Browsing by Author "Gaikwad, Rohit V."

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    Signaling Techniques in channels with asymmetric powers and capacities
    (2006-04-25) Gaikwad, Rohit V.; Baraniuk, Richard G.; Rice University; United States Patent and Trademark Office
    An improved system and method for communicating information on a transmission medium is disclosed. The disclosed system and method provide improved communications on the transmission medium in the presence of interference, which may take the form of uncorrelated interference from different services on neighboring transmission mediums. In one embodiment, the communications system includes a subscriber modem, a central office modem; and a communications channel coupled between the subscriber modem and the central office modem. The communications channel transports uplink signals from the subscriber modem to the central office modem, and downlink signals from the central office modem to the subscriber modem. At frequencies below a selected frequency ME2F, the power spectral density of the transmitted uplink signals is proportional to the power spectral density of the transmitted downlink signals by a positive scale factor, and at frequencies above ME2F, the power spectral density of the uplink signals is limited to one or more uplink frequency bands and the power spectral density of the downlink signals is limited to one or more downlink frequency bands that are disjoint from the uplink frequency bands. Preferably, the total bandwidth of the uplink frequency bands above ME2F is proportional to the total bandwidth of the downlink frequency bands above ME2F by the same positive scale factor.
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    Spectral optimization and joint signaling techniques with multi-line separation for communication in the presence of crosstalk
    (2001-11-13) Gaikwad, Rohit V.; Baraniuk, Richard G.; Rice University; United States Patent and Trademark Office
    A system and method for determining transmission characteristics for a communications channel and for transmitting data on the communications channel. In one embodiment, the method starts by determining the channel's transfer function and determining interference characteristics for the channel. The interference characteristics preferably include transfer functions describing the channel's susceptibility to cross talk from neighboring channels. The channel transfer function and the interference characteristics are then examined and a transmit spectrum (or power spectral density function) is constructed for the channel. The transmit spectrum preferably uses orthogonal separation of upstream and downstream communications to increase channel capacity. This method is useable in communicating data when the channel is subject to interference from one or more other communications channels, including near-end cross talk (NEXT) and far-end cross talk (FEXT), from other channels carrying the same service and/or different services. The present invention may be used in digital subscriber-line (xDSL) communications or in a variety of other applications, such as in well-logging and in systems involving multiple interfering radio transmitters.
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    Spectral optimization and joint signaling techniques with upstream/downstream separation for communication in the presence of crosstalk
    (2001-09-18) Gaikwad, Rohit V.; Baraniuk, Richard G.; Rice University; United States Patent and Trademark Office
    A system and method for determining transmission characteristics for a communications channel and for transmitting data on the communications channel. In one embodiment, the method starts by determining the channel's transfer function and determining interference characteristics for the channel. The interference characteristics preferably include transfer functions describing the channel's susceptibility to cross talk from neighboring channels. The channel transfer function and the interference characteristics are then examined and a transmit spectrum (or power spectral density function) is constructed for the channel. The transmit spectrum preferably uses orthogonal separation of upstream and downstream communications to increase channel capacity. This method is useable in communicating data when the channel is subject to interference from one or more other communications channels, including near-end cross talk (NEXT) and far-end cross talk (FEXT), from other channels carrying the same service and/or different services. The present invention may be used in digital subscriber-line (xDSL) communications or in a variety of other applications, such as in well-logging and in systems involving multiple interfering radio transmitters.
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    Spectral optimization for communication under a peak frequency-domain power constraint
    (2005-01-04) Gaikwad, Rohit V.; Baraniuk, Richard G.; Rice University; United States Patent and Trademark Office
    System and methods for determining an optimized transmit spectra (spectral distributions of transmission power) for a set of communications channels that experience cross-talk among themselves and for transmitting data on the channels. The transmit spectra are preferably constructed so that largely contiguous frequency bands are allocated to each signaling direction (upstream/downstream) on each communications channel and/or to each channel in the set of channels. In one embodiment, each communications channel is restricted to a maximum time-averaged power. The method preferably includes steps of determining the channel transfer functions of the communications channel, determining interference characteristics of the channels, calculating substantially optimal transmit spectra for the communications channels, and redistributing the frequency bins so that they are contiguously grouped in each transmit spectra. The contiguous groupings allow wider frequency bands for signaling in the channel. In one embodiment, the channel is limited by a “peak-power constraint.”