Apparatus and method for fast link adaptation in wireless networks

Abstract

In one embodiment, a Wi-Fi station is disclosed for performing link adaptation (LA) to communicate with at least one further Wi-Fi station over a wireless link. The at least one further station is configured to transmit a sounding frame to the at least one further station over the wireless link using one or more of a plurality of modulation and coding schemes (MCSs) and / or one or more of a plurality of spatial streams, where each MCS of the plurality of MCSs defines a quadrature amplitude modulation (QAM) scheme using a quadrature amplitude modulation (QAM) constellation and a coding rate, and where the coding rate is greater than the constellation. And receive feedback including a wireless link performance metric from the at least one further station. The station is configured to select, based on the feedback from the at least one further station, one of the plurality of MCSs and a number of spatial streams to transmit a data frame to the at least one further station over the wireless link.

Description

Technical Field

[0001] The present invention relates to wireless communication. More specifically, the present invention relates to devices (especially access points and non-AP stations), and methods for fast link adaptation in wireless communication networks (especially Wi-Fi networks). Background Art

[0002] In wireless communication networks, especially in Wi-Fi networks, link adaptation (LA) is a mechanism for adapting transmission (TX) schemes and parameters according to wireless link conditions (channel quality and interference), such as PHY rate (specified by modulation and coding scheme (MCS) and number of streams), frequency allocation, i.e., the selection of resource units (RUs), etc., while adapting to other system constraints and requirements.

[0003] The IEEE 802.11be standard (Wi-Fi 7) supports BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM, 1024-QAM, and 4096-QAM modulations, and coding rates including 1 / 2, 2 / 3, 3 / 4, and 5 / 6 (not all modulation values support all coding rates). Binary convolutional code (BCC) and low-density parity check (LDPC) codes are also supported.

[0004] One of the most popular LA implementations is the Minstrel algorithm, where the rate definition parameters are slowly changed through a "trial and error" process based on the received ACKs reported by the receiving Wi-Fi stations. "Slowly" means that the algorithm may take a very long time to converge to an optimal set of parameters (thus achieving some predefined metric goals, such as a packet error rate (PER) of up to 10%).

[0005] Regarding the feedback provided by a receiving station (STA) for performing link adaptation, several such feedback modes (superior to ACK) are known, such as the SNR (CQI) for each RU, MCS feedback (MFB), and A-CTRL HE link adaptation (HLA). In the SNR (CQI) for each RU, the RX STA can be instructed to calculate and feedback the SNR of a specific RU (based on the sounding NDP). However, based on this feedback, the TX AP may not be able to determine the goodness or credibility of the SNR calculated by the RX STA. In MCS feedback (MFB), the RX STA can indicate its preferred MCS. This feedback mode may be advantageous as it can take into account the specific implementation of the RX STA. However, it is difficult to implement this mode in commercial devices. SUMMARY OF THE INVENTION

[0006] An object of the present invention is to provide a device, particularly an access point and a non-AP station, and a method for improved link adaptation in a wireless communication network, particularly a Wi-Fi network.

[0007] The above and other objects are achieved by the subject matter of the independent claims. Other implementations are apparent from the dependent claims, the description, and the drawings.

[0008] According to a first aspect, there is provided a requesting Wi-Fi station for performing link adaptation (LA) to communicate with at least one other responsive Wi-Fi station via a wireless link. The requesting Wi-Fi station is configured to send a probe (i.e., a probe frame) to the at least one other responsive Wi-Fi station via the wireless link using one or more modulation and coding schemes (MCSs) and / or one or more spatial streams from a plurality of MCSs, wherein each MCS in the plurality of MCSs is defined, i.e., associated with a QAM scheme including a QAM constellation defining a plurality of quadrature-amplitude modulation (QAM) symbols or constellation points. Further, the requesting Wi-Fi station is configured to receive feedback including wireless link performance metrics from the at least one other responsive Wi-Fi station in response to the probe frame. The requesting Wi-Fi station is further configured to select one MCS from the plurality of MCSs (and thus, select one QAM scheme from the plurality of QAM schemes associated with the selected MCS) and the number of spatial streams to be sent, e.g., to send a data frame to the at least one other responsive Wi-Fi station via the wireless link, based on the feedback from the at least one other responsive Wi-Fi station.

[0009] The requesting Wi-Fi station generates the probe frame based on at least one low-density parity-check (LDPC) codeword, that is, one of the intermediate processing steps of generating the probe frame involves at least one LDPC codeword. For each coding rate of the plurality of MCSs, the at least one LDPC codeword is an LDPC codeword according to one or more LDPC codebooks specified by the IEEE 802.11 WLAN standard framework. The one or more LDPC codebooks may be defined by one or more LDPC matrices, particularly the LDPC matrices defined by the IEEE 802.11 WLAN standard framework. For each possible combination of the plurality of MCSs and the plurality of spatial streams, the at least one LDPC codeword is modulated (for finally generating the probe frame) into a corresponding plurality of QAM symbols (i.e., constellation points), where each QAM symbol in the plurality of QAM symbols corresponds to an energy level among a plurality of possible energy levels defined by the corresponding QAM scheme, and for each possible combination of the plurality of MCSs and the plurality of spatial streams, the number of different actual energy levels corresponding to the plurality of QAM symbols is greater than a corresponding predefined threshold. As will be understood and described in more detail below, the probe frame generated by the requesting Wi-Fi station based on the LDPC codeword provides a good coverage of unique energy levels for different QAM schemes (especially high-order QAM schemes), enabling the LA process to converge quickly.

[0010] In another possible implementation, a plurality of consecutive energy level subsets of the plurality of possible energy levels define a plurality of consecutive energy level ranges (i.e., categories), the plurality of energy level ranges including: an energy level range including the minimum energy level among the plurality of possible energy levels and an energy level range including the maximum energy level among the plurality of possible energy levels, where at least one QAM symbol in the plurality of QAM symbols corresponds to an actual energy level within the energy level range including the minimum energy level among the plurality of possible energy levels, and at least one other QAM symbol in the plurality of QAM symbols corresponds to an actual energy level within the energy level range including the maximum energy level among the plurality of possible energy levels.

[0011] In another possible implementation, each energy level range (i.e., category) among the plurality of consecutive energy level ranges includes at least 2, 3, 4, 5, 10, 20, 25, or 50 consecutive energy levels among the plurality of possible energy levels.

[0012] In another possible implementation, for each energy level range (i.e., category), at least one QAM symbol in the plurality of QAM symbols corresponds to an actual energy level within the corresponding energy level range.

[0013] In another possible implementation, the plurality of actual energy levels corresponding to the plurality of QAM symbols are substantially evenly distributed within the plurality of energy level ranges. In other words, according to this implementation, each energy level range should include approximately the same number of QAM symbols.

[0014] In another possible implementation, a plurality of consecutive energy level subsets of the plurality of possible energy levels define a plurality of consecutive energy level ranges (i.e., categories), wherein, for a selected MCS among the plurality of MCSs corresponding to a 4096-QAM modulation scheme (also referred to herein as 4K-QAM), the requesting Wi-Fi station that generates the probe frame based on the at least one LDPC codeword is used to modulate the at least one LPDC codeword into a plurality of 4096-QAM symbols, where at least N 4096 4096-QAM symbols belong to different energy level ranges (i.e., are associated with different energy level ranges), where N 4096 is greater than 120, and in particular equal to 137.

