Method and arrangements in a telecommunication system for handling status information of data units
A method is provided in a receiving node for handling status information of data units transmitted from a sending node to the receiving node over a radio link. The receiving node establishes that a number of data units that has been transmitted by the sending node are missing. The receiving node sends a reduced status message to the sending node over the radio link, which message is reduced such that it comprises the negative acknowledgement for a first part of missing data units and omits negative acknowledgements for the rest of the missing data units. The omitted negative acknowledgement for the rest of the missing data units will not erroneously be interpreted as correctly received data units by the sending node.
1. A method in a receiving side of an Acknowledgement Mode (AM) Radio Link Control (RLC) entity for handling status information of RLC Data Protocol Data Units (PDUs) transmitted from a peer AM RLC entity to the AM RLC entity over a radio link, each RLC Data PDU having a respective Sequence Number (SN), the method comprising the following acts:
(1) detecting that a number of RLC Data PDUs transmitted by the peer AM RLC entity are lost;
(2) constructing a STATUS PDU to include NACK_SNs for a first part of the missing RLC Data PDUs and omitting NACK_SNs for the rest of the missing RLC Data PDUs;
(3) setting an ACK_SN field of the STATUS PDU to the SN of the next not received RLC Data PDU for which a NACK_SN is omitted from the STATUS PDU;
(4) sending the STATUS PDU from the AM RLC entity to the peer AM RLC entity over the radio link; and
(5) preventing sending of a further STATUS PDU from the AM RLC entity to the peer AM RLC entity over the radio link until after expiration of a predetermined time.
2. The method according to claim 1 , wherein the act (2) further comprises:
including a special identifier in a Control PDU Type (CPT) field of the STATUS PDU to indicate the STATUS PDU.
3. The method according to claim 1 , wherein act (2) further comprises:
omitting an ACK_SN from the STATUS PDU to allow transmission of additional NACK_SNs.
4. The method according to claim 1 , further comprising:
maintaining a lower window edge corresponding to an SN of the oldest outstanding RLC Data PDU; and
maintaining an upper window edge corresponding to an SN of the highest received RLC Data PDU.
5. The method according to claim 1 , further comprising starting a timer upon the sending of act (5) and wherein the timer is set to the predetermined time.
6. A receiving side of an Acknowledgement Mode (AM) Radio Link Control (RLC) entity for handling status information of RLC Data Protocol Data Units (PDUs) transmitted from a peer AM RLC entity to the AM RLC entity over a radio link, each RLC Data PDU having a respective Sequence Number (SN), the AM RLC entity comprising at least one processor; at least one memory including computer program code which, when executed by the processor, causes the AM RLC entity to perform the acts of:
(1) detecting that a number of RLC Data PDUs transmitted by the peer AM RLC entity are lost;
(2) constructing a STATUS PDU to include NACK_SNs for a first part of the missing RLC Data PDUs and omitting NACK_SNs for the rest of the missing RLC Data PDUs;
(3) setting an ACK_SN field of the STATUS PDU to the SN of the next not received RLC Data PDU for which a NACK_SN is omitted from the STATUS PDU; (4) sending the STATUS PDU from the AM RLC entity to the peer AM RLC entity over the radio link; and
(5) preventing sending of a further STATUS PDU from the AM RLC entity to the peer AM RLC entity over the radio link until after expiration of a predetermined time.
7. The AM RLC entity according to claim 6 , wherein the STATUS PDU further comprises a special identifier in a Control PDU Type (CPT) field of the STATUS PDU to indicate the STATUS PDU.
8. The AM RLC entity according to claim 6 , wherein the STATUS PDU further lacks an ACK_SN from the STATUS PDU to allow transmission of additional NACK_SNs.
9. The AM RLC entity according to claim 6 , wherein the memory includes computer program code which, when executed by the processor, causes the AM RLC entity to send one or more second STATUS PDUs including NACK_SNs for the rest of the missing RLC Data PDUs, wherein the one or more second STATUS PDUs are incapable of causing the peer AM RLC entity to advance the transmission window.
