Distributed spectrum sharing scheme for multiuser orthogonal frequency-division multiplexing cognitive radio networks

This paper presents a novel spectrum sharing design aiming at optimising the performance of a Multiuser Orthogonal Frequency-Division Multiplexing (MU-OFDM) Cognitive Radio Network (CRN) that consists of multiple secondary Transmitter-Receiver (Tx-Rx) pairs. For most MU-OFDM systems, the Exclusive Subchannel Assignment (ESA) is an efficient resource allocation method. Nonetheless, it is inappropriate for the network considered in this paper, because subchannels sharing among secondary Tx-Rx pairs can further improve the system performance. We investigate the Weighted Sum Rate (WSR) maximization problem under the Shared Subchannel Assignment (SSA), where each subchannel is shared by multiple secondary Tx-Rx pairs. With Lagrangian duality technique, we decompose the original resource allocation problem into several sub-problems on each subchannel and propose a duality-based subchannel sharing approach. For practical realisation in the cognitive systems without central control entity, a distributed duality-based WSR maximization scheme is presented. Simulation results manifest that the proposed scheme achieves significantly better performance than ESA duality scheme.