Uplink Control PHY Design for HARQ Tri-State Feedback Buffer Management

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

IEEE S802.16m-09/0894Date Submitted:2009-05-06

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 15.3.6.4.2.7 HARQ Feedback A-MAP IE Chapter 15.3.9.2.2 UL HARQ feedback control channel

Base Contribution: IEEE C802.16m-09/0894r4Purpose:

To be discussed and approval by IEEE 802.16m TGNotice:

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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

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

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

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

0 [+1 +1 +1 +1] Even numbered channel ACK

1 [+1 -1 +1 -1] Even numbered channel NACK

2 [+1 +1 -1 -1] Odd numbered channel ACK

3 [+1 -1 -1 +1] Odd numbered channel NACK

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

0 [+1 +1 +1 +1] ACK

1 [+ 1 +1 -1 -1] NACK

2 [+1 -1 +1 -1] DROP

3 [+1 - 1 -1 +1] Reserved

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

0 [-0.6124+3.4729j 2.9141 + 0.5138j 1.264 + 0.2229j 0.187-1.0607j] ACK/ACK

1 [-0.6124-0.2229j -1.264+3.4729j -0.187+0.5138j 2.9141+1.0607j] ACK/NACK

2 [-0.6124+1.0607j -1.8371-1.0607j 1.8371+1.0607j -1.8371+3.182j] ACK/DROP

3 [-0.6124-0.5138j 0.187-0.2229j -2.9141+3.4729j -1.264-1.0607j] NACK/ACK

4 [-0.6124+0.5138j 0.187+0.2229j -2.9141-3.4729j -1.264+1.0607j] NACK/NACK

5 [-0.6124-1.0607j -1.8371+1.0607j 1.8371-1.0607j -1.8371-3.182j] NACK/DROP

6 [-0.6124+0.2229j -1.264-3.4729j -0.187-0.5138j 2.9141-1.0607j] DROP/ACK

7 [-0.6124-3.4729j 2.9141-0.5138j 1.264-0.2229j 0.187+1.0607j] DROP/NACK

8 [4.899 0 0 0 ] DROP/DROP

2222222222222222

Simulation Environment

• HMT is referred to AWD• Simulation parameters are referred

to EVMChannel Bandwidth 10MHzOver-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 2x6Receiver HARQ FB: non-coherent

detection, MLD

time

frequency

…...

C2,0 C2,1 C2,0 C2,1 C2,0 C2,1

C2,2 C2,3 C2,2 C2,3 C2,2 C2,3

C0,0 C0,1 C0,0 C0,1 C0,0 C0,1

C0,2 C0,3 C0,2 C0,3 C0,2 C0,3

C1,0 C1,1 C1,0 C1,1 C1,0 C1,1

C1,2 C1,3 C1,2 C1,3 C1,2 C1,3

…...

HARQ FBCH

1, 2

HARQ FBCH

3, 4

HARQ FBCH

5, 6

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

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

Text Proposal[Add the following subclause after 15.3.6.4.2.7]Extended HARQ Feedback A-MAP IE includes two bits and corresponding

value for HARQ ACK/NACK/DROP information is shown in Table XXX. If extended HF-A-MAP IE has the 0b00, 0b01 or 0b10, it shall be interpreted as ACK information, NACK information and DROP information, respectively.

Syntax Size (bit) NotesHF-A-MAP IE format {HF-A-MAP IE value 2 0b00 : ACK feedback info.

0b01 : NACK feedback info.0b10: DROP feedback info.0b11: Reserved

}

Table XXX—Extended HF-A-MAP-IE

Text Proposal[Add the following subclause at the end of 15.3.9.2.2]15.3.9.2.2.1 Extended HARQ feedback control channelTo apply the HARQ buffer management by using tri-state feedback, e.g.,

ACK, NACK, and DROP, the mapping of the tri-state HARQ feedback to its corresponding feedback sequence are show in Table ZYX.

Table ZYX––Orthogonal sequences for UL tri-state HARQ feedback channel

Sequence index Orthogonal sequence Tri-state HARQ feedback0 [+1 +1 +1 +1] ACK1 [+1 +1 -1 -1] NACK2 [+1 -1 +1 -1] DROP3 [+1 -1 -1 +1] Reserved