We study physical layer secure transmission with limited feedback in heterogeneous cellular networks. A transmission protocol is designed to obtain more secure and accurate channel state information (CSI) for enhancing the secrecy performance. Under the proposed protocol, we derive expressions of coverage probability and secrecy outage probability to analyze the security performance with different system parameters such as feedback CSI length and number of antennas. Furthermore, an iteration algorithm is proposed to balance the tradeoff between the feedback and transmission time, and maximize the average secrecy throughput under coverage and secrecy outage constrains. Numeric results demonstrate the optimal feedback overhead and the maximum average secrecy throughput are influenced by the number of antennas.

我们研究异构蜂窝网络中有限反馈的物理层安全传输。设计传输协议以获得更安全和准确的信道状态信息（CSI），以增强保密性能。在提出的协议下，我们推导了覆盖概率和保密中断概率的表达式，以分析不同系统参数（如反馈CSI长度和天线数量）的安全性能。此外，提出了一种迭代算法来平衡反馈和传输时间之间的折衷，并在覆盖和保密中断约束下最大化平均保密吞吐量。数值结果表明，最佳的反馈开销和最大的平均保密吞吐量受天线数量的影响。