位于平流层的高空平台向上连接卫星、向下连接低空无人机,能够有效支撑空天地一体化信息网络,提供灵活的应急通信。然而,针对高空平台至无人机的下行链路,传统算法采用固定速率,降低链路的平均传输速率,增加了链路的中断概率。为此,提...位于平流层的高空平台向上连接卫星、向下连接低空无人机,能够有效支撑空天地一体化信息网络,提供灵活的应急通信。然而,针对高空平台至无人机的下行链路,传统算法采用固定速率,降低链路的平均传输速率,增加了链路的中断概率。为此,提出基于速率匹配的自由空间光通信(free space optical,FSO)和射频(radio frequency,RF)链路的动态切换算法(rate adaptation-based free space optical and RF dynamic switching,RADS)。RADS算法优先使用FSO链路,若FSO链路的瞬时信噪比低于阈值,就切入RF链路。同时,根据所接收信号的信噪比,采用满足最低误码率要求的传输模式,进而满足速率要求。仿真结果表明,相比于传统的固定速率算法,提出的RADS算法降低了链路中断概率,提升了速率。展开更多
自由空间光(Free Space Optical, FSO)通信技术具有高传输容量、免频谱许可、高保密性等优点,然而对于大气激光通信,光束在传输路径上普遍存在大气状况对通信性能的影响,大气湍流会大大降低接受信号的质量。文章设计了一套室内无线激光...自由空间光(Free Space Optical, FSO)通信技术具有高传输容量、免频谱许可、高保密性等优点,然而对于大气激光通信,光束在传输路径上普遍存在大气状况对通信性能的影响,大气湍流会大大降低接受信号的质量。文章设计了一套室内无线激光通信实验系统,模拟真实环境下的大气湍流,并细致分析了如何在室内模拟和测量大气湍流强度,同时提出两种测量室内弱湍流强度的方法并进行对比。文章的成果可用于无线激光通信系统误码率的研究,为无线激光通信系统性能及相关调制技术奠定了一定的理论基础。展开更多
When the light beam propagates in the atmosphere, the signal will be absorbed and scattered by the gas molecules and water mist in the atmosphere, which will cause the loss of power rate. The complex atmospheric envir...When the light beam propagates in the atmosphere, the signal will be absorbed and scattered by the gas molecules and water mist in the atmosphere, which will cause the loss of power rate. The complex atmospheric environment will produce a variety of adverse effects on the signal. The interference produced by these effects overlaps with each other, which will seriously affect the strength of the received signal. Therefore, how to effectively suppress the atmospheric turbulence effect in the random atmospheric turbulence channel, ensure the normal transmission of the signal in the atmospheric channel, and reduce the bit error rate of the communication system, is very necessary to improve the communication system. When processing the received signal, it is an important step to detect the transmitted signal by comparing the received signal with the threshold. In this paper, based on the atmospheric turbulence distribution model, the adaptive signal decision threshold is obtained through the estimation of high-order cumulant. Monte Carlo method is used to verify the performance of adaptive threshold detection. The simulation results show that the high-order cumulant estimation of atmospheric turbulence parameters can realize the adaptive change of the decision threshold with the channel condition. It is shown that the adaptive threshold detection can effectively restrain atmospheric turbulence, improve the performance of free space optical and improve the communication quality.展开更多
在深空通信中引入自由空间光(free space optical,FSO)和射频通信(radio frequency,RF)可改善深空通信的质量。为了提供FSO-RF混合系统的性能分析,推导了从源节点至用户端的两跳中断概率表达式。在从源节点至转发节点间采用FSO链路,并...在深空通信中引入自由空间光(free space optical,FSO)和射频通信(radio frequency,RF)可改善深空通信的质量。为了提供FSO-RF混合系统的性能分析,推导了从源节点至用户端的两跳中断概率表达式。在从源节点至转发节点间采用FSO链路,并通过外差检波或直接检波;转发节点采用非正交多址接入技术,进而可通过RF链路向多个用户转发数据。在FSO链路服从Gamma-Gamma分布和RF链路服从瑞利分布背景下,推导了端到端的中断概率的闭合表达式。性能分析表明,两个用户端的中断概率差异主要取决于功率分配比例、源节点端传输的信噪比。展开更多
