Doppler Effect

Dr. Sheldon cooper

Having read some “pedia”, you can ...

... note that the higher the frequency, the stronger the influence of the Doppler effect.

For a frequency of 2.5 GHz (at which mobile WiMax Yota operates), the Doppler frequency change (Doppler shift) is calculated as follows:


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In the numerator - the speed, in the denominator - the wavelength corresponding to the frequency of the signal.
Let me remind you that the wavelength is the speed of wave propagation divided by its frequency:



Here c is the speed of light, which for simplicity we take equal to 3x10 ^ 8 and f is the frequency of the signal: 2.5 GHz
Thus, the wavelength is 3x10 ^ 8 / 2.5x10 ^ 9 = 0.12 (m)
For a vehicle moving at a speed of 122 km / h (34 m / s), the Doppler frequency change will be 34 / 0.12 = 283 (Hz)

That is, when the subscriber moves relative to the base station at a speed of 122 km / h, the frequency of the signal for him will change to 272 Hz.

The data transfer rate must be less than this frequency, as otherwise the characters may be lost during transmission.

The coherence time is calculated by the formula:


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Here Sheldon suffered
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In order not to pour "water", I propose to consider as a conclusion what kind of brain you need to be in order to compensate for all this at the receiver and the base station.

Have a nice weekend and good wireless.