WO2016125983A1 - Procédé et dispositif d'émission de données dans un système de communications sans fil - Google Patents

Procédé et dispositif d'émission de données dans un système de communications sans fil Download PDF

Info

Publication number
WO2016125983A1
WO2016125983A1 PCT/KR2015/011142 KR2015011142W WO2016125983A1 WO 2016125983 A1 WO2016125983 A1 WO 2016125983A1 KR 2015011142 W KR2015011142 W KR 2015011142W WO 2016125983 A1 WO2016125983 A1 WO 2016125983A1
Authority
WO
WIPO (PCT)
Prior art keywords
sta
field
eim
pip
information
Prior art date
Application number
PCT/KR2015/011142
Other languages
English (en)
Korean (ko)
Inventor
김진민
이욱봉
김정기
최진수
Original Assignee
엘지전자(주)
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 엘지전자(주) filed Critical 엘지전자(주)
Publication of WO2016125983A1 publication Critical patent/WO2016125983A1/fr

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W52/00—Power management, e.g. TPC [Transmission Power Control], power saving or power classes
    • H04W52/04—TPC
    • H04W52/18—TPC being performed according to specific parameters
    • H04W52/24—TPC being performed according to specific parameters using SIR [Signal to Interference Ratio] or other wireless path parameters
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W74/00—Wireless channel access
    • H04W74/08—Non-scheduled access, e.g. ALOHA
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]

