Research On A Network Virtualization Based Integrated Train Ground Communication System For Urban Rail Transit Systems

Nowadays,rail transit has become the lifeblood of urban public traffic and is playing an increasingly important role in urban operation.In the current situation,the central and local governments have put more attention to urban rail transit operation safety,which has been a popular topic of many researchers and scholars.Among the urban rail transit system,the train-ground communication is the center of urban rail traffic safety operation,bearing the Communications-based Train Control(CBTC)System,the Train State Monitor systems,the Radio Train Dispatch systems,the Passenger Information System(PIS)and the Image Monitor System(IMS).However,CBTC,PIS and IMS system are deployed and managed independently in current urban rail transit systems.Investing and constructing communication infrastructures repeatedly not only waste substantial resources but also bring many difficulties in maintaining all these infrastructures.In order to ensure the safety of urban rail transit operation,integrating all these communication systems into an integrated train ground communication system is quite desirable for urban rail transit systems.Long Term Evolution(LTE)is the suitable in an integrated train ground communication system,but the railway line equipment have to be completely transformed,which will lead to greater transformation cost.Besides,each wireless business cannot be effective isolated through the use of LTE.It is difficult to guarantee the business Quality of Service(QoS)requirements.Therefore,in this paper,network virtualization technology is applied to the integrated train ground communication system.Each business can be effective isolated under the premise of without changing the existing railway line communication equipment,guaranteeing their QoS requirements.The paper's main research contents are as follows:(1)We design a network virtualization based integrated train ground communication system for urban rail transit systems.The designed system accomplishes a network carrying a variety of business requirements,which not only reduce construction and operational costs but also improve the spectrum utilization rate.And the designed system can support a variety of wireless access technologies such as WLAN and LTE.(2)In order to satisfy the Quality of Service(QoS)requirements of designed integrated train-ground communication system of each business based on the wireless network virtualization technology,this paper proposes a virtual resource allocation algorithm based on load balancing,fairness and QoS guarantee.At the same time,we define a QoS satisfaction Level(QoSL)from another aspect to reflect the user's satisfaction,which is able to convert the QoS requirements of different users into different rate requirements.The final optimization goal is fairness driven optimization function balancing the load of each cell and ensuring the entire network QoS requirements of different users.(3)In addition,with the further development of distributed convex optimization,we develop an effective method of distributed wireless virtual resource allocation scheme based on Alternating Direction Method of Multipliers(ADMM).Simulation results show that the designed integrated train ground communication system quality of service(QoS)can be improved effectively with the proposed approach.