Different Types Of Modulation Research Articles

MIMO-OFDM-based DVB-H systems: a hardware design for a PAPR reduction technique

Digital video broadcasting - handheld (DVB-H) is the technology driving mobile TV, which uses orthogonal frequency division multiplexing (OFDM) systems with multiple-input multiple-output technology (MIMO). These mobile communication systems have a promising future of supporting high data rate transmissions for both video and data. However, since the OFDM systems are sensitive to the peak-to-average power ratio (PAPR) problem, this work proposes a new technique (novel technique to reduce the PAPR based on turbo coding (NTRPT)), based on the turbo encoding technology, to reduce the PAPR effects for MIMO-OFDM-based DVB-H systems. This technique has been implemented and validated in hardware. It can support different types of modulation and coding techniques, and offers better results in reducing the PAPR than the conventional techniques currently proposed for this purpose, such as the clipping technique and the partial transmit sequence (PTS) technique, presented here using computer simulations

Les effets profibrosants des peptides vasoactifs dans le rein et les vaisseaux passent-ils par la transactivation du facteur de croissance épidermique (EGF)?

1. Autumn K, Sitti M, Liang YA, et al. Evidence for van der Waals adhesion in gecko setae. Proc Natl Acad Sci USA 2002; 99: 12252-6. 2. Thiery JP, Brackenbury R, Rutishauser U, Edelman GM. Adhesion among neural cells of the chick embryo. II: purification and characterization of a cell adhesion molecule from neural retina. J Cell Biol 1977; 252: 6841-5. 3. Takeichi M. Functional correlation between cell adhesive properties and some cell surface proteins J Cell Biol 1977; 75: 464-74. 4. Nollet F, Kools P, van Roy F. Phylogenetic analysis of the cadherin superfamily allows identification of six major subfamilies besides several solitary members. J Mol Biol 2000; 299: 551-72. 5. Wheelock MJ, Johnson KR. Cadherin-mediated cellular signaling. Curr Opin Cell Biol 2003; 15: 509-14. 6. Dufour S, Beauvais-Jouneau A, Delouvee A, Thiery JP. Differential function of N-cadherin and cadherin-7 in the control of embryonic cell motility. J Cell Biol 1999; 146: 501-16. 7. Evans E, Leung A. Adhesivity and rigidity of erythrocyte membrane in relation to wheat germ agglutinin binding. J Cell Biol 1984; 98: 1201-8. 8. Chu YS, Thomas WA, Eder O, et al. Force measurements in E-cadherin-mediated cell doublets reveal rapid adhesion strengthened by actin cytoskeleton remodeling through Rac and Cdc42. J Cell Biol 2004; 167: 1183-94. 9. Yap AS, Kovacs EM. Direct cadherin-activated cell signaling: a view from the plasma membrane. J Cell Biol 2003; 160: 11-6. 10. Martinez-Rico C, Pincet F, Perez E, et al. Separation force measurements reveal different types of modulation of E-cadherin-based adhesion by nectin1 and -3. J Biol Chem 2004; 280: 4753-60.

Separation Force Measurements Reveal Different Types of Modulation of E-cadherin-based Adhesion by Nectin-1 and -3

Nectins are Ca2+-independent cell adhesion molecules found at cadherin-based adherens junctions. We used a dual pipette assay that measures the forces required to separate cell doublets to determine how nectins affect the formation and strength of cell-cell adhesion. Less force was required to separate doublets of L cells expressing nectin-1 or nectin-3 than to separate doublets of E-cadherin-expressing cells. Heterodimers formed between cells expressing nectin-1 or nectin-3 adhered more strongly than homodimers. Nectin-3 that does not trans-interact with nectin-1 inhibited E-cadherin-mediated adhesion. However, the extracellular fragment of nectin-1 did not have an agonistic effect on E-cadherin-dependent cell adhesion when it trans-interacted with nectin-3, expressed at high levels in cells. In contrast, the extracellular fragment of nectin-3 had a significant agonistic effect on cadherin-based adhesion when it interacted with endogenous nectin-1, expressed at low levels in cells. Our results indicate that E-cadherin is the key molecule involved in cell adhesion and that the regulation of E-cadherin-based adhesion involving cellular nectin-1 trans-interacting with nectin-3 is qualitatively different from that involving cellular nectin-3 trans-interacting with nectin-1 and depends on the nectin levels expressed by cells.

