module 1- cellular communication.ppt

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Module 1 –Principles of Cellular Communication


Chapters1. Principles of Cellular Communications2. Features of GSM3. GSM Network Components4. Channels on Air – Interface5. Calls and Handover Sequence6. GSM Identities7. Network Organization


Chapter 1 : Principles of Cellular Communications Principles of Cellular Communications

1st and 2nd generation cellular systemModulation Techniques and Multiple Access TechniquesAdvantages of Cellular Communications

GSM Frequency Spectrum Introduction

Cell Size Large Cells Small Cells The Trade Off – Large v Small

Frequency Re-use Co-channel Interference Adjacent Channel Interference

Sectorization

Switching and Control


1st and 2nd Generation Cellular SystemsThe 1st Generation Cellular System

• The 1st mobile networks in early 1980s were analog modulation systems such as

• AMPS (Advanced Mobile Phone Systems) in the USA• TACS ( Total Access Control System) in the UK• C-Netz in Germany• Radiocom 2000 in France• NMT in Scandinavia

• These networks were planned to achieve maximum coverage with as few antennas as possible.

• In early networks , the emphasis was to provide radio coverage with little consideration for the number of calls to be carried. As the subscriber base grew, the need to provide greater traffic capacity had to be addressed.


Coverage, Capacity and Quality

• Coverage – Getting a usable radio signal to all areas in the network.• Capacity – Handling the call traffic generated by the subscribers• Quality – Low interference, few call drops etc.


The First Generation Problems• Problems with Analog systems included

• Limited Capacity – could not cope with increase in subscribers• Bulky Equipment• Poor Reliability• Lack of Security – Analog Signals could not be intercepted• Incompatibility between systems in different countries – no Roaming

• To improve on the analog systems , the European Conference of Posts and Telecommunications Administration (CEPT) established Group Special Mobile (GSM) to set a new standard.


The Second Generation - Digital• 1987: GSM agreed on a digital standard• The advantages of digital systems were

• Efficient Use of Radio Spectrum• Security for voice transmission• Possibilities of data transmission• Very large Scale Integrated ( VLSI) components along with smaller cheaper

handsets• Compatibility with ISDN land based networks

• The system developed became the Global System for Mobile Telecommunications (also GSM)


Modulation Techniques - Analogue• Analogue modulation is useful for illustrating how information can be

carried by a Radio wave as it is simple to visualize.• Frequency Modulation was used on first generation mobile systems, but it

is very insecure as it can be intercepted and decoded easily.

MODULATION• Process of putting a baseband signal onto a carrier wave.

• Analog Modulation Techniques

ModulatorBaseband signal Modulated Wave

Carr

ier


Modulation Techniques- Digital (PCM)• Before looking at the digital modulation techniques used in GSM, we must

first consider how the voice which is naturally an analog signal is converted into a train of digital pulses prior to being modulated on the radio wave.


Modulation Techniques- PCM• PCM allows us to reproduce speech sound waves accurately upto 4Khz.• The rate of sampling must be able to distinguish each peak and trough of

the highest frequency waveform.• The sampling must thus occur at 8 KHz ( twice each period of the

waveform) which results in 64Kbps data rate.


Modulation Techniques- SKM• Having turned the speech signal into digital pulses, we now need to

modulate these onto the radio wave. We will first look at a range of techniques known as Shift Key Modulation


Modulation Techniques- PSK• In shift key modulation techniques, some property of the wave is changed

each bit period to represent the data.• Various techniques differ in terms of what property is changed ( such as

the phase or frequency of the wave) and how many different states of this property can be distinguished (which determines how many actual bits of data are represented by each state change)


Modulation Techniques- BPSK, QPSK, 8 PSK• Here, the phase of the transmitted wave (compared to a reference state) is the

property which is changed each bit period.• In BPSK techniques, such as that used by GSM, only two phase states are used. Each

bit period thus represents only one actual bit of data.• QPSK and 8 PSK extend the technique to 4 and 8 phase states. Each bit period, thus

represents 2 (QPSK) or 3 (8PSK) actual data bits by mapping the different possible combinations onto the phase states.

