Bidirectional search routing protocol for mobile ad hoc networks


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Bidirectional search routing protocol for mobile ad hoc networks

  1. 1. INTERNATIONALComputer EngineeringCOMPUTER ENGINEERING International Journal of JOURNAL OF and Technology (IJCET), ISSN 0976- 6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME & TECHNOLOGY (IJCET)ISSN 0976 – 6367(Print)ISSN 0976 – 6375(Online)Volume 4, Issue 1, January- February (2013), pp. 229-243 IJCET© IAEME: Impact Factor (2012): 3.9580 (Calculated by GISI) © BIDIRECTIONAL SEARCH ROUTING PROTOCOL FOR MOBILE AD HOC NETWORKS M. Ahmed, S. Yousef, and Sattar J Aboud Telecommunications Engineering Research Group (TERG) Faculty of Science and Technology Anglia Ruskin University, UK ABSTRACT Ad hoc Network is self-configurable, infrastructure-less multi-hop wireless networks, characterized by their frequent topology changes and the need for dynamic routing protocols capable of coping with these characteristics. A new reactive ad hoc routing protocol is proposed in this paper, which relies on the Artificial Intelligence Bidirectional Search Algorithm in discovering routes from source to destination of communication process in a balanced and mutual search mechanism. This allows both source and destination to simultaneously discover the routes to each other reducing the discovery time of reactive routing strategy up to 53% in small and medium scale networks, while this value starts to decrease by increasing the size of the network. The new Bidirectional Search Routing protocol then is compared to both Dynamic Source Routing and Ad-hoc On-Demand Distance Vector Routing in terms of performance metrics of reactive routing strategy such route discovery time and average delay showing promising results. Keywords: Routing, Communication system routing, Protocols, MANET. I. INTRODUCTION Unlike infrastructure-oriented wireless networks, wherein the wireless devices internetwork through relying on fixed network infrastructure to bypass, process or route data packets across the wireless network. Mobile Ad hoc Networks (MANETs) are multi-hop and self-organized infrastructure-less wireless networks. This means that each network node should act as both host and router at the same time traversing data packets across the network. One of the major challenges facing the designers of MANETs is the routing dilemma. Recently, developing a dynamic routing protocol that can cope with the dynamic nature of MANETs and simplifies the finding of feasible routes between the communicating 229
  2. 2. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEMEnodes is the goal behind the extensive research in this field. Such protocol should be able tohandle the shifting characteristics of MANET such as scalability and mobility. Many routingprotocols have been designed and categorized into different categories mainly according totheir working mechanisms [1]. Each of these categories provides partial solutions to one ormore MANET problems. For instance, reactive routing protocols [2] help in minimizing thebandwidth consumption through their idle behavior until a data packet is needed to betransmitted over the network, and then the protocol starts its route discovery process on-demand to find a route to the data packet’s destination. This process which can cause delaybefore starting data transmission is solved in proactive routing strategy [3] where the networknodes keep up to date view of the network topology through exchanging routing informationperiodically, which is mostly considered as bandwidth consumer. Most of the enhancementson routing strategies are carried out as either expansions of the existing mechanisms orchanging of the protocol’s parameters to adapt in new working environments. The goal ofthis article is to propose a core-level improvement on the reactive routing strategy, inparticular on the DSR [4]. The Bidirectional Search Routing protocol (BSR) is introduced inthis article. Namely, it relies on using the bidirectional search algorithm in discovering routesthrough initiating two simultaneous route discovery processes from both source anddestination nodes that meet in most cases somewhere in the middle of the distance betweenthese nodes. The bidirectional search’s computational complexity is low compared tounidirectional search algorithm [5] which makes the former the best candidate to be a partialsolution to the initialization delay in reactive routing strategy. In order to utilize this searchmechanism in MANET routing process, a new approach is proposed to trigger the destinationand inform it to start the backward discovery at the same time of initiating the forward one.This approach theoretically guarantees big reduction in route discovery time compared toother reactive routing protocols which decreases an end-to-end delay. The theoretical modeland working mechanism of BSR are introduced. Then the protocol is compared to both DSRand AODV [6] in terms of performance metrics of reactive routing strategy such as routediscovery time and average delay, while it is compared to the Optimizer Link-State Routing(OLSR) as a proactive protocol, in addition to the DSR and Zone Routing Protocol (ZRP) asa hybrid routing protocol in terms of throughput