1. OMA GSM Fundamentals
ISSUE 4.0

2. Objectives Upon completion of this course, you will be able to:
Grasp basic idea of GSM system such as frequency spectrum, frequency reuse etc.
Grasp the structure of the GSM system and the protocol used.
Grasp certain numbers that refer to BSS
Grasp the 4 kinds of channel combination and understand the idea of multi-frame.
Know some radio techniques
Get the idea of EDGE
Page 2

3. References BSS Feature Description BSS Signaling Analysis Manual
BSC Technical Manual
Page 3

4. Contents Chapter 1 GSM System Overview Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
Page 4

5. GSM system overview
The GSM system is a frequency- and time-division cellular system, each physical channel is characterized by a carrier frequency and a time slot number
Cellular systems are designed to operate with groups of low-power radios spread out over the geographical service area. Each group of radios serve MSs presently located near them. The area served by each group of radios is called a CELL
Uplink and downlink signals for one user are assigned different frequencies, this kind of technique is called Frequency Division Duplex (FDD)
Data for different users is conveyed in time intervals called slots , several slots make up a frame. This kind of technique is called Time Division Multiple Access (TDMA)
Page 5

6. GSM Development 1989 Standard Protocol for GSM take effect 1991
GSM system began to provide service in Europe(2G)
System was named as Global System for Mobile Communication
1992
1994
Provide services for the whole world
1996
Micro Cell Technique is used in GSM system
Page 6

7. Cell Technique Macro Cell and Micro Cell
A certain radio coverage area formed by a set of transceivers that connected to a set of antennas is called a CELL.
Macro Cell
In the beginning , High-Power BTSs are adopted to provide services. The BTS covers a wider area , but its frequency utilization is not efficient. So , it can only provide a few channels for subscribers.
Micro Cell
Later the Low-Power BTS joins the system for getting a better service area with high capacity . At the same time it adopts the frequency reuse technique to improve the efficiency of the frequency utilization and also the whole capacity of the network.
Page 7

8. Multiple Access Technique
Multiple Access Technique allows many subscribers to use the same communication medium.
There are three kinds of basic Multiple Access Technique : FDMA , TDMA and CDMA.
GSM system adopt FDD-TDMA (FDMA and TDMA together).
Page 8

9. FDMA
FDMA uses different frequency channels to accomplish communication.
The whole frequency spectrum available is divided into many individual channels (for transmitting and receiving)，every channel can support the traffic for one subscriber or some control information.
Frequency
Time
Page 9

10. TDMA
TDMA accomplishes the communication in different timeslot.
A carrier is divided into channels based on time. Different signals occupy different timeslots in certain sequence , that is , many signals are transmitted on the same frequency in different time.
Frequency
Time
Page 10

11. CDMA
CDMA accomplishes the communication in different code sequences.
Special coding is adopted before transmission, then different information will lose nothing after being mixed and transmitted together on the same frequency and at the same time.
Frequency
Time
Page 11

12. The Frequency Spectrum
GSM 900
Uplink
MHz
Downlink
Duplex Separation: 45MHz
Channel Bandwidth: 200KHz
Page 12

13. The Frequency Spectrum
DCS 1800
Base Station Receive
MHz
Base Station Transmit
Duplex Separation: 95MHz
Channel Bandwidth: 200KHz
Page 13

14. The Frequency Spectrum
Range (MHz)
Uplink Frequency
Frequency Point Available
Downlink Frequency
GSM 450
450.4~457.6
460.4~467.6
Fu(n)= (n-259)
259<=n<=293
Fd(n)=Fu(n)+10
GSM 480
478.8~486
488.8~496
Fu(n)= (n-306)
306<=n<=340
GSM 850
824~849
869~894
Fu(n)= (n-128)
128<=n<=251
Fd(n)=Fu(n)+45
E-GSM 900
880~ ~960
Fu(n)= n
Fu(n)= (n-1024)
0<=n<=124
975<=n<=1023
R-GSM 900
876~915
921~960
955<=n<=1023
PCS 1900
1850~1910
1930~1990
Fu(n)= (n-512)
512<=n<=810
Fd(n)=Fu(n)+80
Page 14

15. Frequency Reuse
The frequency resource of mobile system is very limited.
The different Subscribers can use the same frequency in different places.
The quality of communication must be ensured.
Page 15

