Made available in DSpace on 2016-04-04T18:31:30Z (GMT). No. of bitstreams: 1 Luis Fernando Fontolan.pdf: 1957918 bytes, checksum: c54c21cddbc7cc91dd162510efebc7c4 (MD5) Previous issue date: 2010-02-26 / The IEEE802.11 standard assumes that the stations (STAs) of a communications network have the same condictions during medium access, through the usage of the DCF (Distributed Coodination Function). The DCF states that all stations have the same probability of medium access, regardless of transmission rates or signal to noise ratios. Furthermore, such networks also presents an anomaly by which it is possible that a station with low transmission rate may request the channel for an extended period of time. In this context, this work proposes a QoS policy-based implementation based on the 802.11e standard, which aims to maintain a scenario of greater justice in IEEE802.11 networks. In doing so, it is proposed an algorithm to determine a Justice Index associated to a specific network, by examining the STAs connection rate, their type of service and the requirements for customer service. Thus, stations are served at rates that consider the physical characteristics of the network, in order to optimize their resources, from the viewpoint of the service provider. Results were obtained on simulated networks using the NS2 software considering the proposed policy of justice and show that the analyzed scenarios yield network troughput gain or at least result in a condition similar to that obtained without the use of the proposed justice policy. / O padr?o IEEE802.11 foi especificado presumindo condi??es de igualdade em rela??o ao acesso ao meio por parte das STAs de uma rede, pelo emprego do m?todo DCF , onde todas as STAs possuem a mesma probabilidade de acesso ao meio, sem levar em considera??o sua taxa de transmiss?o ou sua rela??o sinal-ru?do. No entanto, ? necess?rio ressaltar que tais redes apresentam uma anomalia, atrav?s da qual ? poss?vel que uma STA com baixa taxa de transmiss?o venha a ocupar o canal por um grande per?odo de tempo. Nesse contexto, esse trabalho apresenta uma proposta de pol?tica de QoS baseada na implementa??o do padr?o 802.11e, que objetiva manter um cen?rio de maior justi?a em redes IEEE802.11. Para isso ? proposto um algoritmo de c?lculo de ?ndice de justi?a atrav?s da an?lise da taxa de conex?o, do tipo de servi?o e dos requisitos necess?rios para atendimento do servi?o. Assim, as STAs s?o servidas a taxas que levam em conta as caracter?sticas f?sicas da rede, de forma a otimizar os seus recursos, do ponto de vista do provedor. Resultados obtidos com a pol?tica proposta em redes simuladas atrav?s do software NS2 demonstram que os cen?rios analisados resultaram em um ganho em rela??o ao troughput da rede ou, no m?nimo, em uma condi??o semelhante ? obtida sem a utiliza??o da pol?tica.

Ma Yu Tak. / Thesis submitted in: October 2006. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 70-73). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- IEEE 802.11 Standard --- p.4 / Chapter 3 --- Vulnerabilities of IEEE 802.11 --- p.8 / Chapter 3.1 --- Authentication Vulnerabilities --- p.8 / Chapter 3.2 --- Medium Access Control Vulnerabilities --- p.9 / Chapter 3.3 --- Proposed Counter-Measures --- p.10 / Chapter 4 --- Denial-of-Service Attacks by Exploiting the MAC protocol --- p.12 / Chapter 5 --- Simulation Results --- p.20 / Chapter 5.1 --- General DoS Attack Simulations --- p.21 / Chapter 5.1.1 --- Topology 1: A Simple Wireless Network --- p.21 / Chapter 5.1.2 --- Topology 2: Wireless Network in Ad-Hoc Mode --- p.24 / Chapter 5.1.3 --- Topology 3: Network with Hidden Node Problem --- p.29 / Chapter 5.2 --- Targeted DoS Attack Simulations --- p.32 / Chapter 5.2.1 --- Topology 4: A Simple Wireless Network --- p.32 / Chapter 5.2.2 --- Topology 4: A Simple Network with Reversed TCP Flows --- p.38 / Chapter 6 --- Detecting and Solving the Attacks --- p.41 / Chapter 6.1 --- Detection of Attacker --- p.41 / Chapter 6.1.1 --- Detecting General DoS Attackers --- p.41 / Chapter 6.1.2 --- Detecting Targeted DoS Attackers --- p.44 / Chapter 6.2 --- Possible Solutions to the DoS Attacks --- p.53 / Bibliography --- p.70 / Chapter A --- TCP Exponential Backoff with Non-Zero Throughput --- p.74 / Chapter A.1 --- TCP Exponential Backoff Background --- p.74 / Chapter A.2 --- Illustration by Simulation --- p.76 / Chapter A.3 --- Implication of the Finding --- p.77 / Chapter B --- Idle Sense in networks with Hidden Node Problem --- p.79 / Chapter B.1 --- Simulation findings --- p.79 / Chapter B.1.1 --- Four hidden nodes case --- p.79 / Chapter B.1.2 --- Analysis of the simulation results --- p.81 / Chapter B.1.3 --- Study of mixed node types --- p.82 / Chapter B.2 --- Possible approaches to use Idle Sense with Hidden Node Problem --- p.84 / Chapter B.2.1 --- Performance Evaluation --- p.88 / Chapter B.3 --- Conclusions --- p.91

