5a Broadcast/multicast receive mode

3GPP43.022Functions related to Mobile Station (MS) in idle mode and group receive modeTS

5a.1 General description

The purpose of the broadcast/multicast receive mode process is for a MS to determine the most suitable cell while listening to an MBMS session. The broadcast/multicast receive mode is a substate of packet idle mode, and can only be entered by mobile stations that are GPRS attached.

If no suitable cell can be found the MS immediately returns to packet idle mode.

5a.2 Requirements and technical solutions

5a.2.1 Network provisions

If the PBCCH is not allocated in the serving cell, the necessary information for the computation of the cell reselection criterion for all neighbour cells in the neighbour cell list shall not be read by the mobile station from the system information of the neighbour cells. Instead, this information shall be provided by the network (see 3GPP TS 44.018 and/or 3GPP TS 44.060).

NOTE: If the PBCCH is allocated in the cell, this information is read by the MS from PSI TYPE 3 messages.

5a.2.2 Broadcast/multicast receive mode cell monitoring

The MS shall not read the parameters affecting cell reselection from the BCCH of the surrounding cells. Instead, this information shall be provided by the network. If the necessary information for a neighbour cell has not been received after entering broadcast/multicast receive mode, the MS shall use the the information read from the BCCH or PBCCH of that neighbour cell while in packet idle mode or, if not available, default parameters.

If the information is not available for a suitable cell within 30 seconds after it has become one of the six stronger cells, the mobile station shall read this information from the BCCH of the neighbouring cell. The MS is allowed to interrupt the reception of the MBMS session during this period. The MS shall not attempt to perform periodic updates of this information while in broadcast/multicast receive mode.

The MS determines which of the cells in the list are suitable and computes their reselection criterion, and decides on its own whether one of the surrounding cells should be selected instead of the current one. In computing the cell reselection criterion, the mobile station shall obey the intra-RAT and inter-RAT cell reselection algorithms defined for the GMM Ready state (see 3GPP TS 45.008).

To perform cell change, the MS shall at least have performed measurements on cells of the BA(GPRS) list and read the corresponding BSIC.

5a.2.3 Broadcast/multicast receive mode cell change

Either of the following events trigger a cell change by a MS in broadcast/multicast receive mode:

(i) The pass loss parameter C1 indicates that the path loss to the serving cell has become too high.

(ii) There is a better cell (in terms of the criterion C2 or of the GPRS cell reselection criterion) in the same LA/RA, or a much better cell in another LA/RA and with NCC permitted.

After cell change, the MS either

‑ leaves the broadcast/multicast receive mode and goes to packet idle mode in order to establish a dedicated connection with the network to perform a location update or routing area update if the cell belongs to a new LA/RA;

‑ detects that the selected cell does not belong to the MBMS Service Area and therefore leaves the broadcast/multicast receive mode and goes to packet idle mode;

‑ detects that the selected cell does not belong to an equivalent PLMN and therefore leaves the broadcast/multicast receive mode and goes to packet idle mode;

During these procedures, the MS may not be able to listen to the broadcast or multicast session.

If the mobile station has received information about the location of the p-t-m bearer in the cell that it has reselected to, the mobile station can resume the reception of the MBMS session without the need to complete the acquisition of the system information.