KR20230127122A - Apparatus and method for channel sounding - Google Patents

Abstract

A method for operating a first device communicating with a second device in a wireless local area network (WLAN) system, which includes the first device and the second device according to an exemplary embodiment of the present disclosure, comprises: receiving a null data packet (NDP), which is based on a predetermined protocol standard, from the second device; estimating a channel with the second device based on the NDP; determining whether channel smoothing related conditions are satisfied based on the estimated channel; generating channel smoothing related phase information based on the determination result; and transmitting a feedback frame, which includes the channel smoothing related phase information, to the second device. Therefore, the method can efficiently use the hardware resources of the station and the time-frequency resources for communication.

Description

Apparatus and method for channel sounding {APPARATUS AND METHOD FOR CHANNEL SOUNDING}

The technical idea of the present disclosure relates to wireless communication, and specifically, to an apparatus and method for channel sounding based on a predetermined protocol standard.

As an example of wireless communication, a wireless local area network (WLAN) is a technology for connecting two or more devices to each other using a wireless signal transmission method. The WLAN technology may be based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. The 802.11 standard has evolved into 802.11b, 802.11a, 802.11g, 802.11n, 802.11ac and 802.11ax, and based on orthogonal frequency-division multiplexing (OFDM) technology, transmission rates of up to 1 Gbyte/s are achieved. can support

In 802.11ac, data can be simultaneously transmitted to multiple users through a multi-user multi-input multi-output (MU-MIMO) scheme. On the other hand, in the next-generation protocol standard after 802.11be, EHT (hereinafter referred to as EHT+), which is referred to as EHT (extremely high throughput), supports 6GHz unlicensed frequency band, utilizes bandwidth of up to 320MHz per channel, and hybrid automatic repeat and request (HARQ) introduction, to implement up to 16X16 MIMO support, etc.

Also, in a MU-MIMO communication environment, a beamforming process may be used to improve communication performance. Specifically, a beamformer (or access point) performing a beamforming process may perform beamforming based on feedback about a channel received from a beamformer (or station). The beamformer may provide the beamformed signal to the beamformer. On the other hand, when the beamformer performs a channel smoothing operation on the received signal, when there is a discontinuity between beamforming matrices corresponding to adjacent subcarriers among the subcarriers of the signal, the discontinuity component is lost. The energy of the signal is reduced, and as a result, the packet error rate (PER) may increase. Therefore, beamformy did not perform a separate channel smoothing operation on the beamformed signal.

A problem to be solved by the technical idea of the present disclosure is channel sounding that reduces discontinuity between beamforming matrices corresponding to adjacent subcarriers so that a beamformer can perform a channel smoothing operation on a beamformed signal in a wireless communication system. It provides an apparatus and method for

A method of operating a first device communicating with a second device in a wireless local area network (WLAN) system including a first device and a second device according to an exemplary embodiment of the present disclosure is based on a predetermined protocol standard. Receiving a null data packet (NDP) from the second device, estimating a channel with the second device based on the NDP, and determining whether channel smoothing-related conditions are satisfied based on the estimated channel. Determining, generating the channel smoothing-related phase information based on the determination result, and transmitting a feedback frame including the channel smoothing-related phase information to the second device.

A method of operating a second device communicating with a first device in a wireless local area network (WLAN) system including a first device and a second device according to an exemplary embodiment of the present disclosure is based on a predetermined protocol standard. transmitting a null data packet (NDP) to the first device, and as a response to the NDP, first information about an estimated channel between the first device and the second device and phase information related to channel smoothing receiving, from the first device, a feedback frame including second information indicating whether a PPDU is included, generating a smooth beamformed PPDU based on the first and second information, and and sending a PPDU to the first device.

A first device communicating with a second device in a wireless local area network (WLAN) system according to an exemplary embodiment of the present disclosure, a transceiver configured to receive an NDP based on an EHT protocol standard, and the first device in response to the NDP. a processing circuit configured to determine whether a channel smoothing related condition is satisfied based on an estimated channel between a device and the second device, and to generate the channel smoothing related phase information based on a determination result; is configured to control the transceiver to transmit a feedback frame including phase information related to channel smoothing to the second device.

An access point according to an exemplary embodiment of the present disclosure may receive phase information for minimizing a loss caused by channel smoothing of a station with respect to a beamformed signal from a station and use the phase information for beamforming. Through this, it is possible to maximize the positive effect of the station's channel smoothing operation on the beamformed signal of the access point.

A station according to an exemplary embodiment of the present disclosure determines whether a condition related to channel smoothing is satisfied based on an estimated channel with an access point, and generates phase information related to channel smoothing based on the determination result, thereby generating hardware resources of the station. and time-frequency resources for communication can be efficiently used.

Effects obtainable in the exemplary embodiments of the present disclosure are not limited to the effects mentioned above, and other effects not mentioned are common knowledge in the art to which exemplary embodiments of the present disclosure belong from the following description. can be clearly derived and understood by those who have That is, unintended effects according to the implementation of the exemplary embodiments of the present disclosure may also be derived by those skilled in the art from the exemplary embodiments of the present disclosure.

1 is a diagram illustrating a wireless communication system according to an exemplary embodiment of the present disclosure.
2 is a diagram for explaining a discontinuity of a beamforming matrix for each subcarrier corresponding to a signal beamformed from an access point in a comparative example.
3 is a block diagram illustrating a wireless communication system according to an exemplary embodiment of the present disclosure.
4 is a timing diagram illustrating channel sounding according to an exemplary embodiment of the present disclosure.
5 is a message diagram illustrating a method for channel sounding according to an exemplary embodiment of the present disclosure.
6 and 7 are flowcharts illustrating exemplary embodiments of step S17 in FIG. 5 .
8A and 8B are flowcharts illustrating an exemplary embodiment of step S17 in FIG. 5 .
FIG. 9 is a flowchart illustrating an exemplary embodiment of step S17 in FIG. 5 .
10 is a diagram illustrating an NDPA frame according to an exemplary embodiment of the present disclosure.
11 is a table diagram showing information included in a feedback frame according to an exemplary embodiment of the present disclosure, and FIG. 12 is a diagram showing the configuration of an 'EHT MIMO Control' field of FIG. 11 .
FIG. 13 is a table diagram showing the configuration of the 'EHT Smooth Beamforming Report' field of FIG. 11 .
FIG. 14 is a table diagram showing the configuration of the 'EHT Smooth Beamforming Report' field of FIG. 11 .
15 is a table diagram illustrating subfields of an 'EHT PHY Capabilities Information' field indicating whether smooth beamforming feedback can be supported according to embodiments of the present disclosure.
16A and 16B are timing diagrams specifically illustrating channel sounding according to exemplary embodiments of the present disclosure.
17 is a timing diagram illustrating channel sounding according to an exemplary embodiment of the present disclosure.
18 is a message diagram illustrating a method for channel sounding according to an exemplary embodiment of the present disclosure.
19 is a conceptual diagram illustrating an IoT network system to which exemplary embodiments of the present disclosure are applied.

1 is a diagram illustrating a wireless communication system 10 according to an exemplary embodiment of the present disclosure. Specifically, FIG. 1 shows a wireless local area network (WLAN) system as an example of a wireless communication system 10 .

Advantages and features of the present disclosure, and methods of achieving them, will become clear with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments shown below, but will be implemented in a variety of different forms, and can be used interchangeably, and only the present embodiments make the description of the present disclosure complete. It is also provided to completely inform those skilled in the art of the scope of the disclosure to which the present disclosure belongs, and the scope of the present disclosure is only defined by the scope of the claims. And specific configurations described only in each embodiment of the present disclosure may be used in other embodiments as well. Like reference numbers designate like elements throughout the specification.

Terminology used herein is for describing the embodiments and is not intended to limit the scope of the present disclosure. In this specification, singular forms also include plural forms unless specifically stated otherwise in a phrase. As used herein, "comprises" and/or "comprising" means that a stated component, step, operation, and/or element is present in the presence of one or more other components, steps, operations, and/or elements. or do not rule out additions.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a meaning commonly understood by those of ordinary skill in the art to which this disclosure belongs. In addition, terms defined in commonly used dictionaries are not interpreted ideally or excessively unless explicitly specifically defined.

