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Volume 8 No. 1 April 2010 International Journal of Computer Science - Research Series

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									                                                      (IJCSIS) International Journal of Computer Science and Information Security,
                                                      Vol. 8, No. 1, April 2010




        QoS Routing For Mobile Adhoc Networks And
         Performance Analysis Using OLSR Protocol
                K.Oudidi                                    A.Hajami                                        M.Elkoutbi
            Si2M Laboratory                              Si2M Laboratory                                 Si2M Laboratory
  National School of Computer Science          National School of Computer Science             National School of Computer Science
 and Systems Analysis, Rabat, Morocco         and Systems Analysis, Rabat, Morocco            and Systems Analysis, Rabat, Morocco
           k_oudidi@yahoo.fr                      Abdelmajid_hajami@yahoo.fr                           elkoutbi@ensias.ma

                                                                 categories
Abstract-- This paper proposes a novel routing metrics based on     of MANET routing protocols: Proactive (table-driven),
the residual bandwidth, energy and mobility index of the nodes.  Reactive (on-demand) and Hybrid. Proactive protocols build
Metrics are designed to cope with high mobility and poor
                                                                 their routing tables continuously by broadcasting periodic
residual energy resources in order to find optimal paths that
guarantee the QoS constraints. A maximizable routing metric      routing updates through the network; reactive protocols build
theory has been used to develop a metric that selects, during thetheir routing tables on demand and have no prior knowledge
protocol process, routes that are more stable, offer a maximum   of the route they will take to get to a particular node. Hybrid
throughput and prolong network life time.            The OLSR    protocols create reactive routing zones interconnected by
(Optimized Link State Routing) protocol, which is an             proactive routing links and usually adapt their routing strategy
optimization of link state protocols designed for MANETs
                                                                 to the amount of mobility in the network.
(Mobile Ad hoc Networks) is used as a test bed in this work. We
prove that our proposed composite metrics (based on mobility,       In this paper we reiterate our proposed mobility metric.
energy and bandwidth) selects a more stable MPR set than the     Based on the use of this mobility metric we propose a new
QOLSR algorithm which is a well known OLSR QoS extension.        composite metric, to find the optimal path given the QoS
By mathematical analysis and simulations, we have shown the      constraints. The objective of the composite metric is to find an
efficiency of this new routing metric in term of routing load,   optimal stable path with maximum available bandwidth and to
packet delivery fraction, delay and prolonging the network
lifetime.                                                        prolong network life time.
                                                                    Using the OLSR Protocol, we show that our proposed
Index Terms— Mobile Ad hoc networks, quality of service, routing metric selects stable MPR Set rather than the QOLSR
protocol, routing metric, mobility, residual energy.             algorithm which is a well known OLSR QoS algorithm for
                                                                 MANETs.
                      I. INTRODUCTION                                    This paper is organized as follows. Section 2 gives an
    A Mobile Ad hoc Network (MANET) is a collection of                 overview of the original OLSR protocol. Section 3 summarizes
mobile nodes working on a dynamic autonomous network.                  the state of the art dealing with QoS support in MANETs and
Nodes communicate with each other over the wireless medium             describes the QoS routing problems Section 4 presents our
without need of a centralized access points or a base station.         proposed composite metric based on mobility, residual energy
Since there is no existing communication infrastructure,               and bandwidth as QoS parameters. In Section 5, simulations
adhoc networks cannot rely on specialised routers for path
                                                                       and results are discussed. The last part of this paper concludes
discovery and routing. Therefore, nodes in such a network are
expected to act cooperatively to establish routes instantly.           and presents some future work.
Such a network is also expected to route traffic, possibly over
multiple hops, in distributed manner, and to adapt itself to the              II. OPTIMIZED LINK STATE ROUTING PROTOCOL
highly dynamic changes of its links , mobility and residual
energy patterns of its constituent nodes.                              A. Overview
                                                                          OLSR (Optimized Link State Routing) protocol [2-3] is a
   Providing QoS in MANETs [1] is a tedious task. It’s known
                                                                       proactive table driven routing protocol for mobile ad hoc
that combining multiple criteria in the routing process is a
                                                                       networks and it is fully described on RFC 3626 (Thomas
Hard problem (NP-Complet) A complete QoS model in
                                                                       Clausen & Philippe Jacquet, (October 2003)). As a link state
MANETs will span multiple layers, however the network
                                                                       routing protocol, OLSR periodically advertises the links
layer plays a vital role in providing the required support
                                                                       building the network. However, OLSR optimizes the topology
mechanisms. The goal of QoS routing is to obtain feasible
                                                                       information flooding mechanism, by reducing the amount of
paths that satisfy end-system performance requirements. Most
                                                                       links that are advertised and by reducing the number of nodes
QoS routing algorithms present an extension of existing
                                                                       forwarding each topology message to the set of MPRs only.
classic best effort routing algorithms. There are three main
                                                                       Information topology is called Topology Control (TC) message




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                                                                                                 ISSN 1947-5500
                                                     (IJCSIS) International Journal of Computer Science and Information Security,
                                                     Vol. 8, No. 1, April 2010




and exchanged using broadcasted into the network. TC                           Based on the above notations, the standard algorithm for
messages are only originated by nodes selected as Multipoint             MPR selection is defined as follows (figure 2-b):
Relays (MPRs) by some other node in the network. MPRs are                    OLSR uses hop count to compute the shortest path to an
selected in such a way that a minimum amount of MPRs,                    arbitrary destination using the topology map consisting of all
located one-hop away from the node doing the selection                   its neighbours and of MPRs of all other nodes. Number of hop
(called MPR Selector), are enough to reach every single                  criterion as a routing metric is not suitable for QoS support as
neighbour located two-hops away of MPR selector. By                      a path selected based on the least number of hops may not
applying this selection mechanism only a reduced amount of               satisfy the required QoS constraints.
nodes (depending on the network topology) will be selected as
MPRs[18]. Every node in the network is aware of its one-hop
and two-hop neighbours by periodically exchanging HELLO
messages containing the list of its one-hop neighbours. On the
other hand, TC messages will only advertise the links between
the MPRs and their electors. Then, only a partial amount of
the network links (the topology) will be advertised, also MPRs
are the only nodes allowed to forward TC messages and only
if messages come from a MPR Selector node. These
forwarding constrains considerably decrease the amount of
flooding retransmissions (Figure 1). This example shows the
efficiency of the MPR mechanism because only eight
transmissions are required to reach all the 23 nodes building
the network, which is a significant saving when compared to
traditional flooding mechanism where every node is asked to
                                                                                     Figure 2-b: MPR Selection Algorithm
retransmit to all neighbours.
                                                                                            III. RELATED WORK

