28 research outputs found
Interference analysis of broadband space and terrestrial fixed radio communications systems in the frequency range 12 to 30 GHz
This thesis presents research into the principles of spectrum sharing analysis
methods developed for investigating implications of interference from
Nongeostationary Fixed Satellite Service (NGSO FSS) systems into Geostationary
Fixed Satellite Service (GSO FSS) systems and Fixed Service (FS) terrestrial radio
systems operating or planned for operation in the 12 to 30 GHz frequency range.
Spectrum sharing is an effective way of allowing new services to operate without
cancelling the existing allocations in the same part of the spectrum. The use of
spectrum sharing results in re-use of the available spectrum among different services
and, therefore, increases the efficient use of the radio frequencies. However, it is
necessary to carry out extensive feasibility studies into technical or operational
compatibility between the services involved. Often, sharing constraints are placed
on systems, such as the power of emissions and the transmitter and receiver antenna
pointings to reduce the interference into negligible levels.
Traditionally, radio spectrum allocated to GSO FSS has been shared with FS. In
recent years, there has been a growing interest in the use of low Earth orbits and a
number of NGSO FSS constellations has been designed to provide broadband data
services. This has led to the allocation of certain bands used by the FS and GSO
FSS systems to NGSO FSS.
In line with the new allocations, NGSO FSS, GSO FSS and FS systems are required
to co-exist in parts of the 12 to 30 GHz frequency range. The primary objectives of
this research were to identify principal factors affecting the feasibility of spectrum
sharing and to develop spectrum sharing analysis methodologies to examine the
implications of these factors with a view to identifying sharing constraints that
would give rise to an acceptable sharing environment
A Survey on Non-Geostationary Satellite Systems: The Communication Perspective
The next phase of satellite technology is being characterized by a new evolution in non-geostationary orbit (NGSO) satellites, which conveys exciting new communication capabilities to provide non-terrestrial connectivity solutions and to support a wide range of digital technologies from various industries. NGSO communication systems are known for a number of key features such as lower propagation delay, smaller size, and lower signal losses in comparison to the conventional geostationary orbit (GSO) satellites, which can potentially enable latency-critical applications to be provided through satellites. NGSO promises a substantial boost in communication speed and energy efficiency, and thus, tackling the main inhibiting factors of commercializing GSO satellites for broader utilization. The promised improvements of NGSO systems have motivated this paper to provide a comprehensive survey of the state-of-the-art NGSO research focusing on the communication prospects, including physical layer and radio access technologies along with the networking aspects and the overall system features and architectures. Beyond this, there are still many NGSO deployment challenges to be addressed to ensure seamless integration not only with GSO systems but also with terrestrial networks. These unprecedented challenges are also discussed in this paper, including coexistence with GSO systems in terms of spectrum access and regulatory issues, satellite constellation and architecture designs, resource management problems, and user equipment requirements. Finally, we outline a set of innovative research directions and new opportunities for future NGSO research
Proceedings of the Fifth International Mobile Satellite Conference 1997
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 communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments
IAU Dark and Quiet Skies, UNOOSA, NoirLabs, SATCON2, International Law Working Group Report
International Law Working Group of the IAU's Dark and Quiet Skies Conference; objective to advise the UN Committee on the Peaceful Use of Outer Spac
Dark and Quiet Skies II Working Group Reports:
This Report presents the main results of the Conference “Dark and Quiet Skies for Science and Society II” which took place on-line on 3–7 October 2021. This conference was the logical follow-up of the first one, organized as an on-line workshop with the same title on 5–9 October 2020. Both conferences were co-organized by UNOOSA, IAU and the Government of Spain and were well attended. The focus of the second conference was about the feasibility of implementing the recommendations presented by the first one in its extensive report. The main qualifying difference between the first and the second conferences was a more explicit involvement of the industrial stakeholders and of space policy experts, whose contributions were instrumental in presenting a credible review of the proposed mitigating measures as well as of possible regulatory guidelines
Statistical analysis of C/NOFS planar Langmuir probe data
The planar Langmuir probe (PLP) onboard the Communication/Navigation Outage
