Patent ID: 12238816

DETAILED DESCRIPTION

FIG.1is a schematic diagram illustrating a 2.4G WiFi station (STA)100according to embodiments of the present disclosure. In this embodiment, a receiving circuit104is configured to receive a 2.4G radio frequency (RF) signal drf and generate a baseband signal din to a subsequent baseband circuit, including a first preamble detection circuit106, a second preamble detection circuit108, a third preamble detection circuit110, and a frequency-shifting circuit112. In the present embodiment, the receiving circuit104can include an analog circuit and a mixed-signal circuit; the baseband circuits are digital circuits; and the processing circuit114can be implemented using a digital circuit, firmware or software. The present application is specifically directed to the improvement of methods for performing passive scanning of Wifi station100.

According to the 2.4G specification, the center frequency of each channel is spaced apart by a 5 MHz interval; for example, inFIG.2, the center frequency of CH4to CH11starts from 2.427 GHz and is increased to 2.462 GHz at 5 MHz intervals. When the 2.4G WiFi station100performs the passive scanning, beacons sent by an access point (AP) in each channel are detected to receive information about each channel. According to the 2.4G specification, the bandwidth of WiFi Station100is limited to 20 MHz, which is much smaller than the overall channel distribution range, so the beacons for each channel can only be detected separately.

In the present embodiment, the receiving circuit104receives the RE signal drf in the 20 MHz bandwidth to generate the baseband signal din; for example, in the scenario ofFIG.2, the frequency range received by the receiving circuit104is between 2.427 GHz and 2.447 GHz (labeled as the gray area); that is, the center frequency of the receiving circuit104is 2,437 GHz, corresponding to CH6. As could be seen inFIG.2, the bandwidth of the receiving circuit104further covers CH5and CH7. Hence, the present application uses the first preamble detection circuit106, the second preamble detection circuit108and the third preamble detection circuit110to respectively monitor CH5, CH6and CH7, and once a beacon corresponding to CH5, CH6or CH7is found, the frequency-shifting circuit112is notified to perform corresponding band shifting on the baseband signal din to generate a frequency-shifted baseband signal dout, so that the information in the beacon can be better readout by subsequent circuits.

Specifically, the first preamble detection circuit106continuously detects whether the beacon in the baseband signal din carries a preamble corresponding to CH5. For example, the first preamble detection circuit106uses a set of Barker code corresponding to CH5to perform cross-correlation computation with the preamble in each beacon carried in the baseband signal din and normalizes the results of the cross-correlation computation according to the signal energy of the current baseband signal din. If a value of the normalized cross-correlation computation is greater than a preset threshold, then it is determined that the beacon corresponds to CH5, and the first preamble detection circuit106should immediately notify the frequency-shifting circuit112via a signal fg1, so that the frequency-shifting circuit112performs −5 MHz band shifting computation on the baseband signal din (shifted down from 2.437 GHz by 5 MHz to 2.432 GHz) to receive data payload in the beacon corresponding to CH5, wherein the frequency-shifting circuit112continues the −5 MHz band shifting computation at least until the beacon has been received completely. In contrast, if the beacon does not correspond to CH5, then the frequency-shifting circuit112will not be notified to perform −5 MHz band shifting computation.

It should be noted that although the receiving circuit104uses 2.437 GHz as the center frequency, the bandwidth of the receiving circuit104also covers CH5and CH7, and the signal quality required for the detection of preamble is sufficient. So the present application uses the WiFi station100to simultaneously detect whether a beacon corresponding to any of CH5, CH6, and CH7is received, and once a beacon corresponding to one of them is detected, the frequency-shifting circuit112performs corresponding band shifting computation on the baseband signal din accordingly to improve the signal-to-noise ratio of the data fields in the beacon.

Similarly, the second preamble detection circuit108uses a set of Barker code corresponding to CH6to determine whether each beacon corresponds to CH6. If yes, then the frequency-shifting circuit112is immediately notified via a signal fg2, and since the receiving circuit104receives the RF signal drf using the center frequency of CH6, the frequency-shifting circuit112does not perform band shifting computation on the baseband signal din (i.e., the band shifting is 0), and will directly output the baseband signal as the frequency-shifted output signal dout. Further, the third preamble detection circuit110uses a set of Barker code corresponding to CH7to determine whether each beacon corresponds to CH7. If yes, then the frequency-shifting circuit112is immediately notified via a signal fg3, and the frequency-shifting circuit112performs 5 MHz band shifting computation on the baseband signal din (shifted up from 2.437 GHz by 5 MHz to 2.442 GHz) to receive the data payload in the beacon corresponding to CH7, and the frequency-shifting circuit112continues the 5 MHz band shifting computation at least until the beacon is received completely.

The processing circuit114uses a control signal cf to control the receiving circuit104to use 2.437 GHz as the center frequency to perform the passive scanning, which lasts for a specific period and then hops to the next band. As shown inFIG.3, because the passive scanning of CH5, CH6and CH7has been completed, during the next specific period, the processing circuit114controls the center frequency of the WiFi station100to shift up by 15 MHz to 2.452 GHz (the center frequency of CH9), so as to update the 20 MHz band range (labeled as a gray area) of the next specific period, so that it covers CH8, CH9and CH10, to simultaneously detect the beacons of CH8, CH9and CH10. That is, compared to the approach wherein the center frequency for scan is only moved by the distance of one channel (5 MHz) during each specific period, the present application can speed up the passive scanning by moving a distance of multiple channels each time.

