Open-loop wake-up radio based on transmitter fingerprint

Abstract

To provide a device and method capable of receiving an open-loop wake-up radio based on a fingerprinting feature of a transmitter.SOLUTION: The IoT device (120) includes a first radio (126) and a memory device (227) accessible to the first radio. The memory device stores a fingerprinting feature (229) for a particular transmitter device. The first radio extracts a fingerprinting characteristic of the first received wireless signal, determines that the extracted characteristic matches a fingerprinting characteristic stored in a storage device, and in response to determining that the extracted characteristic matches the characteristic stored in the storage device, causes the second radio (122) to transition from the low power state to a higher power operating state to continue receiving the input signal.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] One issue in wireless networks that include battery - powered devices is battery life. One type of wireless device is an IoT (Internet - of - Things) device. IoT devices often have sensors that can be used to monitor environmental conditions (e.g., temperature), the operating state of a machine, or other types of conditions. IoT devices are generally “headless,” which means they do not have direct user input / output capabilities (e.g., no keyboard, no display, etc.). IoT devices are mostly battery - powered, installed within an environment or machine, and may not be directly accessible by a user. Many application examples for the use of IoT devices benefit from the battery of the IoT device lasting for a long time (e.g., several years).

Summary of the Invention

[0002] In at least one example, a device includes a first wireless and a memory device accessible by the first wireless. The memory device is configured to store characteristics for a particular transmitter device. A second wireless and a processor are also included. The processor is coupled to the first and second wireless. The first wireless extracts the characteristics of a first received wireless signal, determines that the extracted characteristics match the characteristics stored in the storage device, and in response to the determination that the extracted characteristics match the characteristics stored in the storage device, is configured to cause the second wireless to transition from a low - power state to an operation in a higher - power state.

[0003] For a detailed description of various examples, reference is now made to the accompanying drawings.

Brief Description of the Drawings

[0004] [Figure 1] Illustrates a wireless network including IoT devices in some examples.

[0005] [Figure 2] This document demonstrates an example implementation of an IoT device with wake-up wireless capabilities.

[0006] [Figure 3] This document provides an example of a method for IoT devices to verify access points based on features extracted from wireless signals. [Modes for carrying out the invention]

[0007] Some battery-powered wireless devices include a "prime" radio and a "wake-up" radio. The primary radio is used to transmit and / or receive data during the device's runtime operation. The primary radio can enter a low-power state (e.g., sleep, hibernation, etc.) during periods of non-use. The wake-up radio receives a wireless signal from a transmitter in the wireless network to determine when to wake up the primary radio. The wake-up radio can operate in an "open-loop" or "closed-loop" configuration. A closed-loop wake-up radio is pre-configured, for example, to recognize a specific sequence of symbols from the transmitter, or to negotiate with the transmitter about a transmitter-specific sequence of symbols. The closed-loop wake-up radio and transmitter may follow a specific wireless protocol for determining and / or negotiating the wake-up signal. Negotiation of the wake-up signal is additional to data and message signaling.

[0008] Wireless devices operate according to applicable standard protocols (e.g., IEEE 802.11, Bluetooth Low Energy, etc.), but a wireless transmitter within a given wireless network may be distinguished from other wireless transmitters due to imperfections in the transmitter's analog components. Such imperfections may stem from randomness introduced during the manufacturing of the transmitter's components (e.g., digital-to-analog converters, filters, frequency mixers, power amplifiers, etc.). For example, the threshold voltage or on-resistance of a metal oxide semiconductor field-effect transistor (MOSFET) may vary slightly from transistor to transistor, even if they are manufactured using the same process. Such nonlinear effects result in each transmitter having a unique "fingerprint," and thus radio frequency (RF) fingerprinting can be used by a receiver to identify a specific transmitter from among other possible transmitters, thereby activating the main radio. Activating the main radio based on the RF fingerprint is an "open-loop" process in that it does not require negotiation of a specific set of symbols between the transmitter and receiver. Therefore, a wake-up signal (generated internally within the wireless device) to activate the main radio in response to a specific transmitter configuration (extracted "features") is generated based on the transmitter's standard transmission without adding a specific / integrated wake-up signal to the normal data transmission protocol. The receiver determines the RF fingerprint of the transmission that uniquely identifies the specific transmitter it should associate with, and then, when a valid feature is detected (e.g., the extracted feature matches a feature stored in the radio's memory), uses that extracted feature to activate only the main radio. The transmission identified by the fingerprint may also include the identifier of the IoT device that the transmitter is trying to activate. By identifying the transmission by fingerprint using an IoT device-specific identifier, it is possible to activate only the main radio of a specific IoT device when a future transmission using the associated fingerprint is detected.