• Note , the order in which the bit patterns are mapped onto the phase states. This is gray code in which only 1 bit changes between adjacent sates. Using this technique, helps to reduce errors.


Modulation Techniques- QPSK and 8 PSK• The phase states and their mapping onto bit patterns are often shown by

Constellation diagrams, where the angle around the circle represents the phase angle of the modulation.


Modulation Techniques- QAM• The above slide brings in the term ‘symbol’ which is used to distinguish the

changes of state (symbols) from the number of data bits they represent. Using 8 PSK for example , the data rate (in bits per seconds) will be 3 times the symbol rate (in symbols per second)

• The extension of this technique further is limited by the ability of the receiving equipment to resolve many different phase states in the short time span of the bit period.

• A similar modulation scheme is 16 QAM (Quadrature Amplitude Modulation) which combines 4 phase states and 4 Amplitude states to gibe 16 combinations allowing 4 bits to be represented by each symbol,

• Another limitation on PSK schemes is the sharp phase change at each bit period boundary. Sudden changes in the waveform require huge bandwidth to transmit and should be avoided.

• FSK and MSK provide ways of doing this.


Modulation Techniques- FSK

Simple FSK has a sharp transition at the bit period boundaries. By applying aGuassian filter to the data stream, the shift between the frequencies occurSmoothly.


Modulation Techniques- GMSKGuassian Minimum Shift Keying

• Data pulses are shaped using a Guassian filter:• Smoothes phase transitions• Gives a constant envelope

• Comparison of GMSK and QPSK

• GMSK requires greater bandwidth• QPSK reduces interference with adjacent carrier frequencies• GMSK is more power efficient - less battery drain from MS on uplink• GMSK has greater immunity to signal fluctuations

GMSK is used in GSMQPSK is used in CDMA


Multiple Access Techniques• Purpose: To allow several users to share the resources of Air Interface in

one cell

• Methods

• FDMA – Frequency Division Multiple Access• TDMA - Time Division Multiple Access• CDMA – Code Division Multiple Access

• Multiple Access Techniques are essential to allow more efficient use of the Radio Spectrum. 1st Generation system used only FDMA so that a complete radio carrier was allocated to a user throughout the call. This made poor use of the spectrum, but was all that was possible with an analog system


Multiple Access Techniques - FDMA


Multiple Access Techniques - TDMA

• TDMA became possible with digital systems such as GSM in which the data stream could be divided into bursts and allocated to a timeslot. By sharing access to the spectrum, the traffic capacity of the system is enhanced.

• GSM uses both FDMA to provide carriers and TDMA to share access to the carriers


Multiple Access Techniques - CDMACode Division Multiple Access (CDMA)

• Each user is assigned a unique digital code (pseudo-random code sequence)

• Code is used at Mobile Station and Base Station to distinguish different user’s signals

• Many users communications can be transmitted simultaneously over the same frequency band.

• Advantages• Very efficient use of spectrum• Does not require frequency planning

• Used in CDMA – One• Not used in GSM• Wideband CDMA techniques to be used in UMTS


Advantages of Cellular CommunicationCellular networks have many advantages over the existing “land” telephone

networks.There are advantages for the network provider as well as the mobile

subscriber.


GSM FrequenciesGSM 900 Frequencies• GSM systems use radio frequencies between 890-915 MHz for receive and between 935-960 MHz

for transmit, as shown below.• RF carriers are spaced every 200 kHz, allowing a total of 124 carriers for use. Other frequencies

between 917 MHz and 935 MHz are available for use by other (non-GSM) cellular systems.• A guard band of 2 MHz of unused frequencies between 915 and 917 MHz protects against

interference between the transmit and receive frequencies. Guard bands between GSM and non-GSM frequencies depend on the prevailing standards in the country concerned and on agreements reached by network operators. Any such guard bands are likely to be quite small; for example, the last carrier of the frequency range may be left unused.

• Transmit and receive frequencies are always separated by 45 MHz, and this fixed frequency gap reduces the possibility of interference.


