Channel access for multi-user (MU) wake-up signal transmission using an FDMA scheme

Abstract

A method of radio communication, the method comprising: at an access point (AP), receiving a first wake-up radio (WUR) setup request from a first station (STA), the first WUR setup request comprising an indication that the first STA is ready to resolve a multi-user (MU) WUR packet transmitted in frequency division multiple access (FDMA); in response to the WUR establishment request, sending a first WUR establishment response to the first STA, wherein the first WUR establishment response specifies a first frequency channel offset relative to a primary channel of a frequency band, and the first frequency channel offset corresponds to a first frequency channel included in the frequency band; and Sending a first MU-WUR packet to a plurality of STAs including the first STA using FDMA, wherein the first MU-WUR packet comprises a plurality of wake-up signals transmitted using different frequency channels included in the frequency band, the plurality of wake-up signals comprising a first wake-up signal transmitted in the first frequency channel and operative to activate a main radio located in the first STA; the method further comprising: in response to a second WUR setup request from a second STA, sending a second WUR setup response to the second STA, wherein the second WUR setup response assigns a second frequency channel to be used to transmit a second wake-up signal to the second STA, wherein transmitting the first MU-WUR packet further comprises transmitting the first MU-WUR packet without using the second frequency channel and without a wake-up signal directed to the second STA in response to an indication that the second frequency channel is busy or a determination that no wake-up signal is pending for transmission to the second STA.

Description

Cross-reference to related applications

[0001] This application claims priority to U.S. Provisional Patent Application No. 62 / 645,871, entitled "CHANNEL ACCESS PROCEDURE FOR WUR FDMA TRANSMISSION," filed on March 21, 2018; and U.S. Provisional Patent Application No. 62 / 661,660, entitled "CHANNEL ACCESS PROCEDURE FOR WUR FDMA TRANSMISSION," filed on April 24, 2018. Technical area

[0002] Embodiments of the present disclosure relate generally to the field of network communications, and more particularly to the field of communication protocols in radio communications for wake-up radios. Background of the invention

[0003] Wireless local area networks (WLANs) and mobile communication devices have become increasingly ubiquitous, including smartphones, wearable devices, various sensors, the Internet of Things (IoTs), and others. With their overall size limited by portability requirements, such a communication device is typically powered by a built-in battery with a limited charge capacity. Most of the operational loads of a communication device can be communication-related, and therefore, the wireless radio device is a major power consumer, as it must remain operational to ensure immediate responses to data communication requests.

[0004] To reduce power consumption by wireless radios, some communication devices include a main radio and a low-power wake-up radio (WUR). When not involved in data communication tasks, the main radio can be placed in a power-saving state, such as sleep mode, or even turned off. On the other hand, the low-power wake-up radio (WUR) remains active and operates to wake the main radio whenever the WUR receives a data communication request directed to the main radio, such as the request transmitted in a wake-up signal sent by a Wi-Fi access point (AP).

[0005] Compared to a main radio with high-rate data communication capabilities and complex processing functions, a WUR is a low-cost, low-power radio, yet still sufficient to receive and process a wake-up signal and activate the main radio accordingly. For example, the nominal power consumption of a WUR can be 0.5-1 mW or even less.

[0006] The Institute for Electronic and Electrical Engineers (IEEE) 802.11 family specifies technical standards for wireless LANs. The latest generations of IEEE 802.11 standards adopt multi-user (MU) communication schemes, such as multi-user multiple-input multiple-output (MU-MIMO) and orthogonal frequency division multiple access (OFDMA). It is desired to develop FDMA transmission mechanisms that enable simultaneous wake-up signal communication between a transmitter and multiple WUR receivers. Waking up multiple stations simultaneously can advantageously facilitate subsequent OFDMA data transmission.

[0007] Traditionally, when transmitting an MU packet, the frequency channels used in the transmission must be adjacent. Thus, if a particular non-primary channel is unreachable or otherwise unused, some other channels may also be unused, even if they are available and have scheduled transmission tasks. This undesirably limits channel utilization efficiency and hinders the associated ODFMA data transmission.

[0008] US 2018 / 0041961 A1 discloses a negotiation procedure for a low-power wake-up radio device. Furthermore, US 2016 / 0227569 A1 discloses a method and devices that can enable parallel multi-subscriber channel access. Summary of the invention

[0009] Accordingly, systems and methods disclosed herein provide protocols for wake-up signal communication that can improve frequency channel utilization efficiency when transmitting a multi-user (MU) wake-up packet (or herein, a "WUR packet") to multiple communication devices in a wireless local area network (WLAN). Two methods and one device according to the claimed invention are defined in the independent claims. The dependent claims contain advantageous developments of the invention.

