Substation noise at distribution-line communication frequencies

Measurements of noise on the distribution line at power distribution substations in the frequency range from 6 GHz to 14 GHz are presented. This is the frequency range used for distribution-line communication systems by power companies for load control and feeder automation. The measurements reported here are concerned with harmonic and background noise, which are omnipresent on the substation bus. Single-frequency noise may or may not be present in a given frequency band. Impulse noise is intermittent     

Background noise in optical communication systems

The origin and magnitude of the several kinds of background noise that perturb optical communication receivers are discussed, including background radiation sources viewed directly, radiation reflected from background objects, and radiation scattered by the atmosphere into the receiver field of view. An extensive bibliography on this topic is presented.     

Blind identification of digital communication channels withcorrelated noise

Blind identification consists of estimating the impulse response of a linear, time-invariant channel used for transmission of digital data by observing the channel output without knowledge of the transmitted symbol sequence. We show how a previously proposed algorithm (Moulines et al., 1995) based on second-order statistics of the received signal can be modified to account for correlated noise     

Second-order statistics of logarithmic quantization noise in QAMdata communication

When a QAM (quadrature amplitude modulation) data signal is transmitted over a channel that includes PCM codecs, it has frequently been observed and shown that the resulting noise around the final received constellation points grows with the distance of the point from the origin. The authors extend the analysis of this effect, and further show that the noise distribution about each point is elliptical, with greater variance in the radial direction. Formulas giving the signal-dependent noise components as a function of the channel characteristics of the analog transmit and receive access legs are derived. Experimental results confirm the analysis     

单光子卫星量子通信噪声和干扰分析

卫星量子通信是建立全球量子通信网络的最佳选择之一。针对采用偏振编码的卫星量子通信中的偏振保持问题,研究了大气散射和卫星与地面站间相对运动等因素对量子偏振态相位和对准的影响以及相位延迟和对准误差对系统量子误码率的影响,分析了背景噪声和系统硬件噪声对通信产生的影响以及单光子通信过程中可能受到的光子分离攻击干扰,为量子信号认知设计提供借鉴意义。     

乘性噪声干扰下的通信信号偏差控制器设计与研究

乘性噪声干扰相对于加性噪声干扰具有更强的时变特性和抗滤波性,传统方法难以实现有效的滤波控制,乘性噪声在远程无线通信中会导致信道偏差,为解决这一问题提出了一种基于窄带阻抗匹配的乘性噪声干扰下的通信信号偏差控制方法,并进行控制器的硬件系统设计。设计了基于窄带阻抗匹配远程通信信号的乘性噪声干扰滤波算法,以此为基础进行通信信号偏差控制器系统硬件电路设计。在EPM7128AETI100上连入各芯片的读/写程序,得到3种通信信号偏差复位方式,采用MAX7000AE系列器件实现硬件接口设计,采用分段拟合的方式补偿非线性失真,实现乘性噪声干扰滤波器设计和信号偏差控制器设计。实验结果表明,采用该设计系统能有效滤除了通信信号中的乘性噪声污染,接收信号及其频谱的畸变得到有效补偿,改善了通信质量,提高了远程无线通信的稳定性和可靠性。     

ASK digital demodulation scheme for noise immune infrared data communication

A high performance architecture is proposed for the ASK (Amplitude Shift Keying) digital demodulation, which is dedicated to the noise immune wireless infrared data communication. In this architecture, an infrared subcarrier detected by a photodetector is digitized into TTL interface level pulses, and the digitized subcarrier is demodulated by a 1‐bit digital demodulator. To improve the noise immunity against fluorescent lamps, the optical noises from the lamps are analyzed and the behavior of an ASK infrared communication link is modeled under these noises. On the basis of this model, a digital demodulator is synthesized by means of a high level synthesis tool, aiming at implementing an algorithm of discriminating the subcarrier from optical noises. A part of experimental results shows that the ASK receiver realized with the use of this digital demodulator can achieve an error free infrared link even under the intense noises from fluorescent lamps. This revised version was published online in July 2006 with corrections to the Cover Date.     

Nonlinear distortions and noise in optical communication systems due to fiber connectors

The transmission characteristics of optical fiber connectors are analyzed in detail in order to calculate nonlinear distortions and noise due to instable speckle patterns. The fluctuation amplitude of the transmission loss and its sensitivity, with respect to a wavelength shift of the laser source, are determined for coherent and partially coherent laser sources. Nonlinear distortions due to fiber connectors yield a second-order harmonic distortion of typically -36 dB for a single-longitudinal mode injection laser, and typically -65 dB for a multimode laser. The noise performance has also been estimated for both low frequency and high frequency fluctuations.     

Thermal noise in optical fibers and its influence on long-distancecoherent communication systems

The theory of phase noise caused by thermal fluctuations in an optical fiber is revised, accounting for both longitudinal and transverse phonons, and for the anisotropy of the elastooptic effect. A realistic optical mode field is accounted for. The theory is applied to calculations of bit error rates in DPSK coherent fiber-optic communication systems. Numerical results show that the thermal phase fluctuations are unimportant for transmission distances below 10000 km     

Modal noise penalties for data communication links employing largearea VCSELs

For the first time, high mode selective loss (MSL) margins for large area VCSELs are theoretically justified. Calculated speckle visibility and power penalties agree with experiments. The predicted power penalty at 10^-9 BER for a VCSEL link, employing 62.5/125 fibre, with six connectors, each with 1 dB MSL, is 0.75 dB     

Improvement of noise stability of multi-channel communication systems with repetition

The paper is devoted to estimation of multichannel communication systems with repetition. The systems under consideration use adaptive control of signal time delay in each channel during transmission and reception, and adaptive selection at the reception end based on threshold choice of the most noise-stable channel. Adaptation to noise situation by means of programmable variation of carrier frequencies in each channel is also considered.     

