QoS Aware Routing Protocol to Improve Packet Transmission in Shadow-Fading Environment for Mobile Ad Hoc Networks

doi:10.4236/cn.2013.53B2110

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Communications and Network, 2013, 5, 611-617

http://dx.doi.org/10.4236/cn.2013.53B2110 Published Online September 2013 (http://www.scirp.org/journal/cn)

QoS Aware Routing Protocol to Improve Packet

Transmission in Shadow-Fading Environment for Mobile

Ad Hoc Netw ork s

T. Sangeetha1,2, K. K. Venk atesh1,2, Rajesh1,2, M. S. K. Manikandan1,3

1Department of Electronics and Communication Engineering, Madurai, India

2SACS MAVMM Engineering College, Madurai, India

3Thiagarajar College of Engineering, Madurai, India

Email: [email protected], [email protected], smartrajesh9@gmail.com, [email protected]

Received July 2013

ABSTRACT

In Shadow-Fading model, it is difficult to achiev e higher Packet Delivery Ratio (PDR) due to the effects of large scale

fading. The main goal of this paper is to improve the PDR in Shadow-Fading environment. To achieve this objective a

protocol has been proposed that discovers backup routes for active sessions. These backup routes salvage the packets of

active session in case of active route failure. It is found by research that proactively maintaining backup routes for ac-

tive sessions can noticeably improve the PDR in Shadow-Fading environment. This protocol has been implemented

with a mechanism of having backup routes and simulations have been conducted by using both node disjoint paths and

link disjoint paths. Comparisons have been made between new protocol as well as AODV protocol. Simulation has been

carried out using Network Simulator 2 (NS2) and the results show that the proposed QoSAR protocol exhibits higher

PDR than AODV pro toco l in S hadow-fading environment.

Keywords: Shadow-Fading Model ; Adhoc On Demand Distance Vector Routing (AODV); Backup Routes; Node

Disjoint Paths; Link Disjoint Paths; Packet Delivery Ratio (PDR); Quality of Service Aware Routing

(QoSAR)

1. Introduction

In Mobile Ad h oc Netwo rks (MANE Ts), the prov ision of

Quality of Service (QoS) guarantees is much more chal-

lenging than in wireline networks, mainly due to node

mobility, multihop communications, contention for chan-

nel access, and a lack of central coordination. QoS guar-

antees are required by most multimedia and other time or

error sensitive applications. The difficulties in the provi-

sion of such guarantees have limited the usefulness of

MANETs. The QoS routing protocol is an integral part of

any QoS solution since its function is to discover which

nodes, if any, are able to serve applications’ requirements.

Consequently, it also plays a crucial role in data session

admission control.

MANET applications are nowadays used in military

and in emergencies, entertainments and outdoor industry

environments where centralized administration is diffi-

cult and costly to install [1]. Two nodes can communi-

cate if they are within each other’s radio range, otherwise,

routers if they are out of range, thereby it becomes mul-

tipath routing. These networks have several salient fea-

tures like rapid exploitation, robustness, flexibility, in-

trinsic mobility support, highly dynamic network topol-

ogy, the limited battery power of mobile devices, limited

capacity and asymmetric or unidirectional lin ks [2].

Routing has always been one of the key challenges in

Mobile Adhoc Networks and the challenge become more

difficult when the network size increases [5]. Man y multi

path routing protocols have been proposed for Ad Hoc

Networks [3]. The routing protocols mainly are either ta-

ble-driven (Proactive) or on-demand (reactive) routing

protocols. Many hybrid routing protocols having the com-

bination of functionality of both proactive as well as reac-

tive routing protocol are also proposed. The proactive

routing protocols periodically update the routing tables.

When there is a request to forward message the routes

are available in the routing table. On the contrary reac-

tive routing search the route when there is a request for it.

In the route search operation the reactive routing proto-

cols, find multiple paths for the same source and destina-

tion pair. One out of these multiple paths is selected to

forward messages to the destination.

