METHOD AND APPARATUS FOR FAST FFT PROCESSING OF PAGING INFORMATION

Abstract

A method and apparatus for fast FFT processing of paging information in a user equipment (UE). The apparatus comprises a front end receiver (201) adapted to receive and down convert an RF signal to a baseband signal having a first part and a second part. An optional analog filter (202) is coupled to the output of the front end receiver (201) and is adapted to filter the analog signal. An analog to digital (A/D) converter (203) is coupled to the optional analog filter (202) and is adapted to convert the analog signal to a first digital signal. A first digital filter (204) is coupled to a first branch from the output of the A/D converter (203). The first digital filter (204) is adapted to digitally process the first digital signal. A buffer (206) is coupled to the digital filter (204) and is adapted to store the frist digital signal. The first digital filter (204) has a predetermined bandwidth (BWA). An FFTN processor (212) having N stages is adapted to process the digital signal. The FFTN processor is coupled to the output of the buffer (206). An optional digital mixer (208) is switchably coupled to a second branch from the output of the A/D converter (203). A clock timer (205) is adapted to switchably couple the optional digital mixer (208) to the second branch from the output of the A/D converter (203). A second digital filter (209) is coupled to the output of the digital mixer (208). Digital mixer (208) is adapted to digitally down convert the first digital signal to the center frequency of a paging information (fp) signal within the first digital signal. An FFTM processor (210) having M stages is coupled to the output of the second digital low pass filter and a paging detector (211) is coupled to the output of the FFTM processor (210). The paging detector (211) is adapted to detect a paging information signal. Using the method and apparatus of the present invention, the time for FFT processing of the paging information is significantly reduced for wide BW S3G implementations.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a conventional OFDM signal;

FIG. 2 illustrates a block diagram of a UE receiver adapted to process data according to the apparatus of the present invention; and

FIG. 3 is a flow chart of the method of the present invention.

Claims

1. A method for fast FFT processing of paging information in a communications system, comprising the steps of: receiving an analog signal;converting the analog signal to a first digital signal;digitally filtering the first digital signal through a first filter having a first bandwidth (BWA) to obtain a second digital signal;storing the second digital signal in a buffer;digitally filtering the first digital signal through a second filter having a second bandwidth (BWB) to obtain a third digital signal;initiating an FFTM processing of the third digital signal and simultaneously initiating an FFTN processing of the second digital signal;decoding the FFTM processed third digital signal; anddetermining, based on the decoding of the FFTM processed third digital signal, whether to complete the FFTN processing of the second digital signal from the buffer.

2. The method of claim 1, wherein the third digital signal comprises packet paging information.

3. The method of claim 1, wherein the second digital signal includes non-paging data.

4. The method of claim 1, wherein BWA is wider than BWB.

5. The method of claim 1, wherein the received signal is an orthogonal frequency division multiplexed (OFDM) signal.

6. The method of claim 5, for use in a Super third generation (S3G) communication system.

7. The method of claim 1, wherein BWA is about 1.25 MHz.

8. The method of claim 1, further comprising filtering the analog signal prior to converting it to a digital signal.

9. The method of claim 1, further comprising mixing the first digital signal with another signal in a mixer to down convert the first digital signal so that the third digital signal is a center frequency of a paging information (fp) signal.

10. A method of processing paging information, comprising the steps of: maintaining a radio in a user equipment (UE) in standby mode until a time Δ prior to a transmission time interval (TTI) start;switching the radio on when a signal is received by the radio;analog to digital converting the received signal;digital filtering the digital signal through a digital filter having a first bandwidth (BWA) to obtain a first part of a digital signal;storing the first part of the digital signal in a buffer;filtering the digital signal through a digital filter having a second bandwidth (BWB) to obtain a second part of the digital signal;processing the second part of the digital signal via a fast Fourier transform (FFTM); andextracting, via the FFTM processing of the second part of the digital signal, paging information.

11. The method of claim 10, wherein the first part of the digital signal includes non-paging data.

12. The method of claim 11, further comprising the step of decoding the extracted paging information to determine if the non-paging data is intended for the UE.

13. The method of claim 12, further comprising terminating the reception of the received signal and placing the radio in standby mode if the decoded paging information indicates that the non-paging data is not intended for the UE.

14. The method of claim 12, further comprising the step of erasing the buffer.

15. The method of claim 12, further comprising the step of processing the non-paging data stored in the buffer if the extracted paging information indicates that the non-paging data is intended for the UE.

16. The method of claim 15, further comprising the step of FFT processing (FFTN) non-paging data.

17. The method of claim 10 further comprising the step of analog filtering the received signal prior to analog to digital conversion of the received signal.

18. An apparatus for fast FFT processing of paging information in a user equipment (UE), comprising: a front end receiver adapted to receive and down convert an RF signal to a base band signal;an analog-to-digital (A/D) converter coupled to the front end receiver adapted to convert the analog signal to a digital signal;a first digital filter coupled to a first branch from the output of the A/D converter, the first digital filter having a predetermined bandwidth (BWA);a buffer coupled to the digital filter adapted to store the digital signal;an FFTN processor having N stages adapted to process the digital signal, the FFTN processor coupled to the output of the buffer;a second digital filter having a predetermined bandwidth (BWB);a clock/timer coupled to a second branch from the output of the A/D converter, the clock/timer adapted to switchably couple the second branch from the output of the A/D converter to the second digital filter;an FFTM processor having M stages coupled to the output of the second digital filter; anda paging detector coupled to the output of the FFTM processor, the paging detector adapted to detect a paging information signal.

19. The apparatus of claim 18, wherein M of the FFTM processor is less than N of the FFTN processor.

20. The apparatus of claim 19, wherein N of the FFTN processor is about 2048.

21. The apparatus of claim 18, wherein M of the FFTM processor is about 128.

22. The apparatus of claim 18, further comprising the UE adapted to retrieve the information stored in the buffer if the paging information signal detected by the paging detector indicates that the signal is intended for the UE.

23. The apparatus of claim 18, further comprising the UE adapted to place the front end receiver, FFT processors and filters in standby mode if the paging information signal detected by the paging detector indicates that the signal is not intended for the UE.

24. The apparatus of claim 18, adapted to process an orthogonal frequency division multiplexed (OFDM) signal.

25. The apparatus of claim 24, for use in a Super third generation (S3G) system.

26. The apparatus of claim 18 further comprising an analog filter coupled between the output of the front end receiver and the input of the analog-to-digital (A/D) converter, the analog filter adapted to filter the base band signal.

27. The apparatus of claim 18 further comprising a mixer switchably coupled between the second branch from the output of the A/D converter and to the second digital filter, the mixer adapted to down convert to the center frequency of a paging information (fp) signal, the clock/timer adapted to switchably couple the mixer to the second branch from the output of the A/D.