Group-Based Successive Interference Cancellation for Multi-Antenna NOMA System with Error Propagation

Non-orthogonal multiple access(NOMA)is viewed as a key technique to improve the spectrum efficiency and solve the issue of massive connectivity.However,for power domain NOMA,the required overall transmit power should be increased rapidly with the increasing number of users in order to ensure that the signal-to-interference-plus-noise ratio reaches a predefined threshold.In addition,since the successive interference cancellation(SIC)is adopted,the error propagation would become more serious as the order of SIC increases.Aiming at minimizing the total transmit power and satisfying each user’s service requirement,this paper proposes a novel framework with group-based SIC for the deep integration between power domain NOMA and multi-antenna technology.Based on the proposed framework,a joint optimization of power control and equalizer design is investigated to minimize transmit power consumption for uplink multi-antenna NOMA system with error propagations.Based on the relationship between the equalizer and the transmit power coefficients,the original problem is transformed to a transmit power optimization problem,which is further addressed by a parallel iteration algorithm.It is shown by simulations that,in terms of the total power consumption,the proposed scheme outperforms the conventional OMA and the existing cluster-based NOMA schemes.

Error Outage Probabilities of Dual-Hop Relay Channels in a Poisson Interference Field

In the promising cooperative communication systems,network performance is mainly affected by interference instead of noise.In this paper,we consider the performance degraded by the Poisson filed interference in the dual-hop relay channels.We focus on the discussions of error outage probability (EOP) performance with a selective-decode-and-forward (SDF),amplify-and-forward (AF),or fixed-decode-and-forward (DF) cooperation protocol.Finally,the simulation results present the performance with different cooperation protocols with interference in a Poisson field.

Multi-dimensional and complicated electromagnetic interference hardware-in-the-loop simulation method

A typical electronic communication system, such as GPS receiver, unmanned aerial vehicle＇s （UAV＇s） data link, and radar, faces multi-dimensional and complicated electromagnetic interference in operating environment. To measure the anti- interference performance of the electronic communication system in the complicated electromagnetic interference environment, a method of multi-dimensional and complicated electromagnetic interference hardware-in-the-loop simulation in an anechoic room is proposed. It takes into account the characteristics of interference signals and the positional relationship among interference, the receiver and the transmitter of the electronic communication system. It uses the grey relational method and the angular domain mapping error correction method to control the relevant parameters, the microwave switch and so on, thus achieving the approximately actual mapping of the outdoor multi-dimensional and complicated electromagnetic interference in the anechoic room. To verify the effectiveness of this method, the multi-dimensional and complicated electromagnetic interference of the UAV＇s data link is simulated as an example. The results show that the degree of correlation between the calculated signal to interference ratio of the data link receiver in the actual scene and the measured signal to interference ratio of the data link receiver simulated with this method in the anechoic room is 0.968 1, proving that the method is effective for simulating the complicated electromagnetic interference.

Ultra-wideband direct-sequence design approach for multiple narrowb and interference suppression

A novel direct sequence （DS） design method for suppressing the narrowband interference in DS spread spectrum ultra-wideband receivers is proposed. The method has low computational complexity and can be easily implemented in practical systems. Simulation results prove that the proposed method is effective to suppress the narrowband interference. Therefore, the integrity of both the ultra-wide bandwidth and the narrowband systems can be highly enhanced.

New Technique for Estimating and Suppressing Narrowband Interference in DSSS Systems

A generalized approach for narrowband interference （NBI） suppression in direct sequence spread spectrum （DSSS） communication systems using adaptive infinite impulse response （IIR） filter is presented. The excision filter coefficients depend on both the jammer power and its instantaneous frequency. The dependency of the filter construction on the jammer power is significant as it allows optimal tradeoff between interference removal and signal distortion by maximizing the receiver signal to noise ratio improvement（SNRI）. Instead of traditional adaptive line enhancer （ALE） estimator, a preferable NBI estimator-Fourier interpolation estimator （FIE） is proposed. Closed-form expressions of the SNR improvement and theoretical bit error rate （BER） based on the assumption that the output of the correlator is Gaussian distributed are both derived. Performance results obtained by numerical simulation are also presented and compared with theoretical results.

