Cellular Concept And Rf Engineering

ACKNOWLEDGEMENT Apart from my efforts, the success of this project depends largely on the knowledge, experience, encouragement and guidelines of many others. I take this opportunity to express our gratitude to those people who have been instrumental in the successful completion of this project.

I would like to express my greatest appreciation to Mr. Rajendra Mishra, Nishant Srivastava & Vibhash Kumar Jha. I can’t say thank you, enough for their tremendous support and help. I feel motivated and encouraged every time I meet them. Without their encouragement and guidance this project would not have materialized.

The guidance and support received from Mr. Uttam Panda and Mr. Prosenjit (RF Dept.), Mr. Umesh Mishra and Rajesh Kr. Singh (RAN Dept.), Mr. Piyush Kumar & Aniket Kumar (Transmission Dept.), Mr. S.S. Hussain, Mr. Aravind Tanti and Mr. Vibhas (Switching Dept.), Mr. Sanjay Tiwari (Infrastructure Dept.), Mr. Anant Gopal (Wireline Dept.), was vital for the success of the project. I am grateful for their immense support and help.

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INTRODUCTION

Basic Cellular concepts From ancient to modern times, mankind has been looking for means of long distance communications. For centuries, letters proofed to be the most reliable way to transmit information. Fire, flags, horns, etc. were used to transmit information faster. Technical improvements in the 19th century simplified long distance communications: Telegraphy, and later on telephony. Both techniques were wireline. In 1873, J. C. Maxwell laid the foundation of the electro-magnetic theory by summarizing empirical results in four equations, which are still valid today. It would however be several decades before Marconi made economic use of this theory by developing devices for wireless transmission of Morse signals (about 1895). Already 6 years later, the first transatlantic wireless transmission of Morse signals took place. Voice was transmitted the first time in 1906 (R. Fessenden), and one of the first radio broadcast transmission 1909 in New York. The economically most successful wireless application in the first half of the 20th century was radio broadcast. There is one transmitter, the so-called radio station. Information, such as news, music, etc. is transmitted from the radio station to the receiver equipment, the radio device. This type of one-way transmission is called simplex transmission. The transmission takes place only in one direction, from the transmitter to the receiver. When we take a human conversation, a technical solution is required, where the information flow can take place in two directions. This type of transmission is called duplex transmission. Walky-talky was already available the early 30ies. This system already allowed a transmission of user data in two directions, but there was a limitation: The users were not allowed to transmit at the same time. In other words, you could only receive or transmit user information. This type of transmission is therefore often called semi-duplex transmission. For telephony services, a technical solutions is required, where subscribers have the impression, that they can speak (transmit) and hear (receive) simultaneously. This type of transmission solution is regarded as full duplex transmission. The first commercial wireless car phone telephony service started in the late 1940 in St. Louise, Missouri (USA). It was a car phone service, because at that time, the mobile phone equipment was bulky and heavy. Actually, in the start-up, it filled the whole back of the car. But it was a real full duplex transmission solution. In the 50ies, several vehicle radio systems were also installed in Europe. These systems are nowadays called single cell systems. The user data transmission takes place between the mobile phone and the base station (BS). A base station transmits

and receives user data. While a mobile phone is only responsible for its user’s data transmission and reception, a base station is capable to handle the calls of several subscribers simultaneously. The transmission of user data from the base station to the mobile phone is called downlink (DL), the transmission from the mobile phone to the base station uplink (UL) direction. The area, where the wireless transmission between mobile phones and the base station can take place, is the base stations supply area, called cell.

Cellular Systems •

Cellular systems provide service by dividing a coverage region into cells. Each cell is served by a base station. Large macro cells can have radii of several kilo meters.

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Concept behind cellular radio is that a finite spectrum, or bandwidth, allocation is made available throughout a geographical area by dividing the region into a number of smaller cells, each cell uses a portion of the spectrum.

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Dates back to 1980s when AMPS was Introduced in us, TACS in Europe and JTACS in Japan.

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These were all analog technologies using FDMA for multiple access and these systems are known as first generation wireless systems.

GENERATION :1st Generation Cellular Systems Cellular telephony is now in its second generation with the third on the horizon. The 1st generation was designed for voice communication using analog signals. AMPS (Advanced Mobile Phone System):-

Advanced mobile phone System is one of the leading analog Cellular System in NORTH AMERICA. It uses FDMA to separate channels in link. Bands:

AMPS Operates in the ISM 800 MHz band. The system uses two separate analog channels, one for forward (base station to mobile) communication and one for reverse (mobile station to base station) communication. The band between 824 to 849 MHz carries reverse communication and band between 869 to 894 MHz carries forward communication

Forward communication: base to mobile 824 894

30

849

869

MHz MHz

KHz

MHz

M Hz





…… …..................... ..

…………… …….

Mobile statio

Reverse communication: mobile

to base

Each band is divided into 832 channels. However two providers can share an area, which means 416 channels in each cell for each provider. Out of these 416, 21 channels are used for control, which leaves 395 channels. AMPS has a frequency reuse factor of 7; it means only one seventh of these traffic channels are actually available in a cell.

M T S O

B a s e S ta tio n

fig 1.2 1st generation cellular radio system 2ND Generation Cellular Radio Systems To provide higher quality (less noise prone) mobile voice communication, the second generation of the cellular phone network was developed. While the first generation was designed for analog communication, the second generation was mainly designed for digitized voice.

2nd generation

IS-136 D-AMPS

GSM

IS-95 CDMA

Base statio

TDMA-FDMA CDMA-FDMA

TDMA- FDMA

 To overcome the limitations of these analog systems like •

Limited service capability

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Poor service performance

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Inefficient frequency spectrum utilisation

The number of Active users were limited to the number of channels assigned to a particularly frequency zone. Second generation systems were developed using digital modulation – TDMA & CDMA  Some of the 2nd generation digital cellular technologies are : •

CDMA ONE (IS-95) - CDMA

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GSM/DCS-1900

- TDMA

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US TDMA IS-136

- TDMA

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PACS

- TDMA

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PHS

- TDMA

What is CDMA & TDMA?? •

TDMA stands for "time division multiple access", while CDMA stands for "code division multiple access“.

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The two competing technologies differ in the manner in which users share the common resource.

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TDMA does it by chopping up the channel into sequentially time slices, CDMA on the hand really does let everyone transmit at the same time and allow call processing to use entire available bandwidth.

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CDMA is only a means to transmit bits of information, while IS-95 is a transmission protocol that employs CDMA.

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Similarly, TDMA is also a method of transmitting bits, while GSM is a protocol that happens to employ TDMA.

