Time synchronization for wireless devices

Abstract

A method for time synchronization for a wireless device. The method includes receiving a modulated signal from a second wireless device, the modulated signal indicating information of a first PPS signal for time synchronization, and the first PPS signal being received by the second wireless device via a network protocol or GNSS receiver for time synchronization. The method further includes obtaining a second PPS signal by demodulating the received modulated signal. The method also includes determining a delay offset between the first PPS signal and the second PPS signal. In addition, the method includes recovering the first PPS signal for time synchronization based on the second PPS signal and the delay offset. In this way, the precision of time synchronization can be improved, and the cost of the whole network can be reduced.

Description

Background Art

[0001] Time synchronization between Wi-Fi devices is fundamental to optimizing wireless network performance. With the increasing reliance on Wi-Fi connections, accurate timing becomes critical. In an ideal transmission system, pulses are transmitted at precise intervals and arrive at the receiver at exactly the same intervals. In real systems, various factors can cause signal imperfections that result in suboptimal frequency or phase synchronization. Frequency synchronization involves adjusting the clocks to the same frequency, and phase / time synchronization refers to adjusting two devices to the same phase and time of day.

[0002] A pulse per second (PPS) signal is a highly accurate timing signal that generates an electrical pulse at the beginning of each second. It is a reference point for precise timing and synchronization in a variety of applications. PPS signals are typically generated by a very accurate time source, such as an atomic clock or a Global Navigation Satellite System (GNSS) receiver. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] When read in conjunction with the accompanying drawings, embodiments of the present disclosure can be understood from the following detailed description. According to standard practice in the industry, various features are not drawn to scale. In fact, for clarity of discussion, the sizes of various features can be increased or reduced arbitrarily. Some examples of the present disclosure are described with reference to the following drawings.

[0004] Figure 1 is a schematic diagram illustrating an example environment in which example embodiments of the present disclosure may be implemented;

[0005] Figure 2 is a schematic diagram illustrating an example process of generating a modulated signal and transmitting the modulated signal by a host AP according to an embodiment of the present disclosure;

[0006] Figure 3 is a schematic diagram illustrating an example process of recovering a received modulated signal by a client AP according to an embodiment of the present disclosure;

[0007] Figure 4 is a schematic diagram illustrating an example host AP according to an embodiment of the present disclosure;

[0008] Figure 5 is a schematic diagram illustrating an example client AP according to an embodiment of the present disclosure;

[0009] Figure 6 is a schematic diagram illustrating an example of delay compensation performed by a client AP according to an embodiment of the present disclosure;

[0010] Figure 7 is a flow chart illustrating a method for time synchronization performed by a host wireless device according to an embodiment of the present disclosure; and

[0011] Figure 8 is a flow chart illustrating a method for time synchronization performed by a client wireless device according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0012] In some traditional solutions, some wireless devices achieve time synchronization by using a global navigation satellite system (GNSS) receiver. GNSS receivers use signals from global navigation satellite systems, such as the global positioning system (GPS), to determine their precise location and time. Global navigation satellite system receivers should be deployed in strategic locations where satellites are clearly visible in order to acquire satellite signals from the satellites. The GNSS receiver can then extract highly accurate time information from the acquired satellite signals and can share the precise time with wireless devices through a wired or wireless network using a standard time distribution protocol, such as the Precision Time Protocol (PTP). The wireless devices can then adjust their local clocks based on the GNSS reference time. However, GNSS receivers work well in outdoor environments, but may not be able to receive signals in indoor environments.

[0013] In some other traditional schemes, some wireless devices achieve time synchronization by using the 1588 protocol (ie, PTP). In order to achieve time synchronization between wireless devices using the 1588 protocol, all devices in the network should support the 1588 protocol. One device in the wireless network is identified as the master clock, while the other devices are identified as slave clocks. Then, these devices exchange timestamped PTP messages through the network, measure propagation delays, and adjust their local clocks to match the time of the master clock. However, it is expensive for all devices in the network to support the 1588 protocol. In addition, the synchronization delay between wireless devices is about 10 microseconds. Therefore, this accuracy may limit many applications related to Wi-Fi 7 and time-sensitive networks (TSN).

[0014] Therefore, embodiments of the present disclosure provide a time synchronization scheme between wireless devices. A host wireless device (such as a host access point (AP)) can obtain an original pulse per second (PPS) signal and generate a modulated signal based on the original PPS signal. The host AP can then send the modulated signal to a client wireless device (such as a client AP).

