Interference (wave propagation)

About: Interference (wave propagation) is a research topic. Over the lifetime, 26086 publications have been published within this topic receiving 321110 citations.

Smart geometrical antenna design exploiting the LOS component to enhance a MIMO System based on Rayleigh-fading in indoor scenarios

Abstract: In this paper we propose a special antenna design for indoor applications which enables superior transmission properties within a designated and fixed area due to a line of sight (LOS) based MIMO antenna configuration. In the rest of the room the MIMO-system relies on the multi-path signal from the Rayleigh channel background. We derive a simple design recipe to achieve a nearly perfect antenna configuration for a LOS-based MIMO-system and apply this to an indoor application example. Assuming a typical office scenario, capacity issues are discussed and a very simple transmission system is simulated. In the designated area a very simple transmission system delivers nearly the maximum data rate and hence, the application of successive interference (SIC) cancellation is not necessary here. For the rest of the room SIC yields a significant improvement. At last we propose a more symmetrical antenna structure, which reduces the angular dependence of the transmission quality.

Disorder and interference: localization phenomena

Abstract: The specific problem we address in these lectures is the problem of transport and localization in disordered systems, when interference is present, as characteristic for waves, with a focus on realizations with ultracold atoms.

Multiple frequency range imaging to remove measurement ambiguity

Abstract: Range imaging systems use a specialised sensor to capture an image where object distance (range) is measured for every pixel using time-of-flight. The scene is illuminated with an amplitude modulated light source, and the phase of the modulation envelope of the reflected light is measured to determine flight time, hence object distance for each pixel. As the modulation waveform is cyclic, an ambiguity problem exists if the phase shift exceeds 2π radians. To overcome this problem we demonstrate a method that superposes two different modulation frequencies within a single capture. This technique reduces the associated overhead compared with performing two sequential measurements, allowing the system to retain high range measurement precision at rapid acquisition rates. A method is also provided to avoid interference from aliased harmonics during sampling, which otherwise contaminate the resulting range measurement. Experimental results show the potential of the multiple frequency approach; producing high measurement precision while avoiding ambiguity. The results also demonstrate the limitation of this technique, where large errors can be introduced through a combination of a low signal to noise ratio and suboptimal selection of system parameters.

Unequal error protection for digital broadcasting using channel classification

Abstract: The invention provides methods and apparatus for processing information, e.g., audio, video or image information, for transmission in a communication system. In an illustrative embodiment, interference characteristics are determined for a set of n channels to be used to transmit audio information bits, where n is greater than or equal to two. The audio information bits are separated into n classes based on error sensitivity, for example, the impact of errors in particular audio data bits on perceived quality of an audio signal reconstructed from the transmission. The classes of bits are then assigned to the n channels such that the classes of bits having the greatest error sensitivity are transmitted over the channels which are the least susceptible to interference. The interference characteristics associated with the n channels can be determined by, for example, measuring interference levels for one or more of the channels, or obtaining information regarding known interference levels for one or more of the channels. The channels may correspond to different frequency bands, time slots, code division slots or any other type of channels. The invention can provide UEP for different classes of audio information bits even in cases in which the same convolutional code, or the same complementary punctured pair convolutional (CPPC) code pair, is used to encode the classes. The assignment of the classes of bits to the channels, as well as the characteristics of the classes and the channels, may be fixed or dynamic.

Recording Parameters of Spatially Modulated Coherent Wavefronts

Abstract: Various parameters of recording spatially modulated coherent light have been studied, with particular emphasis on the parameters related to constructing holograms These include the ratio of the reference beam's intensity to that of the signal beam, the offset angle, the film's transfer characteristic, and the recording wavelength Experimental results were obtained by recording interference patterns on highresolution film using the 6328-a line of the He-Ne laser The bias level of the interference pattern was varied so as to vary the operating point on the curve representing the film's amplitude transmittance vs exposure characteristics The percent modulation and the spatial frequency were also varied at each of the operating points Interference patterns were recorded, using the 4880-aand 5145-a lines from the argon laser From these data, the optimum bias level and the ratio of the signal beam to the reference beam for recording interference patterns are determined The modulation transfer function of the film can also be determined