gsm fundamentals

Transcript gsm fundamentals

Internal

OMA000001 GSM Fundamentals

ISSUE 4.0

www.huawei.com

HUAWEI TECHNOLOGIES CO., LTD.

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 HUAWEI TECHNOLOGIES CO., LTD.

References

 BSS Feature Description  BSS Signaling Analysis Manual  BSC Technical Manual HUAWEI TECHNOLOGIES CO., LTD.

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

HUAWEI TECHNOLOGIES CO., LTD.

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) HUAWEI TECHNOLOGIES CO., LTD.

GSM Development

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

HUAWEI TECHNOLOGIES CO., LTD.

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.

HUAWEI TECHNOLOGIES CO., LTD.

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).

HUAWEI TECHNOLOGIES CO., LTD.

FDMA

Frequency Time

 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.

HUAWEI TECHNOLOGIES CO., LTD.

TDMA

Frequency Time

 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.

HUAWEI TECHNOLOGIES CO., LTD.

CDMA

Frequency Time

 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.

HUAWEI TECHNOLOGIES CO., LTD.

The Frequency Spectrum

GSM 900

Uplink Downlink

890 915 935 960MHz

Duplex Separation: Channel Bandwidth: 45MHz 200KHz

HUAWEI TECHNOLOGIES CO., LTD.

The Frequency Spectrum

DCS 1800

Base Station Receive Base Station Transmit

1710 1785 1805 1880MHz

Duplex Separation: Channel Bandwidth: 95MHz 200KHz

HUAWEI TECHNOLOGIES CO., LTD.

The Frequency Spectrum

Frequency Spectrum

GSM 450 GSM 480 GSM 850 E-GSM 900 R-GSM 900

Range (MHz)

450.4~457.6

460.4~467.6

478.8~486 488.8~496 824~849 869~894 880~915 925~960 876~915 921~960

Uplink Frequency

Fu(n)=450.6+0.2(n-259) Fu(n)=479+0.2(n-306) Fu(n)=824.2+0.2(n-128) Fu(n)=890+0.2n

Fu(n)=890+0.2(n-1024) Fu(n)=890+0.2n

Fu(n)=890+0.2(n-1024)

Frequency Point Available

259<=n<=293 306<=n<=340 128<=n<=251 0<=n<=124 975<=n<=1023 0<=n<=124 955<=n<=1023

Downlink Frequency

Fd(n)=Fu(n)+10 Fd(n)=Fu(n)+10 Fd(n)=Fu(n)+45 Fd(n)=Fu(n)+45 Fd(n)=Fu(n)+45 PCS 1900 1850~1910 1930~1990 Fu(n)=1850.2+0.2(n-512) 512<=n<=810 Fd(n)=Fu(n)+80 HUAWEI TECHNOLOGIES CO., LTD.

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.

HUAWEI TECHNOLOGIES CO., LTD.

Frequency Reuse

7(Site)X 1(Cell) reuse

2 7 6 1 5 4 HUAWEI TECHNOLOGIES CO., LTD.

Frequency Reuse

1 9 5 2 6 10 3 7 11 4 8 12 R

4 site X 3 cells reuse

HUAWEI TECHNOLOGIES CO., LTD.

Cell Types

Omni-directional Cell

Omni 1

120 Degree Cell

1 3

120 degree

HUAWEI TECHNOLOGIES CO., LTD.

MS MS

GSM-GPRS Network Component

MSC/VLR GMSC GSM /GPRS BSS BSC BTS PCU BSC BTS HLR/AUC

SS7 SMS system

OMC SGSN CG GPRS Backbone GGSN BG PSTN ISDN Internet, Intranet Other PLMN HUAWEI TECHNOLOGIES CO., LTD.

Interface Between Different Entities

MS MS Um GSM /GPRS BSS BTS Abis BSC PCU BSC BTS MSC/VLR GMSC A HLR/AUC C/D/Gs Gb OMC

SS7

Gr/Gs/Gd/Ge Gc GPRS backbone SGSN Ga

SMS system

GGSN Gi CG BG Gp PSTN ISDN Internet, Intranet Other PLMN HUAWEI TECHNOLOGIES CO., LTD.

Mobile Station —MS

MS=ME+SIM

International Mobile Equipment Identity (IMEI) – Mobile Equipment International Mobile Subscriber Identity (IMSI) – Subscriber Identity Module HUAWEI TECHNOLOGIES CO., LTD.

