UE mode and status

Mode and status of a ue
The UE has two basic modes: idle mode and connection mode.

1. idle mode.

There is only one idle status in idle mode. UE stays in idle mode after it is started. It is represented by a non-access layer, such as imsi, P-TMSI, tmsi, etc. UTRAN does not retain ue information in idle mode. Only all the UE in the LAC area or all the UE at the same time.

2 connection mode

UE connection mode has four states: CELL-PCH, URA-PCH, CELL-FACH, cell-dch. When the UE completes RRC connection establishment, it is transferred from idle mode to connection mode, CELL-FACH or cell-dch. When the RRC connection is released, the UE goes from connection mode to idle mode.

1 idle status
After UE is started, it reads system messages in a cell, listens to paging information, and is in the idle status. In the idle state, all connections of UE are closed at the access layer, and recognition of UE is distinguished by non-access layer Identifiers (such as imsi, tmsi and P-TMSI. UTRAN does not create a context for the UE in idle mode. to address a specific UE, only one cell can send paging messages to all ue or to multiple ue listening for the same paging period.

2 cell_dch status
The basic feature of the cell_dch state is that the UE is assigned a dedicated physical channel. In this state, in addition to the dedicated physical channel dpch for upstream and downstream connections, ue may also be allocated physical upstream and downstream shared channels pusch and/or pdsch. Based on the distribution of Utran, the UE can use the dedicated transmission channel dch, the uplink shared transmission channel usch, the downlink shared transmission channel DSCH, and the combination of these transmission channels. Based on the current active channel set, UTRAN knows that the UE is already in the cell recognition level.

3 cell_fach status
The basic feature of cell_fach status is that there is no dedicated physical channel connection between UE and UTRAN, and UE will continuously monitor the Fach transmission channel in the downstream direction, in the uplink direction, public or shared transmission channels (such as Rach) can be used, and UE can initiate the access process on the relevant transmission channels at any time. Based on the distribution of Utran, the UE can use the usch or DSCH transmission channel in this state. The UTRAN can also know the current cell of the UE Based on the cell update process executed by the UE last time. If the UE selects a new cell, the UE reports the current location information to UTRAN through the cell update process. UTRAN can also send data directly to ue on Fach, instead of initiating paging. UTRAN will broadcast system information changes to ue through the corresponding scheduling information on Fach in a timely manner, so that UE can re-read the corresponding system information.

4 cell_pch status
The basic feature of cell_pch state is that there is no dedicated physical channel connection between UE and UTRAN, and UE cannot use any uplink physical channel. To reduce power consumption, the UE can listen to the PCH channel indicated by pich in drx mode. UTRAN knows the current cell of UE based on the last cell update process executed by ue in the cell_fach state. If the UE needs to send upstream data (in response to a page call or initiate a call), it must first switch from cell_pch to cell_fach. In this status, the RRC sub-layer performs connection mobility management through the reselection process of the cell.

5 ura_pch status
The basic feature of ura_pch state is that there is no dedicated physical channel connection between UE and UTRAN, and UE cannot use any uplink physical channel. To reduce power consumption, the UE can listen to the PCH channel indicated by pich in drx mode. UTRAN knows the current ura of UE based on the last URA update process executed by ue in the cell_fach state. If the UE needs to send upstream data (in response to a page call or initiate a call), it must first switch from ura_pch to cell_fach. In this status, the RRC sub-layer performs connection mobility management through the reselection process of the cell.

The transition between idle mode and Connection Mode
After the UE initiates an RRC connection request, the UE is transferred from idle mode to cell_dch or cell_fach in connection mode. If the connection fails, the idle mode is returned. After the UE initiates a request to release the RRC connection, the UE is transferred from cell_dch or cell_fach to idle mode.

1 transition between cell_dch and cell_fach
The UE can enter the cell_dch state by establishing a dedicated physical channel in the cell_fach state. The ue in the cell_dch State can also enter the cell_fach state by releasing all dedicated physical channels.

 
2 cell_dch state and cell_pch (ura_pch) State Transition
When the UE in cell_dch status is reconfigured, you can enter the cell_pch or ura_pch status according to UTRAN instructions. However, the ue in the cell_pch or ura_pch State cannot directly jump to the cell_dch State, and must first jump to the cell_fach state.

3 cell_fach state and cell_pch (ura_pch) State Transition
The ue in the cell_pch (ura_pch) State. If a new URA is selected when the URA is re-selected, the UE will jump to the cell_fach state, and initiate the update process of the community (URA) in the new community. After the update process of the Cell (URA) is completed, if neither UTRAN nor ue has data to send, the UE will return to the cell_pch (ura_pch) state.