Outage Analysis of Cooperative OFDM Relaying System with Opportunistic Spectrum Sharing

In this paper, we analyze the outage performance of an opportunistic spectrum sharing protocol. In the proposed protocol if the primary system (licensed user) is incapable of supporting its target transmission rate, then secondary system (cognitive user) helps the primary system via two phase cooperative Orthogonal Frequency Division Multiplexing (OFDM) relaying. Secondary system acts as an Amplify & Forward (AF) relay by allocating some of its subcarriers to boost the performance of primary transmission whereas remaining subcarriers are used for secondary transmission. Simulation results demonstrate the outage probability with respect to primary transmit power for different sets of subcarriers in both direct & cooperation mode. Through simulation results it is proved that the primary outage probability with cooperation is less than outage probability with direct transmission. Results also demonstrate the outage probability for increasing distance between primary & secondary transmitter. As distance between primary & secondary transmitter increases outage probability increases.