3.4.23 RR procedures related to packet resource maintenance while in dual transfer mode

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

3.4.23.1 General

Once the mobile station enters the dual transfer mode, the existent procedures apply (see 3GPP TS 44.060). Some exceptions to the existent procedures while in dual transfer mode are:

– When all packet resources have been released (or aborted), the mobile station returns to dedicated mode.

– When the mobile station is in dual transfer mode, it shall ignore any PACKET CELL CHANGE ORDER or PACKET ASSIGNMENT messages and shall remain in dual transfer mode.

– When the mobile station receives a HANDOVER COMMAND, HANDOVER TO UTRAN COMMAND, HANDOVER TO CDMA2000 COMMAND, HANDOVER TO IU MODE COMMAND or ASSIGNMENT COMMAND message, it shall abandon the packet resource immediately, enter dedicated mode and perform the handover or assignment procedure, respectively.

– When the mobile station receives a DTM ASSIGNMENT COMMAND message whilst in dual transfer mode, it shall follow procedures specified in sub-clause 3.4.23.2.

– As stated in 3GPP TS 45.008, no GPRS measurement reporting is performed.

In case the network has to change the frequency parameters and needs to specify a start time for the RR connection, the frequency redefinition procedure shall be used (see sub-clause 3.4.5) If the RR connection can be started immediately after resource reallocation with change of frequency parameters, the DTM ASSIGNMENT COMMAND message or the frequency redefinition procedure shall be used.

In case the network has to change the channel mode of the traffic channel, the channel mode modify procedure shall be used (see sub-clause 3.4.6).

The mobile station remains in dual transfer mode until the RR connection or all the packet resources are released.

When the mobile station receives a DTM ASSIGNMENT COMMAND message encapsulated in a PACKET CS COMMAND message, it shall follow procedures specified in sub-clause 3.4.23.2.2 and 3.4.23.2.3 with the exceptions described in 3GPP TS 44.060.

3.4.23.2 RR and packet resource reallocation whilst in dual transfer mode

3.4.23.2.1 General

In dual transfer mode an intracell change of channel can be requested by upper layers for changing the channel type, or decided by the RR sublayer, e.g. for an internal handover or for the reallocation of all the resources of the mobile station. The purpose is to modify completely the physical channel configuration of the mobile station without change in synchronization while staying in the same cell.

The mobile station and the network shall change neither the RLC mode nor TBF mode of an already established TBF during resource reallocation. The change of RLC mode or TBF mode shall be achieved through release of the TBF and establishment of a new TBF with the new RLC mode or TBF mode.

The usage of the DTM ASSIGNMENT COMMAND message depends on whether the mobile station supports multiple TBF procedures, DTM enhancements or Downlink Dual Carrier:

– If the mobile station does not support any of multiple TBF procedures, DTM enhancements or Downlink Dual Carrier, the DTM ASSIGNMENT COMMAND message is used by the network to reallocate the DTM resources assigned to a mobile station when the CS channel needs to be reallocated. All of the ongoing TBFs shall be addressed by the DTM ASSIGNMENT COMMAND message. The procedures in 3GPP TS  44.060 shall be used to establish an additional TBF or to release an ongoing TBF.

– If the mobile station supports multiple TBF procedures, DTM enhancements or Downlink Dual Carrier, the DTM ASSIGNMENT COMMAND message may be used by the network, when the CS channel needs to be reallocated, in order to reallocate the DTM resources assigned to a mobile station, to assign new uplink and downlink TBFs and to implicitly release TBFs.

This procedure includes:

– the suspension of normal operation except for RR management (layer 3);

– the release of the main signalling link and of the other data links as defined in sub-clause 3.1.4;

– the disconnection of TCHs and PDTCHs;

– the deactivation of previously assigned channels (layer 1);

– the activation of the new channels and their connection if applicable;

– the triggering of the establishment of the data link connections for SAPI = 0.