utilization. The rest of the article isorganized as follows. In the following section, the time and space (Scalability of thealgorithm) computational complexity of bidirectional search algorithm is briefly discussed,followed by implicit delay factors in DSR. The BSR algorithm is described, and results ofperformance comparisons to both DSR and AODV are shown. Finally, conclusions are drawnpinpointing the new features of BSR protocol and its ability to outperform other routingprotocols from the same routing strategy.II. TIME AND SPACE COMPUTATIONAL COMPLEXITY OF BIDIRECTIONALSEARCH ALGORITHM The main idea behind bidirectional search is to simultaneously search both forwardfrom the initial state (i.e. Source) towards goal and backward from the goal (i.e. Destination)towards initial state and stop when the two searches meet in – or close to - the middle. Forproblems where the branching factor (which is the number of children of each node) is b inboth directions, bidirectional search can make a big difference. Assuming that there is asolution of depth d, and then the solution will be found in O(2b d / 2 ) = O(b d / 2 ) steps, because 230
  3. 3. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEMEthe forward and backward searches each have to go only half way. For example: let b = 10and d = 8, breadth-first search[7] spawns O(b d ) nodes , and accordingly, the maximumnumber of nodes expanded before finding the solution can be given as a result of: 1+b1 + b2 + b3 +... + bd = 111,111,111 nodes. Whereas bidirectional search succeedswhen each direction is at depth 4 giving the result 2 × (1+ b1 + b2+ ... + bd/2), atwhich point 22,222 nodes have been produced. 120000 Maximuma number of 100000 80000 branches 60000 (O(b^d 40000 ((2O(b^(d/ 20000 0 1 2 3 4 5 6 7 8 Depth of search Figure 1 Computational Complexity of Unidirectional Search vs. Bidirectional Search.III. IMPLICIT CACHE MANAGEMENT AND ROUTE RECORDINGDELAYS IN DSR The source routing protocols (such as DSR) experience initialization delaycaused by the time the source node has to wait until it receives a reply fromdestination -or any intermediate node holding an up to date route to destination-confirming that an available route to destination is found. In addition to the delayadded before starting data communications in reactive routing protocols, particularlyin source routing ones, some additional delay values are neglected in most of therelated research works due to the slight effect of these values compared to overall end-to-end delay (i.e. Request-Reply cycle time). 1. Cache Management Delay (Time-to-Read TTR and Time-to-Check TTC) Caching schemes have only been applied to DSR [8]. There are three maincharacteristics of the caching scheme to cope with time aspects of caching: readpolicy, write policy, and delete policy. These policies add extra little time duringrequest-reply cycle. Request-reply cycle time of DSR using cache is compared to thediscovery time of DSR with disabling the cache scheme. This has been done bybuilding 2 simulation scenarios containing 50 MANET nodes and running DSRprotocol, once with cache enabled, and another disabled. One may argue that thecache is proposed to decrease the request-reply time if routes to destination exist in thecache rather than increasing it. However, in the first simulation scenario, the cache is 231
  4. 4. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEMEpartially enabled, i.e. reading entries and checking for cached routes are enabled,while using cached routes to initiate Route Replies (RREP) is disabled. As a result,time reduction through using cache is put out of action. A timer is set to 0 when anode starts destination’s discovery and stopped when the node receives a reply fromdestination. While in the second scenario, route caching is disabled and the requestsare propagated directly towards the destination without any cache managementprocesses. 2. Route Recording Delay (Time-to-Record TTR) In DSR, when the destination node receives a Route Request (RREQ), itinitiates a RREP back to the source node the intermediate nodes will record routeinformation included in the traversed packet overhead. Simulation has been performedin order to validate this theory by building two network scenarios. First scenario is a50 MANET nodes network running DSR protocol, and with cache enabled for allnodes. Conversely, similar to time calculation of round-trip, the second scenario is asimple Flood-Reply network in which the source node broadcast beacons to allnetwork nodes requesting a reply from a certain node (a same destination in a firstscenario). Any intermediate node role is only to check if it is the desired destination ornot by comparing its IP address with the one indexing the destination tag of thetraversed packet. Neither route recording, nor cache management are involved in theFlood-Reply mechanism.IV. THEORETICAL MODEL OF BSR 1. Originating and Processing Propagating Triggers Similar to DSR, when a MANET node originates an application packet to besent over the network to a destination, the former have to check its own cache foravailable routes to destination and it will use them if there are any. Otherwise it willbroadcast the Propagating Triggers (PT). The PTs are simple beacons that containonly addresses of