Noise Rise Research Articles

Study of High-Speed Ball Screw Vibration and Noise

Ball screw feeding system is a very important part of the machine tool. The ball screw of High-speed at the same time bring the vibration, noise, temperature rise due to friction and many problems. Noise and temperature rise are the key factors constrain the ball screw in the High-speed. The article summarized the ball screw causes of the vibration, noise, comprehensive both at home and abroad research results to the ball screw vibration and noise generating mechanism .Then pointed out that the ball screw noise generation is the main reason of the screw groove waveness arouses nut forced vibration.Introduced the latest progress of the ball screw drive system modeling and the vibration model analysis,specific introduces several methods of reducing vibration and noise reduction. And talk about the development trend of ball screw vibration and noise to the future.

Optimized configuration of the pyroelectric sensor metal electrodes in the photopyroelectric technique

This article deals with the photopyroelectric (PPE) technique, a useful tool for optical spectroscopy and for measurement of thermal properties of condensed mater samples, in particular in the liquid state. It has been demonstrated here that, for constant laser power, the pyroelectric (PE) sensor response does not depend on the spatial distribution of the laser beam intensity. As a consequence of this, it follows that in the case of measurements in voltage mode, the signal amplitude is inversely proportional to the active area of the sensor. Then, if the active area is diminished, leaving the total area of the sensor constant, it is possible to increase the pyroelectric signal. On the basis of this result, a method is proposed to enhance the PPE signal measured in voltage mode by means of the optimization in the configuration of the sensor metal electrodes. It was experimentally demonstrated that using this improved technique, it is possible to increase up to ten times the amplitude of the signal without electrical noise rise.

On Uplink Interference Scenarios in Two-Tier Macro and Femto Co-Existing UMTS Networks

A two-tier UMTS network is considered where a large number of randomly deployed Wideband Code Division Multiple Access (WCDMA) femtocells are laid under macrocells where the spectrum is shared. The cochannel interference between the cells may be a potential limiting factor for the system. We study the uplink of this hybrid network and identify the critical scenarios that give rise to substantial interference. The mechanism for generating the interference is analyzed and guidelines for interference mitigation are provided. The impacts of the cross-tier interference especially caused by increased numbers of users and higher data rates are evaluated in the multicell simulation environment in terms of the noise rise at the base stations, the cell throughput, and the user transmit power consumption.

Load control strategies in 2G mobile network for W-CDMA radio interface

Network planning requires a faithful analysis of each individual cell's capacity. In this paper, we examine load control equations as a resource allocation tool to analyse cell capacity for the uplink and downlink of Wideband Code Division Multiple Access (W-CDMA) networks. In the uplink, the noise rise is a parameter of choice. In the downlink, transmit power for different user loadserves as a means to control the network. We show how these equations can be parametised in a cell-specific way through computer simulation. This allows us to carry over prior results to realistic network settings.

Estimation of Design Parameters for Cellular WCDMA Network

The estimation of design parameters for WCDMA network which support different data rate (Multimedia) services is an essential step in network planning. The estimated parameters includes: Cell coverage range using path loss propagation model, average and maximum path loss, throughput, capacity / km2, number of users per cells blocking capacity, tracking efficiency. The parameters are computed for different data rates. Key words: WCDMA, noise rise, load factors.

Interference-Based Dynamic Pricing for WCDMA Networks Using Neurodynamic Programming

We study the problem of optimal integrated dynamic pricing and radio resource management, in terms of resource allocation and call admission control, in a WCDMA network. In such interference-limited network, one's resource usage also degrades the utility of others. A new parameter noise rise factor, which indicates the amount of interference generated by a call, is suggested as a basis for setting price to make users accountable for the congestion externality of their usage. The methods of dynamic programming (DP) are unsuitable for problems with large state spaces due to the associated ldquocurse of dimensionality.rdquo To overcome this, we solve the problem using a simulation-based neurodynamic programming (NDP) method with an action-dependent approximation architecture. Our results show that the proposed optimal policy provides significant average reward and congestion improvement over conventional policies that charge users based on their load factor.

