Devices and methods for reliable communication in a wireless network

Abstract

A wireless local area network, WTAN, station (110; 120) is disclosed for communication with a further WTAN station (120; 110) in a WTAN (100). The WTAN station (110; 120) is configured to communicate with the further WLAN station (120; 110) using an interference mitigation, IM, operation mode, wherein in the IM operation mode the WLAN station (110; 120) is configured to send a frame to the further WLAN station (120; 110) using a plurality of frequency subcarriers, wherein a payload of the frame comprises data associated with a plurality of data frequency subcarriers and a plurality of IM pilots interleaved with the data and associated with a plurality of IM pilot frequency subcarriers, and wherein the WLAN station (110; 120) is further configured to provide information to the further WLAN station (120; 110) indicative of the location in frequency of the plurality of IM pilot frequency subcarriers.

Description

[0001] DEVICES AND METHODS FOR RELIABLE COMMUNICATION IN A WIRELESS NETWORK

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to wireless communications. More specifically, the present disclosure relates to devices, in particular access points (APs) and non-AP stations, and methods for reliable communication in a wireless local area network, in particular a Wi-Fi network in accordance with the IEEE 802.11 framework of standards.

[0004] BACKGROUND

[0005] Uncontrolled and unexpected interference is one of the main factors preventing high reliability in wireless communication networks, in particular Wi-Fi networks. Interfering signals may occur in any bandwidth used within the Wi-Fi network. Narrowband interference, for instance, may arise from several sources, such as Wi-Fi interference, 3GPP transmissions in unlicensed bands, 2 MHz Narrowband-Assisted UWB (as part of IEEE 802.15.4ab), specifically in the 6GHz band, and 1 / 2 / 4 MHz Bluetooth signals, in the 2.4GHz band. Interference can arise at any time, e.g. before or during the transmission over a Wi-Fi link of a physical protocol data unit, PPDU, namely during transmission of the data-carrying part of a frame or packet. If the Wi-Fi transmitter identifies an ongoing interfering transmission in a certain frequency sub-band, it can refrain from using the corresponding sub-channel, for instance, by using preamble puncturing. This type of solution, however, cannot address unexpected interference arising during the transmission of a PPDU, which threatens the link reliability.

[0006] SUMMARY

[0007] It is an objective of the present disclosure to provide improved devices, in particular access points (APs) and non-AP stations, and methods for reliable communication in a wireless local area network, in particular a Wi-Fi network in accordance with the IEEE 802.11 framework of standards.

[0008] The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures. In the following one or more of the following acronyms and abbreviations may be used:

[0009] AP Access Point

[0010] BSS Basic Service Set

[0011] CFO Carrier Frequency Offset

[0012] IDFT / IFFT Inverse Discrete / F ast F ourier Transform

[0013] IEEE Institute of Electrical and Electronics Engineers

[0014] IM Interference Mitigation

[0015] LDPC Low Density Parity Check

[0016] MCS Modulation and Coding Scheme (Rate)

[0017] OBSS Overlapping Basic Service Set

[0018] OFDM / A Orthogonal Frequency Division Multiplexing / Multiple-Access

[0019] PER Packet Error Rate

[0020] PPDU PHY (PHysical Layer) Protocol Data Unit

[0021] QAM Quadrature Amplitude Modulation

[0022] RU Resource Unit

[0023] SIR Signal to Interference power Ratio

[0024] SNR Signal to Noise power Ratio

[0025] STA Station (used extensively in 802.11 ), may be an AP STA or a non-AP STA

[0026] TXOP Transmission (TX) OpportunityUHR Ultra High Reliability

[0027] U-SIG Universal SIG (name of a signal field in 802.1 Ibe / bn)

[0028] UHR-SIG Ultra High Reliability SIG (name of a field in 802.1 Ibn).

