Competitive access and non-competitive access

 

The random access procedure is saved Med for the following five events:
- Initial access from rrc_idle;
- RRC connection re-establishment procedure;
-Handover;
- DL data arrival during rrc_connected requiring random access procedure;
- E. g. When ul synchronisation status is 'non-synchronised ';
- Ul data arrival during rrc_connected requiring random access procedure;
- E. g. When ul synchronisation status is "non-Synchronised" or there are no pucch resources for Sr
Available.
Furthermore, the random access procedure takes two distinct forms:
- Contention Based (applicable to all five events );
- Non-Contention Based (applicable to only handover and DL data arrival ).

 

There are 5 trigger conditions for random access:
1. rrc_idle initial access
2. Access when the wireless link is disconnected
3. Random Access during switchover
4. When you receive upstream data in the rrc_connected status, you must randomly access the data, for example, "Uplink error"
5. When you receive downstream data in the rrc_connected status, you need to randomly access the data, such as "downloading out"

Competition-based random access is applicable to the above five cases. The first two cases are relatively simple. For the third, fourth, and fifth scenarios, when Random Access is required, the corresponding prach resources are not available, and a competitive access method may also be used.

 

For non-competitive access modes, ENB indicates the preamble sequence used by UE and prach resources. Therefore, in the case of switchover or downlink failure, all downstream data to be sent may use a non-competitive access method.

 

For upstream access that is out of step, the random access process has been canceled after 8.6.0, but resources are released and re-accessed.