The basic idea of On-Demand routing protocol is to

T. Sangeetha ET AL.

612

search route when it is required. Due to the mobility

characteristic of MANET nodes and Dynamic Topology

of the network, there are always multiple paths available

between the sources to destination pair. The On Demand

routing mechanism suggests using the route that is con-

sidered best according to the required Quality of Service

for the transmission, as in [3] hop count, is th e parameter

for selecting a route. Once the best route out of searched

route is chosen, the other routes are not given any con-

siderations. But maintaining information about these ad-

ditional routes will be more advantageous [2-4]. These

additional routes can be used as backup routes in the

events of link failures. In our paper the route failure can

be overcome by disjointness for shadow fading environ-

ments.

This paper mainly focuses on the idea of finding mul-

tiple paths (Multi-path) using Node Disjoint and Link

Disjoint paths to improve Packet Delivery Ratio (PDR)

of the network in Shadow fading environments. In addi-

tion to this, the study also targets to evaluate the perfor-

mances of AODV and QoS Aware Routing (QOSAR)

protocols based on PDR and throughput. The organiza-

tion of the rest of the paper is as follows. Section 2 QoS

routing challenges in MANET. Section 3 briefs about the

related work. Section 4 presents the discussion about pro-

posed routing protocols and in Section 5 Result and Dis-

cussion.

2. QoS Routing Challenges In MANET

The design of efficient routing protocols is a critical issue

for both wired and wireless networks. QoS-Aware Routing

(QoSAR) protocols are facing the following design is-

sues and constraints. These issues and constraints must

be kept in mind while designing these protocols.

2.1. Node Mobility

A MANET consists of mobile nodes. Nodes form the

network only when they are in the communication range

of each other. If they move out of range, link between the

two nodes is broken. At times, f ailure of a single link can

lead to the major network partitioning. Hence, mobility

of the nodes is a major challenging issue for a stable

network. Also, failure of certain links results in routing

decisions to be made again.

2.2. Lack of Centralized Control

The advantage of an ad-hoc network is that it is formed

spontaneously without fixed architecture. Participant nodes

or members can change their positions dynamically and

can join or leave the network independently. Due to this

nature of mobile ad-hoc networks it is difficult to pr ovide

centralized control. Th us it is difficult to achieve efficient

and fair Medium Access Control (MAC). Thu s those com-

munication protocols are preferred which utilize only lo-

cally available states and operate in a completely distri-

buted manner [6]. This increases complexity and an al-

gorithm’s overheads, as information about the participant

nodes must be collected efficiently. There is no central

entity to collect resour ce state information and admission

decisions. Instead of central administration, nodes must

make decisions based on available network resources,

which may lead to potential inaccuracies. Due to lack of

infrastructure the control and management of the network

is distributed among the nodes.

2.3. The Unreliable Wireless Channels

Due to interference from the other transmissions, mul-

ti-path fading and shadowing effects the received signal

are flat to bit errors. Such errors may lead to packets be-

ing not decidable. However, persistent packet error can

result in link failure, leading to re-routing, increased pack-

et delay and cong estion and packet dropping [7 ].

2.4. Multiple Paths

To send data from a source to destination, a path has to

be found beforehand. If a single path is established, send-

ing all the traffic on it will deplete all the nodes faster.

Also, in case of path failure, alternate path ac ts as a back-

up path. Thus, establishing multiple paths aids not only

in traffic engineering but also prevents faster network

degradation.

2.5. Node-Disjoint Paths

Multiple paths between the two nodes can be any link

disjoint or node disjoint. Multiple link disjoint paths may

have one node common among more than one path. Thus,

traffic load on this node will be much higher than the

other nodes of the paths. As a result, this node tends to

die much earlier than the other nodes, primary to the paths

to break down much earlier. Thus, the presence of node

disjoint paths prolongs the network lifetime by reducing

the energy fall rate of a particular node [8-9].

3. Related Works

This section briefs about the research work on the idea of

mul ti-path routing in M obile Ad hoc ne t works.

3.1. Ad Hoc On-Demand Distance Vector

Routing

In this paper titled “Ad Hoc On-Demand Distance V ector

Routing”, Feb- 1999, the authors C.E. Perkins and E.M.

Royer have presented a distance vector algorithm that is

suitable for use with ad-hoc networks. In AODV each

Mobile Host operates as a specialized router, and routes

are obtained as needed (i.e., on-demand) with little or no

T. Sangeetha ET AL.

613

reliance on peri odic a dverti sem ents . Their sim ulati on shows

that on-demand route establishment with AODV is quick

i.e., and accurate. AODV is a reactive routing protocol,

meaning that it provides a route to a destination only on

demand. Because AODV does not require global period-

ic routing advertisements, the demand on the overall

available bandwidth to the mobile nodes is substantially

less than in those protocols that do necessitate such ad-

vertisements.

