# US 2017/0257154 A1 · Precoding a Transmission From an Antenna Array That Includes Co-Polarized Antenna Elements Aligned in a Given Spatial Dimension

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- Number: US 2017/0257154 A1
- Document ID: US20170257154A1
- Status: Published application
- Kind: A1
- Application number: 14/902,749
- Filed: 2015-09-04
- Published: 2017-09-07
- Earliest claimed: 2015-09-04
- Assignees: Telefonaktiebolaget LM Ericsson (publ)
- Applicants: Telefonaktiebolaget LM Ericsson (publ)
- Inventors: Niklas Wernersson; Svante Bergman; Sebastian Faxér
- Web page: https://patentgrep.com/patent/US20170257154A1

## CPC

- H04B 7/0469: {taking special antenna structures, e.g. cross polarized antennas into account}
- H04B 7/0479: {for multi-dimensional arrays, e.g. horizontal or vertical pre-distortion matrix index [PMI]}
- H04B 7/0481: {using subset selection of codebooks}
- H04B 7/065: {Variable contents, e.g. long-term or short-short}
- H04B: TRANSMISSION

## Abstract

A transmitting radio node (10) precodes a transmission from an antenna array (12)to a receiving radio node (50). The array (12) includes co-polarized antenna elements (14) aligned in a given spatial dimension of the array (12). The transmitting radio node (10) precodes the transmission from different subarrays (34a, 34b) of the antenna elements (14) using respective coarse-granularity precoders that are factorizable from a multi-granular precoder targeting the given spatial dimension of the array (12) at different granularities, so as to virtualize the subarrays (34a, 34b) as different auxiliary elements (38a, 38b). The transmitting radio node (10) also precode the transmission from the different auxiliary elements (38a, 38b) using one or more finer-granularity precoders that are also factorizable from the multi-granular precoder. In this case, the coarse granularity precoders and the one or more finer-granularity precoders are represented within one or more codebooks (26) used for said precoding

## Claims

### Claim at position 1

1-34. (canceled)

### Claim 35

A method for precoding a transmission from an antenna array that includes co-polarized antenna elements aligned in a given spatial dimension of the array, wherein the method is performed by a transmitting radio node for precoding the transmission to a receiving radio node and comprises:
precoding the transmission from different subarrays of the antenna elements using respective coarse-granularity precoders that are factorizable from a multi-granular precoder targeting the given spatial dimension of the array at different granularities, so as to virtualize the subarrays as different auxiliary elements; and
precoding the transmission from the different auxiliary elements using one or more finer granularity precoders that are also factorizable from the multi-granular precoder, wherein the coarse granularity precoders and the one or more finer-granularity precoders are represented within one or more codebooks used for said precoding.

### Claim 36 (depends on 35)

The method of claim 35, wherein the transmission comprises user data or a reference signal dedicated to the receiving radio node.

### Claim 37 (depends on 35)

The method of claim 35, further comprising:
transmitting a full-elements reference signal from the antenna elements without precoding;
precoding transmission of an auxiliary-elements reference signal from the different subarrays of the antenna elements using respective coarse-granularity precoders that are factorizable from a multi-granular precoder targeting the given spatial dimension of the array at different granularities, so as to virtualize the subarrays as the different auxiliary elements; and
transmitting the precoded, auxiliary-elements reference signal to the receiving radio node.

### Claim 38 (depends on 37)

The method of claim 37, wherein the full-elements and auxiliary-elements reference signals are common reference signals transmitted from the antenna array to multiple receiving radio nodes.

### Claim 39 (depends on 37)

The method of claim 37, wherein transmitting the precoded, auxiliary-elements reference signal comprises transmitting the precoded, auxiliary-elements reference signal more often than transmitting the full-elements reference signal.

