In order to use the
eDRX feature, the UE requests the eDRX parameters during ATTACH and TAU
procedures. Based on the configuration, the MME may accept or reject the UE’s
request to enable the eDRX feature. If the MME accepts the eDRX request,
different values of the eDRX parameters are provided based on operator
policies, apart from the parameters requested by the UE.
The operator can configure the eDRX parameters Paging Time Window (PTW) and eDRX cycle length duration in the Call Control Profile Configuration mode. The UE requested values of PTW and eDRX cycle is received in the Attach or TAU request. The H-SFN start time and H-SFN reference time for leap second adjustment can also be configured. MME calculates the paging occasion for the UE using the values of H-SFN start time, H-SFN reference time, PTW, and eDRX cycle length. The UE is paged only at the paging occasion until the PTW expires. The MME rejects all other paging requirements which occur in between the paging occasion.
The downlink buffer duration in DDN ACK can be configured when the MME cannot page the UE. This is an optional configuration. For Downlink Data Notifications (DDN), if the UE is not in a paging occasion, the MME does not page the UE. The MME sends a Downlink Data Notification Reject message to the S-GW along with the DL buffering duration and DL suggested packet count IEs as per the operator configuration. The packet count in DDN ACK can be configured to configure the packet count value. The MME starts a timer to page at the next paging occasion. If downlink buffer duration is not configured, the MME rejects the DDN without these IEs. If the packet count value is not configured locally, the subscription provided value is used. The subscription value can be "0" in which case the packet count IE will not be sent for that subscriber even if it is configured locally.
If the UE is not in
a paging occasion, the MME rejects the paging request for dedicated bearer
creation request and sends bearer reject to the S-GW with the cause "UE is
temporarily not reachable due to power saving". The MME starts a timer to page
at the next paging occasion. If the UE is not in a paging occasion during
MME-initiated detach where the MME needs to page the UE to send a detach
request, the MME does not page the UE and performs an implicit detach.
The following new flags are introduced as part of this feature. These flags are supported in GTPCv2 Indication IE:
Pending Network Initiated PDN Connection Signaling Indication (PNSI): The source MME supports sending of PNSI flag in GTPCv2 Indication IE of Context response.
UE Available for Signaling Indication (UASI): The MME supports sending of the UASI flag in GTPCv2 Indication IE of Create Session Request and Modify Bearer Request to indicate to the P-GW that the UE is available for end-to-end signaling.
Delay Tolerant Connection Indication (DTCI): The MME supports receiving the DTCI flag in Create Session Response from the S-GW. The MME supports receiving of the DTCI flag in Context Response and Forward Relocation Request from peer MME or S4-SGSN.
The MME rejects
CBR/UBR when PPF is False. The cause "UE is temporarily not reachable due to
power saving" is sent in the response by the MME if the corresponding PDN was
marked "Delay tolerant" by P-GW.