Definitions

  • the present invention relates to a wireless communication system, and more particularly, to an endurable interference margin (EIM) of a neighbor STA and a predicted interference power (PIP) for a neighbor STA in a wireless local area network (LAN) communication system.
  • EIM endurable interference margin
  • PIP predicted interference power
  • Wi-Fi is a Wireless Local Area Network (WLAN) technology that allows devices to access the Internet in the 2.4 GHz, 5 GHz, or 6 GHz frequency bands.
  • WLAN Wireless Local Area Network
  • WLANs are based on the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard.
  • IEEE 802.11 The Wireless Next Generation Standing Committee (WNG SC) of IEEE 802.11 is an ad hoc committee that considers the next generation wireless local area network (WLAN) in the medium to long term.
  • WNG SC Wireless Next Generation Standing Committee
  • IEEE 802.11n aims to increase the speed and reliability of networks and to extend the operating range of wireless networks. More specifically, IEEE 802.11n supports High Throughput (HT), which provides up to 600 Mbps data rate, and also supports both transmitter and receiver to minimize transmission errors and optimize data rates. It is based on Multiple Inputs and Multiple Outputs (MIMO) technology using multiple antennas.
  • HT High Throughput
  • MIMO Multiple Inputs and Multiple Outputs
  • IEEE 802.11ac supports data processing speeds of 1 Gbps and higher via 80 MHz bandwidth transmission and / or higher bandwidth transmission (eg 200 MHz) and operates primarily in the 5 GHz band.
  • IEEE 802.11ax often discussed in the next-generation WLAN study group called IEEE 802.11ax or High Efficiency (HEW) WLAN, is: 1) 802.11 physical layer and MAC in the 2.4 GHz and 5 GHz bands. (medium access control) layer enhancement, 2) spectral efficiency and area throughput improvement, 3) environments with interference sources, dense heterogeneous network environments, and high user loads. Such as improving performance in real indoor environments and outdoor environments, such as the environment.
  • IEEE 802.11ax High Efficiency
  • IEEE 802.11ax Scenarios considered mainly in IEEE 802.11ax are dense environments with many access points (APs) and stations (STAs), and IEEE 802.11ax discusses spectral efficiency and area throughput improvement in such a situation. . In particular, there is an interest in improving the performance of the indoor environment as well as the outdoor environment, which is not much considered in the existing WLAN.
  • IEEE 802.11ax we are interested in scenarios such as wireless office, smart home, stadium, hotspot, and building / apartment. There is a discussion about improving system performance in dense environments with many STAs.
  • IEEE 802.11ax improves system performance in outdoor basic service set (OBSS) environment, outdoor environment performance, and cellular offloading rather than single link performance in one basic service set (BSS). Discussion is expected to be active.
  • the directionality of IEEE 802.11ax means that next-generation WLANs will increasingly have a technology range similar to that of mobile communication. Considering the situation where mobile communication and WLAN technology are recently discussed in the small cell and direct-to-direct communication area, the technical and business of next-generation WLAN and mobile communication based on IEEE 802.11ax Convergence is expected to become more active.
  • the CCA was performed according to the same CCA level set by BSS. Therefore, spatial bandwidth reuse efficiency between BSSs is very low. This is because STAs belonging to different BSSs cannot detect and transmit signals by occupying the channel even if they can simultaneously transmit according to communication environment and channel quality.
  • the present invention is to propose a method for adjusting the CCA level and a data method accordingly, which can improve the spatial reuse efficiency of bandwidth.
  • a data transmission method of a STA (Station) of a wireless LAN (WLAN) system includes: receiving a signal from a first STA of a first basic service set (BSS); Acquiring endurable interference margin (EIM) information and transmission power information of the first STA from the received signal, wherein the EIM information indicates an amount of interference allowable by the first STA, and the transmission power information is The acquiring step of indicating a transmit power of a first STA; Acquiring a predicted interference power (PIP) using transmission power information of the first STA, wherein the PIP indicates an amount of interference with respect to the first STA when the STA transmits a signal; Comparing the EIM and the PIP and adjusting a CCA level or adjusting a transmission power according to the comparison result.
  • BSS basic service set
  • EIM endurable interference margin
  • the EIM information and the transmission power information may be included in the physical preamble of the received signal.
  • the obtaining of the PIP may include a path loss using transmission power of the first STA and power of a signal received from the first STA.
  • the method may further include acquiring the PIP using the path loss and the transmit power of the STA.
  • adjusting the CCA level according to the comparison result of the EIM and the PIP, the CCA level is increased when the EIM is larger than the PIP, the EIM is If smaller than the PIP may further include maintaining or decreasing the CCA level.
  • the step of adjusting the transmission power according to the comparison result of the EIM and the PIP, if the EIM is larger than the PIP, increase the transmission power or the EIM If it is smaller than the PIP may further include reducing the transmission power.
  • the CCA level may be increased or decreased between a predefined minimum value and a maximum value.
  • an STA (Station) device of a wireless LAN (WLAN) system according to an embodiment of the present invention, the RF (Radio Frequency) unit for transmitting and receiving a radio signal; And a processor for controlling the RF unit, wherein the processor is configured to receive a signal from a first STA device of a first basic service set (BSS) and to receive an endurable interference margin (EIM) of the first STA device from the received signal. ) Information and transmit power information, obtain a predicted interference power (PIP) using the transmit power information of the first STA device, compare the EIM and the PIP, and adjust a CCA level according to the comparison result.
  • BSS basic service set
  • EIM endurable interference margin
  • Transmit power may be adjusted, the EIM information indicates the amount of interference allowable by the first STA device, the transmit power information indicates the transmit power of the first STA device, and the PIP is a signal of the STA
  • the transmission may indicate the amount of interference with respect to the first STA device.
  • the EIM information and the transmit power information may be included in a physical preamble of a received signal.
  • the processor acquires a path loss using the transmission power of the first STA device and the power of the signal received from the first STA device,
  • the PIP may be obtained using path loss and transmit power of the STA.
  • the processor may increase the CCA level when the EIM is larger than the PIP, and maintain or decrease the CCA level when the EIM is smaller than the PIP.
  • the processor may increase the transmission power when the EIM is larger than the PIP or decrease the transmission power when the EIM is smaller than the PIP.
  • the CCA level may be increased or decreased between a predefined minimum value and a maximum value.
  • the first BSS is a BSS different from the BSS to which the STA device belongs, and the first BSS may be an Overlapping Basic Service Set (OBSS) with respect to the BSS.
  • OBSS Overlapping Basic Service Set
  • the CCA level can be adjusted according to the counting number of the ACK frame. Accordingly, even adjacent STAs may perform signal transmission according to respective channel / transmit / receive power states, thereby improving bandwidth usage efficiency. In addition, spatial bandwidth reuse efficiency between STAs belonging to the OBSS may be improved. Since the adjustment of the CCA level is not fixed but is performed dynamically, the communication performance loss may be minimized by actively coping with the state change of the STAs and the channel environment change between the STAs.
  • the performance of the system can be minimized by performing the dynamic CCA, not only to increase the space efficiency but also to consider the quality and margin of the device that may become a victim in the interference environment. have.
  • the CCA level is adjusted in consideration of the interference margin of neighboring STAs, the space efficiency can be maximized within the system throughput.
  • the power consumption of the STA device may be reduced while lowering the interference to the neighboring STAs.
  • FIG. 1 is a diagram illustrating an example of an IEEE 802.11 system to which the present invention can be applied.
  • FIG. 2 is a diagram illustrating a structure of a layer architecture of an IEEE 802.11 system to which the present invention may be applied.
  • FIG. 3 illustrates a non-HT format PPDU and a HT format PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention can be applied.
  • FIG. 5 is a diagram illustrating a constellation for distinguishing a format of a PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 6 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • FIG. 7 is a diagram illustrating a Frame Control field in a MAC frame in a wireless communication system to which the present invention can be applied.
  • FIG. 8 illustrates the VHT format of the HT Control field in a wireless communication system to which the present invention can be applied.
  • FIG. 9 is a diagram for explaining an arbitrary backoff period and a frame transmission procedure in a wireless communication system to which the present invention can be applied.
  • FIG. 10 is a diagram illustrating an IFS relationship in a wireless communication system to which the present invention can be applied.
  • FIG. 11 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.
  • HE 12 illustrates a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • FIG. 13 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • FIG. 14 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • FIG. 15 is a diagram illustrating a HE format PPDU according to an embodiment of the present invention.
  • 16 is a conceptual diagram illustrating a method of performing CCA according to an embodiment of the present invention.
  • FIG. 17 illustrates a dynamic CCA application environment according to an embodiment of the present invention.
  • FIG. 18 illustrates a STA apparatus according to an embodiment of the present invention.
  • FIG. 19 illustrates a data transmission method of an STA apparatus according to an embodiment of the present invention.
  • CDMA code division multiple access
  • FDMA frequency division multiple access
  • TDMA time division multiple access
  • OFDMA orthogonal frequency division multiple access
  • SC-FDMA single carrier frequency division multiple access
  • GSM global system for mobile communications
  • GPRS general packet radio service
  • EDGE enhanced data rates for GSM evolution
  • OFDMA can be implemented with wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.20 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like.
  • UTRA is part of a universal mobile telecommunications system (UMTS).
  • 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink.
  • LTE-A evolution of 3GPP LTE.
  • Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802, 3GPP and 3GPP2. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.
  • FIG. 1 is a diagram illustrating an example of an IEEE 802.11 system to which the present invention can be applied.
  • the IEEE 802.11 structure may be composed of a plurality of components, and a wireless communication system supporting a station (STA) station mobility that is transparent to a higher layer may be provided by their interaction.
  • STA station
  • a basic service set (BSS) may correspond to a basic building block in an IEEE 802.11 system.
  • FIG. 1 there are three BSSs (BSS 1 to BSS 3) and two STAs are included as members of each BSS (STA 1 and STA 2 are included in BSS 1, and STA 3 and STA 4 are BSS 2. Included in, and STA 5 and STA 6 are included in BSS 3) by way of example.
  • an ellipse representing a BSS may be understood to represent a coverage area where STAs included in the BSS maintain communication. This area may be referred to as a basic service area (BSA).
  • BSA basic service area
  • the most basic type of BSS in an IEEE 802.11 system is an independent BSS (IBSS).
  • the IBSS may have a minimal form consisting of only two STAs.
  • BSS 3 of FIG. 1, which is the simplest form and other components are omitted, may correspond to a representative example of the IBSS. This configuration is possible when STAs can communicate directly.
  • this type of LAN may not be configured in advance, but may be configured when a LAN is required, which may be referred to as an ad-hoc network.
  • the membership of the STA in the BSS may be dynamically changed by turning the STA on or off, the STA entering or exiting the BSS region, or the like.
  • the STA may join the BSS using a synchronization process.
  • the STA In order to access all services of the BSS infrastructure, the STA must be associated with the BSS. This association may be set up dynamically and may include the use of a Distribution System Service (DSS).
  • DSS Distribution System Service
  • the direct STA-to-STA distance in an 802.11 system may be limited by physical layer (PHY) performance. In some cases, this distance limit may be sufficient, but in some cases, communication between STAs over longer distances may be required.
  • a distribution system (DS) may be configured to support extended coverage.
  • the DS refers to a structure in which BSSs are interconnected. Specifically, instead of the BSS independently as shown in FIG. 1, the BSS may exist as an extended type component of a network composed of a plurality of BSSs.
  • DS is a logical concept and can be specified by the characteristics of the Distribution System Medium (DSM).
  • DSM Distribution System Medium
  • the IEEE 802.11 standard logically distinguishes between wireless medium (WM) and distribution system medium (DSM). Each logical medium is used for a different purpose and is used by different components.
  • the definition of the IEEE 802.11 standard does not limit these media to the same or to different ones.
  • the plurality of media are logically different, and thus the flexibility of the structure of the IEEE 802.11 system (DS structure or other network structure) can be described. That is, the IEEE 802.11 system structure can be implemented in various ways, the corresponding system structure can be specified independently by the physical characteristics of each implementation.