In addition, in specifically describing the embodiments of the present disclosure, OFDM or OFDMA-based wireless communication systems, in particular, the IEEE 802.11 standard will be the main target, but the main subject matter of the present disclosure is other of communication systems (eg, LTE (Long Term Evolution), LTE-A (LTE-Advanced), NR (New Radio), WiBro (Wireless Broadband), GSM (Global System for Mobile communication) such as cellular) A communication system or a short-range communication system such as Bluetooth or NFC (Near Field Communication)) can also be applied with slight modifications within a range that does not significantly deviate from the scope of the present disclosure, which is a skill skilled in the art of the present disclosure. It will be possible with the judgment of those who have knowledge.

And before proceeding with the detailed description below, it is desirable to set forth the definitions of certain words and phrases used throughout this patent document. The word "connect" and its derivatives refers to any direct or indirect communication between two or more components, whether or not they are in physical contact with each other. The terms “transmit,” “receive,” and “communicate,” as well as their derivatives, include both direct and indirect communications. The terms "comprise" and "comprising" and their derivatives mean an inclusive, non-limiting inclusion. The word "or" is an inclusive term meaning 'and/or'. "Relates to" and its derivatives include, are included in, interconnect with, contain, are contained in, connect to/with, join with/with, communicate with It means to be able to cooperate with, to intervene, to put side by side, to be close to, to be bound by, to have, to have characteristics of, to have a relationship with. The term “controller” means any device, system, or part thereof that controls at least one operation. Such a controller may be implemented in hardware or a combination of hardware and software and/or firmware. Functions associated with any particular controller may be centralized or distributed, either locally or remotely. The phrase “at least one of”, when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be required. For example, “at least one of A, B, and C” includes any one of A, B, C, A and B, A and C, B and C, and combinations of A and B and C.

In addition, various functions described below may be implemented or supported by artificial intelligence technology or one or more computer programs, each of which is composed of computer readable program code and implemented in a computer readable medium. do. The terms "application" and "program" refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or portions thereof suitable for implementation in suitable computer readable program code. The term "computer readable program code" includes all types of computer code, including source code, object code, and executable code. The term "computer readable medium" means a computer memory, such as read only memory (ROM), random access memory (RAM), hard disk drive, compact disc (CD), digital video disc (DVD), or any other type of memory. Includes all types of media that can be accessed by A “non-transitory” computer readable medium excludes wired, wireless, optical, or other communication links that transmit transitory electrical or other signals. Non-transitory computer readable media include media on which data can be permanently stored, and media on which data can be stored and later overwritten, such as rewritable optical discs or removable memory devices.

In various embodiments of the present disclosure described below, a hardware access method will be described as an example. However, since various embodiments of the present disclosure include technology using both hardware and software, various embodiments of the present disclosure do not exclude software-based access methods.

In addition, terms referring to control information, terms referring to entries, terms referring to network entities, terms referring to messages, and components of devices used in the following description are It is illustrated for convenience of description. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

Referring to FIG. 1, a wireless communication system 10 includes first and second access points AP1 and AP2, a first station STA1, a second station STA2, a third station STA3, and a fourth station. (STA4) may be included. The first and second access points AP1 and AP2 may access a network 13 including the Internet, an internet protocol (IP) network, or any other network. The first access point (AP1) provides access to the network 13 within the first coverage area 11 to a first station (STA1), a second station (STA2), a third station (STA3), and a fourth station ( STA4), and the second access point AP2 can also provide access to the network 13 within the second coverage area 12 to the third and fourth stations STA3 and STA4. In some embodiments, the first and second access points (AP1, AP2) are based on wireless fidelity (WiFi) or any other WLAN access technology, the first station (STA1), the second station (STA2), the third It may communicate with at least one of the station STA3 and the fourth station STA4.

An access point may be referred to as a router, a gateway, and the like, and a station may be referred to as a mobile station, a subscriber station, a terminal, a mobile terminal, a wireless terminal, user equipment, and a user. and so on. The station may be a portable device such as a mobile phone, a laptop computer, or a wearable device, or may be a stationary device such as a desktop computer or a smart TV. In this specification, a station may be referred to as a first device and an access point may be referred to as a second device.

The access points AP1 and AP2 may allocate at least one resource unit (RU) to at least one station STA1 to STA4. The access points AP1 and AP2 may transmit data through at least one allocated resource unit, and at least one station may receive data through at least one allocated resource unit. In 802.11ax, access points (AP1, AP2) can allocate only a single resource unit to at least one station, while in 802.11be (hereinafter referred to as EHT) or next-generation IEEE 802.11 standards (hereinafter referred to as EHT+), access points (AP1, AP2) AP2) may allocate a multi-resource unit (MRU) including two or more resource units to at least one station. For example, the first access point AP1 may allocate multiple resource units to at least one of the first station STA1, the second station STA2, the third station STA3, and the fourth station STA4. and data can be transmitted through the allocated multiple resource units.

As an exemplary embodiment, the access points AP1 and AP2 may communicate with at least one station STA1 to STA4 using a beamforming technique. For example, single-user beamforming can improve reception performance of a single user, and multi-user beamforming can improve reception performance of all users by removing interference between multiple users. The access points AP1 and AP2 and the stations STA1 to STA4 may perform channel sounding for beamforming, and the channel sounding may be based on a sounding protocol. As will be described later with reference to the drawings, the access points AP1 and AP2 can efficiently perform channel sounding with the stations STA1 to STA4 supporting various protocol standards (eg, EHT, EHT+, etc.) . Hereinafter, a schematic embodiment of channel sounding between the first access point AP1 and the first station STA1 will be described. The technical concept of channel sounding between the first access point AP1 and the first station STA1 may also be applied to the second access point AP2 and the second to fourth stations STA2 to STA4.

The first access point AP1 may transmit a null data packet (NDP) based on a predetermined protocol standard to the first station STA1. The first station STA1 may estimate a channel with the first access point AP1 in response to the NDP, and generate information about the estimated channel and phase information from the estimated channel. In this specification, phase information may be referred to as channel smoothing-related phase information. Hereinafter, the phase information related to channel smoothing generated by the first station STA1 minimizes the loss generated when the first station STA1 performs channel smoothing on the beamformed signal from the first access point AP1. It may be provided to the first access point AP1 in order to do so. In this specification, the beamformed signal from the first access point AP1 may be a smooth beamformed signal. A method of generating phase information related to channel smoothing of the first station STA1 may be based on the number of antennas of the first station STA1, which will be described in detail later. The information on the estimated channel may include angle information of a beam steering matrix for each subcarrier generated from a singular value decomposition result for the channel estimated by the first station STA1. The first station STA1 may transmit a feedback frame including information about the estimated channel and phase information related to channel smoothing to the first access point AP1. The first access point AP1 may perform beamforming for the first station STA1 by reflecting the phase information on the estimated channel information. That is, the first access point AP1 may generate beamforming matrices in which discontinuity between adjacent subcarriers is reduced by reflecting channel smoothing-related phase information in the estimated channel information. In this specification, a relationship between adjacent subcarriers may be interpreted as a relationship between matrices corresponding to adjacent subcarriers. Beamforming of the first access point AP1 will be described in detail later. The first access point AP1 may transmit a beamformed signal (or a physical layer protocol data unit (PPDU)) to the first station STA1. The first station STA1 may perform channel smoothing on the beamformed signal.

As an exemplary embodiment, the first station STA1 may generate phase information related to channel smoothing based on whether a specific condition is satisfied in order to minimize unnecessary calculation operations and efficiently use time-frequency resources. When the first station STA1 performs channel smoothing on the beamformed signal from the first access point AP1, when the loss is not expected to be large, that is, when a specific condition is not satisfied, channel smoothing An operation operation for the related phase information may be omitted, and meaningless data may be filled in the channel smoothing related phase information and transmitted to the first access point AP1. In addition, when the first station STA1 performs channel smoothing on the beamformed signal from the first access point AP1, when the loss is expected to be large, that is, when a specific condition is satisfied, the channel By performing an operation operation for smoothing-related phase information, channel smoothing-related phase information including phase information that can be used by the first access point AP1 during beamforming is generated, and the channel smoothing-related phase information is converted to the first access point AP1. (AP1).

As an exemplary embodiment, the first station STA1 may determine whether a condition related to channel smoothing is satisfied based on a channel estimated using the NDP received from the first access point AP1. The first station STA1 may generate channel smoothing-related phase information based on the determination result.

