Seamless roaming of a relay station (STA) in a wireless network with multi-link operation (MLO) capability

Abstract

A method performed by a relay station (STA) that is connected to a first access point (AP) and that has multi-link operation (MLO) capability to roam from the first access point (AP) to a second AP. The method includes responsive to determining to roam from the first AP to the second AP, determining whether the relay STA is acting as a relay for one or more STAs, responsive to determining that the relay STA is acting as a relay for the one or more STAs, disconnecting relay links between the relay STA and the one or more STAs, and after disconnecting the relay links between the relay STA and the one or more STAs, performing a MLO roaming procedure to roam from the first AP to the second AP.

Description

SPECIFICATIONSEAMLESS ROAMING OF A RELAY STATION (STA) IN A WIRELESS NETWORK WITH MULTI-LINK OPERATION (MLO) CAPABILITYCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 640,058, filed April 29, 2024, titled “Seamless Roaming for Relay Devices in Multi-link Wireless LANs”, which is hereby incorporated by reference.TECHNICAL FIELD

[0002] The present disclosure generally relates to wireless communications, and more specifically, relates to seamless roaming of a relay station (STA) in a wireless network with multi-link operation capability.BACKGROUND

[0003] Institute of Electrical and Electronics Engineers (IEEE) 802.11 is a set of standards for implementing wireless local area network communication in various frequencies, including but not limited to the 2.4 gigahertz (GHz), 5 GHz, 6 GHz, and 60 GHz bands. These standards define the protocols that enable Wi-Fi devices to communicate with each other. The IEEE 802.11 family of standards has evolved over time to accommodate higher data rates, improved security, and better performance in different environments. Some of the most widely used standards include 802.11a, 802.11b, 802.11g, 802. l ln, 802.11ac, and 802.11ax (also known as “Wi-Fi 6”). These standards specify the modulation techniques, channel bandwidths, and other technical aspects that facilitate interoperability between devices from various manufacturers. IEEE 802.11 has played an important role in the widespread adoption of wireless networking in homes, offices, and public spaces, enabling users to connect their devices to the internet and each other without the need for wired connections.

[0004] IEEE 802.1 Ibe, also known as “Wi-Fi 7”, is the next generation of the IEEE 802.11 family of standards for wireless local area networks. Currently under development, 802.1 Ibe aims to significantly improve upon the capabilities of its predecessor, 802.1 lax / Wi-Fi 6, by offering even higher data rates, lower latency, and increased reliability. The standard is expected to leverage advanced technologies such as multi-link operation (MLO), which allows devices to simultaneously use multiple frequency bands and channels for enhanced performance andreliability. Additionally, 802.1 Ibe will introduce 4096-QAM (Quadrature Amplitude Modulation), enabling higher data rates by encoding more bits per symbol. The standard will also feature improved medium access control (MAC) efficiency, enhanced power saving capabilities, and better support for high-density environments. With these advancements, 802.1 Ibe is expected to deliver theoretical maximum data rates of up to 46 gigabits per second (Gbps), making it suitable for bandwidth-intensive applications such as virtual and augmented reality, 8K video streaming, and high-performance gaming. The IEEE 802.1 Ibe standard is projected to be finalized by the end of 2024, paving the way for the next generation of Wi-Fi devices and networks.

[0005] A multi-link device (MLD) is a device that is capable of transmitting and receiving traffic over multiple links in different channels / bands. A MLD may implement multi-link operation (MLO). Multi-link operation (MLO) is a technology that enables devices to transmit and receive traffic over multiple links in different channels / bands.

[0006] Current research trends for future IEEE 802.11 wireless networks (e.g., IEEE 802.1 Ibn Ultra-High Rate (UHR) wireless network) focus on achieving seamless roaming using MLO technology. The objective is to ensure uninterrupted connectivity for stations (STAs) moving within wireless network environments. In existing IEEE 802.11 wireless networks, the traditional (single-link (non-MLO)) roaming scheme for non-access point (non-AP) stations (STAs) involves a time-consuming process that requires 802. IX re-authentication and a 4-way handshake, which may result in packet loss or transmission interruptions when roaming

[0007] With the introduction of the IEEE 802.1 Ibe Extremely High Throughput (EHT) wireless networking standard and MLO technology, non-AP STA MLDs may communicate with multiple AP MLDs over multiple links concurrently. MLO technology can help facilitate seamless roaming, ensuring uninterrupted transmission as STAs transition between APs. Recent approaches and solutions focus on extending the existing IEEE 802.11 wireless networking standard to support seamless roaming. Seamless roaming may help enhance wireless network performance and the end user experience.

[0008] Relay technology may help enhance wireless network coverage and throughput. With relay technology, a relay STA that is communicatively situated between an AP and a non-AP STA may relay traffic between the AP and the non-AP STA to improve reliability and throughput for the non-AP STA. Relay technology can be enhanced by leveraging MLO capabilities. For example, consider a scenario where a non-AP STA MLD equipped with two radios, operating in the 2.4 GHz and 5 GHz bands respectively, reaches the boundary of an AP's 5 GHz coverage area, experiencing weak link condition. In such a situation, the non-APSTA MLD may establish a 5 GHz link to the AP via a relay STA MLD that is communicatively situated between the AP and the non-AP STA, thereby effectively extending the coverage area and ensuring seamless connectivity even in areas with weak signal conditions beyond the AP's 5 GHz band coverage area.

[0009] A relay STA may play a dual role in that it can act as a relay for other STAs and can also act as an individual non-AP STA. In its capacity / role as an individual non-AP STA, the relay STA may be able to roam to other APs. It is possible that the relay STA roams to another AP while it is acting as a relay for other STA(s). If the relay STA roams to another AP, the non- AP STAs that are associated with the relay STA (and rely on the relay STA to relay traffic on their behalf) may lose their ability to communicate with the original AP, resulting in communication interruptions. Also, the non-AP STAs that are associated with the relay STA may not be aware that the relay STA has roamed to another AP and may continue transmitting traffic to the relay STA even though the relay STA is no longer able to relay traffic to the original AP, resulting in the waste of communication resources.BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The disclosure will be more fully understood from the detailed description provided below and the accompanying drawings that depict various embodiments of the disclosure. However, these drawings should not be interpreted as limiting the disclosure to the specific embodiments shown; they are provided for explanation and understanding only.

[0011] Figure 1 illustrates an example of a wireless local area network (WLAN) with a basic service set (BSS) that includes multiple wireless devices, in accordance with some embodiments of the present disclosure.

[0012] Figure 2 is a schematic diagram of a wireless device, in accordance with some embodiments of the present disclosure.

[0013] Figure 3A illustrates components of a wireless device configured to transmit data, in accordance with some embodiments of the present disclosure.

[0014] Figure 3B illustrates components of a wireless device configured to receive data, in accordance with some embodiments of the present disclosure.

[0015] Figure 4 illustrates interframe space (IFS) relationships, in accordance with some embodiments of the present disclosure.

[0016] Figure 5 illustrates a Carrier Sense Multiple Access with Collision Avoidance (CSMA / CA)-based frame transmission procedure, in accordance with some embodiments of the present disclosure.

[0017] Figure 6 illustrates maximum physical layer (PHY) rates for Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards, in accordance with some embodiments of the present disclosure.

[0018] Figure 7 provides a detailed description of fields in Extremely High Throughput (EHT) Physical Protocol Data Unit (PPDU) frames, including their purposes and characteristics, in accordance with some embodiments of the present disclosure.

[0019] Figure 8 illustrates an example of multi-user (MU) transmission in Orthogonal Frequency -Division Multiple Access (OFDMA), in accordance with some embodiments of the present disclosure.

[0020] Figure 9 illustrates an example of an access point sending a trigger frame to multiple associated stations and receiving Uplink Orthogonal Frequency-Division Multiple Access Trigger-Based Physical Protocol Data Units (UL OFDMA TB PPDUs) in response, in accordance with some embodiments of the present disclosure.

[0021] Figure 10 is a diagram showing a wireless network environment with an access point (AP), relay stations (STAs), and STAs that are capable of multi-link operation (MLO) in a 2.4 Gigahertz (GHz) band and a 5 GHz band, according to some embodiments.

[0022] Figure 11 is a diagram showing a single link operation and a multi-link operation between an AP and a non-AP STA, according to some embodiments.

[0023] Figure 12 is a diagram showing a relay STA multi-link device (MLD) that can relay traffic between an AP MLD and a non-AP STA MLD using MLO, according to some embodiments.

[0024] Figure 13 is a diagram showing an extended service set (ESS) comprising two basic service sets (BSSs) in which MLO-based seamless roaming may occur, according to some embodiments.

[0025] Figure 14 is a diagram showing a wireless network that implements relay technology, according to some embodiments.

[0026] Figure 15 is a diagram showing a MLO seamless roaming procedure, according to some embodiments.

[0027] Figure 16 is a diagram showing frame exchange sequence for performing a MLO seamless roaming procedure, according to some embodiments.

[0028] Figure 17 is a diagram showing a situation in which the roaming technique described herein can be applied, according to some embodiments.

[0029] Figure 18 is a diagram showing a frame exchange sequence for a relay STA MLD that is acting as a relay for two STAs to roam to a new AP, according to some embodiments.

[0030] Figure 19 is a flow diagram of a method for a relay STA to roam to a target AP, according to some embodiments.

[0031] Figure 20 is a diagram showing a format of a disassociation frame, according to some embodiments.

[0032] Figure 21 is a diagram showing a frame exchange sequence for a relay STA MLD that is not acting as a relay for any STAs to roam to a new AP, according to some embodiments.

[0033] Figure 22 is a flow diagram of a method for a relay STA to roam to a new AP, according to some embodiments.DETAILED DESCRIPTION

[0034] The present disclosure generally relates to wireless communications, and more specifically, relates to seamless roaming of a relay station (STA) in a wireless network with multi-link operation (MLO) capability.

[0035] As mentioned above, a relay STA may play a dual role in that it can act as a relay for other STAs and can also act as an individual non-AP STA that can roam between APs. If the relay STA roams to another AP, the non-AP STAs that are associated with the relay STA (and rely on the relay STA to relay traffic on their behalf) may lose their ability to communicate with the original AP, resulting in communication interruptions. Also, the non-AP STAs that are associated with the relay STA may not be aware that the relay STA has roamed to another AP and may continue transmitting traffic to the relay STA even though the relay STA can no longer relay traffic to the original AP, resulting in the waste of communication resources. A relay STA may be a multi-link device (MLD) that is capable of MLO. In such case, the relay STA may seamlessly roam to a new AP using a MLO roaming procedure.

[0036] However, current research in the wireless networking field has not yet explored an approach that integrates relay technology and MLO-based roaming technology, and particularly an approach that is able to seamlessly handle the situation where a relay STA that is acting as a relay for non-AP STAs roams to a new AP.

