3,437 research outputs found
Radio Resource Management Techniques for Multibeam Satellite Systems
Next-generation of satellite communication (SatCom) networks are expected to
support extremely high data rates for a seamless integration into future large
satellite-terrestrial networks. In view of the coming spectral limitations, the
main challenge is to reduce the cost per bit, which can only be achieved by
enhancing the spectral efficiency. In addition, the capability to quickly and
flexibly assign radio resources according to the traffic demand distribution
has become a must for future multibeam broadband satellite systems. This
article presents the radio resource management problems encountered in the
design of future broadband SatComs and provides a comprehensive overview of the
available techniques to address such challenges. Firstly, we focus on the
demand-matching formulation of the power and bandwidth assignment. Secondly, we
present the scheduling design in practical multibeam satellite systems.
Finally, a number of future challenges and the respective open research topics
are described.Comment: Submitted to IEEE Communications Letter
Evolution of High Throughput Satellite Systems: Vision, Requirements, and Key Technologies
High throughput satellites (HTS), with their digital payload technology, are
expected to play a key role as enablers of the upcoming 6G networks. HTS are
mainly designed to provide higher data rates and capacities. Fueled by
technological advancements including beamforming, advanced modulation
techniques, reconfigurable phased array technologies, and electronically
steerable antennas, HTS have emerged as a fundamental component for future
network generation. This paper offers a comprehensive state-of-the-art of HTS
systems, with a focus on standardization, patents, channel multiple access
techniques, routing, load balancing, and the role of software-defined
networking (SDN). In addition, we provide a vision for next-satellite systems
that we named as extremely-HTS (EHTS) toward autonomous satellites supported by
the main requirements and key technologies expected for these systems. The EHTS
system will be designed such that it maximizes spectrum reuse and data rates,
and flexibly steers the capacity to satisfy user demand. We introduce a novel
architecture for future regenerative payloads while summarizing the challenges
imposed by this architecture
Seamless handover in software-defined satellite networking
Satellites have largely been designed as application specific and isolated for the past decades. Though with certain benefits, it might lead to resource under utilization and limited satellite applications. As an emerging networking technology, software-defined networking (SDN) has recently been introduced into satellite networks. In this letter, we propose a software defined satellite networking (SDSN) architecture, which simplifies networking among versatile satellites and enables new protocols to be easily tested and deployed. Particularly, we propose a seamless handover mechanism based on SDSN, and conduct physical layer simulation, which shows significant improvement over the existing hard handover and hybrid handover mechanisms in terms of handover latency, throughput and quality of experience
of users
Carrier Aggregation in Multi-Beam High Throughput Satellite Systems
Carrier Aggregation (CA) is an integral part of current terrestrial networks.
Its ability to enhance the peak data rate, to efficiently utilize the limited
available spectrum resources and to satisfy the demand for data-hungry
applications has drawn large attention from different wireless network
communities. Given the benefits of CA in the terrestrial wireless environment,
it is of great interest to analyze and evaluate the potential impact of CA in
the satellite domain. In this paper, we study CA in multibeam high throughput
satellite systems. We consider both inter-transponder and intra-transponder CA
at the satellite payload level of the communication stack, and we address the
problem of carrier-user assignment assuming that multiple users can be
multiplexed in each carrier. The transmission parameters of different carriers
are generated considering the transmission characteristics of carriers in
different transponders. In particular, we propose a flexible carrier allocation
approach for a CA-enabled multibeam satellite system targeting a proportionally
fair user demand satisfaction. Simulation results and analysis shed some light
on this rather unexplored scenario and demonstrate the feasibility of the CA in
satellite communication systems
Distributed Massive MIMO for LEO Satellite Networks
The ultra-dense deployment of interconnected satellites will characterize
future low Earth orbit (LEO) mega-constellations. Exploiting this towards a
more efficient satellite network (SatNet), this paper proposes a novel LEO
