Architecture of EHARP Routing Protocols in Ad Hoc Wireless Networks

Transcription

1 2009 International Conference on Intelligent Networking and Collaborative Systems Architecture of EHARP Routing Protocols in Ad Hoc Wireless Networks Saud Al otaibi Software Technology Research Laboratory De Montfort University Leicester, UK Francois Siewe Software Technology Research Laboratory De Montfort University Leicester, UK Abstract Ad hoc wireless networks consist of a number of nodes roaming freely, interconnecting with each other by wireless connection without relying on a predefined infrastructure. When comparing ad hoc wireless networks with fixed networks or infrastructure wireless networks, ad hoc wireless networks base on the nodes that work as host and as router. In this paper, we present a new routing protocol for an ad hoc wireless network which is called Enhanced Heading direction Angle Routing Protocol (EHARP). It base on counter of the stability of link (SL) and acknowledge message to provide stability and availability of the network along select route path. Keywords-component: Ad hoc wireless network, HARP, EHARP I. INTRODUCTION An ad hoc wireless network is shaped by a collection of nodes which can communicate with one another by wireless links without a fixed infrastructure, such as base stations or towers [4]. Each node can connect to its neighbouring nodes only, because of limited radio broadcast coverage. When any two nodes are not in the same radio coverage area, communication between them requires a multiple-hop radio connection, relying on other intermediate nodes to link them. These nodes have a mobility facility which enables them to join and leave the network as required. Many protocols have been proposed for mobile ad hoc networks, with the aim of achieving efficient routing [2, 11-17]. These protocols differ in the approach used for searching for a new route and/or modifying a known route when hosts move. In designing routing protocols for ad hoc networks, it is essential to maintain the flow of control packets between communicating nodes as well as establishing new links. However, the flow of control packets should be kept to a minimum. This is because increasing the number of control broadcast packets by flooding is very costly and results in serious problems. Such as generating excessive redundant control message overhead, contention and collision. The latter is due triggering a huge number of packet forwarding that ultimately results in the breakdown of the entire network [12]. Flooding is adopted by many routing protocols, such as Ad hoc On-demand Distance Vector (AODV) [7] and Dynamic Source Routing (DSR) [13] protocols /09 $ IEEE DOI /INCOS

2 These conventional routing protocols used in ad hoc networks flood a route request packet to construct a route. The Heading direction Angle Routing Protocol (HARP) [9], it is based on an on-demand routing scheme. It reduce the control overhead and flooding in the network, and Increased the life of the route in comparison with other routing protocols, such as Ad hoc On-demand Distance Vector (AODV). The main disadvantage of HARP is that the protocol sends the RREQ to the nearest neighbour, whether this node is active or not and irrespective of whether it has a problem. The main problem which might occur is an increase in the number of dropped packets, which would affect the performance of the network. Our contribution is we proposed protocol: Enhanced Heading-direction Angle Routing Protocol (EHARP). As its name suggests, it is an enhancement of HARP [9] and is based on an on-demand routing scheme. We have added important features to overcome its disadvantages and improve its performance, providing the stability and availability required to guarantee the selection of the best path [9].This paper is organized as follows: Section II describes the related work; Section III explains the headingdirection angle routing protocol (HARP); in Section IV, we propose our approach for a new routing protocol (EHARP); Section V presents suggestions for future work and concludes the paper. II. RELATED WORK In an ad hoc wireless network, each node works as a host as well as a router and will propagate packets for other nodes in the network which are not within direct wireless broadcast range of one another. Every node participates in the network administration and routing scheme, owing to the constantly changing network topology. According to routing protocols, each node can discover multiplehop paths through the network to any other node. These can generally be classified according to the routing information update mechanism into three categories: proactive, on-demand and hybrid. Proactive protocols, also known as table-driven protocols, require every node to maintain one or more tables in order to store the network topology and routing information. This information is updated frequently by periodically exchanging routing information, which must thus be updated periodically for example Destination Sequenced Distance-Vector (DSDV) [6]. By contrast, reactive protocols establish necessary routes when required (on demand) by using a route discovery process and source, so unlike proactive routing protocols they do not maintain information on the network topology and routes to each destination of the network for example Ad hoc On-demand Distance Vector (AODV) [7]. Hybrid protocols combine features of reactive and proactive protocols in order to offer routing solutions. They operate by adapting to the specific conditions and are in general the most advantageous option for example Zone Routing Protocol (ZRP) [18]. III. HEADING-DIRECTION ANGLE ROUTING PROTOCOL (HARP) The core of the proposed schemes is the Heading-Direction Angle Routing Protocol (HARP) [49], so called because it utilizes the direction of information of nodes in the network. Heading direction information can be obtained from the node s own instruments and sensors, such as a compass, which delivers the heading direction angle (HDA) of the mobile device relative to magnetic north. This protocol is used to reduce routing overheads and to increase the lifetime of links between communication nodes. It has been assumed that every node can exchange its information frequently with its neighbours. In HARP, every node classifies its neighbouring nodes into eight different zones according to the heading direction of those neighbours. In theory, the nodes are categorised within at least one of the eight zone ranges, regardless of their location. This protocol is based on an on-demand routing technique. The route request (RREQ) packet is transmitted from a source node (ND) to one of the neighbouring nodes (NB) that has an angular heading direction similar or near to the HDA of NB. This protocol reduces overheads and minimises bandwidth usage, since not all neighbouring nodes need to reply to a RREQ. Its main advantage is that it increases the lifetime of links between nodes in the network. The main disadvantage is that the protocol sends the RREQ to the nearest neighbour, whether this node is active or not and irrespective of whether it has a problem. The main problem which might occur is an increase in the number of dropped packets, which would affect the performance of the network. Another disadvantage is that the source node may receive an error message; it will then resend the requested packet without taking into account whether it knows the nature of problem in this path or which node has a problem. A third drawback is that when the source sends a RREQ it will wait for a reply for time Td and if it receives no 203

