TD(98)110

Abstract
The paper presents a new modulation technique called a variable rate M-CPFSK modulation. M-CPFSK consists of 2-CPFSK, 4-CPFSK and 8-CPFSK modulation schemes with modulation indices h=1/2, 1/4 and 1/8 respectively. The number of modulation levels M varies in accordance with the mobile radio channel impair-ments experienced by a radio
signal.

Additive white Gaussian noise, Rayleigh fading and Doppler frequency shift are considered in the simulation model. An eye pattern is used as a basis for the switching thresholds among the modulation schemes.

The results show that a variable rate M-CPFSK modulation with the average of 2 bits per symbol outperforms the constant rate 4-CPFSK modulation giving the same average transmission rate.