铁路LTE-R网络MCPTT的应用研究

Application Research on MCPTT in Railway LTE-R Network

因现网调度语音通信系统的局限性,将基于LTE标准的MCPTT(Mission Critical Push to Talk)应用到下一代铁路移动通信系统LTE-R中。对MCPTT的系统架构、个呼、组呼的呼叫业务流程、话权控制流程进行详细描述,分析了固定终端(FAS)呼叫移动终端(UE)的寻呼机制和寻呼延迟,并利用排队模型计算寻呼延迟。最后在实验室中测试MCPTT呼叫建立延迟及成功率。结果表明:随着非连续接收(DRX)周期的增大,寻呼时延增大。样本数为100的条件下, UE发起个呼、组呼呼叫建立延迟平均值约为580 ms,成功率为100%; FAS发起个呼、组呼呼叫建立延迟平均值约为2 500 ms,成功率为100%。经验证,将MCPTT技术应用于铁路LTE-R网络,能够可靠且快速地建立语音通话,并保证用户话权的公平分配,提高铁路运输安全。

Considering the limitation of current railway voice dispatching system,it is beneficial to apply LTE-based MCPTT(Mission Critical Push to Talk)to the next generation railway mobile communication system(LTE-R).This thesis gives a detailed description of the system structure,private call and group call operation processes,and floor control procedure.Besides,it also analyses paging mechanism and paging delay of the fixed terminal(FAS)of call mobile terminal(UE)and uses queuing theory model to calculate paging delay.The test result of MCPTT in laboratory shows:the paging delay increases with the increase of the Discontinuous Reception period.The average establishing time of point-to-point call and group call(from UE)is 580 ms with 100%success rate;the average establishing time of point-to-point call and group call(from FAS)is 2500 ms with 100%success rate.It has been verified that applying the MCPTT technology to railway LTE-R networks can establish voice calls reliably and quickly,ensure fair distribution of user floor and improve railway transportation security.