WLAN Data Transfer And Time Synchronization Technology Research

As the time synchronization requirements of the WLAN nodes gradually increase and the expansion of the real-time applications, wireless data transmission and time synchronization technology research is becoming more important. However, the current WLAN is often designed to carry the business that its real time capability is not strong, can’t meet the demand of the synchronization precision of the base station. Now WIFI has becoming the main wireless access network and an important complement to 3G networks. As a result, the demand for Clock synchronization also becomes urgent over WIFI networks. Therefore, the realization of WLAN wireless network nodes in a higher precision time synchronization scheme has important practical significance.The research of this paper is based on the WIFI system software development and related technologies such as high precision time synchronization protocol. First, it completes the build structure of the centralized WLAN network. On the other hand, the wireless access controller(AC) monitor the wireless access point(AP) and online state of the terminal equipment, and test the AP and process of the data transmission between terminal nodes. Time synchronization mechanism is introduced, research the design of the time synchronization at the MAC layer, and test delay and jitter occurring in the process of the time synchronization based on the MAC layer. Using IEEE 1588v2 protocol synchronization scheme analysis hardware delay and interrupt handling factor in the process of the data transmission based on WLAN, and research the influence on timestamp measurement such as CPU load and network load, etc. The thesis analysis 802.1as precision time protocol based on the IEEE 1588v2 and simplified version, determining the time synchronization and the mechanism. the simulation result is obtained and compared respectively the offset error and variance. Finally, in the case of hardware to help, it will make PTP standard applied to the timestamp extraction scheme of the physical layer.and gives the design and testing.Test results show that the selected WLAN card pin signal used in synchronous accuracy for the application of microsecond. Its stability is enough, not because of possible jitter is too large to adverse impact on synchronization precision, so the wireless chip pin signal can be as a timestamp information driven signal. In addition, it compared respectively the offset error and variance between IEEE 802.1as and IEEE 1588 adopted two ways. When a timestamp precision is too higher, the effect of the channel competition is more noticeable, IEEE 802.1 as has better performance in this environment. If timestamp accuracy is lower than 310?s, because the main source of the error is that timestamp accuracy is not enough, then the performance of the two ways is approaching slowly.