Issue Description
The private eLTE network operator planned to use the MNC value of (02) in their eLTE network.This MNC has been used by the current LTE operator.By normal practice, we should use different MNC value for 2 different network.
Network Entry Process
When external user accesses the core network (eSCN230) of the private network, the network side rejects the request because no subscription data is available. The cause=8 indicates that the user is an unauthorized user. After receiving the reject message, the terminal does not attempt to initiate a registration again. Therefore, the terminal remains in the network disconnection state unless the terminal is restarted or the network is manually re-accessed.
After a UE is rejected, it triggers different actions based on the rejection cause value on the core network.
If the function is not enabled, the CN sends the default cause value #8 (EPS services and non-EPS services not allowed) to reject undefined subscribers. This cause value causes the UE to stop searching for other available networks. If this parameter is set to ON (On), the CN sends a #15 (No suitable cells in tracking area) message containing the cause value "#15 (No suitable cells in tracking area)." This cause value indicates that the UE continues to search for other available EPS networks.
Solution
There are 2 solutions to prevent the impact of the private network core network on the public network terminal:
1) Change the PLMN or frequency band. It means that we need to use different MNC value for 2 operators (PLMN consist of MCC and MNC)
2) If this switch is turned ON, attach reject cause values can be mapped to #15 (No suitable cells in tracking area). eSCN230: SET EMMPROCTRL:
PROT=ATTACH, ATTACHUNKUSR=CAUSE_15
**If the rejection cause value is #15 (No suitable cells in tracking area), the UE sets the current cell as a forbidden TA and selects another TA to access the network.
Suggestion
It is advisable to always use different MNC value for 2 different network
