Antenna Permuted CDD plus MIMO
Document Number:
IEEE S802.16m-08_1129
Date Submitted:
2008-9-15
Source:
Xiaolong ZHU, Hongwei YANG, Dong LI, Liyu CAI
Alcatel Shanghai Bell Co., Ltd.
E-mail:
Voice:
+86 21 58541240 Ext 7796
Hongwei.yang@alcatel-sbell.com.cn
*<http://standards.ieee.org/faqs/affiliationFAQ.html>
Venue:
SDD Session 56 Cleanup, call for PHY details; response to IEEE 802.16m-08/033 Call for Contributions and Comments on Project 802.16m
System Description Document (SDD) for Session 57
Detailed physical layer comments on: Open-loop MIMO in section 11.8.2.1.1
Base Contribution:
IEEE C802.16m-08_1129
Purpose:
For 802.16m discussion, adoption into the SDD and eventual adoption for standardization
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Introduction
• In session #56, OL SU-MIMO are determined as FFS,
which includes the antenna permuted CDD plus MIMO,
according to July meeting comment #64 in C80216m08_880
• Based on the schedule of OL SU-MIMO subgroup, we
gave the formulation of antenna permuted CDD plus
MIMO in IEEE C80216m-MIMO-08_009
• Basically, candidate OL SU-MIMO schemes can be
divided into two classes. One is based on the common
pilot while the other is applying the dedicated pilot.
Introduction
• There is no consensus yet to which one is better.
– E.g., IEEE C80216m-MIMO-08_058 states that the common pilot
based schemes outperform those with the dedicated pilot
– E.g., IEEE C80216m-MIMO-08_054 concludes that schemes with
dedicated pilot show better performance than those with common
pilot due to pilot overhead gain
• We suggest that dedicated pilot based OL SU-MIMO
should be supported, especially in the case of 4Tx and
8Tx antennas
– Low pilot overhead
– Transparent to terminals
Antenna Permuted CDD plus MIMO
• CDD+MIMO (STBC/SFBC or SM) is useful to map rate-1 and rate-2
MIMO encoding to 4Tx and 8Tx
• Antenna permuted CDD+MIMO applies an antenna permutation (AP)
function on the top of CDD+MIMO to enhance the robustness to the
spatial correlation
• By antenna permutation, the mapping from streams to physical
antennas can change from one RU to another or from one group of
RUs to another.
• For the rate-1 transmit diversity (i.e., AP-CDD+STBC/SFBC) and the
rate-2 spatial multiplexing (i.e., AP-CDD+SM), only the 2-stream
orthogonal (dedicated) pilot pattern is required, which saves the pilot
overhead greatly. Since AP is performed on the basis of RU, APCDD+MIMO is also transparent to terminals.
Simulation conditions
Parameter
Assumption
Carrier frequency = 2.5 GHz
OFDM parameters
FFT size = 1024; CP length = 128 samples
WiMAX downlink, PUSC permutation
Channel model
3GPP SCME - Urban Macro, 30kmph
Channel code
CTC, code rate = 1/2
Modulation scheme
16QAM
Antenna configuration
4Tx with antenna spacing of {0.5 or 10}
Channel estimation
Perfect channel estimation
Delay samples for CDD
 0  0,1  64, 2  0, 3  64
Antenna Permutation
Only in the time domain: slot by slot
Decoder
STBC: Alamouti decoder
SM: QRM-MLD
Simulation results
•
For uncorrelated channel, AP-CDD+MIMO has similar performance to CDD+MIMO
•
For correlated channel, the gain of AP-CDD+MIMO over CDD+MIMO is 0.4~0.8dB
•
More gain will be expected at high correlated channels such as in suburban macro cells
and/or antenna permutation conducted in both time and frequency domains
WiMAX DL, Urban Macro, 30kmph, 16QAM, 1/2CTC
0
WiMAX DL, Urban Macro, 30kmph, 16QAM, 1/2CTC
0
10
10
-1
-1
10
BLER
BLER
10
-2
-2
10
10
AP-CDD+STBC, AS=0.5
CDD+STBC, AS=0.5
AP-CDD+STBC, AS=10
CDD+STBC, AS=10
AP-CDD+SM, AS=0.5
CDD+SM, AS=0.5
AP-CDD+SM, AS=10
CDD+SM, AS=10
-3
-3
10
3
4
5
6
7
8
SNR in dB
AP-CDD + STBC
9
10
10
9
10
11
12
13
14
15
16
SNR in dB
AP-CDD + SM
17
18
19
Text proposal
•
In the precoder for SU-MIMO, both matrixes D
and W may be frequency/time dependent