Experimental analysis of channel interference in ad hoc network

International Journal on Computational Sciences & Applications (IJCSA) Vol.4, No.1, February 2014
DOI:10.5121/ijcsa.2014.4120 197
EXPERIMENTAL ANALYSIS OF CHANNEL
INTERFERENCE IN AD HOC NETWORK
Anup Bhola1
, Uma Sharma2
, Dr. CK Jha3
1,2,3
Department of Computer Science, Banastahli Univeristy, Tonk, Newai
ABSTRACT
In recent times, the use of ad hoc networks is a common research area among a researcher. Designing an
efficient and reliable network is not easy task. Network engineer faces many problems at the time of
deploying a network such as interference; Signal coverage, proper location of access point etc. channel
interference in one of them which must be considered at the time of deploying WLAN indoor environments
because channel interference impacts the network throughput and degrade the network performance.
In this experiment, we design a two WLAN BSS1 and BSS2 and investigate the impact of interference on
nodes. BSS1 contains three FTP clients and BSS2 contains two FTP client and their jobs is to upload data
to FTP Server Initially, they are far from each other. BSS1 moves toward BSS2 and after some time at
particular position both BSSs overlaps to each other. When BSSs overlaps to each other interference is
high and decrease network performance and increase upload time.
KEYWORDS
Keywords—AP, BSS, IEEE,FTP WLAN.
1. INTRODUCTION
In recent times, the use of Wireless local area networks (WLAN) is common in all government
offices, universities and industrial unit and so their use grows every day. The wireless network
replaces wire network because wire technology is expensive and sometime it is prohibitive to lay
cables. Wireless networks have advantages for notebooks and other small computer equipment
for getting access to the internet due to easy installation and maintenance. This wireless
technology has a various other characteristics that enable the user to access network without
having wired connections. The wireless system keeps the user free from being restricted to the
use network in limited location such as their rooms, corridor, and computer laboratories. Wireless
network also eliminates any time restrictions associated with traditional wired network. In short, a
WLAN will enable the user to access information and communicate anytime and anywhere within
coverage area.
Wireless network at the educational institutions is being used to connect staff and students to
outside corporate network. An analysis, found that the use of WLAN at educational institutions is
a good for preparing a suitable study environment for the students, and enhance the work capacity
of the current students and staffs. Most of the universities are switching over from wire to
wireless technology, there are some of them use both wire and wireless.
Wireless technology is crucial to the growth of higher education because it has the following
advantages for higher education.

198
Flexibility
Wireless technology enables students and faculty to access information from anywhere, anytime.
Students and staffs can access information indoor and outdoor without having physically in plug
to network. Whether you are in a library, hostel, lab, classroom, ground, and corridor wireless
technology allows you to communicate with other students, teachers, administrators and the staff.
Deployment
Wireless technology removes the physical obstacles that are in wired deployment. There is no
need of wire in wireless technology that makes it easier to setup, maintain and integrate with
other technologies.
Cost
Wireless is time and cost effective technique because it eliminates the high cost of installing
different types of wire communication media.
Performance
Wireless technology provides high performance compare to wire technology. Wireless
technologies also help in preparing a suitable working environment for the students, and also
improve the working capacity of the current staff.
Wireless network can be deployed in two ways:-
(a) Single-hop infrastructure mode in which APs are connected to the backhaul using wire
Ethernet. The access points work like central hub, giving connectivity to wireless devices,
computer .
In a corporate environment, large number of access points work together to give wireless
coverage for an entire building or campus.
(b)Ad hoc network in which each node is directly connect to each other, without any
infrastructure. Ad hoc network is useful in many applications where infrastructure is either not
available, or impractical, such as: military, scientific, academic, natural, maritime, business-
related, etc
Figure1: Infrastructure and peer to peer mode for WLAN’s