The main difference between AODV and DSR [5,11]

stems out from the fact that DSR uses source routing in

which data packet carries the complete path to be tra-

versed. In AODV, the source node and the intermediate

packet nodes store the next hop information correspond-

ing to each flow for data packet transmission. In this

protocol, the source node floods the Route Request pack-

et in the network when a route is not available for the

desired destination. When an intermediate node receives

a request for route, it either forwards the request or pre-

pares a reply for that route if it has a valid route to the

destination. The validity of a route at the intermediate

node is determined by comparing the sequence number at

the intermediate node with the destination sequence num-

ber in the Route Request packet. It may thus obtain mul-

tiple routes to different destinations from a single Route

Request. Multiple Route Reply packets in response to a

single Route Request packet lead to heavy control over-

head. AODV avoids the counting-to-infinity problem of

other distance-vector protocols by using sequence num-

bers on route updates. AODV has the ability for both

unicast and multicast routing. But considering this case

the AODV protocol not perform well in shadow fading

environments its proved in our simulations.

3.2. QoS Routing Solutions

In this paper titled “A Survey of QoS routing solutions

for Mobile Ad Hoc Networks”, Apr-June 2007 the au-

thors L. Hanzo II and R. Tafazolli have presented a QoS

routing solutions that is suitable for use with ad-hoc

networks [10,13].

This paper offers an up-to-date survey of most major

contributions to the pool of QoS routing solutions for

MANETs published. It includes a thorough overview of

QoS routing metrics, bandwidth, factors affecting per-

formance and classify the protocols found in the litera-

ture. The aim of MAC protocol was to provide a basic

best-effort level of service to ensure network operation in

the face of an unpredictable and shared wireless commu-

nication medium and to maintain a network topology

view and routes in the face of failing links and mobile

devices. QoS routing protocols play a major part in a

QoS mechanism, since it is their task to find which nodes,

if any, can serve an application’s requirements. Therefore,

the QoS routing protocol also plays a major part in Ses-

sion Admission Control (SAC), since that is dependent

on the discovery of a route that can suppo rt the requ ested

QoS.

The majority of the solutions proposed in this litera-

ture till now have focused on providing QoS based on

two metrics: throughput and delay. Of these, the more

common is throughput. This is most likely because as-

sured throughput is somewhat of a “lowest common de-

nominator” requirement; most voice or video applications

require some level of guaranteed throughput in addition

to their other constraints. The proposed protocol will im-

prove the QoS based on the above two metrics.

4. Protocol Implem ent at ion

In this section, we describe the implementation of pro-

posed protocol, which exploits the knowledge of alterna-

tive or backup routes to a source’s destination in order to

improve the robustness of throughput-QoS assurances in

the face of route failures. The main goal of this paper is

to improve the Packet Delivery Ratio (PDR) in shadow

fading environments. Thus by using the proposed proto-

col Quality of Service (QoS) can be improved as much as

possible. Hence in the following sections we are going to

use the name as QoSAR (Qos Aware Routing) for the

propose d protoc ol .

In shadow fading environments, it is difficult to achieve

high PDR only with the use of primary routes from source

to destination. Idea behind QOSAR is to find multiple

routes between source and destination. Hence it improves

PDR as well as it gives solution to the route failures.

In the newly proposed QoSAR protocol, once the ses-

sion is ready to transmit, a backup route for that session

must be found. We have considered two mechanisms to

find multiple routes as follows:

1) Link Disjoint Paths

2) Node Disjoint Paths

4.1. Link Disjoint Paths

Link disjoint paths are paths between sources to destina-

tion which have no overlapping links. The backup route

is selected in such a way they are “sufficiently disjoint”

i.e., it includes no more than half of the links in the cur-

rent/primary route [12].

In Figure 1 three paths (shown in red color) between

sources to destination are called as link disjoint paths. If

the primary and backup routes are selected in such a way

that, they are sufficiently link disjo int then the route fail-

ure is minimized.

