We design, analyze, and optimize distributed detection and estimation algorithms in a large, shared-channel, single-hop wireless sensor network (WSN). The fusion center (FC) is allocated a shared transmission channel to collect local decisions/estimates but cannot collect all of them because of limited energy, bandwidth, or time. We propose a strategy called reliability-based splitting algorithm that enables the FC to collect local decisions/estimates in descending order of their reliabilities through a shared collision channel. The algorithm divides the transmission channel into time frames and the sensor nodes into groups based on their observation reliabilities. Only nodes with a specified range of reliabilities compete for the channel using slotted ALOHA within each frame. Nodes with the most reliable decisions/estimates attempt transmission in the first frame; nodes with the next most reliable set of decisions/estimates attempt in the next frame; etc. The reliability-based splitting algorithm is applied in three scenarios: time-constrained distributed detection; sequential distributed detection; and time-constrained estimation. Performance measures of interest - including detection error probability, efficacy, asymptotic relative efficiency, and estimator variance - are derived. In addition, we propose and analyze algorithms that exploit information from the occurrence of collisions to improve the performance of both time-constrained distributed detection and sequential distributed detection.

With the growth of multimedia services, it is essential to find new transmission schemes to support higher data rates in wireless networks. In this thesis, we study networks in which the Channel State Information (CSI) is only available at the destination. We focus on the analysis of three different network setups. For each case, we propose a transmission scheme which maximizes the average performance of the network. The first scenario, which is studied in Chapter 2, is a multi-hop network in which the channel gain of each hop changes quasi-statically from one transmission block to the other. Our main motivation to study this network is the recent advances in deployment of relay nodes in wireless networks (e.g., LTE-A and IEEE 802.16j). In this setup, we assume that all nodes are equipped with a single antenna and the relay nodes are not capable of data buffering over multiple transmission blocks. The proposed transmission scheme is based on infinite-layer coding at all nodes (the source and all relays) in conjunction with the Decode-and-Forward DF relaying. The objective is to maximize the statistical average of the received rate per channel use at the destination. To find the optimal parameters of this code, we first formulate the problem for a two-hop scenario and describe the code design algorithm for this two-hop setting. The optimality of infinite-layer DF coding is also discussed for the case of two-hop networks. The result is then generalized to multi-hop scenarios. To show the superiority of the proposed scheme, we also evaluate the achievable average received rate of infinite-layer DF coding and compare it with the performance of previously known schemes. The second scenario, studied in Chapter 3, is a single-hop network in which both nodes are equipped with multiple antennas, while the channel gain changes quasi-statically and the CSI is not available at the source. The main reason for selecting this network setup is to study the transmission of video signals (compressed using a scalable video coding technique, e.g., SVC H.264/AVC) over a Multiple-Input Multiple-Output (MIMO) link. In this setup, although scalable video coding techniques compress the video signal into layers with different importance (for video reconstruction), the source cannot adapt the number of transmitted layers to the capacity of the channel (since it does not have the CSI in each time slot). An alternative approach is to always transmit all layers of the compressed video signal, but use unequal error protection for different layers. With this motivation, we focus on the design of multilayer codes for a MIMO link in which the destination is only able to perform successive decoding (not joint-decoding). In this chapter, we introduce a design rule for construction of multilayer codes for MIMO systems. We also propose a algorithm that uses this design rule to determine the parameters of the multilayer code. The performance analysis of the proposed scheme is also discussed in this chapter. In the two previous scenarios, the ambiguity of the source regarding the channel state comes from the fact that the channel gains randomly change in each transmission block and there is no feedback to notify the source about the current state of the channel. Apart from these, there are some scenarios in which the channel state is unknown at the source, even though the channel gain is fixed and the source knows its value. The third scenario of this thesis presents an example of such network setups. More precisely, in Chapter 4, we study a multiple access network with K users and one Access Point (AP), where all nodes are equipped with multiple antennas. To access the network, each user independently decides whether to transmit in a time slot or not (no coordination between users). Considering a two-user random access network, we first derive the optimal value of network average Degrees of Freedom (DoF) (introduced in Section 4.1). Generalizing the result to multiuser networks, we propose an upper-bound for the network average DoF of a K-user random access network. This upper-bound is then analyzed for different network configurations to identify the network classes in which the proposed upper-bound is tight. It is also shown that simple single-stream data transmission achieves the upper-bound in most network settings. However, for some network configurations, we need to apply multi-stream data transmission in conjunction with interference alignment to reach the upper-bound. Some illustrative examples are also presented in this chapter.