                                                                            A. Qos Support in a Manet

                                                                            In this section we discuss the recent work done to provide
                                                                         QoS functionality in Manets.
                                                                            INSIGNIA, [7], is an adaptation of the IntServ Model to the
                                                                         mobile ad hoc networks. QoS guarantee is done by per-flow
          Figure 1: Flooding with MPR mechanism
                                                                         information in each node that is set up by the
    B. MPR Selection Algorithm                                           signalling/reservation protocol. The destination statistically
                                                                         measures QoS parameters (e.g. packet loss, delay, average
   The computation of the MPR set with minimal size is a NP-
complet problem [14-16]. For this end, the standard MPR                  throughput,etc.) and periodically sends QoS reports to the
selection algorithm currently used in the OLSR protocol                  source. Based on those reports, the source node can adapt real-
                                                                         time flows to avoid congestion.
implementations is as follows:
                                                                            SWAN, [13], Service differentiation in stateless Wireless
                                                                         Ad-hoc Network, is an adaptation of the DiffServ Model to the
                                                                         mobile ad-hoc networks. Nodes do not need to keep per-flow
                                                                         information in order to handle packets. QoS guarantee is
                                                                         provided according to the class of the flow once it has been
                                                                         accepted.
                                                                            FQMM, [11], Flexible Qos Model for MANET, has been
                                                                         introduced to offer a better QoS guarantee to a restricted
            Figure 2-a- Example of MRRset calculation.                   number of flows whereas a class guarantee is offered to the
For a node x, let N(x) be the neighborhood of x. N(x) is the set         other flows. FQMM is a hybrid approach combining per-flow
of nodes which are in the range of x and share with x a                  granularity of IntServ for high priority classes and perclass
bidirectional link. We denote by N2(x) the two-neighborhood              granularity of DiffServ for low priority classes.
of x, i.e, the set of nodes which are neighbors of at least one              G. Ying et al [8] have proposed enhancements that allow
node of N(x) but that do not belong to N(x) (see Figure 2-a).            OLSR to find the maximum bandwidth path. The heuristics




                                                                   139                             http://sites.google.com/site/ijcsis/
                                                                                                   ISSN 1947-5500
                                                        (IJCSIS) International Journal of Computer Science and Information Security,
                                                        Vol. 8, No. 1, April 2010




are based on considering only bandwidth as a QoS routing                       • Concave                       {
                                                                                                : M(P) = min M i; j , M i;k ,..., M l;m     }
constraint and revisions to the MPR selection criteria. They                 The proof of NP-Completeness relies heavily on the
identify that MPR selection is vital in optimal path selection.           correlation of the link weight metrics. QoS Routing is NP-
The key concept in the revised MPR selection algorithm is                 Complete when the QoS metrics are independent, real
that a “good bandwidth” link should never be omitted. Based               numbers or unbounded integers.
on this three algorithms were proposed: OLSR_R1, R2 and                      In general, QoS routing focuses on how to find feasible and
R1.                                                                       optimal paths that satisfy QoS requirements of various voice,
   The research group at INRIA [9],[10] proposed a QoS                    video and data applications. However, based on maximizable
routing scheme over OLSR. Their technique used delay and                  routing metrics theory [16], it is shown that two or more
bandwidth metric for routing table computation. Such metrics              routing metrics can be combined to form a composite metric if
are included on each routing table entry corresponding to each            the original metrics are bounded and monotonic.
destination.                                                                 Before we proceed to the mathematical proof, we give
   QOLSR [11] and work presented in [9] enhance OLSR with                 definitions of maximal metric tree and the properties desired
QoS support. Both propose a solution providing a path such                for combining metrics i.e. bounded- ness and monotonicity.
that the bandwidth available at each node on the path is
higher than or equal to the requested bandwidth. Furthermore,             Definition 1: Routing Metric
                                                                          A routing metric for a network N is six-tuple (W,Wf, M, mr, met,
QOLSR considers delay as a second criterion for path
                                                                          R ) where:
selection.
                                                                          1.   M is a set of metric values
   However, all of these solutions do not take into account at
                                                                          2.   Wf is a function that assigns to each edge {i, j} in N a
all mobility and energy parameters induced by the nature of
Manet Network.                                                                 weight Wf( {i, j}) in W
                                                                          3.   W is a set of edge weights
    B. Qos Routing Problems                                               4.   mr is a metric value in M assigned to the root.
   One of the key issues in providing end-to-end QoS in a                 5.   met is a metric function whose domain is MxW and
given network is how to find a feasible path that satisfies the                whose range is M (it takes a metric value and an edge
QoS constraints. The problem of finding a feasible path is NP-                 value and returns a metric value).
Complete if the number of constraints is more than two, it                6.   R is a binary relation over m, the set of metric values that
cannot be exactly solved in polynomial time and mostly dealt                   satisfy the following four conditions of irreflexivity,
with using heuristics and approximations. The network layer               Definition 2: Maximum Metric Tree
has a critical role to play in the QoS provision process. The                A spanning tree of N is called a maximum metric tree with
approaches used by the QoS routing algorithms follow a trade-             respect to an assigned metric iff every rooted path in T is
off between the optimality of paths and the complexity of                 maximum metric with respect to the assigned metric. In
algorithms especially in computing multiconstrained path. A               simple words every node obtains its maximum metric through
survey on such solutions can be found in [14].                            its path along a maximum metric tree.
   The computation complexity is primarily determined by the
                                                                          Definition 3: Boundedness
composition rules of the metrics [16]. The three basic
                                                                          A routing metric (W, Wf, M, mr, met, R ) is bounded iff the
composition rules are: additive (such as delay, delay jitter,
                                                                          following condition holds for every edge weight w in W and
logarithm of successful transmission, hop count and cost),
                                                                          every metric value m in M.
multiplicative (like reliability and probability of successful                             met (m,w) R m ∨ met(m,w) = m
transmission) and concave/min-max (e.g. bandwidth). The
additive and multiplicative metric of a path is the sum and               Definition 4: Monotonicity
multiplication of the metric respectively for all the links               A routing metric (W,Wf, M, mr, met, R ) is monotonic iff the
constituting the path. The concave metric of a path is the                following condition holds hue for every edge weight w in W
maximum or the minimum of the metric over all the links in                and every pair of metric values m and m’ in M:
the path.                                                                         m R m’ ⇒ (met (m,w) R met (m’,w)
  Otherwise, if M i; j is the metric for link {i, j} and P is the                                    ∨ met (m,w) = met (m’,w))
path between (i, j, k,..1,m) nodes, the QoS metric M(P) is                (W,Wf, M, mr, met, R ) is called strict monotonic iff
defined as [14-15]:                                                               m R m’ ⇒ met (m,w) R met (m’,w)
    • Additive        : M(P) =   M i ; j + M i;k +…+ M l ;m
                                                                          Theorem 1 (Necessity condition of Boundedness)
    • Multiplicative : M(P) =    M i ; j x M i;k x…x M l ;m
                                                                            If a routing metric is chosen for any network N, and if N
                                                                          has maximal spanning tree with respect to the metric, then the




