are you sure that the problem comes from the speed of the MS, and not from the fact that the frequencies are interfered ?
– try to stop the car when you see this problem, and check whether it is still happening.
how fast is your going ?
Are we talking about EGPRS (MCS1-9) or GPRS (CS1-4) ? Which coding scheme is used during the problem ?
I’ve read about the doppler effect, but it seems that it doesn’t have any impact on GSM. The example was at 100km/h, it generated a frequency offset of 90Hz… 90Hz compared to 200kHz… it’s neglictible.
So I would really focus on an interference problem rather than a speed problem… but maybe I’m wrong.