WO2017008703A1 - Channel measurement method and sta - Google Patents

Abstract

Provided are a channel measurement method and an STA, which can guarantee that a sub-channel on which channel measurement is conducted is idle, to avoid the influence on OBSS transmission because of conducting UL channel measurement to a certain extent. The method comprises: a station (STA) receiving a measurement notification message sent by an access point (AP), the measurement notification message carrying identification information about a channel to be measured; and the STA sending sounding reference signals via M idle sub-channels, so that the AP measures the M idle sub-channels according to the received sounding reference signals, wherein the M idle sub-channels are M idle sub-channels determined by the STA from at least one sub-channel contained in a channel indicated by the identification information about the channel to be measured, wherein M is an integer greater than or equal to one.

Description

Channel measurement method and STA

This application is required to be submitted to the China Patent Office on July 10, 2015, the application number is 201510405866.5, and the priority of the Chinese patent application filed on December 31, 2015, and the application number is 201511028305.4. This is incorporated herein by reference.

Technical field

The present invention relates to the field of communications, and in particular, to a channel measurement method and an STA (Station).

Background technique

With the evolution of the WLAN (Wireless Local Area Network) standard, the next generation WiFi standard has been studied and developed. The next-generation WiFi standard, referred to as HEW (High Efficiency WLAN), aims to increase the system capacity to more than 10 Gbps, with particular attention to the outdoor deployment and high-density deployment of WiFi devices.

For high-density distribution scenarios, multi-user transmission technologies with higher performance advantages need to be introduced into the next-generation WiFi standard. For example, OFDMA (Orthogonal Frequency Division Multiple Access) and UL MU-MIMO (Uplink Multi-user Multiple Input Multiple Output). Regardless of OFDMA or UL MU-MIMO, an AP needs to allocate and schedule transmission resources of multiple STAs. In order to more efficiently schedule multiple STAs to implement UL multi-user transmission, it is necessary to measure the UL channel.

Currently, an AP may instruct the STA to transmit sounding reference signals on certain channels for UL channel measurements. However, the AP does not know which channels are occupied by other BSS (Basic Service Set) around the STA. If the STA sends sounding in these specific channels according to the AP indication, it is possible to overlap the OBSS (Overlapping Basic Service Set). The basic service set) has an impact. That is, if the STA transmits the sounding reference signal on the occupied channel, it will cause interference to the ongoing transmission in the BSS around the STA.

Summary of the invention

Embodiments of the present invention provide a channel measurement method and an STA, which can ensure a letter is performed. The subchannels of the channel measurement are idle, to a certain extent avoiding the impact on the OBSS transmission due to the UL channel measurement.

In order to achieve the above objective, the technical solution adopted by the embodiment of the present invention is

In a first aspect, a channel measurement method is disclosed, including:

The STA receives the measurement notification message sent by the access point AP, where the measurement notification message carries the identification information of the channel that needs to be measured;

The STA sends a sounding reference signal through M idle subchannels, so that the AP measures the M free subchannels according to the received sounding reference signal, where the M free subchannels are The M free subchannels determined in the channel indicated by the identification information of the channel to be measured, the M being an integer greater than or equal to 1.

In conjunction with the first aspect, in a first possible implementation of the first aspect,

The measurement notification message further carries an ID of a STA that needs to perform channel measurement; and the STA that needs to perform channel measurement includes at least one STA.

In conjunction with the first aspect or the first possible implementation of the first aspect, in a second possible implementation of the first aspect,

Before the STA receives the measurement notification message sent by the access point AP, the method further includes:

The STA performs a clear channel estimation CCA on each subchannel supported by the AP and the STA, and determines the subchannel whose CCA result is idle as a available subchannel.

And determining, by the STA, the M idle subchannels in the at least one subchannel included in the channel indicated by the identifier information of the channel that needs to be measured, specifically:

Among the channels indicated by the identification information, the same M subchannels as the available subchannels are determined as the M free subchannels.

In conjunction with the first aspect or the first possible implementation of the first aspect, in a third possible implementation of the first aspect,

Before the STA sends the sounding reference signal through the M idle subchannels, the method further includes:

Performing, by the STA, CCA for each subchannel in the channel indicated by the identification information within a first preset duration after receiving the measurement notification message, where The M subchannels whose CCA result is idle are determined as the M idle subchannels.

In conjunction with the second or third possible implementation of the first aspect, in a fourth possible implementation of the first aspect,

After the STA determines the M idle subchannels, the method further includes:

The STA sends a clear CTS by using the M idle subchannels at the first time, where the first time is a time interval after the time when the STA receives the measurement notification message.

In conjunction with the first aspect or the first possible implementation of the first aspect, in a fifth possible implementation of the first aspect,

The measurement notification message also carries a long training domain LTF number indication field, and the method further includes:

Determining, by the STA, the second time of sending the sounding reference signal by the STA according to the LTF number indication field, the STA queue, and the time when the STA receives the measurement notification message, where the STA queue is The STAs that need to perform channel measurement are obtained in the order in which the IDs of the STAs appear in the measurement notification message.

In conjunction with the fifth possible implementation of the first aspect, in a sixth possible implementation of the first aspect,

Before the STA sends the sounding reference signal on the M idle subchannels, the method further includes:

The STA determines, according to the LTF number indication field carried in the measurement notification message, the STA queue, and the time when the STA receives the measurement notification message, the last STA that sends the sounding reference signal, and the previous one. The STA that detects the reference signal sends a third moment when the sounding reference signal ends; the last STA that sends the sounding reference signal is the previous STA in the STA queue adjacent to the STA;

The STA performs CCA at a time interval from the third time to the second time, and determines the M subchannels whose CCA result is idle as the M free subchannels.

In conjunction with the second or third or sixth possible implementation of the first aspect, in a seventh possible implementation of the first aspect,

The network allocation vector NAV of the subchannel performing CCA is zero.

With reference to the first aspect, or any one of the first to seventh possible implementation manners of the first aspect, in the eighth possible implementation manner of the first aspect, the measurement notification message indicates that channel measurement is required The number of STAs is N, and the N is an integer greater than or equal to 1.

The measurement notification message carries an LTF number indication field, which is used to indicate the number of LTF fields included in the sounding reference signal sent by the STA that needs to perform channel measurement;

Or the measurement notification message carries N LTF number indication fields, where the N LTF number indication fields are used to indicate the number of LTF fields included in the sounding reference signal frame sent by the STA corresponding to the LTF number indication field. .

In conjunction with the eighth possible implementation of the first aspect, in a ninth possible implementation manner of the first aspect,

If the measurement notification message carries an LTF number indication field, the sounding reference signal sent by the STA includes X LTFs, and the X is the number indicated by the LTF number indication field.

In conjunction with the eighth possible implementation of the first aspect, in a tenth possible implementation manner of the first aspect,

If the measurement notification message carries the N LTF number indication fields, the sounding reference signal sent by the STA includes Y LTFs, where Y is the number indicated by the LTF number indication field corresponding to the STA.

With reference to the first aspect, or any one of the first to the tenth possible implementation manners of the first aspect, in an eleventh possible implementation manner of the first aspect,

The sounding reference signal further includes a bandwidth indication field; the bandwidth indication field is used to indicate a bandwidth of an idle subchannel used by the sounding reference signal.

With reference to the first aspect, or any one of the first to the eleventh possible implementation manners of the first aspect, in the twelfth possible implementation manner of the first aspect, the measurement notification message further includes And a power indication field, where the first power indication field is used to indicate that the AP sends the power of the measurement notification message.

In conjunction with the first aspect or any one of the first to eleventh possible implementations of the first aspect, in a thirteenth possible implementation of the first aspect,

The measurement notification message further includes a second power indication field, and the second power indicator The indication field is used to indicate the power of the STA to send the sounding reference signal, or the expected power when the sounding reference signal sent by the STA reaches the AP.

In conjunction with the first aspect or any one of the first to eleventh possible implementations of the first aspect, in a fourteenth possible implementation of the first aspect,

The method further includes the sounding reference signal further comprising a third power indication field, the third power indication field being used to indicate the power of transmitting the sounding reference signal.

In conjunction with the first aspect, or any one of the first to eleventh possible implementations of the first aspect, in a fifteenth possible implementation of the first aspect,

The sounding reference signal further includes a resource request field, where the resource request field is used to indicate an amount of data that the STA that sends the sounding reference signal needs to transmit, or a time that the STA requests for transmitting data.

In conjunction with the first aspect, or any one of the first to eleventh possible implementations of the first aspect, in a sixteenth possible implementation of the first aspect,

The measurement notification message further includes a sounding reference signal type indication, the type of the sounding reference signal indicating the type of the sounding reference signal, the type including old NDP Sounding and HEW NDP Sounding.

In conjunction with the first aspect, or any one of the first to sixteenth possible implementations of the first aspect, in a seventeenth possible implementation of the first aspect,

The measurement notification message further carries a transmission duration indication field, where the transmission time indication field is used to indicate an expected duration from the end of the measurement notification message transmission to the completion time of the entire channel measurement process;

Then, the method further includes: the STA setting a duration Duration field of the CTS according to the transmission duration indication field.

In a second aspect, a site STA is disclosed, including:

a receiving unit, configured to receive a measurement notification message sent by the access point AP, where the measurement notification message carries identifier information of a channel that needs to be measured;

a sending unit, configured to send, by using the M idle subchannels, the sounding reference signal, so that the AP measures the M free subchannels according to the received sounding reference signal, where the M free subchannels are The M free subchannels determined in the channel indicated by the identification information of the channel that needs to be measured, where the M is greater than An integer equal to 1.

In conjunction with the second aspect, in a first possible implementation of the second aspect,

The measurement notification message further carries an ID of a STA that needs to perform channel measurement; and the STA that needs to perform channel measurement includes at least one STA.

With reference to the second aspect or the first possible implementation manner of the second aspect, in a second possible implementation manner of the second aspect,

a first clear channel estimation CCA unit, configured to perform a clear channel estimation CCA for each subchannel supported by the AP and the STA, and determine the subchannel with the CCA result as idle as a available subchannel;

The first determining unit is further configured to determine, in the channel indicated by the identifier information, the same M subchannels as the available subchannels as the M idle subchannels.

With reference to the second aspect or the first possible implementation manner of the second aspect, in a third possible implementation manner of the second aspect,

Also including a second determining unit, a second CCA unit,

The second CCA unit is configured to perform CCA on each of the channels indicated by the identifier information within a first preset duration after the receiving unit receives the measurement notification message;

The second determining unit is configured to determine, to the M idle subchannels, the M subchannels whose CCA result is idle.

In conjunction with the second or third possible implementation of the second aspect, in a fourth possible implementation of the second aspect,

The sending unit is further configured to: after the determining the M free subchannels, sending, by using the M idle subchannels, a clear sending CTS at a first moment, where the first moment is that the STA receives the The time after the second measurement duration is measured after the time when the notification message is measured.

With reference to the second aspect or the first possible implementation manner of the second aspect, in a fifth possible implementation manner of the second aspect,

The measurement notification message further carries a long training domain LTF number indication field, and further includes a third determining unit,

The third determining unit is configured to: according to the number of LTFs carried by the measurement notification message Determining, by the STA, the STA, and the STA, the second time when the STA sends the sounding reference signal; the STA queue is the STA that needs to perform channel measurement according to the STA The IDs are obtained after the order in which the measurement notification messages appear.

In conjunction with the fifth possible implementation of the second aspect, in a sixth possible implementation manner of the second aspect,

The third determining unit is further configured to: before the sending unit sends the sounding reference signal on the M idle subchannels, according to the LTF number indication field carried by the measurement notification message, the STA queue, and the STA receiving Determining, at the time of the measurement notification message, the STA that sent the last sounding reference signal, and the last time that the STA that sent the sounding reference signal sent the sounding reference signal ends; the last STA that sent the sounding reference signal Is the previous STA in the STA queue adjacent to the STA;

a second CCA unit, where the second CCA unit is configured to perform CCA at a time interval from the third time to the second time, and determine the M subchannels in which the CCA result is idle as the M Free subchannels.

