10 Radio Link Control (RLC) procedures on PDTCH and PACCH

3GPP44.160General Packet Radio Service (GPRS)Mobile Station (MS) - Base Station System (BSS) interfaceRadio Link Control / Medium Access Control (RLC/MAC) protocol Iu modeRelease 16TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

10.1 General

See 3GPP TS 44.060 sub-clause 9.0.

10.2 Procedures and parameters for peer-to-peer operation

10.2.1 Send state variable V(S)

See 3GPP TS 44.060 sub-clause 9.1.1.

10.2.2 Control send state variable V(CS)

See 3GPP TS 44.060 sub-clause 9.1.1a.

10.2.3 Acknowledge state variable V(A)

See 3GPP TS 44.060 sub-clause 9.1.2.

10.2.4 Acknowledge state array V(B)

See 3GPP TS 44.060 sub-clause 9.1.3.

10.2.5 Block sequence number BSN

See 3GPP TS 44.060 sub-clause 9.1.4.

10.2.6 Receive state variable V(R)

See 3GPP TS 44.060 sub-clause 9.1.5.

10.2.7 Receive window state variable V(Q)

See 3GPP TS 44.060 sub-clause 9.1.6.

10.2.8 Receive state array V(N)

See 3GPP TS 44.060 sub-clause 9.1.7.

10.2.9 Starting sequence number (SSN) and received block bitmap (RBB)

See 3GPP TS 44.060 sub-clause 9.1.8.

10.2.10 Window Size

See 3GPP TS 44.060 sub-clause 9.1.9.

10.2.10a RLC buffer

See 3GPP TS 44.060 sub-clause 9.1.9.3.

10.2.11 Compression

See 3GPP TS 44.060 sub-clause 9.1.10.

10.2.12 Segmentation of upper layer PDUs into RLC data units

See 3GPP TS 44.060 sub-clause 9.1.11.

If so ordered by RRC for a given signalling radio bearer using RLC acknowledged mode, in order to assure duplication avoidance at higher layer, RLC shall guarantee that no more than three upper layer PDUs shall be outstanding in the transmit window at any given time: there may be at most three upper layer PDUs that are being transmitted i.e. that have been segmented and for which the RLC PDUs are being transferred to the receiving end.

If so ordered by RRC (CRLC-CONFIG-Req primitive), the RLC transmitter may discard:

– in RLC acknowledged mode, RLC SDU(s) not yet segmented into RLC PDUs. The RLC transmitter shall notify the higher layer of all discarded RLC SDUs, if indicated (RLC-AM-DATA-DiscardReq primitive).

– in RLC unacknowledged mode, RLC SDU(s).

10.2.13 Re-assembly of upper layer PDUs from RLC data units

See 3GPP TS 44.060 sub-clause 9.1.12.

10.2.14 Segmentation of RLC/MAC control messages into RLC/MAC control blocks

See 3GPP TS 44.060 sub-clause 9.1.12a.

10.2.15 Re-assembly of RLC/MAC control messages from RLC/MAC control blocks

RLC/MAC control blocks shall be collected at the receiver until all RLC/MAC control blocks comprising an RLC/MAC control message have been received.

In MAC-Idle state, the mobile station shall be capable of receiving eight RLC/MAC control messages in parallel. If the mobile station receives RLC/MAC control blocks containing part of a ninth RLC/MAC control message while it still has RLC/MAC control blocks for eight partially received RLC/MAC control messages, the mobile station shall discard the RLC/MAC control block of the oldest partially received message.

In MAC-Shared state, MAC-Dedicated state or MAC-DTM state, the mobile station shall be capable of receiving sixteen RLC/MAC control messages in parallel. If the mobile station receives RLC/MAC control blocks containing part of a seventeenth RLC/MAC control message while it still has RLC/MAC control blocks for sixteen partially received RLC/MAC control messages, the mobile station shall discard the RLC/MAC control block of the oldest partially received message.

The mobile station shall start an instance of timer T3200 following the receipt of an RLC/MAC control block whose RTI value does not correspond to the RTI value of a partially received RLC/MAC control message or if the RLC/MAC control blocks were received on different SBPSCHs (respectively DBPSCHs). In non-DRX mode the duration of timer T3200 shall be four BS_CV_MAX block periods. In DRX mode the duration of timer T3200 shall be four times the DRX period (see 3GPP TS 43.064).

On receipt of an RLC/MAC control block containing a segment of an RLC/MAC control message such that the mobile station now has the complete RLC/MAC control message, the mobile station shall stop the corresponding instance of timer T3200.

If the mobile station discards a partially received RLC/MAC control message while the corresponding instance of timer T3200 is running, the mobile station shall stop the corresponding instance of timer T3200.

On expiry of an instance of timer T3200, the mobile station shall discard and ignore all segments of the corresponding partially received RLC/MAC control message.

Upon successful change of SBPSCH (respectively DBPSCH) allocation, the mobile station shall discard all partially received RLC/MAC control messages on SBPSCH (respectively DBPSCH) and stop the corresponding instances of timer T3200.

