Performance Analyses Of Frequency Hopped Spread Spectrum Multiple Access Systems In Fading Environments
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Performance Analyses Of Frequency Hopped Spread Spectrum Multiple Access Systems In Fading Environments
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Author : Usa Svasti-Xuto
language : en
Publisher:
Release Date : 1996
Performance Analyses Of Frequency Hopped Spread Spectrum Multiple Access Systems In Fading Environments written by Usa Svasti-Xuto and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with categories.
The focus of this dissertation is the performance analyses of two classes of frequency-hopped spread-spectrum multiple access (FH-SSMA) systems in various fading environments. The capacity of Viterbi's FH-SSMA system is evaluated under three types of fading, namely Rician, shadowed Rician, and Nakagami fading. The results of recent experiments have indicated that these fading phenomena occur in various environments where the FH-SSMA system may be implemented. In this dissertation, the deletion probability for each fading scenario is derived. Subsequently, the system capacity is analyzed in terms of maximum number of users versus average bit error rate. The effect of a change in the signal-to-noise ratio level on the system capacity is also demonstrated. For Rician fading, it is found that the capacity of the system with a Rician factor of 2 dBis reduced by 13 percent as compared to the capacity of the non-fading case. For shadowed Rician fading, three shadowing scenarios are considered: light, average, and heavy. It is shown that the light and the average shadowing scenarios provide only a slight decrease in the capacity, while the heavy shadowing scenario renders a capacity identical to that for the Rayleigh fading case. Finally, for Nakagami fading the capacity is found to decrease by 50 percent as the fading parameter is reduced to 0.5. The performance of a cellular frequency-hopped spread-spectrum multiple access system is studied under an indoor environment. It is demonstrated how the system capacity, given in terms of the number of users per cell, is affected by the number of cells in the system. Also, the influence of the delay spread, which is the result of multipath propagation, is investigated. The analysis focuses on a worst-case scenario where a user receives both the desired and interfering signals with equal power levels. This scenario applies to both the downlink and the uplink. It is shown that the system capacity is reduced drastically as the number of adjacent interfering cells increases from one to three. Previous work concerning the indoor multipath propagation assumed that the number of paths is fixed, the path delays are uniformly distributed, and the path gains are equal. In this dissertation, a more realistic channel model derived from actual impulse response measurements by Saleh and Valenzuela is employed. The model consists of clusters of rays with constant cluster and ray arrival rates and power-delay time constants. The system performance is shown to be affected strongly by the change in the power-delaytime constants, yet only slightly influenced by the variation in the arrival rates of the rays and clusters. In addition, the degradation in the system performance due to the delay spread becomes more severe as the transmission rate increases.
Performance Analyses Of Frequency Hopped Spread Spectrum Multiple Access Systems In Fading Environments
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Author :
language : en
Publisher:
Release Date : 1997
Performance Analyses Of Frequency Hopped Spread Spectrum Multiple Access Systems In Fading Environments written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with categories.
Performance Analysis Of Frequency Hopped Spread Spectrum Multiple Access Fh Ssma Communication Systems
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Author : Khalid Ali Qaraq'e
language : en
Publisher:
Release Date : 1997
Performance Analysis Of Frequency Hopped Spread Spectrum Multiple Access Fh Ssma Communication Systems written by Khalid Ali Qaraq'e and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with categories.
Performance Analysis Of Direct Sequence Spread Spectrum Multiple Access Communication Via Fading Channels
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Author : David Edward Borth
language : en
Publisher:
Release Date : 1979
Performance Analysis Of Direct Sequence Spread Spectrum Multiple Access Communication Via Fading Channels written by David Edward Borth and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1979 with categories.
The performance of biphase direct-sequence spread-spectrum multiple-access (SSMA) communication for a general class of fading channels is investigated. The channels considered are those for which the channel output consists of a strong stable specular signal plus a faded version of this signal. Such channels are the result of a transmission medium which gives rise to a major stable communication path and a number of additional weaker communication paths. The fading channel is modeled as a general is modeled as a general wide-sense-stationary uncorrelated-scattering (WSSUS) channel -- a model which is general enough to exhibit both time and frequency selectivity and to impose no restrictions on the fading rate. A discussion of the important parameters of the WSSUS channel is given and two important classes of WSSUS channels are developed from the general fading channel model; time-selective fading channels and frequency-selective fading channels. In analyzing the performance of direct-sequence SSMA communications via fading channels two measures of system performance that are considered are average signal-to-noise ratio at the receiver output and the average probability of error. (Author).
