Welcomes you to GSM Foundation Course.

Welcomes you to GSM Foundation Course

GSM Foundation Course Course Content Basic Telephony & Cellular
Principal of Cellular Communication GSM Features GSM Network Components GSM Terrestrial Interfaces Basic GSM Processes GSM Air Interface Radio Interface Optimization, Supplementary services & Contemporary Networks

ESSAR Telecom Telecom Service Provisions GSM Basic Internet ESSAR
GSM Service Provider in Punjab, Delhi, Rajasthan, U.P (East) & Haryana Basic Service Provider in the state of Punjab.

Service Industry Service Provider is not a Equipment Manufacturer.
The Service Provider has a license to operate in a geographical boundary (state/circle/ country). It buys equipment from OEM Suppliers (Vendors). Installs & commissions the equipment thus making it’s own Network. Provides the desired service to it’s subscribers.

ESSAR CELLPHONE Punjab Delhi Haryana Rajasthan U.P (East)
Coverage Area Punjab Delhi Haryana Rajasthan U.P (East)

ORGANISATION STRUCTURE
PROMOTERS TECHNICAL PLANNING IMPLEMENTATION OPERATIONS MARKETING CUSTOMER CARE SALES OPERATIONS SYSTEM SUPPORT BILLING IT ACTIVATIONS SUPPORT FUNCTIONS HR, ADMIN, ACCOUNTS

Basic Telephony Signaling Traffic Off Hook Dial Tone Dialing Digits
SWITCH / EXCHANGE Off Hook Dial Tone Dialing Digits RBT Conversation Ring Off Hook & Conversation

2 Mb E1 (PCM) E1 bit stream 1 1st TCH 15th TCH 16 17th TS 31 30thTCH
1 1st TCH 15th TCH E1 bit stream 16 17th TS Hz Sample Rate 8 kHz 8 bits per sample 64 kbps 31 30thTCH

Wireless Telephony BSC BTS Mobile Subscriber... MSC

Wireless Communication
Alternative means of wireless communication Walkie - Talkie Pagers Trunked private radios Mobile Phone - the magic technology that enables everyone to communicate anywhere with anybody.

Cellular Communication
Principles of Cellular Communication

Cellular Communication
A cellular system links Mobile subscribers to Public Telephone System or to another Mobile subscribers. It removes the fixed wiring used in a traditional telephone installation. Mobile subscriber is able to move around, perhaps can travel in a vehicle or on foot & still make & receive call.

Advantage of Cellular Communication
Mobility Flexibility Convergence Greater QOS Network Expansion Revenue/Profit

WHAT IS CELLULAR TELEPHONY ?
CONSIDERATIONS - FREQUENCY SUBSCRIBER DENSITY COVERAGE Base Station Base Station Base Station Base Station Base Station Base Station

The Cell Cellular Radio involves dividing a large service area into regions called “cells.” Each cell has the equipment to switch, transmit and receive calls. Cells - Reduce the need of High powered transmission Cells - Conventionally regarded as being hexagonal, but in reality they are irregularly shaped. Cell shape is determined by the nature of the surrounding area e.g. Hills , tall building etc.

The CELL What is a cell ? A cell is a certain area that can be reached with one transceiver or A small collection of transceivers on different channels at a single base site. BTS The hexagonal-shaped communication cells are artificial & are generated to simplify the planning & design of a cellular network.

Coverage & Capacity Coverage
Percentage of the geographical area covered by cellular service where mobile telephony is available Capacity - Number of calls that can be handled in a certain area within a certain period of time. Capacity can also refer to the probability that users will be denied access to a system due to the simple unavailability of radio channels.

Cell Size Large Cells 35 Km Remote Areas High Transmission Power
Few subscribers Small Cells Near about 1 KM Urban Areas Low Transmission Power Many Subscribers

MICRO CELL Below Rooftop ~ Railway Platforms, Airports,
~ Busy Shopping Bazaar etc. Low Tx Power ~ 1 Watt max. Limited Coverage ~ 200m - 500m Hotspot Solution Special Algorithms for HO

PICO CELLS Inside offices, Buildings Very Low Tx Power
~ Less than 1 Watt Limited Coverage ~ m Capacity Solution Special Algorithms for HO Pico Cell

Analog Mobile Telephony
End of 1980’s Analog Systems unable to meet continuing demands Severely confined spectrum allocations Interference in multipath fading environment Incompatibility among various analog systems Inability to substantially reduce the cost of mobile terminals and infrastructure required

Digital Mobile Telephony
Spectrum space - most limited and precious resource Solution - further multiplex traffic (time domain) Can be realized with Digital Techniques only.

