A Proposed Route Selection Method in AODV Routing Protocol for MANET

Transcription

1 A Proposed Route Selection Method in AODV Routing Protocol for MANET Aarti Bairagi, Shweta Yadav Abstract A Mobile Ad Hoc Network (MANET) is a network consisting of a set of mobile hosts capable of communicating with each other without the assistance of base stations. The dynamic topology of a mobile ad hoc network poses a real challenge in the design of a MANET routing protocol. In recent years, a variety of routing protocols have been developed and their performance simulations are made by network researchers. Conventional routing protocols such as AODV, DSR and OLSR use minimum hop count or shortest path as the main metric for path selection. However, networks that require high Quality of Service (QoS) needs to consider several criteria s that could affect the quality of the chosen path in packet forwarding process. An efficient approach is to consider routing algorithm in which best available route is determined in the process of establishing routes. Hence, Performance is an important issue for different protocols. Therefore in this paper we try to propose a new method for route selection based on Ad hoc On-demand Distance Vector (AODV) routing protocol, to improve Qos in ad hoc network. we presented a simple method to choose as route the one having the greatest RSP value. The simulation results demonstrate that, compared with traditional AODV and DSR proposed method significantly reduce end to end delay and achieve high throughput. Index Terms Mobile Ad-Hoc Network, Routing, AODV, DSR, RSP, OPNET. I. INTRODUCTION Mobile Ad-hoc Network (MANET) is a network where autonomous mobile nodes with wireless interfaces construct a temporary wireless network. In mobile ad hoc networks there are no dedicated routers. Each node operates as a router and transmits packets between source and destination. The node within the transmission range of the source node and is not the destination node, accepts the packet sent by the source and forwards it along the route to the destination node [1]. A number of MANET routing protocols have been proposed in the last decade. These protocols can be classified according to the routing strategy that they follow to discover route to the destination. These protocols perform variously depending on type of traffic, number of nodes, rate of mobility etc [2]. Manuscript received May Aarti Bairagi, Department Of Information technology, Mahakal Institute Of Technology Ujjain.Ujjain, India, (aarti_bairagi9@rediffmail.com). Shweta Yadav,Department Of Information technology, Mahakal Institute Of Technology Ujjain, Ujjain, India, (shweta_yad@yahoo.co.in). Over the last 10 years, various MANET routing protocols have been proposed by network researchers and designed primarily to improve the MANET performance with respect to establishing correct and efficient routes between a pair of nodes for packet delivery [3]. Examples of popular MANET routing protocols are: Ad Hoc On-Demand Distance Vector (AODV) [5], and Dynamic Source Routing (DSR) [6]. Limited resources in MANETs made a very challenging problem that is represented in designing of an efficient and reliable routing strategy [4]. Conventional routing protocols such as AODV, DSR and OLSR use minimum hop count or shortest path as the main metric for path selection. However, networks that require high Quality of Service (QoS) needs to consider several criteria s that could affect the quality of the chosen path in packet forwarding process [8]. AODV and DSR are two most widely used protocols for routing in mobile ad-hoc networks, So Performance analysis and comparison of these two reactive protocols done through simulations for QoS support [7, 9]. To provide quality of service in routing protocols, extensions can be added to the messages used during route discovery. These extensions specify the service requirements which must be met by nodes rebroadcasting a Route Request or returning a Route Reply for a destination [10]. A new variant M-AODV based on AODV is proposed to improve QoS in ad hoc network that discovers in a first step, all possible paths between sources and destinations and maintain them during all data transfer phase. In case of a failure of the actual route, the data transfer will use one of the previously established routes (secondary routes) [11]. In this paper, the Ad hoc On-demand Distance Vector (AODV) routing protocol is revised by calculating the corresponding QoS provision values to find the best routes and applying the mechanism of carrier sense in IEEE b to obtain the available bandwidth[12]. To adopt more reliable links in making stable end-to-end routes a simple but effective method is proposed for different sizes of application data packets. It shows that link stability and the consequent route s stability can be considered as a function of application packet length seen from the network layer [13]. In this paper a cross-layer design is proposed which present an improvement to DSR Routing protocol, in which one of the aspects of ad hoc networks which is the bandwidth is used as the aspect of QoS by proposing an algorithm of route selection based on the available bandwidth between each pair of intermediate nodes included in the route, to choose as route the one having the greatest available bandwidth [14]. 48

