TECHNICAL FIELD

The present disclosure relates to a wireless network, and generally to Resource Unit (RU) allocation in the wireless network. In particular, the present disclosure is concerned with Multiple Resource Unit (MRU) allocation in the wireless network, wherein the wireless network may be a Wireless Local Area Network (WLAN), e.g., configured according to a WiFi standard. Embodiments of the present disclosure provide a wireless network device and a corresponding method, respectively, suitable for MRU allocation.

BACKGROUND

MRU allocation is generally accepted for future implementation in wireless networks, for instance, in next generations of the WiFi standard. MRU allocation in wireless networks provides a way of achieving more efficient channel utilization. MRU allocation implies non contiguous frequency allocation, i.e., multiple non-contiguous RUs. As it is a new technique in wireless networks, particularly in the WiFi standard, specific implementations of such MRU allocation are yet rare.

In particular, there is need for an efficient implementation of MRU allocation in wireless networks, particularly according to WiFi standards. However, efficient implementations are not straightforward. For instance, as will be shown in the following section of this disclosure, a straightforward implementation of MRU allocation in such wireless networks could significantly impact physical properties of transmission signals in the wireless network. SUMMARY

Embodiments of the present disclosure, as provided later in this disclosure, are based on the following analysis and problems identified by the inventors. In brief, the inventors found that a straightforward MRU allocation in a wireless network may increase a Peak-to-Average-Power- Ratio (PAPR), which is an important metric in wireless network technology.

The 802.1 lax standard introduced the Orthogonal Frequency Division Multiple Access (OFDMA) format, wherein the entire bandwidth (BW) is divided into blocks defined as RUs. A transmitted signal may be combined of multiple RU allocations, wherein different RUs may be allocated to different stations (i.e., wireless network devices). The size of a RU may thereby be defined by a number of frequency tones, which could include 26 or 52 or 106 or 242 or 484 or 996 tones. For instance, the BW of 20MHz may include 9 RUs of 26, 4 RUs of 52, and so on, as depicted in FIG. 1.

The structures of RUs in 40MHz and 80MHz are depicted in FIG. 2 and FIG. 3, respectively. The larger BW (including 240MHz and 320MHz in 802.11be) is a duplication of the 80MHz structure. In the following, index notations are used for each RU, wherein the indexing starts from the left side of the BW (i.e., the left most 26RU is the first 26RU, and the right most 26RU is the ninth 26RU).

In 802.11be, MRU allocation is generally foreseen, wherein more than one RU is allocated to a single station or group of stations (i.e., wireless network devices). This implies a non contiguous BW allocation (for example, as shown in FIG. 4, wherein multiple RUs (here at least a 1 ^st RU and a 2 ^nd RU) are arranged in the frequency domain in one MRU).

Currently, the 802.11be standard foresees two types of MRU allocations:

• Only large RUs, i.e. larger or equal to 20MHz (RU242, RU484, RU996 and etc.), may be combined to a MRU.

• Only small RUs (RU26, RU52, RU106) may be combined to a MRU within the boundaries of 20MHz.

No combination of small and large RUs is currently allowed in this standard. A transmitted signal typically includes one or more training sequences (e.g., Short Training Field (STF), or Long Training Field (LTF), or High Efficiency STF (HE-STF), or High Efficiency LTF (HE-LTF)) before a data portion, which training sequences allow a receive side to synchronize on the transmitted signal, and to perform a wireless channel estimation. Usually, those training sequences are designed with low PAPR (particularly, with lower PAPR than the data portion of the transmitted signal), in order to ensure a high accuracy of the channel estimation. However, in older WiFi standard versions (e.g., in 802.11a/n/ac/ax) the design of the training sequences assumes that a contiguous bandwidth is allocated for the transmission (Downlink (DL) and/or Uplink (UL)). Thus, the PAPR is optimized, at best, with respect to this assumption. If the current training sequences would be reused for MRU allocation in the wireless network, this would result in a higher PAPR (particularly, higher than the PAPR of a contiguous BW).

FIG. 5 shows example comparisons of PAPR of a contiguous BW and PAPR for MRU allocation, in particular for MRUs comprised of large RUs and for MRUs comprised of small RUs, respectively. A sequence of HE-LTF, as defined in the 802.1 lax standard, was used. This HE-LTF was applied for each RU, as it is defined for a single RU transmission. The x-axis in FIG. 5 represents different combinations of RUs, wherein the indexes are aligned with the 802.11be definition (i.e., a first number represents a larger RU index, and a second number represents a smaller RU index). It can be seen that the PAPR of the HE-LTF increases by 1.5- 2dB in case of a large RU combination (see FIG. 5(a), and by 1.5-3dB in case of a small RU combination (see FIG. 5(b)).

