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This paper examines the impact of relay selection on the performance of distributed orthogonal space-time block coding (D-OSTBC) in a wireless network. The relay selection algorithm is based on minimizing the pairwise error probability (PER) or equivalently maximizing the signal to noise ratio (SNR) at the receiver. The receiver can always find the optimal selected relay by exhaustive search where the number of relays rarely exceeds four. It is shown in this work that the proposed scheme achieves full diversity order and provides an additional array gain compared to conventional D-OSTBC. Our results show that the proposed scheme is more power efficient than the conventional D-OSTBC. Since 50% of the time the half of the relay is off, the proposed scheme increases the life time of the relay. [ABSTRACT FROM AUTHOR]

This paper is concerned with a direct sequence spread spectrum system making use of automatic repeat request (ARQ) schemes and operating in the presence of narrow-band (NB) interference and additive white Gaussian noise. In this study, we evaluate the system's throughput efficiency when a suppression filter is employed at the receiver to mitigate the effect of NB interference. Specifically, we investigate how the performance is influenced by various parameters such as the number of filter taps, processing gain, type of interference, and the signal power-to-interference power ratio. The simulation results show that using the suppression filter significantly improves the throughput performance of the hybrid ARQ schemes in the presence of NB interference. Copyright © 2002 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]