AbstractA new reception scheme in which an adaptive equalization‐linear reception circuit and delay detectionlimiter reception circuit are switched optimally on a frequency‐selective fading mobile radio channel with a varying delay spread is proposed. First, the two‐path frequency selective fading propagation model is classified into a fixed delay model and time‐varying delay model in which delay varies according to Markov process. Next, a receiver state model suitable for these propagation models is proposed. the receiver consists of three states: (i) limiter amplifier and delay detection; (ii) linear amplifier and equalizer; and (iii) linear amplifier and baseband delay detection. In addition, a delay spread sensor detecting the delay wave component ratio for state transitions is proposed.Finally, various characteristics have been clarified by computer simulations. It has been clarified that the ratio for selecting adaptive equalization under flat fading can be less than 0.4 and 50 percent with one symbol delay frequency‐selective fading in a delay‐fixed model, and characteristics are infiuenced by the time constant of the processing in a delay transition model.