SummaryMultiple‐input multiple‐output (MIMO) transmission techniques constitute an important technology in modern wireless communication. Hence, performance analysis methods for such systems are of considerable interest. This paper considers first the average pairwise error probability for uncoded MIMO systems employing maximum likelihood detection over a composite Rayleigh‐Lognormal fading channel with spatial correlation. It provides general results, applicable also to a wider class of shadowing models, concerning asymptotical diversity gains and shows that they are not changed by such shadowing. Then, analytical evaluation techniques for bit‐error‐rate (BER) over composite Rayleigh‐Lognormal fading channels, based on the truncated union bound and the transfer function, are considered. Furthermore, these techniques are modified for applications over spatially correlated channels. This paper shows that such performance evaluation techniques provide good approximations to BER of spatially uncorrelated MIMO systems and also in the presence of moderate spatial correlation, over Rayleigh‐Lognormal fading channels. Copyright © 2013 John Wiley & Sons, Ltd.

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Based on the ensemble empirical mode decomposition (EEMD) time-frequency analysis for avoiding mode mixing, an algorithm to delicately separate the Doppler blood flow and vessel wall beat signals is proposed in this paper. Firstly, the proper amplitude of added noise and number of ensemble average for noise cancellation are estimated, and then the mixed Doppler ultrasound signal is decomposed into IMFs by using EEMD method. Finally, the IMFs around the division between the blood flow and vessel wall signals are delicately separated using soft-threshold denoising method. Experiments on both computer simulated with WBSR of 20dB, 40dB and 70dB as well as real human carotid Doppler ultrasound signals are carried out to compare the proposed method with the high pass filter, the original empirical mode decomposition (EMD) method and the improved EMD delicate separation method. It is shown that method proposed in this paper provides the highest accuracy of extracting blood flow signals by elimination of the mode mixture, especially for those signals with larger wall-to-blood signal ratio.

This work considers a simple bit level combining technique, aided by robust bit reliability information, for uplink collaborating multiple-input multiple-output (MIMO) base-stations (also known as macrodiversity MIMO), operating over composite Rayleigh-lognormal fading channels. Bit reliability weights based on a robust modification of the logarithmic likelihood ratio, combined with instantaneous symbol signal-to-noise ratio information, are derived for different local MIMO detection schemes. This bit reliability information is used at the fusion center, together with locally detected data, for combining and producing final information bits delivered to the destination. Computer simulation results confirm that such bit level combining techniques, when used with minimum mean squared error ordered successive interference cancelation and also with sphere decoding maximum likelihood local detectors, provide significant performance improvements over non-collaborative base-stations systems. Performance gains are maintained even when these schemes suffer from channel estimation errors and also in the presence of space correlation. Low backhaul overhead and performance advantages make these bit level combining techniques attractive for applications in next generation cellular systems employing coordinated multi-point (CoMP) technology, as well as for other collaborative MIMO communication schemes. Copyright