The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum （DS-SS） systems. The excision threshold is a non-linear function related t...The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum （DS-SS） systems. The excision threshold is a non-linear function related to the number and the power of interference, and attempting to get the exact relation of threshold related to the number and the power of interference is almost impossible. The N-sigma algorithm determines the excision threshold using subsection function; however, the excision threshold determined by this method is not exact. A new method to determine the threshold of N-sigma algorithm is proposed. The new method modifies the scale factor N by use of the membership function. The threshold determined by this method is consecutive and smooth, and it is closer to the fact than that of the initial N-sigma algorithm. The GPS signal and single-tone （CW） interference （that is, typical narrow-band interference） are implemented in the simulation, and the results are presented to demonstrate the validity of the new algorithm.展开更多
An improved method of generating the self-balanced chaotic spread-spectrum code is presented. The chaotic-map pseudorandom sequence is used as the generated source. After a series of processing two-valued quantization...An improved method of generating the self-balanced chaotic spread-spectrum code is presented. The chaotic-map pseudorandom sequence is used as the generated source. After a series of processing two-valued quantization, inversion, all upside down, radix-S block upside down and shift combination, the proposed code is achieved. Theory analysis and simulation performance of the improved code are illustrated. And the results indicate that the suggested method gains a better performance than the traditional one by reasonable choices of the initial value and the S parameter in the im- proved method. Meanwhile the chaotic sequence＇ s characteristic of large addresses is inherited when the chaotic-map is used as the source. This advantage makes this improved code very suitable for the multiple access application in communication system.展开更多
This paper presents a secure spread-spectrum watermarking algorithm for digital images in discrete wavelet transform (DWT) domain. The algorithm is applied for embedding watermarks like patient identification /source ...This paper presents a secure spread-spectrum watermarking algorithm for digital images in discrete wavelet transform (DWT) domain. The algorithm is applied for embedding watermarks like patient identification /source identification or doctors signature in binary image format into host digital radiological image for potential telemedicine applications. Performance of the algorithm is analysed by varying the gain factor, subband decomposition levels, size of watermark, wavelet filters and medical image modalities. Simulation results show that the proposed method achieves higher security and robustness against various attacks.展开更多
过程分析测量系统被广泛地应用于化工、食品与饮料、生物技术和制药行业的生产实践中。目前,过程分析测量系统大都采用“工控机+总线架构”传感器的方式实现,少部分使用了蓝牙mesh组网的方式,这两种组网架构均存在相应的问题。远距离无...过程分析测量系统被广泛地应用于化工、食品与饮料、生物技术和制药行业的生产实践中。目前,过程分析测量系统大都采用“工控机+总线架构”传感器的方式实现,少部分使用了蓝牙mesh组网的方式,这两种组网架构均存在相应的问题。远距离无线电(Long Range Radio,LoRa)是一种新型的基于1 GHz以下的超长距低、功耗数据传输技术,使用线性调频、扩频调制技术,融合了数字扩频、数字信号处理和前向纠错编码技术,在过程分析测量系统中将拥有前所未有的性能。展开更多
文摘The key to narrow-band interference excision in frequency domain is to determine the excision thresh- old in direct-sequence spread-spectrum （DS-SS） systems. The excision threshold is a non-linear function related to the number and the power of interference, and attempting to get the exact relation of threshold related to the number and the power of interference is almost impossible. The N-sigma algorithm determines the excision threshold using subsection function; however, the excision threshold determined by this method is not exact. A new method to determine the threshold of N-sigma algorithm is proposed. The new method modifies the scale factor N by use of the membership function. The threshold determined by this method is consecutive and smooth, and it is closer to the fact than that of the initial N-sigma algorithm. The GPS signal and single-tone （CW） interference （that is, typical narrow-band interference） are implemented in the simulation, and the results are presented to demonstrate the validity of the new algorithm.
文摘An improved method of generating the self-balanced chaotic spread-spectrum code is presented. The chaotic-map pseudorandom sequence is used as the generated source. After a series of processing two-valued quantization, inversion, all upside down, radix-S block upside down and shift combination, the proposed code is achieved. Theory analysis and simulation performance of the improved code are illustrated. And the results indicate that the suggested method gains a better performance than the traditional one by reasonable choices of the initial value and the S parameter in the im- proved method. Meanwhile the chaotic sequence＇ s characteristic of large addresses is inherited when the chaotic-map is used as the source. This advantage makes this improved code very suitable for the multiple access application in communication system.
文摘This paper presents a secure spread-spectrum watermarking algorithm for digital images in discrete wavelet transform (DWT) domain. The algorithm is applied for embedding watermarks like patient identification /source identification or doctors signature in binary image format into host digital radiological image for potential telemedicine applications. Performance of the algorithm is analysed by varying the gain factor, subband decomposition levels, size of watermark, wavelet filters and medical image modalities. Simulation results show that the proposed method achieves higher security and robustness against various attacks.
文摘过程分析测量系统被广泛地应用于化工、食品与饮料、生物技术和制药行业的生产实践中。目前,过程分析测量系统大都采用“工控机+总线架构”传感器的方式实现,少部分使用了蓝牙mesh组网的方式,这两种组网架构均存在相应的问题。远距离无线电(Long Range Radio,LoRa)是一种新型的基于1 GHz以下的超长距低、功耗数据传输技术,使用线性调频、扩频调制技术,融合了数字扩频、数字信号处理和前向纠错编码技术,在过程分析测量系统中将拥有前所未有的性能。
