行動資訊服務環境的理想，是要提供一個無所不在的資訊環境，讓使用者可以在任何地方、任何時間，利用各種有線或無線的傳輸網路去存取可用資源。行動通訊與行動計算的飛越發展使得行動資訊服務的理想指日可待。而無線網路要支援一些即時多媒體通訊傳輸，服務品質便成為很重要的課題，頻寬計算更是其中最關鍵的議題。除了現有IEEE 802.11無法有效支援多跳接網路使之達到服務品質的保證外，也由於Ad Hoc網路移動性及流量多變性的特性，要在這樣的無線環境下支援服務品質便成為一個困難的挑戰。由於我們參考的論文皆在TDMA的環境下探討頻寬保證的問題，但是這在無線多跳接網路下十分複雜且受限制。因此我們針對此問題提出一個簡單的頻寬計算方法來估算網路現有頻寬，用於頻寬繞徑演算法上以支援無線網路服務品質。實驗結果顯示我們的方法比過去的頻寬計算方法更簡單、誤差少、適用於各種MAC層的通訊協定，也容易與現有頻寬繞徑演算法結合以執行允入控制機制。透過我們的方法，可以有效地支援無線多跳接網路服務品質。 / The idea of mobile computing service is to provide a ubiquitous information environment. However, the present mobile ad hoc networks still can’t support real-time transmission very effectively. In other words, the capability of supporting QoS guarantee has become a very important issue. IEEE 802.11 PCF adopts the polling scheme to provide time-bounded traffic services, which is not suitable in multi-hop networks. Moreover, due to mobility and traffic dynamics, the network resource management is more difficult. Thus, QoS support in such an environment is a challenge. Specifically, path bandwidth calculation is the first key element. All the bandwidth routing papers we referenced were using TDMA. However, they are restricted in TDMA systems and somehow complicated in path bandwidth calculation. We propose a simple path bandwidth calculation solution that can be used whatever MAC protocol is. It is also easy to implement call admission control and to combine with bandwidth routing algorithms. The simulation results illustrate that the statistical error rates of our path bandwidth calculation are within an acceptable range. By path bandwidth calculation, bandwidth routing algorithm is also developed to achieve the objective of supporting QoS in wireless multihop networks effectively.

Shared resource contention is a significant problem in multi-core systems and can have a negative impact on the system. Memory contention occurs when the different cores in a processor access the same memory resource, resulting in a conflict. It is possible to limit memory contention through resource reservation where a part of the system or an application is reserved a partition of the shared resource. We investigated how applying memory bandwidth restrictions using MemGuard can aid in synchronizing execution times of parallel tasks. We further investigate when memory bandwidth restrictions are applicable. We conduct three experiments to investigate when bandwidth restrictions are applicable. Firstly, we conducted an experiment to pinpoint when the memory bandwidth saturates a core. Secondly, we investigated our adaptive memory partitioning scheme performance against static and no partitioning. Finally, we tested how our adaptive partitioning scheme and static partitioning can isolate a workload against an interfering memory intensive workload running on a separate core. As the experiments only were conducted on one system, pinpointing the general point of contention was difficult, seeing that it can differ significantly from system to system. Through our experiments, we see that memory bandwidth partitioning has the ability to decrease the execution time of feature detection algorithms, which means that memory bandwidth partitioning potentially can help threads to reach their synchronization points simultaneously.

In a conventional charge-pump based PLL design, the loop parameters such as the band-width, jitter performance, charge-pump current, pull-in range among others govern the ar-chitecture and implementation details of the PLL. Different loop parameter specificationschange with a change in the reference frequency and inmost cases, requires careful re-designof some of the PLL blocks. This thesis describes the implementation of a semi-digital PLLfor high bandwidth applications, which is self-compensated, low-power and exhibits band-width tracking for all reference frequencies between 40 MHz and 1.6 GHz in 65nm CMOStechnology.This design can be used for a wide range of reference frequencies without redesigning anyblock. The bandwidth can be fixed to some fraction of the reference frequency during designtime. In this thesis, the PLL is designed to make the bandwidth track 5% of the referencefrequency. Since this PLL is self-compensated, the PLL performance and the bandwidthremains same over PVT corners.

Because there has been a rapid development in wireless networks, it is important to provide quality-of-service (QoS) guarantees as they are expected to support multimedia applications. In this paper we propose a new bandwidth reservation scheme based on the characteristic of the cell equipped with sector antenna and 2-tier cell structure. According to this information, the proposed scheme can predict the next location of each connection and precisely reserve bandwidth in appropriate neighboring cells, not all of its neighboring cells. In addition, the proposed scheme incorporates bandwidth borrowing mechanism into call admission control strategy. The combination of bandwidth reservation and bandwidth borrowing provides network users with QoS in terms of guaranteed bandwidth, call blocking and call dropping probabilities.

