Browsing by Subject "Performance analysis"
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Item Analysis of millimeter wave and massive MIMO cellular networks(2016-08) Bai, Tianyang; Heath, Robert W., Ph. D.; Andrews, Jeffrey G; Baccelli, Francois; Qiu, Lili; Sanghavi, SujayMillimeter wave (mmWave) communication and massive multiple-input multiple-output (MIMO) are promising techniques to increase system capacity in 5G cellular networks. The prior frameworks for conventional cellular systems do not directly apply to analyze mmWave or massive MIMO networks, as (i) mmWave cellular networks differ in the different propagation conditions and hardware constraints; and (ii) with a order of magnitude more antennas than conventional multi-user MIMO systems, massive MIMO systems will be operated in time-division duplex (TDD) mode, which renders pilot contamination a primary limiting factor. In this dissertation, I develop stochastic geometry frameworks to analyze the system-level performance of mmWave, sub-6 GHz massive MIMO, and mmWave massive MIMO cellular networks. The proposed models capture the key features of each technique, and allow for tractable signal-to-interference-plus-noise ratio (SINR) and rate analyses. In the first contribution, I develop an mmWave cellular network model that incorporates the blockage effect and directional beamforming, and analyze the SINR and rate distributions as functions of the base station density, blockage parameters, and antenna geometry. The analytical results demonstrate that with a sufficiently dense base station deployment, mmWave cellular networks are capable to achieve comparable SINR coverage and much higher rates than conventional networks. In my second contribution, I analyze the uplink SINR and rate in sub-6 GHz massive MIMO networks with the incorporation of pilot contamination and fractional power control. Based on the analysis, I show scaling laws between the number of antennas and scheduled users per cell that maintain the uplink signal-to-interference ratio (SIR) distributions are different for maximum ratio combining (MRC) and zero-forcing (ZF) receivers. In my third contribution, I extend the sub-6 GHz massive MIMO model to mmWave frequencies, by incorporating key mmWave features. I leverage the proposed model to investigate the asymptotic SINR performance, when the number of antennas goes to infinity. Numerical results show that mmWave massive MIMO outperforms its sub-6 GHz counterpart in cell throughput with a dense base station deployment, while the reverse can be true with a low base station density.Item Analysis, design and implementation of models for housestaff scheduling at outpatient clinics and improving patient flow at a family health clinic(2015-05) Shu, Zhichao, Ph. D.; Bard, Jonathan F.; Morrice, Douglas J. (Douglas John), 1962-; Khajavirad, Aida; Dimitrov, Ned; Leykum, LuciClinical experiences during the three years of residencies occur in inpatient and outpatient settings on generalist and specialist clinical services. Housestaff rotate through different clinical experiences monthly, with their primary care clinic time overlaid longitudinally on these other clinical services. The primary goals of this research are to construct housestaff schedules and improve efficiencies for residency programs. In the first phase of the research, we developed two models for constructing monthly clinic schedules for housestaff training in Internal Medicine. In our first model, the objective is to both maximize clinic utilization and minimize the number of violations of a prioritized set of goals while ensuring that certain clinic-level and individual constraints are satisfied. The corresponding problem is formulated as an integer goal program in which several of the hard constraints are temporarily allowed to be violated to avoid infeasibility. A three-phase methodology is then proposed to find solutions. The second model solves a similar problem with the objective of maximizing the number of interns and residents that are assigned clinic duty each month during their training in Internal Medicine. A complexity analysis is provided that demonstrates that the basic problem can be modeled as a pure network and the full problem can be modeled as a network with gains. In the second phase of the research, the goal was to redesign the monthly templates that comprise the annual block rotations to obtain better housestaff schedules. To implement this model, we investigate two different programs: Family Medicine and Internal Medicine. The problems were formulated as mixed-integer programs but proved too difficult to solve exactly. As an alternative, several heuristics were developed that yielded good feasible solutions. For the last part of the research, we focused on improving patient flow at a family health clinic. The objective was to obtain a better understanding of patient flow through the clinic and to investigate changes to current scheduling rules and operating procedures. Discrete event simulation was used to establish a baseline and to evaluate a variety of scenarios associated with appointment scheduling and managing early and late arrivals.Item Performance Analysis of Fully Joint Diversity Combining, Adaptive Modulation, and Power Control Schemes(2010-01-14) Bouida, ZiedAdaptive modulation and diversity combining represent very important adaptive solutions for future generations of wireless communication systems. Indeed, to improve the performance and the efficiency of these systems, these two techniques recently have been used jointly in new schemes named joint adaptive modulation and diversity combining (JAMDC) schemes. Considering the problem of finding lowcomplexity, bandwidth-efficient, and processing-power efficient transmission schemes for a downlink scenario and capitalizing on some of these recently proposed JAMDC schemes, we propose and analyze three fully joint adaptive modulation, diversity combining, and power control (FJAMDC) schemes. More specifically, the modulation constellation size, the number of combined diversity paths, and the needed power level are determined jointly to achieve the highest spectral efficiency with the lowest possible combining complexity, given the fading channel conditions and the required bit error rate (BER) performance. The performance of these three FJAMDC schemes is analyzed in terms of their spectral efficiency, processing power consumption, and error-rate performance. Selected numerical examples show that these schemes considerably increase the spectral efficiency of the existing JAMDC schemes with a slight increase in the average number of combined paths for the low signal to noise ratio range while maintaining compliance with the BER performance and a low radiated power resulting in a substantial decrease in interference to co-existing systems/users.