# Can a 3G usb modem be used as a mini Cellphone Tower [closed]

I am curious to know whether small USB 3G modems could be used as cellular towers, and if you would need special firmware to do it or if it is not possible at all. They can communicate with the tower, why can't they act as one? Can it not use the right channels or what?

• Without detailed engineering information of a specific modem, this will have to be closed as too broad - usage questions generally are off topic on a design site due to this lack of information. Obviously unique firmware would be required. Additionally, uplink and downlink frequencies are usually more widely separated than the channels within each, so while these things are fairly frequency agile it's not necessarily true that they'd be able to operate (well) on a given frequency in the opposite direction than they were designed to. – Chris Stratton Oct 13 '17 at 18:56

## 1 Answer

In theory yes, but in practice no. Besides the firmware, the hardware in the client device is usually set to communicate on only a few frequencies and the transmitter is limited to the uplink frequencies while the receiver circuitry is limited to the downlink frequencies for noise suppression and other reasons. One would have to change the filter circuits, not something easily done with surface mount technology and it may be directly embedded in the chips. Franklin wireless is keen on making their devices unmodifiable. The DSP's used in the tower are able to handle hundreds or thousands of simultaneous connections and usually have their frequency limits unlocked. Those units also cost \$ and are too large to fit in your pocket.

• I would also say no in theory as well. A 3G USB stick simply does not have the required hardware needed to properly act like a base station. There are multiple features a base station has that a USB stick does not have. – Bimpelrekkie Oct 13 '17 at 21:14