GSM System Architecture 1

GSM interface 2

GSM Network Structure OMC MSC/VLR BSC E BIE PSTN A Abis ISDN PSPDN BTS BSS C Um F H HLR/ AUC EIR SC/VM MS MSS 3

Mobile Station ( MS ) Equipment used by mobile service subscribers for access to services. Mobile Equipment Subscriber Identity Module (SIM) Mobile stations are not fixed to one subscriber. A subscriber is identified with the SIM card. 4

Base Transceiver Station ( BTS ) Wireless transmission Wireless diversity Wireless channel encryption Conversion between wired and wireless signals Frequency Hopping BaseBand Unit: voice and data speed adapting and channel coding RF Unit: modulating/demodulating, transmitter and receiver Common Control Unit: BTS operation and maintenance 5

Base Station Controller ( BSC ) Managing Wireless network-BSS Monitoring BTS Controls: Wireless link distribution between MS and BTS Communication connection and disconnection MS location, handover and paging Voice encoding, transecoding (TC), rate, adaptation, The operation and maintenance functions of BSS. 6

Mobile Service Switching Center ( MSC ) holds all the switching functions manages the necessary radio resources, updating the location registration carrying out the inter-BSC and inter-MSC tender Inter-working with other networks (IWF). 7

Home Location Register ( HLR ) Manages the mobile subscribers database subscriber information part of the mobile location information 3 identities essential the International Mobile subscriber Identity the Mobile station ISDN Number the visitor location register (VLR) address 8

Visitor Location Register ( VLR ) Dynamically stores subscriber information needed to handle incoming/outgoing calls Mobile Station Roaming Number When a roaming mobile enters an MSC area. This MSC warns the associated VLR of this situation; the mobile enters a registration procedure through which it is assigned a mobile subscriber roaming number (MSRN) Temporary Mobile Subscriber Identity, if applicable The location area in which the mobile has been registered Data related to supplementary service parameters 9

AUC/EIR Authentication Center(s) (AUC) Providing the authentication key used for authorizing the subscriber access to the associated GSM PLMN. Equipment Identity Register(s) (EIR) Handling Mobile Station Equipment Identity 10

Overview: Function Layers of GSM-1 11

Protocol Stack Structure of GSM 12

TDMA Concept: channel is composed of a series of timeslots of periodicity. Different signal energies are distributed into different timeslots. The adjacent channel interference is restricted by connection choosing from time to time. So the useful signal is passed only in the specified timeslot. GSM adopts TDMA/FDMA mode channel width: 200KHz, each channel has 8 timeslots time User 3 User 2 User 1 Frequency 13

GSM Timeslot and Frame structure Frequency 200KHz time BP 15/26ms interval 14

GSM Spec 15

Frequency Resource EGSM900 : up: 880~890MHz down: 925~935MHz duplex interval: 45MHz bandwidth: 10MHz， frequency interval: 200KHz GSM900 : up: 890~915MHz down: 935~960MHz duplex interval: 45MHz bandwidth: 25MHz， frequency interval: 200KHz GSM1800 : up: 1710-1785MHz down: 1805-1880MHz duplex interval: 95MHz， working bandwidth: 75MHz， frequency interval: 200KHz GSM1900MHz: up:1850~1910MHz down:1930~1990MHz duplex interval: 80MHz， working bandwidth: 60MHz， frequency interval: 200KHz 16

Frequency Resource General Priority Single Band Network 900MHz High Which one? 900MHz High 1800MHz Low 1900MHz New Operator Reason Propagation Characteristic For Operator For Subscriber 17

Single Band Network Single Band 900MHz Dual Band 1800MHz Triple Band In a sense, the network determines the handsets can be selected. But nowadays, most handsets support dual band. 18

Single Band Network The higher the propagation frequency 900MHz Cell coverage radius : We know Propagation characteristic The higher the propagation frequency The higher the propagation loss The smaller the cell coverage radius. 900MHz 1800MHz 1900MHz 19

