# US 2013/0155975 A1 · Beamforming Codeword Exchange between Base Stations

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- Number: US 2013/0155975 A1
- Document ID: US20130155975A1
- Status: Published application
- Kind: A1
- Application number: 13/716,134
- Filed: 2012-12-15
- Published: 2013-06-20
- Earliest claimed: 2011-12-19
- Assignees: Ofinno Technologies, LLC
- Inventors: Esmael Hejazi Dinan
- Web page: https://patentgrep.com/patent/US20130155975A1

## CPC

- H04W 36/0058: {Transmission of hand-off measurement information, e.g. measurement reports}
- H04B 7/0417: Feedback systems
- H04B 7/043: {using best eigenmode, e.g. beam forming or beam steering}
- H04B 7/0456: Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
- H04B 7/046: {taking physical layer constraints into account}
- H04B 7/0473: {taking constraints in layer or codeword to antenna mapping into account}
- H04B 7/0478: {Special codebook structures directed to feedback optimisation}
- H04B 7/0481: {using subset selection of codebooks}
- H04B 7/0617: {for beam forming}
- H04B 7/0626: {Channel coefficients, e.g. channel state information [CSI]}
- H04B 7/063: {Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection}
- H04B 7/0634: {Antenna weights or vector/matrix coefficients}
- H04B 7/0639: {Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection}
- H04J 11/0056: {Inter-base station aspects}
- H04L 5/0023: {Time-frequency-space}
- H04L 5/0053: {Allocation of signalling, i.e. of overhead other than pilot signals}
- H04L 5/0073: {Allocation arrangements that take into account other cell interferences}
- H04L 25/03955: {in combination with downlink estimations, e.g. downlink path losses}
- H04L 27/2646: {using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length}
- H04W 24/02: Arrangements for optimising operational condition
- H04W 28/0236: {radio quality, e.g. interference, losses or delay}
- H04W 36/0064: {of control information between different access points}
- H04W 36/0072: {of resource information of target access point}
- H04W 36/0094: {Definition of hand-off measurement parameters}
- H04W 36/085: {involving beams of access points}
- H04W 36/30: by measured or perceived connection quality data
- H04W 72/044: based on the type of the allocated resource
- H04W 72/0453: Resources in frequency domain, e.g. a carrier in FDMA
- H04W 72/046: {the resource being in the space domain, e.g. beams}
- H04W 72/20: Control channels or signalling for resource management
- H04W 72/23: in the downlink direction of a wireless link, i.e. towards a terminal
- H04W 72/27: between access points
- H04W 72/541: using the level of interference
- H04W 74/002: {Transmission of channel access control information}
- H04W 88/08: Access point devices
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- H04B: TRANSMISSION
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)

## Abstract

A first base station receives a message from a second base station. The first base station and the second base station communicate to wireless devices employing a downlink carrier comprising downlink resource blocks. The message comprises downlink beamforming information indicating a beamforming codeword of a codebook employed for downlink resource block(s). The first base station selects, for a subset of the downlink resource blocks, beamforming codewords from a codebook based, at least in part, on the downlink beamforming information. The first base station transmits signals on a subset of the downlink resource blocks employing beamforming codewords.

## Claims

### Claim 1

A method comprising:
a) receiving, by a first base station from a second base station, at least one application protocol message, said first base station and said second base station configured to communicate with a plurality of wireless devices employing a downlink carrier, said downlink carrier comprising a plurality of resource blocks, said at least one application protocol message comprising a downlink beamforming information element for at least one resource block in said downlink carrier, said downlink beamforming information element indicating a second beamforming codeword employed by said second base station for said at least one resource block, said second beamforming codeword:
i) having a number of rows or columns equal to a number of antenna ports employed by said second base station for beamforming on said downlink carrier;
ii) included in a second beamforming codebook; and
iii) referenced by an index, correspondence between said beamforming codeword and said index being defined by an application protocol message received prior to said at least one application protocol message reception;
b) selecting, by said first base station for said at least one resource block, a first beamforming codeword from a first beamforming codebook, said selection being based, at least in part, on said downlink beamforming information element received from said second base station; and
c) transmitting, by said first base station, employing said first beamforming codeword, signals on a subset of said at least one resource block to a wireless device.

### Claim 2 (depends on 1)

The method of claim 1, wherein said at least one application protocol message comprises said number of antenna ports for said downlink carrier.

### Claim 3 (depends on 1)

The method of claim 1, wherein said first beamforming codeword has a number of rows or columns equal to a number of antenna ports employed by said first base station for beamforming on said downlink carrier.

