Mobile communication - GSM/CDMA/WIMAX Technologies

Mobile communication - GSM/CDMA/WIMAX Technologies

MOBILE COMMUNICATION

A communication which does not depend on physical connection needed between two communicating entities and have flexibility to move anywhere during communication is called Mobile Communication.

Currently, GSM and CDMA technology offers Mobile Communication. Mobile Communication is one of the fastest growing telecommunication industries which may never suffer from economics of the world. Before discussing more about mobile communication, it is mandatory to know about mobile handset and SIM.

MOBILE HANDSET (PHONE)

A mobile phone or cell phone is a device that can make and receive telephone calls over a radio link while moving around a wide geographic area. A mobile phone operator connects the mobile phone to a cellular network and then to the public telephone network as well. It consists of a battery, keypad, SIM card, control unit, a transceiver and an antenna system. Nowadays, mobile phones also provide other services other than the principal service of telephony such as text messaging (SMS), Internet access, MMS, camera, Bluetooth, Infrared, gaming, business applications, email, etc.

The credit goes to John F. Mitchell for demonstrating the first mobile phone.

SIM CARD

A smart card called SIM (Subscriber Identification Module) is an integrated circuit used to identify the subscriber to the system, a secret key for authentication. By inserting SIM card into a mobile handset, a user can receive and make calls and receive other subscribed services as well. A SIM circuit is embedded into a removable plastic.

TERMINOLOGIES IN MOBILE COMMUNICATION CELL

It is the smallest geographical area considered for mobile communication.

SUBSCRIBER

A mobile phone user who pays subscription charges for using a mobile communication system. 

MOBILE STATION- 

 It is basically a mobile phone intended for use while moving anywhere.

BASE STATION

It provides connection between mobile unit and Mobile Switching Centre. It is located in each cell.

CELL SPLITTING

In high cellular traffic regions, a larger cell is divided into smaller cells to have complete radio coverage. This is called Cell Splitting.

HANDOFF

The handing over of call in progress from one base transreceiver to another one when mobile unit moves from one cell to another so that continuity of call is maintained is called Handoff Mechanism.

CLUSTER

A group of cells is called cluster. Generally, a cluster of 7 cells is preferred.

CELLULAR FREQUENCIES & SPECTRUM

All cellular phone networks worldwide use a portion of the radio frequency spectrum for the transmission and reception of their signals. This is also shared with television, Wi-Fi and Bluetooth transmission. The cellular frequencies are the sets of frequency ranges within the ultra high frequency band that have been allocated for cellular phone use. 

Radio Frequency Spectrum refers to the full frequency range from 3 kHz to 300 GHz that may be used for wireless communication. RF spectrum is a national resource. Each telecom company is allocated a specific frequency spectrum for enabling communication to its subscribers. They have to pay a huge amount in order to buy a specific frequency band or spectrum. For a GSM system, two frequency bands of 25 MHz each are allocated as,890-915 MHz for the uplink (Mobile station to Base Station) 935-960 MHz for the downlink (Base Station to Mobile Station)

The allocated frequency spectrum for BSNL lies in the 2.5 GHz frequency band.

FREQUENCY REUSE

The process of using the same set of frequencies allocated to more than one cell is called Frequency Reuse. This concept is followed for the efficient spectrum utilization. Frequency reuse is applied between the cells of different cell clusters.

TRAFFIC CHANNELS & CONTROL CHANNELS

A frequency channel consists of a pair of frequency bands (one band is in low band and other is in high band). Traffic Channels are used for carrying data or voice connections between different users while Control Channels are for necessary exchange of information related to setting up and establishing cell base stations and the mobile units.

FORWARD CHANNEL & REVERSE CHANNEL

Forward Channel is a radio channel used for transmission of information from base station to the mobile unit, while Reverse Channel transmits the information from the mobile unit to base station.

ROAMER

It is a mobile station that operates in a service area other than the subscribed service area is called Roamer.

SIMPLEX, HALF DUPLEX and FULL DUPLEX SYSTEMS

Communication systems providing only one way of communication are called Simplex Systems, those allowing two way communication but only one at a time by using same radio channel for transmission and reception are called Half Duplex Systems. The systems using two different radio channels for transmission and reception and allowing two ways communication is called Full Duplex System.

OPERATION of CELLULAR MOBILE SYSTEM

Operation of a cellular mobile system is completed into five steps

MOBILE UNIT INITIALIZATION

When a subscriber activates mobile unit, the receiver scans 21 set-up channels among 416 channels. The strongest channel is selected and locks on the for certain time. This strongest channel is from the nearest cell site and it is in idle stage. This feature is called self location scheme. The self location scheme is user independent. This eliminates the load on transmission at cell site for locating mobile unit. No location information of idle mobile units appears at each cell sites. Hence, the paging process is longer when call initiates from land line to mobile unit.

MOBILE ORIGINATED CALL

A mobile subscriber enters the called number into originating register of mobile unit where it is checked to see that number is correct or not on pressing send button. If the number is correct a request for service is sent on setup channel obtained from self-location scheme. The cell site receives this request and selects the best directional antenna for voice channel to use. Simultaneously cell site sends a request to mobile telephone switching office (MTSO) on high speed data link. MTSO selects an appropriate channel for the call and cell site directs to mobile unit.

NETWORK ORIGINATED CALL

A land line subscriber dials a mobile unit number. Telephone office recognizes it as mobile number and forwards the call to MTSO. The MTSO sends a paging message to few cell sites depending on mobile number and search algorithm. Each cell transmits the page on its set up channel. The mobile unit recognizes its own ID on a strong setup channel and responds to cell site. The mobile unit follows the instruction to tune to assigned voice channel and initiate user alert to respond to the call of the user.

