This paper proposes a hybrid routing protocol based on the k-hop clustering structure for MANETs. The source sends packets to the destination directly if it is in the source¡¦s neighbor table; otherwise the source reactively sends the route request packet (RREQ) to trigger the routing process. Instead of adopting the nodes that forwards the RREQ as the route between the source and destination, the route reply packet (RREP) is broadcasted via the nodes in the clusters that the RREQ has ever passed to find the route. The route constructed in this way can avoid the clusterheads always being in the transmission route and collapsing due to overloading. In comparison with the Cluster Based Routing Protocol (CBRP), the proposed protocol can distribute the communication workload from the clusterheads to member nodes. Simulation results demonstrate that the proposed protocol has better packet delivery ratio and end-to-end delay time than that of CBRP.

Zone Routing Protocol (ZRP) is a typical hybrid routing protocol used in Mobile Ad Hoc Networks (MANETs). Hybrid routing protocols are especially suitable for dynamic environments because they combine the best features of proactive and reactive routing protocols. The Gossip-based Zone Routing Protocol (GZRP) uses a gossip scheme, in which the node forwards a packet to some nodes instead of all nodes to further reduce the control overhead. However, GZRP does not perform well when the network includes articulation points since packets will be lost if an articulation node happens not to forward the packet or nodes happen not to forward packets to the articulation point. To raise the packet delivery ratio, the gossip probability of articulation points must be set to 1 and the packets to be forwarded must be sent to the articulation points in peripheral nodes. Accordingly, how to identify articulation nodes in the network becomes a critical issue. This paper proposes an effective scheme, called articulation point detection (APD), to find the articulation points. Simulation results show that the proposed APD-GZRP (GZRP with articulation point detection) can improve the packet delivery ratio and reduce both the control overhead and power consumption.