulation / transmission through Edusat. It can be made available through internet. However for this we need a large member of Computers & the know how of how to operate Computer. Distance Education is not only for education purpose but it can have a large number of applications such as Video Conferencing, Telemedicine etc. It is a gigantic task for educationists as well as policy framers to give a serious thought on ‘Is Education Ready for this century? The youth must also be taken into confidence while preparing the curricula because they have to live in this century with their bullock carts & bicycles along with automobiles, jets and the satellites.

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We have to make plans for the economic breakthrough and the social change, then only the present youth would be able to make a satisfactory balancing act with the rapidly changing world environment. The new generation of youth would be shaken from the present mental frame of complacency & think constructively to achieve the set goals. It is sad to see that when we talk of sociopolitical atmosphere, the universities are also politically motivated. This virus is collapsing the value system. It should be borne in mind that those who are critic of present system have emerged from the same system. It is necessary that all worthy & capable people start national brainstorming sessions involving people at all levels to find the answer to the critical problems to keep our country’s existence as nation. One should bear in mind that there is no system of education free from shortcomings. We are the cause of making system running well or failure. Distance Education concept is not very new. It satisfies the desire of people who want to get education, on earn and learn basis. Due to advent of new technologies like Information, Communication, students can be tutored well through Internet or by preparing DVDs of various subjects at low prices. For this content creation must be started by good teachers and be kept ready for the use of learners. Internet and Edusat are also adding great help in the Distance Education for anybody, anywhere at anytime. It is a social right of every youth to get the knowledge he / she desires. The things stated above can be elaborated with further already discussed else where by the experts, which Author humbly wants to quote as under. The Bharatiya Education System has traveled a long way right from Ramayana, Mahabharata, giving stress on teacher – pupil relation. Our ancient cities Nalanda and Takshashila are internationally famous as a divine places of learning. The heritage, literature were kept alive and carried forward for past several centuries though memorisation. Due to liberalization, the number of students wishing to learn & go for higher studies is also though high, it is proved that more students are leaving the education in the middle due to several Vol. 25, No. 1, Jan-Feb’08

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reasons. Standard of education is a different subject of debate, it is a mirror of present social system. In demand and sale process of education, there is some dilution in the standard due to government rules and our own share. The structure of universities is like a pyramid. Vice chancellor is at the top. The decision making process moves from bottom to top, involving academician, technocrats etc. In India, there is three tier system of education, the best centers like IIT & IIM, the middle one is like Pune, Mumbai, Calcutta, Chennai, Bangalore, universities & last one is for rest of the Institutions. The universities are formed as per the need of the regions run by educationist, Government & Politicians. Government cannot give subsidy to all ; hence the powerful people establish their own universities asking for more fees from the students just to have sufficient finance for running the institution such as building staff, laboratory, non-teaching manpower etc. However they have to strictly adhere the government norms for having needed infrastructure. Because of heavy cost of education any where in the country, abroad, the idea of virtual university came out. The virtual word does not mean only virtual education. It is related with the technology used for creating impression as if actual teachers are teaching them. It means virtual classroom. For creating virtual classroom we need TV Internet, Radio Information Communication Technology, multimedia etc. The use of these modern technologies is made in the Second World War. The education regarding use of weapons, precautions during war etc. was given to American Soldiers. Now we hear about world wide web (www) based or internet. Due to the availability of TV from 1980, computer based training was started. Some years back, distance education was given through postal media, but now we find that ‘ Digitisation’ is the soul of virtual education university. For educating the student from any corner of the world, we can have educational software through web. In 1980 USA developed computer language called ‘Digital Professor’. Through computer based telephony ‘ Digital Professor’ was educating the students anywhere. I E T E

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Laptop culture is coming up in schools & colleges. The marketing is going on very fiercefully by developed countries in this field. To implement the concept of virtual classroom / education, the main requirement is of preparing CDs on various subjects. Content Development / Creation is the most important core of virtual education. It is most heartening that teachers from India are in great demand for content creation in the world. There are many aspects required for this viz. audio, video media, animation, graphics etc. Efforts have been made by Hyderabad to prepare digital medical programs. It has been possible to tackle other branches of engineering such as civil, mechanical, instrumentation through virtual technology. Indira Gandhi National Open University is the first of its kind to establish first virtual university, the benefit of which has been taken by thousands of students. Other states are starting the project on similar lines. Edusat is also useful for the spread of education. Advanced education is made available to those staying at remote places through internet. ISRO is playing an important role by establishing hubs and e-study centers all over India. Government of India has created a sum of Rupeese Thousand Crore for this edusat program. University Grant Commission (UGC) has already taken lead in this matter in preparing ‘ Digitised Programme’, to be released through countrywide programme.

