There are billions of mobile phones all communicating with each other sending wireless signals across the globe. How does each signal know where to go exactly, and how are they not intercepted by other signals?
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Lots of cool ways. I’ll go over just the radio part between a cell phone and tower. The rest of it is the phone companies problem, and mostly uses the internet nowdays anyway.
At the most basic if you have two signals overlapping the receive strength is usually wildly different at the receiver. The receiver adjusts it’s gain to deal with different levels of power receiver even if just one signal is received. With multiple it adjusts to the loudest signal and the weaker signal just show up as noise and is ignored.
So the trick is mostly to keep all your transmitters in sync to avoid ending up with overlapping signals at the receiver. There’s lots of different types of segregation that can be used to achieve this.
Temporal segregation. If you think of like HAM radios where they say over, before someone else can speak. You can do the same with digital stuff. Digital signals compress data so that 1 second of sound might only take a few milliseconds to transfer and by careful coordination they don’t overlap.
Frequency segregation. Receivers and transmitters need to take up a certain range of frequencies to transmit data as a result of the carrier frequency getting deformed as part of encoding, but can pick different ranges within a wider range to avoid overlap. Those are called channels. Modern stuff to avoid getting stuck on any particular channel with lots of interference will jump between channels at different points in time called frequency hopping, and again takes careful coordination to keep all the devices from trying to transmit at the same time.
Spatial segregation. At it’s most basic it’s just adjusting transmit power to the minimum required. Basically just being polite to others, though maximum transmit power is also regulated by law. Two different systems won’t interfere with each other if they are quiet enough and spaced far away enough. Then you can have directional antennas like satellite dishes. You beam your signal in a line and use the dish to receive only in that direction. Beamforming antennas can do this with software/hardware that combines inputs from several antennas in an array with slightly different time delays and filtering depending on the antenna position in the array. This amplifies signals coming from certain directions without the hassle of physically pointing a dish in a direction. You can even control for specific location rather than just direction to a degree.
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