### Claim 40 (depends on 35)

The method of claim 35, further comprising receiving from the receiving radio node, at different times, a complete recommendation that recommends both a coarse granularity precoder and a finer granularity precoder, and a partial recommendation that recommends only a finer granularity precoder, and wherein said precoding uses both a coarse-granularity precoder from the complete recommendation and a finer-granularity precoder from the partial recommendation.

### Claim 41 (depends on 40)

The method of claim 40, further comprising receiving a partial recommendation more often than receiving a complete recommendation.

### Claim 42 (depends on 35)

The method of claim 35, further comprising configuring the receiving radio node to restrict precoders from which the receiving radio node selects, for recommending to the transmitting radio node, to a subset of precoders in a codebook that correspond to one or more coarse-granularity precoders, by transmitting codebook subset restriction signaling to the receiving radio node indicating those one or more coarse-granularity precoders.

### Claim 43 (depends on 35)

The method of claim 35, wherein the different subarrays have the same number of antenna elements, and wherein the respective coarse-granularity precoders are equal among the different subarrays.

### Claim 44 (depends on 35)

The method of claim 35, wherein one or more parameterized codebooks that define sets of different possible coarse-granularity precoders and finer-granularity precoders are signaled from the transmitting radio node to the receiving radio node in the form of a length of said precoders.

### Claim 45 (depends on 35)

The method of claim 35, wherein the antenna array is a one-dimensional array in the spatial domain and said given spatial dimension is either a horizontal dimension or a vertical dimension.

### Claim 46 (depends on 35)

The method of claim 35, wherein the antenna array is a two-dimensional array in the spatial domain such that the antenna array has a horizontal dimension and a vertical dimension, and wherein said given spatial dimension is either the horizontal dimension or the vertical dimension.

### Claim 47 (depends on 35)

The method of claim 35, wherein a multi-granular precoder is based on a Kronecker Product of a coarse-granularity precoder and one or more finer-granularity precoders.

### Claim 48 (depends on 35)

The method of claim 35, wherein the coarse-granularity precoder and the one or more finer-granularity precoders are Discrete Fourier Transform, DFT, vectors, wherein the product of the DFT vectors' lengths equals the number of the antenna elements aligned along the given spatial dimension.

### Claim 49

A method for receiving a transmission from an antenna array that includes co-polarized antenna elements aligned in a given spatial dimension of the array, wherein the antenna array is associated with a transmitting radio node, wherein the method is performed by a receiving radio node and comprises:
receiving a first reference signal transmitted from the antenna array;
based on measurement of the first reference signal, generating a first type of recommendation that recommends either:
a multi-granular precoder in a multi-granular codebook targeting the given spatial dimension of the array at different granularities, each multi-granular precoder in the codebook comprising a combination of a coarse-granularity precoder and one or more finer-granularity precoders; or
a coarse-granularity precoder in a coarse-granularity codebook and one or more finer-granularity precoders in one or more finer-granularity codebooks, the combination of which corresponds to a multi-granular precoder targeting the given spatial dimension of the array at different granularities;
transmitting the first type of recommendation to the transmitting radio node;
receiving a second reference signal transmitted from the antenna array;
based on measurement of the second reference signal, generating a second type of recommendation that recommends one or more finer-granularity precoders factorizable from a multi-granular precoder;
transmitting the second type of recommendation to the transmitting radio node; and
receiving from the antenna array a data transmission that is precoded based on the first and second types of recommendations.

### Claim 50 (depends on 49)

The method of claim 49, wherein the first reference signal is a full-elements reference signal transmitted from the antenna elements without precoding, and the second reference signal is an auxiliary-elements reference signal transmitted from different subarrays of the antenna elements using respective coarse-granularity precoders that are factorizable from a multi-granular precoder targeting the given spatial dimension of the array at different granularities, so as to virtualize the subarrays as different auxiliary elements, wherein the second type of recommendation exclusively recommends one or more finer-granularity precoders, without also recommending a coarse-granularity precoder.

### Claim 51 (depends on 50)

The method of claim 50, further comprising receiving the precoded, auxiliary-elements reference signal more often than receiving the full-elements reference signal.