Timeslot and Frame structure 1 super high frame = 2048 super frame = 2715648 TDMA frame 2045 2046 2047 3 2 1 2044 49 47 48 50 24 25 BCCH 1 super frame = 1326 TDMA frame（6.12s） CCCH SACCH/TCH SDCH FACCH 1 multiplex frame = 26 TDMA frames（120ms） 1 multiplex frame = 51 TDMA frame 1 24 25 1 49 50 1 TDMA frame = 8 timeslot（120/26 = 4.615ms） 1 2 3 4 5 6 7 20

GSM Frame 21

Control Channel Frame 22

Time Slot Data Bursts 23

GSM Frame Structure 24

Physical Channel The physical channel adopts FDMA and TDMA techs. On the time domain, a specified channel occupies the same timeslots in each TDMA frame, so it can be identified by the timeslot number and frame number. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 25

GSM Speech 26

GSM Speech 27

Channel Type-Summary 14.4Kbit/s FR TCH (TCH/F14.4) Data CH 4.8Kbit/s FR TCH (TCH/F4.8) TCH 4.8Kbit/s HR TCH (TCH/H4.8) FR Voice Traffic Channel (TCH/FS) Voice CH Enhanced FR Traffic Channel (TCH/EFR) HR Traffic Channel (TCH/HS) channel FCCH (down) SCH (down) BCH BCCH (down) RACH (up) CCH CCCH AGCH (down) PCH (down) SDCCH DCCH FACCH SACCH 28

Traffic Channel Signaling Channel Channel Type BCH : Transmit voice and data Signaling Channel transmit the signaling and synchronous data between BTS and MS. BCH : Frequency Correction CHannel（FCCH） -- for MS error correction Synchronous Channel（SCH) -- for MS frame synchronization and BTS recognization Broadcasting Control CHannel（BCCH） -- broadcasting information(cell selection information, etc..) 29

Channel Type DCCH Self-help Dedicated Control Channel（SDCCH） for channel distribution information transmission Slow Associated Control Channel （SACCH） combined with one traffic channel or SDCCH, to transmit some specific information of user information Fast Associated Control Channel （FACCH） combined with one traffic channel, taking the same signal as SDCCH. It occupies the service channel to transmit signaling information. 30

Cell Mode Layout Omni-directional cell Adopt omni-directional antenna， the overall directional propagation characteristic is the same. Directional cell In general, cell with multi-sector is in common use. Every directional cell adopts directional antenna. 31

BTS Mode Capacity Note: TRX-transceiver,each TRX handles 1 frequency. When the traffic is very low, and no possibility for quick increment, Omni-directional cell is used in common. Otherwise, we suggest to adopt the sector cell. Note: TRX-transceiver,each TRX handles 1 frequency. Coverage Area Sector cell is often used to enlarge the cell coverage radius because of the higher antenna gain. For special coverage ,such as road coverage, two-sector cell is adopted firstly. 32

System capacity Erlang : GOS: the traffic intensity of a totally occupied channel (i.e. the call hour of a unit hour or the call minute of a unit minute). For example, the traffic of a channel occupied for 30 minutes in an hour is 0.5 Erlang) GOS: defined as the probability of call blocking or the probability when the call delay time is longer than a given queuing time. 33

Reasons for Interference The transmission path is very complex, ranging from the simple line-of-sight transmission to encountering such terrain as buildings, hills and trees. Wireless channels are extremely unpredictable. Abrupt drop, or fading, of signal strength in the land mobile wireless channel is quite common. The fading feature of the mobile channel depends on the radio wave propagation environment. Environmental factors: Terrain (mountains, hills, plains, water bodies, etc.); The quantity, heights, distribution and materials of buildings; The vegetation of the region; Weather conditions; Natural and artificial electromagnetic noises; Frequency; How MS is moved. 34