Subscriber Identity Module – SIM



International Mobile Subscriber Identity (IMSI)



Temporary Mobile Subscriber Identity (TMSI)



Location Area Identity (LAI)



Subscriber Authentication Key (Ki)

SIM

HUAWEI TECHNOLOGIES CO., LTD.

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

HUAWEI TECHNOLOGIES CO., LTD.

Packet Control Unit-----PCU

MSC



Packet data switching



Bridge between SGSN and BSC



Provide Pb and Gb interface

BSS

TC/SM BSC BTS PCU

HUAWEI TECHNOLOGIES CO., LTD.

GPRS Backbone

SGSN

The Network Switching System

NSS

OMC AUC HLR EIR MSC/VLR EC PSTN

Mobile-service Switching Center Home Location Register Visitor Location Register Equipment Identity Register Authentication Center Echo Cancellor – MSC – HLR – VLR – EIR – AUC – EC

HUAWEI TECHNOLOGIES CO., LTD.

BSS

Page 26

Mobile-service Switching Center – MSC

    

Call Processing Operations and Maintenance Support Interface management Inter-network & Inter-working Billing

HUAWEI TECHNOLOGIES CO., LTD.

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

HUAWEI TECHNOLOGIES CO., LTD.

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

HUAWEI TECHNOLOGIES CO., LTD.

Equipment Identity Register – EIR



White List



Black List



Grey List IMEI is Checked In White List EIR focus on the equipment , not the subscriber!!

If NOT found IMEI is Checked in Black/Grey List

HUAWEI TECHNOLOGIES CO., LTD.

OMC Functional Architecture

Event/Alarm Management Fault Management Security Management

MMI OS DB

Configuration Management Performance Management

HUAWEI TECHNOLOGIES CO., LTD.

Service Area

PLMN service area MSC service area...

MSC service area...

Location area...

......

cell cell

HUAWEI TECHNOLOGIES CO., LTD.

LAI

MCC MNC

Location Area Identification

LAC

The LAI is the international code for a location area.

MCC: Mobile Country Code

，

It consists of 3 digits .

MNC: For example: The MCC of China is "460" Mobile Network Code

，

It consists of 2 digits .

LAC: For example: The MNC of China Mobile is "00" Location Area Code

，

It is a two bytes hex code.

The value 0000 and FFFF is invalid.

For example: 460-00-0011

HUAWEI TECHNOLOGIES CO., LTD.

CGI

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 : 460-00-0011-0001

HUAWEI TECHNOLOGIES CO., LTD.

BSIC

BSIC

（

Base Station Identification Color Code) NCC BCC BSIC NCC: PLMN network color code. It comprises 3 bit. It allows various neighboring PLMNs to be BCC: distinguished.

BTS color code. It comprises 3 bit, used to distinguish different cells assigned the same frequency!

HUAWEI TECHNOLOGIES CO., LTD.

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 SN: China Telecom is 139, 138, 137, 136, 135.

Subscriber Number. Format:H0 H1 H2 H3 ABCD Example: 86-139-0666-1234

HUAWEI TECHNOLOGIES CO., LTD.

IMSI

3 digits MCC Not more than 15 digits 2 digits MNC NMSI IMSI MSIN MCC: MNC: Mobile Country Code

，

It consists of 3 digits .

For example: The MCC of China is "460"

。

Mobile Network Code

，

It consists of 2 digits .

For example: The MNC of China Telecom is "00"

。

MSIN: NMSI: Mobile Subscriber Identification Number. H1H2H3 S ABCDEF For example: 666-9777001 National Mobile Subscriber Identification form it together.

For Example of IMSI : 460-00-666-9777001

，

MNC and MSIN

HUAWEI TECHNOLOGIES CO., LTD.

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.

HUAWEI TECHNOLOGIES CO., LTD.

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#

HUAWEI TECHNOLOGIES CO., LTD.

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

0 1 2 3 4 5 6 7 0 1 2 3

Timeslot The information carried in one time slot is called a “burst”

TDMA FRAME TDMA FRAME

HUAWEI TECHNOLOGIES CO., LTD.

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.

HUAWEI TECHNOLOGIES CO., LTD.

Traffic Channel (TCH)

TCH Traffic Channels Speech Data TCH/FS TCH/HS TCH Traffic Channel 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

HUAWEI TECHNOLOGIES CO., LTD.

TCH/9.6

TCH/4.8

Page 44

TCH/2.4

Control Channel (CCH)

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

HUAWEI TECHNOLOGIES CO., LTD.

Synch. CH.