The mobile station shall discard any control message segment that contains an unknown TFI.

10.3 Operation during RLC/MAC control message transfer

See 3GPP TS 44.060 sub-clause 9.2.

10.4 Operation during RLC data block transfer

10.4.1 General

See 3GPP TS 44.060 sub-clause 9.3.0.

10.4.2 Countdown procedure

See 3GPP TS 44.060 sub-clause 9.3.1.

The countdown value that is included in each uplink RLC data block by the mobile station shall correspond to the RLC instance to which the RLC data block belongs. In case SFACCH is used, a TBF shall have a countdown value for each of the RLC instances multiplexed onto the TBF.

10.4.3 Delayed release of downlink Temporary Block Flow

This procedure is applicable in MAC-Shared state and in MAC-DTM state, on SBPSCH only. See 3GPP TS 44.060 sub-clause 9.3.1a.

10.4.4 Extended uplink TBF mode

This procedure is applicable in MAC-Shared state and in MAC-DTM state, on SBPSCH only.

See 3GPP TS 44.060 sub-clause 9.3.1b.

10.4.5 Acknowledged mode operation

10.4.5.1 General

See 3GPP TS 44.060 sub-clause 9.3.2.0.

10.4.5.2 Additional functionality in acknowledged EGPRS TBF Mode

See 3GPP TS 44.060 sub-clause 9.3.2.1.

10.4.5.3 Establishment of Temporary Block Flow

The establishment of a TBF occurs as described in clause 7. RLC functions related to the ARQ function shall not operate until RLC data block transfer has been initiated.

If for a given radio bearer, the uplink TBF ended with an incompletely transmitted upper layer PDU or any unacknowledged upper layer PDUs, the mobile station shall begin transmission on the new TBF corresponding to this radio bearer with the oldest unacknowledged upper layer PDU.

10.4.5.4 Operation of uplink Temporary Block Flow

See 3GPP TS 44.060 sub-clause 9.3.2.3.

10.4.5.5 Release of uplink Temporary Block Flow

See 3GPP TS 44.060 sub-clause 9.3.2.4.

10.4.5.6 Operation of downlink Temporary Block Flow

See 3GPP TS 44.060 sub-clause 9.3.2.5.

10.4.5.7 Release of downlink Temporary Block Flow

See 3GPP TS 44.060 sub-clause 9.3.2.6.

10.4.6 Unacknowledged mode operation

10.4.6.1 General

See 3GPP TS 44.060 sub-clause 9.3.3.0.

10.4.6.2 Establishment of Temporary Block Flow

If for a given radio bearer, the uplink TBF ended with an incompletely transmitted upper layer PDU, the mobile station shall begin transmission on the new TBF corresponding to this radio bearer with the last incompletely transmitted upper layer PDU.

10.4.6.3 Operation of uplink Temporary Block Flow

The network shall send PACKET UPLINK ACK/NACK messages when needed.

The mobile station shall set the Stall indicator (SI) bit to ‘0’ in all RLC data blocks of the TBF.

On SBPSCH, if the mobile station transmits the number of RLC data blocks corresponding to the RLC window size (WS),without receiving a Packet Ack/Nack message the mobile station shall start timer T3182 for the TBF. Timer T3182 shall be stopped upon reception of a PACKET UPLINK ACK/NACK message for this TBF. If timer T3182 expires, the mobile station shall decrement counter N3102 by PAN_DEC, and perform an abnormal release with access retry (see sub-clause 8.7.2).

On SBPSCH, whenever the mobile station receives a PACKET UPLINK ACK/NACK message, the mobile station shall increment N3102 by PAN_INC, however N3102 shall never exceed the value PAN_MAX. Upon cell reselection the mobile station shall set counter N3102 to the value PAN_MAX. When N3102 £ 0 is reached, the mobile station shall perform an abnormal release with cell re-selection (see sub-clause 9.4.2). If PAN_DEC, PAN_INC, or PAN_MAX are set to the value 0, counter N3102 shall be disabled.

On SBPSCH, a mobile station operating with an exclusive allocation shall start or restart timer T3184 upon reception of a PACKET UPLINK ACK/NACK message. If timer T3184 expires, the mobile station shall perform an abnormal release with access retry (see sub-clause 9.4.1).

10.4.6.4 Release of uplink Temporary Block Flow

See 3GPP TS 44.060 sub-clause 9.3.3.3.

10.4.6.5 Operation of downlink Temporary Block Flow

See 3GPP TS 44.060 sub-clause 9.3.3.4.

10.4.6.6 Release of downlink Temporary Block Flow

See 3GPP TS 44.060 sub-clause 9.3.3.5.

10.5 Abnormal release cases

10.5.1 Abnormal release with access retry

Abnormal release with access retry is described in sub-clause 8.8.3. It is applicable in MAC-Shared state and in MAC‑DTM state, on SBPSCH only.

10.5.2 Abnormal release with cell reselection

Abnormal release with cell reselection is applicable in MAC-Shared state only.