1.3.1 FREQUENCY REUSE IN CDMA & TDMA F5 F4

F6 F1 F7

F1 F1

F1 F1

F3 F2

F1

F1 F1

Typical TDMA system each cell uses different frequency Typical CDMA system The pattern is repeated for the next set of cell sites cell uses same frequency

each

CDMA ADVANCED FEATURES •

Multiple, High Quality Vocoders.

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CDMA Short Message Services (SMS)

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Over-The-Air service provisioning.

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CDMA Data and FAX.

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SIX-WAY intelligent soft handoffs.

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Hard and Soft Handoff Enhancements.

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The ability to increase network capacity through an innovative dual basestation controller configuration with inter system soft handoff.

ADVANTAGES OF CDMA •

Increased cellular communications security.

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Simultaneous Conservations.

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Increased efficiency , meaning that the carrier can serve more subscribers.

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Smaller phone.

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Low power requirement and little cell to cell coordination needed by operators.

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Sophisticated Vocoders offer high speed coding and reduce background noise.

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CDMA takes the advantage of various types of diversity to improve speech quality.

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Frequency Diversity (Protection against frequency selective fading).

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Spatial Diversity (TWO RECEIVE ANTENNAS)

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Path Diversity (RAKE RECEIVER IMPROVES RECEPTION OF A SIGNAL EXPERIENCING MULTIPATH "INTERFERENCE," AND ACTUALLY ENHANCES SOUND QUALITY)

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Soft HANDOFFS contribute to high voice quality by providing a “ MAKE BEFORE BREAK” connection.

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The Voice quality for CDMA has been rated very high in mean opinion score (MOS) tests compared to other technologies.

DISADVANTAGES OF CDMA •

Due to its proprietary nature, all of CDMA’s flaws are not known to the engineering community.

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CDMA is relatively new and the network is not mature as GSM.

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Presently CDMA does not offer International Roaming, which is a large GSM advantage.

ADVANTAGES OF GSM

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GSM is already used worldwide with over 450 million subscribers compared to CDMA’s 80 million.

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International roaming permits subscribers to use one phone throughout western Europe. CDMA will work in Asia, but not France, Germany, U.K. and other popular European Destinations.

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GSM is mature, having started in the mid-80s. This maturity means a more stable network with robust features. CDMA is still building its network.

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GSM’s maturity means engineers cut their teeth on the technology, creating unconscious preference.

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The availability of Subscriber Identity Modules, which are smart cards that provide secure data encryption give GSM M-Commerce advantages.

CODE DIVISION MULTIPLE ACCESS (CDMA) WHY CDMA-------? •

Dramatically improving the telephone traffic capacity.

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Dramatically improving the voice quality and eliminating the audible effects of multiple fading.

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Reducing the incidence of dropped calls due to hand off failures.

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It does not allow cross talk and interference as it works on code and it is more secure.

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Providing reliable transport mechanism for data communications such as Facsimile and internet traffic.

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Simplifying Site selection.

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Reducing deployment and operating costs because fewer cell sites are needed to support any given amount of traffic.

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Reducing average transmitted power.

CDMA SYSTEM CONCEPT •

Composed of a series of cells. Cell serves a relatively small area , about one to two Kms in radius in a urban environment. Cell size dependent on a number of variables.

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The level of interference rises with the number of users. Each user has full time use of the entire spectral allocations.

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Most important variables is the output power that can be realized in the subscriber handset.

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CDMA is a scheme in which multiple users are assigned radio resources using the direct sequence – spread spectrum techniques.

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Although all users are transmitting in the same RF band, all users are separated from each other via the use of orthogonal codes.

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Each user’s signal energy is spread over the entire bandwidth and coded so as to appear like broadband to every other user.

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CDMA gets its name from the fact that it uses code division multiple acces to allow separation of individual signals from the summation of signals which share the common base station equipmen

CDMA SYSTEM CAPACITY CDMA CELL CAPACITY DEPENDS ON

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Receiver modulation performance

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Power control accuracy  Interference from other Non-CDMA systems sharing the same band  Number of users in a CDMA system is given by M=

Gp/ (Eb/No)

* 1 /(1+β)

* α *

1 /v

*λ β = Interference Factor (Interference generated by other mobiles in the system) α = Accuracy of Power Control v = Voice Activity Factor λ = Interference Improvement Factor due to Sectorized Antenna •

The link requires a particular Eb/No to attain an accept the link requires a particular e b/n o to attain an acceptable BER and ultimately an acceptable frame error rate (FER).

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Capacity is inversely proportional to the required E b/N o of the link. The lower the required threshold Eb/No , the higher the system capacity.

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Capacity can be increased if one can decrease the amount of loading from users in adjacent cells.

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Spatial filtering, such as sectorization, increases system capacity. For example, a six-sector cell would have more capacity than a three-sector cell.

SPREADING CODES USED IN CDMA •

Spreading Codes are used in CDMA to separate one use from the other

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Two types of codes are used in CDMA (IS-95)



Walsh Codes are used in the Downlink (BS-MS)



PN codes are used in the Uplink and Downlink

Walsh Codes Walsh codes are unique code used for spreading in forward link. It separates individual users while they simultaneously occupy the same RF bandwidth in a cell .The sequence are orthogonal to each other i.e. auto-correlation of a code is 1 and correlation with any other code is 0 and are generated using the HADAMARD matrix .Walsh-0 is not used to transmit any baseband data. There are 64 codes available long lasts for 1/19200 sec. Example: Correlation of Walsh code #23 with Walsh code #59 #23 0110100101101001100101101001011001101001011010011001011010010110 #59 0110011010011001100110010110011010011001011001100110011010011001 Sum 0000111111110000000011111111000011110000000011111111000000001111

Correlation Results: 32 1’s, 32 0’s: Orthogonal!! In IS-95A and IS-95B we use 64 orthogonal codes and in CDMA-2000 we use 128 orthogonal codes. The forward link is divided into as many Walsh Code and a Code Channel. On the reverse link the Walsh codes are not used to differentiate users but for 64-ary modulation. PN SEQUENCES It is used to spread the bandwidth of the modulated signal to larger transmission bandwidths distinguish between different user signals. Multiplication by a short PN sequence is done to provide another layer of isolation on the forward link .We can have a maximum of 512 different PN sequences each with a separation of 64 chips from each other.

CELLULAR CDMA CHANNELS AND FREQUENCY •

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Reverse link frequency – 824-849 MHz A-band

- 825-835 MHz

B-band

- 835-845 MHz

Forward link frequency – 869-894 MHz A-band

- 870-880 MHz

B-band •

- 880-890 MHz

CDMA channels Reverse link -

.03n+825 MHz (1 ≤ n ≤ 777)

Forward link - .03n+870 MHz (1≤ n ≤777)

CDMA IS-95 HIGH LEVEL ARCHITECTURE •

Forward channels Pilot channel (1) Sync channel (1) Forward traffic + paging channels (62) Paging channels (maximum 7)

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Reverse channels Reverse traffic channels Access channels

SYNC CHANNEL •

Sync channel is given the code channel number 32; fixed data rate 1200 kbps

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Allows receiver to obtain frame synchronization on signal

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Messages sent on synch channel are  System time  Characteristics of the system

PILOT CHANNEL •

Pilot signals are transmitted by each cell site to assist mobile radio in acquiring and tracking the cell site downlink signal

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Pilot channel is assigned code channel number zero

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The signal strength of the pilot channels is measured by Ec/Io.

