FAST RETURN TO LTE AFTER
CALL RELEASE DATA
1.
Executive summary
LTE Carrier Aggregation, being one of the major functionalities of the LTEAdvanced,
will further increase the end user data rates. Given the VF-NL spectrum situation,
theoretical maximum data rate of 225 Mbps could be realised.
With an LTE-CA capable terminal, the customer can simultaneously make use
of LTE1800 and LTE2100 spectrum in the downlink
with these 2 frequency bands.
With LTE CAis it possible to combine simultaneously use two LTE frequency
bands for the end user, which creates an increase in user throughput.
1.
Capacity and Throughput
Each Carrier Aggregation UE with one configured SCell consumes the memory of two
connected users in the system.
As a result, the maximum total number of RRC_CONNECTED users decreases by the
number of Carrier Aggregation UEs connected.
3- Enhanced Carrier Aggregation Features
FDD only: Supplemental Downlink for Carrier Aggregation
Dynamic SCell Selection for Carrier Aggregation
Configurable SCell Priority
3CC DL Carrier Aggregation Extension
4CC DL Carrier Aggregation Extension
FDD only: 5CC DL Carrier Aggregation Extension
Cross-DU Carrier Aggregation Support
Carrier Aggregation FDD-TDD
Uplink Carrier Aggregation
Elastic RAN
2- Mobility
There is no change with regards to mobility procedures for a CAUE compared to a legacy non-CAUE.
The PCell is determined by Idle-mode reselection priorities. At incoming intra- or inter-frequency handover
the target cell becomes the new PCell in case the target cell does support CA. PCell mobility for a LTE-CA capable
UEis the same as it is for a Rel-8 legacy UE.
The following mobility use cases arepossible:
Intra FrequencyHandover
o CAto CA(based onPCELL)
o CAto non-CA(based on PCELL)
o Non-CA to CA
Inter FrequencyHandover
o CAto CA(based onPCELL)
o CAto non-CA(based on PCELL)
o Non-CA to CA
Inter Frequency LoadBalancing
o CAto CA(based on PCELL) since IFLB is currently only deployed on co-located sectors.
IRATredirection
o CAto UTRAN
All these mobility use cases are based on event triggers such asA3, A4, A5, B2, etc.
As stated above CAmobility is the same as for Rel-8 legacy UEs and based on the PCELLonly.
Below the applicable events for the VF-NL network in case of a CA capable UEare summarized:
No changes in cell selection / reselection for a CAcapable UE
Mobility is based on only the PCell coverage for a CAcapable UE
EventA3 based intra-frequency handovers for a CAcapable UE
EventA5 based inter-frequency handovers for a CAcapable UE
EventA4 based inter-frequency load balancing for a CA capable UEdue to load balance purposes.
Event B2 based inter RATre-directions for a CAcapable UE
PCell always changes due to an intra- or inter-frequency (both normal and load based) handover
In the new PCell, the old SCell is removed and a new SCell is configured.
All of this is done in the same RRCReconfiguration message at the handover itself.
2- Mobility
To facilitate UE battery savings, the Carrier Aggregation feature supports dynamic activation and deactivation of the
secondary
cell. DL transmissions on an SCell are only possible if the secondary cell is activated. If the secondary cell is deactivated,
although still configured, no transmissions are possible on that carrier. TheUEdoes not monitor the deactivated component
carrier. This results in UEbattery saving.
For reasons like UEbattery consumption, 3GPPhas specified a fast MAClevel activation/deactivation
procedure for SCell (sent on PDSCH). While activated the UElistens to PDCCH channel for both carriers impacting battery
life.
Totake the configured cell into use, the eNodeB will send an
Activation/Deactivation MAC CE to the UE, activating the SCell. Upon activation, the UE will start monitoring
PDCCH,
perform CQI measurements and receive DL transmissions grants.
Once the SCell is activated, the eNodeB scheduler will be able to use downlink resources on both the SCell and the Pcell
which this UE is associated with. The eNodeB monitors the CQI reports for both cells. If the CQI measurements drop below
a
certain threshold for a SCell, the eNodeB will stop scheduling this UEon that cell.
De-configuration of an SCell implicitly also includes deactivation of the SCell, so no separate deactivation command has to
be
sent.
There are triggers for activation and de-activation of the SCELL (read: it does not
concern the de-configuration of the SCELL):
“Need based”
o
Allow activation or deactivation of the SCell based on the amount of data available in the Radio Link Control (RLC) buffer.
