在無線傳輸網路環境日益普遍的今日，以往各類型只在固定網路傳輸上的應用都紛紛的套用在具移動性要求的無線傳輸網路上。然而無線網路的傳輸環境比固定網路有更多使用上的條件限制以及需克服技術上的問題，像是與基地台傳輸距離的限制而產生對傳輸連線上換手( Handover )的需求，以及因為換手而導致傳輸時各種時間上的延遲( Delay )和抖動( Jitter )，若是多媒體 (Multimedia) 的多點傳輸( Multicasting )需求，則更要對傳輸內容的特性和傳輸協定的可靠性、可擴展性及穩定性加以考量。再者因為在無線傳輸環境中接收端和發送端都可能是處於移動的狀態，所以整個傳輸架構的健全性 ( Robustness )也十分重要。基於這些需求，本論文提出利用跨層(Cross Layer)設計來匯集較低網層協定在傳輸速率(Throughput)上的優勢，以及由較高網層協定提供之針對傳輸內容不同需求的應用彈性，降低協定在既有網路中實現的困難度，以期Wireless網路提供多點傳輸時在滿足穩定性及可靠性的要求下，達到最佳的傳輸速率表現。 / Applications of wireless mobile network are prevalent in recent years. Many applications inherited or developed from wired network have been proposed to enable mobile nodes to connect to wireless mobile network to access resources/services from Internet using multicasting protocol. However, wireless mobile networks have difficulty in forwarding information due to its inherent dynamism and frequent topology changes. To multicast multimedia data stream, we have to consider not only the issues of reliability, robustness, scalability and stability of routing protocol, but also the content of transmission. Besides, when handover occurs frequently during transmission, the throughput decreases rapidly due to severe jitter and delay. This thesis presents a hybrid multicasting policy for wireless mobile network to build a multicasting architecture using cross layer design of network layer and application layer to manage quality transmission according to flexible requirements. In summary, our goal is to optimize throughput in order to fulfill the requirement of reliability and stability of multicasting in wireless mobile network.

Delay tolerant networks (DTNs) are a class of emerging networks that exhibit significantly different characteristics from today's Internet, such as intermittent connectivity, large delay, and high loss rates. DTNs have important applications in disaster relief, military, rural Internet access, environmental sensing and surveillance, interplanetary communication, underwater sensing, and vehicular communication. While not the common case for networking, DTNs represent some of the most critical cases, where the ability to communicate can make a huge difference for human lives. Supporting effective communication in DTNs, however, is challenging. First, with intermittent connectivity, DTNs are often extremely limited in capacity. Second, given resource limitations and uncertainty in DTNs, it is critical to deliver data efficiently and robustly. The situation is especially acute for multicast which sends data to multiple destinations. This thesis seeks to address these two issues. To enhance network capacity in DTNs, we propose a message ferrying scheme that exploits the use of special mobile nodes (called message ferries) and controlled device mobility to deliver data. Message ferries are utilized to transport data via mobility between sources and destinations. We develop a foundation for the control of the mobility of message ferries, and nodes if possible, to cooperatively deliver data under a variety of conditions. We also study another approach which deploys new nodes called throwboxes to enhance capacity. Throwboxes are small and inexpensive wireless devices. By relaying data between mobile nodes, throwboxes are able to create data transfer opportunities that otherwise would not exist. We systematically investigate the issues of deployment and routing, and develop algorithms for various deployment and routing approaches. Based on extensive evaluation, we obtain several findings to guide the design and operation of throwbox-augmented DTNs. To address the issue of efficient and robust data delivery, we focus on DTN multicasting. Given the unique characteristics of DTNs, traditional solutions such as IP multicast can not be simply ported to DTNs. We identify the limitations of IP multicast semantics in DTNs and define new semantic models for DTN multicast. Based on these semantic models, we develop and evaluate several multicast routing algorithms with different routing strategies.

Energy is a limited source in wireless sensor networks and in most applications, it is non-renewable / so designing energy-effcient communication patterns is very important. In this thesis, we de

Thesis (M.ICT.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 112-121.