In conjunction with any of the second or third or sixth possible implementation methods of the second aspect, in a seventh possible implementation of the second aspect, the NAV monitoring unit is configured to perform CCA prior to performing CCA And determining that the network allocation vector NAV of the subchannel performing the CCA is 0.

With reference to the second aspect, or any one of the first to seventh possible implementation manners of the second aspect, in an eighth possible implementation manner of the second aspect,

The measurement notification message indicates that the number of STAs that need to perform channel measurement is N, and the N is an integer greater than or equal to 1.

The measurement notification message carries an LTF number indication field, which is used to indicate the number of LTF fields included in the sounding reference signal sent by the STA that needs to perform channel measurement;

Or the measurement notification message carries N LTF number indication fields, where the N LTF number indication fields are in one-to-one correspondence with the N STAs that need to perform channel measurement, and are used to indicate that the STA corresponding to the LTF number indication field is sent. The number of LTF fields contained in the sounding reference signal frame.

In conjunction with the eighth possible implementation of the second aspect, in a ninth possible implementation manner of the second aspect,

If the measurement notification message carries an LTF number indication field, the sounding reference signal sent by the STA includes X LTFs, and the X is the number indicated by the LTF number indication field.

In conjunction with the eighth possible implementation of the second aspect, in a tenth possible implementation manner of the second aspect,

If the measurement notification message carries the N LTF number indication fields, the sounding reference signal sent by the STA includes Y LTFs, where Y is the number indicated by the LTF number indication field corresponding to the STA.

With reference to the second aspect, or any one of the first to tenth possible implementation manners of the second aspect, in an eleventh possible implementation manner of the second aspect,

The sounding reference signal further includes a bandwidth indication field; the bandwidth indication field is used to indicate a bandwidth of an idle subchannel used by the sounding reference signal.

In conjunction with the second aspect or any one of the first to eleventh possible implementations of the second aspect, in a twelfth possible implementation of the second aspect,

The measurement notification message further includes a first power indication field, where the first power indication field is used to indicate that the AP sends the power of the measurement notification message.

With reference to the second aspect, or any one of the first to the eleventh possible implementation manners of the second aspect, in a thirteenth possible implementation manner of the second aspect,

The measurement notification message further includes a second power indication field, where the second power indication field is used to indicate that the STA sends the power of the sounding reference signal, or the expectation when the sounding reference signal sent by the STA reaches the AP power.

With reference to the second aspect, or any one of the first to eleventh possible implementation manners of the second aspect, in the fourteenth possible implementation manner of the second aspect,

The sounding reference signal further includes a third power indication field, where the third power indicator field is used to indicate the power of transmitting the sounding reference signal.

With reference to the second aspect, or any one of the first to the eleventh possible implementation manners of the second aspect, in a fifteenth possible implementation manner of the second aspect,

The sounding reference signal further includes a resource request field, and the resource request field is used by The amount of data that the STA that transmits the sounding reference signal needs to transmit, or the time that the STA is requested to transmit data.

In conjunction with the second aspect, or any one of the first to fifteenth possible implementations of the second aspect, in a sixteenth possible implementation of the second aspect,

The measurement notification message further includes a sounding reference signal type indication, the type of the sounding reference signal indicating the type of the sounding reference signal, the type including old NDP Sounding and HEW NDP Sounding.

In conjunction with the second aspect, or any one of the first to sixteenth possible implementations of the second aspect, in a seventeenth possible implementation of the second aspect,

The measurement notification message further carries a transmission duration indication field, where the transmission time indication field is used to indicate an expected duration from the end of the measurement notification message transmission to the completion time of the entire channel measurement process;

The STA further includes a setting unit,

The setting unit is configured to set a duration Duration field of the CTS according to the transmission duration indication field.

In a third aspect, a station STA is disclosed, including a communication interface and a processor:

The processor is configured to receive, by using a communication interface, a measurement notification message sent by an access point AP, where the measurement notification message carries identifier information of a channel that needs to be measured;

The processor is further configured to send the sounding reference signal through the M idle subchannels through the communication interface, so that the AP measures the M free subchannels according to the received sounding reference signals, where the M free children The channel is M free subchannels determined by the STA in the channel indicated by the identification information of the channel that needs to be measured, and the M is an integer greater than or equal to 1.

In conjunction with the third aspect, in a first possible implementation manner of the third aspect, the measurement notification message further carries an ID of a STA that needs to perform channel measurement; and the STA that needs to perform channel measurement includes at least one STA.

With reference to the third aspect or the first possible implementation manner of the third aspect, in a second possible implementation manner of the third aspect,

The processor is further configured to perform a clear channel estimation CCA for each subchannel supported by the AP and the STA, and determine the subchannel with the CCA result as idle as a available subchannel.

The processor is further configured to determine, in the channel indicated by the identifier information, the same M subchannels as the available subchannels as the M idle subchannels.

With reference to the third aspect or the first possible implementation manner of the third aspect, in a third possible implementation manner of the third aspect,

The processor is configured to perform CCA on each of the channels indicated by the identifier information within a first preset duration after the communication interface receives the measurement notification message; and use the CCA result as idle. M subchannels are determined as the M free subchannels.

In conjunction with the second or third possible implementation of the third aspect, in a fourth possible implementation of the third aspect,

The processor is further configured to: after the determining the M free subchannels, sending, by using the M idle subchannels, the clear sending CTS by using the communication interface, where the first time is the STA A time interval of a second preset duration after receiving the measurement notification message.

With reference to the third aspect or the first possible implementation manner of the third aspect, in a fifth possible implementation manner of the third aspect,

The measurement notification message also carries a long training domain LTF number indication field.

The processor is configured to determine, according to the LTF number indication field carried in the measurement notification message, the STA queue, and the time when the STA receives the measurement notification message, to determine a second time when the STA sends the sounding reference signal; The STA queue is obtained by arranging the STAs that need to perform channel measurement in the order in which the IDs of the STAs appear in the measurement notification message.

In conjunction with the fifth possible implementation of the third aspect, in a sixth possible implementation manner of the third aspect,

The processor is further configured to: before the communication interface sends the sounding reference signal on the M idle subchannels, according to the LTF number indication field carried by the measurement notification message, the STA queue, and the STA receiving the location Determining the time of the measurement notification message, determining the STA that sent the last sounding reference signal, and the last time that the STA that sent the sounding reference signal sent the sounding reference signal ends; the last STA that sent the sounding reference signal is The previous STA in the STA queue adjacent to the STA;

The processor is further configured to perform CCA at a time interval from the third time to the second time, and determine, by the M subchannels whose CCA result is idle, as the M free subchannels.

In conjunction with any of the second or third or sixth possible implementations of the third aspect, in a seventh possible implementation of the third aspect,

The processor is further configured to determine that the NAV of the subchannel performing the CCA is 0 before performing the CCA.

With reference to the third aspect, or any one of the first to seventh possible implementation manners of the third aspect, in an eighth possible implementation manner of the third aspect,

The measurement notification message indicates that the number of STAs that need to perform channel measurement is N, and the N is an integer greater than or equal to 1.

The measurement notification message carries an LTF number indication field, which is used to indicate the number of LTF fields included in the sounding reference signal sent by the STA that needs to perform channel measurement;

Or the measurement notification message carries N LTF number indication fields, where the N LTF number indication fields are respectively used to indicate the LTF field included in the sounding reference signal frame sent by the STA corresponding to the LTF number indication field. number.

In conjunction with the eighth possible implementation of the third aspect, in a ninth possible implementation manner of the third aspect,

If the measurement notification message carries an LTF number indication field, the sounding reference signal sent by the STA includes X LTFs, and the X is the number indicated by the LTF number indication field.

In conjunction with the eighth possible implementation of the third aspect, in a tenth possible implementation manner of the third aspect,

If the measurement notification message carries the N LTF number indication fields, the sounding reference signal sent by the STA includes Y LTFs, where Y is the number indicated by the LTF number indication field corresponding to the STA.

With reference to the third aspect, or any one of the first to the tenth possible implementation manners of the third aspect, in an eleventh possible implementation manner of the third aspect,

The sounding reference signal further includes a bandwidth indication field; the bandwidth indication field is used to indicate a bandwidth of an idle subchannel used by the sounding reference signal.

With reference to the third aspect, or any one of the first to the eleventh possible implementation manners of the third aspect, in a twelfth possible implementation manner of the third aspect,

The measurement notification message further includes a first power indication field, where the first power indication field is used to indicate that the AP sends the power of the measurement notification message.

With reference to the third aspect, or any one of the first to the eleventh possible implementation manners of the third aspect, in a thirteenth possible implementation manner of the third aspect,

The measurement notification message further includes a second power indication field, where the second power indication field is used to indicate that the STA sends the power of the sounding reference signal, or the expectation when the sounding reference signal sent by the STA reaches the AP power.

With reference to the third aspect, or any one of the first to the eleventh possible implementation manners of the third aspect, in a fourteenth possible implementation manner of the third aspect,

The sounding reference signal further includes a third power indication field, where the third power indicator field is used to indicate the power of transmitting the sounding reference signal.

With reference to the third aspect, or any one of the first to the eleventh possible implementation manners of the third aspect, in a fifteenth possible implementation manner of the third aspect,

The sounding reference signal further includes a resource request field, where the resource request field is used to indicate an amount of data that the STA that sends the sounding reference signal needs to transmit, or a time that the STA requests for transmitting data.

With reference to the third aspect, or any one of the first to fifteenth possible implementation manners of the third aspect, in a sixteenth possible implementation manner of the third aspect,

The measurement notification message further includes a sounding reference signal type indication, the type of the sounding reference signal indicating the type of the sounding reference signal, the type including old NDP Sounding and HEW NDP Sounding.

In conjunction with the third aspect, or any one of the first to the sixteenth possible implementation manners of the third aspect, in the seventeenth possible implementation manner of the third aspect, the measurement notification message further carries a transmission a duration indication field, the transmission time indication field being used to indicate an expected duration from the end of the measurement notification message transmission to the completion of the entire channel measurement process;

The processor is further configured to set a duration Duration field of the CTS according to the transmission duration indication field.

The present invention provides a channel measurement method and STA, and the STA receives the measurement sent by the AP. a quantity notification message, where the measurement notification message carries identification information of a channel that needs to be measured, and determines M free subchannels in at least one subchannel included in a channel indicated by the identification information of the channel that needs to be measured; STA And transmitting, by the M idle subchannels, a sounding reference signal, so that the AP measures the M free subchannels according to the received sounding reference signal. Compared with the prior art STA, the sounding reference signal is sent on the channel indicated by the AP, and the AP does not know which channels are occupied by the BSS around the STA, so the STA may send sounding on the occupied channel, and then the ongoing transmission of the OBSS device. Cause interference. The present invention enables the STA to select its own idle subchannel to transmit sounding in the channel designated by the AP, thereby ensuring that the subchannel for performing channel measurement is idle, and to some extent, avoiding the influence of the UL channel measurement on the OBSS transmission.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is a certain embodiment of the present invention, and other drawings can be obtained from those skilled in the art without any creative work.

1 is a schematic flowchart of a channel measurement method according to Embodiment 1 of the present invention;

2 is a schematic diagram of a CTS frame according to Embodiment 1 of the present invention;

FIG. 3(a) is a schematic diagram of a frame structure of a sounding reference signal (HEW NDP Sounding) according to Embodiment 1 of the present invention;

FIG. 3(b) is a schematic diagram showing a frame structure of another sounding reference signal according to Embodiment 1 of the present invention (Legacy NDP Sounding);

4 is a schematic diagram of a TDM mode transmission sounding reference signal according to Embodiment 1 of the present invention;

FIG. 5 is a schematic diagram of a CDM mode transmission sounding reference signal according to Embodiment 1 of the present invention;

6 is a schematic diagram of a method provided by the present invention combined with a DL channel measurement mechanism;

7 is a schematic diagram of a method provided by the present invention combined with a MU-RTS/CTS mechanism;

8 is a structural block diagram of a STA according to Embodiment 2 of the present invention;

9 is another structural block diagram of a STA according to Embodiment 2 of the present invention;

FIG. 10 is a block diagram showing another structure of a STA according to Embodiment 2 of the present invention; FIG.

