Diversity Technique of Receivers with W-ep Soft-decision Decoder in Mimo Systems

This paper examines the diversity technique of receivers in convolutionally encoded MIMO (Multi-Input Multi-Output) systems. We have proposed W-EP (Weighting-by Eigenvalue Power) soft-decision decoder in 2x2 encoded MIMO systems, confirmed that the weighting factor based on the eigenvalue of channel matrix has a significant effect on BER (Bit Error Rate) performances [1]. On the other hand, large interleave size according to Doppler frequency is required in order to fully acquire coding gain. This leads to the increase in both hardware size and decoding process delay [2]. In this point, the technique achieving both interleave size reduction and BER performance improvement is demanded for real systems. In SISO (Single-Input Single-Output) systems, diversity technique is well-known as one of the effective solutions for the both demands mentioned above. We focus on the antenna combining method for achieving both interleave size reduction and BER performance improvement in encoded MIMO systems. We propose a soft-decision decoder with the diversity technique based on the RAC-BME (Receiving Antenna Combining computing Branch Metric using Eigenvalue) technique [3] in 2xn (n=3, 4, 5) encoded MIMO systems. The results show that the RAC-BME decoder plays a greater role to improve BER performances than NWC (No-Weighting Combining) decoder. Moreover, it has been clear that the RAC-BME decoder can achieve the interleave size reduction with the improvement in BER performances.