How DL and UL frequencies are calculated from EARFCN ?

Question

In LTE handover procedure, after UE handover to the target cell, if new TAI is not in the TAI list, the TAU will be triggered.

In HO procedure, UL/DL data has been handover to the target cell.

But before TAU, the UE doesn't register to the new MME, in the new cell, how the the DL/UL data transfer between UE and network(S-GW / P-GW) before TAU and after HO.

Also, as we know, if the TAU fails, the DL/UL data transfer will be interrupted, which network element will release the DL/UL throughput?

Answer 1

The carrier frequency in the uplink and downlink is designated by the E-UTRA Absolute Radio Frequency Channel
Number (EARFCN) in the range 0 - 65535. The relation between EARFCN and the carrier frequency in MHz for the
downlink is given by the following equation, where FDL_low and NOffs-DL are given in table 5.7.3-1 and NDL is the
downlink EARFCN.
FDL = FDL_low + 0.1(NDL – NOffs-DL)
The relation between EARFCN and the carrier frequency in MHz for the uplink is given by the following equation
where FUL_low and NOffs-UL are given in table 5.7.3-1 and NUL is the uplink EARFCN.
FUL = FUL_low + 0.1(NUL – NOffs-UL)

Please check spec 36.101