A network-coded relay cooperative transmission scheme for cognitive radio networks

In this paper, we propose a network-coded relay cooperative transmission scheme (NCRCT) to improve the outage performance of the primary system and the secondary system in a cognitive radio network. In conventional spectrum sharing scheme based on interference temperature (CSS-IT), the transmission power of the secondary user (SU) who only transmits its own data should satisfy peak power constraint and the interference temperature requirement perceived at the primary user (PU). In contrast to CSS-IT, the secondary user in NCRCT will aid the PU with its maximum allowable transmit power by employing network coding when the channel condition from the PU to the SU is good. The exact expressions for the outage probability of the primary system and the secondary system are derived. Theoretical and numerical results show that NCRCT can achieve better outage performance and higher diversity order of the primary system than the case without spectrum sharing and provide superior outage performance of the secondary system to CSS-IT scheme.