CN106533522B

CN106533522B - Method and device for transmitting channel state information

Info

Publication number: CN106533522B
Application number: CN201510574968.XA
Authority: CN
Inventors: 于健; 林梅露; 杨讯; 郭宇宸
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2015-09-10
Filing date: 2015-09-10
Publication date: 2020-10-09
Anticipated expiration: 2035-09-10
Also published as: CN106533522A; WO2017041590A1

Abstract

The invention discloses a method and a device for transmitting channel state information, wherein the method comprises the following steps: by applying the method and the device, resource waste caused when part of sites do not support immediate feedback can be avoided, and further the transmission efficiency of channel state information can be improved.

Description

Method and device for transmitting channel state information

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a method and an apparatus for transmitting channel state information.

Background

Currently, a multi-user transmission (MU-MIMO) technology is known, in which MU-MIMO implements multi-user transmission through Multiple parallel channels by using spatial dimensions. However, this method requires that the transmitting end or the receiving end have all or part of the channel state information, otherwise, the receiving end cannot be enabled to correctly demodulate the multiple effective signals, resulting in transmission failure.

With the development of Wireless Local Area Network (WLAN) technology, it is desirable to apply MU-MIMO technology to a WLAN network, and in order to simultaneously schedule multiple users for feedback of channel state information, when a Station (STA) has limited capability, an Access Point (AP) may send an empty Data Packet announcement (NDPA), an empty Data Packet (NDP), and a beamforming Report Poll (BF Report Poll) frame, so that the STA performs channel estimation according to information carried by the NDPA and an efficient long training sequence (HE-LTF) carried by the NDP, and feeds back channel state information to the AP within a certain time duration range.

However, more STAs are introduced in the 802.11ax standard, and some STAs cannot immediately feed back, for example, the STA has limited capability and does not support immediate feedback or the AP has limited allocated resources.

Disclosure of Invention

In view of this, embodiments of the present invention provide a method and an apparatus for transmitting channel state information, which can improve transmission efficiency of the channel state information.

In a first aspect, an embodiment of the present invention provides a method for transmitting channel state information, including:

generating a Null Data Packet (NDP), wherein the null data packet comprises a high-efficiency long training sequence (HE-LTF) and a filling field, and the filling field is used for allowing a target station to have extra time to receive channel state information;

and transmitting the null data packet.

With reference to the first aspect, in a first possible implementation manner of the first aspect, the padding field includes a packet extension field or an additional HE-LTF.

With reference to the first possible implementation manner of the first aspect, in a second possible implementation manner of the first aspect, the length of the packet extension field or the number of additional HE-LTF symbols is determined by at least one of the following conditions: bandwidth, mode of HE-LTF, estimated number of spatial streams.

With reference to the first possible implementation manner of the first aspect, in a third possible implementation manner of the first aspect, the null data packet includes an indication field, the indication field is located in a high efficiency signaling field HE-SIG of the null data packet, and the indication field is used to define packet extension field information or additional HE-LTF information.

With reference to the third possible implementation manner of the first aspect, in a fourth possible implementation manner of the first aspect, the packet extension field information includes: the length of the packet extension field, or whether the packet extension field is greater than 16 us.

With reference to the third possible implementation manner of the first aspect, in a fifth possible implementation manner of the first aspect, the additional HE-LTF information includes: the number of additional HE-LTF symbols, or whether additional HE-LTFs are present.

With reference to the fifth possible implementation manner of the first aspect, in a sixth possible implementation manner of the first aspect, the P matrix of the HE-LTF in the null data packet is selected according to a sum of an additional HE-LTF and an own HE-LTF.

With reference to the sixth possible implementation manner of the first aspect, in a seventh possible implementation manner of the first aspect, the extra HE-LTF in the null data packet is the same as the self-contained HE-LTF part.

With reference to the sixth possible implementation manner of the first aspect, in an eighth possible implementation manner of the first aspect, the additional HE-LTFs in the null data packet are all the same as their own HE-LTFs.

