Training Report

INDEX 1. Company profile 2. History 3. Comm. In India 4. Cellular system 5. Cellular network • Network switching system • Network switching subsystem • Mobile switch centre server 1. General inspection 2. Cell Tower 3. Cell site range 4. Communication channel reuse 5. Base transceiver station 6. BTS in Mobile communication 7. Diversity techniques 8. Battery Management

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GSM TOWER MAINTENANCE Company profile Bharat Sanchar Nigam Limited (known as BSNL, India Communications Corporation Limited) is a public sector telecommunication company in India. It is India's largest telecommunication company with 24% market share as on March 31, 2008. Its headquarters are at Bharat Sanchar Bhawan, Harish Chandra Mathur Lane, Janpath, New Delhi. It has the status of Mini Ratna, a status assigned to reputed public sector companies in India. BSNL (then known as Department of Telecom) had been a near monopoly during the socialist period of the Indian economy. During this period, BSNL was the only telecom service provider in the country (MTNL was present only in Mumbai and New Delhi). During this period BSNL operated as a typical state-run organization, inefficient, slow, bureaucratic, and heavily unionized. As a result subscribers had to wait for as long as five years to get a telephone connection. The corporation tasted competition for the first time after the liberalization of Indian economy in 1991. Faced with stiff competition from the private telecom service providers, BSNL has subsequently tried to increase efficiencies itself. DoT veterans, however, put the onus for the sorry state of affairs on the Government policies, where in all state-owned service providers were required to function as mediums for achieving egalitarian growth across all segments of the society. The corporation (then DoT), however, failed miserably to achieve this and India languished among the most poorly connected countries in the world. BSNL was born in 2000 after the corporatization of DoT. The efficiency of the company has since improved. However, the performance level is nowhere near the private players. The corporation remains heavily unionized and is comparatively slow in decision making and implementation. Though it offers services at lowest tariffs, the private players continue to notch up better numbers in all areas, years after year. BSNL has been providing connections in both urban and rural areas. Preactivated Mobile connections are available at many places across India. BSNL has also unveiled cost-effective broadband internet access plans (DataOne) targeted at homes and small businesses. At present BSNL enjoy's around 60% of market share of ISP services. 2007 has been declared as "Year of Broadband" in India and BSNL is in the process of providing 5 million Broadband connectivity by the end of 2007. BSNL has upgraded existing Dataone (Broadband) connections for a speed of up to 2 Mbit/s without any extra cost. This 2 Mbit/s 2

broadband service is being provided by BSNL at a cost of just BSNL is planning to increase its customer base to 108 million customers by 2010. With the frantic activity in the communication sector in India, the target appears achievable. BSNL is a pioneer of rural telephony in India. BSNL has recently bagged 80% of US$ 580 m (INR 2,500 crores) Rural Telephony project of Government of India. On the 20th of March, 2009, BSNL advertised the launch of BlackBerry services across its Telecom circles in India. The corporation has also launched 3G services in select cities across the country. Presently, BSNL and MTNL are the only players to provide 3G services, as the Government is still in the process of auctioning the 3G spectrum to private players. History According to internal memos, American Telephone & Telegraph discussed developing a wireless phone in 1915, but were afraid that deployment of the technology could undermine its monopoly on wired service in the U.S. In 1947 Bell Labs was the first to propose a cellular network. The primary innovation was the development of a network of small overlapping cell sites supported by a call switching infrastructure that tracks users as they moved through a network and pass their call from one site to another without dropping the connection. Bell Labs installed the first commercial cellular network in Chicago in the 1970s. Japan's first commercial mobile phone service was launched by NTT in 1978. By November 2007, the total number of mobile phone subscriptions in the world had reached 3.3 billion or half of the human population (although some users have multiple subscriptions or inactive subscriptions), which also makes the mobile phone the most widely spread technology and the most common electronic device in the world. The first mobile phone to enable internet connectivity and wireless email, the Nokia Communicator, was released in 1996, creating a new category of multi-use devices called Smartphone. In 1999 the first mobile internet service was launched by NTT DoCoMo in Japan under the i-Mode service. By 2007 over 798 million people around the world accessed the internet or equivalent mobile internet services such as WAP and i-Mode at least occasionally using a mobile phone rather than a personal computer.

