Applying Deadlock Risk Assessment in Architectural Models of Real-Time Systems

Software Architectural Assessment is a key discipline to identify at early stages of a real-time system (RTS) synthesis the problems that may become critical in its operation. Typical mechanisms supporting concurrency, such as semaphores or monitors, usually lead to concurrency problems in execution time difficult to identify, reproduce and solve. For this reason it is crucial to understand the root causes of these problems and to provide support to identify and mitigate them at early stages of the system lifecycle. This paper aims to present the results of a research work oriented to the creation of a tool to assess deadlock risk in architectural models of a RTS. A concrete architectural style (PPOOA-UML) was used to represent PIM (Platform Independent Models) of a RTS architecture supported by the PPOOA-Visio CASE tool. A case study was used to validate the deadlock assessment tool created. In the context of one of the functions of a military transport aircraft, the auto-tuning function of the communications system was selected for the assessment of the deadlock risk. According to the results obtained some guidelines are outlined to minimize the deadlock risk of the system architecture

Performance modelling for system-level design

xii+208hlm.;24c

PLACES'10: The 3rd Workshop on Programmng Language Approaches to concurrency and Communication-Centric Software

Paphos, Cyprus. March 201

Gbit/second lossless data compression hardware

This thesis investigates how to improve the performance of lossless data compression hardware as a tool to reduce the cost per bit stored in a computer system or transmitted over a communication network. Lossless data compression allows the exact reconstruction of the original data after decompression. Its deployment in some high-bandwidth applications has been hampered due to performance limitations in the compressing hardware that needs to match the performance of the original system to avoid becoming a bottleneck. Advancing the area of lossless data compression hardware, hence, offers a valid motivation with the potential of doubling the performance of the system that incorporates it with minimum investment. This work starts by presenting an analysis of current compression methods with the objective of identifying the factors that limit performance and also the factors that increase it. [Continues.

Content storage and retrieval mechanisms for vehicular delay-tolerant networks

Vehicular delay-tolerant networks (VDTNs) were proposed as a novel disruptive network concept based on the delay tolerant networking (DTN) paradigm. VDTN architecture uses vehicles to relay messages, enabling network connectivity in challenging scenarios. Due to intermittent connectivity, network nodes carry messages in their buffers, relaying them only when a proper contact opportunity occurs. Thus, the storage capacity and message retrieving of intermediate nodes directly affects the network performance. Therefore, efficient and robust caching and forwarding mechanisms are needed. This dissertation proposes a content storage and retrieval (CSR) solution for VDTN networks. This solution consists on storage and retrieval control labels, attached to every data bundle of aggregated network traffic. These labels define cacheable contents, and apply cachecontrol and forwarding restrictions on data bundles. The presented mechanisms gathered several contributions from cache based technologies such as Web cache schemes, ad-hoc and DTN networks. This solution is fully automated, providing a fast, safe, and reliable data transfer and storage management, while improves the applicability and performance of VDTN networks significantly. This work presents the performance evaluation and validation of CSR mechanisms through a VDTN testbed. Furthermore it presents several network performance evaluations and results using the well-known DTN routing protocols, Epidemic and Spray and Wait (including its binary variant). The comparison of the network behavior and performance on both protocols, with and without CSR mechanisms, proves that CSR mechanisms improve significantly the overall network performance