This dissertation provides a study of synchronization and quantization issues in implementing a multistage receiver in fixed-point Digital Signal Processing (DSP) hardware. Current multistage receiver analysis has neglected the effects of synchronization and quantization; however, these effects can degrade system performance and therefore decrease overall system capacity. The first objective is to analyze and simulate various effects of synchronization in a multistage system. These effects include the effect of unsynchronized users on the bit error rate (BER) of synchronized users, and determining whether interference cancellation can be used to improve the synchronization time. This information is used to determine whether synchronization will limit overall system capacity. Both analytical and simulation techniques are presented. The second objective is to study the effects of quantization on the performance of the multistage receiver. A DSP implementation of a practical receiver will require a DSP chip with a fewer number of bits than the computer chips typically used in simulation of receiver performance. Therefore, the DSP implementation performs poorer than the simulation results predict. In addition, a fixed-point implementation is often favored over a floating-point implementation, due to the high processing requirements necessitated by the high chip rate. This further degrades performance because of the limited dynamic range available with fixed-point arithmetic. The performance of the receiver using a fixed-point implementation is analyzed and simulated. We also relate these topics to other important issues in the hardware implementation of multistage receivers, including the effects of frequency offsets at the receiver and developing a multiuser air protocol interface (API). This dissertation represents a contribution to the ongoing hardware development effort in multistage receivers at Virginia Tech. / Ph. D.

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International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / This paper presents the development of two distributed terrestrial radiolocation algorithms that use range estimates derived from DS-CDMA waveforms. The first algorithm, which is RLS-based, is derived as the solution of an approximate least-squares positioning problem. This algorithm has the advantage of reduced computational complexity, compared with the EKF-based algorithm that is presented. It is shown via simulations that both positioning algorithms perform well, with the performance of the EKF-based algorithm being superior.

ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California / A MIMO radar system for target localization is presented which uses direct-sequence CDMA (DS-CDMA) waveforms. The received DS-CDMA signal at each antenna is expressed directly in terms of the target positions. The waveforms employed are Gold sequences, and hence are not exactly orthogonal. A generalized successive interference cancellation (GSIC) approach is used to resolve multiple scatterers and reduce clutter. Simulation results are presented which suggest the capability to detect weak scatterers in the presence of clutter using the cancellation method.

International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The expectation-maximization (EM) algorithm is well established as a computationally efficient method for separable signal parameter estimation. Here, a new geometric derivation and interpretation of the EM algorithm is given that facilitates the understanding of its convergence properties. Geometric considerations then lead to an alternative separable signal parameter estimator based on successive cancellation. The new Generalized Successive Interference Cancellation (GSIC) algorithm may offer better performance than EM in the presence of large signal power disparities. Finally, application of the GSIC algorithm to CDMA-based radiolocation is discussed, and simulation results are presented.

International Telemetering Conference Proceedings / October 23-26, 2000 / Town & Country Hotel and Conference Center, San Diego, California / This paper presents one new type CDMA multi-signal receiving protocol, which is suitable for satellite mobile communication systems. Then it gives the principle analysis and describes the realization of this protocol. Meanwhile, it gives the software protocol implementation scheme. From the long point of view, it will more increase the system flexibility, which is easier to update; and will solve the interoperability and integration application problems. Finally, the simulation results conclude that software implementation of CDMA multi-signal receiving in satellite mobile communication system is feasible, and it may be used in other wireless communication systems.

Abstract Development of the Fourth Generation of mobile communication systems, or 4G, has already begun in various organizations and research institutions worldwide. There is currently no single conclusive definition for 4G systems, and the process of 4G standardization will only begin after the World Radiocommunication Conference in 2007. The purpose of this report is to provide an objective definition of 4G systems based on user requirements, and to use this definition to determine an appropriate 4G access network architecture. By examining the current trends in user requirements, and the methodologies proposed by different researchers, an objective definition of 4G systems was developed. The definition states that the purpose of 4G systems is to provide users with the capacity to access any service at any time at a reasonable cost and at the required levels of quality. There are two developmental methodologies which are currently being considered to achieve this objective: first the evolution and convergence of existing systems, including cellular, IT and broadcasting communication systems, and second, the development of a new 4G access network capable of providing users with access to advanced services. The primary specification for this new access network is that it must provide a throughput of 1 Mbps for mobile users and 1 Gbps for users that are stationary. Other requirements include high spectral efficiency and high capacity and coverage. The primary focus of this report is the examination of the second of the above methodologies by evaluating the performance of candidate 4G air-interface architectures so that a recommendation could be made as to which of the architectures is the preferred choice as the core component in a new 4G access network. Orthogonal Frequency Division Multiplexing (OFDM) modulation is a high performance modulation technique capable of achieving high levels of spectral efficiency and is widely accepted as the technique most capable of meeting 4G access network requirements. There are two primary access network architectures that make use of OFDM modulation and could form the core components of a 4G air-interface, the physical component of a 4G access network. To determine which architecture is the appropriate choice for 4G systems, a series of simulations were run using realistic models of a wireless environment. The results of those simulations were analyzed, and it was determined that, due to the absence of multiple access interference found in MC-CDMA, OFDMA systems better met the defined requirements for a 4G air-interface. The use of additional techniques such as radio resource management, multi-antennae technologies and software defined radios are cited as potential methods for improving both OFDMA and MC-CDMA performance.

El presente trabajo consiste en diseñar una red rural de telecomunicaciones con tecnología CDMA en 450 MHz, que pueda brindar servicio a los distritos de Pacarán, Zúñiga, Catahuasi, Tupe, Chocos, Huangascar, Manden, Viñac, ubicados a orillas del rio Cañete y sus alrededores. En el primer capítulo se muestra el estudio de la tecnología celular CDMA 2000 en frecuencias de 450 MHz, sus características y ventajas favorables para la aplicación en redes rurales. También se describe las características adversas en zonas rurales y la situación normativa actual en este escenario. El segundo capítulo muestra la información obtenida del estudio en sitio de la zona donde se pretende dar cobertura de voz y datos. Con dicha información y datos estadísticos del Instituto Nacional de Estadística e Informática (INEI), se realizan estimaciones y cálculos para obtener la demanda potencial. En el tercer capítulo se realiza el diseño la de red rural, plasmando la topología de red en el valle de cañete. Luego mediante la estimación realizada en el capitulo anterior, dimensionamos la capacidad de los equipos en la red, asegurando la cobertura de la zona y el escalamiento de la red en el futuro; basado en estos requerimientos se presenta el equipamiento elegido. En el último capítulo se detalla los costos de inversión inicial de los activos y servicios necesarios de mayor importancia para iniciar las operaciones de red. También se muestra los costos de operación más importantes. Por último, luego de adquirir en el presente trabajo nuevos conocimientos e interiorizar la problemática de la zona rural del Valle de Cañete, se presentan conclusiones y recomendaciones. / Tesis

Zugl.: Aachen, Techn. Hochsch., Diss., 2007.