A Synchronization Acquisition Algorithm Based on the Frequency Hopping Pulses Combining

As modern electromagnetic environments are more and more complex,the anti-interference performance of the synchronization acquisition is becoming vital in wireless communications.With the rapid development of the digital signal processing technologies,some synchronization acquisition algorithms for hybrid direct-sequence(DS)/frequency hopping(FH)spread spectrum communications have been proposed.However,these algorithms do not focus on the analysis and the design of the synchronization acquisition under typical interferences.In this paper,a synchronization acquisition algorithm based on the frequency hopping pulses combining(FHPC)is proposed.Specifically,the proposed algorithm is composed of two modules:an adaptive interference suppression(IS)module and an adaptive combining decision module.The adaptive IS module mitigates the effect of the interfered samples in the time-domain or the frequencydomain,and the adaptive combining decision module can utilize each frequency hopping pulse to construct an anti-interference decision metric and generate an adaptive acquisition decision threshold to complete the acquisition.Theory and simulation demonstrate that the proposed algorithm significantly enhances the antiinterference and anti-noise performances of the synchronization acquisition for hybrid DS/FH communications.

Gigahertz frequency hopping in an optical phase-locked loop for Raman lasers

Raman lasers are essential in atomic physics,and the development of portable devices has posed requirements for time-division multiplexing of Raman lasers.We demonstrate an innovative gigahertz frequency hopping approach of a slave Raman laser within an optical phase-locked loop(OPLL),which finds practical application in an atomic gravimeter,where the OPLL frequently switches between near-resonance lasers and significantly detuned Raman lasers.The method merges the advantages of rapid and extensive frequency hopping with the OPLL’s inherent low phase noise,and exhibits a versatile range of applications in compact laser systems,promising advancements in portable instruments.

Quantum correlations and entanglement in coupled optomechanical resonators with photon hopping via Gaussian interferometric power analysis

Quantum correlations that surpass entanglement are of great importance in the realms of quantum information processing and quantum computation.Essentially,for quantum systems prepared in pure states,it is difficult to differentiate between quantum entanglement and quantum correlation.Nonetheless,this indistinguishability is no longer holds for mixed states.To contribute to a better understanding of this differentiation,we have explored a simple model for both generating and measuring these quantum correlations.Our study concerns two macroscopic mechanical resonators placed in separate Fabry–Pérot cavities,coupled through the photon hopping process.this system offers a comprehensively way to investigate and quantify quantum correlations beyond entanglement between these mechanical modes.The key ingredient in analyzing quantum correlation in this system is the global covariance matrix.It forms the basis for computing two essential metrics:the logarithmic negativity(E_(N)^(m))and the Gaussian interferometric power(P_(G)^(m)).These metrics provide the tools to measure the degree of quantum entanglement and quantum correlations,respectively.Our study reveals that the Gaussian interferometric power(P_(G)^(m))proves to be a more suitable metric for characterizing quantum correlations among the mechanical modes in an optomechanical quantum system,particularly in scenarios featuring resilient photon hopping.

Joint Beam Scheduling and Power Optimization for Beam Hopping LEO Satellite Systems

Low earth orbit(LEO) satellite communications can provide ubiquitous and reliable services,making it an essential part of the Internet of Everything network. Beam hopping(BH) is an emerging technology for effectively addressing the issue of low resource utilization caused by the non-uniform spatio-temporal distribution of traffic demands. However, how to allocate multi-dimensional resources in a timely and efficient way for the highly dynamic LEO satellite systems remains a challenge. This paper proposes a joint beam scheduling and power optimization beam hopping(JBSPO-BH) algorithm considering the differences in the geographic distribution of sink nodes. The JBSPO-BH algorithm decouples the original problem into two sub-problems. The beam scheduling problem is modelled as a potential game,and the Nash equilibrium(NE) point is obtained as the beam scheduling strategy. Moreover, the penalty function interior point method is applied to optimize the power allocation. Simulation results show that the JBSPO-BH algorithm has low time complexity and fast convergence and achieves better performance both in throughput and fairness. Compared with greedybased BH, greedy-based BH with the power optimization, round-robin BH, Max-SINR BH and satellite resource allocation algorithm, the throughput of the proposed algorithm is improved by 44.99%, 20.79%,156.06%, 15.39% and 8.17%, respectively.