[0037] The present disclosure introduces a roaming technique for gracefully handling a situation where a relay station (STA) that is acting as a relay for other STA(s) roams to a new AP. In particular, the roaming technique described introduced herein may consider disconnecting / disassociating non-AP STAs that are associated with a relay STA before the relay STA roams to a new AP.

[0038] According to some embodiments, when a relay STA decides to roam from a first AP to a second AP, the relay STA may determine whether the relay STA is currently acting as a relayfor one or more STAs. If the relay STA is acting as a relay for one or more STAs, the relay STA may disconnect the any relay links between the relay STA and the one or more STAs. The relay STA may disconnect the relay links by transmitting a disassociation frame to each of the one or more STAs over the respective relay links. The disassociation frame may include a reason code indicating that a reason for disassociation is that a relay is unavailable. The reason code may have a value that is between 69 and 65,535. After disconnecting the relay links between the relay STA and the one or more STAs, the relay STA may perform a MLO roaming procedure to (seamlessly) roam from the first AP to the second AP.

[0039] An advantage of the roaming technique described herein is that it allows a relay STA to seamlessly roam to a new AP. The relay STA may use a MLO roaming procedure to seamlessly roam to the new AP with minimal service interruptions or delays. Also, an advantage of the roaming technique described herein is that it enhances the overall efficiency and reliability of the wireless network. By explicitly disconnecting relay links before a relay STA roams to a new AP, the non-AP STAs that were associated with the relay STA may more quickly find a new relay STA to serve as a relay and may also avoid transmitting traffic to the relay STA, which is no longer able to relay traffic to the original AP. Also, non-AP STAs that have MLO capability and that have a direct connection to the original AP (in addition to the relayed connection through the relay STA) may maintain connectivity with the original AP even when the relay link is disconnected. While certain advantages are mentioned above, those skilled in the relevant art will appreciate that the roaming technique described herein may provide other advantages in view of the present disclosure.

[0040] For purposes of illustration, various embodiments are described herein in the context of wireless networks that are based on IEEE 802.11 standards and using terminology and concepts thereof. Those skilled in the art will appreciate that the embodiments disclosed herein can be modified / adapted for use in other types of wireless networks.

[0041] In the following detailed description, only certain embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

[0042] Figure 1 shows a wireless local area network (WLAN) 100 with a basic service set (BSS) 102 that includes a plurality of wireless devices 104 (sometimes referred to as WLAN devices 104). Each of the wireless devices 104 may include a medium access control (MAC)layer and a physical (PHY) layer according to an IEEE (Institute of Electrical and Electronics Engineers) standard 802.11, including one or more of the amendments(e.g., 802.1 la / b / g / n / p / ac / ax / bd / be). In one embodiment, the MAC layer of a wireless device 104 may initiate transmission of a frame to another wireless device 104 by passing a PHY- TXSTART. request (TXVECTOR) to the PHY layer. The TXVECTOR provides parameters for generating and / or transmitting a corresponding frame. Similarly, a PHY layer of a receiving wireless device may generate an RXVECTOR, which includes parameters of a received frame and is passed to a MAC layer for processing.

[0043] The plurality of wireless devices 104 may include a wireless device 104A that is an access point (sometimes referred to as an AP station or AP STA) and the other wireless devices 104B1-104B4 that are non-AP stations (sometimes referred to as non-AP STAs). Alternatively, all the plurality of wireless devices 104 may be non-AP STAs in an ad-hoc networking environment. In general, the AP STA (e.g., wireless device 104A) and the non-AP STAs (e.g., wireless devices 104B1-104B4) may be collectively referred to as STAs. However, for ease of description, only the non-AP STAs may be referred to as STAs unless the context indicates otherwise. Although shown with four non-AP STAs (e.g., the wireless devices 104B1- 104B4), the WLAN 100 may include any number of non-AP STAs (e.g., one or more wireless devices 104B).

[0044] Figure 2 illustrates a schematic block diagram of a wireless device 104, according to an embodiment. The wireless device 104 may be the wireless device 104A (i.e., the AP of the WLAN 100) or any of the wireless devices 104B1-104B4 in Figure 1. The wireless device 104 includes a baseband processor 210, a radio frequency (RF) transceiver 240, an antenna unit 250, a storage device (e g., memory device) 232, one or more input interfaces 234, and one or more output interfaces 236. The baseband processor 210, the storage device 232, the input interfaces 234, the output interfaces 236, and the RF transceiver 240 may communicate with each other via a bus 260.

[0045] The baseband processor 210 performs baseband signal processing and includes a MAC processor 212 and a PHY processor 222. The baseband processor 210 may utilize the memory 232, which may include a non-transitory computer / machine readable medium having software (e.g., computer / machine programing instructions) and data stored therein.

[0046] In an embodiment, the MAC processor 212 includes a MAC software processing unit 214 and a MAC hardware processing unit 216. The MAC software processing unit 214 may implement a first plurality of functions of the MAC layer by executing MAC software, which may be included in the software stored in the storage device 232. The MAC hardwareprocessing unit 216 may implement a second plurality of functions of the MAC layer in specialpurpose hardware. However, the MAC processor 212 is not limited thereto. For example, the MAC processor 212 may be configured to perform the first and second plurality of functions entirely in software or entirely in hardware according to an implementation.

[0047] The PHY processor 222 includes a transmitting (TX) signal processing unit (SPU) 224 and a receiving (RX) SPU 226. The PHY processor 222 implements a plurality of functions of the PHY layer. These functions may be performed in software, hardware, or a combination thereof according to an implementation.

[0048] Functions performed by the transmitting SPU 224 may include one or more of Forward Error Correction (FEC) encoding, stream parsing into one or more spatial streams, diversity encoding of the spatial streams into a plurality of space-time streams, spatial mapping of the space-time streams to transmit chains, inverse Fourier Transform (iFT) computation, Cyclic Prefix (CP) insertion to create a Guard Interval (GI), and the like. Functions performed by the receiving SPU 226 may include inverses of the functions performed by the transmitting SPU 224, such as GI removal, Fourier Transform computation, and the like.

[0049] The RF transceiver 240 includes an RF transmitter 242 and an RF receiver 244. The RF transceiver 240 is configured to transmit first information received from the baseband processor 210 to the WLAN 100 (e.g., to another WLAN device 104 of the WLAN 100) and provide second information received from the WLAN 100 (e.g., from another WLAN device 104 of the WLAN 100) to the baseband processor 210.

[0050] The antenna unit 250 includes one or more antennas. When Multiple-Input Multiple- Output (MIMO) or Multi-User MIMO (MU-MIMO) is used, the antenna unit 250 may include a plurality of antennas. In an embodiment, the antennas in the antenna unit 250 may operate as a beam-formed antenna array. In an embodiment, the antennas in the antenna unit 250 may be directional antennas, which may be fixed or steerable.

[0051] The input interfaces 234 receive information from a user, and the output interfaces 236 output information to the user. The input interfaces 234 may include one or more of a keyboard, keypad, mouse, touchscreen, microphone, and the like. The output interfaces 236 may include one or more of a display device, touch screen, speaker, and the like.

[0052] As described herein, many functions of the WLAN device 104 may be implemented in either hardware or software. Which functions are implemented in software and which functions are implemented in hardware will vary according to constraints imposed on a design. The constraints may include one or more of design cost, manufacturing cost, time to market, power consumption, available semiconductor technology, etc.

[0053] As described herein, a wide variety of electronic devices, circuits, firmware, software, and combinations thereof may be used to implement the functions of the components of the WLAN device 104. Furthermore, the WLAN device 104 may include other components, such as application processors, storage interfaces, clock generator circuits, power supply circuits, and the like, which have been omitted in the interest of brevity.

[0054] Figure 3 A illustrates components of a WLAN device 104 configured to transmit data according to an embodiment, including a transmitting (Tx) SPU (TxSP) 324, an RF transmitter 342, and an antenna 352. In an embodiment, the TxSP 324, the RF transmitter 342, and the antenna 352 correspond to the transmitting SPU 224, the RF transmitter 242, and an antenna of the antenna unit 250 of Figure 2, respectively.

[0055] The TxSP 324 includes an encoder 300, an interleaver 302, a mapper 304, an inverse Fourier transformer (IFT) 306, and a guard interval (GI) inserter 308

[0056] The encoder 300 receives and encodes input data. In an embodiment, the encoder 300 includes a forward error correction (FEC) encoder. The FEC encoder may include a binary convolution code (BCC) encoder followed by a puncturing device. The FEC encoder may include a low-density parity-check (LDPC) encoder.

[0057] The TxSP 324 may further include a scrambler for scrambling the input data before the encoding is performed by the encoder 300 to reduce the probability of long sequences of 0s or Is. When the encoder 300 performs the BCC encoding, the TxSP 324 may further include an encoder parser for demultiplexing the scrambled bits among a plurality of BCC encoders. If LDPC encoding is used in the encoder, the TxSP 324 may not use the encoder parser.

[0058] The interleaver 302 interleaves the bits of each stream output from the encoder 300 to change an order of bits therein. The interleaver 302 may apply the interleaving only when the encoder 300 performs BCC encoding and otherwise may output the stream output from the encoder 300 without changing the order of the bits therein.

[0059] The mapper 304 maps the sequence of bits output from the interleaver 302 to constellation points. If the encoder 300 performed LDPC encoding, the mapper 304 may also perform LDPC tone mapping in addition to constellation mapping.

[0060] When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324 may include a plurality of interleavers 302 and a plurality of mappers 304 according to a number of spatial streams (NSS) of the transmission. The TxSP 324 may further include a stream parser for dividing the output of the encoder 300 into blocks and may respectively send the blocks to different interleavers 302 or mappers 304. The TxSP 324 may further include a space-time block code (STBC) encoder for spreading the constellation points from the spatial streams into anumber of space-time streams (NSTS) and a spatial mapper for mapping the space-time streams to transmit chains. The spatial mapper may use direct mapping, spatial expansion, or beamforming.

[0061] The IFT 306 converts a block of the constellation points output from the mapper 304 (or, when MIMO or MU-MIMO is performed, the spatial mapper) to a time domain block (i.e., a symbol) by using an inverse discrete Fourier transform (IDFT) or an inverse fast Fourier transform (IFFT). If the STBC encoder and the spatial mapper are used, the IFT 306 may be provided for each transmit chain.

[0062] When the TxSP 324 performs a MIMO or MU-MIMO transmission, the TxSP 324 may insert cyclic shift diversities (CSDs) to prevent unintentional beamforming. The TxSP 324 may perform the insertion of the CSD before or after the IFT 306. The CSD may be specified per transmit chain or may be specified per space-time stream. Alternatively, the CSD may be applied as a part of the spatial mapper.

