RU2696297C1 - Method of transmitting data in wireless communication system and device for - Google Patents

Abstract

FIELD: electrical communication engineering.

SUBSTANCE: invention relates to wireless communication systems and to methods of transmitting data to support data transmission by a plurality of users. Technical result is achieved due to that the method envisages execution of multi-user (MU) uplink (UL) transmission in a wireless communication system, comprising carrying out carrier monitoring on a channel; receiving a start-up frame containing information for UL MU transmission and a carrier control indicator indicating whether the carrier control result is to be displayed from the access point (AP); and transmitting the UL MU frame through the channel based on the UL MU transmission information. UL MU frame is transmitted via channel based on carrier control result, if carrier control indicator indicates display of carrier control result. UL MU-frame is transmitted through a channel regardless of the carrier control result if the carrier control indicator does not indicate the display of the carrier control result.

EFFECT: technical result of invention consists in expansion of arsenal of wireless communication systems.

15 cl, 25 dwg

Description

FIELD OF TECHNOLOGY

The present invention relates to a wireless communication system and, more particularly, to a data transmission method for supporting data transmission by a plurality of users and a device for supporting this.

BACKGROUND OF THE INVENTION

Wi-Fi is a wireless local area network (WLAN) technology that allows your device to access the Internet in the 2.4 GHz, 5 GHz, or 60 GHz frequency band.

WLAN is based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. The IEEE 802.11 Standing Committee for the Next Generation of Wireless Systems (WNG SC) is the special committee for creating the next generation of wireless local area networks (WLANs) in the medium to long term.

IEEE 802.11n aims to increase network speed and reliability and expand wireless coverage. More specifically, IEEE 802.11n supports high bandwidth (HT), providing a maximum data transfer rate of 600 Mbps. In addition, to minimize transmission error and optimize data transfer rate, IEEE 802.11n is based on multiple input and multiple output (MIMO) technology, in which multiple antennas are used at both ends of the transmission unit and the reception unit.

As WLAN spreads and WLAN applications diversify in the next generation WLAN supporting very high throughput (VHT), IEEE 802.11ac is adopted as the next version of the IEEE 802.11n WLAN. IEEE 802.11ac supports a data transfer rate of 1 Gbit / s or more in transmission with a bandwidth of 80 MHz and / or transmission with a larger bandwidth (for example, 160 MHz) and mainly operates in the 5 GHz band.

Recently, the need for a new WLAN system has come to the fore to support higher bandwidth than the data rate supported by IEEE 802.11ac.

The IEEE 802.11ax scope, mainly discussed in the next generation WLAN task group called IEEE 802.11ax or High Performance (HEW) WLAN, includes: 1) an improvement in the 802.11 physical (PHY) layer and the medium access control (MAC) layer in the ranges 2.4 GHz, 5 GHz, etc., 2) improved spectral efficiency and zonal bandwidth, 3) improved performance in real-world indoor and outdoor environments, such as environments in which an interference source is present, a dense heterogeneous network environment and the environment in which tstvuet high user load, etc.

The scenario, mainly addressed in IEEE 802.11ax, is a dense environment in which there are many access points (APs) and many stations (STAs). In IEEE 802.11ax, improvements in spectral efficiency and zonal bandwidth are discussed in this situation. More specifically, there is interest in improving important performance in outdoor environments that have not attracted much attention in existing WLANs, in addition to indoor environments.

In IEEE 802.11ax, there is a lot of interest in scenarios such as wireless offices, smart homes, stadiums, event venues and buildings / apartments. Improving system performance in a dense environment in which there are many APs and many STAs is discussed based on appropriate scenarios.

In the future, IEEE 802.11ax is expected to actively discuss improving system performance, improving the set of overlapping basic services (OBSS), improving the outdoor environment, cellular unloading, etc., instead of improving the performance of single communication lines in a single set basic services (BSS). The focus of this IEEE 802.11ax standard means that the next-generation WLAN will have technical capabilities that are gradually approaching those of mobile communications. Recently, when considering a situation in which mobile communications and WLAN technology are discussed together in small cells and bidirectional (D2D) coverage, it is expected that the next generation IEEE 802.11ax-based WLAN technological and commercial convergence and mobile communications will be further activated.

SUMMARY OF THE INVENTION

TECHNICAL PROBLEM

Embodiments of the present invention are directed to providing a method for transmitting and receiving multi-user uplink / downlink data (UL / DL MU data) in a wireless communication system.

An embodiment of the present invention relates to a method for transmitting an UL MU frame in a next generation WLAN system, and more particularly, to a method for transmitting an UL MU frame via a trigger frame. In an embodiment of the present invention, the trigger frame may indicate whether or not the carrier monitoring result will be displayed for the channel on which the UL MU frame will be transmitted.

The technical problems to be solved by the present invention are not limited to the above problems, and the specialist in the field of technology to which the present invention belongs can easily understand the other tasks from the following description

TECHNICAL SOLUTION

In an embodiment of the present invention, a method for performing an uplink (UL) multi-user (MU) transmission by a station apparatus (STA) in a wireless communication system includes performing channel monitoring on a channel, receiving a trigger frame including information for UL MUs transmissions and a carrier control indicator indicating whether a carrier control result should be displayed from an access point (AP) and transmitting an UL MU frame over a channel based on information for UL MU transmission. The UL MU frame is transmitted through the channel based on the carrier control result if the carrier control indicator indicates the display of the carrier control result. The UL MU frame is transmitted through the channel regardless of the carrier control result if the carrier control indicator does not indicate the display of the carrier control result.

In addition, if the carrier control indicator indicates the display of the carrier control result, the UL MU frame may be transmitted through the channel if the channel corresponds to an idle state as a result of carrier monitoring for the channel, and the UL MU frame may not be transmitted through the channel if the channel corresponds to the busy state as a result of carrier monitoring for the channel.

In addition, the channel idle state may indicate that the channel status estimate (CCA) and the network allocation vector (NAV) correspond to the idle state as a result of carrier monitoring. The channel busy state may indicate that at least one of the result of the carrier monitoring, CCA and NAV corresponds to the busy state.

In addition, if the carrier control indicator does not indicate the display of the carrier control result, the UL MU frame may be transmitted after a predetermined time from the receipt of the trigger frame.

In addition, a predetermined time may include a short interframe interval (SIFS).

In addition, the carrier control indicator may be included in the general information field or the user-specific information field of the trigger frame.

In addition, performing carrier monitoring on the channel may include performing carrier monitoring on the channel during the PCF Frame Interval (PIFS) before the start frame is received.

In addition, a station apparatus (STA) performing multi-user (MU) uplink (UL) transmission in a wireless communication system according to an embodiment of the present invention includes a radio frequency (RF) unit configured to transmit / receive radio signals, and a processor configured to control the RF unit. The processor is configured to perform carrier monitoring on the channel, receive a start frame including information for UL MU transmission and a carrier control indicator indicating whether the carrier control result should be displayed from an access point (AP), and transmit the UL MU frame through information-based channel for UL MU transmission. The UL MU frame is transmitted through the channel based on the carrier control result if the carrier control indicator indicates the display of the carrier control result. The UL MU frame is transmitted through the channel regardless of the carrier control result if the carrier control indicator does not indicate the display of the carrier control result.

In addition, if the carrier control indicator indicates the display of the carrier control result, the processor may be configured to transmit the UL MU frame through the channel if the channel corresponds to an idle state as the carrier control result for the channel and not transmit the UL MU frame through the channel if the channel corresponds to a busy state as a result of carrier monitoring for the channel.

In addition, the channel idle state may indicate that the channel status estimate (CCA) and the network allocation vector (NAV) correspond to the idle state as a result of carrier monitoring. The channel busy state may indicate that at least one of the result of the carrier monitoring, CCA and NAV corresponds to the busy state.

Furthermore, if the carrier control indicator does not indicate the display of the carrier control result, the processor may be configured to transmit the UL MU frame after a predetermined time from the receipt of the start frame.

In addition, a predetermined time may include a short interframe interval (SIFS).

In addition, a carrier control indicator is included in the general information field or user-specific information of the launch frame information.

In addition, the processor may be configured to perform channel monitoring on the channel during the PCF Frame Interval (PIFS) before the start frame is received.

PREFERRED RESULTS

According to an embodiment of the present invention, the advantage is that the STA load can be reduced since the result of the carrier monitoring does not need to be displayed in order to send an UL MU frame.

In addition, in accordance with an embodiment of the present invention, the advantage is that the UL MU frame can be transmitted more efficiently in accordance with the characteristic of the received trigger frame, since whether or not to display the result of the frame check is determined based on the format launch frame.

In addition, according to an embodiment of the present invention, the advantage is that the UL MU frame can be transmitted more efficiently in accordance with the UL MU PPDU characteristic, since whether or not to display the result of the frame inspection is determined based on the length UL MU PPDU to be transmitted via STA.

In addition, other advantages of the present invention are further described in the following embodiments.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an example of an IEEE 802.11 system in which an embodiment of the present invention can be applied.

FIG. 2 is a diagram illustrating a configuration of an IEEE 802.11 layer architecture of a system in which an embodiment of the present invention can be applied.

FIG. 3 illustrates a PPDU of a non-HT format and a PPDU of an HT format in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 4 illustrates a PPDU of a VHT format in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 5 illustrates a MAC frame format for an IEEE 802.11 system in which an embodiment of the present invention can be applied.

FIG. 6 illustrates the VHT format of an HT control field in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 7 is a diagram illustrating a random return rollback period and a frame transmission procedure in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 8 is a diagram illustrating an IFS relationship in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 9 is a diagram illustrating a DL format of multi-user (MU) PPDUs in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 10 is a diagram illustrating a DL format of multi-user (MU) PPDUs in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 11 is a diagram illustrating a high efficiency (HE) format PPDU in accordance with an embodiment of the present invention.

FIG. 12 is a diagram illustrating an HE PPDU format in accordance with an embodiment of the present invention.

FIG. 13 is a diagram illustrating an HE PPDU format in accordance with an embodiment of the present invention.

FIG. 14 is a diagram illustrating an HE PPDU format in accordance with an embodiment of the present invention.

FIG. 15 is a diagram illustrating an UL multi-user (MU) transmission procedure in accordance with an embodiment of the present invention.

FIG. 16 is a diagram illustrating embodiments of a UL / DL MU transmission operation between an AP and an STA.

FIG. 17 is a diagram illustrating embodiments of a UL / DL MU transmission operation between an AP and an STA.

FIG. 18 is a diagram illustrating an MU transmission procedure in accordance with an embodiment of the present invention.

FIG. 19 is a diagram illustrating a trigger frame format in accordance with an embodiment of the present invention.

FIG. 20 is a diagram illustrating a DL / UL method of MU transmission in accordance with a fourth embodiment of the present invention.

FIG. 21 is a diagram illustrating a UL method of MU transmission in accordance with an eleventh embodiment of the present invention.

FIG. 22 is a diagram illustrating an UL MU transmission method for performing without carrier control redundancy.

FIG. 23 is a diagram illustrating a method for performing CCA in accordance with an embodiment of the present invention.

FIG. 24 is a flowchart illustrating a method for transmitting STA data in accordance with an embodiment of the present invention.

FIG. 25 is a block diagram of each STA device in accordance with an embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

The terms used in the present invention are the usual terms currently widely used, taking into account the functions in the present invention, but the terms may vary depending on the intentions of specialists, practice of use or the emergence of new technology. In addition, in a particular case, some terms are arbitrarily selected by the applicant. In this case, the detailed meaning of the corresponding term will be described in the corresponding part of the description of the present invention. Accordingly, the terms used in the present invention should not be interpreted simply on the basis of their names, but should be interpreted on the basis of their substantive meanings and content in this specification.

In addition, although embodiments of the present invention are described in detail with reference to the accompanying drawings and the content described in the drawings, the present invention is not limited to these embodiments.

Below, embodiments of the present invention are described in more detail with reference to the attached drawings.

The following technologies can be used in a variety of wireless communication systems, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single-carrier frequency division multiple access (SC-FDMA) and non-orthogonal multiple access (NOMA). CDMA can be implemented using radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented using radio technology such as Global System for Mobile Communications (GSM) / General Purpose Packet Radio Communication (GPRS) / Enhanced GSM Data Rate (EDGE). OFDMA can be implemented using radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or advanced UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of an advanced UMTS (E-UMTS) using advanced UMTS terrestrial radio access (E-UTRA) and it receives OFDMA in downlink and accepts SC-FDMA in uplink communication. Advanced LTE (LTE-A) is an evolution of 3GPP LTE.

Embodiments of the present invention may be supported by standards documents disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, i.e., radio access systems. That is, steps or parts that relate to embodiments of the present invention and which are not described in order to clearly identify the technical nature of the present invention can be supported by these documents. In addition, all terms disclosed herein may be described in these standards documents.

For clarity of description, 3GPP LTE / LTE-A is mainly described, but the technical characteristics of the present invention are not limited thereto.

GENERAL SYSTEM

FIG. 1 is a diagram showing an example of an IEEE 802.11 system in which an embodiment of the present invention can be applied.

An IEEE 802.11 configuration may include many elements. A wireless communication system supporting transparent station mobility (STA) for the upper layer through inter-element communication can be provided. A set of basic services (BSS) may correspond to a basic configuration unit in an IEEE 802.11 system.

FIG. 1 illustrates that there are three BSSs, from BSS 1 to BSS 3, and two STAs (e.g., STA 1 and STA 2 are included in BSS 1, STA 3 and STA 4 are included in BSS 2, and STA 5 and STA 6 are included in BSS 3) are included as members of each BSS.

In FIG. 1, an ellipse indicating a BSS may be interpreted as indicating an area of coverage in which STAs included in the corresponding BSS are in communication. Such an area may be referred to as a basic service area (BSA). When an STA moves outside the BSA, it is not capable of directly communicating with other STAs within the corresponding BSA.

In an IEEE 802.11 system, the most basic type of BSS is Independent BSS (IBSS). For example, an IBSS may have a minimal shape including only two STAs. In addition, BSS 3 in FIG. 1, which is the simplest form and in which other elements are omitted, may correspond to a representative example of IBSS. Such a configuration may be possible if the STAs can directly communicate with each other. In addition, a LAN of this form is not pre-planned and configured, but can be configured when necessary. It can also be called a self-organizing (ad-hoc) network.

When the power of the STA is turned off or on, or the STA enters or leaves the BSS, the STA's membership in the BSS can be dynamically changed. To become a member of the BSS, the STA may join the BSS using a synchronization process. To access all services in a BSS-based configuration, the STA needs to be associated with the BSS. Such an association may be dynamically configured and may include the use of a distributed system service (DSS).

In an 802.11 system, the distance directly from the STA to the STA may be limited by physical layer performance (PHY). In any case, the limit of this distance may be sufficient, but communication between the STAs at a greater distance may be required if necessary. To support extended coverage, a distributed system (DS) can be configured.

DS means a configuration in which BSSs are interconnected. More specifically, a BSS may be present as an element of an extended form of a network including a plurality of BSSs instead of an independent BSS, as in FIG. one.

DS is a logical concept and can be defined by the characteristics of a distributed system environment (DSM). In IEEE 802.11, the wireless environment (WM) and the distributed system environment (DSM) are logically separated. Each logical environment is used for a different purpose and is used by a different element. In the definition of the IEEE 802.11 standard, such environments are not limited to the same environment, nor are they limited to different environments. Configuration flexibility (i.e., DS configuration or other network configuration) of an IEEE 802.11 system can be described in that many environments are logically different, as described above. That is, the configuration of the IEEE 802.11 system can be implemented in various ways, and the corresponding system configuration can be independently determined by the physical characteristics of each implementation example.

The DS can support the mobile device by providing seamless integration of multiple BSSs and providing the logical services required to process the address to the destination.

An AP denotes an entity that provides access to DS via WM with respect to associated STAs and has STA functionality. Data movement between BSS and DS can be done through the AP. For example, each of STA 2 and STA 3 according to FIG. 1 has STA functionality and provides a function that allows associated STAs (e.g., STA 1 and STA 4) to access the DS. In addition, all APs are basically STA-compliant, and thus all APs are objects that can be addressed. The address used by the AP to communicate via WM and the address used by the AP to communicate via DSM need not be the same.

Data transmitted from one of the STAs associated with the AP to the AP's STA address can always be received by an unmanaged port and processed by an IEEE 802.1X port access object. In addition, when the managed port is authenticated, transmission data (or frame) can be delivered to the DS.

A wireless network having arbitrary size and complexity may include DS and BSS. In an IEEE 802.11 system, a network of this method is called an extended service network (ESS) network. An ESS may correspond to a set of BSSs connected to one DS. However, ESS does not include DS. An ESS network is characterized in that it looks like an IBSS network at a logical link control (LLC) layer. The STAs included in the ESS can communicate with each other. Mobile STAs can move from one BSS to another BSS (within the same ESS) in a way transparent to the LLC level.

