Layer mapping for multi-TRP transmissions
Certain aspects of the present disclosure provide techniques for layer mapping for multiple transmission reception point (TRP) transmission, for example, for code block group (CBG) based hybrid automatic repeat request (HARQ) acknowledgement feedback in new radio (NR). Aspects of the present disclosure provide a method for wireless communications by a user equipment (UE). The UE receives one or more transport blocks (TBs) from a plurality of TRPs. Each of the one or more TBs comprises a plurality of CBs. For one or more of the plurality of CBs, all bits of the CB are received from a same TRP. The UE decodes the one or more TBs.
1 . A method for wireless communications by a user equipment (UE), the method comprising:
receiving an indication of a number of layers at a plurality of transmission reception points (TRPs) and demodulation reference signal (DMRS) port information for the plurality of TRPs;
determining, based on the indicated number of layers and DMRS port information for the plurality of TRPs, a mapping of a plurality of code blocks (CBs) of one or more transport blocks (TBs) to the numbers of layers at the plurality of TRPs, wherein for one or more CBs of the plurality of CBs, all bits of the CB are mapped to a same TRP of the plurality of TRPs; and
decoding the one or more TBs based on the determined mapping.
2 . The method of claim 1 , wherein:
the one or more TBs correspond to a physical downlink shared channel (PDSCH) transmission; and
the one or more TBs are received from the plurality of TRPs at least as a non-coherent joint transmission (NC-JT).
3 . The method of claim 1 , wherein all of the bits of the one or more CBs of the plurality of CBs mapped to the same TRP and that are associated with a same TB are scrambled.
4 . The method of claim 1 , wherein:
the plurality of TRPs comprises N TRPs;
the plurality of CBs comprises, for each of the one or more TBs, N sets of one or more CBs; and
at least one set of the N sets of one or more CBs, for each of the one or more TBs, is mapped to each of the N TRPs.
5 . The method of claim 4 , wherein:
the N TRPs is two TRPs comprising a first TRP and a second TRP;
the one or more TBs is one TB;
a first set of the N sets of one or more CBs is mapped to the first TRP via a first number of layers;
a second set of the N sets of one or more CBs is mapped to the second TRP via a second number of layers; and
a total number of the first and second number of layers is two, three, or four layers.
6 . The method of claim 4 , wherein:
the N TRPs is two TRPs comprising a first TRP and a second TRP;
the one or more TBs is two TBs comprising a first TB and a second TB;
a first set of the N sets of one or more CBs of the first TB is mapped to the first TRP via a first number of layers;
a second set of the N sets of one or more CBs of the second TB is mapped to the first TRP via a second number of layers;
a third set of the N sets of one or more CBs of the first TB is mapped to the second TRP via a third number of layers;
a fourth set of the N sets of one or more CBs of the second TB is mapped to the second TRP via a fourth number of layers;
a total number of the first, second, third, and fourth number of layers is five, six, seven, or eight layers;
a total number of the first and third set of CBs is equal to a total number of CBs within the first TB; and
a total number of the second and fourth set of CBs is equal to the total number of CBs within the second TB.
7 . The method of claim 1 , wherein:
the plurality of TRPs is two TRPs comprising a first TRP and a second TRP;
the one or more TBs is two TBs comprising a first TB and a second TB;
the CBs of the first TB are mapped to the first TRP via a first number of layers;
the CBs of the second TB are mapped to the second TRP via a second number of layers; and
a total number of the first and second number of layers is five, six, seven, or eight layers.
8 . The method of claim 1 , wherein:
the CBs of a same TB, of the one or more TBs, are mapped to at least one of: layers or TRPs having a same modulation and coding scheme (MCS); and
CBs of different TBs, of the one or more TBs, are mapped to at least one of: layers or TRPs having a different MCS.
9 . The method of claim 1 , wherein CBs in a same CB group (CBG) are mapped to layers of a same TRP.
10 . The method of claim 1 , wherein:
at least one of: different bits of at least one CB of the plurality of CBs are mapped to layers of different TRPs or different CBs in at least one CB group (CBG) are mapped to layers of different TRPs; and
the at least one other CB comprises a last CB of a TB or the at least one CBG comprises a last CBG of the TB.
11 . A method for wireless communications by a network entity, the method comprising:
determining a number of layers at a plurality of transmission reception points (TRPs) and demodulation reference signal (DMRS) port information for the plurality of TRPs;
determining a mapping of a plurality of code blocks (CBs) of one or more transport blocks (TBs) to the numbers of layers at the plurality of TRPs, wherein for one or more CBs of the plurality of CBs, all bits of the CB are mapped to a same TRP of the plurality of TRPs; and
allocating, based on the determined mapping, the CBs of the one or more to TBs to layers of plurality of TRPs, for transmission to a user equipment (UE) as part of a multiple-TRP transmission of the one or more TBs UE.