As mentioned earlier, the training sequences are designed with a PAPR lower than the PAPR of the data portion. Thus, the impact of the MRU on the PAPR of the data portion has been checked as well. FIG. 6 presents in this respect a PAPR of the data portion (wherein, e.g., the data in the data portion may be random, thus it is here exemplarily presented by Cumulative Distribution Function (CDF)). It can be seen that the PAPR of the data portion is increased by 0.5-ldB for large RUs (see FIG. 6(a)) and small RUs (see FIG. 6(b)), which is less than the PAPR of the HE-LTF. Thus, it can be understood that there is a problem with reusing the design of the current training sequences, e.g., the HE-LTF sequences, and thus new or updated training sequences should be considered to reduce the PAPR in case of MRU allocation.

A theoretical explanation of the above described PAPR problem is illustrated with respect to FIG. 7. The time-domain signal, in case of a MRU, may be represented as a combination of multiple domain signals, each produced by a single RU (here a 1 ^st RU and a 2 ^nd RU). The impact of the PAPR produced by the MRU allocation is related to combined peaks of those transmitted signals, wherein at some samples the sum of two or more high peaks produces a higher total peak value.

In general, PAPR problems have been addressed in earlier versions of the WiFi standard, for instance, training sequences were designed with respect to minimizing a PAPR metric. In addition, WiFi introduced a constant phase rotation, which is also supposed to reduce the PAPR in case of a large BW. FIG. 8 presents such a phase rotation, as defined for 80MHz BW in 802.1 lac.

Applying a constant phase rotation allows reducing the PAPR, and is defined for a BW of 40/80/160MHz. An extension of this approach was also proposed for BWs of 240MHz and 320MHz, and different options of constant phase rotations were presented as examples.

However, the main problem of this approach, including the extension for 240MHz and 320MHz, is that a constant phase rotation is designed for the allocation of the entire BW:

• A constant phase leads to a non-coherent combination of multiple peaks, but does not change the location of the peaks in the time domain.

• Different MRUs may require different phases to be applied for the same portion of tones, in order to optimize the PAPR. For example, a combination of a 1 ^st 20MHz with a 3 ^rd 20MHz may require different phase values than a combination of a 1 ^st 20MHz with a 4 ^th 20MHz. Thus, PAPR optimization by constant phase rotation applied to the same portion of the BW cannot be ensured.

An additional issue is that this approach can only be applied for the optimization of PAPR for combinations of large RUs, while an efficient implementation is also needed for optimizing the PAPR in case of a MRU combined from small RUs.

In view of the above-described problems and disadvantages, embodiments of the present disclosure aim to provide a solution to the problem of MRU allocation impacting on the PAPR. In particular, an objective is to provide a wireless network device and a corresponding method, which enable MRU allocation in a wireless network, particularly in a wireless network according to the WiFi standard, without any impact (or at least with significantly reduced impact) on the PAPR. The objective is achieved by the embodiments of the present disclosure as described in the enclosed independent claims. Advantageous implementations of the embodiments of the present disclosure are further defined in the dependent claims.

A theoretical consideration, as a basis for embodiments of the present disclosure, is illustrated in FIG. 9. The chance of high peaks combining to a higher value can in principle be decreased, if two properties are addressed: a change of the location of the peak values in the time domain, and avoiding coherent combination of the signals. This, may be achieved by applying a cyclic shift, e.g., for OFDM symbols in the time domain (see FIG. 9) and/or by adding a phase offset. It can be understood from FIG. 9, that the peak location can be shifted, and that thereby a combination of high peaks is prevented. The equivalent of a cyclic shift in the frequency- domain is multiplying frequency tones of a RU by phase values, for instance, by a linear phase and a phase offset. The phase offset may actually be an initial value of the linear phase.

A first aspect of this disclosure provides a wireless network device for MRU allocation, the wireless network device being configured to: select a first training signal for a first MRU, wherein the first MRU comprises two or more RUs arranged in a frequency domain, and wherein the first training signal comprises a training sequence per RU of the first MRU; and apply, for at least one RU of the first MRU, a first subset of phase values to the training sequence of the at least one RU of the first MRU, wherein the first subset of phase values is selected for the at least one RU of the first MRU from a first set of phase values allocated to the first MRU.

The wireless network device of the first aspect may further provide the thus modified training signal (i.e., a signal including the training sequence(s) modified by applying the first subset of phase values), in particular, to a receiving device. The wireless network device may further provide data following the transmission of the training signal, wherein the data is allocated on the first MRU, in particular, to the receiving device. Advantageously, the applying of the first subset of phase values to the training sequence of one or more RUs of the first MRU may lead to a significantly reduced PAPR - in line with the above-described considerations. Notably, if this applying is carried out for more than one RU of the first MRU, different first subsets of phase values may be allocated per RU. A “first subset of phase values” can be any group of phase values included in the “first set of phase values”.