In the IEEE 802.11 system, the relative physical positions of the BSS of FIG. 1 are not intended, and the following forms are possible.

More specifically, BSSs may partially overlap, which is the form commonly used to provide consistent coverage. In addition, the BSSs may not be physically connected, and logically there is no limit to the distance between the BSSs. In addition, BSS can be placed physically in the same position and can be used to provide redundancy. In addition, one or more IBSS or ESS networks may be physically present in the same space as one or more ESS networks. This may correspond to the shape of the ESS network if the ad-hoc network is in a position in which the ESS network is present, if IEEE 802.11 networks that are physically overlapping are configured by different organizations, or if two or more different access and security policies are required in the same position.

In a WLAN system, an STA is a device that complies with IEEE 802.11 Media Access Control (MAC) / PHY regulations. An STA may include an STA AP and a non-AP STA, unless the STA functionality is individually different from the AP functionality. In this case, on the assumption that communication is between the STA and the AP, the STA may be interpreted as a non-AP STA. In the example of FIG. 1, STA 1, STA 4, STA 5 and STA 6 correspond to non-AP STA, and STA 2 and STA 3 correspond to STA AP.

A non-AP STA corresponds to a device that is directly controlled by a user, such as a laptop computer or mobile phone. In the following description, a non-AP STA can also be called a wireless device, terminal, user equipment (UE), mobile station (MS), mobile terminal, wireless terminal, wireless transmit / receive unit (WTRU), network interface device, machine communication device type (MTC), inter-machine (M2M) data transmission device, etc.

In addition, an AP is a concept corresponding to a base station (BS), a Node B, an Advanced Node B (eNB), a base transceiver system (BTS), a femto BS, and the like. in other areas of wireless communications.

Further, in the present description, downlink (DL) means communication from AP to non-AP STA. Uplink (UL) means communication from a non-AP STA to an AP. In DL, the transmitter may be part of the AP, and the receiver may be part of the non-AP STA. In UL, a transmitter may be part of a non-AP STA, and a receiver may be part of an AP.

FIG. 2 is a diagram illustrating a configuration of an IEEE 802.11 layer architecture of a system in which an embodiment of the present invention can be applied.

With reference to FIG. 2, the IEEE 802.11 system layer architecture may include a MAC sublayer and a PHY sublayer.

The PHY sublevel can be divided into a physical layer convergence procedure object (PLCP) and a physical medium dependent object (PMD). In this case, the PLCP object operates to connect the MAC sublayer and the data frame, and the PMD object operates to wirelessly transmit and receive data to / from two or more STAs.

The MAC sublayer and the PHY sublayer may include corresponding administration objects, which may be referred to as the MAC sublayer administration object (MLME) and the PHY sublayer administration object (PLME), respectively. Administration objects provide the level administration service interface through the operation of the level administration function. MLME is connected to PLME and can perform a MAC sublayer administration operation. Similarly, PLME is also connected to MLME and can perform the administration operation of the PHY sublevel.

In order to provide accurate MAC operation, a Station Administration Object (SME) may be present in each STA. The SME is an administration entity that is independent for each tier and collects tier-based status information from MLME and PLME or sets the values of tier-specific parameters. SME can perform this function instead of the usual system administration objects and can implement a standard administration protocol.

MLME, PLME and SME can interact with each other using various primitive methods. More specifically, the XX-GET.request primitive is used to query the value of an attribute of an administration information base (MIB). The XX-GET.confirm primitive returns the value of the corresponding MIB attribute if the state matches “SUCCESS” (successful), and indicates an error in the status field and returns a value in other cases. The XX-SET.request primitive is used to implement the request, so the assigned MIB attribute is set to this value. If the MIB attribute means a specific operation, then such a request requests the execution of a specific operation. In addition, the XX-SET.confirm primitive means that the assigned MIB attribute was set as the requested value if the state matches “SUCCESS”. In other cases, the XX-SET.confirm primitive indicates that the status field corresponds to the error situation. If the MIB attribute indicates a specific operation, the primitive can confirm that the corresponding operation has been completed.

The operation at each sublevel is described briefly as follows.

A MAC sublayer generates one or more MAC Protocol Data Units (MPDUs) by attaching a MAC header of a Frame Check Sequence (FCS) to a MAC Service Data Unit (MSDU) received from a higher layer (e.g., LLC layer), or a fragment MSDU. The generated MPDU is delivered to the PHY sublayer.

If an aggregated MSDU (A-MSDU) scheme is used, multiple MSDUs may be aggregated into one aggregated MSDU (A-MSDU). The MSDU aggregation operation may be performed at a level above the MAC. A-MSDU is delivered to the PHY sublevel as one MPDU (if it is not fragmented).

The PHY sublayer generates a physical protocol data unit (PPDU) by attaching an additional field including information for the PHY transceiver to a physical service data unit (PSDU) received from the MAC sublayer. PPDU is transmitted over a wireless medium.

The PSDU is received by the PHY sublayer from the MAC sublayer, and the MPDU is transmitted from the MAC sublayer to the PHY sublayer. Accordingly, the PSDU is essentially the same as the MPDU.

If an aggregated MPDU (A-MPDU) scheme is used, a plurality of MPDUs (in which case each MPDU can carry A-MSDUs) can be aggregated into one A-MPDU. The aggregation operation of the MPDUs may be performed below the MAC. A-MPDUs may include aggregation of various types of MPDUs (e.g., QoS data, acknowledgment (ACK), and ACK lock (BlockAck)). The PHY sublayer receives the A-MPDU, that is, one PSDU, from the MAC sublayer. That is, the PSDU includes many MPDUs. Accordingly, the A-MPDU is transmitted over a wireless medium in one PPDU.

PHYSICAL PROTOCOL DATA BLOCK FORMAT (PPDU)

PPDU means a data block generated at the physical layer. The PPDU format is described below based on the IEEE 802.11 WLAN system in which an embodiment of the present invention can be applied.

FIG. 3 illustrates a non-HT format PPDU and an HT format PPDU in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 3 (a) illustrates the PPDU of a non-HT format for supporting IEEE 802.11a / g systems. Non-HT PPDUs may also be referred to as inherited PPDUs.

With reference to FIG. 3 (a), a non-HT format PPDU is configured to include a legacy format preamble including an inherited (or non-HT) short training field (L-STF), an inherited (or non-HT) long training field ( L-LTF) and a legacy (or non-HT) signal (L-SIG) signal field and data field.

The L-STF may include a short training symbol of orthogonal frequency division multiplexing (OFDM). The L-STF can be used for frame synchronization detection, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization.

L-LTF may include a long OFDM training symbol. L-LTF can be used for accurate frequency / time synchronization and channel estimation.

The L-SIG field may be used to send control information for demodulating and decoding the data field.

The L-SIG field may include a four-bit rate field, a reserved 1-bit field, a 12-bit length field, a 1-bit parity field, and a 6-bit signal end field.

The rate field includes information about the transmission rate, and the length field indicates the number of octets of the PSDU.

FIG. 3 (b) illustrates a mixed format PPDU HT to support both an IEEE 802.11n system and an IEEE 802.11a / g system.

With reference to FIG. 3 (b), the mixed format PPDU HT is configured to include an inherited format preamble including an L-STF, L-LTF and L-SIG field, an HT format preamble including an HT signal field (HT- SIG), HT short training field (HT-STF) and HT long training field (HT-LTF) and data field.

The L-STF, L-LTF and L-SIG fields mean inherited fields for backward compatibility and are the same as in non-HT format from the L-STF field to the L-SIG field. The L-STA can interpret the data field through the L-LTF, L-LTF, and L-SIG fields, although it accepts HT mixed PPDUs. In this case, the L-LTF may further include channel estimation information performed by the HT-STA to receive the HT mixed PPDU and demodulate the L-SIG field and the HT-SIG field.

The HT-STA can recognize mixed format PPDU HTs using the HT-SIG field following the legacy fields, and can decode the data field based on the mixed format PPDU HTs.

HT-LTF can be used to estimate the channel for demodulation of the data field. IEEE 802.11n supports single-user multiple-input multiple-output (SU-MIMO) technology, and thus may include multiple HT-LTFs for channel estimation with respect to each of the data fields transmitted in the multiple spatial streams.

HT-LTF may include the HT-LTF data used to estimate the channel for the spatial stream, and the HT-LTF extension, further used for full channel sounding. Accordingly, the plurality of HT-LTFs may be the same or greater than the number of transmitted spatial streams.

In mixed format PPDU HTs, the L-STF, L-LTF, and L-SIG fields are first transmitted so that the L-STA can receive the L-STF, L-LTF, and L-SIG fields and receive data. The HT-SIG field is then transmitted to demodulate and decode the data transmitted for the HT-STA.

The L-STF, L-LTF, L-SIG, and HT-SIG fields are transmitted without beamforming to the HT-SIG field, so that the L-STA and HT-STA can receive the corresponding PPDU and receive data. In the HT-STF, HT-LTF and the data field, which are transmitted sequentially, the radio signals are transmitted by precoding. In this case, an HT-STF is transmitted, so that the STA receiving the corresponding PPDU, by performing precoding, can take into account a segment whose power changes due to precoding, and a plurality of HT-LTF and a data field are transmitted sequentially.

Table 1 below illustrates the HT-SIG field.

TABLE 1 Field Bit Description Mcs 7 Indicates modulation and coding scheme CBW 20/40 one Set to “0” if CBW is 20 MHz or 40 MHz or higher / lower
Set to “1” if CBW is 40 MHz NT length sixteen Indicates the number of octets of data in the PSDU Smoothing one Set to “1” if channel smoothing is recommended.
Set to “0” if channel rating is recommended without smoothing for each carrier No sounding one Set to “0” if PPDU is a PPDU sensing
Set to “1” if PPDU is not a sensing PPDU Reserved one Set to “1” Aggregation one Set to “1” if PPDU includes A-PPDU
Set to “0” if not Spatial
temporary block coding (STBC) 2 Indicates the difference between the number of space-time streams (NSTS) and the number of spatial streams (NSS) indicated by MCS
Set to “00” if STBC is not used. FEC encoding one Set to “1” if Low Density Parity Check (LDPC) is used
Set to “0” if binary convolutional coding (BCC) is used Short gi one Set to “1” if a short guard interval is used after NT training
Set to “0” if not Number of spatial extension streams 2 Indicates the number of spatial extension streams (NESS)
Set to “0” if not NESS
Set to “1” if NESS is 1
Set to “2” if NESS is 2
Set to “3” if NESS is 3 CRC eight Enables CRS to detect PPDU errors on the receiver side End bits 6 Used to complete the convolutional decoder matrix
Set to “0”

FIG. 3 (c) illustrates the PPDU of the HT-green field format (PPDU of the HT-GF format) to support only the IEEE 802.11n system.

With reference to FIG. 3 (c), the HT-GF PPDU includes the HT-GF-STF, HT-LTF1, HT-SIG fields, a plurality of HT-LTF2, and a data field.

HT-GF-STF is used to capture frame synchronization and AGC.

HT-LTF1 is used for channel estimation.

The HT-SIG field is used to demodulate and encode the data field.

HT-LTF2 is used for channel estimation to demodulate the data field. Similarly, the HT-STA uses SU-MIMO. Accordingly, a plurality of HT-LTF2 can be configured, since channel estimation is necessary for each of the data fields transmitted in the plurality of spatial streams.

A plurality of HT-LTF2s may include a plurality of HT-LTF data and a plurality of HT-LTF extensions, similar to HT-LTF in mixed format PPDU HT.

In FIG. 3 (a) -3 (c), the data field is a payload and may include an overhead field, a scrambled PSDU (PSDU) field, tail bits and pad bits. All bits of the data field are scrambled.

FIG. 3 (d) illustrates a service field included in a data field. The service field has 16 bits. 16 bits are numbered from No. 0 to No. 15 and transmitted sequentially from bit No. 0. Bits from No. 0 to No. 6 are set to 0 and are used to synchronize the descrambler at the receiving stage.

The IEEE 802.11ac WLAN system supports DL multi-user multi-input multi-output (MU-MIMO) DL transmission, in which multiple STAs access the channel at the same time in order to efficiently use the radio channel. According to the MU-MIMO transmission method, the AP can simultaneously transmit a packet to one or more STAs that obey pairing in the MIMO procedure.

Multilayer downlink transmission (DL MU transmission) means a technology in which an AP transmits PPDUs to a plurality of non-AP STAs through the same time resources using one or more antennas.

In the following description, MU PPDU means PPDU that delivers one or more PSDUs for one or more STAs using MU-MIMO technology or OFDMA technology. In addition, SU PPDU means PPDU having a format in which only one PSDU can be delivered, or which does not have a PSDU.

For MU-MIMO transmission, the size of the control information transmitted to the STA may be relatively larger than the size of the 802.11n control information. The control information additionally required to support MU-MIMO may include information indicating the number of spatial streams received by each STA, and information related to modulation and coding of data transmitted to each STA may correspond, for example, to control information.

Accordingly, when the MU-MIMO transmission is performed to provide the plurality of STA information services at the same time, the size of the transmitted control information can be increased in accordance with the number of STAs that receive the control information.

In order to efficiently transmit management information that has been increased in size, as described above, a plurality of segments of the management information required for MU-MIMO transmission can be divided into two types of management information: general management information, which is required for all STAs in general, and specific management information individually needed for a particular STA and may be transmitted.

FIG. 4 illustrates a PPDU of a VHT format in a wireless communication system in which an embodiment of the present invention can be applied.

FIG. 4 (a) illustrates the VHT-format PPDU to support the IEEE 802.11ac system.

With reference to FIG. 4 (a), the VHT format PPDU is configured to include a legacy format preamble including L-STF, L-LTF and L-SIG fields, a VHT format preamble including a VHT signal-A field ( VHT-SIG-A), VHT short training field (VHT-STF), VHT long training field (VHT-LTF) and VHT signal-B field (VHT-SIG-B), as well as a data field.

The L-STF, L-LTF, and L-SIG fields indicate inherited fields for backward compatibility and have the same formats as in the non-HT format. In this case, the L-LTF may further include channel estimation information that will be performed to demodulate the L-SIG field and the VHT-SIG-A field.

The L-STF, L-LTF, L-SIG fields, as well as the VHT-SIG-A field may be repeated in a 20 MHz channel block and transmitted. For example, when a PPDU is transmitted over four 20 MHz channels (i.e., 80 MHz bandwidth), the L-STF, L-LTF, L-SIG fields, and also the VHT-SIG-A field may be repeated in each 20 MHz channel and transmitted.

The VHT-STA can recognize VHT-format PPDUs using the VHT-SIG-A field following the legacy fields and can decode the data field based on the VHT-SIG-A field.

In VHT format PPDUs, the L-STF, L-LTF and L-SIG fields are transmitted first, so even the L-STA can receive VHT format PPDUs and receive data. Then, a VHT-SIG-A field is transmitted for demodulating and encoding data transmitted for the VHT-STA.

The VHT-SIG-A field is a field for transmitting control information that is common to VHT STAs that form MIMO pairs with the AP, and includes control information for interpreting the received PPDU of the VHT format.

The VHT-SIG-A field may include a VHT-SIG-A1 field and a VHT-SIG-A2 field.

The VHT-SIG-A1 field may include information about the channel bandwidth used (BW), information about whether space-time block coding (STBC) is used or not, a group identifier (ID) to indicate a group of grouped STAs in MU- MIMO, information about the number of streams used (number of space-time streams (NSTS) / part association identifier (AID) and energy-saving prohibition information. In this case, the group ID means the identifier assigned to the target transmission STA to support MU-MIMO before chu, and may indicate whether or not the present process MIMO-transmission method MU-MIMO or SU-MIMO.

Table 2 illustrates the VHT-SIG-A1 field.

