Showing papers on "Phase-shift keying published in 1968"

Error Distribution and Diversity Performance of a Frequency-Differential PSK HF Modem

Abstract: A 4800-bit/s digital data modem is operated over a simulated HF channel to determine the bit-error rate and error distributions of the received serial binary data stream. The measured error distributions for multipath-limited conditions are compared with back-to-back operation and theoretically determined random distributions, and are also used to evaluate forward acting error correction assuming half-rate random error-correcting block codes. This improvement in bit-error rate is compared with that measured by operating the modem at 2400 bit/s with dual in-band frequency diversity. The error distributions for back-to-back operation approach random except for small block lengths where the systematic error resulting from the frequency-differential PSK coding appears. The error distributions for multipath-limited operation deviate from random especially for small multipath delay spreads (low biterror rates) where the correlation bandwidth is large. Forward error correction produces larger improvement factors as the code block length is increased. However, the improvement factor barely exceeds two orders of magnitude for the largest block considered. In fact, the burst nature of the errors is such that improvement factors actually decrease in most cases for multipath-limited operation as the raw bit-error rate decreases. On the other hand, inband diversity is more effective for small multipath delay spreads than for large ones. However, forward error correction appears to offer more potential especially if the bit errors can be spread over a greater number of bits.

Performance Monitor Techniques for Digital Receivers Based on Extrapolation of Error Rate

Abstract: There is a need in many digital communication systems to estimate the current digital error rate of the receiver without the use of special transmissions and without interrupting traffic flow. Devices for performing this function have been termed performance monitor units (PMU). As an element of an adaptive communication system, the PMU could be used to determine when adaptive change is needed and, by comparing the error rates which would result from the various available choices of adaptation, to select the best change to be made at any time. This paper describes a PMU technique which is applicable to a wide class of digital modulation methods. Details are given for the cases of noncoherent frequency shift keying (FSK), differentially coherent phase shift keying (PSK), and coherent PSK receivers operating over a fading channel.

Further Results Concerning the Effect of Frequency-Selective Fading on Differentially Coherent Matched Filter Receivers

Abstract: In this correspondence, error probabilities are calculated for binary DPSK communication through frequency-selective channels with predetection diversity matched filter reception. A method due to Bello and Nelin is used to carry out the calculations. Error probabilities are calculated for three different combinations of signaling pulse shape and channel frequency correlation function. One of these cases was investigated previously by Bello and Nelin, but some errors were made in their calculations. It is shown that for each of the three cases, an irreducible error probability exists that is proportional to the 2L power of the relative data rate (where L is the order of diversity) when the data rate is small. Also, when the results for the three cases are suitably compared, it is found that the error probabilities are more sensitive to the shape of the signaling pulse than to the shape of the channel frequency correlation function.

Performance of Phase-Coherent Receivers Preceded by Bandpass Limiters

Abstract: In phase-coherent communication systems, where bandpass limiters precede the radio frequency (RF) carrier tracking loop, it is of interest to understand how the noisy RF carrier reference effects system performance. This paper characterizes a model probability distribution for the RF phase error and uses this to predict the performance of phase-shifted keyed and differentially coherent systems. The theory developed is directly applicable to the Mariner- and Pioneer-type communication systems. For these systems two physical situations are considered: 1) system performance when the phase error is constant over the duration of one bit, and 2) system performance when the phase error is allowed to vary over the duration of one bit.

Error Performance of Quadrature Pilot Tone Phase-Shift Keying

Abstract: In this paper we exhibit the effect of the data sequence on the reconstruction of the reference (pilot) tone for a quadrature phase-shift keying (Q-PSK) system. This is a binary digital transmission system in which the phase of one quadrature component of the carrier tone is keyed, while the phase of the other component is unkeyed. The integration of several previous keying intervals provides a reference phase. A scheme of this type, called Kathryn, has been built by General Atronics Corporation. We find that the performance of a Q-PSK system is limited by self-noise unless certain message sequences can be avoided. It is concluded that a Q-PSK system can be used effectively only in a decision-directed mode which is also analyzed.

Optimum design of communication links with noisy phase reference

Abstract: Optimum design of phase shift keyed communication links for determination of modulation index with minimum error probability

Performance of binary PSK communication systems.

Abstract: Single channel binary PSK communication systems performance influenced by degree of RF coherence between transmitter and receiver

Irreducible Error-Rate Performance of Phase-Shift Keyed Signals over Correlated Dual-Diversity Channels

Abstract: Dual-diversity reception of 1- and 2-bit per baud differentially coherent phase-shift keyed signals over correlated Rayleigh fading channels is investigated. The mechanism that produces irreducible errors is signal distortion due to multiplicative noise. No additive noise is assumed to be present. As the fading correlation coefficient approaches unity or zero, the system error probability approaches that of single or dual independent diversity, respectively. For correlation as high as 0.7, nearly the entire improvement of dual independent diversity is obtained.