_______________________________________________________

Some part of this chapter appears in LNCS-CCIS, Springer Berlin Heidelberg, Vol.142,

Pages: 544-546, ISBN 978-3-642-19541-9 (Print), ISSN 1865-0929, 2011

102

Chapter 7

Design of Enhanced Quality of

Service Aware Routing Protocol

(EQARP)

7.1 Introduction

The link reliability and delay are very important parameters in the case of

multimedia data transmission in MANET. On demand link reliable and

delay-aware routing protocol is designed by including QoS constraints

(link reliability and delay). As and when the route to transmit the

information is computed, those QoS metrics are also computed

automatically and accordingly the routes are updated in the routing table.

Hence, the route selected will be a link reliable and delay-aware route.

Other routes which are not QoS-aware are discarded from the routing

table. Broadcasting in the route discovery and the route maintenance of

Ad Hoc On demand Distance Vector Routing Protocol provokes a high

number of unsuccessful packet deliveries from the source nodes to the

destination nodes. Studies have been undertaken to optimize the

rebroadcast focused on the route discovery of the AODV. In this work,

Lifetime Ratio (LR) of the active route for the intermediate node is

introduced to improve packet delivery ratio. Lifetime is one of the metrics

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for AODV that is stored in the routing table entry for intermediate nodes.

Lifetime [35] is an expiry time for an active route. It is also known as

deletion time for an invalid route. Initially, the static life time value from

AODV protocol is taken to find the route life time and based on that the

routing decisions are made. The proposed algorithm which takes static life

time is QoS-AODV. The static life time does not help where there is a

frequent change in the network topology and mobility is very high. So

there is a need for the dynamic computation of the link life time. Using

this, it is possible to store only reliable paths in the routing table. The

algorithm which computes multiple node disjoint paths, delay and link life

time dynamically, is designed i.e., EQARP (Enhanced Quality of Service

Aware Routing Protocol) and is compared with QoS-AODV. The proposed

EQARP protocol shows better performance for a highly dynamic network.

7.2 Life time in the original AODV

The life time is one of the parameters in the routing table of the original

AODV protocol as shown in the Figure 7.1.

Destination IP Address

Destination Sequence

Number

Next Hop

Hop count

Life Time

Figure 7.1: Original AODV Routing Table parameters

The route life time value is one of the most important parameters for

the design of an on demand Ad Hoc routing protocol. This parameter

determines the duration of the active path in the routing table to transmit

the packets reliably. The purpose of lifetime is to ensure that the routing

104

protocol does not attempt to discover a new route and/or delete an existing

active route within its lifetime.

Too long route lifetime may lead to retardation in updating the routing

table even though some paths are broken. This results in large routing

delays and control overhead from attempts to transmit across paths that

do not exist. Too short route lifetime may remove some active paths from

the routing table. This result in re-establishing the discovery process for

those paths again, causing large routing delay and traffic overhead due to

the new path search [135].

AODV route lifetime is either determined from the control packet, or it

is initialized to ACTIVE_ROUTE_TIMEOUT [40]. This means that from

the time the route is discovered, it is kept active up to predetermined

amount of time. In this protocol, ART (Active Route Timeout) is set to 3

seconds by default [2][27][136].

7.3 Computation of Route Life time ratio based on

static Lifetime and TTL

The formula for the Percentage Life Time Ratio (PLTR) is shown below:

PLTR =

*100 (7.1)

Life Time is the expiry time for the active route. It is also known as the

deletion time for an invalid route. TTL carries a time to live (TTL) value

that states for how many hops this message should be forwarded. Every

RREQ carries a time to live (TTL) value that specifies the number of times

this message should be re-broadcasted. This value is set to a predefined

value at the first transmission and increased at retransmissions. The

maximum value of the TTL is up to the Network diameter.

