PATENT DOCUMENT

Publication Number: US-10999798-B2
Application Number: US-201816013697-A
Country: US
Kind Code: B2

Title: Efficient scan and service discovery

Abstract:
An interface circuit in an electronic device (such as an access point) may provide a wake-up beacon to a recipient electronic device. During operation, the interface circuit may provide a wake-up beacon associated with a predefined sub-channel in one or more channels in a band of frequencies, where the wake-up beacon is for a wake-up radio in the recipient electronic device. Moreover, the wake-up beacon may be provided within an associated time interval, such as a keep-alive interval of the electronic device. In some embodiments, the wake-up beacon includes a field with channel information that specifies one or more second channels used by a main radio in the recipient electronic device. Alternatively or additionally, the wake-up beacon may include a field with service information that specifies one or more types of services and/or a field with information specifying a transmit power of the interface circuit.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a node configured to communicatively couple to an antenna; and 
 an interface circuit, communicatively coupled to the node, configured to communicate with a recipient electronic device, and configured to:
 provide, to the node, a wake-up beacon associated with a predefined sub-channel in one or more channels in a band of frequencies, wherein the wake-up beacon is for a wake-up radio in the recipient electronic device; 
 wherein the wake-up beacon is provided within an associated time interval that corresponds to a keep-alive interval of the electronic device beyond which the recipient electronic device is to scan for another electronic device; 
 wherein the wake-up beacon comprises a field that comprises service information specifying one or more types of services associated with the electronic device and specifying vendor information for a provider of a service; and 
 wherein the electronic device has received an indication associated with the recipient electronic device indicating that the recipient electronic device will awaken a main radio of the recipient electronic device when there is downlink traffic associated with the one or more types of services. 
 
 
     
     
       2. The electronic device of  claim 1 , wherein the electronic device comprises an access point. 
     
     
       3. The electronic device of  claim 1 , wherein the wake-up beacon comprises a Low Power Wake Up Radio (LP-WUR) packet. 
     
     
       4. The electronic device of  claim 1 , wherein the wake-up beacon comprises a field that comprises channel information specifying one or more second channels used by a main radio in the recipient electronic device; and
 wherein the one or more second channels are different from the one or more channels. 
 
     
     
       5. The electronic device of  claim 1 , wherein, prior to providing the wake-up beacon, the interface circuit is configured to:
 receive, from the node, a wake-up request associated with the recipient electronic device, the wake-up request comprising the indication that specifies the one or more types of services for which the recipient electronic device will awaken a main radio; and 
 provide, to the node, a wake-up response addressed to the recipient electronic device based at least in part on the wake-up request. 
 
     
     
       6. The electronic device of  claim 1 , wherein the interface circuit is configured to provide, to the node, a wake-up packet addressed to the recipient electronic device that comprises information specifying the one or more services associated with the electronic device. 
     
     
       7. The electronic device of  claim 1 , wherein the wake-up beacon comprises a field that comprises information specifying a transmit power of the interface circuit. 
     
     
       8. The electronic device of  claim 1 , wherein, prior to providing the wake-up beacon, the interface circuit is configured to provide, to the node, a packet addressed to the recipient electronic device that comprises information specifying a transmit power of the interface circuit. 
     
     
       9. A recipient electronic device, comprising:
 a node configured to communicatively couple to an antenna; and 
 an interface circuit, communicatively coupled to the node, configured to communicate with an electronic device, wherein the interface circuit comprises a wake-up radio and a main radio, and wherein the wake-up radio is configured to:
 receive, from the node and using the wake-up radio, a wake-up beacon associated with a predefined sub-channel in one or more channels in a band of frequencies, wherein the wake-up beacon is associated with the electronic device; 
 wherein the wake-up beacon is provided within an associated time interval that corresponds to a keep-alive interval of the electronic device beyond which the recipient electronic device is to scan for another electronic device; 
 wherein the wake-up beacon comprises a field that comprises service information specifying one or more types of services associated with the electronic device and specifying vendor information for a provider of a service; and 
 wherein the recipient electronic device has provided an indication addressed to electronic device indicating that the recipient electronic device will awaken the main radio when there is downlink traffic associated with the one or more types of services; and 
 provide, to the main radio, a wake-up signal that transitions the main radio from a low-power mode to a higher-power mode based at least in part on the wake-up beacon comprising the service information. 
 
 
     
     
       10. The recipient electronic device of  claim 9 , wherein the electronic device comprises an access point. 
     
     
       11. The recipient electronic device of  claim 9 , wherein the wake-up beacon comprises a Low Power Wake Up Radio (LP-WUR) packet. 
     
     
       12. The recipient electronic device of  claim 9 , wherein the wake-up beacon comprises a field that includes channel information specifying one or more second channels used by the main radio; and
 wherein the one or more second channels are different from the one or more channels. 
 
     
     
       13. The recipient electronic device of  claim 9 , wherein, prior to receiving the wake-up beacon, the interface circuit is configured to:
 provide, to the node, a wake-up request addressed to the electronic device, the wake-up request comprising the indication that specifies one or more types of services for which the recipient electronic device will awaken the main radio; and 
 receive, from the node, a wake-up response associated with the electronic device based at least in part on the wake-up request. 
 
     
     
       14. The recipient electronic device of  claim 9 , wherein the wake-up beacon comprises a field that includes information specifying a transmit power of the electronic device;
 wherein the recipient electronic device is configured to determining a communication metric based at least in part on the transmit power and a received signal strength associated with the wake-up beacon; and 
 wherein, based at least in part on the communication metric, the wake-up radio is configured to perform a scan for a second wake-up beacon associated with a second electronic device in a second predefined sub-channel in one or more second channels in a second band of frequencies. 
 
     
     
       15. The recipient electronic device of  claim 9 , wherein, prior to receiving the wake-up beacon, the interface circuit is configured to receive, from the node, a packet associated with the electronic device that comprises information specifying a transmit power of the electronic device. 
     
     
       16. The recipient electronic device of  claim 9 , wherein, when another wake-up beacon is not received within a subsequent time interval, the wake-up radio is configured to perform a scan for a second wake-up beacon associated with a second electronic device in a second predefined sub-channel in one or more second channels in a second band of frequencies. 
     
     
       17. A method for providing a wake-up beacon, comprising:
 by a recipient electronic device: 
 receiving, using a wake-up radio in the recipient electronic device, the wake-up beacon associated with a predefined sub-channel in one or more channels in a band of frequencies, wherein the wake-up beacon is associated with an electronic device; and 
 wherein the wake-up beacon is provided within an associated time interval that corresponds to a keep-alive interval of the electronic device beyond which the recipient electronic device is to scan for another electronic device; 
 wherein the wake-up beacon comprises a field that comprises service information specifying one or more types of services associated with the electronic device and specifying vendor information for a provider of a service; and 
 wherein the recipient electronic device has provided an indication addressed to electronic device indicating that the recipient electronic device will awaken the main radio when there is downlink traffic associated with the one or more types of services; and 
 providing, to a main radio in the recipient electronic device, a wake-up signal that transitions the main radio from a low-power mode to a higher-power mode based at least in part on the wake-up beacon comprising the service information. 
 
     
     
       18. The method of  claim 17 , wherein the wake-up beacon comprises a field that comprises channel information specifying one or more second channels used by the main radio; and
 wherein the one or more second channels are different from the one or more channels. 
 
     
     
       19. The method of  claim 17 , wherein, prior to receiving the wake-up beacon, the method comprises:
 providing, using the main radio, a wake-up request addressed to the electronic device, the wake-up request comprising the indication that specifies the one or more types of services for which the recipient electronic device will awaken the main radio; and 
 receiving, using the main radio, a wake-up response associated with the electronic device based at least in part on the wake-up request. 
 
     
     
       20. The method of  claim 17 , wherein the method comprises receiving, using the wake-up radio, a wake-up packet associated with the electronic device that comprises information specifying the one or more services associated with the electronic device.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 62/524,764, entitled “Efficient Scan and Service Discovery, by Guoqing Li, et al., filed Jun. 26, 2017, the contents of which are hereby incorporated by reference. 
    
