Energy Minimization for Multiresolution Multirelay Multicast Networks

This paper investigates the scenario of wireless multicast with a single transmitter and multiple relays that jointly deliver successively refined (or multiresolution) sources to multiple receivers. An asynchronous cooperative joint source-channel coding (JSCC) protocol is proposed, aimed at mitigating the complexity and difficulty in signal synchronization in multicast. Taking end-to-end mean square error distortion (EED) as the quality of service (QoS) measure, the problems of JSCC transmission are formulated to minimize the total power consumption where both relay selection and power allocation at the base station (BS) and all the relays are jointly determined. To solve the formulated problem that is nonetheless nonlinear in nature, a two-step iterative algorithm is investigated for power allocations at all transmitters, where a sequential quadratic programming method is developed to find a strict local minimum. To reduce the computation complexity, a heuristic algorithm for relay selection is presented. Case studies are conducted to verify the proposed formulations and solution methods. We will demonstrate the advantages of using the proposed relay-assisted multiresolution approach.