# Cyber-Physical Systems for Water Supply Network Management: Basics, Challenges, and Roadmap
## 3 CPS Architecture and Applications
### CPS Conceptual Overview
#### 3.1.2 Sensing and Actuation System  
Just like other emerging technologies, CPSs employ sensors to measure and acquire data from the physical environment. With the latest development in semiconductor technology, intelligent sensors with wireless communication capabilities have been developed. These sensors are low-cost devices with data storage and processing potentials and have been deployed to several applications. In the water domain, they have been utilized for WDN monitoring through leakage and water quality detection [9; 12; 15; 16; 18]. A selection of multiple sensing elements forming a sensor array having pressure, acoustic, ultrasonic, and temperature sensors may be positioned on pipes for health monitoring. The sensing devices gather data specific to each application and send the data to a distant processing center. In some cases, in-network processing may take place within the sensor networks. The processed data can be utilized for several objectives, such as leak localization. For water supply network management applications, continuous measurement and monitoring of multiple parameters within the pipe is required. For example, in the water quality applications, parameters such as pH, dissolved oxygen, flow rate, turbidity, and conductivity, amongst others, must be measured continuously. Sensors, as well as actuators, are important elements in a CPS. Sensors are used to acquire data concerning the state of the physical environment. Howbeit, only examining the state of the physical environment is not enough in many applications. It is necessary also to act on the sensed data by performing specific actions. The actuators are therefore used for this purpose. For example, in a water quality application, the sensors gather information regarding the quality of water in a pipe system, while the actuators perform actions such as controlling the opening and closing of the isolation valve to isolate the pipe whose water quality is compromised from the network or to stop the flow of water in such pipe. In a leakage detection application, in the event of leaks, the actuators react by overseeing the control of the pressure reducing valves to reduce pressures at the nodes where the leaky pipe is connected or reduce pressure at the entrance of a district meter area (DMA) where such a pipe is located. This action is to reduce the water loss volume due to the leaking pipes. The actuators are therefore used to trigger various forms of the control command. This step performs the actions determined from the computing phase. For autonomous monitoring, several sensors and actuators used in tracking the physical environment need to provide continuous measurements for a longer period, as such, they are arranged in a network mode connected by a wireless means. This is regarded as a wireless sensor/actuator network, which is a set of sensors and actuators that are dispersed and interconnected via wireless networks [34]. It is then possible for the CPS to sense, communicate, and execute the appropriate actions to alter the behavior of the physical environment. Conventional sensor and actuator nodes are provided with processing and wireless communication capabilities and a power source. Although actuator nodes possess greater computational and communication capacities and a higher energy budget compared to sensors [34], both are still faced with power constraint issues. Different sensors could produce enormous real-time data that need to be aggregated for further processing. Also, the wireless sensor networks use radio communication technology to relay the acquired data and their design for implementation in water supply network applications, such as pipeline leakage detection, relies onthe environment in which the pipe is installed [35]. This is fundamental to selecting the type and positioning of the sensors. Sensors may be put inside the pipeline in touch with the water (known as invasive sensors) or as noninvasive sensors, where they are not in contact with the water inside the pipe [36; 37].