Stable and Reliable Route Identification Scheme for Efficient DSR Route Cache in Mobile Ad Hoc Networks

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					                                     IJASCSE Vol 1, Issue 3, 2012
Oct. 31

          Stable and Reliable Route Identification Scheme for Efficient DSR
                      Route Cache in Mobile Ad Hoc Networks
       S. Sathish,                      K. Thangavel,                     M. Padmapriya,
      Assistant Professor,              Professor,                        Research Scholar,
      Department of Computer            Department of Computer            Department of Computer
      Science,                          Science,                          Science,
      Periyar University, Salem,        Periyar University, Salem,        Periyar University, Salem,

      Abstract - Reactive routing protocol,              rate in multi-radio range transmission
      DSR in MANET, discover routes based                of mobile ad hoc network using NS-2
      on demand with route cache                         random      mobility    model.      The
      mechanism. DSR adapts source                       performance of the proposed SRRI
      routing and aggressive utilize of route            scheme is measured in terms of
      caches. DSR lacks in determining                   reliable and stable routes for the ad
      route validity in route caches using               hoc network, with node mobility rate,
      fixed      time    interval  for     cache         bandwidth      consumption,      routing
      invalidation. Entry in cache is only for a         overhead, packet delivery ratio.
      specified time and removed when time
      expired. Existing work presented a                 Keywords: MANET,           DSR,     Route
      dynamic mechanism to enhance cache                 Cache, SRRI
      strategies for reducing number of stale
      route entries and their dissemination                          I .INTRODUCTION
      with Expected Link Expiration Time
      (ELET) and updated route reply                             A mobile ad hoc network is a
      method        is    used    to     prevent         mobile, multi-hop wireless network
      dissemination of stale routes. In                  with no stationary infrastructure.
      dynamically changing ad hoc mobile                 Dynamic topologies due to mobility
      scenario, route stability and the                  and limited bandwidth and battery
      reliability of the route becomes a major           power make the routing problem in ad
      concern in DSR. However, existing                  hoc networks more challenging than
      work lacked in addressing the issues               traditional wired networks. A key to
      of route stability and reliability factors.        designing efficient routing protocols for
      The proposed work presents a Stable                such networks lies in keeping the
      and Reliable Route Identification                  routing overhead minimal. A new class
      (SRRI) scheme for DSR protocol.                    of on-demand routing protocols (e.g.,
      Route stability is achieved with node              DSR, AODV, TORA) attempt to reduce
      transmission range control procedure.              routing overhead by only maintaining
      Route reliability is maintained in terms           routes between nodes taking part in
      of bandwidth requirement to discover               data     communication.      In    these
      the required route. In addition the                protocols, the source discovers routes
      routing overhead for the bandwidth                 on-demand by initiating a route
      consumption is minimized with pre                  discovery process.
      cache history vector of route
      bandwidth maintained in node caches.               A. Route Discovery in DSR
      Simulation is carried out with varied
      number of nodes and different mobility                                                                         Page 1
                                   IJASCSE Vol 1, Issue 3, 2012
Oct. 31

                                                    cache      (Figure     2)   rather  than
                                                    forwarding the route request. If the
      When a source node originates a new           destination node receives the multiple
      packet addressed to a destination             RREQ propagated from different
      node, it will search its Route Cache for      routes, it replies to all RREQ by RREP.
      a source route. If no route is found in       As a result of single route discovery to
      the cache, the sender initializes Route       a destination node leads to multiple
      Discovery by broadcasting a Route             routes for it. The RREP can be
      Request (RREQ) packet (Figure. 1),            delivered to the initiator by simply
      containing destination node address,          reversing the node list, by using a
      unique request identification, and an         route to the initiator in its own cache,
      initial empty list which together             or “piggybacking” the packet on a new
      uniquely identify this Route Discovery.       Route Request to the original initiator.
                                                    When the initiator receives the RREP,
                                                    it adds the source route in its route
                                                    cache for use in sending subsequent
                                                    packets to the destination and for
                                                    future use.

