The mobile station has to decode some parameters broadcast by the network, in order to know the packet channel multiframing and how to access the network. The following list examines the decoding scheme, which is also shown in Figure 6-9:

Figure 6-9: The mobile station learns by decoding the information.

• PBCCH description The mobile station first decodes the BCCH channel of the initially selected cell. One BCCH is always transmitted on SI 13 (if the cell supports the GPRS service), which indicates all the GPRS relevant parameters, among others, if specific Packet Common Control Channels are used in the cell for GPRS (PBCCH, PRACH, PAGCH, and PPCH). If that is the case, a PCCCH description is sent on SI 13 (on BCCH), indicating that the PDCH is carrying PBCCH. Otherwise, if no PCCCH description is sent on SI 13, all the necessary GPRS information is transmitted on BCCH SI 13 and the mobile station decodes the BCCH of the neighboring cells for the cell reselection process. If PBCCH is used, it carries all the necessary information about the neighboring cells for the cell reselection process, and the mobile station only has to perform level measurements on the neighboring cells declared in the GPRS_BA_list (sent on BCCH or on PBCCH if it exists).

• PBCCH first block (B0) decoding If a PBCCH description is sent on BCCH SI 13, the mobile station listens to the first PBCCH block (B0) on the PDCH...