Moreover, a different set of phase values may be allocated per each MRU. For instance, the first MRU is allocated the first set of phase values, and a second MRU may be allocated a second set of phase values. Further, per each RU of a certain MRU, a specific subset of phase values may be selected from the set of phase values allocated to that certain MRU. As an example, a set or subset of phase values may comprise {-pi, -pi/2, 0, pi/2, pi}, i.e., multiple phase values.

In an implementation form of the first aspect, the wireless network device is further configured to: select a second training signal for a second MRU, wherein the second MRU comprises two or more RUs arranged in the frequency domain, and wherein the second training signal comprises a training sequence per RU of the second MRU; and apply, for at least one RU of the second MRU, a second subset of phase values to the training sequence of the at least one RU of the second MRU, wherein the second subset of phase values is selected for the at least one RU of the second MRU from a second set of phase values allocated to the second MRU.

The first MRU and the second MRU are, in particular, different MRUs. Thus, different MRUs may be allocated different sets of phase values. These different sets of phase values may include different subsets of phase values, but may also have in common certain subsets of phase values. This implementation form may lead to a more efficiently reduced PAPR. Notably, if the applying is carried out for more than one RU of the second MRU, different second subsets of phase values may be allocated per RU. A “second subset of phase values” can be any group of phase values included in the “second set of phase values”.

In an implementation form of the first aspect, the first subset of phase values is composed of a first linear phase and a first phase offset, and the first set of phase values is composed of a first set of linear phases and a first set of phase offsets; and/or the second subset of phase values is composed of a second linear phase and a second phase offset, and the second set of phase values is composed of a second set of linear phases and a second set of phase offsets.

Any linear phase may be or comprise a group of phase values with a constant gap between these phase values. Applying a linear phase to a given RU may mean that the frequency tones of that given RU are multiplied with the phase values of the applied linear phase. For example, a first tone of the given RU may be multiplied with a phase value of 0, a second tone of the given RU may be multiplied with a phase value of pi/N, a third tone of the given RU may be multiplied with a phase value of 2*pi/N, and so on. Thus, a linear phase may also be defined as a sequence of phase values. For instance, if k is denoted as an index of frequency tones within an i ^th RU of a certain MRU (e.g., the first and/or second MRU), wherein the RU comprises K tones, and wherein x _k is a value of a training sequence defined for the k ^th tone, the shifted signal of the i ^th RU may be given by: wherein M is a number of RUs comprised by the certain MRU.

This implementation form may further comprise that:

• For any training sequence, a particular linear phase and a particular phase offset may be defined, which may be applied to the tones of one, or more, or each RU comprised by the certain MRU.

• The linear phase(s) and phase offset(s) may be defined to optimize PAPR per each MRU, while different subsets of phase values may be applied to the same RU in case of different MRUs.

• Multiple RUs, or each RU, within a certain MRU may be multiplied by a different linear phase(s) and/or different phase offset(s).

• The values of the linear phase(s) and phase offset(s) may be known in advance for a transmit side (e.g., at the wireless network device) and for a receive side, in particular, with respect to each MRU. However, the actual implementation design may differ for transmit and receive devices.

In an implementation form of the first aspect, the first MRU and the second MRU have one or more RUs in common; or the first MRU and the second MRU have no RU in common.

In an implementation form of the first aspect, the first set of linear phases includes one or more linear phases, which are not included in the second set of linear phases; and/or the first set of phase offsets includes one or more phase offsets, which are not included in the second set of phase offsets.

In an implementation form of the first aspect, the first set of linear phases and/or the second set of linear phases includes linear phases defined in a range of [-p, p] with a granularity of the linear phase values n being an integer number; and/or the first set of phase offsets and/or the second set of phase offsets comprises phase offsets defined in a range of [-p, p] with a granularity of the phase offsets m being an integer number.

In an implementation form of the first aspect, the wireless network device is further configured to: apply, for each RU of the first MRU and/or the second MRU, the first and/or second subset of phase values to the training sequence of that RU of the first MRU and/or second MRU.

In this way, the PAPR can be even more efficiently reduced.

In an implementation form of the first aspect, the first and/or second subset of phase values is applied to the training sequence of the at least one RU of the first MRU and/or second MRU, by multiplying values of said training sequence by values in the first and/or second subset of phase values.

In an implementation form of the first aspect, the values of the first and/or second linear phase and the first and/or second phase offset are defined by a single set of values; or the values of the first and/or second linear phase and the first and/or second phase offset are defined by a first set of values and a second set of values, wherein the first set of values defines a constant phase offset value and the second set of values defines values of the first and/or second linear phase, wherein the constant phase offset is respectively added to each value of the first and/or second linear phase.

In an implementation form of the first aspect, a different first and/or second subset of phase values is selected for at least two RUs of the first MRU and/or second MRU.

In an implementation form of the first aspect, a different first and/or second subset of phase values is selected for each RU of the first MRU and/or second MRU.