FIG. 11 is a structural block diagram of a STA according to Embodiment 3 of the present invention.

detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings in the embodiments of the present invention. It is obvious that the described embodiments are only a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts are within the scope of the present invention.

With the evolution of the WLAN standard, the current IEEE 802.11 working group has begun research and development of the next generation of WiFi standards. The next-generation WiFi standard project code 802.11ax aims to increase system capacity to more than 10 Gbps and is likely to introduce multi-user transmission technologies with higher performance advantages, such as OFDMA and ULMU-MIMO. The multi-user transmission technology requires the AP to allocate and schedule transmission resources of multiple STAs, and the scheduling information is placed in a Trigger frame sent by the AP. In order to better implement the scheduling of the UL transmission of multiple STAs by the AP, the AP needs to measure the UL channel.

In an existing LTE system, an eNB (Evolved NodeB) indicates that a User Equipment (UE) periodically or non-periodically transmits an SRS (Sounding Reference Signal) on a certain bandwidth to enable an eNB. The uplink channel is measured. Introducing this measurement mechanism into 802.11ax, the AP specifies that the STA sends sounding on a particular channel for the AP to perform channel measurements. Since the AP does not know the interference environment around the STA, if the designated STA sends Sounding on a specific channel, it is highly likely to cause interference to the OBSS, especially in a device-intensive scenario. The BSS is a cell composed of an AP and its associated STA, and the OBSS is an adjacent cell with overlapping coverage.

Based on this, the present invention proposes a channel measurement method suitable for an 802.11 system, which has a small impact on OBSS, enabling the AP to schedule multiple STAs based on channel measurement results, thereby implementing efficient UL MU transmission.

Example 1:

An embodiment of the present invention provides a channel measurement method, where an execution subject is an STA, as shown in the figure. As shown in Figure 1, the method comprises the steps of:

101. The STA receives a measurement notification message sent by the access point AP, where the measurement notification message carries identifier information of a channel that needs to be measured.

The measurement notification message may be a TF-S (Trigger Frame for Sounding). The measurement notification message is used to indicate to the STA which channels need to be measured. The identification information of the channel to be measured is usually a bandwidth indication, for example, the bandwidth is indicated by 2 bits, 00 represents 20 MHz, 01 represents 40 MHz, 01 represents 80 MHz, 11 represents 80+80/160 MHz, and may also be a bit table. For example, 1101 indicates that a total of 60 MHz channels corresponding to the first, second, and third 20 MHz are to be measured, that is, each bit corresponds to a bandwidth of 20 MHz, and 1/0 indicates that measurement is required/not required, respectively.

In addition, the measurement notification message carries an ID (Identifier) of the STA that needs to perform channel measurement, and the ID described herein may be an AID (Association Identifier) or a PAID (Partial Association Identifier). Specifically, the STAs may be represented in the form of a STA ID list, that is, the IDs of the scheduled STAs are listed one by one; or may be represented in the form of a Group ID. However, when the group ID is used to indicate the STA to be scheduled, the AP is required to establish a group in advance. Relatively speaking, the STA ID list is more flexible.

The measurement notification message further carries an LTF (Long Training Field) number indication field, which is used to indicate the number of LTFs that should be included in the sounding reference signal sent by the STA. The LTF may be a HE-LTF (High Efficiency WLAN-Long Training Field). Specifically, if the measurement notification message indicates that the number of STAs that need to perform channel measurement is N, the measurement notification message carries an HE-LTF number indication field, which is used to indicate the detection sent by the STA that needs to perform channel measurement. The number of HE-LTF fields contained in the reference signal. Or the measurement notification message carries N HE-LTF number indication fields, where the N HE-LTF number indication fields are in one-to-one correspondence with the N STAs that need to perform channel measurement, and are used to indicate the number of the HE-LTFs Indicates the number of HE-LTF fields included in the sounding reference signal frame sent by the STA corresponding to the field.

In a specific implementation, if the measurement notification message carries N HE-LTF number indication fields, each HE-LTF number indication field corresponds to one STA. If the measurement is passed The known message carries an HE-LTF number indication field, indicating that all STAs transmit the sounding reference signal including the same number of HE-LTFs. If the number of antennas of a certain STA is smaller than the number of HE-LTFs indicated by the AP, the HE-LTF repetition method may be used to complement the channel, and the AP may use these repeated HE-LTFs to measure the channel more accurately. For example, if the measurement notification message carries a HE-LTF number indication field of 4, STA1 has 2 antennas (A, B), and 4 HE-LTFs are simultaneously transmitted through antennas A and B, and each HE- The LTF corresponds to a set of weighting coefficients (ie, one column in the P matrix), and the weighting coefficients corresponding to the respective HE-LTFs are not the same; if the number of columns of the P matrix is insufficient, the columns in the P matrix can be recycled.

In addition, the measurement notification message further carries a transmission duration indication field, where the transmission time indication field is used to indicate an expected duration from the end of the measurement notification message transmission to the completion time of the entire channel measurement process. In a specific implementation, the transmission duration indication field may be a TXOP (Transmission Opportunity), indicating an expected duration from a TF-S transmission end time to a completion time of the entire channel measurement process.

102. The STA sends a sounding reference signal by using M idle subchannels, so that the AP measures the M free subchannels according to the received sounding reference signal, where the M free subchannels are The M free subchannels determined in the channel indicated by the identification information of the channel to be measured, wherein the M is an integer greater than or equal to 1.

The measurement sounding reference signal may be sounding, and the sounding is a short length frame carrying one or more HE-LTFs, and the receiving end performs channel measurement by receiving the HE-LTFs. The idle subchannel refers to physical carrier sensing (ie, CCA (Clear Channel Assessment)) and virtual carrier sensing (that is, NAV (Network Allocation Vector)). The result is idle. Subchannel. The result of the physical carrier sensing is that the STA does not detect that the power is greater than a certain threshold in the subchannel. The virtual carrier sensing result idle means that no other STA reserves the subchannel by means of RTS/CTS (Request To Send/Clear To Send).

Compared with the existing UL channel measurement mechanism in LTE, the channel measurement method provided by the present invention selects the idle subchannel to transmit sounding in the channel designated by the AP, thereby avoiding interference to the ongoing transmission in the OBSS.

For example, the AP instructs the STA to measure the 80 MHz channel in the measurement notification message, but one STA finds that only 40 MHz is available, and on the other two 20 MHz, there is either a neighboring cell device is transmitting (the CCA result is busy), or is preceded by other STAs. Reserved by frame interaction such as RTS/CTS (NAV value is greater than 0). Thus, the STA only sends Sounding at the available 40 MHz. And in subsequent data transmission scheduling, the AP should not schedule the STA on those subchannels that the STA does not send Sounding.

In addition, in a specific implementation, the STA determines, by using the following methods, M idle subchannels in at least one subchannel included in a channel indicated by the identifier information of the channel that needs to be measured:

First, the STA performs a clear channel estimation CCA for each subchannel supported by the AP and the STA, and determines the subchannel with the CCA result as idle as a available subchannel. Among the channels indicated by the identification information, the same M subchannels as the available subchannels are determined as the M free subchannels.

The so-called "sub-channel supported by the AP and the STA", for example, the AP supports 80 MHz, and a certain STA only supports 40 MHz, and "the sub-channel supported by the AP and the STA" should actually be the STA and the AP. The intersection of the supported channel bandwidths is also the 40 MHz bandwidth supported by the STA. At this time, the STA can only do CCA at 40MHz.

In addition, an intersection of the available subchannel and at least one subchannel included in the AP indication channel is determined as the M idle subchannels.

In a specific implementation, the STA determines that the channel is busy according to the CCA result before receiving the Trigger frame. That is to say, after receiving the TF-S, the STA will transfer to the pending state, and will not do the CCA until the Sounding is sent.

Second, the STA performs CCA on each subchannel in the channel indicated by the identifier information within a first preset duration after receiving the measurement notification message, and the CCA result is an idle M sub-segment The channel is determined as the M free subchannels.

In a specific implementation, the STA performs CCA in the interframe space before receiving the TF-S and before sending the Sounding. The interval between TF-S and Sounding is usually SIFS (10 μs in the 2.4 GHz band and 16 μs in the 5 GHz band). The STA needs to complete aRxRFDelay (ie, receive radio frequency delay), aRxPLCPDelay (ie, receive PLCP delay), aMACProcessingDelay (ie, MAC processing delay) during this time period, aRxTxTurnaroundTime (ie, transceiving), and STAs need at least 4μs for CCA. Therefore, the SIFS time may not be enough for the STA to complete the CCA, so the SIFS can be extended. For example, SIFS adds one time slot (9 μs or 20 μs in the 2.4 GHz band and 9 μs in the 5 GHz band) to PIFS to complete the STA for CCA.

In addition, in the first and second methods, after the STA determines the M idle subchannels, the CTS may also be sent by using the M free subchannels at the first moment, where the first moment is the A time interval after the time when the STA receives the measurement notification message is separated by a second preset duration. Generally, the first preset duration and the second preset duration may be the same.

The reason why the STA sends the CTS after determining the M idle subchannels is because there is still a possibility that the third party WiFi device sends a signal during the time between the completion of the CCA by the STA and the actual transmission of the Sounding by the STA. In order to ensure that the M idle subchannels determined by the STA must be idle when the STA sends Sounding, the STA sends the CTS immediately after the TF-S, so that other STAs set the NAV timer, and reserve the M idle children before sending the sounding. Channels, thus forming protection for subsequent times. The TXOP Duration is included in the TF-S, indicating the expected duration from the end of the TF-S transmission to the completion of the entire channel measurement process. The CTS includes a Duration field whose value is set to the TXOP Duration in the received TF-S minus the second preset duration and subtracts the difference in CTS transmission time. The specific operation is: after receiving the second preset duration of the TF-S interval, each scheduled STA simultaneously sends the CTS on the M idle subchannels determined by itself. In addition, in order to ensure that these CTSs can still be received correctly after they are superimposed, these CTSs should have exactly the same content and use the same MCS and the same scrambling code.

The CTS frame structure is as shown in FIG. 2, and includes a Frame control field, a Duration field, an RA field, and an FCS field. In order to ensure the same content, the RA field in the CTS sent by all STAs is set to the BSSID (usually the MAC address of the AP). The Duration field may be set according to a TXOP (Transmission Opportunity) Duration in the TF-S, and the TXOP Duration represents an expected duration from the end time of the TF-S transmission to the completion time of the entire channel measurement process. Duration in CTS is set to TXOP Duration- (second preset duration) - (CTS transmission time) - (between CTS and Sounding) IFS); if the TXOP Duration is not included in the TF-S, it can be set to N* (IFS+SoundingTime between Sounding). N is the number of currently scheduled STAs, which can be obtained according to TF-S. SoundingTime refers to the time domain length of a Sounding frame, which can be obtained according to the Sounding frame structure and the number of HE-LTFs in the TF-S.

Third, the STA determines, according to the HE-LTF number indication field carried in the measurement notification message, the STA queue, and the time when the STA receives the measurement notification message, the last STA that sends the sounding reference signal, and the STA The third time at which the last STA transmitting the sounding reference signal ends the sounding reference signal;

The STA queue is obtained by arranging the STAs that need to perform channel measurement according to the order in which the IDs of the STAs appear in the measurement notification message. For example, if the STAs in the measurement notification message that need to perform channel measurement appear in the order of A, B, C, and D, where A, B, C, and D are the identifiers of STA1, STA2, STA3, and STA4, respectively, The STA queues determined here are STA1, STA2, STA3, and STA4. In addition, the last STA that transmits the sounding reference signal is the previous STA in the STA queue adjacent to the STA.

