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40120130405017

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    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – INTERNATIONAL JOURNAL OF ELECTRONICS AND 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) ISSN 0976 – 6464(Print) ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October, 2013, pp. 161-168 © IAEME: www.iaeme.com/ijecet.asp Journal Impact Factor (2013): 5.8896 (Calculated by GISI) www.jifactor.com IJECET ©IAEME IMPROVEMENT OF IEEE 802.11G WLANS BASED ON RESPONSE TIMES APPLICATION WITH RADIO – FIBER SYSTEM Dr. Adnan Hussein Ali*, Dalal Abdulmohsin Hammood**, Amal Ibrahim Mahmood*** College of electrical and electronic techniques ABSTRACT The Wireless local area networks WLAN performance is a key factor in spreading and usage of such technologies. The WLAN are more bandwidth limited as compared to the wired networks because they depend on an inexpensive, but prone to errors, physical medium (air).Hence it is important to improve their performance. Fibre-optic media will do better transmitting high frequency radio signals over a longer distance because fibre-optic cables are immune to EMI and noise, provide excessive bandwidth in the region of THz. Application response times are greatly improved irrespective of the nature of the application. Keywords: Wireless LAN, IEEE 802.11g, Radio–Fiber system, OPNET. 1. INTRODUCTION Wireless local area network (WLAN) technologies have emerged as a fast-growing market. Among the various WLAN technologies available in the market, IEEE 802.11 standard has emerged as the dominating technology and is vastly used in WLANs. Low cost, ease of deployment and mobility support has resulted in the vast popularity of IEEE 802.11 WLANs[1,2]. Fibre-optic media will do better transmitting high frequency radio signals over a longer distance because fibre-optic cables are immune to EMI and noise, provide excessive bandwidth in the region of THz, and are more secure[3]. OPNET (Optimized Network Engineering Tools) Modeler will be used to model a typical enterprise wide area network (WAN) network having LAN and WLAN subnetworks as is found in many installations today[4]. 161
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME 2. WLAN TECHNOLOGY Future Wireless local area networks enable people on the move to communicate with anyone, anywhere at anytime with a range of multimedia services. The wireless networks can be employed to provide network connectivity almost anywhere, it provides large companies the option to connect the current wired networks to the new wireless network without any problems and gives user the option to use any kind of applications regardless of its source or vendors[5]. However, the WLAN performance is a key factor in spreading and usage of such technologies. Also the Wireless local area networks (WLAN) are more bandwidth limited as compared to the wired networks because they rely on an inexpensive, but error prone, physical medium (air)[6]. Discrete event simulations are used as the means of analyzing the system performance and behaviour. This sophisticated package comes with a range of tools, which allows us to specify models in detail, identify the elements of the model of interests, execute the simulation, and analyze the generated output data. The IEEE released the 802.11 specifications in June 2000[7]. The initial specification, known as 802.11, used the 2.4 GHz frequency and supported a maximum data rate of 1 to 2 Mbps then the 802.11b specification increased the performance to 11 Mbps in the 2.4 GHz range while the 802.11a specification utilized the 5 GHz range and supported up to 54 Mbps[8]. The 802.11 standard focuses on the two lower layers (1 and 2) of the Open System Interconnection (OSI) reference model. After more than two years in the making, the IEEE 802.11g Draft Standard is nearing completion. In terms of range and throughput, 802.11g is living up to its billing. It utilizes Orthogonal Frequency Division Multiplexing (OFDM) technology in the 2.4 GHz band while preserving backward compatibility with the large installed base of existing 802.11b equipment (about 40 million units worldwide, and growing)[9]. OFDM was previously adopted for WLAN applications as part of the IEEE 802.11a Standard (completed in 1999). Since 802.11g operates at 2.4 GHz, it provides much longer range than 802.11a based equipment because the lower operating frequency has better propagation properties for the indoor WLAN environment[10]. 3. RADIO – FIBER TECHNOLOGY A system for distributing RF signals over optical fibre consists of a Central Site (CS) and a Remote Site (RS) connected by an optical fibre link or network. For WLANs, the CS would be the head-end while the radio access point would act as the RS. Pioneer Fibre-Radio systems such as the one depicted in Figure 1 were primarily used to transport microwave signals, and to achieve mobility functions in the CS. That is, modulated microwave signals had to be available at the input end of the Fibre-Radio system, which subsequently transported them over a distance to the RS in the form of optical signals [11]. Figure 1: Fibre-Radio System [11] 162