Interlingual Interference in the English Language Word Order Structure of Chinese EFL Learners

This paper will focus on some common word order errors that Chinese students make.The author will present a body of contrastive material to illustrate what specific word order errors are in collected writing samples of Chinese students.Then the er⁃rors will be broken down into certain error types and be analyzed in depth.At the end of this paper,each error type occurrence rate will be calculated and the statistics will be represented in a pie chart.The paper finds out interlingual interference leads to these common errors by Chinese English language learners.

Coverage probability of cellular networks using interference alignment under imperfect CSI

Interference alignment （IA） is well understood to approach the capacity of interference channels, and believed to be crucial in cellular networks in which the ability to control and exploit interference is key. However, the achievable performance of IA in cellular networks depends on the quality of channel state information （CSI） and how effective IA is in practical settings is not known. This paper studies the use of IA to mitigate inter-cell interference of cellular networks under imperfect CSI conditions. Our analysis is based on stochastic geometry where the structure of the base station （BS） locations is considered by a Poisson point process （PPP）. Our main contribution is the coverage probability of the network and simulation results confirm the accuracy.

Interference checking approach with tolerance based on assembly dimension chain

CAD model with nominal dimension is implemented in interference checking of assembly simulation of aircraft complex parts at present, which causes inadequate availability. In order to address this challenging issue, interference checking method with tolerance based on assembly dimension chain was proposed. Worst case and maximum error probability of tolerance of composing loop were used, and CAD models were respectively re-constructed and inserted into simulation system. Before dynamic interference checking, engineering semantic interference condition was set to assembly requirements. Finally, the interface checking result was a basis for reasonability of assembly process and tolerance. A prototype system was developed based on the above research.

Opto-mechanical-thermal integration analysis of Doppler asymmetric spatial heterodyne interferometer

In order to improve the detection accuracy of Doppler asymmetric spatial heterodyne(DASH)interferometer in harsh temperatures,an opto-mechanical-thermal integration analysis is carried out.Firstly,the correlation between the interference phase and temperature is established according to the working principle and the phase algorithm of the interferometer.Secondly,the optical mechanical thermal analysis model and thermal deformation data acquisition model are designed.The deformation data of the interference module and the imaging optical system at different temperatures are given by temperature load simulation analysis,and the phase error caused by thermal deformation is obtained by fitting.Finally,based on the wind speed error caused by thermal deformation of each component,a reasonable temperature control scheme is proposed.The results show that the interference module occupies the main cause,the temperature must be controlled within(20±0.05)℃,and the temperature control should be carried out for the temperature sensitive parts,and the wind speed error caused by the part is 3.8 m/s.The thermal drift between the magnification of the imaging optical system and the thermal drift of the relative position between the imaging optical system and the detector should occupy the secondary cause,which should be controlled within(20±2)℃,and the wind speed error caused by the part is 3.05 m/s.In summary,the wind measurement error caused by interference module,imaging optical system,and the relative position between the imaging optical system and the detector can be controlled within 6.85 m/s.The analysis and temperature control schemes presented in this paper can provide theoretical basis for DASH interferometer engineering applications.

Analysis of Lexical Errors in Writing and its Implications for Teaching College English Vocabulary

This paper analyzes the lexical errors that students make in their written work.The errors are classified,and their causes are traced.The implications of the analysis are also provided in the paper.