基于稀疏编码的TPM通信噪声抑制分析

基于独立成分分析(ICA)时域滤波的时相调制(TPM)通信系统中的噪声干扰对系统性能有很大的影响。采用稀疏编码方法对TPM通信中的噪声进行抑制。首先对观测信号采用稀疏编码方法进行稀疏编码,然后对处理后的信号使用压缩方法处理,从而将ICA过程中对噪声所代表的小的变元值变小或置零,最终达到对噪声的削弱。仿真表明,稀疏编码方法对TPM通信中的噪声确实有较好的抑制,与不采用所提方法相比,大约有1 dB的系统误码性能提高。     

白光LED通信系统的噪声与干扰分析

阐述了背景可见光在噪声受限与干扰受限的白光LED通信系统中的影响.利用带通滤波器和光学设计以及噪声匹配等方法提高了作为噪声受限系统的接收机性能;采取带阻滤波器、副载波调制、增设滤波电容等措施,很好地抑制了干扰源对干扰受限系统的影响;提出了基于噪声与干扰双受限的白光LED通信接收机设计方案,根据该方案设计的白光LED通信...     

激光扫描共聚焦显微镜观察近紫外线辐射对兔晶体上皮细胞通讯功能的影响

目的:通过激光扫描共聚焦显微镜荧光漂白恢复技术观察近紫外线对兔晶状体上皮细胞缝隙连接通讯功能的影响。方法:体外培养兔晶状体上皮细胞,设置空白阴性对照,分为对照组和实验组,分别以近紫外线辐射5分钟,10分钟和15分钟,用荧光光漂白恢复技术检测细胞的荧光恢复率。结果:空白对照组荧光恢复率为57.357±5.610,照射5分钟,10分钟和15分钟近紫外线辐射后的荧光恢复率分别为(%)34.205±3.652,18.909±3.017,7.129±2.917。结论:近紫外线损伤可以导致晶状体上皮细胞间通讯功能的受损。     

相干光OFDM通信系统中的IQ补偿和相位估计

文章首先研究了相干光OFDM(正交频分复用)通信系统中的线性损耗,包括IQ(同相/正交相)不平衡以及线性相位噪声;提出了一种DA(基于决策)的不需要周期性地插入训练数据的方法。计算机仿真结果表明,所提出的方法可以有效估计并补偿这两类线性损耗;在此基础上,提出了一种在考虑信道色散噪声的情况下,联合补偿IQ不平衡和线性相位噪声的新算法。     

Phase noise and sub-carrier spacing effects on the performance ofan OFDM communication system

This letter analyzes the phase noise effects on an orthogonal frequency division multiplexing (OFDM) signal and its dependence with the sub-carrier spacing. Pilot-based channel estimation, which has been suggested as a means of combating the channel effects, can also correct the phase noise effects under some circumstances, which are investigated     

基于自适应噪声抵消的无线传感网络信道优化

无线传感器网络通信技术广泛应用在物联网近场通信、水声通信等领域。无线传感网络通信信道受到多途干扰,导致信道失衡,需要进行信道均衡模型设计。提出一种基于自适应噪声抵消的无线传感器网络通信信道优化技术,首先构建了无线传感器网络通信的信道模型,对无线传感器网络信道传播过程中衰减损失和各条路径的信号进行重组,采用自适应噪声抵消算法进行信道的多途干扰滤波,结合最小二乘（ RLS）准则算法进行无线传感器网络通信信道均衡设计。仿真结果表明,采用该通信信道均衡技术能有效提高无线传感器网络通信的信道质量,降低通信传输失真和误比特率,实现信道自适应均衡,提高通信的抗干扰能力。     

Uplink power control based on receiver noise measurements insatellite communication systems

The authors describe a novel procedure for uplink power control in a multicarrier satellite communication system. The purpose of uplink power control is to compensate for rain attenuation so that all carriers are at the same power level at the input of the satellite nonlinear amplifier. The presence and amount of rain attenuation is predicted by continuous monitoring of the receiver noise power. Attractive features of the proposed scheme include its conceptual simplicity, ease of implementation, applicability to a wide variety of scenarios and avoidance of the undesirable overhead coordination, and delay requirements associated with previously used methods     

多径分量噪声干扰下无线电扩频通信优化技术

无线电扩频通信受到多径分量噪声的干扰,导致通信信道均衡性不好,抗干扰能力不强,误码率较高。需要进行噪声干扰抑制,改善无线电扩频通信质量。提出一种基于自适应级联陷波和码间干扰抑制的无线电扩频通信优化技术。构建无线电扩频通信系统传输结构模型,采用自适应陷波器对无线电扩频通信中的多径分量噪声进行有效抑制,降低了进入信号通频带内的干扰功率,提高解调器的输出信噪比和信干比。采用扩展后的序列去调制载波,将信号搬移到载频上,实现信道均衡,提高抗干扰能力。仿真结果表明,该算法能有效降低无线电扩频通信的误比特率,抗干扰性较强,提高通信质量。