Method and apparatus for HARQ in wireless networks

Abstract

To provide a method and apparatus related to HARQ signaling and ACK as well as HARQ MAC procedures in a wireless network.SOLUTION: A method includes: receiving first MU transmission including at least a first set of HARQ bits, a first set of user data for multiple STAs including an STA, a preamble including information indicating that the first MU transmission includes the first set of HARQ bits, and a first set of HARQ process IDs associated with the first set of HARQ bits; determining a subset of a HARQ bit in the first set of HARQ bits; transmitting a response message after receiving the first MU transmission; and receiving second MU transmission including at least a second set of HARQ bits, a second set of user data for multiple STAs, and a second set of HARQ process IDs associated with the second set of HARQ bits.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] The present invention relates to methods and apparatuses in a wireless network, and more particularly, to methods and apparatuses for HARQ in a wireless network.

Background Art

[0002] 1. Overview of WLAN System A WLAN in infrastructure basic service set (BSS) mode (see Non-Patent Document 1) has an access point (AP) for the BSS and one or more stations (STAs) associated with the AP. The AP generally interfaces with a distribution system (DS) or another type of wired / wireless network that conveys traffic within and outside the BSS. Traffic to an STA originating from outside the BSS arrives through the AP and is delivered to the STA. Traffic transmitted from an STA to a destination outside the BSS is transmitted to the AP for delivery to each destination. Traffic between STAs within the BSS may also be transmitted through the AP. The source STA transmits the traffic to the AP, and the AP delivers the traffic to the destination STA. Such traffic between STAs within the BSS is essentially peer-to-peer traffic. Such peer-to-peer traffic may be directly transmitted between the source STA and the destination STA using direct link setup (DLS) that uses 802.11e DLS or 802.11z tunnel DLS (TDLS). A WLAN using independent BSS (IBSS) mode does not have an AP. Rather, in peer-to-peer type mode communication, STAs communicate directly with each other. This mode of communication is called "ad hoc" mode communication.

[0003] In 802.11ac (see Non-Patent Document 2) infrastructure mode operation, an AP may transmit beacons on a fixed channel, typically the primary channel. This channel may be 20 MHz wide and is the operating channel for the BSS. This channel is also used by STAs to establish connections with the AP. The basic channel access mechanism in an 802.11 system is carrier-sense multiple access / collision avoidance (CSMA / CA). In this mode of operation, all STAs, including the AP, sense the primary channel. If the channel is detected to be busy, the STA backs off. Therefore, within a given BSS, only one STA can transmit at any given time.

[0004] In 802.11n (see Non-Patent Document 1), high-throughput (HT) STAs can also use 40 MHz wide channels for communication. This is achieved by combining a primary 20 MHz channel with an adjacent 20 MHz channel to form a continuous 40 MHz wide channel.

[0005] In 802.11ac (see Non-Patent Literature 2), very high-throughput (VHT) STAs can support 20MHz, 40MHz, 80MHz, and 160MHz wide channels. 40MHz and 80MHz channels are formed by combining consecutive 20MHz channels, similar to the methods described above in relation to 802.11n. 160MHz channels can be formed by combining eight consecutive 20MHz channels or two discontinuous 80MHz channels. This type of configuration is sometimes called an 80+80 configuration. In an 80+80 configuration, after channel encoding, the data is passed through a segment parser that splits it into two streams. IFFT and time-domain processing are performed separately for each stream. The streams are then mapped onto two 80MHz channels, and the data is transmitted. At the receiver, this mechanism is reversed, and the combined data is sent to the MAC.

[0006] Sub-1GHz mode operation is supported by 802.11af (see Non-Patent Document 3) and 802.11ah (see Non-Patent Document 4). In these specifications, the channel operating bandwidth and carrier are reduced compared to those used in 802.11n (see Non-Patent Document 1) and 802.11ac (see Non-Patent Document 2). 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV white space (TVWS) spectrum, while 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using the non-TVWS spectrum. A possible use case for 802.11ah is support for meter-type control (MTC) devices in macro coverage areas. MTC devices may have limited functionality, including support only for limited bandwidths, but may also have requirements for very long battery life.

[0007] WLAN systems that support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include a channel designated as the primary channel. The primary channel may, but may not, have a bandwidth equal to the largest common operating bandwidth supported by all STAs within the BSS. Therefore, the bandwidth of the primary channel is limited by the STAs that support the minimum bandwidth operating mode operating within a particular BSS. In the case of 802.11ah, even if the APs and other STAs within the BSS support 2MHz, 4MHz, 8MHz, 16MHz, or other larger channel bandwidth operating modes, the primary channel may be 1MHz wide if there is an STA (e.g., an MTC type device) that supports only 1MHz mode. All carrier sensing and network allocation vector (NAV) settings depend on the status of the primary channel; that is, if the primary channel is busy because, for example, an STA that only supports 1MHz operating mode is transmitting to the AP, the entire available frequency band will be considered busy, even if the majority of it is actually idle and available.

[0008] In the United States, the available frequency band that can be used by 802.11ah is from 902 MHz to 928 MHz. In South Korea, it is from 917.5 MHz to 923.5 MHz, and in Japan, it is from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah is from 6 MHz to 26 MHz, depending on the country. 2. Introduction to 802.11TGax Recently, the IEEE 802.11™ High Efficiency WLAN (HEW) Study Group (SG) was established to explore the scope and objectives of possible future modifications to improve the quality of service experienced by all users across a wide range of wireless users in numerous usage scenarios, including high-density scenarios in the 2.4GHz, 5GHz, and 6GHz bands. New use cases supporting dense deployment of APs and STAs, as well as associated Radio Resource Management (RRM) technologies, are being considered by the HEW SG. Potential applications of HEW include newly emerging usage scenarios (such as data distribution for stadium events), high-user density scenarios (such as railway stations and corporate / retail environments), and wireless services for medical applications.

[0009] In TGax, traffic for various purposes is likely to include short packets. In addition, there may be several network applications that generate short packets, such as virtual office applications, TPC ACKs (Transmit Control Power Acknowledgments), video streaming ACKs, device / controller applications (mouse, keyboard, game controls, etc.), access applications (probe requests / responses), network selection (probe requests and ANQP (Access Network Query Protocol)), and network management applications (control frames).

[0010] Furthermore, 802.11ax can implement UL and DL OFDMA, and / or UL and DL MU-MIMO. Therefore, the design and definition of mechanisms for multiplexing UL random access for different purposes can be addressed in the standard. 2.1 NDP Feedback Design in 11ax Section 27.5.6.4 (NPD Feedback Report Type) of Non-Patent Literature 7 describes a null data packet (NDP) feedback design in 802.11ax. The feedback uses a punctured high-efficiency long training field (HE-LTF) to transmit information, and therefore the receiver does not need to perform channel estimation. For 1-bit feedback, 12 OFDM tones are used, half on and half off. The table in Figure 2 illustrates a tone set allocation for a 20 MHz channel. This scheme has been shown to achieve a very low false positive rate (<1e-6) when the SNR ≥ -24 dB. 3. HARQ technology in wireless standards 3.1 Background of HARQ Hybrid Automatic Retransmission Request (HARQ) has become an essential transmission error control technique in wireless communication networks, relying on a combination of error correction codes and retransmissions. HARQ is adopted in wireless communication standards such as 3GPP UMTS, LTE, and IEEE 802.16 WiMAX.

[0011] The technical literature contains two well-regarded types of HARQ synthesis schemes: Chase Synthesis (CC) HARQ and Increased Redundancy (IR) HARQ.

[0012] In (CC)HARQ, each retransmission contains the same data plus a parity bit. The receiver uses Maximum Ratio Combination (MRC) to combine the received packet with the previous transmission. Chase Combination can be thought of as iterative coding, where each retransmission increases the Eb / No (Energy per bit versus Noise spectral power density ratio) at the receiver.

[0013] In the case of IR HARQ, each retransmission uses a different set of bits to be encoded (different redundant versions generated by puncturing the encoder output). In the case of turbo codes, this means different systematic and parity bits. With each retransmission, the receiver gains additional information. Variations of IR HARQ exist, for example, where retransmissions contain only parity bits, or where it is self-decodeable.

[0014] In general, HARQ schemes can be categorized as either synchronous or asynchronous, and retransmissions in each case can be either adaptive or non-adaptive. In the case of synchronous HARQ, retransmissions for each process occur at a predefined time relative to the initial transmission. Therefore, it is not necessary to communicate the HARQ process ID, as it can be inferred from the timing of the retransmission. On the other hand, in the case of asynchronous HARQ, retransmissions can occur at any time relative to the initial transmission. Therefore, explicit signaling to indicate the HARQ process ID is required to ensure that the receiver can correctly associate each retransmission with the corresponding previous transmission. 3.2 HARQ Scheme in LTE Standards In LTE, the HARQ entity is located at the MAC layer and is responsible for transmit and receive HARQ operations. Transmit HARQ operations include transmitting and retransmitting transport blocks, as well as receiving and processing ACK / NACK signaling. Receiving HARQ operations include receiving transport blocks, synthesizing the received data, and generating ACK / NACK signaling based on the decoding results. To enable continuous transmission while preceding transport blocks are being decoded, up to eight parallel HARQ processes are used to support multi-process "stop-and-wait" (SAW) HARQ operations. Thus, multi-process HARQ interlaces several independent SAW processes in time so that all transmit resources can be used by one of the processes. Each HARQ process is responsible for a separate SAW operation and manages a separate buffer.

[0015] In LTE, asynchronous adaptive HARQ is used for downlink, while synchronous HARQ (either adaptive or non-adaptive) is used for uplink.

[0016] In LTE, the following signaling is used to support HARQ: HARQ process ID (for asynchronous HARQ only), New Data Indicator (NDI) (which is switched each time a new packet transmission begins), Redundancy Version (RV) (RV of the transmit block (for adaptive HARQ only)), and MCS (for adaptive HARQ only). 3.3 HARQ in NR and NR-U 3GPP NR (New Radio) supports the following HARQ features: multiple HARQ processes, dynamic and semi-static HARQ ACK codebooks, CBG-level HARQ retransmission, asynchronous and adaptive HARQ, and flexible timing between data transmission and HARQ ACK feedback.

[0017] In HARQ retransmissions at the codeword block group (CBG) level in NR, a transmit block (TB) may contain one or more CBGs, each having its own HARQ ACK bit. Therefore, a transmitter can retransmit a partial TB. Two CBG-related signaling fields, namely CBG transmit information (CBGTI) and CBG flashout information (CBGFI), are carried by the DCI. CBGTI indicates the CBG being carried by the (re)transmission. CBGFI, set to "0", indicates that a previously received instance of the same CBG being transmitted may be corrupted, while CBGFI, set to "1", indicates that the retransmitted CBG is recombinable with a previously received instance of the same CBG.

[0018] In 3GPP NR Unlicensed (NR-U), HARQ feedback may be transmitted in unlicensed bands. NR-U explores mechanisms to support flexible triggering and multiplexing of HARQ feedback for one or more DL HARQ processes. The following techniques are considered beneficial by 3GPP for NR-U transmissions.

[0019] ● Techniques for addressing HARQ A / N transmission opportunities reduced due to LBT failures for a given HARQ process (potential techniques include mechanisms for providing multiple and / or supplemental time and / or frequency domain transmission opportunities).

[0020] ● The transmission of HARQ A / Ns for corresponding data within the same shared channel occupancy time (COT) (it is understood that in some cases, HARQ Ack / Nack must be transmitted in a separate COT from the one in which the corresponding data was transmitted), and the mechanisms to support this should be identified. 4. Extremely High Throughput Study Group To explore the possibility of further increasing peak throughput and improving the efficiency of IEEE802.11 networks, the IEEE802.11 Extremely High Throughput (EHT) Study Group (SG) was formed. The main use cases and applications to be addressed include high-throughput and low-latency applications such as video over WLAN, augmented reality (AR), and virtual reality (VR) (see Non-Patent Document 5).

[0021] To achieve the goals of increased peak throughput and improved efficiency, the features discussed in the EHT SG include multi-AP, multi-band, 320MHz bandwidth, 16 spatial streams, HARQ, full-duplex (in both time and frequency domains), AP cooperation, semi-orthogonal multiple access (SOMA), and new designs for 6GHz channel access (see Non-Patent Document 6).

[0022] A more detailed understanding may be obtained from the following description, given by way of example, in conjunction with the accompanying drawings, in which like reference numerals in the figures indicate like elements.

Prior Art Documents

Non-Patent Documents

[0023]

Non-Patent Document 1

Non-Patent Document 2

[0024] [Figure 1A] This is a system diagram illustrating an exemplary communication system in which one or more disclosed embodiments may be implemented. [Figure 1B] This is a system diagram illustrating an exemplary wireless transmit / receive unit (WTRU) that may be used in the communication system illustrated in Figure 1A according to the embodiment. [Figure 1C] This is a system diagram illustrating exemplary radio access network (RAN) and exemplary core network (CN) that may be used in the communication system illustrated in Figure 1A of the embodiment. [Figure 1D]This is a system diagram illustrating further exemplary RANs and further exemplary CNs that may be used within the communication system illustrated in Figure 1A of the embodiment. [Figure 2] This table shows the tone set allocation for 20MHz channels for 802.11. [Figure 3] This figure illustrates an exemplary BlockAckReq frame format for implementing a multi-HARQ process BAR according to the embodiment. [Figure 4] This is a diagram of the HARQ feedback report parameter frame according to an embodiment. [Figure 5] This is a diagram of a HARQ NDP feedback frame for a single HARQ feedback for a single STA according to the first embodiment. [Figure 6] This is a diagram of a HARQ NDP feedback frame for a single HARQ feedback for multiple STAs according to a second exemplary embodiment. [Figure 7] This is a diagram of a HARQ NDP feedback frame for multiple HARQ feedback on one or more RUs according to a third exemplary embodiment. [Figure 8] This is a diagram of a HARQ NDP feedback frame for multiple HARQ feedback on the same RU / channel according to a fourth exemplary embodiment. [Figure 9] This is a diagram of a HARQ NDP feedback frame for multiple HARQ feedback and multiple resources according to a fifth exemplary embodiment. [Figure 10A] This diagram illustrates an exemplary tone mapping for HARQ NDP feedback. [Figure 10B] This diagram illustrates an exemplary tone mapping for HARQ NDP feedback. [Figure 11] This is a timing diagram showing the HARQ DL MAC procedure according to the embodiment. [Figure 12]This timing diagram shows the HARQ DL MAC procedure according to another embodiment. [Figure 13] This is a timing diagram showing the DL HARQ multiple stop-and-wait procedure according to the embodiment. [Figure 14] This is a diagram of a HARQ NDP feedback frame for multiple HARQ feedback according to an embodiment. [Figure 15] This is a timing diagram showing the HARQ UL procedure according to the embodiment. [Figure 16] This is a timing diagram showing the HARQ cascading UL and DL procedures according to the embodiment. [Figure 17] A timing diagram showing the HARQ cascading UL and DL procedure according to another embodiment. [Figure 18] This is a timing diagram showing a HARQ MAC procedure using TXT or RAW according to an embodiment. [Figure 19] This is a timing diagram showing a single UL HARQ MAC procedure within a TXOP according to an embodiment. [Figure 20] This is a timing diagram showing a UL HARQ procedure for a single HARQ process across multiple TXOPs according to an embodiment. [Figure 21] This is a timing diagram showing autonomous HARQ transmission according to the embodiment. [Figure 22] This figure illustrates a punctured LTF for an A-PPDU according to an embodiment. [Modes for carrying out the invention]

[0025] 1. Exemplary network for implementing the embodiment Figure 1A illustrates an exemplary communication system 100 in which one or more disclosed embodiments may be implemented. The communication system 100 may be a multiple access system that provides content such as voice, data, video, messaging, and broadcast to multiple wireless users. The communication system 100 may enable multiple wireless users to access such content through the sharing of system resources, including wireless bandwidth. For example, the communication system 100 may utilize one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), quadrature FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tail unique word DFT spread OFDM (ZT UW DTS-s OFDM), unique word OFDM (UW-OFDM), resource block filtered OFDM, and filter bank multicarrier (FBMC).

