Development of a multichannel based low latency asynchronous mac protocol for wireless sensor networks

Abstract

In Wireless Sensor Network (WSN), nodes have to share the medium for data transmission. Therefore, Medium Access Control (MAC) protocol has been developed to provide collision free access through this common channel. Standard MAC protocols for WSNs can be categorized into synchronous, asynchronous and hybrid. Synchronous MAC protocols, specify the duration of wake-up and sleep time to reduce the unnecessary communication time and energy wasted in idle listening. One major drawback of these protocols is that they are highly dependent on clock synchronization. On the other hand, asynchronous MAC protocols are found to be more energy e cient compared to synchronous MAC protocols as they remove the system overhead required for synchronization. However, asynchronous MAC protocols inherently introduce high latency, especially in multi hop communication scenarios. Another drawback is that nodes may severely su er from `hidden node problem' due to the lack of synchronization. In this thesis, a multi-radio multichannel based X-MAC protocol (MX-MAC) with the objective of eliminating hidden node problem of existing asynchronous MAC protocol, as well as reducing average packet delay is proposed. For multi-radio WSNs, each node is equipped with two or more radio interfaces where one radio is dedicated to control channel and the rests to data channel. Both the separate interfaces can be remain active and can send control information and data simultaneously. To address the hidden terminal problem, multi channel enables a receiver to send a preamble with next receiver ID on the control channel to notify its neighbors that an ongoing reception is in progress and alert intended next hop neighbor to wake up on time as well as to forward received data to next hop without sending any additional preamble. In consequence of this process, packet collisions are reduced and the network throughput is increased. In order to carry out the performance analysis, analytical models of the existing XMAC/ CA, ZeroMAC, MCAS-MAC as well as the proposed MX-MAC protocols are developed. Based on these models, di erent performance metrics of the proposed MX-MAC protocol are compared with those of the existing asynchronous MAC protocols. Analytical results show that the proposed protocol can signi cantly improve the throughput as well as can reduce average packet delay.