[0015] In another possible implementation, for a selected MCS among the plurality of MCSs corresponding to a 1024-QAM modulation scheme (also referred to herein as 1K-QAM), the requesting Wi-Fi station that generates the probe frame based on the at least one LDPC codeword is used to modulate the at least one LPDC codeword into a plurality of 1024-QAM symbols, where at least N 1024 1024-QAM symbols belong to different energy level ranges (i.e., are associated with different energy level ranges), where N 1024 is greater than 80, and in particular equal to 90.

[0016] In another possible implementation, for a selected MCS among the plurality of MCSs corresponding to a 256-QAM modulation scheme, the requesting Wi-Fi station that generates the probe frame based on the at least one LDPC codeword is used to modulate the at least one LPDC codeword into a plurality of 256-QAM symbols having 32 256-QAM constellation points, where the 32 256-QAM constellation points have different energy levels.

[0017] In another possible implementation, the at least one LDPC codeword includes an information bit portion based on the following hexadecimal representation, where the rightmost bit is the most significant bit, for example, C = 0011:

[0018] D258B757F74536ABD57CDEC440E7DAF7766C6BD1676196297F90F25733ECE6EAD95D5644B9ACDCE8768C34CD348BC465937DD1CB7BA4B2243A0EF502FBB813FB02690C1016550A9312A3F418E8C7E91B00CE3F2C0009692A604BA72C78101486189D6849C0AC59F16363989333CCBC6BFB0E10D169329F2E96C1FE92B6BE80A92AF402654DBBF1CDE4265998DC3008BA721BE957493B2E479861C078C46FC6C30A840367A621A5AFCE7EA1FF6E36E59303E467A50F3CEFB3B61D7B4E92BD4783847C41F7C5C8AC42733BB。

[0019] In another possible implementation, the at least one LDPC codeword includes an information bit portion based on the following hexadecimal representation, where the rightmost bit is the most significant bit, for example, C = 0011:

[0020] 7D91DB7AFE1704EE00946F932654AECF5F127BA340D5F364479229B1C01DE0FEF3772F362D13B447C1CA03FFA6D8F6011540DCE4DCD8A556681D7B03296FD78F8F8B3491709E30C70921E381461D4CDF965DF0C1D849EE57716CC60EC5B70E6CEAC19E84568ACEE107EDACD681B9D436BBA3122C124F156C785DEB995553878E30C46AC691A23FBFF50DBC1109AF4D62B40D57B2E69245035DB8020D9247C133E2921CBFB66B45C088BF840EA2D03CECCB28847F648FDD5E8E88503300C3614FC936FC36F856301238BAB。

[0021] In another possible implementation, the at least one LDPC codeword includes an information bit portion based on the following hexadecimal representation, where the rightmost bit is the most significant bit, for example, C = 0011:

[0022] 5614AA7AF3390CDC1B0DEBCA5BBB27FD3208A5170E50FB6F6A661ECE631680FC05CA9B42F7C59BEB4A4E6B484ED460013C24F365F2117F3868B061F71B77024C51A62EB852B6AF03AD79039E57EFFEB9A3C9CACA081AD4BE7BB6524931D0B897990F07D32E52FFE12B878F6B995644314918495962128D0FF82B35104864EBF43B9E354C491647EEC42ED77A16288EAAE22608B96F9E1621E6D78D88D59ECE485245626A19A737DB0777B1040F20647AD9E66DE091B383076BBD328EA986AD84B8EEB1CD1CC3021C3985E。

[0023] In another possible implementation, the probe frame is a null-data packet (NDP) frame, especially a fast link adaptation training physical (PHY) protocol data unit (PPDU).

[0024] In another possible implementation, the wireless link performance metric includes the bit error rate (BER) of the at least one additional responding Wi-Fi station to the probe frame.

[0025] In another possible implementation, the requesting Wi-Fi station is an access point (AP), and the at least one additional responding Wi-Fi station is a non-AP station.

[0026] In another possible implementation, the at least one LDPC codeword includes at least a first LDPC codeword and a second LDPC codeword, wherein the first LDPC codeword includes 1944 bits, and wherein the information bit portion has 1458 bits, and the information bit portion includes: 1090 bits corresponding to 109 1024-QAM symbols, 2 padding bits, 360 bits corresponding to 30 4096-QAM symbols, and another 6 padding bits, wherein the another 6 padding bits are the same as the first 6 bits of the 1090 bits corresponding to the 109 1024-QAM symbols.

[0027] In another possible implementation, the second LDPC codeword includes 1944 bits, and wherein the information bit portion has 1458 bits, and the information bit portion includes: the last 4 bits of a subset of the 1090 bits of the first LDPC codeword corresponding to the first 1024-QAM symbol of the 109 1024-QAM symbols, the other 1080 bits of the first LDPC codeword corresponding to the other 108 1024-QAM symbols, 2 padding bits, the 360 bits of the first LDPC codeword corresponding to 30 4096-QAM symbols, and another 12 padding bits.

[0028] In another possible implementation, the information bit portion of the first LDPC codeword and / or the second LDPC codeword is based on the following hexadecimal representation, where the right bit is the most significant bit, for example, C = 0011:

[0029] C21631A2F8930807F4F6AF7400A57F9167DBA82FB4B7F4C545C88CD3BC268696743FDC2A66C64802E4D37D8D55D2F4E6B12AB2FCB79A9A0C1B9E30D8FE783DB385DC724E9E8F37D09153187E92EAB89F1B1A19983CCD96A24808878DE82E497ACC8F46692A75E83D78E39239ED8DB5394A9D54012F3F22DA85 704BAAC4C3CC35C27C77F257F9070FC94FCBB2BC6A656440A5DE521000EFCE764F753E8349DA567D5C26A27EE92A61D10F7CB792D1A07BEAAF86601DC7C949B482B31C58F9BD0DDA664A242AD17FBA28F78

[0030] In another possible implementation, the information bit portion of the first LDPC codeword and / or the second LDPC codeword includes a plurality of padding bits selected from the following 24-bit sequence: 1 1 1 0 0 0 0 0 0 1 0 1 0 1 0 1 0 0 1 0 0 1 1 1. For example, the information bit portion may include the first 6 or 12 bits of the 24-bit sequence.

[0031] In another possible implementation, the requesting Wi-Fi station includes an LPDC encoder for generating the at least one LDPC codeword using one or more systematic LDPC codes.

