GSM Overview Presentation

8/2/2019 GSM Overview Presentation

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E6474A

GSM/GPRS Training


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Agilent Tutorial Agilent Restricted

E6474A - Agilent Network Optimization Platform

After this module, you will be able to:

Understand and describe key applications of E6474A Identify software and hardware components of E6474A Understand key GPRS measurements Configure software to make basic measurements

Objective:


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E6474A - Agilent Network Optimization Platform

GSM Technology Overview

GPRS Technology Overview E6474A Software/Hardware Overview andApplications Configuring the software

GPRS/GSM views and measurements

Agenda:


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Overview of GSM

F1

F2

F3

F4

F1

F2

F3

F4

F2

F1

F2

N=4 Frequency Reuse Concept

Second GenerationTechnology

Global System for MobileCommunications.

Developed by ETSI

International wireless standard

Based on the cellular concept

Frequency reuse

implementation

Over 480 million subscribers

GSM900, DCS1800, PCS1900,

R-GSM

100 200 300 400 5000

GSM

IS-95

IS-136

PDC (Japan)

Analog

Millions of subscribers (Feb 2001)source: EMC


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Series Specification Area

01 General

02 Service Aspects

03 Network Aspects

04 MS-BS Interface and Protocol

05 Physical Layer and the Radio Path

06 Speech Coding Specification

07 Terminal Adapter for MS

08 BS-MSC Interface

09 Network Interworking

10 Service Internetworking

11 Equipment and Type Approval Specs12 Operation and Maintenance

GSM Standards ETSI.

All GSM documents arestandardized by ETSI

Standards are groupedinto 12 series

Allows for easyintegration of networkelements from different

equipment vendors

Significantly reduces thecost of the overall

network deployment


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GSM uses concept of cells One cell covers small part of network Network has many cells Frequency used in one cell can be used

in another cells This is known asFrequency Re-use

F=1

F=2

F=3

F=4,8

F=5,9

F=6,10

F=7

F=1

F=2

F=3

F=4,8

F=5,9

F=6,10

F=7F=1

F=2

F=3

F=4,8

F=5,9

F=6,10

F=7

F= 1,2,3,4,5,6,7,8,9,10

Clusters

Co-Channel ( Re-use ) Cells

Frequency Reuse


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MS

BTS

BTS

BTS

BTSBTS

BTS

BTS

BTS

BSC

BSC

PSTN

VLR

TRAUHLR

EIR

OMC

SMSC

BC

AUC

VMSC

MSC

A

OML

GSM Network Architecture


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GSM - Interfaces

GSM defines

differentinterfacesbetween twosystemcomponents

Allows for multi-vendorimplementation

Promotes more

competition

Lower costs

Air interface islimiting in terms

of capacity

GSM Interfaces


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Separate Bands for Uplink and Downlink

Down link : 1930.20 - 1989.80 MHz ( GSM 935 - 960 MHz )Uplink : 1850.20 - 1909.80 MHz ( GSM 890 - 915 MHz)

TDMA and FDMA Multiplex

299 Frequency Channels (ARFCN) for GSM1900

512 to 810 for current band

200kHz Channels

8 Mobiles share ARFCN by TDMA

0.3 GMSK Modulation270.833 kbits/sec. rate

Variable Tx Power and Timing

GSM Air Interface


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1 Burst = 577usecs

0 1 2 3 4 5 6 71 TDMA Frame = 8 bursts = 4.616 ms

Multiframe

1 TCH Multiframe = 26 TF = 120ms 1 CCH Multiframe = 51 TF = 234.6ms

0 1 2 3 2044 2045 2046 2047

1 Hyperframe = 2048 Superframes = 2715648 TDMA Frames

= 3 hrs 28 min 53 sec 760 ms

00

11

22

4823

4924

5025

0 1 2 23 24 25 0 1 2 48 49 50

1 Superframe = 26 CCH MF = 1326 TF = 6.12

sec

1 Superframe = 51 TCH MF = 1326 TF = 6.12 sec

FRAMES


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Overview of GSM - Physical Channels

Group Name Function UP.

Link

Down.

Link

BCCH Broadcast control Yes No

FCCH Frequency correction Yes No

BCH

SCH Synchronization Yes NoPCH Paging Yes No

AGCH Access Grant Yes No

CCCH

RACH Random Access No Yes

SDCCH Standalone dedicated control Yes Yes

SAACH Slow-associated control Yes Yes

DCCH

FACCH Fast-associated control Yes Yes

TCH TCH Traffic data and voice Yes Yes

A GSM physical channel can carry several different

types of logical channels

Can be divided into two categories: traffic andsignaling

Signaling channels can be further categorized as: Broadcast

Common Control

Dedicated Control


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One ARFCN, On all the time, in every cellAdjacent cells use different ARFCN

Information on BCCH identifies the networkand cell

Occupies Time Slot 0

Cell ID, MCC, MNC

Neighbours, hop sequences, paging information

All timeslots on the BCH ARFCN are always On with the maxpower.