source, final target, and broadcast address ( inaddition to Time-To-live (TTL) value to prevent the PTs from travelling infinitelyacross the network. That is, In order to engage the destination of communicationprocess into the route discovery formula for a balanced bidirectional search, thedestination must be informed in one way or another to start searching backwards.Specifically, on the way to achieve a mutual search mechanism, the source anddestination nodes have to find a route over which they have to meet and startcommunication. Therefore, if no route to destination is found in the route cache, the source mustbroadcast PTs to all over the network. These PT packets are propagated across thenetwork hop-by-hop checking the intermediate node’s address if it is equal to theDestination Address value stored in the header of the PT packet, as a result Figure (2)shows the possible procedures processing the PT afterwards. The PTs have somecharacteristics to prevent flooding and to ensure fast network coverage, such as: 232
  5. 5. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME1) The PTs packet option has 4 fields to be filled prior to broadcast, Source Node Address, Final Destination Address, Broadcast Address (, and TTL.2) The PTs do not record route, nor do they modify or get modified while travelling across the network except the fact that their TTL decreases by propagating through the network. As a result, no implicit factors can delay the PTs other than the time required to check a traversed nodes on a Boolean manner.3) TTL is statically set for PTs as a constant value, this is vital since the absence of TTL for PTs might cause the PT packets to travel infinitely across the network. The same node that initiated the PT should wait certain amount of time known as Forward Route Request (FRREQ) Jitter before starting the forward route discovery process, this delay value is optimally chosen according to the network size, mobility and in a way that assures the BSR in its worst performance to show as no more delay than in the case of DSR (section V explains the way the jitter is optimally set). 2. Originating and Processing FRREQ After sending the PT packets by the source node to trigger the destination’sRRREQ, the former has to wait for FRREQ Jitter which – at most - should be lessthan half the time needed for average source-destination discovery time - beforebroadcasting FRREQ en route for the destination. The choice of this waiting timevalue ensures that even if it was exactly equal to half of the average source-destinationdiscovery time, the overall discovery time of BSR is guaranteed to be equal to thediscovery time of DSR. The optimal value of FRREQ Jitter according to MANET sizeis described later in this paper. FRREQ has some characteristics that can distinguish itfrom both PTs and Reverse Route Requests (RRREQ):1) In the BSR protocol the non-propagating requests which are used in DSR are not employed, although sometimes this could be inexpensive way to get routes to destination IF the destination is within the direct neighbors of the source, however this cannot always be guaranteed in dynamic networks like MANETs. Therefore, the BSR uses only propagating FRREQ for any kind of destination (direct neighbors or not), and builds-up the source route in the FRREQ while traversing across the MANET. Thus it is one-step process for the FRREQ.2) The FRREQ traverse is delayed each time it passes through an intermediate node due to the explicit and implicit delay factors mentioned earlier. This will help us to differentiate between the time needed for FRREQ and PT to travel across the network between a certain source and destination. Thus it will help in validating the BSR theory.3) The BSR’s FRREQ option is encoded in Type-Length- Value (TLV) format.4) A timer is associated with the transmission process of the propagating FRREQ after which the source node has to retransmit a FRREQ if it did not receive a RREP from either the destination node or any other BSR’s supportive node in a mechanism that will be discussed later in this article. 233
  6. 6. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME Originating Application Generate Wait for FRREQ tter Propagating A B Generate Forward PT Route Request No FRREQ Addresse s Yes Retransmit Address Yes Discard Initiate of S? RRREQ,Destroy PT No Done RRREQ Route in Cache? C Yes No Address Discard of D? Yes Reached No No D? No Done Yes Reached S? Initiate Yes Node is RP? Yes Change Status Invert Source No Pop out the to RP Route and Destination Append Start Data Address + Comm. Proceed to the next hop Done Start Data Done S: Source node D: Destination node Figure.2 Working Flowchart 234
