Half-bit offset decision frequency detection of differentially encoded GMSK signals

An efficient frequency detection scheme for GMSK signal reception is described. In this detection scheme, a three-level eye opening of the frequency detector output at the decision instant offset by a half-bit is used to improve bit error rate (BER) performance. Experimental results for 16 kbit/s differentially encoded GMSK transmission with a premodulation filter bandwidth-bit duration product (Bb T) = 0¿25 (typical for mobile radio applications) show that the half-bit offset decision frequency detection scheme can significantly improve BER performance, in comparison with conventional detection schemes.