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
edrx CLI
command in the Call Control Profile Configuration mode is used to configure the
eDRX parameters Paging Time Window (PTW) and eDRX cycle length duration. The
operator can either configure the option to accept the UE requested values or
configure the values using this command. If the
edrx command
is enabled, the MME supports eDRX feature for the UE. The UE requested values
of PTW and eDRX cycle is received in the Attach or TAU request. The
edrx command
in the MME Service Configuration mode is used to configure the H-SFN start
time. The H-SFN start time is the UTC Time at which H-SFN=0 starts. MME
calculates the paging occasion for the UE using the values of H-SFN start 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
edrx command
in the Call Control Profile Configuration mode is also used to configure the
downlink buffer duration in DDN ACK when the MME cannot page the UE. This is an
optional configuration, The
dl-buf-duration keyword added as part of the
edrx CLI command 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.
An optional keyword
packet-count is provided to configure the packet count value. The MME
starts a timer to page at the next paging occasion. If the optional keyword
dl-buf-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 for the
packet_count_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.
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