Browsing by Author "Gaikwad, Rohit"
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Item Joint signaling techniques and spectral optimization for symmetric bit-rate communication over self-NEXT-dominated channels(2004-07-01) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)We present a framework for maximizing the capacity of symmetric bit-rate communication services dominated by Gaussian crosstalk, in particular, digital subscriber line (DSL) services. We solve for optimal transmit power spectral densities (PSDs) that maximize the joint capacity of same-service users and yield significant gains in bit rates (or performance margins) over current schemes. Our results differ from previous work in that we develop transmit spectra in the presence of self-far-end crosstalk in addition to self-near-end crosstalk, present optimal contiguous spectra for practical modulation schemes, and derive optimal spectra under an additional frequency-domain peak-power constraint. Furthermore, by design, the optimal transmit PSDs are spectrally compatible with existing services on neighboring lines.Item Joint Signaling Techniques for Crosstalk-Dominated Communication Channels(1999-12-01) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)We present a framework for maximizing the capacity (or bit rate) of symmetric bit rate communication services dominated by crosstalk, in particular digital subscriber line (DSL) services. We assume the DSL channel is a Gaussian channel, so transmit power spectral density (PSD) design is sufficient to maximize bit rates. Using the channel, noise, and crosstalk transfer functions, we set up an optimization problem and solve for transmit PSDs that maximize the joint capacity of same service users. Joint signaling techniques and optimal power distribution yield significant gains in bit rates (or performance margins) over current schemes. Furthermore, the designed transmit PSDs are inherently spectrally compatible with existing services on neighboring lines. We purposefully design a general framework; it does not depend on the exact choice of modulation scheme, for example. It is also extremely simple and of low computational complexity. The framework can also apply to other channels besides DSLs, such as wireless channels, coaxial cables, power lines, and telemetry cables used in geophysical well-logging tools.Item Optimal Signaling Strategies for Symmetric and Asymmetric Bit-Rate Communication Services in the Presence of Crosstalk(1999-01-15) Gaikwad, Rohit; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)We have invented a new modem technology for transmitting data on conventional telephone lines (twisted pairs) at high speeds. This discovery is timely, as new standards are being developed for this Digital Subscriber Line (DSL) technology at this very moment. The potential market for the new modem technology is massive, as the telephone service providers wish to offer Internet access to the masses using the current phone lines into the home. Key to the deployment of any new service is the distribution of power over frequency, for new services must be designed to be robust to interference that might be caused by other services that are carried by neighboring telephone lines. As well, new services cannot interfere with existing services. We have made two discoveries. The first is an optimization technique that provides the best possible distribution of power (over frequency) for any new DSL service given the interference from other known services that are carried by neighboring telephone lines in the same cable. The second is a power istribution scheme that minimizes the interference caused by the new DSL service into neighboring lines. This new modem technology can be applied to many channels besides the telephone channel (for example, coaxial cables, power lines, wireless channels, and telemetry cables used in geophysical well-logging tools).Item Optimal Transmit Spectra for Communication in the Presence of Crosstalk(1999-06-01) Gaikwad, Rohit; Baraniuk, Richard G.; Center for Multimedia Communications (http://cmc.rice.edu/); Digital Signal Processing (http://dsp.rice.edu/)This paper presents a general framework for designing optimal transmit spectra for symmetric bit-rate communication services dominated by crosstalk, in particular Digital Subscriber Line (DSL) services such as the proposed HDSL2. Using the channel, noise, and interference transfer functions, we set up and solve an optimization problem to maximize the joint capacity of neighboring lines. Joint signaling techniques and optimal power distribution yield significant gains in bit rates (or performance margins) over current schemes. Furthermore, by design, the spectra are spectrally compatible with existing neighboring services. The framework is quite general --- it does not depend on the exact choice of modulation scheme, for example. It is also extremely simple and of low computational complexity.Item Optimal Transmit Spectra for Communication on Digital Subscriber Lines(1999-02-01) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)This paper presents a general framework for designing optimal transmit spectra for symmetric bit-rate communication services dominated by crosstalk, in particular Digital Subscriber Line (DSL) services such as the proposed HDSL2. Using the channel, noise, and interference transfer functions, we set up and solve an optimization problem to maximize