工程科学学报.第42卷，第4期：483-489.2020年4月 Chinese Journal of Engineering,Vol.42,No.4:483-489,April 2020 https://doi.org/10.13374/j.issn2095-9389.2019.09.15.009;http://cje.ustb.edu.cn 面向物联网业务绿色接入的异构蜂窝网络优化 刘娅汐，皇甫伟四 北京科技大学计算机与通信工程学院.北京100083 ☒通信作者，E-mail:huangfuwei(@ustb.edu.cn 摘要物联网是未来赛博使能业务的重要支撑平台.蜂窝网络则被认为是广泛分布在部署区域中的物联网终端数据接入 的主要渠道，尤其在广域覆盖方面具有难以替代的价值.在满足覆盖要求的条件下，降低蜂窝网络基站的下行发射功率在绿 色通信方面具有重要的研究意义.由此提出了一种基于优化目标平滑近似和均方根传播策略的梯度下降算法，在满足物联 网业务覆盖率的条件下最小化基站的总下行发射功率.首先，使用罚函数方法将复杂约束条件的异构蜂窝网络优化问题转 化为简单约束形式的优化问题：其次，将不可导的目标函数通过平滑近似转化为可导形式，并给出其对天线下倾角和下行功 率参数的梯度解析形式：最后.，使用均方根传播梯度下降算法进行转化后的目标函数优化.仿真实验结果表明该算法可以在 满足覆盖率指标的条件下最小化基站的总下行发射功率，与现有元启发算法和普通梯度下降算法相比，具有良好的收敛速 度，并能更好地抑制优化过程中振荡 关键词物联网：覆盖率；总下行功率损耗；天线下倾角；梯度下降法 分类号TN929.5 Heterogeneous cellular network optimization for green access of IoT traffics LIU Ya-xi,HUANGFU Wei School of Computer and Communication Engineering.University of Science and Technology Beijing.Beijing 100083,China Corresponding author,E-mail:huangfuwei@ustb.edu.cn ABSTRACT The Internet of Things (IoT)has become an essential supporting platform for the present and future cyber-enabled services.Cellular networks is considered as the main channel of the data access for IoT terminals distributed in the region of interest,and they have an irreplaceable value,especially in wide-area coverage.Thus,it has a significant application value to reduce the downlink transmit power consumption of base stations under the restrictions of the coverage requirements for the green communication in heterogeneous cellular networks.A gradient descent algorithm was proposed based on smooth approximation and root mean square propagation.The algorithm could minimize the total downlink power consumption of base stations while satisfying the IoT service coverage.First,the penalty function method was used to simplify such an optimization problem with complicated constraints to a new one with simple constraints.Then,the non-derivative objective function was transformed by an approximation method into a derivable form.We also presented the close-form of the gradient of the objective function with respect to both the azimuths of the antennas installed in the base stations and the downlink transmit power levels related to these antennas.Finally,the gradient descent algorithm with root mean square propagation was used to execute the optimization of the newly approximated but smoothed version of the original objective function.Simulation experiments were conducted,and the results show that the proposed algorithm can significantly reduce the total power consumption of the downlink radio frequency transmit under the restrictions of the coverage ratio requirements in the region of interest.Furthermore,not only is the convergence speed of the proposed algorithm very fast,but also the oscillation phenomenon that occurs during the iterative procedure steps of the optimization is greatly suppressed by the proposed algorithm compared with the meta- 收稿日期：2019-09-15 基金项目：教育部一中国移动科研基金资助项目(MCM201601013)面向物联网业务绿色接入的异构蜂窝网络优化 刘娅汐，皇甫伟苣 北京科技大学计算机与通信工程学院，北京 100083 苣通信作者，E-mail：huangfuwei@ustb.edu.cn 摘    要    物联网是未来赛博使能业务的重要支撑平台. 蜂窝网络则被认为是广泛分布在部署区域中的物联网终端数据接入 的主要渠道，尤其在广域覆盖方面具有难以替代的价值. 在满足覆盖要求的条件下，降低蜂窝网络基站的下行发射功率在绿 色通信方面具有重要的研究意义. 由此提出了一种基于优化目标平滑近似和均方根传播策略的梯度下降算法，在满足物联 网业务覆盖率的条件下最小化基站的总下行发射功率. 首先，使用罚函数方法将复杂约束条件的异构蜂窝网络优化问题转 化为简单约束形式的优化问题；其次，将不可导的目标函数通过平滑近似转化为可导形式，并给出其对天线下倾角和下行功 率参数的梯度解析形式；最后，使用均方根传播梯度下降算法进行转化后的目标函数优化. 仿真实验结果表明该算法可以在 满足覆盖率指标的条件下最小化基站的总下行发射功率，与现有元启发算法和普通梯度下降算法相比，具有良好的收敛速 度，并能更好地抑制优化过程中振荡. 关键词    物联网；覆盖率；总下行功率损耗；天线下倾角；梯度下降法 分类号    TN929.5 Heterogeneous cellular network optimization for green access of IoT traffics LIU Ya-xi，HUANGFU Wei苣 School of Computer and Communication Engineering, University of Science and Technology Beijing, Beijing 100083, China 苣 Corresponding author, E-mail: huangfuwei@ustb.edu.cn ABSTRACT    The Internet of Things (IoT) has become an essential supporting platform for the present and future cyber-enabled services. Cellular networks is considered as the main channel of the data access for IoT terminals distributed in the region of interest, and they have an irreplaceable value, especially in wide-area coverage. Thus, it has a significant application value to reduce the downlink transmit power consumption of base stations under the restrictions of the coverage requirements for the green communication in heterogeneous cellular networks. A gradient descent algorithm was proposed based on smooth approximation and root mean square propagation. The algorithm could minimize the total downlink power consumption of base stations while satisfying the IoT service coverage. First, the penalty function method was used to simplify such an optimization problem with complicated constraints to a new one with simple constraints. Then, the non-derivative objective function was transformed by an approximation method into a derivable form. We also presented the close-form of the gradient of the objective function with respect to both the azimuths of the antennas installed in the base stations and the downlink transmit power levels related to these antennas. Finally, the gradient descent algorithm with root mean square propagation was used to execute the optimization of the newly approximated but smoothed version of the original objective function. Simulation experiments were conducted, and the results show that the proposed algorithm can significantly reduce the total power consumption of the downlink radio frequency transmit under the restrictions of the coverage ratio requirements in the region of interest. Furthermore, not only is the convergence speed of the proposed algorithm very fast, but also the oscillation phenomenon that occurs during the iterative procedure steps of the optimization is greatly suppressed by the proposed algorithm compared with the meta- 收稿日期: 2019−09−15 基金项目: 教育部—中国移动科研基金资助项目 (MCM201601013) 工程科学学报，第 42 卷，第 4 期：483−489，2020 年 4 月 Chinese Journal of Engineering, Vol. 42, No. 4: 483−489, April 2020 https://doi.org/10.13374/j.issn2095-9389.2019.09.15.009; http://cje.ustb.edu.cn