Meanwhile, an embodiment of transmitting/receiving phase information between the first access point AP1 and the first station STA1 and performing beamforming using the phase information may be defined in a predetermined protocol standard. For example, the predetermined protocol standard may be an EHT protocol standard or an EHT+ protocol standard.

The access points AP1 and AP2 according to an exemplary embodiment of the present disclosure transmit phase information to the stations STA1 to STA4 to minimize loss caused by channel smoothing on the beamformed signals of the stations STA1 to STA4. Received from , phase information can be used for beamforming. Through this, it is possible to maximize the positive effect of the channel smoothing operation of the stations STA1 to STA4 on the beamformed signals of the access points AP1 and AP2.

The stations STA1 to STA4 according to an exemplary embodiment of the present disclosure determine whether channel smoothing-related conditions are satisfied based on the estimated channels with the access points AP1 and AP2, and channel smoothing-related based on the determination result. By generating the phase information, hardware resources of the stations STA1 to STA4 and time-frequency resources for communication can be efficiently used.

2 is a diagram for explaining a discontinuity of a beamforming matrix for each subcarrier corresponding to a signal beamformed from an access point in a comparative example.

Referring to FIG. 2 , in the comparative example, an access point may perform beamforming for a station based on a feedback frame received from the station. In this case, beamforming performed by the access point may be smooth beamforming. Meanwhile, as indicated by a dotted line, discontinuity may occur between beamforming matrices HF corresponding to arbitrary adjacent subcarriers by smooth beamforming. When a station performs channel smoothing on beamforming matrices HF having discontinuities, a large energy loss may occur as shown in FIG. 2 . To prevent this, the access point may receive a feedback frame including channel smoothing-related phase information from the station and perform beamforming on the station using the channel smoothing-related phase information.

3 is a block diagram illustrating a wireless communication system 20 according to an exemplary embodiment of the present disclosure. The block diagram of FIG. 3 shows a beamformer 21 and a beamformer 22 communicating with each other in a wireless communication system 20 . Each of the beamformer 21 and the beamformer 22 may be any device that communicates in the wireless communication system 20 and may be referred to as a device for wireless communication. In some embodiments, each of beamformer 21 and beamformer 22 may be an access point or station of a WLAN system.

Referring to FIG. 3 , the beamformer 21 may include a controller 21_1, a beamforming circuit 21_2, and a plurality of first antennas AT_11 to AT_x1. The controller 21_1 and the beamforming circuit 21_2 may be defined as processing circuits of the beamformer 21 . The beam formee 22 may include a channel estimator 22_1, a decomposer 22_2, a phase information generator 22_3, a compressor 22_4, and a plurality of second antennas AT_11 to AT_x1. The channel estimator 22_1, the decomposer 22_2, the phase information generator 22_3, and the compressor 22_4 may be defined as processing circuits of the beamforme 22. Hereinafter, the beamforme 22 will be described first.

The beam formee 22 may receive NDP through a plurality of second antennas AT_12 to AT_y2. The channel estimator 22_1 may estimate a channel using a reference signal included in the received NDP. In some embodiments, NDP may also be referred to as a sounding packet. NDP received by the channel estimator 22_1 for channel estimation ( ) can be expressed as in [Equation 1].

[Equation 1]

In [Equation 1], is the channel matrix, is the transmit data stream, can represent thermal noise. k may indicate a subcarrier index of a channel and may have a range of 1 to N _FFT . Accordingly, the channel matrix is generated for each subcarrier. The size of may be Nr × Nt. Here, Nr is the number of second antennas (AT_12 to AT_y2), and Nt is the number of first antennas (AT_11 to AT_x1). Each element of [Equation 1] may be defined as a matrix or vector. outgoing data stream ( ) may have, for example, a size of Ns × 1. Here, Ns is the number of transport streams. thermal noise ( ) may mean white Gaussian noise. thermal noise ( ) may have a size of Nr × 1.

The channel estimator 22_1 may generate channel state information based on the estimated channel. The channel state information may include at least one of a channel quality indicator (CQI), a precoding matrix indicator (PMI), and a rank indicator (RI).

The decomposer 22_2 is a channel estimated from the channel estimator 22_1 ( ) can be singular value decomposition as shown in [Equation 2].

[Equation 2]

In [Equation 2] is a left singular matrix, is a right singular matrix, and may include a Hermitian operator. may be a diagonal matrix containing non-negative singular values.

left singular matrix ( ) may be Nr × Nss. right singular matrix ( ) may be Ntx × Nss. also, The size of may be Nss × Nss. right singular matrix ( ) may be referred to as an initial beam steering matrix. In the wireless communication system 20 (eg, IEEE 802.11n/ac/ax WLAN system) according to some embodiments, the beamformer 21 is configured to ensure orthogonality of N _FFT subcarriers within one symbol. Since the signal is transmitted to the beam formee 22 through orthogonal frequency division multiplexing (OFDM) modulation, the channel estimation operation of the channel estimator 22_1 and the singular value decomposition operation of the decomposer 22_2 can be performed for each subcarrier.

On the other hand, the decomposer 22_2 is an initial beam steering matrix (in order to reduce the feedback overhead transmitted to the beamformer 21) ) is not transmitted to the beamformer 21 as it is, and a diagonal matrix for performing a common phase shift ( ) to the initial beam steering matrix ( ) can be applied as in [Equation 3].

[Equation 3]

Is a beam steering matrix, and a first diagonal matrix ( ) is the beam steering matrix ( ) may be a matrix for having elements in the last row of each column have real values. As an example, the first diagonal matrix ( )silver ), for example, is the initial beam steering matrix ( )of It may mean a phase value of an element corresponding to a row and a first column. In some embodiments, the first diagonal matrix ( ) is the initial beam steering matrix ( ) may include the phase value of the element of the last row of each column.

The compressor 22_4 is a beam steering matrix generated through the decomposer 22_2 ( ) for angle information ( ) can be obtained through [Equation 4] to [Equation 6].

[Equation 4]

In Equation 4, 1 _i−1 is a vector composed of 1s having a length of i−1. is an identity matrix having a size of Ntx × Nss.

In [Equation 4] Can be expressed as a second diagonal matrix as shown in [Equation 5] below.

[Equation 5]

,

In [Equation 4] Is a Givens rotation matrix and can be expressed as in [Equation 6] below.

[Equation 6]

The compressor 22_4 uses the obtained angular information ( ) can be quantized.

As an exemplary embodiment, the phase information generator 22_3 may generate channel smoothing-related phase information in different ways according to the number of second antennas AT_12 to AT_y2. For example, when the number of second antennas is 1, the phase information generator 22_3 has an initial beam steering matrix ( ) from the beam steering matrix ( ) The first diagonal matrix used to generate ( ) may be generated as phase information related to channel smoothing. In the same way as above, the phase information generator 22_3 has a first diagonal matrix for each subcarrier ( ), channel smoothing-related phase information including the phases of ) may be generated. As another example, when the number of second antennas is two or more, the phase information generator 22_3 minimizes geometric distances between beam steering matrices corresponding to adjacent subcarriers, or minimizes cross-correlation between beam steering matrices. ) may be generated as phase information related to channel smoothing. In the above manner, the phase information generator 22_3 may generate channel smoothing-related phase information including phases for maximizing cross-correlation between beam steering matrices corresponding to mutually adjacent subcarriers for each subcarrier. For example, when the subcarriers include first to third subcarriers, the phase information corresponding to the first subcarrier is a mutual relationship between a beam steering matrix of the first subcarrier and a beam steering matrix of an adjacent second subcarrier. Include phases to maximize correlation. The phase information corresponding to the second subcarrier includes phases for maximizing cross-correlation between a beam steering matrix of the second subcarrier and beam steering matrices of an adjacent third subcarrier. Details about this will be described later.

As an exemplary embodiment, the phase information generator 22_3 is an estimated channel ( Beam steering matrices corresponding to the subcarriers obtained from ) ( ) can be used to determine whether channel smoothing-related conditions are satisfied. For example, the phase information generator 22_3 may sequentially determine whether a condition related to channel smoothing is satisfied with respect to subcarriers listed based on an index. For example, the phase information generator 22_3 determines a subcarrier that first satisfies a condition related to channel smoothing as a starting subcarrier, and determines whether or not the condition related to channel smoothing is satisfied for subcarriers after the starting subcarrier. can be omitted.

