Chapter 10 (E)GPRS protocols 10.1 GPRS Protocols 1. The RLC/MAC protocol 2. The Medium Access control (MAC) header DL 3. The GPRS Medium Access Control header UL 4. DL + UL control blocks 5. Control Messages 6. DL control header 7. GPRS Downlink RLC/MAC data block 8. DL RLC header 9. GPRS Uplink RLC/MAC data block 10. UL RLC header 10.2 Coding Schemes and Link Adaptation 1. GPRS Channel Coding 2. Differentiation of the Coding Schemes 3. GPRS Link Adaptation 4. Link Adaptation Algorithm
Transcript
Chapter 10
(E)GPRS protocols
10.1 GPRS Protocols1. The RLC/MAC protocol2. The Medium Access control (MAC) header DL3. The GPRS Medium Access Control header UL4. DL + UL control blocks5. Control Messages6. DL control header7. GPRS Downlink RLC/MAC data block8. DL RLC header 9. GPRS Uplink RLC/MAC data block10. UL RLC header
10.2 Coding Schemes and Link Adaptation1. GPRS Channel Coding2. Differentiation of the Coding Schemes3. GPRS Link Adaptation 4. Link Adaptation Algorithm
Chapter 10
(E)GPRS Protocols10.3 Enhancements of EDGE versus GPRS
1. Enhancements of EDGE versus GPRS2. 8PSK3. 8-PSK phase transitions4. Burst types5. Detailed 8-PSK
6. GPRS and EDGE TS sharing 10.4 Protocol structures
1. EGPRS Channel Coding 2. EGPRS MCS Families3. The padding option4. Combined RLC/MAC Header for EDGE user data5. Differences in the Headertypes6. MAC part of combined RLC/MAC header7. Other new fields in the RLC/MAC header8. The RLC part of combined RLC/MAC Header9. Channel coding in EGPRS10. Coding and Interleaving11. Coding Process Example: MCS-2 DL12. Coding Process Example: MCS-8 DL13. EGPRS Coding Parameters14. EDGE coding compared with GPRS
10.5 RLC MAC enhancements 1. EDGE specific RLC/MAC modifications2. Network access mechanism3. EGPRS Packet Channel Request4. other new RLC/MAC messages for EGPRS
The RLC/MAC protocol
Radio Link Control (RLC) and Medium Access Control (MAC) realize OSI layer 2 functions. Both, RLC and MAC are described in GSM 04.60 (44.060).
The main functions of RLC are: -The segmentation of LLC frames-The provision of an acknowledged and unacknowledged operation mode
The main functions of MAC are:
-The control of the access to the network resources:-The sharing of the network resources to several mobiles:
For the DL: Usage of the TFIFor the UL: Usage of the USF (and TFI)
-The control of the release of the network resources-Release of Uplink TBF: Countdown Procedure-Release of Downlink TBF: Final Block Indicator
Both, for data transfer and transfer of control messages different RLC/MAC blocks are specified in UL and DL direction. That means, that in total 4 different types of RLC/MAC blocks are used in GPRS:
-DL RLC/MAC control blocks (used for GPRS and E-GPRS)-UL RLC/MAC control blocks (used for GPRS and E-GPRS)-GPRS DL RLC/MAC data blocks-GPRS UL RLC/MAC data blocks
MAC
RLC
Radio Block Structures
MAC Header RLC Header RLC Data BCS
MAC Header RLC/MAC Control Message BCS
Radio Block for data transfer
Radio Block for control message
8 bits octets of one or several LLC PDUs
For Radio blocks carrying RLC/MAC control messages CS-1 has to be used
Radio blocks for data transfer may be encoded using CS-1 to CS-4.
A GPRS radio block for data transmission holds following fields:• MAC header; 8 bits, different content in UL and DL • RLC header; This is a variable length field holding control data.• RLC data; This field contains octets from one or several LLC PDUs. • BCS field; Block Check Sequence is used for error detection.
The GPRS radio block for control messages holds an 8 bit long MAC header, one RLC/MAC control message in the RLC/MAC Control Message field, and a BCS field for error detection
The Medium Access control (MAC) header DL
8 7 6 5 3 2 14 Bit-No
USFS/PPayload Type RRBP MAC headerUSF
Payload Type
RRBP
MAC Header In DL
00 RLC/MAC block contains an RLC data block
01 RLC/MAC block contains an RLC/MAC control block that does not include the optional octets of the RLC/MAC control header
10 In the downlink direction, the RLC/MAC block contains an RLC/MAC control block that includes the optional first octet of the RLC/MAC control header.
