5,587 research outputs found
On the capacity of fading channels with amplitude-limited inputs
We address the problem of finding the capacity of fading channels under the assumption of amplitude-limited inputs. Specifically, we show that if the fading coefficients have a finite support and the channel state information is only available at the receiver side, there is a unique input distribution that achieves the channel capacity and this input distribution is discrete with a finite number of mass points. © 2016 IEEE
Low SNR Capacity of Noncoherent Fading Channels
Discrete-time Rayleigh fading single-input single-output (SISO) and
multiple-input multiple-output (MIMO) channels are considered, with no channel
state information at the transmitter or the receiver. The fading is assumed to
be stationary and correlated in time, but independent from antenna to antenna.
Peak-power and average-power constraints are imposed on the transmit antennas.
For MIMO channels, these constraints are either imposed on the sum over
antennas, or on each individual antenna. For SISO channels and MIMO channels
with sum power constraints, the asymptotic capacity as the peak signal-to-noise
ratio tends to zero is identified; for MIMO channels with individual power
constraints, this asymptotic capacity is obtained for a class of channels
called transmit separable channels. The results for MIMO channels with
individual power constraints are carried over to SISO channels with delay
spread (i.e. frequency selective fading).Comment: submitted to IEEE I
The Noncoherent Rician Fading Channel -- Part I : Structure of the Capacity-Achieving Input
Transmission of information over a discrete-time memoryless Rician fading
channel is considered where neither the receiver nor the transmitter knows the
fading coefficients. First the structure of the capacity-achieving input
signals is investigated when the input is constrained to have limited
peakedness by imposing either a fourth moment or a peak constraint. When the
input is subject to second and fourth moment limitations, it is shown that the
capacity-achieving input amplitude distribution is discrete with a finite
number of mass points in the low-power regime. A similar discrete structure for
the optimal amplitude is proven over the entire SNR range when there is only a
peak power constraint. The Rician fading with phase-noise channel model, where
there is phase uncertainty in the specular component, is analyzed. For this
model it is shown that, with only an average power constraint, the
capacity-achieving input amplitude is discrete with a finite number of levels.
For the classical average power limited Rician fading channel, it is proven
that the optimal input amplitude distribution has bounded support.Comment: To appear in the IEEE Transactions on Wireless Communication
Unified Capacity Limit of Non-coherent Wideband Fading Channels
In non-coherent wideband fading channels where energy rather than spectrum is
the limiting resource, peaky and non-peaky signaling schemes have long been
considered species apart, as the first approaches asymptotically the capacity
of a wideband AWGN channel with the same average SNR, whereas the second
reaches a peak rate at some finite critical bandwidth and then falls to zero as
bandwidth grows to infinity. In this paper it is shown that this distinction is
in fact an artifact of the limited attention paid in the past to the product
between the bandwidth and the fraction of time it is in use. This fundamental
quantity, called bandwidth occupancy, measures average bandwidth usage over
time. For all signaling schemes with the same bandwidth occupancy, achievable
rates approach to the wideband AWGN capacity within the same gap as the
bandwidth occupancy approaches its critical value, and decrease to zero as the
occupancy goes to infinity. This unified analysis produces quantitative
closed-form expressions for the ideal bandwidth occupancy, recovers the
existing capacity results for (non-)peaky signaling schemes, and unveils a
trade-off between the accuracy of approximating capacity with a generalized
Taylor polynomial and the accuracy with which the optimal bandwidth occupancy
can be bounded.Comment: Accepted for publication in IEEE Transactions on Wireless
Communications. Copyright may be transferred without notic
One-Bit Massive MIMO: Channel Estimation and High-Order Modulations
We investigate the information-theoretic throughout achievable on a fading
communication link when the receiver is equipped with one-bit analog-to-digital
converters (ADCs). The analysis is conducted for the setting where neither the
transmitter nor the receiver have a priori information on the realization of
the fading channels. This means that channel-state information needs to be
acquired at the receiver on the basis of the one-bit quantized channel outputs.
We show that least-squares (LS) channel estimation combined with joint pilot
and data processing is capacity achieving in the single-user,
single-receive-antenna case.
We also investigate the achievable uplink throughput in a massive
multiple-input multiple-output system where each element of the antenna array
at the receiver base-station feeds a one-bit ADC. We show that LS channel
estimation and maximum-ratio combining are sufficient to support both multiuser
operation and the use of high-order constellations. This holds in spite of the
severe nonlinearity introduced by the one-bit ADCs
Energy Harvesting Wireless Communications: A Review of Recent Advances
This article summarizes recent contributions in the broad area of energy
harvesting wireless communications. In particular, we provide the current state
of the art for wireless networks composed of energy harvesting nodes, starting
from the information-theoretic performance limits to transmission scheduling
policies and resource allocation, medium access and networking issues. The
emerging related area of energy transfer for self-sustaining energy harvesting
wireless networks is considered in detail covering both energy cooperation
aspects and simultaneous energy and information transfer. Various potential
models with energy harvesting nodes at different network scales are reviewed as
well as models for energy consumption at the nodes.Comment: To appear in the IEEE Journal of Selected Areas in Communications
(Special Issue: Wireless Communications Powered by Energy Harvesting and
Wireless Energy Transfer
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