A Non-Monetary Protocol for Peer-to-Peer Content Distribution in   Wireless Broadcast Networks with Network Coding
  This paper studies the problem of content distribution in wireless peer-to-peer networks where all nodes are selfish and non-cooperative. We propose a model that considers both the broadcast nature of wireless channels and the incentives of nodes, where each node aims to increase its own download rate and reduces its upload rate through the course of content distribution. We then propose a protocol for these selfish nodes to exchange contents. Our protocol is distributed and does not require the exchange of money, reputation, etc., and hence can be easily implemented without additional infrastructure. Moreover, we show that our protocol can be easily modified to employ network coding.   The performance of our protocol is studied. We derive a closed-form expression of Nash Equilibriums when there are only two files in the system. The prices of anarchy, both from each node's perspective and the whole system's perspective, are also characterized. Moreover, we propose a distributed mechanism where each node adjusts its strategies only based on local information and show that the mechanism converges to a Nash Equilibrium. We also introduce an approach for calculating Nash Equilibriums for systems that incorporate network coding when there are more than two files. 
I-Hong Hou, Yao Liu, Alex Sprintson
cs.NI