CALL TERMINATION

When mobile user turns off mobile unit, a particular signal is transmitted to cell site. Then both sides free the voice channel. The mobile unit resumes monitoring pages through the strongest channel.

HANDOFF PROCEDURE

As mobile moves out of cell coverage area the reception becomes weak. The cell site calls for handoff i.e. system switches the call to a new frequency channel in new cell site without interrupting and knowing the user. The call continues without interruption.

GLOBAL SYSTEM FOR MOBILE COMMUNICATIONS (GSM)

GSM is a feature rich, digital wireless technology. GSM provides subscribers with highquality digital wireless phone service and clarity, as well as enhanced call security and privacy. This technique is most widely used for digital cellular radio. A GSM system has maximum 200 full duplex channels per cell. Each channel has different uplink and downlink frequencies. GSM handles channel access using a combination of slotted ALOHA, TDM and FDM. Developed in Europe, GSM is a second generation (2 G) cellular system which uses digital modulation and network level architectures and services. Commercial services of GSM started in mid-1991. It can handle both, voice and data traffic, the voice waveform being digitally encoded before transmission. GSM transmission is done within frequency bands of 900 MHz, 1800 MHz and 1900 MHz.

FEATURES of GSM

• Ability to use same phone in different networks.
• Data transmission and reception at 9600 bps speed.
• SMS (Short Message Service) facility allowing sending and receiving 126 character text message
• FAX transmission and reception
• Rapid call setup
• More subscriber capacity in the given spectrum Smaller handsets Encrypted conversions that cannot be tapped Number identification services
• Call forwarding, call holding and conference facility Call restriction services Videotext and teletext transmission
• Emergency services by notifying nearest emergency-service provider by dialling three digits
• Access to users on POTS (Plain Old Telephone Service) 

GSM RADIO LINK ASPECT 

The 25 MHz bandwidth is further divided into 124 carrier frequency channels each 200 kHz apart called ‘Absolute Radio Frequency Channel Numbers’ (ARFCN). The ARFCN indicates a pair of channel which is separated by 45 MHz. Each channel is time shared between 8 subscribers in TDMA scheme with frame duration of 4.615 mili second. Radio transmission on both forward and reverse link are made at channel data rate of 270.833 kbps, using BT= 0.3 GMSK modulation. Therefore, signalling bit period= 3.692 microsecond and effective transmission rate per user is 33.854 kbps. But, user data is sent at a maximum rate of 24.7 kbps because of GSM overload.

Every time slot (TS) has 4156.25 bits, out of which 8.25 bits are used for guard time and 6 bits are used for start and stop bits to prevent overlap with adjacent time slots. Each time slot has duration of 576.92 micro second. Bits= 3 ST 57 1 26 DATA S T 1 57 S DATA TS4 TS5 3 8.25 SP G TIME SLOT Total number of bits= 156.25 ST= Start bits SP= Stop bits S= Stealing bits T= Training bits G= Guard bits TS0 TS1 TS2 TS3 TS6 TS7 GSM FRAME 8 time slots of 0.577 ms each GSM ARCHITECTURE A GSM network consists of several functional entities, whose functions and interfaces are specified. MOBILE STATION (MS)- Mobile Station consists of a mobile unit and SIM card discussed earlier. Each mobile equipment or unit is uniquely identified by the International Mobile

• Equipment Identity (IMEI) number. 
• SIM card is uniquely identified by the International Mobile Subscriber Identity (IMSI) number. 
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• The IMEI and IMSI are independent, thereby allowing personal mobility. 
• The SIM may be protected against unauthorized use by a password or Personal Identity Number (PIN). 
• The power levels supported by GSM MS currently range from 0.8 to 8.0 W. 

BASE STATION SUBSYSTEM (BSS)

It is called access network. The BSS comprises of Base Transceiver System (BTS) Base Station Controller (BSC) Abis interface exists between BTS and BSC, while Um interface is present between MS and BTS. The interface comprises of traffic and control channels. Um interface is also called radio or air interface.Abis interface may be a modem, radio or optical fibre. This interface is defined by GSM equipment manufacturer. The equipment is manufactured by ALCATEL for BSNL. The function of BTS and BSC is given as BTS It handles radio link protocols with MS. It performs interleaving and deinterleaving. It enables full duplex communication to MS. It contains Transcoder Rate Adapter Unit (TRAU), in which GSM specific speech encoding and decoding is carried out. BSC It manages the radio resources of one or more BTSs. It handles radio-channel setup, frequency hopping and handoffs. It connects MS and MSC. It controls the operation of BTSs. 

NETWORK & SWITCHING SUBSYSTEM (NSS)

It is called core network. NSS includes data bases required for subscribers and mobility management as well as switching and routing. The main components of NSS are MOBILE SWITCHING CENTER – MSC performs the function of switching. It connects the subscriber with another subscriber or PSTN. It also performs the function of call setup, supervision and release along with digit collection, translation, billing information collection, registration, echo cancellation and local updating. Any call made by subscriber first comes to MSC and then it is routed to the desired subscriber. 

 Bhopal has two MSCs of BSNL, Arera MSC and Saket Nagar MSC. ‘A’ interface is used between MSC and BSC. These are physically connected by leased lines or microwave links. The physical layer of is a 2 Mbps CCITT digital connection. The ‘A’ interface allows a service provider to use base stations and switching equipment made by different manufacturers.

HOME LOCATION REGISTER (HLR)

HLR contains all the administrative information of each subscriber registered in the corresponding GSM network, along with current location of MS. The HLR database maintains IMSI of each subscriber and VLR address. There is logically one HLR per GSM network. HLR database is of two types- Dynamic and Permanent.