    
     FIELD 
     The described embodiments relate, generally, to wireless communications among electronic devices, and techniques for scanning for beacons in one or more predefined sub-channels using a low-power wake-up radio. 
     BACKGROUND 
     Many electronic devices communicate with each other using wireless local area networks (WLANs), such as those based on a communication protocol that is compatible with an IEEE 802.11 standard (which is sometimes referred to as ‘Wi-Fi’). However, a radio in an electronic device that communicates using wireless communication in a WLAN may consume a significant amount of power. 
     In order to address this challenge, a new radio technology called Low Power Wake Up Radio (LP-WUR) is being considered. The LP-WUR may be a companion to the main Wi-Fi radio in the electronic device. Notably, by using the LP-WUR, the electronic device may turn off its main radio and may wake up the main radio in response to the LP-WUR receiving an LP-WUR packet from an access point. For example, the access point may send the LP-WUR packet when there is a down-link packet for the electronic device. 
     However, the connection to the access point may be lost while the main radio is in a low-power operating mode. For example, the electronic device may roam outside of the range of the access point and, thus, may need to transition to another access point. When this occurs, the electronic device may need to awaken the main radio, and then may need to perform network/service discovery. The network/service discovery typically involves the main radio scanning through multiple channels, and performing multiple frame exchanges. Each scan may take, e.g., 100 ms to capture a beacon from the other access point. Moreover, after the beacon is received, the electronic device and the other access point may need to exchange: a probe request and response, an authentication request and response, an association request and response and/or a service-information request and response. Waking up the main radio to perform the scan and to exchange these frames may increase the power consumption and may delay the operation of the electronic device. 
     SUMMARY 
     A first group of embodiments relate to an electronic device that provides a wake-up beacon. This electronic device may include a node that can be communicatively coupled to an antenna, and an interface circuit communicatively coupled to the node and that communicates with a recipient electronic device. During operation, the interface circuit provides, to the node, a wake-up beacon associated with a predefined sub-channel in one or more channels in a band of frequencies, where the wake-up beacon is for a wake-up radio in the recipient electronic device. Moreover, the wake-up beacon may be provided within an associated time interval. 
     Note that the electronic device may include an access point. 
     Moreover, the wake-up beacon may include a Low Power Wake Up Radio (LP-WUR) packet. Furthermore, the wake-up beacon may be compatible with an IEEE 802.11 communication protocol. 
     Additionally, the time interval may correspond to a keep-alive interval of the electronic device and/or the recipient electronic device. In some embodiments, the wake-up beacon includes a field with channel information that specifies one or more second channels used by a main radio in the recipient electronic device. Note that the one or more second channels may be different from the one or more channels. 
     Alternatively or additionally, the wake-up beacon may include a field with service information that specifies one or more types of services. For example, the service information may be hashed using a predefined hash function and/or the service information may include vendor information. 
     In some embodiments, prior to providing the wake-up beacon, the interface circuit: receives, from the node, a wake-up request associated with the recipient electronic device that specifies one or more types of services for which the recipient electronic device will awaken the main radio; and provides, to the node, a wake-up response associated with the recipient electronic device based at least in part on the wake-up request. 
     Moreover, the interface circuit may provide, to the node, a wake-up packet for the recipient electronic device that includes information specifying one or more services offered by the electronic device. 
     Furthermore, the wake-up beacon may include a field with information specifying a transmit power of the interface circuit. The transmit power may be different from another wake-up beacon provided by the interface circuit. 
     Additionally, prior to providing the wake-up beacon, the interface circuit may provide, to the node, a packet for the electronic device that includes information specifying a transmit power of the interface circuit. 
     Note that the interface circuit may be configured to provide wake-up beacons periodically. 
     Other embodiments provide an interface circuit in the electronic device. 
     Still other embodiments provide a computer-readable storage medium for use with the interface circuit in the electronic device. When program instructions stored in the computer-readable storage medium are executed by the interface circuit, the program instructions may cause the electronic device to perform at least some of the aforementioned operations of the electronic device. 
     Still other embodiments provide a method for providing a wake-up beacon. The method includes at least some of the aforementioned operations performed by the interface circuit in the electronic device. 
     A second group of embodiments relate to the recipient electronic device that receives the wake-up beacon from the first group of embodiments. This recipient electronic device may include a node that can be communicatively coupled to an antenna, and an interface circuit communicatively coupled to the node and that communicates with the electronic device. The interface circuit may include the wake-up radio and the main radio. During operation, the wake-up radio receives, from the node, the wake-up beacon associated with the predefined sub-channel in one or more channels in the band of frequencies, where the wake-up beacon is associated with the electronic device, and the wake-up beacon is provided within the associated time interval. Then, the wake-up radio provides, to the main radio, a wake-up signal that transitions the main radio from a low-power mode to a higher-power mode based at least in part on the wake-up beacon. 
     In some embodiments, prior to receiving the wake-up beacon, the interface circuit: provides, to the node, the wake-up request associated with the electronic device that specifies the one or more types of services for which the recipient electronic device will awaken the main radio; and receives, from the node, the wake-up response associated with the electronic device based at least in part on the wake-up request. 
     Alternatively or additionally, the interface circuit may receive, from the node, the wake-up packet associated with the electronic device that includes the information specifying the one or more services offered by the electronic device. 
     Moreover, the recipient electronic device may determine a communication metric based at least in part on a transmit power of the wake-up beacon and a received signal strength associated with the wake-up beacon. Based at least in part on the communication metric, the wake-up radio may perform a scan for a second wake-up beacon associated with a second electronic device in a second predefined sub-channel in one or more second channels in a second band of frequencies. 
     Furthermore, prior to receiving the wake-up beacon, the interface circuit may receive, from the node, the packet associated with the electronic device that includes the information specifying the transmit power of the electronic device. 
     Additionally, when another wake-up beacon is not received within a subsequent time interval, the wake-up radio may perform a scan for the second wake-up beacon associated with the second electronic device in the second predefined sub-channel in the one or more second channels in the second band of frequencies. 
     Other embodiments provide an interface circuit in the recipient electronic device. 
     Still other embodiments provide a computer-readable storage medium for use with the interface circuit in the recipient electronic device. When program instructions stored in the computer-readable storage medium are executed by the interface circuit, the program instructions may cause the recipient electronic device to perform at least some of the aforementioned operations of the recipient electronic device. 
     Still other embodiments provide a method for receiving a wake-up beacon. The method includes at least some of the aforementioned operations performed by the interface circuit in the recipient electronic device. 
     A third group of embodiments relate to an electronic device that provides a wake-up beacon. This electronic device may include a node that can be communicatively coupled to an antenna, and an interface circuit communicatively coupled to the node and that communicates with a recipient electronic device. During operation, the interface circuit provides, to the node, a wake-up beacon for a wake-up radio in the recipient electronic device with information indicating that the recipient electronic device is to awaken a main radio to receive a beacon with dynamic frequency selection (DFS) information associated with a band of frequencies. 
     Other embodiments provide an interface circuit in the electronic device. 
     Still other embodiments provide a computer-readable storage medium for use with the interface circuit in the electronic device. When program instructions stored in the computer-readable storage medium are executed by the interface circuit, the program instructions may cause the electronic device to perform at least some of the aforementioned operations of the electronic device. 
     Still other embodiments provide a method for providing a wake-up beacon. The method includes at least some of the aforementioned operations performed by the interface circuit in the electronic device. 
     A fourth group of embodiments relate to the recipient electronic device that receives the wake-up beacon from the third group of embodiments. This recipient electronic device may include a node that can be communicatively coupled to an antenna, and an interface circuit communicatively coupled to the node and that communicates with the electronic device. The interface circuit may include the wake-up radio and the main radio. During operation, the wake-up radio receives, from the node, the wake-up beacon associated with the electronic device. Then, the wake-up radio provides, to the main radio, a wake-up signal that transitions the main radio from a low-power mode to a higher-power mode based at least in part on the wake-up beacon. Moreover, the main radio receives, from the node, a beacon associated with the electronic device that includes the DFS information associated with a band of frequencies. 
     Other embodiments provide an interface circuit in the recipient electronic device. 
     Still other embodiments provide a computer-readable storage medium for use with the interface circuit in the recipient electronic device. When program instructions stored in the computer-readable storage medium are executed by the interface circuit, the program instructions may cause the recipient electronic device to perform at least some of the aforementioned operations of the recipient electronic device. 
     Still other embodiments provide a method for receiving a wake-up packet. The method includes at least some of the aforementioned operations performed by the interface circuit in the recipient electronic device. 
     This Summary is provided for purposes of illustrating some exemplary embodiments, so as to provide a basic understanding of some aspects of the subject matter described herein. Accordingly, it will be appreciated that the above-described features are only examples and should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following Detailed Description, Figures, and Claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The included drawings are for illustrative purposes and serve only to provide examples of possible structures and arrangements for the disclosed systems and techniques for intelligently and efficiently managing communication between multiple associated user devices. These drawings in no way limit any changes in form and detail that may be made to the embodiments by one skilled in the art without departing from the spirit and scope of the embodiments. The embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements. 
         FIG. 1  is a block diagram illustrating an example of electronic devices communicating wirelessly. 
         FIG. 2  is a flow diagram illustrating an example method for providing a wake-up beacon using one of the electronic devices in  FIG. 1 . 
         FIG. 3  is a flow diagram illustrating an example method for receiving a wake-up beacon using one of the electronic devices in  FIG. 1 . 
         FIG. 4  is a flow diagram illustrating an example of communication between electronic devices, such as the electronic devices of  FIG. 1 . 
         FIG. 5  is a flow diagram illustrating an example method for providing a wake-up beacon using one of the electronic devices in  FIG. 1 . 
         FIG. 6  is a flow diagram illustrating an example method for receiving a wake-up beacon using one of the electronic devices in  FIG. 1 . 
         FIG. 7  is a flow diagram illustrating an example of communication between electronic devices, such as the electronic devices of  FIG. 1 . 
         FIG. 8  is a drawing illustrating an example interface circuit in one of the electronic devices in  FIG. 1 . 
         FIGS. 9-11  are drawings illustrating example wake-up beacons. 
         FIG. 12  is a block diagram illustrating an example of one of the electronic devices of  FIG. 1 . 
     