  7. 7. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME 3. Originating and Processing RRREQ As described earlier, in the case of matching the addresses of the receiving node withthe target node in the PT header, the receiving node will instantly use the PT originator’saddress as a target address, and its address as a source address to start backward routediscovery towards the original source of communication. The main task of RRREQ is not only to search for the source node, but also to createmeeting points (Named as Rendezvous Points or RP) where at the FRREQ and the RRREQmay connect. Explicitly, when a node receives a PT informing it to start reverse discovery,the node proceeds as follows:1) It first checks the addresses field in the PT header and copy the addresses to be: --The Target Address in the received PT becomes Source Address. --The Source Address in the received PT becomes Target Address. --The destination address stays as it is, i.e. the broadcast address ( After processing the addresses field, it instantaneously originates reverse discovery packets with RRREQ option, this option is identical to the one used for FRREQ except that in the RRREQ, the Target Address is the Source Address in the FRREQ, while the Source Address in the RRREQ is the Target Address in the RREQ.3) The RRREQ packets start traversing across the MANET searching for its target (The source of the RREQ and PT). On their way: They build up the Destination Route (Similar to Source Route in the FRREQ). In otherwords, the traversed nodes starting from the initiator of the RRREQ until the current node arebeing added to the destination route in order to be used whenever both the FRREQ and theRRREQ meet. The addition mechanism is important for RRREQ as the destination routeshould be built up using a stack, the reason behind using stacks is the push and pop order.That is, instead of reversing the destination route when the FRREQ meets the RRREQ, thedestination route gets popped out so that the last traversed node using RRREQ (the lastpushed entry) becomes the first in the route to destination just after the Rendezvous Point. As a result, this mechanism will omit the time needed for inversion of the route incase if First-In-First-Out (FIFO) is used like the case of source route. Change the status ofeach traversed node from Normal node to RP. Any intermediate node that receives a RRREQchanges its own attribute to become a RP which expands the destination territory towards thesource. More details about the characteristics of the RP will be discussed in the next sub-section. If the RRREQ found the source node while the FRREQ still searching, the sourcenode will use the destination route contained within the RRREQ header to start datacommunication. Finally, the destination node in this case will be ready to originate RREP even though ithas initiated RRREQ. The reason behind this is to guarantee as exact as DSR’s discoverytime in cases where the coverage of the RP took place on another direction rather than thesource’s direction. Apart from the similarities between processing a packet containing a FRREQ option andanother containing RRREQ option, the latter generally differs in the way it processes thereceiving node since the receiving node’s attributes get modified the moment it receives aRRREQ packet, although the checking mechanism for the target node (The source of theFRREQ) is identical. 235
  8. 8. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEMETherefore,1) If the address of the receiving node is listed in the RRREQ route then discard the packet to prevent infinite loops. Processing a packet with self address means that the receiving node has processed this packet previously.2) If the address of the receiving node matches the address of the source node (The Target according to the RRREQ) contained in the routing header, this means that the RRREQ has reached the source node directly providing a destination route which – by popping out if the stack – can be used by the source node to send application packets through.3) Otherwise, the status of receiving node will be changed to be a RP and holding the –to the point – destination route to be ready whenever it gets contacted by a FRREQ. After that the RRREQ proceeds to the next hop repeating the same procedure. 4. Rendezvous Points The RP is a normal intermediate MANET node which has been passed trough by apacket containing RRREQ option. Namely, if a RRREQ passes through a MANET node onits way towards destination it checks the status of the intermediate node, if it is a RP node, itwill leave it unchanged, and otherwise it will change the status to RP. Accordingly, during itsTTL, if the RP was found by the FRREQ the RP will initiate a RREP back to the source nodecarrying the inverted destination route. This is considered as the core of time reductionmechanism of BSR. Instead of reaching the destination itself to initiate a RREP, it could behalf the distance when reaching an intermediate RP, thus approximately half the time. On the other hand, the other possibility is to initiate a RREP is from any RP thatcontains the route to the Final Target. In this case, the addresses from the RP to the Sourcenode in addition to the Addresses from the RP to the Destination form the whole route fromsource to destination. That is,(Address [Target], Address [Target-1]... Address [RP]) + (Address [RP-1], Address [RP-2]... Address [Source])V. OPTIMAL FRREQ JITTER There are different situations wherein the timing of initiating the FRREQ afterbroadcasting the PTs plays an effective role in reducing discovery time between a source andits destination and also in the scalability of MANETs. Although these delay values –in smallto medium scale network with 5 m/s mobility speed for example – may vary between 0.01and 0.3 milliseconds respectively, therefore, choosing the right delay value for a