scholarly journals Characteristics of Rain-Induced Attenuation over Signal Links at Frequency Ranges of 25 and 38 GHz Observed in Beijing

2021 ◽  
Vol 13 (11) ◽  
pp. 2156
Author(s):  
Congzheng Han ◽  
Liang Feng ◽  
Juan Huo ◽  
Zhaoze Deng ◽  
Gaoyuan Zhang ◽  
...  
Keyword(s):  
Cellular Networks ◽  
Millimeter Wave ◽  
Measurement Data ◽  
Field Measurements ◽  
Rainfall Rate ◽  
Atmospheric Effects ◽  
International Telecommunication Union ◽  
Communication Links ◽  
Rain Drop ◽  
R Relation

Wireless communication has become a very important part of our lives, and it is well known that meteorological factors affect the quality of communication links, especially at higher frequencies because the physical dimensions of raindrops, hail stones, and snowflakes are on a similar wavelength to the propagating radio frequency. Millimeter-waves are an important technology for fifth-generation cellular networks which are currently being deployed all over the world. Since atmospheric effects are challenging in millimeter-wave transmissions, in this paper, we conducted line-of-sight field measurements at 25 GHz and 38 GHz. We monitored the received signal during rainfall events and compared the theoretical attenuation and the recorded rain-induced attenuation. We also derived the rain-induced attenuation (A) and rainfall rate (R) relation for stratiform and convective rain, respectively, using local rain drop size distribution (DSD) information at our measurement site collected during the period of two years. Furthermore, opportunistic sensing of atmospheric phenomena using microwave or millimeter-wave communication links in commercial cellular networks has recently attracted more attention in meteorological research worldwide. The accuracy of calculating rainfall rates from microwave links highly depends on the retrieval model and values of coefficients in the model, i.e., a and b of the A-R relation model. Here, the coefficients a and b are estimated based on local DSD measurement, and the performance of the improved A-R model is evaluated using propagated signal power based on measurement data. Compared to the (a, b) coefficients in the International Telecommunication Union Recommendation (ITU-R) P.838 document, the derived coefficients achieved an improved rainfall rate estimation.

scholarly journals Analysis of visibility effects on free space earth-to-satellite optical link based on measurement data in Nigeria

2020 ◽  
Vol 9 (1) ◽  
pp. 41-45
Author(s):  
S.E. Falodun ◽  
J.S. Ojo ◽  
O.L. Ojo
Keyword(s):  
Free Space ◽  
Measurement Data ◽  
Optical Systems ◽  
Atmospheric Effects ◽  
Signal Loss ◽  
Free Space Optical ◽  
Specific Attenuation ◽  
Port Harcourt ◽  
Link Margin ◽  
Communication Links

The effect of atmospheric variables on signals propagating from earth to space are of concern in the design and performance of wireless  communications systems. Since atmospheric effects which led to atmospheric losses (attenuations, fading and scintillation) are location-dependent, climatological phenomena such as fog, snow, rain, and haze has much effect on Free Space Optical (FSO) and can cause reduction in the link availability. This paper analysed the effect of fog on FSO communication links from earth to satellite links over five selected locations (Ikeja, Akure, Enugu, Jos and Port-Harcourt) in Nigeria. One year (2012) visibility data obtained at Nigeria Meteorological Agency (NIMET) have been used to estimate the specific attenuation caused by fog on FSO communication links in the selected locations. Link margin was deduced in all the five locations. The estimated specific attenuation caused by fog was based on operating frequencies associated with a typical commercial FSO. The result shows that at 352 THz frequency, Ikeja recorded the highest value of about 38.60 dB/km for the specific attenuation due to fog on FSO link followed by Akure with value of about 30.33 dB/km. Enugu recorded the least estimated attenuation of about 14.19 dB/km . The implication of the result is that Ikeja and Akure will suffer more signal loss, while Enugu will suffer less signal loss. Result on link margin performed on FSO link also showed that Ikeja has the highest link margin of -109.79 dB, Port-Harcourt with link margin value of -91.99 dB while Jos experienced lowest link  margin of about -37.48 dB. Keywords: Free space optical systems; Fog induced specific attenuation; Earth-space links; Link margin

scholarly journals The Impact of Multi-Connectivity and Handover Constraints on Millimeter Wave and Terahertz Cellular Networks

2021 ◽  
pp. 1-1
Author(s):  
Mustafa F. Ozkoc ◽  
Athanasios Koutsaftis ◽  
Rajeev Kumar ◽  
Pei Liu ◽  
Shivendra S. Panwar
Keyword(s):  
Cellular Networks ◽  
Millimeter Wave ◽  
The Impact

Uplink Performance Analysis for Millimeter Wave Cellular Networks With Clustered Users

2020 ◽  
Vol 69 (6) ◽  
pp. 6178-6188
Author(s):  
Nor Aishah Muhammad ◽  
Nur Ilyana Anwar Apandi ◽  
Yonghui Li ◽  
Norhudah Seman
Keyword(s):  
Performance Analysis ◽  
Cellular Networks ◽  
Millimeter Wave

On the Initial Access Design in Millimeter Wave Cellular Networks

2016 ◽  
Author(s):  
Yingzhe Li ◽  
Jeffrey G. Andrews ◽  
Francois Baccelli ◽  
Thomas D. Novlan ◽  
Jianzhong Zhang
Keyword(s):  
Cellular Networks ◽  
Millimeter Wave

Influence of Partial Admission on the Downstream Stages of a Reaction Turbine: An Analytical Approach Verified by Measurements

2013 ◽  
Author(s):  
Wolfgang Beer ◽  
Peter Hirsch
Keyword(s):  
Radial Direction ◽  
Averaging Method ◽  
Measurement Data ◽  
Field Measurements ◽  
Calculation Model ◽  
Steam Turbines ◽  
Partial Admission ◽  
Control Wheel ◽  
Unsteady Effects ◽  
Inflow Conditions

Field measurements on an industrial steam turbine with a rated power output of 5.8 MW, consisting of an impulse type control wheel and a reaction part, showed a significant gap of efficiency from the design calulations. It was suspected, that this gap results from underestimation of the loss created by non-uniform inflow conditions to the reaction part due to partial admission. The experimental results and data of experiments done in the 1990s are therefore recalculated to find possible explanations. It turns out, that probably the data considered for verifcation is not complete. When taking the complete data into account, and using an averaging method, the verification calculations show, that the models used for design and recalculation of industrial steam turbines are accurate enough for industrial purposes, but a calculation model for efficiency loss due to partial admission has to be added. In this work non-uniformity between the flow passages was not observed for the test turbine. Non-uniformity of the flow in radial direction was observed for the test turbine, but was not taken into consideration here, as the whole rotor was treated integrally. Flow seperations as unsteady effects were not considered, as a steady-state investigation was conducted. The calculation models are verified by comparison with field measurement data from industrial steam turbines, by comparison with the results of a 9 MW steam driven test turbine and by recalculated results from literature. Not all verification calculations are presented in detail here.

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