The existing researches on Coordinated Multi-Point transmission (CoMP) secure transmission in heterogeneous cellular networks mainly focus on improving the quality of the main channel to enhance security. However, CoMP also makes the average distance between base station and eavesdropper close which makes the security threat more severe. Based on secrecy guard zone, an enhanced CoMP policy is proposed in this paper. Then, the connection outage probability, secrecy outage probability and secrecy throughput are analyzed. Furthermore, the transmission power and power allocation factor are designed very carefully to maximize the secrecy throughput. Simulation results show that compared with conventional CoMP policy, the proposed policy can not only achieve non-zero secrecy throughput when faced with severe security threats (i.e. for larger eavesdropper density), but also improve the secrecy throughput of 76.1％ at most when faced with small security threats (i.e. for smaller eavesdropper density).%现有针对异构蜂窝网多点协作安全传输的研究集中于增强主信道质量以提升安全性,然而多基站协作又使基站和窃听者之间的平均距离变近,网络的安全性受限于距离协作基站较近的窃听者.针对该问题,该文提出一种基于安全保护域的增强型多点协作传输机制.然后,理论分析了用户的连接中断概率、安全中断概率以及安全吞吐量.进一步,以最大化安全吞吐量为目标,优化协作微基站的发射功率以及有用信息功率分配比例系数.仿真结果表明,相比于传统的多点协作安全传输机制,在存在严重安全威胁(窃听者密度较大)的场景下,所提机制可以实现非零系统安全吞吐量;在存在较小安全威胁(窃听者密度较小)的场景下,系统安全吞吐量最大可提升76.1％.
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