Self-synchronizing equalization techniques and systems

• US 5,937,014 A
• Filed: 03/27/1997
• Issued: 08/10/1999
• Est. Priority Date: 03/27/1997
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Anderson, Soren, Pelin, Per
• Primary Examiner(s): Le, Amanda T.
• Application Number:
  US08/827,169
• Time in Patent Office: 866 Days
• Field of Search: 375/340, 375/341, 375/346, 375/348, 375/262
• US Class Current: 375/340
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7073 Synchronisation aspects
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 2201/709727 GRAKE type RAKE receivers
• CPC Class Codes: H04B 7/04 using two or more spaced independent antennas
• CPC Class Codes: H04L 2025/03401 PSK
• CPC Class Codes: H04L 25/025 using least-mean-square [LMS] method
• CPC Class Codes: H04L 25/03012 operating in the time domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 25/0328 with interference cancellation circuitry adaptations for interference cancellation within a sequence estimator H04L25/03305; interference related aspects of direct sequence spread spectrum H04B1/7097; interference related aspects of frequency hopping spread spectrum H04B1/715; see also H04B1/10

Abstract

Methods and systems for processing received radio signals are described wherein the finite alphabet quality of digital transmissions is utilized to improve performance. Nonsynchronous sampling of received signals introduces intersymbol interference which is compensated for by these methods and systems. Different types of signal modulation, and their impact on this type of intersymbol interference are discussed. A robust diversity combining technique, usable in conjunction with antenna arrays is developed.

Claims

1. A method for processing a signal received in a radiocommunication system comprising the steps of:

(a) sampling said received signal, whereby intersymbol interference is introduced into said received signal;

(b) generating at least one channel estimate and an associated signal sample estimate associated with said received signal;

(c) estimating said introduced intersymbol interference;

(d) updating said at least one channel estimate and said associated signal sample estimate associated with said received signal using said estimated introduced intersymbol interference;

(e) repeating steps (b), (c) and (d) for a predetermined number of iterations; and

(f) outputting said channel estimate and an associated signal sample estimate.

2. The method of claim 1, wherein said step of sampling further comprises the step of:

nonsynchronously sampling said received signal.

3. The method of claim 1, wherein said step of repeating further comprises:

performing, as said predetermined number of iterations, iterations until a value associated with said signal sample estimate converges.

4. The method of claim 1 wherein said at least one channel estimate is generated using a decoupled weighted iterative least squares with projections (DWILSP) algorithm.

5. The method of claim 1, wherein said step of estimating further comprises the step of:

estimating said introduced intersymbol interference based on a type of modulation used to modulate said received signal.

6. A system for processing a radio signal comprising:

means for sampling said radio signal, whereby intersymbol interference is introduced into said received signal;

means for generating at least one channel estimate and an associated signal sample estimate associated with said received signal;

means for estimating said introduced intersymbol interference;

means for updating said at least one channel estimate and said associated signal sample estimate associated with said received signal using said estimated introduced intersymbol interference;

means for iteratively applying said means for estimating and said means for updating for a predetermined number of iterations; and

means for outputting said at least one channel estimate and said associated signal sample estimate.

7. The system of claim 6, wherein said means for sampling further comprises:

means for nonsynchronously sampling said radio signal.

8. The method of claim 6, wherein said step of repeating further comprises:

performing, as said predetermined number of iterations, iterations until a value associated with said signal sample estimate converges.

9. The method of claim 6 wherein said at least one channel estimate is generated using a decoupled weighted iterative least squares with projections (DWILSP) algorithm.

10. The system of claim 6, wherein said means for estimating further comprises:

means for estimating said introduced intersymbol interference based on a type of modulation used to modulate said received signal.