7 Elementary procedures for PDSS2

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

7.1 Overview

The elementary procedures for PDSS2 may be grouped into the following classes:

– PDSS2 establishment procedures.

– PDSS2 termination procedures.

– PDSS2 information phase procedures.

7.2 Procedures for establishment of a PDSS2 connection

The PDSS2 protocol entity in the mobile station in the idle phase shall on request of higher layers to establish a connection, analyse the request: the request contains all information necessary for the IMMEDIATE SETUP message and an indication whether the main or slow associated data link is to be used. The PDSS2 protocol entity shall then verify whether:

1) use of the indicated link for PDSS2 is possible and allowed;

and whether

2) establishment of a PDSS2 connection is possible and allowed.

– If one of these conditions is not fulfilled, the request is rejected.

– If the PDSS2 connection establishment is possible and allowed and the use of the indicated link is possible and allowed, the PDSS2 protocol entity asks the RR sublayer to establish an RR connection. The request contains an IMMEDIATE SETUP message to be transferred to the peer entity. The request from higher layers may already contain data to be transferred which does not exceed a maximum allowed length. In this case the data is included in the IMMEDIATE SETUP message.

If the RR connection establishment fails or the PDSS2 connection establishment is rejected, the PDSS2 protocol entity aborts the establishment and gives an appropriate information to higher layers; it then returns to the idle phase.

An idle PDSS2 protocol entity in the network shall on receipt of an IMMEDIATE SETUP message inform higher layers. If the IMMEDIATE SETUP message contained a data part, it passes the data part to higher layers and then continues as follows:

– If higher layers accept the establishment, the PDSS2 protocol entity shall send a SETUP ACKNOWLEDGE message to its peer entity and enter the PDSS2 information transfer phase. The acceptance from higher layers may already contain data to be transferred which does not exceed a maximum allowed length. In this case the data is included in the SETUP ACKNOWLEDGE message.

– If higher layers reject the establishment, the PDSS2 protocol entity shall send a RELEASE COMPLETE message with appropriate cause to its peer entity.

When a PDSS2 protocol entity in the mobile station has transferred an IMMEDIATE SETUP message to its peer entity and receives as an answer a SETUP ACKNOWLEDGE message, it informs higher layers and enters the PDSS2 information transfer phase.

Abnormal cases

1) If during the establishment of a PDSS2 connection higher layers decide to abort the establishment, the PDSS2 protocol entity shall react as specified in subclause 6.3.

2) If during the establishment of a PDSS2 connection a lower layer failure occurs, the PDSS2 protocol entity shall abort the establishment and inform higher layers.

3) If the request from higher layers to establish a connection contained data with more than the maximum allowed length, the protocol entity shall reject the request with appropriate cause.

4) If the response from higher layers to accept a connection contained data with more than the maximum allowed length, the protocol entity shall reject the response with appropriate cause and then wait for further action from higher layers.

5) If after having informed higher layers that an IMMEDIATE SETUP has been received, no valid response was received from higher layers within 5 seconds, the protocol entity shall send a RELEASE COMPLETE message to its peer entity and inform higher layers that the connection establishment has been aborted.

6) If after having sent the IMMEDIATE SETUP message, no valid response was received from the peer entity within 10 seconds, the protocol entity shall send a RELEASE COMPLETE message to its peer entity and inform higher layers that and why the connection establishment has been aborted.

7.3 Procedures for release and termination of a PDSS1 connection

These procedures are identical to those specified for PDSS1 in subclause 6.3.

7.4 Procedures for the information phase of a PDSS2 connection

During the information phase of a PDSS2 connection, higher layers may request the transfer of data which does not exceed a maximum allowed length. The PDSS2 protocol entity then sends the data to its peer entity in a DATA message.

NOTE: Higher layers may apply activity supervision and, e.g., release a PDSS2 connection when it has been idle for a longer period.

Abnormal cases:

1) During a PDSS2 connection;

(A) after a change of the radio channel (assignment or handover) and the corresponding L2 SAPI 0 establishment or re-establishment (at return to the old channel) the MS shall regard the PDSS2 connection as suspended. It shall then try to resume the connection:

– When the MS receives a message with the transaction identifier of the PDSS2 connection, it shall

– if it is a PDSS2 DATA message, implicitly resume that connection;

– if it is a PDSS2 RELEASE COMPLETE message, release that connection.

– If the MS did not yet perform such a release or implicit resumption, it shall send a PDSS2 RESUME REQUEST which may be:

– explicitly acknowledged by the network with a PDSS2 RESUME ACK, or

– implicitly accepted by the network with transmission of a DATA message, or

– explicitly rejected by the network with the transmission of a PDSS2 RELEASE COMPLETE message;

(all these messages with the same transaction identification).

NOTE: After having transferred the HANDOVER COMPLETE or ASSIGNMENT COMPLETE message, layer two will schedule the remaining part of an PDSS2 message, if there is any, for transmission, so that the network layer 3 may receive a PDSS2 message after the change of radio channel which was required to be transferred by the mobile station PDSS2 protocol entity before it received the indication about the channel change. Cf. GSM 04.06.

(B) after a radio link failure the MS shall regard the PDSS2 connection as suspended. It shall then decide to abort the connection or to resume it.

In order to resume it, the RR sublayer is requested to establish an RR connection. There may be further requests for RR connection establishment, e.g. for CM re-establishment; these shall prevail. The further proceeding is as described below:

– If there are only request from the PDSS2 sublayer, the MS shall send a PDSS2 RESUME REQUEST relating to one of the requesting PDSS2 protocol entities as first layer 3 message.

– Otherwise, and for further PDSS2 entities requesting the resumption. after establishment of the RR connection, the MS continues as in (A).

NOTE: The messages sent by a PDSS2 protocol entity after resumption still use the same transaction identifier and TI flag as before.

2) If during the information phase of a PDSS2 connection, the PDSS2 protocol entity becomes aware that too much data is waiting for transmission ("congestion condition"), it informs higher layers that the data transfer is suspended. If the PDSS2 protocol entity later becomes aware that the congestion condition no more exists, it informs higher layers that data transfer can be resumed.

3) If the request from higher layers to transfer data contained data with more than the maximum allowed length, the protocol entity shall reject the request with appropriate cause.