In an implementation form of the first aspect, a first and/or second subset of phase values that are zero is selected for at least one RU of the first MRU and/or second MRU.

In an implementation form of the first aspect, the first and/or second subset of phase values is selected for the at least one RU of the first MRU and/or second MRU to minimize a PAPR.

Also the first and/or second set of phase values, allocated to the first and/or second MRU, may be selected or created with the purpose of minimizing PAPR. In an implementation form of the first aspect, each RU comprises a plurality of frequency tones, and each value of the first and/or second subset of phase values, selected for the at least one RU of the first MRU and/or second MRU, is associated with one of the frequency tones of the at least one RU of the first MRU and/or second MRU.

In an implementation form of the first aspect, the wireless network device is further configured to: apply, for the at least one RU of the first MRU and/or second MRU, only selected values of the first and/or second subset of phase values, which are selected for the at least one RU of the first MRU and/or second MRU, to the training sequence of the at least one RU of the first MRU and/or second MRU, wherein the selected values are values of the first and/or second subset of phase values that are related to each frequency tone, or are related to each second frequency tone, or are related to each fourth frequency tone, of the at least one RU of the first MRU and/or second MRU.

Thus, the wireless network device of the first aspect is able to use the IX, 2X, and/or 4X formats.

In an implementation form of the first aspect, the first and/or second subset of phase values is selected for the at least one RU of the first MRU and/or second MRU based on whether the selected values are related to each frequency tone, each second frequency tone, or each fourth frequency tone.

In an implementation form of the first aspect, the first MRU and/or second MRU comprises only larger RUs, each RU having a bandwidth above 20 MHz, or the first MRU and/or second MRU comprises only smaller RUs, each RU having a bandwidth below 20 MHz.

Thus, the wireless network device of the first aspect can use all different kinds of MRUs.

In an implementation form of the first aspect, the training sequences of the first training signal and/or second training signal comprise at least one of: a Legacy LTF (L-LTF), sequence, or a Legacy STF (L-STF) sequence, or an Extreme High Throughput STF (EHT-STF) sequence, or an EHT-LTF sequence.

In an implementation form of the first aspect, the wireless network device is further configured to: provide an indication that the first and/or second subset of phase values is used to multiply the training sequence of the at least one RU of the first MRU and/or second MRU; or provide an indication of the first and/or second subset of phase values used to multiply the training sequence of the at least one RU of the first MRU and/or second MRU.

In particular, the indication may be provided to a receive side. Alternatively, no indication may be provided, for instance, if phase values are always applied and known to both the transmit side (wireless network device) and the receive side. The receive side may be preconfigured with the relevant information about the first and/or second subset of phase values.

A second aspect of this disclosure provides a method for Multiple Resource Unit, MRU, allocation in a wireless network, the method comprising: selecting a first training signal for a first MRU, wherein the first MRU comprises two or more RUs, arranged in a frequency domain, and wherein the first training signal comprises a training sequence per RU of the first MRU; and applying, for at least one RU of the first MRU, a first subset of phase values to the training sequence of the at least one RU of the first MRU, wherein the first subset of phase values is selected for the at least one RU of the first MRU from a first set of phase values allocated to the first MRU.

In an implementation form of the second aspect, the method further comprises: selecting a second training signal for a second MRU, wherein the second MRU comprises two or more RUs arranged in the frequency domain, and wherein the second training signal comprises a training sequence per RU of the second MRU; and applying, for at least one RU of the second MRU, a second subset of phase values to the training sequence of the at least one RU of the second MRU, wherein the second subset of phase values is selected for the at least one RU of the second MRU from a second set of phase values allocated to the second MRU.

In an implementation form of the second aspect, the first subset of phase values is composed of a first linear phase and a first phase offset, and the first set of phase values is composed of a first set of linear phases and a first set of phase offsets; and/or the second subset of phase values is composed of a second linear phase and a second phase offset, and the second set of phase values is composed of a second set of linear phases and a second set of phase offsets.

In an implementation form of the second aspect, the first MRU and the second MRU have one or more RUs in common; or the first MRU and the second MRU have no RU in common.

In an implementation form of the second aspect, the first set of linear phases includes one or more linear phases, which are not included in the second set of linear phases; and/or the first set of phase offsets includes one or more phase offsets, which are not included in the second set of phase offsets.

In an implementation form of the second aspect, the first set of linear phases and/or the second set of linear phases includes linear phases defined in a range of [-p, p] with a granularity of the linear phase values n being an integer number; and/or the first set of phase offsets and/or the second set of phase offsets comprises phase offsets defined in a range of [-p, p] with a granularity of the phase offsets m being an integer number.

In an implementation form of the second aspect, the method further comprises: applying, for each RU of the first MRU and/or the second MRU, the first and/or second subset of phase values to the training sequence of that RU of the first MRU and/or second MRU.

