降雪对地表附近自由空间量子信道的影响及参数仿真

量子通信具有覆盖面广、安全保密的优势,是当前通信领域国内外的研究热点.在自由空间量子通信过程中,光量子信号需要在地表上空一定高度进行传输,因此各种环境因素,例如降雪、沙尘暴、降雨、雾霾、浮尘等,不可避免地会影响量子通信性能.然而,迄今为止,降雪对地表附近自由空间量子信道影响的研究尚未展开.为此,根据降雪的强度,将降雪分为小雪(S1)、中雪(S2)、大雪(S3)和暴雪(S4)四个等级.由于空中正在飘落雪花对光量子信号具有能量吸收作用,称为消光效应,不同强度的降雪,其消光效应对自由空间光量子信号的影响不同.本文首先建立了不同等级降雪对光量子信号消光效应的数学模型;然后建立了因降雪导致的自由空间消光衰减定量关系,信道极限生存函数、不同降雪强度下的信道容量和量子误码率等性能参数受降雪影响的变化情况;最后建立了降雪强度、传输距离与链路衰减、幅值阻尼信道容量、信道生存函数以及信道误码率的数学模型.仿真结果表明,当降雪强度为2.1 mm/d(S1),传输距离为2.2 km时,通信链路衰减为0.0362,信道容量为0.7745,信道生存函数为0.2329,信道误码率为0.0105.当降雪强度为3.8 mm/d(S2)。传输距离为3.5 km时,通信链路衰减为0.1326,信道容量为0.4922,信道生存函数为0.2099,信道误码率为0.019.由此可见,降雪对量子通信性能有不同程度的影响.所以在实际应用中应根据降雪强度大小,自适应调节量子通信相关参数,提高量子通信的可靠性.

Influence of snowfall on free-space quantum channel near earth surface and parameter simulation

Quantum communication has the advantages of wide coverage and security,and is currently a hot research topic in the field of communication.In the process of free space quantum communication,quantum signals need transmitting at a certain height above the surface.Various environmental factors in free space,such as snowfall,sandstorms,rainfall,haze and floating dust,will inevitably affect quantum communication performance.However,so far,the influence of snowfall on the performance of quantum channels in free space near the surface has not been investigated.Thus,according to the intensity of snowfall,the snowfall is divided into four levels:light snow(S1),medium snow(S2), heavy snow(S3) and blizzard(S1).When the snow is falling in the air,it has an energy absorption effect on the light quantum signal,which is called the extinction effect.The different intensities of snow extinction have different effects on free space optical quantum signal.In this paper,first,a mathematical model for the extinction effects on optical quantum signal at different levels of snowfall is presented;then the quantitative relationship between snowfall and free space extinction attenuation,as well as the relationship between snowfall and channel limit survival function is established,channel capacities under different snowfall intensities,and quantum bit error rate are also given.Finally,the mathematical models of snowfall intensity,transmission distance and link attenuation,amplitude damping channel capacity,channel survival function and channel error rate are established.Simulation results show that when the snowfall intensity is 2.1 mm/d(S1) and the transmission distance is 2.2 km,the communication link attenuation is0.0362,the channel capacity is 0.7745,the channel survival function is 0.2329,and the channel error rate is0.0105.When the snowfall intensity is 3.8 mm/d(S2) and the transmission distance is 3.5 km,the communication link attenuation is 0.1326,the channel capacity is 0.4922,the channel survival function is0.2099,and the channel error rate is 0.019.Thus,different snowfall intensity has different influence on the performance of free space quantum communication.Therefore,in practical applications,the communication parameters should be adjusted adaptively based on the snowfall intensity to improve the reliability of free space quantum communication.