共查询到20条相似文献,搜索用时 343 毫秒
1.
针对高速运动目标的常用载波同步算法会引起同步失锁的现象,文中基于COSTAS环的设计思想,提出了一种基于OQPSK调制的载波跟踪算法,该算法不仅可消除由多普勒频移引起的载波频偏,还可克服OQPSK信号90°相位的不确定性。 相似文献
2.
通信信号盲载波恢复是非协作模式下接收方解调的关键环节之一。为提高频偏捕获范围与速度,同时有效增强算法跟踪时变频偏能力,本文针对正交幅度调制(QAM)信号,通过理论推导得出滤波器环路带宽的变化特性,提出一种基于自适应判决引导扩展卡尔曼滤波的载波同步算法。该算法在现有卡尔曼滤波载波同步算法的基础上,引入多状态自适应切换机制自适应地改变滤波器参数,并依据实验测试数据分析得出调整原则并完成滤波器参数的选取。理论分析和仿真表明,与已有的卡尔曼载波同步算法及二阶数字锁相环算法相比,该算法不仅捕获速度更快范围更大,且能在存在时变多普勒频移的情况下较好地跟踪时变频偏和相位,在大频偏条件下的算法跟踪性能与鲁棒性等方面均有优势。 相似文献
3.
4.
5.
6.
7.
8.
机载数传设备的高速运动会带来较大的多普勒频移,设计一种不受频偏影响的同步解决方案对数传性能非常重要;突发方式的数据传输也给数传设备的接收同步带来了难度.为此,对于相位调制数传,提出了基于已知相位序列的相关同步算法,可以实现相关输出与收发频偏无关,很好地解决多普勒频移下的同步问题.该算法在FPGA上实现比较简单,性能可靠. 相似文献
9.
10.
11.
不确定环境下的侦察无人机自主航路规划仿真 总被引:2,自引:1,他引:1
自主式无人机是无人机发展的必然趋势,不确定环境下的航路规划是无人机航路规划研究的新领域.为了研究战时条件下侦察无人机的自主航路规划,根据无人机的控制系统工作方式,建立了仿真模型框架,并在此基础上开展仿真研究.首先,针对战时条件下侦察无人机执行任务的不确定环境,从战场使用的实际情况出发,建立了基于目标存在概率的环境信息模型;然后,根据无人机机载探测设备探测区域建立了探测模型,提出了航路控制决策模型,并采用动态规划进行航路规划.最后,设计了一个无人机侦察不确定环境的仿真试验,仿真结果验证了该方法的有效性. 相似文献
12.
The application of unmanned aerial vehicle(UAV)-mounted base stations is emerging as an effective solution to provide wireless communication service for a target region containing some smart objects(SOs)in internet of things(IoT).This paper investigates the efficient deployment problem of multiple UAVs for IoT communication in dynamic environment.We first define a measurement of communication performance of UAVto-SO in the target region which is regarded as the optimization objective.The state of one SO is active when it needs to transmit or receive the data;otherwise,silent.The switch of two different states is implemented with a certain probability that results in a dynamic communication environment.In the dynamic environment,the active states of SOs cannot be known by UAVs in advance and only neighbouring UAVs can communicate with each other.To overcome these challenges in the deployment,we leverage a game-theoretic learning approach to solve the position-selected problem.This problem is modeled a stochastic game,which is proven that it is an exact potential game and exists the best Nash equilibria(NE).Furthermore,a distributed position optimization algorithm is proposed,which can converge to a pure-strategy NE.Numerical results demonstrate the excellent performance of our proposed algorithm. 相似文献
13.
Unmanned aerial vehicle system (UAVs) imaging has become a challenging area of research due to the dynamic atmospheric environment. The images captured by UAVs are often deteriorated by factors such as clouds occlusion, poor atmospheric illumination, and limited capability of the imaging system. To tackle problems, this paper presents a novel visibility restoration scheme for UAVs images by considering the following two assumptions: (1) The actual scene radiance of a UAVs image is bounded. (2) Pixels sharing the same appearance must have the same transmission value in a local neighborhood. Inspired by above assumptions, an image boundary constraint utilizing the median filter has been imposed on the RGB channel for the rough estimation of transmission-map in aerial images. Furthermore, a graph-model based optimization technique has been used for the transmission-map refinement. The experimental results demonstrate the efficiency of the proposed method in terms of metrics correspond to the human-visual-system (HVS). 相似文献
14.