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME By delivering the radio signals directly, the optical fibre link avoids the necessity to generate high frequency radio carriers at the antenna site. Since antenna sites are usually remote from easy access, there is a lot to gain from such an arrangement. However, the main advantage of Fibre-Radio systems is the ability to concentrate most of the expensive, high frequency equipment at a centralized location, thereby making it possible to use simpler remote sites[12]. 4. SIMULATION ENVIRONMENT OPNET Modeler v14.0 is used for all network simulations. OPNET Modeler is a powerful communication system discrete event simulator (DES) developed by OPNET Technologies. OPNET provides a comprehensive development environment supporting the modeling of communication networks and distributed systems. Both behaviour and performance of modelled systems can be analyzed by performing discrete event simulations. The IEEE 802.11 WLAN architecture is built around a Basic Service Set (BSS) [13,14]. A BSS is a set of stations that communicate with one another. Figure 2 shows an outline to the model and is followed by the one wireless LAN sites (Figure 3). The response times of applications (HTTP, FTP, Email, Database and Video Conferencing) at the mobile nodes are also analysed to ascertain the user perceived performance of the WLAN. A simulation time of 5 minutes is set for all scenarios with the Start time Offset for all applications set to 110 seconds. Results from the simulated network model will show the effect of replacing copper cables with fibre-optic cables in the WLAN feeder network infrastructure. 4.1 Radio-Fibre Scenario The baseline scenario is duplicated and then modified. All Fast Ethernet 100BaseT links are replaced by optical fibre using Fibre Distributed Data Interface (FDDI) links while the serial T1 WAN links remain unchanged. Figure 2 shows the modified high-level network environment appropriately named radio_fibre_802_11_g_wlan_deployment. The modified 802.11g WLAN BSS using fibre links and devices is shown in Figure 3. Figure 2: Radio-Fibre WLAN Deployment 163
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME Figure 3: Radio-Fibre 802.11g WLAN BSS 4.2 WLAN Application Response Times The user performance of the WLAN is measured using the response times of the applications deployed on the WLAN. The measured average response times of the applications namely; HTTP (Web Browsing), FTP (File Transfer), Email (Electronic Mail) and DB Entry/Query (Database Access), as observed in the WLAN subnetwork of the baseline model are shown in Figure 4. FIGURE 4 : Response times of applications in baseline WLAN 164
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME Approximate average values of the response times are shown in Table 1 below. Table 1: Response times of applications in baseline WLAN Application Response Time (sec) HTTP 0.57 FTP 0.023 Email 0.43 Database 0.13 4.3 Radio-Fibre Application response time The user perceived performance of the WLAN is measured using the response times of the applications deployed on the WLAN. The measured average response times of the applications namely; HTTP (Web Browsing), FTP (File Transfer), Email (Electronic Mail) and DB Entry/Query (Database Access), as observed in the WLAN subnetwork of the baseline model Here, the analysis effect of the radio-fibre model in the response time of the application shown in fig. 5, the response time of the HTTP application shows that a significant improvement in radio-fibre model with compare with that found in baseline model. Fig. 5: Comparing HTTP Page Response Times between baseline and radio-fibre models In the FTP application, the response time of the fibre model is increased more than the baseline model that make the file transfer be slower typical TCP protocol behaviour explained earlier is responsible for this due to increased time overhead in acknowledgements causing increased delays, as shown in figure 6. 165
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME Fig. 6: Comparing FTP Download Response Times between baseline and radio-fibre models In the EMAIL application, the response time that found in radio-fibre model has shown in figure 7, and relatively the results give a big difference between them. In the DB also there are little increased as same as that found in FTP application in the radiofibre model with compare with baseline model as shown in figure 8. Fig. 7: Comparing (Email Download Response Times) between baseline and radio-fibre models 166
