Research On Resource Allocation Of Urban Rail Transit Communication Based On LTE-U

The capacity of various services carried by urban rail transit is gradually expanding,and LTE-U(LTE in Unlicensed)technology is applied in this field.At the same time,licensed spectrum resources use train-to-train communication technology,which can increase bandwidth resources and improve system communication efficiency.However,the wireless local area network system on unlicensed spectrum resources can seriously affect the quality of urban rail communication,and there is a problem of link multiplexing interference in train control systems based on train-to-train communication technology on licensed spectrum.Wireless resource allocation,as an effective means to solve interference between communication systems,can maximize the utilization of spectrum resources and prevent congestion in business data transmission.The complex and ever-changing wireless communication environment of urban rail transit requires high effectiveness and reliability of resource allocation strategies.Therefore,designing a reasonable dynamic resource allocation strategy based on the quality of the wireless communication environment is of great practical significance for the application of LTE-U technology in the field of urban rail transit.In this thesis,the urban rail transit LTE-U communication system is taken as the research object,based on the current research at home and abroad,with the goal of optimizing communication system performance.Wireless resource allocation on unlicensed and licensed spectrum is thoroughly investigated.The main content of the thesis is as follows:Firstly,the technical background and system architecture of the LTE-U system are discussed,and the channel characteristics of the urban rail transit wireless communication system are analyzed.Research on the coexistence scenarios of urban rail communication systems in the unlicensed spectrum and the quality of service(Qo S)requirements of communication services.At the same time,design the CBTC system architecture and communication establishment process based on T2T(Train-to-Train)communication in the licensed spectrum.Secondly,the direct deployment of the LTE system in the unlicensed spectrum will cause interference with the WLAN system,so the ABS(Almost-Blank Subframes)wireless frame structure is adopted,and a dynamic resource allocation strategy based on heuristic function and qualification trace improvement HQL(λ)is designed.The queuing theory is used to model the delay performance of the unlicensed spectrum,and the communication system performance evaluation index of the data packet transmission delay and transmission rate is combined,and quantify the system satisfaction function to ensure the overall performance of the heterogeneous network in the unlicensed spectrum.From the perspective of dynamically adjusting the ratio of blank subframes,combined with the quality of the wireless communication environment,the optimal subframe ratio of ABS is obtained through calculation of the resource allocation algorithm model.The effectiveness of the resource allocation model is verified through the MATLAB simulation platform to ensure the coexistence of heterogeneous network systems on unlicensed frequency bands.Finally,the joint resource allocation and power control strategy is used to solve the problem of co-channel multiplexing interference between the T2 T communication link and the T2G(Train-to-Ground)communication uplink in the licensed spectrum.The resource allocation model based on the graph coloring algorithm calculates the channel capacity of all links of the same channel according to the interference generated between the links.At the same time,considering that the transmission power of the train will also affect the channel capacity of the system,combined with the signal-to-interference noise ratio(SINR)received by the train,the closed-loop power control strategy is used to dynamically adjust the transmission power of the train to maximize the channel capacity of the system,the optimal coloring scheme for all links is calculated.Through the MATLAB simulation verification,it can be seen that the algorithm can realize the many-to-many matching of the T2 T communication link and the T2 G communication uplink,and improve the system channel capacity and spectrum utilization.