The use and performance of LT codes for multicast with relaying

Rateless codes are ideal for wireless communication to mobile nodes because such codes are well suited to time-varying channels. In this paper we examine the use of Luby Transform (LT) codes in a broadcast system. The goal of such a system is to deliver messages reliably from a single source node to multiple mobile destination nodes. In some instances, however, the source-destination links have high latency, which limits the efficacy of feedback from destination nodes to the source. Three approaches using LT codes to limit feedback are considered. We find that by using a combination of systematic LT and ‘shifted’ LT codes, we are able to offload a significant amount of data transmission from the source-destination links to the destination-destination links, improving reliability while utilizing less bandwidth.