KR102271827B1 - Frame transmitting method for uplink mu-mimo communication - Google Patents

Abstract

A method of transmitting and receiving frames for multi-user-multi-input multi-out (MU-MIMO) communication in an access point (AP) is disclosed. The method for transmitting and receiving a frame according to an embodiment includes determining at least one transmission station, transmitting an uplink multi-user poll (UL MU Poll) frame requesting a data frame to the at least one transmission station, the at least The method may include simultaneously receiving a data frame from one transmitting station and transmitting an Ack frame corresponding to the data frame reception to the at least one transmitting station.

Description

FRAME TRANSMITTING METHOD FOR UPLINK MU-MIMO COMMUNICATION

The present disclosure relates to a protocol of a wireless LAN, and in particular, to a method of transmitting a frame using an uplink MU-MIMO technology.

In recent wireless communication systems, MIMO technology for transmitting and receiving data using two or more antennas has become common. In wireless LAN, two or more transmit antennas can be used from the IEEE 802.11n standard. In 802.11n, up to 4 antennas and 802.11ac up to 8 antennas can be used. In addition, when multiple transmit antennas are used, data may be transmitted using transmit beamforming technology in order to improve signal reception performance.

In IEEE 802.11ac, which is being standardized recently, a downlink MU-MIMO technology in which an access point (hereinafter referred to as an AP) simultaneously transmits a beamforming data frame to multiple STAs in order to use frequency resources more efficiently. In addition, studies are being conducted on uplink MU-MIMO technology in which several STAs transmit data frames to the AP at the same time, and the AP separates and receives data frames transmitted by multiple STAs for each stream separately. .

An operation example of a case in which two or more stations want to transmit data to an AP using the conventional WLAN technology is shown in FIG. 1A . Station 1 (STA 1) and station 1 (STA 2) start a random backoff when the channel becomes idle, and in FIG. 1A , station 1 (STA 1 ), after which the backoff is first completed, sends the first data to the AP. A frame (Data frame 1) is transmitted, and a first acknowledgment (Ack 1) is received. At this time, since the station 1 (STA 2) can listen to the frames transmitted by the station 1 (STA 1), the backoff is stopped, and after the first Ack 1 frame ends, the station 1 (STA 2) backoffs again to the AP for the second time. Transmit a data frame (Data frame 2).

Here, an example of an operation when the Uplink MU-MIMO technology is applied is shown in FIG. 1B.

As in FIG. 1A , when the channel becomes idle, the station 1 (STA 1) and the station 1 (STA 2) start a random backoff, and the station 1 (STA 1), which has finished the backoff first, performs beamforming first data. A frame (Data frame 1) is transmitted to the AP. However, since the frame is beamformed, the station 1 (STA 2 ) cannot hear the frame, so it continues the backoff and then transmits the beamformed second data frame (Data frame 2) to the AP.

However, for the AP, if the second data frame (Data frame 2) is received while the first data frame (Data frame 1) is being received, the PHY layer cannot properly receive data. According to published research results, uplink MU-MIMO frames can be received only when they are time-synchronized within an error of 100 ns or less.

Therefore, it is impossible to receive uplink MU-MIMO data using the existing method.

A method for transmitting and receiving a frame for multi-user-multi-input multi-out (MU-MIMO) communication in an access point (AP) according to an embodiment includes determining at least one transmitting station, and transmitting data to the at least one transmitting station. Transmitting an uplink multi-user poll (UL MU Poll) frame requesting a frame, receiving a data frame simultaneously from the at least one transmitting station, and an acknowledgment corresponding to receiving a data frame to the at least one transmitting station Ack) transmitting the frame.

The uplink multi-user poll frame may include identification information of each of the at least one transmission station.

The identification information of each of the at least one transmission station may include at least one of a MAC address, an AID, and partial AID information in IEEE 802.11ac.

The uplink multi-user poll frame may include at least one of the number of transmission stations and transmission period information.

The step of transmitting the uplink multi-user poll (UL MU Poll) frame may be transmitted based on a multi-user multi-input multi-out (MU MIMO) technique or may be transmitted in a non-beamforming state.

The receiving of the data frame may include receiving the data frame based on a multi-user multi-input multi-out (MU MIMO) technique.

The transmitting of the ACK frame may include transmitting a group ACK frame including at least one of identification information of the at least one transmitting station and a bitmap in which each of the at least one transmitting station is mapped to one bit. can

In the transmitting of the ACK frame, the group ACK may be transmitted without beamforming.

