225 research outputs found
A Queueing Characterization of Information Transmission over Block Fading Rayleigh Channels in the Low SNR
Unlike the AWGN (additive white gaussian noise) channel, fading channels
suffer from random channel gains besides the additive Gaussian noise. As a
result, the instantaneous channel capacity varies randomly along time, which
makes it insufficient to characterize the transmission capability of a fading
channel using data rate only. In this paper, the transmission capability of a
buffer-aided block Rayleigh fading channel is examined by a constant rate input
data stream, and reflected by several parameters such as the average queue
length, stationary queue length distribution, packet delay and overflow
probability. Both infinite-buffer model and finite-buffer model are considered.
Taking advantage of the memoryless property of the service provided by the
channel in each block in the the low SNR (signal-to-noise ratio) regime, the
information transmission over the channel is formulated as a \textit{discrete
time discrete state} queueing problem. The obtained results show that
block fading channels are unable to support a data rate close to their ergodic
capacity, no matter how long the buffer is, even seen from the application
layer. For the finite-buffer model, the overflow probability is derived with
explicit expression, and is shown to decrease exponentially when buffer size is
increased, even when the buffer size is very small.Comment: 29 pages, 11 figures. More details on the proof of Theorem 1 and
proposition 1 can be found in "Queueing analysis for block fading Rayleigh
channels in the low SNR regime ", IEEE WCSP 2013.It has been published by
IEEE Trans. on Veh. Technol. in Feb. 201
Throughput Analysis of Buffer-Constrained Wireless Systems in the Finite Blocklength Regime
In this paper, wireless systems operating under queueing constraints in the
form of limitations on the buffer violation probabilities are considered. The
throughput under such constraints is captured by the effective capacity
formulation. It is assumed that finite blocklength codes are employed for
transmission. Under this assumption, a recent result on the channel coding rate
in the finite blocklength regime is incorporated into the analysis and the
throughput achieved with such codes in the presence of queueing constraints and
decoding errors is identified. Performance of different transmission strategies
(e.g., variable-rate, variable-power, and fixed-rate transmissions) is studied.
Interactions between the throughput, queueing constraints, coding blocklength,
decoding error probabilities, and signal-to-noise ratio are investigated and
several conclusions with important practical implications are drawn
Queueing analysis of opportunistic scheduling with spatially correlated channels
International audienc
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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MIMO Wireless Communications Under Statistical Queueing Constraints
The performance of multiple-input multiple-output (MIMO) wireless systems is investigated in the presence of statistical queueing constraints. Queuing constraints are imposed as limitations on buffer violation probabilities. The performance under such constraints is captured through the effective capacity formulation. A detailed analysis of the effective capacity is carried out in the low-power, wideband, and high signal-to-noise ratio (SNR) regimes. In the low-power analysis, expressions for the first and second derivatives of the effective capacity with respect to SNR at SNR = 0 are obtained under various assumptions on the degree of channel state information at the transmitter. Transmission strategies that are optimal in the sense of achieving the first and second derivatives are identified. It is shown that while the first derivative does not get affected by the presence of queueing constraints, the second derivative gets smaller as the constraints become more stringent. Through the energy efficiency analysis, this is shown to imply that the minimum bit energy requirements do not change with more strict limitations but the wideband slope diminishes. Similar results are obtained in the wideband regime if rich multipath fading is being experienced. On the other hand, sparse multipath fading with bounded number of degrees of freedom is shown to increase the minimum bit energy requirements in the presence of queueing constraints. Following the low-SNR study, the impact of buffer limitations on the high-SNR performance is quantified by analyzing the high-SNR slope and the power offset in Rayleigh fading channels. Finally, numerical results are provided to illustrate the theoretical findings, and to demonstrate the interactions between the queueing constraints and spatial dimensions over a wide range of SNR values
Uplink Age of Information of Unilaterally Powered Two-way Data Exchanging Systems
We consider a two-way data exchanging system where a master node transfers
energy and data packets to a slave node alternatively. The slave node harvests
the transferred energy and performs information transmission as long as it has
sufficient energy for current block, i.e., according to the best-effort policy.
We examine the freshness of the received packets at the master node in terms of
age of information (AoI), which is defined as the time elapsed after the
generation of the latest received packet. We derive average uplink AoI and
uplink data rate as functions of downlink data rate in closed form. The
obtained results illustrate the performance limit of the unilaterally powered
two-way data exchanging system in terms of timeliness and efficiency. The
results also specify the achievable tradeoff between the data rates of the
two-way data exchanging system.Comment: INFOCOM 2018 AOI Wkshp, 6 page
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