Browsing by Subject "Multiplexing"
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Item Computer Generated Multiplex Holography(Texas Tech University, 1980-05) Irby, Carl ArthurNot Available.Item Integrated circuit design of a sequential state machine(Texas Tech University, 1996-12) Venkataraman, Kamala NNot availableItem Mathematical models of wavelength division multiplexing devices(Texas Tech University, 2000-12) Huang, ShunWith the Intemet booming in recent years, the demand for high-speed transmission over communications networks is increasing at a tremendous rate. There has been a lot of effort trying to explore technologies to enhance the capacity and the utility of transmission media. Since it is well-known that the transmission capacity of optical fiber is enormous and that optical fibers are getting cheaper and cheaper, people have been trying to find more effective ways to utilize the available bandwidth. Wavelength division multiplexing (WDM) is one such technology. It is used to transmit multiple wavelengths of light in a single optical fiber (Figure 1.1 [1]). WDM takes advantage of the 25,000 GHz capacity in the passband of light of optical fibers, reaching a capacity 1,000 times greater than the traditional multiplexing technology, time division multiplexing (TDM), which can only carry around 2.5 gigabit per second in a single fiber. It can be expected that as optical technologies become more and more mature, the price of optical devices will drop and communications networks in the fiiture will be dominated by optical networks.Item Sequence matching on holographicaly stored genetic strings(2005-12) Merkling, Joseph L.; Gale, Richard O.; Sari-Sarraf, Hamed; Watson, RichardIn the field of computational biology one of the basic tasks is string matching. This provides the basis for both the sequencing and assembly of chromosomes but also the alignment of homologues strings in order to determine evolutionary and functional relationships. Over the last fifteen years the amount of data available has grown exponentially, but the ability to analyze this data has not kept pace. This paper examines the feasibility of leveraging the power of holographic storage and optical data processing to handle the data flood. The focus of the discussion is on algorithmic and data formatting issues.Item Signal processing and incoherent-MIMO for multimode optical fibers(2013-05) Appaiah, Kumar; Vishwanath, Sriram; Bank, Seth RobertMultimode fibers (MMF) are generally used in short and medium haul optical networks owing to the availability of low cost devices and inexpensive packaging solutions. However, the performance of conventional multimode fibers is limited primarily by the presence of high modal dispersion owing to large core diameters. While electronic dispersion compensation methods improve the bandwidth-distance product of MMFs, they do not utilize the fundamental diversity present in the different modes of the multimode fiber. This thesis draws from developments in wireless communication theory and signal processing to motivate the use of multiple-input multiple-output (MIMO) and signal processing techniques in MMF links. MIMO techniques that utilize the diversity of modes present in the fiber increase data rates and link reliability. Theoretical models for propagation effects in MMF systems are used to analyze and design the geometry of laser and detector arrays for MIMO-MMF links, and study how the design of these arrays impacts link performance. These models are also used to develop and evaluate low-complexity algorithms that efficiently utilize dense detector arrays, with "greedy subset selection" based on submodular optimization. Experimental evaluation of 1 × 1, 2 × 2, 3 × 3 and 4 × 4 MIMO systems have been conducted over various MMF media, including 100 m - 3 km silica MMF with externally modulated distributed feedback lasers and directly modulated vertical cavity surface emitting lasers (VCSELs), as well as with Fabry Perot lasers over 10 m - 100 m plastic MMF. The use of off-the-shelf components as well as the role of axial offset coupling in enhancing modal diversity has been experimentally quantified. The experimental techniques discussed in this thesis have enabled an increase of over 25× in the bandwidth-distance product of the MMF link, when compared to currently deployed MMF systems, such as 10GBASE-SR.Item A software architecture for cross-layer wireless networks(2008-05) Choi, Soon Hyeok, 1972-; Nettles, Scott M.Conventional data networks are based on a layered architecture, in which a layer implements some aspect of the network while hiding the detailed implementation from the other layers. The introduction of wireless networks has created a need to violate this layered discipline to create cross-layer designs or adaptations. Such cross-layer adaptations optimize the performance of wireless networks by using information from any layer in the network. The key problem is that ad-hoc implementations of cross-layer adaptations introduce complex interactions between layers and thus reduce the level of modularity and abstraction in the network's implementation. This gives rise to a significant increase in complexity. We demonstrate that a new software architecture is able to provide a systematic framework that helps us to implement a wide variety of cross-layer adaptations while preserving to a significant degree the modularity found in the existing network's implementation. To develop such an architecture, we first create a taxonomy of possible cross-layer adaptations. The taxonomy allows a precise description of a wide variety of cross-layer adaptations. Thus our taxonomy can serve as a framework for developing a cross-layer architecture. We develop the software architecture by creating two architectures, a conceptual one and a concrete one. We first develop a conceptual architecture, which shows the key mechanisms that are required to implement cross-layer adaptations. This architecture helps us to understand how we can implement cross-layer adaptations by using our architectural framework. We then develop a concrete architecture, which shows how we can implement such a conceptual architecture on real wireless systems. This architecture addresses more detailed implementation issues. We design the concrete architecture for Hydra, which is a flexible wireless network testbed. We then show that our architecture is generic enough to allow us to support a wide set of cross-layer architectures. We evaluate the proposed architecture by performing three case studies, each of which implements a cross-layer adaptation within Hydra based on the concrete architecture. The case studies allow us to implement and evaluate the key mechanisms provided by our architectural framework. We also implement each cross-layer adaptation by using a conventional approach, in which one layer performs the cross-layer adaptation directly communicating with other layers and other nodes. Comparing both the implementation techniques allows us to evaluate how our architectural framework supports a wide variety of cross-layer adaptations while reducing the complexity of implementation of cross-layer adaptations.Item Space-variant processing using phase codes and Fourier-plane sampling techniques(Texas Tech University, 1980-05) Kasturi, RangacharAny slowly varying linear space-variant system can, in principle, be represented holographically by spatially sampling the input plane and multiplexing the respective system transfer functions. A scheme reported earlier for implementing this technique makes use of phase diffusers in the reference beam paths to encode sequentially recorded holograms. However to minimize the cross talk between the holograms upon playback the diffusers should have good correlation properties, In this thesis extensive computer simulations to evaluate the correlation properties of a family of binary phase codes are conducted. An alternative multiplexing technique in which the transfer functions are sampled in the Fourier plane to generate a composite hologram is also described. In this technique the samples of the transfer functions are placed in non-overlapping regions and hence there will be no crosstalk upon playback. However multiple copies of the input function are required during the playback step. The results of preliminary experiments conducted to evaluate this approach for space-variant system representation are presented including the verification of coherent addition using computer multiplexed holograms.