The transmitting of the ACK frame may include transmitting at least one ACK frame, each of which includes identification information of each of at least one transmitting station.

The transmitting of the ACK frame may include transmitting the at least one ACK frame based on a multi-user multi-input multi-out (MU MIMO) technique.

On the other hand, a method for transmitting and receiving a frame for multi-user-multi-input multi-out (MU-MIMO) communication in a transmitting station according to another embodiment includes an uplink multi-user poll (UL) requesting a data frame from an access point (AP). MU Poll) frame, receiving the uplink multi-user poll (UL MU Poll) frame and after a preset time (SIFS), transmitting a data frame to the access point, and corresponding to receiving the data frame It may include the step of receiving an acknowledgment (Ack) frame.

The uplink multi-user poll frame may include identification information of each of the at least one transmission station.

The identification information of each of the at least one transmission station may include at least one of a MAC address, an AID, and partial AID information in IEEE 802.11ac.

The uplink multi-user poll frame may include at least one of the number of transmission stations and transmission period information.

Receiving the uplink multi-user poll (UL MU Poll) frame may be received based on a multi-user multi-input multi-out (MU MIMO) technique or may be received in a non-beamforming state.

The transmitting of the data frame may include transmitting the data frame based on a multi-user multi-input multi-out (MU MIMO) technique.

The receiving of the ACK frame may include receiving a group ACK frame including at least one of identification information of the transmitting station and a bitmap in which each of the transmitting stations is mapped to one bit.

The receiving of the ACK frame may include receiving the group ACK without beamforming.

The receiving of the acknowledgment frame may include receiving an acknowledgment frame including identification information of the transmitting station.

The receiving of the ACK frame may include receiving the ACK frame based on a multi-user multi-input multi-out (MU MIMO) technique.

An access point for multi-user-multi-input multi-out (MU-MIMO) communication according to another embodiment includes a control unit that determines at least one transmission station and an uplink multi-user that requests a data frame from the at least one transmission station A communication unit for transmitting a poll (UL MU Poll) frame, receiving a data frame simultaneously from the at least one transmitting station, and transmitting an Ack frame corresponding to the data frame reception to the at least one transmitting station can

A transmission station for multi-user-multi-input multi-out (MU-MIMO) communication according to another embodiment receives an uplink multi-user poll (UL MU Poll) frame requesting a data frame from an access point (AP) and a control unit controlling the communication unit to receive the uplink multi-user poll (UL MU Poll) frame and to transmit a data frame to the access point after a preset time (SIFS), wherein the communication unit comprises the An acknowledgment frame corresponding to data frame reception may be received.

The communication unit transmits the data frame based on a multi-user multi-input multi-out (MU MIMO) technology, receives a group ACK in a non-beamforming state, and receives an ACK frame including identification information of the transmitting station in multi It can be received based on user multi-input multi-out (MU MIMO) technology.

1A and 1B are conceptual diagrams for explaining an operation when two or more conventional stations want to transmit data to an AP.
2 is a block diagram of an AP and a station according to an embodiment.
3 is a timing diagram illustrating operations of an AP and a station according to an embodiment.
4 is a structure of a UL MU Poll frame according to an embodiment.
5 and 6 are structures of a group ACK according to various embodiments of the present disclosure.
7 and 8 are conceptual diagrams of a UL MU-MIMO data transmission protocol according to various embodiments.

Hereinafter, some embodiments will be described in detail with reference to the accompanying drawings. However, it is not limited or limited by these embodiments. Like reference numerals in each figure indicate like elements.

The terms used in the description below have been selected as currently widely used general terms as possible while considering functions in the present invention, which may vary depending on the intention or custom of those skilled in the art, the emergence of new technologies, and the like.

In addition, in specific cases, there are terms arbitrarily selected by the applicant for understanding and/or convenience of explanation, and in this case, the detailed meaning will be described in the corresponding description. Therefore, the terms used in the description below should be understood based on the meaning of the term and the content throughout the specification, not the simple name of the term.

2 is a block diagram of an AP and a station according to an embodiment.

As shown in FIG. 2 , the AP 100 may include a control unit 110 and a communication unit 120 .

