Optimum combining in fractional domain

Abstract

Fractional domain optimum combining (OC) using fractional Fourier transform has been considered in this article. It has already been established that in an interference-dominated environment, OC is the best among all the diversity techniques used for single-input multiple-output systems. This technique is based on the principle of maximising the signal-to-interference plus noise ratio at the output of the combiner. In this article, a new combiner, which calculates the weights in fractional domain, has been proposed to further enhance the performance of OC in terms of bit error rate (BER). Fractional domain combining gives better signal-to-noise ratio (SNR) at the output of the combiner as compared to time- or frequency-domain combiner due to complete removal of noise. For two receive antennas, the proposed combiner gives an SNR improvement of 7.2 and 2.4 dB as compared to time- and frequency-domain combiners, at a BER of 10−2. It has been concluded that the proposed technique clearly outperforms the existing technique.