WO2024071665A1

WO2024071665A1 - Device and method for transmitting beacon frame

Info

Publication number: WO2024071665A1
Application number: PCT/KR2023/011871
Authority: WO
Inventors: Jeong Soo Lee
Original assignee: Frontside Llc
Priority date: 2022-09-30
Filing date: 2023-08-10
Publication date: 2024-04-04

Abstract

A device for transmitting a frame in a wireless local area network is provided. The device transmits a beacon frame periodically. The beacon frame includes scheduling information about a transmission scheduling of a group addressed frame. The device transmits the group addressed frame to a group of stations in accordance with the scheduling information.

Description

DEVICE AND METHOD FOR TRANSMITTING BEACON FRAME

The present disclosure relates to a wireless local area network (WLAN), and more particularly, to beacon frame transmission in the WLAN.

A wireless local area network (WLAN) may be formed by one or more access points (APs) that provide a shared wireless communication medium for use by a number of client devices also referred to as stations (STAs).

Orthogonal frequency division multiple access (OFDMA) is a multiple access scheme where different subsets of subcarriers are allocated to different users, and this scheme allows simultaneous data transmission to or from one or more users.

A physical layer protocol data unit (PPDU) is a data unit (or data packet) to carry various information in the WLAN. In OFDMA, users are allocated different subsets of subcarriers that can change from one PPDU to the next. Using OFDMA, an AP may allocate different RUs for STAs. The AP can simultaneously transmit various formats of PPDUs to multiple STAs.

A beacon frame is a broadcast message in a WLAN that carries system information about network information. As the characteristics of WLANs diversify and demanded services increase, the amount of system information carried by the beacon frame increases, and it may be insufficient to contain all information in a single message.

The present disclosure provides a method for transmitting a beacon frame in a wireless local area network.

The present disclosure further provides a device for transmitting a beacon frame in a wireless local area network.

In an aspect, a method for transmitting a frame in a wireless local area network is provided. The method includes transmitting, by an access point, a beacon frame periodically, the beacon frame including first system information and scheduling information, the first system information including network information commonly applied to all stations associated with the access point, the scheduling information including a transmission scheduling of a group addressed frame, generating, by the access point, the group addressed frame, and transmitting, by the access point, the group addressed frame to a group of stations in accordance with the scheduling information, the group addressed frame including second system information applied to the group of stations associated with the access point.

In another aspect, a device for a wireless local area network is provided. The device includes a processor, and a memory operatively coupled with the processor and configured to store instructions that, when executed by the processor, cause the device to perform functions. The functions includes transmitting a beacon frame periodically, the beacon frame including first system information and scheduling information, the first system information including network information commonly applied to all stations associated with the device, the scheduling information including a transmission scheduling of a group addressed frame, generating the group addressed frame, and transmitting the group addressed frame to a group of stations in accordance with the scheduling information, the group addressed frame including second system information applied to the group of stations associated with the device.

As new WLAN communication protocols enable enhanced features, new PPDU transmission designs are provided to support signaling regarding features and resource allocations.

FIG. 1 shows a block diagram of an example wireless communication network.

FIG. 2 shows a block diagram of an example wireless communication device.

FIGs. 3 and 4 show various examples of PPDUs usable for wireless communication between an AP and a number of STAs.

FIG. 5 shows an example of wireless channel that includes multiple subchannels.

FIG. 6 shows an example of PPDU transmission.

FIG. 7 shows beacon frame transmission according to an embodiment of the present disclosure.

FIG. 8 shows beacon frame transmission according to another embodiment of the present disclosure.

FIG. 9 shows an example of beacon with MME.

FIG. 10 shows an example of group addressed frame transmission using multiple BSSID.

FIG. 11 shows a format of group addressed frame according to an embodiment of the present disclosure.

FIG. 12 shows group addressed frame transmission according to an embodiment of the present disclosure.

The following description is directed to certain implementations for the purposes of describing innovative aspects of this disclosure. However, a person having ordinary skill in the art will readily recognize that the teachings herein can be applied in a multitude of different ways. The described implementations can be implemented in any device, system or network that is capable of transmitting and receiving radio frequency (RF) signals according to one or more of the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards, the IEEE 802.15 standards, the Bluetooth® standards as defined by the Bluetooth Special Interest Group (SIG), or the Long Term Evolution (LTE), 3G, 4G or 5G (New Radio (NR)) standards promulgated by the 3rd Generation Partnership Project (3GPP), among others. The described implementations can be implemented in any device, system or network that is capable of transmitting and receiving RF signals according to one or more of the following technologies or techniques: code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), single-user (SU) multiple-input multiple-output (MIMO) and multi-user (MU) MIMO. The described implementations also can be implemented using other wireless communication protocols or RF signals suitable for use in one or more of a wireless personal area network (WPAN), a wireless local area network (WLAN), a wireless wide area network (WWAN), or an internet of things (IOT) network.

OFDMA is an OFDM-based multiple access scheme where different subsets of subcarriers are allocated to different users, and this scheme allows simultaneous data transmission to or from one or more users. In OFDMA, users are allocated different subsets of subcarriers that can change from one PPDU to the next. Similar to OFDM, OFDMA employs multiple subcarriers, but the subcarriers are divided into several groups where each group is referred to as a resource unit (RU).

