Ad hoc network

Abstract

A mobile ad hoc network (MANET) is consisting of wireless mobile nodes. The communication of these mobile nodes is carried out without any centralized control. Routing is a critical issue in MANET. The focus of this thesis is on the performance of routing protocols. We compare three routing protocols in MANET i.e. AODV, DSR and OLSR. OPNET is the simulation tool. These routing protocols performance are analyzed by three important metrics: delay, network load and throughput. All the three routing protocols are explained in a deep way with metrics. The comparison analysis will be carrying out about these protocols and in the last the conclusion will be present. That which routing protocol is the best for mobile ad hoc network.

Introduction

MANET stands for Mobile Ad hoc Network. A decentralized autonomous wireless system which consists of free nodes. MANET sometimes called mobile mesh network. MANET is a self configurable wireless network. A MANET consists of mobile nodes, a router with multiple hosts and wireless communication devices. The wireless communication devices are as transmitters, receivers and antennas. These antennas can be of any kind. These nodes can be fixed or mobile. The term node referred to as, which are free to move arbitrarily in every direction. These nodes can be a mobile phone, laptop, personal digital assistance, MP3 player and personal computer. These nodes located, might be in cars, ships, airplanes or with people having small electronic devices [59]. Nodes can connect to each other randomly and forming arbitrary topologies. Nodes communicate to each other and also forward packets to neighbor nodes as a router. The ability of self configuration of these nodes makes them more suitable for urgently required network connection. For example in disaster hit areas where there is no communication infrastructure. It is greatly desired to have a quick communication infrastructure. MANET is the quick remedy for any disaster situation. The word Ad hoc means 'For a special purpose'. So MANET a spontaneous network is useful when dealing with wireless devices in which some of the devices are part of the network only for the duration of a communication session and the need for a dynamic network topology is prominent. The MANET working group (WG) within the Internet Engineering Task Force (IETF) working specifically on developing IP routing protocols topologies. In order to improve mobile routing and interface definition standards for use within the Internet protocol suite [59].

After huge research work on MANET, still MANET does not have complete formed Internet based standards. The identification of experimental Request For Comments (RFCs) since 2003 [1] is used. In these RFCs the questions are unanswered concerning of implementation or deployment of these routing protocols. But these proposed algorithms are identified as a trial technology and there is a high chance that they will develop into a standard [1]. Extensive research work in this area has continued since then with major studies on different routing protocols such as Ad hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR), Temporarily Ordered Routing Algorithm (TORA) and Optimized Link State Routing (OLSR) [1]. Also on the standardization of routing and interface solutions for mobile networking support through Internet Engineering Task Force (IETF) Mobile Ad hoc network (MANET) Working Group WG [59].

Aims and Objectives

There are two groups of routing protocols. Proactive MANET protocol, Reactive MANET Protocol, and the third are derived from both called Hybrid MANET Protocol. The Proactive MANET protocol is generally called table driven protocol. It detects the network layout periodically. It tries to maintain the routing table at every node. From which a route to the destination from the source can be detected with less delay. Proactive MANET protocols provide good reliability and low latency for deciding a route. Proactive MANET protocol is not suitable for the node moving with high speed. The routing information in the routing table cannot be updated in the routing table. If a node is not moving, then its routing table information is updated continuously. It makes much traffic overhead and also waste network resources as bandwidth [21]. Proactive MANET protocol is also not suitable for large scale MANETs.

Whereas Reactive MANET Protocol is called on-demand routing protocol. Reactive MANET Protocol finds the route when a source node requests to communicate with the other. On-demand approach is suitable for the nodes with high mobility. Nodes that transmit data rarely. The main drawback of reactive routing protocols is that the source node broadcasts the routing requests in the whole network. Then it waits for the responses. This route discovery procedure produces significant delay [21].

Hybrid MANET Protocol integrates the merits of Proactive MANET protocol and Reactive MANET Protocol. Zone routing protocol (ZRP) and two zone routing protocols is the example of hybrid of MANET protocol.

Research Question

Our goal in this master thesis is to evaluate the performance of Proactive and Reactive MANET protocols. These protocols have different behaviors for wireless routing aspects. The main problem is to choice the correct and efficient routing protocol for MANET. The main questions arise for the evaluation of these problems.

First question is which routing protocol provides a better performance in Mobile Ad hoc Networks? This will give the overall performance of each routing protocol. Second question is what factors influence the performance of these routing protocols? Finally we address the main key differences in these routing protocols. To answer all these questions, we will model some of MANET scenarios with different parameters. To evaluate the performance of Proactive MANET protocol and Reactive MANET Protocols as, AODV, DSR and OLSR with respect to some parameters as delay, network load and throughput. In simulating these scenarios we come to know that no single routing protocol among Proactive MANET protocol and Reactive MANET Protocol is superior in terms of overall network performance. For example one protocol is good in average delay while other is best in network load and throughput. The performance of these routing protocols greatly depends on network load and delay. So the best protocol can give low delay and high throughput.

Scope of the thesis

As we know the two categories of routing protocols. Reactive, proactive, and the derived one from reactive and proactive protocols are referred to as hybrid routing protocol. The hybrid protocol is a combination of both reactive and proactive routing protocols. In this thesis, we considered three routing protocols. Two of them are reactive protocols i.e. AODV and DSR. One of them is proactive protocol i.e. OLSR. In this thesis we evaluate the behavior of these routing protocols when implemented in the network. We look that how these protocols affect the network performance, and how the routing protocols behave in these networks. There is no need to go in depth the design of these routing protocol algorithms. But we will give a detailed explanation of these routing protocols. That we are able to explain their effects on the network. We did not consider the effects of varying pause time of the mobile nodes in our simulations. These pause time will be kept constant in all the scenarios. Energy consumption of the routing protocol algorithms was also not considered in the thesis.

Thesis structure

The thesis is mainly divided into six chapters. Chapter 1 introduces the topic. In this chapter we discuss the MANET with detail, and also the research question. Chapter 2 presents the background of our work. Types of wireless networks and some part of related work with example. Chapter 3 gives the state of the art. It gives the full theoretical background and concepts of the ad hoc mobile network routing protocols i.e. reactive MANET protocols and proactive MANET protocols. Chapter 4 is about the performance metrics: delay, network load and throughput and also about the simulation tool OPNET Modeler 14.5. Chapter 5 gives the results and an analysis of all the routing protocols simulated. In chapter 6, the conclusion and future work is presented.

