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Showing papers on "Phase-shift keying published in 1983"


Journal ArticleDOI
TL;DR: A class of nonlinear estimation algorithms is described to estimate the unknown phase of a carrier which is fully modulated by m -ary PSK modulation, and the effect of quantization and finite read-only-memory implementation of the nonlinearity are determined by computer simulation.
Abstract: Burst transmission of digital data and voice has become commonplace, particularly in satellite communication systems employing time-division multiple-access (TI)MA) and packet demand-assignment multiple-access (DAMA) techniques. In TDMA systems particularly, phase estimation on each successive burst is a requirement, while bit timing and carrier frequency can be accurately tracked between bursts. A class of nonlinear estimation algorithms is described to estimate the unknown phase of a carrier which is fully modulated by m -ary PSK modulation. Performance of the method is determined in closed form and compared to the Cramer-Rao lower bound for the variance of the estimation error in the phase of an unmodulated carrier. Results are also obtained when the carrier frequency is imprecisely known. Finally, the effect of quantization and finite read-only-memory (ROM) implementation of the nonlinearity are determined by computer simulation.

1,116 citations


Journal ArticleDOI
TL;DR: It is shown that the baseband signal of the modulator, the P_{e} = f(E_{b}/N_{0}) performance, and the spectral characteristics of nonlinearly amplified (hard-limited or saturated) radio systems of XPSK and tamed frequency modems (TFM) are practically the same.
Abstract: A new modulation technique, cross-correlated phase-shift keying ( XPSK ), is introduced. XPSK is a band-limited offset QPSK modulation technique which has an almost constant envelope. In XPSK modulators, a controlled amount of cross correlation between the in-phase ( I ) and quadrature ( Q ) channels is introduced. I and Q cross correlation reduce the envelope fluctuation Of the intersymbol-interference and jitter-free OQPSK (IJF-OQPSK) modulation scheme, introduced by Feher et al. [1], [2], from 3 dB to approximately 0 dB, thus further improving the performance of IJF-OQPSK systems in nonlinear radio systems [7], [14]. It is shown that the baseband signal of the modulator, the P_{e} = f(E_{b}/N_{0}) performance, and the spectral characteristics of nonlinearly amplified (hard-limited or saturated) radio systems of XPSK and tamed frequency modems (TFM) are practically the same. The XPSK demodulator is a conventional OQPSK demodulator, the TFM demodulator requires a somewhat more complex signal processor. For this reason, the XPSK approach may lead to significant demodulator hardware cost savings, particularly in point-to-multipoint distribution systems such as broadcast systems. Simulation results for linear and nonlinear (saturated amplifier) systems operated in an adjacent-channel interference environment (in addition to thermal noise) are presented. Measurement results performed on a 128 kbit/s rate hardware-prototype modem are also reported. Experimental eye diagram and power spectrum density measurement results are in close agreement with the computer simulation results.

173 citations


Journal ArticleDOI
TL;DR: The non-Gaussian nature of CW interference is exploited to suppress the CW via the A/D converter following chip demodulation in a direct sequence pseudonoise (DSPN) communication link and the modulation is coherent BPSK.
Abstract: The non-Gaussian nature of CW interference is exploited to suppress the CW via the A/D converter following chip demodulation in a direct sequence pseudonoise (DSPN) communication link. The modulation is coherent BPSK. The A/D converter quantizes to 2 bits, sign and magnitude. A scheme of threshold adaptation and postquantization weighting gains great advantage from making very reliable decisions on a relatively small percentage of the demodulated chips. The bit error rate performance in CW interference generally surpasses that of an ideal analog DSPN correlator. The performance in Gaussian noise is within 0.6 dB of ideal analog.

82 citations


Journal ArticleDOI
J.-C. Imbeaux1
TL;DR: Spectrum and signal-to-noise ratio in carrier recovery are studied for BPSK and offset quadrature modulation.
Abstract: This paper is concerned with clock and carrier synchronization in digital satellite transmissions, using the delay-line multiplier circuit. For clock recovery from baseband signal, with random data, a closed form formula is derived which gives the spectrum after multiplication, for any arbitrary pulse shape. This spectrum contains spectral lines at the clock frequency and its harmonics, and a continuous part which is the pattern noise. This pattern noise may be decomposed in noise in phase with the recovered clock, and noise in quadrature whose power spectral density is always zero at zero frequency. The effect of Gaussian noise on the channel is taken into account to calculate signal-to-noise ratio at the clock frequency as a function of the classical parameter E/N_{o} . With a modulated input carrier, the signal at the output of the delay-line multiplier may be separated into two parts: a low frequency signal that contains clock information and a bandpass spectrum signal around twice the carrier frequency that contains carrier information, when possible. Spectrum and signal-to-noise ratio in carrier recovery are studied for BPSK and offset quadrature modulation.

