Power allocation for cooperative communications in non-orthogonal cognitive radio vehicular ad-hoc networks

To achieve the better system performance for cooperative communication in non-orthogonal cognitive radio vehicular ad-hoc networks (CR-VANETs), this paper investigates the power allocation considering the interference to the main system in a controllable range. We propose a three-slot one-way vehicle system model where the mobile vehicle nodes complete information interaction with the assistance of other independent nodes by borrowing the unused radio spectrum with the primary networks. The end-to-end SNR relationship in overlay and underlay cognitive communication system mode are analyzed by using two forwarding protocol, namely, decode-and-forward (DF) protocol and amplify-and-forward (AF) protocol, respectively. The system outage probability is derived and the optimal power allocation factor is obtained via seeking the minimum value of the approximation of system outage probability. The analytical results have been confirmed by means of Monte Carlo simulations. Simulation results show that the proposed system performance in terms of outage under the optimal power allocation is superior to that under the average power allocation, and is also better than that under other power allocation systems.