LTE: What is Change Notification Procedure ?

Question

I am looking for actual use of this procedure ?

Answer 1

It is one of the core network procedure. This procedure is mainly used to enable location based charging. If you see "Create session response" message. There are some IEs present in Create session response message to enable/disable location reporting. Based on the subscription details at SPR node, PCRF direct to PGW and then PGW sends this information to SGW/MME while handling create session procedure for initial attach procedure/PDN- connectivity.

Here I am assuming MME/S4- SGSN and SGW supports message related to change notifications.
Based on the request, MME sends "Change notification request with new location of an UE to PGW and PGW reply back to MME with "Change notification response". For this new location PGW changes charging rule for an UE.

For more details please check the 29.274 specification.

Answer 2

UEs in RRC_IDLE are only required to receive the paging message at their normal paging occasions – i.e. no additional wake-ups are expected to detect changes of SI. In order to ensure reliability of reception, the change notification paging message is normally repeated a number of times during the BCCH modification period preceding that in which the new system information is first transmitted. Correspondingly, the modification period is expressed as a multiple of the cell-specific default paging cycle.

When an MBMS session is started, E-UTRAN notifies the UEs about an MCCH information change. This change notification is provided a configurable number of times per modification period, by means of a message on the PDCCH using Downlink Control Information (DCI) Format 1C, using a special identifier, the MBMS Radio Network Temporary Identifier (M-RNTI). This message indicates which of the configured MCCHs will change. UEs that are interested in receiving an MBMS session that has not yet started should try receiving the change notification a minimum number of times during the modification period. If the UE knows which MBSFN area(s) will be used to provide the MBMS session(s) it is interested in receiving, it has to meet this requirement only for the corresponding MCCH(s).