Abstract:
A method for digital communication includes generating time-domain symbols (54) having a predetermined symbol duration in accordance with a discrete multi-tone (DMT) modulation scheme. A cyclic extension (56,58) is added to each of the time-domain symbols so as to form data blocks (50,52) having a block length that is not an integer multiple of the symbol duration. A training pattern is generated on one or more tones of the DMT modulation scheme, wherein the training pattern is periodic over a sequence of the data blocks with a period equal to the symbol duration. The sequence of the data blocks is transmitted over a communication channel (26) to a receiver (24), which processes the training pattern so as to determine a response of the channel to the one or more tones.
Abstract:
Digital data is transmitted in a block-based hyperframe that consists of N frames. Each frame carries multiplexed data from one or more user data channels and a control channel. Control channel information is unequally allocated among the N frames, the amount of information carried in each frame varying according to the frame's position in the hyperframe. All of the user data channels except one carry a predetermined number of transmission units in each frame. The excepted user data channel carries a calculated amount needed to round out the particular frame. Following multiplexing, a block encoder defines the frames and adds error detection or error correction information. The number of frames per hyperframe and the total number of transmission units for the control channel are available to a receiver, which can then demultiplex the hyperframe.
Abstract:
A method for coordinating and synchronizing a mode transition in a Discrete Multi-Tone (DMT) communication system (20) operating over a range of tones. The method includes allocating a set of one or more of the tones in the range to serve as monitor tones (67) for signaling the mode transition. The mode transition is signaled by transmitting a known transition sequence (68) on the monitor tones over two or more successive symbol intervals while simultaneously transmitting data on at least some of the tones in the range other than the monitor tones.
Abstract:
Methods and systems provide an efficient power save mode for multi carrier modems, such as DMT based ADSL and VDSL modems. Fast transitions from power save mode to full operational mode occur, without the overhead of transmitting large quantities of configuration information between the transmitter and receiver. Signal constellation size changes occurring while operating in power save mode to continue to apply once full operational mode is resumed. Multiple power save modes are enabled, each having a different level of power dissipation and crosstalk, both far end crosstalk and near end crosstalk. Power dissipation and crosstalk can thus be graduated on a line, according to a user-requested bit rate.
Abstract:
A method for data communication includes providing an order for assigning bits of an input data stream to tones in a multi-tone modulation scheme, and allocating respective bit-loading values to the tones, such that some of the tones are allocated a first bit-loading value and other tones are allocated at least one second bit-loading value. The order is modified so as to form pairs (59) of the tones that are allocated the first bit-loading value, with one or more of the other tones intervening between at least some of the pairs. The input data stream is modulated by assigning the bits to the tones in accordance with the modified order and the respective bit-loading values, and encoding the bits that are assigned to each of the pairs of the tones as a constellation point.
Abstract:
An ordered dither method is applied to reduce the chromatic resolution of an image represented by channels R (red), G (green), B (blue) and A (brightness), whereby a first and a second dither matrix is provided, both comprising the same threshold values but arranged in a different spatial distribution. The first dither matrix is applied to the R, B, and A channels, and the second dither matrix is applied to the G channel.