Geoopp: Geocasting for opportunistic networks

Geocasting aims to deliver information to all nodes within a geographic area rather than an arbitrary group of nodes. Supporting geocasting in the context of opportunistic networks where nodes are not well-connected is still an open problem. We present a routing algorithm to provide geocasting service for opportunistic networks, termed Geoopp. Geoopp combines unicasting and flooding by first forwarding a message to the specified geographic region and then flooding the message to all nodes inside the region. To forward a message toward a region, Geoopp adapts geographic greedy routing for opportunistic networks. Nodes choose neighbors that can take the message closer to destination. A progress within radius metric (PWRM) is introduced to measure the geographic progress a node can make carrying the message toward its destination region given one of its future visited regions. To determine the future mobility, the regularity embedded in human movement is exploited, since human movements often exhibit a high degree of repetition including regular visits to certain places and regular contacts during daily activities. A node's mobility is characterized by inter-visiting time and contact availability per visiting to capture the regular visits and contacts in a specific region. Chebyshev's inequality is employed to compute the probabilities that a node visiting a region and having contact inside. Our simulation results show that Geoopp can attain 80% of the maximum achievable delivery rate at a cost of 20% of the maximum consumable relays.