WiFi station and related passive scanning method

Abstract

This application discloses a WiFi site and a related passive scanning method, comprising: receiving a radio frequency signal in a specific frequency band to generate a baseband signal; detecting whether the baseband signal contains a first preamble symbol corresponding to a first channel, and thereby outputting a first detection result; detecting whether the baseband signal contains a second preamble symbol corresponding to a second channel, and thereby outputting a second detection result; and, based on the first detection result and the second detection result, determining to shift the baseband signal based on the center frequency of the first channel or the center frequency of the second channel, and generating a frequency-shifted baseband signal.

Description

Technical Field

[0001] This invention application relates to wireless communication, and more particularly to a WiFi site and a related passive scanning method. Background Technology

[0002] In current wireless communication standards, when a device wants to connect to a network via WiFi, it must first scan to collect information about the various transmission channels defined in the standard. This application aims to improve the scanning method to reduce the time required for scanning, enabling faster device connection and thus enhancing the user experience. Summary of the Invention

[0003] This application provides a WiFi site, comprising: a receiving circuit for receiving radio frequency signals within a specific frequency band during passive scanning to generate a baseband signal, wherein the specific frequency band includes the range of a first channel and the range of a second channel; a first pre-symbol detection circuit for detecting whether the baseband signal contains a first pre-symbol corresponding to the first channel, and thereby outputting a first detection result; a second pre-symbol detection circuit for detecting whether the baseband signal contains a second pre-symbol corresponding to the second channel, and thereby outputting a second detection result; a frequency shifting circuit for determining, based on the first detection result and the second detection result, to shift the baseband signal based on the center frequency of the first channel or the center frequency of the second channel, and generating a frequency-shifted baseband signal; and a processing circuit, wherein when the WiFi site remains in the original specific frequency band for a specific period of time, the processing circuit updates the specific frequency band.

[0004] This application provides a passive scanning method for WiFi sites, comprising: receiving a radio frequency signal within a specific frequency band to generate a baseband signal, wherein the range of the specific frequency band includes the range of a first channel and the range of a second channel; detecting whether the baseband signal contains a first preamble corresponding to the first channel, and thereby outputting a first detection result; detecting whether the baseband signal contains a second preamble corresponding to the second channel, and thereby outputting a second detection result; determining, based on the first detection result and the second detection result, to perform frequency shifting on the baseband signal based on the center frequency of the first channel or the center frequency of the second channel, and generating a frequency-shifted baseband signal; and updating the specific frequency band when the time spent in the original specific frequency band reaches a specific period.

[0005] This application can reduce the total time required for a WiFi site to complete a passive scan while complying with 2.4G / 5G specifications. Attached Figure Description

[0006] The various embodiments of this disclosure can be best understood by reading the following description and the accompanying drawings. It should be noted that, in accordance with standard practice in the art, the various features in the figures are not drawn to scale. In fact, the dimensions of certain features may be intentionally enlarged or reduced for clarity of description.

[0007] Figure 1 This is a schematic diagram of an embodiment of the 2.4G WiFi site of this application.

[0008] Figure 2 for Figure 1 A diagram illustrating the frequency bands passively scanned by WiFi stations.

[0009] Figure 3 for Figure 1 A diagram illustrating another frequency band for passive scanning of WiFi sites.

[0010] Figure 4 This is a schematic diagram of an embodiment of the 5G WiFi site of this application.

[0011] Figure 5 for Figure 4 A diagram illustrating the frequency bands passively scanned by WiFi stations.

[0012] Figure 6 for Figure 4 A diagram illustrating another frequency band for passive scanning of WiFi sites.