“Coverage based”
o Allow deactivation of the SCell based on poor channel (SCELLCQI) quality
o Polling when out of SCell coverage
Prohibit timer to avoid ping pong
Dynamic activation and deactivation ensures that the SCell is only activated when there is DL data demand that could benefit from
transmitting on more than just one carrier. Furthermore, the activated secondary cell is only used for DLtransmissions if the SCell DL
The SCELLonce configured is not activated yet. For this a certain conditions need to be fulfilled. Assuming the quality of the channel is considered to
be sufficient, it requires that the number of bits in all queuesis more than a pre-defined threshold. A hysteresis between activate and deactivate is
used. In case the prohibit timer is NOTrunning the SCELLwill be activated and the scheduler is nowallowed to schedule data for both carriers. SCell
activation is achieved through the transmission of an activation Medium Access Control (MAC) Control Element (CE) with the SCell index bit set to
one. The eNodeB sends the Activation MACCEon a PCell,piggybacked on data. TheeNodeBconsiders the activation successful when a HARQ
ACKdetection parameter is received after the DL burst that carried the activation MAC CEoccurred.
Because it is possible to receive a false HARQACKdetection parameter, the activation MACCEis repeated multiple times. Onceactivated, the UEis
polled for SCell channel status information.
One special scenario is when the SCELL, which is active becomes locked. If the cell being used as SCell becomeslocked, then the eNodeB will
trigger a deactivate. If the locked SCell becomesunlocked, then the eNodeBwill trigger an activate since the UEis still configured.
Figure 2624: UESpecificSCELL Deactivation
Once the SCELLis activated, there will be monitoring whether the SCELLcan
or should be deactivated (read: NOTde-configured) due to poor channel
quality, admission control and / or to save UEbattery consumption. For
example when the SCELLis activated the UElistens to PDCCHchannel for both
carriers impacting battery life. In case the prohibit timer is NOTrunning
(otherwise a deactivation of the SCELLis NOTpossible) and one of the
conditions as displayed in Figure 26: UESpecific SCELLDeactivationFigure
22: UESpecific SCELLDeactivation is fulfilled, the SCELL can be deactivated
and the scheduler stops scheduling data for both carriers and continues with
scheduling on the PCELLcarrier only. SCell deactivationis achieved through
the transmission of an deactivationMedium AccessControl (MAC) Control
PDCPcounters(pmPdcpVol – service level) do reflect the situation for the group of UEsusing a cell as PCell, which would look like for Cell Aand Cell B as
follows:
o
o
Cell A= A1 + A2 + A3
Cell B = B1 + B2 + B3
MACcounters do reflect the situation in a cell regardless if scheduledUEsdo use the cell as a PCell or as a SCell, which should look like for Cell A and Cell B as
follows:
pmRadioThpVol ( celllevel )
o
Cell A= A1 + A2 + B1
o
Cell B = A3 + B2 + B3
pmRadioThpVolSCell ( celllevel )
o
Cell A =B1
o
Cell B= A3
As described in 4.4.3.4.124.4.7.4.12 Performance ManagementPerformance Management depending on the amount of LTE-CA capable, configured and
activated UEs,the throughputand latency KPIs can different output after LTE-CAenabling as the case before it was active. These KPIscan be calculated as follows:
Based on the new counter set introduced for LTE-CA specifically the following performance indicators have been defined:
