System and method for low power clear channel assessment
View Patent ↗A method is provided for performing a clear channel assessment in a local device. The local device receives signal energy in a wireless channel and splits the received signal energy into a real portion and an imaginary portion. It determines a real portion of a squared signal energy by subtracting a squared imaginary portion of the signal energy from a squared real portion of the signal energy, and determines an imaginary portion of the squared signal energy by calculating twice the product of the real and imaginary portions of the signal energy. It can perform a signal detection function on the real and imaginary portions of the squared signal energy to produce a clear channel assessment signal that indicates whether a set signal type is present in the wireless channel. This clear channel assessment signal can be used to determine whether the local device should remain in a low-power mode.
1. A method of performing a clear channel assessment in a local device on a wireless channel, comprising:
receiving signal energy in the wireless channel;
splitting the received signal energy into a real portion of the signal energy and an imaginary portion of the signal energy;
squaring the real portion of the signal energy;
squaring the imaginary portion of the signal energy;
determining a real portion of a squared signal energy by subtracting the squared imaginary portion of the signal energy from the squared real portion of the signal energy;
determining an imaginary portion of the squared signal energy by calculating twice the product of the real and imaginary portions of the signal energy;
performing a signal detection function on the real and imaginary portions of the squared signal energy to produce a clear channel assessment signal that indicates whether a set signal type is present in the wireless channel.
2. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the step of splitting the received signal energy into a real portion of the signal energy and an imaginary portion of the signal energy further comprises:
splitting the received signal energy into first and second signal paths;
mixing the first signal path with a first oscillating signal to form the real portion of the signal energy; and
mixing the second signal path with a second oscillating signal to form the imaginary portion of the signal energy,
wherein the second oscillating signal is a copy of the first oscillating signal that is ninety degrees out of phase with the first oscillating signal.
3. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , further comprising:
filtering the real portion of the signal energy with a first low pass filter prior to squaring the real portion of the signal energy; and
filtering the imaginary portion of the signal energy with a second low pass filter prior to squaring the imaginary portion of the signal energy.
4. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , further comprising:
performing a first analog-to-digital conversion on the real portion of the signal energy prior to squaring the real portion of the signal energy; and
performing a second analog-to-digital conversion on the imaginary portion of the signal energy prior to squaring the imaginary portion of the signal energy.
5. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , further comprising:
filtering both the real portion of a squared signal energy and the imaginary portion of a squared signal energy with a third low pass filter prior to performing the signal detection function.
6. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the signal detection function is one of: a decimated fast Fourier transform function, a decimated subspace projection function, an analog filtering function, and a digital filtering function.
7. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the wireless channel is defined by a frequency range around a center frequency of an oscillating carrier signal.
8. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the set signal type is an ultrawide bandwidth signal.
9. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the set signal type includes sinusoidal signals of one or more set frequencies.
10. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the clear channel assessment signal indicates that a set signal type is present in the wireless channel when the clear channel assessment signal strength rises above a noise threshold.
11. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the steps of receiving signal energy, splitting the received signal energy, squaring the real portion of the signal energy, squaring the imaginary portion of the signal energy, determining a real portion of a squared signal energy, determining an imaginary portion of the squared signal energy, and performing an extraction function are repeated over a plurality of frequency ranges in the wireless channel.
12. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the method is implemented in an integrated circuit.
13. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , wherein the method is implemented in an ultrawide bandwidth transceiver.
14. A method of performing a clear channel assessment in a local device on a wireless channel, as recited in claim 1 , further comprising using the clear channel assessment signal to determine whether the local device should exit a power-saving mode.
15. A clear channel assessment circuit, comprising:
an antenna for receiving signal energy in a wireless channel;
a splitting circuit for splitting the received signal energy into a real portion of the signal energy and an imaginary portion of the signal energy;
a first signal squaring circuit for squaring the real portion of the signal energy;
a second signal squaring circuit for squaring the imaginary portion of the signal energy;
a subtracting circuit for determining a real portion of the squared signal energy by subtracting the squared imaginary portion of the signal energy from the squared real portion of the signal energy;
a multiplying circuit for determining an imaginary portion of the squared signal energy by calculating twice the product of the real and imaginary portions of the signal energy; and
a signal detection circuit for processing the real and imaginary portions of the squared signal energy to produce a clear channel assessment signal that indicates whether a set signal type is present in the wireless channel.
16. A clear channel assessment circuit, as recited in claim 15 , wherein the splitting circuit further comprises:
a splitter for splitting the received signal energy into first and second signal paths;
a first mixer for mixing the first signal path with a first oscillating signal to form the real portion of the signal energy; and
a second mixer for mixing the second signal path with a second oscillating signal to form the imaginary portion of the signal energy,
wherein the second oscillating signal is a copy of the first oscillating signal that is ninety degrees out of phase with the first oscillating signal.
17. A clear channel assessment circuit, as recited in claim 15 , further comprising:
a first filter located between the splitting circuit and the first signal squaring circuit; and
a second filter located between the splitting circuit and the second signal squaring circuit.
18. A clear channel assessment circuit, as recited in claim 15 , further comprising:
a first analog-to-digital converter located between the splitting circuit and the first signal squaring circuit; and
a second analog-to-digital converter located between the splitting circuit and the second signal squaring circuit.
19. A clear channel assessment circuit, as recited in claim 15 , further comprising a third filter located between both the subtracting and multiplying circuits and the signal detection circuit.
20. A clear channel assessment circuit, as recited in claim 15 , wherein the signal detecting circuit is one of: a decimated fast Fourier transform circuit, a decimated subspace projection circuit, an analog filter, and a digital filter.
21. A clear channel assessment circuit, as recited in claim 15 , wherein the wireless channel is defined by a frequency range around a center frequency of an oscillating carrier signal.
22. A clear channel assessment circuit, as recited in claim 15 , wherein the set signal type is an ultrawide bandwidth signal.
23. A clear channel assessment circuit, as recited in claim 15 , wherein the set signal type includes sinusoidal signals of one or more set frequencies.
24. A method of controlling power modes in a local device using a clear channel assessment signal, comprising:
entering the local device into a low power mode;
receiving signal energy at the local device in the wireless channel;
splitting the received signal energy into a real portion of the signal energy and an imaginary portion of the signal energy;
determining a real portion of a squared signal energy by subtracting a squared imaginary portion of the signal energy from a squared real portion of the signal energy;
determining an imaginary portion of the squared signal energy by calculating twice the product of the real and imaginary portions of the signal energy;
performing a signal detection function on the real and imaginary portions of the squared signal energy to produce a clear channel assessment signal that indicates whether a set signal type is present in the wireless channel; and
moving the local device from the low power mode to a receive mode when the clear channel assessment signal indicates that the set signal type is present in the wireless channel.