In an implementation form of the second aspect, the first and/or second subset of phase values is applied to the training sequence of the at least one RU of the first MRU and/or second MRU, by multiplying values of said training sequence by values in the first and/or second subset of phase values.

In an implementation form of the second aspect, the values of the first and/or second linear phase and the first and/or second phase offset are defined by a single set of values; or the values of the first and/or second linear phase and the first and/or second phase offset are defined by a first set of values and a second set of values, wherein the first set of values defines a constant phase offset value and the second set of values defines values of the first and/or second linear phase, wherein the constant phase offset is respectively added to each value of the first and/or second linear phase.

In an implementation form of the second aspect, a different first and/or second subset of phase values is selected for at least two RUs of the first MRU and/or second MRU.

In an implementation form of the second aspect, a different first and/or second subset of phase values is selected for each RU of the first MRU and/or second MRU.

In an implementation form of the second aspect, a first and/or second subset of phase values that are zero is selected for at least one RU of the first MRU and/or second MRU. In an implementation form of the second aspect, the first and/or second subset of phase values is selected for the at least one RU of the first MRU and/or second MRU to minimize a PAPR.

In an implementation form of the second aspect, each RU comprises a plurality of frequency tones, and each value of the first and/or second subset of phase values, selected for the at least one RU of the first MRU and/or second MRU, is associated with one of the frequency tones of the at least one RU of the first MRU and/or second MRU.

In an implementation form of the second aspect, the method further comprises: applying, for the at least one RU of the first MRU and/or second MRU, only selected values of the first and/or second subset of phase values, which are selected for the at least one RU of the first MRU and/or second MRU, to the training sequence of the at least one RU of the first MRU and/or second MRU, wherein the selected values are values of the first and/or second subset of phase values that are related to each frequency tone, or are related to each second frequency tone, or are related to each fourth frequency tone, of the at least one RU of the first MRU and/or second MRU.

In an implementation form of the second aspect, the first and/or second subset of phase values is selected for the at least one RU of the first MRU and/or second MRU based on whether the selected values are related to each frequency tone, each second frequency tone, or each fourth frequency tone.

In an implementation form of the second aspect, the first MRU and/or second MRU comprises only larger RUs, each RU having a bandwidth above 20 MHz, or the first MRU and/or second MRU comprises only smaller RUs, each RU having a bandwidth below 20 MHz.

In an implementation form of the second aspect, the training sequences of the first training signal and/or second training signal comprise at least one of: a Legacy LTF (L-LTF), sequence, or a Legacy STF (L-STF) sequence, or an Extreme High Throughput STF (EHT-STF) sequence, or an EHT-LTF sequence.

In an implementation form of the second aspect, the method further comprises: providing an indication that the first and/or second subset of phase values is used to multiply the training sequence of the at least one RU of the first MRU and/or second MRU; or providing an indication of the first and/or second subset of phase values used to multiply the training sequence of the at least one RU of the first MRU and/or second MRU. A third aspect of this disclosure provides a computer program comprising a program code for performing the method according the second aspect or any implementation form thereof, when executed on a computer.

A fourth aspect of this disclosure provides a non-transitory storage medium storing executable program code which, when executed by a processor, causes the method according to the third aspect or any of its implementation forms to be performed.

It has to be noted that all devices, elements, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof.

BRIEF DESCRIPTION OF DRAWINGS

The above described aspects and implementation forms will be explained in the following description of specific embodiments in relation to the enclosed drawings, in which

FIG. 1 shows a RU locations of 20MHz.

FIG. 2 shows RU locations of 40MHz.

FIG. 3 shows RU locations of 80MHz.

FIG. 4 shows an MRU allocation example.

FIG. 5 shows a comparison of PAPR on HE-LTF for MRU allocation.

FIG. 6 shows a comparison of PAPR on data for MRU allocation.

FIG. 7 illustrates a theory of High PAPR in case of MRU allocation. FIG. 8 shows a phase rotation Example as defined in the 1 lac WiFi standard.

FIG. 9 illustrates a time-Domain signal with a cyclic shift.

FIG. 10 shows a wireless network device according to an embodiment of the disclosure.

FIG. 11 shows a wireless network device according to an embodiment of the disclosure applying linear phase and phase offset.

FIG. 12 shows a wireless network device according to an embodiment of the disclosure applying linear phase and phase offset depending on the MRU.

FIG. 13 shows a wireless network device according to an embodiment of the disclosure applying relative linear phase and phase offset.

FIG. 14 shows a PAPR degradation in case of an embodiment of the disclosure.

FIG. 15 shows PAPR in specific cases.

FIG. 16 shows a method according to an embodiment of the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 10 shows a wireless network device 100 according to an embodiment of the present disclosure. The wireless network device 100 is configured for MRU allocation in a wireless network, in particular in a WLAN, more particularly in a wireless network configured according to a WiFi standard. The wireless network device 100 may thus be configured according to, and in-line with, a WiFi standard. The wireless network device 100 may be a station or a terminal, and may communicate with one or more other wireless network devices (stations or terminals) in the wireless network.