certainnetwork size and mobility model is an important issue that guarantees the best performanceof the BSR. In addition to that, the wrong choice of the delay value will show how theprotocol would collapse to the DSR if the delay value was set around 0.01 or 0.3 millisecondsin the same example. In order to investigate the way through which the delay should be set,simulations have been performed on the 3 possibilities below through choosing 3 timeintervals for the FRREQ Jitter statically: in the first case (the immediate FRREQ initiating),the delay is set to uniform distribution between 0 and 0.01 milliseconds. The second casewhere the bounds of the uniform distribution are between 3-4 milliseconds is considered thelate FRREQ originating. Lastly, according to that, the bounds of the distribution are set to bebetween 0.01 and 3 milliseconds for optimal delay value for medium size networks as a casestudy of the investigation. 236
  9. 9. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME 1. Immediate FRREQ Initiating The smallest the FRREQ Jitter, the closer to destination the connecting RP will be.That is, if the delay values between initiating the PT and the FRREQ are statically set assmall as 0-0.01 milliseconds in a medium size MANET (200 nodes) with a 5 m/s speed ofmobile nodes, the FRREQ will be directly following the PT towards the destinationshortening the path the RRREQ should use to create a balanced bidirectional search. In thiscase, the delay times are very similar to the case of source routing because in most cases, theRRREQ does not spread enough to form a bidirectional search while the FRREQ is thedominator in the search process, the result is that the BSR will collapse to DSR in its workingmechanism. 2. Late FRREQ Initiating In this case, the source node waits more time before originating the FRREQ whichcauses the PT to arrive to the destination and initiates the RRREQ before the FRREQ leavesthe source node. This makes the rendezvous points to spread further than the previous case,and since the RRREQ does not use route cache as in the case of FRREQ, the destination nodehas to do route discovery towards the source which takes more time than FRREQ cycle dueto the time added for the PT to arrive to destination, and thus more delay than in the previouscase. In this case, the BSR will collapse to DSR with more delay added for the process ofinitiating the RRREQ. 3. Optimal FRREQ Jitter Considering the scale of the network and the mobility of its nodes as key factors indetermining the delay value that must be set as waiting time between originating the PTs andthen the FRREQ, the effect of this waiting time has been investigated. The simulation runsshow that the bidirectional mechanism is optimized when the value of the FRREQ Jitter isbetween 0.01 and 3 milliseconds for a medium size network with a 5 m/s speed of networknodes, therefore, this attribute’s default value for BSR is set to uniform distribution of lowerbound of value 0.01 milliseconds, and upper of value 3 milliseconds. Figure 3: Shows the effect of FRREQ Jitter on the scalability of MANETs through therelation between the FRREQ Jitter and the average End-to-End Delay while varying thenetwork density, increasing the mobile nodes’ pause time, and using relatively fixed numberof traffic sources for each scenario. The number of traffic sources started as 5 sources per 50nodes in the first scenario, then 10 in the second, 15 for the third and finally 20 traffic sourcesper 200 MANET nodes in the forth scenario. The percentage will be always 10% of thenetwork size to keep a relatively fixed number of sources for all scenarios. It is obvious fromthe example that increasing the number of nodes within a medium scale MANET is lesseffective when the FRREQ Jitter is 0.01-3 milliseconds as the increasing percentage of theaverage value of all the end-to-end delay values from the 50 nodes MANET case to the 200nodes case is 272.8%, while it is 523.3% for the immediate FRREQ initiating, and 579.8%for the late FRREQ initiating. This makes the uniform distribution of 0.01-3 milliseconds theoptimal value of the FRREQ Jitter for BSR in in the above example. 237
  10. 10. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME January ary Figure 3: Delay Increasing Percentage for different network sizes Setting the FRREQ jitter statically will result either collapsing the BSR to become asource routing protocol if the jitter is below a certain threshold, or collapsing to destinationrouting protocol if the jitter is above a certain threshold. In order to avoid setting the jittervalue statically, self-configurable jitter setting is used. In [10], the way through which the configurableZone Routing Protocol (ZRP) sets its own attributes dynamically relying on the networkenvironment was used. Similarly, we have utilized this successful method in setting theFRREQ jitter dynamically, by measuring certain attributes such as network size and mobility ,model, the more the network size, the longer the FRREQ jitter and vice versa. The followingsimulation scenarios concluded the relation between the network size and the FRREQ jitter in thethe form of: FRREQ Jitter = 1/m x (Network Size / C), (where C is constant).m is the mobility represented by the speed of nodes in the network, and