ABSTRACT:FANETs is most evolved researcharea in todays time it make use of multi-UAV. Use of UAVs is increasing day byday due to the advancement of sensors, processor and applications.

FANETs ismostly used in undeployed area such as flood, Drought and most importantly in militaryreason. The main challenge of FANETs is routing of these multiple UAVs due tohigh speed which required highly dynamic routing protocols. In this paper wetried to studied already proposed routing protocols.

 KEYWORDS:UAVs, FANETs INTRODUCTION:FANETs is a wireless ad-hoc networkof multiple UAVS which communicate with each other to complete their applicationsfor which they are designed instead this network make use of location findingsystem and have a central co-ordinator such as Satellite. FANET (Flying Ad-HocNetwork)is a subcategory of MANET(Mobile Ad-hoc Network). As UAVs are cheap,easily installed, have flying capabilities thus these are used inundeterministic areas.Characteristics of FANET areHighly mobileLow density of nodesAccess of LOS (Location of Sight)High computation power of nodesGPS provided for Geospatiallocalization FANETs ROUTING PROTOCOLS:PredeterminedRouting protocols of MANETs or wireless Ad-hoc such as Flooding, Dynamic SourceRouting etc, are not applicable for FANETs because of high speed of Flying Nodesthus new protocols should be introduced and predefined protocols should beredefined.Classesof FANETs Routing Protocols1) STATICROUTING PROTOCOLS:Asthe name suggest STATIC (Constant) that can’t be updated so the routing table,task or application is calculated or defined once and feed to the UAVs System. Advantages:Low overhead of control messages as there no need for updation.Disadvantages:No Fault Tolerance in Dynamic Environment.

 a)Data Centric Routing: In this routing protocol, process of aggregation and disseminationis based on data there is no need for sender or receiver IDs. Interested senderBroadcast the Request on the basis of  typeof data it is interested in and the receiver node decide sending data andbroadcast reply message with requested data. Routing is based on data type noton IDs of sender or receiver node.

This routing executes three scopes of decoupling:•Space decoupling: Communicating parties can be anywhere.•Time decoupling: Data can be transmitted to the subscribers instantly or later.•Flow decoupling: Delivery can be accomplished constantly. b)Load Carry And Deliver Algorithm: source node load data to UAVs and UAVS carrydata by flying and at Destination Node deliver data in this algorithm, UAVsused pipelined path always.Advantage:maximize throughput, increase securityDisadvantages:  if distance increases between UAVs itincrease transmission delay and not tolerated c)  Multi-level Hierarchical Algorithm: in thismodel whole network is divided into multiple number of cluster and each clusterhas Cluster Head to represent whole cluster and do most of the processing. Multiplelayer of cluster is formed and each layer is connected with each other directlyor indirectly.

Layer can be ground station, UAVs, Satellite etc). Head ofcluster broadcast data or control information to its member which are in itsrange. 2)PROACTIVEROUTING PROTOCOLS:Theseprotocols make use of routing tables to store all routing information in thenetwork.Advantagesof PRP are: Easy to find out routing path in less Transmission delay as all theinformation is already store in tables. Latest information is carry out byrouting tables.

Disadvantage:Large number of message exchange to update routing table thus bandwidth wasted.Thus these protocols not used in high mobility environment. a)Directional Optimized Link State Routing: This protocols based on OLSR(OptimizedLink State Routing). Here sender node selects a set of MPR(Multi Point Relay)nodes so that the MPR nodes can cover two hop neighbours. DOLSR can reduce thenumber of MPRs with directional antennas which is most crucial issue in OLSR. b)Destination Sequence Distance Vector (DSDV) routing protocol: In DSDV, eachnode saves a routing table (with sequence number and distance ) for all othernodes. Whenever the topology of the network changes, Routing table is exchangedby using more number of exchange messages.

Destination Sequence Number (Issuedby Destination Node) is used to eliminate routing loops and maintain freshinformation. The main advantages of DSDV are its simplicity and the use ofsequence number. Disadvantages are.

For updation of  routing table, eachnode periodically broadcast routing table updates, which brings overhead to thenetwork. c)Topology Broadcast Based on Reverse Path Forwarding:  This Protocol Based On DSR (Dynamic SourceRouting), developed for dissemination of link state updates. In TBRPF each routingtable contains the state (valid/invalid/loop) of each link.

