Which category of LTE phone supports Carrier Aggregation ?

Question

If only PCELL UL is configured and What is the use of TPC filed in Scell DL DCI?

Answer 1

Ideally any UE above and including cat 5 , Especially cat 5 and Cat 8 should work.

In carrier aggregation operation, the DL-SCH processing capability can be shared by the UE with that of MCH received from a serving cell.
If the total eNB scheduling for DL-SCH and an MCH in one serving cell at a given TTI is larger than the defined processing capability, the prioritization between DL-SCH and MCH is left up to UE implementation.
So even a lower UE CAT can implement CA with modifications.