A Traffic Engineering Algorithm for Provisioning Virtual Private Networks in the Enhanced Hose Model

Abstract: A Virtual Private Network is a logical network established on top of a public packet switched network. To guarantee that quality of service requirements, specified by customers, can be met, the network service provider needs to reserve enough resources on the network and allocate/manage them in an optimal way. Traffic engineering algorithms can be used by the Network Service Provider to establish multiple Virtual Private Networks in an optimal way, while meeting customers' Quality of Service requirements. For delay sensitive network applications, it is critical to meet both bandwidth and delay requirements. In contrast to traditional Virtual Private Network Quality of Service models (customer-pipe model and hose model), which focused only on bandwidth requirements, a new model called the enhanced hose model has been proposed, which considers both bandwidth and delay requirements. However, to the best of our knowledge, thus far, traffic engineering problems associated with establishing multiple enhanced hose model Virtual Private Networks have not been investigated. In this paper, we proposed a novel Virtual Private Network traffic engineering algorithm, called the minimum bandwidth-delay cost tree algorithm to address these problems. According to experimental simulations conducted and reported in our paper, the minimum bandwidth-delay cost tree algorithm can indeed achieved better performance (lower rejection ratios) compared to previous algorithms

On Connected Target Coverage for Wireless Heterogeneous Sensor Networks with Multiple Sensing Units

The paper considers the connected target coverage (CTC) problem in wireless heterogeneous sensor networks (WHSNs) with multiple sensing units, termed MU-CTC problem. MU-CTC problem can be reduced to a connected set cover problem and further formulated as an integer linear programming (ILP) problem. However, the ILP problem is an NP-complete problem. Therefore, two distributed heuristic schemes, REFS (remaining energy first scheme) and EEFS (energy efficiency first scheme), are proposed. In REFS, each sensor considers its remaining energy and its neighbors’ decisions to enable its sensing units and communication unit such that all targets can be covered for the required attributes and the sensed data can be delivered to the sink. The advantages of REFS are its simplicity and reduced communication overhead. However, to utilize sensors’ energy efficiently, EEFS is proposed. A sensor in EEFS considers its contribution to the coverage and the connectivity to make a better decision. To our best knowledge, this paper is the first to consider target coverage and connectivity jointly for WHSNs with multiple sensing units. Simulation results show that REFS and EEFS can both prolong the network lifetime effectively. EEFS outperforms REFS in network lifetime, but REFS is simpler

Cross-Layer Handover Scheme for Multimedia Communications in Next GenerationWireless Networks

ROC NSC [97-2221-230 E-018-020-MY3, 98-2218-E-151-004-MY3]In order to achieve seamless handover for real-time applications in the IP Multimedia Subsystem (IMS) of next generation network, a multiprotocol combined handover mechanism is proposed in this paper. We combine SIP (Session Initiation Protocol), FMIP (Fast Mobile IPv6 Protocol), and MIH (Media Independent Handover) protocols by cross-layer design and optimize those protocols' signaling flows to improve the performance of vertical handover. Theoretical analysis and simulation results illustrate that our proposed mechanism performs better than the original SIP and MIH combined handover mechanism in terms of service interruption time and packet loss

Guaranteed QoS Provision Scheduling Mechanism for CBR Traffic in IEEE 802.16 BWA Systems

[[abstract]]Constant Bit Rate (CBR) traffic is expected to be an important traffic source in wireless networks. Such sources usually have stringent delay and loss requirements and in many cases they should be delivered exactly as they were generated. In this paper, we propose a novel uplink packet scheduling policy for CBR traffic to support real-time applications, with strict delay requirements in IEEE 802.16 broadband wireless access (BWA) systems. Under such a scheme, the CBR traffic was characterized by its sustained traffic rate and tolerated jitter. The proposed transmit permission policy can derive sufficient conditions such that all the CBR sources satisfy their delay constraints to provide deterministic quality of service (QoS) guarantees. In addition to theoretical analysis, simulations are conducted to evaluate the performance of the proposed scheme. As it turns out, our design provides a good quality performance in the IEEE 802.16 BWA systems.[[notice]]補正完畢[[incitationindex]]SCI[[incitationindex]]E

