Improving Water-Filling Algorithm to Power Control Cognitive Radio System Based Upon Traffic Parameters and QoS

Cognitive radio scenario is based upon the ability to determine the radio transmission parameters from its surrounding environment. Power allocation in cognitive radio systems improves secondary network capacity subject to primary receiver interference level threshold. In this paper, statistical property of the injected interference power in primary user channel is used to establish the container bottom for each subcarrier employing water filling algorithm. In other words, the container bottom level of each subcarrier depends on the injected interference in primary user (PU) (most probably from the overloaded neighbor subcarriers). Traffic statistical parameters are also employed to formulate power allocation problem. Within this context, quality of service constraint is considered also to improve performance of power allocation algorithm. Simulation Results show that the injected interference in PU is decreased while the secondary user capacity improves. Indeed, the proposed algorithm is more compatible than a waterfilling algorithm with cognitive radio system constraints.