Real Time Technology and Applications Symposium 

About: Real Time Technology and Applications Symposium is an academic conference. The conference publishes majorly in the area(s): Scheduling (computing) & Dynamic priority scheduling. Over the lifetime, 944 publications have been published by the conference receiving 30711 citations.

WirelessHART: Applying Wireless Technology in Real-Time Industrial Process Control

Abstract: Wireless technology has been regarded as a paradigm shifter in the process industry. The first open wireless communication standard specifically designed for process measurement and control applications, WirelessHART was officially released in September 2007 (as a part of the HART 7 Specification). WirelessHART is a secure and TDMA- based wireless mesh networking technology operating in the 2.4 GHz ISM radio band. In this paper, we give an introduction to the architecture of WirelessHART and share our first-hand experience in building a prototype for this specification. We describe several challenges we had to tackle during the implementation, such as the design of the timer, network wide synchronization, communication security, reliable mesh networking, and the central network manager. For each challenge, we provide a detailed analysis and propose our solution. Based on the prototype implementation, a simple WirelessHART network has been built for the purpose of demonstration. The demonstration network in turn validates our design. To the best of our knowledge, this is the first reported effort to build a WirelessHART protocol stack.

RAP: a real-time communication architecture for large-scale wireless sensor networks

Abstract: Large-scale wireless sensor networks represent a new generation of real-time embedded systems with significantly different communication constraints from traditional networked systems. This paper presents RAP, a new real-time communication architecture for large-scale sensor networks. RAP provides convenient, high-level query and event services for distributed micro-sensing applications. Novel location-addressed communication models are supported by a scalable and light-weight network stack. We present and evaluate a new packet scheduling policy called velocity monotonic scheduling that inherently accounts for both time and distance constraints. We show that this policy is particularly suitable for communication scheduling in sensor networks in which a large number of wireless devices are seamlessly integrated into a physical space to perform real-time monitoring and control. Detailed simulations of representative sensor network environments demonstrate that RAP significantly reduces the end-to-end deadline miss ratio in the sensor network.

An adaptive striping architecture for flash memory storage systems of embedded systems

Abstract: Flash memory is now a critical component in building embedded or portable devices because of its nonvolatile, shock-resistant, and power-economic nature. With the very different characteristics of flash memory, mechanisms proposed for many block-oriented storage media cannot be directly applied to flash memory. Distinct from the past work, we propose an adaptive striping architecture to significantly boost the system performance. The capability of the proposed mechanisms and architecture is demonstrated over realistic prototypes and workloads.

A feedback control approach for guaranteeing relative delays in Web servers

Abstract: The paper presents the design, implementation, and evaluation of an adaptive architecture to provide relative delay guarantees for different service classes on Web servers under HTTP 1.1. The first contribution of the paper is the architecture based on a feedback control loop that enforces desired relative delays among classes via dynamic connection scheduling and process reallocation. The second contribution is our use of feedback control theory to design the feedback loop with proven performance guarantees. In contrast with ad hoc approaches that often rely on laborious tuning and design iterations, our control theory approach enables us to systematically design an adaptive Web server with established analytical methods. The design methodology includes using system identification to establish a dynamic model, and using the Root Locus method to design a feedback controller to satisfy performance specifications of a Web server. The adaptive architecture has been implemented by modifying an Apache Web server. Experimental results demonstrate that our adaptive server achieves robust relative delay guarantees even when workload varies significantly. Properties of our adaptive Web server include guaranteed stability, and satisfactory efficiency and accuracy in achieving the desired relative delay differentiation.

Towards the Design of Certifiable Mixed-criticality Systems

Abstract: Many safety-critical embedded systems are subject to certification requirements; some systems may be required to meet multiple sets of certification requirements, from different certification authorities. Certification requirements in such "mixed-criticality" systems give rise to some interesting scheduling problems, that cannot be satisfactorily addressed using techniques from conventional scheduling theory. In this paper, we propose a formal model for representing such mixed-criticality workloads. We demonstrate the intractability of determining whether a system specified in this model can be scheduled to meet all its certification requirements. For dual-criticality systems -- systems subject to two sets of certification requirements -- we quantify, via the metric of processor speedup factor, the effectiveness of 2 techniques (reservation-based scheduling and priority-based scheduling) that are widely used in scheduling such mixed-criticality systems.