Wc

Wireless communication

presented by p.Prathyusha & k.Anusha, 3rd cse, Rao&Naidu engg college, South by-pass road, Ongole, Prakasham(dt). Email:[email protected]. [email protected]. Contact: 9966625815. 9948260667.

Abstract: The fast development in the field of wireless communication gives access to a wide range of new and unforeseen applications in the sector of train-busses. Innovative technologies offer a promising approach to classical problems like cable-replacement and system upgrade (retrofitting). In this paper we derive the need for intra-train busses, especially for freight trains, and give a short survey of available wireless technologies. In this context we identify the internal and external parameters to which the communication system is subjected. Additionally, special European boundary conditions for train equipment are taken into account. We present our arguments for the usage of DECT as a wireless communication standard suitable for train internal communication. Apart from that, possible topologies of a generic wireless train bus are discussed. Based on the theoretical considerations, we introduce our concept for a testing platform. We show how the platform is designed and how different topologies and their reliability can be evaluated. One aspect of the design of the testing platform was the usage of the off-the-shelf components. Finally, we present the results of initial tests with the chosen communication system. This article reviews space-time modem technology for mobile radio applications. We begin with motivations for the use of space-time modems and then briefly discuss the challenges posed by wireless propagation. Next, we develop a signal model for the wireless environment. Channel estimation, equalization, and filtering techniques for space-time modems in the forward and reverse links are then discussed. Finally, we review applications of space-time modems to cellular systems and discuss industry trends Spatial antenna diversity has been important in improving the radio link between wireless users. Historically, microscopic antenna diversity has been used to reduce the fading seen by a radio receiver, whereas macroscopic diversity provides multiple listening posts to ensure that mobile communication links remain intact over a wide geographic area. In later years, the concepts of spatial diversity have been expanded to build foundations for emerging technologies, such as smart (adaptive) antennas and position location systems. Smart antennas hold great promise for increasing the capacity of wireless communications because they radiate and receive energy only in the intended directions, thereby greatly reducing interference. To properly design, analyze, and implement smart antennas and to exploit spatial processing in emerging wireless systems, accurate radio channel models that incorporate spatial characteristics are necessary. In this tutorial, we review the key concepts in spatial channel modeling and present emerging approaches. We also review the research issues in developing and using spatial channel models for adaptive antennas

Introduction: Wireless communications is one of the most active areas of technology development of our time. This development is being driven primarily by the transformation of what has been largely a medium for supporting voice telephony into a medium for supporting other services, such as the transmission of video, images, text, and data. Thus, similar to the developments in wireline capacity in the 1990s, the demand for new wireless capacity is growing at a very rapid pace. Although there are, of course, still a great many technical problems to be solved in wireline communications, demands for additional wireline capacity can be fulfilled largely with the addition of new private infrastructure, such as additional optical fiber, routers, switches, and so on. On the other hand, the traditional resources that have been used to add capacity to wireless systems are radio bandwidth and transmitter power. The Wireless communications today covers a very wide array of applications. The telecommunications largest industries worldwide, with more than $1 trillion in annual revenues for services and equipment. The largest part of the telecommunications business is telephony. The principal wireless component of telephony is mobile (i.e., cellular) telephony. The worldwide growth rate in cellular telephony is very aggressive, and analysts report that the number of cellular telephony subscriptions worldwide has now surpassed the number of wireline (i.e., fixed) telephony subscriptions. Moreover, at the time of this writing in 2003, the number of cellular telephony subscriptions worldwide is reportedly on the order of 1.2 billion. These numbers make cellular telephony a very important driver of wireless technology development, and in recent years the push to develop new mobile data services, which go collectively under the name third-generation (3G) cellular, has played a key role in motivating research in new signal processing techniques for wireless. However, cellular telephony is only one of a very wide array of wireless technologies that are being developed very rapidly at the present time. Among other technologies are wireless piconetworking (as exemplified by the Bluetooth radio-on-a-chip) and other personal area network (PAN) systems (e.g., the IEEE 802.15 family of standards), wireless local area network (LAN) systems (exemplified by the IEEE 802.11 and HiperLAN families of standards, called WiFi systems), wireless metropolitan area network (MAN) systems.other wireless local loop (WLL) systems, and a variety of satellite systems. These additional wireless technologies provide a basis for a very rich array of applications, including local telephony service, broadband Internet access, and distribution of high-rate entertainment content such as high-definition video and high-quality audio to the home, within the home, to automobiles, and so on.Like 3G, these technologies have spurred considerable research in signal processing for wireless. These technologies are supported by a number of transmission and channel-assignment techniques, including time-division multiple access (TDMA), code-division multiple access (CDMA), and other spread-spectrum systems, orthogonal frequency-division multiplexing (OFDM) and other multicarrier systems, and high-rate single-carrier systems.

Definition: Wireless is a term used to describe telecommunications in which electromagnetic waves (rather than some form of wire) carrythe signal over part or all of the communication path. Some monitoring devices, such as intrusionalarms, employ acoustic waves at frequencies above the range of human hearing; these are also sometimes classified as wireless. The first wireless transmitters went on the air in the early 20th centuryusing radiotelegraphy (Morse code). Later, as modulation made it possible to transmit voicesand music via wireless, the medium came to be called "radio." With theadvent of television, fax, data communication, and the effective use of a larger portion of the spectrum, the term "wireless" hasbeen resurrected. Common examples of wireless equipment in use today include: • • • • •

