Mr. Xueming Liu Profile

Xueming Liu

at Nanjing Xiaozhuang College

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Publications (3)

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Proceedings Article | 24 October 2014 Paper

Aspheric lens based imaging receiver for MIMO visible light communication

Qiuqi Ju, Zhongcheng Liang, Xueming Liu, Tingting Yang, Jin Wang

Proceedings Volume 9270, 927012 (2014) https://doi.org/10.1117/12.2071766

KEYWORDS: Receivers, Reflection, Imaging systems, Sensors, Visible radiation, Light emitting diodes, Signal detection, Telecommunications, Aspheric lenses, Reflectivity

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Visible light communication (VLC) has been regarded as a promising solution in short-range intelligent communication system. Nowadays, the research is focused on integrating the multi-input multi-output (MIMO) technique in the VLC system, to achieve a larger transmission capacity and stronger transmission reliability. However, one important issue should be addressed due to the use of MIMO technology: the multipath inter-symbol interference. The multipath intersymbol interference comes from the reflection of the signal in the room and channel crosstalk between different channels. In this paper, we propose a novel optical system used in the MIMO VLC system to reduce multipath interference dramatically. Signals from different LEDs can be separated by using parabolic lens plated with reflecting film. This structure can reduce the reflection effect effectively as well. We present the simulation results to observe the distribution of optical power on the imaging plane for various receiving positions and low correlation between all channels. We can find that the optical power density becomes stronger than non-imaging system and the interference is sharply decreased, thus the SNR and BER are also optimized. Analysis about the optical system is given in this paper.

Proceedings Article | 27 November 2012 Paper

Wide FOV receiving device for indoor visible light communication systems based on the MIMO principle

Xueming Liu, Zhong-cheng Liang, Xuyin Wang, Qiuqi Ju

Proceedings Volume 8555, 85551S (2012) https://doi.org/10.1117/12.2000612

KEYWORDS: Light emitting diodes, Receivers, Imaging systems, Digital signal processing, Signal to noise ratio, Transmitters, Sensors, Telecommunications, Signal detection, Visible radiation

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Visible light communication (VLC) is expected to be the next generation technology of indoor wireless broadband access. In order to achieve high data transmission rates, the multiple input multiple output (MIMO) VLC is proposed to break the bandwidth limitation due to the slow response time of LED devices, as MIMO-VLC offers the potential to transmit data in parallel between multiple sources and detectors. In addition, MIMO processing removes the need for precise alignment of transmitters and receivers, if the channel matrix is known and of full rank. Therefore, MIMO provides a solution to the design of wide field-of-view (FOV) receiving device for indoor VLC system, which is expensive if traditional optical components are used. This paper demonstrates the feasibility of such FOV receiving device with an integrated small size detector array, and discusses the device properties in terms of optimal channel capacity, complexity and robustness to misalignment. A physical model is proposed for system simulation based on the single lens optical transform. The aim of this effort is to design and realize the integrated receiving device of wide FOV for LED visible light communication systems.

Proceedings Article | 16 October 2009 Paper

Determination of suitable cell size for grid based digital elevation model

Xuejun Liu, Yanfang Wang, Bei Jin

Proceedings Volume 7492, 74924U (2009) https://doi.org/10.1117/12.838600

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Horizontal resolution, one of dominant variables for grid based Digital Elevation Model (DEM), directly determines topographic expression, the accuracy of terrain parameters and geosciences simulations based on DEM. Cell size is determined on relationship between resolution and terrain parameters traditionally, without taking terrain variance information content of the raw data into account. This paper puts forward two methods for suitable DEM horizontal resolution by mining the input contour data based on geostatistics. One is a direct method considering internal and external variance. Regularization variables of serial resolutions are calculated from the sampled data by regularization theory in geostatistics. After the variance comparison between point and serial resolutions, the grid at which the external variance between adjacent grids is larger than average internal variance in grid is named suitable resolution. The other method, which combines macro-topographical variance with micro-topographical variance, is an indirect way. Various large-scale supports and their regularization variables are made by dividing the sampled data using regularization theory. In order to ascertain an optimal support size to express macroscopic spatial variance of terrain, semivariograms of regularization variables are analyzed on various support sizes. Estimation of the optimal bin size that can estimate the probability density function in non-parametric density estimation is referred to decide the microcosmic appropriate resolution in the optimal support. Both methods were experimented in practice, and gave relatively consistent results. The latter was commended considering the computational efficiency.

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