Statistical approach to multiple-q modulated structures: average Patterson analysis

Using a statistical approach, the average unit cells have been constructed for modulated structures with different types of modulation, from simple sinusoidal to square-wave functions. The obtained unit cells fully describe diffraction intensities of the main reflections and their satellites. A universal distribution, valid for different lengths of the modulation vector, has been found. Average Patterson functions have been constructed and used to distinguish between different types of modulation.

Multi-q Modulated Structures and Their Diffraction Patterns

Using a statistical approach, the average unit cells and the average Patterson functions have be constructed for modulated structures with different types of modulations. Universal probability distributions and autocorrelation functions for different lengths of the modulation vector have been found. Such universal behaviour allows to distinguish between differently modulated structures directly from the experimentally obtained average Patterson function.

Energy‐Filtering Transmission Electron Microscopy (EF‐TEM) Study of a Modulated Structure in Metakaolinite, Represented by a 14 Å Modulation

For the first time, a periodicity of 14 Å is recognized as a typical modulation period in metakaolinite. Energy‐filtered electron diffraction data confirm that dehydroxylation does not occur abruptly in kaolinite. The degree of ordering becomes much lower during the progression of dehydroxylation in metakaolinite than in kaolinite. However, different types of modulations, with periods in the range from ∼1.4d001 (9.47 Å) to 2.9d001 (19.89 Å), form along the c*‐axis in metakaolinite. Modules (14.2 Å= 2.1d001) that have a length that is approximately twice as long as the metakaolinite layer (6.86 Å) are the most common. Presumably, the remnant oxygens and vacant anion sites rearrange to acquire stability in the layer structure, which builds modulations along the c*‐axis in the metakaolinite.

Right-left discrimination in a biologically oriented model of the cockroach escape system.

We present a biologically oriented model that accounts for left-right discrimination in the cockroach's escape behavior. The model includes the main groups of neurons found to be involved in the escape response. Each one of the included neurons is described by the actual processes taking place in an individual neuron (formation of an action potential, transmitter release, conductance changes, etc.). Furthermore, realistic chemical synapses (excitatory or inhibitory and able to undergo different types of modulation) connect the various neurons. With this model, we ere able to achieve, for a wide range of inputs representing different wind directions, behavior which resembles that found experimentally. The model indicates that several synaptic properties, in particular postsynaptic inhibition and presynaptic facilitation, play a key role in the discrimination of wind direction.

Modulation and symmetry changes in stellar dynamos

Stellar dynamos are governed by non-linear partial differential equations (PDEs) which admit solutions with dipole, quadrupole or mixed symmetry (i.e. with different parities). These PDEs possess periodic solutions that describe magnetic cycles, and numerical studies reveal two different types of modulation. For modulations of Type 1 there are parity changes without significant changes of amplitude, while for Type 2 there are amplitude changes without significant changes in parity. In stars like the Sun, cyclic magnetic activity is interrupted by grand minima that correspond to Type 2 modulation. Although the Sun’s magnetic field has maintained dipole symmetry for almost 300 yr, there was a significant parity change at the end of the Maunder Minimum. We infer that the solar field may have flipped from dipole to quadrupole polarity (and back) after deep minima in the past and may do so again in the future. Other stars, with different masses or rotation rates, may exhibit cyclic activity with dipole, quadrupole or mixed parity. The origins of such behaviour can be understood by relating the PDE results to solutions of appropriate low-order systems of ordinary differential equations (ODEs). Type 1 modulation is reproduced in a fourth-order system while Type 2 modulation occurs in a third-order system. Here we construct a new sixth-order system that describes both types of modulation and clarifies the interactions between symmetry-breaking and modulation of activity. Solutions of these non-linear ODEs reproduce the qualitative behaviour found for the PDEs, including flipping of polarity after a prolonged grand minimum. Thus we can be confident that these patterns of behaviour are robust, and will apply to stars that are similar to the Sun.

