Download or read book Optimum Jamming Effects on Frequency Hopping M ary FSK Frequency Shift Keying Systems Under Certain ECCM Electronic Counter Countermeasures Receiver Design Strategies written by J. S. Lee and published by . This book was released on 1984 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of M-ary frequency-shift-keying frequency-hopping systems using multiple hops per symbol waveform is derived and evaluated for the cases of worst-case partial-band noise jamming and worst-case partial-band tone jamming. The analyses include the effects of the jamming under certain ECCM receiver design strategies. The receiver design strategies include the convention square-law linear combiner and the several types of unconventional nonlinear combiners. The ECCM receiver design employing the nonlinear combiners are found to provide diversity gains whereas such gains are not realized under the conventional linear combining strategy. (Author).
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1989 with total page 896 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1989 with total page 1332 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Annual Index written by and published by . This book was released on 1985 with total page 878 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book AGARD Index of Publications written by North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development and published by . This book was released on 1986 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Performance Analysis of Frequency Hopping MFSK M ary Frequency Shift Keying Systems Employing Forward Error Control Coding in the Presence of Hostile Interference written by Jhong S. Lee and published by . This book was released on 1987 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Error probability analyses are performed for a coded M-ary frequency-shift-keying (MFSK) system employing L hops per M-ary word frequency-hopping (FH) spread spectrum waveforms transmitted over a partial-band Gaussian noise jamming channel. The information bit error probabilities are obtained for a square-law linear combining demodulator and for a square-law adaptive gain control (AGC) demodulator, both with forward error control (FEC) coding under conditions of worst-case partial-band noise jamming, using exact analyses of the demodulator performance which include both thermal noise and jamming noise. Parametric performance curves are obtained for both block codes and convolutional codes with both binary and M-ary channel modulations. The results show that thermal noise can not be neglected in the analyses if correct determinations of the optimum order of diversity and the worst-case jamming fraction are to be obtained over the whole range of signal-to-thermal noise and signal-to-jamming ratios. It is shown that the combination of non-linear combining, M-ary modulation, and forward error control coding is an effective strategy against worst-case partial-band noise jamming. However, just as was found to be the case for uncoded systems, the linear combiner is ineffective in worst-case partial-band noise jamming. (Author).
Download or read book Anti jam Analysis of Frequency Hopping M ary Frequency Shift Keying Communication Systems in High Frequency Rayleigh Fading Channels written by Dan Avidor and published by . This book was released on 1981 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: A certain type of M-ary Frequency Shift Keying (MFSK) communication systems, which use Frequency Hopping (FH) to combat jamming is studied in this work. In particular, the performance of such systems over High Frequency (HF) sky-wave channels, when subjected to intentional jamming, is the main topic of this study. The channels considered are characterized by Rayleigh fading and additive Gaussian noise. To combat jamming the communication system hops over the total spread spectrum bandwidth, which is many times larger than the 'instantaneous' bandwidth occupied by the MFSK signal. Located within the HF band and using sky-wave as the dominant propagation mode, the spread spectrum bandwidth is typically nonuniform, time dependent, and congested by many other users of the electromagnetic spectrum. In such an environment, Frequency Hopping FH mfsk systems seem to be more practical than 'Direct Sequence' spectrum spreading techniques. A FH/MFSK system can be easily programmed to use a noncontiguous band, thereby avoiding strong interfering signals that should not be interfered with.
Download or read book Electronic Counter countermeasures Considerations in Radar Systems Acquisition written by and published by . This book was released on 1987 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Effect of Worst Case Multiple Jammers on Coded FH SSMA Systems written by Evaggelos Geraniotis and published by . This book was released on 1990 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report characterizes and evaluates the effect of simultaneous multiple partial-band noise or tone jammers and other-user interference on a single communication link employing frequency-hopped spread-spectrum (FH/SS) signaling, M-ary frequency-shift-keying (FSK) modulation with noncoherent demodulation, and Reed-Solomon coding. For the symbol error probability of these systems, we derive exact expressions in the absence of multiple-access (MA) interference and tight upper bounds in the presence of other-user interference. Although our analytical methods are valid for any number of multiple jammers, we restrict our numerical study to the cases of two and three partial-band noise and tone jammers. For fixed values of the spectral densities of noise jammers, or the energies per symbol of tone jammers, we evaluate the worst-case fraction of the band that each jammer should use in order to maximize the error probability of the FH/SS or FH/SSMA system. For the range of the signal-to-jammer power ratios examined, multiple noise or tone jammers appear to have no advantage over a single noise or tone jammer of equivalent spectral density or energy per symbol but achieve approximately the same worst-case performance by jamming smaller fractions of the band. Keywords: Jamming, Antijamming, Frequency hopping, Frequency shift keying, Spread spectrum, Multiuser interference, Multiple access, Error correction codes. (jhd).