A physical layer protocol data unit (PPDU) may span one or more subchannels and may include a preamble portion and a data portion. Signaling refers to control fields or information in the preamble portion that can be used by a wireless communication device to interpret another field or portion of the preamble portion or the data portion of the PPDU. A wireless channel may be formed from multiple subchannels. A subchannel may include a set of subcarriers. Portions of the wireless channel bandwidth can be divided or grouped to form different resource units (RUs). An RU may be a unit for resource allocation and may include one or more subcarriers. Among other things, a preamble portion of a PPDU may include signaling to indicate which RUs are allocated to different devices. Other types of signaling include indicators regarding which subchannels include further signaling or which subchannels may be punctured. There are several formats of PPDUs (and related structures) defined for current wireless communication protocols. As new wireless communication protocols enable enhanced features, new preamble designs are needed support signaling regarding features and resource allocations. Furthermore, it desirable to define a new preamble signaling protocol that can support future wireless communication protocols.

FIG. 1 shows a block diagram of an example wireless communication network.

According to some aspects, the wireless communication network 10 can be an example of a wireless local area network (WLAN) such as a Wi-Fi network (and will hereinafter be referred to as WLAN 10). For example, the WLAN 10 can be a network implementing at least one of the IEEE 802.11 family of wireless communication protocol standards (such as that defined by the IEEE 802.11-2016 specification or amendments thereof including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba and 802.11be). The WLAN 10 may include numerous wireless communication devices such as an access point (AP) 11 and multiple stations (STAs) 12. While only one AP 11 is shown, the WLAN network 10 also can include multiple APs.

Each of the STAs 12 also may be referred to as a mobile station (MS), a mobile device, a mobile handset, a wireless handset, an access terminal (AT), a user equipment (UE), a subscriber station (SS), or a subscriber unit, among other possibilities. The STAs 12 may represent various devices such as mobile phones, personal digital assistant (PDAs), other handheld devices, netbooks, notebook computers, tablet computers, laptops, display devices (for example, TVs, computer monitors, navigation systems, among others), music or other audio or stereo devices, remote control devices (“remotes”), printers, kitchen or other household appliances, key fobs (for example, for passive keyless entry and start (PKES) systems), among other possibilities.

A single AP 11 and an associated set of STAs 12 may be referred to as a basic service set (BSS), which is managed by the respective AP 11. The BSS may be identified to users by a service set identifier (SSID), as well as to other devices by a basic service set identifier (BSSID), which may be a medium access control (MAC) address of the AP 11. The AP 11 periodically broadcasts beacon frames (“beacons”) including the BSSID to enable any STAs 12 within wireless range of the AP 11 to “associate” or re-associate with the AP 11 to establish a respective communication link (hereinafter also referred to as a “Wi-Fi link”), or to maintain a communication link, with the AP 11. For example, the beacons can include an identification of a primary channel used by the respective AP 11 as well as a timing synchronization function for establishing or maintaining timing synchronization with the AP 11. The AP 11 may provide access to external networks to various STAs 12 in the WLAN via respective communication link.

To establish a communication link with an AP 11, each of the STAs 12 is configured to perform passive or active scanning operations (“scans”) on frequency channels in one or more frequency bands (for example, the 2.4 GHz, 5 GHz, 6 GHz or 60 GHz bands). To perform passive scanning, a STA 12 listens for beacons, which are transmitted by respective APs 11 at a periodic time interval referred to as the target beacon transmission time (TBTT) (measured in time units (TUs) where one TU may be equal to 1024 microseconds (μs)). To perform active scanning, a STA 12 generates and sequentially transmits probe requests on each channel to be scanned and listens for probe responses from APs 11. Each STA 12 may be configured to identify or select an AP 11 with which to associate based on the scanning information obtained through the passive or active scans, and to perform authentication and association operations to establish a communication link with the selected AP 11. The AP 11 assigns an association identifier (AID) to the STA 12 at the culmination of the association operations, which the AP 11 uses to track the STA 104.

In some cases, STAs 12 may form networks without APs 11 or other equipment other than the STA. One example of such a network is an ad hoc network (or wireless ad hoc network). Ad hoc networks may alternatively be referred to as mesh networks or peer-to-peer (P2P) networks. In some cases, ad hoc networks may be implemented within a larger wireless network such as the WLAN 10. In such implementations, while the STAs 12 may be capable of communicating with each other through the AP 11 using communication links, STAs 12 also can communicate directly with each other via direct wireless links. Additionally, two STAs 12 may communicate via a direct communication link regardless of whether both STAs 12 are associated with and served by the same AP 11. In such an ad hoc system, one or more of the STAs 12 may assume the role filled by the AP 11 in a BSS. Such a STA may be referred to as a group owner (GO) and may coordinate transmissions within the ad hoc network.

The AP 11 and STAs 12 may function and communicate (via the respective communication links) according to the IEEE 802.11 family of wireless communication protocol standards (such as that defined by the IEEE 802.11-2016 specification or amendments thereof including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba and 802.11be). These standards define the WLAN radio and baseband protocols for the PHY and medium access control (MAC) layers. The AP 11 and STAs 12 transmit and receive wireless communications (hereinafter also referred to as “Wi-Fi communications”) to and from one another in the form of PPDUs. The AP 11 and STAs 12 in the WLAN 10 may transmit PPDUs over an unlicensed spectrum, which may be a portion of spectrum that includes frequency bands traditionally used by Wi-Fi technology, such as the 2.4 GHz band, the 5 GHz band, the 60 GHz band, the 3.6 GHz band, and the 900 MHz band. Some implementations of the AP 11 and STAs 12 described herein also may communicate in other frequency bands, such as the 6 GHz band, which may support both licensed and unlicensed communications. The AP 11 and STAs 12 also can be configured to communicate over other frequency bands such as shared licensed frequency bands, where multiple operators may have a license to operate in the same or overlapping frequency band or bands.

