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 Dissertation Abstracts International written by and published by . This book was released on 2009 with total page 810 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Fairness Oriented Interference Balancing Scheme for Cooperative Frequency Hopping Ad Hoc Networks written by Xavier Pujol i Molist and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: English: It may quite frequently occur in an ad hoc network that the density of users in a given area becomes relatively high during some period of time. At the same time, network resource scheduling is not done regarding these moments with a higher load, but it is done according to average parameters of the network in order to have a trade-off solution that reaches the highest possible quality of service (QoS) while keeping the assigned resources for it as close to be fully exploited as possible. As a result, it may happen that the number of users in a network willing to transmit information is higher than the available resources in that network. On the other hand, in ad hoc networks, the frequency hopping spread spectrum (FHSS) multiple access technique is widely used in the radio interface. In FHSS, the total available bandwidth is partitioned into a certain number of frequency channels having the same bandwidth. In time domain, there is also a division into time intervals. This thesis is focused on the case in which the time intervals have the same duration, called hop period, and specifically on the case where the hop periods for all transmitters are synchronous. Then, in every hop period, every transmitter is been assigned some of those channels to transmit. It means that every transmitter will transmit through some frequency channels, and after the hop period, the transmission will hop into some other channels; and this will happen recursively after every hop period. When, in every hop period, every assigned frequency channel has been assigned to one (and no more) transmitter, then, there is orthogonality among users or, in other words, the hopping sequences or codes, according to which channels are assigned to each user in every hop, are orthogonal. When the hopping sequences are orthogonal, there is no interference among the users of the system because no transmitter coincides with any other in the same frequency channel at the same time (namely, there are no collisions). Orthogonality can always hold when the number of transmitters is less or equal to the number of available frequency channels in the FHSS system. However, when this condition is no longer satisfied, i.e., when there are more transmitters that may simultaneously transmit than available frequency channels, orthogonality is no longer preserved and, so, interference occurs unavoidably. The interference distribution among users depends on the design of the hopping sequences. With conventional approaches for designing the hopping sequences, interference is extremly unbalanced across all users and so, a completely unfair scenario takes place. This work tackles this problem and proposes a method for designing frequency hopping sequences that achieve at the same time a fair interference allocation across all users and an optimal interference reduction. The proposed scheme is optimal in terms of interference level because the overall number of collisions that take place in every hop is the minimum possible. At the same time, this fairness-oriented approach distributes the collisions among nodes in such a way that the variance of the interference power seen by the nodes is considerably reduced. Thereby, this scheme achieves a much more equitable interference balancing across the nodes. The results displayed by the fairness-oriented scheme in terms of fairness are much better than those ones displayed by the two reference studied schemes for both slow and fast frequency hopping.
Download or read book Performance Analysis of Diversity Combining for Frequency hop Communications Under Partial band and Multitone Interference written by Gang Li and published by . This book was released on 1992 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Diversity Combining for M ary Fast Frequency Hopping in a Multiple Access AWGN and Rayleigh Fading Channel written by Elizabeth Donna Spilchen and published by . This book was released on 1996 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Slow Frequency and Time Hopping in Wireless Communication written by Elif Uysal and published by . This book was released on 1999 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Performance of a Fast Frequency Hopping Spread Spectrum Rank Sum Receiver in Partial Band Interference written by James F. Colling and published by . This book was released on 1993 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Performance Evaluation of Frequency Hopped Spread Spectrum Multi Hop Networks written by J. W. Gluck and published by . This book was released on 1988 with total page 55 pages. Available in PDF, EPUB and Kindle. Book excerpt: Primary and secondary multiple-access interference processes are characterized for multi-hop packet radio networks, in which users are assumed to be Poisson-distributed in the plane and to use frequency hopped spread-spectrum signaling with a receiver-oriented assignment of frequency-hopping patterns. The throughput per node and the average forward progress are then evaluated for frequency-hopped multi-hop networks that employ (i) random forward routing with fixed transmission radius (RFR) and(ii) most forward progress routing with fixed transmission radius (MFR). The optimal average number of neighbors and transmission radius are derived for these cases when Reed-Solomon forward-error-control coding with minimum distance decoding or binary convolutional coding with Viterbi decoding is employed.
Download or read book Diversity Combining for Frequency hop Spread spectrum Communications with Partial band Interference and Fading written by Catherine Marie Keller and published by . This book was released on 1985 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents results on the evaluation of several diversity combining techniques that are suggested for frequency-hop (FH) communications with partial-band interference and fading. The analysis covers systems with M-ary orthogonal signaling and noncoherent demodulation. The partial-band interference is modeled as a Gaussian process, although some of the results also apply to general (non-Gaussian) partial-band interference. The performance measures we use to evaluate the diversity combining techniques are the narrowband interference rejection capability and the signal to noise ratio requirement over the entire range of interference duty factors. We evaluate the exact probability of error for each of the diversity combining techniques studied. The performance of the optimum combining technique for receivers with perfect side information is established. It is shown that for receivers with perfect side information, the system performance does not change significantly with the choice of the diversity combining technique. However, the same schemes that work well in receivers with perfect side information perform poorly in receivers without side information. Keywords include: Diversity combining; Frequency-hop; Spread-spectrum; Partial band interference and Fading.
