KR20210084291A - AP-driven Uplink Rate Control method using Trigger Frame in TWT - Google Patents

Abstract

Provided is an access point (AP)-driven uplink control method using a trigger frame in a TWT. In accordance with an embodiment of the present invention, the AP-driven uplink control method using the trigger frame is able to directly control an uplink based on an SNR received from the AP, select the rate on the received SNR, and be realized regardless of the loss statistics. In addition, in accordance with an embodiment of the present invention, the AP-driven uplink control method using the trigger frame is able to observe the standards, apply the technique proposed in the AP, and apply the proposed technique to all apparatuses supporting the 802.11ax without a separate change. That is, thanks to the features of the trigger frame being used, it can be used along with an uplink orthogonal frequency division multiple access (OFDMA), and can serve as the speed control method of the uplink OFDMA regardless of the TWT.

Description

AP-driven Uplink Rate Control method using Trigger Frame in TWT

The present invention relates to an access point-oriented uplink control method using a trigger frame in a target wake time (TWT), and more particularly, to an access point-centered uplink using a trigger frame in an IEEE 802.11ax target wake time. It relates to a control method.

[Description of state-funded R&D]

This study was made with the support of the Ministry of Science and ICT's Broadcasting and Communication Industry Technology Development Project (Smart Cloud-based Multi Radio-structured wireless LAN platform development, project identification number: 1711103025, detailed project number: 2018-0-00815-003) .

The concept of Target Wake Time (TWT), first added to the IEEE 802.11ah standard to provide a low power consumption mode and periodic data transmission, has been extended in IEEE 802.11ax, It provides additional power efficiency of the device. Target Wake Time (TWT) enables the negotiation of wake (active state) and doze (sleep state) periods between an access point (AP) and a station (STA, Station), A doze state that is not active for a period of time may be maintained. That is, time division access is enabled by allocating appropriate wake and doze periods for each base station. Target Wake Time (TWT) can increase energy efficiency while minimizing the level of collision and interference, which can significantly improve the spectrum utilization of the network.

However, such a target wake time (TWT) causes a temporary transmission interruption, and this transmission interruption may cause a new problem while operating with the existing technology of a wireless local area network (WLAN) that assumes continuous transmission. For example, a loss-based rate adjustment technique requires sufficient statistics and sampling to select an appropriate rate for a given channel and environment, and the target wake time (TWT) may interfere with the collection of such statistics.

In particular, since the target wake time (TWT) sometimes puts the stations (STAs) in a doze state without transmitting, statistics cannot be collected during this state, and the rate selection must be performed using only the statistics of the wake state. In this case, the statistics may be inaccurate, and the problem can be exacerbated in rapidly changing channel conditions. Also, in the case of rate adjustment, it is necessary to sample all possible rates to determine which one is the best, but using a target wake time (TWT) requires more time to sample all rates.

The present invention has been devised to solve the above problems, and proposes an access point-centered uplink control method using a trigger frame at a target wake time (TWT).

The access point-oriented uplink control method using a trigger frame in TWT according to an embodiment of the present invention includes receiving a first data packet from a station, wherein the first data packet is a trigger generated based on a current trigger frame. which is a trigger-based PPDU (TB-PPDU); calculating a signal-to-noise ratio of the first data packet; selecting a modulation and coding scheme (MCS) that satisfies a target bit error ratio (BER) based on the calculated signal-to-noise ratio; constructing a next trigger frame including the selected MCS; and transmitting the configured next trigger frame to the station.

An apparatus for controlling an uplink using a trigger frame in TWT according to another embodiment of the present invention includes: a processor; a memory configured to temporarily or permanently store data necessary for the operation of the processor; and a transceiver for exchanging data with a station, wherein the processor receives a first data packet from the station, wherein the first data packet is a trigger-based PPDU (TB-PPDU) generated based on a current trigger frame. , calculates a signal-to-noise ratio of the received first data packet, selects a modulation and coding scheme (MCS) that satisfies a target bit error ratio (BER) based on the calculated signal-to-noise ratio, and includes the selected MCS and configure a next trigger frame, and transmit the configured next trigger frame to the station through the transceiver.

