Phase Shift Keying Communication Research Articles

High-order orbital angular momentum mode-based phase shift-keying communication using phase difference modulation.

Orbital angular momentum (OAM) mode offers a promising modulation dimension for high-order shift-keying (SK) communication due to its mode orthogonality. However, the expansion of modulation order through superposing OAM modes is constrained by the mode-field mismatch resulting from the rapidly increased divergence with mode orders. Herein, we address this problem by propose a phase-difference modulation strategy that breaks the limitation of modulation orders via introducing a phase-difference degree of freedom (DoF) beyond OAM modes. Phase-difference modulation exploits the sensitivity of mode interference to phase differences, thereby providing distinct tunable parameters. This enables the generation of a series of codable spatial modes with continuous variation within the same superposed OAM modes by manipulating the interference state. Due to the inherent independence between OAM mode and phase-difference DoF, the number of codable modes increases exponentially, which facilitates establishing ultra-high-order phase shift-keying by discretizing the continuous phase difference and establishing a one-to-one mapping between coding symbols and constructed modes. We show that a phase shift-keying communication link with a modulation order of up to 4 × 104 is achieved by employing only 3 OAM modes (+1, + 2 and +3), and the decode accuracy reaches 99.9%. Since the modulation order is exponentially correlated with the OAM modes and phase differences, the order can be greatly improved by further increasing the superimposed OAM modes, which may provide new insight for high-order OAM-based SK communication.

PDM-Based Feedforward Power Compensation for FMPSK Communication in WPT Systems

A wireless power transfer (WPT) system usually needs dual-side cooperated control for efficiency optimization and power regulation, and requires wireless communication between the transmitter and the receiver. Phase shift keying (PSK) communication is a good choice for WPT systems because of its advantages of high security and low hardware cost. However, the converter phase modulation required by the PSK communication causes output power and voltage fluctuations. In this brief, we analyze the relationship between the phase modulation depth and the output fluctuation amplitude. Then we propose a pulse density modulation-based feedforward power compensation method to compensate the fluctuations caused by the PSK communication. Experimental results show that the proposed power compensator can suppress the output voltage fluctuations to an insignificant level without a large output filter capacitor. The proposed method overcomes the main drawback of the PSK communication in WPT systems.

Impact of the Chaotic Synchronization’s Stability on the Performance of QCPSK Communication System

The current work presents a study of the implementation of a quadrature chaos phase-shift keying communication system (QCPSK) based on the employment of different chaos oscillators. The research takes two directions, with one being the study of the chaos synchronization’s noise immunity for several chaos oscillators that are the potential core blocks of the QCPSK system. The correlation coefficient over time is used to estimate the synchronization noise immunity. The second direction is the estimation of the QCPSK system’s baseband model performance in the AWGN propagation channel using the bit error ratio (BER) as the estimation method for several chaos oscillators employed as the core of the QCPSK system’s model.

Frequency-Modulated Phase Shift Keying Communication for MEPT Control of Wireless Power Transfer

The closed-loop control of wireless power transfer (WPT) systems requires a communication link between the power transmitter and the power receiver for dual-side cooperation. Near-field communication techniques that utilize the power link are preferred for this purpose due to high reliability and security. In this letter, we propose a frequency-modulated phase shift keying (FMPSK) communication technique for the closed-loop maximum efficiency point tracking (MEPT) control of WPT. The technique uses very shallow phase modulation depth to minimize the disturbance on power flow and reduce the efficiency drop caused by the PSK. Meanwhile, it ensures the signal accuracy and precision by multiple methods and precise frequency modulation and demodulation. In experiment, we obtained 82%-85% system efficiency with a 25-125 W load over a distance equal to the coil diameter, and 93% efficiency over a distance equal to the coil radius. The efficiency drop caused by FMPSK was less than 1%. The dynamic processes of voltage regulation and MEPT took only about 1 ms and 10 ms, respectively.

Application of Kalman filter in frequency offset estimation for coherent optical quadrature phase-shift keying communication system

The frequency offset estimation (FOE) schemes based on Kalman filter are proposed and investigated in detail via numerical simulation and experiment. The schemes consist of a modulation phase removing stage and Kalman filter estimation stage. In the second stage, the Kalman filters are employed for tracking either differential angles or differential data between two successive symbols. Several implementations of the proposed FOE scheme are compared by employing different modulation removing methods and two Kalman algorithms. The optimal FOE implementation is suggested for different operating conditions including optical signal-to-noise ratio and the number of the available data symbols.

Optical Coherent Receiver Front End for Inter-Satellite Laser Communication Link

This paper presents the new concept of optical coherent receiver front end which can obtain optical phase error signals in PSK (Phase Shift Keying) communication data as well as spatial tracking error without any extra tracking sensor, leading to downsizing of inter-satellite laser communication terminals. This new receiver front end consists an optical 90 deg hybrid mixer with free space optical components, segmental photo detectors and RF electronics, to realize not only balanced detection of both in-phase and quadrature components but also heterodyning detection of tip/ tilt error signals.

Semiconductor optical amplifier used as regenerator for degraded differential phase-shift keying signals

Phase and amplitude regeneration are necessary for degraded differential phase-shift keying communication systems. This paper proposes a regenerator based on semiconductor optical amplifier for differential phase-shift keying signals. The key regeneration mechanism is theoretically analysed. The effectiveness of semiconductor optical amplifier based regenerator is demonstrated by comparing the bit error rate and eye diagrams before and after regeneration for 40-Gbit/s differential phase-shift keying 1080-km transmission systems. The results show that regeneration effects are very well. Bit error rate is less than 10−12 with the regenerator.

