A comparison of Gaussian minimum shift keying to frequency shift keying for land mobile radio

Data is presented comparing Gaussian Minimum Shift Keying (GMSK) to Frequency Shift Keying (FSK) for use in the UHF land mobile radio band at 800 MHz. The FSK system uses a Gaussian premodulation filter set at one half the bit Pate. Deviation is set at 0.41 times the bit rate. The FSK receiver has an IF bandwidth of 1.0 times the bit rate and uses discriminator detection. The GMSK system uses coherent detection. Data is presented on the effect of premodulation cutoff frequency and receiver bandwidth on system sensitivity and spectral efficiency. From this data a relationship between channel spacing, frequency stability, IF bandwidth, and transmitter spectrum is derived. Additional data on the performance of the FSK and GMSK systems in Rayleigh fading is presented.