[0015] After receiving the modulated signal, the client AP can demodulate the received modulated signal and obtain the target PPS signal. The client AP can estimate multiple delays during the process and determine the total delay offset between the original PPS signal and the target PPS signal. In addition, the client AP can recover the original PPS signal by compensating for the total delay offset to the target PPS signal.

[0016] In this way, wireless devices that cannot receive GPS signals can synchronize their clocks with the master wireless device without supporting the PTP protocol. In addition, the accuracy of time synchronization can be improved and the cost of the entire network can be reduced.

[0017] Figure 1 1 is a schematic diagram illustrating an example environment 100 in which example implementations of the present disclosure may be implemented. Figure 1 As shown, environment 100 includes a host AP 102 and three client APs 104, 106, and 108. These APs are deployed in a building 110, wherein the host AP 102 is close to a window 112 of the building 110, and the client APs 104, 106, and 108 are far from the window 112. In environment 100, the host AP 102 can receive a PPS signal 114 from a satellite 116 via a GNSS receiver, and the PPS signal 114 is a precise time signal. In some embodiments, the host AP 102 can also receive the PPS signal 114 from other devices via a network protocol (such as the 1588 protocol) for time synchronization. However, because the client APs are deployed in an indoor environment and far from the window 112, they cannot receive the PPS signal from the satellite 116. Therefore, the host AP 102 can provide a precise time signal (i.e., the PPS signal 114), and the client APs 104, 106, and 108 can synchronize their local time with the host AP 102.

[0018] like Figure 1 As shown, the host AP 102 includes a modulator 118 and an antenna 118. The modulator 118 can modulate the PPS signal 114 into a PPS signal 120. In some embodiments of the present disclosure, the modulator 118 may include a sine wave generation module configured to generate a sine wave signal. In these embodiments, the modulator 118 may also include a radio frequency (RF) switch for generating a modulated PPS signal 120 based on the original PPS signal 114 and the generated sine wave. In the environment 100, after generating the modulated PPS signal 120, the host AP 102 can send it to the client APs 104, 106, and 108 for time synchronization between these APs.

[0019] like Figure 1As shown, for example, the client AP 104 includes an antenna 122, a demodulator 126, and a delay control unit 130. The modulated PPS signal 120 may be transmitted in the air and may be received by the antenna 122 of the client AP 104 as a modulated PPS signal 124. The modulated PPS signal 124 may be demodulated by the demodulator 125 to obtain a PPS signal 128. Although the client AP 104 has obtained the PPS signal from the host AP 102, the PPS signal 128 cannot be used for time synchronization because there is a delay offset between the original PPS signal 114 obtained from the satellite 116 and the PPS signal 128. For example, the delay offset may be caused by switching an RF switch included in the modulator 118, an envelope detector included in the demodulator 126, and air propagation of the PPS signal 120 from the antenna 118 of the host AP 102 to the antenna 122 of the client AP 104. Therefore, the client AP 104 may compensate for the delay of the PPS signal 128 by utilizing the delay control unit 130. After the delay compensation, the client AP 104 may obtain the PPS signal 132, wherein the PPS signal 132 has sub-microsecond accuracy.

[0020] It should be noted that host AP 102 is an example of a host wireless device, and client APs 104, 106, and 108 are examples of client wireless devices. The host wireless device and the client wireless device may be other wireless devices, such as switches, routers, clients, and the like.

[0021] In this way, the time of the client wireless device can be synchronized even if the client wireless device is in an environment without GNSS signals. In addition, it is not necessary for all wireless devices in the network to support the PTP protocol, which can reduce the cost of the entire network. In addition, the accuracy of time synchronization can be improved to sub-microsecond level.

[0022] Figure 2 1 is a schematic diagram illustrating an example process of generating a modulated signal and transmitting the modulated signal by a host AP according to an embodiment of the present disclosure. Figure 2As shown, the host AP 200 includes a baseband chip 202, a front-end module (FEM) 204, a modulator 208, and an antenna 212. The baseband chip 202 performs digital signal processing, encoding, and data encapsulation to generate a data frame that complies with the Wi-Fi protocol. The generated Wi-Fi data frame can be sent from the baseband chip 202 to the FEM 204. Then, the FEM 204 can convert the digital signal into an RF signal (i.e., a Wi-Fi signal) and modulate the signal to fit the RF frequency band used for Wi-Fi communication. In addition, the FEM 204 can also amplify the RF signal to ensure that the signal has sufficient power to be sent in a Wi-Fi channel with the coverage required for communication between devices.

