Showing papers on "Phase-shift keying published in 1986"

A BPSK/QPSK Timing-Error Detector for Sampled Receivers

Abstract: A simple algorithm for detection of timing error of a synchronous, band-limited, BPSK or QPSK data stream is proposed. The algorithm requires only two samples per symbol for its operation. One of the two samples is also used for the symbol decision. Derivation of the s curve reveals a sinusoidal shape.

Exact and Approximate Construction of Digital Phase Modulations by Superposition of Amplitude Modulated Pulses (AMP)

Abstract: Minimum shift keying and offset QPSK are two well-known modulations which can be interpreted as a set of time/phase-shifted AM pulses. We show in this paper that any constant amplitude binary phase modulation can also be expressed as a sum of a finite number of time limited amplitude modulated pulses (AMP decomposition). New methods for computing autocorrelation and power frequency spectrum are derived, which give very simple results for half-integer index modulations. We also show that the signal can be built with good accuracy using only one optimized pulse ("main pulse"). This synthesis is particularly satisfactory for modulations that have good spectral characteristics and/ or low index.

Computation of the Bit Error Rate of Coherent M-ary PSK with Gray Code Bit Mapping

Abstract: Efficient computation of the bit error rate (BER) for the coherent M -ary PSK signals with Gray code bit mapping is considered A closed-form expression for the exact BER of 8-ary PSK is presented Tight upper and lower bounds on BER are also obtained for M -ary PSK with larger M

A Class of Optimum Block Codes in Signal Space

Abstract: By using convolutional coding coupled with expanded sets of channel signals, Ungerboeck showed that it is possible to obtain coding gains of several decibels at a given data rate without increasing the transmission bandwidth. In this paper, we construct a class of optimum signal space codes using short binary block (as opposed to convolutional) codes. Our results are compared to those obtained by Ungerboeck. A simplified decoding procedure that is asymptotically optimum is also presented.

Technique for mitigating rain fading in a satellite communications system using quadrature phase shift keying

Abstract: A system for data communication between ground stations using an orbiting satellite as a relay includes a technique for avoiding the loss of signals from the satellite during periods of heavy precipitation. Data is communicated from an orbiting satellite to a plurality of earth stations on a single transmission frequency. The data is communicated on two separate transmission channels on that one frequency by using orthogonal channels of a coherent phase quadrature transmission system. The overall data rate on one of the two transmission channels is much lower than the overall data rate on the other of the two channels. The data on the lower data rate channel is less likely to be affected by heavy precipitation occurring in the line of sight between the satellite and the ground station, and the lower data rate channel is thus used to communicate data to a ground station located in an area of heavy precipitation. The lower data rate channel is further used to maintain phase synchronization so that the probability of losing phase synchronization with the signal transmitted by the satellite is significantly reduced.

Digital communication systems

Abstract: Digital communication systems , Digital communication systems , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Noncoherent Hybrid DS-SFH Spread-Spectrum Multiple-Access Communications

Abstract: The performance of noncoherent reception in synchronous and asynchronous hybrid direct-sequence/slow-frequency-hopped spread-spectrum multiple-access communication systems operating through additive white Gaussian noise channels is investigated. Systems with binary and M -ary frequency-shift-keying modulation and noncoherent demodulation, as well as systems with differential-phase-shift keying modulation and differentially coherent demodulation, are examined and their probability of error is evaluated for random frequencyhopping patterns and signature sequences. The multiple-access capability of noncoherent hybrid spread spectrum is shown to be superior to that of noncoherent purely frequency-hopped spread spectrum and inferior to that of noncoherent purely directsequence spread spectrum for systems with the same bandwidth expansion. Comparison of hybrid systems with coherent and noncoherent demodulation shows a considerable loss in the performance of the noncoherent systems.

Direct-Sequence Spread-Spectrum Multiple-Access Communications Over Nonselective and Frequency-Selective Rician Fading Channels

Abstract: An accurate approximation is obtained for the average probability of error in an asynchronous binary direct-sequence spreadspectrum multiple-access communications system operating over nonselective and frequency-selective Rician fading channels. The approximation is based on the integration of the characteristic function of the multiple-access interference which now consists of specular and scatter components. For nonselective fading, the amount of computation required to evaluate this approximation grows linearly with the product KN , where K is the number of simultaneous transmitters and N is the number of chips per bit. For frequency-selective fading, the computational effort grows linearly with the product KN2. The resulting probability of error is also compared with an approximation based on the signal-to-noise ratio. Numerical results are presented for specific chip waveforms and signature sequences.