[0010] Embodiments of the present disclosure use the frequency division multiple access (FDMA) scheme to transmit an MU-WUR packet, for which each station (STA) informs an access point (AP) of its ability to receive an FDMA MU-WUR packet. All reachable frequency channels can be efficiently used in FDMA transmission due to channel puncturing of the unreachable channels or carrying filler signals in the frequency channels that do not have outstanding wake-up signals. In particular, in the wake-up setup phase, an STA negotiates with the AP regarding wake-up signal communication and informs the AP of its ability to resolve an MU-WUR packet transmitted in FDMA. In particular, the STA indicates whether it is configured to receive a WUR radio signal and an MU-WUR frame transmitted in the same channel or in different channels.To multiple STAs indicating the latter, the AP sends a radio signaling frame over the WUR operating class and WUR channels to be used for transmitting a subsequent wake-up frame. The AP also individually sends a WUR setup response frame to an STA indicating a channel offset with respect to the primary channel.

[0011] In some embodiments of punctured-FMDA MU wake-up operations, if a WUR channel assigned to an STA is busy (or otherwise unreachable), or there is no outstanding wake-up signal for the STA (or the channel is "idle"), the AP may transmit an MU WUR packet that includes wake-up signals in all idle channels. That is, non-adjacent frequency channels are used for transmission, excluding busy or idle channels. However, the WUR packet does not include a wake-up signal destined for the STA, and no signal is transmitted in the busy WUR channel.

[0012] In some other embodiments, if there is no pending wake-up signal for the STA, the AP may transmit an MU-WUR packet including only a legacy preamble intended for the STA but no legacy wake-up signal intended for it, along with the preambles and wake-up signals intended for other STAs. In still other embodiments, if there is no pending wake-up signal for the STA, the AP may transmit an MU-WUR packet including a legacy preamble followed by an invalid wake-up signal intended for the STA, along with the preambles and wake-up signals intended for other STAs.

[0013] According to embodiments of the present disclosure, by puncturing or filling fill signals on busy or idle channels, all other frequency channels can be efficiently utilized in FDMA MU-WUR packet transmission, including channels located farther away from the primary channel than the busy or idle channels. As a result, frequency channel utilization efficiency can be significantly improved.

[0014] The foregoing is a summary and thus necessarily contains simplifications, generalizations, and omissions of detail; consequently, those skilled in the art will recognize that the summary is illustrative only and is not intended to be limiting in any way. Other aspects, inventive features, and advantages of the present invention, as defined only by the claims, will become apparent in the non-limiting detailed description set forth below. Short description of the drawings

[0015] Embodiments of the present invention will be better understood by reading the following detailed description in conjunction with the accompanying figures, in which like reference numerals designate like elements. Fig. 1 illustrates an exemplary WLAN in which an AP sends a MU wake-up packet in FDMA to wake up the main radios of multiple non-AP STAs, according to an embodiment of the present disclosure. Fig. 2 shows timing diagrams illustrating an exemplary communication process between an AP and a STA in FDMA MU-WUR operation according to an embodiment of the present disclosure. Fig. 3 shows timing diagrams illustrating exemplary channel usage and operating states of an AP and multiple STAs in a WUR mode according to an embodiment of the present disclosure. Fig. 4A and Fig. 4B shows the one or more subchannels (WUR channels) that can be used for wake-up signal transmissions in a 20 MHz frequency channel. Fig. 4C illustrates the format of an exemplary MU-WUR packet transmitted in FDMA according to an embodiment of the present disclosure. Fig. Figure 5 illustrates the channel usage in an FDMA MU-WUR packet transmission according to the state of the art. Fig. 6A illustrates exemplary frequency usage in a punctured FDMA WU wake-up operation according to an embodiment of the present disclosure. Fig. 6B illustrates exemplary frequency usage in another punctured FDMA WU wake-up operation according to an embodiment of the present disclosure. Fig. 7 illustrates exemplary frequency usage in yet another punctured FDMA WU wake-up operation according to an embodiment of the present disclosure. Fig. 8A illustrates exemplary frequency usage in an FDMA WU wake-up operation with an invalid wake-up signal transmitted in a WUR channel, according to an embodiment of the present disclosure. Fig. 8B illustrates exemplary frequency usage in an FDMA-MU wake-up operation combining the puncturing scheme and the invalid signal scheme, according to an embodiment of the present disclosure. Fig. 9 is a flowchart illustrating an exemplary process of performing an FDMA WUR operation according to an embodiment of the present disclosure. Fig. 10 is a block diagram illustrating an exemplary radio communication device 1000 capable of generating and transmitting MU wake-up packets according to an embodiment of the present disclosure. Detailed description

[0016] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Although the invention will be described in connection with the preferred embodiments, it will be understood that these are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of embodiments of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be recognized, however, by one of ordinary skill in the art that the present invention may be practiced without these specific details.In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of embodiments of the present invention. Although a method may be described as a sequence of numbered steps for clarity, the numbering does not necessarily dictate the order of the steps. It should be understood that some of the steps may be omitted, performed in parallel, or performed without the requirement of adhering to a strict order. The drawings depicting embodiments of the invention are partial diagrams and not to scale, and in particular, some of the dimensions are exaggerated for clarity of presentation and are shown in the figures.Similarly, although the views in the drawings generally show similar orientations for ease of description, this representation in the figures is largely arbitrary. In general, the invention can be operated in any orientation.

