Background functionality of a mobile phone
Have a look at a teardown of e.g. the iPhone: https://www.ifixit.com/Teardown/iPhone+4S+Teardown/6610 . Especially step 9 of that page. There's the ARM processor, the A5, which counts as the "main" SoC. Next to it is the radio processor, Qualcomm RTR8605, which Chipworks have a teardown of: http://www.chipworks.com/en/technical-competitive-analysis/resources/blog/iphone-4s-teardown-a-closer-look-at-the-chips-inside/?lang=en&amp;Itemid=815

The die shot makes it clear what's going on. You can see several blocks with distinct boundaries, and a number of inductors (the octagonal ring structures). Each of those is for a different radio function.



No mass-market product would use FPGAs, it's too expensive.