Contention-based Access Protocol for Intra-Cluster Communications in Mobile Ad hoc Networks

A Mobile Ad hoc Network (MANET) is characterised by mobile radios (or nodes) and mobile Cluster Heads (or Base Stations) and have no fixed infrastructure. MANETs have extensive applications in military and homeland security theatres. In this paper, a clustered MANET architecture is considered where every cluster contains a group of radios and a Cluster Head (CH). MANET consists of intra-cluster network with radios and an associated CH. The network that connects the CHs is the inter-cluster network. Radios belonging to different clusters can communicate with one another with the help of CHs. This paper introduces a Contention-based Access Protocol (CAP) for communication inside a cluster (intra-cluster communication). All packet exchanges between radios are achieved through CH. In intra-cluster network, when more than one radio wish to communicate with CH, there will be contention. The contention-based protocol proposed here is a MAC layer protocol which allows the radios to contend with their radio Ids. After contention, the radio whose Id is sent by the CH, is allowed to forward a packet without contention. Since only the radio Ids contend, the throughput is comparatively higher than the existing contention-based protocols. The performance of CAP is computed based on the effective transmission time of a packet sent from a radio to the CH and vice versa while executing the protocol. Delay and throughput performances reveal that, for a sensible packet size of 512 bits, CAP offers a throughput close to 46 percent while the delay is about 1.1 millisecond. For larger packets, CAP yields higher throughput, attains a peak value and eventually saturates. MATLAB is used to implement the system in real-time.