Improved design criteria and new codes on space-frequency trellis coding over frequency selective fading channels

In this paper, first we propose a new design criterion on the coding gain of space-frequency trellis codes (SFTC's) over quasi-static frequency selective fading channels when the diversity gain is moderate. Second, we propose a new design criterion on the coding gain of SFTC's with interleaver over quasi-static frequency selective fading channels when the diversity gain is moderate. Moreover, we show that the design criterion on SFTC's with interleaver over quasi-static frequency selective fading channels is equivalent to that on space time trellis codes (STTC's) over fast flat fading channels. Third, we propose a new 4-PSK, 4 state SFTC that achieves the best frame error rate (FER) with and without interleaver by computer search based on the proposed design criteria. We show that the STTC achieving the best FER over quasi-static flat fading channels achieves the best FER as SFTC over quasi-static frequency selective fading channels as well. We also show that the STTC achieving the best FER over fast flat fading channels achieves the best FER as SFTC over quasi-static frequency selective fading channels with interleaver as well.