6.2 Radio Resource operating modes

03.643GPPGeneral Packet Radio Service (GPRS)Overall description of the GPRS radio interfaceStage 2TS

Radio Resource (RR) management procedures are characterised by two different RR operating modes. Each mode describes a certain amount of functionality and information allocated. RR procedures and RR operating modes are specified in GSM 04.07 [5].

6.2.1 Packet idle mode

Packet idle mode is not applicable to an MS supporting DTM that has an ongoing RR connection. An MS that supports DTM, that has an ongoing RR connection and that has no allocated packet resource is in dedicated mode.

In packet idle mode no Temporary Block Flow (see subclause 6.6.4.2) exists. Upper layers can require the transfer of a LLC PDU which, implicitly, may trigger the establishment of TBF and transition to packet transfer mode.

In packet idle mode, the MS listens to the PBCCH and to the paging sub-channel for the paging group the MS belongs to in idle mode. If PCCCH is not present in the cell, the mobile station listens to the BCCH and to the relevant paging sub-channels.

While operating in packet idle mode, a mobile station belonging to GPRS MS class A may simultaneously enter the different RR service modes defined in GSM 04.08 [6]. A mobile station belonging to either of GPRS MS class B or C leaves both packet idle mode and packet transfer modes before entering dedicated mode, group receive mode or group transmit mode.

6.2.2 Packet transfer mode

Packet transfer mode is not applicable to a mobile station supporting DTM that has an ongoing RR connection. A DTM mobile station with an ongoing RR connection and with packet resources allocated is in dual transfer mode (see 6.2.3).

In packet transfer mode, the mobile station is allocated radio resource providing a Temporary Block Flow on one or more physical channels. Continuous transfer of one or more LLC PDUs is possible. Concurrent TBFs may be established in opposite directions. Transfer of LLC PDUs in RLC acknowledged or RLC unacknowledged mode is provided.

When selecting a new cell, mobile station leaves the packet transfer mode, enters the packet idle mode where it switches to the new cell, read the system information and may then resume to packet transfer mode in the new cell.

While operating in packet transfer mode, a mobile station belonging to GPRS MS class A may simultaneously enter the different RR service modes defined in GSM 04.18. A mobile station belonging to either of GPRS MS class B or C leaves both packet idle mode and packet transfer modes before entering dedicated mode, group receive mode or group transmit mode.

6.2.3 Dual transfer mode

In dual transfer mode, the MS has an ongoing RR connection and is allocated radio resource providing a Temporary Block Flow on one or more physical channels. Continuous transfer of one or more LLC PDUs is possible. Concurrent TBFs may be established in opposite directions. Transfer of LLC PDUs in RLC acknowledged or RLC unacknowledged mode is provided.

While in dual transfer mode the MS performs all the tasks of dedicated mode. In addition, upper layers can require:

  • the release of all the packet resources, which triggers the transition to dedicated mode.
  • the release of the RR resources, which triggers the transition to idle mode and packet idle mode.

When handed over to a new cell, the MS leaves the dual transfer mode, enters the dedicated mode where it switches to the new cell, may read the system information messages sent on the SACCH and may then enter dual transfer mode in the new cell.

6.2.4 Correspondence between Radio Resource operating modes and Mobility Management States

The Mobility Management states are defined in GSM 03.60 [3]. Table 1 provides the correspondence between Radio Resource states and Mobility Management states:

Table 1a: Correspondence between RR operating modes and MM states (non-DTM capable MS)

RR BSS

Packet transfer mode

Measurement report reception

No state

No state

RR MS

Packet transfer mode

Packet idle mode

Packet idle mode

MM (NSS and MS)

Ready

Standby

Table 1b: Correspondence between RR operating modes and MM states (DTM capable MS)

RR BSS

Dual

transfer

mode

Dedicated mode

Packet transfer mode

Measurement report reception

No state

Dedicated mode

No state

RR MS

CS idle and packet idle

CS idle and packet idle

GMM (NSS and MS)

Ready

Standby

Each state is protected by a timer. The timers run in the MS and the network.

Packet transfer mode is guarded by RLC protocol timers.

6.2.5 Transitions between RR operating modes

The RR modes, and therefore the transitions between them, are different for each mode of operation (see 23.060).

Figure 3a shows the four RR states for an MS in mode of operation A that does not support DTM. The four states can be regarded as the combination of two state machines with two RR states each:

  • on the circuit switched part, idle mode and dedicated mode
  • on the GPRS part, packet idle mode and packet transfer mode

Figure 3a: RR operating modes and transitions for class A (DTM not supported)

Figure 3b shows the RR modes and transitions for an MS in modes of operation A (when it supports DTM) and B. In the mode of operation B there are three RR modes:

  • (Packet) idle mode
  • Packet transfer mode
  • Dedicated mode (see 04.18)

For a mobile station that supports DTM class A mode of operation, there is an additional RR mode: dual transfer mode. This mode can only be entered via a packet request procedure while in dedicated mode (see 04.18).

Figure 3b: RR operating modes and transitions for classes A (DTM supported) and B

Figure 3c shows the RR modes and transitions for an MS in mode of operation C. The MS can only be attached to either GSM or GPRS:

  • when it is GSM attached (and GPRS detached), there are two RR modes: idle mode and dedicated mode
  • when it is GPRS attached (and GSM detached), there are two RR modes: packet idle mode and packet transfer mode.

Figure 3c: RR operating modes and transitions for class C