[0023] The host AP 200 may obtain the raw PPS signal 206 from a trusted time source (e.g., a GNSS receiver, an atomic clock, a network time server, a precision time device, a satellite ground station, etc.). The modulator 208 in the host AP 200 may modulate the PPS signal 206 into a modulated PPS signal 210. The modulated PPS signal 210 may then be combined with the Wi-Fi signal generated by the FEM 204. The modulated PPS signal 210 and the Wi-Fi signal may then be sent by the antenna 212 to the client AP (e.g., Figure 1 Client AP 104 in.

[0024] In this way, the modulator 208 is connected to the signal transmission path between the FEM 204 and the antenna 212. Therefore, the modulator 208 does not affect the Wi-Fi signal transmission on the original link of the host AP 200.

[0025] Figure 3 is a schematic diagram illustrating an example process of recovering a received modulated signal by a client AP according to an embodiment of the present disclosure. Figure 3 As shown, client AP 300 includes antenna 302, radio chip 306, demodulator 308 and delay control unit 312. Antenna 302 can receive modulated PPS signal 304 and Wi-Fi signal. Wi-Fi signal can be sent to radio chip 306, and radio chip receives Wi-Fi signal and converts it back to digital signal. This process includes RF demodulation and digital signal processing.

[0026] like Figure 3As shown, the received modulated PPS signal 304 can be sent to the demodulator 308. The demodulator 308 can generate a PPS signal 310 by demodulating the modulated PPS signal 304. In some embodiments, the demodulator 308 can include a filter, an amplitude modulation module, and an envelope detector. The filter can be used to filter the Wi-Fi signal from the modulated PPS signal, and the amplitude modulation module and the envelope detector can be used to demodulate the RF signal into the PPS signal 310.

[0027] like Figure 3 As shown, the PPS signal 310 can be sent to a delay control unit 312. The delay control unit 312 can estimate multiple delays during the previous process and determine the total delay offset between the original PPS signal of the host AP (e.g., the PPS signal 206 of the host AP 200) and the PPS signal 310. In some embodiments, the delay control unit 312 may include a timer and a counter for compensating for the delay of the PPS signal 310. The delay control unit 312 can then generate a compensated PPS signal 314, wherein the compensated PPS signal 314 has only a sub-microsecond delay with the original PPS signal of the host AP. Therefore, the time of the client AP 300 can be synchronized with the time of the host AP.

[0028] like Figure 3 As shown, the demodulator 308 is connected to the antenna 302, and the delay control unit 312 is connected to the demodulator 308. In this way, the demodulator 308 and the delay control unit 312 do not affect the transmission of the Wi-Fi signal on the original link of the client AP 300.

[0029] Figure 4 is a schematic diagram illustrating an example host AP 400 according to an embodiment of the present disclosure. Figure 4As shown, the host AP 400 includes a sine wave generation module 402, which is used to generate a sine wave signal. In some embodiments, the sine wave generation module 402 includes a phase-locked loop (PLL) 404 and a voltage-controlled oscillator (VCO) 406. VCO 406 can output a signal with a fixed frequency. Then, the signal can be fed back to PLL 404. The feedback signal is divided by fractions, then compared with the input signal of PLL404, and the two signals are aligned. As a result, the sine wave generation module 402 can generate a sine wave signal with a specific frequency, wherein the specific frequency can be far away from the frequency of the Wi-Fi signal and comply with regulations. In some embodiments, the difference between the frequency of the sine wave signal and the frequency of the Wi-Fi signal of the host AP 400 is greater than the predefined difference. In this way, since the frequency of the modulated signal is far away from the Wi-Fi frequency, the introduction of the modulator and demodulator will not affect normal business or services.

