Thesis (Ph.D.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Richard Wolff. Includes bibliographical references.

Thesis (M.S.) -- Worcester Polytechnic Institute. / Keywords: CMOS; Low noise amplifier; Multistandard RF transceivers. Includes bibliographical references (leaves 147-156).

É apresentado um amplificador de potência (PA) com controle digital da potência de saída, operando na banda S de frequência (2,2 GHz). Este PA utiliza um transformador de entrada para reduzir as flutuações dos sinais de terra. Um estágio de excitação oferece uma impedância apropriada para a fonte de entrada e ganho para o próximo estágio. O estágio de controle é usado para melhorar a eficiência do PA, composto por quatro ramos paralelos de chaves, onde os estados (ligado ou desligado) são separadamente ativados por uma palavra de controle de 4 bits. O estágio de saída implementa um amplificador classe E, usando uma topologia cascode para minimizar o estresse de tensão sobre os transistores, permitindo sua utilização sob tensão de alimentação de 3,3 V para se atingir uma potência de saída máxima em torno de 1 W, em um processo CMOS 130 nm, cuja tensão típica de alimentação é 1,2 V. O PA proposto foi projetado em uma tecnologia CMOS 130 nm para RF, ocupa uma área de 1,900 x 0,875 mm2 e os resultados das simulações em leiaute extraído obtidos demonstram uma potência de saída máxima de 28,5 dBm (707 mW), com PAE (Power- Added Efficiency) correspondente de 49,7%, para uma tensão de alimentação de 3,3 V. O controle de 4 bits permite um ajuste dentro da faixa dinâmica da potência de saída entre 13,6 a 28,5 dBm (22,9 a 707 mW), divididos em 15 passos, com o PAE variando de 9,1% a 49,7%. O PA proposto permite redução do consumo de potência quando este não está transmitindo na potência máxima. A potência consumida atinge um mínimo de 0,21Wquando a potência de saída é de 13,6 dBm (22,9 mW) e um máximo de 1,4 W quando a potência de saída é de 28,5 dBm (707 mW), o que representa 1,19 W de economia, aumentando a vida da bateria. A linearidade obtida neste circuito mostrou-se suficiente para atender os requisitos da máscara de emissão de espúrios de um padrão de comunicação com envoltória constante largamente utilizado, apresentando desempenho adequado para atender as especificações dos sistemas de comunicações modernos. / A power amplifier with digital power control useful to S-Band (2.2 GHz) applications and with an output power around 1 W is presented. It uses an input transformer to reduce ground bounce effects. A tuned driver stage provides impedance matching to the input signal source and proper gain to the next stage. A control stage is used for efficiency improvement, composed by four parallel branches where the state (on or off) is separately activated by a 4-bit input. The class-E power stage uses a cascode topology to minimize the voltage stress over the power transistors, allowing higher supply voltages. The PA was designed in a 130 nm RF CMOS process and the layout has a total area of 1.900 x 0.875 mm2, post-layout simulations resulted a peak output power of 28.5 dBm with a maximum power added efficiency (PAE) around 49.7% under 3.3 V of supply voltage. The 4-bit control allows a total output power dynamic range adjustment of 14.9 dB, divided in 15 steps, with the PAE changing from 9.1% to 49.7%. The proposed PA allows reduce the power consumption when it isn’t transmitting at the maximum output power. Where the power consumption is only 0.21 W when the PA is at the minimum output power level of 13.6 dBm (22.9 mW), which is 1.19 W smaller than the power consumption at full mode (1.4 W), increasing the battery life. The linearity in this circuit meet the emission mask requirements for a widely used communication standard with constant envelope. Post-layout simulation results indicate an overall performance adequate to fulfill the specifications of modern wireless communication systems.