[0029] UWB Ultra-Wide-Band

[0030] According to a first aspect a transmitter wireless local area network, WLAN, station is provided for communication with a further receiver WLAN station in a WLAN. The WLAN station according to the first aspect is configured to communicate with the further WLAN station using an interference mitigation, IM, operation mode, wherein in the IM operation mode the WLAN station according to the first aspect is configured to transmit a PPDU to the further WLAN station using a plurality of frequency subcarriers, wherein a pay load of the frame comprises data associated with a plurality of data frequency subcarriers and a plurality of IM pilots interleaved with, i.e. between the data and associated with a plurality of IM pilot frequency subcarriers. The WLAN station according to the first aspect is further configured to provide information to the further WLAN station indicative of the location in frequency of the plurality of IM pilot frequency subcarriers within the transmitted PPDU. Based on the information indicative of the location in frequency of the plurality of IM pilot frequency subcarriers the WLAN STA that receives the PPDU may use the IM pilots in their correct frequency location, wherein this location is different from the location used by other neighbouring WLAN stations which are also operating in IM operation mode. The WLAN STA that transmits the PPDU can hence reduce the probability of overlap in time and frequency between the IM pilots it deploys and IM pilots deployed by another (e.g. OBSS WLAN) STA that transmits its PPDU.

[0031] In a further possible implementation form, the PPDU comprises a header portion and the header comprises, i.e. contains the information indicative of the location of the plurality of IM pilot frequency subcarriers within the PPDU.

[0032] In a further possible implementation form, the header portion comprises a U-SIG field or a UHR-SIG field and the U-SIG field or the UHR-SIG field comprises the information indicative of the location of the plurality of IM pilot frequency subcarriers.

[0033] In a further possible implementation form, the WLAN station according to the first aspect is an access point, AP, configured to transmit a plurality of Beacon frames and wherein each Beacon frame comprises the information indicative of the location of the plurality of IM pilot frequency subcarriers.

[0034] In a further possible implementation form, the information indicative of the location of the plurality of IM pilot frequency subcarriers comprises an explicit indication of the location of the plurality of IM pilot frequency subcarriers.

[0035] In a further possible implementation form, the WLAN station according to the first aspect comprises a low-density parity check, LDPC, tone mapper and the WLAN station according to the first aspect is configured to interleave the plurality of IM pilots with the data using the LDPC tone mapper.

[0036] In a further possible implementation form, the location of the plurality of IM pilot frequency subcarriers is defined by a parameter associated with the LDPC tone mapper and the information indicative of the location of the plurality of IM pilot frequency subcarriers comprises the parameter.

[0037] In a further possible implementation form, the information indicative of the location of the plurality of IM pilot frequency subcarriers is indicative of a shift parameter indicating a shift of the location of the plurality of IM pilot frequency subcarriers relative to a default location of the plurality of IM pilot frequency subcarriers.In a further possible implementation form, the information indicative of the location of the plurality of IM pilot frequency subcarriers comprises an implicit indication of the location of the plurality of IM pilot frequency subcarriers, wherein the WLAN station and the further WLAN station are configured to determine the location of the plurality of IM pilot frequency subcarriers based on the implicit indication.

[0038] In a further possible implementation form, the WLAN station according to the first aspect and the further WLAN station are configured to determine the location of the plurality of IM pilot frequency subcarriers based on the implicit indication using a modulo operation.

[0039] In a further possible implementation form, the implicit indication of the location of the plurality of IM pilot frequency subcarriers comprises one or more of the following: the BSS colour; the PPDU duration; the TXOP duration; and / or the STA_ID.

[0040] In a further possible implementation form, the plurality of IM pilots are a plurality of zero energy IM pilots.

[0041] In a further possible implementation form, the WLAN station according to the first aspect is an access point, AP, or a non-AP station and the further WLAN station is a non-AP station or an AP.

[0042] According to a second aspect a method is provided for operating a wireless local area network, WLAN, station for communication with a further WLAN station in a WLAN, wherein the WLAN station is configured to communicate with the further WLAN station using an interference mitigation, IM, operation mode, wherein in the IM operation mode the WLAN station is configured to send a PPDU to the further WLAN station using a plurality of frequency subcarriers, wherein a payload of the PPDU comprises data payload associated with a plurality of data frequency subcarriers and a plurality of IM pilots interleaved with, i.e. between the data payload and associated with a plurality of IM pilot frequency subcarriers. The method according to the second aspect comprises a step of providing information to the further WLAN station indicative of the location of the plurality of IM pilot frequency subcarriers.

