cluster based routing protocol for ad hoc networks

Dr. N.S.Yadav

Assoc.Prof.

www.nshubforum.com

Department of Computer Science & Engineering

Sri Balaji College of Engineering & Technology, Jaipur

Performance Evaluation of Cluster Based

Routing Protocol in Ad hoc Networks

1

http://www.nshubforum.com/

Contents 2

Introduction

Routing in mobile adhoc networks

Performance evaluation of CBRP

Conclusions and future scope

Introduction 3

mobile ad hoc network is a collection of mobile nodes that utilize multi-hop radio relaying and are capable of operating without any support from fixed infrastructure

Various authors defined MANET in many different ways and a more precise definition* may be taken as reference, which states it as:

“MANET is an autonomous system of mobile routers (and associated hosts) connected by wireless links - the union of which form an arbitrary graph. The routers are free to move randomly and organize themselves arbitrarily; thus, the network’s wireless topology may change rapidly and unpredictably. Such a network may operate in a stand-alone fashion, or may be connected to the larger Internet”.

*Joseph Macker and Scott Corson, “Mobile ad-hoc networks (manet)”, http://www.ietf.org/proceedings/01dec/183.htm, December 2001.

Characteristics of Ad Hoc Networks 4

The most salient characteristics which should be considered by

protocol designers were addressed within the MANET working

group, listed in RFC 2501 and are summarized here: Distributed Operation

Dynamic Topology

Multi Hop Communications

Changing Link Qualities

Dependence on Battery life

Applications 5

Military applications

Collaborative and distributed computing

Emergency operations

Wireless sensor networks

Hybrid wireless networks

Routing in mobile ad hoc networks 6

The routing protocol has two main functions:

Selection of routes for various source destination pair

The delivery of messages to their correct destination

Characteristics of routing protocols

7

fully distributed

adapt to frequent topology changes

loop-free and free from stale routes

utilize both unidirectional and bi-directional links

localized and involve minimum number of nodes

minimize the number of packet collisions

converge to optimal routes quickly

use scarce resources efficiently

utilize multiple routes

incorporate quality of service (QoS)

Routing classification 8

Routing Protocols for MANET

Based on Information Update

Mechanism Based on Topology

Reactive Flat Proactive Cluster Based

Based on Information Update Mechanism

9

Proactive or table- driven routing protocols

Every node maintains the network topology information in

the form of routing tables, example DSDV

Reactive or on- demand routing protocols

Maintain routes only if needed example DSR

Hybrid protocols

Combine the best features of the above two categories

example ZRP

Based on Topology 10

In a flat structure, all nodes in a network are at the same level

and have the same capability and responsibility. Flat structure

routing is simple and efficient for small networks. Example DSR

In cluster-based routing the nodes in the network are

dynamically organized into partitions called clusters and then

the clusters are aggregated again into larger partitions called

superclusters and so on. Example CBRP

Clustering in Ad hoc network 11

Dynamic routing plays an important role in the performance of a Mobile Ad Hoc Networks (MANET).

A flat structure exclusively based on proactive or reactive routing schemes cannot perform well in a large dynamic MANET

The communication overhead of proactive routing protocols is O(n2), where n is the total number of mobile terminals in a network.

For a reactive routing scheme, the disturbing RREQ (route request) and the considerable route setup delay become intolerable in the presence of both a large number of nodes and mobility.

Consequently, a hierarchical architecture (cluster- based) is essential for achieving a basic performance guarantee in a large-scale MANET.

Cluster Structure 12

CM

CM

CH

CM

CM

CM

CH

CH

GW

GW

GW

CM

GW

CH

Cluster member node

Gateway node

Cluster- Head node member node

Clustering in Ad hoc network 13

In a clustering scheme the nodes in a adhoc network are divided into

different virtual groups, and they are allocated to the cluster according to

some rules.

Under a cluster structure, mobile nodes may be assigned a different status

or function, such as clusterhead, clustergateway, or clustermember.

A clusterhead normally serves as a local coordinator for its cluster,

performing intra-cluster transmission arrangement, data forwarding, and so

on.

A clustergateway is a non-clusterhead node with inter-cluster links, so it

can access neighboring clusters and forward information between clusters.