[0009] Several examples relate to battery-powered IoT (Internet of Things) devices, including a primary radio and a wake-up radio. The primary radio is used by the IoT device to transmit and / or receive data during runtime operation. In one example, a battery-powered IoT device may have one or more integrated or external sensors, and the IoT device's primary radio is used to transmit sensor data or event information to a wireless network. To conserve battery power, the primary radio transitions to a low-power state (e.g., sleep or hibernation). While in a low-power state, the primary radio cannot be used to transmit or receive wireless signals. Rather, the primary radio must be activated for that purpose. The wake-up radio uses RF fingerprinting (i.e., a transient "feature") to detect when a valid transmitter (e.g., an access point) is attempting to communicate with the IoT device, including the wake-up radio. In this context, a valid transmitter is one that the IoT device is paired with and should communicate with. When the wake-up radio detects a valid fingerprint, it activates the main radio (i.e., transitions from a low-power state to a higher-power state) to continue decoding the received wireless signal, thereby enabling runtime operations such as transmitting sensor data and receiving wireless communications from the transmitter. Therefore, the wake-up radio described herein activates the main radio using RF fingerprinting (e.g., comparison of a newly extracted feature with one or more features stored in memory). Since wake-up events are also generated during normal operation while receiving data (i.e., there is no dedicated wake-up signal), negotiation of a specific set of dedicated wake-up symbols between the transmitter and receiver according to a specific protocol is not required for the open-loop wake-up radio described herein.

[0010] Figure 1 shows an example of a wireless network 100 including access points 110 and 111 and IoT devices 120 and 130. Any number of IoT devices (one or more) can be included in the wireless network 100. In this example, each IoT device includes a battery, a primary radio, and a fingerprinting wake-up radio (WUR). IoT device 120 includes a battery 121, a primary radio 122, and a fingerprinting wake-up radio 126. Similarly, IoT device 130 includes a battery 131, a primary radio 132, and a fingerprinting wake-up radio 136. During periods of long-term non-use, the primary radios 122 and 132 of IoT devices 120 and 130 are turned off to conserve battery power. However, the fingerprinting wake-up radios 122 and 132 remain continuously powered on. In the configuration of Figure 1, the primary radio 132 in IoT device 130 is turned off. The wake-up radio 126 in IoT device 120 detects a valid fingerprint from the wireless signal transmitted by access point 110 (e.g., extracts features from the wireless signal and determines that these features match features stored in the radio's memory). In response to the detection of a valid fingerprint, the wake-up radio 126 wakes up the main radio 122 in IoT device 120 to complete reception on the incoming wireless signal (e.g., it is powered on or otherwise transitions to a higher-power full operating state). The wake-up radio 136 in IoT device 130 is not configured to recognize the same RF fingerprint as the wake-up radio 126 (e.g., features extracted by the wake-up radio 136 do not match any features stored in its radio's memory), and therefore the main radio 132 in IoT device 130 remains in a low-power state (e.g., sleep, hibernation, etc.). Alternatively, the wake-up radio 136 of the IoT device 130 may be configured to recognize an RF fingerprint derived from the access point 111.