An access point-oriented uplink control method using a trigger frame according to an embodiment of the present invention directly controls the uplink based on the SNR of a data packet received from the access point, and the data rate is performed based on the received SNR. , can be implemented independently of loss statistics.

In addition, since the uplink control method performed by the access point of the present invention uses a trigger frame and a trigger-based PPDU defined in the 802.11ax standard, it may be an uplink speed control technique that can be implemented while complying with the standard. In particular, since feedback on the received SNR is provided through a trigger frame, other non-standard frame formats or modifications are unnecessary for feedback implementation.

In addition, the uplink control according to the present invention does not require any modification to the station and can be applied sufficiently by changing the access point, so it can be applied more universally.

1 schematically illustrates a wireless communication system in which an access point-centered uplink control method using a trigger frame according to an embodiment of the present invention is implemented.
2 is an exemplary diagram for explaining Trigger-enabled TWT (TE-TWT) scheduling.
3 is a flowchart of an access point-centered uplink control method using a trigger frame in TWT according to an embodiment of the present invention.
4 schematically illustrates an access point-centered uplink control process using a trigger frame.
5 is a diagram illustrating a relationship between an access point and a station according to uplink control centered on the access point.
6 is a block diagram illustrating the configuration of an apparatus for controlling an uplink using a trigger frame in TWT according to another embodiment of the present invention.

Terms used in this specification will be briefly described, and the present invention will be described in detail.

The terms used in the present invention have been selected as currently widely used general terms as possible while considering the functions in the present invention, which may vary depending on the intention or precedent of a person skilled in the art, the emergence of new technology, and the like. In addition, in specific cases, there are also terms arbitrarily selected by the applicant, and in this case, the meaning will be described in detail in the description of the corresponding invention. Therefore, the term used in the present invention should be defined based on the meaning of the term and the overall content of the present invention, rather than the name of a simple term.

When a part "includes" a certain element throughout the specification, this means that other elements may be further included, rather than excluding other elements, unless otherwise stated. In addition, terms such as "...unit" and "module" described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software. .

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the embodiments of the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

1 schematically illustrates a wireless communication system in which an access point-centered uplink control method using a trigger frame according to an embodiment of the present invention is implemented. 2 is an exemplary diagram for explaining Trigger-enabled TWT (TE-TWT) scheduling, which is a TWT including a trigger frame operation.

1 and 2, popular wireless network technologies may include various types of WLANs. WLANs can be used to interconnect nearby devices to each other using widely used networking protocols. The various aspects described herein may be applied to any communication standard, such as a wireless protocol.

In some aspects, wireless signals may be transmitted according to an 802.11 protocol using orthogonal frequency-division multiplexing (OFDM), direct-sequence spread spectrum (DSSS) communications, a combination of OFDM and DSSS communications, or other schemes. Implementations of the 802.11 protocol may be used for sensors, metrology and smart grid networks. Advantageously, aspects of certain devices implementing the 802.11 protocol may consume less power than devices implementing other wireless protocols, and/or wirelessly over relatively long distances, such as about one kilometer or more, for example. can be used to transmit signals.

In some implementations, a WLAN includes various devices that are components that access a wireless network. For example, as shown in FIG. 1 , there may be two types of devices: an access point (AP) 100 and stations (also referred to as clients or “STAs” 200 ). In general, the access point 100 may function as a hub or base station for a WLAN, and the station 200 functions as a user of the WLAN. In one example, station 200 connects to access point 100 via a Wi-Fi (eg, IEEE 802.11 protocol) compliant wireless link to obtain a general connection to the Internet or to other wide area networks. In some implementations, station 200 may also be used as access point 100 .

The access point 100 also includes a NodeB, a Radio Network Controller (RNC), an eNodeB, a Base Station Controller (BSC), a Base Transceiver Station (BTS), a Base Station (BS), a Transceiver Function (TF), a radio router, a radio transceiver. , junction point, or any other terminology may include, embodied as, or known as such.

