235 results about "Impulse noise" patented technology

Several embodiments of a space diversity trellis interleaver system are provided for communicating data over a plurality of separate communication paths in order to inhibit distortion caused by impulse noise or other correlated noise and enhance the data transmission rate of data communications. The transmitter is designed to receive a plurality of data streams from data terminal equipment (DTE), which can be one or more devices. One or more convolutional encoders, preferably trellis encoders, encode each of the data streams. In an alternative embodiment, more than one trellis encoder is used to trellis encode each data stream. Data segments from the convolutionally encoded data streams are interleaved with a switch. The plurality of interleaved convolutionally-encoded data streams are modulated and transmitted onto a respective plurality of separate communication paths. At the receiver, the plurality of data streams is received from the separate communication paths and demodulated. The data segments are de-interleaved with a switch, and then the de-interleaved data streams are convolutionally decoded with convolutional decoders, preferably trellis decoders. The de-interleaved convolutionally decoded data streams are communicated to one or more DTEs.

The invention relates to a method for processing a video image, and discloses a method for de-noising an image. The method comprises the following steps of: A, calculating the joint probability distribution P(I,J) of the image; B, determining the threshold range [LI,UI] of gray scale according to the P(I,J); C, ensuring that Wi,j is a N*N window, the coordinate of a central point of the window is (i,j), x is used for representing the central pixel point of the window Wi,j, and the window Wi,j moves to the top left corner of the image; and D, sequencing N*N pixel points in the Wi,j according to gray scale values, finding a gray scale value J corresponding to a median (N*N+1) / 2 of the sequenced gray scale values, not processing the pixel point if J is in the threshold range [LI,UI] in the step B, and replacing the central point x of the window Wi,j with the gray scale value J if J is not in the threshold range [LI,UI]. The method has the advantage of solving the problems that image detail information is lost and the image blurs when pulse noise is removed by the conventional filtering method.

Method and system for tolerating impulsive burst noise in pilot based OFDM systems, especially using DVB-T standard. The method contains following steps: 1) recognition of the impulse position and possibly length in the time domain symbol, 2) blanking of those samples of the symbol where significant amount of impulse noise is present, 3) calculating the first estimate of the received signal from the blanked symbol, 4) using a prior information (guard band carriers, pilot carriers) an estimate of the blanked symbol is calculated using inverse FFT on the differences of the observed carrier values from the known values in the frequency domain, 5) correction values for the frequency domain carriers are derived taking the FFT of the restored time domain samples, 6) finally the corrected estimate of the received symbol is derived by summing the correction values of step 5 to the first estimate of carriers derived in step 3. The method allows correction of relatively long bursts of impulse noise with minor degradation. The method provides considerably reliable data reception in broadcast systems.

With the current initialization procedures defined in the VDSL and ADSL standards, even though the xDSL system could operate in Showtime in an impulse noise environment where symbols are being corrupted, the transceivers would not be able to reach Showtime because initialization would fail due to initialization message failure. Through the use of an improved initialization procedure for communication systems, operation in environments with higher levels of impulse noise is possible.

An impulse detector which can detect both low and high levels of impulse noise in a CDMA system is comprised of circuitry to calculate the background noise level in unused codes. Another circuit calculates the average noise power in the unused codes of each spreading interval to output the noise power per spreading interval. This average is continuously averaged over spreading intervals by another circuit which outputs the average background noise power. A comparator compares the noise power in the current spreading interval with the background noise power plus a programmable threshold and generates an erasure indication if the background noise power plus a discrimination threshold is exceeded.