WO2018171048A1 - 一种唤醒信号的传输方法及发送设备 - Google Patents

一种唤醒信号的传输方法及发送设备 Download PDF

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Publication number
WO2018171048A1
WO2018171048A1 PCT/CN2017/087033 CN2017087033W WO2018171048A1 WO 2018171048 A1 WO2018171048 A1 WO 2018171048A1 CN 2017087033 W CN2017087033 W CN 2017087033W WO 2018171048 A1 WO2018171048 A1 WO 2018171048A1
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Prior art keywords
wake
signal
sequence
time window
channel
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PCT/CN2017/087033
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English (en)
French (fr)
Inventor
李德怀
杜振国
程勇
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华为技术有限公司
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Priority to CN201780056682.XA priority Critical patent/CN109716852B/zh
Publication of WO2018171048A1 publication Critical patent/WO2018171048A1/zh

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  • the present application relates to the field of communications, and in particular, to a method and a transmitting device for transmitting a wake-up signal.
  • the wake-up signal includes a preamble sequence and a payload (WUR Payload) sequence, wherein the preamble sequence includes a legacy Legacy-Short Training Field (L-STF) sequence, and a legacy long training field (Legacy-Long Training Field, L- LTF) sequence, legacy signaling domain (Legacy-Signal, L-SIG) sequence.
  • L-STF Legacy-Short Training Field
  • L- LTF legacy long training field
  • L-SIG legacy signaling domain
  • AP2 transmits the preamble sequence and the payload sequence in time division, first transmits the preamble sequence, and then inserts a Silent Period for Clear Channel Assessment (CCA) detection. If the result of CCA detection by AP2 is that the channel status is busy (BUSY), AP2 will not transmit the subsequent WUR Payload sequence. If the result of CCA detection by AP2 is that the channel status is idle (Idle), then the subsequent WUR Payload will continue to be transmitted. sequence.
  • CCA Silent Period for Clear Channel Assessment
  • the neighboring AP does have a transmission collision (that is, if the neighboring AP1 and AP2 simultaneously complete the backoff and simultaneously transmit the signal), although AP2 performs the CCA result in the Silent Period after Busy, and AP2 no longer transmits the subsequent WUR Payload, but already
  • the transmitted preamble sequence has already interfered with the WiFi frame, and STA1 receives the L-SIG in the preamble sequence transmitted by AP1, but the L-SIG in the preamble sequence transmitted by AP1 and the L-SIG in the WiFi frame transmitted by AP2 carry The information is usually different, causing the L-SIG of the WiFi frame to be interfered, and STA1 cannot solve the correct information according to the L-SIG, thus causing waste of channel resources.
  • a method for transmitting a wake-up signal including:
  • the sending device sends a short training domain sequence in the wake-up signal to the receiving device by using the first time window, where the wake-up signal is used to trigger the receiving device to perform data transmission with the sending device.
  • the LP-WUR module of the receiving device receives the After the wake-up signal, the activation signal may be sent to the WiFi module of the receiving device, and the receiving device and the transmitting device are triggered to perform data transmission.
  • the short training domain sequence is used to implement synchronization between the transmitting device and the receiving device, such as clock synchronization.
  • the transmitting device then performs channel measurements in a second time window after the first time window. Further, if the result of the channel measurement is that the channel is occupied, the transmitting device stops transmitting the wake-up signal.
  • the synchronization sequence (L-STF) is first occupied, and then the CCA is detected in the second time window to detect whether there is a transmission collision. If the CCA detection result is that the channel channel is occupied, it indicates that the transmitting device and other If there is a transmission conflict between the transmitting devices, the transmission of the wake-up signal is stopped. Since the L-STF of the wake-up signal is the same as the L-STF of the WiFi signal, the first transmitted L-STF does not interfere with the WiFi signal, and the WiFi signal can still be successfully received by the receiving device, thus effectively avoiding the channel when the collision occurs. Waste, improve the channel utilization efficiency of the system.
  • the method further includes: if the channel measurement result is that the channel is idle, the sending device sends the wake-up signal after the second time window.
  • the wake-up signal transmitted by the transmitting device does not interfere with the WiFi signal sent by other neighboring devices, and the channel is effectively utilized.
  • the wake-up signal includes a preamble sequence and a load sequence, where the preamble sequence includes a short training domain sequence, The long training domain sequence and the signaling domain sequence; the payload sequence includes a frame header of the wake-up signal and data of the wake-up signal.
  • the sending by the sending device, the sending the wake-up signal after the second time window, specifically: the sending device is in the second After the time window, the short training domain sequence, the long training domain sequence, the signaling domain sequence, and the payload sequence are sequentially transmitted in sequential order.
  • the short training domain sequence transmitted here includes 10 0.8us repetitive waveforms, and the short training domain sequence transmitted in the first time window may be the same as or different from the short training domain sequence transmitted by the transmitting device at this time, for example:
  • the short training domain sequence transmitted in the first time window includes five repeated waveforms of 0.8 us.
  • the length of the first time window is greater than or equal to a required minimum duration for performing channel measurement,
  • the length of the second time window is less than the inter-frame interval PIFS.
  • the short training domain sequence transmitted by the transmitting device may be detected by other transmitting devices, and then the transmitting devices may perform backoff, and the transmitting device occupies The channel.
  • the length of the second time window is smaller than the inter-frame interframe space PIFS, this is because if the length of the second time window is equal to or higher than the PIFS time, other transmitting devices cannot be in the case where there is no transmission conflict.
  • the PIFS time preempts the channel and transmits a signal so as not to interfere with the wake-up signal subsequently transmitted by the transmitting device.
  • the length of the second time window should be at least Includes a Tx-Rx (receive-transmit) conversion time, an Rx-Tx conversion time, and a full CCA detection time. This is because after transmitting the L-STF, the transmitting device needs to transition from the transmitting state to the receiving state in order to perform CCA detection. In addition, if the detection is in the Idle state, the transmitting device needs to switch from the receiving state back to the transmitting state to continue the transmission of the wake-up signal.
  • the PIFS itself is greater than a Tx-Rx (receive-transmit) conversion time, an Rx-Tx conversion time, and a complete CCA detection time, so that when the second time window is smaller than the PIFS, the second time window can be satisfied.
  • a transmitting device including:
  • a sending unit configured to send, by using a first time window, a short training domain sequence in the wake-up signal to the receiving device; the wake-up signal is used to trigger the receiving device to perform data transmission with the sending device, and the short training domain sequence is used to implement the sending device and the receiving device.
  • the synchronization unit performs channel measurement in the second time window; the second time window is after the first time window; and the transmitting unit is further configured to stop transmitting the wake-up signal if the result of the channel measurement is that the channel is occupied.
  • the sending device When sending the wake-up signal, the sending device first sends a synchronization sequence (L-STF) to occupy the channel, and then performs CCA detection in the second time window to detect whether there is a transmission collision. If the CCA detection result is that the channel channel is occupied, the transmitting device indicates that the transmitting device If there is a transmission conflict with other transmitting devices, the transmission of the wake-up signal is stopped. Since the L-STF of the wake-up signal is the same as the L-STF of the WiFi signal, the first transmitted L-STF does not interfere with the WiFi signal, and the WiFi signal can still be successfully received by the receiving device, thus effectively avoiding the channel when the collision occurs. Waste, improve the channel utilization efficiency of the system.
  • L-STF synchronization sequence
  • the sending unit is further configured to send the wake-up signal after the second time window if the result of the channel measurement is that the channel is idle.
  • the wake-up signal includes a preamble sequence and a load sequence
  • the preamble sequence includes a short training domain sequence, a long training domain sequence, and a signaling domain sequence; the payload sequence includes a frame header of the wake-up signal and data of the wake-up signal.
  • the sending unit is specifically configured to: after the second time window, according to the sequence of time series
  • the short training domain sequence, the long training domain sequence, the signaling domain sequence, and the payload sequence are sequentially transmitted.
  • the length of the first time window is greater than or equal to a required minimum duration for performing channel measurement,
  • the length of the second time window is less than the inter-frame interframe space PIFS.
  • a transmitting device including:
  • a transmitter configured to send a short training domain sequence in the wake-up signal to the receiving device by using the first time window; the wake-up signal is used to trigger the receiving device to perform data transmission with the sending device, and the short training domain sequence is used to implement the sending device and the receiving device Inter-synchronization; the processor performs channel measurement in the second time window; the second time window is after the first time window; and the transmitter is further configured to stop transmitting the wake-up signal if the result of the channel measurement is that the channel is occupied.