[0017] Embodiments of the present disclosure are described in detail with reference to the Physical Layer Convergence Protocol (PLCP) protocol data unit (PPDU) structures as defined in the High-Efficiency (HE) WLAN-based IEEE 802.11 family of specifications and standards. However, the present disclosure is not limited to specific packet or frame formats or structures, nor to any particular industry standards or specifications.

[0018] The communication devices according to embodiments of the present disclosure may include main radio devices configured to use one or more wireless communication technologies, such as Bluetooth®, WI-FI and / or cellular technologies, e.g., LTE, 4G, 5G, etc.

[0019] Overall, embodiments of the present disclosure provide communication protocols for frequency division multiple access (FDMA) multi-user (MU) wake-up signaling communications. In the wake-up setup phase, a STA may negotiate with an access point (AP) regarding various aspects of the wake-up signaling communication, and in particular, inform the AP that it can resolve a MU WUR packet transmitted in FDMA. Accordingly, the AP assigns a frequency channel (including a WUR channel) to the STA in a WUR setup response frame indicating a channel offset relative to a WUR primary channel.Furthermore, if a WUR channel assigned to an STA is unreachable or there is no pending wake-up signal for the STA, no wake-up signal will be included on the WUR channel assigned to the STA, while all other assigned channels can still be used to transmit scheduled wake-up signals. During such a transmission, an unreachable channel may be punctured; and a reachable channel that has no pending wake-up signal may be used to transmit an invalid wake-up signal or a preamble following the existing system followed by no wake-up signal.

[0020] Fig. 1 illustrates an exemplary WLAN 100 in which an AP may transmit an MU wake-up packet 110 in FDMA to wake up the main radios of multiple non-AP STAs, according to an embodiment of the present disclosure. The AP 110 and the STAs 120, 130, and 140 may belong to a Basic Service Set (BSS). Each of the STAs 120, 130, and 140 includes a main radio and a low-power WUR (LP-WUR). For example, to conserve power, the main radio 122 in the STA 120 may be turned off or placed in a sleep or otherwise inactive state. In such a state, the main radio 122 is unable to receive or transmit packets. While the main radio device is in the inactive state, the WUR 121 remains active and can receive a wake-up signal sent by another device, e.g., the AP 110.The WUR 121 operates in response to a received wake-up signal to switch the main radio back to an active state.

[0021] According to embodiments of the present disclosure, STAs may inform the AP if they have the channel switching capability of participating in an FDMA MU wake-up operation. Specifically, an STA indicates whether it is configured to receive WUR radio signals and wake-up frames transmitted in different channels. For an STA with such a capability, the AP sends a WUR setup response indicating a WUR channel assigned to the STA. The WUR channel may be indicated in a representation of an offset from a primary channel of the WUR.

[0022] It is recognized that a specific WUR channel can be assigned to a STA through a negotiation and / or training process between the STA and the AP. A negotiation process can be performed by a master radio on the STA while it is in an active state or by the WUR itself. Wake-up signals for a particular STA are fixed to the negotiated WUR channel, which can be changed through a new negotiation and / or training process according to a specific negotiation protocol.

[0023] The AP 110 can then generate an MU wake-up packet 111 containing the wake-up signals for multiple designated STAs that have channel switching capability. In some embodiments, each wake-up signal can be modulated using on-off keying (OOK) modulation in the assigned WUR channel. By using an MU-WUR packet, more than one STA can receive wake-up signals at the same time and each process its own wake-up signals independently and simultaneously. From an AP perspective, this can advantageously and significantly reduce the number of channel accesses for the AP and reduce the latency of waking up multiple STAs.

[0024] A WUR (e.g., LP-WUR 121) receiving the MU wake-up packet may determine whether the packet contains a wake-up signal intended for the present STA based on whether the carrier wave is present in the expected WUR channel.

[0025] In some embodiments, a WUR itself may have a sleep protocol. For example, a duty cycle is defined for the WUR, allowing it to periodically remain awake for a specific time window ("WUR wake window"), followed by a sleep window ("WUR sleep window"). The AP may send wake-up frames to the STA during a WUR wake window. The wake-up window duration may be determined based on the transmission duration of a wake-up signal, the number of STAs that have WURs in the BSS, and the WUR's power consumption requirements. The WUR sleep protocol may be determined through a negotiation or coordination process with the AP.