"Increasing availability of high-speed Internet and wireless access points has allowed home users to connect not only their computers but various other devices to the Internet. Every device running different applications requires unique Quality of Service (QoS). It has been shown that delay- sensitive applications, such as VoIP, remote login and online game sessions, suffer increased latency in the presence of throughput-sensitive applications such as FTP and P2P. Currently, there is no mechanism at the wireless AP to mitigate these effects except explicitly classifying the traffic based on port numbers or host IP addresses. We propose CHAP, a credit-based queue management technique, to eliminate the explicit configuration process and dynamically adjust the priority of all the flows from different devices to match their QoS requirements and wireless conditions to improve application quality in home networks. An analytical model is used to analyze the interaction between flows and credits and resulting queueing delays for packets. CHAP is evaluated using Network Simulator (NS2) under a wide range of conditions against First-In-First- Out (FIFO) and Strict Priority Queue (SPQ) scheduling algorithms. CHAP improves the quality of an online game, a VoIP session, a video streaming session, and a Web browsing activity by 20%, 3%, 93%, and 51%, respectively, compared to FIFO in the presence of an FTP download. CHAP provides these improvements similar to SPQ without an explicit classification of flows and a pre- configured scheduling policy. A Linux implementation of CHAP is used to evaluate its performance in a real residential network against FIFO. CHAP reduces the web response time by up to 85% compared to FIFO in the presence of a bulk file download. Our contributions include an analytic model for the credit-based queue management, simulation, and implementation of CHAP, which provides QoS with minimal configuration at the AP."