The STA performs CCA at a time interval from the third time to the second time, and determines the M subchannels whose CCA result is idle as the M free subchannels. The second time is a time when the STA sends a sounding according to the HE-LTF number indication field carried by the STA and the STA queue determined by the STA. In this method, the first STA that sends Sounding is CCA at the interval between itself receiving the measurement notification message and transmitting Sounding itself.

As shown in FIG. 3(a), the frame structure of the sounding reference signal provided by the embodiment of the present invention, wherein the sounding is from the L-STF to the HE-STF before the bandwidth indicated by the bandwidth indication field is 20 MHz. The transmission is replicated on the subchannel, and the HE-STF and HE-LTF may be replicated and transmitted on each 20 MHz subchannel in the bandwidth indicated by the bandwidth indication field, or may be sent in full bandwidth on the entire bandwidth indicated by the bandwidth indication field. . The number of HE-LTFs included in the frame structure of the sounding reference signal transmitted by the STA is determined by the HE-LTF number indication field in the measurement notification message received by the STA.

The following describes in detail how the STA determines the second moment and the third moment in conjunction with FIG. 3( a ):

First, the STA determines, according to the STA queue, that it is the Xth STA that sends sounding. For example, if the STA queue is A, B, C, and D, and the ID of the STA is B, it can be determined that the STA sends the second STA that sends sounding.

Next, the STA calculates the time at which the last STA that sent the sounding sends the sounding according to the HE-LTF number indication field and the time when the measurement notification message is received. Exemplarily, the measurement notification message is received as time X, and the time Y of sounding is sent for the first STA after the interval is preset (usually SIFS). As shown in FIG. 3(a), the length of any sounding frame from L-STF to HE-STF is fixed, and the HE-LTF number indication field determines the length of the sounding frame, and the time Y+ preset duration + The length of the L-STF to HE-STF + the length of the N HE-LTF indicated by the HE-LTF number indication field = the end time at which the first STA sends the sounding. Similarly, the third moment when the last STA transmitting the sounding reference signal sends the sounding reference signal can be obtained.

Finally, the preset time duration of the third time interval is the time at which the STA sends the sounding reference signal, that is, the second time.

It should be noted that the third method for determining the M idle subchannels is applicable only to the scenario in which each STA sends a sounding reference signal in a Time Division Multiplexing (TDM) mode, which is not applicable to each STA. A scenario in which a sounding reference signal is transmitted by a CDM (Code Division Multiplexing) method.

Note that in the second and third methods of the embodiment, the M idle subchannels may be all subchannels in which the CCA result is idle in the channel indicated by the identification information, or may be the CCA result in the channel indicated by the identification information. Part of the subchannels of all subchannels that are idle. The former is suitable for the case where non-contiguous channel transmission is allowed. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), and the result of the STA doing CCA is three subchannels (subchannel 1, 3, 4) Idle, the STA sends Sounding on subchannels 1, 3 and 4. For the latter, a specific method is that the STA sends Sounding on a continuous channel including the primary channel. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), and the result of the STA doing CCA is that three subchannels (subchannels 1, 3, 4) are idle, assuming that the current BSS is the master. The primary channel is subchannel 3, then the STA Sounding can be sent only on subchannel 3 and subchannel 4. This has the advantage that the STA transmits the transmission channel always continuously, thereby simplifying the reception processing on the AP side. Optionally, the STA may be further configured to send Sounding only on consecutive 20/40/80/160 MHz channels including the primary channel. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), and the result of the STA doing CCA is that three subchannels (subchannels 1, 2, 3) are idle, assuming that the current BSS is the master. The primary channel is subchannel 1, and the STA transmits Sounding only on subchannel 1 and subchannel 2, and does not transmit on subchannel 3. This has the advantage of being able to reuse the current 20/40/80/160 MHz channel physical signal sequence design without having to redesign the physical signal sequence corresponding to bandwidths such as 60/100/120/140 MHz. The physical signal sequence refers to the frequency domain sequence of the Short Training Field (STF) and the Long Training Field (LTF) in the physical head, such as HE-STF and HE-LTF in Figure 3(a). Frequency domain sequence.

Specifically, for the first method, the M idle subchannels may be all subchannels of the same subchannel as the channel indicated by the identification information, or all the subchannels indicated by the identification information are the same as the available subchannels. Part of the subchannel in the channel. For example, the subchannels supported by the AP and the STA are subchannels 1-8, and the available subchannels include subchannels 1, 2, 3, 5, 7, and 8. The channels indicated by the identification information are subchannels 1-4, and the identification information is All of the subchannels of the indicated subchannels that are the same as the available subchannels are subchannels 1-3. Assuming that the primary channel is subchannel 1, each subchannel has a bandwidth of 20 MHz. Similar to the second method and the third method, a part of the subchannels of all the subchannels whose identification information indicates the same channel as the available subchannels may be a continuous channel including the primary channel, that is, the subchannels of the all subchannels. 1-3; Optionally, it may be a continuous 20/40/80/160 MHz channel including the primary channel in all the subchannels, that is, subchannel 1-2.

In addition, it should be noted that before the STA performs CCA, it is necessary to determine that the network allocation vector NAV of the subchannel performing CCA is 0. That is, the present invention requires each STA that needs to perform channel measurement to monitor and record the channel reservation condition of each of the M idle subchannels determined by itself. In the current 802.11 standard, the channel reservation record (that is, the NAV mechanism) is performed for the primary channel, that is, the STA maintains only one NAV meter. The value of the timer depends on the listening to the Primary channel. This obviously does not satisfy the needs of the present invention. Therefore, the present invention requires the STA to maintain a NAV timer for each of the M idle subchannels, and the STA can determine whether the subchannel virtual carrier sensing result is busy or idle according to the value of the corresponding NAV timer: if NAV If the timer is 0, the subchannel is idle; otherwise, the subchannel is busy. In addition, the STA performs virtual carrier sensing when it is about to transmit Sounding to determine whether the subchannel is idle, without prior determination.

In a preferred embodiment of the present invention, the measurement notification message may further carry at least one of: 1) a frame type indication field indicating that the current measurement notification message is TF-S; 2) a first power indication field, The first power indication field is used to indicate the power of the AP to send the measurement notification message; 3) a second power indication field, where the second power indication field is used to indicate that the STA sends the power of the sounding reference signal, or The desired power or desired power density when the sounding reference signal transmitted by the STA reaches the AP. 4) TXOP Duration: Used to indicate the total length of the Sounding phase, which is used for transmission protection from the end of the TF-S transmission. 5) Sounding reference signal type indication: used to indicate the specific type of NDP Sounding sent by the STA, including legacy NDP Sounding and HEW NDP Sounding.

It should be noted that the measurement notification message may carry one of the first power indication field and the second power indication field.

It should be noted that the purpose of the measurement notification message carrying the sounding reference signal type indication is to reduce the transmission overhead of the UL channel measurement process. Legacy NDP Sounding is shorter than HEW NDP Sounding and has lower transmission overhead. However, in scenarios with large delay spread (such as outdoor scenes), HEW NDP Sounding must be used to complete more accurate channel measurements. In addition to the different lengths, the main difference between Legacy NDP Sounding and HEW NDP Sounding is that the former LTF (LTF after the SIG domain) has a smaller symbol length than the latter HE-LTF, in other words, one of the same bandwidth. The HE-LTF symbol includes more subcarriers than the HEW NDP Sounding LTF (LTF after the SIG domain), which is suitable for measurements in high latency extended scenarios. For example, each symbol in 802.11ax contains 4 times the number of subcarriers in 802.11n, which requires more subcarriers to be measured, so the HE-LTF must also contain more subcarriers. When the AP judges the scheduled STA When the delay spread is small, the STA may be instructed by the STA to send Legacy NDP Sounding for channel measurement in the measurement notification message, thereby saving transmission overhead; if the delay spread is large, the STA is instructed to send HEW NDP Sounding. The structure of HEW NDP Sounding is shown in Figure 3(a); Legacy NDP Sounding can be HT NDP Sounding (802.11n) or VHT NDP Sounding (802.11ac), as shown in Figure 3(b).

In a preferred embodiment of the present invention, the sounding reference signal may further carry at least one of: 1) a signal type indication field for indicating that the current sounding reference signal is NDP Sounding; 2) a bandwidth indication field, the bandwidth The indication field is used to indicate the bandwidth of the idle subchannel used to transmit the sounding reference signal. 3) A third power indication field, the third power indication field is used to indicate the power of transmitting the sounding reference signal. 4) a resource request field, where the resource request field is used to indicate the amount of data that the STA that sends the sounding reference signal needs to transmit, that is, the data buffer/queue size (Buffer/Queue size), or the time that the STA requests the data to be transmitted. (TXOP Duration Requested).

The bandwidth indication field is usually a bandwidth indication, for example, the bandwidth is indicated by 2 bits, 00 represents 20 MHz, 01 represents 40 MHz, 01 represents 80 MHz, 11 represents 80+80/160 MHz, and may also be a bit table, for example, 1101 indicates that measurement is required. The first, second, and third 20 MHz correspond to a total of 60 MHz channels, that is, each bit corresponds to a 20 MHz bandwidth, and 1/0 indicates that a measurement is required/not required.

It should be noted that, if the measurement notification message carries the first power indication field or the second power indication field, the third reference power indicator field does not need to be carried in the sounding reference signal.

In another preferred embodiment of the present invention, after receiving the measurement notification message sent by the AP, the STA sends the sounding reference signal in the following two manners:

1) TDM: As shown in FIG. 4, each STA transmits a sounding reference signal (Sounding) according to an indication in the measurement notification message (TF-S).

Specifically, after the STA receives the TF-S, according to the STA queue, the STA queue is obtained by arranging the STAs that need to perform channel measurement according to the order in which the IDs of the STAs appear in the measurement notification message. Make sure you are the first STA to send Sounding. If the ID of the STA that needs to perform channel measurement in the measurement notification message is implemented by using the STA ID list, it is sequentially according to the STA ID list. The sequence is used to determine the transmission order. For example, the ID of a STA is ranked 5th in the STA ID list, so the STA is the 5th STA that sends Sounding. If the "scheduled STA ID" is implemented in the group ID mode, the order of each STA is specified when the group is established.

According to the frame structure design of the sounding reference signal (Sounding) shown in FIG. 3(a), it can be found that all the fields except the HE-LTF number in the Sounding are fixed, so the "LTF number indication field" in the TF-S is combined. "You can determine the length of each Sounding frame, and then you can figure out when you should send Sounding. According to the current standard discussion, the scheduling information of different STAs in the TF-S may be independent CRC and/or independently coded, and one STA only needs to correctly receive its own scheduling information. In this case, the STA may not be able to solve the scheduling information of all the STAs in front of it, and it is impossible to calculate when it is sending sounding.

If a method of indicating the number of HE-LTFs for each STA is employed, the STA may not be able to obtain the HE-LTF of the previous STA. However, if the STA scheduling information is independent of the CRC, if the TF-S includes only one LTF number indication field, the LTF number indication is placed in a common part before the scheduling information of each STA in the measurement notification message, and each STA does not need to be The STA sequence can be obtained by solving its specific scheduling message. Therefore, in this scenario, the scheme in which only one LTF number indication field is included in the TF-S is better. Of course, if different user scheduling information adopts a joint CRC, a scheme of assigning different HE-LTF numbers to different STAs is still feasible.

2) CDM: As shown in FIG. 5, each STA simultaneously transmits Sounding on the idle subchannel determined by itself in the channel indicated by the AP, but each STA needs to give Sounding a mutually orthogonal CDM code before transmitting. The sounding L-LTF starts) so that the AP can distinguish the Sounding of different STAs.

In this way, the time domain length of each Sounding is longer than that of a single Sounding in TDM, but due to the saving of the interframe space in TDM, the transmission duration may still be smaller than the TDM scheme in general. In the CDM scheme, since all Sounding is aligned in the time domain, the AP only needs to specify one HE-LTF in the TF-S.