Different Standards Worldwide
Till 1982 Cellular Systems were exclusively Analog Radio Technology. Advanced Mobile Phone Service (AMPS) U.S. standard on the 800 MHz Band Total Access Communication System (TACS) U.K. standard on 900 MHz band Nordic Mobile Telephone System (NMT) Scandinavian standard on the 450 & 900 MHz band

GSM History and Organization
1979 Europe wide frequency band reserved for Cellular 1982 “Groupe Speciale Mobile” created within CEPT 1986 GSM had full time in Paris 1988 ETSI takes over GSM Committee 1990 The phase 1 GSM Recommendations frozen 1991 GSM Committee renamed “Special Mobile Group” and GSM renamed as “ Global System for Mobile Communication” 1992 GSM is launched for commercial operations

GSM - IN CELLULAR TELEPHONY
Each Cell in the Cellular Network consists of one or more RF carriers. An RF carrier is a pair of radio frequencies One used in upward direction by MS - Uplink Other used in downward direction by BTS - Downlink The transmit and receive frequencies are separated by a gap of 45 MHz in GSM of 75 MHz in DCS. There are 124 carries in GSM Band. With each carrier carrying 7 timeslots, only 124 x 7 = 868 calls can be made! Frequency Reuse is the solution

dl ul Uplink-Downlink BTS Tx MS Rx BTS Rx MS Tx
Downlink = 935 to 960 MHz BTS Tx dl MS Rx Uplink = 890 to 915 MHz BTS Rx MS Tx ul

Frequency & ARFCN Ful(n) = 890.0 + (0.2) *n MHz Fdl(n) = Ful + 45 MHz
where n =ARFCN ; 1  n  124 dl= 935 to 960 MHz ul= 890 to 915 MHz

TDMA & FDMA T D M A 7 5 3 2 1 7 5 3 2 1 F D M A TDMA FRAME n+1
7 3 5 1 2 TDMA FRAME n+1 4.615 mS 7 3 5 1 2 T D M A TDMA FRAME n Uplink - MS Tx 890MHz to 915MHz F D M A Downlink - BTS Tx 935MHz to 960MHz 200KHz

GSM Burst & TDMA Frame FRAME 1 FRAME 2 1 2 3 4 5 6 7 1 2 3 4 5 6 7
1 2 3 4 5 6 7 1 2 3 4 5 6 7 GUARD PERIOD GUARD PERIOD Information Training sequence Information TAIL BITS TAIL BITS

Frequency Reuse Pattern
Three types of frequency reuse patterns 7 Cell reuse pattern 4 cell reuse pattern 3 cell reuse pattern

FREQUENCY RE - USE Frequency Re-use D/R = (3N)1/2 7/21 cell cluster
Two re-use distances 2 7 3 D/R = (3N)1/2 1 D 6 4 Cell Dia = R where N is Cluster size 5 7/21 cell cluster

Principal Of Sectorization
Omni Directional Cells 120 degree Sectors 60 Degree sectors Each Sector in a Site has its own allocation of Radio Carriers. Advantage By frequent reuse of frequency more capacity can be achieved.

Cell Sectorisation b1 b2 b3 a2 a1 a3 a3 a6 a4 a5 120O CELLS OMNI CELL
3 ANTENNAS OMNI CELL 1 ANTENNA a2 a1 a3 a3 a6 a4 a5 60O CELLS 6 ANTENNAS

3 Site Reuse Pattern c2 c1 c3 b2 b1 a2 b3 a1 a3 c2 c1 Cell Re-use c3

Cellular Planning Steps
Cellular Topology Cell splitting & Cell Repeat Patterns 3 cluster site 3/9 cell cluster 4 cluster site 4/12 cell cluster Sites in the middle

GSM Antennas Directional Antennas Vertically Polarized.
Collinear Dipole Array with 8 to 12 elements. Beam Width 45o, 60o, 90o. High Gain Antennas with gain of 16 to 18 dbi. Mechanically/Electrically Downtiltable.

FEATURES OF GSM

Features of GSM Compatibility Noise Robust
Increased Capacity & Flexibility Use of Standard Open Interfaces Improved Security & Confidentiality Cleaner Handovers Subscriber Identification ISDN Compatibility Enhanced Range of Services

Compatibility With rapid Developments there was a need for a common Standard for Mobile Communication. With GSM, one could drive from Germany to Spain without a Call Drop. Due to versatility of GSM, it was adopted by many countries, even outside Europe.

Noise Robust To combat the problems due to Noise-
Digital Interface is used. Digital Interface Protect these errors using Error Detection & Correction Techniques. Immune to higher levels of noise and interference Improvements in Quality as well as Efficiency- Robust Air Interface.

Increased Capacity and Flexibility
Analogue Air Interface Every connection requires a separate RF carrier and thus RF hardware. System Expansion Time Consuming Costly & Labor Intensive. Intricate RF Planning. Digital Interface 8 simultaneous conversations on one RF carrier.

