ABSTRACT
Orthogonal frequency division multiplexing with index modulation (OFDM-IM) has great potential for the implementation of high spectral-efficiency underwater acoustic (UWA) communications. However, general receivers consisting of the optimal maximum likelihood detection suffer from high computational load, which prohibits real-time data transmissions in underwater scenarios. In this paper, we propose a detection based on a vector approximate message passing (VAMP) algorithm for UWA OFDM-IM communications. Firstly, a VAMP framework with a non-loopy factor graph for index detection is formulated. Secondly, by utilizing the sparsity inherently existing in OFDM-IM symbols, a novel shrinkage function is derived based on the minimum mean square error criterion, which guarantees better posterior estimation. To reduce the errors from estimated non-existing indices, one trick is utilized to search the elements from the look-up table with the minimal Euclidean distance for the replacement of erroneously estimated indices. Experiments verify the advantages of the proposed detector in terms of low complexity, robustness and effectiveness compared with the state-of-art benchmarks.
ABSTRACT
Fluorescence imaging has been widely used in the fields of biomedicine and clinical diagnosis. Compared with traditional fluorescence imaging in the visible spectral region (400-760 nm), near-infrared (NIR, 700-1 700 nm) fluorescence imaging is more helpful to improve the signal-to-noise ratio and the sensitivity of imaging. Highly-sensitive fluorescent probes are required for high-quality fluorescence imaging, and the rapid development of nanotechnology has led to the emergence of organic dyes with excellent fluorescent properties. Among them, organic fluorescent probes with the advantages of high safety, good biocompatibility, and high optical stability, are more favorable than inorganic fluorescent probes. Therefore, NIR fluorescence imaging assisted with organic fluorescent probes can provide more structural and dynamic information of biological samples to the researchers, which becomes a hot spot in the interdisciplinary research field of optics, chemistry and biomedicine. This review summarizes the application of NIR organic fluorescent probes in cervical cancer imaging. Several typical organic fluorescent probes (such as indocyanine green, heptamethine cyanine dye, rhodamine and polymer fluorescent nanoparticles) assisted NIR fluorescence imaging and their applications in cervical cancer diagnosis were introduced, and the future development and application of these techniques were discussed.
