Study of Error Sources in Mobile Network Time Synchronization

Abstract

Mobile networks rely on the availability of accurate synchronization to maintain proper operations and service Quality. TDD-based technologies require high level of frequency stability and accuracy in the air interface while FDD technologies and some advance feature, in LTE and LTE-A, require further phase and time synchronization to function properly.

Network synchronization in mobile networks is generally responsible for the distribution of timing references in the RAN via the transport network. While legacy TDM-based backhauls are capable of delivering frequency synchronization, phase and time synchronization require the use of packet-based timing protocols to propagate time information. The performance of packet-based protocols is, however, highly dependent on the performance of the underlying packet network. Network impairments, such as packet delay variations, generally have a significant impact on the performance of packet-based methods. Considering the high level of accuracy required in phase and time synchronization in mobile networks, it is essential that the potential sources of error need to be identified and appropriate mitigation mechanisms be considered in the design and implementation of the timing functionalities. As such, this thesis focuses on investigating the potential sources of error in distributing time information across packet-based backhaul networks so that the clock recovery algorithms will be designed with the proper detection and compensation mechanisms needed to meet the stringent requirements for phase and time synchronization.