  • the transmitting device When transmitting the wake-up signal, the transmitting device first sends a synchronization sequence (L-STF) to occupy the channel, and then performs CCA detection in the second time window to detect whether there is a transmission collision, if the CCA detection result is a channel. If the channel is occupied, it indicates that there is a transmission conflict between the transmitting device and other transmitting devices, and then the wake-up signal is stopped. Since the L-STF of the wake-up signal is the same as the L-STF of the WiFi signal, the first transmitted L-STF does not interfere with the WiFi signal, and the WiFi signal can still be successfully received by the receiving device, thus effectively avoiding the channel when the collision occurs. Waste, improve the channel utilization efficiency of the system.
  • L-STF synchronization sequence
  • the transmitter is further configured to send the wake-up signal after the second time window if the result of the channel measurement is that the channel is idle.
  • the wake-up signal includes a preamble sequence and a load sequence
  • the preamble sequence includes a short training domain sequence, a long training domain sequence, and a signaling domain sequence; the payload sequence includes a frame header of the wake-up signal and data of the wake-up signal.
  • the transmitter is specifically configured to follow the sequence of time after the second time window
  • the short training domain sequence, the long training domain sequence, the signaling domain sequence, and the payload sequence are sequentially transmitted.
  • the length of the first time window is greater than or equal to a required minimum duration for performing channel measurement
  • the length of the second time window is less than the inter-frame interframe space PIFS.
  • a fourth aspect of the embodiments of the present application discloses a computer storage medium for storing the above-mentioned computer software instructions for use in a transmitting device, the computer software instructions comprising a transmission of a wake-up signal for performing the above first aspect The procedure involved in the method.
  • 1 is a schematic diagram of a communication method in an existing WiFi IoT system
  • FIG. 2 is a schematic diagram of a frame structure of a wake-up signal
  • FIG. 3 is a schematic diagram of a conventional densely distributed scene
  • FIG. 4 is a schematic diagram of a conventional method for transmitting a wake-up signal
  • FIG. 5 is a schematic diagram of a method for transmitting a wake-up signal according to an embodiment of the present invention
  • FIG. 6 is a schematic structural diagram of a sending device according to an embodiment of the present disclosure.
  • FIG. 7 is a schematic flowchart of a method for transmitting a wake-up signal according to an embodiment of the present invention.
  • FIG. 8 is another schematic structural diagram of a sending device according to an embodiment of the present disclosure.
  • FIG. 9 is another schematic structural diagram of a sending device according to an embodiment of the present invention.
  • the IEEE 802.11 standard defines the WiFi IoT standard based on the 2.4G/5 GHz band, which is characterized by low power consumption and long distance.
  • a conventional WiFi module and an LP-WUR module are configured in the receiving device.
  • the AP is a sending device
  • the STA is a receiving device
  • the WiFi module of the STA is in a closed state
  • the LP-WUP module is continuously in a receiving state, or is intermittently in a receiving state.
  • the AP may include only one WiFi module, and send a wake-up signal to the STA through the WiFi module.
  • the WiFi module is usually an Orthogonal Frequency Division Multiplexing (OFDM) wideband transmitter, and the wake-up signal is a narrowband signal.
  • OFDM Orthogonal Frequency Division Multiplexing
  • the OFDM wideband transmitter can be used to generate a narrowband wake-up signal.
  • both the AP and the STA in FIG. 1 have only one antenna. This is because the WiFi module and the WUR module can share the same antenna when the same frequency band carrier (for example, 2.4 GHz) is used, thereby saving cost and simplifying the device structure.
  • the WiFi module and the WUR module use different frequency band carriers, the two should be configured with different antennas.
  • the 802.11 main module uses the 5 GHz band
  • the WUR module uses the 2.4 GHz band. In this case, the two should correspond to different antennas.
  • the wake-up signal includes a preamble sequence and a payload (WUR Payload) sequence.
  • the preamble sequence is the same as the preamble (802.11 legacy preamble) of the conventional WiFi frame, and includes an L-STF (short training domain) sequence, an L-LTF (long training domain) sequence, and an L-SIG (signaling domain) sequence, so that the device can be
  • the preamble sequence determines that the currently received data packet is a WiFi packet, thereby selecting a corresponding CCA decision threshold.
  • the short synchronization sequence ie, the L-STF sequence
  • AGC automatic gain control
  • L-LTF sequence used for channel and fine frequency offset estimation.
  • the wake-up packet payload (WUR Payload) sequence uses an easy-to-demodulate modulation scheme, such as On-Off Keying (OOK) modulation, such as Amplitude Shift Keying (ASK).
  • OSK On-Off Keying
  • ASK Amplitude Shift Keying
  • the sequence can be transmitted over a narrower bandwidth, such as a 2 MHz channel, a 4 MHz channel, a 5 MHz channel, etc., so that the energy consumption at the receiving end is smaller.
  • the WUR Payload includes a Wake-up preamble (frame header) and a MAC portion (ie, data). Part of the Wake-up preamble is similar to the preamble portion of the WiFi frame for implementing synchronization, automatic gain control (AGC), channel estimation, indication control information, etc.
  • AGC automatic gain control
  • the MAC portion is similar to the MAC portion of a conventional WiFi frame. Further, the MAC part includes a MAC header (Header), a frame body (Frame Body), and a Frame Check Sequence (FCS).
  • the MAC part may perform simple channel coding by using a repetition code, a spreading code, a Manchester code, or the like. In order to improve reliability, it is also possible to not use channel coding. Since the wake-up packet function is relatively simple, the frame body part may not exist.
  • the Wake-up preamble includes a string of specific sequences, and the WUR of the STA may not directly receive the Legacy preamble part before the wake-up signal, but directly detect the specific sequence, thereby identifying the wake-up signal.
  • the WUR of the STA receives the wake-up signal and detects its own identity (eg, unicast/multicast/broadcast address) from the MAC portion of the wake-up signal, an activation signal is sent to the WiFi module of the STA.
  • the Wake-up preamble may also include a Wakeup-Signal (WU-SIG) field for indicating the length of the MAC part and the modulation and coding mode used.
  • WU-SIG Wakeup-Signal
  • the current transmitting device generally adopts a carrier sensing access mode.
  • the transmitting device detects that the channel is idle, it performs random backoff. If the backoff completion channel is still idle, the transmitting device sends a signal.
  • the channel is heard to be Busy, the device hangs until the channel is detected as Idle again, and the device continues to perform the random backoff process.
  • the process is avoided, the signal is sent at the same time, and a transmission collision occurs. Since the wake-up signal uses a lower modulation scheme and utilizes narrowband transmission, the signal transmission time is generally longer, for example, 0.5 ms. Therefore, when the wake-up signal and the WiFi signal collide, the conflicting related device cannot successfully transmit the signal during this time, that is, the time is wasted, which will seriously reduce the channel utilization efficiency.
  • STA1, STA2, and STA3 are adjacently distributed, and AP1, AP2, and AP3 are adjacently distributed.
  • AP1 and STA1 are interfered by the AP2 transmit signal
  • STA2 and AP2 are interfered by the AP1 and AP3 transmit signals
  • STA3 and AP3 are interfered by the AP2 transmit signal.
  • AP2 and AP1 complete the backoff process at the same time
  • AP2 sends a wake-up signal to STA2.
  • AP1 sends a WIFI signal to STA1, and a transmission collision occurs. Since the signals transmitted by AP2 and AP1 interfere with each other, STA2 and STA1 cannot successfully receive signals at this time, which causes waste of the channel and the utilization efficiency of the channel decreases.
  • AP2 may transmit a complete wake-up frame (ie, the above-mentioned wake-up signal) in two parts in time, and insert a silent period between the two parts of the transmission.
  • Silent Period for CCA testing For example, referring to FIG. 4, AP2 first transmits a preamble sequence, and after transmitting the preamble sequence, performs CCA detection in a Silent Period (ie, a silent period), and if the CCA detects that the channel is BUSY (ie, the channel is occupied), AP2 stops. The subsequent transmission of the payload sequence; if the device detects that the channel is Idle (ie, the channel is idle), it continues to send a wake-up signal, such as a load sequence of the wake-up signal.
  • a wake-up signal such as a load sequence of the wake-up signal.
  • the AP2 no longer transmits the subsequent WUR Payload (ie, the payload sequence described in the embodiment of the present invention), but the transmitted preamble sequence has already interfered with the WiFi signal transmitted by the AP1.
  • the information carried by the L-SIG in the WiFi signal transmitted by the AP1 and the L-SIG in the preamble sequence transmitted by the AP2 is usually different. After the physical layer is superimposed, the L-SIG of the WiFi signal is Interference, causing STA1 to solve the correct information.
  • NAV network allocation vector
  • AP1 sends a WiFi signal to STA1, and AP2 sends a wakeup signal to STA2.
  • the WiFi signal sent by AP1 has been interfered.
  • the signal received by STA1 is the signal after the preamble sequence transmitted by AP2 and the WiFi signal transmitted by AP1 are superimposed.