  • the DS may support mobile devices by providing seamless integration of multiple BSSs and providing logical services for handling addresses to destinations.
  • the AP means an entity that enables access to the DS through the WM to the associated STAs and has STA functionality. Data movement between the BSS and the DS may be performed through the AP.
  • STA 2 and STA 3 illustrated in FIG. 1 have a functionality of STA, and provide a function of allowing associated STAs STA 1 and STA 4 to access the DS.
  • all APs basically correspond to STAs, all APs are addressable entities.
  • the address used by the AP for communication on the WM and the address used by the AP for communication on the DSM need not necessarily be the same.
  • Data transmitted from one of the STAs associated with an AP to the STA address of that AP may always be received at an uncontrolled port and processed by an IEEE 802.1X port access entity.
  • transmission data (or frame) may be transmitted to the DS.
  • a wireless network of arbitrary size and complexity may be composed of DS and BSSs.
  • this type of network is referred to as an extended service set (ESS) network.
  • the ESS may correspond to a set of BSSs connected to one DS. However, the ESS does not include a DS.
  • the ESS network is characterized by what appears to be an IBSS network at the Logical Link Control (LLC) layer. STAs included in the ESS may communicate with each other, and mobile STAs may move from one BSS to another BSS (within the same ESS) transparently to the LLC.
  • LLC Logical Link Control
  • BSSs can be partially overlapped, which is the form generally used to provide continuous coverage.
  • the BSSs may not be physically connected, and logically there is no limit to the distance between the BSSs.
  • the BSSs can be located at the same physical location, which can be used to provide redundancy.
  • one (or more) IBSS or ESS networks may be physically present in the same space as one or more ESS networks. This may be necessary if the ad-hoc network is operating at the location of the ESS network, if the IEEE 802.11 networks are physically overlapped by different organizations, or if two or more different access and security policies are required at the same location. It may correspond to an ESS network type in a case.
  • an STA is a device that operates according to Medium Access Control (MAC) / PHY regulations of IEEE 802.11. As long as the function of the STA is not distinguished from the AP individually, the STA may include an AP STA and a non-AP STA. However, when communication is performed between the STA and the AP, the STA may be understood as a non-AP STA. In the example of FIG. 1, STA 1, STA 4, STA 5, and STA 6 correspond to non-AP STAs, and STA 2 and STA 3 correspond to AP STAs.
  • MAC Medium Access Control
  • Non-AP STAs generally correspond to devices that users directly handle, such as laptop computers and mobile phones.
  • a non-AP STA includes a wireless device, a terminal, a user equipment (UE), a mobile station (MS), a mobile terminal, and a wireless terminal.
  • WTRU wireless transmit / receive unit
  • MTC machine-type communication
  • M2M machine-to-machine
  • the AP is a base station (BS), Node-B (Node-B), evolved Node-B (eNB), and Base Transceiver System (BTS) in other wireless communication fields.
  • BS base station
  • Node-B Node-B
  • eNB evolved Node-B
  • BTS Base Transceiver System
  • downlink means communication from the AP to the non-AP STA
  • uplink means communication from the non-AP STA to the AP.
  • the transmitter may be part of an AP and the receiver may be part of a non-AP STA.
  • 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 structure of a layer architecture of an IEEE 802.11 system to which the present invention may be applied.
  • the layer architecture of the IEEE 802.11 system may include a MAC sublayer and a PHY sublayer.
  • the PHY sublayer may be divided into a Physical Layer Convergence Procedure (PLCP) entity and a Physical Medium Dependent (PMD) entity.
  • PLCP Physical Layer Convergence Procedure
  • PMD Physical Medium Dependent
  • the PLCP entity plays a role of connecting a data frame with a MAC sublayer
  • the PMD entity plays a role of wirelessly transmitting and receiving data with two or more STAs.
  • Both the MAC sublayer and the PHY sublayer may include a management entity, which may be referred to as a MAC sublayer management entity (MLME) and a PHY sublayer management entity (PLME), respectively.
  • MLME MAC sublayer management entity
  • PLME PHY sublayer management entity
  • These management entities provide layer management service interfaces through the operation of layer management functions.
  • the MLME may be connected to the PLME to perform management operations of the MAC sublayer, and likewise the PLME may be connected to the MLME to perform management operations of the PHY sublayer.
  • a Station Management Entity may be present in each STA.
  • the SME is a management entity independent of each layer.
  • the SME collects layer-based state information from MLME and PLME or sets values of specific parameters of each layer.
  • the SME can perform these functions on behalf of general system management entities and implement standard management protocols.
  • the XX-GET.request primitive is used to request the value of a Management Information Base attribute (MIB attribute), and the XX-GET.confirm primitive, if the status is 'SUCCESS', returns the value of that MIB attribute. Otherwise, it returns with an error indication in the status field.
  • MIB attribute Management Information Base attribute
  • the XX-SET.request primitive is used to request that a specified MIB attribute be set to a given value. If the MIB attribute is meant for a particular action, this request requests the execution of that particular action. And, if the state is 'SUCCESS' XX-SET.confirm primitive, it means that the specified MIB attribute is set to the requested value. In other cases, the status field indicates an error condition. If this MIB attribute means a specific operation, this primitive can confirm that the operation was performed.
  • MIB attribute Management Information Base attribute
  • XX-GET.confirm primitive if the status is 'SUCCESS', returns the value of that MIB attribute. Otherwise, it returns with
  • the MAC sublayer includes a MAC header and a frame check sequence (FCS) in a MAC Service Data Unit (MSDU) or a fragment of an MSDU received from an upper layer (eg, an LLC layer).
  • FCS frame check sequence
  • MSDU MAC Service Data Unit
  • MPDU MAC Protocol Data Unit
  • A-MSDU aggregated MSDU
  • a plurality of MSDUs may be merged into a single A-MSDU (aggregated MSDU).
  • the MSDU merging operation may be performed at the MAC upper layer.
  • the A-MSDU is delivered to the PHY sublayer as a single MPDU (if not fragmented).
  • the PHY sublayer generates a physical protocol data unit (PPDU) by adding an additional field including information required by a physical layer transceiver to a physical service data unit (PSDU) received from the MAC sublayer. . PPDUs are transmitted over wireless media.
  • PPDU physical protocol data unit
  • the PSDU is substantially the same as the MPDU since the PHY sublayer is received from the MAC sublayer and the MPDU is transmitted by the MAC sublayer to the PHY sublayer.
  • A-MPDU aggregated MPDU
  • a plurality of MPDUs may be merged into a single A-MPDU.
  • the MPDU merging operation may be performed at the MAC lower layer.
  • A-MPDUs may be merged with various types of MPDUs (eg, QoS data, Acknowledge (ACK), Block ACK (BlockAck), etc.).
  • the PHY sublayer receives the A-MPDU as a single PSDU from the MAC sublayer. That is, the PSDU is composed of a plurality of MPDUs.
  • A-MPDUs are transmitted over the wireless medium in a single PPDU.
  • PPDU Physical Protocol Data Unit
  • IEEE 802.11 WLAN system to which the present invention can be applied.
  • FIG. 3 illustrates a non-HT format PPDU and a HT format PPDU of a wireless communication system to which the present invention can be applied.
  • Non-HT PPDUs may also be referred to as legacy PPDUs.
  • the non-HT format PPDU includes an L-STF (Legacy (or Non-HT) Short Training field), L-LTF (Legacy (or, Non-HT) Long Training field) and It consists of a legacy format preamble and a data field composed of L-SIG (Legacy (or Non-HT) SIGNAL) field.
  • L-STF Legacy (or Non-HT) Short Training field
  • L-LTF Legacy (or, Non-HT) Long Training field
  • L-SIG Legacy (or Non-HT) SIGNAL
  • the L-STF may include a short training orthogonal frequency division multiplexing symbol (OFDM).
  • L-STF can be used for frame timing acquisition, automatic gain control (AGC), diversity detection, and coarse frequency / time synchronization. .
  • the L-LTF may include a long training orthogonal frequency division multiplexing symbol.
  • L-LTF may be used for fine frequency / time synchronization and channel estimation.
  • the L-SIG field may be used to transmit control information for demodulation and decoding of the data field.
  • the L-SIG field consists of a 4-bit Rate field, 1-bit Reserved bit, 12-bit Length field, 1-bit parity bit, and 6-bit Signal Tail field. Can be.
  • the rate field contains rate information, and the length field indicates the number of octets of the PSDU.
  • FIG. 3B illustrates an HT-mixed format PPDU (HTDU) for supporting both an IEEE 802.11n system and an IEEE 802.11a / g system.
  • HTDU HT-mixed format PPDU
  • the HT mixed format PPDU includes a legacy format preamble including an L-STF, L-LTF, and L-SIG fields, an HT-SIG (HT-Signal) field, and an HT-STF (HT Short). Training field), HT-formatted preamble and data field including HT-LTF (HT Long Training field).
  • L-STF, L-LTF, and L-SIG fields mean legacy fields for backward compatibility, they are the same as non-HT formats from L-STF to L-SIG fields. Even if the L-STA receives the HT mixed PPDU, the L-STA may interpret the data field through the L-LTF, L-LTF and L-SIG fields. However, the L-LTF may further include information for channel estimation that the HT-STA performs to receive the HT mixed PPDU and demodulate the L-SIG field and the HT-SIG field.
  • the HT-STA may know that it is an HT-mixed format PPDU using the HT-SIG field following the legacy field, and may decode the data field based on the HT-STA.
  • the HT-LTF field may be used for channel estimation for demodulation of the data field. Since IEEE 802.11n supports Single-User Multi-Input and Multi-Output (SU-MIMO), a plurality of HT-LTF fields may be configured for channel estimation for each data field transmitted in a plurality of spatial streams.
  • SU-MIMO Single-User Multi-Input and Multi-Output
  • the HT-LTF field includes data HT-LTF used for channel estimation for spatial streams and extension HT-LTF (additional used for full channel sounding). It can be configured as. Accordingly, the plurality of HT-LTFs may be equal to or greater than the number of spatial streams transmitted.
  • the L-STF, L-LTF, and L-SIG fields are transmitted first in order to receive the L-STA and acquire data. Thereafter, the HT-SIG field is transmitted for demodulation and decoding of data transmitted for the HT-STA.
  • the HT-SIG field is transmitted without performing beamforming so that the L-STA and HT-STA can receive the corresponding PPDU to acquire data, and then the HT-STF, HT-LTF and data fields transmitted are precoded. Wireless signal transmission is performed through.
  • the HT-STF field is transmitted to allow the STA to perform precoding to take into account the variable power due to precoding, and then the plurality of HT-LTF and data fields after that.
  • FIG. 3 (c) illustrates an HT-GF format PPDU (HT-GF) for supporting only an IEEE 802.11n system.
  • the HT-GF format PPDU includes HT-GF-STF, HT-LTF1, HT-SIG field, a plurality of HT-LTF2 and data fields.
  • HT-GF-STF is used for frame timing acquisition and AGC.
  • HT-LTF1 is used for channel estimation.
  • the HT-SIG field is used for demodulation and decoding of the data field.
  • HT-LTF2 is used for channel estimation for demodulation of data fields. Similarly, since HT-STA uses SU-MIMO, channel estimation is required for each data field transmitted in a plurality of spatial streams, and thus HT-LTF2 may be configured in plural.
  • the plurality of HT-LTF2 may be configured of a plurality of Data HT-LTF and a plurality of extended HT-LTF similarly to the HT-LTF field of the HT mixed PPDU.
  • the data field is a payload, and includes a service field, a SERVICE field, a scrambled PSDU field, tail bits, and padding bits. It may include. All bits of the data field are scrambled.
  • FIG. 3 (d) shows a service field included in a data field.
  • the service field has 20 bits. Each bit is assigned from 0 to 15, and transmitted sequentially from bit 0. Bits 0 to 6 are set to 0 and used to synchronize the descrambler in the receiver.
  • the IEEE 802.11ac WLAN system supports downlink multi-user multiple input multiple output (MU-MIMO) transmission in which a plurality of STAs simultaneously access a channel in order to efficiently use a wireless channel.
  • MU-MIMO downlink multi-user multiple input multiple output
  • the AP may simultaneously transmit packets to one or more STAs that are paired with MIMO.
  • DL MU transmission (downlink multi-user transmission) refers to a technology in which an AP transmits a PPDU to a plurality of non-AP STAs through the same time resource through one or more antennas.
  • the MU PPDU refers to a PPDU that delivers one or more PSDUs for one or more STAs using MU-MIMO technology or OFDMA technology.
  • the SU PPDU means a PPDU having a format in which only one PSDU can be delivered or in which no PSDU exists.
  • control information transmitted to the STA may be relatively large compared to the size of 802.11n control information for MU-MIMO transmission.
  • An example of control information additionally required for MU-MIMO support includes information indicating the number of spatial streams received by each STA, information related to modulation and coding of data transmitted to each STA, and the like. Can be.
  • the size of transmitted control information may be increased according to the number of receiving STAs.
  • control information required for MU-MIMO transmission is required separately for common control information common to all STAs and specific STAs.
  • the data may be transmitted by being divided into two types of information of dedicated control information.
  • FIG. 4 illustrates a VHT format PPDU format of a wireless communication system to which the present invention can be applied.
  • VHT format PPDU VHT format PPDU
  • a VHT format PPDU includes a legacy format preamble including a L-STF, L-LTF, and L-SIG fields, a VHT-SIG-A (VHT-Signal-A) field, and a VHT-STF ( A VHT format preamble and a data field including a VHT Short Training field (VHT-LTF), a VHT Long Training field (VHT-LTF), and a VHT-SIG-B (VHT-Signal-B) field.
  • VHT-LTF VHT Short Training field
