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Top1. Introduction
With the recent developments in the field of Wireless Sensor Networks (WSNs), these networks have got research attention to fulfill the dream of Industrial Wireless Automation (IWA). For wirelessly industrial automation, small and inexpensive sensor nodes are installed in machines to sense the surroundings parameters, perform the collaborative signal processing and communicate wirelessly (Christin et al., 2010; Gungor & Hancks, 2009; Kumar et al., 2014; Willig, A., 2008). In addition to collecting normal sensory measures, WSNs helps to collect the real-time data from the places which are hazardous or inaccessible through wired networks. Moreover, it alerts in relation to system failure in advance so the remedial action may timely initiate. Apart from best effort real-time services there may be need of timeliness data delivery that cannot afford the delay or loss of in-time packet delivery. The out-of-date delivery of data may adversely affect the performance of system regarding industrial monitoring and control (Kumar et al., 2013; Niu et al., 2014; Willig, A., 2008).
The other aspect of real-time data delivery is the reliability of data delivery. This may be defined as the amount of successful packet delivery at the destination. Since, the adverse industrial environment condition may cause node or link failure. That consequences change in network topology and connectivity over time. To forward a packet consistently, multiple retransmissions may needed at each node. This results in undesirable delay and additional energy consumption. Therefore, the proper link selection may help to optimize the retransmission which in turn save energy and improve the deadline time data delivery (Niu et al., 2014).
In case of critical application such as radiation monitoring, intrusion detection, fire detection or emergency situation like life saving condition, the warning message requires the real-time and reliable delivery. Therefore, the working group of IEEE 802.15 (http://www.ieee802.org/15/pub/TG4e.html) has advocated for the need of suitable routing protocol to facilitate the industrial application need. Hence, IWA necessitates a routing protocol for industrial applications that can adopt the network dynamics and can secure real-time timeliness data delivery.
As the WSNs and Industrial Wireless Sensor Networks (IWSNs) have the similar communication and routing characteristics. Thus, real-time routing protocols of WSNs may accept for IWSNs applications. In (Akyildiz et al., 2002; Felemban et al., 2006; He et al., 2005) a number of existing real-time routing protocols have been discussed for WSNs. They follow the spatiotemporal approach for real-time data delivery. Each node knows the information of its one hop neighbor. As a request of data delivery arrives at source node the source node estimates the desired delivery speed by dividing distance between source and sink by deadline time. Using the one-hop neighbor information, requesting node selects the forwarding node. A neighboring node that has the higher delivery speed is selected as optimum forwarding node. In (Cho et al., 2011; Dulman et al., 2003; Marina & Das, 2001; Nasehi et al., 2013) great efforts have been made for real-time and reliable data delivery. These protocols are either designed for energy awareness or they occupy the heavy control overheads to maintain the routing information. As we know that the energy consumption optimization is an important issue for WSNs and IWSNs but in comparison to reliability and real-time performance the prime emphasis cannot be given to energy consumption. As we know that the adverse industrial environmental condition greatly deteriorates the protocol performance. Therefore, this is required that as a link or node failed the other link should be alive as soon as possible to fulfill the real-time reliable communication need. None of the existing studies are in such a situation to provide the real-time, reliable timeliness data delivery simultaneously to fulfill the IWSNs need.