Impacts of GPS Loss of Synchronization on TD-SCDMA Network Performance
Hui Fen Dong · ZTE communications · 2010
There often occurs Global Positioning System (GPS) loss of synchronization in Time Division Synchronous Code Division Multiple Access (TD-SCDMA) system because GPS signals may be disturbed by other system signals and sheltered from some buildings.Long-time loss of synchronization will lead to time deviation between NodeBs.When this time deviation is big enough,neighboring cell searching of mobile phones and intercell handover may fail and Downlink Pilot Time Slot (DwPTS) interfere with Uplink Pilot Time Slot (UpPTS),which will make network quality bad with handover failure,call dropping and low call succeeding ratio.In such a case,user experience will be badly affected.With our tests and analysis,we find that the TD-SCDMA network quality has obvious decrease when the GPS loss of synchronization goes over 4 chips,that the mobile phone fails to search a neighboring cell when the loss of synchronization goes over 10 chips,and that there is little UpPTS interference in the first-circle and second-circle neighboring cells when the loss of synchronization goes below 16 chips.The study results show that the allowable GPS loss of synchronization should be below 4 chips in TD-SCDMA system.