Amplitude modulation of the equatorial electrojet (EEJ) during a magnetospheric storm

Abstract An encounter of the Earth with a high velocity solar wind stream triggered the magnetic storm of 29 January 1995. The storm lasted for the following seven days, keeping the level of the Dst index in the range of −25–−50 nT. At the dip-equator, a regular enhancement of the magnetic H component during daytime, referred to as the Equatorial Electrojet (EEJ), was seen to be suppressed and modified during this storm interval. We attempted to classify the type of the EEJ modification by analyzing magnetometer data from two stations at the dip-equator but located in the opposite hemisphere, and energetic particle data from two geosynchronous satellites located close to the ground magnetometer meridian. As a result, three different types of modulation of EEJ amplitudes, with time scales of 15 min to 1 day, were found to appear during the periods when the flux level of low energy charged particles (>30 keV) in the midnight magnetosphere was increased above the quiet level. These modulations were characterized by referring to the nightside particle signatures. We argue that, although the EEJ is a local enhancement of the ionospheric currents at the dayside dip-equator, the EEJ is definitely affected by changes of the magnetosphere, probably in various ways arising from the complexities of the storm effects.

Algorithms for automatic modulation recognition of communication signals

This paper introduces two algorithms for analog and digital modulations recognition. The first algorithm utilizes the decision-theoretic approach in which a set of decision criteria for identifying different types of modulations is developed. In the second algorithm the artificial neural network (ANN) is used as a new approach for the modulation recognition process. Computer simulations of different types of band-limited analog and digitally modulated signals corrupted by band-limited Gaussian noise sequences have been carried out to measure the performance of the developed algorithms. In the decision-theoretic algorithm it is found that the overall success rate is over 94% at the signal-to-noise ratio (SNR) of 15 dB, while in the ANN algorithm the overall success rate is over 96% at the SNR of 15 dB.

Full length article

Cutaneous signals are modulated at the various relays just preceding and during voluntary movements. In these conditions, neuronal discharge in the primary somatosensory cortex (SI) related to movement per se is still evident while discharge to air puff stimulation on the skin is diminished. This selective modulation could be explained by rapid movement-related changes in receptive field (RF) configuration. We tested this hypothesis by giving air puff stimuli at different sites within and at the edges of the RF of SI cells during rest and elbow flexions in one awake monkey. For 40 cells, analysis of the global response yielded four different types of modulation: non-modulated cells, completely gated cells, partially and uniformly modulated cells, and non-uniformly modulated cells. Cell discharge for successive 5-ms intervals was also analyzed at the different sites and showed that response uniformity across time is more robust at the RF center than at peripheral sites in the RF. While this study did not show any clear RF displacement, intra-RF excitability seems to be affected by movement in various ways at the level of the cortex. These facts could have implications for information processing during movement.

Transmission system for coded speech signals and/or voiceband data

A digital coder receives either speech or audio-band data. When receiving speech this is coded by a digital speech coder and formatted into frames with parity bits. If modulated data are present this is recognized by a detector which routes the signals instead via a demodulator. Parity bits are generated from the same frame portions but parity is inverted so that a parity checking unit at a receiver can readily recognise the change. Preferably means are provided to insert into data frames codewords identifying the start and end and indicating the type of modulation in use. Additional detectors and demodulators can be added for different types of modulation. Such coded signals are decoded by performing parity checks on received frames to produce a parity indication signal of a first data mode sense or a second speech mode sense. In a data mode, the received signals modulated in accordance with a predetermined modulation scheme are provided as an output and in a speech mode the received signals are decoded to provide a speech output.

High-resolution electron microscopy of triclinic modulations in bismuth-barium cuprates

In order to investigate the role of incommensurate modulations in high- T c superconductor oxide structures, a compound with bulk composition Bi 2Ba 2NdCu 2O 8+δ has been investigated by high-resolution transmission electron microscopy (HRTEM) as well as selected area electron diffraction (SAD) techniques. The SAD patterns reveal a tetragonal unit cell of this material, with parameters a=5.60 A ̊ and c=31.4 A ̊ ; these are significantly larger than those of the bismuth-strontium analogue, Bi 2Sr 2CaCu 2O 8. The HRTEM images and the satellites (i.e. their positions as well as their intensities) observed in the SAD patterns suggest that the basic structure is modulated by two different types of modulation. These two superlattices both have triclinic symmetry; however, they differ in their cell parameters.