If there is anychange in the state of link, it is quickly detected and immediately find analternative path therefore it is suitable for FANET. The process of TBRPFconsists of two steps; first, it perform neighbourdiscovery and seconditbroadcast link state updates rapidly. TBRPF uses min-hop pathspanning trees rooted at the source to send the updates efficiently. The tree isused to travel topology updates using reverse path forwarding.3.

) REACTIVE ROUTING PROTOCOL(RRP):RRP referred to as On-Demand Routing Protocol. If there is no data to transferthere is no need to find a route between two nodes.There are two differentmessages in this protocol: Route Request messages (RREQ) and Route Replymessages (RREP). RREQ Messages are Broadcasted by Source Node and RRP is theResponse from Destination node.Advantages: Efficient Utilizationof Bandwidth because there is no periodic messages and overcome overheadproblem as in PRP.

Disadvantage: High path Set up Delay. a) Dynamic Source Routing(DSR): In DSR, the source node broadcasts a route request message to itsneighbour nodes in its vicinity which include (TTL, Path, sequence number,source ID and Destination ID) when this message is received by Destination Nodeit Start Backtracking the path stored in RREQ packet and this backtracking inunicast fashion and send RREP to its backtrack node until it is received bysource node and as route is established then data transmission can take place.  b) Ad-Hoc On DemandVector Routing (AODV) :In AODV, there is asingle record for each destination and the source node only stores the next-hopinformation consistent toeach data communication. AODV routing protocol consists of three phases: route discovery, packettransmitting and route maintaining.

Its RREQ packet contain (Source ID,Destination ID, Destination Sequencenumber, Source sequence number, next hop, Broadcast ID which is incrementedfor each retransmision).            c) Time Slotted On-Demand Routing:Itis the time slotted version AODV, It uses dedicated time slots in which onlyone node can send data packet. Although it increases the use of networkbandwidth but mitigates the packet collisions and ensure packet delivery. 4.

)HYBRID ROUTING PROTOCOLS (HRP):Itovercome the limitation of PRP and RRP. As RRP need Extra Time for routeDiscovery and huge overhead in PRP. HRP is appropriate for large networks. Anetwork can be divided into a number of zones where within the Zone we used PRPwhile inner-zone routing uses RRP.Advantages: low space utilization,Efficient bandwidth Utilization using Multicasting, less delay if source andDestination lie in same zone. a)Zone Based Routing Protocol: ZRP is based on the concept of Zones in Zone isdefined by predefined Radius R. The Nodes maintain a routing table for nodeswhich lie within R hop distance and outside of it, it process RRP by sending RREQpacket for highest hop distance nodes. The routing inside the zone is called asintra-zone routing, and it uses proactivemethod.

If thesource and destination nodes are in the same zone, the source node can startdata communication instantly. When the data packets need to send outside thezone the inter-zone routing is used and reactive method is applied usingMulticasting. b)Temporarily Ordered Routing Algorithm (TORA): Temporarily OrderedRouting Algorithm (TORA) routers only preserve info about adjacent routers .TORA mainly uses a reactive routing protocol but it also use some proactiveprotocol.

It constructs and preserves a Directed Acyclic Graph (DAG) from thesource node to the destination. TORA does not use a shortest path solution.Each node has a parameter value termed as “height” using 5 tuples  in DAG, which is unique for each node. Dataflow from the higher height nodes to lower height node that is Downstream . Itis loop-free because data always flow in downstreaming path not upstreaming.

Ithas 3 mechanism : Route Creation, Route Maintenance, Route Erasure. 5.)POSITIONAL BASED ROUTING PROTOCOL:Position-based routingneeds information about the physical position of the contributing nodes in thenetwork. Generally, each node calculates its own location through the use ofGPS or some other type of positioning facilities. Position based routing isprimarily motivated by two subjects, (i) A position facility is used by the senderof a packet to decide the position of the destination and (ii) A forwardingapproach used to forward the packets. a) Greedy PerimeterStateless Routing: GPSR is a responsive and efficient routing protocol for mobile, wirelessnetworks. GPSR exploits the correspondence between geographic position and connectivity in a wireless network,by using the positions of nodes to make packet forwarding decisions.

