Time of arrival estimation for edge/GSM

• US 6,687,507 B2
• Filed: 04/17/2001
• Issued: 02/03/2004
• Est. Priority Date: 05/03/2000
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Fischer, Sven, Kangas, Ari
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Ewart, James D
• Application Number:
  US09/835,404
• Publication Number:
  US 20020004400A1
• Time in Patent Office: 1,022 Days
• Field of Search: 455/425, 455/456.1, 455/456.6, 455/334, 455/414.2, 342/450-457, 375/142, 375/150, 375/262, 375/343, 375/349
• US Class Current: 455/456.6
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements

Abstract

In systems which transmit both GSM modulated and EDGE modulated signals, time of arrival estimations can be improved without requiring the detection of the type of modulation used on the received signal. In accordance with the present invention, a received signal is initially demodulated by a receiver in accordance with a first demodulation scheme. The demodulated signal is split into two copies. Taking into account the initial demodulation, one of the copies is demodulated in accordance with another demodulation scheme, thereby resulting in a first signal demodulated in accordance with the first demodulation scheme and a second signal demodulated in accordance with a second demodulation scheme. A training sequence is used to correlate the two signals which are then summed in a incoherent integration process. The result of the incoherent integration is used to estimate the time of arrival of the received signal.

Claims

1. In a mobile telecommunications network wherein each burst of data is modulated in accordance with one of a first or a second modulation scheme, a method for estimating time of arrival comprising the steps of:

receiving a plurality of data bursts;

generating, from the plurality of received data bursts, a first sequence of demodulated data bursts based on the first modulation scheme;

generating, from the first sequence of demodulated data bursts, a second sequence of demodulated data bursts based on the second modulation scheme;

correlating each data burst associated with the first sequence of demodulated data bursts and each data burst associated with the second sequence of demodulated data bursts with a training sequence; and

incoherently integrating the correlation results to estimate said time of arrival.

2. The method of claim 1, wherein said step of generating, from the plurality of received data bursts, the first sequence of demodulated data bursts based on the first modulation scheme comprises the step of:

rotating each of the received plurality of data bursts by an angular amount that corresponds with the first modulation scheme.

3. The method of claim 1, wherein said step of generating, from the first sequence of demodulated data bursts, the second sequence of demodulated data bursts based on the second modulation scheme comprises the step of:

rotating each data burst associated with the first sequence of demodulated data bursts by an angular amount that corresponds with the second modulation scheme.

4. The method of claim 1, wherein said step of incoherently integrating the correlation results to estimate said time of arrival comprises the step of:

applying a weighting factor to each correlation result, wherein the weighting factor that is applied to any one correlation result is based on a corresponding signal-to-noise ratio.

5. The method of claim 1, wherein said step of incoherently integrating the correlation results to estimate said time of arrival comprises the step of:

applying a maximum likelihood criterion.

6. In a Global System for mobile telecommunications (GSM) based network that employs Enhanced Data Rates for Global Evolution (EDGE), a method for estimating time of arrival comprising the steps of:

receiving a plurality of data bursts;

demodulating each of the plurality of data bursts based on a Gaussian Minimum Shift Keying (GMSK) modulation scheme, thereby producing a first sequence of demodulated data bursts;

demodulating each data burst associated with the first sequence of demodulated data bursts based on a Phase Shift Keyed (PSK) modulation scheme, thereby producing a second sequence of demodulated data bursts;

correlating each data burst associated with the first sequence of demodulated data bursts and each data burst associated with the second sequence of demodulated data bursts with a training sequence; and

incoherently integrating the correlation results to estimate said time of arrival.

7. The method of claim 6, wherein said step of demodulating each of the plurality of data bursts based on a GMSK modulation scheme comprises the step of:

derotating each of the plurality of data bursts by an angular amount that corresponds with the GMSK modulation scheme.

8. The method of claim 7, wherein said step of derotating each of the plurality of data bursts by an angular amount comprises the step of:

derotating each of the plurality of data bursts by an amount equal to π

/2.

9. The method of claim 6, wherein said step of demodulating each data burst associated with the first sequence of demodulated data bursts based on a PSK modulation scheme comprises the step of:

rotating each data burst associated with the first sequence of demodulated data bursts by an angular amount that corresponds with the PSK modulation scheme.

10. The method of claim 9, wherein said step of rotating each data burst associated with the first sequence of demodulated data bursts by an angular amount comprises the step of:

rotating each data burst associated with the first sequence of demodulated data bursts by an amount equal to π

/8.

11. The method of claim 6, wherein the PSK modulation scheme is an 8-PSK modulation scheme.

12. The method of claim 6, wherein said step of incoherently integrating the correlation results to estimate said time of arrival comprises the steps of:

mathematically squaring each correlation result; and

summing the square of each correlation result.

13. The method of claim 12, wherein said step of incoherently integrating the correlation results to estimate said time of arrival further comprises the step of:

applying a weighting factor to the square of each correlation result, wherein the weighting factor that is applied to the square of any one correlation result is based on a corresponding signal-to-noise ratio.

14. The method of claim 12, wherein said step of incoherently integrating the correlation results to estimate said time of arrival further comprises the step of:

applying a maximum likelihood criterion.

15. In a mobile station comprising:

means for receiving a plurality of data bursts;

means for generating, from the plurality of received data bursts, a first sequence of demodulated data bursts based on a first modulation scheme;

means for generating, from the first sequence of demodulated data bursts, a second sequence of demodulated data bursts based on a second modulation scheme;

means for correlating each data burst associated with the first sequence of demodulated data bursts and each data burst associated with the second sequence of demodulated data bursts with a training sequence; and

means for incoherently integrating the correlation results to estimate said time of arrival.

16. The mobile station of claim 15, wherein said means for generating, from the plurality of received data bursts, the first sequence of demodulated data bursts based on the first modulation scheme comprises:

means for rotating each of the received plurality of data bursts by an angular amount that corresponds with the first modulation scheme.

17. The mobile station of claim 15, wherein said means for generating, from the first sequence of demodulated data bursts, the second sequence of demodulated data bursts based on the second modulation scheme comprises:

means for rotating each data burst associated with the first sequence of demodulated data bursts by an angular amount that corresponds with the second modulation scheme.

18. The mobile station of claim 15, wherein said means for incoherently integrating the correlation results to estimate said time of arrival comprises:

means for applying a weighting factor to each correlation result, wherein the weighting factor that is applied to any one correlation result is based on a corresponding signal-to-noise ratio.

19. The mobile station of claim 15, wherein said means for incoherently integrating the correlation results to estimate said time of arrival comprises:

means for applying a maximum likelihood criterion.