  • the L-SIG part is contaminated, although the subsequent interference is no longer interfered by WUR Payload, but because The L-SIG is interfered.
  • STA1 cannot correctly solve the 802.11 Legacy Preamble sent by AP1.
  • STA1 cannot obtain the correct parameters from it, and the signal transmitted by AP1 cannot be correctly decoded. Therefore, AP1 and AP2 fail to transmit signals. Time is wasted.
  • the AP3 neighboring AP2 has received the preamble sequence transmitted by AP2, and can correctly solve the L-SIG.
  • AP3 will set its own NAV according to the information in the L-SIG, and suspend the backoff process until the NAV ends.
  • AP2 abandoned the transmission of WUR Payload, it did not notify AP3 to release the NAV, and AP3 still thought that the channel was busy. In other words, AP3 still cannot transmit signals, and channel resources are wasted.
  • the principle of the embodiment of the present invention is: when transmitting the wake-up signal, first transmit a short training domain sequence (L-STF) occupying channel, and then perform CCA (ie, channel measurement) to detect whether there is a transmission conflict. If the result of the channel measurement is busy (ie, the channel is occupied), it indicates that there is a transmission collision and the transmission of the wake-up signal is stopped. Since the L-STF of the wake-up signal is the same as the L-STF of the WiFi signal, the first transmitted L-STF does not interfere with the WiFi signal, and the WiFi signal can still be successfully received by the receiving device, thus effectively avoiding the channel when the collision occurs. Waste, improve the channel utilization efficiency of the system. In addition, if the result of the channel measurement is idle (ie, the channel is idle), indicating that there is no transmission collision, the wake-up signal is transmitted.
  • L-STF short training domain sequence
  • FIG. 6 is a schematic diagram of a composition of a sending device according to an embodiment of the present invention.
  • the sending user device may be an AP in the system shown in FIG.
  • the transmitting user equipment may include at least one processor 11, a memory 12, a communication interface 13, and a communication bus 14.
  • the processor 11 is a control center of the transmitting device, and may be a processor or a collective name of a plurality of processing elements.
  • the processor 11 is a central processing unit (CPU), may be an Application Specific Integrated Circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present invention.
  • CPU central processing unit
  • ASIC Application Specific Integrated Circuit
  • DSPs digital signal processors
  • FPGAs Field Programmable Gate Arrays
  • the processor 11 can perform various functions of the transmitting device by running or executing a software program stored in the memory 12 and calling data stored in the memory 12.
  • processor 11 may include one or more CPUs, such as CPU0 and CPU1 shown in FIG.
  • the transmitting device can include multiple processors, such as processor 11 and processor 15 shown in FIG.
  • processors can be a single core processor (CPU) or a multi-core processor (multi-CPU).
  • a processor herein may refer to one or more devices, circuits, and/or processing cores for processing data, such as computer program instructions.
  • the memory 12 can be a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (RAM) or other type that can store information and instructions.
  • the dynamic storage device can also be an Electrically Erasable Programmable Read-Only Memory (EEPROM), a Compact Disc Read-Only Memory (CD-ROM) or other optical disc storage, and a disc storage device. (including compact discs, laser discs, CDs, digital versatile discs, Blu-ray discs, etc.), disk storage media or other magnetic storage devices, or can be used for carrying or storing Any other medium having the desired program code in the form of an instruction or data structure and accessible by a computer, but is not limited thereto.
  • the memory 12 can be stand-alone and connected to the processor 11 via a communication bus 14.
  • the memory 12 can also be integrated with the processor 11.
  • the memory 12 is used to store a software program that executes the solution of the present invention, and is controlled by the processor 11.
  • the communication bus 14 may be an Industry Standard Architecture (ISA) bus, a Peripheral Component (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus.
  • ISA Industry Standard Architecture
  • PCI Peripheral Component
  • EISA Extended Industry Standard Architecture
  • the bus can be divided into an address bus, a data bus, a control bus, and the like. For ease of representation, only one thick line is shown in Figure 6, but it does not mean that there is only one bus or one type of bus.
  • the device structure shown in FIG. 6 does not constitute a limitation to the transmitting device, and may include more or less components than those illustrated, or a combination of certain components, or different component arrangements.
  • the processor 11, the memory 12, the communication interface 13, and the communication bus 14 can be integrated in a WiFi module of the transmitting device.
  • An embodiment of the present invention provides a method for transmitting a wake-up signal. As shown in FIG. 7, the method includes the following steps:
  • the sending device sends a short training domain sequence in the wake-up signal to the receiving device by using the first time window.
  • the wake-up signal is used to trigger data transmission between the receiving device and the sending device, and the synchronization sequence is used to implement synchronization between the sending device and the receiving device, such as clock synchronization, frequency synchronization, and the like. It can be L-STF. Additionally, the length of the first time window is greater than or equal to the length of time required to transmit the L-STF.
  • the frame structure of the wake-up signal is as shown in FIG. 2, and specifically includes a preamble sequence and a payload sequence.
  • the leader sequence includes an L-STF sequence, an L-LTF sequence, and an L-SIG sequence.
  • the transmitting device first transmits an L-STF sequence, then performs CCA in a second time window, and transmits a wake-up signal according to the result of the CCA after the second time window.
  • the preamble sequence of the wake-up signal includes three parts: L-STF, L-LTF, and L-SIG, and only L-STF can be transmitted, and L-LTF and L-SIG cannot be transmitted. This is because the role of L-LTF is to perform channel estimation. When a collision occurs, L-LTF is interfered, which affects the accuracy of channel estimation.
  • the length of the first time window cannot be less than the minimum duration required for channel measurement, since the length of the first time window exceeds the time required to perform CCA (ie, channel measurement) (eg 4us), when sent
  • CCA channel measurement
  • other devices can detect that a signal is being transmitted, thereby performing the backoff, that is, achieving the purpose of occupying the channel.
  • the reason why only L-STF is transmitted is because the L-STF of the wake-up signal and the L-STF content of the WiFi frame are identical, the duration is the same (both 8us), and the L-STF does not contain direct or implicit Duration information.
  • the STA that successfully received the L-STF cannot set the NAV based on the information that is solved. Therefore, when a collision occurs, when the transmitting device no longer transmits a subsequent portion of the wake-up signal, the already transmitted L-STF does not affect the contention channels of the STAs (ie, the STAs that receive the L-STF transmitted by the transmitting device). In other words, they can still preempt the channel and transmit signals.
  • the transmitting device performs channel measurement by using a second time window after the first time window.
  • the second time window is after the first time window, and further, the end time of the first time window may be the same as the start time of the second time window. That is, the transmitting device performs CCA within a second time window after transmitting the short training domain sequence described above.
  • (1) should be less than the PIFS time. This is because if the length of the second time window is equal to or higher than the PIFS time, in the absence of a transmission collision, other transmitting devices may preempt the channel and transmit a signal at this PIFS time, thereby causing interference to the subsequent transmitted wake-up signal. .
  • the length of the second time window shall contain at least one Tx-Rx (receive-transmit) conversion time, one Rx-Tx conversion time, and one complete CCA detection time. This is because after transmitting the L-STF, the transmitting device needs to transition from the transmitting state to the receiving state in order to perform CCA detection. In addition, if the detection is in the Idle state, the transmitting device needs to switch from the receiving state back to the transmitting state to continue the transmission of the wake-up signal.
  • PIFS is a point (coordination function) interframe space
  • SIFS is a short interframe space
  • Slot is a time slot
  • RxRFdelay is a radio frequency delay time
  • RxPLCPDelay is a transmitting PLCP Delay time
  • MACProcessingDelay is the Mac layer processing delay time
  • RxTxTurnaroundTime is the receiving transmission conversion time
  • AirPropagationTime is the air propagation time.
  • the length of the second time window is less than the PIFS.
  • the sending device does not send the wake-up signal.
  • do not send wake-up signal that is, “stop sending wake-up signal” according to the embodiment of the present invention, that is, if the sending device performs busy in the second time window as the result of busy, the transmitting device does not A wake-up signal is transmitted to the receiving device.
  • the transmission setting is explained.
  • the L-STF of the WiFi signal sent by the other transmitting device and the L-STF generated by the transmitting device are superimposed.
  • the main function of L-STF is synchronization
  • the L-STF of the WiFi signal is exactly the same as the already transmitted synchronization sequence.
  • the receiving device receiving the WiFi signal can still correctly solve the L-STF signal, so even The WiFi frame and the WUR frame conflict, and the already transmitted L-STF has little influence on the synchronization of the WiFi frame, and the receiving device may still correctly solve the WiFi signal. That is to say, there is no waste of channel resources due to transmission conflicts.
  • the sending device sends the wake-up signal after the second time window.
  • the wake-up signal is transmitted.
