# US 10,484,063 B1 · Transmission of beamforming weight coefficients from digital baseband unit to remote radio unit

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- Number: US 10,484,063 B1
- Document ID: US10484063B1
- Status: Granted
- Kind: B1
- Application number: 15/971,578
- Filed: 2018-05-04
- Published: 2019-11-07
- Granted: 2019-11-19
- Earliest claimed: 2018-05-04
- Assignees: AT&T Intellectual Property I, L.P.
- Applicants: At&T Intellectual Property I, L.P.
- Inventors: Aditya Chopra; Arunabha Ghosh; Milap Majmundar; SaiRamesh Nammi
- Web page: https://patentgrep.com/patent/US10484063B1

## CPC

- H04B 7/0617: {for beam forming}
- H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
- H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection}
- H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]}
- H04B: TRANSMISSION

## Abstract

A split radio access network is provided that efficiently transmits beamforming coefficients from a distributed baseband unit device to a remote radio unit device to facilitate beamforming at the remote radio unit. The beamforming coefficients can be determined at the baseband unit device and transmitted along with the data to be beamformed to the remote radio unit device. Due to the large number of antenna ports however, there can still be a very large number of coefficients to transmit, and the disclosure provides for a compressed set of coefficients that reduces the overhead signaling requirements. Instead of sending coefficients for every kth antenna port, the system can select a subset of the coefficients corresponding to a set of k antenna ports which can be used by the remote radio unit to approximate the full set of beamforming coefficients.

## Claims

### Claim 1

A baseband unit device, comprising:
a processor; and
a memory that stores executable instructions that, when executed by the processor, facilitate performance of operations, comprising:
determining a group of beamforming coefficients for a stream of data, wherein the group of beamforming coefficients comprises respective subgroups of beamforming coefficients associated with respective antenna ports of a group of antenna ports;
selecting a portion of the subgroups of beamforming coefficients to add to a reduced size group of beamforming coefficients; and
transmitting the reduced size group of beamforming coefficients to a remote radio unit device to facilitate digital beamforming of a transmission to occur at the remote radio unit device.

### Claim 2 (depends on 1)

The baseband unit device of claim 1, wherein the operations further comprise:
precoding the stream of data based on channel state information associated with a user equipment device.

### Claim 3 (depends on 1)

The baseband unit device of claim 1, wherein the stream of data comprises a group of streams, and wherein a number of the group of streams corresponds to a number of layers associated with the transmission.

### Claim 4 (depends on 1)

The baseband unit device of claim 1, wherein a number of subgroups of beamforming coefficients in the portion of the subgroups of beamforming coefficients is based on a number of layers associated with the transmission.

### Claim 5 (depends on 4)

The baseband unit device of claim 4, wherein the reduced size group of beamforming coefficients is compressed.

### Claim 6 (depends on 1)

The baseband unit device of claim 1, wherein the selecting the portion of the subgroups of beamforming coefficients is based on an estimate of a beamforming vector that is a function of the group of beamforming coefficients, a basis vector, and the group of antenna ports.

### Claim 7 (depends on 6)

The baseband unit device of claim 6, wherein the basis vector is a defined basis vector common to the baseband unit device and the remote radio unit device.

### Claim 8 (depends on 7)

The baseband unit device of claim 7, wherein the basis vector is determined based on a transmission of a known codeword to the remote radio unit device.

### Claim 9 (depends on 1)

The baseband unit device of claim 1, wherein the selecting the portion of the subgroups of beamforming coefficients is based on the beamforming coefficients of the portion of the subgroups of beamforming coefficients being determined to be above a defined value.

### Claim 10 (depends on 1)

The baseband unit device of claim 1, wherein there are two beamforming coefficients per subgroup of the subgroups of beamforming coefficients.

### Claim 11 (depends on 1)

The baseband unit device of claim 1, wherein the baseband unit device and the remote radio unit device are part of a split radio access network.

### Claim 12

A method, comprising:
determining, by a baseband unit device comprising a processor, beamforming coefficients that are able to facilitate beamforming, by a remote radio unit device, of a transmission to be sent to a user equipment device;
compressing, by the baseband unit device, the beamforming coefficients to generate a group of compressed beamforming coefficients by selecting a pair of beamforming coefficients from the beamforming coefficients, wherein the pair of beamforming coefficients correspond to an antenna port of a group of antenna ports; and
transmitting, by the baseband unit device, the pair of beamforming coefficients to the remote radio unit device via a digital transmission.

### Claim 13 (depends on 12)

The method of claim 12, wherein a beamforming vector for a data stream associated with the antenna port is a function of the beamforming coefficients and a basis vector.

### Claim 14 (depends on 13)

The method of claim 13, wherein the basis vector is a defined basis vector common to the baseband unit device and the remote radio unit device.

### Claim 15 (depends on 12)

The method of claim 12, further comprising:
precoding, by the baseband unit device, the transmission based on precoding matrix indicator information received from the user equipment device.

### Claim 16 (depends on 12)

The method of claim 12, wherein the group of compressed beamforming coefficients comprises additional pairs of beamforming coefficients associated with other antenna ports other than the antenna port.

### Claim 17 (depends on 16)

The method of claim 16, wherein a number of pairs of beamforming coefficients of the group of compressed beamforming coefficients is based on a number of layers associated with the transmission.

### Claim 18 (depends on 16)

The method of claim 16, wherein a number of pairs of beamforming coefficients of the group of compressed beamforming coefficients is based on a number of antenna ports associated with the transmission.

### Claim 19

A non-transitory machine-readable medium, comprising executable instructions that, when executed by a processor of an baseband unit device, facilitate performance of operations, comprising:
determining beamforming coefficients in a split radio access network that facilitates beamforming of a transmission to a user equipment device, wherein the beamforming is performed by a remote radio unit device of the split radio access network;
selecting a portion of the beamforming coefficients by selecting a pair of beamforming coefficients from the beamforming coefficients, wherein the pair of beamforming coefficients correspond to an antenna port of a group of antenna ports; and
transmitting the portion of the beamforming coefficients to the remote radio unit device via a transmission.

### Claim 20 (depends on 19)

The non-transitory machine-readable medium of claim 19, wherein the selecting the portion of the beamforming coefficients is based on an estimate of a beamforming vector that is a function of the beamforming coefficients, a basis vector, and the group of antenna ports.