Combinational Fuzzy-Decision Viterbi Decoding Scheme and Device for Vehicular Communications System via Time-Varying Channels

摘要

The invention presents a combinational fuzzy-decision Viterbi decoder, which combines the modified Π and S-membership functions, to further improve the performance of the dedicated short-range communications (DSRC) system operated in the time-varying fading channel. The combinational fuzzy-decision Viterbi decoder includes parallel-to-serial converter, fuzzy-decision constellation decoder and analog Viterbi decoder. The coding gain of the DSRC system using the proposed combinational fuzzy-decision Viterbi decoder is compared with both the hard-decision and soft-decision Viterbi decoder for the BPSK, QPSK, 16-QAM and 64-QAM OFDM DSRC systems. The improvement in performance of the DSRC system achieved by replacing the hard decision and soft decision Viterbi decoder with the proposed combinational fuzzy-decision Viterbi decoder will be validated with simulations.;The simulation results demonstrate that the bit error rates (BERs) of BPSK, QPSK, 16-QAM and 64-QAM OFDM DSRC system for both the four-level soft-decision and combinational fuzzy-decision Viterbi decoders can meet the requirements specified in the IEEE802.11p standard. The combinational fuzzy-decision decoder demonstrated a 1.5 dB to 2 dB coding gain as compared with the four-level soft-decision decoder when the DSRC system is operated in the time-varying fading channels. For the case of 12 Mbps data transmission rate, the 16-QAM OFDM DSRC system using the soft-decision and fuzzy-decision decoders will be reduced to less than 10⁻⁵ at the minimum SNR (17 dB), which meet the requirements specified in the IEEE802.11p standard. It is noted that the combinational fuzzy-decision Viterbi decoder results in a coding gain improvement of 2 dB and 6 dB as compared to the soft-decision Viterbi decoder and hard-decision Viterbi decoder, respectively. Many other high mobility wireless communication systems related with OFDM modulations in conjunction with the proposed scheme are possible.