Showing papers on "Phase-shift keying published in 1969"

Quantizing for Noisy Channels

Abstract: We consider the transmission of numerical data over a noisy channel. Two sources of error exist. The first is the quantizer where the input data is mapped into a finite set of rational numbers and the second is the channel which includes the encoder, transmitter, transmission medium, receiver, and decoder. For any given probability density on the input data and any given channel matrix, we determine the quantization values and transition levels which minimize the total mean-square error. We also determine the best quantizer structure under the constraint that quantization values and transition levels be equally spaced. For the special case of a noiseless channel both results reduce to those of Max [2]. As an example we consider the case of Gaussian input data and phase-shift keyed (PSK) transmission in additive white Gaussian noise. The transmitter is both peak and average power limited, and the system operates in real time. Both the natural and Gray codes are considered. The mean-square error, quantizer entropy, channel capacity, and information rate are computed for the system using the optimum uniform quantizer. Finally, we show that it is important to take the channel into consideration when designing the quantizer even when the system is not constrained to operate in real time.

An Optimum Phase Reference Detector for Fully Modulated Phase-Shift Keyed Signals

Abstract: Many modern telemetry systems which use phase-shift keying (PSK) have receivers which derive a coherent reference from the fully modulated PSK signal itself and thus conserve the energy which otherwise would be allocated to a discrete reference signal. In this paper, an optimum receiver structure for estimating a phase reference from the PSK signal itself is derived and its realization discussed. It is shown that at low signal-to-noise ratios, the optimum detector can be realized with a Costas loop. Since a Costas loop and squaring loop exhibit identical performance, it follows that either of these simple devices gives optimum performance for low-input signal-to-noise ratios.

The Effects of Filtering and Limiting a Double-Binary PSK Signal

Abstract: This paper describes a digital computer simulation of a double-binary phase-shift keying system. This simulation program is used to investigate the effects of limiting action and of the shape and bandwidth of the filter on the system performance, expressed in terms of error probability

Digital data transmission system utilizing phase shift keying

Abstract: A digital data transmission system utilizing differential phase shift keying. In the transmitter serial data bits are grouped and the carrier wave is phase shifted by an angle determined from a comparison of successive data groups. In the receiver the successive phase shifts are detected by comparing the received signal in digital form with a digital reference, at a plurality of points in each cycle. When several matches are obtained for one phase, that phase is accepted as the phase of the received signal. The difference between the phases of successive portions of the received signal is utilized to reconstitute the transmitted data. Changes in polarity of the received signal are compared with the local reference signal to generate a control for the reference.

Binary Decoding Extended to Nonbinary Demodulation of Phase Shift Keying

Abstract: The required energy per information bit E_{B}/N_{o} to achieve a specified error probability with a binary error correcting code is reduced by retaining partial knowledge of digit amplitudes. Quantization to three or four levels is the minimum step of demodulator complexity beyond hard decisions. A simple extension of binary decoding is described which achieves a large part of the maximum improvement theoretically available with unquantized demodulation. The usual decoding process is modified only to the extent that two decoding operations are performed, rather than one. Also, storage is needed to compare the two resulting words to select the preferred one. With four-level demodulation, an improvement of more than one decibel is demonstrated even for small code word lengths over a nonfading phase shift keyed (PSK) coherent channel with white Gaussian noise.

Phase-Locked-Loop Detection of Binary PSK Signals Utilizing Decision Feedback

Abstract: A modified quadrature channel phase-locked-loop demodulator for binary phase-shift-keyed signals is presented. The modification, called decision feedback, is a practical implementation of decisiondirected channel measurement. Noise analyses are carried out for both additive and phase noise. An optimum loop filter is derived and the analyses include determination of probability of error for the system. The results of an analog simulation of the decision feedback technique are also included.

Voice transmission and receiving system employing pulse duration modulations with a suppressed clock

Abstract: A voice transmission system including coded voice information using pulse duration modulation (PDM) with a suppressed clock and wherein this suppressed clock pulse duration modulated voice signal is used to modulate a phase shift keying modulator (PSK). The receiver includes a phase shift keying demodulator which feeds a limiter having a wide bandwidth so as to achieve the highest possible processing gain. The receiver also includes a voltage controlled oscillator which is fed an error signal derived from an integrator so as to produce an output signal from the voltage controlled oscillator to replace the suppressed clock.

A Class of Efficient High-Speed Digital Modems for Troposcatter Links

Abstract: A class of power and bandwidth efficient high-speed digital data modems is described and corresponding theoretical error rate performances presented as a function of signal-to-noise ratio for a range of typical links.

Performance of Self-Synchronized Phase-Shift Keyed Systems

Abstract: Tight upper and lower bounds on the probability of error P(E) are derived for self-synchronized binary phase-shift keyed (PSK) communication systems. It is shown that the differential, decision feedback, and phase, doubling PSK receivers can all be represented by a single system block diagram. A new maximum-likelihood system is also derived and studied. Monte Carlo computer simulation results are presented for the various systems, and their performance is found to be very similar. Finally, differentially encoded self-synchronized PSK systems are compared to transmitted reference systems, and regions of operation are specified where each class of systems is superior.