Wireless digital video broadcasting has experienced much success in recent years with some industrial systems deployed. We study in this paper how to recover lost packets in video broadcasting by means of a free broadcast-based secondary channel (such as IEEE-802.11 or bluetooth). In our scheme, termed BOPPER (Broadcasting with Peer-to-Peer Error Recovery), mobile devices collaboratively help each other to recover packet lost by broadcasting to their neighborhood. BOPPER achieves high scalability, low recovery delay, independence of a backward channel and low bandwidth cost. We study how to minimize the total number of retransmissions while achieving a certain level of recovery capability. We first consider the case with global knowledge (in terms of peer connectivity, loss status and pairwise loss rates of all peers) and formulate the problem as a linear program which can be solved efficiently. The result also serves as the optimum for our distributed protocol. We then propose and study a scalable, adaptive and distributed protocol which makes use of local information and message exchange to achieve efficient packet loss recovery. Simulation results show that our distributed scheme achieves close to the optimum with fast convergence time.
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