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Ad hoc network, for the communication process wired and wireless methods are applied nowadays. Wireless mechanism is a most popular communication in this century. There are many protocol is working in the wireless networks. Reactive and proactive protocol are the important methods are applied in the wireless networks, in reactive protocol method has two important protocol called AODV and DSR, Such as proactive protocol has OLSR. Reactive protocol, if there is no link between the nodes, the reactive protocol makes connection between the nodes for exchange information. Proactive protocol which makes connection between networks nodes regularly for exchange information.
This thesis is examining about reactive (AODV and DSR) and proactive protocols (OLSR) analysis in the wireless networks. For the comparison result will be implementing in the opnet modular 14.5.the performance of the routing protocols will be examined by to metrics delay and throughput. Three routing protocols described through a different methods and different trajectories. The protocol evaluation study will be observed and conclusion will be presented, explaining which protocol method is the best for mobile ad hoc networks. Dynamic and the reliable protocols are very important for the ad hoc networks and it does not have base station. And the network topologies vary regularly.
Wireless network is essential is important nowadays because of wireless devices improvement is increasing and it performs the best in higher data rate.ad hoc and infrastructure are the two types of mode in wireless network. In the ad hoc network every single node play as a router. So that it can easily maintain the route between the nodes. In the infrastructure mode there will be access point between wirelesses network and wired network through the access point. MANET is nothing but Mobile Adhoc Network that means every single node can make establish the connection and communicate with other nodes. Here the radio waves only the intermediate between the mobile nodes which carries the signal (Packets) between the mobile nodes. This wireless structure easily can make in anywhere. In the wireless structure many different protocol are performing operation this thesis shows some of protocol operation and best protocol operation in wireless network. This thesis describes about three important protocols AODV,DSR and OLSR. This AODV is comes under and the reactive or on demand method. And it uses a bi-directional links and this maintenance the active route. And also this provides unicast and multicast relation between the nodes. In the AODV method there is sequence number to find the destination node and most recent path. There is low delay when connection establishes.DSR (Dynamic Routing Protocol) this protocol is like AODV. This method is comes under on-demand method. It uses a routing table in between the nodes. By using this routing table easily the source node will find the destination node. This routing table has the details about the destination node. Shortest path is also find by using this routing table. OLSR (Optimized link state routing protocol) this protocol works under the link state algorithm and this protocol comes under the proactive. This protocol is used to exchange the information between the nodes. It is updating the topological information in every single node. And it has a multipoint relays (MPRs) which is used to reduce the duplicate retransmission when flooding occur. This OSLR protocol which uses shortest path algorithm. This algorithm which is used to find the shortest route for destination. In the wireless network on-demand protocols are performs well when compared to table driven protocols. AODV protocol has important characteristic like sending hello messages to work the route perfect. It has very low delay.
Research different protocols in wireless network such as on-demand and table-driven
Best protocol for wireless network.
Discuss routing protocols in wireless network.
Review the characteristic different between the on-demand and table driven protocols
Propose AODV process in wireless network.
Analyze AODV in wireless network.
Implement the protocol result in opnet tool and shows the best protocol in wireless network
1.3 Research problems
In the wireless networks routing protocols are performing in a different ways. AODV performs three important mechanisms in wireless network which increase the speed of the network and it find the lower cost route. AODV has hello message method which is used to find the broken link and also which is used to find new nodes. This protocol is also called as on-demand protocol. Which perform well in wireless network.
In DSR, route discovery and maintenance which is used to find the route in the network and it will maintain the route properly to transmit.Which is also called as on-demand or proactive protocol.
In OLSR, it has topological information about each node. And it uses the shortest path algorithm. This is also called as proactive or table driven protocol.
This is thesis focus on researching about best protocol in wireless network. Wireless network has different protocol like AODV, DSR and OLSR. This is based on the analysing the protocol performance and the mechanism. AODV has different characteristics that are going to be analysing here.
1.4 Research methods.
The solution of the AODV performance will be implementing in the opnet. This performance is based on the analysing all the results of the routing protocol.
Structure of the report
Chapter1: Introduction: Aim and Objectives, researching problems in routing protocols.
over view of the protocol.