To deal with the secrecy issues and energy efficiency issues in the unmanned aerial vehicles ( UAVs) assisted communication systems, an UAV-enabled multi-hop mobile relay system is studied in an urban environment. Multiple rotary-wing UAVs with energy budget considerations are employed as relays to forward confidential information between two ground nodes in the presence of multiple passive eavesdroppers. The system secrecy energy efficiency ( SEE), defined by the ratio of minimum achievable secrecy rate ( SR) to total propulsion energy consumption (PEC), is maximized via jointly optimizing the trajectory and transmit power of each UAV relay. To solve the formulated non-convex fractional optimization problem subject to mobility, transmit power and information-causality constraints, an effective iterative algorithm is proposed by applying the updated-rate-assisted block coordinate decent method, successive convex approximation (SCA) technique and Dinkelbach method. Simulation 相似文献
15.
联邦学习是6G关键技术之一,其可以在保护数据隐私的前提下,利用跨设备的数据训练一个可用且安全的共享模型。然而,大部分终端设备由于处理能力有限,无法支持复杂的机器学习模型训练过程。在异构网络融合环境下移动边缘计算(MEC)框架中,多个无人机(UAVs)作为空中边缘服务器以协作的方式灵活地在目标区域内移动,并且及时收集新鲜数据进行联邦学习本地训练以确保数据学习的实时性。该文综合考虑数据新鲜程度、通信代价和模型质量等多个因素,对无人机飞行轨迹、与终端设备的通信决策以及无人机之间的协同工作方式进行综合优化。进一步,该文使用基于优先级的可分解多智能体深度强化学习算法解决多无人机联邦学习的连续在线决策问题,以实现高效的协作和控制。通过采用多个真实数据集进行仿真实验,仿真结果验证了所提出的算法在不同的数据分布以及快速变化的动态环境下都能取得优越的性能。 相似文献
16.
17.
18.
19.
针对应急移动物联网在缺少地面基站的情况下,可靠节能地远距离传输重点区域全信息的要求,本文将无人机(Unmanned Aerial Vehicle,UAV)作为空基通信平台,研究应急移动物联网应用中大规模移动物联网设备能量受限条件下的远距离通信问题,提出基于无人机的移动物联网远距离通信节能策略.首先,对该类物联网进行系统建模;其次,根据所建模型中地面设备无序立体地分散于重点区域的特点,通过优化无人机的布署位置,在提供可靠通信的同时,降低地面设备的通信耗能;再次,根据地面设备运动性能强、活动范围广的特点,通过研究无人机与地面移动设备的联合运动策略,避免无人机频繁换簇覆盖所引起的远距离移动等大运动状态变化问题,实现无人机的移动节能.最后,通过实验,从通信耗能和运动耗能两方面验证了本文所提策略的有效性. 相似文献
20.
计算机视觉导航技术具有精度高、不受电子干扰,成本低等特点,被誉为未来无人机自主着陆的必备手段之一。作为新一代着陆技术手段,视觉自主着陆技术需要进行大量的算法研究和飞行试验,因此有必要建立一个在实验室环境来验证所提方案的可行性。本文将虚拟现实、 可视化技术与计算视觉导航算法紧密结合起来,开发了一种无人机视觉自主着陆仿真验证系统, 构建场景模块,能够在复杂三维地形、不同气象条件下对无人机视觉自主着陆算法进行仿真验证, 实时计算和输出无人机着陆所需位置姿态参数。实验结果表明:该系统真实反映了无人飞行器飞行过程中的动态特性以及姿态角等的变化,并且具备良好的用户显控界面,验证了视觉自主着陆算法的可行性。 相似文献