385 research outputs found
On Single-Antenna Rayleigh Block-Fading Channels at Finite Blocklength
This article concerns the maximum coding rate at which data can be transmitted over a noncoherent, single-antenna, Rayleigh block-fading channel using an error-correcting code of a given blocklength with a block-error probability not exceeding a given value. A high-SNR normal approximation of the maximum coding rate is presented that becomes accurate as the signal-to-noise ratio (SNR) and the number of coherence intervals over which we code tend to infinity. Numerical analyses suggest that the approximation is accurate at SNR values above 15dB and when the number of coherence intervals is 10 or more.The work of A. Lancho and T. Koch was supported in part by the Spanish Ministerio de Economia y Competitividad under Grant TEC2013-41718-R and Grant TEC2016-78434-C3-3-R (AEI/FEDER, EU), in part by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme under Grant 714161, and in part by the Comunidad de Madrid under Grant S2103/ICE-2845. The work of A. Lancho further was supported by an FPU fellowship from the Spanish Ministerio de Educación, Cultura y Deporte under Grant FPU14/01274. The work of T. Koch further was supported in part by the Spanish Ministerio de EconomÃa y Competitividad under Grant RYC-2014-16332 and in part by the 7th European Union Framework Programme under Grant 333680. The work of G. Durisi was supported by the Swedish Research Council under Grant 2012-4571 and Grant 2016-03293
Low-latency Ultra Reliable 5G Communications: Finite-Blocklength Bounds and Coding Schemes
Future autonomous systems require wireless connectivity able to support
extremely stringent requirements on both latency and reliability. In this
paper, we leverage recent developments in the field of finite-blocklength
information theory to illustrate how to optimally design wireless systems in
the presence of such stringent constraints. Focusing on a multi-antenna
Rayleigh block-fading channel, we obtain bounds on the maximum number of bits
that can be transmitted within given bandwidth, latency, and reliability
constraints, using an orthogonal frequency-division multiplexing system similar
to LTE. These bounds unveil the fundamental interplay between latency,
bandwidth, rate, and reliability. Furthermore, they suggest how to optimally
use the available spatial and frequency diversity. Finally, we use our bounds
to benchmark the performance of an actual coding scheme involving the
transmission of short packets
Delay Performance of MISO Wireless Communications
Ultra-reliable, low latency communications (URLLC) are currently attracting
significant attention due to the emergence of mission-critical applications and
device-centric communication. URLLC will entail a fundamental paradigm shift
from throughput-oriented system design towards holistic designs for guaranteed
and reliable end-to-end latency. A deep understanding of the delay performance
of wireless networks is essential for efficient URLLC systems. In this paper,
we investigate the network layer performance of multiple-input, single-output
(MISO) systems under statistical delay constraints. We provide closed-form
expressions for MISO diversity-oriented service process and derive
probabilistic delay bounds using tools from stochastic network calculus. In
particular, we analyze transmit beamforming with perfect and imperfect channel
knowledge and compare it with orthogonal space-time codes and antenna
selection. The effect of transmit power, number of antennas, and finite
blocklength channel coding on the delay distribution is also investigated. Our
higher layer performance results reveal key insights of MISO channels and
provide useful guidelines for the design of ultra-reliable communication
systems that can guarantee the stringent URLLC latency requirements.Comment: This work has been submitted to the IEEE for possible publication.
Copyright may be transferred without notice, after which this version may no
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Finite-Blocklength Bounds on the Maximum Coding Rate of Rician Fading Channels with Applications to Pilot-Assisted Transmission
We present nonasymptotic bounds on the maximum coding rate achievable over a
Rician block-fading channel for a fixed packet size and a fixed packet error
probability. Our bounds, which apply to the scenario where no a priori channel
state information is available at the receiver, allow one to quantify the
tradeoff between the rate gains resulting from the exploitation of
time-frequency diversity and the rate loss resulting from fast channel
variations and pilot-symbol overhead
Optimizing Pilot Overhead for Ultra-Reliable Short-Packet Transmission
In this paper we optimize the pilot overhead for ultra-reliable short-packet
transmission and investigate the dependence of this overhead on packet size and
error probability. In particular, we consider a point-to-point communication in
which one sensor sends messages to a central node, or base-station, over AWGN
with Rayleigh fading channel. We formalize the optimization in terms of
approximate achievable rates at a given block length, pilot length, and error
probability. This leads to more accurate pilot overhead optimization.
