To enable reasonable
UE battery consumption when CA is configured, an activation/deactivation
mechanism of SCells is supported.
If the UE is
configured with one or more SCells, the eNodeB may activate and deactivate the
configured SCells. Activation/Deactivation does not apply to PCell.
After Configuring/Adding
the SCell, as explained here, the SCell is in deactivated state. When the SCell is
modified, the UE does not change the activation status.
During Handover, if
the same SCell is in use in the target PCell (i.e., SCell is not released
during Handover), the SCell in the target Cell in initially in the deactivated
state.There is no explicit activation/deactivation of uplink component carriers whenever a downlink component carrier is activated/deactivated, the corresponding uplink component carrier is also activated/deactivated.
In order for the UE
to receive data (PDSCH/PDCCH) on the SCell, it has to be activated which is
different from configuring the SCell. If the SCell is deactivated, the UE
maintains the configuration provided by RRC but it is not possible to receive either
PDCCH or PDSCH.
Activation/Deactivation
of Secondary Cell
A typical use case of
Activation of the SCell would that the network configures the UE
with one or more component carriers (CCs) but deactivate all of them except the
Primary CC. When there is a need of more data throughput (for example, there is
a huge amount of data to delivered to the UE in the downlink), the network can
activate several secondary CCs to maximize downlink throughput.
Another use case
could be that if the PCell is fully loaded, the SCell can be activated and the
data transfer can be scheduled only on the SCell (Load balancing).
The network can
deactivate the SCell when there is no more data to be delivered to the UE or the channel
quality of the SCell turning to be bad.
The UE (and the
network) can deactivate the activated SCell without explicit signaling which is
based on sCellDeactivationTimer. This
is the amount of time (in radio frames) the UE has not received any data on the
SCell.
SCell Activation is
done via MAC Control Element whereas the deactivation mechanism is either by
using MAC control element or by the expiry of the sCellDeactivationTimer.
The
Activation/Deactivation MAC control element is identified by a MAC PDU
subheader with unique LCID: 11011. It has a fixed size and consists of a single
octet containing seven C-fields and one R-field (Reserved bit and is set to “0”).
Each C-field represents an SCell with SCellIndex
which ranges from 1-7.
The MAC control
element carries a bitmap for the activation and deactivation of SCells: set to
1 denotes activation of the corresponding SCell, while a bit set to 0 denotes
deactivation.
With the bitmap,
SCells can be activated and deactivated individually, and a single
activation/deactivation command can activate/deactivate a subset of the SCells.
The
Activation/Deactivation MAC CE and its subheader are illustrated in the below
Figure. 
E-UTRAN configures sCellDeactivationTimer only if the UE is configured with one or more SCells. If the
field is absent, the UE shall delete any existing value for this field and
assume the value to be set to infinity.
UE maintains a sCellDeactivationTimer (as configured by
the RRC) timer per configured SCell and deactivates the associated SCell upon
its expiry. The same initial timer value applies to each instance of the sCellDeactivationTimer.
If the UE receives an
Activation/Deactivation MAC CE in subframe
#n activating the SCell, the UE
shall start (SCell Activation) or restart (SCell Reactivation) the sCellDeactivationTimer associated with
the SCell in subframe #n+8.
If the UE receives
PDCCH on the activated SCell indicating an uplink grant or a downlink
assignment it shall restart the sCellDeactivationTimer associated with the
SCell.
Similarly, if the UE
receives PDCCH on the serving cell scheduling the activated SCell (Cross
Carrier Scheduling) indicating an uplink grant or a downlink assignment, the UE
shall restart the sCellDeactivationTimer associated with the SCell.
If the UE receives an
Activation/Deactivation MAC CE in subframe
#n deactivating the SCell or if
the sCellDeactivationTimer associated
with the activated SCell expires in subframe
#n, the UE shall deactivate the SCell no later than in subframe #n+8.