2 A cross-layer QoS-provision algorithm is proposed that supports multipath routing schemes for video-streaming applications over Ad Hoc networks. This approach allows using the available network resources more efficiently, which is certainly important in this type of networks [15]. Another algorithm using cross layer design is proposed for reliable links. A high throughput routing protocol for Multi-Rate Ad-hoc Networks using lower layer information is proposed, in which a new routing metric named Route Assessment Index is defined. Maximize the proposed Route Assessment Index metric ensures that the selected route has high throughput and reliable links [16]. Therefore in this we try to propose a new method for route selection based on On Demand AODV routing protocol. The rest of this paper is organized as follows. Section I briefly describes the MANET introduction and related work. Section II discusses the most important on-demand routing protocols. Section III defines a proposed method for route selection. Section IV presents performance analysis of proposed method through simulation. Section V represents a conclusion of the paper. II. SOME IMPORTANT ON DEMAND OR REACTIVE PROTOCOLS A. AODV Protocol ROUTING The Ad hoc On Demand Distance Vector (AODV) routing algorithm is a routing protocol designed for ad hoc mobile networks. AODV is a modification of the DSDV algorithm. AODV is capable of both unicast and multicast routing. It is an on demand algorithm, meaning that it builds routes between nodes only as desired by source nodes. It maintains these routes as long as they are needed by the sources. Additionally, AODV forms trees which connect multicast group members. The trees are composed of the group members and the nodes needed to connect the members. AODV uses sequence numbers to ensure the freshness of routes. It is loop-free, self-starting, and scales to large numbers of mobile nodes. AODV builds routes using a route request / route reply query cycle. 1) Route Discovery: When a source node desires a route to a destination for which it does not already have a route, it broadcasts a route request (RREQ) packet the network. Nodes receiving this packet update their information for the source node and set up backwards pointers to the source node in the route tables. In addition to the source node's IP address, current sequence number, and broadcast ID, the RREQ also contains the most recent sequence number for the destination of which the source node is aware. A node receiving the RREQ may send a route reply (RREP) if it is either the destination or if it has a route to the destination with corresponding sequence number greater than or equal to that contained in the RREQ. If this is the case, it unicast a RREP back to the source. Otherwise, it rebroadcasts the RREQ. Nodes keep track of the RREQ's source IP address and broadcast ID. If they receive a RREQ which they have already processed, they discard the RREQ and do not forward it. 2) Route Reply: As the RREP propagates back to the source, nodes set up forward pointers to the destination. Once the source node receives the RREP, it may begin to forward data packets to the destination. If the source later receives a RREP containing a greater sequence number or contains the same sequence number with a smaller hop count, it may update its routing information for that destination and begin using the better route. 3) Route Maintenance: As long as the route remains active, it will continue to be maintained. A route is considered active as long as there are data packets periodically travelling from the source to the destination along that path. Once the source stops sending data packets, the links will time out and eventually be deleted from the intermediate node routing tables. If a link break occurs while the route is active, the node upstream of the break propagates a route error (RERR) message to the source node to inform it of the now unreachable destination(s). After receiving the RERR, if the source node still desires the route, it can reinitiate route discovery. B. DSR Protocol The Dynamic Source Routing protocol (DSR) is a simple and efficient routing protocol designed specifically for use in multi-hop wireless ad hoc networks of mobile nodes. DSR allows the network to be completely self-organizing and self-configuring, without the need for any existing network infrastructure or administration. DSR has been implemented by numerous groups, and deployed on several test beds. Networks using the DSR protocol have been connected to the Internet. DSR can interoperate with Mobile IP, and nodes using Mobile IP and DSR have seamlessly migrated between WLANs, cellular data services, and DSR mobile ad hoc networks. The protocol is composed of the two main mechanisms of "Route Discovery" and "Route Maintenance", which work together to allow nodes to discover and maintain routes to arbitrary destinations in the ad hoc network. 1) Route Discovery: When anode wishes to establish a route, or issues a Route Request to all of its neighbours. Each neighbour rebroadcasts this Request, adding its own address in the header of the packet. 2) Route Maintenance: When the Request is received by the destination or by a node with a route to the destination; a Route Reply is generated and sent back to the sender along with the addresses accumulated in the Request header. The responsibility for assessing the status of a route falls to each node in the route. Each must insure that packets successfully cross the link to the next node. If it doesn t receive an acknowledgement, it reports the error back to the source, and leaves it to the source to establish a new route. While this process could use up a lot of bandwidth, DSR gives each node a route cache for them to use aggressively to reduce the number of control messages sent. If it has a cache entry for any destination request received, it uses the cached copy rather than forward the request. In addition, it promiscuously listens to other control messages for additional routing data to add to the cache. 49

