Systems and methods for improved wireless channel estimation

• US 9,325,533 B2
• Filed: 10/21/2014
• Issued: 04/26/2016
• Est. Priority Date: 11/06/2013
• Status: Active Grant

• Current Assignee: Keysight Technologies Singapore (Holdings) Pte. Limited. (Keysight Technologies, Inc.)
• Original Assignee: Ixia (Keysight Technologies, Inc.)
• Inventors: Wicker, David Jennings Jr., Alexander, Thomas
• Primary Examiner(s): Vo, Don N
• Application Number:
  US14/520,261
• Publication Number:
  US 20150124911A1
• Time in Patent Office: 553 Days
• Field of Search: 375/267, 375/340
• US Class Current: 1/1
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0242 using matrix methods

Abstract

Systems and methods are disclosed herein to provide improved channel estimation in a wireless data communication system, including but not limited to Multiple Input Multiple Output (MIMO) and Orthogonal Frequency Division Multiplexing (OFDM) communication systems. In accordance with one or more embodiments and aspects thereof, a channel estimation system is disclosed that regenerates a representation of the original transmitted signal from the received digital bitstream and selectively applies it to refine and improve channel estimation and signal equalization calculations using the data symbols contained within received frames. Such a system may offer improved capabilities such as more accurate signal reception, reduced bit error ratio, and improved Multi-User MIMO (MU-MIMO) reception.

Claims

1. A system for generating channel estimates or a channel equalization matrix for digital communications over a wireless channel, comprising:

a receive processor for receiving information carried via radio frequency (RF) signals over said wireless channel and converting the information to a first stream of modulated symbols;

a buffer for storing said first stream of modulated symbols as a buffered stream of modulated symbols;

an equalizer coupled to said receive processor for removing effects of said wireless channel on said RF signals and generating a version of originally transmitted modulated symbols;

a demodulation function for converting said version of originally transmitted modulated symbols to a digital bitstream;

a modulation function coupled to said demodulation function for recreating a version of originally transmitted modulated symbols from said digital bitstream; and

a channel estimation processor operatively coupled to said buffer and said modulation function, for obtaining delayed copies of said first stream of modulated symbols from said buffer upstream from said equalizer, for obtaining said recreated version of the originally transmitted modulated symbols, for performing a channel estimation calculation using said delayed copies and said recreated version to produce equalization parameters, and for feeding the equalization parameters to said equalizer for improving channel estimation performed by said equalizer.

2. The system of claim 1, further including a processor for extracting at least one predetermined training sequence from said information received over said wireless channel, wherein said channel estimation processor calculates at least one of:

a second wireless channel estimate and a second channel equalization matrix from said predetermined training sequence.

3. The system of claim 2, wherein said channel estimation processor calculates a third channel equalization matrix from said second wireless channel estimate.

4. The system of claim 1, wherein said channel estimation processor calculates said first channel equalization matrix from said first wireless channel estimate.

5. The system of claim 4, wherein said channel estimation processor is adapted to calculate said first channel equalization matrix for a Multiple Input Multiple Output (MIMO) wireless channel.

6. The system of claim 1, further including an error-correction function for detecting and correcting errors in said digital bitstream prior to conversion back to said second stream of modulated symbols.

7. The system of claim 6, wherein said error-correction function is a Viterbi decoder.

8. The system of claim 1, wherein said system includes a transmit datapath for transmitting modulated symbols, converted from a second digital bitstream, over said wireless channel.

9. The system of claim 8, wherein said modulation function comprises a portion of said transmit datapath that is normally inactive during reception.

10. The system of claim 1, wherein said receive processor and said demodulation function are adapted to perform Multiple Input Multiple Output (MIMO) reception.

11. The system of claim 1, wherein said channel estimation processor is adapted to generate said first channel estimate for a Multiple Input Multiple Output (MIMO) wireless channel.

12. A method for generating channel estimates or a channel equalization matrix for digital communications over a wireless channel, the method comprising:

receiving, by a receive processor, information carried via radio frequency (RF) signals over said wireless channel and converting the information to a first stream of modulated symbols;

storing, in a buffer, said first stream of modulated symbols as a buffered stream of modulated symbols;

removing, by an equalizer, effects of said wireless channel on said RF signals and generating a version of originally transmitted modulated symbols;

converting, by a demodulation function, said version of originally transmitted modulated symbols to a digital bitstream;

recreating, by a modulation function, a version of originally transmitted modulated symbols from said digital bitstream; and

using a channel estimation processor, obtaining delayed copies of said first stream of modulated symbols from said buffer upstream from said equalizer, obtaining said recreated version of the originally transmitted modulated symbols, performing a channel estimation calculation using said delayed copies and said recreated version to produce equalization parameters, and feeding the equalization parameters to said equalizer for improving channel estimation performed by said equalizer.

13. The method of claim 12, comprising extracting at least one predetermined training sequence from said information received over said wireless channel and calculating at least one of:

a second wireless channel estimate and a second channel equalization matrix from said predetermined training sequence.

14. The method of claim 13, wherein said channel estimation processor calculates a third channel equalization matrix from said second wireless channel estimate.

15. The method of claim 12, wherein said channel estimation processor calculates said first channel equalization matrix from said first wireless channel estimate.

16. The method of claim 15, wherein calculating said first channel equalization matrix includes calculating said first channel equalization matrix for a Multiple Input Multiple Output (MIMO) wireless channel.

17. The method of claim 12, further including an error-correction function for detecting and correcting errors in said digital bitstream prior to conversion back to said second stream of modulated symbols.

18. The method of claim 17, wherein said error-correction function is a Viterbi decoder.

19. The method of claim 12, comprising transmitting modulated symbols, converted from a second digital bitstream, over said wireless channel.

20. The method of claim 12, wherein receiving said information comprises receiving a Multiple Input Multiple Output (MIMO) signal.

21. The method of claim 12, wherein generating said first channel estimate includes generating said first channel estimate for a Multiple Input Multiple Output (MIMO) wireless channel.

22. A non-transitory computer readable medium having stored therein executable instructions that when executed by the processor of a computer control the computer to perform steps comprising:

receiving, by a receive processor, information carried via radio frequency (RF) signals over said wireless channel and converting the information to a first stream of modulated symbols;

storing, in a buffer, said first stream of modulated symbols as a buffered stream of modulated symbols;

removing, by an equalizer, effects of said wireless channel on said RF signals and generating a version of originally transmitted modulated symbols;

converting, by a demodulation function, said version of originally transmitted modulated symbols to a digital bitstream;

recreating, by a modulation function, a version of originally transmitted modulated symbols from said digital bitstream; and

using a channel estimation processor, obtaining delayed copies of said first stream of modulated symbols from said buffer upstream from said equalizer, obtaining said recreated version of the originally transmitted modulated symbols, performing a channel estimation calculation using said delayed copies and said recreated version to produce equalization parameters, and feeding the equalization parameters to said equalizer for improving channel estimation performed by said equalizer.