Co-channel interference comparison for conventional land mobile frequency modulation and 2400 BPS LPC/FSK system

The bit error rate (BER) performance of a Narrowband Frequency Shift Keyed (FSK) data transmission system is examined under co-channel interference conditions. Bit error rate data is presented as a function of carrier-to-interference (C/I) ratio for both static and simulated Rayleigh fading signals. Gaussian baseband premodulation data filtering is used in the FSK transmitter. The receiver has a 2.4 kHz bandwidth and discriminator detection. Methods of testing are described. Voice intelligibility of the Linear Predictive Coded (LPC) Speech is compared to that of a conventional 5 kHz deviation FM receiver for various C/I ratios. An equivalent audio tone-to-interference ratio (T/I) was determined for the Narrowband LPC/FSK system by comparing BER data and C/I measurements to FM audio T/I and C/I data. Rayleigh fading C/I performance is also compared.