SatNet architecture based on distributed massive multiple-input multiple-output
(DM-MIMO) technology allowing ground user terminals to be connected to a
cluster of satellites. To this end, we investigate various aspects of
DM-MIMO-based satellite network design, the benefits of using this
architecture, the associated challenges, and the potential solutions. In
addition, we propose a distributed joint power allocation and handover
management (D-JPAHM) technique that jointly optimizes the power allocation and
handover management processes in a cross-layer manner. This framework aims to
maximize the network throughput and minimize the handover rate while
considering the quality-of-service (QoS) demands of user terminals and the
power capabilities of the satellites. Moreover, we devise an artificial
intelligence (AI)-based solution to efficiently implement the proposed D-JPAHM
framework in a manner suitable for real-time operation and the dynamic SatNet
environment. To the best of our knowledge, this is the first work to introduce
and study DM-MIMO technology in LEO SatNets. Extensive simulation results
reveal the superiority of the proposed architecture and solutions compared to
conventional approaches in the literature.Comment: arXiv admin note: text overlap with arXiv:2106.0983
Dynamic frequency assignment for mobile users in multibeam satellite constellations
Els nivells de flexibilitat i escalabilitat mai vistos de la propera generació de sistemes de comunicació per satèl·lit exigeixen nous algorismes de gestió de recursos que s'adaptin a contextos dinà mics. El futur entorn dels serveis de comunicació per satèl·lit estarà definit per un nombre més gran d'usuaris, una gran part dels quals correspondrà a usuaris mòbils com avions o vaixells. El repte addicional que introdueixen aquests usuaris és abordar la incertesa espai-temporal que es presenta en forma de retards, canvis en la seva trajectòria, o tots dos. Atès que els usuaris mòbils constituiran un segment important del mercat, els operadors de satèl·lits prioritzen l'aprofitament dels avançats sistemes digitals per desenvolupar estratègies flexibles d'assignació de recursos que siguin robustes davant de les bases d'usuaris dinà miques.
Un dels problemes clau en aquest context és com gestionar l'espectre de freqüències de manera eficient. Mentre que nombroses solucions aborden escenaris d'assignació de dinà mica freqüències, el nivell addicional de complexitat que presenten els usuaris mòbils no ha estat prou estudiat, i no és clar si els nous algorismes d'assignació de freqüències poden abordar la incertesa espai-temporal. Concretament, sostenim que els canvis inesperats en la posició dels usuaris introdueixen noves restriccions en l'assignació de freqüències que els algoritmes la literatura podrien no ser capaços de complir, especialment si les decisions s'han de prendre en temps real i a escala.
Per solucionar aquesta limitació, proposem un algorisme de gestió dinà mica de freqüències basat en programació lineal entera que assigna recursos a escenaris amb usuaris tant fixos com mòbils, tenint en compte la incertesa espai-temporal d'aquests últims. El nostre mètode inclou tant la planificació a llarg termini com l'operació en temps real, una sinergia que no ha estat prou explorada per a les comunicacions per satèl·lit i que és crÃtica quan s'opera sota incertesa. PLos niveles de flexibilidad y escalabilidad nunca vistos de la próxima generación de sistemas de comunicación por satélite exigen nuevos algoritmos de gestión de recursos que se adapten a contextos dinámicos. El futuro entorno de los servicios de comunicación por satélite estará definido por un mayor número de usuarios, una gran parte de los cuales corresponderá a usuarios móviles como aviones o barcos. El reto adicional que introducen estos usuarios es abordar la incertidumbre espacio-temporal que se presenta en forma de retrasos, cambios en su trayectoria, o ambos. Dado que los usuarios móviles constituirán un segmento importante del mercado, los operadores de satélites dan prioridad al aprovechamiento de los avanzadas sistemas digitales para desarrollar estrategias flexibles de asignación de recursos que sean robustas frente a las bases de usuarios dinámicas.
Uno de los problemas clave en este contexto es cómo gestionar el espectro de frecuencias de forma eficiente. Mientras que numerosas soluciones abordan escenarios de asignación dinámica de frecuencias, el nivel adicional de complejidad que presentan los usuarios móviles no ha sido suficientemente estudiado, y no está claro si los nuevos algoritmos de asignación de frecuencias pueden abordar la incertidumbre espacio-temporal. En concreto, sostenemos que los cambios inesperados en la posición de los usuarios introducen nuevas restricciones en la asignación de frecuencias que los algoritmos la literatura podrÃan no ser capaces de cumplir, especialmente si las decisiones deben tomarse en tiempo real y a escala.
