350 research outputs found
MIMO CDMA-based Optical SATCOMs: A New Solution
A new scheme for MIMO CDMA-based optical satellite communications (OSATCOMs)
is presented. Three independent problems are described for up-link and down-
link in terms of two distinguished optimization problems. At first, in up-link,
Pulse-width optimization is proposed to reduce dispersions over fibers as the
terrestrial part. This is performed for return-to-zero (RZ) modulation that is
supposed to be used as an example in here. This is carried out by solving the
first optimization problem, while minimizing the probability of overlapping for
the Gaussian pulses that are used to produce RZ. Some constraints are assumed
such as a threshold for the peak-to-average power ratio (PAPR). In down-link,
the second and the third problems are discussed as follows, jointly as a
closed-form solution. Solving the second optimization problem, an objective
function is obtained, namely the MIMO CDMA-based satellite weight-matrix as a
conventional adaptive beam-former. The Satellite link is stablished over flat
un-correlated Nakagami-m/Suzuki fading channels as the second problem. On the
other hand, the mentioned optimization problem is robustly solved as the third
important problem, while considering inter-cell interferences in the multi-cell
scenario. Robust solution is performed due to the partial knowledge of each
cell from the others in which the link capacity is maximized. Analytical
results are conducted to investigate the merit of system.Comment: IEEE PCITC 2015 (15-17 Oct, India
Architectures and Key Technical Challenges for 5G Systems Incorporating Satellites
Satellite Communication systems are a promising solution to extend and
complement terrestrial networks in unserved or under-served areas. This aspect
is reflected by recent commercial and standardisation endeavours. In
particular, 3GPP recently initiated a Study Item for New Radio-based, i.e., 5G,
Non-Terrestrial Networks aimed at deploying satellite systems either as a
stand-alone solution or as an integration to terrestrial networks in mobile
broadband and machine-type communication scenarios. However, typical satellite
channel impairments, as large path losses, delays, and Doppler shifts, pose
severe challenges to the realisation of a satellite-based NR network. In this
paper, based on the architecture options currently being discussed in the
standardisation fora, we discuss and assess the impact of the satellite channel
characteristics on the physical and Medium Access Control layers, both in terms
of transmitted waveforms and procedures for enhanced Mobile BroadBand (eMBB)
and NarrowBand-Internet of Things (NB-IoT) applications. The proposed analysis
shows that the main technical challenges are related to the PHY/MAC procedures,
in particular Random Access (RA), Timing Advance (TA), and Hybrid Automatic
Repeat reQuest (HARQ) and, depending on the considered service and
architecture, different solutions are proposed.Comment: Submitted to Transactions on Vehicular Technologies, April 201
Virtual SATCOM, Long Range Broadband Digital Communications
The current naval strategy is based on a distributed force, networked together with high-speed communications that enable operations as an intelligent, fast maneuvering force. Satellites, the existing network connector, are weak and vulnerable to attack. HF is an alternative, but it does not have the information throughput to meet the distributed warfighting need. The US Navy does not have a solution to reduce dependency on space-based communication systems while providing the warfighter with the required information speed.
Virtual SATCOM is a solution that can match satellite communications (SATCOM) data speed without the vulnerable satellite. It is wireless communication on a High Frequency (HF) channel at SATCOM speed. We have developed an innovative design using high power and gain, ground-based relay systems. We transmit extremely wide-wideband HF channels from ground stations using large directional antennas. Our system starts with a highly directional antenna with a narrow beam that enables increased bandwidth without interfering with other spectrum users. The beam focus and power provide a high SNR across a wideband channel with data rates of 10 Mbps; 1000 times increase in HF data speed.
Our modeling of the ionosphere shows that the ionosphere has more than adequate bandwidth to communicate at 3000 km and high speeds while avoiding detection. We designed a flexible structure adjustable to the dynamic ionosphere. Our design provides a high-speed communications path without the geo-location vulnerability of legacy HF methods.
Our invention will benefit mobile users using steerable beam forming apertures with wide bandwidth signals. This dissertation will focus on three areas: an examination of the ionosphere’s ability to support the channel, design of a phased array antenna that can produce the narrow beam, and design of signal processing that can accommodate the wideband HF frequency range.