Chan Pak To Patrick. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 82-86). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.viii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.2 --- The Problems --- p.3 / Chapter 1.3 --- My Contribution --- p.4 / Chapter 1.4 --- Thesis Organization --- p.5 / Chapter 2 --- Wireless LAN Security Model --- p.6 / Chapter 2.1 --- Preliminary Definitions on WLAN --- p.6 / Chapter 2.2 --- Security Model --- p.7 / Chapter 2.2.1 --- Security Attributes --- p.7 / Chapter 2.2.2 --- Security Threats in WLAN --- p.8 / Chapter 2.2.3 --- Attacks on Authentication Scheme --- p.10 / Chapter 2.2.4 --- Attacks on Keys --- p.10 / Chapter 2.3 --- Desired Properties of WLAN Authentication --- p.11 / Chapter 2.3.1 --- Security Requirements of WLAN Authentication --- p.11 / Chapter 2.3.2 --- Security Requirements of Session Keys --- p.12 / Chapter 2.3.3 --- Other Desired Properties of WLAN Authentication --- p.12 / Chapter 3 --- Cryptography --- p.14 / Chapter 3.1 --- Overview on Cryptography --- p.14 / Chapter 3.2 --- Symmetric-key Encryption --- p.15 / Chapter 3.2.1 --- Data Encryption Standard (DES) --- p.15 / Chapter 3.2.2 --- Advanced Encryption Standard (AES) --- p.15 / Chapter 3.2.3 --- RC4 --- p.16 / Chapter 3.3 --- Public-key Cryptography --- p.16 / Chapter 3.3.1 --- RSA Problem and Related Encryption Schemes --- p.17 / Chapter 3.3.2 --- Discrete Logarithm Problem and Related Encryption Schemes --- p.18 / Chapter 3.3.3 --- Elliptic Curve Cryptosystems --- p.19 / Chapter 3.3.4 --- Digital Signature --- p.19 / Chapter 3.4 --- Public Key Infrastructure --- p.20 / Chapter 3.5 --- Hash Functions and Message Authentication Code --- p.21 / Chapter 3.5.1 --- SHA-256 --- p.22 / Chapter 3.5.2 --- Message Authentication Code --- p.22 / Chapter 3.6 --- Entity Authentication --- p.23 / Chapter 3.6.1 --- ISO/IEC 9798-4 Three-pass Mutual --- p.23 / Chapter 3.6.2 --- ISO/IEC 9798-4 One-pass Unilateral --- p.24 / Chapter 3.7 --- Key Establishment --- p.24 / Chapter 3.7.1 --- Diffie-Hellman Key Exchange --- p.24 / Chapter 3.7.2 --- Station-to-Station Protocol --- p.25 / Chapter 3.8 --- Identity-Based Cryptography --- p.25 / Chapter 3.8.1 --- The Boneh-Franklin Encryption Scheme --- p.26 / Chapter 3.8.2 --- Au and Wei's Identification Scheme and Signature Scheme --- p.27 / Chapter 4 --- Basics of WLAN Security and WEP --- p.29 / Chapter 4.1 --- Basics of WLAN Security --- p.29 / Chapter 4.1.1 --- "Overview on ""Old"" WLAN Security" --- p.29 / Chapter 4.1.2 --- Some Basic Security Measures --- p.29 / Chapter 4.1.3 --- Virtual Private Network (VPN) --- p.30 / Chapter 4.2 --- WEP --- p.31 / Chapter 4.2.1 --- Overview on Wired Equivalent Privacy (WEP) --- p.31 / Chapter 4.2.2 --- Security Analysis on WEP --- p.33 / Chapter 5 --- IEEE 802.11i --- p.38 / Chapter 5.1 --- Overview on IEEE 802.11i and RSN --- p.38 / Chapter 5.2 --- IEEE 802.1X Access Control in IEEE 802.11i --- p.39 / Chapter 5.2.1 --- Participants --- p.39 / Chapter 5.2.2 --- Port-based Access Control --- p.40 / Chapter 5.2.3 --- EAP and EAPOL --- p.40 / Chapter 5.2.4 --- RADIUS --- p.41 / Chapter 5.2.5 --- Authentication Message Exchange --- p.41 / Chapter 5.2.6 --- Security Analysis --- p.41 / Chapter 5.3 --- RSN Key Management --- p.43 / Chapter 5.3.1 --- RSN Pairwise Key Hierarchy --- p.43 / Chapter 5.3.2 --- RSN Group Key Hierarchy --- p.43 / Chapter 5.3.3 --- Four-way Handshake and Group Key Handshake --- p.44 / Chapter 5.4 --- RSN Encryption and Data Integrity --- p.45 / Chapter 5.4.1 --- TKIP --- p.45 / Chapter 5.4.2 --- CCMP --- p.46 / Chapter 5.5 --- Upper Layer Authentication Protocols --- p.47 / Chapter 5.5.1 --- Overview on the Upper Layer Authentication --- p.47 / Chapter 5.5.2 --- EAP-TLS --- p.48 / Chapter 5.5.3 --- Other Popular ULA Protocols --- p.50 / Chapter 6 --- Proposed IEEE 802.11i Authentication Scheme --- p.52 / Chapter 6.1 --- Proposed Protocol --- p.52 / Chapter 6.1.1 --- Overview --- p.52 / Chapter 6.1.2 --- The AUTHENTICATE Protocol --- p.56 / Chapter 6.1.3 --- The RECONNECT Protocol --- p.59 / Chapter 6.1.4 --- Packet Format --- p.61 / Chapter 6.1.5 --- Ciphersuites Negotiation --- p.64 / Chapter 6.1.6 --- Delegation --- p.64 / Chapter 6.1.7 --- Identity Privacy --- p.68 / Chapter 6.2 --- Security Considerations --- p.68 / Chapter 6.2.1 --- Security of the AUTHENTICATE protocol --- p.68 / Chapter 6.2.2 --- Security of the RECONNECT protocol --- p.69 / Chapter 6.2.3 --- Security of Key Derivation --- p.70 / Chapter 6.2.4 --- EAP Security Claims and EAP Methods Requirements --- p.72 / Chapter 6.3 --- Efficiency Analysis --- p.76 / Chapter 6.3.1 --- Overview --- p.76 / Chapter 6.3.2 --- Bandwidth Performance --- p.76 / Chapter 6.3.3 --- Computation Speed --- p.76 / Chapter 7 --- Conclusion --- p.79 / Chapter 7.1 --- Summary --- p.79 / Chapter 7.2 --- Future Work --- p.80 / Bibliography --- p.82

