The decision schemes on the concatenation of space-time block code and convolutional code in WCDMA system

This paper discusses the decision issue on the concatenation of the space-time block code and convolutional code in the WCDMA system. We compare the performance of three decision schemes, i.e., hard-decision, uniform quantization (UQ) soft-decision and adaptive uniform quantization (AUQ) soft-decision over a Rayleigh fading channel. Simulation results show that both soft-decision schemes have a gain of over 1dB than the hard-decision. Moreover, if we divide the Rayleigh fading item from the output of space-time block combining, a little more performance gain is possible, thus the soft-decision advantage is about 2dB more than that of hard-decision. Because the AUQ scheme changes its quantization scope according to the signal-noise-ratio (SNR), it has an extra performance advantage over the UQ scheme in the fading channel especially at a very high or low SNR. However, all of the performance gain is based on increasing the hardware implementation complexity.