Bibliography: leaves 156-165. / xvi, 174 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis analyses the design of a Dynamic RAM in gallium arsenide for use as a buffer in an ATM switch. The causes of leakage are investigated and methods to overcome or compensate the leakage are devised, resulting in a memory cell with a large storage time, high speed and low power dissipation. A 14 kbit RAM array is designed and laid out in gallium arsenide. The RAM array is designed to operate over a -25oC to +125oC temperature range using process parameters which vary by up to 2 [sigma] from typical. / Thesis (M.Eng.Sc.)--University of Adelaide, Dept. of Electrical & Electronic Engineering, 1996?

Thesis (M. S. in Electrical Engineering)--Vanderbilt University, Aug. 2008. / Title from title screen. Includes bibliographical references.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographical references (p. 112-113).

This thesis outlines the design and implementation of a single channel, dual polarization pulsar timing instrument for the Hartebeesthoek Radio Astronomy Observatory (HartRAO). The new timer is designed to be an improved, temporary replacement for the existing device which has been in operation for over 20 years. The existing device is no longer reliable and is di±cult to maintain. The new pulsar timer is designed to provide improved functional- ity, higher sampling speed, greater pulse resolution, more °exibility and easier maintenance over the existing device. The new device is also designed to keeping changes to the observation system to a minimum until a full de-dispersion timer can be implemented at theobservatory. The design makes use of an 8-bit Reduced Instruction Set Computer (RISC) micro-processor with external Random Access Memory (RAM). The instrument includes an IEEE-488 subsystem for interfacing the pulsar timer to the observation computer system. The microcontroller software is written in assembler code to ensure optimal loop execution speed and deterministic code execution for the system. The design path is discussed and problems encountered during the design process are highlighted. Final testing of the new instrument indicates an improvement in the sam- pling rate of 13.6 times and a significant reduction in 60Hz interference over the existing instrument.

This thesis is dealing with the problem of MTC (Machine Type Communication) devices accessing LTE (Long Term Evolution) network. First part of work contains theoretical description of MTC, LTE network and possibility of using QoS (Quality of Service) for this type of communication. Influence of simultaneous access of large number of MTC devices into LTE network is examined. A solution is proposed -- usage of MTCG. In simulation enviroment NS-3 (Network Simulator 3), two scenarios are created for simulation with and without MTCG. The results of these simulations are then compared.

Memory wall is becoming a more and more serious bottleneck of the processing speed of microprocessors. The mismatch between CPUs and memories has been increasing since three decades ago. SRAM was introduced as the bridge between the main memory and the CPU. SRAM is designed to be on the same die with CPU and stores temporary data and instructions that are to be processed by the CPU. Thus, the performance of SRAMs has a direct impact on the performance of CPUs. With the application of mass amount data to be processed nowadays, there is a great need for high-performance CPUs. Three dimensional CPUs and CPUs that are specifically designed for machine learning are gaining popularity. The objective of this work is to design high-performance SRAM for these two emerging applications. Firstly, a novel delay cell based on dummy TSV is proposed to replace traditional delay cells for better timing control. Secondly, a unique SRAM with novel architecture is custom designed for a high-performance machine learning processor. Post-layout simulation shows that the SRAM works well with the processing core and its design is optimized to work well with machine learning processors based on convolutional neural networks. A prototype of the SRAM is also tapped out to further verify our design.