[0043] The method according to the second aspect can be performed by the WLAN station according to the first aspect. Thus, further features of the method according to the second aspect result directly from the functionality of the WLAN station according to the first aspect, as well as its different implementation forms described above and below.

[0044] According to a third aspect a computer program product is provided, comprising program code which causes a computer or a processor to perform the method according to the second aspect, when the program code is executed by the computer or the processor.

[0045] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims.

[0046] BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:

[0048] Fig. 1 shows a schematic diagram illustrating a wireless local area network including a WLAN station according to an embodiment in the form of an AP in communication with a plurality of further WLAN stations in the form of non-AP stations;Figs. 2a, 2b and 2c show diagrams illustrating an adverse effect of overlapping zero-energy IM pilots;

[0049] Fig. 3 shows a diagram illustrating an adverse impact of overlapping zero-energy IM pilots on link performance;

[0050] Fig. 4 shows a schematic diagram illustrating a transmission processing chain implemented by a WLAN station according to an embodiment; and

[0051] Fig. 5 shows a flow diagram illustrating a method according to an embodiment for operating a WLAN station.

[0052] In the following, identical reference signs refer to identical or at least functionally equivalent features.

[0053] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] In the following description, reference is made to the accompanying figures, which form part of the disclosure, which illustrate specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

[0055] For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and / or aspects described herein may be combined with each other, unless specifically noted otherwise.

[0056] Figure 1 shows a wireless local area network, WLAN, 100 in accordance with the IEEE 802.11 framework of standards (also referred to as a Wi-Fi network 100). The Wi-Fi network 100 comprises a transmitter WLAN station 110 (also referred to as Wi-Fi station 110 herein), which may be implemented in the form of a multi-antenna AP 110, and a plurality of receiver WLAN stations 120 (also referred to as further WLAN or Wi-Fi stations 120 herein) in the form of, for instance, non-AP stations 120. As illustrated in figure 1, by way of example, the non-AP stations 120 may comprise smartphones, laptop computers, tablet computers, desktop computers or other types of wireless devices 120. In the following several embodiments of the AP 110 as transmitter WLAN station 110 will be described in more detail below. As will be appreciated, however, the non-AP stations 120 may be implemented as a transmitter WLAN station as well in accordance with the following embodiments.

[0057] As further illustrated in figure 1, the AP 110 comprises a processing circuitry 111 and a communication interface 113, in particular a wireless communication interface 113 enabling communication in accordance with the IEEE 802.11 framework of standards over a channel 130. The processing circuitry 111 may be implemented in hardware and / or software and may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs),or general-purpose processors. The AP 110 may further comprise a memory 115 configured to store executable program code which, when executed by the processing circuitry 111, causes the AP 110 to perform the functions and methods described herein.

[0058] Likewise, as indicated in figure 1, the non-AP station(s) 120 comprise aprocessing circuitry 121 and a communication interface 123, in particular a wireless communication interface 123 enabling a communication in accordance with the IEEE 802.11 framework of standards over the channel 130. The processing circuitry 121 may be implemented in hardware and / or software and may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The non-AP station(s) 120 may further comprise a memory 125 configured to store executable program code which, when executed by the processing circuitry 121, causes the non-AP station(s) 120 to perform the functions and methods described herein.

[0059] As will be described in more detail further below, the AP 110 (or likewise each of the non-AP stations 120) is configured to incorporate dedicated Interference Mitigation, IM, pilots (that are known to both transmitter and receiver) into a transmitted PPDU for using these IM pilots to estimate the covariance (including its variation in time and frequency) of the interference at the receiver, e.g. the non-AP stations 120 and then mitigate the interference. More specifically, the AP 110 is configured to use an IM operation mode, wherein in the IM operation mode the AP 110 is configured to send a PPDU to the non-AP station(s) 120 using a plurality of frequency subcarriers, wherein a payload of the frame comprises data payload associated with a plurality of data frequency subcarriers and a plurality of IM pilots interleaved with, i.e. between the data payload and associated with a plurality of IM pilot frequency subcarriers. Such an IM operation mode is disclosed in more detail in PCT / EP2024 / 055923, which is fully incorporated by reference herein.