Download or read book Electronic Counter counter Measures Potential of a Noncoherent FH written by George T. Katsoulis and published by . This book was released on 1997 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates the performance degradation resulting from multitone interference of orthogonal, noncoherent, frequency-hopped, M-ary frequency-shift keyed receivers (FH/MFSK) where the effect of thermal and other wideband noise is not neglected. The multiple, equal power jamming tones are assumed to correspond to some or all of the possible FH M-ary orthogonal signaling tones. Furthermore, the channel is modeled as a Ricean fading channel, a possibility precluded when thermal noise is neglected. Both the signaling tones and the multiple interference tones are assumed to be affected by channel fading. Both band and independent band multitone interference are considered. Performance is evaluated by obtaining a union bound on the probability of bit error, and receiver performance is compared with exact results for band multitone interference of a noncoherent FH/MFSK receiver under comparable circumstances. Except for the case of Rayleigh fading of the signal, the union bound is very tight for those cases that can be compared with exact results. The advantages of the union bound approach are twofold. First, the union bound approach yields a solution that is far less computationally intensive than that obtained with the exact approach. Second, the union bound approach allows numerical results to be obtained for interference conditions that are not amenable to exact analysis, such as independent multitone interference of FH/ MFSK.
Download or read book The Effect of Rician Fading and Partial Band Interference on Noise Normalized Fast Frequency Hopped MFSK Receivers written by Melody Kragh and published by . This book was released on 1994 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of an M-ary orthogonal frequency-shift keying (MFSK) communication system employing fast frequency-hopped spread spectrum waveforms transmitted over a frequency-nonselective, slowly fading channel with partial- band interference is analyzed. A procedure referred to as noise-normalization combining is employed by the system receiver to minimize partial-band interference effects. Each hop is assumed to fade independently. The partial- band interference is modeled as a Gaussian process. Both the signal and the partial-band interference are assumed to be affected by the fading channel which is modeled as Rician. The effect of fading of the partial-band interference on worst-case receiver performance is relatively minor. When there is no signal fading or when the signal fading is Rician, then the counter-intuitive result of poorer receiver performance when the partial-band interference experiences fading is obtained. This effect is most pronounced when the signal does not fade and the partial-band interference experiences Rayleigh fading. Communications, Noise-normalized receiver, Noncoherent receiver, Spread spectrum, FFH, M-ary FSK.
Download or read book Frequency Hopping Multiple Frequency Shift Keying Coding and Optimal Partial Band Jamming written by Don J. Torrieri and published by . This book was released on 1982 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of frequency-hopping systems with multiple frequency-shift keying is determined for operation against optimal partial-band jamming. The effects of Reed-Solomon, binary block, convolutional, and concatenated codes are analyzed. Continuous-phase frequency-shift keying with limiter-discriminato demodulation is shown to offer potentially improved performance in frequency-hopping systems. (Author).
Download or read book An Analysis of Coherent Digital Receivers in a Jamming Environment written by and published by . This book was released on 1984 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of various jammer waveforms on known optimum coherent digital receivers is analyzed and evaluated in terms of receiver performance. The optimum jammer waveform for the specified receiver is derived and several jamming strategies are studied and compared to the optimum case. These jammer waveforms strategies include deterministic models of tonal, weighted signals, frequency modulated, and additive white noise jammers. An M-ARY digital coherent receiver using orthogonal modulation (FSK), is subjected to various jammer waveforms and the receiver performance analyzed. Graphical results based on numerical analyzes are presented to show the effects of jammer waveforms on receiver performance. (Author).
