A study of QoS support for real time multimedia communication over IEEE802.11 WLAN : a thesis presented in partial fulfillment of the requirements for the degree of Master of Engineering in Computer Systems Engineering, Massey University, Albany, New Zealand

Quality of Service (QoS) is becoming a key problem for Real Time (RT) traffic transmitted over Wireless Local Area Network (WLAN). In this project the recent proposals for enhanced QoS performance for RT multimedia is evaluated and analyzed. Two simulation models for EDCF and HCF protocols are explored using OPNET and NS-2 simulation packages respectively. From the results of the simulation, we have studied the limitations of the 802.1 le standard for RT multimedia communication and analysed the reasons of the limitations happened and proposed the solutions for improvement. Since RT multimedia communication encompasses time-sensitive traffic, the measure of quality of service generally is minimal delay (latency) and delay variation (jitter). 802.11 WLAN standard focuses on the PHY layer and the MAC layer. The transmitted data rate on PHY layer are increased on standards 802.1 lb, a, g, j, n by different code mapping technologies while 802.1 le is developed specially for the QoS performance of RT-traffics at the MAC layer. Enhancing the MAC layer protocols are the significant topic for guaranteeing the QoS performance of RT-traffics. The original MAC protocols of 802.11 are DCF (Distributed Coordination Function) and PCF (Point Coordinator Function). They cannot achieve the required QoS performance for the RT-traffic transmission. IEEE802.lle draft has developed EDCF and HCF instead. Simulation results of EDCF and HCF models that we explored by OPNET and NS-2, show that minimal latency and jitter can be achieved. However, the limitations of EDCF and HCF are identified from the simulation results. EDCF is not stable under the high network loading. The channel utilization is low by both protocols. Furthermore, the fairness index is very poor by the HCF. It means the low priority traffic should starve in the WLAN network. All these limitations are due to the priority mechanism of the protocols. We propose a future work to develop dynamic self-adaptive 802.11c protocol as practical research directions. Because of the uncertainly in the EDCF in the heavy loading, we can add some parameters to the traffic loading and channel condition efficiently. We provide indications for adding some parameters to increase the EDCF performance and channel utilization. Because all the limitations are due to the priority mechanism, the other direction is doing away with the priority rule for reasonable bandwidth allocation. We have established that the channel utilization can be increased and collision time can be reduced for RT-traffics over the EDCF protocol. These parameters can include loading rate, collision rate and total throughput saturation. Further simulation should look for optimum values for the parameters. Because of the huge polling-induced overheads, HCF has the unsatisfied tradeoff. This leads to poor fairness and poor throughput. By developing enhanced HCF it may be possible to enhance the RI polling interval and TXOP allocation mechanism to get better fairness index and channel utilization. From the simulation, we noticed that the traffics deployment could affect the total QoS performance, an indication to explore whether the classification of traffics deployments to different categories is a good idea. With different load-based traffic categories, QoS may be enhanced by appropriate bandwidth allocation Strategy

A WiFi-based Reliable Network Architecture for Rural Regions

WiFi is being considered as an attractive option in providing low cost Internet connectivity to rural areas, and thereby reducing Digital Divide with urban areas. Most of the WiFi-based Long Distance network architectures extend Internet to rural regions through a single gateway node which is connected to high speed Internet. If the gateway node fails in such single gateway-based rural networks, the entire network gets collapsed. In this paper, we propose a reliable and low-cost WiFi based rural network architecture using multi-gateway concept. The proposed network architecture also allows load balancing among the available gateways. In such multi-gateway architecture, the network recovers from gateway failure and reestablishes the ongoing communication within 2-4 seconds time. The simulation results in NS-2 validate the claims of the paperKeywords—Digital Divide, WiFi, WiFi based Long Distance Network

IMPLEMENTATION OF WIRELESS LAN IN UTP

This paper, entitled Implementation ofWireless LAN in UTP environment, looks into the way to implement wireless network in UTP. The main objectives ofthis project are to provide mobile network and internet access using university's network system to students and lecturers and to make it easier and convenient for student to download lecture notes and for lecturers to upload them. Currently, there is no wireless LAN access in UTP environment that can be use by students and staff as alternative opportunity to access and share instant information. Therefore, this project research area is to find out the way to implement wireless LAN using secure Wi-Fi in UTP external environment. For this study, the scope is narrow down to the architecture and design ofwireless LAN network and its developing methodology. Anetwork simulation tool called Network Simulator version 2, or simply known as ns-2, is used to test the efficiency and functionality ofthe designed network. The outcome ofthis project is a good network architecture design that will give high network performance to all users in UTP

