Pre-coding in multi-user MIMO

• US 10,200,227 B2
• Filed: 12/31/2016
• Issued: 02/05/2019
• Est. Priority Date: 05/14/2002
• Status: Expired due to Fees

• Current Assignee: Genghiscomm Holdings, LLC
• Original Assignee: Genghiscomm Holdings, LLC
• Inventors: Shattil, Steve
• Primary Examiner(s): Lam, Yee F
• Application Number:
  US15/396,567
• Publication Number:
  US 20170126458A1
• Time in Patent Office: 766 Days
• CPC Class Codes: H04B 17/3911 Fading models or fading generators
• CPC Class Codes: H04B 7/026 Co-operative diversity, e.g. using fixed or mobile stations as relays
• CPC Class Codes: H04B 7/0452 Multi-user MIMO systems
• CPC Class Codes: H04J 13/0003 Code application, i.e. aspects relating to how codes are applied to form multiplexed channels
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04L 1/0077 Cooperative coding
• CPC Class Codes: H04L 1/0681 adapting space time parameters, i.e. modifying the space time matrix
• CPC Class Codes: H04L 2001/0097 Relays
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/2615 Reduction thereof using coding
• CPC Class Codes: H04L 45/24 Multipath
• CPC Class Codes: H04L 5/0021 in which codes are applied as a frequency-domain sequences, e.g. MC-CDMA
• 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
• CPC Class Codes: H04W 52/241 taking into account channel quality metrics, e.g. SIR, SNR, CIR, Eb/lo
• CPC Class Codes: H04W 52/346 distributing total power among users or channels
• CPC Class Codes: H04W 72/046 the resource being in the space domain, e.g. beams

Abstract

In a multi-user communication system, a pre-coder in a transmitter comprises a Discrete Fourier Transform (DFT) spreader provides data symbols spread with Fourier coefficients to generate DFT-spread data symbols. An OFDM modulator, such as an inverse-DFT, modulates the DFT-spread data symbols onto OFDM subcarriers to produce a pre-coded OFDM transmission signal. The Fourier coefficients reduce the transmission signal'"'"'s peak to average power.

Claims

1. A non-transitory computer-readable medium including computer-readable program code stored thereon, the computer-readable program code configured to be executed by at least one processor to implement a method for generating an Orthogonal Frequency Division Multiplexing (OFDM) transmission signal, the method comprising:

employing an invertible transform to spread a plurality of data symbols with complex-valued coefficients to generate a plurality of spread data symbols;

mapping the spread data symbols to a plurality of OFDM subcarriers; and

responsive to the mapping, modulating the spread data symbols onto the plurality of OFDM subcarriers to produce the OFDM transmission signal comprising a superposition of the OFDM subcarriers, wherein employing the invertible transform is configured to provide the superposition with a reduced peak-to-average power ratio.

2. The non-transitory computer-readable medium recited in claim 1, wherein the invertible transform comprises an N-point discrete Fourier Transform (DFT), and the modulating comprises performing an M-point inverse-DFT, wherein M>

N.

3. The non-transitory computer-readable medium recited in claim 1, wherein the modulating comprises performing an inverse fast Fourier transform.

4. The non-transitory computer-readable medium recited in claim 1, wherein the data symbols comprise reference-signal symbols, which comprise at least one of known training symbols and synchronization symbols.

5. The non-transitory computer-readable medium recited in claim 1, wherein the plurality of OFDM subcarriers comprise at least one of contiguous OFDM subcarriers and equally spaced non-contiguous OFDM subcarriers.

6. The non-transitory computer-readable medium recited in claim 1, further comprising computer-readable program code configured to perform pulse-shaping module to provide the OFDM transmission signal with a predetermined pulse shape.

7. The non-transitory computer-readable medium recited in claim 1, further comprising computer-readable program code configured to append at least one of a cyclic prefix, a postfix, and a guard interval to the OFDM transmission signal.

8. The non-transitory computer-readable medium recited in claim 1, further comprising computer-readable program code to provide channel precoding.

