CORA: Collaborative Opportunistic Recovery Algorithm for loss controlled, delay bounded ad hoc multicast

In this paper, we present Collaborative Opportunistic Recovery Algorithm (CORA) designed for multicast multimedia applications with low loss as well as latency constraints in ad hoc networks. CORA is an independent service that can run atop any ad hoc multicast routing protocol. The main features of CORA are localized recovery process, deterministic (as opposed to probabilistic) peer-to-peer recovery, and ability to trade off recovery with latency. A key component of CORA is the Cached Packet Distance Vector (CPDV) protocol for local peer-to-peer loss recovery. CPDV finds and retrieves the nearest copy of the missing packet while providing other useful NACK aggregation features. We use simulation experiments to demonstrate the effectiveness of CORA and explore the tradeoffs of CPDV localized recovery benefits versus memory and processor overhead. In a typical simulation experiment with mobile nodes CORA yields up to 99% delivery ratio as compared to 91% delivery ratio by Gossip. This improvement is achieved with negligible overhead.