    
    
     Note that like reference numerals refer to corresponding parts throughout the drawings. Moreover, multiple instances of the same part are designated by a common prefix separated from an instance number by a dash. 
     DETAILED DESCRIPTION 
     An interface circuit in an electronic device (such as an access point) may provide a wake-up beacon to a recipient electronic device. During operation, the interface circuit may provide a wake-up beacon (such as a LP-WUR packet) associated with a predefined sub-channel in one or more channels in a band of frequencies, where the wake-up beacon is for a wake-up radio in the recipient electronic device. Moreover, the wake-up beacon may be provided within an associated time interval, such as a keep-alive interval of the electronic device. 
     In some embodiments, the wake-up beacon includes a field with channel information that specifies one or more second channels used by a main radio in the recipient electronic device. Note that the one or more second channels may be different from the one or more channels. Alternatively or additionally, the wake-up beacon may include a field with service information that specifies one or more types of services and/or a field with information specifying a transmit power of the interface circuit. The transmit power may be different from another wake-up beacon provided by the interface circuit. Moreover, the wake-up beacon may include information indicating that the recipient electronic device is to awaken a main radio to receive a beacon with DFS information associated with a band of frequencies. 
     Furthermore, the recipient electronic device may include an interface circuit that includes a wake-up radio (such as the LP-WUR) and a main radio. During operation, the wake-up radio may receive the wake-up beacon associated with the predefined sub-channel in one or more channels in the band of frequencies, where the wake-up beacon is associated with the electronic device, and the wake-up beacon is provided within the associated time interval. Then, the wake-up radio provides, to the main radio, a wake-up signal that transitions the main radio from a low-power mode to a higher-power mode based at least in part on the wake-up beacon. When a communication metric based at least in part on a transmit power of the wake-up beacon and a received signal strength associated with the wake-up beacon degrades, the wake-up radio may perform a scan for a second wake-up beacon associated with a second electronic device (such as a second access point) in a third predefined sub-channel in one or more third channels in a third band of frequencies. Alternatively, when another wake-up beacon is not received within a subsequent time interval, the wake-up radio may perform the scan for the second wake-up beacon. 
     By providing the wake-up beacon, this communication technique may maintain a connection between the electronic device and the recipient electronic device. Moreover, the communication technique may facilitate more efficient operation of the main radio. For example, the main radio may not be awakened as often and/or may not need to perform scans of the wireless environment of the recipient electronic device. Consequently, the communication technique may reduce power consumption and delays, and may improve the communication performance of the electronic device and/or the recipient electronic device. Thus, the communication technique may improve the user experience when using the electronic device or the recipient electronic device, and therefore may increase customer satisfaction and retention. 
     Note that the communication technique may be used during wireless communication between electronic devices in accordance with a communication protocol, such as a communication protocol that is compatible with an IEEE 802.11 standard (which is sometimes referred to as Wi-Fi). In some embodiments, the communication technique is used with IEEE 802.11BA and/or IEEE 802.11ax, which are used as illustrative examples in the discussion that follows. However, this communication technique may also be used with a wide variety of other communication protocols, and in electronic devices (such as portable electronic devices or mobile devices) that can incorporate multiple different radio access technologies (RATs) to provide connections through different wireless networks that offer different services and/or capabilities. 
     An electronic device can include hardware and software to support a wireless personal area network (WPAN) according to a WPAN communication protocol, such as those standardized by the Bluetooth® Special Interest Group (in Kirkland, Wash.) and/or those developed by Apple (in Cupertino, Calif.) that are referred to as an Apple Wireless Direct Link (AWDL). Moreover, the electronic device can communicate via: a wireless wide area network (WWAN), a wireless metro area network (WMAN) a WLAN, near-field communication (NFC), a cellular-telephone or data network (such as using a third generation (3G) communication protocol, a fourth generation (4G) communication protocol, e.g., Long Term Evolution or LTE, LTE Advanced (LTE-A), a fifth generation (5G) communication protocol, or other present or future developed advanced cellular communication protocol) and/or another communication protocol. In some embodiments, the communication protocol includes a peer-to-peer communication technique. 
     The electronic device, in some embodiments, can also operate as part of a wireless communication system, which can include a set of client devices, which can also be referred to as stations or client electronic devices, interconnected to an access point, e.g., as part of a WLAN, and/or to each other, e.g., as part of a WPAN and/or an ‘ad hoc’ wireless network, such as a Wi-Fi direct connection. In some embodiments, the client device can be any electronic device that is capable of communicating via a WLAN technology, e.g., in accordance with a WLAN communication protocol. Furthermore, in some embodiments, the WLAN technology can include a Wi-Fi (or more generically a WLAN) wireless communication subsystem or radio, and the Wi-Fi radio can implement an IEEE 802.11 technology, such as one or more of: IEEE 802.11a; IEEE 802.11b; IEEE 802.11g; IEEE 802.11-2007; IEEE 802.11n; IEEE 802.11-2012; IEEE 802.11ac; IEEE 802.11ax, or other present or future developed IEEE 802.11 technologies. 
     In some embodiments, the electronic device can act as a communications hub that provides access to a WLAN and/or to a WWAN and, thus, to a wide variety of services that can be supported by various applications executing on the electronic device. Thus, the electronic device may include an ‘access point’ that communicates wirelessly with other electronic devices (such as using Wi-Fi), and that provides access to another network (such as the Internet) via IEEE 802.3 (which is sometimes referred to as ‘Ethernet’). 
     Additionally, it should be understood that the electronic devices described herein may be configured as multi-mode wireless communication devices that are also capable of communicating via different 3G and/or second generation (2G) RATs. In these scenarios, a multi-mode electronic device or UE can be configured to prefer attachment to LTE networks offering faster data rate throughput, as compared to other 3G legacy networks offering lower data rate throughputs. For example, in some implementations, a multi-mode electronic device is configured to fall back to a 3G legacy network, e.g., an Evolved High Speed Packet Access (HSPA+) network or a Code Division Multiple Access (CDMA) 2000 Evolution-Data Only (EV-DO) network, when LTE and LTE-A networks are otherwise unavailable. 
     In accordance with various embodiments described herein, the terms ‘wireless communication device,’ ‘electronic device,’ ‘mobile device,’ ‘mobile station,’ ‘wireless station,’ ‘wireless access point,’ ‘station,’ ‘point’ and ‘user equipment’ (UE) may be used herein to describe one or more consumer electronic devices that may be capable of performing procedures associated with various embodiments of the disclosure. 
       FIG. 1  presents a block diagram illustrating an example of electronic devices communicating wirelessly. Notably, one or more electronic devices  110  (such as a smartphone, a laptop computer, a notebook computer, a tablet, or another such electronic device) and access point  112  may communicate wirelessly in a WLAN using an IEEE 802.11 communication protocol. Thus, electronic devices  110  may be associated with access point  112 . For example, electronic devices  110  and access point  112  may wirelessly communicate while: detecting one another by scanning wireless channels, transmitting and receiving beacons or beacon frames on wireless channels, establishing connections (for example, by transmitting connect requests), and/or transmitting and receiving packets or frames (which may include the request and/or additional information, such as data, as payloads). Note that access point  112  may provide access to a network, such as the Internet, via an Ethernet protocol, and may be a physical access point or a virtual or ‘software’ access point that is implemented on a computer or an electronic device. In the discussion that follows, electronic devices  110  are sometimes referred to as ‘recipient electronic devices.’ 
     As described further below with reference to  FIG. 12 , electronic devices  110  and access point  112  may include subsystems, such as any/all of a networking subsystem, a memory subsystem, and/or a processor subsystem. In addition, electronic devices  110  and access point  112  may include radios  114 , e.g., in the networking subsystems. More generally, electronic devices  110  and access point  112  can include (or can be included within) any electronic devices with networking subsystems that enable electronic devices  110  and access point  112  to wirelessly communicate with another electronic device. This can include transmitting beacons on wireless channels to enable the electronic devices to make initial contact with or to detect each other, followed by exchanging subsequent data/management frames (such as connect requests) to establish a connection, configure security options (e.g., IPSec), transmit and receive packets or frames via the connection, etc. 
     As can be seen in  FIG. 1 , wireless signals  116  (represented by a jagged line) are communicated by radios  114 - 1  and  114 - 2  in electronic device  110 - 1  and access point  112 , respectively. For example, as noted previously, electronic device  110 - 1  and access point  112  may exchange packets using a Wi-Fi communication protocol in a WLAN. As illustrated further below with reference to  FIGS. 2-7 , radio  114 - 1  may receive wireless signals  116  that are transmitted by radio  114 - 2 . Alternatively, radio  114 - 1  may transmit wireless signals  116  that are received by radio  114 - 2 . However, as described further below with reference to  FIG. 8 , radio  114 - 1  consumes additional power in a higher-power mode. If radio  114 - 1  remains in the higher-power mode even when it is not transmitting or receiving packets, the power consumption of electronic device  110 - 1  may be needlessly increased. Consequently, electronic devices  110  may include wake-up radios  118  that listen for and/or receive wake-up beacons (and/or other wake-up communications) from access point  112 . When a particular electronic device (such as electronic device  110 - 1 ) receives a wake-up beacon, wake-up radio  118 - 1  may selectively wake up radio  114 - 1 , e.g., provide a wake-up signal that selectively transitions radio  114 - 1  from a low-power mode to the higher-power mode. 
