Processing a sequence of samples of a signal using downsampling

• US 7,830,950 B2
• Filed: 11/15/2006
• Issued: 11/09/2010
• Est. Priority Date: 11/18/2005
• Status: Expired due to Fees

• Current Assignee: Conversant Wireless Licensing S.à.r.l. (f/k/a Core Wireless Licensing S.a.r.l.) (MOSAID Technologies Inc. (f/k/a Conversant Intellectual Property Management))
• Original Assignee: Nokia Corporation
• Inventors: Valio, Harri, Qin, Zhengdi
• Primary Examiner(s): Torres; Juan A
• Application Number:
  US11/600,592
• Publication Number:
  US 20070116098A1
• Time in Patent Office: 1,455 Days
• Field of Search: 375/147, 375/130
• US Class Current: 375/147
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073

Abstract

For processing a sequence of samples of a signal, it is assumed that the signal comprises a carrier that is modulated by a code composed of a sequence of chips. A method of wiping-off an influence by the carrier on the sequence of samples and downsampling the sequence of samples (step 105; step 205; step 301) is shown, as well as utilizing the downsampled sequence of samples as a new sequence of samples for further processing (step 108; step 209; step 302). Also shown are a corresponding processing component 72, a corresponding electronic device 71, a corresponding system, a corresponding software program code and a corresponding software program product.

Claims

1. A method for processing a sequence of samples of a signal, said signal comprises a carrier that is modulated by a code composed of a sequence of chips, said method comprising at a receiver:

a) wiping-off, by said receiver, an influence by said carrier on said sequence of samples and downsampling said sequence of samples, said wiping-off and downsampling comprising combining respective subsequent samples of a predetermined number of said sequence of samples and exploiting regularities in said sequence of samples in said combining, to obtain a sequence of combined values as a downsampled sequence of samples; and

b) utilizing said downsampled sequence of samples as a new sequence of samples for further processing.

2. The method according to claim 1, wherein a respective combined value lies within a predetermined range or outside of a predetermined range, said method further comprising the following step preceding step b):

in case a combined value lies within said predetermined range, shifting said sequence of samples by one sample and combining respective subsequent samples of a predetermined number of said shifted sequence of samples to obtain a sequence of combined values.

3. The method according to claim 1, further comprising shifting said sequence of samples by one sample and combining respective subsequent samples of a predetermined number of said shifted sequence of samples to obtain a further sequence of combined values, wherein b) comprises utilizing said sequence of combined values and said further sequence of combined values as a respective new sequence of samples for further processing in which an influence by said carrier has been wiped-off, and combining said processed sequence of combined values and said processed further sequence of combined values to a single sequence of values.

4. The method according to claim 1, wherein said combining respective subsequent samples comprises combining respective two subsequent samples.

5. The method according to claim 1, wherein said carrier is a binary offset carrier and wherein said code is a pseudo-random noise code.

6. The method according to claim 5, wherein said binary offset carrier is a BOC(n,n), with n being a natural number, wherein said sampling rate is four samples per chip of said pseudo-random noise code, said sequence of samples being denoted by X={x₁, x₂, x₃, x₄, x₅, x₆, . . . }, and wherein said combining is performed by applying the following equation on said sequence of samples:

Y={[y₁, y₂], . . . [y_2n+1, y_2n+2], . . . }

where,

y_2n+1=(x_4n+1+x_4n+2)/2 (n=0, 1, 2, 3, . . . )

y_2n+2=−

(x_4n+3+x_4n+4)/2

Y being said sequence of combined values.

7. The method according to claim 5, wherein said binary offset carrier is a BOC(2n,n), with n being a natural number, wherein said sampling rate is four samples per chip of said pseudo-random noise code, said sequence of samples being denoted by X={x₁, x₂, x₃, x₄, x₅, x₆, . . . }, and wherein said combining is performed by applying the following equation on said sequence of samples:

Y={y₁, y₂, y₃, . . . }

where,

y_n=(x_2n+1−

x_2n+2)/2 (n=0, 1, 2, 3, . . . )

Y being said sequence of combined values.

