Two-Tier Slotted Aloha in Mobile Ad Hoc Networks

Although cluster-based routing schemes are active research topics in mobile ad hoc networks (MANET), few people investigated the throughput of MANET under such schemes. This paper attempts to obtain throughput of a special cluster-based MANET in which the distance between each ordinary node and a cluster head is one hop. When the underlying media access control (MAC) protocol is slotted Aloha, we propose a model called two-tier aloha to describe such a communication scenario. In this model each cluster head is responsible for collecting data from the ordinary nodes in its cluster and forwarding data to a super cluster head. Channel contentions following slotted Aloha exist in communications from ordinary nodes to cluster heads and from cluster heads to the super cluster head. We use a Markov chain to analyze this model and present an approach to obtain a theoretical network throughput. The theoretical results are validated through simulations.