80 citations


Journal ArticleDOI
TL;DR: A new approach to PSK signal detection over a slow nonselective Rayleigh fading channel which does not require a carrier recovery loop is considered and coherent demodulation is achieved by making use of estimates of the quadrature amplitudes of the received PSK signals.
Abstract: We consider here a new approach to PSK signal detection over a slow nonselective Rayleigh fading channel which does not require a carrier recovery loop. The receiver achieves coherent demodulation by making use of estimates of the quadrature amplitudes of the received PSK signals in its likelihood ratio test. The receiver is assumed to have a memory containing information on the past received signals which enables it to generate the estimates. The error rate of the receiver can be evaluated analytically and computer simulation results are presented to verify the predicted performance.

73 citations


Journal ArticleDOI
A. Leclert1, P. Vandamme1
TL;DR: A new carrier recovery loop which applies to quadrature amplitude shiftkeying (QASK) and phase shift keying (PSK) modulation schemes is presented and is shown to provide significant advantages compared with those already used.
Abstract: A new carrier recovery loop which applies to quadrature amplitude shift keying (QASK) and phase shift keying (PSK) modulation schemes is presented. This loop is shown to provide significant advantages compared with those already used. Furthermore, the baseband processing of the demodulated signals allows an easy implementation, especially for high-speed digital modems. Both geometrical interpretation and theoretical justification using estimation criteria are provided. Finally, experimental results are reported.

68 citations


Journal ArticleDOI
TL;DR: This paper investigates the combination of chirp modulation and pseudonoise phase shift keying for spread-spectrum transmission of digital data by assignment of positive and negative dispersive slope chirps for binary ones and zeros.
Abstract: This paper investigates the combination of chirp modulation and pseudonoise phase shift keying for spread-spectrum transmission of digital data. Data encoding is accomplished by assignment of positive and negative dispersive slope chirps for binary ones and zeros. Each chirp is then modulated by one period of a PN signature sequence. The performance in additive white Gaussian noise is analyzed, measures of performance being mean acquisition time, mean hold-in time, and bit error probability. Calculated and experimental results are presented for a 105 kbit/s modem. In the test system, SAW dispersive delay lines with a bandwidth of 16.4 MHz and 9.5 μs dispersion time serve for the key operations of chirp generation and pulse compression, and the signature codes are 127 bit m -sequences.

60 citations


Journal ArticleDOI
TL;DR: The error rate performance of the proposed demodulation method is theoretically and experimentally studied for quaternary DPSK and experimental results agree with the theory, which indicates that performance is superior to conventional DPSK, but poorer than coherent detection.
Abstract: Theoretical analysis and experimental results for a DPSK system with nonredundant error correction are described. The error correction capability of the proposed demodulation method is achieved without utilizing additional bandwidth. The demodulator utilizes outputs of differentially coherent detectors that employ the received signal delayed by two or more time slots as references. These outputs are shown to be the parity check sums of two or more conSecutive outputs of the conventional detector under noise-free conditions. The error rate performance of the proposed demodulation method is theoretically and experimentally studied for quaternary DPSK. Experimental results agree with the theory, which indicates that performance is superior to conventional DPSK by 1.2 dB, but poorer than coherent detection by 1.3 dB. This method can be applied effectively to TDMA communications and to on-board regenerative repeaters.

41 citations


Journal ArticleDOI
TL;DR: It is shown that if the filter is used for rejecting CW interference only, the one-sided decision-feedback filter is preferred, and an approximate solution for the error probability is obtained.
Abstract: In this paper, the performance of QPSK systems using complex transversal filters with additional decision-feedback taps, in the presence of Gaussian noise and a single CW interferer, is analyzed. Both one-sided (with lagging taps) and two-sided transversal filters with additional decision-feedback taps are considered. Analytic expressions for the tap weights and the minimum mean square errors are obtained. The effect of error propagation on the error probability is discussed and an approximate solution for the error probability is obtained. The transient behavior of the filters using the LMS adaptation algorithm is analyzed. It is shown that if the filter is used for rejecting CW interference only, the one-sided decision-feedback filter is preferred.

