Routing and Medium Access Control (MAC) in wireless sensor network for monitoring emergency applications

Abstract

In recent years, Wireless Sensor Networks (WSNs) have been implemented in many applications including emergency applications. Emergency applications require different characteristics than others, such as robust communication, low energy consumption and minimum end-to-end delay. Routing and Medium Access Control (MAC) are two protocols that have been used by many researchers to achieve those requirements. This thesis mainly focuses on studying distributive clustering routing and MAC protocol for emergency applications. To design robust communication in emergency applications, this thesis has proposed a modified LEACH protocol considering the health status of sensor nodes. LEACH is a benchmark protocol employing distributive clustering-based routing with low energy consumption, however this protocol is not suitable for emergency applications. The health status refers to the condition of nodes, safe or in danger, with the danger status shows the high probability to be destroyed sooner because of external factors such as fire. The proposed approach avoids selecting the nodes in danger as cluster heads. Furthermore, efficient multi-hop communication is employed to minimise energy consumption. The simulation result shows that total data received, energy consumption , packet delivery ratio, and energy efficiency of the proposed approach are stable with an increasing number of destroyed nodes. Furthermore, a grid-based clustering approach with health status is proposed to further enhance energy constraint and robust communication. The proposed approach includes distributive clustering and incorporate constant number of CHs in every round. The remaining energy, the health status of node, and the distance to the centre of the grid are consided when choosing the cluster head. Simulation results have revealed that the proposed protocol has a significant effect on the time for first node to destroy due to energy consumption, an increase of 45% compared to LEACH. Furthermore, packet delivery ratio of the proposed approach is enhanced by 16% compared to LEACH. In order to reduce end to end delay, a priority-based grid Time Division Multiple Access (TDMA) has been proposed. In this approach, traffic is classified into two categories: emergency traffic from danger nodes, and monitoring traffic from safe nodes. This scheme was implemented using three steps: formation of a new TDMA frame, the arrangement of slots and priority allocation. Simulations results showed an improvement of around 65% and 70% in end to end delay compared to Grid and LEACH approaches.