varying form 0.1-20 , 0.1m/s. The mobility plays a vital role in determining how long the delay should be for thereason that the faster the nodes move in the network, the shorter the delay should be and viceversa.VI. PERFORMANCE COMPARISON 1. Simulation Model Optimized Network Engineering Tool (OPNET) has been used in designing and (OPNET)testing BSR, in addition to performing all the experiments and comparisons in this paper.Constant Bit Rate (CBR) traffic sources have been used for all the simulation scenarios with512-byte data packets and 3 packets/second packet rate. For mobility scenarios, Random Way cketsPoint (RWP) mobility model is used with different specifications in each experiment such asvarying ground speed of nodes and changing the pause time of moving nodes. This meansthat the nodes travel at the speed on which the nodes were configured to travel, and then twhen they reach their destinations, they stop for pause time. After the pause times the nodesstart to travel again towards a random destination and on the same ground speed and so on. A speedrectangular field with 2000m x 500m configuration is used and the number of nodes in fixednetwork sizes is 100 nodes, while this number varies in the networks where altering thenumber of network nodes is part of the experiment. 238
  11. 11. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME 2. Observations Key performance metrics of BSR protocol are examined through a set of simulation runsin different scenarios and different MANET environments. Some of the performance metricswhich have been evaluated are scalability, adaptability to mobility and traffic intensity, andcomparability to other routing protocols.2.1 Discovery Time for Different Size Networks Generally, the time to discover a route to a specific destination is the time when a routerequest was sent out to discover a route to that destination until the time a RREP is received witha route to that destination. This term is only used by reactive routing protocols as they shoulddiscover the available routes to destinations on demand. Theoretically, the BSR aims to reducethe discovery time in reactive routing strategies up to 50%-60% of the time consumed in otherprotocols such as DSR and AODV. This can be achieved by distributing the route discovery loadon the source and destination simultaneously instead of relying on the source only to find its routeto the destination as in the case of DSR. On the other hand, 4 network scenarios have beendesigned to examine the BSR algorithm’s ability in reducing the discovery time compared bothDSR and AODV in different size MANETs and 8% CBR traffic sources of the overall number ofnodes. Figure 4-A. Average Route Discovery Time for Different MANET sizes As the traffic starts to flow (i.e. after 100 simulation seconds) the protocols – according to the reactive strategy – start to discover the routes to destinations to which the application packets should be transmitted. The BSR shows promising performance in the chosen network intensities and close to what it is supposed to be theoretically. Figure 4-A describes the low discovery time of BSR compared to both DSR and AODV where average discovery time of BSR reaches 53.3% of the DSR’s over 700 seconds of simulation time. This is due to the bidirectional mechanism which guarantees a simultaneous route discovery from both source towards destination and vice versa. Additionally, the reasons that prevent the BSR of achieving exactly half of DSR’s discovery times are because of the time needed to initiate and traverse the PTs, and the FRREQ Jitter which at its maximum must not exceed 10 milliseconds as described later in this article. As the network intensity all the values of discovery time shift up which is logical because the RREQs need to travel further and discover more nodes. In the case of BSR, its discovery time similarly increases as the number of nodes increases where the discovery time in the case of 100 nodes network is 60.1% of it for DSR. The discovery time value keeps linearly increasing as we increase the number of nodes in the network for all protocols including BSR as shown in Figure. 6-A therefore the BSR’s discovery time value reaches 72.4% of it for DSR in the case of 150 nodes, and finally 65.5% in the case of 200 nodes MANET. 239
  12. 12. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME2.2 Average End-to-End Delay for Different Mobility Patterns The MANETs are known by their dynamic and stochastic nature that is caused bythe mobility of nodes under unexpected conditions and to uncertain destinations inaddition to their limited wireless coverage. These factors affect the overall performanceof MANET in a way that makes it difficult for routing protocols – the reactive ones inparticular - to handle the basic control overhead needed for reactive routing managementin addition to the overhead needed to maintain the routes in high mobility scenarios. Thisexperiment is to examine the stability of BSR in different mobility scenarios, compared toDSR only as the AODV reacts to link breakage by initiating new RREQ since itoriginally has at most one route per destination in its routing table, therefore it is affectedby mobility more than DSR which tends to check its cache for routes in case of