Abstract
Water is a crucial resource for all life on earth, and it is fast becoming one of the limited natural resources to humankind, especially clean drinking water and water for agricultural uses. Sensor technologies and wireless communications (both terrestrial and underwater) have been seriously investigated by researchers to find ways to integrate these technologies for a novel data-sensing and data-collecting network for long-term water pollution monitoring purposes. This chapter describes an IoT-based underwater wireless sensor network (UWSN) which is believed to have a huge potential for monitoring the health of river, lake, reservoir, and marine environment. The sensed data from IoT sensors are communicated wirelessly via acoustic channels to a data collection center for further processing and interpretation. It is foreseeing that judicious deployment of IoT-based UWSN is a promising solution for long-term water quality surveillance.
TopBackground
A handful of underwater wireless sensor network (UWSN) have been deployed for water quality or pollution monitoring and two prominent works in this area are briefly mentioned here. Smart-Coast (Regan, Lawler, & McCarthy, 2009) was a project aimed to develop a wireless sensor network with a distinct “plug-and-play” feature that incorporates novel sensor nodes and low power consumption. This system was based on Zigbee communications standard. The “plug-and-play” platform was designed to sense pH level, temperature, conductivity, depth, and turbidity.
The Fraser River Water Quality System by Ethier & Bedard (2007) was a project initiated for monitoring water quality and meteorological parameters in real-time mode all year round. A moored buoy platform was used for station location and in-situ water sampling. A 3m tall Oceanographic Data Acquisition System (ODAS) buoy was designed for this purpose. The monitoring operation was scheduled in continuous mode with a biweekly sampling. ODAS was claimed to be able to distinguish tidally driven events to initiate sampling of organic contaminates.
Practically there are three general network scenarios for UWSN deployment: static two-dimensional UWSN for underwater bottom environment monitoring, static three-dimensional UWSN for underwater column monitoring, and three-dimensional mobile network with autonomous underwater vehicles (Akyildiz, Pompili, & Melodia, 2005). However, in terms of aquatic applications, UWSN can be classified into two categories: long-term non-time critical aquatic monitoring, and short-term time critical exploration (Cui, Kong, Gerla, & Zhou, 2006). The use case study in this chapter falls in the first category. The use case in this chapter is about a long-term water pollution monitoring application. Other applications fall into the first category may include marine biology, oceanography, ocean floor seismic monitoring, etc. As for the second category, the applications may include setting up of ad-hoc UWSN at the site of a shipwreck for liquid toxic leakage monitoring, radiation detection, etc.
This chapter starts by describing the possible UWSN architecture for underwater pollution monitoring application which includes the description of a basic architecture and an extended architecture. It should be mentioned here that the use case study in this chapter is based on the extended architecture. Then, the details of data transmission and data acquisition scheduling process for the proposed UWSN monitoring is described which leads to a proposed scheduling algorithm. Next, the sink node battery power capacity issue is discussed, and a battery power capacity estimation method is proposed. A conclusion is provided at the end of this chapter.
Key Terms in this Chapter
Pollution Monitoring: Pollution monitoring in this chapter is referring to as a kind of environment monitoring via periodic sampling of water quality for the purpose to observe and study the impact of the pollution.
Acoustic Channel: Is a communication channel or a link for underwater communication using acoustic wave for data or information transmission.
IoT Node: Is a sensor node deployed in the UWSN to perform some gathering of sensory information and able to communicate with other nodes in the network. This node can be accessed via Internet.
Long-Term Monitoring: Is referring to the time span of a UWSN node for pollution monitoring. Typically for 3 months or more of continuous monitoring operation.
Sensor Node: Is a physical sensor deployed in the UWSN for gathering and processing sensory information for underwater environment.
Battery Power Estimation: A technique to systematically estimate the power of a battery to be used in a node in UWSN.
UWSN: Underwater wireless sensor networks (UWSN) is a wireless network deployed in underwater environment using some forms of physical sensors with acoustic capability to perform collaborative monitoring and data collection tasks.
Sink Node: A node in the UWSN to aggregate data from other sensor nodes deployed in the network.
IoT: The internet of things (or in short IoT) is a term referring to the millions or billions of physical devices that are connected to the internet for collecting and sharing data. As many as 100 billion of connected IoT devices is forecasted by 2025. ]