[0011] Figure 2 shows additional details regarding the implementation of IoT device 120, but the same architecture may be applied to IoT device 130 and / or other IoT devices in the wireless network 100. In this example, IoT device 120 includes a battery 121, a main radio 122, a fingerprinting wake-up radio 126, a processor 210, sensors 220, and a memory device 227. The main radio 122 and the fingerprinting wake-up radio 126, as well as the sensors 220, are coupled to the processor 210. The battery 121 provides operating power to some or all of the active components in IoT device 120. In this example, one processor 210 is shown, but other implementations may include two or more processors. Similarly, two or more sensors 220 may be provided. The sensors 220 are application-specific. Examples of sensors 220 include temperature sensors, current sensors, voltage sensors, etc.

[0012] Each radio 122, 126 is coupled to an antenna. The main radio 122 is coupled to antenna 225, and the wake-up radio 126 is coupled to antenna 235. Thus, each radio may be connected to its own antenna. In other examples, one antenna or antenna array is shared between the two radios 122, 126. As described above, the main radio 122 is used for a different purpose than the fingerprinting wake-up radio. The main radio 122 is used to exchange (transmit and / or receive) wireless signals with the access point during device execution time. For example, the main radio 122 may be used to receive requests from an access point (e.g., access point 110) for sensor readings and to send data and / or signals from sensor 220 to the access point (e.g., access point 110), etc. In an implementation where the IoT device 120 responds to requests received from the access point, the main radio 122 in the IoT device may be powered off after transmitting / receiving information to / from the access point while the IoT device waits for another request from the access point. Alternatively, the main radio 122 may be powered off after a predetermined period of inactivity (e.g., 30 seconds, 2 minutes, etc.).

[0013] The fingerprinting wake-up radio 126, in at least some implementations, remains continuously powered on and operational and is used to detect a valid fingerprint from the access point's standard wireless signal. In response to the detection of a valid RF fingerprint, the main radio 122 is transitioned from a low-power state to a higher-power state to receive the incoming signal.

[0014] RF fingerprinting can be performed based on the following illustrative categories: transient-based RF fingerprinting generation and steady-state-based RF fingerprinting generation. In transient-based RF fingerprinting generation, a transmitter transmitting from an off state to an on state triggers a unique transient feature in the transmitted wireless signal that appears before the actual data packet is transmitted. In steady-state-based RF fingerprinting generation, a unique feature exists in the transmitter's wireless signal during the modulation phase. In this case, the fingerprinting wake-up radio generates a fingerprint from at least one received symbol. To verify a transmitter, an IoT device can implement any of many different types of RF fingerprinting techniques. Transmitter verification means that the IoT device confirms that the wireless signal it receives is from the transmitter to which the IoT device is associated (e.g., paired), and that the extracted features match features already stored in the device's memory.

[0015] One example of transient-based RF fingerprinting involves determining the power spectral density (PSD) of a preamble, such as in an IEEE 802.1la preamble. In this particular RF fingerprinting technique, the PSD can be calculated as follows: It is characterized by the PSD coefficient. TIFF0007911669000001.tif722 Here, X(k) is the coefficient of the discrete Fourier transform of the input signal x(m), and is given by the following equation. TIFF0007911669000002.tif834

[0016] The PSD of a wireless signal received from a particular transmitter can be used to uniquely identify that transmitter. Therefore, the PSD varies between transmitters and is generally repeatable for a given transmitter. The fingerprinting wake-up radio described herein can be used to determine the PSD for an incoming wireless signal. The PSD for one or more transmitters associated with an IoT device is stored as a fingerprint 229 in memory 227 within the IoT device. The determined PSD for a given wireless signal can be compared to the PSD stored in memory within the IoT device to determine whether a valid transmitter is attempting to communicate with the IoT device. If the PSD calculated by the IoT device matches the PSD stored in memory within the IoT device, the primary radio is transitioned from a low-power state to a higher-power state (i.e., awake).

[0017] The fingerprint 229 stored in memory 227 can be provided to the IoT device 120 by any appropriate method, or can be determined by the IoT device 120. In one example, a user device 211 may be used to indicate to the processor 210 that it is about to enter a training mode in which the processor 210 determines the fingerprint of the wireless signal it receives, and that it is about to receive the fingerprint for subsequent use in order to enable the main radio 122 and store it in memory 227. In another example, a user may program one or more fingerprints 229 via a graphical user interface implemented on a computer system outside the IoT device 120, and cause the external computer system to send the fingerprint to the IoT device for storage in memory 227.

