###### Abstract  
A new era of the fifth-generation (5G) networks is realized to satisfy user demands on higher data rate and massive connectivity for information sharing and utilization. The vertical applications such as vehicle-to-everything (V2X) communications, industrial automation, smart factory, smart farm and smart cities require ultra-fast communications and wide service range. Coverage extension is a key issue to support the required demands on higher performance, but requires an additional deployment of base or relay stations. Therefore, an efficient solution needs to be cost-effective and easy, in order to deploy more stations. An unmanned aerial vehicle (UAV) has been considered as a candidate to overcome these issues because it is much more cost-effective than the ground stations and does not require network or cell replanning, thereby enhancing the network coverage without additional excessive deployment procedures of the existing networks. UAVs will play important roles in 5G and beyond networks assisting as macro base stations, relay stations, small cells, or a moving aggregator. The performance of UAV wireless networks highly depends on the position or the trajectory of UAVs and the resource managements of entire networks. Recently, there have been extensive studies on performance analysis, UAV deployment, UAV trajectory and resource management of UAV wireless networks to achieve the required demands on performance. This paper surveys research conducted for the UAV deployment and trajectory to construct UAV wireless networks for the coverage extension, the throughput improvement and the resource management for different use cases and scenarios, so as to encourage further studies in this area. 5G and beyond wireless communication networks; UAV deployment and trajectory; coverage extension; machine learning +
Footnote †: journal: Information  
usage scenarios for IMT-2020 and beyond; enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communications (uRLLC) and Massive Machine Type Communications (mMTC), and eight key performance indicators (KPIs) as 5G requirements [2]. The key technologies for 5G networks have been developed and studied by researchers and experts from the organizations, institutes, and companies all over the world. Specially, 3 GPP approved the first 5G New Radio (NR) non-standalone (NSA) specifications, and completed Release 15 including NR standalone (SA) specifications in 2018. The third 5G standard, 3 GPP Release 17, reached stage 3 functional freeze in March 2022, which indicates the system design completion, and is expected to further enhance system performance and expand into new vertical applications. Coverage enhancements and broadcast/multicase expansion are the key 5G milestone in 3 GPP Release 17 to enhance the capacity of 5G networks [3]. Communications service providers commercially launched 5G networks in 2019, and the first 5G device was released in early 2020. 5G networks are expected to support 12% of mobile traffic by the end of 2022, and will drive the enormous amount of traffic through its connectivity with large bandwidth (i.e., 100 MHz) and ultra low latency (i.e., one millisecond) [1]. 5G networks will take over more portion of mobile traffic from 4G networks, and the amount of mobile data traffic through 5G connectivity will increase exponentially. To satisfy user demands on higher data rate and massive connectivity for information delivery, coverage extension is a key as pointed out in 3 GPP Release 17 for enhancing 5G capability. The coverage extension can be realized with additional base or relay stations in 5G networks. However, the deployment of ground base or relay stations is costly due to cell reorganization to optimize the location of existing stations along with new stations to provide a required QoS. Hence, a smart solution for coverage extension and capacity enhancement is being highly required.