Columbia University

At&t Bell Laboratories

University of Illinois

Merunetworks, Inc.

Kannan Ramchandran

Martin F Vetterli

Douglas L Jones

Dimitris Anastassiou

Kamil M Uz

Kimerie Walzer Javitt

Igor Kozintsev

Yanbin Yu

Brian Scott Krongold

Jim Chou

Method and apparatus for image transmission using arithmetic coding, based on continuous error detection uses a controlled amount of added redundancy. A continuous error detection scheme is provided, wherein there is a trade-off between the amount of added redundancy and the time needed to detect an error once it occurs. Herein, there is no need for the cyclic redundancy check (CRC) to wait until an entire block of data has been received and processed before an error can be detected. The invention can be used to great advantage both in the automatic repeat request (ARQ) and other concatenated coding schemes. Errors in the received bit stream are detected by introducing added redundancy, e.g., a forbidden symbol, in the arithmetic coding operation. The forbidden symbol is never intended to be encoded. The redundancy error causes loss of synchronization, which is used to detect errors. If a forbidden symbol gets decoded, it means that an error has occurred. In this invention, there is direct control over the amount of redundancy added vs. the amount of time it takes to detect an error. For image compression systems, by using the invention and ARQ, only one device would suffice both for source compression and channel coding.

Data transmission using arithmetic coding based continuous error detection

Optimum bit rates and power levels are determined for subchannels in multicarrier communication systems. A tangent of the rate-power curve has a slope &lgr;. The slope is defined by the quotient difference between high/low power and high/low rate. A particular &lgr; is evaluated to find its corresponding total power followed by an update of &lgr;, in the form of an increase or decrease, to get closer to the optimal solution. Each &lgr; is evaluated to find the optimal operating point for each subchannel on the rate-power curve by summing the power allocated to the subchannels, and comparing the result to the power budget. Look-up tables are stored for individual channels, but similarity between channels permits joint use of look-up tables by multiple channels. The tables are used to determine the rate-power characteristics at each iteration. An optimal solution is found when either a newly chosen power allocation meets the power budget exactly or a newly chosen power budget equals the high or low power of a previous iteration.

Section division operating point determination method for multicarrier communication systems

For encoding signals corresponding to still images or video sequences, respective standards known as JPEG and MPEG have been proposed. These standards are based on digital cosine transform (DCT) compression. For economy of transmission, DCT coefficients may be 'thresholded' prior to transmission, by dropping the less significant DCT coefficients. While maintaining JPEG or MPEG compatibility, threshold selection for the DCT coefficients of an image or video frame is based on optimizing for minimum distortion for a specified maximum target coding bit rate or, equivalently, for minimized coding bit rate for a specified maximum allowable distortion constraint. In the selection process, a dynamic programming method is used.

JPEG/MPEG decoder-compatible optimized thresholding for image and video

In a digital TV broadcast system, an embedded multiresolution scheme implementing joint source/channel coding is employed to offer at least relatively fine and relatively coarse resolution services. The relatively fine resolution service is intended for receivers within a first radius of a TV signal transmitter and the relatively coarse resolution service is intended for receivers between the first radius and a second, longer radius thereof. Video signals broadcast from the transmitter represent individual signal points which are selected from a signal constellation. The latter comprises signal-point groups each including a multiplicity of the signal points. The selected signal points represent video images in the relatively fine resolution, while the signal-point groups from which the selected signal points originate represent the relatively coarse version of the images. The relative length of the first radius to the second radius is a function of the ratio of the interdistance of two neighboring signal points within a signal-point group to the interdistance of two neighboring signal-point groups in the signal constellation.

Multiresolution digital television broadcast system

Disclosed is a circuit for adding loss to a signal in a loop carrier transmission system. As data is being transmitted, the circuit determines the digital output needed for an appropriate amount of loss for each channel unit at the end user interface.

Growing community of inventors

Champaign, IL, United States of America

Kannan Ramchandran