With reference to the third possible implementation manner of the first aspect, in a ninth possible implementation manner of the first aspect, the method for indicating the packet extension field information and the additional HE-LTF information at least includes any one of: extra bits in the HE-SIG, Modulation Coding Set (MCS) in the HE-SIG, and packet expansion PE domain in the HE-SIG.

In a second aspect, an embodiment of the present invention provides an apparatus for transmitting channel state information, including:

the base band circuit generates a null data packet NDP, wherein the null data packet comprises a high-efficiency long training sequence HE-LTF and a filling field, and the filling field is used for allowing a target station to have extra time to receive channel state information;

radio frequency circuitry to transmit the null data packet.

With reference to the second aspect, in a first possible implementation manner of the second aspect, the padding field includes a packet extension field or an additional HE-LTF.

With reference to the first possible implementation manner of the second aspect, in a second possible implementation manner of the second aspect, the length of the packet extension field or the number of additional HE-LTF symbols is determined by at least one of the following conditions: bandwidth, mode of HE-LTF, estimated number of spatial streams.

With reference to the first possible implementation manner of the second aspect, in a third possible implementation manner of the second aspect, the null data packet includes an indication field, the indication field is located in a high efficiency signaling field HE-SIG of the null data packet, and the indication field is used to define packet extension field information or additional HE-LTF information.

With reference to the third possible implementation manner of the second aspect, in a fourth possible implementation manner of the second aspect, the packet extension field information includes: the length of the packet extension field, or whether the packet extension field is greater than 16 us.

With reference to the third possible implementation manner of the second aspect, in a fifth possible implementation manner of the second aspect, the additional HE-LTF information includes: the number of additional HE-LTF symbols, or whether additional HE-LTFs are present.

With reference to the fifth possible implementation manner of the second aspect, in a sixth possible implementation manner of the second aspect, the P matrix of the HE-LTF in the null data packet is selected according to a sum of an additional HE-LTF and an own HE-LTF.

With reference to the sixth possible implementation manner of the second aspect, in a seventh possible implementation manner of the second aspect, the additional HE-LTF in the null data packet is the same as the HE-LTF part of the null data packet.

With reference to the sixth possible implementation manner of the second aspect, in an eighth possible implementation manner of the second aspect, the additional HE-LTFs in the null data packet are all the same as their own HE-LTFs.

With reference to the third possible implementation manner of the second aspect, in a ninth possible implementation manner of the second aspect, the indication method of the packet extension field information and the additional HE-LTF information at least includes any one of the following: extra bits in the HE-SIG, Modulation Coding Set (MCS) in the HE-SIG, and packet expansion PE domain in the HE-SIG.

According to the embodiment of the invention, by generating the null data packet NDP, the null data packet comprises the HE-LTF and the packet extension field for enabling the target STA to carry out channel estimation, or the null data packet comprises the HE-LTF and the extra HE-LTF for enabling the target STA to carry out channel estimation, so that resource waste caused when part of sites do not support immediate feedback can be avoided, and the transmission efficiency of channel state information can be improved.

Drawings

Fig. 1 is a diagram of an application scenario of the present invention.

FIG. 2 is a flowchart of a method according to a first embodiment of the present invention;

fig. 3 is a structure diagram of a null data packet in accordance with a first embodiment of the present invention.

Fig. 4 is a structure diagram of a null data packet in accordance with a first embodiment of the present invention 2.

Fig. 5 is a block diagram of a physical device according to a second embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention are described in further detail below with reference to the accompanying drawings. It is to be understood that the embodiments described below are only some of the embodiments of the present invention, and not all of them. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The embodiment of the invention can be applied to a Wireless Local Area Network (WLAN for short), and the standard adopted by the WLAN at present is IEEE (Institute of Electrical and electronics Engineers, Chinese) 802.11 series. The WLAN may include a plurality of Basic Service Sets (BSS), where a network node in a BSS is a Station (STA), and the Station includes an Access Point (AP) and a Non-Access Point (Non-AP STA). Each basic service set may include one AP and a plurality of Non-AP STAs associated with the AP.

