Showing papers on "Bandwidth (signal processing) published in 1996"

A Brief Survey of Bandwidth Selection for Density Estimation

Abstract: There has been major progress in recent years in data-based bandwidth selection for kernel density estimation. Some “second generation” methods, including plug-in and smoothed bootstrap techniques, have been developed that are far superior to well-known “first generation” methods, such as rules of thumb, least squares cross-validation, and biased cross-validation. We recommend a “solve-the-equation” plug-in bandwidth selector as being most reliable in terms of overall performance. This article is intended to provide easy accessibility to the main ideas for nonexperts.

Low-jitter and process independent DLL and PLL based on self biased techniques

Abstract: Delay-locked loop (DLL) and phase-locked loop (PLL) designs based upon self-biased techniques are presented. The DLL and PLL designs achieve process technology independence, fixed damping factor, fixed bandwidth to operating frequency ratio, broad frequency range, input phase offset cancellation, and, most importantly, low input tracking jitter. Both the damping factor and the bandwidth to operating frequency ratio are determined completely by a ratio of capacitances. Self-biasing avoids the necessity for external biasing, which can require special bandgap bias circuits, by generating all of the internal bias voltages and currents from each other so that the bias levels are completely determined by the operating conditions. Fabricated in a 0.5-/spl mu/m N-well CMOS gate array process, the PLL achieves an operating frequency range of 0.0025 MHz to 550 MHz and input tracking jitter of 384 ps at 250 MHz with 500 mV of low frequency square wave supply noise.

A revision of Zwicker's loudness model

Abstract: Zwicker's loudness model has the following stages: (a) A fixed filter representing transfer through the outer and middle ear; (b) Calculation of an excitation pattern from the physical spectrum; (c) Transformation of the excitation pattern to a specific loudness pattern. The area under the specific loudness pattern is assumed to determine loudness. This paper presents some modifications and extensions to Zwicker's loudness model. Changes are made in: (a) The assumed transfer function for the outer and middle ear; (b) The way that excitation patterns are calculated; (c) The way that specific loudness is related to excitation for sounds in quiet and in noise. The revised model accounts more accurately than Zwicker's model for the way that equal-loudness contours change with level. It also provides a more satisfactory explanation of why the loudness of a sound of fixed intensity remains constant when the sound has a bandwidth less than the critical bandwidth (CB). Finally, the revised model is able to account for the loudness of partially masked sounds without the introduction of correction factors. The revised model has the advantage that the excitation patterns on which it is based are calculated from analytical formulae rather than by reference to charts or tables. This avoids discontinuities in the predicted values of loudness.

Adaptive OFDM for wideband radio channels

Abstract: An OFDM (orthogonal frequency division multiplexing) transmission system is simulated with time-variant transfer functions measured with a wideband channel sounder. The individual subcarriers are modulated with fixed and adaptive signal alphabets. Furthermore, a frequency-independent as well as the optimum power distribution are used. The simulations show that with adaptive OFDM, the required signal power for an error probability of 10/sup -3/ can be reduced by 5...15 dB compared with fixed OFDM. The fraction of channel capacity which can be achieved with adaptive OFDM depends on the average signal-to-noise ratio and the propagation scenario.

Reducing WWW latency and bandwidth requirements by real-time distillation

Abstract: 1. Low Bandwidth Surfing in a High Bandwidth World 2. How Distillation and Refinement Can Help 1. The Concept of Datatype-Specific Distillation 2. Refinement 3. Trading Cycles for Bandwidth 4. Using Refinement for Bandwidth Management 5. Optimizing for a Target Display 6. Optimizing for Rendering on Impoverished Devices 3. An Implemented HTTP Proxy Based on Real-Time Distillation 1. Statistical Models for Real-Time Distillation 2. Pythia’s User Interface 4. Implementation and Performance 1. URL Munging and HTML Modification 2. Exploiting URL-Level Parallelism 3. Refinement Cache 5. Implementation Status, Limitations, and Future Work 6. Conclusions 7. References

Method and apparatus for providing high bandwidth, low noise mechanical i/o for computer systems

Abstract: A method and apparatus (25') for providing high bandwidth and low noise mechanical input and output for computer systems. A closed-loop, five member gimbal mechanism (46, 58, 48a, 48b, 50a and 50b) provides two revolute degrees of freedom to an object about two axies of rotation. A linear axis member (40) can be coupled to the gimbal mechanism at the axes' intersection and be translated along a third axis to provide a third degree of freedom. Transducers (42) associated with the provided degrees of freedom include sensors and actuators and provide an electromechanical interface between the objet (44) and a digital processing system (14). Capstan drive mechanisms (58) transmit forces between the transducers (42) and the object (44).