3 DSR has the advantage that no routing tables must be kept to route a given packet, since the entire route is contained in the packet header. The caching of any initiated or overheard routing data can significantly reduce the number of control messages being sent, reducing overhead. Using only triggered updates furthers that same goal. All aspects of the protocol operate entirely on-demand, allowing the routing packet overhead of DSR to scale automatically to only that needed to react to changes in the routes currently in use. The protocol allows multiple routes to any destination and allows each sender to select and control the routes used in routing its packets, for example for use in load balancing or for increased robustness. Other advantages of the DSR protocol include easily guaranteed loop-free routing, support for use in networks containing unidirectional links, use of only "soft state" in routing, and very rapid recovery when routes in the network change. The DSR protocol is designed mainly for mobile ad hoc networks of up to about two hundred nodes, and is designed to work well with even very high rates of mobility. III. PROPOSED METHOD FOR ROUTE SELECTION In simple reactive protocol like AODV and DSR, the route discovery is done by selection of best route on the basis of coordinate distance & some other methods are also proposed but they all are based on fixed rate system. Here we are proposing an enhancement on AODV for multirate multihops system which ensures the best route selection to get minimum delay & also minimum route maintenance. In our proposed method, we are considering the multiple characteristics of nodes & then decide the route according to their scores on the basis of our developed formula explained below. Our proposed method for route selection is based on RSP (route selection parameter) calculation, in which each node calculates the RSP value and uses it as metric for route selection combined with the number of hops. In order to use RSP as a metric for route selection each node in the network has to maintain the value of its RSP in their routing table (or cache).the calculation of value of RSP at each node is given by: RSP = PFR X (1-MOB) X MBW X MNN The definitions of terms used are: 1) PFR (packet forwarding ratio) = Successful forwarded packets/total packets 2) MOB (Mobility index) = Non availability of node/total requirement to node It represents the mobility lesser the stability. Hence it reduces the selection chances of node for route. 3) MBW (Maximum Bandwidth) = Maximum Bandwidth of the node (Because of multirate consideration) 4) MNN (maximum numbers of neighbors) = Maximum number of nodes attached at any node (With maximum bandwidth) In our proposed method the route search is done according to algorithm below: Every time when a node forwards a packet to any other node successfully it must update the value of packet forwarding ratio. Every node must check for the time it can sense the signals from other nodes and use it to update its Mobility value. It is considered that node knows the maximum bandwidth or transmission rate of network. Every node records the ID of other nodes communicates with it as number of neighbors to which it sends the packet. All four metrics PFR, MOB, MBW and MNN are combined to calculate the value of RSP at each node. Therefore each node has an estimated value of its available RSP, which is injected in the header of route discovery request to be used for route selection by the destination. Now, finally for each received route the destination node calculates the complete RSP value, which is given by: K RSP max = 1/K ( PFRi X (1-MOBi) X MBWi X MNNi ) i=1 where, k = total number of nodes in selected route. According to above explanation destination node calculate the RSP for each route and list them in descending order which helps it on selection of another route in case of failure of one route. Hence when a destination node receiving a set of route requests, it chooses as main route the one having the maximum RSP. A. Simulation Setup IV. PERFORMANCE EVALUATION To test the performance or effectiveness of our proposed method we have used as tool the OPNET simulator [15], which is one of the most widely used commercial simulator based on Microsoft windows platform. The purpose of this simulation is to show the effectiveness of the proposed method as compared to original AODV and DSR routing protocols. The 10 mobile nodes are placed randomly within certain gap from each other in 1000m 1000m campus environment. The simulation duration was set to 1000 seconds and the IEEE802.11b MAC protocol is used as it allows data rates up to 11 Mbps. Mobility is assigned randomly. Table I summarizes the most important simulation parameters and other protocol specific parameters are kept default as recommended in [5]. B. Quantitative Metrics The following is a list of quantitative metrics used to assess the performance. Average End-to-end delay: the average delay experienced by all successfully delivered packets. Average Throughput: the sum of the size of the total data packets received by the destinations per unit time. 50

