8 Support for packet service

07.033GPPTerminal Adaptation Functions (TAF) for services using synchronous bearer capabilitiesTS

There are two ways of supporting packet services, namely as Basic PacketMode Service and Dedicated PacketMode Service. In the Basic Packet Access case the GSM PLMN provides a connection to the PSPDN port or the PH of other networks, where as in the Dedicated Packet Mode Service case the GSM PLMN provides access to the PSPDN of its own (see GSM 09.06 [10]).

8.1 Terminal configurations

The terminal configurations are shown in figure 12. The TE2 can be connected to MT2 or TA via X.21, X.21 bis or V‑series interface. Table 9 shows various interface types at R reference point.

Figure 12: Packet mode terminal configurations

NOTE: For all configurations:

The proper operation of LAPB requires fixing of working parameters, this is detailed in specification GSM 09.06 [10].

Table 9: TE2/MT2 layer 1 specifications and procedures to initiate Bm channel establishment


TE2/MT2 Layer 1 specification

Events at the R reference point

Procedures according to:

X.21 leased circuit

TE2 sets C=N

CCITT Rec X.25 section 1.1


X.21 bis

TE2 sets circuit 108=ON

CCITT Rec X.25 section 1.2

Hot-line access (note)

V-series interface

TE2 sets circuit 108=ON

CCITT Rec X.25 section 1.3

X.21 circuit-switched

TE2 signals direct call

CCITT Rec X.21 section 4.4

X.21 bis direct call

TE2 signals direct call

CCITT Rec X.21 bis section 2.3.1

X.21 addressed call

TE2 enters call control phase

CCITT Rec X.21 section 4

Full circuit-switched access

X.21 bis addressed call

TE2 performs automatic address call

CCITT Rec X.21 bis section 2.3.2 iii

V25 bis addressed call

TE2 uses address call mode

CCITT Rec V.25 section 4

NOTE: In this case the terminal equipment assumes a semipermanent connection. After appropriate event at R reference point the MT2 will establish Bm channel to the PSPDN port or the PHF. MT2 requires the address of the PSPDN port or the PH and the setting of the parameters of the BC/LLC‑IEs as described in sections 8.2 and 8.3.

8.2 Support for basic packet access

The GSM PLMN shall support the Basic Packet Mode Service in line with TS 09.06, thus the definitions laid down therein apply accordingly to the subject matter of this section.

For mobile originated call the Call Set‑up message contains the E.164 address of the PSPDN port or the PHAU. This address will be provided by TE1 or TA in the case of S interface or by TE2 (R interface). The address must be provided either by MMI or by internal settings of MT2, if the TE2 is an ordinary X.25 terminal connected via "X.21 leased line", "X.21 bis" or "V‑series" interface.

The required settings of the parameters of the BC/LLC‑IE is shown in GSM 07.01 [8]. This setting might be performed via the MMI or being based on internal settings within the MT2.

For an incoming call the connection establishment is in line with GSM 09.06, 09.07 and 04.08. In the case of V‑series interface (full circuit switched access) the TE2 must support V.25 bis Auto Answer procedure.

When the connection between the PSPDN port and the PH, respectively, and the TE is established, the TAF shall take care of mapping Bm channel to/from:

a) V series or X series interface data circuits

b) B channel in case of S interface

TE/MT and PSPDN port and the PH, respectively, take care of higher layer protocols, e.g. X.32 identification and X.25 LAPB and PLP.

8.3 Support for dedicated packet access

GSM 09.06 [10] applies in its parts dealing with the Dedicated Packet Mode Service.

In this case the GSM PLMN gives a uniform access to packet services based on the PH‑concept of the ISDN for case A, confined to mobile originated calls. The mobile subscriber indicates BC‑IE elements as per GSM 07.01 [8]. The short code indicates the case of Dedicated Packet Access.

The mapping of data over V, X or S interface to/from Bm channel is identical to the Basic Packet Mode Service case.

The format of the numbering plan used in the X.25 Call Request Packet will be X.121. Numbering plan interworking in case of E.164 address is according to GSM 09.06 [10].

Annex A (normative):
L2R Functionality