Unmanned aerial vehicle (UAV) as a carrier of small cell base station (SBS) becomes a promising solution to reduce infrastructure deployment cost. At the same time, Licensed-assisted Access (LAA) is proposed by 3GPP to apply the Long Term Evolution (LTE) technology into the unlicensed spectrum to expand the available bandwidth. To enhance and supplement the next generation 5G wireless network, this paper integrates LAA technology into UAV network to provide communication service for high-density mobile users. An enhanced LAA (eLAA) network is adopted to coordinate unlicensed band for LTE and WiFi by leveraging IEEE 802.11e protocol. The limited on-board energy is the main challenge for UAV to support mobility and communication. Under the UAV enabled eLAA network, we propose a joint trajectory design and transmission optimization algorithm to maximize the energy efficiency (EE) of the UAV. Firstly, for single UAV network, the formulated nonlinear fractional problem is solved by block coordinate descent (BCD) method and Dinkelbach-type algorithm. Our algorithm is proved to converge to a stationary point of the original nonconvex problem. Then, the proposed algorithm is extended to multi-UAV network through the sum-of-ratios algorithm. Numerical results demonstrate that the EE performance is significantly improved by UAV mobility. Based on the optimal trajectories, frequency reuse among multiple UAVs can further improve the EE performance.

作为小型基站（SBS）的载体的无人机（UAV）成为降低基础架构部署成本的有前途的解决方案。同时，3GPP提出了许可辅助访问（LAA），以将长期演进（LTE）技术应用于非许可频谱，以扩展可用带宽。为了增强和补充下一代5G无线网络，本文将LAA技术集成到UAV网络中，以为高密度移动用户提供通信服务。采用增强型LAA（eLAA）网络通过利用IEEE 802.11e协议来协调LTE和WiFi的免许可频段。机载能量有限是无人机支持机动性和通信的主要挑战。在启用了无人机的eLAA网络下，我们提出了一种联合轨迹设计和传输优化算法，以最大化无人机的能效（EE）。首先，对于单个无人机网络，通过块坐标下降法（BCD）和Dinkelbach型算法解决了拟定的非线性分数问题。证明我们的算法收敛到原始非凸问题的平稳点。然后，通过求和比算法将该算法扩展到多UAV网络。数值结果表明，UAV机动性显着提高了EE性能。基于最佳轨迹，多个无人机之间的频率复用可以进一步提高EE性能。通过块坐标下降法（BCD）和Dinkelbach型算法解决了提出的非线性分数问题。证明我们的算法收敛到原始非凸问题的平稳点。然后，通过求和比算法将该算法扩展到多UAV网络。数值结果表明，UAV机动性显着提高了EE性能。基于最佳轨迹，多个无人机之间的频率复用可以进一步提高EE性能。通过块坐标下降法（BCD）和Dinkelbach型算法解决了提出的非线性分数问题。证明我们的算法收敛到原始非凸问题的平稳点。然后，通过求和比算法将该算法扩展到多UAV网络。数值结果表明，UAV机动性显着提高了EE性能。基于最佳轨迹，多个无人机之间的频率复用可以进一步提高EE性能。