[0030] like Figure 4 As shown, the sine wave generation module 402 is connected to a power amplifier 408. Therefore, the generated sine wave signal can be sent to the power amplifier 408. The power amplifier 408 is configured to amplify the power of the sine wave signal. In the host AP 400, the power amplifier 408 is connected to the RF switch 410, and the sine wave signal can be sent to the RF switch 410. The RF switch 410 can be controlled by the original precise PPS signal 412. If the RF switch 410 detects the rising edge (or high level) of the original PPS signal 412, the state of the RF switch 410 can be changed to allow the sine wave signal to pass through the RF switch 410. Otherwise, if the RF switch 410 detects the falling edge (or low level) of the original PPS signal 412, the state of the RF switch 410 can be changed so that the sine wave signal is blocked by the RF switch 410. As a result, the demodulator can output a modulated PPS signal, and the modulated PPS signal can be sent to the directional coupler 414. In addition, the RF switch 410 can also be connected to the terminal 418. Terminal 418 is used to absorb the matching load of RF switch 410 .

[0031] like Figure 4As shown, the RF switch 410 is connected to a directional coupler 414. The directional coupler 414 has four ports, and they are connected to the FEM 416, the antenna 422, the RF switch 410, and the terminal 420. The FEM 416 can generate a Wi-Fi signal for the host AP 400, and the terminal 420 can be used to absorb the matching load. The directional coupler 414 can be used to couple the modulated PPS signal with the Wi-Fi signal generated by the FEM 416. Then, the modulated PPS signal and the Wi-Fi signal can be sent to the client AP through the antenna 422 of the host AP 400. In the process of generating the modulated PPS signal, the switching of the RF switch 410 can introduce a delay in the modulated PPS signal. The delay can be estimated, and is conventionally about 10 nanoseconds, which means that the modulated PPS signal has a delay of about 10 nanoseconds compared to the original precise PPS signal.

[0032] In this way, the original PPS signal of the host AP 400 can be modulated and sent to the client AP by using hardware. In addition, the delay between the modulated PPS signal and the original accurate PPS signal can be estimated. Therefore, the delay can be compensated and the accuracy of time synchronization can be improved.

[0033] Figure 5 is a schematic diagram illustrating an example client AP 500 according to an embodiment of the present disclosure. Figure 5 As shown, antenna 502 of client AP 500 can receive power from a host AP (e.g., Figure 4 The host AP 400 in the client AP 500 receives the modulated PPS signal, and the modulated PPS signal indicates information of the original precise PPS signal used for time synchronization between the host AP and the client AP 500. In the client AP 500, the directional coupler 504 is connected to the antenna 502 and is configured to distribute the received modulated PPS signal to the FEM 506 and the filter 510. In addition, the terminal 508 is connected to the directional coupler 504 and is configured to absorb the matching signal. In the client AP 500, the FEM 506 is connected to the directional coupler 504 to process the Wi-Fi signal portion of the received modulated PPS signal.

[0034] like Figure 5As shown, the filter 510 is connected to the directional coupler 504 and is configured to obtain a filtered signal indicating information of the original PPS signal (e.g., the original PPS signal 412 in the host AP 400) by filtering the Wi-Fi signal from the received modulated PPS signal. In addition, the filter 510 can also remove other interference signals from the received modulated PPS signal. In the client AP 500, the amplitude modulation module 514 is connected to the filter 510 and is configured to generate an adjusted signal based on the filtered signal by adjusting the amplitude of the filtered signal so that the adjusted amplitude of the filtered signal meets the optimal detection level of the envelope detector (i.e., the Schottky detector 520). Therefore, the amplitude of the signal input to the Schottky detector 520 will not be too large or too small.

[0035] exist Figure 5 In the illustrated embodiment, the amplitude modulation module 514 includes an amplifier 516 connected to the filter 510 and an attenuator 518 connected to the amplifier 516. In order to adjust the parameters of the amplifier 516 and the attenuator 518, a demodulation logarithmic detector 512 can be connected to the branch between the filter 510 and the amplitude modulation module 514. The logarithmic detector 512 has a high detection sensitivity. Therefore, it can be used to detect weak signals. Therefore, the filtered signal can be sent to the logarithmic detector 512, and the logarithmic detector 512 can detect the signal (even when the signal is weak) and adjust the parameters of the amplifier 516 and the attenuator 518. Figure 5 As shown, although the signal detection of the logarithmic detector 512 may take some time, there is a path between the filter 510 and the amplitude modulation module 514. In this way, the filtered signal can be sent directly to the amplitude modulation module 514, and the logarithmic detector 512 does not introduce a delay offset into the PPS signal. In some embodiments, the logarithmic detector 512 can be replaced by other suitable detectors, but the logarithmic detector is preferred because of its high detection sensitivity.

