Abstract
In wireless sensor network, node localization is helpful in reporting the event's origin, assisting querying of sensors, routing, and various cyber-physical system applications, where sensors are required to report geographically meaningful data for location-based applications. One of the accurate ways of localization is the use of anchor nodes which are generally equipped with global positioning system. However, in range-based approaches used in literature, like Angle of Arrival, the accuracy and precision decreases in case of multipath fading environment. Therefore, this chapter proposes an angle of signal propagation-based method where each node emits only two signals in a particular direction and knows its approximate position while receiving the second signal. Further, a method is proposed to define the coordinates of the nodes in reference to a local coordinate frame. The proposed method does the work with a smaller number of transmissions in the network even in the presence of malicious adversaries.
TopIntroduction
Wireless Sensor Network (WSN) is a set of nodal sensor modules which connect to each other using wireless communication. WSNs can also be classified into: structured WSN and unstructured WSN (Maraiya et al., 2011). In the structured WSN, the sensor nodes are deployed in the network according to some pre-defined pattern giving an organized structure to the network. However, the unstructured WSN is just opposite to the structured. In unstructured WSN, the nodes are randomly deployed in the network. The unstructured WSN are mainly used in the region which is not accessible. In this undefined topology of the network, the sensor nodes have to maintain the topology dynamically by communicating with each other (Gupta et al., 2018). WSN is one of the significant area due to its major contribution in many applications. Main application areas for WSNs are healthcare applications, battlefield surveillance, forest fire detection, routing applications and monitoring environmental conditions (Fadel et al., 2015; Han et al., 2016; Rashid et al., 2016; Noel, 2017; Li, 2017). However, due to some of the limitations of the WSN, they are constrained in some areas as compared to traditional networks. These limitations of the WSNs are generally low power constraint, due to large number of applications it’s heavy processing requirement and low memory constraint (Vijay et al., 2013).
Localization is one of the most important technology in WSNs (Chelouah, 2018; Boukerche et al., 2017; Halder & Ghosal, 2016; Chowdhury, 2016; Paul, 2017). Nodes in WSNs are randomly deployed, not planned & it is required to know their location to inform about events (Kumari, 2019; Tuna et al., 2017). This method of determining the location of the unknown nodes in the network is known as localization. Location of nodes provide various support for many location-based protocols such as routing algorithms to make efficient data routing decisions (Cadger et al., 2013; Ndiaye, 2017; Kumar, 2017). The location of the nodes can be found out using Global Positioning System (GPS) but it’s not feasible for this case due to its large cost and large number of nodes (Xiao, 2016; Yassin, 2016). GPs unit is unable to work correctly inside buildings or dense forested areas and it may also expose to jamming and spoofing thereby creating a threat to many military applications (Bandiera et al., 2015). Basically, the localization is done using the information of the nodes whose location is already known or by using the communication information between the two unknown nodes in the network. The localization algorithm in WSNs has been classified in many ways. Zhu et al. (2014) has classified the localization as: direction-based approach and distance-based approach. In direction-based approach mainly the direction related parameters like received signal strength (RSS) are taken into account for the estimation (Azmi et al., 2018). Whereas, in direction-based approach directional parameters like Angle of Arrival (AoA) is considered. Angle of Arrival is defined to be the angle at which the signal has arrived. Mostly, the localization algorithms are mainly categorized into range based and range free. The range-based method employs range measurements, angle of arrival and angle of signal propagation. Angle of signal propagation is the particular angle at which the signal is send. Range free approach for localization is an economic approach; it does not provide high precision as much as range-based approach. It depends on the connectivity of two nodes which are fixed nodes. Some example of these range free methods is pattern matching based and hop-count-based localization techniques. Also, the range free approach does not need angle information or the range measurements and range free approach is favorable due its low cost and low energy utilization.
Key Terms in this Chapter
Angle of Signal Propagation: Angle of signal propagation is the particular angle at which the signal is send.
Localization: To know the exact location coordinates of the sensing nodes.
Range Based Localization: The range based method employs range measurements, angle of arrival and angle of signal propagation.
Range Free Localization: Range free approach for depends on the connectivity of two nodes which are fixed nodes.
Wireless Sensor Network: A network consists of sensing nodes and one or more sinks connected through wireless connection. Sensing nodes sense some particular event and disseminate collected data through multihop communication through various intermediate nodes to the sink.
Anchor Nodes: The sensing nodes which already know their location through some method like GPS.
Angle of Arrival: Angle of Arrival is the angle at which the signal has arrived.