水下光通信防恶性码卷积码设计

为了防止在水下光通信系统中激光器发送长"0"或长"1"信号序列,避免通信系统发生无穷多个比特错误,采用一种新的卷积码编码方案,进行了编码设计和Viterbi译码理论分析与误比特性能仿真验证,用VHDL语言实现了编码器现场可编程门阵列设计,得到了编码系统与未编码系统的误比特率和达到同样误码性能所需的信噪比。结果表明,这种编码能够降低水下无线光通信系统的误比特率,提高通信的可靠性,降低系统对信噪比的需求。     

弱湍流条件下LDPC码室内FSO通信系统调制性能分析

为了克服光在弱湍流大气条件传输时,光强闪烁造成的突发错误,理论分析了基于开关键控、脉冲位置调制、差分脉冲位置调制和数字脉冲间隔调制方式的自由空间光通信系统性能。首先推导了无线光通信未编码系统在各调制方式下的平均误比特率公式;在此基础上,将低密度奇偶校验码和置信传播算法应用到无线光通信系统中,研究了相应系统模型下的译码,并在大气湍流信道中进行了理论分析和实验仿真验证。结果表明,脉冲位置调制可获得最好的误比特率性能;采用低密度奇偶校验的大气弱湍流光通信系统比未编码的通信系统性能好,并且可以有效地增加信噪比增益,能够提高系统的抗干扰能力,在无线光通信系统中将有一定的应用前景。     

载波频偏对编码OFDM系统性能的影响

OFDM系统具有抗多径干扰和频带利用率高的优点,信道编码可以有效地提高传输系统的可靠性,但载波频率偏移会降低OFDM系统的性能。通过研究在有频率偏移和无频率偏移两种条件下OFDM系统中卷积编码和Turbo编码的传输性能,并进行了对比。根据仿真结果表明,Turbo编码的性能优于卷积码且编码效率越高,误比特率越小。在小信噪比情况下,信噪比对系统性能的影响大于频率偏移所产生的影响。而在大信噪比情况下,频率偏移的影响远远大于信噪比的影响。     

孔径接收下各向异性海洋湍流UWOC系统误码分析

为了研究孔径接收对各向异性海洋湍流条件下水下无线光通信(UWOC)系统误比特率的影响, 系统采用高斯光束传输, 接收端通过孔径接收, 在脉冲位置调制方式下通过各向异性海洋湍流信道。引入各向异性海洋湍流结构常数, 通过对闪烁的形成原理和各向异性海洋湍流条件下闪烁系数的分析, 数值模拟得到了在不同接收孔径和各向异性因子下, 海洋湍流参量、传输距离、雪崩光电二极管(APD)平均增益和调制阶数对系统误比特率的影响。结果表明, 相同各向异性因子和海洋湍流参量下, 大孔径接收能有效提升系统误比特率性能; 相同孔径直径和海洋湍流参量下, 各向异性因子越大, 系统通信性能越好; 均方温度耗散率、温度和盐度对海洋功率谱变化贡献的比值较小, 湍流动能耗散率、动力粘度较大以及传输距离越短, 系统误码性能越好; APD增益为100或150时, 系统通信性能最佳; 调制阶数M=8时, 系统通信性能最佳, M>64时, 系统误比特率变化程度几乎饱和。该研究为UWOC系统平台搭建和性能估计提供了参考。     

无线光通信中PPM的RS级联编码调制研究

在脉冲位置调制(PPM)直接检测光通信系统中插入RS级联编码构成一种新的PPM光通信系统(RS-PPM),该方式对PPM直接检测光通信系统进行了改进,并用Mat l ab对编码系统和未编码系统的误比特率进行了仿真比较,仿真结果表明,基于RS级联编码的PPM系统具有较好纠错和抗干扰能力。     

卷积码在UWB Rake接收机中的应用

针对有码间干扰的TH-PPM-UWB通信系统,研究了基于卷积码Rake接收机的性能,并在IEEE 15.3a UWB的LOS信道和NLOS信道下对采用卷积码Rake接收机的误比特率进行计算机仿真,仿真结果表明,当SNR达到一定值后,无论是LOS信道还是NLOS信道,相对未编码的Rake接收机,采用卷积码的Rake接收机性能明显提高,在NLOS信道更为显著。     