Chapter2: Types of protocols in the table driven and on-demand protocol in the wireless network, comparison between on-demand and table driven protocols.
Chapter3: Review about the AODV protocol characteristics and techniques.
Reactive and Proactive protocols in MANET
MANET is nothing but mobile ad hoc network , nowadays cellular,satellite and wireless fidelity are most important for exchange information. This is the methods is used in wireless technology for best communication. There is a special meaning in latin "for this". Early Ad-hoc network only designed for the military application. Early 1990's this method will combined with the wireless LAN and Bluetooth . 1997 internet engineering group launched MANET with the routing protocols. They implement routing protocols because to improve the data rate and theefficiency. At present there are more than fifty protocols are implemented in the wireless environment.
This is the structure of the ad hoc mobile networks.
Ad hoc characteristic, it offers the multi-hop communication. This is challenging for the wireless network. There is no master and the slave in this structure.Because each node act as router. When the packet travel between the nodes each nodes act as a router to forward the packets. Here reactive and the proactive protocols performs good operation in the mobile ad hoc network for the best operation.when compare to the proactive protocol, reactive protocol performs the best operation in wireless.
Charaterstic of AODV protocol
It does not have any central administrative for controlling forwarding packets.
This protocol is mainly reduce traffic in the network.
AODV reduces the traffic and increase the latency and find the new route for packets.
Hello messages are support for route.
Characteristic for DSR
It has machnisam called packet salvaging.
Through the CRC it can easily find the corrupted messages.
Route discovery and route maintain are the basic mechanisms for the DSR protocol.
It does not need a "hello messages" .
Characteristic of OLSR
Multipoint relays are important in the OLSR.
When the flood occur this protocol,MPR reduce the retransmission.
Reduce the duplicate retransimission.
Routing protocols for Mobile Ad hoc network
Table - Driven
In the on-demand protocol is most important for the wireless because this protocol has hell messages. When it sends the hello messages to the destination the source will get the acknowledgement from the destination. This is the method to find the broken path and this protocol is used for the scalability. This on-demand protocol has types DSR.AODV,TORA and ABR. The following part is explaining about only AODV and DSR.
AODV(Ad-hoc on demand Distance protocol)
This protocol is similar to DSR protocol. These two protocols maintain some table entry by using this table it can find the destination. All the routing tables contain the following details Active neighbour node. Next hop address, sequence number, hopes to reach destination.
There is two important mechanism are involved AODV protocol.
Route discovery and maintenance: before sending the data to the destination, source search the destination address in the routing table when it finds the table it will send the data to the destination. If the destination path address is not there in the table .it will choose the route discovery method, in this method the source will send route request to all neighbour nodes. And the neighbour node sends to nearest node. This will send the request until it will find the route. When it finds the route it will update the route in the table. And it will send hello message to the destination node for the availability.
AODV special advantage is control the overhead messages and the processing is also very low. Easily it will adapt to the network topology more than 10000 node it will give the reliable and scalable result in the wireless network. It has only one disadvantages is bi-directional. Because of the bi-directional it will get delay. When the link gets break it will get delay.
DSR(DYNAMIC ROUTING PROTOCOL)
DSR, this protocol before it sends the data to the destination. Source node knows all the intermediate node details towards to the destination node. All the routing nodes has cache which has all the information about the routing information.
This protocol has same features like AODV route discovery and maintenance. When the source node knows about the destination node it will send the data directly. When it needs to find the destination it will send the route request message to the neighbour node. In the request node it has details about the source address, destination address and the particular unique no. When the other node receive this route request message it will check in the cachewhen the neighbour find the destination node information then it will sent route reply message to the source node. Once it receives the request reply message it will send the data to the destination node through the neighbour node.
2.1 table driven protocol
2.1.1 Wireless Routing protocol
In this, each node maintaining the following four tables:
Distance Table: Each entry of this table contains distance between a destination and neighbour. For example, assume that node W has three neighbor nodes X, Y, Z and a destination A; W will calculate three paths (through by X, Y, Z to A respectively) distances added in the entry.
Routing table: used to find the chosen path to each destination node. Each and every entry contains the destination, distance to the destination, previous node, next node, and a note showing whether that the path is correct optimal path, having a lop error or unavailable error.