The control unit 110 may generate a frame transmitted from the communication unit 120 . The control unit 110 may process the frame received from the communication unit 120 . The controller 110 may control the communication unit 120 to communicate with at least one of the communication units 220-1, 220-2, and 220-n of the station based on the MIMO method.

Meanwhile, the control unit 210-1, 210-2, 210-n may process a frame received from the communication unit 220-1, 220-2, 220-n or generate a frame transmitted by the communication unit 220-1,220-2, 220-n. . The controllers 210 - 1 , 210 - 2 , and 210 -n may control the communication units 220 - 1 , 220 - 2 and 220 -n to transmit a data frame after, for example, a UL MU poll frame is received and SIFS is received.

The control unit 110 or 210-1, 210-2, 210-n may be implemented as an IC chip, a microprocessor, a mini computer, or the like, and for example, the communication unit 120 may determine a communication station. The operation of the control unit 110 or 210-1, 210-2, 210-n will be described later in more detail.

The communication unit 120 of the AP 100 may communicate with at least one of the communication units 220 - 1 , 220 - 2 and 220 -n of the station 200 . The communication unit 120 of the AP 100 includes at least one of the communication units 220-1, 220-2, and 220-n of the station 200 and an Up-link multi user Poll frame (hereinafter, UL MU Poll frame). , a data frame and an acknowledgment frame may be transmitted and received. The communication unit 120 may include various communication modules such as an antenna, a demodulator, a frequency processing device, and a filter device.

3 is a timing diagram illustrating operations of an AP and a station according to an embodiment.

In step 310, the AP 100 may determine a transmitting station to transmit the data frame. For example, the AP 100 may determine at least one of the plurality of stations in the environment shown in FIG. 2 as the transmission station.

In step 320 , the AP 100 may transmit a UL MU Poll frame to the station 200 . The UL MU Poll frame may be a frame indicating a transmitting station, and may also be a frame instructing the transmitting station to transmit a data frame. After receiving the UL MU Poll frame, the transmitting station may be preset to transmit the data frame after a preset time (SIFS). Meanwhile, in another embodiment, the AP 100 may use the RTS/CTS exchange before transmitting the UL MU Poll frame for protection.

The structure of the UL MU Poll frame according to an embodiment may be as shown in FIG. 4 . 4, the UL MU Poll frame includes a frame control field (Frame Control), an RA field (RA), a TA field (TA), a UL MU-MIMO common information field (UL MU-MIMO Info), and a transmission station. Fields STA1, STA2, and STAn may include an FCS field (FCS). As described above, the UL MU Poll frame may include the transmission station fields STA1, STA2, and STAn, and may include identification information for the transmission station. In an embodiment, the identification information for the transmitting station may include at least one of information such as MAC address, AID, and Partial AID as in IEEE 802.11ac.

Meanwhile, the UL MU Poll frame may include UL MU-MIMO common information. The UL MU-MIMO common information may include the number of stations that will simultaneously transmit data frames, and an L-LENTGH value included in the L-SIG among the PHY layer overhead. Here, simultaneity may mean the same thing in time or may mean within a preset error range. The transmission period information field (L-LENGTH) may be used as a LENGTH value included in the L-SIG of a beamformed data frame to be transmitted by stations during an uplink MU-MIMO transmission period.

If the PPDU type of the beamformed data frame is HT or VHT PPDU, the LENGTH field of the L-SIG is converted into the temporal length of the frame. Accordingly, when stations transmit a data frame, they can transmit an amount of data corresponding to a temporal length specified in L-LENGTH.

Again referring to FIG. 3 , the station 200 may receive a UL MU Poll frame. The station 200 may determine whether the station itself is a transmitting station by checking identification information on the transmitting station in the UL MU Poll frame.

In step 330 , when the station 200 is a transmitting station, it may receive a UL MU Poll frame and transmit a data frame after SIFS. In addition, as other transmitting stations also receive the UL MU Poll frame and transmit the data frame after SIFS, all transmitting stations may transmit the data frame to the AP at the same time.

In step 340 , the AP 100 may transmit an Ack frame to the transmitting station 200 . The AP 100 should transmit an Ack frame to all transmission stations, and for this, a group address indicating a preset UL MU-MIMO group may be used as an RA. The Ack frame including the group address may be referred to as a group Ack.

5 and 6 are structures of a group ACK according to various embodiments of the present disclosure. As shown in FIG. 5 , it can be confirmed that the group address (UL MU Group) is included in the RA field. In an embodiment, the group address may include identification information of a transmitting station successfully receiving the data frame, which is to indicate whether the data frame is received.

