Transcript IEEE C802.16m-09/0850

Performance Comparison of CDM and FDM for Sounding Channel of 802.16m AWD
IEEE 802.16 Presentation Submission Template (Rev. 9)
Document Number:
IEEE C80216m-0850
Date Submitted:
2009-04-27
Source: KeunChul Hwang, Jing Li, Inseok Hwang, Soon Young Yoon
Samsung Electronics
[email protected]
Venue: IEEE 802.16m Session#61, Cairo, Egypt
Base Contributions:
N/A
Re:
Call for Contributions on Project 802.16m Amendment Working Document (AWD) Content
Purpose:
To discuss and adopt in TGm
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Motivation
• There are Two Options for sounding multiplexing in the current UL CTRL
AWD text (80216m-09_0010r1a),
– Option 1: decimation separation (FDM) or cyclic shift separation (CDM)
– Option 2: decimation separation (FDM)
• Link-level and system-level simulation results are provided to compare the
performance of decimation separation (FDM) and cyclic shift separation
(CDM).
Summary
• Performance of CDM and FDM depends on the number of MS per sector,
the channel estimation scheme and interference level
Preferred
Scheme
K=1 MS/sector
K=6 MS/sector
LS
LS+MMSE
LS
LS+MMSE
Noise limited
CDM
CDMFDM
CDM
FDM
Interference
limited
CDM
CDM
CDM
CDMFDM
• Option 1 is needed for 16m Sounding due to different performance of
CDM and FDM
UL SINR distribution (57 sectors)
• Performance at low SINR ( less than 0dB) should be paid more attention
• The following simulations focus on performance at SINR [-10, 10]dB
UL SINR distribution
1
98% of MSs have SIR less than 0dB
0.9
0.8
0.7
55% of MSs have SIR less than 0dB
CDF
0.6
0.5
0.4
0.3
6MS/sctr
1 MS/sctr
0.2
0.1
0
-30
-25
-20
-15
-10
-5
SINR (dB)
0
5
10
15
Simulation parameters
OFDM parameters
Sounding sequence
10 MHz (1024 subcarriers, 864 used subcarriers)
CDM cyclic shift (P): 6, 18
cyclic shift index: 0,1,2,…,K for both serving and interference cell
FDM decimation value (D): 6, 18
subcarrier offset (g=0,1…D) for both serving and interference cell
Loading size
72 tones (one band)
# of sectors
1 for noise limited case
2 for interference limited case
# of MS per sector (K)
Channel model
1 or 6
ITU modified Ped.-B (3km/h, 2.4GHz)
Channel estimation
-LS
-LS+MMSE: perform LS over each P tones, then MMSE over 18 tones
Performance Metric
MSE
LLS results (K=1,P=D=18)
• In noise limited case, using LS+MMSE, CDM and FDM have similar
performance
• In the other cases, CDM performs better than FDM
Noise limited, K=1, P=D=18
2 sectors, K=1, P=D=18
0
10
CDM LS
FDM LS
CDM LS+MMSE
FDM LS+MMSE
-2
-4
5
0
MSE (dB)
-6
MSE (dB)
CDM LS+MMSE
FDM LS+MMSE
CDM LS
FDM LS
-8
-10
-12
-5
-10
-14
-15
-16
-18
-10
-8
-6
-4
-2
0
SNR (dB)
2
4
6
8
10
-20
-10
-8
-6
-4
-2
0
SIR (dB)
2
4
6
8
10
LLS results (K=1,P=D=6)
• In noise limited case, using LS+MMSE, CDM and FDM have similar
performance
• In the other cases, CDM performs better than FDM
Noise limited, K=1, P=D=6
2 sectors, K=1, P=D=6
5
10
CDM LS
FDM LS
CDM LS+MMSE
FDM LS+MMSE
0
CDM LS
FDM LS
CDM LS+MMSE
FDM LS+MMSE
5
-5
MSE (dB)
MSE (dB)
0
-10
-5
-10
-15
-15
-20
-20
-10
-8
-6
-4
-2
0
SNR (dB)
2
4
6
8
10
-25
-10
-8
-6
-4
-2
0
SIR (dB)
2
4
6
8
10
LLS results (K=6,P=D=18)
• In noise limited case, using LS+MMSE, FDM performs better
• In the other cases, CDM performs better than FDM
Noise limited, K=6, P=D=18
2 sectors, K=6, P=D=18
0
CDM LS
FDM LS
CDM LS+MMSE
FDM LS+MMSE
-2
-4
CDM LS
FDM LS
CDM LS+MMSE
FDM LS+MMSE
0
-6
MSE (cB)
MSE (dB)
-5
-8
-10
-10
-12
-14
-15
-16
-18
-10
-8
-6
-4
-2
0
SNR (dB)
2
4
6
8
10 -20
-10
-8
-6
-4
-2
0
SIR (dB)
2
4
6
8
10
LLS results (K=6,P=D=6)
• CDM and FDM have similar performance when P=D=6 and K=6
Noise limited, K=6, P=D=6
2sectors, K=6, P=D=6
5
5
CDM LS
FDM LS
CDM LS+MMSE
FDM LS+MMSE
0
-5
MSE (dB)
MSE (dB)
0
-10
-15
-20
-10
CDM LS
FDM LS
CDM LS+MMSE
FDM LS+MMSE
-5
-10
-15
-8
-6
-4
-2
0
SNR (dB)
2
4
6
8
10
-20
-10
-8
-6
-4
-2
0
SIR (dB)
2
4
6
8
10
SLS results (P=D=6)
• SLS results (57 sectors) are provided with LS+MMSE channel estimation
• CDM is obviously better than FDM when K=1/Sector, and CDM is slightly
better than FDM when K=6/Secoter
P=D=6
1
CDM K=1
FDM K=1
CDM K=6
FDM K=6
0.9
0.8
0.7
CDF
0.6
0.5
0.4
0.3
0.2
0.1
0
-10
-5
0
5
10
SINR (dB)
15
20
25
30
Proposed Remedy
•
Modify the text in lines 65, page 118 (section 15.3.9.2.3.2. in 80216m09_0010r1a)
15.3.9.2.3.2 Multiplexing for multi-antenna and multi-AMS
AMS and multiple antennas per AMS can be multiplexed through [Option 1: decimation separation or
cyclic shift separation][Option2: decimation separation] in each sounding allocation. Also, in case of
multiple UL subframes for sounding, time division separation can be applied by assigning different AMS to
different UL subframe. For cyclic shift separation each AMS occupies all subcarriers within sounding
allocation and uses the different sounding waveform [Editor's note: remove this sentence if Option 2 will be
adopted]. For frequency decimation separation each AMS uses decimated subcarrier subset from the
sounding allocation set with different frequency offset. For antenna switching capable AMS, ABS can
command the AMS to switch the physical transmit antenna(s) for sounding transmission. The details for
supporting antenna switching on sounding is TBD.
Appendix. Channel estimation methods
• System model
y  Wh  n
T
 W  [ s1 s2
sK ] sk   sk [0], sk [1],...sk [ P  1]  is the sounding seq. of user k

