pre-finalfrequencylist(LTE2008)
3.5 LTE2276: Measurement-based SCell Selection
The LTE2276: Measurement-based SCell Selection feature introduces a measurement-based secondary cell (SCell) selection for carrier aggregation (CA).
3.5.1 LTE2276 benefits
The main benefit of the LTE2276: Measurement-based SCell Selection feature is that the eNB can select the secondary cells (SCells) which are to be added, based on the
respective UE quality indication rather than blindly via configuration parameters.
Additionally, by selecting the SCells for carrier aggregation (CA) based on the UE measurements, the LTE2276 feature optimizes:
• SCell resource utilization
• UE power consumption
• data throughput
3.5.2 LTE2276 functional description
The LTE2276: Measurement-based SCell Selection feature enhances the eNB secondary cell (SCell) selection criteria for carrier aggregation (CA). It is done by supplying the list of candidate SCells that are measured by the UE with a pre-defined minimum channel quality. The operator can decide per frequency layer whether to enable a measurement-based SCell selection or a blind SCell selection. The
measurement type to apply to SCell discovery is the A3 event with “report on leave” – a neighbor cell becomes offset better than a serving cell.
Figure 3 SCell discovery measurement Measured
quantity
Time-to-trigger Time
PCell
candidateSCell
In order to minimize the impacts on the UE throughput, the inter-frequency measurements are activated only on those frequencies for which the UE does not require measurement gaps. The eNB first tries to add SCells that have been measured
by the UE with sufficient quality, using normalized load compare value (NLCV biased by the respective sFreqPrio) as discriminating factor if there are multiple choices for the SCell addition selection, for more information, see LTE2233: N-out-of-M Downlink Carrier Aggregation feature. Only if no UE measured SCell can be added, the eNB will try to add SCells blindly, that is not measured SCells.
The LTE2276: Measurement-based SCell Selection feature works only with step-wise SCell addition (when the numTxWithHighNonGbr parameter value is greater than 0) and is activated with the Activate A3-based SCell
selection (actA3ScellSelect) activation flag.
The operator decides for which frequency layer the measurement for A3 event is enabled by configuring the Enable measurements for A3
event (enableA3Event) parameter. Additionally the following parameters are defined for A3 event configuration:
• A3 trigger quantity (a3TriggerQuantity) – this parameter defines which quantity (reference symbol received power (RSRP) or reference signal received quality (RSRQ)) the UE has to use for triggering an event A3 SCell discovery measurement report.
Additionally thresholds for filtering candidate SCells out of the cells reported by the UE can be defined by setting:
– SCell measurement threshold for RSRP (scellMeasThreshRsrp) – SCell measurement threshold for RSRQ (scellMeasThreshRsrq)
• A3 time to trigger (a3TimeToTrigger)
This parameter defines the time for which the specific criteria for the A3 event SCell discovery measurement must be met in order to trigger a measurement report.
• A3 offset (a3Offset)
This parameter defines a margin for the A3 event for an SCell discovery
measurement. The default value of this parameter is -3. Negative values for this parameter are recommended.
• Related hysteresis of offset a3Offset neighbor becomes offset better than serving cell (hysA3Offset)
This parameter defines a related hysteresis of a3Offset.
Candidate SCells on a frequency layer that has not been enabled for the A3 event SCell discovery measurement is assumed by the system to have the same radio coverage of the PCell and therefore have assigned the same priority as the UE measured candidate SCells in the SCell addition selection.
Candidate SCells on a frequency layer that has been enabled for the A3 event SCell discovery measurement but that not measured by the UE (because it would have needed measurement gaps) have assigned lower priority than the UE measured candidate SCells, therefore are selected for addition only if there is no better choice.
