Research And Application Of The Monitoring Systems And Improvement Of The VoIP Performance Based On WiMAX

The development of Mobile communication technology provides solid technical support for the construction and perfection of railway communication technology improvement and railway control system, but also makes the high quality communication service applications in railway become possible. VoIP technology being applied to the wireless network of WiMAX achieves the wireless train dispatching system, will greatly improve the efficiency of railway communication, but for railway communication network security and reliability have higher requirements, which requires to measure the performance of VoIP based on WiMAX network, and improve the quality of VoIP services.Based on the project "Application and research of railway mobile communication based on WiMAX", aiming at measuring the traffic of wireless train dispatching system, this paper designed and implemented the performance monitoring system of VoIP, which is completed in Windows with WinPcap development kit, real-time measuring and displaying the performance parameters of the network.This paper discusses the overall architecture of the performance monitoring system of VoIP and the design and implementation of each module. Specifically, the system is divided into eight modules, WiMAX network access monitoring module, server connectivity test module, network packet captures module, network delay monitoring module, real-time statistics of the VoIP traffic and displaying module, SIP signaling response delay test module, logging module and the information of VoIP application process monitoring module. It provides reference data to improve the voice quality of service and network performance of multi-service coexistence under the overall network of WiMAX, to ensure that railway communications is safe and efficient in WiMAX wireless network.Refer to the data provided by the performance monitoring system of VoIP, this paper discusses the encodeing method period controlling algorithm and the sending method period controlling algorithm to ensure the intergrity, low delay and stability of the voice packet on the sender, to improve the quality of the voice.Along with the increase of the number of VoIP system users, it has to increase the number of servers to meet the system requirements. Based on SIP signaling transmission process in a multi-server environment, by using the theory of queuing theory, we put forward a SIP server deployment model based on M/D/1queue theory, used to guide the deployment of the server of the wireless train dispatching system, to improve the scalability of the system, and meet the performance requirements.The performance monitoring system of VoIP which was completed in this paper was tested, the delay and jitter control algorithm on the sender and the deployment model based on M/D/1queue theory are simulated. And the results show that the performance monitoring system of VoIP basically achieved the function of monitoring the performance of the network and could provide effective reference data for the optimization of the VoIP system. The delay and jitter control algorithm on the sender can ensure the quality of the voice on the sender effectively. And the deployment model based on the M/D/1can provide stable and fast VoIP service under the condition of multiple servers. Finally, we gave a summary of this thesis, and proposed further research that it is necessary to do.