TABLE 2 Field Bit Description Bw 2 Set to “0” if BW is 20 MHz
Set to “1” if BW is 40 MHz
Set to “2” if BW is 80 MHz
Set to “3” if BW is 160 MHz or 80 + 80 MHz Reserved one STBC one In the case of VHT SU PPDU:
Set to “1” if STBC is used.
Set to “0” if not
In the case of VHT MU PPDU:
Set to “0” Group id 6 Indicates group ID
“0” or “63” indicates VHT SU PPDU, but indicates VHT MU PPDU otherwise NSTS /
Partial aid 12 In the case of VHT MU PPDU, it is divided into 4 user positions “p”, each has three bits
“0” if the space-time stream is 0
“1” if the space-time flow is –1
“2” if the space-time stream is -2
“3” if the space-time stream is -3
“4” if the space-time flow is –4
In the case of VHT SU PPDU, the upper 3 bits are set as follows:
“0” if the space-time flow is –1
“1” if the space-time flow is –2
“2” if the space-time flow is –3
“3” if the space-time flow is –4
“4” if the space-time flow is –5
“5” if the space-time flow is –6
“6” if the space-time flow is –7
“7” if the space-time flow is –8
Lower 9 bits indicate partial AID TXOP_PS
_NOT_
ALLOWED one Set to “0” if the VHT AP allows non-APs. The VHT STA will switch to power-saving mode when transmitting is possible (TXOP)
Set to “1” if not
In the case of a VHT PPDU transmitted through a non-AP VHT STA
Set to “1” Reserved one

The VHT-SIG-A2 field may include information about whether a short guard interval (GI) is used or not, forward error correction (FEC) information, modulation and coding scheme (MCS) information for one user, channel type information encoding for multiple users, information related to beamforming, redundancy bit for cyclic redundancy check (CRC), end bit of convolutional decoder, etc.

Table 3 illustrates the VHT-SIG-A2 field.

TABLE 3 Field Bit Description Short gi one Set to “0” if a short GI is not used in the data field
Set to “1” if a short GI is used in the data field Disambiguation
short gi one Set to “1” if a short GI is used and an extra character is required for the PPDU payload
Set to “0” if no extra character is required SU / MU coding one In the case of VHT SU PPDU:
Set to “0” in the case of a binary convolutional code (BCC)
Set to “1” for Low Density Parity (LDPC)
In the case of VHT MU PPDU:
Indicates the encoding used if the NSTS field of a user whose user position is “0” is not equal to “0”
Set to “0” for BCC
Set to “1” for PDPC
Set to “1” as a reserved field if the NSTS field of a user whose user position is “0” is “0” LDPC optional
OFDM symbol one Set to “1” if an additional OFDM symbol is required due to the PDPC PPDU encoding procedure (in the case of PPDU SU) or the PPDU encoding procedure of at least one PDPC user (in the case of VHT MU PPDU)
Set to “0” if not SU VHT MCS / MU-
coding four In the case of VHT SU PPDU:
Indicates VHT-MCS Index
In the case of VHT MU PPDU:
Indicates encoding for user positions “1” - “3” sequentially from the upper bits
Indicates the encoding used if the NSTS field of each user is not “1”
Set to “0” for BCC
Set to “1” in case of LDPC
Set to “1” as a reserved field if each user's NSTS field is “0” Beamforming one In the case of VHT SU PPDU:
Set to “1” if the beamforming control matrix is applied to SU transmission
Set to “0” if not
In the case of VHT MU PPDU:
Set to “1” as a reserved field Reserved one CRC eight Enables CRS to detect PPDU errors on the receiver side End field 6 Used to complete the convolutional decoder matrix
Set to “0”

VHT-STF is used to improve the performance of AGC scores in MIMO transmission.

VHT-LTF is used for the VHT-STA to evaluate the MIMO channel. Since the VHT WLAN system supports MU-MIMO, the VHT-LTF can be configured by the number of spatial streams through which PPDUs are transmitted. Additionally, if full channel sounding is supported, the number of VHT-LTFs may be increased.

The VHT-SIG-B field includes special control information that is required for multiple MU-MIMO-paired VHT-STAs to receive PPDUs and receive data. Accordingly, only if the general control information included in the VHT-SIG-A field indicates that the received PPDU is for MU-MIMO transmission, the VHT-STA may be configured to decode the VHT-SIG-B field. In contrast, if the general control information indicates that the received PPDU is for one VHT-STA (including SU-MIMO), the STA may be configured so as not to decode the VHT-SIG-B field.

The VHT-SIG-B field includes a VHT-SIG-B length field, a VHT-MCS field, a reserved field, and an end field.

The VHT-SIG-B length field indicates the length of the A-MPDU (until filling to the end of the frame (EOF)). The VHT-MCS field includes modulation, coding, and rate matching information for each VHT-STA.

The size of the VHT-SIG-B field may vary depending on the type (MU-MIMO or SU-MIMO) of the MIMO transmission and the channel bandwidth used for transmitting the PPDU.

FIG. 4 (b) illustrates the VHT-SIG-B field in accordance with the PPDU transmission bandwidth.

With reference to FIG. 4 (b), in 40 MHz transmission, the VHT-SIG-B bits are repeated twice. In 80 MHz transmission, the VHT-SIG-B bits are repeated four times, and the padding bits set to 0 are joined.

In 160 MHz transmission and 80 + 80 MHz transmission, first, the VHT-SIG-B bits are repeated four times as in 80 MHz transmission, and the fill bits set to 0 are added. In addition, a total of 117 bits are repeated again.

In a system supporting MU-MIMO, to transmit PPDUs having the same size to STAs pairing with APs, information indicating the bit size of the data field forming the PPDUs and / or information indicating the size of the bit streams forming special field, may be included in the VHT-SIG-A field.

In this case, the L-SIG field can be used to effectively use the PPDU format. The length field and the velocity field, which are included in the L-SIG field and transmitted so that PPDUs of the same size are transmitted to all STAs, can be used to provide the required information. In this case, additional padding may be required at the physical level because the MAC Protocol Data Unit (MPDU) and / or the aggregated MAC PDU (A-MPDU) are set based on the MAC layer bytes (or octets).

In FIG. 4, the data field is a payload and may include an overhead field, a scrambled PSDU, an end bit, and padding bits.

The STA must determine the format of the received PPDUs because the various PPDU formats are mixed and used as described above.

In this case, the semantic meaning that the PPDU (or PPDU format) is defined is different. For example, the meaning of the PPDU being determined may include determining whether the received PPDU is such a PPDU that can be decoded (or interpreted) by the STA. In addition, the meaning of the PPDU being determined may include determining whether the received PPDU is such a PPDU that can be supported by the STA. In addition, the meaning of the PPDU being determined may include determining what information is information transmitted by the received PPDU.

MAS FRAME FORMAT

FIG. 5 illustrates a MAC frame format for an IEEE 802.11 system in which an embodiment of the present invention can be applied.

With reference to FIG. 5, a MAC frame (i.e., MPDU) includes a MAC header, a frame body, and a frame check sequence (FCS).

A MAC header is defined as an area including a frame control field, a duration / ID field, an address field 1, an address field 2, an address field 3, a sequence control field, an address field 4, a QoS control field and an HT control field.

The frame control field includes information about the characteristics of the corresponding MAC frame.

The duration / ID field may be implemented to have a different value depending on the type and subtype of the corresponding MAC frame.

If the type and subtype of the corresponding MAC frame is a PS poll frame for a power saving operation (PS), the duration / ID field may be configured to include the association identifier (AID) of the STA that transmitted the frame. In other cases, the duration / ID field may be configured to have a specific duration value depending on the type and subtype of the corresponding MAC frame. In addition, if the frame conforms to the MPDU format included in the aggregated MPDU (A-MPDU), the duration / ID field included in the MAC header can be configured to have the same value.

The fields from address field 1 to address field 4 are used to indicate the BSSID, source address (SA), destination address (DA), transmission address (TA) indicating the address of the transmitting STA, and the receiving address (RA) indicating the address of the receiving STA .

An address field implemented as a TA field may be set as a TA value indicating a bandwidth. In this case, the TA field may indicate that the corresponding MAC frame includes additional information in the scrambling sequence. The TA signaling the bandwidth can be represented as the MAC address of the STA, which transmits the corresponding MAC frame, but the individual / group bits included in the MAC address can be set as a specific value (for example, “1”).

The sequence control field is configured to include a sequence number and a fragment number. The sequence number may indicate the sequence number assigned to the corresponding MAC frame. The fragment number may indicate the number of each fragment of the corresponding MAC frame.

The QoS control field includes QoS related information. A QoS control field may be included if it indicates a frame of QoS data in a subfield of a subtype.

The HT control field includes control information related to the HT and / or VHT transmission / reception scheme. The HT control field is included in the control packer frame. In addition, the HT control field is present in the QoS data frame having a value of 1 order subfield and the administration frame.

The frame body is defined as the MAC payload. Data to be transmitted at a higher level is placed in the body of the frame. The frame body is variable in size. For example, the maximum MPDU size may be 11454 octets, and the maximum PPDU size may be 5.484 ms.

FCS is defined as a MAC footer and is used to search for MAC frame errors.

The first three fields (i.e., the frame control field, duration / ID field, address field 1) and the last field (i.e., FCS field) form the minimum frame format and are present in all frames. The remaining fields can only be present in a particular type of frame.

FIG. 6 illustrates the VHT format of an HT control field in a wireless communication system in which an embodiment of the present invention can be applied.

With reference to FIG. 6, the NT control field may include a VHT subfield, a middle HT control subfield, an AC constraint subfield, and a reverse direction grant (RDG) / additional PPDU subfield.

The VHT subfield indicates whether the HT control field has the format of the HT control field for VHT (VHT = 1) or the format of the HT control field for HT (VHT = 0). In FIG. 8, it is assumed that the NT control field is an NT control field for VHT (i.e., VHT = 1). The NT control field for VHT may be called the VHT control field.

The middle HT-control subfield can be implemented in a different format depending on the indication of the VHT subfield. The average NT control subfield is described in more detail below.

The AC-restriction subfield indicates whether the displayed access category (AC) of the reverse data frame (RD) is limited to one AC.

The RDG / incremental PPDU subfield can be interpreted in different ways depending on whether the corresponding field is transmitted through an RD initiator or an RD responder.

Assuming that the corresponding field is transmitted by the RD initiator, the RDG / additional PPDU subfield is set to “1” if RDG is present, and the RDG / additional PDU subfield is set to “0” if RDG is not present. Assuming that the corresponding field is transmitted by the RD responder, the RDG / additional PPDU subfield is set to “1” if the PPDU including the corresponding subfield is the last frame transmitted by the RD responder and the RDG / additional PPDU subfield is set to “0 ”If another PPDU is being transmitted.

As described above, the average NT control subfield may be implemented in a different format, depending on the indication of the VHT subfield.

The average HT control sub-field of the HT-control field for VHT may include a reserved bit subfield, a feedback request (MRQ) subfield of the modulation and coding scheme (MCS), an MRQ sequence identifier (MSI) / space-time block coding (STBC) subfield ), the MCS feedback sequence identifier subfield (MFSI) / low-order bit (LSB) of the group ID (GID-L), the MCS feedback subfield (MFB), the high-order bit field (MSB) of the group ID (GID-H), the type subfield coding, feedback transmission type subfield (FB Tx type) and non-random subfield ennoy MFB.

Table 4 illustrates the description of each subfield included in the middle sub-field of the NT-control of the VHT format.

TABLE 4 Subfield Value Definition Mrq MCS Request Set to “1” if MCS feedback (requested by MFB) is not requested.
Set to “0” if not. Msi Identifier
sequences
Mrq The MSI subfield includes a sequence number in the range of 0 to 6 to identify a particular request if the unsolicited MFB subfield is set to “0” and the MRQ subfield is set to “1”.
It includes the compressed MSI subfield (2 bits) and the STBC indication subfield (1 bit) if the unsolicited MFB subfield is set to “1”. MFSI / GID-L Identifier
sequences
MFB / LSB Group ID The MFSI / GID-L subfield includes the received value of the MSI included in the frame related to the MFB information if the unsolicited MFB subfield is set to “0”.
The MFSI / GID-L subfield includes the lower three bits of the PPDU group ID estimated by the MFB if the MFB is estimated from the PPDU MU. Mfb Feedback
VHT N_STS, MCS,
BW, SNR The MFB subfield includes the recommended MFB.
VHT-MCS = 15, NUM_STS = 7 indicates that there is no feedback. Gid-h MSB Group ID The GID-H subfield includes the upper 3 bits of the PPDU group ID, the unsolicited MFB of which was evaluated if the unsolicited MFB field was set to “1” and the MFB was evaluated from the VHT MU PPDU.
All GID-H subfields are set to “1” if the MFB was evaluated from SU PPDU. Type of
coding Coding type
or MFB answer If the unsolicited MFB subfield is set to “1”, the encoding type subfield includes the encoding type (binary convolutional code (BCC) includes 0, and the low density parity check (LDPC) includes 1) the frame whose requested MFB was evaluated. Type FB Tx MFB response transmission type A subfield of type FB Tx is set to “0” if the subfield of the unsolicited MFB is set to “1” and the MFB was evaluated from the VHT PPDU without beamforming.
A subfield of type FB Tx is set to “1” if the subfield of the unsolicited MFB is set to “1” and the MFB was evaluated from the VHT PPDU with beamforming. Unsolicited
Mfb Pointer
unsolicited
feedback mcs Set to “1” if the MFB is an MRQ response.
Set to “0” if the MFB is not an MRQ response.

In addition, the MFB subfield may include a sub-field of the VHT number of space-time streams (NUM_STS), a VHT-MCS subfield, a bandwidth subfield (BW), and a signal to noise ratio (SNR) subfield.

Subfield NUM_STS indicates the number of recommended spatial streams. The VHT-MCS subfield indicates the recommended MCS. Subfield BW indicates bandwidth information related to the recommended MCS. The SNR subfield indicates the average SNR of the data subcarriers and spatial streams.

Information included in each of the aforementioned fields may correspond to the definition of an IEEE 802.11 system. In addition, each of the aforementioned fields corresponds to and is not limited to example fields that may be included in a MAC frame. That is, each of the aforementioned fields may be replaced by another field, additional fields may be included, and essentially all fields may not be included.

ENVIRONMENTAL ACCESS MECHANISM

In IEEE 802.11, communication is generally different from that in a wired channel environment because it runs in a shared wireless environment.

In a wired channel environment, communication is possible based on multiple access with carrier control / conflict detection (CSMA / CD). For example, when a signal is transmitted once through a transmitting stage, it is transmitted to the receiving stage without experiencing much signal attenuation, since there is no significant change in the channel environment. In this case, when a conflict is detected between two or more signals, detection is possible. The reason is that the power detected by the receiving stage becomes instantly higher than the power transmitted by the transmitting stage. In a radio channel environment, however, since various factors (for example, signal attenuation varies depending on distance, or instantaneous deep fading can occur) affect the channel, the transmitting stage is not able to accurately monitor the carrier as to whether the signal was correctly transmitted to the receiving step or a conflict has been generated.

Accordingly, in a WLAN system according to IEEE 802.11, a Conflict Resolution Carrier Multiple Access (CSMA / CA) mechanism has been introduced as a basic MAC access mechanism. The CAMA / CA mechanism is also called the IEEE 802.11 MAC Distributed Coordination Function (DCF), and basically adopts a “listen before speaking” access mechanism. In accordance with this type of access mechanism, the APs and / or STAs perform a Channel Condition Assessment (CCA) for monitoring a radio channel or medium for a particular time interval (e.g., DCF Frame Interval (DIFS)) before transmission. If, as a control result, the medium is determined to be in an idle state, the APs and / or STAs begin to transmit a frame through the corresponding medium. On the contrary, if, as a control result, the medium is defined as corresponding to the state of employment (or the status of employment), the AP and / or STA do not start their transmission, they can wait for a delay time (for example, a random period of rollback with return) to access the medium in addition to DIFS, on the assumption that various STAs are already waiting to use the appropriate environment, and may then try to perform frame transmission.

Assuming that there are different STAs trying to transmit frames, they will wait for different times because the STAs stochastically have different return rollback times and will try to transmit the frame. In this case, the conflict can be minimized by applying a random rollback period with a return.

In addition, the IEEE 802.11 MAC protocol provides a hybrid coordination function (HCF). HCF is based on DCF point coordination function (PCF). The PCF is a polling-based synchronous access method and relates to a method for periodically polling so that all of the receiving APs and / or STAs can receive a data frame. In addition, HCF has enhanced distributed channel access (EDCA) and HCF managed channel access (HCCA). At EDCA, a provider performs an access method for providing a data frame to multiple users on a competitive basis. HCCA uses a non-competitive channel access method using a polling mechanism. In addition, the HCF includes a medium access mechanism to improve the quality of service (QoS) of the WLAN, and can transmit QoS data both in the competition period (CP) and the non-competition period (CFP).

FIG. 7 is a diagram illustrating a random return rollback period and a frame transmission procedure in a wireless communication system in which an embodiment of the present invention can be applied.

When a particular medium switches from a busy state (or busy) to an idle state, various STAs may attempt to transmit data (or frames). In this case, as a scheme for minimizing the conflict, each of the STAs may select a random return rollback count, may wait for a time interval corresponding to the selected random return rollback count, and may attempt to transmit. A random rollback count with a return has a pseudo-random integer value and can be defined as one of the uniformly distributed values in the range from 0 to the competition window (CW). In this case, CW is the value of the CW parameter. In the CW parameter, CW_min is set as the initial value. If the transmission is unsuccessful (for example, if the ACK for the transmitted frame is not accepted), CW_min may have a double value. The CW parameter becomes CW_max, it can maintain the CW_max value until the data transfer is successful, and an attempt can be made to transfer the data. If the data transfer is successful, the CW parameter is set to CW_min. The values of CW, CW_min and CW_max can be set to 2 ^ n-1 (n = 0, 1, 2, ...,).