Rate 5/6 Trellis-Coded 8-PSK

Abstract: Some new short constraint length codes are described for satellite channels which are constant-envelope and which have spectral and energy efficiencies intermediate to other recent coded techniques, namely r = 2/3 coded 8-PSK and r = 3/4 coded 16-PSK. We use two intervals of 8-PSK transmission to form a modulation base for r = 5/6 trellis codes. A particularly attractive design is an eight-state code, producing 6.2 dB gain on the Gaussian channel over uncoded 8-PSK, yet sacrificing only 16 percent in spectral efficiency.

A matched nonlinearity for phase estimation of a PSK- modulated carrier (Corresp.)

Abstract: A nonlinear phase estimator for a phase-shift keyed (PSK)-modulated carrier has been developed by Viterbi and Viterbi. Their analysis is extended, and an optimal or "matched" nonlinearity is derived for the estimator.

Suppression of stimulated brillouin backscattering by psk modulation for high-power optical transmission

Abstract: High-power optical fibre transmission combined with coherent detection offers a significant advantage in terms of length between repeaters. However, nonlinear optical effects limit the level of power into a fibre to a few milliwatts. The paper reports on the initiation and suppression of stimulated Brillouin scattering using phase shift keying at 1320 nm, discusses the effect of signal statistics on the level at which the nonlinear effect appears, and introduces and experimentally confirms an upper bound on the digital sum variation of codes. It emerges that the code requirements for high power, high bit rate, coherent systems can easily be met.

Performance of the Adaptive A/D Converter in Combined CW and Gaussian Interference

Abstract: Previous analyses are extended to give the performance of the adaptive 2 bit A/D converter in combined CW and Gaussian interference. The converter is seen to give substantial conversion gain even when the direct sequence pseudonoise (DSPN) spread signal is much weaker than the Gaussian component of interference. The upper bound on conversion gain depends primarily on the relative strengths of the Gaussian and CW components of interference. The relevant relationships are given in graphical form.

Performance of homodyne detection of binary PSK optical signals

Abstract: This study evaluates the performance of an optical receiver for binary phase shift keyed (BPSK) signals in the presence of noise originating from the photodetectors and the phase fluctuations of the optical sources. Analysis of the homodyne detection process shows that the performance is degraded by two effects: One due to the phase error fluctuations of the recovered carrier and the other due to reduction of the energy per bit available for data recovery. The resulting power penalty can be minimized by dividing in an optimal way the received optical signal between the carrier recovery and the data recovery circuits of the receiver. The minimum penalty thus obtained depends on the 3-dB linewidth and on the transmission rate. For example, a penalty of 0.5 dB, relative to the quantum limit of 9 photon bit needed to achieve a BER of 10-9, imposes a minimum transmission rate of about 180 Gbit/s when the optical source has a 3-dB linewidth of 20 MHz.

Acquisition of Direct Sequence Signals with Modulation and Jamming

Abstract: The effects of data modulation and/or narrow-band interference on the acquisition time of direct sequence (DS) systems are assessed when particular acquisition schemes are selected. Finally, the results of these analyses are used to propose receivers which mitigate the deleterious effects of the data or jamming. The analyses demonstrate that the I-Q detector, modified for a data modulated carrier, is superior to the correlator/square-law detector despite the latter's robustness to data. When the average pulsed jammer power is constrained, the analyses illustrate that the jammer's duty factor does not impact acquisition time when the pulse repetition frequency (PRF) is high; a duty factor of unity maximally degrades acquistion performance when the PRF is low. A proposed adaptive receiver provides considerable jamming protection; the acquistion performance of such a receiver bounds the performance of all adaptive acquistion receivers.

Self-amplitude modulation in PSK coherent optical transmission systems

Abstract: Self-amplitude modulation due to group velocity dispersion (chromatic dispersion of an optical fiber) in phase-shift keying (PSK) coherent optical transmission systems is presented. It may place a serious limitation on performance of such systems by limiting the maximum transmission distance attainable at a given bit rate. The maximum transmission distance for any prescribed degree of self-amplitude modulation is derived for PSK coherent systems. The result shows that the distance over which appreciable amplitude modulation is impressed on a phase-modulated signal is considerably less than the dispersion-limited transmission distance for intensity modulated direct detection systems.

