| 摘要 |
Time Advance (TA) values are used to compensate for the time of flight propagation delay in the uplink from a user equipment (UE) to a node (eg. e-NodeB or repeater). The TA will be valid for a limited time due to movement of the UE. This validity period is monitored using a Timing Alignment Timer (TAT) which determines when the TA needs to be updated/refreshed. In situations where the UE 16 communicates with multiple nodes 10,12 each air link will have its own propagation delay and TA. Movement of the UE may be such that it travels tangentially to one node 12 but radially to another 10. Hence the rate of change of the two TAs will be different and separate TATs will be required, however if the motion is such that the changes to the TA are correlated a single TAT would suffice. The invention monitors changes in the TA values to check for correlations, and rationalises the number of TATs where correlation is found. |
