Reception of downlink data for coordinated multi-point transmission in the event of fall-back

Abstract

Systems and methods for fall-back rate-matching and timing for user equipment (UE) configured for downlink (DL) Coordinated Multi-Point Transmission (CoMP) are disclosed. In one embodiment, when a UE configured in DL CoMP receives a fall-back transmission, PDSCH is rate-matched around the serving cell CRS. In an alternative embodiment, when a UE configured in DL CoMP receives a fall-back transmission, PDSCH is rate-matched or uses timing around one of the cell-specific reference symbol (CRS) resource element (RE) set indicated by RRC-higher layer signaling. For example, PDSCH may be rate-matched or use timing around the first RRC higher layer configured CRS RE set.

What is claimed is: 
     
         1 . A method for determining physical downlink shared channel (PDSCH) rate-matching comprising:
 receive a fall-back transmission from a base station at a user equipment (UE) configured for downlink coordinated multi-point transmission (CoMP); and   in response to the fall-back transmission, perform PDSCH demodulation assuming PDSCH rate-matching based upon a default cell-specific reference symbol (CRS) resource element (RE) set.   
     
     
         2 . The method of  claim 1 , wherein the default CRS RE set is the serving base station CRS RE set. 
     
     
         3 . The method of  claim 1 , wherein the default CRS RE set is the first CRS RE set of a plurality of CRS RE sets configured by a radio resource control (RRC) higher layer. 
     
     
         4 . The method of  claim 1 , wherein the fall-back transmission is on a compact downlink control information (DCI) format. 
     
     
         5 . The method of  claim 4 , wherein the DCI format is fall-back scheduling on a DCI 1A format. 
     
     
         6 . The method of  claim 1 , further comprising:
 determine a value of a CRS resource element (RE) signaling field in a downlink control information (DCI) signal received from a base station; and   if no fall-back transmission is received, perform PDSCH demodulation assuming rate-matching based upon a CRS RE set corresponding to the value in the downlink control signal.   
     
     
         7 . The method of  claim 6 , wherein the default CRS RE set is a serving base station CRS RE set. 
     
     
         8 . The method of  claim 6 , wherein the default CRS RE set is a first CRS RE set of a plurality of CRS RE sets configured by a radio resource control (RRC) higher layer. 
     
     
         9 . The method of  claim 6 , wherein the value of the CRS RE signaling field in the DCI signal corresponds to a CRS RE set configured by a radio resource control (RRC) higher layer. 
     
     
         10 . A method for determining physical downlink shared channel (PDSCH) timing comprising:
 receive a fall-back transmission from a base station at a user equipment (UE) configured for downlink coordinated multi-point transmission (CoMP); and   in response to the fall-back transmission, perform PDSCH demodulation using a default PDSCH timing assumption.   
     
     
         11 . The method of  claim 10 , wherein the default PDSCH timing is timing for a default cell-specific reference symbol (CRS) resource element (RE) set or a channel state information reference signal (CSI-RS) resource. 
     
     
         12 . The method of  claim 10 , wherein the default PDSCH timing is timing of a serving base station CRS, or a first channel state information reference signal (CSI-RS) resource of a plurality of CSI-RS resources configured by a Radio Resource Control (RRC) higher layer. 
     
     
         13 . The method of  claim 10 , wherein the fall-back transmission is on a compact downlink control information (DCI) format. 
     
     
         14 . The method of  claim 13 , wherein the DCI format is fall-back scheduling on a DCI 1A format. 
     
     
         15 . The method of  claim 10 , further comprising:
 determine a value of a CRS resource element (RE) signaling field in a downlink control information (DCI) signal received from a base station;   if no fall-back transmission is received, perform PDSCH demodulation using downlink timing for a channel state information reference signal (CSI-RS) resource corresponding to the value in the downlink control signal; and   in response to the fall-back transmission, perform PDSCH demodulation using downlink timing for a default CRS RE set or a first CSI-RS resource of a plurality of CSI-RS resources configured by a radio resource control (RRC) higher layer.   
     
     
         16 . The method of  claim 15 , wherein the default CRS RE set is a serving cell CRS. 
     
     
         17 . The method of  claim 15 , wherein the value of a CSI-RS resource signaling field in the DCI signal corresponds to a CSI-RS resource configured by the RRC higher layer. 
     
     
         18 . A user equipment device, comprising:
 a receiver circuit configured to:
 receive a fall-back transmission from a base station when the user equipment device is configured for downlink coordinated multi-point transmission (CoMP); and 
   a processor circuit configured to:
 in response to the fall-back transmission, perform PDSCH demodulation assuming PDSCH rate-matching based upon a default cell-specific reference symbol (CRS) resource element (RE) set. 
   
     
     
         19 . The user equipment of  claim 18 , the processor further configured to:
 determine a value of a CRS resource element (RE) signaling field in a downlink control information (DCI) signal received from a base station; and   if no fall-back transmission is received, perform PDSCH demodulation assuming rate-matching based upon a CRS RE set corresponding to the value in the downlink control signal, wherein the value of the CRS RE signaling field in the DCI signal corresponds to a CRS RE set configured by a radio resource control (RRC) higher layer.   
     
     
         20 . The user equipment of  claim 18 , wherein the default CRS RE set is selected from a serving base station CRS RE set, a first CRS RE set of a plurality of CRS RE sets configured by a radio resource control (RRC) higher layer.