Retransmissions occur if no replies are received. TTL can be counter or

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timestamp. Here timestamp interpretation is used. TTL in milliseconds is

calculated as:

TTL(in ms) = 2*Node_Traversal_Time*TTL(in hops) (7.2)

This value is set to a predefined value at the first transmission and

increased at retransmissions. Retransmissions occur if no replies are

received. The default value of AODV Node_Traversal_Time is 40ms. The

TTL is multiplied by two to include the time for acknowledgement

message. The LTR multiplied by 100 gives the PLTR (percentage lifetime

ratio) for a route. If the PLTR is above 50%, then the intermediate node

allows the rebroadcasting of RREQ messages. Consider a sample network

to demonstrate the PLTR, shown in Figure 7.2:

Figure 7.2: Sample network taking A as the source and F as the

destination node

In this network having a path (A→B→C→F) from source node (A) to

destination node (F) with 3 hops distance and suppose the lifetime is

150ms then, PLTR can be computed as:

PLTR =

*100

= 62.5%

In this case, the path from node A to F can be taken as a QoS path and

stored in the routing table, since the PLTR>50%.

C

A B F

D E

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The lifetime is set to predetermined value as soon as the route is found.

TTL is computed based on the number of hops to reach to the particular

destination. The PLTR value should be greater than 50% to ensure that ,

the time in which route exist in that routing table must be at least half

more than the time required to traverse the nodes in that path.

7.3.1 Experimental Results

The performances of two on-demand routing protocols, viz. AODV and

QoS-AODV are compared using NS-2 simulation. The parameters used for

the simulation is shown in the Table 7.1.

Table 7.1: Simulation Parameters

Simulation time 200 seconds

Number of nodes 10,20,30,40,50,60,70,80,90,100

Map size 1000m X 1000m

Speed 10 m/s

Mobility Model Random Way Point

Traffic type Single CBR flow per node

Packet size 512 bytes

Number of Seeds 25

Propagation range 250m

Packet rate 10 packets/sec

Pause time 40 seconds

7.3.1.1 PDR vs. number of nodes at low mobility

Table 7.2 and Figure 7.3 show the PDR for each protocol versus number of

nodes for AODV and QoS-AODV protocols.

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Table 7.2: PDR versus No. of nodes at low mobility

Figure 7.3: PDR versus no. of

nodes at low mobility

7.3.1.2 PDR vs. number of nodes at high mobility

Table 7.3 and Figure 7.4 show the PDR for each protocol versus No. of

nodes by fixing the pause time to 10 seconds and the node speed to 25m/s.

Table 7.3: PDR versus no. of nodes at high mobility

Figure 7.4: PDR versus no. of

nodes at high mobility

7.3.2 Analysis of Simulation Results

The performance of AODV and QoS-AODV routing protocols is compared

and analyzed using NS-2.34 simulator. The QoS parameter PDR is

measured by varying the node density and the node speed.

0

20

40

60

80

100

120

PD

R (

in %

)

No. of nodes

PDR vs. number of nodes at low mobility

AODV

QoS-AODV

0

20

40

60

80

100

120

PD

R (

in %

)

No. of nodes

PDR vs. number of nodes at high mobility

AODV

QoS-AODV

PDR in %

No. of nodes AODV QoS-AODV

10 99.5 99.9

20 99.3 99.8

30 99 99.75

40 98.75 99.5

50 98 99.3

60 96 99

70 92 98.7

80 90 98.5

90 86.5 98.2

100 83 98

PDR in %

No. of nodes AODV QoS-AODV

10 95 99

20 92 98.5

30 89 97

40 85 94.5

50 83 92

60 80 87

70 75 84

80 69 80

90 63 79

100 60 73

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a) PDR vs. number of nodes at low mobility: It is observed that at

low mobility, the PDR of QoS-AODV is better in increasing the number

of nodes as compared to AODV. For example, at 80 nodes, the PDR of

AODV and QoS-AODV is 90% and 98.5% respectively. The reason is

due to reduction in routing overhead and keeping more active paths in

routing table.

b) PDR vs. number of nodes at high mobility: It is observed that

at high mobility, the PDR of QoS-AODV and AODV reduce rapidly. For

example, at 80 nodes, the PDR of AODV and QoS-AODV is 69% and

80% respectively.