Forecasting System (C/NOFS) satellite has been monitoring ionospheric plasma
densities and their irregularities with high resolution almost seamlessly
since May 2008. Considering the recent changes in status of the C/NOFS
mission, it may be interesting to summarize some statistical results from
these measurements. PLP data from 2 different years (1 October 2008–30 September 2009 and 1 January 2012–31 December 2012) were selected for
analysis. The first data set corresponds to solar minimum conditions and the
second one is as close to solar maximum conditions of solar cycle 24 as
possible at the time of the analysis. The results from the analysis show how
the values of the standard deviation of the ion density which are greater
than specified thresholds are statistically distributed as functions of
several combinations of the following geophysical parameters: (i) solar
activity, (ii) altitude range, (iii) longitude sector, (iv) local time
interval, (v) geomagnetic latitude interval, and (vi) season
1-D broadside-radiating leaky-wave antenna based on a numerically synthesized impedance surface
A newly-developed deterministic numerical technique for the automated design of metasurface antennas is applied here for the first time to the design of a 1-D printed Leaky-Wave Antenna (LWA) for broadside radiation. The surface impedance synthesis process does not require any a priori knowledge on the impedance pattern, and starts from a mask constraint on the desired far-field and practical bounds on the unit cell impedance values. The designed reactance surface for broadside radiation exhibits a non conventional patterning; this highlights the merit of using an automated design process for a design well known to be challenging for analytical methods. The antenna is physically implemented with an array of metal strips with varying gap widths and simulation results show very good agreement with the predicted performance
Beam scanning by liquid-crystal biasing in a modified SIW structure
A fixed-frequency beam-scanning 1D antenna based on Liquid Crystals (LCs) is designed for application in 2D scanning with lateral alignment. The 2D array environment imposes full decoupling of adjacent 1D antennas, which often conflicts with the LC requirement of DC biasing: the proposed design accommodates both. The LC medium is placed inside a Substrate Integrated Waveguide (SIW) modified to work as a Groove Gap Waveguide, with radiating slots etched on the upper broad wall, that radiates as a Leaky-Wave Antenna (LWA). This allows effective application of the DC bias voltage needed for tuning the LCs. At the same time, the RF field remains laterally confined, enabling the possibility to lay several antennas in parallel and achieve 2D beam scanning. The design is validated by simulation employing the actual properties of a commercial LC medium
P&I Club Membership As Potential Incentivization For Adherence To Best Space Traffic Management Practices: A Maritime Analogue
It has been said that the space environment is becoming so accessible, we are at risk of depleting it as a resource, thereby risking society’s space-dependent functions. Law, regulations, policies, and guidelines exist to guide entities to act to preserve the space environment. However, best space traffic management (STM) practice implementation and regulatory compliance could be costly and resource-intensive, especially for a small business. Some entities may not undertake innovative space endeavors at all, or worse, ignore laws, regulations, policies, and guidelines. A question arises of how space actors could be persuaded to work toward meeting STM laws, regulations, policies, and guidelines and perhaps take on potentially costly practices to follow them. This thesis attempts to answer whether liability apportionment and risk-pooling through a space protection and indemnity (P&I) club membership could benefit a space actor enough to drive implementation of best space traffic management practices where actors could be more likely to adhere to laws, regulations, policies, and guidelines.
The study is limited to one example model space P&I club in the U.S. as a foundation for a potential larger international group in the future. The study assumes both insurance and P&I calls can be based on publicly available financial information, though need for more detailed information on insurance premiums and P&I calls is needed to create a fine-tuned model. The study also assumes a potential space P&I club member would be subject to U.S. law, regulations, and policy. Methods include document and policy analysis, interviews with space insurance and risk management subject matter experts, and cost analyses. Arguably, a case does indeed exist wherein a potential space P&I club membership could benefit a space actor enough to encourage implementation of best space traffic management practices. However, it would be best used as part of the bigger STM picture alongside existing regulations and policies. Still, a P&I club membership could provide a significant enough benefit where actors could be more likely to adhere to regulations and policies, which would, in turn, have a positive impact on keeping the space environment sustainable for current and future activities