Communications over millimeter wave (mmWave) frequencies is a key component of the fifth generation (5G) cellular networks due to the large bandwidth available at mmWave bands. Thanks to the short wavelength of mmWave bands, large antenna arrays (32 to 256 elements are common) can be mounted at the transceivers. The array sizes are typical of a massive MIMO communication system, which makes fully digital beamforming difficult to implement due to high power consumption and hardware cost. This motivates the development of hybrid beamforming due to its versatile tradeoff between implementation cost (including hardware cost and power consumption) and system performance. However, due to the non-convex constraints on hardware (phase shifters), finding the global optima for hybrid beamforming design is often intractable. In this thesis, we focus on hybrid beamforming design for mmWave cellular communications both narrowband and wideband scenarios are considered. Starting from narrowband SU-MIMO mmWave communications, we propose a Gram-Schmidt orthogonalization (GSO) aided hybrid precoding algorithm to reduce computation complexity. GSO is a recursive process that depends on the order in which the matrix columns are selected. A heuristic solution to the order of column selection is suggested according to the array response vector along which the full digital precoder has the maximum projection. The proposed algorithm, not only constrained to uniform linear arrays (ULAs), can avoid the matrix inversion in designing the digital precoder compared to the orthogonal matching pursuit (OMP) algorithm. For the narrowband MU-MIMO mmWave communications, we propose an interference cancellation (IC) framework on hybrid beamforming design for downlink mmWave multi-user massive MIMO system. Based on the proposed framework, three successive interference cancellation (SIC) aided hybrid beamforming algorithms are proposed to deal with inter-user and intra-user interference. Furthermore, the optimal detection order of data streams is derived according to the post-detection signal-to-interference- plus-noise ratio (SINR). When considering wideband MU-MIMO mmWave communications, how to design a common RF beamformer across all subcarriers becomes the main challenge. Furthermore, the common RF beamformer in wideband channels leads to the need of more effective baseband schemes. By adopting a relaxation of the original mutual information and spectral efficiency maximization problems at the transceiver, we design the radio frequency (RF) precoder and combiner by leveraging the average of the covariance matrices of frequency domain channels, then a SIC aided baseband precoder and combiner are proposed to eliminate inter-user and intra-user interference / Graduate

The major application of active noise control (ANC) has been focused on using a single reference signal; the work on multiple reference ANC is very scarce. Here, the behavior of multiple reference ANC is analyzed in both the frequency and time domain, and the coherence functions are provided to evaluate the effectiveness of multiple reference ANC. When there are multiple noise sources, multiple reference sensors are needed to generate complete reference signals. A simplified method combines those signals from multiple reference sensors into a single reference signal. Although this method could result in satisfactory noise control effects under special circumstances, the performance is generally compromised. A widely adopted method feeds each reference signal into a different control filter. This approach suffers from the problem of ill-conditioning when the reference signals are correlated. The problem of ill-conditioning results in slow convergence rate and high sensitivity to measurement error especially when the FXLMS algorithm is applied. To handle this particular problem, the decorrelated Filtered-X LMS (DFXLMS) algorithm is developed and studied in this thesis. Both simulations and experiments have been conducted to verify the DFXLMS algorithm and other issues associated with multiple reference ANC. The results presented herein are consistent with the theoretical analysis, and favorably indicate that the DFXLMS algorithm is effective in improving the convergence speed. To take the maximum advantage of the TMS320C30 DSP board used to implement the controller, several DSP programming issues are discussed, and assembly routines are given in the appendix. Furthermore, a graphical user interface (GUI) running under Windows' environment is introduced. The main purpose of the GUI is to facilitate parameters modification, real time data monitoring and DSP process control. / Master of Science

Indiana University-Purdue University Indianapolis (IUPUI) / The nanotechnology materials have been used for high sensitivity sensing devices due to their ability to alter their properties in response to the environmental parameters such as temperature, pressure, gas, electromagnetic, and chemicals. The features of employing nanoparticles on top of graphene thin film have driven the hypothesis of achieving high sensing nanotechnology devices. This study demonstrates a novel approach for designing a low noise nanoparticle based gas sensing device with internet of things (IoT) capability. The system is capable of minimizing cross-talk between multiple channels of amplifiers arranged on one chip using guard rings. Graphene mono-layer is utilized as sensing material with the sensitivity catalyzed by addition of gold nano-particles on its surface. The signal from the sensing unit is received by an offset cancellation amplifying system using a system on chip (SoC) approach. IoT capability of the sensing device is developed using FRDM K64f micro-controller board which sends messages on IoT platform when a gas is sensed. The message is received by an application created and sent as an email or message to the user. This study details the mathematical models of the graphene based gas sensing devices, and the interface circuitry that drives the differential potentials, resulting from the sensing unit. The study presents the simulation and practical model of the device, detailing the design approach of the processing unit within the SoC system and wireless implementation of it. The sensing device was capable of sensing gas concentration from 5% to 100% using both the resistive and capacitive based models. The I-V characteristics of the FET sensing device was in agreeable with the other models. The SoC processing unit was designed using cadence tools, and simulation results showed very high CMRR that enable the amplifier to sense a very low signal received from the gas sensors. The cross talk noise was reduced by surrounding guard rings around the amplifier circuits. The layout was accomplished with 45nm technology and simulation showed an offset voltage of 17μV.

