QoS-aware joint power allocations and relay selection for NLOS coherent optical wireless communications

Abstract

In order to improve the energy efficiency of the optical wireless communications, a joint power allocation and relay selection scheme is proposed for a relay assisted non-line-of-sight optical wireless communication system employing coherent detection with a dual optical channel multiplexing technique. The proposed joint power allocation and relay selection scheme aims to improve energy efficiency of the optical wireless communication system by minimizing the total average transmit power, and provides the delay aware quality-of-service guarantee through maintaining a minimum required effective capacity over the atmospheric turbulence fading channels. The joint power allocation and relay selection problem is formulated as a non-convex and combinatorial optimization problem, and the solution of this optimization problem is obtained using a time-sharing relaxation technique. Subsequently, a fast-convergent algorithm is proposed for the joint power allocation and relay selection by considering the delay aware quality-of-service requirements of the services transmitted over the optical wireless communication channels. Numerical results demonstrate the advantages of the proposed joint power allocation and relay selection scheme in terms of the energy saving for different statistical delay constraints.