The wireless network device 100 is configured to select a first training signal 101 for a first MRU 102. Generally, the wireless network device 100 may be configured to select a training signal 101 per each MRU. The first MRU 102 comprises two or more RUs 103 arranged in a frequency domain, i.e., the two or more RUs 103 are separated/distanced in the frequency direction, e.g., they occupy different sets of subcarriers (e.g., in case of OFDM). The first training signal 101 comprises a training sequence 104 per RU 103 of the first MRU 102 (here two RUs 103 and two training sequences 104 are exemplarily illustrated).

The wireless network device 100 may apply, for at least one RU 103 of the first MRU 102 (in particular, for one or more RUs 103, or for each RU 103, of the first MRU 102), a first subset 105 of phase values. For example, a first subset 105 of phase values may be applied, per given RU 103, to the training sequence 104 of that given RU 103. In FIG. 1, exemplarily, a first subset 105 of phase values (denoted qi(1...N)) is applied to a first RU 103 of the first MRU 102, and a different first subset 105 of phase values (denoted 0 ₂ (1... N)) is applied to a second RU 103 of the first MRU 102.

Any first subset 105 of phase values may include one or more phase values. The first subset 105 of phase values is selected for the at least one RU 103 of the first MRU 102. In particular, the first subset 105 of phase values is selected from a first set of phase values, which is allocated to the first MRU 102. Notably, a set of phase values may include one or more subsets of phase values, and/or may include one or more phase values.

A different first subset 105 of phase values may be applied to multiple or each RU 103 of the first MRU 102. Applying one or more first subsets 105 of phase values to one or more training sequences 104 of one or more RUs 103 of the first MRU 102 results in a modified training signal 106, which the wireless network device 100 may provide/transmit.

The wireless network device 100 may comprise a processor or processing circuitry (not shown) configured to perform, conduct or initiate the various operations of the wireless network device 100 described herein. The processing circuitry may comprise hardware and/or the processing circuitry may be controlled by software. The hardware may comprise analog circuitry or digital circuitry, or both analog and digital circuitry. The digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or multi-purpose processors.

The wireless network device 100 may further comprise memory circuitry, which stores one or more instruction(s) that can be executed by the processor or by the processing circuitry, in particular under control of the software. For instance, the memory circuitry may comprise a non-transitory storage medium storing executable software code which, when executed by the processor or the processing circuitry, causes the various operations of the wireless network device 100 to be performed. In one embodiment, the processing circuitry comprises one or more processors and a non- transitory memory connected to the one or more processors. The non-transitory memory may carry executable program code which, when executed by the one or more processors, causes the wireless network device 100 to perform, conduct or initiate the operations or methods described herein.

FIG. 11 shows the wireless network device 100 according to an embodiment of the disclosure, which builds on the embodiment shown in FIG. 10. In this embodiment of FIG. 11, first subsets 105 of phase values are composed of first linear phases and first phase offsets, respectively, and accordingly the first set of phase values is composed of a first set of linear phases and a first set of phase offsets. That is, a first linear phase and first phase offset may be applied, as the first subset 105, of phase values to one or more or each RU 103 of the first MRU 102. A different first linear phase and a different first phase offset may be applied to each given RU 103 of the first MRU 102. For instance, a different first linear phase and first phase offset may independently be applied to each of multiple selected RUs 103 comprised by the first MRU 102. FIG. 11 shows exemplarily that two different first linear phases and first phase offsets are, respectively, applied to the training sequences 104 of a first RU 103 and the training sequence 104 of a second RU 103 of the first MRU 102. Notably a “first linear phase” is any linear phase included in the “first set of linear phases”. Likewise a “first phase offset” is any phase offset included in the “first set of phase offsets”.

First, the first training signal 101 is selected (based e.g. on the BW, the specific first MRU etc.) and then the values of the training signal 101 (particularly the training sequences 104 for the different RUs 103) are multiplied by the values of the first linear phase(s) with the first phase offset(s), as they may be predefined for each RU 103 within the MRU 102.