Chapter 2 Background and Related Work

In this chapter we present the background of our work. Types of wireless networks and some part of related work with example.

MANET have a dynamic nature, a large number of applications make them ideal to use. Quick deployment and minimal configuration of MANET in emergencies such as natural disaster makes them more suitable. The growth of technology makes increase in Wi-Fi capable laptops, mobile phones, MP3 players and other small portable devices. Hence a reason for MANET popularity.

Extensive research work has been done on the performance evaluation of routing protocols using NS2 network simulator. Different methods and simulation environments give different results for MANET routing protocols performance. We need to look in a broader view for the effects of these routing protocols which are not considered in a specific environment. The theme of this project is to evaluate the performance of Proactive MANET protocols (PMP) and Reactive MANET Protocols (RMP) in OPNET Modeler 14.5 under varying network load [2]. For all these comparisons we will use FTP traffic to look the effects of the ad hoc network protocols. The project goal is to give an extra source of comparison statistics in the research field. In our simulation we have wireless routing protocols carrying FTP traffic. These simulations performed will have a strong link with the theoretical concepts and also with the expected performance in practical implementations. This study work will give a great benefit in the future research work.

Related work

Extensive research works has been done in the field of MANET routing protocols. Different routing protocols were simulated in different kind of simulators. Here we will discuss different research papers on the performance of MANET routing protocols. In this thesis work we simulate three MANET routing protocols in the OPNET modeler 14.5. AODV, DSR and OLSR were simulated against three different parameters i.e. delay, network load and throughput. The results show that OLSR is best in network delay than AODV and DSR. The protocols best in the network delay must be the finest in the network throughput. Below we will study now different simulators with different routing protocols and their performance.

These routing protocols DSDV, AODV, DSR and TORA were simulated using NS2 [3]. Analysis gives different results for every parameter differently. In finding shortest path between the source and destination nodes, delay, DSDV performs well than AODV, DSR and TORA. DSR perform well in network load balancing than DSDV, AODV and TORA. DSDV has good jitter than AODV, TORA and DSR respectively. The results given in [5] analyse DSR and DSDV in idealized and realistic simulation environments on their performance. Another paper in reference [4] gives conclusion in mobile ad hoc network that reactive protocols i.e. AODV and DSR perform well when the network load is moderate. In reference [4] the reactive protocols are saving much resource like energy. It analyse that the proactive protocols perform well in heavy network traffic load.

In [6] there are different conclusions about the MANET routing protocols. DSDV, AODV and DSR were simulated in NS2. The reactive protocol AODV outperforms than DSDV and DSR in maintaining connection by sequentially exchange of information for TCP based traffic. The packets are delivered when the node mobility is low and failed to deliver at high mobility. DSR perform well than DSDV at all mobility. In [6] DSR perform well than DSDV and AODV for packet dropping rate (PDR), delay and throughput. DSR generates less network load than AODV.

In reference [7], the simulation was done in QUALNET simulator. The author wrote that AODV shows best performance in low and medium node density. Where as in high node density both OLSR and DSR outperforms. The author wrote in [7], that DSR is selected for file transfers where delivery and throughput are critical factors. OLSR performs well in both low and high node density. It is stated in [7] that OLSR is best suited in application oriented traffic e.g. streaming traffic, voice and video traffic. In application based traffic delay is a critical factor.

Types of Wireless Networks

Before we discuss the wireless networks types, a small difference between wired and wireless network is discussed. A network that sends data from one point to another point with cable or wire is called wired network. The data sent over a network which uses wireless medium from one device to another device is called wireless network. In wireless network data is transmitted from one point to another through wireless links. For communication the devices have to be in the transmission or radio range of each other. Wireless networks are divided into two main groups. First infrastructure wireless network and second is Ad hoc or infrastructure-less network.

Infrastructure Networks

Fixed network topology is deployed in infrastructure network. These deployed, fixed networks have base stations or access points from which wireless nodes can get connected. All the base stations or access points are connected with the main network through wired links (fiber optic, twisted or coaxial cable) or wireless link. The base station or access point is one of the important units of infrastructure networks. All of the connections will have to pass from the access point. A wireless node can connect to anyone of the access points in its range.

Ad hoc Networks

An Ad hoc network is deployed where wireless network infrastructure is not available. This kind of ad hoc network is called infrastructure less network. In ad hoc network each node is connected through wireless links. These nodes connected to each other and also act as a router, by forwarding data to other nodes. There is no restriction on these nodes to join or leave the network. Thus the network has no vital infrastructure. Ad hoc networks have two forms; one is static ad hoc networks (SANET), the other is called mobile ad hoc network (MANET). Commercial implementation of ad hoc network becomes possible due to the development of new technology such as 802.11 [5].

The main reason to deploy this kind of network is the flexibility and easiness of deployment. A suitable network for emergency and surveillance use. But with all these qualities, ad hoc network operation is very difficult to handle. Each and every node is responsible for its operation to maintain its routing table and also forwarding packets to its neighbors as routers. MANET has different topology changes while deployed. So ad hoc network need an efficient routing protocol. To construct an efficient routing protocol is a tough and tedious task.

Mobile Ad hoc Networks

As mentioned before an ad hoc network is a wireless network, which do not have a centralized and fixed infrastructure. MANET is referred to a wireless ad hoc network. In which nodes are free to move arbitrarily. In a MANET, mobile nodes transmit and receive the traffic. Also mobile nodes can act like routers by forwarding the neighbors traffic to the destination. As the routers are mostly multi hops [60]. MANET does not need base stations of wired infrastructure. The mobile nodes in wireless network range can communicate with each other. MANET is self organized network. The mobile nodes form a network automatically without a fixed infrastructure and central management [60]. The mobile nodes have transmitters and receivers with smart antennas, which enable the mobile nodes to communicate with other mobile nodes in the network. The topology of the network change every time by getting in and out of the mobile nodes in the network. In the beginning MANET was designed for military use but now the MANET is used in many areas. Such as in disaster hit areas, data collection in some region, in rescue missions, virtual classes and conferences [60]. This concept with ad hoc network makes the full name of mobile ad hoc network (MANET). By growing the network, combined with the node mobility. The challenges of self configuration of the network become more evident. Security in the MANET is a very important issue. Many techniques were defined for the security of MANET. Intrusion detection technique is investigated in reference [60]. Mobile nodes in the network waste much energy by joining in and out with connection to wireless network. This connection and reconnection create energy limitation in the network.

