Method and arrangements in a telecommunication system for handling status information of data units

Abstract

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 detects that a number of RLC Data PDUs transmitted by the peer AM RLC entity are missing, and 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. The receiving node further sets the ACK_SN field of the status PDU such that the status PDU includes only acknowledgments for PDUs having a sequence number equal to or less than the minimum sequence number omitted from the status PDU, and sends sending the STATUS PDU from the AM RLC entity to the peer AM RLC entity over the radio link.

What is claimed is: 
     
         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:
 detecting that a number of RLC Data PDUs transmitted by the peer AM RLC entity are missing;   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;   setting an ACK_SN field of the STATUS PDU such that the STATUS PDU includes only acknowledgments for PDUs having a sequence number equal to or less than a minimum sequence number omitted from the STATUS PDU; and   sending the STATUS PDU from the AM RLC entity to the peer AM RLC entity over the radio link.   
     
     
         2 . The method according to  claim 1 , wherein the constructing step 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 the constructing step 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:
 constructing one or more second STATUS PDUs to include 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.   
     
     
         5 . 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.   
     
     
         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:
 detecting that a number of RLC Data PDUs transmitted by the peer AM RLC entity are missing;   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;   set an ACK_SN field of the STATUS PDU such that the STATUS PDU includes only acknowledgments for PDUs having a sequence number equal to or less than a minimum sequence number omitted from the STATUS PDU; and   send the STATUS PDU from the AM RLC entity to the peer AM RLC entity over the radio link.   
     
     
         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 . 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 such that the STATUS PDU includes only acknowledgments for PDUs having a sequence number equal to or less than a minimum sequence number omitted from the STATUS PDU; and 
   interpreting the STATUS PDU as comprising NACK_SNs for the first part of the missing RLC Data PDUs, and omitting NACK_SNs for the rest of the missing RLC Data PDUs.   
     
     
         12 . The method according to  claim 11 , further comprising:
 receiving 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 AM RLC entity to advance the transmission window.   
     
     
         13 . The method according to  claim 11 , 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 11 , 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 11 , 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 such that the STATUS PDU includes only acknowledgments for PDUs having a sequence number equal to or less than a minimum sequence number 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. 
     
     
         19 . 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 maintain a lower window edge corresponding to an SN of the oldest outstanding RLC Data PDU for which no ACK_SN has been received. 
     
     
         20 . The AM RLC entity according to  claim 19 , wherein the memory includes computer program code which, when executed by the processor, causes the AM RLC entity to advance 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.