1. PHY Structure for UL Fast Feedback Channel in 802.16m Systems
IEEE Presentation Submission Template (Rev. 9)
Document Number: C80216m-08/1037
Date Submitted:
Source:
Chih-Yuan Lin Pei-Kai Liao ), Yu-Hao Chang
Ciou-Ping Wu and Paul Cheng
MediaTek Inc.
No.1, Dusing Road 1,
Science-Based Industrial Park,
Hsinchu, Taiwan 300, R.O.C.
Re: PHY: SDD Session 56 Cleanup; in response to the TGm Call for Contributions and Comments m-08/033 for Session 57.
Base Contribution: This is the base contribution
Purpose:
Propose to be discussed and adopted by TGm for the use in Project m SDD
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2. Outline Introduction Proposed UL control tile Analysis results
Conclusion
Text proposal

3. Introduction UL control channel types
CQI feedback channel
Precoder matrix index (PMI) feedback
MIMO mode selection
ACK/NACK channel
This contribution focuses on UL fast feedback channel, which includes above feedback channels except ACK/NACK
UL fast feedback control tile
Corresponding pilot pattern

4. UL Control Tile (1/2) Considerations of determining UL control tile
UL tile size should be multiple of UL control tile
Convenient to partition control and data channels in a subframe
No data tones would be wasted
Tile size
Since CQI is in general small information, tile size should not be too large
Smaller tile size can provide larger frequency diversity gain

5. UL Control Tile (2/2) Proposed control tile Pilot location
Two subcarriers and six OFDM symbols
Other sizes are FFS
Pilot location
CQI feedback is in general supposed to be used for closed-loop transmission
It would be better to design pilot pattern to cover low and medium mobility cases
We propose that each tile contains two pilots for channel estimation
Pilots are located such that average distance between each data and pilots is minimized
Pilot density: 16.7 % P
Freq.
Time

6. Analysis Results (1/3) PER performance Simulation parameters
One MS TX and four BS RX
Receiver type: maximal ratio combiner
Channel estimator: 2D-MMSE
Doppler spread matches 100 km/hr
MCS: QPSK ½
Channel model: PB 3 km/hr and VA 120 km/hr
SNR
(dB)
SNR
(dB)
2.5 5
7.5 10
12.5
2.5 5
7.5 10
12.5
PER
0.891
0.852
0.840
0.841
2.17e-3
1.17e-3
PER
0.886
0.861
0.860
0.862
2.31e-3
1.71e-3
PB3
VA120

7. Analysis Results (2/3) UL control example
Considered feedback information
CQI: 5 bits
MIMO mode: 2 bits
PMI: 3 bits
Number of repetitions: 2 (repetition code is used)
MCS: QPSK ½
Num of
CQICH+MIMO mode + PMI
Num of Tiles
Num of CQICH
Num of Tiles 1 1 1 2 2 2 2 4 3 3 3 6 4 4 4 8 5 5 5 10 6 6 6 12 7 7 7 14 8 8 8 16 9 9 9 18 10 10 10 20

8. Analysis Results (3/3)
Based on above analysis we have following discussions
Considered scenarios : each subframe is allocated to 8 users under 10 MHz bandwidth
Case 1: each user feedbacks one CQI per frame
Case 2: each user feedbacks 5 CQI values for five subbands per frame and feedback MIMO mode index and PMI every two frames
For case 1, UL control overhead is about 2%
For case 2, UL control overhead is about %
Note that multiuser MIMO requires relatively larger UL feedback overhead trading DL spectral efficiency
Note that above results are derived without considering any overhead reduction techniques

9. Conclusion
In general case, proposed UL control tile structure can efficiently support UL channel quality feedback
For advanced multi-user case, feedback overhead is largely increased, and thus it is suggested to utilize overhead reduction technique to eliminate the incurrence

10. Text Proposal 11.9.2.1.2 PHY Structure
The UL control tile and corresponding pilot pattern are as Figure X. P
Freq.
Time
Figure X. UL control tile.