Hybrid digital and analog beamforming for large antenna arrays

Patent metadata

Field	Value
Publication number	US-9647735-B2
Application number	US-201314784256-A
Country	US
Kind code	B2
Filing date	Dec 12, 2013
Priority date	May 31, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

A hybrid digital and analog beamforming device for a node operable with an antenna array is disclosed. In an example, the hybrid digital and analog beamforming device can include computer circuitry configured to: Segment antenna elements of an antenna array into at least two groups of antenna elements; map antenna ports for transmission chains to one group of the antenna elements; constrain digital precoding weights for a digital precoder for the antenna elements, where the digital precoding weight includes a digital phase and amplitude; and determine analog precoding weights for an analog precoder for the antenna elements, where the analog precoding weight includes an analog phase.

First claim

What is claimed is:

1. A hybrid digital and analog beamforming device for a node operable with an antenna array, having computer circuitry configured to:
segment antenna elements of an antenna array into at least two groups of antenna elements;
map antenna ports for transmission chains to one group of the antenna elements;
constrain digital precoding weights for a digital precoder for the antenna elements, wherein the digital precoding weight includes a digital phase and amplitude;
determine analog precoding weights for an analog precoder for the antenna elements, wherein the analog precoding weight includes an analog phase;
assign at least one group of the antenna elements to a channel state information reference signal (CSI-RS) feedback period;
select a group of antenna elements as a feedback group and another group of antenna elements as a non-feedback group;
determine the digital precoding weights for the feedback group from CSI-RS feedback from a user equipment (UE); and
interpolate the digital precoding weights for the non-feedback group based on the digital precoding weights for the feedback group.

2. The computer circuitry of claim 1 , wherein computer circuitry configured to segment the antenna elements of the antenna array is further configured to:
segment the antenna elements into blocks of rows or columns, a pattern of rows or columns in a same group, or a zigzag pattern in the same group.

3. The computer circuitry of claim 1 , wherein computer circuitry configured to constrain the digital precoding weight is further configured to:
select a group of antenna elements as a first feedback group and another group of antenna elements as a second feedback group;
determine the digital precoding weights for a first feedback group from CSI-RS feedback from a user equipment (UE);
determine the digital precoding weights for a second feedback group from CSI-RS feedback from the user equipment; and
resolve a phase ambiguity between the digital precoding weights for the first feedback group and the digital precoding weights for the second feedback group.

4. The computer circuitry of claim 1 , wherein computer circuitry configured to constrain the digital precoding weight is further configured to:
reconstruct a quantized precoding matrix indicator (PMI) codeword of an eight transmitter (8Tx), four transmitter (4Tx), or two transmitter (2Tx) codebook as specified in a Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard Release 11 based on the CSI-RS feedback from a user equipment (UE); and
assign the quantized PMI codeword to the digital precoding weights.

5. The computer circuitry of claim 1 , wherein computer circuitry configured to determine the analog precoding weights is further configured to:
solve for each analog precoding weight F ls,i (k) based on least squares (LS) for a unconstrained solution for a rank r>1 transmission, where the unconstrained solution is represented by F ls,i (k) =arg min∥V T *F i T −W des,i (k)T ∥ 2 , i=1, . . . , a max where arg min is an argument of a minimum function, ( ) T is a transpose function, V is a digital precoding weight matrix, F i is an element of an analog precoding weight matrix, W des is a desired precoding matrix indicator (PMI) codeword based on CSI-RS feedback for a user k, and a max is a number of antenna elements in the antenna array, wherein for single user multiple-input and multiple-output (MIMO) (SU-MIMO), V and W des are variable-amplitude codewords, and for multiple user MIMO (MU-MIMO), V and W des are constant-amplitude codewords; and
quantize the unconstrained solution to a closest point in a phase-shift keying (PSK) alphabet for each user k, wherein the PSK alphabet is a 2-bit 4-PSK, a 3-bit 8-PSK, or a 4-bit 16-PSK alphabet.