### Claim 4 (depends on 1)

The method of claim 1, wherein said first base station selecting a subset of said first plurality of beamforming codewords further comprises employing a zero-forcing criterion.

### Claim 5 (depends on 1)

The method of claim 1, wherein said first base station selecting a subset of said first plurality of beamforming codewords further comprises employing a minimum mean squared error criterion.

### Claim 6 (depends on 1)

The method of claim 1, further comprising configuring said first plurality of beamforming codewords to reduce inter-cell interference from said first base station.

### Claim 7 (depends on 6)

The method of claim 6, further comprising said first base station computing inter-cell interference to said second base station employing information received from at least one wireless device.

### Claim 8 (depends on 7)

The method of claim 7, wherein said first base station selecting a subset of said first plurality of beamforming codewords further comprises employing a maximum signal to leakage ratio criterion.

### Claim 9

A method comprising:
a) receiving, by a first base station from a second base station, at least one application protocol message, said first base station and said second base station configured to communicate with a plurality of wireless devices employing a downlink carrier, said downlink carrier comprising a plurality of resource blocks, said at least one application protocol message comprising a downlink beamforming information element for at least one resource block in said downlink carrier, said downlink beamforming information element indicating a second beamforming codeword employed by said second base station for said at least one resource block, said second beamforming codeword referenced by an index and included in a second beamforming codebook;
b) selecting, by said first base station for said at least one resource block, a first beamforming codeword from a first beamforming codebook, said selection being based, at least in part, on said downlink beamforming information element received from said second base station; and
c) transmitting, by said first base station, employing said first beamforming codeword, signals on a subset of said at least one resource block to a wireless device.

### Claim 10 (depends on 9)

The method of claim 9, wherein said first beamforming codebook or said second beamforming codebook is defined for a number of transmit antennas and comprises a set of original codewords, each original codeword having a number of rows or columns equal to said number of transmit antennas.

### Claim 11 (depends on 10)

The method of claim 10, further comprising constructing codewords for a subset of transmit antennas employing a subset of rows or columns of said original codewords.

### Claim 12 (depends on 9)

The method of claim 9, further comprising defining said first beamforming codebook or said second beamforming codebook for a number of layers, and wherein said first beamforming codebook or said second beamforming codebook comprises a set of codewords, each codeword having a number columns or rows equal to said maximum number of layers.

### Claim 13 (depends on 12)

The method of claim 12, further comprising constructing codewords for a subset of layers employing a subset of columns or rows of said original codewords.

### Claim 14 (depends on 9)

The method of claim 9, further comprising aid second base station transmitting the same second application protocol message to a plurality of first base stations.

### Claim 15 (depends on 14)

The method of claim 14, further comprising said plurality of first base stations selecting respective first plurality of beamforming codewords based on information received from said second base station in said second application protocol message.

### Claim 16

A first base station comprising:
a) one or more communication interfaces;
b) one or more processors; and
c) memory storing instructions that, when executed, cause said first base station to:
i) receive from a second base station, at least one application protocol message, said first base station and said second base station configured to communicate with a plurality of wireless devices employing a downlink carrier, said downlink carrier comprising a plurality of resource blocks, said at least one application protocol message comprising a downlink beamforming information element for at least one resource block in said downlink carrier, said downlink beamforming information element indicating a second beamforming codeword employed by said second base station for said at least one resource block, said second beamforming codeword:
(1) having a number of rows or columns equal to or less than a number of antenna ports employed by said second base station for beamforming on said downlink carrier; and
(2) included in a second beamforming codebook;
ii) select for said at least one resource block, a first beamforming codeword from a first beamforming codebook, said selection being based, at least in part, on said downlink beamforming information element received from said second base station; and
iii) transmit employing said first beamforming codeword, signals on a subset of said at least one resource block to a wireless device.

### Claim 17 (depends on 16)

The first base station of claim 16, wherein said first beamforming codebook or said second beamforming codebook is defined for a number of transmit antennas and comprises a set of original codewords, each original codeword having a number columns or rows equal to said number of transmit antennas.

### Claim 18 (depends on 17)

The first base station of claim 17, wherein said instructions, when executed, further cause said first base station to construct codewords for a smaller number of transmit antennas by employing a subset of columns or rows of said original codewords.

### Claim 19 (depends on 16)

The first base station of claim 16, wherein said first beamforming codebook or said second beamforming codebook is defined for a number of layers and comprises a set of original codewords, each original codeword having a number rows or columns equal to said maximum number of layers.

### Claim 20 (depends on 19)

The first base station of claim 19, wherein codewords for a smaller number of layers are constructed by employing a subset of rows or columns of said original codewords.