[0036] like Figure 5As shown, the Schottky detector 520 is connected to the amplitude modulation module 514 and is configured to generate a demodulated PPS signal 524. In addition, the terminal 522 is connected to the Schottky detector 520 and is configured to absorb the matching load of the Schottky detector 520. The Schottky detector 520 is used to convert the high-frequency signal into a direct current (DC) signal for subsequent processing, and it relies on the nonlinear characteristics of the Schottky diode. When the diode is forward biased, it allows a certain level of conduction current to flow. On the contrary, when the diode is reverse biased, it can be changed to a cut-off state. Due to the nonlinear characteristics of the diode, when the envelope of the high-frequency signal enters the diode, the diode can generate a very small DC voltage, the magnitude of which is proportional to the signal strength. In this way, the Schottky detector 520 can effectively convert the high-frequency signal into a DC signal.

[0037] In some embodiments, the Schottky detector 520 can be configured to detect the conditioned signal from the amplitude modulation module 514. In some embodiments, the Schottky detector 520 can be replaced by other envelope detectors, such as a logarithmic detector or a root mean square (RMS) detector. However, the Schottky detector is preferred because the delay of the Schottky detector is about 10 nanoseconds, which is smaller than the logarithmic detector and the RMS detector. In this way, the delay caused by the Schottky detector 520 is small and can be estimated. Therefore, the delay can be compensated and the accuracy of time synchronization can be improved.

[0038] like Figure 5 As shown, the Schottky detector 520 can generate a demodulated PPS signal 524, and the demodulated PPS signal 524 can be sent to a delay control unit 526. The delay control unit 526 is connected to the demodulator (e.g., the Schottky detector 520) and is configured to determine the original accurate PPS signal (e.g., Figure 4In some embodiments, the delay control unit 526 may further determine the delay caused by the signal detection process of the envelope detector in the client AP (e.g., the Schottky detector 520 in the client AP 500). In some embodiments, the delay control unit 526 may further determine the delay caused by the air propagation of the modulated PPS signal from the host AP to the client AP. Therefore, the delay control unit 526 can determine the delay offset between the original precise PPS signal and the demodulated PPS signal 524 based on these delays to generate a recovered PPS signal 528, wherein the recovered PPS signal 528 can have a sub-microsecond delay offset compared to the original precise PPS signal.

[0039] In some embodiments, in order to compensate for the delay offset, the delay control unit 526 may include a counter connected to the demodulator and configured to generate a pulse edge of the recovered first PPS signal based on the delay offset. In some embodiments, the delay control unit 526 may obtain a default value of the counter for generating the pulse edge of the recovered PPS signal 528. In addition, the delay control unit 526 may determine a compensation value of the counter based on the default value and the delay offset, wherein the compensation value is less than the default value. Then, the delay control unit 526 may generate a pulse edge of the recovered PPS signal 528 based on the compensation value of the counter. For example, if the counter generates a rising edge every C clock cycles, each clock cycle is t (nanoseconds), and the delay offset is D (nanoseconds), the counter may generate the next rising edge after CD / t cycles.

[0040] In this way, the client AP 500 can obtain the recovered PPS signal 528 from the received modulated PPS signal. In addition, because the delay in the demodulator can be estimated, the delay offset between the recovered PPS signal 528 and the original accurate PPS signal in the host AP can be reduced to sub-microsecond level. Therefore, the accuracy of time synchronization between the host AP and the client AP can be improved.

[0041] Figure 6 6 is a schematic diagram illustrating an example 600 of delay compensation performed by a client AP according to an embodiment of the present disclosure. Figure 6 As shown, the original PPS signal 602 (eg, Figure 1 The original PPS signal 114 in the host AP (e.g., Figure 1 The host AP 102 in FIG. 10A receives the original PPS signal 602, and the rising edge of the original PPS signal 602 occurs at time 612. The original PPS signal 602 may then be modulated into a modulated PPS signal 604 (eg, Figure 1 Because the modulator in the host AP (e.g., modulator 118) can generate the modulated PPS signal 604 using an RF switch, and the switching process of the RF switch may take some time, the rising edge of the modulated PPS signal 604 is delayed to time 614, so that there is a delay 622 between time 612 and time 614.

[0042] The modulated PPS signal 604 may be sent by the host AP to the client AP (eg, Figure 1 104 in the client AP) and as a modulated PPS signal 606 transmitted by the antenna of the client AP (e.g., Figure 1 Because the air propagation of the modulated PPS signal may take some time, the rising edge of the modulated PPS signal 606 is delayed to time 616, so that there is a delay 624 between time 614 and time 616.

