1. Performance Comparison of Antenna Selection and DSTBC
July 2004
doc.: IEEE /681r0
July 2004
Performance Comparison of Antenna Selection and DSTBC
Huaning Niu, Henry Horng and Chiu Ngo
Samsung Electronics
Chiu Ngo, Samsung Electronics

2. Contents Motivation Down-link transmission for MIMO-OFDM
July 2004
Contents
Motivation
Down-link transmission for MIMO-OFDM
Antenna selection: closed loop approach
Double space time block code (DSTBC): open loop approach
Simulation parameters and results
Conclusions
Chiu Ngo, Samsung Electronics

3. July 2004
Motivation
The number of antennas is dependant on the physical size of the transmitter/receiver
For some types of application, Nt>Nr
Small/low cost mobile terminals with Nr antennas
Large/high cost access point with Nt antennas
Only Nr (<Nt) data streams can be supported at the AP
Channel correlation induces performance loss
Two MIMO approaches:
closed loop: antenna selection
open loop: spatial multiplexing w/ STBC
Chiu Ngo, Samsung Electronics

4. Antenna Selection (Closed loop)
July 2004
Antenna Selection (Closed loop)
Exact channel knowledge (ECK):
Statistical channel knowledge (SCK): where Rt is the first cluster’s transmitter covariance matrix, Rt,select_i is the principal subset that corresponds to the selected transmit antennas.
Need feedback overheads
Chiu Ngo, Samsung Electronics

5. Double Space Time Block Codes (Open Loop w/ 4×2 configuration)
July 2004
Double Space Time Block Codes (Open Loop w/ 4×2 configuration)
Higher diversity order than the antenna selection
More RF chains and higher complexity in MIMO detection
Chiu Ngo, Samsung Electronics

6. Simulation Parameters
July 2004
Simulation Parameters
IEEE a PHY based frame
Number of Subcarriers (data subcarriers): 64 (48)
Number of Cyclic Prefix: 16
Sampling Rate: 20MHz
Modulation and Coding: 16QAM with ½ coding
MIMO detection: zero-forcing w/o interference cancellation
Antenna configuration: 4×2
Packet size: 720Byte
11n channel models B and D
Chiu Ngo, Samsung Electronics

7. Channel Model Channel Model: 802.11n Channel B
July 2004
Channel Model
Channel Model: n Channel B
First cluster autocorrelation w/ antenna spacing 0.5λ : Highly spatial correlated
First cluster autocorrelation with antenna spacing λ :Less spatial correlated
Chiu Ngo, Samsung Electronics

8. Simulation Results with channel B (I)
July 2004
Simulation Results with channel B (I)
PER using ZF detector over channel B with antenna spacing 0.5
BER using ZF detector over channel B with antenna spacing 0.5
Chiu Ngo, Samsung Electronics

9. Simulation Results with Channel B (II)
July 2004
Simulation Results with Channel B (II)
BER using ZF detector over channel B with antenna spacing 0.75
PER using ZF detector over channel B with antenna spacing 0.75
Chiu Ngo, Samsung Electronics

10. Simulation Results with Channel B (III)
July 2004
Simulation Results with Channel B (III)
BER using ZF detector over channel B with antenna spacing
PER using ZF detector over channel B with antenna spacing
Chiu Ngo, Samsung Electronics

11. Simulation Results with Channel D (I)
July 2004
Simulation Results with Channel D (I)
BER using ZF detector over channel D with antenna spacing 0.5
PER using ZF detector over channel D with antenna spacing 0.5
Chiu Ngo, Samsung Electronics

12. Simulation Results with Channel D (II)
July 2004
Simulation Results with Channel D (II)
BER using ZF detector over channel D with antenna spacing
PER using ZF detector over channel D with antenna spacing
Chiu Ngo, Samsung Electronics

13. July 2004
Conclusions
Channel correlation matrix plays an important role in system design
Performance of the antenna selection is highly sensitive to channel correlation.
DSTBC has less performance sensitivity to channel correlation. It provides better performance but with higher complexity (Require more RF chains, higher MIMO detection complexity).
When channel is highly correlated (channel B with λ/2 spacing), SCK antenna selection gives the best design tradeoff (less RF chains, less complexity in feedbacks)
The effectiveness of antenna selection is reduced with higher frequency selectivity (as in the case of channel model D)
Chiu Ngo, Samsung Electronics

14. July 2004
Reference
D.A. Gore, R.W. Heath and A.J. Paulraj, “Transmit selection in spatial multiplexing systems,” IEEE Comm. Letters, Vol. 6, No. 11, Nov. 2002, pp
R.W. Heath, S. Sandhu and A. Paulraj, “Antenna selection for spatial multiplexing systems with linear receivers,” IEEE Comm. Letters, Vol. 5, No. 4, Apr. 2001, pp
D.A. Gore and A.J. Paulraj, “MIMO Antenna subset selection with space-time coding,” IEEE Trans. On Signal Processing, Vol. 50, No. 10, Oct. 2002, pp
3GPP document, “3GPP TR v.1.3.1, Multiple input multiple output in UTRA,” May 2004
Chiu Ngo, Samsung Electronics