Coherent Optical Receivers: Performance Analysis And Laser Linewidth Requirements

Abstract: The performance of coherent optical receivers is affected by the phase noise of the laser transmitter and the laser local oscillator and by the shot noise due to the detectors employed in the receiver. In this paper, the performance of coherent optical receivers is discussed, taking into account both noise sources. Further, the maximum permissible laser linewidth AP for coherent optical communications systems is reported. Both heterodyne and homodyne systems are considered. It is shown that the value of AP depends on the system bit rate Rb and on the modulation/demodulation technique employed: for heterodyne receivers with noncoherent postdetection processing [used in conjunction with amplitude-shift keying (ASK) or frequency-shift keying (FSK) modulation formats], Av_0.09 Rb; for heterodyne receivers with coherent postdetection processing [used in conjunction with the phase-shift keying (PSK) modulation format], Av< 2.26 X 10-3 Rb; and for PSK homodyne receivers, Av 3.1 X 10-4Rb. This paper presents the main results only; details of the mathematics involved have been published elsewhere. The purpose is to give a user a set of simple laser linewidth requirements without forcing him to analyze the research results scattered among several publications.

The effect of sample timing on bit error rate performance in a multipath fading channel

Abstract: Digital mobile radio often suffers from fatal effects caused by frequency-selective fading, resulting in severe bit error rate (BER) degradation. The feasibility of digital mobile radio largely depends on the multipath-distortion tolerant capability of modulation technique. The BER performance is compared among four digital modulation techniques in a frequency selective fading channel with large multipath delay spread. In particular, taking the timing fluctuation of eye patterns due to delay distortion of a fading channel into account, the effect of sample timing on BER is analyzed. The analyses have revealed that BER performance markedly depends on the choice of sample timing, and also an interesting fact that BPSK is outstanding in the multipath-distortion tolerance, if coupled with adaptive sampling, and its BER curves remain almost the same as that of frequency-flat fading as long as multipath delay difference is less than a bit interval.

Novel receiver structures for systems using differential detection

Abstract: Novel receiver structures are introduced which improve the bit error rate performance of differentially detected MSK and QPSK systems. These new receiver structures are based on 1) combining with feedback, 2) a simple Viterbi decoder which uses one- and two-bit detector outputs for maximum-likelihood sequence estimation, and 3) using the correlation of noise for the partial removal of its effect prior to decision. The new receiver structures presented are useful in mobile radio and mobile satellite communications where power efficiency, synchronization, and implementation complexity are of primary concern.

Error correction mechanism

Abstract: An error correcting scheme for processing data which is transmitted on a broadcast and/or CATV network and utilizes the IEEE 802.4 three-level duobinary AM/PSK (phase shift keying) coding format. The error correcting scheme utilizes two thresholders. One of the thresholders makes data (1 or 0) decisions while the other thresholder makes non-data or no non-data (non-data) decisions. Pattern matching and windowing are used to detect non-data symbols which are corrected if the non-data symbols deviate from a predetermined pattern. The template used in the pattern matching is determined from the state of a demodulator.

Interface between a broadcast satellite system and a catv system

Abstract: @ A CATV (cable television) signal transmitting for use with a broadcast satellite system includes a receiving stage (21, 22) for receiving a broadcast satellite station signal consisting of a base-band video signal and a sub-channel digital audio signals PSK (phase shift keying)-modulated on a subcarrier, a demodulator (231 to 234) for deriving the video signal and digital audio signals, a first modulator (261 to 264) for modulating one main carrier of a plurality of channels of CATV channels by the video signal, a second modulator (265) for modulating the other main carrier of different channels by the digital audio signals in time-division manner The mixed output signal from the first and second modulators is transmitted through a CATV transmission line (6) A CATV signal receiving system is also provided to produce video signals and digital audio signals which are converted into a plurality of channels of analog audio signals

Multiple-User Interference in FHMA-DPSK Spread-Spectrum Communications

Abstract: In this paper, we investigate the performance of a nearoptimum receiver in a frequency-hopped multiple-access (FHMA) differential phase-shift-keyed (DPSK) spread-spectrum communication system. We obtain upper bounds on the bit error rates (BER's) for the chipsynchronous system and the chip-asynchronous system in the presence of a single interfering signal which interferes in one time-chip. We also obtain upper bounds on the BER for the chip-synchronous system with multiple-user interference, for the special case where each time-chip has at most one interfering signal of the same power as the desired signal. We find that, for the chip-synchronous system, the upper bound on the BER when one time-chip has two interfering signals is larger than the upper bound on the BER when each of the two time-chips has a single interfering signal. We also discuss system performance for a large number of simultaneous users, and examine the additive white Gaussian noise (AWGN) approximation for the multiple-user interference. Finally, results for the chip-synchronous system with single interference in one time-chip over a Rayleigh fading channel are presented.