[0018] Figure 3 illustrates an example of a method used by an IoT device (e.g., IoT device 120) to verify a transmitter using RF fingerprinting. In step 306, the IoT device communicates with another transmitter, and in step 308, it determines and stores the transmitter's fingerprint. The fingerprinting technique described above can be used. The IoT device's main radio 122 may be active during steps 306 and 308 and may be used to provide a signal from the transmitter to the IoT device's processor 210 for fingerprint determination. The processor 210 may store the fingerprint in memory 227.

[0019] In 310, the main radio 122 is transitioned to a low-power state (e.g., sleep, hibernation, etc.). In one example, the processor 210 sends a signal to the main radio 122 to transition to a low-power state following the use of the main radio to respond to a request received from the transmitter. In another example, the processor 210 sends a signal to the main radio 122 to transition to a low-power state when a timer times out during a period when the main radio 122 is not being used.

[0020] At 320, the fingerprinting wake-up radio (which remains on and operational) begins receiving wireless signals. The received wireless signals may be from an active or inactive transmitter. If the wireless signal is from an active transmitter, the main radio 122 should transition to a higher power (operational) state; however, if the wireless signal is not from an active transmitter, the main radio 122 should not transition to a higher power state and should therefore remain in a low power state. As mentioned above, an active transmitter is the transmitter to which the IoT device is paired and to which the IoT device should communicate. The wireless signals received at 320 may include the reception of a preamble for an IEEE 802.11 message. Transitioning the main radio 122 to a higher power state may include one or more of the following: turning on power to the main radio, increasing the operating voltage to the main radio, or clocking the main radio at a higher frequency.

[0021] In 330, this method includes extracting features from the received wireless signal. In one example, the extracted features include calculating the PSD of the received wireless signal, as described above. The fingerprinting wake-up radio 126 can calculate the PSD of the received wireless signal.

[0022] In 340, this method includes determining whether the extracted features match any features stored in memory 229 within the IoT device 120. In one implementation, the fingerprinting wake-up radio 126 performs this determination. In another example, the fingerprinting wake-up radio 126 provides the extracted features to the processor 210, which compares the extracted features with features stored in memory 227. In either case, a comparison is made between the newly extracted features and any features previously stored in memory 227. The extracted features and features stored in memory 227 may include, for example, the PSD of the wireless packet preamble.

[0023] At 350, if the extracted feature does not match any of the features stored in the memory 227, the power state of the main radio 122 remains in the low power state. Therefore, the main radio 122 is not activated.

[0024] At 360, if the extracted feature matches at least one of the features stored in the memory 227, the main radio is activated and continues to decode the received signal. In one example, the fingerprint wake-up radio 126 determines the match and sends the signal to the processor 210 to activate the main radio 122. In another example, at 330, the fingerprint wake-up radio extracts features from the wireless signal and provides those features to the processor 210, which determines that a match exists and instructs (e.g., by providing an enable signal to the main radio 122) the main radio 122 to transition to a higher power state. When the main radio 122 transitions to a higher power state, the main radio continues to receive incoming wireless signals and provides such signals to the processor 210 for further processing. While in the higher power state, the main radio 122 can also be used to transmit data (e.g., sensor data).

[0025] The term "coupled" is used throughout this specification. This term can encompass connections, communications, or signal paths that enable a functional relationship consistent with this description. For example, if device A generates a signal for controlling device B to perform a certain action, in a first example, device A is coupled to device B, or in a second example, device A is coupled to device B via an intervening component C if the intervening component C does not substantially change the functional relationship between device A and device B and device B is controlled by device A via the control signal generated by device A.

[0026] Within the scope of the claims of the present invention, modifications may be made to the illustrated embodiments described, and other embodiments are possible.

