With the development of 3G and LTE mobile communication systems, the mobile networks have entered the era of broadband. And the requirement for high-precision time/phase synchronization becomes more and more important. In systems of CDMA2000, TD-SCDMA, TD-LTE, LTE-A, it needs to synchronize precisely between each base station, otherwise it will cause severe interference problem in transmit and receive ends. To synchronize, the traditional solution is to configure GPS/BDS synchronous module in each base station.
However, it brings a lot of problems, such as high cost of GPS/BDS module, difficult maintenance, limited indoor deployment, high fault rate, and security risks as well. When the satellite system is not available, a large number of base stations will not be able to use. Another solution is to build up time synchronization network with timing information provided by transmission network according to synchronous protocols. China Mobile adopts the ground transmission of PTP signal over PTN network, provides time synchronization for LTE base station, establishes PTP network in more than 300 cities, and provides time precision of ±1.5μs for TD-SCDMA and TD-LTE. By the end of June 2016, PTP functions are supported by 670 time servers, 1.5 million PTN nodes, 44,000 OTN nodes, 1.3 million TD-LTE base stations and 560,000 TD-SCDMA base stations. Our instrument provides solution for time and clock synchronization performance testing of LTE base station equipment.
Fig 1 Time/Frequency Measurement on LTE Devices
Fig 2 Time/Frequency Measurement on Present LTE