The main purpose of developing the ad hoc routing protocols to cope with the dynamic nature of MANET. The routing protocols efficiency can be determined by the battery power consumption. Energy is consumed during participation of a node in a network and also in routing of traffic. The routing protocol which adapts to the connection tearing and mending is also considered vital. Such routing protocols are AODV, DSR and OLSR, TORA, Wireless Routing Protocol (WRP), Zone Routing Protocol, and Two-Zone Routing Protocol (TZRP) [21]. We will discuss reactive and proactive routing protocols i.e. AODV, DSR and OLSR in chapter 3 respectively. The internet engineering task force (IETF) MANET working group (WG) was dedicated to standardize the routing protocols in MANET. RFC 2501 specifies the charter of the working group [8].

An Example of MANET Application

The versatility and self configuration of MANET makes them a best choice for a wide range of applications. MANET can be used in natural disaster areas, pre planed strategic event like surveillance, data collecting in some regions, conferences and virtual classes. In such areas where the fixed infrastructure is not available before. Like earthquake hit areas where the fixed infrastructure has been destroyed, in flooded areas, fire or explosion hit areas, train or air plane crash [21]. A very common use of MANET is during business conferences. The only and key attribute that make MANET ideal is their self configuration and low cost of deployment.

Here we will present one practical example. In a virtual class, a WiMAX radio link may be established. Then a MANET access network can be established to give coverage to those areas that is difficult to cover. The nodes far away from the base station rely on midway nodes for communication. Thus provide a best communication network in such hostile situation. Above in figure 1, a deployed MANET over WiMAX backbone is shown. In this figure the mobile nodes and the WiMAX_WLAN Router form a MANET. These nodes are connected to the WiMAX_WLAN router and the router is further connected to the WiMAX network. The router is working like a boundary between the MANET and the WiMAX. The WiMAX_WLAN router is capable of translation between the MANET protocols and the WiMAX network protocols, and also the backbone protocols the WiMAX is connected with. The figure 1 is shown above.

Chapter 3 Ad hoc Networks Routing Protocols

The theoretical concepts of ad hoc routing protocols are discussed in this chapter. The behaviors of proactive and reactive routing protocols will be analyzed.

Routing

Routing means to choose a path. Routing in MANET means to choose a right and suitable path to the destination from the source. Routing terminology is used in different kinds of networks. In telephony technology, electronic data networks and in the internet network, the term routing is used. Here we are more concern about routing in mobile ad hoc networks. Routing protocols in mobile ad hoc network means that the mobile nodes will search for a route or path to connect to each other and share the data packets. Protocols are the set of rules through which two or more devices (mobile nodes, computers or electronic device) can communicate to each other. In mobile ad hoc networks the routing is mostly done with the help of routing tables. These tables are kept in the memory cache of these mobile nodes. When routing process is going on, it route the data packets in different mechanisms. The first is unicast, in which the source directly sends the data packets to the destination. The second is broadcast; it means the source node sends messages to all the near and far nodes in the network. The third is anycast, in this the source node sends data packet to anyone which is not in the node group.

Routing types

Routing has two basic types, which are as under

  1. Static Routing
  2. Dynamic Routing
  1. Static routing is done by the administrator manually to forward the data packets in the network. Static routing is permanent. No any administrator can change this setting [29]. These static routers are configured by the administrator, which means there is no need to make routing tables by the router.
  2. Dynamic Routing is automatically done by the choice of router. It can route the traffic on any route depend on the routing table. Dynamic routing allows the routers to know about the networks and the interesting thing is to add this information in their routing tables. This is shown in the figure 3.1 below. In dynamic routing the routers exchange the routing information if there is some change in the topology [61]. Exchanging information between these dynamic routers learn to know about the new routes and networks. Dynamic routing is more flexible than static routing. In dynamic routing it have the capability to overcome the overload traffic. Dynamic routing uses different paths to forward the data packets. Dynamic routing is better than static routing.
Routing protocols

There are several kinds of routing protocols for wireless ad hoc networks. These routing protocols are categorized as reactive or proactive routing protocols [8]. The ad hoc routing protocols which have both proactive and reactive merits, is called hybrid routing protocols. The first kind of protocol is proactive or table driven routing protocol. The second kind of protocol is called reactive or on-demand routing protocol. The first kind of protocol is simply called Proactive MANET Protocol (PMP). Proactive routing protocol detects the layout of the network actively. A routing table can be maintained at every node. From which a route can be determined with less delay. The proactive routing protocols provide good reliability on the current network topology [21] and low latency for deciding a route. The OLSR is a proactive routing protocol.

The second kind of protocol is simply called Reactive MANET Protocol (RMP). In these kinds of protocols the communication is only possible when the source node requests to communicate with the other node. Reactive MANET Protocols are mostly suited for nodes with high mobility or nodes that transmit data rarely. There are some reactive routing protocols which we will consider here. These reactive routing protocols include AODV, DSR and TORA.

An ad hoc routing protocol is a standard. That controls the decision of the nodes that which route the nodes have to take to the destination from the source node. When a node wants to join a network, it discovers the topology by announcing its presence, and listening to broadcasts from other nodes in the network. This routing discovery is performed differently according to the routing protocol algorithm implemented in the network.

Proactive Routing Protocols

The routing information about all the nodes is build and maintained by the proactive protocols. The proactive routing protocols are independent of whether or not the route is needed [62]. Control messages are transmitted with periodically intervals. Even if there is no data flow still control messages are transmitted. Because of these control messages proactive routing protocols are not bandwidth efficient. There are many advantages and disadvantages of proactive routing protocols. One of its advantages is that the nodes can easily get routing information, and it easily starts a session. The disadvantages are, too much data kept by the nodes for route maintenance, when there is a particular link failure its reform is too slow.