Performance Study Of Hybrid Spread Spectrum Techniques
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Author :
language : en
Publisher:
Release Date : 2005
Performance Study Of Hybrid Spread Spectrum Techniques written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
This thesis focuses on the performance analysis of hybrid direct sequence/slow frequency hopping (DS/SFH) and hybrid direct sequence/fast frequency hopping (DS/FFH) systems under multi-user interference and Rayleigh fading. First, we analyze the performance of direct sequence spread spectrum (DSSS), slow frequency hopping (SFH) and fast frequency hopping (FFH) systems for varying processing gains under interference environment assuming equal bandwidth constraint with Binary Phase Shift Keying (BPSK) modulation and synchronous system. After thorough literature survey, we show that hybrid DS/FFH systems outperform both SFH and hybrid DS/SFH systems under Rayleigh fading and multi-user interference. Also, both hybrid DS/SFH and hybrid DS/FFH show performance improvement with increasing spreading factor and decreasing number of hopping frequencies.
Performance Of Fast Frequency Hopping Diversity Combiners In Multiple Access Interference For Ad Hoc Networks
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Author : Helene Ejenyi Tayong
language : en
Publisher:
Release Date : 2006
Performance Of Fast Frequency Hopping Diversity Combiners In Multiple Access Interference For Ad Hoc Networks written by Helene Ejenyi Tayong and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with Dissertations, Academic categories.
The objective of this work is to evaluate the performance of fast frequency-hopping diversity combiners in multiple access interference for ad hoc networks. Multiple access interference (MAI) is the interference that is common in a network with many devices sharing the channel. A model developed in, i.e. the alpha-stable distribution suggested for modeling impulsive signals, is investigated to characterize MAI for an ad hoc network. Impulsive processes are characterized by the presence of spikes or extreme outliers. As such, their probability density functions (pdfs) have heavier tails. Such impulsive behaviors have been verified experimentally in various radio and underwater acoustic channels. The characteristic exponent (the parameter alpha) controls the impulsive behavior of the process. Techniques based on characteristic functions, the Fourier transform of the probability density function (pdf), are used to calculate the probability of error since no-closed form exists for their distributions. Frequency-hopping spread spectrum (FHSS) multiple access radio networks using the same modulation and power is considered. FHSS is a powerful technique used in communication systems to provide protection against jamming and fading. The problem is applicable in wireless random-access communication systems where information about transmitters' positions is not provided. The signal strength attenuates with distance. The focus is on Fast Frequency-hopping (FFH) in order to exploit frequency diversity; a condition where the same data bit is transmitted on multiple independently faded hops. A modulation technique called frequency hopping multilevel frequency shift keying (FH-MFSK) is used to allow many users to effectively share the same frequency band. The Reduced Fuzzy Rank Order Detector (R-FROD), a FFH diversity combiner is studied in this interference environment and its performance is compared with that of hard decision majority vote (HDMV) detector, maximum rank sum receiver (MRSR) and order statistic normalized envelope detector (OS-NED). Simulation results show that the R-FROD is able to outperform the MRSR, OS-NED and HDMV detectors across a range of values for alpha. R-FROD is analyzed in alpha-stable environment using Gaussian and Cauchy membership functions. Simulation results show that either membership function can be used in R-FROD to analyze its performance in an alpha-stable environment. Increasing the hop sequence length reduces the probability of error. The analysis presented is important in the design of efficient interference suppression techniques and in solving mobile wireless communication systems. -- Abstract.
Performance Analysis For Fast Frequency Hopped Spread Spectrum Multiple Access Communications
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Author : E. A. Geraniotis
language : en
Publisher:
Release Date : 1981
Performance Analysis For Fast Frequency Hopped Spread Spectrum Multiple Access Communications written by E. A. Geraniotis and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1981 with categories.
Performance Study Of Modified Frequency Hopping Spread Spectrum Multiple Access Packet Communication Systems
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Author : Ki Jong Hong
language : en
Publisher:
Release Date : 1982
Performance Study Of Modified Frequency Hopping Spread Spectrum Multiple Access Packet Communication Systems written by Ki Jong Hong and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1982 with categories.
Performance Analysis Of Noncoherent Slow Frequency Hopped Spread Spectrum Communications Over Specular Multipath Fading Channels
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Author : Kuo Tung Chiang
language : en
Publisher:
Release Date : 1986
Performance Analysis Of Noncoherent Slow Frequency Hopped Spread Spectrum Communications Over Specular Multipath Fading Channels written by Kuo Tung Chiang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1986 with categories.
Performance Analysis For A New Model Of The Fast Frequency Hopped Code Division Multiple Access Spread Spectrum Communication System
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Author : Ming-li Shen
language : en
Publisher:
Release Date : 1993
Performance Analysis For A New Model Of The Fast Frequency Hopped Code Division Multiple Access Spread Spectrum Communication System written by Ming-li Shen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1993 with categories.