In an exemplary embodiment, the channel smoothing related condition is beam steering matrices corresponding to mutually adjacent subcarriers for each subcarrier ( ), satisfaction can be determined based on the relationship between For example, channel smoothing-related conditions include beam steering matrices corresponding to mutually adjacent subcarriers ( Beam steering matrices corresponding to the first condition that the geometric distance between ) is equal to or greater than the first reference value and mutually adjacent subcarriers ( ) may include at least one of the second conditions that the cross-correlation between the second reference value or less. As an exemplary embodiment, the phase information generator 22_3 may determine at least one of a plurality of criteria as a condition related to channel smoothing based on a communication state between the beamformer 21 and the beamformer 22 . For example, the phase information generator 22_3 determines only one of the first condition and the second condition as a condition related to channel smoothing when the communication state between the beamformer 21 and the beamformer 22 is poor, When the communication state between the beamformer 21 and the beamformer 22 is good, the first condition and the second condition may be determined as conditions related to channel smoothing.

As an exemplary embodiment, the phase information generator 22_3 may generate channel smoothing-related phase information including phase information corresponding to a starting subcarrier and subsequent subcarriers among subcarriers. A detailed structure of a feedback frame related to phase information related to channel smoothing will be described later.

The compressor 22_4 according to an exemplary embodiment provides quantized angle information ( ) and channel smoothing-related phase information. In this specification, quantized angle information ( ) may be referred to as information about a channel estimated from the channel estimator 22_1. The beam former 22 may transmit the feedback frame to the beam former 21 through a transceiver (not shown) of the beam former 22 and a plurality of second antennas AT_12 to AT_y2.

The beamformer 21 may receive a feedback frame from the beamformer 22 through a transceiver (not shown) and a plurality of first antennas AT_11 to AT_x1. The controller 21_1 may control overall operations of the beamformer 21 for communication. The controller 21_1 may generate a Null Data Packet Announcement (NDPA) frame and NDP, which will be described later, and process information included in the feedback frame so that the beamforming circuit 21_2 can use them. A format of an NDPA frame and a format of a feedback frame according to an exemplary embodiment of the present disclosure will be described later.

The beamforming circuit 21_2 according to an exemplary embodiment may perform smooth beamforming on the beamformee 22 based on the feedback frame. Performing beamforming may refer to an operation of determining a beamforming matrix for each subcarrier of a signal transmitted from the beamformer 21 to the beamformer 22 . As an exemplary embodiment, the beamforming circuit 21_2 may include angle information of the feedback frame ( ), a beamforming operation may be performed by reflecting channel smoothing-related phase information. As shown in FIG. 2 , the beamforming circuit 21_2 may use channel smoothing-related phase information to reduce discontinuity of beamforming matrices HF corresponding to adjacent subcarriers. Meanwhile, as an exemplary embodiment, the beamformer 21 may check whether phase information related to channel smoothing is included in the feedback frame. The beamformer 21 may check whether there is phase information related to channel smoothing by checking a specific field of the feedback frame or checking whether data indicating that the phase information related to channel smoothing is empty is included in the phase information related to channel smoothing. . When the feedback frame includes phase information related to channel smoothing, the following operation may be performed.

For example, the beamforming circuit 21_2 provides angle information ( ), an initial beamforming matrix for each subcarrier may be generated, and a beamforming matrix for each subcarrier may be generated by applying channel smoothing-related phase information to the initial beamforming matrix.

In summary, the discontinuity of the beamforming matrices HF in the comparative example of FIG. 2 is the first diagonal matrix ( ) using the beam steering matrix ( ), the beamformer 21 may be caused by generating a first diagonal matrix from the beamformer 22 ( Discontinuity of beamforming matrices can be reduced by receiving phase information related to ) and reflecting it to a beamforming operation.

The beamformer 21 transmits a beamformed signal (or PPDU) according to the beamforming matrices determined by the beamforming circuit 21_2 through a transceiver (not shown) and the first antennas AT_11 to AT_x1. (22) can be sent. The beamformer 22 may process the beamformed signal after performing channel smoothing on the beamformed signal.

4 is a timing diagram illustrating channel sounding according to an exemplary embodiment of the present disclosure. Specifically, the timing diagram of FIG. 4 shows channel sounding performed by a beamformer and a first beamformee 1. Channel sounding can be based on various protocol standards. In some embodiments, the beamformer may be an access point and the first beamformer may be a first station. However, since FIG. 4 is only an exemplary embodiment of the present disclosure, it is noted that the exemplary embodiments of the present disclosure are not limited to the channel sounding of FIG. 4 .

Referring to FIG. 4, at time t11, the beamformer may transmit an NDPA frame to the first beamformer. For example, the beamformer may transmit an NDPA frame notifying transmission of a sounding NDP to the first beamformer in order to acquire downlink channel state information. The NDPA frame may be a control frame, and the first beam formee may prepare to receive a sounding NDP based on the NDPA frame. As an exemplary embodiment, the NDPA frame may include a subfield indicating whether to request phase information PI1 related to first channel smoothing from the first beamformer. The first beamformer may determine whether to feed back phase information PI1 related to first channel smoothing to the beamformer by checking the value of the subfield of the NDPA frame. A specific format of the NDPA frame will be described later with reference to FIG. 10 .

At time t21, the beamformer may transmit a sounding NDP to the first beamformer. For example, after transmitting the NDPA frame to the first beamformer, the beamformer may transmit a sounding NDP to the first beamformer after a short interframe space (SIFS) time. The first beam formee can generate information about the estimated first channel by estimating the first channel (or first lower link channel) based on the sounding NDP. As an exemplary embodiment, the first beamformer may confirm that the first channel smoothing-related phase information PI1 is requested from the subfield of the NDPA frame and generate the first channel smoothing-related phase information PI1. Meanwhile, in the present specification, sounding NDP may be interchangeably referred to as NDP.

At time t41, the first beamformer may transmit a first feedback frame to the beamformer. For example, the first beam formee includes information about the first channel estimated after a short interframe space (SIFS) time from time t31 after receiving the sounding NDP and phase information PI1 related to first channel smoothing. 1 feedback frame may be transmitted to the beamformer.

At time t51, the beamformer performs smooth beamforming by reflecting first channel smoothing-related phase information PI1 to the estimated first channel information, and obtains a PPDU smooth beamformed based on the determined beamforming matrices. It can be transmitted to the first beam formee.

From time t61 to time t71 after the SIFS time to time t81, the first beamformer may process the smooth beamformed PPDU after performing channel smoothing on the smooth beamformed PPDU.

5 is a message diagram illustrating a method for channel sounding according to an exemplary embodiment of the present disclosure. Specifically, the message diagram of FIG. 5 shows operations of the beamformer 31 as an access point and the beamformer 32 as one of a plurality of stations over time. As shown in FIG. 5 , the method for channel sounding may include a plurality of steps S10 to S22.

Referring to FIG. 5 , in step S10, the beamformer 31 may generate an NDPA frame. For example, the beamformer 31 may select one beamformer 32 to perform channel sounding (or to provide beamforming) among associated beamformers, and the selected beamformer 32 An NDPA frame can be generated based on. The NDPA frame may include a control frame, and the beam formee 32 may prepare to receive NDP based on the NDPA frame. As an exemplary embodiment, the NDPA frame may include a plurality of fields, and any one of the plurality of fields may include a subfield indicating whether to request phase information related to channel smoothing from the beam formee 32 .

In step S11, the beamformer 31 may provide the NDPA frame to the beamformer 32. For example, the beamformer 31 may transmit the PPDU including the NDPA frame generated in step S10 to the beamformer 32, and the beamformer 32 may transmit a PPDU including the NDPA frame from the beamformer 31. PPDU can be received.

In step S12 , the beamformer 31 may generate an NDP corresponding to the beamformer 32 .

In step S13, the beamformer 32 may check whether the beamformer 31 requests phase information related to channel smoothing from the NDPA frame. In some embodiments, the beamforme 32 may recognize the protocol standard corresponding to the current NDPA frame by identifying the version of the NDPA frame. Accordingly, the beamformer 32 may recognize a protocol standard corresponding to the NDP subsequently received from the beamformer 31 .

In step S14, the beamformer 31 may provide the NDP to the beamformer 32.

In step S15, the beamformee 32 may identify the NDP. That is, the beamformer 32 may extract information (or data) included in fields of the NDP transmitted from the beamformer 31 towards itself.

In step S16, the beamforme 32 may perform channel estimation using information extracted from fields of the NDP.

