Heterogeneous cellular networks (HCNs) are envisioned as a promising architecture to provide seamless wireless coverage and increase network capacity. However, the densified multi-tier network architecture introduces excessive intra- and cross-tier interference and makes HCNs vulnerable to eavesdropping attacks. In this article, a dynamic spectrum control (DSC)-assisted transmission scheme is proposed for HCNs to strengthen network security and increase the network capacity. Specifically, the proposed DSC-assisted transmission scheme leverages the idea of block cryptography to generate sequence families, which represent the transmission decisions, by performing iterative and orthogonal sequence transformations. Based on the sequence families, multiple users can dynamically occupy different frequency slots for data transmission simultaneously. In addition, the collision probability of the data transmission is analyzed, which results in closed-form expressions of the reliable transmission probability and the secrecy probability. Then, the upper and lower bounds of network capacity are further derived with given requirements on the reliable and secure transmission probabilities. Simulation results demonstrate that the proposed DSC-assisted scheme can outperform the benchmark scheme in terms of security performance. Finally, the impacts of key factors in the proposed DSC-assisted scheme on the network capacity and security are evaluated and discussed.

异构蜂窝网络 (HCN) 被设想为一种有前途的架构，可提供无缝无线覆盖并增加网络容量。然而，密集的多层网络架构引入了过多的层内和层间干扰，使 HCN 容易受到窃听攻击。在本文中，为 HCN 提出了一种动态频谱控制 (DSC) 辅助传输方案，以加强网络安全并增加网络容量。具体而言，所提出的 DSC 辅助传输方案利用块密码学的思想通过执行迭代和正交序列变换来生成代表传输决策的序列族。基于序列族，多个用户可以同时动态占用不同的频隙进行数据传输。此外，分析了数据传输的碰撞概率，得到可靠传输概率和保密概率的封闭式表达式。然后，根据对可靠和安全传输概率的给定要求，进一步导出网络容量的上限和下限。仿真结果表明，所提出的 DSC 辅助方案在安全性能方面可以优于基准方案。最后，评估和讨论了所提出的 DSC 辅助方案中关键因素对网络容量和安全性的影响。根据对可靠和安全传输概率的给定要求，进一步导出网络容量的上限和下限。仿真结果表明，所提出的 DSC 辅助方案在安全性能方面可以优于基准方案。最后，评估和讨论了所提出的 DSC 辅助方案中关键因素对网络容量和安全性的影响。根据对可靠和安全传输概率的给定要求，进一步导出网络容量的上限和下限。仿真结果表明，所提出的 DSC 辅助方案在安全性能方面可以优于基准方案。最后，评估和讨论了所提出的 DSC 辅助方案中关键因素对网络容量和安全性的影响。