FIG. 12 shows the wireless network device 100 according to an embodiment, which builds on the embodiments of FIG. 10 and FIG. 11. In particular, FIG. 12 shows that a different set of linear phases and a different set of phase offset may be applied for RUs 103/203 of different MRUs 102/202, in particular for each different MRU that is used. Accordingly, the wireless network device 100 may be further configured to select a second training signal 201 for a second MRU 202 (different from the first MRU 102), wherein the second MRU 202 comprises two or more RUs 203 (RUs 103/203 may differ or not) arranged in the frequency domain, i.e., they are separated in the frequency direction, e.g., they occupy different sets of subcarriers (e.g. in case of OFDM). The second training signal 201 comprises a training sequence 204 per RU 203 of the second MRU 202. Further, the wireless network device 100 is configured to apply, for at least one RU 203 of the second MRU 202 (i.e., for one or more RUs 203, or for each RU 203, of the second MRU 202), a certain second linear phase and second phase offset (or generally a second subset 205 of phase values) to the training sequence 201 of the at least one RU 203. The second linear phase may be selected from a second set of linear phases, and the second phase offset may be selected from a second set of phase offsets for the at least one RU 203 of the second MRU 203. The second set of linear phases and the second set of phase offsets may thereby be allocated to the second MRU 202. Notably a “second linear phase” is any linear phase included in the “second set of linear phases”. A “second phase offset” is any phase offset included in the “second set of phase offsets”.

As an example, different MRU (types) 102, 202, comprising RUs 103, 203, may be optimized for PAPR using different (fist/second) linear phase(s) and phase offset (s). Thus, when the same RU 103 or 203 is allocated within two different MRUs 102, 202, a different linear phase and phase offset may be applied. FIG. 12 present an example, wherein in the first case the MRU 102 comprises a 1 ^st RU and a 2 ^nd RU, and in the second case a different MRU 202 comprises the (same) 1 ^st RU and a 3 ^rd RU. The linear first/second phase(s) and first/second phase offset(s) applied to the training sequences 104 for the 1 ^st RU in the first MRU 102 and second MRU 202, respectively, are shown to be different in those two cases.

Moreover, the wireless network device 100 can work with all the types of MRUs 102, 202. For instance, the first MRU 102 and/or the second MRU 103 may comprise large RUs 103, 203 only for any BW larger than 20MHz, or may comprise small RUs 103, 203 only for BW of 20MHz.

The wireless network device 100 may also work with different formats of training signals 101, 201. For instance, the 802.11be standard adopted training sequence designs of various carrier spacing, where the same BW may be sampled with a different number of frequency tones. The maximum number of frequency tones in the training signal format is thereby denoted by 4X. If every second tone is used, the format is denoted by 2X. If only every fourth tone is used, the format denoted as IX. The linear phase(s) and the phase offset(s) that may be applied for different formats may be designed in two ways: • For 2X and IX formats, the subset of the 4X format may be applied (i.e., meaning every second and fourth value of, e.g., the first and/or second linear phase may be used, respectively) and the phase offset is the same as for the 4X format.

• Different linear phase(s) and phase offset(s) may be designed for every format.

It is also possible to combine between the two ways described above, while only a linear phase or only a phase offset may be designed specifically for each format.

The wireless network device 100 may furthermore work with at least the following training signals 101/201 or training sequences 104/204: L-LTF; L-STF; EHT-STF; and/or EHT-LTF.

The first/second linear phase(s) and phase offset(s) may be moreover applied as absolute or relative linear phase(s) and phase offset(s). As described above in the theoretical consideration, embodiments of the disclosure can be considered to implement a cyclic shift in the time domain, wherein the goal is to separate high peaks of different signals related to RUs 103, 203 within a MRU 102, 202. The shift in the time domain may be considered as an absolute value, wherein each signal is shifted with a number of time samples greater than zero (as depicted in FIG. 11), or a relative shift can be considered, wherein one signal is not shifted (zero linear phase) and all the others are shifted with number of time samples greater than zero (as depicted in FIG. 13). The same may be applied for the phase offset as well. Any RU 102, 202 may be selected to be an RU 102, 202 with a zero linear phase and/or zero phase offset.

Any first/second linear phase and first/second phase offset may be defined in two different ways:

• Defined as single set of values v _k = b^ ^2pq>ί+f

• Defined as two sets of values wv _k = wherein w defines a constant phase offset applied to all the tones within a RU 103, 203, and v _k defines a linear phase applied to each tone within a MRU 102, 202.

The values of the first/second linear phase(s) and first/second phase offset(s) may be predefined, while for each RU 103, 203 within a specific MRU 102, 202, a value may be selected from a predefined list: • Any linear phase may be defined in a range of Q E {— p, p) with a granularity of where

D e {1,2, ...,N _Lin }. N _Lin may define the maximum possible granularity of linear phase values.

• Any phase offset may be defined in a range of f E {— p, p) with a granularity of where

D e {1,2, ...,N _0ffset ) _· N o _f r _sct may defines the maximum possible granularity of phase offset values.

Further, the wireless network device 100 may provide an indication of the applied linear phase(s) and phase offset(s). For example, in order to allow a receive side to detect a transmitted signal successfully, several indication methods may be defined to be used by the transmit side (wireless network device 100):

• No indication: in this case, a linear phase and phase offset are always applied to a given MRU (transmission), and the specific values are known in advance to both the transmit side (wireless network device 100) and receive side.

