Proposal for IEEE 802.16m CQI Feedback Channel Design
Document Number: IEEE C80216m-08/937r2
Date Submitted: 2008-09-05
Source:
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 #57
Base Contribution:
N/A
Purpose:
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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1
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
2
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
3
UL Fast Feedback channel & PHY Structure
(2)
Distribute PRUs to
localized and
distributed groups
Permutation
Permutation
Outer
Permutation
of PRU to
Freq.
partitions
Freq. Part2
Physical frequency
Freq. Part1
(1)
Distribute PRU to Freq.
Partitions
Resource groups
Inter-cell (semi static)
Localized
(3)
Distribute subcarriers
to subchannels (LRUs)
Data
Control
Distributed
group
Data
Localized
Data
Control
Distributed
group
Tile
permutation [or
hopping]
00
01
02
03
04
05
06
07
08
09
...
Tile
permutation [or
hopping]
Data
Single resource
Intra-cell (potentially dynamic)
UL Fast feedback channels are carried in UL Control DRU
4
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
5
UL Fast Feedback Channel Structure
– Semi orthogonal sequence of PCQICH
#
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
sequence
111111111111
101011100010
100101110001
110010111000
101001011100
100100101110
100010010111
110001001011
111000100101
111100010010
101110001001
110111000100
001111110011
010001000101
001000101100
001010000011
#
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
sequence
001011011111
010001111001
010010111111
010011000010
010110001000
011000010100
011101011110
000100010110
011000100010
011111001101
000010011001
000010100110
000111100000
001001001001
001001110000
001100010001
• Max cross-correlation ≤ 4
• Support payload bits up to 5 bits
• Non-coherent detection
6
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
2 subcarries
6 OFDM sysmbols
A1
A3
2x6
A1
A4
2x6
A2
A1
2x6
A2
A5
2x6
P
P
one coded block
A3
Tile structure of 2x6
A2
2x6
11bits payload
(rep. 2)
A3
A6
2x6
22 bits payload
7
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
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
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
9
Simulation Setting
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
Note: identical transmit power per symbol is assumed
10
Performance results : PCQICH with 4/5bits CQI
10
PER
10
10
10
10
•
4bits: 1x2
5bits:1x2
4bits: 1x4
5bits: 1x4
-1
-2
-3
-4
-10
•
PPBCH: 4~5bits: PB3
0
-9
-8
-7
-6
-5
-4
SNR (dB)
-3
-2
-1
0
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
11
Performance results : SCQICH with 11/22 bits CQI
10
10
PER
10
10
10
10
10
SFBCH: 2x6, 11/22bit (PB3) (non-ideal CE)
0
11bits: 1x2
11bits: 1x4
22bits: 1x2
22bits: 1x4
-1
-2
-3
-4
-5
-6
-8
-6
-4
-2
0
2
SNR (dB)
4
6
8
10
12
12
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
13
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
14
Backup Slides
15
UL Channel Feedback Design Requirements
•
Overhead: Should reduce the overhead
–
–
•
•
•
•
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:
–
–
–
•
•
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;
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
16
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:
3
log
(
C
2
24 )
• Format 2 of OL MU-MIMO:
3
)
• others: log 2 (C12
17
MIMO Feedback message information (cont.)
• Narrow band feedback bits per user for different MIMO modes
Inf. type
Long period
OL MU-MIMO
CL MU-MIMO
Format 1
Format 2
8
8
11
2~4
1x3=3
n/a
Total bits
10~12
11
11
2x2=4
CQI
4x3=12
4x3=12
4x3=12
4x3=12
PMI
(Transformed
codebook)
3x3=9
n/a
3x3=9
3x3=9
21
12
21
21
Subband Index
Rank index
Short period
CL SU-MIMO
Total bits
Note: assuming best-M base
7
18
PCQICH: 4 bits: 2x6 vs. 3x6
10
10
PER
10
10
10
10
PPBCH: 4bits, 2x6 vs. 3x6 (PB3)
0
-1
2x6:
3x6:
2x6:
3x6:
4bits, 1x2
4bits, 1x2
4bits: 1x4
4bits: 1x4
-2
-1
-2
-3
-4
-5
-10
-9
-8
-7
-6
-5
-4
SNR (dB)
-3
0
• tile size 2x6 is preferred than 3x6
19
SCQICH: 11 bits, 2x6 vs. 3x6
10
10
PER
10
10
10
10
10
PB3 - 11 bits - 1x2
0
2x6:
2x6:
3x6:
3x6:
-1
ideal
CE
ideal
CE
-2
-3
-4
-5
-6
-10
-8
-6
-4
-2
0
2
4
SNR (dB)
6
8
10
12
14 15
• 2x6 is preferred compared with 3x6 due to more freq. diversity gain
20
SCQICH: 22 bits, 2x6 vs. 3x6
10
10
PER
10
10
10
10
10
PB3 - 22 bits - 1x2
0
2x6:
2x6:
3x6:
3x6:
-1
-2
Ideal
CE
ideal
CE
-3
-4
-5
-6
-10
-8
-6
-4
-2
0
2
4
SNR (dB)
6
8
10
12
14 15
• 2x6 has 1dB gain over 3x6
21