Trajectory control of mobile gateways for range extension in ad hoc networks

In order to facilitate scalability in a mobile ad hoc network (MANET) and to provide connectivity between partitions that might occur in wireless networks as a consequence of mobility, we can envision a 'range extension' network that consists of airborne communication platforms, and satellites. These airborne or satellite nodes will maintain communication links with specific 'gateway' nodes among the mobile ground nodes. To communicate with a node that is geographically distant or belongs to a different network partition, an ad hoc node can relay its data packets through an appropriate mobile gateway and via the range extension network. If we envision that the MANET is divided into different groups and a mobile gateway is deployed for each such group, an objective then, is to determine the trajectory of the mobile gateway to best serve the ad hoc group to which it belongs, in terms of network performance metrics such as throughput and latency. In this paper, this problem of computing the optimal position for a gateway is reduced to a linear optimization problem by means of some simplifying but realistic assumptions. We suggest methods that may be deployed to enable the gateway to follow this optimal trajectory as closely as possible (within the practical constraints imposed by its velocity and maneuverability). Simulation results for various scenarios show a 10-15% improvement in the throughput and in latency (per group containing a gateway) if a gateway has a dynamic trajectory whose locus follows the computed optimal position, as compared to a gateway that is statically placed at a regular position, or to a gateway that has a random trajectory. (C) 2002 Elsevier Science B.V. All rights reserved.