When the random rollback rollback process begins, the STA counts down the return rollback time interval based on the determined rollback count value and continues to monitor the environment for the countdown. If the result of the environmental monitoring is a busy state, the STA stops the countdown and waits. When the environment becomes idle, the STA resumes the countdown.

In the example of FIG. 7, when the packet transmission moment in the STA 3 MAC is reached, the STA 3 can verify that the medium is in an idle state through DIFS and can immediately transmit the frame.

The rest of the STAs discover in the monitoring process that the environment is busy and waiting. In the meantime, data can be generated for transmitting each of STA 1, STA 2, and STA 5. When the control finds that the medium is in an idle state, each of the STAs waits for DIFS and counts down the return rollback interval based on each selected random countdown rollback with return.

The example of FIG. 7 shows that STA 2 selected the smallest rollback count value, and STA 1 selected the largest rollback count value. That is, FIG. 7 illustrates that the remaining STA 5 rollback time is shorter than the remaining STA 1 rollback value at the point in time when STA 2 ends the rollback count and starts transmitting the frame.

STA 1 and STA 5 stops the countdown and waits while STA 2 takes up the medium. When the occupation of the medium through the STA is downloaded, and the medium again becomes idle, each of the STA 1 and STA 5 waits for DIFS and resumes the stopped rollback count. That is, each of STA 1 and STA 5 can start transmitting a frame after counting down the remaining rollback interval corresponding to the remaining rollback time. STA 5 starts frame transmission because STA 5 has a shorter remaining rollback time than STA 1.

When STA 2 occupies the medium, data to be transmitted by STA 4 can be generated. In this case, from the point of view of STA 4, when the medium again becomes idle, STA 4 waits for DIFS and counts down the rollback interval corresponding to its chosen random rollback count value.

FIG. 7 shows an example in which the remaining rollback time of STA 5 coincides with a random countdown value of STA 4. In this case, a conflict can be generated between STA 4 and STA 5. When a conflict is generated, both STA 4 and STA 5 do not accept ACK, so the data transfer is unsuccessful. In this case, each of STA 4 and STA 5 doubles its CW value, selects a random value of the rollback count, and counts down the rollback interval.

STA 1 waits while the medium is in a busy state due to transmission of STA 4 and STA 5. When the medium returns to an idle state, STA 1 can wait for DIFS and start transmitting the frame after the remaining rollback time has elapsed.

The CSMA / CA mechanism includes virtual carrier monitoring in addition to physical carrier monitoring, in which the AP and / or STA directly monitor the environment.

Virtual carrier control is designed to complement a task that can be created as part of access to an environment, such as a hidden node task. To control the virtual carrier, the WLAN MAC system uses a network allocation vector (NAV). NAV is a value indicated by the APs and / or STAs that now use the medium or have the right to use the medium to notify the other APs and / or STAs of the remaining time until the medium returns to the availability state. Accordingly, the value set as NAV corresponds to the period in which the medium is reserved to be used by the AP and / or STA, which transmits the corresponding frames. For an STA that accepts a NAV value, access to the medium is denied for the corresponding period. NAV can be set, for example, based on the value of the duration field of the MAC header of the frame.

The APs and / or STAs may perform a procedure for exchanging a Transmission Request (RTS) frame and a Continue Transmission Capability (CTS) frame to provide notification that they will access the medium. The RTS frame and the CTS frame include information indicating a time segment in which the wireless medium required for transmitting / receiving the ACK frame is reserved for access if substantial transmission of the data frame and acknowledgment response (ACK) are supported. Another STA that has received an RTS frame from the AP, and / or an STA trying to transmit a frame, or that has received a CTS frame transmitted by an STA to which the frame will be transmitted, may be configured to not access the medium during the time segment, indicated by the information included in the RTS / CTS frame. This can be done by setting NAV over a period of time.

INTERFrame INTERVAL (IFS)

The time interval between frames is defined as the inter-frame interval (IFS). The STA can determine whether the channel is used during the IFS time slot through carrier monitoring (including physical carrier monitoring and virtual carrier monitoring). In an 802.11 WLAN system, a plurality of IFSs are defined to provide a priority level according to which a wireless environment can be occupied.

FIG. 8 is a diagram illustrating an IFS relationship in a wireless communication system in which an embodiment of the present invention can be applied.

All synchronization elements can be defined with reference to physical layer interface primitives, i.e., PHY-TXEND.confirm primitive, PHYTXSTART.confirm primitive, PHY-RXSTART.indication primitive, and PHY-RXEND.indication primitive.

Frame Interval (IFS) depending on the type of IFS is as follows.

a) Shortened Frame Interval (IFS) (RIFS)

b) Short Frame Interval (IFS) (SIFS)

c) PCF Frame Interval (IFS) (PIFS)

d) DCF Interframe Interval (IFS) (DIFS)

e) Arbitration Inter-Frame Interval (IFS) (AIFS)

f) Extended Interframe Interval (IFS) (EIFS)

Different IFSs are defined based on attributes specified by the physical layer regardless of the STA bit rate. The time characteristics of IFS are defined as the time interval in the medium. The temporal characteristics of IFS, other than AIFS, are fixed for each physical layer.

SIFS is used to transmit a PPDU including an ACK frame, a CTS frame, an ACK request blocking frame (BlockAckReq), or an ACK blocking frame (BlockAck), i.e., an instant response to A-MPDU, a second or sequential MPDU fragment packet, and a response from STA in relation to the survey according to PCF. SIFS has the highest priority. In addition, SIFS can be used for the point frame coordinator regardless of the type of frame during the non-competitive period (CFP) time. SIFS indicates the time before the start of the first preamble character of the next frame, which follows the end of the last character of the previous frame, or from the signal extension (if present).

SIFS timing characteristics are realized when the transmission of consecutive frames within the Tx SIFS interval begins.

SIFS is the shortest in IFS between transmissions from different STAs. SIFS can be used if the STA occupying the environment needs to support occupying the environment during the period in which the sequence of frames is being exchanged.

Other STAs that need to wait for the medium to become idle for a longer interval are not allowed to attempt to use the medium because it uses the smallest interval between transmissions within the frame sequence. Accordingly, priority can be assigned to the completion of the frame exchange sequence that is currently underway.

PIFS is used to gain priority when accessing the medium.

PIFS can be used in the following cases.

- STA works with PCF

- STA sends a channel switch alert frame

- STA sends a traffic indication map frame (TIM)

- Hybrid Coordinator (HC) triggers CFP or Transmission Capability (TXOP)

- HC or non-AP QoS STA, that is, the TXOP holder is polled to recover from the no-expected state in the managed access phase (CAP)

- HT STA uses dual CTS protection before sending CTS2

- TXOP holder for continuous transmission after transmission failure

- backup direction initiator (RD) for continuous transmission using error recovery

- HT AP during the PSMP sequence in which the frame energy-saving multi-query (PSMP) recovery is transmitted

- HT AT performs CCA on the secondary channel before sending the PPDU 40 MHz mask using EDCA channel access.

In the illustrated examples, an STA using PIFS starts transmission after a carrier control (CS) mechanism has been executed to determine that the medium is in an idle state within the Tx PIFS interval other than in the case where the CCA is performed in the secondary channel.

DIFS can be used through the STA, which acts to send a data frame (MPDU) and an administration frame for a MAC Administration Protocol Data Unit (MMPDU) in DCF. An STA using DCF can transmit data within the TxDIFS interval if the medium is determined to be in an idle state through the Carrier Control (CS) mechanism after the time of a precisely received frame and rollback expires. In this case, a precisely received frame means a frame indicating that the PHY-RXEND.indication primitive does not indicate an error, and FCS indicates that the frame is not erroneous (i.e., free from errors).

SIFS time (“aSIFSTime”) and slot (slot) time (“aSlotTime”) can be defined for each physical layer. SIFS time has a fixed value, but the interval time can dynamically change depending on the change in the “aAirPropagationTime” wireless delay time.

“ASIFSTime” is defined as indicated in equations 1 and 2 below.

[Equation 1]

aSIFSTime (16 μs) = aRxRFDelay (0.5) + aRxPLCPDelay (12.5) + aMACProcessingDelay (1 or <2) + aRxTxTurnaroundTime (<2)

[Equation 2]

aRxTxTurnaroundTime = aTxPLCPDelay (1) + aRxTxSwitchTime (0.25) + aTxRampOnTime (0.25) + aTxRFDelay (0.5)

“ASlotTime” is defined as in equation 3 below.

[Equation 3]

aSlotTime = aCCATime (<4) + aRxTxTurnaroundTime (<2) + aAirPropagationTime (<1) + aMACProcessingDelay (<2)

In equation 3, the default physical layer parameter is based on “aMACProcessingDelay” (MAC processing delay), which has a value that is equal to or less than 1 μs. A radio wave propagates as 300 m / μs in free space. For example, 3 μs may be the upper limit for a maximum unidirectional distance in BSS of ~ 450 m (bidirectional distance corresponds to ~ 900 m).

PIFS and SIFS are defined as in equations 4 and 5, respectively.

[Equation 4]

PIFS (16 μs) = aSIFSTime + aSlotTime

[Equation 5]

DIFS (34 μs) = aSIFSTime + 2 * aSlotTime

In equations 1-5, the numerical value in parentheses illustrates the total value, but the value may be different for each STA or for the position of each STA.

The above SIFS, PIFS and DIFS are measured based on the boundaries of the MAC interval (for example, Tx SIFS, Tx PIFS and TxDIFS), different from the environment.

The boundaries of the MAC interval SIFS, PIFS and DIFS are defined as in equations 6-8, respectively.

[Equation 6]

TxSIFS = SIFS-aRxTxTurnaroundTime

[Equation 7]

TxPIFS = TxSIFS + aSlotTime

[Equation 8]

TxDIFS = TxSIFS + 2 * aSlotTime

MU-MIMO DOWNLOAD (DL) FRAME

FIG. 9 is a diagram illustrating a DL format of multi-user (MU) PPDUs in a wireless communication system in which an embodiment of the present invention can be applied.

With reference to FIG. 9, the PPDU is configured to include a preamble and a data field. The data field may include a service field, a scrambled PSDU field, tail bits, and padding bits.

An AP can aggregate MPDUs and transmit a data frame using an aggregated MPDU format (A-MPDU). In this case, the scrambled PSDU field may include A-MPDUs.

A-MPDU includes a sequence of one or more subframes of A-MPDU.

In the case of VHT PPDUs, the length of each A-MPDU subframe is a set of 4 octets. Accordingly, the A-MPDU may include a frame end filling (EOF) of 0 to 3 octets after the last sub-frame of the A-MPDUs to match the A-MPDUs with the last octet of the PSDUs.

The A-MPDU subframe includes an MPDU delimiter, and the MPDU may optionally include a delimiter after the MPDU. In addition, a placeholder octet is attached to the MPDU to make the length of each A-MPDU subframe in a set of 4 octets different from the last A-MPDU subframe within the same A-MPDU.

The MPDU delimiter includes a fallback field, an MPDU length field, a cyclic redundancy check (CRC) field, and a delimiter signature field.

In the case of the VHT PPDU, the MPDU delimiter may further include an end-of-frame (EOF) field. If the MPDU length field is 0 and the A-MPDU or A-MPDU subframe used for filling includes only one MPDU, in the case of the A-MPDU subframe on which the corresponding MPDU is transferred, the EOF field is set to “1.” If not , the EOF field is set to “0.”

The MPDU length field includes MPDU length information.

If the MPDU is not present in the corresponding A-MPDU subframe, the MPDU length field is set to “0.” The A-MPDU subframe in which the MPDU length field is “0” is used to populate the corresponding A-MPDU to match the A-MPDU with available octets in VHT PPDU.

The CRC field includes CRC information for error checking. The delimiter signature field includes pattern information used to search for the MPDU delimiter.

In addition, the MPDU includes a MAC header, a frame body, and a Frame Check Sequence (FCS).

FIG. 10 is a diagram illustrating a DL format of multi-user (MU) PPDUs in a wireless communication system in which an embodiment of the present invention can be applied.

In FIG. 10, the number of STAs receiving the corresponding PPDU is assumed to be 3, and the number of spatial streams allocated to each STA is assumed to be 1, but the number of STAs pairing with the AP and the number of spatial streams allocated to each STA are not limited to this.

With reference to FIG. 10, the MU PPDU is configured to include L-TF fields (i.e., L-STF and L-LTF), L-SIG field, VHT-SIG-A field, VHT-TF fields (i.e. , VHT-STF and VHT-LTF), VHT-SIG-B field, service field, one or more PSDUs, padding field and tail bit. The L-TF fields, the L-SIG field, the VHT-SIG-A field, the VHT-TF fields and the VHT-SIG-B field are the same as those in FIG. 4, and a detailed description thereof is omitted.

Information for indicating the duration of the PPDU may be included in the L-SIG field. In PPDUs, the PPDU duration indicated by the L-SIG field includes the character to which the VHT-SIG-A field is allocated, the character to which the VHT-TF is allocated, the field to which the VHT-SIG-B field is allocated, the bits forming the service field , bits forming the PSDU, bits forming the fill field, and bits forming the trailer field. The STA receiving the PPDU may obtain PPDU duration information by means of information indicating the PPDU duration included in the L-SIG field.

As described above, the group ID information and the space-time stream number information for each user are transmitted by VHT-SIG-A, and the encoding method information and MCS information are transmitted by VHT-SIG-B. Accordingly, the assigned beam shapers can check the VHT-SIG-A and VHT-SIG-B and can recognize whether the MU frame is the MIMO frame to which the assigned beam shaper belongs. Accordingly, an STA that is not an STA member of the corresponding group ID or is a member of the corresponding group ID, but in which the number of threads allocated to the STA is “0”, is configured to stop receiving the physical layer to the end of the PPDU from the VHT-SIG field -A, and thus able to reduce power consumption.

In the group ID, the STA can recognize that the assigned beam former belongs to some MU group, and this is a user who belongs to the users of the group to which the STA belongs and who is in which place, that is, that the PPDU is received through some stream , by first receiving the group ID administration frame transmitted by the beamformer.

All MPDUs transferred to the VHT MU PPDU based on 802.11ac are included in the A-MPDU. In the data field of FIG. 10, each VHT A-MPDU may be transmitted in a different stream.

In FIG. 10, A-MPDUs may have different bit sizes because the size of the data transmitted to each STA may be different.

In this case, zero padding can be performed so that the time when the transmission of the plurality of data frames transmitted by the radiation conditioner is completed is the same as the time when the transmission of the data frame of the maximum transmission interval is completed. The maximum interval transmission data frame may be a frame in which the actual downlink data is transmitted by the beamformer for the longest time. Valid downlink data may be downlink data that has not been filled with zeros. For example, valid downlink data may be included in the A-MPDUs and transmitted. Zero padding can be performed on the remaining data frames other than the maximum interval transmission data frame from the plurality of data frames.

To fill with zeros, the beamformer can populate one or more A-MPDU subframes placed in time in the last part of the multiple A-MPDU subframes in the A-MPDU frame, only with the MPDU delimiter field, by encoding. An A-MPDU subframe having an MPDU length of 0 may be referred to as a zero subframe.

As described above, in the zero subframe, the MPDU delimiter EOF field is set to “1.” Accordingly, when the EOF field set to 1 is detected in the STA MAC layer at the receiving side, the physical layer reception is stopped, thereby making it possible to reduce power consumption .

METHOD UL MULTI-USER (MU) TRANSFER

The new frame format and numerology for the 802.11ax system, that is, the next-generation WLAN systems, are being actively discussed in a situation in which providers of various areas have a strong interest in next-generation Wi-Fi, and the need for high bandwidth and improved impression performance (QoE) increased after 802.11ac.

IEEE 802.11ax is one of the WLAN systems recently proposed as the next generation WLAN system to support higher data rates and high user load processing, and is also referred to as the so-called High Performance WLAN (HEW).

The IEEE 802.11ax WLAN system can operate in the 2.4 GHz frequency band and the 5 GHz frequency band similar to existing WLAN systems. In addition, the IEEE 802.11ax WLAN system can also operate in the higher frequency range of 60 GHz.

In an IEEE 802.11ax system, an FFT size four times larger than that of existing IEEE 802.11 OFDM systems (e.g., IEEE 802.11a, 802.11n, and 802.11ac) can be used in each frequency band to increase average throughput and sustainable outdoor transmission with respect to intersymbol interference. This is described below with reference to the relevant drawings.