Modulation-transfer noise effects among FM and digital signals in memoryless nonlinear devices

Abstract: When two or more frequency-modulated and/or digital carriers of various sizes and modulation formats are transmitted through a common memoryless nonlinear device with AM/AM and AM/PM characteristics such as a traveling-wave tube amplifier, interactions among the carriers will occur. One of the impairments caused by these interactions results in modulation-transfer noise effects. In particular, in satellite communications, depending on the manner multicarrier transponders are used, the modulation-transfer impairment manifests itself under various forms and subjective interference effects. This tutorial-review paper presents an introduction to this type of impairment, methods of analysis and examples, and measurement results. General practical guidelines are suggested for controlling these effects.

Minimax Noncoherent Detection of BFSK Signals in Nonwhite Gaussian Noise

Abstract: We derive an optimum receiver for noncoherent detection of binary frequency shift keyed (BFSK) signals in nonwhite Gaussian noise. It will be shown that the achieved symbol error rates are smaller when operating on a nonwhite Gaussian noise channel than on a white Gaussian noise channel. The well-known BFSK receiver designed for white noise proves to be a minimax receiver when used in nonwhite noise. We show that the symbol error probability of the minimax receiver does not depend on the noise characteristics.

A characterization of the frequency selective fading of the mobile radio channel

Abstract: An experiment has been designed to determine the frequency selective behavior of a mobile radio channel for a medium bandwidth (maximum of 128 kHz). The measurement technique uses a multitone approach. The transmitted signal consists of several tones (five) with fixed phase and amplitude relationships. Coherent demodulation and separation of each tone is performed at the receiving end. Quantification of the mobile radio channel is conveniently described by its frequency correlation function. Measurements for several types of environments (rural, suburban, urban) were taken and analyzed. The results characterize the amplitude and phase behaviors of a signal for each type of environment. Finally, the computations of the probability of error for a differential phase shift keying (DPSK) modulation scheme in the presence of frequency selective fading show the dominance of this factor as the signal-to-noise ratio (SNR) increases.

Performance of Receivers in Digital Radio Applications Operating in the Presence of Noise and Jamming

Abstract: The performance of digital communication systems operating in the presence of noise and jamming is analyzed and evaluated. Specifically, by modeling the jamming as additive colored Gaussian noise, and considering transmission via M-ary phase shift keyed (MPSK) modulation as well as Quadrature Amplitude Modulation (QAM), receiver performance is determined in terms of symbol error probability, P s . The receiver analyzed is optimum for the modulation used when the channel interference consists of additive white Gaussian noise (AWGN) only, and does not process signals utilizing spread spectrum modulation or forward error correction schemes. Furthermore, the derived results for P s are used in order to optimize the shape of the colored noise (jamming) spectrum so as to cause maximum receiver degradation, subject to a jamming power constraint. Results on numerical evaluations are presented graphically, thus displaying receiver vulnerability to a specific form of jamming.

Transmit and receive filters for QPSK signals to optimise the performance on linear and hard-limited channels

Abstract: Bandlimited offset QPSK systems are analysed and attempts are made to find new combinations of transmit and receive filters which give improved performance trade-offs when compared with recently proposed filters such as quadrature overlapped raised-cosine (QORC) and squared raised-cosine (QOSRC), and superposed quadrature amplitude modulation (SQAM). The filters are based on finite impulse responses of up to five symbol periods (ten bit periods) duration. The results indicate that advantages can be gained over QORC, QOSRC and SQAM, if a good performance with linear channels is required as well as low degradation under hard limiting. This probably also implies good performance under soft limiting. The results are presented graphically, showing how the bit error rate performance with each filter pair degrades as the adjacent channel spacing of the system is reduced.