Jeongchang Kim

Unitary space-time constellations based on quasi-orthogonal sequences

In this paper, we propose a novel class of unitary space-time constellations based on quaternary quasi-orthogonal sequences (QOSs), minimizing the maximum correlation between the signal matrices. The proposed design, owing to the underlying algebraic structure of the QOSs, allows for an efficient decoder structure while offering performance virtually identical to the unitary space-time constellation design by Hochwald et al.

An efficient decoding algorithm for QO-STBCs based on iterative interference cancellation

We propose an efficient decoding algorithm targeted for quasi-orthogonal space-time block codes which can be viewed as an iterative extension of the parallel detection algorithm using iterative interference cancellation. The essence of the algorithm is in the realization of the fact that the number of candidate symbols at the end of each interference cancellation iteration reduces very quickly, and that no more than two iterations are required.

Symbol Timing Synchronization Algorithms for Wireless LAN Systems in Multipath Channels

In this paper, we propose an efficient symbol timing synchronization algorithm for IEEE 802.11a/g wireless LAN systems in multipath channels is proposed. The algorithm utilizes an elongated training symbol together with soft-limiting of the correlator output and estimates the position of the first arriving path. Simulation results show that the proposed algorithm significantly outperforms conventional algorithms

Efficient Detection of Space-Time Block Codes Based on Parallel Detection

Algorithms based on the QR decomposition of the equivalent space-time channel matrix have been proved useful in the detection of V-BLAST systems. Especially, the parallel detection (PD) algorithm offers ML approaching performance up to 4 transmit antennas with reasonable complexity. We show that when directly applied to STBCs, the PD algorithm may suffer a rather significant SNR degradation over ML detection, especially at high SNRs. However, simply extending the PD algorithm to allow p ≥2 candidate layers, i.e. p -PD, regains almost all the loss but only at a significant increase in complexity. Here, we propose a simplification to the p-PD algorithm specific to STBCs without a corresponding sacrifice in performance. The proposed algorithm results in significant complexity reductions for moderate to high order modulations.

Improved Decoding Algorithms for Quasi-Orthogonal Space-Time Block Codes

Recently, a variety of full-rate, full-diversity quasi-orthogonal space-time block codes (QO-STBCs) have been designed. Though the quasi-orthogonality does reduce the decoding complexity from order of MQN to MQN/2 for Q-ary QAM modulation with N transmit and M receive antennas, there is still need for improvement. Several simple suboptimum decoding algorithms were proposed but suffer quite severe performance losses over maximum likelihood (ML) decoding. Here, we propose a class of decoding algorithms for QO-STBCs based on interference cancellation with complexity on the order of MQ N/2 -1 and performance virtually identical to that of ML decoding. A modification to the base algorithm is also developed with complexity approximately 1/radic(Q) times that of the base algorithm.

Reduced Complexity Decoding Algorithm for Quasi-Orthogonal Space-Time Block Codes

The quasi-orthogonality of quasi-orthogonal space-time block codes (QO-STBCs) does reduce the decoding complexity from order of MQN to MQN/2 for Q-ary QAM modulation with N transmit and M receive antennas. Here, we propose a decoding algorithm for QO-STBCs based on interference cancellation with complexity on the order of MQ N/2-1 and performance virtually identical to that of ML decoding

Generalization of the /spl Sigma//sub 0/-rank criteria for space-time codes

Recently, Liu et al., developed the /spl Sigma//sub 0/-rank criteria for space-time codes. It provides a sufficient condition on codeword and generator matrices defined over finite rings /spl Zopf//sub 2k/(j) to ensure full spatial diversity with 2/sup 2k/-QAM modulation. Here, we generalize the /spl Sigma//sub 0/-rank criteria and derive a sufficient condition on the generator matrices defined over finite rings /spl Zopf//sub 2l/(j) to ensure full spatial diversity with 2/sup 2k/-QAM modulation for any positive integer l/spl les/k. We also show that generator matrices defined over GF(2) satisfying the BPSK stacking construction constraint of Mammons and El Gamal achieve full spatial diversity when used with 2/sup 2k/-QAM modulation.