Communications in India

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Indian Telecommunication industry, with about 464.82 million phone connections (June 2009) [update] , is the third largest telecommunication network in the world and the second largest in terms of number of wireless connections. For the past decade or so, telecommunication activities have gained momentum in India Efforts have been made from both governmental and nongovernmental platforms to enhance the infrastructure. The idea is to help modern telecommunication technologies to serve all segments of India’s culturally diverse society, and to transform it into a country of technologically aware people. Modern Growth A large population, low telephony penetration levels, and a rise in consumers' income and spending owing to strong economic growth have helped make India the fastest-growing telecom market in the world. The first and largest operator is the state-owned incumbent BSNL, which is also the 7th largest telecom company in the world in terms of its number of subscribers. BSNL was created by corporatization of the erstwhile DTS (Department of Telecommunication Services), a government unit responsible for provision of telephony services. Subsequently, after the telecommunication policies were revised to allow private operators, companies such as Bharti Telecom, Tata Indicome Vodafone, MTNL, Idea, Vodafone and BPL have entered the space. Major operators in India. However, rural India still lacks strong infrastructure. Growth of mobile technology India has become one of the fastest-growing mobile markets in the world. The mobile services were commercially launched in August 1995 in India. In the initial 5–6 years the average monthly subscribers additions were around 0.05 to 0.1 million only and the total mobile subscribers base in December 2002 stood at 10.5 millions. However, after the number of proactive initiatives taken by regulator and licensor, the monthly mobile subscriber additions increased to around 2 million per month in the year 2003-04 and 2004-05. India has opted for the use of both the GSM (global system for mobile communications) and CDMA (code-division multiple access) technologies in the mobile sector. In addition to landline and mobile phones, some of the companies also provide the WLL service. The mobile tariffs in India have also become lowest in the world. A new mobile connection can be activated with a monthly commitment of US$0.15 only. In 2005 alone 32 million handsets were sold in India. The data reveals the real potential for growth of the Indian mobile market. In March 2008 the total GSM and CDMA mobile subscriber base in the country was 375 million, which represented a nearly 50% growth when compared with previous year. In April 2008 the Indian Department of Telecom (DoT) has directed all mobile phone service users to disconnect the usage of unbranded Chinese mobile phones that do not have International Mobile Equipment Identity (IMEI) numbers, because they pose a serious security risk to the country. Mobile network operators therefore planned to suspend the usage of around 30 million mobile phones (about 8 % of all mobiles in the country) by April 30. Cellular System Mobile phones send and receive radio signals with any number of cell site base stations fitted with microwave antennas. These sites are usually mounted on a tower, pole or building, located 4

throughout populated areas, then connected to a cabled communication network and switching system. The phones have a low-power transceiver that transmits voice and data to the nearest cell sites, normally not more than 8 to 13 km (approximately 5 to 8 miles) away. When the mobile phone or data device is turned on, it registers with the mobile telephone exchange, or switch, with its unique identifiers, and can then be alerted by the mobile switch when there is an incoming telephone call. The handset constantly listens for the strongest signal being received from the surrounding base stations, and is able to switch seamlessly between sites. As the user moves around the network, the "handoffs" are performed to allow the device to switch sites without interrupting the call. Cell sites have relatively low-power (often only one or two watts) radio transmitters which broadcast their presence and relay communications between the mobile handsets and the switch. The switch in turn connects the call to another subscriber of the same wireless service provider or to the public telephone network, which includes the networks of other wireless carriers. Many of these sites are camouflaged to blend with existing environments, particularly in scenic areas. The dialogue between the handset and the cell site is a stream of digital data that includes digitized audio (except for the first generation analog networks). The technology that achieves this depends on the system which the mobile phone operator has adopted. The technologies are grouped by generation. The first-generation systems started in 1979 with Japan, are all analog and include AMPS and NMT. Second-generation systems, started in 1991 in Finland, are all digital and include GSM, CDMA and TDMA.

