Power Allocation and Relay Assignment for Shared-Band Nonregenerative Relaying in Cognitive Radio Systems

The use of multiple relays can increase the performance of a cooperative communication system. A well-designed multiple-relay-assignment and power-allocation scheme can be helpful in reducing interference induced to primary users (PUs) in a cognitive radio system (CRS). In this correspondence, we propose a joint multiple-relay-assignment and power-allocation (JRAPA) scheme in shared-band nonregenerative relaying in CRSs. The main aim of JRAPA in CRSs is to maximize sum capacity under the constraint that the interference to the PUs is below their specified levels. The proposed JRAPA is an NP-hard nonconvex mixed-integer nonlinear optimization problem (NC-MINLP). We propose a greedy iterative JRAPA (IJRAPA) scheme for CRSs. The complexity of the proposed IJRAPA is quadratic with the number of relays. The effectiveness of IJRAPA is verified through simulation results satisfactorily.