### Claim 52 (depends on 49)

The method of claim 49, further comprising transmitting the second type of recommendation to the transmitting radio node more often than transmitting the first type of recommendation to the transmitting radio node.

### Claim 53 (depends on 49)

The method of claim 49, wherein both the first and second reference signals are full elements reference signals transmitted from the antenna elements without precoding, and wherein said generating the second type of recommendation comprises generating the second type of recommendation to exclusively recommend one or more finer-granularity precoders, without also recommending a coarse-granularity precoder.

### Claim 54 (depends on 49)

The method of claim 49, wherein both the first and second reference signals are full elements reference signals transmitted from the antenna elements without precoding, wherein generating the second type of recommendation comprises generating the second type of recommendation to recommend either:
a multi-granular precoder in the multi-granular codebook, wherein the multi-granular precoder factors into the coarse-granularity precoder from the first recommendation; or
a coarse-granularity precoder in the coarse-granularity codebook and one or more finer-granularity precoders in one or more finer-granularity codebooks, wherein the coarse granularity precoder is the coarse-granularity precoder from the first type of recommendation.

### Claim 55 (depends on 49)

The method of claim 49, wherein the antenna array is a one-dimensional array in the spatial domain and said given spatial dimension is either a horizontal dimension or a vertical dimension.

### Claim 56 (depends on 49)

The method of claim 49, wherein the antenna array is a two-dimensional array in the spatial domain such that the antenna array has a horizontal dimension and a vertical dimension, and wherein said given spatial dimension is either the horizontal dimension or the vertical dimension.

### Claim 57 (depends on 49)

The method of claim 49, wherein a multi-granular precoder is based on a Kronecker Product of a coarse-granularity precoder and one or more finer-granularity precoders.

### Claim 58 (depends on 49)

The method of claim 49, wherein the coarse-granularity precoder and the one or more finer-granularity precoders are Discrete Fourier Transform, DFT, vectors, wherein the product of the DFT vectors' lengths equals the number of the antenna elements aligned along the given spatial dimension.

### Claim 59

A method for receiving a transmission from an antenna array that includes co-polarized antenna elements aligned in a given spatial dimension of the array, wherein the antenna array is associated with a transmitting radio node, wherein the method is performed by a receiving radio node and comprises:
receiving codebook subset restriction signaling from the transmitting radio node that indicates one or more coarse-granularity precoders, each coarse-granularity precoder factorizable along with one or more finer-granularity precoders from a multi-granular precoder targeting the given spatial dimension of the array at different granularities; and
based on said signaling, restricting precoders from which the receiving radio node selects for recommending to the transmitting radio node to a subset of precoders in a codebook that correspond to the one or more indicated coarse-granularity precoders;
transmitting to the transmitting radio node a recommended precoder that is selected according to said restricting; and
receiving from the antenna array a data transmission that is precoded based on the recommended precoder.

### Claim 60 (depends on 59)

The method of claim 59, further characterized by:
receiving a full-elements reference signal transmitted from the antenna elements without precoding;
based on measurement of the full-elements reference signal, selecting said recommended precoder as either:
a multi-granular precoder in a multi-granular codebook, from amongst a subset of multi-granular precoders in the codebook that factorize into any of the one or more coarse-granularity precoders indicated by the codebook subset restriction signaling; or
a coarse-granularity precoder in a coarse-granularity codebook, from amongst the one or more coarse-granularity precoders indicated by the codebook subset restriction signaling; and
transmitting the recommendation to the transmitting radio node.

### Claim 61 (depends on 59)

The method of claim 59, wherein one or more parameterized codebooks that define sets of different possible coarse-granularity precoders and finer-granularity precoders are signaled from the transmitting radio node to the receiving radio node in the form of a length of said precoders.

### Claim 62 (depends on 59)

The method of claim 59, wherein the antenna array is a one-dimensional array in the spatial domain and said given spatial dimension is either a horizontal dimension or a vertical dimension.