     During operation, access point  112  (such as radio  114 - 2 ) may determine whether to send a wake-up beacon to one or more recipient electronic devices (such as electronic device  110 - 1 ) with information that specifies that one or more recipient electronic devices are to transition from the low-power mode. For example, access point  112  may determine whether to send a wake-up beacon to electronic device  110 - 1  based at least in part on one or more types of services for which electronic device  110 - 1  previously indicated it will awaken radio  114 - 1  (such as in a wake-up request previously provided by electronic device  110 - 1  to access point  112 ). Then, radio  114 - 2  may provide a wake-up beacon (such as a LP-WUR packet) for the one or more recipient electronic devices (and, notably, for one or more wake-up radios  118 ). This wake-up beacon may be associated with a predefined sub-channel in one or more channels in a band of frequencies (e.g., radio  114 - 2  may transmit the wake-up beacon in the sub-channel), and the wake-up beacon may be provided within an associated time interval, such as a keep-alive interval of access point  112  (such as a keep-alive interval between, e.g., 1 and 10 s). 
     As described further below with reference to  FIG. 9 , the wake-up beacon may include a field with channel information that specifies one or more second channels used by radio  114 - 1  in electronic device  110 - 1 . Note that the one or more second channels may be different from the one or more channels. Thus, the wake-up beacon may be used to keep or maintain a connection between electronic device  110 - 1  and access point  112  and to specify the one or more second channels for radio  114 - 1 . Alternatively or additionally, as described further below with reference to  FIG. 10 , the wake-up beacon may include a field with service information that specifies one or more types of services. For example, the service information may be hashed using a predefined hash function and/or the service information may include vendor information. In these embodiments, the wake-up beacon may be used to alert electronic device  110 - 1  to downlink traffic associated with a service provided by or facilitated by access point  112 , such as a service for which electronic device  110 - 1  may have previously indicated it wants to be awakened. Furthermore, as described further below with reference to  FIG. 11 , the wake-up beacon may include a field with information indicating that wake-up radio  118 - 1  is to awaken radio  114 - 1  to receive a beacon with DFS information associated with the band of frequencies (which may be the same of different than the band of frequencies associated with the wake-up beacon). This information may allow radio  114 - 1  to be awoken so that it can transition to one or more different channels when the band of frequencies includes a shared spectrum, thereby cleaning the band of frequencies for a higher-priority user. 
     After receiving the wake-up beacon, wake-up radio  118 - 1  may provide, to radio  114 - 1 , a wake-up signal that transitions radio  114 - 1  from the low-power mode to the higher-power mode. Then, radio  114 - 1  may operate using the one or more second channels. Alternatively, when the information does not specify electronic device  110 - 1 , wake-up radio  118 - 1  may take no further action, e.g., radio  114 - 1  may remaining in the low-power mode. More generally, in some embodiments after wake-up radio  118 - 1  receives the wake-up beacon, the wake-up radio  118 - 1  may analyze the information in the wake-up beacon to determine if radio  114 - 1  should transition from the lower power mode. Thus, in the embodiments, the ‘intelligence’ as to whether to transition from the low-power mode in the communication technique may be implemented by access point  112  (such as when access point  112  determines whether it will send the wake-up beacon to electronic device  110 - 1 ) and/or in electronic device  110 - 1  (which may analyze the information included in the wake-up beacon). 
     In some embodiments, electronic device  110 - 1  determines a communication metric based at least in part on a transmit power of the wake-up beacon and a received signal strength associated with the wake-up beacon. Note that the transmit power of the wake-up beacon may be specified by information included in the wake-up beacon. This may allow radio  114 - 2  to dynamically vary the transmit power in different instances of wake-up beacons provided by access point  112 . Alternatively or additionally, radio  114 - 2  may have previously provided a packet to electronic device  110 - 1  that included information specifying a transmit power of radio  114 - 1  (in which case the transmit power may be quasi-static). Based at least in part on the communication metric, wake-up radio  118 - 1  may perform a scan for a second wake-up beacon associated with a second electronic device (such as a second access point) in a second predefined sub-channel in one or more third channels in a third band of frequencies. For example, wake-up radio  118 - 1  may scan for another access point in a different sub-channel in the same or different channel(s) and/or band of frequencies than those used by access point  112 . In some embodiments, when another wake-up beacon is not received within a subsequent time interval, wake-up radio  118 - 1  performs a scan for the second wake-up beacon associated with the second electronic device in the third predefined sub-channel in the one or more third channels in the third band of frequencies. 
     Note that wake-up radio  118 - 1  may operate continuously or in a duty-cycle mode. For example, wake-up radio  118 - 1  may wake up to or transition to the higher-power mode from the low-power mode to receive the wake-up beacon. In some embodiments, radio  114 - 2  may provide wake-up beacons once, as needed (such as when there is downlink traffic) or periodically (such as within the associated time interval). 
     In these ways, the communication technique may allow electronic devices  110  and access point  112  to communicate efficiently (such as with low latency and high throughput) while significantly reducing the power consumption associated with radios  114  in electronic devices  110 . These capabilities may improve the user experience when using electronic devices  110 . 
     Note that access point  112  and at least some of electronic devices  110  may be compatible with an IEEE 802.11 standard that includes trigger-based channel access (such as IEEE 802.11ax). However, access point  112  and at least this subset of electronic devices  110  may also communicate with one or more legacy electronic devices that are not compatible with the IEEE 802.11 standard (i.e., that do not use multi-user trigger-based channel access). In some embodiments, at least a subset of electronic devices  110  use multi-user transmission (such as orthogonal frequency division multiple access or OFDMA). For example, radio  114 - 2  may provide a trigger frame for the subset of recipient electronic devices. This trigger frame may be provided after a time delay (such as a time delay between, e.g., 10 and 300 ms), so that radio  114 - 1  has sufficient time to transition to the higher-power mode. Moreover, after radio  118 - 1  receives the wake-up beacon and radio  114 - 1  transitions to the higher-power mode, radio  114 - 1  may provide a group acknowledgment to radio  114 - 2 . Notably, radio  114 - 1  may provide the acknowledgment during an assigned time slot and/or in an assigned channel in the group acknowledgment. However, in some embodiments the one or more recipient electronic devices may individually provide acknowledgments to radio  114 - 2 . Thus, after radio  118 - 1  receives the wake-up beacon and radio  114 - 1  transitions to the higher-power mode, radio  114 - 1  (and, more generally, the main radios in the one or more recipient electronic devices) may provide an acknowledgment to radio  114 - 2 . 
     In the described embodiments, processing a packet or frame in one of electronic devices  110  and access point  112  includes: receiving wireless signals  116  encoding a packet or a frame; decoding/extracting the packet or frame from received wireless signals  116  to acquire the packet or frame; and processing the packet or frame to determine information contained in the packet or frame (such as data in the payload). 
     In general, the communication via the WLAN in the communication technique may be characterized by a variety of communication-performance metrics. For example, the communication-performance metric may include: a received signal strength (RSS), a data rate, a data rate for successful communication (which is sometimes referred to as a ‘throughput’), a latency, an error rate (such as a retry or resend rate), a mean-square error of equalized signals relative to an equalization target, inter-symbol interference, multipath interference, a signal-to-noise ratio (SNR), a width of an eye pattern, a ratio of number of bytes successfully communicated during a time interval (such as a time interval between, e.g., 1 and 10 s) to an estimated maximum number of bytes that can be communicated in the time interval (the latter of which is sometimes referred to as the ‘capacity’ of a communication channel or link), and/or a ratio of an actual data rate to an estimated data rate (which is sometimes referred to as ‘utilization’). 
     Although we describe the network environment shown in  FIG. 1  as an example, in alternative embodiments, different numbers and/or types of electronic devices may be present. For example, some embodiments may include more or fewer electronic devices. As another example, in other embodiments, different electronic devices can be transmitting and/or receiving packets or frames. 
       FIG. 2  presents a flow diagram illustrating an example method  200  for providing a wake-up beacon. This method may be performed by an electronic device, such as an interface circuit in access point  112  in  FIG. 1 . During operation, the interface circuit may determine to provide the wake-up beacon (operation  210 ) for a wake-up radio in a recipient electronic device. For example, the interface circuit may determine to provide the wake-up beacon when there is downlink traffic (such as data associated with a service) for the recipient electronic device. Then, the interface circuit may provide the wake-up beacon (operation  212 ) associated with a predefined sub-channel in one or more channels in a band of frequencies, where the wake-up beacon is provided within an associated time interval. 
     Note that the electronic device may include an access point. Moreover, the wake-up beacon may include a LP-WUR packet. Furthermore, the wake-up beacon may be compatible with an IEEE 802.11 communication protocol. Additionally, the time interval may correspond to a keep-alive interval of the electronic device and/or the recipient electronic device. 