16. Frequency Reuse 2
7(Site)X 1(Cell) reuse 2 7 3 1 6 4 5
Page 16

17. Frequency Reuse 4 site X 3 cells reuse 7 5 3 1 11 9 6 8 2 4 10 12 R
Page 17

18. 1 1 2 3 Cell Types Omni-directional Cell 120 Degree Cell Omni 120
Page 18

19. Contents Chapter 1 GSM System Overview Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
Page 19

20. GSM-GPRS Network Component
PSTN
ISDN
MSC/VLR
GMSC
GSM /GPRS BSS
BSC MS
HLR/AUC
BTS
PCU
SS7
BSC
SMS system MS
BTS
GPRS Backbone
Internet,
Intranet
此页标题禁止有多级标题，更不要出现所在章节的名称。
此页标题要简练，能直接表达出本页的内容。
内容页可以除标题外的任何版式，如图、表等。
该页在授课和胶片＋注释中都要使用。
SGSN
GGSN
OMC CG BG
Other PLMN
BSS
NSS
Page 20

21. Interface Between Different Entities
PSTN
ISDN
MSC/VLR
GMSC
GSM /GPRS BSS A
Abis
BSC MS
HLR/AUC
BTS
C/D/Gs
PCU
SS7 Gb
BSC
SMS system MS Um
Gr/Gs/Gd/Ge Gc
BTS
Internet,
Intranet
GPRS backbone
此页标题禁止有多级标题，更不要出现所在章节的名称。
此页标题要简练，能直接表达出本页的内容。
内容页可以除标题外的任何版式，如图、表等。
该页在授课和胶片＋注释中都要使用。
SGSN Gi Ga
GGSN
OMC CG BG Gp
Other PLMN
BSS
NSS
Page 21

22. Mobile Station—MS MS=ME+SIM
International Mobile Equipment Identity (IMEI)
– Mobile Equipment
International Mobile Subscriber Identity (IMSI)
– Subscriber Identity Module
Page 22

23. Subscriber Identity Module – SIM
International Mobile Subscriber Identity (IMSI)
Temporary Mobile Subscriber Identity (TMSI)
Location Area Identity (LAI)
Subscriber Authentication Key (Ki)
SIM
Page 23

24. Base Station Subsystem – BSS
MSC
The Base Station Controller – BSC
The Base Transceiver Station – BTS
The Trans-coder – TC and Sub multiplexer (SM)
BSS
TC/SM
BSC
BTS
Page 24

25. Packet Control Unit-----PCU
MSC
Packet data switching
Bridge between SGSN and BSC
Provide Pb and Gb interface
BSS
TC/SM
GPRS Backbone
BSC
PCU
SGSN
BTS
Page 25

26. The Network Switching System
NSS
AUC
OMC
HLR
EIR
PSTN EC
MSC/VLR
Mobile-service Switching Center – MSC
Home Location Register – HLR
Visitor Location Register – VLR
Equipment Identity Register – EIR
Authentication Center – AUC
Echo Cancellor – EC
BSS
Page 26

27. Mobile-service Switching Center – MSC
Call Processing
Operations and Maintenance Support
Interface management
Inter-network & Inter-working
Billing
Inter-network: communication between GSM network and other network
Inter-working : communication between different entities inside the GSM network
Page 27

28. Home Location Register – HLR
Subscriber ID (IMSI and MSISDN)
Current subscriber VLR (current location)
Supplementary service information
Subscriber status (registered/deregistered)
Authentication key and AuC functionality
Page 28

29. Visitor Location Register – VLR
Mobile Status (IMSI attached / detached / busy / idle etc.)
Location Area Identity(LAI)
Temporary Mobile Subscriber Identity(TMSI)
Allocating the Roaming Number
Page 29

30. Equipment Identity Register – EIR
White List
Black List
Grey List
IMEI is Checked In White List
If NOT found
EIR focus on the equipment , not the subscriber!!
IMEI is Checked in Black/Grey List
Page 30

31. OMC Functional ArchitectureOS
MMI DB
Event/Alarm
Management
Security
Configuration
Performance Management
Fault Management
Page 31

32. Contents Chapter 1 GSM System Overview Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
Page 32

33. ...... Service Area Service Area PLMN service area PLMN service area
MSC service area...
MSC service area...
......
Location area...
Location area...
cell
cell
Page 33

34. Location Area Identification
LAI
MCC
MNC
LAC
Location Area Identification
The LAI is the international code for a location area.
MCC: Mobile Country Code，It consists of 3 digits .
For example: The MCC of China is "460"
MNC: Mobile Network Code，It consists of 2 digits .
For example: The MNC of China Mobile is "00"
LAC: Location Area Code，It is a two bytes hex code.
The value 0000 and FFFF is invalid.
For example:
Page 34