Station 200 also includes or includes an access terminal (AT), subscriber station, subscriber unit, mobile station, remote station, remote terminal, user terminal, user agent, user device, user equipment, or any other terminology. may be implemented, or known as such. In some implementations, the station connects to a cellular phone, a cordless phone, a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless connectivity capability, or a wireless modem. any other suitable processing device. Accordingly, one or more aspects taught herein may include a phone (eg, a cellular phone or smart phone), a computer (eg, a laptop), a portable communication device, a headset, a portable computing device (eg, a personal digital assistant), entertainment It may be incorporated into a device (eg, a music or video device or satellite radio), a gaming device or system, a global positioning system device, or any other suitable device configured to communicate over a wireless medium.

As discussed above, certain devices described herein may implement, for example, the 802.11 standard. Such devices, whether used as station 200 , access point 100 , or other devices, may be used in smart metrology or smart grid networks. Such devices may provide sensor applications or may be used in home automation.

Various processes and methods may be used for transmissions in a wireless communication system between the access point 100 and the stations 200 . For example, signals may be transmitted and received between the access point 100 and the stations 200 according to OFDM or orthogonal frequency-division multiple access (OFDMA) techniques, and the wireless communication system will be referred to as an OFDM/OFDMA system. can Alternatively, signals may be transmitted and received between access point 100 and stations 200 in accordance with CDMA techniques, and the wireless communication system may be referred to as a CDMA system. In an aspect, a wireless communication system may support MIMO transmissions, including single-user MIMO and multi-user MIMO. The wireless communication system may also support multi-user OFDMA and the like.

A communication link that enables transmission from the access point 100 to one or more of the stations 200 may be referred to as a downlink (DL), and from the stations 200 to the access point 100 . The communication link that enables transmission may be referred to as an uplink (UL). Alternatively, the downlink may be referred to as a downlink, a forward link, or a forward channel, and the uplink may be referred to as an uplink, a reverse link, or a reverse channel.

The access point 100 may operate as a base station and may provide wireless communication coverage to a basic service area (BSA). The BSA is the coverage area of the access point 100 . The access point 100 and the stations 200 using the access point 100 for communication may be referred to as a basic service set (BSS). The access point 100 serves a number of stations 200 in the BSS. When the stations 200 have data to transmit or receive, the stations 200 exchange UL/DL frames with the AP (eg, within a multi-user environment). UL/DL frames refer to UL only, DL only, or both.

In the wireless communication system of the present invention, for efficient data exchange between the access point 100 and the station 200, the access point 100 or the station 200) sleeps (dose) and wakes up at specific times. A target wake time (TWT) scheduling protocol may be applied that may be scheduled and may be scheduled for transmission at predetermined or negotiated times. This TWT scheduling protocol may be beneficial to any scheduling mechanism that may be negotiated between devices or may be dictated by one device to schedule time intervals for exchanging information between two or more devices. .

In addition, in the wireless communication system of the present invention, a trigger frame for uplink data transmission control may be supported for aligned uplink transmission between stations 200 . That is, the station 200 needs to receive a trigger frame from the access point 100 in order to transmit data. The trigger frame may include a resource allocation set for uplink transmission.

That is, the wireless communication system according to the embodiment of the present invention may be implemented based on Trigger-enabled TWT (TE-TWT) scheduling. In TE-TWT, the trigger frame may be transmitted to all stations 200 prior to all uplink transmission regardless of OFDMA transmission. Specifically, the access point 100 may select the size and location of one or more resource units (RUs) to which each of its associated stations 200 may transmit data. Then, as shown in FIG. 2 , the access point 100 sends the uplink data of the station 200 on the set of allocated resource units (RUs) using a trigger frame to each of the plurality of stations 200 . can direct

A trigger frame may refer to a frame instructing each of a plurality of identified stations 200 to transmit uplink (UL) multi-user (MU) data on a resource unit allocated to the station 200 . Specifically, the trigger frame may include uplink transmission related parameters such as uplink length, modulation and coding scheme (MCS) and spatial stream number, transmission power and target RSSI as well as resource unit allocation information.