Each of the frequency bands may include multiple channels (which may be used as subchannels of a larger bandwidth channel). For example, PPDUs conforming to the IEEE 802.11n, 802.11ac and 802.11ax standard may be transmitted over the 2.4 and 5 GHz bands, each of which is divided into multiple 20 MHz channels. As such, these PPDUs are transmitted over a physical channel having a minimum bandwidth of 20 MHz, but larger channels can be formed through channel bonding. For example, PPDUs may be transmitted over physical channels having bandwidths of 40 MHz, 80 MHz, 160 or 320 MHz by bonding together multiple 20 MHz channels (which may be referred to as subchannels).

Each PPDU is a composite structure that includes a PHY preamble and a payload in the form of a PHY service data unit (PSDU). The information provided in the preamble may be used by a receiving device to decode the subsequent data in the PSDU. In instances in which PPDUs are transmitted over a bonded channel, the preamble fields may be duplicated and transmitted in each of the multiple component channels. The PHY preamble may include both a first portion (or “legacy preamble”) and a second portion (or “non-legacy preamble”). The first portion may be used for packet detection, automatic gain control and channel estimation, among other uses. The first portion also may generally be used to maintain compatibility with legacy devices as well as non-legacy devices. The format of, coding of, and information provided in the second portion of the preamble is based on the particular IEEE 802.11 protocol to be used to transmit the payload.

Uplink (UL) means that the signal (or message or PPDU) is transmitted by a STA to an AP, and downlink (DL) means that the signal (or message or PPDU) is transmitted by the AP to one or more STAs.

FIG. 2 shows a block diagram of an example wireless communication device.

In some implementations, the wireless communication device 50 can be an example of a device for use in a STA such as one of the STAs 12 described above with reference to FIG. 1. In some implementations, the wireless communication device 50 can be an example of a device for use in an AP such as the AP 11 described above with reference to FIG. 1. The wireless communication device 50 is capable of transmitting (or outputting for transmission) and receiving wireless communications (for example, in the form of wireless packets). For example, the wireless communication device can be configured to transmit and receive packets in the form of PPDUs and/or medium access control (MAC) protocol data units (MPDUs) conforming to an IEEE 802.11 wireless communication protocol standard, such as that defined by the IEEE 802.11-2016 specification or amendments thereof including, but not limited to, 802.11ah, 802.11ad, 802.11ay, 802.11ax, 802.11az, 802.11ba and 802.11be.

The wireless communication device 800 can be, or can include, a chip, system on chip (SoC), chipset, package or device that includes one or more processor 51. The processor 51 can include an intelligent hardware block or device such as, for example, a processing core, a processing block, a central processing unit (CPU), a microprocessor, a microcontroller, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a programmable logic device (PLD) such as a field programmable gate array (FPGA), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. The processor 51 processes information received through a transceiver 53, and processes information to be output through the transceiver 53 through the wireless medium. For example, the processor 806 may implement a physical (PHY) layer and/or a MAC layer configured to perform various operations related to the generation and transmission of PPDUs, MPDUs, frames or packets.

A memory 52 can include tangible storage media such as random-access memory (RAM) or read-only memory (ROM), or combinations thereof. The memory 808 also can store non-transitory processor- or computer-executable software code containing instructions that, when executed by the processor 51, cause the wireless communication device 50 to perform various operations described herein for wireless communication, including the generation, transmission, reception and interpretation of PPDUs, MPDUs, frames or packets. For example, various functions of components disclosed herein, or various blocks or steps of a method, operation, process or algorithm disclosed herein, can be implemented as one or more modules of one or more computer programs.

The transceiver 53 generally includes at least one radio frequency (RF) transmitter (or “transmitter chain”) for transmitting radio signals and at least one RF receiver (or “receiver chain”) for receiving radio signals. For example, the RF transmitters and receivers may include various DSP circuitry including at least one power amplifier (PA) and at least one low-noise amplifier (LNA), respectively. The RF transmitters and receivers may, in turn, be coupled to one or more antennas. For example, in some implementations, the wireless communication device 50 can include, or be coupled with, multiple transmit antennas (each with a corresponding transmit chain) and multiple receive antennas (each with a corresponding receive chain).

An PPDU may include a preamble portion and a data portion. ‘Data’ of FIGs. 3-4 denotes the data portion which includes one or more PSDUs and appears after the preamble portion. The data portion may be referred to as a payload.

A non-high-throughput (non-HT) PPDU supporting IEEE 802.11a/g includes a Legacy-Short Training Field (L-STF), a Legacy-Long Training Field (L-LTF), a Legacy-Signal (L-SIG) and a data portion. L-SIG may be called as non-HT Signal. A high-throughput (HT) PPDU supporting IEEE 802.11n includes an L-STF, a HT-SIG, a HT-STF, a HT-LTF and a data portion. A very high throughput (VHT) PPDU supporting IEEE 802.11ac includes an L-STF, L-SIG, a VHT-SIG-A, a VHT-STF, a VHT-LTF, a VHT-SIG-B and a data portion.

A high-efficiency (HE) PPDU supporting IEEE 802.11ax may include an HE single-user (SU) PPDU for SU transmission and an HE multi-user (MU) PPDU for MU transmission. An extremely high throughput (EHT) PPDU supporting IEEE 802.11be may include an EHT MU PPDU for MU transmission and an EHT trigger based (TB) PPDU.