OLSR (Optimized Link State Routing)

It is a proactive routing protocol in MANET. It is also called as table driven protocol because it permanently stores and updates its routing table. OLSR keeps track of routing table in order to provide a route if needed. OLSR can be implemented in any ad hoc network. Due to its nature OLSR is called as proactive routing protocol. MPR nodes are shown in the given figure 3.2. All nodes in the network do not broadcast the route packets. Just Multipoint Relay (MPR) nodes broadcast route packets. These MPR nodes can be selected in the neighbor of source node. Each node in the network keeps a list of MPR nodes. This MPR selector is obtained from HELLO packets sending between in neighbor nodes. These routes are built before any source node intends to send to a specified destination. Each and every node in the network keeps a routing table. This is the reason the routing overhead for OLSR is minimum than other reactive routing protocols and it provide a shortest route to the destination in the network. There is no need to build the new routes, as the existing in use route does not increase enough routing overhead. It reduces the route discovery delay.

Nodes in the network send HELLO messages to their neighbors. These messages are sent at a predetermined interval in OLSR to determine the link status. Here we can understand this by Figure 3.3. If node A and node B are neighbors, node A sends HELLO message to B node. If B node receives this message, we can say the link is asymmetric. If now B node sends the same HELLO message to A node. This is the same as first case, called asymmetric link. Now if the two way communication is possible then we can call it symmetric link, as shown in Figure 3.3. The HELLO messages contain all the neighbor information. This enables the mobile node to have a table in which it has information about all its multiple hop neighbors. A node chooses minimal number of MPR nodes, when symmetric connections are made. It broadcast TC messages with information about link status at predetermined TC interval [62]. TC messages also calculate the routing tables. In TC messages MPR node information are also included.

Reactive Routing Protocols

Reactive routing protocols are called on-demand routing protocols. These routing protocols are called when they are required. So the routes are built when they are needed. These routes can be acquired by sending route requests through the network. Disadvantage of this algorithm is that it offers high latency in searching a network. We will consider AODV and DSR in this report. But the analysis will be of AODV and DSR in the fifth chapter.

AODV (Ad hoc On-demand Distance Vector)

AODV is an on-demand routing protocol. The AODV algorithm gives an easy way to get change in the link situation. For example if a link fails notifications are sent only to the affected nodes in the network. This notification cancels all the routes through this affected node. It builds unicast routes from source to the destination. The network usage is least. Since the routes are build on demand so the network traffic is minimum. AODV not allowing keeping extra routing which is not in use [63]. Two nodes wish to establish a connection in an ad hoc network. AODV is responsible to enable them to build a multihop route. AODV is loop free. AODV uses Destination Sequence Numbers (DSN) to avoid counting to infinity. This is the characteristic of this algorithm. When a node send request to a destination, it sends its DSNs together with all routing information. It also selects the most favorable route based on the sequence number [11].

There are three AODV messages. One is Route Request (RREQs), Route Replies (RREPs), and Route Errors (RERRs) [1]. By using UDP packets, the sources to destination routes are discovered and maintain by these messages. For example the node which request, will use its IP address as Originator IP address for the message for broadcast. It simply means that the AODV not blindly forwarded every message. The number of hops of routing messages in ad hoc network is determined by Time-To-Live (TTL) in the IP header.

When the source node wants to create a new route to the destination, the requesting node broadcast an RREQ message in the network. In the figure 3.4 the RREQ message is broadcasted from source node A to the destination node B. The RREQ message is shown by the black line from source node A to many directions. The source node A broadcast the RREQ message in the neighbor nodes. When the neighbor nodes receive the RREQ message it creates a reverse route to the source node A. This neighbor node is the next hop to the source node A. The hop count of the RREQ is incremented by one. The neighbor node will check if it has an active route to the destination or not. If it has a route so it will forward a RREP to the source node A. If it does not have an active route to the destination it will broadcast the RREQ message in the network again with an incremented hop count value. The figure 3.4 shows the procedure for finding the destination node B. The RREQ message is flooded in the network in searching for finding the destination node B. The intermediate nodes can reply to the RREQ message only if they have the destination sequence number (DSN) equal to or greater than the number contained in the packet header of RREQ. The intermediate nodes forward the RREQ message to the neighbor nodes and record it in their routing table. The addresses of the neighbor nodes from which it get the RREQ message. This information will be used to make a reverse path for RREP message from the destination node. When the message reach to the destination node. It calculates the shortest path to the source. In the figure 3.4 it is shown. The destination node B replies with RREP message denoted by the dotted orange color line. From node A to node B the shortest path is the lower one shown with dotted line. These nodes routes information were saved in the routing tables and were used to build a reverse route from destination to the source node with the message RREP. The request reach to the destination and then RREP has reached to the originator of the request. This route is only available by unicasting a RREP back to the source. The nodes receiving these messages are cached from originator of the RREQ to all the nodes.

When a link is failed an RERR message is generated. RERR message contains information about nodes that are not reachable. The IP addresses of all the nodes which are as their next hop to the destination.

All the routing information about the network is stored in the table. The routing table have these route entries; (i) destination IP address, (ii) Destination Sequence Number (DSN), (iii) Valid Destination Sequence Number flag (iv) other state and routing flags (e.g., valid, invalid, repairable being repaired) (v) network interface (vi) hop count (number of hops needed to reach destination) (vii) next hop (viii) the list of precursors and lifetime (Expiration time of the route).

DSR (Dynamic Source Routing)

Dynamic Source Routing Protocol is a reactive routing protocol. DSR is on demand routing protocol. It is a source routing protocol. It is a simple and efficient protocol. It can be used in multi hop wireless ad hoc networks [64]. The DSR network is totally self organizing and self configuring. The protocols is just compose of two mechanisms i.e. route discovery and route maintenance.

The DSR regularly updates its route cache for the sake of new available easy routes. If some new available routes were found the node will directs the packet to that route. The packet has to know about the route direction. So the information about the route was set in the packet to reach its destination from its sender. This information was kept in the packet to avoid periodic findings. DSR has the capability to find out its route by this way. DSR has two basic mechanisms for its operation i.e. route discovery and route maintenance. In route discovery, it has two messages i.e. route request (RREQ) and route reply (RREP). When a node wish to send a message to a specific destination. It broadcast the RREQ packet in the network. The neighbor nodes in the broadcast range receive this RREQ packet and add their own address and again rebroadcast it in the network. This RREQ packet if reached to the destination, so that is the route or if not reached to the destination then the node which received the RREQ packet will look that previously a route used for the specific destination.