Moisture‑Electric–Moisture‑Sensitive Heterostructure Triggered Proton Hopping for Quality‑Enhancing Moist‑Electric Generator

Moisture-enabled electricity(ME)is a method of converting the potential energy of water in the external environment into electrical energy through the interaction of functional materials with water molecules and can be directly applied to energy harvesting and signal expression.However,ME can be unreliable in numerous applications due to its sluggish response to moisture,thus sacrificing the value of fast energy harvesting and highly accurate information representation.Here,by constructing a moisture-electric-moisture-sensitive(ME-MS)heterostructure,we develop an efficient ME generator with ultra-fast electric response to moisture achieved by triggering Grotthuss protons hopping in the sensitized ZnO,which modulates the heterostructure built-in interfacial potential,enables quick response(0.435 s),an unprecedented ultra-fast response rate of 972.4 mV s^(−1),and a durable electrical signal output for 8 h without any attenuation.Our research provides an efficient way to generate electricity and important insight for a deeper understanding of the mechanisms of moisture-generated carrier migration in ME generator,which has a more comprehensive working scene and can serve as a typical model for human health monitoring and smart medical electronics design.

Satellite Navigation Method Based on High-Speed Frequency Hopping Signal

Global navigation satellite system has been widely used,but it is vulnerable to jamming.In military satellite communications,frequency hopping(FH)signal is usually used for anti-jamming communications.If the FH signal can be used in satellite navigation,the anti-jamming ability of satellite navigation can be improved.Although a recently proposed timefrequency matrix ranging method(TFMR)can use FH signals to realize pseudorange measurement,it cannot transmit navigation messages using the ranging signal which is crucial for satellite navigation.In this article,we propose dual-tone binary frequency shift keyingbased TFMR(DBFSK-TFMR).DBFSK-TFMR designs an extended time-frequency matrix(ETFM)and its generation algorithm,which can use the frequency differences in different dual-tone signals in ETFM to modulate data and eliminate the negative impact of data modulation on pseudorange measurement.Using ETFM,DBFSK-TFMR not only realizes the navigation message transmission but also ensures the precision and unambiguous measurement range of pseudorange measurement.DBFSK-TFMR can be used as an integrated solution for anti-jamming communication and navigation based on FH signals.Simulation results show that DBFSK-TFMR has almost the same ranging performance as TFMR.

NOMA-Based Collaborative Beam Hopping Frequency Allocation Mechanism for Future LEO Satellite Systems

Low Earth orbit(LEO) satellite systems provide terrestrial users with services that are not limited by geographical location. However, the conflict between existing allocation schemes and the business variability between beams is becoming increasingly prominent. Beam hopping technology allows for a more flexible and versatile approach to satellite resource allocation. This paper proposes a beam hopping pattern optimization scheme that jointly considers the interference threshold distance and beam service priority, reducing the inter-beam co-channel interference(CCI). In the cluster area, a non-orthogonal multiple access(NOMA)-based collaborative beam hopping(NCBH) scheme is proposed to minimize the cell-edge user(CEU) interference. Since there is a difference in channel gain between the CEU and cellcenter user(CCU), this scheme forms a NOMA cluster to perform power domain multiplexing and formulates a NOMA cluster pairing strategy according to the user location to reduce the CCI of the CEU. After NOMA cluster pairing, the optimal carrier frequency of the NOMA cluster is selected by a reinforcement learning algorithm. The simulation results verify the excellent performance of the proposed NCBH scheme regarding the user’s received power, transmission rate, and outage probability.

