908 research outputs found
Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges
With the rapid development of marine activities, there has been an increasing
number of maritime mobile terminals, as well as a growing demand for high-speed
and ultra-reliable maritime communications to keep them connected.
Traditionally, the maritime Internet of Things (IoT) is enabled by maritime
satellites. However, satellites are seriously restricted by their high latency
and relatively low data rate. As an alternative, shore & island-based base
stations (BSs) can be built to extend the coverage of terrestrial networks
using fourth-generation (4G), fifth-generation (5G), and beyond 5G services.
Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs.
Despite of all these approaches, there are still open issues for an efficient
maritime communication network (MCN). For example, due to the complicated
electromagnetic propagation environment, the limited geometrically available BS
sites, and rigorous service demands from mission-critical applications,
conventional communication and networking theories and methods should be
tailored for maritime scenarios. Towards this end, we provide a survey on the
demand for maritime communications, the state-of-the-art MCNs, and key
technologies for enhancing transmission efficiency, extending network coverage,
and provisioning maritime-specific services. Future challenges in developing an
environment-aware, service-driven, and integrated satellite-air-ground MCN to
be smart enough to utilize external auxiliary information, e.g., sea state and
atmosphere conditions, are also discussed
Fade Depth Prediction Using Human Presence for Real Life WSN Deployment
Current problem in real life WSN deployment is determining fade depth in indoor propagation scenario for link power budget analysis using (fade margin parameter). Due to the fact that human presence impacts the performance of wireless networks, this paper proposes a statistical approach for shadow fading prediction using various real life parameters. Considered parameters within this paper include statistically mapped human presence and the number of people through time compared to the received signal strength. This paper proposes an empirical model fade depth prediction model derived from a comprehensive set of measured data in indoor propagation scenario. It is shown that the measured fade depth has high correlations with the number of people in non-line-of-sight condition, giving a solid foundation for the fade depth prediction model. In line-of-sight conditions this correlations is significantly lower. By using the proposed model in real life deployment scenarios of WSNs, the data loss and power consumption can be reduced by the means of intelligently planning and designing Wireless Sensor Network
Emc aerospace systems analysis Interim scientific report
Analysis and data requirements for solving potential aerospace electromagnetic compatibility problem
The Effect of Sand and Dust Storms (SDSs) and Rain on the Performance of Cellular Networks in the Millimeter Wave Band
Future cellular systems are expected to use millimeter-wave (mm-Wave) frequency bands in
addition to the existing microwave bands under 6 GHz. Severe weather conditions, including sand and dust
storms (SDSs) and heavy rainfalls, challenge reliable communications over wireless links at those higher
frequencies. In such conditions, besides frequency-dependent path-loss, radio signals experience additional
attenuation. The SDS attenuation is related to visibility, receiver distance to the storm origin point, soil
type, frequency, temperature and humidity. On the other hand, the rainfall attenuation is affected by rainfall
rate, polarization, carrier frequency, temperature and raindrop size distribution. Leveraging on experimental
measurements carried out in previous works, a novel unified mathematical framework is introduced in this
paper to include SDS/rainfall-dependent attenuation in the performance evaluation of terrestrial wireless
cellular networks in terms of coverage probability, bit error rate (BER) and achievable rate in the mm-Wave
band. Extensive numerical results are presented to show the effects of the different SDS/rainfall parameters
on performance, showing that the degradation due to SDS is generally higher than that due to rain and may
cause a reduction of even six orders of magnitude in the average achievable bit rate when the frequency
increases from 28 to 38 GHz
Optical Data Downlinks from Earth Observation Platforms
The increasing resolution of earth observation sensors will require much higher data rates for the data downlink in future than is feasible with conventional RF-technology. This applies for earth observation satellites as well as for aeronautic observation platforms, such as aircraft or stratospheric high altitude platforms. The most promising solution for this data downlink bottleneck is the application of optical free space transmission technologies. DLR has built diverse atmospheric flight terminals and performed several trials of optical downlinks from space (together with partnering organizations) as well as from atmospheric carriers in recent years. Here we present and compare results of such communication system trials
Tropospheric attenuation on Satellite-aircraft propagation: A concise review
The attenuation time together with the Complementary Cumulative Distribution
Function of attenuation values play a vital role in the design of communication systems.
Passengers on-board during flight can be connected to the internet either via satellite or earthstation
depending on the nature of the flight. For long distance flight, this internet connectivity
is provided through satellite when the aircraft is flying at the upper troposphere. However, the
satellite-aircraft link is subject to attenuation due to the troposphere. A model to characterize
the channel has been proposed. In particular, a methodology for the synthesis of attenuation on
aircraft-satellite is given by ITU-R P2041 recommendation. However, it has been shown that
the impact of tropospheric parameters such as rainfall, cloud, gases etc. On the satellite-aircraft
link at different frequencies are insignificant (i.e decreases with height) on the upper
troposphere since the aircraft is flying (about 12 km) above the rain height (5 km). The
findings will be useful for researchers, scientists and the aviation industries in planning, design
and establishing link budget for aircraft-satellite path
A Vision and Framework for the High Altitude Platform Station (HAPS) Networks of the Future
A High Altitude Platform Station (HAPS) is a network node that operates in
the stratosphere at an of altitude around 20 km and is instrumental for
providing communication services. Precipitated by technological innovations in
the areas of autonomous avionics, array antennas, solar panel efficiency
levels, and battery energy densities, and fueled by flourishing industry
ecosystems, the HAPS has emerged as an indispensable component of
next-generations of wireless networks. In this article, we provide a vision and
framework for the HAPS networks of the future supported by a comprehensive and
state-of-the-art literature review. We highlight the unrealized potential of
HAPS systems and elaborate on their unique ability to serve metropolitan areas.
The latest advancements and promising technologies in the HAPS energy and
payload systems are discussed. The integration of the emerging Reconfigurable
Smart Surface (RSS) technology in the communications payload of HAPS systems
for providing a cost-effective deployment is proposed. A detailed overview of
the radio resource management in HAPS systems is presented along with
synergistic physical layer techniques, including Faster-Than-Nyquist (FTN)
signaling. Numerous aspects of handoff management in HAPS systems are
described. The notable contributions of Artificial Intelligence (AI) in HAPS,
including machine learning in the design, topology management, handoff, and
resource allocation aspects are emphasized. The extensive overview of the
literature we provide is crucial for substantiating our vision that depicts the
expected deployment opportunities and challenges in the next 10 years
(next-generation networks), as well as in the subsequent 10 years
(next-next-generation networks).Comment: To appear in IEEE Communications Surveys & Tutorial
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