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Ec/Io is the energy per chip per interference density measured on the pilot channel

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Ec/Io effectively determines the forward coverage area of a cell or a sector

FORWARD TRAFFIC AND PAGING CHANNELS •

Paging channels are given the code channel number 1thru 7

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Forward traffic channels grouped into rate set 1( 9.6, 4.8, 2.4 or 1.2 kbps) and rate set 2 (14.4, 7.2, 3.6 or 1.8 kbps)

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Rate set 1 is required for is-95 whereas rate set 2 is optional

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Speech is encoded with variable rate VOCODER to generate forward traffic channel data depending on voice activity

REVERSE TRAFFIC CHANNELS •

Identified by long user code offset

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Data transmitted on reverse channel is convolution encoded, block interleaved, modulated by means of 64-ary orthogonal modulation, and direct sequence spread prior to transmission

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Data rate is 9.6, 4.8, 2.4 or 1.2 kbps

ACCESS CHANNELS

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Enables the mobile to communicate nontraffic information

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Data rate is fixed at 4.8 kbps

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Identified by a distinct access channel long-code sequence offset

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A paging channel number is associated with access channel

TYPES OF HANDOFFS •

SOFT HANDOFF -

Handoff between 2-3 different base stations

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SOFTER HANDOFF- Handoff between 2-3 sectors of same cell

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SOFT-SOFTER HANDOFF- Handoff between 2 sectors of same base station and with another base station

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HARD HANDOFF- Two base stations are not synchronized handset must change frequency during handoff.

NEED FOR POWER CONTROL Power control is essential for the smooth operation of a CDMA system. Because all users share the same RF band through the use of PN codes .each user looks like random noise to other users. the power of each individual user therefore, must be carefully controlled so that no one user is unnecessarily interfering with others who are sharing the same band. Near mobiles must transmit at lower power than distant ones to balance link. need for power control in a CDMA arises because of the nearfar problem all the handsets in a CDMA system transmit and receive on the same radio frequency signals form one mobile appear as noise to the other mobile if two mobiles at different distances from the base station transmit at same power than the mobile which is nearer to the base station increases the noise floor for the mobile which is far from the base station. in other words if the power of the mobile which is near to the base station is not controlled than it increases interference at the receiver for the other mobiles which are far from the base station. the mobiles far from the base station in this case have to increase their transmit power to overcome this interference level therefore power control is implemented in CDMA system to overcome this near-far problem. POWER CONTROL IN A CDMA SYSTEM

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Handset measures data errors and sends signal quality to bs

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BS makes minor changes in power level (+- 3 db)

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Base station measures data errors from handset

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BS commands the mobile to increase or decrease power by 1 db

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power control occurs 800 times per second

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values for initial power on access or traffic channels are sent on overhead message on paging channel

CDMA NETWORK ARCHITECTURE

The major components of the subsystem are discusses as below:-

MOBILE STATION

The MS is a physical equipment used by the CDMA mobile system subscriber. It provides a subscriber with the network. There are 2 types of MS:- the mobile equipped MS and he portable MS. The voice communication requires only the mobile termination (MT) function. The other services require the additional functions such as the terminal equipment (TE), theterminal adapter (TA), or the combination thereof. The MS is equipped with the mobile equipment identity (MEI) and the mobile subscriber identity (MSI) for identification.

BASE STATION The BS is a physical equipment used in providing the BS area subscribers with the radio paths. The BS consists of 3 kinds of equipments: BTS for the transmission and reception of the radio signals, BSC for the BS control, and BSM for the BS OAM.

BTS The BTS is the physical equipment needed to communicate with the subscribers of its cell area. For the radio transmission and reception , low noise amplifier, power amplifier, signal combiner/distributor, and frequency converter are installed int the radio frequency unit (RFU). For the radio signal processing , the modulation/demodulation, CDMA channel coding/decoding, and the GPS receiver are in the CDMA digital unit (CDU). The call process and OAM functions are executed in the BTS control processor (BCP). The packet routes and the path between the BTS and the BSC are provided by the BTS interconnection network (BIN).

BSC The BSC manages the BS resources and controls the BS area subscribers. All the traffic packets from MSs are processes in the BSC . The packet selection during the hand-offs and voice packet conversion between code excited linear prediction (CELP) and PCM are executed in the transcoder & selector bank (TSB). The TSB connects to the MX using the E1 trunks. The BSC call process and BSC resource management are executed in the call control processor (CCP). The CDMA interconnection network (CIN) switches the BSC internal packets and provides the path to the BTS . The clock generator & distributor (CKD) provides TSBs with te clock signals derived from the GPS.

MOBILE EXCHANGE The MX is a physical equipment needed to communicate with the subscribers of its MX area. For the connection between the originating MS and the destination, the MX call process , PCM based time switch , and MX resource mangement carried out in the access switching subsystem (ASS). The location management and internetworking with the with PSTN or ISDN is also done via the ASS. The MX

location management is performed by the VLR . VLR is realized in the central control subsystem(CCS). The MX communicates with the HLR/AC for the location management and authentication. The interconnection network subsystem(INS) is the MX internal switches.

HLR/AC The HLR/AC stores and manges the CMS subscriber information including the subscriber location and service profiles . The authentication data are also stored in this subsystem . This is a data base to register CMS subscriber data . The HLR/AC communicates directly with the MX utilizing the common channel signalling 7(CCS 7).

SMS –MESSAGE CENTER The SMS-MC is used in providing the short message services. This stores and remits short messages upon subscriber request. The SMS-MC communicates directly with the MX utilizing the CCS 7.

CDMA RF PLANNING PURPOSE •

Proper planning at the initial stage ensures that the radio sytem design handle expected and unforeseen demand as the system matures.

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proper planning also ensures that the system level parameters defined and agreed in the initial system design guidelines are met

INPUTS REQUIRED FOR RF PLANNING General spectrum information •

Licensed spectrum to the operator

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Path loss drive testing frequencies

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Competing carriers in the market

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General spectrum allocations in the area of deployment

Network planning parameters •

Traffic model

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Voice / data rates

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Grade of service

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Building penetration loss (morphology based)

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Log normal shadowing standard deviation

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Frame erasure rate

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Cell edge reliability criteria

Coverage requirements •

Coverage area information

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Type of service requirments

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Type of morphologies

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Zoning restrictions

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Priority areas , Highway coverage and coverage restriction if any.