Claims

1. A wireless device, Wireless circuit and It is a processor, While the wireless circuit is operating in a low-power state, The first part of the first wireless signal is received via the aforementioned wireless circuit. A first fingerprint is determined based on the first portion of the first wireless signal. To determine whether the first wireless signal is associated with the first device, the first fingerprint is compared with a reference fingerprint associated with the first device. In response to determining that the first wireless signal is associated with the first device, the wireless circuit is transitioned to a high-power state to receive a second portion of the first wireless signal. The processor is configured as follows: Wireless devices, including those mentioned above.

2. A wireless device according to Claim 1, The aforementioned wireless circuit includes a wake-up wireless and a main wireless, A wireless device in which the processor is further configured to receive a first portion of the first wireless signal via the wake-up radio and a second portion of the first wireless signal via the main radio.

3. A wireless device according to claim 2, A wireless device in which the wake-up radio and the main radio are connected to the same antenna terminal.

4. A wireless device according to claim 2, A wireless device in which the wake-up radio is connected to a first antenna terminal and the main radio is connected to a second antenna terminal.

5. A wireless device according to claim 2, A wireless device in which the wireless circuit is configured to be in the low-power state, the main wireless to be off, and the wake-up wireless to be on.

6. A wireless device according to claim 5, A wireless device configured such that the main radio is turned on when the wireless circuit is in the high-power state.

7. A wireless device according to claim 6, A wireless device configured such that the wake-up radio is turned on when the wireless circuit is in the high-power state.

8. A wireless device according to claim 1, Including additional memory, The aforementioned processor A second wireless signal related to the first device is received via the wireless circuit. Based on the second wireless signal, the reference fingerprint is determined. The aforementioned reference fingerprint is stored in the memory. A wireless device further configured in this way.

9. A wireless device according to claim 1, A wireless device in which the first fingerprint is based on the power spectral density of a first portion of the first wireless signal.

10. A wireless device according to claim 1, A wireless device in which the processor is further configured to determine the first fingerprint from at least one symbol of the first portion of the first wireless signal.

11. A wireless device according to claim 1, The first portion of the first wireless signal includes a packet preamble, A wireless device in which the processor is further configured to determine the first fingerprint from the preamble of the packet.

12. A wireless device according to claim 11, A wireless device in which the aforementioned packet is a packet conforming to the IEEE 802.11 protocol.

13. A wireless device according to claim 1, A wireless device in which the first wireless signal does not include a dedicated wake-up symbol.

14. A wireless device according to claim 1, A wireless device in which the processor is further configured to receive a first portion of the first wireless signal after the first device has been paired with the wireless device.

15. A wireless device according to claim 1, It further includes sensors, A wireless device wherein the processor is further configured to transmit sensor data using the wireless circuit after the wireless circuit transitions to the high-power state.

16. A method, Receiving a first portion of a first wireless signal via the wireless circuit of a wireless device, Determining a first fingerprint based on a first portion of the first wireless signal, To determine whether the first wireless signal is associated with the first device, the first fingerprint is compared with a reference fingerprint associated with the first device, In response to determining that the first wireless signal is associated with the first device, the wireless circuit is transitioned to a high-power state to receive a second portion of the first wireless signal. Methods that include...

17. The method according to claim 16, Receiving a second wireless signal via the wireless circuit, wherein the second wireless signal is related to the first device, The reference fingerprint is determined based on the second wireless signal, The aforementioned reference fingerprint is stored in memory, Methods that further include the above.

18. The method according to claim 16, A method wherein the first fingerprint is based on the power spectral density of a first portion of the first wireless signal.

19. The method according to claim 16, A method for determining the first fingerprint, comprising determining the first fingerprint from at least one symbol of a first portion of the first wireless signal.

20. The method according to claim 16, The first portion of the first wireless signal includes a packet preamble, A method for determining the first fingerprint, comprising determining the first fingerprint based on the preamble of the packet.

21. The method according to claim 16, A method wherein the first wireless signal does not include a dedicated wake-up symbol.

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