Future advanced applications will work hand in glove with UAVs in 6G environments. Imagining the role of drones in futuristic applications in 6G environments has unprecedented dimensions. UAVs will have countless employment roles in future applications. Brain computer interface, wearable clothing and technology are futuristic ideas that demand robust security for sharing the data. Current wireless networks including 5G are not capable to utilize numerous future prospects that are beyond the traditional medical ways. Extended reality multi-sensory applications are designed in a way for the provision of user experience that is entirely enchanting by amalgamating the reception from human sensory, environment and, human body moves, and several data originators.
3.2. 6G Application Requirements
With the goal of making blockchain utility more understandable, 6G applications are separated into two major groups. Ultra-reliability, low latency, increased data speeds and huge connection are among the typical criteria. I view of the pertinent factor in almost entire wireless communication generations, these needs are made part of the first category. These are referred as Qualification Group-I (QG-I). QG-I standards necessitate considerable improvement for potential 6G applications. The prime features for any reliable and secure network include non-reputability, confidentiality, defined level of secrecy, data integrity and auditability. These features are catered in second group named Qualification Group-II (QG-II).
3.2.1. High-Precision Positioning and Seamless Coverage
Unmanned aerial vehicles performing operations while airborne at various level of air space necessitate accurate positioning, precise navigation and excellent network coverage and the same aspects are vital for the network’s growing infrastructure, expansion and convergence as shown in Figure 5
. While the UAVs are flying independently, a secure connection and vast network coverage ensures uninterrupted connectivity. Covering a wide range of coverage at varied elevations while maintaining seamless connectivity is a critical problem for 4G/5G cellular networks. Positioning based on high precision is expected to be provided by 6G while employing radar technology. Moreover, utilization of modern concepts such as 3D placement permits the accurate locating of unmanned aerial vehicles and moving devices in the sky 
. Upcoming, 6G communication networks may enhance the quantity of connected unmanned aerial vehicles in densely populated scenarios by 107 devices/km2
which is 10 times greater than its predecessor, wireless communication model density. Beyond the vision line of sight, improved quality, robust, reliable and secure networks with vast speedy coverage, the 6G network is expected to provide connectivity that is efficient, cost effective and speedy, promising the future needs of the world 
. The high-speed OWC system’s high-capacity backhaul network enables a significant volume of UAV traffic data.
Figure 5. Multiple layers of the airspace with high-precision positioning.
3.2.2. Remote and Real-Time Control (RRC)
Unmanned aerial vehicles are operated through remote and real-time links and a continuous feedback from designated UAVs is received by establishing links through this media. Equipment status, location and other sensory data are received at ground stations from UAVs. In order to ensure seamless command and control of UAVs over wireless communication media, latency and data rate are pertinent considerations and specific required criteria must be fulfilled. In potential 6G networks, a bigger number of unmanned aerial vehicles can be operated and even these machines can accomplish different mission profiles in autonomous mode without direct operator control 
3.2.3. Multimedia Transmission
Based on mission profiles and to ensure the prompt provision of data to ground stations, unmanned aerial vehicles transport live data such as video, other sensors data for timely analysis and subsequent decision making. In future, modern multimedia services will be one of major demands through UAV platforms. These include multimedia applications related to virtual reality, 4K and beyond films, holograms, etc. These advance multimedia services require high data rates and bandwidth to provide true experience to users in connection with applications such as virtual reality and 3D holograms. The envisaged 6G network is capable of providing high bandwidth and throughput in UTM 
. In order to ensure, seamless communication of UAVs with the ground control station and reliable traffic between the two ends, mandatory high bandwidth requirements are required to be promised, which will be offered by 6G in future. A data rate of 10 Gbps is anticipated in upcoming 6G technology 
. The multimedia application of UAV is depicted in Figure 6
Multimedia application of UAVs.
3.2.4. Aircraft Identification and Regulation
An automated dependent surveillance broadcast (ADS-B) system is utilized for the identification of commercial aircrafts. Because of the increased number of UAVs in future applications, the usage of ADS-B may inundate the designated frequency band 
. In view of this fact, a new scheme for the identification of commercial flights is deemed necessary. Radio waves are used to convey the remote ID. Registration, identification, tracking and regulation of aircraft all require reliable cellular network connectivity. In the same way, remote ID data can be utilized in the integration with future 6G networks. By effective monitoring of UAVs status data, positioning and related information, early warning along with subsequent remedial measures can be executed on the basis of monitoring parameters. Probable threats can also be contained after due analysis of the received data 
4. Authentication in UAV Networks
Unmanned aerial systems (UASs) consist of one or more than one UAVs. The stated unmanned aerial vehicles are operated and controlled through a reliable communication channel by GCS 
. Utilization of UAVs is found in commercial, civilian and military uses. From surveillance to reconnaissance, security purposes, traffic monitoring, items delivery, etc., all are applications of UAVs employing modern communication networks in the future. Swarm employment is providing promising advantages in multiple civilian applications 
. Graceful degradation is achieved in case of any technical fault as alternate UAV can take over the mission role and task in such scenarios. Moreover, robustness as well as availability of communication with GCS is ensured beyond the line of sight through establishment of the Adhoc network 
. The probability of mission failure is minimized as in the swarm system, multiple UAVs are employed which act as system redundancy.