Para solventar esta limitación, proponemos un algoritmo de gestión dinámica de frecuencias basado en la programación lineal entera que asigna recursos en escenarios con usuarios tanto fijos como móviles, teniendo en cuenta la incertidumbre espacio-temporal de estos últimos. Nuestro método incluye tanto la planificación a largo plazo como la operación en tiempo real, una sinergia que no ha sido suficientThe unprecedented levels of flexibility and scalability of the next generation of communication satellite systems call for new resource management algorithms that adapt to dynamic environments. The upcoming landscape of satellite communication services will be defined by an increased number of unique users, a large portion of which will correspond to mobile users such as planes or ships. The additional challenge introduced by these users is addressing the spatiotemporal uncertainty that comes in the form of delays, changes in their trajectory, or both. Given that mobile users will constitute an important segment of the market, satellite operators prioritize leveraging modern digital payloads to develop flexible resource allocation strategies that are robust against dynamic user bases.
One of the key problems in this context is how to manage the frequency spectrum efficiently. While numerous solutions address dynamic frequency assignment scenarios, the additional layer of complexity presented by mobile users has not been sufficiently studied, and it is unclear whether novel frequency assignment algorithms can address spatiotemporal uncertainty. Specifically, we argue that unexpected changes in the position of users introduce new restrictions into the frequency assignment, which previous algorithms in the literature might not be able to meet, especially if decisions need to be made in real-time and at scale.
To address this gap, we propose a dynamic frequency management algorithm based on integer linear programming that assigns resources in scenarios with both fixed and mobile users, accounting for the spatiotemporal uncertainty of the latter. Our method includes both long-term planning and real-time operation, a synergy that has not been sufficiently explored for satellite communications and proves to be critical when operating under uncertainty. To fulfill the problem’s scope, we propose different strategies that extend a state-of-the-art frequency management algOutgoin
Future Ultra-Dense LEO Satellite Networks: A Cell-Free Massive MIMO Approach
Low Earth orbit (LEO) satellite networks (SatNets) are envisioned to play a
crucial role in providing global and ubiquitous connectivity efficiently.
Accordingly, in the coming years, thousands of LEO satellites will be launched
to create ultradense LEO mega-constellations, and the Third Generation
Partnership Project (3GPP) is working on evolving fifth-generation (5G) systems
to support such non-terrestrial networks (NTN). However, many challenges are
associated with the deployment of LEOs from communications and networking
perspectives. In this paper, we propose a novel cell-free massive
multiple-input multiple-output (CF-mMIMO) based architecture for future
ultra-dense LEO SatNets. We discuss various aspects of network design, such as
duplexing mode, pilot assignment, beamforming, and handover management. In
addition, we propose a joint optimization framework for the power allocation
and handover management processes to maximize the network throughput and
minimize the handover rate while ensuring quality-of-service (QoS) satisfaction
for users. To the best of our knowledge, this is the first work to introduce
and study CF-mMIMO-based LEO SatNets. Extensive simulation results demonstrate
the superior performance of the proposed architecture and solutions compared to
those of conventional single-satellite connectivity and handover techniques
from the literature.Comment: 6 pages, 3 figure
Impact of Scheduling in the Return-Link of Multi-Beam Satellite MIMO Systems
The utilization of universal frequency reuse in multi-beam satellite systems
introduces a non-negligible level of co-channel interference (CCI), which in
turn penalizes the quality of service experienced by users. Taking this as
starting point, the paper focuses on resource management performed by the
gateway (hub) on the return-link, with particular emphasis on a scheduling
algorithm based on bipartite graph approach. The study gives important insights
into the achievable per-user rate and the role played by the number of users
and spot beams considered for scheduling. More interestingly, it is shown that
a free-slot assignment strategy helps to exploit the available satellite
resources, thus guaranteeing a max-min rate requirement to users. Remarks about
the trade-off between efficiency-loss and performance increase are finally
drawn at the end of the paper.Comment: Submitted and accepted to IEEE GLOBECOM 2012 Conference, 6 pages, 10
figure
High-Throughput Air-to-Ground Connectivity for Aircraft
Permanent connectivity to the Internet has become the defacto standard in the second decade of the 21st century. However, on-board aircraft connectivity is still limited. While the number of airlines offering in-flight connectivity increases, the current performance is insufficient to satisfy several hundreds of passengers simultaneously. There are several options to connect aircraft to the ground, i.e. direct air-to-ground, satellites and relaying via air-to-air links. However, each single solution is insufficient. The direct air-to-ground coverage is limited to the continent and coastal regions, while the satellite links are limited in the minimum size of the spot beams and air-to-air links need to be combined with a link to the ground. Moreover, even if a direct air-to-ground or satellite link is available, the peak throughput offered on each link is rarely achieved, as the capacity needs to be shared with other aircraft flying in the same coverage area. The main challenge in achieving a high throughput per aircraft lies in the throughput allocation. All aircraft should receive a fair share of the available throughput. More specifically, as an aircraft contains a network itself, a weighted share according to the aircraft size should be provided. To address this problem, an integrated air-to-ground network, which is able to provide a high throughput to aircraft, is proposed here. Therefore, this work introduces a weighted-fair throughput allocation scheme to provide such a desired allocation. While various aspects of aircraft connectivity are studied in literature, this work is the first to address an integrated air-to-ground network to provide high-throughput connectivity to aircraft.