Standardized Open Interfaces
Low Price Uses standard interfaces like C7, X.25 etc. Versatility to choose equipment from different manufacturer thereby reducing the pricing monopoly. Flexibility Great flexibility in situating Network components because of Standard Interfaces. Efficient use of terrestrial links.

Better Security & Confidentiality
High Security risk for Analogue System operators. GSM No Eavesdropping High speech and data confidentiality. Digitized, Encoded and Encrypted (A8 algorithm) Subscriber Authentication (A3 algorithm)

Cleaner Handovers The mobile measures up to 32 adjacent cells for
Signal Strength (RxLevel) Signal Quality (RxQual) updated every 480 mS and sends to BTS Sophisticated Handover based on RxLevel Interference RxQual Timing Advance Power Budget

Handovers Base Station 2 Base Station 3 Base Station 1

ISDN Compatibility ISDN (Integrated Services Digital Network)
Advanced Telecom Network designed to carry voice and user data over the standard telephones lines. 2B+D Signalling and information on ISDN line. The GSM Network is designed to operate within the ISDN System. GSM provides features compatible with ISDN.

Don't be afraid to ask !!!

GSM NETWORK ELEMENTS

GSM NETWORK ELEMENTS ME SIM MS HLR VLR EC PSTN AUC MSC EIR IWF
Network Switching System ME TRAU BSC SIM BTS BSS MS

GSM Network Components
Mobile Station consists of two parts- Mobile Equipment (ME) Subscriber Identity Module (SIM) ME Hardware e.g. Telephone, Fax Machine, Computer. SIM Smart Card which plugs into the ME. NETCOMP

Mobile Equipment (ME) ME are of three types- Vehicle Mounted
Portable Mobile Unit Handportable Unit ME’s have distinct features-Classmarks sent in initial message to Network. NETCOMP

ME (Classmark Information)
Revision Level Phase of the GSM specs ME comply with. RF Power Capability Max power ME is able to Transmit. Ciphering Algorithm Used Presently A5 Phase 2 specifies Algorithms A5/0 to A5/7. Frequency Capability SMS Capability NETCOMP

Mobile Equipment 1 20 W 2 8 W 3 5 W 4 2 W 5 0.8 W Typical Settings
Class Power O/p W 2 8 W 3 5 W 4 2 W W Typical Settings NETCOMP

SIM The SIM stores Subscriber Interface Identity Module
Subscriber Parameters Personal Data for identifying Subscriber to the Network. IMSI,, MSISDN, PIN, PUK, Ki, A3, A8 (for Kc generation) Space reserved for TMSI & LAI Full Size SIM Card Small SIM NETCOMP

SIM - Internal Structure
EEPROM ROM Basic Operating System 16 to 24 kB User Data 16 kB I/O 8 CPU RAM Working Area for CPU 256 to 512 bytes NETCOMP

SIM(IMSI) IMSI(International Mobile Subscriber Identity) IMSI
Transmitted over Air Interface on initialization Permanently stored on SIM card 15 digit Decimal MCC (3) MNC (2) MSIC (10) IMSI NETCOMP

SIM (LAI) LAC MCC MNC CI 0-65535 LAI (Location Area Identity)
MCC 3 digit number (BCD), two Octets ( A & B) MNC 2 digit number (BCD), one Octet LAC 3 digit number (Binary) , two Octets CI 5 digit number (Binary) , two Octets LAC MCC MNC CI NETCOMP

SIM MSISDN 10 digit number to which a subscriber is being called.
PIN (Personal Identification Number) Four digit PIN An internal security to Protect the SIM from illegal use. Card blocks itself after three wrong entries PUK (Personal Unblocking Key) 8 digit code to unblock the SIM Card Ki (Authentication Key), A3 & A8 Algorithms NETCOMP

SIM (TMSI) Temporary Mobile Subscriber Identity
Periodically changed by the System Management on instances like location update etc. Reason for use of TMSI To prevent a possible intruder from identifying GSM users, TMSI is used Management Assignment, Administration & Updating is performed by VLR. NETCOMP

Transcoder Converts 64 Kbps PCM circuits from MSC to 16 Kbps BSS circuits. Each 30 channel 2 Mbps PCM link can carry 120 GSM - specified voice channels. NETCOMP

Transcoder MSC BSS XCDR 1 2 3 4 1 2 3 4 30 Channel PCM 120 GSM TCH
NETCOMP MSC BSS XCDR 30 Channel PCM 1 2 3 4 120 GSM TCH 1 2 3 4 Transcoder Information from FOUR calls (4x16 KBPS put into ONE 64 KBPS timeslot

Transcoder is collocated with MSC so as to reduce the number of
Generally, Transcoder is collocated with MSC so as to reduce the number of 2 Mbps A-links to efficiently use the BW.