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cellular phones and pagers -- provide connectivity for portable and mobile applications, both personal and business Global Positioning System (GPS) -- allows drivers of cars and trucks, captains of boats and ships, and pilots of aircraft to ascertain their location anywhere on earth Cordless computer peripherals -- the cordless mouse is a common example; keyboards and printers can also be linked to a computer via wireless Cordless telephone sets -- these are limited-range devices, not to be confused with cell phones Home-entertainment-system control boxes -- the VCR control and the TV channel control are the most common examples; some hi-fi sound systems and FM broadcast receivers also use this technology Remote garage-door openers -- one of the oldest wireless devices in common use by consumers; usually operates at radio frequencies Two-way radios -- this includes Amateur and Citizens Radio Service, as well as business, marine, and military communications Baby monitors -- these devices are simplified radio transmitter/receiver units with limited range satellite television -- allows viewers in almost any location to select from hundreds of channels wireless LANs or local area networks -- provide flexibility and reliability for business computer users

Applications: Today wireless communication is used in many applications.They are • • •

Audio Automotive Broadband

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Computers & Peripherals Consumer Electronics Industrial

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Military Security Video and Imaging

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Communications & Telecom

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Medical

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Wireless

Video&Imaging: 3D metrology has become more abundantly used with the rapid growth of computer modeling. Using DLP® technology, with its high switching rates and digital precision for exact synchronized gray level output, objects can be measured with finer detail and less ambiguity. Traditionally, because of the extensive time required only a single frame snap-shot was used to capture points of an object. Today, high-speed cameras and DLP® technology allow a series of patterns to be projected onto the surface of an object and captured in less than a second by a camera. The surface shape is obtained fully with finer detail. Because the of the quick speed, 3D metrology using DLP ® technology lends itself to hand-held systems, or the capture of data from living objects, or a production line measurements. Z-Snapper Speed and Precision The z-Snapper provides full-field 3D surface data at a recording time that compares with a standard CCD camera. The high density of data points per measurement reveals even small object features with high reliability. The z-Snapper logic is based upon the wellknown fringe projection methodology combined with sophisticated phase measuring algorithms. A sequence of patterns is projected and recorded by a precisely synchronized camera. Optimized algorithms are provided for the fast and reliable evaluation of the intensity patterns; the user benefits from the ViALUX 3D library shipped with the application

programming interface (API). The z-Snapper uses a LED based lighting system. The device is self contained (no fiber bundle input) and does not need a cooling fan so that the housing is completely closed and dust protected. The LED does not require a high voltage so the system may be battery powered. And the LED based system enables the user the ability to be tilted and operated in any desired position.

Bluetooth Headset(Wireless):

A Bluetooth headset is a wireless headset. It implements Bluetooth technology to provide 2.45GHz-radio wireless connectivity for audio communication. The core subsystems include: RF Front-End - includes RF filter, balun (line matching), and RF transceiver (Modulator/Demodulator/ADC/DAC). The RF front-end provides the wireless link through the antenna. • Baseband DSP/Microcontroller/Memory - the DSP processes physical layer protocols and audio data. The microcontroller runs the Bluetooth software stack stored in memory and controls the RF/host interfaces. The Bluetooth software and data are stored in ROM/RAM. Upgraded firmware may be loaded from FLASH memory. • Audio Codec - connected to microphone and earpiece to perform analog/digital conversions and bit stream coding/decoding to create audio radio. • Host Interface/Volume Control - host or user can use this serial interface to configure the processor, codec, or changes the volume. • Power Conversion - converts input battery power to run various functional blocks. • Battery Management - charges the battery using wall or USB voltage. •

Medical: Wireless communication is very useful in medical field such as:  Automated External Defibrillator  Blood Pressure Monitor  Confocal Microscopy  Dialysis Machine  Digital Hearing Aids  Electrocardiogram (ECG) Front End  Magnetic Resonance Imaging (MRI)  Portable Blood Gas Analyzer  Portable Medical Instruments  Pulse Oximetry  Ultrasound System

Advantages and disadvantages Advantages: A wireless communication system has a number of advantages, not least the mobility of the devices within the environment. It is a simple matter to relocate a communicating device, and no additional cost of rewiring and excessive downtime is associated with such a move. It is also a simple matter to add in a communication device to the system or remove one from the system without any disruption to the remainder of the system. Other than the initial outlay on setting up the cell sites, the cost of running and maintaining a radio based communications solution is minimal.

Transferring Data The embedded chip at each end of the wireless communication runs software for interacting with the end user and managing the transmission. For example, a personal organizer could run software that lets the consumer connect through a PC to the Internet and download updates to its scheduling program.

Establishing Communication A common example of a wireless mobile device that uses IR to establish a communication link is a television or stereo remote. You may point the remote at the television or stereo from across the room, and click buttons to turn the target device on or off and change channels. This is possible because the remote has an IR transmitter and its target device has an IR receiver that enables the one-way communication of data. cell phones are wireless devices that use radio frequency (RF) to communicate with cellular base stations . This is done at UHF and microwave frequencies. New versions of mobile or portable devices are being designed with an internal wireless link capability to connect to a stationary device such as a personal computer (PC) or office telephone system. This lets the user to move around the office or even around the building and still maintain connection with the stationary system. Satellites are also wireless systems that use RF to communicate. Satellite communications include such things as the Global Positioning System (GPS) that you can use to easily find your current location within 50 feet.

Disadvantage: One of the major problems that presents itself is the already limited spectrum available for communications. The remaining free spectrum has to be used to its maximum potential, spread spectrum technology presenting itself as a suitable means of increasing performance. Splitting up of the environment into a number of small cells also increases the overall accessible bandwidth of the communication system, but also increases the cost as more cell sites are required. Techniques such as diversity combining can also be used to increase the available bandwidth through improved reception capabilities.

Conclusion Consumers are rapidly embracing wireless devices, and the possibilities are limited only by the imagination. Java-based consumer and embedded technologies make application development fast, efficient, and easy because applications written to a reference implementation run on any device that supports the reference implementation.