What is RRC connection EstablishmentCause : emergency, highPriorityAccess, mt-Access, mo-Signalling,mo-Data?

Question

Q-1-I observed a scenario like when initiating MO call ,RRC connection establishment fails(RRC connection reject) due to cell reselection completion prior to receiving RRC connection setup.In this case which will be given a priority ,Cell reselection or Call ?

Q-2: What are other possible RRC connection failure reasons could happen from UE or Network perspective ?

Answer 1

The establishment cause within the RRC Connection Request message is determined by the Non-Access Stratum (NAS) procedure for which the connection is being established (Refer 3GPP TS 24.301). Following is the list -
- Emergency
- High Priority Access
- Mobile Terminating Access
- Mobile Originating Signalling
- Mobile Originating Data

The relation between them and NAS message is following -

Comments

Missed the High Priority Access -

NAS procedures initiated by UEs of access class 12, 13 or 14 in their home country, the RRC establishment cause will be set to "High priority access AC 11 – 15".
For NAS procedures initiated by UE of access class 11 or 15 in their HPLMN or EHPLMN, the RRC establishment cause will be set to "High priority access AC 11 – 15".