Error propagation determined iterative channel estimation with ICI mitigation for fast time-varying OFDM channels

The intersubcarrier interference(ICI) degrades the performance of the pilot-aided channel estimation in fast time-varying orthogonal frequency division multiplexing(OFDM) systems.To solve the error propagation in joint channel estimation and data detection due to this ICI,a scheme of error propagation determined iterative estimation is proposed,where in the first iteration,Kalman filter based on signal to interference and noise is designed with ICI transformed to be part of the noise,and for the later iterations,a determined iterative estimation algorithm obtains an optimal output from all iterations using the iterative updating strategy.Simulation results present the significant improvement in the performance of the proposed scheme in high-mobility situation in comparison with the existing ones.

Errors Analysis in Chinese Students＇ Compositions

This paper analyzes the errors in Chinese college students＇ compositions. The study finds that among the three types of errors： interference errors, intralingual errors and developmental errors, developmental errors are the most important errors in the Chinese college students＇ writing. The results will help Chinese EFL teachers （especially college teachers） and students better judge the errors in the English writings of the Chinese students. It will also help the students avoid different kinds of errors in English writing.

外界干扰下车对车2×2 MIMO-VLC系统研究

为了研究干扰车辆和穿越道路行人对车对车可见光通信系统的影响,本文提出了带有外界干扰的车对车2×2 MIMO可见光通信模型.该模型以基于市场加权灯束模型的汽车前照灯作为2个发射器,以光电探测器作为2个接收器,考虑了间隔车道车辆和过道行人对系统性能的影响.研究结果表明:当误码率小于为10^(−4)时,同道、邻道和间隔车道车辆的纵向通信距离分别为:28 m、5~18 m、0 m;间隔车道的两车不能直接通信,但其前照灯发射光线会进入信号接收车辆从而对正常通信两车产生影响;行人穿越道路会使正常通信两车的误码率产生较大波动且存在积极影响,正常通信两车横向距离越大积极影响占比越高;本文提出的模型考虑了行人和车辆的干扰,为改善可见光通信在复杂交通网的应用效果提供了理论依据.

一种适用于卫星通信的自适应窄带干扰抑制方法

针对卫星通信系统中的抗干扰问题,提出一种能够根据干扰变化自适应调整策略的干扰抑制方法。该方法通过子带分割、按功率排序、依次陷波等方式进行陷波,然后对比陷波前后信号信噪比的增益,从而确定信噪比增益最大时所对应的子带陷波个数,最终得到信噪比增益最高也即性能最优的陷波方式。该方法不需要预先进行干扰检测,也不需要寻找和设置门限阈值,就可以对多种类型干扰进行自适应陷波,从而达到有效抑制包含单音、窄带、梳状或部分频带等不同干扰的目的,能够显著改善链路的通信性能,提高通信系统的抗干扰能力。

面向高速移动环境的二级信号检测算法

正交时间序列复用(OTSM)可以以更低的复杂度实现类似正交时频空间(OTFS)调制的传输性能,为未来需要低复杂度收发器的高速移动性通信系统提供一种有前景的解决方法。针对现有的基于时域的高斯-赛德尔(GS)迭代均衡效率不高的问题,提出二级信号检测算法。首先在时域进行低复杂度线性最小均方误差(LMMSE)检测,其次采用连续超松弛(SOR)迭代算法进一步消除残余符号干扰。为进一步提高收敛效率和检测性能,对SOR算法进行线性优化得到改进SOR(ISOR)算法。仿真实验结果表明,与SOR算法相比,ISOR算法在增加较低复杂度前提下可以提升检测性能并加快算法收敛。与GS迭代算法相比,ISOR算法采用16QAM调制且误码率为10-4时有1.61 dB的增益。

考虑制造误差的摆线轮减速器转臂轴承承载分析

摆线轮减速器转臂轴承的承载性能和磨损状况与减速器的回转精度和寿命有密切关系。针对某150BX型摆线轮减速器轴承孔实际磨损状况,首先,建立转臂轴承的承载模型,明确了最大载荷及其方向的变化规律;然后,建立含制造误差的摆线轮和曲柄轴的运动模型,分析制造误差对转臂轴承运动过程中的干涉情况,获得了转臂轴承上最大干涉位置和误差选配方法。研究为摆线轮减速器转臂轴承的磨损计算和关键零部件的误差选配提供了依据。