3 reply in this time it will wait for the error message; thus the source will wait for time 2Td. IV. ENHANCED HEADING DIRECTION ANGLE ROUTING PROTOCOL (EHARP) This section explains the operation of the proposed protocol: Enhanced Heading-direction Angle Routing Protocol (EHARP). As its name suggests, it is an enhancement of HARP [16] and is based on an on-demand routing scheme. We have added important features to overcome its disadvantages and improve its performance, providing the stability and availability required to guarantee the selection of the best path. Each node in the network is able to classify its neighbouring nodes according to their heading directions into four different zone-direction groups (z1, z2, z3, z4). The zone direction is reduced until the node can select the strongest the stability of link and so increase availability in the network. Each node in the network has a counter for the stability of link (SL) to its neighbouring nodes. The SL counter will indicate which nodes are active in the network and this will improve the performance of the network and increase the likelihood of selecting the best or optimal path. The SL counter will have an initial value of zero and this will be increased by 1 after every successful sending or receiving and reduced by 1 after every failure in sending or receiving. The strongest of SL is based on the greatest value in the counter. This protocol is based on the time and acknowledgement message in order to guarantee the selection of the path and link stability. The source node should resend the RREQ whenever the time elapses before receiving the error message, in order to make use of the full lifetime of the links. Each node will send an acknowledgement message after receiving an RREQ and forwarding it, so the acknowledgement message should provide information on which nodes have problems or could not forward the RREQ. seen in Figure 1, according to their heading directions, each mobile node in the ad hoc network divides the heading directions into different sectors. The heading directions between 0 and 90 comprise zone-direction 1 (z1); those between 90 and 180 comprise zone-direction 2 (z2); and so on until 360. Figure 1. The four basic heading directions ranges and neighbours classified in these ranges After the source node S has classified its cache table, as shown in Figure 1, and wants to send a request packet to its neighbour, S then selects that neighbour. This selection depends on two factors; the first being that it has an angular heading direction of one of the four axis angular values (0, 90, 180, and 270 ) ±δ, where δ is an angular value that represents the range of angles that are considered near to the axis. The second factor is the value of the stability of link of its neighbours. A. EHARP Architecture In EHARP, every mobile node in the network classifies its neighbouring nodes into four different zone-direction groups (z1, z2, z3, z4). As can be 204