After receiving the trigger frame from the station 200, the station 200 transmits a trigger-based PPDU (TB-PPDU) along with the transmission parameters indicated in the trigger frame, such as resource unit allocation, transmission MCS, and uplink transmission power, to the access point. (100) is transmitted.

Here, the access point 100 according to an embodiment of the present invention may control uplink transmission of the corresponding station 100 based on a trigger-based PPDU (TB-PPDU) received from the station 100 . Specifically, the access point 100 may configure the following trigger frame to adjust the uplink transmission rate of the corresponding station 100 based on the received trigger-based PPDU.

Hereinafter, an access point-centered uplink control method using a trigger frame in TWT according to an embodiment of the present invention will be described in more detail with reference to FIGS. 3 to 5 .

The configuration and operation of the access point will be described in more detail.

3 is a flowchart of an access point-centered uplink control method using a trigger frame in TWT according to an embodiment of the present invention. 4 schematically illustrates an access point-centered uplink control process using a trigger frame. 5 is a diagram illustrating a relationship between an access point and a station according to uplink control centered on the access point.

3 to 5 , the access point-centered uplink control method using a trigger frame in TWT according to an embodiment of the present invention may be performed in the access point. The method includes receiving a first data packet from a station, wherein the first data packet is a trigger-based PPDU (TB-PPDU) generated based on a current trigger frame (S100); calculating a signal-to-noise ratio of the first data packet (S110); selecting a modulation and coding scheme (MCS) that satisfies a target bit error ratio (BER) based on the calculated signal-to-noise ratio (S120); Constructing a next trigger frame including the selected MCS (S130); and transmitting the configured next trigger frame to the station (S140).

First, a first data packet is received from the station (S100).

The access point 100 may receive the first data packet from the station 200 . Here, the first data packet corresponds to a trigger-based PPDU (TB-PPDU) generated based on the current trigger frame. The trigger-based PPDU (TB-PPDU) corresponds to a PPDU format that the station 200 should use for the next uplink transmission upon receiving the trigger frame. That is, the station 200 may generate a trigger-based PPDU (TB-PPDU) according to the trigger frame previously transmitted by the access point 100 . The access point 100 may receive the generated trigger-based PPDU (TB-PPDU) from the station 200 .

Next, the signal-to-noise ratio of the first data packet is calculated (S110).

This step S110 includes measuring a received signal strength indication (RSSI) of the first data packet, and calculating a signal-to-noise ratio (SNR) by applying a noise floor to the measured RSSI. . Here, if it is assumed that there is only one access point 100 and one station 200 within one TWT service period (SP), the SNR is a signal to noise ratio (SNR) and a signal to interference plus noise ratio (SINR). It can be calculated without confusion. In addition, in order to cope with temporary channel fluctuations and temporary SNR decrease/increase, the measured SNR value may be tracked and calculated according to an exponential weighted moving average (EWMA) method.

Next, an MCS that satisfies a target bit error ratio (BER) is selected based on the calculated signal-to-noise ratio (S120).

In this step (S120), a threshold SNR that satisfies the target BER for each MCS may be calculated. That is, the access point 200 may include an MCS index in which a threshold SNR that satisfies the target BER for each MCS is defined. A corresponding MCS may be selected by substituting the calculated signal-to-noise ratio into the MCS index. When there are a plurality of MCSs corresponding to the calculated signal-to-noise ratio in the MCS index, an MCS having the highest data rate may be selected. That is, the MCS having the highest data rate while satisfying the target bit error ratio (BER) may be selected in this step S120 .

Next, the next trigger frame including the selected MCS is configured (S130).

The selected MCS may be included in the next trigger frame. That is, the next trigger frame may be configured to include the MCS having the highest data rate while satisfying the target BER. In addition, for the next trigger frame, the uplink transmission power and length may be set to the maximum value for the best possible performance.

The next configured trigger frame is transmitted to the station (S140).