[0013] Symbol Explanation

[0014] 100, 200: WiFi sites

[0015] 104, 204: Receiving circuit

[0016] 106, 206: First Pre-sign Detection Circuit

[0017] 108, 208: Second pre-sign detection circuit

[0018] 110: Third Pre-sign Detection Circuit

[0019] 112, 212: Frequency shift circuit

[0020] 114, 214: Processing circuits

[0021] DRF: Radio Frequency Signal

[0022] din: baseband signal

[0023] fg1, fg2, fg3: Signals

[0024] dout: Output signal after frequency shift

[0025] cf: Control signal Detailed Implementation

[0026] Figure 1 This is a schematic diagram of an embodiment of the 2.4G WiFi station (STA) 100 of this application. The receiving circuit 104 receives the 2.4G radio frequency signal drf and generates a baseband signal din for subsequent baseband circuitry. It includes a first pre-symbol detection circuit 106, a second pre-symbol detection circuit 108, a third pre-symbol detection circuit 110, and a frequency shift circuit 112. In this embodiment, the receiving circuit 104 may include analog circuitry and mixed-signal circuitry; these baseband circuits are digital circuits; and the processing circuit 114 can be implemented using digital circuitry, hardware, or software. This application specifically improves the passive scanning method of the WiFi station 100.

[0027] According to the 2.4G specification, the center frequencies of each channel are distributed at 5MHz intervals. Figure 2 For example, the center frequencies of CH4 to CH11 start at 2.427GHz and increase upwards to 2.462GHz in 5MHz increments. When the 2.4G WiFi site 100 performs a passive scan, it needs to detect beacons sent by WiFi access points (APs) on each channel to receive information about each channel. According to the 2.4G specification, the bandwidth of WiFi site 100 is limited to 20MHz, which is much smaller than the overall channel distribution range. Therefore, it can only detect the beacons of each channel in batches.

[0028] In this embodiment, the receiving circuit 104 receives the radio frequency signal drf in a bandwidth of 20MHz to generate the baseband signal din. Figure 2 Taking the scenario as an example, the receiving frequency range of the receiving circuit 104 is from 2.427GHz to 2.447GHz (marked in gray), that is, the center frequency of the receiving circuit 104 is 2.437GHz, corresponding to CH6. From Figure 2 It is known that the bandwidth of the receiving circuit 104 also includes CH5 and CH7. Therefore, this application uses the first pre-symbol detection circuit 106, the second pre-symbol detection circuit 108, and the third pre-symbol detection circuit 110 to monitor CH5, CH6, and CH7 respectively. Once a beacon corresponding to CH5, CH6, or CH7 is detected, the frequency shift circuit 112 is notified to shift the baseband signal din accordingly to generate the frequency-shifted baseband signal dout, so that the data in the beacon can be better read by subsequent circuits.

[0029] Specifically, the first pre-symbol detection circuit 106 continuously detects whether the beacons in the baseband signal din contain a pre-symbol corresponding to CH5. For example, the first pre-symbol detection circuit 106 uses a set of Barker codes corresponding to CH5 to perform cross-correlation operations with the pre-symbols in each beacon in the baseband signal din, and normalizes the result of the cross-correlation operation based on the signal energy of the baseband signal din at this time. If the value of the normalized cross-correlation operation is greater than a preset threshold, it is determined that the beacon corresponds to CH5. The first pre-symbol detection circuit 106 should immediately notify the frequency shift circuit 112 through the signal fg1, so that the frequency shift circuit 112 performs a -5MHz frequency shift operation on the baseband signal din (shifting down 5MHz from 2.437GHz to 2.432GHz) to receive the data payload in the beacon corresponding to CH5. The frequency shift circuit 112 continues the -5MHz frequency shift operation at least until the beacon is completely received. Conversely, if the beacon does not correspond to CH5, the frequency shift circuit 112 will not be notified to perform a -5MHz frequency shift operation.

[0030] It should be understood that although the receiving circuit 104 uses 2.437 GHz as its center frequency, the bandwidth of the receiving circuit 104 also includes CH5 and CH7, which is sufficient for the signal quality requirements for detecting the preamble. Therefore, this application uses the WiFi station 100 to simultaneously detect whether any of the corresponding CH5, CH6 and CH7 beacons are received. Once a beacon corresponding to one of them is detected, the frequency shift circuit 112 will perform a corresponding frequency shift operation on the baseband signal din to improve the signal-to-noise ratio of the data field in the beacon.

