Comparison of GMSK and linear approximated GMSK for use in software radio

In Wiesler and Jondral (1998) a common software radio structure for second generation mobile systems has been introduced. This SWRADIO combines different standards of mobile communication systems like GSM, DECT, IS-54 and PDC. All baseband functions like channel coding, modulation and equalisation are implemented in a general, parametrized way, so that all of them can be used for the selected standards. This structure has several advantages like a reduced size of the hardware platform, fast performance by changing the air interface for a system handover and the possibility of global roaming. The linear approximated GMSK is used in the SWRADIO because this enables a common I/Q-modulator for all second generation systems. In this paper it is proved, that with the usual receiver (Viterbi equalizer with least square channel estimate) there is no performance loss by using the approximated GMSK instead of the original GMSK