In step S17, the beam formee 32 may generate channel smoothing-related phase information according to the number of its own antennas. That is, the beam formee 32 may generate phase information in different ways according to the number of its own antennas. Details on this will be described later with reference to FIGS. 6 and 7 .

In step S18, the beam formee 32 may generate a feedback frame including information about the estimated channel and phase information related to channel smoothing.

In step S19, the beamformer 32 may provide a feedback frame to the beamformer 31. For example, the feedback frame may include a field in which phase information related to channel smoothing is disposed and a field including a subfield having a value indicating whether the phase information related to channel smoothing is present.

In step S20, the beamformer 31 extracts information about the estimated channel and phase information related to channel smoothing from the feedback frame, and performs smooth beamforming by reflecting the phase information related to channel smoothing to the information about the estimated channel. can do. For example, the beamformer 31 may check whether phase information related to channel smoothing is present through some fields of the feedback frame, and obtain the phase information related to channel smoothing. For example, the beamformer 31 may obtain channel smoothing-related phase information after checking whether the channel smoothing-related phase information includes data indicating that the corresponding information is empty.

In step S21, the beamformer 31 may provide the beamformed PPDU to the beamformer 32 based on the beamforming matrices for each subcarrier determined in step S20.

In step S22, the beamformer 32 may perform channel smoothing on beamforming matrices corresponding to the beamformed PPDU. After that, the beamformer 32 may process the beamformed PPDU.

6 and 7 are flowcharts illustrating exemplary embodiments of step S17 in FIG. 5 . Specifically, in FIG. 6, it is assumed that the number of antennas of the beamforme 32 is one, and in FIG. 7, the number of antennas of the beamformee 32 is plural. However, FIGS. 6 and 7 are merely exemplary embodiments, and the technical spirit of the present disclosure is not limited thereto. In the following, FIG. 5 may be further referred to.

Referring to FIG. 6 , in step S30a, the beam formee 32 may obtain an initial beam steering matrix for each subcarrier by performing singular value decomposition on the estimated channel. In step S31a, the beam formee 32 may acquire the first phase of the last element of the initial beam steering matrix for each subcarrier. Specifically, the beam formee 32 may obtain the first phase of at least one element corresponding to the last row of each column of the initial beam steering matrix for each subcarrier. In step S32a, the beam formee 32 may generate channel smoothing-related phase information including a first phase for each subcarrier. As an example, the phase information related to channel smoothing is the first diagonal matrix described in FIG. 3 ( ) may contain information that corresponds to

Referring to FIG. 7 , in step S30b, the beam formee 32 may obtain a beam steering matrix for each subcarrier by performing singular value decomposition on the estimated channel. As described above in FIG. 3, a beam steering matrix may be generated from an initial beam steering matrix. In step S31b, the beam formee 32 may obtain a second phase that minimizes a geometric distance between adjacent beam steering matrices or maximizes cross-correlation between adjacent beam steering matrices.

As an exemplary embodiment, the beam formee 32 is obtained by [Equation 7], the beam steering matrices of two adjacent subcarriers (eg, , ) can use the geometric distance (Euclidean distance) between them.

[Equation 7]

In [Equation 7] is the norm operator, and the beam steering matrices of adjacent subcarriers (eg, , ) where the geometric distance between can be obtained. can be expressed as Is a third diagonal matrix and may be sequentially processed for all subcarriers (k=0, 1,??,N _FFT ).

As an exemplary embodiment, the beam formee 32 is obtained by [Equation 8], the beam steering matrices of two adjacent subcarriers (eg, , ) can be used.

[Equation 8]

As in [Equation 8], beam steering matrices of adjacent subcarriers (eg, , ) where the cross-correlation between can be obtained.

Beam for me 32 is based on [Equation 7] or [Equation 8] Is a third diagonal matrix and may be sequentially processed for all subcarriers (k=0, 1,??,N _FFT ). For example, using [Equation 7] or [Equation 8] for the k-th subcarrier When finding , the previously obtained Is the beam steering matrix of the k-1th subcarrier ( ) is reflected in can be expressed as As an exemplary embodiment, the beamformie is performed for each subcarrier. The second phases of the elements of may be generated as channel smoothing-related phase information.

The solutions of [Equation 7] and [Equation 8] can be defined as [Equation 9].

[Equation 8]

In an exemplary embodiment, the second phases are can include

In step S32b, the beam formee 32 may generate channel smoothing-related phase information including the second phases.

8A and 8B are flowcharts illustrating an exemplary embodiment of step S17 in FIG. 5 . In the following, FIG. 5 may be further referred to.

Referring to FIG. 8A, following step S16 of FIG. 5, in step S17_1a, the beam formee 32 may determine whether a condition related to channel smoothing is satisfied based on the estimated channel.

As an exemplary embodiment, the beam formee 32 is obtained by [Equation 9], the beam steering matrices of two adjacent subcarriers (eg, , ), it can be determined whether channel smoothing-related conditions are satisfied based on the geometric distance between them.

[Equation 9]

Is the beam steering matrices of each of the k th subcarrier and the k−1 th subcarrier adjacent thereto ( , ) represents the geometric distance between The beam formee 32 may determine whether or not the first condition of [Equation 10] is satisfied for each subcarrier.

[Equation 10]

The beam formee 32 has a geometric distance (calculated for each subcarrier) ) is the first reference value ( ) can be determined. geometric distance ( ) is the first reference value ( ) or more, it can be determined that the channel smoothing related condition is satisfied for the corresponding subcarrier.

As an exemplary embodiment, the beam formee 32 is obtained by [Equation 11], the beam steering matrices of two adjacent subcarriers (eg, , ), it is possible to determine whether a condition related to channel smoothing is satisfied based on the cross-correlation between .

[Equation 11]

Is the beam steering matrices of each of the k th subcarrier and the k−1 th subcarrier adjacent thereto ( , ) represents the cross-correlation between The beam formee 32 may determine whether or not the second condition of [Equation 12] is satisfied for each subcarrier.

[Equation 12]

The beam formee 32 calculates the cross-correlation for each subcarrier ( ) is the second reference value ( ) or less can be determined. Correlation ( ) is the second reference value ( ) or less, it can be determined that the channel smoothing related condition is satisfied for the corresponding subcarrier.

However, this is an exemplary embodiment and is not limited thereto, and at least one of various conditions other than the first and second conditions may be set as a channel smoothing related condition.

When step S17_1a is 'YES', following step S17_2a, the beam formee 32 may generate phase information related to channel smoothing according to the number of antennas. As an exemplary embodiment, the beam formee 32 may generate channel smoothing-related phase information including phase information generated for each subcarrier.

After step S17_2a or when step S17_1a is 'NO', following step S18a, the beamformee 32 may generate a feedback frame including information indicating whether channel smoothing-related phase information is included. As an exemplary embodiment, in step S18a after step S17_2a, the beamforme 32 disposes information indicating that the channel smoothing-related information is included in a first specific field of the feedback frame, and in a second specific field of the feedback frame. Information related to smoothing can be arranged. As an exemplary embodiment, in step S18a when step S17_1a is 'NO', the beamformee 32 disposes information indicating that channel smoothing-related information is not included in a first specific field of the feedback frame, and Data indicating that the channel smoothing-related information is bin information may be disposed in the second specific field. In some embodiments, the data may have a predetermined pattern agreed between the beam formee 32 and the beam formee 31 . After that, step S19 of FIG. 5 follows.

Further referring to FIG. 8B , in step S17_1b following step S16 of FIG. 5 , the beamformee 32 may select at least one of a plurality of conditions as a condition related to channel smoothing. As an exemplary embodiment, the beamformer 32 may select at least one of a plurality of conditions as a condition related to channel smoothing based on a communication state with the beamformer 31 . For example, the beamformer 32 may operate based on a rougher channel smoothing condition by selecting only one of a plurality of conditions as a channel smoothing related condition when the communication state with the beamformer 31 is good, When the communication state with the beamformer 31 is poor, two or more of a plurality of conditions may be selected as channel smoothing related conditions to operate based on more stringent channel smoothing related conditions. However, this is an example. When the communication state with the beamformer 31 is good, the beamformer 32 selects two or more of a plurality of conditions as channel smoothing-related conditions, and the communication state with the beamformer 31 is At a bad time, only one of a plurality of conditions may be selected as a condition related to channel smoothing.

