Reduction of errors due to random FM noise

This paper proposes a technique for reducing errors caused by random FM noise in land mobile communication systems. With this technique, we do not need the pilot or preamble signals that up to now have been indispensable. Changing the received signal by using this technique reduces the effect of random FM noise even in currently available radio systems without any change in signal format standards. Computer simulation results with DPSK, QDPSK, and 16-star QAM demonstrated the feasibility of this technique. Errors were reduced to about 1/100 of the conventional level for QDPSK when f_DT was 0.012 (where f_D is the maximum Doppler frequency and T is the symbol duration).