1,189 research outputs found
A General Framework for Transmission with Transceiver Distortion and Some Applications
A general theoretical framework is presented for analyzing information
transmission over Gaussian channels with memoryless transceiver distortion,
which encompasses various nonlinear distortion models including transmit-side
clipping, receive-side analog-to-digital conversion, and others. The framework
is based on the so-called generalized mutual information (GMI), and the
analysis in particular benefits from the setup of Gaussian codebook ensemble
and nearest-neighbor decoding, for which it is established that the GMI takes a
general form analogous to the channel capacity of undistorted Gaussian
channels, with a reduced "effective" signal-to-noise ratio (SNR) that depends
on the nominal SNR and the distortion model. When applied to specific
distortion models, an array of results of engineering relevance is obtained.
For channels with transmit-side distortion only, it is shown that a
conventional approach, which treats the distorted signal as the sum of the
original signal part and a uncorrelated distortion part, achieves the GMI. For
channels with output quantization, closed-form expressions are obtained for the
effective SNR and the GMI, and related optimization problems are formulated and
solved for quantizer design. Finally, super-Nyquist sampling is analyzed within
the general framework, and it is shown that sampling beyond the Nyquist rate
increases the GMI for all SNR. For example, with a binary symmetric output
quantization, information rates exceeding one bit per channel use are
achievable by sampling the output at four times the Nyquist rate.Comment: 32 pages (including 4 figures, 5 tables, and auxiliary materials);
submitted to IEEE Transactions on Communication
A Mixed-ADC Receiver Architecture for Massive MIMO Systems
Motivated by the demand for energy-efficient communication solutions in the
next generation cellular network, a mixed-ADC receiver architecture for massive
multiple input multiple output (MIMO) systems is proposed, which differs from
previous works in that herein one-bit analog-to-digital converters (ADCs)
partially replace the conventionally assumed high-resolution ADCs. The
information-theoretic tool of generalized mutual information (GMI) is exploited
to analyze the achievable data rates of the proposed system architecture and an
array of analytical results of engineering interest are obtained. For
deterministic single input multiple output (SIMO) channels, a closed-form
expression of the GMI is derived, based on which the linear combiner is
optimized. Then, the asymptotic behaviors of the GMI in both low and high SNR
regimes are explored, and the analytical results suggest a plausible ADC
assignment scheme. Finally, the analytical framework is applied to the
multi-user access scenario, and the corresponding numerical results demonstrate
that the mixed system architecture with a relatively small number of
high-resolution ADCs is able to achieve a large fraction of the channel
capacity without output quantization.Comment: 5 pages, 5 figures, to appear in IEEE Information Theory Workshop
(ITW2015
Orthogonal Codes for Robust Low-Cost Communication
Orthogonal coding schemes, known to asymptotically achieve the capacity per
unit cost (CPUC) for single-user ergodic memoryless channels with a zero-cost
input symbol, are investigated for single-user compound memoryless channels,
which exhibit uncertainties in their input-output statistical relationships. A
minimax formulation is adopted to attain robustness. First, a class of
achievable rates per unit cost (ARPUC) is derived, and its utility is
demonstrated through several representative case studies. Second, when the
uncertainty set of channel transition statistics satisfies a convexity
property, optimization is performed over the class of ARPUC through utilizing
results of minimax robustness. The resulting CPUC lower bound indicates the
ultimate performance of the orthogonal coding scheme, and coincides with the
CPUC under certain restrictive conditions. Finally, still under the convexity
property, it is shown that the CPUC can generally be achieved, through
utilizing a so-called mixed strategy in which an orthogonal code contains an
appropriate composition of different nonzero-cost input symbols.Comment: 2nd revision, accepted for publicatio
- …