LTE: In RRC connected mode, when an UE moves from one cell to another cell what messaging happen ?

Question

If I am right, an eNodeB can support multiple cells and each cell has different pci.
Now suppose enodeB has two cells i.e cell1 and cell2. If I am going right, both the cell(s) should have different PCIs.
I have assumed UE is attached to cell1 and due to mobility, it is moved to cell2. During this movement, what message shall be exchanged between UE and enodeB. And Is there any message send to MME regarding the new cell ?

Answer 1

You don't need to message the Core because for intra eNB handovers the eNodeB can carry out horizontal key derivation and calculate the new security keys for the new PCI, E-ARFCN-DL without having to increment the NCC. The UE would handover from once cell to the other via the usual Connection Reconfiguration mechanism

Answer 2

Answer on Feb 14th is a perfect one.
One thing I would like to add is to consider if the two cell are in the same TA.

Because if not the TAU must be triggered and there will be exchange of messages between eNB/UE and MME.