GSM-P (Primary) denotes the core frequency band for GSM, operating in the range of 890 – 915 MHz (uplink) and 935 – 960 MHz (downlink). It accommodates 124 channels, each occupying 200 kHz. This primary band has been expanded with E-GSM. In addition to this primary band, GSM also utilizes other frequency bands, with GSM1800 (at 1800 MHz) and GSM1900 (at 1900 MHz) being the most prevalent. This frequency band is sometimes referred to as P-GSM, and it serves as the foundation for GSM mobile communications.