Towards Reliable Mobile Ad Hoc Networks
Ricardo Lent, Javier Barri · InTech eBooks · 2011
It is expected that future networks will interconnect an even larger number of devices then today, ranging from servers to micro-devices embedded in objects. These devices will provide useful services thanks to the possibility of a networked operation, for example, localization services to support a variety of situation-aware applications. A very significant number of these devices will be carried by users-on-the-move. While a wireless infrastructure could serve to provide a near permanent network access to these devices, structural network dynamics and service demand patterns could impact the main features of the solutions relying on this network. Mobile ad hoc networks (MANETs) may serve to bridge these devices to the network in situations where a connection to a wireless infrastructure may not be feasible or desirable because of coverage limitations, network failures, congestion, policies, or cost. MANETs can be quickly created for a wide variety of applications and whenever needed to operate on virtually any environment. A main feature of a MANET is its self-organizing ability over a network that is assumed by temporarily linking each mobile with other nodes within wireless coverage. In this situation, nodes can serve as routers, at least temporarily, to forward packets for other nodes. One of the main technical drawbacks of these type of networks is that the network tends to change quite often. Nodes may arrive at or depart from the network without notice and direct node-to-node communication may or may not be possible at any given time due to node mobility and changes on the surrounding environment. These characteristics determine a highly dynamic network that makes difficult a reliable forwarding of packets on multi-hop routes over long periods of time. Communications tend to be very unreliable and inefficient, because a route break not only disrupts immediately a communication, but also can introduce additional overhead into the network because of the potential need for retransmissions and re-routing operations. In this chapter, we discuss a feasible approach to obtain improved routing reliability on a MANET. The approach consists in identifying and using links with the most availability to setup and maintain routes. Link availability is related to the residual lifetime of links, which can be calculated from various sources, including signal power, packet transit times, or nodes’ location and moving trends. We focus mainly on the latter possibility as localization services are becoming widespread for mobile devices and the trend is expected to continue in the future. In particular, we explore the case where the localization services are provided by a sensor network purposely deployed to track mobile nodes. Most of the ideas discussed in this chapter are widely applicable to the other cases as well. A simulation-based evaluation under