  • VHT-LTF VHT Long Training field
  • VHT-SIG-B VHT-Signal-B
  • L-STF, L-LTF, and L-SIG mean legacy fields for backward compatibility, they are the same as non-HT formats from L-STF to L-SIG fields.
  • the L-LTF may further include information for channel estimation to be performed to demodulate the L-SIG field and the VHT-SIG-A field.
  • the L-STF, L-LTF, L-SIG field, and VHT-SIG-A field may be repeatedly transmitted in 20 MHz channel units. For example, when a PPDU is transmitted on four 20 MHz channels (i.e., 80 MHz bandwidth), the L-STF, L-LTF, L-SIG field, and VHT-SIG-A field are repeatedly transmitted on every 20 MHz channel. Can be.
  • the VHT-STA may know that it is a VHT format PPDU using the VHT-SIG-A field following the legacy field, and may decode the data field based on the VHT-STA.
  • the L-STF, L-LTF and L-SIG fields are transmitted first in order to receive the L-STA and acquire data. Thereafter, the VHT-SIG-A field is transmitted for demodulation and decoding of data transmitted for the VHT-STA.
  • the VHT-SIG-A field is a field for transmitting control information common to the AP and the MIMO paired VHT STAs, and includes control information for interpreting the received VHT format PPDU.
  • the VHT-SIG-A field may include a VHT-SIG-A1 field and a VHT-SIG-A2 field.
  • the VHT-SIG-A1 field includes information on channel bandwidth (BW) used, whether space time block coding (STBC) is applied, and group identification information for indicating a group of STAs grouped in MU-MIMO.
  • Group ID Group Identifier
  • NSTS space-time streams
  • Partial AID Partial Association Identifier
  • Transmit power save forbidden information can do.
  • the Group ID means an identifier assigned to the STA group to be transmitted to support MU-MIMO transmission, and may indicate whether the currently used MIMO transmission method is MU-MIMO or SU-MIMO.
  • the VHT-SIG-A2 field contains information on whether a short guard interval (GI) is used, forward error correction (FEC) information, information on modulation and coding scheme (MCS) for a single user, and multiple information.
  • GI short guard interval
  • FEC forward error correction
  • MCS modulation and coding scheme
  • Information on the type of channel coding for the user beamforming-related information, redundancy bits for cyclic redundancy checking (CRC), tail bits of convolutional decoder, and the like. Can be.
  • VHT-STF is used to improve the performance of AGC estimation in MIMO transmission.
  • VHT-LTF is used by the VHT-STA to estimate the MIMO channel. Since the VHT WLAN system supports MU-MIMO, the VHT-LTF may be set as many as the number of spatial streams in which a PPDU is transmitted. In addition, if full channel sounding is supported, the number of VHT-LTFs may be greater.
  • the VHT-SIG-B field includes dedicated control information required for a plurality of MU-MIMO paired VHT-STAs to receive a PPDU and acquire data. Therefore, the VHT-STA may be designed to decode the VHT-SIG-B field only when the common control information included in the VHT-SIG-A field indicates the MU-MIMO transmission currently received. . On the other hand, if the common control information indicates that the currently received PPDU is for a single VHT-STA (including SU-MIMO), the STA may be designed 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 a tail field.
  • the VHT-SIG-B Length field indicates the length of the A-MPDU (before end-of-frame padding).
  • the VHT-MCS field includes information on modulation, encoding, and rate-matching of each VHT-STA.
  • the size of the VHT-SIG-B field may vary depending on the type of MIMO transmission (MU-MIMO or SU-MIMO) and the channel bandwidth used for PPDU transmission.
  • FIG. 4 (b) illustrates the VHT-SIG-B field according to the PPDU transmission bandwidth.
  • the VHT-SIG-B bits are repeated twice.
  • the VHT-SIG-B bits are repeated four times and pad bits set to zero are attached.
  • VHT-SIG-B bits are repeated four times, as with the 80 MHz transmission, and pad bits set to zero are attached. Then, all 117 bits are repeated again.
  • information indicating a bit size of a data field constituting the PPDU and / or indicating a bit stream size constituting a specific field May be included in the VHT-SIG-A field.
  • the L-SIG field may be used to effectively use the PPDU format.
  • a length field and a rate field included in the L-SIG field and transmitted may be used to provide necessary information.
  • MPDU MAC Protocol Data Unit
  • A-MPDU Aggregate MAC Protocol Data Unit
  • the data field is a payload and may include a service field, a scrambled PSDU, tail bits, and padding bits.
  • the STA Since the formats of various PPDUs are mixed and used as described above, the STA must be able to distinguish the formats of the received PPDUs.
  • the meaning of distinguishing a PPDU may have various meanings.
  • the meaning of identifying the PPDU may include determining whether the received PPDU is a PPDU that can be decoded (or interpreted) by the STA.
  • the meaning of distinguishing the PPDU may mean determining whether the received PPDU is a PPDU supported by the STA.
  • the meaning of distinguishing the PPDU may also be interpreted to mean what information is transmitted through the received PPDU.
  • FIG. 5 is a diagram illustrating a constellation for distinguishing a format of a PPDU of a wireless communication system to which the present invention can be applied.
  • FIG. 5 (a) illustrates the constellation of the L-SIG field included in the non-HT format PPDU
  • FIG. 5 (b) illustrates the phase rotation for HT mixed format PPDU detection
  • 5 (c) illustrates phase rotation for VHT format PPDU detection.
  • Phase is used. That is, the STA may distinguish the PPDU format based on the phase of the constellation of the OFDM symbol transmitted after the L-SIG field and / or the L-SIG field of the received PPDU.
  • binary phase shift keying (BPSK) is used for an OFDM symbol constituting the L-SIG field.
  • the STA determines whether it is an L-SIG field. That is, the STA tries to decode based on the constellation as shown in the example of FIG. If the STA fails to decode, it may be determined that the corresponding PPDU is an HT-GF format PPDU.
  • the phase of the constellation of OFDM symbols transmitted after the L-SIG field may be used. That is, the modulation method of OFDM symbols transmitted after the L-SIG field may be different, and the STA may distinguish the PPDU format based on the modulation method for the field after the L-SIG field of the received PPDU.
  • the phase of two OFDM symbols transmitted after the L-SIG field in the HT mixed format PPDU may be used.
  • the phases of OFDM symbol # 1 and OFDM symbol # 2 corresponding to the HT-SIG field transmitted after the L-SIG field in the HT mixed format PPDU are rotated by 90 degrees in the counterclockwise direction. That is, quadrature binary phase shift keying (QBPSK) is used as a modulation method for OFDM symbol # 1 and OFDM symbol # 2.
  • QBPSK constellation may be a constellation rotated by 90 degrees in a counterclockwise direction based on the BPSK constellation.
  • the STA attempts to decode the first OFDM symbol and the second OFDM symbol corresponding to the HT-SIG field transmitted after the L-SIG field of the received PPDU based on the properties as shown in the example of FIG. 5 (b). If the STA succeeds in decoding, it is determined that the corresponding PPDU is an HT format PPDU.
  • the phase of the constellation of the OFDM symbol transmitted after the L-SIG field may be used.
  • the phase of two OFDM symbols transmitted after the L-SIG field in the VHT format PPDU may be used.
  • phase of the OFDM symbol # 1 corresponding to the VHT-SIG-A field after the L-SIG field in the VHT format PPDU is not rotated, but the phase of the OFDM symbol # 2 is rotated by 90 degrees counterclockwise. . That is, BPSK is used for the modulation method for OFDM symbol # 1 and QBPSK is used for the modulation method for OFDM symbol # 2.
  • the STA attempts to decode the first OFDM symbol and the second OFDM symbol corresponding to the VHT-SIG field transmitted after the L-SIG field of the received PPDU based on the properties as illustrated in FIG. 5 (c). If the STA succeeds in decoding, it may be determined that the corresponding PPDU is a VHT format PPDU.
  • the STA may determine that the corresponding PPDU is a non-HT format PPDU.
  • FIG. 6 illustrates a MAC frame format of an IEEE 802.11 system to which the present invention can be applied.
  • a MAC frame (ie, an MPDU) includes a MAC header, a frame body, and a frame check sequence (FCS).
  • FCS frame check sequence
  • MAC Header includes Frame Control field, Duration / ID field, Address 1 field, Address 2 field, Address 3 field, Sequence control It is defined as an area including a Control field, an Address 4 field, a QoS Control field, and an HT Control field.
  • the Frame Control field includes information on the MAC frame characteristic. A detailed description of the Frame Control field will be given later.
  • the Duration / ID field may be implemented to have different values depending on the type and subtype of the corresponding MAC frame.
  • the Duration / ID field is an AID (association identifier) of the STA that transmitted the frame. It may be set to include. Otherwise, the Duration / ID field may be set to have a specific duration value according to the type and subtype of the corresponding MAC frame.
  • the Duration / ID fields included in the MAC header may be set to have the same value.
  • the Address 1 to Address 4 fields include a BSSID, a source address (SA), a destination address (DA), a transmission address (TA) indicating a transmission STA address, and a reception address indicating a destination STA address (TA).
  • SA source address
  • DA destination address
  • TA transmission address
  • TA reception address indicating a destination STA address
  • RA It is used to indicate Receiving Address.
  • the address field implemented as a TA field may be set to a bandwidth signaling TA value, in which case, the TA field may indicate that the corresponding MAC frame contains additional information in the scrambling sequence.
  • the bandwidth signaling TA may be represented by the MAC address of the STA transmitting the corresponding MAC frame, but the Individual / Group bit included in the MAC address may be set to a specific value (for example, '1'). Can be.
  • the Sequence Control field is set to include a sequence number and a fragment number.
  • the sequence number may indicate a sequence number allocated to the corresponding MAC frame.
  • the fragment number may indicate the number of each fragment of the corresponding MAC frame.
  • the QoS Control field contains information related to QoS.
  • the QoS Control field may be included when indicating a QoS data frame in a subtype subfield.
  • the HT Control field includes control information related to the HT and / or VHT transmission / reception schemes.
  • the HT Control field is included in the Control Wrapper frame. In addition, it exists in the QoS data frame and the management frame in which the order subfield value is 1.
  • the frame body is defined as a MAC payload, and data to be transmitted in a higher layer is located, and has a variable size.
  • the maximum MPDU size may be 11454 octets
  • the maximum PPDU size may be 5.484 ms.
  • FCS is defined as a MAC footer and is used for error detection of MAC frames.
  • the first three fields (Frame Control field, Duration / ID field and Address 1 field) and the last field (FCS field) constitute the minimum frame format and are present in every frame. Other fields may exist only in a specific frame type.
  • FIG. 7 is a diagram illustrating a Frame Control field in a MAC frame in a wireless communication system to which the present invention can be applied.
  • the Frame Control field includes a Protocol Version subfield, a Type subfield, a Subtype subfield, a To DS subfield, a From DS subfield, and more fragments.
  • the Protocol Version subfield may indicate the version of the WLAN protocol applied to the corresponding MAC frame.
  • the Type subfield and the Subtype subfield may be set to indicate information for identifying a function of a corresponding MAC frame.
  • the type of the MAC frame may include three frame types: a management frame, a control frame, and a data frame.
  • Each frame type may be further divided into subtypes.
  • control frames include request to send (RTS) frames, clear-to-send (CTS) frames, acknowledgment (ACK) frames, PS-Poll frames, content free (End) frames, CF End + CF-ACK frame, Block Acknowledgment request (BAR) frame, Block Acknowledgment (BA) frame, Control Wrapper (Control + HTcontrol) frame, VHT null data packet notification (NDPA) It may include a Null Data Packet Announcement and a Beamforming Report Poll frame.
  • Management frames include beacon frames, announcement traffic indication message (ATIM) frames, disassociation frames, association request / response frames, reassociation requests / responses Response frame, Probe Request / Response frame, Authentication frame, Deauthentication frame, Action frame, Action No ACK frame, Timing Advertisement It may include a frame.
  • ATIM announcement traffic indication message
  • disassociation frames association request / response frames
  • reassociation requests / responses Response frame Probe Request / Response frame
  • Authentication frame Deauthentication frame
  • Action frame Action No ACK frame
  • Timing Advertisement It may include a frame.
  • the To DS subfield and the From DS subfield may include information necessary to interpret the Address 1 field or the Address 4 field included in the corresponding MAC frame header.
  • both the To DS subfield and the From DS subfield are set to '0'.
  • the To DS subfield and the From DS subfield are set to '1' and '0' in order if the frame is a QoS Management frame (QMF), and in order if the frame is not QMF. Both can be set to '0', '0'.
  • QMF QoS Management frame
  • the More Fragments subfield may indicate whether there is a fragment to be transmitted following the corresponding MAC frame. If there is another fragment of the current MSDU or MMPDU, it may be set to '1', otherwise it may be set to '0'.
  • the Retry subfield may indicate whether the corresponding MAC frame is due to retransmission of a previous MAC frame. In case of retransmission of the previous MAC frame, it may be set to '1', otherwise it may be set to '0'.
  • the power management subfield may indicate a power management mode of the STA. If the value of the Power Management subfield is '1', the STA may indicate switching to the power save mode.
  • the More Data subfield may indicate whether there is an additional MAC frame to be transmitted. If there is an additional MAC frame to be transmitted, it may be set to '1', otherwise it may be set to '0'.
  • the Protected Frame subfield may indicate whether the frame body field is encrypted. If the Frame Body field includes information processed by the encryption encapsulation algorithm, it may be set to '1', otherwise it may be set to '0'.