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                                                                                                     ISSN 1947-5500
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routing metric is bounded                                             Mob QOLSR
                                                                        To the best of our knowledge, this work is amongst the first
Theorem 2 (Necessity condition of Monotonicity)                         efforts to consider nodes with mobility and energy
  If a routing metric is chosen for any network N, and if N           constraints in Manets.
has maximal spanning tree with respect to the metric, then the
routing metric is monotonic                                               B. Proposed criterion
Theorem 3 (sufficiency of Boundedness and Monotonicity)                  Our goal is to select the metric to maximize network
  If a routing metric is chosen for any network N, and if N           throughput taking into account taking into account the key
has maximal spanning tree with respect to the metric, then the        constraints of MANET environment (mobility, energy). The
routing metric is monotonic.                                          idea behind the composite metric is that a cost function is
                                                                      computed locally at each node during the topology
                   IV. OUR IMPROVEMENT                                information dissemination during the flooding process.
                                                                         Once the network converges, each node runs a shortest path
   A. Presentation of the solution                                    algorithm based on the calculated composite metric to find the
   Our solution can be summarized as follows. Bandwidth is            optimal route to the destination. An underlying implication of
one of the most important factors required and requested by           this is that each node should also be able to measure or gather
customer’s applications. Mobility and energy are crucial              the information required. Bandwidth, mobility and remaining
problem in MANETs, and up to now, the majority of routing             energy information’s are available and could simply be
protocols have shown some weaknesses to face a high mobility          gathered from lower layers. This paper is mainly focused on
and poor energy resources in the network.                             solving the routing issues based on the assumption that an
   Our objective consists in positively manage the network            underlying mechanism is there to gather the necessary
bandwidth taking into account the constraints of energy and           information about the individual metrics.
mobility, in order to adapt and improve the performance of               We suggest the simple solutions already proposed in [7] can
manet routing protocol and prolog network life time.                  be used to get bandwidth. Mobility estimation will be based on
   Initially, we start by giving the results of comparing our         our lightweight proposed mobility measure cited [4-6] due to
approach based solely on mobility parameter. Thus we                  its simplicity and lightweight. Energy information is derived
evaluate the modified OLSR (Mob-OLSR) that uses our                   from the energy model used in NS2 simulator at MAC Layer
proposed mobility metric [4]. Mob-OLSR is then compared to            [4].
the standard version of the OLSR protocol (without QoS                   Individual metrics must be combined according to the
extension) and QOLSR (The well known OLSR QoS                         following dependencies:
extension for Manets).                                                    • Nodes with no energy must be rejected in the process of
   Simulations results conduct us to think to use mobility                  route discovery and maintenance
parameters to fulfil QoS requirements. So, we focus on                    • Nodes with a high degree of mobility should be avoided
maximizing the bandwidth based on the parameters of                         in the process of routes construction.
mobility. In this regard, two metrics are proposed. The first is          • Tolerate a slight decrease in throughput in order to
based on the sum criteria and the second is based on the                    maximize other performance parameters (delay,
product criteria.                                                           collisions, NRL)
   We have processed in the performance comparison between                • Nodes start with a maximum energy and bandwith
the OLSR protocol using the MPR standard algorithm, and                     ressources. The residual energy decreases over time
the two modified OLSR protocols: SUM-OLSR and PRD-                          depending on node’s states (transmitting/receiving, in
OLSR protocols. The SUM-OLSR protocol is related to the                     idle/transition mode, etc.).
sum criteria, and the PRD-OLSR protocol is related to the                Based on these results, the proposed relationship for the
product criteria. By the end we have eliminated the sum               composite metric is given below:
criteria for his hard cost in terms of PDR (comparing to
product critéria). However, it is important to mention that the
eliminated criteria (the sum) also perform well comparing to
QOLSR protocol.
   In a second step, and in order to maximize bandwidth while
taking into account the constraints of energy, a new
generalized metric is presented.
   The proposed metric (EN-OLSR) will be compared to
different proposed metrics so called PRD-OLSR and OLSR-




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                                                                                                ISSN 1947-5500
                                                       (IJCSIS) International Journal of Computer Science and Information Security,
                                                       Vol. 8, No. 1, April 2010