[0032] According to a second aspect, there is provided a method for performing link adaptation (LA) to communicate with at least one other responsive Wi-Fi station via a wireless link. The method includes the following steps:

[0033] Generating a probe frame based on at least one low-density parity-check (LDPC) codeword;

[0034] Transmit the sounding frame to the at least one other responsive Wi-Fi station via the wireless link using one or more modulation and coding schemes (MCS) out of a plurality of MCSs and / or one or more spatial streams out of a plurality of spatial streams, wherein each MCS out of the plurality of MCSs defines a QAM scheme using a quadrature-amplitude modulation (QAM) constellation and a coding rate;

[0035] Receive feedback including link performance metrics from the at least one other responsive Wi-Fi station;

[0036] Based on the feedback from the at least one other responsive Wi-Fi station, select one MCS out of the plurality of MCSs and the number of spatial streams of the plurality of spatial streams to transmit to the at least one other responsive Wi-Fi station via the wireless link;

[0037] For each coding rate of the plurality of MCSs, the at least one LDPC codeword is an LDPC codeword according to one or more LDPC codebooks specified by the IEEE802.11WLAN Wi-Fi standard;

[0038] For each possible combination of the plurality of MCSs and the plurality of spatial streams, the at least one LDPC codeword is modulated into a corresponding plurality of QAM symbols (i.e., constellation points), wherein each QAM symbol out of the plurality of QAM symbols corresponds to an energy level out of a plurality of possible energy levels defined by the corresponding QAM scheme, and for each possible combination of the plurality of MCSs and the plurality of spatial streams, the number of different actual energy levels corresponding to the plurality of QAM symbols is greater than a corresponding predefined threshold.

[0039] The method provided by the second aspect of the present invention can be executed by the requesting Wi-Fi station provided by the first aspect of the present invention. Therefore, other features of the method provided by the second aspect of the present invention are directly implemented through the functions of the requesting Wi-Fi station provided by the first aspect of the present invention and its different implementation manners described above and below.

[0040] According to a third aspect, there is provided a computer program product. The computer program product includes program code which, when executed by a computer or a processor, causes the computer or the processor to execute the method provided by the second aspect.

[0041] The following drawings and description elaborate one or more embodiments in detail. Other features, objects, and advantages are apparent in the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the drawings:

[0043] Figure 1 A schematic diagram of a wireless communication network is shown. Specifically, the shown Wi-Fi network includes a requesting Wi-Fi station according to an embodiment, and the requesting Wi-Fi station performs a LA process with a plurality of other responding Wi-Fi stations;

[0044] Figure 2a A schematic diagram of a module of a Wi-Fi station for generating a sounding frame based on an LDPC codeword and a modulation scheme according to an embodiment is shown;

[0045] Figure 2b A diagram showing QAM symbols of an exemplary 16QAM modulation scheme is shown;

[0046] Figure 3a and Figure 3b A schematic diagram showing the structure of an LDPC codeword used by a Wi-Fi station for generating a sounding frame according to different embodiments is shown;

[0047] Figure 4 A table showing the values of the number of different energy levels generated by the modulation of an LDPC codeword used by a Wi-Fi station for different QAM schemes, coding rates, and numbers of spatial streams according to an embodiment is shown;

[0048] Figure 5 A flowchart showing the steps of a method for performing link adaptation by a Wi-Fi station according to an embodiment is shown.

[0049] In the following, the same reference numerals refer to the same or at least functionally equivalent features. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0050] In the following description, reference is made to the accompanying drawings which form a part of the present invention, and which show specific aspects of embodiments of the present invention or specific aspects in which embodiments of the present invention can be used. It should be understood that embodiments of the present invention can be used in other aspects and can include structural or logical changes not described in the drawings. Therefore, the following detailed description should not be understood in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0051] For example, it should be understood that the disclosure related to the described method is also applicable to the corresponding device or system for performing the method, and vice versa. For example, if one or more specific method steps are described, the corresponding device may include one or more units (e.g., functional units) to perform the one or more described method steps (e.g., one unit performs one or more steps, or multiple units each perform one or more of the multiple steps), even if such one or more units are not explicitly described or illustrated in the drawings. On the other hand, for example, if a specific apparatus is described based on one or more units (e.g., functional units), the corresponding method may include a step to perform the functions of the one or more units (e.g., one step performs the functions of one or more units, or multiple steps each perform the functions of one or more of the multiple units), even if such one or more steps are not explicitly described or shown in the drawings. Additionally, it should be understood that, unless otherwise specifically indicated, the features of the various exemplary embodiments and / or aspects described herein may be combined with each other.

[0052] Figure 1 A wireless communication network 100 is shown, specifically a wireless communication network according to the IEEE 802.11 standard framework (also referred to as Wi-Fi network 100). The Wi-Fi network 100 includes a Wi-Fi station 110 in the form of a multi-antenna AP 110 (also referred to herein as the requesting Wi-Fi station 110) and a plurality of additional Wi-Fi stations 120 in the form of non-AP stations 120 (also referred to herein as one or more responding Wi-Fi stations 120). As Figure 1 shown, by way of example, the non-AP station 120 may include a smart phone, a laptop computer, a tablet computer, a desktop computer, or other types of wireless devices 120.

[0053] As Figure 1 shown, the AP 110 includes a processing circuit 111 and a communication interface 113 (specifically a wireless communication interface 113 enabling communication according to the IEEE 802.11 standard framework). The processing circuit 111 may be implemented in hardware and / or software, and may include digital circuits, or include both analog and digital circuits. The digital circuits may include components such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or a general-purpose processor. The AP 110 may also include a memory 115 for storing executable program code, which, when executed by the processing circuit 111, causes the AP 110 to perform the functions and methods described herein.

[0054] Similarly, as Figure 1 shown, one or more non-AP stations 120 include processing circuitry 121 and a communication interface 123 (specifically, a wireless communication interface 123 enabling communication according to the IEEE 802.11 standard framework). The processing circuitry 121 may be implemented in hardware and / or software and may include digital circuitry, or may include both analog and digital circuitry. The digital circuitry may include components such as an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a digital signal processor (DSP), or a general-purpose processor. One or more non-AP stations 120 may also include a memory 125 for storing executable program code, which, when executed by the processing circuitry 121, causes the one or more non-AP stations 120 to perform the functions and methods described herein.

[0055] The multi-antenna AP 110 is requested to communicate with a plurality of non-AP stations 120 via respective wireless links, which may be dynamic (i.e., vary over time), e.g., to download data to the plurality of non-AP stations 120 and / or upload data from the plurality of non-AP stations 120 to a network connected to the multi-antenna AP, such as the Internet. Thus, the AP 110 may be regarded as a bridging device connecting the plurality of non-AP stations 120 to a wired backbone network. Although the following more detailed embodiments of performing link adaptation (LA) are described in the context of the AP 110, it should be understood that the embodiments disclosed herein for the AP 110 may also be implemented by the non-AP stations 120.

[0056] To adapt to the possibly varying nature of the wireless links to the non-AP stations 120, the multi-antenna AP 110 is requested to perform link adaptation (LA), i.e., implement an LA algorithm. To this end, the AP 110 is requested to send a probe (i.e., a probe frame), in particular a probe PPDU, to one or more responsive non-AP stations 120 using one or more of a plurality of modulation and coding schemes (MCS) and / or one or more of a plurality of spatial streams (e.g., 1, 2, or 4 spatial streams). In other words, the probe frame may be generated by the communication interface 113 of the AP 110 based on one or more MCSs and / or using one or more spatial streams selected for probing the wireless links for subsequent LA. In one embodiment, the probe frame may be a single-user frame or a multi-user frame.