The LTE2276 feature is beneficial in the following scenarios:
• Scenario 1: the PCell has two candidate SCells on the same frequency layer, with different radio coverage
• Scenario 2: the PCell has several candidate micro SCells on the same frequency layer, with different radio coverage
Figure 4 Scenario 1 for LTE2276
Figure 5 Scenario 2 for LTE2276
3.5.3 LTE2276 system impact
Interdependencies between features
The following features must be activated before activating the LTE2276: Measurement-based SCell Selection feature:
• At least one of the following downlink (DL) carrier aggregation features:
– LTE1089: Downlink Carrier Aggregation – 20 MHz – LTE1558: TDD Downlink Carrier Aggregation
– LTE1858: FDD Inter-band/Intra-band Carrier Aggregation with Two Flexi Zone Micro BTSs
– LTE1332: Downlink Carrier Aggregation – 40 MHz – LTE1803: Downlink Carrier Aggregation 3CC – 40 MHz
The LTE2276: Measurement-based SCell Selection feature is impacted by the following features:
• LTE1541: Advanced SCell Measurement Handling
In the step-wise Scell selection, UE measured candidate SCells as well as candidate SCells on a frequency layer not enabled for A3 event Scell discovery measurements have highest priority in the Scell addition selection.
Impact on interfaces
The LTE2276: Measurement-based SCell Selection feature has no impact on interfaces.
Impact on network management tools
The LTE2276: Measurement-based SCell Selection feature has no impact on network management tools.
Impact on system performance and capacity
The LTE2276: Measurement-based SCell Selection feature has no impact on system performance and capacity.
3.5.4 LTE2276 reference data
Requirements
Table 22 LTE2276 hardware and software requirements System release Flexi Multiradio
BTS
Flexi Multiradio 10 BTS
Flexi Zone Micro BTS
Flexi Zone Access Point
FDD-LTE 16A not supported FL16A FL16A FL16A
Flexi Zone Controller
OMS UE NetAct MME SAE GW
FL16A LTE OMS16A 3GPP R10 UE capabilities 3GPP R11 UE capabilities 3GPP R12 UE capabilities
NetAct 16.8 Support not required
Support not required
BTS faults and reported alarms
There are no faults related to the LTE2276: Measurement-based SCell Selection feature.
Commands
There are no commands related to the LTE2276: Measurement-based SCell Selection feature.
Measurements and counters
There are no measurements or counters related to the LTE2276: Measurement-based SCell Selection feature.
Key performance indicators
There are no key performance indicators related to the LTE2276: Measurement-based SCell Selection feature.
Parameters
Table 23 New parameters introduced by LTE2276
Full name Abbreviated name Managed object Parent structure Activate A3-based
SCell selection
actA3ScellSelec t
MRBTS/LNBTS
-A3 offset a3Offset MRBTS/LNBTS/CADPR
-A3 time to trigger a3TimeToTrigger MRBTS/LNBTS/CADPR -A3 trigger quantity a3TriggerQuanti
ty
MRBTS/LNBTS/CADPR
-Enable measurements for A3 event
enableA3Event MRBTS/LNBTS/CADPR
-Related hysteresis of offset a3Offset neighbor becomes offset better than serving cell
hysA3Offset MRBTS/LNBTS/CADPR
-SCell measurement threshold for RSRP
scellMeasThresh Rsrp
MRBTS/LNBTS/CADPR
-SCell measurement threshold for RSRQ
scellMeasThresh Rsrq
MRBTS/LNBTS/CADPR
-A3 offset a3Offset MRBTS/LNBTS/LNCEL/C APR
-A3 time to trigger a3TimeToTrigger MRBTS/LNBTS/LNCEL/C APR
-A3 trigger quantity a3TriggerQuanti ty
MRBTS/LNBTS/LNCEL/C APR
-Enable measurements for A3 event
enableA3Event MRBTS/LNBTS/LNCEL/C APR
-Related hysteresis of offset a3Offset neighbor becomes offset better than serving cell
hysA3Offset MRBTS/LNBTS/LNCEL/C APR
-SCell measurement threshold for RSRP
scellMeasThresh Rsrp
MRBTS/LNBTS/LNCEL/C APR
-SCell measurement threshold for RSRQ
scellMeasThresh Rsrq
MRBTS/LNBTS/LNCEL/C APR
-Table 24 Existing parameters related to LTE2276
Full name Abbreviated name Managed object Parent structure Activation of downlink
carrier aggregation
actDLCAggr MRBTS/LNBTS
-Number of sampled subframes with High Non-GBR traffic
numTxWithHighNonG br
MRBTS/LNBTS
-For parameter descriptions, see FDD-LTE BTS Parameters.
Sales information
Table 25 LTE2276 sales information
Product structure class License control Activated by default Application software (ASW) SW Asset Monitoring No