1,721,138 research outputs found
Beam Size Design for New Radio Satellite Communications Systems
Get PDFSatellite Communication (SatCom) systems are a promising solution to extend and complement terrestrial networks in un-/under- served areas, as reflected by several recent commercial and standardisation endeavours. Recently, 3GPP initiated a Study Item for 5G (New Radio, NR) Non-Terrestrial Networks (NTN) to foster the integration of SatCom in future 5G systems. After the definition of the system architecture and main design parameters, the focus is currently on the feasibility assessment of NR PHY/MAC layer procedures when a satellite channel is involved. In this letter, we propose a flexible methodology to design the beam footprint taking into account any source of differential delay between User Terminals (UTs) as, e.g., Random Access (RA) and Timing Advance (TA) procedures. In the numerical assessment, we compare the obtained beam footprint sizes with those currently being considered within 3GPP NTN studies, showing that larger/smaller dimensions can be assumed when considering the RA and TA procedures
Federated Cell-Free MIMO in Non-Terrestrial Networks: Architectures and Performance
Get PDFWhile 5G networks are being rolled out, the definition of 5G-Advanced features and the identification of disruptive technologies for 6 G systems are being addressed by the scientific and academic communities to tackle the challenges that 2030 communication systems will face, such as terabit-capacity and always-on networks. In this framework, it is globally recognised that Non-Terrestrial Networks (NTN) will play a fundamental role in support to a fully connected world, in which physical, human, and digital domains will converge. Notably, one of the main challenges that NTN have to address is the provision of the high throughput requested by the new ecosystem. In this paper, we focus on Cell-Free massive Multiple Input Multiple Output (CF-MIMO) algorithms for NTN. In particular: i) we discuss the architecture design supporting centralised and federated CF-MIMO in NTN, with the latter implementing distributed MIMO algorithms from multiple satellites in the same formation (swarm); ii) we design a location-based CF-MIMO algorithm, which does not require Channel State Information (CSI) at the transmitter; and iii) we design normalisation approaches for federated CF-MIMO in NTN, to cope with the constraints on non-colocated radiating elements. The numerical results substantiate the good performance of the proposed algorithm, also in the presence of non-ideal information
Feeder Link Precoding for Future Broadcasting Services: Architecture and Performance
Get PDF5G systems are becoming a reality and the evolution towards Beyond 5G (B5G) and 6G systems is already being defined, also to cope with the ever increasing capacity demanded by on-ground users. This will pose challenging requirements on the feeder link of future satellite systems, which risks to become a bottleneck for the overall system performance. In this paper, we propose a novel architecture of linear precoding for the feeder link of a broadcast satellite system operating with full frequency reuse to significantly enhance the achievable capacity. The architecture has been simulated and tested in a challenging multi-frequency scenario, where Ku, Ka, Q/V, and W band have been considered for transmission. The numerical performance analysis and the open issues related to the practical realisation of the proposed architecture are also thoroughly discussed
Measuring Service Continuity in Integrated TN/NTN for 5G-Advanced and 6G
No full textService continuity has been defined in 3GPP TS 22.261 as the " uninterrupted user experience of a service that is using an active communication when a UE undergoes an access change without, as far as possible, the user noticing the change". Such definition remains open, is not associated with KPIs and thus, cannot be used to compare the many architecture and business options that can be envisaged to deploy and operate 3D networks. In this paper, we propose a generic three-phased approach, with KPIs, to quantify the seamless performance of TN / NTN switching. We also discuss the purpose, applicability and order of magnitude of each KPI, based on concrete examples
Clustering strategies for multicast precoding in multibeam satellite systems
Get PDFNext generation multibeam SatCom architectures will heavily exploit full frequency reuse schemes along with interference management techniques, eg, precoding or multiuser detection, to drastically increase the system throughput. In this framework, we address the problem of the user selection for multicast precoding by formulating it as a clustering problem. By introducing a novel mathematical framework, we design fixed/variable size clustering algorithms that group users into simultaneously precoded and served clusters while maximising the system throughput. Numerical simulations are used to validate the proposed algorithms and to identify the main system-level trade-offs