It should be noted that the channel measurement mechanism provided by the embodiment of the present invention may also be combined with other mechanisms, including:

1) Combined with the DL channel measurement mechanism

As shown in FIG. 6, the channel measurement method of the present invention can be combined with the DL in 802.11ac. The channel measurement mechanism is combined. The existing DL channel measurement mechanism, that is, the NDPA (Null Data Packet Announcement) broadcasted by the AP, includes a STA list that needs feedback channel measurement results. The AP sends NDP Sounding to the STA (the STA is used to measure the channel sounding reference signal of the downlink channel), so that the STA measures the downlink channel. Subsequently, the AP requests each STA to feed back channel measurement results through a polling mechanism.

The channel measurement method provided by the present invention is combined with the DL channel measurement mechanism to enable uplink channel measurement while performing uplink channel measurement. The NDPA is required to include not only the DL channel measurement user set S1 that needs feedback channel measurement results, but also the UL channel measurement user set S2 that needs to transmit UL Sounding. S1 and S2 may be identical, or may be empty or partially intersected. This is equivalent to combining the NDPA frame and the UL channel measurement TF-S of the DL channel measurement into one frame NDPA & TF-S. If S1=S2, NDPA&TF-S only needs to include a list of users. Specifically, the AP transmits NDP Sounding (ie, the DL sounding reference signal in FIG. 6) for DL channel measurement. NDP Sounding can also be combined with NDPA & TF-S as a frame. Then, the STA sends UL Sounding (the sounding reference signal sent by the STA), and the STA may first feed back the DL channel measurement result to the AP, and then send the UL Sounding to the AP. Alternatively, the STA may also first send UL Sounding to the AP, and then feed back the DL channel measurement result to the AP. If S1=S2, or there is a partial intersection between S1 and S2, the UL Sounding and DL channel measurement reports of the same STA may be combined into one frame, that is, the MAC part is added in the UL Sounding frame sent by the STA for carrying the DL channel measurement. report.

2) Combined with the MU-RTS/CTS mechanism

Typically, the MU-RTS/CTS mechanism is used to protect subsequent DL transmissions. A problem with the current MU-RTS/CTS mechanism is that even if the AP can determine which STAs do not reply to the CTS according to the reception of the CTS (ie, the STA does not correctly receive the MU-RTS or is in a dormant state), the CTS and subsequent downlink data transmissions are sent. It is too late to re-adjust the resource allocation, which leads to the waste of some resources. As shown in FIG. 7, according to the method provided by the present invention, the AP can determine which STAs can correctly receive the AP data according to the reception of the UL Sounding, and thus can be transmitted during the entire MU-RTS/CTS (ie, the transmission protection in FIG. 7). Phase) Allocation, making more efficient use of resources.

The present invention provides a channel measurement method, in which a STA receives a measurement notification message sent by an AP, where the measurement notification message carries identification information of a channel that needs to be measured, and is included in a channel indicated by the identification information of the channel that needs to be measured. M idle subchannels are determined in the at least one subchannel; the STA transmits the sounding reference signal through the M idle subchannels, so that the AP measures the M free subchannels according to the received sounding reference signals. Compared with the prior art STA, the sounding reference signal is sent on the channel indicated by the AP, and the AP does not know which channels are occupied by the BSS around the STA, so the STA may send sounding on the occupied channel, and then the ongoing transmission in the OBSS. Cause interference. The present invention enables the STA to select its own idle subchannel to transmit sounding in the channel designated by the AP, thereby ensuring that the subchannel for performing channel measurement is idle, and to some extent, avoiding the influence of the UL channel measurement on the OBSS transmission.

Example 2:

An embodiment of the present invention provides a STA. As shown in FIG. 8, the STA includes: a receiving unit 201 and a sending unit 202.

The receiving unit 201 is configured to receive a measurement notification message sent by the access point AP, where the measurement notification message carries identifier information of a channel that needs to be measured.

The measurement notification message may be a TF-S (Trigger Frame for Sounding, a trigger frame for scheduling measurement notification messages). The measurement notification message is used to indicate to the STA which channels need to be measured.

In addition, the measurement notification message carries the ID of the STA that needs to perform channel measurement, and the ID described herein may be an AID or a PAID. Specifically, it may be expressed in the form of a STA ID list, that is, the IDs of the scheduled STAs are listed one by one; or may be represented in the form of a Group ID. However, when the ID of the STA is expressed in the form of a Group ID, the AP is required to establish a Group in advance. Relatively speaking, the STA ID list is more flexible.

The sending unit 202 is configured to send, by using the M idle subchannels, the sounding reference signal, so that the AP measures the M free subchannels according to the received sounding reference signal, where the M free subchannels are the STAs. M idle subchannels determined in the channel indicated by the identification information of the channel to be measured, the M being an integer greater than or equal to 1.

The measurement sounding reference signal may be sounding. The idle subchannel refers to a subchannel in which both physical carrier sensing (ie, CCA) and virtual carrier sensing (ie, NAV) result are idle. The result of the physical carrier sensing is that the STA does not detect that the power is greater than a certain threshold in the subchannel. The virtual carrier sensing result idle means that no other STA reserves the subchannel in advance by means of RTS/CTS or the like.

Compared with the existing UL channel measurement mechanism in LTE, the channel measurement method provided by the present invention selects the idle subchannel to transmit sounding in the channel designated by the AP, thereby avoiding interference to the ongoing transmission of the OBSS device.

For example, the AP instructs the STA to measure the 80 MHz channel in the measurement notification message, but one STA finds that only 40 MHz is available, and on the other two 20 MHz, there is either a neighboring cell device is transmitting (the CCA result is busy), or is preceded by other STAs. Reserved by frame interaction such as RTS/CTS (NAV value is greater than 0). Thus, the STA only sends Sounding at the available 40 MHz. And in subsequent data transmission scheduling, the AP should not schedule the STA on those subchannels that the STA does not send Sounding.

It should be noted that the measurement notification message also carries the identity ID of the STA that needs to perform channel measurement.

As shown in FIG. 9, the STA further includes a first clear channel estimation CCA unit 203.

The first CCA unit is configured to perform a clear channel estimation CCA for each subchannel supported by the AP and the STA, and determine the subchannel with the CCA result as idle as a available subchannel.

As shown in FIG. 10, the STA further includes a first determining unit 204.

The first determining unit is specifically configured to determine, in the at least one subchannel included in the AP indication channel, the same M subchannels as the available subchannels as the M idle subchannels.

In addition, the STA further includes a second determining unit, a second CCA unit.

The second CCA unit is configured to perform CCA on each of the subchannels indicated by the identifier information, respectively, within a first preset duration after the receiving unit receives the measurement notification message.

The second determining unit is configured to determine, to the M idle subchannels, the M subchannels whose CCA result is idle.

The transmitting 202 unit is further configured to: determine the M idle subchannels in the Then, the clearing and transmitting CTS is sent by using the M idle subchannels at the first time, where the first time is a time interval of a second preset duration after the time when the STA receives the measurement notification message.

It should be noted that the measurement notification message further carries an LTF number indication field, and the LTF may be an HE-LTF.

The STA further includes a third determining unit.

The third determining unit is configured to determine, according to the HE-LTF number indication field carried in the measurement notification message, the STA queue, and the time when the STA receives the measurement notification message, to determine that the STA sends the sounding reference signal Two times; the STA queue is obtained by arranging the STAs that need to perform channel measurement according to the order in which the IDs of the STAs appear in the measurement notification message.

The third determining unit is further configured to: according to the HE-LTF number indication field carried by the measurement notification message, the STA queue, the foregoing, before the sending unit sends the sounding reference signal on the M idle subchannels The STA receives the measurement notification message, determines the STA that sent the last sounding reference signal, and the third time that the last STA that sent the sounding reference signal sends the sounding reference signal. The STA that sent the sounding reference signal is the previous STA in the STA queue that is adjacent to the STA.

The STA also includes a second CCA unit.

The second CCA unit is configured to perform CCA at a time interval from the third time to the second time, and determine the M subchannels whose CCA result is idle as the M free subchannels.

Note that in the second and third determining units of the embodiment, the M free subchannels may be all subchannels in which the CCA result is idle in the channel indicated by the identification information, or may be the CCA result in the channel indicated by the identification information. Part of the subchannels of all subchannels that are idle. The former is suitable for the case where non-contiguous channel transmission is allowed. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), and the result of the STA doing CCA is three subchannels (subchannel 1, 3, 4) Idle, the STA sends Sounding on subchannels 1, 3 and 4. For the latter, a specific method is that the STA sends Sounding on a continuous channel including the primary channel. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), The result of the STA doing CCA is that three subchannels (subchannels 1, 3, 4) are idle, and assuming that the primary channel of the current BSS is subchannel 3, the STA can transmit Sounding only on subchannel 3 and subchannel 4. . This has the advantage that the STA transmits the transmission channel always continuously, thereby simplifying the reception processing on the AP side. Optionally, the STA may be further configured to send Sounding only on consecutive 20/40/80/160 MHz channels including the primary channel. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), and the result of the STA doing CCA is that three subchannels (subchannels 1, 2, 3) are idle, assuming that the current BSS is the master. The primary channel is subchannel 1, and the STA transmits Sounding only on subchannel 1 and subchannel 2, and does not transmit on subchannel 3. This has the advantage of being able to reuse the current 20/40/80/160 MHz channel physical signal sequence design without having to redesign the physical signal sequence corresponding to bandwidths such as 60/100/120/140 MHz. The physical signal sequence refers to the frequency domain sequence of the Short Training Field (STF) and the Long Training Field (LTF) in the physical head, such as HE-STF and HE-LTF in Figure 3(a). Frequency domain sequence.

Specifically, for the first determining unit, the M free subchannels may be all subchannels of the same subchannel as the channel indicated by the identification information, or all the same channels indicated by the identification information and the available subchannels. Part of the subchannel in the channel. For example, the subchannels supported by the AP and the STA are subchannels 1-8, and the available subchannels include subchannels 1, 2, 3, 5, 7, and 8. The channels indicated by the identification information are subchannels 1-4, and the identification information is All of the subchannels of the indicated subchannels that are the same as the available subchannels are subchannels 1-3. Assuming that the primary channel is subchannel 1, each subchannel has a bandwidth of 20 MHz. Similar to the second determining unit and the third determining unit, the partial subchannels of all the subchannels whose identification information indicates the same channel as the available subchannels may be consecutive channels including the primary channel in the whole subchannel, that is, the subchannels 1-3; Optionally, it may be a continuous 20/40/80/160 MHz channel including the primary channel in all the subchannels, that is, subchannel 1-2.

The STA also includes a network allocation vector NAV monitoring unit.

The NAV monitoring unit is configured to determine that the NAV of the subchannel performing the CCA is 0 before performing the CCA.

It should be noted that the measurement notification message indicates that channel measurement needs to be performed. The number of STAs is N, and the N is an integer greater than or equal to 1. The measurement notification message carries an HE-LTF number indication field, which is used to indicate the number of HE-LTF fields included in the sounding reference signal sent by the STA that needs to perform channel measurement;

Or the measurement notification message carries N HE-LTF number indication fields, where the N HE-LTF number indication fields are in one-to-one correspondence with the N STAs that need to perform channel measurement, and are used to indicate the number of the HE-LTFs Indicates the number of HE-LTF fields included in the sounding reference signal frame sent by the STA corresponding to the field.

If the measurement notification message carries an HE-LTF number indication field, the sounding reference signal sent by the STA includes X HE-LTFs, where X is the number indicated by the HE-LTF number indication field.

If the measurement notification message carries N HE-LTF number indication fields, the sounding reference signal sent by the STA includes Y HE-LTFs, where Y is the number indicated by the HE-LTF number indication field corresponding to the STA. .

In addition, the sounding reference signal further includes a bandwidth indication field; the bandwidth indication field is used to indicate a bandwidth of an idle subchannel used by the sounding reference signal.

