# UAV IoT Framework Views and Challenges: Towards Protecting Drones as \"Things\"
## 2 Overview on UAVs as Members of IoT
### Protection for UAVs
#### 2.5.1 Aerial Networking  
Multi-UAV networks should demonstrate highly dynamic behavior on complex operating scenarios baring all the constraints related to energy consumption and connectivity that may jeopardize the fleet mission. Research on aerial networks focuses on the definition of routing protocols that ensure quick communication recovery by employing flexible aerial nodes and energy-consumption management techniques that enable increased flight lifetime. At the moment, configurations like Mobile Ad-hoc NETworks (MANETs) that are destined for mobile-device communications, Vehicle Ad-hoc NETworks (VANETs) that mainly consider land vehicles, and Flying Ad-hoc NETworks (FANETs) are adopted, each of them presenting certain advantages and disadvantages in context-specific deployments [71]. All of the above adopt ad hoc routing protocols that allow the exchange of data from one node to another without any direct links. There are three main types of routing protocols, namely, proactive, reactive, and geographic [70]. * Proactive protocols [72] incorporate tables for each node that are periodically updated to store routing information for all other nodes of the topology. The main advantage of proactive protocols is that the tables of each node contain up-to-date information on routes due to continuous message exchanges; a fact, though, that causes bandwidth constraints. * Reactive protocols [73] search and store routing paths between two nodes only when the need for communication between them arises. These types of protocols present the advantage of consuming low bandwidth, but there are many cases, specifically in large topologies, where route-path calculation is very slow, causing high latency. * Geographic protocols [74] assume that the source node is aware of the geographic position of the receiving node and therefore sends the message directly without the need for searching for a route path. This protocol is very effective in terms of latency, bandwidth, and throughput, though localization information should be available. Such information can be very challenging to obtain in GPS-denied environments; however, this is quite unlikely to occur in the case of FANETs, while signal-based tracking methods (such as the one introduced in Reference [75]) can be additionally adopted. Energy conservation in UAV networks is also very important in protecting network continuity and increasing the carried payload. In terms of networking, saving energy in UAVs can be achieved [76] by (a) data reduction, (b) network coding, and (c) energy-efficient routing. Data reduction is possible by adopting aggregation schemes that perform data fusion, combining data derived from nodes on the same path. In this direction, adaptive data sampling is also an option for data-gathering tasks performed by UAVs by adjusting the sampling rate (images, videos, etc.) without compromising the required information precision. Network Coding (NC) is also used to reduce data traffic in broadcast scenarios by sending a linear combination of several packets instead of a copy of each packet. On the other hand, energy conservation can also be enabled through the appropriate energy-routing mechanisms that take into consideration metrics relevant to power utilization and load distribution. Power utilization is related to the remaining battery of a node, while load distribution refers to the queue status of a node measured as the number of packets received and waiting to be transmitted. To this end, there are three main energy-aware routing protocols: multipath-based protocols, node-based protocols, and cluster-based protocols [70]. Multipath-based protocols balanceenergy consumption among nodes by alternating forwarding nodes. These protocols discover multiple node-disjoint routes utilizing a cost function based on the hop distances and the energy levels of the nodes, and allocate the traffic rate to each selected route. Node-based protocols do not only consider the shortest paths, but select the next candidate hops based on their residual energy.