     In some embodiments, the wake-up beacon includes a field with channel information that specifies one or more second channels used by a main radio in the recipient electronic device. Note that the one or more second channels may be different from the one or more channels. Alternatively or additionally, the wake-up beacon may include a field with service information that specifies one or more types of services. For example, the service information may be hashed using a predefined hash function and/or the service information may include vendor information. 
     Moreover, the interface circuit may be configured to provide wake-up beacons periodically. 
     In some embodiments, the interface circuit optionally performs one or more additional operations (operation  214 ). For example, prior to providing the wake-up beacon (operation  212 ), the interface circuit may: receive a wake-up request associated with the recipient electronic device (such as from the recipient electronic device) that specifies one or more types of services for which the recipient electronic device will awaken the main radio; and provide a wake-up response associated with the recipient electronic device (such as to the recipient electronic device) based at least in part on the wake-up request. Moreover, the interface circuit may provide a wake-up packet for the recipient electronic device that includes information specifying one or more services offered by the electronic device. 
     Furthermore, the wake-up beacon may include a field with information specifying a transmit power of the interface circuit. The transmit power may be different from another wake-up beacon provided by the interface circuit, such as a wake-up beacon that was previously provided by the interface circuit. Alternatively or additionally, prior to providing the wake-up beacon (operation  212 ), the interface circuit may provide a packet for the electronic device that includes information specifying a transmit power of the interface circuit. 
       FIG. 3  presents a flow diagram illustrating an example method  300  for receiving a wake-up beacon. This method may be performed by a recipient electronic device, such as an interface circuit in electronic device  110 - 1  in  FIG. 1 . This interface circuit may include a wake-up radio and a main radio. During operation, the wake-up radio may receive the wake-up beacon (operation  310 ) associated with the predefined sub-channel in one or more channels in the band of frequencies, where the wake-up beacon is associated with the electronic device (such as from the electronic device), and the wake-up beacon is provided within the associated time interval. Then, the wake-up radio may optionally analyze the wake-up beacon (operation  312 ) to determine whether to wake up the main radio. If yes (operation  312 ), the wake-up radio may provide, to the main radio, a wake-up signal (operation  314 ) that transitions (operation  316 ) the main radio from a low-power mode to a higher-power mode based at least in part on the wake-up beacon. Otherwise (operation  312 ), the wake-up radio may not take further action (operation  318 ). 
     In some embodiments, the interface circuit optionally performs one or more additional operations (operation  320 ). For example, prior to the wake-up radio receiving the wake-up beacon (operation  310 ), the main radio may: provide the wake-up request associated with the electronic device (such as to the electronic device) that specifies the one or more types of services for which the recipient electronic device will awaken the main radio; and receive the wake-up response associated with the electronic device (such as from the electronic device) based at least in part on the wake-up request. Alternatively or additionally, the main radio may receive the wake-up packet associated with electronic device (such as from the electronic device) that includes the information specifying the one or more services offered by the electronic device. 
     Moreover, the recipient electronic device may determine a communication metric based at least in part on a transmit power of the wake-up beacon and an RSS associated with the wake-up beacon. Based at least in part on the communication metric, the wake-up radio may perform a scan for a second wake-up beacon associated with a second electronic device (such as another access point) in a second predefined sub-channel in one or more second channels in a second band of frequencies. 
     Furthermore, prior to receiving the wake-up beacon (operation  310 ), the main radio may receive the packet associated with the electronic device (such as from the electronic device) that includes the information specifying the transmit power of the electronic device. 
     Additionally, when another wake-up beacon (such as a subsequent wake-up beacon) is not received within a subsequent time interval, the wake-up radio may perform a scan for the second wake-up beacon associated with the second electronic device in the second predefined sub-channel in the one or more second channels in the second band of frequencies. 
     In some embodiments of methods  200  ( FIG. 2 ) and/or  300 , there may be additional or fewer operations. Moreover, the order of the operations may be changed, and/or two or more operations may be combined into a single operation or performed at least partially in parallel. 
     In some embodiments, at least some of the operations in methods  200  ( FIG. 2 ) and/or  300  are performed by an interface circuit in the electronic device. For example, at least some of the operations may be performed by firmware executed by an interface circuit, such as firmware associated with a MAC layer, as well as one or more circuits in a physical layer in the interface circuit. 
     The communication technique is further illustrated in  FIG. 4 , which presents a flow diagram illustrating an example of communication between electronic device  110 - 1  and access point  112 . After associating with access point  112 , interface circuit  418  in access point  112  may provide a wake-up packet  416  for electronic device  110 - 1  that includes information specifying one or more services offered by access point  112 . After receiving wake-up packet  416 , main radio  410  (such as radio  114 - 1 ) in interface circuit  412  in electronic device  110 - 1  may transmit a wake-up request  420  to access point  112  that specifies one or more types of services  422  for which electronic device  110 - 1  will awaken main radio  410 . In response, interface circuit  418  provides a wake-up response  424  (such as an acknowledgment to wake-up request  420  to electronic device  110 - 1 ). In some embodiments, interface circuit  418  optionally provides a packet  426  (or a frame) to electronic device  110 - 1  that includes information specifying a transmit power  428  of interface circuit  418 . Main radio  410  may provide the information to a wake-up radio  414  (such as wake-up radio  118 - 1 ) in interface circuit  412 . 
     Subsequently, main radio  410  may transition to a low-power mode  430 . Next, interface circuit  418  may determine  432  to provide wake-up beacon  434  for wake-up radio  414 . For example, interface circuit  418  may determine  432  to provide wake-up beacon  434  when there is downlink traffic (such as data associated with a service) for electronic device  110 - 1 . Moreover, interface circuit  418  may provide wake-up beacon  434  associated with a predefined sub-channel in one or more channels in a band of frequencies, where wake-up beacon  434  is provided within an associated time interval (such as a keep-alive interval of access point  112 ). 
     In some embodiments, wake-up beacon  434  includes a field with information  436 . For example, information  436  may include channel information that specifies one or more second channels used by main radio  410 . Note that the one or more second channels may be different from the one or more channels. Alternatively or additionally, information  436  may include service information that specifies one or more types of services. For example, the service information may be hashed using a predefined hash function and/or the service information may include vendor information. Furthermore, information  436  may a transmit power of interface circuit  418 . The transmit power may be different from another wake-up beacon provided by interface circuit  418 . 
     After receiving wake-up beacon  434 , wake-up radio  414  may extract and analyze information  436 . Then, wake-up radio  414  may perform a remedial action. For example, wake-up radio  414  may provide, to main radio  410 , a wake-up signal  438  that transitions main radio  410  from low-power mode  430  to a higher-power mode  440  based at least in part on wake-up beacon  434 . Alternatively or additionally, wake-up radio  414  may determine a communication metric  442  based at least in part on a transmit power of wake-up beacon  434  (which may be transmit power  428  and/or the transmit power specified in information  436 ) and the RSS associated with wake-up beacon  434 . Based at least in part on communication metric  442  (such as a comparison of communication metric  442  and the RSS or when the RSS is a predefined fraction of transmit power  428 ), wake-up radio  414  may perform a scan  444  for a second wake-up beacon associated with a second electronic device in a second predefined sub-channel in one or more second channels in a second band of frequencies. 
     In some embodiments, when wake-up radio  414  does not receive a wake-up beacon (such as wake-up beacon  434  or a subsequent wake-up beacon) within a subsequent time interval, wake-up radio  414  may perform a scan for the second wake-up beacon associated with the second electronic device in the second predefined sub-channel in the one or more second channels in the second band of frequencies. 
       FIG. 5  presents a flow diagram illustrating an example method  500  for providing a wake-up beacon. This method may be performed by an electronic device, such as an interface circuit in access point  112  in  FIG. 1 . During operation, the interface circuit may determine to provide the wake-up beacon (operation  510 ) for a wake-up radio in a recipient electronic device with information indicating that the recipient electronic device is to awaken a main radio to receive a beacon with DFS information associated with a band of frequencies. Then, the interface circuit may provide the wake-up beacon (operation  512 ) for the wake-up radio in the recipient electronic device. 
       FIG. 6  presents a flow diagram illustrating an example method  600  for receiving a wake-up beacon. This method may be performed by a recipient electronic device, such as an interface circuit in electronic device  110 - 1  in  FIG. 1 . This interface circuit may include a wake-up radio and a main radio. During operation, the wake-up radio may receive the wake-up beacon (operation  610 ) associated with the electronic device (such as from the electronic device). Then, the wake-up radio may optionally analyze the wake-up beacon (operation  612 ) to determine whether to wake up the main radio. If yes (operation  612 ), the wake-up radio may provide, to the main radio, a wake-up signal (operation  614 ) that transitions (operation  616 ) the main radio from a low-power mode to a higher-power mode based at least in part on the wake-up beacon. Moreover, the main radio may receive a beacon (operation  618 ) associated with the electronic device (such as from the electronic device) with the DFS information associated with the band of frequencies. Otherwise (operation  612 ), the wake-up radio may not take further action (operation  620 ). 