Capacity requirements •

The subscriber nos in the area

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Gridwise subscriber distribution

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Subscriber demand in the area (minutes of use)

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Subscriber mix for the coverage area

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The cdma rf environment is governed by the reverse link because of the limited transmit power of the mobile

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Rf parameters for the reverse link or the reverse link budget are most critical in the rf design of any cdma system

Reverse link

RF parameters •

Mobile transmit power (dBm)

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Mobile antenna gain (dBi)

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Head / body loss (dB)

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Soft handoff gain (dB)

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System loading (dB)

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Interference margin (loading) (dB)

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Log normal shadowing fade margin (dB)

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Eb/No requirments of the reciever (dB)

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Desired FER

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Base Rx sensitivity (dBm)

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Base Rx diversity gain

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Base station antenna gain (dBi)

FACTORS IMPACTING CDMA RF ENGG.

CAPACITY •

Cdma system capacity can be termed as the no of users supported simultaneously by a cell or a sector

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Capacity in a cdma system is inherently dynamic because it depends on a no of variable such as traffic distribution within and outside a cell

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Capacity limits occur when the mobile stations have insufficient transmit power to overcome interference levels

COVERAGE •

The area in which cdma coverage can be achieved is where the requirement of pilot chip energy to the total interference can be met .

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Coverage is also dependent on the effective radiated power of the mobile at any location .

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Coverage probability requirements, percentage power allocation for the pilot channel and Ec/Io threshold are the main factores governing the coverage.

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Capacity also impacts the coverage area. Capacity and coverage in a cdma system are inversely proportional to each other .

PROPAGATION LOSS •

Consists of all the impairments that a signal is likely to suffer when it travels from transmitter to reciever.

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Propagation loss heavily depends on the distance of transmitter to reciever .

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Other factos include the reflection and refraction of signals from buildings, trees and other obstacles on the way from transmitter to the reciever.

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Different modles used for the calculation of propagation loss are free space model, LEE model and HATA model.

LOG NORMAL SHADOWING •

The signal power in the direct path decreases relatively slowly as the distance between the transmitter and the reciever increases.

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The obstacles in the path may cause ocasional drops in the recvieved signal, this decrease occurs over many wavelengths of the carrier and is known as slow fading.

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This degradation is taken care by introducing a log normal shdowing fade margin in the link budget.

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Log normal shadowing fade margin directely affects the system reliability.

LINK BUDGET – REVERSE LINK •

Reverse link budget is critical in CDMA RF design because of the limited transmit power of the mobile.

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Maximum allowable path loss is a function of the mobile transmit power.

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Maximum allowable path loss is calculated based on Eb/No, cell loading, mobile transmit power, transmit and receive antenna gain, reciever noise figure, fade margin and propagation loss.

BASE STATION ANTENNA AND DIVERSITY REQUIREMENTS

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Most critical component that can either enhance or constrain system performance.

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Basic function is to couple electromagnetic energy between free space and a guiding device such as transmission line, waveguide etc.

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Antenna parameters include operating bandwidth, antenna gain, beamwidth, return loss and polarization.

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Antenna diversity at the base station helps to overcome fading caused by multipathpropagation ( reflection, refraction & scattering).

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Diversity helps to reduce severity of fading and provides significant link improvement of the reception.

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Two types of diversity can be used in the network : space diversity or polarization diversity

CDMA RF PLANNING METHODOLOGY The CDMA RF planning involves the following steps •

Nominal design

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Prelimnery design

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Site acquisition, survey and evaluation

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Final rf design

NOMINAL DESIGN Reverse link budget is calculated taking into accout all the RF parameters for the reverse link including the building penetration losses specified according to different morphologies .A nominal coverage assessment is done for the entire coverage area which is a function of the maximum allowable pathloss.Coverage assessment is done with the CDMA RF planning tool using the land use and digital elevation map as different layers.A nominal cell count is obtained from this process which is purely based on reverse link coverage . PRELIMNERY RF DESIGN The area demand map showing subscriber demand distribution in the coverage area is also imported in the CDMA RF planning tool which already has land use and dem as different layers. RF drive testing is conducted in the coverage area to obtain actual propagation losses for different morphologies. The RF drive testing data is analysed to derive propagation model correction co-efficients.The propagation

model correction co-efficients are imported to the CDMA RF planning tool for propagation model tweaking.Prelimnery RF design obtained for coverage and capacity obtained after different iterations PRELIMNERY RF DESIGN – DELIVERABLES •

Site search area maps

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Ec/Io plot for the coverage area

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MEIRP plots

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Forward link coverage area (best server plot)

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Reverse link coverage area (best server plot) site acquisition and evalution

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Searching for candidate sites based on search area maps

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Candidate site survey and evaluation

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Base station sites and perform coverage evaluation is finalised using the cdma rfplanning tool like ACTIX , AGILENT, MAPINFO

FINAL RF DESIGN Once the suitable locations for the base station sites have been finalized, final coverage and capacity analysis is performed using the CDMA planning tool The configuration is finalised for each cell. FINAL RF DESIGN – DELIVERABLES •

Final Ec/Io plot for the coverage area

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Final MEIRP plots

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Forward link service area ( best server plot)

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Reverse link service area ( best server plot)

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Final base station site configuration which includes - antenna hieghts ,sector azimuths for each site ,antenna downtilts,site coordinates

THE RAKE RECEIVER

BASE TRANSCEIVER STATION

The BTS contains the radio equipment (hardware and software) needed to implement the network side of the cdma2000-1X Air Interface (IS-95.C) in a Packet Super Cell CDMA system. The BTS provides both signalling and voice connection to the Mobile Station (MS) over the air (RF) as well as a voice and control connection to the Centralized Base Station Controller (CBSC) via span links (T1/E1/JT1) utilizing the Multi-Link Point to Point (MLPPP) protocol. The BTS provides the signal processing functions necessary to implement the various IS-95.A/B CDMA channel functions including the Pilot Channel (F-PICH), Sync Channel (F-SYCH), Paging Channel (FPCH), Access Channel (R-ACH), and Fundamental Traffic Channels (F/R-FCH). In addition, sites that have installed the IS-2000 capabilities will support Supplemental Traffic Channels (F/R-SCH), Enhanced Access Channel (R-EACH/F-CPCH), Common Control Channel (F/R-CCCH), Broadcast Channel (F-BCH), Dedicated Control Channel (F/R-DCCH) and Quick Paging Channel (F-QPCH) functions.

