1 Proposal for IEEE 802.16m CQI Feedback Channel Design Document Number: IEEE C80216m-08/937r2 Date Submitted: 2008-09-05 Source: Hongmei Sun, Changlong.

1

Proposal for IEEE 802.16m CQI Feedback Channel Design

Document Number: IEEE C80216m-08/937r2Date Submitted: 2008-09-05Source: Hongmei Sun, Changlong Xu, Jong-Kae (JK) Fwu, Email: {hongmei.sun, changlong.xu, jong-kae.fwu Jiacheng Wang, Senjie Zhang, Yang Gao, jiacheng.wang, senjie.zhang, yang.gao, Hujun Yin, Rath Vannithamby, Roshni Srinivasan, hujun.yin, rath.vannithamby, roshni.m.srinivasan, Sassan Ahmadi sassan.ahmadi} @ intel.com Intel Corporation

Venue: IEEE Session #57, Kobe, Japan.Re: PHY: SDD Text cleanup; in response to the TGm Call for Contributions and Comments 802.16m-08/033 for Session #57Base Contribution:

N/APurpose:

For TGm discussion and adoption of 802.16m SDD text.Notice:

This document does not represent the agreed views of the IEEE 802.16 Working Group or any of its subgroups. It represents only the views of the participants listed in the “Source(s)” field above. It is offered as a basis for discussion. It is not binding on the contributor(s), who reserve(s) the right to add, amend or withdraw material contained herein.

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2

Outline

• Requirements on CQI feedback• Fast Feedback Channel Design

– 2-level primary/secondary feedback reporting protocol

– Primary fast feedback channel structure

– Secondary fast feedback channel structure

– Performance and analysis

• Conclusions• SDD Text

3

Primary/Secondary Fast Feedback Channel Protocol

• UL Primary Fast Feedback channel (PCQICH)– Wideband CQI reports with fixed robust rate periodically

– Designed to cover all users

– BS makes decision and regulates UE’s CQI feedback behavior• Resource allocation• Feedback frequency

– Non-coherent detection

• UL Secondary fast feedback channel (SCQICH)– To covers users needing narrowband CQI feedback

– supports advance features efficiently with link adaptation• Adaptation is coarse on users’ long term statistics• Margin is added to guarantee reliability of adaptation

– BS decides and schedule SCQICH• whether to allocate, when to allocate, the amount of resource and

corresponding index, transmission frequency, rate

– Coherent detection

4

UL Fast Feedback channel & PHY Structure

Ph

ysic

al f

req

ue

ncy

Localized

Distributed group

(1)Distribute PRU to Freq.

Partitions

(2)Distribute PRUs to

localized and distributed groups

Localized

Distributed group

(3)Distribute subcarriers to subchannels (LRUs)

010203040506070809

00

...Outer Permutation of PRU to

Freq. partitions

Inter-cell (semi static) Intra-cell (potentially dynamic)

Resource groups Single resource

Data

Control

Data

Data

Control

DataP

erm

uta

tion

Fre

q.

Pa

rt1

Fre

q.

Pa

rt2

Pe

rmu

tatio

n

Tile permutation [or

hopping]

Tile permutation [or

hopping]

UL Fast feedback channels are carried in UL Control DRU

5

Fast feedback channel structure -- PCQICH

• Information Content– 4~5 bits payload

– Wideband CQI: 4bits

• Multiplexing:– PFBCH is FDM-ed with UL data and other control channels

– Multiple users are FDM/TDM-ed within PCQICH

• PHY Structure– FMT (Feedback Mini-Tile, Nsub x Nsym): 2x6

– Each logical FBCH occupies 3 FMTs

– Each LRU (18x6) can accommodate 3 FBCH

– Coding: semi-orthogonal sequence with BPSK, w. repetition 3

6

UL Fast Feedback Channel Structure – Semi orthogonal sequence of PCQICH

• Max cross-correlation ≤ 4• Support payload bits up to 5 bits• Non-coherent detection

# sequence 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 1 0 1 1 1 0 0 0 1 0 2 1 0 0 1 0 1 1 1 0 0 0 1 3 1 1 0 0 1 0 1 1 1 0 0 0 4 1 0 1 0 0 1 0 1 1 1 0 0 5 1 0 0 1 0 0 1 0 1 1 1 0 6 1 0 0 0 1 0 0 1 0 1 1 1 7 1 1 0 0 0 1 0 0 1 0 1 1 8 1 1 1 0 0 0 1 0 0 1 0 1 9 1 1 1 1 0 0 0 1 0 0 1 010 1 0 1 1 1 0 0 0 1 0 0 111 1 1 0 1 1 1 0 0 0 1 0 012 0 0 1 1 1 1 1 1 0 0 1 113 0 1 0 0 0 1 0 0 0 1 0 114 0 0 1 0 0 0 1 0 1 1 0 015 0 0 1 0 1 0 0 0 0 0 1 1

