WO2023151774A1

WO2023151774A1 - Devices and methods for wireless communication in a wireless network

Info

Publication number: WO2023151774A1
Application number: PCT/EP2022/052957
Authority: WO
Inventors: Genadiy Tsodik; Shimon SHILO; Oded Redlich; Yoav Levinbook; Doron Ezri
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2022-02-08
Filing date: 2022-02-08
Publication date: 2023-08-17
Also published as: CN118648245A

Abstract

A wireless transmitter (120, 110) for communicating with a wireless receiver (110, 120) via a channel is disclosed. The wireless transmitter comprises a processing circuitry (121, 111) configured to obtain a digital sequence for generating a power amplifier transfer function estimation signal. Moreover, the wireless transmitter comprises a communication interface (123, 113) having a power amplifier (123a, 113a), wherein the communication interface is configured to amplify the power amplifier transfer function estimation signal using the power amplifier and to transmit the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver for estimating a transfer function of the power amplifier. The digital sequence has a peak-to-average power ratio, PAPR, larger than a first threshold value and a time domain power variance larger than a second threshold value.

Description

DEVICES AND METHODS FOR WIRELESS COMMUNICATION IN A WIRELESS NETWORK

TECHNICAL FIELD

The present disclosure relates to wireless communications. More specifically, the present disclosure relates to devices and methods for wireless communication in a wireless communication network.

BACKGROUND

IEEE 802.11 -based WLANs (also referred to as Wi-Fi networks) have become popular at an unprecedented rate. The 802.11 family of standards is constantly expanded by amendments and new generations to provide WLAN technology with new and improved technical features.

802.11 be (also referred to as "Wi-Fi 7") has introduced a new modulation of 4K-QAM which provides very high throughput but also requires a very high error vector magnitude (EVM). One of the impairments that contributes to EVM reduction is the nonlinearity of the power amplifier (PA) at the transmitter. In order to reduce the level of nonlinear components within the transmitted signal, a very large back-off is required which reduces the efficiency of the PA. However, if the nonlinearity can be compensated at the receiver, the trade-off between PA efficiency and EVM requirements can be resolved. Moreover, a smaller back-off results in a larger transmission power and, thus, extends the maximum transmission range of the transmitter.

SUMMARY

It is an objective to provide improved wireless devices for wireless communication in a wireless network, in particular an IEEE 802.11 based wireless communication network, i.e. a Wi-Fi network, as well as a corresponding method allowing for an efficient compensation of nonlinearities introduced by the power amplifier of a wireless transmitter.

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. According to a first aspect a wireless transmitter, in particular a non-access point, non-AP, station for communicating with a wireless receiver, in particular an AP, via a wireless communication channel is provided. The wireless transmitter comprising a processing circuitry configured to obtain a digital sequence for generating a power amplifier transfer function estimation signal. Moreover, the wireless transmitter comprises a communication interface having a power amplifier, wherein the communication interface is configured to amplify the power amplifier transfer function estimation signal using the power amplifier and to transmit the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver for estimating a transfer function of the power amplifier. The digital sequence has a peak-to-average power ratio, PAPR, larger than a first predefined threshold value and a time domain power variance larger than a second predefined threshold value. In an implementation form, the first predefined threshold value may be in a range between 10 and 20 dB, in particular 14 dB. In an implementation form, the second predefined threshold value may be in a range from 10'⁸ to 10'⁶, in particular the second predefined threshold value may have a value of 10'⁷, for instance, for a transmission bandwidth of 80 MHz. As will be appreciated, for other transmission bandwidths, such as 40, 160 or 320 MHz the preferred second predefined threshold value may differ.

Thus, a wireless transmitter is provided allowing for an efficient compensation of nonlinearities introduced by the power amplifier of the wireless transmitter. Embodiments disclosed herein make use of a digital sequence that has a large PAPR for ensuring the existence of nonlinear components in the power amplifier transfer function estimation signal as well as a large variance of power of time domain samples for allowing an accurate estimation of the power amplifier transfer function.

In a further possible implementation form, the processing circuitry is further configured to generate a channel transfer function estimation signal, wherein the communication interface is configured to amplify the channel transfer function estimation signal using the power amplifier and to transmit the amplified channel transfer function estimation signal via the channel to the wireless receiver for estimating a transfer function of the channel.