VISITOR LOCATION REGISTER (VLR)

VLR is a temporary database that stores the IMSI and customer information for each roaming subscriber who is visiting the coverage area of a particular MSC. When a roaming mobile enters in MSC area, the MSC informs the associated VLR about the mobile and this information is registered. The temporary subscriber information in VLR includes

IMSI
Features currently activated
Temporary mobile subscriber identity (TMSI)
Current location information about MS
Location where mobile is registered
Copy of subscriber data from HLR.
MS ISDN number

EQUIPMENT IDENTITY REGISTER (EIR)

EIR is a database that contains a list of all valid mobile equipments on the network identified by IMEI numbers. An IMEI is marked as invalid if it has been reported stolen or is not approved. White list Valid IMEI numbers Grey list IMEI under suspicion Black list Prohibited IMEI numbers

AUTHENTICATION CENTER (AuC)

AuC is a protected database that stores a copy of the secret key stored in each subscriber’s SIM card, which is used for authentication and encryption over radio channel.

OPERATION & SUPPORT SUBSYSTEM (OSS)

OSS is the command centre used to monitor and control GSM system. Main functions of OSS are
Network support and maintenance Subscription management (charging and billing)


Mobile equipment and BTS management. If any emergency occurs at BTS, the OSS determines the location of the BTS, and the failure occurred. COMPONENTS OF BTS BTS is a set of equipments that facilitates wireless communication. A BTS in general consists of Trans-receiver module, Antenna Network Combiner, Controller (SUMA) and Alarm Extension System (XIBM). It is a self contained unit for transmitting and receiving signal for mobile communication.

Types of BTS:

Indoor BTS
Outdoor BTS
Dual Band BTS
Twin TRX BTS

Indoor BTS is placed in a shelter and Air condition is a must as it is very sensitive to temperature. On the other hand, no shelter is required for outdoor BTS and Air condition is also not a must. BSNL uses the equipments manufactured by ALCATEL.

BTS SHELTER

Shelter is a portable sealed cabin made up of sandwiched insulated panels with polyurethane as filler material between galvanized pre-coated steel sheets. Floor is made up of 19mm thick marine plywood and is covered with PVC antistatic flooring. MS tube is reinforced inside floor panel for higher floor load capacity.Secondary slanting roof is provided to protect primary roof from direct sunlight and rainwater. Door is fixed with heavy-duty hinges, and is equipped with hydraulic closer and three way locking arrangement.

ROOF TOP TOWER

This is manufactured into Square Lattice Type and Triangular type. All members of RTT are made up of structural steel as per IS2062 Grade A & hot dip Zinc galvanized as per IS 4759. It can carry 6 numbers of GSM/WLL Antenna and 3 numbers of 0.6 diameter Microwave Antenna. It can survive wind velocity up to 210 km/h for short duration. TRANSCEIVER- Alcatel’s new Twin TRX radio transceiver doubles the capacity of existing equipment, while occupying the same space in the rack. The new Twin TRX is particularly adapted for densely populated urban areas, with a maximum capacity of 24 TRX per Base Station cabinet.Twin TRX transceivers can be installed in the full range of Alcatel’s indoor and outdoor BTS.

ANTENNA NETWORK COMBINER

ANC performs combination of signal from multiple antennas or amplifiers. These are high quality coaxial combiners available in various configurations covering full octave bands from 700MHz to 2.5 GHz. These units are ideally suited for use in Cellular PCS and Wi-Fi systems. All have N female terminations, can handle 10 watts of power and provides 20dB of isolation between ports. Antenna Network Combiner ensures the combiner and duplex functions.

TRANSCODER & RATE ADAPTATION UNIT

Transcoder and Rate Adaptation Unit (TRAU), performs transcoding function for speech channels and Rate Adaptation for data channels in the GSM network. TRAU is a data rate conversion unit. The PSTN/ISDN switch is a switch for 64 kbps voice. Current technology permits to decrease the bit-rate (in GSM radio interface it is 13kbit/s for full rate and 6.5kbit/s for half rate). Since MSC is basically a PSTN/ISDN switch its bit-rate is still 64kbit/s. That is why a rate conversion is required in between the BSC and MSC Transcoding is the compression of speech data from 64kbit/s to 13/12.2/5.6kbit/s in case FR/EFR/HR (respectively) speech coding.For an MS-to-MS call, the transmission path covers the radio access network (RAN) as well as the core network (CN). Since the transmission modes and coding standards are different for RAN and CN, speech data is converted at the transition points from RAN to CN. This conversion is performed in the TRAU network element which connects RAN and CN. 13kbit/s for FR (Full Rate), Redundancy (Channel Coding) = 9.8kbit/s => Gross data rate after adding redundancy = 22.8kbit/s = 12.2kbit/s for EFR (Enhanced Full Rate), Redundancy (Channel Coding) = 10.6kbit/s => Gross data rate after adding redundancy = 22.8kbit/s TRAU changes the bit rate of 16kbit/s of the BSS side to 64kbit/s of NSS side. = 5.6kbit/s for HR (Half Rate), Redundancy (Channel Coding) = 5.8kbit/s => Gross data rate after adding redundancy = 11.4kbit/s

3G TECHNOLOGY

3G stands for third generation is the third generation of mobile telecommunications technology. 3G telecommunication networks support services that provide an information transfer rate of at least 2Mb/s. However, many services advertised as 3G provide higher speed than the minimum technical requirements for a 3G service. Recent 3G releases, often denoted 3.5G and 3.75G, also provide mobile broadband access of several Mb/s to smart phones and mobile modems in laptop computers. 3G is also called Wideband CDMA or WCDMA.

