Performance Research For Buffer-assisted UAV Emergency Communication Network

As a key equipment in the future emergency communications,unmanned aerial vehicle(UAV)can provide users in disaster areas with flexible and efficient communication coverage by virtue of its air superiority.Due to the mobility and flexibility of UAV,it can get rid of the geographical restrictions of disaster areas in emergency communications and provide communication services according to the users’ needs.For the scenarios in severe disaster areas where ground communication facilities are completely damaged,this article uses UAVs equipped with a Wi-Fi access point(WAP)to forward users’ data in the disaster area to a ground base station(GBS)outside the disaster area.Due to the limited communication power of UAV,the backhaul capacity of the network is usually limited when UAV is used for emergency communications.Therefore,this article considers applying buffer technology to UAV communication to achieve the effect of reducing network congestion while providing users with communication services.This article models the UAV emergency communication network based on a stochastic geometry model,and studies the successful access probability of users in the network,the transmission rate of the uplink and backhaul links,and the total delay in the transmission process.Among them,the UAV is equipped with a high-speed cache to store the uplink data from the user and forward it to the GBS through the backhaul link.In the uplink,user equipment(UE)accesses the WAP according to the carrier sense multiple access with a collision avoidance(CSMA/CA)scheme.In the backhaul link,in order to increase the backhaul link capacity,the UAV uses millimeter waves for wireless backhaul.According to the system model,we first get the distance distribution of interfering users in the uplink.Based on the stochastic geometry theory,we analyze the average power of the interference received in the uplink and backhaul links and the user’s successful access probability,and obtain a closed-form expression for the average transmission rate of the uplink and backhaul links.According to the queuing theory,we get the expression of the average queuing delay in the UAV buffer,and obtain the expression of the total transmission delay.The simulation shows that the total delay is affected by factors such as buffer capacity,UAV height and UAV deployment density.Through simulation,we find that there is an appropriate UAV density to achieve a balance between the high cost of UAV deployment and the system performance.These works will provide valuable references for specific application scenarios in the future.