[CA_CapableUE_pen1_Scell_%] =(100*pmCaCapableDlSum_1/(pmCaCapableDlSum_0+pmCaCapableDlSum_1+pmCaCapableDlSum_2+pmCaCapableDlSum_3+pmCaCapableDlSum_4)
[CA_CapableUE_pen2_Scell_%] = (100*pmCaCapableDlSum_2 / (pmCaCapableDlSum_0+pmCaCapableDlSum_1+pmCaCapableDlSum_2+pmCaCapableDlSum_3+pmCaCapableDlSum_4)
[CA_CapableUE_pen3_Scell_%] = (100*pmCaCapableDlSum_3 / (pmCaCapableDlSum_0+pmCaCapableDlSum_1+pmCaCapableDlSum_2+pmCaCapableDlSum_3+pmCaCapableDlSum_4)
[CA_CapableUE_pen4_Scell_%] = (100*pmCaCapableDlSum_4 / (pmCaCapableDlSum_0+pmCaCapableDlSum_1+pmCaCapableDlSum_2+pmCaCapableDlSum_3+pmCaCapableDlSum_4)
[Num_CA_CapableUE_0_Scell_ROP] = pmCaCapableDlSum_0/(ROP * 12)
[Num_CA_CapableUE_1_Scell_ROP] = pmCaCapableDlSum_1/(ROP * 12)
[Num_CA_CapableUE_2_Scell_ROP] = pmCaCapableDlSum_2/(ROP * 12)
[Num_CA_CapableUE_3_Scell_ROP] = pmCaCapableDlSum_3/(ROP * 12)
[Num_CA_CapableUE_4_Scell_ROP] = pmCaCapableDlSum_4/(ROP * 12)
[CA_ConfiguredUE_1_Scell_%] = (100*pmCaConfiguredDlSum_1 / (pmCaConfiguredDlSum_0+pmCaConfiguredDlSum_1+pmCaConfiguredDlSum_2+pmCaConfiguredDlSum_3+pmCaConfiguredDlSum_4)
[CA_ConfiguredUE_2_Scell_%] = (100*pmCaConfiguredDlSum_2 / (pmCaConfiguredDlSum_0+pmCaConfiguredDlSum_1+pmCaConfiguredDlSum_2+pmCaConfiguredDlSum_3+pmCaConfiguredDlSum_4)
[CA_ConfiguredUE_3_Scell_%] = (100*pmCaConfiguredDlSum_3 / (pmCaConfiguredDlSum_0+pmCaConfiguredDlSum_1+pmCaConfiguredDlSum_2+pmCaConfiguredDlSum_3+pmCaConfiguredDlSum_4)
[CA_ConfiguredUE_4_Scell_%] = (100*pmCaConfiguredDlSum_4 / (pmCaConfiguredDlSum_0+pmCaConfiguredDlSum_1+pmCaConfiguredDlSum_2+pmCaConfiguredDlSum_3+pmCaConfiguredDlSum_4)
[Num_CA_ConfiguredUE_0_Scell_ROP] = pmCaConfiguredDlSum_0/(ROP * 12)
[Num_CA_ConfiguredUE_0_Scell_ROP] = pmCaConfiguredDlSum_1/(ROP * 12)
[Num_CA_ConfiguredUE_0_Scell_ROP] = pmCaConfiguredDlSum_2/(ROP * 12)
[Num_CA_ConfiguredUE_0_Scell_ROP] = pmCaConfiguredDlSum_3/(ROP * 12)
[Num_CA_ConfiguredUE_0_Scell_ROP] = pmCaConfiguredDlSum_4/(ROP * 12)
Since feature “FAJ 121 3046, Carrier Aggregation” does only support 1 static SCELL configuration per PCELL it is unlikely to see stepping of those counters for UEs having more than one
SCELL per PCELL. Also in the case of introduction of feature “FAJ 121 3063, Dynamic SCell Selection for Carrier Aggregation” it is unlikely to see these counters being stepped since the
UE will still use only one SCELL at a time but it might be more dynamically assigned based on measurements and more than a single static SCELL configuration will be possible. A
change is expected to be observed when carrier aggregation will be done over more than two component carriers
[CA_ActivatedUE_0_Scell_%] = (100*pmCaActivatedDlSum_0 / (pmCaActivatedDlSum_0+pmCaActivatedDlSum_1+pmCaActivatedDlSum_2+pmCaActivatedDlSum_3+pmCaActivatedDlSum_4)
[CA_ActivatedUE_1_Scell_%] = (100*pmCaActivatedDlSum_1 / (pmCaActivatedDlSum_0+pmCaActivatedDlSum_1+pmCaActivatedDlSum_2+pmCaActivatedDlSum_3+pmCaActivatedDlSum_4)
[CA_ActivatedUE_2_Scell_%] = (100*pmCaActivatedDlSum_2 / (pmCaActivatedDlSum_0+pmCaActivatedDlSum_1+pmCaActivatedDlSum_2+pmCaActivatedDlSum_3+pmCaActivatedDlSum_4)
[CA_ActivatedUE_3_Scell_%] = (100*pmCaActivatedDlSum_3 / (pmCaActivatedDlSum_0+pmCaActivatedDlSum_1+pmCaActivatedDlSum_2+pmCaActivatedDlSum_3+pmCaActivatedDlSum_4)
[CA_ActivatedUE_4_Scell_%] = (100*pmCaActivatedDlSum_4 / (pmCaActivatedDlSum_0+pmCaActivatedDlSum_1+pmCaActivatedDlSum_2+pmCaActivatedDlSum_3+pmCaActivatedDlSum_4)
