US 5,479,447 AGranted

Method and apparatus for adaptive, variable bandwidth, high-speed data transmission of a multicarrier signal over digital subscriber lines

AssigneeThe Board of Trustees of the Leland Stanford Junior University

InventorsPeter S. Chow, John M. Cioffi

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Abstract

A method and apparatus for adaptive, variable bandwidth, high-speed data transmission of a multicarrier signal over digital subscriber lines wherein the initial optimal transmission bandwidth is identified based on initial signal-to-noise ratio (SNR) estimates of the orthogonal carriers of the multicarrier system. Maximum data throughput, or system performance margin, is achieved by assigning the total amount of information, or number of bits, to be transmitted in each multicarrier symbol to particular carriers through an initial bit allocation procedure, which is possibly subject to variable target bit error rates among the carriers. A transmit power mask, of any shape and level, is imposed upon the system by an initial energy allocation procedure that limits the maximum amount of power to be transmitted in each of the several carriers. Lastly, run-time adaptivity is achieved by monitoring the mean-squared-errors (MSE) of the orthogonal carriers, and the transmission bandwidth, as well as the bit allocation within the multicarrier symbol, is caused to change in real-time corresponding to changes in the channel characteristics in order to maintain optimal system performance.

Claims35

Dependent claims

In a multicarrier data transmission system that transmits data continuously over dispersive, noisy subscriber loops for digital service from a telephone central office to a user location and corresponding digital service between transmitters and receivers at said user location and said central office, a method for implementing variable transmission bandwidth as a function of line frequency-variable attenuation, noise power spectrum, a set of programmed and possibly variable carrier target bit-error-rates, and a programmed and possibly frequency-variable transmit power mask to improve data transmission speed or to improve performance margin at any given transmission speed subject to a power or power-spectral-density constraint, said method using subcarrier-indexed measurements of channel gains, channel noises, desired carrier bit-error-rates, and the programmed power mask to provide subcarrier-indexed estimates of transmission quality and to maintain the transmission quality at high levels, comprising the steps of:

(a) sorting the subcarrier-indexed estimates of the transmission quality, scaled by the desired subcarrier bit-error-rates, into an invertible ordering for assessment of the relative data-carrying capabilities of the subcarriers at initialization and/or during data transmission;
(b) calculating bit and energy allocation tables for said multicarrier data transmission system based on the sorted subcarrier-indexed estimates for either improving aggregate transmitted data rate at fixed performance margin with said power or power-spectral-density constraint or improving performance margin at a fixed data rate with said power or power-spectral-density constraint;
(c) communicating said bit and energy allocation tables between the transmitters and the receivers of said multicarrier transmission system;
and
(d) implementing said bit and energy allocation tables in coordination between the transmitters and the receivers during initialization of said multicarrier transmission system and/or during simultaneous transmission of said digital data by said multicarrier transmission system.

2 more elements

A multicarrier communication system comprising:

a transmitter means and a receiver means communicatively linked together by a datalink, the signal carrying characteristics of which are randomly variable, said transmitter means including,
means for establishing a plurality of frequency domain subchannels for respectively communicating various quantities of data bits selected from a stream of data bits;
means for measuring the capability of the datalink to efficiently communicate the data bits in each said subchannel and for developing an optimum energy allocation and an optimum data bit allocation for each said subchannels;
and
means for causing an input data stream to be divided and modulated onto a plurality of frequency domain carriers, each corresponding to one of said subchannels for transmission over said datalink to said receiver means, the quantity of data bits transmitted over each said subchannel being selected as a function of said optimum data bit allocation;
and said receiver means including,
means for monitoring the quality of the transmission over each said subchannels;
and
means for returning an indication of the monitored quality to said transmitter means.

6 more elements

In a multicarrier transmission system having transmitters and receivers to transmit and receive data continuously over communication lines, a method for implementing variable bandwidth data transmission with a plurality of subcarriers as a function of measured signal-to-noise ratios of the subcarriers, comprising the steps of:

calculating signal-to-noise factors for the subcarriers as functions of the measured signal-to-noise ratios of the subcarriers to a signal-to-noise gap approximation of the subcarriers, said gap approximation being a function of a system performance margin;
sorting the calculated signal-to-noise factors;
computing a plurality of bit allocation tables for the subcarriers using the first k subcarriers as provided in the order of the sorted factors and where k increases from one to the number of subcarriers;
determining bit allocation to the subcarriers by selecting from the plurality of bit allocation tables the table with the highest bit allocation to the subcarriers;
calculating energy allocation to each of the subcarriers according to its bit allocation;
and
implementing said calculated bit allocation and energy allocation to the subcarriers in the transmission of data to optimize data transmission speed during initialization of said multicarrier transmission system and/or during simultaneous transmission of said data by said multicarrier transmission system.

4 more elements

In a multicarrier transmission system having transmitters and receivers to transmit and receive data continuously over communication lines, a method for implementing variable bandwidth data transmission with a plurality of subcarriers and as a function of measured signal-to-noise ratios of the subcarriers, comprising the steps of:

sorting the signal-to-noise ratios of the subcarriers;
computing preliminary system performance margins using the subcarriers in the order of the sorted ratios, the preliminary subsystem performance margins being a function of the signal-to-noise ratios, the number of subcarriers, a target data rate, a total effective coding gain, a desired bit-error-rate, and energy for the subcarriers;
selecting the maximum system performance margin from said computed preliminary system performance margins;
calculating bit allocations to the subcarriers using said maximum system performance margin;
calculating energy allocation to the subcarriers according to its bit allocation;
and
implementing said calculated bit allocation and energy allocation to the subcarriers in the transmission of data to optimize data transmission speed during initialization of said multicarrier transmission system and/or during simultaneous transmission of said data by said multicarrier transmission system.

4 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/057,301Filed 3 May 1993
Granted: 26 Dec 1995
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H04W 52/18
Transmission power control [TPC]: tPC being performed according to specific parameters
H04L 5/0042
Arrangements for allocating sub-channels of the transmission path: intra-user or intra-terminal allocation
H04L 5/0044
Arrangements for allocating sub-channels of the transmission path: allocation of payload; Allocation of data channels, e.g. PDSCH or PUSCH
H04L 5/0053
Arrangements for allocating sub-channels of the transmission path: allocation of signalling, i.e. of overhead other than pilot signals