     In some embodiments of methods  500  ( FIG. 5 ) and/or  600 , there may be additional or fewer operations. Moreover, the order of the operations may be changed, and/or two or more operations may be combined into a single operation or performed at least partially in parallel. 
     In some embodiments, at least some of the operations in methods  500  ( FIG. 5 ) and/or  600  are performed by an interface circuit in the electronic device. For example, at least some of the operations may be performed by firmware executed by an interface circuit, such as firmware associated with a MAC layer, as well as one or more circuits in a physical layer in the interface circuit. 
     The communication technique is further illustrated in  FIG. 7 , which presents a flow diagram illustrating an example of communication between electronic device  110 - 1  and access point  112 . Notably, after associating with access point  112 , main radio  410  in interface circuit  412  in electronic device  110 - 1  may transition to a low-power mode  710 . 
     Subsequently, interface circuit  418  may receive wireless signals  712  in a band of frequencies. Based at least in part on wireless signals  712 , interface circuit  418  may determine  714  that main radio  410  cannot continue to use at least a portion of the band of frequencies. Consequently, interface circuit  418  may determine  716  provide wake-up beacon  718  for a wake-up radio  414  in interface circuit  412  with information indicating that electronic device  110 - 1  is to awaken main radio  410  to receive a beacon  724  with DFS information  726  associated with the band of frequencies. Then, interface circuit  418  may provide wake-up beacon  718  for wake-up radio  414 . 
     Next, wake-up radio  414  may receive wake-up beacon  718 . In response, wake-up radio  414  may provide, to main radio  410 , a wake-up signal  720  that transitions main radio  410  from low-power mode  710  to a higher-power mode  722  based at least in part on wake-up beacon  718 . 
     Subsequently, interface circuit  418  may provide beacon  724  with DFS information  726  for main radio  410 . Based at least in part on DFS information  726 , main radio  410  may discontinue using at least a portion of the band of frequencies. For example, main radio  410  may switch  728  to another channel. 
     In some embodiments of the LP-WUR radio technology, the communication technique is used to maintain an existing connection between an access point and a recipient electronic device, to perform scans more efficiently and/or to reduce power consumption. When a main radio of a recipient electronic device (which is sometimes referred to as a ‘station’) is in deep sleep mode for a very long time, the recipient electronic device can roam out range of an associated access point and may need to transition to another access point. 
     In order to discover which access point to associate with, the recipient electronic device may need to wake up the main radio to perform network/service discovery, which usually involves scanning through multiple channels, and performing multiple frame exchanges. For example, as noted previously, each channel scan may take, e.g., 100 ms to receive one or more beacons. Moreover, the frames exchanged may include: a probe request/response, an authentication request/response, an association request/response; and/or a service information request/response. Waking up the main radio to conduct these frame exchanges can consume more power and may increase a delay in the operation of the recipient electronic device. Consequently, these challenges may degrade the communication performance, which can negatively impact user experience. 
     In order to address these challenges, in the communication technique a LP-WUR or wake-up beacon may be used to selectively wake-up the main radio in at least the recipient electronic device. As shown in  FIG. 8 , which presents a drawing illustrating an example of an interface circuit  412  in electronic device  110 - 1 , in the communication technique a LP-WUR  812  (such as wake-up radio  414 ) may be a companion radio to a main (Wi-Fi) radio  114 - 1  in interface circuit  412 . LP-WUR  812  may allow electronic device  110 - 1  to turn off main radio  114 - 1 , e.g., whenever possible. Moreover, LP-WUR  812  may wake up main radio  114 - 1  when wake-up beacon  434  (such as a LP-WUR beacon), sent from optional LP-WUR  810  or radio  114 - 2  in access point  112 , specifies electronic device  110 - 1 . Note that in some embodiments LP-WUR  812  is configured to receive wireless signals, while main radio  114 - 1  is configured to transmit and to receive wireless signals. In these ways, the power consumption of LP-WUR  812  may be very low, e.g., lower than Bluetooth Low Energy. LP-WUR  812  can operate in an always-on mode and/or in a duty-cycle mode. For example, in the duty-cycle mode, LP-WUR  812  may turn on or listen for a wake-up beacon from access point  112  based at least in part on a keep-alive interval of access point  112 . 
     In such a basic service set (BSS) initiated transition trigger, electronic device  110 - 1  may use wake-up beacon  434  (or its absence) to determine when to transition to a different BSS. For example, based at least in part on a maximum wake-up beacon interval (such as the keep-alive interval of access point  112 ), electronic device  110 - 1  may determine when to scan for another access point. Therefore, access point  112  may send a wake-up beacon or a regular WUR wake-up packet to electronic device  110 - 1  within this interval. If electronic device  110 - 1  does not receive anything from access point  112  within the time interval, then electronic device  110 - 1  may infer that it has roamed out of range of access point  112  and that it needs to discover another access point (e.g., it needs to start an active scan). 
     Moreover, in order to facilitate fast scanning in a LP-WUR, one or more, e.g., fixed 20 MHz channels (e.g., channel 6) may be defined in which access point  112  is allowed to send a wake-up beacon. Note that the wake-up beacon may be communicated in a narrow band (or sub-channel) or multiple narrow bands in such a 20 MHz channel. For example, a predefined sub-channel may include a middle, narrow tone in a 20 MHz channel. In some embodiments, the wake-up beacon includes information that specifies the operating channel information for the main radio and/or service/vendor information. As described further below, the wake-up beacon may include hashed information, such as a hashed value of a service set identifier (SSID) of electronic device  110 - 1 . 
     The LP-WUR may also facilitate service discovery. For example, simplified service information may be included in a wake-up beacon so electronic device  110 - 1  can discovery the service it desires without waking up the main radio. Moreover, the wake-up beacon may optionally include transmit power information to help electronic device  110 - 1  estimate the distance between access point  112  and electronic device  110 - 1  in order to facilitate BSS transition (e.g., to assist electronic device  110 - 1  in determining when to start an active scan). 
       FIG. 9  presents a drawing illustrating an example wake-up beacon  900  (which may be a special type of LP-WUR packet). This wake-up beacon may have a packet format that supports service discovery on or via a LP-WUR. Notably, wake-up beacon  900  may include and/all of: a wake-up-radio header  910 , a service-information field  912 , an optional transmit power  914 , and/or one or more additional fields  916 . Service-information field  912  may include information such as a service identifier  918  subfield and/or a vendor identifier  920  subfield for a provider of a service. The service identifier may be defined for different services. Thus, service identifier  918  may specify one or more types of services. For example, a cable service may use a service identifier of ‘0000’, a television service may use service identifier ‘0001’, etc. As noted previously, at least some of the information in wake-up beacon  900  (such as an SSID) may be hashed using a predefined hash function (e.g., the hash function may be defined in an IEEE standard, such as IEEE 802.11BA, so that access point  112  and electronic device  110 - 1  use the same hash function). This is because wake-up beacon  900  may have a low data rate (e.g., the modulation may include on-off keying or OOK, or similar modulation that has a very low data rate, such as, e.g., 250 kbps). Therefore, it may be advantageous for service-information field  912  to include a smaller number of bits. Consequently, one or more hash functions may be used to reduce the number of bits that are needed. 
     As noted previously, wake-up beacon  900  may facilitate service discovery and wake up. For example, access point  112  and electronic device  110 - 1  may negotiate which service identifier(s) and/or vendor identifier(s) will be used to wake up the main radio using a LP-WUR request frame and a LP-WUR response frame. When electronic device  110 - 1  sends the LP-WUR request, it may include the specific service identifier and/or the vendor identifier that it wishes to be notified using a wake-up beacon. In response, access point  112  may send a LP-WUR response frame. Subsequently, access point  112  may send a wake-up beacon to electronic device  110 - 1  when it has traffic for the particular services and/or vendors. Thus, electronic device  110 - 1  may only wake up its main radio for a particular service from a particular vendor, and more generally based at least in part on one or more wake-up criteria. Note that access point  112  can also send a broadcast LP-WUR packet to broadcast the one or more types of services provided by access point  112  to electronic devices  110  in its BSS. In other embodiments, the order of items in the wake-up beacon  900  can vary and additional and/or different items can be included. 
     In some embodiments, transmit-power information for access point  112  is used for the BSS transition. Notably, in order to facilitate the BSS transition, access point  112  can notify electronic device  110 - 1  of the transmission power used to send or transmit the LP-WUR packet or the wake-up beacon (such as optional transmit power  914  in wake-up beacon  900 ), and electronic device  110 - 1  can use the RSS together with the transmit power to calculate the path loss and distance between electronic device  110 - 1  and access point  112  (either of which may be examples of the communication metric) without waking up the main radio. Note that the transmit power used by access point  112  for communicating with the LP-WUR and the main radio can be different. 