In addition, as shown in FIG. 6 , a UL MU Ack bitmap may be further included. Here, the UL MU ACK bitmap may be a bitmap in which one bit is mapped to one STA. The UL MU ACK bitmap may be prepared based on the list of stations included in the UL MU Poll frame and their order.

At least one of the UL MU Poll frame and the Ack frame according to an embodiment may be transmitted based on a downlink MU-MIMO (downlink MU-MIMO) scheme or may be transmitted without performing beamforming.

7 and 8 are conceptual diagrams of a UL MU-MIMO data transmission protocol according to various embodiments. In more detail, FIG. 7 is a data transmission protocol for a case where UL MU Poll and Group Ack do not use MU-MIMO technology.

Referring to FIG. 7 , for protection, the AP may use RTS/CTS exchange before transmission of a UL MU Poll frame. In more detail, the AP may perform backoff after a channel busy period. When the backoff is performed, the AP may transmit an RTS to the stations STA1 and STA2. When the stations STA1 and STA2 receive the RTS, they may transmit the CTS to the AP after SIFS.

When the AP receives the CTS, it may transmit a UL MU Poll frame to the transmitting stations STA1 and STA2 after SIFS. Transmission of the UL MU Poll frame may be performed in a non-beamforming state.

The transmitting stations STA1 and STA2 may transmit data frames (Data frame1, Data frame2) after SIFS from receiving the UL MU Poll frame. Here, the data frames (Data frame1, Data frame2) may be transmitted based on MU-MIMO technology.

The AP may receive the data frame (Data frame1, Data frame2) and transmit the group ACK frame to the transmitting stations after SIFS. Here, the group ACK frame may be performed in a non-beamforming state.

Meanwhile, FIG. 8 illustrates a case in which UL MU Poll and Ack are transmitted using Downlink MU-MIMO technology.

Referring to FIG. 8 , for protection, the AP may use RTS/CTS exchange before transmission of a UL MU Poll frame. In more detail, the AP may perform backoff after a channel busy period. When the backoff is performed, the AP may transmit an RTS to the stations STA1 and STA2. When the stations STA1 and STA2 receive the RTS, they may transmit the CTS to the AP after SIFS.

When the AP receives the CTS, it may transmit a UL MU Poll frame to the transmitting stations STA1 and STA2 after SIFS. The UL MU Poll frame may be transmitted based on MU-MIMO technology.

The transmitting stations STA1 and STA2 may transmit data frames (Data frame1, Data frame2) after SIFS from reception of the UL MU Poll frame. Here, the data frames (Data frame1, Data frame2) may be transmitted based on MU-MIMO technology.

The AP may receive the data frames (Data frame1, Data frame2) and transmit each of the first ACK frame and the second frame to the transmitting stations after SIFS. Here, the first and second ACK frames may be transmitted based on MU-MIMO technology. In this case, each of the first ACK frame and the second frame may include the first station identification information and the second station identification information, respectively.

The device described above may be implemented as a hardware component, a software component, and/or a combination of the hardware component and the software component. For example, devices and components described in the embodiments may include, for example, a processor, a controller, an arithmetic logic unit (ALU), a digital signal processor, a microcomputer, a field programmable array (FPA), It may be implemented using one or more general purpose or special purpose computers, such as a programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. The processing device may execute an operating system (OS) and one or more software applications running on the operating system. The processing device may also access, store, manipulate, process, and generate data in response to execution of the software. For convenience of understanding, although one processing device is sometimes described as being used, one of ordinary skill in the art will recognize that the processing device includes a plurality of processing elements and/or a plurality of types of processing elements. It can be seen that can include For example, the processing device may include a plurality of processors or one processor and one controller. Other processing configurations are also possible, such as parallel processors.

The software may comprise a computer program, code, instructions, or a combination of one or more thereof, which configures a processing device to operate as desired or is independently or collectively processed You can command the device. The software and/or data may be any kind of machine, component, physical device, virtual equipment, computer storage medium or device, to be interpreted by or to provide instructions or data to the processing device. , or may be permanently or temporarily embody in a transmitted signal wave. The software may be distributed over networked computer systems, and stored or executed in a distributed manner. Software and data may be stored in one or more computer-readable recording media.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be specially designed and configured for the embodiment, or may be known and available to those skilled in the art of computer software. Examples of the computer-readable recording medium include magnetic media such as hard disks, floppy disks and magnetic tapes, optical media such as CD-ROMs and DVDs, and magnetic such as floppy disks. - includes magneto-optical media, and hardware devices specially configured to store and carry out program instructions, such as ROM, RAM, flash memory, and the like. Examples of program instructions include not only machine language codes such as those generated by a compiler, but also high-level language codes that can be executed by a computer using an interpreter or the like. The hardware devices described above may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.