Base Station System (BSS)
BSS (Base Station System) BSC (Base Site Controller) BTS (Base Transceiver Station) XCDR (Transcoder) Network Switching System (NSS) XCDR BSC BTS BTS NETCOMP

Base Station System (BSS)
BSC Controls upto 40 BTS Conveys information to/from BTS Connects terrestrial circuits & Air Interface Channels Controls handovers between BTSs under itself BTS Contains RF Hardware Limited control functionality 1 - 6 carriers in a BTS Cabinet simultaneous calls per BTS BTS NETCOMP

A BTS Cabinet NETCOMP INNER VIEW OUTER VIEW

BSS Configuration Collocated BTS Remote BTS Daisy Chain BTS
Star Configuration Loop Configuration BTS NETCOMP

Daisy Chain Configuration
BSC BTS BTS All BTS on 1 E1 BTS NETCOMP

Star Configuration BTS BTS BSC BTS BTS NETCOMP

Loop Configuration BTS BTS BSC BTS Loop Configuration BTS NETCOMP

Network Switching System(NSS)
NSS (Network Switching System) MSC (Mobile Switching Centre) HLR (Home Location Register) VLR (Visitor Location Register) EIR (Equipment Identity Register) AUC (Authentication Centre) IWF (Interworking Function) EC (Echo Canceller) MSC NETCOMP

MOBILE SWITCHING CENTRE
NETCOMP

GSM Network Component MSC Call Switching
Operation & Management Support Internetwork Interworking Collects call billing data Gateway MSC MSC which provides interface between PSTN & BSS’s in the GSM Network. NETCOMP

Home Location Register (HLR)
Reference database for the Subscriber profiles- Subscriber ID (IMSI & MSISDN) Current VLR Address Supplementary Services subscribed Supplementary Service Information Subscriber Status (Registered/deregistered) Authentication Key and AUC functionality TMSI MSRN NETCOMP

Visitor Location Register (VLR)
Temporary Data, which exists as long as the subscriber is active in a particular Coverage area. Contains the following- Mobile Status (Busy/ Free/ No Answer/etc.) Location Area Identity (LAI) TMSI MSRN (Mobile Station Roaming Number) NETCOMP

Equipment Identity Register (EIR)
Contains Database for validating IMEI White List (valid ME) Black List (Stolen ME) Grey List (Faulty ME) NETCOMP

Inter Working Function
Provides function to enable the GSM System to interface with Public/Private Data Networks. The basic feature of the IWF are Rate Conversion Protocol adaptation IWF incorporates Modem Bank. e.g. GSM DTE PSTN DTE IWF Analogue Modem NETCOMP

Echo Canceller Echo is apparent only in Mobile - Land conversation & is generated at the 2 wire to 4 wire interface. To avoid it, Echo Canceller (EC) is used. Echo is irritating to MS Subscriber Total Round Trip delay of 180 ms in the GSM system EC is placed on the PSTN side of the Switch Cancellation up to 68 ms with EC NETCOMP

Operation & Maintenance Centre
Event & Alarm Management Fault Management Performance Management Configuration Management Security Management

Operation & Maintenance Centre
The OMC has access to the (G)MSC, BSC. Handles error messages being reported from the Network Controls the traffic load of the BSC, and the BTS.

NETWORK MANAGEMENT CENTRE
NETWORK MANAGEMENT CENTRE (NMC) Offers Hierarchical Regionalised Network Management of a complete GSM system. Functionality of the NMC Monitors Nodes on the Network Monitors Network Element Statistics Monitors OMC regions & provides information to OMC staff Enables Long Term Planning for entire Network MMI RAM> MMI RAM> MMI RAM>

NETWORK MANAGEMENT CENTRE
NMC OMC OMC OMC REGION 3 REGION 2 REGION 1 NETWORK

GSM Terrestrial Interfaces
Broadly classified into two types of interfaces- Standard Interfaces 2 Mbps Trunks (E1) Signalling System No. 7 SS7 ( CCS7) X.25 (Packet Switched Mode) GSM Interfaces

GSM Interfaces Um MS - BTS Abis BTS - BSC A BSC - MSC B MSC - VLR
C MSC - HLR D VLR - HLR E MSC - MSC F MSC - EIR G VLR - VLR H HLR - AUC

BASIC PROCESSES

Basic Processes AUTHENTICATION CIPHERING REGISTRATION
CALL ESTABLISHMENT HANDOVER / HANDOFF ROAMING

AUTHENTICATION ALGORITHM
Ki HLR SRES AUTH. ALGORITHMS NSS COMPARE AUC A3 RAND AIR INTERFACE RAND SRES SIM Ki AUTH. ALGORITHMS MS MS A3

A8 Ciphering RAND Ki Kc A5 algorithm is used.
Data protection is required on air interface. A5 algorithm is used. A specific key called Ciphering Key (Kc), is generated from RAND and A8 algorithm. A8 is on the SIM. A8 RAND Ki Kc

Ciphering Kc Kc Ciphered Data A5 A5 Data Data

ROAMING PSTN MSC HLR INDIA ME MSC VLR UK ME

ROAMING The mobile roams to another country (UK) and requests a Location Update when switched ‘ON’. The VLR (UK) informs the home HLR (India) of the mobile’s new location (UK). The HLR updates its location information and sends the subscriber information to the VLR (UK). The HLR requests the subscriber information be removed from the VLR (India). The VLR (India) acknowledges, and removes the subscriber information from its database. After the mobile’s registration is completed in UK’s MSC/VLR, the mobile is able to use network services (MOC, MTC etc.)