A clustermember is usually called an ordinary node, which is a non-

clusterhead node without any inter-cluster links

Motivation 14

Clustering is important for a network to achieve scalability in presence

of a large number of mobile nodes and high mobility

However, constructing and maintaining a cluster structure usually

requires additional control overhead compared to a flat-based structure

in an ad hoc wireless network.

This additional control overhead involved in clustering is a key issue to

validate the effectiveness and scalability enhancement of a cluster

structure.

Contribution 15

A flat architecture based Dynamic Source Routing (DSR), and

cluster architecture based Cluster Based Routing Protocol (CBRP)

are evaluated and compared in terms of

packet delivery fraction,

normalized routing load,

average end to end delay,

channel utilization and

control overhead in terms of packets and bytes

by varying number of nodes per sq. km, traffic sources, mobility,

speed and network load. It is shown through results that CBRP is a

better routing protocol in the presence of large number of nodes,

increased network traffic and load.

DSR – Dynamic source routing 16

on-demand routing protocol designed to restrict the bandwidth

consumed by control packets by eliminating the periodic table-update

messages required in the table-driven approach.

beacon-less and hence does not require periodic hello packet.

When node S wants to send a packet to node D, but does not know a

route to D, node S initiates a route discovery.

Source node S floods Route Request (RREQ)

Each node appends own identifier when forwarding RREQ

Destination D on receiving first RREQ, sends a Route Reply (RREP)

RREP is sent on a route obtained by reversing the route appended to

received RREQ

If any link on a source route is broken, the source node is notified

using a route error RERR

CBRP - Cluster Based Routing Protocol 17

In CBRP 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.

Clusterheads communicate with each other through gateway

nodes.

Operation of CBRP 18

The operation of CBRP can be divided in three phases:

Cluster formation

Routing process

Cluster maintenance

Cluster Formation 19

At any time, a node is in one of the three states: a cluster member (CM), a cluster head (CH), or undecided (UNDECIDED).

When a node comes up, it enters the undecided state and broadcasts a Hello message.

When a cluster-head gets this hello message it responds with a triggered hello message immediately. When the undecided node gets this message, it sets its state to member.

If the undecided node times out, then it declares itself the cluster-head, if it has bi-directional link to some neighbor otherwise it remains in undecided state and repeats the process again.

20

A node in undecided state changes its status to one of the three states: CH, CM or

UNDECIDED as per the state transition diagram

UNDECIDED STATE

Receiving Hello from

non –CH member Times out

Receive Hello

from CH

Neighbor table

Update

u_timer

Is neighbour

table empty?

YES

Schedule new

u_timer

Send triggered

Hello as CH

Terminate u_timer

Neighbor table as CM

Update

NO

CH STATE CM STATE

21

When two clusterheads are within transmission range of each other, the one

satisfying the state transition diagram will continue in clusterhead CH state and

the other will give up its role as CH and acquire the status of cluster member

CM.

Receive Hello

from CH

Set c_timer

CH STATE

Receiving Hello from

non –CH member c_timer

Neighbor table

Update

expires

Is still in contention

with other CH?

NO YES

CM STATE

Send triggered

Hello as CH

Is

my_CH_ID <

Other CH_ID YES

Send triggered

hello as CM

NO

22

A node in cluster member CM state changes its status to one of the three states:

CH, CM or UNDECIDED as per the state transition diagram

Receive Hello

Schedule u_timer

CM STATE

Last head lost

NO

YES

CH STATE

Send triggered

Hello as CH

Is

my__ID <

any_other_ID

Update

neighbor table

UNDECIDED STATE

Routing process 23

The routing process works in two steps. First, it discovers a route from a source node S to a destination node D, afterwards it routes the packets.

On receiving the request a clusterhead checks to see if the destination is in its cluster.

When the destination receives the request packet, it replies back with the route that had been recorded in the request packet.

While forwarding the packet if a node detects a broken link it sends back an error message to the source and then uses local repair mechanism.