[0057] It should be understood that each of the multiple MCSs defines (i.e., is associated with) a coding rate and a modulation scheme, in particular a quadrature-amplitude modulation (QAM) scheme, including a QAM constellation that defines multiple possible QAM symbols (also referred to as QAM constellation points). For example, the IEEE 802.11ax standard defines a total of 12 different MCSs (each MCS is identified by an MCS index), and among these MCSs, 9 MCSs are respectively associated with QAM schemes, namely 16-QAM, 64-QAM, 256-QAM, and 1024-QAM schemes. The IEEE 802.11be standard supports two additional coding rates with further modulation, namely the 4096-QAM scheme.

[0058] The requesting AP 110 is also used to receive (based on the probe frame) feedback from the responding non-AP stations 120 that includes information about the wireless link performance metric. In one embodiment, the wireless link performance metric may be the bit error rate (BER) of the probe frames received by one or more responding non-AP stations 120. Based on the feedback from one or more responding non-AP stations 120, for example, the BER determined by one or more responding non-AP stations 120, the requesting AP 110 is also used to select one of the multiple MCSs and the number of spatial streams that is optimally suitable for transmitting the actual data, for example, in an upcoming transmission opportunity, to transmit one or more data frames to one or more responding non-AP stations 120 via the corresponding wireless link.

[0059] As will be described in more detail below, the communication interface 113 of the requesting AP 110 is used to generate an LA probe frame based on one or more low-density parity-check (LDPC) codewords c. Figure 2a Illustrated are several modules that can be implemented by the transmission processing chain of the requesting AP 110 for generating an LA probe frame and (after link adaptation) for transmitting data to one or more responding non-AP stations 120 according to an embodiment.

[0060] As Figure 2aAs shown, in one embodiment, the processing circuitry 111 of the requesting AP 110 may implement an LDPC encoder 201 for encoding a message m into an LDPC codeword c at a predefined coding rate. In one embodiment, the LPDC encoder 201 is used to generate the LDPC codeword c using a systematic LDPC code. It should be understood that for a systematic LDPC code, each LDPC codeword c includes the message m. In other words, the information bit portion of the LPDC codeword c includes the bits of the message m, and the parity bit portion of the codeword c is generated by the systematic LDPC encoder 201 based on the bit sequence of the message m. In one embodiment, the LPDC encoder 201 is used to generate the LPDC codeword c using one or more of the multiple LDPC codes defined by the IEEE802.11 standard framework (such as IEEE 802.11n, IEEE 802.11ac, or any future evolution of the IEEE 802.11 standard framework).

[0061] As Figure 2a As shown, in one embodiment, the requesting AP 110 further includes a modulator 203 for modulating the LDPC codeword c generated by the LPDC encoder 201 into a plurality of QAM symbols s based on a QAM scheme. In one embodiment, the modulator 203 is used to modulate the codeword c generated by the LPDC encoder 201 based on BPSK, QPSK, 16-QAM, 64-QAM, 256-QAM, 1024-QAM, and / or 4096-QAM schemes into a plurality of QAM symbols s (i.e., symbol stream s). In one embodiment, the modulator 203 is used to modulate the codeword c generated by the LPDC encoder 201 based on the modulation scheme defined by the IEEE802.11 standard framework.

[0062] In Figure 2a In the embodiment shown, the transmission processing link of the AP 110 implemented by the processing circuitry 111 and / or the communication interface 113 of the AP 110 may further include an OFDM module 205 and an analog RF module 207. For example, in the case of IEEE 802.11ac, the symbol stream s may be transmitted through OFDM technology, which may include additional steps implemented by the OFDM module 205, such as serial-to-parallel conversion before calculating the inverse fast Fourier transform (IFFT). The analog RF module 207 may be used to generate an actual antenna feed signal based on the output from the OFDM module 205 to generate an RF transmission to one or more responding non-AP stations 120.

[0063] As will be described in more detail below, the requesting AP 110 causes, for each coding rate of a plurality of MCSs, at least one LDPC codeword c for generating an LA probe frame to be an LDPC codeword c of one or more LDPC codebooks specified according to the IEEE 802.11 standard framework. It should be understood that one or more LDPC codebooks may be associated with one or more corresponding LDPC coding matrices. As described above, the AP 110 causes at least one LDPC codeword c to be modulated by the modulator 203 into a sequence of corresponding QAM symbols s (also referred to as QAM constellation points s), i.e., a QAM symbol stream s. It should be understood that each QAM symbol among the plurality of QAM symbols included in the QAM symbol stream s corresponds to an energy level among a plurality of possible energy levels defined by the corresponding QAM scheme. At least one LDPC codeword c is designed such that for each possible combination of a plurality of MCSs and a plurality of spatial streams, the modulator 203 modulates the LDPC codeword c into a plurality of QAM symbols such that the number of different actual energy levels corresponding to the plurality of QAM symbols s is greater than a corresponding predefined threshold. These predefined thresholds will be described in more detail below, i.e., in the context of the results provided in the table shown in Figure 4 and will be described in more detail in the context of the results provided in the table shown below.

[0064] In other embodiments of the AP 110 described below, the AP 110 and the LDPC codewords used by the AP 110 to generate the probe frames of the LA scheme are described. These embodiments are based on one or more of the following considerations.

[0065] It should be understood that for high modulation orders and / or a large number of spatial streams, a single LPDC codeword may not be able to sample all possible energy levels defined by the corresponding QAM scheme. However, once the LA process is complete, this is an ideal characteristic for probing the entire data range that the frame simulation may transmit. For example, in the case of a 4K-QAM scheme with a single spatial stream, a LDPC codeword of 1944 bits is modulated using 162 4K-QAM symbols. Thus, in this case, randomly selecting 162 constellation points from the entire 4096 constellation points of the 4K-QAM scheme can only cover a small subset of 398 unique energy levels (defined by the 4096 constellation points of the 4K-QAM scheme). Refer to Figure 2b which further illustrates this, where, as an example, 16 constellation points of a 16-QAM scheme are shown. From Figure 2b it can be seen that for the 16 QAM points, there are 4 constellation points (represented by stars) defining the highest energy level, 4 constellation points (represented by circles) defining the lowest energy level, and 8 constellation points (represented by crosses) defining the intermediate energy level. It should be understood that for higher modulation schemes, such as 64-QAM, 256-QAM, 1K-QAM, and 4K-QAM, there are more unique energy levels than the Figure 2b 3 energy levels shown.

[0066] As described above, the requesting AP 110 causes, for each coding rate of a plurality of MCSs, at least one LDPC codeword c for generating the LA probe frame to be an LDPC codeword c of one or more LDPC codebooks specified according to the IEEE 802.11 standard framework. There are a total of 4 LDPC codebooks, and the coding rate of each codebook is 1 / 2, 2 / 3, 3 / 4, or 5 / 6 (where only coding rates 3 / 4 and 5 / 6 are used for MCS256-QAM, 1024-QAM, and 4096-QAM). The LDPC codebooks specified by the IEEE 802.11 standard framework do not share common LDPC codewords (except for the all-zero codeword), in other words, the codewords generated by each of the 4 LDPC codebooks are unique.

