Harq handling at relay node reconfiguration

Abstract

A radio access network comprises a donor base station node ( 29 ) and a relay base station node ( 20 ). The relay base station node ( 29 ) participates in communications across a first radio interface with a wireless terminal ( 30 ) and also participates in communications over a backhaul link across a second radio interface, the second radio interface reusing at least some functionality of the first interface. The donor base station node ( 28 ) configures a subframe configuration pattern. The subframe configuration pattern is arranged to specify which subframe(s) of a frame structure may be utilized for the backhaul link. As a result of subframe configuration, a HARQ process state in a HARQ process at one of the base station nodes is known by the other base station node by any of several operational modes.

1 - 42 . (canceled) 
     
     
         43 . A method of operating a radio access network comprising:
 recognizing, by a first base station node, a HARQ process state comprising a subframe configuration pattern specifying at least one subframe of a frame structure that is utilized for a backhaul link between the first base station node and a second base station node;   reconfiguring, by the first base station node the HARQ process state by modifying the subframe configuration pattern; and   in response to the reconfiguration of the HARQ process state, making, by the first base station node, the reconfiguration known to the second base station node.   
     
     
         44 . The method of  claim 43 , wherein the first base station node comprises a relay base station and the second base station node comprises a donor base station. 
     
     
         45 . The method of  claim 43 , wherein the first base station node comprises a donor base station and the second base station node comprises a relay base station. 
     
     
         46 . The method of  claim 45 , wherein reconfiguring the HARQ process state is selected from the group consisting of:
 changing a number of HARQ processes in at least one of the donor base station or the relay station; and   changing a mapping of HARQ processes to subframes of the frame structure.   
     
     
         47 . The method of  claim 43 , wherein making the HARQ process state in known to the second base station node comprises:
 mapping a HARQ process executed at the first base station node and a corresponding HARQ process executed at the second base station node to one or more subframes; and   providing a value for a HARQ process state variable to the HARQ process executed at the first base station node and to the corresponding HARQ process executed at the second base station node.   
     
     
         48 . The method of  claim 47 , wherein the HARQ process state variable comprises a new data indicator (NDI). 
     
     
         49 . The method of  claim 43 , wherein making the HARQ process state in a HARQ process at the first base station node known to the second base station node comprises performing a medium access control (MAC) reset procedure at the first base station node. 
     
     
         50 . The method of  claim 43 , wherein making the HARQ process state in a HARQ process at the first base station node known by the second base station node comprises:
 flushing uplink HARQ buffers in the first base station node; and   either:
 considering a next received transmission of a transport block in the first base station node as a new transmission; or 
 flushing downlink HARQ buffers in the first base station node. 
   
     
     
         51 . The method of  claim 50 , wherein considering the next received transmission of the transport block as the new transmission is selected from the group consisting of:
 setting a new data indicator (NDI) to a value which is toggled compared to a previously used NDI value for the transport block for the HARQ process; and   considering the NDI to have been toggled compared to a previous transmission on the same transport block on the same HARQ process if a change in the subframe configuration pattern has occurred since the previous transmission.   
     
     
         52 . The method of  claim 43 , wherein making the HARQ process state in a HARQ process at the first base station node known by the second base station node comprises:
 for a downlink HARQ process after the subframe configuration, scheduling the first base station node with a specified value of a new data indicator (NDI) on each downlink HARQ process corresponding to a toggling of the NDI from a last transmission on each HARQ process by first scheduling a first transmission with an NDI, and then scheduling a second transmission with an NDI which is toggled compared to the first transmission;   for a uplink HARQ process, providing a wireless terminal communicating with the first base station node with a first uplink grant and associating with the first uplink grant a new data indicator (NDI) value for the HARQ process and transport block and subsequently providing the wireless terminal with a second uplink grant associated with a new NDI value which is toggled compared to the first uplink (UL) grant NDI.   
     
     
         53 . The method of  claim 52 , wherein the method further comprises using dummy data in the first transmission. 
     
     
         54 . The method of  claim 52 , wherein for the downlink HARQ process scheduling the first base station node with the specified value of the new data indicator (NDI) on each HARQ process comprises keeping a record of a previous state of each HARQ process and toggling the new data indicator (NDI) in a next downlink assignment. 
     
     
         55 . The method of  claim 43 , wherein making the HARQ process state in a HARQ process at the first base station node known by the second base station node comprises providing the HARQ process executed at the first base station node and the corresponding HARQ process executed at the second base station node with common knowledge of HARQ process mapping and HARQ process states. 
     
     
         56 . The method of  claim 55 , wherein providing the HARQ process executed at the first base station node and the corresponding HARQ process executed at the second base station node with common information of HARQ process mapping comprises providing common information regarding at least one of:
 mapping of HARQ process number to subframe(s); and   pre-configuration HARQ process number to post-configuration HARQ process number.   
     
     
         57 . The method of  claim 55 , wherein providing common information of HARQ process mapping and HARQ process states comprises the providing common information as predetermined information or as information signaled between the donor base station node and the relay base station node. 
     
     
         58 . The method of  claim 55 , further comprising reusing pre-configuration soft information stored in HARQ buffers of the HARQ processes after the configuration. 
     
     
         59 . The method of  claim 55 , further comprising:
 determining that a number of HARQ processes in use after the configuration is less than a number of HARQ processes in use before the configuration whereby after the reconfiguration at least one HARQ process is a superfluous HARQ process; and   performing a step selected from the group consisting of:
 removing any superfluous downlink HARQ processes in a predetermined pattern; and 
 for both uplink HARQ processes and downlink HARQ processes, prioritizing removal of HARQ processes that have no pending transmission. 
   
