100 research outputs found
Detection and mitigation of indirect conflicts between xApps in Open Radio Access Networks
In Open Radio Access Networks, the Conflict Mitigation component, which is
part of the Near-RT RIC, aims to detect and resolve any conflicts between xApp
decisions. In this paper, we propose a universal method for detecting and
resolving of indirect conflicts between xApps. Its efficiency is validated by
extensive computer simulations. Our results demonstrate that, in the considered
scenario, the mean bitrate satisfaction of users increases by 2%, while the
number of radio link failures and ping-pong handovers in the network is
significantly reduced
DVB-T signal detection for indoor environments in low-SNR regime
The problem of coexistence between the primary
(licensed) and secondary (non-licensed) users can be solved
in various ways. One of them assumes the application of the
detailed Radio Environment Maps being a kind of database,
where some crucial information about the licensed
transmission can be stored. In this paper we propose the
new methods for signal detection in low signal-to-noise
regime and compare it through hardware experiment with
other known techniques used for spectrum sensing.Peer ReviewedPostprint (author’s final draft
Federated Learning-Based Interference Modeling for Vehicular Dynamic Spectrum Access
A platoon-based driving is a technology allowing vehicles to follow each
other at close distances to, e.g., save fuel. However, it requires reliable
wireless communications to adjust their speeds. Recent studies have shown that
the frequency band dedicated for vehicle-to-vehicle communications can be too
busy for intra-platoon communications. Thus it is reasonable to use additional
spectrum resources, of low occupancy, i.e., secondary spectrum channels. The
challenge is to model the interference in those channels to enable proper
channel selection. In this paper, we propose a two-layered Radio Environment
Map (REM) that aims at providing platoons with accurate location-dependent
interference models by using the Federated Learning approach. Each platoon is
equipped with a Local REM that is updated on the basis of raw interference
samples and previous interference model stored in the Global REM. The model in
global REM is obtained by merging models reported by platoons. The nodes
exchange only parameters of interference models, reducing the required control
channel capacity. Moreover, in the proposed architecture platoon can utilize
Local REM to predict channel occupancy, even when the connection to the Global
REM is temporarily unavailable. The proposed system is validated via computer
simulations considering non-trivial interference patterns
Crystallized Rate Regions for MIMO Transmission
International audienceWhen considering the multiuser SISO interference channel, the allowable rate region is not convex and the maximization of the aggregated rate of all the users by the means of transmission power control becomes inefficient. Hence, a concept of the crystallized rate regions has been proposed, where the time-sharing approach is considered to maximize the sumrate.In this paper, we extend the concept of crystallized rate regions from the simple SISO interference channel case to the MIMO/OFDM interference channel. As a first step, we extend the time-sharing convex hull from the SISO to the MIMO channel case. We provide a non-cooperative game-theoretical approach to study the achievable rate regions, and consider the Vickrey-Clarke-Groves (VCG) mechanism design with a novel cost function. Within this analysis, we also investigate the case of OFDM channels, which can be treated as the special case of MIMO channels when the channel transfer matrices are diagonal. In the second step, we adopt the concept of correlated equilibrium into the case of two-user MIMO/OFDM, and we introduce a regret-matching learning algorithm for the system to converge to the equilibrium state. Moreover, we formulate the linear programming problem to find the aggregated rate of all users and solve it using the Simplex method. Finally, numerical results are provided to confirm our theoretical claims and show the improvement provided by this approach
Path Loss and Shadowing Modeling for Vehicle-to-Vehicle Communications in Terrestrial TV Band
Vehicle platooning is considered as one of the key use cases for
vehicle-to-vehicle (V2V) communications. However, its benefits can be realized
only with highly reliable wireless transmission. As the 5.9GHz frequency band
used for V2V suffers from high congestion, in this paper, we consider the use
of the terrestrial TV frequencies for intra-platoon communications. In order to
be able to evaluate the potential of the new bands fully, propagation models
for V2V communications at such frequencies are needed. Therefore, this paper
reports new V2V propagation measurements and their modeling results.
Particularly, we propose a Double Slope Double Shadowing model as the most
accurate one, based on a comparison of various models using the Bayesian
Information Criteria. We also investigate the space-time autocorrelation
properties of the shadowing, which turned out to be dependent on the speed of
vehicles. The proposed path loss and shadowing model differs from the ones
proposed for the 5.9GHz band. Mostly, in favor of the TV band, as shown by,
e.g., no statistically significant impact of a blocking car
Technical advances in the design and deployment of future heterogeneous networks
The trend in wireless communications systems is the enhancement of the network infrastructure with the introduction of small cells, where a specific geographical area is served by low-range, low-power access points. The result is the creation of a heterogeneous topology where macrocells coexist with a variety of small-cell types. In this editorial article we briefly summarize the recent technical advances in the design and deployment of future heterogeneous networks addressed in the papers that compose this special issue. In particular the following aspects are considered: the design of interference and radio resource management algorithms, the analysis of the energy efficiency and power control issues in heterogeneous networks, the concept of coordination in small cell networks, key backhaul aspects of HetNets, deployment issues and overall management strategies.Peer ReviewedPostprint (published version
DVB-T channels power measurements in indoor/outdoor cases
In this paper the analysis of the spectrum
occupancy in the TV band is provided based on the indoor and
outdoor measurements campaigns carried out in Poznan, Poland,
and Barcelona, Spain, in 2013. The goal of this work is to discuss
the stability and other important features of the observed
spectrum occupancy in the context of indoor/outdoor Radio
Environment Maps database deployment. Reliable deployment of
these databases seems to be one of the critical points in practical
utilization of the TV White Spaces for cognitive purposes inside
buildings and in densely populated cities.Postprint (published version
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