the joint capacity of neighboring lines. Joint signaling techniques and optimal power distribution yield significant gains in bit rates (or performance margins) over current schemes. Furthermore, by design, the spectra are spectrally compatible with existing neighboring services. The framework is quite general --- it does not depend on the exact choice of modulation scheme, for example. It is also extremely simple and of low computational complexity.Item Optimal Transmit Spectra for HDSL2(1998-01-15) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)We present a general framework for designing optimal transmit spectra for the HDSL2 service. Using the channel and interference transfer functions and SNR estimates, we set up and solve an optimization problem to maximize the capacity. Sizable gains in performance margins (or bit rates) result. Furthermore, by design, the spectra are spectrally compatible with other services. While the framework is quite general - it does not depend on the exact choice of modulation scheme, for example - it is also extremely simple and of low computationaly complexity. Our results can be used either for dynamically adapting the signaling spectra to account for changing noise or intereference conditions or for the design of new fixed transmit spectral masks using worst-case analysis.Item Optimal Transmit Spectra for HDSL2 under a Peak Frequency-Domain Power Constraint(1998-01-15) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)We present a technique for designing optimal transmit spectra for the HDSL2 service subject to a peak power constraint in the frequency domain. The peak power constraint might be imposed either due to engineering considerations or in order to optimize the transmission under a fixed transmit spectral mask (the OPTIS mask, for example). Using the channel and intereference transfer functions, SNR estimates, and the peak constraint, we set up and solve an optimization problem to maximize the capacity. Sizable gains in performance margins (or bit rates) result. While the technique is quite general - it does not depend on the exact choice of modulation scheme, for example - it is also extremely simple and of low computational complexity.Item Spectral Optimization and Joint Signaling Techniques for Communication in the Presence of Crosstalk(1998-01-15) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)We have invented a new modem technology for transmitting data on conventional telephone lines (twisted pairs) at high speeds. This discovery is timely, as new standards are being developed for this Digital Subscriber Line (DSL) technology at this very moment. The potential market for the new modem technology is massive, as the telephone service providers wish to offer Internet access to the masses using the current phone lines into the home. Key to the deployment of any new service is the distribution of power over frequency, for new services must be designed to be robust to interference that might be caused by other services that are carried by neighboring telephone lines. As well, new services cannot interfere with existing services. We have made two discoveries. The first is an optimization technique that provides the best possible distribution of power (over frequency) for any new DSL service given the interference from other known services that are carried by neighboring telephone lines in the same cable. The second is a power istribution scheme that minimizes the interference caused by the new DSL service into neighboring lines. This new modem technology can be applied to many channels besides the telephone channel (for example, coaxial cables, power lines, wireless channels, and telemetry cables used in geophysical well-logging tools).Item Spectral Optimization for Communication in the Presence of Crosstalk(1999-03-01) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)This paper presents a general framework for designing optimal transmit spectra for communication services dominated by crosstalk --- for example Digital Subscriber Lines (DSLs) and wireless LANs. Using the channel, noise, and interference transfer functions, we set up and solve an optimization problem to maximize the joint channel capacity. We employ joint signaling techniques and optimal power distribution to yield significant gains in bit rates (or performance margins). Furthermore, by design, the spectra are spectrally compatible with existing neighboring services. The framework is quite general; it does not depend on the exact choice of the modulation scheme, for example. It is also extremely simple and of low computational complexity.Item Transmit Spectra Adaptive to Noise and Interference at Activation for HDSL2(1998-01-15) Gaikwad, Rohit; Baraniuk, Richard G.; Digital Signal Processing (http://dsp.rice.edu/)We present several methods for implementing optimal HDSL2 transmit spectra that, at activation, adapt to the surrounding interference and noise. The methods are based around either a set of fixed transmit filters or a single adaptive transmit filter that uses the optimal transmit spectrum. Designing optimal spectra with minimum required power can further increase the spectral compatibility of the system. Transmit spectrum can be adapted on-line to changes in intereference characteristics desired margin is reached (power control). Adaptation of transmit spectra to intereference and noise could be made an option in the HDSL2 standard.