It should be noted that the WiFi station100can simultaneously monitor beacons from three channels during a specific period, so that the time for the overall passive scanning can be reduced to as few as one-third of the original time. However, in certain embodiments, it is feasible to simultaneously monitor two channels. Moreover, the order for performing passive scanning of the 14 channels is not particularly limited, and after all channels are subject to the passive scanning for the specific period, the processing circuit114stops updating the 20 MHz band range of the WiFi station100. Further, the specific period can be 100 ms that is in compliance with the 2.4G specification or integer multiples thereof.

FIG.4is a schematic diagram illustrating a 5G WiFi station200according to embodiments of the present disclosure. Since the channel band and receiving band according to 5G specification differ from those according to 2.4G specification, the infrastructures of the WiFi station200and the WiFi station100are different. In this embodiment, a receiving circuit204is configured to receive a 5G RF signal drf and generate a baseband signal din to a subsequent baseband circuit, including a first preamble detection circuit206, a second preamble detection circuit208, and a frequency-shifting circuit212. In the present embodiment, the receiving circuit204can include an analog circuit and a mixed-signal circuit; the baseband circuits are digital circuits; and the processing circuit214can be implemented using a digital circuit, firmware or software.

According to the 5G specification, the center frequency of each channel is spaced apart by a 10 MHz interval; for example, inFIG.5, the center frequency of CH34to CH50starts from 5.17 GHz and is increased to 5.25 GHz at 10 MHz intervals. When the 5G WiFi station200performs the passive scanning, beacons from each channel are detected to receive information about each channel. According to the 5G specification, the bandwidth of WiFi Station200can be set as 40 MHz, which is much smaller than the overall channel distribution range, so the beacons for each channel can only be detected separately. In the present embodiment, the application setting is in certain regions which allows an available channel interval of 20 MHz. For example, inFIG.5, only CH36, CH40, CH44and CH48are available.

In the present embodiment, the receiving circuit204receives the RF signal drf in the 40 MHz bandwidth to generate the baseband signal din; for example, in the scenario ofFIG.5, the frequency range received by the receiving circuit204is between 5.17 GHz and 5.21 GHz (labeled as the gray area); that is, the center frequency of the receiving circuit204is 5.19 GHz, corresponding to CH38. As could be seen inFIG.5, the bandwidth of the receiving circuit204further covers CH36and CH40. Hence, the present application uses the first preamble detection circuit206and the second preamble detection circuit208to respectively monitor CH36and CH40, and once a beacon corresponding to CH36or CH40is found, the frequency-shifting circuit212is notified to perform corresponding band shifting on the baseband signal din to generate a frequency-shifted baseband signal dout, so that the information in the beacon can be better readout by subsequent circuits.

Specifically, the first preamble detection circuit206continuously detects whether the beacon in the baseband signal din carries a preamble corresponding to CH36. For example, the first preamble detection circuit206uses a set of L-STF sequence corresponding to CH36to perform cross-correlation computation with the preamble in each beacon carried in the baseband signal din and normalizes the results of the cross-correlation computation according to the signal energy of the current baseband signal din. If a value of the normalized cross-correlation computation is greater than a preset threshold, then it is determined that the beacon corresponds to CH36, and the first preamble detection circuit206should immediately notify the frequency-shifting circuit212via a signal fg1, so that the frequency-shifting circuit212performs −10 MHz band shifting computation on the baseband signal din (shifted down from 5.19 GHz by 10 MHz to 5.18 GHz) to receive data payload in the beacon corresponding to CH36, wherein the frequency-shifting circuit212continues the −10 MHz band shifting computation at least until the beacon has been received completely. In contrast, if the beacon does not correspond to CH36, then the frequency-shifting circuit212will not be notified to perform −10 MHz band shifting computation.

Similarly, the second preamble detection circuit208uses a set of L-STF sequence corresponding to CH40to determine whether each beacon corresponds to CH40. If yes, then the frequency-shifting circuit212is immediately notified via a signal fg2, and the frequency-shifting circuit212performs 10 MHz band shifting computation on the baseband signal din (shifted up from 5.19 GHz by 10 MHz to 5.2 GHz) to receive the data payload in the beacon corresponding to CH40, and the frequency-shifting circuit212continues the 10 MHz band shifting computation at least until the beacon is received completely.

The processing circuit214uses a control signal cf to control the receiving circuit204to use 5.19 GHz as the center frequency to perform the passive scanning, which lasts for a specific period and then move to the next band. As shown inFIG.6, because the passive scanning of CH36and CH40has been completed, during the next specific period, the processing circuit214controls the center frequency of the WiFi station200to shift up by 40 MHz to 5.23 (the center frequency of CH46), so as to update the 40 MHz band range (labeled as a gray area) of the next specific period, so that it covers CH44and CH48, to simultaneously detect the beacons of CH44and CH48. That is, compared to the approach wherein the center frequency for scan is only moved by the distance of one channel (10 MHz) during each specific period, the present application can speed up the passive scanning by moving a distance of multiple channels each time, so that the WiFi station200can simultaneously monitor beacons from two channels during a single specific period, thereby reducing the time for the overall passive scanning to as few as one-half of the original time.

other principles for use in the 5G WiFi station200are similar to those for use in the 2.4G WiFi station100; in certain embodiments, the WiFi station100and the WiFi station200can be combines to perform the passive scanning under 2.4G and 5G simultaneously or sequentially.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand various aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of embodiments introduced herein. Those skilled in the art should also realize that such equivalent embodiments still fall within the spirit and scope of the present disclosure, and they may make various changes, substitutions, and alterations thereto without departing from the spirit and scope of the present disclosure.