                                                                          starting from root, the metric is non-increasing. The metric
Where                                                                     relation is given by: met {m,W(i,j)}.
 BW : Available Bandwidth in kilobits per second
 E : residual energy of node (number in range 0 to 5; 0                      Given m is the metric of the root. It is evident that this
 refers no energy for node to perform)                                    meets the boundedness and that monotonicity conditions hold
                                                                          for the selected metric. The available bandwidth is always
   The constants K0, K1, K2, will be set by the administrator             positive, hence for any node located at distance “d” from the
 based on network nature. For example, in a very dynamic                  root W(i,j) would always be less than or equal to the metric
 environment, and to give more importance to the mobility of              value at the root. Since the bandwidth is always positive and
 nodes, we can fix K0 to 0, K1 to 1 and K2 to 10.                         greater than zero hence it satisfies the boundedness and
   Constant k3 is not null and is used to indicate if the                 monotonicity conditions.
 environment takes into account the energy or not. Thus, an               Mobility & energy:
 important value of K3 indicates that energy is important in
 the process of routing.                                                     The mobility metric represents the rate of changes in the
   Composite metric scales Bandwidth metric with following                neighbouring of a node at time t compared to the previous
 calculations:                                                            state at time t − ∆t . In a previous work [18], We define the
                 BW = 106 / available bandwidth                           mobility degree of a mobile node i at a time t by the following
   The proposed metric reflects a real dynamic environment                formula:
 where nodes have limited energy resources, and bandwidth                                    NodesOut( t )              NodesIn( t )
                                                                              M iλ ( t ) = λ                 + (1 − λ )              (7)
 constraints are crucial (streaming application). The idea                                   Nodes( t − ∆t )             Nodes( t )
 behind the proposed metric is that in Manets environments,                  Where:
 durable-stable link with optimal bandwidth should never be                   NodesIn( t ) : The number of nodes that joined the
 omitted.
                                                                          communication range of i during the interval [t − ∆t,t ] .
    C. Proprieties of the proposed metrics                                   NodesOut( t ) : The number of nodes that left the
                                                                          communication range of i during the interval [t − ∆t,t ] .
   In this subsection we prove that each of the individual
 metrics satisfies the conditions of houndness and monotonicity               Nodes( t ) : The number of nodes in the communication
 conditions then we prove the proposed metric.                            range of i at time t.
                                                                              λ : The mobility coefficient between 0 and 1 defined in
   Node and Link Available Bandwidth:                                     advance. For example, in an environment where the number
                                                                          of entrants is large relative to the number of leavers, we can
    The bandwidth metric represents the available bandwidth at            encourage entrants taking λ = 0.25
 the link. A simple technique proposed in [17], which                        Many simulations have been done for different values of λ
 computes available bandwidth based on throughput can be                  ( λ =0, 0.25, 0.5, 0.75, 1). Simulation result [4] shows that for
 used to measure the bandwidth on any given node (respect.                 λ =0.75 the network performs well (in term of delay, Packet
 link L(i,j)).                                                            delivery fraction and throughput). For this reason, we consider
    Available bandwith “ α ” for each node could be estimated              λ =0,75 in the rest of this work.
 by calculating the percentage of free time TL which is then
 multiplied by the maximum capacity of the medium Cmax as                 Let Wij =   M               be the edge weight on the link L(i,j). The
                                                                                          L (i, j )
 follows [17]:                                                            link mobility between two nodes A and B is defined as the
      α = TL * C max                                      (4)             average mobility of the involved nodes (see Figure 4), as
   Let Bav (i,j) represent available bandwidth of the link then,          showed in following equation:
                                                                                                    λ          λ
                                                                                                  M A (t ) + M B (t )
              Bav (i , j) = min{Bav (i ); Bav ( j )}
                                                                                λ
                                                           (5)                M L ( A,B ) =                                                        (8)
                                                                                                           2
   Where Bav (i ) is the available bandwidth of the node i
 Also let Wi,j be the edge weight on the link L(i,j). Wi,j can be
 estimated from the following relationship given below.
                          1                                               Figure 4. Link mobility estimation example: M L ( A; B ) = 45%
           Wi , j =                                          (6)             As node’s mobility reflects how likely it is to either corrupt
                      Bav (i, j )
                                                                          or drop data. It could be considered as reliability metrics [15].
   The condition of boundness implies that along any path




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                                                                                                            ISSN 1947-5500
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Because the reliability metric is bounded and strictly                        By exchanging Hello messages, every node is aware of its
monotonic, it may be sequenced with the partial metric while                  neighbor nodes and can simply compute its Cost-to-Forward
preserving boundedness and monotonicity.                                      value (i.e. to forward packet).
   Moreover, residual energy function is monotonic and                           The Cost-to-Forward function (F(i)) for each of the four
bounded its value decreases (depending on the state of the                    models can be defined as shown in figure 6.
node: transmission / reception, transition/sleep mode,etc.)                      To motivate the nodes to reveal their exact Cost-to-Forward
from a maximum value (ex 200) to 0. it also reflects how                      value during the cluster head election and the MPR selection,
likely it is to either corrupt or drop data. Consequently, it can             a reputation-based incentive mechanism using the VCG
be sequenced with the partial metric while preserving                         mechanism could be used [20]. The nodes participating
boundedness and monotonicity.                                                 truthfully to these processes see their reputation to increase.
                                                                                 Since the network services are offered according to the
  Energy consumption parameters are derived from the                          reputation of the nodes, they would benefit to participate
energy model defined in NS2 [19] as follows :                                 honestly.
Pt_consume= 1.320 (~ 3.2W drained for packet transmission);
                                                                                             V. SIMULATIONS AND RESULTS
Pr_consume= 0.8 (2.4W drained for reception); P_idle=0.07,
P_sleep =06; P_transition=0.5                                                    In this section we have compared the performance of the
                                                                              original OLSR protocol based on the MPR selection standard
The edge weight        E ij for the link L(i,j) (see figure 5) can be         algorithm, and the two modified OLSR protocols related to
estimated         from        the      following       relationship:          different proposed model: : bandwidth model (QOLSR) ,
Eij = Min ( E i , E j ) .                                                     mobility model (MobOLSR), sum_bandwidth-mobility Model
                                                                              (Sum-OLSR), prd_bandwidth-mobility model (prd-OLSR)
Where Ei : the remaining energy for the node i and             Ei =0          and bandwidth-energy-mobility model(EN-OLSR).
means that the node i have drained out its energy. Thus,
routing protocol should omit such node in the process of
learning routes.                                                                 A.   Performance metrics
                                                                                 For comparison process, we have used the most important
                                                                              metrics for evaluating performance of MANET routing
                                                                              protocols during simulation. These considered metrics are:
   Figure 5. Link energy estimation example: E L (i ; j ) = 200                  Normalized Routing Overhead (NRL): It represents the ratio
                                                                              of the control packets number propagated by every node in the
 To validate the robustness and efficiency of the proposed
                                                                              network to the data packets number received by the
Metrics , we use four models: bandwidth model , mobility
                                                                              destination nodes. This metric reflect the efficiency of the
model, sum_bandwidth-mobility Model, prd_bandwidth-
                                                                              implemented routing protocols in the network.
mobility model and bandwidth-energy-mobility model.
                                                                                 Packet Delivery Fraction (PDF): This is a total number of
                                                                              delivered data packets divided by total number of data packets
                                                                              transmitted by all nodes. This performance metric will give us
                                                                              an idea of how well the protocol is performing in terms of
                                                                              packet delivery by using different traffic models.
                                                                                 Average End-to-End delay (Avg-End-to-End): This is the
                                                                              average time delay for data packets from the source node to
                                                                              the destination node. This metric is calculated by subtracting
                                                             (9)
                                                                              ”time at which first packet was transmitted by source” from
                                                                              ”time at which first data packet arrived to destination”. This
                                                            (10)              includes all possible delays caused by buffering during route
                                                                              discovery latency, queuing at the interface queue,
                                                                              retransmission delays at the MAC layer, propagation and
                                                                              transfer times.
                                                            (11)
                                                                                 Collision: It represents the number of interfered packets
                                                                              during simulation time. It occurs when two or more stations
              Figure 6: the proposed metrics for QoS                          attempt to transmit a packet across the network at the same
                                                                              time. This is a common phenomenon in a shared medium .
 Metrics serves as Cost-to-Forward function. In OLSR,                         Packet collisions can result in the loss of packet integrity or
metrics will be used as criterion in MPR selection algorithm.                 can impede the performance of a network




