A Deterministic MAC Protocol to Handle Emergency Traffic in IWSN
Abstract: Characteristic driven benets of wireless sensor networks increased the tendency of applying this technology in industrial automation systems. While WSN is a low cost and easy maintenance solution for the current wired systems, it also introduces some challenges to design and development of protocols suitable for industrial environment. Some of essential requirements of industrial automation systems are reliability and real-time communication. Wireless communication on the other hand, essentially cannot offer any guarantee on timely or reliable delivery of data specially considering harsh industrial environments with high possibility of noise and interference. To this end, different techniques and methods in form of transport, MAC or cross-layer protocols is needed to overcome shortcomings of IWSNs to meet requirements of industrial automation systems.The problem though gets more complicated when any uncommon event such as industrial accident or device failure occurs in the network solely or simultaneously. In both case, these events need to be delivered for further process by network manager and possible repercussion by actuators. This thesis addresses the open issue of timely delivery of this safety critical tracin IWSN with no assumption of solely appearance of them with minimum disturbance of cyclic traffic of not effected portion of the network. In this thesis a TDMA based MAC protocol for handling critical trac in IWSN is proposed. Handling critical trac is done by introducing contention free periods which formed of several TDMA subslots for transmitting fixed reduced size emergency packets. This protocol narrows delay of the critical trac to less than a timeframe in cost of less than 8:85% of cyclic packet delay in the worst case with 20% of offered load being emergency. Performanceanalysis of proposed MAC protocol shows improvement of event delivery and packet delivery ratio in comparison with WirelessHART MAC protocol.
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