基于随机波束成型的MISO OFDMA物理层安全算法

在多用户非互易性信道场景下，基于信道状态信息的物理层安全算法需要接收端反馈大量的信道状态信息，导致系统保密吞吐量降低。针对这一问题，文章设计了一种基于随机波束成型的MISO-OFDMA物理层安全算法。在用户选择阶段，发送端依次发送随机生成的正交波束，每个接收用户反馈各个子载波上信干噪比（SINR）最大的波束索引，以减少反馈数据量；发送端将子载波分配给SINR最大的接收用户。在加密传输阶段，发送端在SINR最大的波束上发送有用信号，保证相应合法用户的正常通信；在其余波束上发送人工噪声，扰乱窃听者的监听。性能分析和仿真结果表明：当天线数为16，合法用户数为150时，相对于人工噪声方法，所提算法的保密吞吐量提高了2bit／s。

Random Beamforming Based Physical-Layer Security in MISO-OFDMA System

In the scenario of multi-user nonreciprocal channel, the physical layer security methods based on channel state information require a lot of channel state information feedback, but the feed- back delay will reduce the throughput of securing system. To solve the problem, a physical layer se- curity method based on random beamforming in MISO-OFDMA systems is designed. In the phase of user selection, the sender transmits randomly-generated orthogonal beams by the promised se- quence, each user feeds back the index of beams with the maximum SINR in every subcarrier, which reduces the feedback overhead, then the subcarrier is assigned to the user with the maximum SINR in the corresponding subcarrier. In the phase of securing transmission, the useful signal is transmitted on the beam with the maximum SINR, and the artificial noise is transmitted on the re- maining beams. Through the cycle of the two phases, the fairness among users is ensured. The per- formance analysis and simulation result show that when the number of antenna is 16, the securing throughout of the proposed method is 2bit/s more than artificial noise method.