12 Extended DRX in Idle mode

25.3003GPPGeneral descriptionRelease 17Stage 2TSUniversal Terrestrial Radio Access Network (UTRAN)

The extended DRX (eDRX) feature enables DRX 10,24 seconds up to 2621.44 seconds (~44 minutes) in Idle mode for the PS domain.

The eDRX feature in Idle mode uses the Paging Occasions (PO) as determined by the CN domain specific DRX cycle length coefficient (PS domain) in SIB1 [12] and specified by the Discontinuous Reception for Paging [9]. However the UE is not required to monitor every PO, but only the POs that belong to the Paging Transmission Window (PTW):

Figure 12-1: Extended DRX in Idle mode

The eDRX parameter in Idle mode values, i.e. timer values for T_eDRX and T_PTW are negotiated and configured during ATTACH and RAU procedure ([4] and [5]). Timer T_eDRX is (re-)started when upper layers indicate successful completion of the ATTACH/RAU procedure, including eDRX parameters in Idle mode. When timer T_eDRX expires, the UE wakes-up from sleep, it checks the MIB for any system information changes and it starts monitoring the paging occasions in the PS DRX in Idle mode. When timer T_eDRX expires it is re-started, and timer T_PTW is started. When timer T_PTW expires the UE stops monitoring paging occasions in the PS DRX in Idle mode. The timer T_eDRX and T_PTW do not stop/reset when the UE transitions from Idle to Connected or transitions from Connected to Idle. The timers T_eDRX and T_PTW are stopped, if running, when upper layer indicates that the eDRX parameters in Idle mode are not included in the ATTACH/RAU complete. The timers T_eDRX and T_PTW are reset when upper layer indicates that a new value is configured in ATTACH/RAU complete. The value of T_eDRX is signaled in IE “eDRX value” in ATTACH/RAU [4] for timer T331 in RRC [12]. The value of T_PTW is signaled in IE “Paging Time Window” in ATTACH/RAU [4] for timer T332 in RRC [12].