3.4.21 Application Procedures

3GPP44.018GSM/EDGE Radio Resource Control (RRC) protocolMobile radio interface Layer 3 specificationRelease 17TS

3.4.21.1 General

While in dedicated mode, the following applications associated with the Radio Resource management layer may be supported in the network and MS:

3.4.21.2 Location Services (LCS)

Common procedures are defined in the Radio Resource management layer to assist these applications.

3.4.21.2A Earthquake and Tsunami Warning System (ETWS)

Mobile station support for reception of ETWS Primary Notification message is optional.

Common procedures are defined in the Radio Resource management layer to assist this application.

3.4.21.3 Application Information Transfer

The Application Information Transfer procedure enables an Application on the network side and a peer application in the MS to exchange Application Protocol Data Units (APDUs).

3.4.21.3.1 Normal Procedure without Segmentation

The maximum size of an APPLICATION INFORMATION message is 251 octets as defined in 3GPP TS 44.006. Segmentation shall not be used when an APDU fits into a single APPLICATION INFORMATION message of maximum or smaller size.

Figure 3.4.21.3.4.1: Application Information Transfer without segmentation

Either the network or MS may send an APPLICATION INFORMATION message once the MS is in dedicated mode. The APDU Data in the APPLICATION INFORMATION message shall contain a complete APDU according to the protocol in use. The APDU ID IE identifies the protocol and associated application. The APDU Flags IE indicates "First or Only Segment", "Last or Only Segment" and conveys a C/R flag transparently between the communicating applications. The C/R Flag may be used to distinguish a command from other messages and a final response from a non-final response. The use of the C/R flag is defined with respect to each application. If one or several APDUs are awaiting delivery to the data link layer in the MS and other layer 3 messages are ready to be sent on the uplink, the RR layer may allow these other layer 3 messages to be sent before the next pending APPLICATION INFORMATION message is delivered to the data link layer. On receiving an APPLICATION INFORMATION message, the receiving layer 3 entity shall deliver the message contents to the identified local application.

3.4.21.3.2 Normal Procedure with Segmentation

Segmentation is only included for support of interoperability with Legacy (3GPP R4 and older) equipment when a segmented message is received from a Legacy node.

Segmentation is applicable when an APDU is too large to fit into a single APPLICATION INFORMATION message. The procedure is applicable for either direction of transfer.

Figure 3.4.21.3.2.1: Application Information Transfer with segmentation

The sending layer 3 entity shall segment an APDU by dividing it into one or more segments exactly fitting into maximum sized APPLICATION INFORMATION messages plus a final segment fitting into an APPLICATION INFORMATION message of maximum size or smaller. Once segmented, the resulting APPLICATION INFORMATION messages shall be transferred in sequence to the data link layer for transmission, without being intersperced by other level 3 messages. The first APPLICATION INFORMATION message in the sequence shall indicate "First Segment" and "Not Last Segment". Subsequent APPLICATION INFORMATION messages except for the last shall indicate "Not First Segment" and "Not Last Segment". The last APPLICATION INFORMATION message shall indicate "Not First Segment" and "Last Segment" and shall include a C/R flag as provided by the sending application.

The receiving layer 3 entity shall reassemble any segmented APDU before transfer to the local application. The receiver may employ a timer to detect possible loss of APDU segments. If employed, the timer shall be started when the first APDU segment is received and cancelled after the last segment is received.

3.4.21.3.3 Abnormal Cases

APPLICATION INFORMATION messages are sent using "low" priority at the data link layer except for the case of ETWS, see sub-clause 3.1.6. This can lead to message loss or truncation when preempted by other "high" priority messages. A receiving layer 3 entity shall detect APDU truncation if an APPLICATION INFORMATION message is received carrying an APDU or APDU segment that is shorter than indicated by the length indicator for the APDU Data IE. This test is reliable because preemption in the data link layer guarantees that at least the first 2*N201 octets of any truncated message will be reliably transferred.

An APPLICATION INFORMATION transfer error shall be detected due to any of the following:

a) Receipt of a truncated APDU or APDU segment;

b) While performing APDU reassembly:

– receipt of any other layer 3 message defined to use SAPI 0 on the main DCCH;

– receipt of an APDU or APDU segment indicating "First or Only Segment";

– expiration of the reassembly timer (if supported);

c) While not performing APDU reassembly, receipt of an APDU segment indicating "not First or only segment";

d) Detection of any other error for a received message as defined in clause 8.

If APDU reassembly was in process when the error occurred, the receiving layer 3 entity shall discard the partially reassembled APDU and reprocess any received APDU or APDU segment that caused the error provided not an error defined in clause 8. In all other cases, any received APDU or APDU segment shall be discarded.