Comparison of DSR and CBRP

Parameter DSR CBRP

Routing structure Flat Cluster

Hello messages No Yes

Multiple routes Yes No

Critical nodes No Yes

Route maintained Route Cache Route table at cluster-Head

Routing metric Shortest path or next available in route

cache

First available route

Time complexity (route discovery) O (2D) O (2D)

Time complexity (route maintenance) O (2D) O (2d)

Communication complexity (route discovery) O (2N) O (2C)

Communication complexity (route maintenance) O (2N) O (2n)

Advantages Multiple routes, beacon less cluster heads exchange routing information

Disadvantages Scalability problem, large delays Cluster maintenance

Abbreviations:

D = Diameter of the network

N = Number of nodes in the Network

d = Diameter of affected area

C = Number of Clusters

n = Number of affected nodes

24

Simulation Parameters

Parameter Stage I Stage II Stage III Stage IV

Number of nodes 150 150 150 30,60,90,120,150

Traffic type CBR (UDP) CBR (UDP) CBR (UDP) CBR (UDP)

Traffic sources 30% of nodes

70% of nodes

30% of nodes

70% of nodes

10%,30%,50%,70%, 90% of

nodes

30% of nodes

70% of nodes

Simulation time 300s 300s 300s 300s

Simulation area 2000 m x 500 m 2000 m x 500 m 2000 m x 500 m 2000 m x 500 m

Transmission range 250 m 250 m 250 m 250 m

Node movement model Random waypoint Random waypoint Random waypoint Random waypoint

Propagation model Two ray ground Two ray ground Two ray ground Two ray ground

Data payload 512 bytes/packet 512 bytes/packet 512 bytes/packet 512 bytes/packet

Packet rate 4 packets/sec 2,4,6,8,10 packets/sec 4 packets/sec 4 packets/sec

Node pause time 0,60,120,180, 240,300 s 0s highest mobility

300 s lowest mobility

0s highest mobility


0s highest mobility


Speed 10 m/s 10 m/s 10 m/s 10 m/s

Bandwidth 2 Mb/s 2 Mb/s 2 Mb/s 2 Mb/s 25

Performance Metrics 26

Packet Delivery Fraction: The ratio of the data packets delivered to

the destinations to those generated by the sources.

Channel utilization capacity: This metric gives the fraction of

channel capacity used for data transmitted by the network and is

computed as

where PR is the number of data packets received by the destination

nodes, SZ is the size of the data packets, SET is simulation end time

and BW is the nominal channel bandwidth.

BWSET

SZPRCU

27

Average end-to-end delay: This includes all possible delays

caused by buffering during route discovery latency, queuing at

the interface queue, retransmission delays at the MAC, and

propagation and transfer times.

Normalized routing load: The number of routing packets

transmitted per data packet delivered at the destination.

Control Overhead: The total number of non data packets

transmitted by the protocol. It is an important measure for the

scalability of a protocol. If a protocol requires sending many

control packets, it will most likely cause congestion, collision,

data delay and increase energy consumption in larger networks.

SIMULATION RESULTS

28

Influence of node mobility 29

To observe the effect of node mobility on the performance of DSR

and CBRP for a network under different traffic scenarios a network

of 150 nodes is simulated over a network area of size 2000m × 500

m with parameters listed in Table in stage I and the simulation

results are presented in this section.

Packet Delivery Fraction

0

10

20

30

40

50

60

70

80

0 60 120 180 240 300

Pause time (sec)

Packet deliv

ery

fra

ctio

n (

%)

DSR

CBRP 0

5

10

15

20

25

30

35

40

45

0 60 120 180 240 300Pause time (sec)

Packet deliv

ery

fra

ctio

n (

%)

DSR

CBRP

30

(a) 30% sources (b) 70% sources

Packet delivery fraction as a function of Pause time and 30%, 70% traffic

sources.

Channel Utilization

0

2

4

6

8

10

12

14

0 60 120 180 240 300

Pause time (sec)

Channel u

tiliz

atio

n (

%)

DSR

CBRP 0

2

4

6

8

10

12

14

16

18

0 60 120 180 240 300

Pause time (sec)

Channel u

tiliz

atio

n (

%)

DSR

CBRP

31


Channel utilization as a function of Pause time and 30%, 70% traffic

sources.

Average End To End Delay

0

0.5

1

1.5

2

2.5

3

3.5

4

0 60 120 180 240 300

Pause time (sec)

avera

ge e

nd to e

nd d

ela

y (

sec)

DSR

CBRP 0

1

2

3

4

5

6

7

8

9

0 60 120 180 240 300

Pause time (sec)

avera

ge e

nd to e

nd d

ela

y (

sec)

DSR

CBRP

32


Average end to end delay as a function of Pause time and 30%, 70% traffic

sources.