Study of Optical OFDM System for Wireless LAN Applications

The advantages of optical fiber make it possible to extend the data rate transmission and propagation distance. Orthogonal frequency division multiplexing (OFDM) as a multicarrier technique (MC) is used in hybrid optical-wireless system designs because it has the best spectral efficiency to radio frequency (RF) interference and lower multipath distortion. In this dissertation, a study and evaluation of optical OFDM based wireless local area network (W-LAN) systems are presented. The baseband of the OFDM signal is fully transmitted and up-converted to a radio frequency signal. Also, to reduce system costs, simple base stations (BSs) are interconnected to a central office (CO) via an optical fiber. All the required operations are achieved in the CO. The directly modulated laser (DML) and continuous wave (CW) laser are used in the system simulations as optical laser sources. Identical rectangular microstrip patch antennas have been used at the transmitter and the receiver as well. The simulations were carried out for different SMF and MMF lengths, and the variable wireless distance between the transmitting and receiving antennas was in a range of 40 dB to 80 dB. The purpose of this work is to provide a framework for integrating wireless and optical technologies in one system with the presence of OFDM technology. The required microstrip patch antenna parameters for the system are analyzed and designed. The microstrip patch antenna (S-parameters) is loaded into the Optisystem communication software tool in Touchstone format. As a result, this achievement gives a greater impetus to design an integrated optical-wireless system, and simulation results validate the proposed technique. Then, the integration of the microstrip patch antenna and optical OFDM system is achieved, and the performance is intensely studied. The entire system has been presented by developing analytical models and simulations. The system performance results are obtained regarding EIRP, SNR, signal constellations and BER. The results show that this integrated optical wireless link is very robust for carrying OFDM based wireless LAN signals over an optical fiber. Moreover, using an active patch antenna in the system helps to increase the coverage service to more than 30 meters when an SMF of 80 km length is utilized

A Unified End-to-End Communication Paradigm for Heterogeneous Networks

The aim of this thesis research is to develop a unified communication paradigm that provides an end-to-end bursting model across heterogeneous realms. This model generates end-to-end bursts, thereby eliminating edge node burst assembly and its effect on TCP performance. Simulation models are developed in ns-2 to validate this work by comparing it with edge burst assembly on OBS networks. Analysis shows improved end-to-end performance for a variety of burst sizes, timeouts, and other network parameters

Modeling of On-line Traffic Control and Management Network for Operational and Communication Performance Evaluation

Communication systems are the backbone of every effective and reliable traffic control and management application. While traditional fiber optics and telephone communications have long been used in managing and controlling highway traffic, wireless communication technology shows great promise as an alternative solution in traffic management applications due to their suitability for deployment in rural areas, and their flexibility and cost-effectiveness for system expansion. However, the detailed characteristics of various wireless communication technologies and real performance in the field have not been systematically studied. To augment this existing knowledge so that traffic professionals may better utilize these technologies to improve traffic safety, mobility and efficiency, this study aims to 1) identify existing wireless communication technologies used in ITS, and potential wireless communication alternatives that can be widely used in ITS, 2) evaluate the performance, cost and reliability of existing and potential wireless communication technologies in supporting on-line traffic control and management functions, and 3) apply benefit-cost analysis to identify the impacts of using these wireless technologies to support on-line traffic management. To achieve these research objectives, the author first conducted an interview to discover the specifications of existing communication infrastructures deployed for various ITS related applications and the usage of wireless technologies in different states. Moreover, the author proposed a network design process that considered wireless coverage range and network topology, followed with case studies utilizing Wireless Fidelity (WiFi) and Worldwide Interoperability for Microwave Access (WiMAX) technologies to support a traffic surveillance system in seven metropolitan areas throughout South Carolina. Field tests were conducted to evaluate the performance and reliability of wireless transmissions between adjacent sensor nodes. After that, the author applied a communication simulator, ns-2, to compare the communication performance of a traffic sensor network with WiFi and WiMAX technologies under infrastructure and mesh topologies, and environmental conditions. Based on these simulation results, the author conducted performance-cost analysis for these selected technologies and topologies. The WiFi field test results indicated that wireless communication performance between two traffic sensors significantly degrades after 300 ft; this distance, however, may vary with the modulation rates and transmission power upon which the system operates. WiMAX nomadic test suggested that line-of-sight (LOS) greatly affects the connectivity level. Moreover, the capabilities and the performance of the WiMAX network are sometimes affected by the characteristics of the client radio. The simulation analysis and benefit-cost analysis indicated a WiFi mesh network solution has the highest throughput-cost ratio, 109 bits/dollar for supporting traffic surveillance systems, while the WiMAX infrastructure option provides the greatest amount of excess bandwidth, 9.15Mbps per device, which benefits the system\u27s future expansion. This dissertation provides an important foundation for further investigation of the performance and reliability of different wireless technologies. In addition, research results presented in this dissertation will benefit transportation agencies and other stakeholders in evaluating and selecting wireless communication options for different traffic control and management applications

