Study On Optimization Algorithm Of Transmission Performance Of Communication Services For L-DACS

L-DACS(L-band Digital Aeronautical Communication System)is an air-to-ground data link candidate system of the future aeronautical communication which is proposed by FAA,NASA and EUROCONTROL.It can guarantee the safe and reliable communication of aeronautical communication services.The dynamic change of the wireless channel capacity of the air-to-ground data link results in the change of the transmission quality of the air-to-ground data link and affects the performance of the aeronautical communication.It is one of the key problems in L-DACS system to analyse the communication quality of airborne communication service under the condition of dynamic change of the channel environment of air-to-ground data link,reduce the communication delay and packet loss rate of airborne communication service by resource allocation and scheduling and ensuring the Service Quality(QoS)of airborne communication service.The thesis combines the requirements of the project requirements of "Development and Testing of Prototype of Air-to-Ground Broadband Data Link Communication System" of China Commercial aircraft Co.,Ltd.Main Study Contents and results are as below:(1)To solve the issue of dynamic change related to capacity of air-to-ground link,we select a general ?-? channel model to represent the air-to-ground data link.The analytical formula of average channel capacity is given,which provides a quantifiable mathematical expression for the channel capacity of air-to-ground links.Then,the average channel capacity of ?-? channel is used in combination with M/M/1/K model of queue theory to analyze communication performance of Air Traffic Management(ATM).According to the proposed method,the correlation curve between parameters valued to cabin ATM system(including queue length,queueing delay and packet loss rate)and parameters valued to channel state(including SNR and allocated bandwidth)can be analyzed,and the impact of the increase in APC traffic on the cabin communication performance can be analyzed.(2)In the L-DACS system,the characteristics of airborne communication services are analyzed.To solve the problem of resource allocation for a single aircraft node needs to meet the transmission needs of airborne communication services,a minimum bandwidth resource prediction model of a single aircraft node is given.The bandwidth prediction model can predict the required minimum bandwidth resources for a single aircraft node and improve the spectrum resource utilization under the premise of satisfying the multi-service QoS index.Considering the differentiated QoS requirements of different aviation services,an ATM multi-service queue scheduling algorithm(QAA)based on exponential proportional fairness algorithm is proposed.The queue scheduling algorithm can prioritize the ATS services related to navigation safety,as the same time,distinguishing the priorities of real-time AOC services and non-real-time APC services to ensure the safety of aircraft navigation.The related content and results can provide theoretical support for the prediction and allocation of the bandwidth resources of the aircraft under different channel conditions in L-DACS,and serve as a theoretical reference for the deployment of future air-to-ground link.