The modulated structure and excess oxygen in superconducting Bi 2(Sr, Nd) 2CuO y

The modulated structure of the Nd-substituted Bi-2201 phase was examined by observing the electron diffraction pattern. Three different types of modulation were found for the range of the oxygen content. The modulation period decreased continuously with the decrease of oxygen content, although it changed discontinuously at the type boundaries. This is consistent with the excess oxygen model as reported previously.

Different classes of glutamate receptors and GABA mediate distinct modulations of a neuronal oscillator, the medullary pacemaker of a gymnotiform electric fish

Gymnotiform electric fish generate distinct communicatory signals by modulating the rate of their electric organ discharges (EODs). Each EOD is triggered by a command pulse from the medullary pacemaker nucleus (PN), which contains pacemaker cells and relay cells. The firing rate of this nucleus is modulated by inputs from the diencephalic prepacemaker nucleus (PPN). The NMDA receptor blocker APV and the kainate/quisqualate receptor blocker CNQX, administered to the PN, suppress different types of modulations, indicating that different classes of glutamate receptors mediate the generation of different modulations. A comparison of the 2 genera, Hypopomus and Eigenmannia, reveals that sustained modulations, such as smooth rises in the rate of pacemaker cell firing and the selective silencing of the relay cells (only observed in Hypopomus), are mediated by NMDA receptors, whereas the brief and rapid acceleration, called "chirp" or "decrement burst," is mediated by kainate/quisqualate receptors. Application of the GABA blocker bicuculline reveals that the 2 genera differ in the mechanism by which they slow the firing rate of their pacemaker. Whereas Hypopomus uses GABAergic inhibition to slow down and ultimately silence its pacemaker cells, Eigenmannia reduces tonic, APV-sensitive excitation originating from its PPN and lacks GABAergic inhibition in the PN.

Synthesizing optimal controls for modulated discrete-time systems

The methods of steepest descent and gradient projection are used to solve the two-point boundary value problem associated with the optimal control of open-loop aperiodically modulated discrete-time systems. A comparison of optimal systems employing various combinations of pulse-width and pulse-amplitude modulation is presented. Numerous examples illustrate the diverse nature of the open-loop solutions for different types of modulation.

Single-Sideband Operation for International Telegraph

The increased demands for multiple and direct international radiotelegraph channels between the nations of the world and the shortage of usable high-frequency spectrum has greatly increased the importance of the single-sideband radio system for this purpose. The world's requirements for high frequencies, 4 mc to 30 mc, are so large that they are assigned over and over again to various services on the basis of geographical and time sharing. Single-sideband operation with multiple subcarriers and automaticfrequency control permit a high order of frequency utilization efficiency. Single-sideband operation offers a high degree of flexibility in meeting the various requirements of international communications. The number of its subcarriers can be changed to meet varying load conditions; they can be shifted to avoid temporary interference; and they can be used to operate with more than one point in the same geographical area. Codes with various numbers of signal elements either equal or unequal in length, and different types of modulation, and speeds can be carried on any or all subcarriers.

The use of tone modulation over complex carrier channels

The need for tone modulation of power line carrier channels is shown to arise from the necessity of conserving spectrum space. Different types of modulation are analyzed to show what frequencies actually are transmitted. The characteristics of carrier channels are discussed and the results of uneven attenuation and phase displacement over the transmission bandwidth are pointed out. Methods of improving carrier channel characteristics are included, as well as recommendations for selection of tone equipment to avoid the adverse effects of channel distortion.

Long-Range Communication Trends

The long-range communication problem is briefly reviewed with respect to the problems brought about by the use of inosphere transmission. A description is given of the multipath transmission involved and the various types of fading which result. Methods of reducing the different fading effects are discussed. These include the use of diversity reception and exalted-carrier detection. The different types of modulation are considered with respect to their application to ionosphere transmission. The recent trend away from amplitude-actuated modulations towards angle and single-sideband modulation is considered.