无人机(unmanned aerial vehicle,UAV)作为移动基站(movable base stations,MBS),可有效提升蜂窝网络的通信性能。设计稳定的MBS与地面用户间的下行链路是该UAV-MBS网络的关键。为此,提出移动感知的混合射频与自由空间光(free space opt...无人机(unmanned aerial vehicle,UAV)作为移动基站(movable base stations,MBS),可有效提升蜂窝网络的通信性能。设计稳定的MBS与地面用户间的下行链路是该UAV-MBS网络的关键。为此,提出移动感知的混合射频与自由空间光(free space optical,FSO)下行链路方案。该方案依据MBS的移动状态对RF链路和FSO链路进行切换。该方案分别推导了RF链路、FSO链路和混合RF/FSO链路的误码率,并通过仿真分析上述3种链路的误码率性能。仿真结果表明,混合RF/FSO链路的误码率性能优于RF链路和FSO链路。展开更多
文摘位于平流层的高空平台向上连接卫星、向下连接低空无人机,能够有效支撑空天地一体化信息网络,提供灵活的应急通信。然而,针对高空平台至无人机的下行链路,传统算法采用固定速率,降低链路的平均传输速率,增加了链路的中断概率。为此,提出基于速率匹配的自由空间光通信(free space optical,FSO)和射频(radio frequency,RF)链路的动态切换算法(rate adaptation-based free space optical and RF dynamic switching,RADS)。RADS算法优先使用FSO链路,若FSO链路的瞬时信噪比低于阈值,就切入RF链路。同时,根据所接收信号的信噪比,采用满足最低误码率要求的传输模式,进而满足速率要求。仿真结果表明,相比于传统的固定速率算法,提出的RADS算法降低了链路中断概率,提升了速率。
文摘自由空间光(Free Space Optical, FSO)通信技术具有高传输容量、免频谱许可、高保密性等优点,然而对于大气激光通信,光束在传输路径上普遍存在大气状况对通信性能的影响,大气湍流会大大降低接受信号的质量。文章设计了一套室内无线激光通信实验系统,模拟真实环境下的大气湍流,并细致分析了如何在室内模拟和测量大气湍流强度,同时提出两种测量室内弱湍流强度的方法并进行对比。文章的成果可用于无线激光通信系统误码率的研究,为无线激光通信系统性能及相关调制技术奠定了一定的理论基础。
文摘When the light beam propagates in the atmosphere, the signal will be absorbed and scattered by the gas molecules and water mist in the atmosphere, which will cause the loss of power rate. The complex atmospheric environment will produce a variety of adverse effects on the signal. The interference produced by these effects overlaps with each other, which will seriously affect the strength of the received signal. Therefore, how to effectively suppress the atmospheric turbulence effect in the random atmospheric turbulence channel, ensure the normal transmission of the signal in the atmospheric channel, and reduce the bit error rate of the communication system, is very necessary to improve the communication system. When processing the received signal, it is an important step to detect the transmitted signal by comparing the received signal with the threshold. In this paper, based on the atmospheric turbulence distribution model, the adaptive signal decision threshold is obtained through the estimation of high-order cumulant. Monte Carlo method is used to verify the performance of adaptive threshold detection. The simulation results show that the high-order cumulant estimation of atmospheric turbulence parameters can realize the adaptive change of the decision threshold with the channel condition. It is shown that the adaptive threshold detection can effectively restrain atmospheric turbulence, improve the performance of free space optical and improve the communication quality.
文摘在深空通信中引入自由空间光(free space optical,FSO)和射频通信(radio frequency,RF)可改善深空通信的质量。为了提供FSO-RF混合系统的性能分析,推导了从源节点至用户端的两跳中断概率表达式。在从源节点至转发节点间采用FSO链路,并通过外差检波或直接检波;转发节点采用非正交多址接入技术,进而可通过RF链路向多个用户转发数据。在FSO链路服从Gamma-Gamma分布和RF链路服从瑞利分布背景下,推导了端到端的中断概率的闭合表达式。性能分析表明,两个用户端的中断概率差异主要取决于功率分配比例、源节点端传输的信噪比。
文摘无人机(unmanned aerial vehicle,UAV)作为移动基站(movable base stations,MBS),可有效提升蜂窝网络的通信性能。设计稳定的MBS与地面用户间的下行链路是该UAV-MBS网络的关键。为此,提出移动感知的混合射频与自由空间光(free space optical,FSO)下行链路方案。该方案依据MBS的移动状态对RF链路和FSO链路进行切换。该方案分别推导了RF链路、FSO链路和混合RF/FSO链路的误码率,并通过仿真分析上述3种链路的误码率性能。仿真结果表明,混合RF/FSO链路的误码率性能优于RF链路和FSO链路。
