Using Particle Swarm Optimization for Enhancing the Hierarchical Cell Relay Routing Protocol
An ad hoc network is usually assumed to be homogeneous, such that each mobile node uses the same radio capability. However, a homogenous ad hoc network suffers from poor scalability. Nodes that use different radio powers at different tiers can be used to solve this problem. This study proposes zone-based hierarchical routing in two-tier ad hoc networks (HRTT). The hierarchical structure of a wireless network is typically organized in clusters, so establishing stable clusters to manage every node is important. HRTT provides a stable clustering scheme according to the rate of degree variations of nodes. Stable nodes are selected as the cluster heads to manage the other nodes. The cluster heads become the backbone nodes (BNs), which use large power to transmit packets and form the backbone network. In the proposed maintenance scheme, nodes exchange their state messages with neighbors and determine whether a new cluster head is required. Routing is classified into two types - low tier routing and high tier routing - to lighten the backbone network. HRTT yields promising results concerning the hierarchical structure, according to simulations.