Normalized Routing Load

0

1

2

3

4

5

6

7

8

0 60 120 180 240 300

Pause time (sec)

Norm

aliz

ed r

outin

g lo

ad

DSR

CBRP

0

2

4

6

8

10

12

14

16

18

20

0 60 120 180 240 300

Pause time (sec)

Norm

aliz

ed r

outin

g lo

ad

DSR

CBRP

33


Normalized routing load as a function of Pause time and 30%, 70% traffic

sources.

Control Overhead

0

10

20

30

40

50

60

70

80

90

0 60 120 180 240 300

Thousands

Pause time (sec)

Contr

ol o

verh

ead (

packets

)DSR

CBRP

0

20

40

60

80

100

120

140

160

180

0 60 120 180 240 300

Thousands

Pause time (sec)

Contr

ol o

verh

ead (

packets

)

DSR

CBRP

0

1

2

3

4

5

6

7

0 60 120 180 240 300

Millio

ns

Pause time (sec)

Contr

ol o

verh

ead (

Byte

s)

DSR

CBRP

0

2

4

6

8

10

12

14

0 60 120 180 240 300

Millio

ns

Pause time (sec)C

ontr

ol o

verh

ead (

Byte

s)

DSR

CBRP

34


Control Overhead as a function of Pause time and 30%, 70% traffic sources.

Influence of network load 35

In this section the results of the simulations carried out by varying

the number of packets transmitted per second from 2 to 10 with two

different pause times are presented separately with 30% and 70% of

the nodes forming the traffic.


0

20

40

60

80

100

120

2 4 6 8 10

Packets per sec

Packet deliv

ery

fra

ctio

n (

%)

DSR, p = 0s CBRP, p = 0sDSR, p = 300s CBRP, p = 300s

0

10

20

30

40

50

60

70

2 4 6 8 10

Packets per sec

Packet deliv

ery

fra

ctio

n (

%)


36


Packet delivery fraction as a function of load and 30%, 70% traffic sources.

Channel Utilization

0

2

4

6

8

10

12

14

16

18

2 4 6 8 10

Packets per sec

Channel u

tiliz

atio

n (

%)


0

2

4

6

8

10

12

14

16

18

20

2 4 6 8 10

Packets per sec

channel u

tiliz

atio

n (

%)


37


Channel utilization as a function of Load and 30%, 70% traffic sources.


0

1

2

3

4

5

6

2 4 6 8 10

Packets per sec

Avera

ge e

nd to e

nd d

ela

y (

sec)


0

1

2

3

4

5

6

7

8

9

10

2 4 6 8 10

Packets per sec

Avera

ge e

nd to e

nd d

ela

y (

sec)


38


Average end to end delay as a function of Load and 30%, 70% traffic sources.


0

1

2

3

4

5

6

7

8

9

10

2 4 6 8 10

Packets per sec

Norm

aliz

ed r

outin

g lo

ad


0

2

4

6

8

10

12

14

16

18

20

2 4 6 8 10

Packets per sec

Norm

aliz

ed r

outin

g lo

ad


39


Normalized routing load as a function of Load and 30%, 70% traffic sources.

Control Overhead

0

20

40

60

80

100

1 2 3 4 5

Thousands

Packets per sec

Contr

ol O

verh

ead


0

20

40

60

80

100

120

140

160

180

2 4 6 8 10

Thousands

Packets per sec

Contr

ol o

verh

ead


0

1

2

3

4

5

6

7

8

2 4 6 8 10

Millio

ns

Packets per sec

Contr

ol o

verh

ead (

byte

s)


0

2

4

6

8

10

12

14

2 4 6 8 10

Millio

ns

Packets per sec

Contr

ol o

verh

ead (

byte

s)


40


Control Overhead as a function of Load and 30%, 70% traffic sources.

Influence of traffic sources 41

To observe the effect of number of traffic sources on the

performance of DSR and CBRP for a network, in constantly

changing network topology and in static case, a network of 150

nodes is simulated over a network area of size 2000m × 500m with

parameters listed in Simulation Table in stage-III and the number of

nodes forming the traffic are increased from 15 to 135 in the step of

30 and the simulation results obtained are presented in this section.

Packet Delivery Fraction 42

0

20

40

60

80

100

120

15 45 75 105 135

Number of sources

Packet deliv

ery

fra

ctio

n (

%)


Packet delivery fraction as a function of Traffic sources in low and

high mobility scenarios.

