CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/CN2020/128210, filed on Nov. 11, 2020, the disclosure of which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

This application relates to the field of wireless communication technologies, and in particular, to a Wi-Fi communication method and a device.

BACKGROUND

With popularization of wireless local area network (wireless local area network, WLAN) technologies and intelligent terminals, more people start getting used to working by using smartphones and tablet computers.

Wi-Fi, also referred to as a “wireless hotspot” or a “wireless network”, is a WLAN technology based on a next-generation institute of electrical and electronics engineers (institute of electrical and electronics engineers, IEEE) 802.11 standard. Wi-Fi has become the first choice for more users to access networks and tends to gradually replace wired access. To adapt to new service applications and reduce a gap with a wired network bandwidth, in six generations of Wi-Fi systems (including 802.11, 802.11b, 802.11a/g, 802.11n, 802.11ac, and 802.11ax) that have been developed and popularized, each generation of IEEE 802.11 standard proposes a plurality of communication technologies, such as an orthogonal frequency division multiplexing (orthogonal frequency division multiplexing, OFDM) technology, a multiple-input multiple-output (multiple-input multiple-output, MIMO) technology, and a transmit beamforming (transmit beamforming, TxBF) channel detection mechanism, to improve a rate and spectrum utilization of the standard.

However, because performance of a wireless communication system is greatly affected by a wireless channel, such as shadow fading and frequency selective fading, a propagation path between a transmitter and a receiver is very complex. Unlike a wired channel, the wireless channel is neither fixed nor predictable, but has great randomness. This poses a great challenge to design of a receiver. To accurately restore a transmitted signal of a transmitter end at a receiver end, people use various measures to resist impact of multipath effect on the transmitted signal.

At present, during coherent detection of an OFDM system, channel estimation needs to be performed, and whether detailed channel information can be obtained to correctly demodulate a transmitted signal at a receiver is an important indicator for measuring performance of a wireless communication system. With development and popularization of wireless communication systems, a supported modulation scheme is increasingly high, and correspondingly, a signal-to-noise ratio (signal to noise ratio, SNR) required for demodulation is also increasingly high. However, how to perform channel estimation noise reduction is still one of difficulties that need to be urgently resolved.

SUMMARY

This application provides a Wi-Fi communication method and a device, to help improve accuracy of channel estimation in a communication system, thereby improving a demodulation capability of a communication device serving as a receive end.

According to a first aspect, an embodiment of this application provides a Wi-Fi communication method. The method may be applied to a first communication device, and the first communication device may be a transmit end or a receive end during information exchange. When the first communication device serves as a transmit end, in the method, the first communication device may generate a first physical frame, and send the first physical frame to a second communication device. The first physical frame includes signaling information and a plurality of training sequences used for channel estimation, the signaling information indicates a quantity of space-time streams and a quantity of the plurality of training sequences, and the quantity of the plurality of training sequences is greater than the quantity of space-time streams.

According to this solution, in a scenario in which channel estimation or the like needs to be performed, the quantity of training sequences that are included in the first physical frame generated by the first communication device and that are used for channel estimation may be greater than the quantity of space-time streams, and the signaling information may be used to indicate the quantity of space-time streams and the quantity of the plurality of training sequences. Therefore, the second communication device receiving the first physical frame can know the quantity of space-time streams and the quantity of training sequences, and obtain more training sequences, so that accuracy of a related algorithm can be improved when processing such as channel estimation or frequency offset/phase tracking is performed based on the plurality of obtained training sequences, thereby helping improve a demodulation capability of the second communication device, and ensure a data demodulation effect.

In a possible implementation, the quantity of the plurality of training sequences is an integer multiple of the quantity of space-time streams.

According to this solution, to improve channel estimation noise reduction, the quantity of training sequences may be designed as an integer multiple of the quantity of space-time streams. Therefore, the quantity of training sequences is increased, so that the second communication device can obtain more training sequences, to improve accuracy of a related algorithm, thereby helping improve a demodulation capability of a receive end communication device, and ensure a data demodulation effect.

In a possible implementation, the plurality of training sequences are obtained by precoding, based on a precoding matrix, time domain symbols corresponding to the space-time streams, where the precoding matrix is an M×N matrix, M is the quantity of space-time streams, N is the quantity of the plurality of training sequences, and M and N are positive integers.

According to this solution, because a quantity of rows of the used precoding matrix corresponds to the quantity of space-time streams, and a quantity of columns of the precoding matrix corresponds to the quantity of the plurality of training sequences, after the time domain symbols of the space-time streams are precoded based on the precoding matrix, the plurality of training sequences corresponding to the time domain symbols of the space-time streams can be correspondingly obtained. Therefore, the quantity of training sequences in the to-be-generated first frame is increased, to implement channel estimation noise reduction.

