Distributional properties of d-FCSR sequences

AbstractIn this paper we study the distribution properties of d-FCSR sequences. These sequences have efficient generators and have several good statistical properties. We show that for d=2 the number of occurrences of an fixed size subsequence differs from the average number of occurrences by at most a small constant times the square root of the average

Secuencias binarias y sus aplicaciones

ABSTRACT: The generation of families of sequences with a bounded correlation, among other properties, is of interest in several fields such as cryptography, wireless communications and digital watermarks. Commercial applications such as GPS or military uses such as Radar have been developed and improved thanks to the search of these sequences and the analysis of their autocorrelation function and the correlation between members of the same family. In this project, we focus on a technique for the algebraic construction of sequences where a sequence of shifts and a sequence with good properties generate a new sequence. The aim is the exhaustive search of longer sequences then the ones already present in the literature. To do so, a software intended to provide support to a designer has been developed to assist in the search of said sequences and check their properties, which can be deployed in a supercomputer. The applications of these sequences are, among others, radars and location systems with higher spatial resolution.RESUMEN: Generar familias de secuencias con correlación acotada, entre otras propiedades, es de interés en diversas áreas como criptografía, comunicaciones inalámbricas y marcas de agua digitales. Aplicaciones comerciales como el GPS, o con usos militares como el Radar se han desarrollado y mejorado a partir de la búsqueda de estas secuencias mediante el estudio de su función tanto de autocorrelación como de la correlación entre los miembros de una misma familia. En este proyecto, nos centramos en una técnica para la construcción algebraica de secuencias donde, a través de una secuencia de desplazamientos y una secuencia con buenas propiedades, se genera una nueva secuencia. El objetivo es la búsqueda exhaustiva de secuencias de mayor longitud que las ya existentes en la literatura. Para este fin, se ha desarrollado un software de apoyo al diseñador con capacidad de ser desplegado en un nodo de supercomputación para asistir a la búsqueda de dichas secuencias y la comprobación de sus propiedades. La finalidad de estas secuencias, entre otros posibles usos, son radares y sistemas de localización con mayor resolución espacial.Grado en Ingeniería Informátic

Communications techniques and equipment: A compilation

This Compilation is devoted to equipment and techniques in the field of communications. It contains three sections. One section is on telemetry, including articles on radar and antennas. The second section describes techniques and equipment for coding and handling data. The third and final section includes descriptions of amplifiers, receivers, and other communications subsystems

Application of bit-slice microprocessors to digital correlation in spread spectrum communication systems

This thesis describes the application of commercially available microprocessors and other VLSI devices to high-speed real-time digital correlation in spread spectrum and related communication applications. Spread spectrum communications are a wide-band secure communication system that generate a very broad spectral bandwidth signal that is therefore hard to detect in noise. They are capable of rejecting intentional or unintentional jamming, and are insensitive to the multipath and fading that affects conventional high frequency systems. The bandwidth of spread spectrum systems must be large to obtain a significant performance improvement. This means that the sequence rate must be fast and therefore very fast microprocessors will be required when they are used to perform spread spectrum correlation. Since multiplication cannot be performed efficiently by microprocessors considerable work, since 1974, has been published in the literature which is devoted to minimising the requirement of multiplications in digital correlation and other signal processing algorithms. These fast techniques are investigated and implemented using general-purpose microprocessors. The restricted-bandwidth problem in microprocessor-based digital correlator has been discussed. A new implementation is suggested which uses bit-slice devices to maintain the flexibility of microprocessor-based digital correlation without sacrificing speed. This microprocessor-based system has been found to be efficient in implementing the correlation process at the baseband in the digital domain as well as the post-correlation signal processing- demodulation, detection and tracking, especiaJIy for low rate signals. A charge coupled-device is used to obtain spectral density function. An all-digital technique which is programmable for any binary waveform and can be used for achieving initial acquisition and maintaining synchronisation in spread spectrum communications is described. Many of the practical implementation problems are discussed. The receiver performance, which is measured in terms of the acquisition time and the bit-error rate, is also presented and results are obtained which are close to those predicted in the system simulations

