METHOD AND SYSTEM FOR JOINT TIME-OF-ARRIVAL AND AMPLITUDE ESTIMATION BASED ON A SUPER-RESOLUTION TECHNIQUE

• US 20080267304A1
• Filed: 04/18/2008
• Published: 10/30/2008
• Est. Priority Date: 04/27/2007
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Chong, Chia-Chin, Inamura, Hiroshi, Watanabe, Fujio
• Granted Patent: US 8,208,587 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 3/043 Receivers
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0221 Receivers
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04L 25/0202 Channel estimation

Abstract

In a geolocation application, a method is provided to jointly estimate the time-of-arrival (TOA) and the amplitude of a received signal based on super-resolution technique. The super-resolution joint TOA-amplitude estimators are provided based on either the expectation-maximization (EM), parallel-interference-cancellation space-alternating generalized expectation maximization (PIC-SAGE) or serial-interference-cancellation SAGE (SIC-SAGE). The SIC-SAGE estimator minimizes the ranging estimation error especially under a non-line-of-sight (NLOS) condition. The SIC-SAGE estimator is a simplified version of the maximum likelihood estimator with more stable performance in a multipath rich environment, such as the ultra-wideband (UWB) based applications. These techniques provide the following benefits: 1) it is generic, so that signal processing can be deployed on both time-domain (e.g., UWB impulse-radio) and frequency-domain (e.g., multi-band orthogonal frequency-division multiplexing (MB-OFDM)) based transceiver schemes and applicable for both UWB and non-UWB systems; 2) it is robust especially under NLOS condition and multipath rich environment.

Claims

1. A method for jointly estimating parameters of a signal received in a multipath environment, comprising:

Iterating until convergence;

(a) an expectation step that estimates signal components of the received signal in one or more paths of the multipath environment; and

(b) a maximization step that provides, for each signal component estimated by the expectation step, maximum likelihood estimates of a parameter vector that includes two or more parameters.

2. A method as in claim 1, wherein the parameter vector includes time-of-arrival and amplitude.

3. A method as in claim 1, wherein the parameter vector includes one or more of:

time-of-arrival, amplitude and angle-of-arrival.

4. A method as in claim 1, wherein the expectation step is based on decomposition of the received signal according to a model which regards the received signal as incomplete data and each signal component as complete data characterized a signal parameter and a weighted noise component.

5. A method as in claim 1, wherein the method is practiced in a time-domain based receiver.

6. A method as in claim 1, wherein the method is practiced in a frequency-domain based receiver.

7. A method as in claim 1, wherein the expectation step estimates the signal components according to a selected one of EM technique, a PIC-SAGE technique and a SIC-SAGE technique.

8. A method as in claim 7, wherein the SIC-SAGE technique is applied in the expectation step, and wherein the paths are ordered according to their received powers.

9. A method as in claim 8, wherein paths are estimated and cancelled successively.

10. A method as in claim 1, wherein the parameter vector comprises two or more overlapping subsets, and wherein each subset is updated independently.

11. A method as in claim 1, wherein the maximization step is carried out using a cost function that includes a two-folded correlation function.

12. A method as in claim 11, wherein the correlation function includes a spatial correlation component and a delay correlation component.

13. A method as in claim 11, wherein the correlation function includes a frequency correlation component and a delay correlation component.

14. A method as in claim 1, further comprising an initialization step to provide initial conditions prior to iterating.

15. A method as in claim 14, wherein the initialization step comprises apply a joint SIC and SIC-SAGE techniques.

16. An estimator for jointly estimating parameters of a signal received in a multipath environment, comprising:

a control element that iterates until convergence the operations of;

(a) an expectation element that estimates signal components of the received signal in one or more paths of the multipath environment; and

(b) a maximization element that provides, for each signal component estimated by the expectation element, maximum likelihood estimates of a parameter vector that includes two or more parameters.

17. An estimator as in claim 16, wherein the parameter vector includes time-of-arrival and amplitude.

18. An estimator as in claim 16, wherein the parameter vector includes one or more of:

time-of-arrival, amplitude and angle-of-arrival.

19. An estimator as in claim 16, wherein the expectation element decomposes the received signal according to a model which regards the received signal as incomplete data and each signal component as complete data characterized a signal parameter and a weighted noise component.

20. An estimator as in claim 16, wherein the estimator is provided in a time-domain based receiver.

21. An estimator as in claim 16, wherein the estimator is provided in a frequency-domain based receiver.

22. An estimator as in claim 16, wherein the expectation element estimates the signal components according to a selected one of EM technique, a PIC-SAGE technique and a SIC-SAGE technique.

23. An estimator as in claim 16, wherein the SIC-SAGE technique is applied in the expectation step, and wherein the paths are ordered according to their received powers.

24. An estimator as in claim 23, wherein paths are estimated and cancelled successively.

25. An estimator as in claim 16, wherein the parameter vector comprises two or more overlapping subsets, and wherein each subset is updated independently.

26. An estimator as in claim 16, wherein the maximization element uses a cost function that includes a two-folded correlation function.

27. An estimator as in claim 26, wherein the correlation function includes a spatial correlation component and a delay correlation component.

28. An estimator as in claim 26, wherein the correlation function includes a frequency correlation component and a delay correlation component.

29. An estimator as in claim 16, wherein the control element initializes to provide initial conditions prior to iterating.

30. An estimator as in claim 29, wherein the control element applies joint SIC and SIC-SAGE techniques to initialize.