Local oscillator phase noise tracking for single carrier transmission

• US 9,258,107 B1
• Filed: 12/23/2014
• Issued: 02/09/2016
• Est. Priority Date: 12/23/2014
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Warke, Nirmal C., Jorgensen, Lars Morten, Hosur, Srinath
• Primary Examiner(s): Singh, Hirdepal
• Application Number:
  US14/580,595
• Time in Patent Office: 413 Days
• US Class Current: 1/1
• CPC Class Codes: H04L 2027/0053 Closed loops
• CPC Class Codes: H04L 2027/0093 Intermittant signals
• CPC Class Codes: H04L 27/0014 Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657

Abstract

A system and method for tracking noise in a received signal uses a forward/backward Decision-Directed Phase Tracking Loop to generate a phase-noise compensation signal that removes phase noise from received single-carrier signals.

Claims

1. A decision-directed phase lock loop for correcting phase error in a received signal, comprising:

a first buffer configured to store a block of input symbols, the block of input symbols starting with a first pilot symbol and ending with a last pilot symbol;

a phase rotator configured to apply a phase-noise compensation to the block of input symbols on a symbol-by-symbol basis;

a feedback loop coupled to the phase rotator, the feedback loop providing a phase-noise compensation signal to the phase rotator;

a first output buffer configured to store a first block of phase-noise-compensated symbols output from the phase-rotator, where the symbols in the first block of phase-noise-compensated symbols are sequentially received from the phase rotator starting with the first pilot symbol;

a second output buffer configured to store a second block of phase-noise-compensated symbols output from the phase-rotator, where the symbols in the second block of phase-noise-compensated symbols are sequentially received from the phase rotator starting with the last pilot symbol; and

a combiner configured to combine associated symbols from the first and second blocks of phase-noise-compensated symbols to create output symbols, wherein the associated symbols from the first and second blocks of phase-noise-compensated symbols are combined using a process selected from the group consisting of;

weighted symbol-by-symbol combining using a Log-Likelihood Ratio (LLR) metric; and

weighted symbol-by-symbol combining using a Minimum-Mean-Square Error (MMSE) error metric.

2. A decision-directed phase lock loop for correcting phase error in a received signal, comprising:

a first buffer configured to store a block of input symbols, the block of input symbols starting with a first pilot symbol and ending with a last pilot symbol, wherein the block of input symbols comprises unknown data symbols and additional pilot symbols between the first pilot symbol and the last pilot symbol;

a phase rotator configured to apply a phase-noise compensation to the block of input symbols on a symbol-by-symbol basis;

a feedback loop coupled to the phase rotator, the feedback loop providing a phase-noise compensation signal to the phase rotator, wherein the phase compensation signal provided to the phase rotator is generated using a process selected from the following group;

phase-noise-error detection over an entire block of input symbols; and

phase-noise-error detection using every N^th pilot symbol in the block of input symbols;

a first output buffer configured to store a first block of phase-noise-compensated symbols output from the phase-rotator, where the symbols in the first block of phase-noise-compensated symbols are sequentially received from the phase rotator starting with the first pilot symbol;

a second output buffer configured to store a second block of phase-noise-compensated symbols output from the phase-rotator, where the symbols in the second block of phase-noise-compensated symbols are sequentially received from the phase rotator staring with the last pilot symbol; and

a combiner configured to combine associated symbols from the first and second blocks of phase-noise-compensated symbols to create output symbols.

3. A decision-directed phase lock loop for correcting phase error in a received signal, comprising:

a first buffer configured to store a block of input symbols, the block of input symbols starting with a first pilot symbol and ending with a last pilot symbol;

a phase rotator configured to apply a phase-noise compensation to the block of input symbols on a symbol-by-symbol basis, wherein the phase rotator is configured to apply an initial phase-noise-error compensation to a first-received pilot symbol from the block of input symbols based upon a phase-noise-error compensation applied to a prior block of input symbols;

a feedback loop coupled to the phase rotator, the feedback loop providing a phase-noise compensation signal to the phase rotator;

a first output buffer configured to store a block of phase-noise-compensated symbols output from the phase-rotator, where the symbols in the first block of phase-noise-compensated symbols are sequentially received from the phase rotator starting with the first pilot symbol;

a second output buffer configured to store a second block of phase-noise-compensated symbols output from the phase-rotator, where the symbols in the second block of phase-noise-compensated symbols are sequentially received from the phase rotator staring with the last pilot symbol; and

a combiner configured to combine associated symbols from the first and second blocks of phase-noise-compensated symbols to create output symbols.

4. The decision-directed phase lock loop of claim 3, wherein the initial phase-noise-error compensation of a first-received pilot symbol from the block of input symbols is based upon a phase-noise-error compensation applied to a last symbol in a prior block of input symbols.