É apresentado um amplificador de potência (PA) com controle digital da potência de saída, operando na banda S de frequência (2,2 GHz). Este PA utiliza um transformador de entrada para reduzir as flutuações dos sinais de terra. Um estágio de excitação oferece uma impedância apropriada para a fonte de entrada e ganho para o próximo estágio. O estágio de controle é usado para melhorar a eficiência do PA, composto por quatro ramos paralelos de chaves, onde os estados (ligado ou desligado) são separadamente ativados por uma palavra de controle de 4 bits. O estágio de saída implementa um amplificador classe E, usando uma topologia cascode para minimizar o estresse de tensão sobre os transistores, permitindo sua utilização sob tensão de alimentação de 3,3 V para se atingir uma potência de saída máxima em torno de 1 W, em um processo CMOS 130 nm, cuja tensão típica de alimentação é 1,2 V. O PA proposto foi projetado em uma tecnologia CMOS 130 nm para RF, ocupa uma área de 1,900 x 0,875 mm2 e os resultados das simulações em leiaute extraído obtidos demonstram uma potência de saída máxima de 28,5 dBm (707 mW), com PAE (Power- Added Efficiency) correspondente de 49,7%, para uma tensão de alimentação de 3,3 V. O controle de 4 bits permite um ajuste dentro da faixa dinâmica da potência de saída entre 13,6 a 28,5 dBm (22,9 a 707 mW), divididos em 15 passos, com o PAE variando de 9,1% a 49,7%. O PA proposto permite redução do consumo de potência quando este não está transmitindo na potência máxima. A potência consumida atinge um mínimo de 0,21Wquando a potência de saída é de 13,6 dBm (22,9 mW) e um máximo de 1,4 W quando a potência de saída é de 28,5 dBm (707 mW), o que representa 1,19 W de economia, aumentando a vida da bateria. A linearidade obtida neste circuito mostrou-se suficiente para atender os requisitos da máscara de emissão de espúrios de um padrão de comunicação com envoltória constante largamente utilizado, apresentando desempenho adequado para atender as especificações dos sistemas de comunicações modernos. / A power amplifier with digital power control useful to S-Band (2.2 GHz) applications and with an output power around 1 W is presented. It uses an input transformer to reduce ground bounce effects. A tuned driver stage provides impedance matching to the input signal source and proper gain to the next stage. A control stage is used for efficiency improvement, composed by four parallel branches where the state (on or off) is separately activated by a 4-bit input. The class-E power stage uses a cascode topology to minimize the voltage stress over the power transistors, allowing higher supply voltages. The PA was designed in a 130 nm RF CMOS process and the layout has a total area of 1.900 x 0.875 mm2, post-layout simulations resulted a peak output power of 28.5 dBm with a maximum power added efficiency (PAE) around 49.7% under 3.3 V of supply voltage. The 4-bit control allows a total output power dynamic range adjustment of 14.9 dB, divided in 15 steps, with the PAE changing from 9.1% to 49.7%. The proposed PA allows reduce the power consumption when it isn’t transmitting at the maximum output power. Where the power consumption is only 0.21 W when the PA is at the minimum output power level of 13.6 dBm (22.9 mW), which is 1.19 W smaller than the power consumption at full mode (1.4 W), increasing the battery life. The linearity in this circuit meet the emission mask requirements for a widely used communication standard with constant envelope. Post-layout simulation results indicate an overall performance adequate to fulfill the specifications of modern wireless communication systems.

abstract: Traditional wireless communication systems operate in duplexed modes i.e. using time division duplexing or frequency division duplexing. These methods can respectively emulate full duplex mode operation or realize full duplex mode operation with decreased spectral efficiency. This thesis presents a novel method of achieving full duplex operation by actively cancelling out the transmitted signal in pseudo-real time. With appropriate hardware, the algorithms and techniques used in this work can be implemented in real time without any knowledge of the channel or any training sequence. Convergence times of down to 1 ms can be achieved which is adequate for the coherence bandwidths associated with an indoor environment. By utilizing adaptive cancellation, additional overhead for re-calibrating the system in other open-loop methods is not needed. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016

abstract: Recently, the location of the nodes in wireless networks has been modeled as point processes. In this dissertation, various scenarios of wireless communications in large-scale networks modeled as point processes are considered. The first part of the dissertation considers signal reception and detection problems with symmetric alpha stable noise which is from an interfering network modeled as a Poisson point process. For the signal reception problem, the performance of space-time coding (STC) over fading channels with alpha stable noise is studied. We derive pairwise error probability (PEP) of orthogonal STCs. For general STCs, we propose a maximum-likelihood (ML) receiver, and its approximation. The resulting asymptotically optimal receiver (AOR) does not depend on noise parameters and is computationally simple, and close to the ML performance. Then, signal detection in coexisting wireless sensor networks (WSNs) is considered. We define a binary hypothesis testing problem for the signal detection in coexisting WSNs. For the problem, we introduce the ML detector and simpler alternatives. The proposed mixed-fractional lower order moment (FLOM) detector is computationally simple and close to the ML performance. Stochastic orders are binary relations defined on probability. The second part of the dissertation introduces stochastic ordering of interferences in large-scale networks modeled as point processes. Since closed-form results for the interference distributions for such networks are only available in limited cases, it is of interest to compare network interferences using stochastic. In this dissertation, conditions on the fading distribution and path-loss model are given to establish stochastic ordering between interferences. Moreover, Laplace functional (LF) ordering is defined between point processes and applied for comparing interference. Then, the LF orderings of general classes of point processes are introduced. It is also shown that the LF ordering is preserved when independent operations such as marking, thinning, random translation, and superposition are applied. The LF ordering of point processes is a useful tool for comparing spatial deployments of wireless networks and can be used to establish comparisons of several performance metrics such as coverage probability, achievable rate, and resource allocation even when closed form expressions for such metrics are unavailable. / Dissertation/Thesis / Ph.D. Electrical Engineering 2014