The measurement notification message further includes a first power indication field, where the first power indication field is used to indicate that the AP sends the power of the measurement notification message. Or the measurement notification message further includes a second power indication field, where the second power indication field is used to indicate that the STA sends the power of the sounding reference signal, or the sounding reference signal sent by the STA reaches the AP. Expected power. Or the sounding reference signal further includes a third power indication field, where the third power indication field is used to indicate the power of transmitting the sounding reference signal. Or, the sounding reference signal further includes a resource request field, where the resource request field is used to indicate the amount of data that the STA that sends the sounding reference signal needs to transmit, that is, a data buffer/queue size (Buffer/Queue size), or STA The time requested for the transmission of data (TXOP Duration Requested).

It should be noted that the measurement notification message may further carry at least one of the following: 1) a frame type indication field indicating that the current measurement notification message is a TF-S; 2) a first power indication field, the first power indication The field is used to indicate the power of the AP to send the measurement notification message; 3) a second power indication field, where the second power indication field is used to indicate that the STA sends the power of the sounding reference signal, or the STA sends The expected power of the sounding reference signal when it reaches the AP. 4) TXOP Duration: The total length of time used to indicate the Sounding phase, the timing of which begins with the end of the TF-S transmission and is used for transmission protection. 5) Sounding reference signal type indication: used to indicate the specific type of NDP Sounding sent by the STA, including legacy NDP Sounding and HEW NDP Sounding.

The measurement notification message carries one of the first power indication field and the second power indication field.

It should be noted that the purpose of the measurement notification message carrying the sounding reference signal type indication is to reduce the transmission overhead of the UL channel measurement process. Legacy NDP Sounding is shorter than HEW NDP Sounding and has lower transmission overhead. However, in scenarios with large delay spread (such as outdoor scenes), HEW NDP Sounding must be used to complete more accurate channel measurements. The main difference between Legacy NDP Sounding and HEW NDP Sounding is that the former LTF (LTF after the SIG field) has a smaller symbol length than the latter HE-LTF, in other words, the same bandwidth, one The HE-LTF symbol includes more subcarriers than the HEW NDP Sounding LTF (LTF after the SIG domain), which is suitable for measurements in high latency extended scenarios. For example, each symbol in 802.11ax contains 4 times the number of subcarriers in 802.11n, which requires more subcarriers to be measured, so the HE-LTF must also contain more subcarriers. When the AP determines that the delay spread of the scheduled STA is small, the STA may instruct the STA to send Legacy NDP Sounding to perform channel measurement in the measurement notification message, thereby saving transmission overhead; if the delay spread is large, instructing the STA to send HEW NDP Sounding. The structure of HEW NDP Sounding is shown in Figure 3(a); Legacy NDP Sounding can be HT NDP Sounding (802.11n) or VHT NDP Sounding (802.11ac), as shown in Figure 3(b).

In addition, the sounding reference signal may further carry at least one of the following: 1) a signal type indication field for indicating that the current sounding reference signal is NDP Sounding; 2) a bandwidth indication field; and the bandwidth indication field is used to indicate the sending station The bandwidth of the idle subchannel used by the sounding reference signal. 3) A third power indication field, the third power indication field is used to indicate the power of transmitting the sounding reference signal. 4) a resource request field, where the resource request field is used to indicate the amount of data that the STA that sends the sounding reference signal needs to transmit, that is, a data buffer/queue size (Buffer/Queue size), or STA The time requested for the transmission of data (TXOP Duration Requested).

As shown in FIG. 3(a), the frame structure of the sounding reference signal provided by the embodiment of the present invention, wherein the Sounding from the L-STF to the HE-STF is on each 20 MHz subchannel in the bandwidth indicated by the bandwidth indication field. The transmission is replicated, and the HE-LTF can either be replicated on each 20 MHz subchannel in the bandwidth indicated by the Bandwidth Indicator field or on the entire bandwidth indicated by the Bandwidth Indicator field. The number of HE-LTFs included in the frame structure of the sounding reference signal transmitted by the STA is determined by the HE-LTF number indication field in the measurement notification message received by the STA.

It should be noted that, if the measurement notification message carries the first power indication field or the second power indication field, the third reference power indicator field does not need to be carried in the sounding reference signal.

In a specific implementation, after the STA receives the measurement notification message sent by the AP, the sending unit 202 sends the sounding reference signal in the following two manners:

1) TDM: As shown in FIG. 4, each STA transmits a sounding reference signal (Sounding) according to an indication in the measurement notification message (TF-S).

Specifically, after the STA receives the TF-S, according to the STA queue, the STA queue is obtained by arranging the STAs that need to perform channel measurement according to the order in which the IDs of the STAs appear in the measurement notification message. Make sure you are the first STA to send Sounding. If the ID of the STA that needs to perform channel measurement in the measurement notification message is implemented in the STA ID list, the sending order is determined according to the sequence in the STA ID list. For example, the ID of a STA is ranked in the STA ID list. Therefore, the STA is the fifth STA that sends Sounding. If the "scheduled STA ID" is implemented in the group ID mode, the order of each STA is specified when the group is established.

According to the frame structure design of the sounding reference signal (Sounding) shown in FIG. 3(a), it can be found that all the fields except the HE-LTF number in the Sounding are fixed, so the "LTF number indication field" in the TF-S is combined. "You can determine the length of each Sounding frame, and then you can figure out when you should send Sounding. According to the current standard discussion, the scheduling information of different STAs in the TF-S may be independent CRC and/or independently coded, and one STA only needs to correctly receive its own scheduling information. In this case, the STA may not be able to solve the scheduling information of all the STAs in front of it, and it is impossible to calculate when it is sending sounding. If each is used to indicate each STA The method of the number of HE-LTF, the STA may not be able to obtain the HE-LTF of the previous STA. However, if the STA scheduling information is independent of the CRC, if the TF-S includes only one LTF number indication field, the LTF number indication is placed in a common part before the scheduling information of each STA in the measurement notification message, and each STA does not need to be The STA sequence can be obtained by solving its specific scheduling message. Therefore, in this scenario, the scheme in which only one LTF number indication field is included in the TF-S is better. Of course, if different user scheduling information adopts a joint CRC, a scheme of assigning different HE-LTF numbers to different STAs is still feasible.

2) CDM: As shown in FIG. 5, each STA simultaneously transmits Sounding on the idle subchannel determined by itself in the channel indicated by the AP, but each STA needs to give Sounding a mutually orthogonal CDM code before transmitting. The sounding L-LTF starts) so that the AP can distinguish the Sounding of different STAs.

In this way, the time domain length of each Sounding is longer than that of a single Sounding in TDM, but due to the saving of the interframe space in TDM, the transmission duration may still be smaller than the TDM scheme in general. In the CDM scheme, since all Sounding is aligned in the time domain, the AP only needs to specify one HE-LTF in the TF-S.

It should be noted that the channel measurement mechanism provided by the embodiment of the present invention may also be combined with other mechanisms, including:

1) Combined with the DL channel measurement mechanism

As shown in FIG. 6, the channel measurement method of the present invention can be combined with the DL channel measurement mechanism in 802.11ac. The existing DL channel measurement mechanism, that is, the NDPA (Null Data Packet Announcement) broadcasted by the AP, includes a STA list that needs feedback channel measurement results. The AP sends NDP Sounding to the STA (the STA is used to measure the channel sounding reference signal of the downlink channel), so that the STA measures the downlink channel. Subsequently, the AP requests each STA to feed back channel measurement results through a polling mechanism.

The channel measurement method provided by the present invention is combined with the DL channel measurement mechanism to enable uplink channel measurement while performing uplink channel measurement. The NDPA is required to include not only the DL channel measurement user set S1 that needs feedback channel measurement results, but also the UL channel measurement user set S2 that needs to transmit UL Sounding. S1 and S2 may be identical, or may be empty or partially intersected. This is equivalent to combining the NDPA frame and the UL channel measurement TF-S of the DL channel measurement into one frame NDPA & TF-S. If S1=S2, NDPA&TF-S only needs to include a list of users. Specifically, the AP transmits NDP Sounding for DL channel measurement. NDP Sounding can also be combined with NDPA & TF-S as a frame. Then, the STA sends UL Sounding (so-called UL sounding, that is, the sounding reference signal according to the present invention), and the STA may first feed back the DL channel measurement result to the AP, and then send the UL Sounding to the AP. Alternatively, the STA may also first send UL Sounding to the AP, and then feed back the DL channel measurement result to the AP. If S1=S2, or there is a partial intersection between S1 and S2, the UL Sounding and DL channel measurement reports of the same STA may be combined into one frame, that is, the MAC part is added in the UL Sounding frame sent by the STA for carrying the DL channel measurement. report.

2) Combined with the MU-RTS/CTS mechanism

Typically, the MU-RTS/CTS mechanism is used to protect subsequent DL transmissions. A problem with the current MU-RTS/CTS mechanism is that even if the AP can determine which STAs do not reply to the CTS according to the reception of the CTS (ie, the STA does not correctly receive the MU-RTS or is in a dormant state), the CTS and subsequent downlink data transmissions are sent. It is too late to re-adjust the resource allocation, which leads to the waste of some resources. As shown in FIG. 7, according to the method provided by the present invention, the AP can determine which STAs can correctly receive the AP data according to the reception of the UL Sounding, and thus can be transmitted during the entire MU-RTS/CTS (ie, the transmission protection in FIG. 7). Phase) Resource redistribution to make more efficient use of resources.

The present invention provides a STA that receives a measurement notification message sent by an AP, where the measurement notification message carries identification information of a channel that needs to be measured, and at least one of the channels included in the channel indicated by the identification information of the channel that needs to be measured. The M idle subchannels are determined in the channel; the STA sends the sounding reference signal through the M idle subchannels, so that the AP measures the M free subchannels according to the received sounding reference signals. Compared with the prior art STA, the probe reference signal is sent on the channel indicated by the AP, and the AP does not know that the AP does not know which channels are occupied by the cells around the STA, so the STA may send sounding on the occupied channel, and thus the OBSS device is The transmission made causes interference. The present invention enables the STA to select the idle subchannel to transmit sounding in the channel designated by the AP, thereby avoiding that the subchannel for performing channel measurement is idle, and to some extent, avoiding the influence of the UL channel on the transmission of the OBSS.

Example 3:

An embodiment of the present invention provides a STA. As shown in FIG. 11, the STA includes: the STA may include a processor 301, a system bus 302, a communication interface 303, and a memory 304.

The processor 301 can be a central processing unit (English: central processing unit, abbreviation: CPU).

The memory 304 is configured to store the program code and transmit the program code to the processor 301. The processor 301 executes the following instructions according to the program code. The memory 304 may include a volatile memory (English: volatile memory), such as a random access memory (English: random-access memory, abbreviation: RAM); the memory 304 may also include a non-volatile memory (English: non-volatile memory) ), such as read-only memory (English: read-only memory, abbreviation: ROM), flash memory (English: flash memory), hard disk (English: hard disk drive, abbreviation: HDD) or solid state drive (English: solid-state Drive, abbreviation: SSD). Memory 304 may also include a combination of the above types of memory. The processor 301, the memory 304, and the communication interface 303 are connected by the system bus 302 and complete communication with each other.

Communication interface 303 can be implemented by an optical transceiver, an electrical transceiver, a wireless transceiver, or any combination thereof. For example, the optical transceiver can be a small form-factor pluggable transceiver (sFP) transceiver (English: transceiver), and the enhanced small form-factor pluggable (English: enhanced small form-factor pluggable, Abbreviation: SFP+) Transceiver or 10 Gigabit small form-factor pluggable (XFP) transceiver. The electrical transceiver can be an Ethernet (Ethernet) network interface controller (English: network interface controller, abbreviation: NIC). The wireless transceiver can be a wireless network interface controller (English: wireless network interface controller, abbreviation: WNIC). The STA may have multiple communication interfaces 303.

