Method and system for angle of arrival estimation and data detection using vector per-survivor processing of signals from an array of antennas

• US 6,614,859 B2
• Filed: 05/26/1998
• Issued: 09/02/2003
• Est. Priority Date: 05/27/1997
• Status: Expired due to Term

• Current Assignee: Trellisware Technologies, Inc. (ViaSat Incorporated)
• Original Assignee: Trellisware Technologies, Inc. (ViaSat Incorporated)
• Inventors: Lay, Norman E.
• Primary Examiner(s): Bocure, Tesfaldet
• Assistant Examiner(s): BURD, KEVIN MICHAEL
• Application Number:
  US09/084,615
• Publication Number:
  US 20020122472A1
• Time in Patent Office: 1,925 Days
• Field of Search: 375/316, 375/340, 375/343, 375/324, 375/349, 375/148, 375/152, 375/341, 375/262, 714/796, 342/156, 342/378
• US Class Current: 375/341
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence
• CPC Class Codes: H04L 25/03337 Arrangements involving per-survivor processing

Abstract

A method and a system are provided which uses vector per-survivor processing (PSP) on the outputs of an array of antennas of arbitrary geometry to jointly estimate angles of arrival of multipath components of the transmitted data sequence (i.e., the modulated data signal) while extracting an estimate of the modulated data. The system includes an antenna array of arbitrary geometry (i.e., arbitrary spacing between elements, directional, omnidirectional, etc.), each element of which has its output applied to a corresponding matched filter. The matched filter outputs in turn are sampled and applied to a vector-type PSP engine, wherein the vector PSP engine computes an estimate of the channels between the transmitter antenna and the receiver antenna elements to construct a channel estimation matrix. Angle of arrival estimates of each of the multipath components are extracted from the channel estimation matrix for the best survivor. An estimate of the transmitted data sequence is also extracted based on the best survivor. The PSP engine performs its function in the form of equations that solve for the vector estimates of complex channels, where the channel models include multipath angles of arrival.

Claims

1. A method for estimating a transmitted data sequence based on an actual received signal vector and for estimating respective angles of arrival comprises:

receiving multipath components of a digitally-phase-modulated signal at an array of antennas of arbitrary geometry to produce the actual received signal vector of received components from the array of antennas;

sampling the received components of the actual received signal vector at regular symbol times to produce an actual sampled received signal vector; and

applying vector per-survivor processing to the actual sampled received signal vector to yield an estimate of the transmitted data sequence and an estimated angle of arrival of each of the multipath components of the digitally-phase-modulated signal.

2. The method according to claim 1 wherein said vector per-survivor processing step comprises:

multiplying components of a channel estimation matrix comprising scalar values representing multipath components for each of the antennas by a corresponding coefficient of a hypothesized transmitted data sequence for a surviving path to produce the estimate of the sampled received signal vector;

comparing the estimate of the sampled received signal vector with the actual sampled received signal vector to yield an error term;

selecting as the best surviving path that path with the minimum accumulated error metric as determined by the error term;

updating the channel estimation matrix using the error term;

reporting the hypothesized transmitted data sequence for selected best surviving path; and

reporting selected parameters in the channel estimation matrix comprising the estimated angle of arrival for each of the multipath components.

3. The method according to claim 2 wherein the updating step comprises:

computing a coefficient gradient estimation vector with respect to each received power and phase coefficient; and

subtracting said coefficient gradient estimation vector as weighted by a scaling coefficient from the current estimate of the coefficient vector to obtain an updated estimate of the coefficient vector.

4. The method according to claim 3 wherein the updating step further includes the steps of:

computing a gradient estimation vector with respect to each angle of arrival component;

subtracting said angle gradient estimation vector as weighted by a scaling coefficient from the current estimate of the angle of arrival vector to obtain an updated estimate of the angle of arrival vector; and

combining the updated estimate of the coefficient vector and the updated estimate of the angle of arrival vector to obtain an updated channel estimation matrix.

5. The method according to claim 1 wherein the step of applying vector per-survivor processing to the actual sampled received signal vector comprises:

calculating the estimate of the transmitted data sequence and the estimated angle of arrival substantially simultaneously; and

calculating the estimated angle of arrival in response to the estimate of the transmitted data.

8. The system according to claim 5 wherein the updating means comprises:

means for computing a coefficient gradient estimation vector with respect to each received power and phase coefficient; and

means for subtracting said coefficient gradient estimation vector as weighted by a scaling coefficient from the current estimate of the coefficient vector to obtain an updated estimate of the coefficient vector.

6. A system for estimating a transmitted data sequence based on an actual received signal vector for estimating angles of arrival of multipath components of the actual received signal vector comprises:

an array of antennas of arbitrary geometry receiving multipath components of a digitally-phase-modulated signal of a digital transmission to produce the actual received signal vector of received components from the array of antennas;

sampling circuitry for sampling the received components of the actual received signal vector at regular symbol times to produce an actual sampled received signal vector; and

a vector per-survivor processor for processing the actual received signal vector to yield an estimate of the transmitted data sequence and an estimated angle of arrival of each of the multipath components of the digitally-phase-modulated signal.

7. The system according to claim 6 wherein said vector per-survivor processor comprises:

a matrix multiplier for multiplying components of a channel estimation matrix comprising scalar values representing multipath components for each of the antennas by a corresponding coefficient of a hypothesized transmitted data sequence for a surviving path to produce the estimate of the sampled received signal vector;

comparators for comparing the estimate of the sampled received signal vector with the actual sampled received signal vector to yield an error term;

a best surviving path selector for selecting as the best surviving path that path with the minimum accumulated error metric as determined by the error term;

updating means for updating the channel estimation matrix using the error term;

output means for reporting the hypothesized transmitted data sequence for selected best surviving path; and

output means for reporting selected parameters in the channel estimation matrix comprising an estimated angle of arrival for each of the multipath components.

9. The system according to claim 6 wherein the updating moans further includes:

means for computing a gradient estimation vector with respect to each angle of arrival component;

means for subtracting said angle gradient estimation vector as weighted by a scaling coefficient from the current estimate of the angle of arrival vector to obtain an updated estimate of the angle of arrival vector; and

means for combining the updated estimate of the coefficient vector and the updated estimate of the angle of arrival vector to obtain an updated channel estimation matrix.

10. The system according to claim 6 where the vector per-survivor processor calculating the estimate of the transmitted data sequence and the estimated angle of arrival substantially simultaneously, and calculating the estimated angle of arrival in response to the estimate of the transmitted data.