Conventional and best-relay-selection cooperative protocols under nodes-mobility and imperfect-CSI impacts: BER performance

In this paper, we analyze the performance of M-relay amplify-and-forward (AF) cooperative network in the presence of imperfect channel-state-information (CSI) and taking into account the impact of the nodes mobility. Two relaying protocols are considered; conventional-relaying (CR), in which all relays are active and participate in the relaying process via orthogonal transmissions, and best-relay-selection-relaying (BR), in which the relay that achieves the highest signal-to-noise-ratio (SNR) at the destination only participates in the relaying process. We first derive exact expressions for the destination SNRs through the direct and the ith-indirect paths. Moreover, closed-form expressions for the pdfs of the upper-bounded total SNRs and for the lower-bounded average bit error rates (BERs) are derived for both protocols. Under these considerations, the system BER performance experiences asymptotic floors, which are also obtained. All of the derived expressions are general and valid for mobile as well as static nodes for both perfect and imperfect estimations. We also show that, in the case of mobile nodes, the BR protocol provides worse BER performance than that of the CR at high values of the average SNR. Numerical results along with Monte-Carlo simulation results are also provided to verify the accuracy of the derived analytical expressions and to show the system performance under several nodes mobility scenarios.