35. CGI The CGI is a unique international identification for a cell
CGI: Cell Global Identification
The CGI is a unique international identification for a cell
The format is LAI+CI
LAI: Location Area Identification
CI: Cell Identity. This code uses two bytes hex code to identify the cells within an LAI.
For example :
Page 35

36. BSIC NCC BCC BSIC BSIC（Base Station Identification Color Code)
NCC: PLMN network color code. It comprises 3 bit. It allows various neighboring PLMNs to be distinguished.
BCC: BTS color code. It comprises 3 bit, used to distinguish different cells assigned the same frequency!
Page 36

37. National (significant) Mobile station international
MSISDN CC
NDC SN
National (significant)
Mobile number
Mobile station international
ISDN number
CC: Country Code. For example: The CC of China is "86".
NDC: National Destination Code. For example: The NDC of China Telecom is 139, 138, 137, 136, 135.
SN: Subscriber Number. Format:H0 H1 H2 H3 ABCD
Example:
Page 37

38. IMSI MCC MNC MSIN Not more than 15 digits 3 digits 2 digits NMSI IMSI
MCC: Mobile Country Code，It consists of 3 digits .
For example: The MCC of China is "460"。
MNC: Mobile Network Code，It consists of 2 digits .
For example: The MNC of China Telecom is "00"。
MSIN: Mobile Subscriber Identification Number. H1H2H3 S ABCDEF
For example:
NMSI: National Mobile Subscriber Identification，MNC and MSIN form it together.
For Example of IMSI :
Page 38

39. TMSI TMSI: Temporary Mobile Subscriber Identification)
The TMSI is assigned only after successful subscriber authentication.
The VLR controls the allocation of new TMSI numbers and notifies them to the HLR.
TMSI is used to ensure that the identity of the mobile subscriber on the air interface is kept secret.
The TMSI consists of 4 bytes( 8 HEX numbers) and determined by the operator.
Page 39

40. IMEI IMEI IMEI: International Mobile Station Equipment Identification
TAC
FAC
SNR SP
IMEI
TAC: Type approval code, 6 bit, determined by the type approval center
FAC: Final assembly code, 2 bit, It is determined by the manufacturer.
SNR: Serial number, 6 bits, It is issued by the manufacturer of the MS. SP: 1 bit , Not used. Check the IMEI in your MS : *#06#
Page 40

41. Contents Chapter 1 GSM System Overview Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
Page 41

42. Physical Channel and Logical Channel
The physical channel is the medium over which the information is carried: 200KHz and 0.577ms
The logical channel consists of the information carried over the physical channels 1 2 3 4 5 6 7 1 2 3
Timeslot
The information carried in one time
slot is called a “burst”
TDMA FRAME
TDMA FRAME
Page 42

43. Two types of Logical Channel
Traffic Channel (TCH) :
Transmits traffic information, include data and speech.
Control Channel (CCH) :
Or Signaling Channel, transmits all kinds of control information.
Page 43

44. Traffic Channel (TCH) TCH Traffic Channels Speech Data TCH/FS TCH/HS
TCH/FS Full rate Speech Channel
TCH/HS Half rate Speech Channel
TCH/9.6 Data Channel 9.6kb/s
TCH/4.8 Data Channel 4.8kb/s
TCH/2.4 Data Channel 2.4Kb/s
TCH/4.8
Page 44

45. CCH (Control Channels)
Control Channel (CCH)
CCH (Control Channels)
DCCH
BCH
SDCCH
ACCH
Synch. CH.
BCCH
CCCH
FACCH
SACCH
SCH
FCCH
RACH
CBCH
Broadcast Control Channel – BCCH
Common Control Channel – CCCH
Dedicated Control Channel – DCCH
Associated Control Channel – ACCH
PCH/AGCH
Page 45

46. Broadcast Control Channel – BCCH
The information carried on the BCCH
is monitored by the MS
periodically when it is in idle mode
BCCH: Broadcast Control Channel
FCCH: Frequency Correction Channel
SCH: Synchronization Channel
BCH
Synch.
Channels
BCCH
SCH
FCCH
Page 46

47. Common Control Channel – CCCH
The CCCH is responsible for transferring control information between all mobiles and the network.
RACH: Random Access Channel
PCH: Paging Channel
AGCH: Access Granted Channel
CBCH: Cell Broadcast Channel
CCCH
RACH
uplink
CBCH
downlink
PCH/AGCH
downlink
Page 47