In step S17_2b, the beamformee 32 may determine whether the condition related to channel smoothing is satisfied based on the condition related to channel smoothing determined in step S17_1b.

When step S17_2b is 'YES', following step S17_3b, the beam formee 32 may generate phase information related to channel smoothing according to the number of antennas.

After step S17_3b or when step S17_2b is 'NO', following step S18b, the beamformee 32 may generate a feedback frame including information indicating whether phase information related to channel smoothing is included. After that, step S19 of FIG. 5 follows.

FIG. 9 is a flowchart illustrating an exemplary embodiment of step S17 in FIG. 5 . In the following, FIG. 5 may be further referred to.

Referring to FIG. 9 , following step S16 of FIG. 5 , in step S17_1c, the beamforme 32 sets n to '0'. n represents an index of a subcarrier, and m subcarriers may be listed in index order. In step S17_2c, the beam formee 32 may select an nth subcarrier from among the subcarriers. In step S17_3c, the beam formee 32 may determine whether a condition related to channel smoothing in the nth subcarrier is satisfied. When step S17_3c is 'NO', subsequent to step S17_4c, the beamformee 32 may determine whether n and m are the same. When step S17_4c is 'NO', following step S17_5c, the beamformee 32 may count up n, and may perform step S17_2c.

When step S17_3c is 'YES', subsequent to step S17_6c, the beamformee 32 may determine the nth subcarrier as the starting subcarrier. In step S17_7c, the beam formee 32 may generate channel smoothing-related phase information including phase information from the start subcarrier to the last subcarrier. As an exemplary embodiment, the phase information related to channel smoothing may include information indicating a start subcarrier and phase information from the start subcarrier to the last subcarrier.

Meanwhile, when step S17_4c is 'YES', the beam formee 32 may generate channel smoothing-related phase information including data indicating bin information.

After that, step S19 of FIG. 5 follows.

10 is a diagram illustrating an NDPA frame according to an exemplary embodiment of the present disclosure.

Referring to FIG. 10 , an NDPA frame may include a MAC header, a frame body, and a Frame Check Sequence (FCS) field. The NDPA frame may include a frame control field, duration field, RA field, and TA field in the MAC header, and a sounding dialog token field in the frame body, n (where n is an integer greater than zero) STA information fields can include The NDPA frame may include information necessary for beamformes to perform channel sounding.

The frame control field may include information about a version of a media access control (MAC) protocol and other additional control information. The duration field may include time information for setting a network allocation vector (NAV) or information about a user's identifier (eg, association identifier (AID)). The RA field may include address information of a beamformer receiving the NDPA frame, and the TA field may include address information of a beamformer transmitting the NDPA frame. The sounding dialog token field may be referred to as a sounding sequence field, and may include identification information about the NDPA frame as described below. The STA information field may be referred to as a user information field, and the NDPA frame may include first to nth STA information fields corresponding to first to nth beamformes receiving the NDPA frame.

As an exemplary embodiment, the first STA information field includes an 'AID11' field in which information about an identifier (AID11) for the first STA (or first user) is disposed, and 'Partial BW Info' in which partial bandwidth information is disposed field, 'Smooth Beamformed' field, in which information about whether or not phase information related to channel smoothing is requested, 'Nc' field, in which information about the number of subcarriers is arranged, 'Feedback Type And Ng', in which information about feedback type is arranged field, 'Disambiguation' field, 'Codebook Size' field, and 'Reserved' field. Specifically, a beamformer (or station) targeted for the first STA information field may check whether the beamformer requests phase information related to channel smoothing by referring to the 'Smooth Beamformed' field. The configuration of the first STA information field may also be applied to the configuration of the other STA information fields.

11 is a table diagram showing information included in a feedback frame according to an exemplary embodiment of the present disclosure, and FIG. 12 is a diagram showing the configuration of an 'EHT MIMO Control' field of FIG. 11 . In the following, it is assumed that the feedback frame is based on the EHT protocol standard, but this is only an exemplary embodiment, and is not limited thereto. The feedback frame may be implemented in a format based on various protocol standards including the EHT + protocol standard. there is. Meanwhile, since the details of the fields and subfields in FIGS. 11 and 12 are described in IEEE 802.11be, they are omitted.

Referring to FIG. 11, the feedback frame generated by the beamforme includes a 'Category' field, an 'EHT Action' field, an 'EHT MIMO Control' field, an 'EHT Compressed Beamforming Report' field, and an 'EHT MU Exclusive Beamforming' field arranged in order of order. Report' field, 'EHT CQI Report' field, and 'EHT Smooth Beamforming Report' field. As an exemplary embodiment, channel smoothing-related phase information generated by a beamformer according to exemplary embodiments of the present disclosure may be disposed in the 'EHT Smooth Beamforming Report' field.

12, the 'EHT MIMO Control' field includes 'Nc Index' subfield, 'Nr Index' subfield, 'BW' subfield, 'Grouping' subfield, 'Codebook Information' subfield, and 'Feedback Type' subfield. ' subfield, 'Remaining Feedback Segments' subfield, 'First Feedback Segment' subfield, 'Partial BW Info' subfield, 'Sounding Dialogue Token Number' subfield, and 'Smooth Beamformed' subfield. Example In an exemplary embodiment, the 'Smooth Beamformed' subfield may have a value indicating whether phase information of a beamformer is present. For example, when phase information is included in the 'EHT Smooth Beamforming Report' field, the 'Smooth Beamformed' subfield The field value may be set to '1', and the 'Smooth Beamformed' subfield value may be set to '0' when phase information is not included in the 'EHT Smooth Beamforming Report' field. Beamformer (or access point) checks the existence of the phase information of the beamforme by referring to the 'EHT MIMO Control' field of the feedback frame, and obtains the phase information from the 'EHT Smooth Beamforming Report' field of the feedback frame when it is confirmed that the phase information exists. can

FIG. 13 is a table diagram showing the configuration of the 'EHT Smooth Beamforming Report' field of FIG. 11 .

Referring to FIG. 13, a 'Start Subcarrier Index' subfield and a 'Smooth Beamforming Information' subfield for each subcarrier corresponding to phase information related to channel smoothing for each subcarrier may be included.

As an exemplary embodiment, the size of the 'Start Subcarrier Index' subfield may be set to 16 bits. However, this is only an exemplary embodiment and is not limited thereto, and the size of the 'Start Subcarrier Index' subfield may be set to match the number of subcarriers used for communication between the beamformer and the beamformee.

As an exemplary embodiment, the 'Smooth Beamforming Information' subfield for each subcarrier corresponds to the result of dividing the product of the number of subcarriers (N _c ) and the number of bits (b _φ ) of channel smoothing-related phase information of the corresponding subcarrier by 2. It can be set to a bit that does.

As an exemplary embodiment, the beamformer may identify a starting subcarrier that satisfies a condition related to channel smoothing by referring to a 'Start Subcarrier Index' subfield, and may identify a starting subcarrier and subcarriers subsequent to the starting subcarrier. Channel smoothing-related phase information can be obtained from the 'Smooth Beamforming Information' subfields. The beamformer may perform smooth beamforming based on the acquired phase information related to channel smoothing.

FIG. 14 is a table diagram showing the configuration of the 'EHT Smooth Beamforming Report' field of FIG. 11 .

Referring to FIG. 14, channel smoothing-related phase information included in the 'EHT Smooth Beamforming Report' field is information about the size of an initial beam steering matrix V (or beam steering matrix Q), angles (or phases) and phase values for each subcarrier. As described above, N _r may mean the number of antennas of a beamformie, N _c may mean the number of subcarriers, and k may mean the index of a subcarrier. Meanwhile, the phase information related to channel smoothing of FIG. 14 may be arranged according to the 'EHT Smooth Beamforming Report' field described in FIG. 13 .

15 is a table diagram illustrating subfields of an 'EHT PHY Capabilities Information' field indicating whether smooth beamforming feedback can be supported according to embodiments of the present disclosure. Whether smooth beamforming feedback can be supported means whether the beamformer side can request a feedback frame including phase information related to channel smoothing according to an exemplary embodiment of the present disclosure, and whether the beamformer side can generate it.

Referring to FIG. 15 , the 'EHT PHY Capabilities Information' field defined in the standard protocol of IEEE 802.11be may include a subfield indicating whether smooth beamforming feedback is supported. For example, when the beamformer can support reception of smooth beamforming information feedback including phase information related to channel smoothing, the corresponding subfield may be set to '1'. Also, as an example, when there is no beamformie capable of supporting transmission of smooth beamforming information feedback including phase information related to channel smoothing, a corresponding subfield may be set to '0'.