And the access point type station is also called as a wireless access point or a hot spot, and the like. The AP is an access point for a mobile subscriber to enter a wired network, and is mainly deployed in a home, a building, and a campus, and typically has a coverage radius of several tens of meters to hundreds of meters, and may be deployed outdoors. The AP acts as a bridge connecting the network and the wireless network, and mainly functions to connect the wireless network clients together and then to access the wireless network to the ethernet. Specifically, the AP may be a terminal device or a network device with a WiFi (Wireless Fidelity, chinese) chip. Optionally, the AP may be a device supporting 802.11ax standard, and further optionally, the AP may be a device supporting multiple WLAN standards such as 802.11ac, 802.11n, 802.11g, 802.11b, and 802.11 a.

A Non-Access Point (Non-AP STA) may be a wireless communication chip, a wireless sensor, or a wireless communication terminal. For example: the mobile phone supporting the WiFi communication function, the tablet computer supporting the WiFi communication function, the set top box supporting the WiFi communication function, the smart television supporting the WiFi communication function, the smart wearable device supporting the WiFi communication function, the vehicle-mounted communication device supporting the WiFi communication function and the computer supporting the WiFi communication function. Optionally, the station may support an 802.11ax system, and further optionally, the station supports multiple WLAN systems such as 802.11ac, 802.11n, 802.11g, 802.11b, and 802.11 a.

Fig. 1 is a system diagram of a typical WLAN deployment scenario, including an AP in communication with STA1, STA2, and STA3, and 3 STAs.

In the WLAN system 802.11ax introduced after the OFDMA technique, the AP may perform uplink and downlink transmission with different STAs on different time-frequency resources. The AP may use different modes for uplink and downlink transmission, such as an OFDMA Single-User Multiple-Input Multiple-Output (SU-MIMO) mode, or an OFDMA Multi-User Multiple-Input Multiple-Output (MU-MIMO).

The AP may send a Physical Layer Protocol Data Unit (PPDU) to a plurality of stations or a plurality of station groups at the same time. Here, the plurality of stations may refer to stations in SU-MIMO mode, and the plurality of station groups may refer to station groups in MU-MIMO mode.

Specifically, the PPDU sent by the AP includes a Physical Layer Convergence Protocol (PLCP) Header field (Header) and a data field, where the PLCP Header includes a conventional Preamble (L-Preamble) and a High-efficiency Preamble, and the High-efficiency Preamble includes a High-efficiency signaling a (HE-SIGA) portion and a High-efficiency signaling B (HE-SIGB) portion. The PPDU may further include a Media Access Control (MAC) part.

Example 1

Embodiment 1 of the present invention provides a method for transmitting a channel state message, where the method may be applied to a station, for example: AP and STA1 in fig. 1-STA3, which may support next generation WLAN standards such as: 802.11ax format. Fig. 2 is a flowchart of the method for transmitting a channel status message, which includes the following specific steps:

step 110: generating a null data packet NDP, wherein the null data packet comprises a high efficiency long training sequence HE-LTF and a padding field, and the padding field is used for allowing the target station to have extra time to receive the channel state information.

Step 120: and transmitting the null data packet.

It should be noted that the role of PE (chinese: Packet Extension) in data frame is to provide extra time for the station to process data, so the length of PE is related to the capability of the station to process data. For example, for the same group (bandwidth BW, spatial streams Nsts, modulation and coding strategy MCS), different stations may need PEs of different lengths; different (BW, Nsts, MCS) combinations may require PEs of different lengths for the same station. That is, the length of a PE is related to the ability of the station to process data. For a data frame, the possible lengths of the PEs are 0us,4us,8us,12us,16 us. For NDP, the NDP does not contain a data portion, and the station uses the NDP to calculate the channel state information. Thus, if a PE needs to be added after an NDP, the length of the PE of the NDP requires additional negotiation of capabilities between the station and the access point, or is pre-specified by the system.

Optionally, the padding field includes a packet extension field or an additional HE-LTF. The null data packet further comprises an own HE-LTF which is positioned behind the HE-STF and is used for channel estimation of a target station, and specifically, the own HE-LTF is an HE-LTF symbol corresponding to the number of the spatial streams to be estimated.