Each node maintains its route cache which is kept in the memory for the discovered route by that node. That node will check its route cache for the desired destination before rebroasting the RREQ packet. By maintaining the route cache at every node in the network, it reduces the memory overhead which is generated by the route discovery procedure. If a route is found in that node cache then it will not rebroadcast the RREQ in the whole network. So it will forward the RREQ message to the destination node. The first packet reached to the destination has full information about the route. That node will send a RREP packet to the sender having complete route information. This route is considered the shortest path taken by the RREQ packet. The source node now has complete information about the route in its route cache and can starts routing of packet. Figure 3.5 shows the route discovery procedure. Here are four nodes i.e. A, B, C and D. Node A is the source and node D is destination. When node A wish to send a data packet to the node D. It will first check its route cache that whether it has direct route to node D or not. If node A does not have a direct route to node D. Then it will broadcast a RREQ message in the network. The neighbor node B will get the RREQ message. First node B will check its route cache that whether it have a direct route to the destination node D or not. If it find a route to the destination node D. So it will send a RREP message to the source node A. In the reply of that message the source node A will start sending the data packets (DP) on the discovered route. If it didn't discover the route from node B to node D so it forwards the message RREQ to the next node C and store the route AB in the cache. The process is going on until the RREQ message reached to its destination D. The destination node D caches the routes AB, BC and CD in its memory and sends a RREP message to the source node A.

The next mechanism is the route maintenance. The route maintenance uses two kind of messages i.e. route error (RERR) and acknowledgement (ACK). The messages successfully received by the destination nodes send an acknowledgement ACK to the sender. Such as the packets transmitted successfully to the next neighbors nodes gets ACK. If there is some problem in the communication network. A route error message denoted by RERR is transmitted to the sender. That there is some problem in the transmission. In other words the source didn't get the ACK packet due to some problem. So the source gets the RERR packet in order to re initiate a new route discovery. By receiving the RERR message the nodes remove the route entries. In figure 3.6 four nodes are shown i.e. A, B, C and D. The node A sends a message to destination node D. The message goes on up to the node C, while receiving the ACK message up to node B. When the node C forward the RREQ message to the node D and it does not receive the ACK message from node D. The node C recognizes that there is some problem in the transmission. So the node C sends a RRER message to the source node A. Which in return search for a new route to the destination node D.

Chapter 4 Performance Evaluation of Proactive and Reactive Protocols

In this chapter we present different metrics considered in the performance evaluation of proactive and reactive routing protocols. First we will briefly discuss the performance parameters considered in the comparisons. The simulation design will also be discussed.

Performance Parameters

There are different kinds of parameters for the performance evaluation of the routing protocols. These have different behavior of the overall network performance. We will evaluate three parameters for the comparison of our study on the overall network performance. These parameters are delay, network load, and throughput for protocols evaluation. These parameters are important in the consideration of evaluation of the routing protocols in a communication network. These protocols need to be checked against certain parameters for their performance. To check a protocol effectives in finding a route towards destination, we will look to the source that how much control messages it sends. It gives the routing protocol internal algorithm's efficiency. If the routing protocol gives much end to end delay so probably this routing protocol is not efficient as compare to the protocol which gives low end to end delay. Similarly a routing protocol carrying high network traffic consuming low network resources is called efficient routing protocol. The same is the case with the throughput. Throughput shows successful deliveries of packets in time. If a protocol shows high throughput so it is the efficient protocol than the routing protocol which have low throughput. These parameters have great influence in the selection of an efficient routing protocol in any communication network.

Delay

The packet end-to-end delay is the time of generation of a packet by the source up to the destination reception. So this is the time that a packet takes to go across the network. This time is expressed in seconds. So all the delays in the network called as packet end-to-end delay, like buffer queues and transmission time. Sometimes this delay can be called as latency. It has the same meaning as delay. There are many applications which require different kinds of packet delay in the sense that they give delay. Some applications are sensitive to packet delay. The voice is a delay sensitive application. So the voice requires a low average delay in the network. The FTP is tolerant to a certain level of delays. There are different kinds of activities because of which network delay is increase. Packet end-to-end delay is a measure of how sound a routing protocol adapts to the various constraints in the network to give reliability in the routing protocol. We have several kinds of delays which are processing delay (PD), queuing delay (QD), transmission delay (TD) and propagation delay (PD). The queuing delay (QD) is not included as the network delay has no concern with it [54]. Mathematically it can be shown as.

Network Load

Network load represents the total load in bits/sec submitted to wireless LAN layers by all higher layers in all WLAN nodes of the network [65]. When there is more traffic coming on the network, and it is difficult for the network to handle all this traffic. So it is called the network load. The efficient network can easily cope with large traffic coming in, and to make a best network many techniques have been introduced. Network load is shown in the figure below 4.1.

Throughput

Throughput is defined as; the ratio of the total data reaches a receiver from the sender. The time it takes by the receiver to receive the last message is called as throughput [15]. Throughput is expressed as bytes or bit per second (byte/sec or bit/sec). Some factors affect the throughput as; if there are many topology changes in the network, unreliable communication between nodes, limited bandwidth available and limited energy [15]. A high throughput is absolute choice in every network. Throughput can be represented mathematically as;

Throughput=Number of delivered packet * Packet size * 8 total duration of simulation

Software Environment

We are using the Optimized Network Engineering Tool (OPNET v14.5) software for our simulations. OPNET is a network simulator. It provides multiple solutions for managing networks and applications e.g. network operation, planning, research and development (R&D), network engineering and performance management. OPNET 14.5 is designed for modeling communication devices, technologies, protocols and to simulate the performance of these technologies.