[0026] Before generating an MU wake-up packet, the AP may receive an indication that certain assigned WUR channels are busy, or may determine that no wake-up signal is pending for a particular STA, e.g., according to its duty cycle. According to embodiments of the present disclosure, in such a case, the AP may send an MU WUR packet that includes wake-up signals to all idle channels while the busy or idle channels are not used. However, the WUR packet does not include a wake-up signal intended for the STA. In some other embodiments, if there is no pending wake-up signal for the STA, the AP may send an MU WUR packet that includes only a preamble intended for the STA according to the existing system but no wake-up signal, along with the preambles and wake-up signals intended for other STAs.In still other embodiments, if there is no outstanding wake-up signal for the STA, the AP may send an MU-WUR packet including a preamble according to the existing system followed by an invalid wake-up signal intended for the STA, along with the preambles and wake-up signals intended for other STAs.

[0027] By puncturing or filling invalid wake-up signals on busy or idle channels, all available frequency channels can be advantageously and efficiently used in FDMA MU-WUR packet transmission, including channels located farther away from the primary channel than the busy or idle channels. As a result, frequency channel utilization efficiency can be significantly improved.

[0028] Fig. 2 shows timing diagrams illustrating an exemplary communication process between an AP and a STA in FDMA-MU WUR operation according to an embodiment of the present disclosure. To enable FDMA-MU wake-up mode, station STA1 sends a WUR setup request frame 211 to the AP, which includes an indication of whether WUR channel switching capability is enabled, e.g., whether STA1 is capable of receiving WUR radio beacon frames and wake-up frames transmitted in different channels. WUR radio beacon frames are typically transmitted in the same channel to multiple STAs. In some embodiments, the switchability indication is included in a WUR parameter field of the WUR setup request frame. However, it is recognized that the discussions of specific formats, fields, and values ​​of specific fields herein are exemplary only.The various indications and messages disclosed herein may be placed in any suitable field of a package or frame without departing from the scope of the present disclosure.

[0029] When an AP receives a WUR Establishment Request indicating that the STA lacks channel switching capability, the AP provides a WUR operating class and a WUR channel number so that the STA can receive both WUR radio signals and wake-up frames. The WUR operating class and WUR channel number can be included in a WUR mode element of a WUR Establishment Response frame in accordance with IEEE 802.11 standards and specifications.

[0030] On the other hand, if an AP receives a WUR setup request indicating that the STA has channel switching capability, the AP uses a radio beacon frame to provide the WUR operating class and WUR channel number so that the STA receives the WUR radio beacon frames. The AP uses a WUR setup response frame to specify a WUR channel offset relative to the WUR primary channel, which corresponds to a channel used to transmit wake-up frames to the STA.

[0031] In one example, the WUR channel offset is encoded as follows: "0" represents the WUR primary channel; "1" represents the first upper 20 MHz channel relative to the WUR primary channel; "2" represents the first lower 20 MHz channel relative to the WUR primary channel; "3" represents the second upper 20 MHz channel relative to the WUR primary channel; "4" represents the second lower 20 MHz channel relative to the WUR primary channel; "5" represents the third upper 20 MHz channel relative to the WUR primary channel; and "6" represents the third lower 20 MHz channel relative to the WUR primary channel.

[0032] In some other embodiments, an assigned WUR channel is indicated by a combination of a WUR bandwidth indication and a WUR offset indication. For example, the WUR setup response frame includes an indication of the WUR bandwidth associated with the AP, e.g., indicating 40 MHz or 80 MHz. More specifically, if the WUR operating class has an indication of 40 MHz, the WUR channel offset field is set to "0" for the lower 20 MHz and "1" for the upper 20 MHz. If the WUR operating class has an indication of 80 MHz, the WUR channel offset field is set to "0" for the first 20 MHz, "1" for the second 20 MHz, "2" for the third 20 MHz, and "3" for the fourth 20 MHz.

[0033] The WUR offset indications may be included in a WUR channel offset field, a WUR operating class field, or a WUR channel number field of the WUR setup response frame in accordance with IEEE 802.11 standards and specifications.

[0034] In the illustrated example, when an AP receives the WUR setup request 211, which indicates that the STA has channel switching capability, the AP returns an acknowledgment frame (ACK) 221 and a WUR setup response frame 222. The response frame 222 specifies an assigned WUR offset, as described above.

[0035] STA 1 then sends an ACK 212 and a QoS Null frame 213 to the AP, and the AP returns an ACK 223. Once WUR mode is established, the STA transitions to WUR mode, in which the main radio is turned off (block 214), and the WUR receiver is periodically activated according to the negotiated duty cycle (blocks 232 and 233) to listen for WUR frames.

