Optimal Subcarrier Power Allocation in OFDM Based Cognitive Radio Networks by Using Gradient Based Methods

The Power allocation in Orthogonal Frequency Division Multiplexing (OFDM)-based cognitive radio networks is designed by gradient based method. The gradient based method in which the power allocated between subcarriers by considering the interference constraint, capacity of CR users and channel gain. Utilize the gradient based descent approach to allocate power to subcarriers in Cognitive Radio (CR) networks. The gradient-based power allocation method with the Euclidean Projection technique is used for selection of step size and weighting factor. A well-designed step size can provide approximate optimal solution within little iteration. The analysis for the selection of the step size and weighting factor is required. The objective of this method is to use spectrum efficiency by allocating power between subcarriers. This method is required far less iteration. Gradient –based method with the adaptive step size has a fast rate to achieve a near –optimal solution within an extremely small number of iterations and has quite a low computational complexity.