[0026] As shown in Figure 1A, the communication system 100 may include wireless transmit / receive units (WTRUs) 102a, 102b, 102c, 102d, RAN 104 / 113, CN 106 / 115, public switched telephone network (PSTN) 108, the internet 110, and other networks 112, but it will be understood that the disclosed embodiments intend any number of WTRUs, base stations, networks, and / or network elements. Each of the WTRUs 102a, 102b, 102c, 102d may be any type of device configured to operate and / or communicate in a wireless environment. For example, any of them may be called a “station” and / or “STA,” and WTRU102a, 102b, 102c, and 102d may be configured to transmit and / or receive wireless signals and may include user equipment (UEs), mobile stations, fixed or mobile subscriber units, subscription-based units, pagers, cellular phones, personal digital assistants (PDAs), smartphones, laptops, netbooks, personal computers, wireless sensors, hotspots or Mi-Fi devices, Internet of Things (IoT) devices, watches or other wearables, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain situations), consumer electronics devices, and devices operating on commercial and / or industrial wireless networks. Any of WTRU102a, 102b, 102c, and 102d may be interchangeably referred to as a UE.

[0027] The communication system 100 may also include base stations 114a and / or base stations 114b. Each of the base stations 114a and 114b may be any type of device configured to wirelessly interface with at least one of the WTRUs 102a, 102b, 102c, and 102d to facilitate access to one or more communication networks, such as CN 106 / 115, the Internet 110, and / or other networks 112. For example, base stations 114a and 114b may be base transceiver stations (BTS), node B, enode B, home node B, home enode B, gNB, NR node B, site controller, access point (AP), and wireless router. Although each of the base stations 114a and 114b is depicted as a single element, it will be understood that base stations 114a and 114b may include any number of interconnected base stations and / or network elements.

[0028] Base station 114a may be part of RAN 104 / 113, which may also include other base stations and / or network elements (not shown) such as base station controllers (BSCs), radio network controllers (RNCs), and relay nodes. Base station 114a and / or base station 114b may be configured to transmit and / or receive wireless signals on one or more carrier frequencies, which may be called cells (not shown). These frequencies may be in licensed spectrum, unlicensed spectrum, or a combination of licensed and unlicensed spectrum. A cell may provide coverage for wireless services to a particular geographic area that may be relatively constant or may change over time. A cell may be further divided into cell sectors. For example, a cell associated with base station 114a may be divided into three sectors. Thus, in one embodiment, base station 114a may include three transceivers, i.e., one for each sector of the cell. In embodiments, the base station 114a may utilize multiple-input multiple-output (MIMO) technology and may utilize multiple transceivers for each sector of the cell. For example, beamforming may be used to transmit and / or receive signals in a desired spatial direction.

[0029] Base stations 114a and 114b may communicate with one or more WTRUs 102a, 102b, 102c, and 102d over the air interface 116, and the air interface 116 may be any suitable wireless communication link (e.g., radio frequency (RF), microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet (UV), visible light, etc.). The air interface 116 may be established using any suitable radio access technology (RAT).

[0030] More specifically, as mentioned above, the communication system 100 may be a multiple access system and may utilize one or more channel access schemes, such as CDMA, TDMA, FDMA, OFDMA, and SC-FDMA. For example, base stations 114a and WTRUs 102a, 102b, and 102c in RAN 104 / 113 may implement radio technologies such as Universal Mobile Communications System (UMTS) Terrestrial Radio Access (UTRA), which may establish air interfaces 115 / 116 / 117 using broadband CDMA (WCDMA). WCDMA may include communication protocols such as High Speed ​​Packet Access (HSPA) and / or Evolved HSPA (HSPA+). HSPA may include High Speed ​​Downlink (DL) Packet Access (HSDPA) and / or High Speed ​​UL Packet Access (HSUPA).

[0031] In embodiments, base stations 114a and WTRUs 102a, 102b, and 102c may implement radio technologies such as Advanced UMTS Terrestrial Radio Access (E-UTRA) that can establish an air interface 116 using Long-Term Evolution (LTE) and / or LTE Advanced (LTE-A) and / or LTE Advanced Pro (LTE-A Pro).

[0032] In this embodiment, base station 114a and WTRUs 102a, 102b, and 102c may implement radio technologies such as NR radio access, which can use New Radio (NR) to establish an air interface 116.

[0033] In embodiments, base station 114a and WTRUs 102a, 102b, and 102c may implement multiple radio access technologies. For example, base station 114a and WTRUs 102a, 102b, and 102c may implement LTE radio access and NR radio access together, for example, using the dual connectivity (DC) principle. Thus, the air interface utilized by WTRUs 102a, 102b, and 102c may be characterized by multiple types of radio access technologies, as well as / from multiple types of base stations (e.g., eNBs and gNBs).

[0034] In other embodiments, base stations 114a and WTRUs 102a, 102b, and 102c may implement radio technologies such as IEEE 802.11 (i.e., Wireless Fidelity (WiFi)), IEEE 802.16 (i.e., Global Interoperability for Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO, Provisional Standard 2000 (IS-2000), Provisional Standard 95 (IS-95), Provisional Standard 856 (IS-856), Global System for Mobile Communications (GSM), High Speed ​​Data Rate for GSM Evolution (EDGE), and GSM EDGE (GERAN).

[0035] In Figure 1A, base station 114b may be, for example, a wireless router, home node B, home enode B, or access point, and any suitable RAT may be used to facilitate wireless connectivity in localized areas such as offices, homes, vehicles, campuses, industrial facilities, air corridors (used by drones, for example), and roadways. In one embodiment, base station 114b and WTRU 102c, 102d may establish a wireless local area network (WLAN) by implementing radio technology such as IEEE 802.11. In another embodiment, base station 114b and WTRU 102c, 102d may establish a wireless personal area network (WPAN) by implementing radio technology such as IEEE 802.15. In another embodiment, base station 114b and WTRUs 102c and 102d may establish a picocell or femtocell using a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, LTE-A Pro, NR, etc.). As shown in Figure 1A, base station 114b may have a direct connection to the internet 110. Therefore, base station 114b may not need to access the internet 110 via CN 106 / 115.

[0036] RAN104 / 113 may communicate with CN106 / 115, which may be any type of network configured to provide voice, data, applications, and / or Voice over Internet Protocol (VoIP) services to one or more of WTRU102a, 102b, 102c, and 102d. The data may have various Quality of Service (QoS) requirements, including different throughput requirements, latency requirements, error tolerance requirements, reliability requirements, data throughput requirements, and mobility requirements. CN106 / 115 may provide call control, billing services, mobile location-based services, prepaid calling, internet connectivity, video distribution, and / or perform high-level security functions, such as user authentication. Although not shown in Figure 1A, it will be understood that RAN104 / 113 and / or CN106 / 115 may communicate directly or indirectly with other RANs utilizing the same or different RATs as RAN104 / 113. For example, in addition to being connected to RAN104 / 113, which may utilize NR radio technology, CN106 / 115 may also communicate with other RANs (not shown) that utilize GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

[0037] CN106 / 115 may also serve as a gateway for WTRU102a, 102b, 102c, and 102d to access PSTN108, the Internet 110, and / or other networks 112. PSTN108 may include a circuit-switched telephone network providing basic telephone services (POTS). The Internet 110 may include a global system of interconnected computer networks and devices using common communication protocols such as Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and / or Internet Protocol (IP) within the TCP / IP Internet Protocol suite. Network 112 may include wired and / or wireless communication networks owned and / or operated by other service providers. For example, network 112 may include another CN connected to one or more RANs that may utilize the same or different RAT as RAN104 / 113.

[0038] Some or all of the WTRUs 102a, 102b, 102c, and 102d in the communication system 100 may include multimode functionality (for example, WTRUs 102a, 102b, 102c, and 102d may include multiple transceivers for communicating with different wireless networks on different wireless links). For example, WTRU 102c, shown in Figure 1A, may be configured to communicate with base station 114a that can utilize cellular-based radio technology and with base station 114b that can utilize IEEE 802 radio technology.

[0039] Figure 1B is a system diagram illustrating an exemplary WTRU 102. As shown in Figure 1B, the WTRU 102 may include, among other things, a processor 118, a transceiver 120, a transmit / receive element 122, a speaker / microphone 124, a keypad 126, a display / touchpad 128, a non-removable memory 130, a removable memory 132, a power supply 134, a Global Positioning System (GPS) chipset 136, and / or other peripherals 138. It will be understood that the WTRU 102 may include any subcombinations of the above elements while maintaining consistency with the embodiment.

[0040] The processor 118 could be a general-purpose processor, a dedicated processor, a conventional processor, a digital signal processor (DSP), multiple microprocessors, one or more microprocessors working with a DSP core, a controller, a microcontroller, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) circuit, any other type of integrated circuit (IC), and a state machine. The processor 118 can perform signal coding, data processing, power control, input / output processing, and / or any other functionality that enables the WTRU 102 to operate in a wireless environment. The processor 118 can be coupled to a transceiver 120 which can be coupled to a transmit / receive element 122. Although Figure 1B depicts the processor 118 and the transceiver 120 as separate components, it will be understood that the processor 118 and the transceiver 120 can be integrated together in an electronic package or chip.

[0041] The transmit / receive element 122 may be configured to transmit signals to or receive signals from a base station (e.g., base station 114a) over the air interface 116. For example, in one embodiment, the transmit / receive element 122 may be an antenna configured to transmit and / or receive RF signals. In another embodiment, the transmit / receive element 122 may be a radiator / detector configured to transmit and / or receive, for example, IR, UV, or visible light signals. In yet another embodiment, the transmit / receive element 122 may be configured to transmit and / or receive both RF and optical signals. It will be understood that the transmit / receive element 122 may be configured to transmit and / or receive any combination of wireless signals.

[0042] In Figure 1B, the transmit / receive element 122 is depicted as a single element, but the WTRU 102 may include any number of transmit / receive elements 122. More specifically, the WTRU 102 may utilize MIMO technology. Therefore, in one embodiment, the WTRU 102 may include two or more transmit / receive elements 122 (e.g., multiple antennas) for transmitting and receiving wireless signals over the air interface 116.

[0043] The transceiver 120 may be configured to modulate the signal to be transmitted by the transmit / receive element 122 and to demodulate the signal received by the transmit / receive element 122. As mentioned above, the WTRU 102 may have multimode capabilities. Therefore, the transceiver 120 may include multiple transceivers to enable the WTRU 102 to communicate via multiple RATs, such as NR and IEEE 802.11.

[0044] The processor 118 of the WTRU102 may be coupled to a speaker / microphone 124, a keypad 126, and / or a display / touchpad 128 (e.g., a liquid crystal display (LCD) display unit or an organic light-emitting diode (OLED) display unit) and may receive user input data from them. The processor 118 may also output user data to the speaker / microphone 124, the keypad 126, and / or the display / touchpad 128. In addition, the processor 118 may obtain information from any type of suitable memory, such as non-removable memory 130 and / or removable memory 132, and may store data in them. Non-removable memory 130 may include random access memory (RAM), read-only memory (ROM), a hard disk, or any other type of memory storage device. Removable memory 132 may include a subscriber identification module (SIM) card, a memory stick, and a secure digital (SD) memory card, etc. In other embodiments, the processor 118 may obtain information from memory located on a server or home computer (not shown) or the like, which is not physically located on the WTRU 102, and may store data in it.

[0045] The processor 118 may receive power from the power supply 134 and may be configured to distribute power to and / or control power to other components within the WTRU 102. The power supply 134 may be any suitable device for supplying power to the WTRU 102. For example, the power supply 134 may include one or more dry cell batteries (e.g., nickel-cadmium (NiCd), nickel-zinc (NiZn), nickel-metal hydride (NiMH), lithium-ion (Li-ion), etc.), a solar cell, and a fuel cell.

[0046] The processor 118 may also be coupled to a GPS chipset 136, which may be configured to provide location information (e.g., longitude and latitude) regarding the current location of the WTRU 102. In addition to, or instead of, the WTRU 102 may receive location information from base stations (e.g., base stations 114a, 114b) on the air interface 116 and / or determine its own location based on the timing of signals received from two or more nearby base stations. It will be understood that the WTRU 102 may acquire location information using any appropriate location determination method, while maintaining consistency with the embodiments.

[0047] Furthermore, the processor 118 may be coupled to other peripherals 138, which may include one or more software modules and / or hardware modules that provide additional features, functionality, and / or wired or wireless connectivity. For example, peripherals 138 may include an accelerometer, e-compass, satellite transceiver, digital camera (for photos and / or video), Universal Serial Bus (USB) port, vibration device, television transceiver, hands-free headset, Bluetooth® module, frequency modulation (FM) radio unit, digital music player, media player, video game player module, internet browser, virtual reality and / or augmented reality (VR / AR) device, and activity tracker. Peripheral 138 may include one or more sensors, which may be one or more of the following: gyroscope, accelerometer, Hall effect sensor, magnetometer, compass sensor, proximity sensor, temperature sensor, time sensor, geolocation sensor, altimeter, light sensor, touch sensor, magnetometer, barometer, gesture sensor, biometric sensor, and / or humidity sensor.

[0048] WTRU102 may include a full-duplex radio (for example, one in which the transmission and reception of some or all of the signals associated with specific subframes for both UL (for example, for transmission) and downlink (for example, for reception) may be in parallel and / or simultaneous. The full-duplex radio may include an interference management unit to reduce and / or substantially eliminate self-interference via hardware (e.g., chokes) or via signal processing via a processor (e.g., a separate processor (not shown) or processor 118). In embodiments, WTRU102 may include a half-duplex radio (for example, one in which the transmission and reception of some or all of the signals associated with specific subframes for either UL (for example, for transmission) or downlink (for example, for reception) may be in parallel and / or simultaneously.

[0049] Figure 1C is a system diagram illustrating RAN104 and CN106 according to an embodiment. As mentioned above, RAN104 can communicate with WTRU102a, 102b, and 102c over the air interface 116 using E-UTRA radio technology. RAN104 can also communicate with CN106.

[0050] RAN104 may include enodes B160a, 160b, and 160c, but it will be understood that RAN104 may include any number of enodes B while maintaining consistency with the embodiment. Each of enodes B160a, 160b, and 160c may include one or more transceivers for communicating with WTRU102a, 102b, and 102c over the air interface 116. In one embodiment, enodes B160a, 160b, and 160c may implement MIMO technology. Thus, enode B160a may, for example, use multiple antennas to transmit a wireless signal to and / or receive a wireless signal from WTRU102a.

[0051] Each of the e-nodes B160a, 160b, and 160c may be associated with a specific cell (not shown) and may be configured to handle wireless resource management decisions, handover decisions, and user scheduling in UL and / or DL. As shown in Figure 1C, the e-nodes B160a, 160b, and 160c can communicate with each other over the X2 interface.

[0052] The CN106 shown in Figure 1C may include a Mobility Management Entity (MME) 162, a Serving Gateway (SGW) 164, and a Packet Data Network (PDN) Gateway (or PGW) 166. Although each of the above elements is depicted as part of CN106, it will be understood that any of these elements may be owned and / or operated by an entity different from the CN operator.

