Navigation/traffic control satellite mission study. Volume 3 - System concepts

Satellite network for air traffic control, solar flare warning, and collision avoidanc

On the Road to 6G: Visions, Requirements, Key Technologies and Testbeds

Fifth generation (5G) mobile communication systems have entered the stage of commercial development, providing users with new services and improved user experiences as well as offering a host of novel opportunities to various industries. However, 5G still faces many challenges. To address these challenges, international industrial, academic, and standards organizations have commenced research on sixth generation (6G) wireless communication systems. A series of white papers and survey papers have been published, which aim to define 6G in terms of requirements, application scenarios, key technologies, etc. Although ITU-R has been working on the 6G vision and it is expected to reach a consensus on what 6G will be by mid-2023, the related global discussions are still wide open and the existing literature has identified numerous open issues. This paper first provides a comprehensive portrayal of the 6G vision, technical requirements, and application scenarios, covering the current common understanding of 6G. Then, a critical appraisal of the 6G network architecture and key technologies is presented. Furthermore, existing testbeds and advanced 6G verification platforms are detailed for the first time. In addition, future research directions and open challenges are identified for stimulating the on-going global debate. Finally, lessons learned to date concerning 6G networks are discussed

Proceedings of the Mobile Satellite Conference

A satellite-based mobile communications system provides voice and data communications to mobile users over a vast geographic area. The technical and service characteristics of mobile satellite systems (MSSs) are presented and form an in-depth view of the current MSS status at the system and subsystem levels. Major emphasis is placed on developments, current and future, in the following critical MSS technology areas: vehicle antennas, networking, modulation and coding, speech compression, channel characterization, space segment technology and MSS experiments. Also, the mobile satellite communications needs of government agencies are addressed, as is the MSS potential to fulfill them

Visible Light Communication (VLC)

Visible light communication (VLC) using light-emitting diodes (LEDs) or laser diodes (LDs) has been envisioned as one of the key enabling technologies for 6G and Internet of Things (IoT) systems, owing to its appealing advantages, including abundant and unregulated spectrum resources, no electromagnetic interference (EMI) radiation and high security. However, despite its many advantages, VLC faces several technical challenges, such as the limited bandwidth and severe nonlinearity of opto-electronic devices, link blockage and user mobility. Therefore, significant efforts are needed from the global VLC community to develop VLC technology further. This Special Issue, “Visible Light Communication (VLC)”, provides an opportunity for global researchers to share their new ideas and cutting-edge techniques to address the above-mentioned challenges. The 16 papers published in this Special Issue represent the fascinating progress of VLC in various contexts, including general indoor and underwater scenarios, and the emerging application of machine learning/artificial intelligence (ML/AI) techniques in VLC

A High-speed Reconfigurable Free Space Optical Communication System Utilizing Software Defined Radio Environment

Free space optical (FSO) communication allows for high-speed data transmissions while also being extremely cost-effective by using visible or infrared wavelengths to transmit and receive data wirelessly through the free space channel. However, FSO links are highly susceptible to the effects of the atmosphere, particularly turbulence, smoke, and fog. On the other hand, FSO itself does not provide enough flexibility to address the issue of such blockage and obstruction caused by objects and atmospheric conditions. This research investigates, proposes, and evaluates a software defined multiple input multiple output (MIMO) FSO system to ensure link availability and reliability under weather conditions as part of the last mile access in the 5th generation, 6th generation, and beyond. Software defined radio (SDR) technology is adopted in order to provide a certain degree of flexibility to the optical wireless communications system. The scope of this research focuses on the design, validation, implementation, and evaluation of a novel adaptive switching algorithm i.e., activating additional transmitters of a MIMO FSO system using a software defined ecosystem. The main issues are the compactness of the experimental design; the limitation of software-oriented signal generation; robustness; reliability; and the quality of service. As part of the system design, the thresholding method, a decision-making process via the feedback link, and a spatial diversity technique is adopted to carry out the adaptive switching. The adaptive switching is performed via a feedback link in which the atmospheric loss and scintillation index are calculated for fog and turbulence respectively. The initial design is implemented in SDR/ GNURadio for a real-time emulation of the proposed system to enhance the system flexibility of a traditional MIMO FSO system. A bit-by-bit comparison is performed with the GNURadio signal processing block and BERT for a real-time BER estimation. However, based on the initial results, the switching mechanism can only overcome the effect of turbulence at a certain level. A new design to mainly mitigate the varying fog conditions is proposed based on the SDR-based adaptive switching for a gigabit ethernet (GbE) MIMO FSO system and tested in a 5 m dedicated atmospheric chamber. The proposed system is implemented using off-the-shelf components such as a media converter, small form pluggable transceivers, optical switch, and power meter to estimate the channel state information. A new Schmitt trigger-based thresholding method is also introduced. The proposed software defined GbE MIMO FSO with an adaptive switching algorithm is fabricated, implemented, and investigated. The results are also compared with the real-time simulated data. Since the purpose of this Ph.D. is to explain and demonstrate the proof of concept for the proposed SDR-MIMO FSO system, the emphasis has been on the design, evaluation, and minimal performance requirements rather than maximizing the data rate. The outcome of the thesis will be a huge degree of flexibility and mitigation property MIMO FSO can offer with the help of SDR. It will be shown that the designed system has the capability to provide data transmission with 99.999% availability with a packet error rate and data rate of 7.2 ×10−2 and ~120 Mbps respectively, under extremely harsh fog conditions with visibility V of < 11 m

