quest (IMSI, P-TMSI, Area, Channel Needed, QoS, DRX Parameters) message to the BSS serving the MS. IMSI is needed Radio Network Planning and Optimisation 1. PDP PDU 2. Paging Request 3. GPRS Paging Request 4. Any LLC Frame 5. Any LLC Frame Figure 2.39 Paging procedure by the BSS in order to calculate the MS paging group. P-TMSI is the identifier by which the MS is paged. Area indicates the routing area in which the MS is paged. Channel Needed indicates GPRS paging. DRX Parameters indicates whether the MS uses discontinuous reception or not. If the MS uses discontinuous reception, then DRX Parameters also indicates when the MS is in a nonsleep mode able to receive paging requests. The BSS pages the MS with one Paging Request (P-TMSI, Channel Needed) message in each cell belonging to the addressed routing area. Upon receipt of a GPRS Paging Request message, the MS will respond with any single valid LLC frame (e.g. a Receive Ready or Information frame) that implicitly is interpreted as a page response message by the SGSN. When responding, the MS changes the MM state to READY. The response is preceded by the Packet Channel Request and Packet Immediate Assignment procedures as described in GSM 03.64. Upon reception of the LLC frame, the BSS adds the Cell Global Identity including the RAC (routing area code) and LAC of the cell and sends the LLC frame to the SGSN. The SGSN will then consider the LLC frame to be an implicit paging response message and stop the paging response timer. Routing Area Identity Routing Area Identity (RAI) is a parameter defined by the operator and identifies one or several cells. RAI is broadcast as system information and is used by the MS to determine, when changing a cell, whether an RA border was crossed. If that was the case, the MS initiates the RA update procedure. The location of an MS in the STANDBY state is known in the SGSN on an RA level. This means that the MS is paged in the RA where the MS is located when mobile-terminated traffic arrives in the SGSN. An RA is a subset of one, an