OPNET Technologies provides solutions for the academic research, for example assessment and improvement of wireless network technologies such as WiMAX (Worldwide Interoperability for Microwave Access), Wi-Fi and UMTS (Universal Mobile Telecommunications System). Design and assessment of MANET protocols, analysis of optical network, and enhancement in the core network technologies such as IPv6, MPLS, and power management schemes in wireless sensor network [2]. Now a day OPNET is very useful software in research fields. The OPNET usability can be divided in four main steps. The OPNET first step is the modeling, it means to create network model. The second step is to choose and select statistics. Third step is to simulate the network. Fourth and last step is to view and analyse results. All these steps are shown in the below figure 4.2.

Building Model

Run the OPNET modeler 14.5 to make a network model. The first step is to create a blank scenario by start-up wizard. The project editor workspace will be opened. Now we will design the network in this work space. The network design is done through two methods, one is automatically and the other is manually. The first method is automatically generating different topologies using rapid configuration. The second method is by dragging different kind of objects from the object palette to the project editor workspace. A user can also import some predefined scenarios from the hard drive. But however wireless network cannot be designed by importing scenarios [16]. When the network is designed then the nodes need to be configured. This configuration can also be performed manually or by using pre-defined parameters in the workspace.

Simulation results and Statistics

In OPNET there are two kinds of statistics, one is Object statistics and the other is Global statistics. Object statistics can be defined as the statistics that can be collected from the individual nodes. On the other hand Global statistics can be collected from the entire network. When someone chosen the desired statistics then run the simulation to record the statistics. These collected results are viewed and analyzed. To view the results right click in the project editor workspace and choose view results or click on DES, results then view results. Then a browser pops up as shown in this figure 4.3.

Simulation environment

The master thesis simulation is carried out in the OPNET Modeler 14. Below in figure 4.4, showing simulation environment of one scenario having 20 nodes for OLSR routing protocol. The key parameters are provided here i.e. delay, network load and throughput. We run three scenarios. In every scenario there are different numbers of mobile nodes. In first scenario we have 20 mobile nodes. In second we have 40 mobile nodes and third we have 80 mobile nodes.

We simulated three scenarios. Each scenario was run for 240 seconds (simulation time). All the simulations show the required results. Under each simulation we check the behavior of AODV, DSR and OLSR. We got multiple graphs for our analysis of simulations. First we got for delay. The second is for the network load. The third is for the throughput. Main goal of our simulation was to model the behavior of the routing protocols. We collected DES (global discrete event statistics) on each protocol and WLAN. We examined average statistics of the delay, network load and throughput for the MANET. A campus network was modeled within an area of 1000m x 1000m. The mobile nodes were spread within the area. We take the FTP traffic to analyse the effects on routing protocols. We configured the profile with FTP application. The nodes were wireless LAN mobile nodes with date rate of 11Mbps.

Random waypoint mobility model was used in this simulation. The mobility model used is simple and it show more good mobility behavior [17]. Mobile nodes move at a constant speed of 100 m/s, and when reaches the destination, the pause time is 200 seconds and after that it choose a new random destination.

Chapter 5 Analysing Results

We will analyse and discuss the results of simulations we done. We begin the analysis of AODV, DSR and OLSR. We check these protocols by three parameters as delay, network load, and throughput. These parameters and simulations environment have been discussed before. The results obtained in the form of graphs, all the graphs are displayed as average. We used three scenarios i.e. 20 nodes, 40 nodes and the last one is 80 nodes. All these scenarios were discussed against three protocols.

Simulation of First scenario

Here in first scenario we used 20 mobile nodes. There is one fixed wlan server. The network size is of 1000 x 1000 meters. After that IPv4 addressing was assigned to all the nodes. The application configuration and profile configuration was drag to workspace. All the settings must be done according to the requirement. The FTP was selected as traffic High Load. Now deploy the configured profile by clicking Protocol tab and select Deploy Defined Application. Drag the Mobility Config to the workspace. Set all the attributes and in last random mobility was set to MANET as a profile. The first scenario figure 5.1 is shown below. The three protocols such as AODV, DSR and OLSR are tested against three parameters i.e. delay, network load and throughput.

Simulation of Second Scenario

The second scenario is consisting of 40 mobile nodes. All the attributes remain the same except the number of nodes were increased. By clicking the scenario and then new scenario, give an appropriate name. In this second scenario the same protocols are tested against the same parameters. The second scenario figure 5.2 is as shown below.

Simulation of third Scenario

In third scenario the numbers of nodes are 80. The same procedure was followed by making this third scenario. By clicking the scenario then new scenario and giving an appropriate name. All the steps remains the same just the number of nodes are increased. The reason of increasing the mobile nodes is that we can have a profound look on the performance of routing protocols. The scenario figure 5.3 is shown as below.

Analysing simulation

The three scenarios were made in the OPNET Modeler 14.5. We run the simulation for four minutes and save the graphs for analysis and calculation. These graphs were found very helpful in the statistical analysis of these routing protocols performance. The graphs were saved in the bitmap for the statistical analysis. The result graphs of delay, network laod and throughput were saved in bitmap images. These figures will be discussed in the next coming section. Here the DES execution manager window for the simulation is shown below.

AODV performance

The first scenario simulated and it gives the required result shown in the figure 5.5 below. In this scenario 20 mobile nodes were simulated. The Ad hoc On Demand Vector protocol was checked by three parameters such as delay, network load and throughput. The graphs are shown in the time average form. Here in the given graph the upper window shows delay. Delay is represented by second. The x-axis denotes time in minutes and y-axis in seconds. The upper figure shows the average peak delay at 0.022 sec. This value gradually drops to 0.001 sec and attains a constant value of 0.0008 sec. This value remains constant after some minutes. The middle graph shows the network load for AODV for 20 mobile nodes. In this graph the x-axis represents time in minutes and the y-axis represents data rate in bits/sec. The network load peak value is 2475666 bits/sec. After this value the graph gradually drops to a constant value but with slight changes at value 75375 bit/seconds. At 237 seconds the last value of network load is 64012 bits/sec. The last graph is for throughput of AODV protocol. The x-axis represents time in minutes and the y-axis data rates in bits/sec. The peak value of throughput is 2633360 bits/sec. This throughput is gradually drops to 280087 bits/sec after one minute. The throughput keeps changing and the last value of throughput is 145070 bits/seconds.