[0063] When the TxSP 324 performs a MIMO or MU-MIMO transmission, some blocks before the spatial mapper may be provided for each user.

[0064] The GI inserter 308 prepends a GI to each symbol produced by the IFT 306. Each GI may include a Cyclic Prefix (CP) corresponding to a repeated portion of the end of the symbol that the GI precedes. The TxSP 324 may optionally perform windowing to smooth edges of each symbol after inserting the GI.

[0065] The RF transmitter 342 converts the symbols into an RF signal and transmits the RF signal via the antenna 352. When the TxSP 324 performs a MIMO or MU-MIMO transmission, the GI inserter 308 and the RF transmitter 342 may be provided for each transmit chain.

[0066] Figure 3B illustrates components of a WLAN device 104 configured to receive data according to an embodiment, including a Receiver (Rx) SPU (RxSP) 326, an RF receiver 344, and an antenna 354. In an embodiment, the RxSP 326, RF receiver 344, and antenna 354 may correspond to the receiving SPU 226, the RF receiver 244, and an antenna of the antenna unit 250 of Figure 2, respectively.

[0067] The RxSP 326 includes a GI remover 318, a Fourier transformer (FT) 316, a demapper 314, a deinterleaver 312, and a decoder 310.

[0068] The RF receiver 344 receives an RF signal via the antenna 354 and converts the RF signal into symbols. The GI remover 318 removes the GI from each of the symbols. When the received transmission is a MIMO or MU-MIMO transmission, the RF receiver 344 and the GI remover 318 may be provided for each receive chain.

[0069] The FT 316 converts each symbol (that is, each time domain block) into a frequency domain block of constellation points by using a discrete Fourier transform (DFT) or a fast Fourier transform (FFT). The FT 316 may be provided for each receive chain.

[0070] When the received transmission is the MEMO or MU-MIMO transmission, theRxSP 326 may include a spatial demapper for converting the respective outputs of the FTs 316 of the receiver chains to constellation points of a plurality of space-time streams, and an STBC decoder for despreading the constellation points from the space-time streams into one or more spatial streams.

[0071] The demapper 314 demaps the constellation points output from the FT 316 or the STBC decoder to bit streams. If the received transmission was encoded using LDPC encoding, the demapper 314 may further perform LDPC tone demapping before performing the constellation demapping.

[0072] The deinterleaver 312 deinterleaves the bits of each stream output from the demapper 314. The deinterleaver 312 may perform the deinterleaving only when the received transmission was encoded using BCC encoding, and otherwise may output the stream output by the demapper 314 without performing deinterleaving.

[0073] When the received transmission is the MEMO or MU-MIMO transmission, theRxSP 326 may use a plurality of demappers 314 and a plurality of deinterleavers 312 corresponding to the number of spatial streams of the transmission. In this case, the RxSP 326 may further include a stream deparser for combining the streams output from the deinterleavers 312.

[0074] The decoder 310 decodes the streams output from the deinterleaver 312 or the stream deparser. In an embodiment, the decoder 310 includes an FEC decoder. The FEC decoder may include a BCC decoder or an LDPC decoder.

[0075] The RxSP 326 may further include a descrambler for descrambling the decoded data. When the decoder 310 performs BCC decoding, the RxSP 326 may further include an encoder deparser for multiplexing the data decoded by a plurality of BCC decoders. When the decoder 310 performs the LDPC decoding, the RxSP 326 may not use the encoder deparser.

[0076] Before making a transmission, wireless devices such as wireless device 104 will assess the availability of the wireless medium using Clear Channel Assessment (CCA). If the medium is occupied, CCA may determine that it is busy, while if the medium is available, CCA determines that it is idle.

[0077] The PHY entity for IEEE 802.11 is based on Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiple Access (OFDMA). In eitherOFDM or OFDMA Physical (PHY) layers, a STA (e.g., a wireless device 104) is capable of transmitting and receiving Physical Layer (PHY) Protocol Data Units (PPDUs) (also referred to as PLCP (Physical Layer Convergence Procedure) Protocol Data Units) that are compliant with the mandatory PHY specifications. A PHY specification defines a set of Modulation and Coding Schemes (MCS) and a maximum number of spatial streams. Some PHY entities define downlink (DL) and uplink (UL) Multi-User (MU) transmissions having a maximum number of space-time streams (STS) per user and employing up to a predetermined total number of STSs. A PHY entity may provide support for 10 Megahertz (MHz), 20 MHz, 40 MHz, 80 MHz, 160 MHz, 240 MHz, and 320 MHz contiguous channel widths and support for an 80+80, 80+160 MHz, and 160+160 MHz non-contiguous channel width. Each channel includes a plurality of subcarriers, which may also be referred to as tones. A PHY entity may define signaling fields denoted as Legacy Signal (L-SIG), Signal A (SIG- A), and Signal B (SIG-B), and the like within a PPDU by which some necessary information about PHY Service Data Unit (PSDU) attributes are communicated. The descriptions below, for sake of completeness and brevity, refer to OFDM-based 802.11 technology. Unless otherwise indicated, a station refers to a non-AP STA.

[0078] Figure 4 illustrates Inter-Frame Space (IFS) relationships. In particular, Figure 4 illustrates a Short IFS (SIFS), a Point Coordination Function (PCF) IFS (PIFS), a Distributed Coordination Function (DCF) IFS (DIFS), and an Arbitration IFSs corresponding to an Access Category (AC) ‘ i’ (AIFS[i]). Figure 4 also illustrates a slot time and a data frame is used for transmission of data forwarded to a higher layer. As shown, a WLAN device 104 transmits the data frame after performing backoff if a DIFS has elapsed during which the medium has been idle.

[0079] A management frame may be used for exchanging management information, which is not forwarded to the higher layer. Subtype frames of the management frame include a beacon frame, an association request / response frame, a probe request / response frame, and an authentication request / response frame.

[0080] A control frame may be used for controlling access to the medium. Subtype frames of the control frame include a request to send (RTS) frame, a clear to send (CTS) frame, and an acknowledgement (ACK) frame.

[0081] When the control frame is not a response frame of another frame, the WLAN device 104 transmits the control frame after performing backoff if a DIFS has elapsed during which the medium has been idle. When the control frame is the response frame of another frame, the WLAN device 104 transmits the control frame after a SIFS has elapsed without performing backoff or checking whether the medium is idle.

[0082] A WLAN device 104 that supports Quality of Service (QoS) functionality (that is, a QoS STA) may transmit the frame after performing backoff if an AIFS for an associated access category (AC) (i.e., AIFS[AC]) has elapsed. When transmitted by the QoS STA, any of the data frame, the management frame, and the control frame, which is not the response frame, may use the AIFS[AC] of the AC of the transmitted frame.

[0083] A WLAN device 104 may perform a backoff procedure when the WLAN device 104 that is ready to transfer a frame finds the medium busy. The backoff procedure includes determining a random backoff time composed of N backoff slots, where each backoff slot has a duration equal to a slot time and N being an integer number greater than or equal to zero. The backoff time may be determined according to a length of a Contention Window (CW). In an embodiment, the backoff time may be determined according to an AC of the frame. All backoff slots occur following a DIFS or Extended IFS (EIFS) period during which the medium is determined to be idle for the duration of the period.

[0084] When the WLAN device 104 detects no medium activity for the duration of a particular backoff slot, the backoff procedure shall decrement the backoff time by the slot time. When the WLAN device 104 determines that the medium is busy during a backoff slot, the backoff procedure is suspended until the medium is again determined to be idle for the duration of a DIFS or EIFS period. The WLAN device 104 may perform transmission or retransmission of the frame when the backoff timer reaches zero.

[0085] The backoff procedure operates so that when multiple WLAN devices 104 are deferring and execute the backoff procedure, each WLAN device 104 may select a backoff time using a random function and the WLAN device 104 that selects the smallest backoff time may win the contention, reducing the probability of a collision.

[0086] Figure 5 illustrates a Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) based frame transmission procedure for avoiding collision between frames in a channel according to an embodiment. Figure 5 shows a first station STA1 transmitting data, a second station STA2 receiving the data, and a third station STA3 that may be located in an area where a frame transmitted from the STA1 can be received, a frame transmitted from the second station STA2 can be received, or both can be received. The stations STA1, STA2, and STA3 may be WLAN devices 104 of Figure 1.

[0087] The station STA1 may determine whether the channel is busy by carrier sensing. The station STA1 may determine channel occupation / status based on an energy level in the channel or an autocorrelation of signals in the channel, or may determine the channel occupation by using a network allocation vector (NAV) timer.

[0088] After determining that the channel is not used by other devices (that is, that the channel is IDLE) during a DIFS (and performing backoff if required), the station STA1 may transmit a Request-To-Send (RTS) frame to the station STA2. Upon receiving the RTS frame, after a SIFS the station STA2 may transmit a Clear-To-Send (CTS) frame as a response to the RTS frame. If Dual-CTS is enabled and the station STA2 is an AP, the AP may send two CTS frames in response to the RTS frame (e g., a first CTS frame in a non-High Throughput format and a second CTS frame in the HT format).

[0089] When the station STA3 receives the RTS frame, it may set a NAV timer of the station STA3 for a transmission duration of subsequently transmitted frames (for example, a duration of SIFS + CTS frame duration + SIFS + data frame duration + SIFS + ACK frame duration) using duration information included in the RTS frame. When the station STA3 receives the CTS frame, it may set the NAV timer of the station STA3 for a transmission duration of subsequently transmitted frames using duration information included in the CTS frame. Upon receiving a new frame before the NAV timer expires, the station STA3 may update the NAV timer of the station STA3 by using duration information included in the new frame. The station STA3 does not attempt to access the channel until the NAV timer expires.

[0090] When the station STA1 receives the CTS frame from the station STA2, it may transmit a data frame to the station STA2 after a SIFS period elapses from a time when the CTS frame has been completely received. Upon successfully receiving the data frame, the station STA2 may transmit an ACK frame as a response to the data frame after a SIFS period elapses.

[0091] When the NAV timer expires, the third station STA3 may determine whether the channel is busy using the carrier sensing. Upon determining that the channel is not used by other devices during a DIFS period after the NAV timer has expired, the station STA3 may attempt to access the channel after a contention window elapses according to a backoff process.

[0092] When Dual-CTS is enabled, a station that has obtained a transmission opportunity (TXOP) and that has no data to transmit may transmit a CF-End frame to cut short the TXOP. An AP receiving a CF-End frame having a Basic Service Set Identifier (BSSID) of the AP as a destination address may respond by transmitting two more CF-End frames: a first CF-End frame using Space Time Block Coding (STBC) and a second CF-End frame using non-STBC. A station receiving a CF-End frame resets its NAV timer to 0 at the end of the PPDU containing the CF-End frame. Figure 5 shows the station STA2 transmitting an ACK frame to acknowledge the successful reception of a frame by the recipient.

