Reception of Downlink Data for Coordinated Multi-Point Transmission in the Event of Fall-Back
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.
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.