近年来,伴随着无线通信技术的不断发展,网络中数据通信速率呈指数增长,系统容量显著增加,人们对通信系统安全性能要求也越来越高。由于无线信道的广播特性,无线通信网络特别容易受到非法接收器的窃听和模拟攻击。物理层安全技术利用信道噪声、衰落和多径效应等固有特性增大合法接收端和窃听者之间的信道差异,在提高无线通信安全性能上有着重要的作用。智能反射表面(Intelligent Reflecting Surface,IRS)作为一种可以改变无线通信传输环境的无源设备,通过远程控制IRS单元调整入射信号,并且不消耗发射端功率,近两年来成为无线通信中重要的研究内容之一。本文研究IRS在无线通信物理层安全上的应用,主要内容如下:(1)考虑IRS辅助多输入多输出(Multiple-Input and Multiple-Output,MIMO)和多天线窃听(Multiple Eavesdropper,ME)通信系统模型,在该模型下,发射端已知窃听者信道状态信息(Channel State Information,CSI)。对于该窃听场景,在发射端功率和IRS单位相移模量的约束下,以最大化保密速率为目标建立优化问题,针对非凸的目标函数和互不相关的约束条件,采用交替优化算法将优化问题转换成两个子问题。优化子问题发射端协方差矩阵时,使用障碍法将不等式约束问题转换成等式约束问题,再结合牛顿法以及回溯直线搜索法求解障碍函数卡罗需卡塔尔定理(Karush-Kuhn-Tucker,KKT)条件的解,并证明了该最优解便是原子问题的最优解;优化IRS相移矩阵时,首先将关于相移矩阵的隐式目标函数改写成关于单个相移的显式目标函数,然后逐个优化每个反射单元相移,再迭代求解出最优反射相移矩阵。仿真结果表明所提算法在提高系统安全性能上有显著作用。除此之外,还研究了该模型下IRS只反射单条链路信号到合法接收端或窃听者对系统保密速率的影响。(2)针对IRS辅助MIMO系统中发射端未知窃听者CSI的情况,加入人工噪声(Artificial Noise,AN)干扰窃听者接收的信号,从而提高系统安全性能。在满足合法接收端服务质量(Quantity of Service,Qo S)需求的前提下,以最大化AN功率为目标建立优化问题。针对IRS单位模量约束,采用黎曼流形优化算法,将欧式空间的单位模量约束问题转换成流形空间的约束问题,仿真结果表明当发射端未知窃听者CSI时,所提算法能显著提高系统的安全性能。
Objective:To observe the effect of moxa-stick moxibustion plus recombinant human granulocyte-colony stimulating factor(rhG-CSF)in preventing chemotherapy infection in gastric cancer and its effect on immune ***:A tota...
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Objective:To observe the effect of moxa-stick moxibustion plus recombinant human granulocyte-colony stimulating factor(rhG-CSF)in preventing chemotherapy infection in gastric cancer and its effect on immune ***:A total of 70 patients with gastric cancer treated by chemotherapy were randomly divided into an observation group and a control group,with 35 cases in each *** control group was given rhG-CSF,and the observation group was given additional moxa-stick moxibustion on the basis of *** groups were treated for 2 chemotherapy cycles,totally 6 *** number of patients with infection,the duration of infection and the duration of continuous use of antibiotics were *** leukocytes and granulocytes counts,the levels of tumor necrosis factor-a(TNF-a)and interferon-γ(IFN-γ)were measured before and after treatment,and the levels of CD4,CD8 and natural killer(NK)cells were ***:The infection rate of the observation group was significantly lower than that of the control group(P<0.05),and the duration of infection and the duration of continuous use of antibiotics were also shorter(P<0.05).After treatment,the leukocytes and granulocytes counts in the two groups were higher than those before treatment(all P<0.05).After treatment,the levels of TNF-α and IFN-γ of the patients in the two groups were improved(all P<0.05),and there were significant differences between the observation group and the control group(P<0.05).After treatment,the numbers of CD4,CD8,and NK cells in the observation group increased significantly(all P<0.05);but the changes in the control group were not significant(P>0.05).Conclusion:Moxa-stick moxibustion plus rhG-CSF can significantly reduce the incidence and severity of chemotherapy infection in gastric cancer,increase the leukocytes and granulocytes counts,and regulate the levels of inflammatory factors,which may be related to the improvement of the immune function of the patients.
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