16A and 16B are timing diagrams specifically illustrating channel sounding according to exemplary embodiments of the present disclosure.

Referring to FIG. 16A, at time t12, the beamformer may transmit an NDPA frame to the first beamformer. Specifically, in the NDPA frame, a 'Smooth Beamforemd' field may be set to '1' to request first channel smoothing-related phase information PI1' from the first beamformer.

At time t22, the beamformer may transmit a sounding NDP to the first beamformer. After transmitting the NDPA frame to the first beamformer, the beamformer may transmit a sounding NDP to the first beamformer after SIFS time. The first beam formee may estimate the first channel based on the sounding NDP and generate information about the estimated first channel. Meanwhile, when the 'Smooth Beamforming Feedback' subfield of FIG. 15 related to the first beamformer is set to '1', the first beamformer determines whether a condition related to channel smoothing is satisfied based on the estimated first channel, and determines Based on the result, phase information PI1' related to first channel smoothing may be generated.

At time t42, which is after the SIFS time from time t32, the first beamformer may transmit a first feedback frame including phase information PI1' related to first channel smoothing to the beamformer.

At time t52, the beamformer may perform smooth beamforming based on the first channel smoothing related phase information PI1′ and transmit the smooth beamformed PPDU based on the determined matrices to the first beamformer. The beamformer may set the 'Beamformed' field of the PPDU to '1' to notify the first beamformer that the corresponding PPDU has been smooth beamformed.

From time t62 to time t72 after the SIFS time to time t82, the first beamformer checks that the 'Beamformed' field of the PPDU is '0' and performs channel smoothing on the smooth beamformed PPDU. PPDU can be processed.

Referring further to FIG. 16B, at time t13, the beamformer may transmit an NDPA frame to the first beamformer. Specifically, in the NDPA frame, a 'Smooth Beamforemd' field may be set to '1' to request first channel smoothing-related phase information PI1' from the first beamformer.

At time t23, the beamformer may transmit a sounding NDP to the first beamformer. After transmitting the NDPA frame to the first beamformer, the beamformer may transmit a sounding NDP to the first beamformer after SIFS time. The first beam formee may estimate the first channel based on the sounding NDP and generate information about the estimated first channel. Meanwhile, when the 'Smooth Beamforming Feedback' subfield of FIG. 15 related to the first beamformer is set to '0', the first beamformer may not be able to generate channel smoothing-related phase information PI1'.

At time t43, which is after the SIFS time from time t33, the first beamformer may transmit a first feedback frame that does not include phase information PI1' related to first channel smoothing to the beamformer. The first feedback frame may include only information about the estimated first channel.

At time t53, the beamformer may perform smooth beamforming based on the first feedback frame and transmit the smooth beamformed PPDU to the first beamformer based on the determined matrices. The beamformer may set the 'Beamformed' field of the PPDU to '0' to notify the first beamformer that the corresponding PPDU is not smooth beamformed in order to prevent the first beamformer from performing channel smoothing.

From time t63 to time t73 after the SIFS time to time t83, the first beamformer checks that the 'Beamformed' field of the PPDU is '0' and does not perform channel smoothing on the smooth beamformed PPDU. PPDU can be processed.

However, since the contents described in FIGS. 16A and 16B are merely exemplary embodiments, it is clear that the technical idea of the present disclosure is not limited thereto.

17 is a timing diagram illustrating channel sounding according to an exemplary embodiment of the present disclosure. Specifically, the timing diagram of FIG. 17 shows channel sounding performed by a beamformer and first through n-th beamformees (n is an integer greater than 1). In the example of FIG. 17 , the first through n-th beamformes may each support the same or different protocol standards. In some embodiments, the beamformer may be an access point, and each of the first through nth beamformers may be a station. It is noted that the exemplary embodiments of this disclosure are not limited to the channel sounding of FIG. 17 .

Referring to FIG. 17, at time t14, the beamformer may transmit an NDPA frame to the first to nth beamformers. The first to nth beamformes may prepare to receive sounding NDP based on the NDPA frame. As an exemplary embodiment, the NDPA frame may include subfields indicating whether to request the first to nth channel smoothing-related phase information PI1 to PIn from the first to nth beamformes.

At time t24, the beamformer may transmit sounding NDP to the first through nth beamformers. For example, the beamformer may transmit the NDPA frame to the first to nth beamformers, and then transmit the sounding NDP to the first to nth beamformers after a short interframe space (SIFS) time. As an exemplary embodiment, the sounding NDP may include 1st to nth NDPs corresponding to 1st to nth beamformes, respectively, and the 1st to nth NDPs may be aggregated in different bands. The 1st to nth beamformers may estimate the 1st to nth channels (or the 1st to nth downlink channels) based on the sounding NDP, respectively, and generate information about the estimated 1st to nth channels. there is. As an exemplary embodiment, the first to nth beamformes confirm that the first to nth channel smoothing-related phase information (PI1 to PIn) has been requested from the subfields of the NDPA frame, respectively, and the first to nth channel smoothing-related phase information Phase information (PI1 to PIn) may be respectively generated. In some embodiments, some of the first to nth beamformes may not support an operation of generating channel smoothing-related phase information or a channel smoothing operation, and in this case, some of them do not include corresponding channel smoothing-related phase information. You can create a feedback frame that does not.

At time t34, the beamformer may transmit a beamforming report poll (BFRP) trigger frame to the first through nth beamformers. For example, after transmitting the sounding NDP to the first to n-th beamformers, the access point transmits a BFRP trigger frame for triggering uplink transmission of the first to n-th beamformers after SIFS to the first to nth beamformers. can be provided to The BFRP trigger frame may include information necessary for the first to nth beamformers to transmit a feedback frame to the beamformer, that is, the access point. For example, the BFRP trigger frame may include information on resources to be used in uplink transmission.

At time t44, after receiving the BFRP trigger frame, the 1st to nth beamformers may transmit the 1st to nth feedback frames to the beamformer after SIFS. At least one of the first through nth feedback frames may include phase information related to channel smoothing according to the above-described embodiments. In an exemplary embodiment, the first to n th feedback frames may be aggregated in different bands. In some embodiments, the first to n-th feedback frames may be transmitted in bands corresponding to bands in which the first to n-th NDPs are transmitted. For example, the first feedback frame may be transmitted in the band in which the first NDP was transmitted.

At time t54, the beamformer performs smooth beamforming on the first to nth beamformers using the first to nth channel smoothing-related phase information (PI1 to PIn) included in the first to nth feedback frames. Based on the determined beamforming matrices, the smooth beamformed PPDU may be transmitted to the first through nth beamformers. As an exemplary embodiment, the smooth beamformed PPDU may include 1st to nth PPDUs corresponding to 1st to nth beamformers, respectively, and the 1st to nth PPDUs may be aggregated in different bands. .

From time t74, which is a predetermined time after time t65, to time t84, the 1st to nth beamformers may perform channel smoothing on the 1st to nth PPDUs, respectively. In some embodiments, among the first through n-th beamformers that do not support channel smoothing, channel smoothing may not be performed.

18 is a message diagram illustrating a method for channel sounding according to an exemplary embodiment of the present disclosure. As shown in FIG. 18 , the method for channel sounding may include a plurality of steps S40 to S52.

Referring to FIG. 18 , in step S40, the beamformer 41 may generate an NDPA frame. For example, the beamformer 41 may select a plurality of beamformers 42 to perform channel sounding among associated beamformers and generate an NDPA frame based on the selected beamformers 42 . As an exemplary embodiment, the NDPA frame may include subfields indicating whether phase information related to channel smoothing is requested for each of the beamformes 42 .

In step S41, the beamformer 41 may provide the NDPA frame to the beamformers 42.

In step S42, the beamformer 41 may generate a plurality of NDPs corresponding to each of the beamformers 42.

In step S43, each of the beamformers 42 may check whether the beamformer 41 requests channel smoothing-related phase information from the beamformers 42 by referring to the NDPA frame.

In step S44, the beamformer 41 may provide NDPs aggregated in different bands to the beamformers 42.

In step S45, the beamformes 42 may identify their own NDPs among the aggregated NDPs.

In step S46, the beamformes 42 may estimate their own channels using their identified NDPs.

