Providing reliable and efficient coverage for cell-edge mobile users (MUs) is a key issue in wireless communication networks. With non-uniform structure and heterogeneity of network topology in the 5G/B5G networks, performance improvement of cell-edge MUs becomes even more challenging. Unmanned aerial vehicle (UAV) exhibits a comparable advantage in enhancing cell edge performance due to its flexible mobility and line-of-sight air-to-ground links. In this paper, we study UAV-assisted cell-edge MU offloading in the non-uniform heterogeneous cellular networks. A base station (BS) coordination and ground-to-air offloading scheme is proposed to enhance the cell-edge MUs’ performance, whereby cell-edge MUs are periodically scheduled between coordinated ground BSs and a flying UAV. Furthermore, a theoretical framework is developed to analyze the average spectral efficiency (SE) and average network throughput. Specifically, closed-form expressions for the average SE are derived for MUs associated with the ground BSs. Upper and lower bounds for the average SE are also obtained when the MU is offloaded to the flying UAV. Finally, numerical and simulation results are provided to validate the theoretical analysis and investigate the impact of key system parameters on the system performance, which also demonstrate the advantages of the UAV-assisted offloading scheme, compared with benchmark solutions.

中文翻译：

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在非均匀异构蜂窝网络中通过飞行无人机卸载小区边缘用户

为小区边缘移动用户 (MU) 提供可靠高效的覆盖是无线通信网络中的一个关键问题。由于 5G/B5G 网络中网络拓扑结构的不统一和异构，小区边缘 MU 的性能提升变得更具挑战性。由于其灵活的移动性和视距空对地链路，无人机 (UAV) 在增强小区边缘性能方面表现出相当的优势。在本文中，我们研究了非均匀异构蜂窝网络中无人机辅助的小区边缘 MU 卸载。提出了一种基站 (BS) 协调和地空卸载方案来增强小区边缘 MU 的性能，由此小区边缘 MU 在协调的地面 BS 和飞行无人机之间定期调度。此外，开发了一个理论框架来分析平均频谱效率 (SE) 和平均网络吞吐量。具体来说，对于与地面基站相关联的 MU，可以推导出平均 SE 的封闭形式表达式。当 MU 卸载到飞行的 UAV 时，也会获得平均 SE 的上限和下限。最后，提供数值和仿真结果来验证理论分析并研究关键系统参数对系统性能的影响，这也证明了无人机辅助卸载方案与基准解决方案相比的优势。当 MU 卸载到飞行的 UAV 时，也会获得平均 SE 的上限和下限。最后，提供数值和仿真结果来验证理论分析并研究关键系统参数对系统性能的影响，这也证明了无人机辅助卸载方案与基准解决方案相比的优势。当 MU 卸载到飞行的 UAV 时，也会获得平均 SE 的上限和下限。最后，提供数值和仿真结果来验证理论分析并研究关键系统参数对系统性能的影响，这也证明了无人机辅助卸载方案与基准解决方案相比的优势。