Hopping-Aware Cluster Header Capability for Sensor Relocation in Mobile IoT Networks

Mobile sensor nodes such as hopping sensors are of critical importance in data collection.However,the occurrence of sensing holes is unavoidable due to the energy limitation of the nodes.Thus,it is evident that the relocation of mobile sensors is the most desirable method to recover the sensing holes.The previous research conducted by the authors so far demonstrated the most realistic hopping sensor relocation scheme,which is suitable for the distributed environment.In previous studies,the cluster header plays an essential role in detecting the sensing hole and requesting the neighboring cluster to recover the sensing hole that occurred in the sensor node.However,the limitations of the cluster header in the previously proposed relocation protocol are not fully considered.Because the cluster header jumps more frequently than non-header nodes,its energy con-sumption is relatively high compared to other nodes.Therefore,it is most likely to lead to header node failure and can lead to data loss on the network.In this paper,the jumping ability and energy consumption of the cluster header are seriously considered.Additional ability to replace cluster headers in case of failure is also implemented.Simulation results show that the data collection time can be further increased,which demonstrates the validity of the proposed algorithms.

A Fine Synchronization Method for Coherent Fast Frequency Hopping

Coherent fast frequency hopping(CFFH)is attracting growing attention owing to its good antijamming performance and the coherent combining ability.However,compared with the conventional non-coherent fast frequency hopping,CFFH requires a more precise system synchronization.In this paper,we propose a new fine synchronization algorithm for CFFH.This algorithm consists two stages,namely,open-loop stage and closed-loop stage.In the openloop stage,a grid-based search parameter estimation method is proposed.In the closed-loop stage,we construct a fully coherent phase-locked loop(PLL)and a delay-locked loop(DLL)with decoding feedback structure to perform further fine estimation of the system clock skew and time delay,respectively.Moreover,we analyze the effect of the search parameter settings on the estimation error and derive the root mean squared error(RMSE)of estimates in the steady state of the closed-loop stage.Finally,through simulation,the RMSE performance are compared with the corresponding Cramer-Rao low bound(CRLB)and conventional code loop estimation to show the effectiveness of proposed algorithm.

Topological properties of tetratomic Su-Schrieffer-Heeger chains with hierarchical long-range hopping

We propose a new generalized Su–Schrieffer–Heeger model with hierarchical long-range hopping based on a onedimensional tetratomic chain. The properties of the topological states and phase transition, which depend on the cointeraction of the intracell and intercell hoppings, are investigated using the phase diagram of the winding number. It is shown that topological states with large positive/negative winding numbers can readily be generated in this system. The properties of the topological states can be verified by the ring-type structures in the trajectory diagram of the complex plane. The topological phase transition is strongly related to the opening(closure) of an energy bandgap at the center(boundaries) of the Brillouin zone. Finally, the non-zero-energy edge states at the ends of the finite system are revealed and matched with the bulk–boundary correspondence.

Beam Position and Beam Hopping Design for LEO Satellite Communications

The numbers of beam positions(BPs)and time slots for beam hopping(BH)dominate the latency of LEO satellite communications.Aiming at minimizing the number of BPs subject to a predefined requirement on the radius of BP,a low-complexity user density-based BP design scheme is proposed,where the original problem is decomposed into two subproblems,with the first one to find the sparsest user and the second one to determine the corresponding best BP.In particular,for the second subproblem,a user selection and smallest BP radius algorithm is proposed,where the nearby users are sequentially selected until the constraint of the given BP radius is no longer satisfied.These two subproblems are iteratively solved until all the users are selected.To further reduce the BP radius,a duplicated user removal algorithm is proposed to decrease the number of the users covered by two or more BPs.Aiming at minimizing the number of time slots subject to the no co-channel interference(CCI)constraint and the traffic demand constraint,a low-complexity CCI-free BH design scheme is proposed,where the BPs having difficulty in satisfying the constraints are considered to be illuminated in priory.Simulation results verify the effectiveness of the proposed schemes.