If the UE receives an
Activation/Deactivation MAC CE in subframe
#n activating the SCell, the UE
shall apply the below defined actions no earlier than subframe #n+8 and no later than subframe
#n+24 or subframe #n+34 (as defined in section 7.7.2 of 36.133)
― Transmit SRS on the
SCell in case if UL CA and SRS on the SCell is configured;― PDCCH monitoring on the SCell;
― PDCCH monitoring for the SCell (Cross Carrier Scheduling);
― CSI reporting for the SCell. The UE should start transmitting valid CSI report no later than subframe #n+24 or #n+34 (as defined in section 7.7.2 of 36.133) but it can report out of range (CQI index = 0) values from subframe #n+8, otherwise the eNodeB have to perform blind decoding of PUSCH (if scheduled) from subframe #n+8 till subframe #n+24 or #n+34
If the SCell is
deactivated, the UE shall apply the following activations:
― SRS shall not be
transmitted in case if UL CA and SRS on the SCell is configured― The UE shall not transmit UL-SCH on the SCell (UL CA)
― PDCCH on/for the SCell shall not be monitored.
― The UE shall flush all HARQ buffers associated with the SCell.
― The UE shall not transmit RACH on the SCell (Introduced in Release-11, and the RA procedure on an SCell shall only be initiated by a PDCCH order). When SCell is deactivated, the ongoing RA procedure on the SCell, if any, is aborted
― The UE shall stop
reporting CSI from subframe #n+8 if
the sCellDeactivationTimer associated
with the SCell expires in subframe #n or
if the UE receives an Activation/Deactivation MAC CE in subframe #n deactivating the SCell
I have created a tool to display timings of different actions defined above based on the activation or deactivation SFN/subframe. Try this timing calculator here.
Watch the following deck for more details and a demo of the timing calculator
I have created a tool to display timings of different actions defined above based on the activation or deactivation SFN/subframe. Try this timing calculator here.
Watch the following deck for more details and a demo of the timing calculator
Reference:
3GPP TS 36.321, 36.213, 36.331, 36.133, and 36.300
Hello Mr. Kumar, While the carrier aggregation is in process and a device is connected to 2 carriers(assume). The sub-frames received by PCC and SCC to the UE why they are always simultaneous. If they are not simultaneous then why? So please eleborate this part..
ReplyDeleteThe PDCCH received in PCC and SCC need not be simultaneous. As long as SCC is active, the data can be received in any subframe irrespective of PCC receiving data in that subframe. For that matter, only SCC could be used to send data. It all depends on how much data eNodB has for this perticular user and what is the load situation. Scheduling on SCC and PCC is completely flexible.
DeleteHello Mr. Kumar.I am doing some job about carrier aggregation and I have some question. If I aggregated 2 CCs, both of them are 10MHz, so I get a 20Mhz carrier aggregated. What's the differences between this carrier aggregated and a normal 20MHz carrier when I use them?My English is not good, thank you !
ReplyDeleteHI ,
DeleteWe can take from network side as wel.
In case PCC cell having only 10MHZ bandwidth due to licence or Band limitation.But still UE wants to send more data within a short time.So this time can use CA if Network have additional spectrum.
Compared to CA and non CA device cost also bit high.
Here everything based on demand,Network implementation and bandwidth availaility.
It depends on where you are looking at the difference.
ReplyDeleteFor example on the UE side:
In case of CA, the UE needs two receivers to decode data from two CCs, where as with single 20MHz carrier, one Rx is sufficient. More processing in case of CA (including decoding, measurements etc...)
On the eNodeB side, it is same...two different Transmitters. But the Network has the flexibility in (for example) load sharing ...at the cost of signalling overhead.
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ReplyDeleteHi Kumar,
ReplyDeleteI have 10 Mhz L18 and 20 Mhz L26 and we make CA on those 2 carrier, when we did DT by nemo, sometime the Scell THP not detected, is that the CA is not working?
Hi,
DeleteSorry, I don't have any practical information on this band combination.
Good luck!!!
what's the reason UE cannot monitor PDCCH/SCH on the newly activated carrier earlier than subframe #n+8? Cannot find it in 36133.
ReplyDeleteThanks!
The timing requirements are carefully defined in order to ensure that there is a common understanding between the UE and the eNB.
DeleteFor example in case of Activation, the UE need to send HARQ Feedback after 4ms after receiving activation MAC CE ->> The eNB only knows that the UE has successfully received the MAC CE in about 4 + (1.5 to 2ms) uplink signally processing delay at the eNB...eNB would take about 1.5 to 2ms to schedule a UE before actual transmission.
