Research On The Performance Analysis Of UAV-aided Terrestrial Small-Cell Caching Networks

With the development of 5G networks and the emergence of multimedia services,the rapid growth of wireless data traffic triggers many problems such as backhaul link congestion and big transmission delay.Caching at terrestrial small-cell base stations(SBS)can effectively alleviate backhaul congestion and reduce transmission delay.To improve the poor signal of single base station transmission(ST)and enhance coverage,JT is introduced in SBS caching network.Furthermore,an Unmanned aerial vehicle(UAV)with caching functionality assists the terrestrial SBS.Moreover,this paper designs a UAV-assisted SBS service scheme and analyzes the caching performance.The massive multiple-input multiple-output(mMIMO)technology is implemented in UAV transmission to improve wireless transmission.The research content as following.(1)A novel UAV-assisted terrestrial SBS content caching scheme is proposed,in which SBSs act as the major caching servers for content delivery due to their dense deployment.Only when a user cannot obtain its requested file from SBSs,it turns to UAVs for help.The mobility of UAV is utilized to shorten the serving distance.Using stochastic geometry,the caching performance including the average cache hit probability and the average transmission rate is analyzed.Moreover,the caching strategy is optimized to obtain the optimal caching probability of files with different popularity.The simulation results prove the validity of the theoretical derivation and show that the proposed UAV-assisted terrestrial SBS caching scheme is significantly better than the traditional single-base station service mechanism,or the terrestrial caching network without utilizing UAV’s mobility.Besides,the obtained optimal caching probabilities of SBS and UAV significantly improve the caching performance of the overall network.(2)Moreover,the performance improvement in UAV transmission brought by the mMIMO technology is studied.By stochastic geometric,the relationship between the number of antennas,the number of pilots,the number of UAVs,and the number of users in MIMO system is investigated.Besides,this paper focus on the impact of pilot contamination on channel estimation and precoding in a mMIMO system.Finally,the average cache hit probability and the average transmission rate is derived.The simulation results show that the mMIMO technology can improve the performance of the UAV caching network.From the analytical and simulation results,it can be found that the proposed UAV-assisted terrestrial SBS content caching scheme in this paper can achieve a gain of 40% for the average cache hit probability,which inclued 30% from JT scheme and 20% from UAV enhance.Furthermore,the optimal caching strategy compared with baseline increases the average cache hit probability by 25%.At last,employing mMIMO on UAVs improves caching performance nearly doubled.The proposed UAV-assisted terrestrial SBS content caching scheme in this paper,can complete fast delivery of content,improve caching performance and achieve a gain of 40% for the average cache hit probability.The research shed light on the UAV-assisted wireless caching,and engineering applications of UAV-assisted wireless networks.