If a new backup route must be discovered, the search

packet, referred to as RReq backup carries a copy of the

session’s primary route. To avoid fully flooding the net-

work with the RReq-backup, once the RReq backup has

traveled at least half of the length of the primary route,

T. Sangeetha ET AL.

614

Figure 1. Link and Node Disj oint paths.

the disjointness condition is enforced and the packet is

dropped if the partially discovered route does not comply.

Also, the RReq backup Time to Live (TTL) is only one

greater than the primary route length, again to reduce the

extent to which the network is flooded [12].

4.2. Node Disjoint Paths

In node-disjoint paths no node is common other than the

source and destination. This work enables discovery of

two node disjoint paths from source to destination. In this

protocol Hello messages have been used to identify two

node disjoint paths. Three control packets are required

for setup two node-disjoint routes, which reduce control

overhead in the network and also setup backup route

faster that reduces the end to end delay.

In QOSAR protocol, each node periodically broadcasts

the HELLO messages to inform its neighbors that it has

not moved away. When a node receives a HELLO mes-

sage from a neighbor, a route to this neighbor is only

added to the routing table when the neighbor does not

already exists. If the neighbor exists, its lifetime is in-

creased. When the network topology changes and HEL-

LO, message does not received for a defined period of

time the route expires.

In the above Figure 1, Intermediate node 4 is a pri-

mary route (1-4-7) from source to destination. If any

failure occurred in the primary route it will take alternate

route as (1-2-3- 4) and (1-5-6-7) using node disjoint

paths. If the primary and backup routes are selected in

such a way that, they are sufficiently node disjoint then

the route failure is minimized.

5. Results and Discussion

Simulations have been conducted in the environment of

Network Simulator (NS2) . The simulations start with t he

small network of 7 nodes.

Figure 2 shows small network with minimum number

of nodes and the simulation parameters are listed in Ta-

ble 1. We con sidering node 0 as a TCP traffic source and

node 3 assumed to be TCP sink. This simulation results are

presented in Table 2.

Figure 2. Small network with 7 nodes.

Table 1. Simulation Parameters Used for small network.

Parameter Va lue

Simulation area size 100 m × 100 m

Number of nodes 7

Number of traffic source 1

Simulation time 100 s

Traffic source type TCP

Propagation model Shadowing

Path loss exponent 2, 2.2

Table 2. Simulation Results for small network.

Path Loss Parameter AODV Proposed Protocol

Packets sent 35983 42896

Packets received 32547 42567

PDR 90.451 99.233

Throughput 4.72127 × 107 7.3808 × 107

2.2

Packets sent 5132 19948

Packets received 4196 18498

PDR 81.7615 92.7311

Throughput 876858 1.4964 × 107

After observing the performance of QoSAR protocol

in small network, then our simulations focused to ob-

serve the performance in large network. We have taken a

network of 50 nodes in which node movements are ran-

dom. Initially the network is as shown in Figure 3. The

simulation parameters are presented in Table 3. Three

CBR flows with packet size of 100 0 bytes are estab lished

between Nodes 37 and 18, Nodes 19 and 47 and Nodes

29 and 7. Propagation model used as shadowing model

with path loss exponent varied from 1.6 to 2.8. The node

movements are random and the speed of mobile node

varied from 4 - 20 m/s.

Performances are analyzed for these two cases:

T. Sangeetha ET AL.

615

Figure 3. Large network with 50 nodes.

Table 3. Simulation Parameters Used for large network.

Parameter Va lue

Simulation area size 500 m × 500 m

Number of nodes 50

Node movement Random

Node Speed when mobile 4 - 20 m/s

Node pause time when mobile 50 s

Number of traffic source 3

Simulation time 200 s

Traffic source type CBR

Propagation model Shadowing

Path loss exponent 1.6 to 2.8

 Finding backup routes by using Node Disjoint Paths

termed in this paper as QoSAR Node Disjoint.

 Finding backup routes by using Link Disjoint Paths

termed in this paper as QoSAR Link Disjoint.

The following graphs show the performance of QoSAR

protocol.

The Figure 4 is clearly shows that the Packet Delivery

Ratio (PDR) higher for proposed protocol (QOSAR) com-

pared to AODV protocol. AODV protocol achieved low

PDR due to link failure. This link failure can be achieved

in our prop os ed protocol by the use of backup ro utes.

