7/27/2019 GSM Discussion

1/17

REFRESHING GSM FUNDAMENTALS

7/27/2019 GSM Discussion

2/17

N E M H A N S SOLUTIONS Pvt. Ltd.

Managovinda Mishra

Date: 28 th April 2008

N - Nokia E - Ericsson M - Motorola H - Huawei A - Alcatel Lucent N - Nortel S - Siemens

7/27/2019 GSM Discussion

3/17

7/27/2019 GSM Discussion

4/17

BASICS - I

Frequencies: Primary GSMUL 890-915 MHz. / DL in 935-960 MHz

One channel 200KHz : 125 ARFCN from 0 to 124 . Ch 0 is guard band from other applications. Each ARFCN pair is separated by 45 MHz with 3 time slots spacing.

Each channel carries 8 time slots, each of 577Micro seconds.

Frequencies: EGSMUL 880-915 MHz. / DL in 925-960 MHz

50 more channels added.

Fequencies : DCS1800UL 1710 to 1785 DL 1805 to 1880

Channel numbers 512 to 885 ( total 374 Channels)

ModulationGaussian Mean Shift Keying

Multiple AccessTDMA , FDMA, TDD, FDD ( No

Duplexer, only fast switchingsynthesizer)

7/27/2019 GSM Discussion

5/17

Voice Coding / Signaling coding

50 132 78

378 78

Class Ia Class Ib Class II

Block codingwith 3

CRC bits

4 bits of zeros toreset codec

Convolution coding with rate1/2

184 signaling bit

40 parity bit

4 bits of zeros toreset codec

456 bits after coding

7/27/2019 GSM Discussion

6/17

BASICS - II

7/27/2019 GSM Discussion

7/17

Signaling and traffic multi frame mapping

7/27/2019 GSM Discussion

8/17

Logical Channels - I

Channel MS BTS

TCH FACCH BCCH

PCH

7/27/2019 GSM Discussion

9/17

Logical Channels - II

Logicalchannels

Traffic Control

FR HR Broad castControl Ch

CommonControl Ch

DedicatedControl Ch

TCH/F TCH/H

BCCH FCH SCH

DL UL

PCH AGCH RACH

Slow Fast

SACCH SDCCH FACCH

7/27/2019 GSM Discussion

10/17

RF Planning a DCS 1800 MHz network

Coverage planning Link budget

Marketing feed back Municipal boundary

Site Sharing Info

Anchor sites

Digital map

Loss Classification

Capacity planning

Expected subscriber

base Mean holding time

QOS Tolerance

Erlang B Table Speech Rate

Rail way planning is more of a capacity planning

7/27/2019 GSM Discussion

11/17

Spectrum Management

BCCH planning

Frequency Reuse

7*3 Reuse pattern 4*3 reuse pattern

3*3 Reuse pattern

TCH planning1. Without hopping

2. With Hopping BBH

SFH 1*3 1*1

7/27/2019 GSM Discussion

12/17

Hand over

Types of Hand Over

Intra cell HO

Intra BSS HO

Intra MSC Ho

Inter MSC HO

Cause Of hand over

Quality ( RX Qual is high )

Level ( RXLEV is poor)

MS BTS Distance too High

Better Neighboring Cell ( PBGT)

Speed Sensitive HO

RXQUAL HO 1. RXQUAL_XX > L_RXQUAL_XX_H2. RXLEV_XX < L_RXLEV_XX_IH3. XX_TXPWR = min(XX_TXPWR_MAX, P)

RXLEV HO 1. RXLEV_XX < L_RXLEV_XX_H

2. XX_TXPWR = min(XX_TXPWR_MAX, P)

DIST HO 1. MS_BS_DIST > MS_RANGE_MAX

RXQUAL HO intracell 1. RXQUAL_XX > L_RXQUAL_XX_H2. RXLEV_XX > L_RXLEV_XX_IH

PBGT HO 1. RXLEV_NCELL(n) > RXLEV_MIN(n) +max(0,MS_TXPWR_MAX(n) P)2. PBGT(n) > HOMARGIN(n)