48. Dedicated Control Channel – DCCH
DCCH is assigned to a single wireless connection for measurement and handover purpose.
SDCCH: Stand-alone Dedicated Control Channel
ACCH: Associated Control Channel
SACCH: Slow Associated Control Channel
FACCH: Fast Associated Control Channel
DCCH
SDCCH
ACCH
FACCH
SACCH
Page 48

49. Uplink Logical channel
RACH
CCCH
CCH
1、 随机接入信道（RACH）
上行信道，用于移动台随机提出入网申请，请求分配一个SDCCH，请求包括3bit的建立原因（呼叫请求、寻呼响应、位置更新请求以及短消息请求等）和5bit的参考随机数供MS区别属于自己的接入允许消息。
2、 独立专用控制信道（SDCCH）
是双向专用信道，传送建立连接的信令消息、位置更新消息、短消息、鉴权消息、加密命令、信道分配消息、以及各种附加业务等。可分为独立专用控制信道（SD/8）与CCCH相组合的专用控制信道（SD/4）。
3、 慢速随路控制信道（SACCH）
与业务信道或SDCCH联用，在传送用户信息期间带传某些特定信息，上行链路主要传递无线测量报告，下行链路主要传递部分系统消息。这些消息包括通信质量、LAI、CELL ID、邻区BCCH信号强度、NCC限制、小区选项、TA、功率控制级别等。
4、快速随路控制信道（FACCH）
与TCH联用，用于在传输过程中给系统提供比慢速随路控制信道（SACCH）速度和及时性高得多的信令信息。通过从业务信道借取帧来实现接续，传送如“越区切换”等指令信息。由于话音译码器会重复最后20ms的话音，所以这种偷帧中断不会被用户察觉。除了上述三类控制信道外，还有一种小区广播控制信道（CBCH），它用于下行线，载有短消息业务小区广播（SMSCB）信息，使用像SDCCH相同的物理信道。
SDCCH
DCH
DCCH
SACCH
FACCH
TCH/F
TCH
TCH/H
Page 49

50. Downlink Logical channel
FCCH
SCH
BCCH
PCH
AGCH
CCCH
CCH
1、频率校正信道（FCCH）
载有供移动台频率校正用的信息，通过FCCH，MS就可以定位一个小区并解调出同一小区的其它信息。通过FCCH，MS也可以知道该载频是不是BCCH载频。
2、 同步信道（SCH）
在FCCH解码后，MS接着要解出SCH信道消息，该消息含移动台帧同步和基站识别的信息：基站识别码(BSIC)，它占有6个比特其中3个比特为0～7范围的PLMN色码，另3个比特为0～7 范围的基站色码(BCC)。
简化的TDMA帧号（RFN），它占有22个比特。
3、广播控制信道（BCCH）
通常，在每个基站收发信台中总有一个收发信机含有这个信道，以向移动台广播系统消息，这些系统消息使得MS可以在空闲模式下有效工作。
4、 寻呼信道（PCH）
这是一个下行信道，用于寻呼被叫的移动台，当网络想与某一MS建立通信时，它会根据MS当前所登记的LAC向该LAC区域内所有小区通过PCH信道发寻呼消息，标示为TMSI或IMSI。
5、准予接入信道（AGCH）
这是一个下行信道，用于基站对移动台的入网请求作出应答，即分配一个SDCCH或直接分配一个TCH。
SDCCH
DCH
DCCH
SACCH
FACCH
TCH
TCH/F
TCH/H
Page 50

51. How to use these channels?
Power-off
Search for frequency correction burst
FCCH
SCH
BCCH
PCH
RACH
AGCH
SDCCH
TCH
FACCH
Search for synchronous burst
Extract system information
Idle mode
Monitor paging message
Send access burst
Allocate signaling channel
Dedicated mode
Set up the call
Allocate voice channel
Conversation
Release the call
Idle mode
Page 51

52. Packet logic channel TCH TCH BCCH CCCH SACCH
Packet data channel (PDCH)
Comprising packet service channel and packet control channel
Packet service channel (PDTCH)
Combined into the single-directional service channel
Packet control channel
Broadcast control channel: PBCCH
Public control channel: PPCH, PRACH, PAGCH
Private control channel: PACCH, PTCCH
TCH
BCCH
CCCH
SACCH
Page 52