3G finds application in wireless voice telephony, mobile Internet access, wireless Internet access, video calls and mobile TV.Services advertised as 3G are required to meet IMT-2000 technical standards, including standards for reliability and speed (data transfer rates).

FEATURES of 3G

DATA RATE-ITU has not provided a clear definition of the data rate users can expect from 3G equipment or providers. Thus users sold 3G service may not be able to point to a standard and say that the rates it specifies are not being met. It is expected that IMT-2000 will provide higher transmission rates: a minimum data rate of 2Mb/s for stationary or walking users, and 384kb/s in a moving vehicle, the ITU does not actually clearly specify minimum or average rates or what modes of the interfaces qualify as 3G, so various rates are sold as 3G intended to meet customers’ expectations of broadband data.

SECURITY-3G networks offer greater security than their 2G predecessors. By allowing the User Equipment to authenticate the network it is attaching to, the user can be sure the network is the intended one and not an impersonator. 3G networks use the KASUMI block cipher instead of the older A5/1 stream cipher. However, a number of serious weaknesses in the KASUMI cipher have been identified. In addition to the 3G network infrastructure security, end-to-end security is offered when application frameworks such as IMS are accessed, although this is not strictly a 3G property.

GPRS

General packet radio service (GPRS) is a packet oriented mobile data service on the2G and 3G cellular communication system's global system for mobile communications (GSM). GPRS was originally standardized by European Telecommunications Standards Institute (ETSI). It is now maintained by the 3rd Generation Partnership Project (3GPP). It provides services midway between 2G and 3G. Hence, it is also termed as 2.5G. The data transfer takes place at the rate of 128 kbps. GPRS usage is typically charged based on volume of data transferred, contrasting with circuit switched data, which is usually billed per minute of connection time.

GPRS extends the GSM Packet circuit switched data capabilities and makes the following services possible

1. "Always on" internet access
2. Multimedia messaging service (MMS)
3. Internet applications for smart devices through wireless application protocol (WAP)
4. Point-to-point (P2P) service: inter-networking with the Internet (IP)
5. SMS messaging and broadcasting If SMS over GPRS is used, an SMS transmission speed of about 30 SMS messages per minute may be achieved. This is much faster than using the ordinary SMS over GSM, whose SMS transmission speed is about 6 to 10 SMS messages per minute.

GPRS supports the following protocols:

Internet protocol (IP).
Point-to-point protocol
X.25 connections
When TCP/IP is used, each phone can have one or more IP addresses allocated. GPRS will store and forward the IP packets to the phone even during handover. The TCP handles any packet loss (e.g. due to a radio noise induced pause).

A GPRS connection is established by reference to its access point name (APN). The APN defines the services such as wireless application protocol(WAP) access, short message service (SMS), multimedia messaging service (MMS), and for Internet communication services such as email and World Wide Web access.

EDGE

EDGE (also known as Enhanced GPRS or EGPRS) is a data system used on top of GSM networks. It provides nearly three times faster speeds than the outdated GPRS system. The theoretical maximum speed is 473 kbps for 8 timeslots but it is typically limited to 135 kbps in order to conserve spectrum resources. Both phone and network must support EDGE; otherwise the phone will revert automatically to GPRS.

EDGE meets the requirements for a 3G network but is usually classified as 2.75G. EDGE is standardized also by 3GPP as part of the GSM family. EDGE delivers higher bit-rates per radio channel, resulting in a threefold increase in capacity and performance compared with an ordinary GSM/GPRS connection. EDGE can be used for any packet switched application, such as an Internet connection. EDGE is a superset to GPRS and can function on any network with GPRS deployed on it, provided the carrier implements the necessary upgrade. EDGE requires no hardware or software changes to be made in GSM core networks. EDGE compatible transceiver units must be installed and the base station subsystem needs to be upgraded to support EDGE. If the operator already has this in place, which is often the case today, the network can be upgraded to EDGE by activating an optional software feature. Today EDGE is supported by all major chip vendors for both GSM and WCDMA/HSPA. In addition to Gaussian minimum-shift keying (GMSK), EDGE uses higher-order PSK/8 phase shift keying (8PSK) for the upper five of its nine modulation and coding schemes. EDGE produces a 3-bit word for every change in carrier phase.

This effectively triples the gross data rate offered by GSM. EDGE, like GPRS, uses a rate adaptation algorithm that adapts the modulation and coding scheme (MCS) according to the quality of the radio channel, and thus the bit rate and robustness of data transmission. It introduces a new technology not found in GPRS, Incremental Redundancy, which, instead of re-transmitting disturbed packets, sends more redundancy information to be combined in the receiver. This increases the probability of correct decoding. EDGE can carry a bandwidth up to 236kb/s (with end-to-end latency of less than 150 ms) for 4 timeslots (theoretical maximum is 473.6kb/s for 8 timeslots) in packet mode. This means it can handle four times as much traffic as standard GPRS. EDGE meets the International Telecommunications Union's requirement for a 3G network, and has been accepted by the ITU as part of the IMT-2000 family of 3G standards.

It also enhances the circuit data mode called HSCSD, increasing the data rate of this service. UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM Commonly abbreviated as UMTS, Universal Mobile Telecommunications Systemis a third generationmobile cellular system for networks based on the GSM standard. Developed and maintained by the 3GPP (3rd Generation Partnership Project), UMTS is a component of the International Telecommunications Union IMT-2000 standard set and compares with the CDMA2000 standard set for networks based on the competing CDMA Onetechnology. UMTS uses (W-CDMA) radio access technology to offer greater spectral efficiency and bandwidth to mobile network operators.UMTS includes the original W-CDMA scheme using paired or unpaired 5 MHz wide channels in globally agreed bandwidth around 2 GHz, though subsequently, further bandwidth has been allocated by the ITU on a regional basis. The UMTS Radio Access Network (UTRAN) technology is specified in the 3GPPTM TS 25.series specifications.

