A system of distributing video and/or audio information employs digital signal processing to achieve high rates of data compression. The compressed and encoded audio and/or video information is sent over standard telephone, cable or satellite broadcast channels to a receiver specified by a subscriber of the service, preferably in less than real time, for later playback and optional recording on standard audio and/or video tape.

Audio and video transmission and receiving system

We establish a statistical model for the ultra-wide bandwidth (UWB) indoor channel based on an extensive measurement campaign in a typical modern office building with 2-ns delay resolution. The approach is based on the investigation of the statistical properties of the multipath profiles measured in different rooms over a finely spaced measurement grid. The analysis leads to the formulation of a stochastic tapped-delay-line (STDL) model of the UWB indoor channel. The averaged power delay profile can be well-modeled by a single exponential decay with a statistically distributed decay constant. The small-scale statistics of path energy gains follow Gamma distributions whose parameters m are truncated Gaussian variables with mean values and standard deviations decreasing with delay. The total received energy experiences a lognormal shadowing around the mean energy given by the path-loss power law. We also find that the correlation between multipath components is negligible. Finally, we propose an implementation of the STDL model and give a comparison between the experimental data and the simulation results.

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The ultra-wide bandwidth indoor channel: from statistical model to simulations

Surface-enhanced Raman scattering (SERS) is a spectroscopic technique which combines modern laser spectroscopy with the exciting optical properties of metallic nanostructures, resulting in strongly increased Raman signals when molecules are attached to nanometre-sized gold and silver structures. The effect provides the structural information content of Raman spectroscopy together with ultrasensitive detection limits, allowing Raman spectroscopy of single molecules. Since SERS takes place in the local fields of metallic nanostructures, the lateral resolution of the technique is determined by the confinement of the local fields, which can be two orders of magnitude better than the diffraction limit. Moreover, SERS is an analytical technique, which can give information on surface and interface processes. SERS opens up exciting opportunities in the field of biophysical and biomedical spectroscopy, where it provides ultrasensitive detection and characterization of biophysically/biomedically relevant molecules and processes as well as a vibrational spectroscopy with extremely high spatial resolution. The article briefly introduces the SERS effect and reviews contemporary SERS studies in biophysics/biochemistry and in life sciences. Potential and limitations of the technique are briefly discussed.

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Surface-enhanced Raman scattering and biophysics

An ultra-wide bandwidth (UWB) signal propagation experiment is performed in a typical modern laboratory/office building. The bandwidth of the signal used in this experiment is in excess of 1 GHz, which results in a differential path delay resolution of less than a nanosecond, without special processing. Based on the experimental results, a characterization of the propagation channel from a communications theoretic view point is described, and its implications for the design of a UWB radio receiver are presented. Robustness of the UWB signal to multipath fading is quantified through histograms and cumulative distributions. The all RAKE (ARAKE) receiver and maximum-energy-capture selective RAKE (SRAKE) receiver are introduced. The ARAKE receiver serves as the best case (bench mark) for RAKE receiver design and lower bounds the performance degradation caused by multipath. Multipath components of measured waveforms are detected using a maximum-likelihood detector. Energy capture as a function of the number of single-path signal correlators used in UWB SRAKE receiver provides a complexity versus performance tradeoff. Bit-error-probability performance of a UWB SRAKE receiver, based on measured channels, is given as a function of the signal-to-noise ratio and the number of correlators implemented in the receiver.

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Characterization of ultra-wide bandwidth wireless indoor channels: a communication-theoretic view

Introduction. UWB Channel Models. Modulation Schemes. Receiver Structures. Integrated Circuit Topologies. UWB Antennas. Medium Access Control. Positioning.

UWB theory and applications

This paper describes the high value of cognitive radio technology and characterizes the opportunity space in four distinct classes. A Chicago-based spectrum occupancy study illustrates the opportunity showing that 82.6% of the spectral capacity is unused. A set of spectral signatures is presented for common devices in the unlicensed frequency band with the view that this technique can be widely deployed across the spectrum. The limitations of current network simulation tools in an interference environment are identified. Finally, the paper briefly discusses several of the non-technology related issues that impact the deployment of cognitive radio techniques.

Spectral Occupancy and Interference Studies in support of Cognitive Radio Technology Deployment

This paper studies wireless communication systems using technology that does not require a carrier signal. The vehicle used for transmission is a monopulse waveform. Such waveforms possess a bandpass nature, having no DC content. The short time duration of these waveforms, typically nanoseconds, provides has an ultrawide bandpass characteristic, with a spectrum in the range of hundreds of megahertz, making them ideally suited for a spread spectrum communication system. The temporal representations of several monopulse signals are illustrated, and the power spectral densities of the Gaussian and Rayleigh monopulse waveshapes are presented. The relationship between effective time duration, peak-to-RMS value, and bandwidth is detailed. The spectral effect of pulse amplitude modulated data and pulse position modulated data is compared. A methodology for efficient data transmission and a technique for rate doubling at no cost in bandwidth is described. Diversity methods to mitigate a harsh environment, such as those encountered in fading channels, jamming, and multipath situations, are introduced.

Communication techniques using monopulse waveforms

The MicroWave Oven (MWO) is a popular appliance that acts as an unintentional interferer for 2.4 GHz IEEE 802.11 Wi-Fi communication signals. An interference mitigation technique is developed that incorporates cognitive radio paradigms allowing Wi-Fi devices to reliably transmit information while a residential MWO is operating. This technique is applied in the experimental case where Barker spread Wi-Fi signals carry data in the presence of MWO emissions. Bit error rate is evaluated to provide a performance metric for the mitigation technique.

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Microwave Oven Signal Interference Mitigation For Wi-Fi Communication Systems

Analyse detaillee de ce systeme entierement compatible avec les normes NTSC. Amelioration des performances. Circuits codeurs et decodeurs

A Compatible High-Definition Television System (SLSC) with Chrominance and Aspect Ratio Improvements

A television (TV) system having a fully compatible high-definition signal with extended aspect ratio information receivable at conventional resolution by conventional TV receivers without auxiliary apparatus with one TV channel carrying the conventional TV signal while high-frequency luminance and chrominance information plus extended aspect ratio information are provided in a second TV channel. The television system uses a video camera that produces the Y, I, and Q video signals with a bandwidth of 9.4 megahertz (MHz). These, Y, I, and Q signals have already been line decimated to 525 lines per frame with a scan rate of the standard 15.7 kiloherts (kHz). The resulting 63.5 microseconds line scan time comprises 42 microseconds of center information and 10.5 microseconds of edge information with 11 microseconds being allowed for the blanking and synchronization interval. The low-frequency center luminance and chrominance information is first time expanded and inserted into the first channel, and the high-frequency center chrominance and luminance information is time expanded and inserted into the second channel. The extended aspect ratio chrominance and luminance information is contained within the edge information and is transmitted during the horizontal retrace interval in the second TV channel.

J.L. LoCicero

Papers

Spectral Occupancy and Interference Studies in support of Cognitive Radio Technology Deployment

Communication techniques using monopulse waveforms

Microwave Oven Signal Interference Mitigation For Wi-Fi Communication Systems

A Compatible High-Definition Television System (SLSC) with Chrominance and Aspect Ratio Improvements

Compatible high-definition television with extended aspect ratio