[0060] In PCI7EP2024 / 055923 it has been suggested that the IM pilots used by the AP 110 may have a nonzero energy or contain no energy (meaning, in effect, that nothing is transmitted on the time-frequency resources dedicated to the IM pilots). If zeroenergy IM pilots are transmitted, then concurrent transmissions (from multiple transmitters) employing zero-energy IM pilots occupying the same frequency resources can create a problem where the WLAN STA that is intended to receive the PPDU cannot ‘see’ or ‘observe’ the interference, and thus can neither estimate nor mitigate it. As will be appreciated, this problem is unique to zero-energy IM pilots. In the case of nonzero energy IM pilots, even if they are overlapping (using the same frequency resources), the receiver can subtract the known signal and the resulting residual signal is the interfering signal (plus some noise) whose covariance can still be reliably estimated. In the following, the terms ‘(non)zero IM pilots’ and ‘(non)zero-energy IM pilots’, respectively, will be used interchangeably, conveying the same meaning.

[0061] The problem outlined above is illustrated in figures 2a-c, wherein (for the sake of simplifying the discussion) it is assumed that, in the two WLAN links involved in the considered communication scenario, the two STAs operating in IM operation mode both transmit either zero or nonzero IM pilots. Figure 2a shows an overlay of desired data subcarriers (solid light grey), desired nonzero IM pilots (dashed light grey), interfering data subcarriers (solid dark grey) and interfering nonzero IM pilots (dashed dark grey). After subtracting the known (nonzero) IM pilots, the receiver ‘sees’ on these resources only the interfering IM pilots (as illustrated in figure 2b) and can use those to estimate and mitigate the interference. Figure 2c shows what happens when the IM pilots (both desired and interference) are zero-energy and occupy the same resources. In this case the receiver cannot ‘see’ the interference and therefore cannot mitigate it.

[0062] Figure 3 illustrates the impact of overlapping zero-energy IM pilots on the performance. Here the packet error rate, PER, measured at a receiver of a STA (equipped with 4 receive antennas) performing IM in the presence of a single-stream interference (occupying the full 20MHz channel bandwidth and characterized by SIR of 5 dB) is plotted as a function of theSNR; the desired signal is a single stream with MCS 6 (64QAM rate 2 / 3) transmitted from a (ITx-antenna) STA operating in IM mode. The curve A shows the performance when both desired and interfering signals are generated using nonzero IM pilots whose location is set with a random offset in OFDM symbol timing and a random carrier frequency offset, CFO (uniformly distributed in the range [— 20ppm, +20ppm] ), between the desired and interference signals. The curve C shows the performance with zero IM pilots with perfect frequency synchronization (no CFO) but with a random timing offset. As will be appreciated, there is a major impact on the performance in this case, as the random time offset means many packets still experience an IM-pilot overlap where the interference cannot be identified (or ‘seen’ by the receiver). The curve B shows the performance using zero IM pilots with random time and frequency offsets. As will be appreciated, the results for curve B are far better than for curve C, because with random frequency offsets there is little overlap and the receiver is able to ‘see’ much of the interference. However, there is still enough overlap to cause a non-negligible performance degradation (higher PER) compared to the nonzero IM pilot case (curve A).

[0063] To address the problem illustrated in figures 2a-c and 3, the AP 110 (or likewise the non-AP station(s) 120), in addition to using the IM operation mode described above by interleaving IM pilots with the data payload in the PPDU transmitted to the peer WLAN STA that is intended to receive it, is configured to transmit the IM pilots on particular frequency locations (which can be different between neighbouring transmitters belonging to different BSSs) and provide information to the WLAN STA that is intended to receive this PPDU, e.g. the non-AP station(s) 120 indicative of the location of the plurality of IM pilots, in particular the location of the plurality of IM pilot frequency subcarriers associated with the plurality of IM pilots. This allows both the WLAN STA that transmits the PPDU, e.g. the AP 110 and the WLAN STA that is intended to receive the PPDU, e.g. the non-AP station(s) 120 to know on what resources the IM pilots, which in an embodiment may be zero-energy IM pilots, are transmitted, and to reduce the probability of an overlap between the location of IM pilots in PPDUs that are transmitted by neighbouring BSSs.