COMPONENTS OF BTS

FAN MODULE It helps to maintain the BTS at ambient temperature. It avoids heating of equipment. The speed of these Fan can be controlled according to ambience. POWER MODULE The DC Power Supply Converter Cards installed in the Combined CDMA Channel Processing (CCCP) shelf and the SCCP shelf convert the input voltage to the necessary DC voltages required to power the various modules in the C–CCP shelf. The primary input voltage is +27 Volts-DC. Power Supply modules work on a loadsharing basis. If one fails, the others will deliver full power to the remaining modules in the shelves. They are hot swappable. Each power converter card has individual power modules that convert filtered DC input power (+21V to +30 V, +27 V nominal) to +5 V, +6.5 V, or +15 V-DC power outputs. The output of each power module is routed to an over current detector and applied through a diode “OR” gate

to a corresponding power bus. The power bus is routed through the C–CCP and SCCP shelf backplane.

ALARM MONITORING AND REPORTING (AMR) Alarm Monitoring and Reporting (AMR) board is designed for use in both the SuperCell transcoder (XC) Cabinet and Super Cell Modem Cabinet (SC4812 frame family).

The primary functions of the AMR cards are to do the following: • Collect alarm status and Electronic Identification (EID) information from power supplies, cabinet alarms, HSO/LFR, and Multicoupler Preselector. • Monitor and report fan status to the GLI. • Interface between the GLI and the input/output connections for customer external alarm equipment connected to the ALARM connector. • Control LED alarm/status indicators for fan modules, AMR, and cabinet Frame Status Indicator (FSI) LED through 8 relays on the module. The major categories of alarms are: • • • • • •

Span Customer Timing LPA Link Hardware

GROUP LINE INTERFACE (GLI) The GLI card functions as the BTS controller and provides routing of traffic and control information and O&M functions for all active devices in the cage. It is the controller of the processing subsystem cage and acts as a message router between the CBSC and the BTS equipment. The GLI interfaces to the CBSC via a LAPD control link on a 64/56 Kbps timeslot allocated on the digital span line connecting the cell site to the CBSC. Each SC7224, SC4812, SC4840 and SC2440 BTS has multiple GLIs with one being Active and the other(s) in Standby mode, whereas the SC48X has a

single GLI card. In Active mode, the GLI provides traffic information to the MCC cards, control information to the MCC and BBX cards, and control information to the other GLI card(s) via the LAN. This GLI to GLI card(s) communication can be within a BTS frame or between frames of a BTS. The GLI also provides an LMF interface via the LAN and a serial port for remote dial-up via a dial-in modem. The GLI is 2N redundant - one CCP12/C-CCP cage supports up to two GLI cards. In standby mode, the GLI stays in sync with the active GLI so that it can become the active GLI if necessary. MULTIPLE CHANNEL CDMA (MCC) The Multiple Channel CDMA (MCC) card contains all the circuitry necessary to implement Code Division Multiple Access (CDMA) channels of any kind required from the 2G and 3G standards. The standard Super Cell form factor card is used for the MCC. This card will plug into any of the twelve MCC slots of the C-CCP and CCP12 backplanes. The MCC contains a Board Control Processor (BCP), two Channel Modules, an Ethernet Hub to interface the BCP, a Baseband Data Interface and a System Clock Interface section. BROAD BAND TRANSCEIVER ( BBX) The Broad Band Transceiver (BBX) provides all the CDMA unique RF-to-base-band functions for the reverse and forward paths for a CDMA Radio Channel. A BBX contains a two-branch diversity receiver and one transmitter branch. For the reverse link, the BBX down-converts one pair of diversity receive antenna signals to the digitized base band outputs, which are routed to the MCC cards. The BBX contains an AGC function that maintains the magnitude of the digitized received waveforms that are sent to the MCC. Alarms, such as synthesizer lock and LO output powers, are reported to the GLI card via the CHI bus. For the forward link, the BBX combines the serial forward link data from each MCC card into a single composite signal and the pilot channel is added. The composite signal is limited in magnitude by a programmable clipping circuit. The clipped signal is then spread by an in-phase (I) and quadrature (Q) pilot PN sequence. The complex spread signal is filtered by the TX baseband filter that determines the spectral mask. The filter output is then up sampled before going to the output DAC. The analog baseband signal is then up converted to the transmit band frequency. The transmitter output is then routed to the power amplifiers. The GLI card controls the BBX via SCAP messaging via the CHI bus. HIGH STABILITY OSCILLATOR (HSO) The SC48X BTS uses a High Stability Oscillator as a 24 hour backup timing reference in the event of primary (GPS) timing resource failure once BTS is initialized with the GPS and has been operating for 24 hours. It generates reference frequency of 3 MHz and CSM2 sync with it.

CLOCK SYNCHRONIZATION MANAGER (CSM)

The Clock Synchronization Manager (CSM) maintains CDMA system time and generates the master clock and reference signals for other CDMA system modules. To provide the required synchronization for the CDMA frame, the CSM can phase lock up to two types of sources: a GPS receiver, or the HSO. The GPS receiver is the pri- mary source and the HSO is the redundant source. The CSM generates three clock/synchronization signals. These signals are: • • •

3 MHz sync reference (sinusoidal frequency) for the GLI and BBX cards. 2 second pulse (i.e., Even-Second Signal) for synchronizing all timing references to the GPS time. 19.6608 MHz system clock signal to synchronize all traffic channel data.

The CSM also generates the ‘CSM active’ signal. The CSM active signal indicates which CSM is active in a frame employing redundant CSMs. LINEAR POWER AMPLIFIER (LPA) Two power amplifier options, Multi-tone Expandable Linear Power Amplifiers (ELPAs) and Japan Common linear Power Amplifiers (JCLPA) are used in the SC2440 and SC4840 frames. Two types of each option are available, and are designated as Single Density (SD) and Double Density (DD) PAs. The two PA types are physically interchangeable. The DD-ELPA and SD/DD JCLPA only supports HiTACS frequency band. One SD-ELPA/JCLPA can support at the SIF output a single sector-carrier of 25W, while the DD-ELPA/JCLPA will support a 50W sector-carrier. The gain of the DD is 3 dB more gain than the SD, and the DD can produce double the output power. To handle more carriers, up to four SD-PAs or two DD-PAs can be grouped together in a shelf. SD-ELPA/JCLPA and DD-ELPA/JCLPA can not be mixed within the same ELPA shelf. Also JCLPA and ELPA (even if both are SD or DD) can not be mixed in a shelf.