[0093] The IEEE 802.1 Ibn (Ultra High Reliability, UHR) working group has been established to address the growing demand for higher peak throughput and reliability in Wi-Fi. As shown inFigure 6, the peak PHY rate has significantly increased from IEEE 802.1 lb to IEEE 802.1 Ibe (Wi-Fi 7), with the latter focusing on further improving peak throughput. The UHR study group aims to enhance the tail of the latency distribution and jitter to support applications that require low latency, such as video-over- WLAN, gaming, AR, and VR. It is noted that various characteristics of UHR (e.g., max PHY rate, PHY rate enhancement, bandwidth / number of spatial streams, and operating bands) are still to be determined.

[0094] The focus of IEEE 802.1 Ibe is primarily on WLAN indoor and outdoor operation with stationary and pedestrian speeds in the 2.4, 5, and 6 GHz frequency bands. In addition to peak PHY rate, different candidate features are under discussion. These candidate features include (1) a 320MHz bandwidth and a more efficient utilization of a non-contiguous spectrum, (2) multi-band / multi-channel aggregation and operation, (3) 16 spatial streams and Multiple Input Multiple Output (MIMO) protocol enhancements, (4) multi-Access Point (AP) Coordination (e.g., coordinated and joint transmission), (5) an enhanced link adaptation and retransmission protocol (e.g., Hybrid Automatic Repeat Request (HARQ)), and (6) adaptation to regulatory rules specific to a 6 GHz spectrum.

[0095] The focus of IEEE 802.1 Ibn (UHR) is still under discussion, with candidate features including MLO enhancements (e.g., in terms of increased throughput / reliability and decreased latency), latency and reliability improvements (e g., multi-AP coordination to support low latency traffic), bandwidth expansion (e.g., to 240, 480, 640 MHz), aggregated PPDU (A- PPDU), enhanced multi-link single-radio (eMLSR) extensions to AP, roaming improvements, and power-saving schemes for prolonging battery life.

[0096] Some features, such as increasing the bandwidth and the number of spatial streams, are solutions that have been proven to be effective in previous projects focused on increasing link throughput and on which feasibility demonstration is achievable.

[0097] With respect to operational bands (e.g., 2.4 / 5 / 6 GHz) for IEEE 802.1 Ibe, more than 1 GHz of additional unlicensed spectrum is likely to be available because the 6 GHz band (5.925- 7.125 GHz) is being considered for unlicensed use. This would allow APs and STAs to become tri -band devices. Larger than 160MHz data transmissions (e.g., 320 MHz or 640 MHz) could be considered to increase the maximum PHY rate. For example, 320 MHz or 160+160MHz data could be transmitted in the 6 GHz band. For example, 160+160 MHz data could be transmitted across the 5 and 6 GHz bands.

[0098] In the process of wireless communication, a transmitting station (STA) creates a Physical Layer Protocol Data Unit (PPDU) frame and sends it to a receiving STA. The receiving STA then receives, detects, and processes the PPDU.

[0099] The Extremely High Throughput (EHT) PPDU frame encompasses several components. It includes a legacy part, which comprises fields such as the Legacy Short Training Field (L-STF), Legacy Long Training Field (L-LTF), Legacy Signal Field (L-SIG), and Repeated Legacy Signal Field (RL-SIG). These fields are used to maintain compatibility with older Wi-Fi standards.

[0100] In addition to the legacy part, the EHT PPDU frame also contains the Universal Signal Field (U-SIG), EHT Signal Field (EHT-SIG), EHT Short Training Field (EHT-STF), and EHT Long Training Field (EHT-LTF). These fields are specific to the EHT standard and are used for various purposes, such as signaling, synchronization, and channel estimation.

[0101] Figure 7 provides a more detailed description of each field in the EHT PPDU frame, including their purposes and characteristics.

[0102] Regarding the Ultra High Reliability (UHR) PPDU, its frame structure is currently undefined and will be determined through further discussions within the relevant working group or study group. This indicates that the specifics of the UHR PPDU are still under development and will be finalized based on the outcomes of future deliberations.

[0103] The distributed nature of channel access networks, such as IEEE 802.11 WLANs, makes the carrier sense mechanism useful for ensuring collision-free operation. Each station (STA) uses its physical carrier sense to detect transmissions from other STAs. However, in certain situations, it may not be possible for a STA to detect every transmission. For instance, when one STA is located far away from another STA, it might perceive the medium as idle and start transmitting a frame, leading to collisions. To mitigate this hidden node problem, the network allocation vector (NAV) has been introduced.

[0104] As the IEEE 802.11 standard continues to evolve, it now includes scenarios where multiple users can simultaneously transmit or receive data within a basic service set (BSS), such as uplink (UL) and downlink (DL) multi-user (MU) transmissions in a cascaded manner. In these cases, the existing carrier sense and NAV mechanisms may not be sufficient, and modifications or newly defined mechanisms may be required to facilitate efficient and collision- free operation.

[0105] For the purpose of this disclosure, MU transmission refers to situations where multiple frames are transmitted to or from multiple STAs simultaneously using different resources. Examples of these resources include different frequency resources in Orthogonal Frequency Division Multiple Access (OFDMA) transmission and different spatial streams in Multi-User Multiple Input Multiple Output (MU-MIMO) transmission. Consequently, downlink OFDMA (DL-OFDMA), downlink MU-MIMO (DL-MU-MIMO), uplink OFDMA (UL-OFDMA), uplink MU-MIMO (UL-MU-MIMO), and OFDMA with MU-MIMO are all considered examples of MU transmission.

[0106] Figure 8 illustrates an example of multi-user (MU) transmission in Orthogonal Frequency -Division Multiple Access (OFDMA), in accordance with some embodiments of the present disclosure.

[0107] In the IEEE 802.1 lax and 802 1 Ibe specifications, the trigger frame plays a useful role in facilitating uplink multi-user (MU) transmissions. The purpose of the trigger frame is to allocate resources and solicit one or more Trigger-based (TB) Physical Layer Protocol Data Unit (PPDU) transmissions from the associated stations (STAs).

[0108] The trigger frame contains information required by the responding STAs to send their Uplink TB PPDUs. This information includes the Trigger type, which specifies the type of TB PPDU expected, and the Uplink Length (UL Length), which indicates the duration of the uplink transmission.

[0109] Figure 9 illustrates an example scenario where an access point (AP) operating in an 80MHz bandwidth environment sends a Trigger frame to multiple associated STAs. Upon receiving the Trigger frame, the STAs respond by sending their respective Uplink Orthogonal Frequency Division Multiple Access (UL OFDMA) TB PPDUs, utilizing the allocated resources within the specified 80 MHz bandwidth.

[0110] After successfully receiving the UL OFDMA TB PPDUs, the AP acknowledges the STAs by sending an acknowledgement frame. This acknowledgement can be in the form of an 80MHz width multi-STA Block Acknowledgement (Block Ack) or a Block Acknowledgement with a Direct Feedback (DF) OFDMA method. The multi-STA Block Ack allows the AP to acknowledge multiple STAs simultaneously, while the Block Ack with DF OFDMA enables the AP to provide feedback to the STAs using the same OFDMA technique employed in the uplink transmission.

[0111] The trigger frame is a useful component in enabling efficient uplink MU transmissions in IEEE 802.1 lax and 802.1 Ibe networks, by allocating resources and coordinating the uplink transmissions from multiple STAs within the same bandwidth.

[0112] Wireless network systems can rely on retransmission of media access control (MAC) protocol data units (MPDUs) when the transmitter (TX) does not receive an acknowledgement from the receiver (RX) or MPDUs are not successfully decoded by the receiver. Using an automatic repeat request (ARQ) approach, the receiver discards the last failed MPDU before receiving the newly retransmitted MPDU. With requirements of enhanced reliability andreduced latency, the wireless network system can evolve toward a hybrid ARQ (HARQ) approach.

[0113] There are two methods of HARQ processing. In a first type of HARQ scheme, also referred to as chase combining (CC) HARQ (CC-HARQ) scheme, signals to be retransmitted are the same as the signals that previously failed because all subpackets to be retransmitted use the same puncturing pattern. The puncturing is needed to remove some of the parity bits after encoding using an error-correction code. The reason why the same puncturing pattern is used with CC-HARQ is to generate a coded data sequence with forward error correction (FEC) and to make the receiver use a maximum-ratio combining (MRC) to combine the received, retransmitted bits with the same bits from the previous transmission. For example, information sequences are transmitted in packets with a fixed length. At a receiver, error correction and detection are carried out over the whole packet. However, the ARQ scheme may be inefficient in the presence of burst errors. To solve this more efficiently, subpackets are used. In subpacket transmissions, only those subpackets that include errors need to be retransmitted.

[0114] Since the receiver uses both the current and the previously received subpackets for decoding data, the error probability in decoding decreases as the number of used subpackets increases. The decoding process passes a cyclic redundancy check (CRC) and ends when the entire packet is decoded without error or the maximum number of subpackets is reached. In particular, this scheme operates on a stop-and-wait protocol such that if the receiver can decode the packet, it sends an acknowledgement (ACK) to the transmitter. When the transmitter receives an ACK successfully, it terminates the HARQ transmission of the packet. If the receiver cannot decode the packet, it sends a negative acknowledgement (NAK) to the transmitter and the transmitter performs the retransmission process.

[0115] In a second type of HARQ scheme, also referred to as an incremental redundancy (IR) HARQ (IR-HARQ) scheme, different puncturing patterns are used for each subpacket such that the signal changes for each retransmitted subpacket in comparison to the originally transmitted subpacket. IR-HARQ alternatively uses two puncturing patterns for odd numbered and even numbered transmissions, respectively. The redundancy scheme of IR-HARQ improves the log likelihood ratio (LLR) of parity bit(s) in order to combine information sent across different transmissions due to requests and lowers the code rate as the additional subpacket is used. This results in a lower error rate of the subpacket in comparison to CC-HARQ. The puncturing pattern used in IR-HARQ is indicated by a subpacket identity (SPID) indication. The SPID of the first subpacket may always be set to 0 and all the systematic bits and the punctured parity bits are transmitted in the first subpacket. Self-decoding is possible when the receiving signal-to-noise ratio (SNR) environment is good (i.e., a high SNR). In some embodiments, subpackets with corresponding SPIDs to be transmitted are in increasing order of SPID but can be exchanged / switched except for the first SPID.