Wideband indoor channel measurements and BER analysis of frequency selective multipath channels at 2.4, 4.75, and 11.5 GHz

Abstract: Results from propagation measurements, conducted in an indoor office environment at 2.4, 4.75, and 11.5 GHz, are presented. The data were obtained in small clusters of six measurements, using a coherent wideband measurement system. The channel characteristics for the three frequencies are compared by evaluating path loss, rms delay spread, and coherence bandwidth. An analytical model for evaluation of the bit-error rate (BER) of the stationary frequency selective indoor channel is developed for a coherent binary phase shift keying (BPSK) receiver, based on the complex impulse response of the channel. Computational BER results are obtained for data rates up to 50 Mb/s, using the measured multipath channel impulse responses. The BER results for a number of clusters are presented and compared for the maximum reliable data rate as inferred by the measured rms delay spread of the channel.

Derivative analysis of hyperspectral data

Abstract: With the goal of applying derivative spectral analysis to analyze high resolution, spectrally continuous remote sensing data, several smoothing and derivative computation algorithms have been reviewed and modified to develop a set of cross-platform spectral analysis tools. Emphasis was placed on exploring different smoothing and derivative algorithms to extract subtle spectral features from any continuous spectral data sets. With interactive selection of bandwidth and sampling interval (band separation), the algorithm can optimize noise reduction and better match the scale of spectral features of interest. Laboratory spectral data were used to test the performance of the implemented derivative analysis modules. An algorithm for detecting the absorption band positions was executed on synthetic spectra and a soybean fluorescence spectrum to demonstrate the usage of the implemented modules in extracting spectral features. Upon examination of the developed modules, issues related to the smoothing and the spectral deviation caused by the smoothing or derivative computation algorithms were also observed and discussed. The scaling effect resulting from the migration of band separations when using the finite approximation derivative algorithm was thoroughly inspected to understand the relationship between the scaling effect and noise removal.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Accurate distance measurement by an autonomous ultrasonic system combining time-of-flight and phase-shift methods

Abstract: Ultrasonic sensor distance measurements are based on the evaluation of the time-of-flight or on the determination of the phase difference between a transmitted and a received signal. Digital signal processing methods are developed in order to extract the useful information from the samples acquired from the received wave. This paper presents an efficient algorithm for distance measurement combining both the propagation time method and the phase difference method and relying on a low rate sampling technique allowed by the limited bandwidth of the ultrasonic transducers. The measuring system was implemented and tested on a compact Motorola MC68HC16 based platform, with a minimum of attached hardware. Experimental results show an accuracy better than 1 mm.

Pilot spacing in orthogonal frequency division multiplexing systems on practical channels

Abstract: The performance of two different channel interpolation methods to be used with orthogonal frequency division multiplexing systems are investigated. The considered schemes use constant pilot frequencies for channel response estimation. The interpolation techniques are piecewise-constant and piecewise-linear methods which due to their inherent simplicity are straightforward to implement. The results are given as error probability vs. pilot separation for a channel with exponential type power-delay profile and M-ary quadrature amplitude (MQAM) submodulation with M=4, 16 and 64.

Capacity and power control in spread spectrum macrodiversity radio networks

Abstract: What is the capacity of the uplink of a radio network of receivers? We consider a spread spectrum model in which each user is decoded by all the receivers in the network (macrodiversity). We use a carrier-to-interference performance criterion that we derive from Shannon theory; each user must find the right transmitter power level to satisfy its carrier-to interference constraint. Satisfying this requirement for all users is equivalent to solving a fixed point problem. We use this power control problem to derive the network capacity region and find that the feasibility of a configuration of users is independent of their positions in the network; each user can be assigned a bandwidth that is independent of the user's position in the network. Our capacity region is an upper bound over all schemes that treat the interference of other users as pure noise. To show that the capacity can be realized in practice, we propose a decentralized power adaptation algorithm and prove global convergence to the fixed point via a monotonicity argument.