Performance Analysis of Wired, Wireless and Optical Network using NS2

In computer terminology, the definition for networks is simply a group of computers physically or logically connected with each other for sharing information or services. In this paper, wired, wireless and optical networks have been analyzed and implemented using network simulator tool NS2. A systematic simulation based performance analysis of wired, wireless and optical networks using distance vector routing protocol has been carried out. Analysis of the performance of these networks on the basis of three metrics- Packet delivery ratio, end to end delay, throughput using NS2 based Simulation has been undertaken

DYNAMIC ROUTING WITH CROSS-LAYER ADAPTATIONS FOR MULTI-HOP WIRELESS NETWORKS

In recent years there has been a proliferation of research on a number of wireless multi-hop networks that include mobile ad-hoc networks, wireless mesh networks, and wireless sensor networks (WSNs). Routing protocols in such networks are of- ten required to meet design objectives that include a combination of factors such as throughput, delay, energy consumption, network lifetime etc. In addition, many mod- ern wireless networks are equipped with multi-channel radios, where channel selection plays an important role in achieving the same design objectives. Consequently, ad- dressing the routing problem together with cross-layer adaptations such as channel selection is an important issue in such networks. In this work, we study the joint routing and channel selection problem that spans two domains of wireless networks. The first is a cost-effective and scalable wireless-optical access networks which is a combination of high-capacity optical access and unethered wireless access. The joint routing and channel selection problem in this case is addressed under an anycasting paradigm. In addition, we address two other problems in the context of wireless- optical access networks. The first is on optimal gateway placement and network planning for serving a given set of users. And the second is the development of an analytical model to evaluate the performance of the IEEE 802.11 DCF in radio-over- fiber wireless LANs. The second domain involves resource constrained WSNs where we focus on route and channel selection for network lifetime maximization. Here, the problem is further exacerbated by distributed power control, that introduces addi- tional design considerations. Both problems involve cross-layer adaptations that must be solved together with routing. Finally, we present an analytical model for lifetime calculation in multi-channel, asynchronous WSNs under optimal power control

Modelling and Analysis of Smart Grids for Critical Data Communication

Practical models for the subnetworks of smart grid are presented and analyzed. Critical packet-delay bounds for these subnetworks are determined, with the overall objective of identifying parameters that would help in the design of smart grid with least end-to-end delay. A single-server non-preemptive queueing model with prioritized critical packets is presented for Home Area Network (HAN). Closed-form expressions for critical packet delay are derived and illustrated as a function of: i) critical packet arrival rate, ii) service rate, iii) utilization factor, and iv) rate of arrival of non-critical packets. Next, wireless HANs using FDMA and TDMA are presented. Upper and lower bounds on critical packet delay are derived in closed-form as functions of: i) average of signal-to interference-plus-noise ratio, ii) random channel scale, iii) transmitted power strength, iv) received power strength, v) number of EDs, vi) critical packet size, vii) number of channels, viii) path loss component, ix) distances between electrical devices and mesh client, x) channel interference range, xi) channel capacity, xii) bandwidth of the channel, and xiii) number of time/frequency slots. Analytical and simulation results show that critical packet delay is smaller for TDMA compared to FDMA. Lastly, an Intelligent Distributed Channel-Aware Medium Access Control (IDCA-MAC) protocol for wireless HAN using Distributed Coordination Function (DCF) is presented. The protocol eliminates collision and employs Multiple Input Multiple Output (MIMO) system to enhance system performance. Simulation results show that critical packet delay can be reduced by nearly 20% using MA-Aware protocol compared to IDCA-MAC protocol. However, the latter is superior in terms throughput. A wireless mesh backbone network model for Neighbourhood Area Network (NAN) is presented for forwarding critical packets received from HAN to an identified gateway. The routing suggested is based on selected shortest path using Voronoi tessellation. CSMA/CA and CDMA protocols are considered and closed{form upper and lower bounds on critical packet delay are derived and examined as functions of i) signal-to-noise ratio, ii) signal interference, iii) critical packet size, iv) number of channels, v) channel interference range, vi) path loss components, vii) channel bandwidth, and viii) distance between MRs. The results show that critical packet delay to gateway using CDMA is lower compared to CSMA/CA protocol. A fiber optic Wide Area Network (WAN) is presented for transporting critical packets received from NAN to a control station. A Dynamic Fastest Routing Strategy (DFRS) algorithm is used for routing critical packets to control station. Closed-form expression for mean critical packet delay is derived and is examined as a function of: i) traffic intensity, ii) capacity of fiber links, iii) number of links, iv) variance of inter-arrival time, v) variance of service time, and vi) the latency of links. It is shown that delay of critical packets to control station meets acceptable standards set for smart grid