Opportunistic forwarding in wireless networks with duty cycling

Opportunistic forwarding, by which data is randomly relayed to a neighbor based on local network information, is a fault-tolerant distributed algorithm particularly useful for challenged ad hoc and sensor networks where it is difficult to obtain global topology information because of frequent disruptions. Also, duty cycling is a common technique that constrains the RF operations of wireless devices for saving the battery energy and thus extending the longevity of the network. The combination of opportunistic forwarding and duty cycling is a useful approach for wireless ad hoc and sensor networks that are plagued with energy constraints and poor connectivity. However, such a design is hampered by the difficulty of analyzing and controlling its performance, particularly, the end-to-end latency. This paper presents analytical results that shed light on the latency of opportunistic forwarding in wireless networks with duty cycling. In particular, we give approximation formulas and bounds for the expected latency of opportunistic forwarding in presence of duty cycling for general finite network topologies, and an exact formula for a specific regular network topology that captures some common sensor network deployment scenarios. Moreover, our results concern finite-sized networks, and hence, are practically more useful than other asymptotic analyses in the literature.