Context- and Template-Based Compression for Efficient Management of Data Models in Resource-Constrained Systems

The Cyber Physical Systems (CPS) paradigm is based on the deployment of interconnected heterogeneous devices and systems, so interoperability is at the heart of any CPS architecture design. In this sense, the adoption of standard and generic data formats for data representation and communication, e.g., XML or JSON, effectively addresses the interoperability problem among heterogeneous systems. Nevertheless, the verbosity of those standard data formats usually demands system resources that might suppose an overload for the resource-constrained devices that are typically deployed in CPS. In this work we present Context-and Template-based Compression (CTC), a data compression approach targeted to resource-constrained devices, which allows reducing the resources needed to transmit, store and process data models. Additionally, we provide a benchmark evaluation and comparison with current implementations of the Efficient XML Interchange (EXI) processor, which is promoted by the World Wide Web Consortium (W3C), and it is the most prominent XML compression mechanism nowadays. Interestingly, the results from the evaluation show that CTC outperforms EXI implementations in terms of memory usage and speed, keeping similar compression rates. As a conclusion, CTC is shown to be a good candidate for managing standard data model representation formats in CPS composed of resource-constrained devices.Research partially supported by the European Union Horizon 2020 Programme under Grant Agreement Number H2020-EeB-2015/680708 - HIT2GAP, Highly Innovative building control Tools Tackling the energy performance GAP. Also partially supported by the Department of Education, Universities and Research of the Basque Government under Grant IT980-16 and the Spanish Research Council, under grant TIN2016-79897-P

A Method for Dynamically Selecting the Best Frequency Hopping Technique in Industrial Wireless Sensor Network Applications

Industrial wireless applications often share the communication channel with other wireless technologies and communication protocols. This coexistence produces interferences and transmission errors which require appropriate mechanisms to manage retransmissions. Nevertheless, these mechanisms increase the network latency and overhead due to the retransmissions. Thus, the loss of data packets and the measures to handle them produce an undesirable drop in the QoS and hinder the overall robustness and energy efficiency of the network. Interference avoidance mechanisms, such as frequency hopping techniques, reduce the need for retransmissions due to interferences but they are often tailored to specific scenarios and are not easily adapted to other use cases. On the other hand, the total absence of interference avoidance mechanisms introduces a security risk because the communication channel may be intentionally attacked and interfered with to hinder or totally block it. In this paper we propose a method for supporting the design of communication solutions under dynamic channel interference conditions and we implement dynamic management policies for frequency hopping technique and channel selection at runtime. The method considers several standard frequency hopping techniques and quality metrics, and the quality and status of the available frequency channels to propose the best combined solution to minimize the side effects of interferences. A simulation tool has been developed and used in this work to validate the method.Research partially supported by the European Union's Seventh Framework Programme for research, technological development and demonstration under Grant Agreement Number FP7-SEC-2013-1/607292 ZONeSEC-Towards a EU framework for the security of Widezones, in the scope of the activities related to develop technologies that foster the Plug, Play&Forget paradigm. Also partially supported by the Department of Education, Universities and Research of the Basque Government under Grant IT980-16 and the Spanish Research Council, under grant TIN2016-79897-P

Failure detectors and communication efficiency in the crash and general omisión failure models

122 p.Consensus is one of the fundamental problems in fault tolerant distributed systems. In addition to the importance of the problem itself, consensus can be a way to solve many other problems in distributed systems, so it is considered a key topic in the Distributed Computing area. Although many solutions have been proposed to solve consensus in synchronous systems, [Fischer, Lynch, and Paterson, 1985] presented an impossibility result, namely Fischer-Lynch-Paterson or FLP, that states that it is impossible to reach consensus in asynchronous systems where even one process may crash. In order to circumvent FLP, [Chandra and Toueg, 1996] proposed the unreliable failure detector abstraction, which has been widely studied in several systems, especially those where processes can only fail by crashing. Failure detectors offer a modular approach that allows other applications such as consensus to use them as a building block. Additionally, the failure detector abstraction allows to encapsulate the synchrony assumptions of the system, so that applications which make use of failure detectors can be designed as if they run in pure asynchronous systems. In this work we show that failure detectors can also be applied to the general omission failure model, in which processes may fail by crashing and by omitting messages either when sending or receiving. As a practical example, we propose a solution to a security area problem called Secure Multiparty Computation by using failure detectors for general omission. In the context of failure detectors in the crash failure model we also study communication efficiency, a performance measure achieved when there are only n links that carry messages forever, being n the number of processes. We improve this measure by defining communication optimality, in which only c links are needed, being c the number of correct processes. In this regard, we propose some communication-optimal implementations of the eventually perfect failure detector class P. Finally, we propose a communication-efficient implementation of a failure detector for the general omission failure model. In this case, we define communication efficiency as a linear number of links carrying messages forever

Failure detectors and communication efficiency in the crash and general omisión failure models

122 p.Consensus is one of the fundamental problems in fault tolerant distributed systems. In addition to the importance of the problem itself, consensus can be a way to solve many other problems in distributed systems, so it is considered a key topic in the Distributed Computing area. Although many solutions have been proposed to solve consensus in synchronous systems, [Fischer, Lynch, and Paterson, 1985] presented an impossibility result, namely Fischer-Lynch-Paterson or FLP, that states that it is impossible to reach consensus in asynchronous systems where even one process may crash. In order to circumvent FLP, [Chandra and Toueg, 1996] proposed the unreliable failure detector abstraction, which has been widely studied in several systems, especially those where processes can only fail by crashing. Failure detectors offer a modular approach that allows other applications such as consensus to use them as a building block. Additionally, the failure detector abstraction allows to encapsulate the synchrony assumptions of the system, so that applications which make use of failure detectors can be designed as if they run in pure asynchronous systems. In this work we show that failure detectors can also be applied to the general omission failure model, in which processes may fail by crashing and by omitting messages either when sending or receiving. As a practical example, we propose a solution to a security area problem called Secure Multiparty Computation by using failure detectors for general omission. In the context of failure detectors in the crash failure model we also study communication efficiency, a performance measure achieved when there are only n links that carry messages forever, being n the number of processes. We improve this measure by defining communication optimality, in which only c links are needed, being c the number of correct processes. In this regard, we propose some communication-optimal implementations of the eventually perfect failure detector class P. Finally, we propose a communication-efficient implementation of a failure detector for the general omission failure model. In this case, we define communication efficiency as a linear number of links carrying messages forever