The preamble portion of a PPDU may include a first portion (or "legacy preamble") and a second portion (or “non-legacy preamble”). The first portion may include L-STF, L-LTF and L-SIG. The second portion may include at least one of HT-SIG, HT-STF, HT-LTF, VHT-SIG-A, VHT-STF, VHT-LTF, VHT-SIG-B, RL-SIG, HE-SIG-A, HE-STF, HE-LTF, HE-SIG-B, EHT-SIG, EHT-STF, EHT-LTF and U-SIG.

The L-STF may be used for frame detection, Automatic Gain Control (AGC), diversity detection, and coarse frequency/time synchronization. The L-LTF may be used for fine frequency/time synchronization and channel estimation. The L-SIG may include information indicating a total length of a corresponding PPDU (or information indicating a transmission time of a PSDU).

The VHT-SIG-A field carries information required to interpret VHT PPDUs. The VHT-STF field is used to improve automatic gain control estimation in a MIMO. The VHT-LTF field provides a means for the receiver to estimate the MIMO channel between the set of constellation mapper outputs and the receive chains. The VHT-SIG-B field may be used for MU transmissions and may contain as signaling information usable by the STAs to decode data received in the DATA field, including, for example, a modulation and coding scheme (MCS) and beamforming information.

The repeated legacy (RL)-SIG field in the HE PPDU and EHT PPDU is a repeat of the L-SIG field and is used to differentiate the HE PPDU and the EHT PPDU from non-HT PPDU, HT PPDU, and VHT PPDU.

HE-SIG-A carries information necessary to interpret HE PPDUs. HE-SIG-A may indicate locations and lengths of HE-SIG-Bs, available channel bandwidths, etc. HE-SIG-B may carry STA-specific scheduling information such as, for example, per-user MCS values and per-user RU allocation information. In the context of DL MU-OFDMA, such information enables the respective STA to identify and decode corresponding RUs in the associated data field.

VHT-STF, HE-STF or EHT-STF may be used to improve an AGC estimation in a MIMO transmission. VHT-LTF, HE-LTF or EHT-LTF may be used to estimate a MIMO channel.

The universal signal field (U-SIG) field of EHT PPDU carries information necessary to interpret EHT PPDUs. The U-SIG may include version independent fields and version dependent fields. The version independent fields may include at least one of a version identifier, a PPDU bandwidth, an indication of whether the PPDU is a UL or a DL PPDU, a BSS color identifying a BSS, and a transmission opportunity (TXOP). The PPDU bandwidth in the version independent fields indicates a transmission bandwidth of the PPDU, for example, 20 MHz, 40 MHz, 80 MHz, 160 MHz or 320 MHz. The version identifier in the version independent fields may indicate a version (and associated format) for the version dependent fields. A PPDU format may determine which other indicators are included in the version dependent fields as well as the version identifier. In some implementations, if the PPDU format indicates that the PPDU is an EHT TB PPDU, then the EHT-SIG may be omitted as shown in EHT TB PPDU of FIG. 4. The version dependent fields of U-SIG may include punctured channel Information and EHT-SIG MCS. The EHT-SIG MCS may Indicate an MCS used for modulating the EHT-SIG. The PPDU bandwidth and the punctured channel information may be referred to collectively as frequency occupation indications. The frequency occupation indications may permit WLAN devices on the wireless channel to determine the utilization of the various parts of the wireless channel. For example, the frequency occupation information may be used to indicate puncturing of some subchannels.

The EHT-SIG field provides additional signaling to the U-SIG field for STAs to interpret an EHT MU PPDU. The EHT-SIG may carry STA-specific scheduling information such as, for example, per-user MCS values and per-user RU allocation information. EHT-SIG includes a common field and at least one STA-specific field ("user specific field”). The common field can indicate RU distributions to multiple STAs, indicate the RU assignments in the frequency domain, indicate which RUs are allocated for MU-MIMO transmissions and which RUs correspond to MU-OFDMA transmissions, and the number of users in allocations. The user specific fields are assigned to particular STAs 104 and may be used to schedule specific RUs and to indicate the scheduling to other WLAN devices.

The EHT-SIG field of a 20 MHz EHT MU PPDU contains one EHT-SIG content channel. For OFDMA transmission and for non-OFDMA transmission to multiple users, the EHT-SIG field of an EHT MU PPDU that is 40 MHz or 80 MHz contains two EHT-SIG content channels. For OFDMA transmission and for non-OFDMA transmission to multiple users, the EHT-SIG field of an MU PPDU that is 160 MHz or wider contains two EHT-SIG content channels per 80 MHz. The EHT-SIG content channels per 80 MHz are allowed to carry different information when EHT MU PPDU bandwidth for OFDMA transmission is wider than 80 MHz. The EHT-SIG field of an EHT MU PPDU sent to a single user and the EHT-SIG field of an EHT sounding NDP contains one EHT-SIG content channel and it is duplicated in each non-punctured 20 MHz when the EHT PPDU is equal to or wider than 40 MHz

For OFDMA transmission, the Common field of an EHT-SIG content channel contains information regarding the resource unit allocation such as the RU assignment to be used in the EHT modulated fields of the PPDU, the RUs allocated for MU-MIMO and the number of users in MU-MIMO allocations. In non-OFDMA transmission, the Common field of the EHT-SIG content channel does not contain the RU allocation.

The User Specific fields in the EHT-SIG content channels contains information for all users in the PPDU on how to decode their payload.

