Routing with persistent link modeling in intermittently connected wireless networks

This paper presents a link state protocol for routing with persistent link modeling (RPLM) in intermittently connected wireless networks. The key idea behind RPLM is to design a link cost metric which reflects the state of a link based on its historical connectivity characteristics. In other words, connectivity and disconnectivity of a link is made to appear persistent using a gradually changing link metric. Persistent link modeling has the advantage of capturing any spatial and temporal locality of link disconnection and leveraging it for better route selection in intermittently connected networks. The link metric in this paper is designed specifically for minimizing data delivery latency. We developed ns-2 based simulation models of RPLM to validate its functional correctness, and compare its performance with an existing probabilistic routing protocol PROPHET. Performance has been evaluated for two intermittently connected networks with IEEE 802.11 based wireless links. Experimental results demonstrate that RPLM is able to consistently deliver packets with lower delivery latency compared to PROPHET. It is also shown that lower delivery latency ensures that packets stay in the network for shorter durations, resulting in efficient buffer usage. Based on these results we conclude that RPLM succeeds in its goal to provide "persistent" link cost modeling for low-delay data delivery in intermittently connected networks.