Delay and Capacity Trade-off in Wireless Ad Hoc Networks with Random Mobility

In this paper, we study the delay and capacity trade-off in mobile ad hoc networks. We consider an ad hoc network with n nodes distributed uniformly on a sphere. The nodes are mobile, and move in accordance with the random way-point mobility model, used widely in the ad hoc networks literature. We show that the 2-hop relaying algorithm proposed by Grossglauser and Tse (2001), incurs an expected packet delay of Θ(nTp(n)), where Tp(n) is the packet duration. We show that any protocol that allows only nearest neighbor transmissions, incurs an expected packet delay of Ω(Tp(n) √ n). We show that the trade-off: delay/capacity ≥ Θ(Tp(n)n), is both necessary as well as sufficient in mobile ad hoc networks. A protocol which introduces redundancy into the 2-hop relaying algorithm, and offers a throughput of Θ(1/k(n)) and an expected packet delay of Θ(nTp(n)/k(n)), for any k(n) = O( √ n), is developed.