11.2.2 Packet Control Acknowledgement

3GPP44.060General Packet Radio Service (GPRS)Mobile Station (MS) - Base Station System (BSS) interfaceRadio Link Control / Medium Access Control (RLC/MAC) protocolRelease 17TS

This message is sent on the PACCH from the mobile station to the network. In Iu mode, it is also sent on FACCH, SACCH and SDCCH from the mobile station to the network. The message is formatted either as an RLC/MAC control block using the PACCH block format defined in 3GPP TS 44.004 or as 4 identical access bursts using the PACCH short acknowledgement block format defined in 3GPP TS 44.004. If the CTRL_ACK_EXTENSION field is to be included (i.e. the MS is sending acknowledgement information for a RLC/MAC control message which it knows to have been segmented using extended RLC/MAC control message segmentation – see Table 11.2.2.2) the message shall be formatted as an RLC/MAC control block. Otherwise, if sent as response to a Packet Polling Request message this latter message shall specify the format of the Packet Control Acknowledgement message. Otherwise the System Information parameter CONTROL_ACK_TYPE indicates which format the mobile station shall use. The order of bit transmission is defined in 3GPP TS 44.004. The numbering, assembling and field mapping conventions defined for RLC/MAC control blocks in sub-clause 10.0b shall apply.

The RLC/MAC control block format is shown in table 11.2.2.1 and table 11.2.2.2.

The access burst format is either 11-bit or 8-bit and is coded as shown in table 11.2.2.1. The mobile station shall use the format indicated by the System Information parameter ACCESS_BURST_TYPE. The mobile station shall transmit the access burst four times, one time in each TDMA frame of the uplink radio block.

Message type: PACKET CONTROL ACKNOWLEDGEMENT

Direction: mobile station to network

Table 11.2.2.1: PACKET CONTROL ACKNOWLEDGEMENT

< Packet Control Acknowledgement message content > ::= — RLC/MAC control block format

< TLLI/G-RNTI : bit (32) >

< CTRL_ACK : bit (2) >

{ null | 0 bit** = < no string > — Receiver backward compatible with earlier version of the protocol

| 1 — Release 5 additions

{ 0 | 1 < TN_RRBP : bit (3) > }

{ 0 | 1 < G-RNTI extension : bit (4) > }

{ null | 0 bit** = < no string > — Receiver backward compatible with earlier version of the protocol

| 1 — Release 6 additions

{ 0 | 1 < CTRL_ACK_EXTENSION : bit (9) > }

< padding bits > } } ;

< Packet Control Acknowledgement 11 bit message > ::= — 11-bit access burst format

< MESSAGE_TYPE : bit (9) == 1111 1100 1 >

| { < MESSAGE_TYPE : bit (6) == 110111 >

< TN_RRBP : bit (3) > }

< CTRL_ACK : bit (2) > ;

< Packet Control Acknowledgement 8 bit message > ::= — 8-bit access burst format

< MESSAGE_TYPE : bit (6) == 0111 11 >

| { < MESSAGE_TYPE : bit (3) == 000>

< TN_RRBP : bit (3) > }

< CTRL_ACK : bit (2) > ;

Table 11.2.2.2: PACKET CONTROL ACKNOWLEDGEMENT

TLLI/G-RNTI (32 bit field)
This field contains the TLLI/G-RNTI of the mobile station. This field is encoded as defined in sub-clause 12.16.

CTRL_ACK (2 bit field)
This field contains acknowledgement information for the group of RLC/MAC control blocks that make up an RLC/MAC control message. The mobile station shall set the CTRL_ACK field to indicate which segments of an RLC/MAC control message have been received by the time of transmission of the PACKET CONTROL ACKNOWLEDGEMENT message.

This field can also be coded to contain the information if the mobile station is requesting the establishment of new TBF. This coding is allowed only when the message is sent in access burst format as a response to the PACKET UPLINK ACK/NACK message with Final Ack Indicator set to ‘1’ and TBF Est is set to ‘1’.

If the PACKET CONTROL ACKNOWLEDGEMENT message is being transmitted in response to a valid RRBP field received as part of an RLC/MAC block with Payload Type equal to ’10’, the CTRL_ACK field shall be set according to the following table:

bit

2 1

0 0 in case the message is sent in access burst format, the same meaning as for the value ’11’ except that the mobile station is requesting new TBF. Otherwise the bit value ’00’ is reserved and shall not be sent. If received it shall be intepreted as bit value ’01’.