In a further possible implementation form, the communication interface is configured to transmit a physical protocol data unit, PPDU, with a preamble via the channel to the wireless receiver, wherein the preamble of the PPDU comprises the amplified power amplifier transfer function estimation signal. In a further possible implementation form, the preamble of the PPDU comprises an indication indicative of the presence of the amplified power amplifier transfer function estimation signal in the preamble of the PPDU.

In a further possible implementation form, the communication interface is configured to transmit the PPDU using a modulation and coding scheme, MCS, of a plurality of selectable MCSs to the wireless receiver, wherein using one or more of the plurality of selectable MCSs is indicative of the presence of the amplified power amplifier transfer function estimation signal in the preamble of the PPDU.

In a further possible implementation form, the preamble of the PPDU comprises a plurality of OFDM symbols and one or more of the plurality of OFDM symbols comprise, i.e. define the power amplifier transfer function estimation signal, wherein the preamble of the PPDU further comprises an indication indicative of the number of the more of the plurality of OFDM symbols comprising the power amplifier transfer function estimation signal.

In a further possible implementation form, the wireless transmitter comprises at least one further power amplifier and the processing circuitry is further configured to generate at least one further power amplifier transfer function estimation signal for the at least one further power amplifier and to generate a MIMO signal including the power amplifier transfer function estimation signal and the at least one further power amplifier transfer function estimation signal based on a P matrix, e.g. by multiplying each preamble comprising the one or more of the plurality of OFDM symbols of the respective signal with a respective portion of the P matrix.

In a further possible implementation form, the one or more of the plurality of OFDM symbols comprising the power amplifier transfer function estimation signal are one or more extra long training field, EHT-LTF, symbols of the PPDU.

In a further possible implementation form, the preamble of the PPDU comprises an indication indicative of the presence of the power amplifier transfer function estimation signal in the one or more EHT-LTF symbols of the PPDU.

In a further possible implementation form, the digital sequence comprises a sequence of constellation points In a further possible implementation form, the sequence of constellation points comprises a subsequence of constellations points and at least one further subsequence of constellations points and wherein the subsequence and the further subsequence are equal, i.e. the subsequence of constellations points comprises the same constellation points as the at least one further subsequence of constellation points.

In a further possible implementation form, the communication interface is configured to transmit the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver, if the communication interface has received an indication from the wireless receiver indicative of the wireless receiver being configured to perform a nonlinearity cancellation.

In a further possible implementation form, the communication interface is configured to receive a message from the wireless receiver comprising a PHY Capabilities Information Field, wherein the PHY Capabilities Information Field comprises the indication indicative of the wireless receiver being configured to perform a nonlinearity cancellation.

In a further possible implementation form, the wireless transmitter is a non-access point, non-AP, station or an access point, AP.

According to a second aspect a communication method between a wireless transmitter, in particular a non-AP station, and a wireless receiver, in particular an AP, via a wireless communication channel. The method comprises the steps of: obtaining a digital sequence for generating a power amplifier transfer function estimation signal; amplifying the power amplifier transfer function estimation signal using a power amplifier of the wireless transmitter; and transmitting the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver for estimating a transfer function of the power amplifier, wherein the digital sequence has a peak-to-average power ratio, PAPR, larger than a first predefined threshold value and a time domain power variance larger than a second predefined threshold value.

The method according to the second aspect of the present disclosure can be performed by the wireless transmitter according to the first aspect of the present disclosure. Thus, further features of the method according to the second aspect of the present disclosure result directly from the functionality of the wireless transmitter according to the first aspect of the present disclosure as well as its different implementation forms described above and below.

According to a third aspect a computer program product is provided, comprising a computer-readable storage medium for storing 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.

According to a further aspect a wireless receiver, in particular an AP, for communicating with a wireless transmitter, in particular a non-AP station, via a wireless communication channel is provided. The wireless receiver comprises a communication interface configured to receive a power amplifier transfer function estimation signal amplified by a power amplifier of the wireless transmitter via the channel from the wireless transmitter. Moreover, the wireless receiver comprises a processing circuitry configured to estimate a transfer function of the power amplifier of the wireless transmitter based on the power amplifier transfer function estimation signal for performing a nonlinearity cancellation based on the transfer function of the power amplifier. The digital sequence has a peak-to- average power ratio, PAPR, larger than a first predefined threshold value and a time domain power variance larger than a second predefined threshold value.