基于跟踪误差约束的机器鱼抗扰动路径跟踪控制

为了解决机器鱼在扰动下跟踪效率低的问题,本工作提出了一种抗扰动和自适应的误差约束控制方案。首先,通过设计虚拟控制输入,并利用积分环节更新了自适应视线制导律,消除了侧滑导致的运动位置偏离,增强了机器人的抗干扰能力。其次,通过构造机器鱼的偏航和浪涌自适应控制器,使神经网络函数拟合模型的不确定项和水流扰动,并用逼近值补偿系统的控制输入。这提升了机体的环境适应性。最后,利用障碍Lyapunov理论,机器鱼跟踪位置和角度的一致最终有界性被证明。通过模拟和实验,与经典制导方案相比,所提方案提高了机器鱼的跟踪效率和稳态性能,使机器鱼的位置误差收敛速率平均提升了14.57%。

基于多波长干涉的瞬态轮廓检测Mirau显微镜

针对单波长Mirau干涉显微镜存在测量范围小和2π模糊等问题,提出了多波长Mirau偏振干涉显微镜,以实现微观轮廓的大动态范围测量的和表面粗糙度等显微结构的瞬态检测。系统利用R、G、B三个单色LED光源实现多波长干涉;利用彩色偏振相机获取瞬态相移干涉条纹图,降低实时瞬态检测中复杂的环境扰动影响;利用线栅偏振片调节条纹对比度,满足不同被测对象的反射率检测要求。为验证系统方案的可行性,经过系统误差补偿校准后测量标称值为1.9939μm的标准微米台阶,结果与标称值的偏差约为5.4 nm。利用该方法与Wyko干涉仪对金刚石车削凸面反射镜表面微观轮廓和表面粗糙度进行测量,表面粗糙度测量结果均方根值偏差为3.7 nm,验证了该系统可实现高精度的大动态范围测量。

电力通信数据流量异常的并行检测方法设计

数据流量异常监测是电力通信网络运行过程中不可缺少的环节,但异常监测过程易受不同信道流量冗余性、异常数据类型等问题的干扰,导致监测过程耗时较长和误差较大。为了解决上述问题,设计了一种电力通信数据流量异常的并行检测方法。采用自适应邻域算法对电力通信数据流量作降维处理,并通过并行的思路实现不同信道内电力通信数据流量的分解,从而有效地降低了数据流量的冗余性干扰。设计并行检测方法对数据流量作并行分解处理,将分解后的数据流量输入到检测模型中,通过计算样本点对应的异常得分,完成电力通信数据流量的异常监测。试验结果显示,该方法的均方误差小、时间消耗少、召回率高。该方法的电力通信数据流量异常监测性能较优,具有一定的实用价值。

电子剪切散斑3CCD传感图像特征去噪优化检测方法

针对CCD(Charge-Coupled Device)光学传感器采集电子剪切散斑干涉图像特征由于散斑指数高、峰值信噪比低,导致剪切散斑图质量差、检测效果不佳的问题,提出一种电子剪切散斑3CCD传感图像特征去噪优化检测方法。该方法分析了电子剪切散斑技术在三维物体表面变形检测中产生问题的原因,采用3CCD图像传感器替代单CCD图像传感器,引入同态滤波降噪处理图像,设计一种相位干涉技术,结合Canny检测算法,实现电子剪切散斑去噪优化检测。实验结果表明,应用3CCD传感器结合去噪技术的电子剪切散斑智能检测方法,图像散斑指数更低、峰值信噪比更高、检测时间更短,分别为0.0234、19.5 dB、16.2 ms,并且三维物体表面变形测量误差在0.09 mm内,该方法有效提高了图像质量,从而提高了实际应用价值。