This section is only applicable to the lab application.
IMS is the 3GPP voice over IP solution which is being deployed in the LTE networks as the voice solution. When a UE is camped on the LTE network, it would need to fallback to the legacy 2G/3G networks when coverage or capacity dictates. SRVCC provides the solution for the UE to transfer the voice call from IMS/IP to standard CS domain. As defined in 3GPP TS 23.216 V8.8.0 "SRVCC (Single Radio Voice Call Continuity) refers to the voice call continuity between IMS over PS access and CS access for calls that are anchored in IMS when the UE is capable of transmitting/receiving on only one of those access networks at a given time."
With the support of the Keysight PXT (E6621A) as the LTE BSE emulator, the test set can be used to test the UE SRVCC implementation.
Operating Mode
is
Active Cell
. The setting will be ignored in other operating modes.The following table shows the result of attempting to perform SRVCC Handover in each of the possible UE states.
State | Inbound SRVCC Handover Setup |
---|---|
Idle | OK |
Attached | OK |
PDP Active | OK |
Transferring | Error |
Connected | Error |
Connected/Attached | Error |
Connected/Suspended | Error |
Connected/PDP Active | Error |
Connected/Transferring | Error |
Handover | Error |
Manual Operation: You can access the following menu from the
CALL SETUP
hardkey, go to the right side
Handover Parameters (
F11
)
, then navigate to the
SRVCC Handover 2 of 2
(
F8
).
EPS Bearer ID
Specifies the EPS Bearer ID which carries the IMS voice traffic on LTE.
GPIB Command: CALL:HANDoff:SRVCc:EBID
Setup Inbound
This action creates the resources waiting on the inbound UE to move the test set to a Handover state. The resources are described in the inbound transparent hex string, which can be retrieved via CALL:HANDoff:SRVCc:INBound:HOCommand? .
GPIB Command: CALL:HANDoff:SRVCc:INBound[:IMMediate]
Abort Inbound
When the test set is in the Handover state, this action removes the dedicated resources created by Setup Inbound and clears the inbound transparent hex string.
GPIB Command: CALL:HANDoff:SRVCc:INBound:ABORt
The general network procedure for SRVCC from E-UTRAN to GERAN is as follows:
The UE sends measurement reports to E-UTRAN.
The E-UTRAN (based on measurement reports or some triggers) decides to initiate an SRVCC handover to GERAN and sends the Handover Required message to the MME.
The MME triggers the SRVCC procedure for the voice bearer towards MSC Server.
The MSC Server initiates the Session Transfer procedure to IMS and coordinates it with the CS handover procedure to the GERAN. And standard IMS Service Continuity procedures are applied for execution of the Session Transfer.
The MSC Server sends PS-CS handover response to MME, including CS handover command information for the UE to access the GERAN.
The MME sends a Handover Command message to the E-UTRAN, which includes the information about the voice bearer.
This message is encapsulated within a Mobility From E-UTRA Command and sent to the UE.
The UE tunes to GERAN and resumes its voice call.
The figure below shows a typical Physical connection for SRVCC Test.
For detailed guidance on how to use the E6621A PXT, please refer to the E6621A user's guide at
http://cp.literature.keysight.com/litweb/pdf/E6621-90002.pdf
Note that there are two LAN Ports on the rear panel of the test set (See Rear Panel Connectors ). For E-UTRAN /GERAN interworking, LAN 2 PORT is required to exchange signaling message or packet data. LAN 1 PORT is optional, but it is still useful for other LAN operations such as protocol logging, firmware downloads or screen captures.
Before the test, you need to make the following operations:
The following steps are required to configure the test set:
Call Status
should switch to
Handover
At this point, the scenario file can be used for the SRVCC test. Phase 1 is only required to create the mobility message, which is only subject to the change of the 8960 configuration.
Using the scenario file created in Phase 1.
Call Status
should switch to
Handover
Control 1 of 2
,
LAN IP Address 2(Data+)
setting is at the bottom of
Instrument Setup
(F1) menu.
Ext EPC IP Addr
must not be identical to the
LAN IP Address
setting. When the connection is successfully set up,
Ext EPC IP Addr
can not be changed.