In the Cell_FACH, the UE location is known to the cell level.
If the UE detects the change in cell identity, it performs a cell update procedure.
The UE is addressed by the C-RNTI(cell radio network temporary identifier) from the RNC that controls the cell which the UE is in.
Cell_FACH
is
one of states in RRC connected mode.
The UE is assigned to use common channels.
This state is triggered as either part of RRC connection request or some RB reconfiguration process.
The UE can move to any of other connected states as commanded by the network.
*Idle mode: CN-level
UE is identified with TMSI (temporary mobile subscriber identity)
*RRC connected mode: UTRAN-level
UE is identified with C-RNTI and U-RNTI
Cell_FACH and Cell_PCH: every cell change needs to be reported via cell update
URA_PCH: every URA change needs to be reported via cell update
(less signal overhead from UE perspective, but more paging messages need to be injected [...]
When a paging arrives at a UE,
in idle mode, UE sends RRC connection establishment
in Cell_PCH and URA_PCH, the UE moves to Cell_FACH and sends Cell Update message with cause “paging response”
Note that it is not efficient to have a code sequence allocated to an inactive user since this may block the assignment of new connections due to the code availability in downlink.
Thus, in such case, DCH channel needs to be de-allocated and the UE should use RACH/FACH channel.
On the other hand, when the buffer of [...]