     
     
         60 . A first base station node of a radio access network which participates in communications over a backhaul link across a radio interface with a second base station node, the first base station node comprising:
 a memory configured to store; and   a processor in communication with the memory, the processor operable to:
 recognizing a HARQ process state comprising a subframe configuration pattern specifying at least one subframe of a frame structure that is utilized for the backhaul link between the first base station node and the second base station node; 
 reconfiguring the HARQ process state by modifying the subframe configuration pattern; and 
 in response to the reconfiguration of the HARQ process state, making the reconfiguration known to the second base station node. 
   
     
     
         61 . The first base station node of  claim 60 , wherein the first base station node comprises a relay base station and the second base station node comprises a donor base station. 
     
     
         62 . The first base station node of  claim 60 , wherein the first base station node comprises a donor base station and the second base station node comprises a relay base station. 
     
     
         63 . The first base station node of  claim 62 , wherein the processor is operable to reconfigure the HARQ process state by performing at least one step selected from the group consisting of:
 changing a number of HARQ processes in at least one of the donor base stator the relay station node; and   changing a mapping of HARQ processes to subframes of the frame structure.   
     
     
         64 . The first base station node of  claim 60 , wherein the processor is operable to make the HARQ process state known to the second base station node:
 mapping a HARQ process executed at the first base station node and a corresponding HARQ process executed at the second base station node to one or more subframes; and   providing a value for a HARQ process state variable to the HARQ process executed at the first base station node and to the corresponding HARQ process executed at the second base station node.   
     
     
         65 . The first base station node of  claim 64 , wherein the HARQ process state variable comprises a new data indicator (NDI). 
     
     
         66 . The first base station node of  claim 60 , wherein the processor is operable to make the HARQ process state in a HARQ process at the first base station node known to the second base station node by performing a medium access control (MAC) reset procedure at the first base station node. 
     
     
         67 . The first base station node of  claim 60 , wherein the processor is operable to make the HARQ process state in a HARQ process at the first base station node known by the second base station node by:
 flushing uplink HARQ buffers in the first base station node; and   either:
 considering a next received transmission of a transport block in the first base station node as a new transmission; or 
 flushing downlink HARQ buffers in the first base station node. 
   
     
     
         68 . The first base station node of  claim 67 , wherein when considering the next received transmission of the transport block as the new transmission the processor is operable to perform at least one step selected from the group consisting of:
 setting a new data indicator (NDI) to a value which is toggled compared to a previously used NDI value for the transport block for the HARQ process; and   considering the NDI to have been toggled compared to a previous transmission on the same transport block on the same HARQ process if a change in the subframe configuration pattern has occurred since the previous transmission.   
     
     
         69 . The first base station node of  claim 60 , wherein the processor is operable to make the HARQ process state in a HARQ process at the first base station node known by the second base station node by:
 for a downlink HARQ process after the subframe configuration, scheduling the first base station node with a specified value of a new data indicator (NDI) on each downlink HARQ process corresponding to a toggling of the NDI from a last transmission on each HARQ process by first scheduling a first transmission with an NDI, and then scheduling a second transmission with an NDI which is toggled compared to the first transmission;   for a uplink HARQ process, providing a wireless terminal communicating with the first base station with a first uplink grant and associating with the first uplink grant a new data indicator (NDI) value for the HARQ process and transport block and subsequently providing the wireless terminal with a second uplink grant associated with a new NDI value which is toggled compared to the first uplink (UL) grant NDI.   
     
     
         70 . The first base station node of  claim 69 , wherein the processor is further operable to use dummy data in the first transmission. 
     
     
         71 . The first base station node of  claim 69 , wherein for the downlink HARQ process the processor is operable to schedule the first base station node with the specified value of the new data indicator (NDI) on each HARQ process by keeping a record of a previous state of each HARQ process and toggling the new data indicator (NDI) in a next downlink assignment. 
     
     
         72 . The first base station node of  claim 60 , wherein the processor is operable to make the HARQ process state in a HARQ process at the first base station node known by the second base station node by providing the HARQ process executed at the first base station node and the corresponding HARQ process executed at the second base station node with common knowledge of HARQ process mapping and HARQ process states. 
     
     
         73 . The first base station node of  claim 72 , wherein, when providing the HARQ process executed at the first base station node and the corresponding HARQ process executed at the second base station node with common information of HARQ process mapping, the processor is operable to provide common information regarding at least one of:
 mapping of HARQ process number to subframe(s); and   pre-configuration HARQ process number to post-configuration HARQ process number.   
     
     
         74 . The first base station node of  claim 72 , wherein the processor is operable to provide common information of HARQ process mapping and HARQ process states by providing common information as predetermined information or as information signaled between the donor base station node and the relay base station node. 
     
     
         75 . The first base station node of  claim 72 , wherein the processor is operable to reuse pre-configuration soft information stored in HARQ buffers of the HARQ processes after the configuration. 
     
     
         76 . The first base station node of  claim 72 , wherein the processor is further operable to:
 determine that a number of HARQ processes in use after the configuration is less than a number of HARQ processes in use before the configuration, whereby after the reconfiguration at least one HARQ process is a superfluous HARQ process; and   perform a step selected from the group consisting of:
 removing any superfluous downlink HARQ processes in a predetermined pattern; and 
 for both uplink HARQ processes and downlink HARQ processes, prioritizing removal of HARQ processes that have no pending transmission.