Gain of spatial diversity with conjoint signals

Abstract

This paper proposes a novel method of achieving conjoint coding gain without additional signal measurement requirements. In the proposed scheme, received signals in a spatial diversity system are used to synthesize additional conjoint signals within the neighbourhood of receive antennas. These excess signals are assumed to be from virtual antennas. In an N r branch system and in order to retain the diversity order, a total of N2 r output signals are obtained, where N r (N r − 1) is the number of conjoint signals or virtual antennas. When combined, a coding gain of at least 1 [dB] is achieved. It is shown that the bit error rate (BER) of selection combining (SC) with conjoint signals results in coding gains over that of the conventional SC. Also, equal gain combiner (EGC) results in BER that is equal to that of the maximal ratio combiner (MRC). The coding gains are achieved through a dual transformation that does not require the measurement of signal information. As a result, the EGC can be used to obtain BER results similar to the computationally complex MRC scheme. The proposed system is tested under flat Rayleigh fading channels.