A Hyper-SFN (H-SFN) frame structure is defined for regular idle mode DRX. Each H-SFN value corresponds to a legacy SFN cycle comprised of 1024 radio frames (10.24 seconds). The eDRX consists of values that are a power of 2, ranging from 5.12 seconds (that is, 5.12, 10.24, 20.48 seconds and so on) up to a maximum of 2621.44 seconds (43.69 minutes). When EDRX is enabled for a UE, the UE is reachable for paging in specific Paging Hyperframes (PH), which is a specific set of H-SFN values. The PH computation is a formula that is function of the EDRX cycle, and a UE specific identifier. This value can be computed at all UEs and MMEs without need for signalling. The MME includes the extended idle mode DRX cycle length in paging message to assist the eNodeB in paging the UE.

The MME also assigns a Paging Time Window length, and provides this value to the UE during attach/TAU procedures together with the extended idle mode DRX cycle length. The UE first paging occasion is within the Paging Hyperframe. The UE is assumed reachable for paging for an additional Paging Time Window

length after first paging occasion. After the Paging Time Window length, the MME considers the UE unreachable for paging until the next Paging Hyperfame.

In order for the UE to be paged at roughly similar time, the H-SFN of all eNodeBs and MMEs should be loosely synchronized.

Each eNodeB and MME synchronizes internally the H-SFN counter so that the start of H-SFN=0 coincides with a preconfigured time. It is assumed that eNodeBs and MMEs are able to use the same H-SFN value with accuracy in the order of legacy DRX cycle lengths (For example, 1 to 2 seconds). There is no need for synchronization at SFN level.

There is no signaling between network nodes required to achieve this level of loose H-SFN synchronization.

When the MME receives trigger for paging and the UE is reachable for paging, the MME sends the paging request. If the UE is not reachable for paging, then the MME pages the UE just before the next paging occasion.

The MME determines the Paging Time Window length based on paging retransmission strategy, and uses it to execute the retransmission scheme.

The following CLI configuration enables the eDRX feature on the MME.

The below configuration is available under the Call Control Profile Configuration mode.

configure
   call-control-profile profile_name
         edrx { ue-requested | ptw ptw_value edrx-cycle cycle_length_value [ dl-buf-duration [ packet-count packet_count_value 
] ] }
         remove edrx
         end

Notes:

• remove: disables the eDRX configuration on the MME.

• edrx : configures Extended Discontinuous Reception parameters.

• ue-requested : specifies the accepted UE requested values of the eDRX cycle length .

• ptw : specifies the Paging Time Window (PTW) value received from the UE in the Attach Request/TAU Request message. The PTW value is an integer ranging from 0 to 20 seconds.

• edrx-cycle : specifies the accepted UE requested values of the Paging Time Window and the eDRX Cycle Length.

• dl-buf-duration: sends Downlink Buffer Duration data in the DDN ACK message when MME is unable to page the UE.

• packet-count : send DL Buffering Suggested Packet Count data in DDN ACK when MME is unable to page the UE.

• MME sends Downlink Buffer Duration IE in Downlink Data Notification Acknowledgment message to the gateway when MME is unable to page the UE.

• MME sends Downlink Buffering Suggested Packet Count value to gateway in Downlink Data Notification Acknowledgment message when MME is unable to page UE. the packet count is an integer that ranges from 0 to 65535.

Verifying eDRX on the MME

The below given command displays the following new fields that are added to support the eDRX feature:

show call-control-profile full name cp_name

Extended DRX:
    Paging Time Window                                      : 10 Seconds
    eDRX Cycle Length                                       : 512 Seconds
    Downlink Buffer Duration in DDN Ack                     : Enabled
    DL Buffering Suggested Packet count in DDN Ack          : 10

The following CLI allows to configure the Hyper SFN Synchronization start time.

configure
   context context_name
      mme-service service_name
         edrx hsfn-start UTC_Time
         no edrx hsfn-start
         end

Notes:

• The no option disables the H-SFN synchronization time configuration.

• The edrx command specifies the Extended Discontinuous Reception H-SFN start time.

• The hsfn-start keyword specifies the UTC Time at which H-SFN=0 starts. The time should be entered in the UTC Time format as follows: YYYY:MM:DD:hh:mm:ss. For example: 2016:03:01:12:34:56.

Verifying H-SFN Synchronization

The below given command displays the following new fields that are added to verify H-SFN Synchronization:

show mme-service full <service-name>

Extended DRX:
      H-SFN Start: 2016:03:01:12:34:56