On the correct modeling of semiconductor optical amplifier RIN and phase noise for optical phase shift keyed communication systems

Phase modulation schemes are attracting much interest for use in ultra-fast optical communication systems because they are much less affected by fiber nonlinearities than conventional modulation formats. Semiconductor optical amplifiers (SOAs) can be used to amplify and process phase modulated signals. However, existing SOA nonlinear phase noise (NLPN) models are simplistic and, sometimes, inaccurate. It is, therefore, important to correctly model their behavior since NLPN is the main drawback in these applications. In this paper we show that a more accurate model can be used leading to simple nonlinear noise expressions at the SOA output of differential phase shift keying systems. To demonstrate the utility of this model, we have used it to calculate the optical signal to noise ratio penalties introduced by a power booster SOA and the first inline amplifier of a 40 Gb/s NRZ-DQPSK single channel link. The model parameters have been estimated from measurements taken of a commercial SOA.

SNR estimation in time-varying fading channels

Signal-to-noise ratio (SNR) estimation is considered for phase-shift keying communication systems in time-varying fading channels. Both data-aided (DA) estimation and nondata-aided (NDA) estimation are addressed. The time-varying fading channel is modeled as a polynomial-in-time. Inherent estimation accuracy limitations are examined via the Cramer-Rao lower bound, where it is shown that the effect of the channel's time variation on SNR estimation is negligible. A novel maximum-likelihood (ML) SNR estimator is derived for the time-varying channel model. In DA scenarios, where the estimator has a simple closed-form solution, the exact performance is evaluated both with correct and incorrect (i.e., mismatched) polynomial order. In NDA estimation, the unknown data symbols are modeled as random, and the marginal likelihood is used. The expectation-maximization algorithm is proposed to iteratively maximize this likelihood function. Simulation results show that the resulting estimator offers statistical efficiency over a wider range of scenarios than previously published methods.

PSK communications systems using fully saturated power amplifiers

Quasiconstant envelope phase-shift keying (PSK) is analyzed to assess its ability to overcome nonlinearities caused by fully saturated RF power amplifiers in communications systems. These modulations can achieve bit error rate (BER) performance comparable to linear BPSK in additive white Gaussian noise (AWGN) channel. Quasiconstant envelope offset quadrature PSK (OQPSK) is presented as a design example. At a BER = 10/sup -5/, the SNR degradation caused by fully saturated power amplifiers is 0.1 dB. The simulated BER matches analytically derived results. For a communications system employing the quasiconstant envelope OQPSK and a rate 1/2 convolutional code with K = 7, the demodulation performance is degraded by 0.25 dB at a BER = 10/sup -5/ when a fully saturated power amplifier is employed.

High sensitivity optically preamplified direct detection DPSK receiver with active delay-line stabilization

The authors present experimental results for a 3 Gb/s optically preamplified, optically demodulated, differential phase shift keyed communication link achieving 62 photons/bit receiver sensitivity and using an actively stabilized optical delay line demodulator.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance of phase-shift keying communication systems with partial fading channel statistical information

In this paper, a method of evaluating the performance of phase-shift keying systems over non-Rayleigh fading channels is presented. The technique is based on utilizing a quasi-moment expansion of the probability density function. The results obtained using fourth-order statistics show good agreement with those obtained using full statistical information which is not available in practice.

Error rate of phase-shift keying in the presence of discrete multipath interference (Corresp.)

Several expressions are derived for the probability of error of a binary coherent phase-shift keyed communication system in the presence of interference due to discrete multipath propagation.

Phase-Ambiguity Resolution in a Four-Phase PSK Communications System

The constraints of digital satellite communications systems have led to the derivation of a method for resolving the problem of recovered-carrier phase ambiguity in a coherent fourphase phase-shift-keying (PSK) communications system while simultaneously providing synchronization information. This method is described for the general case and a general implementation is given. In addition, implementations are given for two particularly simple special cases.

The Effects of Video Clipping on the Performance of an Active Satellite PSK Communication System

A phase-shift-keying (PSK) satellite communication system is considered in which 1) clutter (other users and/or jamming) is added to the desired signal on the up-link, 2) the repeater contains a hard-limiter, 3) thermal noise is added on the down-link, 4) the receiver consists of a synchronous detector followed by an infinite clipper, and 5) the output of the clipper is sampled at the Nyquist rate, and the decision is based upon whether the majority of the samples are positive or negative. The error probability of this system is given by a binomial distribution, the parameters of which are determined by the clutter and noise statistics. Explicit results are obtained for the case where the down-link noise may be neglected and the clutter is Gaussian. It is shown that the video clipper results in a degradation of performance of at most 2 dB relative to an ideal linear system and only about 1 dB relative to a system in which a limiting repeater is employed without clipping on the ground. For the case of strong clutter and strong noise, the degradation relative to an ideal linear system is shown to be 3 dB. The use of infinite clipping provides a two-fold advantage: 1) The error analysis can be performed at all signal-to-clutter and signal-to-noise ratios, not only in an asymptotic limit; 2) Digital signal processing of large time-bandwidth product signals is facilitated. (Infinite clipping corresponds to one-bit quantization.)