Further, in the description of the HE-format PPDUs in accordance with an embodiment of the present invention, the descriptions of the above non-HT format PPDUs, HT mixed format PPDUs, HT green field format PPDUs and / or VHT format PPDUs can be mapped to PPDUs HE format, although they are not described otherwise.

FIG. 11 is a diagram illustrating a high performance format (HE) PPDU in accordance with an embodiment of the present invention.

FIG. 11 (a) illustrates a schematic configuration of a HE format PPDU, and FIG. 21 (b) -21 (d) illustrate more detailed configurations of the PPDU of the NOT format.

With reference to FIG. 11 (a), the HE format PPDU for the HEW may mainly include the legacy part (L part), the HE part, and the HE data field.

The L part includes the L-STF, L-LTF, and L-SIG fields in the form supported by the existing WLAN system. The L-STF, L-LTF, and L-SIG fields may be referred to as the inherited preamble.

The HE part is a part newly defined for the 802.11ax standard and may include the HE-STF, HE-SIG, and HE-LTF fields. In FIG. 25 (a) the sequence of the HE-STF, HE-SIG, and HE-LTF fields is illustrated, but the HE-STF, HE-SIG, and HE-LTF fields can be configured in a different sequence. In addition, HE-LTF may be omitted. Not only the HE-STF and HE-LTF fields, but also the HE-SIG field can usually be called the HE-preamble (“preamble”).

In addition, the L-part and the HE-part (HE-preamble) may, in general, be called the physical (PHY) preamble.

The HE-SIG may include information (eg, OFDMA, UL MU MIMO, and enhanced MCS) for decoding the HE data field.

The L part and the HE part can have different Fourier transform (FFT) sizes (i.e., different subcarrier intervals) and use different cyclic prefixes (CP).

In an 802.11ax system, the FFT size is four times (4x) larger than that which can be used in an inherited WLAN system. That is, the L part may have a 1 × symbol structure, and the HE part (more specifically, the HE preamble and HE data) may have a 4 × symbol structure. In this case, a 1 ×, 2 ×, or 4 × FFT means the relative size for the legacy WLAN system (e.g., IEEE 802.11a, 802.11n, and 802.11ac).

For example, if the FFT sizes used in the L-part are 64, 128, 256 and 512 at 20 MHz, 40 MHz, 80 MHz and 160 MHz, respectively, the FFT sizes used in the HE-part can be 256, 512, 1024 and 2048 at 20 MHz, 40 MHz, 80 MHz and 160 MHz, respectively.

If the FFT size is larger than the FFT size in the legacy WLAN system, as described above, the interval between subcarriers is reduced. Accordingly, the number of subcarriers per unit frequency increases, but the length of the OFDM symbol increases.

That is, if a larger FFT size is used, this means that the subcarrier span is narrowing. Similarly, this means that the period of the inverse discrete Fourier transform (IDFT) / discrete Fourier transform (DFT) is increased. In this case, the IDFT / DFT period may mean a character length other than the guard interval (GI) in the OFDM symbol.

Accordingly, if the FFT size is four times larger than that in the L part in the HE part (more specifically, in the HE preamble and the HE data field), the HE subcarrier spacing becomes 1/4 times the subcarrier interval L-part, and the IDFT / DFT period of the HE-part is equal to four times the IDFT / DFT period of the L-part. For example, if the L-subcarrier spacing is 312.5 kHz (= 20 MHz / 64, 40 MHz / 128, 80 MHz / 256 and / or 160 MHz / 512), the HE-subcarrier spacing may be 78.125 kHz (= 20 MHz / 256, 40 MHz / 512, 80 MHz / 1024 and / or 160 MHz / 2048). In addition, if the IDFT / DFT period of the L part is 3.2 μs (= 1 / 312.5 kHz), the IDFT / DFT period of the HE part may be 12.8 μs (= 1 / 78.125 kHz).

In this case, since one of 0.8 μs, 1.6 μs and 3.2 μs can be used as a GI, the length of the OFDM symbol (or symbol interval) of the HE part including the GI can be 13.6 μs, 14.4 μs or 16 μs depending on the GI.

With reference to FIG. 11 (b), the HE-SIG field may be divided into the HE-SIG-A field and the HE-SIG-B field.

For example, the HE portion of a PPDU HE format may include a HE-SIG-A field having a length of 12.8 μs, and a HE-STF of 1 OFDM symbol, one or more HE-LTFs, and a HE-SIG-B field of 1 OFDM symbol.

In addition, in the HE part, the FFT size, four times larger than that for the existing PPDU, can be applied to the HE-STF other than the HE-SIG-A field. That is, FFTs having sizes of 256, 512, 1024 and 2048 can be applied to the HE-STF PPDU HE format at 20 MHz, 40 MHz, 80 MHz and 160 MHz, respectively.

In this case, if the HE-SIG field is divided into the HE-SIG-A field and the HE-SIG-B field, as in FIG. 11 (b), the positions of the HE-SIG-A field and the HE-SIG-B field may differ from those in FIG. 21 (b). For example, the HE-SIG-B field may be transmitted after the HE-SIG-A field, and HE-STF and HE-LTF may be transmitted after the HE-SIG-B field. In this case, the FFT size, four times larger than that for the existing PPDU, can be applied to the HE-STF.

With reference to FIG. 11 (c), the HE-SIG field may not be divided into the HE-SIG-A field and the HE-SIG-B field.

For example, the HE portion of the PPDU HE format may include a HE-STF of 1 OFDM symbol and a HE-SIG field of 1 OFDM symbol and one or more HE-LTFs.

In a similar way, as described above, the FFT size, four times larger than that for the existing PPDU, can be applied to the HE part. That is, FFT sizes of 256, 512, 1024 and 2048 can be applied from the HE-STF PPDU HE format at 20 MHz, 40 MHz, 80 MHz and 160 MHz, respectively.

With reference to FIG. 11 (d), the HE-SIG field not divided into the HE-SIG-A field and the HE-SIG-B field and the HE-LTF may be omitted.

For example, the HE portion of the PPDU HE format may include a HE-STF of 1 OFDM symbol, a HE-SIG field of 1 OFDM symbol.

In a similar way, as described above, the FFT size, four times larger than that for the existing PPDU, can be applied to the HE part. That is, FFT sizes of 256, 512, 1024 and 2048 can be applied from the HE-STF PPDU HE format at 20 MHz, 40 MHz, 80 MHz and 160 MHz, respectively.

HE format PPDUs for a WLAN system in accordance with an embodiment of the present invention may be transmitted through at least one 20 MHz channel. For example, HE-format PPDUs can be transmitted in the 40 MHz, 80 MHz, or 160 MHz frequency band through just four 20 MHz channels. This is described in more detail.

FIG. 12 is a diagram illustrating a PPDU of a HE format in accordance with an embodiment of the present invention.

In the embodiment of FIG. 12, the HE-SIG 1 (or HE-SIG A) field is located after the L-part (i.e., the L-STF, L-LTF and L-SIG field) using legacy numerology and can be duplicated in a 20 MHz block, like the L-part. The HE-SIG-1 field may include general information (e.g., BW, GI length, BSS index, CRC, and trailer). 4 × FFT can be applied to the HE data field, and 1024-FFT can be used in the HE data field.

FIG. 13 is a diagram illustrating a PPDU of a HE format in accordance with an embodiment of the present invention.

In the embodiment of FIG. 13, the HE-SIG A field may further include user allocation information (eg, ID (eg, PAID or GID) of the STA and resource allocation information N_sts) in addition to general information. In addition, the HE-SIG 1 field may be transmitted depending on the OFDMA resource allocation. In the case of MU-MIMO, the HE-SIG 2 field (HE-SIG B) can be identified by STA via SDM. The HE-SIG B field may include additional user distribution information (e.g., MCS, encoding, STBC, and TSBF).

FIG. 14 is a diagram illustrating a PPDU of a HE format in accordance with an embodiment of the present invention.

In the embodiment of FIG. 14, the HE-SIG 1 field and the HE-SIG 2 field may be included after the inherited preamble, and then the HE-STF and HE-LTF may be included. The HE-SIG 2 field may be transmitted over the entire range after the HE-SIG 1 field using the information (numerology) of the HE-SIG 1 field. The HE-SIG 2 field may include user distribution information (e.g., ID (e.g., PAID or GID ) STA and resource allocation information N_sts).

HE-STF and HE-LTF can be included in the corresponding resource block range depending on the resource allocation of the OFDMA scheme for each user, as in FIG. 12.

The multi-user UL transmission method in a WLAN system is described below.

The method of transmitting, by an AP operating in a WLAN system, data to a plurality of STAs on the same temporary resource may be referred to as multi-user (MU) downlink (DL) transmission. In contrast, a method of transmitting, by a plurality of STAs operating in a WLAN system, data to an AP on the same temporary resource may be referred to as multi-user (MU) uplink transmission (UL).

Such a DL MU transmission or UL MU transmission may be multiplexed in the frequency domain or in the spatial domain.

If the DL MU transmission or UL MU transmission is frequency domain multiplexed, different frequency resources (e.g., subcarriers or tones) can be allocated to each of the plurality of STAs as DL or UL resources based on orthogonal frequency division multiplexing (OFDMA). A method of transmitting through different frequency resources in such same time resources may be referred to as “DL / UL MU OFDMA Transmission”.

If the DL MU transmission or UL MU transmission is multiplexed in the spatial domain, different spatial streams may be allocated to each of the plurality of STAs as DL or UL resources. A method of transmitting through different spatial streams on the same time resources may be referred to as a “DL / UL MU MIMO transmission”.

Modern WLAN systems do not support UL MU transmission due to the following limitations.

Modern WLAN systems do not support synchronization for transmitting time characteristics of UL data transmitted by multiple STAs. For example, on the assumption that a plurality of STAs transmits UL data via the same time resources in an existing WLAN system, in real WLAN systems, each of the plurality of STAs is not aware of the timing of the transmission of UL data of another STA. Accordingly, the AP may not receive UL data from each of the plurality of STAs on the same temporary resource.

In addition, in the present WLAN systems, overlapping may occur between frequency resources used by multiple STAs to transmit UL data. For example, if a plurality of STAs have different oscillators, the frequency shifts may be different. If a plurality of STAs having different frequency offsets performs UL transmissions at the same time through different frequency resources, the partial ranges used by the plurality of STAs may partially overlap.

In addition, in an existing WLAN system, power control is not performed for each of the plurality of STAs. The AP, depending on the distance between each of the multiple STAs and the APs and the channel medium, can receive signals of different powers from the multiple STAs. In this case, a signal having a low power may not be detected by the AP compared to a signal having a high power.

Accordingly, an embodiment of the present invention provides an UL MU transmission method in a WLAN system.

FIG. 15 is a diagram illustrating an UL multi-user (UL MU) transmission procedure in accordance with an embodiment of the present invention.

With reference to FIG. 15, the AP issues a command to the STAs participating in the UL MU transmission to prepare the UL MU transmission, receives UL MU data frames from the corresponding STAs, and transmits an ACK frame (or an ACK blocking frame (BA)) as a response to the UL MU- data frames.

First, the AP issues a command to the STAs, which will transmit UL MU data, to prepare the UL MU transmission by transmitting the UL MU trigger frame 1510, including various information for the UL MU transmission. In this case, the UL MU trigger frame may also be called the “UL MU planning frame” or the “trigger frame”.

In this case, the UL MU start frame 1510 may include control information such as STA identifier / ID information, resource allocation information to be used by each STA, and duration information, that is, information for UL MU- transmission.

STA-ID / address information means identifier or address information for specifying each STA that transmits UL data.

Resource allocation information means information about UL transmission resources (e.g., frequency / subcarrier information allocated by each STA in the case of UL MU OFDMA transmission and the stream index allocated by each STA in the case of UL MU MIMO transmission) allocated by each STA .

Duration information means information for determining time resources for transmitting an UL data frame transmitted by each of a plurality of STAs.

For example, the duration information may include information on a transmission capability interval (TXOP) allocated for UL transmission of each STA, or information (for example, a bit or symbol) on the length of the UL frame.

In addition, the UL MU trigger frame 1510 may further include control information such as MCS information to be used by each STA for the UL MU transmission data frame, coding information, SU / MU information, power adjustment information, information about the number of streams, STBC information and information about the formation of the radiation pattern, that is, information for UL MU transmission.

Such control information may be transmitted in the HE part (for example, the HE-SIG A field or the HE-SIG B field) of the PPDU in which the UL MU trigger frame 1510 is delivered, or in the UL control field of the MU trigger frame 1510 (for example, the field frame control MAC frame).

In addition, the UL MU trigger frame 1510 may be defined to have a new format in the 802.11ax system, and may include UL MU PPDU resource allocation information and segments of information important for STA verification that transmit UL MU PPDUs. The UL MU format of the trigger frame is described in more detail with reference to FIG. nineteen.

The PPDU, in which the UL MU trigger frame 1510 is delivered, has a structure that begins with the L-part (for example, the L-STF, L-LTF and L-SIG field). Accordingly, legacy STAs can perform network allocation vector (NAV) setup through L-SIG protection from the L-SIG field. For example, legacy STAs may calculate the interval for setting the NAV (hereinafter referred to as the “L-SIG guard interval”) based on information about the data length and data rate in the L-SIG field. In addition, legacy STAs may determine that there is no data to be transmitted to them during the computed L-SIG guard interval.

For example, the L-SIG guard interval can be defined as the sum of the value of the MAC field of the UL duration of the MU trigger frame 1510 and the rest of the interval after the L-SIG PPDU field that carries the UL MU trigger frame 1510. Accordingly, the L-SIG guard interval can be set to a value up to the interval in which an ACK frame 1530 (or BA frame) is transmitted to each STA based on the MAC value of the UL duration of the MU trigger frame 1510.

STAs transmit the respective UL MU data frames 1521, 1522, and 1523 to the APs based on the UL MU trigger frame 1510 transmitted by the AP. In this case, the STAs can receive the UL MU start frame 1510 from the AP and then transmit the UL MU data frames 1521, 1522, and 1523 to the AP after the SIFS.

Each of the STAs may determine a specific frequency resource for UL MU OFDMA transmission or spatial stream for UL MU MIMO transmission based on UL resource allocation information of the trigger MU 1510.

More specifically, in the case of UL MU OFDMA transmission, each STA can transmit an UL MU data frame on the same time resource through a different frequency resource.

In this case, various frequency resources for transmitting the UL data frame may be allocated to STA 1 ... STA 3 based on the STA ID / address information and resource allocation information included in the UL MU trigger frame 1510. For example, STA ID / address information can sequentially indicate STA 1 ... STA 3, and resource allocation information can sequentially indicate frequency resource 1, frequency resource 2 and frequency resource 3. In this case, frequency resource 1, frequency resource 2 and frequency resource 3, sequentially indicated on the basis of information distribution Lenia resources may be allocated to STA 1 ... STA 3 successively indicated on the basis of the STA ID / address information. That is, STA 1, STA 2, and STA 3 can transmit corresponding UL data frames 1521, 1522, and 1523 to the APs via frequency resource 1, frequency resource 2, and frequency resource 3, respectively.

In addition, in the case of UL MU MIMO transmission, each STA can transmit an UL data frame on the same time resource through at least one different from the plurality of spatial streams.

In this case, the spatial stream for the UL transmission data frame may be allocated for each of the STA 1 ... STA 3 based on the STA ID / address information and resource allocation information included in the UL MU trigger frame 1510. For example, the STA ID / address the information may sequentially indicate STA 1 ... STA 3, and the resource allocation information may sequentially indicate spatial stream 1, spatial stream 2 and spatial stream 3. In this case, spatial stream 1, spatial stream 2 and spatial stream 3, successive but indicated on the basis of resource allocation information may be respectively allocated to STA 1 ... STA 3 successively indicated on the basis of the STA ID / address information. That is, STA 1, STA 2, and STA 3 can transmit the respective UL data frames 1521, 1522, and 1523 to the AP through spatial stream 1, spatial stream 2, and spatial stream 3, respectively.

The PPDU, in which UL data frames 1521, 1522 and 1523 are delivered, can be configured to have a new structure even without an L part.

Additionally, in the case of UL MU MIMO transmission or UL MU OFDMA transmission having a subband form of less than 20 MHz, the L-part of the PPDU in which UL data frames 1521, 1522 and 1523 are delivered may be transmitted in the form of SFN (i.e. e. all of the STAs transmit the same L-part configuration and contents at the same time). In contrast, in the case of UL MU OFDMA transmission having a sub-band shape of 20 MHz or more, the L-part of the PPDU in which UL data frames 1521, 1522 and 1523 are delivered can be transmitted in the 20 MHz block in the band allocated to each STA.