11 Reserved. In this version of the protocol, the mobile station shall ignore all fields of the RLC/MAC block except for the USF field
S/P 0 RRBP field is not valid
1 RRBP field is valid
00 (N+13) mod 2715648
01 (N+17 or N+18) mod 2715648
10 (N+21 or N+22) mod 2715648
11 (N+26) mod 2715648
The Uplink State Flag (USF) field is sent in all downlink RLC/MAC blocks and indicates who is allowedto send in the next uplink radio block on the same timeslot (see
3GPP TS 45.002). The USF field is three bits in length and eight different USF values can be assigned, except on PCCCH, where the value '111' (USF=FREE) indicates that the corresponding uplink radio block contains PRACH.The Relative Reserved Block Period (RRBP)
field specifies a single uplink block in which the mobile station shall transmit either a PACKET CONTROL ACKNOWLEDGEMENT message or a PACCH block to the network Supplementary/Polling (S/P) Bit is used to indicate whether the RRBP field is valid or not valid
USF
The GPRS Medium Access Control header UL
MAC Header In ULspare
8 7 6 5 3 2 14 Bit-No
Payload Type R UL MAC header for control
Payload Type
R
00 RLC/MAC block contains an RLC data block
01 RLC/MAC block contains an RLC/MAC control block
10 Reserved.
11 Reserved.
The Retry (R) bit shall indicate whether the mobile station transmitted the CHANNEL REQUEST message (see 3GPP TS 44.018), PACKET CHANNEL REQUEST message, or EGPRS PACKET CHANNEL REQUEST message one time or more than one time during its most recent channel access
spareSet to zero - bits are ignored
Payload Type Countdown Value SI R UL MAC header for data
SI
Countdown Value
The Stall indicator (SI) bit indicates whether the mobile's RLC transmit window can advance (i.e.is not stalled) or can not advance (i.e. is stalled). The mobile station shall set the SI bit in all uplink RLC data blocks.
The Countdown Value (CV) field is sent by the mobile station to allow the network to calculate the number of RLC data blocks remaining for the current uplink RLC
entity. The CV field is 4 bits in length and is encoded as a binary number with range 0 to 15
DL + UL control blocks
Control Message Contents
sparePayload Type R
UL control block
For the UL control block no optional control header is preseen
System information messages: Packet System Information Type 1
Packet System Information Type 2
Packet System Information Type 3
Packet System Information Type 3 bis
Packet System Information Type 4
Packet System Information Type 5
Packet System Information Type 13
Control Messages (Rel 97/98) II
Packet Control Acknowledgement
Packet Cell Change Failure
Packet Cell Change Order
Packet Downlink Dummy Control Block
Packet Uplink Dummy Control Block
Packet Measurement Report
Packet Measurement Order
Packet Mobile TBF Status
Packet PDCH Release
Packet Polling Request
Packet Power Control/Timing Advance
Packet PRACH Parameters
Packet PSI Status
Packet Timeslot Reconfigure
Downlink RLC/MAC control messages and Uplink RLC/MAC control messages, except those using the access burst formats, are received in the RLC/MAC control block format. The different types of messages are distinguished by the MESSAGE_TYPE field
Miscellaneous messages:
TFIPR D
DL control header
The Power Reduction (PR) field indicates the power level reduction of the current RLC block. (important for DL PC).
In downlink RLC/MAC control blocks, the TFI identifies the Temporary Block Flow (TBF) to which the RLC/MAC control message contained in the downlink RLC/MAC control block relates.
The Direction (D) bit indicates the direction of the TBF identified by the TFI field in the downlink RLC/MAC control block header.(0-UL, 1-DL).
TFI
PR
D
The Reduced Block Sequence Number (RBSN) bit carries the sequence number of the downlink RLC/MAC control blocks. The RBSN bit is encoded as a binary number with range 0 to 1.
RBSN
RTIThe Radio Transaction Identifier (RTI) field is used to group the downlink
RLC/MAC control blocks that make up an RLC/MAC control message and identifies the segmented control message sequence with which the downlink RLC/MAC control block is associated. The RTI field is five bits in length with range 0 to 31.
FS
AC The Address Control (AC) bit is used to indicate the presence of the optional TFI/D octet in the header of downlink RLC/MAC control block. The Final Segment (FS) bit indicates that the downlink RLC/MAC control block contains the final segment of an RLC/MAC control message .