It is to be noted that the structure of the null data packet including the packet extension field is shown in fig. 3, and the structure of the null data packet including the additional HE-LTF is shown in fig. 4.

Optionally, the length of the packet extension field or the number of additional HE-LTF symbols is determined by at least one of the following conditions: bandwidth, mode of HE-LTF, estimated number of spatial streams.

Specifically, for the predefined mode of the system, the predefined mode can be only defined according to the number of the spatial stream Nsts or HE-LTF symbols; or preset according to the mode of the HE-LTF, namely 2x or 4x, wherein 2x HE-LTF refers to the HE-LTF containing 128 subcarriers, 4x HE-LTF refers to the HE-LTF containing 256 subcarriers, and the mode of the LTF in the original 11ac is 1x, namely containing 64 subcarriers; or may be only specified in advance according to the bandwidth BW; and the preset regulation can be made according to any combination of a plurality of factors such as spatial stream, HE-LTF mode, bandwidth and the like. Of course, the system may also directly pre-define the addition of one or more PEs of different lengths after the NDP, without depending on the relevant parameters.

An example is to make a pre-defined only in terms of the number of spatial streams Nsts, e.g. for 4x or 2x HE-LTF with Nsts > n1, specify that a PE of x1 is added after NDP; for 4x or 2x HE-LTFs with Nsts < n2, PE with x2 added after NDP is specified; in particular, n1 may be 4, n2 may be 5, x1 may be 16us, and x2 may be 8 us.

Another example is to make a pre-specification based only on the pattern of the HE-LTF, e.g., for a 4x HE-LTF, specify that a PE of x1 be added after NDP; for 2x HE-LTF, PE with x2 added after NDP is specified; in particular, x1 can be 16us and x2 can be 8 us.

Another example is pre-specified in terms of patterns of HE-LTF and number of spatial streams Nsts, e.g., for 4x HE-LTF with Nsts > n1, specifying that PE of x1 is added after NDP; for 4x HE-LTF with Nsts < n2, PE with x2 added after NDP is specified; for a 2x HE-LTF with Nsts > n1, a PE of x3 was added after NDP; for a 2x HE-LTF with Nsts < n2, a PE of x4 was added after NDP; in particular, n1 may be 4, n2 may be 5, x1 may be 16us, x2 may be 8us, x3 may be 8us, and x4 may be 4 us.

Another example is a pre-defined number of bandwidth BW and spatial streams Nsts, e.g. for 4x or 2x HE-LTF (BW > m1MHz, Nsts > n1), a PE with x1 added after NDP is defined; for 4x or 2x HE-LTFs (BW < m2MHz, Nsts < n2), PE with x2 added after NDP is specified; for 4x or 2x HE-LTFs of (BW > m1MHz, Nsts < n2), PE with x3 added after NDP is specified; for 4x or 2x HE-LTFs of (BW < m2MHz, Nsts > n1), PE with x4 added after NDP is specified;

another example is that no pre-specification is made on any parameter, e.g. it may be directly specified that a PE of length x1 is added after NDP.

Specifically, for the capability negotiation between the station and the access point, the station may report the capability of preparing the channel state information and the capability of processing data to the access point, or may report the capability of preparing the channel state information by itself.

One example is that for different (BW, Nsts) combinations, two thresholds (threshold _ x1 and threshold _ x2) are defined in the HE Capability domain, with threshold _ x1 being used to decide when the maximum PE length is x1us and threshold _ x2 being used to decide when the maximum PE length is x2 us. The largest PE refers to the length of PE required under the largest supportable spatial stream. For each threshold, a 1-bit indication may be used. Specifically, when the 1 bit is a first value, it indicates that the current threshold is not used, and when the 1 bit is a second value, it indicates that the current threshold is used. For example, if both bits are the first value, then it is stated that no PE is needed for either a 2x or 4x HE-LTF, or that the largest PE needed is less than x1us and x2 us. If the two bits are both the second value, it means that the maximum PE length is x1us for 2x HE-LTF; for a 4x HE-LTF, the maximum PE length is x2 us; if 1 bit corresponding to threshold _ x2 is a first value and 1 bit corresponding to threshold _ x1 is a second value, it indicates that the maximum PE length is x1us regardless of 2x or 4x HE-LTF; if 1 bit corresponding to threshold _ x2 is the second value and 1 bit corresponding to threshold _ x1 is the first value, it indicates that the maximum PE length is x2us regardless of 2x or 4x HE-LTF.