Channel Utilization 43

0

2

4

6

8

10

12

14

16

15 45 75 105 135

Number of sources

Channel u

tiliz

atio

n (

%)


Channel utilization as a function of Traffic sources in low and high

mobility scenarios.


0

1

2

3

4

5

6

7

8

9

10

15 45 75 105 135

Number of sources

Avera

ge e

nd to e

nd d

ela

y (

sec)


44

Average end to end delay as a function of Traffic sources in low and



0

2

4

6

8

10

12

14

16

18

20

15 45 75 105 135

Number of sources

Norm

aliz

ed r

outin

g lo

ad


45

Normalized routing load as a function of Traffic sources in low and


Control Overhead

0

2

4

6

8

10

12

14

15 45 75 105 135

Millio

ns

Number of sources

Contr

ol o

verh

ead (

byte

s)


0

20

40

60

80

100

120

140

160

180

200

15 45 75 105 135

Thousands

Number of sources

Contr

ol o

verh

ead (

packets

)


46

Control Overhead load as a function of Traffic sources in low and


Influence of node density 47

In this section the results of the simulations carried out by varying

the number of nodes over the network area from 30 to 150 with two

different pause times are presented separately with 30% and 70% of

the nodes forming the traffic.


0

20

40

60

80

100

120

30 60 90 120 150

Number of nodes per sq. km

Packet deliv

ery

fra

ctio

n (

%)


0

10

20

30

40

50

60

70

80

30 60 90 120 150


Packet deliv

ery

fra

ctio

n (

%)


48


Packet delivery fraction as a function of number of nodes per sq. km. and

30%, 70% traffic sources.

Channel Utilization

0

2

4

6

8

10

12

14

16

30 60 90 120 150


Channel u

tiliz

atio

n (

%)


0

2

4

6

8

10

12

14

16

18

20

30 60 90 120 150


Channel u

tiliz

atio

n (

%)


49


Channel utilization as a function of number of nodes per sq. km. and



0

0.5

1

1.5

2

2.5

3

3.5

4

30 60 90 120 150


Avera

ge e

nd to e

nd d

ela

y (

sec)


0

1

2

3

4

5

6

7

8

9

30 60 90 120 150


Avera

ge e

nd to e

nd d

ela

y (

sec)


50


Average end to end delay as a function of number of nodes per sq. km. and



0

1

2

3

4

5

6

7

8

30 60 90 120 150


Norm

aliz

ed r

outin

g lo

ad


0

2

4

6

8

10

12

14

16

18

20

30 60 90 120 150


Norm

aliz

ed r

outin

g lo

ad


51


Normalized routing load as a function of number of nodes per sq. km. and


Control Overhead

0

10

20

30

40

50

60

70

80

90

30 60 90 120 150

Thousands


Contr

ol o

verh

ead (

packets

)DSR, p = 0s CBRP, p = 0sDSR, p = 300s CBRP, p = 300s

0

20

40

60

80

100

120

140

160

180

30 60 90 120 150

Thousands


Contr

ol o

verh

ead (

packets

)


0

1

2

3

4

5

6

7

30 60 90 120 150

Millio

ns


Contr

ol o

verh

ead (

byte

s)


0

2

4

6

8

10

12

14

30 60 90 120 150

Millio

ns

Number of nodes per sq. kmC

ontr

ol o

verh

ead (

byte

s)


52


Control Overhead as a function of number of nodes per sq. km. and 30%,

70% traffic sources.

Conclusions 53

DSR has a lower PDF than CBRP in high mobility (0s pause time)

scenarios and more or less same PDF in stationary (300s pause

time) scenarios. In high mobility scenarios, the PDF due to 30%

traffic sources is better than that due to 70% traffic sources. The

performance degradation in PDF is due to packet drops by the

routing algorithm after being failed to transfer data in the active

routes. The packet drops are due to network partitioning, link break,

collision and congestion in the ad hoc network.

54

CBRP has lower NRL than DSR in high mobility (0s pause time)

and a higher NRL in case of stationary (300s pause time) scenarios.

This is because CBRP only broadcasts route requests to cluster

heads. Gateway nodes receive the route requests as well but they

forward them to the next cluster-heads. This largely reduces the

route discovery packets which in turn reduces NRL. CBRP has a

better throughput than DSR in high mobility and stationary

scenarios with both traffic sources. This better throughput comes

from its cluster based structure which largely reduces network

traffic.

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