     Alternatively or additionally, access point  112  can notify electronic device  110 - 1  of the transmit power for the wake-up beacons when electronic device  110 - 1  negotiates the LP-WUR mode with access point  112 , in which case the transmit power may have a semi-static value. However, in some embodiments the transmit power is included in the wake-up beacon, in which case the transmit power used to send the wake-up beacon or a LP-WUR packet can be dynamically changed for each wake-up beacon or LP-WUR packet.  FIG. 10  presents a drawing illustrating an example wake-up beacon  1000 , with a subfield that includes information specifying transmit power  1010 . 
     Using the transmit power and the RSS for the wake-up beacon, electronic device  110 - 1  may determine a communication metric. Moreover, based at least in part on the determined communication metric, electronic device  110 - 1  may determine it needs to perform an active scan. For example, access point  112  may notify electronic device  110 - 1  of its coverage distance (such as a distance of, e.g., 30 m) while they negotiate the LP-WUR mode (such as by exchanging the wake-up request and the wake-up reply). Then, when electronic device  110 - 1  determines that the distance to access point  112  is larger than the coverage distance, electronic device  110 - 1  may perform an active scan. Alternatively or additionally, electronic device  110 - 1  may determine whether to perform an active scan based at least in part on a transmit power and/or an RSS, such as based at least in part on a threshold of, e.g., −82 dBm, −90 dBm or −100 dBm. In other embodiments, the order of items in wake-up beacon  1000  can vary and additional and/or different items can be included. 
     In some embodiments, channel information is included in the wake-up beacon. For example, the channel information may indicate whether the main radio is on a different channel from the wake-up beacon. If the main radio and the LP-WUR do not use the same channel then the wake-up beacon may indicate channel number for the main radio.  FIG. 11  presents a drawing illustrating an example wake-up beacon  1100 , including an indication whether the main radio and the LP-WUR use the same channel  1110  and/or a main-radio channel  1112  (such as a channel number for the main radio). 
     Furthermore, in some embodiments the wake-up beacon includes a check-beacon field. Notably, because the wake-up beacon may have a very low data rate (such as a data rate associated with on-off keying modulation), it may be difficult to convey some system-update information in this radio, such as: channel switch announcement, quiet channel announcement etc. In order for electronic device  110 - 1  to get this system-update information, the wake-up beacon may include a check-beacon field to notify electronic device  110 - 1  to wake up the main radio to receive a beacon using the main radio. For example, the check-beacon field may include, e.g., a one-bit indication. This indication may indicate that access point  112  need to leave a DFS channel or has to quiet electronic device  110 - 1 . Thus, the wake-up beacon may indicate that the main radio needs to scan for DFS and/or needs to switch channels. In other embodiments, the order of items in wake-up beacon  1100  can vary and additional and/or different items can be included. 
     In summary, a wake-up beacon may be used to allow electronic device  110 - 1  to selectively transition to the higher-power mode and/or to enable fast BSS discovery via a LP-WUR. This wake-up beacon may be communicated using, e.g., a fixed 20 MHz channel. Alternatively, the wake-up beacon may be communicated using, e.g., a fixed narrowband WUR channel within the 20 MHz. Moreover, the wake-up beacon or another LP-WUR packet may include service information to help electronic device  110 - 1  discover services and/or to facilitate a BSS transition. The service information may include a service identifier and/or vendor information. Furthermore, the service information may be sent using one or more hash functions to reduce the number of bits. The specific service identifier and/or the vendor identifier that are used to wake up electronic device  110 - 1  can be requested and agreed with access point  112 . Additionally, the wake-up beacon may include channel information for the main radio, which may allow electronic device  110 - 1  to receive the main-radio beacon faster. In some embodiments, access point  112  provides the transmit power to electronic device  110 - 1  in order to help electronic device  110 - 1  decide whether to transition to a different access point or to which access point to transition. The transmit-power information can be sent to the main radio or can be included in the wake-up beacon, in which case the transmit power can be dynamically changed. In some embodiments, in order to help electronic device  110 - 1  discover system-update information, the wake-up beacon includes a check-beacon field. When the check-beacon field is set, electronic device  110 - 1  may need to wake up the main radio to receive the main beacon. 
     While access point  112  woke up main radio  114 - 1  using wake-up beacon  434  in the preceding example, in some embodiments wake-up beacon  434  may be used to wake up main radios (and, more generally, to convey information to) one or more recipient electronic devices. For example, during the communication technique, access point  112  may define a group of one or more recipient electronic devices and may use a single wake-up beacon to wake up the main radios in the group of recipient electronic devices. However, the recipient electronic devices in the group may not all have traffic when the group wake-up beacon is received. Consequently, the wake-up beacon may include a group wake-up indication map (WIM) that is carried or conveyed in the wake-up beacon. The group-WIM may be a bitmap that is used to indicate which recipient electronic devices are being awakened (such as a subset of the group of recipient electronic devices). For example, in some embodiments, if there are ten recipient electronic devices in a group, then the group-WIM may be, e.g., a 10-bit field. In other embodiments, other mapping schemes or techniques can be used. 
     In general, access point  112  may group recipient electronic devices into a wake-up group based at least in part on one or more criteria. For example, access point  112  may define a group based at least in part on recipient electronic devices that have similar keep-alive intervals and/or that have previously specific a common service for which they will wake up their main radios. 
     We now describe embodiments of an electronic device.  FIG. 12  presents a block diagram of an electronic device  1200  (which may be a cellular telephone, an access point, another electronic device, etc.) in accordance with some embodiments. This electronic device includes processing subsystem  1210 , memory subsystem  1212 , and networking subsystem  1214 . Processing subsystem  1210  includes one or more devices configured to perform computational operations. For example, processing subsystem  1210  can include one or more microprocessors, application-specific integrated circuits (ASICs), graphics processing units (GPUs), microcontrollers, programmable-logic devices, and/or one or more digital signal processors (DSPs). 
     Memory subsystem  1212  includes one or more devices for storing data and/or instructions for processing subsystem  1210  and networking subsystem  1214 . For example, memory subsystem  1212  can include dynamic random access memory (DRAM), static random access memory (SRAM), a read-only memory (ROM), flash memory, and/or other types of memory. In some embodiments, instructions for processing subsystem  1210  in memory subsystem  1212  include: program instructions or sets of instructions (such as program instructions  1222  or operating system  1224 ), which may be executed by processing subsystem  1210 . For example, a ROM can store programs, utilities or processes to be executed in a non-volatile manner, and DRAM can provide volatile data storage, and may store instructions related to the operation of electronic device  1200 . Note that the one or more computer programs may constitute a computer-program mechanism, a computer-readable storage medium or software. Moreover, instructions in the various modules in memory subsystem  1212  may be implemented in: a high-level procedural language, an object-oriented programming language, and/or in an assembly or machine language. Furthermore, the programming language may be compiled or interpreted, e.g., configurable or configured (which may be used interchangeably in this discussion), to be executed by processing subsystem  1210 . In some embodiments, the one or more computer programs are distributed over a network-coupled computer system so that the one or more computer programs are stored and executed in a distributed manner. 
     In addition, memory subsystem  1212  can include mechanisms for controlling access to the memory. In some embodiments, memory subsystem  1212  includes a memory hierarchy that comprises one or more caches coupled to a memory in electronic device  1200 . In some of these embodiments, one or more of the caches is located in processing subsystem  1210 . 
     In some embodiments, memory subsystem  1212  is coupled to one or more high-capacity mass-storage devices (not shown). For example, memory subsystem  1212  can be coupled to a magnetic or optical drive, a solid-state drive, or another type of mass-storage device. In these embodiments, memory subsystem  1212  can be used by electronic device  1200  as fast-access storage for often-used data, while the mass-storage device is used to store less frequently used data. 
     Networking subsystem  1214  includes one or more devices configured to couple to and communicate on a wired and/or wireless network (i.e., to perform network operations), including: control logic  1216 , an interface circuit  1218  and a set of antennas  1220  (or antenna elements) in an adaptive array that can be selectively turned on and/or off by control logic  1216  to create a variety of optional antenna patterns or ‘beam patterns.’ (While  FIG. 12  includes set of antennas  1220 , in some embodiments electronic device  1200  includes one or more nodes, such as nodes  1208 , e.g., a pad, which can be coupled to set of antennas  1220 . Thus, electronic device  1200  may or may not include set of antennas  1220 .) For example, networking subsystem  1214  can include a Bluetooth™ networking system, a cellular networking system (e.g., a 3G/4G/5G network such as UMTS, LTE, etc.), a universal serial bus (USB) networking system, a networking system based on the standards described in IEEE 802.11 (e.g., a Wi-Fi® networking system), an Ethernet networking system, and/or another networking system. 
     In some embodiments, networking subsystem  1214  includes one or more radios, such as a wake-up radio that is used to receive wake-up beacons, and a main radio that is used to transmit and/or receive frames or packets during a higher-power mode. The wake-up radio and the main radio may be implemented separately (such as using discrete components or separate integrated circuits) or in a common integrated circuit. 