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The nature of cellular technology renders many phones vulnerable to 'cloning': anytime a cell phone moves out of coverage (for example, in a road tunnel), when the signal is re-established, the phone sends out a 're-connect' signal to the nearest cell-tower, identifying itself and signaling that it is again ready to transmit. With the proper equipment, it's possible to intercept the reconnect signal and encode the data it contains into a 'blank' phone -- in all respects, the 'blank' is then an exact duplicate of the real phone and any calls made on the 'clone' will be charged to the original account. Third-generation (3G) networks began in Japan in 2001. They are all digital, and offer highspeed data access in addition to voice services and include W-CDMA (known also as UMTS, and CDMA2000 EV-DO. China will launch a third generation technology on the TD-SCDMA

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standard. Operators use a mix of predestinated frequency bands determined by the network requirements and local regulations. In an effort to limit the potential harm from having a transmitter close to the user's body, the first fixed/mobile cellular phones that had a separate transmitter, vehicle-mounted antenna, and handset (known as car phones and bag phones) were limited to a maximum 3 watts Effective Radiated Power. Modern handheld cell phones which must have the transmission antenna held inches from the user's skull are limited to a maximum transmission power of 0.6 watts ERP. Regardless of the potential biological effects, the reduced transmission range of modern handheld phones limits their usefulness in rural locations as compared to car/bag phones, and handhelds require that cell towers be spaced much closer together to compensate for their lack of transmission power. Some handhelds include an optional auxiliary antenna port on the back of the phone, which allows it to be connected to a large external antenna and a 3 watt cellular booster. Alternately in fringe-reception areas, a cellular repeater may be used, which uses a long distance high-gain dish antenna or yagi antenna to communicate with a cell tower far outside of normal range, and a repeater to rebroadcast on a small short-range local antenna that allows any cell phone within a few meters to function properly. Cellular network A cellular network is a radio network made up of a number of radio cells (or just cells) each served by at least one fixed-location transceiver known as cell site or base station. These cells cover different land areas to provide radio coverage over a wider area than the area of one cell, so that a variable number of portable transceivers can be used in any one cell and moved through more than one cell during transmission. Cellular networks offer a number of advantages over alternative solutions: •

increased capacity

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reduced power usage

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larger coverage area

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reduced interference from other signals

An example of a simple non-telephone cellular system is an old taxi driver's radio system where the taxi company has several transmitters based around a city that can communicate directly with each taxi.

General characteristics To distinguish signals from several different transmitters, frequency division multiple access (FDMA) and code division multiple access (CDMA) were developed. 7

With FDMA, the transmitting and receiving frequencies used in each cell are different than the frequencies used in each neighboring cell. In a simple taxi system, the taxi driver manually tuned to a frequency of a chosen cell to obtain a strong signal and to avoid interference from signals from other cells. The principle of CDMA is more complex, but achieves the same result; the distributed transceivers can select one cell and listen to it. Other available methods of multiplexing such as polarization division multiple access (PDMA) and time division multiple access (TDMA) cannot be used to separate signals from one cell to the next since the effects of both vary with position and this would make signal separation practically impossible. Time division multiple access, however, is used in combination with either FDMA or CDMA in a number of systems to give multiple channels within the coverage area of a single cell. In the simple case of the taxi company, each radio had a manually operated channel selector knob to tune to different frequencies. As the drivers moved around, they would change from channel to channel. The drivers know which frequency covers approximately what area. When they do not receive a signal from the transmitter, they will try other channels until they find one that works. The taxi drivers only speak one at a time, when invited by the base station operator (in a sense TDMA).

Network switching subsystem (NSS) It is the component of a GSM system that carries out switching functions and manages the communications between mobile phones and the Public Switched Telephone Network (PSTN). It is owned and deployed by mobile phone operators and allows mobile phones to communicate with each other and telephones in the wider telecommunications network. The architecture closely resembles a telephone exchange, but there are additional functions which are needed because the phones are not fixed in one location. Each of these functions handles different aspects of mobility management and are described in more detail below. The Network Switching Subsystem, also referred to as the GSM core network, usually refers to the circuit-switched core network, used for traditional GSM services such as voice calls, SMS, and circuit switched data calls. There is also an overlay architecture on the GSM core network to provide packet-switched data services and is known as the GPRS core network. This allows mobile phones to have access to services such as WAP, MMS, and Internet access. Network switching subsystem The mobile switching center (MSC) is the primary service delivery node for GSM, responsible for handling voice calls and SMS as well as other services (such as conference calls, FAX and circuit switched data). The MSC sets up and releases the end-to-end connection, handles mobility and hand-over requirements during the call and takes care of charging and real time prepaid account monitoring. In the GSM mobile phone system, in contrast with earlier analogue services, fax and data information is sent directly digitally encoded to the MSC. Only at the MSC is this re-coded into 8