With Frequency Re-use, also need BSIC toassist in identifying the cell

Broadcast CHannel

Base Station Identity Code


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What is the BSIC ?

Base Station Identity Code

Part of the BCH

Coded into the synchronization burst

Two octal digits (value 0 to 7)

Broadcast Colour Code (BCC)

National Colour Code (NCC)

T3

Coded Data39 bits

GP8.5

Synchronization Sequence64 bits

Coded Data39 bits

T3

148 bits Synchronization Burst

GSMDefinitions.

BSIC discriminates re-use cells within the network and between other networks


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Traffic CHannel

ARFCN on which on BCH and CCH logicalchannels dont exist.

TCH ARFCN is not used for camping On

TCH ARCN is used to increase traffic capacityin the cell.

TCH ARCN will not be On always.

Signals can be measured on the TCH ARCNonly when a call is going on.

TCH received power will be bursty, if less callsare going on.

Base Station can use downlink power controlon the TCH ARFCN


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Phone Idle Mode Measurements

NCell

NCell

NCell

Serving Cell

Reports to HP E74xx

RXLEV + BSIC for Serving Cell

RXLEV + BSIC for top 6 NcellsC1 & C2 for serving cellC1 & C2 for top 6 Ncells


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C1 measurement

C1 is the path loss criterion, which is used toestimate the balance between uplink and downlink

Mobile camps on to a cell where C1 is the maximum

Mobile in idle mode will at regular intervals carry outC1 measurements for both serving cell and Top 6neighbor cells.

Mobile will do a cell reselection to a neighbor whoseC1 exceeds the C1 of the server

Mobile will provided addition hysterisis value to beadded to the C1 of the server when the neighbor is indifferent LAC.


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Phone Dedicated Mode Measurement Reporting

NCell

NCell

NCell

Serving Cell

Measurement

Report

1 Report every 480 ms in active mode

RXQUAL and RXLEV for Serving CellRXLEV + BSIC for top 6 NcellsTransmit Power and Timing Advance


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Phone Measurement Report

Rxlev

During reception of burst for serving cell

Minimum one neighbor cell measured in 1 frame

RxQual

BER measurements carried over 26 bits of midamble

Ranges between 0 - 7 ( 0 indicates no errors )

Full and Sub

Rxlev_Full & RxQual_Full : Measurements taken over full set of TDMA frames

Full set of TDMA frames : 102 for SDCCH

Full set of TDMA frames : 104 TCH

Rxlev_Sub & RxQual_Sub : Measurements taken over subset of TDMA frames

If even one frame is not transmitted in the measurement period, then it is considered assubset of TDMA frames.


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4

3

2

1

0SACCH Blocks

BCCH : Max value = 4 Max value broadcasted on BCCH Range : 4 - 24 For every bad frame of SACCH,

counter decrements by 1 For every good frame , counter

increments by 2 Radio link failure is declared,

when counter equal 0

Call is dropped Mobile returns to idle mode

Radio Link Failure(RLTC)


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Frame Erasure Rate (FER)

3 bits CRC is added to the dedicated channels and on Type 1a

bits of speech , in the coding processIf the CRC detection at the Mobile is invalid, it indicates a Badframe and FER counter goes up.

The effect perceived by the user is a Ping-Pong sound.

FER is very useful to estimate quality under frequency hoppingconditions, when Rxqual is bursty.

Under Frequency Hopping condition , Rxqual does not resemblea true picture of quality, FER is the preferred parameter .

Since only 3 bits are used for CRC , the probability of detectingbad frames is only 12.5%

How do we measure FER % ?

% of speech frames erased over last 4 measurement periods


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System Info Messages Summary

Not with Sagem Not with Sagem

TYPE 1 TYPE 2 TYPE 3 TYPE 4 TYPE 5, 6 TYPE 7 TYPE 8

BCCH BCCH BCCH BCCH SACCH BCCH BCCH

Cell channel description BA List Cell ID LAI BA List Cell selection Cell selectionRACH control params RACH control params LAI Cell selection params Cell ID

Access control classes MCC RACH control NCC permit

MNC CBCH description

LAC CBCH MA

Cell selection params

System Info Summary Table


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Documents

GSM Overview Presentation