In a possible implementation, row vectors in the precoding matrix are orthogonal; and/or elements in an (M+1)^thcolumn to an Nth column are the same as elements in the first column to a j^thcolumn in the precoding matrix, and the row vectors in the precoding matrix are orthogonal, where j is equal to N-M.

According to this solution, when the quantity of training sequences is increased and the row vectors in the precoding matrix are orthogonal, the second communication device receiving the first frame can obtain more training sequences, to improve accuracy of a channel estimation algorithm, thereby improving demodulation performance of the device, and ensuring a data demodulation effect.

In this embodiment of this application, to obtain the precoding matrix, for example, a reference matrix may be preset. The precoding matrix may be a matrix including elements in first M rows and first N columns in the preset reference matrix; or the precoding matrix may be obtained by reconstructing elements in the first M rows and first j columns in the reference matrix, and j is equal to N-M, where the reference matrix is obtained by concatenating at least two specified matrices P, and the matrix P is a predefined matrix used to precode the time domain symbols corresponding to the space-time streams.

In this embodiment of this application, the matrix P may be configured or obtained based on an application scenario, a service requirement, an algorithm, or the like. For example, the matrix P may be self-defined, or may be a 4-row and 4-column matrix specified in a Wi-Fi communication protocol. Elements in the matrix P may be shown as follows:

P

4
×
4

=

[

1

-
1

1

1

1

1

-
1

1

1

1

1

-
1

-
1

1

1

1

]

.

In a possible implementation, before the first physical frame is generated, the method further includes: determining the precoding matrix based on the quantity of space-time streams, the quantity of the plurality of training sequences, and preset frame format configuration information.

According to this solution, frame format configuration information may be preconfigured based on an application scenario, a service requirement, or the like. When the first communication device needs to generate the first physical frame, the first communication device may determine the to-be-used precoding matrix based on the frame format configuration information, to obtain more training sequences used for channel estimation, and generate the first physical frame.

In a possible implementation, when the first physical frame is sent to the second communication device, transmit power of at least one of the plurality of training sequences is greater than transmit power of an original training sequence of the training sequence.

According to this solution, power of some of the training sequences is increased to improve accuracy of an algorithm, such as channel estimation or frequency offset/phase tracking, performed by a receive end communication device, thereby helping improve a demodulation capability of the receive device.

In a possible implementation, a transmission resource that carries at least one of the plurality of training sequences further carries data that needs to be transmitted.

According to this solution, data (for example, data with a relatively low modulation and coding rate) that needs to be transmitted is carried in some of transmission resources that carry increased training sequences, to reduce impact on some content located behind the training sequences in the frame, and reduce, as much as possible, cases in which transmitted data is reduced due to an increase in training sequences.

In a possible implementation, the first physical frame is a frame generated when a transmit beamforming TxBF technology is used and a used modulation scheme is higher than or equal to 4K quadrature amplitude modulation.

In this manner, in a scenario in which the TxBF technology and a higher order modulation scheme such as 4K QAM are used, a demodulation capability of a communication device can be improved, and a data demodulation effect can be ensured.

In a possible implementation, the signaling information is located in a reserved field in the first physical frame, and the plurality of training sequences are located in a training sequence field in the first physical frame.

According to a second aspect, an embodiment of this application further provides a Wi-Fi communication method. The method may be applied to a second communication device, and the second communication device may be a transmit end and a receive end during information exchange. When the second communication device serves as a receive end, in the method, the second communication device may receive a first physical frame from a first communication device, where the first physical frame includes signaling information and a plurality of training sequences used for channel estimation, the signaling information indicates a quantity of space-time streams and a quantity of the plurality of training sequences, and the quantity of the plurality of training sequences is greater than the quantity of space-time streams; and perform channel estimation or frequency offset/phase tracking based on the signaling information and the plurality of training sequences that are included in the first physical frame.

According to this solution, the second communication device may further serve as a receive end to receive the first physical frame from the first communication device, and improve accuracy of an algorithm such as channel estimation or frequency offset/phase tracking by using information included in the first physical frame, thereby helping improve a demodulation capability of the second communication device, and ensure a data demodulation effect.

In a possible implementation, the performing channel estimation or frequency offset/phase tracking based on the signaling information and the plurality of training sequences that are included in the first physical frame includes: determining a precoding matrix based on preset frame format configuration information, and the quantity of space-time streams and the quantity of the plurality of training sequences that are included in the signaling information, where the precoding matrix is an M×N matrix, M is the quantity of space-time streams, N is the quantity of the plurality of training sequences, and M and N are positive integers; and after processing the plurality of training sequences based on the precoding matrix, performing channel estimation or frequency offset/phase tracking by using a plurality of training sequences obtained after processing.

In a possible implementation, the quantity of the plurality of training sequences is an integer multiple of the quantity of space-time streams.

In a possible implementation, row vectors in the precoding matrix are orthogonal; and/or elements in an (M+1)^thcolumn to an N^thcolumn are the same as elements in the first column to a j^thcolumn in the precoding matrix, and the row vectors in the precoding matrix are orthogonal, where j is equal to N-M.