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                                                                                                       ISSN 1947-5500
                                                      (IJCSIS) International Journal of Computer Science and Information Security,
                                                      Vol. 8, No. 1, April 2010




  Avg_throughput: is the average rate of successful message            ensure a good enhancement in terms of delay when compared
delivery over a communication channel. Throughput and                  to the original OLSR protocol for all maximum speeds.
quality-of-service (QoS) over multi-cell environments are two             Precisely, the QOLSR and MobOLSR protocols delay is
of the most challenging issues that must be addressed when             around 1.25 seconds (enhancement by 0.4s comparing to he
developing next generation wireless network standards                  original OLSR) with higher mobility rate (maximum speed
                                                                       equal to 140km/h) and decreases to almost 1.25 seconds
                                                                       (enhancement by 0.1sec comparing to he original OLSR) with
   B. Simulation environment
                                                                       static topology conditions.
   For simulating the original OLSR protocol and the modified             For the original OLSR protocol the delay gets more than
OLSR protocols related to our proposed criterions, we have             twice as large being almost 2.1 sec for high mobility and
used the OLSR protocol implementation which runs in version            surprisingly increasing to over 1.4 seconds when the mobility
2.33 of Network Simulator NS2 [19-22].                                 is decreased.
   We use a network consisting of 50 mobile nodes to simulate             For the intermediate speed (from 40m/s to 100m/s) a
a high-density network. These nodes are randomly moved in              lightweight difference between MobLSR and QOLSR is
an area of 800m by 600m according to the Random Waypoint               noticed (enhancement by 0.1sec for MobOLSR when
(RWP) mobility model [21]. Moreover, to simulate a high                compared to QOLSR for maximum speeds (0m/s and 30m/s))
dynamic environment (the worst case), we have consider the             . This allows us to conclude that MobOLSR performs well
RWP mobility model with a pause time equal to 0. nodes can             than QOLSR for intermediate speed. According to the
move arbitrarily with a maximum velocity of 140km/h. All               Figure7-b, the original OLSR and MobOLSR protocols ensure
simulations run for 100s.                                              in the whole the same packet delivery fraction for all
   A random distributed CBR (Constant Bit Rate) traffic                maximum speeds with a slight improvement for the original
model is used which allows every node in the network to be a           OLSR for all maximum speed.
potential traffic source and destination. The CBR packet size
is fixed at 512 bytes. The application agent is sending at a rate                     OLSR
                                                                                      QOLSR                    De lay
of 10 packets per second whenever a connection is made. All                           MOBOLSR

peer to peer connections are started at times uniformly                 2.5

distributed between 5s and 90s seconds. The total number of
connections and simulation time are 8 and 100s, respectively.
   For each presented sample point, 40 random mobility                          2
                                                                        delay (s)




scenarios are generated. The simulation results are thereafter
statistically presented by the mean of the performance metrics.
This reduces the chances that the observations are dominated            1.5


by a certain scenario which favors one protocol over another.
As we are interested in the case of high mobility (i.e. high link
status and topology changes) we have reduced the HELLO                          1
                                                                                         0        20      40            60      80        100
interval and TC interval at 0.5s and 3s, respectively, for quick                                           pause time(s)

updates of the neighbors and topology data bases.                                   Figure 7-a. Comparison of the three versions of the OLSR
                                                                                                   protocol in term of delay.
   C. Results and discussion                                              Indeed, it can be seen that the number of packets dropped
  To show how the modified versions of the OLSR protocol               along the path is quite similar for all maximum speed being
are more adapted to the link status and topology changes               approximately 45% at worst for the original OLSR and
comparing to the original OLSR protocol, we have made                  MobOLSR and 35% for QOLSR.
several performance comparison based on the five                          Moreover, the ratio is worse for a continuously changing
performance metrics cited in Section 5-A. Moreover, with the           network (i.e. high maximum speed) than for the static path
supposed configuration cited above, we have run simulations            conditions, because the number of link failures grows along
in different mobility levels by varying maximum speed of               with the mobility. However, it is interesting to notice that even
nodes between 0km/h (no mobility) to 140km/h (very high                with static topology conditions, sending nodes do not achieve
mobility) in steps of 10km/h. To maximize performances we              100% packet delivery but only 85%-89%. This clearly shows
have chosen the mobility coefficient equal to λ =0.75.                 the impact of the network congestion and packet interference
                                                                       as the load on the network increases. Moreover, when
a) Comparing MobOLSR to OLSR and QOLSR                                 comparing MobOLSR and original OLSR to QOLSR, QOLSR
  Figure 7-a shows that Mob-OLSR and QOLSR protocols                   protocol presents a remarkable degradation in PDF for all




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maximum speeds. This is because QOLSR does not take into                             maximum speed.
account the state of links in MPR selection process. In
                                                                                        Figure7-d illustrates the normalized routing load (NRL)
summary, we can say that the MobOLSR protocol is more
                                                                                     introduced into the network for the three versions of OLSR
adapted to all levels of mobility from 0m/s (no mobility) to
                                                                                     protocol, where the number of routing packets is normalized
40m/s (very high mobility).
                                                                                     against sent data packets. A fairly stable normalized control
              OLSR
              QOLSR                       Pdf                                        message overhead would be a desirable property when
              MOBOLSR
                                                                                     considering the performance as it would indicate that the
                                                                                     actual control overhead increases linearly with maximum
             90
                                                                                     speed of nodes due to the number of messages needed to
                                                                                     establish and maintain connection. The original OLSR
             75
                                                                                     protocol and MobOLSR protocol produces the lowest amount
                                                                                     of NRL when compared to QOLSR protocol during all
  rate (%)




             60
                                                                                     maximum speed values. Moreover, original OLSR and
                                                                                     MobOLSR protocol produce the sme routing load for all the
             45
                                                                                     maximum speed.

