lte connect procedure contact flow
First, the UE should register with all the network to receive services that need registration. This kind of registration is known as the network attachment. IP connectivity for UE is usually enabled after establishing a default EPS bearer during the network attachment method. Attach process may bring about one or multiple Dedicated Bearer Establishment types of procedures to establish devoted EPS bearer for that UE.
Throughout the LTE Preliminary Attach procedure, the Portable Equipment Personality (MEI) can be obtained from the UE. The MME (Mobility Management Entity) operator may well check the Portable Equipment Id with EIR (Equipment Identity Register).
In running around situations, the MME should pass the ME Personality to the HSS (Home Reader Server), and, if a PGW (PDN (Packet Data Network) Gateway) away from the VPLMN (Visited Community Land Mobile Network) should pass the ME Identity to the PGW.
Below is the LTE Attach Procedure Call Stream, broken down into steps, extracted by 3GPP.
The first step. The UE initiates the attach procedure by sending an add request for the eNodeB.
Step 2. The eNodeB comes the MME from the RRC parameters transporting the old GUMMEI (Globally One of a kind MME Identity) and the indicated Selected Network.
Step 3. If the UE identifies by itself with GUTI (Globally Exclusive Temporary Identity) and the MME has changed seeing that detach, the brand new MME uses the GUTI received from your UE to derive this MME/SGSN addresses, and send an Id Request to the old MME/SGSN to demand the IMSI.
Step four. If the UE is unfamiliar in both old MME/SGSN and fresh MME, the brand new MME transmits an Identification Request to the UE to request the IMSI. The UE responds with Personality Response (IMSI).
Stage 5a. In the event no UE context for the UE exists anywhere in the network, if the Add Request (sent in step 1) was not sincerity protected, or if the check of the ethics failed, then simply authentication and NAS reliability setup to activate honesty protection and NAS ciphering are mandatory.
Stage 5b. The ME Identification shall be recovered from the UE.
Step six. If the UE has set the Ciphered Options Transfer Flag inside the Attach Request message, the Ciphered Options i. e. PCO or APN or perhaps both, shall now be recovered from the UE.
Step 7. If you will discover active bearer contexts in the new MME for this particular UE (i. e. the UE re-attaches to the same MME without having properly unattached before), the new MME deletes these bearer contexts simply by sending Delete Session Request (LBI) emails to the GWs involved.
Step almost eight. If the MME has changed considering that the last remove, or if you have no valid subscription circumstance for the UE in the MME, the MME directs an Update Location Request concept to the HSS.
Step 9. The HSS sends Cancel Site (IMSI, Cancelling Type) to the old MME.
Stage 10. In the event there are effective bearer contexts in the outdated MME/SGSN with this particular UE, the old MME/SGSN deletes these types of bearer situations by mailing Delete Period Request (LBI) messages for the GWs involved.
Stage 11. The HSS acknowledges the Upgrade Location meaning by mailing an Update Area Acknowledgement meaning to the new MME.
Step 12. For an unexpected emergency Attach scenario, the MME applies the parameters via MME Urgent Configuration Data for the emergency bearer establishment performed in this step and virtually any potentially stored IMSI related subscription info are overlooked by the MME.
Step 13. The Serving GW creates a fresh entry in its EPS Bearer table and sends a Create Treatment Request message to the PDN GW indicated by the PDN GW address received in the last step.
Step 18. If active PCC is usually deployed plus the Handover Indication is not really present, the PDN GW performs a great IP-CAN Session Establishment treatment.
Stage 15. The PGW makes a new access in its EPS bearer framework table and generates a Charging Id.
Stage 16. In case the MS Details Change Credit reporting Action (Start) or the CSG Information Credit reporting Action (Start) are received for this bearer context, then the SGW shops this pertaining to the bearer context plus the SGW studies to that PGW whenever a UE’s location and User CSG information alter occurs that meets the PGW ask for.
Stage 17. In the event that an APN Limitation is received, then the MME shall shop this benefit for the Bearer Context and the MME shall take a look received worth with the placed value pertaining to the Maximum APN Restriction to make sure there are not any conflicts among values.
Step 18. The eNodeB sends the RRC Connection Reconfiguration meaning including the EPS Radio Bearer Identity to the UE, and the Attach Acknowledge message will be sent along to the UE.
Step 19. The UE delivers the RRC Connection Reconfiguration Complete meaning to the eNodeB.
Step 20. The eNodeB transmits the Initial Context Response meaning to the new MME.
Step 21. The UE sends an immediate Transfer communication to the eNodeB, which includes the Attach Finish message.
Step twenty-two. The eNodeB forwards the Attach Finish message towards the new MME in an Uplink NAS Transfer message.
Step twenty three. Upon reception of the two, the Initial Framework Response message in step 20 and the Affix Complete meaning in step twenty two, the new MME sends a Modify Bearer Request concept to the Offering GW.
Step 23a. If the Handover Indication is roofed in step twenty-three, the Providing GW delivers a Change Bearer Ask for (Handover Indication) message towards the PDN GW to quick the PDN GW to tunnel bouts from not 3GPP IP access to 3GPP access system and instantly start routing packets towards the Serving GW for the default and any dedicated EPS bearers established.
Step 23b. The PDN GW acknowledges by sending Modify Bearer Response to the Serving GW.
Step 24. The Serving GW acknowledges by sending Upgrade Bearer Response (EPS Bearer Identity) meaning to the fresh MME.
Step 25. After the MME receives Alter Bearer Response (EPS Bearer Identity) meaning, if Ask for Type will not indicate handover and an EPS bearer was established plus the subscription data indicates the user is usually allowed to perform handover to non-3GPP has access to, and if the MME chosen a PDN GW that may be different from the PDN GW identity which has been indicated by HSS inside the PDN registration context, the MME shall send a Notify Ask for including the APN and PDN GW identity to the HSS for freedom with non-3GPP accesses. The message shall include data that identifies the PLMN in which the PDN GW is found.
Stage 26. The HSS shops the APN and PDN GW personality pair and sends a Notify Respond to the MME.
