Selected Modulation Scheme Research Articles

Joint Light Planning and Error-Rate Prediction for Dual-Use Lighting/Visible Light Communication

We consider error-rate prediction for dual-use lighting systems with visible light communication (VLC) functionality. Since <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">light planning</i> rather than communications engineering is usually the driving discipline for practical dual-use settings, we extract VLC channel parameters as a by-product from advanced 3-dimensional (3D) light-planning models. By this means, we attain realistic signal-to-noise ratios for exemplary positions of a VLC receiver, which allows us to predict corresponding end-to-end bit error rates (BERs). Specifically, our procedure accounts for important aspects of state-of-art lighting systems, such as realistic light distribution curves of employed luminaires, possible presence unmodulated light sources, and, particularly, adaptive dimming operations in response to prevalent sunlight. In this paper, we (i) devise a methodology for VLC systems with optical receive filtering to convert photometric quantities into radiometric quantities, (ii) present examples of BER predictions for selected modulation schemes within some basic office environments, and (iii) conduct an analysis of the resulting simulation accuracy for a particular 3D light-planning tool. Simulation results show that our approach is indeed suited to predict realistic end-to-end BERs for dual-use lighting/VLC systems. Moreover, our procedure is fairly general and may be tailored to specific practical office settings and particular light plans of interest.

Design of Low-Inductance Switching Power Cell for GaN HEMT Based Inverter

In this paper, an ultralow inductance power cell is designed for a three-level active neutral point clamped (3L-ANPC) based on 650-V gallium nitride (GaN) high electron mobility transistor (HEMT) devices. The 3L-ANPC topology with GaN HEMT devices and the selected modulation scheme suitable for wide-bandgap devices are presented. The commutation loops, which mainly contribute to voltage overshoots and increase of switching losses, are discussed. The ultralow inductance power cell design based on a four-layer printed circuit board with the aim to maximize the switching performance of GaN HEMTs is explained. The design of gate drivers for the GaN HEMT devices is presented. Parasitic inductance and resistance of the proposed design are extracted with finite-element analysis and is discussed. Common-mode behaviors based on the simulation program with integrated circuit emphasis (SPICE) model of the converter are analyzed. Experimental results on the designed 3L-ANPC with output power of up to 1 kW are presented, which verifies the performance of the proposed design in terms of ultralow inductance.

Joint recovery of carrier frequency and symbol timing for extremely bandwidth‐efficient satellite links

Efficient estimation and synchronisation of transmission parameters is key for any satellite receiver, which is especially true for the recovery of carrier frequency and symbol timing. In this respect, a joint feedback solution has been analysed and tested in some recent work conducted by the authors. However, it turned out that the capture range of the carrier frequency is limited by the selected roll-off factor (excess bandwidth), which means that the synchroniser would not work properly for extremely bandwidth-efficient transmission schemes. This motivated them to modify the feedback structure by introducing a different filter operated in parallel to the receiver matched filter. In the sequel, it could be verified by analytical and simulation results that the initial frequency offset synchronised successfully can reach up to ±50% of the symbol rate irrespective of the selected modulation scheme, the roll-off factor, the signal-to-noise ratio value and the timing offset the satellite link is operated with. On top of that, a non-linear modification of the timing error detector has been investigated in detail, since the output of the conventional solution is nullified in case of extremely small excess bandwidths.

Analysis of Intermodulation Distortion in OFDM Based Transmitter Using EER Technique