             30
                                                                                        In the worst case (at the maximum speed value equal to
                      0        20       40                60   80     100            40m/s), the NRL increases to 2.1% for QOLSR protocol and
                                             pause time
                                                                                     1.3% for the original OLSR. Precisely, comparing to QOLSR
    Figure 7-b. Comparison of the three versions of the OLSR                         protocol, the MobOLSR and original OLSR protocols produce
          protocol in terms of packet delivery fraction.                             twice less routing packets. This explains that our proposed
   Figure7-c, shows the average throughput for the three                             criterion based on mobility parameter request less routing
version of protocols. The original OLSR and MobOLSR                                  packets to establish and maintain routes in the network.
protocols ensure in the whole the same average throughput
                                                                                                    OLSR
for all maximum speeds being approximately 125 kbps at                                              QOLSR               NRL
                                                                                                    MOBOLSR
worst.
                                                                                                  2.5

   The ratio is worse for a continuously changing network
                                                                                                   2
than for the static conditions. Moreover, it is interesting to
notice that even with static topology conditions, the network
                                                                                                  1.5
average throughput does not reach the channel capacity
                                                                                       rate (%)




(5Mbps) but only 230 kbps. This clearly shows the impact of                                        1
the network congestion and packet interference as the load on
the network increases.                                                                            0.5


              OLSR
              QOLSR                 Avg Throughput                                                 0
              MOBOLSR                                                                                    0    20       40           60       80        100
                                                                                                                        pause time (s)

                                                                                      Figure 7-d. Comparison of the three versions of the OLSR protocol in term of
230                                                                                                                       NRL
                                                                                        Collision is a common phenomenon in a shared medium.
200
                                                                                     Packet collisions can result in the loss of packet integrity or
                                                                                     can impede the performance of a network especially qualtity of
170
                                                                                     service sensed by the end user. Interference and quality-of-
                                                                                     service (QoS) over multi-cell environments are two
                                                                                     challenging issues that must be addressed when developing
140
                                                                                     next generation wireless network standards.
110                                                                                    Figure 7-e, shows that the original OLSR produces the
                  0       20          40            60         80     100
                                       pause time (s)                                lowest amount of collision packet comparing to MobOLSR
    Figure 7-c. Comparison of the three versions of the OLSR                         and QOLSR. However, we can see that our proposed protocol
                 protocol in term of throughput.                                     MobOLSR ensures an enhancement by 56% comparing to
                                                                                     QOLSR, The well known OLSR QoS extension for Manets.
  Thus, QOLSR ensures an enhancement by 10kbps                                           The average number of collision packet for QOLSR (respct
comparing to MobOLSR and the original OLSR for all




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MobOLSR and the Original OLSR) is 30000 (respect 17000,                                                 OLSR
                                                                                                                                      Pdf
                                                                                                        QOLSR
and 11000) for all maximum speed.                                                                       Sum-OLSR
                                                                                                        Prd-MET

               OLSR                                                                                90
               QOLSR                     Collision
               MOBOLSR

                                                                                                   75
              35000


              30000                                                                                60

              25000

                                                                                                   45
   Nbre (#)




              20000


              15000
                                                                                                   30
              10000                                                                                           0       20         40         60          80        100
                                                                                                                                  paus e tim e
               5000
                                                                                                Figure 8-b. Comparison of the proposed versions of the OLSR protocol in terms
                  0                                                                                                               of delay
                          0        20         40                60        80      100
                                                   pause time

    Figure 7-e. Comparison of the three versions of the OLSR                                    However , we notice that Prd-OLSR performs well comparing
                  protocol in term of collision.                                                to MomOLSR and Sum-OLSR. This is because Prd-OLSR
                                                                                                select stable routes offering an optimal bandwidth. This is
b) Comparing Sum-OLSR and Prd-OLSR to QOLSR                                                     confirmed by the improvement seen in the PDF parameter.
                                                                                                   MobOLSR protocol produces the lowest amount of NRL
   Figure8-a illustrates the average end to end delay for the
                                                                                                when compared to Sum-OLSR and Prd-OLSR protocols
proposed protocols (Sum-OLSR and OLSR Met2 MOBOLSR
                                                                                                during all maximum speed values (figure8-d). Moreover, we
and QOLSR). Comparing to QOLSR, it is interesting to notice
                                                                                                notice that Sum-OLSR and Prd-OLSR protocols produce less
that our proposed protocols MOBOLSR and Prd-OLSR
                                                                                                amount of NRL compared to QOLSR for all the maximum
perform well in a dynamic topology (enhancement by 0.5 sec
                                                                                                speed.
for maximum speed 40m/s to 80m/s).
                                                                                                        OLSR
                                                                                                        QOLSR                Avg Throughput
   Furthermore, we can see that (figure8-b) Prd-OLSR                                                    Sum -OLSR
performs well in term of PDF, when compared to the other                                                Prd-OLSR

proposed protocol (Sum-OLSR MOBOLSR and QOLSR) for
all maximum speed. Precisely, Prd-OLSR gets more than                                            230

twice as large comparing to QOLSR.
                                                                                                 200
                OLSR
                                             Delay
                QOLSR
                Sum -OLSR
                                                                                                 170
                Prd-OLSR
 2,5
                                                                                                 140



     2                                                                                           110
                                                                                                          0          20         40          60         80         100
 delay




                                                                                                                                 pause tim e

 1,5                                                                                            Figure 8-c. Comparison of the proposed versions of the OLSR protocol in terms
                                                                                                                                of throughput


     1
                      0       20        40              60           80        100                This explains that our proposed criterion based on mobility
                                        pause tim e                                             parameter request less routing packets to establish and
                                                                                                maintain routes in the network.
Figure 8-a. Comparison of the proposed versions of the OLSR protocol in terms
                                  of delay.