          Figure 1: Node N1 Sends RREQ

      B. Route Reply in DSR

               A node receiving the RREQ [1],
      if it is not the intended destination,
      appends its address to the node list
      and forwards the packet. However,              Figure 2: Nodes N5, N3 Sends RREP
      first it checks whether it has recently
      seen another RREQ from the same               C. Caching Mechanism
      source node with the same request
      identification and target address, or                The majority of work related to
      whether its own address has already           route caches in mobile ad hoc
      presented in the traveled node list of        networks focused on Dynamic Source
      this RREQ. If either check is true, the       Routing (DSR). DSR is an on-demand
      node silently drops this packet. When         protocol that uses source routing and
      the RREQ packet reaches the                   makes aggressive use of route
      destination node, this node returns a         caches. The current specification of
      Route Reply (RREP) to the source              DSR lacks a mechanism to determine
      node (Fig. 2) with a copy of the node         the validity of routes in the route
      list from the RREQ. If an intermediate        caches. DSR uses fixed time interval
      node receiving the RREQ contains the          for cache invalidation, i.e., entry in
      route to the destination in its Route         cache appoints a fixed time and
      Cache then this node returns a RREP           removed when time expired. This
      to the source node from its own route         mechanism is not efficient as waiting
                                                    too long to invalidate route introduces                                                                 Page 2
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                                                     information and does not require any
                                                     external support.
      stale     route    cache     and    its
      dissemination. Also not waiting long                  This paper has been organized
      enough removes the routes from                 as follow, section II describes the
      cache which are still valid and causes         related work, section III describes the
      unnecessary retransmission of route            proposed work, section IV illustrates
      request and route reply. The weakness          the results and discussions and finally
      of this scheme is that it cannot adapt         section V concludes the paper.
      to the change of the network topology.
      Because of these, setting the timeout
      close to the expected link expiration                   II. RELATED WORK
      time is considered to improve the
      performance. Since the actual lifetime                 In   paper[5],      the   authors
      of a link highly depends on node               proposes a novel MANETs routing
      mobility, to achieve good performance,         protocol by using a link lifetime based
      dynamic caching schemes are desired.           multipath mechanism to improve route
                                                     stability, which is called Link lifetime
      D. Expected Link Expiration Time               based Backup Routing protocol (LBR).
                                                     During the local backup paths setup,
              Existing    Work       suggested       LBR conduct a local optimization,
      scheme to develop and analyze                  which guarantees the backup path to
      enhanced       cache     strategies   for      have the maximum lifetime in local
      reducing number of stale route entries         area. These mechanisms predict the
      and their dissemination. The basic             timeout of a route cache using pre
      idea of the scheme is to use the               determined parameters. However,
      Expected Link Expiration Time (ELET)           predetermined value of timeout may
      [6] as its cache timeout and preventing        work for certain scenarios but may not
      the distribution of stale information by       work well for all. In [3], a smart packet
      updated route reply. The ELET is a             is generated periodically which travels
      measure of time duration in which a            through the network, collects topology
      node will become out of transmission           information, and the nodes update
      range of another node. ELET is                 their route caches. Route entries then
      determined       dynamically    by   the       contain new routes reflecting the most
      Enhanced DSR (EDSR) when it                    recent topology changes. In [6] the
      receives RREQ from nearby node                 authors presented a cross-layer
      using the cross layer information.             approach for predicting the route
      Cross layer design refers to protocol          cache lifetime. The author assigns
      stack that intercommunicate the useful         timeouts of individual links in route
      information to collectively achieve the        cache by utilizing RSSI values
      desired optimization goal by allowing          received from physical layer. This
      the different protocols to share               scheme requires RSSI thresholds for
      information related to the network             link timeout on every node of the ad
      status. Therefore, cross layer based           hoc network. In this method the
      cache mechanism in which DSR                   timeout value directly depends on
      computes timeout value of individual           thresholds value selected. In [4], the
      links by utilizing received signal             authors developed a caching strategy
      strength from physical layer. This             that permits nodes to update their
      method uses locally available network          cache, when the topology of the
                                                     network changes. To achieve it, all                                                                   Page 3
                                  IJASCSE Vol 1, Issue 3, 2012
Oct. 31