Optical Wireless Data Center Networks

Bandwidth and computation-intensive Big Data applications in disciplines like social media, bio- and nano-informatics, Internet-of-Things (IoT), and real-time analytics, are pushing existing access and core (backbone) networks as well as Data Center Networks (DCNs) to their limits. Next generation DCNs must support continuously increasing network traffic while satisfying minimum performance requirements of latency, reliability, flexibility and scalability. Therefore, a larger number of cables (i.e., copper-cables and fiber optics) may be required in conventional wired DCNs. In addition to limiting the possible topologies, large number of cables may result into design and development problems related to wire ducting and maintenance, heat dissipation, and power consumption. To address the cabling complexity in wired DCNs, we propose OWCells, a class of optical wireless cellular data center network architectures in which fixed line of sight (LOS) optical wireless communication (OWC) links are used to connect the racks arranged in regular polygonal topologies. We present the OWCell DCN architecture, develop its theoretical underpinnings, and investigate routing protocols and OWC transceiver design. To realize a fully wireless DCN, servers in racks must also be connected using OWC links. There is, however, a difficulty of connecting multiple adjacent network components, such as servers in a rack, using point-to-point LOS links. To overcome this problem, we propose and validate the feasibility of an FSO-Bus to connect multiple adjacent network components using NLOS point-to-point OWC links. Finally, to complete the design of the OWC transceiver, we develop a new class of strictly and rearrangeably non-blocking multicast optical switches in which multicast is performed efficiently at the physical optical (lower) layer rather than upper layers (e.g., application layer). Advisors: Jitender S. Deogun and Dennis R. Alexande

Customer premise service study for 30/20 GHz satellite system

Satellite systems in which the space segment operates in the 30/20 GHz frequency band are defined and compared as to their potential for providing various types of communications services to customer premises and the economic and technical feasibility of doing so. Technical tasks performed include: market postulation, definition of the ground segment, definition of the space segment, definition of the integrated satellite system, service costs for satellite systems, sensitivity analysis, and critical technology. Based on an analysis of market data, a sufficiently large market for services is projected so as to make the system economically viable. A large market, and hence a high capacity satellite system, is found to be necessary to minimize service costs, i.e., economy of scale is found to hold. The wide bandwidth expected to be available in the 30/20 GHz band, along with frequency reuse which further increases the effective system bandwidth, makes possible the high capacity system. Extensive ground networking is required in most systems to both connect users into the system and to interconnect Earth stations to provide spatial diversity. Earth station spatial diversity is found to be a cost effective means of compensating the large fading encountered in the 30/20 GHz operating band

Proceedings of the Third International Mobile Satellite Conference (IMSC 1993)

Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial cellular communications services. While the first and second International Mobile Satellite Conferences (IMSC) mostly concentrated on technical advances, this Third IMSC also focuses on the increasing worldwide commercial activities in Mobile Satellite Services. Because of the large service areas provided by such systems, it is important to consider political and regulatory issues in addition to technical and user requirements issues. Topics covered include: the direct broadcast of audio programming from satellites; spacecraft technology; regulatory and policy considerations; advanced system concepts and analysis; propagation; and user requirements and applications