an "analogue" signal (although actually this will almost certainly mean sound encoded digitally as PCM signal in a 64-kbit/s timeslot, known as a DS0 in America). There are various different names for MSCs in different contexts which reflects their complex role in the network, all of these terms though could refer to the same MSC, but doing different things at different times. The gateway MSC (G-MSC) is the MSC that determines which visited MSC the subscriber who is being called is currently located. It also interfaces with the PSTN. All mobile to mobile calls and PSTN to mobile calls are routed through a G-MSC. The term is only valid in the context of one call since any MSC may provide both the gateway function and the Visited MSC function, however, some manufacturers design dedicated high capacity MSCs which do not have any BSSs connected to them. These MSCs will then be the Gateway MSC for many of the calls they handle. The visited MSC (V-MSC) is the MSC where a customer is currently located. The VLR associated with this MSC will have the subscriber's data in it. Mobile switching centre server (MSS) The mobile switching centre server is a soft-switch variant of the mobile switching centre, which provides circuit-switched calling, mobility management, and GSM services to the mobile phones roaming within the area that it serves. MSS functionality enables split between control (signaling) and user plane (bearer in network element called as media gateway/MG), which guarantees more optimal placement of network elements within the network. The MSC connects to the following elements: •

The home location register (HLR) for obtaining data about the SIM and mobile services ISDN number (MSISDN; i.e., the telephone number).

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The base station subsystem which handles the radio communication with 2G and 2.5G mobile phones.

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The UMTS terrestrial radio access network (UTRAN) which handles the radio communication with 3G mobile phones.

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The visitor location register (VLR) for determining where other mobile subscribers are located.

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Other MSCs for procedures such as handover.

Procedures implemented Tasks of the MSC include: •

Delivering calls to subscribers as they arrive based on information from the VLR.

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Connecting outgoing calls to other mobile subscribers or the PSTN.

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Delivering SMSs from subscribers to the short message service centre (SMSC) and vice versa.

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Arranging handovers from BSC to BSC.

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Carrying out handovers from this MSC to another. 9

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Supporting supplementary services such as conference calls or call hold.

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Generating billing information.

Mobile phone networks The most common example of a cellular network is a mobile phone (cell phone) network. A mobile phone is a portable telephone which receives or makes calls through a cell site (base station), or transmitting tower. Radio waves are used to transfer signals to and from the cell phone. Large geographic areas (representing the coverage range of a service provider) may be split into smaller cells to avoid line-of-sight signal loss and the large number of active phones in an area. In cities, each cell site has a range of up to approximately ½ mile, while in rural areas; the range is approximately 5 miles. Many times in clear open areas, a user may receive signals from a cell site 25 miles away. All of the cell sites are connected to cellular telephone exchanges "switches", which connect to a public telephone network or to another switch of the cellular company. As the phone user moves from one cell area to another cell, the switch automatically commands the handset and a cell site with a stronger signal (reported by each handset) to switch to a new radio channel (frequency). When the handset responds through the new cell site, the exchange switches the connection to the new cell site. With CDMA, multiple CDMA handsets share a specific radio channel. The signals are separated by using a pseudo noise code (PN code) specific to each phone. As the user moves from one cell to another, the handset sets up radio links with multiple cell sites (or sectors of the same site) simultaneously. This is known as "soft handoff" because, unlike with traditional cellular technology, there is no one defined point where the phone switches to the new cell. Modern mobile phone networks use cells because radio frequencies are a limited, shared resource. Cell-sites and handsets change frequency under computer control and use low power transmitters so that a limited number of radio frequencies can be simultaneously used by many callers with less interference. Since almost all mobile phones use cellular technology, including GSM, CDMA, and AMPS (analog), the term "cell phone" is used interchangeably with "mobile phone". However, satellite phones are mobile phones that do not communicate directly with a ground-based cellular tower, but may do so indirectly by way of a satellite. Old systems predating the cellular principle may still be in use in places. The most notable real hold-out is used by many amateur radio operators who maintain phone patches in their clubs' VHF repeaters.

