129 research outputs found
Integration of Satellites in 5G through LEO Constellations
The standardization of 5G systems is entering in its critical phase, with
3GPP that will publish the PHY standard by June 2017. In order to meet the
demanding 5G requirements both in terms of large throughput and global
connectivity, Satellite Communications provide a valuable resource to extend
and complement terrestrial networks. In this context, we consider a
heterogeneous architecture in which a LEO mega-constellation satellite system
provides backhaul connectivity to terrestrial 5G Relay Nodes, which create an
on-ground 5G network. Since large delays and Doppler shifts related to
satellite channels pose severe challenges to terrestrial-based systems, in this
paper we assess their impact on the future 5G PHY and MAC layer procedures. In
addition, solutions are proposed for Random Access, waveform numerology, and
HARQ procedures.Comment: Submitted to IEEE Global Communications Conference (GLOBECOM) 201
RAN Functional Splits in NTN: Architectures and Challenges
While 5G networks are already being deployed for commercial applications,
Academia and industry are focusing their effort on the development and
standardization of the next generations of mobile networks, i.e., 5G-Advance
and 6G. Beyond 5G networks will revolutionize communications systems providing
seamless connectivity, both in time and in space, to a unique ecosystem
consisting of the convergence of the digital, physical, and human domains. In
this scenario, NonTerrestrial Networks (NTN) will play a crucial role by
providing ubiquitous, secure, and resilient infrastructure fully integrated
into the overall system. The additional network complexity introduced by the
third dimension of the architecture requires the interoperability of different
network elements, enabled by the disaggregation and virtualization of network
components, their interconnection by standard interfaces and orchestration by
data-driven network artificial intelligence. The disaggregation paradigm
foresees the division of the radio access network in different virtualized
block of functions, introducing the concept of functional split. Wisely
selecting the RAN functional split is possible to better exploit the system
resources, obtaining costs saving, and to increase the system performances. In
this paper, we firstly provide a discussion of the current 6G NTN development
in terms of architectural solutions and then, we thoroughly analyze the impact
of the typical NTN channel impairments on the available functional splits.
Finally, the benefits of introducing the dynamic optimization of the functional
split in NTN are analyzed, together with the foreseen challenges
Density-Aware Smart Grid Node Allocation in Heterogeneous Radio Access Technology Environments
Smart grid (SG) is an intelligent enhancement of the conventional energy grid allowing a smarter management. In order to be implemented, SG needs to rely on a communication network connecting different node types, implementing the SG services, with different communication and energy requirements. Heterogeneous network (Het-Net) solutions are very attractive, gaining from the allocation of different radio access technologies (RATs) to the different SG node types; however, due to the heterogeneity of the system, an efficient radio resource optimization and energy management are a complex task. Through the exploitation of the most significant key performance indicators (KPIs) of the SG node types and the key features of the RATs, a joint communication and energy cost function are here defined. Through this approach it is possible to optimally assign the nodes to the RATs while respecting their requirements. In particular, we show the effect of different nodes’ density scenarios on the proposed allocation algorithm
Adaptive Network Coding Schemes for Satellite Communications
In this paper, we propose two novel physical layer aware adaptive network
coding and coded modulation schemes for time variant channels. The proposed
schemes have been applied to different satellite communications scenarios with
different Round Trip Times (RTT). Compared to adaptive network coding, and
classical non-adaptive network coding schemes for time variant channels, as
benchmarks, the proposed schemes demonstrate that adaptation of packet
transmission based on the channel variation and corresponding erasures allows
for significant gains in terms of throughput, delay and energy efficiency. We
shed light on the trade-off between energy efficiency and delay-throughput
gains, demonstrating that conservative adaptive approaches that favors less
transmission under high erasures, might cause higher delay and less throughput
gains in comparison to non-conservative approaches that favor more transmission
to account for high erasures.Comment: IEEE Advanced Satellite Multimedia Systems Conference and the 14th
Signal Processing for Space Communications Workshop (ASMS/SPSC), 201
Network Coding Channel Virtualization Schemes for Satellite Multicast Communications
In this paper, we propose two novel schemes to solve the problem of finding a
quasi-optimal number of coded packets to multicast to a set of independent
wireless receivers suffering different channel conditions. In particular, we
propose two network channel virtualization schemes that allow for representing
the set of intended receivers in a multicast group to be virtualized as one
receiver. Such approach allows for a transmission scheme not only adapted to
per-receiver channel variation over time, but to the network-virtualized
channel representing all receivers in the multicast group. The first scheme
capitalizes on a maximum erasure criterion introduced via the creation of a
virtual worst per receiver per slot reference channel of the network. The
second scheme capitalizes on a maximum completion time criterion by the use of
the worst performing receiver channel as a virtual reference to the network. We
apply such schemes to a GEO satellite scenario. We demonstrate the benefits of
the proposed schemes comparing them to a per-receiver point-to-point adaptive
strategy
Energy Efficient Adaptive Network Coding Schemes for Satellite Communications
In this paper, we propose novel energy efficient adaptive network coding and
modulation schemes for time variant channels. We evaluate such schemes under a
realistic channel model for open area environments and Geostationary Earth
Orbit (GEO) satellites. Compared to non-adaptive network coding and adaptive
rate efficient network-coded schemes for time variant channels, we show that
our proposed schemes, through physical layer awareness can be designed to
transmit only if a target quality of service (QoS) is achieved. As a result,
such schemes can provide remarkable energy savings.Comment: Lecture Notes of the Institute for Computer Sciences, Social
Informatics and Telecommunications Engineering, 24 March 201
Windowed Decoding of Protograph-based LDPC Convolutional Codes over Erasure Channels
We consider a windowed decoding scheme for LDPC convolutional codes that is
based on the belief-propagation (BP) algorithm. We discuss the advantages of
this decoding scheme and identify certain characteristics of LDPC convolutional
code ensembles that exhibit good performance with the windowed decoder. We will
consider the performance of these ensembles and codes over erasure channels
with and without memory. We show that the structure of LDPC convolutional code
ensembles is suitable to obtain performance close to the theoretical limits
over the memoryless erasure channel, both for the BP decoder and windowed
decoding. However, the same structure imposes limitations on the performance
over erasure channels with memory.Comment: 18 pages, 9 figures, accepted for publication in the IEEE
Transactions on Information Theor
Location-assisted precoding in 5G LEO systems: architectures and performances
Satellite communication systems are a fundamental component in support of
Europe's ambition to deploy smart and sustainable networks and services for the
success of its digital economy. To cope with the 5G and beyond ever increasing
demand for larger throughput, aggressive frequency reuse schemes (i.e., full
frequency reuse), with the implementation of precoding/beamforming to cope with
the massive co-channel interference, are recognised as one of the key
technologies. While the best performance can be obtained with the knowledge of
the Channel State Information (CSI) at the transmitter, this also poses some
technical challenges related to signalling and synchronisation. In this paper,
we focus on precoding solutions that only needs the knowledge of the users'
positions at the transmitter side, namely the recently introduced Switchable
Multi-Beam (MB) and Spatially Sampled MMSE (SS-MMSE) precoding. Compared to the
vast majority of the studies in the literature, we take into account both the
users' and the satellite movement in a Low Earth Orbit (LEO)
mega-constellation, also proposing two system architectures. The extensive
numerical assessment provides a valuable insight on the performance of these
two precoding schemes compared to the optimal MMSE solution.Comment: Accepted for publication to EuCNC 202
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