User`s guide

Agilent PXT Wireless Communications Test Set
User’s Guide
178
Specifically, to successfully perform a reselection to LTE when the UE is PDP (Packet Data Protocol)
Active on the legacy network, the TrackingAreaUpdateAccept message must have the
EPSBearerContextStatus information element present. This requires the following:
• The EBID matching the active NSAPI (Network Service Access Point Identifier) on
UTRAN/GERAN is marked as “true”.
• The appropriate DRBs (Data Radio Bearers) with matching eps-BearerIdentity are sent in the
rrcConnectionReconfiguration message.
When following the above requirements, the IP address allocated by the EPC when the UE was on
UTRAN/GERAN, will continue to provide IP throughput while on LTE.
Only when performing the TAU procedure will IP connectivity be preserved
during the cell reselection.
Cell Reselections from LTE to UTRAN/GERAN
With a UE camped on LTE, it is possible to reselect to the 8960, acting as a UTRAN or GERAN cell.
For a typical network, the LTE cell will normally broadcast SIB6 UTRAN or
SIB7 GERAN neighbor information. Even though the UE may require this, it is
not essential from an operational perspective.
The PXT (LTE Cell) must be running a scenario file that allocates an EBID which is valid for use on the
legacy cell. (This means values which are within the range 5-15.) Although the IP address configured on
the EPC UI does not have to match that allocated in the scenario file, it can be beneficial to maintain IP
address consistency. This enables the UE to deactivate the PDP context and re-establish another; being
allocated the same IP address. However it is not required.
Other than the EPC connection and any other specific settings for the UE, there is no need to set any
parameters on the 8960.
Only when performing the RAU (Routing Area Update) procedure will IP
connectivity be preserved during the cell reselection.
When performing cell reselections to UTRAN only one context is preserved.
This restriction does not apply for reselections to GERAN.
Performing PS (Packet Switched) Handovers
PS Handovers from UTRAN/GERAN to LTE
PS Handovers require the target cell to setup dedicated resources for an incoming UE. The source cell
queries the target cell for the resource configuration, and then communicates this information to the UE to
enable it to access the target cell. This technique bypasses the RRC connection setup procedure and
subsequently minimizes the data flow interruptions.
The LTE scenario must contain the RrcConnectionReconfiguration message describing the waiting
resources. The same message (as a transparent hex string) must be communicated to the 8960 via SCPI
(refer to WCDMA PS Handovers
or GSM/GPRS/EGPRS Documentation). It is important that the EBIDs
used match between the two formats. (Specifically, the UE requested NSAPI must match the EBID in the
RrcConnectionReconfiguration.)
The LTE scenario must also correctly process a TAU procedure, with the EPSBearerContextStatus bitmap
set as described above.