[0116] AP coordination has been considered as a potential technology to improve WLAN system throughput in the IEEE 802.1 Ibe standard and is still being discussed in the IEEE 802.1 Ibn (UHR) standard. To support various AP coordination schemes, such as coordinated beamforming, OFDMA, TDMA, spatial reuse, and joint transmission, a predefined mechanism for APs is necessary.

[0117] In the context of coordinated TDMA (C-TDMA), the AP that obtains a transmit opportunity (TXOP) is referred to as the sharing AP. This AP initiates the AP coordination schemes to determine the AP candidate set by sending a frame, such as a Beacon frame or probe response frame, which includes information about the AP coordination scheme capabilities. The AP that participates in the AP coordination schemes after receiving the frame from the sharing AP is called the shared AP. The sharing AP is also known as the master AP or coordinating AP, while the shared AP is referred to as the slave AP or coordinated AP.

[0118] The operation of various AP coordination schemes has been discussed in theIEEE 802.1 Ibe and UHR standards:

[0119] Coordinated Beamforming (C-BF): Multiple APs transmit on the same frequency resource by coordinating and forming spatial nulls, allowing for simultaneous transmission from multiple APs.

[0120] Coordinated OFDMA (C-OFDMA): APs transmit on orthogonal frequency resources by coordinating and splitting the spectrum, enabling more efficient spectrum utilization.

[0121] Joint Transmission (JTX): Multiple APs transmit j ointly to a given user simultaneously by sharing data between the APs.

[0122] Coordinated Spatial Reuse (C-SR): Multiple APs or STAs adjust their transmit power to reduce interference between APs.

[0123] By implementing these AP coordination schemes, WLAN systems can improve their overall throughput and efficiency by leveraging the cooperation between multiple APs.

[0124] Figure 10 is a diagram showing a wireless network environment with an AP, relay STAs, and STAs that are capable of MLO in a 2.4 GHz band and a 5 GHz band, according to some embodiments.

[0125] As shown in the diagram, the wireless network environment may include an AP 1010, two relay STAs (relay STA 1020-1 and relay STA 1020-2), and five non-AP non-relay STAs (STA 1030-1, STA 1030-2, STA 1030-3, STA 1030-4, and STA 1030-5). The AP 1010, relaySTAs 1020, and STAs 1030 may be multi-link devices (MLDs) that are capable of MLO. Unlike traditional non-MLD APs and non-MLD STAs, MLD APs and STAs (also referred to herein as AP MLDs and STA MLDs, respectively) may have multiple wireless interfaces and may be capable of MLO in multiple channel s / bands. In this example, it is assumed that the AP 1010, relay STAs 1020, and non-relay STAs 1030 are capable of MLO in a first channel in the 2.4 GHz band and a second channel in the 5 GHz band. It is noted that MLDs having multiple wireless interfaces may still have a unique MAC instance at the upper layers, without losing the independent parameters of each wireless interface.

[0126] The AP 1010 may operate a basic service set (BSS) in the 2.4 GHz band and the 5 GHz band (using two wireless interfaces). In the example shown in the diagram, the AP’s 1010 coverage area in the 2.4 GHz band may extend further than the AP’s 1010 coverage area in the 5 GHz band (due to the 2.4 GHz band being a lower frequency band).

[0127] The relay STAs (relay STA 1020-1 and relay STA 1020-2) may act as a relay for STAs 1030 (and thus relay traffic between the STAs 1030 and the AP 1010). For example, relay STA 1020-1 may act as a relay for STA 1030-2 and STA 1030-5. Also, relay STA 1020-2 may act as a relay for STA 1030-3 and 1030-4.

[0128] For sake of explanation only, various embodiments may be described herein in the context of the wireless network environment shown in Figure 10. It should be appreciated, however, that the techniques described herein may be applicable to other wireless network environments having different configurations.

[0129] Figure 11 is a diagram showing a single link operation and a multi-link operation between an AP and a non-AP STA, according to some embodiments.

[0130] As shown in the diagram, with a single link operation, an AP 1110 and a non-AP STA 1130 may communicate with each other over a single link. In contrast, with a multi-link operation (MLO), an AP MLD 1150 and a non-AP STA MLD 1170 may communicate with each other over multiple links. For example, as shown in the diagram, the AP MLD 1150 may have a first instance (“API”) and a second instance (“AP2”). Similarly, the non-AP STA MLD 1170 may also have a first instance (“STA1”) and a second instance (“STA2”). The AP MLD 1150 may communicate with the non-AP STA MLD 1170 over a first link (“Linkl”) between API and STA1 and also over a second link (“Link2”) between AP2 and STA2.

[0131] A relay STA (rSTA) may be a non-AP STA that can relay traffic between an AP and a non-AP STA. Relay operations may help extend the possible communication range and provide improved QoS (e.g., reliability and throughput) in a wireless network. For example, relay STA 1020-1 shown in Figure 10 may relay traffic between the AP 1010 and STA 1030-2 and / orSTA 1030-5. Also, relay STA 1020-2 shown in Figure 10 may relay traffic between AP 1010 and STA 1030-3 and / or STA 1030-4.

[0132] Figure 12 is a diagram showing a relay STA MLD that can relay traffic between an AP MLD and a non-AP STA MLD using MLO, according to some embodiments.

[0133] When MLO is supported in a wireless network, the relay operations can also use MLO. For example, as shown in the diagram, an AP MLD 1210 may have a first instance (“API”) and a second instance (“AP2”), a relay STA MLD 1220 may have a first instance (“rSTAl”) and a second instance (“rSTA2”), and the non-AP STA MLD 1230 may have a first instance (“STA1”) and a second instance (“STA2”). API and rSTAl may communicate with each other over a link (“Linkl-1”) that operates in a first channel (e.g., a channel in the 2.4 GHz band). rSTAl and STA1 may communicate with each other over a link (“Linkl-2”) that operates in the first channel. AP2 and rSTA2 may communicate with each other over a link (“Link2-1”) that operates in a second channel (e.g., a channel in the 5 GHz band) that is different from the first channel. rSTA2 and STA2 may communicate with each other over a link (“Link2-2”) that operates in the second channel. API and STA1 may communicate with each other in the first channel via rSTAl . For example, downlink traffic going from API to STA1 may be transmitted in the first channel over Linkl-1 and Linkl-2 (in that order) and uplink traffic going from STA1 to API may be transmitted in the first channel over Linkl-2 and Linkl- 1 (in that order). Similarly, AP2 and STA2 may communicate with each other in the second channel via rSTA2. For example, downlink traffic going from AP2 to STA2 may be transmitted in the second channel over Link2-1 and Link2-2 (in that order) and uplink traffic going from STA2 to AP2 may be transmitted in the second channel over Link2-2 and Link2-1 (in that order). In this way, the AP MLD 1210 may be able to communicate with the non-AP STA MLD 1230 via the relay STA MLD 1220 (using relay operations) in two different channels over two different sets of links. The links over which traffic is relayed may be referred to herein as relay links. For example, Linkl-1, Linkl-2, Link2-1, and Link 2-2 may be considered to be relay links.

[0134] Figure 13 is a diagram showing an extended service set (ESS) comprising two BSSs in which MLO-based seamless roaming may occur, according to some embodiments.

[0135] As shown in the diagram, the ESS 1350 may include a first AP MLD 1310-1 (“AP MLD1”) that operates a first BSS and a second AP MLD 1310-2 (“AP MLD2”) that operates a second BSS. The AP MLDs 1310 may operate their respective BSSs in both the 2.4 GHz band and the 5 GHz band (using two wireless interfaces). An AP’s 1030 coverage area in the 2.4 GHz band may extend further than the AP’s 1030 coverage area in the 5 GHz band (due tothe 2.4 GHz band being a lower frequency band). As shown in the diagram, the coverage areas of AP MLD1 1310-1 and AP MLD2 1310-2 may overlap.

[0136] The ESS may also include multiple non-AP STA MLDs (STA 1330-1, STA 1330-2, STA 1330-3, and STA 1330-4). The ESS may also include a relay STA MLD 1320 that can relay traffic between an AP 1310 and a STA 1030. For example, the relay STA MLD 1320 may relay traffic between AP MLD1 1310-1 and STA 1030-2 and / or between AP MLD1 1310-1 and STA 1030-3.

[0137] AP MLD1 1310-1 and AP MLD2 1310-2 may be connected to a centralized distribution system (DS) controller 1360 of the network via a wired and / or wireless backhaul links. The DS controller 1360 may be a logical component that connects multiple APs together and that may distribute traffic across the network. The DS controller 1360 may include an upper service access point (U-SAP) component , which may serve as an interface between the MAC sublayer and higher-layer entities, enabling higher-level AP functionalities such as data forwarding or management services.

[0138] A STA 1330 may initially be associated with one of the AP MLDs 1310 in the ESS 1350. As the STA 1330 moves around the wireless network environment, the STA 1330 may seamlessly roam to another AP 1310 using a MLO seamless roaming procedure. For example, STA 1330-1 may initially be connected to AP MLD1 1310-1 but may then seamlessly roam to AP MLD2 1310-2 using a MLO seamless roaming procedure when it enters the coverage area of AP MLD2 1310-2. A MLO seamless roaming procedure is shown in Figure 15 and further described herein in relation thereto.

[0139] Figure 14 is a diagram showing a wireless network that implements relay technology, according to some embodiments. The example shown in the diagram assumes a network configuration that is similar to the one shown in Figure 13. Like reference numbers are used for like entities.

[0140] As shown in the diagram, the wireless network includes AP MLD1 1310-1, AP MLD2 1310-2, a relay STA MLD 1320, STA MLD 1330-1, STA MLD 1330-2, and STA MLD 1330-3. AP MLD1 1310-1 and AP MLD2 1310-2 may be connected to U-SAP component of a DS controller 1360. Each AP MLD 1310 may include two AP instances operating in different channels / bands. For example, AP MLD1 1310-1 may include instance API operating in a first band (e.g., 2.4 GHz band) and instance AP2 operating in a second band (e.g., 5 GHz band) and AP MLD2 1310-2 may include instance AP3 operating in the first band and instance AP4 operating in the second band. Also, the relay STA MLD 1320 may include two relay STA instances operating in different channels / bands. For example, the relay STAMLD 1320 may include instance rSTAl operating in the first band and instance rSTA2 operating in the second band. Also, each (non-AP) STA 1330 may include two STA instances operating in different channels / bands. For example, STA MLD 1330-1 may include instance STA1 operating in the first band and instance STA2 operating in the second band, STA MLD 1330-2 may include instance STA3 operating in the first band and instance STA4 operating in the second band, and STA MLD 1330-3 may include instance STA5 operating in the first band and STA6 operating in the second band.

