Coherent GFSK receiver on MIMO frequency selective channels

GFSK (Gaussian-filtered Frequency Shift Keying) signal has a constant envelope and is suited to power efficient nonlinear amplification. However, the application of GFSK signal to spectrally efficient and reliable MIMO (Multiple Input Multiple Output) communication schemes has not been so popular up to now. Maybe this comes from the fact that the signal processing for spatially multiplexed MIMO signal is usually done using linear matrix algebra and the application of linear signal processing techniques to nonlinear digital FM signal such as GFSK is difficult. In this paper, we study the coherent detection of GFSK signal based on MLD (Maximum Likelihood Detection) approach on MIMO frequency selective channels. In the proposed receiver, the receive replica signal which is frequency and phase synchronized is generated and the signal distance between the receive signal and the receive replica signal is minimized. By extending the observation length of receive signal, we further improved the BER characteristics. We also reduced the complexity of MLD by using the SE (Schnorr Euchner) algorithm of Sphere Decoding to obtain ML (Maximum Likelihood) solution.