Multiple-user interference in FH-MFSK mobile radio

The authors consider practical approaches to multiple-access communication in spread-spectrum mobile radio. Efficient field test and data processing methods are given, and the field test results are described. Bit-error-rate (BER) performance with both one and four interferers is measured, with good agreement between field and laboratory results. In the single interferer case, the BER is 10^-1 when a mobile transmitter located 350 m from the base station interferes with a mobile transmitter 3.5 km away. In the case of interferers, for DUR (desired-to-undesired signal ratio) of -20 dB, the BER approaches 10^-2. The performance of synchronous code-division multiaccess (CDMA), in which the frame timing of hopping patterns among users is synchronized, is also measured. The improvement obtained by using synchronous CDMA amounts to 15 dB compared with the use of asynchronous CDMA