Download or read book Probability of Capture and Rejection of Primary Multiple Access Interference in Spread Spectrum Networks written by and published by . This book was released on 1987 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: The probability of capture is evaluated for the situation in which several transmitters use the same spread-spectrum code to contend for the attention of a single receiver. The first stage in the capture mechanism is that of acquisition of capture; randomization of the arrival time has been proposed by Davis and Cronemayer to provide delay capture and the probability of this occurrence has been derived. We are concerned with the second stage, that of retaining capture in the presence of interference from the contending users. The probability of retaining capture is computed via accurate approximations and upper bounds for direct-sequence, frequency-hopped and hybrid spread- spectrum signaling formats and for different data modulation and demodulation schemes. The calculation of the overall probability of capture is carried out for spread-spectrum systems with and without forward-error-control; in the latter case Reed-Solomon codes, as well as binary convolutional codes, are considered. Finally, the capability of rejecting primary multiple-access interference in spread-spectrum radio networks is examined by computing the maximum number of users which can contend for the same receiver without causing the probability of capture to fall below some desirable level.
Download or read book Spread Spectrum in Mobile Communication written by Olav Berg and published by IET. This book was released on 1998 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presenting a technology that adapts radio communication to computational data information processing networks, first reviews the concepts of modern mobile communication and the user requirements and operational environment that influence the design of mobile systems. Then focuses on mobility issues for a decentralized network topology and the effects of spread spectrum modulation on radios used in packet-switched networks. Shows how connecting radio terminals using packet switching provides a highly flexible and efficient solution for mobile users. Annotation copyrighted by Book News, Inc., Portland, OR
Download or read book Proceedings of the Conference on Information Sciences and Systems written by and published by . This book was released on 1987 with total page 794 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Security of Self Organizing Networks written by Al-Sakib Khan Pathan and published by CRC Press. This book was released on 2016-04-19 with total page 614 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reflecting recent advancements, Security of Self-Organizing Networks: MANET, WSN, WMN, VANET explores wireless network security from all angles. It begins with a review of fundamental security topics and often-used terms to set the foundation for the following chapters. Examining critical security issues in a range of wireless networks, the bo
Download or read book 3rd European Conference on Satellite Communications 2 4 November 1993 written by and published by . This book was released on 1993 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Poetry from Bombay written by Jagdish Shivpuri and published by . This book was released on 1977 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1991 with total page 1588 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Kane Bill 1951 written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The folder may include clippings, announcements, small exhibition catalogs, and other ephemeral items.
Download or read book A Multiple Access Interference Rejection Technique Using Weighted Despreading Functions for Direct Sequence Code Division Multiple Access Communications written by Yuejin Huang and published by . This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "A Multiple Access Interference Rejection Technique Using Weighted Despreading Functions for Direct-sequence Code Division Multiple Access Communications" by 黃耀進, Yuejin, Huang, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b3123707 Subjects: Wireless communication systems Code division multiple access Spread spectrum communications
Download or read book A Knowledge Based Interference Rejection Scheme for Direct Sequence Spread Spectrum Systems written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spread-spectrum signals are used widely in military and commercial communication systems due to their interference rejection capability and their lower probability of interception. In military applications the effects of intentional interference (jamming) are mitigated by the processing gain of the spread-spectrum system. In many spread-spectrum systems, processing gain alone is not sufficient to achieve satisfactory system performance and additional interference rejection techniques need to be employed. The interference suppression circuit is placed prior to the spectrum despreader with the goal of reducing the jammer/interferer energy to an adequately low level that can be handled by the system processing gain. We have presented a novel knowledge-based interference cancellation scheme for direct sequence spread-spectrum systems. This innovative approach utilizes: (1) IPUS, an expert system for the Integrated processing and Understanding of signals, to monitor the communication signal environment in order to determine the parameters of interfering signals within a pre-specified accuracy, and (2) Expert system rules to select from a library of preselected techniques, suitable interference rejection schemes based upon the knowledge obtained from monitoring the signal environment. The effectiveness of this novel interference rejection capability is demonstrated by considering a number of interference scenarios and using the software package SPW(copyright), a time-domain Signal Processing Worksystem.