In recent years, space-time block coding (STBC) has emerged as an effective transmit-diversity technique to combat the detrimental effects of channel fading. In addition to STBC, high-order modulation schemes will be used in future wireless communication systems aiming to provide ubiquitous-broadband wireless access. Hence, advanced receiver schemes are necessary to achieve high performance. In this thesis, advanced and computationally-efficient receiver schemes are investigated and developed for single-carrier space-time (ST) block-coded transmissions over frequency-selective fading (FSF) channels. First, we develop an MMSE-based turbo equalization scheme for Alamouti ST block-coded systems. A semi-analytical method to estimate the bit error rate (BER) is devised. Our results show that the proposed turbo equalization scheme offers significant performance improvements over one-pass equalization. Second, we analyze the convergence behavior of the proposed turbo equalization scheme for Alamouti ST block-coded systems using the extrinsic information transfer (EXIT)-band chart technique. Third, burst-wise (BW)-STBC is applied for uplink transmission over FSF channels in block-spread-CDMA systems with multiuser interference-free reception. The performances of different decision feedback sequence estimation (DFSE) schemes are investigated. A new scheme combining frequency-domain (FD) linear equalization and modified unwhitened-DFSE is proposed. The proposed scheme is very promising as the error-floor behavior observed in the existing unwhitened DFSE schemes is eliminated. Fourth, we develop a FD-MMSE-based turbo equalization scheme for the downlink of ST block-coded CDMA systems. We adopt BW-STBC instead of Alamouti symbol-wise (SW)-STBC considered for WCDMA systems and demonstrate its superior performance in FSF channels. Block spreading is shown to be more desirable than conventional spreading to improve performance using turbo equalization. We also devise approximate implementations (AprxImpls) that offer better trade-offs between performance and complexity. Semi-analytical upper bounds on the BER are derived. Fifth, turbo multicode detection is investigated for ST block-coded downlink transmission in DS-CDMA systems. We propose symbol-by-symbol and chip-by-chip FD-MMSE-based multicode detectors. An iterative channel estimation scheme is also proposed. The proposed turbo multicode detection scheme offers significant performance improvements compared with non-iterative multicode detection. Finally, the impact of channel estimation errors on the performance of MMSE-based turbo equalization in ST block-coded CDMA systems is investigated. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This thesis considers the problem of cross layer scheduling and radio resource allocation of multiple users in the downlink of time-slotted and frequency-slotted cellular data networks. For these networks, opportunistic scheduling algorithms improve system performance by exploiting time variations of the radio channel. Within the broader framework of opportunistic scheduling, this thesis solves three distinct problems and proposes efficient and scalable solutions for them. First, we present novel optimal and approximate opportunistic scheduling algorithms that combine channel fluctuation and user mobility information in their decision rules. The algorithms propose the use of dynamic fairness constraints. These fairness constraints adapt according to the user mobility. The optimal algorithm is an off-line algorithm that precomputes constraint values according to a known mobility model. The approximate algorithm is an on-line algorithm that relies on the future prediction of the user mobility locations in time. We show that the use of mobility information increases channel capacity. We also provide analytical bounds on the performance of the approximate algorithm. Second, this thesis presents a new opportunistic scheduling solution that maximizes the aggregate user performance subject to certain minimum and maximum performance constraints. By constraining the performance experienced by individual users, who share a common radio downlink, to some upper bounds, it is possible to provide the system operator with a better control of radio resource allocations and service differentiation among different classes of users. The proposed solution offers better performance than existing solution under practical channel conditions. Finally, we present a dynamic subcarrier allocation solution for fractional frequency reuse in multicell orthogonal frequency division multiple access systems. We formulate the subcarrier allocation as an equivalent set partitioning problem and then propose an efficient hierarchical solution which first partitions subcarriers into groups and next schedules subcarriers opportunistically to users. Simulation results for three solutions illustrate the usefulness of the proposed schemes. