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26
Real-Time Scheduling for WirelessHART Networks
"... WirelessHART is an open wireless sensor-actuator network standard for industrial process monitoring and control that requires real-time data communication between sensor and actuator devices. Salient features of a WirelessHART network include a centralized network management architecture, multi-chan ..."
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Cited by 48 (21 self)
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WirelessHART is an open wireless sensor-actuator network standard for industrial process monitoring and control that requires real-time data communication between sensor and actuator devices. Salient features of a WirelessHART network include a centralized network management architecture, multi-channel TDMA transmission, redundant routes, and avoidance of spatial reuse of channels for enhanced reliability and real-time performance. This paper makes several key contributions to real-time transmission scheduling in WirelessHART networks: (1) formulation of the end-to-end real-time transmission scheduling problem based on the characteristics of WirelessHART; (2) proof of NP-hardness of the problem; (3) an optimal branch-and-bound scheduling algorithm based on a necessary condition for schedulability; and (4) an efficient and practical heuristic-based scheduling algorithm called Conflict-aware Least Laxity First (C-LLF). Extensive simulations based on both random topologies and real network topologies of a physical testbed demonstrate that C-LLF is highly effective in meeting end-to-end deadlines in WirelessHART networks, and significantly outperforms common real-time scheduling policies. 1
End-to-End Delay Analysis for Fixed Priority Scheduling in WirelessHART Networks
"... Abstract—The WirelessHART standard has been specifically designed for real-time communication between sensor and actuator devices for industrial process monitoring and control. End-toend communication delay analysis for WirelessHART networks is required for acceptance test of real-time data flows fr ..."
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Cited by 26 (16 self)
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Abstract—The WirelessHART standard has been specifically designed for real-time communication between sensor and actuator devices for industrial process monitoring and control. End-toend communication delay analysis for WirelessHART networks is required for acceptance test of real-time data flows from sensors to actuators and for workload adjustment in response to network dynamics. In this paper, we map the scheduling of real-time periodic data flows in a WirelessHART network to realtime multiprocessor scheduling. We, then, exploit the response time analysis for multiprocessor scheduling and propose a novel method for the end-to-end delay analysis of the real-time flows that are scheduled using a fixed priority scheduling policy in a WirelessHART network. Simulations based on both random topologies and real network topologies of a physical testbed demonstrate the efficacy of our end-to-end delay analysis in terms of acceptance ratio under various fixed priority scheduling policies. I.
Priority Assignment for Real-Time Flows in WirelessHART Networks
"... Abstract—WirelessHART is a new wireless sensor-actuator network standard specifically developed for process industries. A key challenge faced by WirelessHART networks is to meet the stringent real-time communication requirements imposed by process monitoring and control applications. Fixed-priority ..."
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Cited by 10 (6 self)
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Abstract—WirelessHART is a new wireless sensor-actuator network standard specifically developed for process industries. A key challenge faced by WirelessHART networks is to meet the stringent real-time communication requirements imposed by process monitoring and control applications. Fixed-priority scheduling, a popular scheduling policy in real-time networks, has recently been shown to be an effective real-time transmission scheduling policy in WirelessHART networks. Priority assignment has a major impact on the schedulability of real-time flows in these networks. This paper investigates the open problem of priority assignment for periodic real-time flows for feedback control loops closed through a WirelessHART network. We first propose an optimal priority assignment algorithm based on local search for any given worst case delay analysis. We then propose an efficient heuristic search algorithm for priority assignment. We also identify special cases where the heuristic search is optimal. Simulations based on random networks and the real topology of a physical sensor network testbed showed that the heuristic search algorithm achieved near optimal performance in terms of schedulability, while significantly outperforming the traditional priority assignment policies for real-time systems. I.
Interference-Aware Real-Time Flow Scheduling for Wireless Sensor Networks
"... Abstract—With the emergence of wireless sensor networks, an enabling communication technology for distributed real-time systems, we face the critical challenge of meeting the end-to-end deadlines of real-time flows. This paper presents Real-time Flow Scheduling (RFS), a novel conflict-free real-time ..."