Transmission Media Access Network Backbone Network
Microwave 15 /23 GHz Backbone Network Microwave 7 GHz Optical Fibers Leased Line( From Dot or any other service provider on any media)

Access Microwave ( 15 GHz)
to MHz and to MHz 4 QAM & 16 QAM Modulation Split Mount Version with Hot Standby Facility Bandwidth ranging from 1.25 MHz to 28 MHz depending upon Data Rate and Modulation type 4 E1 Radio with 3 spot frequencies in our case

Backbone Microwave (7 GHz)
7.125 to MHz and to MHz 4 QAM & 16 QAM Modulation Split Mount Version with hot standby facility Bandwidth ranging from 1.25 MHz to 28 MHz depending upon Data Rate and Modulation type 16 E1 Radio with 1 spot frequencies in our case

Optical Fiber Low Losses 0.5 dB/km & High Data Rates Types of Fiber
Step Index Graded Index Graded Index are better. Modes of Light in fiber Mono Mode Multi Mode Mono Mode has less losses than Multi Mode.

Optical Fiber Different Possible Combinations
Mono Mode Step Index 10 / 125 m Mono Mode Graded index Multi Mode Step Index 100 / 300 m Multi Mode Graded Index 75 / 130 m Mono Mode Graded Index would have been the best but fabrication not possible 140 Mbps OLTE , Mono Mode Step Index in our case

LOGICAL CHANNELS PHYSICAL CHANNELS

Channels On Air Interface
Physical Channel Logical Channel Physical channel is the medium over which the information is carried. Logical channels consists of the information carried over the Physical Channel.

TDMA & FDMA T D M A 7 5 3 2 1 7 5 3 2 Uplink - MS Tx 1
7 3 5 1 2 TDMA FRAME n+1 4.615 mS 7 3 5 1 2 T D M A TDMA FRAME n Uplink - MS Tx 890MHz to 915MHz Downlink - BTS Tx 935MHz to 960MHz F D M A 200KHz

LOGICAL CHANNELS 3 1 2 3 4 5 6 7 Normal Burst TDMA Frame
57 encrypted 26 training 1 S 3 T 8.25 GP Normal Burst 577S 1 2 3 4 5 6 7 TDMA Frame 577S x 8 = 4.615mS 26 Frame Multi-frame

BURST Time is divided into discrete periods called “Timeslots”
The Time Slots are arranged in a sequence , conventionally numbered 0 to 7. Each repetition of this sequence is called a TDMA Frame. The information content carried in one time slot is called a “burst”.

Used to indicate beginning and end of the burst.
Information Main Area where the Speech, Data or Control info is held Guard Period To enable the burst to hit the time slot (0.031ms) Stealing Flags 2 bits are set when TCH is to stolen by a FACCH Training Sequence For estimation of transfer characteristics of physical media Tail Bits Used to indicate beginning and end of the burst.

Five Types of Burst Normal Burst Frequency Correction Burst
Traffic & Control Channels Bi-directional Frequency Correction Burst FCCH Downlink Synchronization Burst SCH Downlink Dummy Burst BCCH Carrier Downlink Access Burst RACH Uplink

GSM Logical Channels TCH Control Channels SACCH FACCH BCCH CCCH ACCH
DCCH

LOGICAL CHANNELS 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 TDMA Frame 26 Frame Multi-frame

Frames & Multiframes Several Logical channels share one time slot.
Individual channels are sequenced, & each channel gets the time it requires. Sequence is carried out using Multiframes. Traffic Channel occupy a 26-frame multiframe (120 ms) Control Channel occupy a 51-frame multiframe (235 ms).

Traffic Channels - TCH TCH TCH DATA TCH / FS TCH / HS 9.6 2.4 4.8
SAACH FACCH

Synchronizing Channels
BCCH Channel CCH Broadcast Control Channel - Downlink only BCCH Synchronizing Channels BCCH SCH FCH

BCCH Transmitted at all times & conveys information about Cell Timing and Configuration BCCH, FCCH, SCH CCCH Used by BSS & MS when trying to initiate a connection over the air RACH, PCH, AGCH, CBCH

DCCH Used to convey signaling information during call setup SDCCH ACCH Used to transmit signaling information when a call is in progress FACCH & SACCH

ACCH SAACH Conveys Power Control & Timing Information in the downlink direction. RSSI and Quality reports in the uplink direction. FACCH To carry out user authentication and handovers. It steals the TCH burst and inserts its own information.

