针对可见光通信(visible light communication,VLC)系统中用户分布动态变化及非理想信道状态信息(channel state information,CSI)反馈带来的性能退化问题,对两用户协作非正交多址接入(non-orthogonal multiple access,NOMA)VLC系统进...针对可见光通信(visible light communication,VLC)系统中用户分布动态变化及非理想信道状态信息(channel state information,CSI)反馈带来的性能退化问题,对两用户协作非正交多址接入(non-orthogonal multiple access,NOMA)VLC系统进行了研究。建立了基于远端用户位置分布的信道增益概率密度函数模型,并推导了系统误比特概率(bit error probability,BEP)的解析表达式。在此基础上,结合最大比合并(maximal ratio combining,MRC)技术,对协作与非协作系统性能进行了对比分析。仿真结果表明:随信噪比增加,采用MRC的协作系统能够显著提升系统性能,并有效降低BEP;在对比的L-脉冲位置调制(pulse position modulation,PPM)和开关键控(on-off keying,OOK)调制方式中,8-PPM表现最佳,其次为4-PPM与OOK,而2-PPM性能最差;系统性能随外环半径减小而改善,说明外环参数对动态分布用户的覆盖性能影响更为显著;此外,非理想CSI会导致误码率上升,验证了精确信道估计的重要性。所建立的动态信道模型和协作机制为NOMA-VLC系统在智能家居与工业物联网中的应用提供了理论支撑。展开更多
In this paper,we investigate a multi-UAV aided NOMA communication system,where multiple UAV-mounted aerial base stations are employed to serve ground users in the downlink NOMA communication,and each UAV serves its as...In this paper,we investigate a multi-UAV aided NOMA communication system,where multiple UAV-mounted aerial base stations are employed to serve ground users in the downlink NOMA communication,and each UAV serves its associated users on its own bandwidth.We aim at maximizing the overall common throughput in a finite time period.Such a problem is a typical mixed integer nonlinear problem,which involves both continuous-variable and combinatorial optimizations.To efficiently solve this problem,we propose a two-layer algorithm,which separately tackles continuous-variable and combinatorial optimization.Specifically,in the inner layer given one user association scheme,subproblems of bandwidth allocation,power allocation and trajectory design are solved based on alternating optimization.In the outer layer,a small number of candidate user association schemes are generated from an initial scheme and the best solution can be determined by comparing all the candidate schemes.In particular,a clustering algorithm based on K-means is applied to produce all candidate user association schemes,the successive convex optimization technique is adopted in the power allocation subproblem and a logistic function approximation approach is employed in the trajectory design subproblem.Simulation results show that the proposed NOMA scheme outperforms three baseline schemes in downlink common throughput,including one solution proposed in an existing literature.展开更多
文摘针对可见光通信(visible light communication,VLC)系统中用户分布动态变化及非理想信道状态信息(channel state information,CSI)反馈带来的性能退化问题,对两用户协作非正交多址接入(non-orthogonal multiple access,NOMA)VLC系统进行了研究。建立了基于远端用户位置分布的信道增益概率密度函数模型,并推导了系统误比特概率(bit error probability,BEP)的解析表达式。在此基础上,结合最大比合并(maximal ratio combining,MRC)技术,对协作与非协作系统性能进行了对比分析。仿真结果表明:随信噪比增加,采用MRC的协作系统能够显著提升系统性能,并有效降低BEP;在对比的L-脉冲位置调制(pulse position modulation,PPM)和开关键控(on-off keying,OOK)调制方式中,8-PPM表现最佳,其次为4-PPM与OOK,而2-PPM性能最差;系统性能随外环半径减小而改善,说明外环参数对动态分布用户的覆盖性能影响更为显著;此外,非理想CSI会导致误码率上升,验证了精确信道估计的重要性。所建立的动态信道模型和协作机制为NOMA-VLC系统在智能家居与工业物联网中的应用提供了理论支撑。
基金supported by Beijing Natural Science Fund–Haidian Original Innovation Joint Fund(L232040 and L232045).
文摘In this paper,we investigate a multi-UAV aided NOMA communication system,where multiple UAV-mounted aerial base stations are employed to serve ground users in the downlink NOMA communication,and each UAV serves its associated users on its own bandwidth.We aim at maximizing the overall common throughput in a finite time period.Such a problem is a typical mixed integer nonlinear problem,which involves both continuous-variable and combinatorial optimizations.To efficiently solve this problem,we propose a two-layer algorithm,which separately tackles continuous-variable and combinatorial optimization.Specifically,in the inner layer given one user association scheme,subproblems of bandwidth allocation,power allocation and trajectory design are solved based on alternating optimization.In the outer layer,a small number of candidate user association schemes are generated from an initial scheme and the best solution can be determined by comparing all the candidate schemes.In particular,a clustering algorithm based on K-means is applied to produce all candidate user association schemes,the successive convex optimization technique is adopted in the power allocation subproblem and a logistic function approximation approach is employed in the trajectory design subproblem.Simulation results show that the proposed NOMA scheme outperforms three baseline schemes in downlink common throughput,including one solution proposed in an existing literature.
