Multiple-copy Routing in Intermittently Connected Mobile Networks

Intermittently connected mobile networks are wireless networks where most of the time there does not exist a complete path from the source to the destination. There are many real networks that fall into this paradigm, for example, wildlife tracking sensor networks, military networks, inter-planetary networks, etc. In this context, conventional routing schemes would fail. To deal with such networks researchers have suggested to use flooding-based routing schemes. While floodingbased schemes have a high probability of delivery, they waste a lot of energy and suffer from severe contention which can significantly degrade their performance. With this in mind, we introduce a new routing scheme, called Spray and Wait, that “sprays” a number of copies into the network, and then “waits” till one of these nodes meets the destination. We compare this scheme to a number of different routing algorithms including an oracle-based optimal algorithm that minimizes average message delivery delay while using the lowest possible number of transmissions. Theory and simulations show that Spray and Wait has a number of desirable properties: it is very simple to implement, it is highly scalable, it performs close to the optimal scheme, and quite surprisingly, it outperforms all existing schemes with respect to both average message delivery delay and number of transmissions per message delivered.