Dynamic frequency selection with discrimination

Patent metadata

Field	Value
Publication number	US-9838882-B1
Application number	US-201615333786-A
Country	US
Kind code	B1
Filing date	Oct 25, 2016
Priority date	Oct 25, 2016
Publication date	Dec 5, 2017
Grant date	Dec 5, 2017

Abstract

Dynamic frequency selection (DFS) is often a requirement for a wireless local area network (WLAN) apparatus to prevent the apparatus from interfering with other systems that have a priority to a radio frequency (RF) channel. When DFS is executed, the WLAN apparatus ceases WLAN operations on the channel and searches for an open channel to resume WLAN operations. Often a WLAN apparatus misinterprets signals from another system as operating on the channel when actually the received signals are signals leaked into the channel from a system transmitting on a different channel. Presented herein are methods and apparatuses for preventing unnecessary DFS operations resulting from misinterpreted signals through the use of a signal to noise ratio determined from a pulse spectral density of the received signal.

First claim

What is claimed is:

1. A wireless local area network (WLAN) apparatus, comprising:
an antenna subsystem tuned to a radio-frequency (RF) band;
a transceiver subsystem connected to the antenna subsystem and configured to transmit and receive on a first channel, wherein the first channel is one of a plurality of channels in the RF band; and
a processor communicatively coupled to the transceiver subsystem and configured by instructions to:
receive a signal from the transceiver subsystem; and
analyze a portion of the signal, wherein the analysis of the portion of the signal includes:
estimating a center frequency (Fc) of the portion of the signal,
determining a power spectral density (PSD) of the portion of the signal,
calculating a signal-to-noise ratio (SNR) of the PSD,
comparing the SNR of the PSD to an on-channel threshold
upon determining that the SNR of the PSD exceeds the on-channel threshold,
performing a dynamic frequency selection (DFS) operation to tune the transceiver subsystem to a second channel in the RF band based on the comparison of the SNR to the on-channel threshold, and
upon determining that the SNR of the PSD does not exceed the on-channel threshold,
preventing the DFS operation to tune the transceiver subsystem to a second channel in the RF band based on the comparison of the SNR to the on-channel threshold.

2. The WLAN apparatus according to claim 1 , wherein the signal is a pulse with nonlinear distortion from a radar transmitting on a channel other than the first channel.

3. The WLAN apparatus according to claim 1 , wherein determining the PSD of the portion of the signal comprises:
computing a fast-Fourier transform (FFT) of the portion of the signal, wherein the FFT is comprised of FFT-bins.

4. The WLAN apparatus according to claim 1 , wherein calculating a signal-to-noise ratio (SNR) of the PSD, comprises:
determining a signal region of the PSD, wherein the signal region is centered at Fc and spans a signal-occupied bandwidth (BW);
determining one or more noise regions of the PSD, the one or more noise regions are regions of the PSD not in the signal region;
computing a signal power from the signal region and a noise power from the one or more noise regions; and
calculating the SNR as the ratio of the signal power to the noise power.

5. A method comprising:
receiving a signal from a transceiver subsystem that is configured to transmit and receive via an antenna subsystem on a first channel, wherein the first channel is one of a plurality of channels in a radio frequency (RF) band; and
analyzing a portion of the signal, wherein the analysis of the portion of the signal includes:
estimating a center frequency (Fc) of the portion of the signal,
determining a power spectral density (PSD) of the portion of the signal,
calculating a signal-to-noise ratio (SNR) of the PSD,
comparing the SNR of the PSD to an on-channel threshold,
upon determining that the SNR of the PSD exceeds the on-channel threshold,
performing a dynamic frequency selection (DFS) operation to tune the transceiver subsystem to a second channel in the RF band based on the comparison of the SNR to the on-channel threshold, and
upon determining that the SNR of the PSD does not exceed the on-channel threshold, preventing the DFS operation to tune the transceiver subsystem to a second channel in the RF band based on the comparison of the SNR to the on-channel threshold.

6. The method according to claim 5 , wherein the signal is a pulse with nonlinear distortion from the radar transmitting on the channel other than the first channel.

7. The method according to claim 5 , wherein determining the PSD of the portion of the signal comprises:
computing a fast-Fourier transform (FFT) of the portion of the signal, wherein the FFT is comprised of FFT-bins.

8. The method according to claim 5 , wherein calculating a signal-to-noise ratio (SNR) of the PSD, comprises:
determining a signal region of the PSD, wherein the signal region is centered at Fc and spans a signal-occupied bandwidth (BW);
determining one or more noise regions of the PSD, the one or more noise regions are regions of the PSD not in the signal region;
computing a signal power from the signal region and a noise power from the one or more noise regions; and
calculating the SNR as the ratio of the signal power to the noise power.

9. A non-transitory computer readable storage medium containing computer readable instructions that when executed by a processor cause the processor to perform a method comprising:
receiving a signal from a transceiver subsystem communicatively coupled to the processor, the transceiver subsystem configured to transmit and receive via an antenna subsystem on a first channel, wherein the first channel is one of a plurality of channels in a radio frequency (RF) band;
analyzing a portion of the signal, wherein the analysis of the portion of the signal includes:
estimating a center frequency (Fc) of the portion of the signal;
determining a power spectral density (PSD) of the portion of the signal,
calculating a signal-to-noise ratio (SNR) of the PSD,
comparing the SNR of the PSD to an on-channel threshold,
upon determining that the SNR of the PSD exceeds the on-channel threshold,
performing a dynamic frequency selection (DFS) operation to tune the transceiver subsystem to a second channel in the RF band based on the comparison of the SNR to the on-channel threshold, and
upon determining that the SNR of the PSD does not exceed the on-channel threshold, preventing the DFS operation to tune the transceiver subsystem to a second channel in the RF band based on the comparison of the SNR to the on-channel threshold.

10. The non-transitory computer readable storage medium according to claim 9 , wherein the signal is a pulse with nonlinear distortion from the radar transmitting on the channel other than the first channel.

11. The non-transitory computer readable storage medium according to claim 9 , wherein determining the PSD of the portion of the signal comprises:
computing a fast-Fourier transform (FFT) of the portion of the signal, wherein the FFT is comprised of FFT-bins.

12. The non-transitory computer readable storage medium according to claim 9 , wherein calculating a signal-to-noise ratio (SNR) of the PSD, comprises:
determining a signal region of the PSD, wherein the signal region is centered at Fc and spans a signal-occupied bandwidth (BW);
determining one or more noise regions of the PSD, the one or more noise regions are regions of the PSD not in the signal region;
computing a signal power from the signal region and a noise power from the one or more noise regions; and
calculating the SNR as the ratio of the signal power to the noise power.

Assignees

• Cisco Tech Inc

Inventors

• Yankevich Evgeny
• Chuang Jack

Classifications

• H04W48/16

  Discovering, processing access restriction or access information · CPC title

• H04W24/08

  Testing, {supervising or monitoring} using real traffic · CPC title

• H04K3/226 Primary

  Selection of non-jammed channel for communication (spectrum sharing arrangements H04W16/14; selection of wireless resources by user or terminal H04W72/02) · CPC title

• H04K2203/18

  for wireless local area networks or WLAN · CPC title

• H04W16/14 Primary

  Spectrum sharing arrangements {between different networks} · CPC title