[0141] STA MLD 1330-1 may be directly connected to API MLD1 1310-1 through multiple links. For example, STA1 of STA MLD 1330-1 may be connected to API of AP MLD-1 1310- 1 through a link operating in the first band (“Linkl”) and STA2 of STA MLD 1330-1 may be connected to AP2 of AP MLD1 1310-1 through a link operating in the second band (“Link2”). As used herein, Linkl may refer to a wireless link operating in the first channel / band and Link2 may refer to a wireless link operating in the second channel / band (where the second channel / band is different from the first channel / band). STA MLD 1330-2 may be directly connected to AP MLD-1 1310-1 in the first band but connected to AP MLD1 1310-1 via the relay STA MLD 1320 in the second band. For example, STA3 of STA MLD 1330-2 may be connected to API of AP MLD1 1310-1 through Linkl and STA4 of STA MLD 1330-2 may be connected to rSTA2 of the relay STA MLD 1320 through Link2. STA MLD 1330-3 may not have a direct connection to AP MLD1 1310-1 but may be connected to AP MLD1 1310-1 through the relay STA MLD 1320. For example, STA6 of STA MLD 1330-3 may be connected to rSTA2 of the relay STA MLD 1320 through Link2. In this example, STA MLD 1330-3 is connected to the relay STA MLD 1320 through a single link (although it is possible for a STA MLD to be connected to the relay STA MLD 1320 through more than one link). The relay STA MLD 1320 may be connected to AP MLD1 1310-1 through multiple links. For example, rSTAl of the relay STA MLD 1320 may be connected to API of AP MLDl 1310-1 through Linkl and rSTA2 of the relay STA MLD 1320 may be connected to AP2 of AP MLD1 1310-1 through Link2.

[0142] In the example shown in the diagram, STA MLD 1330-1 may be connected to AP MLD1 1310-1 over two direct links (Linkl and Link2). STA MLD 1330-1 may receive downlink (DL) traffic directly (without using relay operations) from AP MLD1 1310-1 over either link (Linkl between STA1 and API or Link2 between STA2 and AP2) and may transmit uplink (UL) traffic directly to AP MLD1 1310-1 over either link.

[0143] In the example shown in the diagram, STA MLD 1330-2 may be able to receive beacon frames and / or other DL traffic from AP MLD1 1310-1 (over Linkl between STA3 andAPI), but it may be unable to transmit UL traffic directly to AP MLD1 1310-1 due to a DL / UL power asymmetry (e.g., where the DL transmit power is higher than the UL transmit power). The relay STA MLD 1320 may help resolve this DL / UL power asymmetry by relaying uplink traffic from STA MLD 1330-2 to AP MLD1 1310-1 (over Link2 between STA4 and rSTA2 and Link2 between rSTA2 and AP2). Thus, STA MLD 1330-2 may receive DL traffic directly from AP MLD1 1310-1 (over Linkl between STA3 and API) and transmit UL traffic to AP MLD1 1310-1 via the relay STA MLD 1320 (over Link2 between STA4 and rSTA2 and Link2 between rSTA2 and AP2).

[0144] In the example shown in the diagram, all links of STA MLD 1330-3 are beyond the one-hop range of AP MLD1 1310-1 (e.g., out of beacon frame transmission range), but the relay STA MLD 1320 may assist in effectively extending the coverage of AP MLD1 1310-1 using MLO. For example, STA MLD 1330-3 may receive DL traffic from AP MLD1 1310-1 via the relay STA MLD 1320 and transmit UL traffic to AP MLD1 1310-1 via the relay STA MLD 1320 over a single link (over Link2 between STA6 and rSTA2).

[0145] Figure 15 is a diagram showing a MLO seamless roaming procedure, according to some embodiments.

[0146] As shown in the diagram, a STA MLD 1530 may initially be connected to a first AP MLD (AP MLD1 1510-1) through two MLD links (“Linkl” and “Link2”). The STA 1530 may periodically assess the link quality of the MLD links based on management frames transmitted by AP MLD1 1510-1 and may decide to roam to a second AP MLD (AP MLD2 1510-2) if the STA 1530 is within the coverage area of AP MLD2 1510-2 and the MLD links with AP MLD1 1510-1 have poor link quality. Linkl may be a link that operates in a first channel / band (e.g., a 2.4 GHz channel) and Link2 may be a link that operates in a second channel / band (e.g., a 5 GHz channel).

[0147] As shown in the diagram, if the STA 1530 decides to roam to AP MLD2 1510-2, it may disconnect Linkl from AP MLD1 1510-1 and establish a new link with AP MLD2 1510-2 in the same channel. The STA 1530 may maintain Link2 with AP MLD1 1510-1 until the new link with AP MLD2 1510-2 is established. Thus, the STA 1530 may be connected to AP MLD1 1510-1 through Link2 and connected to AP MLD2 1510-2 through Linkl for a period of time. During this period of time, the STA 1530 is said to be in a roaming transition state.During the roaming transition state, the U-SAP component may direct DL traffic for the STA 1530 to either AP MLD 1 1510-1 or AP MLD2 1510-2. AP MLD1 1510-1 may transmit DL traffic to the STA 1530 over Link2 with the STA 1530 and AP MLD2 1510-2 may transmit DL traffic to the STA 1530 over Linkl with the STA 1530. After the new link (Linkl) with APMLD2 1510-2 is established, the STA 1530 may disconnect Link2 from AP MLD1 1510-1 and establish a new link with the neighboring AP MLD2 1510-2 in the same channel. As a result, the STA 1530 is now connected to AP MLD2 1510-2 through two MLD links (Linkl and Link2), completing the MLO seamless roaming procedure. The transition may be managed by the U-SAP component, including the re-authentication, re-association, and 4-way handshake. In this way, the STA 1530 may transition from being connected to AP MLD1 1510-1 to being connected to AP MLD2 1510-2 without experiencing delays (e.g., authentication delays) and interruptions that are typical with single-link roaming operations.

[0148] Figure 16 is a diagram showing frame exchange sequence for performing a MLO seamless roaming procedure, according to some embodiments.

[0149] As shown in the diagram, AP MLD1 1610-1 and AP MLD2 1610-2 may be connected to U-SAP component (e g., via a backhaul link) Also, as shown in the diagram, at step (1), the non-AP STA MLD 1630 may be connected to AP MLD1 1610-1 through Linkl and Link2. At step (2), the non-AP STA MLD 1630 may periodically assess the link quality of its MLD links (Linkl and Link2) based on management frames (e.g., beacon frame, power save polling (PS- Poll) frames, etc.) transmitted by AP MLD1 1610-1 and potential candidate AP MLDs (e.g., AP MLD2 1610-2). Various metrics can be used to assess link quality such as channel state information (CSI), received signal strength indicator (RSSI), signal -to-noise ratio (SNR), channel quality indicator (CQI), and the like. The non-AP STA MLD 1630 may consider roaming from AP MLD1 1610-1 to AP MLD2 1610-2 if the result of the link quality assessment indicates that the MLD links with AP MLD1 1610-1 have poor link quality. What is considered “poor” link quality may be configurable and depend on the implementation. At step (3), the non-AP STA MLD 1630 may probe the MLD links with a candidate AP MLD, which in this case is AP MLD2 1610-2. For example, the non-AP STA MLD 1630 may transmit a probe request frame to AP MLD2 1610-2 over Linkl (between STA1 and AP3). Responsive to receiving the probe request frame from non-AP STA MLD 1630 over Linkl, AP MLD2 1610-2 may transmit a probe response frame to the non-AP STA MLD 1630 over Linkl . The non-AP STA MLD 1630 may also transmit a probe request frame to AP MLD2 1610-2 over Link2 (between STA2 and AP4). Responsive to receiving the probe request frame from non-AP STA MLD 1630 over Link2, AP MLD2 1610-2 may transmit a probe response frame to the non-AP STA MLD 1630 over Link2. At step (4), the non-AP STA MLD 1630 may assess the link quality of the MLD links with AP MLD2 1610-2 based on the probe response frames transmitted by AP MLD2 1610-2. At step (5), based on the result of the link quality assessment, the non-AP STA MLD 1630 may decide whether to roam to AP MLD2 1610-2 (thecandidate / target AP) or to stay in the current BSS (stay connected to AP MLD1 1610-1). If the non-AP STA MLD 1630 decides to roam to AP MLD2 1610-2, it may perform the MLO seamless roaming procedure shown in Figure 15 or similar procedure to seamlessly roam to AP MLD2 1610-2.

[0150] As mentioned above, a relay STA may play a dual role in that it can act as a relay for non-AP STAs and can also act as an individual non-AP STA that can roam between APs. If the relay STA roams to another AP, the non-AP STAs that are associated with the relay STA (and rely on the relay STA to relay traffic on their behalf) may lose their ability to communicate with the original AP, resulting in communication interruptions. Also, the non-AP STAs that are associated with the relay STA may not be aware that the relay STA has roamed to another AP and continue transmitting traffic to the relay STA even though the relay STA cannot relay to the original AP, resulting in the waste of communication resources. Existing roaming techniques are not equipped to handle this situation in a graceful manner.

[0151] Figure 17 is a diagram showing a situation in which the roaming technique described herein can be applied, according to some embodiments.

[0152] The diagram shows a wireless network having a similar configuration as the wireless network shown in Figure 14. Thus, details of the wireless network configuration are not repeated here for the sake of conciseness. However, a situation that may occur in the wireless network where the roaming technique described herein may be useful is described.

[0153] A relay STA MLD 1320 may be connected to AP MLD1 1310-1 and may be acting as a relay for one or more STA MLDs 1330 such as STA MLD 1330-2 and STA MLD 1330-3 (e.g., the relay STA MLD 1320 may relay traffic between those STA MLDs 1330 and AP MLD1 1310-1 in the uplink direction and / or downlink direction). The relay STA MLD 1320 may decide to roam from AP MLD1 1310-1 to AP MLD2 1310-2 (e.g., because the link quality of the MLD links between the relay STA MLD 1320 and AP MLD1 1310-1 have poor link quality). In this situation, if the relay STA MLD 1320 roams to AP MLD2 1310-2, the STA MLDs 1330 that are associated with the relay STA MLD 1320 (e.g., STA MLD 1330-2 and STA MLD 1330-3, which rely on the relay STA MLD 1320 to act as a relay on their behalf) may lose their connections to AP MLD1 1310-1. The roaming technique described herein may provide a protocol that leverages MLO-based relaying to support more seamless roaming and / or extended coverage. In particular, the roaming technique described herein considers cases where a relay STA may be mobile, and aims to manage such situations in a way that can help reduce connectivity disruptions for associated devices.

[0154] Figure 18 is a diagram showing a frame exchange sequence for a relay STA MLD that is acting as a relay for two STAs to roam to a new AP, according to some embodiments. The frame exchange sequence shown in the diagram assumes a network configuration that is similar to the one shown in Figure 13. Like reference numbers are used for like entities.

