Linear Receivers for Correlatively Coded MSK

In this paper we show that many spectrally efficient modified MSK schemes, termed generalized MSK, although not representable as OQPSK, may nevertheless be (suboptimally) demodulated using an receiver with a proper choice of carrier-phase offset. Correlatively coded MSK schemes with receivers are studied, and it is concluded that duobinary MSK and MSK represent good performance-bandwidth tradeoffs among first- and second-order correlative coding polynomial schemes. The optimal design of these receivers are considered subject to the constraint of a finite duration impulse response, especially for asymptotic cases of arbitrarily small and large SNR. Filter design based on a zero-intersymbol interference constraint for PAM-based approximations of the signals is also considered. The optimized linear receivers for MSK and MSK are presented. These receivers are only 0.28 and 1.24 dB poorer than the optimal (Viterbi) receivers at high SNR.