In a possible implementation, the precoding matrix is a matrix including elements in first M rows and first N columns in a preset reference matrix; or the precoding matrix is obtained by reconstructing elements in the first M rows and first j columns in the reference matrix, and j is equal to N-M, where the reference matrix is obtained by concatenating at least two specified matrices P, and the matrix P is a predefined matrix used to precode time domain symbols corresponding to the space-time streams.

In a possible implementation, the matrix P is a 4-row and 4-column matrix specified in a Wi-Fi communication protocol, and elements in the matrix P are shown as follows:

P

4
×
4

=

[

1

-
1

1

1

1

1

-
1

1

1

1

1

-
1

-
1

1

1

1

]

.

In a possible implementation, a transmission resource that carries at least one of the plurality of training sequences further carries data that needs to be transmitted.

In a possible implementation, the first physical frame is a frame generated when a transmit beamforming TxBF technology is used and a used modulation scheme is higher than or equal to 4K quadrature amplitude modulation QAM.

In a possible implementation, the signaling information is located in a reserved field in the first physical frame, and the plurality of training sequences are located in a training sequence field in the first physical frame.

According to a third aspect, an embodiment of this application further provides a Wi-Fi communication apparatus, including: a processing unit, configured to generate a first physical frame, where the first physical frame includes signaling information and a plurality of training sequences used for channel estimation, the signaling information indicates a quantity of space-time streams and a quantity of the plurality of training sequences, and the quantity of the plurality of training sequences is greater than the quantity of space-time streams; and a transceiver unit, configured to send the first physical frame to a second communication device.

In a possible implementation, the quantity of the plurality of training sequences is an integer multiple of the quantity of space-time streams.

In a possible implementation, the plurality of training sequences are obtained by precoding, based on a precoding matrix, time domain symbols corresponding to the space-time streams, where the precoding matrix is an M×N matrix, M is the quantity of space-time streams, N is the quantity of the plurality of training sequences, and M and N are positive integers.

In a possible implementation, row vectors in the precoding matrix are orthogonal; and/or elements in an (M+1)^thcolumn to an N^thcolumn are the same as elements in the first column to j^thcolumn in the precoding matrix, and the row vectors in the precoding matrix are orthogonal, where j is equal to N-M.

In a possible implementation, the precoding matrix is a matrix including elements in first M rows and first N columns in a preset reference matrix; or the precoding matrix is obtained by reconstructing elements in the first M rows and first j columns in the reference matrix, and j is equal to N-M, where the reference matrix is obtained by concatenating at least two specified matrices P, and the matrix P is a predefined matrix used to precode the time domain symbols corresponding to the space-time streams.

In a possible implementation, the matrix P is a 4-row and 4-column matrix specified in a Wi-Fi communication protocol, and elements in the matrix P are shown as follows:

P

4
×
4

=

[

1

-
1

1

1

1

1

-
1

1

1

1

1

-
1

-
1

1

1

1

]

.

In a possible implementation, before generating the first physical frame, the processing unit is further configured to determine the precoding matrix based on the quantity of space-time streams, the quantity of the plurality of training sequences, and preset frame format configuration information.

In a possible implementation, when the transceiver unit sends the first physical frame to the second communication device, transmit power of at least one of the plurality of training sequences is greater than transmit power of an original training sequence of the training sequence.

In a possible implementation, a transmission resource that carries at least one of the plurality of training sequences further carries data that needs to be transmitted.

In a possible implementation, the first physical frame is a frame generated when a transmit beamforming TxBF technology is used and a used modulation scheme is higher than or equal to 4K quadrature amplitude modulation QAM.

In a possible implementation, the signaling information is located in a reserved field in the first physical frame, and the plurality of training sequences are located in a training sequence field in the first physical frame.

According to a fourth aspect, an embodiment of this application further provides a Wi-Fi communication apparatus, including: a transceiver unit, configured to receive a first physical frame from a first communication device, where the first physical frame includes signaling information and a plurality of training sequences used for channel estimation, the signaling information indicates a quantity of space-time streams and a quantity of the plurality of training sequences, and the quantity of the plurality of training sequences is greater than the quantity of space-time streams; and a processing unit, configured to perform channel estimation or frequency offset/phase tracking based on the signaling information and the plurality of training sequences that are included in the first physical frame.

In a possible implementation, the processing unit is configured to: determine a precoding matrix based on preset frame format configuration information, and the quantity of space-time streams and the quantity of the plurality of training sequences that are included in the signaling information, where the precoding matrix is an M×N matrix, M is the quantity of space-time streams, N is the quantity of the plurality of training sequences, and M and N are positive integers; and after processing the plurality of training sequences based on the precoding matrix, perform channel estimation or frequency offset/phase tracking by using a plurality of training sequences obtained after processing.