Rohit V. Gaikwad

Optimal transmit spectra for communication in the presence of crosstalk

We present 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.

Joint signaling techniques for crosstalk-dominated communication channels

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.

A 2×2 MIMO baseband for high-throughput wireless local-area networking (802.11n)

This article consists of a collection of slides from the authors conference presentation on a 2X2 MIMO basedband system for high throughput wireless local area networking. Some of the specific topics discussed include: the demand for wireless LAN, 2000-2011; schemas of multipath channels; exploiting multipath processing for high rates and the impact on energy capacity planning; system architecture for MIMO-ODFM; system processing capabilities and performance summaries; the need for flexible transceivers; and block diagrams and system topologies.

Joint signaling techniques and spectral optimization for symmetric bit-rate communication over self-NEXT-dominated channels

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.