I want to find out why, say in a GSM/cellular system, a base station can be up to 50 watts however the mobile units can be only 100mw (for example).
Surely if the base station ever uses 50w to reach a mobile at long range, the mobile will have no chance to transmit back.
I understand that on a base station receiver tech is perhaps more sophisticated / bigger and better then on a mobile unit, but why would there be such a large difference in max power? - why not limit the base stations to 5 watts or such?
Note: Only using GSM as an example, but question stands for any technology. Here is what I think I know already:
- Difference between a 1W mobile and 50W base station is 17 dB.
- Base Station Diversity can add up to 5-6 dB gain, which would balance a 1W mobile to a ~4w basestation
- MIMO is on both sides, so this would be roughly equal gain and so would probably not be relevant in this topic (although the BTS with its larger antennas + better spacing may be able to get a few more dB gain).
Is the antenna technology in the base station that much better - they are larger, higher, and directional...