Bit Selection for 16m Downlink Transmission and Simulation Result
Document Number: IEEE C802.16m-09/0494
Date Submitted: 2009-03-02
Source:
Jin Xu, Bo Sun
E-mail:
ZTE Corporation
E-mail:
Venue:
IEEE Session #60, Vancouver, BC, Canada
xu.jin7@zte.com.cn
sun.bo1@zte.com.cn
RE: Comments on final draft of Channel Coding and HARQ Drafting Group
Base Contribution:
Purpose:
To be discussed and adopted by TGm for use in the IEEE 802.16m Amendment Working Document.
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Instruction
•
IEEE 802.16m uses adaptive HARQ scheme in the downlink [1].
•
The overlapping of successive transmission/retransmission is serious with 16e’s bit
selection method in 16m DL [2].
•
New defined starting positions should be considered to reduce the overlapping
between successive transmission/retransmission.
-
The gain of bit selection depends on the first retransmission particularly, considering the
possibility of the following retransmission is very low.
- Mother code bits should to be covered as much as possible within the first two
transmissions .
Proposed Bit Selection Method
•
the first
transmission
the second
transmission
the third
transmission
P2
2K
33.3333%
K
the fourth
transmission
S
33.3333%
•
Suggested in C80216m-09_0203r1
33.3333%
•
The first transmitting subpacket starts from
the beginning of mother code. It contains the
first L0 bits of the mother code, where L0
denotes the first subpacket length.
The second subpacket contains the last L1
bits of the mother code. The starting
position is Nm - L1, where Nm and L1 denote
the mother code length and the second
subpacket length respectively. Nm=3×Nep.
The mother code bits are indexed from 0 to
Nm -1.
The third subpacket starts from the
beginning of the first parity bit branch (or
named “Y parity bits”). The starting position
is Nep, where Nep denotes the number of bits
in the encoder packet (before encoding).
The forth subpacket starts from the
beginning of the second parity bit branch (or
named “W parity bits”). The starting
position is 2*Nep.
P1
K
•
Baseline for comparison
•
4 SPIDs equally spaced
 SPIDi  3 N EP 
Pi  24  

4  24

Where, Pi denotes the starting position for the ith subpacket. Li denotes the ith subpacket length.
Simulation Results (1)
•
Simulation Parameters
Parameters
Assumption
Bandwidth
10 MHz
Number of subcarrier
1024
Frame length
5ms
Channel estimation
Perfect
Channel code
CTC
Modulation
16 QAM for each transmission
MIMO configuration
SISO
HARQ mode
Adaptive
Channel model
PED B, 3km/h
Code Length
384 bits
Code Rate
[123/256, 204/256, 204/256,204/256]
Maximum number of retransmission
3
Simulation Results (2)
Simulation Results (3)
•
Simulation Parameters
Parameters
Assumption
Bandwidth
10 MHz
Number of subcarrier
1024
Frame length
5ms
Channel estimation
Perfect
Channel code
CTC
Modulation
[16QAM, QPSK, QPSK, QPSK]
MIMO configuration
SISO
HARQ mode
Adaptive
Channel model
Veh-A, 30km/h
Code Length
480 bits
Code Rate
[123/256, 199/256, 199/256,199/256]
Maximum number of retransmission
3
Simulation Results (4)
Simulation Results (5)
•
Simulation Parameters
Parameters
Assumption
Bandwidth
10 MHz
Number of subcarrier
1024
Frame length
5ms
Channel estimation
Perfect
Channel code
CTC
Modulation
[QPSK, QPSK, QPSK, QPSK]
MIMO configuration
SISO
HARQ mode
Adaptive
Channel model
PED B, 30km/h
Code Length
960 bits
Code Rate
[131/256, 229/256, 229/256,229/256]
Maximum number of retransmission
3
Simulation Results (6)
Conclusion
• From above analysis and simulation, we conclude that the
proposed bit selection method could improve the performance
of retransmission with small complexity.
• We suggest this new bit selection method to be adopted for
CTC IR HARQ in 16m.
Reference
[1] IEEE 802.16m-08/003r7, “IEEE 802.16m System Description Document”
[2] C80216m-09_0203r1,“The Bit Selection Method of CTC IR HARQ for IEEE
802.16m”
Text Proposal for Amendment Working Document
•15.x.2.1 IR HARQ
HARQ IR is used in 802.16m, by changing the starting position of the bit selection for HARQ
retransmissions. The starting position for each subpacket Pi is defined as:
(1)The first transmitting subpacket, starts from the beginning of mother code. The starting
position for the first transmitting subpacket is P1=0;
(2) The second subpacket contains the last L1 bits of the mother code. The starting position is for
the second transmitting subpacket is P2=3×Nep-mod(L1, 3×Nep);
(3) The third subpacket starts from the beginning of the first parity bit branch (named “Y parity
bits”). The starting position is P3=Nep;
(4) The forth subpacket starts from the beginning of the second parity bit branch (named “W
parity bits”). The starting position is P4=2×Nep