  • the transmitting device sequentially sends the L-STF, the L-LTF sequence, the L-SIG sequence, and the load sequence of the wake-up signal of the wake-up signal in a sequential order.
  • the transmitting device since the transmitting device transmits the short training domain sequence using the first time window in step 101, the purpose of occupying the channel is achieved. Then, when the result of performing CCA in the preset window is Idle, the transmitting device still occupies a channel, and can transmit a wake-up signal.
  • the transmitting device when transmitting the wake-up signal, the transmitting device first sends the L-STF occupied channel in the wake-up signal, and performs CCA detection in the second time window after the L-STF is sent. There is a transmission collision, and if there is a transmission collision, the other part of the wake-up signal is stopped. Since the L-STF of the wake-up signal is the same as the L-STF of the WiFi signal, the first transmitted L-STF does not interfere with the WiFi signal, and the WiFi signal can still be successfully received by the receiving device, thus effectively avoiding the channel when the collision occurs. Waste, improve the channel utilization efficiency of the system.
  • the transmitting device involved in the embodiment of the present invention includes a hardware structure and/or a software module corresponding to each function in order to implement the above functions.
  • the present application can be implemented in a combination of hardware or hardware and computer software in combination with the algorithmic steps of the various examples described in the embodiments disclosed herein. Whether a function is implemented in hardware or computer software to drive hardware depends on the specific application and design constraints of the solution. A person skilled in the art can use different methods to implement the described functions for each particular application, but such implementation should not be considered to be beyond the scope of the present application.
  • the embodiment of the present application may divide the function module into the sending device according to the foregoing method example.
  • each function module may be divided according to each function, or two or more functions may be integrated into one processing module.
  • the above integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of the module in the embodiment of the present application is schematic, and is only a logical function division, and the actual implementation may have another division manner.
  • FIG. 8 is a schematic diagram of a possible configuration of the sending device involved in the foregoing embodiment.
  • the sending device may include: a sending unit 201, Measurement unit 202.
  • the sending unit 201 is configured to support the transmitting device to perform the method for transmitting the wake-up signal shown in FIG. 7. Steps 101, 103, and 104.
  • the measuring unit 202 is configured to support the transmitting device to perform step 102 in the method for transmitting the wake-up signal shown in FIG. 7.
  • the transmitting device provided by the embodiment of the present application is configured to execute the foregoing data receiving state reporting method, so that the same effect as the data receiving state reporting method described above can be achieved.
  • FIG. 9 shows another possible composition diagram of the transmitting apparatus involved in the above embodiment.
  • the transmitting device includes a processing module 301 and a communication module 302.
  • the processing module 301 is configured to control and manage the actions of the server.
  • the processing module 301 is configured to support the sending device to perform step 102 in FIG. 7, and/or other processes for the techniques described herein.
  • Communication module 302 is used to support communication between the transmitting device and other network entities, such as with the STA shown in FIG.
  • the sending device may further include a storage module 303 for storing program code and data of the server.
  • the processing module 301 can be a processor or a controller. It is possible to implement or carry out the various illustrative logical blocks, modules and circuits described in connection with the present disclosure.
  • the processor can also be a combination of computing functions, for example, including one or more microprocessor combinations, a combination of a DSP and a microprocessor, and the like.
  • the communication module 302 can be a transceiver, a transceiver circuit, a communication interface, or the like.
