Symbol request sharing scheme for mobile cooperative receivers in OFDM systems

In this paper, we introduce the symbol request sharing (SRS) cooperative scheme. Assuming a system with one source and several receivers, spatial diversity can be achieved by performing maximum ratio combining (MRC) on selected subcarriers of a coded OFDM-based system. The receivers are physically separated from each other and not restricted to be static. Furthermore, any receiver can be configured as a destination or as a relay. Systems with multiple receivers present some advantages compared to the traditional point-to-point communication. Additional degrees of freedom are available for improving the system performance by means of exploiting the spatial diversity inherent in any wireless communication. Nevertheless, traditional cooperation schemes designed for static relays may not be viable for mobile receivers. These may necessitate a higher cooperation overhead. SRS is a request-answer scheme, in which the destination requests symbols in specific subcarriers from the remaining receivers. It is shown that the proposed scheme can double the diversity gain given by other partial cooperation schemes and reaches the highest throughput by means of sharing a small percentage of received symbols.