[0036] The AP can send WUR frames (e.g., 224) to the STA while its WUR receiver is enabled. Once the STA receives a wake-up frame addressed to itself, it can transition from power-save mode to wake-up by sending a trigger frame (e.g., QoS-null) or a PS-Poll frame 214. In response, the AP sends an ACK 226 and begins sending data 227 to the STA's main radio. After receiving the data, the STA reenters WUR mode (blocks 234 and 235).

[0037] Fig. Figure 3 shows timing diagrams illustrating exemplary channel usage and operating states of an AP and multiple STAs in a WUR mode according to an embodiment of the present disclosure. After the WUR mode setup process is completed, the AP periodically transmits the MU-WUR frames to stations STA1~STA4, assuming they have the same duty cycle. During the WUR duty cycle, the main radios of the STAs remain off, and the WUR receivers of the STAs wake up to listen on the respective assigned WUR channels.

[0038] In this example, all assigned WUR channels are accessible for FDMA WUR frame transmissions. The STA1 WUR listens on the primary 20 MHz channel corresponding to a coded offset of "0"; the STA2 WUR listens on the secondary 20 MHz channel corresponding to a coded offset of "1"; and the STA3 and STA4 WURs listen on the secondary 40 MHz channel corresponding to coded offsets of "2" and "3."

[0039] Generally, a WUR operates to achieve area coverage of the entire WLAN, preferably in a narrow band. For example, a frequency bandwidth for transmitting a wake-up signal can be 1 MHz, 2 MHz, 4 MHz, or 5 MHz. As described below, a frequency channel normally allocated for data transmission can be divided into multiple subchannels, and selected subchannels can be used to transmit wake-up signals. Fig. 4A and Fig. 4B shows the one or more subchannels (WUR channels) that can be used for wake-up signal transmissions in a 20 MHz frequency channel. Fig. Figure 4A shows that a single 4 MHz subchannel contained within the 20 MHz channel is used for wake-up signal transmissions at an 8 MHz spacing from the ends of the 20 MHz channel. Fig. Figure 4B shows that two 4 MHz channels included in the 20 MHz channel, with a 4 MHz spacing between them, are used for wake-up signal transmissions. However, it is recognized that any suitable bandwidth may be used to transmit a wake-up signal without departing from the scope of the present disclosure.

[0040] Fig. 4C illustrates the format of an exemplary MU-WUR packet transmitted in FDMA according to an embodiment of the present disclosure. The MU wake-up packet 400 includes a legacy system preamble 410 and payload 420 modulated in on / off-key (OOK) modulation. The legacy system preamble may be used to deceive legacy system devices that are not equipped to process MU wake-up packets, for example, because they lack a WUR. The legacy system preamble may carry information about the length of the MU-WUR packet and indicate to a legacy system device receiving the packet to refrain from transmitting signals during packet transmission.The device corresponding to the legacy system can be a high-throughput (HT) device, a very high-throughput (VHT) device, a high-efficiency (HE) device, as defined in various IEEE 802.11 standards, or another type of device corresponding to the legacy system. The preamble according to the legacy system can include a short training field (L-STF), a long training field (L-LTF), and a signaling field (L-SIG).

[0041] Additionally, the payload 420 may include a WUR preamble 421, a MAC header 422, a frame body 423 containing a wake-up frame, and a frame check sequence (FCS) 424. The WUR preamble may include a wake-up signature sequence, a receive STA ID, a BSS ID, an AP ID, a data part, an optional length part, and / or any other suitable fields and information. In some embodiments, instead of specific STA IDs, an MU wake-up packet includes a group ID of a group of STAs to identify the receive STAs, e.g., all STAs in a home network. Well-known fields and information that may be included in MU wake-up packets are omitted from the figures and description for brevity.

[0042] Traditionally, FDMA MU wakeup operations are subject to several conditions that require the used frequency channels to be adjacent. Thus, if there is an indication from the physical layer (PHY) that the secondary 20 MHz is busy or otherwise unreachable, the AP cannot send wakeup frames to the STAs that have the negotiated WUR channels in the secondary 40 MHz or 80 MHz channel, even though those channels are idle and available. Similarly, if there is an indication from the physical layer (PHY) that the secondary 40 MHz is unreachable, the AP cannot send wakeup frames to the STAs that have the negotiated WUR channels in the secondary 80 MHz channel, even though they are idle and available.Furthermore, if the AP does not have a pending wake-up frame to an STA that has the negotiated WUR channel in the secondary 20 MHz, the AP also cannot send wake-up frames to STAs that have the negotiated WUR channels in the secondary 40 MHz or 80 MHz. If the AP does not have a pending wake-up frame to an STA that has the negotiated WUR channel in the secondary 40 MHz, the AP also cannot send wake-up frames to STAs that have the negotiated WUR channels in the secondary 80 MHz.