  • each field described above corresponds to an example of fields that may be included in the MAC frame, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included.
  • FIG. 8 illustrates the VHT format of the HT Control field in a wireless communication system to which the present invention can be applied.
  • the HT Control field includes a VHT subfield, an HT Control Middle subfield, an AC Constraint subfield, and a Reverse Direction Grant (RDG) / More PPDU (More PPDU). It may consist of subfields.
  • RDG Reverse Direction Grant
  • More PPDU More PPDU
  • the HT Control field for the VHT may be referred to as a VHT Control field.
  • the HT Control Middle subfield may be implemented to have a different format according to the indication of the VHT subfield. A more detailed description of the HT Control Middle subfield will be given later.
  • the AC Constraint subfield indicates whether a mapped AC (Access Category) of a reverse direction (RD) data frame is limited to a single AC.
  • the RDG / More PPDU subfield may be interpreted differently depending on whether the corresponding field is transmitted by the RD initiator or the RD responder.
  • the RDG / More PPDU field When transmitted by the RD initiator, the RDG / More PPDU field is set to '1' if the RDG exists, and set to '0' if the RDG does not exist. When transmitted by the RD responder, it is set to '1' if the PPDU including the corresponding subfield is the last frame transmitted by the RD responder, and set to '0' when another PPDU is transmitted.
  • the HT Control Middle subfield may be implemented to have a different format according to the indication of the VHT subfield.
  • the HT Control Middle subfield of the HT Control field for VHT includes a reserved bit, a Modulation and Coding Scheme feedback request (MRQ) subfield, and an MRQ Sequence Identifier (MSI).
  • STBC Space-time block coding
  • MCS MCS feedback sequence identifier
  • LSB Least Significant Bit
  • MSB MCS Feedback
  • MSB Group ID Most Significant Bit
  • Coding Type Subfield Feedback Transmission Type (FB Tx Type: Feedback transmission type) subfield and a voluntary MFB (Unsolicited MFB) subfield.
  • the MFB subfield may include a VHT number of space time streams (NUM_STS) subfield, a VHT-MCS subfield, a bandwidth (BW) subfield, and a signal to noise ratio (SNR). It may include subfields.
  • NUM_STS VHT number of space time streams
  • BW bandwidth
  • SNR signal to noise ratio
  • the NUM_STS subfield indicates the number of recommended spatial streams.
  • the VHT-MCS subfield indicates a recommended MCS.
  • the BW subfield indicates bandwidth information related to the recommended MCS.
  • the SNR subfield indicates the average SNR value on the data subcarrier and spatial stream.
  • each field described above corresponds to an example of fields that may be included in the MAC frame, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included.
  • IEEE 802.11 communication is fundamentally different from the wired channel environment because the communication takes place over a shared wireless medium.
  • CSMA / CD carrier sense multiple access / collision detection
  • the channel environment does not change so much that the receiver does not experience significant signal attenuation.
  • detection was possible. This is because the power sensed by the receiver is instantaneously greater than the power transmitted by the transmitter.
  • a variety of factors e.g., large attenuation of the signal depending on distance, or instantaneous deep fading
  • the transmitter cannot accurately perform carrier sensing.
  • a carrier sense multiple access with collision avoidance (CSMA / CA) mechanism is introduced as a basic access mechanism of a MAC.
  • the CAMA / CA mechanism is also called the Distributed Coordination Function (DCF) of the IEEE 802.11 MAC. It basically employs a “listen before talk” access mechanism.
  • the AP and / or STA may sense a radio channel or medium during a predetermined time interval (eg, DCF Inter-Frame Space (DIFS)) prior to starting transmission.
  • DIFS DCF Inter-Frame Space
  • CCA Clear Channel Assessment
  • the AP and / or STA does not start its own transmission and assumes that several STAs are already waiting to use the medium.
  • the frame transmission may be attempted after waiting longer for a delay time (eg, a random backoff period) for access.
  • the STAs are expected to have different backoff period values, so that they will wait for different times before attempting frame transmission. This can minimize collisions.
  • HCF hybrid coordination function
  • the PCF refers to a polling-based synchronous access scheme in which polling is performed periodically so that all receiving APs and / or STAs can receive data frames.
  • the HCF has an Enhanced Distributed Channel Access (EDCA) and an HCF Controlled Channel Access (HCCA).
  • EDCA is a competition-based approach for providers to provide data frames to a large number of users
  • HCCA is a non-competition-based channel access scheme using a polling mechanism.
  • the HCF includes a media access mechanism for improving the quality of service (QoS) of the WLAN, and can transmit QoS data in both a contention period (CP) and a contention free period (CFP).
  • QoS quality of service
  • FIG. 9 is a diagram for explaining an arbitrary backoff period and a frame transmission procedure in a wireless communication system to which the present invention can be applied.
  • the random backoff count has a pseudo-random integer value and may be determined as one of values uniformly distributed in the range of 0 to a contention window (CW).
  • CW is a contention window parameter value.
  • the CW parameter is given CW_min as an initial value, but may take a double value when transmission fails (eg, when an ACK for a transmitted frame is not received). If the CW parameter value is CW_max, data transmission can be attempted while maintaining the CW_max value until the data transmission is successful. If the CW parameter value is successful, the CW parameter value is reset to the CW_min value.
  • the STA counts down the backoff slot according to the determined backoff count value and continuously monitors the medium during the countdown. If the media is monitored as occupied, the countdown stops and waits, and when the media is idle the countdown resumes.
  • the STA 3 may confirm that the medium is idle as much as DIFS and transmit the frame immediately.
  • each STA monitors and wait for the medium to be busy.
  • data may be transmitted in each of STA 1, STA 2, and STA 5, and each STA waits for DIFS when the medium is monitored in an idle state, and then backoff slots according to a random backoff count value selected by each STA. Counts down.
  • STA 2 selects the smallest backoff count value and STA 1 selects the largest backoff count value. That is, at the time when STA 2 finishes the backoff count and starts frame transmission, the remaining backoff time of STA 5 is shorter than the remaining backoff time of STA 1.
  • STA 1 and STA 5 stop counting and wait while STA 2 occupies the medium.
  • the STA 1 and the STA 5 resume the stopped backoff count after waiting for DIFS. That is, the frame transmission can be started after counting down the remaining backoff slots by the remaining backoff time. Since the remaining backoff time of STA 5 is shorter than that of STA 1, frame transmission of STA 5 is started.
  • STA 2 occupies the medium
  • data to be transmitted may also occur in STA 4.
  • the STA 4 waits for DIFS and then counts down the backoff slot according to the random backoff count value selected by the STA.
  • the remaining backoff time of STA 5 coincides with an arbitrary backoff count value of STA 4, and in this case, a collision may occur between STA 4 and STA 5. If a collision occurs, neither STA 4 nor STA 5 receive an ACK, and thus data transmission fails. In this case, STA4 and STA5 select a random backoff count value after doubling the CW value and perform countdown of the backoff slot.
  • the STA 1 may wait while the medium is occupied due to the transmission of the STA 4 and the STA 5, wait for DIFS when the medium is idle, and then start frame transmission after the remaining backoff time passes.
  • the CSMA / CA mechanism also includes virtual carrier sensing in addition to physical carrier sensing in which the AP and / or STA directly sense the medium.
  • Virtual carrier sensing is intended to compensate for problems that may occur in media access, such as a hidden node problem.
  • the MAC of the WLAN system uses a Network Allocation Vector (NAV).
  • the NAV is a value that indicates to the other AP and / or STA how long the AP and / or STA currently using or authorized to use the medium remain until the medium becomes available. Therefore, the value set to NAV corresponds to a period in which the medium is scheduled to be used by the AP and / or STA transmitting the frame, and the STA receiving the NAV value is prohibited from accessing the medium during the period.
  • the NAV may be set according to a value of a duration field of the MAC header of the frame.
  • the AP and / or STA may perform a procedure of exchanging a request to send (RTS) frame and a clear to send (CTS) frame to indicate that the AP and / or STA want to access the medium.
  • the RTS frame and the CTS frame include information indicating a time interval in which a wireless medium required for transmission and reception of an ACK frame is reserved when substantial data frame transmission and acknowledgment (ACK) are supported.
  • the other STA that receives the RTS frame transmitted from the AP and / or the STA to which the frame is to be transmitted or receives the CTS frame transmitted from the STA to which the frame is to be transmitted during the time period indicated by the information included in the RTS / CTS frame Can be set to not access the medium. This may be implemented by setting the NAV during the time interval.
  • the time interval between frames is defined as Interframe Space (IFS).
  • IFS Interframe Space
  • the STA may determine whether the channel is used during the IFS time interval through carrier sensing.
  • Multiple IFSs are defined to provide a priority level that occupies a wireless medium in an 802.11 WLAN system.
  • FIG. 10 is a diagram illustrating an IFS relationship in a wireless communication system to which the present invention can be applied.
  • All timings can be determined with reference to the physical layer interface primitives, namely the PHY-TXEND.confirm primitive, the PHYTXSTART.confirm primitive, the PHY-RXSTART.indication primitive and the PHY-RXEND.indication primitive.
  • Frame spacing according to IFS type is as follows.
  • IFS timing is defined as the time gap on the medium. Except for AIFS, IFS timing is fixed for each physical layer.
  • SIFS is a PPDU containing a ACK frame, a CTS frame, a Block ACK Request (BlockAckReq) frame, or a Block ACK (BlockAck) frame that is an immediate response to an A-MPDU, the second or consecutive MPDU of a fragment burst, or PCF. Used for transmission of the STA's response to polling by and has the highest priority. SIFS can also be used for point coordinator of frames regardless of the type of frame during non-competition interval (CFP) time. SIFS represents the time from the end of the last symbol of the previous frame or the signal extension (if present) to the start of the first symbol of the preamble of the next frame.
  • CCP non-competition interval
  • SIFS timing is achieved when the transmission of consecutive frames at the TxSIFS slot boundary begins.
  • SIFS is the shortest of the IFS between transmissions from different STAs.
  • the STA occupying the medium may be used when it is necessary to maintain the occupation of the medium during the period in which the frame exchange sequence is performed.
  • PIFS is used to gain priority in accessing media.
  • PIFS can be used in the following cases:
  • TIM Traffic Indication Map
  • Hybrid Coordinator initiating CFP or Transmission Opportunity (TXOP)
  • HC or non-AP QoS STA which is a polled TXOP holder for recovering from the absence of expected reception in a controlled access phase (CAP)
  • the STA using the PIFS starts transmission after the CS (carrier sense) mechanism that determines that the medium is idle at the TxPIFS slot boundary.
  • DIFS may be used by a STA operative to transmit a data frame (MPDU) and a management frame (MMPDU: MAC Management Protocol Data Unit) under DCF.
  • the STA using the DCF may transmit on the TxDIFS slot boundary if it is determined that the medium is idle through a carrier sense (CS) mechanism after a correctly received frame and backoff time expire.
  • the correctly received frame means a frame in which the PHY-RXEND.indication primitive does not indicate an error and the FCS indicates that the frame is not an error (error free).
  • SIFS time 'aSIFSTime' and slot time 'aSlotTime' may be determined for each physical layer.
  • the SIFS time has a fixed value, but the slot time may change dynamically according to a change in the air delay time (aAirPropagationTime).
  • FIG. 11 is a diagram illustrating a downlink MU-MIMO transmission process in a wireless communication system to which the present invention can be applied.
  • MU-MIMO is defined in downlink from the AP to the client (ie, non-AP STA).
  • client ie, non-AP STA.
  • a multi-user frame is simultaneously transmitted to multiple receivers, but acknowledgments should be transmitted separately in the uplink.
  • Block Ack Request is sent in response to a frame.
  • the AP transmits a VHT MU PPDU (ie, preamble and data) to all receivers (ie, STA 1, STA 2, and STA 3).
  • the VHT MU PPDU includes a VHT A-MPDU transmitted to each STA.
  • STA 1 Receiving a VHT MU PPDU from the AP, STA 1 transmits a block acknowledgment (BA) frame to the AP after SIFS.
  • BA block acknowledgment
  • the AP After receiving the BA from the STA 1, the AP transmits a block acknowledgment request (BAR) frame to the next STA 2 after SIFS, and the STA 2 transmits a BA frame to the AP after SIFS.
  • BAR block acknowledgment request
  • the AP receiving the BA frame from STA 2 transmits the BAR frame to STA 3 after SIFS, and STA 3 transmits the BA frame to AP after SIFS.
  • the AP transmits the next MU PPDU to all STAs.
  • next generation WLAN system is a next generation WIFI system, which may be described as an example of IEEE 802.11ax as an embodiment of the next generation WIFI system.
  • HE High Efficiency
  • frames, PPDUs, and the like of the system are referred to as HE frames, HE PPDUs, HE preambles, HE-SIG fields, HE-STFs, and HE-LTFs. May be referred to.
  • the description of the existing WLAN system such as the above-described VHT system may be applied to the HE system, which is not further described below.
  • VHT-SIG A field VHT-STF, VHT-LTF and VHT-SIG-B fields described above for the HE-SIG A field, HE-STF, HE-LTF and HE-SIG-B fields. Description may apply.
