Dynamic group support in LANMAR routing ad hoc networks

In Mobile Ad Hoc Networks (MANETs) mobile nodes are often organized in groups with different tasks and, correspondingly, different functional and operational characteristics. In particular, nodes in the same group will have coordinated motion. The coordinated motion pattern considerably simplifies the mobility management and allows efficient and scalable routing. Such a mobile network can easily use Landmark Ad Hoc Routing Protocol (LANMAR) to effectively explore the motion feature. In this way, one can take advantage of an existing path to one node in a group (say, a landmark) in order to route a packet to any other destinations within that group. However, groups may form very dynamically in mobile ad hoc networks. Thus, the network layer must keep track of the dynamic formation (splitting and merging) of the groups. For example, due to the group dynamics, nodes may often change group membership. Thus, a source may need to re-discover the group ID of the destination. In this paper, we propose an efficient scheme to discover the group identifier of a given destination. Our scheme utilizes the underlying LANMAR routing structures. In our scheme, when a communication is scheduled, the source queries the landmarks for destination’s group information. The newly retrieved group information is then used in normal LANMAR routing operations. Caches are used for retrieval optimization and for search overhead reduction. Different from on-demand flood-search scheme, our new approach only generates a few unicast search packets to landmarks instead of flooding the whole networks. The main advantages are that less search overhead is incurred by our scheme and as a results, there is no need to introduce into the system a separate distributed hashing based peer-to-peer look up scheme or a centralized name server. Simulation results show that LANMAR with group discovery outperforms a typical on-demand search scheme. Keywords— Mobile ad hoc networks, ad hoc routing, group mobility, group identifier retrieval, address look up, proactive routing.