HARQ Buffer Management for Aggressive HARQ transmission

IEEE 802.16 Presentation Submission Template (Rev. 9) Document Number:

IEEE S802.16m-09/0891r1Date Submitted:2009-4-30

Source: Zheng Yan-Xiu, Yu-Chuan Fang, Chang-Lan Tsai, Chung-Lien Ho, Hsi-Min Hsiao E-mail: zhengyanxiu@itri.org.tw. ITRI

Venue:

Re: IEEE 802.16m-09/0020, Call for contributions on 16m AWD content. Amendment Working Document (IEEE 802.16m-09/0010r1a).

Chapter 15.3.6 DL control information elements Base Contribution:

Purpose:To be discussed and approval by IEEE 802.16m TG

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Motivation

• 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

• This contribution introduces tri-state HARQ feedback to maintain the reliable HARQ performance

Proposed Mechanism

• 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

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

IR-HARQ with PB 3km/hrNo 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

IR-HARQ with VA 30km/hrNo 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

IR-HARQ with VA 120km/hrNo 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

Conclusions

• Tri-State HARQ mechanism guarantees HARQ reliability even there is package drop due to buffer overflow

• Tri-State HARQ mechanism can boosts throughput by 5~8 times• Tri-State HARQ mechanism is recommended to adopted to 16m to increase

transmission rate with buffer constraint• Recommend to adopt the proposed text #1 in C802.16m-09/0894r1• Recommend to adopt the proposed text #2 in C802.16m-09/0894r1• Recommend to adopt the proposed text #3 in C802.16m-09/0894r1• Recommend to adopt the proposed text #4 in C802.16m-09/0894r1• Recommend to adopt the proposed text #5 in C802.16m-09/0894r1

APPENDIX

AGGRESSIVE IR-HARQ TRANSMISSION WITH 3DB CQI REPORT ERROR

IR-HARQ with PB 3km/hr3dB CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism and two-state HARQ mechanism without buffer constraint

• At high SNR, aggressive HARQ mechanism provides more transmission rate• 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

IR-HARQ with VA 30km/hr3dB CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism• Aggressive HARQ mechanism increases more throughput when SNR is high• Two-state HARQ mechanism introduces large HARQ failure rate when HARQ buffer

is below than 60K soft bits or SNR is below than 16dB• Two-state HARQ mechanism introduces less transmission rate due to high HARQ

failure rate

IR-HARQ with VA 120km/hr3dB CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism• Aggressive HARQ mechanism increases more throughput when SNR is high• Two-state HARQ mechanism introduces large HARQ failure rate when HARQ buffer

is below than 60K soft bits or SNR is below than 16dB• Two-state HARQ mechanism introduces less transmission rate due to high HARQ

failure rate

AGGRESSIVE CC-HARQ TRANSMISSION WITH NO CQI REPORT ERROR

CC-HARQ with PB 3km/hrNo CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism• Two-state HARQ mechanism introduces large HARQ failure rate when

HARQ buffer is below than 60K soft bits• Link reliability significantly decreases due to highly correlated channel

condition

CC-HARQ with VA 30km/hrNo CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism• Two-state HARQ mechanism introduces large HARQ failure rate when

HARQ buffer is below than 60K soft bits• Tri-State HARQ mechanism provides better link quality

CC-HARQ with VA 120km/hrNo CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism• Two-state HARQ mechanism introduces large HARQ failure rate when

HARQ buffer is below than 60K soft bits• Tri-State HARQ mechanism provides better link quality

AGGRESSIVE IR-HARQ TRANSMISSION WITH 3DB CQI REPORT ERROR

CC-HARQ with PB 3km/hr3dB CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism• Two-state HARQ mechanism introduces large HARQ failure rate when

HARQ buffer is below than 60K soft bits• Link reliability significantly decreases due to highly correlated channel

condition

CC-HARQ with VA 30km/hr3dB CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism• Two-state HARQ mechanism introduces large HARQ failure rate when

HARQ buffer is below than 60K soft bits• Tri-State HARQ mechanism provides better link quality

CC-HARQ with VA 120km/hr3dB CQI Report Error

• Transmission rate increases by 2~8 times for tri-state HARQ mechanism• Two-state HARQ mechanism introduces large HARQ failure rate when

HARQ buffer is below than 60K soft bits• Tri-State HARQ mechanism provides better link quality