If the UL data frame can be sufficiently configured based on the UL information of the trigger MU 1510, the HE-SIG field (i.e., the area in which control information for the method of configuring the frame data) is transmitted is not required in the PPDU, which delivers UL data frames 1521, 1522, and 1523. For example, the HE-SIG-A and / or HE-SIG-B field may not be transmitted. In addition, the HE-SIG-A and HE-SIG-B fields may be transmitted, and the HE-SIG-B field may not be transmitted.

An AP may transmit an ACK frame 1530 (or a BA frame) in response to UL data frames 1521, 1522, and 1523 received from respective STAs. In this case, the AP can receive UL data frames 1521, 1522, and 1523 from the respective STAs and then transmit the ACK frame 1530 to each of the STAs after SIFS.

If the structure of the existing ACK frame is used in an identical manner, the existing ACK frame can be configured to include the AID (or part of the AID) of the STAs participating in the UL MU transmission in an RA field having a size of 6 octets.

Alternatively, if the ACK frame of the new structure is configured, the ACK frame may be configured in the form for DL SU transmission or DL MU transmission.

The AP can only transmit the ACK 1530 frame for the UL MU data frame that was successfully received to the corresponding STA. In addition, the AP may provide a notification whether the UL MU data frame has been successfully received by the ACK frame 1530 using the ACK or NACK. If the ACK frame 1530 includes NACK information, the ACK frame may include a NACK reason or information for a subsequent procedure (eg, UL MU scheduling information).

Alternatively, the PPDU in which the ACK frame 1530 is delivered may be configured to have a new structure without an L part.

The ACK frame 1530 may include STA ID or address information, but the STA ID or address information may be omitted if the STA sequence indicated in the UL MU start frame 1510 is applied in the same way.

In addition, the TXOP (i.e., L-SIG guard interval) of the ACK frame 1530 can be extended so that a frame for the next UL MU scheduling or a control frame including tuning information for the next UL MU transmission can be included in TXOP.

For UL MU transmission, a tuning process for STA synchronization can be added.

FIG. 16 is a diagram showing embodiments of an UL / DL MU transmission operation between an AP and an STA.

With reference to FIG. 16 (a), the AP may transmit a beacon frame including a traffic indication card (TIM) to the STA. In addition, the AP may transmit a trigger frame for transmitting the UL MU of the PS poll frame after the initial offset indicated in the beacon frame. In this case, the STAs may transition to a dormant (inactive) state during the interval indicated by the initial shift. In addition, STAs may receive a trigger frame and may transmit UL MU PS polling frames after SIFS. An AP may receive MU PS polling frames and may transmit a DL MU data frame or an ACK frame in response to MU PS polling frames after SIFS.

With reference to FIG. 16 (b), the AP may transmit a DL MU data frame. In addition, the AP can transmit DL MU data and can transmit a trigger frame for UL MU ACK frames or UL MU BA frames after SIFS or immediately. In this case, STAs can receive a trigger frame and can transmit UL MU frames ACK and UL MU frames BA after SIFS. Alternatively, STAs may transmit UL MU frames ACK and UL MU frames BA after competing for the transmission of UL frames.

With reference to FIG. 16 (c), the AP may transmit a trigger frame for UL MU resource request / buffer status response. STAs may receive a trigger frame and may transmit UL MU frames of a resource status / buffer status response (BS) after SIFS. If the AP sends a trigger frame, STAs can compete with each other for accessing the medium and receive TXOP for UL MU transmission. In this case, the STAs may receive a trigger frame and may transmit UL data frames in the format indicated by the AP after SIFS. Alternatively, after competing with each other to send UL frames, STAs may transmit UL data frames in the format indicated by the AP. APs may respond to received UL data frames using an ACK frame.

FIG. 17 is a diagram showing embodiments of an UL / DL MU transmission operation between an AP and an STA.

With reference to FIG. 17 (a), the AP may transmit a trigger frame for UL CTS MU frames after competition for gaining access to the medium. In this case, STAs may receive a trigger frame and may transmit UL MU frames of CTS after SIFS. An AP can receive CTS UL MU frames and can transmit a DL MU data frame after SIFS.

With reference to FIG. 17 (b), the AP may transmit a trigger frame for UL MU NDP frames. STAs may receive a trigger frame and may transmit UL MDP NDP frames after SIFS or after channel contention for UL frame transmission.

FIG. 18 is a diagram illustrating a multi-user (MU) transmission procedure in accordance with an embodiment of the present invention.

As shown in FIG. 18 (a), the AP may transmit a DL MU frame and a trigger frame (or trigger information) (not shown) using the same time resource (or at the same time). In this case, the DL MU frame and the trigger frame may be included in the same DL MU PPDU and may be subject to DL MU transmission at the same time. STAs that have received both a trigger frame and a DL MU frame from the AP can perform UL MU transmission on ACK frames (or ACK lock frames (BA)), that is, responses to the UL MU frame and DL MU frame corresponding to the start frame using one UL MU PPDU. That is, STAs can perform UL MU transmission on one UL MU PPDU including UL MU frames and ACK frames in accordance with the received DL MU PPDU. In this case, temporary resources can be reduced, and data transfer efficiency can be improved, since the overhead associated with the additional start frame, SIFS and physical preamble is reduced.

According to the above embodiment, DL MU PPDUs and UL MU PPDUs can be transmitted / received in a cascaded manner, as shown in FIG. 18 (b).

FIG. 19 is a diagram showing a trigger frame format in accordance with an embodiment of the present invention.

With reference to FIG. 19, the trigger frame may include an FC frame control field, a Duration / ID field, a General Information field, a User-specific information field (Per User Info 1 ~ Per User Info N), and FCS. The descriptions of the frame control field, the duration / ID field, and the FCS are the same as the descriptions related to FIG. five.

The general information field indicates a field including general information that is required for all STAs in general. A user-specific information field indicates a field including user-specific information that is individually required for a particular STA. A user-specific information field may be included in the trigger frame by a number of STAs receiving user-specific information. User-specific information included in each field may be information for a specific STA.

The 802.11 system has been generally described above. The following describes a method of performing CCA in an existing system and a procedure for transmitting CTS / RTS, which relate to an embodiment of the present invention. The UL MU transmission method related to performing CCA in accordance with an embodiment of the present invention is described in detail.

METHOD FOR PERFORMING CCA (802.11ac)

Before transmitting a frame on a channel, the STA can verify the CCA by performing energy determination on the corresponding channel. The STA may observe the channel during the CCA observation time. In this case, the CCA observation time may be less than 18 μs. If the energy level of the observed channel does not exceed a threshold corresponding to a predetermined power level, the channel can be considered as corresponding to an idle (or idle) state, and the STA can transmit a frame through the channel.

On the contrary, if the energy level of the observed channel exceeds a threshold corresponding to a pre-set power level, the channel can be considered as corresponding to a busy state, and the STA cannot transmit a frame through the channel. In this case, the STA may perform an extended CCA check on the observed channel for a random time ranging between 18 μs and at least 160 μs. In this case, if the STA determines that the monitored channel is no longer in a busy state through the extended CCA check, the STA can resume transmission for the channel (if there is no transmission during the specific period in which the extended CCA check is performed, this particular time may be considered as the time of unemployment (or the period of unemployment) between transfers). The STA may continue to transmit a short control signaling over the channel.

If data is transmitted simultaneously through multiple channels (adjacent or non-adjacent channels), the STA may continue to transmit data through a separate channel in which no other signals are detected by performing a CCA check.

The total time that the STA transmits data using the channel can be up to the maximum channel busy time after the STA performs a new CCA. In this case, the maximum channel busy time may be less than 10 μs.

When the STA successfully receives the packet, it can skip the CCA and immediately send administration and control frames (for example, an ACK frame or an ACK lock frame). In this case, the time during which the STA continues to transmit frames without performing a new CCA does not exceed the maximum channel busy time. In this case, the transmission of the ACK frame (associated with the same data packet) to each multicast STA may continue to be performed.

The power level for transmission may be 23 dB per mW e.i.r.p. (equivalent isotropic emitter power) or more. At the receiving stage, the CCA threshold level may be a minimum of -73 dB per mW / MHz (estimated as 0 dB per mW in the antenna). When transmitting a power level of 23 dB per mW or less, the CCA threshold level (TL = -73 dB per mW / MHz + (23 dB per mW – PH) / (1 MHz)) in the receiving stage may be proportional to the maximum transmit power (PH )

CTS / RTS TRANSMISSION PROCEDURE

In an 802.11ac system, an STA that receives an RTS frame may consider NAV to determine whether to send a CTS frame in response to a received RTS frame (if the NAV is not set by a frame transmitted by the STA that transmitted the RTS frame).

If the NAV indicates an idle state, and the CCA indicates that all of the secondary channels (e.g., 20 MHz secondary channel, 40 MHz secondary channel, and 80 MHz secondary channel) included in the channel width indicated by the RTS frame are in the idle state during PIFS before the start of the RTS frame (if a particular channel is unoccupied in the case of dynamic allocation, and if all channels are unoccupied in the case of static allocation), the VHT STA may receive an RTS frame and may transmit a CTS frame in response to the RTS frame after SIFS. In contrast, if the NAV does not indicate an idle state and the CCA does not correspond to the idle state, the VHT STA cannot transmit the CTS frame as a response to the RTS frame. In this case, the fact that “NAV indicates an idle state” can be defined as i) the case where the NAV count value is “0”, ii) the case when the NAV count value is not “0” (ie non-zero) but the TA out-of-band signaling transmitted in the TA field of the trigger frame is the same as the TXOP holder address, or iii) the case where the NAV count value is not “0” but the NAV is set to busy using the MyBSS packet.

If the NAV indicates an idle state, the non-VHT STA may receive an RTS frame and may transmit a CTS frame as a response to an RTS frame after SIFS. In contrast, if the NAV does not indicate an idle state, the non-VHT STA cannot transmit the CTS frame.

The CCA execution method and CTS / RTS transmission procedures have been described above. An UL MU transmission method related to performing CCA in accordance with an embodiment of the present invention is described in detail below.

METHOD OF UL MULTI-USER (MU) TRANSMISSION IN WHICH THE CCA RESULTS ARE TAKEN INTO ACCOUNT

The trigger frame may also trigger the transmission of a short administration / control frame, in addition to the UL MU data frame. In this case, a short administration / management frame may indicate an administration or management frame having a length shorter than a predetermined length and may correspond, for example, to a PS poll, ACK / BA, a resource request / buffer status response, CTS or frame NDP

In an 802.11ax system, if the STA receives at least one frame including the MAC address (or RA) of another STA other than its own MAC address, the STA may update the NAV based on the duration field information in the PSDU included in the corresponding frame , or can set the NAV count value to non-zero. In an 802.11ax system, however, the TXOP sequence may include a different UL transmission stage (or transmitter) in each PPDU UL MU. Accordingly, although the NAV count value is nonzero, it may be necessary for the STA to transmit the UL MU frame in response to the received trigger frame during the established MU TXOP. For example, it can be assumed that the AP is a TXOP holder that has transmitted a trigger frame to STA 1 ~ 3, and STA 3 is an STA that has updated NAV. In this case, if the STA 3 receives the trigger frame intended for it, the STA 3 may need to transmit the UL MU frame as a response to the received trigger frame, regardless of whether the NAV is updated or not (or the NAV count value).

Accordingly, as in the method of transmitting RTS and CTS frames in a legacy system, in an 802.11ax system, STAs that have received a trigger frame can be configured to transmit UL MU data frame (s), short administration frame (s) / control, etc. through appropriate channels, if i) NAV indicates an idle state, and ii) channels (e.g. secondary channels) are in an idle state (i.e., if a particular channel corresponds to an idle state in the case of dynamic allocation, and if all of the channels correspond to the state unemployment in case of static distribution). In this case, as described above, the fact that “NAV indicates an idle state” can be defined as i) the case when the value of the NAV count is equal to “0”, ii) the case when the value of the NAV count is not equal to “0” (t ie non-zero), but the TA transmitted in the TA field of the trigger frame is the same as the TXOP holder address, or iii) the case when the NAV count value is not “0” but the NAV is set as busy state by packet MyBSS

In this case, if the AP transmits the start frame through the channel in the idle state, and the STA transmits UL MU frames in response to the start frame through the same channel, the likelihood that the AP can successfully receive the UL MU frames is high. In addition, the likelihood that each STA can successfully receive an ACK / BA frame transmitted by the AP through the same channel is also high.

More specifically, since a short frame has a short transmission time, the likelihood that a short frame may impact another AP or STA in an overlapping set of basic services (OBSS) situations is low. Accordingly, if the start frame triggers the transmission of a short administration / control frame, it may be more efficient that the STA receives the start frame regardless of whether the channel according to the carrier monitoring result is idle or busy, and then transmits a short administration / control frame after SIFS. In this case, carrier control is a concept that generally encompasses a physical carrier control mechanism and a virtual carrier control mechanism. Whether the NAV indicates an idle state can be determined by a virtual carrier monitoring mechanism (or virtual carrier monitoring results). Whether CCA indicates unemployment can be determined through a physical carrier control mechanism (or physical carrier control results).

Accordingly, various embodiments of an STA operation for transmitting an UL MU frame (e.g., an UL MU data frame or a short administration / control frame) as a response to a start frame without reflecting (or accounting for) a carrier control result (CCA results and NAV status) described below. For convenience of description, UL MU transmission is generally described, but the present invention is not limited thereto. The content described below can be applied identically to UL SU transmission.

- FIRST OPTION

An STA that has received a trigger frame can verify that the channel (or channel dedicated to the STA) on which the UL MU PPDU (or UL MU frame) will be transmitted is idle by checking (or executing) the CCA for the channel and can then transmit the UL MU PPDU through the appropriate channel. Accordingly, a conflict between signals can be prevented when UL MU PPDU is transmitted.

- SECOND EMBODIMENT

An STA that has received a trigger frame may transmit the UL MU PPDU (or UL MU frame) through a channel (or a channel dedicated to the STA) through which the UL MU PPDU will be transmitted regardless of the CCA result for the corresponding channel. That is, in this embodiment, the STA that has received the start frame can transmit the UL MU PPDUs through the channel, regardless of whether the corresponding channel allocated to the STA is in an idle state or in a busy state. In this case, the STA may receive a trigger frame regardless of the result of the CCA and may transmit UL MU PPDUs after SIFS.

- THIRD IMPLEMENTATION

In the third embodiment, the STA that has received the trigger frame may or may not display the CCA result for the channel on the UL MU PPDU (or UL MU frame) according to a predefined criterion.

For example, the STA that has received the trigger frame can determine whether to display the CCA result for the channel in the UL MU PPDU based on the length of the UL MU PPDU and can transmit the UL MU PPDU. The STA may determine whether the length of the UL MU of the PPDU to be transmitted is a specific threshold PPDU or greater. If the length of the UL MU PPDU is less than the threshold PPDU, the STA may not display the result of the CCA and transmit the UL MU PPDU through the channel dedicated to this.

In contrast, if the length of the UL MU of the PPDU to be transmitted is equal to the threshold value of the PPDU or more, the STA can display the CCA result for the channel allocated to it and transmit the UL MU of the PPDU. Accordingly, if the channel allocated to it is in an idle state based on the results of the CCA, the STA can transmit the UL MU PPDU through the corresponding channel. If the dedicated channel is in a busy state, the STA cannot transmit the UL MU PPDU through the corresponding channel.

In addition to the length of the UL MU PPDU, various criteria can be set to display the result of the CCA. The STA that has received the trigger frame can determine whether to display the CCA result based on predefined criteria and transmit the UL MU PPDU.

In the present embodiment, the trigger frame may correspond to a single trigger frame, a trigger frame aggregated with data, multiple trigger frames, or cascaded trigger frames. In addition, the UL MU frame transmitted as a response to the trigger frame may correspond to a buffer status report, NDP, or PS polling frame.

- FOURTH EMBODIMENT

FIG. 20 is a diagram illustrating a DL / UL MU transmission method in accordance with a fourth embodiment of the present invention.

With reference to FIG. 20, an STA that has received a trigger frame may receive a trigger frame regardless of the CCA result (performed during the PIFS before the trigger frame is received) and may transmit the UL MU frame (or UL MU PPDU) after a specific period (e.g., SIFS) . In this case, the STA may transmit the UL MU frame through the channel allocated to it by the trigger frame. The reason for this is that, as described above, the UL MU frame is transmitted through the same channel as the channel through which the start frame was successfully received, and the likelihood that a short administration / control frame may affect other OBSSs, low because the short administration / management frame is short. In this case, the STA that transmitted the UL MU frame may be an STA indicating that the NAV corresponds to an idle state.