On the design of turbo codes

In this article, we design new turbo codes that can achieve near-Shannon-limit performance. The design criterion for random interleavers is based on maximizing the effective free distance of the turbo code, i.e., the minimum output weight of codewords due to weight-2 input sequences. An upper bound on the effective free distance of a turbo code is derived. This upper bound can be achieved if the feedback connection of convolutional codes uses primitive polynomials. We review multiple turbo codes (parallel concatenation of q convolutional codes), which increase the so-called 'interleaving gain' as q and the interleaver size increase, and a suitable decoder structure derived from an approximation to the maximum a posteriori probability decision rule. We develop new rate 1/3, 2/3, 3/4, and 4/5 constituent codes to be used in the turbo encoder structure. These codes, for from 2 to 32 states, are designed by using primitive polynomials. The resulting turbo codes have rates b/n (b = 1, 2, 3, 4 and n = 2, 3, 4, 5, 6), and include random interleavers for better asymptotic performance. These codes are suitable for deep-space communications with low throughput and for near-Earth communications where high throughput is desirable. The performance of these codes is within 1 dB of the Shannon limit at a bit-error rate of 10(exp -6) for throughputs from 1/15 up to 4 bits/s/Hz

Investigations in the design and analysis of key-stream generators

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Performance Evaluation of Phase Optimized Spreading Codes in Non Linear DS-CDMA Receiver

Spread spectrum (SS) is a modulation technique in which the signal occupies a bandwidth much larger than the minimum necessary to send the information. A synchronized reception with the code at the receiver is used for despreading the information before data recovery. Bandspread is accomplished by means of a code which is independent of the data. Bandspreading code is pseudo-random, thus the spread signal resembles noise. The coded modulation characteristic of SS system uniquely qualifies it for navigation applications. Any signal used in ranging is subject to time/distance relations. A SS signal has advantage that its phase is easily resolvable. Direct-sequence (DS) form of modulation is mostly preferred over Frequency Hopping system (FH) as FH systems do not normally possess high resolution properties. Higher the chip rate, the better the measurement capability. The basic resolution is one code chip. Initially, some existing code families e.g. Gold, Kasami (large and smal..

High-Performance Parallel Implementation of Genetic Algorithm on FPGA

Genetic algorithms (GAs) are used to solve search and optimization problems in which an optimal solution can be found using an iterative process with probabilistic and non-deterministic transitions. However, depending on the problem’s nature, the time required to find a solution can be high in sequential machines due to the computational complexity of genetic algorithms. This work proposes a full-parallel implementation of a genetic algorithm on field-programmable gate array (FPGA). Optimization of the system’s processing time is the main goal of this project. Results associated with the processing time and area occupancy (on FPGA) for various population sizes are analyzed. Studies concerning the accuracy of the GA response for the optimization of two variables functions were also evaluated for the hardware implementation. However, the high-performance implementation proposed in this paper is able to work with more variable from some adjustments on hardware architecture. The results showed that the GA full-parallel implementation achieved throughput about 16 millions of generations per second and speedups between 17 and 170,000 associated with several works proposed in the literature

Periodic binary sequence generators: VLSI circuits considerations

Feedback shift registers are efficient periodic binary sequence generators. Polynomials of degree r over a Galois field characteristic 2(GF(2)) characterize the behavior of shift registers with linear logic feedback. The algorithmic determination of the trinomial of lowest degree, when it exists, that contains a given irreducible polynomial over GF(2) as a factor is presented. This corresponds to embedding the behavior of an r-stage shift register with linear logic feedback into that of an n-stage shift register with a single two-input modulo 2 summer (i.e., Exclusive-OR gate) in its feedback. This leads to Very Large Scale Integrated (VLSI) circuit architecture of maximal regularity (i.e., identical cells) with intercell communications serialized to a maximal degree