GSM FrequenciesExtended GSM (EGSM)

• A further 10MHz of bandwidth on both transmit and receive allocations has now extended the GSM bandwidth as follows:


GSM FrequenciesDCS 1800 Frequencies• DCS1800 systems use radio frequencies between 1710-1785 MHz for receive and

between 1805-1880 MHz for transmit, as shown below.• RF carriers are spaced every 200 kHz, allowing a total of 373 carriers for use, with

one used as a guard band. • A guard band of 20 MHz of unused frequencies between 1785 and 1805 MHz protects

against interference between the transmit and receive frequencies.• There is a 100 kHz guard band between 1710.0 MHz and 1710.1 MHz and between

1784.9 MHz and 1785.0 MHz for receive, and between 1805.0 MHz and 1805.1 MHz and between 1879.9 MHz and 1880.0 MHz for transmit.



GSM FrequenciesPCS 1900 Frequencies• PCS1900 systems use radio frequencies between 1850-1910 MHz for receive and

between 1930-1990 MHz for transmit, as shown below. • RF carriers are spaced every 200 kHz, allowing a total of 299 carriers for use.• A guard band of 20 MHz of unused frequencies between 1910 and 1930 MHz

protects against interference between the transmit and receive frequencies. There is a 100 kHz guard band between 1850.0 MHz and 1850.1 MHz and between 1909.9 MHz and 1910.0 MHz for receive, and between 1930.0 MHz and 1930.1 MHz and between 1989.9 MHz and 1990.0 MHz for transmit.



Cell Size

The number of cells in any geographic area is determined by the number of MSsubscribers who will be operating in that area, and the geographic layout of the area (hills, lakes, buildings etc).

The Trade Off – Large vs Small Cells


Frequency Re-UseExample: A network provider has been allocated 48 frequencies to provide coverage over a large area, let us take for example Great Britain.As we have already seen, the maximum cell size is approximately 70 km in diameter,thus our 48 frequencies would not be able to cover the whole of Britain.To overcome this limitation the network provider must re-use the same frequencies over and over again, in what is termed a “Frequency Re-Use Pattern”.

• Co-channel Interference- This occurs when RF carriers of the same frequency are transmitting in close proximity to each other, the transmission from one RF carrier interferes with the other RF carrier.• Adjacent Channel Interference - This occurs when an RF source of a nearby frequency interferes with the RF carrier


Site Sectorization


Switching and Control• Having established radio coverage through the use of cells, consider what happens

when the MS is in motion (as MSs tend to be).• At some point the MS will have to move from one cell’s coverage area to another cell’s

coverage area.• To perform a handover, the network must know which neighbors cell to hand the MS

over to. • Handovers from one cell to another could be for a number of reasons (e.g. the signal

strength of the “serving cell” is less than the signal strength of a“neighbour cell”, or the MS is suffering a quality problem in the serving cell) and by handing over to one of its neighbours this may stop the quality problem.

• To ensure that we handover to the best possible candidate the MS performs measurements of its surrounding neighbor cells and reports its findings to the network.

• Regardless of the reason for a “handover” it has to be controlled by some entity, and in GSM that entity is the Mobile services Switching Centre (MSC).

• These are then analyzed together with the measurements that the network performs and a decision is made on a regular basis as to the need for a handover.

• When a handover is required the MS is informed which radio channels to go to to continue the call. In most cases the subscriber is unaware that a handover has occurred.


Chapters1. Principles of Cellular Telecommunications2. Features of GSM3. GSM Network Components4. Channels on Air – Interface5. Calls and Handover Sequence6. GSM Identities7. Network Organization


Chapter 2 : Features of GSM• GSM Cellular Structure and its compatibility

• Noise Robust

• Flexibility/Increased Capacity

• Use of Standardized Open Interfaces

• Improved Security and Confidentiality

• Flexible Handover Processes

• Enhanced Range Of Services

Speech Services Telephony Emergency Calls (with/without SIM Card inserted in MS) Short Message Service Point To Point Short Message Cell Broadcast Advanced Message Handling Service

• Supplementary Services


GSM Cellular Structure• The aim of a GSM System is to make best use of available frequencies

(spectrum) to provide

• Coverage – Getting a usable radio signal to all areas in the network.• Capacity – Handling the call traffic generated by the subscribers• Quality – Low interference, few call drops etc.