Acronyms BCCH Broadcast Control Channel CCCH Common Control Channel DCCH Dedicated Control Channel ACCH Associated Control Channel SDCCH Standalone Dedicated Control Channel RACH Random Access Channel PCH Paging Channel AGCH Access Grant Channel

BCCH Location Area Identity List of neighbouring cells, to be monitored List of frequencies used in the cell Cell Identity Power Control Indicator DTX permitted Access Control (e.g emergency calls, call barring)

Always transmitted at constant power at all times Dummy burst are sent to ensure continuity when no traffic information is sent. FCCH Mobile corrects the frequency of its internal time base by reading this logical channel. Easily detected by the mobile. After FCCH, mobile is able to detect SCH which contains timing information.

SCH Carries the information for mobile to synchronize to the TDMA frame structure & know the timing of the individual timeslots. Frame Number & BSIC (Base Station Identity Code) CCCH RACH Transmitted by the Mobile when it wishes to gain access to the system

PCH Transmitted by the BTS when it wishes to contact a specific mobile. AGCH Transmitted by the BTS to assign dedicated resources to an MS such as SDCCH CBCH To transmit messages to all mobiles within a cell. CBCH will steal some time of an SDCCH to do this.

Channel Combinations SDCCH8 + SACCH8
Full rate Traffic Channel Combination TCH8/FACCH + SACCH Broadcast Channel Combination BCCH + CCCH Dedicated Channel Combination SDCCH8 + SACCH8 Combined Channel Combination BCCH + CCCH + SDCCH4 + SACCH4

Channel Combinations (Timeslots)
Traffic Channel Combination TCH8/FACCH +SACCH Can be on any Time slot Broadcast Channel Combination BCCH +CCCH Can be on Timeslot 0, 2, 4, 6 Dedicated Channel Combination SDCCH8 + SACCH8 Any Time slot Combined Channel Combination BCCH + CCCH +SDCCH4 + SACCH4 Can only be on 0 Timeslot

TCH Multiframe I D L E 5 10 15 20 SACCH Downlink & Uplink SACCH

BCCH/CCCH Multiframe BCCH/CCCH
In Downlink direction the timeslot (physical channel) is shared by a different logical channels. In the Uplink direction all timeslots are allocated to RACH.

BCCH/CCCH Multiframe Downlink to MS 10 20 30 40 50 Uplink from MS 10
10 20 30 40 50 F S I CCCH 8 TS 4 TS BCCH Uplink from MS R 10 20 30 40 50

Combined Multiframe BCCH and SDCCH share a common timeslot
Less No. of subscribers support (as only 4 SDCCH) 102 frame structure Superframes And Hyperframes 1326 TDMA frames (26*51) make a superframe 2048 superframes make one hyperframe, after which ciphering and frequency hopping algorithm are restarted.

Combined Multiframe Downlink to MS 10 20 30 40 50 Uplink from MS 10 20
BCCH CCCH 4 TS F S CCCH 8 TS F S D0 D1 F S D2 D3 F S A0 A1 I F S BCCH CCCH 4 TS F S CCCH 8 TS F S D0 D1 F S D2 D3 F S A2 A3 I 10 20 30 40 50 Uplink from MS D3 R R A0 A1 R R R R R R R R R R R R R R R R R R R R R R R D0 D1 R R D2 D3 R R A2 A3 R R R R R R R R R R R R R R R R R R R R R R R D0 D1 R R D2 10 20 30 40 50

SDCCH Multiframe Downlink to MS 10 20 30 40 50 Uplink from MS 10 20 30
10 20 30 40 50 Uplink from MS I I I A0 A1 A2 A3 D0 D1 D2 D3 D4 D5 D6 D7 I I I A5 A6 A7 D0 D1 D2 D3 D4 D5 D6 D7 A4 10 20 30 40 50

Voice Coding LPC RPE LTP 20 mS Class Ia Class Ib Class II
104 kbps 20 mS Sample Rate 8 kHz 13 bits per Sample 160 Samples 2080 bits LPC RPE Class Ia Class Ib Class II 50 bits 132 bits 78 bits Divided into 4 Blocks of 40 Samples each Reduction in Data Speech Encoder selects Block with Most Energy Block - 1 : 1, 5, 9 ….. Samples Block - 2 : 2, 6, 10, …… Samples & so on for Block - 3 & Block - 4. LTP

Channel Coding Error Protection And Detection
To protect the logical channel from transmission errors by the radio path, different coding schemes are used. Coding & Interleaving Schemes dependent upon logical channel to be encoded. 3 Coding Protection schemes Speech Channel Encoding Control Channel Encoding Data Channel Encoding

