Wireless Detection Technology Under The Wireless Communication Integrated Architechture For High Speed Railways

As the operating speed of high speed railway(HSR)ever increases,train operation safety attracts more and more attention,especially on hazard warning for railways.In railways,natural disasters,such as landslides,and foreign matter invasions become serious threats to railway operation safety,then some relevant monitoring methods have emerged.These monitoring methods include Global Positioning System(GPS)monitoring,wireless sensor monitoring,and video monitoring.However,some of them are vulnerable to be damaged and the performance of them is limited by the light and weather.In contrast,the light and natural disasters less affect the performance of millimeter wave detection.Thus,millimeter wave detection can keep work all the time.Furthermore,its equipment is simple,and the resolution is high.On the other hand,the future 5G wireless communication needs to increase the capacity of 1000 times to meet the wireless traffic demands,and the millimeter wave communication is bound to become the trend of wireless communications for its large available continuous bandwidth.Based on the above mentioned,it is necessary to integrate the two technologies into one system,which makes the fusion system possess wireless transmission function and disaster monitoring function.All researches in this thesis are based on the wireless communication and radar detection integrated architecture for HSR.First,we design the integrated architecture for the fusion system according to the wireless monitoring and wireless communication demands in actual railway scenarios.To mitigate handovers and increase baseband processing resource utilization,the proposed integrated network is deployed based on the cloud radio access network(C-RAN)architecture.The Building Baseband Unit(BBU)is responsible for resource allocation and data processing,and the Radio Remote Unit(RRU)is only responsible for data transceiver.In this proposed integrated architecture,two kinds of RRUs are employed,where millimeter wave bands RRUs are time-division multiplexed to transmit large-volume communication data for trains,or to execute environment detection,and the licensed lower frequency bands RRUs carry low-volume communication data(critical signaling and data).As millimeter wave bands RRUs execute wireless communication and radar detection in a time-sharing way,the train cannot connect to the source base station forever once hard handover occurs.Based on this,we propose a "Double insurance" approach.The simulation results show that the proposed method has a significant improvement in the handover success rate and the probability of link outage compared to the traditional LTE-R hard handover.As to detection function,the radar target detection algorithm directly determines the system performance.For the complex detection environment in railways,we propose a two-dimensional VIS-CFAR algorithm,which can adaptively select the corresponding target detection algorithm according to the surrounding environment and greatly reduce the system leakage alarm rate.Finally,we simulate three different detection scenarios and other five classical CFAR algorithms,and the simulation results show that the proposed two-dimensional VIS-CFAR algorithm keeps well performance in uniform clutter environment,clutter edge environment and multi-target interference environment,which greatly improves the monitoring efficiency for the fusion system.