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.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Fig. 1 shows an exemplary wireless communication system including a wireless transmitter and a wireless receiver according to an embodiment;

Fig. 2 shows a schematic diagram illustrating a nonlinearity cancellation scheme implemented by a wireless receiver according to an embodiment; Fig. 3 shows a schematic diagram illustrating processing steps for determining a digital sequence for generating a power amplifier transfer function estimation signal by a wireless transmitter according to an embodiment;

Figs. 4a and 4b illustrate a time domain power of a first selected digital sequence with a large time domain power variance and a second non-selected sequence with a small time domain power variance;

Fig. 5 shows a table illustrating a BPSK based digital sequence of 242 tones (20 MHz) used by a wireless transmitter according to an embodiment;

Figs. 6a-d show tables illustrating a 4K-QAM based digital sequence of 242 tones (20 MHz) used by a wireless transmitter according to an embodiment;

Fig. 7 shows a table illustrating a BPSK based digital sequence of 484 tones (40 MHz) used by a wireless transmitter according to an embodiment;

Figs. 8a-d show tables illustrating a 4K-QAM based digital sequence of 484 tones (40 MHz) used by a wireless transmitter according to an embodiment;

Fig. 9 shows a table illustrating a BPSK based digital sequence of 996 tones (80 MHz) used by a wireless transmitter according to an embodiment;

Figs. 10a-i show tables illustrating a 4K-QAM based digital sequence of 996 tones (80 MHz) used by a wireless transmitter according to an embodiment; and

Fig. 11 shows a flow diagram illustrating steps of a communication method according to an embodiment.

In the following, identical reference signs refer to identical or at least functionally equivalent features. DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, 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.

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.

Figure 1 shows a wireless communication system 100 including an access point (AP) 110 configured to communicate with at least one associated non-AP station 120, which together may define a BSS. As will be appreciated, both the AP 110 as well as the non-AP station 120 can be a wireless transmitter and a wireless receiver. In the following, by way of example, the non-AP station 120 will be described as the wireless transmitter 120, while the AP 110 is described as the wireless receiver.

As illustrated in figure 1 and as will be described in more detail below, the wireless transmitter in the form of the non-AP station 120 comprises a processing circuitry or processor 121 and a communication interface 123, in particular a communication interface 123 in accordance with the 802.11 standards. As will be described in more detail below, the communication interface 123 comprises a power amplifier 123a configured to amplify a transmission signal to be transmitted by the communication interface 123 via the wireless communication channel to the wireless receiver 110, e.g. the AP 110. 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 arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The non-AP station 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 120 to perform the functions and methods described herein.

Likewise, the AP 110 may comprise a processing circuitry or processor 111 and a communication interface 113, in particular a communication interface 113 in accordance with the 802.11 standards. Like the non-AP station 120 the communication interface 113 of the AP may comprise a power amplifier 113a configured to amplify a transmission signal to be transmitted by the communication interface 113 via the wireless communication channel to the non-AP station 120. 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 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.

The processing circuitry 121 of the non-AP station 120 is configured to obtain a digital sequence, in particular a bit sequence for generating a power amplifier transfer function estimation signal. In an embodiment, the digital sequence may be predefined and stored in the memory 125 of the non-AP station 120. As will be described in more detail below, the digital sequence may comprise a sequence of constellation points.

The communication interface 123 is configured to amplify the power amplifier transfer function estimation signal using the power amplifier 123a and to transmit the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver, e.g. the AP 110 for allowing the AP 110 to estimate a transfer function of the power amplifier 123a of the non-AP station. As will described in more detail below, the digital sequence and, thus, the power amplifier transfer function estimation signal has a peak-to- average power ratio, PAPR, larger than a first threshold value and a time domain power variance larger than a second threshold value.

In an embodiment, the first predefined threshold value may be in a range between 10 and 20 dB, in particular 14 dB. In an embodiment, the second predefined threshold value may be in a range from 10'⁸ to 10'⁶, in particular the second predefined threshold value may have a value of 10'⁷, for instance, for a transmission bandwidth of 80 MHz. As will be appreciated, for other transmission bandwidths, such as 40, 160 or 320 MHz the preferred second predefined threshold value may differ.

Thus, embodiments disclosed herein make use of a digital sequence that has a large PAPR for ensuring the existence of nonlinear components in the power amplifier transfer function estimation signal as well as a large variance of power of time domain samples for allowing an accurate estimation of the power amplifier transfer function by the wireless receiver 110.