                                                   between strong and weak channels.
                                                   Each channel is characterized as
      reachable nodes that have cached a           strong or weak by the average signal
      broken link are notified when it fails.      strength at which packets are
      Based on it, the proposed algorithm          exchanged between the hosts at either
      notifies all reachable nodes that have       end of the channel. In SRRI based
      cached the link in a distributed             DSR route discovery, a source initiates
      manner. In this work, timeout for route      a route discovery request when it has
      cache entry is not used, thus if nodes       data to send to a destination which is
      become unreachable in some cases             not in the routing table. The route-
      then they will not remove the stale          search is broadcast to all neighboring
      route from their caches.                     hosts. These hosts propagate the
                                                   broadcast if (1) it is received over a
             III. PROPOSED WORK                    strong channel and (2) the request has
                                                   not been propagated previously (to
              Proposed work present a Stable       avoid looping). The route-search
      and Reliable Route Identification            packet stores the address of each
      (SRRI) scheme for DSR protocol in            intermediate host in the route taken.
      extremely dynamic mobile node                The destination chooses the route
      communication setting. Route stability       recorded in the first arriving request,
      is      accomplished     with    node        since this route is probably shorter and
      transmission range control process, in       less congested than routes for slower
      which transmission range of every            arriving requests. The destination
      node in DSR cache is updated                 returns the route-reply along the
      occasionally to discover the node            selected route, and each intermediate
      accessibility for link broadcast with        node includes the new next-hop,
      other nodes. Route reliability is            destination pairs in its routing table.
      sustained in terms of bandwidth
      requirement to determine the required
      route with enhanced DSR as is                B. Reliability Based DSR Routing In
      justified in the existing work.              MANET
      Furthermore the routing overhead for
      the bandwidth consumption is reduced                In order to reduce the broadcast
      with pre cache account vector of route       storm and routing overhead, an
      bandwidth preserved in node caches.          intermediate node can re-broadcast a
                                                   second RREQ packet only if it has
      A. Stability Based DSR Routing In            higher reliability and stability than the
      MANET                                        first RREQ packet, otherwise the
                                                   RREQ will be discarded. When the first
              A new routing paradigm can be        RREQ packet enabled reaches the
      obtained by considering the route            destination node, the node starts the
      stability as routing metric. Stability       timer interval and during that time it
      based routing aims at choosing routes        examines the reliability and stability of
      which are more stable in time. The           every arrived RREQ packet. When the
      Signal     Stability  based    Routing       timer interval expired, the destination
      performs on demand route discovery           node selects the RREQ packet that
      by selecting longer-lived routes based       has the highest QOS function and
      on signal strength and location              sends the route reply (RREP) packet
      stability. The signal strength criteria      carrying the route information to the
      allow the protocol to differentiate          source node. When another RREQ                                                                 Page 4
                                    IJASCSE Vol 1, Issue 3, 2012
Oct. 31

                                                     bandwidth consumption is minimized
                                                     with pre cache history vector of route
      packet with the same preference                bandwidth maintained in node caches.
      arrives after the threshold time interval,
      it will not be considered and do not
      process it further.                            D. PROCEDURE FOR SRRI

      C. Stable and Reliable             Route       SRRI Procedure
      Identification (SRRI)
                                                     Procedure SRRI (For each node
              We have developed an ad hoc            from source to Destination)
      routing protocol by introducing a                    For Node 1 to Total Number
      Stable       and      Reliable     Route       of Nodes Do
      Identification (SRRI) scheme to the                        If GT = 1 & GR = 1
      widely used DSR routing protocol. This
      routing metric is concerned with finding
      optimal paths between the source and
      the destination nodes that can avoid
      the congested regions in the network.                        Else
      It focuses on multiple objectives to be                               Error
      optimized,      such    as     Bandwidth                     End If
      consumption (which refers to the                      End
      number of bits per second (bps) that
      can be sent along the path between                   For Node 1 to Total Number
      the source and the destination nodes)          of Nodes Do
      and signal strength.
              In this modification, we include
      the local availability of the bandwidth               End
      at a node in addition to the hop count         End
      metric to maximize the end-to-end                    TR  Transmission Range
      throughput in MANETs and at the
                                                           PT  Power of Transmitter
      same time to control the end-to-end
                                                           GT  Gain of Transmitter
      delay time. SRRI helps the routing
      protocol to determine the available                  GR  Receiver Gain
      bandwidth at the node in order to                    HT  Height of Transmitter
      improve the network performance by                   HR  Height or Receiver
      avoiding routing traffic through the                 D  Distance between two
      congested areas.                                      consecutive nodes at time T
              Route stability is achieved with             L  Signal Loss
      node transmission range control                      P  Power
      procedure, in which transmission                     R  Success Rate
      range of every node in DSR cache is                  T  Time
      updated periodically to identify the
      node availability for link transmission          IV. RESULTS AND DISCUSSION
      with other nodes. Route reliability is
      maintained in terms of bandwidth                      We chose the popular network
      requirement to discover the required           simulator NS2 as the simulator
      route with enhanced DSR as is                  primarily to implement methods
      explained in the existing work. In             because it is widespread use in the
      addition the routing overhead for the          academic community and the                                                                Page 5
                                     IJASCSE Vol 1, Issue 3, 2012
Oct. 31

      comprehensive manuals and tutorials
      that are freely available. It is possible
      to simulate a mobile multi-hop ad hoc
      wireless network in ns-2 using
      simulated 802.11 MAC layer.

