A Research On Energy-efficient Networking Theory For Integrated Air-ground Networks

In recent years,with the development of stratosphere communication technologies,the realization of integrated air-ground communication has gradually become possible.Stratosphere communication refers to a method of using high-altitude platforms(HAPs)to carry base stations for communication,which has a wider coverage and a better channel quality than terrestrial communication,and it is one of the future development directions of wireless communication.Stratosphere communication can not only provide wireless service for the ground area,but also serve the aerial users.Stratosphere communication is less affected by natural or man-made disasters,which has been widely used in emergency communications.In the future,if it is possible to achieve compatibility between the stratospheric communications and terrestrial communications,a joint air-ground network will be constructed by combining HAPs and terrestrial base stations to achieve seamless three-dimensional network coverage.This thesis first studies the performance of the stratospheric communication system.According to the characteristics of high altitude and wide coverage of HAPs,multi-beam antennas are deployed in HAPs for directional coverage,and frequency multiplexing and antenna gain of multi-beam antennas are analyzed.Considering that the HAPs channel is dominated by the direct path,this thesis uses the Rician channel to model the air-air and airground multipath time-varying channels,and gives two estimation methods of Rician factors.According to the coverage characteristics of HAPs,the values of Rice factors under different elevation angles are given.Considering the high complexity of Rician channel,a generalized Rayleigh channel model is used to fit it.Then,this thesis aims at the Doppler frequency offset of mobile users under HAPs coverage,and estimates the frequency offset based on Orthogonal Frequency Division Multiple(OFDM)and direct path,then analyzes the maximum and average Doppler frequency offset of mobile users in stratospheric communication.The effect of Doppler frequency offset on the user's signal-to-noise ratio is also studied.Finally,this thesis studies the service outage probability of fixed and mobile users under Rician channel and fitting Rician channel,and simulates it.Based on the research of stratospheric communication,this thesis studies the joint networking scheme of HAPs and terrestrial base stations based on stochastic geometric theory.Firstly,the Poisson Point Process(PPP)is introduced to construct an air-ground integration layered heterogeneous network,and the network handover probability of terrestrial users under the coverage of the dual-layer heterogeneous network is studied.Then considering the spectrum multiplexing rate of the multi-beam antenna on aerial base stations,this thesis analyze the interference of the heterogeneous network,including the intra-layer and cross-layer interference.Considering the increasing energy consumption of communication networks and the difficulties in power supply to HAPs,this thesis introduces the concept of network energy efficiency.Considering the Doppler frequency offset of aerial users and the multi-layer interference of terrestrial users,the outages probability and transmission rate of aerial and terrestrial users are derived.Finally,according to the PPP distribution density of base stations and users,the energy efficiency expressions of aerial and terrestrial network are respectively obtained,and the correlation between the network energy efficiency and the base station density is analyzed and verified by simulation.