Pre-coding in multi-user MIMO

• US 9,485,063 B2
• Filed: 12/14/2015
• Issued: 11/01/2016
• Est. Priority Date: 04/26/2001
• Status: Expired due to Term

• Current Assignee: Genghiscomm Holdings, LLC
• Original Assignee: Genghiscomm Holdings, LLC
• Inventors: Shattil, Steve
• Primary Examiner(s): HA, DAC V
• Application Number:
  US14/967,633
• Publication Number:
  US 20160094318A1
• Time in Patent Office: 323 Days
• US Class Current: 1/1
• CPC Class Codes: H04B 1/0003 Software-defined radio [SDR] systems, i.e. systems wherein components typically implemented in hardware, e.g. filters or modulators/demodulators, are implented using software, e.g. by involving an AD or DA conversion stage such that at least part of the signal processing is performed in the digital domain digital baseband systems H04L25/00; digital modulation/demodulation H04L27/00; CDMA H04B1/707; TDMA H04B7/2643; image transmission H04N5/00
• CPC Class Codes: H04B 7/024 Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
• 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: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• 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: H04J 13/12 Generation of orthogonal codes
• CPC Class Codes: H04L 27/01 Equalisers baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005
• CPC Class Codes: H04L 27/148 using filters, including PLL-type filters
• 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 27/2636 with FFT or DFT modulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] transmitter or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 27/2646 using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/26526 with inverse FFT [IFFT] or inverse DFT [IDFT] demodulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] receiver or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]
• CPC Class Codes: H04L 27/26534 Pulse-shaped multi-carrier, i.e. not using rectangular window
• CPC Class Codes: H04L 45/24 Multipath
• CPC Class Codes: H04L 47/10 : Flow control; Congestion control
• CPC Class Codes: H04L 5/0007 : the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0021 : in which codes are applied as a frequency-domain sequences, e.g. MC-CDMA
• CPC Class Codes: H04L 5/0023 : Time-frequency-space
• CPC Class Codes: H04L 5/0035 : Resource allocation in a cooperative multipoint environment
• CPC Class Codes: H04L 5/0037 : Inter-user or inter-terminal allocation
• CPC Class Codes: H04L 5/0073 : Allocation arrangements that take into account other cell interferences for intercell interference mitigation or co-ordination in orthogonal multiplex systems H04J11/005
• CPC Class Codes: H04W 72/046 : the resource being in the space domain, e.g. beams
• CPC Class Codes: H04W 84/18 : Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

In a multi-user communication system, a pre-coder in a transmitter comprises a Discrete Fourier Transform (DFT) spreader configured to spread reference-signal symbols with Fourier coefficients to generate DFT-spread reference symbols. An OFDM modulator, such as an inverse-DFT, modulates the DFT-spread reference symbols onto OFDM subcarriers to produce a pre-coded OFDM transmission signal.

Claims

1. An OFDM transmitter, comprising:

an OFDM spreader configured to spread a plurality of reference-signal symbols with Fourier coefficients to generate a Discreet Fourier Transform (DFT)-spread reference signal;

a mapper configured to map the DFT-spread reference signal to a plurality of OFDM subcarriers; and

an OFDM modulator configured to modulate the DFT-spread reference signal onto the plurality of OFDM subcarriers to produce an OFDM transmission signal, wherein the OFDM transmission signal comprises a superposition of the OFDM subcarriers, and wherein the OFDM spreader is configured to provide the superposition with at least one predetermined time-domain signal characteristic comprising at least one of a plurality of uniformly spaced pulse waveforms and a signal with low peak-to-average power ratio.

2. The OFDM transmitter recited in claim 1, wherein the OFDM spreader comprises an N-point DFT and the OFDM modulator comprises an M-point inverse Fast Fourier Transform, wherein M>

N.

3. The OFDM transmitter recited in claim 1, wherein the OFDM modulator comprises an inverse fast Fourier transform.

4. The OFDM transmitter recited in claim 1, wherein the reference-signal symbols comprise at least one of known training symbols and synchronization symbols.

5. The OFDM transmitter 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 OFDM transmitter recited in claim 1, further comprising a pulse-shaping module configured to provide the OFDM transmission signal with a predetermined pulse shape.

7. The OFDM transmitter recited in claim 1, further comprising a cyclic prefix appender configured to append at least one of a cyclic prefix, a postfix, and a guard interval to the OFDM transmission signal.

8. The OFDM transmitter recited in claim 1, wherein the OFDM spreader is configured to provide channel precoding.

9. The OFDM transmitter recited in claim 1, wherein the plurality of reference-signal symbols are at least one of time-multiplexed with user-data symbols, frequency-multiplexed with user-data symbols, and code-multiplexed with user-data symbols.

10. The OFDM transmitter recited in claim 1, further comprising a Cyclic Delay Diversity (CDD) module configured to provide CDD to the OFDM transmission signal.

11. A method, comprising:

generating at least one reference-signal symbol;

multiplying a plurality of data symbols by a Discrete Fourier Transform (DFT) spreading matrix to produce a plurality of DFT-spread symbols, the plurality of data symbols comprising the at least one reference-signal symbol;

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

modulating the plurality of DFT-spread symbols onto a plurality of OFDM subcarriers to produce a DFT-spread OFDM signal, wherein the DFT-spread OFDM signal comprises a superposition of the OFDM subcarriers, and wherein the DFT spreading matrix is configured to provide the superposition with at least one predetermined time-domain signal characteristic comprising at least one of a plurality of uniformly spaced pulse waveforms and a signal with low peak-to-average power ratio.

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 channel quality of the subcarriers.

14. The method recited in claim 11, wherein the mapping are configured to provide the DFT-spread OFDM signal with low PAPR.

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

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

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

18. The method recited in claim 11, wherein the DFT spreading matrix comprises an N-point 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 DFT-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 memory coupled to the processor, the memory including a set of instructions stored therein and executable by the processor to;

for a set of data symbols of a reference signal, perform an N-point discrete Fourier transform (DFT) spreading on the set of data symbols to generate a plurality N of DFT-spread components of the data symbols;

map the N DFT-spread components to 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 comprising a plurality M of discrete time-domain values, wherein the time-domain sequence comprises a superposition of the OFDM subcarriers, and wherein the N-point DFT spreading is configured to provide the superposition with at least one predetermined time-domain signal characteristic comprising at least one of a plurality of uniformly spaced pulse waveforms and a signal with low 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.