Omni-directional transmission in large-scale MIMO systems

Patent metadata

Field	Value
Publication number	US-10271222-B2
Application number	US-201415506750-A
Country	US
Kind code	B2
Filing date	Aug 28, 2014
Priority date	Aug 28, 2014
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

Described herein is an omni-directional transmission scheme allowing signals to transmit from a base station to multiple users in massive MIMO systems with reduced pilot overhead and system complexity. The transmission scheme uses a low-dimensional space-time coding scheme to generate a K-dimensional vector signal, and based on the K-dimensional vector signal, using an omni-directional precoding matrix W to generate an M-dimensional vector signal for transmission over a large number of transmitting antennas, wherein the matrix W comprises M rows and K columns, and K is much smaller than M.

First claim

What is claimed is:

1. A method for omni-directional transmissions in large scale MIMO systems, comprising:
generating one or more K-dimensional vector signals, said K-dimensional vector signal including at least a K-dimensional data signal and a K-dimensional pilot signal, wherein said K-dimensional data signal is generated by using a space-time coding scheme;
applying an omni-directional pre-coding matrix W to said one or more K-dimensional vector signals to generate one or more M-dimensional vector signals, wherein M rows of said omni-directional pre-coding matrix W have the same 2-norm, and K is much smaller than M; and
transmitting said M-dimensional vector signals over M transmitting antennas in a base station of said large scale MIMO system.

2. The method of claim 1 , further comprising:
said K-dimensional vector signals including at least a sequence of K-dimensional pilot signals of length P, wherein P≥K.

3. The method of claim 1 , further comprising processing a data stream to generate one or more symbol streams, wherein said symbol streams are encoded with said space-time encoding scheme to generate said K-dimensional data signal.

4. The method of claim 1 , wherein all K columns of the said matrix W have the same 2-norm and are orthogonal to each other.

5. The method of claim 1 , wherein when said pre-coding matrix W is left-multiplied by an matrix constructed from the array manifold in discrete spatial directions to generate a different matrix, all rows of said different matrix have the same 2-norm.

6. The method of claim 5 , wherein said matrix constructed from the array manifold in discrete spatial directions can be an M-point DFT matrix for the linear antenna array.

7. The method of claim 4 , wherein when said pre-coding matrix W is left-multiplied by an matrix constructed from the array manifold in discrete spatial directions to generate a different matrix, all rows of said different matrix have the same 2-norm.

8. The method of claim 7 , wherein said matrix constructed from the array manifold in discrete spatial directions can be an M-point DFT matrix for the linear antenna array.

9. The method of claim 1 , wherein the number of transmit antennas equipped in said base station is M, wherein M is of or over the level of tens.

10. The method of claim 1 , wherein said omni-dimensional precoding matrix W is generated by applying different linear modulation schemes to a Constant Amplitude Zero Auto Correlation(CAZAC) sequence, and choosing K number of modulation sequences from any K columns of the M-point DFT matrix.

11. The method of claim 1 , wherein said omni-directional precoding matrix W is generated by performing different cyclic shifts to one CAZAC sequence to obtain K columns of said matrix W.

12. The method of claim 1 , wherein said omni-directional precoding matrix W is generated by longitudinally copying a K×K identity matrix M/K times and multiplying a diagonal matrix consisted of a CAZAC sequence to obtain K columns of said matrix W.

13. The method of claim 1 , wherein signals transmitted from said base station in all spatial directions have the same signal power.

14. The method of claim 13 , wherein signals transmitted from all antenna units equipped in said base station have the same transmission power.

15. The method of claim 14 , wherein said space-time coding scheme provides a first degree of diversity, said method providing a second degree of diversity that is as much as said first degree of diversity.

16. The method of claim 1 , wherein said M-dimensional vector signal is transmitted to multiple users in said system, each user receiving a signal comprising a data signal and a pilot signal, and wherein said data signal is decoded at a K-dimensional equivalent channel to recover original data from said base station.

17. A method for data transmission in a wireless communication system, said method comprising:
receiving a downlink signal at a mobile terminal, said downlink signal resulting from an M-dimensional vector signal transmitted from a base station;
wherein said M-dimensional vector signal is generated using an omni-directional pre-coding matrix W applied to K-dimensional vector signal, M rows of the omni-directional pre-coding matrix W having the same 2-norm;
wherein said K-dimensional vector signal including at least a K-dimensional data signal and a K-dimensional pilot signal;
wherein K is much smaller than M; and
wherein said K-dimensional data signal is generated by a space-time coding scheme, and decoding said downlink signal based on said space-time coding scheme.

18. The method of claim 17 , said method further comprising:
separating said downlink signal into received data signal and received pilot signal;
performing channel estimation based on said received pilot signal; and
decoding said received data signal based on said space-time coding scheme and said channel estimation to recover original data streams sent from said base station.

19. A transmitting device comprising:
M transmitting antennas;
a spatial processor coupled to said transmitting antennas, said spatial processor configured to spatially process a K-dimensional vector signal by using an omni-directional pre-coding matrix W and generate an M-dimensional vector signal for transmission over said M transmitting antennas;
wherein said omni-directional pre-coding matrix W comprises M rows and K column, and M rows of said omni-directional pre-coding matrix W have the same 2-norm; and
K is much smaller than M.

Assignees

• Univ Southeast

Inventors

• Gao Xiqi
• Meng Xin
• Zhong Wen

Classifications

• H04B7/0452

  Multi-user MIMO systems · CPC title

• H04B7/0456

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

• H04B7/0465

  taking power constraints at power amplifier or emission constraints, e.g. constant modulus, into account · CPC title

• H04W16/28 Primary

  using beam steering · CPC title

• H04L1/0042

  Encoding specially adapted to other signal generation operation, e.g. in order to reduce transmit distortions, jitter, or to improve signal shape (H04L1/0067 takes precedence) · CPC title