The specifications cater for Frequency Division Duplex (FDD) and Time Division Duplex (TDD) forms, with high (3.84 Mc/s) and low (1.28 Mc/s) chip rate flavours. AS a development of the original radio scheme, a high speed download packet access (HSDPA, offering download speeds potentially in excess of 10 Mb/s), and an uplink equivalent (HSUPA, called as EDCH) were developed. Collectively, the pair called HSPA permits the reception of multimedia broadcast/multicast, fixed-line broadband internet access, interactive gaming and business applications. The radio frames are divided into 2ms sub frames of 3 slots, and gross channel transmission rates are around 14Mb/s. NODE B Node B is a term used in UMTS (Universal Mobile Telecommunications System) equivalent to BTS in GSM. It can be coined as ‘BTS of 3G’. It is the hardware that is connected to the mobile phone network that communicates directly with mobile handsets. In contrast with GSM base stations, Node B uses WCDMA/TD-SCDMA as the air interface technology.

As in all cellular systems, such as UMTS and GSM, the Node B contains radio frequency transmitter/s and the receiver/s used to communicate directly with mobile devices, which move freely around it. In this type of cellular network, the mobile devices cannot communicate directly with each other but have to communicate with the Node B.WCDMA technology enables the cells of same or different Node Bs and those controlled by different RNC to overlap and still use the same frequency pair. Soft handovers make use of this effect. Power requirements on Node Bs and user equipment (UE) are much lower. It is connected to RNC of UMTS network through IUB interface. A full cell site has a cabinet, an antenna mast and actual antenna. An equipment cabinet contains e.g. power amplifiers, digital signal processors and backup batteries. A Node B can serve several cells, also called sectors, depending on the configuration and type of antenna. Common configuration include Omni cell (360°), 3 sectors (3x120°) or 6 sectors (3 sectors 120° wide overlapping with 3 sectors of different frequency).

RADIO NETWORK CONTROLLER

The Radio Network Controller (RNC) is a governing element in the UMTS radio access network (UTRAN) and is responsible for controlling the Node B is that are connected to it. The RNC carries out radio resource management, some of the mobility management functions and is the point where encryption is done before user data is sent to and from the mobile. The RNC connects to the Circuit Switched Core Network through Media Gateway (MGW) and to the SGSN (Serving GPRS Support Node) in the Packet Switched Core Network.In a relationship to a UE (in a soft handover situation) an RNC can play two different roles.

These are:

D-RNC: Drift RNC

S-RNC: Serving RNC However, as far as the Node B is concerned, the RNC may play a third role:

C-RNC: Controlling RNC One RNC can assume more than one role at any time. An RNC also control the power of a NODE B.

The logical connections between the network elements are known as interfaces. The interface between the RNC and the Circuit Switched Core Network (CS-CN) is called Iu-CS and between the RNC and the Packet Switched Core Network is called Iu-PS. Other interfaces include Iub (between the RNC and the Node B) and Iur (between RNCs in the same network). Iu interfaces carry user traffic (such as voice or data) as well as control information (see Protocols), and Iur interface is mainly needed for soft handovers involving 2 RNCs though not required as the absence of Iur will cause these handovers to become hard handovers.

RADIO NETWORK CONTROLLER (NODE B)

LUB Interface Iub interface connects Node B and RNC.The physical interface to a base station will be such that the Iub capacity from a given base station has some discreet value.Because of signalling, O&M, and ATM overhead, the Iub interface should be sized to a bandwidth that is almost twice that of the actual raw user traffic. Of course, the user traffic is likely to be asymmetrical, and weare likely to find that the downlink traffic is greater than the uplink traffic. The actual Iub transmission facilities, however, will be symmetrical. Inother words, if there are 2 Mbps capacity on one direction, there is also 2Mbps in the other direction. Therefore, when dimensioning the Iub, we needonly to consider the user traffic in one direction—the direction of greater demand. This will usually be the downlink direction.

OPERATIONS & MAINTENENCE CENTRE

Operations and Maintenance Centre (OMC) is the central location to operate and maintain the network. There are various types of OMCs depending on the functionality: i. ii. iii. iv. v. vi. OMC-B (for maintaining Node B) OMC-R (radio for maintaining RNC) UMTS OMC-U GPRS OMC-G OMC-DO OMC-IP PLANNING and OPTIMISATION GSM Radio Network Planning and Optimization provides a solid understanding of how to design and plan a high quality GSM radio network. This includes expansion of network, techniques to boost capacity, lowering interference and increasing quality in the network. Macro cell planning is emphasised.Planning is the process of assigning frequencies, transmitter locations and parameters of a wireless communications system to provide sufficient coverage and capacity for the services required. The RF plan of a cellular communication system has two objectives: coverage and capacity. Coverage relates to the geographical footprint within the system that has sufficient RF signal strength to provide for a call/data session. Capacity relates to the capability of the system to sustain a given number of subscribers. Capacity and coverage are interrelated. To improve coverage, capacity has to be sacrificed, while to improve capacity, coverage will have to be sacrificed. Planning consists of four stages

1. INITIAL RADIO LINK BUDGETING

The first level of the RF planning process is a budgetary level. It uses the RF Link Budget along with a statistical propagation model. The statistical propagation model does not include terrain effects and has a slope and intercept value for each type of environment. This fairly simplistic approach allows for a quick analysis of the number of sites that may be required to cover a certain area. Estimated Number of Sites is the output produced at this stage.

