ABSTRACT: As a result of recent advancement in sensors,processors, usage of multi-UAV is rapidly evolved their usage in naturalcalamities such as drought, flood ,emergency, military and in civilian andcommercial area. FANETs is evolved to tackle communication between multi-UAV(UnmannedAerial Vehicle) . The main challenge in FANET is routing because of highmobility and long distance between UAVs ,The routing protocols designed forVANET and MANET partially failed in FANET; In this paper we have studieddifferent routing protocols for FANET. INTRODUCTION1:UAVs are used in many Applicationssuch as emergency, battlefield,Traffic & crop monitoring,search and rescue etc, Because of low Cost , Easy installation, better flyingcapabilities. Co-operating between multiple UAVs useful in many ways although it’s a majorchallenge in FANETs too.
FANET is a subclass of MANET wherethere is a communication between UAVs in wireless fashion but they make use oflocation tracking devices or satellite for central administration of multi UAVs, in wireless network we are not allowed to use any central administration thusit break basic principle of ad-hoc network,Common characteristics of FANETare:21.high mobility of nodes2,low node density3. rapid change in topology4. nodes are located high above theground level and there LoS accessible in most cases5. Nodes computing power is veryhigh6.
GPS, AGPS , DGPS, provided forGeospatial Localization FANETsROUTING PROTOCOLS3:There are many routing protocolsused in wireless and ad-hoc networks such as flooding, dynamic source routing,and pre-computed routing etc. But due to speed of UAVs and rapid changes in links between nodes,these protocols need to be modified and the others will be established to adoptthis network issues.SIX MAIN CLASSES OF FANETs ROUTINGPROTOCOLS3:1) Static protocols: They contain arouting table that is not edited at any time3.2) Proactive protocols: It containsa routing table for each node that is refreshed periodically3. 3) Reactive Protocols: It is calledon-demand routing protocol, which fills the routing tables when there is a needto send data and the path is not known3.4) Hybrid Protocols: It takesadvantages from proactive and reactive protocols3.5)Position/Geographic Basedprotocols: that use position or area coverage4.
6)Hierarchical protocols: that usehierarchy model for routing4. 1) STATIC ROUTING PROTOCOLS:As the name suggest STATIC whichcant be updated so these protocols basic characteristics is in which a routingtable is calculated and feed to the UAVs and it can’t be updated during itsapplications. Thus there is no Fault Tolerance for dynamic environment. Advantages:Low overhead of control messages as there no need for updation.Disadvantages:No Fault Tolerance in Dynamic Envionment. a) Data Centric Routing: Thismethod is selected when data is requested by a number of nodes and datadistribution is on-demand process.
Data requesting and gathering is done on thebasis of data attributes instead of sender and receiving nodes. This modelworks well in clustering, the consumer node broadcast queries in order tocollect data from a particular area. Routing is done with respect to thecontent of data. Data aggregation algorithms may be used for energy efficientdata broadcasting. This routing executes three scopes of decoupling:• Space decoupling: Communicatingparties can be anywhere.• Time decoupling: Data can betransmitted to the subscribers instantly or later.• Flow decoupling: Delivery can beaccomplished constantly.
b) Load Carry And DeliverAlgorithm:In this model, a UAV loads data from a Fixed ground node; then thedata is being carried to the destination by flying; and at the end the datareached to the Fixed destination ground node. this algorithm always used a pipelined routing path. The main objectivesof load carry and deliver routing is to maximize throughput and increase thesecurity. And the main drawback of this protocol is whenever the distance ofcommunicating parts growth, the transmission delay becomes tremendously hugeand unendurable. To solve this problem multi-UAVs system can be developed sothat it decreases transmission delay as well as the distance among UAVs. c) Multi-level Hierarchical Algorithm:In this model the network is dividedinto hierarchy of clusters .Each cluster has a cluster head (CH), which willrepresent the whole cluster; this CH do most of the processing . Each CH is in connection with theupper/lower clusters containing multiple layers (ground stations, UAVs, satellites, etc.
) directly orindirectly. To broadcast data and control info to other UAVs in the cluster, CHshould be in direct communication range of other UAVs in cluster. This model isbetter if UAVs are controlled in larged mission area, and several UAVs are usedin the network. 2)PROACTIVE ROUTING PROTOCOLS:These protocols make use of routingtables to store all routing information in the network.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 onOLSR(Optimized Link State Routing). Here sender node selects a set of MPR(MultiPoint Relay) nodes so that the MPR nodes can cover two hop neighbours. DOLSRcan reduce the number of MPRs with directional antennas which is most crucialissue 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 onReverse Path Forwarding: This ProtocolBased On DSR (Dynamic Source Routing), developed for dissemination of linkstate updates.In TBRPF each routing table contains the state (valid/invalid/loop) of eachlink. If there is any change in the state of link, it is quickly detected and immediatelyfind an alternative path therefore it is suitable for FANET. The process ofTBRPF consists of two steps; first, it perform neighbourdiscovery and second it broadcast link stateupdates rapidly. TBRPFuses min-hop path spanning trees rooted at the source to send the updatesefficiently. The tree is used to travel topology updates using reverse pathforwarding.