A device receiving an PPDU may initially begin or continue its determination of the wireless communication protocol version used to transmit the PPD based on the presence of RL-SIG and the modulation scheme used to modulate the symbols in U-SIG (or HE-SIG-A). In some implementations, the receiving device may initially determine that the wireless communication protocol used to transmit the PPDU is an HE or later version based on the presence of RL-SIG (that is, a determination that the first symbol of the second portion of the preamble is identical to L-SIG) and a determination that both the first symbol and the second symbol following RL-SIG are modulated according to a BPSK modulation scheme.

'UHR' is used to represent any later (post-EHT) version of a new wireless communication protocol conforming to a future IEEE 802.11 wireless communication protocol standard or other standard, and is for illustration purpose only. 'UHR' may be referred to as other terms, for example, Ultra Low Latency (ULL), High Reliability (HR), etc. The UHR PPDU may support future amendments to the IEEE 802.11 wireless communication standard. For example, an UHR PPDU includes L-STF, L-LTF, RL-SIG, U-SIG, UHR-STF, UHR-LTF, a Data field and a packet extension (PE) field. Not all fields are essential and a field may be omitted or added. Names and lengths of the fields in the UHR PPDU are for illustration purpose only.

The techniques in this description are not limited to PPDU formats shown in FIGs. 3-4, but the concepts may apply to any PPDU conforming to IEEE 802.11 wireless communication protocol version.

FIG. 5 shows an example of wireless channel that includes multiple subchannels.

A channel map for a frequency band (such as the 2.5 GHz, 5 GHz, 6 GHz frequency band, etc.) may define multiple subchannels. Each subchannel may have a uniform channel width W=20 MHz, but the techniques in this description are not limited to 20 MHz. The channel width W may be smaller than or larger than 20 MHz.

Some WLAN devices are capable of transmitting at higher bandwidths using a wireless channel that is made up of multiple subchannels. When WLAN devices is capable of transmitting at BSS operating channel width is 80 MHz, a group of four subchannels (a primary 20 MHz channel, a secondary 20 MHz channel and a secondary 40 MHz channel) are used. In FIG. 5, BSS operating channel has a bandwidth of 20 MHz, 40 MHz, 80 MHz and 160 MHz. Although depicted as contiguous subchannels in the channel map, in some implementations, the BSS operating channel may contain one or more subchannel which are not adjacent in the channel map. Additionally, larger groups of channels may be used in some implementations. For example, operating channel has a bandwidth of 320 MHz, 640- MHz or larger. The 320 MHz bandwidth may be divided into sixteen 20 MHz subchannels.

FIG. 6 shows an example of PPDU transmission.

A WLAN device transmits a PPDU by using a four subchannels CH1, CH2, CH3 and CH4 of 80 MHz operating channel. The PPDU may have any PDDU format shown in FIGs. 3-4. A preamble and data in the PPDU may be duplicated every 20 MHz subchannel. Or only a part of the preamble in the PPDU may be duplicated every 20 MHz subchannel.

The WLAN device would perform a clear channel assessment (CCA) before sending a non-triggered transmission. The CCA is a type of collision avoidance technique. Other types may be referred to as carrier sense, carrier detect, listen-before-talk. CCA is performed by a WLAN device to determine if the wireless communication medium (such as the group of subchannels) is available or busy (by another transmission). If the wireless communication medium is in use, the WLAN device may postpone the transmission until the CCA is performed again and the wireless communication medium is idle by another device.

There may be an incumbent system transmission that occupies part of the second subchannel CH2. Therefore, the wireless channel may be punctured to exclude the second subchannel CH2 from the transmission. Thus, the PPDU is sent only on the first subchannel CH1, the third subchannel CH3 and the fourth subchannel CH4.

The punctured channel information may be indicated in a signal field (for example, HE-SIG-A, U-SIG, or EHT-SIG). The punctured channel information may indicate which channels in the total bandwidth (such as 160 MHz or 320 MHz) are punctured, as well as the puncturing mode, such that the receiving STA knows which channels to process for information and which channels are punctured and thus not available or otherwise not including information for processing by the STA.

Hereinafter, beacon frame transmission according to the embodiments of the present disclosure is described.

A beacon frame is one of the management frames in IEEE 802.11 based WLAN. It contains all the information about the network. Beacon frames are transmitted periodically, they serve to announce the presence of WLAN and to synchronize the members of the service set. Beacon frames are transmitted by AP in an infrastructure basic service set (BSS). Delivery traffic indication map (DTIM) interval is the interval between the consecutive target beacon transmission times (TBTTs) of beacons containing a DTIM.

A beacon frame is a broadcast message in a WLAN that carries system information about network information. The system information in the beacon frame is applied to all member stations associated with the AP. The system information includes operation parameters to support various operations applied to all member stations associated with the AP. For an example, the contents in the system information beacon frame include beacon interval, Traffic indication map (TIM), (multiple) BSSID, supported operating class, transmit power envelope, etc.

As the characteristics of WLANs diversify and demanded services increase, the amount of system information carried by beacon frames increases, and it may be insufficient to contain all information in a single message.

A method of dividing information to be included in a beacon frame (or management frame) and transmitting the divided information through a plurality of frames (management frames or action frames) is proposed.

Assume that the information included in the beacon frame is divided into three divided parts. These three divided parts can be transmitted through a beacon frame and two sub-beacon frames (sub-beacon 1 and sub-beacon 2).

A sub-beacon frame is a frame transmitted in a new cycle, unlike a beacon frame transmitted according to a DTIM interval. The sub-beacon frame may be a broadcast frame, a multicast frame, or a unicast frame. A broadcast frame is a frame that can be received by all STAs in the BSS, a multicast frame is a frame that can be received by a plurality of STAs in the BSS, and a unicast frame is a frame that can be received by a specific STA in the BSS.

