# Context-Aware Caching Distribution and UAV Deployment: A Game-Theoretic Approach
## 1 Introduction  
During the past decades, unmanned aerial vehicles (UAVs) have been popular in military applications due to their characteristics of high mobility and low cost [1; 2; 3; 4; 5], e.g., reasonable use of UAVs can reduce the amount of casualties of front-line soldiers. With the development of the manufacturing process and the reduction of manufacturing costs, UAVs have realized the transition from the military to the civilian domain. Recently UAVs have been widely utilized in civilian applications, including weather monitoring [6; 7], forest fire monitoring [8; 9], and first aid search and rescue [10; 11], which have benefited the public. Specifically, when UAVs are combined with wireless communication networks, users will experience better communication services due to the fact that traditional cellular networks have several of the following shortcomings [12]: (i) the potential damage of communication facilities caused by natural disasters; (ii) an increasingly unbearable communication burden resulting from growing smart devices and communication demands. Fortunately, it happens that the unique characteristics of UAVs can make up for these deficiencies. The characteristics of high mobility and low cost ensure that UAVs can quickly fly to the disaster area to provide services. Moreover, cache-enabled UAVs may increase the degree of file reuse and decrease the file caching cost [13]. Thus, especially in this era of data explosion, the combination of UAVs and the cache is considered to be a promising technology for dealing with the relevant challenges [13; 14]. Recently, progress in related research has shown the validity and reliability of the aforementioned technology. In our existing work [15], the problem of selecting caching nodes was studied and a selection algorithm was proposed. However, it ignored the potential cooperation among caching nodes. The authors studied the problem of hybrid caching in device-to-device (D2D) networks in Reference [16], which considered the cooperation but ignored the dynamics among nodes. In Reference [17], a secure transmission scheme based on interference alignment was proposed, which made the caching UAVs provide services similar tothe small base stations (SBSs). Idle SBSs replaced by UAVs would disrupt eavesdropping. However, the caching content sharing of UAVs is not considered. Moreover, the authors studied the problem of resource allocation in a cloud network with cache-enabled UAVs in Reference [18], where the users' content request distribution can be predicted based on the proposed algorithm. However, the research mentioned above, to a great extent, only focused on the resource allocation and optimization of caching contents but ignored the optimization of UAVs' service locations. This problem is rarely considered in existing studies to the best of our knowledge. Although, the authors took the change of UAVs' location into account in Reference [14], the potential cooperation among UAVs was not considered. In our prior work, we investigated the problem of both caching contents and service locations in UAV-assisted emergency networks by multi-hop in Reference [19]. However, the following shortcomings still exist. We considered the cooperation among UAVs by multi-hop based on the assumption that users within the coverage of UAVs were served perfectly. Nevertheless, in practical scenarios, the influence of propagation groups, line-of-sight (_LOS_) and non-line-of-sight (_NLOS_), which may result in users within the coverage of UAVs communicating with UAVs successfully by probability, should be taken into account. Meanwhile, a multi-hop service will result in more delay for ground users. Therefore, it is necessary and significant to improve the shortcomings mentioned above. In this paper, we consider the joint optimization of UAVs' caching contents and service locations with the goal of balancing the tradeoff between user's service probability and transmission overhead.