No abstract

Cognitive radio (CR) networks are expected to offer huge bandwidth to wireless users through dynamic spectrum access techniques. To realize this new network paradigm, effective distributed coordination schemes to exchange control information without assuming the availability of a pre-specified common control channel (CCC) are needed. In this paper, we propose a distributed group-based spectrum-aware coordination scheme for CSMA/CA-based CR networks (CRNs), called Virtual Clustering Distributed Coordination (VCDC). By using a CSMA/CA access mechanism, VCDC allows neighboring CR users with similar view to spectrum opportunities to asynchronously organize themselves into virtual clusters, and coordinate their communications using locally available CCCs. VCDC differs from previous cluster-based schemes in that it exploits the Discrete Orthogonal Frequency Division Multiplexing (D-OFDM) technology to reduce neighbor-discovery time and facilitate intercluster communication and broadcasting. Three variants of the VCDC scheme are proposed, which are One-hop, Two-hop, and constrained VCDC. These variants provide different cluster size based on the number of adopted local CCCs. We compare the performance of the VCDC scheme with existing clustering schemes. Simulation results show that VCDC constructs fewer number of larger size clusters with an appropriate number of common idle channels, and introduces a lower percentage of clusters with no shared idle channels. Thus, VCDC performs better without imposing synchronization.

Cyber-Physical Systems (CPSs) represent a new paradigm of future intelligent systems. They consist of loosely coupled subsystems which interact with mechanisms of Serviceoriented Architecture (SoA). In this paper we try to open a new topic in industrial communications. This topic is focused on basic communication patterns within CPSs. Patterns are abstract and generic solutions for common problems in the design of systems. They have a defined feature set, their flaws are known, and they help to avoid repeating errors. Furthermore, patterns introduce a common vocabulary within a community, which simplifies communication between people and documentation. Patterns often represent best practices that are used in already existing protocols. Therefore this work starts to evaluate different existing communication protocols in the scope of SoA and loosely coupled systems, extracts common tasks and implementations, and identifies common communication patterns.

Cyber-physical systems (CPSs) represent a new generation of control systems where distributed local control systems are connected not only physically, but also computationally by means of communication networks. CPSs target introducing intelligence beside traditional monitoring and control functionalities in a way that optimize the performance of the overall system. However, the realization of many CPS applications requires reliable communication systems that provide quality of service (QoS) control. In this domain, Long Term Evolution (LTE) standard offers a comprehensive QoS frame work. Nevertheless, commercial implementations of the standard provide only best effort type of service. In this paper, we demonstrated the benefits of using LTE networks with QoS support for CPSs by comparing the performance of a CPS application over LTE network with and without QoS support. The results clearly indicate the benefit to enable the QoS features in commercial implementations of LTE in order to realize reliable CPS applications

Multipath (MP) communication is widely used to improve the reliability of communication networks in different domains. With this regard, we have also proposed MP communication to improve communication reliability for cyberphysical systems (CPSs) when using the Internet [1]. More specifically, we proposed using different end-to-end (e2e) paths that use different pairs of Internet service providers (ISPs) to achieve MP communication. In this paper, we evaluated MP protocols proposed in the transport layer and above of the Open Systems Interconnection (OSI) model. This evaluation is based on a number of requirements drawn from our previous work in order to a achieve highly reliable MP communication. We also considered the technical requirements set by the Internet. Our results indicate that almost all evaluated MP protocols are throughput-oriented and were mostly proposed for local or private networks. We conclude the paper by highlighting a MP protocol candidate that fulfills most of the stated requirements. This candidate will be considered in future work to provide a reliable MP communication solution for Internet-based CPSs