0 1 the MS received an RLC/MAC control block addressed to itself and with RBSN = 1, and did not receive an RLC/MAC control block with the same RTI value and RBSN = 0.

1 0 the MS received an RLC/MAC control block addressed to itself and with RBSN = 0, and did not receive an RLC/MAC control block with the same RTI value and RBSN = 1. This value is sent irrespective of the value of the FS bit.

1 1 the MS received two RLC/MAC blocks with the same RTI value, one with RBSN = 0 and the other with RBSN = 1.

If the PACKET CONTROL ACKNOWLEDGEMENT message is being transmitted in response to a valid RRBP field received as part of an RLC/MAC block with Payload Type not equal to ’10’, the CTRL_ACK field shall be set to the value ’11’ in case the message is sent in normal burst format or in case the mobile station is not requesting new TBF. In case the message is sent in access burst format and the mobile station is requesting new TBF, the CTRL_ACK field shall be set to the value ’00’.

If the PACKET CONTROL ACKNOWLEDGEMENT message is being transmitted in response to a polling request in an IMMEDIATE ASSIGNMENT message received on CCCH, the CTRL_ACK field shall be set to the value ’11’.

If the mobile station receives an RLC/MAC block with Payload Type equal to ’10’ and RLC/MAC block with Payload Type not equal to ’10’ with different RRBP values such that they specify the same uplink block, the mobile station shall set the CTRL_ACK field according to the group of RLC/MAC control blocks that the RLC/MAC block with Payload Type equal to ’10’ belongs.

CTRL_ACK_EXTENSION (9 bit field)
This field contains acknowledgement information for the group of up to nine RLC/MAC control blocks that make up an RLC/MAC control message sent using extended RLC/MAC control message segmentation. The mobile station shall set the CTRL_ACK_EXTENSION field to indicate which segments of an RLC/MAC control message addressed to itself have been received by the time of transmission of the PACKET CONTROL ACKNOWLEDGEMENT message. Bit at index n in the CTRL_ACK_EXTENSION field indicates whether RLC/MAC control block "10 – n" has been received. This bit shall be set to ‘1’ if the corresponding RLC/MAC control block has been received and to ‘0’ otherwise. When CTRL_ACK_EXTENSION field is present, the CTRL_ACK field shall be ignored. The CTRL_ACK_EXTENSION field shall be included only if the MS knows an RLC/MAC control message has been segmented using extended RLC/MAC control message segmentation (i.e. the MS has received at least one segment other than the first segment of an RLC/MAC control message segmented using extended RLC/MAC control message segmentation). The CTRL_ACK_EXTENSION field shall not be included if the MS has only received the first segment of an RLC/MAC control message and hence does not know whether extended RLC/MAC control message segmentation is used.

bit
9 8 7 6 5 4 3 2 1

0 0 0 0 0 0 0 0 0 this value is reserved and shall not be sent.

1 0 0 0 0 0 0 0 0 this value is reserved and shall not be sent.

…

0 0 1 0 1 0 0 0 0 the MS received the 3rd and 5th segments (i.e. with RBSN = ‘1’ and RBSNe = ‘001’ and RBSN = ‘1’ and RBSNe = ‘011’ respectively) of an RLC/MAC control message sent using a given RTI value and did not receive any other RLC/MAC control block(s) with other RBSN and RBSNe values having that same RTI value.

…

1 1 1 1 1 1 1 1 1 the MS received all nine segments of an RLC/MAC control message.

If the mobile station receives an RLC/MAC block with Payload Type equal to ’10’ and an RLC/MAC block with Payload Type not equal to ’10’ with different RRBP values such that they specify the same uplink block, the mobile station shall set the CTRL_ACK_EXTENSION field according to the group of RLC/MAC control blocks that the RLC/MAC block with Payload Type equal to ’10’ belongs.

TN_RRBP (3 bit field)
This field contains the timeslot number of the downlink PDCH on which the RRBP was received. The TN_RRBP field is coded as the binary representation of the timeslot number as defined in 3GPP TS 45.002.

G-RNTI extension (4 bit field)
This field contains the extra 4 bits of the G-RNTI not included in the TLLI / G-RNTI field which are necessary to provide a unique identifier in Iu mode.