[0155] At step (1), the relay STA MLD 1320 may be connected to AP MLD1 1310-1 through Linkl (between rSTAl and API) and Link2 (between rSTA2 and AP2). Links that operate in a first channel (Linkl) are shown in dashed lines in the diagram and links that operate in a second channel (Link2) are shown in solid lines in the diagram. Non-AP STA MLD 1330-2 may be connected to AP MLD1 1310-1 through Linkl (between STA3 and API). Also, non-AP STA MLD 1330-2 may be connected to the relay STA MLD 1320 through Link2 (between STA4 and rSTA2). Also, non-AP STA MLD 1330-3 may be connected to the relay STA MLD 1320 through Link2 (between STA6 and rSTA2). The relay STA MLD 1320 may act as a relay for non-AP STA MLD 1330-2 and non-AP STA MLD 1330-3. For example, relay STA MLD 1320 may relay traffic received from non-AP STA MLD 1330-2 over Link2 (between STA4 and rSTA2) to AP MLD1 1310-1 over Link2 (between rSTA2 and AP2). As another example, relay STA MLD 1320 may relay traffic received from STA MLD 1330-3 over Link2 (between STA6 and rSTA2) to AP MLD1 1310-1 over Link2 (between rSTA2 and AP2) and may relay traffic received from AP MLD1 1310-1 over Link2 (between rSTA2 and AP2) to STA MLD 1330-3 over Link2 (between STA6 and rSTA2).

[0156] At step (2), the relay STA MLD 1320 (in its capacity / role as an individual non-AP STA) may periodically assess the link quality of its MLD links (Linkl and Link2) based on management frames (e.g., beacon frame, power save polling (PS-Poll) frames, etc.) transmitted by AP MLD1 1310-1 and potential candidate AP MLDs (e.g., AP MLD2 1310-2). Various metrics can be used to assess link quality such as CSI, RSSI, SNR, CQI, and the like. The relay STA MLD 1320 may consider roaming from AP MLD 1 1310-1 to AP MLD2 1310-2 if the result of the link quality assessment indicates that the MLD links with AP MLD1 1310-1 have poor link quality. What is considered “poor” link quality may be configurable and depend on the implementation.

[0157] At step (3), the relay STA MLD 1320 may probe the MLD links with a candidate AP MLD, which in this case is AP MLD2 1310-2. For example, the relay STA MLD 1320 may transmit a probe request frame to AP MLD2 1310-2 over Linkl (between rSTAl and AP3). Responsive to receiving the probe request frame from the relay STA MLD 1320 over Linkl, AP MLD2 1310-2 may transmit a probe response frame to the relay STA MLD 1320 over Linkl. The relay STA MLD 1320 may also transmit a probe request frame to AP MLD2 1310-2 overLink2 (between rSTA2 and AP4). Responsive to receiving the probe request frame from the relay STA MLD 1320 over Link2, AP MLD2 1310-2 may transmit a probe response frame to the relay STA MLD 1320 over Link2. This example assumes that the relay STA MLD 1320 and AP MLD2 1310-2 can operate in two bands / channels. If, the relay STA MLD 1320 and AP MLD2 1310-2 are able to operate in more than two bands / channels, the relay STA MLD 1320 may transmit a probe request frame in each band / channel.

[0158] At step (4), the relay STA MLD 1320 may assess the link quality of the MLD links with AP MLD2 1310-2 based on the probe response frames transmitted by AP MLD2 1310-2.

[0159] At step (5), based on the result of the link quality assessment, the relay STA MLD 1320 may decide whether to roam to AP MLD2 1310-2 (the target AP) or to stay in the current BSS (stay connected to AP MLD1 1310-1).

[0160] If the relay STA MLD 1320 decides to roam to AP MLD2 1310-2, the relay STA MLD 1320 may determine whether it is acting as a relay for any STAs. If the relay STA MLD 1320 is acting as a relay for at least one STA, the relay STA MLD 1320 may perform step (6). In this particular example, the relay STA MLD 1320 is acting as a relay for non-AP STA MLD 1330-2 and non-AP STA MLD 1330-3 so the relay STA MLD 1320 performs step (6).

[0161] At step (6), the relay management component of the relay STA MLD 1320 may decide to disconnect the relay links (e.g., the link between rSTA2 and STA4 and the link between rSTA2 and STA6). At step (7), the relay STA MLD 1320 may disconnect the relay links by transmitting disassociation frames over each relay link. For example, the relay STA MLD 1320 may transmit a disassociation frame to non-AP STA MLD 1330-2 over Link2 between rSTA2 and STA4 and may transmit a disassociation frame to non-AP STA MLD 1330- 3 over Link2 between rSTA2 and STA6. In existing IEEE 802.11 wireless networks, a disassociation frame is used when a STA wishes to safely disconnect from an AP (e.g., if the STA wishes to leave the network or connect to another AP). Using the disassociation frame may help manage network resources efficiently when STAs leave the network or connect to another AP. However, the relay technique described herein may use a disassociation frame to allow the relay STA MLD 1320 to disconnect relay links before roaming to a new AP. An example format of a disassociation frame is shown in Figure 20. The disassociation frame may include a reason code field for carrying a reason code indicating the reason for the disassociation. In an embodiment, a disassociation frame transmitted by the relay STA MLD 1320 over a relay links may include a reason code indicating that the reason for the disassociation is that the relay is unavailable. In an embodiment, the reason code for indicatingthat the reason for the disassociation is that the relay is unavailable has a value that is between 69 and 65,635 (e.g., the value may be 69).

[0162] At step (8), after the relay STA MLD 1320 has transmitted disassociation frames over the relay links, the relay STA MLD 1320 (in its capacity as an individual non-AP STA) may perform a MLO seamless roaming procedure to roam from the currently associated AP (which is AP MLD 1310-1 in this example) to the candidate / target AP (which in AP MLD2 1310-2 in this example).

[0163] In step (5) mentioned above, if the relay STA MLD 1320 is not acting as a relay for any STAs, then the relay STA MLD 1320 may perform the MLO seamless roaming procedure to roam to the candidate / target AP without transmitting disassociation frames (without performing step (7)). An example of such procedure is shown in Figure 21.

[0164] Figure 19 is a flow diagram of a method for a relay STA to roam to a target AP, according to some embodiments.

[0165] As shown in the diagram, a MLD links status monitoring component 1905 of the relay STA may monitor the link status of the relay STA’s MLD links (e.g., assess link quality) with its currently associated AP. At operation 1910, the relay STA may decide to roam to the target AP based on the link status of its MLD links with its currently associated AP (e g., if the MLD links have poor link quality). At operation 1915, the relay STA may determine whether it is currently acting as a relay for any (non-AP) STAs. If the relay STA is acting as a relay for at least one STA, the relay management component 1920 of the relay STA may decide that the relay links should be disconnected before the relay STA roams to the target AP. Accordingly, at operation 1925, the relay STA may disconnect any relay links between the relay STA (rSTA) and the STAs for which the relay STA is acting as a relay. The method may then move to operation 1930. At operation 1930, the relay STA may perform a MLO seamless roaming procedure to (seamlessly) roam to the target AP. Returning to operation 1915, if the relay STA is not acting as a relay for any STAs, the method may move directly to operation 1930 (without performing operation 1925).

[0166] Figure 20 is a diagram showing a format of a disassociation frame, according to some embodiments.

[0167] As shown in the diagram, the disassociation frame includes a frame control field 2005 (2 bytes), a duration field 2010 (2 bytes), a destination address (DA) field 2015 (6 bytes), a source address (SA) field 2020 (6 bytes), a sequence (seq.) control field 2025 (2 bytes), a frame body 2030 (variable length), and a frame check sequence (FCS) field 2035 (4 bytes). The frame control field 2005, the duration field 2010, the destination address field 2015 (which may also bereferred to as the receiver address field), the source address field 2020 (which may also be referred to as the transmitter address field), and the sequence control field 2025 may be part of the MAC header of the disassociation frame. The frame control field 2005 may carry information regarding the frame type and subtype. In the case of a disassociation frame, the frame control field 2005 may carry a value indicating a frame type and subtype that corresponds to the disassociation frame. The duration field 2010 may carry information regarding the duration for which the wireless network should wait for transmission to complete. The destination address field 2015 may carry information regarding the destination (receiver) of the frame. The source address field 2020 may carry information regarding the sender (transmitter) of the frame. As previously mentioned, a relay STA may transmit a disassociation frame to a non-AP STA to disconnect a relay link with the non-AP STA. In such case, the destination address (indicated in the destination address field 2015) of the disassociation frame may be the MAC address of the non-AP STA, and the source address (indicated in the source address field 2020) of the disassociation frame may be the MAC address of the non-AP relay STA.

[0168] The frame body 2030 may include a reason code field 2040 (2 bytes) among other fields. The reason code field 2040 may carry a reason code indicating the reason for disassociation. There may be various reasons for disassociation such as the STA leaving the network / BSS, roaming to another AP, etc. The reason code may be a value that is between 0 and 65,535.

[0169] Table I is a table showing the reason codes for disassociation / deauthentication as defined by IEEE 802.11 wireless networking standards.

[0170] As shown in Table I, reason codes 69 to 65535 may be reserved. In an embodiment, one of the reserved reason codes may be used for indicating that the reason for disassociation is that a relay is unavailable.

[0171] Figure 21 is a diagram showing a frame exchange sequence for a relay STA MLD that is not acting as a relay for any STAs to roam to a new AP, according to some embodiments.

[0172] At step (1), the relay STA MLD 2120 may be connected to AP MLD1 2110-1 through Linkl (between rSTAl and API) and Link2 (between rSTA2 and AP2). It is noted in this example that the relay STA MLD 2120 is not connected to any non-AP STA MLDs (and thus not acting as a relay for any non-AP STAs).

[0173] At step (2), the relay STA MLD 2120 (in its capacity / role as an individual non-AP STA) may periodically assess the link quality of its MLD links (Linkl and Link2) based on management frames (e.g., beacon frame, power save polling (PS-Poll) frames, etc.) transmitted by AP MLD1 1310-1 and potential candidate AP MLDs (e.g., AP MLD2 2110-2). Various metrics can be used to assess link quality such as CSI, RSSI, SNR, CQI, and the like. The relay STA MLD 2120 may consider roaming from AP MLD1 2110-1 to AP MLD22110-2 if the result of the link quality assessment indicates that the MLD links with AP MLD1 2110-1 have poor link quality. What is considered “poor” link quality may be configurable and depend on the implementation.