• The cellular structure allows the reuse of frequencies across the Network

• Planning the pattern of this re-use is a key part of the system design.


Compatibility• GSM has been specified and developed by many European countries

working in co-operation with each other. The result is a cellular system allowing you, for example, to drive from Germany to Spain without dropping your telephone call.

• Due to GSM standardization and features, it is accepted throughout the world.

• An additional advantage resulting from this is the large market for GSM equipment. This means that manufacturers can produce equipment in higher quantities and of better quality, and also, due to the number of manufacturers, a competitive and aggressive pricing structure exists. This has resulted in lower costs for the MS subscriber.


Noise Robust ( when compared with Analog)


Flexibility/Increased Capacity


Use of standardized Open Interfaces


Improved Security and Confidentiality


Flexible Handover Process• Handovers take place as the MS moves between cells, gradually losing the RF signal

of one and gaining that of the other.• The MS switches from channel to channel and cell to cell as it moves to maintain call

continuity. With analogue systems, handovers are frequently a problem area and the subscriber is only too well aware that a handover has occurred!

• When GSM was specified a great deal of thought went into the design and implementation of handovers. Although the GSM system is more complicated than analogue in this area, the flexibility of the GSM handover processes offer significant improvements which provide a much better quality of service to the subscriber.

• GSM provides handover processes for the following:• Quality (uplink/downlink).• Interference (uplink/downlink).• RF level (uplink/downlink).• MS distance.• Power budget.

• More handover algorithms have been developed for specific applications, such as microcellular, and are currently being implemented.


Flexible Handover Process


Speech Services


Supplementary Services


Circuit Switched Data Services

•Packet data Services like GPRS/Edge will be covered in detail in the subsequent modules


Roaming

• Allows subscribers to travel to different network areas, different countries – keeping the services and features they use at home.

• Billing is done through home network operator who pays any other serving network operator involved.

• Requires agreements between operators on change rates, methods of payment etc.

• Clearing house companies carry out data validation on roamer data records, billing of home network operators and allocation of payments.


Chapter 3: GSM Network Components• GSM Network Overview• Mobile Station (MS) • Mobile Equipment (ME) • Subscriber Identity Module (SIM) • Base Station System (BSS) • Base Station Controller (BSC)

Base Transceiver Station (BTS) • BSS Configurations • Transcoder (XCDR) • Network Switching System • Operations and Maintenance System (OMS)

Network Management Centre (NMC) Operations and Maintenance Centre (OMC)


GSM Network Components

The principle component groups of a GSM network are: The Mobile Station (MS)This consists of the mobile telephone, fax machine etc. This is the part of the network that the subscriber will see. The Base Station System (BSS)This is the part of the network which provides the radio interconnection from the MS to the land-based switching equipment. The Network Switching SystemThis consists of the Mobile services Switching Centre (MSC) and its associated system-control databases and processors together with the required interfaces.This is the part which provides for interconnection between the GSM network and the Public Switched Telephone Network (PSTN). The Operations and Maintenance SystemThis enables the network provider to configure and maintain the network from a central location


Mobile Station• The MS consists of two parts, the Mobile Equipment (ME) and an electronic ‘smart

card’ called a Subscriber Identity module (SIM). The ME is the hardware used by the subscriber to access the network. The hardware has an identity number associated with it, which is unique for that particular device and permanently stored in it. This identity number is called the International Mobile Equipment Identity (IMEI) and enables the network operator to identify mobile equipment which may be causing problems on the system. The SIM is a card which plugs into the ME. This card identifies the MS subscriber and also provides other information regarding the service that subscriber should receive.

• The subscriber is identified by an identity number called the International Mobile Subscriber Identity (IMSI). Mobile Equipment may be purchased from any store but the SIM must be obtained from the GSM network provider. Without the SIM inserted, the ME will only be able to make emergency calls.

• By making a distinction between the subscriber identity and the ME identity, GSM can route calls and perform billing based on the identity of the ‘subscriber’ rather than the equipment or its location.