The next configured trigger frame may be transmitted to the station 200 . After receiving the trigger frame, the station 200 may use the data rate newly selected by the access point 100 in step S120 for the next transmission through the MCS specified in the trigger frame. That is, the station 200 transmits the next first data (TB-PPDU) through the data rate provided through the trigger frame. The access point 100 receives the next first data (TB-PPDU) and prepares the next trigger frame by measuring the RSSI and SNR. That is, as shown in FIG. 5 , the uplink control of the access point 100 based on the trigger frame and the TB-PPDU may be continuously performed.

Since the uplink control performed by the access point 100 of the present invention uses a trigger frame and a trigger-based PPDU defined in the 802.11ax standard, it may be an uplink speed control technique that can be implemented while completely complying with the standard. In particular, since feedback on the received SNR is provided through a trigger frame, other non-standard frame formats or modifications are unnecessary for feedback implementation. In addition, the uplink control of the present invention does not require any modification to the station 200 , and can be sufficiently applied to the access point 100 by changing the access point 100 , so it can be applied more universally.

Hereinafter, an apparatus for controlling uplink using a trigger frame in TWT according to another embodiment of the present invention will be described.

6 is a block diagram illustrating the configuration of an apparatus for controlling an uplink using a trigger frame in TWT according to another embodiment of the present invention. The uplink control apparatus using the trigger frame in the TWT of FIG. 6 may be the access point 100, and FIGS. 1 to 5 may be referred to for the description of the present embodiment.

Referring to FIG. 6 , the access point 100 includes a processor 101 , a memory 102 , and a transceiver 103 .

The processor 101 may control the operation of each component of the access point 100 . The memory 120 is configured to temporarily or permanently store data necessary for the operation of the processor 101 . The transceiver 103 is configured to exchange data with the station 200 .

The processor 101 may configure a trigger frame for uplink control of the station 200 based on the first data packet received from the station 200 through the transceiver 103 . Here, the first data packet corresponds to a trigger-based PPDU (TB-PPDU) generated based on the current trigger frame. The trigger-based PPDU (TB-PPDU) corresponds to a PPDU format that the station 200 should use for the next uplink transmission upon receiving the trigger frame. That is, the station 200 may generate a trigger-based PPDU (TB-PPDU) according to the trigger frame previously transmitted by the access point 100 . The access point 100 may receive the generated trigger-based PPDU (TB-PPDU) from the station 200 .

The processor 101 measures a received signal strength indication (RSSI) of the first data packet, and calculates a signal-to-noise ratio (SNR) by applying a noise floor to the measured RSSI. Here, if it is assumed that there is only one access point 100 and one station 200 within one TWT service period (SP), the SNR is a signal to noise ratio (SNR) and a signal to interference plus noise ratio (SINR). It can be calculated without confusion. In addition, in order to cope with temporary channel fluctuations and temporary SNR decrease/increase, the measured SNR value may be tracked and calculated according to an exponential weighted moving average (EWMA) method.

Next, the processor 101 selects an MCS that satisfies a target bit error ratio (BER) based on the calculated signal-to-noise ratio (SNR). The memory 102 may include an MCS index in which a threshold SNR satisfying a target BER is defined for each MCS. The processor 101 may select the corresponding MCS by substituting the calculated signal-to-noise ratio into the MCS index. When there are a plurality of MCSs corresponding to the calculated signal-to-noise ratio in the MCS index, the processor 101 may select an MCS having the highest data rate.

The processor 101 constructs the next trigger frame including the selected MCS. In addition, the processor 101 may configure the next trigger frame by setting the uplink transmission power and length to the maximum values for the best possible performance.

The processor 101 may transmit the next configured trigger frame to the station 200 . After receiving the trigger frame, the station 200 may use the newly selected data rate for the next transmission through the MCS specified in the trigger frame. That is, the station 200 transmits the next first data (TB-PPDU) using the parameters of the received trigger frame including the data rate. The access point 100 receives the next first data (TB-PPDU) and prepares the next trigger frame by measuring the RSSI and SNR. That is, the uplink control for the station 200 of the access point 100 based on the trigger frame and the TB-PPDU may be continuously performed.

