Oleg Zabluda's blog
Saturday, August 25, 2018
 
Wireless communication breaks through water-air barrier
Wireless communication breaks through water-air barrier
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when the transmitter wants to send a 0, it can transmit a wave traveling at 100 hertz; for a 1, it can transmit a 200-hertz wave. When the signal hits the surface, it causes tiny ripples in the water, only a few micrometers in height, corresponding to those frequencies.

To achieve high data rates, the system transmits multiple frequencies at the same time, building on a modulation scheme used in wireless communication, called orthogonal frequency-division multiplexing. This lets the researchers transmit hundreds of bits at once.

Positioned in the air above the transmitter is a new type of extremely-high-frequency radar that processes signals in the millimeter wave spectrum of wireless transmission, between 30 and 300 gigahertz. (That’s the band where the upcoming high-frequency 5G wireless network will operate.)

The radar, which looks like a pair of cones, transmits a radio signal that reflects off the vibrating surface and rebounds back to the radar. Due to the way the signal collides with the surface vibrations, the signal returns with a slightly modulated angle that corresponds exactly to the data bit sent by the sonar signal. A vibration on the water surface representing a 0 bit, for instance, will cause the reflected signal’s angle to vibrate at 100 hertz.
[...]
A key challenge was helping the radar detect the water surface. [...] The next major challenge was capturing micrometer waves surrounded by much larger, natural waves. [...] Natural waves occur at about 1 or 2 hertz [...] The sonar vibrations of 100 to 200 hertz, [...].
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https://news.mit.edu/2018/wireless-communication-through-water-air-0822
https://news.mit.edu/2018/wireless-communication-through-water-air-0822

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