1. IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number:
Uplink Control PHY Design for HARQ Tri-State Feedback Buffer Management
IEEE Presentation Submission Template (Rev. 9)
Document Number:
IEEE S802.16m-09/0890r3
Date Submitted:
Source:
Zheng Yan-Xiu, Yu-Chuan Fang, Chang-Lan Tsai, Chung-Lien Ho, Hsi-Min Hsiao
ITRI
Venue:
Re: IEEE m-09/0020, Call for contributions on 16m AWD content.
Amendment Working Document (IEEE m-09/0010r1a).
Chapter HARQ Feedback A-MAP IE
Chapter UL HARQ feedback control channel
Base Contribution:
Purpose:
To be discussed and approval by IEEE m TG
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2. Motivation
This contribution shows the buffer management performance and related uplink control PHY structure for tri-state HARQ feedback
The feedback facilitates HARQ buffer management by three states ACK/NACK/DROP
The buffer management occurs for high throughput scenario and each HARQ process will carry large HARQ burst
Since larger burst applied in this scenario, we can apply more resource for the tri-state HARQ feedback

3. Aggressive HARQ Transmission
Buffer management is necessary to accommodate packet dropped on receiver side
Aggressive HARQ transmission releases buffer constraint from receiver side
HARQ entity can boost transmission rate beyond HARQ buffer capability
Receiver may not store the HARQ burst when buffer is full
Packet is dropped due to buffer outage
It further introduces HARQ failure and makes HARQ performance unpredicatible
Tri-state HARQ mechanism
If decoded data is correct, MS feedbacks ACK
If decoded data is incorrect and the redundancy version can be stored in the HARQ buffer, MS feedbacks NACK
If decoded data is incorrect and redundancy version can not be stored in the HARQ buffer, MS feedbacks DROP
BS will retransmit the dropped packet when DROP is received, otherwise, BS will follow existing HARQ mechanism

4. Simulation Environments
Three mechanisms are compared
Tri-State HARQ feedback
Two-State HARQ feedback with buffer constraint
Two-State HARQ feedback without buffer constraint
Simulation Environments
HARQ burst = 600 bytes
Maximum 8 HARQ processes
Maximum 4 successful transmissions
HARQ buffer ranges from 10K~80K soft bits
Round trip delay=20ms
Peak rate= 1.92Mbps
No feedback error
PB 3km/hr, VA 30km/hr and 120km/hr
Aggregation buffer is applied

5. IR-HARQ with PB 3km/hr No CQI Report Error
Transmission rate increases by 2~8 times for tri-state HARQ mechanism and two-state HARQ mechanism without buffer constraint
Tri-state HARQ mechanism further provides throughput gain when buffer is insufficient
Two-state HARQ mechanism introduces large HARQ failure rate when Buffer is insufficient

6. IR-HARQ with VA 30km/hr No CQI Report Error
Transmission rate increases by 2~8 times for tri-state HARQ mechanism and
Tri-state HARQ mechanism further provides throughput gain 30~80% throughput gain when HARQ buffer is below 20K soft bits
Two-state HARQ mechanism introduces large HARQ failure rate when HARQ buffer is below than 60K soft bits

7. IR-HARQ with VA 120km/hr No CQI Report Error
Transmission rate increases by 2~8 times for tri-state HARQ mechanism and
Tri-state HARQ mechanism further provides throughput gain 30~80% throughput gain when HARQ buffer is below 20K soft bits
Two-state HARQ mechanism introduces large HARQ failure rate when HARQ buffer is below than 60K soft bits

8. 1-bit HARQ feedback Four orthogonal sequences indexes ACK/NACK
Each MS chooses one sequence from even numbered channel or odd number numbered channel
The MS sends the chosen sequence as the HARQ feedback
Sequence index
Orthogonal sequence
1-bit Feedabck
[ ]
Even numbered channel ACK 1
[ ]
Even numbered channel NACK 2
[ ]
Odd numbered channel ACK 3
[ ]
Odd numbered channel NACK

9. Tri-State HARQ feedback
Three sequences are chosen from orthogonal sequences.
The power boosting level is identical to 1-bit HARQ feedback
Sequence index
Orthogonal sequences
Tri-state HARQ feedback
[ ]
ACK 1
[ ]
NACK 2
[ ]
DROP 3
[ ]
Reserved

10. Nine-State HARQ feedback
Nine sequences constructed by orthogonal sequences with linear combination.
Unified receiver architecture can be applied
The power boosting level is identical to 1-bit HARQ feedback
Sequence index
Sequences
Nine-state HARQ feedback
[ j j j j]
ACK/ACK 1
[ j j j j]
ACK/NACK 2
[ j j j j]
ACK/DROP 3
[ j j j j]
NACK/ACK 4
[ j j j j]
NACK/NACK 5
[ j j j j]
NACK/DROP 6
[ j j j j]
DROP/ACK 7
[ j j j j]
DROP/NACK 8
[ ]
DROP/DROP

11. Simulation Environment
HMT is referred to AWD
Simulation parameters are referred to EVM
Channel Bandwidth
10MHz
Over-sampling Factor
28/25
FFT Size
1024
Cyclic prefix (CP) ratio
1/8
Channel condition
PB3, VA120, VA350
The number of antennas
Tx:1, Rx:2
Modulation
BPSK/MPSK
FMT size
2x6
Receiver
HARQ FB: non-coherent detection, MLD

12. Performance Comparison
Tri-State HARQ feedback provides similar performance to 1-bit HARQ feedback
Nine-State HARQ feedback provides similar performance to 1-bit HARQ feedback

13. Conclusion
Tri-state HARQ feedback enhances the HARQ throughput without HARQ failure
The proposed tri-state HARQ feedback provides similar performance than 1-bit HARQ feedback
Nine-state HARQ feedback provide similar performance to 1-bit HARQ feedback with identical radio resource
Recommend to adopt the proposed text #1 in C802.16m-09/0894r4