4 memory of the source node S, there are two possibilities: ) If S does not find a neighbour in its cache table, 2) If the only neighbour has a negative LS value Source Destination Figure 2. Propagating a route request from the source node S to the destination node D. B. Route Request process at the source node If a source node S wants to send requests to a destination node D, it will first look in its cache table for the destination node. When this is found as a neighbour in its cache table, S will start forwarding the data packets to D Then it will apply an increment of ±δ around the heading angle of S, to extend the search for another neighbour in a new direction. The source node will again trigger a route request: When it does not find a neighbour in the time Td (S will repeat the route request for a limited number of times, to avoid the searchto-infinity), and every time it will increment an angle value ±δ around the heading angle of the source node S. If it does not receive a route reply (RREP) from the destination node D in the time Td. If it receives a route reply (RREP) from the destination node D before the time Td is finished. If the source node S finds a neighbour in its cache (in case more than one neighbour is found, the greatest value of stability of link (SL) will be selected. If a destination node is not found in the source node cache table, then S will set up a time Td required to discover D. S then searches its cache table for a neighbour that has a reference or near reference angle, matching or close to the heading direction angle of S (in order to extend the lifetime of the route). If it finds more than one neighbour it will select the one which has the greatest value of stability of link. The best matching neighbour with a nearly similar heading direction to the node itself and with the greatest value of SL will be chosen (see Figure 2). This protocol performs well in a network where nodes form groups and where the members of each group move together in one direction, such as military units or vehicles on a road. Here, after searching for a neighbour in the cache C. Route Request process at intermediate nodes All the nodes that receive a route request message will update their route cache table by updating the information of the neighbouring node which sent the message. Only intermediate nodes to which the message is broadcast will accept the received route request message; other nodes will silently discard it. The intermediate node to which the message is broadcast will search in its cache table of neighbours for D, then: If the intermediate node is found, D in the cache table will be updated in the LRR list by adding the record containing the information about the node itself, then it will broadcast a reply message along the nodes that have records in their LRR backtracked to the initiating source node. If the intermediate node does not find D in 205

5 the cache table, axis mapping will apply, increasing the heading angle of S by ±δ to extend the search for another neighbour in a new direction. Before forwarding the route request message, the intermediate node will add a record to the LRR containing information about the node itself. It will then set up a time Tn, where Tn is the determined time required to discover its neighbour. After the intermediate node forwards the route request message, an acknowledgement message will be sent to S. Each intermediate node received again triggers an RREQ, which will be checked in the cache memory to see whether it has received an acknowledgement message from its nearest neighbour. This will be propagated to the same neighbour. If it has not received an acknowledgement message from its nearest neighbour, then an increment of ±δ will be applied around the heading angle of S to extend the search for another neighbour in a new direction. V. CONCLUSION AND FUTURE WORK In this paper, we have proposed improvements to the head-direction angle routing protocol, which is the protocol for ad hoc networks. Our approach depends on the stability of links and acknowledgment messages to select the best and most robust path. The main functionality of the routing protocol is to select the optimal path between source and destination; thus our approach should satisfy this function. The performance of the routing protocol will be improved by the stability of nodes and the use of acknowledgment messages in our approach. Our proposed methodology makes use of the longest-lived link between any communicating nodes; therefore, each node should resend the RREQ whenever the time ends before receiving an error message. We plan in future to Design a routing protocol simulator using Network Simulator-2 (NS-2). Analyse simulated results of our protocol taking into account the time delay, packet drop, the success rate of delivering router requests and overheads. D. Route Reply Process Study the performance of the network. Route reply messages can be triggered in two cases: 1) If D receives a route request packet, it will piggyback the LRR in the reply message and send the message along the reversed path in the network, which is determined by the nodes recorded in the LRR. 2) If an intermediate node has received a route request message and has information about D stored in its cache table (a valid path to the destination), then the intermediate node will update the LRR by adding its information. It will also piggyback the LRR in the reply message, then send the message along the reversed path in the network which is determined by the nodes recorded in the LRR. REFERENCES [1] C. Siva Ram Murthy and B.S. Manoj, Ad Hoc Wireless Networks: Architectures and Protocols, Communications Engineering and Emerging Technologies Series, Upper Saddle River: Prentice Hall, [2] C.-K. Toh, Ad Hoc Mobile Wireless Networks: Protocols and Systems, New Jersey: Prentice-Hall, [3] C. Siva Ram Murthy and B.S. Manoj, Ad Hoc Wireless Networks: Architectures, ISBN X, [4] C.-K. Toh, Maximum battery life routing to support ubiquitous mobile computing in wireless ad hoc networks, Communications Magazine, IEEE, Volume 39, Issue 6, June 2001, pp [5] G. Holland, N. Vaidya, Impact of routing and link layers on TCP performance in mobile ad hoc networks, in Wireless Communications and Networking Conference, IEEE, Sept. 1999, pp [6] C. E. Perkins, T. J. Watson, Highly dynamic destination sequenced distance vector routing (DSDV) for mobile computers, in: ACM SIGCOMM 94 Conference on Communications Architectures, London, UK, [7] C. E. Perkins, E. M. Belding-Royer, S. R. Das, Ad hoc On- Demand Distance Vector (AODV) Routing, (Internet-draft), in: Mobile Ad-hoc Network (MANET) Working Group, IETF, 17 February

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