How to inform a new TAI list to UE

The easiest way to include a new TAI list to UE is GUTI REALLOCATION COMMAND.

This Message includes a TAI list IE which is optional.
This message is sent by the network to the UE to reallocate a GUTI and optionally to provide a new TAI list.

GUTI Reallocation Command is a EMM common procedure.
Which needs a existing  NAS signalling connection to happen (Another mobility management procedure).

Access Class

It is not intended that access control be used under normal operating conditions.
The use of this facility allows the network operator to prevent overload of the access channel under critical conditions.

Under certain circumstances, it will be desirable to prevent UE users from making access attempts (including emergency call attempts) or responding to pages in specified areas of a PLMN. Such situations may arise during states of emergency, or where 1 of 2 or more co-located PLMNs has failed.

All UE's are member of one out of 10 access class - given randomly (0 to 9).
The population number is stored in the SIM/USIM.In addition, mobiles may be members of one or more out of 5 special categories (Access Classes 11 to 15), also held in the SIM/USIM.
These are allocated to specific high priority users as follows. (The enumeration is not meant as a priority sequence):

Class 15 - PLMN Staff;
-"- 14 - Emergency Services;
-"- 13 - Public Utilities (e.g. water/gas suppliers);
-"- 12 - Security Services;
-"- 11 - For PLMN Use.


EF_ACC 6F78 is the location in sim card for access class.
This is 2 byte.

Example:
Bellow specified  entry tells that sim card has only 15 as a Access Class (Which is wrong)
EF_ACC (6F78) to 0x80 (Byte 1), 0x00 (Byte 2) - only class 15 bit is set

Bellow specified  entry tells that sim card has 15 and 0 as  Access Class (Which is correct)
EF_ACC (6F78) to 0x80 (Byte 1), 0x01 (Byte 2) - class 15 and class 0 bit is set

link: http://www.qtc.jp/3GPP/Specs/22011-940.pdf

X2AP procedures

The X2 interface X2AP procedures are divided into two modules as follows:

1. X2AP Basic Mobility Procedures; 
2. X2AP Global Procedures; 

The X2AP Basic Mobility Procedures module contains procedures used to handle the UE mobility within E-UTRAN.

The Global Procedures module contains procedures that are not related to a specific UE. The procedures in this module are in contrast to the above module involving two peer eNBs. 

PTI Procedure Transaction Identity

Procedure Transaction Identity: An identity which is dynamically allocated by the UE for the UE requested ESM procedures. The procedure transaction identity is released when the procedure is completed.

The EPS bearer identity and the procedure transaction identity are only used in messages with protocol discriminator EPS session management.

The PTI is been used to identify the transaction particular transaction.

2018 Mar 19  20:54:15.081  [97]  0xB0E3  LTE NAS ESM Plain OTA Outgoing Message  --  PDN connectivity request Msg

trans_id = 4 (0x4)
2018 Mar 19  20:54:15.168  [74]  0xB0E2  LTE NAS ESM Plain OTA Incoming Message  --  Activate default EPS bearer context request Msg
trans_id = 4 (0x4)
2018 Mar 19  20:54:15.170  [D9]  0xB0E3  LTE NAS ESM Plain OTA Outgoing Message  --  Activate default EPS bearer context accept Msg
trans_id = 0 (0x0)
This follows the figure 6.3.2.3
By sending trans_id as 0 the procedure will be ended.

LTE PDN CONNECTIVITY REQUEST message content

Request Type (9.9.4.14)
Based on 10.5.6.17 Request type of 24.008
The purpose of the Request type information element is to indicate whether the MS requests to establish a new
connectivity to a PDN or keep the connection(s) to which it has connected via non-3GPP access.
The Request type information element is also used to indicate that the MS is requesting connectivity to a PDN that
provides emergency bearer services.

Request Type Can be Initial , Handover or Emergency.
Handover will be set as request type when the PDN established over Wi-Fi needs to be continued over LTE.

Device Properties (9.9.2.0A)
Based on 10.5.7.8 in 3GPP TS 24.008
The purpose of the Device properties information element is to indicate if the MS is configured for NAS signalling low
priority. The network uses the Device properties information element for core-network congestion handling and for
charging purposes.

IMS voice call concurrency handling scenarios

SIM1 status	SIM2 event	SIM2 action
Active call on Wi-Fi (VoWiFi)	Receives IMS call (SIP INVITE) over Wi-Fi	Rejects call with 486 – Busy here
Active call on Wi-Fi (VoWiFi)	Receives IMS call (SIP INVITE) over LTE	Rejects call with 486 – Busy here
Active call on Wi-Fi (VoWiFi)	Receives SMS/MMS on either SIM1 or SIM2	SMS/MMS is accepted/received on corresponding SUB
Active call on Wi-Fi (VoWiFi)	Receives CSFB call over LTE on either SIM1 or SIM2	Drops CS page/call in LTE
Active call on Wi-Fi (VoWiFi)	Receives CS call on GSM/WCDMA on either SIM1 or SIM2	Drops CS page in GSM/WCDMA
Active call on LTE (VoLTE)	Receives IMS call (SIP INVITE) over Wi-Fi	Rejects call with 486 – Busy here