2. DETAILED RF PROPAGATION MODELLING

The second level of the RF Planning process relies a more detailed propagation model. Automatic planning tools are often employed in this phase to perform detailed predictions. The propagation model takes into account the characteristics of the selected antenna, the terrain, and the land use and land clutter surrounding each site. Since these factors are considered, this propagation model provides a better estimate of the coverage of the sites than the initial statistical propagation model.

3. FINE TUNING & OPTIMISATION

This stage includes items such as collecting drive data to be used to tune or calibrate the propagation prediction model, predicting the available data throughput at each site, fine tuning of parameter settings (e.g. antenna orientation, down tilting, frequency plan). This process is required in the deployment of the system or in determining service contract based coverage. Following is a typical list of outputs produced at this stage: A final List of Sites and Site Locations (and Height) Optimised Antenna Directions and Down tilts An optimised Neighbour Cell Lists for each site Mobility (Handover and Cell Reselection) Parameters for each site An optimised Frequency Plan Detailed Coverage Predictions (e.g. Signal Strength (RSRP), Signal Quality (RSRQ) Best CINR, Best Server Areas, Uplink and Downlink Throughput

4. CONTINOUS OPTIMISATION

The final phase of the RF planning process involves continuous optimisation of the RF plan to accommodate for changes in the environment or additional service requirements (e.g. additional coverage or capacity). This phase starts from initial network deployment and involves collecting measurement data on a regular basis that could be via drive testing or centralised collection. The data is then used to plan new sites or to optimize the parameter settings (e.g. antenna orientation, down tilting, frequency plan) of existing sites. Radio Frequency Optimization is a process through which different soft (Cell Reselect Offset, BTS power) and hard (e.g. Electrical Tilt, Mechanical Tilt, Azimuth etc.) parameters of the Base transceiver stations are changed in order to improve the coverage area and improve quality of signal. Besides that there are various key performance indicators which have to be constantly monitored and necessary changes proposed in order to keep KPIs in agreed limits with the mobile operator.

OVERVIEW of MOBILE TECHNOLOGIES

Mobile technology makes living life on the go easier. Gone are the days of being tied to a desk or staying close to a landline phone to avoid a missed call. Communication, entertainment, exercising and travel are merely a few lifestyle improvements made possible with mobile technology.

Mobile phones are the most obvious mobile devices and are available to millions and millions of people. Callers are almost instantly connected to each other through a series of cellular connections that reach even to the most remote areas of the world. These cellular connections are not only for mobile phones. Laptops and PDAs share data across the cellular system. In fact, some Smart phones act as modems for laptops. Expensive connection to the internet or to a network is not always necessary. Small MP3 players store hundreds of songs. PDAs take the place of bulky day planner systems, address books and photo albums. Portable handheld televisions pickup broadcasts of sports events, news shows and soap operas. GPS Receivers have gained tremendous popularity replacing those hard to refold paper maps. Long battery life and tiny footprints make finding your direction easier in your vehicle. Whether you need to plan a route across the county or whether you need to find a good restaurant a GPS device offers a helping hand.

MOBILE TECHNOLOGY DEVICES

• Cell phones
• Smartphones/PDA phones
• Laptop computers
• PDAs
• MP3 players
• Handheld televisions
• GPS (Global Positioning System)

INSIDE A MOBILE PHONE

Mobile phones are some of the most intricate devices people play with on a daily basis. Modern digital mobile phones can process millions of calculations per second. An amazing circuit board containing the brains of the phone An antenna A liquid crystal display (LCD) A keyboard (not unlike the one you find in a TV remote control A microphone A speaker A battery The circuit board is the heart of the system. Here is one from a typical Nokia digital phone:

The front of the circuit board The back of the circuit board The analog-to-digital and digital-to-analog conversion chips translate the outgoing audio signal from analog to digital and the incoming signal from digital back to analog.

The digital signal processor (DSP) is a highly customized processor designed to perform signal-manipulation calculations at high speed.The microprocessor handles all of the housekeeping chores for the keyboard and display, deals with command and control signalling with the base station and also coordinates the rest of the functions on the board.

The ROM and Flash memory chips provide storage for the phone's operating system and customizable features, such as the phone directory.

The radio frequency (RF) and power section handles power management and recharging, and also deals with the hundreds of FM channels. Finally, the RF amplifiers handle signals travelling to and from the antenna. Microprocessor

CONNECTION of MOBILE DEVICES with NETWORK or INTERNET-

Bluetooth Wi-Fi (Local Area) -
Hot Spots Broadband (Wide Area) -
Air Card VPN 3G Cell phone Dial Up Satellite

ADVANTAGES OF MOBILE TECHNOLOGY-

Time saving Information sharing Freedom of movement Safety Improved customer service Improved productivity

DISADVANTAGES OF MOBILE TECHNOLOGY

Cost
Distraction
Security threats
Theft
Short battery life
Disposal of spent batteries
Data loss

INFRASTRUCTURE

Telecommunications infrastructure refers to telecommunications spaces (e.g. rooms) and pathways (e.g. conduit, cable tray), cables and related components such as jacks, crossconnection hardware, etc. When a telecommunications infrastructure is designed following a holistic approach, the designer has created a single integrated infrastructure serving the entire building. In contrast, when a telecommunications infrastructure is designed following a non-holistic or legacy approach, the building's telecommunications infrastructure is a piece-meal collection of separate telecommunications infrastructures, each serving the specific space occupied by an individual tenant or department. Telecom Infrastructure is classified into two types-

1. ACTIVE INFRASTRUCTURE-

Active infrastructure compares the core clement of cellular telephony in the form of a network and contiguous radio cells providing coverage through operating on dedicated set of radio channels of defined frequency. Elements of the active infrastructure are the basic transceiver station (BTS), the base station controller (BSC), the mobile switching centre (MSC), and microwave and GSM antenna along with telecom equipments and routers. The antenna enables both the transmission and reception of the radio signal, enabling the cellular telephony to proceed interrupted as the subscriber is mobile.