[0064] Figure 4 illustrates the transmission processing chain implemented by the AP 110 (or likewise the non-AP station(s) 120) according to an embodiment for LDPC-encoded data transmission as defined by the IEEE 802.11 framework of standards, in particular IEEE 802.11bn, 802.11be and 802.1 lax. Bits from the MAC layer undergo pre-FEC padding in a block 401 (if applicable), scrambling in a block 403, encoding using an LDPC encoder 405, and post-FEC padding 406. If multiple spatial streams are used the post-FEC padded bits are divided by a stream parser 407 between the spatial streams before they are fed into a respective constellation mapper 409 which applies a constellation mapping procedure, such as QAM, as illustrated in figure 4, onto the bit streams. The resulting modulation symbols, in particular QAM symbols are interleaved in frequency using a LDPC Tone Mapper 411 followed by spatial mapping (e.g. beamforming) and then mapping to subcarriers (see block 413) before the application of the IDFT / IFFT operation by blocks 415, which creates the samples of the OFDM symbol in time domain. Finally, a respective CP may be inserted by block 417 and further analog and RF blocks (not illustrated) may generate the actual antenna feed signals, based on the output from the preceding blocks, for generating the RF transmission to the receivers). In the embodiment illustrated in figure 4 the transmission processing chain implemented by the AP 110 (or likewise the non-AP station(s) 120) may further comprise a block 414 for including CFO pilots in the transmission.

[0065] As will be appreciated, in the embodiment shown in figure 4, the ability to spread the IM pilots over the signal’s bandwidth is achieved by the additional block 410. Thus, instead of inputting N_SD QAMs into the LDPC Tone Mapper 411 (which interleaves them in frequency), the blocks 409 and the block 410 of the AP 110 insert N_SD_IM QAMs and N_SP_IM IM pilots (where N_SD_IM+N_SP_IM=N_SD) into the LDPC tone mapper 411. The IM Pilots can be inserted contiguously at the beginning or the end (more sophisticated locations can be used as well). The operation of the LDPC tone mapper 411 ensures that the IM Pilots are almost evenly spread at the output. At the output of the LDPC tone mapper 411, the distance between consecutively inserted inputs (e.g. IM pilots) is defined by the parameter D_TM. Further details of the embodimentof the transmission chain architecture illustrated in figure 4 are provided in PCT / EP2024 / 055923, which is fully incorporated herein by reference.

[0066] If the block of IM pilots illustrated in figure 4 is denoted as an ‘IM Pilot Block’, then shifting this block up or down by the length of a single ‘block’ would shift the location of the IM pilots at the output of the LDPC tone mapper 411 by a single subcarrier either up or down, depending on the direction of the shift at the input.

[0067] According to a further embodiment, the AP 110 (or likewise the non-AP station(s) may be configured to spread the IM pilots by defining fixed locations (i.e. fixed frequency subcarriers) for the IM pilots. This means both IM pilot and data tones have pre-defined locations known to both transmitter, e.g. AP 110, and receiver, e.g. non-AP station(s) 120.

[0068] In an embodiment, the information indicative of the location of the plurality of IM pilot frequency subcarriers provided by the transmitter, e.g. AP 110, to the receiver, e.g. non-AP station(s) 120, comprises an explicit indication of the location of the plurality of IM pilot frequency subcarriers. In an embodiment, the explicit indication may be contained in a U-SIG or UHR-SIG field of the PHY preamble of the frame. In a further embodiment, the explicit indication of the location of the plurality of IM pilot frequency subcarriers may be provided as part of a beacon frame.