The processor 301 is configured to receive, by using the communication interface 303, a measurement notification message sent by the access point AP, where the measurement notification message carries an identification letter of a channel that needs to be measured. interest.

The measurement notification message may be a TF-S (Trigger Frame for Sounding, a trigger frame for scheduling measurement notification messages). The measurement notification message is used to indicate to the STA which channels need to be measured.

In addition, the measurement notification message carries the ID of the STA that needs to perform channel measurement, and the ID described herein may be an AID or a PAID. Specifically, it may be expressed in the form of a STA ID list, that is, the IDs of the scheduled STAs are listed one by one; or may be represented in the form of a Group ID. However, when the ID of the STA is expressed in the form of a Group ID, the AP is required to establish a Group in advance. Relatively speaking, the STA ID list is more flexible.

The processor 301 is further configured to send, by using the communication interface 303, the sounding reference signal through the M idle subchannels, so that the AP measures the M free subchannels according to the received sounding reference signal, where the M free children The channel is M free subchannels determined by the STA in the channel indicated by the identification information of the channel that needs to be measured, and the M is an integer greater than or equal to 1.

The measurement sounding reference signal may be sounding. The idle subchannel refers to a subchannel in which both physical carrier sensing (ie, CCA) and virtual carrier sensing (ie, NAV) result are idle. The result of the physical carrier sensing is that the STA does not detect that the power is greater than a certain threshold in the subchannel. The virtual carrier sensing result idle means that no other STA reserves the subchannel in advance by means of RTS/CTS or the like.

Compared with the existing UL channel measurement mechanism in LTE, the channel measurement method provided by the present invention selects the idle subchannel to transmit sounding in the channel designated by the AP, thereby avoiding interference to the ongoing transmission of the OBSS device.

For example, the AP instructs the STA to measure the 80 MHz channel in the measurement notification message, but one STA finds that only 40 MHz is available, and on the other two 20 MHz, there is either a neighboring cell device is transmitting (the CCA result is busy), or is preceded by other STAs. Reserved by frame interaction such as RTS/CTS (NAV value is greater than 0). Thus, the STA only sends Sounding at the available 40 MHz. And in subsequent data transmission scheduling, the AP should not schedule the STA on those subchannels that the STA does not send Sounding.

It should be noted that the measurement notification message also carries the identity ID of the STA that needs to perform channel measurement.

The processor 301 is configured to: support each sub-letter that is simultaneously supported by the AP and the STA The channel performs a net channel estimation CCA, and determines the subchannel whose CCA result is idle as a usable subchannel.

The processor 301 is specifically configured to determine, in the at least one subchannel included in the AP indication channel, the same M subchannels as the available subchannels as the M idle subchannels.

The processor 301 is configured to perform CCA on each of the channels indicated by the identifier information within a first preset duration after the communication interface receives the measurement notification message.

The processor 301 is configured to determine, by using the M subchannels whose CCA result is idle, the M idle subchannels.

The processor 301 is further configured to: after the determining the M free subchannels, sending, by using the M idle subchannels, a clear sending CTS at a first moment, where the first moment is that the STA receives the The time at which the second predetermined duration is separated after the time at which the notification message is measured.

It should be noted that the measurement notification message further carries a long training domain LTF number indication field, and the LTF may be an HE-LTF.

The processor 301 is configured to determine, according to the HE-LTF number indication field carried in the measurement notification message, the STA queue, and the time when the STA receives the measurement notification message, to determine a second time when the STA sends the sounding reference signal; The STA queue is obtained by arranging the STAs that need to perform channel measurement in the order in which the IDs of the STAs appear in the measurement notification message.

The processor 301 is further configured to: before the communication interface sends the sounding reference signal on the M idle subchannels, according to the HE-LTF number indication field carried by the measurement notification message, the STA queue, and the STA receiving The moment of the measurement notification message, determining the last STA that sent the sounding reference signal, and the last time that the STA that sent the sounding reference signal sent the sounding reference signal ends. The STA that sent the sounding reference signal is the previous STA in the STA queue that is adjacent to the STA.

The processor 301 is configured to perform CCA at a time interval from the third time to the second time, and determine, by the M subchannels whose CCA result is idle, as the M free subchannels. The processor 301 is configured to determine to perform before performing CCA. The NAV of the subchannel of the CCA is zero.

Note that, in the processor 301 unit of this embodiment, the M free subchannels may be all subchannels in which the CCA result is idle in the channel indicated by the identification information, or may be all the CCA results in the channel indicated by the identification information being idle. Part of the subchannel in the subchannel. The former is suitable for the case where non-contiguous channel transmission is allowed. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), and the result of the STA doing CCA is three subchannels (subchannel 1, 3, 4) Idle, the STA sends Sounding on subchannels 1, 3 and 4. For the latter, a specific method is that the STA sends Sounding on a continuous channel including the primary channel. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), and the result of the STA doing CCA is that three subchannels (subchannels 1, 3, 4) are idle, assuming that the current BSS is the master. The primary channel is subchannel 3, and the STA can transmit Sounding only on subchannel 3 and subchannel 4. This has the advantage that the STA transmits the transmission channel always continuously, thereby simplifying the reception processing on the AP side. Optionally, the STA may be further configured to send Sounding only on consecutive 20/40/80/160 MHz channels including the primary channel. For example, the channel indicated by the identification information includes four subchannels (subchannels 1, 2, 3, 4), and the result of the STA doing CCA is that three subchannels (subchannels 1, 2, 3) are idle, assuming that the current BSS is the master. The primary channel is subchannel 1, and the STA transmits Sounding only on subchannel 1 and subchannel 2, and does not transmit on subchannel 3. This has the advantage of being able to reuse the current 20/40/80/160 MHz channel physical signal sequence design without having to redesign the physical signal sequence corresponding to bandwidths such as 60/100/120/140 MHz. The physical signal sequence refers to the frequency domain sequence of the Short Training Field (STF) and the Long Training Field (LTF) in the physical head, such as HE-STF and HE-LTF in Figure 3(a). Frequency domain sequence.

In particular, in the processor 301 unit of this embodiment, the M free subchannels may be all subchannels of the same subchannel as the channel indicated by the identification information, or the channel indicated by the identification information and the available subchannel. Part of the subchannels of all the same subchannels. For example, the subchannels supported by the AP and the STA are subchannels 1-8, and the available subchannels include subchannels 1, 2, 3, 5, 7, and 8. The channels indicated by the identification information are subchannels 1-4, and the identification information is The indicated channel is in the same subchannel as the available subchannel All subchannels are subchannels 1-3. Assuming that the primary channel is subchannel 1, each subchannel has a bandwidth of 20 MHz. Similar to the second method and the third method, a part of the subchannels of all the subchannels whose identification information indicates the same channel as the available subchannels may be a continuous channel including the primary channel, that is, the subchannels of the all subchannels. 1-3; Optionally, it may be a continuous 20/40/80/160 MHz channel including the primary channel in all the subchannels, that is, subchannel 1-2.

It should be noted that the measurement notification message indicates that the number of STAs that need to perform channel measurement is N, and the N is an integer greater than or equal to 1. The measurement notification message carries an HE-LTF number indication field, which is used to indicate the number of HE-LTF fields included in the sounding reference signal sent by the STA that needs to perform channel measurement;

Or the measurement notification message carries N HE-LTF number indication fields, where the N HE-LTF number indication fields are in one-to-one correspondence with the N STAs that need to perform channel measurement, and are used to indicate the number of the HE-LTFs Indicates the number of HE-LTF fields included in the sounding reference signal frame sent by the STA corresponding to the field.

If the measurement notification message carries an HE-LTF number indication field, the sounding reference signal sent by the STA includes X HE-LTFs, where X is the number indicated by the HE-LTF number indication field.

If the measurement notification message carries N HE-LTF number indication fields, the sounding reference signal sent by the STA includes Y HE-LTFs, where Y is the number indicated by the HE-LTF number indication field corresponding to the STA. .

In addition, the sounding reference signal further includes a bandwidth indication field; the bandwidth indication field is used to indicate a bandwidth of an idle subchannel used by the sounding reference signal.

The measurement notification message further includes a first power indication field, where the first power indication field is used to indicate that the AP sends the power of the measurement notification message. Or the measurement notification message further includes a second power indication field, where the second power indication field is used to indicate that the STA sends the power of the sounding reference signal, or the sounding reference signal sent by the STA reaches the AP. Expected power. Or the sounding reference signal further includes a third power indication field, where the third power indication field is used to indicate the power of transmitting the sounding reference signal. Or, the sounding reference signal further includes a resource request field, where the resource request field is used to indicate the amount of data that the STA that sends the sounding reference signal needs to transmit, that is, a data buffer/queue size (Buffer/Queue size), or The time that the STA is requested to transmit data (TXOP Duration Requested).

It should be noted that the measurement notification message may further carry at least one of the following: 1) a frame type indication field indicating that the current measurement notification message is a TF-S; 2) a first power indication field, the first power indication The field is used to indicate the power of the AP to send the measurement notification message; 3) a second power indication field, where the second power indication field is used to indicate that the STA sends the power of the sounding reference signal, or the STA sends The expected power of the sounding reference signal when it reaches the AP. 4) TXOP Duration: Used to indicate the total length of the Sounding phase, which is used for transmission protection from the end of the TF-S transmission. 5) Sounding reference signal type indication: used to indicate the specific type of NDP Sounding sent by the STA, including legacy NDP Sounding and HEW NDP Sounding.

The measurement notification message carries one of the first power indication field and the second power indication field.

It should be noted that the purpose of the measurement notification message carrying the sounding reference signal type indication is to reduce the transmission overhead of the UL channel measurement process. Legacy NDP Sounding is shorter than HEW NDP Sounding and has lower transmission overhead. However, in scenarios with large delay spread (such as outdoor scenes), HEW NDP Sounding must be used to complete more accurate channel measurements. In addition to the different lengths, the main difference between Legacy NDP Sounding and HEW NDP Sounding is that the former LTF (LTF after the SIG domain) has a smaller symbol length than the latter HE-LTF, in other words, one of the same bandwidth. The HE-LTF symbol includes more subcarriers than the HEW NDPSounding LTF (LTF after the SIG domain), which is suitable for measurements in high latency extended scenarios. For example, each symbol in 802.11ax contains 4 times the number of subcarriers in 802.11n, which requires more subcarriers to be measured, so the HE-LTF must also contain more subcarriers. When the AP determines that the delay spread of the scheduled STA is small, the STA may instruct the STA to send Legacy NDP Sounding to perform channel measurement in the measurement notification message, thereby saving transmission overhead; if the delay spread is large, instructing the STA to send HEW NDP Sounding. The structure of HEW NDP Sounding is shown in Figure 3(a); Legacy NDP Sounding can be HT NDP Sounding (802.11n) or VHT NDP Sounding (802.11ac), as shown in Figure 3(b).

In addition, the sounding reference signal may further carry at least one of the following: 1) a signal type indication field for indicating that the current sounding reference signal is NDP Sounding; 2) a bandwidth indication field; and the bandwidth indication field is used to indicate the sending station The bandwidth of the idle subchannel used by the sounding reference signal. 3) A third power indication field, the third power indication field is used to indicate the power of transmitting the sounding reference signal. 4) a resource request field, where the resource request field is used to indicate the amount of data that the STA that sends the sounding reference signal needs to transmit, that is, the data buffer/queue size (Buffer/Queue size), or the time that the STA requests the data to be transmitted. (TXOP Duration Requested).

As shown in FIG. 3(a), a frame structure of a sounding reference signal provided by an embodiment of the present invention, wherein Sounding from the L-STF to the HE-STF is each 20 MHz in the bandwidth indicated by the bandwidth indication field. The transmission is replicated on the channel, and the HE-LTF may be replicated and transmitted on each 20 MHz subchannel in the bandwidth indicated by the bandwidth indication field, or may be transmitted on the entire bandwidth indicated by the bandwidth indication field. The number of HE-LTFs included in the frame structure of the sounding reference signal transmitted by the STA is determined by the HE-LTF number indication field in the measurement notification message received by the STA.