Geographical Scheduling for Multicast Precoding in Multi-Beam Satellite Systems
No full textCurrent State-of-The-Art High Throughput Satellite systems provide wide-Area connectivity through multi-beam architectures. Due to the tremendous system throughput requirements that next generation Satellite Communications (SatCom) expect to achieve, traditional 4-colour frequency reuse schemes are not sufficient anymore and more aggressive solutions as full frequency reuse are being considered for multi-beam SatCom. These approaches require advanced interference management techniques to cope with the significantly increased inter-beam interference both at the transmitter, e.g., precoding, and at the receiver, e.g., Multi User Detection (MUD). With respect to the former, several peculiar challenges arise when designed for SatCom systems. In particular, multiple users are multiplexed in the same transmission radio frame, thus imposing to consider multiple channel matrices when computing the precoding coefficients. In previous works, the main focus has been on the users' clustering and precoding design. However, even though achieving significant throughput gains, no analysis has been performed on the impact of the system scheduling algorithm on multicast precoding, which is typically assumed random. In this paper, we focus on this aspect by showing that, although the overall system performance is improved, a random scheduler does not properly tackle specific scenarios in which the precoding algorithm can poorly perform. Based on these considerations, we design a Geographical Scheduling Algorithm (GSA) aimed at improving the precoding performance in these critical scenarios and, consequently, the performance at system level as well. Through extensive numerical simulations, we show that the proposed GSA provides a significant performance improvement with respect to the legacy random scheduling
NB-IoT over Non-Terrestrial Networks: Link Budget Analysis
No full textMachine Type Communications (MTC) and Internet of Things (IoT) applications are growing exponentially and are forecast to play an even more important role in Future Networks and Systems. The Third Generation Partnership Project (3GPP) introduced the Narrowband IoT (NB-IoT) air interface as a response to the IoT use case requirements. However, it is widely accepted that the terrestrial network alone is not able to serve the requirement of the IoT market of a truly ubiquitous coverage. To this aim, several initiatives are currently addressing the inclusion of a satellite component into the telecommunication infrastructure to extend its coverage to those areas that are unserved or underserved by the terrestrial network. The recently approved 3GPP study item on NB-IoT over Non-Terrestrial Network (NTN) is the most important of these initiatives. The study item, starting at the beginning of 2021, will assess the performance of the NB- IoT air interface over satellite and will identify which adaptations are needed to enable its use. In this context, our work provides an assessment of the system level performance, in terms of the link budget parameters, of the NB-IoT air interface in typical satellite scenarios. In particular, we provide a detailed discussion of the system architecture supporting the NB-IoT over NTN, a description of the link budget computation methodology, and the numerical results of the link budget analysis in both single- satellite and multi-satellite scenarios
Computer added proton density and T2 weighted spin echo images improving quantitative semiautomated computer assessment of lesion load in multiple sclerosis
No full textThe Role of Satellite in 5G and Beyond
No full textThe first global standard for Satellite Communications (SatCom) was published in April 2022 within 3GPP Release 17. It specifies the features enabling 4G/5G systems to support a satellite component. More than technical specifications, it also enables the integration of the satellite industry in the 3GPP ecosystem, involving organizations at a worldwide level to ensure a global market. Already the decision has been made to define, as part of 3GPP Release 18, some enhancing features to improve the performances and/or to provide new capabilities. Discussions on the contents of Release 19 for the satellite enabling features have started in the service requirement working group of 3GPP. In this framework, it is timely to undertake a study on the technologies for SatCom as part of Beyond 5G (B5G), i.e., 5G-Advanced and 6G. In fact, while Release 17 Non-Terrestrial Network (NTN) provides a solid ground for future satellite networks integrated into the 5G system, a significant innovation breakthrough in technologies, techniques, and architectures is needed to prepare for the next generation. In this chapter, we: (1) detail the 3GPP NTN ecosystem in terms of architectures and challenges; (2) discuss the services and applications; and (3) identify the research challenges to be addressed towards B5G
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