[0174] At step (3), the relay STA MLD 2120 may probe the MLD links with a candidate AP MLD, which in this case is AP MLD2 2110-2. For example, the relay STA MLD 2120 may transmit a probe request frame to AP MLD2 2110-2 over Linkl (between rSTAl and AP3). Responsive to receiving the probe request frame from the relay STA MLD 2120 over Linkl, AP MLD2 2110-2 may transmit a probe response frame to the relay STA MLD 2120 over Linkl. The relay STA MLD 2120 may also transmit a probe request frame to AP MLD2 2110-2 over Link2 (between rSTA2 and AP4). Responsive to receiving the probe request frame from the relay STA MLD 2120 over Link2, AP MLD2 2110-2 may transmit a probe response frame to the relay STA MLD 2120 over Link2.

[0175] At step (4), the relay ST A MLD 2120 may assess the link quality of the MLD links with AP MLD22110-2 based on the probe response frames transmitted by AP MLD2 2110-2.

[0176] At step (5), based on the result of the link quality assessment, the relay STA MLD 2120 may decide whether to roam to AP MLD2 2110-2 (the target AP) or to stay in the current BSS (stay connected to AP MLD1 2110-1).

[0177] If the relay STA MLD 2120 decides to roam to AP MLD22110-2, the relay STA MLD 2120 may first determine whether it is acting as a relay for any non-AP STAs. If the relay STA MLD 2120 is not acting as a relay for any STAs, which is assumed in this example, the relay STA MLD 2120 may perform step (6). At step (6), the relay STA MLD 2120 (in its capacity / role as an individual non-AP STA) may perform a MLO seamless roaming procedure to roam to the candidate / target AP, which in this example is AP MLD2 2110-2. As previously described, if the relay STA MLD 2120 is acting as a relay for at least one non-AP STA then the relay STA MLD 2120 may disconnect any relay links before performing a MLO seamless roaming procedure (e.g., as shown in Figure 18).

[0178] The present disclosure proposes a roaming technique that allows a relay STA that is acting as a relay for one or more non-AP STAs to gracefully roam to a new AP by disconnecting any relay links before roaming to the new AP. Existing relay techniques do not provide a way to gracefully handle situations when the relay STA, acting in its capacity / role as an individual STA, decides to roam to a new AP. Also, the present disclosure proposes a new reason code to include in a disassociation frame transmitted by a relay STA to a (non-AP) STA to indicate to the STA that the reason for disassociation is that a relay is unavailable. While the roaming technique has been primarily described in the context of a wireless network that has MLO capability, those skilled in the art will appreciate that some features of the roaming technique described herein can be applied to a wireless network that does not have MLO capability to achieve similar benefits (e.g., it may be beneficial for a relay STA to explicitly disconnect relay links before roaming to a new AP even in a non-MLO scenario).

[0179] Turning now to Figure 22, a method 2200 will be described for a relay STA to roam to a new AP, in accordance with an example embodiment. The method 2200 may be performed by a relay STA (MLD) that has MLO capability to roam from a first AP to a second AP. The relay STA may be implemented by a wireless device (e.g., wireless device 104).

[0180] At operation 2205, responsive to determining to roam from the first AP to the second AP, the relay STA determines whether it is acting as a relay for one or more STAs. If the relay STA is acting as a relay for one or more STAs, the method proceeds to operation 2215. Otherwise, the method proceeds to operation 2230.

[0181] At operation 2215, the relay STA disconnects relay links between the relay STA and the one or more STAs. In an embodiment, operation 2215 involves operation 2220. At operation 2220, the relay STA transmits a disassociation frame to the one or more STAs over the relay links between the relay STA and the one or more STAs. In an embodiment, as shown in block 2225, the disassociation frame includes a reason code indicating that a reason for disassociation is that a relay is unavailable. In an embodiment, the reason code has a value that is between 69 and 65,535. In an embodiment, the relay STA transmits a disassociation frame to a particular STA over multiple relay links between the relay STA and the particular STA (e.g., if there are multiple relay links (operating in different bands / channels) between the relay STA and the particular STA).

[0182] At operation 2230, the relay STA performs a MLO roaming procedure (e.g., the MLO roaming procedure shown in Figure 15) to (seamlessly) roam from the first AP to the second AP.

[0183] In an embodiment, before performing the MLO roaming procedure, the relay STA is connected to the first AP via a first link operating in a first channel and a second link operating in a second channel. In such an embodiment, the performing the MLO roaming procedure may comprise: disconnecting the first link while maintaining the second link, establishing a third link between the STA and the second AP while maintaining the second link to enter a roaming transition state, wherein the third link operates in the first channel, after establishing the third link, disconnecting the second link, and establishing a fourth link between the STA and the second AP, wherein the fourth link operates in the second channel.

[0184] In an embodiment, the relay links between the relay STA and the one or more STAs include a relay link between the relay STA and a particular STA, wherein the particular STA is connected to the first AP via a direct link between the particular STA and the first AP and also connected to the first AP via the relay link, wherein the direct link operates in a first channel and the relay link operates in a second channel (that is different from the first channel).

[0185] In an embodiment, the relay STA transmits a first probe request frame to the second AP over a first link between the relay STA and the second AP, wherein the first link operates in a first channel, receives a first probe response from the second AP over the first link, transmits a second probe request frame to the second AP over a second link between the relay STA and the second AP, wherein the second link operates in a second channel, and receives a second probe response from the second AP over the second link, wherein the determination to roam from the first AP to the second AP is based on the first probe response frame and the second probe response frame.

[0186] In an embodiment, the first channel is in a 2.4 GHz band and the second channel is in a 5 GHz band (or it can be vice versa).

[0187] Although many of the solutions and techniques provided herein have been described with reference to a WLAN system, it should be understood that these solutions and techniques are also applicable to other network environments, such as cellular telecommunication networks, wired networks, etc In some embodiments, the solutions and techniques provided herein may be or may be embodied in an article of manufacture in which a non-transitory machine-readable medium (such as microelectronic memory) has stored thereon instructions which program one or more data processing components (generically referred to here as a “processor” or “processing unit”) to perform the operations described herein. In other embodiments, some of these operations might be performed by specific hardware components that contain hardwired logic (e g., dedicated digital filter blocks and state machines). Those operations might alternatively be performed by any combination of programmed data processing components and fixed hardwired circuit components.

[0188] In some cases, an embodiment may be an apparatus (e g., an AP STA, a non-AP STA, or another network or computing device) that includes one or more hardware and software logic structures for performing one or more of the operations described herein. For example, as described herein, an apparatus may include a memory unit, which stores instructions that may be executed by a hardware processor installed in the apparatus. The apparatus may also include one or more other hardware or software elements, including a network interface, a display device, etc.

[0189] Some portions of the preceding detailed descriptions have been presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consi stent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

[0190] It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. The present disclosure can refer to the action and processes of a computersystem, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage systems.

[0191] The present disclosure also relates to an apparatus for performing the operations herein. This apparatus can be specially constructed for the intended purposes, or it can include a general-purpose computer selectively activated or reconfigured by a computer program stored in the computer. For example, a computer system or other data processing system may carry out the computer-implemented methods described herein in response to its processor executing a computer program (e.g., a sequence of instructions) contained in a memory or other non- transitory machine-readable storage medium. Such a computer program can be stored in a computer readable storage medium, such as, but not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, each coupled to a computer system bus.

[0192] The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general-purpose systems can be used with programs in accordance with the teachings herein, or it can prove convenient to constmct a more specialized apparatus to perform the method. The structure for a variety of these systems will appear as set forth in the description below. In addition, the present disclosure is not described with reference to any particular programming language. It will be appreciated that a variety of programming languages can be used to implement the teachings of the disclosure as described herein.

[0193] The present disclosure can be provided as a computer program product, or software, that can include a machine-readable medium having stored thereon instructions, which can be used to program a computer system (or other electronic devices) to perform a process according to the present disclosure. A machine-readable medium includes any mechanism for storing information in a form readable by a machine (e.g., a computer). In some embodiments, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium such as a read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory components, etc.

[0194] In the foregoing specification, embodiments of the disclosure have been described with reference to specific example embodiments thereof. It will be evident that various modifications can be made thereto without departing from the broader spirit and scope ofembodiments of the disclosure as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense.

Claims

CLAIMSWhat is claimed is:

1. A method performed by a relay station (STA) that is connected to a first access point (AP) and that has multi-link operation (MLO) capability to roam from the first access point (AP) to a second AP, the method comprising: responsive to determining to roam from the first AP to the second AP, determining whether the relay STA is acting as a relay for one or more STAs; responsive to determining that the relay STA is acting as a relay for the one or more STAs, disconnecting relay links between the relay STA and the one or more STAs; and after disconnecting the relay links between the relay STA and the one or more STAs, performing a MLO roaming procedure to roam from the first AP to the second AP.

2. The method of claim 1, wherein the disconnecting the relay links between the relay STA and the one or more STAs comprises transmitting a disassociation frame to the one or more STAs over the relay links between the relay STA and the one or more STAs.

3. The method of claim 2, wherein the disassociation frame includes a reason code indicating that a reason for disassociation is that a relay is unavailable.

4. The method of claim 3, wherein the reason code has a value that is between 69 and 65,535.

5. The method of claim 1, wherein before performing the MLO roaming procedure, the relay STA is connected to the first AP via a first link operating in a first channel and a second link operating in a second channel.

6. The method of claim 5, wherein the performing the MLO roaming procedure comprises: disconnecting the first link while maintaining the second link; establishing a third link between the STA and the second AP while maintaining the second link to enter a roaming transition state, wherein the third link operates in the first channel; after establishing the third link, disconnecting the second link; andestablishing a fourth link between the STA and the second AP, wherein the fourth link operates in the second channel.

7. The method of claim 5, wherein the first channel is in a 2.4 Gigahertz (GHz) band and the second channel is in a 5 GHz band.

8. The method of claim 1, wherein the relay links between the relay STA and the one or more STAs include a relay link between the relay STA and a STA, wherein the STA is connected to the first AP via a direct link between the STA and the first AP and also connected to the first AP via the relay link, wherein the direct link operates in a first channel and the relay link operates in a second channel.

9. The method of claim 1, further comprising: transmitting a first probe request frame to the second AP over a first link between the relay STA and the second AP, wherein the first link operates in a first channel; receiving a first probe response from the second AP over the first link; transmitting a second probe request frame to the second AP over a second link between the relay STA and the second AP, wherein the second link operates in a second channel; and receiving a second probe response from the second AP over the second link, wherein the determination to roam from the first AP to the second AP is based on the first probe response frame and the second probe response frame.

10. A wireless device to implement a relay station (STA), the wireless device comprising: a radio frequency transceiver; a memory device storing a set of instructions; and a processor coupled to the memory device, wherein the set of instructions, when executed by the processor, causes the relay STA to perform the method of any one of claims 1-9.

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