  • the HE frame and the preamble of the proposed HE system may be used only for other wireless communication or cellular systems.
  • the HE STA may be a non-AP STA or an AP STA as described above. Although referred to as STA in the following specification, such a STA device may represent an HE STA device.
  • HE 12 illustrates a High Efficiency (HE) format PPDU according to an embodiment of the present invention.
  • FIGS. 12 (a) to (d) illustrate a more specific structure of the HE format PPDU.
  • a HE format PPDU for an HEW may be largely composed of a legacy part (L-part), an HE part (HE-part), and a data field (HE-data).
  • L-part legacy part
  • HE-part HE part
  • HE-data data field
  • the L-part is composed of an L-STF field, an L-LTF field, and an L-SIG field in the same manner as the conventional WLAN system maintains.
  • the L-STF field, L-LTF field, and L-SIG field may be referred to as a legacy preamble.
  • the HE-part is a part newly defined for the 802.11ax standard and may include an HE-STF field, an HE-SIG field, and an HE-LTF field.
  • 12 (a) illustrates the order of the HE-STF field, the HE-SIG field, and the HE-LTF field, but may be configured in a different order.
  • HE-LTF may be omitted.
  • the HE-SIG field may be collectively referred to as HE-preamble.
  • the L-part, the HE-SIG field, and the HE-preamble may be collectively referred to as a physical preamble (PHY) / physical preamble.
  • the HE-SIG field may include information (eg, OFDMA, UL MU MIMO, enhanced MCS, etc.) for decoding the HE-data field.
  • information eg, OFDMA, UL MU MIMO, enhanced MCS, etc.
  • the L-part and the HE-part may have different fast fourier transform (FFT) sizes (ie, subcarrier spacing), and may use different cyclic prefixes (CP).
  • FFT fast fourier transform
  • CP cyclic prefixes
  • 802.11ax systems can use FFT sizes that are four times larger than legacy WLAN systems. That is, the L-part may have a 1 ⁇ symbol structure, and the HE-part (particularly, HE-preamble and HE-data) may have a 4 ⁇ symbol structure.
  • 1 ⁇ , 2 ⁇ , 4 ⁇ size FFTs represent relative sizes for legacy WLAN systems (eg, IEEE 802.11a, 802.11n, 802.11ac, etc.).
  • the FFT size used for the L-part is 64, 128, 256, and 512 at 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively
  • the FFT size used for the HE-part is 256 at 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively. , 512, 1024, 2048.
  • the number of subcarriers per unit frequency increases because the subcarrier frequency spacing becomes smaller, but the OFDM symbol length becomes longer.
  • the use of a larger FFT size means that the subcarrier spacing becomes narrower, and similarly, an Inverse Discrete Fourier Transform (IDFT) / Discrete Fourier Transform (DFT) period is increased.
  • IDFT Inverse Discrete Fourier Transform
  • DFT Discrete Fourier Transform
  • the IDFT / DFT period may mean a symbol length excluding the guard period (GI) in the OFDM symbol.
  • the subcarrier spacing of the HE-part is 1/4 of the subcarrier spacing of the L-part.
  • the ID-FT / DFT period of the HE-part is four times the IDFT / DFT period of the L-part.
  • the GI can be one of 0.8 ⁇ s, 1.6 ⁇ s, 3.2 ⁇ s, so the OFDM symbol length (or symbol interval) of the HE-part including the GI is 13.6 ⁇ s, 14.4 ⁇ s, 20 according to the GI. It can be
  • the HE-SIG field may be divided into an HE-SIG-A field and an HE-SIG-B field.
  • the HE-part of the HE format PPDU may include a HE-SIG-A field having a length of 12.8 kHz, a HE-STF field of 1 OFDM symbol, one or more HE-LTF fields, and a HE-SIG-B field of 1 OFDM symbol. It may include.
  • the FFT having a size four times larger than the existing PPDU may be applied from the HE-STF field. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively.
  • the HE-SIG when the HE-SIG is divided into the HE-SIG-A field and the HE-SIG-B field and transmitted as shown in FIG. 12 (b), the positions of the HE-SIG-A field and the HE-SIG-B field are shown in FIG. It may differ from 12 (b).
  • the HE-SIG-B field may be transmitted after the HE-SIG-A field
  • the HE-STF field and the HE-LTF field may be transmitted after the HE-SIG-B field.
  • an FFT of 4 times larger than a conventional PPDU may be applied from the HE-STF field.
  • the HE-SIG field may not be divided into an HE-SIG-A field and an HE-SIG-B field.
  • the HE-part of the HE format PPDU may include a HE-STF field of one OFDM symbol, a HE-SIG field of one OFDM symbol, and one or more HE-LTF fields.
  • the HE-part may be applied to an FFT four times larger than the existing PPDU. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively.
  • the HE-SIG field is not divided into an HE-SIG-A field and an HE-SIG-B field, and the HE-LTF field may be omitted.
  • the HE-part of the HE format PPDU may include a HE-STF field of 1 OFDM symbol and a HE-SIG field of 1 OFDM symbol.
  • the HE-part may be applied to an FFT four times larger than the existing PPDU. That is, FFTs of 256, 512, 1024, and 2048 sizes may be applied from the HE-STF field of the HE format PPDU of 20 MHz, 40 MHz, 80 MHz, and 200 MHz, respectively.
  • the HE format PPDU for the WLAN system according to the present invention may be transmitted on at least one 20 MHz channel.
  • an HE format PPDU can be transmitted in a 40 MHz, 80 MHz or 200 MHz frequency band using a total of four 20 MHz channels. This will be described in more detail with reference to the drawings below.
  • FIG. 13 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • FIG. 13 illustrates a PPDU format when 80 MHz is allocated to one STA (or OFDMA resource units are allocated to a plurality of STAs within 80 MHz) or when different streams of 80 MHz are allocated to a plurality of STAs.
  • L-STF, L-LTF, and L-SIG may be transmitted as OFDM symbols generated based on 64 FFT points (or 64 subcarriers) in each 20MHz channel.
  • the HE-SIG-A field may include common control information that is commonly transmitted to STAs receiving a PPDU.
  • the HE-SIG-A field may be transmitted in one to three OFDM symbols.
  • the HE-SIG-A field is copied in units of 20 MHz and contains the same information.
  • the HE-SIG-A field informs the total bandwidth information of the system.
  • the HE-SIG-A field may include information as shown in Table 1 below.
  • each field described above corresponds to an example of fields that may be included in the PPDU, but is not limited thereto. That is, each field described above may be replaced with another field or additional fields may be further included, and all fields may not be necessarily included.
  • HE-STF is used to improve the performance of AGC (Automatic Gain Control) estimation in MIMO transmission.
  • HE-STF may be generated using a sequence of frequency domains for a particular band.
  • Long Trainig Field HE-LTF is a field used at the receiver to estimate the MIMO channel between the receive chains and the set of constellation mapper outputs.
  • the HE-SIG-B field may include user-specific information required for each STA to receive its own data (eg, PSDU).
  • PSDU user-specific information required for each STA to receive its own data
  • the HE-SIG-B field may be transmitted in one or two OFDM symbols.
  • the HE-SIG-B field may include information on the modulation and coding scheme (MCS) of the corresponding PSDU and the length of the corresponding PSDU.
  • MCS modulation and coding scheme
  • the L-STF, L-LTF, L-SIG, and HE-SIG-A fields may be repeatedly transmitted in units of 20 MHz channels. For example, when a PPDU is transmitted on four 20 MHz channels (i.e., 80 MHz band), the L-STF, L-LTF, L-SIG and HE-SIG-A fields may be repeatedly transmitted on every 20 MHz channel. have.
  • legacy STAs supporting legacy IEEE 802.11a / g / n / ac may not be able to decode the HE PPDU.
  • the L-STF, L-LTF, and L-SIG fields are transmitted through a 64 FFT on a 20 MHz channel so that the legacy STA can receive them.
  • the L-SIG field may occupy one OFDM symbol, one OFDM symbol time is 4 ms, and a GI may be 0.8 ms.
  • the FFT size for each frequency unit may be larger from the HE-STF (or HE-SIG-A). For example, 256 FFTs may be used in a 20 MHz channel, 512 FFTs may be used in a 40 MHz channel, and 1024 FFTs may be used in an 80 MHz channel. As the FFT size increases, the number of OFDM subcarriers per unit frequency increases because the interval between OFDM subcarriers becomes smaller, but the OFDM symbol time becomes longer. In order to improve the efficiency of the system, the length of the GI after the HE-STF may be set equal to the length of the GI of the HE-SIG-A.
  • the HE-SIG-A field may include information required for the HE STA to decode the HE PPDU.
  • the HE-SIG-A field may be transmitted through a 64 FFT in a 20 MHz channel so that both the legacy STA and the HE STA can receive it. This is because the HE STA can receive not only the HE format PPDU but also the existing HT / VHT format PPDU, and the legacy STA and the HE STA must distinguish between the HT / VHT format PPDU and the HE format PPDU.
  • FIG. 14 is a diagram illustrating an HE format PPDU according to an embodiment of the present invention.
  • the FFT size per unit frequency may be larger from the HE-STF (or HE-SIG-B).
  • 256 FFTs may be used in a 20 MHz channel
  • 512 FFTs may be used in a 40 MHz channel
  • 1024 FFTs may be used in an 80 MHz channel.
  • the HE-SIG-B field may include information specific to each STA, but may be encoded over the entire band (ie, indicated by the HE-SIG-A field). That is, the HE-SIG-B field includes information on all STAs and may be transmitted so that all STAs receive.
  • the HE-SIG-B field may inform frequency bandwidth information allocated to each STA and / or stream information in a corresponding frequency band.
  • the HE-SIG-B may be allocated 20 MHz for STA 1, 20 MHz for STA 2, 20 MHz for STA 3, and 20 MHz for STA 4.
  • STA 1 and STA 2 may allocate 40 MHz, and STA 3 and STA 4 may then allocate 40 MHz.
  • STA 1 and STA 2 may allocate different streams, and STA 3 and STA 4 may allocate different streams.
  • the HE-SIG C field may be added to the example of FIG. 14.
  • the HE-SIG-B field information on all STAs may be transmitted over the entire band, and control information specific to each STA may be transmitted in units of 20 MHz through the HE-SIG-C field.
  • the HE-SIG-C field may be transmitted after the HE-LTF field.
  • the HE-SIG-B field may be transmitted in units of 20 MHz in the same manner as the HE-SIG-A field without transmitting over the entire band. This will be described with reference to the drawings below.
  • FIG. 15 is a diagram illustrating a HE format PPDU according to an embodiment of the present invention.
  • the HE-SIG-B field is not transmitted over the entire band, but is transmitted in 20 MHz units in the same manner as the HE-SIG-A field. However, at this time, the HE-SIG-B is encoded and transmitted in 20 MHz units differently from the HE-SIG-A field, but may not be copied and transmitted in 20 MHz units.
  • the FFT size per unit frequency may be larger from the HE-STF (or HE-SIG-B).
  • 256 FFTs may be used in a 20 MHz channel
  • 512 FFTs may be used in a 40 MHz channel
  • 1024 FFTs may be used in an 80 MHz channel.
  • the HE-SIG-A field is duplicated and transmitted in units of 20 MHz.
  • the HE-SIG-B field may inform frequency bandwidth information allocated to each STA and / or stream information in a corresponding frequency band. Since the HE-SIG-B field includes information about each STA, information about each STA may be included for each HE-SIG-B field in units of 20 MHz. In this case, in the example of FIG. 15, 20 MHz is allocated to each STA. For example, when 40 MHz is allocated to the STA, the HE-SIG-B field may be copied and transmitted in units of 20 MHz.
  • the data field is a payload and may include a service field, a scrambled PSDU, tail bits, and padding bits.
  • the HE format PPDU as shown in FIGS. 13 to 15 may be identified through a RL-SIG (Repeated L-SIG) field, which is a repetitive symbol of the L-SIG field.
  • the RL-SIG field is inserted before the HE SIG-A field, and each STA may identify the format of the received PPDU as the HE format PPDU using the RL-SIG field.
  • CCA clear channel assessment
  • the STA performs CCA in the physical layer and reports the result to the MAC layer.
  • the STA may perform CCA-ED (Energy Detection) and CCA-CS (Carrier sensing) as two modes of CCA.
  • the STA may determine the occupancy / idle mode of the channel by performing CCA-ED, performing CCA-CS, or using a combination of CCS-CS and CCA-ED.
  • the STA may perform CCA by first performing CCA-CS and additionally performing CCA-ED, performing CCA-ED first, and then further CCA-ED.
  • CCA may be performed by performing CS.
  • the CCA-CS is performed through signal detection for the preamble, and the threshold of the CCA-CS is determined based on the minimum modulation and code rate sensitivity.
  • the level of the CCA-CS that is, the threshold value may be set to a different value according to the bandwidth. For example, the STA determines that the channel is busy when the received preamble signal is greater than -82 dBm in the case of 20 MHz channel spacing, and when the magnitude of the received preamble signal is greater than -85 dBm in the case of 10 MHz channel spacing.
  • the STA may perform CCA-CS using the correlation of the STF in the preamble of the 802.11a signal.
  • a CCA threshold / threshold value in dBm may be referred to as a CCA level.
  • the STA determines to occupy when any signal is detected with an intensity (dBm) equal to or greater than the threshold value regardless of the signal defined in the 802.11 system.
  • the threshold can be estimated to be 20dBm higher than the CCA-CS.
  • the STA determines that the channel is occupied if it is -62 dBm or more, and in case of 10 MHz channel spacing, the STA determines that the channel is busy when the magnitude of the received preamble signal is -65 dBm or more, and 5 MHz In the case of channel spacing, if the received preamble signal has a magnitude of -68 dBm or more, it may be determined that the channel is busy.
  • each channel bandwidth CCA level (threshold values) according to the can be defined as shown in Table 2.
  • 16 is a conceptual diagram illustrating a method of performing CCA according to an embodiment of the present invention.
  • AP1 and STA1 may belong to the first BSS and AP2 and STA2 may belong to the second BSS.
  • AP2 may transmit a PPDU to STA2 through a 20 MHz channel.
  • AP1 determines that the channel is occupied and does not transmit a signal to STA1.
  • it is more efficient for AP1 to transmit a signal to STA1.
  • space resource usage efficiency is reduced. This may be a problem especially when the BSS to which AP1 and STA1 belong and the BSS to which AP2 and STA2 belong are different, especially when the two BSSs are OBSS.
  • the dynamic CCA refers to adjusting the CCA level according to a specific criterion instead of using a fixed CCA level, and performing the CCA according to the adjusted CCA level.
  • the CCA level change may be applied to STAs belonging to different BSSs.