  A lightweight degradation in average throughput for Prd-
OLSR protocol is shown in figure8-c comparing to QOLSR.




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        OLSR                                                                                   OLSR
                                     NRL                                                                                Collision
        QOLSR                                                                                  QOLSR
        Sum -OLSR                                                                              Sum-OLSR
        Prd-OLSR                                                                               Prd-OLSR
  2,5
                                                                                       35000

   2                                                                                   30000

                                                                                       25000
  1,5
                                                                                       20000
   1
                                                                                       15000

  0,5                                                                                  10000

                                                                                        5000
   0
           0         20         40          60         80         100                     0
                                 pause tim e                                                       0         20         40          60         80        100
                                                                                                                         pause tim e
Figure 8-d. Comparison of the proposed versions of the OLSR protocol in terms
                                  of NRL                                                        Figure 8-e. Comparison of the proposed versions: Collision

  Figure8-e, shows that the original QOLSR produces the                                  OLSR provides the worst delay when compared to the
highest amount of collision packet comparing to the others                            proposed protocols. Precisely, the QOLSR and ENOLSR
proposed protocols.                                                                   protocols delay is around 1.65 seconds (enhancement by
  The average number of collision packet for QOLSR (respct                            0.3sec comparing to the original OLSR) with higher mobility
Sum-OLSR and Prd-OLSR) is 33000 (respect 25000) for all                               rate (maximum speed equal to 140km/h) and decreases to
maximum speed.                                                                        almost 1.25 seconds (enhancement by 0.1sec comparing to he
                                                                                      original OLSR) with static topology conditions. This allows us
  QOLSR produces an interfered environment in comparison                              to conclude that ENOLSR and QOLSR protocols ensure in
with our proposed protocols.                                                          the whole the same delay. However, it is interesting to notice
                                                                                      that all of the proposed protocols perform well than the
  ENOLSR uses the composite metric with energy
                                                                                      original OLSR protocol in term of delay.
constraints, from figures 9-a we notice that the proposed
ENOLSR find a compromise between bandwidth, energy and                                  A tolerable degradation in throughput is shown for our
mobility. Our proposed protocol selects stable routes providing                          QOLSR protocol provides the worst amount of RNL when
an optimum bandwidth while prolonging the lifetime of the                             compared to the others protocols. ENOLSR ensures an
network.                                                                              optimal NRL. It exceeds the NRL induced by OLSR and
                                                                                      MobOLSR and performs QQLSR . In the worst case (at the
                                                                                      maximum speed value equal to 40m/s), the NRL increases to
                                                                                      2.1% for QOLSR protocol, 1.3% for the original OLSR and
                                                                                      1.6% for ENOLSR,MOBOLSR and Sum-OLSR&2.
                                                                                        In addition, QOLSR ensures the worst PDF when compared
                                                                                      to the proposed protocols. An enhancement of 10% (resp
                                                                                      65%) when comparing to the Original OLSR protocol (resp
                                                                                      MobOLSR) is noticed.




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                       Figure 9-a. Performance comparison of the proposed versions of the OLSR protocol
                                                                private information revealed by the nodes. Selfish nodes can
                                                                misbehave and reveal false information if this behavior can
            OLSR
            QOLSR              Collision
            MOBOLSR                                                 save their energy and mobility degree. Moreover, one of the
            Prd-MET
            EN_OLSR                                                 main drawback of the classical OLSR is the malicious use of
    35000                                                           the broadcast TC messages A malicious compromised node
    30000
                                                                    can flood the network with fake TC messages.
                                                                       In order to increase the network lifetime, ENOLSR
    25000
                                                                    protocol use the node residual energy for the routing process
    20000
                                                                    (equation 1).
    15000                                                              In particular, for the following sub-sections, simulation run
    10000                                                           for 70 sec. Nodes are nodes moves randomly according to the
    5000
                                                                    Random Waypoint (RWP) mobility model [22]. Nodes
                                                                    velocity can reach 40m/s and the pause time is equal to 10sec.
       0
              0       20      40        60    80      100           We choose the energy model defined in NS to model nodes
                              paus e tim e                          energy consumption with (Pt_consume= 3 ; Pr_consume= 2;
Figure 9-b. Comparison of the ENOLSR protocol : collision
                                                                       P_idle=0.07, P_sleep =06; P_transition=0.5). Nodes
c) Prolonging network life time                                     initial energy is fixed to 160. For comparison, we measure the
                                                                    average energy for nodes in MPRSet for both OLSR and
   Selfish nodes can have a major impact on the performance         ENOLSR protocols.
of the solutions presented in Section VI. In some extreme
cases, these malicious nodes can cause serious denials of            Figure10 shows that energy consumption for original
service. The main problem comes from the fact that the MPRs         OLSR is linear. For the ENOLSR protocol network life time
and the optimal network paths are selected based some




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is prolonged. Indeed, for the original OLSR (resp ENOLSR)                        [2] P. Jacquet, P. Muhlethaler, A. Qayyum, A. Laouiti, L. Viennot, T.
                                                                                 Clauseen, "Optimized Link State Routing Protocol draft-ietf-manet-olsr-05.txt", INTERNET-
the first node dies after 17sec (resp 43s). This is because                      DRAFT, IETF MANET Working Group
during the normal process of selecting the MPR used by                           [3] T. Clausen (ed) and P. Jacquet (ed). “Optimized Link State Routing
standard OLSR protocol, the MPRs are selected based on the                       protocol (OLSR)”. RFC 3626 Experimental, October 2003.
parameters of reachebality (number of node they can reach in                     [4] K.oudidi, N.enneya, A. Loutfi, and M.Elkoutbi ’Mobilité et Routage
                                                                                 OLSR’, In Proceedings of African Conference on Research in Computer Science
level 2 : 2 hop neighbors). This induces a loss of energy for                    and Applied Mathematics CARI’08, pp. 646-657, October 2008, Rabat,
the nodes that have been elected several times as MPRs.                          Morocco.
              OLSR                                                               [5] A. Laouiti, P. Muhlethaler, A. Najid, E. Plakoo, ”Simulation Results of the
                               MPR_Set Avg_Residual_energy
              EN_OLSR                                                            OLSR Routing Protocol for Wireless Network”, 1st Mediterranean Ad-Hoc
                                                                                 Networks workshop (Med-Hoc-Net), Sardegna, Italy, 2002.
             180
                                                                                 [6] Nourddine Enneya, Kamal Oudidi, and Mohammed El Koutbi, "Enhancing
                                                                                 Delay in MANET Using OLSR Protocol", International Journal of Computer
             150
                                                                                 Science and Network Security IJCSNS", vol. 9, No. 1, 2009.
             120                                                                 [7] S-B. Lee, G-S. Ahn, X. Zhang, A.T. Campbell: INSIGNIA: An IP-Based
                                                                                 Quality of Service Framework for Mobile ad Hoc Networks, in Journal of
  ene rg y