[0031] Similarly, the second pre-symbol detection circuit 108 uses a set of Barker codes corresponding to CH6 to determine whether each beacon corresponds to CH6. If so, it immediately notifies the frequency shift circuit 112 via signal fg2. Since the receiving circuit 104 originally receives the radio frequency signal drf at the center frequency of CH6, the frequency shift circuit 112 does not need to perform frequency shifting operations on the baseband signal din (i.e., the frequency shift is 0), and directly outputs the baseband signal as the frequency-shifted output signal dout. The third pre-symbol detection circuit 110 uses a set of Barker codes corresponding to CH7 to determine whether each beacon corresponds to CH7. If so, it immediately notifies the frequency shift circuit 112 via signal fg3. The frequency shift circuit 112 will perform a 5MHz frequency shift operation on the baseband signal din (shifting it up 5MHz from 2.437GHz to 2.442GHz) to receive the data payload in the beacon corresponding to CH7. The frequency shift circuit 112 continues this 5MHz frequency shift operation until the beacon is completely received.

[0032] The processing circuit 114 controls the receiving circuit 104 to perform a passive scan at a center frequency of 2.437 GHz via the control signal cf, and then jumps to the next frequency band after a specific period. For example... Figure 3 As shown, since CH5, CH6, and CH7 have completed passive scanning, the processing circuit 114 will control the center frequency of the WiFi station 100 to shift up by 15MHz to 2.452GHz (the center frequency of CH9) in the next specific cycle to update the 20MHz frequency band range (marked in gray) for the next specific cycle, so that it includes CH8, CH9, and CH10, so as to simultaneously detect the beacons of CH8, CH9, and CH10. That is to say, compared to shifting the scanning center frequency by only one channel (5MHz) per specific cycle, this application shifts the distance of multiple channels to accelerate passive scanning.

[0033] It should be noted that WiFi station 100 can simultaneously monitor beacons on three channels within a specific period, reducing the overall passive scanning time to approximately one-third of the original time. However, in some embodiments, only two channels may be monitored simultaneously. Furthermore, there are no special restrictions on the order of passive scanning across the 14 channels. Once all channels have undergone a specific period of passive scanning, the processing circuit 114 stops updating the 20MHz frequency band range of WiFi station 100. The specific period can be 100ms conforming to the 2.4GHz specification or an integer multiple thereof.

[0034] Figure 4 This is a schematic diagram of an embodiment of the 5G WiFi site 200 of this application. Because the channel and receive frequency bands of the 5G standard differ from those of 2.4G, the architecture of WiFi site 200 differs from that of WiFi site 100. The receiving circuit 204 receives the 5G radio frequency signal drf and generates a baseband signal din for subsequent baseband circuits, including a first pre-symbol detection circuit 206, a second pre-symbol detection circuit 208, and a frequency shift circuit 212. The receiving circuit 204 may include analog circuits and mixed-signal circuits; these baseband circuits are digital circuits; and the processing circuit 214 can be implemented using digital circuits, hardware, or software.

[0035] According to 5G specifications, the center frequencies of each channel are distributed at 10MHz intervals. Figure 5For example, the center frequencies of CH34 to CH50 start at 5.17GHz and increase upwards to 5.25GHz in 10MHz intervals. When the 5G WiFi site 200 performs passive scanning, it needs to detect the beacons of each channel to receive information about each channel. According to the 5G specification, the bandwidth of the WiFi site 200 can be set to 40MHz, but this is still much smaller than the overall channel distribution range. Therefore, the beacons of each channel can only be detected in stages. In this embodiment, the application scenario is set in certain areas, and the interval between the channels that are open for use is 20MHz. Figure 5 For example, only CH36, CH40, CH44 and CH48 are allowed to be used.

[0036] In this embodiment, the receiving circuit 204 receives the radio frequency signal drf in a bandwidth of 40MHz to generate the baseband signal din. Figure 5 Taking the scenario as an example, the receiving frequency range of the receiving circuit 204 is from 5.17GHz to 5.21GHz (marked in gray), that is, the center frequency of the receiving circuit 204 is 5.19GHz, corresponding to CH38. From Figure 5 It is known that the bandwidth of the receiving circuit 204 also includes CH36 and CH40. Therefore, this application uses the first pre-symbol detection circuit 206 and the second pre-symbol detection circuit 208 to monitor CH36 and CH40 respectively. Once a beacon corresponding to CH36 or CH38 is detected, the frequency shift circuit 212 is notified to shift the baseband signal din accordingly to generate the frequency-shifted baseband signal dout, so that the data in the beacon can be better read by subsequent circuits.