  • it can be used to increase the spatial reuse efficiency of bandwidth between STAs in OBSS.
  • FIG. 17 illustrates a dynamic CCA application environment according to an embodiment of the present invention.
  • FIG. 17 illustrates an embodiment in which AP1 and STA1 belong to one BSS, AP2 and STA2 belong to another BSS, and AP2 performs a dynamic CCA.
  • the type (data or ACK) of the signals transmitted and received by the STAs is shown as an example, and the following embodiments may be applied regardless of the type of the signal.
  • the signal may include a control frame including a data frame, a measurement frame, a management frame, or an RTS / CTS frame except ACK, and the type of the signal is ACK.
  • the case signal may comprise an ACK frame, a block ACK frame or a multiplexed ACK frame.
  • the STA1 transmits an ACK after the SIFS time, indicating that the data transmitted by the AP1 is properly received.
  • AP2 in order to improve space utilization, AP2 must be able to transmit data or ACK to STA2 in a period in which AP1 transmits data or a period in which STA1 transmits ACK.
  • AP2 determines that the channel is occupied and does not transmit data / ACK.
  • the present invention proposes a method of adjusting the CCA level of the STA in consideration of the space utilization as well as the transmission and reception status of the neighboring STA.
  • the section in which AP2 transmits data or ACK by applying dynamic CCA may be limited to the section in which AP1 transmits data to STA1. This is because the data transmission takes longer than the transmission of the ACK, so that AP2 may apply dynamic CCA to transmit data / ACK in the corresponding interval, thereby maximizing space utilization.
  • an embodiment of the present invention described below may also be applied to a period during which STA1 transmits an ACK.
  • STA 1 Information required for AP2 to perform a dynamic CCA and transmit a signal without degrading the link quality of STA1 is required at the MCS level of the signal frame received by the STA1, and signal to inteference-plus-noise ratio. Or received desired power for Signal to Noise Ratio (SNR).
  • SNR Signal to Noise Ratio
  • STA 1 receives a signal with MCS (#n)
  • the minimum requested SINR or SNR for recovering the signal to this MCS level is x dB
  • the SINR or SNR of the signal actually received by STA1 is y dB. If, STA1 has a margin for interference by (xy) dB.
  • the margin for such interference is referred to as an endurable interference margin (EIM), and a unit of the EIM may be expressed in dB.
  • the EIM indicates the amount of interference that the STA is further allowable for the current MCS level.
  • the EIM may be expressed in dBm units.
  • the STA may calculate an EIM in dBm units using at least one of Received Signal Strength Indication (RSSI) information and Received Channel Power Indicator (RCPI) information.
  • RSSI and RCPI are absolute received power (dBm) combined with target signal, interference, and noise.
  • the absolute power (dBm) of the desired signal (desired) from the requested SINR (dB) or SNR (dB) and the actual received signal's SINR (dB) or SNR (dB), and the remaining power (interference + Absolute power (dBm) of noise or noise) can also be calculated.
  • the margin for interference may be calculated using the calculated absolute power values, thereby calculating an EIM in absolute power units (dBm).
  • an EIM of an absolute power unit will be described as an example.
  • AP2 may transmit data or ACK even in a period in which the STA transmits and receives a signal.
  • the STA In order to perform such a dynamic CCA, the STA must transmit the above-described EIM information and transmission power information to the STA of another BSS.
  • the STA may transmit the calculated EIM information to neighboring STAs to inform the margin of its interference.
  • the method for transmitting the EIM may use a physical preamble or a MAC header.
  • the physical header is a physical preamble and may include a HE-STF, HE-LTF, and HE-SIG field. Therefore, the EIM information may be included in the MAC header of the MAC layer and transmitted instead of being included in the physical preamble.
  • the EIM information may be included in the SIA-A field of the physical header.
  • the EIM may be represented by a ⁇ dBm value, and the ⁇ value may be in a range of a ⁇ ⁇ ⁇ b.
  • the quantization signal In order to transmit the EIM value ⁇ , the quantization signal must be transmitted after the quantization is performed.
  • the a value, the b value, and the step size of the number of steps between a and b can be defined as predetermined values as a system parameter. have.
  • the EIM value may have one of ⁇ -12, -10, -8, -6 ⁇ . Since the total number is 4, it may be signaled using 2 bits.
  • the STA may transmit the mapped integer value after mapping the calculated EIM value to an integer by rounding, rounding, and rounding the decimal point unit before signal transmission.
  • the AP / STA may transmit information about transmit power of a signal transmitted by the AP / STA, that is, how many dB the STA transmits at present to the neighboring STAs.
  • the method of transmitting the transmit power information may use a physical preamble or a MAC header.
  • the physical header is a physical preamble and may include a HE-STF, HE-LTF, and HE-SIG field. Therefore, the transmit power information may be included in the MAC header of the MAC layer and transmitted instead of being included in the physical preamble.
  • the transmission power information may be included in the SIA-A field of the physical header.
  • the transmit power may be expressed as a ⁇ dBm value, and the ⁇ value may be in the range of p ⁇ ⁇ ⁇ q.
  • the p value, the q value, and the step size of how many steps between p and q are to be defined as predetermined values as system parameters. Can be.
  • the p value is defined as -5 dBm
  • the q value is defined as 30 dBm
  • the step size is defined as 5 dB
  • the transmit power value is among ⁇ -5, 0, 5, 10, 15, 20, 25, 30 ⁇ . It can have one value, and since the total number is eight, it can be signaled using 3 bits.
  • the STA may express the calculated transmission power value by rounding, rounding, and rounding down the decimal point before signal transmission, mapping the nearest integer value, and then transmitting the mapped integer value.
  • the STA may calculate the received power using a parameter such as RSSI or RCPI or calculate a more accurate receive power using the SNR of the received signal.
  • the formula for calculating the path loss according to the system environment may use the following equations, but as one of the embodiments for calculating the path loss, the path loss may be calculated using an equation or coefficient suitable for the system characteristic.
  • Equation 1 is a formula for calculating the loss in the path
  • L (d) value represents the path loss (dB) value according to the distance.
  • A, B, and C values may have different values according to the radio channel environment.
  • Equation 2 considers the small and medium cities environment, Equation 3 the metropolitan area environment, Equation 4 the suburban environments, and Equation 5 the rural areas.
  • d denotes a distance in km
  • fc denotes a center frequency
  • hb denotes an antenna height of a transmitting terminal
  • hm denotes an antenna height of a receiving terminal.
  • the STA that wants to perform the dynamic CCA may calculate a path loss between the STA and the neighboring STA currently transmitting and receiving, and thus may predict the amount of interference affecting the neighboring STA.
  • the amount of interference that the STA gives to the neighbor STAs during the transmission of the neighbors is defined as a predicted interference power (PIP), and a unit uses dBm.
  • PIP PIP
  • dBm Tx power ( AP2)-Path Loss ⁇ .
  • the STA may perform the dynamic CCA by comparing the EIM received from the neighboring STAs with the amount of interference (PIP) that can be given.
  • PIP amount of interference
  • the STA may increase the current CCA level by + n dB.
  • the increase amount (n value) of the CCA level may use a fixed value or a changeable value depending on the comparison result of the EIM-PIP.
  • the increased CCA level may be limited to the maximum value.
  • the maximum CCA level may be limited to the threshold of the CCA-ED according to the bandwidth.
  • the STA may maintain the current CCA level or reduce the signal by n dB.
  • the reduced CCA level may be limited to a minimum value.
  • the minimum CCA level may be the minimum CCA level of the legacy STA according to the corresponding bandwidth.
  • the STA may maintain the current CCA level.
  • the STA may reduce the current CCA level by m dB or immediately change to the minimum value of the CCA level.
  • the STA may maintain the CCA level.
  • the CCA level may be increased or decreased as described above according to the system situation and the communication environment of the STA.
  • the minimum and maximum values of the above-described CCA level may be -82 dBm and -62 dBm in the case of the 20 MHz band in the embodiment of Table 1, respectively.
  • the 40MHz band can be -79dBm and -59dBm, respectively
  • in the case of the 80MHz band can be -76dBm and -86dBm, respectively.
  • the STA may adjust the transmit power in conjunction with or instead of adjusting the CCA level. For example, (1) when the EIM is larger than the PIP, the transmission power can be increased. In this case, the increased transmission power may be limited to a range in which the EIM is equal to the PIP or the EIM is larger than the PIP. And (2) when the EIM is smaller than the PIP, transmission power can be reduced. The reduced transmit power may be limited in consideration of the EIM, MCS level, channel environment, etc. of the target STA of the signal.
  • FIG. 18 illustrates a STA apparatus according to an embodiment of the present invention.
  • a STA device may include a memory 1802 0, a processor 1820, and an RF unit 1830. As described above, the STA device may be an AP or a non-AP STA as an HE STA device.
  • the RF unit 1830 may be connected to the processor 1820 to transmit / receive a radio signal.
  • the RF unit 1802 may up-convert data received from the processor into a transmission / reception band to transmit a signal.
  • the processor 1820 may be connected to the RF unit 1830 to implement a physical layer and / or a MAC layer according to the IEEE 802.11 system.
  • the processor 1802 may be configured to perform operations according to various embodiments of the present disclosure according to the above-described drawings and descriptions.
  • a module that implements the operation of the STA according to various embodiments of the present disclosure described above may be stored in the memory 18010 and executed by the processor 1820.
  • the memory 18010 is connected to the processor 1820 and stores various information for driving the processor 1820.
  • the memory 18010 may be included in the processor 1820 or may be installed outside the processor 1820 and connected to the processor 1820 by known means.
  • the STA apparatus may include a single antenna or multiple antennas.
  • the specific configuration of the STA apparatus of FIG. 18 may be implemented such that the matters described in the above-described various embodiments of the present invention are applied independently or two or more embodiments are simultaneously applied.
  • FIG. 19 illustrates a data transmission method of an STA apparatus according to an embodiment of the present invention.
  • the STA may receive a signal from a first STA of another BSS (S19010).
  • the BSS to which the STA belongs and the first BSS to which the first STA belongs may be OBSS.
  • the received signal may not be a signal transmitted by the first STA to the STA, or may be data or an ACK signal transmitted by the first STA to neighboring STAs.
  • the STA may obtain EIM information and transmit power information from the received signal (S19020).
  • the EIM information indicates the amount of allowable interference allowed by the first STA
  • the transmit power information indicates the transmit power of the first STA.
  • the EIM information and the transmit power information may be included in the physical header or the MAC header of the received signal. When included in the physical header, the EIM information and the transmit power information may be included in the SIG-A field.
  • the STA may acquire a PIP using the transmit power information (S19030).
  • the PIP may indicate the amount of interference given to the first STA when the STA transmits a signal.
  • the PIP acquisition method of the STA is as described above. That is, the STA can obtain a path loss between the STA and the first STA using the transmission power of the first STA and the power of the signal received from the first STA. The PIP may be obtained using the obtained path loss and the transmit power of the STA.
  • the STA may adjust the CCA level or adjust the transmission power based on the EIM and the PIP (S19040).
  • the method of adjusting the CCA level and the transmission power of the STA is as described above.
  • the STA may increase the CCA level when the EIM is larger than the PIP and maintain or decrease the CCA level when the EIM is smaller than the PIP.
  • the STA may increase the transmit power when the EIM is larger than the PIP or decrease the transmit power when the EIM is smaller than the PIP.
  • the CCA level to be adjusted may be adjusted between the minimum and maximum values as described above.
  • the STA may perform CCA according to the adjusted CCA level and may start signal transmission according to a result of comparing the received signal strength with the CCA level.
  • the STA performs CCA according to the predefined CCA level, initiates signal transmission according to the result of comparing the received signal strength with the CCA level, and describes the power of the transmitted signal as described above. It can be adjusted and transmitted together.
  • the STA If the received signal strength is greater than the adjusted CCA level as a result of performing the CCA, the STA detects the corresponding wireless medium as the occupied condition, and if the received signal strength is less than the adjusted CCA level, the STA detects the corresponding wireless medium as the late condition. Can be. And if the wireless medium is in an idle condition, the STA can initiate data transmission.
  • the start of the data transmission may further include the steps of transmitting the RTS frame as well as simply transmitting the data, receiving the CTS frame and transmitting the data as described above.
  • the data transmission and reception method has been described with reference to the example applied to the IEEE 802.11 system, but it is possible to apply to various wireless communication systems in addition to the IEEE 802.11 system.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Mobile Radio Communication Systems (AREA)