Download or read book The Probability of Multiple Correct Packet Receptions in a Multireceiver Frequency Hopped Spread Spectrum System written by and published by . This book was released on 1991 with total page 49 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this report we develop exact expressions and approximations for the probability of exactly l correct packet receptions in a group of m receivers, given that k packets are transmitted simultaneously from users employing frequency-hopping spread-spectrum (FH/SS) and Reed-Solomon (RS) coding. This quantity is essential for the design and performance evaluation of multiple-access protocols in spread-spectrum packet radio networks. The evaluations are carried out for MFSK modulation with noncoherent demodulation and various types of RS minimum-distance decoding with erasures and/or errors decoding. Packet synchronous FH/SSMA systems that are hop-synchronous or hop- asynchronous are considered. The exact expressions developed have computational complexity that grows exponentially with m, thus making their evaluation for large m prohibitive. In light of such difficulties, two approximations are considered: one based on Gaussian multivariate distributions with linear computational requirements in m and k, and another based on the assumption of independent receiver operation (IROA), which has minimum computational complexity. Extensive comparisons of the approximations with the exact results establish their validity over different ranges of the system parameters. (Author).
Download or read book Error Probability for Direct Sequence Spread Spectrum Multiple Access Communications Part I Upper and Lower Bounds written by Michael B. Pursley and published by . This book was released on 1981 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multiple Access Interference Characterization for Direct Sequence Spread Spectrum Communications Using Chip Waveform Shaping written by Matthew G. Glen and published by . This book was released on 2004-03-01 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research characterizes MAI effects on DS/SSMA system performance through simulation in Matlab , and explores the impact of multiple access code selection, chip waveform shaping, and multiple access code length on BER for both synchronous and asynchronous multiple access networks. In addition, the simulated DS/SSMA model permits rapid research into the effects of additional factors on BER. Prior to experimental testing, model validation is conducted through single user trials and by comparison with existing research for similar system designs. For synchronous and asynchronous networks, Gold coding improves BER by 7.5 and 4.0 dB, respectively, relative to aperiodic random spreading codes. Synchronous network results show that chip waveform shaping provides no significant BER improvement for the Blackman or Lanczos shapes. However, asynchronous network results show a potential BER improvement for Blackman and Lanczos shapes. Increasing code length from 31 to 511 resulted in a 7.5 dB BER improvement. Collectively, these results directly relate changes in BER to waveform cross-correlation statistics.
Download or read book Error Probability for Direct Sequence Spread Spectrum Multiple Access Communications Part II Approximations written by Evaggelos A. Geraniotis and published by . This book was released on 1981 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bit to Bit Error Dependence in Direct Sequence Spread Spectrum Multiple Access Packet Radio Systems written by Robert K Morrow (Jr) and published by . This book was released on 1988 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: Slotted direct-sequence spread-spectrum multiple-access (DS/SSMA) packet broadcasting systems with random signature sequences are analyzed within the framework of the lower three layers of the International Standards Organization Reference Model of Open Systems Interconnection. At the physical layer, we show that a widely-used Gaussian approximation (which we call the Standard Gaussian Approximation) for the probability of data bit error in a chip and phase asynchronous system is accurate only when there are a large number of simultaneous users on the channel; otherwise, this approximation can be optimistic by several orders of magnitude. For interfering signals with fixed delays and phases relative to the desired signal, however, the Standard Gaussian Approximation is quite accurate for any number of simultaneous users. To obtain a closer approximation to the probability of data bit error for an asynchronous system, we introduce the Improved Gaussian Approximation, which involves finding the distribution of the multiple-access interference variance over all possible delay and phase values and then taking a Gaussian approximation over the support of the distribution and averaging the results. To accurately analyze packet performance at the data link layer, we first use the theory of moment spaces to gain insight on the effect of bit-to-bit error dependence caused by the constant relative delays and (possibly) phases of the interfering signals over the duration of a desired packet. (rh).
Download or read book Performance of Fast Frequency hopping Diversity Combiners in Multiple Access Interference for Ad Hoc Networks written by Helene Ejenyi Tayong and published by . This book was released on 2006 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Performance of Cellular Frequency Hopped Spread Spectrum Radio Networks written by Jeffrey W. Gluck and published by . This book was released on 1989 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multiple access interference is characterized for cellular mobile networks, in which users are assumed to be Poisson-distributed in the plane and employ frequency-hopped spread-spectrum signaling with transmitter-oriented assignment of frequency-hopping patterns. Exact expressions for the bit error probabilities are derived for binary coherently demodulated systems without coding. Approximations for the packet error probability are derived for coherent and noncoherent systems and these approximations are applied when forward-error-control coding is employed. In all cases, the effects of varying interference power are accurately taken into account according to some propagation law. Numerical results are given in terms of bit error probability for the exact case and throughput for the approximate analyses. Comparisons are made with previously derived bounds and it is shown that these tend to be very pessimistic. Keywords: Communications network; Multiple access; Frequency hopping; Spread spectrum; Error control coding. (jhd).
