Integrated circuit implementation of methods and apparatuses for monitoring occupancy of wideband GHz spectrum, and sensing respective frequency components of time-varying signals using sub-nyquist criterion signal sampling

Patent metadata

Field	Value
Publication number	US-9313072-B2
Application number	US-201414548238-A
Country	US
Kind code	B2
Filing date	Nov 19, 2014
Priority date	Nov 19, 2013
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

An ASIC for monitoring wideband GHz spectrum to sense respective frequency components present in the spectrum. The ASIC implements Fast Fourier Transform (FFT) techniques to facilitate identification of one or more frequency components of a sparse signal after the signal is sub-sampled at a rate below the Nyquist criterion. The ASIC computes a first Fast Fourier Transform (FFT) of a first sub-sampled set of samples of a time-varying signal representing the monitored spectrum and sampled at a first sampling rate, and further computes a second FFT of a second sub-sampled set of samples of the time-varying signal sampled at a second sampling rate different from the first sampling rate. In one example, each of the first FFT and the second FFT is a low-radix FFT to facilitate a low-power and low-cost ASIC implementation of wideband spectrum sensing.

First claim

What is claimed is:

1. An integrated circuit apparatus to determine an N-point Fast Fourier Transform (FFT) of a time-varying signal so as to sense one or more frequency components of the time-varying signal, the apparatus comprising:
an input/output interface to receive a first sub-sampled set of samples of the time-varying signal sampled at a first sampling rate below a Nyquist rate of the time-varying signal and a second sub-sampled set of samples of the time-varying signal sampled at a second sampling rate below the Nyquist rate of the time-varying signal, wherein the second sampling rate is different from the first sampling rate; and
at least one processor communicatively coupled to the input/output interface to:
A) compute a first Fast Fourier Transform (FFT) for the first sub-sampled set of samples of the time-varying signal; and
B) compute a second FFT for the second sub-sampled set of samples of the time-varying signal,

wherein:
each of the first FFT and the second FFT is a low-radix FFT;
the time-varying signal has a frequency bandwidth of interest BW and a Nyquist sampling criteria of N samples in a sampling time T, wherein N=T×BW;
the first sampling rate is BW/p 1 samples/second, wherein p 1 is less than N;
the second sampling rate is BW/p 2 samples/second, wherein p 2 is less than N; and
p 2 and p 1 are co-prime numbers.

2. The apparatus of claim 1 , wherein the apparatus is implemented as an Application Specific Integrated Circuit (ASIC).

3. The apparatus of claim 1 , wherein the at least one processor computes the N-point FFT of the time-varying signal based at least in part on A) and B), and wherein the input/output interface is configured to output a digital representation of the N-point FFT so as to provide an indication of the one or more frequency components of the sampled time-varying signal.

4. The apparatus of claim 1 , wherein:
at least one of the first and second FFTs is a radix-2 FFT; and
another of the first and second FFTs is a radix-3 FFT.

5. An integrated circuit apparatus to determine an N-point Fast Fourier Transform (FFT) of a time-varying signal so as to sense one or more frequency components of the time-varying signal, the apparatus comprising:
an input/output interface to receive a first sub-sampled set of samples of the time-varying signal sampled at a first sampling rate below a Nyquist rate of the time-varying signal and a second sub-sampled set of samples of the time-varying signal sampled at a second sampling rate below the Nyquist rate of the time-varying signal, wherein the second sampling rate is different from the first sampling rate; and
at least one processor communicatively coupled to the input/output interface to:
A) compute a first Fast Fourier Transform (FFT) for the first sub-sampled set of samples of the time-varying signal; and
B) compute a second FFT for the second sub-sampled set of samples of the time-varying signal,

wherein:
each of the first FFT and the second FFT is a low-radix FFT;
the input/output interface is configured to provide to the at least one processor:
the first sub-sampled set of samples at the first sampling rate;
the second sub-sampled set of samples at the second sampling rate;
a third sub-sampled set of samples at the first sampling rate and time-shifted from the first sub-sampled set by a first number of samples; and
a fourth sub-sampled set of samples at the second sampling rate and time-shifted from the second sub-sampled set by a second number of samples; and

the at least one processor further is configured to compute:
C) a third FFT for the third sub-sampled set of samples of the time-varying signal; and
D) a fourth FFT for the fourth sub-sampled set of samples of the time-varying signal, wherein the N-point FFT of the time-varying signal is based at least in part on A), B), C) and D).