DSR Performance

The below image gives the DSR required results. The results are shown in the below figure 5.6. The same number of mobile nodes i.e. 20 and one wlan fixed server was used as before. Dynamic Source Routing protocol was checked by three parameters as delay, network load and throughput. In the given figure 5.6 the small upper window shows the network delay. The peak value of delay is 0.0238 seconds. A sudden drop in the graph value is at 4.8 seconds which is 0.0160 seconds. From here a slight changes come in the graph value and remain constant at 189 seconds is 0.0059 seconds.

In the given figure 5.6 the middle graph shows the network load. The peak value of network load is 1707800 bits/sec. Network load is gradually drops to 79782 bits/sec and the last value at 237 seconds is 67615 bits/sec. The simulation time of our thesis is 4 minutes. The third graph in the same given figure 5.6 is for throughput. The peak value of throughput is 1950226 bits/sec. Throughput values gradually drops to 169464 bits/sec and remains constant at 79949 bits/sec. The last value of throughput after 4 minutes is 69086 bits/sec. Our simulation time is 4 minutes.

OLSR performance

The below given image shows Optimized Link State Routing protocol for the three parameters as Delay, Network Load and Throughput. The number of mobile nodes was still kept as 20 and one wlan fixed server. In the given figure 5.7, the first upper graph shows the network delay. The fist peak delay is at 0.0108 sec. After some time the delay graph drops to a value of 0.0010 sec. The last value of delay from the given figure 5.7 is 0.0006 sec. By comparing this value with the two routing protocols, it was found that the OLSR delay is very low. OLSR is giving less delay as compared to AODV and DSR.

The network load is shown by the middle graph in the given figure 5.7. The first peak value of network load is 1311993 bits/sec. The network load value gradually drops to 107690 bits/ seconds. The last value of network load is 75953 bits/sec. The last graph in the given figure 5.7 is for the throughput of OLSR 20 nodes. The peak value of the throughput in OLSR is 1485440 bits/sec. This value is taken from the graph shown below. This value gradually drops to 329617 bits/sec. The last value of throughput is 291522 bits/sec.

Analyses of Increased Nodes i.e. 40

In the second scenario the numbers of mobile nodes were increased from 20 to 40 and 80 mobile nodes. AODV, DSR and OLSR will be checked against three parameters such as delay, network load and throughput. The reason of increasing mobile nodes was to check the behavior of these routing protocols in the large Ad hoc mobile network. The routing protocols will be simulated in the same environment of OPNET Modeler 14.5.

AODV Performance

The performance of AODV will be checked in the increased number of mobile nodes. The number of mobile nodes will be 40. The AODV will be checked against the three parameters i.e. delay, network load and throughput. In the given figure 5.8, the upper graph shows the delay of AODV 40 nodes. The difference in the graph can be seen clearly. When the numbers of mobile nodes were increased the delay of AODV is increased. The peak value of AODV delay is 0.0337 sec. This AODV delay value is taken from the graph. The delay is gradually decreased up to 0.0031 sec. The last AODV delay value is 0.0027 sec.

The middle graph in the given figure 5.8 is of AODV network load. The difference in the AODV network load can be seen from the given figure 5.8 as compared to 20 mobile nodes. The peak AODV network load value is 3061760 bits/sec. The AODV network load value is gradually decreased to a value of 166977 bits/sec. The last value of AODV network load is 113623 bits/sec. The AODV throughput is also clear from the given figure 5.8. The peak throughput value is 3539966 bits/sec. That is last graph of the figure 5.8.

DSR Performance

The performance of DSR will be checked by increasing the number of mobile nodes while the wlan fixed server will be one. The numbers of mobile nodes are 40. The DSR will be checked against three parameters such as delay, network load and throughput. The given figure 5.9 shows the graph for the DSR delay, network load and throughput. The first upper part of the graph shows the DSR delay. From the figure 5.9, the difference in DSR delay can be seen clearly. In the above figure 5.6 when the numbers of mobile nodes were 20 the DSR delay were low as 0.0238 seconds, and here the DSR delay is increased as 0.0647 sec. The difference in DSR delay is clear when the numbers of mobile nodes were 20 and when the numbers of mobile nodes were 40. This increase in delay is because of when the data was passing from more mobile nodes to its destination, the delay will be introduced.

In the same figure 5.9 the middle graph shows the DSR network load. The DSR network load is also increased in the increased 40 number of mobile nodes. The peak value of DSR network delay in 20 mobile nodes were 1707800 bits/sec which is shown in the above figure 5.6, and the peak value of DSR network load when the number of mobile nodes were 40, is 3099920 bits/sec. The difference in the peak DSR network load of both scenarios can be seen clearly. The network load in 40 mobile nodes is high than 20 mobile nodes. The DSR throughput can be seen also from the same figure 5.9. The peak DSR value of throughput when the numbers of mobile nodes were 40 is 4519960 bits/sec. When network delay will be low so the network throughput will be high.

OLSR Performance

The OLSR routing protocol can be checked when the numbers of mobile nodes were 40 and the wlan fixed server is one. The graph is given in the figure 5.10 below. The upper part of the figure 5.10 shows the delay. The middle part of the figure shows network load and the third part shows the OLSR throughput. The OLSR delay has very minor changes when the numbers of nodes were 20 and the numbers of nodes were 40. In the 20 mobile nodes the OLSR peak delay value is 0.0108 sec and the 40 mobile nodes OLSR peak delay value is 0.0138 sec. There are very slight changes in the OLSR delay after 4 minutes.

The middle part of the given figure 5.10 shows the OLSR network load. The peak value of OLSR network load when the numbers of mobile nodes are 40 is 2032246 bits/sec. By comparing this value with the OLSR network load when the numbers of mobile nodes were 20 is 1311993 bits/sec. This change is because of the increased numbers of mobile nodes as the data has to pass from the more mobile nodes to their destination. So because of increased number of mobile nodes the network load is increased. The last graph in the given figure 5.10 is for OLSR throughput. The peak value of OLSR throughput is 3033646 bits/sec when the numbers of mobile nodes were 40. The OLSR throughput peak value when the numbers of mobile nodes were 20 is 1485440 bits/sec. The difference can be seen from the graph as well.

Analysis of increased Nodes i.e. 80

In this scenario we increased the number of mobile nodes from 40 mobile nodes to 80 mobile nodes. It means we doubled the number of mobile nodes. To check the behavior of these routing protocols that when the number of mobile nodes were increased so how they react to different parameter such as delay, network load and throughput. Here the behavior of these routing protocols can be checked against the same parameters just increasing the number of mobile nodes.