See 3GPP TS 44.060 sub-clause 9.4.2.

10.6 Uplink TBF release in extended uplink TBF mode

This procedure is applicable in MAC-Shared state and in MAC-DTM state, on SBPSCH only.

In the extended uplink TBF mode (see sub-clause 10.4.4), the network may initiate the release an uplink TBF by sending a PACKET UPLINK ACK/NACK message with the Final Ack Indicator set to ‘1’. The network shall include a valid RRBP field in the RLC/MAC control block header and clear counter N3103. The network may use the TBF Est field in the PACKET UPLINK ACK/NACK message to allow the mobile station to request the establishment of new TBF. The release of the uplink TBF, using this procedure, may be initiated at a point determined by the network.

If the PACKET UPLINK ACK/NACK message has the Final Ack Indicator bit set to ‘1’ and the following conditions are fulfilled: TBF Est field is set to ‘1’; the mobile station has new data to transmit; the mobile station has no ongoing downlink TBF, the mobile station shall release the TBF and may request the establishment of new TBF using one of the following procedures:

– If Control Ack Type parameter in System Information indicates acknowledgement is access burst, the mobile station shall transmit the PACKET CONTROL ACKNOWLEDGEMENT message with the Ctrl Ack bits set to ’00’. The mobile station shall start timer T3168 and continue to monitor the PDCH used for transmitting the PACKET CONTROL ACKNOWLEDGEMENT message. The mobile station shall stop timer T3168 upon reception of the PACKET UPLINK ASSIGNMENT message including Single Block Allocation structure or the PACKET ACCESS REJECT message. The mobile station shall use the same procedures as are used for TBF establishment using two phase access described in sub-clause 7.2.4 starting from the point where the mobile station receives the PACKET UPLINK ASSIGNMENT message including Single Block Allocation structure or the PACKET ACCESS REJECT message.

– If Control Ack Type parameter in System Information indicates acknowledgement is RLC/MAC control block, the mobile station shall transmit the PACKET RESOURCE REQUEST message and start timer T3168. The mobile station shall use the same procedures as are used for TBF establishment using two phase access described in sub-clause 7.2.4 starting from the point where the mobile station transmits the PACKET RESOURCE REQUEST message.

If the PACKET UPLINK ACK/NACK message has the Final Ack Indicator bit set to ‘1’ and the mobile station does not initiate the establishment of a new uplink TBF according to one of the procedures described above, the mobile station shall transmit the PACKET CONTROL ACKNOWLEDGEMENT message and release the TBF. If there is no ongoing downlink TBF, the mobile station in MAC-Shared state shall return to respectively MAC-Idle state; the mobile station in MAC-DTM state shall return to MAC-Dedicated state. The DRX mode procedures shall be applied as specified in sub-clause 5.4.1.8.

When the network receives the PACKET CONTROL ACKNOWLEDGEMENT message or the PACKET RESOURCE REQUEST message in the radio block indicated by the RRBP field, it may reuse the TFI and USF resources.

If the network receives the PACKET CONTROL ACKNOWLEDGEMENT message with Ctrl Ack bits set to ’00’ or the PACKET RESOURCE REQUEST message in the radio block indicated by the RRBP field and the network has set the TBF Est field to ‘1’ in the PACKET UPLINK ACK/NACK message, the network shall follow one of the following procedures:

– In case the mobile station requested the establishment of new TBF with the PACKET CONTROL ACKNOWLEDGEMENT message, the network shall respond to the mobile station with the PACKET UPLINK ASSIGNMENT message including Single Block Allocation structure or the PACKET ACCESS REJECT message on the same PDCH as the mobile station has sent the PACKET CONTROL ACKNOWLEDGEMENT message. The G-RNTI shall be used to identify the mobile station. The network shall use the same procedures as are used for TBF establishment using two phase access described in sub-clause 7.2.4 starting from the point where the network transmits the PACKET UPLINK ASSIGNMENT message including Single Block Allocation structure or the PACKET ACCESS REJECT message.

– In case the mobile station requested the establishment of new TBF with the PACKET RESOURCE REQUEST message, the network shall use the same procedures as are used for TBF establishment using two phase access described in sub-clause 7.2.4 starting from the point where the network has received the PACKET RESOURCE REQUEST message. The G-RNTI shall be used to identify the mobile station.

If the network does not receive the PACKET CONTROL ACKNOWLEDGEMENT message or the PACKET RESOURCE REQUEST message in the radio block indicated by the RRBP field, it shall increment counter N3103 and retransmit the PACKET UPLINK ACK/NACK message. If counter N3103 exceeds its limit, the network shall stop scheduling new uplink resources for the TBF, stop sending the PACKET UPLINK ACK/NACK message to the mobile station and start timer T3169.

When timer T3169 expires, the network may reuse the TFI and USF resources.

If for a given radio bearer the uplink TBF was operating in RLC acknowledged mode and there is an incompletely transmitted upper layer PDU or an upper layer PDU, which is not fully acknowledged, it shall be transmitted after establishing a new uplink TBF for this radio bearer.