52 research outputs found
Stable Wireless Network Control Under Service Constraints
We consider the design of wireless queueing network control policies with
particular focus on combining stability with additional application-dependent
requirements. Thereby, we consequently pursue a cost function based approach
that provides the flexibility to incorporate constraints and requirements of
particular services or applications. As typical examples of such requirements,
we consider the reduction of buffer underflows in case of streaming traffic,
and energy efficiency in networks of battery powered nodes. Compared to the
classical throughput optimal control problem, such requirements significantly
complicate the control problem. We provide easily verifyable theoretical
conditions for stability, and, additionally, compare various candidate cost
functions applied to wireless networks with streaming media traffic. Moreover,
we demonstrate how the framework can be applied to the problem of energy
efficient routing, and we demonstrate the aplication of our framework in
cross-layer control problems for wireless multihop networks, using an advanced
power control scheme for interference mitigation, based on successive convex
approximation. In all scenarios, the performance of our control framework is
evaluated using extensive numerical simulations.Comment: Accepted for publication in IEEE Transactions on Control of Network
Systems. arXiv admin note: text overlap with arXiv:1208.297
Autonomous Algorithms for Centralized and Distributed Interference Coordination: A Virtual Layer Based Approach
Interference mitigation techniques are essential for improving the
performance of interference limited wireless networks. In this paper, we
introduce novel interference mitigation schemes for wireless cellular networks
with space division multiple access (SDMA). The schemes are based on a virtual
layer that captures and simplifies the complicated interference situation in
the network and that is used for power control. We show how optimization in
this virtual layer generates gradually adapting power control settings that
lead to autonomous interference minimization. Thereby, the granularity of
control ranges from controlling frequency sub-band power via controlling the
power on a per-beam basis, to a granularity of only enforcing average power
constraints per beam. In conjunction with suitable short-term scheduling, our
algorithms gradually steer the network towards a higher utility. We use
extensive system-level simulations to compare three distributed algorithms and
evaluate their applicability for different user mobility assumptions. In
particular, it turns out that larger gains can be achieved by imposing average
power constraints and allowing opportunistic scheduling instantaneously, rather
than controlling the power in a strict way. Furthermore, we introduce a
centralized algorithm, which directly solves the underlying optimization and
shows fast convergence, as a performance benchmark for the distributed
solutions. Moreover, we investigate the deviation from global optimality by
comparing to a branch-and-bound-based solution.Comment: revised versio
Zuverlässige und herstellerübergreifende Medizingeräteinteroperabilität: Beiträge zur IEEE 11073 SDC-Normenfamilie
Medizingeräte im Krankenhaus sind heute fast ausschließlich isolierte Insellösungen. Sie stellen nach außen keine Informationen und Interaktionsmöglichkeiten bereit - oder nur innerhalb ihres geschlossenen Ökosystems. Daher führt diese Arbeit in die neue IEEE 11073 Service-oriented Device Connectivity (SDC)-Normenfamilie ein, die eine herstellerübergreifende Interoperabilität ermöglicht. Es werden drei Anwendungsbereiche betrachtet: zuverlässige Fernauslösung von Gerätefunktionalitäten, dynamische Assoziierung von Fernsteuerungselementen und -operationen und verteilte Alarmierungssysteme.Medical devices in today's hospitals are almost always isolated systems, which do not transmit information to or interact with external devices. At the most, this is possible within closed company ecosystems. Thus, this work introduces the new IEEE 11073 Service-oriented Device Connectivity (SDC) family of standards, which provides manufacturer-independent interoperability. Three fields of application are considered: safe activation of a device's functionality, dynamic association of a random number of remote-control elements and remote-controllable operations, and distributed alarm systems
QoS prediction in radio vehicular environments via prior user information
Reliable wireless communications play an important role in the automotive
industry as it helps to enhance current use cases and enable new ones such as
connected autonomous driving, platooning, cooperative maneuvering, teleoperated
driving, and smart navigation. These and other use cases often rely on specific
quality of service (QoS) levels for communication. Recently, the area of
predictive quality of service (QoS) has received a great deal of attention as a
key enabler to forecast communication quality well enough in advance. However,
predicting QoS in a reliable manner is a notoriously difficult task. In this
paper, we evaluate ML tree-ensemble methods to predict QoS in the range of
minutes with data collected from a cellular test network. We discuss radio
environment characteristics and we showcase how these can be used to improve ML
performance and further support the uptake of ML in commercial networks.