GENERAL INSPECTION •

Inspection of Antenna Mounting Structures

a. Visual check for physical damage to structure and foundation b. Verify obstruction marker operation 10

c. Verify proper operation of strobe if equipped d. Note environmental effects on bolts and braces e. Check structure plumb of guyed tower using transit f. Guy wire tension check using visual method g. Check for loose and missing hardware h. Supply photos i. Submit cost estimate for corrective action items j. Prepare report

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Inspection of Antenna Systems

a. Check for physical damage to radomes, waveguide and hanger system

b. Check for environmental effects on bolts, braces and other hardware c. Check ground connections on antennas and waveguide d. Loose and missing hardware check e. Supply photos f. Prepare report

CELL TOWER A Cell Tower is a term used primarily for a site where antennas and electronic communications equipment are placed on a radio mast or tower to create a cell in a network. A cell site is composed of a tower or other elevated structure for mounting antennas, and one or more sets of transmitter/receivers transceivers, digital signal processors, control electronics, a GPS receiver for timing (for CDMA2000 or IS-95 systems), regular and backup electrical power sources, and sheltering.

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A synonym for "cell tower" is "cell site ", although many cell site antennas are mounted on buildings rather than as towers. In GSM networks, the technically correct term is Base Transceiver Station (BTS), and colloquial British English synonyms are "mobile phone mast" or "base station". The term "base station site" might better reflect the increasing co-location of multiple mobile operators, and therefore multiple base stations, at a single site. Depending on an operator's technology, even a site hosting just a single mobile operator may house multiple base stations, each to serve a different air interface technology ( GSM, for example). Preserved treescapes can often hide cell towers inside an artificial tree or preserved tree. These installations are generally referred to as concealed cell sites or stealth cell sites.

CELL SITE RANGE The working range of a cell site - the range within which mobile devices can connect to it reliably is not a fixed figure. It will depend on a number of factors, including  The frequency of signal in use (i.e. the underlying technology). 

The transmitter's rated power.

 The transmitter's size. 

The array setup of panels may cause the transmitter to be directional or Omni-directional.

 It may also be limited by local geographical or regulatory factors and weather conditions. Generally, in areas where there are enough cell sites to cover a wide area, the range of each one will be set to:  Ensure there is enough overlap for "handover" to/from other sites (moving the signal for a mobile device from one cell site to another, for those technologies that can handle it - e.g. making a GSM phone call while in a car or train).  Ensure that the overlap area is not too large, to minimize interference problems with other sites. In practice, cell sites are grouped in areas of high population density, with the most potential users. Cell phone traffic through a single cell mast is limited by the mast's capacity; there is a 12

finite number of calls that a mast can handle at once. This limitation is another factor affecting the spacing of cell mast sites. In suburban areas, masts are commonly spaced 1-2 miles apart and in dense urban areas, masts may be as close as ¼-½ mile apart. Cell masts always reserve part of their available bandwidth for emergency calls.

Objects intruding into the fresnel zone between radio transmitters and receivers can greatly impact signal strength. The maximum range of a mast (where it is not limited by interference with other masts nearby) depends on the same circumstances. Some technologies, such as GSM, have a fixed maximum range of 40km (25 miles), which is imposed bytechnical limitations. CDMA and iDEN have no built-in limit, but the limiting factor is really the ability of a low-powered personal cell phone to transmit back to the mast. As a rough guide, based on a tall mast and flat terrain, it is possible to get between 50 to 70 km (30-45 miles). When the terrain is hilly, the maximum distance can vary from as little as 5 kilometres (3.1 mi) to 8 kilometres (5.0 mi) due to encroachment of intermediate objects into the wide center fresnel zone of the signal.[2] Depending on terrain and other circumstances, a GSM Tower can replace between 2 and 50 miles of cabling for fixed wireless networks.