RTI ACRBSN FS octet 1
octet 2
optionaloctets
Controlheader
GPRS Downlink RLC/MAC data block
BSN
8 7 6 5 3 2 14 Bit-No
USFS/PPayload Type RRBP
TFI FBIPR
Length Indicator
E
EM
Length Indicator EM
RLC data
Spare bitsSpare bits
MAC header
octet 1
octet 2
octet 3
octet M+1octet M
octet N-1octet N(if present)
optionaloctets
RLCheader
RLCdataunit
Optional octets: one octet may be present for each LLC (or part of LLC) contained. Length indicator indicates the length of the LLC in octetts. Only the last segment of any Upper Layer PDU of a TBF (either this segment carries the entire Upper Layer PDU or not) shall be identified with a Length Indicator within the corresponding RLC data block.
DL RLC header
BSN
TFI FBIPR
E
TFI
FBI
PR The Power Reduction (PR) field indicates the power level reduction of the current RLC block. (important for DL PC).
In RLC data blocks, the TFI (Temporary Floww Identity) identifies the Temporary Block Flow (TBF) to which the RLC data block belongs. For the downlink and the uplink TFI the TFI field is 5 bits in length.
The Final block indicator (FBI) bit indicates that the downlink RLC data block is the last RLC data block of the downlink TBF. (0 - not the last block, 1 – the last block)
E
BSN The Block Sequence Number (BSN) field carries the sequence absolute Block Sequence Number (BSN') modulo Sequence Number
Space (SNS) of each RLC data block within the TBF. In GPRS, the BSN is 7 bits in length and is encoded as a binary number with range 0 to 127.
The Extension (E) bit is used to indicate the presence of an optional octet in the RLC data block header.
Length Indicator EM
if received by the mobile station it shall ignore all fields of the RLC/MAC block except for the fields of the MAC headerno LLC data after the current LLC PDU, no more extension octetsa new LLC PDU starts after the current LLC PDU and there is another extension octet, which delimits the new LLC PDUa new LLC PDU starts after the current LLC PDU and continues until the end of the RLC information field, no more extension octets
M E bit in optional part
0 0
0 11 0
1 1
octet 1
octet 2 of RLC header
Optional octets
DL RLC header II
Optional octets
E=0 in RLC header
Length Indicator EM
Y 11 MACX 01
LLC 1 and 2 completely contained, LLC 3 starts, continues in next RLC Data block:
LLC 1 X octetsLLC 2 Y octetsLLC 3
1 optional octet 1 optional octet Start of LLC 3
E=0 in RLC header MACLLC 1 X octets X 01
LLC 1 continued from previous block and LLC fits2 precisely into the RLC:
1 optional octet
Y 10LLC 2 Y octets
1 optional octet Rest of LLC 1
E=1 in RLC header MAC X octets of LLC1
LLC 1 continued from previous block and continues in next block, no optional octet needed:
Part of LLC 1 that started in a former RLC and continuous in next
E=0 in RLC header MACY octets of LLC1 Y 01
1 optional octet
LLC 2 Y octets
Rest of LLC 1 Part of LLC 2
Next radio block
Optional octets are always present, if there is a LLC border, inside the RLC, exceptions are defined for last blocks.
GPRS Uplink RLC/MAC data block
BSN
.
.
.
8 7 6 5 3 2 14 Bit-No
Payload Type Countdown Value
TFI TI
Length Indicator
E
EM
Length Indicator EM
RLC data
Spare bitsSpare bits
MAC header
octet 1
octet 2
octet 3
octet M+5
octet M
octet N-1
octet N(if present)
Optionaloctets
RLCheader
RLCdataunit
TLLI
SI R
octet M+1
octet M+4
PIspare
PFI E
UL RLC header
BSN
TFI TI
E
PIspare octet 1
octet 2 of RLC header
BSN
TFI
TI
E
PI
spare
The TLLI Indicator (PI) bit indicates the presence of an optional PFI field within the RLC data block.0- field not present1- field present
TLLITheTLLI field is present during one phase access in all UL datablocks until the first Acknowledgement is received in DL (Contention resolution procedure).
If the network indicates that it supports packet flow procedures (Network support of packet flow context (PFC) procedures is indicated by the PFC_FEATURE_MODE parameter that is broadcast on either the BCCH or PBCCH) and a PFC exists for the LLC data to be transferred the packet flow identifier has to be present
The PFI Indicator (TI) bit indicates the presence of an optional PFI field within the RLC data block.0- field not present1- field present
Length Indicator EM
PFI (Packet Flow Indication)
Used as in DL.
Remaining fields are used as in DL.