基于级联交织码的水下LED光通信误码性能分析

为了提升系统误比特率,减小基线漂移以及海水信道的吸收散射等特性对光信号产生的影响,采用了基于水下发光二极管(LED)光通信系统的低密度奇偶校验码(LDPC)-里所(RS)级联交织码方案,在模拟水下LED光通信实验系统的情况下,分析码字方案中RS码、LDPC码以及交织参量对系统误比特率性能的影响,得到了级联交织码方案的优化参量,并进行了实验模拟验证。结果表明,优化后的级联交织码系统与未编码系统、RS码系统、LDPC码系统相比分别可获得3.8dB,2dB,1.2dB的增益,可有效提高系统的误比特率性能。该研究为提高水下无线光通信系统的可靠性提供了参考。     

基于MATLAB对卷积码的性能分析

本文对比了在加性高斯白噪声（AWGN）信道下经BPSK调制后的数据不编码与添加卷积编码后接收到的信道输出的误码性能,并通过对比对卷积码性能进行分析。采用MATLAB自编函数对[2,1,8]卷积码以及维特比译码进行仿真,且对其性能进行分析。由于卷积码有性能floor,编码增益随信噪比降低而体现不明显。仿真结果表明：当信噪比等于-1dB时,一个序列通过加性高斯白噪声信道后接收到的信道输出误比特率大于10-1,且该序列运用[2,1,8]卷积码编码,维特比译码（硬判决）后所得的序列误比特率升高。当信噪比为2dB时,一个序列通过加性高斯白噪声信道后接收到的信道输出误比特率约为4＊10-2,且该序列运用[2,1,8]卷积码编码,维特比译码后所得的序列误比特率小于10-3,误码率远低于不编码时的误码率。因此卷积码适用于信道输出误码率比较低时候。     

基于LDPC码的无线光通信副载波误码性能分析

为了研究信道编码技术对无线光通信副载波系统差错性能的影响,基于无线光通信链路噪声特性,建立了大气信道等效数学模型。采用低密度奇偶校验(LDPC)码作为信道编码方式引入无线光通信,在不同光强闪烁指数下对基于副载波相移键控调制无线光通信系统进行了差错性能仿真,比较分析了LDPC编码前后副载波调制系统的误比特率,并对二相相移键控及四相相移键控两种系统进行了对比。结果表明,副载波二相相移键控调制系统的差错性能优于四相相移键控系统,同时LDPC码在弱湍流信道具有优越的纠错能力,可以获得比未编码系统较高的编码增益,在无线光通信领域具有一定的应用价值。     

一种改进的OFDM水下可见光无线通信系统

在水下直流偏置光无线通信正交频分复用(UOWC-DCO-OFDM)系统中, 为了保证光信号在发射端具有较低峰均比(PAPR)并在水下可进行远距离低误比特率传输,采用了子载波预留、最小二乘算法(TR-LSA)与压扩变换相结合的方法,同时运用优化的神经网络对水下环境进行信道估计,并基于该方法在接收端设计信道均衡器,以应对水下环境对光信号的强衰减。结果表明,UOWC-DCO-OFDM系统的PAPR降低9dB,且在信噪比为10dB时误比特率低于10-3,达到水下无线光通信的误比特率标准。该系统可实现光信号水下远距离、低误比特率传输。     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks     

Call for Papers—Feature Topic,Vol.12,No.7,2015

正Information Centric Networking Information-Centric Networking(ICN) is an emerging direction in Future Internet architecture research,gaining significant tractions among academia and industry.Aiming to replace the conventional host-to-host communication model by a data-centric model,ICN treats data content as the first     

JOURNAL OF ELECTRONICS(CHINA)

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NEXT GENERATION WIRELESS NETWORKS–ESPECIALLY THE USE OF MILLI-MICROWAVE BANDS

The global bandwidth shortage of wireless communications has motivated the exploration of the naillimeter wave （ram-wave） frequency spectrum for the next generation wireless communications. Recent advances in RF CMOS technology and high speed baseband signal processing technologies have enabled tile extensive research and development of turn-wave wireless communications. The multi gigabit per second data rate of ram-wave system will lead to applications in many important scenarios, such as WPAN, WLAN,back-haul for cellular system. And the frequency bands include 28 GHz, 38 GHz, 45GHz, 60GHz, E-BAND and even beyond 100 GHz. The propagation and the imitation of the RF circuits design in these frequency bands make the directional antennas be inevitable for mm-wave communications.