linkbreakage instead of initiating RREQs which makes DSR more stable than AODV in mostof the mobility scenarios. In this experiment two factors are used to determine thestability of the protocols which are the speed of moving nodes and the pause times. Thesefactors can take different values to control the mobility of nodes as the more the pausetime value and the lower speed of nodes’ value the lower the mobility of nodes is. Fourscenarios of 100 nodes are designed to measure the average delay of BSR and DSR withrespect to increasing the nodes speed every time, and in each time the pause time will bevaried from 0 (constant mobility) to 750 simulation seconds (low mobility). Figure 4-B Average delay for different mobility patterns At low ground speed (0.1-5 m/s), the DSR and BSR perform very similarly withmaximum average delay of around 0.99 seconds when the traffic sources start to flow,then it decreases slightly with increasing the pause time with a gap of 5.8% between theaverage delay values of DSR and BSR in favor of the latter. This gap starts to increasewhile increasing the ground speed of nodes to become 13.6% in the case of 8 m/s groundspeed, then it becomes 14.6% in the case of 12 m/s, and finally it gets smaller to 11.2% inthe case of 16 m/s ground speed. This means that the average delay of both protocolsincreases almost equally by increasing the mobility of nodes as shown in Figure.4-B.However, the increasing ratio of the average delay of BSR in the 16 m/s case to it in the 4m/s case is 160% while this value in the case of DSR is 170% which means that the DSRis more to get affected by mobility changes than BSR. 240
  13. 13. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEMEVII. CONCLUSION Motivated by the accelerated research and development of MANET routingprotocols and inspired by DSR. A new reactive MANET protocol has been proposedwhich utilizes the AI’s bidirectional search algorithm to reduce the route discoverytime and therefore reduce the end-to-end delay in MANETs. BSR uses a newapproach in order to inform the destination of communication process to start itsbackward search (RRREQ) towards the source at the same time of the forward searchtowards the destination through broadcasting small packets called PropagatingTriggers which travel across the network check for destination only. After a smalljitter called FRREQ jitter, the source has to start its normal forward discovery process(FRRREQ) searching either the destination itself or any Rendezvous Point created bythe RRREQ. This work shows that there are some implicit delay values in DSR thathave been neglected due to their slightness compared to the overall route discoverytime. These values have been shown to explain the way in which the PTs travel fasterthan normal route requests across the network. By guaranteeing the faster networkcoverage by the PTs followed by the FRREQs, both FRREQ and RRREQ should meetat around the middle of the distance between the source and the destination. The BSR is compared to both DSR and AODV in different simulationscenarios by varying traffic sources, mobility patterns, and network intensity. BSRshows promising performance compared to other reactive routing protocols such asDSR and AODV in terms of route discovery time, average end-to-end delay and otherperformance metrics which will be presented in future work such as packet deliveryfraction, routing load, and others. The BSR shows up to 47% reduction in discoverytime compared to DSR in small to medium scale networks. This is due to thebidirectional mechanism which guarantees a simultaneous route discovery from bothsource towards destination and vice versa. Additionally, the reasons that prevent theBSR of achieving exactly half of DSR’s discovery times are because of the timeneeded to initiate and traverse the PTs, and the FRREQ Jitter which at its maximummust not exceed 10 milliseconds. The BSR then shows less reaction to changing themobility patterns through changing the ground speed and pause time of moving nodesthan DSR. Both protocols show similar average delay on low node speeds with a gapof 5.8% between the average delay values of DSR and BSR in favor of the latter. Thisgap starts to increase slightly as we increase the ground speed of nodes to reach 11.2%in favor of BSR.REFERENCES[1] Elizabeth M. Royer and Chai-Keong Toh “A Review of Current Routing Protocols for Ad Hoc Mobile Wireless Networks,” IEEE Personal Communications, pp. 46-55, April 1999. 241
  14. 14. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEME[2] D. Maltz et al., “The Effects of On-demand Behavior in Routing Protocols for Multihop Wireless Ad Hoc Networks,” IEEE JSAC, vol. 17, no. 8, Aug. 1999.[3] S.-J. Lee, M. Gerla, and C.-K. Toh, “A Simulation Study of Table driven and On-Demand Routing Protocols for Mobile Ad Hoc Networks,” IEEE Network, vol. 13, no. 4, pp. 48-54, July-Aug. 1999.[4] D. B. Johnson and D. A. Maltz, "Dynamic Source Routing in Ad-Hoc Wireless Networks," Mobile Computing, T. lmielinski and H. Korth, Eds., Kluwer, 1996, pp. 153-81.