[0067] The implementation of the requesting AP 110 using the LDPC codewords, which addresses the challenge of enabling an effective LA process for all possible combinations of MCS and N SS and how to determine these LDPC codewords will be described below.

[0068] In a first embodiment, the requesting AP 110 generates a probe frame using an LDPC codeword determined based on the following. The LDPC codeword of this first embodiment is designed to be an LPDC codeword of 1944 bits, for a coding rate of 3 / 4 (corresponding to 1458 information bits) and a 1K-QAM scheme (e.g., defined by MCS10 and 11 according to the IEEE 802.11 standard framework). It should be understood that for a 1K-QAM scheme, there are 109 unique energy levels (i.e., each 1K-QAM symbol corresponds to one of the 109 unique energy levels).

[0069] For this first embodiment, candidate LDPC codewords can be determined by performing multiple search rounds, and the final LDPC codeword can be selected based on the candidate LDPC codewords, where each search round includes one or more of the following 6 stages.

[0070] In the first stage, 109 1K-QAM symbols are randomly drawn, but limited by the fact that each 1K-QAM symbol has a different energy level. The order of different energy levels can be randomized. It should be understood that 109 1K-QAM symbols (each 1K-QAM symbol having 10 bits) correspond to 1090 bits, so that 1458 - 1090 = 368 additional information bits can be further determined. According to this first embodiment, these 368 additional information bits are designed such that the complete LDPC codeword has improved properties in terms of distribution over different energy levels, and is also applicable to the case of applying a 4K-QAM scheme (12 bits / QAM symbol) to the same LDPC codeword. By filling the 1090 bits defining 109 1K-QAM symbols with 2 random bits, 1092 = 12 * 91 bits are obtained, corresponding to 91 4K-QAM symbols. Thus, the remaining 366 information bits (out of a total of 1458 bits) will be designed to correspond to 30 4K-QAM symbols, with 6 bits remaining.

[0071] In the second stage, 2 + 6 = 8 padding bits and the remaining bits can be randomly selected. Additionally, 30 4K-QAM symbols (corresponding to 360 bits) can be randomly selected, with the constraint that each resulting 4K-QAM symbol corresponds to a different energy level. The structure of 109 1K-QAM symbols, 2 padding bits, 30 4K-QAM symbols, and 6 additional padding bits is as Figure 3a shown.

[0072] In the third stage, the 1458 bits obtained in the first two stages are LDPC encoded with a coding rate of 3 / 4 to obtain a first LDPC rate 3 / 4 candidate codeword with 1944 bits.

[0073] In the fourth stage, the first 1620 bits of the first LDPC rate 3 / 4 candidate codeword generated in the previous stage are LDPC encoded with a coding rate of 5 / 6 to obtain a second LDPC rate 5 / 6 candidate codeword with 1944 bits. Since one or more LDPC codes used by the AP 110 according to the embodiment are systematic codes, the first 1620 bits common to the first LDPC candidate codeword and the second LDPC candidate codeword uniquely determine all the bit contents of the first LDPC candidate codeword and the second LDPC candidate codeword.

[0074] In the fifth stage, 256-QAM, 1K-QAM, and 4K-QAM schemes with 1, 2, and 4 spatial streams are used to modulate the first LDPC candidate codeword and the second LDPC candidate codeword, thereby generating a total of 18 different QAM symbol streams s (for 18 different combinations of the two candidate codewords, three potential QAM schemes, and three potential values of the number of spatial streams).

[0075] In the sixth stage, for each sequence of QAM symbols s generated, the number of unique energy levels associated with the QAM symbol s of the corresponding QAM scheme is determined. In this stage, only those first candidate codewords and second candidate codeword pairs can be stored as "good" candidate codewords, the number of different energy levels corresponding to multiple QAM symbols s of which is greater than the corresponding predefined threshold for each QAM scheme used. In one embodiment, for the 4K-QAM scheme, the corresponding predefined threshold for the number of different energy levels corresponding to multiple QAM symbols s is 137 (out of a total of 398 energy levels). For 1K-QAM modulation, the corresponding predefined threshold for the number of different energy levels corresponding to multiple QAM symbols s is 90 (out of a total of 109). For 256-QAM modulation, all 32 energy levels must be covered.

[0076] It should be understood that performing multiple search rounds using the above stages results in multiple first LDPC candidate codeword and second LDPC candidate codeword pairs, where each pair is associated with a specific number of unique energy levels for the 4K-QAM scheme, 1K-QAM scheme, and 256-QAM scheme. From this plurality of first LDPC candidate codeword and second LDPC candidate codeword pairs, the final actual LDPC codeword pair can be selected based on the following max-min criterion:

[0077]

[0078] It should be understood that the first LDPC codeword and the second LDPC codeword of the final pair are uniquely specified by a sequence of 1620 information bits corresponding to a coding rate of 5 / 6. In one embodiment, LDPC codewords for smaller coding rates of 1 / 2, 2 / 3, and 3 / 4 can be generated by taking the first 972, 1296, and 1458 bits of the 1620 information bit sequence as information bits, respectively.

[0079] For this first embodiment, the LDPC codeword determined by the above search process includes the following 1620 information bits (in hexadecimal format with the most significant bit on the right, e.g., C = 0011):

[0080] D258B757F74536ABD57CDEC440E7DAF7766C6BD1676196297F90F25733ECE6EAD95D5644B9ACD CE8768C34CD348BC465937DD1CB7BA4B2243A0EF502FBB813FB02690C1016550A9312A3F418E8C7E91B00CE3F2C0009692A604BA72C78101486189D6849C0AC59F16363989333CCBC6BFB0E10D169329F2E96C1FE92B6BE80A92AF402654DBBF1CDE4265998DC3008BA721BE957493B2E479861C078C46FC6C30A840367A621A5AFCE7EA1FF6E36E59303E467A50F3CEFB3B61D7B4E92BD4783847C41F7C5C8AC42733BB。

[0081] In the second embodiment, the requesting AP 110 is used to generate a sounding frame based on an LDPC codeword determined in the following manner. The LDPC codeword of this second embodiment is designed to be an LPDC codeword with 1944 bits, for a coding rate of 3 / 4 (corresponding to 1458 information bits) and a 4K-QAM scheme (e.g., defined by MCS12 and 13 according to the IEEE 802.11 standard framework). It should be understood that for the 4K-QAM scheme, there are 398 unique energy levels (i.e., each 4K-QAM symbol corresponds to one of the 398 unique energy levels). In one embodiment, these 398 unique energy levels can be divided into energy level ranges of multiple consecutive energy levels. For example, in one embodiment, the 398 unique energy levels of the 4K-QAM scheme can be divided into 121 energy level ranges or groups, each energy level range or group including 3 to 4 consecutive energy levels.

[0082] For this second embodiment, candidate LDPC codewords can be determined by performing multiple search rounds, and the final LDPC codeword can be selected based on the candidate LDPC codewords, where each search round includes one or more of the following 6 stages.

