14,931 research outputs found
Effective Capacity in Wireless Networks: A Comprehensive Survey
Low latency applications, such as multimedia communications, autonomous
vehicles, and Tactile Internet are the emerging applications for
next-generation wireless networks, such as 5th generation (5G) mobile networks.
Existing physical-layer channel models, however, do not explicitly consider
quality-of-service (QoS) aware related parameters under specific delay
constraints. To investigate the performance of low-latency applications in
future networks, a new mathematical framework is needed. Effective capacity
(EC), which is a link-layer channel model with QoS-awareness, can be used to
investigate the performance of wireless networks under certain statistical
delay constraints. In this paper, we provide a comprehensive survey on existing
works, that use the EC model in various wireless networks. We summarize the
work related to EC for different networks such as cognitive radio networks
(CRNs), cellular networks, relay networks, adhoc networks, and mesh networks.
We explore five case studies encompassing EC operation with different design
and architectural requirements. We survey various delay-sensitive applications
such as voice and video with their EC analysis under certain delay constraints.
We finally present the future research directions with open issues covering EC
maximization
Distributed Scheduling in Multiple Access with Bursty Arrivals and Delay Constraints
A multiple access system with bursty data arrivals to the terminals is
considered. The users are frame-synchronized, with variable sized packets
independently arriving in each slot at every transmitter. Each packet needs to
be delivered to a common receiver within a certain number of slots specified by
a maximum delay constraint. The key assumption is that the terminals know only
their own packet arrival process, i.e. the arrivals at the rest of the
terminals are unknown to each transmitter, except for their statistics. For
this interesting distributed multiple access model, we design novel online
communication schemes which transport the arriving data without any outage,
while ensuring the delay constraint. In particular, the transmit powers in each
slot are chosen in a distributed manner, ensuring at the same time that the
joint power vector is sufficient to support the distributed choice of
data-rates employed in that slot. The proposed schemes not only are optimal for
minimizing the average transmit sum-power, but they also considerably
outperform conventional orthogonal multiple access techniques like TDMA.Comment: 39 pages, 16 figures, presented in part at ISIT 201
Delay-limited Source and Channel Coding of Quasi-Stationary Sources over Block Fading Channels: Design and Scaling Laws
In this paper, delay-limited transmission of quasi-stationary sources over
block fading channels are considered. Considering distortion outage probability
as the performance measure, two source and channel coding schemes with power
adaptive transmission are presented. The first one is optimized for fixed rate
transmission, and hence enjoys simplicity of implementation. The second one is
a high performance scheme, which also benefits from optimized rate adaptation
with respect to source and channel states. In high SNR regime, the performance
scaling laws in terms of outage distortion exponent and asymptotic outage
distortion gain are derived, where two schemes with fixed transmission power
and adaptive or optimized fixed rates are considered as benchmarks for
comparisons. Various analytical and numerical results are provided which
demonstrate a superior performance for source and channel optimized rate and
power adaptive scheme. It is also observed that from a distortion outage
perspective, the fixed rate adaptive power scheme substantially outperforms an
adaptive rate fixed power scheme for delay-limited transmission of
quasi-stationary sources over wireless block fading channels. The effect of the
characteristics of the quasi-stationary source on performance, and the
implication of the results for transmission of stationary sources are also
investigated.Comment: 22 pages,5 figure
Channel-Adaptive Sensing Strategy for Cognitive Radio Ad Hoc Networks
In Cognitive Radio (CR) ad hoc networks, secondary users (SU) attempt to
utilize valuable spectral resources without causing significant interference to
licensed primary users (PU). While there is a large body of research on
spectrum opportunity detection, exploitation, and adaptive transmission in CR,
most existing approaches focus only on avoiding PU activity when making sensing
decisions. Since the myopic sensing strategy results in congestion and poor
throughput, several collision-avoidance sensing approaches were investigated in
the literature. However, they provide limited improvement. A channel-aware
myopic sensing strategy that adapts the reward to the fading channel state
information (CSI) of the SU link is proposed. This CSI varies over the CR
spectrum and from one SU pair to another due to multipath and shadow fading,
thus randomizing sensing decisions and increasing the network throughput. The
proposed joint CSI adaptation at the medium access control (MAC) and physical
layers provides large throughput gain over randomized sensing strategies and/or
conventional adaptive transmission methods. The performance of the proposed
CSI-aided sensing strategy is validated for practical network scenarios and
demonstrated to be robust to CSI mismatch, sensing errors, and spatial channel
correlation.Comment: 6 pages, 8 figures, CCNC 201
Power Control and Performance Analysis of Outage-Limited Cellular Network with MUD-SIC and Macro-Diversity
In this paper, we analyze the uplink goodput (bits/sec/Hz successfully
decoded) and per-user packet outage in a cellular network using multi-user
detection with successive interference cancellation (MUD-SIC). We consider
non-ergodic fading channels where microscopic fading channel information is not
available at the transmitters. As a result, packet outage occurs whenever the
data rate of packet transmissions exceeds the instantaneous mutual information
even if powerful channel coding is applied for protection. We are interested to
study the role of macro-diversity (MDiv) between multiple base stations on the
MUD-SIC performance where the effect of potential error-propagation during the
SIC processing is taken into account. While the jointly optimal power and
decoding order in the MUD-SIC are NP hard problem, we derive a simple on/off
power control and asymptotically optimal decoding order with respect to the
transmit power. Based on the information theoretical framework, we derive the
closed-form expressions on the total system goodput as well as the per-user
packet outage probability. We show that the system goodput does not scale with
SNR due to mutual interference in the SIC process and macro-diversity (MDiv)
could alleviate the problem and benefit to the system goodput
Power Controlled Adaptive Sum-Capacity of Fading MACs with Distributed CSI
We consider the problem of finding optimal, fair and distributed power-rate
strategies to achieve the sum capacity of the Gaussian multiple-access
block-fading channel. In here, the transmitters have access to only their own
fading coefficients, while the receiver has global access to all the fading
coefficients. Outage is not permitted in any communication block. The resulting
average sum-throughput is also known as `power-controlled adaptive
sum-capacity', which appears as an open problem in literature.