PASSIVE INFRASTRUCTURE-

Passive infrastructure comprises of the elements which enable the active infra to operate as described above .The telecom towers are used for hosting the antenna to predetermined and technically viable heights for optimum coverage of cellular network. The towers are typically elected at site themselves and also comprise poles for mounting the antennas, shelters and house for electrical and telecom equipment. Passive infrastructure can be divided as1. Air Conditioners- Air Conditioners are used to prevent the components and hardwares from high temperature and heat so that they may not be damaged and the temperature of the room where components are placed should remain moderate. Freon is an element used in air conditioners. The temperature is maintained at (22+3)0 C to (22-3)0C.

Tower-

A cell site or Tower is a cellular telephone site where antennas and electronic communications equipment are placed, usually on radio mast or other high place, to create a cell in a cellular network. The elevated structure typically supports antennas, and one or more sets of transmitter /receivers transceivers, digital signal processors, control electronics, a GPS receiver for timing (for CDMA2000/IS-95 or GSM systems), primary and backup electrical power sources, and sheltering. 3. Power Supply- Power Supply is a must for any instrument to work in Telecom. Two types of Power Supplies are used

DC Power Supply- This is also called uninterrupted power supply. It is used for the operation of BTS, BSC, MSC,etc and providing power to media gateways and recharge the battery as well.

AC Power Supply- This power supply is taken from the main line. Any telecom operator has to pay a huge amount (above 10lacs) to the power supplying company in order to use the power needed for air conditioners, components and telecom equipments, electricity, etc. This supply is needed to feed servers, routers and switches.

The AC power coming from the transmission line feeder is given to step down transformer to reduce its voltage level as all telecom equipments in exchanges, MSCs, BTSs, etc operate on -48V DC supply. This alternating voltage is then passed through rectifiers to get converted into pulsating DC voltage, and then to filter to get pure DC supply. To get regulated DC power supply, Regulator is also used. The unused DC power supply is converted into AC by invertor to act as Backup or UPS.

TRANSMISSION MEDIA MULTI LABEL PROTOCOL SWITCHING

It is a part of Data Communication. Multiprotocol Label Switching (MPLS) is a mechanism in high performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. The labels identify virtual links (paths) between distant nodes rather than endpoints. MPLS can encapsulate packets of various network protocols. MPLS supports a range of access technologies, including T1/E1, ATM, Frame Relay, and DSL. Packet-forwarding decisions are made solely on the contents of this label, without the need to examine the packet itself. This allows one to create end-to-end circuits across any type of transport medium, using any protocol. The primary benefit is to eliminate dependence on a particular OSI model data link layertechnology, such as Asynchronous Transfer Mode (ATM), Frame Relay, Synchronous Optical Networking (SONET) or Ethernet, and eliminate the need for multiple layer-2 networks to satisfy different types of traffic. MPLS belongs to the family of packet-switched networks.MPLS operates at a layer that is generally considered to lie between traditional definitions of layer 2 (data link layer) and layer 3 (network layer), and thus is often referred to as a "layer 2.5" protocol. MPLS attempts to preserve the traffic engineering and out-of-band control that made Frame Relay and ATM attractive for deploying large-scale networks. While the traffic management benefits of migrating to MPLS are quite valuable (better reliability, increased performance), there is a significant loss of visibility and access into the MPLS cloud for IT departments. MPLS works by prefixing packets with an MPLS header, containing one or more labels. This is called a label stack. Each label stack entry contains four fields:  A 20-bit label value.  A 3-bit Traffic Class field for QoS (quality of service) priority (experimental) and ECN (Explicit Congestion Notification).

A 1-bit bottom of stack flag. If this is set, it signifies that the current label is the last in the stack. An 8-bit TTL (time to live) field.


These MPLS-labelled packets are switched after a label lookup/switch instead of a lookup into the IP table. As mentioned above, when MPLS was conceived, label lookup and label switching were faster than a routing table or RIB (Routing Information Base) lookup because they could take place directly within the switched fabric and not the CPU. Routers that perform routing based only on the label are called label switch routers (LSRs). The entry and exit points of an MPLS network are called label edge routers (LERs), which, respectively, push an MPLS label onto an incoming packetand pop it off the outgoing packet. Alternatively, under penultimate hop popping this function may instead be performed by the LSR directly connected to the LER. MPLS technology has two routers- code router and edge router. The format of the information provided by the router is- Device ID Local Interface Hold time Capability Platform Port ID

DATA CENTRE OF BILLING

It consists of databases for storing data.A data centre or computer centre is a facility used to house computer systems and associated components, such as telecommunications and storage systems. It generally includes redundant or backup power supplies, redundant data communications connections, environmental controls (e.g., air conditioning, fire suppression) and security devices. Large data centres are industrial scale operations using as much electricity as a small townand sometimes are a significant source of air pollution in the form of diesel exhaust. The Data Centres are always placed on a large raised platform. Below the platform air conditioning is provided to prevent the equipments from getting damaged owing to high temperature. The main data centre of BSNL WEST is located in Pune, which houses a large database of the subscribers of the entire WEST Zone. The backup of the data centre resides in the MSC Saket Nagar, Bhopal, which in case of any fault occurred in the main data centre of Pune, will automatically take the entire database so that it may not be lost. Data Centre uses the servers of ‘hp’. A data centre keeps high standards for assuring the integrity and functionality of its hosted computer environment. This is accomplished through redundancy of both fibre optic cables and power, which includes emergency backup power generation. The Telecommunications Industry Association's TIA-942 Telecommunications Infrastructure Standard for Data Centres, specifies the minimum requirements for telecommunications infrastructure of data centres and computer rooms including single tenant enterprise data centres and multitenant Internet hosting data centres.