Communications service billing based on bandwidth use

Abstract: In a bandwidth-on-demand type communications system, like that provided with a code division multiple access (CDMA) cellular communications system, charging subscribers for calls based on communications length provides an inaccurate measure of communication cost, and further serves to discourage use of the system for data transmission applications. To provide a more accurate cost determination, the amount of bandwidth used by each communication is metered and multiplied by a charging rate. In particular, measurements (104) of the maximum amount of bandwidth (106, 108) used during predetermined time intervals (110) are made during the course of each communication, with the maximum bandwidth measurements being summed (112) to determine an estimate of the total amount of bandwidth used during the communication. The charge for the communication is then determined by multiplying (116) the estimated total bandwidth measurement by a charging rate multiplier.

Information handling systems with broadband and narrowband communication channels between repository and display systems

Abstract: A bidirectional or unidirectional information handling system for data exchange and distribution. The system includes a data repository system and a data display system. The systems are linked for data exchange by a broadband channel for unidirectional high data flow rates and, in some embodiments, by a narrowband channel for bidirectional lower data flow rates. The display system may take a number of forms, including personal communications assistants, desktop personal computers, and set top boxes. The data communication channels may be defined by a number of different protocols and bandwidth segments and may be wireline or wireless.

Minimal Energy Requirements in Communication

Abstract: The literature describing the energy needs for a communications channel has been dominated by analyses of linear electromagnetic transmission, often without awareness that this is a special case. This case leads to the conclusion that an amount of energy equal to kTln 2, where kT is the thermal noise per unit bandwidth, is needed to transmit a bit, and more if quantized channels are used with photon energies hnu > kT. Alternative communication methods are proposed to show that there is no unavoidable minimal energy requirement per transmitted bit. These methods are invoked as part of an analysis of ultimate limits and not as practical procedures.

Implementation of a foveated image coding system for image bandwidth reduction

Abstract: We have developed a preliminary version of a foveated imaging system, implemented on a general purpose computer, which greatly reduces the transmission bandwidth of images. The system is based on the fact that the spatial resolution of the human eye is space variant, decreasing with increasing eccentricity from the point of gaze. By taking advantage of this fact, it is possible to create an image that is almost perceptually indistinguishable from a constant resolution image, but requires substantially less information to code it. This is accomplished by degrading the resolution of the image so that it matches the space-variant degradation in the resolution of the human eye. Eye movements are recorded so that the high resolution region of the image can be kept aligned with the high resolution region of the human visual system. This system has demonstrated that significant reductions in bandwidth can be achieved while still maintaining access to high detail at any point in an image. The system has been tested using 256 by 256 8 bit gray scale images with a 20 degree field-of-view and eye-movement update rates of 30 Hz (display refresh was 60 Hz). users of the system have reported minimal perceptual artifacts at bandwidth reductions of up to 94.7% (a factor of 18.8). Bandwidth reduction factors of over 100 are expected once lossless compression techniques are added to the system.

A 900-MHz RF front-end with integrated discrete-time filtering

Abstract: Discrete-time analog filters, rather than off-chip components, have been used to perform frequency selection and down conversion in the integrated front-end for a 900-MHz RF receiver. The first stage of frequency down conversion is implemented with a subsampling switched-capacitor sample-and-hold circuit clocked at 78 MHz. Subsequent stages of discrete-time filtering are realized using switched-capacitor biquadratic filters. An experimental prototype of the front-end had been integrated in a 0.6-/spl mu/m BiCMOS technology. The circuit provides a system gain of 36 dB and 32 dB suppression of interfering channels over a 40 MHz bandwidth. Referred to the system input, the third-order intercept-point is -16 dBm, and the spot input-referred noise is -82 dBm over a 30 kHz bandwidth. The experimental circuit dissipates 90 mW from a 3.3-V supply and occupies an active area of 1.9/spl times/1.9 mm/sup 2/.

Speech formant frequency and bandwidth tracking using multiband energy demodulation

Abstract: In this paper, the amplitude and frequency (AM–FM) modulation model and a multiband demodulation analysis scheme are applied to formant frequency and bandwidth tracking of speech signals. Filtering by a bank of Gabor bandpass filters is performed to isolate each speech resonance in the signal. Next, the amplitude envelope (AM) and instantaneous frequency (FM) are estimated for each band using the energy separation algorithm (ESA). Short‐time formant frequency and bandwidth estimates are obtained from the instantaneous amplitude and frequency signals; two frequency estimates are proposed and their relative merits are discussed. The short‐time estimates are used to compute the formant locations and bandwidths. Performance and computational issues of the algorithm are discussed. Overall, multiband demodulation analysis (MDA) is shown to be a useful tool for extracting information from the speech resonances in the time–frequency plane.

