Once, talking with a friend, he said that cable Internet works much better than mobile Internet. I asked him if he knows what the reason is but he shrugged. Then, I told him why, not to die stupid.
The signal transmitted by cable travels through electrical field that always has the same speed, which is the speed value of the electromagnetic field in vacuum. The cable is the same uniform and isotropic propagation environment. The cable is also a non-disturbing medium.
Instead, the mobile Internet signal (such as WiFi) is propagated through electromagnetic field. The signal does not undergo a uniform and isotropic medium, because air can be more or less polluted in some parts and then the speed is not always the same, but it decreases. Lowering speed automatically decreases the frequency or length of the wave, or both, so it intersects with other signals of the same frequency and jamming. This is just one of the reasons. There are others. When I asked what the signal is, again he shrugged.
Another disturbing factor is that in the way of their propagation, electromagnetic waves can meet absorbent surfaces. Not the same thing can be said about electric waves propagating through cable that are not disrupted by anything. But, what is the signal?
The signal can be produced by varying the voltage, intensity, frequency, wavelength, modulation, etc. All these are signals and the electric current must be alternative.