Quality of Service Guarantees in IEEE 802.11 Wireless LANs

隨著通訊技術的發展，無線網路已成為電腦網路中日趨重要的研究領域，但是，大部份無線網路的媒體存取控制協定卻因缺乏優先等級或一套完整的存取控制策略而無法支援未來傳輸多媒體資訊的需求，在本文中，我們提出優先權的概念來支援多媒體資訊的傳輸，並分別為兩種不同的無線網路設計一套以優先等級為基礎的無線網路存取控制機制。In wireless local area networks (WLANs), the medium access control (MAC) layer protocol is the main element that determines the efficiency of sharing the limited and unreliable communication bandwidth of the wireless channel. IEEE 802.11, the standard of Wireless Local Area Networks (WLANs), allows the coexistence of asynchronous and time-bounded traffic using the Distributed Coordination Function (DCF) and Point Coordination Function (PCF) modes of operations, respectively. In spite of its increasing popularity in real-world applications, the protocol suffers from the lack of any priority and access control policy to cope with various types of multimedia traffic as well as user mobility. Besides, the backoff parameters of its collision avoidance mechanism are hard-wired in the physical layer, and are far from the optimal setting in some network configuration conditions especially in heavy load or error-prone WLAN environments. To expand support for applications with Quality-of-Service (QoS) requirements, the 802.11E Task Group was formed to enhance the original IEEE 802.11 Medium Access Control (MAC) protocol. However, the problem of choosing the right set of MAC parameters and QoS mechanism to provide predictable QoS in IEEE 802.11 networks is still remain unsolved. In this dissertation, we propose a polling with non-preemptive priority based access control scheme for the IEEE 802.11 protocol. Under such a scheme, modifying the DCF access method in the contention period supports multiple levels of priorities such that user handoff call can be supported in wireless LANs. The proposed transmit-permission policy and adaptive bandwidth allocation scheme derive sufficient conditions such that all the time-bounded traffic sources satisfy their time constraints to provide various QoS guarantees in the contention free period while maintaining efficient bandwidth utilization at the same time. In addition, our proposed scheme is provably optimal for voice traffic in that it gives minimum average waiting time for voice packets. In addition to theoretical analysis, simulations are conducted to evaluate the performance of the proposed scheme. As it turns out, our design indeed provides a good performance in the IEEE 802.11 WLANs environment, and can be easily incorporated into the Hybrid Coordination Function (HCF) access scheme in the IEEE 802.11e standard.Table of Contents Dedication…….…iii Acknowledgements……………...……iv List of Tables………...…vii List of Figures……………………….viii Chapters 1. Introduction………………..1 1.1 QoS Sensitive Wireless LANs…………..……1 1.2 Overview of Existing Approaches…………2 1.3 Main Contributions………………..6 1.4 Organization of the Dissertation……………………..8 2. Preliminaries…….………10 2.1 IEEE 802.11 Standard……………….10 2.2 IEEE 802.11 Topology……………..…11 2.2.1 Independent BSS Networks………...…11 2.2.2 Extended Service Set Networks...……...12 2.3 IEEE 802.11 MAC Layer…..……13 2.3.1 Distributed Coordination Function....14 2.3.2 Point Coordination Function…………15 2.4 IEEE 802.11E Standard……………………..17 2.4.1 The Enhanced DCF……...17 2.4.2 Direct Link Protocol………………..…19 2.4.3 The Controlled HCF…………………..…20 2.5 WiFi…………………20 3. Current Research Activities………………………...22 3.1 Differentiation Mechanism……………….…22 3.2 Admission Control and Bandwidth Reservation…....24 3.3 Link Adaptation……26 4. Dynamic Optimization for DCF Access Method……28 5. Quality-of-Service Provisioning System for Multimedia Transmission……..35 5.1 Priority Enforcement Mechanism for Request Access……37 5.2 The Packet Transmit-Permission Policy for Real-Time Traffic…….…45 5.3 Adaptive Bandwidth Management Strategy……………………………...……53 6. Simulations and Performance Evaluation…………………………………………56 6.1 Simulation Environment………….………..56 6.2 Numerical and Simulation Results…….…..….…..58 6.2.1 Dynamic Optimization for DCF Access……...……58 6.2.2 QoS Provisioning System for Multimedia Transmission…...…….………62 7. Conclusions and Future Work……………..68 7.1 Research Contributions…………..…..68 7.2 Future Research Directions…………..…..69 Bibliography…….………….7