9. The non-transitory computer-readable medium recited in claim 1, wherein the plurality of data symbols are at least one of time-multiplexed with reference-signal symbols, frequency-multiplexed with reference-signal symbols, and code-multiplexed with reference-signal symbols.

10. The non-transitory computer-readable medium recited in claim 1, further comprising computer-readable program code to provide Cyclic Delay Diversity (CDD) to the OFDM transmission signal.

11. A method, comprising:

performing an invertible transform, comprising multiplying a plurality of data symbols by a complex-valued spreading matrix to produce a plurality of spread symbols;

mapping the plurality of spread symbols to a plurality of Orthogonal Frequency Division Multiplexing (OFDM) subcarriers; and

modulating the plurality of spread symbols onto the plurality of OFDM subcarriers to produce a spread OFDM signal to be transmitted into a wireless channel, wherein the spread OFDM signal comprises a superposition of the OFDM subcarriers, and wherein the complex-valued spreading matrix is configured to provide the superposition with a reduced peak-to-average power ratio (PAPR).

12. The method recited in claim 11, wherein the plurality of OFDM subcarriers is a subset of subcarriers, the subset comprising at least one of a block of contiguous subcarriers, and a set of non-contiguous subcarriers.

13. The method recited in claim 11, wherein the plurality of OFDM subcarriers is selected based on measured channel quality of the subcarriers.

14. The method recited in claim 11, wherein the mapping is configured to provide the spread OFDM signal with reduced PAPR.

15. The method recited in claim 11, wherein at least one of the spreading matrix and the mapping is configured to provide a spread reference signal comprising a coherent superposition of reference symbol components on different subcarriers.

16. The method recited in claim 11, wherein the plurality of data symbols comprises at least one reference-signal symbol employed for at least one of synchronization and channel estimation.

17. The method recited in claim 11, further comprising appending at least one of a cyclic prefix, a postfix, and a guard interval onto the spread OFDM signal.

18. The method recited in claim 11, wherein the spreading matrix comprises an N-point Discrete Fourier Transform (DFT), and the modulating comprises employing an M-point inverse-DFT, and wherein N<

M.

19. The method recited in claim 11, further comprising providing Cyclic Delay Diversity to the spread OFDM signal.

20. The method recited in claim 11, further comprising pulse shaping to provide the OFDM transmission signal with a predetermined pulse shape.

21. A User Equipment configured to perform the method recited in claim 11.

22. An apparatus comprising:

a processor; and

a non-transitory memory coupled to the processor, the non-transitory memory including a set of instructions stored therein and executable by the processor to;

perform an invertible transform on a set of data symbols to generate a plurality N of spread data symbols, the invertible transform comprising complex-valued spreading codes;

map the N spread data symbols to at least N subcarriers of a plurality M of Orthogonal Frequency Division Multiplexing (OFDM) subcarriers to generate a set of complex subcarrier amplitudes; and

perform an M-point inverse discrete Fourier transform (IDFT) on the set of complex subcarrier amplitudes to generate a time-domain sequence to be transmitted into a wireless channel, the time-domain sequence comprising a superposition of the OFDM subcarriers, wherein the invertible transform is configured to provide the superposition with a reduced peak-to-average power ratio.

23. The apparatus recited in claim 22, wherein the N subcarriers comprise at least one of contiguous OFDM subcarriers and non-contiguous OFDM subcarriers.

24. The apparatus recited in claim 22, configured to reside on a User Equipment.

25. The apparatus recited in claim 22, wherein M>

N.

26. The apparatus recited in claim 22, wherein the IDFT comprises an inverse fast Fourier transform.

27. The apparatus recited in claim 22, wherein the non-transitory memory further comprises instructions to perform pulse-shaping on at least one of a set of signals, the set comprising the plurality of spread data symbols and the time-domain sequence, in order to provide the superposition with a predetermined pulse shape.

28. The apparatus recited in claim 22, wherein the non-transitory memory further comprises instructions to append at least one of a cyclic prefix, a postfix, and a guard interval to the time-domain sequence.

29. The apparatus recited in claim 22, wherein the at least N subcarriers is selected based on a measured channel quality.