              90                                                                 Parallel and Distributed Computing, n.60, pp. 374-406, 2000.
                                                                                 [8] Ying Ge Kunz, T. Lamont, L. ‘’Quality of service routing in ad-hoc
              60                                                                 networks using OLSR ‘’ Commun. Res. Centre, Ottawa, Ont., Canada;
                                                                                 Proceedings of the 36th Annual Hawaii International Conference on System
              30                                                                 Sciences, (HICSS’03).
                                                                                 [9] H. Badis, A. Munareto, K. A1 Agba, “QoS for Ad Hoc Networking Based
               0
                                                                                 on Multiple Metrics: Bandwidth and Delay” The Fifth IEEE International
                        0
                      27
                   5 .7 2
                   1 9.9
                   1 2.7
                   1 7.2
                   2 4.5
                   2 3.9
                   2 8.4
                   3 2.1
                   3 9.7
                   3 8.5
                   4 2.6
                   4 7.7
                   4 9.5
                   5 1.1
                   5 6.3
                      60
                   6 4.3




                                                                                 Conference on Mobile and Wireless Communications Networks (MWCN 2003)
                                                                                 Singapore - October, 2003
                                            time
                                                                                 [10] A. Munareto H. Badis, , K. AI Agba, “A Linl-state QoS Routing Protocol
         Figure 10 : MPRSet average residual energy for OLSR & ENOLSR            for Ad Hoc Networks” IEEE Conference on Mobile and Wireless
                                                                                 Communications Networks - MWCN 2002 Stockholm, Suede - September,
                                                                                 2002
                                                                                 [11] H. Badis and K. A. Agha. Internet draft draft-badis-manetqolsr- 01.txt:
Contribution appears clearly in an environment where the                         Quality of service for ad hoc Optimized Link State Routing Protocol (QOLSR).
nodes are intelligent and therefore does not revel true                          IETF MANET working group, September 2005.
information during the process of MPR selection for fear they                    [12] Nauman Aslam', William Phillips', William Robertson' composite metric
                                                                                 for quality of service routing in OLSR IEEE Conference 2004 - CCECE 2004-
lose their energy. So, the generalized criterion is designed to                  CCGEI 2004, Niagara Falls, May/mai 2004 –
cope with selfish nodes.                                                         [13] G.-S. Ahn, A. Campbell, A. Veres, L.-H. Sun, SWAN: Service
                                                                                 Differentiation in stateless Wireless Ad hoc Networks, INFOCOM’2002, New
                        VI. CONCLUSION AND FUTURE WORK                           York, New York, June 2002.


   Satisfying QoS requirements of the traffic in MANETs are
the key functions for transmission required for multimedia
applications. In this paper we have discussed the different
approaches used to provide QoS functionality in OLSR. Our
proposed metric is an attempt to make use of the available
resources and find the most optimal path based on multiple
metrics taking into account mobility and energy parameters.
The proposed metric selects the most stable path based on
mobility and energy information and QoS requirements on
bandwidth. Our proposed approaches are , totally or partially,
based on a mobility degree, residual energy and available
bandwidth that is quantified and evaluated in time by each
mobile node in the network.
   The proposed metric is expected to efficiently support real-
time multimedia traffic with different QoS requirements.
Simulation results show that the proposed protocols perform
well when compared to the QOLSR protocol which is a well
known OLSR QoS extension.
   The next step is to extend the proposed approaches to
Wireless Sensor Network routing protocols.

                                   REFERENCES
[1] IETF Mobile Ad-hoc Networking (manet) Working                 Group.
http://www.ietf.org/html.charters/manet-charter.html, 2004.




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                                                                                                                     ISSN 1947-5500
                                                                 (IJCSIS) International Journal of Computer Science and Information Security,
                                                                 Vol. 8, No. 1, April 2010




F.A. Kuipers, T. Korkmaz, M. Krunz, P. Van Mieghem, “Performance
evaluation of constraint-based path selection algorithms”, IEEE Network 18 (5)
(2004) 16–23
[14] S. Yilmaz, I. Matta, “Unicast Rotuing: Cost- Performance Tradeoffs”
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[15] G. Mohammad, S. Marco, “Maximizable Routing Metrics” IEEE/ACM
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[16] Cheikh SARR « De l’apport d’une évaluation précise des ressources de la
qualité de service des réseaux ad hoc basés sur IEEE802.11 » thèse de doctorat,
Institut Nationale des Sciences Appliquées de Lion, année 2007.
[17] A. Qayyum, L. Viennot and A. Laouiti. “Multipoint relaying for flooding
broadcast messages in mobile wireless networks”. In Proceedings of the Hawaii
International Conference on System Sciences (HICSS’02), Big Island, Hawaii,
January 2002.
[18] P. Anelli & E. Horlait «NS-2: Principes de conception et d'utilisation»
[19] Luzi Anderegg, Stephan Eidenbenz, “Ad hoc-VCG: a truthful and cost-
efficient routing protocol for mobile ad hoc networks with selfish agents”,
Proceedings of the 9th annual international conference on Mobile computing and
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[20] C. Bettstetter, G. Resta, and P. Santi. The Node Distribution of the
Random Waypoint Mobility Model for Wireless AdHoc Networks. IEEE
Transactions on Mobile Computing, 2(3):257–269, 2003.
[21] http://isi.edu/nsnam/ns

                            AUTHORS PROFILE
K.Oudidi Born in 1976 at Marrakech Morocco. Completed his B. Tech and M.
Tech. from Faculty of Sciences, My Ismail University - Errachidia in 1995 and
1999, respectively.
He is a Ph.D. Student at the University of Mohammed –V- National School of
Computer Science and Systems Analysis, His present field of interest is the
mobility and Qos routing in mobile ad hoc networks.




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