[Num_CA_ActivatedUE_0_Scell_ROP] = pmCaActivatedDlSum_0/(ROP *60*1000)
[Num_CA_ActivatedUE_1_Scell_ROP] = pmCaActivatedDlSum_1/(ROP *60*1000)
[Num_CA_ActivatedUE_2_Scell_ROP] = pmCaActivatedDlSum_2/(ROP *60*1000)
[Num_CA_ActivatedUE_3_Scell_ROP] = pmCaActivatedDlSum_3/(ROP *60*1000)
[Num_CA_ActivatedUE_4_Scell_ROP] = pmCaActivatedDlSum_4/(ROP *60*1000)
[CA_ScheduledUE_1_Cell_%] = (100*pmCaScheduledDlSum_0 /
[CA_ScheduledUE_2_Cell_%] = (100*pmCaScheduledDlSum_1 /
[CA_ScheduledUE_3_Cell_%] = (100*pmCaScheduledDlSum_2 /
[CA_ScheduledUE_4_Cell_%] = (100*pmCaScheduledDlSum_3 /
[CA_ScheduledUE_5_Cell_%] = (100*pmCaScheduledDlSum_4 /
(pmCaScheduledDlSum_0+pmCaScheduledDlSum_1+pmCaScheduledDlSum_2+pmCaScheduledDlSum_3+pmCaScheduledDlSum_4)
(pmCaScheduledDlSum_0+pmCaScheduledDlSum_1+pmCaScheduledDlSum_2+pmCaScheduledDlSum_3+pmCaScheduledDlSum_4)
(pmCaScheduledDlSum_0+pmCaScheduledDlSum_1+pmCaScheduledDlSum_2+pmCaScheduledDlSum_3+pmCaScheduledDlSum_4)
(pmCaScheduledDlSum_0+pmCaScheduledDlSum_1+pmCaScheduledDlSum_2+pmCaScheduledDlSum_3+pmCaScheduledDlSum_4)
(pmCaScheduledDlSum_0+pmCaScheduledDlSum_1+pmCaScheduledDlSum_2+pmCaScheduledDlSum_3+pmCaScheduledDlSum_4)
[Num_CA_ScheduledUE_1_Cell_ROP] = pmCaScheduledDlSum_0/(ROP *60*1000)
[Num_CA_ScheduledUE_2_Cell_ROP] = pmCaScheduledDlSum_1/(ROP *60*1000)
[Num_CA_ScheduledUE_3_Cell_ROP] = pmCaScheduledDlSum_2/(ROP *60*1000)
[Num_CA_ScheduledUE_4_Cell_ROP] = pmCaScheduledDlSum_3/(ROP *60*1000)
[Num_CA_ScheduledUE_5_Cell_ROP] = pmCaScheduledDlSum_4/(ROP *60*1000)
1.
Solution
This paragraph provides an overview of the LTE-CAsolution. For the functional introduction the following technical requirements
should be fulfilled:
The enode-B should be HW capable forLTE-CA:
o
The site should be equipped with both LTE800and LTE1800.Radio units of each frequency band should be
connected to the same Digital Unit. TheDU should be either of type DUS31
o
or DUS41, the older DUL20 does not support LTECAand thus needs to be replaced.
In order to control both LTE800 and LTE1800 from DUS , existing sites have to be reconfigured. In most cases
this requires the swap of 2 DUL20 for 1 DUS41. For macro sites
this also requires redistribution of the radio units over the cabinets.
o
The DUS41 has to beintroduced.
o
Although not technically required, the DUL20s need to be re-used in new to-be modernised
sites. This reduces the CAPEX needed for the combination of LTE-CAand Spring modernization.
The enode-B should be SW capable forLTE-CA:
o In order to support the make the enode-Bs HWcapable (ie. dual-band DUSoperation) L13B SW is required on the
enode-Bs. TheSWupgrade is a dependency to this project.
o Next, the make the SW level at the enode-Bs is again to be upgraded to L14A. The SW upgrade is a dependency
to this project.
o The final step in to enable to optional SW feature LTEcarrier aggregation at the enode-Bs
The backhaul should be capable for handling the maximum bit rates. In order to upgrade the backhaul capacity or more
of the following changes could be required (varies per site):
o
No change needed (the case with dark fibre connected sites)
o
Upgrade microwave capacity from 170 to 340 Mbps by using more spectrum
o
Exchange the type of microwave
o
Changethe microwave path and replace the microwave
o
Deploy FTTS,either from Eurofiber or KPN leased fibre.
o
The PTNportcapacity shouldbe 1Gbpsor more. All100 Mbpsports needed to be upgraded.
Recommende parameters for Fast return to LTE:
The improvement: