Optimized Gateway Discovery in Hybrid Manets

Mobile users are expected to demand access to the Internet anywhere and anytime. In a MANET context, a device which is about to connect to external hosts needs the route to the element which communicates the MANET with the Internet. This element is the Internet Gateway. To inform about its presence as well as about some configuration parameters, the Gateway sends MRA messages. In a similar way to ad hoc routing protocols, the Gateway can generate the messages on demand (reactively), periodically (proactively) or combining both previous strategies in a hybrid gateway discovery. Specifically, in the hybrid gateway discovery, the Gateway periodically sends the MRA messages in a restricted area. The nodes that are outside this area demand the Gateway information reactively. This gateway discovery requires the setting of the number of hops that define the proactive area, also called the TTL value. Network performance can be improved when the Gateway uses information such as the position of the sources to adjust the TTL value. In this paper, we transfer the decision about the dimensions of the proactive zone to the mobile nodes so more network conditions are taken into account. Simulation results show that the proposed gateway discovery outperforms other hybrid gateway discovery schemes.