Download or read book The Diversity ECCM Performance of Frequency Hopping CPFSK in Partial Band Noise Jamming written by L. E. Miller and published by . This book was released on 1988 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: A thorough analysis is made of the uncoded probability of error achieved by by a hopped CPFSK (narrowband digital FM) radio link while subject to partial band noise jamming. Included in the analysis are the effects of thermal noise, FM clicks, and intersymbol interference, in addition to the jamming. For both limiter-discriminator and differential detection, it is shown that a repeat diversity combining method of summing detector samples does not yield a diversity gain against worst-case partial-band noise jamming, despite the nonlinearity of the receiver. The analytical procedures formulated, and computer programs, developed, can be modified to treat other CPFSK combining metrics; it is recommended that other soft-decision metrics be evaluated for ECCM properties, since it is known that at diversity gain is theoretically possible using perfect side information. In the report, easily calculated approximations and short-cut expressions for the error probability are assessed for accuracy, using the more complicated exact formulas. Keywords: Frequency shift keyers; Continuous phase, Frequency hopping, Digital FM radio, ECCM, jamming, Statistical communication theory; Phase distributions. (JD/RH).
Download or read book An Analysis of Coherent Digital Receivers in a Jamming Environment written by Faris T. Farwell (Jr.) and published by . This book was released on 1984 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of various jammer waveforms on known optimum coherent digital receivers is analyzed and evaluated in terms of receiver performance. The optimum jammer waveform for the specified receiver is derived and several jamming strategies are studied and compared to the optimum case. These jammer waveforms strategies include deterministic models of tonal, weighted signals, frequency modulated, and additive white noise jammers. An M-ARY digital coherent receiver using orthogonal modulation (FSK), is subjected to various jammer waveforms and the receiver performance analyzed. Graphical results based on numerical analyzes are presented to show the effects of jammer waveforms on receiver performance. (Author).
Download or read book Studies of ECCM Improvements for Frequency Hopping CPFSK Systems written by J. S. Lee and published by . This book was released on 1990 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of frequency-hopping CPFSK modulations (such as used in several Army radio systems) in the presence of worst-case partial-band noise jamming (WCPBNJ) is derived for both limiter-discriminator and differential detector forms of receiver. The transmitter is assumed to repeat the data L times on different hops, and the receiver combines the L chips for each data symbol in a way to mitigate the effects of the jamming. Hard-decision combining simply makes a binary decision on each chip, then a majority decision on the whole symbol; this limits a jammed chip to one vote. AGC combining weights each analog chip sample in inverse proportion to the received noise power and decides on the basis of the sum of weighted chip samples; jammed chips tend to be weighted less. Analysis and computations show that either form of ECM combining can produce a 27 dB gain against WCPBNJ, and with error-control coding, a 31-33 dB gain. Coding alone can give a 28-29 dB gain. Soft decoding of hard-decision diversity combining gives 1.4 dB more gain than hard decoding. It is also shown that, due to the spectral attenuation characteristics of the receiver's IF filter, the effects of the transient phase difference between the incoming hopping waveform and the receiver's synthesizer are primarily confined to an interval of duration T + ts + tau, where T is the symbol duration (inverse of IF bandwidth), ts is the synthesizer switching time, and tau is the offset in synchronization between the received signal and the receiver's synthesizer. (rh).
Download or read book Jamming Effects on M ary Coherent and Binary Noncoherent Digital Receivers Using Random Jammer Models written by Luis A. Munoz and published by . This book was released on 1985 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this work is to analyze and evaluate the effect of jamming waveforms on both coherent and noncoherent digital communications receivers. Specifically, random processes are utilized as jamming models in which it is assumed that the jamming waveforms have been produced by a shaping filter driven by white Gaussian noise. Such jamming waveforms are then assumed to be present at the input of known receiver structures (in addition to the signals and channel noise normally present), and optimum jamming waveform spectra are determined for different receiver schemes and modulation techniques. Graphical results based on numerical analyses are presented in order to demonstrate the effect of different jamming strategies on receiver performance. In order to quantify receiver performance, bit error probabilities are determined for binary modulation systems and symbol error probabilities are determined for M-ary modulation systems. In each case, the error probabilities are functions of signal-to-noise ratio (SNR) and jammer-to-signal ratio(JSR). Results show that it is generally possible to significantly degrade the performance of binary as well as M-ary modulation communication receivers by introducing suitably chosen jamming waveforms. (Theses).
