A Cross-layer Decentralized BitTorrent for Mobile Ad hoc Networks

In recent years, a number of P2P systems, for instance, Gnutella, KaZaA, Napster, and BitTorrent, have been proposed for the wired Internet. However, these protocols are not immediately applicable to the mobile ad hoc networks (MANETs) owing to the extreme conditions MANETs operate under. Of the above protocols, although BitTorrent has several features which make it an ideal candidate for adapting to MANETs, the current specification of BitTorrent has several drawbacks which make a straightforward implementation of BitTorrent for MANETs an undesirable solution. In this paper, we investigate a straightforward implementation of BitTorrent in MANETs, termed BTI, and compare its performance with a cross-layer adaptation of BitTorrent for MANETs, termed BTM. We resolve the issues of centralized control and single point of failure in BTI by proposing mechanisms to decentralize the BitTorrent model for MANETs and provide resource/data redundancy to improve the protocol performance. In addition, the cross-layer model of BTM is more suited for use in a MANET. Our performance comparison studies show that BTM is able to outperform BTI in terms of goodput, and the number of pieces delivered, in the context of amortizing the client download expenses over more connections (that is, BTM has a higher average peer degree)