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COMMUNICATION CHANNEL REUSE

The concept of "maximum" range is misleading, however, in a cellular network. Cellular networks are designed to create a mass communication solution from a limited amount of channels (slices of radio frequency spectrum necessary to make one conversation) that are licensed to an operator of a cellular service. To overcome this limitation, it is necessary to repeat and reuse the same channels. Just as a station on a car radio changes to a completely different local station when you travel to another city, the same radio channel gets reused on a cell mast only a few miles away. To do this, the signal of a cell mast is intentionally kept at low power and many cases tilting downward to limit its area. The area sometimes needs to be limited when a large number of people live, drive or work near a particular mast; the range of this mast has to be limited so that it covers an area small enough not to have to support more conversations than the available channels can carry. Due to the sectorized arrangement of antennas on a tower, it is possible to vary the strength and angle of each sector depending on the coverage of other towers in view of the sector. A cellphone may not work at times, because it is too far from a mast, but it may also not work because the phone is in a location where there is interference to the cell phone signal from thick building walls, hills or other structures. The signals do not need a clear line of sight but the more interference will degrade or eliminate reception. Too many people may be trying to use the cell mast at the same time, e.g. a traffic jam or a sports event, then there will be a signal on the phone display but it is blocked from starting a new connection. The other limiting factor for cell phones is the ability of the cell phone to send a signal from its low powered battery to the mast. Some cellphones perform better than others under low power or low battery, typically due to the ability to send a good signal from the phone to the mast. The base station controller (a central computer that specializes in making phone connections) and the intelligence of the cellphone keeps track of and allows the phone to switch from one mast to the next during conversation. As the user moves towards a mast it picks the strongest

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signal and releases the mast from which the signal has become weaker; that channel on that mast becomes available to another user.

Temporary cell sites

Cell-on-wheels, or COW Although cell antennas are normally attached to permanent structures, cell providers maintain a fleet of temporary cell sites. When mounted on a trailer, they are called a COW or Cell On Wheels. These usually include a base station controller and a telescoping tower with antennas attached. A generator may be included when electrical power isn't available, and an additional backhaul antenna may be mounted to link the temporary tower into the network. COWs are often used at the site of a permanent cell site. Floods, fires, terrorism, and other disasters may destroy permanent antennas or base stations controllers, and fast dispatch of COWs can maintain vital communications during an emergency. They are also used in planned outages, such as when an antenna site is unavailable due to construction or maintenance. Finally, they are often used to augment capacity when large number of additional cell phone users are expected such as at large football games or NASCAR races.

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BASE TRANSCIEVER STATION

A typical GSM base station A base transceiver station or cell site (BTS) is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless internet connectivity, WiFi and WiMAX gadgets etc. The network can be that of any of the wireless communication technologies like GSM, CDMA, WLL, WAN, WiFi, WiMAX etc. BTS is also referred to as the radio base station (RBS), node B (in 3G Networks) or, simply, the base station (BS). For discussion of the LTE standard the abbreviation eNB for enhanced node B is widely used.

BTS in Mobile Communication A GSM BTS network is made up of three subsystems: 16

• The Mobile Station (MS) • The Base Station subsystem (BSS) – comprising a BSC and several BTSs • The Network and Switching Subsystem (NSS) – comprising an MSC and associated registers. Though the term BTS can be applicable to any of the wireless communication standards, it is generally and commonly associated with mobile communication technologies like GSM andCDMA. In this regard, a BTS forms part of the base station subsystem (BSS) developments for system management. It may also have equipment for encrypting and decrypting communications, spectrum filtering tools (band pass filters) etc. antennas may also be considered as components of BTS in general sense as they facilitate the functioning of BTS. Typically a BTS will have several transceivers (TRXs) which allow it to serve several different frequencies and different sectors of the cell (in the case of sectorised base stations). A BTS is controlled by a parent base station controller via the base station control function (BCF). The BCF is implemented as a discrete unit or even incorporated in a TRX in compact base stations. The BCF provides an operations and maintenance (O&M) connection to the network management system (NMS), and manages operational states of each TRX, as well as softwarehandling and alarm collection. The basic structure and functions of the BTS remains the same regardless of the wireless technologies. General Architecture

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Base transceiver station Antenna

A mobile BTS

A BTS mounted on a building A BTS in general has the following units: 1. Transceiver (TRX)

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Quite widely referred to as the driver receiver (DRX). Basically does transmission and reception of signals. Also does sending and reception of signals to/from higher network entities (like the base station controller in mobile telephony) 2. Power amplifier (PA) Amplifies the signal from DRX for transmission through antenna; may be integrated with DRX. 3. Combiner Combines feeds from several DRXs so that they could be sent out through a single antenna. Allows for a reduction in the number of antenna used. 4. Duplexer For separating sending and receiving signals to/from antenna. Does sending and receiving signals through the same antenna ports (cables to antenna). 5. Antenna This is also considered a part of the BTS. 6. Alarm extension system Collects working status alarms of various units in the BTS and extends them to operations and maintenance (O&M) monitoring stations.

7. Control function Control and manages the various units of BTS including any software. On-the-spot configurations, status changes, software upgrades, etc. are done through the control function.