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Cited by 7 (3 self)
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Abstract—With the emergence of wireless sensor networks, an enabling communication technology for distributed real-time systems, we face the critical challenge of meeting the end-to-end deadlines of real-time flows. This paper presents Real-time Flow Scheduling (RFS), a novel conflict-free real-time transmission scheduling approach for periodic real-time flows in wireless sensor networks. In contrast to existing transmission scheduling algorithms that ignore interference between transmissions or prevent spatial reuse within the same channel, RFS supports spatial reuse through a novel interference-aware transmission scheduling. While recent work on conflict-free transmission scheduling focused on specialized communication patterns such as queries and converge cast, RFS is designed for peer-to-peer real-time flows with arbitrary inter-flow interference. Moreover, RFS has three salient that make it particularly suitable for real-time systems: First, RFS includes a real-time schedulability analysis that accounts for interference between real-time flows. Second, RFS improves reliability by incorporating retransmissions in a flexible scheduling scheme. Finally, RFS enhances scalability by dividing the network into neighborhoods and provides real-time performance for flows crossing multiple neighborhoods through a novel application of the Release Guard protocol. RFS was evaluated through simulations based on the traces collected from an indoor wireless sensor network testbed. Compared to a traditional TDMA protocol, RFS reduces flow latencies by up to 2.5 times, while improving the real-time capacity by as much as 3.9 times. I.
Providing OS Support for Wireless Sensor Networks: Challenges and Approaches
- IEEE COMMUNICATIONS SURVEYS AND TUTORIALS
"... Recently, wireless sensor networks (WSNs) attract a great deal of research attention, and are envisioned to support a variety of applications, including military surveillance, habitat monitoring, and infrastructure protection, etc. Operating system (OS) support for WSNs plays a central role in build ..."
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Cited by 5 (3 self)
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Recently, wireless sensor networks (WSNs) attract a great deal of research attention, and are envisioned to support a variety of applications, including military surveillance, habitat monitoring, and infrastructure protection, etc. Operating system (OS) support for WSNs plays a central role in building scalable distributed applications that are efficient and reliable. Over the years, we have seen a variety of OSes emerging in the sensornet community to facilitate developing WSN applications. Aside from the basic system implementations, there is also a large body of work devoted to improving OS capabilities in different dimensions. In this paper, we provide a comprehensive review of existing work in sensornet OS design. We first examine the challenges in the OS design space. We then introduce the major components of a sensornet OS. Next, we provide an overview of existing work, present a taxonomy of state-of-the-art OSes, and discuss various approaches to address the design challenges. Finally we discuss evaluations of a sensornet OS and present some recommendations in the perspectives of OS developers and OS users. We have also identified several open problems that need further investigation to make the OS provide stronger support for WSNs.
Analysis of EDF Scheduling for Wireless Sensor-Actuator Networks
"... Abstract—Industry is adopting Wireless Sensor-Actuator Net-works (WSANs) as the communication infrastructure for process control applications. To meet the stringent real-time performance requirements of control systems, there is a critical need for fast end-to-end delay analysis for real-time flows ..."
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Cited by 5 (5 self)
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Abstract—Industry is adopting Wireless Sensor-Actuator Net-works (WSANs) as the communication infrastructure for process control applications. To meet the stringent real-time performance requirements of control systems, there is a critical need for fast end-to-end delay analysis for real-time flows that can be used for online admission control. This paper presents a new end-to-end delay analysis for periodic flows whose transmissions are scheduled based on the Earliest Deadline First (EDF) policy. Our analysis comprises novel techniques to bound the communication delays caused by channel contention and transmission conflicts in a WSAN. Furthermore, we propose a technique to reduce the pessimism in admission control by iteratively tightening the delay bounds for flows with short deadlines. Experiments on a WSAN testbed and simulations demonstrate the effectiveness of our analysis for online admission control of real-time flows. I.
Accounting for Failures in Delay Analysis for WirelessHART Networks
"... Abstract—WirelessHART networks are gaining ground as a real-time communication infrastructure in industrial wireless control systems. Because wireless communication is often susceptible to transmission failures in industrial environments, it is essential to account for failures in the delay analysis ..."
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Cited by 3 (2 self)
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Abstract—WirelessHART networks are gaining ground as a real-time communication infrastructure in industrial wireless control systems. Because wireless communication is often susceptible to transmission failures in industrial environments, it is essential to account for failures in the delay analysis for realtime flows between sensors and actuators in process control. WirelessHART networks handle transmission failures through retransmissions using dedicated and shared time slots through different paths in the routing graphs. While these mechanisms for handling transmission failures are critical for process control requiring reliable communication, they introduce substantial challenges to worst-case end-to-end delay analysis for real-time flows. This paper presents the first worst-case end-to-end delay analysis for periodic real-time flows in a WirelessHART network that takes into account transmission failures. The delay bounds can be used to quickly assess the schedulability of real-time flows for industrial wireless control applications with stringent requirements on both high reliability and network latency. Simulations based on the topologies of a wireless sensor network testbed consisting of 69 TelosB motes indicate that our analysis provides safe upper bounds of the end-to-end delays of real-time flows at an acceptable level of pessimism. I.
