## 5 A Case Study on Reliable Pipeline Monitoring Using Cyber Physical Sensor Networks
### Architecture for Remote Pipeline Monitoring  
The structured WSN deployment on pipeline simplifies the routing protocols and increases efficiency and cost-effectiveness of the network. A hierarchical structure for pipeline monitoring based on sensor networks has been described in [40] wherein the functionalities are distributed among the nodes. The nodes at the lowest level are the sensing nodes that sense the parameters from the environment [67]. Relay nodes closer to sensing nodes collect sensed data and pass it on to data dissemination nodes which finally transmit the data over long haul communication links to the control center. The advantage of such a topology is that it adds redundancy to the whole architecture while reducing the range of each node that ultimately induces low energy consumption [68]. The functionalities of nodes on each level can be made distinctively diverse so as to make the data collecting system more intelligent (Figure 11). Data relay nodes require larger memory compared to the sensing nodes while the data dissemination nodes require transmitting at longer distances. The hierarchy based architecture helps adding extra features only in the places where required. Work described in [40] also emphasizes having more than one node in the transmission range of any arbitrary node so as to add redundancy and prevent disconnection for node failures. Moreover, it has been noted in [41] that the nodes' power consumption increases depending on the nodes proximity to the main node on a pipeline. Nodes' power consumption doubles for every next hop [69]. If the gateway node is placed on the right most part, the left most node utilizes minimum power and the one nearest to the main gateway node utilizes the maximum due to data aggregation over several hops. In order to prevent excess power consumption and maximize the network lifetime, work described in [41] proposes equal-power placement schemes to improve the WSNs lifetime by up to 29% with a properly selected number of sensor nodes and adjusting the distance corresponding to transmission power levels. WSN require the capability to reorganize when the new nodes are added to a network, and it should be able to heal when nodes die out due to any foreseen reason (battery damage _etc._). Routing protocols must be intelligent enough to cope with such situations. For a hierarchical WSN with tree routing algorithm including self-organizing and self-healing network capability, a transport level fragmentation of large sized packets to prevent loss of information is required [66]. Figure 11: Interacting elements of cyber physical sensor network for infrastructure monitoring. Oil and gas sector of different countries in the world has excelled in the technology and using CPSN based monitoring system to gather up-to-date information of its different processing stations. Besides real-time monitoring of various stations, a number of countries are also using wireless sensor nodes to collaborate accurate reading from different operational points. We conducted field visits of oil refineries and gas industries in the Middle East, who are using CPSN based monitoring systems for many years. These surveys were conducted in the vicinity of Saudi Aramco refineries in KSA (Yanboh Refinery run by Saudi Aramco Luberef), Kohinoor Mills gas distribution plants, ExxonMobil and Pak-Arab refinery. Information reported in this paper is gathered by field visits and provided by trained and experienced technical staff of the respective industries. Insights gained through industrial visits show that important WSN features such as mobility of the system and nodes, knowledge of node attachment locality in the operational plant, selection of network topology, scale of the network, availability of router nodes and battery lifetime, physical separation among nodes, and reliability and flexibility of nodes, and their operations define the overall system reliability. Practically, refineries and gas distribution fields do not follow any specific strategy in sensing nodes' deployment.