[5] Stuart J. Russell and Peter Norvig,” Artificial Intelligence - A Modern Approach,” 2nd edition, 2012, p. 80-82[6] C. E. Perkins and E. M. Royer, "Ad-hoc On-Demand Distance Vector Routing," Proc. 2nd IEEE Workshop for Mobile Comp. Sys., and Apps. , pp. 9C100, Feb. 1999[7] Thomas H. Cormen, Charles E. Leiserson, Ronald L. Rivest, and Clifford Stein, “Introduction to Algorithms,” 2nd edition, p.531, 2001[8] Roberto Beraldi and Roberto Baldoni, “A Caching Scheme for Routing in Mobile Ad Hoc Networks and its Application to ZRP,” IEEE Transactions on Computers, VOL.52, NO.8 August 2003[9] Network Routing: Algorithms, Protocols, and Architectures, by Deepanker Medhe and Karthikeyan Ramasamy. P.26. 2007[10] Maamoun Ahmed and Sufian Yousef, “Self-Configurable Zone Routing Protocol Attributes”, 978-1-4244-1666-0/08/ procc. P. 2119. Cambridge 2008 IEEE[11] Sunita Kushwaha, Bhavna Narain, Deepti Verma and Sanjay kumar, “Effect Of Scenario Environment On The Performance of Manets Routing Protocol: AODV” International journal of Computer Engineering & Technology (IJCET), Volume 2, Issue 1, 2011, pp. 33 - 38, Published by IAEME.[12] V.Ramesh and Dr.P.Subbaiah, “Energy Efficient Preemptive Dynamic Source Routing Protocol For Manet” International journal of Computer Engineering & Technology (IJCET), Volume 3, Issue 1, 2012, pp. 213 - 222, Published by IAEME.[13] S.Sridhar and P.Chandrasekar, “A Survey On Trust Based Routing In Manet” International journal of Computer Engineering & Technology (IJCET), Volume 3, Issue 3, 2012, pp. 213 - 222, Published by IAEME.[14] S. Kanimozhi Suguna and Dr.S.Uma Maheswari, “Comparative Analysis Of Bee-Ant Colony Optimized Routing (Bacor) With Existing Routing Protocols For Scalable Mobile Ad Hoc Networks (Manets)” International journal of Computer Engineering & Technology (IJCET), Volume 3, Issue 1, 2012, pp. 232 - 240, Published by IAEME.[15] M. Pushpalatha, T. Ramarao, Revathi Venkataraman and Sorna Lakshmi, “Mobility Aware Data Replication Using Minimum Dominating Set In Mobile Ad Hoc Networks” International journal of Computer Engineering & Technology (IJCET), Volume 3, Issue 2, 2012, pp. 645 - 658, Published by IAEME. 242
  15. 15. International Journal of Computer Engineering and Technology (IJCET), ISSN 0976-6367(Print), ISSN 0976 – 6375(Online) Volume 4, Issue 1, January- February (2013), © IAEMEAUTHORS’ INFORMATIONM. AHMED (M’08) Assistant professor at the Middle East University (MEU) Maamounreceived his BSc in Computer Engineering from Mu’tah University, Jordan in 2004; hestarted his career right after that and worked for the Jordan’s e-Government as a core systemadministrator assistant for a year. In 2005 he has joined the TERG at Anglia RuskinUniversity in UK and in 2009 he received his PhD degree in computer engineering. Hisresearch interests are in designing routing protocols for Ad-hoc networks, modeling andsimulation, and Artificial Intelligence applications. Ahmed is a member of IEEE and theBritish Computer Society (BCS) since early 2008.S. YOUSEF Graduated in 1978 as Electrical Engineer. Worked for 18 Years in theTelecommunication Corporation of Jordan as Operation & Maintenance engineer, and then ashead of Transmission. He moved to Anglia Ruskin University (ARU) in 1993 to gain hisMSc in Telecommunication Systems Management. In 1994 he was Offered studentship fromEPSRC to complete his PhD at ARU on ATM modeling and queuing which has beenachieved in 1998. He worked as a research fellow at ARU from 1998 until 2002 and thenpromoted to a senior lecturer. He established and headed the TelecommunicationEngineering Research Group (TERG) since year 2003 which currently hoists 28 MPhil/PhDstudents. His main theme of expertise is telecommunication networks in their wired andwireless status. Most of the research is performed recently on mobile communications atdifferent generations through considering quality of service, security, physical layermeasurements of fading, modulation techniques, noise cancellation, coding theory, Ad Hocmobile networks, knowledge transfer management, 4th generation mobile networks issues andall electronic engineering relevant designs. Dr. Yousef has published around 80 paperscovering all the aforementioned fields and he is a member of editorial committees of manyjournals, keynote speaker and chair in many conferences around the globe and externalexaminer to PhD students and postgraduate degrees in many universities. TERG has tobecome a research centre of excellence in Mobile and security research. TERG has wideinternational links through the European consortium for bidding to FP7 fund and to TempusFund.SATTAR J ABOUD is currently a visitor professor in Telecommunications EngineeringResearch Group at Anglia Ruskin University in Britain. He received his education (PhD andMaster) in 1982 and 1988 respectively from Britain. He worked in various academic placesand research centres cross the continents. During this long period he has gathered wide andvery rich experiences in both teaching, researching fields and in quality assurance inuniversity education areas. Thus, he awarded the Quality Assurance Certificate ofPhiladelphia University, Faculty of Information Technology in 2002, and also the IraqiCouncil of Representatives medal, for organizing the first International Conference for IraqiExpatriates Scientists & Qualifiers, Baghdad-Iraq in 2008. His research interests include theareas of both symmetric and asymmetric cryptography, area of verification and validation, andperformance evaluation. 243