Performance Comparison of Antenna Selection and DSTBC July 2004 doc.: IEEE 802.11-04/681r0 July 2004 Performance Comparison of Antenna Selection and DSTBC Huaning Niu, Henry Horng and Chiu Ngo Samsung Electronics Chiu Ngo, Samsung Electronics

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

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

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

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

Simulation Parameters July 2004 Simulation Parameters IEEE 802.11a 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

Channel Model Channel Model: 802.11n Channel B July 2004 Channel Model Channel Model: 802.11n 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

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

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

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

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

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

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

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. 491-493 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.142-144 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.2580-2588 3GPP document, “3GPP TR 25.876 v.1.3.1, Multiple input multiple output in UTRA,” May 2004 Chiu Ngo, Samsung Electronics