[0053] The MME162 may be connected to each of the e-nodes B160a, 160b, and 160c within RAN104 via the S1 interface and can act as a control node. For example, the MME162 may be responsible for authenticating users of WTRU102a, 102b, and 102c, activating / deactivating bearers, and selecting a specific serving gateway during the initial attachment of WTRU102a, 102b, and 102c. The MME162 may provide control plane functionality for exchanges between RAN104 and other RANs (not shown) utilizing other radio technologies such as GSM and / or WCDMA.

[0054] The SGW164 can be connected to each of the e-nodes B160a, 160b, and 160c within RAN104 via the S1 interface. The SGW164 can generally route and forward user data packets to and from WTRU102a, 102b, and 102c. The SGW164 can perform other functions, such as anchoring the user plane during e-node B handovers, triggering paging when DL data is available to WTRU102a, 102b, and 102c, and managing and remembering the context of WTRU102a, 102b, and 102c.

[0055] SGW164 may be connected to PGW166, which can provide WTRU102a, 102b, and 102c with access to packet-switched networks such as the Internet 110, thereby facilitating communication between WTRU102a, 102b, and 102c and IP-enabled devices.

[0056] CN106 can facilitate communication with other networks. For example, CN106 can provide WTRU102a, 102b, and 102c with access to circuit-switched networks such as PSTN108, thereby facilitating communication between WTRU102a, 102b, and 102c and conventional fixed-line communication devices. For example, CN106 may include, or communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) acting as an interface between CN106 and PSTN108. In addition, CN106 may provide WTRU102a, 102b, and 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers.

[0057] In Figures 1A to 1D, the WTRU is described as a wireless terminal, but in a typical embodiment, such a terminal is intended to be able to use a wired communication interface with a communication network (e.g., temporarily or permanently).

[0058] In a typical embodiment, the other network 112 may be a WLAN.

[0059] A WLAN in Infrastructure Basic Service Set (BSS) mode may have access points (APs) for the BSS and one or more stations (STAs) associated with the APs. APs may have access to or interfaces with a distribution system (DS) or another type of wired / wireless network that carries traffic within and / or outside the BSS. Traffic originating from outside the BSS to an STA may arrive through an AP and be delivered to the STA. Traffic originating from an STA to a destination outside the BSS may be sent to an AP for delivery to its respective destination. Traffic between STAs within the BSS may be transmitted through an AP; for example, a source STA may send traffic to an AP, which can then deliver the traffic to a destination STA. Traffic between STAs within the BSS may be considered and / or referred to as peer-to-peer traffic. Peer-to-peer traffic may be transmitted (e.g., directly) between a source STA and a destination STA using a Direct Link Setup (DLS). In one typical embodiment, the DLS may use 802.11e DLS or 802.11z Tunnel DLS (TDLS). A WLAN using Independent BSS (IBSS) mode may not have APs, and STAs within or using IBSS (e.g., all STAs) may communicate directly with one another. Communication in IBSS mode is sometimes referred to herein as “ad hoc” mode communication.

[0060] When using 802.11ac infrastructure mode operation or a similar mode operation, an AP may transmit beacons on a fixed channel, such as a primary channel. The primary channel may have a fixed width (e.g., a 20 MHz bandwidth) or a dynamically set width via signaling. The primary channel may be the operating channel of the BSS and may be used by an STA to establish a connection with the AP. In a typical embodiment, for example in an 802.11 system, carrier sense multiple access / collision avoidance (CSMA / CA) may be implemented. In the case of CSMA / CA, an STA, including the AP (e.g., any STA), may sense the primary channel. If the primary channel is sensed / detected by a particular STA and / or determined to be busy, that particular STA may backoff. Within a given BSS, at any given time, one STA (e.g., just one station) may transmit.

[0061] A high-throughput (HT) STA may use a 40MHz wide channel for communication, for example, by combining a primary 20MHz channel with adjacent or non-adjacent 20MHz channels to form a 40MHz wide channel.

[0062] Ultra-high throughput (VHT) STAs may support 20MHz, 40MHz, 80MHz, and / or 160MHz wide channels. 40MHz and / or 80MHz channels may be formed by combining consecutive 20MHz channels. 160MHz channels may be formed by combining eight consecutive 20MHz channels, or by combining two discontinuous 80MHz channels, sometimes referred to as an 80+80 configuration. In the 80+80 configuration, after channel encoding, data may be passed through a segment parser that can split the data into two streams. Inverse fast Fourier transform (IFFT) processing and time-domain processing may be performed separately for each stream. The streams may be mapped onto two 80MHz channels, and the data may be transmitted by a transmitting STA. At the receiver of a receiving STA, the operation described above for the 80+80 configuration may be reversed, and the combined data may be sent to a media access control (MAC).

[0063] Sub-1GHz mode operation is supported by 802.11af and 802.11ah. Channel operating bandwidth and carrier are reduced in 802.11af and 802.11ah compared to those used in 802.11n and 802.11ac. 802.11af supports 5MHz, 10MHz, and 20MHz bandwidths in the TV white space (TVWS) spectrum, while 802.11ah supports 1MHz, 2MHz, 4MHz, 8MHz, and 16MHz bandwidths using the non-TVWS spectrum. According to a typical embodiment, 802.11ah may support meter-type control / machine-type communications, such as MTC devices in macro coverage areas. MTC devices may have limited functionality, including support for certain bandwidths and / or limited bandwidths (e.g., only support for those). MTC devices may include batteries with battery life exceeding a threshold (e.g., to maintain very long battery life).

[0064] A WLAN system that can support multiple channels and channel bandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, includes a channel that can be designated as the primary channel. The primary channel may have a bandwidth equal to the largest common operating bandwidth supported by all STAs within the BSS. The bandwidth of the primary channel may be set and / or limited by the STA that supports the minimum bandwidth operating mode among all STAs operating within the BSS. In the case of 802.11ah, even if the APs and other STAs within the BSS support 2MHz, 4MHz, 8MHz, 16MHz, and / or other channel bandwidth operating modes, the primary channel may be 1MHz wide for an STA (e.g., an MTC type device) that supports (e.g., only) the 1MHz mode. Carrier sensing and / or NAV settings may depend on the status of the primary channel. For example, if the primary channel is busy because an STA (which only supports 1MHz operating mode) is transmitting to the AP, the majority of the available frequency band may remain idle, and even if it could be available, the entire available frequency band may be considered busy.

[0065] In the United States, the available frequency bands that can be used by 802.11ah are from 902 MHz to 928 MHz. In South Korea, the available frequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the available frequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidth available for 802.11ah is from 6 MHz to 26 MHz, depending on the country.

[0066] Figure 1D is a system diagram showing RAN113 and CN115 according to an embodiment. As mentioned above, RAN113 can communicate with WTRU102a, 102b, and 102c over air interface 116 using NR radio technology. RAN113 can also communicate with CN115.

[0067] RAN113 may include gNB180a, 180b, and 180c, but it will be understood that RAN113 may include any number of gNBs while maintaining consistency with the embodiment. Each of gNB180a, 180b, and 180c may include one or more transceivers for communicating with WTRU102a, 102b, and 102c over the air interface 116. In one embodiment, gNB180a, 180b, and 180c may implement MIMO technology. For example, gNB180a and 180b may use beamforming to transmit signals to and / or receive signals from gNB180a, 180b, and 180c. Thus, gNB180a may, for example, use multiple antennas to transmit wireless signals to and / or receive wireless signals from WTRU102a. In embodiments, gNB180a, 180b, and 180c may implement carrier aggregation techniques. For example, gNB180a may transmit multiple component carriers to WTRU102a (not shown). A subset of these component carriers may be on the unlicensed spectrum, while the remaining component carriers may be on the licensed spectrum. In embodiments, gNB180a, 180b, and 180c may implement multipoint coordination (CoMP) techniques. For example, WTRU102a may receive coordinated transmissions from gNB180a and gNB180b (and / or gNB180c).

[0068] WTRU102a, 102b, and 102c may communicate with gNB180a, 180b, and 180c using transmissions associated with scalable numerology. For example, OFDM symbol intervals and / or OFDM subcarrier intervals may vary for different transmissions, different cells, and / or different parts of the wireless transmission spectrum. WTRU102a, 102b, and 102c may communicate with gNB180a, 180b, and 180c using subframes or transmit time intervals (TTIs) of varying or scalable lengths (e.g., containing varying numbers of OFDM symbols and / or lasting for varying absolute times).

[0069] gNB180a, 180b, and 180c can be configured to communicate with WTRU102a, 102b, and 102c in standalone and / or non-standalone configurations. In a standalone configuration, WTRU102a, 102b, and 102c can communicate with gNB180a, 180b, and 180c without accessing other RANs (e.g., e-nodes B160a, 160b, and 160c). In a standalone configuration, WTRU102a, 102b, and 102c can use one or more of gNB180a, 180b, and 180c as mobility anchor points. In a standalone configuration, WTRU102a, 102b, and 102c can communicate with gNB180a, 180b, and 180c using signals within the unlicensed band. In a non-standalone configuration, WTRU102a, 102b, and 102c can communicate with and connect to other RANs, such as e-nodes B160a, 160b, and 160c, while also communicating with and connecting to other RANs. For example, WTRU102a, 102b, and 102c can implement DC principles to communicate substantially simultaneously with one or more gNB180a, 180b, and 180c, and one or more e-nodes B160a, 160b, and 160c. In a non-standalone configuration, e-nodes B160a, 160b, and 160c may act as mobility anchors for WTRU102a, 102b, and 102c, while gNB180a, 180b, and 180c may provide additional coverage and / or throughput to service WTRU102a, 102b, and 102c.

[0070] Each of the gNB180a, 180b, and 180c may be associated with a specific cell (not shown) and may be configured to handle radio resource management decisions, handover decisions, user scheduling in UL and / or DL, support for network slicing, dual connectivity, interworking between NR and E-UTRA, routing of user plane data to user plane functions (UPF) 184a and 184b, and routing of control plane information to access and mobility management functions (AMF) 182a and 182b. As shown in Figure 1D, the gNB180a, 180b, and 180c can communicate with each other over the Xn interface.

[0071] The CN115 shown in Figure 1D may include at least one AMF182a, 182b, at least one UPF184a, 184b, at least one Session Management Function (SMF)183a, 183b, and possibly a Data Network (DN)185a, 185b. Although each of the above elements is depicted as a part of CN115, it will be understood that any of these elements may be owned and / or operated by an entity different from the CN operator.

[0072] AMF182a and 182b may be connected to one or more of gNB180a, 180b, and 180c within RAN113 via the N2 interface and can act as control nodes. For example, AMF182a and 182b may be responsible for authenticating users of WTRU102a, 102b, and 102c, supporting network slicing (e.g., handling different PDU sessions with different requirements), selecting specific SMF183a and 183b, managing registration areas, terminating NAS signaling, and mobility management. Network slicing may be used by AMF182a and 182b to customize CN support for WTRU102a, 102b, and 102c based on the type of service being used. For example, different network slices may be established for different use cases, such as services that rely on ultra-high reliability low latency (URLLC) access, services that rely on high-speed high-capacity mobile broadband (eMBB) access, and / or services for machine-type communications (MTC) access. The AMF182 may provide control plane functionality for exchange between RAN113 and other RANs (not shown) that utilize other radio technologies, such as LTE, LTE-A, LTE-A Pro, and / or non-3GPP access technologies like WiFi.

[0073] SMF183a and 183b can be connected to AMF182a and 182b in CN115 via the N11 interface. SMF183a and 183b can also be connected to UPF184a and 184b in CN115 via the N4 interface. SMF183a and 183b can select and control UPF184a and 184b and configure the routing of traffic through UPF184a and 184b. SMF183a and 183b can perform other functions, such as managing and assigning UE IP addresses, managing PDU sessions, controlling policy enforcement and QoS, and providing downlink data notifications. PDU session types can be IP-based, non-IP-based, and Ethernet-based, among others.

[0074] UPF184a and 184b may be connected via the N3 interface to one or more of the gNB180a, 180b, and 180c in RAN113, which may provide WTRU102a, 102b, and 102c with access to packet-switched networks such as the Internet 110, thereby facilitating communication between WTRU102a, 102b, and 102c and IP-enabled devices. UPF184a and 184b may perform other functions such as routing and forwarding packets, enforcing user plane policies, supporting multihoming PDU sessions, handling user plane QoS, buffering downlink packets, and providing mobility anchoring.

[0075] CN115 can facilitate communication with other networks. For example, CN115 may include, or can communicate with, an IP gateway (e.g., an IP Multimedia Subsystem (IMS) server) that acts as an interface between CN115 and PSTN108. In addition, CN115 may provide WTRU102a, 102b, 102c with access to other networks 112, which may include other wired and / or wireless networks owned and / or operated by other service providers. In one embodiment, WTRU102a, 102b, 102c may be connected to local data networks (DN) 185a, 185b through UPF184a, 184b via an N3 interface to UPF184a, 184b, and an N6 interface between UPF184a, 184b and DN185a, 185b.

[0076] In view of Figures 1A to 1D and their corresponding descriptions, one or more or all of the functions described herein relating to one or more of the WTRU102a to d, base stations 114a to b, e-nodes B160a to c, MME162, SGW164, PGW166, gNB180a to c, AMF182a to b, UPF184a to b, SMF183a to b, DN185a to b, and / or any other devices described herein may be performed by one or more emulation devices (not shown). An emulation device may be one or more devices configured to emulate one or more or all of the functions described herein. For example, an emulation device may be used to test other devices and / or to simulate network and / or WTRU functions.

[0077] Emulation devices may be designed to perform one or more tests of other devices in a laboratory environment and / or an operator network environment. For example, one or more emulation devices may perform one, more, or all functions while fully or partially implemented and / or deployed as part of a wired and / or wireless communication network to test other devices in a communication network. One or more emulation devices may perform one, more, or all functions while temporarily implemented and / or deployed as part of a wired and / or wireless communication network. Emulation devices may be directly coupled to another device for testing purposes and / or may perform testing using over-the-air wireless communications.

[0078] One or more emulation devices may perform one or more functions, including all functions, while not being implemented / deployed as part of a wired and / or wireless communication network. For example, an emulation device may be used in a test scenario, in a test laboratory and / or in an undeployed (e.g., test) wired and / or wireless communication network, to perform testing of one or more components. One or more emulation devices may be test equipment. Direct RF coupling and / or wireless communication via RF circuitry (which may include, for example, one or more antennas) may be used by the emulation device to transmit and / or receive data. 2. HARQ signaling and acknowledgment procedures in WLANs To support HARQ operation in a WLAN, new signaling procedures and designs specifically targeting HARQ operation are required to enable communication between HARQ-enabled STAs. The above signaling may include ACK, NACK, trigger frames, BlockAck, and multi-STA BlockAck. 2.1 HARQ signaling and affirmative response procedures using ACK / NACK and multi-STA ACK To support HARQ operation in WLANs, new signaling should be defined that includes one or more of the following types of designs: HARQ ACK, HARQ NACK, HARQ trigger frame, multi-HARQ process ACK / NACK / BA, multi-TID multi-HARQ process ACK / NACK / BA, and multi-STA multi-TID multi-HARQ process ACK / NACK / BA, HARQ block ACK request (BAR) frame, and multi-user (MU) HARQ BAR frame.