Link cost table: it describes the cost to relay data to each neighbor node and updation of frequent link.
Message retransmission List: this monitors neighbor node acknowledgement of update messages and transmitting to the specific neighbour.
Every node sends Hello messages based on periodical to show its status. These two nodes exchanging their routing table entries and add content to the corresponding table, when a node meets a next new neighbour.
Whether a new optimal route is found based on the updated distance table, node will inform the respective neighbors to modify their routing table. The MRL monitors the neighbor updating progress. To prevent the loop problem, frequently check the predecessor and successor node contents in the routing table.
The Wireless Routing protocol Pros are
Prevents the looping issue error
Reduce delay and save resources more than DSDV.
The Wireless Routing protocol cons are
High control traffic
High update computation
Need more storage device
OLSR is a proactive routing protocol and is also referred as table driven protocol since is permanently a store and updates its routing table. OLSR keeps track of routing table in order to offer a route if needed. OLSR can be implemented in any ad hoc network. The nodes which are selected as a multipoint relay (MPR) by some neighbor nodes announce this information periodically in their control messages. Thereby, a node announces to the network, that it has reachability to the nodes which have selected it as MPR. In route calculation, the MPRs are used to form the route from a given node to any destination in the network. The protocol uses the MPRs to facilitate efficient flooding of control messages in the net- work. OLSR inherits the concept of forwarding and relaying from HIPERLAN (a MAC layer protocol) which is standardized by ETSI.
2.3 Comparison study
This part describes will compare the properties and performance routing technologies ad hoc network: table-driven and on-demand. After comparison, AODV and its most relevant protocol DSR is compared to study the main objective points of AODV performance.
2.3.1 Contrast between table-driven and on-demand protocols
The number of simulations and analyses available between ADOV and DSR. The outputs are depending on different regulations used. The following table shows the aspects between ADODV and DSR.
2.3.2 Comparison of AODV with DSR
The two most popular protocols in On-demand distance vector algorithms are AODV and DSR. These two have same Discovery of Route and Mechanism of Maintenance Route in which routing information is had in all intermediate nodes along the path.
The important contrasts are
i) DSR uses source routing: While in AODV, the source know all path toward the destination while in AODV, source only know the next hop and number of hops toward the destination its routing table
ii) While DSR does not, AODV has to broadcast Hello packets periodically.
iii) While AODV has only one route for each, DSR can cache multiple routes toward from one destination.
AODV starts Route Rediscovery once the link is disconnected, while DSR can find out a new route in the cache, therefore AODV has more overhead for route maintenance. Anyway, DSR has to add on the address of each node in the path to the packet header. This makes bulky packet size, more transmitting overhead and less scalable. While AODV may fail , DSR has no problem with network which has unidirectional links.
2.3.3 Comparison of AODV with OLSR
OLSR as proactive protocol provides bulky control traffic overhead on the network. It consumes bandwidth. OLSR in terms of storage and memory overhead for the reason that maintaining of the routing table for the entire network requires a large amount of communication between the nodes as well as more cargo space than by using the AODV. Routes too for no reason used are maintained.
Latency is the major drawback of AODV reactive protocol. AODV route finding process can take much more time. This hold-up can be a critical issue in a network. In addition, a proactive part of AODV enlarges the control messages capacity and the transmission cost. It also damages the reactive property of the AODV.
The scalability is another drawback of AODV protocol: with expansion of the network the average path length increases, and so does the chance that a link becomes worthless. So the AODV is appropriate only for small and medium size networks, the scalability maximum value is about 1000 nodes.
Therefore the AODV protocol can be used in networks with limited resources: bandwidth, energy, computational power, but with a limited number of nodes, too. AODV is a large amount of adjustable to greatly dynamic topologies as OLSR does.
The above chapter describes general information about ad hoc network and detail about its several routing protocols. The protocols can be classified into two types: table-driven and on-demand.
This thesis shows that on-demand protocols are more suitable for ad hoc network because it can store resource. Comparative study describes the AODV has better performance that other on-demand protocols in high mobility network for heavy load. The next one describes will present about different aspects for improving AODV. The main conclusion of this is that the choice of which protocol to use depends on the properties of the network.