Research On Performance Of EDGE System In GSM-R Network Packet Domain

EDGE is an enhanced technology based on the GSM/GPRS system.It introduces 8PSK modulation in the GSM-R packet domain,in which each symbol transmits three bits of information.Theoretically,the maximum transmission rate of the air interface can be increased three times.EDGE introduced adaptive transmission technology to improve the GPRS system performance in term of transmission delay,packet loss rate,throughput and other indicators.Compared with GPRS,EDGE improves the performance of air interface.Furthemore,EDGE system can utilize the existing railway GSM-R/GPRS communication system infrastructure,so the performance of GPRS system is improved via the most economical way.With the rapid development of China railways and the further growth of business demands,EDGE can alleviate the contradiction between the demand for vehicle-ground communication services and the GSM-R network bearing capacity in a short period of time.EDGE will be a bridge for the railway communication system to evolve from GSM-R/GPRS to LTE-R.However,there is no EDGE technology application experience in the global railways.It is urgent to conduct research on EDGE system performance.This thesis focuses on the performance of EDGE technology in railway scenarios.First of all,the key technologies of EDGE are introduced.In order to evaluate the performance of the EDGE system in the railway scenario,theoretical analysis,measurements in laboratory and trials are adopted,based on the measurement results,the performance gain of the EDGE system are discussed.The main content of this thesis is as follows:(1)A hardware-in-the-loop simulation platform is set up in the laboratory.Channel simulator C8 and EDGE network are used to test the performance under the moving scenario.With three fixed modulation and coding schemes,the performance under different moving speeds is studied.(2)The transmission of railway data services are simulated on the Huhhot-Zhangjiakou General Speed Railway and Xi'an-Chengdu High-speed Railway to test the transmission delay,throughput,and packet loss rate of the EDGE system in the railway scenario.The impact of the mobile speed on the performance of the EDGE system is measured.Based on the measurement results,the EDGE system application strategy suitable for the railway scenario is proposed.(3)A large number of retransmissions on the Xicheng High-speed Railway led to a significant deterioration of the system delay.Through the combination of theoretical analysis and simulation,the time delay,packet loss rate,and throughput performance under different channel conditions are studied.The impact of retransmission mechanisms on performance delay,packet loss rate,and throughput are compared.(4)Three system optimization ashemes are adopted to improve the latecy performance:network-assisted cell reselection,extended uplink TBF release,and PFC(Packet Flow Context).Through laboratory tests,it has been proved that the extended release of uplink TBF and network-assisted cell reselection can effectively reduce the delay of EDGE networks;it has been tested that high-priority services under non-congestion conditions can be preferentially protected when useing PFC function.A QoS guarantee strategy is adopted to ensure the transmission of key business services in case of resource constraints.