Reducing the Requirement in FEC Codes via Capillary Routing

In off-line packetized streaming, rateless forward error correction (FEC) codes spectacularly improve the reliability of transmission over lossy networks. This success relies on time diversity, which in its turn relies on unrestricted buffering time at the receiver. In realtime streaming the playback buffering time is very limited (shorter than one second) and even strong FEC codes cannot protect single path communication against failures lasting longer than the buffering time at the receiver. Path diversity is a strategy that is orthogonal to time diversity and can make FEC applicable also in case of limited buffering time of real-time streaming. In this paper we introduce capillary routing algorithm offering layer by layer a wide range of multi-path routing topologies of increasing path diversity. We introduce redundancy overall requirement (ROR), which for a given multi-path routing is the coefficient of the total number of redundant FEC packets to be transmitted by the sender for protecting the communication against non-simultaneous link failures. A dozen of capillary routing layers, built on several hundreds of network samples obtained from a random walk wireless mobile ad-hoc network (MANET), are rated with ROR. We show that flow diversity patterns built by capillary routing algorithm reduce substantially the amount of FEC codes required for protection of communication