Specifically, we use the correlations of the measurements coming from the radio
environment by including information of prior vehicles to enhance the
prediction of the target vehicles. Moreover, we are extending prior art by
showing how longer prediction horizons can be supported
MIMO Systems with Reconfigurable Antennas: Joint Channel Estimation and Mode Selection
Reconfigurable antennas (RAs) are a promising technology to enhance the
capacity and coverage of wireless communication systems. However, RA systems
have two major challenges: (i) High computational complexity of mode selection,
and (ii) High overhead of channel estimation for all modes. In this paper, we
develop a low-complexity iterative mode selection algorithm for data
transmission in an RA-MIMO system. Furthermore, we study channel estimation of
an RA multi-user MIMO system. However, given the coherence time, it is
challenging to estimate channels of all modes. We propose a mode selection
scheme to select a subset of modes, train channels for the selected subset, and
predict channels for the remaining modes. In addition, we propose a prediction
scheme based on pattern correlation between modes. Representative simulation
results demonstrate the system's channel estimation error and achievable
sum-rate for various selected modes and different signal-to-noise ratios
(SNRs)
Machine Learning-based Methods for Reconfigurable Antenna Mode Selection in MIMO Systems
MIMO technology has enabled spatial multiple access and has provided a higher
system spectral efficiency (SE). However, this technology has some drawbacks,
such as the high number of RF chains that increases complexity in the system.
One of the solutions to this problem can be to employ reconfigurable antennas
(RAs) that can support different radiation patterns during transmission to
provide similar performance with fewer RF chains. In this regard, the system
aims to maximize the SE with respect to optimum beamforming design and RA mode
selection. Due to the non-convexity of this problem, we propose machine
learning-based methods for RA antenna mode selection in both dynamic and static
scenarios. In the static scenario, we present how to solve the RA mode
selection problem, an integer optimization problem in nature, via deep
convolutional neural networks (DCNN). A Multi-Armed-bandit (MAB) consisting of
offline and online training is employed for the dynamic RA state selection. For
the proposed MAB, the computational complexity of the optimization problem is
reduced. Finally, the proposed methods in both dynamic and static scenarios are
compared with exhaustive search and random selection methods
5GNOW: Challenging the LTE Design Paradigms of Orthogonality and Synchronicity
LTE and LTE-Advanced have been optimized to deliver high bandwidth pipes to
wireless users. The transport mechanisms have been tailored to maximize single
cell performance by enforcing strict synchronism and orthogonality within a
single cell and within a single contiguous frequency band. Various emerging
trends reveal major shortcomings of those design criteria: 1) The fraction of
machine-type-communications (MTC) is growing fast. Transmissions of this kind
are suffering from the bulky procedures necessary to ensure strict synchronism.
2) Collaborative schemes have been introduced to boost capacity and coverage
(CoMP), and wireless networks are becoming more and more heterogeneous
following the non-uniform distribution of users. Tremendous efforts must be
spent to collect the gains and to manage such systems under the premise of
strict synchronism and orthogonality. 3) The advent of the Digital Agenda and
the introduction of carrier aggregation are forcing the transmission systems to
deal with fragmented spectrum. 5GNOW is an European research project supported
by the European Commission within FP7 ICT Call 8. It will question the design
targets of LTE and LTE-Advanced having these shortcomings in mind and the
obedience to strict synchronism and orthogonality will be challenged. It will
develop new PHY and MAC layer concepts being better suited to meet the upcoming
needs with respect to service variety and heterogeneous transmission setups.
Wireless transmission networks following the outcomes of 5GNOW will be better
suited to meet the manifoldness of services, device classes and transmission
setups present in envisioned future scenarios like smart cities. The
integration of systems relying heavily on MTC into the communication network
will be eased. The per-user experience will be more uniform and satisfying. To
ensure this 5GNOW will contribute to upcoming 5G standardization.Comment: Submitted to Workshop on Mobile and Wireless Communication Systems
for 2020 and beyond (at IEEE VTC 2013, Spring
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