[0079] An ACK frame may be sent immediately by the receiving STA in response to a HARQ transmission to indicate that the HARQ transmission has been successfully received and decoded. The HARQ transmission transmitter may then delete the copy of the packet associated with the HARQ transmission and continue its attempt to send the remaining packets in its queue. In another embodiment, the ACK frame may include the HARQ process ID or redundancy version (RV) number to which the ACK is sent.

[0080] A multi-HARQ process BAR can be used to obtain ACK / NACK / BA from an STA. A multi-HARQ process BAR can be implemented using the common BlockAckReq frame format shown in Figure 3. To indicate that the current frame is a multi-HARQ process BAR, one or more reserved bits in the BAR control field may be used to indicate that the current frame is a multi-HARQ process BAR.

[0081] In one example, the multi-TID (Traffic Identifier) ​​subfield (not shown) of the BAR control field may be set to "0", and one or more bits from B5 to B11 in the BAR control field may be used to indicate that the current frame is a multi-HARQ process variation of a BlockAckReq frame. In addition, one or more bits in the TID_Info subfield (not shown) of the BAR control field, or one or more bits from the currently reserved bits B5 to B11, may be used to indicate one or more HARQ process IDs for which an ACK / NACK / BA is requested. One or more bits in the BAR control field may indicate whether an ACK / NACK / BA is requested. In another example, a multi-HARQ process variation of a BlockAckReq frame can be shown by setting the multi-TID subfield of the BAR control field to "0", the compressed bitmap subfield of the BAR control field to "0", and the GCR mode subfield of the BAR control field to "0" (the subfields are not shown in Figure 3).

[0082] In another example, one of the reserved values ​​in the "BAR Type" subfield of the Bar control field may be used to indicate that the current frame is a multi-HARQ process BAR. The TID_Info field of the BAR control field may be used to indicate the HARQ process ID for which ACK / NACK / BA is requested. Alternatively, or in addition, the BAR Info subfield of the BAR control field may include an indication of the HARQ process ID for which ACK / NACK / BA is requested. In one example, the BAR Info subfield may include all the HARQ process IDs for which ACK / NACK / BA is requested. In another example, in addition to the bitmap, a "Starting HARQ Process ID" may be indicated. The bitmap may use "1" to indicate that the HARQ process ID for which ACK / NACK / BA is requested starts with the HARQ process ID indicated in the "Starting HARQ Process ID" field. The size of the bitmap, or the number of HARQ process IDs it contains, may be negotiable and may be limited by the number of concurrent HARQ processes supported by the STA, or the number of concurrent HARQ processes per TID supported by the STA, which are parameters that may be shown as part of the EHT capability during the association process.

[0083] In addition, or alternatively, a multi-TID multi-HARQ BAR may be used to request ACK / NACK / BA from the STA for one or more HARQ processes in one or more traffic streams identified by one or more TIDs. A multi-TID multi-HARQ process BAR may be implemented using the common BlockAckReq frame format shown in Figure 3. To indicate that it is a multi-TID multi-HARQ process BAR, one or more reserved bits in the BAR control field may be used to indicate that the current frame is a multi-TID multi-HARQ process BAR. For example, the BAR type subfield may be used to indicate that the current BAR frame is of the multi-TID multi-HARQ process type. For example, B1 of the BAR type subfield may be set to "1". Thus, the BAR type subfield may be set to an odd number such as 7, 9, or 11 to indicate that the current BAR frame is a multi-TID multi-HARQ process variation. The TID information field may indicate the number of TIDs for which ACK / NACK / BA is requested. In another example, the TID information field may indicate the number of TID / HARQ process ID combinations for which ACK / NACK / BA is requested. The BAR information field may contain several fields, the number of which is indicated within the TID information subfield, each containing a TID value, HARQ information, and a bitmap. The TID value may indicate the value of the TID for which a HARQ response may be requested. In one example, each TID / HARQ process ID field contains all HARQ process IDs for which ACK / NACK / BA is requested. In another embodiment, in addition to the bitmap, a "starting HARQ process ID" may be indicated. The bitmap may use "1" to indicate which of the HARQ process IDs for which ACK / NACK / BA is requested starts with the HARQ process ID indicated in the "starting HARQ process ID" field.The size of the bitmap, or the number of HARQ process IDs it contains, may be limited by the number of concurrent HARQ processes supported by the STA, or the number of concurrent HARQ processes per TID supported by the STA, which are negotiable parameters that may be shown as part of the EHT capability during the association process.

[0084] In addition, a multi-STA multi-TID multi-HARQ BAR may be defined to request HARQ responses for multiple STAs, each having multiple TIDs and multiple HARQ process IDs. A multi-STA multi-TID multi-HARQ BAR may largely follow the definition of a MU-BAR, where the BAR type in the BAR control field is set to indicate that the current frame is a multi-STA multi-TID multi-HARQ BAR. The BAR information field may include one or more bits indicating not only the HARQ process IDs but also the TIDs. For example, one or more reserved bits in the per-TID information field may be used to indicate the HARQ process ID for which a HARQ response is requested. One or more specific values ​​may be used to indicate that a normal ACK / BA (and therefore no HARQ response) is requested for a non-HARQ transmission. An STA, e.g., an AP, may use a multi-STA multi-TID multi-HARQ BAR to request responses from one or more STAs for one or more TIDs and one or more HARQ process IDs. Alternatively, the BAR information field may use one or more reserved bits that indicate, for example, the number of HARQ process IDs as well as the initiating HARQ process ID for which a HARQ response is requested. One or more specific values ​​may be used to indicate that a normal ACK or BA (and therefore not HARQ) response is requested for a non-HARQ transmission, in which case the BAR information field may follow that of a normal multi-STA BA.

[0085] STA may use multi-HARQ BA, multi-TID multi-HARQ BA, and / or multi-STA multi-TID multi-HARQ BA as a response to multi-HARQ BAR, multi-TID multi-HARQ BAR, and / or multi-STA multi-TID multi-HARQ BAR. A multi-HARQ BA generally follows the format of a generic BlockAck frame, with the BA type field set to a value indicating that the current frame is a multi-HARQ BA. The STA may set the TID_Info field to a value for a specific TID, as well as indicating the HARQ process ID bitmap size or the number of HARQ process ID bitmaps. The STA may set the BA information field in such a way that it may include the initiating HARQ process ID as well as a bitmap containing bits indicating which HARQ response is provided for which HARQ response. The encoding for each HARQ process ID may include one or more bits to indicate one or more potential responses, including ACK, NACK, No Signal Detected, interference, collision, and restart of the HARQ process request.

[0086] The STA may respond to a multi-TID multi-HARQ BAR using a multi-TID multi-HARQ BA to provide a response for one or more TIDs having one or more HARQ process IDs. The STA may set the BA type in the BA control field to indicate that the frame is of the multi-TID multi-HARQ BA type. The BA information field may contain one or more TID / HARQ fields for each TID. The STA may indicate the starting HARQ process ID in the per-TID information field. In another implementation, the block ACK start sequence control field may contain the starting HARQ process ID. The block ACK bitmap may contain a response indicating for which HARQ response is provided for each HARQ process ID. The encoding for each HARQ process ID may contain one or more bits to indicate one or more potential responses, including ACK, NACK, signal not detected, interference, collision, and restart of the HARQ process request.

[0087] An STA, for example, an AP, may use a multi-STA multi-TID multi-HARQ BA to provide a response to one or more STAs, each having one or more TIDs, each having one or more HARQ process IDs, and the STA may set the BA type in the BA control field to indicate that the frame is of the multi-STA multi-TID multi-HARQ BA type. The BA information field may include one or more AID / TID / HARQ fields for each AID / TID. The STA may indicate the starting HARQ process ID in the AID / TID information field. In another implementation, the block Ack start sequence control field may include the starting HARQ process ID. The block ACK bitmap may include a response indicating which HARQ process IDs are provided with a HARQ response starting from the starting HARQ process ID. The encoding for each HARQ process ID may include one or more bits to indicate one or more potential responses, including ACK, NACK, signal not detected, interference, collision, and restart of the HARQ process request.

[0088] An AP may use a HARQ trigger frame to trigger a transmission that may include one or more HARQ transmissions. The design of a HARQ trigger frame may largely follow the design of a generic trigger frame. The trigger type subfield in the common information field may contain a value indicating that the trigger frame is a HARQ trigger frame. Alternatively, or in addition, the user information field in a trigger frame intended to trigger a HARQ transmission may contain one or more bits indicating that it is. The trigger-dependent user information field may contain information about the triggered HARQ transmission, such as the HARQ process ID, and / or information about whether a new transmission, retransmission, or new RV has been triggered. One or more STAs triggered by a HARQ trigger frame may begin their transmissions one short interframe interval (SIFS) or HARQ IFS (HIFS) after the end of the HARQ trigger frame, or an aggregated MAC protocol data unit (A-MPDU) or aggregated PLCP (Physical Layer Convergence Procedure) protocol data unit (A-PPDU) containing the HARQ trigger frame. One or more of the triggered transmissions may include one or more HARQ transmissions, which may be implemented as A-MDPU or A-PPDU. Each HARQ transmission may be contained within a separate PPDU or within an A-PPDU. 2.2 HARQ Signaling and Response Procedure Using NDP Feedback Reports To request HARQ feedback from multiple STAs simultaneously, an AP may use a null data packet (NDP) feedback report. In this method, a set of STAs receives a HARQ NDP Feedback Report Polling (HARQ NFRP) trigger frame from the AP and, after a SIFS duration from the frame's reception, sends a HARQ NDP feedback frame to the transmitter indicating the status of one or more HARQ transmissions for a specific HARQ process ID. For example, the NFRP may include a feedback type field indicating NDP HARQ feedback. HARQ NDP feedback can be ACK or NACK. Alternatively, HARQ NDP feedback can be ACK, NAK, collision indication (COL), signal not detected, or interference.

[0089] In one embodiment, the STA may set the HARQ NDP Feedback Report Support subfield within the High Efficiency (HE) or EHT capability element to 1 if it supports HARQ NDP Feedback Reports, and to 0 otherwise. In an embodiment, the STA shall not send HARQ NDP Feedback Report responses unless it is explicitly enabled by the AP. In an embodiment, the interframe interval between the PPDU containing the HARQ NFRP trigger frame and the HARQ NDP Feedback Report polling response is SIFS.

[0090] In the embodiment, the STA begins sending a HARQ NDP feedback report response at the SIFS time boundary after the completion of the received PPDU when all of the following conditions are met.

[0091] - The received PPDU includes the HARQ NFRP trigger frame.

[0092] -STA is scheduled by the HARQ NFRP trigger frame.

[0093] - The HARQ NDP Feedback Report Support subfield in the HE or EHT MAC Capability Information field is set to 1.

[0094] -STA is intended to provide a response to the type of HARQ NDP feedback contained in the HARQ NFRP trigger frame.

[0095] In this embodiment, an STA that does not necessarily satisfy all of the above conditions will not respond to the HARQ NFRP trigger frame.

[0096] In this embodiment, the STA is scheduled to respond to an NFRP trigger frame if all of the following conditions are met.

[0097] -STA is associated with a basic service set identifier (BSSID) as indicated in the TA field of the HARQ NFRP trigger frame, or STA has dot11MultiBSSIDActivated set to true and is associated with a non-transmitted BSSID of a multiBSSID set, and the TA field of the HARQ NFRP trigger frame is set to a transmitted BSSID of that multiBSSID set.

[0098] - The AID of an STA is greater than or equal to the associated identifier (AID) of the start, and less than the start AID + NSTA, using the start AID subfield in the eliciting trigger frame, while the NSTA is the total number of STAs scheduled to respond to the HARQ NFRP trigger frame. The NSTA is calculated based on the UL BW subfield and the multiplexing flag subfield of the eliciting trigger frame.

[0099] - The AID of the STA is explicitly communicated in the HARQ NFRP trigger frame. In one embodiment, the AID of the STA and the number of HARQ feedback bits are communicated.

[0100] A non-AP HE STA shall obtain HARQ NDP feedback report parameter values ​​from the most recently received HARQ NDP feedback report parameter set elements carried in the management frame received from its associated AP.

[0101] In an embodiment, the HARQ NFRP transmits the required information to the STA. This may include the following fields:

[0102] 1. The STAs to be addressed and their resource allocation.

[0103] 2. The number of HE-LTF symbols. This changes from 1 (for NDP feedback for traffic requests) to the maximum number of HARQ feedback for all STAs addressed.

[0104] 3. The HARQ ID of the feedback process (which may be placed in the user information field).

[0105] To indicate the maximum number of ACK / NAK / collision values ​​that can be fed back, a HARQ feedback report parameter frame, as illustrated in Figure 4, may be used.

[0106] The HARQ NDP feedback frame can transmit the HARQ status in HE-LTF. In one embodiment, the HARQ NDP feedback may be limited to just one OFDM symbol, as shown in Figure 5.

[0107] Information about a single packet may be fed back, or information about multiple packets may be fed back. In the case of single-packet feedback (as shown in Figure 6), a resource, such as the RU_TONE_SET_INDEX parameter, may be set based on the AID, start AID, and bandwidth (BW) using the following formula, using the value of the start AID subfield in the user information field of the triggered draw frame. RU_TONE_SET_INDEX=(AID-StartAID) mod (18×2 BW ) This is the result.

[0108] Alternatively, it may be set based on the relative position of the AID within the user information field; for example, for user(i), RU_TONE_SET_INDEX(i) = user_information_field1(i). Note that if the number of user information fields is less than the maximum RU_TONE_SET_INDEX, additional resources will be padded. In this case, no information is transmitted on the resource, or all tones of the resource are transmitted (to satisfy the channel bandwidth requirements).

[0109] In the case of multiple packet feedback (as shown in Figure 7), the resource, for example, the RU_TONE_SET_INDEX parameter, may be set using the following formula, based on the AID, start AID, bandwidth (BW), and the number of resources N allocated for HARQ feedback for that particular STA, using the values ​​N of the start AID subfield and user resource subfield in the user information field of the triggered draw frame. Relative position AID(i) = (AID - start AID) mod (18 × 2) BW ) RU_TONE_SET_INDEX(i,1)=sum{relative position AID(i-1)×N(i-1)}+1 RU_TONE_SET_INDEX(i,N)=sum{relative position AID(i-1)×N(i-1)}+N This is the result.

[0110] Alternatively, it may be set based on the relative position of the AID in the user information field and the value N.

[0111] In one example, feedback for two or more packets (e.g., N packets) may be transmitted in N HARQ feedback symbols, as shown in Figure 8. This may be allocated to multiple users, as shown in Figure 9, with a single frequency resource allocated to a single STA. Alternatively, multiple frequency resources may be allocated to a single STA.

[0112] To communicate the presence of ACK, NAK, or collision, the STA may select values ​​from a subset of LTFs using specific tone mappings for each type. In one example, the NDP feedback allocation may consist of 12 subcarriers, with ACK being assigned 4 subcarriers, NAK 4 subcarriers, and COL 4 subcarriers. In another example, the NDP feedback allocation may consist of 12 subcarriers, with ACK being assigned 6 subcarriers, NAK 6 subcarriers, and COL 6 subcarriers. In yet another example, the NDP feedback allocation may consist of 18 subcarriers, with ACK being assigned 6 subcarriers, NAK 6 subcarriers, and COL 6 subcarriers.

