Subcarrier power allocation scheme for OFDM based hybrid spectrum sharing systems

For orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems, in which overlay and underlay spectrum sharing modes were both applied, a subcarrier power allocation scheme maximizing the transmission capacity of CR systems was proposed. In the proposed scheme, the power allocation was modeled as a convex optimization problem by taking both the total power budget of CR system and the interference constraint introduced to the primary user into account. Compared with the pure overlay and underlay schemes, both analytical and numerical results all showed that the OFDM based hybrid spectrum sharing CR system with the proposed power allocation could achieve capacity improvement.