Alternatively, the first and second electrodes may be,

for each threshold, 2 bits may be used for indication, and 2 bits correspond to 4 values. Specifically, when the 2 bits are a first value, it indicates that the PE can reach the current threshold in the 2x HE-LTF mode and the 4x HE-LTF mode; when the 2 bits are a second value, the PE can reach the current threshold in a 4x HE-LTF mode; when the 2 bits are a third value, null or invalid is indicated. For example, if both of the 2 bits are the third value, it is stated that no PE is needed for the HE-LTF of 2x or 4x, or only PEs smaller than x1us and x2us are needed. If 2 bits corresponding to threshold _ x2 are the second value and 2 bits corresponding to threshold _ x1 are the third value, it indicates that the maximum PE length is x2us in the 4x HE-LTF mode; in the 2x HE-LTF mode, neither PE is needed, or the largest PE needed is smaller than x1us and x2 us. If 2 bits corresponding to threshold _ x2 is the third value and 2 bits corresponding to threshold _ x1 is the first value, it indicates that the maximum PE length is x1us in the 2x and 4x HE-LTF modes.

Another example is that a station locally defines multiple HE-LTF thresholds based on its own capabilities.

	x1μs	x2μs	x3μs	x4μs	x5μs
						2x HE-LTF	n1	n2	n3	n4	n5
4x HE-LTF	m1	m2	m3	m4	m5

In the above table, the first row represents the possible lengths of PEs, and may be x1 to x5 as listed in the table, or any one or some of these 5 values. The first column shows the pattern of the HE-LTF, including the 2x and 4x HE-LTFs. The contents of the table indicate the number of HE-LTF symbols. Taking n3 as an example, if NDP transmits 2 × HE-LTF, when the number of HE-LTF symbols is greater than (greater than or equal to) n3 and less than or equal to (less than) n4, it is necessary to add x3us PEs to the station. Since the NDP may be addressed to a group of sites, the PE that needs the longest PE among all sites is taken as the PE that the current NDP needs to add.

Specifically, a specific example of the above table is:

	0μs	4μs	8μs	12μs	16μs
						2x HE-LTF	1	2	4	6	8
4x HE-LTF	0	1	2	4	8

in particular, for NDP, a maximum of 16us of PEs (16 us maximum for data frames) may not be sufficient to provide the station with sufficient additional time to prepare the channel state information. Thus PEs larger than 16us, such as 32us, 48us etc. can be designed specifically for NDP.

Taking the above table as an example, a station may define multiple HE-LTF thresholds according to its own capability, as follows:

	4μs	8μs	16μs	32μs	48μs
						2x HE-LTF	1	2	4	6	8
4x HE-LTF	0	1	2	4	8

specifically, explaining the above table, when the number of 2 × HE-LTF symbols is greater than (equal to or greater than) 6 and less than (equal to or less than) 8, the PE length used is 32 us.

Optionally, the null data packet includes an indication field located in a high efficiency signaling field HE-SIG of the null data packet, the indication field to define packet extension field information or additional HE-LTF information.

Optionally, the packet extension field information includes: the length of the packet extension field, or whether the packet extension field is greater than 16 us.

Optionally, the indication method of the packet extension field information and the additional HE-LTF information at least includes any one of: extra bits in the HE-SIG, Modulation Coding Set (MCS) in the HE-SIG, and packet expansion PE domain in the HE-SIG.

The following mainly describes an indication method of packet extension field information.