Download or read book Performance Study of Modified Frequency Hopping Spread Spectrum Multiple Access Packet Communication Systems written by Ki Jong Hong and published by . This book was released on 1982 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Performance Analysis for Fast Frequency Hopped Spread Spectrum Multiple Access Communications written by E. A. Geraniotis and published by . This book was released on 1981 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Analysis Method for Direct Sequence Systems Employing Noncoherent Reception with Applications to Fast Frequency Hopping Multiple Access Jamming and Soft Limit Diversity Combining written by Ronald Paul Smith and published by . This book was released on 1994 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reducing Multiple Access Interference in Broadband Multi user Wireless Networks written by Ali Nayef Alqatawneh and published by . This book was released on 2015 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation is devoted to developing multiple access interference (MAI) reduction techniques for multi-carrier multi-user wireless communication networks. In multi-carrier code division multiple access (MC-CDMA) systems, a full multipath diversity can be achieved by transmitting one symbol over multiple orthogonal subcarriers by means of spreading codes. However, in frequency selective fading channels, orthogonality among users can be destroyed leading to MAI. MAI represents the main obstacle to support large number of users in multi-user wireless systems. Consequently, MAI reduction becomes a main challenge when designing multi-carrier multi-user wireless networks. In this dissertation, first, we study MC-CDMA systems with different existing MAI reduction techniques. The performance of the studied systems can be further improved by using a fractionally spaced receivers instead of using symbol spaced receivers. A fractionally spaced receiver is obtained by oversampling received signals in a time domain. Second, a novel circular-shift division multiple access (CSDMA) scheme for multi-carrier multi-user wireless systems is developed. In CSDMA, each symbol is first spread onto multiple orthogonal subcarriers in the frequency domain through repetition codes. The obtained frequency-domain signals are then converted to a time-domain representation. The time-domain signals of different users are then circularly shifted by different numbers of locations. The time-domain circular shifting enables the receiver to extract signals from different users with zero or a small amount of MAI. Our results show that the CSDMA scheme can achieve a full multipath diversity with a performance outperforms that of orthogonal frequency division multiple access (OFDMA). Moreover, multipath diversity of CSDMA can be further improved by employing the time-domain oversampling. Performance fluctuations due to a timing offset between transmitter and receiver clocks in MC-CDMA and CSDMA systems can be removed by employing the time-domain oversampling. Third, we study the theoretical error performance of high mobility single-user wireless communication system with doubly selective (time-varying and frequency-selective) fading channel under impacts of imperfect channel state information (CSI). Throughout this dissertation, intensive computer simulations are performed under various system configurations to investigate the obtained theoretical results, excellent agreements between simulation and theoretical results were observed in this dissertation.
Download or read book Fundamentals of Wireless Communication written by David Tse and published by Cambridge University Press. This book was released on 2005-05-26 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: This textbook takes a unified view of the fundamentals of wireless communication and explains cutting-edge concepts in a simple and intuitive way. An abundant supply of exercises make it ideal for graduate courses in electrical and computer engineering and it will also be of great interest to practising engineers.
Download or read book Interference Mitigation in Frequency Hopping Ad Hoc Networks written by Jens Elsner and published by . This book was released on 2012 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Principles of Mobile Communication written by Gordon L. Stüber and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 670 pages. Available in PDF, EPUB and Kindle. Book excerpt: Principles of Mobile Communication provides an authoritative treatment of the fundamentals of mobile communications, one of the fastest growing areas of the modern telecommunications industry. The book stresses the fundamentals of mobile communications engineering that are important for the design of any mobile system. Less emphasis is placed on the description of existing and proposed wireless standards. This focus on fundamental issues should be of benefit not only to students taking formal instruction but also to practising engineers who are likely to already have a detailed familiarity with the standards and are seeking to deepen their knowledge of this important field. The book stresses mathematical modeling and analysis, rather than providing a qualitative overview. It has been specifically developed as a textbook for graduate level instruction and a reference book for practising engineers and those seeking to pursue research in the area. The book contains sufficient background material for the novice, yet enough advanced material for a sequence of graduate level courses. Principles of Mobile Communication treats a variety of contemporary issues, many of which have been treated before only in the journals. Some material in the book has never appeared before in the literature. The book provides an up-to-date treatment of the subject area at a level of detail that is not available in other books. Also, the book is unique in that the whole range of topics covered is not presently available in any other book. Throughout the book, detailed derivations are provided and extensive references to the literature are made. This is of value to the reader wishing to gain detailed knowledge of a particular topic.
Download or read book Wireless Communications Networking written by Vijay Garg and published by Elsevier. This book was released on 2010-07-28 with total page 931 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides comprehensive coverage of mobile data networking and mobile communications under a single cover for diverse audiences including managers, practicing engineers, and students who need to understand this industry. In the last two decades, many books have been written on the subject of wireless communications and networking. However, mobile data networking and mobile communications were not fully addressed in a unified fashion. This book fills that gap in the literature and is written to provide essentials of wireless communications and wireless networking, including Wireless Personal Area Networks (WPAN), Wireless Local Area Networks (WLAN), and Wireless Wide Area Networks (WWAN). The first ten chapters of the book focus on the fundamentals that are required to study mobile data networking and mobile communications. Numerous solved examples have been included to show applications of theoretical concepts. In addition, unsolved problems are given at the end of each chapter for practice. (A solutions manual will be available.)After introducing fundamental concepts, the book focuses on mobile networking aspects. Four chapters are devoted on the discussion of WPAN, WLAN, WWAN, and internetworking between WLAN and WWAN. Remaining seven chapters deal with other aspects of mobile communications such as mobility management, security, cellular network planning, and 4G systems.A unique feature of this book that is missing in most of the available books on wireless communications and networking is a balance between the theoretical and practical concepts. Moreover, this book can be used to teach a one/two semester course in mobile data networking and mobile communications to ECE and CS students. *Details the essentials of Wireless Personal Area Networks(WPAN), Wireless Local Are Networks (WLAN), and Wireless Wide Area Networks (WWAN)*Comprehensive and up-to-date coverage including the latest in standards and 4G technology*Suitable for classroom use in senior/first year grad level courses. Solutions manual and other instructor support available