Thus, from the experimental analysis, it is observed that the

performance of QoS-AODV routing protocol is better in terms of PDR

compared to AODV under low mobility situations. But the performance

degrades, as the mobility is increased. This is due to the static life time

enhancement to QoS-AODV.

7.4 Link life time based on Position and Direction

of movement

It is very difficult to determine the stability of the route based on the

lifetime value which is taken as a static, during route discovery process. In

Mobile Ad Hoc Networks, each node acts as a router. In a reactive

protocol, if a node does not know the QoS metrics of its neighbors it simply

broadcasts route request (RREQ) message to the neighboring nodes. Upon

receiving this RREQ packet, the neighboring nodes can get the QoS

metrics across their paths such as the position and movement information.

Using this information it is possible to make a routing decision regarding

whether the path is reliable or not.

In recent years, many routing algorithms were proposed for MANETs

that need the coordinates of nodes for routing process. In order to obtain

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this information, Global Positioning System (GPS) can be employed

[137][138]. The stability of the routing path can be calculated using

current and future position of nodes. Therefore, the best path is

mathematically determined which need not be a shortest path. Clearly, if

the routing process is accomplished without any consideration to the

movement of nodes and the stability of routing path, the links can be

easily broken.

The proposal by Shahram Jamali et al. [50], provides link life time

extension to an AODV. Due to the dynamic topology changes in MANETs

the links can be easily broken. The link life time must be dynamically

computed and using this parameter and using this it is possible to check

the stability of the link. This work also concludes that it is important to

find and set up a route with longer life time as possible [139].

7.4.1 Calculation of Link Life time (LLT)

The link life time prediction is a method which requires that each mobile

device be equipped with a GPS receiver for obtaining the longitude and

latitude. Using this geographical information and considering the

network area, map position of each node can be determined. For

calculating the nodes direction and speed, the position information of

them should be updated continuously [50]. The proposed method makes

use of dynamic route lifetime instead of taking a fixed route lifetime as

mentioned in the previous section.

The Figure 7.5 shows the two mobile nodes A and B with present

locations (xa1, ya1) and (xb1, yb1) respectively. These two nodes are

within the radio range r. The first node is moving with a constant speed

Va at an angle (direction) of Ɵa with respect to x axis. Similarly, second

node is moving with a constant speed Vb at an angle (direction) of Ɵb with

respect to x axis. As nodes are mobile, the future locations of nodes A and

B are (xa2, ya2) and (xb2, yb2) respectively after the time duration t.

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The future locations of mobile node A and B are calculated using the

following equations:

xa2(t) = xa1+ Va cosƟa t (7.3)

ya2(t) = ya1+ Va sinƟa t (7.4)

xb2(t) = xb1+ Vb cosƟb t (7.5)

yb2(t) = yb1+ Vb sinƟb t (7.6)

The distance S between mobile nodes A and B after time t is given by:

S= √ (7.7)

The mobile nodes A and B will be able to communicate with each other

as long as they will remain within the transmission range, r. So the

duration t = LLT, if S<=r. After solving equation 7.7 with s<=r and

considering t=LLT, we get

LLT √

(7.8)

where,

a = VacosƟa–Vb cosƟb , c = VasinƟa–Vb sinƟb

b = Xa–Xb , d = Ya–Yb

111

Figure 7.5: Mobile nodes A and B with current and future locations

7.4.2 Calculation of Route life time (RLT) based on

Position and direction of movement

Since a route consists of multiple links in series, it is said to be broken if

any single link among its links is broken, and thus, the lifetime of the

route becomes minimum lifetime of all links in this route [80]. Suppose a

route P consists of n links, the route P is said to be broken if any one of the

connections is broken because the corresponding two adjacent nodes move

out of each other’s communication range. The lifetime of route P or route

life time is expressed as the minimum value of the connections involved in

route P. Therefore, the RLT is equal to the minimum of LLTs among the

link life time LLT1, LLT2, and so on till the last link life time LLTn.

