Channel Adaptive Real-Time MAC Protocols for a Two-Level Heterogeneous Wireless Network
Wireless technology is becoming an attractive mode of communication for real-time applications in typical settings such as in an industrial setup because of the tremendous advantages it is capable of offering. However, the high bit error rate characterist
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Abstract. Wireless technology is becoming an attractive mode of communication for real-time applications in typical settings such as in an industrial setup because of the tremendous advantages it is capable of offering. However, the high bit error rate characteristics of wireless channel due to conditions like attenuation, noise, fading and interference seriously impact the timeliness and guarantees that need to be provided for realtime traffic. Existing wireless protocols either do not adapt well to the erroneous channel conditions or do not provide real-time guarantees. The goal of our work is to design and evaluate novel real-time MAC (Medium Access Control) protocols for scheduling messages in a 2-level hierarchical wireless industrial network taking into account the time-varying channel condition. Our objective is to minimize the loss rate of messages using the slot exchange protocol[9] that actively combats the erroneous channel conditions and maximize the channel utilization by enabling parallel transmissions in a collision-free manner. Unfortunately, these two goals have inherent conflicts in shared medium wireless networks. We propose a distributed protocol, called the Adaptive protocol that arbitrates between these two design criteria in order to resolve the inherent conflict between them. Through simulation studies, we show that the proposed Adaptive protocol achieves significant improvement in deadline miss ratio compared to the baseline protocols that exploit complete parallelism and full exchange, for a wide range of channel conditions.
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Introduction
The term industrial traffic refers to the transfer of messages in applications such industrial automation, process control, communication systems in automobiles etc. Such communication must be performed under stringent hard real-time and reliability constraints since missing a deadline can be disastrous. For guaranteeing this low level of stringent real-time requirements, fieldbuses are able to support time-critical communication between sensors, actuators, programmable logic controllers and operator workstations. These networks are traditionally based on wired technology and a deterministic medium access control. However, the current wired infrastructure is plagued by problems of limited mobility and high deployment and maintenance costs that constrains the viability of any smart real-time system. S. Aluru et al. (Eds.): HiPC 2007, LNCS 4873, pp. 625–636, 2007. c Springer-Verlag Berlin Heidelberg 2007
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K. Balasubramanian, G.S.A. Kumar, and G. Manimaran
The wireless evolution offers numerous benefits for industrial applications, where wired solutions have prohibitive problems in terms of cost and feasibility. The growing popularity of wireless communication in different fields including home and office environments has led to its increased dependability, performance improvement and cost reduction. With its widespread standardization, it is very likely in the near future, there will be a proliferation of wireless implementations of factory communication sys
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