A Practical Step Forward Toward Software-Defined Radio Transmitters

After many years of research and development in the wireless communication community, software defined radio (SDR) is no longer an unachievable dream. In this paper, we present a significant step forward toward practical SDR transmitters. Motivated by the reconfigurability, programmability and available computational power in a commercial Digital RF Processor (DRP^TM)-based single-chip GSM/EDGE radio, we succeeded to modulate the RF carrier with P25 compliant C4FM (continuous 4-level FM) data. P25 is a digital public safety standard that operates in the 746-806 MHz frequency band, which is different from the normal operation band of the GSM/EDGE chip. The modulation is based completely on software without need for any hardware modifications. The measurement results show that the transmitted signal spectrum is compliant with the P25 standard specifications. We also show that the work presented in this paper can be extended to provide more elaborate modulation schemes.