- FIFTH EMBODIMENT

An STA that belongs to STAs that have received a start frame and that indicates that its NAV corresponds to an idle state can transmit a UL MU frame (or UL MU PPDU) based on an energy determination value obtained by performing energy determination (determination) ( or CCA) for a specific period (e.g., SIFS) after the trigger frame is received. For example, if the energy determination value obtained for a particular channel during SIFS after receiving the trigger frame is a specific threshold (or CCA-ED threshold) or less (or CCA corresponds to an idle state), the STA may transmit the UL MU frame through the corresponding channel . In this case, the STA may transmit the UL MU frame in a specific period (eg, SIFS) after receiving the trigger frame.

The specific threshold value may be predetermined, or the AP may transmit the specific threshold value to the STA using a beacon or trigger frame (more specifically, a general information field or a user-specific trigger frame information field).

- SIXTH EMBODIMENT

An STA that belongs to an STA that has received a trigger frame and that indicates that its NAV corresponds to an idle state can transmit a UL MU frame based on the size (or length) of resources allocated to it (e.g., frequency resources, spatial streams, or TXOP ) or the size (or length) of the UL MU frame (or UL MU PPDU, A-MPDU or TXOP) to be transmitted by the trigger frame.

For example, if the size (or length) of the resources allocated to it through the start frame, or the size (or length) of the UL MU frame to be transmitted to it, is a specific threshold value or less, the STA may receive a start frame and may transmit the UL MU- frame after a specific period (for example, SIFS) regardless of the CCA result (performed during the PIFS before the trigger frame is received). Alternatively, if the size (or length) of the resources allocated to it by the start frame, or the size (or length) of the UL MU frame to be transmitted to it exceeds a specific threshold, the STA can transmit the UL MU frame by displaying the result of the CCA (executed during PIFS before the trigger frame is received) in the UL MU frame. In this case, the STA can transmit the UL MU frame through a channel that is in an idle state based on the results of the CCA.

- SEVENT OPTION

The seventh embodiment may correspond to an embodiment in which the fifth and sixth embodiments are combined. More specifically, an STA that belongs to STAs that have received a start frame and that indicates that its NAV corresponds to an idle state can transmit a UL MU frame (UL MU data frame or short administration / management frame) based on resources allocated to it through the trigger frame (or UL MU frame to be transmitted), and the energy determination value obtained over a specific period.

For example, if the size (or length) of resources allocated to it (or the UL MU frame to be transmitted) is equal to or lower than the first threshold value, an STA (i.e., an STA indicating that its NAV corresponds to an idle state) may receive a frame start and then perform the determination of energy (or CCA) on the channel allocated to it for a specific period (for example, SIFS). If the energy determination value obtained by the energy determination is equal to the second threshold value or less, the STA may transmit the UL MU frame through the channel allocated to it after a specific period (eg, SIFS) after the trigger frame is received.

That is, STAs can perform energy determination if the size of the resources allocated to them by the start frame (or UL MU frame to be transmitted) is equal to or lower than the first threshold value, and they can transmit UL MU frames if the energy determination value obtained by performing an energy determination equal to the second threshold value or less.

In this case, the first threshold value may be determined in accordance with various embodiments.

For example, the first threshold value may be set as a “bit value × y-octet block” (where y is a specific positive number) of information transmitted by the AP. For example, if an octet block is 4 octets (y = “4”), and the AP transmits “0111” (ie, bit value = “7”), the STA that received “0111” (ie, bit value = “7”) (i.e., the STA indicates that its NAV corresponds to the idle state), can transmit the UL MU frame regardless of the CCA result (performed during the PIFS before the start frame is received), if the size of the resources allocated to it, equal to 28 octets (= 4 * 7) or less. In this case, the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (e.g., SIFS). In contrast, if the size (or length) of the resources allocated to it exceeds 28 octets (= 4 * 7), the STA can transmit the UL MU frame by displaying the CCA result (performed during the PIFS before the start frame is received) in the UL MU- frame.

As another example, the first threshold value may be set as a duration in accordance with a bit value transmitted by the AP. In this case, the unit of duration may be, for example, μs. For example, if the AP transmits “0111” (ie, bit value = “7”), an STA that belongs to STAs that have adopted “0111” (ie, bit value = “7”), and which indicates that its NAV corresponds to the idle state, it can transmit the UL MU frame regardless of the CCA result (performed during the PIFS before the start frame is received) if the duration of the resources allocated to it or the duration of the UL MU frame (or UL MU PPDU, A -MPDU or TXOP) to be transmitted is 7 μs or less. In this case, the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (e.g., SIFS). On the contrary, if the duration of the resources allocated to it and the duration of the UL MU frame to be transmitted exceeds 7 μs, the STA can transmit the UL MU frame by displaying the CCA result (performed during PIFS before the start frame is received) in UL MU- frame.

As another example, a mapping table may be defined in which the bit transmitted by the AP is mapped to a specific threshold value. In this case, the STA may set a specific threshold value mapped to a bit received from the AP as the first threshold value through a specific mapping table.

For example, if “0111” is mapped to 2000 bytes in a predefined mapping table, an STA that has received “0111” (ie, an STA indicating that NAV corresponds to an idle state) can transmit a UL MU frame regardless of the CCA result ( performed during PIFS before the start frame is received) if the size (or length) of the resources allocated to it or the size (or length) of the UL MU frame to be transmitted is 2000 bytes or less. In this case, the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (e.g., SIFS). In contrast, if the size (or length) of resources allocated to it, or the size (or length) of the UL MU frame to be transmitted exceeds 2000 bytes, the STA can transmit the UL MU frame by displaying the result of the CCA (performed during PIFS before start frame received) per UL MU frame.

As another example, a particular bit sequence may be defined as a specific threshold value. The AP may notify the STA of the first threshold value by transmitting a specific bit sequence. For example, if “0111” was previously defined as 3 μs, the STA that received “0111” transmitted by the AP (ie, the STA indicating that its NAV corresponds to an idle state) may transmit the UL MU frame regardless of the CCA result ( performed during PIFS before the start frame is received) if the duration of the resources allocated to it or the duration of the UL MU frame to be transmitted is 3 μs or less. In this case, the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (e.g., SIFS). In contrast, if the duration of the resources allocated to it or the duration of the UL MU frame to be transmitted exceeds 3 μs, the STA can transmit the UL MU frame by displaying the CCA result (performed during PIFS before the start frame is received) in the UL MU- frame.

In the above examples, transmitting an UL MU frame by displaying (or taking into account) a CCA result may include that each STA transmits an UL MU frame through a channel allocated to it if the channel corresponds to an idle state, taking into account the CCA result for channel, and that each STA does not transmit the UL MU frame through the corresponding channel if the corresponding channel is in a busy state.

The first threshold value information may be transmitted to each STA via a beacon or administration frame for the CCA or dynamic CCA setup. Alternatively, information about the first threshold value may be transmitted to each STA via a beacon or trigger frame (more specifically, general information fields or user-specific trigger frame information fields). Alternatively, information about the first threshold value may be transmitted to each STA using the HE-SIG field (i.e., HE-SIG A or HE-SIG B) of the trigger frame, MAC header, or reserved bits of the service field in the data field.

The second threshold value may be predetermined. Alternatively, the AP can transmit second threshold information to each STA using the HE-SIG field (i.e., HE-SIG A or HE-SIG B) of the trigger frame, MAC header, or reserved bits of the service field in the data field.

- EIGHTH EMBODIMENT

An STA that belongs to STAs that have received a start frame, and which indicates that its NAV corresponds to an idle state, can transmit a UL MU frame regardless of the CCA result (performed during PIFS before the start frame is received) if the ACK policy The UL MU frame (or UL MU PPDU) to be transmitted is not an ACK or a delayed BA. In this case, STAs can receive a trigger frame and then transmit UL MU frames after a specific period (e.g., SIFS).

For example, in the case of an NDP or ACK / BA frame of a short control frame, the AP does not need to separately transmit an ACK indicating that the NDP or ACK / BA frame was normally received. Accordingly, the STA can transmit the UL MU frame regardless of the CCA result if it performs UL MU transmission on an NDP or ACK / BA frame.

- NINTH EMBODIMENT

The ninth embodiment may correspond to an embodiment in which the fifth and eighth embodiments are combined. More specifically, an STA that belongs to STAs that have received a start frame and that indicates that its NAV corresponds to an idle state can transmit a UL MU frame based on an energy determination value (or CCA level) obtained over a specific period (e.g. , SIFS) after the trigger frame is received if the ACK policy of the UL MU frame (or UL MU PPDU) to be transmitted, not transmitted, is an ACK or delayed BA.

For example, an STA may transmit a UL MU frame through a channel allocated to it if the energy determination value for the channel is equal to a specific threshold value or less. In this case, the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (e.g., SIFS). The specific threshold value may be predetermined, or the AP may transmit the specific threshold value to the STA using a beacon or trigger frame (more specifically, a general information field or a user-specific trigger frame information field).

In the case of an NDP or ACK / BA short control frame, the AP does not need to separately transmit an ACK indicating that the NDP or ACK / BA frame was normally received. Accordingly, if the STA performs UL MU transmission on an NDP or ACK / BA frame, it can receive a trigger frame and then transmit the UL MU frame if the energy determination value obtained by performing the energy determination for a specific period is equal to a specific threshold value or less.

- TENTH EMBODIMENT

If the STA that has received the start frame (i.e., an STA indicating that its NAV corresponds to an idle state) transmits only a UL MU data frame, each STA can perform CCA for a specific period (e.g., PIFS or SIFS) before than the trigger frame is received, or during a specific period (eg, SIFS), after the trigger frame is received, and can transmit the UL MU frame through the channel in the idle state based on the results of the CCA.

Alternatively, the STA that has received the trigger frame and the DL MU PPDU may transmit the ACK for the DL MU PPDU via the UL MU PPDU by embedding the ACK in the UL MU data. In this case, the STA may receive the DL MU PPDU and then transmit the UL MU PPDU after a specific period (e.g., SIFS). In this case, as described above, each STA may perform CCA for a specific period (e.g., PIFS or SIFS) before a trigger frame is received, or for a specific period (e.g., SIFS) after a trigger frame is received, and can transmit the corresponding UL MU frame through the channel in the idle state based on CCA results. Alternatively, each STA may transmit a corresponding UL MU PPDU regardless of CCA results. Accordingly, each STA may receive a trigger frame regardless of the result of the CCA and transmit the corresponding UL MU frame after a specific period (e.g., SIFS).

- ELEVENTH IMPLEMENTATION

FIG. 21 is a diagram illustrating an UL MU transmission method according to an eleventh embodiment of the present invention.

With reference to FIG. 21, in the present embodiment, unlike the previous embodiments, the AP can directly instruct the STA whether or not to display the result of the monitoring of the carrier by means of a start frame. In this case, as described above, carrier control is a concept that generally covers both the physical carrier control mechanism and the virtual carrier control mechanism. Whether the NAV indicates an idle state (i.e., NAV state) can be determined by the virtual carrier control mechanism (or virtual carrier control results), or whether the CCA corresponds to an idle state (i.e., the result of the CCA) can be defined by a physical carrier control mechanism (or physical carrier control results). That is, in the present embodiment, the AP can directly instruct each STA whether the STA should display the physical carrier and virtual carrier monitoring results (or CCA result and NAV status) when performing UL transmission of the MU frame via a trigger frame.

In this case, the AP may include a carrier control indicator (CS) (or a CS request indicator) indicating whether to display the carrier control result in a start frame and transmit a start frame to each STA. For example, the AP may include a CS indicator indicating whether to display the carrier control result (or whether to display the CCA result and NAV status) in the HE-SIG field (i.e., HE-SIG field A, B or C), MAC is a header or a Common Information field of a launch frame or a user-specific information field (Per User Info 1 ~ N) and can transmit a launch frame to each STA.

In this case, the CS pointer may have a size of z bits. In this case, z may be a specific positive number. For example, a 1-bit CS indicator indicating whether to include a carrier monitoring result may be included in a general information field or a user-specific field of a trigger frame information and then transmitted.

In this case, if the AP sets the CS pointer to “1” (or “0”) and transmits the CS pointer (ie, if the CS pointer does not indicate a CCA result display and / or NAV state (or if the CS pointer is “off” )), The STA that has received the appropriate trigger frame can transmit the UL MU frame (or UL MU PPDU) (see FIG. 21 (a)) regardless of the NAV status and / or CCA result. More specifically, an STA that has received an appropriate trigger frame i) can transmit an UL MU frame (i.e., only the NAV status is displayed) regardless of the CCA result, if the NAV indicates an idle state, ii) can transmit an UL MU frame (t ie, only the CCA result is displayed) regardless of the NAV state if the CCA corresponds to the idle state, and iii) can transmit the UL MU frame (the NAV state and CCA result are not displayed) regardless of the NAV state and CCA result. In this case, the STA may receive a trigger frame and then transmit the corresponding UL MU frame after a specific period (eg, SIFS).

Alternatively, if the AP sets the CS indicator to “0” (or “1”) and transmits the CS indicator (ie, if the CS indicator indicates the display of the CCA result and the NAV status (if the CS indicator is “on”)), an STA that received an appropriate trigger frame, can display the result of the carrier monitoring and can transmit the UL MU frame (or UL MU PPDU) through a channel (e.g., a secondary channel) in an idle state (i.e., if a particular channel corresponds to an idle state in case of dynamic allocation , and if all channels are idle in beam of static distribution). More specifically, the STA that has received the corresponding trigger frame may transmit the UL MU frame through the corresponding channel (see FIG. 21 (b)) if the NAV indicates an idle state and the CCA corresponds to an idle state as a result of carrier monitoring for the channel.

If the CS indicator is included in the general information field, the general information field may include one CS indicator that is common to the STAs receiving the trigger frame, or may include all CS indicators for the corresponding STAs. If the CS indicator is included in the user-specific information frame of the start frame, the CS indicator for each STA may be indicated in the user-specific information field for each STA. For example, a first user-specific information field for STA 1 may include a CS indicator for STA 1, and a CS indicator for STA 2 may be included in a second user-specific information field for STA 2.

In addition, similarly to the above, the AP can directly instruct the STA whether to perform carrier monitoring by means of a start frame. Accordingly, the AP may include a CS progress indicator instructing each STA whether to perform carrier monitoring before transmitting the UL MU frame to the start frame and transmit the start frame. In this case, the CS progress bar may have a size of z bits. The CS progress bar may be included in the HE-SIG field (i.e., the HE-SIG field A, B or C), the MAC header or the general information frame of the trigger frame, or the user-specific information field (Per User Info 1 ~ N) and then transmitted. If the received CS progress bar indicates carrier monitoring, the STA may perform carrier monitoring before transmitting the UL MU frame and then transmit the UL MU frame if the channel corresponds to an idle state. In contrast, if the received CS progress bar does not indicate carrier monitoring, the STA may transmit the UL MU frame without performing carrier monitoring before transmitting the UL MU frame.

In this case, the STA may not redundantly control the same carrier for the channel within the same TXOP. FIG. 22 is a diagram illustrating an UL MU transmission method in which carrier monitoring is not redundantly performed.

With reference to FIG. 22, it can be assumed that STA 2 performs carrier monitoring on a particular channel within the same TXOP and then transmits the first UL MU frame through the corresponding channel. In this case, the STA 2 may not redundantly monitor the same carrier before transmitting the second UL MU frame through the same channel. The reason for this is that redundant carrier monitoring for the same channel is not required because STA 2 successfully transmitted the first UL MU frame through a channel that corresponds to an idle state as a result of performing carrier monitoring in the previous step.

As described above with reference to FIG. 18, if DL / UL MU PPDUs are transmitted using a cascaded method within the same TXOP, the interval between DL MU PPDUs and UL MU PPDUs can be defined as SIFS. In this case, it is difficult to check the CCA during the PIFS as in the existing RTS / CTS frame procedure and to apply the method for transmitting the UL MU PPDU without any response to respond to the trigger frame transmitted to the DL MU PPDU, which is not the first within this TXOP either changes. The reason for this is because the time (i.e. SIFS) between the DL MU PPDU and UL MU PPDU is shorter than the time (i.e. PIFS) required to verify the CCA in the RTS / CTS frame procedure (i.e. PIFS> SIFS). Accordingly, in this case, the CCA procedure can be redefined. The response procedure after transmitting the trigger frame may be associated with “information indicating that the corresponding PPDU is a cascading structure” included in the trigger frame.

FIG. 23 is a diagram related to a method for performing CCA in accordance with an embodiment of the present invention.

With reference to FIG. 23 (a) if DL / UL MU PPDUs are transmitted in a cascaded manner, an STA that belongs to STAs that have received a start frame initiating UL transmission of the MU frame, and which indicates that its NAV corresponds to an idle state, may determine energy (or CCA) for a specific period (for example, SIFS) before receiving the trigger frame transmitted by the DL MU PPDU (transmitted after the first or second within the same TXOP). If the energy determination value is a specific threshold value or less (if the CCA corresponds to an idle state), the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (eg, SIFS).

