Seem also like detect UE excess cell radius or not, it is same like use preamble ID to identify. Like below case
Optimization of Non-Contention-based Random Access Beyond Cell Radius
This function can optimize the procedure of non-contention-based random access initiated by a UE beyond the cell radius to ensure the successful access.
The optimized procedure is as follows:
An eNodeB receives a dedicated preamble that is a retransmission preamble, and both of the following conditions are met:
- The eNodeB detects that the index of the preamble is N but not N+1.
- The eNodeB allocates preamble N+1 to a UE but not preamble N.
Then the eNodeB delivers the RAR message that carries the preamble index of N+1 to the UE.
Detection of non-contention-based random access beyond cell radius is controlled by the NonContRaOptSwitch option under the CellAlgoSwitch.RachAlgoSwitch parameter.
This function is recommended during off-peak hours when the non-contention-based random access success rate in a cell is lower than expected. This function takes effect only when all of the following conditions are met:
- The cell is a normal low-speed cell.
- The distance between the UE and the eNodeB is greater than the cell radius and is less than twice the cell radius.
- The distance between the UE and the eNodeB is less than or equal to 100 km.
The distance between the UE and the eNodeB is greater than the cell radius and less than twice the cell radius. The eNodeB parse the preamble ID as a value less than 1 compare Assign preamble ID . If the following conditions are met, the eNodeB considers that the preamble ID of a non-contention UE exceeds the radius and sends an RAR message to the UE based on the normal procedure.
For example: at point 0,UE received dedicated preamble ID 63 which assigned by eNodeB, but at point 1 eNodeB calculate the preamble is 62 as it is based on UE access distance which is exceed cell radius. Preamble ID 62≠63，normally eNodeB will reject UE access，but after we enable NonContRaOptSwitch, eNodeB will consider it is ok as 62 is near 63 and eNodeB will send RAR with preamble ID 63 to UE at point 2，then UE access successful.