It should be noted that, if the measurement notification message carries the first power indication field or the second power indication field, the third reference power indicator field does not need to be carried in the sounding reference signal.

In a specific implementation, after receiving the measurement notification message sent by the AP, the processor 301 sends the sounding reference signal in the following two manners:

1) TDM: As shown in FIG. 4, each STA transmits a sounding reference signal (Sounding) according to an indication in the measurement notification message (TF-S).

Specifically, after receiving the TF-S, the STA determines, according to the STA queue, which is obtained by arranging the STAs that need to perform channel measurement according to the order in which the IDs of the STAs appear in the measurement notification message. It is the first STA to send Sounding. If the ID of the STA that needs to perform channel measurement in the measurement notification message is implemented in the STA ID list, the sending order is determined according to the sequence in the STA ID list. For example, the ID of a STA is ranked in the STA ID list. Therefore, the STA is the fifth STA that sends Sounding. If the "scheduled STA ID" is implemented in the group ID mode, the order of each STA is specified when the group is established.

According to the frame structure design of the sounding reference signal (Sounding) shown in Fig. 3(a), it can be found that all the fields except the HE-LTF number in the Sounding are fixed. This can be combined with the "LTF number indication field" in the TF-S to determine the frame length of each Sounding, and then to figure out when should I send Sounding. According to the current standard discussion, the scheduling information of different STAs in the TF-S may be independent CRC and/or independently coded, and one STA only needs to correctly receive its own scheduling information. In this case, the STA may not be able to solve the scheduling information of all the STAs in front of it, and it is impossible to calculate when it is sending sounding.

If a method of indicating the number of HE-LTFs for each STA is employed, the STA may not be able to obtain the HE-LTF of the previous STA. However, if the STA scheduling information is independent of the CRC, if the TF-S includes only one LTF number indication field, the LTF number indication is placed in a common part before the scheduling information of each STA in the measurement notification message, and each STA does not need to be The STA sequence can be obtained by solving its specific scheduling message. Therefore, in this scenario, the scheme in which only one LTF number indication field is included in the TF-S is better. Of course, if different user scheduling information adopts a joint CRC, a scheme of assigning different HE-LTF numbers to different STAs is still feasible.

2) CDM: As shown in FIG. 5, each STA simultaneously transmits Sounding on the idle subchannel determined by itself in the channel indicated by the AP, but each STA needs to give Sounding a mutually orthogonal CDM code before transmitting. The sounding L-LTF starts) so that the AP can distinguish the Sounding of different STAs.

In this way, the time domain length of each Sounding is longer than that of a single Sounding in TDM, but due to the saving of the interframe space in TDM, the transmission duration may still be smaller than the TDM scheme in general. In the CDM scheme, since all Sounding is aligned in the time domain, the AP only needs to specify one HE-LTF in the TF-S.

It should be noted that the channel measurement mechanism provided by the embodiment of the present invention may also be combined with other mechanisms, including:

1) Combined with the DL channel measurement mechanism

As shown in FIG. 6, the channel measurement method of the present invention can be combined with the DL channel measurement mechanism in 802.11ac. The existing DL channel measurement mechanism, that is, the NDPA (Null Data Packet Announcement) broadcasted by the AP, includes a STA list that needs feedback channel measurement results. The AP sends NDP Sounding to the STA (the STA is used to measure the channel sounding reference signal of the downlink channel), so that the STA measures the downlink channel. Subsequently, the AP requests each STA to feed back channel measurement results through a polling mechanism.

The channel measurement method provided by the present invention is combined with the DL channel measurement mechanism to enable uplink channel measurement while performing uplink channel measurement. The NDPA is required to include not only the DL channel measurement user set S1 that needs feedback channel measurement results, but also the UL channel measurement user set S2 that needs to transmit UL Sounding. S1 and S2 may be identical, or may be empty or partially intersected. This is equivalent to combining the NDPA frame and the UL channel measurement TF-S of the DL channel measurement into one frame NDPA & TF-S. If S1=S2, NDPA&TF-S only needs to include a list of users. Specifically, the AP transmits NDP Sounding for DL channel measurement. NDP Sounding can also be combined with NDPA & TF-S as a frame. Then, the STA sends UL Sounding (so-called UL sounding, that is, the sounding reference signal according to the present invention), and the STA may first feed back the DL channel measurement result to the AP, and then send the UL Sounding to the AP. Alternatively, the STA may also first send UL Sounding to the AP, and then feed back the DL channel measurement result to the AP. If S1=S2, or there is a partial intersection between S1 and S2, the UL Sounding and DL channel measurement reports of the same STA may be combined into one frame, that is, the MAC part is added in the UL Sounding frame sent by the STA for carrying the DL channel measurement. report.

2) Combined with the MU-RTS/CTS mechanism

Typically, the MU-RTS/CTS mechanism is used to protect subsequent DL transmissions. A problem with the current MU-RTS/CTS mechanism is that even if the AP can determine which STAs do not reply to the CTS according to the reception of the CTS (ie, the STA does not correctly receive the MU-RTS or is in a dormant state), the CTS and subsequent downlink data transmissions are sent. It is too late to re-adjust the resource allocation, which leads to the waste of some resources. As shown in FIG. 7, according to the method provided by the present invention, the AP can determine which STAs can correctly receive the AP data according to the reception of the UL Sounding, and thus can be transmitted during the entire MU-RTS/CTS (ie, the transmission protection in FIG. 7). Phase) Resource redistribution to make more efficient use of resources.

The present invention provides a STA that receives a measurement notification message sent by an AP, where the measurement notification message carries identification information of a channel that needs to be measured, and at least one of the channels included in the channel indicated by the identification information of the channel that needs to be measured. The M idle subchannels are determined in the channel; the STA sends the sounding reference signal through the M idle subchannels, so that the AP measures the M free subchannels according to the received sounding reference signals. Transmitting the probe parameter on the channel indicated by the AP compared to the prior art STA The AP does not know that the AP is not occupied by the cells around the STA. Therefore, the STA may send sounding on the occupied channel, thereby causing interference to the ongoing transmission of the OBSS device. The present invention enables the STA to select its own idle subchannel to transmit sounding in the channel designated by the AP, thereby avoiding that the subchannel for performing channel measurement is idle, and to some extent, avoiding the influence of the UL channel on the OBSS transmission.

Through the description of the above embodiments, those skilled in the art can clearly understand that for the convenience and brevity of the description, only the division of the above functional modules is illustrated. In practical applications, the above functions can be allocated according to needs. It is completed by different functional modules, that is, the internal structure of the device is divided into different functional modules to complete all or part of the functions described above. For the specific working process of the device described above, refer to the corresponding process in the foregoing method embodiment, and details are not described herein again.

The units described as separate components may or may not be physically separated, and the components displayed as units may be one physical unit or multiple physical units, that is, may be located in one place, or may be distributed to multiple different places. . Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of the embodiment. In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a standalone product, may be stored in a readable storage medium. Based on such understanding, the technical solution of the present invention may contribute to the prior art or all or part of the technical solution may be embodied in the form of a software product stored in a storage medium. A number of instructions are included to cause a device (which may be a microcontroller, chip, etc.) or a processor to perform all or part of the steps of the methods described in various embodiments of the present invention. The foregoing storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk, and the like. .

The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention It is not limited thereto, and any one skilled in the art can easily conceive changes or substitutions within the scope of the present invention. Therefore, the scope of the invention should be determined by the scope of the claims.

Claims (13)

1. A channel measurement method, comprising:

   The STA receives the measurement notification message sent by the access point AP, where the measurement notification message carries the identification information of the channel that needs to be measured;

   The STA sends a sounding reference signal through M idle subchannels, so that the AP measures the M free subchannels according to the received sounding reference signal, where the M free subchannels are The M free subchannels determined in the channel indicated by the identification information of the channel to be measured, the M being an integer greater than or equal to 1.
2. The method according to claim 1, wherein the measurement notification message further carries an ID of a STA that needs to perform channel measurement; and the STA that needs to perform channel measurement includes at least one STA.
3. The method according to claim 1 or 2, wherein before the STA receives the measurement notification message sent by the access point AP, the method further includes:

   The STA performs a clear channel estimation CCA for each subchannel supported by the AP and the STA, and determines the subchannel with the CCA result as idle as a available subchannel;

   And determining, by the STA, the M idle subchannels in the at least one subchannel included in the channel indicated by the identifier information of the channel that needs to be measured, specifically:

   Among the channels indicated by the identification information, the same M subchannels as the available subchannels are determined as the M free subchannels.
4. The method according to claim 1 or 2, wherein before the STA sends the sounding reference signal through the M free subchannels, the method further includes:

   The STA performs CCA on each of the subchannels indicated by the identifier information within a first preset duration after receiving the measurement notification message, and determines the M subchannels in which the CCA result is idle as The M free subchannels.
5. The method according to claim 1 or 2, wherein the measurement notification message further carries a long training domain LTF number indication field, the method further comprising:

   Determining, by the STA, the second time when the STA sends the sounding reference signal according to the LTF number indication field, the STA queue, and the time when the STA receives the measurement notification message, where the STA queue is The STAs that need to perform channel measurement are obtained in the order in which the IDs of the STAs appear in the measurement notification message.
6. The method according to claim 5, wherein the method further comprises: before the STA sends the sounding reference signal on the M idle subchannels, the method further comprises:

   The STA determines, according to the LTF number indication field carried in the measurement notification message, the STA queue, and the time when the STA receives the measurement notification message, the last STA that sends the sounding reference signal, and the previous one. The STA that detects the reference signal sends a third moment when the sounding reference signal ends; the last STA that sends the sounding reference signal is the previous STA in the STA queue adjacent to the STA;

   The STA performs CCA at a time interval from the third time to the second time, and determines the M subchannels whose CCA result is idle as the M free subchannels.
7. The method according to claim 3 or claim 4 or claim 6, wherein the network allocation vector NAV of the subchannel performing the CCA is zero.
8. The method according to any one of claims 1 to 7, wherein the measurement notification message indicates that the number of STAs that need to perform channel measurement is N, and the N is an integer greater than or equal to 1.

   The measurement notification message carries an LTF number indication field, which is used to indicate the number of LTF fields included in the sounding reference signal sent by the STA that needs to perform channel measurement;

   Or the measurement notification message carries N LTF number indication fields, where the N LTF number indication fields are respectively used to indicate the LTF field included in the sounding reference signal frame sent by the STA corresponding to the LTF number indication field. number.
9. The method according to claim 8, wherein if the measurement notification message carries an LTF number indication field, the probe reference signal sent by the STA The number includes X LTFs, and the X is the number indicated by the LTF number indication field.
10. The method according to claim 8, wherein if the measurement notification message carries N LTF number indication fields, the sounding reference signal sent by the STA includes Y LTFs, and the Y is corresponding to the STA. The number of LTFs indicates the number of fields indicated.
11. The method according to any one of claims 1 to 10, wherein the method further comprises:

    The sounding reference signal further includes a resource request field, where the resource request field is used to indicate an amount of data that the STA that sends the sounding reference signal needs to transmit, or a time that the STA requests for transmitting data.
12. The method according to any one of claims 1 to 11, wherein the measurement notification message further comprises a sounding reference signal type indication, the sounding reference signal type indication indicating a type of the sounding reference signal, The types include the old NDP Sounding and HEW NDP Sounding.
13. A station STA, characterized in that it comprises:

    a receiving unit, configured to receive a measurement notification message sent by the access point AP, where the measurement notification message carries identifier information of a channel that needs to be measured;

    a sending unit, configured to send, by using the M idle subchannels, the sounding reference signal, so that the AP measures the M free subchannels according to the received sounding reference signal, where the M free subchannels are The M free subchannels determined in the channel indicated by the identification information of the channel to be measured, wherein the M is an integer greater than or equal to 1.

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