### Claim 63 (depends on 59)

The method of claim 59, wherein the antenna array is a two-dimensional array in the spatial domain such that the antenna array has a horizontal dimension and a vertical dimension, and wherein said given spatial dimension is either the horizontal dimension or the vertical dimension.

### Claim 64 (depends on 59)

The method of claim 59, wherein a multi-granular precoder is based on a Kronecker Product of a coarse-granularity precoder and one or more finer-granularity precoders.

### Claim 65 (depends on 59)

The method of claim 59, wherein the coarse-granularity precoder and the one or more finer-granularity precoders are Discrete Fourier Transform, DFT, vectors, wherein the product of the DFT vectors' lengths equals the number of the antenna elements aligned along the given spatial dimension.

### Claim 66

A transmitting radio node configured to precode a transmission from an antenna array to a receiving radio node, wherein the antenna array includes co polarized antenna elements aligned in a given spatial dimension of the array, the transmitting radio node comprising one or more processing circuits and a memory, the memory containing program code executable by the one or more processing circuits whereby the transmitting radio node is configured to:
precode the transmission from different subarrays of the antenna elements using respective coarse-granularity precoders that are factorizable from a multi-granular precoder targeting the given spatial dimension of the array at different granularities, so as to virtualize the subarrays as different auxiliary elements; and
precode the transmission from the different auxiliary elements using one or more finer granularity precoders that are also factorizable from the multi-granular precoder, wherein the coarse granularity precoders and the one or more finer-granularity precoders are represented within one or more codebooks used for said precoding.

### Claim 67

A receiving radio node configured to receive a transmission from an antenna array that includes co-polarized antenna elements aligned in a given spatial dimension of the array, wherein the antenna array is associated with a transmitting radio node, the receiving radio node comprising one or more processing circuits and a memory, the memory containing program code executable by the one or more processing circuits whereby the receiving radio node is configured to
receive a first reference signal transmitted from the antenna array;
based on measurement of the first reference signal, generate a first type of recommendation that recommends either:
a multi-granular precoder in a multi-granular codebook targeting the given spatial dimension of the array at different granularities, each multi-granular precoder in the codebook comprising a combination of a coarse-granularity precoder and one or more finer-granularity precoders; or
a coarse-granularity precoder in a coarse-granularity codebook and one or more finer-granularity precoders in one or more finer-granularity codebooks, the combination of which corresponds to a multi-granular precoder targeting the given spatial dimension of the array at different granularities;
transmit the first type of recommendation to the transmitting radio node;
receive a second reference signal transmitted from the antenna array;
based on measurement of the second reference signal, generate a second type of recommendation that recommends one or more finer-granularity precoders factorizable from a multi-granular precoder in the multi-granular codebook, without also recommending a coarse-granularity precoder;
transmit the second type of recommendation to the transmitting radio node; and
receive from the antenna array a data transmission that is precoded based on the first and second types of recommendations.

### Claim 68

A receiving radio node configured to receive a transmission from an antenna array that includes co-polarized antenna elements aligned in a given spatial dimension of the array, wherein the antenna array is associated with a transmitting radio node, the receiving radio node comprising one or more processing circuits and a memory, the memory containing program code executable by the one or more processing circuits whereby the receiving radio node is configured to:
receive codebook subset restriction signaling from the transmitting radio node that indicates one or more coarse-granularity precoders, each coarse-granularity precoder factorizable along with one or more finer-granularity precoders from a multi-granular precoder targeting the given spatial dimension of the array at different granularities; and
based on said signaling, restrict precoders from which the receiving radio node selects for recommending to the transmitting radio node to a subset of precoders in a codebook that correspond to the one or more indicated coarse-granularity precoders;
transmit to the transmitting radio node a recommended precoder that is selected according to said restricting; and
receive from the antenna array a data transmission that is precoded based on recommended precoder.