In order to avoid the Signaling Storm resulted from Smartphone Apps Heartbeats (e.g., Facebook and WhatsApp notifications)-which cause huge CPU load- two scenarios are introduced:
1-Enhanced Fast Dormancy (EFD) feature is used with Smartphones when the session ends, instead of normal release it send a SCRI (Signaling Connection Release Indicator) message with contents “UE Requested PS Data session end”. In this case the network instead of moving to idle mood state it directly sends the UE to the PCH if the EFD is enabled.
2-For non-EFD UEs processing bad effect services, heartbeats bad effect was making repetitive RRC/RAB request and release cycles which resulted in massive signaling storm an CPU load , the D2P (CELL_DCH to CELL_PCH) state transition can be performed.
Previously when a mobile was not supporting Fast Dormancy feature, operators made a workaround by using IMEI of this mobile to not to release RRC assigned for it if the mobile sent release request as it may be fake and the mobile may need access again. So, RNC transfers the mobile to PCH instead of releasing RRC.