# Cyber Physical Systems Dependability Using CPS-IOT Monitoring
## 1 Introduction
### The Impacts of Emerging Trends on CPS-IoT  
CPS-IoT systems are often a combination of diverse subsystems, including numerous sensors from diverse manufacturers, varied gateways, and networking devices, as well as multiple actuation systems, all of which might run different protocols. The relevance of a dependable CPS-IoT system can therefore not be over-emphasised. However, serious considerations must be paid to the impacts of complex emerging IoT platforms and standards on CPS infrastructure. These impacts can be viewed from three dimensions, viz. :  
1. The impact of complexity on CPS: By enabling information to be collected and communicated among everybody, everything, and from any where, CPS-IoT will usher in a new era where the cyber, physical, and human knowledge, as well as social activities are integrated into a unified platform. Though advantageous, the down side is that the CPS system might become very complex with heterogeneous components, multiple functionalities, rules, and feedback loops. These could lead to new kinds of risks and vulnerabilities. For instance, the failure of a single component could cascade into large-scale, system-wide failures as a result of the interconnection between the various components. The management of such complexity will require accurate modelling in order to guarantee the dependability of the CPS and the safety of the critical infrastructures it controls;
2. The impact of IoT standards on CPS: Current generation CPS are often managed by Orchestration Systems (OS), wherein physical processes are controlled by networks of sensors, actuators, and controllers. These networks are often built around static topologies with pre-planned routing and scheduling mechanisms mandated by standard wireless protocols such the WirelessHART [2]. Though these standards provide real-time guarantees for delay-sensitive applications, they do not consider performance-related tasks, such as management of resources at the physical layer, scheduling of nodes at the link layer, and/or end-to-end network layer routing of traffic. Next generation CPS will require performance-aware OS that are capable of dynamically interacting with the underlying IoT subsystem for sensing and actuation through IoT communication infrastructure as well as support lightweight CPS protocols. Finally, they would be capable of providing varied services to users while meeting the requirements of high throughput, high reliability, and energy efficiency yet operating within bounded communication delays;
3. The impact of information collection on CPS: The CPS of the future will be designed around a network infrastructure that interconnects islands of IoT networks, with information shared using a \"m-to-1\" network model from all the nodes connected to unique sink(s) rooted at the gateway(s). Collection Tree Protocols (CTPs) [3; 4; 5; 6; 7] are rapidly gaining ground in the IoT field and are predicted to dominate the CPS-IoT of the future. They are protocols that rely on spanning tree structures for information diffusion from sensor nodes to the sink through local structures referred to as diffusion sets in [8]. Sink nodes often serve as sources of beacon messages, broadcasted to guide routing updates. However, this raises the issue of a trade off between stability and safety. Frequent/excessive updates may result in routing oscillation, leading to the network wasting most of its resources in signalling instead of forwarding data to the sink. Conversely, infrequent updates may result in premature and/or delayed actuation and subsequent safety risks.