Transcript IEEE C802.16m-08/1037

PHY Structure for UL Fast Feedback Channel in 802.16m Systems
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number: C80216m-08/1037
Date Submitted: 2008-09-05
Source:
Chih-Yuan Lin ([email protected]), Pei-Kai Liao ([email protected] ), Yu-Hao Chang ([email protected]),
Ciou-Ping Wu ([email protected]), and Paul Cheng ([email protected])
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 802.16m-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 802.16m SDD
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Outline
•
•
•
•
•
Introduction
Proposed UL control tile
Analysis results
Conclusion
Text proposal
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
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
UL Control Tile (2/2)
• Proposed control tile
– Two subcarriers and six OFDM symbols
• Other sizes are FFS
• Pilot location
– CQI feedback is in general supposed to be used for closedloop 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
Time
Freq.
• Pilots are located such that average distance
between each data and pilots is minimized
• Pilot density: 16.7 %
P
P
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)
0
2.5
5
7.5
10
12.5
SNR
(dB)
0
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
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
Num of Tiles
Num of
CQICH+MIMO
mode + PMI
1
1
1
2
2
3
2
3
2
3
4
6
4
4
4
8
5
6
5
6
5
6
10
12
7
7
7
14
8
9
8
9
8
9
10
10
10
16
18
20
Num of Tiles
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 19.29 %
• 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
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
Text Proposal
• 11.9.2.1.2 PHY Structure
The UL control tile and corresponding pilot pattern are as Figure X.
Freq.
Time
P
P
Figure X. UL control tile.