6. The apparatus of claim 5 , wherein:
the first number of samples is one sample; and
the second number of samples is one sample.

7. The apparatus of claim 5 , wherein:
the input/output interface is configured to further provide to the at least one processor:
a fifth sub-sampled set of samples at the first sampling rate and time-shifted from the first sub-sampled set by a third number of samples; and
a sixth sub-sampled set of samples at the second sampling rate and time-shifted from the second sub-sampled set by the third number of samples; and
the at least one processor further is configured to compute:
E) a fifth FFT for the fifth sub-sampled set of samples of the time-varying signal; and
F) a sixth FFT for the sixth sub-sampled set of samples of the time-varying signal, wherein the N-point FFT of the time-varying signal is based at least in part on A), B), C), D), E) and F).

8. The apparatus of claim 7 , wherein:
the first number of samples is one sample;
the second number of samples is one sample; and
the third number of samples is 32 samples.

9. A system, comprising:
the integrated circuit apparatus of claim 1 ; and
an analog-to-digital converter (ADC) apparatus, communicatively coupled to the input/output interface of the integrated circuit apparatus, to provide the first sub-sampled set of samples at the first sampling rate and the second sub-sampled set of samples at the second sampling rate.

10. The system of claim 9 , wherein:
the input/output interface is configured to provide to the at least one processor:
the first sub-sampled set of samples at the first sampling rate;
the second sub-sampled set of samples at the second sampling rate;
a third sub-sampled set of samples at the first sampling rate and time-shifted from the first sub-sampled set by a first number of samples; and
a fourth sub-sampled set of samples at the second sampling rate time-shifted from the second sub-sampled set by a second number of samples; and
the at least one processor of the integrated circuit apparatus further computes:
C) a third FFT for the third sub-sampled set of samples of the time-varying signal; and
D) a fourth FFT for the fourth sub-sampled set of samples of the time-varying signal, wherein the N-point FFT of the time-varying signal is based at least in part on A), B), C) and D).

11. The system of claim 10 , wherein:
the first number of samples is one sample; and
the second number of samples is one sample.

12. The system of claim 11 , wherein:
the at least one input/output interface is configured to further provide to the at least one processor:
a fifth sub-sampled set of samples at the first sampling rate and time-shifted from the first sub-sampled set by a third number of samples; and
a sixth sub-sampled set of samples at the second sampling rate and time-shifted from the second sub-sampled set by the third number of samples; and

the at least one processor of the integrated circuit apparatus further computes:
E) a fifth FFT for the fifth sub-sampled set of samples of the time-varying signal; and
F) a sixth FFT for the sixth sub-sampled set of samples of the time-varying signal,

wherein the N-point FFT of the time-varying signal is based at least in part on A), B), C), D), E) and F).

13. The system of claim 12 , wherein:
the first number of samples is one sample;
the second number of samples is one sample; and
the third number of samples is 32 samples.

14. The apparatus of claim 1 , wherein Nis greater than 700,000.

15. The apparatus of claim 14 , wherein N=746,496.

16. The apparatus of claim 1 , wherein:
the first FFT is a B 1 -point FFT, wherein R 1 =N/p 1 ; and
the second FFT is a B 2 -point FFT, wherein R 2 =N/p

Assignees

• Katabi Dina
• Salehi-Abari Omid
• Hamed Ezzeldin
• Al-Hassanieh Haitham Z
• Shi Lixin
• Agarwal Abhinav
• Chandrakasan Anantha
• Stojanovic Vladimir
• Massachusetts Inst Technology

Inventors

• Katabi Dina
• Salehi-Abari Omid
• Hamed Ezzeldin
• Al-Hassanieh Haitham Z
• Shi Lixin
• Agarwal Abhinav
• Chandrakasan Anantha
• Stojanovic Vladimir

Classifications

• H04L27/263

  modification of IFFT/IDFT modulator for performance improvement · CPC title

• H04L27/265 Primary

  Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators (H04L27/26524 takes precedence) · CPC title

• H04B1/40

  Circuits · CPC title

• H04L27/0006

  Assessment of spectral gaps suitable for allocating digitally modulated signals, e.g. for carrier allocation in cognitive radio (for spectrum sharing between different networks H04W16/14) · CPC title

• H04L25/03038

  with a non-recursive structure (H04L25/03031 takes precedence) · CPC title