[0083] In the first stage, 121 4K-QAM symbols are randomly drawn, subject to each 4K-QAM symbol having a different energy level. The order of the different energy levels can be randomized. It should be understood that 121 4K-QAM symbols (each 4K-QAM symbol having 12 bits) correspond to 1452 bits, so that 1458 - 1452 = 6 additional information bits can be designed as padding bits.

[0084] In the second stage, 6 padding bits can be randomly selected.

[0085] In the third stage, the 1458 bits obtained in the previous two stages are LDPC-encoded with a coding rate of 3 / 4 to obtain a first LDPC rate 3 / 4 candidate codeword with 1944 bits.

[0086] In the fourth stage, the first 1620 bits of the first LDPC rate 3 / 4 candidate codeword generated in the previous stage are LDPC-encoded with a coding rate of 5 / 6 to obtain a second LDPC rate 5 / 6 candidate codeword with 1944 bits. Since one or more LDPC codes used by the AP 110 according to the embodiment are systematic codes, the first 1620 bits common to the first LDPC candidate codeword and the second LDPC candidate codeword uniquely determine all the bit contents of the first LDPC candidate codeword and the second LDPC candidate codeword.

[0087] In the fifth stage, 256-QAM, 1K-QAM, and 4K-QAM schemes with 1, 2, and 4 spatial streams are used to modulate the first LDPC candidate codeword and the second LDPC candidate codeword, thereby generating a total of 18 different QAM symbol streams s (for 18 different combinations of the two candidate codewords, three potential QAM schemes, and three potential values of the number of spatial streams).

[0088] In the sixth stage, for each generated sequence of QAM symbols s, the number of unique energy levels associated with the QAM symbol s of the corresponding QAM scheme is determined. At this stage, only those pairs of the first candidate codeword and the second candidate codeword can be stored as "good" candidate codewords, the number of different energy levels corresponding to multiple QAM symbols s of which is greater than the corresponding predefined threshold for each QAM scheme used. In one embodiment, for the 4K-QAM scheme, the corresponding predefined threshold for the number of different energy levels corresponding to multiple QAM symbols s is 137 (a total of 398 energy levels). For 1K-QAM modulation, the corresponding predefined threshold for the number of different energy levels corresponding to multiple QAM symbols s is 90 (a total of 109). For 256-QAM modulation, all 32 energy levels must be covered.

[0089] It should be understood that performing multiple search rounds using the above stages generates multiple pairs of the first LDPC candidate codeword and the second LDPC candidate codeword, each pair being associated with a specific number of unique energy levels for the 4K-QAM scheme, 1K-QAM scheme, and 256-QAM scheme. From the multiple pairs of the first LDPC candidate codeword and the second LDPC candidate codeword, the final actual LDPC codeword pair can be selected based on the following max-min criterion:

[0090]

[0091] It should be understood that the first LDPC codeword and the second LDPC codeword of the pair are uniquely specified by a sequence corresponding to 1620 information bits with a coding rate of 5 / 6. In one embodiment, LDPC codewords for smaller coding rates of 1 / 2, 2 / 3, and 3 / 4 can be generated by taking the first 972, 1296, and 1458 bits of the 1620 - bit information - bit sequence as information bits, respectively.

[0092] For this second embodiment, the LDPC codewords determined by the above - mentioned search process include the following 1620 information bits (in hexadecimal format with the most - significant bit on the right, e.g., C = 0011):

[0093] 7D91DB7AFE1704EE00946F932654AECF5F127BA340D5F364479229B1C01DE0FEF3772F362D13B44 7C1CA03FFA6D8F6011540DCE4DCD8A556681D7B03296FD78F8F8B3491709E30C70921E381461D4CDF9 65DF0C1D849EE57716CC60EC5B70E6CEAC19E84568ACEE107EDACD681B9D436BBA3122C124F156C7 85DEB995553878E30C46AC691A23FBFF50DBC1109AF4D62B40D57B2E69245035DB8020D9247C133E2921CBFB66B45C088BF840EA2D03CECCB28847F648FDD5E8E88503300C3614FC936FC36F856301238BAB.

[0094] In a third embodiment, the requesting AP 110 is used to generate a sounding frame based on one or more LDPC codewords determined by the following method for cases where more than one spatial stream is used, such as 2 or 4 spatial streams. It should be understood that if more than one spatial stream is used, the unique number of energy levels described in the context of the first and second embodiments above is actually divided among the different spatial streams. For example, for modulation using a 4K - QAM scheme and 4 spatial streams, there are approximately 140 unique energy levels, i.e., approximately 35 energy levels per spatial stream.

[0095] To increase the total number of unique energy levels and the number of energy levels per spatial stream, the requesting AP 110 according to this third embodiment is used to generate a sounding frame designed in the following manner using one or more LDPC codewords. To reduce the complexity and memory footprint of the one or more LDPC codewords used to generate the sounding frame according to this third embodiment, the LDPC codewords used in the above first embodiment can be reused by bit shifting and appending padding bits of a single stored LDPC codeword. More specifically, for the case of 2 streams, one or more LDPC codewords can be generated based on the following stages (some of which have been described in the context of the above first and second embodiments).

[0096] In the first stage, as in the first stage of the first embodiment, an LDPC codeword is generated, i.e., 109 1K-QAM symbols, 2 random bits, and 30 4K-QAM symbols are drawn.

[0097] In the second stage, 6 padding bits are copied from the first 6 bits (which will not be randomized) of the bits corresponding to the 109 1K-QAM symbols, as Figure 3b shown.

[0098] In the third stage, the information content of the next (e.g., second) LDPC codeword starts from the 7th bit of the 109 1K-QAM symbols, which represents a shift of the information bits including the codeword. In fact, the shift generates multiple different codeword contents (different information bits and thus different parities).

[0099] In the fourth stage, 12 padding bits are randomized and inserted at the end of the information part of the second LDPC codeword, and then encoded, i.e., 2 codewords with a rate of 3 / 4, to obtain a total of 2 * 1944 = 3888 bits.

[0100] After the fourth stage, this third embodiment can continue with the third to sixth stages described above for the first embodiment.

[0101] For this third embodiment, the LDPC codewords determined by the above process include the following 1620 information bits (in hexadecimal format with the most significant bit on the right, e.g., C = 0011):

[0102] C21631A2F8930807F4F6AF7400A57F9167DBA82FB4B7F4C545C88CD3BC268696743FDC2A66C64802E4D37D8D55D2F4E6B12AB2FCB79A9A0C1B9E30D8FE783DB385DC724E9E8F37D09153187E92EAB89F1B1A19983CCD96A24808878DE82E497ACC8F46692A75E83D78E39239ED8DB5394A9D54012F3F22DA85 704BAAC4C3CC35C27C77F257F9070FC94FCBB2BC6A656440A5DE521000EFCE764F753E8349DA567D5C26A27EE92A61D10F7CB792D1A07BEAAF86601DC7C949B482B31C58F9BD0DDA664A242AD17FBA28F78。

[0103] The 12, 18, or 24 padding bits corresponding to 2, 3, or 4 spatial streams respectively may include a plurality of padding bits selected from the following bit sequences: 1 1 1 0 0 0 0 0 0 1 0 1 0 1 0 1 0 0 1 0 0 1 1 1.