7/27/2019 GSM Discussion

13/17

Power Control

U_RXQUAL_XX_P

7

L_RXQUAL_XX_P

Power Increase (bad quality)

Power Increase (bad level)

Power decrease (good level)

Power

Decrease

(good quality)

L_RXLEV_XX_P U_RXLEV_XX_P

0

63

7/27/2019 GSM Discussion

14/17

ModeBitrate(kbit/s)

Channel

AMR_12.20 12.2 FR AMR_10.20 10.2 FR AMR_7.95 7.95 FR/HR AMR_7.40 7.4 FR/HR AMR_6.70 6.7 FR/HR AMR_5.90 5.9 FR/HR AMR_5.15 5.15 FR/HR AMR_4.75 4.75 FR/HR AMR_SID 1.8 FR/HR

PARAMETER AHS AFSCodec 1: AHS 5.9 Codec 1: AFS 7.4Codec 2: AHS 6.7 Codec 2: AFS 7.95Codec 3: AHS 7.4 Codec 3: AFS 10.2

Codec 4: AHS 7.95 Codec 4: AFS 12.2

Threshold Range 0 - 31.5 dB (Step Size: .5 dB) 0 - 31.5 dB (Step Size: .5 dB)Codec 1 to 2 Threshold: 8 dB Codec 1 to 2 Threshold: 6.5 dBCodec 2 to 3 Threshold: 12 dB Codec 2 to 3 Threshold: 15.5 dBCodec 3 to 4 Threshold: 16 dB Codec 3 to 4 Threshold: 18.5 dB

Hysteresis Range 0 - 7.5 dB (Step Size: .5 dB) 0 - 7.5 dB (Step Size: .5 dB)Codec 1 to 2 Hysteresis: 2 dB Codec 1 to 2 Hysteresis: 2 dBCodec 2 to 3 Hysteresis: 2 dB Codec 2 to 3 Hysteresis: 2 dB

Codec 3 to 4 Hysteresis: 2 dB Codec 3 to 4 Hysteresis: 2 dB

Default Active Codec Set

Default Threshold Values

Default Hysteresis Values

AMR

AMR is all bout packing and unpacking

7/27/2019 GSM Discussion

15/17

DATA CAPABILITY OF GSM

Coding Schemes Speed ( kbits/s)CS-1 8CS-2 12CS-3 14.4CS-4 20

Coding Schemes Speed ( kbits/s) Modulation

MCS-1 8.8 GMSKMCS-2 11.2 GMSKMCS-3 14.8 GMSKMCS-4 17.6 GMSKMCS-5 22.4 8-PSKMCS-6 29.6 8-PSKMCS-7 44.8 8-PSKMCS-8 54.4 8-PSKMCS-9 59.2 8-PSK

EDGE :-Enhanced data Rate for GSM Evolution

GPRS EDGE

Modulation GMSK 8-PSK/GMSKSymbol rate 270ksym/s 270ksym/sModulation bit rate 270kbs 810kbsRadio data rate per time slot 22.8kbs 69.2kbsUser data rate per time slot 20kbs (CS4) 59.2kbs (MCS9)User data rate (8 time slots) 160kbs 473.6kbs

Comparison

EDGE is all about Link adaptation andBLER management

7/27/2019 GSM Discussion

16/17

GSM Network Optimization

Optimization

Field optimization OMCR- optimization

Site Audit Drive test

Coverage /Rxlev

Quality /Rxqual

Power Control

Handover

Network accessibility

Radio serviceability

DCR

Handover matrixanalysis

Congestion report

analysis SD/TCh

Traffic analysis Hr /Fr

Drop call analysisanalysis

Busy Hour analysis

Paging analysisRF DatabaseAudit

7/27/2019 GSM Discussion

17/17

THANKS.

We can go much beyond we can go.