[0069] In the following example it is assumed that ~10% of the resources, i.e. frequency subcarriers, are used for IM pilots (out of all subcarriers available for data when IM operation mode is not activated). In this case the choice of one out of ~10 options for the IM pilot location would have to be signalled. For instance, a shift of up to 9 subcarriers from the default (zero-index) location of the IM pilots (with IM pilots spread by the LDPC Tone Mapper 411, indicating a shift of a contiguous IM pilot block at the input to the LDPC tone mapper 411 (for fixed location, it means a direct shift of the IM pilots). Additionally or alternatively, a different value for the parameter D_TM may be provided (specifically for the LDPC tone mapper approach). According to a first possible implementation 2-4 bits may be used in the U-SIG field (which means a per-PPDU indication, e.g. a shift of 0-9 from the default / zero-index). Alternatively, 2-4 bits in the UHR-SIG field may be used (which means a per-PPDU indication as well). According to a further variant the indication may be included in a beacon frame (transmitted semi-periodically every ~102 msec), which means a fixed indication to be used by STAs in the BSS, at least until the next beacon (all PPDUs within the beacon interval).

[0070] According to further embodiments the information indicative of the location of the plurality of IM pilot frequency subcarriers comprises an implicit indication of the location of the plurality of IM pilot frequency subcarriers in that the transmitter, e.g. the AP 110, and the receiver, e.g. the non-AP station(s) 120, are configured to determine the location of the plurality of IM pilot frequency subcarriers based on the implicit indication. In other words, both the transmitter, e.g. the AP 110, and the receiver, e.g. the non-AP station(s) 120, use an agreed rule for determining the location of the plurality of IM pilot frequency subcarriers based on the implicit indication.

[0071] In an embodiment, the location of the IM pilots used by each STA 110, 120 (transmitting in the IM mode) is pseudo-randomly defined either dynamically (per PPDU) based on a specified function of the bit content of certain predefined field(s) in the PHY preamble, or semi-statically, depending e.g. on the BSS colour characterizing the BSS to which the STA is associated. The location indication may be defined using one of the following operations on the decimal value of the bit combination of the predefined field(s): Modulo (e.g. 10) to determine how many subcarriers to shift, in multiples of “IM pilot block size”, at the input to LDPC tone mapper 411; Modulo (e.g. 10) to determine how many subcarriers to shift the IM pilots (without LDPC tone mapper, meaning a fixed parameter-dependent subcarrier allocation for IM pilots); Change the value of D_TM (used for specifying the LDPC tone mapper operation), which may be done either explicitly or via a shift from the spec-defined value. In an embodiment, the modulo operation for determining the location of the plurality of IM pilotfrequency subcarriers based on the implicit indication may be performed using one of the following PHY preamble fields: BSS colour; PPDU duration; TXOP duration; and / or STA_ID. For example, if BSS colour = 13, then 13 (mod 10) = 3 and the IM pilots are shifted by 3 'IM blocks' (30% of subcarriers) at the input to the LDPC tone-mapper 411.

[0072] Figure 5 shows a flow diagram illustrating steps of a method 500 for operating a WLAN station, such as the AP 110, for communication with a further WLAN station, such as the non-AP station(s) 120, in the WLAN 100. As already described above, the WLAN station, e.g. AP 110, is configured to communicate with the further WLAN station, e.g. non-AP station(s) 120, using an interference mitigation, IM, operation mode, wherein in the IM operation mode the WLAN station, e.g. AP 110, is configured to send a frame to the further WLAN station, e.g. non-AP station(s) 120, using a plurality of frequency subcarriers, wherein a payload of the frame comprises data associated with a plurality of data frequency subcarriers and a plurality of IM pilots interleaved with, i.e. between the data and associated with a plurality of IM pilot frequency subcarriers. The method 500 comprises a step 501 of providing information to the further WLAN station, e.g. non-AP station(s) 120, indicative of the location of the plurality of IM pilot frequency subcarriers.

[0073] The person skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step).

[0074] In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely logical function division and may be another division in an actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

[0075] The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

[0076] In addition, functional units in the embodiments of the disclosure may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.

Claims

CLAIMS1. A wireless local area network, WLAN, station (110; 120) for communication with a further WLAN station in a WLAN (100), wherein the WLAN station (110; 120) is configured to communicate with the further WLAN station (120; 110) using an interference mitigation, IM, operation mode, wherein in the IM operation mode the WLAN station (110; 120) is configured to transmit a PPDU to the further WLAN station (120; 110), wherein the PPDU comprises data payload associated with a plurality of data frequency subcarriers and a plurality of IM pilots interleaved with the data pay load and associated with a plurality of IM pilot frequency subcarriers, and wherein the WLAN station (110; 120) is further configured to provide information to the further WLAN station (120; 110) indicative of the location of the plurality of IM pilot frequency subcarriers within the transmitted PPDU.

