Allocation of power and modulation order (rate) to secondary users in competitive cognitive radio networks

In this paper, we study allocation of power and modulation order (rate) to secondary users in a competitive cognitive radio network (CRN). In a competitive CRN, multiple secondary users share a single channel and multiple channels are simultaneously used by a single secondary user (SU) to satisfy their rate requirements [1]. In such an environment, we compute optimal power and modulation order choices that each secondary user needs to make in order to maintain their quality of service (QoS). Our measures for QoS include bit error rate (BER) and minimum rate requirement. We consider M-ary phase shift keying (M-ary PSK) modulation scheme and following the concept in [1], we work on transforming the BER constraint into a convex constraint in order to guarantee optimality of the resulting solutions. Simulation results demonstrate that optimal transmit power follows “reverse water filling” process and rate allocation follows signal to interference plus noise ratio (SINR).