AES Algorithm of Improving WPAN Throughput

The throughput of WPAN (Wireless Personal Area Network) based on Bluetooth was decided by the interference of Bluetooth piconets in the network. The interference was decided by the hamming correlation of Bluetooth FH (Frequency Hopping) selected sequence. In order to improve the WPAN throughput, the WPAN model and data packet collision model were built and the relations about WPAN throughput, the maximum hamming correlation of FH selected sequence, the numbers of Bluetooth piconets and the SNR of channel were analyzed. The functions of WPAN throughput were deduced. After analyzing the performance of Bluetooth FH selected sequence, the original algorithm was replaced by the AES (Advanced Encryption Standard) algorithm. The theoretical analysis proved that the AES FH sequences selected algorithm could improve the WPAN throughput. The simulation results proved the theoretical analysis. The test result with ARM926EJs SoC (System on Chip) + RF (Radio Frequency) chip nRF2401 and CSR??s Bluecore4 Bluetooth module got the same conclusion. All of these could prove that the AES algorithm can improve the WPAN throughput efficiently.     

Affine invariant image watermarking using intensity probability density-based Harris Laplace detector

Feature point based image watermarking against geometric distortions has attracted great attention in recent years. However, for the state-of-the-art intensity based feature points detectors, the feature points often gather at textured portions of the image or on the edges where the change of intensity is significant, so that many feature points capture the same portion of the image, which makes the watermark be vulnerable to local geometric distortions. In this paper, we propose an affine invariant image watermarking scheme with good visual quality and reasonable resistance toward local geometric distortions, which utilizes the intensity probability density-based Harris–Laplace detector. Firstly, the uniform and robust feature points are extracted by utilizing modified Harris–Laplace detector, in which the intensity probability density gradient is used instead of intensity gradient. Then, the affine invariant local ellipse regions (LERs) are constructed adaptively according to the variation of local intensity probability density. Finally, the digital watermark is embedded into the affine invariant LERs in nonsubsampled contourlet transform (NSCT) domain by modulating the lowpass NSCT coefficients. By binding the watermark with the affine invariant LERs, the watermark detection can be done without synchronization error. Experimental results show that the proposed image watermarking is not only invisible and robust against common image processing operations such as sharpening, noise adding, and JPEG compression, but also robust against the global affine transforms and local geometric distortions.     

Model-based adaptive resolution upconversion of degraded images

Resolution upconversion of a degraded image is an ill-posed inverse problem that is even harder than video superresolution due to lack of redundant observations from reference frames. To overcome this difficulty an adaptive 2D piecewise autoregressive (PAR) model is used to strengthen the constraints on the solution of the inverse problem. The PAR model can be fit to local image waveforms by adjusting its parameters. But estimating the model parameters needs the knowledge of the very original high-resolution pixels to be estimated by the model. We resolve this chicken-and-egg dilemma by adaptive nonlinear least-squares joint estimation of both model parameters and original pixels. This non-linear estimation problem is solved by the method of structured total least-squares, constrained by the degradation function (e.g., the point spread function of a camera plus noises) that forms the observed low-resolution image. As such, this work offers a unified general framework for joint upsampling, deconvolution, and denoising. Moreover, the upsampling can be carried out at an arbitrary scale rather than power of two. Experiments show that the proposed NEARU technique outperforms current methods in both PSNR and subjective visual quality, and its advantage becomes greater for larger scaling factors.     

Efficient Terahertz Photoconductive Emitters with Improved Electrode Structures

We present the design,fabrication,and characterization of two new types of terahertz photoconductive emitters.One has an asymmetric four-contact electrode structure and the other has an arc-shaped electrode structure,which are all modified from a traditional strip line antenna.Numerical simulations and real experiments confirm the good performance of the proposed antennas.An amplitude increase of about 40%is experimentally observed for the terahertz signals generated from the new structures.The special electrode structure and its induced local bias field enhancement are responsible for this radiation efficiency improvement.Our work demonstrates the feasibility of developing highly efficient terahertz photoconductive emitters by optimizing the electrode structure.     

PTN承载网同步传送方案

简要介绍了时钟和日寸间2种同步技术,重点阐述了PTN承载网同步技术方案、时钟保护和规划设计原则。     

基于TMS320LF2407A的电机控制实验平台的设计

采用TI公司最新的面向电机控制的DSP芯片TMS320LF2407A，设计了一个通用的电机控制实验平台，用户可以在这个平台上进行异步电机、同步电机、直流电机等多种电机的各种控制策略的实验，使用非常方便灵活。     

YD31200－23型高压电选机工业生产测试结果浅析

详细介绍了国产ＹＤ３１２００－２３型高压电选机的结构和技术性能，测试了工业生产的各项指标。将该设备与国产ＹＤ－３型高压电选机和引进的美国ＨＴＰ（２５）２３１－２００型高压电选机进行的试验结果对比，作出了综合分析及评价。