  • the storage module 303 can be a memory.
  • the processing module 301 is a processor
  • the communication module 302 is a communication interface
  • the storage module 303 is a memory
  • the sending device involved in the embodiment of the present application may be the transmitting device shown in FIG. 6.
  • the disclosed system, apparatus, and method may be implemented in other manners.
  • the device embodiments described above are merely illustrative.
  • the division of the modules or units is only a logical function division.
  • there may be another division manner for example, multiple units or components may be used. Combinations can be integrated into another system, or some features can be ignored or not executed.
  • the mutual coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection through some interface, device or unit, and may be in an electrical, mechanical or other form.
  • the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, may be located in one place, or may be distributed to multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment.
  • each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.
  • the above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.
  • the integrated unit if implemented in the form of a software functional unit and sold or used as a standalone product, may be stored in a computer readable storage medium.
  • a computer readable storage medium A number of instructions are included to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to perform all or part of the steps of the methods described in various embodiments of the present application.
  • the foregoing storage medium includes: a flash memory, a mobile hard disk, a read only memory, a random access memory, a magnetic disk, or an optical disk, and the like, which can store program codes.

Abstract

本发明实施例提供一种唤醒信号的传输方法及发送装置，涉及通信领域。该方法包括：发送设备利用第一时间窗向接收设备发送唤醒信号中的短训练域序列；所述唤醒信号用于触发所述接收设备与所述发送设备进行数据传输，所述短训练域序列用于实现所述发送设备与所述接收设备之间的同步；所述发送设备在利用所述第一时间窗之后的第二时间窗进行信道测量；若所述信道测量的结果为信道被占用，所述发送设备停止发送所述唤醒信号。

Description

一种唤醒信号的传输方法及发送设备
本申请要求于2017年3月21日提交中国专利局、申请号为201710171120.1、发明名称为“一种WUR帧冲突检测和避免的方法和设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及通信领域，尤其涉及一种唤醒信号的传输方法及发送设备。
背景技术
WiFi IoT(Wireless Fidelity Internet of Things，无线保真物联网)系统中，STA(station，站点)配置了传统WiFi模块(即802.11标准射频模块)以及LP-WUR(Lower Power-Wake-up Radio，低功耗唤醒射频)模块。通常，STA的WiFi模块处于关闭状态，而LP-WUP模块持续处于接收状态，或间歇性处于接收状态。当LP-WUR模块在接收状态中收到来自AP(Access Point，接入点)的唤醒信号(Wake-up Packet)时，LP-WUR模块向WiFi模块发送激活信号，以激活处于关闭状态的WiFi模块。WiFi模块激活后，与AP进行数据通信。
唤醒信号包括前导序列和载荷(WUR Payload)序列，其中，前导序列包括旧有短训练域(Legacy-Short Training Field，L-STF)序列、旧有长训练域(Legacy-Long Training Field，L-LTF)序列、旧有信令域(Legacy-Signal，L-SIG)序列。
如果邻近的AP1、AP2同时完成退避，同时发射信号。AP1向STA1发射的传统的WiFi帧，与AP2向STA2发射的唤醒信号之间会互相干扰。目前，AP2将前导序列和载荷序列分时发射，先发射前导序列，然后插入一段静默期(Silent Period)进行净信道估计(Clear Channel Assessment，CCA)检测。如果AP2进行CCA检测的结果是信道状态为忙(BUSY)，AP2则不再发射后续的WUR Payload序列，如果AP2进行CCA检测的结果是信道状态为空闲(Idle)，则继续发射后续的WUR Payload序列。
如果邻近的AP确实存在发射冲突(即如果邻近的AP1、AP2同时完成退避，同时发射信号)，虽然AP2在Silent Period进行CCA的结果为Busy之后，并且AP2不再发射后续的WUR Payload，但是已经发射的前导序列已经对WiFi帧产生了干扰，STA1会接收到AP1发射的前导序列中的L-SIG，但是AP1发射的前导序列中的L-SIG与AP2发射的WiFi帧中的L-SIG携带的信息通常是不同的，导致WiFi帧的L-SIG就会被干扰，STA1根据L-SIG解不出正确的信息，如此，就造成了信道资源的浪费。
发明内容
本发明的实施例提供一种唤醒信号的传输方法及发送设备，当邻近设备存在发射冲突，避免某些设备发送的唤醒信号对其他设备发送的WiFi信号造成干扰，从而避免由于发射冲突造成的信道浪费，提高了信道的利用率。
为达到上述目的，本发明的实施例采用如下技术方案：
第一方面，公开了一种唤醒信号的传输方法，包括：
发送设备利用第一时间窗向接收设备发送唤醒信号中的短训练域序列，其中，该唤醒信号用于触发接收设备与发送设备进行数据传输，示例的，接收设备的LP-WUR模块接收到该唤醒信号后可以向接收设备的WiFi模块发送激活信号，触发接收设备与发送设备进行数据传输。另外，短训练域序列用于实现发送设备与接收设备之间的同步，如：时钟同步。随后，发送设备在第一时间窗之后的第二时间窗内进行信道测量。进一步，若信道测量的结果为信道被占用，发送设备停止发送唤醒信。
在发送唤醒信号时，先发送同步序列(L-STF)占有信道，随后在第二时间窗内进行CCA检测是否存在发射冲突，如果CCA检测结果为信道信道被占用，则表明该发送设备与其他的发送设备之间存在发射冲突，则停止发射唤醒信号。由于唤醒信号的L-STF与WiFi信号的L-STF相同，先发送的L-STF不会对WiFi信号造成干扰，WiFi信号仍可以被接收设备成功接收，这样就有效避免了冲突发生时信道的浪费，提高了系统的信道利用效率。
结合第一方面，在第一方面的第一种可能的实现方式中，上述方法还包括：若信道测量的结果为信道空闲，发送设备在第二时间窗之后发送唤醒信号。
如果信道测量的结果为信道空闲，表明该发送设备与其他发送设备不存在发射冲突，那么该发送设备发射的唤醒信号不会对邻近其他设备发送的WiFi信号造成干扰，有效利用了信道。
结合第一方面以及以上第一方面任意一种可能的实现方式，在第一方面的第二种可能的实现方式中，唤醒信号包括前导序列和载荷序列；其中，前导序列包括短训练域序列、长训练域序列以及信令域序列；载荷序列包括唤醒信号的帧头以及唤醒信号的数据。
结合第一方面以及以上第一方面任意一种可能的实现方式，在第一方面的第二种可能的实现方式中，发送设备在第二时间窗之后发送唤醒信号具体包括：发送设备在第二时间窗之后，按照时序的先后顺序依次发送短训练域序列、长训练域序列、信令域序列以及载荷序列。
这里发送的短训练域序列包括10个0.8us的重复波形，在第一时间窗内发射的短训练域序列可以与发送设备在此时发射的短训练域序列相同，也可以不同，如：在第一时间窗内发射的短训练域序列包括5个0.8us的重复波形。
结合第一方面以及以上第一方面任意一种可能的实现方式，在第一方面的第二种可能的实现方式中，第一时间窗的长度大于等于进行信道测量的所需的最短时长，第二时间窗的长度小于点帧间间隔PIFS。