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Many universities have developed e-journals & e-libraries benefiting thousands of students. IIT’s & IIM’s are taking lead in this subject by developing different types of network such as Brihaspati etc. Looking at the scenario all over India, it appears that efforts by Government of Maharashtra should be accelerated in respect of virtual university. Distance Education has been taking good shape aided with multimedia & internet. It is one kind of movement definitely doing good progress in right direction. For this we require willpower and a mindset to accept the changes in systems of education. In foreign countries also the efforts are going on with right perspectives in number of fields. Educationist, technocrats, politicians, society all criticise the system of education. There should be positive criticism because even Lord Macaulay when desired to start, new method of imparting education i.e. chalk, board and classroom, it was under criticism and for last more than 150 years the same criticism is going on and will be criticised in future also. We should think of how to get good out of that with the open mind. Uttar-Ramcharit written by Bhavabhuti never received praise during his lifetime but after long time it received much more laurel than even Kalidas who wrote Shakuntala. Bhavabhuti has said

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Author S K Kshirsagar did MSc Physics with Wireless and Electronics from University of Pune. He was HOD of Post Graduate Deptt of Physics NWadia College, Pune. He has written more than 55 books in Physics / Electronics / Instrumentation for Pune / Bombay / North Maharashtra University. His field of interest is Semi-conductor Physics / Instrumentation / Classical Mechanics / Statistical Mechanics. He is a visiting Professor from MSc Physics / Electronic Science. He has published paper on ‘Determination of Mesospheric Temperature in IMAP. His biodata is published in who’s who of women & men in Encyclopedia of Asia / International. He is recipient of awards for proficiency in Education on 26th Jan 92 & as a Best Teacher on 15th August 98. At present he is Chairman of IETE Pune Centre. He delivered lectures in Marathi to popularize Science Topics on AIR. Email : <[email protected]>

Paper No 154-A; Copyright © 2008 by the IETE.

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Vol. 25, No. 1, Jan-Feb’08

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CALL FOR PAPERS Special Issue of IETE Technical Review on ‘Next Generation Networking in Converging Regime’ Every year IETE brings out a Special Issue of IETE Technical Review on the occasion of Annual Technical Convention (ATC). This year the theme for this Special Issue is “Next Generation Networking in Converging Regime”. The purpose of the Special Issue is:

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To present an overview of the state-of-art in the subject of the theme in the national and international perspective

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To present important work being done in these areas in India and globally at different Institutes/ organizations

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To highlight important problem areas from a research and technological point of view and how these can be specifically addressed.

Areas to be covered: Conceptual original research / quality review articles covering the theme “Next Generation Networking in Converging Regime” are invited for the ATC Special Issue of IETE journal Technical Review. Articles should describe the latest technologies and future trends in the field. Articles should be about 3000 to 4000 words including figures, graphs, tables and references. The manuscript (in English only) should be typed neatly on A4 size paper in double space on one side only and preferably in 11 point Times Roman Font. It should conform to IETE’s guidelines to the authors available on IETE website: www.iete.org under the heading “Publications”. Three hard copies along with a soft copy on CD ROM in MS Word should be sent to the Hony Guest Editor at the address given below. An e-mail copy should also be addressed to save time. All the articles received will go through the normal review process. Last date of receiving papers Review of papers Last date for receiving revised papers Expected schedule of publication

: : : :

15 May 2008 15 Jun 2008 01 July 2008 July-August 2008

Prof R K Shevgaonkar Hony Guest Editor, ATC Special Issue of IETE Technical Review Dept of Elect Engg & Dean Resource Mobilization IIT Bombay, Powai, Mumbai 400 076 e-mail : [email protected] Tel: (O) 022 2576 7440 (R) 011 2576 8440

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