doppler effect

[sreedhar]

If Doppler Effect is what really happens then why is not all the cellular communication taking place have a lot of noise ,low S/N-ratio.(means if doppler effect takes place then the frequency of the wave changes and receiver is receiving another signal of different frequency but change in frequency has occured due to doppler shift and no means of differenciating at reciever.

[New Forester]

It will only matter if the speed of the vehicle, aircraft, spacecraft or whatever is a significant proportion of the speed of the communication waves. For sound (only a few hundred miles per hour) quite a low speed is easily detectable by our ears as a change in pitch. For ocean waves, the effect can be quite extreme. Sailing downwind, a wave might catch up with you every minute or so, while sailing the other way at the same speed you might hit a dozen a minute -- their speed is very close to yours. However, for radio waves (light-speed -- hundreds of millions of miles an hour) the speed of most things will cause such a small doppler shift it'll still appear to be the same frequency. Perhaps spacecraft do need some small adjustment, as their relative speed can be very high.