Outage probability and power allocation for ANC with channel estimation errors in cognitive radio

In practice, imperfect channel-state information (CSI) is one of the main causes of performance degradation in wireless networks. In this paper, we investigated the impact of channel estimation error on the outage probability from the perspective of the secondary communication in cognitive radio (CR). It is found that an error floor appears in the outage probability with imperfect channel knowledge due to the channel estimation error. Further, to mitigate the negative impact of imperfect CSI, a power allocation strategy is proposed by minimizing the weaker link´s individual outage probability under the sum-power constraints. Particularly, the algorithm of proposed scheme only used statistical CSI rather than instantaneous CSI, which can facilitate practical implementation. Simulation results presented that the proposed power allocation scheme provides significant performance gain over the traditional scheme in terms of outage performance and is robust to the channel uncertain. Moreover, the best location for the relay is near by the middle point of the two end nodes irrespective of the power allocation.