A sub-beacon frame is a message carrying system information, and may be called various names such as a fragmented beacon message and a partitioned beacon message. The system information in the sub-beacon frame can be applied to one or more recipients which receive the sub-beacon frame. The system information in the sub-beacon frame include operation parameters to support various operations applied to one or more recipients which receive the sub-beacon frame.

A beacon frame may include scheduling information for one or more sub-beacon frames. The AP may inform STAs of the scheduling information through the beacon frame. The scheduling information indicates a transmission schedule of the sub-beacon frame.

The following table shows an example of contents in the scheduling information. Not all elements are essential, and names are illustrative only.

NAME	DESCRIPTION
transmission type	The type of sub-beacon frames transmission (e.g. broadcast/multicast/unicast)
periodicity	The period at which the sub-beacon frame is to be transmitted (may be expressed as an offset relative to the period of the current frame)
type	The type of sub-beacon frame. May indicate the type of system information included in the sub-beacon frame.
ID	ID of the sub-beacon frame.

The scheduling information may include channel information which indicates a frequency channel (or RU) in which the sub-beacon frame is to be transmitted. When the channel information indicates a secondary channel, the sub-beacon frame can be transmitted in the secondary channel and the beacon frame can be transmitted in the primary channel.

In the example of FIG. 7, the beacon frame includes first scheduling information for sub-beacon 1 and second scheduling information for sub-beacon 2. Upon receiving the beacon frame, the STA may receive sub-beacon 1 and sub-beacon 2 based on the first and second scheduling information.

Compared to the embodiment shown in FIG. 7, according to FIG. 8, a beacon frame (or sub-beacon frame) includes scheduling information of a lower sub-frame. Assume that the lower part of the beacon frame is sub-beacon 1 and the lower part of sub-beacon 1 is sub-beacon 2. The beacon frame includes scheduling information for sub-beacon 1. Sub-beacon 1 includes scheduling information for sub-beacon 2.

Hereinafter, a method of transmitting a sub-beacon frame through a group addressed frame (or multicast frame) is proposed.

Broadcast/multicast integrity protocol (BIP) provides data integrity and replay protection for group addressed robust Management frames after establishment of an integrity group temporal key security association (IGTKSA) and for Beacon frames after establishment of a beacon integrity group temporal key security association (BIGTKSA).

BIP-CMAC-128 provides data integrity and replay protection, using AES-128 in CMAC Mode with a 128-bit integrity key and a CMAC TLen value of 128 (16 octets). BIP-CMAC-256 provides data integrity and replay protection, using AES-256 in CMAC Mode with a 256-bit integrity key and a CMAC TLen value of 128 (16 octets). NIST Special Publication 800-38B defines the CMAC algorithm, and NIST Special Publication 800-38D defines the GMAC algorithm. BIP processing uses AES with a 128-bit or 256-bit integrity key and a CMAC TLen value of 128 (16 octets). The CMAC output for BIP-CMAC-256 is not truncated and shall be 128 bits (16 octets). The CMAC output for BIP-CMAC-128 is truncated to 64 bits: Message integrity code (MIC) = Truncate-64(CMAC Output).

BIP-GMAC-128 uses AES with a 128-bit integrity key, and BIP-GMAC-256 uses AES with a 256-bit integrity key. The authentication tag for both BIP-GMAC-128 and BIP-GMAC-256 is not truncated and shall be 128 bits (16 octets).

BIP uses integrity group temporal key (IGTK) or beacon integrity group temporal key (BIGTK) to compute the MMPDU MIC. The Authenticator shall distribute one new IGTK and IGTK PN (IPN) whenever it distributes a new GTK. The IGTK is identified by the MAC address of the transmitting STA plus an IGTK identifier that is encoded in the MME Key ID field. If beacon protection is enabled, the Authenticator may distribute one new BIGTK and BIPN when it distributes a new GTK. The BIGTK is identified by the MAC address of the transmitting STA plus a BIGTK identifier that is encoded in the MME Key ID field.

FIG. 9 shows an example of beacon with MME.

To protect beacons against outsider forgeries, each beacon includes Management MIC Element (MME) that can be used to verify its authenticity. The Message Integrity Code (MIC) field is an authentication tag calculated by the AP. The Beacon Integrity Packet Number (BIPN) is initialized to zero and incremented after every transmitted beacon and hence is unique. When using GMAC, the unique nonce required by this algorithm equals the BIPN. To calculate the MIC, BIGTK is introduced. This BIGTK is distributed to clients when they are connecting and authenticating with the network. As a result, the authenticity of beacon frames can only be validated after connecting to the AP.

An AP transmits protected beacon frames if beacon protection is enabled. Protected beacon frames cannot be validated until a BIGTKSA has been established. If a BIGTKSA exists, the non-AP STA validates the Management MIC Element (MME) in received Beacon frames.

For multiple BSSIDs, each Authenticator maintains and transmits the BIGTK and BIPN which are common to all of the co-located transmitted and nontransmitted BSSs, and the supplicant uses the received BIGTK and BIPN to maintain a BIGTKSA. If a supplicant that has a BIGTKSA with an Authenticator that is using a nontransmitted BSSID receives a protected Beacon frame from the AP with the transmitted BSSID, it executes the BIP procedures to validate the Beacon frame.

The group management cipher suite of the AP transmitting a Beacon frame is used to protect Beacon frames. Beacon protection is not applicable to IBSS and MBSS.