[0043] Fig. Figure 5 illustrates the channel usage in an FDMA MU-WUR packet transmission according to the prior art. The 80 MHz frequency band is divided into a primary 20 MHz channel 501 assigned to an STA1, a secondary 20 MHz channel 502 assigned to an STA2, and a secondary 40 MHz channel 503 assigned to an STA3 and an STA4 (not explicitly shown). As in Fig. 4A and Fig. As shown in Figure 4C, a WUR channel can be located within each assigned channel. Before the FDMA transmission, the AP receives an indication that the secondary 20 MHz is occupied or there is no outstanding wake-up signal for STA2. Therefore, in the next MU packet transmission, the secondary 20 MHz is unused. This wastes the secondary 40 MHz channel, even though it is idle and has the outstanding tasks of transmitting wake-up signals to STA3 and STA4.

[0044] According to some embodiments of the present disclosure, when a non-primary channel is busy or there is no corresponding pending wake-up frame, an AP does not transmit a signal in the corresponding WUR channel, but may still transmit the wake-up signal on other idle channels, or referred to herein as "punctured" FDMA MU wake-up operation.

[0045] Fig. 6A illustrates exemplary frequency usage in a punctured FDMA WU wake-up operation according to an embodiment of the present disclosure. Before the FDMA transmission, the AP receives an indication that the secondary 20 MHz 602 is busy or there is no outstanding wake-up signal for STA2. Therefore, in the FDMA transmission, the secondary 20 MHz 602 is unused. However, the WUR channels 603 and 604 in the secondary 40 MHz are still used to transmit wake-up signals for STA3 and STA4, even though they are not contiguous in frequency range with the primary 20 MHz. Fig. 6B illustrates exemplary frequency usage in another punctured FDMA WU wake-up operation according to an embodiment of the present disclosure. In this scenario, the WUR channels 652 assigned to STA2 and STA3 are busy or there are no outstanding wake-up frames for them. Therefore, in FDMA transmission, the WUR channels 652 are unused for any signal, including the secondary 20 MHz and the lower 20 MHz of the secondary 40 MHz. However, the WUR channels 651 for STA1 and 654 for STA4 are used to transmit wake-up signals.

[0046] According to some other embodiments of the present disclosure, if there is no pending wake-up frame for an assigned WUR channel, the AP does not transmit a wake-up signal, but still transmits a preamble according to the existing system in the WUR channel. Fig. Figure 7 illustrates exemplary frequency usage in yet another punctured FDMA WU wake-up operation according to an embodiment of the present disclosure. In this scenario, WUR channel 702 is unoccupied, but there is no pending frame for STA2. The AP transmits the wake-up signals following the legacy preambles in WUR channels 701, 703, and 704, assigned to STA1, STA2, and STA3, respectively. The WUR channel assigned to STA2 is used to transmit the legacy preamble, which is not followed by a wake-up signal.

[0047] According to some other embodiments of the present disclosure, if there is no pending wake-up frame for an assigned WUR channel, the AP does not transmit a wake-up signal, but instead transmits a preamble according to the existing system followed by an invalid wake-up signal in the WUR channel. Fig. 8A illustrates exemplary frequency usage in an FDMA WU wake-up operation with an invalid wake-up signal transmitted in a WUR channel, according to an embodiment of the present disclosure. In this scenario, channels 802 and 803 are unoccupied, but there are no pending wake-up frames for STA2 or STA3. The AP transmits the wake-up signals following the legacy preambles in WUR channels 801 and 804, assigned to STA1 and STA4, respectively. The WUR channels assigned to STA2 and STA3 are used to transmit both an invalid wake-up signal and the legacy preambles. An invalid wake-up signal may be a signal that does not wake up the corresponding master radios, such as a wake-up radio signal frame or a wake-up detect frame.

[0048] This mechanism also applies to the scenario where the WUR primary channel has no pending wake-up frames. Thus, the WUR channel can transmit an invalid signal in the primary 20 MHz band, while all other reachable WUR channels with pending wake-up frames can be used to transmit the wake-up signals. Fig. 8B illustrates exemplary frequency usage in an FDMA WU wake-up operation combining the puncturing scheme and the invalid signal scheme, according to an embodiment of the present disclosure. WUR channels 851 and 854 transmit the wake-up signals for STA1 and STA4, respectively. WUR channel 852 in the secondary 20 MHz transmits a legacy preamble intended for STA2 without a wake-up signal. WUR channel 853 in the lower 20 MHz of the secondary 40 MHz transmits both a legacy preamble and an invalid wake-up signal. In a different combination, when WUR channel 852 is unreachable, it remains unused, and WUR channel 853 transmits an invalid signal in the FDMA WU wake-up operation.

