Research And Implementation Of Highly Stable Master Clock In 5G System

In order to achieve higher spectral efficiency,full development and utilization of spatial dimension is 5G system's inevitable choice.Large-scale antenna and digital beamforming(DBF)as this key 5G technology require the antenna to receive and transmit signals with accurate time synchronization.According to the overall program of the 863 major special issue"SS2014AA012104 5G key technology research and development of large-scale collaborative wireless transmission" developed by research projects' group,the synchronization accuracy between RRU antennas is required to reach the nanosecond level.Thus,one high-precision time reference system is needed.Firstly,the thesis describes the concept of GPS system and characteristics of GPS second pulse.It introduces the basic principles of clock synchronization protocol.Then,IEEE1588V2 protocol in clock synchronization protocol is discussed in detail.Also,this thesis introduced the synchronization mechanism,clock attribute,PTP state machine,message format and so on about IEEE1588 protocol.Secondly,this thesis implements the hardware and software of the highly stable master clock system with a precision of nansecond.The hardware design includes micro-processor,DDS module,PHY chip and so on.The software design finishes GPS clock taming software module and adapts to transplante IEEE 1588 protocol engine state machine module,lwip light protocol stack module autonomously.Finally,this thesis performs some tests about this highly stable master clock system when it is applied to 5G high precision time reference system.The test results show:the hourly root mean square error of the GPS clock tame is less than 5ns.And the root mean square error between master clock and slave clock from 1PPS tracking is less than 2 ns.Thus,the thesis meets 5G system's requirements of high precision time reference.