Adaptive Rayleigh fading compensation for coherent GMSK signals in digital mobile communications

摘要

A new fading compensation scheme for coherent Gaussian minimum shift keying (GMSK) in a fast Rayleigh fading mobile environment is described. The proposed scheme employs the adaptive extended Kalman filter (EKF) and a new decision-aided predictive algorithm to achieve accurate channel fading estimation and cancellation even when the Doppler spread is large. Our study shows that the proposed scheme requires only 18 dB E/sub b//N/sub o/ to achieve a bit error rate (BER) of P/sub e/=10/sup -2/ which is within 2 dB of the theoretical GMSK performance in a mobile channel with normalised Doppler spread of f/sub D/T=6.25/spl times/10/sup -3/. The corresponding E/sub b//N/sub o/ requirement for the conventional Costas loop coherent receiver is 28 dB. In addition, the proposed scheme achieves a residual error rate which is more than one order of magnitude lower than that of the conventional receivers. Our scheme is particularly attractive for mobile communications where a high Doppler spread is expected.