In an embodiment, the processing circuitry 121 of the non-AP station 120 is configured to generate in addition to the power amplifier transfer function estimation signal a channel transfer function estimation signal, wherein the communication interface 123 is configured to amplify the channel transfer function estimation signal using the power amplifier 123a and to transmit the amplified channel transfer function estimation signal via the channel to the wireless receiver, e.g. the AP 110 for estimating a transfer function of the channel.

Complementary to the wireless transmitter, e.g. the non-AP station 120, the wireless receiver, e.g. the AP 110 by means of its communication interface 113 is configured to receive the power amplifier transfer function estimation signal amplified by the power amplifier 123a of the non-AP station 120 via the channel from the non-AP station 120. Moreover, the processing circuitry 111 of the AP 110 is configured to estimate a transfer function of the power amplifier 123a of the non-AP station 120 based on the received power amplifier transfer function estimation signal and to perform a nonlinearity cancellation. In an embodiment, the processing circuitry 111 of the AP 110 is configured to perform the nonlinearity cancellation based on the so determined transfer function of the power amplifier 123a of the non-AP station 120. Figure 2 illustrates an exemplary nonlinearity cancellation scheme implemented by the processing circuitry 111 of the AP 110 according to an embodiment. A channel estimation module 111a implemented by the processing circuitry 111 of the AP 110 is configured to perform a channel estimation based on a preamble of the transmission signal received from the non-AP station 120. A power amplifier transfer function estimation module 111 b implemented by the processing circuitry 111 of the AP 110 is configured to estimate the transfer function of the power amplifier 123a of the non-AP station 120 based on the received power amplifier transfer function estimation signal. As already described above, the power amplifier transfer function estimation signal is based on a special digital sequence having a peak-to-average power ratio, PAPR, larger than the first threshold value and a time domain power variance larger than the second threshold value. As illustrated in figure 2, the power amplifier transfer function estimation module 111b may also take into account the channel distortion determined by the channel estimation module 111a. An initial data decoder 111c implemented by the processing circuitry 111 of the AP

110 is configured to decode the data symbols received from the non-AP station 120. The decoded data symbols are provided to a nonlinear components reconstructing module

111 d, because the data symbols decoded by the initial data decoder 111c may provide a non-accurate linear component of the transmitted signal. The nonlinear components reconstructing module 111d is configured to reproduce the nonlinear components based on the original signal and non-linear transfer function. A nonlinear component reduction module 111e is configured to subtract these nonlinear components from the received signal so that fully decoded clean signal may be provided by a final data decoder 111f.

As already described above, the power amplifier transfer function estimation signal generated by the non-AP station 120 is based on a special digital sequence, e.g. bit sequence having a peak-to-average power ratio, PAPR, larger than the first threshold value and a time domain power variance larger than the second threshold value. Figure 3 shows processing steps for determining such a special digital sequence, e.g. bit sequence for generating the power amplifier transfer function estimation signal with the desired properties.

In a first processing stage 301 of figure 3 an arbitrary digital candidate sequence, e.g. bit sequence is generated in the frequency domain. In an embodiment, the processing stage 301 may generate the arbitrary digital candidate sequence, e.g. bit sequence using a random number generator. In a second processing stage 303 of figure 3, the digital candidate sequence is transformed from the frequency domain to the time domain, for instance, by means of an inverse Fourier transformation. In a third processing stage 305 of figure 3 the peak-to-average power ratio, PAPR, is determined for the digital candidate sequence in the time domain. In a fourth processing stage 307 of figure 3, it is checked whether the PAPR of the digital candidate sequence in the time domain is larger than the first threshold value. If this is not the case, the digital candidate sequence is discarded and a new arbitrary digital candidate sequence may be generated by processing stage 301 . If the PAPR of the digital candidate sequence in the time domain is larger than the first threshold value, then in a fifth processing stage 309 of figure 3 the time domain power variance of the digital candidate sequence is computed. In the embodiment shown in figure 3, this time domain power variance of the digital candidate sequence is computed for the N highest samples (i.e. the N samples of the time domain signal with the highest power). In a fifth processing stage 311 of figure 3, it is checked whether the time domain power variance of the digital candidate sequence is larger than the second threshold value. If this is not the case, the digital candidate sequence is discarded and a new arbitrary digital candidate sequence may be generated by processing stage 301. If the time domain power variance of the digital candidate sequence is larger than the second threshold value, then the digital candidate sequence has the desired properties for generating the power amplifier transfer function estimation signal. As will be appreciated, in a further embodiment, steps 309 and 311 may be performed prior to or substantially in parallel with steps 305 and 307, i.e. first the second threshold value is checked and then the first threshold value, and the same results would be obtained.

