UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item HARDWARE AND SOFTWARE ARCHITECTURES FOR ENERGY- AND RESOURCE-EFFICIENT SIGNAL PROCESSING SYSTEMS(2014) Cho, Inkeun; Bhattacharyya, Shuvra S.; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)For a large class of digital signal processing (DSP) systems, design and implementation of hardware and software is challenging due to stringent constraints on energy and resource requirements. In this thesis, we develop methods to address this challenge by proposing new constraint-aware system design methods for DSP systems, and energy- and resource-optimized designs of key DSP subsystems that are relevant across various application areas. In addition to general methods for optimizing energy consumption and resource utilization, we present streamlined designs that are specialized to efficiently address platform-dependent constraints. We focus on two specific aspects in development of energy- and resource-optimized design techniques: (1) Application-specific systems and architectures for energy- and resource- efficient design. First, we address challenges in efficient implementation of wireless sensor network building energy monitoring systems (WSNBEMSs). We develop new energy management schemes in order to maximize system lifetime for WSNBEMSs, and demonstrate that system lifetime can be improved significantly without affecting monitoring accuracy. We also present resource efficient, field programmable gate array (FPGA) architecture for implementation of orthogonal frequency division multiplexing (OFDM) systems. We have demonstrated that our design provides at least 8.8% enhancement in terms of resource efficiency compared to Xilinx FFT v7.1 within the same OFDM configuration. (2) Dataflow-based methods for structured design and implementation of energy- and resource- efficient DSP systems. First, we introduce a dataflow-based design approach based on integrating interrupt-based signal acquisition in context of parameterized synchronous dataflow (PSDF) modeling. We demonstrate that by applying our approach, energy- and resource-efficient embedded software can be derived systematically from high level models of dynamic, data-driven applications systems (DDDASs) functional structure. Also, we present an in-depth development of lightweight dataflow-Verilog (LWDF-V), which is an integration of the LWDF programming model with the Verilog hardware description language (HDL), and we demonstrate the utility of LWDF-V for design and implementation of digital systems for signal processing. We emphasize efficient of LWDF with HDLs, and emphasize the application of LWDF-V to design DSP systems with dynamic parameters on FPGA platforms.Item Resource Allocation Schemes for OFDMA Based Wireless Systems with Quality of Service Constraints(2007-10-08) Girici, Tolga; Ephremides, Anthony; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)With its capabilities like elimination of intersymbol interference, intercell interference averaging, scalability and high bandwidth efficiency OFDMA is becoming the basis for current wireless communication technologies. In this dissertation we study the problem of multiple access and resource allocation for OFDMA-based cellular systems that support users with various quality of service (QoS) requirements. In Chapters 2 and 3 of the dissertation, we consider the problem of downlink transmission (from base station to users) for proportional fairness of long term averaged received rates of data users as well as QoS for voice and video sessions. Delay requirements of real time sessions are converted into rate requirements at each frame. The base station allocates available power and bandwidth to individual users based onreceived rates, rate constraints and channel conditions. We formulate and solve the underlying constrained optimization problem and propose an algorithm that achieves the optimal allocation. In Chapter 3, we obtain a resource allocation scheme that is simpler but achieves a performance comparable to the optimal algorithm proposed in Chapter 2. The algorithms that we propose are especially intended for broadband networks supporting mobile users as the subchannelization scheme we assume averages out the fading in subchannels and performs better under fast fading environment. This also leads to algorithms that are simpler than the ones available in the literature. In Chapter 4 of the dissertation we include relay stations to the previousmodel. The use of low-cost relay stations in OFDM based broadband networks receives increasing attention as they help to improve the cell coverage. For a network supporting heterogeneous traffic we study TDMA based subframe allocation for base and relay stations as well as joint power/bandwidth allocation for individual sessions. We propose an algorithm again using the constrained optimization framework. Our numerical results prove that our multihop relay scheme indeed improves the network coverage and satisfy QoS requirements of user at the cell edge. In the last Chapter, we deviate from the previous chapters and consider an OFDMA based system where the subchannels experience frequency selective fading. We investigate a standard subchannel allocation scheme that exploits multiuser diversity by allocating each subchannel to the user with maximum normalized SNR. Using extreme value theory and generating function approach we did a queueing analysis for this system and estimated the QoS violations through finding the tail distribution of the queue sizes of users. Simulation results show that our estimates are quite accurate and they can be used in admission control and rate control to improve the resource utilization in the system.