[0043] The modulated PPS signal 606 may be demodulated by a demodulator in the client AP, and the demodulator may generate a demodulated PPS signal 608 (eg, Figure 1 Because the detection process of the envelope detector may take some time, the rising edge of the demodulated PPS signal 608 is delayed to time 618, so that there is a delay 626 between time 616 and time 618.

[0044] like Figure 6As shown, therefore, there is a total delay 628 between the rising edge of the demodulated PPS signal 608 and the original precise PPS signal 602. In some embodiments, the delay control unit in the client AP can determine the total delay 628 by estimating the delay 622, the delay 624, and the delay 626. In some embodiments, the delay 622 caused by the RF switch can be measured and estimated as a predefined value (e.g., 10 nanoseconds). In some embodiments, the delay 624 caused by air propagation can be estimated as a predefined value based on the average distance between APs in an indoor environment. In some embodiments, considering that the longest distance between an AP or an AP and a client is within 100 meters, the delay 624 can be estimated as a small predefined value or zero. In some embodiments, the delay 626 caused by the Schottky detector can be measured and estimated as 10 nanoseconds. After delay compensation, the recovered PPS signal 610 is very close to the original precise PPS signal 602, and the delay 630 between the rising edge of the recovered PPS signal 610 and the original PPS signal 602 can be less than 1 microsecond.

[0045] In this way, the delay offset between the demodulated PPS signal and the original accurate PPS signal can be measured or estimated, so that the delay offset can be compensated. Therefore, the accuracy of time synchronization between the host AP and the client AP can be improved.

[0046] Figure 7 7 is a flow chart illustrating a time synchronization method 700 performed by a host wireless device according to an embodiment of the present disclosure. Figure 7 As shown, at block 702, the host wireless device may receive a first PPS signal for time synchronization via a network protocol or a GNSS receiver for time synchronization. Figure 1 In the illustrated environment 100 , a host AP 102 near a window 112 of a building 110 may receive a raw PPS signal 114 from a satellite 116 .

[0047] At block 704, the host wireless device may generate a sine wave signal. Figure 1 In the illustrated environment 100 , the modulator 118 of the host AP 102 can generate a sine wave signal. The sine wave signal can be used to modulate the original PPS signal 114 .

[0048] At block 706, the host wireless device may utilize an RF switch to generate a modulated signal based on the received first PPS signal and the sine wave signal. Figure 1 In the illustrated environment 100 , the modulator 118 of the host AP 102 may generate a modulated PPS signal 120 based on the original PPS signal 114 and the generated sine wave signal.

[0049] At block 708, the host wireless device may send the modulated signal to the client wireless device for time synchronization between the host wireless device and the client wireless device. Figure 1 In the illustrated environment 100 , the host AP 102 may transmit a modulated signal 120 to the client AP 104 via an antenna 118 of the host AP 102 for time synchronization.

[0050] In this way, the original PPS signal of the host wireless device can be modulated by using hardware and sent to the client wireless device. In addition, the delay between the modulated signal and the first PPS signal can be measured or estimated. Therefore, the delay can be compensated and the accuracy of time synchronization can be improved.

[0051] Figure 8 8 is a flow chart illustrating a method 800 for time synchronization performed by a client wireless device according to an embodiment of the present disclosure. Figure 8 As shown, at block 802, a client wireless device may receive a modulated signal from a host wireless device, wherein the modulated signal indicates information of a first PPS signal for time synchronization, and the first PPS signal is received by a second wireless device via a network protocol or a GNSS receiver for time synchronization. Figure 1 In the illustrated environment 100 , the client AP 104 may receive a modulated PPS signal 124 via an antenna 122 of the client AP 104 , wherein the modulated PPS signal 124 corresponds to the modulated PPS signal 120 .

[0052] At block 804, the client wireless device may obtain a second PPS signal by demodulating the received modulated signal. Figure 1 In the illustrated environment 100, the demodulator 126 in the client AP 104 can receive and demodulate the modulated PPS signal 124. Thus, the client AP 104 can obtain a demodulated PPS signal 128.

[0053] At block 806, the client wireless device may determine a delay offset between the first PPS signal and the second PPS signal. Figure 1 In the illustrated environment 100, the delay control unit 130 may determine a delay offset between the original PPS signal 114 and the demodulated PPS signal 128. For example, the delay offset may be caused by an RF switch in the host AP 102, air propagation of the modulated PPS signal 120, or a detection process of an envelope detector in the demodulator 126.