RLT = min (LLT1, LLT2,………, LLTn) (7.9)

The percentage route life time (PLTR) is computed using the following

equation:

PLTR =

*100 (7.10)

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The intermediate node gets the PLTR value for each path, which it

stores in its routing table. If the PLTR for any path is above 50% then the

intermediate node stores such routes in its routing table. Otherwise, it

removes such routes from the routing table.

7.5 Algorithm for Route discovery in EQARP

(Enhanced QoS Aware Routing Protocol) by

dynamically computing average time stamp and

link life time

Suppose n is the number of mobile nodes and N is the set of mobile nodes,

N={N1, N2,…..,Nn}. Assume that the node Ni seeks to find a path to node Nj

and Nt receives the RREQ packet, where Ni, Nj, Ntϵ N and 1<i, j, t<n and

i ≠ j.

1. At the source node Ni :

a) Calculate the time taken for the packet to reach the

destination using the formula: [ Algorithm:6.3]

Timetaken = receive time – send time

b) Check whether the concerned node has an entry in

the Routing Table

c) If no entry found in the Routing table then create the

RREQ packet with field values set as :

Source = Ni, Destination = Nj, TTL =1

LLT =PLTR=0, Velocity = direction = Coordinate

position =0

d) Send the RREQ packet to the neighboring node Nt

and compute the parameters LLT and TTL

2. If ( the neighboring Node Nt is the destination node Nj ) then

begin

a) Receive all the paths arriving to it for wait period T

113

b) Select the paths which are node disjoint among the

list of paths

c) For the selected paths compute the RLT by taking

minimum value of LLT for each path

d) Compute the parameters PLTR and Average delay at

the destinationNode using the following equations:

avgTimeTakenByPackets=totalTimeTakenByPackets/C

Percentage Life Time Ratio=RLT/TTL * 100

e) Store the Average delay and PLTR in the Routing

table for these paths

f) Generate the RREP packet for unicasting to the source

node for all the node disjoint paths selected and the

paths with PLTR>50

g) Store the paths in the Routing table of Source node

end

3. If ( the neighboring Node Nt has a route to the destination node )

then

begin

a) Compute RLT and PLTR

b) Send the RREP packet to the Source node having

PLTR>50

end

4. If ( the neighboring Node Nt is neither the destination nor

having route to node Nj ) then

begin

a) Compute the delay, LLT.

b) If (the delay>=average delay) then

Do not broadcast RREQ from there.

Else

begin

Update the parameters of RREQ packet.

Rebroadcast the RREQ.

114

end

end

5. Stop

7.6 Flowchart for Route discovery in EQARP

The figure 7.6 and 7.7 show the route discovery process and QoS metrics

computation in EQARP respectively.

YES

NO

YES NO

YES NO

NO

YES

Figure 7.6: Flowchart for EQARP Route Discovery Process

Whether the

intermediate node is

destination?

Forward RREQ message along

with LLT and TTL

Start

If an intermediate

node has an entry?

Store that path in routing table

Delay>Avg_delay?

Stop

Copy RREQ and

Rebroadcast

Discard RREQ

Start with new

Route discovery A

Receive all the paths and

select node disjoint

paths among them

Compute QoS metrics

Avg_delay and PLTR for

the selected paths

Compute Delay

A

PLTR>50%

?