12 . The method of claim 11 , wherein:
the one or more TBs correspond to a physical downlink shared channel (PDSCH) transmission; and
the multiple-TRP transmission comprises a non-coherent joint transmission (NC-JT).
13 . The method of claim 11 , further comprising:
scrambling the all of the bits of the one or more CBs of the CBs that are associated with a same TB of the plurality of TBs; and
transmitting the scrambled bits to the UE.
14 . The method of claim 13 , further comprising ordering the all of the bits of the one or more CBs in increasing order of a CB index associated with the bits.
15 . The method of claim 14 , wherein the scrambling comprises scrambling the ordered bits based on a scrambling identifier (ID) configured by the network entity.
16 . The method of claim 13 , further comprising:
modulating the scrambled bits to modulated symbols based on a modulation order configured by the network entity; and
mapping the modulated symbols to layers at the network entity at least in order of layer or in order of time.
17 . The method of claim 11 , wherein:
the plurality of TRPs comprises N TRPs;
the plurality of CBs comprises, for each of the one or more TBs, N sets of one or more CBs; and
at least one set of the N sets of one or more CBs, for each of the one or more TBs, is mapped to each of the N TRPs.
18 . The method of claim 17 , wherein:
the N TRPs is two TRPs comprising a first TRP and a second TRP;
the one or more TBs is one TB;
a first set of the N sets of one or more CBs is mapped to the first TRP via a first number of layers;
a second set of the N sets of one or more CBs is mapped to the second TRP via a second number of layers; and
a total number of the first and second number of layers is two, three, or four layers.
19 . The method of claim 17 , wherein:
the N TRPs is two TRPs comprising a first TRP and a second TRP TRPs;
the one or more TBs is two TBs comprising a first TB and a second TB;
a first set of the N sets of one or more CBs of the first TB is mapped to the first TRP via a first number of layers;
a second set of the N sets of one or more CBs of the second TB is mapped to the first TRP via a second number of layers;
a third set of the N sets of one or more CBs of the first TB is mapped to the second TRP via a third number of layers;
a fourth set of the N sets of one or more CBs of the second TB is mapped to the second TRP via a fourth number of layers;
a total number of the first, second, third, and fourth number of layers is five, six, seven, or eight layers;
a total number of the first and third set of CBs is equal to a total number of CBs within the first TB; and
a total number of the second and fourth set of CBs is equal to the total number of CBs within the second TB.
20 . The method of claim 11 , wherein:
the plurality of TRPs is two TRPs comprising a first TRP and a second TRP;
the one or more TBs is two TBs comprising a first TB and a second TB;
the CBs of the first TB are mapped to the first TRP via a first number of layers;
the CBs of the second TB are mapped to the second TRP via a second number of layers; and
a total number of the first and second number of layers is five, six, seven, or eight layers.
21 . The method of claim 11 , wherein:
at least one of: different bits of at least one CB of the plurality of CBs are mapped to layers of different TRPs or different CBs in at least one CB group (CBG) are mapped to layers of different TRPs; and
the at least one CB comprises a last CB of a TB or the at least one CBG comprises a last CBG of the TB.
22 . An apparatus for wireless communications, the apparatus comprising:
means for receiving an indication of a number of layers at a plurality of transmission reception points (TRPs) and demodulation reference signal (DMRS) port information for the plurality of TRPs;
means for determining, based on the indicated number of layers and DMRS port information for the plurality of TRPs, a mapping of a plurality of code blocks (CBs) of one or more transport blocks (TBs) to the numbers of layers at the plurality of TRPs, wherein for one or more CBs of the plurality of CBs, all bits of the CB are mapped to a same TRP of the plurality of TRPs; and
means for decoding the one or more TBs based on the determined mapping.
23 . An apparatus for wireless communications, the apparatus comprising:
means for determining a number of layers at a plurality of transmission reception points (TRPs) and demodulation reference signal (DMRS) port information for the plurality of TRPs;
means for determining a mapping of a plurality of code blocks (CBs) of one or more transport blocks (TBs) to the numbers of layers at the plurality of TRPs, wherein for one or more CBs of the plurality of CBs, all bits of the CB are mapped to a same TRP of the plurality of TRPs; and
means for allocating, based on the determined mapping, the plurality of CBs of the one or more to TBs to layers of plurality of TRPs, for transmission to a user equipment (UE) as part of a multiple-TRP transmission of the one or more TBs UE.