10. The AM RLC entity according to claim 6 , wherein the memory includes computer program code which, when executed by the processor, causes the AM RLC entity to:
maintain a lower window edge corresponding to an SN of the oldest outstanding RLC Data PDU; and
maintain an upper window edge corresponding to an SN of the highest received RLC Data PDU.
11. The AM RLC entity according to claim 6 , the computer program code, when executed by the processor, starts a timer upon the sending of act (5) and wherein the timer is set to the predetermined time.
12. A method in a transmitting side of an Acknowledgement Mode (AM) Radio Link Control (RLC) entity for handling status information of RLC Data Protocol Data Units (PDUs) transmitted from the AM RLC entity to a peer AM RLC entity over a radio link, the method comprising:
transmitting a stream of RLC Data PDUs over the radio link to the peer AM RLC entity, the peer AM RLC entity correctly receiving some of the RLC Data PDUs but missing a number of RLC Data PDUs, each RLC Data PDU having a respective Sequence Number (SN);
receiving a STATUS PDU from the peer AM RLC entity over the radio link, wherein an ACK_SN field of the STATUS PDU is set to the SN of the next not received RLC Data PDU for which a NACK_SN is omitted from the STATUS PDU;
interpreting the STATUS PDU as comprising NACK_SNs for a first part of the missing RLC Data PDUs, and omitting NACK_SNs for the rest of the missing RLC Data PDUs; and
retransmitting at least a portion of the stream of RLC Data PDUs over the radio link to the peer AM RLC entity before receiving a further STATUS PDU from the peer AM RLC entity.
13. The method according to claim 12 , further comprising:
maintaining a lower window edge corresponding to an SN of the oldest outstanding RLC Data PDU for which no ACK_SN has been received.
14. The method according to claim 13 , further comprising:
advancing the lower window edge up to a next oldest outstanding RLC Data PDU in response to receiving the ACK_SN for the oldest outstanding RLC Data PDU in the STATUS PDU.
15. The method according to claim 12 , further comprising:
maintaining an upper window edge corresponding to an SN of the next RLC Data PDU to be transmitted.
16. The method according to claim 12 , wherein the STATUS PDU is interpreted as the STATUS PDU with reference to a special identifier included in a Control PDU Type (CPT) field of the STATUS PDU.
17. A transmitting side of an Acknowledgement Mode (AM) Radio Link Control (RLC) entity for handling status information of RLC Data Protocol Data Units (PDUs) transmitted from the AM RLC entity to the peer AM RLC entity over a radio link, the AM RLC entity comprising at least one processor; at least one memory including computer program code which, when executed by the processor, causes the AM RLC entity to:
(1) transmit a stream of RLC Data PDUs over the radio link to the peer AM RLC entity, the peer AM RLC entity correctly receiving some of the RLC Data PDUs but missing a number of the RLC Data PDUs, each RLC Data PDU having a respective Sequence Number (SN);
(2) receive a STATUS PDU from the peer AM RLC entity over the radio link, wherein an ACK_SN field of the STATUS PDU is set to the SN of the next not received RLC Data PDU for which a NACK_SN is omitted from the STATUS PDU; and
(3) interpret the STATUS PDU as comprising NACK_SNs for a first part of the missing RLC Data PDUs, and omitting NACK_SNs for the rest of the missing RLC Data PDUs; and
(4) retransmit at least a portion of the stream of RLC Data PDUs over the radio link to the peer AM RLC entity before receiving a further STATUS PDU from the peer AM RLC entity.
18. The AM RLC entity according to claim 17 , wherein the memory includes computer program code which, when executed by the processor, causes the AM RLC entity to interpret the STATUS PDU as the STATUS PDU with reference to a special identifier included in a Control PDU Type (CPT) field of the STATUS PDU.