Capacity Maximized Power Allocation for Secondary Users in OFDM-Based Cognitive Networks

Cognitive Radio (CR) is widely considered as a novel approach to improve the utilization efficiency of precious radio spectrum resource. Orthogonal Frequency Division Multiplexing (OFDM) is one of the best candidates to realize cognitive networks because of its characteristic of agile frequency bands access. In this paper, a novel power allocation model for OFDM-based Cognitive Networks (CR) is presented. An water-filling algorithm is proposed to realize power and subcarrier allocation together with bit loading in OFDM-based CR networks; during power allocation, mutual interference between Primary User (PU) and Secondary User (SU) are comprehensively considered, which restrains the interference to PU together with maximizing the capacity of SU. Symbol Error Rate (SER), power consumption and coverage are considered as Quality of Service (QoS) parameters, and all of them can be ensured in the power allocation. By a simplified model, simulation result is exhibited to illuminate the influence of mutual interference on subcarrier and power allocation together with system capacity.