Prenons en exemple une salle de classe composée d’un professeur et de nombreux élèves, lorsque trop d’élèves s’adressent en même temps au professeur ce dernier n’est plus en mesure de comprendre les paroles transmisses par les élèves. Cette illustration s’étend évidemment aux systèmes de communications sans fil (la 4G par exemple). Dans ces systèmes, les terminaux (les élèves par analogie) transmettent sur un canal, nommé canal en accès aléatoire, des messages qui sont potentiellement réceptionnés par la station de base (le professeur par analogie). Ces canaux ne sont habituellement pas surchargés car leur capacité (nombre de messages reçus par seconde) est tellement importante qu’il est très complexe de surcharger le canal. L’émergence de l’Internet des objets où des milliards de petits objets devraient être déployés partout dans le monde a changé la donne. Étant donné leur nombre et leur type de trafic, ces derniers peuvent surcharger les canaux en accès aléatoire. Ainsi, le sujet : « contrôle de charge des canaux en accès aléatoire » a connu un gain d’intérêts ces dernières années. Dans cette thèse nous avons développé des algorithmes de contrôle de charge permettant d’éviter qu’une station de base soit surchargée. Cela est très utile pour les opérateurs Télécoms, ils sont désormais certains qu’il y n’y aura pas de perte de service à cause de ces surcharges. Tous les principes développés dans cette thèse seront intégrés dans un futur proche aux produits IoT d’Airbus. / Take for example a classroom composed of a teacher and many students. When too many students address at the same time to the teacher, the latter is no longer able to understand the words transmitted by students. This illustration obviously extends to wireless communication systems (the 4G for example). In these systems, terminals (students by analogy) transmit on a channel, named random access channel, messages that are potentially received by the base station (the teacher by analogy). These channels are usually not overloaded because their capacity (number of messages received per second) is so important that it is very complex to overload the channel. The emergence of the Internet of Things, where billions of small objects should be deployed around the world, has changed the game. Due to their number and type of traffic, they can overload random access channels. Therefore, the subject: "load control of random access channels" has seen an increase in interest in recent years. In this PhD we have developed load control algorithms to prevent a base station from being overloaded. This is very useful for telecom operators, they are now certain that there will be no loss of service because of these overloads. All the principles developed in this thesis will be integrated in the near future within Airbus IoT products

The increasing popularity and widespread deployment of wireless data systems fuel the increasing demand for more spectrum. On the other hand, various studies measuring spectrum utilization show that there is a huge variation in spectrum utilization at different times and locations. In view of this, various dynamic spectrum access (DSA) methods have been proposed in order to achieve more efficient utilization of spectrum resources by virtue of exploiting the variations in spectrum demand over time and space. Implementing DSA systems in a centralized way can lead to complexity and scalability problems due to the extensive control signaling involved. Therefore distributed implementations of DSA systems in which the users can access the system resources at their own discretion have been proposed. These distributed mechanisms typically incorporate cognitive radio systems which act as agents on behalf of users to measure the radio environment and make decisions based on these measurements. On the other hand, the freedom of the users in distributed systems to form their actions can lead each user to try to maximize its benefit from the system without regard the overall performance of the DSA system. Therefore, selfish behavior can prevail in distributed systems, which is likely to degrade the system performance.In this thesis we investigate the implications of selfish decision making in dynamic spectrum access systems. To address this broad problem, we focus our analysis on a particular system which can represent the essential properties of DSA systems and thus can shed light on the performance of the broad class of DSA systems with selfish users. Specifically, we model a DSA system as a multichannel random access system which uses ALOHA for medium access, and we analyze the behavior of the selfish users by modeling the system as a non-cooperative game. In this analysis we incorporate the effect of channel state information on the decision making of the users; we consider both cases when the users act on global (complete) and on local (incomplete) information. We determine the behavior of the selfish users at the Nash equilibria of the non-cooperative game and measure the performance of the system in terms of sum and individual utilities for various user loads and amount of available resources. We try to identify how the performance of the DSA system with selfish users compares with its cooperative counterpart. By performing these analyses we provide insights into the broader question of whether selfish users can utilize spectrum resources in a DSA system as well as cooperative users. / <p>QC 20111208</p> / MultiOperator Dynamic Spectrum access (MODyS)