[0104] Figure 4 A table is shown that summarizes the realized values of the number of different energy levels resulting from the modulation of at least one LDPC codeword used by the AP 110 for different QAM schemes, coding rates, and numbers of spatial streams according to the different embodiments described above. In one embodiment, one or more of these values may constitute or may be used to determine one or more predefined thresholds.

[0105] Figure 5FIG. 0 shows a flowchart of steps of a method 500 for performing link adaptation (LA) for communication between a requesting AP 110 and one or more responsive non-AP stations 120. Method 500 includes step 501: generating a sounding frame based on at least one low-density parity-check (LDPC) codeword. Additionally, method 500 includes step 503: transmitting the sounding frame over a wireless link to one or more responsive non-AP stations (120) using one or more of a plurality of modulation and coding schemes (MCS) and / or one or more of a plurality of spatial streams, where each of the plurality of MCS defines a QAM scheme using a quadrature-amplitude modulation (QAM) constellation and a coding rate. Method 500 further includes step 505: receiving feedback including link performance metrics from one or more responsive non-AP stations 120. Additionally, method 500 includes step 507: based on the feedback from one or more responsive non-AP stations 120, selecting one of the plurality of MCS and a number of spatial streams of the plurality of spatial streams for transmitting data over the wireless link to one or more responsive non-AP stations 120.

[0106] As described above, for each coding rate of the plurality of MCS, at least one LDPC codeword is an LDPC codeword according to one or more LDPC codebooks specified by the IEEE802.11 WLAN Wi-Fi standard. Additionally, for each possible combination of the plurality of MCS and the plurality of spatial streams, at least one LDPC codeword is modulated into a corresponding plurality of QAM symbols (i.e., constellation points), where each QAM symbol of the plurality of QAM symbols corresponds to an energy level among a plurality of possible energy levels defined by the corresponding QAM scheme, and for each possible combination of the plurality of MCS and the plurality of spatial streams, the number of different actual energy levels corresponding to the plurality of QAM symbols is greater than or equal to a corresponding predefined threshold, e.g., based on Figure 4 the corresponding values listed in the table shown.

[0107] Since method 500 can be implemented by AP 110, other features of method 500 are directly implemented through the functions of AP 110 and the functions of its different embodiments described above and below.

[0108] Those skilled in the art should understand that the "blocks" ("units") in the various figures (methods and apparatuses) represent or describe the functions of the embodiments of the present invention (not necessarily independent "units" in hardware or software), thus equally describing the functions or features of the apparatus embodiments and the method embodiments (unit equivalent steps).

[0109] In the multiple embodiments provided in this application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the described device embodiments are merely exemplary. For example, the unit division is only a logical function division, and there can be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Additionally, the shown or described mutual coupling, direct coupling, or communication connection can be achieved through some interfaces. The indirect coupling or communication connection between devices or units can be achieved in electronic, mechanical, or other forms.

[0110] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units. They can be located in one place or distributed over multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment solution.

[0111] Furthermore, the functional units in the embodiments of the present invention can be integrated into one processing unit, or each unit can physically exist alone, or two or more than two units can be integrated into one unit.

Claims

1. A station (110) for performing link adaptation to communicate with at least one other station (120) via a wireless link, characterized in that, the station (110) is configured to: send a probe frame to the at least one other station (120) via the wireless link using one or more of a plurality of modulation and coding schemes (MCSs) and / or one or more of a plurality of spatial streams, wherein each of the plurality of MCSs defines a QAM scheme using an orthogonal amplitude modulation (QAM) constellation and a coding rate, and receive feedback including wireless link performance metrics from the at least one other station; select one of the plurality of MCSs and the number of spatial streams to send to the at least one other station (120) via the wireless link based on the feedback from the at least one other station (120); generate the probe frame based on at least one low density parity check (LDPC) codeword, wherein, for each coding rate of the plurality of MCSs, the at least one LDPC codeword is an LDPC codeword according to one or more LDPC codebooks specified by the IEEE 802.11 WLAN standard; for each combination of the plurality of MCSs and the plurality of spatial streams, the at least one LDPC codeword is modulated into a plurality of QAM symbols, wherein each of the plurality of QAM symbols corresponds to one of a plurality of energy levels defined by a corresponding QAM scheme, and for each combination of the plurality of MCSs and the plurality of spatial streams, the number of different energy levels corresponding to the plurality of QAM symbols is greater than a corresponding predefined threshold.

2. The station (110) according to claim 1, characterized in that, a plurality of consecutive energy level subsets of the plurality of energy levels define a plurality of energy level ranges, the plurality of energy level ranges including: an energy level range including the minimum energy level of the plurality of energy levels and an energy level range including the maximum energy level of the plurality of energy levels, wherein at least one of the plurality of QAM symbols corresponds to an energy level within the energy level range including the minimum energy level of the plurality of energy levels, and at least one other QAM symbol of the plurality of QAM symbols corresponds to an energy level within the energy level range including the maximum energy level of the plurality of energy levels.

3. The station (110) according to claim 2, characterized in that, each of the plurality of energy level ranges includes at least 2, 3, 4, 5, 10, 20, 25 or 50 consecutive energy levels of the plurality of energy levels.

4. The station (110) according to claim 2 or 3, characterized in that, for each energy level range, at least one of the plurality of QAM symbols corresponds to an energy level within the energy level range.

5. The station (110) according to claim 4, characterized in that, the plurality of energy levels corresponding to the plurality of QAM symbols are substantially uniformly distributed within the plurality of energy level ranges.

6. The station (110) according to any one of the above claims, Characterized in that, The multiple consecutive energy level subsets of the multiple energy levels define multiple energy level ranges, wherein, for the MCS corresponding to the 4096-QAM modulation scheme among the multiple MCSs, the station (110) is configured to modulate the at least one LPDC codeword into multiple 4096-QAM symbols, wherein at least N 4096 4096-QAM symbols belong to different energy level ranges, where N 4096 is greater than 120, especially equal to 137.

7. The station (110) according to any one of the above claims, Characterized in that, The multiple consecutive energy level subsets of the multiple energy levels define multiple energy level ranges, wherein, for the MCS corresponding to the 1024-QAM modulation scheme among the multiple MCSs, the station (110) is used to modulate the at least one LPDC codeword into multiple 1024-QAM symbols, wherein at least N 1024 1024-QAM symbols belong to different energy level ranges, where N 1024 is greater than 80, especially equal to 90.

8. The station (110) according to any one of the above claims, Characterized in that, For the MCS corresponding to the 256-QAM modulation scheme among the plurality of MCSs, the station (110) is configured to modulate the at least one LDPC codeword into a plurality of 256-QAM symbols having 32 256-QAM constellation points, wherein the 32 256-QAM constellation points have different energy levels.