3.)REACTIVE ROUTING PROTOCOL(RRP): RRP referred to as On-Demand Routing Protocol.If there is no data to transfer there is no need to find a route between twonodes.Thereare two different messages in this protocol: Route Request messages (RREQ) andRoute Reply messages (RREP). RREQ Messages are Broadcasted by Source Node andRRP is the Response 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 routerequest message to its neighbour nodes in its vicinity which include (TTL,Path, sequence number, source ID and Destination ID) when this message isreceived by Destination Node it Start Backtracking the path stored in RREQpacket and this backtracking in unicast fashion and send RREP to its backtrack nodeuntil it is received by source node and as route is established then datatransmission can take place. b)Ad-Hoc On Demand Vector Routing (AODV) :InAODV, there is a single record for each destination and the source node onlystores the next-hopinformationconsistent to each data communication. AODV routing protocol consists of threephases: route discovery,packet transmitting and route maintaining. Its RREQ packet contain (Source ID,Destination ID, DestinationSequence number, Source sequence number, next hop, Broadcast ID which isincremented for eachretransmision). 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):It overcome the limitation of PRPand RRP. As RRP need Extra Time for route Discovery and huge overhead in PRP. HRP is appropriate forlarge networks.
A network can be divided into a number of zones where withinthe Zone we used PRP while 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: ZRPis based on the concept of Zones in Zone is defined by predefined Radius R. TheNodes maintain a routing table for nodes which lie within R hop distance andoutside of it, it process RRP by sending RREQ packet for highest hop distancenodes. Therouting inside the zone is called as intra-zone routing, and it uses proactive method. If the source anddestination nodes are in the same zone, the source node can start data communicationinstantly. When the data packets need to send outside the zone the inter-zonerouting is used and reactive method is applied using Multicasting. b) Temporarily Ordered RoutingAlgorithm (TORA): TemporarilyOrdered Routing Algorithm (TORA) routers only preserve info about adjacentrouters .
TORA mainly uses a reactive routing protocol but it also use someproactive protocol. It constructs and preserves a Directed Acyclic Graph (DAG)from the source node to the destination. TORA does not use a shortest pathsolution.
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 ROUTINGPROTOCOL:Position-basedrouting needs information about the physical position of the contributing nodesin the network. Generally, each node calculates its own location through theuse of GPS or some other type of positioning facilities. Position based routingis primarily 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 Perimeter Stateless Routing: GPSR is a responsive and efficientrouting protocol for mobile, wireless networks. GPSR exploits thecorrespondence between geographicposition and connectivity in a wireless network, by using thepositions of nodes to make packet forwarding decisions. GPSR uses greedy forwarding to forwardpackets to nodes that are always progressively closer to the destination. Inregions of the network where such a greedy path does not exist (i.e. the only path requires that onemove 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 Position Mobility Oriented Routing: In GPMOR Firstly,they used Gauss-Markov mobility model for predicting the node position todecrease routing failure. Secondly, they used the mobility relationship toselect next-hop for routing more accurately.
The proposed approach improves thestability of cluster and cluster heads. 6.)HIERARCHICAL ROUTING PROTOCOL:Inhierarchical routing protocols the choice of proactive and of reactive routingdepends on the hierarchic level. The routing is primarily established with someproactive planned routes and then helps the request from by triggered nodesthrough reactive protocol at the lower levels. The main drawbacks of thisprotocol are: complexity and addressing scheme which response to trafficrequest as a result it 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)Clustering algorithm of UAV networking: It constructsthe clusters on the ground, and then updates the clusters through the missionin the multi-UAV system 13.Twotype of Clustering algorithms are there :I.LEACH(Low Energy AdaptiveClustering Hierarchy): LEACH is atypical hierarchical clustering routing protocol, which adopts distributedclustering algorithm where cluster-head rotation mechanism, data aggregation,and data fusion technologies effectively improves the lifetime of network. Inorder to optimize energy in the network, nodes are selected as cluster headcircularly and randomly.
The normal nodes called cluster members join thecorresponding cluster head nodes on the basis of principle of proximity. Normalnodes sense data and send directly to the cluster head nodes. The cluster headnodes receive sensed data, aggregate the data to remove redundancy and fusionprocesses are carried out and data is send to 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 particularcluster is covered. Therefore, a hierarchy of clusters is formed.
EFFICENCYOF SOME OF THE PROTOCOLS1: Load Carry and Deliver: High throughput by arranging multiple UAVs inpipeline manner.Data Centric Routing Algorithm: Usedwhen limited number of UAVs for particular applications.Topology Based Reverse PathForwarding: reduce overhead.DOSLR: Lower end to end delay.DSR: Adaptable to Dynamic Topologyof FANETs.
AODV: Suitable for dynamic natureand reduced packet collision. Time Slotted ON Demand Routingprotocol: Enhanced packet delivery.GPSR: Outperform many existing nonposition based protocol GMPOR: Better latency, packet delayratio position based protocol Mobility Prediction Algorithm: Increase the stabilityof clusters and CH Clustering Algorithm: Increase the stability,guarantee the ability of dynamic networking CONCLUSION:The routing protocols for FANET arecurrently taking more interest of researchers due to their differentcharacteristics. Here we have tried to mention almost maximum number ofprotocols used for FANET. Since there is a lot of work to do in this particularfield and there is a need to find more efficient routing protocols.
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