37 citations


Journal ArticleDOI
TL;DR: Three popular constant-envelope modulation schemes for efficient transmission of digital data are quadri phase-shift keying (QPSK), offset (or staggered) quadriphase-shiftkeying (OQPSk), and minimum-shiftKeying (MSK).
Abstract: IGITAL communications links capable of conveying data at hundreds of megabits per second (Mb/s) are becoming increasingly important in various applications. An example is the use of time division multiple access (TDMA) transmission through a satellite relay wherein several data channels are routed through single uplink and downlink paths (antenna beams). Separation of the channels from each other is accomplished through interleaving and deinterleaving in time, with possible rerouting taking place in the satellite. When carrying traffic from large metropolitan areas, the required data rates can exceed 100 Mb/s. One such implementation, currently under study by NASA,' involves data transmission at rates of up to 550 Mb/s. Such applications require the use of modulation schemes that use the available bandwidth efficiently. Furthermore, because power is at a premium on board a satellite, the utmost in power efficiency is desired of the chosen modulation scheme. This implies the use of a constant-envelope modulation scheme since amplifiers, such as traveling wavetube amplifiers, are most efficient when operated near saturation. Three popular constant-envelope modulation schemes for efficient transmission of digital data are quadriphase-shift keying (QPSK), offset (or staggered) quadriphase-shift keying (OQPSK), and minimum-shift keying (MSK). Two excellent recent articles [1,2] in IEEE Communications Magazine have discussed their general properties and attributes as well as those of other modulation schemes with constant (or nearly constant) envelopes. Other recent papers [3-61 have presented analytical results and computer

34 citations


Journal ArticleDOI
TL;DR: It is shown that the analytical values agree well with the data observed by ATS-5 experimental tests, and a joint probability density function of two consecutive differential phase errors in the DPSK outputs is newly derived.
Abstract: Double symbol error rates of M -ary differentially coherent phase shift keying (DPSK) systems in a satellite-aircraft multipath channel are evaluated. A joint probability density function (pdf) of two consecutive differential phase errors in the DPSK outputs is newly derived. Numerically calculated results are shown in figures for binary, quaternary, and octonary DPSK systems. It is further shown that the analytical values agree well with the data observed by ATS-5 experimental tests.

Journal ArticleDOI
TL;DR: In this paper, the bit error of a PSK heterodyne optical communication system considering the FM noise of the transmitter and the local oscillator is investigated and a theory is presented giving the BER of such a system considering FM-noise effect.
Abstract: In a PSK heterodyne optical communication system, the FM noise of the transmitter and local oscillator degrades the bit-error rate (BER). A theory is presented giving the BER of such a system considering the FM-noise effect. To verify the theory, BER measurement is performed using a simulation model of the PSK heterodyne system.

Journal ArticleDOI
TL;DR: Bandwidth- and power-efficient quadrature carrier modulation techniques are identified, evaluated, and compared, and the agreement between simulated and measured results is shown to be excellent.
Abstract: Bandwidth- and power-efficient quadrature carrier modulation techniques are identified, evaluated, and compared. The modulation techniques include quadrature phase shift keying (QPSK), staggered QPSK (SQPSK), and minimum (frequency) shift keying (MSK). High quality QPSK, SQPSK, and MSK transmitters and receivers were used in the evaluation, along with a computer simulation program which modeled the hardware. Both linear and nonlinear channels were included in the comparative investigation. The agreement between simulated and measured results is shown to be excellent. In the comparison of modulation techniques, the effects of channel filtering (band limiting), nonlinearities, detection techniques, and phase equalization are addressed. The application-oriented results are intended to be an aid in selecting modulation and detection implementations, and in predicting the performance of linear and nonlinear communication systems. For systems with imperfections, data are presented for determination of passive detection filters which can outperform "matched" integrate and dump (I&D) filters.

