Precoding codebook for LOS MIMO

1 . An apparatus for wireless communication at a base station, comprising:

memory; and

at least one processor coupled to the memory and configured to:

identify a first antenna configuration of the base station and a second antenna configuration of a wireless device;

select one or more codebook-based precoders for communication with the wireless device with line-of-sight (LOS) multiple-input-multiple-output (MIMO), wherein the selected one or more codebook-based precoders are associated with a relative relationship between the first antenna configuration or the second antenna configuration; and

communicate with the wireless device with LOS MIMO based on the selected one or more codebook-based precoders.

2 . The apparatus of claim 1 , wherein to identify the second antenna configuration of the wireless device, the at least one processor is further configured to:

receive, from the wireless device, a device capability information message,

wherein the device capability information message comprises one or more indications of at least one of: LOS MIMO support, an antenna configuration, an antenna activation status, a panel configuration, an antenna geometry, a number of antennas, a number of panels, an antenna element distance matrix, antenna polarization information, a sounding capability, or an antenna alignment capability.

3 . The apparatus of claim 2 , wherein the at least one processor is further configured to receive the device capability information message via a user equipment (UE)-assisted information (UAI) message.

4 . The apparatus of claim 1 , wherein the one or more codebook-based precoders comprise a first codebook-based precoder for transmission from the base station to the wireless device and a second codebook-based precoder for transmission from the wireless device to the base station.

5 . The apparatus of claim 4 , wherein the at least one processor is further configured to:

transmit, to the wireless device, an indication of the second codebook-based precoder.

6 . The apparatus of claim 5 , wherein the at least one processor is further configured to transmit the indication of the second codebook-based precoder to the wireless device via one of a radio resource control (RRC) configuration message, a downlink medium access control (MAC)—control element (CE) (MAC-CE), or a downlink control information (DCI) message.

7 . The apparatus of claim 1 , wherein the at least one processor is further configured to:

identify LOS MIMO as suitable for communication between the base station and the wireless device based on at least one of: a channel condition, a mobility scenario between the base station and the wireless device, a distance between the base station and the wireless device, an antenna alignment condition, an antenna configuration, or a sounding capability.

8 . The apparatus of claim 1 , wherein to select the one or more codebook-based precoders, the at least one processor is further configured to:

select at least one of: a Legendre precoder, a block-discrete Fourier transform (DFT) (block-DFT) precoder, a DFT precoder, a block-Walsh precoder, a Walsh precoder, a block-Legendre precoder, a Kronecker Legendre precoder, a Kronecker block-DFT precoder, or a Kronecker block-Walsh precoder.

9 . The apparatus of claim 1 , wherein to select the one or more codebook-based precoders, the at least one processor is further configured to:

select a Legendre precoder when both the base station and the wireless device are associated with one-dimensional (1D) uniform linear array (ULA) antennas and a receiving device between the base station and the wireless device is associated with more antenna elements than a transmitting device between the base station and the wireless device, or is associated with an equal number of antenna elements as the transmitting device.

10 . The apparatus of claim 1 , wherein to select the one or more codebook-based precoders, the at least one processor is further configured to:

select a block-discrete Fourier transform (DFT) (block-DFT) precoder when both the base station and the wireless device are associated with one-dimensional (1D) uniform linear array (ULA) antennas and a receiving device between the base station and the wireless device is associated with fewer antenna elements than a transmitting device between the base station and the wireless device.

11 . The apparatus of claim 1 , wherein to select the one or more codebook-based precoders, the at least one processor is further configured to:

select a precoder that is a Kronecker product of two one-dimensional (1D) precoders when both the base station and the wireless device are associated with two-dimensional (2D) uniform linear array (ULA) antennas each including two axes, wherein each of the two 1D precoders corresponds to one of the two axes of the 2D ULA antennas.

12 . The apparatus of claim 11 , wherein for each axis, the corresponding 1D precoder is a Legendre precoder when a number of receiving antenna elements is greater than or equal to a number of transmitting antenna elements along the axis, and the corresponding 1D precoder is a block-discrete Fourier transform (DFT) (block-DFT) precoder when the number of the receiving antenna elements is less than the number of the transmitting antenna elements along the axis.

13 . The apparatus of claim 1 , wherein to select the one or more codebook-based precoders, the at least one processor is further configured to:

select a block-discrete Fourier transform (DFT) (block-DFT) precoder when both the base station and the wireless device are associated with uniform circular array (UCA) antennas.

14 . The apparatus of claim 1 , further comprising a transceiver coupled to the at least one processor.

15 . A method of wireless communication at a base station, comprising:

identifying a first antenna configuration of the base station and a second antenna configuration of a wireless device;

selecting one or more codebook-based precoders for communication with the wireless device with line-of-sight (LOS) multiple-input-multiple-output (MIMO), wherein the selected one or more codebook-based precoders are associated with a relative relationship between the first antenna configuration or the second antenna configuration; and

communicating with the wireless device with LOS MIMO based on the selected one or more codebook-based precoders.

