MULTISTAGE BEAMFORMING OF MULTIPLE-ANTENNA COMMUNICATION SYSTEM

• US 20150124688A1
• Filed: 10/28/2014
• Published: 05/07/2015
• Est. Priority Date: 11/04/2013
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Xu, Gang, Nam, Young Han, Li, Yang, Xin, Yan, Zhang, Jianzhong
• Granted Patent: US 9,806,926 B2
• Time in Patent Office: Days
• US Class Current: 370/312
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/0639 Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/005 of common pilots, i.e. pilots destined for multiple users or terminals
• CPC Class Codes: H04L 5/0051 of dedicated pilots, i.e. pilots destined for a single user or terminal

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.

Claims

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; 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, 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.

2. The multistage beamforming circuit of claim 1, wherein the data unit comprises:

a frequency domain precoding module configured to receive and precode the K input 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.

3. The multistage beamforming circuit of claim 2, 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.

4. The multistage beamforming circuit of claim 2, 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.

5. The multistage beamforming circuit of claim 4, 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.

6. The multistage beamforming circuit of claim 2, 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.

7. The multistage beamforming circuit of claim 1, wherein the remote radio head further comprises a time-domain broadband beamforming module that includes a precoding 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 beamwidth cell-specific reference signal (CRS),

wide beam width channel-state-information reference signals (CSI-RS), and

wide beamwidth 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 beamwidth CSI-RS,

narrow beamwidth user equipment specific reference signal (UE-RS), and

narrow beamwidth UE data channels associated with UE-RS.

8. 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 wide-band 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.

9. The multistage beamforming circuit of claim 8, 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.

10. The multistage beamforming circuit of claim 9, 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.

11. 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.

12. 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 the 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 output streams into M OFDM time-domain signals, wherein each IFFT processing block is configured to transform a 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 orthogonal frequency-division multiplexing (OFDM) time-domain signals into N transmit streams of time-domain samples, the RRH comprising;

a time-domain broadband beamforming module configured to receive and precode the M output streams into N precoded output signals using a wide-band precoding matrix,

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 in the time domain.

13. The base station of claim 12, 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.

14. The base station of claim 12, wherein the data unit further comprises:

N_CRS cell-specific reference signal (CRS) ports, each port configured to receive common control signals in the frequency-domain;

M resource element mappers configured to map the M precoding output streams to resource elements in a frequency domain; and

N_CRS resource element mappers configured to map the common control signals to resource elements in the frequency domain;

an antenna virtualization module configured to apply a common control signals specific antenna virtualization precoding to the N_CRS resource-element-mapped common control signals to generate M virtualized common control signals in the frequency domain; and

M adders, each of the M adders configured to combine the M virtualized common control signals with the M resource-element-mapped precoding output streams, and

wherein the each of the M wherein each IFFT processing blocks is coupled to a respective one of the M adders and further configured to receive the combined frequency-domain signal from the adder as the received frequency-domain signal.

15. The base station of claim 12, wherein the data unit further comprises:

N_CRS CRS ports, each CRS port configured to receive common control signals in the frequency-domain;

N_CSI-RS CSI-RS ports, each CSI-RS port configured to receive CSI-RS signals in the frequency-domain;

an antenna virtualization module configured to apply a common control signals specific antenna virtualization precoding to the N_CRS common control signals to generate M virtualized common control signals in the frequency domain, and to 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;

M adders configured to combine the M virtualized CSI-RS signals with the M precoding output streams, each adder configured to combine a respective one of the M virtualized common control signals with a respective one of the M precoding output streams;

wherein each of the M IFFT processing blocks is coupled to a respective one of the M adders and further configured to receive a combined frequency-domain signal from the adder as the received frequency-domain signal.

16. The base station of claim 12, wherein the time-domain broadband beamforming module comprises a precoding 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 beamwidth cell-specific reference signal (CRS),

wide beam width channel-state-information reference signals (CSI-RS), and

wide beamwidth 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 beamwidth CSI-RS,

narrow beamwidth user equipment specific reference signal (UE-RS), and

narrow beamwidth UE data channels associated with UE-RS.

17. The base station of claim 12, 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.

18. The base station of claim 17, 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.

19. The base station of claim 12, 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.

20. A multistage beamforming method comprising:

implementing a frequency domain beamforming stage by converting K data streams in a frequency-domain into M precoding output streams in a frequency domain;

transforming the M output streams to M orthogonal frequency-division multiplexing (OFDM) time-domain signals;

implementing a time-domain broadband beamforming stage by converting the M OFDM time-domain signals into N transmit streams of time-domain samples,

transmitting, by a transmit antenna array including a plurality of physical antennas, the N transmit streams that together form broadcast beams and user-specific beams,

wherein the number N of physical antennas is greater than the number M of precoding output streams.

21. The method of claim 20, wherein converting K data streams in a frequency-domain into the M precoding output streams comprises receiving and precoding the K data streams into M precoding output streams by applying frequency domain precoding matrices;

wherein transforming the M output streams to M OFDM time-domain signals comprises;

mapping the M output streams to resource elements in a frequency domain,

transforming the M mapped frequency-domain signals to M streams of time domain samples using Inverse Fast Fourier Transform (IFFT), and

adding a cyclical prefix to each of the M streams of time domain samples yielding the M OFDM time-domain signals.

22. The method of claim 20, wherein converting the M OFDM time-domain signals into the N transmit streams comprises:

receiving and precoding the M OFDM time-domain signals into the N transmit streams of time-domain samples using a wide-band precoding matrix.

23. The method of claim 20, further comprising one of:

applying a common control signals specific antenna virtualization precoding to common control signals to generate N virtualized common control signals in the time domain, and combining the N virtualized common control signals with the N transmit streams;

applying a common control signals specific antenna virtualization precoding to common control signals to generate M virtualized common control signals in the frequency domain, and combining the M virtualized common control signals with the M precoding output streams; and

further comprising one of;

applying a CSI-RS specific antenna virtualization precoding to time-domain CSI-RS signals to generate N virtualized CSI-RS signals, and combining the N virtualized CSI-RS signals with the N transmit streams; and

applying a CSI-RS specific antenna virtualization precoding to frequency-domain CSI-RS signals to generate M virtualized CSI-RS signals, and combining the M virtualized CSI-RS signals with the with the M precoding output streams.

24. The method of claim 21, wherein converting the M OFDM time-domain signals into the N transmit streams of time-domain samples comprises using a precoding 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 beamwidth cell-specific reference signal (CRS),

wide beam width channel-state-information reference signals (CSI-RS), and

wide beamwidth 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 beamwidth CSI-RS,

narrow beamwidth user equipment specific reference signal (UE-RS), and

narrow beamwidth UE data channels associated with UE-RS.