9. The station (110) according to any one of claims 1 to 8, Characterized in that, The at least one LDPC codeword includes an information bit portion, and the information bit portion of the at least one LDPC codeword is based on the following hexadecimal representation, wherein the right bit is the most significant bit: D258B757F74536ABD57CDEC440E7DAF7766C6BD1676196297F90F25733ECE6EAD95D5644B9ACD CE8768C34CD348BC465937DD1CB7BA4B2243A0EF502FBB813FB02690C1016550A9312A3F418E8C7E91B00CE3F2C0009692A604BA72C78101486189D6849C0AC59F16363989333CCBC6BFB0E10D169329F2E96C1FE92B6BE80A92AF402654DBBF1CDE4265998DC3008BA721BE957493B2E479861C078C46FC6C30A840367A621A5AFCE7EA1FF6E36E59303E467A50F3CEFB3B61D7B4E92BD4783847C41F7C5C8AC42733BB.

10. The station (110) according to any one of claims 1 to 8, Characterized in that, The at least one LDPC codeword includes an information bit portion, and the information bit portion of the at least one LDPC codeword is based on the following hexadecimal representation, wherein the right bit is the most significant bit: 7D91DB7AFE1704EE00946F932654AECF5F127BA340D5F364479229B1C01DE0FEF3772F362D13B44 7C1CA03FFA6D8F6011540DCE4DCD8A556681D7B03296FD78F8F8B3491709E30C70921E381461D4CDF9 65DF0C1D849EE57716CC60EC5B70E6CEAC19E84568ACEE107EDACD681B9D436BBA3122C124F156C7 85DEB995553878E30C46AC691A23FBFF50DBC1109AF4D62B40D57B2E69245035DB8020D9247C133E2921CBFB66B45C088BF840EA2D03CECCB28847F648FDD5E8E88503300C3614FC936FC36F856301238BAB。 11. The station (110) according to any one of claims 1 to 8, characterized in that, the at least one LDPC codeword includes an information bit part, and the information bit part of the LDPC codeword is based on the following hexadecimal representation, wherein the right bit is the most significant bit: 5614AA7AF3390CDC1B0DEBCA5BBB27FD3208A5170E50FB6F6A661ECE631680FC05CA9B42F7C59BEB4A4E6B484ED460013C24F365F2117F3868B061F71B77024C51A62EB852B6AF03AD79039E57EFFEB9A3C9CACA081AD4BE7BB6524931D0B897990F07D32E52FFE12B878F6B995644314918495962128D0FF82B35104864EBF43B9E354C491647EEC42ED77A16288EAAE22608B96F9E1621E6D78D88D59ECE485245626A19A737DB0777B1040F20647AD9E66DE091B383076BBD328EA986AD84B8EEB1CD1CC3021C3985E。 12. The station (110) according to any one of the above claims, characterized in that, the sounding frame is an empty data packet NDP frame, in particular a fast link adaptation training physical layer protocol data unit PPDU.

13. The station (110) according to any one of the above claims, characterized in that, the wireless link performance metric includes the bit error rate BER of the probe frames of the at least one additional station (120).

14. The station (110) according to any one of the above claims, characterized in that, the station (110) is an access point AP (110), and the at least one additional station (120) is a non-AP station (120).

15. The station (110) according to any one of the above claims, characterized in that, the at least one LDPC codeword includes at least a first LDPC codeword and a second LDPC codeword, wherein the first LDPC codeword includes 1944 bits, wherein the information bit part has 1458 bits, and the information bit part includes: 1090 bits corresponding to 109 1024-QAM symbols, 2 padding bits, 360 bits corresponding to 30 4096-QAM symbols, and another 6 padding bits, wherein the another 6 padding bits are the same as the first 6 bits of the 1090 bits corresponding to the 109 1024-QAM symbols.

16. The station (110) according to claim 15, characterized in that, the second LDPC codeword includes 1944 bits, wherein the information bit part has 1458 bits, and the information bit part includes: the last 4 bits of a subset of the 1090 bits of the first LDPC codeword corresponding to the first 1024-QAM symbol of the 109 1024-QAM symbols, the other 1080 bits of the first LDPC codeword corresponding to the other 108 1024-QAM symbols, 2 padding bits, the 360 bits of the first LDPC codeword corresponding to 30 4096-QAM symbols, and another 12 padding bits.

17. The station (110) according to claim 15 or 16, characterized in that, the information bit part of the first LDPC codeword and / or the second LDPC codeword is based on the following hexadecimal representation, wherein the right bit is the most significant bit: C21631A2F8930807F4F6AF7400A57F9167DBA82FB4B7F4C545C88CD3BC268696743FDC2A66C64802E4D37D8D55D2F4E6B12AB2FCB79A9A0C1B9E30D8FE783DB385DC724E9E8F37D09153187E92EAB89F1B1A19983CCD96A24808878DE82E497ACC8F46692A75E83D78E39239ED8DB5394A9D54012F3F22DA85 704BAAC4C3CC35C27C77F257F9070FC94FCBB2BC6A656440A5DE521000EFCE764F753E8349DA567D5C26A27EE92A61D10F7CB792D1A07BEAAF86601DC7C949B482B31C58F9BD0DDA664A242AD17FBA28F78。 18. The station (110) according to claim 17, wherein, the information bit part of the first LDPC codeword and / or the second LDPC codeword includes a plurality of padding bits selected from the following bit sequences: 1 1 1 0 0 0 0 0 0 1 0 1 0 1 0 1 0 0 1 0 0 1 1 1.

19. The station (110) according to any one of the above claims, wherein, the station includes an LPDC encoder for generating the at least one LDPC codeword using a systematic LDPC code.

20. A method (500) for performing link adaptation to communicate with at least one other station (120) via a wireless link, wherein, the method (500) includes: generating (501) a sounding frame based on at least one low density parity check LDPC codeword; transmitting (503) the sounding frame to the at least one other station (120) via the wireless link using one or more of a plurality of modulation and coding schemes MCS and / or one or more of a plurality of spatial streams, wherein each MCS of the plurality of MCSs defines a QAM scheme using an orthogonal amplitude modulation QAM constellation and a coding rate; receiving (505) feedback including link performance metrics from the at least one other station; selecting (507) one MCS of the plurality of MCSs and the number of spatial streams to transmit to the at least one other station via the wireless link based on the feedback from the at least one other station, wherein, For each coding rate of the plurality of MCSs, the at least one LDPC codeword is an LDPC codeword according to one or more LDPC codebooks specified by the IEEE 802.11 WLAN standard; For each combination of the plurality of MCSs and the plurality of spatial streams, the at least one LDPC codeword is modulated into a plurality of QAM symbols, wherein each QAM symbol among the plurality of QAM symbols corresponds to one energy level among a plurality of energy levels defined by a corresponding QAM scheme, and for each combination of the plurality of MCSs and the plurality of spatial streams, the number of different energy levels corresponding to the plurality of QAM symbols is greater than a corresponding predefined threshold.

21. A computer program product comprising a computer-readable storage medium, characterized in that, the computer-readable storage medium is configured to store program code which, when executed by a computer or a processor, causes the computer or the processor to execute the method (500) according to claim 20.

Images