[0054] At block 808, the client wireless device may recover the first PPS signal for time synchronization based on the second PPS signal and the delay offset. Figure 1 In the illustrated environment 100, the client AP 104 can recover the original PPS signal 114 based on the demodulated PPS signal 128 and the delay offset. Then, a recovered PPS signal 132 can be generated. The recovered PPS signal will be very close to the original PPS signal 114, and the resulting delay offset between the two signals can be reduced to sub-microsecond levels.

[0055] In this way, the client wireless device can obtain the recovered PPS signal from the received modulated PPS signal. In addition, because the delay in the demodulator can be estimated, the delay offset between the recovered PPS signal in the host wireless device and the original accurate PPS signal can be reduced to sub-microsecond level. Therefore, the accuracy of time synchronization between the host wireless device and the client wireless device can be improved.

[0056] In the context of the present disclosure, although operations are described in a particular order, this should not be understood as requiring such operations to be performed in the particular order shown or in sequence, or requiring all illustrated operations to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0057] In the above detailed description of the present disclosure, reference is made to the accompanying drawings which form a part of the present disclosure, in which examples of how the present disclosure may be practiced are shown by way of illustration. These examples are described in sufficient detail to enable one of ordinary skill in the art to practice the examples of the present disclosure, and it is understood that other examples may be utilized and process, electrical and / or structural changes may be made without departing from the scope of the present disclosure.

Claims

1. A method comprising: receiving, by the first wireless device, a modulated signal from the second wireless device, the modulated signal indicating information of a first pulse per second (PPS) signal for time synchronization, and the first PPS signal is received by the second wireless device via a network protocol for time synchronization or a global navigation satellite system (GNSS) receiver; Acquiring, by the first wireless device, a second PPS signal by demodulating the received modulated signal; determining, by the first wireless device, a delay offset between the first PPS signal and the second PPS signal; as well as The first PPS signal for time synchronization is recovered by the first wireless device based on the second PPS signal and the delay offset.

2. The method according to claim 1, wherein acquiring the second PPS signal by demodulating the received modulated signal comprises: obtaining a filtered signal indicative of the information of the first PPS signal by filtering a Wi-Fi signal from the received modulated signal; as well as The second PPS signal is generated based on the filtered signal.

3. The method of claim 2, wherein generating the second PPS signal based on the filtered signal comprises: generating an adjusted signal by adjusting an amplitude of the filtered signal based on the filtered signal, the adjusted amplitude of the filtered signal satisfying a detection level of an envelope detector; as well as The second PPS signal is generated based on the adjusted signal by utilizing the envelope detector.

4. The method of claim 3, wherein generating the adjusted signal by adjusting the amplitude of the filtered signal based on the filtered signal comprises: adjusting parameters of an amplifier and an attenuator based on the filtered signal by utilizing a demodulated logarithmic detector; as well as The amplitude of the filtered signal is adjusted by utilizing the amplifier and the attenuator.

5. The method of claim 3, wherein generating the second PPS signal based on the adjusted signal by utilizing the envelope detector comprises: outputting a high voltage in response to detection of the adjusted signal by the envelope detector; as well as In response to the conditioned signal not being detected by the envelope detector, a low voltage is output. The method of claim 3 , wherein the envelope detector is a Schottky detector.

7. The method of claim 3, wherein determining the delay offset between the first PPS signal and the second PPS signal comprises: determining a first delay caused by switching of a radio frequency (RF) switch in the second wireless device, the RF switch being used to generate the modulated signal based on the first PPS signal; as well as The delay offset between the first PPS signal and the second PPS signal is determined based on the first delay.

8. The method of claim 7, wherein determining the delay offset between the first PPS signal and the second PPS signal based on the first delay comprises: determining a second delay caused by the envelope detector; as well as The delay offset between the first PPS signal and the second PPS signal is determined based on the first delay and the second delay.

9. The method of claim 8, wherein determining the delay offset between the first PPS signal and the second PPS signal based on the first delay and the second delay comprises: determining a third delay caused by air propagation of the modulated signal from the second wireless device to the first wireless device; as well as The delay offset between the first PPS signal and the second PPS signal is determined based on the first delay, the second delay, and the third delay.

