Experimental Investigation of Throughput Performance of IEEE g OFDM based Systems in a Campus Environment

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1 International Journal of Engineering Sciences, 2() August 13, Pages: TI Journals International Journal of Engineering Sciences ISSN Experimental Investigation of Throughput Performance of IEEE 02.11g OFDM based Systems in a Campus Environment Joseph Isabona *1, Olayinka A.Samson 2 1,2 Department of Basic Sciences, Benson Idahosa University, PMB 10, Benin City, Nigeria. A R T I C L E I N F O Keywords: Throughput Performance Packet data IEEE 02.11g OFDM based Systems A B S T R A C T In recent years, most Wireless Local Area Networks (WLAN) are based on the IEEE 02.11b, 02.11a, 02.11g or 02.11n standards. These standards define how to wirelessly connect computers or devices to a network. Wireless enabled devices can send and receive data anywhere within the range of a wireless access point. The choice of the Wireless LAN protocol depends on the requirements of the individuals or a company who aims to implement the WLAN infrastructure. Some of the parameters that should be considered in selecting an appropriate WLAN working protocol are data communications speed and range. In this paper, an experimental investigation of the impact of packet data communication on IEEE 02.11g OFDM based systems for throughput performance evaluation was conducted on the campus of Benson Idahosa University. The results at different routes show a very interesting feature that the throughput is not susceptible to be affected by change in distance between the Aps and the measurement locations. This may indicates that the data communication links are able to support the required bandwidth and there are no network failures. It also shows that that the packet drop rate on the communication links is low. This phenomenon can be explained by the fact that the WLAN system with OFDM interface can effectively use multipath component because of guard period incorporated in the system. 13 Int. j. eng. sci. All rights reserved for TI Journals. 1. Introduction The world of wireless telecommunications is fast evolving. Technologies under research and development promise to deliver more services to more users in less time. The Wireless Local Area Network (WLAN) technologies are growing fast with new emerging standards being developed. WLAN technologies have been leading the Internet distribution in education, business and home environments is a set of WLAN standards developed by the Institute of Electrical and Electronics Engineers (IEEE) and are mainly used for local wireless communications in the 2.4 and GHz unlicensed frequency bands [1] standards consist of physical layer and media access control (MAC) protocols. Since its first release, there are a number of major additions and amendments to the physical layer whilst the basic functions of MAC remain largely unchanged. Many standards have been developed over the years to address various aspects of WLAN requirements and are nicely summarized in [2] by Hiert and co. WLAN devices often advertise their capabilities based on the implemented physical layer version. The popular ones include 02.11b, 02.11a, 02.11g and more recently 02.11n (see table for details). Release Date Standard Band (GHz) Table 1. Comparison of IEEE physical layer standards Bandwidth (MHz) Modulation Advanced Antenna Technologies Max Data Rate DSSS, FHSS N/A 2 Mbps b 2.4 DSSS N/A 11 Mbps a OFDM N/A 4 Mbps g 2.4, DSSS, OFDM N/A 4 Mbps n 2.4, OFDM MIMO, up to 4 spatial Streams 600 Mbps 13 (exp ) 02.11ac, 0, 0 OFDM MIMO, MU-MIM, up to spatial streams 6.93 Mbps IEEE 02.11g is based on the orthogonal frequency division multiplexing (OFDM) modulation technique and the CCK modulation for backward compatibility with 02.11b. The OFDM physical layer (PHY) provides the capability to transmit data frames at multiple rates up to 4 Mbps for WLAN networks where transmission of multimedia content is a consideration [3]. * Corresponding author. address: josabone@yahoo.com

2 42 Isabona Joseph and Olayinka A.Samson International Journal of Engi neering Sciences, 2() August 13 While wireless networking is classified according to its standards- based signaling rate, such as 4 Mbps for 02.11g, the actual data throughput, or data being transmitted, is often just a fraction of the theoretical maximum rate. Research conducted by [4] showed that the user throughput performance changes radically when access points or clients are located near an interfering transmitter or when frequency planning is not carefully conducted. Data throughput can also be limited due to a number of important environmental and product-specific factors. Therefore, even though the new 02.11g products available are capable of a 4 Mbps signaling rate, the practical, or actual, data throughput is more likely to be much less than that (in the Mbps range). There are few papers that discuss the performance of the 02.11b standards such as in [, 6], and to the best of our knowledge, there is no work in the literature that discusses the throughput performance of 02.11g WLANs in small campus environments. In this paper, we present a full scale experimental study of throughput performance of IEEE 02.11g, with OFDM interface deployed in Benson Idahosa University (BIU). Our focus is on evaluation of success rate of packet data communication at the end user application-level in the studied outdoor WLAN propagation environment. 2. Materials and methods 2.1 Description of the study area The scope of this study is limited to the Benson Idahosa University (BIU) campus located in GRA Benin City; the university campus covers an area approximately six square-kilometer of plane land. The majority of its area has a significant green-space with a lot of trees and other vegetation more than what is supposed to be in the average urban area. The access points (APs) used in this study is herein referenced with respect to which campus building they were mounted on, namely Faculty of Basic and Applied Sciences (FBAS) Wi-Fi and University Library Wi-Fi. These Aps were chosen because of availability of their hardware specifications, configuration and service availability. 2.2 Radio Frequency Site Survey A radio frequency (RF) site survey is one of the first steps carried out before or after the deployment of a Wireless network. According to [7], it is the most important step to ensure desired wireless network operation. A site survey is a task-by-task process by which the surveyor studies the facility to understand the RF behavior, investigate the user data throughput performance, checks for RF interference and determines the appropriate placement of Wireless devices. There is no substitute for measuring real-world network performance, only onsite measurements and surveys can give the complete picture. RF site survey is conducted using surveying tools that enable data to be collected from a base station or an access point, example of such data is the user throughput at the application level. 2.3 Surveying Tools In surveying, generally wireless sniffing tools are used to sniff wireless packets from an infrastructure network setup using an access point. The software and hardware equipment used in this study are presented with their specification. 1. Software: Microsoft windows 7 ultimate 2. Hardware Equipment and Specifications (a) Laptop Vendor: emachine Model: TravelMate CPU: 1.GHz Memory: MB Wireless Card: D-Link DWA-1 (b) IEEE 02.11b/g Access Point Vendor: Mikrotik Model: 133C Transmitter Power 1W Frequency Range: 2.4GHz to 2.43GHz (c) External Antenna: Vendor: HyperGain Model: HGU Type: Omnidirectional Gain: dbi Operating Frequency: 2.4GHz to 2.GHz. Polarization: Vertical. (d) -foot measuring tape.

