Section: A.13 Monitoring of Mobility Robustness Optimization (MRO)
Content: The following measurement is defined specifically to monitor the performance of handover optimisation: - Number of handover failures for MRO. The measurement examines “handover related events” in which the serving cell of a RRC connected UE is changed. Handover related events are either normal successful handovers, or they are failures. Different failure modes are possible and the measurement provides counts for the occurrences of the failure modes related with MRO, “too early”, “too late” and “to wrong cell”. The detailed definitions of these modes are captured in [12]. The counters provide visibility of the mix of failure problems that the handover optimistion function is tackling. In “handover to wrong cell” case, an RLF occurs shortly after a successful handover from a source cell (cell A in Figure A.13-1) to a target cell (cell B in Figure A.13-1) or a HOF occurs during the handover procedure; the UE attempts to re-establish the radio link connection in a cell (Cell C in Figure A.13-1) other than the source cell and the target cell. (See 36.300 [12]). Figure A.13-1 Handover to wrong cell case For the “handover to wrong cell” case (ABC) above-mentioned, the handover parameters on Neighbour Relation AB, Neighbour Relation AC or both may be problematic and need to be corrected. So the performance measurements for both Neighbour Relation AB and Neighbour Relation AC are needed for problem detection. In addition to event-based (i.e. reactive) optimization of handover performance, a pro-active optimization is possible by monitoring the dynamics of handover triggering from UE measurement reports.