BSS- BASE STATION SUBSYSTEM• The GSM Base Station System is the equipment located at a cell site. It comprises a

combination of digital and RF equipment. The BSS provides the link between the MS and the MSC.

• The BSS communicates with the MS over the digital air interface and with the MSC via 2 Mbit/s links.

• The BSS consists of three major hardware components:• The Base Transceiver Station – BTS

The BTS contains the RF components that provide the air interface for a particular cell. This is the part of the GSM network which communicates with the MS. The antenna is included as part of the BTS.

• The Base Station Controller – BSCThe BSC as its name implies provides the control for the BSS. The BSC communicates directly with the MSC. The BSC may control single or multiple BTSs.

• The Transcoder – XCDRThe Transcoder is used to compact the signals from the MS so that they are more efficiently sent over the terrestrial interfaces. Although the transcoder is considered to be a part of the BSS, it is very often located closer to the MSC.


Functions of BSC and BTS


Colocated and Daisy Chained BTS

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Transcoder Functionality• The Transcoder (XCDR) is required to convert the speech or data output from the

MSC (64 kbit/s PCM), into the form specified by GSM specifications for transmission over the air interface, that is, between the BSS and MS (64 kbit/s to 16 kbit/s and vice versa).

• The 64 kbit/s Pulse Code Modulation (PCM) circuits from the MSC, if transmitted on the air interface without modification, would occupy an excessive amount of radio bandwidth.

• This would use the available radio spectrum inefficiently.• The required bandwidth is therefore reduced by processing the 64 kbit/s circuits so

that the amount of information required to transmit digitized voice falls to a gross rate of 16 kbit/s.

• The transcoding function may be located at the MSC, BSC, or BTS.• As can be seen from the diagram in the next slide, although the reason for

transcoding was to reduce the data rate over the air interface, the number of terrestrial links is also reduced approximately on a 4:1 ratio.

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Transcoder Functionality


Functions of MSC , HLR and VLR


MSC Functions


Authentication Process


GSM INTERFACES

(A-ter+ A)


Network Mangement Centre


Functional Architecture


Chapter 4 :Channels on Air Interface• Physical and Logical Channels• Timeslots and TDMA Frame• Super Frame and Hyper Frame


Physical and Logical ChannelsThe physical channel is the medium over which the information is carried, in the case of a terrestrial interface. This would be a cable.

The logical channels consist of the information carried over the physical channel.

• GSM Physical Channels

• A single GSM RF carrier can support up to eight MS subscribers simultaneously. The diagram shows how this is accomplished. Each channel occupies the carrier for one eighth of the time. This is a technique called Time Division Multiple Access.

• Time is divided into discrete periods called “timeslots”. The timeslots are arranged in sequence and are conventionally numbered 0 to 7. Each repetition of this sequence is called a “TDMA frame”.

• Each MS telephone call occupies one timeslot (0–7) within the frame until the call is terminated, or a handover occurs. The TDMA frames are then built into further frame structures according to the type of channel. We shall later examine how the information carried by the air interface builds into frames and multi-frames and discuss the associated timing.

• For such a system to work correctly, the timing of the transmissions to and from the mobiles is critical. The MS or Base Station must transmit the information related to one call at exactly the right moment, or the timeslot will be missed. The information carried in one timeslot is called a “burst”.

• Each data burst, occupying its allocated timeslot within successive TDMA frames, provides a single GSM physical channel carrying a varying number of logical channels between the MS and BTS.


Timeslots and TDMA Frame


Physical and Logical Channels (contd)• Logical Channels:

There are two main groups of logical channels, traffic channels and control channels

• Traffic Channels (TCH)

The traffic channel carries speech or data information. The different types of traffic channel are listed below:

• Full rate• TCH/FS: Speech (13 kbit/s net, 22.8 kbit/s gross)• TCH/EFR: Speech (12.2 kbit/s net, 22.8 kbit/s gross)• TCH/F9.6: 9.6 kbit/s – data• TCH/F4.8: 4.8 kbit/s – data• TCH/F2.4 2.4 kbit/s – data

• Half rate• TCH/HS: speech (6.5 kbit/s net, 11.4 kbit/s gross)• TCH/H4.8 4.8 kbit/s – data• TCH/H2.4 2.4 kbit/s – data

