Responsive orbits have exhibited advantages in emergencies for their excellent responsiveness and coverage to targets.Generally,there are several conflicting metrics to trade in the orbit design for responsive space.A...Responsive orbits have exhibited advantages in emergencies for their excellent responsiveness and coverage to targets.Generally,there are several conflicting metrics to trade in the orbit design for responsive space.A special multiple-objective genetic algorithm,namely the Nondominated Sorting Genetic AlgorithmⅡ(NSGAⅡ),is used to design responsive orbits.This algorithm has considered the conflicting metrics of orbits to achieve the optimal solution,including the orbital elements and launch programs of responsive vehicles.Low-Earth fast access orbits and low-Earth repeat coverage orbits,two subtypes of responsive orbits,can be designed using NSGAI under given metric tradeoffs,number of vehicles,and launch mode.By selecting the optimal solution from the obtained Pareto fronts,a designer can process the metric tradeoffs conveniently in orbit design.Recurring to the flexibility of the algorithm,the NSGAI promotes the responsive orbit design further.展开更多
水声通信作为海洋信息传输的核心技术,广泛应用于海洋探测、海事监管及海底工程等领域。然而,水声信道因双重色散特性而极具挑战性,对系统设计构成重大障碍。尽管正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术...水声通信作为海洋信息传输的核心技术,广泛应用于海洋探测、海事监管及海底工程等领域。然而,水声信道因双重色散特性而极具挑战性,对系统设计构成重大障碍。尽管正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术已在水声通信中得到广泛应用,但其性能仍受限于信道状态估计的准确性。正交时频空(Orthogonal Time Frequency Space, OTFS)调制技术通过将数据转换到时延-多普勒域内传输,能够有效地应对水声信道中的多径效应和多普勒频移,提高通信系统的性能和可靠性。综述了OTFS在水声通信中的关键处理技术,涵盖信道估计、信道均衡及多址接入技术三个核心方面,并从天线拓展、机器学习融合及同步创新等方面探讨了未来发展趋势,同时详细分析了复杂信道环境下的信号检测、计算复杂度与实时性平衡、参数估计准确性及水下环境对数据可靠性的影响面临的技术挑战。展开更多
针对车辆边缘计算(VEC)中存在的用户体验质量需求不断增加、高度移动车辆引起的链路状态获取困难和异构边缘节点为车辆提供资源的时变性等问题,制定一种联合任务卸载和资源优化(JTO-RO)的VEC方案。首先,在不失一般性的前提下,综合考虑...针对车辆边缘计算(VEC)中存在的用户体验质量需求不断增加、高度移动车辆引起的链路状态获取困难和异构边缘节点为车辆提供资源的时变性等问题,制定一种联合任务卸载和资源优化(JTO-RO)的VEC方案。首先,在不失一般性的前提下,综合考虑边缘内和边缘间干扰,提出一种车辆到基础设施(V2I)的传输模型,该模型通过引入非正交多址接入(NOMA)技术使边缘节点不仅无需依赖链路状态信息,还可以提升信道容量;其次,为了提高系统的性能和效率,设计一种多智能体双延迟深度确定性(MATD3)算法用于制定任务卸载策略,这些策略可通过与环境的交互学习进行动态调整;再次,联合考虑2种策略的协同作用,并制定将最大化任务服务比率作为目标的优化方案,从而满足不断提升的用户体验质量需求;最后,对真实车辆轨迹数据集进行仿真实验。结果表明,相较于当前具有代表性的3种方案(分别以随机卸载(RO)算法、D4PG(Distributed Distributional Deep Deterministic Policy Gradient)算法和MADDPG(Multi-Agent Deep Deterministic Policy Gradient)算法为任务卸载算法的方案)在3类场景下(普通场景、任务密集型场景和时延敏感型场景),所提方案的平均服务比率分别提高了20%、10%和29%以上,验证了该方案的优势和有效性。展开更多
文摘Responsive orbits have exhibited advantages in emergencies for their excellent responsiveness and coverage to targets.Generally,there are several conflicting metrics to trade in the orbit design for responsive space.A special multiple-objective genetic algorithm,namely the Nondominated Sorting Genetic AlgorithmⅡ(NSGAⅡ),is used to design responsive orbits.This algorithm has considered the conflicting metrics of orbits to achieve the optimal solution,including the orbital elements and launch programs of responsive vehicles.Low-Earth fast access orbits and low-Earth repeat coverage orbits,two subtypes of responsive orbits,can be designed using NSGAI under given metric tradeoffs,number of vehicles,and launch mode.By selecting the optimal solution from the obtained Pareto fronts,a designer can process the metric tradeoffs conveniently in orbit design.Recurring to the flexibility of the algorithm,the NSGAI promotes the responsive orbit design further.
文摘水声通信作为海洋信息传输的核心技术,广泛应用于海洋探测、海事监管及海底工程等领域。然而,水声信道因双重色散特性而极具挑战性,对系统设计构成重大障碍。尽管正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术已在水声通信中得到广泛应用,但其性能仍受限于信道状态估计的准确性。正交时频空(Orthogonal Time Frequency Space, OTFS)调制技术通过将数据转换到时延-多普勒域内传输,能够有效地应对水声信道中的多径效应和多普勒频移,提高通信系统的性能和可靠性。综述了OTFS在水声通信中的关键处理技术,涵盖信道估计、信道均衡及多址接入技术三个核心方面,并从天线拓展、机器学习融合及同步创新等方面探讨了未来发展趋势,同时详细分析了复杂信道环境下的信号检测、计算复杂度与实时性平衡、参数估计准确性及水下环境对数据可靠性的影响面临的技术挑战。
文摘针对车辆边缘计算(VEC)中存在的用户体验质量需求不断增加、高度移动车辆引起的链路状态获取困难和异构边缘节点为车辆提供资源的时变性等问题,制定一种联合任务卸载和资源优化(JTO-RO)的VEC方案。首先,在不失一般性的前提下,综合考虑边缘内和边缘间干扰,提出一种车辆到基础设施(V2I)的传输模型,该模型通过引入非正交多址接入(NOMA)技术使边缘节点不仅无需依赖链路状态信息,还可以提升信道容量;其次,为了提高系统的性能和效率,设计一种多智能体双延迟深度确定性(MATD3)算法用于制定任务卸载策略,这些策略可通过与环境的交互学习进行动态调整;再次,联合考虑2种策略的协同作用,并制定将最大化任务服务比率作为目标的优化方案,从而满足不断提升的用户体验质量需求;最后,对真实车辆轨迹数据集进行仿真实验。结果表明,相较于当前具有代表性的3种方案(分别以随机卸载(RO)算法、D4PG(Distributed Distributional Deep Deterministic Policy Gradient)算法和MADDPG(Multi-Agent Deep Deterministic Policy Gradient)算法为任务卸载算法的方案)在3类场景下(普通场景、任务密集型场景和时延敏感型场景),所提方案的平均服务比率分别提高了20%、10%和29%以上,验证了该方案的优势和有效性。
