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Enhanced Load Balanced AODV Routing Protocol

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					                                                        (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                         Vol. 9, No. 1, January 2011



                          Enhanced Load Balanced AODV Routing Protocol

                                             Iftikhar Ah mad and Hu maira Jabeen
                                               Depart ment of Co mputer Science
                                            Faculty of Basic and Applied Sciences
                                     International Islamic University Islamabad, Pakistan
                                    ify_ia@yahoo.com, humaira_jabeen_83@yahoo.com

Abstract— Excessive load on the MANET is the main reason              are proposed to achieve good load balancing in MANET. In
for link breakage and performance degradation. A congested            Load balancing we transfer the jobs fro m overloaded nodes
node in the network dies more quickly than other nodes. A             to less busy nodes or idle nodes. In the result, total time to
good load balancing technique share the traffic load evenly           process all jobs can be reduced and also guarantee that no
among all the nodes those can take part in transmission.              node will remain idle while some jobs are there to process.
Transferring of load from congested nodes to less busy nodes              Numbers of algorith ms are proposed for load balancing
and involvement of other nodes in transmission that can take          that consider traffic load for route selection, but these
part in route can improve the overall network life. We                algorithms are not suitable for large scale transmissions.
proposed a load balancing scheme for AODV that improves
overall network life, throughput and reduce average end to end        While selecting the route we must consider that the
                                                                      distribution of load should be even. Mobile nodes having
delay.
                                                                      low traffic load should be preferred to the heavily loaded
   Keywords: AODV, load balancing,congestion,delay.                   mobile nodes.

                                                                                            II. RELATED WORK
                     I.    INT RODUCTION
                                                                         Dynamic Load-Aware Routing [2] protocol, DLA R
   A mobile ad hoc network is defined as a collection of              defined the network load of a mobile node as the number of
mobile nodes with no central management, running on                   packets in its interface queue. Load-Balanced Ad hoc
batteries and changing topology [12]. The routing in                  Routing protocol [1] LBAR defined network load in a node
MANET is difficult due to its changing topology. There are            as the total number of routes passing through the node and its
three types of protocols for MANET proactive, reactive and            neighbors.
hybrid routing protocols. Proactive routing protocols stores              In Load-Sensitive Routing protocol [3] the network load
and maintains routing state of every other node in the                in a node is defined as the summation of the number of
network. Reactive routing protocols discover route on                 packets being queued in the interface of the mobile host and
demand, when there is need. Hybrid routing protocols                  its neighboring hosts. Even though the load metric of LSR is
combines advantages of both reactive and proactive classes            more accurate than those of DLAR or LBA R, but it does not
of protocols. In this study we proposed a load balanced ad            consider the effect of access contentions in the MAC layer
hoc routing protocol by modifying basic AODV routing                  .Therefore, LSR produce contention delay. WLAR [4]
protocol. AODV [13] is the main reactive routing protocol             distributes traffic among mobile nodes through load
for mobile ad hoc networks which is most widely used for              balancing mechanism which is product of average queue size
routing in MANET. It is especially designed for MANET                 and number of shared nodes. Load Aware Routing in Ad hoc
and performs well then other routing protocols for MANET.             (LA RA) networks protocol [5] defines a new metric called
    The basic function of AODV is depended on two                     traffic density that is used to select the route with minimu m
mechanisms; one is route discovery mechanism and second               load. Traffic density means the degree of contention at the
is route mentainence mechanism. Both of these mechanisms              mediu m access control layer.
works through four different type of messages those are                   Simp le Load-balancing Approach (SLA)[6] not allowing
RREQ, RREP, Route error message and Hello message.                    traffic to be concentrated on the node and allowing each
Whenever a node wants to transmit data to any other node in           node to drop RREQ or to give up packet forwarding
the network, it starts route discovery process by sending a           depending on its own traffic load to save energy. It also
broad cost of RREQ to all its neighbors those are within              suggests a payment scheme called Protocol-Independent
transmission rang. A route reply is sent back to the source           Fairness Algorithm (PIFA) for packet forwarding.
node by the destination or any intermediate node that have                A novel load-balancing technique [7] for ad hoc on-
fresher route to destination. The reply is sent through the           demand routing is very effective method to achieve load
route which is having less number of hops.                            balance and congestion alleviation. If a node ignores RREQ
    In this way a route with less number of hops is selected          messages within a specific period, it can comp letely be
during the route discovery mechanism. In the route discovery          excluded fro m the additional commun ications that might
mechanism the route is discovered and selected through                have occurred for that period otherwise. A node can decide
route discovery algorithm. Lot of work has been done on this          not to serve a traffic flow by dropping the RREQ for that
algorithm and improvements are made in order to increase              flow. The interface queue occupancy and workload on node
performance of protocol. Certain Load balancing schemes               is used to control RREQ messages adaptively.