Simulation results show that it is important to take into account the packet
size and the error probability when optimizing the pilot overhead.Comment: To be published on IEEE ICC 2017 Communication Theory Symposiu
Short Packets over Block-Memoryless Fading Channels: Pilot-Assisted or Noncoherent Transmission?
We present nonasymptotic upper and lower bounds on the maximum coding rate
achievable when transmitting short packets over a Rician memoryless
block-fading channel for a given requirement on the packet error probability.
We focus on the practically relevant scenario in which there is no \emph{a
priori} channel state information available at the transmitter and at the
receiver. An upper bound built upon the min-max converse is compared to two
lower bounds: the first one relies on a noncoherent transmission strategy in
which the fading channel is not estimated explicitly at the receiver; the
second one employs pilot-assisted transmission (PAT) followed by
maximum-likelihood channel estimation and scaled mismatched nearest-neighbor
decoding at the receiver. Our bounds are tight enough to unveil the optimum
number of diversity branches that a packet should span so that the energy per
bit required to achieve a target packet error probability is minimized, for a
given constraint on the code rate and the packet size. Furthermore, the bounds
reveal that noncoherent transmission is more energy efficient than PAT, even
when the number of pilot symbols and their power is optimized. For example, for
the case when a coded packet of symbols is transmitted using a channel
code of rate bits/channel use, over a block-fading channel with block
size equal to symbols, PAT requires an additional dB of energy per
information bit to achieve a packet error probability of compared to
a suitably designed noncoherent transmission scheme. Finally, we devise a PAT
scheme based on punctured tail-biting quasi-cyclic codes and ordered statistics
decoding, whose performance are close ( dB gap at packet error
probability) to the ones predicted by our PAT lower bound. This shows that the
PAT lower bound provides useful guidelines on the design of actual PAT schemes.Comment: 30 pages, 5 figures, journa
Peak-Age Violation Guarantees for the Transmission of Short Packets over Fading Channels
We investigate the probability that the peak age of information in a
point-to-point communication system operating over a multiantenna wireless
fading channel exceeds a predetermined value. The packets are scheduled
according to a last-come first-serve policy with preemption in service, and are
transmitted over the channel using a simple automatic repetition request
protocol. We consider quadrature phase shift keying modulation, pilot-assisted
transmission, maximum-likelihood channel estimation, and mismatched scaled
nearest-neighbor decoding. Our analysis, which exploits nonasymptotic tools in
information theory, allows one to determine, for a given information packet
size, the physical layer parameters such as the SNR, the number of transmit and
receive antennas, the amount of frequency diversity to exploit, and the number
of pilot symbols, to ensure that the system operates below a target peak-age
violation probability.Comment: 6 pages, 6 figures. To be presented at Infocom 201
Diversity versus Multiplexing at Finite Blocklength
A finite blocklenth analysis of the diversity-multiplexing tradeoff is
presented, based on nonasymptotic bounds on the maximum channel coding rate of
multiple-antenna block-memoryless Rayleigh-fading channels.The bounds in this
paper allow one to numerically assess for which packet size, number of
antennas, and degree of channel selectivity, diversity-exploiting schemes are
close to optimal, and when instead the available spatial degrees of freedom
should be used to provide spatial multiplexing. This finite blocklength view on
the diversity-multiplexing tradeoff provides insights on the design of
delay-sensitive ultra-reliable communication links.Comment: Proc. IEEE Int. Symp. Wirel. Comm. Syst. (ISWCS), Aug. 2014, to
appea
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