AODV Performance

In the given figure 5.11, the first upper part of the graph shows the AODV delay when the numbers of mobile nodes were 80. The middle graph shows the AODV network load and the last part shows the AODV throughput. The AODV delay peak value when the numbers of mobile were 80 is 0.1137 sec. The AODV delay peak value when the numbers of mobile nodes were 20 and 40 is 0.0223 sec and 0.0337 sec respectively. The difference can be seen clearly from the given peak values. The AODV delay value for 80 mobile nodes is high as compared to 20 and 40 mobile nodes. The AODV delay gradually decreases and reached to a value of 0.0046 sec after 4 minutes. The reason of increasing the delay is that when the numbers of mobile nodes are increased then the data which is needed to deliver to the specific destination. So the data have to pass from many mobile nodes which cause more delay.

The middle graph in the given figure 5.11 shows the AODV network load. The peak value of the AODV network load is 3252066 bits/sec. The peak values of AODV network load when the numbers of nodes were 20 and 40 i.e. 2475666 bits/seconds and 3061760 bits/sec respectively. The third graph in the given figure 5.11 is of AODV throughput. The peak value of AODV throughput when the numbers of mobile nodes were 80 is 7760206 bits/seconds. These values are taken from the graph which is given in the figure 5.11 below. The peak value of the AODV throughput when the numbers of mobile nodes were 20 and 40 are 2633360 bits/sec and 3630800 bits/sec respectively. The difference can be seen from the given peak values when the number of mobile nodes were 20, 40 and 80. The last value of AODV throughput after 4 minute is 2376336 bits/sec.

DSR Performance

In the given figure 5.12 the DSR protocol will be checked against three parameters such as delay, network load and throughput. The changes in the graph can be seen clearly from the figure 5.12. The DSR shows its peak delay value at 0.0153 sec. The network load is 2779086 bits/sec. The DSR throughput can be seen from the given figure 5.12, which is 12888146 bits/sec. The simulation time is 4 minutes.

OLSR Performance

In the given figure 5.13 the OLSR protocols is simulated. The first part of the figure 5.13 shows the OLSR delay. The second middle part shows the OLSR network load and the third and last part shows the OLSR throughput. The OLSR delay peak value is 0.0153 sec. The graph gradually decreased to a value 0.0020 sec. The last OLSR delay value is 0.0010 sec. The OLSR delay values when the mobile nodes were 20 and 40 were 0.0108 sec and 0.0138 sec respectively. The difference is clear from the given values. These values were taken from the graph, which is given in the figure 5.13. The OLSR network load peak value is 2783173 bits/sec. The OLSR throughput peak value is 11023736 bits/sec.

Analysing overall scenarios

Till now the analysis of these routing protocols were done separately. Now the discussion will be thoroughly to have these all on a single platform. The first discussion will be on AODV routing protocol. The second will be on DSR and the third will be on OLSR routing protocol. The results will be discussed by using one routing protocol and all scenarios.

Analysing AODV by all scenarios

AODV protocol was simulated in all the three scenarios using all the three parameters such as delay, network load and throughput. The three parameters can be checked in all the 20, 40 and 80 mobile nodes. From the given results in figure 5.14, it can be seen that the AODV delay shows almost the same behavior with a small fluctuations in all the three scenarios, while the AODV network load and throughput shows different results. The AODV network load is low in 20 and 40 mobile nodes. The graph shows the AODV network load which is 3,252,066 bits/sec for 80 mobile nodes. The AODV throughput results can be seen from the graph. The AODV throughput of the 80 mobile nodes is much high i.e. 4655800 bits/sec.

Conclusion and Future work

Our thesis report is mainly consists of two studies, one is analytical study and the other is simulation study. From analytical study we concluded that routing protocols in new modern arena of telecommunication, internet systems and in seamless communication play prominent role to develop better communication between end users. Different routing protocols have different attributes according to their environmental scenarios. The selection of suitable protocol according to the network definitely increases the credibility of that network, for example in case of mobile ad hoc networks routing protocols should be loop free according to our research. Categorically it has been analyzed that there are two categories of routing protocols used in mobile ad hoc networks that are reactive routing protocols and proactive routing protocols, both categories have their own usage, so the selection of these categories in ad-hoc networks is very important.

The simulation study of our thesis consisted of three routing protocols AODV, DSR and OLSR deployed over MANET using FTP traffic analyzing their behavior with respect to three parameters, delay, network load and throughput. Our motive was to check the performance of these three routing protocols in MANET in the above mentioned parameters.

From the entire above figures 5.17, 5.18 and 5.19 the behaviors of all the routing protocols in different numbers of mobile nodes, it can be seen that which routing protocol perform well. From the above analysis of routing protocols, the OLSR outperforms the two AODV and DSR protocols in terms of delay, network load and throughput in 20 mobile nodes. In 40 mobile nodes again the OLSR perform well than AODV and DSR in delay and throughput. While the AODV is putting low load than OLSR and DSR respectively. In 80 mobile nodes OLSR is again showing good results in delay and throughput than AODV and DSR respectively. While AODV offer good results in offering low load on the network than OLSR and DSR respectively. The average values are taken from the graphs. From the above given graphs it is shown clearly that the OLSR gives the outstanding results in delay and throughput and the AODV performs well in the network load. By comparing AODV and DSR the results in the entire figures it can be seen that AODV perform well than DSR in delay, network load and throughput. Average values are shown in the above table 5.1.

The study of these routing protocols shows that the OLSR is better in MANET according to our simulation results but it is not necessary that OLSR performs always better in all the networks, its performance may vary by varying the network. At the end we came to the point from our simulation and analytical study that performance of the routing protocols vary with network and selection of accurate routing protocols according to the network ultimately influence the efficiency of that network in magnificent way. From our research and study we propose to overcome the disadvantages of routing protocols such as some routing protocols are centralized, some protocols are not loop free, so there should be research in a very vast way to create the coherence between network and routing protocols.

Another aspect of our thesis work about future work is that these routing protocols can be simulated for the performance of mobile wimax.

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