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

• US 20030086489A1
• Filed: 09/13/2002
• Published: 05/08/2003
• Est. Priority Date: 10/25/2001
• Status: Active Grant

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Goren, David, Hernandez, David
• Granted Patent: US 7,197,092 B2
• Time in Patent Office: Days
• US Class Current: 375/239
• CPC Class Codes: H04B 1/7075 with code phase acquisition
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference

Abstract

A method of determining and correcting for 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. Various sample shifted versions of the template are subtracted from the modulation-compensated (using the estimate of A for the particular time, n) received signal. 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. The squared error is determined between the normalized and the corrected template (A, B) for the received signal.

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:

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

subtracting various sample-shifted versions of the normalized template from the modulation-compensated (using the estimate of A for the particular time, n) received signal;

calculating the average difference between the normalized template and the modulated signal [p(n)] to determine the magnitude of the offset B for a particular time, n; and

determining the squared error between the normalized template and the corrected (for A and B) received signal, assuming the minimum error to correspond to the correct position of the predetermined shape within the signal.

2. The method according to claim 1 further comprises:

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

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.

6. The method according to claim 1 further comprises:

any signal offsets or modulations present in the received signal are removed or minimized prior to position estimation using either digital or analog signal processing.

7. The method according to claim 1 further comprises:

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

10. The method according to claim 1 or 3 further comprising:

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

11. The method according to claim 1 or 3 comprising:

averaging and calculating the difference between the template and the modulated signal [p(n)] to determine the magnitude of the offset B for a particular time, n.

3. 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 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 template with the received signal for multiple sample shifts to estimate modulation effects of A at a particular time, n;

subtracting various sample-shifted versions of the normalized template from the modulation-compensated (using the estimate of A for the particular time, n) received signal;

calculating the average difference between the normalized template and the modulated signal [p(n)] to determine the magnitude of the offset B for a particular time, n; and

determining the squared error between the normalized template and the corrected (for A and B) received signal, assuming the minimum error to correspond to the correct time of arrival for the received data

4. The method according to claim 3 further comprises the communication system is compliant with the IEEE standard 802.11.

5. The method according to claim 4 further comprises:

the template is based on receiver correlation outputs rather than the received signals, themselves.

8. The method according to claim 3 further comprises:

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

9. The method according to claim 3 further comprises:

transmit channel estimation is used to determine the amplitude offset and/or modulations.

12. A system 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:

storing apparatus which stores a template of length N incorporating a replica of a signal [s(n)] without multipath or vertical offset;

normalizing apparatus which normalizes the template and generates either an extended template or a balanced template;

receiving apparatus which receives 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; and

determining apparatus which determines the squared error between the normalized template and the corrected (for A and B) received signals, assuming the minimum error to correspond to the correct position of the predetermined shape within the signal.

13. The system of claim 12 further comprises:

correlating apparatus which correlates the extended or balanced template with the received signal for multiple sample shifts to estimate modulation effects of A at a particular time, n.

14. The system of claim 12 further comprises:

subtracting apparatus which subtracts various sample-shifted versions of the normalized template from the modulation-compensated (using the estimate of A for the particular time, n) received signal.

15. The system of claim 12 further comprises:

calculating apparatus which calculates the average difference between the normalized template and the modulated signal [p(n)] to determine the magnitude of the offset B for a particular time, n.

17. The medium of claim 12 further comprises:

program instructions conducting real-time location tracking in an IEEE 802.11-compliant environment.

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

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

program instructions 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; and

program instructions determining the squared error between the normalized template and the corrected (for A and B) received signals, assuming the minimum error to correspond to the correct position of the predetermined shape within the signal.