Mobility-Induced Capacity-Delay Tradeoffs In Wireless Multihop Networks

Wireless mobile multihop networks, such as ad hoc and sensor networks, have become rather popular in realizing seamless distributed computation and accommodating autonomic behavior. In these networks, the lack of central infrastructure, the spatio-temporal dynamic nature of wireless communications along with their mobility-induced dynamic topology, pose additional challenges on the traffic-carrying capacity of the system and raise concerns on the delay performance of packet delivery mechanisms. Despite such impediments of the wireless multihop environment, it has been recently shown that mobility can be exploited by various relay techniques for increasing the capacity of such networks. However, the throughput-effectiveness of the mobility-exploiting relay methods takes place at the cost of a greater number of intermediate hops traversed by packets traveling in the network in order to reach their final destination and additional buffering required at the intermediate nodes, revealing an inherent tradeoff between capacity and delay in mobile multihop networks. In this chapter, we first briefly review various mobility models, and then focus on the inherent mobility-induced tradeoff between capacity and delay in multihop networks. Mobility is treated as both a constructive (increasing capacity), as well as a destructive (increasing delay) factor in wireless infrastructureless networks. Formal problem setting are presented, followed by applications and protocols that could be used in actual networks for increasing performance and realizing viable networking services. We also provide a qualitative and quantitative comparison among the various protocols, from which directions for future research studies are indicated.