International Journal of Computer Applications (0975 – 8887) Volume 48– No.1, June 2012 27 OPNET based Wireless LAN Performance Improvisation Rajan Vohra Department of Electronics Technology Guru Nanak Dev University Amritsar, Punjab, India Ravinder Singh Sawhney Department of Electronics Technology Guru Nanak Dev University Amritsar, Punjab, India Gurpreet Singh Saini Department of Electronics and Communication ARNI University Himachal Pradesh, India ABSTRACT In order to analyze the performance of Wireless Local Area Networks (WLANs) effectively, it is important to identify those network settings that can cause the networks performance to go from good to poor. Low throughput, high packet loss rate, delayed round trip time (RTT), increased retransmissions, and increased collisions are the detrimental attributes to look for, when poor network performance is encountered. In this paper, our main focus is to analyze and evaluate the role of the media access delay as well as processing delay towards the performance of WLANs. The simulation tool OPNET has been used for fine- tuning the WLAN parameters and simulation demonstrate that WLAN performance can be enhanced by tuning different metrics such as buffer size, fragmentation threshold and request to send (RTS) thresholds. In this paper, we emphasized on buffer size and its subsequent effect on service quality. By varying the buffer size to a value other than specified in the standards, will reduce WLAN delay, media access delay with minutest changes observed in throughput. General Terms WLAN, OPNET, Video conference Keywords- OPNET, Delay, Throughput, Media Access delay 1. INTRODUCTION The technological advances in the field of information, communication and technology have pushed the wireless networks in to a league, where these are spearheading the all other current technologies because of the ease, mobility and transmission and reception of the timely as well as secured data. Users are happy to get the timely data and that too without any hassles. The use of the biometric authentication and other improved access mechanisms have improved the security of the wireless networks many folds in recent years but still unauthorized users look for the loopholes in the system and the detection of these loop holes can lead to the exploitation of the media to gain access to sensitive and valuable data. The main objective of the wireless networks has been to establish a secure, fast and reliable communication channel, which can cater to the needs of the users without compromising their convenience and security. The above cited advantages and reasons have made the WLANs more widely recognized as a general- purpose connectivity alternative for a broad range of business customers [1]. Though many standards have been proposed and developed in the last two decades but those really survived and remained acceptable belong to the IEEE 802.11 family which includes the popular 802.11b, the 802.11a, 802.11g and 802.11n. Other standards, such as HIPERLAN and HIPERLAN/2, have been co-existent but don’t find much acceptance. [2][7] 2. RELATED WORK Many researchers have worked on simulating different WLAN parameters using various simulation tools e.g. Qualnet, OMNET, NS2 as well as OPNET. Also, there exists a wide range of techniques or methods for evaluating and proposing various enhancements in the wireless local area network metrics. The most of the work conducted, has been postulated from both analytic and simulation-based studies carried on mobile communication networks. This section describes a perspective of these methods that have been designed specifically for enhancements and performance evaluation of Wireless Local Area Networks. Previous researches (Amardeep Kaur et.al) focused on improving the performance via network layer and performance optimization has been shown performing a series of simulation tests with different parameters such as RTS/CTS threshold. To reduce the effect of throughput reduction owing to hidden stations, 802.11 specifies as an option the exchange of Request-to-Send/Clear-to- Send (RTS/CTS) frames. Before transmitting a data frame, a station may transmit a short RTS frame, which must be followed by a CTS frame transmitted by the receiving station. The RTS/CTS mechanism is very effective in terms of system performance, especially when large packets are considered, as it reduces the length of the frames involved in the contention process, can be found in [8], in details. Several modifications of the IEEE 802.11 DCF access method have been proposed recently to improve the performance of wireless LANs. (Q.NI et.al)[9] Up to now, such proposals have only been compared under ideal channel conditions (Elena Lopez-Aguilera et.al)[10]. Several investigations have been made with different methods for improving the performance of WLANs, Such as Adaptive (rather than basic) back-off algorithms in the MAC Layer, proxy approaches in the link-layer, such as snoop protocol, and TULIP , Split-connection approaches, such as I-TCP or M-TCP and Other link-layer approaches, such as AIRMAI[11-13]. Our paper focused on the buffer size parameter of wireless Local Area networks in various simulated environments using OPNET TM [3]. This Paper has been based on modeling and simulating a WLAN scenario and it has been verified that WLAN performance can be improved by fine tuning buffer size parameter. By varying the buffer size to a value other than specified in the standards gives remarkable reduction in WLAN delay and media access delay. [4- 7] 3. OUR APPROACH OPNET has been used for the network simulation tool for evaluating various performance metrics by the most network scientists and planners. In this paper, we have focused on creating a WLAN scenario that has been configured for videoconferencing at dual data rates of 11 Mbps and 1 Mbps for parameters like WLAN delay, throughput and load. OPNET tool has been used in our