actually, don't those figures relate to the frequency of the carrier signal and not the bandwidth? If so, then it has not (or very little) effect on the data throughput.
Normal landlines have a bandwidth mesured in kHz (going back to school now - could have changed recently, but not much?) for voice. 2.5Ghz sounds a bit high for me.
If the velocity of a wave = Frequency * wavelength then:
wavelength = velocity / frequency.
velocity = speed of light (3*10^8 m/s)
frequency = 2.5 * 10^9 (Gigahertz) (of carrier)
this makes the wavelength about 0.1m, which is about right - very long microwaves or short wave radio. All that is needed in a household situation.
R.