[0049] Fig. 9 is a flowchart illustrating an exemplary process 900 of performing FDMA WUR operation according to an embodiment of the present disclosure. The process 900 may be performed by an AP device. At 901, the AP receives WUR setup requests from a plurality of STAs, each request indicating whether the STA is capable of resolving MU-FDMA WUR packets or whether it has WUR channel switching capability. At 902, the AP sends WUR setup responses individually to the STAs specifying an allocation of WUR channels, e.g., in the form of a frequency offset. At 903, the AP receives one or more indications identifying one or more busy frequency channels. At 904, the AP identifies the STAs that have outstanding wake-up signals, e.g., based on their respective negotiated duty cycles.At 905, the AP generates an MU wake-up packet including the wake-up signals and invalid wake-up signals in respective WUR channels, as described in more detail with reference to FIG. Fig. 6A ∼ Fig. 8. At 906, the AP sends the MU wake-up packet to the majority of STAs in the FDMA, while some WUR channels may be punctured, as described in more detail with reference to Fig. 6A ∼ Fig. 8 described.

[0050] Fig. 10 is a block diagram illustrating an exemplary wireless communication device 1000 capable of generating and transmitting MU wake-up packets according to an embodiment of the present disclosure. The communication device 1000 may be an AP, a repeater, or a non-AP device having a transceiver configured for data communication, e.g., a general-purpose computer, a smartphone, a portable tablet device, a sensor used in the Internet of Things (IoT), etc.

[0051] The device 1000 comprises a main processor 1030, a memory 1020, and a transceiver 440 connected to an array of antennas 1001-1004. The memory 1020 comprises a wake-up manager 1021, which contains processor-executable instructions for generating both wake-up signals and configurations of other parts of MU wake-up packets, as described in more detail with reference to Fig. 1 ∼ Fig. 8A. Wake-up manager 1021 also stores other information related to wake-up packet generation and organization, such as the STA IDs, STA group IDs, sleep protocols of the main radios and WURs of the STAs, negotiation protocols, frequency subchannel assignment to the respective WURs, MU wake-up packet formats, and so on. In some other embodiments, wake-up manager 1021 is stored in a memory within transceiver 1040.

[0052] The transceiver 1040 includes an OOK baseband module 1041, a pulse shaping module 1042, and a digital mixing module 1043, which operate to generate OOK wake-up signals for transmission in FDMA. However, other well-known suitable modulation mechanisms may be used without departing from the scope of the present disclosure. The transceiver 1040 further includes various transmission path modules configured to generate each portion of an MU wake-up packet or a data packet or other type of communication transmission unit. For example, it includes a transmit first-in-first-out (TX-FIFO) 1044, an encoder 1046, a scrambler 1043, an interleaver 1048, a constellation allocator 1047, an inverted discrete Fourier transform (IDFT) unit 1049, and a Gl and windowing insertion module 1050.

[0053] Although certain preferred embodiments and methods have been disclosed herein, it will be apparent to those skilled in the art from the foregoing disclosure that variations and modifications of such embodiments and methods may be made without departing from the spirit and scope of the invention. It is intended that the invention be limited only to the extent permitted by the appended claims and the rules and principles of applicable law.