3.4.23.2.2 Normal resource reallocation case

The reallocation of resources assigned to a mobile station is initiated by the network using a DTM ASSIGNMENT COMMAND message. Once the DTM ASSIGNMENT COMMAND message has been transmitted the timer T3107 is started on the network side. The DTM ASSIGNMENT COMMAND message may be used to change the ciphering mode by including the Ciphering Mode Setting IE when a mobile station supports the reception of this IE in the DTM ASSIGNMENT COMMAND message. The DTM ASSIGNMENT COMMAND message shall not contain a Cipher Mode Setting IE that indicates "start ciphering" unless a CIPHERING MODE COMMAND message has been transmitted earlier in the RR connection or ciphering has been started earlier in UTRAN. If such a DTM ASSIGNMENT COMMAND message is received it shall be regarded as erroneous, a DTM ASSIGNMENT FAILURE with cause "Protocol error unspecified" message shall be returned immediately, and no further action taken.

Upon receipt of the DTM ASSIGNMENT COMMAND message, the mobile station initiates a local end release of link layer connections, disconnects the physical channels, commands the switching to the assigned channel and initiates the establishment of lower layer connection (this includes the activation of the channel, their connection and the establishment of the main signalling link).

Upon receipt of the DTM ASSIGNMENT COMMAND message, the mobile station shall then switch to the assigned PDCHs and follow the applicable procedures specified in 3GPP TS 44.060. Neither the TLLI (in A/Gb mode) nor the G-RNTI (in Iu mode) shall be included in any of the uplink RLC data blocks in that case. If the mobile station supports multiple TBF procedures or DTM enhancements and the network addresses only a subset of the ongoing TBFs, the mobile station shall consider all ongoing TBFs not addressed by the DTM ASSIGNMENT COMMAND message as released. If while waiting for the frame number indicated by the TBF starting time the mobile station receives the DTM ASSIGNMENT COMMAND message, the mobile station shall act upon the most recently received uplink or downlink assignment and shall ignore the previous uplink or downlink assignment.

After the main signalling link is successfully established, the mobile station returns an ASSIGNMENT COMPLETE message, specifying cause "normal event", to the network on the main DCCH. The reallocation of resources is completed for the mobile station when the ASSIGNMENT COMPLETE message is sent and for the network when it is received. The network then stops timer T3107. The sending of the ASSIGNMENT COMPLETE message on the mobile station side and its receipt on the network side allow the resumption of the transmission of signalling layer messages other than those belonging to RR management.

If the mobile station has requested one or more new uplink TBFs (as specified in 3GPP TS 44.060) and a DTM ASSIGNMENT COMMAND message is received from the network before resources are allocated for the requested uplink TBFs, the mobile station shall:

– follow the reallocation procedure as specified in this sub-clause;

– if the mobile station supports multiple TBF procedures or DTM enhancements it shall stop the instance of the RLC timer T3168 associated with the uplink TBF receiving a resource allocation (as specified in 3GPP TS 44.060);

– wait for the network response to the outstanding uplink TBF requests on the newly allocated resources.

3.4.23.2.3 Abnormal cases

In the following cases, a resource re-allocation failure has occurred :

a) If a DTM ASSIGNMENT COMMAND message indicates resources in a non-supported frequency band.

b) If the information available in the mobile station after the reception of a DTM ASSIGNMENT COMMAND message does not satisfactorily define uplink packet resources if uplink packet resources were established or downlink packet resources if downlink packet resources were established.

c) If a DTM ASSIGNMENT COMMAND message includes a mobile allocation or a frequency list that indexes frequencies in more than one frequency band.

d) If a DTM ASSIGNMENT COMMAND message assigns resources not compliant with the multislot capabilities of the mobile station.

e) If the mobile station has no current CA and if it needs a CA to analyse the DTM ASSIGNMENT COMMAND message.