BASE STATION CONTROLLER

Fig. Components of Motorola BSC

COMPONENTS OF BSC MOBILITY MANAGER (MM)

Purpose / Functions  Highest Level of Call Management and Control in the CDMA RAN  Mobile Registration, Paging, Origination, Termination, Handoffs  Resource Allocation for cBTS (Channel Elements, Walsh Codes)  Circuit BTS Device State Management  Initialization, Code & Data Downloads, Recent Change, Alarms, Surveillance, Fault Recovery  Resource Management

 Dynamic Discovery of Network Elements and Resource Data  Link Fault Management  SCTP Link Establishment, Surveillance, Alarms, Recovery, Diagnostics  Super Cell Database (SCDB) Configuration Control  DB Population via CDFs, Recent Change, Interface with OMC MIB

SELECTION DISTRIBUTION UNIT (SDU) Based on Motorola's Common Platform technology and High Availability Platform software, the SDU (Selector Distribution Unit) is a key component in the migration to a fully IP, peer-to-peer, high capacity, highly available Radio Access Network (RAN). Enabled on Motorola's CDMA Software Release (CSR) 16.1, the SDU is a new element to the Motorola network offering. The SDU's primary function is to perform Software Hand-off selection and distribution function previously performed by the Transcoder (XC) and key Packet Control Functions (PCF) for 3G data services. The transition of the SHO selection function from the XC to the SDU allows for additional voice transcoding capacity in the XC. In conjunction with Packet Backhaul support on CSR 16.1, the SDU enables CBSC transcoder capacity expansion to 3,000 voice erlangs. Enhancing network integrity, the SDU features an independent fault zone, pool resource architecture that enables improved system availability. SDU resources are shared and pooled among a cluster of BTSs and CBSCs; therefore, an outage of any one SDU, in a multiple SDU deployment, will not cause a coverage outage. The SDU platform will be the basis for several key future network enhancements such as enabling higher data rates and concurrent services.

VOCODER PROCESSING UNIT (VPU) Human voice is made up of a combination of voiced and unvoiced sounds. Vocoders exploit these properties of speech production mechanism .Vocoders do not respond to music, non-human sounds and tones from voice band modems. SDU forwards

voice call to VPU. VPU converts voice calls to the format compatible with MSC. Then it latches the voice call on channels to MSC.

AGNODE

It connects MM & BTS through Gb interface. Each Agnode has 5 routers .Each router has 16 bundles. So at most it can connect to 80 BTSs. Further it has 10 cards. Each card has 8 ports.

MULTI LAYER SWITCH (MLS) MLS connects different components of the BTS. The components of BTS can not be directly connected to each other as these are products of different companies and that’s why follow different protocols. e.g. TTSL BSCs employ:MM manufactured by HP VPU & SDU by Motorola AGNODE by CISCO CISCO MLS connects all these components.

TRANSMISSION & SYNCHRONISATION

fig. CDMA Mobile System Transmission System Model

The transmission system model is shown in the figure. The radio transmission is critical to the system performance. The CDMA is interference limited. In order to minimize the interference in the radio link, the variable length packet transmissions with the data rate of 1~ 8 kbps have been adopted. The mobile station transmits packets every 20 ms . These packets are combined with the signaling message. The fast packet routers are utilized for transmission in the BS. They enhance the BS integrity without causing excessive transmission delay between the BTS and the BSC. These also ensure the maximum BS trunk efficiency. The BS packets are HDLC formatted and are transferred to the destination. During the soft handoff, 2 or 3 BTSs send packets to one selector simultaneously. A selector chooses the best packet among the received packets which bear the same information. In the case of voice services, the variable length packets of the radio link are converted into PCM at the vocoder and transferred to the MX. The MX cancels echo contained in the voice from PSTN and sends the voice to MSs. In the case of data services, the packets transferred from MSs are converted into 64 kbps formatted data at the BSC and transferred to the interworking function (IWF) via the MX. At the IWF, in the case of PSTn access, the data are converted to voice band data and sent

to PSTN through a modem. In the case of ISDN or PSPDN access, the data are transmitted to ISDN or PSPDN with the 64 kbps ISDN type format. Time synchronization is requisite for the transmission. The BTS needs the absolute time to acquire the CDMA signal transmitted from the MS. During the soft handoffs, the packet order mismatch can happen at selector due to the queuing delay of the BS packet routers. In order to prevent this mismatch, all BTSs and the BSC must be synchronized. The current BS maintains the synchronization by distributing clock signals derived from the GPS receiver equipped in the BTS and BSC. The BSC and the MX are synchronized by utilizing the frame synchronization. An MS receives the frame signals from its BTS. In the frame signals, 25c synch channel super frames are transmitted during every even seconds synchronized with the GPS clock. The synch channel super frame length is 80 ms and it consists of 3 synch channel frames. Transmission employs Synchronous Digital Hierarchy(SDH).

The basis of SDH is the STM-1 Frame. The STM-1 frame runs at 155.52Mbit/s, and is 125uS long. This means that you get 8,000 STM-1 frames per second. 8,000 frames a second is a very common rate in telecommunications networks operates at 8,000 frames a second. This means that each Byte in the frame is equal to a 64kbit/s channel. The Frame is made up of a “Section Overhead” field and a “Payload” field. STM-1 Frames are usually represented as 9 Rows by 270 Columns for a total of 2430 Bytes . The bytes are transmitted from Left to Right, Top to Bottom. The first 9

Columns are the section overhead and the other 261 columns are used to carry the payload.

The Section Overhead has three parts:* Regenerator Section Overhead * Pointers * Multiplex Section Overhead In SDH the actual user data is carried in “Virtual Containers”. The Virtual Containers have a Path Overhead field and they come in a number of different sizes. E1 CARRIER SYSTEM An E1 carrier is a telecommunications facility designed to carry digital information at a bit rate of 2.048 Mbps. In conventional telecommunications, the most common use for an E1 carrier is to connect central offices within an individual telephone company. Telephone companies also lease E1 carriers to their customers for their own private purposes. Most systems use E1 circuits to transmit digitized voice, management, and control traffic between zones. The Frame Relay and Cell Relay protocols provide the means for exchanging information over the E1 communication facilities that connect remote zones.

Various types of transmission media can be used in implementing a private E1 facility, such as various types of privately installed cabling or point-to-point microwave circuits. An E1 circuit is divided into 32 time slots, each of which implements a separate communication channel that can support a bit rate of 64,000 bps. Each of these individual channels is referred to as a Digital Signal Level zero (DS0) channel. The term framing refers to the order in which user bits and other information is transmitted over a physical transmission medium. An E1 frame comprises a total of 256 bits. Each of the 32 inputs is assigned a fixed time slot; the E1 uses a timedivision multiplexing technique to divide the capacity of the carrier into 32

channels. The framing bit is used to create a pattern to help synchronize the equipment. Picture above illustrates the format of the E1 transmission frame.