PFI field
PFI, if the network indicates that it supports packet flow procedures (Network support of packet flow context (PFC) procedures is indicated by the PFC_FEATURE_MODE parameter that is broadcast on either the BCCH or PBCCH) and a PFC exists for the LLC data to be transferred. PFI, if the network indicates that it supports packet flow procedures (If the network indicates it supports multiple TBF (Rel 6) procedures then it shall also indicate support for PFC procedures ) and a PFC exists for the LLC data to be transferred. In case no valid PFI value is allocated for the LLC data to be transmitted, and the network indicates support for the PFC procedures, an MS supporting PFC procedures shall associate and indicate the following PFI values for the LLC data:PFI = 0 (Best Effort) for user data, PFI = 1 (Signalling) for GMM/SM signalling (LLC SAPI 1), orPFI = 2 (SMS) for Short Message Service (LLC SAPI 7), orPFI = 3 (TOM8) for LLC SAPI 8 data. BSS packet flow contexts describe QoS characteristics for the data transmission.
BSSContext
PFC1
PFC2
TBF
Buffer 1
Buffer 2
BSS
Um
Gb
SGSN
Chapter 10.2
The Air Interface
10.2 Coding Schemes and Link Adaptation1. GPRS Channel Coding2. Differentiation of the Coding Schemes3. GPRS Link Adaptation 4. Link Adaptation Algorithm
GPRS Channel Coding
USF BCS
Radio Block
convolutionary coding: rate 1/2
Puncturing for CS 2 and 3
Channel coding forCS-1, CS-2, CS-3
Coding Parameters
1/2
2/3
3/4
1
181
268
312
428
3
3
3
3
40
16
16
16
456
588
676
456
0
132
220
-
9.05
13.4
15.6
21.4
CS-1
CS-2
CS-3
CS-4
coderate
radio block excl.USF and BCS
USFbits
BCSbits
codedbits
puncturedbits
data ratekbps
Radio Blocks for
control messages
CS-1
data transfer
CS-1CS-2CS-3CS-4
Differentiation of the Coding Schemes
In GPRS existing coding techniques are used. In DL blocks the USF is treated separately (stronger encoded) but the same type of encoding is used in UL and DL (That means the first 3 bits of the UL Mac header are unnecessarily strong protected. CS 1 is the same as that used for SACCH coding (1/2 rate encoding). CS 2 and 3 is a punctured version (some doubled bits are deleted, more for CS 3). CS 4 has no redundancy. The used CS is indicated by the Stealing Bits. This allows blind detection. GPRS MS have to support all CSs, the network may support only a subset.
USF Header + Data + BCS
Encoded and punctured bits (456)
The Radio block is now interleaved onto 4 normal bursts in the same way as for SACCH
11
00
10
00
CS 2
11
11
11
11
CS 1
00
10
00
01
CS 3
00
01
01
10
CS 4
The Stealing bits in the normal bursts indicate the CS.
GPRS Link Adaptation
CS 1 - 4: Bit Rate Comparison
18 17 16 15 14 13 12 11 10 9 8 7 6
Net
Th
rou
gh
pu
t (k
bit
/s)
16
18
20
CS1CS2CS3CS4
0
2
4
6
8
10
12
14
5Carrier / Interference C/I (dB)
Link Adaptation Algorithm
9 8 7 6
CS1CS2CS3CS4
518
Net
Th
rou
gh
pu
t (k
bit
/s)
0
2
4
6
8
10
12
14
Carrier / Interference C/I (dB)
CS1 & CS2Crosspoint
The coding scheme will change based on defined BLER Thresholds
The BLER thresholds are a result of simulations
Different thresholds for hopping and non hopping networks
The PCU defines which CS to use in UL and DL
From CS1 to CS2
CS1 FH 14%
CS1 NFH 69%
From CS2 to CS1
CS2 FH 43% =(5.2/12) x 100 %
CS2 NFH 79%
Crosspoint FH 6.8 Kbit/s
Max C
S 2: 1
2 Kbit/s (no heade
r)
Retransmissionrate 5.2Kbit/s
Example !!!!!