Claims

[1] A method of radio communication, the method comprising: at an access point (AP), receiving a first wake-up radio (WUR) setup request from a first station (STA), the first WUR setup request comprising an indication that the first STA is ready to resolve a multi-user (MU) WUR packet transmitted in frequency division multiple access (FDMA); in response to the WUR establishment request, sending a first WUR establishment response to the first STA, wherein the first WUR establishment response specifies a first frequency channel offset relative to a primary channel of a frequency band, and the first frequency channel offset corresponds to a first frequency channel included in the frequency band; and Sending a first MU-WUR packet to a plurality of STAs including the first STA using FDMA, wherein the first MU-WUR packet comprises a plurality of wake-up signals transmitted using different frequency channels included in the frequency band, the plurality of wake-up signals comprising a first wake-up signal transmitted in the first frequency channel and operative to activate a main radio located in the first STA; the method further comprising: in response to a second WUR setup request from a second STA, sending a second WUR setup response to the second STA, wherein the second WUR setup response assigns a second frequency channel to be used to transmit a second wake-up signal to the second STA, wherein transmitting the first MU-WUR packet further comprises transmitting the first MU-WUR packet without using the second frequency channel and without a wake-up signal directed to the second STA in response to an indication that the second frequency channel is busy or a determination that no wake-up signal is pending for transmission to the second STA. [2] The method according to claim 1, wherein the first and second frequency channels are non-primary channels of the frequency band, and further wherein the second frequency channel is arranged between the first frequency channel and the primary channel. [3] The method of claim 1, further comprising: in response to a third WUR setup request from a third STA, sending a third WUR setup response to the third STA, wherein the third WUR setup response assigns a third frequency channel to be used to transmit a third wake-up signal to the third STA, and wherein transmitting the first MU-WUR packet further comprises transmitting a preamble using the third frequency channel and without transmitting a wake-up signal in the third frequency channel in response to an indication that the third frequency channel is busy, and further wherein the third frequency channel is arranged between the first frequency channel and the primary channel. [4] The method according to claim 1, further comprising: in response to a fourth WUR setup request from a fourth STA, sending a fourth WUR setup response to the fourth STA, wherein the fourth WUR setup response assigns a fourth frequency channel to be used to transmit a fourth wake-up signal to the fourth STA, and wherein transmitting the first MU-WUR packet further comprises transmitting an invalid wake-up signal using the fourth frequency channel and without a wake-up signal directed to the fourth STA in response to a determination that no wake-up signal is pending for transmission to the fourth STA, the invalid wake-up signal not operative to activate a main radio located in the fourth STA. [5] The method of claim 4, wherein the invalid wake-up signal is one of: a wake-up radio signal frame; and a wake-up detection frame. [6] The method of claim 4, wherein the fourth frequency channel is the primary channel. [7] The method of claim 1, further comprising periodically transmitting radio signal frames to the plurality of STAs using a fifth frequency channel different from the first frequency channel. [8] A method of radio communication, the method comprising: at an access point (AP), receiving (901) wake-up radio (WUR) setup requests from a plurality of stations (STAs), the plurality of STAs comprising a first STA and a second STA; in response to the WUR setup requests, sending (902) a WUR setup response to each of the plurality of STAs to assign a respective frequency channel included in a frequency band for transmitting a respective wake-up signal, wherein the first STA is assigned a first frequency channel and the second STA is assigned a second frequency channel, the first frequency channel being located between the second frequency channel and a primary channel of the frequency band; Receiving (903) a first indication that the first frequency channel is busy or a second indication that no wake-up signal is pending for transmission to the first STA; and Transmitting (906) a first multi-user (MU) WUR packet comprising a plurality of wake-up signals in frequency division multiple access (FDMA) using assigned frequency channels included in the WUR establishment requests, wherein each of the plurality of wake-up signals is operative to activate a master radio located in an STA of the plurality of STAs, the plurality of wake-up signals comprising a wake-up signal transmitted in the second frequency channel for the second STA and further not comprising a wake-up signal directed to the first STA. [9] The method of claim 8, wherein transmitting (906) the first MU-WUR packet in the FDMA is performed without transmitting a signal in the first frequency channel. [10] The method of claim 8, wherein transmitting (906) the first MU-WUR packet in the FDMA comprises transmitting an invalid wake-up signal in the first frequency channel. [11] The method of claim 8, wherein transmitting (906) the first MU-WIR packet in the FDMA comprises: transmitting a preamble in the first frequency channel; and not transmitting any payload data following the preamble. [12] The method of claim 8, wherein each of the WUR setup requests comprises an indication that a respective STA is ready to receive a WUR radio signal frame and a wake-up signal transmitted in different frequency channels. [13] The method of claim 8, wherein the WUR setup response assigns the respective frequency channel by indicating a frequency channel offset from the primary channel. [14] Radio communication station (1000), comprising: a memory (1020); a processor (1030) connected to the memory (1020); and a transceiver (1040) connected to the processor (1030), the transceiver (1040) being configured to: receive wake-up radio (WUR) setup requests from a plurality of stations (STAs) comprising a first STA and a second STA; in response to the WUR setup requests, send a WUR setup response to each of the plurality of STAs to assign a respective frequency channel included in a frequency band for transmitting a respective wake-up signal, wherein the first STA is assigned a first frequency channel and the second STA is assigned a second frequency channel, the first frequency channel being located between the second frequency channel and a primary channel; receive a first indication that the first frequency channel is busy or a second indication that no wake-up signal is pending for transmission to the first STA; and transmit a first multi-user (MU) WUR packet comprising a plurality of wake-up signals in frequency division multiple access (FDMA) using assigned frequency channels included in the WUR establishment requests, wherein each of the plurality of wake-up signals is operative to activate a master radio located in an STA of the plurality of STAs, the plurality of wake-up signals comprising a wake-up signal transmitted in the second frequency channel for the second STA and not comprising a wake-up signal directed to the first STA. [15] The radio communication device (1000) according to claim 14, wherein transmitting the first MU-WUR packet is performed in the FDMA without transmitting a signal in the first frequency channel. [16] The radio communication device (1000) of claim 15, wherein transmitting the first MU-WUR packet in the FDMA comprises transmitting an invalid wake-up signal in the first frequency channel. [17] The radio communication device (1000) of claim 15, wherein transmitting the first MU-WUR packet in the FDMA comprises transmitting a preamble in the first frequency channel, with no transmitting of payload data following the preamble. [18] The radio communication device (1000) of claim 15, wherein each of the WUR setup requests comprises an indication that a respective STA is ready to receive a WUR radio signal frame and a wake-up signal transmitted in different frequency channels. [19] The radio communication device (1000) of claim 15, wherein the WUR setup response comprises a specification of a frequency channel offset from the primary channel.

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