During the last two decades, new digital modu- lation systems have appeared in the audio broadcasting. Such broadcasting systems require new transmitters' con- cepts to enable the transmission of digitally modulated sig- nals. Moreover, the selected modulation schemes (e.g. or- thogonal frequency division multiplexing) require a high lin- earitypowerstage,whichtypicallyexhibitslowecienc ydue to high peak-to-average power ratio of the modulated signal. One of the promising transmitter concepts is the Kahn enve- lope elimination and restoration technique, where the origi- nal Cartesian in-phase and quadrature baseband signals are transformed to the envelope and phase signals. The main ad- vantageofthistechniqueisanabilitytoemploysuitabletypes of highly ecient amplitude modulation transmitters for en- velope amplification, while the phase modulated carrier is produced by an additional phase modulator. The substantial drawback of envelope elimination and restoration is non- ideal recombination of linearly distorted amplitude signal and phase modulated carrier at the output power stage. The aim of this paper is twofold. Firstly, to analyze the eect oftheenvelopeandphasesignalsbandwidthlimitationonthe modulated signal in-channel distortion and out-of-channel emission. Secondly, to present the performance results as a reference for transmitter designers to properly set the en- velope and phase paths to reach required in-channel signal quality and suppress out-of-channel products.

Jitter floor elimination for blind feedforward/feedback symbol‐timing recovery exploiting the extended zero‐crossing property

SummaryCarrier‐blind and non‐data‐aided recovery of the symbol timing is of paramount importance in digital receivers, that is, detailed knowledge about carrier frequency and phase or any pilot sequence is not necessary for proper operation. In this context, feedforward algorithms are particularly helpful in packet‐oriented systems, where rapid and stable acquisition of the major transmission parameters is essential for subsequent processing stages. On the other hand, feedback algorithms are typically used to track small deviations from the stable equilibrium point. In the current paper, we propose a new approach for blind feedforward and feedback recovery of the symbol timing, which needs just one or two samples per symbol. The method is characterized by a second filter operated in parallel to the receiver‐matched filter. Under Nyquist conditions, exemplified by baseband pulses having a square‐root raised cosine spectrum, this filter exhibits an impulse response satisfying the extended zero‐crossing property, that is, it vanishes for all integer multiples of the symbol period including the origin. Using this idea for symbol‐timing recovery, it is shown that the annoying jitter floor – typical for most timing recovery schemes and caused by inter‐symbol interference – can be avoided irrespective of the selected modulation scheme. Copyright © 2015 John Wiley &amp; Sons, Ltd.

A Novel Series Expansion for Symbol Error Rates of Selected Modulation Schemes in Slow Fading Weibull Channels

In this paper, a comparative study of the simulated symbol error rate (SER) with the theoretical SER of uncoded communication systems is made for selected modulation schemes with and without fading. Slow fading Weibull and Rayleigh channels are considered in this paper. The modulation schemes considered are (1) Binary Phase Shift Keying, (2) Quadrature Phase Shift Keying, (3) Orthogonal Frequency Shift Keying and (4) M-ary Quadrature Amplitude Modulation. A novel series expansion for SER of selected modulation schemes in slow fading Weibull channels is considered. In addition, closed-form expressions for the upper and lower bounds of the SER for the aforementioned modulation schemes in the presence of AWGN and Weibull fading channels are derived and plotted. The simulated results are validated by comparing them with their theoretical results, upper and lower bounds.

COMPARATIVE ANALYSIS OF MODULATION SCHEMES USING ADAPTIVE EQUALIZATION AS FADING MITIGATION TECHNIQUE

Inter-symbol interference (ISI) due to multipath fading is a vital problem in high-speed wireless communication which restricts communication quality and capacity. Therefore, in addition to choosing a fading mitigation technique, it is also important to strategically select a modulation scheme for effective data transmission. Recent literature review on wireless standards, such as 3G and 4G indicates that QAM and QPSK are suitable choices for data transmission. In this paper, a comparative analysis on selected modulation schemes is performed in a fading environment. The mitigation of fading is done using adaptive equalization technique. Also, we show that the signal to noise ratio (SNR) is an important parameter to choose. It is observed that, even when an adaptive equalizer is used at the receiver, a very low SNR gives very high symbol error rate (SER). We derive some important conclusions from our simulation result: QPSK shows minimum SER, whereas 256-PSK and 256-PAM perform worse. Given its spectral efficiency and a low SER, the best choice is 256- QAM.