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Brainstem Auditory Evoked Potentials (BAEP) contain valuable information about the condition of the neural fibers associated with the auditory pathways. Extraction of this information is a difficult task due to contamination by on-going scalp EEG. This thesis reviews the current processing techniques and introduces adaptive noise cancellation (ANC) using systolic arrays as an alternative to existing technology. Q-R decomposition theory is reviewed and an explanation of the mechanics of systolic adaptive noise cancellation (SANC) is presented. A modified Given's rotation algorithm is derived resulting in a saving of up to 2/3 in memory requirements. Real data were collected in the laboratory. Real and simulated data were processed to determine the characteristics and effectiveness of adaptive noise cancellation strategies. Successful ANC of BAEP was performed on simulated data using a number or signal-to-noise ratios (S/N), data sequence lengths, reference signals and filter parameter values. We conclude that systolic arrays are a very powerful and appropriate technique for the extraction or BAEPs. Correlation studies indicated that the pre-stimulus EEG signal is inadequately correlated to the primary signal for successful ANC or BAEP in real data. A multi-channel collection scheme is outlined for future collection or Evoked Potential data. A summary or experimental results is presented to address the problem or data collection and signal processing optimization. / Thesis / Master of Engineering (MEngr)

A common problem encountered in phased array signal processing is how to remove sources of interference from a desired signal. Two existing methods to accomplish this are the Linearly Constrained Minimum Variance (LCMV) beamformer and the Side-Lobe Canceller (SLC). LCMV provides better performance than SLC, but comes with much higher computational costs. The Steered Auxiliary Beam Canceller (SABC) presented in this thesis is a new algorithm developed to improve the performance of SLC without the computational costs of LCMV. SABC performs better than SLC because it uses high-gain auxiliary channels for cancellation. This new technique is now possible because digital arrays allow for direction finding algorithms such as Estimation of Signal Parameters via Rotational Invariance Techniques (ESPRIT) to estimate the directions of the interference sources. With this added knowledge, high gain beams similar to the main beam may be used as auxiliaries instead of low-gain antenna elements. Another contribution is a method introduced to calculate the computational complexity of LCMV, SLC, and SABC much more accurately than existing methods which only provide order-of-magnitude estimates. The final contribution is a derivation of the signal loss experienced by SLC and SABC and simulations that verify the performance of LCMV, SLC, and SABC. / Master of Science

We consider a continuous time dynamic pricing model where a seller needs to sell a single item over a finite time horizon. Customers arrive in accordance with a Poisson process. Upon arrival, a customer either purchases the item if the posted price is lower than his/her reservation price, or leaves empty-handed. After purchasing the item, some customers, however, will return the item to the seller at an exponential rate for a full refund. We assume that a returned item is in mint condition and the seller can resell it to future customers. The objective of the seller is to dynamically adjust the price in order to maximize the expected total revenue when the sale horizon ends. We formulate the dynamic pricing problem as a dynamic programming model and derive the structural properties of the optimal policy and the optimal value function. For cases in which the customer's reservation price is exponentially distributed, we derive the optimal policy in a closed form. For general reservation price distribution, we consider an approximation of the original model by discretizing both time and the allowable price set. We then present an algorithm for numerically computing the optimal policy in this discrete time model. Numerical examples show that if the discrete price set is carefully chosen, the expected total revenue is nearly the same as that when the allowable price set is continuous. / Master of Science

It is well known that common-mode (CM) conducted electromagnetic interference (EMI) is caused by the common-mode current flowing through the parasitic capacitance of transistors, diodes, and transformers to ground in the power circuit. Because of the potential for interference with other systems as well as governmental regulations, it is necessary to attenuate this noise. Ordinarily this must be accomplished by using a magnetic choke on the input power lines, which can result in large penalties to the overall size, weight, and cost of the completed system. In order to lessen the requirement for this magnetic choke, there has been in recent years a desire to introduce noise cancellation techniques to the area of EMI. This text introduces a method of canceling the common-mode EMI by using a compensating transformer winding and a capacitor. Compared with active cancellation techniques, it is much simpler and requires no additional transistors and gate-drive circuitry since it merely adds a small copper winding and a small capacitor. By using this technique the size of the EMI filter can be reduced, especially for applications requiring high currents. In this thesis a survey of CM noise reduction techniques is presented, encompassing conventional and active cancellation techniques. The new method for passive noise cancellation is presented, which is then applied to families of isolated DC/DC converters, non-isolated DC/DC converters, and DC/AC inverters and motor drives. The method, results, and ramifications of this technique are presented in order of appearance. / Master of Science