Carrier Aggregation Interview Question Answer 1-8

Q01. In which release Carrier Aggregation introduce?

Ans. Carrier Aggregation Introduction in 3GPP Release 10. When there was no CA, the data was transmitted or received on a single carrier called the primary component carrier and the corresponding cell is called the primary cell.

Q02. What is the pupose of C.A?

Ans. To increase throughput without purchasing additional spectrum.
One or more component carriers are aggregated with the primary component carrier to support wider transmission bandwidth.

Q03. What is Primary Cell and Secondary Cell?

Ans.

Primary serving cell always remain with UE until handover not complete, means Primary Cell can be change only at the time of handover.
In CA primary cell is those cell by which UE do initial registration, measurement reporting. although it’s also control the mobility of UE, dynamically activate or deactivate secondary cell.
Handle all the RRC and NAS procedure

In release 10 a ue can aggregate maximum upto 5 component carrier 1 PCC and 4 SCC.
Maximum bandwidth that can be allocated is 100MHz (20+20+20+20+20)
Actul no’s of SCC that can be allocated to an UE depends on UE’s capabilities.
It’s not possible to configure an UE with more UL Ccs than DL Ccs, but reverse can be true.

Q04. Who add remove Secondary Cell dynamically?

Ans. it’s Primary Cell, who can dynamically add or remove secondary cell as per ue capability or radio conditions.

Q05. What is MCG and SCG?

Ans. In ENDC(Eutra NR Dual Connectivity), LTE should be MCG(Master Cell Group) and NR should be SCG(Secondary Cell Group).
MCG work as the anchor and UE performs initial registration to this Master cell group, and this MCG can add one or more Secondary Cells (SCG).
Reference:
TS 36.331-5.3.1.1, there are three different ways of adding SCGs to the LTE anchor cell as follows.
1 : Reconfiguration with sync and key change
2 : Reconfiguration with sync but without key change
3 : Regular NR SCG reconfiguration without Sync / SCG Security

Q06. A ue can remove Primary Cell? If Yes, than how if No, then why?

Ans. YES, a ue can change primary cell.
Whatever the conditions we had learnt for change serving cell in single component carrier, The same conditions would follow by ue to change primary cell.

Q07. What is the condition of change Primary cell?

Ans.

in connected state by handover.
in idle condition cell re-selection should change primary cell.

Q08. What is ue Capability Report?

Ans.

The purpose of this procedure is to transfer UE radio access capability information from the UE to E-UTRAN.
If the UE has changed its E-UTRAN radio access capabilities, the UE shall request higher layers to initiate the necessary NAS procedures that would result in the update of UE radio access capabilities using a new RRC connection.
Please Refer to know more conditions TS 36.331-5.6.3.3 what happen when Reception of the UECapabilityEnquiry by the UE

NOTE: Change of the UE's GERAN UE radio capabilities in RRC_IDLE is supported by use of Tracking Area Update.
Reference:
TS 36.331-5.6.3.1