In step S47, channel smoothing-related phase information according to the number of antennas may be generated only for beamformes for which phase information is requested among the beamformes 42.

In step S48, each of the beamformes 42 may generate a feedback frame.

In step S49, the beamformers 42 may provide aggregated feedback frames in different bands to the beamformer 41.

In step S50, the beamformer 41 may perform smooth beamforming on the beamformers 42 based on the feedback frames. The beamformer 41 may perform smooth beamforming in which the phase information related to channel smoothing is reflected on the feedback frame including the phase information related to channel smoothing.

In step S51, the beamformer 41 may provide PPDUs obtained by aggregating a plurality of PPDUs in different bands to the beamformers 42 based on the beamforming matrices determined in step S50.

In step S52, channel smoothing for its own PPDU can be performed only for beamformes capable of supporting channel smoothing among the beamformers 42.

19 is a conceptual diagram showing an IoT network system 1000 to which exemplary embodiments of the present disclosure are applied.

Referring to FIG. 19, the IoT network system 1000 includes a plurality of IoT devices 1100, 1120, 1140, and 1160, an access point 1200, a gateway 1250, a wireless network 1300, and a server 1400. can include The Internet of Things (IoT) may refer to a network between objects using wired/wireless communication.

Each of the IoT devices 1100, 1120, 1140, and 1160 may form a group according to characteristics of each IoT device. For example, IoT devices may be grouped into a home gadget group 1100, a home appliance/furniture group 1120, an entertainment group 1140, or a vehicle 1160 group. The plurality of IoT devices 1100 , 1120 , and 1140 may be connected to a communication network or to other IoT devices through the access point 1200 . The access point 1200 may be embedded in one IoT device. The gateway 1250 may change a protocol to connect the access point 1200 to an external wireless network. The IoT devices 1100, 1120, and 1140 may be connected to an external communication network through the gateway 2250. The wireless network 1300 may include the Internet and/or a public network. The plurality of IoT devices 1100, 1120, 1140, and 1160 may be connected to the server 1400 providing a predetermined service through the wireless network 1300, and the plurality of IoT devices 1100, 1120, 1140, and 1160 ) through at least one of which the user can use the service.

According to embodiments of the present disclosure, the plurality of IoT devices 1100, 1120, 1140, and 1160

Phase information related to mutual channel smoothing may be transmitted and received, and smooth beamforming may be performed based on the phase information related to channel smoothing. Through this, the IoT devices 1100, 1120, 1140, and 1160 can perform efficient and effective communication to provide quality services to users.

As above, exemplary embodiments have been disclosed in the drawings and specifications. Although the embodiments have been described using specific terms in this specification, they are only used for the purpose of explaining the technical idea of the present disclosure, and are not used to limit the scope of the present disclosure described in the claims. . Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. Therefore, the true technical scope of protection of the present disclosure should be determined by the technical spirit of the appended claims.

Claims (20)

A method of operating a first device communicating with a second device in a wireless local area network (WLAN) system including a first device and a second device, the method comprising:
Receiving a null data packet (NDP) based on a predetermined protocol standard from the second device;
estimating a channel with the second device based on the NDP;
determining whether a condition related to channel smoothing is satisfied based on the estimated channel;
generating phase information related to the channel smoothing based on the determination result; and
and transmitting a feedback frame including phase information related to the channel smoothing to the second device. According to claim 1,
Determining whether or not the channel smoothing related condition is satisfied,
obtaining beam steering matrices corresponding to subcarriers from the estimated channel; and
A method of operating a first device comprising determining whether the channel smoothing related condition is satisfied for each subcarrier based on a relationship between beam steering matrices corresponding to mutually adjacent subcarriers. According to claim 2,
In the step of determining whether the channel smoothing-related condition is satisfied for each subcarrier,
Sequentially performed on the subcarriers listed based on index,
The method of operation of the first device, characterized in that the step of determining is omitted after the starting subcarrier that first satisfies the condition related to channel smoothing. According to claim 3,
Generating the channel smoothing-related phase information includes:
and generating the phase information related to channel smoothing including phase information corresponding to the starting subcarrier and subcarriers after the starting subcarrier among the listed subcarriers. According to claim 2,
The relationship between the beam steering matrices is
At least one of a eucliean distance between the beam steering matrices and a cross-correlation between the beam steering matrices;
The channel smoothing related conditions are,
The operating method of the first device comprising at least one of a condition that the geometric distance between the beam steering matrices is greater than or equal to a first reference value and a condition that a cross correlation between the beam steering matrices is less than or equal to a second reference value. According to claim 1,
When the channel smoothing-related condition is satisfied and the number of antennas of the first device is one,
Generating the channel smoothing-related phase information includes:
and generating first phases of elements corresponding to the last row of each column in the beam steering matrix for each subcarrier obtained from the estimated channel as the channel smoothing-related phase information. . According to claim 1,
When the channel smoothing related condition is satisfied and the number of antennas of the first device is plural,
Generating the channel smoothing-related phase information includes:
Second phases for minimizing the geometric distance between beam steering matrices corresponding to mutually adjacent subcarriers obtained from the estimated channel or maximizing the cross correlation between the beam steering matrices are generated as the channel smoothing-related phase information. A method of operating a first device comprising the step of: According to claim 1,
If the conditions related to channel smoothing are not satisfied,
Generating the channel smoothing-related phase information includes:
A method of operating a first device comprising the step of generating the channel smoothing-related phase information including data indicating bin information. According to claim 1,
Receiving a smooth beamformed physical layer protocol data unit (PPDU) based on the phase information related to channel smoothing; and
The operating method of the first device further comprising performing channel smoothing on the smooth beamformed PPDU. According to claim 1,
The feedback frame,
The operating method of the first device comprising a 'smooth beamforming report' field in which the phase information related to channel smoothing is disposed. According to claim 10,
The feedback frame,
The operating method of the first device, characterized in that it further comprises a 'multi-input multi-output (MIMO) control' field in which a subfield having a value indicating whether the phase information related to channel smoothing is disposed. According to claim 11,
The 'smooth beamforming report' field,
characterized in that it includes a subfield including an index of a starting subcarrier that first satisfies the channel smoothing-related condition and subfields each including phase information corresponding to subcarriers including the starting subcarrier. How the device works. According to claim 1,
The predetermined protocol standard,
A method of operating a first device, characterized in that EHT (extremely high throughput) protocol standard. According to claim 1,
Determining whether or not the channel smoothing related condition is satisfied,
and selecting at least one of a plurality of conditions as the channel smoothing-related condition based on a communication state with the second device. A method of operating a second device communicating with a first device in a wireless local area network (WLAN) system including a first device and a second device, the method comprising:
Transmitting a null data packet (NDP) based on a predetermined protocol standard to the first device;
As a response to the NDP, a feedback frame including first information about an estimated channel between the first device and the second device and second information indicating whether or not channel smoothing-related phase information is included is transmitted to the first device. receiving from the device;
generating a smooth beamformed PPDU based on the first and second information; and
and transmitting the smooth beamformed PPDU to the first device. According to claim 15,
When the second information indicates that the channel smoothing-related phase information is included,
Generating the smooth beamformed PPDU comprises:
and generating the smooth beamformed PPDU by reflecting the phase information related to channel smoothing in the first information about the estimated channel. According to claim 15,
When the second information indicates that the channel smoothing-related phase information is not included,
Generating the smooth beamformed PPDU comprises:
and generating the smooth beamformed PPDU based on the first information on the estimated channel. According to claim 15,
The first information includes angle information about a beam steering matrix for each subcarrier,
The channel smoothing-related phase information includes information for reducing discontinuity between beamforming matrices corresponding to adjacent subcarriers in the smooth beamformed PPDU. According to claim 15,
The channel smoothing-related phase information,
A method of operating a second device, characterized in that phase information corresponding to a starting subcarrier and subcarriers after the starting subcarrier among subcarriers listed based on an index is included. A first device communicating with a second device in a wireless local area network (WLAN) system,
a transceiver configured to receive NDP based on the EHT protocol standard; and
Processing configured to determine whether a condition related to channel smoothing is satisfied based on a channel estimated between the first device and the second device in response to the NDP, and generate the phase information related to channel smoothing based on the determination result. contains a circuit;
The processing circuit,
The first device, characterized in that configured to control the transceiver to transmit a feedback frame including the phase information related to channel smoothing to the second device.

Images