Cui, Yuanyuan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (p. 64-68). / Abstract also in Chinese. / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1 .1 --- Motivations and Contributions --- p.1 / Chapter 1.2 --- Related Works --- p.3 / Chapter 1.3 --- Organization of the Thesis --- p.4 / Chapter Chapter 2 --- Background --- p.5 / Chapter 2.1 --- IEEE 802.11 --- p.5 / Chapter 2.1.1 --- IEEE 802.11 Topologies --- p.5 / Chapter 2.1.2 --- IEEE 802.11 MAC --- p.8 / Chapter 2.2 --- Voice over Internet Protocol (VoIP) --- p.11 / Chapter 2.2.1 --- A VoIP system --- p.11 / Chapter 2.2.2 --- QoS requirements for VoIP --- p.11 / Chapter 2.2.3 --- VoIP speech codecs --- p.12 / Chapter 2.3 --- VoIP over WLAN --- p.13 / Chapter 2.3.1 --- System Architecture of VoIP over WLAN --- p.14 / Chapter 2.3.2 --- VoIP Capacity over WLAN --- p.15 / Chapter 2.4 --- Skype --- p.16 / Chapter Chapter 3 --- Skype Rate Adaptation Mechanism --- p.17 / Chapter 3.1 --- Experimental Setting --- p.17 / Chapter 3.2 --- Overview --- p.19 / Chapter 3.3 --- Flow Rate Region --- p.20 / Chapter 3.4 --- Feedback: Receiver Report (RR) --- p.21 / Chapter 3.5 --- Bandwidth Usage Target (BM) --- p.24 / Chapter 3.6 --- Summary of Skype Rate Adaptation Mechanism --- p.28 / Chapter 3.7 --- Skype-emulating Traffic Generator --- p.28 / Chapter Chapter 4 --- "Call Admission, Fairness and Stability Control" --- p.32 / Chapter 4.1 --- Unfair and Instability problems for AVoIP --- p.32 / Chapter 4.1.1 --- Analysis --- p.32 / Chapter 4.1.2 --- Simulation Evaluation --- p.34 / Chapter 4.2 --- CFSC scheme --- p.37 / Chapter 4.2.1 --- Pre-admission Bandwidth-reallocation Call Admission Control (PBCAC) --- p.39 / Chapter 4.2.2 --- Fairness Control --- p.42 / Chapter 4.2.3 --- Stability Control --- p.43 / Chapter Chapter 5 --- Performance Evaluation of CFSC --- p.44 / Chapter 5.1 --- Evaluation of Fairness Control --- p.44 / Chapter 5.2 --- Evaluation of Stability Control --- p.46 / Chapter 5.3 --- Evaluation of PBCAC --- p.46 / Chapter 5.4 --- Evaluation of complete CFSC --- p.49 / Chapter Chapter 6 --- Conclusion --- p.51 / Appendices --- p.53 / References --- p.64

Information raining has been shown to address the problem of delivering Internet access to high-speed rail passengers. However, a wireline repeater or heterogeneous wireless relay design complicates implementation. Recent developments in extending mobile multihop relaying to the IEEE 802.16e standard have made it feasible to deploy an information raining using a common radio and physical layer. Two automatic repeat request techniques and two network coding techniques are proposed. An upper and lower bound on delay is established for a single fully network coded relay system operating in static signal to noise ratio conditions. Simulations involving a physical layer model demonstrate that network coding schemes can attain the maximum downlink capacity.

Information raining has been shown to address the problem of delivering Internet access to high-speed rail passengers. However, a wireline repeater or heterogeneous wireless relay design complicates implementation. Recent developments in extending mobile multihop relaying to the IEEE 802.16e standard have made it feasible to deploy an information raining using a common radio and physical layer. Two automatic repeat request techniques and two network coding techniques are proposed. An upper and lower bound on delay is established for a single fully network coded relay system operating in static signal to noise ratio conditions. Simulations involving a physical layer model demonstrate that network coding schemes can attain the maximum downlink capacity.

