节选自36.300 ca0 10.1.5
The random access procedure is performed for the following events related to the PCell:
- Initial access from RRC_IDLE;
只有竞争
- RRC Connection Re-establishment procedure;
只有竞争
RLC重传->达到最大次数:RLC Reset->达到最大次数->RRC重建
- Handover;
优先非竞争
- DL data arrival during RRC_CONNECTED requiring random access procedure:
优先非竞争
E.g. when UL synchronisation status is “non-synchronised”. - UL data arrival during RRC_CONNECTED requiring random access procedure:
只有竞争
E.g. when UL synchronisation status is “non-synchronised” or there are no PUCCH resources for SR available. - For positioning purpose during RRC_CONNECTED requiring random access procedure;
只有非竞争
E.g. when timing advance is needed for UE positioning.