Available bandwidth is a time-dependant variable that defines the spare bandwidth in an end-to-end network path. Currently, there is significant focus in the research community on the design and development of Available Bandwidth Estimation Tools (ABETs), and a few tools have resulted from this research. However, there is no comprehensive evaluation of these tools and the research work in this thesis attempts to fill that gap. A performance evaluation of important ABETs like Pathload, IGI and pathChirp in terms of their accuracy, convergence time and intrusiveness is conducted in several scenarios. A 2k factorial design is carried out to analyze the importance of the size of probe packets, number of probe packets per train, number of trains, and frequency of runs in these performance metrics. ABETs are very important because of their potential in solving many network research problems. For example, ABETs can be used in congestion control in transport layer protocols, network management tools, route selection and configuration in overlay networks, SLA verification, topology building in peer to peer networks, call admission control, dynamic encoding rate modification in streaming applications, traffic engineering, capacity planning, intelligent routing systems, etc. This thesis looks at applying ABETs in the congestion control of transmission control protocol (TCP).Current implementations of TCP in the Internet perform reasonably well in terms of containing congestion, but their sending rate adjustment algorithm is unaware of the accurate network conditions and available resources. TCP's Additive Increase Multiplicative Decrease (AIMD) congestion control algorithm cannot efficiently utilize the available bandwidth to the full potential and this is especially true in high bandwidth networks.

We study the maximum differential coloring problem, where an n-vertex graph must be colored with colors numbered 1, 2...n such that the minimal difference between the two colors of any edge is maximized. This problem is motivated by coloring maps in which not all countries are contiguous. Since it is known that this problem is NP-hard for general graphs; we consider planar graphs and subclasses thereof. In Chapter 1 we introduce the topic of this thesis and in Chapter 2 we review relevant definitions and basic results. In Chapter 3 we prove that the maximum differential coloring problem remains NP-hard even for planar graphs. Then, we present tight bounds for regular caterpillars and spider graphs and close-to-optimal differential coloring algorithms for general caterpillars and biconnected triangle-free outer-planar graphs. In Chapter 4 we introduce the (d, kn)-differential coloring problem. While it was known that the problem of determining whether a general graph is (2, n)-differential colorable is NP-complete, in this chapter we provide a complete characterization of bipartite, planar and outerplanar graphs that admit (2, n)-differential colorings. We show that it is NP-complete to determine whether a graph admits a (3, 2n)-differential coloring. The same negative result holds for the ([2n/3], 2n)-differential coloring problem, even when input graph is planar. In Chapter 5 we experimentally evaluate and compare several algorithms for coloring a map. Motivated by different application scenarios, we classify our approaches into two categories, depending on the dimensionality of the underlying color space. To cope with the one dimensional color space (e.g., gray-scale colors), we employ the (d, kn)-differential coloring. In Chapter 6 we describe a practical approach for visualizing multiple relationships defined on the same dataset using a geographic map metaphor, where clusters of nodes form countries and neighboring countries correspond to nearby clusters. The aim is to provide a visualization that allows us to compare two or more such maps. In the case where we are considering multiple relationships we also provide an interactive tool to visually explore the effect of combining two or more such relationships. Our method ensures good readability and mental map preservation, based on dynamic node placement with node stability, dynamic clustering with cluster stability, and dynamic coloring with color stability. Finally in Chapter 7 we discuss future work and open problems.

Many next-generation e-science applications require fast and reliable transfer of large volumes of data, now frequently termed as ``big data", with guaranteed performance, which is typically enabled by the bandwidth reservation service in high-performance networks (HPNs). Users normally specify the properties and requirements of their data transfers in the bandwidth reservation requests (BRRs), and want to make bandwidth reservations on the HPNs to satisfy the requirements of their data transfers. The challenges of the bandwidth reservation arise from the requirements desired by both the users and the bandwidth reservation service providers of the HPNs. We focus on two important bandwidth reservation problems formulated from the combinations of the requirements from both users and the bandwidth reservation service providers of the HPNs: (i) Problem of scheduling all BRRs in one batch while achieving their best average data transfer earliest completion time and shortest duration, and (ii) Problem of scheduling two generic types of BRRs concerning data transfer reliability with different objectives and constraints in unreliable HPNs that are subject to node and link failures. We prove the two subproblems of the first problem are NP-complete problems, and fast and efficient heuristic algorithms are proposed. While the two subproblems of the second problem can be optimally solved in polynomial time. The corresponding optimal algorithms and proofs are given. We conduct extensive simulations to compare the performance of the proposed heuristic and optimal algorithms with naive scheduling algorithms and the algorithms currently used in production network in various performance metrics. The performance superiority of the proposed heuristic and optimal algorithms is verified.

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No / A miniaturized modified planar inverted-F antenna (PIFA) is presented and experimentally studied. This antenna consists of a planar rectangular monopole top-loaded with a rectangular patch attached to two rectangular plates, one shorted to the ground and the other suspended, both placed at the optimum distance on each side of the planar monopole. The fabricated antenna prototype had a measured impedance bandwidth of 125%, covering 3 to 13GHz for reflection coefficient better than -10 dB. The radiator size was 20 x 10 x 7.5 mm(3), making it electrically small over most of the band and suitable for incorporation in mobile devices. The radiation patterns and gains of this antenna have been cross-validated numerically and experimentally and confirm that this antenna has adequate characteristics for short range ultra-wideband wireless applications.