f) If the DTM ASSIGNMENT COMMAND message instructs the mobile station to use a channel description or mode that it does not support.

g) If the DTM ASSIGNMENT COMMAND message does not include any uplink or downlink packet resources, except if encapsulated in a PACKET CS COMMAND message (as specified in 3GPP TS 44.060).

h) If the DTM ASSIGNMENT COMMAND message includes a Channel Mode IE indicating multi-rate speech codec but the Multi-Rate configuration IE is missing and no old multi-rate configuration exists.

i) If the DTM ASSIGNMENT COMMAND message includes a Channel Mode IE indicating multi-rate speech codec and the possibly included Multi-Rate configuration IE is inconsistent.

The MultiRate Configuration IE shall be considered as inconsistent by the mobile station if:

– the active set does not include any codec mode or the active set includes more than four codec modes; or

– one or more codec modes of the active codec set are not supported by the assigned channel; or

– the threshold and hysteresis values are not set according to requirements given in 3GPP TS 45.009.

j) If the DTM assignment command message, sent to a mobile station that does not support any of multiple TBF procedures, DTM enhancements or Downlink Dual Carrier, addresses more or fewer TBFs than the MS currently has been allocated.

If the DTM assignment command message, sent to a mobile station that supports multiple TBF procedures, DTM enhancements or Downlink Dual Carrier, contains uplink assignments (including PFI values) for which no TBF was requested.

k) If the DTM ASSIGNMENT COMMAND message includes the description of a SDCCH channel.

l) If the DTM ASSIGNMENT COMMAND message includes a mode of ciphering not supported by the mobile station.

In any of these cases, the mobile station shall remain in DTM mode on the old configuration and return a DTM ASSIGNMENT FAILURE message on the current main DCCH with one of the following corresponding cause values:

– In case of abnormal cases a), c) above, "frequency not implemented";

– In case of abnormal cases b), d), g), k), j), l) above, "protocol error unspecified";

– In case of abnormal case e) above, "no cell allocation available";

– In case of abnormal cases f), h), i) above, "channel mode unacceptable".

In addition:

– If the establishment of the new main DCCH fails, all the allocated packet resources described in the new configuration in the DTM ASSIGNMENT COMMAND message are released; the mobile station shall revert to the old channel in dedicated mode, trigger the establishment of the main DCCH and send a DTM ASSIGNMENT FAILURE message on the main DCCH with cause value "lower layer failure" ; if an uplink TBF was active when the mobile station received the DTM ASSIGNMENT COMMAND message, the mobile station shall initiate the establishment of a new uplink TBF using the appropriate DTM procedure on the main DCCH, defined in sub-clause 3.4.22.1.

– If a lower layer failure happens on the circuit switched resource while attempting to connect back to the old channel, the radio link failure procedure is applied (see sub-clause 3.4.13.2).

– If a lower layer failure happens on re-allocated packet resources (such as T3180 or T3190 expiry ; see 3GPP TS 44.060) before the ASSIGNMENT COMPLETE message has been sent, all packet resources are released ; the mobile station shall revert to dedicated mode on the new channel ; if an uplink TBF was active when the mobile station received the DTM ASSIGNMENT COMMAND message, the mobile station shall initiate the establishment of a new uplink TBF using the appropriate DTM procedure on the main DCCH, defined in sub-clause 3.4.22.1 once the new main DCCH has been successfully established.

When receiving the DTM ASSIGNMENT FAILURE message, the network stops T3107.

On the network side, if timer T3107 elapses before either the ASSIGNMENT COMPLETE message has been received on the new channel or a DTM ASSIGNMENT FAILURE message is received on the old channel; the old channel and the new channel are released.

On the network side, lower layer failures occurring on the old channel after the sending of the DTM ASSIGNMENT COMMAND message are ignored. Lower layer failures occurring after the receipt of the SABM frame on the new main DCCH are treated following the general rules (cf. sub-clause 3.5.2).