T

hk is the freq. channel response of user k
where h  [h1 h2 hK ]
K is No. of users/sector
n denotes white noise
FDM

• LS
hLS  W H W HW 
1
y
CDM
1
1
2
2
:
:
D
P
hLS1
1
1
1
H
1
h
Rhp ( Rpp   2 I )1 hLS
diag ( Bias)
:
D
hLS2
1
2
MMSE
2
Loading size (one band)
Bias  Rhp ( Rpp   I ) Rhp
2
2
Loading size (one band)
• LS+MMSE
:
2
:
hLS3
P
hLS3
1
2
2
hLS4
:
:
Number of OFDMA
symbols
MMSE
1
1
D
hLS2
P
:
D
hLS1
P
hLS4
Number of OFDMA
symbols
Appendix. Impact of power difference
• Power difference has little impact on MSE performance of both FDM and
Noise limited, P=D=18
CDM
0
CDM LS wo powdiff
FDM LS wo powdiff
CDM LS+MMSE wo powdiff
FDM LS+MMSE wo powdiff
CDM LS w/ powdiff
FDM LS w/ powdiff
CDM LS+MMSE w/ powdiff
FDM LS+MMSE w/ powdiff
-2
MSE (dB)
-4
-6
-8
-10
-12
-10
•
Simulation condition
–
–
–
-5
0
5
SNR (dB)
10
15
20
Power difference between center and edge users : 10dB
Relative power difference at SNR = -10, -5, 0 (low geometry)
• [desired user#0, interf#1, interf#2,…interf#5] = [0dB 0dB 0dB 10dB 10dB 10dB]
Relative power difference at SNR = 5, 10 (high geometry)
• [desired user#0, interf#1, interf#2,…interf#5] = [0dB 0dB 0dB -10dB -10dB -10dB]