53. GSM Logical Channel Combination
Main BCCH combination – FCCH + SCH + BCCH + CCCH
SDCCH combination – SDCCH/8 + SACCH/8
Combined BCCH – BCCH + CCCH +SDCCH/4 + SACCH/4
TCH/FR combination – TCH/F + FACCH/F + SACCH/F
TCH/HR combination – TCH/H + FACCH/H + SACCH/H
Page 53

54. Combination of packet logic channel
Packet logic channels (PDCH) can be combined via the following three modes
Mode 1: PBCCH+PCCCH+PDTCH+PACCH+PTCCH;
Mode 2: PCCCH+PDTCH+PACCH+PTCCH;
Mode 3: PDTCH+PACCH+PTCCH
In case of small GPRS traffic, GPRS and circuit services use the same BCCH and CCCH in the cell. In this case, only combination mode 3 is needed in the cell
With the increase of traffic, the packet public channel should be configured in the cell. Channel combination mode 1 and mode 2 should be adopted
Page 54

55. CONTROL CHANNELS GSM Multi-frames TDMA Frames 1 2 4 3 46 47 48 50 491 2 4 3 46 47 48 50 49
51 – Frame Multi-frames
CONTROL CHANNELS 5 6 7
Page 55

56. TRAFFIC CHANNELS GSM Multi-frames TDMA Frames 1 2 4 3 21 22 23 25 241 2 4 3 21 22 23 25 24
26 – Frame Multi-frames
TRAFFIC CHANNELS 5 6 7
Page 56

57. Contents Chapter 1 GSM System Overview Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
Page 57

58. Power Control 5W 0.8W 8W Saves battery power Reduces co-channel and
Both Uplink and Downlink power settings can be controlled independently and individually. 5W
0.8W
Saves battery power
Reduces co-channel and
adjacent channel interference 8W
BCCH
Does not attend Power control
Page 58

59. Discontinuous Transmission – DTX
DTX and VAD
Discontinuous Transmission – DTX
Voice Activity Detection – VAD
Battery Saving
Interference reduction
Page 59

60. Timing Advance (TA) TA Transmission delay t Transmission delay t
The mobile phone should
send the signal in advance! TA
Transmission delay t
When the MS is in idle mode, the time sequence within the MS can be adjusted via the SCH channel. However, the mobile station does not know how far it is away from the base station. If the distance between the MS and the base station is 30km, the time sequence of the MS will be 100μs slower than that of the base station. When the mobile phone sends its first RACH signal, it is already 100μs later. For there is still another 100μs of transmission delay, when the signal reaches the base station, the total delay is 200μs . It is very possible that the signal collides with the pulse of the adjacent timeslot around the base station. Therefore, RACH and some other channel access pulses will be shorter than other pulses. Only after receiving the time sequence adjustment signal (TA) from the base station, MS can send pulses of normal length. In this case, the MS needs to send signals by 200μs in advance.
Transmission delay t
Page 60

61. Multi-path Fading
Time Dispersion
Diversity
Frequency Hopping
Page 61

62. Diversity – What’s Diversity?
Receive diversity provides an effective technique for both overcoming the impact of fading across the radio channel and increasing the received signal to interference ratio.
The former is achieved by ensuring “uncorrelated” (i.e. low enough correlated) fading between antenna branches i.e. not all antennas experience fades at the same time.
Page 62

63. Kinds of Diversity Time diversity Frequency diversity Space diversity
Coding, interleaving
Frequency diversity
Frequency hopping
Space diversity
Multiple antennas
Polarization diversity
Dual-polarized antennas
Multi-path diversity
Equalizer f
Page 63

64. Frequency Hopping
Frequency
f 0
f 1
f 2
f 3
f 4
Frame
Time
Page 64

65. Contents Chapter 1 GSM System Overview Chapter 2 GSM Network Structure
Chapter 3 Service Area and Number Planning
Chapter 4 Channels on the Wireless Interface
Chapter 5 Radio Techniques
Chapter 6 GPRS & EDGE Introduction
Page 65

66. GSM Development Evolution
57.6
kbps
115
384 2
Mbps
GSM
HSCSD
GPRS
EDGE
IMT-2000
9.6 2G
2.5G 3G
Page 66

67. Data rate of EDGE and GPRS
8PSK
GMSK
Page 67

68. Huawei EDGE Test Result
Downlink, 4 TS, MCS-9：
Page 68

69. Summary The basic idea of GSM The frequency spectrum used in GSM
The structure of GSM
Certain service area and numbers
Some radio techniques used in GSM
Evolution of GSM
Summary
Page 69