Figures 4a and 4b illustrate a time domain power of a first selected digital sequence with a large time domain power variance and a second non-selected sequence with a small time domain power variance, but similar PAPR. The first selected digital sequence may have been determined by the selection scheme shown in figure 3, while the second nonselected sequence may have been discarded in processing step 311 of figure 3.

In an embodiment, the communication interface 123 of the non-AP station 120 is configured to transmit a physical protocol data unit, PPDU, in particular a data PPDU with a preamble via the channel to the AP 110, wherein the preamble of the PPDU comprises the amplified power amplifier transfer function estimation signal, for instance, when high modulation is selected for data transmission.

In an embodiment, the preamble of the PPDU comprises an indication indicative of the presence of the amplified power amplifier transfer function estimation signal in the preamble of the PPDU. In an embodiment, this indication may be part of the U-SIG field of the preamble.

In an embodiment, the communication interface 123 of the non-AP station 120 is configured to transmit the PPDU using a modulation and coding scheme, MCS, of a plurality of selectable MCSs to the AP 110, wherein using one or more of the plurality of selectable MCSs, for instance, a MCS with a high modulation is indicative of the presence of the amplified power amplifier transfer function estimation signal in the preamble of the PPDU.

In an embodiment, the preamble of the PPDU comprises a plurality of OFDM symbols, wherein one or more of the plurality of OFDM symbols comprise the power amplifier transfer function estimation signal and wherein the preamble of the PPDU further comprises an indication indicative of the number of the more of the plurality of OFDM symbols comprising the power amplifier transfer function estimation signal. Thus, similar to a conventional training field that may comprise multiple OFDM symbols (for the case of multiple streams), the special digital sequence disclosed herein may be transmitted on several symbols.

In an embodiment, the processing circuitry 121 of the non-AP station 120 is further configured to generate at least one further power amplifier transfer function estimation signal for at least one further wireless receiver and to generate a MIMO signal including the power amplifier transfer function estimation signal and the at least one further power amplifier transfer function estimation signal based on a P matrix.

802.11 be introduced an optional feature of extra LTF symbols (up to 2 times NLTFs). In an embodiment, the extra LTF symbols may be replaced by a training field based on the special digital sequence disclosed herein. Thus, in an embodiment, the one or more of the plurality of OFDM symbols comprising the power amplifier transfer function estimation signal are one or more extra long training field, EHT-LTF, symbols of the PPDU. In an embodiment, a single bit indication may be provided in the preamble (e.g. in the U-SIG field) to indicate that the extra LTF symbols are replaced by the special digital sequence disclosed herein. In a further embodiment, if a high MCS and the presence of extra LTF symbols are indicated, this may automatically imply the replacement of all the extra LTF symbols by the training field based on the special digital sequence disclosed herein. In a further embodiment, an explicit indication of the number of extra LTF symbols may be provided that were replaced by the training field based on the special digital sequence disclosed herein.

A digital sequence having the required properties, namely a large PAPR for ensuring the existence of nonlinear components in the power amplifier transfer function estimation signal as well as a large variance of power of time domain samples for allowing an accurate estimation of the power amplifier transfer function by the wireless receiver, can be designed based on any modulation scheme. In the following exemplary embodiments of the digital sequence will be described that are designed based on BPSK and 4K-QAM.

Figure 5 shows a table illustrating a BPSK based digital sequence of 242 tones (20 MHz) used by the non-AP station 120 according to an embodiment for generating the power amplifier transfer function estimation signal. As will be appreciated, in the table shown in figure 5 the digital sequence comprises a plurality of bits, more specifically 242 bits.

Figures 6a-d show tables illustrating a 4K-QAM based digital sequence of 242 tones (20 MHz) used by the non-AP station 120 according to an embodiment for generating the power amplifier transfer function estimation signal. As will be appreciated, in the tables shown in figures 6a-d the digital sequence comprises a plurality of constellation points, more specifically 242 constellation points, wherein each constellation point comprises 12 bits.

Figure 7 shows a table illustrating a BPSK based digital sequence of 484 tones (40 MHz) used by the non-AP station 120 according to an embodiment for generating the power amplifier transfer function estimation signal.

