Raptor-based file delivery protocol for satellite-CDNs (RFDPS)

This paper describes a new reliable transport protocol designed to run on the integrated satellite-terrestrial content delivery network (S-CDN) to multicast files over a wide geographical area. The motivation for this work is to make the satellite multicast system scalable under different packet loss rates with reliability ensured and throughput maintained. Current multicast protocols mainly study the terrestrial communications. They often use packet-based NACK messages to request retransmissions of lost packets, but the feedback overhead scales up sharply when the packet loss rate is large. Other schemes that proactively multicast FEC packets results in unfair redundancy among the receivers with different packet loss rates. We propose a Raptor-based file delivery protocol for satellite-CDNs (RFDPS). The novelty lies in that RFDPS is a joint FEC and feedback protocol, and supports block-based feedback and cooperative transmissions both through satellite multicast and terrestrial unicast. We analyze the retransmission strategy when considering the delivery cost, and propose a simplified method to estimate the optimal number of multicast packet for the retransmission strategy. The prototype of RFDPS is designed, and is evaluated on the OPNET platform in terms of throughput and feedback overhead. Simulation results show the significant performance gain of the proposed protocol. And our simplified estimation method is verified to be effective.