当第一时间窗的长度大于或等于进行信道测量的所需的最短时长时，该发送设备发射的短训练域序列可以被其他发送设备检测到，进而这些发送设备会进行退避，该发送设备占用了信道。另外，当第二时间窗的长度小于点帧间间隔PIFS时，这是由于如果第二时间窗的长度等于或高于PIFS时间，在不存在发射冲突的情况下，其他发送设备就不能在这PIFS时间抢占到信道并发射信号，从而不会对该发送设备后续发射的唤醒信号造成干扰。第二时间窗的长度应至少包 含一个Tx-Rx(接收-发射)转换时间、一个Rx-Tx转换时间、以及一个完整的CCA检测时间。这是因为发射L-STF之后，发送设备需要从发射状态转变成接收状态，才能进行CCA检测。另外，如果检测为Idle状态，发送设备则需要从接收状态转换回发射状态，继续唤醒信号的发射。PIFS本身大于一个Tx-Rx(接收-发射)转换时间、一个Rx-Tx转换时间、以及一个完整的CCA检测时间之和，因此，当第二时间窗小于PIFS时，可以满足对第二时间窗的上述要求。
第二方面，公开了一种发送设备，包括：
发送单元，用于利用第一时间窗向接收设备发送唤醒信号中的短训练域序列；唤醒信号用于触发接收设备与发送设备进行数据传输，短训练域序列用于实现发送设备与接收设备之间的同步；测量单元，在第二时间窗内进行信道测量；第二时间窗在第一时间窗之后；发送单元还用于，若信道测量的结果为信道被占用，则停止发送唤醒信号。
发送设备在发送唤醒信号时，先发送同步序列(L-STF)占有信道，随后在第二时间窗内进行CCA检测是否存在发射冲突，如果CCA检测结果为信道信道被占用，则表明该发送设备与其他的发送设备之间存在发射冲突，则停止发射唤醒信号。由于唤醒信号的L-STF与WiFi信号的L-STF相同，先发送的L-STF不会对WiFi信号造成干扰，WiFi信号仍可以被接收设备成功接收，这样就有效避免了冲突发生时信道的浪费，提高了系统的信道利用效率。
结合第二方面，在第二方面的第一种可能的实现方式中，发送单元还用于，若信道测量的结果为信道空闲，在第二时间窗之后发送唤醒信号。
结合第二方面以及第二方面的第一种可能的实现方式，在第二方面的第二种可能的实现方式中，唤醒信号包括前导序列和载荷序列；
其中，前导序列包括短训练域序列、长训练域序列以及信令域序列；载荷序列包括唤醒信号的帧头以及唤醒信号的数据。
结合第二方面以及以上第二方面的任意一种可能的实现方式，在第二方面的第三种可能的实现方式中，发送单元具体用于，在第二时间窗之后，按照时序的先后顺序依次发送短训练域序列、长训练域序列、信令域序列以及载荷序列。
结合第二方面以及以上第二方面的任意一种可能的实现方式，在第二方面的第四种可能的实现方式中，第一时间窗的长度大于等于进行信道测量的所需的最短时长，第二时间窗的长度小于点帧间间隔PIFS。
第三方面，公开了一种发送设备，包括：
发射器，用于利用第一时间窗向接收设备发送唤醒信号中的短训练域序列；唤醒信号用于触发接收设备与发送设备进行数据传输，短训练域序列用于实现发送设备与接收设备之间的同步；处理器，在第二时间窗内进行信道测量；第二时间窗在第一时间窗之后；发射器还用于，若信道测量的结果为信道被占用，停止发送唤醒信号。
发送设备在发送唤醒信号时，先发送同步序列(L-STF)占有信道，随后在第二时间窗内进行CCA检测是否存在发射冲突，如果CCA检测结果为信道 信道被占用，则表明该发送设备与其他的发送设备之间存在发射冲突，则停止发射唤醒信号。由于唤醒信号的L-STF与WiFi信号的L-STF相同，先发送的L-STF不会对WiFi信号造成干扰，WiFi信号仍可以被接收设备成功接收，这样就有效避免了冲突发生时信道的浪费，提高了系统的信道利用效率。
结合第三方面，在第三方面的第一种可能的实现方式中，发射器还用于，若信道测量的结果为信道空闲，在第二时间窗之后发送唤醒信号。
结合第三方面以及第三方面的第一种可能的实现方式，在第三方面的第二种可能的实现方式中，唤醒信号包括前导序列和载荷序列；
其中，前导序列包括短训练域序列、长训练域序列以及信令域序列；载荷序列包括唤醒信号的帧头以及唤醒信号的数据。
结合第三方面以及以上第三方面的任意一种可能的实现方式，在第三方面的第三种可能的实现方式中，发射器具体用于，在第二时间窗之后，按照时序的先后顺序依次发送短训练域序列、长训练域序列、信令域序列以及载荷序列。
结合第三方面以及以上第三方面的任意一种可能的实现方式，在第三方面的第四种可能的实现方式中，第一时间窗的长度大于等于进行信道测量的所需的最短时长，第二时间窗的长度小于点帧间间隔PIFS。
本申请实施例的第四方面，公开了一种计算机存储介质，用于存储上述设置于发送设备所用的计算机软件指令，该计算机软件指令包含用于执行上述第一方面的一种唤醒信号的传输方法所涉及的程序。
附图说明
图1为现有的WiFi IoT系统中的通信方式的示意图；
图2为唤醒信号的帧结构示意图；
图3为现有的密集分布场景示意图；
图4为现有的唤醒信号的传输方法示意图；
图5为本发明实施例提供的唤醒信号的传输方法示意图；
图6为本发明实施例提供的发送设备的结构示意图；
图7为本发明实施例提供的唤醒信号的传输方法的流程示意图；
图8为本发明实施例提供的发送设备的另一结构示意图；
图9为本发明实施例提供的发送设备的另一结构示意图。
具体实施方式
IEEE802.11标准制定了基于2.4G/5GHz频段的WiFi IoT标准，其基本特征是低功耗和长距离。为了实现低功耗，在接收设备中配置了传统WiFi模块和LP-WUR模块。如图1所示，AP为发送设备，STA为接收设备，STA的WiFi模块处于关闭状态，而LP-WUP模块持续处于接收状态，或间歇性处于接收状态。当LP-WUR模块在接收状态中收到来自AP(Access Point，接入点)的唤醒信号(Wake-up Packet)时，LP-WUR模块向WiFi模块发送激活信号，以激活处于关闭状态的WiFi模块。WiFi模块激活后，与AP进行数据通信。
另外，AP可以仅包括一个WiFi模块，并且通过WiFi模块向STA发送唤醒信号。WiFi模块通常为正交频分复用(Orthogonal Frequency Division Multiplexing，OFDM)宽带发射机，而唤醒信号为窄带信号，出于降低成本和结构简单考虑，可以利用OFDM宽带发射机产生窄带唤醒信号。另外，图1中的AP和STA都只有一个天线，这是由于WiFi模块和WUR模块使用相同频段载波(例如，2.4GHz)情况下，可共用同一天线，以节省成本和简化设备结构。但当WiFi模块和WUR模块使用不同频段载波时，两者应配置不同天线。例如，802.11主模块使用5GHz频段，WUR模块使用2.4GHz频段，此时两者应对应不同天线。
图2为唤醒信号的帧结构示意图。参考图2，唤醒信号包括前导序列和载荷(WUR Payload)序列。前导序列与传统WiFi帧的前导(802.11legacy preamble)相同，包括L-STF(短训练域)序列、L-LTF(长训练域)序列以及L-SIG(信令域)序列，使得设备可据该前导序列判断当前接收的数据包为WiFi包，从而选择相应的CCA判决阈值。其中，短同步序列(即所述L-STF序列)，用于实现信号检测、自动增益控制(Automatic Gain Control，AGC)、分集选择、粗频率频偏估计以及时间同步；长同步序列(即所述L-LTF序列)，用来进行信道和细频偏估计。
唤醒包的载荷(WUR Payload)序列采用易于解调的调制方式，如二进制启闭键控(On-Off Keying(OOK)调制，如二进制卷积码(Amplitude Shift Keying，ASK)。唤醒包的载荷序列可以在较窄的带宽上传输，例如2MHz信道、4MHz信道、5MHz信道等，使得接收端的能耗更小。参考图2，WUR Payload包括Wake-up preamble(帧头)和MAC部分(即数据部分)。其中，Wake-up preamble类似WiFi帧的前导部分，用于实现同步、自动增益控制(Automatic Gain Control，AGC)、信道估计、指示控制信息等。MAC部分类似传统WiFi帧的MAC部分。进一步，MAC部分包括MAC头(Header)、帧体(Frame Body)、帧校验序列(Frame Check Sequence，FCS)。MAC部分可能采用重复码、扩频码、曼彻斯特码等方式进行简单信道编码，以提高可靠性，但也有可能不使用信道编码。由于唤醒包功能比较简单，帧体部分也可能不存在。
需要说明的是，Wake-up preamble中包括一串特定序列，STA的WUR可以不接收唤醒信号前面的Legacy preamble部分，而是直接检测该特定序列，从而识别唤醒信号。当STA的WUR接收到唤醒信号，且从唤醒信号的MAC部分检测到自己的标识(如：单播/多播/广播地址)，则向STA的WiFi模块发送激活信号。Wake-up preamble中还可能包括唤醒信令(Wakeup-Signal，WU-SIG)域，用于指示MAC部分的长度以及所使用的调制编码方式等。
目前的发送设备一般采用载波侦听的接入方式，当发送设备侦听到信道为空闲(idle)时，进行随机退避，如果退避完成信道仍然为空闲(idle)状态，发送设备才会发送信号；当侦听到信道为忙(Busy)时，设备挂起，直到再次侦听到信道为Idle时，设备继续执行随机退避过程。当至少两个设备同时完成退 避过程，就会同时发送信号，这时就会产生发射冲突。由于唤醒信号采用较低的调制方式并且利用窄带传输，信号传输时间一般较长，例如0.5ms。因此，当唤醒信号和WiFi信号产生冲突时，冲突的相关设备在这段时间内都不能成功发送信号，也就是说这段时间被浪费掉了，这将严重降低信道的利用效率。
图3所示的密集分布场景下，STA1、STA2、STA3相邻分布，AP1、AP2、AP3相邻分布。通常，AP1和STA1会受到AP2发射信号的干扰，STA2和AP2会受到AP1以及AP3发射信号的干扰，STA3和AP3会受到AP2发射信号的干扰。当AP2和AP1同时完成退避过程，AP2向STA2发送唤醒信号，同时，AP1向STA1发送WIFI信号，此时就会产生发射冲突。由于AP2和AP1发射的信号相互干扰，此时STA2和STA1均不能成功接收信号，造成这段时间内信道的浪费，信道的利用效率下降。
为了避免信道资源的浪费，在上述场景中，AP2在完成退避后，可以将一个完整的唤醒帧(即上述唤醒信号)在时间上分成两部分先后发射，并在两部分发射中间插入一段静默期(Silent Period)以便进行CCA检测。示例的，参考图4，AP2先发送前导序列，在发射完前导序列之后，在Silent Period(即静默期)中进行CCA检测，如果CCA检测到信道为BUSY(即信道被占用)，AP2则停止后续的载荷序列的发射；如果设备检测到信道为Idle(即信道空闲)，则继续发送唤醒信号，如：唤醒信号的载荷序列。
如果CCA检测的结果为信道忙，则表明AP2与AP1确实存在发射冲突。虽然Silent Period期间的CCA检测为Busy之后，AP2不再发射后续的WUR Payload(即本发明实施例所述的载荷序列)，但是已经发射的前导序列已经对AP1发射的WiFi信号产生了干扰。具体地，AP1发射的WiFi信号中的L-SIG和AP2发射的前导序列中的L-SIG携带的信息通常是不同的，两者在物理层发生叠加之后，WiFi信号的L-SIG就会被干扰，导致STA1解不出正确的信息。另外，其他STA(如：STA3)接收到AP2发射的前导序列后，会根据其中的L-SIG设置自己的网络分配矢量(Network allocation vector，NAV)。NAV本身是一个定时器，STA3在NAV对应的时间段内不进行数据发射。也就是说，虽然AP2后续不再发射载荷序列，但是NAV不能得到释放，导致信道仍然被浪费掉了。
