Abstract: We compared the simulated Bit Error Rate (BER) performance for the coherently differential detection of a single carrier differentially encoded 16 level amplitude/phase shift keying (16 DAPSK) in presence of Additive White Gaussian Noise (AWGN), flat fading and Rician fading channel with the BER rate performance for the coherently differential detection of multi carrier differentially encoded 16 level amplitude/phase shift keying (16 DE-APSK) in presence of Additive White Gaussian Noise (AWGN), flat fading and Rician fading channel. Differential detection comprises eight level Differential Phase Detection (DPD) and two Amplitude Ratio Detector (ARD). This study investigates the BER performance of differentially coherent demodulation in presence of AWGN, frequency flat and Rician fading channels for single carrier mode of 16 level DE-APSK and multi carriers mode of 16 level DE-APSK via Monte Carlo simulation. The BER performance is also compared with 16 DE-PSK. The results showed a large degradation system performance for both single and MC 16 level DE-APSK over Rician fading compared with Additive white Gaussian channel, this is due to the increase of the Doppler rate from 0.01 to 0.1 Hz.