Error Control Techniques for Efficient Multicast Streaming in UMTS Networks

In this paper we introduce techniques for efficient multicast video streaming in UMTS networks. Multicast streaming is based on the fact that the same video content is conveyed to multiple users in the same cell. Efficient multicast data delivery in UMTS is still an open issue. In particular, suitable solutions have to be found to cope with wireless channel errors, while maintaining both an acceptable channel utilization and a controlled delivery delay over the wireless link between the serving base station and the mobile terminals. We first highlight that standard solutions such as unequal error protection of the video flow are ineffective in the UMTS systems due to the large feedback delay. Then, we propose a local approach to solve errors directly at the UMTS link layer while keeping a reasonably high channel efficiency and saving, as much as possible system resources. The solution we propose in this paper is based on the usage of the common channel to serve all the interested users in a cell. In this way, we can save resources with respect to the case where multiple dedicated channels are allocated. Moreover, we present a hybrid ARQ proactive protocol that, at the cost of some redundancy (added on the link layer flow), is able to greatly improve channel efficiency with respect to the simple ARQ case by making the use of a single common channel for multicast data delivery feasible. Furthermore, we envision the usage of suitably encoded video streams.