Modified Reverse AODV Routing
Algorithm using Route Stability in
Mobile Ad Hoc Networks
出處：Multitopic Conference,INMIC 2008. IEEE International
23-24 Dec. 2008 Page(s):255 - 259
作者：Zarei.M.；Faez.K. ；Nya.J.M.
任課教授：陳朝鈞 教授
學生：王志嘉、馬敏修
2009/12/30
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Outline
1.
2.
3.
4.
5.
6.
7.
Introduction
Ad-Hoc On Demand Distance Vector Routing
Protocol (AODV)
Reverse AODV algorithm (RAODV)
Modified Reverse Ad Hoc On Demand Distance
Vector(MRAODV) routing algorithm
Path Maintenance in MRAODV Routing
Algorithm
Simulation environment and results
Conclusions
Introduction (1/4)

Mobile ad hoc networks (MANET) consist of mobile platform
which communicate with each other through wireless links,
without any predetermined infrastructure.

If the source and destination nodes are not within the
transmission range of each other, then intermediate nodes would
be served as intermediate routers for the communication
between the two nodes.
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Introduction (2/4)

Moreover, mobile platform moves autonomously and
communicates via dynamically changing network.

Frequent change of the network topology is a main
challenge for many important topics
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Introduction (3/4)

In this paper,we consider the Ad-hoc On-Demand Distance
Vector Routing Protocol (AODV) that uses a demanddriven route establishment procedure.

We present an optimized version of this algorithm namely
Reverse AODV (RAODV).

We also present our routing protocol namely ModifiedRAODV (MRAODV) routing algorithm which it can be an
extension for RAODV.
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Introduction (4/4)
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The MRAODV routing algorithm can present good
performance for high mobility environments
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Ad-Hoc On Demand Distance Vector
Routing Protocol (AODV)

The Ad-hoc On-Demand Distance Vector outing Protocol
(AODV), is one of more common routing algorithm in ad
hoc networks and is based on the principle of discover
routes as needed.

AODV is a reactive algorithm that has some capabilities
such as; low processing, memory overhead, low network
utilization.

AODV routing algorithm is a prominent method for
building routes between network nodes.
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Ad-Hoc On Demand Distance Vector
Routing Protocol (AODV)

In AODV routing algorithm, the source node distributes a
route request packet at the time when a path is needed to the
destination node.

The source node initiates path discovery by broadcasting a
route request (RREQ) packet to its neighbors.
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Ad-Hoc On Demand Distance Vector
Routing Protocol (AODV)

The source node initiates path discovery by broadcasting a
route request (RREQ) packet to its neighbors. The RREQ
has following fields:

When the intermediate nodes receive route reply packet
(RREP), they update the forward route to the destination.
The route reply packet contains the following fields:

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Ad-Hoc On Demand Distance Vector
Routing Protocol (AODV)
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AODV protocol uses sequence numbers to determine the
timeliness of each packet and to prevent creation of loops.
AODV algorithm uses Route Error Message (RERR) route
failures and link failures propagated by a RERR from a
broken link to the source node of the corresponding route.
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Ad-Hoc On Demand Distance Vector
Routing Protocol (AODV)

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When the next hop link breaks, RERR packets are sent by
the starting node of the link to a set of neighboring nodes
that communicate over the broken link with the destination.
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Reverse AODV algorithm (RAODV)
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
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AODV routing algorithm builds a single loop-free path to
each other node on the network.
One disadvantage of AODV and most on-demand routing
protocols is a route reply message loss.
In route discovery phase, a route reply message (RREP) of
AODV obtains by the spending cost of flooding the entire
network or a partial area.
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Reverse AODV algorithm (RAODV)
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Route request packet in RAODV like AODV contain
following fields where, the source and destination addresses,
together with the broadcast ID, uniquely identify this RREQ
packet.
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Fig.1
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Reverse AODV algorithm (RAODV)
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When the destination node receives first route request
message, it generates reverse request (R-RREQ) message
and broadcasts it to neighbor nodes within transmission
range.
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Fig.2
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Reverse AODV algorithm (RAODV)
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When broadcasted reverse request packet arrives to
intermediate node, it will check for redundancy.
If it already received the same message, the message is
dropped, otherwise forwards to next nodes and when the
source node receives first reverse request message, then it
starts packet transmission, and late arrived R-RREQs are
saved for future use.
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Modified Reverse Ad Hoc On Demand Distance
Vector(MRAODV) routing algorithm


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RAODV routing algorithm increases performance and when
route fails occurs, the source node should select the best
route between available routs.
In this paper, we apply stability estimation method for rout
selection and to increase performance.
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Modified Reverse Ad Hoc On Demand Distance
Vector(MRAODV) routing algorithm


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RAODV algorithm solves this problem with selecting the
rout with minimum length in available set of routes that
have been already found.
In our proposed routing algorithm (MRAODV), when a
source node wants to communicate with a destination node,
first it broadcasts a RREQ packet.
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Modified Reverse Ad Hoc On Demand Distance
Vector(MRAODV) routing algorithm


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When destination receives a RREQ message, it broadcasts
R-RREQ message to find source node.
Each intermediate node which receives the R-RREQ
message, calculates route stability by equation (2) and the
route stability for each router is calculated by the following
equation.
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Modified Reverse Ad Hoc On Demand Distance
Vector(MRAODV) routing algorithm
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Modified Reverse Ad Hoc On Demand Distance
Vector(MRAODV) routing algorithm

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When source node receives R-RREQ, it will have multiple
routes to destination, so it selects stable route to destination
node. This process is illustrated in figure 3.
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Modified Reverse Ad Hoc On Demand Distance
Vector(MRAODV) routing algorithm


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According to this figure when one intermediate node moves
and causes link breaks then active route fails and a new
route must be selected.
In AODV, this process is done by initializing route
discovery procedure and in RAODV with selecting one
available route with minimum hop count.
In MRAODV, a new route with maximum stability is
selected between available routes.
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Path Maintenance in MRAODV Routing Algorithm
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When a route established between source and destination,
data transmission stage can be started.
In high mobility environments, link failure is a common
phenomenon which can be occurred.
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Path Maintenance in MRAODV Routing
Algorithm
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In both reverse RAODV and AODV routing algorithms,
source node selects new path based on shortest path method
and when mobile node moves quickly, these algorithms can
not show good performance.
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Simulation environment and results(1/2)


We used the ns-2 simulator to implement our routing
algorithm for comparison with RAODV and AODV
routing algorithms and to check the effectiveness of the
proposed method.
For evaluation of MRAODV routing algorithm
performance, we used two metrics:
1.
2.
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Packet Delivery Ratio
Control Packet Overhead
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Fig.4
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Fig.5
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Fig.6
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Conclusions(1/2)

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This paper presented a new protocol for mobile ad hoc
networks based on link stability and reverse packet
transmission. We changed RAODV routing algorithm and
made an optimized version of AODV.
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Conclusions(2/2)
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According to the simulation results, this algorithm is better
than other version of AODV algorithm.
We compared our method with AODV and RAODV routing
algorithm in average to end delay and packet delivery ratio .
We found that the presented protocol is suitable for high
mobility rate environment and it shows a good performance
when the number of nodes increases.
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