Specifically, the station PE length is informed with packet extension field information in HE-SIG. The HE-SIG comprises 1 bit and is used for indicating whether the current frame contains a PE larger than 16 us; if so, reusing the PE field or MCS field in the HE-SIG to indicate the length of the current PE. As another example, considering that the current 3-bit PE field contains 2 unused combinations, the 2 unused combinations can be used to indicate that the current frame contains a PE greater than 16 us. The 2 unused combinations can also respectively represent specific PE lengths, for example, one of the unused combinations represents a PE containing 32 us; another unused combination represents a PE containing 48 us.

Optionally, as another embodiment, the additional HE-LTF information includes: the number of additional HE-LTF symbols, or whether additional HE-LTFs are present.

It should be noted that the indication of the additional HE-LTF information may be determined by negotiation between stations or specified by a standard.

Further, the P matrix of the HE-LTF in the null data packet is selected as a sum of the additional HE-LTF and the self-contained HE-LTF.

Optionally, the additional HE-LTFs in the null data packet are partially identical to the self-contained HE-LTFs, or the additional HE-LTFs in the null data packet are all identical to the self-contained HE-LTFs.

The following mainly describes an indication method of additional HE-LTF information.

Specifically, the station is informed of whether additional HE-LTFs exist or not by using the additional HE-LTF information in the HE-SIG, or the number of additional HE-LTF symbols.

Illustratively, the number of additional HE-LTF symbols in the NDP is n1, and the number of HE-LTF symbols carried by the NDP itself is n2, so the total number of HE-LTF symbols in the NDP is n1+ n 2. One way, the P matrix for the HE-LTFs in the null data packet is selected as a function of the sum of the additional HE-LTFs and the actual HE-LTFs n1+ n 2; alternatively, n1 copies of the n2 HE-LTFs serve as additional HE-LTFs. For some stations with weak processing capability, the number of the HE-LTF symbols carried by the stations can be only used for estimating the channel; for some stations with strong processing capability, additional HE-LTFs can be utilized to improve the accuracy of channel estimation.

The NDP specifies how many additional HE-LTF symbols are needed, and the negotiation of capabilities between the station and the access point is required, or is predefined by the system. Since the NDP may be addressed to a group of stations, the number of extra HE-LTF symbols that are needed most in all stations is taken as the number of extra HE-LTF symbols that the current NDP needs to add.

A first way to indicate the number of additional HE-LTF symbols is to include an indication bit in the HE-SIG (HE-SIG-a or HE-SIG-B or both) that indicates the number of the current additional HE-LTF symbols.

After reading the field of the number of the extra HE-LTF symbols in the HE-SIG, the receiving end can know the number of the total HE-LTF symbols contained in the current frame, and further can know the end position of the current frame. And the number of the HE-LTF symbols carried by the HE-SIGA is determined by the number of spatial streams indicated by Nsts in the HE-SIGA.

Alternatively, the indication bit indicates whether the current frame includes an additional HE-LTF or whether the current frame is an NDP. For such an indication, the station also needs to be informed of the number of additional HE-LTF symbols. The informed manner may be to reuse a part of the fields in the HE-SIG, such as the PE field, the MCS field, and so on. Whether the current frame contains additional HE-LTFs or not can be indicated at the same time by reusing partial fields in the HE-SIG, or whether the current frame is NDP or not and the number of additional HE-LTF symbols can be indicated.

An example of reusing a partial field in the HE-SIG considers that 2 unused combinations are included in the current 3-bit PE field, and thus, the 2 unused combinations may be used to indicate that the current frame includes additional HE-LTFs or that the current frame is an NDP. The 2 unused combinations may also represent the number of additional HE-LTF symbols as m1 and m2 (pre-agreed by the access point and station), respectively. Or, the current frame is only represented by some unused combination to contain additional HE-LTFs, or is NDP, and then the MCS field is reused to indicate the number of additional HE-LTF symbols.

After reading the HE-SIG of the above structure, the receiving end knows that the current frame is a special frame (including an extra HE-LTF or the current frame is an NDP) through a reused field or an extra instruction. Then, the number of extra HE-LTF symbols contained in the current frame is known through the reused domain, and the total number of HE-LTF symbols contained in the current frame can be known by combining the number of HE-LTF symbols, so that the end position of the current frame can be known. The number of HE-LTF symbols is determined by the spatial stream indicated by Nsts in HE-SIGA.

