Multistage beamforming of multiple-antenna communication system

Patent metadata

Field	Value
Publication number	US-9806926-B2
Application number	US-201414526284-A
Country	US
Kind code	B2
Filing date	Oct 28, 2014
Priority date	Nov 4, 2013
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

A multistage beamforming circuit includes a data unit that implements a frequency domain beamforming stage and a remote radio head that implements a time-domain broadband beamforming stage. The data unit implements the frequency domain beamforming stage by converting K received data streams into M precoding output streams in a frequency-domain. The data unit is configured to transform the M output streams to M OFDM time-domain signals. The remote radio head, or integrated radio unit is configured to implement a time-domain broadband beamforming stage by converting the M OFDM time-domain signals into N transmit streams of time-domain samples. The remote radio head, or integrated radio unit includes a transmit antenna array configured to transmit the N transmit streams that together form broadcast beams and user-specific beams. The antenna array includes a plurality of physical antennas. The number N of transmit streams is greater than the number M of precoding output streams.

First claim

What is claimed is:

1. A multistage beamforming circuit in a wireless communication network, the circuit comprising:
a data unit configured to:
implement a frequency domain beamforming stage by converting K received data streams into M precoding output streams in a frequency-domain, and
transform the M output streams to M orthogonal frequency-division multiplexing (OFDM) time domain signals;
the data unit comprising:
a frequency domain precoding module configured to receive and precode the K received data streams into the M precoding output streams by applying frequency domain precoding matrices:
M Inverse Fast Fourier Transform (IFFT) processing blocks for processing the M precoding output streams to yield the M OFDM time-domain signals, each IFFT processing block configured to:
receive a frequency-domain signal,
map the frequency-domain signal to resource elements in a frequency domain,

transform the frequency-domain signal to a stream of time domain samples, and
add a cyclical prefix to the stream of time domain samples yielding an OFDM time-domain signal; and

a remote radio head configured to implement a time-domain broadband beamforming stage by converting the M OFDM time-domain signals into N transmit streams of time-domain samples based on beamforming control signals received from the data unit, the beamforming control signals indicating a wideband precoding matrix or a set of indicators to construct the wideband precoding matrix, the remote radio head comprising a transmit antenna array configured to transmit the N transmit streams that together form broadcast beams and user-specific beams, the antenna array including a plurality of physical antennas,
wherein the number N of transmit streams is greater than the number M of precoding output streams, and
wherein N. M. and K are positive integers.

2. The multistage beamforming circuit of claim 1 , wherein the data unit further comprises:
N CRS CELL - SPECIFIC REFERENCE SIGNAL (CRS) PORTS CONFIGURED TO RECEIVE COMMON CONTROL SIGNALS AS FREQUENCY DOMAIN SIGNALS; AND
N CRS IFFT processing blocks for processing the common control signals to yield N CRS OFDM time-domain signals.

3. The multistage beamforming circuit of claim 1 , wherein the data unit further comprises:
an antenna virtualization module configured to receive N CRS common control signals as frequency domain signals, apply a common control signals specific antenna virtualization precoding to the N CRS frequency domain common signals to generate M virtualized common control signals; and
M adders configured to combine the M virtualized common control signals with the M precoding output streams.

4. The multistage beamforming circuit of claim 3 , wherein the antenna virtualization module is further configured to:
receive N CSI-RS frequency-domain CSI-RS signals, and apply a CSI-RS specific antenna virtualization precoding to the N CSI-RS frequency-domain CSI-RS signals to generate M virtualized CSI-RS signals; and
wherein the M adders are further configured to combine the M virtualized CSI-RS signals with the M precoding output streams.

5. The multistage beamforming circuit of claim 1 , further comprising a beamforming control module configured to receive uplink feedback including at least one of precoding matrix indicator (PMI) and channel-state-information (CSI), and based on the feedback, generate beamforming control signals including:
a first beamforming control signal configured to control the frequency domain precoding module to select the frequency domain precoding matrices, and
a second beamforming control signals configured to control a time-domain broadband beamforming module to select a wide-band precoding matrix.