[0113] Subcarrier allocation may be contiguous or distributed (e.g., interlaced) within a resource. For example, Figure 10A illustrates distributed subcarrier allocation, where ACK is allocated four subcarriers, NAK is allocated four subcarriers, and COL is allocated four subcarriers, while Figure 10B illustrates contiguous allocation of the same subcarriers. 3. HARQ MAC Procedure in WLAN Many new MAC features were introduced in the 802.11ax draft, including UL and DL OFDMA, Broadcast Target Wake Time (TWT), and trigger-based UL transmission. To enable HARQ operation in WLANs, common media access procedures, including scheduled and triggered random access HARQ designs, should be defined to include efficient and appropriate media access protocols to support efficient HARQ operation in WLANs. 3.1 HARQ DL MAC Procedure Method 1: A HARQ DL MAC procedure according to the first embodiment is shown in Figure 11. In Figure 11, each block represents a resource unit (RU), and the vertical dimension represents elapsed time. An RU can be any type of resource (e.g., time, frequency, space, or any combination thereof). The following MAC procedure may be used to support HARQ operation in the downlink between an AP and one or more STAs.

[0114] An AP may send a HARQ transmission simultaneously to multiple STAs, e.g., STA1 to STAN, on different resource units (RUs) in a DL OFDMA transmission. The preamble of a multi-user (MU) packet may include an indication that the current transmission may contain one or more HARQ transmissions. The preamble of each A-MPDU or A-PPDU or PPDU may include an indication that it may contain one or more HARQ transmissions. Each HARQ transmission may contain, or be preceded by, a HARQ indication, and may contain, or be preceded by, a clear delimiter pattern so that a receiving STA can discover the start of a HARQ transmission. A HARQ transmission may contain a HARQ process ID in its preamble, or in the delimiter pattern, or in any other part indicated by the A-MPDU or A-PPDU preamble.

[0115] The AP may carry a trigger frame in the same A-MPDU or A-PPDU as the HARQ transmission to trigger a response to the HARQ process. The trigger frame may include not only the desired HARQ process ID but also an indication that it is a trigger frame for the HARQ process. Similarly, the response may be scheduled by a response scheduling preamble or header, which may include the desired HARQ process ID.

[0116] A receiving STA may send a response that can be scheduled by a response scheduling header / preamble, or triggered by a trigger frame, for example, SIFS time or HARQ IFS (HIFS) away from the end of a preceding transmission. A response to a HARQ process or transmission can contain a number of possible values, including ACK, NACK, No Signal Detected, Collision, and Restart HARQ Process Requested.

[0117] Subsequently, the AP may make additional transmissions and HARQ transmissions based on the feedback received from the STA. For example, as shown in Figure 11, since ACKs have been received from STA1 and STA N indicating that the preceding HARQ transmission was successfully decoded by STA1 and STA N, the AP may initiate a new HARQ process with a new transmission associated with HARQ ID 2 to STA1 and STA N. Since a NACK has been received from STA2 indicating that STA2 did not successfully decode the HARQ transmission, the AP may initiate sending transmission 2 of HARQ process ID 1 to STA2. The NACK frame may also include additional feedback from STA2 regarding recommended next steps, including MCS recommendations and whether retransmission or additional RVs are desired. Transmission 2 of HARQ process ID 1 may be a retransmission or a different RV of HARQ process ID 1, which may be based on the recommended action included in the NACK from STA2.

[0118] Similarly, a new HARQ transmission by the AP may be part of an A-MPDU or A-PPDU, which may include a trigger frame or response scheduling header to solicit a response from the receiving STA.

[0119] Subsequently, the receiving STA may provide a response.

[0120] In another implementation, an A-MPDU or A-PPDU carrying a downlink HARQ transmission may consist of two parts, one of which may contain an A-MPDU, as shown in Figure 12, while the other may contain an A-PPDU that may contain one or more HARQ transmissions. The A-MPDU may contain all normal packet transmissions, such as ACK / NACK / BA packets, trigger frames, and other management or control frames, which may be transmitted first and may be separated by a delimiter between MPDUs. The A-MPDU may also contain indications and / or scheduling for subsequent HARQ transmissions. The A-MPDU may contain information for the next HARQ transmission, such as the HARQ process ID, target receiving STA, HARQ transmission start time, modulation coding scheme (MCS), and HARQ transmission RV number, for each HARQ transmission. Any or all of these indications may also be included in the PLCP or MAC header of the entire A-MPDU. In addition, or possibly any or all of these indications may also be included in the PLCP or MAC header of the entire A-PPDU, which may contain the PPDU carrying the A-MPDU.

[0121] In another implementation, one or more MPDUs that are not part of the HARQ transmission may also be grouped into one or more A-MPDUs, which may be transmitted in multiple PPDUs of the A-PPDU.

[0122] After transmitting a PPDU carrying an A-MPDU, the transmitting STA may continue transmitting one or more PPDUs, which may include HARQ transmissions. Each PPDU or HARQ transmission may include a preamble or delimiter field, which may include a set of delimiters and / or training fields, or may be preceded by a preamble or delimiter field. The preamble or delimiter field may include, for example, a clear bit pattern such as a delimiter, a training field such as LTF, STF, or other types of fields to announce the start of a new PPDU or new HARQ transmission. Furthermore, the preamble or delimiter field may also include information about the next HARQ transmission, such as the HARQ process ID, target receiving STA, start time of the HARQ transmission, MCS, RV number of the HARQ transmission, retransmission of the preceding HARQ transmission, length of the next HARQ transmission or PPDU, and length or duration of the next HARQ transmission or PPDU, as well as whether further PPDUs or HARQ transmissions follow the next HARQ transmission or PPDU.

[0123] The remainder of the procedure may be largely the same as described above, except that an A-MPDU or A-PPDU includes a HARQ transmission that carries one or more PPDUs carrying an A-MPDU that is not sent as part of the HARQ process, and in addition, carries one or more PPDUs carrying a HARQ transmission. A PPDU carrying an (A-)MPDU that is not part of any HARQ transmission may contain scheduling, indications, or information related to the next PPDU and / or HARQ transmission. Such information may also be contained within the first PPDU of an A-PPDU, or within the first preamble of the first PPDU of an A-PPDU. A PPDU carrying a HARQ transmission may contain, or may be preceded by, a preamble and isolation field that may contain a delimiter, an identifier for the HARQ transmission, a training field, and / or information related to the next HARQ transmission or PPDU.

[0124] In another implementation, an (A-)MPDU or PPDU containing one or more MPDUs that are not transmitted as part of a HARQ transmission may be transmitted at the end of the A-PPDU or at any point within the A-PPDU. Method 2: The following design describes an exemplary DL HARQ operation and transmission procedure.

[0125] In one embodiment, the TF or (A-)PPDU header assigns in response whether NDP feedback or BA should be sent. In one option, if the assignment is BA / ACK feedback, the AP or non-STA may instruct the HARQ buffer to flush so that MPDU-level retransmission may be initiated using a different MCS.

[0126] In one embodiment, the TF may also allocate a HARQ feedback resource to the slave AP for reporting any overheard HARQ transmissions. Based on the feedback, the master AP may initiate a joint HARQ retransmission.

[0127] In one embodiment, the NDP feedback resource / tone set may match the RU assigned to the STA. When the STA performs NDP feedback, the feedback "on" tone may function as a supplementary reciprocal NDP sounding signal to the master and slave APs.

[0128] In one embodiment, HARQ resources are implicitly assigned based on the ID of the assigned RU. In another embodiment, HARQ resources are implicitly assigned based on the identity of a non-AP STA.

[0129] In the original HARQ transmission, one or more IDs may be associated with the (A-)PPDU, which are referenced in the retransmission.

[0130] In retransmission, the (A-)PPDU or TF header may use a reference ID to the original HARQ transmission to identify the portion of the OFDM symbol / codeword being retransmitted, and / or its redundant version.

[0131] In one embodiment, the receiver simply responds using a BA, optionally including an indication that the receiver is buffering undecoded HARQ samples. The transmitter derives the OFDM symbols / codewords to be retransmitted based on the bitmap on the BA.

[0132] In one embodiment, a HARQ ACK / NACK from any STA resets the initiator contention window. Unresponsive NDP feedback from all STAs may increase the initiator contention window for the AP. 3.2 HARQ DL Multiple Stop and Wait MAC Procedure The following exemplary method may enable and support HARQ downlink multiple stop-and-wait MAC procedures. Method 1: An exemplary design of a DL HARQ multiple stop-and-wait procedure is shown in Figure 13. The procedure for a DL HARQ multiple stop-and-wait procedure may include the following steps:

[0133] APs and several STAs can exchange their ability to support multiple stop-and-wait HARQ processes. They can exchange window sizes or the number of concurrently running HARQ processes. Without loss of generality, it is assumed that the number of concurrent HARQ processes per STA, or per TID per STA, can be N.

[0134] Given that the STA has indicated it supports multiple stop-and-wait HARQ processes, the AP may, on a particular RU, make HARQ transmissions for multiple HARQ processes to each of the STAs. For example, as shown in Figure 13, the AP may transmit an A-MPDU or A-PPDU to STA1 on RU0. The A-MPDU or A-PPDU may contain a number of PPDUs or MPDUs, which may include multiple transmissions for multiple HARQ processes. For example, the PPDU or MPDU may include a first transmission to STA1 on RU0 for HARQ processes 1-N. As in the previous section, each HARQ transmission may contain, or may be preceded by, a preamble and / or delimiter field, which may contain a clear bit pattern of delimiters, e.g., a training field such as LTF, STF, or other types of fields, to announce the start of a new PPDU or a new HARQ transmission. Furthermore, the preamble or separation field may also include information about the next HARQ transmission, such as the HARQ process ID, target receiver STA, HARQ transmission start time, MCS, HARQ transmission RV number, retransmission of preceding HARQ transmissions, length of the next HARQ transmission or PPDU, and length or duration of the next HARQ transmission or PPDU, as well as whether a further PPDU or HARQ transmission follows the next HARQ transmission or PPDU.

[0135] Similarly, AP may transmit an A-MPDU or A-PPDU for STA2 on RU1, which may include a mixture of HARQ and non-HARQ transmissions. One or more PPDUs transmitted on RU1 may include the first transmission of HARQ processes 1 to N for STA2.

[0136] Within the same A-MPDU or A-PPDU transmitted to the STA on a particular RU, the AP may also include a trigger frame or multi-HARQ BAR frame to trigger a HARQ response from the STA. Trigger frames, MPDUs such as multi-HARQ BARs, and other types of frames such as management or control frames may be transmitted within a single A-MPDU. An A-MPDU may be transmitted within a separate PPDU that is part of an A-PPDU. A PPDU may include, or be preceded by, a preamble and / or delimiter field, which may include, for example, a clear bit pattern such as a delimiter, a training field such as LTF or STF, or other types of fields, in addition to other HARQ-related information as described above, to announce the start of a new PPDU or a new HARQ transmission. A PPDU or MPDU containing a non-HARQ transmission may be transmitted at the beginning or end of an A-MPDU or A-PPDU, or somewhere within them. In addition, or alternatively, a response to a HARQ transmission may be triggered or scheduled by the response scheduling headers of one or more PPDUs or MPDUs contained within the same A-MPDU or A-PPDU.

[0137] In another implementation, the AP may send a multi-STA multi-TID multi-HARQ BAR, or a multi-STA multi-HARQ BAR, to one or more STAs to request a response to one or more HARQ processes that may be associated with one or more TIDs.

[0138] A receiving STA may send a response after HARQ transmission, for an IFS time (such as SIFS, HIFS, or HARQ response time). Such a response may be triggered or scheduled by a trigger frame, a multi-HARQ BAR, or a response scheduling header. The response may be a BA with ACK / NACK, a multi-HARQ BA, or a multi-TID multi-HARQ BA.

[0139] After receiving a response from the STA, the AP may then decide to make further HARQ transmissions. If one or more HARQ processes have been acknowledged by the STA, and the number of concurrent HARQ processes is still less than or equal to the number indicated by the STA, the AP may continue to send HARQ transmissions for new HARQ processes. If no response is received for a HARQ process, or if a NACK is received, the AP may decide to retransmit or send an additional RV in a subsequent HARQ transmission. Method 2: In another embodiment, as illustrated in Figure 14, an NDP feedback PPDU may have two or more concatenated LTFs to accommodate multiple HARQ transmissions. The LTFs and the index of the tone sets within the LTFs may be identified by the header of each PPDU or specified within the LTFs. Alternatively, the association between the HARQ TX time / frequency resources and the feedback resources may be implicit based on mapping rules.

[0140] A MU-BAR requesting HARQ feedback can be used as a TF for HARQ feedback. The message may include the ID of the (A-)PPDU and / or the RU, symbol / time index within the (A-)PPDU.

[0141] A timer may be negotiated between the AP and non-AP STA, associated with the HARQ process. The timer starts upon failure of HARQ(re)transmission.

[0142] When the time expires, the STA may (1) send a poll to the AP requesting a retransmission of the HARQ process, and after the poll, a second timer may be started. Upon expiration, the STA may declare the HARQ process to have failed and proceed to the next packet / HARQ process, and (2) send a BA identifying the lost MPDU and flush the HARQ buffer associated with the process.

[0143] In one embodiment, the STA does not need to send a BA to report a successfully received MPDU due to an established BA agreement with HARQ support, unless it receives a BAR to trigger a BA. In another embodiment, it may send one. 3.3 HARQ UL MAC Procedure An exemplary HARQ uplink procedure is shown in Figure 15. The HARQ uplink MAC procedure may include one or more of the following steps:

[0144] APs and one or more STAs may have the capability to exchange not only HARQ parameters but also UL HARQ transmission and / or HARQ reception.

[0145] An AP may trigger an uplink HARQ transmission by sending a trigger frame to an STA on a specific RU. In addition, or alternatively, an AP may trigger uplink HARQ transmissions from multiple STAs by sending trigger frames to one or more STAs across the entire channel bandwidth. Such trigger frames may be HARQ trigger frames. A trigger frame may contain information that a particular HARQ transmission is being triggered. In addition, a trigger frame may also indicate specific information about the triggered HARQ transmission, such as the HARQ process ID, RV number, HARQ transmission size, MCS, and RU allocation.

[0146] In response to a trigger frame, the STA may transmit a UL A-MDPU or A-PPDU on a specific RU or across the entire bandwidth. For example, as shown in Figure 15, STA1 may transmit a PPDU containing HARQ transmission 1 for HARQ process ID 1 to the AP. The PPDU containing the HARQ transmission may include a preamble and / or isolation field that may be preceded by, or include, other HARQ transmission-related information as described above, including the training field, delimiter, HARQ transmission indicator, and expected HARQ transmission duration and / or MCS.

[0147] If the AP and STA indicate that they support UL multiple stop-and-wait HARQ processes, and if the number of concurrent HARQ processes, as indicated by their capability exchange, can be supported by the AP and STA, then the STA may transmit a number of HARQ transmissions associated with the number of concurrent HARQ processes.

[0148] Furthermore, an STA may also include a HARQ BAR frame to request a response to a HARQ transmission. Alternatively, an STA may include an NDP packet in an A-PPDU or A-MPDU with a MAC header that indicates that an "immediate ACK" is requested, or a frame that only has a MAC header. In another example, an STA may also include a multi-HARQ BAR or multi-TID multi-HARQ BAR to request a response to multiple HARQ processes associated with one or more TIDs. As described above, packets such as BARs, ACKs, or other types of management or control frames that are not part of a HARQ transmission may be contained in a single A-MPDU carried within a single PPDU. A PPDU may include or be preceded by a preamble or isolation field. This PPDU may also be transmitted as the first PPDU within an A-MPDU, or as the last PPDU within an A-MPDU.

[0149] An AP may respond to HARQ transmissions and / or BAR frames by sending an A-MPDU downlink, which may include not only a trigger frame but also a BAR. For example, a trigger frame for a specific HARQ process ID for a particular STA may also function as a NACK for that HARQ process. For multiple stop-and-wait HARQ processes, the trigger frame may contain a bitmap or list of HARQ process IDs for which a UL HARQ transmission may be triggered.

