3 Circuit switched access to a PAD in the PSPDN (Basic PAD access)

09.053GPPInterworking between the PLMN and the PSPDN for PAD AccessTS

3.1 General

The basic PAD access is the access to a X.28 dial in port in a PSPDN without or via one or more transit ISDN or PSTN networks. This access is provided by GSM bearer services 21 – 26. However, it should be noted that the X.28 PAD does not support out-band flow control and does not support 7 bit characters without parity. The general interworking requirements are defined in GSM 09.07.

NOTE: In cases where no transit networks are used, the interface between the PLMN and the PAD is outside the scope of the present document and implementation dependent.

Table 09.05/1: Network interworking requirements for basic PAD access

Bearer

Access at

Bearer service

Bearer service

Bearer

Service in

Mobile

in ISDN

in PSTN

service

GSM PLMN

Station

(note 1)

(note 1)

in PSPDN

21

Data Cct

300 bit/s

22

Data Cct

1,2kbit/s

23

Data Cct

Cct mode

Cct mode

1 200/75 bit/s

3.1 kHz Audio

3.1 KHz Audio

(note 2)

24

Data Cct

2,4kbit/s

25

Data Cct

4,8kbit/s

26

Data Cct

9,6kbit/s

NOTE 1: If used as a transit network.

NOTE 2: The default profile of the accessed PAD applies.

3.2 Home PAD access

Home PAD access would normally be available for a mobile subscriber both when he/she is present in the home PLMN and when in a visited PLMN. Figure 09.05/1 illustrates both of these examples where he/she is accessing a PAD via the home PSTN. To access the PAD the user would need to be registered with the PSPDN and have his/her own NUI if a specific profile or local charging are required.

In this instance to initiate a call to the PAD the mobile subscriber sets up a call to the PSTN number associated with the PAD. The interworking function provides only the necessary modem, RLP (if required) etc., as indicated in the call set-up message and does not provide any additional functionality associated with PAD access. This access being available to the mobile subscriber from the home PLMN implies the use of a national PSTN call and when in a foreign PLMN the use of an international PSTN call.

+——+ |

| HOST | COUNTRY A | COUNTRY B

+——+ (home country) | (visited country)

| | |

…|.|……………………….. |

: | | : |

: | | PSPDN : |

: | | : |

: | +———————-+ : |

: +——————–+ | : |

: | | : |

……………………|…|…… |

| | |

+┴—┴+ |

| PAD | |

+—–+ |

| | |

+————-┼—┼-+ | +—————+

| PSTN/ISDN A : :.┼————–┼.. PSTN/ISDN B |

+————-┼—–+ | +-┼————-+

| | |

| | |

| | +—-┼————-+

+———┼——+ | | :….. PLMN B |

| PLMN A : | | | : |

+———┼——+ | +———┼——–+

| | |

+–┴——+ | +—-┴—-+

| Mobile | | | Mobile |

| Station | | | Station |

+———+ +———+

Figure 09.05/1: Home PAD access

3.3 Visited PAD access

When the mobile subscriber is within a PLMN in a foreign country an alternative to home PAD access is given in figure 09.05/2. The PAD used in this case is a PAD within the visited country.

In this case the mobile subscriber initiates a PSTN call to the PAD in the visited country, and utilises the international link within the PSPDN.

The mobile subscriber would need to be registered with the visited PSPDN to obtain an NUI if a specific profile or local charging are required, plus needing to know the correct PSTN number for accessing the PAD. The mobile subscriber would also need to know the user procedure for connecting to the PAD including the presentation of the NUA (international/national). Again the interworking function would not provide any additional requirements over and above the normal PSTN interworking.

+——+ |

| HOST | COUNTRY A | COUNTRY B

+——+ (home country) | (visited country)

| |

…..|……………………. | …………………

: | : | : :

: | PSPDN : | : PSPDN :

: | : | : :

: +———————————————–+ :

…………………………. | ……………|…..

| |

| +—┴-+

| | PAD |

| +—–+

| |

| +————–┼–+

| | PSTN/ISDN B : |

| +————–┼–+

| |

| +———-┼——-+

| | PLMN B : |

| | : |

| +———-┼——-+

| |

| +—–┴—+

| | Mobile |

| | Station |

| +———+

Figure 09.05/2: Visited PAD Access