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.
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Papers
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TL;DR: In this paper, a novel distributed dynamic spectrum access algorithm based on deep multi-user reinforcement leaning is proposed to solve the problem of spectrum access for network utility maximization in multichannel wireless networks.
Abstract: We consider the problem of dynamic spectrum access for network utility maximization in multichannel wireless networks. The shared bandwidth is divided into K orthogonal channels. In the beginning of each time slot, each user selects a channel and transmits a packet with a certain transmission probability. After each time slot, each user that has transmitted a packet receives a local observation indicating whether its packet was successfully delivered or not (i.e., ACK signal). The objective is a multi-user strategy for accessing the spectrum that maximizes a certain network utility in a distributed manner without online coordination or message exchanges between users. Obtaining an optimal solution for the spectrum access problem is computationally expensive in general due to the large state space and partial observability of the states. To tackle this problem, we develop a novel distributed dynamic spectrum access algorithm based on deep multi-user reinforcement leaning. Specifically, at each time slot, each user maps its current state to spectrum access actions based on a trained deep-Q network used to maximize the objective function. Game theoretic analysis of the system dynamics is developed for establishing design principles for the implementation of the algorithm. Experimental results demonstrate strong performance of the algorithm.
118 citations
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TL;DR: A D-connected model for correlated channels defined by a virtual spatial channel matrix consisting of D nonvanishing diagonals with independent and identically distributed (i.i.d.) Gaussian entries is proposed, which provides a meaningful and tractable measure of the richness of scattering.
Abstract: The dramatic linear increase in ergodic capacity with the number of antennas promised by multiple-input multiple-output (MIMO) wireless communication systems is based on idealized channel models representing a rich scattering environment. Is such scaling sustainable in realistic scattering scenarios? Existing physical models, although realistic, are intractable for addressing this problem analytically due to their complicated nonlinear dependence on propagation path parameters, such as the angles of arrival and delays. In this paper, we leverage a recently introduced virtual representation of physical models that is essentially a Fourier series representation of wide-band MIMO channels in terms of fixed virtual angles and delays. Motivated by physical considerations, we propose a D-connected model for correlated channels defined by a virtual spatial channel matrix consisting of D nonvanishing diagonals with independent and identically distributed (i.i.d.) Gaussian entries. The parameter D provides a meaningful and tractable measure of the richness of scattering. We derive general bounds for the coherent ergodic capacity and investigate capacity scaling with the number of antennas and bandwidth. In the large antenna regime, we show that linear capacity scaling is possible if D scales linearly with the number of antennas. This, in turn, is possible if the number of resolvable paths grows quadratically with the number of antennas. The capacity saturates for linear growth in the number of paths (fixed D). The ergodic capacity does not depend on frequency selectivity of the channel in the wide-band case. Increasing bandwidth tightens the bounds and hastens the convergence of scaling behavior. For large bandwidth, the capacity scales linearly with the signal-to-noise ratio (SNR) as well. We also provide an explicit characterization of the wide-band slope recently proposed by Verdu. Numerical results are presented to illustrate the key theoretical results.
118 citations
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02 Dec 1986TL;DR: In this article, a steep filter (almost rectangular) is connected to the output of a cosine filter, forming a composite filter, wherein the cut-off frequency of the rectangular filter is less than the Nyquist frequency by a predetermined amount which is inversely proportional to the amount in percentage by which the data transmission rate exceeds the NN rate.
Abstract: Partial response and quadrature partial response data transmission system characterized by increased transmission rate, lower signal-to-noise ratio, low cost and simpler hardware implementation than prior art systems. A steep filter (almost rectangular) is connected to the output of a cosine filter, forming a composite filter, wherein the cut-off frequency of the rectangular filter is less than the Nyquist frequency by a predetermined amount which is inversely proportional to the amount in percentage by which the data transmission rate exceeds the Nyquist rate. The system is thus capable of signalling at the Nyquist rate and greater, without requiring that channel filter parameters or the basic clock rate be adjusted. A smaller number of signal levels can be selected (as compared to previously existing methods) for spectrally efficient applications, and the resulting more robust system can also be used to transmit PAM, QAM, and other baseband or modulated signals.
118 citations
01 Jan 2010
TL;DR: In this paper, a two-pole filter with an internal volume of 1.5 cm and an insertion loss of 4.91-3.18- and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, is presented.
Abstract: This paper presents a miniature high- tunable evanescent-mode cavity filter using planar capacitive RF micro- electromechanical system (MEMS) switch networks and with a frequency coverage of 4.07-5.58 GHz. The two-pole filter, with an internal volume of 1.5 cm , results in an insertion loss of 4.91-3.18- and a 1-dB bandwidth of 17.8-41.1 MHz, respectively, and an ulti- mate rejection of 80 dB. RF-MEMS switches with digital/analog tuning capabilities were used in the tunable networks so as to align the two poles together and result in a near-ideal frequency response. The measured of the filter is 300-500 over the tuning range, which is the best reported using RF-MEMS technology. The filter can withstand an acceleration of 55-110 g without affecting its frequency response. The topology can be extended to a multiple-pole design with the use of several RF-MEMS tuning networks inside the evanescent-mode cavity. To our knowledge, these results represent the state-of-the-art in RF-MEMS tunable filters.
118 citations
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11 Jun 1986TL;DR: In this article, a code lock loop circuit is used in the receiver to recover the original narrow band signals, which are subsequently averaged to obtain the advantage in signal-to-noise ratio.
Abstract: In a receiverfor the reception of satellite television signals sub-carrier signals carrying, for example, data are recovered from the demodulated television signal and themselves demodulated to provide data outputs. Prior to the second demodulation, each sub-carrier signal is averaged to improve its signal-to-noise ratio, thereby taking advantage of the relatively small basic bandwidth of the sub-carrier signal to enable satisfactory reception of the signal in poor reception conditions when the received signal is too weak to obtain an acceptable television picture signal. Impulse noise in the received signal is reduced prior to averaging. To avoid intermodulation products being generated by the transmission and reception of several sub-carriers together, direct sequence modulation of the transmitted sub-carriers can be used to spread their power over a wider frequency band. A code lock loop circuit is then used in the receiver to recover the original narrow band signals, which are subsequently averaged to obtain the advantage in signal-to-noise ratio.
118 citations