Each AP associated with the transmitted BSSID and the nontransmitted BSSIDs is sending group addressed management frames after DTIM beacon.

As the number of the nontransmitted BSSIDs increases, the protocol overhead increases. Especially, when the contents of the group addressed management frames are the same, multiple transmissions of the group addressed management frames may not be efficient.

The proposed group address frame can be referred to a group addressed management encapsulation frame. This encapsulated frame may encapsulate the group addressed management frame.

An Address 1 field in the MAC header in the group addressed management encapsulation frame may indicate an intended group of receiving stations for the roup addressed management encapsulation frame. An Address 2 field in the MAC header in the group addressed management encapsulation frame may indicate the transmitted BSSID (or transmitting STA).

When the protection of the group addressed frame is enabled, the MME field in the group addressed management encapsulation frame mqy contain Key ID, Encapsulation Integrity Packet Number (EIPN), and MIC that can be verified from all intended STAs which are associated with either the transmitted BSSID or the nontransmitted BSSID. The Encapsulation Integrity Group Temporal Key (EIGTK) is an integrity group temporal key for integrity check of the group addressed frame and may be used to calculate EIPN.

For multiple BSSIDs, each Authenticator can maintain and transmit the EIGTK and EIPN which are common to all of the co-located transmitted and nontransmitted BSSs, and the supplicant uses the received EIGTK and EIPN to maintain a EIGTKSA. If a supplicant that has an EIGTKSA with an Authenticator that is using a nontransmitted BSSID receives a protected Group-addressed management encapsulation frame from the AP with the transmitted BSSID, it can execute the BIP procedures to validate the group addressed management encapsulation frame.

The AP associated with the transmitted BSSID sends a group addressed frame as a sub-beacon frame after sending a beacon frame. The group addressed frame may be a group addressed management encapsulation frame.

The group addressed management encapsulation frame may be an action frame but the beacon frame is a management frame. The group addressed management encapsulation frame is a multicast frame or a unicast frame, but the beacon frame is a broadcast frame.

The group addressed frame can be transmitted in OFDMA PPDU (e.g., HE MU PPDU, EHT MU PPDU). In such case, in order to allow simultaneous transmission with other group-addressed data frames, the STA-ID field in the PHY header of the OFDMA PPDU is set to a special value to indicate that the PSDU contains the group addressed frame.

Since a legacy STA (L-STA, VHT STA and/or HE STA) can't decode a group addressed frame, (i) the group addressed frame may be sent after transmitting other group addressed data/management frames, (ii) the group addressed frame can be sent immediately before the DTIM Beacon frame, or (iii) the group addressed frame can be sent at the scheduled time within the Beacon interval.

For multiple BSSIDs, if the same group addressed frame is needed to be delivered to intended STAs associated with either the transmitted BSSID or the nontransmitted BSSID, the AP associated with the transmitted BSSID sends the group addressed frame.

For multiple BSSIDs, the STA associated with the nontransmitted BSSID that received the group addressed frame considers that the corresponding frame is originally sent by its associated AP (i.e., the nontransmitted BSSID's AP) but it was tunneled through the transmitted BSSID. The STA associated with the transmitted BSSID that received the group addressed frame processes it as a normal group addressed management frame because it was sent by its associated AP.

When management frame protection is negotiated, the receiver maintains a 48-bit replay counter for each EIGTK. The receiver sets the replay counter to the value of the EIPN in the EIGTK Key Delivery element (KDE) provided by the Authenticator in the 4-way handshake, FT 4-way handshake, FT handshake, group key handshake, or FILS authentication. The transmitter maintains a single EIPN for each EIGTK. The EIPN can be implemented as a 48-bit strictly increasing integer, initialized to 1 when the corresponding EIGTK is initialized. The transmitter may reinitialize the sequence counter when the EIGTK is refreshed.

A STA can transmit a protected group addressed frame by performing following steps (a)~(e).

Step (a): Select the EIGTK currently active for transmission of frames to the intended group of recipients and construct the MME (see 9.4.2.54 (MME)) with the MIC field masked to 0 and the Key ID field set to the corresponding EGTK Key ID value. The transmitting STA shall insert a strictly increasing integer into the MME EIPN field. For BIP-GMAC-128 and BIP-GMAC-256, the initialization vector passed to GMAC shall be a concatenation of Address 2 from the MAC header of the MPDU and the non-negative integer inserted into the MME EIPN field.

Step (b): Compute AAD as specified in 12.5.3.3 (BIP AAD construction).

Step (c): Compute an integrity value over the concatenation of AAD and the management frame body including MME, and the Timestamp field masked to 0, and insert the output into the MME MIC field. For BIP-CMAC-128, the integrity value is 64 bits and is computed using AES-128-CMAC; for BIP-CMAC-256, the integrity value is 128 bits and is computed using AES-256-CMAC; for BIP-GMAC-128, the integrity value is 128 bits and is computed using AES-128-GMAC; and, for BIP-GMAC-256, the integrity value is 128 bits and is computed using AES-256-GMAC.

Step (d): Compose the frame as the IEEE 802.11 header, management frame body, including MME, and FCS. The MME shall appear last in the frame body.

Step (e): Transmit the frame.

Once a STA transmits the protected group addressed frame based on an updated EIGTK, the STA may not transmit any protected group addressed frame using the previous EIGTK.

A STA with management frame protection negotiated may receive the protected group addressed frame by performing following steps (a)~(e).