3 Experimental Investigation of Throughput Performance of IEEE 02.11g OFDM based Systems in a Campus Environment International Journal of Engineeri ng Sciences, 2() August Data Collection Methods An emachine laptop equipped with a wireless D-link card, running on Microsoft windows7 platform installed was used to collect Packet sent and packet received data over time from the selected APs at different locations on the BIU Campus. Two (02) APs were selected on Campus at different locations; the selected Aps were from the same vendor and had the same technical specifications and operate using IEEE g standard. At each AP, a straight path was mark-out at different directions from the AP to the mobile receiver (laptop) to cover for both main and side loops of the radiating antenna. On each of these paths, test points were manually measured at a m about 113m interval using a measuring tape. 2. Precautions Taken During Data Collection The following precautions were taken to minimize errors during the data collection: Data was collected during lecture hours (between 9 am to pm and 2 pm to 4 pm) from Monday to Friday, were most students were having lectures; this is to minimize attenuation due to movement of people and vehicles. The laptop has an internal antenna located behind the screen, so the screen of the laptop was oriented toward the zenith sky in order to increase the likelihood that the direct-rays signal path falls within the half-power beamwidth of the antenna. 2.6 Performance Metric In wireless data communication systems, throughput is one of the foremost performance metrics. It is what the user perceives as a device s performance as he uses it in everyday ways. Throughput is the transmission capability that is available to applications after the overhead required to address the needs of upper layer protocols has been addressed. By description, throughput is a subset of a device s physical layer data rate (data rate). Data rate is an expression of a device s raw transmission capability at the lowest, physical layer. It is an essential contributor to device performance, but an end user will not experience performance equivalent to a device s data rate. As an end user indicator, it expresses the average rate of successful data transmissions over the overall propagation channel. Specifically, throughput which is indicated by Thr, in equation (1) is measure of number of packets successfully delivered in a network. It is measured in terms of packets/second [7]: i PacketDeliverd Thr (1) PacketArrival PacketStarttime i 3. Results and analysis Shown in figure 1-11 are graphs of data throughput performance measured at different measurement locations. As can be observed from the graphs, the throughput performance at different routes shows a very interesting feature that the throughput is not susceptible to be affected by change in distance between the Aps and the measurement locations. This indicates that the data communication links are able to support the required bandwidth and there are no network failures. It also shows that that the packet drop rate on the packet data communication links is low. This phenomenon can be explained by the fact that the Wifi system with OFDM interface can effectively use multipath component because of guard period incorporated in the system. Throughput (Mb/s) Figure 1. Wifi BIU FBAS, Throughput Performance in the Morning for route 1 Figure 2. Wifi BIU FBAS, Throughput Performance in the Morning for route 2

4 4 Isabona Joseph and Olayinka A.Samson International Journal of Engi neering Sciences, 2() August Figure 3. Wifi BIU FBAS, Throughput Performance in the afternoon for route 1 Figure 4. Wifi BIU FBAS, Throughput Performance in the afternoon for route Figure. Wifi BIU FBAS, Throughput Performance in the Evening for route 1 Figure 6. Wifi BIU FBAS, Throughput Performance in the Evening for route Figure 7. Wifi BIU 7, Throughput Performance in the Morning for route 1 Figure. Wifi BIU 7, Throughput Performance in the Morning for route 2