LA operation
MS BSC
RACH
CHNREQ (UplinkTBF)
BTS
CHNRD (UplinkTBF)
IACMD (IMASS) Packet UL Ass.: TFI; USF; CS
AGCHI (IMASS)
Packet UL Ass.: TFI; USF; CS
RMAC- UL (DATA) TLLI; BSN=0; CV=15
( ... )
PCU - UL (DATA) TLLI; BSN=0; CV=15
( ... )
PDTCH
RMAC- UL (PUDCB) PCU - UL (PUDCB)PDTCH
PCU - DL (PUAN) TLLI:Cont.R.; Ack BSN=0; USF
PCU - UL (DATA) TLLI; BSN=x; CV=15
PCU - UL (DATA) TLLI; BSN=x+1; CV=15
( ... ) ( ... )
PCU - DL (PDDCB) USF
( ... )RMAC- DL (PDDCB) USF
( ... ) PDTCH
UL – LLC data in MS
Initial CS is told to MS
PCU may command a new CS
IACMD (IMASS)
PDDCB Packet Downlink Dummy Control Block PUDCB Packet Uplink Dummy Control BlockPUAN Packet Uplink Ack/NackPDAN Packet Downlink Ack/NackCont R contention Resolution
RMAC- UL (DATA) TLLI; BSN=x; CV=15
RMAC- UL (DATA) TLLI; BSN=x+1; CV=15
RMAC- DL (PUAN) TLLI:Cont. R.; ...
PDTCH
PDTCH
PACCH
Chapter 10
EGPRS Protocols
10.3 Enhancements of EDGE versus GPRS1. EGPRS enhancements2. 8PSK3. 8-PSK phase transitions4. Burst types5. Detailed 8-PSK6. GPRS and EDGE TS sharing
EGPRS enhancements
UmMS
GSM RFGSM RF
MAC
RLC
MAC
RLC
GSM RF
MAC
RLC
GSM RFPCM
PCU Frames
PCM
PCU Frames
MAC
RLC
BTSUmMS PCUAbis
BSS
EGPRS is mainly an BSS internal enhancement of existing GPRS protocols.-modified RLC/MAC protocol-Option to use 8PSK on the air-Requires the support of MS
-Requires new transport solution on Abis
Option to use 8PSK
New control messagesNew data block formats
Dynamic Abis
8PSK
Q
I
(1,1,1)
(0,1,1)
(0,0,1)
(0,0,0)
(1,1,0)(1,0,1)
(0,1,0)
(1,0,0)
Q0
I0(1,1,1)
(0,1,1)
(0,0,1)
(0,0,0)
(1,1,0)(1,0,1)
(0,1,0)
(1,0,0)
Q1
I 1
(1,1
,1)
(0,1
,1)
(0,0
,1)
(0,0
,0)
(1,1
,0)
(1,0
,1)
(0,1
,0)
(1,0
,0)
With every symbol duration (which is equal to the bit duration in standard GSM, 3.7 µs), it rotates by 3p/8 corresponding to 67.5° to avoid zero crossings.
• 3/8-8-PSK which is used for EDGE
The assignment of the different symbols to the coordinates in the I/Q diagram seems to be
random. But it follows a GRAY code. If a symbol is falsely interpreted as one of its
neighbours, only one bit is wrong.
GSM RF enhancement
8-PSK phase transitions
Q0
I0
Possible phase transitions in I-Q-diagram(for EDGE several successive symbols define the phase transitions)
8PSK burst may be used in UL and Downlink for the transfer of user data. The lower shows the 8PSK burst where 1 Symbol=3bits. So it carries 3 times more bits as the GMSK burst.
1 Timeslot = 0.577 msec
Detailed 8-PSK burst
57 Payload Symbols/8-PSK
Guard period 8.25 Symbols for Ramping
26 Training sequence Symbols/8PSK but reduced subset
1 Symbol Stealing Flag
-10
-50
-30
-40
Time not
Power/dB
-20
1.5
0
3 Tail Symbols
The payload is 116*3 = 348 bits (minus stealing symbols). Tail bits and training sequence are also 8PSK modulated, however, they take only advantage of a subset of 8PSK symbols, which reduces the dynamic range enormously. The training sequence in the mid-amble consists of 26 symbols.
GPRS and EDGE TS sharing
1 radio block (20 msec)
Time
DL
UL
It is possible to send an USF to a GPRS MS in a EDGE Radio block.
GMSK has to be used (MCS 1-4)
EDGE
EDGEGPRS
GPRS
It is possible to send an USF to an EDGE MS in a GPRS Radio block. The EDGE user can use any MCS
EDGE
EDGE+GPRS
GPRS
EDGE and GPRS users can share a TS. 8-PSK is allowed in DL (if no GPRS user shall
send in the next UL block) and UL
√
√√
CS 1Controlblock
GPRS
For synchronisation reasons every MS with an active TBF on that TS has to get a readable block in DL every 360 ms. This means if there was no CS 1-4 block in DL, and there is
a GPRS MS in UL, the network has to schedule a control block every 18 th block (propably this will be dummy block).√
Timeslot sharing is possible. The potential throughput for the EDGE user will be degraded. As a consequence there is the possibility to have separate EDGE and non EDGE resources in one cell or one may enable EDGE in one cell and disable EDGE in the neighbour (with advanced features it is possible to move EDGE MSs to EDGE cells and GPRS MSs to GPRS cells). Additionally the PCU (being responsible for resource allocation) tries to avoid these situations.
