Texas Instruments Corporation

Cory Samuel Modlin

Tarik Muharemovic

Jacky S Chow

Eugene Yuk-Yin Tang

Po Tong

A method for Orthogonal Frequency Division Multiplexing Access (OFDMA) ranging is provided. The method includes receiving a signal having OFDMA symbols. An FFT is performed on this signal. Matching ranging codes are found. The power for a given hypothesized ranging code is determined and compared to a power threshold to determine if the code was transmitted. The timing offset and power are reported as the result of ranging.

Orthogonal frequency division multiplexing access (OFDMA) ranging

A system and method for improving bit-loading in discrete multitone (DMT)-based digital subscriber line (DSL) modems. In one embodiment, the system includes: (1) a model generator configured to generate a model containing a calculated total bit loading for an assumed gross coding gain and estimated total bit loadings for a other plurality of assumed gross coding gains and (2) a bit loader associated with the model generator and configured to load bits in accordance with the model.

System and method for improving bit-loading in discrete multitone-based digital subscriber line modems

A method for changing the data rate over an interleaved latency path overcomes shortfalls of the ADSL2 seamless rate adaptation (SRA) and dynamic rate repartitioning (DRR). The interleaver depth is allowed to change during either a rate charge or rate repartioning so that the interleaver delay is constant before and after the change. The transmitter pauses its transmission for a time approximately equal to the delay of the interleaver so that there are approximately no errors introduced at the receiver.

Error free dynamic rate change in a digital subscriber line DSL with constant delay

A method for designing an equalizer and tracking performance for upstream PCM in a digital communications network is described. The invention optimizes upstream data rate rates for data transmissions in a network between a client modem a server modem. During training, the upstream channel impulse response is identified compensating for any robbed bit signalling. The upstream transmit equalizer is computed in closed form based on the identified channel. An equalizer in the receiver is also used to track timing and channel variations. The invention approximates bit error rate performance by looking for code violations in the trellis code decoder and tracking their frequency. The bit error rate is used to determine if the current modem parameters need to be re-designed.

PCM upstream data transmission server

A method selects the data rate for pulse code modulation upstream transmission by determining an approximate transmit power before the upstream transmission reaches a transmit equalizer based on a recorder power output and a distance halfway between an outermost constellation point and a point following the outermost point. The determined approximate transmit power is multiplied by the power of the transmit equalizer to determine a post-equalizer transmit value. A data rate is selected which is less than a predetermined regulatory limit.

Method for selecting the data rate for PCM upstream transmission

A method for constellation design in a telecommunications network using pulse code modulation to transmit data signals upstream between client and server voice-band modems. The invention selects a constellation for transmission over an analog channel of an equivalence class of data points using pulse code modulation based on the presence or absence of robbed bit signaling and interference from echo levels. The constellation is designed by determining noise in a PCM channel using a cumulative distribution function for echo, determining the extent of said noise for an array of possible constellation points, and selecting constellation points such that the largest negative noise of a first point remains above the largest positive noise level of a neighboring second point. Constellations are created off-line and stored for retrieval during modulation depending on the level of the echo.

Constellation design for PCM upstream modulation

Improved approaches to provide flexibility in setting user data rates and managing delay in data transmission systems using a superframe structure and Time Division Duplexing (TDD) are disclosed. These improved approaches operate to provide intelligent insertion of dummy words (bits or bites) into a data stream to be transmitted. By inserting the dummy words, the invention is able to render codewords, symbols and superframes independent from user data rates. As a result, a wide range of user data rates are available in data transmission systems using a superframe and TDD.

Method and system for accomodating a wide range of user data rates in a multicarrier data transmission system

For PCM upstream, the analog modem must transmit a filtered sequence of symbols so that the samples of the signal at the input to the codec at the central office (CO) are at a predetermined set of levels. This requires that the analog modem use an 8 kHz symbol rate synchronized to the CO clock. Typical telephone channels have nulls at DC and at 4 kHz. Therefore, for best performance, the signal transmitted by the analog modem should be spectrally shaped to match the channel. The present invention utilizes a generalized Laroia-Tretter-Farvardin (LTF) precoder similar to the one used in V.34. This precoder structure allows spectral shaping and could also allow for constellation shaping gains. Using this precoder structure with spectral shaping has the potential to improve data rates by 3-3.5 kbps.

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Chevy Chase, MD, United States of America

Cory Samuel Modlin