FCCH

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 BCCH CCH BCH Synch. Channels

HUAWEI TECHNOLOGIES CO., LTD.

SCH

Page 46

FCCH

Common Control Channel – CCCH

The CCCH is responsible for transferring control information between network.

all mobiles and the RACH: Random Access Channel PCH: Paging Channel AGCH: Access Granted Channel CBCH: Cell Broadcast Channel RACH uplink CCH CCCH CBCH downlink

HUAWEI TECHNOLOGIES CO., LTD.

PCH/AGCH downlink

Page 47

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 SDCCH CCH DCCH ACCH FACCH SACCH

HUAWEI TECHNOLOGIES CO., LTD.

Uplink Logical channel

RACH CCCH

CCH

SDCCH SACCH FACCH TCH/F TCH/H DCCH TCH

DCH

HUAWEI TECHNOLOGIES CO., LTD.

Downlink Logical channel

CCH

BCCH CCCH FCCH SCH BCCH PCH AGCH

DCH

DCCH TCH SDCCH SACCH FACCH TCH/F TCH/H

HUAWEI TECHNOLOGIES CO., LTD.

How to use these channels?

Power-off Search for frequency correction burst Search for synchronous burst Extract system information Idle mode Dedicated mode Monitor paging message Send access burst Allocate signaling channel Set up the call Allocate voice channel Conversation Release the call Idle mode

HUAWEI TECHNOLOGIES CO., LTD.

Packet logic channel

 Packet data channel (PDCH) TCH  Comprising packet service channel and packet control channel TCH  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 BCCH CCCH SACCH HUAWEI TECHNOLOGIES CO., LTD.

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

HUAWEI TECHNOLOGIES CO., LTD.

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 HUAWEI TECHNOLOGIES CO., LTD.

GSM Multi-frames

TDMA Frames 0 1

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

0 1 2 3 4 46 47 48 49 50 51 – Frame Multi-frames

CONTROL CHANNELS

HUAWEI TECHNOLOGIES CO., LTD.

GSM Multi-frames

TDMA Frames 0 1

0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7

0 1 2 3 4 21 22 23 24 25 26 – Frame Multi-frames

TRAFFIC CHANNELS

HUAWEI TECHNOLOGIES CO., LTD.

Power Control

Both Uplink and Downlink power settings can be controlled independently and individually.

Saves battery power Reduces co-channel and adjacent channel interference BCCH ------ Does not attend Power control

HUAWEI TECHNOLOGIES CO., LTD.

DTX and VAD

Discontinuous Transmission – DTX Voice Activity Detection – VAD

Battery Saving Interference reduction

HUAWEI TECHNOLOGIES CO., LTD.

Timing Advance (TA)

The mobile phone should send the signal in advance!

Transmission delay t Transmission delay t

HUAWEI TECHNOLOGIES CO., LTD.

Multi-path Fading



Diversity



Frequency Hopping

HUAWEI TECHNOLOGIES CO., LTD.

Time Dispersion

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. HUAWEI TECHNOLOGIES CO., LTD.

Kinds of Diversity

 Time diversity Coding, interleaving  Frequency diversity Frequency hopping  Space diversity Multiple antennas  Polarization diversity Dual-polarized antennas  Multi-path diversity Equalizer

t f

HUAWEI TECHNOLOGIES CO., LTD.

Frequency Hopping

Frequency f 0 f 1 f 2 f 3 f 4

Frame HUAWEI TECHNOLOGIES CO., LTD.

Time

HUAWEI TECHNOLOGIES CO., LTD.

GSM Development Evolution

2G 9.6 kbps GSM 2.5G

384kbps EDGE 57.6 kbps 115 kbps GPRS HSCSD 3G 2Mbps IMT-2000

HUAWEI TECHNOLOGIES CO., LTD.

Data rate of EDGE and GPRS

60.0

Kbps 59.2

54.4

50.0

40.0

GPRS EGPRS

44.8

8.8

11.2

14.8

17.6

29.6

30.0

20.0

10.0

9.0

13.4

15.6

21.4

22.4

0.0

CS-1 CS-2 CS-3 CS-4 MCS-1 MCS-2 MCS-3 MCS-4 MCS-5 MCS-6 MCS-7 MCS-8 MCS-9 GMSK

HUAWEI TECHNOLOGIES CO., LTD.

8PSK

Page 67

Huawei EDGE Test Result

Downlink, 4 TS, MCS-9

： HUAWEI TECHNOLOGIES CO., LTD.

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 HUAWEI TECHNOLOGIES CO., LTD.