2. The WLAN station (110; 120) of claim 1, wherein the PPDU comprises a header portion and wherein the header portion comprises the information indicative of the location of the plurality of IM pilot frequency subcarriers within the PPDU.

3. The WLAN station (110; 120) of claim 2, wherein the header portion comprises a U-SIG field or a UHR-SIG field and wherein the U-SIG field or the UHR-SIG field comprises the information indicative of the location of the plurality of IM pilot frequency subcarriers.

4. The WLAN station (110) of claim 1, wherein the WLAN station (110) is an access point, AP, (110) configured to transmit a plurality of Beacon frames and wherein each Beacon frame comprises the information indicative of the location of the plurality of IM pilot frequency subcarriers.

5. The WLAN station (110; 120) of any one of the preceding claims, wherein the information indicative of the location of the plurality of IM pilot frequency subcarriers comprises an explicit indication of the location of the plurality of IM pilot frequency subcarriers.

6. The WLAN station (110; 120) of claim 5, wherein the WLAN station (110; 120) comprises a low-density parity check, LDPC, tone mapper (411) and wherein the WLAN station (110; 120) is configured to interleave the plurality of IM pilots with the data using the LDPC tone mapper (411).

7. The WLAN station (110; 120) of claim 6, wherein the location of the plurality of IM pilot frequency subcarriers is defined by a parameter associated with the LDPC tone mapper (411) and wherein the information indicative of the location of the plurality of IM pilot frequency subcarriers comprises the parameter.

8. The WLAN station (110; 120) of claim 5 or 6, wherein the information indicative of the location of the plurality of IM pilot frequency subcarriers is indicative of a shift parameter indicating a shift of the location of the plurality of IM pilot frequency subcarriers relative to a default location of the plurality of IM pilot frequency subcarriers.

9. The WLAN station (110; 120) of any one of claims 1 to 4, wherein the information indicative of the location of the plurality of IM pilot frequency subcarriers comprises an implicit indication of the location of the plurality of IM pilot frequency subcarriers and wherein the WLAN station (110; 120) and the further WLAN station (120; 110) are configured to determine the location of the plurality of IM pilot frequency subcarriers based on the implicit indication.

910. The WLAN station (110; 120) of claim 9, wherein the WLAN station (110; 120) and the further WLAN station (120; 110) are configured to determine the location of the plurality of IM pilot frequency subcarriers based on the implicit indication using a modulo operation.

11. The WLAN station (110; 120) of claim 10, wherein the implicit indication of the location of the plurality of IM pilot frequency subcarriers comprises one or more of the following: a BSS colour; a PPDU duration; a TXOP duration; and / or a STA_ID.

12. The WLAN station (110; 120) of any one of the preceding claims, wherein the plurality of IM pilots are a plurality of zero energy IM pilots.

13. The WLAN station (110; 120) of any one of the preceding claims, wherein the WLAN station (110; 120) is an access point, AP, (110) or a non-AP station (120) and wherein the further WLAN station (120; 110) is a non-AP station (120) oran AP (110).

14. A method (500) for operating a wireless local area network, WLAN, station (110; 120) for communication with a further WLAN station in a WLAN (100), wherein the WLAN station (110; 120) is configured to communicate with the further WLAN station (120; 110) using an interference mitigation, IM, operation mode, wherein in the IM operation mode the WLAN station (110; 120) is configured to send a PPDU to the further WLAN station (120; 110), wherein the PPDU comprises data payload associated with a plurality of data frequency subcarriers and a plurality of IM pilots interleaved with the data payload and associated with a plurality of IM pilot frequency subcarriers, and wherein method (500) comprises providing (501) information to the further WLAN station (120; 110) indicative of the location of the plurality of IM pilot frequency subcarriers.

15. A computer program product comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method (500) of claim 14 when the program code is executed by the computer or the processor.

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