[0150] Upon receiving a BA and / or trigger frame for one or more HARQ process IDs, the STA may use the information contained within the BA and / or trigger frame to decide on subsequent transmissions and HARQ transmissions. If it determines that the HARQ process has been successfully decoded and acknowledged by the AP, and the number of concurrent HARQ processes with the AP is still less than or equal to the maximum number of concurrent HARQ processes agreed upon by the AP and the STA, it may continue to transmit one or more HARQ transmissions associated with one or more new HARQ processes. Otherwise, it may retransmit the HARQ process that was denied or not acknowledged. Alternatively, it may decide to transmit a different RV for the requested HARQ process, or for a HARQ process that was denied or not acknowledged.

[0151] The AP may also send a multi-STA multi-TID multi-HARQ BA to provide a response to one or more STAs that have sent a UL transmission about one or more HARQ processes associated with one or more TIDs. 3.4 HARQ Cascading MAC Procedure Exemplary HARQ cascading uplink and downlink procedures are shown in Figure 16. Cascading UL and DL HARQ procedures may include one or more of the following steps:

[0152] AP and one or more STAs may exchange their ability to support HARQ, or in particular to support cascading HARQ procedures.

[0153] An AP may transmit an A-MPDU or A-PPDU to a specific STA on a specific RU or across a channel bandwidth of 20 MHz or more. For example, as shown in Figure 16, an AP may transmit an A-MPDU or A-PPDU to STA1 on RU0, which includes a HARQ transmit for HARQ process ID 1, and a trigger frame that causes the STA to transmit a response to the DL HARQ transmit and a UL transmit. Before STA1 initiates the UL HARQ process, the trigger frame may only include an indication that only HARQ transmits are permitted, or that both HARQ and non-HARQ transmits are permitted. After STA1 has transmitted one or more UL HARQ transmits, the trigger frame may also include a specific HARQ process or retransmission, or a specific RV number for the HARQ process that it wishes to trigger on the uplink. Alternatively, an AP may trigger an uplink transmit using a response scheduling header or trigger frame across a channel width of 20 MHz or more. The trigger frame may include a resource allocation for the UL transmit. The transmission of the trigger frame may depend on the STA's indicated buffer status, which may be obtained from a previous NDP feedback report or buffer status report, which may be included in the MAC header.

[0154] DL A-MPDU or A-PPDU may include an indication in the transmitting STA whether additional HARQ processing is pending, for example, by setting additional data or additional fragment bits within the MAC header of the A-MPDU or A-PPDU, or within the PPDU carrying a HARQ transmission, or within the PPDU carrying an MPDU that is not part of a HARQ transmission.

[0155] A receiving STA of such a DL A-MPDU or A-PPDU may transmit the A-MPDU or A-PPDU to the AP on the uplink, on the RU allocated to it by the trigger frame or response scheduling header within the DL A-MPDU or A-PPDU. The STA may include an ACK / NACK / BA / HARQ response to the AP, in addition to HARQ transmission 1 associated with HARQ process ID 1. The UL A-MPDU or A-PPDU may include an indication at the transmitting STA whether additional HARQ processes are pending, for example, by setting additional data or additional fragment bits within the MAC header of the A-MPDU or A-PPDU, or within the PPDU carrying the HARQ transmission, or within the PPDU carrying an MPDU that is not part of the HARQ transmission.

[0156] After receiving a UL A-MPDU or A-PPDU, the AP may determine the status of the DL HARQ transmission and whether it can decode one or more transmissions associated with one or more UL HARQ process IDs. It may then send an ACK / NACK / BA / response for the UL HARQ transmission. Depending on the status of the UL HARQ transmission, the buffer status, or indications of additional pending HARQ transmissions by the STA in the UL, it may also decide to send a trigger frame to trigger additional UL HARQ transmissions.

[0157] Based on feedback received from the STA, the AP may include additional DL HARQ transmissions to the STA. For example, as shown in Figure 16, since HARQ transmission 1 associated with HARQ ID 1 to STA1 and STA2 was affirmed, the AP may transmit transmission 1 associated with HARQ ID 2 to STA1 and STA2 on RU0 and RU1, respectively. Since the processed HARQ was negatively responded to, the AP may transmit transmission 2 associated with HARQ ID 1 to STA N on RU L.

[0158] After receiving a DL A-MPDU or A-PPDU from the AP, which may include a HARQ transmission and / or trigger and response request frames, the STA may determine the status of its UL HARQ transmission from itself to the AP and whether it can decode one or more transmissions associated with one or more DL HARQ process IDs sent to it by the AP. It may then send an ACK / NACK / BA / response for the DL HARQ transmission as part of the UL A-MPDU or A-PPDU. It may also indicate whether it has additional transmissions or pending HARQs that have been processed to be sent.

[0159] STA may also include additional UL HARQ transmissions to AP based on feedback received from AP in DL A-MPDU or A-PPDU. For example, as shown in Figure 16, STA N may transmit transmission 1 associated with HARQ ID 1 to AP on RU L because STA N's transmission 1 associated with HARQ ID 1 was not acknowledged (or was denied). STA2 and STA1 may transmit transmission 1 associated with HARQ ID 2 to AP on RU0 and RU1, respectively, because the HARQ process was acknowledged.

[0160] Another exemplary design of the cascading UL and DL HARQ procedure is shown in Figure 17.

[0161] In this embodiment, the AP and STA may still transmit A-MPDU or A-PPDU. MPDUs such as ACK / NACK / BA, BAR, trigger frames, other types of management or control frames, or other types of frames that are not part of the HARQ transmission may be grouped together within a single A-MPDU, which may be carried within a single PPDU. In another embodiment, these MPDUs may be grouped into one or more A-MPDUs, which are carried within one or more PPDUs.

[0162] Each HARQ transmission may be carried in a separate PPDU, which may be part of an A-PPDU transmitted by an AP or STA. The PPDU may include, or may be preceded by, a preamble and / or delimiter field, which may include a clear bit pattern such as a delimiter, a training field such as LTF, STF, or other types of fields, to announce the start of a new PPDU or new HARQ transmission. Furthermore, the preamble or delimiter field may also include information about the next HARQ transmission, such as the HARQ process ID, target receiving STA, start time of the HARQ transmission, MCS, RV number of the HARQ transmission, retransmission of the preceding HARQ transmission, length of the next HARQ transmission or PPDU, and length or duration of the next HARQ transmission or PPDU, as well as whether further PPDUs or HARQ transmissions follow the next HARQ transmission or PPDU.

[0163] PPDUs or MPDUs, including non-HARQ transmissions, may be transmitted at the beginning or end of an A-MPDU or A-PPDU, or at any point within either of them. 3.5 HARQ MAC procedure using TWT or RAW STA can utilize scheduling designs for HARQ MAC procedures, such as TWT (Target Wake Time), Broadcast TWT, or RAW (Restricted Access Window), or other types of scheduling designs. Figure 18 illustrates an exemplary design for a HARQ MAC procedure using TWT or RAW.

[0164] TWT or RAW may have a slotted structure. Information about TWT or RAW may be included within beacons, short beacons, FILS discovery frames, or other types of frames.

[0165] STA may determine one or more DL or UL slots based on its own ID, such as its AID or parameters announced by AP, or other types of parameters.

[0166] The AP may indicate that one or more of the slots are for HARQ transmission.

[0167] The STA may determine its UL slot and send a HARQ transmission to the AP, and then determine its DL slot for receiving one or more responses to the UL HARQ transmission.

[0168] The STA may also determine its DL slot for receiving one or more HARQ transmissions, and then determine one or more UL slots for sending responses regarding the DL HARQ transmissions.

[0169] For a group, the DL slot may be used by the AP to send group-based HARQ transmissions on the downlink, and / or multi-STA multi-TID multi-HARQ BAs, or multi-STA multi-HARQ BAs, to provide responses to one or more STAs for one or more HARQ processes associated with one or more TIDs. 3.6 UL HARQ MAC Procedure within TXOP In this section, we consider the UL HARQ procedure within a Transmit Opportunity (TXOP). Within a TXOP, STAs / APs can acquire channels and share them with others. Therefore, transmissions are more schedule-based, and thus receivers can know which STAs are likely to be the desired transmitters and receivers, and that transmission failures may be attributed primarily to bad channels or low SNR. APs and STAs may need to exchange their capabilities to support HARQ transmissions or HARQ transmissions within a TXOP using management / control frames.

[0170] An example procedure is shown in Figure 19.

[0171] An AP may acquire a channel and send a trigger frame / MU transmission request (RTS) to a group of STAs, including STA1 and STA2. A MU RTS frame can be considered a special form of a trigger frame. Therefore, any reference to a trigger frame in this document implies that it may be a MU RTS frame. Alternatively, a trigger frame may be used in a UL single-user transmission. In a trigger frame, the AP may provide one or more of the following pieces of information about the next HARQ transmission from the STA:

[0172] For example, a HARQ trigger field may indicate that the trigger frame can be used to trigger a HARQ transmission. In one embodiment, the field may be interpreted as a TXOP HARQ trigger, indicating that a HARQ procedure may be valid within a TXOP. The AP and STA may flush the HARQ buffer after the TXOP has finished.

[0173] When two or more HARQ processes are permitted, the HARQ process ID field may be used. Specifically, this field may be used to indicate a transmission associated with a set of information bits. A retransmission of the same set of information bits may use the same HARQ process ID. Therefore, the STA may use the HARQ process ID to identify related new transmissions and retransmissions.

[0174] The redundancy version field may be used when increased redundancy is used for the next HARQ transmission. This field may be used to indicate which parts of the codeword may be used in the (re)transmission. In one way, this field may be used to indicate the specific puncturing scheme used to generate the codeword for that (re)transmission.

[0175] A retransmission indication field may be used to indicate whether the next transmission is a new transmission or a retransmission. In one embodiment, the retransmission indication field may function as an implicit negation transmission indicating that the previous transmission may have failed.

[0176] The MCS field may or may not be the same from the initial transmission to the retransmission.

[0177] Some of the fields described above may be common to all users, while others may be exclusive to a single user. Common fields may be sent to all users in general user fields, such as the EHT SIG-A field, while fields exclusive to a single user may be sent in user information fields, such as the EHT SIG-B field.

[0178] Upon receiving a trigger frame, the STA may detect that it is a desirable STA for UL HARQ transmission. It may then transmit a HARQ frame containing a Physical Layer Convergence Procedure (PLCP) header and a MAC body.

[0179] In the PLCP header embodiment, everything is determined by the AP, and since the AP knows the HARQ parameters, HARQ-related information does not need to be carried by the trigger-based PPDU.

[0180] In another embodiment, the HARQ process ID, RV, retransmission indication, and / or MCS may be carried by the TB PPDU within a user-specific SIG field. This method may be used in cases where the HARQ transmission is initiated and controlled by the STA, in which case the trigger frame that triggers the transmission may not contain HARQ-related information.

[0181] The AP can receive and decode an UL TB PPDU. If the AP successfully decodes the packet, it can prepare an acknowledgment and DL transmission to the STA, if necessary. If the AP fails to successfully decode the packet, it can store the received packet in a HARQ buffer. In one embodiment, the AP may send a NAK frame to trigger a retransmission from the STA. In another embodiment, the AP may send a trigger frame to trigger a retransmission, which may be an implicit NAK for the previous transmission. In yet another embodiment, the AP may send both a NAK frame and a trigger frame to the STA.

[0182] STA can perform transmission as indicated by AP.

[0183] Using UL HARQ data transmission as described herein, the AP may maintain a HARQ buffer. The buffer may be flushed after the TXOP has finished. This means that the transmission may be synthesized for HARQ detection only within the TXOP. In another embodiment of DL HARQ transmission, the STA may maintain a HARQ buffer. The buffer may be flushed after the TXOP has finished. In one method, the HARQ buffer may be flushed automatically without signaling. In another embodiment, the AP / STA may explicitly signal the buffer state.

[0184] For example, for UL data transmissions, the AP may include buffer status within the trigger frame. The AP may indicate to the STA that the buffer has been reset / flushed and is ready for a new HARQ transmission. Alternatively, the AP may indicate that the buffer may contain transmissions from one or more previous HARQ procedures that are ready for retransmission and synthesis.

[0185] For example, in the reverse case, i.e., for DL ​​data transmissions, the STA may include the buffer status in the acknowledgment frame. The STA may indicate to the AP that the buffer has been reset / flushed and is ready for a new HARQ transmission. Alternatively, the STA may indicate that the buffer may contain one or more transmissions from previous HARQ procedures that are ready for retransmission and synthesis. 3.7 UL HARQ MAC Procedures Spanning Multiple TXOPs In this section, we consider UL HARQ procedures spanning multiple TXOPs. In one embodiment, a HARQ procedure may occur in one or more TXOPs. A TXOP may include a transmit protected by an RTS / CTS (Request to Transmit / Ready to Transmit). In this case, the transmit is more schedule-based, and therefore the receiver may know which STAs are the desired transmitter and receiver, and that transmit failures may be assumed to be primarily due to a bad channel or low SNR. In one way, a HARQ procedure may occur in one or more TXOPs or in an autonomous uplink transmit. An autonomous uplink transmit may represent a transmit initiated and determined by a non-AP STA.

[0186] APs and STAs can exchange their ability to support HARQ transmissions or HARQ transmissions within TXOPs using management / control frames.

[0187] Since HARQ procedures can be lengthy, a timer may be provided to indicate the buffer validity period. In embodiments, a HARQ timer may be introduced on the transmitter and / or receiver side, and both the transmitter and receiver know that packets transmitted before the timer expires can be decoded using HARQ synthesis. An exemplary procedure is shown in Figure 20.

[0188] An AP may acquire a channel and send a trigger frame / MU RTS to a group of STAs, including STA1 and STA2. The MU RTS frame can be considered a special form of the trigger frame. Alternatively, the trigger frame may also be used in UL single-user transmissions. Within the trigger frame, the AP may provide one or more of the following pieces of information regarding the next HARQ transmission from the STA:

[0189] The HARQ trigger field may be used to indicate that a trigger frame is used to trigger a HARQ transmission. In one embodiment, the field may be interpreted as a TXOP HARQ trigger, indicating that a HARQ procedure may be valid across multiple TXOPs. Therefore, the AP and STA should not flush the HARQ buffer after the completion of one TXOP. The maximum HARQ buffer duration field may be communicated so that the transmitter and receiver know when the timer has expired and the HARQ buffer may be flushed. Once the HARQ timer exceeds the maximum HARQ buffer duration, the receiver may flush the HARQ buffer. Alternatively, the maximum HARQ buffer duration may be predefined / predetermined without needing to be communicated. The HARQ timer start field may be communicated to indicate that the timer may be started. Alternatively, a retransmission indication may be used for this purpose. For example, if a retransmission indication indicates that this is a new transmission, the HARQ timer should be started.

[0190] When two or more HARQ processes are permitted, the HARQ process ID field may be used. Specifically, this field may be used to indicate a transmission associated with a set of information bits. Retransmissions of the same set of information bits may use the same HARQ process ID. Therefore, the STA may use the HARQ process ID to determine which original transmission a retransmission is associated with.

[0191] When increased redundancy is used for the next HARQ transmission, the redundancy version field may be used. This field may be used to indicate which part of the codeword will be used in the (re)transmission. In one embodiment, this field may be used to indicate the specific puncturing scheme used to generate the codeword for that (re)transmission.