Chapter 10
10.4 Protocol structures 1. EGPRS Channel Coding 2. EGPRS MCS Families3. The padding option4. Combined RLC/MAC Header for EDGE user data5. Differences in the Headertypes6. MAC part of combined RLC/MAC header7. Other new fields in the RLC/MAC header8. The RLC part of combined RLC/MAC Header9. Channel coding in EGPRS10. Coding and Interleaving11. Coding Process Example: MCS-2 DL12. Coding Process Example: MCS-8 DL13. EGPRS Coding Parameters14. EDGE coding compared with GPRS
EGPRS Protocols
EGPRS Channel Coding
In total 4 different types of RLC/MAC blocks are used: DL RLC/MAC control blocks (CS 1, used for GPRS and E-GPRS, content may be different) UL RLC/MAC control blocks (CS 1, used for GPRS and E-GPRS, content may be different) E-GPRS DL RLC/MAC data blocks (MCS 1-9) E-GPRS UL RLC/MAC data blocks (MCS 1-9)For the transfer of user data, nine Modulation and Coding Schemes (MCS) have been specified.
Four MCSs use GMSK, the remaining 5 MCSs use 8PSK.The transmission of information is again organised in radio blocks. After the use of a MCS,The resulting bits have to be transmitted on four normal burst on four consecutive TDMA frames In other words, after adding redundancy and performing the modulation scheme, 456symbols have to be transmitted.
EGPRS Modulation and Coding Scheme E-GPRS RLC data unit size (in octets)
MCS-1 22
MCS-2 28
MCS-3 37
MCS-4 44
MCS-5 56
MCS-6 74
MCS-7 2x56
MCS-8 2x68
MCS-9 2x74
GMSK
8PSK
For userdata
In EDGE basic unit of payload are defined.This allows retransmissions with another MCS within the same family. E.g. one of the 2 RLC blocks of MCS 8 may be retransmitted using MCS 3 (requires 2 Radio blocks) or MCS 6 (within one Radioblock).
EGPRS MCS Families
37 octets 37 octets 37 octets37 octets
MCS-3
MCS-6
Family A
MCS-9
28 octets 28 octets 28 octets28 octets
MCS-2
MCS-5
MCS-7
Family B
22 octets22 octets
MCS-1
MCS-4
Family C
34 +3 octets34 +3 octets
MCS-3
MCS-6Family A padding
MCS-8
34 octets 34 octets 34 octets34 octets
37 octets
34 octets
28 octets
22 octets
The modulation and coding schemes are organised in families. Each family is characterised by a basic unit of payload resp. RLC data length:
The padding option
When switching to MCS-3 or MCS-6 from MCS-8, 6 padding octets are added to the data octets.
34 octets 34 octets 34 octets34 octets
First transmission with MCS-8 in 1 Radio blockRLC-1 RLC-2
Contains 2 RLC blocks, 2 Block sequence numbers are required. BSN 2 (10 bits) provides the BSN of the second block relative to the first one (11 bits).
Header type 2for MCS 1,2,3,4
BSN1 11 bit
Contains 1 RLC block, 1 Block sequence numbers is required.
BSN1 11 bit
Contains 1 or ½ RLC block, 1 Block sequence numbers is required. The case of retransmitted half blocks is indicated by the Split Block Indicator field
SPB
RLC
1 RLC½ RLC
or
bits SPB
0 0 No retransmission0 1 Reserved1 0 Retransmission – first part of block1 1 Retransmission – second part of block
Uplink
Downlink
MAC part of combined RLC/MAC header
Countdown value SI R
ES/P USFRRBP
6 5 3 2 14
7 6 5 3 2 14
Countdown value, Stall Indication, Retransmission bit, used as for GPRS
USF is exactly defined as for GPRS. Within EDGE it will be encoded separatly in exactly the same way as for GPRS. This allows sending EDGE blocks (of course GMSK blocks) to EDGE users, while addressing GPRS MSs in Uplink.
RRBP value specifies a single uplink block in which the mobile station shall transmit either a PACKET CONTROL ACKNOWLEDGEMENT message or a PACCH block to the network in the same way as for GPRS.
