Topic
Bandwidth (signal processing)
About: Bandwidth (signal processing) is a research topic. Over the lifetime, 48550 publications have been published within this topic receiving 600741 citations. The topic is also known as: Bandwidth (signal processing) & bandwidth.
Papers published on a yearly basis
Papers
More filters
TL;DR: If the error criterion is Integrated Squared Error then, even under very strong assumptions on the underlying density, relative error of the selected bandwidth cannot be reduced below ordern−1/10 (as the sample size grows), and performance in minimizing MISE should become the benchmark for measuring performance of bandwidth selection methods.
Abstract: This paper establishes asymptotic lower bounds which specify, in a variety of contexts, how well (in terms of relative rate of convergence) one may select the bandwidth of a kernel density estimator. These results provide important new insights concerning how the bandwidth selection problem should be considered. In particular it is shown that if the error criterion is Integrated Squared Error (ISE) then, even under very strong assumptions on the underlying density, relative error of the selected bandwidth cannot be reduced below ordern
−1/10 (as the sample size grows). This very large error indicates that any technique which aims specifically to minimize ISE will be subject to serious practical difficulties arising from sampling fluctuations. Cross-validation exhibits this very slow convergence rate, and does suffer from unacceptably large sampling variation. On the other hand, if the error criterion is Mean Integrated Squared Error (MISE) then relative error of bandwidth selection can be reduced to ordern
−1/2, when enough smoothness is assumed. Therefore bandwidth selection techniques which aim to minimize MISE can be much more stable, and less sensitive to small sampling fluctuations, than those which try to minimize ISE. We feel this indicates that performance in minimizing MISE, rather than ISE, should become the benchmark for measuring performance of bandwidth selection methods.
115 citations
TL;DR: It is suggested that opportunistic spectrum sharing can significantly improve spectrum efficiency and system capacity, even under unreliable spectrum detection.
Abstract: We analyze the performance of a wireless system consisting of a set of secondary users opportunistically sharing bandwidth with a set of primary users over a coverage area. The secondary users employ spectrum sensing to detect channels that are unused by the primary users and hence make use of the idle channels. If an active secondary user detects the presence of a primary user on a given channel, it releases the channel and switches to another idle channel, if one is available. In the event that no channel is available, the call waits in a buffer until either a channel becomes available or a maximum waiting time is reached. Spectrum sensing errors on the part of a secondary user cause false alarm and mis-detection events, which can potentially degrade the quality-of-service experienced by primary users. We derive system performance metrics of interest such as blocking probabilities. Our results suggest that opportunistic spectrum sharing can significantly improve spectrum efficiency and system capacity, even under unreliable spectrum detection. The proposed model and analysis method can be used to evaluate the performance of future opportunistic spectrum sharing systems.
115 citations
01 May 1958
TL;DR: In this article, the simple types of nonlinear capacitor modulators, demodulators, and negative conductance amplifiers, in which components at only two signal frequencies are present, are studied by means of the well-known small-signal analysis.
Abstract: The simplest types of nonlinear capacitor modulators, demodulators, and negative conductance amplifiers, in which components at only two signal frequencies are present, are studied by means of the well-known small-signal analysis. The results of this analysis of course agree with the general energy relations of Part I, but in addition give the gain, bandwidth, terminal admittances, and sensitivity (to changes in the terminal admittances or in the local oscillator drive) of these devices, and show the way in which these quantities depend on the amount of nonlinearity. In general, the bandwidth of all of these devices approaches zero as the nonlinearity approaches zero. Three cases are considered; f1 is the local oscillator frequency. 1) Noninverting modulator and demodulator-signal frequencies fl and f+=f1+fl. This device is stable and yields maximum gain with matched source and load. Under matched conditions the gain is equal to the ratio of output to input frequency; for widely separated signal frequencies the modulator has substantial gain, the demodulator an equal loss. Only a relatively small amount of nonlinearity is required to attain a bandwidth equal to the low-signal frequency. Since source and load are matched the sensitivity is zero. 2) Inverting modulator and demodulator-signal frequencies fl and f-=f1-fl. This device is potentially unstable; its input conductance is negative and match is impossible.
115 citations
TL;DR: Results demonstrate benefits of focusing techniques whose performance is not conditioned on the array size, and are intended as a basis for adaptive system implementation in which channel estimates will replace the actual values.
Abstract: High rate underwater communications have traditionally relied on equalization methods to overcome the intersymbol interference (ISI) caused by multipath propagation. An alternative technique has emerged in the form of time-reversal, which comes at virtually no cost in computational complexity, but sacrifices the data rate and relies on the use of large arrays to reduce ISI. In this paper, spatiotemporal processing for optimal multipath suppression is addressed analytically. A communication link between a single element and an array is considered in several scenarios: uplink and downlink transmission, with and without channel state information and varying implementation complexity. Transmit/receive techniques are designed which simultaneously maximize the data detection signal-to-noise ratio and minimize the residual ISI, while maintaining maximal data rate in a given bandwidth and satisfying a constraint on transmitted energy. The performance of so-obtained focusing techniques is compared to the standard ones on a shallow water channel operating in a 5 kHz bandwidth around a 15 kHz center frequency. Results demonstrate benefits of focusing techniques whose performance is not conditioned on the array size. Optimal configurations are intended as a basis for adaptive system implementation in which channel estimates will replace the actual values.
115 citations
TL;DR: In this paper, the authors investigate the usefulness of softening springs in a microelectromechanical system electrostatic energy harvester under colored noise vibrations and show that the nonlinear harvesters has performance benefits when the vibration's center frequency varies in the frequency range of its softening response.
Abstract: We experimentally investigate the usefulness of softening springs in a microelectromechanical systems electrostatic energy harvester under colored noise vibrations. It is shown that the nonlinear harvester has performance benefits when the vibration's center frequency varies in the frequency range of its softening response. With a vibration 3-dB bandwidth of 50 Hz, less than 3-dB variation in output power can be obtained over a 85-Hz wide range of vibration center frequencies. Compared to a simulated linear-spring device, the nonlinear device gives more output power for a wide range of vibration bandwidths. The nonlinear device shows less than 1-dB variation in output power when the vibration bandwidth varies from 12 to 120 Hz and is centered on the resonant frequency.
115 citations