                                                                 98                              http://sites.google.com/site/ijcsis/
                                                                                                 ISSN 1947-5500
                                                         (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                          Vol. 9, No. 1, January 2011


    Delay-based load-aware on-demand routing (D-LAOR)                      Instead of increasing load on already busy nodes we are
protocol [8], discovers the optimal path based on the                  distributing traffic load among the other available nodes.
estimated total path delay and the hop count.
    AOMDV routing protocol [9] used Queue Length and                   C. Use of less Busier Nodes
Hop Count value together to select a route from source to                  During the trans mission the selected route exp ires fro m
destination that avoids congestion and load balancing. A
                                                                       time to time to check the availability of less busier node for
threshold value is defined after a threshold alternate path is
                                                                       further transmission of data. There is greater chance that
chosen. Intermediate nodes avoids broad cast of RREQ if the
                                                                       more nodes come closer to the active route that can provide
routes are already congested.
     Aggregate Interface Queue Length (AIQL) scheme has                better route for transmission. For this purpose we exp ires
been proposed in this paper [10] to deal with load balancing           route after fixed intervals of t ime during the transmission of
issues. A route is selected on the bases of AIQL to transmit           data. Instead of using the same route for entire transmission
the data. AIQL is the sum of queue length of all nodes in the          of data new route are discovered.
path form source to destination.
    All proposed protocols work well for small scale                   The follo wing figure 1 displaying the scenario of
transmissions but in case of large scale transmission the ad-          transmission with basic AODV routing protocol.
hoc on demand distance vector load and mobility
(AODVLM) routing protocol [11] shows better results in
terms of throughput and delivery ratio with little increase in
routing overhead. The proposed load balancing scheme in
this paper further extends the AODVLM implementation.

          III.   PROPOSD LOAD BALANCING SCHEME

    The proposed mod ification extends AODV and
distributes the traffic among ad hoc nodes through a simple
load balancing mechanis m. The protocol adopts basic
AODV procedure.
                                                                                 Figure 1. Example AODV Transmsion Scenerio.
A. Selecting Route Selection Procedure
    When a source node initiates a route discovery procedure                     In figure 1 node 5 is co mmunicating with node 7
by flooding RREQ messages, each node that receives the                 and node 0 is the source node for node 4. We can easily
RREQ looks in its routing table to see if it has a fresh route         analyze that node 3 is busiest node that will be dead very
to the destination.
                                                                       soon. For large scale t ransmission there will be more bad
     If it doesn't have the route it calculates the number of
packets in its interface queue and divides it with its queue           results as for as through put is concerned. As from the figure
length and adds calculated ratio in RREQ and broadcasts it             it is clear that node 5 can co mmunicate through node s
further. The process is repeated till either the destination is        instead of node 3. With the passage of time as in part 2 of
reached or no destination is found.                                    the figure the node 0 can transmit data through node 2
                                                                       which is more efficient path but it does not happening in
B. Averaged Aggregated Load Ratio (AALR)                               case of basic AODV. After new proposed load balancing
    If P are packets in the queue of a node and L is the length        scheme the figure 1 will be like the figure 2.
of queue then ratio of the load on node is R =P/L and sum of
ratio on each node in the route is = R then
    AALR = R/N,               where N is number of hops the
RREQ has passed through.
    The AALR metric has been used in order to find out the
heavily loaded route. Because if the aggregate queue length
for the path is higher, then it obviously means that either all
the nodes on the path are loaded or there is at least one node
lying on the route that is overloaded.
    Hence by considering a route with lesser value of
averaged aggregate load ratio for selecting the path we are
have diverge the packets from heavily loaded route to
comparatively lighter route.
    In this way traffic load is distributed among the available
                                                                            Figure 2. AODV T ransmsion Scenerio after Implementation.
reachable nodes that can provide a path to destination.