On multi‐cell admission control in CDMA networks

AbstractWe consider a multi‐cell (MC) code division multiple access (CDMA) system that supports multiple service classes, including peak rate allocated and elastic ones. Peak rate allocated sessions—when admitted into the system—transmit at a constant bit rate, while elastic sessions can be slowed down at the expense of increasing their residency time. Admitted sessions cause an instantaneous bit rate‐dependent interference in neighbour cells. In this rather general setting, we propose a method to calculate the class‐wise blocking probabilities as the functions of the estimated so‐called inter‐cell coupling factors. In the paper this coupling factor is the ratio between the uplink path gains to different Node‐B:s (that can be easily obtained in a CDMA system from pilot measurement reports), but our model could include other coupling measures as well. We find that when these coupling factors are underestimated, the system may get into false states (FSs) or false rate states (FRSs) that lead to violating the noise rise threshold. As traffic becomes increasingly elastic, the probability of FSs decreases, but the probability of FRSs increases. Based on numerical results, we make the point that as the traffic becomes more elastic, avoiding the underestimation of these coupling factors as well as exercising MC admission control plays an increasingly important role in guaranteeing proper service quality. Copyright © 2007 John Wiley & Sons, Ltd.

Uplink Load in CDMA Cellular Radio Systems

Well-operating resource-management algorithms are crucial in wireless networks for ensuring the quality of service and, perhaps more importantly, for securing stability when operating at high load. These algorithms benefit from accurate feedback of the current network load. In the uplink of a code-division-multiple-access cellular network, the load is strongly related to the uplink noise rise, i.e., the ratio between total received power and background-noise power. This paper is primarily concerned with characterizing and approximating the uplink load. Two different load definitions are made. These relate to the received and transmitted carrier powers, respectively. Bounds that can be established in practice, e.g., before a resource decision is made, are used to develop a procedure for approximating the uplink load in practice. Furthermore, a stochastic approach to link budgets is used to establish the uplink load's role in the tradeoff between coverage and individual user satisfaction. Simulations indicate that the average error of the proposed load approximations is small for all load levels expected to appear in practice

Is multiuser detection beneficial to mixed service UMTS networks?

Abstract The main objective of this paper is to investigate linear multiuser detection for the uplink of present mixed service UMTS Terrestrial Radio Access Network (UTRAN) Frequency Division Duplex (FDD) networks in terms of system capacity, system coverage as well as power reduction. For the system performance assessments we apply a two-stage power control multiuser detection algorithm where the users are detected by a multiuser block detection. We evaluate the UTRAN FDD load control parameter noise rise and show corresponding system capacity bounds for different service mixes carried over dedicated channels with data rates up to 64 kbit/s. Note that for typical UTRAN FDD services the signal-to-noise operating points of a multiuser detector are very low (less than 0 dB). These low signal-to-interference-plus-noise ratios (SINR) operating points severely limit multiuser detection performance gains. Compared to single-user-matched filtering the minimum mean square error (MMSE) detector leads to fairly modest system capacity gains up to 60% dependent on the service mix assumed while the decorrelator is even worse. With respect to coverage as well as mobile station power, MMSE detection indicates fair to high improvements.

Measurements of the performance degradation of UMTS receivers due to UWB emissions

Results of experimental trials performed to assess the coexistence of the UMTS systems and the UWB emissions are presented. The performance degradation of the UMTS system vs. the in-channel UWB interference power has been measured in terms of the bit error rate and the noise rise.

The effect of higher receiver sensitivity on the coverage of a spread spectrum CDMA system

We examine the effect of higher receiver sensitivity on coverage of a code division multiple access (CDMA) cellular system. The reduced system noise figure of a base station is achieved by placing low noise amplifier (LNA) between receive antenna and base station radio. Using noise figure theory, we develop an analytical model of sensitivity improvement which is a function of reverse-link noise rise and antenna noise temperature. Since CDMA has reverse power control, sensitivity improvement is manifested in the reduction of mobile transmit power. Field experiments are performed and data collected to test the model. The positive result shows that LNA can be used to reduce mobile transmit power and their loading on adjacent cells.

