Amplitude-offset invariant template detection for pulse position estimation; methods, systems and program products

• US 7,197,092 B2
• Filed: 09/13/2002
• Issued: 03/27/2007
• Est. Priority Date: 10/25/2001
• Status: Expired due to Fees

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Goren, David, Hernandez, David
• Primary Examiner(s): Bocure; Tesfaldet
• Assistant Examiner(s): Panwalkar; Vineeta
• Application Number:
  US10/242,363
• Publication Number:
  US 20030086489A1
• Time in Patent Office: 1,656 Days
• Field of Search: 375/239, 375/316, 375/320, 375/362, 375/340, 375/343, 375/364, 375/354, 375/130, 375/140, 375/141, 375/142, 375346-349, 375/147, 375/150, 375/268, 375/259, 375/144, 375/148, 455/39, 455/500, 455/501, 455/504, 455/506, 455/296, 455/130, 455/65, 455/62
• US Class Current: 375/340
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference

Abstract

A method and system of determining and correcting modulation and offset effects in a received signal. A signal [s(n)] is received subject to modulation effects A on pulse shape or peak [p(n)] and vertical offset B due to multipath where “n” is a pulse rate or samples of the signal. A template of length N incorporates a replica of the original signal [s(n)] without multipath or vertical offset. The template is normalized and generates either an extended template or a balanced template. The extended template is correlated with the received signal [s(n)] by shifting the extended template along the received signal to estimate modulation effects of A at a particular time, n. The average difference between the template and the modulated signal [p(n)] is calculated to determine the magnitude of the offset B for a particular time, n.

Claims

1. A method of detecting the position in time of a predetermined shape within an analog or digital signal, irrespective of any amplitude modulations and/or offsets within the signal comprising the steps of

storing a template of length N incorporating a replica of the signal [s(n)] without multipath;

and

receiving the signal [s(n)] subject to modulation effects A on pulse shape or peak [p(n)] and vertical offset B where “

n”

is representative of a time index or samples of the signal;

correlating the template with the received signal or multiple sample shifts to create a modulation-compensated received signal to estimate modulation effects of A at a particular time, n;

subtracting various sample-shifted versions of the template from the modulation-compensated received signal to produce a corrected modulation-compensated received signal;

calculating the average difference between the template and the corrected modulation-compensated received signal to determine the magnitude of the offset B for a particular time, n; and

determining the squared error between the template, modified by the determined magnitude of the offset B, and the corrected modulation-compensated received signal, assuming the minimum error to correspond to the correct position of the predetermined shape within the signal.

2. The method of claim 1 further comprising:

normalizing the template and generating either an extended template (antisymmetric concatenation) or a balanced template (DC-shifting), the integral (analog) or sum (discrete) of which is precisely equal to zero.

3. The method according to claim 2 wherein the communication system is compliant with IEEE standard 802.11.

4. The method according to claim 1 further comprising:

removing or minimizing any signal offsets or modulations present in the received signal prior to position estimation using either digital or analog signal processing.

5. The method according to claim 1 further comprising:

pulse shaping the signal to diminish the effects of any amplitude offset and/or modulation.

6. The method according to claim 2 further comprising

received multipath estimation/profiling to determine any amplitude offset and/or modulations.

7. The method according to claim 2 further comprising:

transmit channel estimating to determine the amplitude offset and/or modulations.

8. The method according to claim 2 further comprising:

shifting the extended template along the received signal to estimate modulation effects of A at a particular time.

9. A method of detecting the time of arrival of received data in a wireless communication system using analog or digital analysis, irrespective of any amplitude modulations and/or DC offsets in the received signal, comprising the steps of:

storing a template of length N incorporating a replica of the transmitted signal [s(n)] without multipath;

normalizing the template and generating either an extended template (antisymmetric concatenation) or a balanced template (DC-shifting), the integral (analog) or sum (discrete) of which is precisely equal to zero;

receiving the modulated signal [s(n)] subject to modulation effects A on pulse shape or peak [p(n)] and vertical offset B due to multipath where “

n”

is representative of a time index or samples of the signal;

correlating the extended or balanced template with the received signal for multiple sample shifts to create a modulation-compensated received signal to estimate modulation effects of A at a particular time, n;

subtracting various sample-shifted versions of the normalized template from the modulation-compensated received signal to produce a corrected modulation-compensated received signal;

calculating the average difference between the normalized template and the corrected modulation-compensated received signal to determine the magnitude of the offset B for a particular time, n; and

determining the squared error between the normalized template, modified by the determined magnitude of the offset B, and the corrected modulation-compensated received signal, assuming the minimum error to correspond to the correct time of arrival for the received data.

10. The method according to claim 9 further comprising:

basing the extended or balanced template on receiver correlation outputs rather than the received signals.

11. A medium, executable in a computer system, for detecting a position in time of a predetermined shape within an analog or digital signal, irrespective of any amplitude modulations and/or offsets within the signal comprising:

program instructions for storing a template of length N incorporating a replica of a signal [s(n)] without multipath;

program instructions for normalizing the template and generating either an extended template or a balanced template;

program instructions for receiving a modulated signal [s(n)] subject to modulation effects A on pulse shape or peak [p(n)] and vertical offset B where “

n”

is representative of a time index or samples of the signal; and

program instructions for correlating the extended template with the received signal for multiple sample shifts to create a modulation-compensated received signal to estimate modulation effects of A at a particular time, n;

program instructions for subtracting various sample-shifted versions of the normalized template from the modulation-compensated received signal to produce a corrected modulation-compensated received signal;

program instructions for calculating the average difference between the normalized template and the corrected modulation-compensated received signal to determine the magnitude of the offset B for a particular time, n; and

program instructions for determining the squared error between the normalized template, modified by the determined magnitude of the offset B, and the corrected modulation-compensated received signal, assuming the minimum error to correspond to the correct position of the predetermined shape within the signal.

12. The medium of claim 11 further comprising:

program instructions for conducting real-time location tracking in the IEEE 802.11 local-area-network signal environment.

13. A system for detecting the position in time of a predetermined shape within an analog or digital signal, irrespective of any amplitude modulations and/or offsets within the signal, comprising:

at least one processor;

at least one memory coupled to the at least one processor and containing instructions which when executed by the processor cause the at least one processor to perform the steps of;

storing a template of length N incorporating a replica of the transmitted signal [s(n)] without multipath;

normalizing the template and generating either an extended template (antisymmetric concatenation) or a balanced template (DC-shifting), the integral (analog) or sum (discrete) of which is precisely equal to zero;

receiving the modulated signal [s(n)] subject to modulation effects A on pulse shape or peak [p(n)] and vertical offset B due to multipath where “

n”

is representative of a time index or samples of the signal;

correlating the extended or balanced template with the received signal for multiple sample shifts to create a modulation-compensated received signal to estimate modulation effects of A at a particular time, n;

subtracting various sample-shifted versions of the normalized template from the modulation-compensated received signal to produce a corrected modulation-compensated received signal;

calculating the average difference between the normalized template and the corrected modulation-compensated received signal to determine the magnitude of the offset B for a particular time, n; and

determining the squared error between the normalized template, modified by the determined magnitude of the offset B, and the corrected modulation-compensated received signal, assuming the minimum error to correspond to the correct time of arrival for the received data.