UAVs are expected to be an important complementary component for 5G (and beyond) communication systems to achieve the goal of global access to the Internet for all. To fully exploit the benefits of the distinct features of various UAVs, this article proposes a novel hierarchical network architecture enabled by software defined networking, which integrates cross-layer high and low altitude platforms into conventional terrestrial cellular networks to inject additional capacity and expand the coverage for underserved areas in a flexible, seamless, and cost-effective manner. Specifically, we first present a comprehensive comparison and review of different types of UAVs for communication services. Then, we propose an integrated airground heterogeneous network architecture and outline its characteristics and potential advantages. Next, several key enabling techniques for the integrated system are discussed in detail. In addition, we identify the potential application scenarios where the system can further enhance the performance of traditional terrestrial networks, followed by a case study to demonstrate the effectiveness of the proposed architecture. Finally, the discussions on challenges and open research issues are given.

中文翻译：

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通过集成高空和低空平台实现5G及更高级别的空地异构网络

无人机有望成为5G（及以后）通信系统的重要补充组件，以实现全球所有人接入互联网的目标。为了充分利用各种无人机的独特功能的优势，本文提出了一种由软件定义的网络支持的新型分层网络架构，该架构将跨层高低平台集成到传统的地面蜂窝网络中，以注入更多的容量并扩大覆盖范围灵活，无缝且具有成本效益的方式为服务不足的地区提供服务。具体来说，我们首先对通信服务的不同类型的无人机进行全面的比较和评估。然后，我们提出了一种综合的飞机场异构网络架构，并概述了其特点和潜在优势。下一个，详细讨论了集成系统的几种关键启用技术。此外，我们确定了系统可以进一步提高传统地面网络性能的潜在应用场景，然后通过案例研究来证明所提出体系结构的有效性。最后，给出了关于挑战和开放研究问题的讨论。