On hybrid power allocation scheme for OFDM based cognitive radio

In this paper we have considered a hybrid power allocation algorithm for OFDM based cognitive radio. In a centralized power allocation scheme there is a centralized controller that has information about available spectrum holes and each cognitive user´s channel state information. However, the overhead involved is very high. In an de-centralized power allocation scheme each cognitive user allocates power to different subcarriers based on local information, however maximum achievable throughput is less compared to the centralized approach. In this paper we present a hybrid approach based on a centralized controller that does not require information about instantaneous channel gains of cognitive radio and distributed controllers. We show that maximum achievable transmission rate of our hybrid approach is very close to the case of centralized power allocation with full knowledge of instantaneous channel gains but at a substantially reduced overhead cost.