[0192] A retransmission indication field may be used to indicate whether the next transmission is a new transmission or a retransmission. In one embodiment, the retransmission indication field may function as an implicit negation transmission indicating that the previous transmission failed.

[0193] The MCS field may indicate the modulation coding scheme of the transmission. The MCS for retransmission of information may be the same as or different from the MCS of the original transmission.

[0194] Some of the fields mentioned above may be common to all users, while others may be exclusive to a single user.

[0195] Upon receiving a trigger frame, the STA may detect that it is a desirable STA for a UL HARQ transmission. In an embodiment, if the STA realizes that the trigger frame is triggering a new transmission (for example, by checking the retransmission indication field or the HARQ timer start indication field), the STA starts the HARQ timer. Otherwise, the STA checks whether the HARQ timer has expired. If the timer has not expired, or if the STA has started a new timer, the STA prepares the HARQ transmission as indicated by the AP. On the other hand, if the timer has expired and the AP has requested a retransmission, the STA prepares a new transmission of the packet and may indicate in the PLCP header that it may be a new transmission and not a retransmission.

[0196] STA may transmit a HARQ frame that includes a PLCP header and a MAC body. Generally, within the PLCP header of a HARQ transmission, STA may include the following information:

[0197] In the first exemplary embodiment, everything is determined by the AP, and since the AP knows the HARQ parameters, HARQ-related information may not be carried within the PLCP header of the PPDU.

[0198] In a second exemplary embodiment, the HARQ process ID, RV, retransmission indication, and / or MCS may be carried by the TB PPDU within a user-specific SIG field. This embodiment may be used when the HARQ transmission is initiated and controlled by the STA, because in that case the trigger frame from the AP that triggers the transmission may not contain HARQ-related information, or the HARQ transmission may not be trigger-based.

[0199] In this embodiment, the AP receives a UL TB PPDU and checks the PLCP header. If it is a new transmission, the AP starts the HARQ timer. If it is a retransmission, the AP checks whether the timer has expired. If the timer has not expired, the AP prepares to combine the received packet with the packets stored in the HARQ buffer. If the timer has expired, the AP does not combine the packet with the packets in the buffer.

[0200] The AP then decodes the received packet (or, if the received packet has been combined with other packets in the buffer, the combined packets). If the AP has successfully decoded the packet, it prepares to send an acknowledgment and DL to the STA, if necessary.

[0201] On the other hand, if the AP fails to decode the packet successfully, the AP stores the received packet in its HARQ buffer, provided the HARQ timer has not expired. In one embodiment, the AP sends a NAK frame to trigger a retransmission from the STA. In an alternative embodiment, the AP sends a trigger frame to trigger a retransmission, which acts as an implicit NAK for the previous transmission. In yet another embodiment, the AP may send both a NAK frame and a trigger frame to the STA. In one embodiment, the AP sends the NAK frame to the STA immediately, but the HARQ retransmission may be performed later. In an alternative embodiment, the AP does not send any acknowledgment to the STA, and the HARQ retransmission is performed later.

[0202] The STA may perform retransmissions, as indicated by the AP, in the same TXOP, later in a different TXOP, or autonomously by the STA.

[0203] When using UL HARQ data transmission as described above, the AP and STA may each maintain a HARQ buffer. The buffer may be flushed after the HARQ timer expires. This means that transmissions can only be synthesized for HARQ detection when the timer is active (not expired). This protocol can also be applied to DL HARQ data transmission. In one embodiment, the HARQ buffer may be flushed automatically without signaling. Alternatively, the AP / STA may explicitly communicate the buffer state. 3.8 UL HARQ MAC Procedure Outside of TXOP: UE Autonomous HARQ Transmission In the case of autonomous UL HARQ performed outside of TXOP, the STA may compete for resources and send one or more HARQ packets to the AP. This may be an OFDM transmission in which the STA acquires resources based on Extended Distributed Channel Access (EDCA), or an OFDMA transmission in which the STA acquires resource units (RUs) based on Uplink OFDMA Random Access (UORA). Since the HARQ transmission is sent autonomously by the STA, the following processes should be performed:

[0204] ○Since the transmission is not initiated by the AP, the packet for the STA should indicate that it is a HARQ transmission so that the receiver understands that buffer resources need to be reserved for the current transmission and any possible retransmissions in case decoding fails.

[0205] ○Since the transmission is not AP-initiated, information regarding the specific parameters of the current transmission should be included in the autonomous HARQ transmission.

[0206] Since the STA is not directed by the AP, information regarding the AP's buffer status may be required by the STA. Such information can be provided through capability exchange with the STA associated with the AP.

[0207] The following information may be carried in autonomous UL HARQ transmissions.

[0208] ○HARQ Process ID: This field may be used when two or more HARQ processes may be allowed. Specifically, the field may be used to indicate a transmission associated with a set of information bits. Retransmissions of the same set of information bits may use the same HARQ Process ID. The STA may autonomously determine the HARQ Process ID to use to identify new transmissions and retransmissions associated with each other.

[0209] ○Redundancy Version: This field may be used when increased redundancy is used for the next HARQ transmission. This field may be used to indicate to the AP which parts of the codeword are used in the (re)transmission. In one way, this field may be used to indicate the specific puncturing scheme used to generate the codeword for that (re)transmission.

[0210] ○Retransmission Indication: This field may be used to indicate whether the current transmission is a new transmission or a retransmission.

[0211] ○MCS: Modulation coding scheme field. The original transmission and its retransmission may have the same or different MCS values.

[0212] The above parameters can be derived by the STA from the ACK / NAK information of previous transmissions.

[0213] STA may transmit a HARQ frame, which includes a PLCP header and a MAC body. In the PLCP header, the HARQ process ID, RV, retransmission indication, and / or MCS may be carried by the TB PPDU within a user-specific SIG field.

[0214] The AP receives either an UL TB PPDU (for UORA) or an UL PPDU (for conventional transmission), and it can decode it.

[0215] It should be noted that since this HARQ transmission is an STA origin, there may be scenarios where the transmission fails due to a collision rather than low SNR. Information regarding the cause of the failure can be useful to the STA when determining the retransmission version (e.g., RV selection for retransmission, retransmission resource selection, CW size selection, etc.). Therefore, the AP feedback may be a NAK, a Collision Indicator (COL), or a Non-Received Indicator (NTX). Without loss of generality, understanding that it may be any one of the signals listed below (in addition to the signal, the appropriate STA response is also listed), for the purposes of the following explanation, it will be described as a NAK.

[0216] [Table 1]

[0217] If the AP successfully decodes the packet, it may prepare to send an acknowledgment and DL to the STA, if necessary.

[0218] If the AP fails to decode a packet successfully, the AP may store the received packet in a HARQ buffer and then send an appropriate message to the STA. For example, in one embodiment, the AP may send a NAK frame to trigger a retransmission from the STA. In this case, the STA behavior remains autonomous. In another embodiment, the AP may send a trigger frame to trigger a retransmission, and the trigger frame may act as an implicit NAK for the previous transmission. In this case, the STA behavior becomes directed by the AP. In yet another embodiment, the AP may send both a NAK frame and a trigger frame to the STA. In this case, the STA behavior becomes directed by the AP.

[0219] STA may perform retransmission as indicated by AP.

[0220] Using UL HARQ data transmission as described above, the AP can maintain a HARQ buffer that needs to be managed. In one embodiment, the HARQ buffer may be automatically flushed without signaling.

[0221] Alternatively, the AP may explicitly communicate the buffer status. For example, for UL data transmissions, the AP may send a buffer status frame to a single STA or multiple STAs. Alternatively, the buffer status may be transmitted in an ACK / NAK / COL frame or as part of a trigger frame. The AP may indicate to the STA that the buffer has been reset / flushed and is ready for a new HARQ transmission. Alternatively, or in addition, the AP may indicate to the STA that the buffer contains transmissions from previous HARQ procedures that can be combined with the current transmission in a synthesized retransmission frame.

[0222] This procedure is illustrated in Figure 21. 3.9 FDD HARQ and NDP Feedback for HARQ-Compatible A-PPDU If frequency division duplexing (FDD) is possible, the AP and STA can transmit and receive simultaneously on different frequency bands. In FDD mode, HARQ feedback can be acquired and retransmitted within the same TXOP or within the same (A-)PPDU. Since the STA receiving in the DL band (DL STA) and the STA transmitting in the UL band (UL STA) may be different, it is desirable that the STA does not need to decode a PPDU in the other direction to acquire HARQ feedback information. According to an exemplary embodiment that provides the above functionality, a bidirectional HARQ TXOP can be initiated by the AP by transmitting a trigger frame (TF) on the DL channel and / or the UL channel (for receiver protection in the UL band and CFO / power / timing correction in the UL band). The AP may perform a CCA check on both channels before transmitting the TF.

[0223] The DL STA set and the UL STA set may be different. The DL STA set may be indicated in the header of the DL PPDU or TF. The DL STA may need to perform synchronization and CFO correction based on the TF so that it can transmit HARQ feedback for DL ​​reception.

[0224] In HARQ-enabled (A-)PPDUs in either UL or DL, the LTF may be transmitted periodically as a mid-amble.

[0225] A mid-SIG field may be inserted in the middle of the (A-)PPDU to convey the information necessary for the receiver to decode / synthesize the data.

[0226] Within the same MU / TB-(A-)PPDU, the temporal locations of Mid-Amble / LTF and Mid-SIG may differ for different users due to user-specific codeword sizes.

[0227] The data field can be punctured as NDP feedback (i.e., by inserting the LTF portion of the NDP feedback PPDU).

[0228] If punctured, the AP cannot use the full set of tone set indices defined for the channel. Unused tone sets can be used for data and pilot transmissions.

[0229] If punctured, NDP feedback is not precoded as neighbor data tones.

[0230] If a data field is not punctured as HARQ feedback, a separate resource other than the data field may be allocated for HARQ feedback.

[0231] The TF / (A-)PPDU header / mid-SIG may specify the tone set index for the DL / UL HARQ ACK (sent in UL / DL) and the timing (e.g., offset, periodicity) for sending / receiving the HARQ ACK / NAK.

[0232] Different STAs may be assigned different NDP feedback tone set indices for the same symbol, or they may be assigned the same tone set in different symbols.

[0233] Alternatively, the HARQ feedback timing and tone set index can be implicitly derived from the ID of the assigned RU.

[0234] Packet extension fields (PEs) can also be punctured for NDP feedback symbols.

[0235] An example of a punctured LTF for A-PPDU is shown in Figure 22.

[0236] In NDP feedback, NAK implicitly allows the same UL resources (as indicated in TF) for HARQ retransmission. In NDP feedback, ACK implicitly allows the same UL resources for new data transmission.

[0237] Each NDP feedback tone set is uniformly spread across most of the 20MHz channel, and reception does not require channel estimation. Therefore, STAs (who may or may not be able to communicate directly with the AP) may use NDP feedback to estimate the most appropriate RU (for example, by comparing power on on-tones or noise on off-tones), and non-AP STAs may report this information to the AP. For HARQ feedback, "no response" cannot be used.

[0238] The tone set index assigned for HARQ feedback can vary at different symbols / times so that the transmitted HARQ feedback over time covers (almost) the entire channel by the end of transmission. This can be used as an auxiliary sounding sequence with a granularity that requires up to 3 tones of interpolation in the worst case.

[0239] STA observing HARQ feedback as a sounding sequence: 10 when SNR > -24dB -6 It requires "on" tone detection, which has a lower false positive rate. 4 Conclusion Those skilled in the art will understand that, although features and elements are described above in specific combinations, each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented in computer programs, software, or firmware contained within a computer-readable medium for execution by a computer or processor. Examples of non-temporary computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as internal hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital multipurpose disks (DVDs). A processor associated with software may be used to implement a radio frequency transceiver for use in a WTRU102, UE, terminal, base station, RNC, or any host computer.

[0240] Furthermore, in the embodiments described above, other devices including processing platforms, computing systems, controllers, and processors have been mentioned. These devices may include at least one central processing unit ("CPU") and memory. In accordance with the practice of those skilled in the art in the field of computer programming, references to symbolic representations of acts and operations or instructions may be performed by various CPUs and memories. Such acts and operations or instructions may be said to be "executed," "executed by the computer," or "executed by the CPU."

[0241] Those skilled in the art will understand that actions, and symbolically represented operations or instructions, involve the manipulation of electrical signals by the CPU. The electrical system represents data bits, which can cause the resulting transformation or reduction of electrical signals and the preservation of data bits in memory locations within the memory system, thereby reconfiguring or otherwise altering the CPU's operation and other processing of signals. The memory locations where data bits are preserved are physical locations having specific electrical, magnetic, optical, or organic properties corresponding to or representing the data bits. Representative embodiments are not limited to the platforms or CPUs mentioned above, and it should be understood that other platforms and CPUs may support the methods provided.

[0242] Data bits may also be maintained on computer-readable media, including magnetic disks, optical disks, and any other volatile (e.g., Random Access Memory ("RAM")) or non-volatile (e.g., Read-Only Memory ("ROM")) mass storage systems, which are readable by the CPU. Computer-readable media may include cooperative or interconnected computer-readable media, which may reside exclusively on a processing system or be local or remote to a processing system, and may be distributed among multiple interconnected processing systems. Typical embodiments are not limited to the memories mentioned above, and it is understood that other platforms and memories may support the methods described.

[0243] In descriptive embodiments, any of the operations, processes, etc., described herein may be implemented as computer-readable instructions stored on a computer-readable medium. These computer-readable instructions may be executed by a processor in a mobile unit, a network element, and / or any other computing device.

[0244] There is little remaining distinction between hardware and software implementations of a system configuration. The choice between using hardware or software is generally (but not always) a design choice representing a cost-effectiveness trade-off, as, for example, in certain situations the choice between hardware and software can be important. Various means (e.g., hardware, software, and / or firmware) may exist that can influence the processes and / or systems, and / or other technologies described herein, and the preferred means may change depending on the context in which the processes and / or systems, and / or other technologies are deployed. For example, if the implementer determines that speed and accuracy are paramount, they may primarily choose hardware and / or firmware means. If flexibility is paramount, they may primarily choose software implementation. Alternatively, they may choose any combination of hardware, software, and / or firmware.

[0245] The detailed descriptions above illustrate various embodiments of devices and / or processes through the use of block diagrams, flowcharts, and / or examples. To the extent that such block diagrams, flowcharts, and / or examples include one or more functions and / or operations, it will be understood by those skilled in the art that each function and / or operation within such block diagrams, flowcharts, or examples can be implemented individually and / or collectively by a wide range of hardware, software, firmware, or substantially any combination thereof. Suitable processors include, by example, general-purpose processors, dedicated processors, conventional processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microcontrollers, application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), field-programmable gate array (FPGA) circuits, any other type of integrated circuit (IC), and / or state machines.

[0246] While features and elements are provided above in specific combinations, those skilled in the art will understand that each feature or element can be used alone or in any combination with other features and elements. This disclosure should not be limited to the specific embodiments described herein, intended as illustrative examples of various aspects. As will be apparent to those skilled in the art, many modifications and variations can be made without departing from its spirit and scope. Elements, actions, or commands used in the description of this application should not be construed as important or essential to the invention unless expressly provided as such. In addition to those enumerated herein, functionally equivalent methods and apparatus within the scope of this disclosure will be apparent to those skilled in the art from the foregoing description. Such modifications and variations are intended to be covered within the appended claims. This disclosure should be limited only by the claims of the appended claims, together with the entire scope of equivalents to which such claims are eligible to include it. It should be understood that this disclosure is not limited to any particular method or system.