基于知识图谱多跳推理的中文矿物知识问答方法与系统

已有相关矿物数据库用于存储和查询相关矿物知识,常用的搜索引擎也可以对矿物知识进行查询,但无法回答用自然语言进行提问的矿物问题,查询返回的答案需要进一步筛选。亦有基于知识图谱进行矿物知识问答的相关研究,但只能回答涉及知识图谱中一个三元组的简单问题,无法回答涉及多个三元组的多跳复杂问题。为此,本文提出基于知识图谱多跳推理的矿物复杂知识问答方法,采用ComplEx模型将矿物实体、关系和问句表示为复数向量,以更好地获取相互之间的语义及推理关系。输入矿物问句后,通过Bert-LSTM-CRF获取其中心词,采用基于编辑距离及分词的方法获得中心词的候选实体集合,然后采用全连接网络确定最相关的实体作为推理起点,与矿物问句拼接后通过全连接网络获得当前跳的最相关关系。根据当前跳的起始实体及最相关关系,在矿物知识图谱中获得另一实体作为下一跳的推理起点,并将下一跳的问句更新为原问句,与当前跳最相关关系拼接,以将当前跳的推理信息带入到下一跳推理中,直到获得的最相关推理关系为预定义的结束标识符,推理结束,返回最后一跳的实体为答案,并给出推理路径。采用Python语言,在Tensorflow框架下实现了本文提出的矿物复杂知识问答并与相关模型进行对比,证明了本文方法的有效性。采用前后端分离架构,使用RESTful API、React、Ajax、echarts和Flask等框架和技术,开发了基于知识图谱多跳推理的矿物复杂知识问答系统,为矿物知识获取及相关地质研究提供了平台和工具。

DSFH系统的双信道接收平衡检测及判决结构设计

对偶序列跳频系统较传统跳频通信具有很强的抗综合干扰能力,基于实际情况中存在的接收结构双信道平衡问题,提出了AWGN环境下仿真模型的信道平衡检测方法,分析了在AWGN环境平衡信道下的误码率及非平衡信道下的门限调整,设计了动态门限的判决结构。由链路仿真结果表明:在无信号时能够检测双信道接收结构的平衡状态;当信噪比在-22 dB~-14 dB变化时,非平衡信道下判决结构的检测性能达到了平衡信道时的性能要求。

基于WBOA的3D-DV-Hop节点定位算法

针对三维(3D)-DV-Hop定位算法未知节点从最近的锚节点获取平均跳距估算距离时定位精度低的问题,提出了一种新的基于WBOA的3D-DV-Hop算法。首先,该算法去除了网络中无法通信和无法定位的节点;然后添加了修正因子,修正平均跳距。接着创建一个用于优化的蝴蝶初始种群,构建目标函数。采用自适应权重来平衡全局搜索与局部搜索的能力,使得算法不易陷入局部最优,加快了算法的收敛精度;最终求得全局最优平均跳距。仿真结果表明:尽管算法的平均运行时间略有增加,但算法的定位精度得到了有效提高。

资源块间跳频的高可靠SCMA系统设计与分析

传统稀疏码分多址(Sparse Code Division Multiple Access,SCMA)系统在固定时频资源块(Resource Block,RB)上传输信息,系统性能易受到信道污染(外在干扰和信道衰落)的影响。为了解决这一问题,提出一种基于资源块间跳频(Frequency Hopping,FH)的SCMA系统(FH-SCMA系统)。借助跳频技术实现动态SCMA码字复用,使得各用户能够均匀、随机地使用所有资源块。同时,基于素数序列设计了一种动态码字正交复用的跳频策略(跳频码),提升了FH-SCMA系统容量以及抗干扰能力。该系统接收端采用对数域消息传递(MAX-log-MPA)多用户检测算法,推导了该FH-SCMA系统的理论误码率上界。对比传统的SCMA系统,该资源块间FH-SCMA系统能均匀化资源块被污染对用户性能的影响,使得每个用户的传输误码率达到可接受的程度;相比传统SCMA系统和采用完全随机跳频策略的FH-SCMA系统(干扰时频资源占比η=25%时),设计的跳频策略及FH-SCMA系统在误码平层处分别获得4 dB和8 dB的信噪比增益。

