Fano space-time multiple symbol differential detectors

We present in the paper a multiple-symbol differential detector (MSDD) for differential space-time (ST) codes in Rayleigh flat fading channel. The detector, termed a Fano ST-MSDD, uses the Fano algorithm as its decoding engine and is capable of delivering excellent error performance at moderate implementation complexity over a wide range of fading rates. Essentially, the detector is an "intelligent" decision feedback detector (DFD) that uses a running threshold and the accumulated path metric as navigation tools when it roams the decoding tree. In the static channel, our best Fano ST-MSDD scheme with a detection window size of N=6 is able to narrow the original 3 dB gap between ideal coherent and conventional ST differential detection by 1 dB. In a fast fading channel with a Doppler frequency of three percent the ST symbol rate, the error curve of our best TV-10 Fano ST-MSDD is able to "track" that of the ideal coherent detector (with a 3-dB gap in between) and there is no irreducible error floor. All these performances become even more remarkable when we consider the rather moderate implementation complexity reported in the paper. Because of its close relationship with a DFD, the Fano ST-MSDD has a similar complexity as the DFD at large signal-to-noise ratio (SNR). Actually, we found that the complexity of the Fano ST-MSDD is a relatively stable function of the SNR