Abstract: Based on the onclaycr hierarchical structure, a multi-layer hierarchical structure was introduced to solve the scalability problem in ad hoc networks better. Aiming at the problems in this structure such as poor structure stability and large structure maintenance overheads,a multi layer centerless hierarchical structure was proposed. It adopts a centerless scheme, and the structure depends on some relatively stable clusters, which will make the structure stabler. To reduce structure maintenance overheads, a new addressing scheme was adopted, which can avoid the frequent alterations of a node' s hierarchical ID caused by a clusterhead' s change. Both theoretical analysis and simulative analysis were made to compare the two structures' performance. hhe conclusion shows that multi-layer centerless hierarchical struclure outperforms the current multi-layer hierarchical structure on structure stability and structure maintenance overheads.

Key words: Ad hoc networks, Hierarchical structure, Multi-layer hierarchical structure, Stability, Addressing scheme