199
2. Problem Statement & Methodology
The channel interference is one of the areas of concern when designing large network indoor
environments because channel interference, expected in WLANs, causes severe throughput
degradation, and eliminating. This problem has become an important step in order to improve the
network performance. In these experiments, we will only study how channel interference impacts
the network delay, throughput, and retransmission and degrade the network performance.
In this experiment, we design a network using a powerful simulation tool, which is called
Optimum Network (OPENT) performance [1]. OPNET provides various powerful features for
designing and simulation of network like object oriented, GUI, thousands of different vender
devices and protocol. OPNET visualized simulation environment make it more intercalative for
network modeling. The popularity of OPNET is to test new applications and protocols in field of
data communication and computer network environment. Several network equipment
manufacturers also use OPNET to evaluate the performance of newly developed products prior to
introducing in market. OPNET is structured into a number of modeling layers.
In this experiment, we designed scenario by creating a two WLAN BSS 1 and BSS 2. BSS1 has
three and BSS2 has two FTP wlan_station_adv mobile nodes and they are doing regular upload,
and both have one FTP server. In BSS1 WLAN uses data rate 2 Mbps and BSS2 uses 5.5 Mbps.
In this, BSS 1 we set channel 1 and BSS 2 channel 5. Since both of the channels overlap to each
other, so the both IBSSs get closer to each other, and that become precise problem because
distance of two networks gets smaller.
The nodes of BSS 1 moves towards BSS 2 along their trajectory and both of them finish their
movement before the end of the simulation and pause at the starting and in the mid of simulation.
They pause for 2 minutes when two BSSs (BSS_One and BSS_Two) on top of each other and in
the same geographical location. The current network configuration details of overall network are
shown in table1 and fig 2.
WLAN IBSS1 & IBSS2
Client 5 FTP client for frequent upload
operation and 5 FTP Client for
receiving data
Server One FTP server
Data Rate 2 Mbps and 5 Mbps
Channel 1(2.401-2.423 and 5( 2.421-2.443
GHz band
Table 1: current network configuration details of overall network
Figure 2: current network configuration details of overall network

200
3. Literature Review
A literature survey is both a summary and explanation of the complete and current state of
knowledge on a limited topic as found in academic journal articles and books, including projects
report, research papers, and organizational projects. A summary of previously related work is
discussed below.
The problem of coexistence between IEEE 802.11 and IEEE 802.15.4 networks has received
significant interest from the research community. Most early work concentrated on developing
probabilistic models that capture the dependence of interference-related packet loss in a 802.15.4
network based on frequency overlap and duty cycle, transmit power and distance of an 802.11
interferer [2]. Others analyzed the reverse problem, that is the impact of 802.15.4 networks on
802.11devices [3], concluding that it is little to non-existing. A recent experimental study comes
to a different conclusion, reporting that 802.15.4 devices may cause significant packet loss in an
802.11 network under conditions [4]. Prior work assessing the impact of WLAN interference on
static 802.15.4 networks in lab environments typically reported on severe packet loss at small
distances between the interfering devices [5].
Recently several 802.15.4 radio chip manufacturers have published guidelines to mitigate
interference effects between the two technologies [8,9,10], for example, through minimal
frequency of set of 20MHz, spatial separation of 2 m and the use of the complete protocol stack
(using ARQ to translate losses into latency) [6]. Acknowledging the problem, the IEEE 802.15
Task Group 4e currently investigates how to incorporate frequency hopping in the MAC layer.
Meanwhile, recent revisions of standards that build on top of the 802.15.4 already incorporate
simple frequency agility methods like periodic random channel hopping [11, 12].
Study of the Impact of WLAN Interference on IEEE 802.15.4 BANs 15There is not so much
experimental work on the specific challenges and opportunities of 802.15.4 BANs. Some recent
studies have examined the performance of mobile 802.15.4 person-to-person communication, as
well as with static receivers [3, 12]. This work targets the impact of the human body on an inter-
BAN communication link under specific mobility patterns, rather than external RF interference.
Despite their static setup, the study presented in [7] is closest to our work: it focuses on detecting
and mitigating the WLAN interference impact on 802.15.4 networks in a once setting. Targeting
stationary networks, their measurement setup is optimized for more stable interference
configurations, which is also reflected in the significantly higher duration of the sweep time
compared to our setup (1.6 s vs. 85 ms). Their results confirm the correlation between 802.15.4
packet loss and 802.11 activities, as well as the suitability of noise-based predictors of WLAN
interference.
Taher et al.[13] used laboratory measurements to develop an analytical model of microwave oven
signals. Karhima et al.[14] performed measurements on an ad-hoc wireless LAN under
narrowband and wideband jamming. They found that in case of wideband jamming, 802.11g can
offer higher transmission rates due to its DSSS modulation scheme. Golmie et al.[15] explored
the mutual impact of interference on a closed loop environment consisting of Wi-Fi and
Bluetooth networks. They found that even by sufficiently increasing the transmission power
levels of the Wi-Fi network to that of the Bluetooth network could not reduce packet loss. Our
work complements these studies. We use measurements to characterize a wide range of
common non-Wi-Fi devices(including microwave ovens and Bluetooth) at the physical
layer and use experiments to qualify their impact on different traffic workloads.