Interference Co-Channel Interference Adjacent Channel Interference Conception: the interference among the signals of co- channel cells is called co-channel interference. Result from : Frequency reuse Reduction method: co-channel cells must physically be spaced at a minimum interval to ensure adequate isolation of transmissions. Adjacent Channel Interference Conception: The signal interference from the frequency adjacent to that of the signal used is called adjacent channel interference. Reduction method: accurate filtering and channel allocation (maximizing channel intervals of the cell). Interval of frequency reuse inter-cell interference, such as C/I, C/A 35

Solution -Anti-interference FH technology Dynamic power control (DPC) Discontinuous Transceiving (DTX) Diversity receiving technique 36

Frequency Hopping Technique Reason: counteract Rayleigh Fading scatter interference among multiple calls Types: Base band frequency hopping keeps the transmission and receiving frequency of each carrier unit unchanged, but merely sends FU transmission data to different carrier units at different FN moments. radio frequency hopping controls the frequency synthesizer of each transceiver, making it hop according to different schemes in different time slots. 37

Discontinuous Speech Transmission (DTX) Two aims can be achieved by adopting DTX mode: lower the total interference electric level in the air save transmitter power. TRAU BTS BTS MS Speech frame 480 ms comfort noise frame 38

Diversity Reception Technique The multi-path propagation of radio signals causes magnitude fading and delay time. Space Diversity (antenna diversity) Polarization Diversity orthogonal polarization diversity. horizontal polarization and vertical polarization. Frequency Diversity The working principle of this technology is that such fading won’t take place on the frequency outside the coherence bandwidth of the channel. 39

Frequency Reuse “4 ´ 3” reuse mode: one group includes 3 sectors /site ,12 frequency which are distributed to 4 sites. Every site owns 3 frequency. 40

Frequency Reuse “3 ´ 3” reuse mode: one group includes 3 sectors /site ,9 frequency which are distributed to 3 sites. Every site owns 3 frequency. 41

Numbering Arrangement International Mobile Subscriber Identification number (IMSI) It identifies a unique international universal number of a mobile subscriber, which consists of MCC+MNC+MSIN. 1) MCC: country code, 460 2）MNC: network code, 00 or 01 3）MSIN: subscriber identification, H1H2H3H4 9XXXXXX, H1H2H3H4: subscriber registering place H1H2: assigned by the P&T Administrative Bureau (operator )to different provinces, to each province H3H4: assigned by each province/city the IMSI of user will be written into the SIM card by specific device and software and be stored into the HLR with other user information. 42

Mobile Subscriber ISDN Number（MSISDN） It is the subscriber number commonly used. China uses the TDMA independent numbering plan: CC+NDC+ H1H2H3H4 +ABC CC: country code, 86 NDC: network code, 135—139, 130 H1H2H3H4: HLR identification code ABCD: mobile subscriber number inside each HLR 43

International Mobile Equipment Identification code (IMEI) It will uniquely identify a mobile station. It is a decimal number of 15 digits. Its structure is: TAC+FAC+SNR+SP TAC=model ratification code, 6 digits FAC=factory assembling code, 2 digits SNR=sequence code, 6 digits SP=reserved, 1 digit 44

Mobile Subscriber Roaming Number (MSRN) The MSRN is temporarily distributed to the subscriber by the VLR according to the request by the HLR when this subscriber is called. The MSRN is released and can be assigned to other subscriber later. 　　 CC + NDC + 00 + M1M2M3 + ABC 　 CC: country code, 86 　　 NDC: mobile network code, 135—139, 130 　　 M1M2: same as the H2H3 of MSISDN 　　 ABC: 000 -- 999 Temporarily Mobile Subscriber Identification Number (TMSI) To insure the IMSI security, the VLR will assign an unique TMSI number for the accessed subscriber. It is used locally only and is a 4-byte TMSI number BCD code. 45