On the routing overhead in infrastructureless multihop wireless networks

ON THE ROUTING OVERHEAD IN
INFRASTRUCTURELESS MULTIHOP WIRELESS NETWORKS
Narendra Singh Yadav1
, Bhaskar P Deosarkar2
, Dr.R.P.Yadav3
Member IEEE, FIETE
1,2
Research Scholar, 3
Professor and Head
Department of Electronics and Communication Engineering,
Malaviya National Institute of Technology, Jaipur.
1
narensinghyadav@yahoo.com, 2
bhaskar44_nanded@yahoo.co.in, 3
rp_yadav@yahoo.com
ABSTRACT
Routing in infrastructureless multihop wireless networks
is a challenging task and has received a vast amount of
attention from researchers. This has lead to development
of many different routing protocols each having their own
superiorities and pitfalls making it very difficult to decide
on a better protocol under vulnerable scenarios in such
networks. In this paper the performance of three routing
protocols (DSR, AODV and CBRP) in terms of routing
overhead in bytes and in packets is presented under
growing density and varying mobility in different traffic
conditions. The simulation results show that CBRP
outperforms both DSR and AODV in all scenarios.
Index Terms —Wireless networks, routing protocol,
overhead, DSR, AODV, CBRP.
1. INTRODUCTION
In recent years growth in the user driven application
demand and technological advancement caused the
emergence of various wireless communication networks
which are broadly classified as infrastructured or
infrastructureless. The most important component of a
infrastructured wireless network is a base station which
provides the necessary communication to and from the
mobile units in its coverage area. If a communicating
mobile node moves from the coverage area of one base
station to another, the centralized administration
maintains the seamless communication by handing over
the responsibility to new base station. Typical examples
are WLANs and Mobile Cellular Networks. The
infrastructureless network utilizing multihop radio
relaying, capable of operating without any support from
fixed infrastructure, is a collection of mobile nodes
capable of cooperatively communicating with each other
without any centralized administration. Ad Hoc networks,
Sensor Networks are some of the examples.
The lack of centralized administration in
infrastructureless network makes the routing and resource
management task difficult and challenging. Several
routing protocols are proposed in the literature each
having their own advantages and disadvantages. These
protocols are classified based on underlying topology as
flat or hierarchical. In this paper the Dynamic source
routing protocol (DSR) and Ad Hoc On-demand Distance
Vector protocol (AODV) from flat architecture and
Cluster based Routing Protocol (CBRP) from hierarchical
architecture are investigated for routing overhead in bytes
and in packets under increasing node density and varying
mobility with different traffic sources.
The rest of the paper is organized as follows: Section
II discusses the related work. The routing protocols under
investigation are described in Section-III. Simulation
environment and results alongwith performance metric
are presented in Section-IV and Section-V concludes the
paper.
2. RELATED WORK
In this section the previous studies concerning routing
performance of infrastructureless wireless networks are
summarized. Node mobility is the main network
characteristic that reveals the vigilance of a routing
protocol to respond to network topology changes, and to
perform fast route establishment and recovery. The
number of nodes per unit area (node density) and number
of nodes communicating (traffic sources) simultaneously
are also the important factors affecting the performance of
the network. Most of the previous studies compare the
behavior of the protocols as a function of the node
mobility. More specifically, authors in [1] compare four
ad hoc routing protocols using a maximum number of 50
nodes but the traffic they assumed is relatively low. Their
mobility metric involves pause time: nodes move towards
a specific point and as soon as they reach at it, they stay
static for a certain amount of time called pause time.
Authors in [2] compare three routing protocols: AODV,
DSR and STAR. Their results are quite valuable but they
assume a relatively small geographical region. In [3]
authors have performed an extended performance
evaluation between DSR and AODV, in which the basic
mobility metric is the node pause time. This work
however does not include large-scale networks. DSR and
DSDV are compared to Cluster-based Routing Protocol
(CBRP) in [4] where simulations are performed with
pause times from 0 to 600 seconds and with nodes upto
150 only.