Acronyms:TCH Traffic Channel

TCH/FS Full rate speech channelTCH/EFR Enhanced full rate speech

TCH/HS Half rate speech channelTCH/9.6 Data channel 9.6 kbit/sTCH/4.8 Data channel 4.8 kbit/sTCH/2.4 Data channel 2.4 kbit/s


Traffic Channels


Control Channels

• Control Channels

• Broadcast Control Channel• Common Control Channel• Dedicated control Channel


Control Channels


Broadcast Control Channel


Common Control Channel


Dedicated Control Channel


Channel Combinations and Timeslots


Mobile Activity – Transmit and Receive Timeslots


Process of change in state• Changing from an idle to active state will involve different

types of traffic cases:

• Location Updating• Call Set-up• Handover


Location Update• Need for Location Update

• It should be possible for the Ms to receive a call from the network at any time at any location.

• While the MS moves freely within a network, the network should know about its whereabouts, in terms of its location and the cell with which it is attached.

• The MS should update the network whenever it changes the location and is called “Location Update”

• There are 3 types of location updates• Location Update Normal• IMSI attach• Periodic Registration


Call Set-Up• Call Set-up can be classified into 2 major categories

• Call from MS (Mobile Originated Call)

• Call to MS (Mobile Terminated Call)


Handover• Handover takes place, when an active mobile changes cells.• The mobile always measures and sends the report regarding the

signal strength, quality etc. to the BSC.• BSC makes the decision to change cells based on the results

calculated in the location algorithm.• Locating algorithm will be mainly based on signal strength and

sometimes based on quality also.• There are 3 different types of Handovers

• Intra BSC Handover• Inter BSC Handover• Inter MSC Handover


Chapter 5 :GSM Basic Call Sequence


Call Sequence (MS to Land)


Call Sequence (Land to MS)


Mobile Initiated Call Clearing Sequence


Handover Sequence


Location Update Sequence


Authentication and Ciphering Sequence


Equipment Identification Sequence


GSM Identities• MOBILE STATION ISDN NUMBER (MSISDN)• INTERNATIONAL MOBILE SUBSCRIBER IDENTITY (IMSI)• TEMPORARY MOBILE SUBSCRIBER IDENTITY (TMSI)• INTERNATIONAL MOBILE EQUIPMENT IDENTITY (IMEI)• MOBILE STATION ROAMING NUMBER (MSRN)• LOCATION AREA IDENTITY (LAI)• CELL GLOBAL IDENTITY (CGI)• BASE STATION IDENTITY CODE (BSIC)


GSM IDENTITIES• MOBILE STATION ISDN NUMBER (MSISDN)

• A number, which uniquely identifies a mobile telephone subscription in the public switched telephone network numbering plan.

• These are the digits dialed when calling a mobile subscriber

• In GSM 900/1800, the MSISDN consists of the following:

• MSISDN = CC + NDC +SNCC = Country CodeNDC= National Destination Code

SN = Subscriber Number

• A NDC is allocated to each PLMN . In some countries, more than one NDC may be required for each PLMN.

• The international MSISDN number maybe of variable length.• The maximum length is 15 digits, prefixes not included.


GSM IDENTITIES• INTERNATIONAL MOBILE SUBSCRIBER IDENTITY (IMSI)

• The IMSI is a unique identity allocated to each subscriber to allow correct identification over the radio path and through the network.

• Is used for all signaling in the PLMN.• All network related subscriber information is connected to the IMSI.• The IMSI is stored in the SIM, as well as in the HLR and in the serving

VLR.• The IMSI consists of three different parts:

IMSI = MCC+MNC+MSIN

MCC= Mobile Country CodeMNC= Mobile Network CodeMSIN= Mobile Station Identification Number


GSM IDENTITIES• TEMPORARY MOBILE SUBSCRIBER IDENTITY (TMSI)

• Is a temporary number instead of IMSI, to identify a MS.

• Is used for subscribers confidentiality on the air-interface.

• Has only local significance (that is, within the MSC/VLR area).

