03.633GPPPacket Data on Signalling channels service (PDS) Service description, Stage 2TS
Identifiers for packet data protocols to be served must be specified. A special identifier indicates "unstructured"; in this case, a called party BCD number as specified in TS GSM 04.08 may be used to identify the destination of packets.
Mobile identity: For certain applications, a new mobile identity type "anonymous" has to be specified which may contain an operator specific group id and otherwise consists in a random number. A mobile station which applies the anonymous mobile identity for establishment of a PDSS1 or PDSS2 connection shall use for that establishment the access class A-AC(i) determined from its IMEI i by application of an algorithm A-AC defined below.
Algorithm A-AC: This algorithm is manufacturer dependent; it is the same for all mobile stations with equal type approval code and final assembly code. A-AC computes an access class A-AC(i) between 0 and 9 from an IMEI i. The choice of A-AC and the assignment of serial numbers to mobile equipment shall guarantee that for each access class x between 0 and 9, among the mobile stations with equal type approval code and final assembly code, more than 8% and less than 12% have access class x determined from their IMEI by application of A-AC. This requirement applies if there are more than 49 mobile stations with equal type approval code and final assembly code.