Transceiver Design Of Wireless Cellular Networks Based On Caching And UAV

Nowadays,small cell networks are very popular because of its plenty of advantages.However,some challenges still exist.With the ever-increasing number of mobile users,interference will appear and severely affect the transmission performance between the small-cell base stations(SBSs)and mobile users.Furthermore,the coverage area of small cell network is limited.Therefore,the transmission performance cannot be guaranteed for the mobile users at the edge of the small cells.In addition,in disaster areas,the electric power cannot be guaranteed,and SBSs will be destroyed by disaster.Accordingly,SBSs may not be used to perform transmission.Thus,in this paper,with the help of caching and unmanned aerial vehicle(UAV),transceiver design schemes are proposed to improve the transmission performance of small cell networks.Specifically speaking,the work includes:(1)As for the mobile users in the coverage area of small cell networks: First of all,the files with high popularity will be stored in SBSs at off-peak period,so that the backhaul load is reduced and the transmission rate can be increased.Then,greedy algorithm and interference alignment(IA)technique are combined to download files when mobile users need them in real time.Meanwhile,possible network topologies such as interference network and interfering broadcast network are analyzed in detail.Furthermore,the feasible conditions of IA are analyzed for these possible topologies.Finally,simulation results are presented to show the effectiveness of the proposed schemes.(2)As for the mobile users at the edge of small cell networks: First of all,the files with high popularity will be cached at the mobile users who are at the edge of small cell networks.An optimal caching problem is formulated to maximize the total offloading probability of the D2 D system.Then,KM algorithm and distributed algorithm are proposed to construct D2 D links,which can help increase transmission rate.Finally,simulation results are presented to show the effectiveness of the proposed schemes.(3)As for communications in disaster areas with the help of UAV that equipped with multiple antennas: First of all,UAV and D2 D are combined to perform transmission in disaster area.Then,SPR algorithm is used to establish D2 D links.The closed-form expressions of the number of hops and the outage probability are derived for the uplink and downlink.The multi-antenna resource of UAV is fully exploited with optimal transceiver design to guarantee reliable communications for both the UAV uplink and downlink.Finally,simulation results are presented to show the effectiveness of the proposed schemes.(4)As for communications in disaster areas with the help of UAV that equipped with single antenna: First of all,an optimal location is selected for the UAV;Then,a power allocation scheme for non-orthogonal multiple access(NOMA)is used to maximize the sum rate.Finally,simulation results are presented to show the effectiveness of the proposed schemes.