Interference free cooperative spectrum sharing in cognitive radio networks using spatial modulation

Cognitive radio (CR) and spatial modulation (SM) are two exciting and emerging techniques to increase the spectrum efficiency for 5G. In this paper, we present a novel cooperative spectrum sharing protocol using SM. A two phases uncoded decode-and-forward (UDF) relaying scheme is considered. A secondary transmitter (ST) consisting of M_t transmit antennas act as UDF relay for the primary system (PS). In the first phase, a block of information bits of the primary transmitter (PT) is mapped into two information carrying units: a symbol which is chosen from a constellation diagram and a particular antenna number from a set of transmit antennas. The ST is then uses iterative-maximum ratio combining (i-MRC) to de-map the transmitted block of information bits. In the second phase, the ST forwards the estimated primary data by activating only one antenna based on the own secondary data. The primary receiver is then uses i-MRC to estimate the forwarded primary symbol and the secondary receiver uses i-MRC to estimate own secondary data by detecting only transmit antenna indices of the ST. As a result, mutual interference between the PS and secondary system (SS) is avoided. We investigate the bit error rate (BER) of the PS and SS. Simulation results show the efficacy of the proposed system.