Experimental Studies on a Decision-Feedback Channel Tracking Scheme Implemented in FPGA for MIMO-OFDM Systems

Yusuke ASAI
Wenjie JIANG

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E90-A    No.11    pp.2423-2430
Publication Date: 2007/11/01
Online ISSN: 1745-1337
DOI: 10.1093/ietfec/e90-a.11.2423
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Wideband Systems)
Category: MIMO-OFDM
MIMO,  OFDM,  channel tracking,  channel estimation,  Doppler shift,  IEEE 802.11n,  wireless LAN,  frame aggregation,  

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This paper describes the experimental evaluation of a testbed with a simple decision-feedback channel tracking scheme for MIMO-OFDM systems. The channel tracking scheme periodically estimates the channel state matrix for each subcarrier from received signals and replicas of the transmitted signal. The estimated channel state matrices, which are obtained at mutually different timings, are combined based on maximum ratio combining and used for MIMO signal detection. The testbed was implemented on field programmable gate arrays (FPGAs) of 1/5 scale, which confirms the implementation feasibility of the channel tracking scheme. The packet error rate (PER) and mobility performance of the testbed were measured. The testbed employed a 22 MIMO channel, zero-forcing algorithm for MIMO signal detection, 16QAM for the subcarrier modulation scheme, and coding rate of 1/2. The proposed scheme suppressed the increase in the required SNR for PER of 10-2 to less than 1 dB when the relative velocity between the transmitter and the receiver was less than 45 km/h assuming 5 GHz band operation. In addition, the proposed scheme offers 6.3% better throughput than the conventional scheme. The experimental results demonstrate that the channel tracking scheme implemented in the testbed effectively tracks the fluctuation of a MIMO channel.