Majority of the previous work is based on performing
simulations for infrastructureless networks with a limited
number of nodes deployed in small geographical areas. In
this paper, a systematic comparison of the routing
protocols under varying node density is carried out to
observe their behavior and usefulness in dense networks
to judge their scalability.
3. PROTOCOLS UNDER CONSIDERATION
In this section DSR, AODV and CBRP routing protocols
considered for the study are described in brief.
3.1. Dynamic Source Routing (DSR)
DSR [5] is a beaconless demand driven routing protocol
designed for controlling the bandwidth consumed by
control packets in infrastructureless multihop wireless
networks with elimination of the periodic table update
messages required in table driven approaches. In this
protocol when a mobile (source) node has a packet to
send to some destination, it first checks its route cache to
see if there exists already a route to the destination. If
there exist an unexpired route to the destination it uses
this route for data transfer otherwise it initiates a route
discovery by broadcasting a route request packet
containing the destination address and the unique
identification number. The node receiving the route
request rebroadcast the packet to its neighbouring nodes
by adding its own address to the associated route record if
it is not forwarded already or if it is not a destination node
itself. A reply to route request is generated by the
destination or an intermediate node of which route cache
contains an unexpired route to the destination. Route
cache is populated with routes that can be extracted from
the information contained in data packets that get
forwarded.
The route maintenance is accomplished with the
use of route error packets and acknowledgements. While
operating in promiscuous mode the intermediate nodes
learn about the link breaks. Information so gained is used
by the route cache to deactivate maintained route.
3.2. Ad Hoc On-demand Distance Vector (AODV)
AODV [6] is also a demand driven routing protocol based
on DSDV [7] algorithm which employs destination
sequence numbers to identify the most recent path. When
a source node has a packet to send to some destination it
initiates a path discovery process by broadcasting a route
request packet to all the neighbouring nodes in its range
which then forward the request to their neighbours. This
process is repeated by all the intermediate nodes receiving
the route request till the intermediate node is either a
destination or has a fresh enough path to the destination.
The freshness of the path available at the intermediate
node is checked by comparing the sequence number in the
request packet to the number available at the node. While
forwarding the route request the intermediate nodes,
discarding the duplicate copies, record the address of the
neighbouring node from which it has received the first
copy of the route request along with its broadcast identity.
Upon receipt of route request the destination or an
intermediate node (with a fresh enough path to the
destination) sends a route reply along the reverse path. A
route discovery process is reinitiated by the source if it
receives a link failure error message propagated by the
node in the upstream of the path break.
3.3. Cluster Based Routing Protocol (CBRP)
In CBRP [8] the nodes of a wireless network are divided
into clusters. The diameter of a cluster is only two hops
and clusters can be disjoint or overlapping. Each cluster
elects one node as the clusterhead, responsible for the
routing process. The head of a cluster know the addresses
of its members. Clusterheads communicate with each
other through gateway nodes. A gateway is a node that
has two or more clusterheads as its neighbors when the
clusters are overlapping or at least one clusterhead and
another gateway node when the clusters are disjoint.
The routing process works in two steps. First, it
discovers a route from a source node to a destination
node, afterwards it routes the packets. When a source has
to send data to destination, it floods route request packets
(but only to the neighboring cluster-heads). On receiving
the request a clusterhead checks to see if the destination is
in its cluster. If yes, then it sends the request directly to
the destination else it sends it to all its adjacent cluster-
heads. The cluster-heads address is recorded in the packet
so a cluster-head discards a request packet that it has
already seen. When the destination receives the request
packet, it replies back with the route that had been
recorded in the request packet. If the source does not
receive a reply within a time period, it backs off
exponentially before trying to send route request again. In
CBRP, routing is done using source routing. It also uses
route shortening that is on receiving a source route
packet, the node tries to find the farthest node in the route
that is its neighbor and sends the packet to that node thus
reducing the route. While forwarding the packet if a node
detects a broken link it sends back an error message to the
source and uses local repair mechanism.
4. SIMULATION AND RESULTS
4.1. Simulation model
Network Simulator2 [9] is used for the simulations. The
traffic sources are CBR. The source-destination pairs are
spread randomly over the network. The node movement
generator of ns-2 is used to generate node movement
scenarios. The movement generator takes the number of
nodes, pause time, maximum speed, field configuration
and simulation time as input parameters. The propagation
model is the two ray ground model. Simulations consist of
two stages. In stage1 simulations are carried out by
varying the mobility and in stage2 by varying the node
density. The simulation parameters used are shown in
table 1. Several runs of each scenario are simulated for
enough time to reach and collect the desired data at steady
state to obtain statistically confident averages.