Figures 8a-d show tables illustrating a 4K-QAM based digital sequence of 484 tones (40 MHz) used by the non-AP station 120 according to an embodiment for generating the power amplifier transfer function estimation signal.

Figure 9 shows a table illustrating a BPSK based digital sequence of 996 tones (80 MHz) used by the non-AP station 120 according to an embodiment for generating the power amplifier transfer function estimation signal. Figures 10a-i show tables illustrating a 4K-QAM based digital sequence of 996 tones (80 MHz) used by the non-AP station 120 according to an embodiment for generating the power amplifier transfer function estimation signal.

In an embodiment, the digital sequence for a bandwidth of 40 MHz may be designed as a concatenation of two digital sequences for a bandwidth of 20 MHz. In other words, denoting the digital sequence for 20 MHz as x₂42 the digital sequence for 40 MHz may be generated as: X484 = {x₂42(1),... , x₂ 2(242), x₂ 2(1),... , x₂ 2(242)}. Thus, in an embodiment, the sequence of constellation points comprises a subsequence of constellations points and at least one further subsequence of constellations points and wherein the subsequence and the further subsequence are equal.

In a further embodiment, for a total bandwidth larger than 80 MHz, such as a bandwidth of 160 or 320 MHz, the digital sequence can be a combination of the digital sequence(s) for 80 MHz. In other words, denoting the digital sequence for 80 MHz as x₉₉₆ the digital sequence for 160 MHz may be generated as: x_2X996 = {x₉9₆(1),... , x₉9₆(996), x₉9₆(1),... , X₉9₆(996)} (i.e. a combination of 2 replicas). The digital sequence for 320 MHz may be generated as X4x996 = {x₉9₆(1 ),... , x₉9₆(996), x₉9₆(1 ),... , x₉9₆(996), x₉9₆(1 ),... , x₉9₆(996), x₉9₆(1 ),... , X₉9₆(996)} (i.e. a combination of 4 replicas).

In an embodiment, the communication interface 123 of the non-AP station 120 is configured to transmit the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver, e.g. the AP 1 10, if the communication interface 123, has received an indication indicative of the AP 1 10 being configured to perform a nonlinearity cancellation based on the amplified power amplifier transfer function estimation signal. In an embodiment, the communication interface 123 of the non-AP station 120 is configured to receive a message from the AP 1 10 comprising a PHY Capabilities Information Field, wherein the PHY Capabilities Information Field comprises the indication indicative of the AP 1 10 being configured to perform a nonlinearity cancellation, for instance, based on the amplified power amplifier transfer function estimation signal.

Figure 1 1 is a flow diagram illustrating a communication method 1 100 between a wireless transmitter, e.g. the non-AP station 120, and a wireless receiver, e.g. the AP 1 10, via a wireless communication channel. The method 1 100 comprises a first step 1 101 of obtaining a special digital sequence for generating a power amplifier transfer function estimation signal. Moreover, the method 1100 comprises a step 1103 of amplifying the power amplifier transfer function estimation signal using the power amplifier 123a of the non-AP station 120. The method 1100 further comprises a step 1105 of transmitting the amplified power amplifier transfer function estimation signal via the channel to the AP 110 for estimating a transfer function of the power amplifier 123a. As already described above, the special digital sequence has a peak-to-average power ratio, PAPR, larger than the first threshold value and a time domain power variance larger than the second threshold value.

As the method 1100 can be implemented by the AP 110 or each of the non-AP stations 120, further features of the method 1100 result directly from the functionality of the AP 110 and the non-AP stations 120 and their different embodiments described above and below.

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).

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.

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. In addition, functional units in the embodiments disclosed herein 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

1 . A wireless transmitter (120, 110) for communicating with a wireless receiver (110, 120) via a channel, the wireless transmitter (120, 110) comprising: a processing circuitry (121 , 111) configured to obtain a digital sequence for generating a power amplifier transfer function estimation signal; and a communication interface (123, 113) having a power amplifier (123a, 113a), wherein the communication interface (123, 113) is configured to amplify the power amplifier transfer function estimation signal using the power amplifier (123a, 113a) and to transmit the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver (120, 110) for estimating a transfer function of the power amplifier (123a, 113a); wherein the digital sequence has a peak-to-average power ratio, PAPR, larger than a first threshold value and a time domain power variance larger than a second threshold value.

