Alamouti Codes for Wireless Communications

Alamouti codes for wireless communications

Abstract— This report presents a simple two-branch transmit diversity

scheme of space-time coding. we derive the theoretical performance of the Alamouti space-time code in time-varying Rayleigh fading channels with noisy channel estimates. The receiver algorithms presented in this report are the maximum-likelihood (ML) symbol detector with the linear combining scheme, which was suggested by Alamouti and the ML space-time decoder. The bit error probability for the linear combining scheme and the sequence error probability for the ML space-time decoder are presented as functions of the pilot filter coefficients. We also compare the bit error performance of the linear combining scheme with the bit error performance of the system using BPSK and QPSK. The results indicate that the Alamouti space-time code with the linear combining scheme is outperformed by the no transmit diversity system.

Keywords—Alamouti, maximum ratio combining, space–time coding,

transmit diversity, wireless communications.

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I. INTRODUCTION

Space–time block coding is a technique used in wireless

communications to transmit multiple copies of a data stream across a number of antennas and to exploit the various received versions of the data to improve the reliability of data-transfer. Over the last decade, space-time coding has gained attention both from the research community, as seen in a large number of space-time code related papers published, and the industrial community, where several space-time coding schemes are included as parts of future wireless communication standards. The fact that the transmitted signal must traverse a potentially difficult environment with scattering, reflection and so on and may then be further corrupted by thermal noise in the receiver means that some of the received copies of the data will be 'better' than others. This redundancy results in a higher chance of being able to use one or more of the received...