Hybrid fiber-coax system having at least one digital fiber node and increased upstream bandwidth

Abstract: Increased upstream bandwidth and reduced ingress noise in a shared hybrid fiber-coax transmission system (100) are obtained by modulating at least a portion of upstream signals received from subscribers to a high frequency band (e.g., 750-1000 MHz), thereby increasing the upstream bandwidth. The high frequency upstream signals are then digitally regenerated in the coaxial cable (200) plant prior to receipt at a fiber node (180). At the fiber node, the high-frequency upstream signals are again digitally regenerated and are then transmitted optically in a baseband digital format between the fiber node (180) and a head end (120). The digital regeneration of the high frequency upstream signals, and the optical transmission of such signals in a baseband digital format reduces the incidence of ingress noise.

Capacitively loaded PIFA

Abstract: A planar inverted-F antenna is described that is provided with a capacitive load that allows the dimensions of the antenna to be reduced from a conventional λ/4 to λ/8. To maintain good bandwidth and impedance matching in spite of the presence of the capacitive load, a capacitive feed is also provided.

Analysis Multispectral Image Capture

Abstract: Multispectral image capture (i.e, more than three channels) facilitates both more accurate tristimulus estimation and possibilities for spectral reconstruction of each scene pixel. A seven-channel camera was assembled using approximately 50 nm bandwidth interference filters, manufactured by Melles Griot, in conjunction with a Kodak Professional DCS 200m digital camera. Multichannel images were recorded for the Macbeth ColorChecker chart as an illustrative example. Three methods of spectral reconstruction were evaluated: spline interpolation, modified-discrete-sine-transformation (MDST) interpolation, and an approach based on principal-component analysis (PCA). The spectral reconstruction accuracy was quantified both spectrally and by computing CIELAB coordinates for a single illuminant and observer. The PCA-based technique resulted in the best estimated spectral-reflectance-factor functions. These results were compared with a least-squares colorimetric model that does not include the spectral-reconstruction step. This direct mapping resulted in similar colorimetric performance to the PCA method. The multispectral camera had marked improvement compared with traditional three-channel devices. Techniques The use of multispectral cameras can lead to dramatically improved colorimetric accuracy in comparison with three-channel devices. 1,2

Multiband-96: a program for variable-bandwidth progression optimization of multiarterial traffic networks

Abstract: Progression schemes are widely used for traffic signal control in urban arterial streets. Commonly available programs such as the MAXBAND or PASSER programs use the traditional approach, which consists of a uniform bandwidth design for each arterial. The multiband criterion, on the other hand, has the ability to adapt the progressions to the specific characteristics of each link in the network and thus obtain improved performance. The development and application of the multiband signal optimization scheme in multiarterial grid networks are described. The MULTIBAND-96 model optimizes all the signal control variables, including phase lengths, offsets, cycle time, and phase sequences, and generates variable bandwidth progressions on each arterial in the network. It uses the MINOS mathematical programming package for the optimization and offers considerable advantages compared with existing models. Simulation results using TRAF-NETSIM are given.

Satellite for increasing the utility of satellite communication systems

Abstract: An existing TDRSS satellite communication system is incorporated, together with low-power ground-based remote transceivers of special design, and additional beam forming and steering elements at the ground terminals, to make possible digital communication between low power field transceivers and satellite ground terminals. The satellite communication system transmits to its ground terminals a composite signal, comprising amplified, phase-coherent signals received by an array of broad-coverage antennas on the satellite. The field transceiver transmits a pseudonoise coded signal spread across all or a portion of the satellite's receive bandwidth. At the ground terminal, the downlinked composite signal is processed by a beamformer to define a narrow, high-gain beam between the satellite and low-power transceiver. Signal processing gain and beamformer gain in combination serve to elevate the received, demodulated signals well above the noise level at the receiver. Through this invention, a large multiplicity of non-interfering reverse-link (remote-to-central) narrow-band communication channels may be supported by a host satellite communication system of the nature described. By the introduction of forward link signal channels into the satellite ground terminal, and scheduling of forward link transmissions to the set of low-power remote transceivers along with normal transmit activities, highly useful two-way communication can be extended to a class of users not initially served by the satellite communication system.