[0247] It should be understood that the terms used herein are intended solely to describe specific embodiments and are not intended to be limiting. Where used herein, the terms “station” and its abbreviation “STA,” “user equipment” and its abbreviation “UE” may mean (i) a wireless transmit and / or receive unit (WTRU) as described below, (ii) any of the various embodiments of a WTRU as described below, (iii) a wireless-enabled and / or wired-enabled (e.g., connectable) device configured to use some or all of the structures and functionalities of a WTRU, in particular, as described below, (iii) a wireless-enabled and / or wired-enabled device configured to use fewer structures and functionalities than all of a WTRU, as described below, or (iv) something similar. Details of exemplary WTRUs that may represent any UE listed herein are provided below with respect to Figures 1A to 1D.

[0248] In some representative embodiments, some parts of the present invention described herein may be implemented via application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), and / or other integrated configurations. However, those skilled in the art will recognize that some aspects of the embodiments disclosed herein may be equivalently implemented, in whole or in part, as integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g., as one or more programs running on one or more microprocessors), as firmware, or substantially any combination thereof, and that designing circuits and / or writing code for software and / or firmware is well within the scope of the skills of those skilled in the art in light of this disclosure. In addition, those skilled in the art will understand that the mechanisms of the present invention described herein can be distributed in various forms as program products, and that the descriptive embodiments of the present invention described herein are applicable regardless of the specific type of signal-retaining medium used to carry out the distribution. Examples of signal-retaining mediums include, but are not limited to, recording-type media such as floppy disks, hard disk drives, CDs, DVDs, digital tapes, and computer memory, as well as transmission-type media such as digital and / or analog communication media (e.g., fiber optic cables, waveguides, wired communication links, wireless communication links, etc.).

[0249] The invention as described herein sometimes illustrates different components that are contained within or connected to other different components. Such described architectures are merely examples, and it should be understood that in practice, many other architectures can be implemented to achieve the same functionality. Conceptually, any arrangement of components to achieve the same functionality is effectively “associated” in such a way that the desired functionality can be achieved. Therefore, any two components in this specification that are combined to achieve a particular functionality can be seen as “associated” with each other, regardless of the architecture or intervening components, in such a way that the desired functionality can be achieved. Similarly, any two components thus associated can also be seen as “operably connected” or “operably coupled” with each other to achieve the desired functionality, and any two components that can be associated in such a way can also be seen as “operably coupled” with each other to achieve the desired functionality. Specific examples of components that can be operationally coupled include, but are not limited to, components that can be physically paired and / or interact physically, as well as components that are wirelessly interactable and / or interact wirelessly, and / or interact logically and / or interact logically.

[0250] In substantially any use of plural and / or singular terms herein, a person skilled in the art can convert from plural to singular and / or singular to plural as appropriate to the context and / or use. For clarity, various singular / plural substitutions may be explicitly described herein.

[0251] In general, it will be understood by those skilled in the art that the terms used herein, and in particular in the appended claims (e.g., the text of the appended claims), are generally intended as “open” terms (for example, the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” and the term “includes” should be interpreted as “including but not limited to,” etc.). If a specific number of claims to be introduced is intended, such intention will be explicitly stated in the claim; if no such statement is made, such intention does not exist, it will be understood by those skilled in the art. For example, if only one item is intended, the term “single” or similar wording may be used. For the sake of understanding, the following appended claims and / or descriptions herein may include the use of the introductory phrases “at least one” and “one or more” to introduce claims. However, the use of such phrases should not be interpreted as implying that the introduction of a claim enumeration by the indefinite article "a" or "an" limits any particular claim containing such introduced claim enumeration to embodiments containing only one such enumeration (for example, "a" and / or "an" should be interpreted as meaning "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim enumerations. In addition, even if the specific number of claim enumerations introduced is explicitly stated, a person skilled in the art will recognize that such statement should be interpreted as meaning at least the stated number (for example, the unmodified enumeration of "two enumerations" without other modifiers means at least two enumerations or two or more enumerations).

[0252] Furthermore, when conventions similar to “at least one of A, B, and C, etc.” are used, generally, such syntax is generally intended in a sense that those skilled in the art will understand the convention (for example, “a system having at least one of A, B, and C” includes, but is not limited to, a system having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together). When conventions similar to “at least one of A, B, or C, etc.” are used, generally, such syntax is generally intended in a sense that those skilled in the art will understand the convention (for example, “a system having at least one of A, B, or C” includes, but is not limited to, a system having only A, only B, only C, A and B together, A and C together, B and C together, and / or A, B, and C together). It will be further understood by those skilled in the art that substantially any disjunctive words and / or phrases presenting two or more alternatives, whether within the description, within the claims, or within the drawings, are intended to contemplate the possibility of including one of the terms, either of the terms, or both of the terms. For example, the phrase “A or B” is understood to include the possibilities of “A”, or “B”, or “A and B”. Further, as used herein, the term “any of” following a list of multiple items and / or multiple categories of items is intended to include “any of” the items and / or categories of items, “any combination”, “any plurality of”, and / or “any combination of a plurality of” the items and / or categories of items, either individually or in combination with other items and / or other categories of items. Further, as used herein, the term “set” or “group” is intended to include any number of items, including zero. Additionally, as used herein, the term “number” is intended to include any number, including zero.

[0253] In addition, when a feature or aspect of the present disclosure is described with respect to a Markush group, one of ordinary skill in the art will recognize that the present disclosure is thereby also described with respect to any individual member or subgroup of members of the Markush group.

[0254] As will be understood by one of ordinary skill in the art, for any and all purposes, such as in providing written descriptions, all ranges disclosed herein include any and all possible subranges, and combinations thereof. Each of the disclosed ranges can readily be recognized as also fully describing and enabling the same range broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range disclosed herein can readily be broken down into a lower third, a middle third, and an upper third, etc. Also as will be understood by one of ordinary skill in the art, all words such as "up to," "at least," "greater than," and "less than," include the recited number and refer to ranges that can later be divided into subranges as described above. Finally, as will be understood by one of ordinary skill in the art, ranges include each individual member. Thus, for example, a group having 1-3 cells refers to a group having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to a group having 1, 2, 3, 4, or 5 cells, and so on for the others.

[0255] Furthermore, the claims should not be read as being limited to the order or elements provided unless stated to that effect in the claims. In addition, the use of the term "means for" in any claim is intended to invoke 35 U.S.C. § 112, paragraph 6, or a means-plus-function claim format, and any claim that does not use the term "means for" is not intended to be such.

[0256] A software-associated processor may be used to implement a radio frequency transceiver for use in a Wireless Transmitter / Receiver Unit (WTRU), User Equipment (UE), Terminal, Base Station, Mobility Management Entity (MME) or Evolutionary Packet Core (EPC), or any host computer. The WTRU may be used in conjunction with other components such as hardware and / or software-implemented modules, including software-defined radio (SDR), as well as other components such as cameras, video camera modules, videophones, speakerphones, vibration devices, speakers, microphones, television transceivers, hands-free headsets, keyboards, Bluetooth® modules, frequency modulation (FM) radio units, near-field communication (NFC) modules, liquid crystal display (LCD) units, organic light-emitting diode (OLED) display units, digital music players, media players, video game player modules, internet browsers, and / or wireless local area network (WLAN) or ultra-wideband (UWB) modules.

[0257] Although the present invention has been described in relation to a communication system, it is intended that the system may be implemented in software on a microprocessor / general-purpose computer (not shown). In some embodiments, one or more functions of various components may be implemented in software that controls the general-purpose computer.

[0258] In addition, although the present invention has been illustrated and described herein with reference to specific embodiments, the present invention is not intended to be limited to the details shown. Rather, various modifications can be made in detail within the scope and range of the equivalents of the claims and without departing from the present invention.

[0259] Those skilled in the art will understand through this disclosure that one representative embodiment may be used selectively with or in combination with other representative embodiments.

[0260] While features and elements are described above in specific combinations, those skilled in the art will understand that each feature or element can be used alone or in any combination with other features and elements. In addition, the methods described herein may be implemented in computer programs, software, or firmware contained in computer-readable media for execution by a computer or processor. Examples of non-temporary computer-readable storage media include, but are not limited to, read-only memory (ROM), random access memory (RAM), registers, cache memory, semiconductor memory devices, magnetic media such as built-in hard disks and removable disks, magneto-optical media, and optical media such as CD-ROM disks and digital multi-purpose disks (DVDs). A processor associated with software may be used to implement a radio frequency transceiver for use in a WTRU, UE, terminal, base station, RNC, or any host computer.

[0261] Furthermore, in the embodiments described above, other devices including processing platforms, computing systems, controllers, and processors have been mentioned. These devices may include at least one central processing unit ("CPU") and memory. In accordance with the practice of those skilled in the art in the field of computer programming, references to acts and symbolic representations of actions or instructions may be performed by various CPUs and memories. Such acts and actions or instructions may be said to be “executed,” “executed in the computer,” or “executed in the CPU.”

[0262] Those skilled in the art will understand that actions, and symbolically represented actions or instructions, involve the manipulation of electrical signals by the CPU. Electrical systems represent data bits, which can cause the resulting transformation or reduction of electrical signals and the preservation of data bits in memory locations within the memory system, thereby reconfiguring or otherwise altering the CPU's operation and other processing of signals. Memory locations where data bits are preserved are physical locations having specific electrical, magnetic, optical, or organic properties corresponding to or representing the data bits.

[0263] Data bits may also be maintained on computer-readable media, including magnetic disks, optical disks, and any other volatile (e.g., Random Access Memory ("RAM")) or non-volatile (e.g., Read-Only Memory ("ROM")) mass storage systems, which are readable by the CPU. Computer-readable media may include cooperative or interconnected computer-readable media, which may reside exclusively on a processing system or be local or remote to a processing system, and may be distributed among multiple interconnected processing systems. Typical embodiments are not limited to the memories mentioned above, and it is understood that other platforms and memories may support the methods described.

[0264] Suitable processors include, for example, general-purpose processors, dedicated processors, conventional processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microcontrollers, application-specific integrated circuits (ASICs), application-specific standard products (ASSPs), field-programmable gate array (FPGA) circuits, any other type of integrated circuit (IC), and / or state machines.

[0265] Although the present invention has been described in relation to a communication system, it is intended that the system may be implemented in software on a microprocessor / general-purpose computer (not shown). In some embodiments, one or more functions of various components may be implemented in software that controls the general-purpose computer.

[0266] In addition, although the present invention has been illustrated and described herein with reference to specific embodiments, the present invention is not intended to be limited to the details shown. Rather, various modifications can be made in detail within the scope and range of the equivalents of the claims and without departing from the present invention. [Explanation of Symbols]

[0267] 100 Communication Systems 102a Receiver Unit (WTRU) 102b Receiver Unit (WTRU) 102c Receiver Unit (WTRU) 102d Receiver Unit (WTRU) 108 Public Switched Telephone Network (PSTN) 110 Internet 112 Network 114a base station 114b base station 116 Air Interface 162 Mobility Management Entity (MME) 164 Serving Gateway (SGW) 166 Gateway (or PGW) 182a Mobility Management Function (AMF) 182b Mobility Management Function (AMF) 183a Session Management Function (SMF) 183b Session Management Function (SMF) 184a User Plane Function (UPF) 184b User Plane Function (UPF) 185a Local Data Network (DN) 185a Data Network (DN) 185b Local Data Network (DN) 185b Data Network (DN)

Claims

1. A method for hybrid automatic retransmission request (HARQ) communication of a station (STA), The step of receiving a first MU transmission in the STA, the MU transmission comprising a first HARQ transmission, a preamble containing information indicating that a first multi-user (MU) transmission includes the first HARQ transmission, and a first set of HARQ process identifiers (IDs) associated with the first HARQ transmission, wherein the first set of HARQ process IDs comprises a first subset of HARQ process IDs for the STA, The steps include determining the portion of the first HARQ transmission associated with the STA, The steps include: transmitting a response message after receiving the first MU transmission, which indicates at least the reception status of the portion of the first HARQ transmission by the STA; The STA receives a second MU transmission which includes a second HARQ transmission and a second set of HARQ process IDs associated with the second HARQ transmission. Equipped with, The second HARQ transmission differs from the first HARQ transmission, The second set of HARQ process IDs includes a second subset of HARQ process IDs for the STA, The second subset of HARQ process IDs is based at least on the reception state of the portion of the first HARQ transmission. method.

2. The method according to claim 1, wherein the response message includes information indicating any of ACK, NACK, no signal detected, interference, collision, or restart HARQ process request.

3. The method according to claim 1, wherein the response message includes information relating to the first subset of HARQ process IDs.

4. The method according to claim 1, wherein the first MU transmission includes a delimiter pattern indicating the start of the first HARQ transmission.

5. The method according to claim 1, wherein the preamble is a preamble for a Physical Layer Convergence Procedure (PLCP) protocol data unit (PPDU).

6. The method according to claim 5, wherein the PPDU includes one or more bits for non-HARQ transmission, and the one or more bits for non-HARQ transmission are grouped at the beginning of the PPDU.

7. The method according to claim 5, wherein the first MU transmission includes a trigger frame in the PPDU.

8. The method according to claim 7, wherein the trigger frame includes an indication that it is a trigger frame for a HARQ process.

9. The method according to claim 1, wherein the first and second HARQ transmissions use different redundancy versions.

10. The method according to claim 1, wherein the first MU transmission includes an initiating HARQ process ID and a bitmap showing the first set of HARQ process IDs that are being requested while HARQ feedback is initiated by the initiating HARQ process ID.

11. A station (STA) for wireless communications, Receiving a first MU transmission comprising a first Hybrid Automatic Retransmission Request (HARQ) transmission, a preamble containing information indicating that a first Multi-User (MU) transmission includes the first HARQ transmission, and a first set of HARQ process identifiers (IDs) associated with the first HARQ transmission, wherein the first set of HARQ process IDs includes a first subset of HARQ process IDs for the STA, To determine the portion of the first HARQ transmission associated with the STA, After receiving the first MU transmission, the STA sends a response message indicating at least the reception status of the portion of the first HARQ transmission, Receiving a second MU transmission which includes a second HARQ transmission and a second set of HARQ process IDs associated with the second HARQ transmission, Equipped with a processor and transceiver configured to perform, The second HARQ transmission differs from the first HARQ transmission, The second set of HARQ process IDs includes a second subset of HARQ process IDs for the STA, The second subset of HARQ process IDs is based at least on the reception state of the portion of the first HARQ transmission. STA.

12. The STA according to claim 11, wherein the response message includes information indicating any of ACK, NACK, no signal detected, interference, collision, or restart HARQ process request.

13. The STA according to claim 11, wherein the response message includes information relating to the first subset of HARQ process IDs.

14. The STA according to claim 11, wherein the first MU transmission includes a delimiter pattern indicating the start of the first HARQ transmission.

15. The STA according to claim 11, wherein the preamble is a preamble for a Physical Layer Convergence Procedure (PLCP) protocol data unit (PPDU).

16. The STA according to claim 15, wherein the PPDU includes one or more bits for non-HARQ transmission, and the one or more bits for non-HARQ transmission are grouped at the beginning of the PPDU.

17. The STA according to claim 15, wherein the first MU transmission includes a trigger frame in the PPDU.

18. The STA according to claim 17, wherein the trigger frame includes an indication that it is a trigger frame for a HARQ process.

19. The STA according to claim 17, wherein the trigger frame includes a HARQ process ID.

20. The STA according to claim 11, wherein the first MU transmission includes an initiating HARQ process ID and a bitmap showing the first set of HARQ process IDs that are being requested while HARQ feedback is initiated by the initiating HARQ process ID.

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