Incremental cooperative diversity for wireless networks under opportunistic spectrum access

This paper analyzes the performance of incremental cooperative networks under opportunistic spectrum access where the best relay opportunistically borrows spectrum allocated to a primary user to help the source transmission if the direct link is below a given threshold. Specially, we provide the system outage probability and bit error probability derived in closed-form expression over Rayleigh fading channels. Theoretical analysis and computer simulation are in good agreement showing that the proposed system always outperforms direct transmission and full diversity gain cannot be achieved under opportunistic spectrum access.