EGPRS Supplementary/Polling (ES/P) Field
Other new fields in the RLC/MAC header
CPS
RSB
Coding and Puncturing Scheme indicator field (CPS)In EGPRS header, the Coding and Puncturing Scheme indicator field is used to indicate the kind of channel coding (MCS) and puncturing (PS) used for data blocks.5 bits - header type 13 bits - header type 24 bits - header type 3
MCS Puncturing Schemens
MCS-1 PS 1, 2
MCS-2 PS 1, 2
MCS-3 PS 1, 2, 3
MCS-4 PS 1, 2, 3
MCS-5 PS 1, 2
MCS-6 PS 1, 2
MCS-7 PS 1, 2, 3
MCS-8 PS 1, 2, 3
MCS-9 PS 1, 2, 3
CPS
CPS
CPS
The Resent Block Bit (RSB) indicates whether any of the RLC data blocks contained within the EGPRS radio block have been sent previously.
bit
0 All of the RLC data blocks contained within the EGPRS radio block are being transmitted for the first time
1 At least one RLC data block contained within the EGPRS radio block has been transmitted before.
Uplink only
UplinkDownlink
The RLC part of combined RLC/MAC Header
EGPRS RLC Data block
EGPRS RLC data unitFBIE EGPRS RLC data unitTIE
FBI
E
Final Block Indication and Extension bit give the RLC header
TI
E
TLLI Indication and Extension bit give the RLC header
Optionaloctets
DLRLCdatablock
8 7 6 5 3 2 14 Bit-NoLength Indicator E
Length Indicator E
RLC data
octet 1
octet 2
octet M+1
octet M
octet N2
octet N2-1
8 7 6 5 3 2 14 Bit-No
octet N2-1octet N2
.
.
.
Length Indicator E
Length Indicator E
RLC data
octet 1
octet 2
octet M+5
octet M
Optionaloctets
UL RLCData block
TLLI
octet M+1
octet M+4PFI E
Length Indicator E Extension and length Indication used almost in the same way as in GPRS(no ‘more’ bit in EGPRS)
Channel coding in EGPRS
RLC/MACHeader RLC Data Block USF
Two RLC blocks for MCS 7,8,and 9, each block is treated separately.
Downlink
Uplink
RLC/MACHeader RLC Data Block
RLC Data Block
RLC Data Block
Within EDGE the channel coding process is different for USF (only DL), RLC/MAC Header and RLC Data Block.
USF
RLC/MACHeader
RLC Data Block
Precoding to 12 bits is performed to get the same type of encoding as in GPRS.
Parity bits are calculated and added to the end (For DL RLC/MAC part without USF). An 1/3 rate convolutional encoder is used to get 3 times the bits, then some bits are deleted again (punctured)
Parity bits are calculated and added to the end of an RLC data block. Additional tailbits are added. An 1/3 rate convolutional encoder is used to get 3 times the bits, then some bits are deleted again (punctured). For one MCS different Puncturing Schemes (2 or 3) are applied.
puncturingpuncturing
x3x4 x3
Coding and Interleaving
RLC/MACHeader RLC Data Block USF
The number of bits in header or data part and the number of punctured bits depends on the MCS and direction (UL or DL).GSM rec 3.64
Header with parity bits RLC with parity and tail bits
Bits sent over the air:For MCS 1-6: 1 RLC block for MCS 7-9: 2 RLC blocks
Next step is interleaving. The bits are distributed on 4 bursts of one radio block.
USF (only UL) part is interleaved on four bursts
Header part is interleaved on four bursts.
RLC blocks are interleaved on 4 bursts except for MCS 8 and 9 where each RLC is on interleaved on 2 bursts .
