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Author: Publisher: ISBN: Category : Languages : en Pages : 80
Book Description
This report presents a comprehensive summary of a number of methods used in filtering narrowband jammers and interference out of direct sequence spread spectrum communication systems. The basic concept is presented first followed by a discussion of several analog techniques for interference suppression. Most of the emphasis is on digital adaptive methods, which rely on adaptive filtering algorithms. Many of these algorithms are highlighted. This is followed by a discussion on the research which has been conducted in digital excision over the past several years. Two cases based on the author's work are also presented. The first details the performance one can expect from the recursive least squares algorithm when the interferer is a stable tone. An analytical model, which predicts the bit error rate performance for the recursive algorithm under certain conditions, is derived. This model is compared to results obtained from computer simulation, the tracking and filtering capabilities of hte block and recursive least square algorithms when the interference is of the FM-type, i.e., a swept tone having a bandwidth which is approximately 20% of the chip rate. (Author).
Author: Publisher: ISBN: Category : Languages : en Pages : 80
Book Description
This report presents a comprehensive summary of a number of methods used in filtering narrowband jammers and interference out of direct sequence spread spectrum communication systems. The basic concept is presented first followed by a discussion of several analog techniques for interference suppression. Most of the emphasis is on digital adaptive methods, which rely on adaptive filtering algorithms. Many of these algorithms are highlighted. This is followed by a discussion on the research which has been conducted in digital excision over the past several years. Two cases based on the author's work are also presented. The first details the performance one can expect from the recursive least squares algorithm when the interferer is a stable tone. An analytical model, which predicts the bit error rate performance for the recursive algorithm under certain conditions, is derived. This model is compared to results obtained from computer simulation, the tracking and filtering capabilities of hte block and recursive least square algorithms when the interference is of the FM-type, i.e., a swept tone having a bandwidth which is approximately 20% of the chip rate. (Author).
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Time-Frequency distribution are being recognized as powerful tools in signal analysis and processing. Although time-frequency analysis has been of interest for some-time, several advances in recent years have broaden its application areas to include both civilian and military use. The capability of the time-frequency distributions to properly represent multiple component signals in time and frequency permits the development of new and efficient approaches for interference excision in direct sequence spread spectrum communication systems. This report addresses techniques for mitigating nonstationary interference in spread spectrum communication systems; and fast algorithms and efficient realizations of excision techniques based on time-frequency distributions. The scope of this effort is to develop technology to immunize the spread spectrum communication systems to smart jamming and demonstrate the ability to yield improved receiver performance in a highly nonstationary interference environment. This is achieved by utilizing the jammer temporal, spectral, and spatial characteristics to provide accurate and sufficient information leading to its full and effective excision.
Author: Amer A. Hassan Publisher: Springer Science & Business Media ISBN: 9780792382652 Category : Technology & Engineering Languages : en Pages : 178
Book Description
Perspectives in Spread Spectrum brings together studies and recent work on six exciting topics from the spread spectrum arts. The book gives a wide, collective view of trends, ideas, and techniques in the spread spectrum discipline, due to the authors' extensive work on spread spectrum techniques and applications from different vantage points. The inexorable march of electronics towards ever faster, ever smaller, and ever more powerful electronic and optical circuitry has wrought, and will continue to enable, profound changes in the spread spectrum arts, by allowing increasingly complex signalling waveforms and statistical tests to be implemented as the theory beyond spread spectrum continues to evolve. Perspectives in Spread Spectrum is divided into six chapters. The first chapter deals with sequence spreading design. There is not a single metric for design of spreading sequences; rather, the design is ideally tailored to the specific scenario of usage. This chapter delves into recent and very promising synthesis work. The second chapter deals with OFDM techniques. As channels become wider and trans-channel fading (or jamming) becomes frequency selective across the band, OFDM techniques may provide a powerful alternative design perspective. The third chapter is a generalization of the venerable Walsh functions. A new modulation scheme, Geometric Harmonic Modulation, GHM for short, is reviewed and characterized as a form of OFDM. From GHM, a further generalization of the Walsh functions is derived for non-binary signalling. The fourth chapter is concerned with some new and exciting results regarding the follower jammer paradigm. A counter-countermeasure technique is reviewed, notable for its counterintuitive characteristic which can be understood from a simple yet elegant game framework. The fifth chapter recounts some results pertaining to random coding for an optical spread spectrum link. The technique is based on laser speckle statistics and uses a coherent array of spatial light modulators at the transmitter but allows the receiver to be realized as a spatially distributed radiometric and therefore incoherent structure. The sixth and final chapter looks at an important and interesting application of spread spectrum to accurately locate a wideband, ‘bent pipe’, satellite transponder. It is, in a strong sense, an inverted GPS technique. Perspectives in Spread Spectrum serves as an excellent reference and source of ideas for further research, and may be used as a text for advanced courses on the topic.
Author: Brian W. Kozminchuk Publisher: ISBN: Category : Languages : en Pages : 47
Book Description
A Computer Simulation of a BPSK Direct Sequence Spread Spectrum System has been developed to investigate the effects of adaptively filtering stable tone interferers covering twenty per cent of the communication band. Preliminary results for the swept tone interfering signal are also presented and shows that the block filter is effective when the tones are stable, but degrades in performance as the tone sweeps quickly across the band. To combat the non-stationary signal environment, either shorter block lengths may be required or the use of recursive algorithms that are based on gradient or least square concepts may have to be examined. Keywords: Spread spectrum; Binary phase shift keyers; Spectrum estimation; Computer simulation; Autoregressive processes; Maximum entropy method; Least squares; Adaptive filtering; Signal excision; Weiner filtering; Linear prediction; Canada. (jd/rh).
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Author: Amer A. Hassan
Author: Harvey Hum
Author: John William Porter
Author: Marvin K. Simon
Author: Brian W. Kozminchuk
Author: Ngoc Hoa Thach
Author: Zhiyuan Yan
Author: J. E. Hershey