An analytical model for reverse link rate control in cdma2000 1xEV-DO systems

The cdma2000 1xEV-DO standard has a distributed rate control on the reverse link. If a mobile has data to transmit, it determines the data rate of the next frame in response to a reverse activity bit broadcast by the base station. This paper proposes an analytical framework for the 1xEV-DO rate control by adopting the noise rise as the reverse traffic load, and by modeling the rate control as a discrete Markov process. We validate the proposed model through a simulation, in which 1xEV-DO reverse power control is applied to a Rayleigh fading channel. In addition, we illustrate the operation principle of the 1xEV-DO rate control based on the data rate distribution of mobiles.

An analytical model for reverse link rate control in cdma2000 1xEV-DO systems

The cdma2000 1xEV-DO standard has a distributed rate control on the reverse link. If a mobile has data to transmit, it determines the data rate of the next frame in response to a reverse activity bit broadcast by the base station. This paper proposes an analytical framework for the 1xEV-DO rate control by adopting the noise rise as the reverse traffic load, and by modeling the rate control as a discrete Markov process. We validate the proposed model through a simulation, in which 1xEV-DO reverse power control is applied to a Rayleigh fading channel. In addition, we illustrate the operation principle of the 1xEV-DO rate control based on the data rate distribution of mobiles.

On the Performance of Multiuser MIMO in UTRA FDD Uplink

We study the uplink performance of MIMO systems in UTRA FDD using noise rise and system load as performance measures. Results show that the uplink coverage and capacity of the UTRA FDD mode are significantly improved by SIMO and MIMO techniques that require only minor modifications to existing 3GPP specifications. Receive diversity in base station increases coverage and capacity in a straightforward manner, but the gain from transmit diversity in mobile station is small because of the fast closed-loop power control, which is essential to CDMA uplink performance. However, multiple transmit antennas in the mobile can be used to achieve higher than 2 Mbps single-user data rates. Keywords and phrases: MIMO, UTRA FDD uplink.

Shot noise in YBCO bicrystal Josephson junctions

We measured spectral noise density in YBCO symmetric bicrystal Josephson junctions on sapphire substrates at bias voltages up to 100 mV and T=4.2 K. Normal state resistance of the Josephson junctions, R/sub N/=20-90 /spl Omega/ and I/sub C/R/sub N/ up to 2.2 mV have been observed in the experimental samples. Noise measurements were carried out within frequency bands of 1-2 GHz and 0.3-300 kHz. At bias voltages 10/spl les/V/spl les/60 mV a linear voltage dependence of noise power has been registered, while at V/spl les/5 mV a noticeable noise rise has been observed. The latter may explain the experimentally measured linewidth broadening of Josephson oscillations at mm and submm wave frequencies in high-Tc superconducting junctions. Experimental results are discussed in terms of bound states existing at surfaces of d-wave superconducting electrodes.

The relative detectability for mice of gaps having different ramp durations at their onset and offset boundaries.

The effect on gap detectability of varying noise fall time (FT) and rise time (RT) of the gap boundary ramps was examined in mice using reflex modification audiometry, measuring inhibition of acoustic startle reflexes by variously shaped gaps just preceding reflex expression. In experiment 1 (n = 12) inhibition increased up to near-asymptotic values with longer FT (0, 1, 2, 3, 5, or 10 ms) and QT (quiet time, 0 to 13 ms), with a 2:1 trade-off between FT and QT. In experiment 2 (n = 24) inhibition increased for any RT above 0 ms (2, 3, 5, or 7 ms) if QT= 1 ms, but diminished with increased RT when QT = 3 or 8 ms. Enhanced detectability for subthreshold gaps by longer ramps results from their extending the apparent gap duration. The negative effect of increased RT for threshold gaps suggests the importance for gap detection of the stronger neural responses to sharp edges at the end of the gap shown previously in the mouse inferior colliculus. These effects are specific to gaps: inhibition for fixed (70-dB SPL) or varied level pulses (30 to 60 dB) was unaffected by varying the ramped edges (experiments 3 and 4, n = 9).

