Rate - Adaptive Error Control for Multimedia Multicast Services

| This paper presents a rate-adaptive error control (RAEC) protocol for multimedia multicast services in satellite-terrestrial hybrid networks. The proposed scheme considers user fairness to multicast group and adapts code rate according to the channel conditions. In order to provide fairness perceived by user application, a packet is transmitted via satellite, while the retransmission of the packet is carried out over either terrestrial links or satellite link based on the number of negative acknowledgments of the packet. For code rate adaptation, a code is chosen adaptively based on the estimated channel condition. In the RAEC protocol, transmitter uses a combination of forward and backward channel estimation. Throughput performance shows that the proposed RAEC protocol outperforms the static hybrid ARQ protocol under diierent channel conditions. I. Introduction In terrestrial networks, commercial proliferation of telephone and data services has created a great demand for various multimedia applications. In the other domain, communication satellites have become the dominant carriers of long distance communications in less than 30 years. These two network infrastructures have been developed as stand-alone systems. Recently, a concept of integrating the satellite and terrestrial systems has been introduced. These satellite-terrestrial hybrid networks (in short, we call hybrid networks) are becoming increasingly popular for multimedia multicast services due to several advantages. Many multimedia applications , particularly in case of le transfer, video multicast, and database services are asymmetric in nature, i.e., the bandwidth requirement from a receiver is much less than that from its counterpart. Although two-way satellite channels can be used for such asymmetric applications, it is also possible to combine a one-way satellite channel for information ow with a parallel terrestrial channel for control data ow. This can remarkably reduce the cost of expensive satellite feedback channel. Furthermore, satellites are able to ooer eecient bandwidth services to a large geographical area and easy to add new users to the system by simply installing the stations. Hence, the satellite network is an excellent infrastructure for multicast services. Possible applications in the hybrid networks are: Data transfer to large user populations, Continuous sensor data feed to large user pop