SIGNALLING

In the CMS, there are nine functional entities: MTS, BTS, BSC, MSC, VLR, EIR, HLR, AC, and SMS-MC. The MSC, VLR, EIR, HLR,AC and SMS-MC correspond to mobile switching center, visitor location register, equipment identity register, home location register, authentication center and short message service/message center, respectively. The MSC, VLR and EIR are implemented in the MX. The HLR and AC are implemented in the HLR/AC. The figure shows the CMS protocol structure. The interconnections between any two entities are established according to the international standard system reference model of the cellular system. The protocols employed in the CMS are found to work well. The layer 1 and layer 2 of the open system interconnection (OSI) are as follows:

• • • •

MS-BTS: radio link control protocol(RCP) BTS-BSC: internal protocol(BIP) BSC-MX: TDX interprocessor protocol(TIP) MX-HLR/AC: message transfer part 1 (MTP 1) and MTP 2

The upper layer protocol above the OSI layer 3 is connected with the call management, mobility management, radio resource management, and so on. These transfer, for example, the call control information such as the subscriber identification number and the service type. The upper layer protocols employed are as follows: • • • •

MS-BTS: mobile processing part(MCPP) BTS-BSC: BS application part( BSAP) BSC-MX: BS mobile application part(BSMAP) MX-HLR/AC or SMS-MC: MTP 3, signaling connection control part (SCCP), transaction capability (TCAP), and mobile application part(MAP). These upper layers protocols are executed in the control blocks. Each functional entity has its own control blocks, which consists of a number of processors. The processors in each block employ the fast packet transmission technique to handle a large amount of traffic. All the control blocks performing the management functions have redundant processors to warrant system reliability. SIGNALING

SYSTEM NO. 7 Common Channel Signaling System No. 7 (SS7 or C7) is a global standard for telecommunications defined by the International Telecommunication Union (ITU) Telecommunication Standardization Sector (ITU-T). The standard defines the procedures and protocol by which network elements in the public switched telephone network (PSTN) exchange information over a digital signaling network to effect wireless (cellular) and wire line call setup, routing and control. The ITU

definition of SS7 allows for national variants such as North America’s American National Standards Institute (ANSI) and Bell Communications Research (Telcordia Technologies) standards and Europe’s European Telecommunications Standards Institute (ETSI) standard.

The SS7 network and protocol are used for: • • • • • •

Basic call setup, management and tear down Wireless services such as personal communications services (PCS), wireless roaming and mobile subscriber authentication Local number portability (LNP) Toll-free (800/888) and toll (900) wireline services Enhanced call features such as call forwarding, calling party name/number display and three-way calling Efficient and secure worldwide telecommunications

SIGNALING LINKS SS7 messages are exchanged between network elements over 56 or 64 kilobit per second (kbps) bidirectional channels called signaling links. Signaling occurs out-ofband on dedicated channels rather than in-band on voice channels. Compared to inband signaling, out-of-band signaling provides: • • • •

Faster call setup times (compared to in-band signaling using multi-frequency (MF) signaling tones) More efficient use of voice circuits Support for Intelligent Network (IN) services, which require signaling to network elements without voice trunks (e.g., database systems) Improved control over fraudulent network usage

SIGNALING POINTS Each signaling point in the SS7 network is uniquely identified by a numeric point code. Point codes are carried in signaling messages exchanged between signaling points to identify the source and destination of each message. Each signaling point uses a routing table to select the appropriate signaling path for each message. There are three kinds of signaling points in the SS7 network (Figure. 1):

• • •

SSP (Service Switching Point) STP (Signal Transfer Point) SCP (Service Control Point)

Figure 1. SS7 Signaling Points

SSPs are switches that originate, terminate or tandem calls. An SSP sends signaling messages to other SSPs to setup, manage and release voice circuits required to complete a call. An SSP may also send a query message to a centralized database (an SCP) to determine how to route a call (e.g., a toll-free 1- 800/888 call in North America). An SCP sends a response to the originating SSP containing the routing number(s) associated with the dialed number. An alternate routing number may be used by the SSP if the primary number is busy or the call is unanswered within a specified time. Actual call features vary from network to network and from service to service.

Network traffic between signaling points may be routed via a packet switch called an STP. An STP routes each incoming message to an outgoing signaling link based on routing information contained in the SS7 message. Because it acts as a network hub, an STP provides improved utilization of the SS7 network by `eliminating the need for direct links between signaling points. An STP may perform global title translation, a procedure by which the destination signaling point is determined from digits present in the signaling message (e.g., the dialed 800 number, calling card number or mobile subscriber identification number).

An STP can also act as a "firewall" to screen SS7 messages exchanged with other networks. Because the SS7 network is critical to call processing, SCPs and STPs are usually deployed in mated pair configurations in separate physical locations to ensure network-wide service in the event of an isolated failure. Links between signaling points are also provisioned in pairs. Traffic is shared across all links in the

linkset. If one of the links fails, the signaling traffic is rerouted over another link in the linkset. The SS7 protocol provides both error correction and retransmission capabilities to allow continued service in the event of signaling point or link failures.

SS7 SIGNALING LINK TYPES Signaling links are logically organized by link type ("A" through "F") according to their use in the SS7 signaling network.

Figure 2. SS7 Signaling Link Types

A Link: An "A" (access) link connects a signaling end point (e.g., an SCP or SSP) to an STP. Only messages originating from or destined to the signaling end point are transmitted on an "A" link. B Link: A "B" (bridge) link connects one STP to another. Typically, a quad of "B" links interconnect peer (or primary) STPs (e.g., the STPs from one network to the STPs of another network). The distinction between a "B" link and a "D" link is rather arbitrary. For this reason, such links may be referred to as "B/D" links. C Link: A "C" (cross) link connects STPs performing identical functions into a mated pair. A "C" link is used only when an STP has no other route available to a destination signaling point due to link failure(s). Note that SCPs may also be deployed in pairs to improve reliability; unlike STPs however, mated SCPs are not interconnected by signaling links. D Link: A "D" (diagonal) link connects a secondary (e.g., local or regional) STP pair to a primary (e.g., inter-network gateway) STP pair in a quad-link configuration. Secondary STPs within the same network are connected via a quad of "D" links. The distinction between a "B" link and a "D" link is rather arbitrary. For this reason, such links may be referred to as "B/D" links.

E Link: An "E" (extended) link connects an SSP to an alternate STP. "E" links provide an alternate signaling path if an SSP’s "home" STP cannot be reached via an "A" link. "E" links are not usually provisioned unless the benefit of a marginally higher degree of reliability justifies the added expense. F Link: An "F" (fully associated) link connects two signaling end points (i.e., SSPs and SCPs). "F"links are not usually used in networks with STPs. In networks without STPs, "F" links directly connect signaling points.

SS7 PROTOCOL STACK The hardware and software functions of the SS7 protocol are divided into functional abstractions called "levels." These levels map loosely to the Open Systems Interconnect (OSI) 7-layer model defined by the International Standards Organization (ISO).

