Reliable Communications within Cyber-Physical Systems Using the Internet (RC4CPS)

Abstract

An important requirement to realize cyber-physical systems (CPSs) in critical infrastructures such as power grids is communication reliability where such reliability is usually measured in terms of communication service unavailability. With this regard, applications proposed for smart grids have reliability requirements of 99-99.9999%. To achieve this, most power utilities rely on dedicated networks and/or leased lines. The alternative for such solutions is the Internet which represents a global, cost-effective network for CPSs that span large geographical areas. Unfortunately, the reliability of today's Internet is inadequate and varies over time. A widely adopted approach in other domains to enhance reliability utilizes mainly redundancy in terms of communication paths and transmitted data. However, this requires knowledge about the topology to ensure disjointness of used paths, which is difficult in case of the Internet. Even with such knowledge, most of the available multipath (MP) communication protocols are throughput-oriented or proposed for dedicated networks and, therefore, cannot be utilized directly. Nevertheless, MP communication is still expected to improve the communication reliability of the Internet. In this dissertation, data duplication and dynamic MP selection during runtime when using multiple end-to-end (e2e) paths are proposed to improve the communication reliability for Internet-based CPSs. With this regard, the problem of paths selection is formulated as an optimization problem to select the minimum number of e2e paths and limit the redundant data by the needed reliability. The multiple e2e paths are realized using different access internet service providers and MP communication protocols. In addition, real world measurements to investigate the reliability gains of MP communication in the Internet were conducted. The obtained results proved the existence of e2e paths that traverse completely different networks and, consequently, are likely to be disjoint. They also showed that the concurrent unavailability of different subsets of paths with two and three paths was 0%. Those results motivated proposing the Reliable Multipath Communication for Internet-based CPSs (RC4CPS) approach. It is an e2e approach that utilizes the inherent redundancy of the Internet and the concept of MP communication protocols to improve reliability. It also provides online monitoring and dynamic MP selection that considers the diversity and unavailability probability of e2e paths to maximize the reliability gains. RC4CPS was first implemented in MATLAB for initial evaluations and, then, using the iPRP (Parallel Redundancy Protocol for IP Networks) MP transport protocol. The resulting protocol, called iPRP-RC4CPS, incorporates the RC4CPS features and extends the original iPRP implementation, proposed for dedicated WAN networks, to support the Internet. The evaluation results carried out using both implementations of RC4CPS in the Internet indicated the ability of iPRP-RC4CPS to achieve 0% unavailability while selecti...

Peningkatan Ketersediaan Fisik Dan Waktu Rata-Rata Antara Kegagalan Unit Komatsu Pc2000-8 Pada Pt. United Tractors, TBK Dengan Metode Fmea

“…Penelitian sebelumnya [31][32] menunjukkan adanya korelasi antara variabel tindak lanjut inspeksi dengan variabel PA dan MTBF, dan variabel scheduled breakdown hours dengan variabel PA dan MTBF yang mempengaruhi hasil pemeliharaan. Physical Availability (PA) adalah nilai yang menyatakan jumlah unit siap pakai untuk melakukan produksi pada interval waktu tertentu [33] . Mean Time Between Failure (MTBF) merupakan nilai statistik yang menunjukkan waktu rata-rata antara kegagalan sebelumnya hingga terjadinya kegagalan berikutnya [34] .…”