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FANETs have evolved using the concept of MANETs and VANETs. To apply routing protocols to FANETs is one of the common challenges. Unlike FANETs, generic ADHOC networks are not capable of sending information quickly and correctly is  some situations like at the time of natural disaster like flooding, earthquakes and even in military battlefield. Optimized Link-State Routing (OLSR), and Predictive-OLSR (P-OLSR) are the techniques for dynamic topology adaptation in accordance with the mobility pattern. OLSR is a routing protocol where every node maintains one or more tables representing the entire topology of the network. P-OLSR which is designed for FANETs is an extension of Optimized Link-State Routing. OLSR have a benefit of having routes quickly available whenever required. Simulation results verify that the proposed scheme could significantly increase the performance of flying ad hoc networks.


A Wireless ad hoc network is a set of different network nodes forming the temporary networks without the aid of any infrastructure or any centralized administrator. They do not have gateway, each node can act as the gateway. The wireless arena has been experiencing exponential growth in 21st Century. The IEEE Standard 802.11 is used for ad hoc networks which specifies Medium Access control and Physical layer. In ad hoc network every node has its own transmission range, which in turn combine to form a bigger transmission area. Nodes use hopping technique to transmit data.  To make this process more effective , an appropriate routing algorithm should be implemented.

Routing protocols are designed based on the requirement such as when the data is to be exchanged,  what data should be exchanged, how routes are calculated etc. In proactive algorithms routes are calculated in the before hand , so nodes use these routes for information exchange. OLSR routing algorithm is an example of proactive. Whereas in reactive algorithms route is calculated only when there are nodes that need to be communicated. AODV is an example of reactive algorithm. Multiple paths between any two given nodes can have better throughput and recovering connection failure is also easy , but overhead of route discovery in multi path routing more when compared with a single path routing algorithm. In table driven routing protocol information about each node to other node is updated. Where as in on demand routing ,nodes calculate if they have to exchange data from each other. They don’t have to update information. For a routing algorithm to be best, it should overcome the routing problems in ad hoc network. Some of the routing problems are given below

Asymmetric Link: If node 1 can hear node 2, that does not imply vice versa, hence routing algorithms should be asymmetric.
Redundant connection: It consumes lot of time to update routing table , if there are many redundant connections.
Interference: Interference is very common as the data transfer is done trough waves. Natural effects like weather, scattering  can cause interference.
Dynamic topology : Since nodes can enter and leave network freely, it causes node to make frequent changes in their routing table. 

FANETs are the special form of MANETs and VANETs. They have much mobility degree and because of this topology changes more frequently than that of MANETs and VANETs. Distance between the nodes is also longer than that of the VANETs and MANETs. Hence communication range in FANETs also should be longer than that of others. Since the topology changes in an unpredictable manner, robust algorithm with dynamic routing are better to maintain communication among the nodes in the FANETs. Dynamic routing in ad hoc network is an reactive algorithm where the nodes recover the routes each time a node transfers data to other node. Since FANETs have high mobility nodes, route breakage is very common. Hence route is maintained in order to minimize the breakage. 

Network Simulator widely known as NS2, is an event driven simulation tool that has proved useful in studying dynamic nature of FANETs. NS2 enables users by providing with ways to specify network protocols and simulate their behavior. The paper has three sections. In the first section , OLSR protocol is analyzed , in the second part P-OLSR is analyzed. Third section is about the simulation results.