Generate the RREP for QoS paths

115

Figure 7.7: Flowchart on Creating a Routing Path along with QoS metrics

computation

TTL=1, LLT=RLT=PLTR=0.0, C=0, Total_Timetaken=0.0, AvgTime=0.0

Increment the Counter C to keep track of number of times an entry is made to the

Routing table at every node and Compute the Time taken

Total_Timetaken+=Timetaken

PLTR = (RLT/TTL_in_Seconds)*100

TTL=TTL+1

vgTime=Total_Timetaken/C

Store the Metrics PLTR and AvgTime in Routing Table

Stop

While destination is not

reached

Compute LLT

Compute the RLT as minimum of LLTs for each path at destination

TTL_in_Seconds=TTL*2*Node_traversal_Time

Start

116

7.7 Modelling the network and simulation

parameters

The NS-2.34 is used to analyze the performance of AODV and the new

protocol EQARP. In the simulations the following three network scenarios

are taken: (1) a low density network with N = 25 nodes; (2) a medium sized

network with 25<N<=80 nodes; and (3) a high density network with

80<N<=150 nodes. The mobile nodes are placed randomly within a 1000 m

x 1000 m area. Radio propagation range for each node is 250m and

channel capacity is 11 Mbps. Each node moves in this area according to

the random waypoint mobility model, with a speed of 5m/sec (low),

15m/sec (medium) and 25m/sec (high). Similarly, the pause time values

are considered to be 10sec as low pause time, 40sec as medium pause time

and 80sec as high pause time. The two metrics End-to-End packet and

PDR were used for performance study of AODV and EQARP. The Table

7.4 shows the standard values of QoS metrics viz. PDR and End-to-End

delay.

Table 7.4: Standard QoS metric values

Standard QoS metric values

QoS Metrics Low Medium High

1. PDR <=95% >=96% and <98% >=98%

2. Delay <=50ms 51ms to 150ms >150ms

7.7.1 Experimental Results

The base protocol used to compare the performance of EQARP is the QoS-

AODV. The metrics used in comparing these two protocols are PDR and

End-to-End delay.

7.7.1.1 PDR vs. number of nodes at high mobility

Table 7.5 and Figure 7.8 show the PDR for each protocol versus speed by

fixing the pause time to 10 seconds and the node speed to 25m/s.

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Table 7.5: PDR vs. no. of nodes at high mobility

Figure 7.8: PDR vs. no. of nodes at

high mobility

7.7.1.2 Delay vs. No. of nodes at high mobility

Table 7.6 and Figure 7.9 show the Delay for each protocol versus speed by

fixing the pause time to 10 seconds and the node speed to 25m/s.

Table 7.6: Delay vs. No. of nodes at high mobility

Figure 7.9: Delay vs. no. of nodes

at high mobility

0

20

40

60

80

100

120

PD

R (

in %

)

No. of nodes

PDR vs. number of nodes

EQARP

QoS-AODV

0

50

100

150

200

250

Dela

y (

in m

s)

No. of nodes

Delay vs. number of nodes

EQARP

QoS-AODV

PDR in %

No.of

nodes

EQARP QoS-

AODV

10 99.8 99

20 99.5 98.5

30 99.2 97

40 98.5 94.5

50 98 92

60 97.6 87

70 96.8 84

80 96.2 80

90 95.8 79

100 95.2 73

Delay in ms

No.of

nodes

EQARP QoS-AODV

10 90 105

20 98 120

30 105 131

40 112 145

50 120 168

60 126 175

70 132 182

80 138 195

90 141 202

100 148 210

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7.7.2 Analysis of Simulation Results

The performance of QoS-AODV and EQARP routing protocols is compared

and analyzed using NS-2.34 simulator. The QoS metrics Average delay

and PDR is measured.

a) PDR comparison: It is observed that the PDR of EQARP is better

than QoS-AODV in increasing the mobility. For example, at 80

nodes, the PDR of QoS-AODV and EQARP is 80% and 96.5%

respectively. The reason behind this is EQARP has less routing

overhead.

b) Delay comparison: It is observed that the delay of EQARP is also

improved at high mobility situations. For example, at 80 nodes, the

Delay of QoS-AODV and EQARP is 195ms and 138ms respectively.

The reason behind this is route discovery latency of EQARP is less

than that of QoS-AODV.

7.8 Summary

The performance of the routing protocols AODV and QoS-AODV are

compared. The QoS-AODV is designed initially by taking delay and static

life time into consideration. The performance of QoS-AODV is better than

original AODV. But at high mobility, this QoS-AODV fails to perform in

terms of QoS metrics. Next, AODV is improved by computing the link life

time dynamically across every link. This parameter is very important for a

highly dynamic network where the link break and route failure occurs

more frequently. It is observed from the experimental analysis that the

proposed protocol EQARP, works better than QoS-AODV protocol for high

density and high mobility situations. The improvement in performance

EQARP is due to the usage of dynamic life time.