From Figure 5, the throughput assurance reliability

achieved for proposed protocol increases with the speed

of mobile nodes. It has been observed that QoSAR Node

Disjoint and Link Disjoint protocol exhibits higher

throug hp ut than AOD V protocol .

Still considering the Figure 6 QoSAR not only im-

proves PDR and Throughput but it also reduces the delay

considerably. From Figure 7, we can decide the Loss

ratio also increases with increasing speed of mobile nodes

in AODV protocol. Our proposed protocol gives much

better performance compared to AODV.

Figure 4. Speed vs Packet Delivery Ratio.

Figure 5. Speed vs Throughput.

Figure 6. Speed vs Delay.

T. Sangeetha ET AL.

616

Figure 7. Speed vs Loss Ratio.

Figures 5, 6 and 8 confirm that the protocol proposed

in this paper, in general, able to uphold throughput guar-

antees more in shadow fading environments. We can

overcome route failure using backup routes. Compari-

sons show that QoSAR protocol provides better quality

of service.

In this scenario we consider constant number of mo-

bile nodes only variation in path loss exponential and the

results obtained for packet delivery ratio. The Figure 8

shows that effects on the PDR and path loss exponential.

As shown in Figure 8. When increasing the path loss

exponent the packet delivery ratio deceased to zero by

both proposed and AODV protocol. Considering another

case we can obtain high the packet delivery ratio for

QoSAR protocol.

The simulation para meters for varia ble nodes show n in

Table 4 and simulation results for variable nodes are

shown in Table 5. In these simulation there are 10 - 50

mobile hosts randomly distributed in 100 × 100 meters.

As per the performance analysis when increasing the

number of mobile nodes in shadow fading environment

the QOSAR disjoint paths achieve better performance

compared to AODV. (i.e) considering the number of mo-

bile node as 20 the PDR is achieved 95.2165 for AODV

protocol and 99.8169 is achieved for QOSAR disjoint

paths. While increasing the mobile nodes the source and

destination has multiple paths to transmit and receive

packets. So we can achieve higher throughput for QO-

SAR disjoints paths.

6. Conclusion

In MANET, it is difficult to provide QoS assur ances due

to node mobility, contention for channel access, lack of

centralized coordination etc, as discussed previously. Si-

mulation shows that backup routes improves Throughput

and Packet Delivery Ratio ( PDR) and also reduces Delay

Figure 8. Path loss exponent vs Packet Delivery Ratio

(PDR).

Table 4. Simulation Parameters for variable nodes.

Parameter Value

Simulation area size 100 m × 100 m

Number of nodes 10 - 50

Number of traffic source 1

Simulation time 100 s

Traffic source type TCP

Propagation model Shadowing

Path loss exponent 2

Table 5. Simulation Results for variable nodes.

Number of

nodes Parameter AODV QoSAR (Node

disjoint Paths)

Packets sent 36,089 54,879

Packets received 32,829 54,609

PDR 90.9668 99.508

Throughput 4.78226 × 107 1.21047 × 108

Packets sent 51,448 66,644

Packets received 48,987 66,522

PDR 95.2165 99.8169

Throughput 1.01773 × 108 1.79061 × 108

Packets sent 50,831 64,862

Packets received 48,630 64,740

PDR 95.67 99.8119

Throughput 1.002 × 108 1.69629 × 108

Packets sent 54,190 66,269

Packets received 51,617 66,158

PDR 95.2519 99.8325

Throughput 1.13166 × 108 1.77077 × 108

Packets sent 53,503 61,604

Packets received 51,083 61,512

PDR 95.4769 99.8507

Throughput 1.10681 × 108 1.53093 × 108

T. Sangeetha ET AL.

617

and loss ratio in shadow fading environments. As per the

performance analysis the QoSAR protocol gives better

performance in shadow fading environments.

However, it was found that with severe shadowing in-

duced signal strength fluctuations, the backup routes was

less significant, although merely proactively seeking back-

up routes still improved to achieve QoS. This suggests

that routing protocols benefit from proactively requiring

that backup routes exist. However, the more than one

backup route is counter-productive due to the excess

overhead incurred when initiating state information setup.

The required level of link disjointness between data ses-

sions’ primary and backup routes was also studied [12].

Thus it is suggested that by using node disjoint and link

disjoint paths, we can achieve better Quality of Service

(QoS) in shadow fading environments.

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