[0037] Specifically, the first pre-symbol detection circuit 206 continuously detects whether the beacons in the baseband signal din contain a pre-symbol corresponding to CH36. For example, the first pre-symbol detection circuit 206 uses a set of short training symbols (L-STF) sequences corresponding to CH36 to perform cross-correlation operations with the pre-symbols in each beacon in the baseband signal din, and normalizes the result of the cross-correlation operation based on the signal energy of the baseband signal din at this time. If the value of the normalized cross-correlation operation is greater than a preset threshold, it is determined that the beacon corresponds to CH36. The first pre-symbol detection circuit 206 should immediately notify the frequency shift circuit 212 through the signal fg1, so that the frequency shift circuit 212 performs a -10MHz frequency shift operation on the baseband signal din (shifting down 10MHz from 5.19GHz to 5.18GHz) to receive the data payload in the beacon corresponding to CH36. The frequency shift circuit 212 continues the -10MHz frequency shift operation at least until the beacon is completely received. Conversely, if the beacon does not correspond to CH36, the frequency shift circuit 212 will not be notified to perform a -10MHz frequency shift operation.

[0038] Similarly, the second pre-symbol detection circuit 208 uses a set of short training symbol sequences corresponding to CH40 to determine whether each beacon corresponds to CH40. If so, it immediately notifies the frequency shift circuit 212 via signal fg2. The frequency shift circuit 212 performs a 10MHz frequency shift operation on the baseband signal din (shifting up 10MHz from 5.19GHz to 5.2GHz) to receive the data payload in the beacon corresponding to CH40. The frequency shift circuit 212 continues this 10MHz frequency shift operation at least until the beacon is completely received.

[0039] The processing circuit 214 controls the receiving circuit 204 to perform a passive scan at a center frequency of 5.19 GHz via the control signal cf, and then jumps to the next frequency band after a specific period. For example... Figure 6 As shown, since CH36 and CH40 have completed passive scanning, the processing circuit 214 will control the center frequency of the WiFi station 200 to shift by 40MHz to 5.23GHz (the center frequency of CH46) in the next specific cycle to update the 40MHz frequency band range (marked in gray) for the next specific cycle, so that it includes CH44 and CH48, so as to simultaneously detect the beacons of CH44 and CH48. In other words, compared to shifting the scanning center frequency by only one channel (10MHz) per specific cycle, this application shifts the distance of multiple channels to accelerate passive scanning, enabling the WiFi station 200 to simultaneously listen to the beacons of two channels within a specific cycle, reducing the overall passive scanning time to at most about 1 / 2 of the original.

[0040] The principles for WiFi site 200 for 5G and WiFi site 100 for 2.4G are largely the same. In some embodiments, WiFi site 100 and WiFi site 200 may be combined to perform passive scanning under 2.4G and 5G simultaneously or sequentially.

[0041] The foregoing description briefly illustrates the features of certain embodiments of this application, enabling those skilled in the art to more fully understand the various solutions to the content of this application. Those skilled in the art should understand that, using the content of this application as a basis, other processes and structures can be easily designed or modified to achieve the same purpose and / or the same advantages as the embodiments described herein. Those skilled in the art should also understand that these equivalent embodiments still fall within the spirit and scope of this application, and various changes, substitutions, and modifications can be made without departing from the spirit and scope of this application. The scope of protection of this invention is determined by the claims of this application.

Claims

1. A WiFi station, characterized in that, The WiFi station comprises: receiving circuitry configured to receive a radio frequency signal in a specific frequency band to generate a baseband signal during passive scanning, wherein the specific frequency band ranges include a range of a first channel and a range of a second channel; first preamble detection circuitry configured to detect whether the baseband signal contains a first preamble corresponding to the first channel, and output a first detection result based on the detection; second preamble detection circuitry configured to detect whether the baseband signal contains a second preamble corresponding to the second channel, and output a second detection result based on the detection; frequency shifting circuitry configured to determine, based on the first detection result and the second detection result, whether to shift the baseband signal based on a center frequency of the first channel or a center frequency of the second channel, and generate a shifted baseband signal; and processing circuitry configured to update the specific frequency band when the WiFi station stays in the specific frequency band for a specific period of time. When the first detection result indicates that the baseband signal contains the first preamble corresponding to the first channel, the frequency shifting circuitry shifts the baseband signal downward by a predetermined frequency to generate a shifted baseband signal; and When the second detection result indicates that the baseband signal contains the second preamble corresponding to the second channel, the frequency shifting circuitry does not shift the baseband signal or shifts the baseband signal upward by the predetermined frequency to generate a shifted baseband signal.

