Water Vapor Water Vapor Monitoring using Monitoring using
Wireless Wireless Communication Communication
Networks Networks Measurements Measurements
Noam DavidNoam DavidThe Department of Geophysics & Planetary The Department of Geophysics & Planetary Sciences, TAUSciences, TAU
TheThe ResearchResearch TeamTeam
Prof. Pinhas Alpert –Prof. Pinhas Alpert –meteorologymeteorology
Team members:Team members: Dr. Rana SamuelsDr. Rana Samuels Artem ZinevichArtem Zinevich Ori AuslenderOri Auslender
Prof. Hagit Messer – Prof. Hagit Messer – signal processingsignal processing
Noam DavidNoam David Dani CharkaskyDani Charkasky Ronen RadianRonen Radian Yoni OstromtzkiYoni Ostromtzki
WirelessWireless CommunicationCommunication NetworksNetworks
Base Station 1
Base Station 2
User 1
User 2
• These links are built close to the ground, and operate in a frequency range of tens of GHz
• In many wireless communication systems the Received Signal Level (RSL) is measured and recorded.
• In wireless communication, the RSL depends on atmospheric conditions.
Transmission losses due to atmosphericTransmission losses due to atmospheric conditionsconditions
Absorption and scattering of the radiation, at frequencies of tens of GHz, are directly related to the atmospheric conditions, primarily precipitation,
oxygen, water vapor, mist and fog (Ulaby, 1981).
The idea: Water Vapor The idea: Water Vapor MonitoringMonitoring• In typical conditions of:
• 1013 hPa pressure
• 15ºC temperature
• water vapor density of 7.5 gr/m3
The water vapor density can be measured!
• Part of the wireless systems have a magnitude resolution of 0.1 dB per link.
)/( 2.0 kmdB
The model: microwave The model: microwave propagation in moist airpropagation in moist air
- The attenuation due to water vapor and due to dry air [dB/km]
f - The link's frequency [GHz].
N” - The imaginary part of the complex refractivity measured in N units, a function of the frequency f [GHz], pressure p[hPa], temperature T [°C] and the water vapor density ρ[gr/m3].
*ITU-R Recommendations P. 676-6: Attenuation by atmospheric gases, September 2005
[dB/km] ),,,("1820.0 TpffNwO
ResulResultsts
Water Vapor MonitoringWater Vapor Monitoring
4.53
km
Tzrifin
Ramla
Ben Gurion Airport
Frequency: 22.525 GHzSurface station-link distance: ~6.5 kmLength: 4.53 kmReceiver and transmitter heights: 95, 63 [m] ASL
Water Vapor MonitoringWater Vapor Monitoring
Number of days: 25Correlation: 0.89RMSD: 3.4 [g/m3]
Water Vapor Density- Central Israel 09/2007 (03:00 a.m.)
05
1015202530
26/08/2007 31/08/2007 05/09/2007 10/09/2007 15/09/2007 20/09/2007 25/09/2007 30/09/2007
Date
Wat
er V
apo
r D
ensi
ty (
g/m
^3)
Microwave Humidity Gauge (Lod Airport)
Water Vapor MonitoringWater Vapor Monitoring
3.86
km
Harduf
Kiryat Ata
Frequency: 22.725 GHzSurface station-link distance: ~7.5 kmLength: 3.86 kmReceiver and transmitter heights: 265, 233 [m] ASL
Water Vapor MonitoringWater Vapor Monitoring
Correlation: 0.9RMSD: 1.8 [gr/m3]2 rainy days were excluded (7 and 22 November)
Water Vapor Density- North Israel 11/2005 (03:00 a.m)
0
5
10
15
20
25
30/10/2005 04/11/2005 09/11/2005 14/11/2005 19/11/2005 24/11/2005 29/11/2005 04/12/2005
Date
Wate
r V
ap
or
Den
sit
y
[g/m
^3]
Microwave Humidity Gauge (K. Ata)
SummarySummary Our results show relatively good agreement between the
conventional way to measure water vapor and our proposed, novel method
The technique is restricted to weather conditions which exclude rain, fog or clouds along the propagation path
Since measurements from the microwave link are line integrated data, where in-situ measurements are point measurements in a humidity gauge, some disparities are expected
The method only requires standard data (saved by the communication system anyway), therefore the costs are minimal