Coding Process Example: MCS-2 DL
RLC/MACHeader RLC Data = 22 octetsHCS BCSUSF E FBI TB
12 bits 108 bits 732 bits
12 bits 68 bitsSB=12 bits 372 bits
normal burst normal burst normal burst normal burst
convolutionary coding: rate 1/3
Puncturing (P1, P2)
3 bits 36 bits 244 bits
Coding Process Example: MCS-8 DL
RLC/MACHeader
RLC Data = 2 x 34 octetsHCS BCSUSF E FBI TB
36 bits 135 bits 1692 bits
36 bits 124 bitsSB=8 bits 612 bits
normal burst normal burst normal burst normal burst
convolutionary coding:rate 1/3
Puncturing(P1, P2, P3)
3 bits 45 bits 564 bits
RLC Data = 2 x 34 octets BCSE FBI TB
564 bits
1692 bits
convolutionary coding:rate 1/3
612 bits
Puncturing(P1, P2, P3)
Puncturing
EGPRS Coding Parameters
MCS-1
MCS-2
MCS-3
MCS-4
MCS-5
MCS-6
MCS-7
MCS-8
MCS-9
0.53
0.66
0.85
1.0
0.37
0.49
0.76
0.92
1.0
GMSK
8PSK
0.53
0.53
0.53
0.53
1/3
1/3
0.36
0.36
0.36
176
224296
48+248352
448592
48+544448
544
592
1
1
1
1
1
1
2
2
2
12
2x12
8
RLC blocksper radio
block
RLCblocklength
BCSlength
HCSlength
modu-lation
coderate
headercoderate
8.8
11.214.8
13.617.6
22.429.6
27.244.8
54.4
59.2
datarate
(kbps)family
C
BA
A (p)C
BA
A (p)B
A (p)
A
A (p) = family A padding
Please note, different Code Rates for header and data!
EDGE coding compared with GPRS
EDGE introduces a new 1/3 rate convolutional coder, which alllows a very strong encoding.Different types of coding are used for the USF (DL only), header- and datapart.Encoding rules are slightly different for UL and DL.
9 Channel coding schemes (MCS) are defined. The MCS is indicated in the RLC/MAC header (blind detection). EDGE MSs have to support all GPRS CS and all MCS in DL, the usage of 8 PSK in UL is optional.Networks may only support a subset of all MCS.
EDGE introduces introduces for each MCS 2 or 3 different Puncturing Schemes. Puncturing is done differently for header- and data-part.
EDGE defines new interleaving rules. Header- and data-part are treated differently.For the USF the SACCH encoding and interleaving is emulated.For MCS 1-7 the RLC block is interleaved on all 4 bursts of one block, for MCS 8 and 9 one
RLC block is found only on two bursts. The idea is to offer better performance of these MCSs in a hopping network.
9 MCSs
Interleaving
Channel coding
Puncturing
Chapter 10
10.5 RLC MAC enhancements 1. EDGE specific RLC/MAC modifications2. Network access mechanism3. EGPRS Packet Channel Request4. other new RLC/MAC messages for EGPRS
EGPRS Protocols
EDGE specific RLC/MAC modifications
New messages: EGPRS PACKET CHANNEL REQUEST EGPRS PACKET DOWNLINK ACK/NACK
Use PACKET CHANNEL REQUEST on PRACH (8 or 11 bits)
Use EGPRS_PACKET_CHANNEL_REQUEST on RACH
Network access mechanism
MS
Sys info 13 on BCCH
Sys info 13: support of PBCCH
yes no
Switch to PBCCH: EDGE support?
yes no
Use CHANNEL REQUEST on CCCH
Support of EGPRS PACKET CHANNEL REQUEST?
EDGE support?
yes no
Use CHANNEL REQUEST on RACH
PACKET CHANNEL REQUEST
CHANNEL REQUEST
EGPRS PACKET CHANNEL REQUEST
PSI 13 on PBCCH
or
or
The message used by an EDGE capable MS to gain access to the network depends
on some conditions . A new EDGE PACKET CHANNEL REQUEST
control message is defined
GPRS only
GPRS only
Use PACKET CHANNEL REQUEST on PRACH (8 or 11 bits)
yes
no
Use EGPRS_PACKET_CHANNEL_REQUEST on PRACH
Support of EGPRS PACKET CHANNEL
REQUEST?
Whether 8 or 11 bit burst is used is indicated in Sys info or PSI
EGPRS Packet Channel Request
EGPRS PACKET CHANNEL REQUEST 11 Bits of Information
when used for:
One-Phase Packet Access Request
Short Access Request
Two-Phase Packet Access Request
Signalling (GMM/MM)
0
1 0 0
1 1 0 0 0 0
1 1 0 0 1 1
Radio Priority
Radio Priority
Radio Priority
Randomreference
Randomreference
Randomreference
Randomreference
Number of slots
Multislot class
There are different Training Sequences defined. By choosing one the MS indicates whether it supports 8-PSK in UL or not.
Encoded data Training Sequence Tail tail
413 836
Number of Bits
Format of access burst:
other new RLC/MAC control messages (3GPP 4.60)
Global TFIThis information element contains the TFI of the mobile station's uplink TBF, if available, or the TFI of the mobile station's downlink TBF. If no TFI is available, this field is omitted. TLLI IE (32 bit field)MS Radio Access Capability 2This information element is sent during one phase and two phase access procedures on CCCH or PCCCH .