2. The WiFi station of claim 1, wherein, The range of the specific frequency band further includes a range of a third channel, and the WiFi station further comprises third preamble detection circuitry configured to detect whether the baseband signal contains a third preamble corresponding to the third channel, and output a third detection result based on the detection; and The frequency shifting circuitry is further configured to determine, based on the third detection result, whether to shift the baseband signal based on the center frequency of the first channel, the center frequency of the second channel, or the center frequency of the third channel, and generate a shifted baseband signal.

3. The WiFi station of claim 2, wherein, The WiFi station performs the passive scanning on channels of 2.4G, and the bandwidth of the specific frequency band is 20MHz, the center frequency of the second channel is the center frequency of the specific frequency band, the center frequency of the first channel is 5MHz lower than the center frequency of the specific frequency band, and the center frequency of the third channel is 5MHz higher than the center frequency of the specific frequency band.

4. The WiFi station of claim 3, wherein, When the processing circuitry updates the specific frequency band, the processing circuitry shifts the center frequency of the specific frequency band by 15MHz.

5. The WiFi station of claim 3, wherein: When the first detection result indicates that the baseband signal contains the first preamble corresponding to the first channel, the frequency shifting circuitry shifts the baseband signal by -5MHz to generate a shifted baseband signal; When the second detection result indicates that the baseband signal contains the second preamble corresponding to the second channel, the frequency shifting circuitry does not shift the baseband signal; and ​ When the third detection result indicates that the baseband signal contains the third preamble corresponding to the third channel, the frequency shifting circuit shifts the baseband signal by 5MHz to generate a frequency shifted baseband signal.

6. The WiFi station of claim 4, wherein, When the WiFi station stays in the original specific frequency band for a specific period of time, the WiFi station completes scanning of channels in the specific frequency band, and when scanning of all 2.4G channels is completed, the processing circuit stops updating the specific frequency band and the WiFi station stops performing the passive scanning.

7. The WiFi station of claim 1, wherein, The WiFi station performs the passive scanning on channels of 5G, wherein the bandwidth of the specific frequency band is 40MHz, the center frequency of the first channel is 10MHz lower than the center frequency of the specific frequency band, and the center frequency of the second channel is 10MHz higher than the center frequency of the specific frequency band.

8. The WiFi station of claim 7, wherein, When the processing circuit updates the specific frequency band, the processing circuit moves the center frequency of the specific frequency band by 40MHz.

9. The WiFi station of claim 8, wherein: When the first detection result indicates that the baseband signal contains the first preamble corresponding to the first channel, the frequency shifting circuit shifts the baseband signal by -10MHz to generate a frequency shifted baseband signal; and When the second detection result indicates that the baseband signal contains the second preamble corresponding to the second channel, the frequency shifting circuit shifts the baseband signal by 10MHz to generate a frequency shifted baseband signal. The passive scanning method comprises:

10. A passive scanning method of a WiFi station, characterized by, receiving a radio frequency signal in a specific frequency band to generate a baseband signal, wherein the specific frequency band ranges from a first channel to a second channel; detecting whether the baseband signal contains a first preamble corresponding to the first channel, and outputting a first detection result based on the detection; detecting whether the baseband signal contains a second preamble corresponding to the second channel, and outputting a second detection result based on the detection; determining, based on the first detection result and the second detection result, whether to shift the baseband signal by a center frequency of the first channel or a center frequency of the second channel, and generating a frequency shifted baseband signal; and updating the specific frequency band when staying in the original specific frequency band for a specific period of time, wherein, when the first detection result indicates that the baseband signal contains the first preamble corresponding to the first channel, the baseband signal is shifted downward by a predetermined frequency to generate a frequency shifted baseband signal; and when the second detection result indicates that the baseband signal contains the second preamble corresponding to the second channel, the baseband signal is not shifted or is shifted upward by the predetermined frequency to generate a frequency shifted baseband signal. ​

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