Topic
Continuous phase modulation
About: Continuous phase modulation is a research topic. Over the lifetime, 3199 publications have been published within this topic receiving 37245 citations. The topic is also known as: CPM.
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TL;DR: This paper surveys the suitable modulation techniques for Li-Fi including those which explore time,frequency and colour domains including thoseWhich are considered to offer a practical solution forLi-Fi.
Abstract: Modulation techniques for light fidelity(Li-Fi) are reviewed in this paper.Li-Fi is the fully networked solution for multiple users that combines communication and illumination simultaneously.Light emitting diodes(LEDs) are used in Li-Fi as visible light transmitters,therefore,only intensity modulated direct detected modulation techniques can be achieved.Single carrier modulation techniques are straightforward to be used in Li-Fi,however,computationally complex equalization processes are required in frequency selective Li-Fi channels.On the other hand,multicarrier modulation techniques offer a viable solution for Li-Fi in terms of power,spectral and computational efficiency.In particular,orthogonal frequency division multiplexing(OFDM) based modulation techniques offer a practical solution for Li-Fi,especially when direct current(DC) wander,and adaptive bit and power loading techniques are considered.Li-Fi modulation techniques need to also satisfy illumination requirements.Flickering avoidance and dimming control are considered in the variant modulation techniques presented.This paper surveys the suitable modulation techniques for Li-Fi including those which explore time,frequency and colour domains.
109 citations
TL;DR: An iterative algorithm for constructing fully continuous phase screens for tailoring far-field intensity profiles is presented and is robust, stable, and, if run properly, maintains the continuous nature of the phase throughout the iterative process.
Abstract: An iterative algorithm for constructing fully continuous phase screens for tailoring far-field intensity profiles is presented. The algorithm is robust, stable, and, if run properly, maintains the continuous nature of the phase throughout the iterative process. The iterative procedure is applied to generate continuous phase screens to produce a 12th-power super-Gaussian far-field intensity profile.
99 citations
TL;DR: In this article, the modulation and differential detection characteristics of optical CPFSK transmission systems are investigated both theoretically and experimentally, and it is shown that the linewidth requirement is less than 0.68 m percent of the bit rate, where m is modulation index.
Abstract: The modulation and differential detection characteristics of optical CPFSK transmission systems are investigated both theoretically and experimentally. The error rate expressions of differentially detected CPFSK are derived by considering phase noise of LD's. It is clear that the linewidth requirement is less than 0.68 m percent of the bit rate, where m is modulation index. The performances of CPFSK are then experimentally presented at 400 Mbit/s using external optical feedback DFB LD's as the optical source. A beat spectral linewidth of less than 200 kHz for the transmitter and local oscillator LD's is achieved. The frequency response nonuniformity of frequency modulation efficiency is compensated by electrical circuits within 3 dB and 60°. To reduce IF thermal noise, a resonance-type preamplifier is used, with a 4.8 pA/ \sqrt{Hz} average input noise current density, and a receiver sensitivity 1.3 dB better than the conventional preamplifier. Differential detection of the 400-Mbit/s CPFSK modulation is performed. The generation of CPFSK is confirmed by good correlation between the output spectrum and theory. The average received optical power at a 10-9bit error rate is -49.9 dBm which improves direct detection by 10.3 dB. No additional power penalties due to 290-km transmission exist.
99 citations
15 Oct 1989
TL;DR: A modulation recognizer that automatically reports modulation types of constant-envelope modulated signals is developed using zero-crossing techniques, and results demonstrate that reasonable average probability of correct classification is achievable at CNR=15 dB and higher.
Abstract: A modulation recognizer that automatically reports modulation types of constant-envelope modulated signals is developed using zero-crossing techniques. The zero-crossing sampler, as a signal conditioner, has the advantage of providing accurate phase transition information over a wide dynamic frequency range. Signal parameters, such as zero-crossing variance, carrier-to-noise ratio (CNR), and carrier frequency, are estimated. Phase-difference and zero-crossing-interval histograms play the roles of features for modulation recognition. The classifier performance is given in the form of a confusion matrix. The obtained simulation results demonstrate that reasonable average probability of correct classification is achievable at CNR=15 dB and higher. >
98 citations
TL;DR: It is demonstrated that for almost all schemes of interest in practice, it is quite sufficient for the receiver to implement only four or six linear filters which represent proper reference signals, which makes possible an almost continuous tradeoff between receiver complexity and SNR (signal/noise ratio) losses.
Abstract: By separating the two complexity problems connected with optimum coherent CPM (continuous phase modulation) receivers, namely, the number of linear filters and the number of memory states required, a straightforward procedure for reducing the complexity is proposed and its usefulness is evaluated. A concise analysis of the inherent trellis encoder associated with CPM is given. It is then demonstrated that for almost all schemes of interest in practice, it is quite sufficient for the receiver to implement only four or six linear filters which represent proper reference signals. For a reduction in the number of memory states, decision-feedback sequence estimation together with minimization of the unprocessed intersymbol interference is proposed. Modifications of this procedure allow a state reduction without losses or with only negligible losses because only error events with large distances are affected. Combinations of these methods make possible an almost continuous tradeoff between receiver complexity and SNR (signal/noise ratio) losses. Several examples are considered for which evaluations of minimum Euclidean distances and simulation results are given. >
98 citations