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ABSTRACT: The performance degradation in convolutionally coded V-BLAST system is analyzed in this paper. Compared with coded linear filtering approach, it is shown that the coded V-BLAST suffers from serious degradation due to the effect of error propagation. Considering the constraint of the system, a performance improvement method is proposed. It adjusts the weighting of soft bits, where the weighting for one stream is found based on the equivalent error rate of that stream. Additional computation needed by the proposed method is neglectable. Both theoretical analysis and simulation verify the effectiveness of the proposed method.
Vehicular Technology Conference, 2008. VTC Spring 2008. IEEE; 06/2008
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Proceedings of the 67th IEEE Vehicular Technology Conference, VTC Spring 2008, 11-14 May 2008, Singapore; 01/2008
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ABSTRACT: The problem of pilot placement for channel estimation in time-frequency-space lattice in MIMO- OFDM system under frequency-selective fast fading MIMO channel is addressed in this paper. Given the least square channel estimation algorithm and orthogonal pilot signal format design, four different pilot placement schemes are analyzed in a uniformed manner. The theoretical and simulated mean square errors of the schemes show that, the scheme of placing pilots on frequency-equal-spaced and time-shifted subcarriers has good performance and balanced complexity.
Wireless Telecommunications Symposium, 2007. WTS 2007; 05/2007
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ABSTRACT: This paper investigates the effective gain of antennas in indoor channels. A metric called instantaneous effective gain is proposed, and a multiple-cluster 3D channel model is used to facilitate the proposed antenna effective gain. In the multiple-cluster channel model, Laplacian and double exponential distribution are utilized to model azimuth and elevation signal power distribution respectively, and multiple clusters are built to describe the instantaneous channel power distribution. The modified antenna effective gain and multiple-cluster channel model are suitable for evaluating the antennas in antenna switching system. By using the proposed metric and the channel model, it is also found by simulation that the elevation mismatch of antenna patterns with indoor channels reduces the effective gain in the antenna switching system.
Sarnoff Symposium, 2007 IEEE;