This paper presents the power-controlled adaptive sum-capacity of a
wide-class of popular MAC models. In particular, we propose a power-rate
strategy in the presence of distributed channel state information (CSI), which
is throughput optimal when all the users have identical channel statistics. The
proposed scheme also has an efficient implementation using successive
cancellation and rate-splitting. We propose an upperbound when the channel laws
are not identical. Furthermore, the optimal schemes are extended to situations
in which each transmitter has additional finite-rate partial CSI on the link
quality of others.Comment: 15 pages, 5 figures, combined and extended version of ITW 2011 and
ISITA 2012 paper
Effective Capacity Analysis of Cognitive Radio Channels for Quality of Service Provisioning
In this paper, cognitive transmission under quality of service (QoS)
constraints is studied. In the cognitive radio channel model, it is assumed
that the secondary transmitter sends the data at two different average power
levels, depending on the activity of the primary users, which is determined by
channel sensing performed by the secondary users. A state-transition model is
constructed for this cognitive transmission channel. Statistical limitations on
the buffer lengths are imposed to take into account the QoS constraints. The
maximum throughput under these statistical QoS constraints is identified by
finding the effective capacity of the cognitive radio channel. This analysis is
conducted for fixed-power/fixed-rate, fixed-power/variable-rate, and
variable-power/variable-rate transmission schemes under different assumptions
on the availability of channel side information (CSI) at the transmitter. The
impact upon the effective capacity of several system parameters, including
channel sensing duration, detection threshold, detection and false alarm
probabilities, QoS parameters, and transmission rates, is investigated. The
performances of fixed-rate and variable-rate transmission methods are compared
in the presence of QoS limitations. It is shown that variable schemes
outperform fixed-rate transmission techniques if the detection probabilities
are high. Performance gains through adapting the power and rate are quantified
and it is shown that these gains diminish as the QoS limitations become more
stringent
On Green Multicasting over Cognitive Radio Fading Channels
In this paper, an underlay cognitive radio (CR) multicast network, consisting
of a cognitive base station (CBS) and multiple multicast groups of secondary
users (SUs), is considered. All SUs, belonging to a particular multicast group,
are served by the CBS using a common primary user (PU) channel. The goal is to
maximize the energy efficiency (EE) of the system, through dynamic adaptation
of target rate and transmit power for each multicast group, under the PUs'
individual interference constraints. The optimization problem formulated for
this is proved to be non quasi-concave with respect to the joint variation of
the CBS's transmit power and target rate. An efficient iterative algorithm for
EE maximization is proposed along with its complexity analysis. Simulation
results illustrate the performance gain of our proposed scheme.Comment: 5 pages, 4 figures, Submitted in IEEE Transactions on Vehicular
Technolog
On the Capacity of Joint Fading and Two-path Shadowing Channels
The ergodic and outage channel capacity of different optimal and suboptimal
combinations of transmit power and modulation rate adaptation strategies over a
joint fading and two-path shadowing (JFTS) fading/shadowing channel is studied
in this paper. Analytically tractable expressions for channel capacity are
obtained, assuming perfect channel side information (CSI) at the receiver
and/or the transmitter with negligible feedback delay. Furthermore, the impacts
of the JFTS parameters on the channel capacity achieved by these adaptive
transmission techniques are determined
An Intercell Interference Model based on Scheduling for Future Generation Wireless Networks (Part 1 and Part 2)
This technical report is divided into two parts. The first part of the
technical report presents a novel framework for modeling the uplink and
downlink intercell interference (ICI) in a multiuser cellular network. The
proposed framework assists in quantifying the impact of various fading channel
models and multiuser scheduling schemes on the uplink and downlink ICI.
Firstly, we derive a semi-analytical expression for the distribution of the
location of the scheduled user in a given cell considering a wide range of
scheduling schemes. Based on this, we derive the distribution and moment
generating function (MGF) of the ICI considering a single interfering cell.
Consequently, we determine the MGF of the cumulative ICI observed from all
interfering cells and derive explicit MGF expressions for three typical fading
models. Finally, we utilize the obtained expressions to evaluate important
network performance metrics such as the outage probability, ergodic capacity
and average fairness numerically. Monte-Carlo simulation results are provided
to demonstrate the efficacy of the derived analytical expressions {\bf The
first part of the technical report is currently submitted to IEEE Transactions
on Wireless Communications}. The second part of the technical report deals with
the statistical modeling of uplink inter-cell interference (ICI) considering
greedy scheduling with power adaptation based on channel conditions. The
derived model is utilized to evaluate important network performance metrics
such as ergodic capacity, average fairness and average power preservation
numerically. In parallel to the literature, we have shown that greedy
scheduling with power adaptation reduces the ICI, average power consumption of
users, and enhances the average fairness among users, compared to the case
without power adaptation
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