It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

Nonlocal means method using weight refining for despeckling of ultrasound images

The Analytic of Image Processing Smoothing Spaces Using Wavelet

Broken and degraded document images binarization

Multiplicative noise appears in various image processing applications, such as synthetic aperture radar, ultrasound imaging, single particle emission-computed tomography, and positron emission tomography. Hence multiplicative noise removal is of momentous significance in coherent imaging systems and various image processing applications. This paper proposes a nonconvex Bayesian type variational model for multiplicative noise removal which includes the total variation (TV) and the Weberized TV as regularizer. We study the issues of existence and uniqueness of a minimizer for this variational model. Moreover, we develop a linearized gradient method to solve the associated Euler-Lagrange equation via a fixed-point iteration. Our experimental results show that the proposed model has good performance.

Multiplicative noise removal via a novel variational model

Speckle reduction by adaptive window anisotropic diffusion

Directional wavelet can effectively capture the directional dependence in images. However, the computational complexity is high. Based on the image statistics estimated by the structure tensor, a novel directional lifting image coder locally adapting the filtering directions to image content is presented. Before performing wavelet transform (WT), the proposed algorithm detects all the image blocks in a given image to decide whether the block is homogenous or not. For homogeneous block, the conventional 2-D discrete WT is used. This will considerably reduce the computational complexity and the number of bits needed to code the directional information. On the other hand, heterogeneous block is decomposed using directional lifting wavelet transform, which can effectively capture the directional dependence in the selected image and improve the coding gain of the image coder. Experimental results have shown that, compared to some existing methods, the proposed scheme has a better performance in terms of peak signal to noise ratio (PSNR) and subjective quality.

A novel direction-adaptive wavelet based image compression

Connected vehicles have received much attention in recent years due to their significant societal benefit and commercial value. However, a suitable channel model for vehicle-to-vehicle (V2V) communications is difficult to build due to the dynamic communication environment. In this paper, a three-dimensional (3D) geometrical propagation model that includes line-of-sight (LoS), single bounced (SB), and multiple bounced (MB) rays is proposed. Each of multiple scatterers in the model is moving with a random velocity in a random direction. Based on the geometrical propagation model, a generalized 3D reference model for narrowband multiple-input-multiple-output (MIMO) V2V multipath fading channels is developed. The corresponding space-time correlation functions (ST-CFs), time correlation functions (T-CFs), and space correlation functions (S-CFs) are analytically investigated and numerically simulated in terms of various factors. Several notable ST-CFs for V2V and fixed-to-mobile (F2M) communications become the special cases of ST-CFs of the proposed model by adjusting the corresponding channel parameters. Finally, the theoretical results of the space-Doppler power spectral density (SD-PSD) are compared with the available measured data. The close agreements between the theoretical and measured SD-PSD curves confirm the utility and generality of the proposed model.

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Three-Dimensional Vehicle-to-Vehicle Channel Modeling with Multiple Moving Scatterers

Through decreasing inter-cell interferences, CoMP (Coordinated Multi-Point) can enhance system capacity and spectral efficiency of cell-edge users significantly. BSs (Base stations) are the front-end accesses of CoMP and their planning influences the overall performance of the system directly. Different from the traditional cellular network, the coverage of BSs in CoMP always overlaps with each other to some degree. In order to investigate the BSs planning for CoMP, this paper builds two optimization models to obtain the location and the number of the BSs. A joint optimization algorithm is proposed to solve models, in which the methodologies of mesh adaptive direct search and successive elimination have been used. Numerical results show that the proposed models can effectively reduce the total transmission power and the number of BSs without losing the quality of service for users, which verifies the effectiveness of the proposed algorithms and the inherent advantage of CoMP.

Xiaoping Zeng

Papers

Speckle reduction by adaptive window anisotropic diffusion

A novel direction-adaptive wavelet based image compression

Three-Dimensional Vehicle-to-Vehicle Channel Modeling with Multiple Moving Scatterers

Optimal base stations planning for Coordinated Multi-Point system