With reference to FIG. 23 (b) if DL / UL MU PPDUs are transmitted in a cascaded manner, an STA that belongs to STAs that have received a start frame initiating UL transmission of the MU frame, and which indicates that its NAV corresponds to an idle state, may determine energy (or CCA) for a specific period (eg, SIFS) after receiving a trigger frame transmitted by the PPU DU MU (transmitted after the first or second within the same TXOP). If the energy determination value is a specific threshold value or less (if the CCA corresponds to an idle state), the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (eg, SIFS).

In this case, the specific threshold value may be predetermined, and the AP may transmit the specific threshold value to the STA via a beacon or trigger frame (more specifically, a general information field or a user-specific trigger frame information field).

Alternatively, unlike the aforementioned embodiments, the STA may receive a trigger frame regardless of the result of the CCA and then transmit the UL MU frame after a specific period (e.g., SIFS).

If multiple trigger frames are transmitted within the same TXOP, the AP may not be required to perform EDCA, etc., as in the existing method, to transmit a trigger frame. In this case, a specific interval (for example, SIFS) may be set between the frame transmitted by the AP or STA and the start frame transmitted by the AP. In this case, the above method for transmitting DL / UL MU PPDUs using the cascaded method can be applied in a similar manner.

In addition to the above embodiment, a different trigger response procedure may be applied depending on the type of frame (or content) in which the STA that has received the trigger frame performs UL MU transmission.

METHOD FOR DISPLAYING CCA RESULT

A method for displaying a CCA result using some method may be predefined depending on the format of the trigger frame received by the STA. For example, the STA may determine that the CCA result should be displayed using some method and determine whether to transmit the UL MU frame depending on whether the received trigger frame is a single trigger frame, a trigger frame aggregated with data, multiple trigger frames or cascading start frame.

More specifically, for example, a method for displaying a CCA result may be determined depending on whether a trigger frame is aggregated with data and transmitted. For example, if the trigger frame is not aggregated with data and not transmitted, the trigger frame can be pre-configured so that the result of the CCA performed during the “PIFS” before the trigger frame is received is mapped to the trigger frame and the UL MU frame is transmitted. if the channel corresponds to an idle state. In addition, if the trigger frame is aggregated with data and transmitted, the trigger frame can be pre-configured so that the result of the CCA performed during the “SIFS”, after the trigger frame is received, is displayed in the trigger frame, and the UL MU frame is transmitted. if the channel corresponds to an idle state.

Alternatively, if the trigger frame is aggregated with data and transmitted, the trigger frame may be pre-configured so that the result of the CCA executed during the PIFS before the trigger frame is received and the result of the CCA executed during the SIFS after the trigger frame is received, can be mapped to a trigger frame, and the UL MU frame is transmitted. In this case, the STA transmits the UL MU frame if the channel corresponds to the idle state as a result of the CCA performed during the PIFS and SIFS.

As another example, a method for displaying a CCA result may be determined depending on whether the trigger frame is a single trigger frame or a cascaded trigger frame.

For example, if the trigger frame is a single trigger frame, the trigger frame may be preconfigured so that the result of the CCA performed during “PIFS” before the trigger frame is received is mapped to the trigger frame, the UL MU frame is transmitted if the channel corresponds to an idle state . In addition, if the trigger frame is a cascaded trigger frame, the trigger frame may be pre-configured so that the result of the CCA performed during “SIFS” after the trigger frame is received is mapped to the trigger frame and the UL MU frame is transmitted if the channel corresponds to an idle state.

Alternatively, a single trigger frame may be preconfigured so that the result of the CCA performed during the “PIFS” before the trigger frame is received is displayed, and the UL MU frame is transmitted if the channel corresponds to an idle state. In addition, the cascading trigger frame may be preconfigured so that the CCA result is not displayed (i.e., regardless of whether the channel is in an idle state), and the UL MU frame is transmitted for a specific period (e.g., SIFS), after the start frame is accepted. Alternatively, the cascading trigger frame may be preconfigured so that the UL MU frame is transmitted if the channel corresponds to an idle state as a result of CCA performed for a specific period (e.g., PIFS) before the trigger frame is transmitted in the case of a trigger frame that transmitted first in one TXOP. In addition, a trigger frame (or DL MU frame, UL MU frame, DL MU PPDU or UL MU PPDU) transmitted after the second may be transmitted without displaying a CCA result.

In addition to the above embodiments, a method for displaying a CCA result depending on the UL format of the trigger MU frame transmitted as a response to the trigger frame may be pre-configured.

METHOD FOR INDICATING PERFORMANCE POSITION CCA

The AP may directly indicate the position (or time) at which the CCA (or energy determination) of the STA is performed, by means of a start frame or a beacon frame and the like. That is, the AP can directly indicate whether the STA should perform CCA (or energy determination) for a specific period (eg, PIFS or SIFS) “before” receiving a trigger frame or perform CCA (or energy determination) for a specific period (eg, SIFS ) “After” receiving the trigger frame to transmit the UL MU frame. As a result, if the CCA result at the position (or at the time) indicated by the AP corresponds to an idle state (or if the energy determination value is a specific threshold value or less), the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (e.g. SIFS).

In this case, the AP may transmit a pointer indicating the time when the CCA is executed to the STA by means of a start frame. Relevant information may be included in the general information field or the user-specific information field of the trigger frame and then transmitted.

For example, the AP may indicate a CCA execution position to be displayed by the STA using a 1-bit pointer. If the AP sets the pointer to “1” and passes the pointer to the STA, the STA may perform CCA (or energy determination) for a specific period (eg, PIFS or SIFS) before the trigger frame is received. If the CCA corresponds to an idle state (or if the energy determination value is equal to a specific threshold or less) as a result of performing the CCA, the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (for example, SIFS). Alternatively, if the AP sets the pointer to “0” and passes the pointer to the STA, the STA may perform CCA (or energy determination) for a specific period (eg, SIFS) after the trigger frame is received. If the CCA corresponds to an idle state (or if the energy determination value is equal to a specific threshold or less) as a result of performing the CCA, the STA may receive a trigger frame and then transmit the UL MU frame after a specific period (for example, SIFS).

In this case, the AP may optionally transmit the CCA indicator described in the eleventh embodiment to the STA together with a pointer indicating the time when the CCA is executed.

In a manner similar to that described above, the AP may indicate the position (or time) of the execution of the CCA to be displayed before the STA transmits the UL MU frame. That is, the AP can directly indicate whether the STA should display the CCA (or energy determination) performed during a specific period (eg, PIFS or SIFS) “before” the reception of the trigger frame, or whether the STA should display the CCA (or energy determination) in during a specific period (for example, SIFS) “after” receiving the trigger frame. As a result, if the CCA at the position (or at the time) indicated by the AP corresponds to an idle state (or if the energy determination value is equal to a specific threshold value or less), the STA may receive a trigger frame and then transmit the UL MU frame after a specific period ( e.g. SIFS).

INTERVAL BETWEEN START-UP FRAME AND UL MU-FRAME

The AP may determine the interval between periods in which the trigger frame and the UL MU frame are transmitted as specific values, and may directly indicate which one of the specific values will be used by the trigger frame. An STA that has received such an indication may transmit a UL MU frame after a specified interval after receiving a trigger frame. For example, an AP may indicate one of the SIFS and the newly defined SSIFS value (= D1 (aRxPHYDelay) + M1 (aMACProcessingDelay) + CCADel (aCCATime – D1) + RX / TX (aRxTxTurnaroundTime)) as the interval between the periods in which the start frame and UL MU frame.

If only a single trigger frame is transmitted, the AP may transmit a pointer instructing the STA to receive the trigger frame and then transmit the UL MU frame after the SIFS to the STA via the trigger frame. After receiving the pointer, the STA may receive a trigger frame and then transmit the UL MU frame after SIFS. In addition, if a cascaded trigger frame is transmitted, the AP may transmit a pointer instructing the STA to receive the trigger frame and then transmit the UL MU frame after SSIFS to the STA via the trigger frame. After receiving the pointer, the STA may receive a trigger frame and then transmit the UL MU frame after SSIFS.

The AP may randomly set such a pointer and transmit a pointer, or may set a period for a pointer and transmit a pointer.

The STA may apply a predetermined interval depending on the format of the received trigger frame. For example, if a single trigger frame is received, the STA may set the interval between the trigger frame and the UL MU frame as SIFS. In other cases (for example, if a cascading trigger frame is received), the STA may set the interval between the trigger frame and the UL MU frame as SSIFS.

In the above embodiments, the interval between transmitting the trigger frame and transmitting the UL MU frame, as well as whether to display the result of the CCA, can be set independently.

METHOD FOR TRANSFERRING UL MU-FRAME

If, as a result of the CCA, a particular resource channel (or channels) allocated by the trigger frame is in an idle state and the remaining channels are in a busy state, the STA can transmit the UL MU frame through a specific channel that belongs to the resources allocated through the AP, and which is in a state of unemployment. That is, the STA may transmit the UL MU frame using an unallocated resource having a size equal to or less than the size of the allocated resources. For example, if the 20 MHz channel of the 40 MHz channel allocated to the STA is in an idle state and the remaining 20 MHz channel is in the idle state, the STA can transmit the UL MU frame using the 20 MHz channel that is in the idle state.

In this case, the STA may include information about the channel through which the UL MU frame was transmitted to the HE-SIG A, HE-SIG B or HE-SIG C UL MU frame in the form of a bitmap and transmit the UL MU frame. An AP that has received the UL MU frame may know that the STA has transmitted the UL MU frame using some channel, and may thus receive the UL MU frame transmitted by the STA.

FIG. 24 is a flowchart illustrating a method for transmitting STA data in accordance with an embodiment of the present invention. The above described embodiments may likewise apply to the flowchart of FIG. 24. Accordingly, a redundant description is omitted.

With reference to FIG. 24, the STA may perform carrier monitoring in step S2401. More specifically, the STA may perform carrier monitoring during PIFS before it receives a trigger frame from the AP.

Then, the STA may receive a start frame in step S2402. In this case, the trigger frame may include information for the UL MU transmission and a carrier control indicator indicating whether to display the result of the carrier control. In addition, the trigger frame may be a single trigger frame, a trigger frame aggregated with data, multiple trigger frames, or a cascaded trigger frame.

Then, the STA may transmit the UL MU frame in step S2403. More specifically, the STA may transmit the UL MU frame based on information for the UL MU transmission that was included in the received trigger frame. In this case, if the carrier control indicator included in the start frame indicates the display of the carrier control result, the STA may transmit the UL MU frame through the channel based on the carrier control result performed in step S2401. Alternatively, if the carrier control indicator does not indicate the display of the carrier control result, the STA may transmit the UL MU frame via the channel regardless of the carrier control result of step S2401.

In addition, step S2401 may be performed after step S2402. Accordingly, the STA may perform carrier monitoring for a specific period (eg, SIFS) after receiving a trigger frame. Then, the operation performed in step S2303 is the same as that described above.

FIG. 25 is a block diagram of each STA device in accordance with an embodiment of the present invention.

With reference to FIG. 25, the STA 2510 may include a memory 2512, a processor 2511, and a radio frequency (RF) unit 2513. In addition, as described above, the STA is a NOT STA device and may be an AP or non-AP STA.

The RF unit 2513 is connected to the processor 2511 and can transmit / receive radio signals. The RF unit 2513 can upconvert data received from the processor 2511 into a transmit / receive range and can transmit a signal.

The processor 2511 is connected to the RF unit 2513 and implements the physical layer and / or MAC layer in accordance with the IEEE 802.11 system. The processor 2511 may be configured to perform operations in accordance with various embodiments of the present invention based on the drawings and description. In addition, a module for implementing operations of the STA 2510 in accordance with various embodiments of the present invention may be stored in memory 2512 and may be executed by processor 2511.

The memory 2512 is connected to the processor 2511 and stores various segments of information for execution by the processor 2511. The memory 2512 may be included in the processor 2511 or installed outside the processor 2511 and may be connected to the processor 2511 by known means.

In addition, the STA 2510 may include a single antenna or multiple antennas.

A detailed configuration of the STA 2510 device according to FIG. 25 may be implemented by independently applying the objects described in various embodiments of the present invention, or by applying two or more of the various embodiments simultaneously.

Although the drawings are separated and described for convenience of description, the embodiments described with reference to the drawings may be combined to implement a new embodiment. In addition, the configurations and methods of the above embodiments are not limited and apply to the device as described above, and embodiments can be created by selectively combining some or all of the embodiments so that they are modified in various ways.

Furthermore, although some embodiments have been illustrated and described above, the present specification is not limited to the above specific embodiments, and one skilled in the art to which this specification relates can modify the present invention in various ways without departing from the gist of the claims. Such modified embodiments should not be individually interpreted from the technical nature or perspective of this specification.

Various embodiments have been described in exemplary form for implementing the present invention.

INDUSTRIAL APPLICABILITY

Although the methods for transmitting / receiving data in wireless communication systems in accordance with embodiments of the present invention have been described based on an example in which the methods are applied to IEEE 802.11 systems, they can also be applied to various wireless communication systems in addition to IEEE 802.11 systems.

Claims (35)

1. A method for a device to perform a station, STA, multi-user, MU, uplink transmission, UL, in a wireless communication system, the method comprising the steps of: receiving a trigger frame containing information for UL MU transmission and a pointer indicating whether or not to perform carrier monitoring; moreover, the method further comprises stages in which: if the pointer indicates the performance of the monitoring of the carrier, perform monitoring of the carrier on a particular channel, take into account the result of the monitoring of the carrier and transmit the UL MU frame in response to the start frame, if the pointer indicates carrier control failure, transmit an UL MU frame in response to a start frame without carrier control. 2. The method of claim 1, wherein performing the carrier control comprises performing energy determination in the corresponding channel to check the channel status estimate, CCA, for a short frame interval, SIFS, after receiving the trigger frame. 3. The method according to claim 1, in which the accounting of the result of the control of the carrier includes accounting for both CCA and the distribution network vector, NAV. 4. The method according to p. 3, in which the accounting of the result of the control of the carrier includes: if a particular channel is considered unoccupied as a result of CCA and NAV accounting, then an UL MU frame is transmitted through the specific channel and if a particular channel is considered busy as a result of CCA and NAV accounting, then the UL MU frame is not transmitted through the specific channel. 5. The method of claim 4, wherein the particular channel corresponds to a channel dedicated to the STA. 6. The method according to p. 4, in which a particular channel is considered idle when the CCA and NAV indicate an idle state, and in which a particular channel is considered busy when at least one of the CCA or NAV indicates a busy state. 7. The method of claim 6, wherein the NAV indicates an idle state when the NAV count value is zero or the NAV count value is not zero, but the out-of-band signaling TA of the trigger frame is the same as the address of the transmission capability holder, TXOP. 8. The method of claim 6, wherein the CCA indicates an idle state when the energy level determined by determining the energy does not exceed a threshold corresponding to a predetermined power level, and the CCA indicates a busy state when the energy level determined by determining the energy exceeds threshold corresponding to a preset power level. 9. The method of claim 1, further comprising the step of: if the access point, the AP transmitting the start frame, is the TXOP holder setting the NAV for the STAs, transmit the UL MU frame without considering the NAV. 10. The method of claim 1, wherein the pointer is included in the general information field of the trigger frame. 11. A station device, an STA, performing multi-user, MU, uplink transmission, UL, in a wireless communication system, the STA device comprising: radio frequency, RF, a unit configured to transmit / receive radio signals, and a processor configured to control the RF unit, moreover, the processor is configured to: receive a trigger frame containing information for UL MU transmission and a pointer indicating whether or not to perform carrier monitoring, moreover, the processor is additionally configured to: if the pointer indicates the implementation of the monitoring of the carrier, then carry out the monitoring of the carrier on a particular channel, take into account the result of the monitoring of the carrier and transmit UL MU frame in response to the start frame if the pointer indicates carrier control failure, transmit the UL MU frame in response to the start frame without carrier control. 12. The STA device according to claim 11, wherein the processor is further configured to perform energy determination in the corresponding channel to check the channel status estimate, CCA, for a short frame interval, SIFS, after receiving the trigger frame. 13. The STA device according to claim 11, wherein the processor is further configured to take into account the CCA and the network distribution vector, NAV, when taking into account the result of the carrier control. 14. The STA device according to claim 11, wherein the processor is further configured to: if a particular channel is considered unoccupied as a result of CCA and NAV accounting, transmit the UL MU frame through the specific channel, and if a particular channel is considered busy as the result of CCA and NAV accounting, do not transmit the UL MU frame through the specific channel. 15. The method according to p. 14, in which a particular channel is considered idle when the CCA and NAV indicate an idle state, and in which a particular channel is considered busy when at least one of the CCA or NAV indicates a busy state.

Images