201
Vogeler et al.[16] presented methods for detection and suppression of interference due to
Bluetooth in 802.11g networks. Ho et al.[17] studied the performance impact on a Wi-Fi
network due to Bluetooth and HomeRF devices using simulations and described.
4. Result
In simulation, source nodes of IBSS1 moves towards destination nodes of IBSS2 during
simulation and continually sends traffic, at some point during the simulation, both BSSs overlaps
to each other and increase the interference and upload time and degrade network performance.
In this experiment, we analysis the effect on interference on following parameter:-
4.1 FTP Upload Response Time
Figure 3 shows the FTP upload response time of client 4 of BSS2. This graph clearly shows the
negative effects of interference for the node 4. When the IBSSs do not overlap each other, the
interference is low and FTP uploads take less time. On the other side, while two IBSSs overlap to
each other, interference is high and upload time take more time.
Figure3: FTP upload response time (in sec) in clients on left and right BSS
4.2 Delay
In, figure 4 we observed wireless LAN delay of clients of right side BSS. In figure4 shows very
low delay at beginning position which is around 0.011 sec. because IBSSs are far from each
other. On the other side, while two IBSSs are overlap to each other, delay is very high and
reaches up to 0.017 sec and Figure 5 shows the wireless LAN media access delay observed on the
clients of right hand side BSS. The graph shows that when the IBSSs do not overlaps to each
other and are far from each other, the media access delay is low and are below to 0.008 sec. and
on the other side, while two IBSSs overlap to each other, the media access delay is high and reach
up to 0.013 sec.

202
Figure4: Wireless LAN delay (sec)
Figure5: WLAN Media Access Delay (sec)
4.3 Retransmission Attempts
Figure 6 shows the wireless LAN retransmission attempts (packets) of clients of BSS Right: The
graph clearly shows that when the IBSSs are at distance of each other, the retransmission attempts
is low around 0.015 to 0.040 and on the other side, while two IBSSs overlaps on each other, the
retransmission attempts is high and reach up to 0.070 packets.
Figure 6: Wireless LAN Retransmission Attempts (Packets)

203
5. Conclusion
A Channel Interference of network depends on distance .Network provides a smooth
performance when two BSS are at particular distance but when BSS overlaps on each other,
increase the interference and degrade the network performance.
6. References
[1] Wireless Network Performance Optimization Using Opnet Modeler
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[2] S. Y. Shin, D. G. Yoon, W. H. Kwon, and H. S. Park. Packet error rate analysis of IEEE 802.15.4
under IEEE 802.11b interference. Vehicular Technology Conference,2006. VTC 2006-Spring. IEEE
63rd, 3:1186{1190, May 2006.
[3] J. Gutierrez and I. Howitt IEEE 802.15.4 low rate - wireless personal area network coexistence issues.
Wireless Communications and Networking, 2003. WCNC 2003.2003 IEEE, 3:1481{1486 vol.3,
March 2003
[4] S. Pollin, I. Tan, B. Hodge, C. Chun, and A. Bahai. Harmful coexistence between 802.15.4 and
802.11: A measurement-based study. Cognitive Radio Oriented Wireless Networks and
Communications, 2008. CrownCom 2008. 3rd International Conference on, pages 1{6, May 2008.
[5 ]N. Golmie, D. Cypher, and O. R ebala. Performance analysis of low rate wireless technologies for
medical applications. Computer Communications, 28(10):1255{1275, 2005.
[6] G. Thonet, P. Allard-Jacquin, and P. Colle. ZigBee - WiFi coexistence, white paper and test report.
Technical report, Schneider Electric, 2008. [7] R.Musaloiu-E.andA.Terzis.Minimising the effect of
WiFi interference in 802.15.4 wireless sensor networks. Int. J. Sen. Netw., 3(1):43{54, 2008
[8] Jennic Ltd. Co-existence of IEEE 802.15.4 at 2.4 GHz - application note. http://www.jennic.com/.
[9] G. Thonet, P. Allard-Jacquin, and P. Colle. ZigBee - WiFi coexistence, white paper and test report.
Technical report, Schneider Electric, 2008.
[10] Freescale Semiconductor. Mc1319x coexistence - application note. http://www.freescale.com.
[11] HART field communication protocol specification:TDMA data link layer specification.HCF-SPEC-
15.2008
[12] ZigBee Alliance.ZigBee Specification.ZigBee Document 053474r17, 2008.
[13] Taher,T.,Al Banna,A.,Ucci,D.,LoCicero,J.: Characteriz –tion of an Unintentional Wi-Fi Interference
Device-The Residential Microwave Oven.In:Proc of Military Communications
Conference(MILCOM).Washington D.C.,U.S.A.(October,2008).
[14] Karhima,T.,Silvennoinen,A.,Hall,M.,Haggman,S:IEEE 802.11 b/g WLAN Tolerance to
Jamming.In:Proc of Military Communications conference(MILCOM).PP.1364-
1370.Monterey,U.S.A.(October,2004).
[15] olmie,N.,VanDyck,R.,Soltanian,A.,Tonnerre,A.,Rebala,O.:Interference evaluation of Bluetooth and
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[17] Ho,M.J.,Rawles,M.,Vrijkork,M.,Fei,L.:RF Challenges for 2.4 and 5GHz WLAN Deployment and
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