Step (a): Identify the appropriate EIGTK and associated state based on the MME Key ID field. If no such EIGTK exists, silently discard the frame and terminate BIP processing for this reception.

Step (b): Perform replay protection on the received frame. The receiver shall interpret the MME EIPN field as a 48-bit unsigned integer. The receiver shall compare this MME EIPN value to the value of the replay counter for the EIGTK identified by the MME Key ID field. If the integer value from the received MME EIPN field is less than or equal to the replay counter value for this EIGTK, the receiver shall discard the frame and increment the dot11RSNAStatsCMACReplays counter by 1.

Step (c): Compute AAD for this Management frame. For BIP-GMAC-128 and BIP-GMAC-256, an initialization vector for GMAC is constructed as the concatenation of Address 2 from the MAC header of the MPDU and the 48-bit unsigned integer from the MME EIPN field.

Step (d): Extract and save the received MIC value, and compute a verifier over the concatenation of AAD, the management frame body, with the Timestamp field masked to 0, and MME, with the MIC field masked to 0 in the MME. For BIP-CMAC-128, the integrity value is 64 bits and is computed using AES-128-CMAC; for BIP-CMAC-256, the integrity value is 128 bits and is computed using AES-256-CMAC; for BIP-GMAC-128, the integrity value is 128 bits and is computed using AES-128-GMAC; and, for BIP-GMAC-256, the integrity value is 128 bits and is computed using AES-256-GMAC. If the result does not match the received MIC value, then the receiver shall discard the frame, increment the dot11RSNAStatsBIPMICErrors counter by 1, and terminate BIP processing for this reception.

Step (e): If the frame is a protected group addressed frame, update the replay counter for the EIGTK identified by the MME Key ID field with the value of the MME EIPN field.

EIGTK KDE is included in the Extensible Authentication Protocol over LAN (EAPOL) frame sent by the Authenticator during the group key handshake procedure. An example of the format for the EIGTK KDE is shown in the below table.

	Key ID	EIPN	EIGTK
Octets:	2	6	Variable

The EIPN corresponds to the EIPN value that was carried in the MME of the last protected group addressed frame and it is used by the receiver as the initial value for the BIP replay counter for the EIGTK.

In other embodiment, the BIGTK and the BIPN can be used for integrity check of the group addressed frame instead of EIGTK and EIPN. In such case, when the protection is enabled, the MME field in the group addressed frame can contain Key ID, BIPN, and MIC.

As used herein, a phrase referring to “at least one of” or “one or more of” a list of items refers to any combination of those item, including single members. For example, “at least one of: a, b, and c” is intended to cover the possibilities of: a only, b only, c only, a combination of a and b, a combination of a and c, a combination of b and c, and a combination of a and b and c.

The various illustrative components, logic, logical blocks, modules, circuits, operations and algorithm processes described in connection with the implementations disclosed herein may be implemented as electronic hardware, firmware, software, or combinations of hardware, firmware or software, including the structures disclosed in this specification and the structural equivalents thereof. The interchangeability of hardware, firmware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and processes described above. Whether such functionality is implemented in hardware, firmware or software depends upon the particular application and design constraints imposed on the overall system.

While operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flowchart or flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In some circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

Claims

A method for transmitting a frame in a wireless local area network, the method comprising:

transmitting, by an access point, a beacon frame periodically, the beacon frame including first system information and scheduling information, the first system information including network information commonly applied to all stations associated with the access point, the scheduling information including a transmission scheduling of a group addressed frame;

generating, by the access point, the group addressed frame; and

transmitting, by the access point, the group addressed frame to a group of stations in accordance with the scheduling information, the group addressed frame including second system information applied to the group of stations associated with the access point.
The method of claim 1, wherein the group addressed frame includes an identifier identifying the group of stations.
The method of claim 1, wherein generating the group addressed frame includes:

selecting an Integrity Group Temporal Key (IGTK) for checking an integrity to the group of stations; and

generating the group addressed frame based on the IGTK.
The method of claim 3, wherein the beacon frame is generated based on a Beacon Integrity Group Temporal Key (BIGTK) for beacon frame protection.
The method of claim 1, wherein the scheduling information includes at least one of a periodicity of the group addressed frame and a channel in which the group addressed frame is to be transmitted.
The method of claim 1, wherein the beacon frame is transmitted as a management frame, and the group addressed frame is transmitted as an action frame.
The method of claim 1, wherein the group of stations includes at least one station that supports a reception of the group addressed frame and is selected from stations associated with the access point.
A device for a wireless local area network, the device comprising:

a processor; and

a memory operatively coupled with the processor and configured to store instructions that, when executed by the processor, cause the device to perform functions comprising:

transmitting a beacon frame periodically, the beacon frame including first system information and scheduling information, the first system information including network information commonly applied to all stations associated with the device, the scheduling information including a transmission scheduling of a group addressed frame;

generating the group addressed frame; and

transmitting the group addressed frame to a group of stations in accordance with the scheduling information, the group addressed frame including second system information applied to the group of stations associated with the device.
The device of claim 8, wherein the group addressed frame includes an identifier identifying the group of stations.
The device of claim 8, wherein generating the group addressed frame includes:

selecting an Integrity Group Temporal Key (IGTK) for checking an integrity to the group of stations; and

generating the group addressed frame based on the IGTK.
The device of claim 10, wherein the beacon frame is generated based on a Beacon Integrity Group Temporal Key (BIGTK) for beacon frame protection.
The device of claim 8, wherein the beacon frame is transmitted as a management frame, and the group addressed frame is transmitted as an action frame.