Modeling air-to-ground path loss for low altitude platforms in urban environments

2014 ◽  
Author(s):  
Akram Al-Hourani ◽  
Sithamparanathan Kandeepan ◽  
Abbas Jamalipour
Keyword(s):  
Path Loss ◽  
Urban Environments ◽  
Low Altitude

scholarly journals Bounding the Practical Error of Path Loss Models

2012 ◽  
Vol 2012 ◽  
pp. 1-21 ◽  
Author(s):  
Caleb Phillips ◽  
Douglas Sicker ◽  
Dirk Grunwald
Keyword(s):  
A Priori ◽  
Path Loss ◽  
Urban Environments ◽  
Production Networks ◽  
Modeling Error ◽  
Propagation Models ◽  
Performance Accuracy ◽  
Rural And Urban ◽  
Standard Models ◽  
Loss Models

We seek to provide practical lower bounds on the prediction accuracy of path loss models. We describe and implement 30 propagation models of varying popularity that have been proposed over the last 70 years. Our analysis is performed using a large corpus of measurements collected on production networks operating in the 2.4 GHz ISM, 5.8 GHz UNII, and 900 MHz ISM bands in a diverse set of rural and urban environments. We find that the landscape of path loss models is precarious: typical best-case performance accuracy of these models is on the order of 12–15 dB root mean square error (RMSE) and in practice it can be much worse. Models that can be tuned with measurements and explicit data fitting approaches enable a reduction in RMSE to 8-9 dB. These bounds on modeling error appear to be relatively constant, even in differing environments and at differing frequencies. Based on our findings, we recommend the use of a few well-accepted and well-performing standard models in scenarios wherea prioripredictions are needed and argue for the use of well-validated, measurement-driven methods whenever possible.

Engine Design Studies for a Silent Aircraft

2006 ◽  
Vol 129 (3) ◽  
pp. 479-487 ◽  
Author(s):  
Cesare A. Hall ◽  
Daniel Crichton
Keyword(s):  
Thermodynamic Cycle ◽  
Urban Environments ◽  
Operating Conditions ◽  
Speed Reduction ◽  
Fuel Burn ◽  
Engine Design ◽  
Low Altitude ◽  
Noise Benefits ◽  
Bypass Ratio ◽  
Maximum Thrust

The Silent Aircraft Initiative is a research project funded by the Cambridge-MIT Institute aimed at reducing aircraft noise to the point where it is imperceptible in the urban environments around airports. The propulsion system being developed for this project has a thermodynamic cycle based on an ultrahigh bypass ratio turbofan combined with a variable area exhaust nozzle and an embedded installation. This cycle has been matched to the flight mission and thrust requirements of an all-lifting body airframe, and through precise scheduling of the variable exhaust nozzle, the engine operating conditions have been optimized for maximum thrust at top-of-climb, minimum fuel consumption during cruise, and minimum jet noise at low altitude. This paper proposes engine mechanical arrangements that can meet the cycle requirements and, when installed in an appropriate airframe, will be quiet relative to current turbofans. To reduce the engine weight, a system with a gearbox, or some other form of shaft speed reduction device, is proposed. This is combined with a low-speed fan and a turbine with high gap-chord spacing to further reduce turbomachinery source noise. An engine configuration with three fans driven by a single core is also presented, and this is expected to have further weight, fuel burn, and noise benefits.

Engine Design Studies for a Silent Aircraft

2006 ◽  
Author(s):  
Cesare A. Hall ◽  
Daniel Crichton
Keyword(s):  
Thermodynamic Cycle ◽  
Urban Environments ◽  
Operating Conditions ◽  
Speed Reduction ◽  
Fuel Burn ◽  
Engine Design ◽  
Low Altitude ◽  
Noise Benefits ◽  
Bypass Ratio ◽  
Maximum Thrust

The Silent Aircraft Initiative is a research project funded by the Cambridge-MIT Institute aimed at reducing aircraft noise to the point where it is imperceptible in the urban environments around airports. The propulsion system being developed for this project has a thermodynamic cycle based on an ultra-high bypass ratio turbofan combined with a variable area exhaust nozzle and an embedded installation. This cycle has been matched to the flight mission and thrust requirements of an all-lifting body airframe, and through precise scheduling of the variable exhaust nozzle, the engine operating conditions have been optimized for maximum thrust at top-of-climb, minimum fuel consumption during cruise and minimum jet noise at low altitude. This paper proposes engine mechanical arrangements that can meet the cycle requirements and, when installed in an appropriate airframe, will be quiet relative to current turbofans. To reduce the engine weight a system with a gearbox, or some other form of shaft speed reduction device, is proposed. This is combined with a low-speed fan and a turbine with high gap-chord spacing to further reduce turbomachinery source noise. An engine configuration with three fans driven by a single core is also presented and this is expected to have further weight, fuel burn and noise benefits.

Path Loss Characteristics in Urban Environments Using Ray-Tracing Methods

2017 ◽  
Vol 16 ◽  
pp. 3063-3066 ◽  
Author(s):  
Daisy Green ◽  
Zhengqing Yun ◽  
Magdy F. Iskander
Keyword(s):  
Ray Tracing ◽  
Path Loss ◽  
Urban Environments

scholarly journals Vehicular Channel in Urban Environments at 23 GHz for Flexible Access Common Spectrum Application

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Longhe Wang ◽  
Bo Ai ◽  
Jingya Yang ◽  
Hao Qiu ◽  
Wanqiao Wang ◽  
...  
Keyword(s):  
Mobile Networks ◽  
Dynamic Spectrum Access ◽  
Radio Channel ◽  
Path Loss ◽  
Radio Spectrum ◽  
Urban Environments ◽  
Delay Spread ◽  
Access Technology ◽  
Rms Delay Spread ◽  
New Radio

With the development of the vehicular network, new radio technologies have been in the spotlight for maximizing the utilization of the limited radio spectrum resource while accommodating the increasing amount of services and applications in the wireless mobile networks. New spectrum policies based on dynamic spectrum access technology such as flexible access common spectrum (FACS) have been adopted by the Korea Communications Commission (KCC). 23 GHz bands have been allocated to FACS bands by the KCC, which is expected extensively for vehicular communications. The comprehensive knowledge on the radio channel is essential to effectively support the design, simulation, and development of such radio technologies. In this paper, the characteristics of 23 GHz vehicle-to-infrastructure (V2I) channels are simulated and extracted for the urban environment in Seoul. The path loss, shadow factor, Ricean K-factor, root-mean-square (RMS) delay spread, and angular spreads are characterized from the calibrated ray-tracing simulation results, and it can help researchers have a better understanding of the propagation channel for designing vehicular radio technologies and a communication system in a similar environment.

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