# US 10,484,059 B2 · Multi-beam codebooks with further optimized overhead

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- Number: US 10,484,059 B2
- Document ID: US10484059B2
- Status: Granted
- Kind: B2
- Application number: 15/759,400
- Filed: 2017-08-11
- Published: 2018-09-13
- Granted: 2019-11-19
- Earliest claimed: 2016-08-12
- Assignees: Telefonaktiebolaget LM Ericsson (publ)
- Applicants: Telefonaktiebolaget LM Ericsson (publ)
- Inventors: Sebastian Faxér; Shiwei Gao; Stephen Grant; Robert Mark Harrison; Siva Muruganathan
- Web page: https://patentgrep.com/patent/US10484059B2

## CPC

- H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection}
- H04B 7/0452: Multi-user MIMO systems
- H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
- H04B 7/0617: {for beam forming}
- H04B 7/063: {Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection}
- H04B 7/066: {Combined feedback for a number of channels, e.g. over several subcarriers like in orthogonal frequency division multiplexing [OFDM]}
- H04B: TRANSMISSION

## Abstract

A method, wireless device and network node for determining an indication of a precoder are provided. According to one aspect, a method in a wireless device includes determining and the indication of the precoder from a codebook, the indication comprising a first beam phase parameter and a second beam phase parameter corresponding to a first beam and a second beam respectively. The first beam phase parameter takes on one of a first integer number of phase values and the second beam phase parameter takes on one of a second integer number of phase values. At least one of the following conditions apply: the second integer number of phase values is less than the first number of phase values, and the second frequency-granularity is greater than the first frequency-granularity. The method includes transmitting the determined indication of a precoder to the network node. According to another aspect, the second beam has less power than the first beam and the second integer number of phase values is less than the first integer number of phase values.

## Claims

### Claim 1

A method for a user equipment to transmit an indication of a precoder to a base station, the method comprising:
determining from a codebook an indication of a precoder comprising a first beam phase parameter and a second beam phase parameter corresponding to a first beam and second beam, respectively;
the first beam phase parameter taking on one of a first integer number of phase values; and
the second beam phase parameter taking on one of a second integer number of phase values, the second beam having a lesser power than the first beam and the second integer number of phase values being less than the first integer number of phase values, each of the first and second beam phase parameters corresponding to a plurality of frequency subbands; and
reporting the determined indication of the precoder to a base station.

### Claim 2 (depends on 1)

The method of claim 1, further comprising determining the first and second integer number of phase values, and, optionally, transmitting the first and second integer number of phase values to the base station.

### Claim 3 (depends on 1)

The method of claim 1, further comprising determining a frequency-granularity of each beam to be a multiple of a subband size.

### Claim 4 (depends on 1)

The method of claim 1, wherein the first and second integer number of phase values are respective numbers of values attainable in a phase shift keyed, PSK, constellation.

### Claim 5 (depends on 4)

The method of claim 4, wherein the PSK constellation is 8 PSK for beams having a beam strength above a first threshold and the PSK constellation is quadrature PSK (QPSK) for beams having a beam strength below a second threshold.

### Claim 6 (depends on 5)

The method of claim 5, wherein the first and second thresholds are the same.

### Claim 7 (depends on 1)

The method of claim 1, wherein each of the first and second beams is a kth beam, d(k), that has associated a set of complex numbers and has index pair (lk,mk), each element of the set of complex numbers being characterized by at least one complex phase shift such that:
dn(k)=di(k)αi,nej2π(pΔ1,k+qΔz,k);
dn(k), and di(k) are an ith and nth elements of d(k), respectively;
αi,n is a real number corresponding to the ith and nth elements of d(k);
p and q are integers; and
beam directions Δ1,k and Δ2,k are real numbers corresponding to beams with index pair (lk,mk) that determine complex phase shifts ej2πΔ1,k and ej2πΔ2,k respectively; and
each of the first and second beam phase parameters is a complex coefficient ck for d(k) used to adjust at least the phase of the ith element of d(k) according to ckdi(k).