This work models the problem of throughput allocation as a mixed integer linear program. Two throughput allocation schemes are proposed, a centralized optimal solution and a distributed heuristic solution. For the optimal solution, two different objectives are introduced, a max-min-based and a threshold-based objective. The optimal solution is utilized as a benchmark for the achievable throughput for small scenarios, while the heuristic solution offers a distributed approach and can process scenarios with a higher number of aircraft. Additionally, an option for weighted-fair throughput allocation is included. Hence, large aircraft obtain a larger share of the throughput than smaller ones. This leads to fair throughput allocation with respect to the size of the aircraft. To analyze the performance of throughput allocation in the air-to-ground network, this work introduces an air-to-ground network model. It models the network realistically, but independent from specific network implementations, such as 5G or WiFi. It is also adaptable to different scenarios. The aircraft network is studied based on captured flight traces. Extensive and representative parameter studies are conducted, including, among others, different link setups, geographic scenarios, aircraft capabilities, link distances and link capacities. The results show that the throughput can be distributed optimally during high-aircraft-density times using the optimal solution and close to optimal using the heuristic solution. The mean throughput during these times in the optimal reference scenario with low Earth orbit satellites is 20 Mbps via direct air-to-ground links and 4 Mbps via satellite links, which corresponds to 10.7% and 1.9% of the maximum link throughput, respectively. Nevertheless, during low-aircraft-density times, which are less challenging, the throughput can reach more than 200 Mbps. Therefore, the challenge is on providing a high throughput during high-aircraft-density times. In the larger central European scenario, using the heuristic scheme, a minimum of 22.9 Mbps, i.e. 3.2% of the maximum capacity, can be provided to all aircraft during high-aircraft-density times. Moreover, the critical parameters to obtain a high throughput are presented. For instance, this work shows that multi-hop air-to-air links are dispensable for aircraft within direct air-to-ground coverage. While the computation time of the optimal solution limits the number of aircraft in the scenario, larger scenarios can be studied using the heuristic scheme. The results using the weighted-fair throughput allocation show that the introduction of weights enables a user-fair throughput allocation instead of an aircraft-fair throughput allocation. As a conclusion, using the air-to-ground model and the two introduced throughput allocation schemes, the achievable weighted-fair throughput per aircraft and the respective link choices can be quantified
Multicasting Over 6G Non-Terrestrial Networks: A Softwarization-Based Approach
Multicast/broadcast delivery is a critical challenge of future 6G mobile networks where massive Internet of Things (IoT) deployment and extended reality multimedia such as teleportation are target application scenarios. Non-terrestrial networks (NTNs) are considered essential for the success of 6G, which aims to provide true 'global' services by extending mobile access worldwide, thus overcoming the coverage limit of current terrestrial networks (TNs). This article discusses how the main distinguishing features of NTNs can be effectively exploited for 6G multicasting. Furthermore, in line with the evolution of future 6G networks toward softwarized systems, we evaluate the potential of using the softwarization paradigm in the heterogeneous TN-NTN architecture to deliver multicast services
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