10. The method of claim 1, wherein recovering the first PPS signal for time synchronization based on the second PPS signal and the delay offset comprises: Obtaining a first value of a counter used to generate a pulse edge of the recovered first PPS signal; determining a second value for the counter based on the first value and the delay offset, the second value being less than the first value; and The pulse edge of the recovered first PPS signal is generated based on the second value of the counter.

11. A first wireless device, comprising: an antenna configured to receive a modulated signal from a second wireless device, the modulated signal indicating information of a first pulse per second (PPS) signal for time synchronization, and the first PPS signal is received by the second wireless device via a network protocol for time synchronization or a global navigation satellite system (GNSS) receiver; a directional coupler connected to the antenna and configured to distribute the received modulated signal; a demodulator connected to the directional coupler and configured to demodulate the received modulated signal into a second PPS signal; A delay control unit is connected to the demodulator and is configured to: determining a delay offset between the first PPS signal and the second PPS signal; and The first PPS signal for time synchronization is restored based on the second PPS signal and the delay offset.

12. The first wireless device of claim 11, wherein the demodulator comprises: a filter connected to the directional coupler and configured to obtain a filtered signal indicating the information of the first PPS signal by filtering a Wi-Fi signal from the received modulated signal; as well as A demodulation module is connected to the filter and configured to generate the second PPS signal based on the filtered signal.

13. The first wireless device of claim 12, wherein the demodulation module comprises: an amplitude modulation module connected to the filter and configured to generate an adjusted signal by adjusting the amplitude of the filtered signal based on the filtered signal; as well as an envelope detector connected to the amplitude modulation module and configured to detect the adjusted signal used to generate the second PPS signal, Wherein the adjusted amplitude of the filtered signal satisfies a detection level of an envelope detector.

14. The first wireless device of claim 13, wherein the amplitude modulation comprises: an amplifier connected to the filter and an attenuator connected to the amplifier, the attenuator configured to adjust the amplitude of the filtered signal; as well as A demodulation logarithmic detector is connected between the filter and the amplitude modulation module and is configured to adjust parameters of the amplifier and the attenuator based on the filtered signal.

15. The first wireless device of claim 13, wherein the envelope detector is a Schottky detector and the demodulator is further configured to: In response to detecting the adjusted signal by the Schottky detector, outputting a high voltage; and In response to the conditioned signal not being detected by the Schottky detector, a low voltage is output.

16. The first wireless device of claim 13, wherein the delay control unit comprises: a counter connected to the demodulator and configured to generate a pulse edge of the recovered first PPS signal based on the delay offset; as well as A delay determination module is connected to the counter and configured to determine the delay offset between the first PPS signal and the second PPS signal.

17. The first wireless device of claim 16, wherein the delay determination module is further configured to: The delay offset between the first PPS signal and the second PPS signal is determined based on at least one of the following: a first delay caused by switching of a radio frequency switch used to generate the modulated signal based on the first PPS signal in the second wireless device, a second delay caused by the envelope detector, and A third delay caused by air propagation of the modulated signal from the second wireless device to the first wireless device.

18. A second wireless device, comprising: A signal generating module, configured to generate a sine wave signal; a power amplifier connected to the signal generating module and configured to amplify the power of the sinusoidal wave signal; A radio frequency (RF) switch is connected to the power amplifier and is configured to: receiving a first pulse per second (PPS) signal for time synchronization via a network protocol for time synchronization or a global navigation satellite system (GNSS) receiver, and generating a modulated signal based on the received first PPS signal and the sine wave signal; a directional coupler connected to the RF switch and configured to couple the modulated signal with a Wi-Fi signal; An antenna is connected to the directional coupler and is configured to transmit the modulated signal to a second wireless device for time synchronization between the first wireless device and the second wireless device.

19. The second wireless device of claim 18, wherein the signal generation module comprises: A voltage controlled oscillator VCO connected to the power amplifier; as well as The phase-locked loop PLL is connected to the VCO, The VCO and the PLL are configured to generate the sinusoidal wave signal, and a difference between a frequency of the sinusoidal wave signal and a frequency of the Wi-Fi signal of the second wireless device is greater than a predefined difference.

20. The second wireless device of claim 18, wherein the RF switch is further configured to: in response to detecting a rising edge of the first PPS signal, passing the sinusoidal wave signal through the RF switch; and In response to detecting a falling edge of the first PPS signal, the sine wave signal is blocked.

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