Multiple Input Multiple Output (MIMO) systems are a key technology for next generation high speed wireless communication standards like 802.11n, WiMax etc. MIMO enables spatial multiplexing to increase channel bandwidth which requires the use of multiple antennas in the receiver and transmitter side. The increase in bandwidth comes at the cost of high silicon complexity of MIMO detectors which result, due to the intricate algorithms required for the separation of these spatially multiplexed streams. Previous implementations of MIMO detector have mainly dealt with the issue of complexity reduction, latency minimization and throughput enhancement. Although, these detectors have successfully mapped algorithms to relatively simpler circuits but still, latency and throughput of these systems need further improvements to meet standard requirements. Additionally, most of these implementations don’t deal with the requirements of reconfigurability of the detector to multiple modulation schemes and different antennae configurations. This necessary requirement provides another dimension to the implementation of MIMO detector and adds to the implementation complexity. This thesis focuses on the efficient VLSI implementation of the MIMO detector with an emphasis on performance and re-configurability to different modulation schemes. MIMO decoding in our detector is based on the fixed sphere decoding algorithm which has been simplified for an effective VLSI implementation without considerably degrading the near optimal bit error rate performance. The regularity of the architecture makes it suitable for a highly parallel and pipelined implementation. The decoder has intrinsic traits for dynamic re-configurability to different modulation and encoding schemes. This detector architecture can be easily tuned for high/low performance requirements with slight degradation/improvement in Bit Error Rate (BER) depending on needs of the overlying application. Additionally, various architectural optimizations like pipelining, parallel processing, hardware scheduling, dynamic voltage and frequency scaling have been explored to improve the performance, energy requirements and re-configurability of the design.

The IEEE 802.15.4 standard defines the implementation of a Low-Rate Wireless Personal Area Network (WPAN). While the current version of the standard was ratified in 2006, there is still no readily available Medium Access Control (MAC) layer and/or Physical (PHY) layer for Altera Field Programmable Gate Arrays (FPGAs) in the public domain. This research investigates the implementation of the standard using an Altera FPGA for the MAC layer and PHY layer drivers. The Freescale MC13192 transceiver was used for the physical portion of the PHY layer, which includes the RF front end of the system. The purpose of this research was to implement a basic full function device (FFD), which is capable of acting as a node in the network, as well as co-ordinating it. This allows a simple network to be tested by loading the same code on two FPGA boards, with one configured to act as a coordinator and the other as a device. The flexibility of the standard means that there are several implementation choices to be made, each of which limits the compatibility with devices using other implementation options. The implementation and design decisions made in producing a preliminary core are described in detail. The implementation of the MAC layer primitives is discussed at length as these were not available as source code. These primitives are the building blocks for the core functions of the system. Specifically, the functionality of the Energy Detection (ED) scan, stream transmit and stream receive functions are explored in detail. The code has been implemented using C and is run on the Altera Nios II soft-core processor. The work presented here is an initial implementation meant to serve as a foundation for further research. Additional functionality defined by the standard could be added, or optimization of individual functions could be explored. The current implementation also has the potential to serve as the foundation for research into various sensors which may be part of end devices in the network.

IEEE 802.11-based wireless local area networks (WLANs) have been set up in many public places in last few years. It provides convenient network connectivity to mobile nodes (MNs) and allows users moving from one wireless network to another. With mobility protocol support, such as Mobile IPv6 (MIPv6), people can roam across wireless IP subnets without loss of network-layer connectivity. However, the handover latency may make users feel uncomfortable in MIPv6. To support seamless handover, an enhanced MIPv6 scheme, Fast Handovers for Mobile IPv6 (FMIPv6)[13], was been proposed. In order to further reduce the handover latency, integrating the lower layer procedure with the upper layer procedure is necessary. Unfortunately, when integrating the IEEE 802.11-based standard with FMIPv6, FMIPv6 always fails to perform predictive handover procedure. This may make the handover procedure result in reactive handover. It is because of the protocol nature of IEEE 802.11 and the weak relation between IEEE 802.11 and FMIPv6. Furthermore, a MN can¡¦t receive packets destined to it when it sends the Fast Binding Update (FBU) to the original access router (OAR). This would cause unnecessary packet loss and make the redictive handover have more packet loss then reactive. Those issues will cause quality of services degradation and make real-time applications unreachable. In this dissertation, a low-latency MIPv6 handover scheme will be proposed. It is a FMIPv6-based scheme which is assisted by an active-scan link layer scheme. It has the advantage of FMIPv6 and can reduce unnecessary packet loss when the handover occurs. Also, with the assistance of the active scheme, it can avoid the longest phase that IEEE 802.11 will enter, and can lower the handover latency.