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME Fig. 8: Comparing DB Query Response Times between baseline and radio-fibre models 5. CONCLUSION This chapter presented conclusions drawn from the research results and provided recommended areas for future work. The aim of this research was to design, implement and compare the performance of a WLAN subnetwork model fed by a copper wired enterprise network with that of a fibre-optic based feeder network. The results have shown that this research goal was achieved. They showed that wireless broadband multimedia communication in a WLAN can be achieved with a fibre-optic based feeder network. REFERENCES [1] [2] [3] [4] [5] [6] [7] Ms. Kaur, Dr. Sandip Vijay, Dr. S.C.Gupta," Performance Analysis and Enhancement of IEEE Wireless Local Area Networks" Vol. 9 Issue 5 (Ver 2.0), January 2010 S. Mangold, S. Choi, G.R. Hiertz, O. Klein, B. Walke, Analysis of IEEE 802.11e for QoS support in wireless LANs, IEEE Wireless Communications Magazine, December 2003 H. Al-Raweshidy and S. Komaki, eds., Radio Over Fiber Technologies for Mobile Communications Networks. Artech House Publishers, first ed., 2002. OPNET. Optimum Network Performance Simulation Tool for Communication Networks Online: www.opnet.com T. Regu and Dr. G. Kalivarathan, “Prediction of Wireless Communication Systems in the Context of Modeling”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 1, 2013, pp. 11 - 17, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. Sameh H. Ghwanmeh and Abedel Rehman Al-Zoubidi, "Wireless network performance optimization using OPNET Modeler”, Information Technology Journal, Volume: 5, Issue: 1, 2006. DOI: 10.3923/itj.2006.18.24 Guido R. Hiertz, D. Denteneer, L. Stibor and Y. Zang, The IEEE 802.11 Universe, IEEE Communications Magazine, January 2010 167
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 5, September – October (2013), © IAEME [8] [9] [10] [11] [12] [13] [14] [15] [16] IEEE Standards Board, “IEEE Standard for Wireless LAN: Medium Access Control and Physical Layer Specifications”, IEEE Std. 802.11-1997, November 1997. M. Ergen, S. Coleri, P. Varaiya. QoS Aware Adaptive Resource Allocation Techniques for Fair Scheduling in OFDMA Based Broadband Wireless Access System. IEEE Transaction on Broadcasting, vol.49, December 2003 Yang Xiao and Jon Rosdahl. Performance analysis and enhancement for the current and future IEEE 802.11 MAC protocols. SIGMOBILE Mob. Comput. Commun. Rev. 7, 2 (April 2003), 6-19. 2003. DOI=10.1145/950391.950396 Fuster J. M., Marti J., Candelas P., Martinez F.J. and Sempere L., “Optical Generation of Electrical Modulation Formats”, in Proceedings of the 27th European Conference on Optical Communication 2001 (ECOC’01), Amsterdam, Sept. 30 - Oct. 4, 2001, pp 536-537. Gliese U., Nielsen T. N., Norskov S., and Stubkjaer K. E., “Multifunction Fibre-Optic Microwave Links Based on Remote Heterodyne Detection”, IEEE Transactions On Microwave theory and Techniques, Vol. 46, No. 5, May 1998. Acharya, R., Vityanathan, V. and Chellaih, P.R. 2010." WLAN QoS Issues and IEEE 802.11e QoS Enhancement", International Journal of Computer Theory and Engineering. February, 2010. PP (1793-8201). T. Soungalo, Li Renfa and Z. Fanzi, “Evaluating and Improving Wireless Local Area Networks Performance, “International Journal of Advancements in Computing Technology, Vol. 3, No. 2, March 2011. Dheyaa Jasim Kadhim and Sanaa Shaker Abed, “Performance and Handoff Evaluation of Heterogeneous Wireless Networks (Hwns) using OPNET Simulator”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 2, 2013, pp. 477 - 496, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. Asish B. Mathews and Dr. Pavan Kumar Yadav, “Improved Linearization of Laser Source and Erbium Doped Fiber Amplifier in Radio Over Fiber System”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 5, 2013, pp. 46 - 55, ISSN Print: 0976-6480, ISSN Online: 0976-6499. AUTHOR’S PROFILE The Author is an assistant Professor in the Computer Engineering Department at Institute of Technology, Baghdad, IRAQ. He has been awarded a Doctor of Philosophy in Laser and Opto-Electronics Engineering from University of Technology, Baghdad, in 2007. He has studied Master of Science in Electronics Engineering, Cupper Vapor Laser's Power supply at University of Technology, Baghdad in 2000. He has gained Bachelor in Electrical and Electronic Engineering from University of Technology, Baghdad, in 1987. Currently he is the Deputy Dean of Institute of Technology, Baghdad, IRAQ. His research interests are Radio over Fiber, Wireless Network, Laser's Power supply and OPNET. 168