                                                                  99                                http://sites.google.com/site/ijcsis/
                                                                                                    ISSN 1947-5500
                                                         (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                          Vol. 9, No. 1, January 2011




    The new scheme is adopting the better and less busy                               TABLE I.       SIMULATION SETTING

route. It avoids the congested nodes during route discovery                Channel type                 Channel/Wireless Channel
and later on during transmissions makes use of all available            Radio-propagation model         Propagation/TwoRay Ground
less busy nodes. In this way our scheme is shift ing the                   Network interface               Phy/WirelessPhy
traffic load form busier nodes to less busy nodes. New                     MAC type                        Mac/802_11
proposed scheme not using the certain nodes for entire                     Interface queue              Queue/Drop Tail/PriQueue
traffic but sharing t raffic load with all available nodes that            Link layer type                 LL
can take part in co mmun ication as in shown in figure 2.                  Antenna model                   Antenna/Omni Antenna
    As long as a particular node remains busy means it has to              Max packet in ifq               25
transmit or forward more packets to its neighboring nodes.                 Packet size                     1024
With transmission of each data and control packet node is                  Number of mobile nodes          20
consuming energy (power). Mobile node relies on batteries                  Simu lation time                150 seconds
and battery life decrease with the forwarding of each and
every packet.
                                                                        C. Simulation Results
    So, more load means lesser life time of the node and
lesser network life intern. To calculate the node’s load share            The results are compared and presented in graphical form
we calculate number of packets forward by that particular               after implementing Enhanced load balancing AODV routing
node and compare that number against each other and the                 protocol. We analyzed the results by taking pause time on x-
network. Our proposed protocol give more even load                      axis and performance metric throughput and end to end
balancing in MANET then existing load balancing protocols.              delay on Y-axis and for load distribution nu mber of
                                                                        forwarded packets on y-axis and Node ID on x-axis.
              IV. PERFORMANCE EVALUATION                                  1) Throughput:
   We imp lemented basic and our load balancing algorithm                 Throughput at different time interval is compared as
in NS2 [15]. NS2 is discrete event simulator for the                    shown in figure 5.
simulation of wireless ad hoc networks. It supports Two Ray
Ground propagation and Random Way Point mobility
models those are required for the implementation of our
work. We used the following performance metric to evaluate
the performance of our load balancing algorithm against
basic AODV algorithm.
A. Performance Metric
   1) Average end to end delay:
    This is the average overall delay occurs for a packet to
travel fro m a source node to a destination node. This
includes all possible delays caused by buffering during route
discovery, queuing at the interface-queue, contention and
retransmission delays at the MAC layer, and propagation and
transfer times.
                                                                                      Figure 3. Throughput vs Pause time.
  2) Throughput:
    It is defined as the total number of packets transmitted in         Total number of packets transmitted by AODV is lesser then
a given time period.                                                    Load balanced AODV and with passage of time throughput
                                                                        of load balanced AODV is increasing as more packets are
  3) Traffic load Distribution:                                         transmitting in given time.
    It is the total number of packets that are forwarded by a              2) Average end to end delay:
node during transmission. Because each forwarded packet
consume node’s power that reduce node life.                                Average end to end delay of load balanced is round about
                                                                        18 mille seconds at the start of transmission and as
B. Parameter Setting                                                    transmission goes on it becomes 10 mille second but for
    The radio propagation model [14] that is considered for             AODV its min imu m value is 14 mille seconds. It means
the protocol is the Two-Ray Ground and Random way point                 averaged end to end delay is reduced in greater extend. This
mobility model is used in our implementation of protocol.               reduction in delay improves throughput that means now
    The table I shows complete detail of parameter used in              source node is sending packets more quickly to the
our simulation setting.                                                 destination then basic AODV.



                                                                  100                              http://sites.google.com/site/ijcsis/
                                                                                                   ISSN 1947-5500
                                                         (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                          Vol. 9, No. 1, January 2011


                                                                                                 V.     CONCLUSION

                                                                         New load balanced AODV routing protocol for
                                                                      distributing traffic load evenly among nodes in ad hoc
                                                                      networks is proposed. The idea is to provide a scheme for
                                                                      load distribution and to reduce congestion in high load
                                                                      networks. We performed a simu lation study and compared
                                                                      the modified version of AODV with basic AODV protocol.
                                                                      The results of simu lation shows that the proposed load
                                                                      balanced protocol can improve average throughput, reduce
                                                                      average end to end delay and improves overall network life.
                                                                      Hence, the proposed AODV is more useful for longer
                                                                      transmission and for moderately loaded high mobility
             Figure 4. End to end delay vs Pause time.                networks.

   3) Load distribution:                                                                           REFERENCES
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