1,278 research outputs found
GroundâtoâGEO optical feeder links for very high throughput satellite networks: Accent on diversity techniques
This paper studies the use of optical feeder links in very high throughput satellites (VHTS) networks with emphasis on gateway diversity techniques to mitigate the inherent propagation losses in optical frequencies. Focusing on a GEO scenario, the paper considers a systemâwide approach investigating various challenges of optical feeder links. These include transmission schemes amenable for transparent onâboard processing, optical channel models taking into account blockage by clouds and fading caused by atmospheric turbulence in addition to complexity of onâboard and onâground processing. The channel models are then used to dimension the ground segment towards ensuring a given availability percentage (e.g., 99.9%). The channel model and payload complexity further influence the choice of link layer techniques used for counteracting fading due to atmospheric turbulence in the absence of blockage. An elaborate endâtoâend simulator incorporating the proposed channel models capturing the nuances of various processing blocks like opticalâelectrical conversion is developed. The system performance results provide interesting insights and a framework for assessing the feasibility and advantages of optical feeder links in VHTS systems
Lasercomm Activities at the German Aerospace Centerâs Institute of Communications and Navigation
The German Aerospace Center (DLR) has a heritage of more than 25 years in working on optical inter-satellite and satellite-to-ground links. The Institute of Communications and Navigation (IKN), as a research organization of DLR, has developed coherent homodyne BPSK transmission schemes with world record sensitivity as they are now implemented in the space-proven Laser Communication Terminals (LCT) for the European Data Relay System (EDRS). Further research being pursued at IKN includes the development of transmission systems optimized for atmospheric scenarios such as LEO downlinks, aircraft downlinks and inter-HAP links (High Altitude Platforms). For such scenarios with extreme index-of-refraction turbulence, robust adaptive optics technologies have been investigated and suitable data transceivers have been tested. Furthermore, several verification campaigns with prototype flight terminals and optical ground stations (fixed and transportable) have been performed in recent years, providing a large data basis for optimizing the long-range FSO technology
Current optical technologies for wireless access
The objective of this paper is to describe recent activities and investigations on free-space optics (FSO) or optical wireless and the excellent results achieved within SatNEx an EU-framework 6th programme and IC 0802 a COST action. In a first part, the FSO technology is briefly discussed. In a second part, we mention some performance evaluation criterions for the FSO. In third part, we briefly discuss some optical signal propagation experiments through the atmosphere by mentioning network architectures for FSO and then discuss the recent investigations in airborne and satellite application experiments for FSO. In part four, we mention some recent investigation results on modelling the FSO channel under fog conditions and atmospheric turbulence. Additionally, some recent major performance improvement results obtained by employing hybrid systems and using some specific modulation and coding schemes are presented
Techno-economics of Fiber vs. Microwave for Mobile Transport Network Deployments [Invited]
One of the challenges for network operators is to design and deploy cost-efficient transport networks (TNs) to meet the high capacity and strict latency/reliability requirements of todayâs emerging services. Therefore, they need to consider different aspects, including the appropriate technology, the level of reconfigurability, and the functional split option. A crucial aspect of network design is assessing the impact of these aspects against the total cost of ownership (TCO), latency, and reliability performance of a given solution. For this reason, this paper proposes a framework to investigate the TCO, latency, and reliability performance of a set of fiber and microwave-based TN architectures. They are categorized based on their baseband functional split option and the reconfigurability capabilities of the equipment used. The results, based on real data from a non-incumbent operator, show that in most of the considered scenarios, a microwavebased TN exhibits lower TCO than a fiber-based one. The TCO gain may vary with the choice of the functional split option, geo-type, reconfigurability features, fiber trenching costs, and cost of microwave equipment, with a more significant impact in a dense urban geo-type, where for a low layer functional split option the fiber- and microwave-based architectures have a comparable TCO. Finally, it was found that the considered fiber and microwave architectures have almost similar average latency and connection availability performance. Both are suitable to meet the service requirements of 5G and beyond 5G services in most of the considered scenarios. Only in extreme latency-critical scenarios, a small number of the cells might not fully satisfy the latency requirements of a low layer split option due to multiple microwave hops in the microwave-based architecture
LEO Satellite Constellations for 5G and Beyond: How Will They Reshape Vertical Domains?
The rapid development of communication technologies in the past decades has
provided immense vertical opportunities for individuals and enterprises.
However, conventional terrestrial cellular networks have unfortunately
neglected the huge geographical digital divide, since high bandwidth wireless
coverage is concentrated to urban areas. To meet the goal of ``connecting the
unconnected'', integrating low Earth orbit (LEO) satellites with the
terrestrial cellular networks has been widely considered as a promising
solution. In this article, we first introduce the development roadmap of LEO
satellite constellations (SatCons), including early attempts in LEO satellites
with the emerging LEO constellations. Further, we discuss the unique
opportunities of employing LEO SatCons for the delivery of integrating 5G
networks. Specifically, we present their key performance indicators, which
offer important guidelines for the design of associated enabling techniques,
and then discuss the potential impact of integrating LEO SatCons with typical
5G use cases, where we engrave our vision of various vertical domains reshaped
by LEO SatCons. Technical challenges are finally provided to specify future
research directions.Comment: 4 figures, 1 table, accepted by Communications Magazin
Non-Terrestrial Networks in the 6G Era: Challenges and Opportunities
Many organizations recognize non-terrestrial networks (NTNs) as a key
component to provide cost-effective and high-capacity connectivity in future
6th generation (6G) wireless networks. Despite this premise, there are still
many questions to be answered for proper network design, including those
associated to latency and coverage constraints. In this paper, after reviewing
research activities on NTNs, we present the characteristics and enabling
technologies of NTNs in the 6G landscape and shed light on the challenges in
the field that are still open for future research. As a case study, we evaluate
the performance of an NTN scenario in which satellites use millimeter wave
(mmWave) frequencies to provide access connectivity to on-the-ground mobile
terminals as a function of different networking configurations.Comment: 8 pages, 4 figures, 2 tables, submitted for publication to the IEE
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