The access point-centered uplink control using a trigger frame according to an embodiment of the present invention directly controls the uplink based on the SNR of a data packet received from the access point, and the data rate is performed based on the received SNR, It can be implemented independent of loss statistics.

In addition, since the uplink control performed by the access point 100 of the present invention uses a trigger frame and a trigger-based PPDU defined in the 802.11ax standard, it may be an uplink speed control technique that can be implemented while completely complying with the standard. In particular, since feedback on the received SNR is provided through a trigger frame, other non-standard frame formats or modifications are unnecessary for feedback implementation. In addition, the uplink control of the present invention does not require any modification to the station 200 , and can be sufficiently applied to the access point 100 by changing the access point 100 , so it can be applied more universally.

Although described above with reference to the embodiments, the present invention should not be construed as being limited by these embodiments or drawings, and those skilled in the art will appreciate the spirit and scope of the present invention described in the claims below. It will be understood that various modifications and variations of the present invention can be made without departing from the scope of the present invention.

100: access point
200: station
101: processor
102: memory
103: transceiver

Claims (10)

An access point-centered uplink control method using a trigger frame in TWT,
Receiving a first data packet from a station, wherein the first data packet is a trigger-based PPDU (TB-PPDU) generated based on a current trigger frame;
calculating a signal-to-noise ratio of the first data packet;
selecting a modulation and coding scheme (MCS) that satisfies a target bit error ratio (BER) based on the calculated signal-to-noise ratio;
constructing a next trigger frame including the selected MCS; and
sending the configured next trigger frame to the station. According to claim 1,
Calculating the signal-to-noise ratio of the first data packet comprises:
measuring the RSSI of the first data packet and calculating a signal-to-noise ratio by applying a noise floor to the measured RSSI. According to claim 1,
Selecting a modulation and coding scheme (MCS) that satisfies a target bit error ratio (BER) based on the calculated signal-to-noise ratio comprises:
A method comprising selecting a corresponding MCS by substituting the calculated signal-to-noise ratio into an MCS index in which a threshold SNR satisfying a target BER for each MCS is defined. 4. The method of claim 3,
Selecting a modulation and coding scheme (MCS) that satisfies a target bit error ratio (BER) based on the calculated signal-to-noise ratio comprises:
and selecting an MCS having a highest data rate among a plurality of MCSs when there are a plurality of MCSs corresponding to the calculated signal-to-noise ratio in the MCS index. According to claim 1,
The trigger-based PPDU (TB-PPDU) corresponds to a PPDU format that the station should use for next uplink transmission in response to the trigger frame reception. As an uplink control device using a trigger frame in TWT,
The apparatus includes: a processor; a memory configured to temporarily or permanently store data necessary for the operation of the processor; and a transceiver for exchanging data with the station,
The processor is
Receive a first data packet from the station, wherein the first data packet is a trigger-based PPDU (TB-PPDU) generated based on a current trigger frame,
calculating a signal-to-noise ratio of the received first data packet;
selecting a modulation and coding scheme (MCS) that satisfies a target bit error ratio (BER) based on the calculated signal-to-noise ratio;
Configure the next trigger frame including the selected MCS,
and transmit the configured next trigger frame to the station through the transceiver. 7. The method of claim 6,
Calculating the signal-to-noise ratio of the first data packet comprises:
and measuring the RSSI of the first data packet and calculating a signal-to-noise ratio by applying a noise floor to the measured RSSI. 7. The method of claim 6,
The memory includes an MCS index in which a threshold SNR satisfying a target BER is defined for each MCS,
The processor selects a corresponding MCS by substituting the calculated signal-to-noise ratio into the MCS index. 9. The method of claim 8,
The processor selects an MCS having a highest data rate among a plurality of MCSs when there are a plurality of MCSs corresponding to the calculated signal-to-noise ratio in the MCS index. 7. The method of claim 6,
The trigger-based PPDU (TB-PPDU) corresponds to a PPDU format that the station should use for the next uplink transmission in response to receiving the trigger frame.

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