So it make sense to have at least 8 ms.
how CQI/AperiodicCQI feedback works with Carrier aggregation?
ReplyDelete1- ue report CQI for both Cells each Periodic CQI report?
2- or Ue report CQI for only one cell each Periodic CQI?
UE would send Periodic CSI for each configured cell separately based on the configuration provided by the RRC
DeleteI have CA (blind activation, not Buffer based) between 1800 15M and 800 10Mhz.
ReplyDeleteDuring Ping Test (32bytes) repeated 3 time for each test,
CA is always configured. but not activated.
I want to enabled CA active during Ping Test. How can i do ? Thanks.
Well, if you are talking about UE side, we can't do much about it. On the network side, depending upon the (implemented) options, you should be able to find an option for this. I have experienced only two options though, one to always activate sCell after sCell has been configured (not being used by networks in Live) and the other one is buffer based. Please try to set the buffer threshold to the minimum value and increase the size of the ping to that extend to see it works.
DeleteHi kumar,
ReplyDeleteWhy ue release the secondary scell before handover?
is it possible to perform handover with scells? if yes in which release its supported?
and what are the benefit of performing handover with scells and without Scells?
HI Kumar,
ReplyDeleteI can see the Scell configuration or addition in Layer 3 messages , but from which exact L3 or L1 message can I see details of MAC CE to identify from Ue logs exactly when Scell is activated and deactivated?
thanks in Advance
Hi kumar
ReplyDeleteWhat is the minimum power which can be maintained in scc when the device latches on PCC.
bruh pls help me i beg you,how do i stop ca? my network keeps on swithcing from 4g to 4g+ i get a better speed at 4g and terrible speed at 4g+ i am from india using airtel sim
ReplyDeleteHi Mr. Kumar,
ReplyDeleteWhen ScellDeactivatedTimer will start if Scell activated in subframe number 5 and Timer set as 20ms???
I have a query related to the frame timing requirement for different carriers in carrier aggregation scenario.
ReplyDeleteIS IT NECESSARY AND MANDATORY FOR DIFFERENT CARRIERS IN CARRIER AGGREGATION TO BE ALIGNED IN SFN (SYSTEM FRAME NUMBER) OR ONLY SUBFRAME ALIGNMENT/FRAME BOUNDARY ALIGNMENT IS REQUIRED ?
I referred to 36.104 and it only mandates subframe alignment or frame boundary alignment and not SFN alignment. PLease advise.
This requirement applies to frame timing in TX diversity, MIMO transmission, carrier aggregation and their combinations.
Frames of the LTE signals present at the BS transmitter antenna port(s) are not perfectly aligned in time. In relation to each other, the RF signals present at the BS transmitter antenna port(s) experience certain timing differences.
For a specific set of signals/transmitter configuration/transmission mode, time alignment error (TAE) is defined as the largest timing difference between any two signals.
6.5.3.1 Minimum Requirement For E-UTRA: -
For MIMO or TX diversity transmissions, at each carrier frequency, TAE shall not exceed 65 ns.
For intra-band contiguous carrier aggregation, with or without MIMO or TX diversity, TAE shall not exceed 130 ns. –
For intra-band non-contiguous carrier aggregation, with or without MIMO or TX diversity, TAE shall not exceed 260 ns. –
For inter-band carrier aggregation, with or without MIMO or TX diversity, TAE shall not exceed 260ns.
For NB-IoT: - For TX diversity transmissions, at each carrier frequency, TAE shall not exceed 65 ns.
This is great post. I like this post.
ReplyDeletePing Speed test
Ping Speed
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ReplyDeleteHi,
ReplyDeleteIf Scell is deacitvated, could be because of RLF based on RLM/Poor SNR which UE triggers by itself. How would network know the SCC is deactivated? As there would be no CSI?
If the Scell remain deactive as UE might be in poor network coverage area, does network removes the SCC/or move it to not configured state?
Looking forward to get insights on these points.
Thanks!
This comment has been removed by the author.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteHi kumar,
ReplyDeleteWhat is the criteria for scell activation by enodeb
Ping Speed Test
ReplyDelete4G Internet Speed Test
ReplyDelete5myqted3
ReplyDeletesightcare
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