Speech Channel Coding Speech Information of 20 ms block is divided over 8 GSM burst. 260 bits are grouped in three classes depending upon the intelligible part of speech After encoding 456 bits block is interleaved

Speech Channel Coding Class 1a 50 bits Class 1b 132 bits Class 2
Parity Check Tail Bits 50 3 132 4 Convolutional Coding Convolutional Code 378 78 378 78 456 bits

Control Channel Encoding
Block of 184 bits received by BTS Bits are protected by Cyclic Codes of Class Fire Codes Adds 40 Parity Bits 4 Tail Bits are added Convolution Coding is done O/p from 184 Signalling bits is 456 bits.

Control Channel Coding
184 Coding 184 40 Parity Bits 4 TB Convolutional Coding 456 456 bits

Data Channel Coding 240 184 4 Convolutional Coding 488 Punctuate 456

Interleaving Responsible for Robustness of the GSM air interface
% burst destroyed or corrupted on the air interface. Spreads the content of one information block across several TDMA timeslots. Two types of Interleaving - Diagonal Interleaving Rectangular Interleaving

DIAGONAL INTERLEAVING SPEECH
Speech Blocks EIGHT blocks of 57 bits, Sent on 8 ALTERNATE timeslots 456 bits 456 bits 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7

RECTANGULAR INTERLEAVING CONTROL CHANNEL
Data Blocks 456 bits FOUR blocks of 114 bits, Sent on 4 timeslots 114 Bits Odd 114 Bits Even 114 Bits Odd 114 Bits Even 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7

Interleaving Interleaving Depths Speech - 8 blocks Control - 4 blocks
Data - 22 blocks Speech & Data blocks are diagonally interleaved Control block is rectagularly interleaved

Interleaving TRAU Frame Type Number of GSM Burst Spread Over Speech 8
Control 4 Data 22 TRAU = Transcoder Rate Adaption Unit

Call Sequence

MOBILE TO LAND PSTN BTS BSC MSC

Multiple Point of Interconnect
CITY A 7 GHz BACKBONE POI TRAFFIC BSS TRAFFIC CITY B BSS TRAFIC POI TRAFIC

Call Scenarios Mobile to Mobile Intra-city Inter-city Mobile to Land
Land to Mobile

Mobile To Land Sequence
MS BSS MSC VLR HLR PSTN EIR RACH 1 CHANNEL REQUEST AGCH DCCH ASSIGN 2 SIGNALLING LINK ESTABLISHED CR 3 REQUEST FOR SERVICE SDCCH 4 AUTHENTICATION CC 5 SET CIPHER MODE 6 SET-UP SDCCH Call Info 7 EQUIPMENT ID REQUEST

INITIAL & FINAL ADDRESS
MS BSS MSC VLR HLR PSTN EIR 8 COMPLELTE CALL SDCCH CALL PROCEEDING SDCCH (circuit) 9 ASSIGNMENT COMMAND (channel) ASSIGNMENT COMPLELTE FAACH INITIAL & FINAL ADDRESS (IFAM) (TCH) ASSIGNMENT COMPLETE (ACM) 10 ALTERING FACCH MS HEARS RINGTONE FROM LAND PHONE Hello! ANSWER(ANS) 11 CONNECT RING TONE STOPS FACCH BILLING STARTS FACCH CONNECT ACKNOWLEDGE TCH

Land to Mobile Sequence
MS BSS MSC VLR HLR GMSC PSTN Initial & Final Address Msg. (IFAM) MSISDN Send Routing Information IMSI MSISDN Routing Information Ack MSRN INITIAL & FINAL ADDRESS (IFAM) MSRN Send Info for I/c Call Setup MSRN LAI & TMSI PAGE PCH Paging Request TMSI TMSI RACH Channel Request AGCH DCCH Assign SDCCH Signalling Link Established SDCCH TMSI & Status Page Response TMSI status

Land to Mobile Sequence
MS BSS MSC VLR HLR GMSC PSTN Complete Call TMSI SETUP SDCCH CALL Confirmation SDCCH ADDRESS COMPLETE RingTone at Land Phone <SDCCH> Assignment Command Channel Circuit FACCH Assignment Complete Ringing Stops at Land Phone FACCH Alert Ring Tone at MS TCH FACCH Connect Subscriber Picks Up BILLING STARTS FACCH Connect ACK ANSWER TCH Hello

Mobile Initiated Call Clearing
MS BSS MSC VLR HLR PSTN FACCH 1 DISCONNECT PSTN RELEASE FACCH MOBILE RELEASE 2 PSTN RELEASE COMPLETE FACCH MOBILE RELEASE COMPLETE MS -MSC Signalling Released 3 CLEAR COMMAND FACCH CHANNEL RELEASE FACCH 4 DISC FACCH UA CLEAR COMPLETE 5 RLSD RELEASE COMPLETE