Figure 3. The OSI Reference Model and the SS7 Protocol Stack

MESSAGE TRANSFER PART The Message Transfer Part (MTP) is divided into three levels. The lowest level, MTP Level 1, is equivalent to the OSI Physical Layer. MTP Level 1 defines the physical, electrical and functional characteristics of the digital signaling link. Physical interfaces defined include E-1 (2048 kb/s; 32 64 kb/s channels), DS-1 (1544 kb/s; 24 64kb/s channels), V.35 (64 kb/s), DS-0 (64 kb/s) and DS-0A (56 kb/s).

MTP Level 2 ensures accurate end-to-end transmission of a message across a signaling link. Level 2 implements flow control, message sequence validation and error checking. When an error occurs on a signaling link, the message (or set of messages) is retransmitted. MTP Level 2 is equivalent to the OSI Data Link Layer. MTP Level 3 provides message routing between signaling points in the SS7 network. MTP Level 3 reroutes traffic away from failed links and signaling points and controls traffic when congestion occurs. MTP Level 3 is equivalent to the OSI Network Layer.

ISDN User Part (ISUP) The ISDN User Part (ISUP) defines the protocol used to set-up, manage and release trunk circuits that carry voice and data between terminating line exchanges (e.g., between a calling party and a called party). ISUP is used for both ISDN and nonISDN calls. However, calls that originate and terminate at the same switch do not use ISUP signaling.

Telephone User Part (TUP) In some parts of the world (i.e., China and Brazil), the Telephone User Part (TUP) is used to support basic call setup and tear-down. TUP handles analog circuits only. In many countries, ISUP has replaced TUP for call management.

Signaling Connection Control Part (SCCP) SCCP provides connectionless and connection-oriented network services and global title translation (GTT) capabilities above MTP Level 3. A global title is an address (e.g., a dialed 800 number, calling card number or mobile subscriber identification number) that is translated by SCCP into a destination point code and subsystem number. A subsystem number uniquely identifies an application at the destination signaling point. SCCP is used as the transport layer for TCAP-based services.

Transaction Capabilities Applications Part (TCAP) TCAP supports the exchange of non-circuit related data between applications across the SS7 network using the SCCP connectionless service. Queries and responses sent between SSPs and SCPs are carried in TCAP messages. For example,

an SSP sends a TCAP query to determine the routing number associated with a dialed 800/888 number and to check the personal identification number (PIN) of a calling card user. In mobile networks (IS-41 and GSM), TCAP carries Mobile Application Part (MAP) messages sent between mobile switches and databases to support user authentication, equipment identification and roaming.

Operations, Maintenance and Administration Part (OMAP) and ASE OMAP and ASE are areas for future definition. Presently, OMAP services may be used to verify network routing databases and to diagnose link problems.

WIRELINE

It consists of Switching Module , Communication Module and Administrative Module. Switchi ng Module

PICB

Communicat ion Module

Administrati ve Module

PICB – 32 slot, peripheral Interference Control Bus for Voice; PIDB – Data

SWITCHING MODULE (SM) •

The entire external lines trunk is terminated in this module.

•

It performs almost 95% of call processing and maintains the functions.

•

It performs all the digit analysis.

•

Call routing, Routing maintenance and self maintenance.

COMMUNICATION MODULE (CM) •

AM and SM are connected through CM.

•

It provides the path to send information between process to process calls, maintains records and performs the system tasks.

•

Data transfer between AM and CM is through the metallic bus.

•

CM has call switching – interconnect the path between SM to complete the telephone call and data.

•

It provides network timing – accurate timing and synchronization to switch.

ADMINISTRATIVE MODULE (AM) •

It supports all the activities of SM

•

Back up data base and program storage.

•

It stores the billing data and traffic.

It has three main units – •

Control Unit (CU) – It monitors overall system operation

•

I/O Processor (IOP) – It connects with two terminals –

•



MTTY (MCC Terminal)- visual display program



ROP

Disk File Controller (DFC)- It controls magnetic tape drive and magnetic hard disk.

INTEGRATED SERVICES DIGITAL NETWORK (ISDN) It is system of digital phone connections. It defines end to end Digital Network. It use Digital signal for transmission. It allows transfer of Voice, Data, Video, Text ,Graphics etc. It allows the multiple digital channels to be operated simultaneously.

TYPES OF ISDN SERVICE

13.1.1 BRI (Basic Rate Interface) : It provides connection from the ISDN office to the user location for access to three channels. The channels are two 64Kb B-channels and one 16Kb D-channel. 13.1.2PRI (Primary Rate Interface) :

It provides digital access via a T1 line which provides 1.544 bandwidth. This BW is divided into 23 B channels and one D channel for signaling process. ISDN PROTOCOLS •

E -Protocols recommend telephone network standards for ISDN (International Telephone Numbering Plans).

•

I - Protocols for I.400=User-Network Interface & I.100=Concepts, Structures & Terminology.

•

Q - Protocols, how switching and signalling should operate, call setup etc. (Q.921=LAPD* & Q.931=ISDN Network layer) * LAPD is used to deliver signalling messages to the switch (call setup).

ADVANTAGES OF ISDN •

Faster Data transfer rate : 128kbps

•

Highly supports interactive application like GAMING, Video Conferencing.

•

Allows multiple devices to share a single link.

•

Reduced noise and interference.

•

ISDN phone equipments are able to make intelligent decisions.

•

Faster call setup.

NOTE: - Nowadays ISDN is getting replaced by low cost broadbands for internet accesing

INRFASTRUCTURE Infrastructure department in TTSL deals with the development of new BTS and supporting equipments e.g. Shelter, Tower, Antenna, Power Supply includes Diesel Generator, Battery, and Electrical Supply etc. Infrastructure manager gives the responsibility of stabilising these things to the project planner. WTTIL (Wireless Tata Tele Info Ltd) looks after the site development work for TTSL.

FLOWCHART OF PROJECT

Planning

Site acquisition

Infrastructure (RF Infrastructure)

BTS Integration

Power Tapping

Ready for service (RFS)

Passive for Electrical Equipments

Alarm System

Active – for BTS

Operation and Maintenance

CONCLUSION The CDMA mobile system consists of six subsystems:- MS, BTS, BSC, MX,HLR/AC, AND SMS-MC. These subsystems are implemented based on the international standard system reference model of the cellular systems. The signaling and network protocols confirm to the OSI structure.

Each subsystem consists of a number of modularized cards. The system size can be customized to meet the user requirement. The CMS capacity is flexible and expandable. The BTS and BSC can provide maximum 320 and 23,040 voice channels; respectively. The MX can accommodate up to 23,040 mobiles at the same time. The CMS control blocks are built with redundancy to warrant system reliability.