5 Main concepts

04.633GPPPacket Data on Signalling channels Service (PDS) Service Description, Stage 3TS

The present document specifies the protocols for connection management of packet data on signalling channels which is applied on the air interface: the

  • PDSS1 (Packet Data on Signalling channels Service 1) protocol, and the
  • PDSS2 (Packet Data on Signalling channels Service 2) protocol.

Both are protocols of the Connection Management (CM) sublayer (see GSM 04.07).

PDSS1 and PDSS2 transactions can be active in parallel to other CM transactions.

A PDSS1 transaction may be initiated by the mobile station or the network. A PDSS2 transaction shall only be initiated by the mobile station.

The present document describes the PDSS1 and PDSS2 protocols with regard to two peer entities, one in a mobile station, the other one in the network. The call control entities are described as communicating finite state machines which exchange messages across the radio interface and communicate internally with other protocol (sub)layers.(see note[ In the model, for PDSS1, for each Transaction Identifier (TI) value there are two protocol entities in the mobile station and two protocol entities in the network: one which may originate a transaction and one which may use the transaction originated bt its peer entity; the protocol entity receiving messages with a given TI and TI flag value x may send messages with equal TI value and with TI flag value (1-x) mod 2. The originator uses TI flag value 0.]) A protocol entity is idle (also called: in the idle phase) until it has received a message from its peer entity or lower or higher layers have passed an abstract service primitive to it.

[NOTE: Text not yet approved for this version].

In particular, the

– PDSS1 protocol uses the MM and RR sublayer specified in GSM 04.08, and the

– PDSS2 protocol uses the RR sublayer specified in GSM 04.08.

This description in only normative as far as the consequential externally observable behaviour is concerned.

Certain sequences of actions of the two peer entities compose "elementary procedures" which are used as a basis for the description in the present document. These elementary procedures are defined in section 6 and 7.

NOTE: Whereas PDSS1 provides connections between mobile station and MSC, PDSS2 provides connections between the mobile station and the PDSS2 support node, see GSM 03.63.

The mobile station receives on lower sublayers information from the network whether the mobile station is allowed to establish a PDSS1 and/or PDSS2 connection. The network is informed by the mobile station in the classmark whether the mobile station supports PDSS1 and/or PDSS2.

The PDSS1 and PDSS2 protocols may use the main signalling link or the slow associated signalling link for communication, always on the SAP with SAPI=0 and in acknowledged mode (for the definition of these terms, see GSM 04.06). It is informed by the network whether it is allowed to establish a PDSS1 and/or PDSS2 connection by sending the SETUP and/or the IMMEDIATE SETUP message on the main signalling link and/or slow associated signalling link. If the mobile station supports PDSS1 and/or PDSS2, it shall be able to receive messages of the supported protocol(s) on both data links. Once a protocol entity in the mobile station has received a message, the mobile station shall send any further message pertaining to the same transaction on the data link on which it had received the last message.