Inter-BSS Handover Sequence
MS BSS BSS MSC HLR PSTN SAACH 1 Periodic Measurement Reports 2 Handover Required TMSI Cct. Code 3 Handover Request HO ref No. 4 Handover Req Ack 5 Handover Command FACCH HO Ref No. 6 Information Interchange FACCH 7 Handover Complete 8 Clear Command SAACH 9 Periodic Measurements Reports

RADIO OPTIMISATION

Radio Interface Optimization
Transmission Timing Power Control VAD and DTX Multipath Fading Equalization Diversity Frequency Hopping

THREE TIMESLOT OFFSET Mobile Rx 1 2 3 4 5 6 7 1 2 3 4 5 6 7 3 TS
1 2 3 4 5 6 7 1 2 3 4 5 6 7 3 TS Offset Mobile Tx

TIMING ADVANCE BURST arrives LATE BURST sent early BURST arrives
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 BURST arrives LATE BURST sent early BURST arrives IN TIME T = 3.69S to 233S Cell Radius = 35km

Power Control In steps of 2dB Enhances Battery Life
Reduces Interference 13 dBm (min) 33 dBm (max) Cell Radius = 35km

Dis-Continuos Transmission
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7 VAD - Voice Activity Detection MS identifies presence/ absence of speech Generates Comfort noise DTX - Dis-Continuous Transmission MS does not TX during silence period

MULTI-PATH PROPAGATION

DIVERSITY Diversity Receiver Approx. 10 Wavelengths 3.3 meters

FREQUENCY HOPPING FN F4 F3 F2 FREQUENCY F1 F0 T I M E

FREQUENCY HOPPING Mobile Activity
1 2 3 4 5 6 7 Rx1 Mobile Rx 1 2 3 4 5 6 7 Rx2 Tx1 6 7 1 2 3 4 5 Mobile Tx 6 7 1 2 3 4 5 Tx2 MONITORING Other Cell

GSM FEATURES

Speech Services Telephony (13 kbps full rate)
Emergency Call (with/without SIM card in the Mobile Station) Short Message Services (SMS) Point to Point (128 Byte Max.) Cell Broadcast(75 bytes Max.) Dual Personal and Business Numbers. Allows calls to be made and billed, either to business or personal numbers.

Data Services (Bearer Services)
Data rates supported as of today are 2.4 Kbps 4.8 Kbps 9.6 Kbps

Supplementary Service - Call Waiting
Call in Progress PSTN Phone Another Mobile Calls. Kept Waiting ……...

Supplementary Services - Call Hold
1. Call in Progress 2. Put on Hold 3. Calls another Mobile

Supplementary Services - Call Forwarding
Voice Mail System Divert if All Calls Busy Not Reachable No Answer Another Mobile PSTN Phone Incoming Call

Supplementary Services
Calling Line Identification Present Absent Connect Line Identification Closed User Group - CUG Only incoming Only outgoing Operator Controlled Barring

Voice Mail System ANSWERING MACHINE

Voice Mail System MSC

Short Message Service SMSC MSC BTS

Short Message Service SMSC MSC
Point to Point Point to Multipoint MSC BTS

PRE - PAID SYSTEM SIM BASED Data on SIM Decrements with use
Over the air charging !!?? NETWORK BASED Data secure on with the network Over the air re-charging Features Inquiry Warnings …..

CONTEMPORARY NETWORKS
& FUTURE

SEPARATE GSM & WLL INFRASTRUCTER
CDMA BTS CDMA BSC PSTN FIXED LINE SWITCH CDMA BTS GSM BTS DUAL BAND / MODE HANDEST MSC GSM BSC GSM BTS

SEPARATE GSM & WLL INFRASTRUCTER
CDMA Coverage GSM Coverage Call Drop. Toggle to GSM GSM CDMA GSM + CDMA On WLL Still on GSM. Toggle to WLL DUAL BAND / MODE HANDEST Every individual is a WLL subscriber under any and only one CDMA BTS and is a regular subscriber for the rest of the GSM network in the whole of Punjab. The subscriber also has the advantage of roaming within & outside the country. GSM GSM

COMMON GSM & CDMA INFRASTRUCTER
A - INTERFACE CDMA BSC CDMA BTS PSTN MSC DUAL BAND / MODE HANDEST A - INTERFACE GSM BTS GSM BSC

IRRIDIUM BTS in the Sky LEO ~1400km
Inter Satellite Links GHz to 23.55GHz L-Band (1616MHz to MHz) Band Width MHz Use TDM/FDMA scheme World-Wide Coverage 60+ Now Operational Small Hand held terminals Dual Mobiles under development

Welcomes you to GSM Foundation Course.

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Welcomes you to GSM Foundation Course.

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