ABSTRACT
WLAN performance in Nigeria is adversely affected by incessant traffic overloads that constantly lead to congestion, since bandwidth is very limited. This work, therefore, addressed the issue of defining optimum performance parameters in WLAN under traffic saturation. A WLAN model was developed and simulated using MATLAB block oriented simulation package. The model was validated through extensive simulation results related to the simulation result of Nurul I. Sarkar. The relationships between the networks Quality of Service (QoS) parameters under excessive traffic loading were
investigated. Results show that the IEEE 802.11b protocol does not perform well in terms of providing high throughput, low mean delay and low loss rate at saturated traffic load condition. Since the operation of WLAN is highly influenced by the number of workstations that it supports, the IEEE 802.11b optimum parameters under high traffic loadings, at 11Mbps data rate are 4.6 Mbps throughput, 300 ms delay and 0.00017 loss rate. Therefore, a useful control tool was derived for the exploitation of WLAN 802.11b under heavy traffic loadings.
1.0 Background
CHAPTER ONE INTRODUCTION
In recent years, the family of IEEE 802.11 protocols has become the most popular access method for Wireless LANs (WLANs) [1]. With wireless access, a user can connect its wireless network-equipped laptop or portable devices to the network anywhere and anytime without cumbersome cable or wire connections [1].
The IEEE 802.11 Wireless LAN [2] is the predominant technology for wireless access in local areas. The IEEE 802.11b Wi-Fi networks with data rates up to 11 Mbps in the 2.4 GHz frequency band have been widely deployed as hotspots. Furthermore, The IEEE 802.11a in the 5 GHz band and IEEE 802.11g in dual bands (2.4 GHz and 5
GHz) are being deployed to provide data rates up to 54 Mbps. To further increase data rates and throughput, the IEEE 802.11 work group created a new task group, namely IEEE 802.11n, which focuses on the standardization issues of next-generation WLANs to achieve 100 Mbps net throughput [3]. In other words, the last decade has witnessed rapid growth in the deployment of wireless LANs (WLANs) based on the IEEE 802.11 standard. This growth has been propelled by the high capacity links offered by these networks. Unlike 3G cellular networks, which offer a data rate of 2Mbps, Wi-Fi networks offer 11Mbps (IEEE 802.11b) and 54Mbps (IEEE 802.11a/g) [1]. It is envisioned that this growth would continue till the goals of 4G to offer ubiquitous WLAN services integrated with other wireless technologies like IEEE 802.15, 3G etc are met [1]. Due to the universality in the application of WLANs access protocol in connecting mobile users, an in-depth analysis of WLAN access protocol is necessary.
When nodes or stations are connected to a common link, there is need to coordinate the access to the link. A number of access protocols have been devised to handle access to a shared link. The protocols for WLAN are basically random access protocols which may include ALOHA and Carrier Sense Media Access with Collision Avoidance (CSMA/CA) [4].
Distributed Coordinated function (DCF), Point Coordinated function (PCF) and the combination of DCF and PCF are for IEEE 802.11 WLAN [5].
WLAN performance in Nigeria is adversely affected by incessant traffic overloads that constantly lead to congestion, since bandwidth is very limited. This work, therefore, addressed the issue of defining optimum performance parameters in WLAN under traffic saturation.
1.1 Objective of the Study
The objective of this thesis was to determine the optimum WLAN performance parameters under saturated traffic loading. This is intended to provide a congestion control measure for WLAN in a high traffic loading situation for network service providers.
The said objective is to be realized by pursuing the following sub-objectives:
1. The development of WLAN network model.
2. The conversion of the WLAN network model into a computer simulation model using MATLAB block oriented simulated package.
3. The simulation of the computer model and collection of simulation results.
4. The analysis of the simulation results to establish the set of optimum performance parameters.
1.2 Scope of the Study
The scope of this work covers both the Physical layer architecture and MAC layer architecture. The distributed coordination function (DCF) of WLAN popularly known as Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), the RTS/CTS mechanism, MAC sub-layer service specifications, physical layer description and specifications, frame structure and addressing, WLAN spectrum allocation and network performance management are also addressed. Logical link control (LLC) layer, Centralized and hybrid coordination function, power management, security etc., are not considered.
1.3 Methodology.
The approach used in the actualization of optimum performance in this project work, is based on the principles of CSMA/CA using the MATLAB Simulink Simevent Block oriented simulation package.
Subsequently, the physical architecture used for the modeling was converted into computer simulation model using MATLAB Block oriented simulation package. The computer simulation model is probed and simulated, for Quality of service parameter collation.
1.4 Thesis Outline. The rest of this thesis is organized as follows. Chapter 2 presents the literature review of the thesis. Chapter 3 presents the Network model for IEEE 802.11 MAC DCF saturated Traffic Loading for achieving optimum performance. Chapter 4 presents the simulation results and results analysis. Finally, the observations and conclusion were presented in Chapter 5.
This material content is developed to serve as a GUIDE for students to conduct academic research
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