FCC CRF part 15.249 restricts the fundamental radiated power to 50 mV/m at 3 meters distance (-1 dBm EIRP) in the 902-915 MHz ISM band in the US. FCC 15.247 specify additional requirements that allows the application to increase the output power above what is specified in part 15.249. There are in general two possibilities for higher output power. That is by implementing a Frequency Hopping Spread Spectrum (FHSS) system or use a digital modulation that spreads the power into a certain bandwidth.

This design note describes how to comply with these digital spread wideband requirements in 15.247 for CC11xx in order to increase the output power more than -1 dBm without the use of frequency hopping.

http://www.ti.com/lit/swra123