16 . An apparatus for wireless communication at a wireless device, comprising:

memory; and

at least one processor coupled to the memory and configured to:

receive, from a base station, an indication of a second codebook-based precoder for transmission from the wireless device to the base station with line-of-sight (LOS) multiple-input-multiple-output (MIMO); and

communicate with the base station with LOS MIMO based on one or more codebook-based precoders including the second codebook-based precoder, wherein the one or more codebook-based precoders are associated with a relative relationship between an antenna configuration of the base station and an antenna configuration of the wireless device.

17 . The apparatus of claim 16 , wherein the at least one processor is being further configured to:

transmit, to the base station, a device capability information message,

wherein the device capability information message comprises one or more indications of at least one of: LOS MIMO support, an antenna configuration, an antenna activation status, a panel configuration, an antenna geometry, a number of antennas, a number of panels, an antenna element distance matrix, antenna polarization information, a sounding capability, or an antenna alignment capability.

18 . The apparatus of claim 17 , wherein the at least one processor is further configured to transmit the device capability information message via a user equipment (UE)-assisted information (UAI) message.

19 . The apparatus of claim 16 , wherein the one or more codebook-based precoders further comprise a first codebook-based precoder for transmission from the base station to the wireless device.

20 . The apparatus of claim 16 , wherein the at least one processor is further configured to receive the indication of the second codebook-based precoder via one of a radio resource control (RRC) configuration message, a downlink medium access control (MAC)-control element (CE) (MAC-CE), or a downlink control information (DCI) message.

21 . The apparatus of claim 16 , wherein the codebook-based precoder used includes at least one of: a Legendre precoder, a block-discrete Fourier transform (DFT) (block-DFT) precoder, a block-Walsh precoder, a block-Legendre precoder, a Kronecker Legendre precoder, a Kronecker block-DFT precoder, or a Kronecker block-Walsh precoder.

22 . The apparatus of claim 16 , wherein a Legendre precoder is used when both the base station and the wireless device are associated with one-dimensional (1D) uniform linear array (ULA) antennas and a receiving device between the base station and the wireless device is associated with more antenna elements than a transmitting device between the base station and the wireless device, or is associated with an equal number of antenna elements as the transmitting device.

23 . The apparatus of claim 16 , wherein a block-discrete Fourier transform (DFT) (block-DFT) precoder is used when both the base station and the wireless device are associated with one-dimensional (1D) uniform linear array (ULA) antennas and a receiving device between the base station and the wireless device is associated with fewer antenna elements than a transmitting device between the base station and the wireless device.

24 . The apparatus of claim 16 , wherein a precoder that is a Kronecker product of two one-dimensional (1D) precoders is used when both the base station and the wireless device are associated with two-dimensional (2D) uniform linear array (ULA) antennas each including two axes, and each of the two 1D precoders corresponds to one of the two axes of the 2D ULA antennas.

25 . The apparatus of claim 24 , wherein for each axis, the corresponding 1D precoder is a Legendre precoder when a number of receiving antenna elements is greater than or equal to a number of transmitting antenna elements, and the corresponding 1D precoder is a block-discrete Fourier transform (DFT) (block-DFT) precoder when the number of the receiving antenna elements is less than the number of the transmitting antenna elements along the axis.

26 . The apparatus of claim 16 , wherein a block-discrete Fourier transform (DFT) (block-DFT) precoder is used when both the base station and the wireless device are associated with uniform circular array (UCA) antennas.

27 . The apparatus of claim 16 , wherein the wireless device comprises one of a user equipment (UE), an integrated access and backhaul (IAB) node, a repeater, or a customer premises equipment (CPE).

28 . The apparatus of claim 16 , further comprising a transceiver coupled to the at least one processor.

29 . A method of wireless communication at a wireless device, comprising:

receiving, from a base station, an indication of a second codebook-based precoder for transmission from the wireless device to the base station with line-of-sight (LOS) multiple-input-multiple-output (MIMO); and

communicating with the base station with LOS MIMO based on one or more codebook-based precoders including the second codebook-based precoder, wherein the one or more codebook-based precoders are associated with a relative relationship between an antenna configuration of the base station and an antenna configuration of the wireless device.

30 . The method of claim 29 , further comprising:

transmitting, to the base station, a device capability information message,

wherein the device capability information message comprises one or more indications of at least one of: LOS MIMO support, an antenna configuration, an antenna activation status, a panel configuration, an antenna geometry, a number of antennas, a number of panels, an antenna element distance matrix, antenna polarization information, a sounding capability, or an antenna alignment capability.