### Claim 8 (depends on 1)

The method of claim 1, wherein the first and second integer number of phase values are respective granularities of respective co-phasing factors for the first and second beams.

### Claim 9 (depends on 1)

The method of claim 1, further comprising differentially encoding at least one of the first and second beam phase parameters.

### Claim 10 (depends on 1)

The method of claim 1, wherein a first plurality of first beam phase parameters and a second plurality of second beam phase parameters correspond to the first beam and second beam, respectively, and further comprising parametrically encoding at least one of the first plurality and second plurality of first and second beam phase parameters, wherein the at least one of the first plurality and second plurality of beam phase parameters are coefficients within a predetermined function over frequency.

### Claim 11

A user equipment configured to transmit an indication of a precoder to a base station, the method comprising:
processing circuitry configured to:
determine from a codebook an indication of a precoder comprising a first beam phase parameter and a second beam phase parameter corresponding to a first beam and second beam, respectively;
the first beam phase parameter taking on one of a first integer number of phase values; and
the second beam phase parameter taking on one of a second integer number of phase values, the second beam having a lesser power than the first beam and the second integer number of phase values being less than the first integer number of phase values, each of the first and second beam phase parameters corresponding to a plurality of frequency subbands; and
a transceiver configured to transmit the determined indication of the precoder to a base station.

### Claim 12 (depends on 11)

The user equipment of claim 11, further comprising determining the first and second integer number of phase values, and, optionally, transmitting the first and second integer number of phase values to the base station.

### Claim 13

A base station for receiving an indication of a precoder from a user equipment, the method comprising:
processing circuitry configured to:
receive an indication of a precoder comprising a first beam phase parameter and a second beam phase parameter corresponding to a first beam and second beam, respectively;
the first beam phase parameter taking on one of a first integer number of phase values; and
the second beam phase parameter taking on one of a second integer number of phase values, the second beam having a lesser power than the first beam and the second integer number of phase values being less than the first integer number of phase values, each of the first and second beam phase parameters corresponding to a plurality of frequency subbands;
determine a precoder based on the received indication of the precoder; and
generate the first and second beams based on the precoder.

### Claim 14 (depends on 13)

The base station of claim 13, further comprising receiving the first and second integer number of phase values.

### Claim 15 (depends on 13)

The base station of claim 13, wherein a frequency-granularity of each beam is determined to be a multiple of a subband size.

### Claim 16 (depends on 13)

The base station of claim 13, wherein the first and second integer number of phase values are respective numbers of values attainable in a phase shift keyed, PSK, constellation.

### Claim 17 (depends on 16)

The base station of claim 16, wherein the PSK constellation is 8 PSK for beams having a beam strength above a first threshold and the PSK constellation is quadrature PSK (QPSK) for beams having a beam strength below a second threshold.

### Claim 18 (depends on 17)

The base station (14) of claim 17, wherein the first and second thresholds are the same.

### Claim 19 (depends on 13)

The base station of claim 13, wherein each of the first and second beams is a kth beam, d(k), that has associated a set of complex numbers and has index pair (lk,mk), each element of the set of complex numbers being characterized by at least one complex phase shift such that:
dn(k)=di(k)αi,nej2π(pΔ1,k+qΔz,k);
dn(k), and di(k) are an ith and nth elements of d(k), respectively;
αi,n is a real number corresponding to the ith and nth elements of d(k);
p and q are integers; and
beam directions Δ1,k and Δ2,k are real numbers corresponding to beams with index pair (lk,mk) that determine complex phase shifts ej2πΔ1,k and ej2πΔ2,k respectively; and
each of the first and second beam phase parameters is a complex coefficient ck for d(k) used to adjust at least the phase of the ith element of d(k) according to ckdi(k).

### Claim 20 (depends on 13)

The base station of any one of claim 13, wherein the first and second integer number of phase values are respective granularities of respective co-phasing factors for the first and second beams.