Multi-TRP codebook

1. A method for communication, comprising:

measuring downlink channel conditions related to a plurality of network devices in communication with a terminal device;

selecting a precoding matrix from a codebook based on the downlink channel conditions, elements in a column of the codebook representing respective beam sets for the plurality of network devices, the precoding matrix indicating respective beams for the plurality of network devices; and

transmitting an index of the precoding matrix to at least one of the plurality of network devices.

2. The method of claim 1 , wherein transmitting the index of the precoding matrix comprises:

transmitting a first beam index for a first network device of the plurality of network devices; and

transmitting an offset between the first beam index and a second beam index for a second network device of the plurality of network devices.

3. The method of claim 1 , wherein transmitting the index of the precoding matrix comprises:

transmitting a group index of a group of beams; and

transmitting beam indices of the group of beams for the plurality of network devices.

4. The method of claim 1 , wherein the elements in the column of the codebook comprise:

a first element representing a reference beam set, and

a second element comprising a power parameter representing a ratio of power for a respective beam set to power for the reference beam set.

5. The method of claim 1 , wherein at least one of the elements in the column of the codebook comprises a control parameter for enabling or disabling a respective one of the plurality of network devices.

6. The method of claim 1 , wherein selecting the precoding matrix comprises:

excluding a first beam subset from a first beam set of the respective beam sets for the plurality of network devices; and

excluding a second beam subset from a second beam set of the respective beam sets for the plurality of network devices.

7. The method of claim 1 , wherein selecting the precoding matrix comprises:

excluding a predetermined beam combination of respective beams for the plurality of network devices.

8. The method of claim 1 , wherein selecting the precoding matrix comprises:

excluding a first beam index for a first network device of the plurality of network devices; and

excluding a second beam index for a second network device of the plurality of network devices, based on the first beam index and an offset between the first beam index and the second beam index.

9. The method of claim 1 , wherein selecting the precoding matrix comprises:

determining a group of beams for a network device of the plurality of network devices; and

combining a plurality of beams in the group of beams to form a combined beam for the network device.

10. A terminal device, comprising:

a processor; and

a memory storing instructions,

the memory and the instructions being configured, with the processor, to cause the terminal device to:

measure downlink channel conditions related to a plurality of network devices in communication with a terminal device;

select a precoding matrix from a codebook based on the downlink channel conditions, elements in a column of the codebook representing respective beam sets for the plurality of network devices, the precoding matrix indicating respective beams for the plurality of network devices; and

transmit an index of the precoding matrix to at least one of the plurality of network devices.

11. The terminal device of claim 10 , wherein the memory and the instructions are further configured, with the processor, to cause the terminal device to:

transmit a first beam index for a first network device of the plurality of network devices; and

transmit an offset between the first beam index and a second beam index for a second network device of the plurality of network devices.

12. The terminal device of claim 10 , wherein the memory and the instructions are further configured, with the processor, to cause the terminal device to:

transmit a group index of a group of beams; and

transmit beam indices of the group of beams for the plurality of network devices.

13. The terminal device of claim 10 , wherein the elements in the column of the codebook comprise:

a first element representing a reference beam set, and

a second element comprising a power parameter representing a ratio of power for a respective beam set to power for the reference beam set.

14. The terminal device of claim 10 , wherein at least one of the elements in the column of the codebook comprises a control parameter for enabling or disabling a respective one of the plurality of network devices.

15. The terminal device of claim 10 , wherein the memory and the instructions are further configured, with the processor, to cause the terminal device to:

exclude a first beam subset from a first beam set of the respective beam sets for the plurality of network devices; and

exclude a second beam subset from a second beam set of the respective beam sets for the plurality of network devices.

16. The terminal device of claim 10 , wherein the memory and the instructions are further configured, with the processor, to cause the terminal device to:

exclude a predetermined beam combination of respective beams for the plurality of network devices.

17. The terminal device of claim 10 , wherein the memory and the instructions are further configured, with the processor, to cause the terminal device to:

exclude a first beam index for a first network device of the plurality of network devices; and

exclude a second beam index for a second network device of the plurality of network devices, based on the first beam index and an offset between the first beam index and the second beam index.

18. The terminal device of claim 10 , wherein the memory and the instructions are further configured, with the processor, to cause the terminal device to:

determine a group of beams for a network device of the plurality of network devices; and

combine a plurality of beams in the group of beams to form a combined beam for the network device.

19. A non-transitory computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor of a device, causing the device to perform act comprising:

measuring downlink channel conditions related to a plurality of network devices in communication with a terminal device;

selecting a precoding matrix from a codebook based on the downlink channel conditions, elements in a column of the codebook representing respective beam sets for the plurality of network devices, the precoding matrix indicating respective beams for the plurality of network devices; and

transmitting an index of the precoding matrix to at least one of the plurality of network devices.

20. The non-transitory computer readable medium of claim 19 , wherein transmitting the index of the precoding matrix comprises:

transmitting a first beam index for a first network device of the plurality of network devices; and

transmitting an offset between the first beam index and a second beam index for a second network device of the plurality of network devices.