5 Experimental Investigation of Throughput Performance of IEEE 02.11g OFDM based Systems in a Campus Environment International Journal of Engineeri ng Sciences, 2() August Figure 9. Wifi BIU 7, Throughput Performance in the Afternoon for route Figure. Wifi BIU 7, Throughput Performance in the Afternoon for route Figure 11. Wifi BIU 7, Throughput Performance in the Evening for route 1 Figure. Wifi BIU 7, Throughput Performance in the Evening for route 2 Here, the data throughput performances at different periods of the day are presented graphically for comparison. For each week, (throughput vs distance) for morning, afternoon, and evening periods were evaluated for comparison as displayed in figure to 26. As can be realized from the figures above, a relatively steady throughput performance can be observed at the different period of the day even as the distance between the server and the Aps measurement location s increases. The steady throughput of 02.11g comes through two pathways. Several features in 02.11g increase data rate in the physical layer, with some proportion of that effect visible in throughput steady performance g also includes innovations that reduce overhead and improve efficiency of transmissions directly contributing to steady throughput. This is in addition to the fact earlier stressed, that the Wifi system with OFDM interface can effectively use multipath component because of guard period incorporated in the system g Wifi also includes innovations that reduce overhead and improve efficiency of transmissions directly contributing to steady throughput.

6 432 Isabona Joseph and Olayinka A.Samson International Journal of Engi neering Sciences, 2() August 13 (morning) (afternoon) (evening) 2 26 Throughput(dBm) Signal Strenght(dBm) (morning) (afternoon) (evening) Figure 13. Wifi BIU FBAS, Throughput for Week 1, route 1 Figure. Wifi BIU FBAS, Throughput for Week 2, route 1 Throughput(dBm) (morning) (afternoon) (evening) Throughput(dBm) (morning) (afternoon) (evening) distance(m) Figure. Wifi BIU FBAS, Throughput for Week 3, route 1 Figure. Wifi BIU FBAS, Throughput for Week 4, route 1 2 morning afternoon evening 26 (morning) (afternoon) (Evening) Figure 17. Wifi BIU FBAS, Throughput for Week 1, route 2 Figure. Wifi BIU FBAS, Throughput for Week 2, route 2

7 Experimental Investigation of Throughput Performance of IEEE 02.11g OFDM based Systems in a Campus Environment International Journal of Engineeri ng Sciences, 2() August (morning) (afternoon) (evening) morning afternoon evening Figure 19. Wifi BIU FBAS, Throughput for Week 3, route 2 Figure. Wifi BIU FBAS, Throughput for Week 4, route (morning) (afternoon) (evening) (morning) (afternoon) (evening) Figure 21. Wifi BIU 7, Throughput for Week 1, route 1 Figure. Wifi BIU 7, Throughput for Week 2, route (morning) (afternoon) (evening) (morning) (afternoon) (evening) Figure 23. Wifi BIU 7, Throughput for Week 1, route 2 Figure. Wifi BIU 7, Throughput for Week 2, route 2

8 434 Isabona Joseph and Olayinka A.Samson International Journal of Engi neering Sciences, 2() August Conclusion In recent years, most Wireless Local Area Networks (WLAN) are based on the IEEE 02.11b, 02.11a, 02.11g or 02.11n standards. These standards define how to wirelessly connect computers or devices to a network. Wireless enabled devices can send and receive data anywhere within the range of a wireless access point. The choice of the Wireless LAN protocol depends on the requirements of the individuals or a company who aims to implement the WLAN infrastructure. Some of the parameters that should be considered in selecting an appropriate WLAN working protocol are data communications speed and range. The main objective of this study was to carry out an experimental investigation of the impact of packet data communication link of WLAN based OFMD systems in a campus environment. The results show that data throughput remains relatively stable even as the distance between the access points and the user measurement location increases. The steady throughput may be attributed to the fact that the Wifi system with OFDM interface can effectively use multipath component because of guard period incorporated in the system. The steady throughput performance results may also come through two pathways. Several features in 02.11g increase data rate in the physical layer, with some proportion of that effect visible in throughput steady performance g also includes innovations that reduce overhead and improve efficiency of transmissions directly contributing to steady throughput. References [1] IEEE standard Wireless Medium Access Control and Physical Layer Specifications [2] Hiertz, G. Denteneer, D. Stibor, L. Zang, Y. Costa, X.P. Walke, B., The IEEE Universe IEEE Communications Magazine page 62-70, January,. [3] Ergen, M IEEE Tutorial University of California Berkeley, June 02 [4] Henry, B. E. "Throughput Measurements and Empirical Prediction Models for IEEE 02.11b Wireless LAN (WLAN) Installations" M.Sc. thesis, Virginia Polytechnic Institute and State University, Virginia, USA, 01. [] Rose, C. Ulukus, S, and Yates. R.D. "Wireless systems and interference avoidance". IEEE Transactions on wireless Communications, pp. 4-42, 02. [6] Zahur, Y. Doctor, M. Davari, S. and Andrew Yang, T. "02.11b Performance Evaluation". Proceeding of the 2nd IASTED International Conference Communications, Internet, and Information Technology, Scottsdale, AZ, USA, 03. [7] Ngala, D. K (), Studying the Impact of the Environment on Radio Frequency Signal Quality, a case study of Knust Wireless Local Network, M.Sc. Thesis, College of Engineering, Department of Telecommunication Engineering, Kwame Nkrumah University of Science and Technology, Ghana.