8. An apparatus for processing a sequence of samples of a signal, said signal comprises a carrier that is modulated by a code composed of a sequence of chips, said apparatus comprising, implemented at least partly in hardware:

a carrier wipe-off and downsampling portion configured to wipe-off an influence by said carrier on said sequence of samples and to downsample said sequence of samples, wherein said carrier wipe-off and downsampling portion is configured to combine respective subsequent samples of a predetermined number of said sequence of samples and to exploit regularities in said sequence of samples in said combining, to obtain a sequence of combined values as a downsampled sequence of samples; and

a processing component configured to utilize a downsampled sequence of samples provided by said carrier wipe-off and downsampling portion as a new sequence of samples for further processing.

9. System comprising an apparatus according to claim 8.

10. The apparatus according to claim 8, further comprising an analog-to-digital converter configured to obtain said samples of said signal with a sampling rate, which is at least equal to a frequency of said carrier and at least twice a chiprate of said code.

11. The apparatus according to claim 8, wherein a respective combined value lies within a predetermined range or outside of a predetermined range, and wherein said carrier wipe-off and downsampling portion is configured to shift said sequence of samples by one sample and combining respective subsequent samples of a predetermined number of said shifted sequence of samples to obtain a sequence of combined values, in case a combined value lies within said predetermined range.

12. The apparatus according to claim 11, wherein said predetermined range comprises only a single value of zero.

13. The apparatus according to claim 8, wherein said carrier wipe-off and downsampling portion is configured to shift said sequence of samples by one sample and to combine respective subsequent samples of a predetermined number of said shifted sequence of samples to obtain a further sequence of Combined values, and wherein said processing component is configured to utilize said sequence of combined values and said further sequence of combined values as a respective new sequence of samples for further processing in which an influence by said carrier has been wiped-off, and to combine said processed sequence of combined values and said processed further sequence of combined values to a single sequence of values.

14. The apparatus according to claim 8, wherein said carrier is a binary offset carrier and wherein said code is a pseudo-random noise code.

15. The apparatus according to claim 14, wherein said binary offset carrier is a BOC(n,n), with n being a natural number, wherein said sampling rate is four samples per chip of said pseudo-random noise code, said sequence of samples being denoted by X={x₁, x₂, x₃, x₄, x₅, x₆, . . . }, and wherein said carrier wipe-off and downsampling portion is configured to perform said combining by applying the following equation on said sequence of samples:

Y={[y₂], . . . [y_2n+1, y_2n+2], . . . }

where,

y_2n+1=(x_4n+1+x_4n+2)/2 (n=0, 1, 2, 3, . . . )

y_2n+2=−

(x_4n+3+x_4n+4)/2

Y being said sequence of combined values.

16. Apparatus according to claim 14, wherein said binary offset carrier is a BOC(2n,n), with n being a natural number, wherein said sampling rate is four samples per chip of said pseudo-random noise code, said sequence of samples being denoted by X={x₁, x₂, x₃, x₄, x₅, x₆, . . . }, and wherein said carrier wipe-off and downsampling portion is configured to perform said combining by applying the following equation on said sequence of samples:

Y={y₁, y₂, y₃, y₄, y₅, y₆, . . . }

where,

y_n=(x_2n+1−

x_2n+2)/2 (n=0, 1, 2, 3, . . . )

Y being said sequence of combined values.

17. The apparatus according to claim 8, wherein said processing component is configured to perform a further processing which comprises a decoding, using at least one of a matched filter and a correlator.

18. The apparatus according to claim 8, wherein said signal originates from a Global Navigation Satellite Systems signal, which is modulated with said modulated carrier.

19. The apparatus according to claim 8, wherein said apparatus is one of:

a module for an electronic device;

an electronic device;

a satellite signal receiver;

a GALILEO receiver; and

a mobile station.

20. A non-transitory computer readable medium embedded with a software program code for processing a sequence of samples of a signal, said signal comprises a carrier that is modulated by a code composed of a sequence of chips, said software program code being configured realize the following when being executed by a processing unit:

a) wiping-off an influence by said carrier on said sequence of samples and downsampling said sequence of samples, said wiping-off and downsampling comprising combining respective subsequent samples of a predetermined number of said sequence of samples and exploiting regularities in said sequence of samples in said combining, to obtain a sequence of combined values as a downsampled sequence of samples; and

b) utilizing said downsampled sequence of samples as a new sequence of samples for further processing.