Cluster stability includes intra-cluster and inter-cluster stability. They will make important influence on clustering performance. So they should be paid attention at the same time. MSWCA only considers on intra-cluster stability, but neglects inter-cluster stability, which is bound to affect the clustering performance. Aiming at the above problem, NCA (New Clustering Algorithm) was proposed in this paper. NCA considers on intra-cluster and inter-cluster stability, which can improve cluster stability and reduce clustering overheads.

In MANET, the scheme for maintaining an inter-zone route in ZRP makes ZRP take more lost packets and more route re-discovering times; the former makes ZRP take lower delivery ratio of data packets, which makes ZRP take less reliability; the latter makes ZRP take more transmission delay and more routing overheads. Aiming at the problem above, a MANET-based reliable zone routing protocol (MRZRP) was proposed. In MRZRP, each node saved multiple backup routes from the node to each intra-zone node by maintaining an directed acyclic graph based on an intra-zone topology, and an inter-zone route was repaired by using backup segment routes as much as possible. The simulation results show that MRZRP improves delivery ratio of data packets, which shows that MRZRP improves the protocol reliability, and MRZRP also reduces the transmission delay and routing overheads.

At present, hierarchical routing protocols have been the main solution of routing scalability problem in MANET. Based on the deep research on hierarchical routing protocols, hierarchical routing protocols were divided into two parts. The situations of the main routing protocols of each part were reviewed and analyzed. This work will contribute to the further study of hierarchical routing protocols.

In ad hoc networks, ZRP (Zone Routing Protocol) combines a proactive routing protocol with an on-demand routing protocol. Proactive routing is adopted in the intra-zone, and on-demand routing is adopted in the inter-zone. During the process of the inter-zone routing maintenance in ZRP, there is a low reliability problem. So NHRP (New Hybrid Routing Protocol) was proposed, and the protocol reliability relationship between ZRP and NHRP was demonstrated by a comparative analysis on route reliabilities of ZRP and NHRP. The theoretical analysis shows that NHRP takes higher reliability than ZRP.

In MANET, MSWCA is a typical algorithm in clustering algorithms with consideration on motion-correlativity. Aiming at MSWCA’s problem that “it only considers on intra-cluster stability, and neglects the inter-cluster stability”, a MANET-based stable clustering algorithm (MSCA) was proposed. Firstly, MSCA clustering algorithm and its cluster maintenance scheme were designed. Secondly, the theoretical quantitative analyses on average variation frequency of clusters and clustering overheads were conducted. The results show that MSCA can improve cluster stability and reduce clustering overheads.