具体地，以图3所示场景为例，当AP1和AP2同时完成退避过程，AP1发送WiFi信号给STA1，AP2发送唤醒信号给STA2。当AP2发送前导序列之后，进入静默期进行CCA检测，检测到CCA＝Busy，表示在发送唤醒信号的同时有WiFi信号在发送，AP2则进行退避，不再发送WUR Payload，但是已经发送的前导序列已经干扰了AP1发送的WiFi信号，STA1接收到的信号是AP2发射的前导序列和AP1发射的WiFi信号叠加之后的信号，L-SIG部分受到污染，虽然后续不再受到WUR Payload的干扰，但是由于L-SIG被干扰，STA1无法正确解出AP1发送的802.11Legacy Preamble，STA1不能从中得到正确的参数，也就无法正确解出AP1发射的信号，所以AP1和AP2发射信号失败，也就是说这段时间被浪费掉了。
其次，AP2邻近的AP3已经收到了AP2发射的前导序列，并且能够正确解出其中的L-SIG，AP3会根据L-SIG中的信息设置自己的NAV，暂停退避过程，直到NAV结束。AP2放弃WUR Payload的发射后，并没有通知AP3进行释放NAV的操作，导致AP3仍然以为信道在忙。也就是说，AP3仍然不能发射信号，信道资源被浪费掉了。
参考图5，本发明实施例的原理在于：在发送唤醒信号时，先发送短训练域序列(L-STF)占有信道，随后再进行CCA(即信道测量)检测是否存在发射冲突。如果信道测量的结果为busy(即信道被占用)，说明存在发射冲突则停止发射唤醒信号。由于唤醒信号的L-STF与WiFi信号的L-STF相同，先发送的L-STF不会对WiFi信号造成干扰，WiFi信号仍可以被接收设备成功接收，这样就有效避免了冲突发生时信道的浪费，提高了系统的信道利用效率。另外，如果信道测量的结果为idle(即信道空闲)，说明不存在发射冲突，则发射唤醒信号。
在具体的实现中，图6为本发明实施例提供的一种发送设备的组成示意图，该发送用户设备可以是图1所示系统中的AP。如图6所示，该发送用户设备可以包括至少一个处理器11，存储器12、通信接口13、通信总线14。
下面结合图6对该发送设备的各个构成部件进行具体的介绍：
处理器11是发送设备的控制中心，可以是一个处理器，也可以是多个处理元件的统称。例如，处理器11是一个中央处理器(central processing unit，CPU)，也可以是特定集成电路(Application Specific Integrated Circuit，ASIC)，或者是被配置成实施本发明实施例的一个或多个集成电路，例如：一个或多个微处理器(digital signal processor，DSP)，或，一个或者多个现场可编程门阵列(Field Programmable Gate Array，FPGA)。
其中，处理器11可以通过运行或执行存储在存储器12内的软件程序，以及调用存储在存储器12内的数据，执行发送设备的各种功能。
在具体的实现中，作为一种实施例，处理器11可以包括一个或多个CPU，例如图6中所示的CPU0和CPU1。
在具体实现中，作为一种实施例，发送设备可以包括多个处理器，例如图6中所示的处理器11和处理器15。这些处理器中的每一个可以是一个单核处理器(single-CPU)，也可以是一个多核处理器(multi-CPU)。这里的处理器可以指一个或多个设备、电路、和/或用于处理数据(例如计算机程序指令)的处理核。
存储器12可以是只读存储器(read-only memory，ROM)或可存储静态信息和指令的其他类型的静态存储设备，随机存取存储器(random access memory，RAM)或者可存储信息和指令的其他类型的动态存储设备，也可以是电可擦可编程只读存储器(Electrically Erasable Programmable Read-Only Memory，EEPROM)、只读光盘(Compact Disc Read-Only Memory，CD-ROM)或其他光盘存储、光碟存储(包括压缩光碟、激光碟、光碟、数字通用光碟、蓝光光碟等)、磁盘存储介质或者其他磁存储设备、或者能够用于携带或存储 具有指令或数据结构形式的期望的程序代码并能够由计算机存取的任何其他介质，但不限于此。存储器12可以是独立存在，通过通信总线14与处理器11相连接。存储器12也可以和处理器11集成在一起。
其中，所述存储器12用于存储执行本发明方案的软件程序，并由处理器11来控制执行。
通信接口13，使用任何收发器一类的装置，用于与其他设备或通信网络通信，如以太网，无线接入网(radio access network，RAN)，无线局域网(Wireless Local Area Networks，WLAN)等。通信接口13可以包括接收单元实现接收功能，以及发送单元实现发送功能。
通信总线14，可以是工业标准体系结构(Industry Standard Architecture，ISA)总线、外部设备互连(Peripheral Component，PCI)总线或扩展工业标准体系结构(Extended Industry Standard Architecture，EISA)总线等。该总线可以分为地址总线、数据总线、控制总线等。为便于表示，图6中仅用一条粗线表示，但并不表示仅有一根总线或一种类型的总线。
图6中示出的设备结构并不构成对发送设备的限定，可以包括比图示更多或更少的部件，或者组合某些部件，或者不同的部件布置。处理器11，存储器12、通信接口13、通信总线14可以集成在发送设备的WiFi模块中。
本发明实施例提供一种唤醒信号的传输方法，如图7所示，所述方法包括以下步骤：
101、发送设备利用第一时间窗向接收设备发送唤醒信号中的短训练域序列。
其中，所述唤醒信号用于触发所述接收设备与所述发送设备进行数据传输，所述同步序列用于实现所述发送设备与所述接收设备之间的同步，如时钟同步、频率同步等，可以是L-STF。另外，所述第一时间窗的长度大于或等于发射L-STF所需的时间长度。
唤醒信号的帧结构如图2所示，具体包括前导序列和载荷序列。前导序列包括L-STF序列、L-LTF序列以及L-SIG序列。在本发明实施例中，发送设备首先发送是L-STF序列，随后在第二时间窗内进行CCA，在第二时间窗之后根据CCA的结果发送唤醒信号。
需要说明的是，唤醒信号的前导序列中包括L-STF、L-LTF、L-SIG三部分，只能发射L-STF，不能发射L-LTF以及L-SIG。这是因为L-LTF的作用是用来进行信道估计，当产生冲突时，L-LTF受到干扰，影响信道估计的准确性。
其次，第一时间窗的长度不能小于进行信道测量所需的最短时长，这是由于，第一时间窗的长度超过执行CCA(即进行信道测量)所要求的时间(如：4us)，当发送设备在第一时间窗发射信号时，其他设备才可以检测到有信号在发射，从而进行退避也就说达到了占用信道的目的。
具体实现中，L-STF包含10个完全相同的持续时间为0.8us的重复波形，即L-STF持续时间为8us。考虑到CCA检测的时间需要4us，因此，利用第 一时间窗发射L-STF时可以适当缩短L-STF。示例的，第一时间窗的长度为4us，也就是5*0.8，因此第一时间窗可以发射5个0.8us的重复波形。
另外，之所以仅发射L-STF，是因为唤醒信号的L-STF和WiFi帧的L-STF内容完全相同，持续时间相同(均为8us)，L-STF不含有直接或隐含的Duration信息，成功接收到L-STF的STA不能根据解出来的信息设置NAV。因此，当冲突发生时，发送设备不再发射唤醒信号的后续部分时，已经发射的L-STF不会对这些STA(即接收到发送设备发射的L-STF的STA)的竞争信道产生影响，也就是说它们仍可以抢占信道，并发射信号。
102、发送设备利用第一时间窗之后的第二时间窗进行信道测量。
具体实现中，上述第二时间窗在第一时间窗之后，进一步，第一时间窗的结束时刻可以与所述第二时间窗的开始时刻相同。也就是说，发送设备在发送完上述短训练域序列之后的第二时间窗内执行CCA。
需要说明的是，上述第二时间窗的长度(即持续时间)需要满足的条件包括以下两点：
(1)应该小于PIFS时间。这是由于如果第二时间窗的长度等于或高于PIFS时间，在不存在发射冲突的情况下，其他发送设备可能在这PIFS时间抢占到信道并发射信号，从而对后续发射的唤醒信号造成干扰。
(2)第二时间窗的长度应至少包含一个Tx-Rx(接收-发射)转换时间、一个Rx-Tx转换时间、以及一个完整的CCA检测时间。这是因为发射L-STF之后，发送设备需要从发射状态转变成接收状态，才能进行CCA检测。另外，如果检测为Idle状态，发送设备则需要从接收状态转换回发射状态，继续唤醒信号的发射。
根据现有IEEE 802.11标准的规定，PIFS＝SIFS+Slot；其中，SIFS＝RxRFDelay+RxPLCPDelay+MACProcessingDelay+RxTxTurnaroundTime；Slot＝A CCTime+RxTxTurnaroundTime+AirPropagationTime+MACProcessingDelay。
需要说明的是，PIFS是点帧间间隔[point(coordination function)interframe space]；SIFS是短帧间间隔(short interframe space)；Slot是一个时隙；RxRFdelay是发射射频延迟时间；RxPLCPDelay是发射PLCP延迟时间；MACProcessingDelay是Mac层处理延迟时间；RxTxTurnaroundTime是接收发射转换时间；AirPropagationTime是空中传播时间。
由于RxTxTurnaroundTime与TxRxTurnaroundTime相等，可以得出PIFS>RxTx TurnaroundTime+TxRxTurnaroundTime+aCCA，因此PIFS本身就满足上述条件(2)，进一步，当此第二时间窗的长度小于PIFS时间内，可以满足上述两点要求。
因此，在一些实施例中，第二时间窗的长度小于PIFS。
103、若所述信道测量的结果为信道被占用，所述发送设备则不发送所述唤醒信号。
需要说明的是，“不发送唤醒信号”即本发明实施例所述的“停止发送唤醒信号”也就是说，如果发送设备在上述第二时间窗内执行CCA的结果为busy时，发送设备不会向接收设备发射唤醒信号。