6. The multistage beamforming circuit of claim 1 , wherein the remote radio head further comprises a time-domain broadband beamforming module that includes a preceding matrix having at least one of:
rows that are Discrete Fourier Transform (DFT) vectors, and
columns that are DFT vectors; and wherein the broadcast beams comprise:
a wide beam width cell-specific reference signal (CRS),
wide beam width channel-state-information reference signals (CSI-RS), and
wide beam width common control channels associated with the CRS and including at least one of: Physical Downlink Control Channel and Physical Broadcast Channel, and
wherein the user-specific beams comprise:
narrow beam width CSI-RS,
narrow beam width user equipment specific reference signal (UE-RS), and
narrow beam width UE data channels associated with UE-RS.

7. The multistage beamforming circuit of claim 1 , wherein the remote radio head comprises:
a time-domain broadband beamforming module configured to receive and precode the M output streams into the N precoded output signals using a wideband precoding matrix; and
N transmission paths respectively coupled to at least one of the physical antennas, each transmission path Including a series of a digital-to-analog converter, a mixer, and a power amplifier together configured to form a respective one of the N transmit streams using a respective one of the N precoded output signals.

8. The multistage beamforming circuit of claim 7 , wherein the remote radio head further comprises:
an antenna virtualization module configured to receive N CSI-RS time-domain CSI-RS signals, and apply a CSI-RS specific antenna virtualization precoding to the N CSI-RS time-domain CSI-RS signals to generate N virtualized CSI-RS signals; and
N adders configured to combine the N virtualized CSI-RS signals with the N precoded output signals.

9. The multistage beamforming circuit of claim 8 , wherein the antenna virtualization module is further configured to:
receive N CRS common control time-domain signals from the data unit, and
apply a common control signals specific antenna virtualization precoding to the N CRS time domain common signals to generate N virtualized common control signals, and
wherein the N adders are further configured to combine the N virtualized common control signals with the N precoded output signals.

10. The multistage beamforming circuit of claim 1 , further comprising a common public radio interface (CPRI) interface configured to transmit the M precoding output streams from the data unit to the remote radio head.

11. A base station for multistage beamforming in a wireless communication network, the base station comprising:
a data unit configured to implement a frequency domain beamforming stage, the data unit comprising:
a frequency domain precoding module configured to receive and precode K data streams into M precoding output streams in a frequency domain by applying frequency domain precoding matrices,

M pairs of an Inverse Fast Fourier Transform (IFFT) processing block coupled to M cyclic prefix processing block, each pair configured to transform the M precoding output streams into M orthogonal frequency-division multiplexing (OFDM) time-domain signals, wherein each IFFT processing block is configured to receive a frequency-domain signal, map the frequency-domain signal to resource elements in a frequency domain, transform the received frequency-domain signal to a stream of time domain samples, and each cyclic prefix processing block is configured to add a cyclical prefix to the stream of time domain samples to generate the M precoding output streams; and
a remote radio head (RRH) configured to implement a time-domain broadband beamforming stage by converting the M OFDM time-domain signals into N transmit streams of time-domain samples based on beamforming control signals received from the data unit, the beamforming control signals indicating a wide-band precoding matrix or a set of ind

Assignees

• Samsung Electronics Co Ltd

Inventors

• Xu Gang
• Nam Young Han
• Li Yang
• Xin Yan
• Zhang Jianzhong

Classifications

• H04L27/2647

  Arrangements specific to the receiver only (equalisation H04L27/01) · CPC title

• H04L5/0051

  of dedicated pilots, i.e. pilots destined for a single user or terminal · CPC title

• H04L27/2607 Primary

  Cyclic extensions · CPC title

• H04B7/0452

  Multi-user MIMO systems · CPC title

• H04L5/005

  of common pilots, i.e. pilots destined for multiple users or terminals · CPC title