The Research On Relay Selection And Power Allocation In Bidirectional Cooperative Networks With Imperfect Channel State Information

Abstract:Cooperative relay networks can increase the communication range and capacity of the system greatly. One-way relays are often used in traditional cooperative relay schemes, which may lead to low bandwidth efficiency. To improve the channel utilization, bidirectional relays are often employed. With bidirectional relays, nodes can communicate with each other simultaneously, so the time slot decreases. But bidirectional relays may bring some new challenges in cooperative relay networks, especially the networks with imperfect channel state information (CSI). In this paper, the relay selection and power allocation is considered to improve the channel quality and the power efficiency.First, a max-min relay selection in cooperative networks with imperfect CSI is proposed by considering the channel estimation error on the performance of the networks, to improve the communication quality and spectrum efficiency. The system model of the analog network coding (ANC) networks is constructed and the parameters are verified. The performance of the network, including signal-to-noise ratio (SNR), outage probability and average bit error ratio (BER) is analyzed. Then the outage probability and BER is expressed equivalently as the instantaneous SNR received at the sources, based on which, the max-min relay selection scheme in cooperative networks with imperfect CSI is proposed, and the performance is further investigated.Second, a joint optimization algorithm of sources and relays is proposed to improve the power utilization in bidirectional cooperative network with imperfect CSI. The channel gain of the ANC amplify-and-forward bidirectional cooperative network with imperfect CSI is estimated with least mean square error method, considering the self-interference of the sources. The desired maximum rate of the bidirectional network is derived and the rate optimization index is simplified according to equivalent power ration rule. Then the impact of the location of relays on power allocation is analyzed and optimization problem is solved. At last, the channel estimation, relay selection and power allocation of bidirectional cooperative networks with imperfect CSI is valuated in MATLAB. Simulations demonstrate the effectiveness of the proposed scheme.