As described above, although the embodiments have been described with reference to the limited embodiments and drawings, various modifications and variations are possible from the above description by those skilled in the art. For example, the described techniques are performed in a different order than the described method, and/or the described components of the system, structure, apparatus, circuit, etc. are combined or combined in a different form than the described method, or other components Or substituted or substituted by equivalents may achieve an appropriate result.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (13)

A method for a station (Station, STA) to transmit an uplink (UL) physical layer protocol data unit (PPDU) in a wireless communication system, the method comprising:
receiving, by the STA, a first frame requesting an immediate response from one or more STAs including the STA from an access point (AP); and
transmitting, by the STA, a second frame included in the UL PPDU to the AP; and
Receiving, by the STA, an acknowledgment (ACK) frame from the AP in response to the UL PPDU;
The first frame includes length information, the length information is commonly applied to one or more frames simultaneously transmitted from the one or more STAs including the STA, and the ACK frame identifies the one or more STAs. UL PPDU transmission method, including information.
The method of claim 1,
The length information indicates a value of a Legacy-Signal (L-SIG) length field of the UL PPDU that is a response of the first frame.
The method of claim 1,
The first frame further includes one or more user fields corresponding to each of the one or more STAs.
4. The method of claim 3,
Each of the one or more user fields includes a Partial Association Identifier (AID) of an STA, UL PPDU transmission method.
The method of claim 1,
The UL PPDU is transmitted after the first frame is transmitted and a Short Inter-Frame Space (SIFS) is transmitted.
The method of claim 1,
The UL PPDU is transmitted based on a multiple user transmission scheme.
The method of claim 1,
The UL PPDU includes one or more data units transmitted from the one or more STAs.
delete The method of claim 1,
The ACK frame includes bitmap information,
Each bit of the bitmap information indicates whether reception of each data unit of the one or more data units is successful.
delete In a method for an access point (AP) to receive an uplink (UL) physical layer protocol data unit (PPDU) in a wireless communication system,
transmitting, by the AP, a first frame requesting an immediate response to one or more stations (STAs);
receiving, by the AP, one or more second frames included in the UL PPDU from the one or more STAs; and
transmitting, by the AP, an acknowledgment (ACK) frame to the one or more STAs in response to the UL PPDU;
The first frame includes length information, and the length information is commonly applied to the one or more second frames transmitted simultaneously from the one or more STAs;
The ACK frame includes identification information for the one or more STAs.
In an apparatus for a station (Station, STA) for transmitting an uplink (UL) physical layer protocol data unit (PPDU) in a wireless communication system,
transceiver; and
Including a control unit for controlling the transceiver,
The control unit is
Receiving a first frame requesting an immediate response from one or more STAs including the STA from an access point (AP) through the transceiver,
Transmitting a second frame included in the UL PPDU to the AP through the transceiver,
Receives an acknowledgment (ACK) frame from the AP in response to the UL PPDU through the transceiver,
The first frame includes length information, and the length information is commonly applied to one or more frames transmitted simultaneously from the one or more STAs including the STA,
The apparatus for transmitting a UL PPDU, wherein the ACK frame includes identification information for the one or more STAs.
An apparatus for an access point (AP) for receiving an uplink (UL) physical layer protocol data unit (PPDU) in a wireless communication system, the apparatus comprising:
transceiver; and
Including a control unit for controlling the transceiver,
The control unit is
Transmitting a first frame requesting an immediate response to one or more stations (STAs) through the transceiver,
Receive one or more second frames included in the UL PPDU from the one or more STAs through the transceiver, and
Transmitting an acknowledgment (ACK) frame to the one or more STAs in response to the UL PPDU through the transceiver,
The first frame includes length information, and the length information is commonly applied to the one or more second frames transmitted simultaneously from the one or more STAs;
The apparatus for an AP receiving a UL PPDU, wherein the ACK frame includes identification information for the one or more STAs.

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