# sequence16 0 0 1 0 1 1 0 1 1 1 1 117 0 1 0 0 0 1 1 1 1 0 0 118 0 1 0 0 1 0 1 1 1 1 1 119 0 1 0 0 1 1 0 0 0 0 1 020 0 1 0 1 1 0 0 0 1 0 0 021 0 1 1 0 0 0 0 1 0 1 0 022 0 1 1 1 0 1 0 1 1 1 1 023 0 0 0 1 0 0 0 1 0 1 1 024 0 1 1 0 0 0 1 0 0 0 1 025 0 1 1 1 1 1 0 0 1 1 0 126 0 0 0 0 1 0 0 1 1 0 0 127 0 0 0 0 1 0 1 0 0 1 1 028 0 0 0 1 1 1 1 0 0 0 0 029 0 0 1 0 0 1 0 0 1 0 0 130 0 0 1 0 0 1 1 1 0 0 0 031 0 0 1 1 0 0 0 1 0 0 0 1

7

UL Fast Feedback Channel Structure -- SCQICH • Information Content

– Up to 11/22 bits payload– Narrowband CQI (effective SINR, PMI, RI, indexing)

• Multiplexing:– SCQICH is FDM-ed with UL data and other control channels– Multiple users are FDM/TDM-ed within SCQICH

• PHY Structure– FMT size of 2x6– Each logical SCQICH occupies 3 FMTs (diversity order = 3)– Coding/Modulation : information is encoded to 30bits by puncturing block codes

(32, 11, 12), then modulated to 15 QPSK symbols

A1 A3

A2 A1

2x6

2x6

A3 A2 2x6

A1 A4

A2 A5

2x6

2x6

A3 A6 2x6one coded block

P

P

6 OFDM sysmbols2 subcarries

Tile structure of 2x611bits payload (rep. 2) 22 bits payload

8

UL Fast Feedback Channel Structure-- SCQICH – Basis sequences for block code (32, 6≤K≤11)

n S0,n S1,n S2,n S3,n S4,n S5,n S6,n S7,n S8,n S9,n S10,n

0 1 0 0 0 0 0 0 0 0 0 0

1 0 1 0 0 0 0 0 0 0 0 0

2 1 0 0 0 0 1 0 0 0 0 0

3 1 1 0 0 1 0 0 0 0 0 0

4 0 1 0 0 0 1 1 0 0 0 0

5 0 0 0 0 1 1 0 1 0 0 0

6 0 0 0 0 1 0 1 0 1 0 0

7 1 0 0 0 0 0 1 1 0 1 0

8 0 1 0 0 0 0 0 1 1 0 1

9 0 0 1 0 0 1 0 0 1 1 0

10 1 0 0 1 1 0 0 0 0 1 1

11 1 1 1 0 0 0 1 0 0 0 1

12 0 1 1 1 0 1 0 1 0 0 0

13 1 0 0 1 1 1 0 0 1 0 0

14 1 1 0 0 1 0 1 0 0 1 0

15 0 1 0 0 0 1 1 1 0 0 1

9

UL Fast Feedback Channel Structure--SCQICH – Basis sequences for block code (32, 6≤K≤11)

n S0,n S1,n S2,n S3,n S4,n S5,n S6,n S7,n S8,n S9,n S10,n

16 1 0 1 0 1 1 0 1 1 0 0

17 0 1 0 1 1 0 1 0 1 1 0

18 1 0 0 0 0 1 1 1 0 1 1

19 0 1 1 0 1 0 0 1 1 0 1

20 1 0 1 1 0 1 1 0 1 1 0

21 0 1 0 1 1 0 0 1 0 1 1

22 0 0 1 0 0 1 1 0 1 0 1

23 0 0 1 1 1 0 0 1 0 1 0

24 0 0 0 1 0 0 1 0 1 0 1

25 0 0 1 0 0 0 0 1 0 1 0

26 0 0 0 1 0 0 0 0 1 0 1

27 0 0 1 0 0 0 0 0 0 1 0

28 0 0 0 1 0 0 0 0 0 0 1

29 0 0 1 0 0 0 0 0 0 0 0

30 0 0 0 1 0 0 0 0 0 0 0

31 1 1 1 1 1 1 1 1 1 1 1

10

Simulation Setting

Note: identical transmit power per symbol is assumed

Channel Bandwidth 10MHz

Over-sampling Factor 28/25

FFT Size 1024

Cyclic prefix (CP) ratio 1/8

Channel condition PedB 3km/h, PedA 3km/h

The number of antennas Tx:1, Rx:2, 4

Modulation BPSK/QPSK

Channel estimation 2-D MMSE

Tile size 2x6

Block size 6x6

Receiver PCQICH: non-coherent, MLD

SCQICH: coherent MLD

11

Performance results : PCQICH with 4/5bits CQI

• 4/5bit: -9/-8dB SNR to achieve PER=10% (1x4) guarantees the 95% coverage up to 5km cell size

• PCQICH: 5bit payload has only 0.5dB loss than that of 4bits payload

PCQICH can support very robust CQI transmission

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

10-4

10-3

10-2

10-1

100

SNR (dB)

PE

R

PPBCH: 4~5bits: PB3

4bits: 1x25bits:1x24bits: 1x45bits: 1x4

12

Performance results : SCQICH with 11/22 bits CQI

-8 -6 -4 -2 0 2 4 6 8 10 1210

-6

10-5

10-4

10-3

10-2

10-1

100

SNR (dB)

