Energy optimal multi-resolution multicast with asynchronous relaying

The paper investigates the scenario of wireless multicast with a single transmitter and multiple relays that jointly deliver successively refined (or multi-resolution) sources to multiple receivers. An asynchronous cooperative joint source-channel coding (JSCC) protocol is proposed, which can mitigate the complexity and difficulty in signal synchronization under the wireless multicast with cooperative relays. By considering the end-to-end mean square error distortion (EED), the problems of JSCC multicast are formulated to minimize the total power consumption by jointly selecting proper relays and the power allocations at the base station as well as the selected relays. To solve the formulated problem that is nonetheless nonlinear in nature, a two-step iterative algorithm is investigated for power allocations at all transmitters. Case studies are conducted to demonstrate the advantages of using the proposed JSCC in a relay-assisted multi-resolution wireless multicast network.

I. Introduction

Due to the nature of wireless channels, wireless communication suffers from multipath fading and the time-varying characteristic, that causes distortion to the delivered information. This has imposed a stringent limitation on some applications where retransmission is not possible, such as broadcast/multicast. To resolve the problem, Joint source-channel coding (JSCC) [1] and cooperative transmissions [10] are two classes of solutions that exploit different design dimensions of communication systems.