GSM Packet Switched Channel Processing through physical layer
Introduction
This article on packet switched channel processing through physical layer covers GPRS Channel Coding(CS1,CS2,CS3,CS4) and EGPRS Channel Coding (MCS1,MCS2,MCS3,MCS4,MCS5,MCS6,MCS7,MCS8,MCS9) processing.
Coding parameters for GPRS Modulation and Coding Schemes-CS1,CS2,CS3,CS4
In GPRS various coding schemes are available to take care of noise,interference and fading of the air interface. These coding schemes have inverse relation ship between data rates and robustness. These schemes CS1,CS2,CS3,CS4 are outlined below in the table.
| Scheme | Code rate | USF | Pre- coded USF |
Radio block (exclude USF/BCS) |
BCS | Tail | Coded Bits |
Punc- tured bits |
Data rate (kbps) |
|---|---|---|---|---|---|---|---|---|---|
| CS1 | 1/2 | 3 | 3 | 181 | 40 | 4 | 456 | 0 | 9.05 |
| CS2 | 2/3 | 3 | 6 | 268 | 16 | 4 | 588 | 132 | 13.4 |
| CS3 | 3/4 | 3 | 6 | 312 | 16 | 4 | 676 | 220 | 15.6 |
| CS4 | 1 | 3 | 12 | 428 | 16 | - | 456 | - | 21.4 |
EDGE/EGPRS Modulation and Coding Schemes
In the EGPRS radio interface is the same as that in GPRS. Concept of 52-frame multiframe, physical channels(PDCH), logical channels (PBCCH/PCCCH/PRACH/PDTCH/PTCCH and PACCH) and logical channel to physical channel mapping is the same as that in GPRS. The difference is only in modulation and coding schemes as outlined below in the table.
| Modulation- coding scheme |
Modulation | Code rate | Max. throughput (kbps) |
Raw data within radio block |
RLC Blocks/ Radio Block |
Family |
|---|---|---|---|---|---|---|
| MCS1 | GMSK | 0.37 | 8.8 | 178 | 1 | C |
| MCS2 | GMSK | 0.49 | 11.2 | 226 | 1 | B |
| MCS3 | GMSK | 0.53 | 14.8 | 298 | 1 | A |
| MCS4 | GMSK | 0.66 | 17.6 | 354 | 1 | C |
| MCS5 | 8-PSK | 0.76 | 22.4 | 450 | 1 | B |
| MCS6 | 8-PSK | 0.85 | 29.6 | 594 | 1 | A |
| MCS7 | 8-PSK | 0.92 | 44.8 | 2 x 450 | 2 | B |
| MCS8 | 8-PSK | 1.0 | 54.4 | 2 x 546 | 2 | A |
| MCS9 | 8-PSK | 1.0 | 59.2 | 2 x 594 | 2 | A |
Useful Links
GSM tutorial covering GSM basics,network architecture,network elements,system specifications,applications,GSM burst types,GSM frame structure or frame hierarchy, logical channels,physical channels, GSM physical layer or speech processing and GSM mobile network entry or call setup procedure,
Read more.
GSM Protocol stack , covers layer 1,2 and 3 of GSM network elements MS,BTS,BSC and MSC.READ MORE.
GSM Standard References
3GPP TS 45.002 describes burst building and burst multiplexing
3GPP TS 45.003 describes coding and interleaving
3GPP TS 45.004 describes differential encoding and modulation
3GPP TS 45.005 describes transmitter,receiver and antenna part
3GPP TS 43.020 & 23.221 describes encryption/ciphering part
GPRS useful Links
GPRS protocol stack
GPRS Modem vendors
GSM versus GPRS
EDGE/EGPRS Basics
What is GPRS
GPRS/EGPRS Modulation-Coding Schemes