Soft linear and non-linear interference cancellation

• US 8,774,261 B2
• Filed: 06/11/2012
• Issued: 07/08/2014
• Est. Priority Date: 10/17/2011
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Abrishamkar, Farrokh, Sikri, Divaydeep, Delgado, Ken
• Primary Examiner(s): DSouza, Adolf
• Application Number:
  US13/493,203
• Publication Number:
  US 20130148711A1
• Time in Patent Office: 757 Days
• Field of Search: None
• US Class Current: 375/232
• CPC Class Codes: H04L 25/0202 Channel estimation
• CPC Class Codes: H04L 25/03012 operating in the time domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 27/01 Equalisers baseband equalizers at the transmitter end H04L25/03343; in analogue transmission systems H04B3/04, H04B7/005

Abstract

A two stage interference cancellation (IC) process includes a linear IC stage that suppresses co-channel interference (CCI) and adjacent channel interference (ACI). The linear IC stage disambiguates otherwise super-trellis data for non-linear cancellation. Soft linear IC processing is driven by a-posteriori probability (Apop) information. A second stage performs expectation maximization/Baum Welch (EM-BW) processing that reduces residual ISI left over from the first stage and also generates the Apop which drives the soft linear IC in an iterative manner.

Claims

1. A communication receiver comprising:

a first equalizer section configured to operate on a first portion of a received signal received over a channel to produce a first equalized signal and a first estimate of the channel;

an inner loop soft linear estimator section comprising a Hidden Markov Model (HMM) estimator configured to perform Estimation Maximization/Baum Welsh processing of the first equalized signal to produce an updated vector upon completion of the Estimation Maximization/Baum Welsh processing; and

an outer loop equalizer section configured to operate on the updated vector to produce a first estimate of symbols in the received signal and a second estimate of the channel, the outer loop equalizer section configured to iteratively feedback the updated vector to the inner loop soft linear estimator.

2. The communication receiver of claim 1, in which the first portion of the received signal comprises a known signal.

3. The communication receiver of claim 2, in which the known signal comprises a midamble.

4. A signal reception method, comprising:

processing a first portion of a received signal received over a channel to produce a first equalized signal and a first estimate of the channel;

performing an inner loop process comprising Estimation Maximization/Baum Welsh processing on the first equalized signal using a Hidden Markov Model (HMM) estimator to produce an updated vector upon completion of the Estimation Maximization/Baum Welsh processing; and

performing an outer loop process comprising operating on the updated vector to produce a first estimate of symbols in the received signal and a second estimate of the channel, the outer loop process further comprising iteratively providing the updated vector as input to the inner loop process.

5. The signal reception method of claim 4, in which the first portion of the received signal comprises a known signal.

6. The signal reception method of claim 5, in which the known signal comprises a midamble.

7. A signal reception apparatus, comprising:

means for processing a first portion of a received signal received over a channel to produce a first equalized signal and a first estimate of the channel;

means for performing an inner loop process comprising Estimation Maximization/Baum Welsh processing on the first equalized signal using a Hidden Markov Model (HMM) estimator to produce an updated vector upon completion of the Estimation Maximization/Baum Welsh processing; and

means for performing an outer loop process comprising operating on the updated vector to produce a first estimate of symbols in the received signal and a second estimate of the channel, the outer loop process further comprising iteratively providing the updated vector as input to the inner loop process.

8. The signal reception apparatus of claim 7, in which the first portion of the received signal comprises a known signal.

9. The signal reception apparatus of claim 8, in which the known signal comprises a midamble.

10. A system for wireless communication, comprising:

a memory; and

at least one processor coupled to the memory, the at least one processor being configured;

to process a first portion of a received signal received over a channel to produce a first equalized signal and a first estimate of the channel;

to perform an inner loop process comprising Estimation Maximization/Baum Welsh processing on the first equalized signal using a Hidden Markov Model (HMM) estimator to produce an updated vector upon completion of the Estimation Maximization/Baum Welsh processing; and

to perform an outer loop process comprising operating on the updated vector to produce a first estimate of symbols in the received signal and a second estimate of the channel, the outer loop process further comprising iteratively providing the updated vector as input to the inner loop process.

11. The system of claim 10, in which the first portion of the received signal comprises a known signal.

12. The system of claim 11, in which the known signal comprises a midamble.

13. A communication receiver comprising:

a first equalizer section configured to operate on a first portion of a received signal received over a channel to produce a first equalized signal and a first estimate of the channel;

an inner loop section configured to perform iterative estimation of the first equalized signal to produce an updated vector upon completion of the iterative estimation; and

an outer loop section configured to operate on the updated vector to produce a first estimate of symbols in the received signal and a second estimate of the channel, the outer loop equalizer section configured to iteratively feedback the updated vector to the inner loop section.