There has been a significant rise in the provision of television and video services over IP (IPTV) in recent years. Increasing network capacity and falling bandwidth costs have made it both technically and economically feasible for service providers to deliver IPTV services. Several telecommunications (telco) operators worldwide are rolling out IPTV solutions and view IPTV as a major service differentiator and alternative revenue source. The main challenge that IPTV providers currently face, however, is the increasingly congested television service provider market, which also includes Internet Television. IPTV solutions therefore need strong service differentiators to succeed. IPTV solutions can doubtlessly sell much faster if they are more affordable or low-cost. Advertising has already been used in many service sectors to help lower service costs, including traditional broadcast television. This thesis therefore explores the role that advertising can play in helping to lower the cost of IPTV services and to incentivise IPTV billing. Another approach that IPTV providers can use to help sell their product is by addressing the growing need for control by today's multimedia users. This thesis will therefore explore the varied approaches that can be used to achieve viewer focused IPTV implementations. To further lower the cost of IPTV services, telcos can also turn to low-cost, open source platforms for service delivery. The adoption of low-cost infrastructure by telcos can lead to reduced Capital Expenditure (CAPEX), which in turn can lead to lower service fees, and ultimately to higher subscriptions and revenue. Therefore, in this thesis, the author proposes a CustOmisable, INcentive (COIN) driven Video on Demand (VoD) framework to be developed and deployed using the Mobicents Communication Platform, an open source service creation and execution platform. The COIN framework aims to provide a viewer focused, economically competitive service that combines the potential cost savings of using free and open source software (FOSS), with an innovative, incentive-driven billing approach. This project will also aim to evaluate whether the Mobicents Platform is a suitable service creation and execution platform for the proposed framework. Additionally, the proposed implementation aims to be interoperable with other IPTV implementations, hence shall follow current IPTV standardisation architectures and trends. The service testbed and its implementation are described in detail and only free and open source software is used; this is to enable its easy duplication and extension for future research. / TeX output 2012.03.02:1241 / Adobe Acrobat 9.2 Paper Capture Plug-in

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Network coding is a technique used to increase the capacity of a network by combining messages sent over the network. The combined messages could be separated by using sufficient original messages which were used to combine the messages. Network coding can be implemented in different layers of the 051 stack, but to date a complete comparison between different implementations of network coding has not been done. The goal of this dissertation is to implement a wireless node model with network coding in the MAC layer and evaluate the performance characteristics of reference networks that implement the new node model. This will serve as the first step of a greater goal, namely finding the most favourable position in the 051 stack to implement network coding. The characteristics of the different implementations of network coding are presented in this dissertation. Simulations were done in OPNET® to find further attributes concerning the implementation of network coding in the MAC layer. The simulation process used is presented and explained, and the results from the simulations are analysed. Network coding in the simulations was implemented opportunistically. The results show that the more often different nodes send frames to the coding node, the better network coding performs. The work contributes to finding the best layer for implementing network coding for its increased throughput. A benchmark network was created so that network coding could be implemented in all the layers of the 051 stack, and then be compared to each other. An implementation of network coding in the MAC layer was simulated and analyzed. We conclude that, because there are so many different purposes for which networks are used, a single instance of network coding is unlikely to be similarly beneficial to all purposes. There still remains work to find the most favourable position for network coding in the 051 stack for all the different types of network coding. / Thesis (M. Ing. (Computer and Electronical Engineering))--North-West University, Potchefstroom Campus, 2011