One of the pertinent advantages of these systems is reduced maintenance cost. Communication is of key importance in a flock of UAVs. The major reasons for communication needing to be robust and reliable in operation of such UAV networks is the high mobility of UAVs, irregular distance between each UAV nodule which results in inconsistent link quality, limited capacity of UAVs in terms of onboard available power and the ever-changing topology of the UAV network due to the mobile nature. Moreover, due to limited battery storage, unmanned aerial systems communication becomes challenging 
. Secure networks are an essential requirement of worldwide users in connection with different applications and have been an unvarying challenge for researchers in ever-evolutionary modern communication models. Similarly, it has been a growing concern in unmanned aerial vehicle systems. It is a significant consideration in wireless networks that they are intrinsically insecure 
Wireless networks can be victim of sniffing, eavesdropping and other related wireless network attacks that include MitM, impersonation attacks, DoS 
and Sybli. These attacks are vulnerable as they compromise privacy; moreover, they can result in major denial of the overall system by exhausting system bandwidth, memory, power, etc. 
. The jamming of wireless communication between unmanned aerial vehicle system elements can be devastating. Functional as well as operational control of the unmanned vehicle can be lost through such attacks, causing overall system hacking by the enemy 
. The classic example of eavesdropping is through man in the middle attacks as malicious element records and the transport of information is through passive means to attacker.
UASs work with a minimum or no human interaction and the authentication process in such system is node to node. Approaching GCS by any node in UAS, it is vital that all nodes are authenticated. However, the limited computing and power resources of UAVs make off-the-shelf security solutions impractical 
. To construct a secure communication channel, authentication and encryption are essential security features 
. Cryptography is frequently employed in authentication systems. Typical authentication systems utilize cryptography during the basic steps of verification and certification 
4.1. Light Weight Authentication Protocols
The use of WiFi has significantly increased over the years both at individual and commercial levels. Due to no complexity involved in installation and operational use of WiFi technology, the popularity of this wireless communication system is ever-increasing 
. Moreover, it is a cost-effective solution in comparison to typical cable network. wireless sensor nodes are exploding in popularity, with applications as diverse as in any possible fields for the future 
. These sensors are expected to be a ground-breaking addition in the consumer and business world. For example, the information collected by these sensors in a market place, in a particular section of a store, can turned into meaningful data for targeted advertisement, thus engaging visitors through tapped data by these small sensors for attracting customers and providing better services in consumer field 
In a wireless sensor network (WSN), each sensor collects a query from numerous wireless nodes and transports it to a database for subsequent analysis for converting data into meaningful information. The vital requirement in a secure network is authentication of network nodes. Similarly, in WSN, valid authentication of each element is vital. Light weight authentication is considered to be one of the time efficient schemes, mandatory in a heterogeneous network to reduce the period required for authentication process 
. Reducing handoff latency is thought to be a difficult task. Once a mobile user requires to maintain utilizing the wireless service uninterrupted and remain connected while during a journey across the diverse communication network, this issue arises. For example, the access networks are switched by a user during traveling, staying connected on internet and accessing real-time mobile applications 
. Interruptions, link quality and reliability issues, security concerns, loss of data packets is experienced whenever there is delay in vertical handoff. Security, reliability, negligible interruption, appropriate handoff scheme are demanded in such applications 
. In this arena, a number of strategies for reducing authentication delays have been presented. These solutions, on the other hand, do not entirely solve all of the concerns in the problem area; for example, they have security, monetary cost, signaling cost and packet latency flaws.
4.2. 6G Enabled Light Weight Authentication Protocols
In the study 
, a light weight authentication protocol is described that promises the privacy and security of a wireless network that is 6G enabled and supports a maritime IoT-based transportation mechanism. In order to critically verify the security features, methods such as real or random oracle scheme are employed. IoT integrated with blockchain schemes is one of the promising designs in connection with future applications ensuring inherent requirements including security-focused authentication-based needs on data integrity, non-reputability and audibility. Major light weight authentication domains in UAV systems are shown in Figure 7
Figure 7. UAV systems light weight authentication domains.
Routinely, Internet of Things networked together employs a relatively weak model of security in use of the communication link. The communication is encrypted through the utilization of session keys. Moreover, in networked IoTs, the limitation of resource utilization is experienced which gives way to inefficient algorithms such as dynamic key generation. Secure interoperability and operation of IoT protocols is a significant issue in embedded devices with several resource limitations. It offers a new scheme of dynamic key generation that is capable of functioning and producing a hefty number of keys that are unique. The suitability of such key generation algorithms is principally proven for Internet of Things modules and dependent conditions in which such devices cannot depend upon re-utilization of already in use keys for encryption and on unvarying key conciliation 
. Light weight authentication in UAV systems is shown in Figure 8
Figure 8. Light weight authentication in UAV systems.