A second way to indicate the number of extra HE-LTF symbols is to add extra 1 bit in the Nsts field of HE-SIGA to indicate more spatial streams. For example, current Nsts contains only 3 bits, support indicates up to a maximum of 8 spatial streams. By adding an extra 1 bit, 4 bits of Nsts can indicate the situation to a maximum of 16 spatial streams. The space stream corresponds to the number of the HE-LTF symbols, and the expanded Nsts domain corresponds to the sum of the number of the HE-LTF symbols and the number of the extra HE-LTF symbols. In order to inform the receiving end of the number of the additional HE-LTF symbols, additional bits may be added to the HE-SIG, or a part of the field of the HE-SIG, such as the PE field and the MCS field, may be reused to carry an indication of the number of the additional HE-LTF symbols. Or, for NDP, for different numbers of HE-LTF symbols, appointing different numbers of additional HE-LTF symbols (appointed in advance by the access point and the station), for example, if the number of HE-LTF symbols is 4, appointing 2 additional HE-LTF symbols; if the number of the HE-LTF symbols is 8, 4 additional HE-LTFs are appointed. It should be noted that, the number of additional HE-LTF symbols told to the receiving end is substantially the same as the number of actual spatial streams or HE-LTF symbols told to the receiving end. Therefore, a partial field of the HE-SIG, such as the PE field or the MCS field, may also be reused to carry an indication of the number of spatial streams or HE-LTF symbols carried by itself.

After reading the HE-SIGA with the structure, the receiving end can know that the current number is NDP by calculating OFDM symbols of the data part, and then subtracts the number of the extra HE-LTF symbols from the number of the HE-LTF symbols indicated by Nsts through the indication of the reused domain or the number of the extra HE-LTF symbols which is agreed in advance, so that the number of the HE-LTF symbols can be obtained. The number of the current total HE-LTF symbols can be known from the Nsts indication, and the end position of the current frame can be further known.

Example 2

Fig. 5 is a schematic block diagram of an apparatus for transmitting a channel status message in a wireless local area network according to embodiment 2 of the present invention. The data transmission means are for example stations or dedicated circuits or chips implementing the relevant functions. The station 1000 includes a processor 1010, memory 1020, baseband circuitry 1030, radio frequency circuitry 1040, and antennas 1050. The means for transmitting the trigger frame may be the AP or STA1-STA3 shown in fig. 1.

In particular, processor 1010 controls the operation of station 1000. Memory 1020 may include read-only memory and random-access memory and provides instructions and data to processor 1010, which may be a general-purpose processor, a digital signal processor, an application specific integrated circuit, a field programmable gate array, or other programmable logic device. A portion of the memory 1020 may also include non-volatile row random access memory (NVRAM). The baseband circuit 1030 is used to synthesize a baseband signal to be transmitted or decode a received baseband signal. The radio frequency circuit 1040 is used to modulate a low frequency baseband signal to a high frequency carrier signal that is transmitted via the antenna 1050. The radio frequency circuitry is also used to demodulate the high frequency signals received by the antenna 1050 into a low frequency carrier signal. The various components of station 1000 are coupled together by a bus 1060, where bus system 1060 includes a power bus, a control bus, and a status signal bus, in addition to a data bus. For clarity of illustration, however, the various buses are designated as the bus system 1060 in the figure. It should be noted that the above description of the station structure can be applied to the following embodiments.

The base band circuit 1030 is configured to generate a null data packet NDP, where the null data packet includes a high efficiency long training sequence HE-LTF and a padding field, and the padding field is used for allowing a target station to have extra time to receive channel state information;

and a radio frequency circuit 1040 for transmitting the null data packet.

Optionally, the padding field includes a packet extension field or an additional HE-LTF.

It should be noted that the length of the packet extension field or the number of additional HE-LTF symbols may be determined by negotiation between stations, or may be defined by the standard.

Optionally, the null data packet includes an indication field located in a high efficiency signaling field HE-SIG of the null data packet, the indication field to define packet extension field information and additional HE-LTF information.

