Performance of a multihop cognitive radio network with diversity under imperfect CSI

This paper analyses the outage performance of a multihop relay-based cognitive radio network under imperfect channel state information. A backoff power control scheme is applied to ensure both the quality of service (QoS) and interference constraints of the primary network. To reduce the interference at the primary network, we have proposed a new multihop transmission method where a relay node forwards the signal to the next relay node only when the signal is decoded successfully and QoS of the primary network is satisfied. Unlike the conventional relay transmission scheme, in our system model, a relay node receives signals not only from the previous node but also from the previous-to-previous node. The selection combining (SC) and maximum ratio combining (MRC) diversity schemes are applied to enhance the outage performance of the secondary network. The Monte Carlo simulation is adopted to validate the analysis. It is observed from the simulation results that the outage probability of the secondary network and interference probability of the primary network are impacted by the correlation coefficient between real and estimated channels, the number of hops and the backoff power coefficient.