A network technician is installing a cellular repeater in a remote office to improve mobile communication for field agents. The agents report that mobile connectivity is often lost, impacting critical real-time data communication. The most used carrier in this area operates on the GSM network. Which frequency band should the technician ensure the cellular repeater supports to provide the best connectivity for GSM carriers?
2.4/5 GHz
1700/2600 MHz
700/2100 MHz
850/1900 MHz