Low voltage excess noise and shot noise in YBCO bicrystal junctions

Abstract The spectral density of background noise emitted by symmetric bicrystal YBaCuO Josephson junctions on sapphire substrates have been measured by a low noise cooled HEMT amplifier for bias voltages up to V ≈50 mV. At relatively low voltages V V >30 mV a clear dependence of noise power, exactly coinciding to the asymptote of the Schottky shot noise function, has been observed for the first time. Experimental results are discussed in terms of multiple Andreev reflections which may take place in d-wave superconducting junctions with low transparency D ≪1.

Experimental study of noise and Josephson oscillation linewidths in bicrystal YBCO junctions

The intensities of the noise in a bicrystal high-TC (HTS) Josephson junction have been precision-measured at 1–2 GHz frequency band at bias voltages up to 50 mV at T = 4.2 K. At large bias voltages, V > 30 mV, the dependence of current noise density was found exactly coinciding with the Schottky shot noise asymptote 2eI. At relatively low voltages, V < 4 mV, a noticeable noise rise has been registered. The broadening of Josephson oscillation linewidths ΔfJ over the values ΔfRSJ predicted by the RSJ model has been experimentally studied at different frequencies in the mm and submm wave range up to voltages V = 2 mV in connection with low-voltage noise rise. Both the features observed, the linewidth broadening and the excess noise over the noise level of thermal fluctuations, are discussed in terms of multiple Andreev reflection, giving rise to a nonequilibrium shot noise—the case which may take place in the d-wave superconducting junctions. Experimental results on noise performance are also compared with the qualitatively similar dependences of the current noise, known for the s-superconducting ballistic point-like or diffusive-type SNS junctions, where the excess low-voltage noise is manifested due to multiple Andreev reflections. Increasing the operating temperature, the thermal (equilibrium) fluctuations were found to predominate, resulting in a decrease of ratio ΔfJ/ΔfRSJ. The characteristics of the ac Josephson effect in HTS junctions measured at submm wave frequencies at temperatures close to the transition temperature TC are also discussed.

IGBT model validation for soft-switching applications

Techniques are described for validating the performance of insulated gate bipolar transistor (IGBT) circuit simulator models for soft-switching circuit conditions. The circuits used for the validation include a soft-switched boost converter similar to that used in power-factor correction, and a new half-bridge testbed that is specially designed to examine the details of IGBT soft-switching waveforms. The new testbed is designed to emulate the soft-switching circuit conditions of actual applications circuits, while allowing the easy change of IGBT operating conditions. The testbed also eliminates the problems of commutating diode noise and IGBT temperature rise found in actual application circuits. Simulations of IGBT models provided in circuit simulator component libraries are compared with measurements obtained using these test circuits for the soft-switching conditions of zero-voltage turn-on, zero-voltage turn-off, or zero-current turn-off. Finally, the results are summarized by comparing the switching energies for the various measurements and simulations presented in this work.

Increasing mixed service uplink capacity of UMTS by smart antennas

Plans for possible business cases express the number of users in the system as a function of the service-mix and system loading. In this paper, the increase of mixed service capacity of UMTS by smart antennas is investigated. System capacity for mixed traffic in the uplink of the FDD mode (Wideband CDMA) is analyzed. The results are expressed in terms of multiple-access noise rise and effective data throughput, which are derived by a stationary system simulator. Smart antennas provide a clear advantage in mixed rate traffic services in comparison to non-adaptive antennas. The system capacity can be enhanced by a factor of 2.5 or higher, depending on the multi-service mix. The maximum achievable effective throughput is found as a function of both the service mix and the system loading.