Data transmitting apparatus, data receiving apparatus and data transmission control apparatus

Abstract: It is objected to simplify a procedure concerning bandwidth acquisition. Bandwidth acquiring means 809 of a second transmitting apparatus 814 acquires a bandwidth which was used by a first transmitting apparatus 806 by using a propagation delay identifier 804 read from first transmitting apparatus 806 and a maximum transmission data size 805 after stopping transmission of first transmitting apparatus 806. Each apparatus is composed so that transmission is started using this bandwidth and because returning and re-acquisition are not accompanied when the transmission is switched, necessary procedure can be simplified. Further, it is possible to effectively use the bandwidth by using a propagation delay identifier.

Adaptive, High Bandwidth Control of a Hydraulic Actuator

Abstract: Hydraulic servovalve controlled systems contain many time-varying dynamic characteristics that are difficult to model. Controllers for such systems must either adapt to these changing parameters or be robust enough to handle the parameter variations. In order to achieve the highest possible bandwidth, an adaptive controller is developed for the system that uses full-state feedback for simultaneous parameter identification and tracking control. This controller takes into account the hydraulic fluid compressibility with an on-line identification scheme. Experimental results demonstrate a four fold improvement in bandwidth as compared to a conventional fixed gain proportional controller.

Tunable and adaptive bandpass filter using a nonlinear dielectric thin film of SrTiO3

Abstract: We have prepared an electrically tunable and adaptive 3‐pole half‐wave bandpass coplanar waveguide filter incorporating a 1.2‐μm‐thick paraelectric SrTiO3 bottom layer and a 0.4‐μm‐thick superconducting YBa2Cu3O7−x top electrode layer on a LaAlO3 substrate. By applying a separate bias voltage on each pole and also on each coupling capacitance of the device at 4 and 76 K, the filter response is not only fine tuned to achieve symmetric and optimized filter characteristics with less than 2% bandwidth centered around 2.5 GHz, but also broadband tuned to shift the passband by more than 15%.

Frequency-diversity spread-spectrum communication system to counter bandlimited Gaussian interference

Abstract: A spread spectrum system to counter bandlimited Gaussian interference is proposed. The optimum receiver for this system is easy to build. Frequency diversity which allows the receiver to distinguish unjammed signal replicas from their jammed versions is used. The system can also resist bandlimited partial-time jamming. The only choice left to a smart jammer to maximize the error probability is to spread its signal like the communicator. The optimum receiver, which jointly performs symbol detection and interference rejection, is derived. Side information needed by this receiver can easily be estimated. However, if the interference bandwidth is narrow compared to the signal bandwidth, side information on noise and interference levels is not needed by a simpler and near-optimum receiver. Bit-error probability is evaluated for quaternary phase shift keying (QPSK) modulation and compared to that of direct sequence spread spectrum. We also propose the use of polyphase filters for simple system implementation.

Method and system for cellular communication with centralized control and signal processing

Abstract: A cellular system includes wide band digital signal processing at a central office that is connected to one or more cellular sites by optical fiber cables. Data signals are exchanged between the cell sites and the central office using intensity modulated optical data signals. Control of call supervision and handling is consolidated in the central office to enable dynamic variation of wireless service reception and transmission capabilities at a cell site in response to changing demands for wireless service. Each antenna at a cell site may receive and transmit an assigned RF bandwidth using any frequency within that band. The central office processes the entire received spectrum for controlling detection and transmitting range, RF carrier frequency and transmit power level for an active channel link established between a cellular station and the system in a cell site.

Multiple audio and video signal providing apparatus

Abstract: A video signal provider multiplexes digital video signals for four channels and provides a signal the bandwidth of which is limited to 6 MHz by RF-modulation. An analog video signal provider provides another signal the bandwidth of which is limited to 6 MHz by RF-modulation. A digital audio signal provider multiplexes digital audio signals for 32 channels and provides another signal the bandwidth of which is limited to 6 MHz by RF-modulation. Such signals are combined and transmitted through a coaxial cable 14 to a controller. In this example, such signal providing apparatus can provide a maximum of 84 channels (=126 MHz (the bandwidth for video signal of the coaxial cable)/6 MHz×4 ch), which number is significantly larger than the 20 channels provided in the prior art.