2. The wireless transmitter (120, 110) of claim 1 , wherein the processing circuitry (121 , 111) is further configured to generate a channel transfer function estimation signal and wherein the communication interface (123, 113) is configured to amplify the channel transfer function estimation signal using the power amplifier (123a, 113a) and to transmit the amplified channel transfer function estimation signal via the channel to the wireless receiver (110, 120) for estimating a transfer function of the channel.

3. The wireless transmitter (120, 110) of claim 1 or 2, wherein the communication interface (123, 113) is configured to transmit a physical protocol data unit, PPDU, with a preamble via the channel to the wireless receiver (110, 120), wherein the preamble of the PPDU comprises the amplified power amplifier transfer function estimation signal.

4. The wireless transmitter (120, 110) of claim 3, wherein the preamble of the PPDU comprises an indication indicative of the presence of the amplified power amplifier transfer function estimation signal in the preamble of the PPDU.

5. The wireless transmitter (120, 110) of claim 3, wherein the communication interface (123, 113) is configured to transmit the PPDU using a modulation and coding scheme, MCS, of a plurality of selectable MCSs to the wireless receiver (110, 120) and wherein using one or more of the plurality of selectable MCSs is indicative of the presence of the amplified power amplifier transfer function estimation signal in the preamble of the PPDU.

6. The wireless transmitter (120, 110) of claim 3, wherein the preamble of the PPDU comprises a plurality of OFDM symbols and wherein one or more of the plurality of OFDM symbols comprise the power amplifier transfer function estimation signal, wherein the preamble of the PPDU further comprises an indication indicative of the number of the more of the plurality of OFDM symbols comprising the power amplifier transfer function estimation signal.

7. The wireless transmitter (120, 110) of claim 6, wherein the wireless transmitter comprises at least one further power amplifier and wherein the processing circuitry (121 ,

111) is further configured to generate at least one further power amplifier transfer function estimation signal for the at least one further power amplifier and to generate a MIMO signal including the power amplifier transfer function estimation signal and the at least one further power amplifier transfer function estimation signal based on a P matrix.

8. The wireless transmitter (120, 110) of claim 6 or 7, wherein the one or more of the plurality of OFDM symbols comprising the power amplifier transfer function estimation signal are one or more extra long training field, EHT-LTF, symbols of the PPDU.

9. The wireless transmitter (120, 110) of claim 8, wherein the preamble of the PPDU comprises an indication indicative of the presence of the power amplifier transfer function estimation signal in the one or more EHT-LTF symbols of the PPDU.

10. The wireless transmitter (120, 110) of any one of the preceding claims, wherein the digital sequence comprises a sequence of constellation points.

11 . The wireless transmitter (120, 110) of claim 10, wherein the sequence of constellation points comprises a subsequence of constellations points and at least one further subsequence of constellations points and wherein the subsequence and the further subsequence are equal.

12. The wireless transmitter (120, 110) of any one of the preceding claims, wherein the communication interface (123, 113) is configured to transmit the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver (110, 120), if the communication interface (123, 113) has received an indication indicative of the wireless receiver (110, 120) being configured to perform a nonlinearity cancellation.

13. The wireless transmitter (120, 110) of claim 12, wherein the communication interface (123, 113) is configured to receive a message from the wireless receiver (110, 120) comprising a PHY Capabilities Information Field, wherein the PHY Capabilities Information Field comprises the indication indicative of the wireless receiver (110, 120) being configured to perform a nonlinearity cancellation.

14. The wireless transmitter (120, 110) of any one of the preceding claims, wherein the wireless transmitter (120, 110) is a non-access point station (120) or an access point (110).

15. A communication method (1100) between a wireless transmitter (120, 110) and a wireless receiver (110, 120) via a channel, the method (1100) comprising: obtaining (1101) a digital sequence for generating a power amplifier transfer function estimation signal; amplifying (1103) the power amplifier transfer function estimation signal using a power amplifier (123a, 113a) of the wireless transmitter (120, 110); and transmitting (1105) the amplified power amplifier transfer function estimation signal via the channel to the wireless receiver (110, 120) for estimating a transfer function of the power amplifier (123a, 113a), wherein the digital sequence has a peak-to-average power ratio, PAPR, larger than a first threshold value and a time domain power variance larger than a second threshold value.

16. 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

(1100), when the program code is executed by the computer or the processor.