IAA: interference aware anticipatory algorithm for scheduling and routing periodic realtime streams in wireless sensor networks
- in INSS
, 2010
"... Abstract—This paper provides a polynomial time heuristic for the real-time communication scheduling problem in multi-hop wireless sensor networks. Wireless networks add a new dimension to the real-time communication problem because of interference: a transmission cannot be scheduled on a radio link ..."
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Cited by 3 (0 self)
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Abstract—This paper provides a polynomial time heuristic for the real-time communication scheduling problem in multi-hop wireless sensor networks. Wireless networks add a new dimension to the real-time communication problem because of interference: a transmission cannot be scheduled on a radio link if another transmission is scheduled on any interfering link. The problem being NP-hard in nature, we propose a novel heuristic that comes into two parts: (1) a scheduler that uses a topological analysis of the network to anticipate the effects of radio interference in order to improve scheduling prioritization, (2) an iterative route update scheme that pushes apart interfering streams and spreads them out over the network to reduce interference and improve schedulability while meeting the deadline requirements. The whole algorithm runs in polynomial time of O(N 3 d), where N and d are the number of streams and maximum deadline respectively. We use a simulation-based study to demonstrate that this algorithm produces near-optimal schedules for approximately 10 packet streams in a 100 node network, where the optimal schedule can be computed. We also show that the overall algorithm is able to schedule as much as 47 % more steams than simple heuristics that takes only deadline or interference into account. Of this improvement, 4 % − 26 % contribution comes from the iterative route update scheme. I.
Interference-Aware Real-Time Flow Scheduling for Wireless Sensor Networks
"... Abstract—With the emergence of wireless sensor networks, an enabling communication technology for distributed real-time systems, we face the critical challenge of meeting the end-to-end deadlines of real-time flows. This paper presents Real-time Flow Scheduling (RFS), a novel conflict-free real-time ..."
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Abstract—With the emergence of wireless sensor networks, an enabling communication technology for distributed real-time systems, we face the critical challenge of meeting the end-to-end deadlines of real-time flows. This paper presents Real-time Flow Scheduling (RFS), a novel conflict-free real-time transmission scheduling approach for periodic real-time flows in wireless sensor networks. In contrast to existing transmission scheduling algorithms that ignore interference between transmissions or pre-vent spatial reuse within the same channel, RFS supports spatial reuse through a novel interference-aware transmission schedul-ing. While recent work on conflict-free transmission scheduling focused on specialized communication patterns such as queries and converge cast, RFS is designed for peer-to-peer real-time flows with arbitrary inter-flow interference. Moreover, RFS has three salient that make it particularly suitable for real-time systems: First, RFS includes a real-time schedulability analysis that accounts for interference between real-time flows. Second, RFS improves reliability by incorporating retransmissions in a flexible scheduling scheme. Finally, RFS enhances scalability by dividing the network into neighborhoods and provides real-time performance for flows crossing multiple neighborhoods through a novel application of the Release Guard protocol. RFS was evaluated through simulations based on the traces collected from an indoor wireless sensor network testbed. Compared to a traditional TDMA protocol, RFS reduces flow latencies by up to 2.5 times, while improving the real-time capacity by as much as 3.9 times. I.
1 End-to-End Communication Delay Analysis in Industrial Wireless Networks
"... Abstract—WirelessHART is a new standard specifically designed for real-time and reliable communication between sensor and actuator devices for industrial process monitoring and control applications. End-to-end communication delay analysis for WirelessHART networks is required to determine the schedu ..."
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Abstract—WirelessHART is a new standard specifically designed for real-time and reliable communication between sensor and actuator devices for industrial process monitoring and control applications. End-to-end communication delay analysis for WirelessHART networks is required to determine the schedulability of real-time data flows from sensors to actuators for the purpose of acceptance test or workload adjustment in response to network dynamics. In this paper, we consider a network model based on WirelessHART, and map the scheduling of real-time periodic data flows in the network to real-time multiprocessor scheduling. We then exploit the response time analysis for multiprocessor scheduling and propose a novel method for the delay analysis that establishes an upper bound of the end-to-end communication delay of each real-time flow in the network. Simulation studies based on both random topologies and real network topologies of a 74-node physical wireless sensor network testbed demonstrate that our analysis provides safe and reasonably tight upper bounds of the end-to-end delays of real-time flows, and hence enables effective schedulability tests for WirelessHART networks. Index Terms—Wireless sensor networks, scheduling, Real-time and embedded systems. 1