4 Table I Simulation Parameters Parameters Value Simulation area 1000 m x 1000 m Number of nodes 10 nodes Packet size random Packet transmission rate: 5 packets/s Data Rate (bps) 11 Mbps Physical Characteristics Direct Sequence MAC Layer Protocol b Transmitter power Watt Packet Reception Power Threshold -95 Buffer Size (bits) Node mobility 30 (m/s) AP Beacon Interval 0.02 Sec Simulation duration 1000 seconds C. Simulation Results The work attempts to investigate the performance with the effect of different packet size, we consider three different scenarios with Specified distribution name and arguments to be used for generating the size (in bits) of the packets that will be generated. The first one is the normal distribution of packet size with mean=1024bits and variance=512bits.the second one is the log normal distribution of packet size with mean=1024bits and variance=512bits and the third one is the Poisson distribution of packet size with mean=1024 bits. Results obtained after simulation are plotted in the time average graphs. Fig. 1. Average End to End Delay with normal distribution. I. Average End-to-end delay(sec): The graph shows that the proposed method reduces the end to end delay, this is due to the parameter used by proposed method for route selection which is the RSP of each node in the route which gives fast packet forwarding. we can observe in figure 1 and 3 proposed method gives the minimum delay in normal and Poisson distribution respectively compared to AODV and DSR. However, with log normal distribution the efficiency of the proposed method is poor, as delay is increased rapidly after some time. Fig. 2. Average End to End Delay with log normal distribution. 51

5 Fig. 3. Average End to End Delay with Poisson distribution Fig. 5. Average Throughput with log normal distribution. II. Average Throughput (bits/sec): The Figure 4, 5 and 6 shows that the proposed method reduces the packet drop rate almost at the factor of two which shows the increment in throughput of network. We can observe in all three figures that proposed method gives increased throughput in every scenario compared to AODV and DSR. Fig. 6. Average Throughput with Poisson distribution. Fig. 4. Average Throughput with normal distribution. 52

6 V. CONCLUSION The field of ad-hoc mobile networks is rapidly growing and changing and while it is not clear that any particular algorithm or class of algorithm is the best for all environment, each protocol has definite advantages and disadvantages, and is well suited for certain situations. The Efficient routing protocols can provide significant benefits to mobile ad hoc networks, in terms of both performance and reliability. Many routing protocols for such networks have been proposed so far. Amongst the most popular ones are Ad hoc On-demand Distance Vector (AODV) and Dynamic Source Routing Protocol (DSR). Most of the existing MANET routing protocols optimize hop count as building a route selection. But routing in MANET using the shortest path metric is not a sufficient condition to construct high quality paths, because minimum hop count routing often choose routes that have significantly less capacity than the best paths that exist in the network. To provide an optimum MANET routing solution, in this paper we presented a simple method for route selection in which the best available route is based on the maximum RSP value of route. To calculate this parameter packet forwarding ratio (PFR), Maximum Bandwidth (MBW), Mobility (MOB) and Maximum Number of neighbors (MNN) are considered as prime concern. It is proposed here that for each node all the metrics are combined to calculate the value of its RSP. The estimated RSP value of each node contained in the received route discovery requests used as a metric for route selection by destination node. Finally, the route having the maximum RSP value is selected for routing packets from source to destination. The proposed method is compared with the well known AODV and DSR reactive routing protocols in terms of end to end delay and throughput. Results obtained from simulation shows that it gives the minimum delay and maximize value of throughput. In future work we will try to include other aspects of ad hoc networks like security and energy constraints to define a routing protocol tacking into account all the aspects of ad hoc networks. ACKNOWLEDGMENT The authors of this paper would like to acknowledge the help and support from our organization in this work. REFERENCES [1] S. Corson, J. Macker, Mobile Ad hoc Networking (MANET): Routing Protocol Performance Issues and Evaluation Considerations, RFC 2501, January [2] G.Vijaya Kumar, Y.Vasudeva Reddyr, Dr.M.Nagendra, Current Research Work on Routing Protocols for MANET: A Literature Survey, G.Vijaya Kumar et. al. / (IJCSE) International Journal on Computer Science and Engineering Vol. 02,pp , No. 03, [3] Sunil Taneja, Ashwani Kush, A Survey of Routing Protocols in Mobile Ad Hoc Networks, International Journal of Innovation, Management and Technology, Vol. 1, No. 3,( ISSN: ) August [4] Arun Kumar B. R., Lokanatha C. Reddy, Prakash S. 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[16] Cao Trong Hieu, Choong Seon Hong, RAI: A High Throughput Routing Protocol for Multi-hop Multi-rate Ad hoc Networks. [17] OPNET Simulator, Ms.Aarti Bairagi is currently pursuing M.TECH in Information Technology from Mahakal Institute of Technology Ujjain,M.P.,India. She has published many papers in International Journals and Conferences. Her research interests include MANET, Network security and Web security. Mrs.Shweta Yadav is currently working as an Associate. Professor and Head in Department of Information Technology in Mahakal Institute of Technology Ujjain,M.P.,India. She has published many papers in International Journals and Conferences. Her research interests include MANET, Network security and Web security. She had 5 years of Teaching Experience. 53