Proceedings ArticleDOI
01 Oct 1983
TL;DR: The non-Gaussian nature of CW interference is exploited to suppress the CW via the A/D converter following chip demodulation in a direct sequence pseudonoise (DSPN) communication link and the modulation is coherent BPSK.
Abstract: The non-Gaussian nature of CW interference is exploited to suppress the CW via the A/D converter following chip demodulation in a direct sequence pseudonoise (DSPN) communication link. The modulation is coherent BPSK. The A/D converter quantizes to 2 bits, sign and magnitude. A scheme of threshold adaptation and post-quantization weighting gains great advantage from making very reliable decisions on a relatively small percentage of the demodulated chips. The bit error rate performance in CW interference generally surpasses that of an ideal analog DSNP correlator. The performance in Gaussian noise is within 0.6 dB of ideal analog.

Journal ArticleDOI
TL;DR: Using the results, it is shown that the error rate does not depend on the noise correlation so long as the a priori symbol probabilities are equal, thereby solving an "open problem" posed by Lee, French, and Hong.
Abstract: New results are given for the bit error probability for binary DPSK modulation over both terrestrial and satellite channels taking into account noise correlation and power imbalance. The new expressions are remarkably simpler than their previously published counterparts. For the terrestrial channel, the results are in closed form in terms of tabulated functions and, for the hard-limiting satellite channel, both in terms of integrals readily evaluated by quadrature and in terms of infinite series. Using the results, it is shown that the error rate does not depend on the noise correlation (down-link in the satellite case) so long as the a priori symbol probabilities are equal, thereby solving an "open problem" posed by Lee, French, and Hong. Also, the satellite case in which each of the up-link and down-link channels contains nonzero noise correlations is briefly treated.


01 Sep 1983
TL;DR: Four-D modulations based upon subsets of lattice-packings in four-D, which afford simplification of encoding and decoding are described, providing a (Nyquist) spectral efficiency of up to 10 bps/Hz.
Abstract: Four dimensional modulation as a means of improving communication efficiency on the band-limited Gaussian channel, with the four dimensions of signal space constituted by phase orthogonal carriers (cos omega sub c t and sin omega sub c t) simultaneously on space orthogonal electromagnetic waves are discussed. "Frequency reuse' techniques use such polarization orthogonality to reuse the same frequency slot, but the modulation is not treated as four dimensional, rather a product of two-d modulations, e.g., QPSK. It is well known that, higher dimensionality signalling affords possible improvements in the power bandwidth sense. Four-D modulations based upon subsets of lattice-packings in four-D, which afford simplification of encoding and decoding are described. Sets of up to 1024 signals are constructed in four-D, providing a (Nyquist) spectral efficiency of up to 10 bps/Hz. Energy gains over the reuse technique are in the one to three dB range t equal bandwidth.


Journal ArticleDOI
TL;DR: It is expected that the IJF-OQPSK scheme will have applications in low-cost power and bandwidth efficient earth-stations and terrestrial radio systems with transmit high-power amplifiers operating in saturation.
Abstract: The error probability (P e ) performance of intersymbolinterference and jitter-free offset-QPSK (IJF-OQPSK) modems in a cochannel and adjacent-channel interference environment is evaluated using a computer simulation technique. Hardware design and experiments have been completed to verify the simulation results. The results indicate that a spectral efficiency of 1.5 bits/s/Hz can be obtained with hard-limited IJF-OQPSK channels. This is a significant improvement compared to hard-limited QPSK, OQPSK, and MSK systems. It is expected that the IJF-OQPSK scheme will have applications in low-cost power and bandwidth efficient earth-stations and terrestrial radio systems with transmit high-power amplifiers operating in saturation.

Journal ArticleDOI
TL;DR: A receiver structure, called a "pseudo maximum likelihood sequence estimation" (pseudo MLSE), which approximates MLSE with a simple hardware configuration, was derived by introducting a tentatively estimated sequence and detects symbols with threshold detection, suitable for high bit rate operation.
Abstract: A receiver structure, called a "pseudo maximum likelihood sequence estimation" (pseudo MLSE), which approximates MLSE with a simple hardware configuration, was derived. By introducting a tentatively estimated sequence, the pseudo MLSE detects the received sequence symbol by symbol, retaining the MLSE optimum decision property. The number of arithmetic operations required in one symbol duration is reduced from M^{L + 1} to (L + 1)M in an M -ary signaling case with channel memory length L . An adaptation algorithm for the variation in the channel characteristics was also developed. Pseudo MLSE application to quadrature phase shift keying (QPSK) for a band-limited nonlinear channel is described. The most practical application of pseudo MSLE, named the "adaptive threshold detector with estimated sequence" (ATDES), detects symbols with threshold detection and is suitable for high bit rate operation. For both the pseudo MLSE processor and ATDES, most of the hardware is occupied by a replica memory stored in the receiver. Performance in a typical nonlinear satellite channel model is evaluated by computer simulation. Simulation results show a 0.8 dB improvement by ATDES with 64 replica memories and 1.3 dB improvement by the pseudo MLSE processor with 3072 replica memories. The tentative estimation error effect is estimated to be less than 0.1 dB in the simulated satellite channel.