• Is changed at certain events or time intervals.

• The TMSI structure can be chosen by each operator but should not consist of more than four octets (8 digits)


GSM IDENTITIES• INETRNATIONAL MOBILE EQUIPMENT IDENTITY (IMEI):

• Is used for equipment identification and uniquely identifies a MS as a piece of or assembly of equipment.

• The IMEI consists of the following

IMEI = TAC+FAC+SNR+spare TAC = Type approval Code. Determined by a central GSM

body FAC = Final Assembly code, identifies the manufacturer SNR= Serial number, an individual serial number of six

digits uniquely identifies all equipment within each TAC and FAC

spare= A spare bit for future use. When transmitted by the MS , this digit should be always zero.


GSM IDENTITIES• MOBILE STATION ROAMING NUMBER (MSRN)

• Is used during the call set up phase for mobile terminating calls.• Each mobile terminating call enters the GMSC in the PLMN. The call is

then routed by the GMSC, to the MSC, where the called mobile subscribers are located. For this purpose, a unique number (MSRN) is allocated by the MSC and provided to the GMSC.

• The MSRN is seized for the Call Set Up phase only and released immediately afterwards.

MSRN consists of three parts:MSRN = CC + NDC + SN

CC= Country Code

NDC= National destination codeSN= Subscriber Number


GSM IDENTITIES• LOCAL AREA IDENTITY (LAI)

• Used for paging, to indicate to the MS in which Location Area (LA), the MS is currently situated.

• Also used for location updating of mobile subscribers.• The LAI consists of the following

LAI = MCC+MNC+LAC

MCC= Mobile Country CodeMNC= Mobile Network CodeLAC= Location Area Code, the maximum length of the Lac is 16 bits, enabling 65,536 different location areas to be defined in one PLMN.


GSM IDENTITIES• CELL GLOBAL IDENTITY (CGI)

• Is used for cell identification within a location area.

• Done by adding a Cell Identity to the components of a LAI.

• CI has a maximum length of 16 bits

• CGI consists of

CGI = MCC+MNC+LAC+CI


GSM IDENTITIES• BASE STATION IDENTITY CODE (BSIC)

• Allows a mobile station to distinguish between different neighboring base stations

• BSIC consists of

BSIC = NCC +BCC

NCC= Network Colour Code (3 bits), identifies the PLMN. NCC does not uniquely identify the operator. NCC is primarily used to distinguish between operators on each side of a border.

BCC= base Station Colour Code (3 bits), identifies the base station to help distinguish between BTS using the same BCCH frequencies.


GSM IDENTITIES


Chapter 6 : Network Organization

Network Head / Circle Head

Planning ProjectsO and MOptimization NSS

ComplaintResolution


Planning Team• RF Team

• Coverage and Capacity Planning • Site Survey and Drive Tests• New Site Integration Database (Physical and Parameter)• RF Plan for Data Network

• Transmission Team• BSC Planning• Transmission Planning for New Sites and various interfaces• Fibre Planning

• Core Planning Team• Number of Core Nodes – MSCs and MGWs• Expansion Plan – All Core Nodes• Data Network Planning – Centralized core nodes


Optimization Team• RF Optimization

• Network KPIs and Quality• Daily Analysis of Statistics and Performance Reports• In Co-ordination with Planning Team

• Transmission Optimization• Interface Augmentation• Analysis of Outages due to Transmission Failures


Operations and Maintenance team• Maintenance of BTS and BSC• Maintain Network Uptime• Fault Rectification and Alarm resolution• Support to Projects Team• Analysis of critical faults in the network• Handling Power Outages


Projects Team• Build Up of new sites and other network elements• Build Up of Site Infrastructure• Installation and Commissioning of all nodes• Inventory Management


NSS Team• Core Optimization

• Interface Augmentation (Internal and External)• Core Equipment Maintenance• IN and VAS Support• Handling Alarm , Overload and Outage Conditions


Customer Complaint Resolution Team• Handling Network Complaint Resolution• Meeting Customers for Resolution• Reverting to Customer Care Teams• Ensuring customer satisfaction by Resolution


End of Module 1

module 1- cellular communication.ppt

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