GPSRuses greedy forwarding toforward packets to nodes that are always progressively closer to thedestination. In regions of the network where such a greedy path does not exist(i.e. the only path requiresthat one move temporarily farther away from the destination), GPSR recovers byforwarding in perimeter mode,in which a packet traverses successively closer faces of a planar subgraph of the full radio networkconnectivity graph, until reaching a node closer to the destination, wheregreedy forwarding resumes. b) Geographic PositionMobility Oriented Routing: In GPMOR Firstly, theyused Gauss-Markov mobility model for predicting the node position to decreaserouting failure. Secondly, they used the mobility relationship to selectnext-hop for routing more accurately. The proposed approach improves the stabilityof cluster and cluster heads. 6.

) HIERARCHICAL ROUTINGPROTOCOL:In hierarchical routingprotocols the choice of proactive and of reactive routing depends on thehierarchic level. The routing is primarily established with some proactiveplanned routes and then helps the request from by triggered nodes throughreactive protocol at the lower levels. The main drawbacks of this protocol are:complexity and addressing scheme which response to traffic request as a resultit hang the interconnecting factors. a)Mobility prediction clustering: It operates on thedictionary of Tree-structure calculation algorithm and link termination timemobility model to guess network topology updates.

In this way, it can buildmore constant clusterformation. b) Clusteringalgorithm of UAV networking: It constructs the clusters on the ground, and thenupdates the clusters through the mission in the multi-UAV system 13.Twotype of Clustering algorithms are there :I.LEACH(LowEnergy Adaptive Clustering Hierarchy): LEACH  is a typical hierarchical clustering routingprotocol, which adopts distributed clustering algorithm where cluster-headrotation mechanism, data aggregation, and data fusion technologies effectivelyimproves the lifetime of network. In order to optimize energy in the network,nodes are selected as cluster head circularly and randomly. The normal nodescalled cluster members join the corresponding cluster head nodes on the basisof principle of proximity. Normal nodes sense data and send directly to thecluster head nodes.

The cluster head nodes receive sensed data, aggregate thedata to remove redundancy and fusion processes are carried out and data is sendto the Base Station II.EECA(Energy Efficient ClusteringAlgorithm): In this algorithm the energy loss per cluster round is decreasedand have less number of transmission and a better data hierarchy. The clusterheads on each round is selected from all the multipoint relays of the networkon the basis of residual energy of all the multipoint relay (MPRs) nodes andthe distance between them and the base station. Now these cluster head chosenact as a base station and further in the cluster of this cluster head,sub-cluster heads are choose from the multipoint relays of the nodes in thiscluster on the basis of their distance to this cluster head and energy levels,thus forming a sub cluster which further goes on to make another sub-subcluster and thus continuing this process till the last node in a particular clusteris covered. Therefore, a hierarchy of clusters is formed.EFFICENCY OF SOME OF THE PROTOCOLS1:LoadCarry and Deliver:  High throughput byarranging multiple UAVs in pipeline manner.

DataCentric Routing Algorithm: Used when limited number of UAVs for particularapplications.TopologyBased Reverse Path Forwarding: reduce overhead.DOSLR:Lower end to end delay.DSR:Adaptable to Dynamic Topology of FANETs.AODV:Suitable for dynamic nature and reduced packet collision.

TimeSlotted ON Demand Routing protocol: Enhanced packet delivery.GPSR:Outperform many existing non position based protocol GMPOR:Better latency, packet delay ratio position based protocol MobilityPrediction Algorithm: Increase the stability of clusters and CH ClusteringAlgorithm: Increase the stability, guarantee the ability of dynamic networking  CONCLUSION:Therouting protocols for FANET are currently taking more interest of researchersdue to their different characteristics. Here we have tried to mention almostmaximum number of protocols used for FANET.

Since there is a lot of work to doin this particular field and there is a need to find more efficient routingprotocols. REFERENCEs:1.  Banshi D.Soni, Jigar H. Jobanputra, Lakshmi Saraswat,  A Comprehensive Survey on Communication Protocols for FANET  IJSRD – International Journal for ScientificResearch & Development | Sp.

Issue- Computer Networking | ISSN(online):2321-06132. Smriti Iyer Review of Flying Ad-hocNetworks (FANETs) internationalJournal on recent and innovative Computingand Communication.3.

Muneer Bani Yassein and Nour Alhuda “FlyingAd-Hoc Networks: Routing Protocols, Mobility Models, Issues” (IJACSA)International Journal of Advanced Computer Science and Applications, Damer JordanUniversity of Science and Technology.4. Md. HasanTareque, Md. Shohrab Hossain& Mohammed Atiquzzaman “On the Routing inFlying Ad hoc Networks” The Federated Conference on Computer Science andInformation Systems          

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