Table 1. Simulation parameters
Parameters Stage 1 Stage 2
Network size 300 50, 100, 150, 200,
250 and 300 nodes
Area 2000m x 500m
Traffic model CBR
Traffic sources 30% and 70%
Packet size 512 bytes
Packet rate 4 packets/s
Max. speed 20m/s
Transmission
range
250m
Bandwidth 2 Mb/s
Node movement
model
Random way point
Simulation Time 100 s
Pause time 0, 20, 40, 60, 80,
100 sec.
20 sec.
4.2. Performance Metric
The protocol with large routing overhead increases the
probability of packet collisions resulting increased
latency. Hence routing overhead is an important
performance metric. The total number of routing packets
transmitted during the simulations and the corresponding
total number of bytes transported in these packets gives
routing overhead in packets and in bytes respectively. So
in order to compare the performance of cluster
architecture based CBRP with the flat architecture based
DSR and AODV this work is focused on the routing
overhead in packets and in bytes as performance metric
for evaluation.
4.3. Results
Following graphs show performance comparison of three
protocols used in this study. The routing overhead in
packets as well as in bytes with 30% and 70% traffic
sources under different mobility conditions is shown in
Fig. 1-4.
0
10
20
30
40
50
60
70
0 20 40 60 80 100
Thousands
Pause time (s)
Routingoverhead(packets)
AODV
DSR
CBRP
Figure 1. Routing overhead in packets with 30 % traffic sources
It is clear from Fig. 1 that in a low traffic in
highly dynamic scenario DSR is better than AODV in
terms of routing overhead (in packets) and in moderate
mobility (pause time 30-70 sec.) AODV is better to DSR
but CBRP outperforms DSR and AODV in both the
scenarios.
0
20
40
60
80
100
120
140
160
180
0 20 40 60 80 100
Thousands
Pause time (s)
AODV
DSR
CBRP
With the increase in traffic in high to moderate
mobility conditions AODV outperforms DSR and in both
the situations performance of CBRP is better as shown in
Fig.2. As system approaches to steady state DSR
outperforms both AODV and CBRP as shown in Fig.1
and Fig. 2.
0
1
2
3
4
5
6
0 20 40 60 80 100
Millions
Pause time (s)
Routingoverhead(bytes)
AODV
DSR
CBRP
Figure 3. Routing overhead in bytes with 30 % traffic sources
0
5
10
15
20
0 20 40 60 80 100
Millions
Pause time (s)
AODV
DSR
CBRP
Fig.3 and Fig.4 show that in highly dynamic
scenario CBRP is better to DSR and AODV both in terms

of routing overhead (in bytes) and in moderate to low
mobility AODV is better to DSR and CBRP both.
The routing overhead in packets as well as in
bytes with 30% and 70% traffic sources with different
node densities is shown in Fig. 5-8.
0
10
20
30
40
50
60
50 100 150 200 250 300
Thousands
Number of nodes per sq. km
AODV
DSR
CBRP
0
20
40
60
80
100
120
140
160
180
50 100 150 200 250 300
Thousands
AODV
DSR
CBRP
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
50 100 150 200 250 300
Millions
AODV
DSR
CBRP
Fig. 5-8 show that for low traffic DSR is
comparatively better to AODV and in high traffic with
number of nodes more than 150 per sq. km. AODV
performs better to DSR in terms of overhead in packets
and bytes both and performance of CBRP is much better
in both the traffic conditions.
0
2
4
6
8
10
12
14
16
50 100 150 200 250 300
Millions
AODV
DSR
CBRP
5. CONCLUSION AND FUTURE SCOPE
In this paper three routing protocols DSR, AODV
and CBRP are compared on the basis of routing overhead
in terms of packets and in terms of bytes as the
performance metric. It is clear from simulation results
that CBRP is a better routing protocol for
infrastructureless multihop wireless networks.
Fluctuations in the performance of DSR and AODV
under different scenarios justify the comparison of CBRP
with DSR and AODV. The results show the need of a
better routing mechanism for scaling the network.
6. REFERENCES
[1] Broch, D. A. Maltz, D. B. Johnson, Y. C. Hu, and J.
Jetcheva “A Performance Comparison of Multi-Hop Wireless
Ad Hoc Network Routing Protocols”, In Proc. of the
ACM/IEEE MobiCom, October 1998.
[2] C Hong Jiang, J. J. Garcia-Luna-Aceves, “Performance
Comparison of Three Routing Protocols for Ad Hoc Networks”,
In Proc. of the IEEE ICCN 2001,2001.
[3] S. R. Das, C. E. Perkins, and E. M. Royer. Performance
Comparison of Two On-demand Routing Protocols for Ad Hoc
Networks. Proceedings of the IEEE Conference on Computer
Communications (INFOCOM), Tel Aviv, Israel, March 2000,
pp. 3-12,
[4] Mingliang Jiang, “CBRP: A Cluster-based routing
protocol for mobile ad hoc networks”,
www.comp.nus.edu.sg/~tayyc/cbrp/hon.ppt
[5] D.Johnson, D.Maltz, Y.Ho, “The dynamic source routing
protocol for mobile ad hoc networks”, IETF Manet working
group, Internet RFC 2026.
[6] C. E. Perkins and E. M. Royer, “Ad Hoc On-Demand
Distance Vector Routing,” Proceedings of IEEE Workshop on
Mobile Computing Systems and Applications 1999, February
1999, pp. 90-100.
[7] C. E. Perkins and P. Bhagwat, “Highly Dynamic
Destination-Sequenced Distance-Vector Routing (DSDV) for
Mobile Computers,” in Proceedings of ACM SIGCOMM 1994,
August 1994, pp. 234-244.
[8] Mingliang Jiang, Jinyang Li and Y.C.Tay, “Cluster Based
Routing Protocol”, August 1999 IETF Draft.
http://www.ietf.org/internet-drafts/draft-ietf-manetcbrp-spec-
01.txt
[9] K. Fall and K. Vardhan, The Network Simulator (ns-2).
Available: http://www.isi.edu/nsnam/ns

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