# Internet of Drones: Routing Algorithms, Techniques and Challenges
## 2 Related Work  
In order to develop a desired research outcome, the study of previous research done is an integral and important part of the study. This section presents the discussion regarding IoDs. IoD networks have become popular in recent years. Due to the advanced deployment and flexibility of IoD devices, IoD networks are being used as the future wireless communication technology. The reasons for this are low cost and availability of IoD devices. The rapid deployment of technologies such as IoT devices, sensors, embedded microcomputers, low-cost Wi-Fi radio interfaces, global positioning systems (GPS), and batteries has enabled IoDs to be widely used in numerous applications in military as well as civil domains [9; 10]. In recent years, routing protocols for IoD networks have been included in the literature. In a previous work [9], it was investigated that a number of cluster-based routing protocols in IoD networks can be used. In [8], the authors provided a comprehensive survey of routing protocols in different categories, including topology-based, position-based, and forwarding-based routing in IoD networks. In traditional and emerging IoD networks, multiple IoDs communicate with each other and with ground stations. IoD-aided WSNs are different from WSNs in terms of communication entities, communication distance, drone mobility, dynamic link quality, and frequent changes in network topology. IoD networks are wireless enabled networks with a drone as a sink, where a drone is used to collect data from ground sensor nodes. A number of routing protocols for IoDs were reported in literature [8]. IoDs have been an integral part of technologies starting from early 2000s. Drone technology has been the favourite of children as well, but it is incorporated in various domestic and commercial applications. Currently, IoD is being used to enhance the operation of WSNs. The various applications include event monitoring [11; 12], vehicle monitoring [13], wildfire management [14], remote sensing [15], farming [16], search and rescue [17; 18], emergency communications [19], and infrastructure monitoring [20]. IoDs are effectively applied to data collection from sensors [21], data relay [22], and drone-aided wireless communications [23; 24]. In wireless communication networks and particularly in WSNs, the nodes sometimes operate in a collaborative manner to perform tasks [25]. The function of nodes is specific to the applications. In many cases, the network is deployed in harsh environments such as battlefields where the nodes are susceptible to damage, resulting in worn out nodes. In addition, nodes may suffer from energy depletion and breakdown in the electronics setting [26]. An important feature in battery operated IoDs is battery failure, which makes a faulty node. In [27], the author have introduced a method that selects new cluster heads  
Figure 2: Structure of the article. to replace the faulty ones. In [28], the authors introduce a packet loss recovery model based on mobile cluster heads. A tendency to move out of coverage of each other affects clusters' ability to communicate with each other. In [29], the authors use \"Cluster of CHs\" definition to have a master cluster head and detection and replacement of faulty cluster heads. In [30], the authors utilizes time division multiple access (TDMA) in clusters to detect faulty nodes. In [31], the authors use a fault detection method by using acknowledgment from cluster heads in member nodes and neighbour nodes in the same cluster. Similarly in [32], the authors introduce a method that detects types of failure including battery failure, micro controller failure, sensor failure, and transmitter/receiver failure. Author have proposed an energy efficient cluster head (CH) selection scheme for IoD networks to enhance the lifetime and average residual energy of a single IoD cluster [6].