6. The computer circuitry of claim 1 , wherein computer circuitry configured to constrain the digital precoding weight is further configured to:
calculate each analog precoding weight F ls,i based on least squares (LS) for a unconstrained solution, where the unconstrained solution is represented by F ls,i =arg min∥W 8Tx T *F i T −W des,i T ∥ 2 , i=1, . . . , a max where arg min is an argument of a minimum function, ( ) T is a transpose function, W is a quantized precoding matrix indicator (PMI) codeword of an eight transmitter (8Tx) codebook based on the CSI feedback for a user k, F i is an element of an analog precoding weight matrix, W des is a desired PMI codeword based on CSI-RS feedback for the user k, and a max is the number of antenna elements in the antenna array; and
quantize an unconstrained solution F ls to F (Q) using a closest point in a phase-shift keying (PSK) alphabet for each user k; and
calculate the digital precoding weights V by solving for min V ∥W des −F (Q) *V∥ 2 , i=1, . . . , a max to reduce quantization error.

7. The computer circuitry of claim 1 , wherein the computer circuitry is further configured to:
precode a signal for amplitude or phase using the digital precoder with the digital precoding weights to generate a digital precoded signal; and
phase shift the digital precoded signal using a radio frequency (RF) phase shifter with the analog precoding weights.

8. The computer circuitry of claim 1 , wherein a number of antennas associated with the antenna elements is greater than eight antennas, and the antennas are co-polarized antennas or cross-polarized antennas, and the node can include a base station (BS), a Node B (NB), an evolved Node B (eNB), a baseband unit (BBU), a remote radio head (RRH), a remote radio equipment (RRE), a remote radio unit (RRU), or a central processing module (CPM).

9. A method for hybrid digital and analog beamforming for an antenna array at a node, comprising:
grouping antennas of an antenna array into at least two antenna segments to receive channel state information reference signal (CSI-RS) feedback for at least one antenna segment;
estimating digital precoding weights for a digital precoder for the antenna array based on the CSI-RS feedback;
calculating analog precoding weights for a radio frequency (RF) phase shifter corresponding to the antenna elements of the antenna array;
one-stage beamforming training of CSI-RS for an antenna segment H 1 for each CSI period, wherein the antenna segment comprises a group antennas as blocks of rows or columns, a pattern of rows or columns in a same antenna segment, or a zigzag pattern within the same antenna segment;
wherein estimating the digital precoding weights further comprises:
determining the digital precoding weights for the antenna segment H 1 based on H 1 CSI-RS feedback; and

phase-only interpolating the digital precoding weights for an antenna segment without corresponding CSI-RS feedback based on the digital precoding weights for the antenna segment H 1 .

10. The method of claim 9 , wherein grouping the antennas of the antenna array further comprises:
mapping each antenna port for a radio frequency (RF) chain to an antenna for an antenna set for the CSI-RS feedback.

11. The method of claim 9 , wherein calculating the analog precoding weights further comprises:
determining unconstrained analog precoding weights based on a minimization of a least squares (LS) form; and
selecting a constrained analog precoding weights to a closest point in a phase-shift keying (PSK) alphabet.

12. The method of claim 9 , further comprising:
multiple-stage beamforming training of CSI-RS for at least a first antenna segment H 1 and a second antenna segment H 2 for multiple CSI periods;
wherein estimating the digital precoding weights further comprises:
determining the digital precoding weights for the fir

Assignees

• Intel Ip Corp

Inventors

• Sajadieh Masoud
• Shirani-Mehr Hooman
• Xue Feng
• Li Qinghua

Classifications

• H04B7/0486

  taking channel rank into account · CPC title

• H04B7/0632

  Channel quality parameters, e.g. channel quality indicator [CQI] · CPC title

• H04W12/02

  Protecting privacy or anonymity, e.g. protecting personally identifiable information [PII] · CPC title

• H04B7/0456 Primary

  Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting · CPC title

• H04W76/023

  Electricity · mapped topic