5. A decision-directed phase lock loop for correcting phase error in a received signal, comprising:

a first buffer configured to store a block of input symbols, the block of input symbols starting with a first pilot symbol and ending with a last pilot symbol;

a phase rotator configured to apply a phase-noise compensation to the block of input symbols on a symbol-by-symbol basis;

a feedback loop coupled to the phase rotator, the feedback loop providing a phase-noise compensation signal to the phase rotator, wherein a hard decision module in the feedback loop receives an output from the phase rotator and determines a closest point in a modulation constellation for each received symbol, wherein a phase estimator in the feedback loop receives a first input from the phase rotator and a second input from the hard decision module;

a first output buffer configured to store a first block of phase-noise-compensated symbols output from the phase-rotator, where the symbols in the first block of phase-noise-compensated symbols are sequentially received from the phase rotator starting with the first pilot symbol;

a second output buffer configured to store a second block of phase-noise-compensated symbols output from the phase-rotator, where the symbols in the second and block of phase-noise-compensated symbols are sequentially received from the phase rotator starting with the last pilot symbol;

a combiner configured to combine associated symbols from the first and second blocks of phase-noise-compensated symbols to create output symbols; and

a Forward Error Correction (FEC) decoder coupled to an output of the combiner and configured to decode the output symbols, wherein an output of FEC decoder is coupled to the phase estimator, the phase estimator configured to use decoded output symbols in place of the input from the hard decision module.

6. A method for correcting phase error in a received signal, comprising:

receiving a block of input symbols starting with a first pilot symbol and ending with a last pilot symbol;

applying phase-noise compensation to the block of input symbols in a forward direction starting with the first pilot symbol;

storing a first block of phase-noise-compensated symbols to a first output buffer, the first block of phase-noise-compensated symbols corresponding to the forward-direction block of input symbols;

applying phase-noise compensation to the block of input symbols in a backward direction starting with the last pilot symbol;

storing a second block of phase-noise-compensated symbols to a second output buffer, the second block of phase-noise-compensated symbols corresponding to the backward-direction block of input symbols; and

combining the associated symbols from the first and second blocks of phase-noise-compensated symbols to create output symbols using a process selected from the group consisting of;

weighted symbol-by-symbol combining using a Log-Likelihood Ratio (LLR) metric; and

weighted symbol-by-symbol combining using a Minimum-Mean-Square Error (MMSE) error metric.

7. A method for correcting phase error in a received signal, comprising:

receiving a block of input symbols staring with a first pilot symbol and ending with a last pilot symbol, wherein the block of input symbols comprises unknown data symbols and additional pilot symbols between the first pilot symbol and the last pilot symbol;

applying phase-noise compensation to the block of input symbols in a forward direction starting with the first pilot symbol;

generating said phase-noise compensation using a process selected from the following group;

phase-noise-error detection over an entire block of input symbols; and

phase-noise-error detection using every Nth pilot symbol in the block of input symbols,

storing a first block of phase-noise-compensated symbols to a first output buffer, the first block of phase-noise-compensated symbols corresponding to the forward-direction block of input symbols;

applying said selected phase-noise compensation to the block of input symbols in a backward direction starting with the last pilot symbol, said compensation;

storing a second block of phase-noise-compensated symbols to a second output buffer, the second block of phase-noise-compensated symbols corresponding to the backward-direction block of input symbols;

combining the associated symbols from the first and second blocks of phase-noise-compensated symbols to create output symbols.

8. A method for correcting phase error in a received signal, comprising:

receiving a block of input symbols starting with a first pilot symbol and ending with a last pilot symbol;

applying phase-noise compensation to the block of input symbols in a forward direction starting with the first pilot symbol;

wherein an initial phase-noise-error compensation of a first-received pilot symbol from the block of input symbols is based upon a phase-noise-error compensation applied to a prior block of input symbols;

storing a first block of phase-noise-compensated symbols to a first output buffer, the first block of phase-noise-compensated symbols corresponding to the forward-direction block of input symbols;

applying phase-noise compensation to the block of input symbols in a backward direction starting with the last pilot symbol;

storing a second block of phase-noise-compensated symbols to a second output buffer, the second block of phase-noise-compensated symbols corresponding to the backward-direction block of input symbols; and

combining the associated symbols from the first and second blocks of phase-noise-compensated symbols to create output symbols.

9. The method of claim 8, wherein an initial phase-noise-error compensation of the first-received pilot symbol from the block of input symbols is based upon a phase-noise-error compensation applied to a last symbol in a prior block of input symbols.

10. A method for correcting phase error in a received signal, comprising:

receiving a block of input symbols starting with a first pilot symbol and ending with a last pilot symbol;

applying phase-noise compensation to the block of input symbols in a forward direction starting with the first pilot symbol;

storing a first block of phase-noise-compensated symbols to a first output buffer, the first block of phase-noise-compensated symbols corresponding to the forward-direction block of input symbols;

applying phase-noise compensation to the block of input symbols in a backward direction starting with the last pilot symbol;

storing a second block of phase-noise-compensated symbols to a second output buffer, the second block of phase-noise-compensated symbols corresponding to the backward-direction block of input symbols;

combining the associated symbols from the first and second blocks of phase-noise-compensated symbols to create output symbols;

providing the output symbols to a Forward Error Correction (FEC) decoder; and

using decoded symbols from the FEC decoder to apply phase-noise compensation to the block of input symbols in a forward direction and backward direction during one or more additional iterations.