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The proliferation of data hungry wireless devices, such as smart phones and intelligent sensing networks, is pushing modern wireless networks to their limits. A significant shortfall in the ability of networks to meet demand for data is imminent. This thesis addresses this problem through examining the design of distributed antenna systems (DAS) to support next generation high speed wireless services that require high densities of access points and must support multiple-input multiple-output (MIMO) protocols. First, it is shown that fibre links in DAS can be replaced with low-cost, broadband free-space optical links, termed radio over free-space optics (RoFSO) links. RoFSO links enable the implementation of very high density DAS without the need for prohibitively expensive cabling infrastructure. A 16m RoFSO link requiring only manual alignment is experimentally demonstrated to provide a spurious-free dynamic range (SFDR) of > 100dB/Hz^2/3 over a frequency range from 300MHz- 3.1GHz. The link is measured to have an 802.11g EVM dynamic range of 36dB. This is the first such demonstration of a low-cost broadband RoFSO system. Following this, the linearity performance of RoFSO links is examined. Because of the high loss nature of RoFSO links, the directly-modulated semiconductor lasers they use are susceptible to high-order nonlinear behaviour, which abruptly limits performance at high powers. Existing measures of dynamic range, such as SFDR, assume only third-order nonlinearity and so become inaccurate in the presence of dominant high-order effects. An alternative measure of dynamic range called dynamic-distortion-free dynamic range (DDFDR) is then proposed. For two different wireless services it is observed experimentally that on average the DDFDR upper limit predicts the EVM knee point to within 1dB, while the third-order SFDR predicts it to within 6dB. This is the first detailed analysis of high-order distortion effects in lossy analogue optical links and DDFDR is the first metric able to usefully quantify such behaviour. Next, the combination of emerging MIMO wireless protocols with existing DAS is examined. It is demonstrated for the first time that for small numbers of MIMO streams (up to ~4), the capacity benefits of MIMO can be attained in existing DAS installations simply by sending the different MIMO spatial streams to spatially separated remote antenna units (RAU). This is in contrast to the prevailing paradigm of replicating each MIMO spatial stream at each RAU. Experimental results for two representative DAS layouts show that replicating spatial streams provides an increase of only ~1% in the median channel capacity over merely distributing them. This compares to a 3-4% increase of both strategies over traditional non-DAS MIMO. This result is shown to hold in the multiple user case with 20 users accessing 3 base stations. It is concluded that existing DAS installations offer negligible capacity penalty for MIMO services for small numbers of spatial streams, including in multi-user MIMO scenarios. Finally, the design of DAS to support emerging wireless protocols, such as 802.11ac, that have large numbers of MIMO streams (4-8) is considered. In such cases, capacity is best enhanced by sending multiple MIMO streams to single remote locations. This is achieved using a novel holographic mode division multiplexing (MDM) system, which sends each separate MIMO stream via a different propagation mode in a multimode fibre. Combined channel measurements over 2km of mode-multiplexed MMF and a typical indoor radio environment show in principle a 2x2 MIMO link providing capacities of 10bit/s/Hz over a bandwidth of 6GHz. Using a second experimental set-up it is shown that the system could feasibly support at least up to a 4x4 MIMO system over 2km of MMF with a condition number >15dB over a bandwidth of 3GHz, indicating a high degree of separability of the channels. Finally, it is shown experimentally that when a fibre contains sharp bends (radius between 20mm and 7.2mm) the first 6 mode-groups used for multiplexing exhibit no additional power loss or cross-coupling compared with unbent fibre, although mode-groups 7, 8 and 9 are more severely affected. This indicates that at least 6x6 multiplexing is possible in standard installations with tight fibre bends.

With technology advancements and the prices of electronic components reducing over the last fifteen years, many devices and systems that would have been proprietary only for large companies or industry giants are becoming an everyday household item. Various areas of technology have been benefiting from this but one of the biggest is the Internet of Things (IoT).With the prevalence of IoT, it has been integrated into houses, small businesses, farms, agriculture, building automation, etc. and the user population is now a resource to the industry as they complete personal projects. Within any project there are always limitations, this might be a limited time, limited funds, limited distance, or limitations of the devices being used. This study proposes to evaluate two low-powered networks, Narrowband Internet of Things (NB-IoT)and Long-Range Wide-Area Network(LoRaWAN), in different environments with the goal of understanding where the signal propagation is better and what distances can be reached despite obstructions. Distances and signal propagations, when measured by the manufacturers are often evaluated in ideal conditions which is rarely the case when utilized in the field. This creates a gap in the deployment and the end-users are frequently faced with diminished performances. As IoT is predominantly employed in urban and rural areas this study will focus on those two settings by testing the Received Signal Strength Indicator (RSSI)at various distances. The evaluation testing of the two systems showed each system performing more consistently in rural areas but neither had 100% coverage at any locations.