A scalable quorum based location update scheme for routing in ad hoc wireless networks

Most previously proposed position based routing algorithms for wireless ad hoc networks were based on forwarding the actual message along multiple paths toward an area where destination is hopefully located. The significant communication overhead can be avoided if the routing strategy is changed. We first propose to apply a variant of well-known route discovery scheme. The source node issues several search 'tickets' (each ticket is a 'short' message containing sender's id and location, destination's best known location and time that location is reported, and constant amount of additional information) that will look for the exact position of destination node. When the first ticket arrives at the destination node D, D will report back to source with brief message containing its exact location, and possibly creating a route for the source. The source node then sends full data message ('long' message) toward exact location of destination. We then propose a quorum based location update scheme, in which nodes report their new positions to their neighbors whenever a link is broken or created. After certain number of such link changes, nodes forward their new position to all nodes located in its ‘column’, that is, to the north and south of their current location with certain 'thickness' of reporting. The destination search then begins with two tickets being sent in the east and west direction, with certain 'thickness', looking for the most up to date information of destination's position. When the tickets reach each end of current 'row', the search is continued toward best reported destination position, with corrections along the path as better information becomes available closer to destination. One of tickets can be sent from the source directly toward destination, to take advantage of possibly correct information on destination location. The intersection of ‘row’ and ‘column’ can be guaranteed by adding outer face of the ad hoc network both of them. We show through simulation that the proposed routing and location update schemes provide scalable routing scheme with high success rates and reasonable communication overhead. The proposed method is also applicable in scenarios when all nodes move out of original region, preserving connectivity.