...what parts of the electromagnetic spectrum have been allocated for various purposes in different areas. For example, Military or Emergency services may be using a particular frequency in India but not in North America, etc.
Arguably the U.S. frequency band situation for cellular is the most annoying of all. Here's a table which may help a little-
Does anyone have an explanation on why the 3G implemented in the US is different from the one that is implemented from Asia?
From what I know:
US: There is Uplink and Downlink and both are on different Frequency
Ex - AT&T 850MHz uplink and 1900MHz downlink
Ex - T-Mobile 1700MHz uplink 2100MHz downlink
Asia: Both Uplink and Downlink is on the same frequency
Ex - Singtel 2100MHz