The Research On Grid-based Predictable Location Service In Ad Hoc Networks

Ad hoc networks are no fixed infrastructure, self-organizing and dynamic topology novel wireless networks. They have good mobility and scalability. Due to node mobility, before a packet can be forwarded, the source node has to discover the location of a node to which the packet is destined. Location service is how to manage, update and query location information of nodes effectively. Existing location service protocols cost a lot of network resources, whose reliability and scalability are poor. To solve these problems, we propose the grid-based, predictable location service protocols:GPLS and GPLS-H.Based on the flat and hierarchical hash location service protocols, we propose grid-based, predictable location service protocol (GPLS). The Network is partitioned into girds, and grids are divided into groups by a HASH function. The network is a two-layer structure. The proposed GPLS protocol can reduce the overhead of location services and has good scalability. A node updates its location information to the grid it located in and its location server group directly. A source node can get the location information of its destination node through its location server group; the proposed location service scheme has accurate location query capability by means of location prediction of mobile nodes. GPLS improves the efficiency of location service and reduces the overhead of the network by using predictable query.Based on GPLS, we propose GPLS-H protocol that can detour "hole" in grid networks. When a forwarding package encounter "hole" area, it is forwarded in counter-clockwise direction to bypass the "hole" area. GPLS-H protocol improves the success ratio of location update and query, and has better scalability.Finally, we use NS-2 to simulate the GPLS, GPLS-H, CRLS and SLURP protocols. GPLS and GPLS-H has higher query success rate and location availability, fewer query hops and less query delay than CRLS and SLURP. GPLS-H has higher query success rate than GPLS, because it can tolerate the "hole" in the network.