     Networking subsystem  1214  includes processors, controllers, radios/antennas, sockets/plugs, and/or other devices used for coupling to, communicating on, and handling data and events for each supported networking system. Note that mechanisms used for coupling to, communicating on, and handling data and events on the network for each network system are sometimes collectively referred to as a ‘network interface’ for the network system. Moreover, in some embodiments a ‘network’ or a ‘connection’ between the electronic devices does not yet exist. Therefore, electronic device  1200  may use the mechanisms in networking subsystem  1214  for performing simple wireless communication between the electronic devices, e.g., transmitting advertising or beacon frames and/or scanning for advertising frames transmitted by other electronic devices. 
     Within electronic device  1200 , processing subsystem  1210 , memory subsystem  1212 , and networking subsystem  1214  are coupled together using bus  1228  that facilitates data transfer between these components. Bus  1228  may include an electrical, optical, and/or electro-optical connection that the subsystems can use to communicate commands and data among one another. Although only one bus  1228  is shown for clarity, different embodiments can include a different number or configuration of electrical, optical, and/or electro-optical connections among the sub systems. 
     In some embodiments, electronic device  1200  includes a display subsystem  1226  for displaying information on a display, which may include a display driver and the display, such as a liquid-crystal display, a multi-touch touchscreen, etc. Display subsystem  1226  may be controlled by processing subsystem  1210  to display information to a user (e.g., information relating to incoming, outgoing, or an active communication session). 
     Electronic device  1200  can also include a user-input subsystem  1230  that allows a user of the electronic device  1200  to interact with electronic device  1200 . For example, user-input subsystem  1230  can take a variety of forms, such as: a button, keypad, dial, touch screen, audio input interface, visual/image capture input interface, input in the form of sensor data, etc. 
     Electronic device  1200  can be (or can be included in) any electronic device with at least one network interface. For example, electronic device  1200  may include: a cellular telephone or a smartphone, a tablet computer, a laptop computer, a notebook computer, a personal or desktop computer, a netbook computer, a media player device, an electronic book device, a MiFi® device, a smartwatch, a wearable computing device, a portable computing device, a consumer-electronic device, an access point, a router, a switch, communication equipment, test equipment, as well as any other type of electronic computing device having wireless communication capability that can include communication via one or more wireless communication protocols. 
     Although specific components are used to describe electronic device  1200 , in alternative embodiments, different components and/or subsystems may be present in electronic device  1200 . For example, electronic device  1200  may include one or more additional processing subsystems, memory subsystems, networking subsystems, and/or display subsystems. Additionally, one or more of the subsystems may not be present in electronic device  1200 . Moreover, in some embodiments, electronic device  1200  may include one or more additional subsystems that are not shown in  FIG. 12 . Also, although separate subsystems are shown in  FIG. 12 , in some embodiments some or all of a given subsystem or component can be integrated into one or more of the other subsystems or component(s) in electronic device  1200 . For example, in some embodiments program instructions  1222  are included in operating system  1224  and/or control logic  1216  is included in interface circuit  1218 . 
     Moreover, the circuits and components in electronic device  1200  may be implemented using any combination of analog and/or digital circuitry, including: bipolar, PMOS and/or NMOS gates or transistors. Furthermore, signals in these embodiments may include digital signals that have approximately discrete values and/or analog signals that have continuous values. Additionally, components and circuits may be single-ended or differential, and power supplies may be unipolar or bipolar. 
     An integrated circuit (which is sometimes referred to as a ‘communication circuit’) may implement some or all of the functionality of networking subsystem  1214 . This integrated circuit may include hardware and/or software mechanisms that are used for transmitting wireless signals from electronic device  1200  and receiving signals at electronic device  1200  from other electronic devices. Aside from the mechanisms herein described, radios are generally known in the art and hence are not described in detail. In general, networking subsystem  1214  and/or the integrated circuit can include any number of radios. Note that the radios in multiple-radio embodiments function in a similar way to the described single-radio embodiments. 
     In some embodiments, networking subsystem  1214  and/or the integrated circuit include a configuration mechanism (such as one or more hardware and/or software mechanisms) that configures the radio(s) to transmit and/or receive on a given communication channel (e.g., a given carrier frequency). For example, in some embodiments, the configuration mechanism can be used to switch the radio from monitoring and/or transmitting on a given communication channel to monitoring and/or transmitting on a different communication channel. (Note that ‘monitoring’ as used herein comprises receiving signals from other electronic devices and possibly performing one or more processing operations on the received signals) 
     In some embodiments, an output of a process for designing the integrated circuit, or a portion of the integrated circuit, which includes one or more of the circuits described herein may be a computer-readable medium such as, for example, a magnetic tape or an optical or magnetic disk. The computer-readable medium may be encoded with data structures or other information describing circuitry that may be physically instantiated as the integrated circuit or the portion of the integrated circuit. Although various formats may be used for such encoding, these data structures are commonly written in: Caltech Intermediate Format (CIF), Calma GDS II Stream Format (GDSII) or Electronic Design Interchange Format (EDIF). Those of skill in the art of integrated circuit design can develop such data structures from schematic diagrams of the type detailed above and the corresponding descriptions and encode the data structures on the computer-readable medium. Those of skill in the art of integrated circuit fabrication can use such encoded data to fabricate integrated circuits that include one or more of the circuits described herein. 
     While the preceding discussion used a Wi-Fi communication protocol as an illustrative example, in other embodiments a wide variety of communication protocols and, more generally, wireless communication techniques may be used. Thus, the communication technique may be used in a variety of network interfaces. Furthermore, while some of the operations in the preceding embodiments were implemented in hardware or software, in general the operations in the preceding embodiments can be implemented in a wide variety of configurations and architectures. Therefore, some or all of the operations in the preceding embodiments may be performed in hardware, in software or both. For example, at least some of the operations in the communication technique may be implemented using program instructions  1222 , operating system  1224  (such as a driver for interface circuit  1218 ) or in firmware in interface circuit  1218 . Alternatively or additionally, at least some of the operations in the communication technique may be implemented in a physical layer, such as hardware in interface circuit  1218 . In some embodiments, the communication technique is implemented, at least in part, in a MAC layer and/or in a physical layer in interface circuit  1218 . 
     While examples of numerical values are provided in the preceding discussion, in other embodiments different numerical values are used. Consequently, the numerical values provided are not intended to be limiting. 
     While the preceding embodiments illustrated the use of a wake-up beacon that is communicated using Wi-Fi, in other embodiments of the communication technique Bluetooth Low Energy is used to communicate the wake-up beacon. Furthermore, the wake-up beacon may be communicated in the same or a different band of frequencies that the band(s) of frequencies used by the main radio. For example, the wake-up beacon may be communicated in one or more bands of frequencies, including: 900 MHz, 2.4 GHz, 5 GHz, 60 GHz, and/or a band of frequencies used by LTE. 
     In the preceding description, we refer to ‘some embodiments.’ Note that ‘some embodiments’ describes a subset of all of the possible embodiments, but does not always specify the same subset of embodiments. 
     The foregoing description is intended to enable any person skilled in the art to make and use the disclosure, and is provided in the context of a particular application and its requirements. Moreover, the foregoing descriptions of embodiments of the present disclosure have been presented for purposes of illustration and description only. They are not intended to be exhaustive or to limit the present disclosure to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Additionally, the discussion of the preceding embodiments is not intended to limit the present disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.

Metadata:
Filing Date: 20180620
Publication Date: 20210504
Grant Date: 20210504
Priority Date: 20170626
Inventors: LI, GUOQING
LIU, YONG
SHANI, OREN
HARTMAN, CHRISTIAAN A.
WANG, XIAOWEN
MUCKE, Christian W.
SHAH, TUSHAR R.
KNECKT, JARKKO L.
SEMERSKY, Matthew L.
BOGER, YOEL
PEERY, JOSEF
KUMAR, RAJNEESH
Assignee: APPLE INC
CPC Classifications: [{"code": "Y02D30/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/0229", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/0222", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W84/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/0222", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02D30/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/0235", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/0274", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/0229", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/0235", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/0225", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W52/0274", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/0235", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W52/0229", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04W84/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/0222", "inventive": true, "first": false, "tree": "[]"}, {"code": "Y02D30/70", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04W52/0274", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 62904250