      A. Packet Delivery Ratio
      Packet delivery ratio is the ratio of the        Figure 4: Mobility Vs Routing Overhead
      number of data packets received by a
      destination over the number of data                    The above Figure 4 shows the
      packets      delivered       by       the       routing overhead of SRRI and ELET
      corresponding source.                           with different number of mobile nodes
                                                      and mobility speeds, respectively. As
                                                      shown in Figure 4 routing overhead
                                                      increases as the number of mobile
                                                      nodes or the mobility speed increases.
                                                      The routing overhead for ELET is
                                                      higher than SRRI.

                                                      C. Bandwidth Consumption

                                                            The number of packets can be
                                                      sent along the path between the
          Figure 3: Mobility Vs Packet Delivery       source and the destination nodes.
                          Ratio                       These metrics was chosen due to
                                                      these performance metrics was well
      The Figure 3 shows the packet                   known in showing the routing
      delivery ratio of SRRI and ELET with            performance of the selected protocol.
      different number of mobility speeds.
      We can observe that SRRI transmits
      and receives more data packet than
      ELET. The ELET path may break
      easily. SRRI will always choose the
      most stable and reliable path, the
      chance of link breakage for SRRI is
      lower than ELET since ELET didn’t
      consider the stability of the selected

      B. Routing Overhead

      Routing Overhead can be termed as
      the total number of overhead packets                Figure 5: Mobility Vs Bandwidth-
      is transmitted per second. This metric                        Consumption
      indicates the routing cost.
                                                           The Figure 5 shows the
                                                      bandwidth consumption of SRRI and
                                                      ELET with different number of mobility                                                                   Page 6
                                    IJASCSE Vol 1, Issue 3, 2012
Oct. 31


      speeds. As shown in Figure bandwidth           [1] Johnson, D., Maltz, D., Hu, Y.-C,
      consumption increases as the number            “The Dynamic Source Routing for
      of mobility speed increases. Bandwidth         mobile ad hoc networks. IETF Internet
      consumption for ELET is higher than            Draft                            (2004)”,
      SRRI.      SRRI      consumes     less draft-
      bandwidth. This is because discovery           ietf-manet-dsr-10.txt
      of reliable and stable path in SRRI
      based DSR.                                     [2] Srivastava, V., Motani, M., “Cross-
                                                     layer design: a survey and the road
                 V. CONCLUSION                       ahead”,      IEEE      Communication
                                                     Magazine 43(12), pp. 1112–1119,
              In this work, we have presented        2005
      a new mechanism, Stable and Reliable
      Route Identification (SRRI) scheme for         [3] Ashokraj, N., Arun, C., Murugan, K.
      DSR protocol in highly dynamic mobile          “Route        Cache         Optimization
      node communication scenario. To                Mechanism Using Smart Packets For
      reduce the stale cache information and         On-Demand Routing Protocol in
      its dissemination, SRRI scheme                 MANET”, In International Conference
      dynamically computes the ELET and              on Information Technology (ICIT), pp.
      adds this value when a route is                141–146, 2008.
      discovered by source node. SRRI
      considers with multiple constraints            [4] Garrido, J., Marandin, D: A
      such as routing overhead, bandwidth,           Linkcache Invalidation Mechanism for
      and signal strength to find the most           Dynamic Source Routing (DSR) in Ad
      feasible route from the source node to         Hoc Networks. In: 18th IEEE
      the destination node. It also selects the      International Symposium on Personal,
      most stable links which leads to               Indoor      and      Mobile    Radio
      longer-lived routes and reduces route          Communications, pp. 3–7 (2007)
              The simulation results show that       [5] Wen Jing Yang, Xinyu Yang,
      SRRI scheme can considerably                   Shusen Yang, Yage Gong, “Improving
      improve the performance. It achieved           Route Stability In Mobile Ad Hoc
      the route stability and reliability with       Networks Based On Link Lifetime”,
      node transmission range control                Journal Of Communications, Vol. 6,
      procedure and bandwidth requirement.           No. 3, May 2011.
      SRRI scheme attains data delivery
      ratio about 99.5 % in MANET.                   [6] Gaurav Bhatia , Vivek Kumar, “An
      Compared with ELET, proposed SRRI              Enhanced DSR Caching Scheme
      scheme achieves 18% better result in           Based on Cross Layer Information”, In
      Bandwidth consumption and 5% to 9%             Springer-Verlag Berlin Heidelberg
      better result in Routing overhead. We          2011, pp. 191–203, 2011.
      can conclude that our proposed SRRI
      scheme provides the improvement in             [7] The Network Simulator – ns-2,
      terms of data delivery ratio with lower
      routing overhead and Bandwidth
      consumption for route reliability and
      stability in mobile ad hoc networks.                                                                    Page 7

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