Journal ArticleDOI
TL;DR: A distance measure is derived for simplified coherent receivers for general digital modulation schemes that gives the asymptotic error probability performance on the additive white Gaussian noise channel.
Abstract: A distance measure is derived for simplified coherent receivers for general digital modulation schemes. This measure gives the asymptotic error probability performance on the additive white Gaussian noise channel. It is applied to some simple examples considering phase modulated signals.

Patent
Toshihiko Ryu1
14 Sep 1983
TL;DR: A demodulator is a circuit where a signal to effect carrier recovery and elimination of intersymbol interference is produced by digitizing and processing demodulated signals in a manner that in the case of phase deviations due to noise or the like, the deviations fall within zones having predetermined digital identifications enabling the generation of appropriate digital correction signals via which the above mentioned signal production is controlled as mentioned in this paper.
Abstract: A demodulator features a circuit wherein a signal to effect carrier recovery and elimination of intersymbol interference etc. is produced by digitizing and processing demodulated signals in a manner that in the case of phase deviations due to noise or the like, the deviations fall within zones having predetermined digital identifications enabling the generation of appropriate digital correction signals via which the above mentioned signal production is controlled.



Book ChapterDOI
01 Jan 1983
TL;DR: In this article, the basic structures, principles of operations, and characteristics of these receivers are examined to provide an understanding of the important parameters in the design and performance evaluation of deep space communications.
Abstract: This chapter presents an introductory discussion of the receivers used in deep space communications. The basic structures, principles of operations, and characteristics of these receivers are examined to provide an understanding of the important parameters in the design and performance evaluation.

Journal ArticleDOI
TL;DR: The effect of intersymbol and quadratures channel interference on the average error probability of 16-ary offset quadrature amplitude modulation with rectangular or sinusoidal shaping functions is studied.
Abstract: In this paper we study the effect of intersymbol and quadrature channel interference on the average error probability of 16-ary offset quadrature amplitude modulation with rectangular or sinusoidal shaping functions. We present numerical results assuming that the transmitter and receiver filters are identical Butterworth filters of order N = 1,2,..., 6, and the decision rule is either fixed or adaptive.



Patent
Toshihiko Ruy1
14 Sep 1983
TL;DR: A demodulator is a circuit wherein a signal to effect carrier recovery and elimination of intersymbol interference etc is produced by digitizing and processing demodulated signals in a manner that in the case of phase deviations due to noise or the like, the deviations fall within zones having predetermined digital identifications enabling the generation of appropriate digital correction signals via which the above mentioned signal production is controlled as mentioned in this paper.
Abstract: not available for EP0106163Abstract of corresponding document: US4540948A demodulator features a circuit wherein a signal to effect carrier recovery and elimination of intersymbol interference etc. is produced by digitizing and processing demodulated signals in a manner that in the case of phase deviations due to noise or the like, the deviations fall within zones having predetermined digital identifications enabling the generation of appropriate digital correction signals via which the above mentioned signal production is controlled.

DOI
01 Oct 1983
TL;DR: In this article, an expression for the bit error probability of offset quaternary phase shift keying (OQPSK) signals which have been transmitted through nonlinear satellite channels after bandlimiting was derived.
Abstract: An expression is derived for the bit error probability of minimum shift keying (MSK) and offset quaternary phase shift keying (OQPSK) signals which have been transmitted through nonlinear satellite channels after bandlimiting. The transponder nonlinearity considered in the paper is of the bandpass type, which exhibits AM/AM and AM/PM conversion effects. The effects of up-link and down-link thermal noise are also taken into consideration in the analysis. The resulting expression for the bit error probability is an infinite series containing double integrals. In order to illustrate the usefulness of the method, the error rates of MSK and OQPSK signals are computed for a Butterworth bandlimiting filter hard limiting transponder channel model. The error rates of MSK and OQPSK signals are compared with the error rate of binary PSK signals for this communication system model.