The MS radio access capability information element contains the A/Gb mode radio capabilities of the MS (e.g. multislot capability, power class), and more generally all the information that should be known by the BSS in order to handle radio resources for that MS with GERAN. The UTRAN Inter RAT handover information that can be sent in the Attach Complete/RA Update Complete contains the information that the BSS needs for inter-RAT handover to other RATs.
The MS radio access capability is a container for a multiplicity of radio access technology-dependent information, i.e. within the MS radio access capability there are independent sub-fields for various technologies such as GSM 900 and GSM 1800. The coding shall allow a BSS to extract only the sub-fields relevant to it without interpreting the other sub fields. This ensures that the MS radio access capability does not need to be interpreted by the NSS, and the full MS radio access capability is always sent by the MS to the SGSN, and thereafter provided to the BSS irrespective of the actual BSS capabilities.
The SGSN shall provide the MS radio access capability as an information element on the Gb interface. It is the responsibility of the SGSN to provide the BSS with the most recent MS radio access capability received from the MS. The MS radio access capability information element can be included in a downlink transfer request, or be sent in a specific message that updates the MS radio access capability information in the BSS. The BSS may at any time request the MS radio access capability for a given MS to be transmitted from the SGSN to the BSS.
Together with the MS radio access capability, the SGSN shall provide the IMSI of the MS when this is known. For a BSS supporting DTM, the IMSI is stored at the BSS and used for radio resource co-ordination; e.g. for a DTM MS.
A specific optimisation allows the BSS to receive a reduced MS radio access capability at initial access directly from the MS. This enables the BSS not to wait for the full MS radio access capability to be provided by the SGSN, and is therefore quicker for the initial MS-originated transmission. The reduced MS radio access capability can be carried in several RR messages depending on the access method, e.g. in the initial random access message, or in the first uplink radio block. Details are provided in TS 24.008
and TS 44.060
If stored, the SGSN shall provide the Inter RAT handover information and MS Classmark 2 and MS Classmark 3 as information elements on the Gb interface when a Packet Flow Context is established. MS Classmark 2 and 3 are included to support the case that a SRVCC handover is needed following PS domain handover from GERAN to UTRAN/E-UTRAN.
When the MS performs a Routeing Area Update (e.g. at GERAN-UTRAN change with change of RA in idle mode, and, GERAN-UTRAN Handover) the MS radio access capability shall be sent to the SGSN in the Routeing Area Update Request message. The SGSN then provides the BSS with the MS radio access capability.
At inter-RAT Handover, the source, target and all other RATs' MS/UE radio capability (except the UE E-UTRA capability) are exchanged within the container information elements. To support subsequent connections, an A/Gb mode SGSN supporting inter-RAT handover requests the MS to send the Inter RAT handover information in the RA Update Complete message.
To allow for the addition of future radio technologies, frequency bands, and other enhancements, the SGSN shall store the Inter RAT handover information even if it is larger than specified in TS 24.008
, up to a maximum size of 255 octets.
To allow for the addition of future radio technologies, frequency bands, and other enhancements, the SGSN shall store the MS radio access capability even if it is larger than specified in TS 24.008
, up to a maximum size of 255 octets.