Subcarriers assignment scheme for multiple secondary users in OFDMA-based IEEE 802.22 WRAN: A game theoretic approach

In this work, cognitive radio and orthogonal frequency division multiple access–based IEEE 802.22 wireless regional area networks is considered. Generally, subchannel is assigned to the user having the best channel gain to that subchannel and problem is known to be NP-hard. This assignment sometimes results in the unfair allocation where user with best channel gain is allocated more carriers as compared with the user with worst channel condition. In this work, a suboptimal algorithm is developed in which initially optimal number of subcarriers are found considering the equal power distribution. The problem is formulated as an oligopoly market competition and a noncooperative Cournot game is used in which different unlicensed secondary users (SUs) compete for the number of subcarriers based upon the data rate they are getting from current channel condition. The fair distribution of subcarriers is ensured by finding the Nash equilibrium. After subchannels are assigned to the SUs, power allocation is performed for each user with the water-filling algorithm. Simulation results show that the proposed approach can attain superior performance over considered benchmark scheme in the literature in terms of minimum data rate and fairness achieved by the SU. Results validating fair allocation of subcarriers is also shown.