Racks of Telecommunications equipments as part of Data Centre Effective data centre operation requires a balanced investment in both the facility and the housed equipment. The first step is to establish a baseline facility environment suitable for equipment installation. Standardization and modularity can yield savings and efficiencies in the design and construction of telecommunications data centres. Standardization means integrated building and equipment engineering. Modularity has the benefits of scalability and easier growth, even when planning forecasts are less than optimal. For these reasons, telecommunications data centres should be planned in repetitive building blocks of equipment, and associated power and support (conditioning) equipment when practical. The "lights-out" data centre, also known as a darkened or a dark data centre, is a data centre that, ideally, has all but eliminated the need for direct access by personnel, except under extraordinary circumstances. Because of the lack of need for staff to enter the data centre, it can be operated without lighting.

All of the devices are accessed and managed by remote systems, with automation programs used to perform unattended operations. In addition to the energy savings, reduction in staffing costs and the ability to locate the site further from population centres, implementing a lights-out data centre reduces the threat of malicious attacks upon the infrastructure. A data centre can occupy one room of a building, one or more floors, or an entire building. Most of the equipment is often in the form of servers mounted in 19 inch rack cabinets, which are usually placed in single rows forming corridors (so-called aisles) between them. This allows people access to the front and rear of each cabinet. Servers differ greatly in size from 1U servers to large freestanding storage silos which occupy many square feet of floor space. Some equipment such as mainframe computers and storage devices are often as big as the racks themselves, and are placed alongside them. Very large data centres may use shipping containers packed with 1,000 or more servers each;when repairs or upgrades are needed, whole containers are replaced (rather than repairing individual servers). Local building codes may govern the minimum ceiling heights.

The physical environment of a data centre is rigorously controlled. Air conditioning is used to control the temperature and humidity in the data centre. ASHRAE's "Thermal Guidelines for Data Processing Environments"recommends a temperature range of 16–24 °C (61–75 °F) and humidity range of 40–55% with a maximum dew point of 15 °C as optimal for data centre conditions. The temperature in a data centre will naturally rise because the electrical power used heats the air. Unless the heat is removed, the ambient temperature will rise, resulting in electronic equipment malfunction. By controlling the air temperature, the server components at the board level are kept within the manufacturer's specified temperature/humidity range.

Air conditioning systems help control humidity by cooling the return space air below the dew. Too much humidity and water may begin to condense on internal components. In case of a dry atmosphere, ancillary humidification systems may add water vapour if the humidity is too low, which can result in static electricity discharge problems which may damage components. Subterranean data centres may keep computer equipment cool while expending less energy than conventional designs.To prevent single points of failure, all elements of the electrical systems, including backup systems, are typically fully duplicated, and critical servers are connected to both the "A-side" and "B-side" power feeds. Data centres typically have raised flooringmade up of 60 cm (2 ft) removable square tiles. The trend is towards 80–100 cm (31–39 in) void to cater for better and uniform air distribution.

These provide a plenum for air to circulate below the floor, as part of the air conditioning system, as well as providing space for power cabling. A back up of batteries in a data centre providing power until diesel generators can start BILLING-The billing centre is responsible for processing the toll tickets generated by the VLRs and HLRs and generating a bill for each subscriber. It is also responsible for generating billing data of roaming subscriber. It is a part of NSS (Network and Switching Subsystem). Dotsoft is in-house developed software, integrating software, integrating the Commercial Activities, Telecom Billing& Accounting, FRS and Directory Enquiry. It has been implemented in SSAs across the country.

INTELLIGENT NETWORK

The Intelligent Network (IN) is the standard network architecture specified in the ITU-T Q.1200 series recommendations. It is intended for fixed as well as mobile telecom networks. It allows operators to differentiate themselves by providing value-added services in addition to the standard telecom services such as PSTN, ISDN and GSM services on mobile phones. The intelligence is provided by network nodes on the service layer, distinct from theswitching layer of the core network, as opposed to solutions based on intelligence in the core switches or telephone equipment. The IN nodes are typically owned bytelecommunications operators (telecommunications service providers).IN is supported by the Signalling System #7 (SS7) protocol between telephone network switching centres and other network nodes owned by network operators. Services provided by IN are Televoting Call screening.

Telephone number portability Toll free calls/Free phone Prepaid calling Account card calling Virtual private networks (such as family group calling) Centrex service (Virtual PBX) Private-number plans (with numbers remaining unpublished in directories) Universal Personal Telecommunication service (a universal personal telephone number) Mass-calling service Prefix free dialling from cell phones abroad Seamless MMS message access from abroad. Reverse charging Home Area Discount Call distribution based on various criteria associated with the call Location Based Routing Time-based routing Proportional call distribution (such as between two or more call centres or offices). Call queuing Call transfer The initial use of IN technology was for number translation services, e.g. when translating toll free numbers to regular PSTN numbers. But much more complex services have since been built on IN, such as Custom Local Area Signalling Services (CLASS) and prepaid telephone calls.