利用无线电极化特征的跳频网台分选方法

针对现有方法在跳频通信用户“空时频能”域特征相近、跳频参数捷变等条件下,跳频网台分类识别效果不佳的问题,该文提出一种基于无线电极化特征的跳频用户分选方法。该方法将无线电双极化特征引入到跳频侦察,充分利用各用户的交叉极化鉴别度差异,实现了跳频网台精准分选。针对同类用户交叉极化鉴别度参数易受噪声污染的问题,构建了双通道双极化接收系统,抑制了信号噪声,保证了极化特征提取的精度。在此基础上,基于谱聚类思想,完成了极化特征的分类软判决,进一步提升了跳频网台分选效果,实现了跳频信号的精准识别。仿真实验表明,在5 dB信噪比条件下,所提方法可对同步正交和非正交组网方式下的多跳频网台准确识别,识别分类成功率达99%以上,验证了新方法的有效性。

一种改进的距离向量跳段定位算法

针对无线传感器网络距离向量跳段算法(DV-Hop)存在的跳数与平均跳距误差问题,提出一种基于跳数修正和改进鲸鱼算法优化的DV-Hop定位算法。首先利用多个通讯半径对节点的位置进行广播并引入调整因子,减小跳数误差;然后在鲸鱼算法中加入Circle混沌映射优化初始化种群,利用自适应权重和正余弦优化避免其过早陷入局部最优,之后将改进后鲸鱼算法用于计算信标节点之间的平均跳距;再通过加权方法对未知节点的平均跳距进行校正,从而减小跳距误差。实验结果表明:在仿真条件一致时,改进算法的定位精度相比DV-Hop算法、IPSO-D算法和IGWO-D算法均明显提高。

复杂环境下多策略改进麻雀搜索的定位算法

为了提高传统DV-HOP(Distance vector hop)算法在三维复杂环境场景下的节点定位精度,提出了一种利用多策略改进麻雀搜索算法优化的3D-DVHop定位算法.首先通过重新定义距离加权因子划分最优跳数,其次利用距离相似链路法来修正节点间的跳数大小,最后采用麻雀搜索算法实现3D-DVHop算法未知节点的位置寻优,并通过优化位置控制因子,同时引入蝴蝶搜索算法和自适应的局部搜索策略,增强麻雀搜索算法初始种群的多样性以及全局收敛速度和跳出局部最优的能力.仿真结果表明,该算法与传统DV-Hop算法以及其他同类算法相比,具有更好的稳定性和更高的定位精度.

利用知识图谱的多跳可解释问答

基于知识图谱的多跳问答需要分析和理解自然语言问题并在知识图谱的实体和关系上经过多次推理获取答案,是自然语言处理的重要研究领域.现有的模型一般通过知识图谱与问题嵌入,利用神经网络推断答案;或使用一阶逻辑规则结合概率方法预测答案;前者缺乏可解释性,后者在复杂问题中性能欠佳.为解决上述问题,本文提出一种基于知识图谱的多跳可解释问答方法(MIQA),它通过在实体间的多次跳跃推理来获取答案.MIQA首先使用BERT预训练模型获取自然语言问题表征向量以及问题分词后的词向量矩阵,在每一跳中,结合问题向量提取问题当前时刻的特征向量,根据特征向量的分类结果计算下一跳的关系分数和实体分数,多次跳跃后,综合分数最高的实体被作为答案,而获取该答案所对应的路径为推理路径.该方法推理准确率高,同时具有明显的可解释性.在MetaQA、WebQuestionsSP、ComplexWebQuestions这3个数据集上,通过和其他8个知名算法相比较,仿真结果表明MIQA性能优异,达到了当前的SOTA.

面向无人驾驶车避障的光跳频激光雷达探测目标智能主动跟踪方法

无人驾驶车避障主动跟踪方法在与激光雷达目标融合的过程中,受激光雷达光跳频信号散射作用的影响,信号回波接收精度出现严重偏差,导致避障跟踪稳定性及其精准度均出现不同程度降低,严重威胁无人驾驶车辆行驶安全。为解决此问题,从激光雷达目标跟踪技术入手,首先建立雷达目标跟踪模型,确定优化目标系数;接着对光跳频激光雷达探测信号进行扰动优化,修正扰动偏差数据及其参量;最后通过避障目标的主动跟踪数据对优化数据进行合成,整理收尾数据输出效果。对提出方法进行仿真测试,结果表明其各项性能均符合设计预期设定标准,满足实际应用与推广的相关要求,具有广阔的发展前景。