需要说明的是，在第二时间窗内执行CCA结果为Busy时，说明发送设 备与其他发送设备存在发射冲突。示例的，其他发送设备发送的WiFi信号的L-STF和该发送设备已经发射的L-STF产生叠加。因为L-STF主要的作用就是同步，WiFi信号的L-STF与已经发射同步序列完全相同，在多径干扰的范围内，接收WiFi信号的接收设备仍然可以正确解出L-STF信号，所以即使WiFi帧和WUR帧产生冲突，已经发射的L-STF对WiFi帧的同步影响也不大，接收设备仍然可能正确解出WiFi信号。也就是说，没有因为发射冲突造成信道资源的浪费。
104、若所述信道测量的结果为信道空闲，所述发送设备在第二时间窗之后发送所述唤醒信号。
也就是说，如果发送设备在上述时间窗内执行CCA的结果为idle，则发射所述唤醒信号。
具体实现中，发送设备按照时序的先后顺序依次发送唤醒信号的L-STF、L-LTF序列、L-SIG序列以及唤醒信号的载荷序列。
另外，由于发送设备在步骤101中利用第一时间窗发射短训练域序列达到了占用信道的目的。那么，当在预设窗口执行CCA的结果为Idle时，发送设备仍占有信道，可以发射唤醒信号。
本发明实施例提供的唤醒信号的传输方法中，发送设备在发送唤醒信号时，先发送唤醒信号中的L-STF占有信道，在发送完L-STF的之后第二时间窗内进行CCA检测是否存在发射冲突，如果存在发射冲突则停止发射唤醒信号的其他部分。由于唤醒信号的L-STF与WiFi信号的L-STF相同，先发送的L-STF不会对WiFi信号造成干扰，WiFi信号仍可以被接收设备成功接收，这样就有效避免了冲突发生时信道的浪费，提高了系统的信道利用效率。
上述主要从各个网元之间交互的角度对本申请实施例提供的方案进行了介绍。可以理解的是，本发明实施例中涉及的发送设备为了实现上述功能，其包含了执行各个功能相应的硬件结构和/或软件模块。本领域技术人员应该很容易意识到，结合本文中所公开的实施例描述的各示例的算法步骤，本申请能够以硬件或硬件和计算机软件的结合形式来实现。某个功能究竟以硬件还是计算机软件驱动硬件的方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本申请的范围。
本申请实施例可以根据上述方法示例对发送设备进行功能模块的划分，例如，可以对应各个功能划分各个功能模块，也可以将两个或两个以上的功能集成在一个处理模块中。上述集成的模块既可以采用硬件的形式实现，也可以采用软件功能模块的形式实现。需要说明的是，本申请实施例中对模块的划分是示意性的，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式。
在采用对应各个功能划分各个功能模块的情况下，图8示出了上述实施例中涉及的发送设备的一种可能的组成示意图，如图8所示，该发送设备可以包括：发送单元201、测量单元202。
其中，发送单元201，用于支持发送设备执行图7所示的唤醒信号的传输方法中 的步骤101、103以及104。
测量单元202，用于支持发送设备执行图7所示的唤醒信号的传输方法中的步骤102。
需要说明的是，上述方法实施例涉及的各步骤的所有相关内容均可以援引到对应功能模块的功能描述，在此不再赘述。
本申请实施例提供的发送设备，用于执行上述数据接收状态报告方法，因此可以达到与上述数据接收状态报告方法相同的效果。
在采用集成的单元的情况下，图9示出了上述实施例中所涉及的发送设备的另一种可能的组成示意图。如图9所示，该发送设备包括：处理模块301和通信模块302。
处理模块301用于对服务器的动作进行控制管理，例如，处理模块301用于支持发送设备执行图7中的步骤102、和/或用于本文所描述的技术的其它过程。通信模块302用于支持发送设备与其他网络实体的通信，例如与图1示出的STA之间的通信。发送设备还可以包括存储模块303，用于存储服务器的程序代码和数据。
其中，处理模块301可以是处理器或控制器。其可以实现或执行结合本申请公开内容所描述的各种示例性的逻辑方框，模块和电路。处理器也可以是实现计算功能的组合，例如包含一个或多个微处理器组合，DSP和微处理器的组合等等。通信模块302可以是收发器、收发电路或通信接口等。存储模块303可以是存储器。
当处理模块301为处理器，通信模块302为通信接口，存储模块303为存储器时，本申请实施例所涉及的发送设备可以为图6所示的发送设备。
通过以上的实施方式的描述，所属领域的技术人员可以清楚地了解到，为描述的方便和简洁，仅以上述各功能模块的划分进行举例说明，实际应用中，可以根据需要而将上述功能分配由不同的功能模块完成，即将装置的内部结构划分成不同的功能模块，以完成以上描述的全部或者部分功能。上述描述的系统，装置和单元的具体工作过程，可以参考前述方法实施例中的对应过程，在此不再赘述。
在本申请所提供的几个实施例中，应该理解到，所揭露的系统，装置和方法，可以通过其它的方式实现。例如，以上所描述的装置实施例仅仅是示意性的，例如，所述模块或单元的划分，仅仅为一种逻辑功能划分，实际实现时可以有另外的划分方式，例如多个单元或组件可以结合或者可以集成到另一个系统，或一些特征可以忽略，或不执行。另一点，所显示或讨论的相互之间的耦合或直接耦合或通信连接可以是通过一些接口，装置或单元的间接耦合或通信连接，可以是电性，机械或其它的形式。
所述作为分离部件说明的单元可以是或者也可以不是物理上分开的，作为单元显示的部件可以是或者也可以不是物理单元，即可以位于一个地方，或者也可以分布到多个网络单元上。可以根据实际的需要选择其中的部分或者全部单元来实现本实施例方案的目的。
另外，在本申请各个实施例中的各功能单元可以集成在一个处理单元中，也可以是各个单元单独物理存在，也可以两个或两个以上单元集成在一个单元中。上述集成的单元既可以采用硬件的形式实现，也可以采用软件功能单元的形式实现。
所述集成的单元如果以软件功能单元的形式实现并作为独立的产品销售或使用时，可以存储在一个计算机可读取存储介质中。基于这样的理解，本申请的技术方案本质上或者说对现有技术做出贡献的部分或者该技术方案的全部或部分可以以软件产品的形式体现出来，该计算机软件产品存储在一个存储介质中，包括若干指令用以使得一台计算机设备(可以是个人计算机，服务器，或者网络设备等)或处理器执行本申请各个实施例所述方法的全部或部分步骤。而前述的存储介质包括：快闪存储器、移动硬盘、只读存储器、随机存取存储器、磁碟或者光盘等各种可以存储程序代码的介质。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何在本申请揭露的技术范围内的变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以所述权利要求的保护范围为准。

Claims (15)

  1. 一种唤醒信号的传输方法，其特征在于，包括：
    发送设备利用第一时间窗向接收设备发送唤醒信号中的短训练域序列；所述唤醒信号用于触发所述接收设备与所述发送设备进行数据传输，所述短训练域序列用于实现所述发送设备与所述接收设备之间的同步；
    所述发送设备在利用所述第一时间窗之后的第二时间窗进行信道测量；
    若所述信道测量的结果为信道被占用，所述发送设备停止发送所述唤醒信号。
  2. 根据权利要求1所述的方法，其特征在于，所述方法还包括：
    若所述信道测量的结果为信道空闲，所述发送设备在所述第二时间窗之后发送所述唤醒信号。
  3. 根据权利要求2所述的方法，其特征在于，所述唤醒信号包括前导序列和载荷序列；
    其中，所述前导序列包括所述短训练域序列、长训练域序列以及信令域序列；所述载荷序列包括所述唤醒信号的帧头以及所述唤醒信号的数据。
  4. 根据权利要求3所述的方法，其特征在于，所述发送设备在所述第二时间窗之后发送所述唤醒信号具体包括：
    所述发送设备在所述第二时间窗之后，按照时序的先后顺序依次发送所述短训练域序列、所述长训练域序列、所述信令域序列以及所述载荷序列。
  5. 根据权利要求1-4任一项所述的方法，其特征在于，所述第一时间窗的长度大于等于进行信道测量的所需的最短时长，所述第二时间窗的长度小于点帧间间隔PIFS。
  6. 一种发送设备，其特征在于,包括：
    发送单元，用于利用第一时间窗向接收设备发送唤醒信号中的短训练域序列；所述唤醒信号用于触发所述接收设备与所述发送设备进行数据传输，所述短训练域序列用于实现所述发送设备与所述接收设备之间的同步；
    测量单元，在利用所述第一时间窗之后的第二时间窗进行信道测量；
    所述发送单元还用于，若所述信道测量的结果为信道被占用，则停止发送所述唤醒信号。
  7. 根据权利要求6所述的发送设备，其特征在于，所述发送单元还用于，若所述信道测量的结果为信道空闲，在所述第二时间窗之后发送所述唤醒信号。
  8. 根据权利要求7所述的发送设备，其特征在于，所述唤醒信号包括前导序列和载荷序列；
    其中，所述前导序列包括所述短训练域序列、长训练域序列以及信令域序列；所述载荷序列包括所述唤醒信号的帧头以及所述唤醒信号的数据。
  9. 根据权利要求8所述的发送设备，其特征在于，所述发送单元具体用于，在所述第二时间窗之后，按照时序的先后顺序依次发送所述短训练域序列、所述长训练域序列、所述信令域序列以及所述载荷序列。
  10. 根据权利要求6-9任一项所述的发送设备，其特征在于，所述第一时间窗的长度大于等于进行信道测量的所需的最短时长，所述第二时间窗的长度小于点帧间间隔PIFS。
  11. 一种发送设备，其特征在于，包括：
    发射器，用于利用第一时间窗向接收设备发送唤醒信号中的短训练域序列；所述唤醒信号用于触发所述接收设备与所述发送设备进行数据传输，所述短训练域序列用于实现所述发送设备与所述接收设备之间的同步；
    处理器，在利用所述第一时间窗之后的第二时间窗进行信道测量；
    所述发射器还用于，若所述信道测量的结果为信道被占用，停止发送所述唤醒信号。
  12. 根据权利要求11所述的发送设备，其特征在于，所述发射器还用于，若所述信道测量的结果为信道空闲，在所述第二时间窗之后发送所述唤醒信号。
  13. 根据权利要求12所述的发送设备，其特征在于，所述唤醒信号包括前导序列和载荷序列；
    其中，所述前导序列包括所述短训练域序列、长训练域序列以及信令域序列；所述载荷序列包括所述唤醒信号的帧头以及所述唤醒信号的数据。
  14. 根据权利要求13所述的发送设备，其特征在于，所述发射器具体用于，在所述第二时间窗之后，按照时序的先后顺序依次发送所述短训练域序列、所述长训练域序列、所述信令域序列以及所述载荷序列。
  15. 根据权利要求11-14任一项所述的发送设备，其特征在于，所述第一时间窗的长度大于等于进行信道测量的所需的最短时长，所述第二时间窗的长度小于点帧间间隔PIFS。
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