PE

R

SFBCH: 2x6, 11/22bit (PB3) (non-ideal CE)

11bits: 1x211bits: 1x422bits: 1x222bits: 1x4

13

Summary

• 2-level adaptive Primary/Secondary fast feedback channel framework

• UL Fast feedback channels are carried in UL Control DRU

• CQI Coding Block size: 6x6 (36 tones total)

• FMT size: 2x6, with diversity order = 3 for frequency diversity

• Coding:– PCQICH: semi-orthogonal code, support 4~5 payload bits– SCQICH: Block codes (32, 11, 12), support up to 11/22 payload bits

• Recommendation– UL Fast feedback channels are classified into 2 types: PCQICH and SCQICH– UL control DRU carries a fast feedback channel consists of 3 distributed tiles– FMT size of 2x6– Semi-orthogonal sequences are used for PCQICH w/ BPSK– Block codes are used as channel coding scheme for SCQICH w/ QPSK

14

Text proposal to SDD Text

Revise the text in red with following modified text in blue (Chapter 11 in [IEEE 802.16m-08/003r4 ])

11.9.2.1.2 PHY Structure• Replace

“The structure of the resource blocks, pilots and resource mapping for the UL fast feedback channel are TBD.”

with “ UL fast feedback channels are carried in UL control DRU, each feedback

channel is 6x6 composed by 3 fast feedback mini-tiles (FMT). Each FMT is 2 contiguous subcarries by 6 OFDM symbols. Primary fast feedback channel uses semi-orthogonal sequences with BPSK modulation, while secondary fast feedback channel uses block codes with QPSK modulation.”

• Adopt SCQICH block sequence shown in page 8,9• Adopt semi-orthogonal sequences shown in page 6• Adopt CQICH design text and figure shown on page 7

15

Backup Slides

16

UL Channel Feedback Design Requirements

• Overhead: Should reduce the overhead– less than 15% on average. Overhead for distributed is low, but for localized with

MIMO would be high– CQI Feedback granularity: Tradeoff between accurate reporting vs. broader

reporting; allow optimization for different scenarios;

• Coverage: CQICH design should be optimized for 1.5km/5km cell sizes with the assumed propagation models;

• Reliability: In 95% of coverage should be able to decode the relevant CQICH with less than 10% PER;

• Mobility: CQICH should be able to support optimal DL performance up to 10km/h.

• CQI feedback mechanism should support advanced PHY/MAC techniques:– frequency selective scheduling (FSS)– MIMO – Fractional frequency reuse (FFR)

• Error recovery: Error propagation possibility should be avoided or minimized;

• Complexity: The complexity involved in the CQI feedback scheme should be minimized

17

MIMO Feedback message information

• Distributed Mode: 4~6bits payload– OL SU-MIMO 5~6bits

– Average CQI only: 4 bits

2x2/4x2 4x4

CQI (bits) 4 4

Rank index (bits) 1 2

Total (bits) 5 6

• Localized mode: ~10-21 bits payload– 12 sub-bands (assuming RB size of 18x6 and each sub-band includes 4 RBs) – best-M based CQI reporting: M=3 (assuming 10 users)– MIMO modes:

• CL SU-MIMO, OL MU-MIMO, CL MU-MIMO

• 2x2, 4x2, 4x4

– Indexing:• Format 2 of OL MU-MIMO:

• others: )(log 3122 C

)(log 3242 C

18

MIMO Feedback message information (cont.)

• Narrow band feedback bits per user for different MIMO modes

Inf. type CL SU-MIMO OL MU-MIMO CL MU-MIMO

Format 1 Format 2

Long period Subband Index 8 8 11 7

Rank index 2~4 1x3=3 n/a

Total bits 10~12 11 11 2x2=4

Short period CQI 4x3=12 4x3=12 4x3=12 4x3=12

PMI(Transformedcodebook)

3x3=9 n/a 3x3=9 3x3=9

Total bits 21 12 21 21

Note: assuming best-M base

19

PCQICH: 4 bits: 2x6 vs. 3x6

• tile size 2x6 is preferred than 3x6

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0

10-5

10-4

10-3

10-2

10-1

100

SNR (dB)

PE

RPPBCH: 4bits, 2x6 vs. 3x6 (PB3)

2x6: 4bits, 1x23x6: 4bits, 1x22x6: 4bits: 1x43x6: 4bits: 1x4

20

SCQICH: 11 bits, 2x6 vs. 3x6

• 2x6 is preferred compared with 3x6 due to more freq. diversity gain

-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 1510

-6

10-5

10-4

10-3

10-2

10-1

100

SNR (dB)

PE

R

PB3 - 11 bits - 1x2

2x6: ideal2x6: CE3x6: ideal3x6: CE

21

SCQICH: 22 bits, 2x6 vs. 3x6

• 2x6 has 1dB gain over 3x6

-10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 1510

-6

10-5

10-4

10-3

10-2

10-1

100

SNR (dB)

PE

RPB3 - 22 bits - 1x2

2x6: Ideal2x6: CE3x6: ideal3x6: CE