Virtual SATCOM is exciting research that can reduce cost and increase access to long-range, high data rate wireless communications
Satellite-Based Communications Security: A Survey of Threats, Solutions, and Research Challenges
Satellite-based Communication systems are gaining renewed momentum in
Industry and Academia, thanks to innovative services introduced by leading tech
companies and the promising impact they can deliver towards the global
connectivity objective tackled by early 6G initiatives. On the one hand, the
emergence of new manufacturing processes and radio technologies promises to
reduce service costs while guaranteeing outstanding communication latency,
available bandwidth, flexibility, and coverage range. On the other hand,
cybersecurity techniques and solutions applied in SATCOM links should be
updated to reflect the substantial advancements in attacker capabilities
characterizing the last two decades. However, business urgency and
opportunities are leading operators towards challenging system trade-offs,
resulting in an increased attack surface and a general relaxation of the
available security services. In this paper, we tackle the cited problems and
present a comprehensive survey on the link-layer security threats, solutions,
and challenges faced when deploying and operating SATCOM systems.Specifically,
we classify the literature on security for SATCOM systems into two main
branches, i.e., physical-layer security and cryptography schemes.Then, we
further identify specific research domains for each of the identified branches,
focusing on dedicated security issues, including, e.g., physical-layer
confidentiality, anti-jamming schemes, anti-spoofing strategies, and
quantum-based key distribution schemes. For each of the above domains, we
highlight the most essential techniques, peculiarities, advantages,
disadvantages, lessons learned, and future directions.Finally, we also identify
emerging research topics whose additional investigation by Academia and
Industry could further attract researchers and investors, ultimately unleashing
the full potential behind ubiquitous satellite communications.Comment: 72 page
Experimental L-band SST satellite communications/surveillance terminal study. Volume 5 - Aircraft terminal definition
Aircraft terminal designs for experimental and operational supersonic transport for L band satellite air traffic contro
Concepts for 18/30 GHz satellite communication system, volume 1
Concepts for 18/30 GHz satellite communication systems are presented. Major terminal trunking as well as direct-to-user configurations were evaluated. Critical technologies in support of millimeter wave satellite communications were determined
Satellite Data Communications Link Requirements for a Proposed Flight Simulation System
The purpose of this study was to investigate the requirements necessary for data and voice communication via satellite, linking Embry-Riddle Aeronautical University (ERAU) and other flight training facilities. The proposed research was conducted following a descriptive method of collecting information, generating and analyzing data, and listing the results for the proposed link requirements. The current fiber-optic communications link at ERAU in Daytona Beach was presented to establish a general foundation of communications. Research was done into methods used by satellite common carriers for realistic data and calculations. A proposed data link to connect flight simulators at the ERAU Prescott campus with the air traffic control simulation facilities at the ERAU Daytona Beach campus was developed. Data link requirements based on this scenario were gathered and the final assessment was presented. A suggested method of implementing this proposal, including carrier service and equipment selection, was developed and further research into expanding this proposal into a network was suggested
U.S. Air Force Long-Range Strike Aircraft White Paper
As a result of DoD transformation plans and recent operational experience (Air War Over Serbia and Operation ENDURING FREEDOM) portions of the 1999 U.S. Air Force White Paper on Long Range Bombers have become outmoded. In October 2001, the Secretary of the Air Force directed an updated Long-Range Strike Aircraft White Paper incorporating our new defense planning guidance. This document provides an update to the 1999 White Paper and reflects current decisions concerning bomber force structure and basing. While modification plans remain largely intact, the focus has been refined to support the Global Strike Task Force concept
The applications of satellites to communications, navigation and surveillance for aircraft operating over the contiguous United States. Volume 1 - Technical report
Satellite applications to aircraft communications, navigation, and surveillance over US including synthesized satellite network and aircraft equipment for air traffic contro
Evaluation of a Two-way Datalink for Airborne Surveillance of and Communication with a Remotely Operated Aircraft Operating in the National Airspace System
The purpose of this study is to examine the use of a two-way digital datalink to implement the airborne surveillance and communication functions with a Remotely Operated Aircraft in the National Airspace System. These Air Traffic Control functions are currently implemented using primary and secondary radar systems for airborne surveillance, and radio transmissions for voice communications.
The present Air Traffic Control system was examined, as well as existing datalink technologies and surveillance and communication equipment. Remotely Operated Aircraft are currently employed almost exclusively by the military, and operational experience in the National Airspace System is very limited. Several key military Remotely Operated Aircraft systems were evaluated, including their operations in the National Airspace System. There are numerous potential uses for commercial Remotely Operated Aircraft operations in the National Airspace System to satisfy varied missions and roles, and the issues associated with large numbers of unmanned aircraft operating in the National Airspace System was investigated. The information used in this study was collected from various published sources, as well as from a number of interviews with knowledgeable persons in the Remotely Operated Aircraft industry and the Federal Aviation Administration.
Remotely Operated Aircraft have been established as viable military platforms, and a variety of civilian missions are under consideration to extend their demonstrated usefulness. As civilian Remotely Operated Aircraft system designs and concepts of operation are refined, many cost-effective applications have been identified for using Remotely Operated Aircraft in new roles or in roles currently being performed by manned aircraft. Large numbers of Remotely Operated Aircraft are expected to be operated in the National Airspace System in the future, and the Air Traffic Control system must be able to accommodate their unique needs and facilitate the safe and efficient operation of Remotely Operated Aircraft in the National Airspace System.
Two-way digital datalink technology has significant potential for use in implementing the airborne surveillance and communication functions with Remotely Operated Aircraft in the National Airspace System. A datalink-based Air Traffic Control system provides more accurate and comprehensive time-critical surveillance information to the air traffic controller, and facilitates more efficient communications of large amounts of useful information between the air traffic controller and Remotely Operated Aircraft remote operator. It is recommended that two-way digital datalink technology should be pursued for implementing the airborne surveillance and communication functions with a Remotely Operated Aircraft in the National Airspace System. Although this technology has many key benefits, there are several important operational, safety and security issues that must be addressed before the system can be fully implemented in the National Airspace System
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