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8. Baseband receiver unit (BBxx)

Frequency hopping, signal DSP, etc.. Important terms regarding a mobile BTS

BTS camouflage

DIVERSITY TECHNIQUES In order to improve the quality of received signal, often two receiving antennas are used, placed at an equal distance to an uneven multiple of a quarter of wavelength (for 900 MHz the wavelength it is 30 cm). This technique, famous as antenna diversity or diversity in the space, concurs to resolve the problems connected to the fading. The antennas can be spaced horizontally or vertically; in the first case though a greater facility of installation is required, advanced performance is obtained. Other than antenna or space diversity, there are other diversity techniques like frequency/time diversity, antenna pattern diversity, polarization diversity, etc.. •

Splitting

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The process of creating more coverage and capacity in a wireless system by having more than one cell site cover a particular amount of geography. Each cell site covers a smaller area, with lower power MHz and thus offers the ability to reuse frequencies more times in a larger geographic coverage area, such as a city or MTA. •

Sectoring A cell is subdivided to a sure number of fields, every one of which “is illuminated” from an antenna directive (or panel), that is an antenna that “does not illuminate” in all the directions, but concentrates the flow of power within a particular area of the cell, known as sector. Every field can therefore be considered like one new cell. By using directional antennas, the co-channel interference is reduced. A typical structure is the trisector, also known as clover, in which there are 3 sectors, each one served by separate antennas. Every sector has a separate direction of tracking of 120° with respect to the adjacent ones. If not sectorised, the cell will be served by an omnidirectional antenna, which radiates in all directions. Bisectored cells are also implemented with the antennas serving sectors of 180° separation to one another.

BATTERY MANAGEMENT Development and field testing a new Battery Management technique: Reserve batteries in wireless telecommunication tower applications

The Battery Health Manager - BHM, is a newly developed microprocessor-based device that automatically monitors and manages back-up battery power supplies without disrupting operations. The BHM subjects each cell (or module) in a battery pack to full load discharges to site specific levels, and smart charges to manufacturer's specifications, without removing the cells from the battery string or compromising inter-cell connections. The BHM gives the user the in-service condition and capacity of their battery-run emergency power back-up system. The system is configurable to most backup power systems and is chemistry independent. Nickel21

cadmium or lead-acid cells or batteries can be managed. This includes flooded types and valve regulated lead-acid. ESTCO Battery Management Inc.'s BHM informs the user of the exact capacity of each cell in the battery bank. This can be translated into time of operation in case of grid power failure. The microprocessor- control and signal conditioning allows all battery data to be stored and/or communicated from remote sites or locations to a central control station via the BHM-NET. Various alarm functions can be user-programmed to application specific requirements i.e. lowest safe capacity, low electrolyte levels, low pack and/or cell voltages, or external rectifier problems. The BHM can be configured in a variety of ways depending on the application. In this paper, we will report results of field tests of a 100A BHM system that was operated for the last two years in wireless tower sites in Ottawa, Canada. Two standard BHM systems, for up to 30amp or 100amp charge/discharge, will be described, but the system can be scaled up to higher or lower currents by changing the size of the single cell charger and load module. The BHM discharges the individual cell via an onboard load module. On the standard BHM this is set to a maximum of 100 amps for the 100amp system and is completely user programmable to on-site load emulation. Recharge is accomplished via the BHMTM single cell charger, which is powered (as is the BHM) from the battery pack As well as providing a monitor function, the BHMTM smart charges and discharges each cell, so that fully cycled, the life of the cell and battery pack is extended, saving more frequent replacement costs of expensive batteries. Cell charging can be programmed as constant voltage, constant current, or even specialized, more sophisticated profiles. This can be accomplished due to the software base control of the BHM. The charge control has temperature compensation to ensure optimum charging. Charge and discharge cut-off can be set by manufacturers recommended levels i.e. voltage, current or time or combinations of these charge parameters.

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CONCLUSION This project deals with the GSM TOWER MAINTENANCE in the department of GSM in BHARAT SANCHAR NIGAM LIMITED.Under this training, I have come through the complete knowledge of communication and GSM. This project also gave me the idea to deal GSM-CDMA tower projects. I have also come across with the knowledge that how to work with a great professionalism in any organization.it helped me to enhance skills such as leadership quailities as well as practical knowledge.

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