Harnessing multiple wireless interfaces for guaranteed QoS in proximate P2P networks

We consider the problem of content distribution to a group of cooperative wireless peer devices that desire the same block of information. The QoS metric is that peers are all required to receive the block by a fixed deadline, with a certain target probability. The block is divided into chunks, which are received via two methods that can be used simultaneously - (i) the B2P (base-station-to-peer) network: each peer has an unreliable, expensive, unicast channel to a cellular base station, and (ii) the P2P (peer-to-peer) network: peers can share the content over a free, lossless internal wireless broadcast network. Chunks are coded using random linear codes to alleviate the duplicate chunk reception issue. We seek an algorithm that can attain the QoS metric at the lowest cost of using B2P network. We transform the problem into two questions of (i) deciding which peer should broadcast on the P2P channel at each time, and (ii) how long B2P transmissions should take place. We use dynamic programming and queueing ideas to show that for large field sizes, a combination of Max-Rank-First and Non-min-Rank-First policies for P2P transmissions is optimal, and determine the stopping time for B2P transmissions using a Markov chain model. We provide performance bounds for finite field sizes, and illustrate our insights using simulations.