在耐延遲網路環境下節點的相遇情況不是很頻繁，這可能導致節點間的連線斷斷續續，使得有效地將訊息傳遞成為一件困難的事情。藉由社群感知轉送機制的中間度指標特性，可以來提升傳送成功率。雖然大多數研究幾乎都是將訊息轉送到單一目的地或是多個且已知的目的地。然而，一些應用像是廣告的散佈，要將訊息送給對訊息有興趣的人，但卻不知道是誰。因此，關鍵的問題為如何建立社群網路關係的親密度機制，來選擇作為轉送訊息的節點，並利用群體廣播的方式盡可能有效地傳播至最多可能目標目的地，進而提升效能。 本論文以群播機制和社群感知當作基礎概念，來設計新的轉送訊息的方法和公式化選擇中繼節點的機制。最後，我們使用政治大學實際軌跡來模擬，將模擬結果與其它路由演算法比較，其結果證明我們所提出的方法能提高訊息傳送成功率和正確率，降低傳送延遲時間和傳送訊息的成本。 / In delay tolerant networks (DTNs), nodes infrequently encounter with each others. This results in intermittent connectivity of the nodes, and makes it difficult to deliver the message effectively. A social-aware forwarding scheme can help for successful delivery ratio by utilizing the characteristic of their centrality metric. Most of the previous studies focus on message delivery to single destination or some priori known destinations. However, some applications like advertisement dissemination may not know who will be the interested persons to be delivered. Therefore, the key challenge is how to establish the social relationship strategy to select appropriate nodes as relays, and furthermore to use multicasting to disseminate effectively as many “target” destinations as possible to improve the performance. This thesis developed a new strategy which has a new forwarding message scheme and formulates the selection of the relay nodes based on the concept of the multicasting and the social network. Finally, we used the reality trace data of National Chengchi University to simulate. The simulation results are compared to others DTNs routing protocols as well as other social-aware forwarding schemes. The results showed that our proposed approach can enhance the successful delivery ratio and delivery accuracy, decrease the delivery delay and reduce the delivery overhead.

Simulation has become an important way to observe and understand various networking phenomena under various conditions. As the demand to simulate larger and more complex networks increases, the limited computing capacity of a single workstation and the limited simulation capability of a single network simulator have become apparent obstacles to the simulationists. In this research we develop techniques that can scale a simulation to address the limited capacity of a single workstation, as well as techniques that can compose a simulation from different simulator components to address the limited capability of a single network simulator. We scale a simulation with two different approaches: 1) We reduce the resource requirement of a simulation substantially, so that larger simulations can fit into one single workstation. In this thesis, we develop three technqiues (Negative Forwarding Table, Multicast Routing Object Aggregation and NIx-Vector Unicast Routing) to aggregate and compress the large amount of superfluous or redundant routing state in large multicast simulations. 2) The other approach to scale network simulations is to partition a simulation model in a way that makes the best use of the resources of the available computer cluster, and distribute the simulation onto the different processors of the computer cluster to obtain the best parallel simulation performance. We develop a novel empirical methodology called BencHMAP (Benchmark-Based Hardware and Model Aware Partitioning) that runs small sets of benchmark simulations to derive the right formulas of calculating the weights that are used to partition the simulation on a given computer cluster. On the other hand, to address the problem of the limited capability of a network simulator, we develop techniques for building complex network simulations by composing from independent components. With different existing simulators good at different protocol layers/scenarios, we can make each simulator execute the layers where it excels, using a simulation backplane to be the interface between different simulators. In this thesis we demonstrate that these techniques enable us to not only scale up simulations by orders of magnitude with a good performance, but also compose complex simulations with high fidelity.

This work focuses on the performance characterization of distributed collaborative ad-hoc networks, focusing on such metrics as the lifetime, latency, and throughput capacity of two such classes of networks. The first part concerns modeling and optimization of static Wireless Sensor Networks, specifically dealing with the issues of energy efficiency, lifetime, and latency. We analyze and characterize these performance measures and discuss various fundamental design tradeoffs. For example, energy efficiency in wireless sensor networks can only be improved at the cost of the latency (the delay incurred during communication). It has been clearly shown that improvement in energy efficiency through data aggregation increases the latency in the network. In addition, sleep-active duty cycling of nodes (devices constituting the network), a commonly employed mechanism to conserve battery lifetime in such networks, has adverse effects on their functionality and capacity. Hence these issues deserve a detailed study. The second part of this work concerns performance modeling of Delay Tolerant Networks (DTNs) and Sparse Mobile Ad-Hoc Networks (SPMANETs) in general. We first investigate the effect of modern coding, such as the application of packet-level rateless codes, on the latency, reliability, and energy efficiency of the network. These codes provide us the means to break large messages into smaller packets thereby enabling efficient communication. The work then focuses on developing and formalizing an information-theoretic framework for Delay Tolerant- and other Sparse Mobile Networks. This is enabled by the use of an embedded-Markov-chain approach used for complex queuing-theoretic problems. An important goal of this work is to incorporate a wide range of mobility models into the analysis framework. Yet another important question will be the effect of changing the mobility on the comparative performance of networking protocols. Lastly, the framework will be extended to various communication paradigms such as two-hop vs multi-hop routing, unicast, and multicast.