## 2 UAV Communication
### Security in UAV Communication  
Internet of Things (IoT) acts as an interface between the physical world and computing systems; IoTs perform this role by transfer of information regarding the physical atmosphere after sensing and necessary analysis. Internet of Drones (IoD) is a classic mobile IoT system [52; 53]. Figure 5: UAVs relaying packets for clients/sensor data to control centers. In the latest years, unmanned aerial vehicles and drones have become a popular application in several fields due to its inherent characteristics including reach, exploratory abilities, flexibility, speed, life safety in case of difficult missions and coverage, etc. Keeping in mind advancements in this domain, the public's demand has invariably increased. Moreover, there is increased demand against consumer grade drones across the globe as engagement of UAVs in different applications and roles is becoming widespread. The employment of UAVs in various fields has increased manifold, including in shooting movies, drone selfies, agriculture businesses, and security objectives; all are utilizing these aerial devices. Growth in UAV commerce is expected to accelerate upwards at a rate of at least 29.9% per annum in upcoming years. Moreover, the industry volume is expected to rise to approximately 4.9 billion dollars at the end of the coming three years [54]. The prominent progress UAVs have made is in the IoTs, and they have promising applications in the future that will accompany generations to come. One of the major concerns that needs to be addressed before time is security of communication in the employment of Internet of Drones (IoD). For example, to accomplish unlawful border breaches in 2016, drug dealers from Mexico carried out signal spoofing of navigation satellite and attacked border patrolling aerial carriers. In July 2016, [PERSON] cautioned very clearly that drones without encryption features are prone to hijacking, raising serious security concerns of drones. [PERSON] is a well-known security expert from IBM and presented this important concern in a security summit held in Asia. Similarly, the Iranian military caused a serious loss of information when they successfully hijacked and seized US MQ-9 UAV in 2019. Therefore, communication security of unmanned aerial vehicles during different roles such as patrolling and surveillance necessitates immediate and robust measures to ensure the same [55]. Two critical properties of UAVs as a smart IoT apparatus are resource limitations and the varying environment. Moreover, UAV network connection conditions including AP servers are subject to constantly changing position and environments. Consequently, the identity of every element of the UAV network must be periodically authenticated in multiple cycles. Moreover, due to the mobility of these smart devices, which are embedded with smart features, they face noteworthy limitations such as power constraints and processing power. Furthermore, the endurance of these devices and other abilities will be adversely affected if an excessively recurrent and sophisticated authentication scheme is defined for them [56]. In the IoD paradigm, avoiding mishaps such as loss of assets, loss of  
Figure 6: UAVs wireless mesh networks. the drone itself, and most importantly loss of life and vital information due to breach of network and any compromise, ensuring the overall protection of the IoD environment is currently a decisive issue. Pertinent threats to the IoD environment include jamming [57], spoofing, Denial of Service (DoS), eavesdropping and MiTM. Figure 7 symbolizes major issues relating to the IoD security environment. There is a considerable boost in utilization of UAVs in different applications as stated above and this aspect has surfaced potential security concerns, specifically in networking and communication protocols [58; 59]. [PERSON] et al. [18] have highlighted that, in order to detect the invasion of proteratum UAVs, 60 GHz frequency band have relatively superior performance than the over-cluttered frequencies, i.e., 2.5-5 GHz.