It should be noted that the definition of the packet extension field information has been explained in detail in embodiment 1, and is not described again.

Optionally, the additional HE-LTF information includes: the number of additional HE-LTF symbols, or whether additional HE-LTFs are present.

Optionally, the P matrix of HE-LTFs in the null data packet is selected as a sum of additional HE-LTFs and their own HE-LTFs.

Optionally, the additional HE-LTF in the null data packet is the same as the self-contained HE-LTF part.

Optionally, the additional HE-LTFs in the null data packet are all the same as their own HE-LTFs.

It should be noted that how to obtain additional HE-LTFs is explained in detail in example 1 and will not be described again.

Through the above description of the embodiments, those skilled in the art will clearly understand that the present invention can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better embodiment. Based on such understanding, the technical solutions of the present invention may be substantially implemented or a part of the technical solutions contributing to the prior art may be embodied in the form of a software product, which is stored in a readable storage medium, such as a floppy disk, a hard disk, or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a server, or a network device) to execute the methods according to the embodiments of the present invention.

Claims

1. A method of transmitting channel state information, comprising:

and transmitting the null data packet.

2. The method of claim 1, the padding field comprising a packet extension field or an additional HE-LTF.

3. The method of claim 2, the length of the packet extension field or the number of additional HE-LTF symbols is determined by at least one of: bandwidth, mode of HE-LTF, estimated number of spatial streams.

4. The method of claim 2, wherein the null data packet includes an indication field located in a high efficiency signaling field (HE-SIG) of the null data packet, the indication field to define packet extension field information or additional HE-LTF information.

5. The method of claim 4, wherein the packet extension field information comprises: the length of the packet extension field, or whether the packet extension field is greater than 16 us.

6. The method of claim 4, wherein the additional HE-LTF information comprises: the number of additional HE-LTF symbols, or whether additional HE-LTFs are present.

7. The method of claim 6, wherein the P matrix for the HE-LTF in the null data packet is selected as a sum of additional HE-LTFs and their own HE-LTFs.

8. The method of claim 7, wherein an additional HE-LTF part of the null data packet is the same as an own HE-LTF part.

9. The method of claim 7, wherein additional HE-LTFs in the null data packet are all the same as their own HE-LTFs.

10. The method of claim 4, the indication methods of the packet extension field information and the additional HE-LTF information include at least any one of: extra bits in the HE-SIG, Modulation Coding Set (MCS) in the HE-SIG, and packet expansion PE domain in the HE-SIG.

11. An apparatus for transmitting channel state information, comprising:

radio frequency circuitry to transmit the null data packet.

12. The apparatus of claim 11, the padding field comprising a packet extension field or an additional HE-LTF.

13. The apparatus of claim 12, the length of the packet extension field or the number of additional HE-LTF symbols is determined by at least one of: bandwidth, mode of HE-LTF, estimated number of spatial streams.

14. The apparatus of claim 12, wherein the null data packet includes an indication field located in a high efficiency signaling field (HE-SIG) of the null data packet, the indication field to define packet extension field information or additional HE-LTF information.

15. The apparatus of claim 14, wherein the packet extension field information comprises: the length of the packet extension field, or whether the packet extension field is greater than 16 us.

16. The apparatus of claim 14, wherein the additional HE-LTF information comprises: the number of additional HE-LTF symbols, or whether additional HE-LTFs are present.

17. The apparatus of claim 16, wherein the P matrix for HE-LTFs in the null data packet is selected as a sum of additional HE-LTFs and their own HE-LTFs.

18. The apparatus of claim 17, wherein an additional HE-LTF part of the null data packet is the same as an own HE-LTF part.

19. The apparatus of claim 17, wherein additional HE-LTFs in the null data packet are all the same as their own HE-LTFs.

20. The apparatus of claim 14, the packet extension field information and the indication method of the additional HE-LTF information at least include any one of: extra bits in the HE-SIG, Modulation Coding Set (MCS) in the HE-SIG, and packet expansion PE domain in the HE-SIG.