Abstract

L'invention concerne un procédé par lequel un dispositif de station (STA) émet des données dans un système de LAN sans fil (WLAN). Le procédé d'émission des données du dispositif de STA, selon la présente invention, comporte les étapes consistant à: recevoir un signal provenant d'une première STA d'une première cellule de service de base (BSS); acquérir une information de marge de brouillage tolérable (EIM) et une information de puissance d'émission de la première STA à partir du signal reçu; acquérir une puissance prédite de brouillage (PIP) en utilisant l'information de puissance d'émission de la première STA; et en comparant l'EIM à la PIP, et régler un niveau de CCA ou la puissance d'émission en fonction du résultat de comparaison.
PCT/KR2015/011142 2015-02-05 2015-10-21 Procédé et dispositif d'émission de données dans un système de communications sans fil WO2016125983A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201562112173P 2015-02-05 2015-02-05
US62/112,173 2015-02-05

Publications (1)

Publication Number Publication Date
WO2016125983A1 true WO2016125983A1 (fr) 2016-08-11

Family

ID=56564292

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/KR2015/011142 WO2016125983A1 (fr) 2015-02-05 2015-10-21 Procédé et dispositif d'émission de données dans un système de communications sans fil

Country Status (1)

Country Link
WO (1) WO2016125983A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11432247B2 (en) 2019-04-22 2022-08-30 Cypress Semiconductor Corporation Methods, systems and devices for varying wireless transmit power based on path loss information
US12096278B2 (en) 2019-02-14 2024-09-17 Google Llc Dynamic resource allocation across multiple network service providers

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030022686A1 (en) * 2001-06-29 2003-01-30 Koninklijke Philips Electronics N.V. Noise margin information for power control and link adaptation in IEEE 802.11h WLAN
US20060253736A1 (en) * 2005-04-08 2006-11-09 Interdigital Technology Corporation Method for transmit and receive power control in mesh systems
US20080167063A1 (en) * 2007-01-05 2008-07-10 Saishankar Nandagopalan Interference mitigation mechanism to enable spatial reuse in uwb networks
WO2014071308A1 (fr) * 2012-11-02 2014-05-08 Interdigital Patent Holdings, Inc. Procédés et procédures de régulation de puissance pour réseaux locaux sans fil
WO2015003057A2 (fr) * 2013-07-03 2015-01-08 Interdigital Patent Holdings, Inc. Procédés multi-bandes pour systèmes de réseau local sans fil à brouillage limité

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030022686A1 (en) * 2001-06-29 2003-01-30 Koninklijke Philips Electronics N.V. Noise margin information for power control and link adaptation in IEEE 802.11h WLAN
US20060253736A1 (en) * 2005-04-08 2006-11-09 Interdigital Technology Corporation Method for transmit and receive power control in mesh systems
US20080167063A1 (en) * 2007-01-05 2008-07-10 Saishankar Nandagopalan Interference mitigation mechanism to enable spatial reuse in uwb networks
WO2014071308A1 (fr) * 2012-11-02 2014-05-08 Interdigital Patent Holdings, Inc. Procédés et procédures de régulation de puissance pour réseaux locaux sans fil
WO2015003057A2 (fr) * 2013-07-03 2015-01-08 Interdigital Patent Holdings, Inc. Procédés multi-bandes pour systèmes de réseau local sans fil à brouillage limité

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12096278B2 (en) 2019-02-14 2024-09-17 Google Llc Dynamic resource allocation across multiple network service providers
US11432247B2 (en) 2019-04-22 2022-08-30 Cypress Semiconductor Corporation Methods, systems and devices for varying wireless transmit power based on path loss information

Similar Documents

Publication Publication Date Title
WO2016159513A1 (fr) Procédé et appareil pour transmettre des données dans un système de communication sans fil
WO2016089059A1 (fr) Procédé de transmission de données dans un système de communication sans fil et son dispositif
WO2016143970A1 (fr) Procédé et appareil de transmission de données dans un système de communication sans fil
WO2016053024A1 (fr) Procédé de transmission de données dans un système de communication sans fil et dispositif associé
WO2016028125A2 (fr) Procédé destiné à une transmission en liaison montante dans un système de communication sans fil, et appareil correspondant
WO2016032258A2 (fr) Procédé de transfert de données dans un système de communication sans fil, et dispositif associé
WO2016028124A1 (fr) Procédé de transmission de données dans un système de communication sans fil et appareil associé
WO2016099139A1 (fr) Procédé de transmission de données dans un système de communication sans fil et dispositif associé
WO2017022898A1 (fr) Procédé de transmission de données dans un système de communications sans fil, et appareil associé
WO2017034081A1 (fr) Procédé et dispositif de transmission de données dans un système de communication sans fil
WO2016024750A1 (fr) Procédé et dispositif pour une transmission multiutilisateur en liaison descendante dans un système de communication sans fil
WO2016028131A1 (fr) Procédé de transmission à plusieurs utilisateurs en liaison montante dans un système de communication sans fil et appareil correspondant
WO2016021838A1 (fr) Procédé pour la transmission d'un signal dans un système de communication sans fil et dispositif correspondant
WO2020045891A1 (fr) Procédé et dispositif destinés à établir une transmission commune dans un système de réseau local sans fil
WO2015199306A1 (fr) Procédé de transmission de données de liaison montante multi-utilisateur dans un système de communications sans fil, et dispositif correspondant
WO2016021831A1 (fr) Procédé de transmission à multiples utilisateurs dans un système de communication sans fil et dispositif associé
WO2016039526A1 (fr) Procédé et dispositif de transmission de données dans un système wlan
WO2016099140A1 (fr) Procédé de transmission de données dans un système de communication sans fil et dispositif associé
WO2016125998A1 (fr) Procédé de transmission et de réception multiutilisateur dans un système de communication sans fil, et dispositif correspondant
WO2016167608A1 (fr) Procédé de sondage de canal dans un système de communication sans fil et appareil correspondant
WO2016167609A1 (fr) Procédé de sondage de canal dans un système de communication sans fil et dispositif à cet effet
WO2017043713A1 (fr) Procédé de transmission de données dans un système de communication sans fil et appareil associé
WO2016182390A1 (fr) Procédé d'envoi ou de réception de trame dans un système lan sans fil, et appareil associé
WO2016017946A1 (fr) Dispositif et procédé de transmission et de réception dans un système de communications sans fil
WO2016089003A1 (fr) Procédé pour transmettre/recevoir une unité de données de protocole physique (ppdu) dans un système de communication sans fil et appareil associé

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 15881301

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 15881301

Country of ref document: EP

Kind code of ref document: A1