Optimization gateway discovery mechanisms for hybrid ad hoc networks

The overall performance of hybrid ad hoc networks, which is the integration of ad hoc networks and fixed IP networks like the Internet is affected heavily by the discovery and selection of Internet gateways. Each of existing proposals is suited only for a limited range of network conditions and its performance can vary dramatically as the network conditions change. The obvious unidirectional links and the rebroadcasting of gateway discovery packets blindly during ad hoc nodes discovery available Internet gateway also degraded the Internet connectivity. In this paper, an internetworking algorithm with adaptive mechanisms has been proposed to enhance Internet connectivity for mobile ad hoc networks. Firstly, through exchanging hello packets which are identical to the AODV hello packets except for the additional symmetric neighbor list and asymmetric neighbor list fields, unidirectional links are removed from route computations and redundant or even harmful rebroadcasting of the broadcast packets are inhibited simultaneously in the procedure of gateway discovery. Secondly, based on the dynamic adjustment of the scope of the gateway advertisement packets and the intervals of sending hello packets according to the network conditions change, a lot of unnecessary overhead was reduced. Performance results using ns-2 simulations, under varying number of unidirectional links and node speeds, show that this adaptive Internet connectivity scheme can provide better performance than others due to its adaptive mechanisms, avoiding unidirectional links as well as relieving broadcast storm, and is a step closer to making the large-scale deployment of mobile ad hoc networks a reality.