• Indication of using the linear phase(s) and phase offset(s): in this case, the transmit side (wireless network device 100) may decide to apply, or not to apply, the first/second linear phase(s) and phase offset(s), and should indicate this within the transmitted signal. The values of the first/second linear phase(s) and phase offset(s) may be known in advance.

• Indication of using the linear phase(s) and phase offset(s) with specific values: in this case, the transmit device (wireless network device 100) may decide, which values to use for a current transmission. Thus, the indication may include both an indication of using the liner phase(s) and phase offset(s), and also the indication of the specific values that were selected for the current transmission.

In the following, it is demonstrated that the wireless network device 100 and corresponding methods achieve a required target of PAPR reduction. Thereby, the focus is on the difference between the degradation of the PAPR on the training sequence(s) 104 and the data portion.

FIG. 14 shows an example of PAPR reduction on the training sequences 104 that can be achieved in the different cases of MRUs 102, 202. It can be seen that in most of the cases, the PAPR degradation is reduced to values comparable to the degradation of the PAPR on the data portion (0.5-ldB). FIG. 15 summarizes PAPR values for the specific cases that are currently discussed in the 802.11 be standard.

FIG. 16 shows a method 300 according to an embodiment of the disclosure. The method 300 may be performed by the wireless network device 100 of the previous description. The method 300 is suitable for MRU allocation in a wireless network, e.g., in a WLAN. The method 300 comprises: a step 301 of selecting a first training signal 101 for a first MRU 102, wherein the first MRU 102 comprises two or more RUs 103 arranged in a frequency domain, and wherein the first training signal 101 comprises a training sequence 104 per RU 103 of the first MRU 102. Further, a step 302 of applying, for at least one RU 103 of the first MRU 102 (particularly for one or more or each RU 103 of the first MRU 102), a first subset of phase values to the training sequence 104 of the at least one RU 103 of the first MRU 103, wherein the first subset of phase values is selected for the at least one RU 103 of the first MRU 102 from a first set of phase values allocated to the first MRU 102.

The described embodiments of the disclosure are not limited to a specific training signal 101, 201. However, they allow reusing the existing sequences defined by older WiFi standards. Further, the embodiments of the disclosure can be applied for lx, 2x and 4x signals lx and 2x linear phase values may be considered as a subset of 4x (no additional memory is required). With the embodiments of the disclosure, the impact of MRU allocation on PAPR may be minimized. The ratio between PAPR on the training signal 101, 202 and the data portion of a transmitted signal may be affected by only 0.5dB. Moreover, the implementation of subsets of phase values, e.g. realized by linear phase(s) and phase offset(s), i.e., constant phase, is simple and does not require high computational complexity.

The present disclosure has been described in conjunction with various embodiments of the disclosure as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed embodiments of the disclosure, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation. In the following examples useful for understanding the invention are presented. Example of Linear Phase Valid Values

Q E {—p, p} with granularity of p , i.e. total number of 129 values

5 Example of Phase Offset Valid Values f p j with granularity of i e. total number of 9 values

Example of Linear Phase Valid Values for MRU Combined of Two 26RU for BW of 20MHz Below we give an example of linear phase and phase offset that lead to a PAPR reduction0 with respect to linear phase and phase offset valid values as given in example above

Example of Linear Phase Valid Values for MRU Combined of Two 52RU for BW of 20MHz Below we give an example of linear phase and phase offset that lead to a PAPR reduction with respect to linear phase and phase offset valid values as given in example above

Example of Linear Phase Valid Values for MRU Combined of 26RU and 52RU for BW of 20MHz

Below we give an example of linear phase and phase offset that lead to a PAPR reduction with respect to linear phase and phase offset valid values as given in example above

Example of Linear Phase Valid Values for MRU Combined of 26RU and 106RU for BW of

20MHz

Below we give an example of linear phase and phase offset that lead to a PAPR reduction with respect to linear phase and phase offset valid values as given in example above

Example of Linear Phase Valid Values for MRU Combined of 242RU and 484RU for BW of 80MHz Below we give an example of linear phase and phase offset that lead to a PAPR reduction with respect to linear phase and phase offset valid values as given in example above Example of Linear Phase Valid Values for MRU Combined of 484RU and 996RU for BW of 160MHz

Below we give an example of linear phase and phase offset that lead to a PAPR reduction with respect to linear phase and phase offset valid values as given in example above

Example of Linear Phase Valid Values for MRU Combined of 242RU. 484RU and 996RU for BW of 160MHz Below we give an example of linear phase and phase offset that lead to a PAPR reduction with respect to linear phase and phase offset valid values as given in example above

Example of Linear Phase Valid Values for MRU Combined of three 996RU for BW of 320MHz

Below we give an example of linear phase and phase offset that lead to a PAPR reduction with respect to linear phase and phase offset valid values as given in example above

Example of Linear Phase Valid Values for MRU Combined of 484RU and two 996RU for BW of 240MHz Below we give an example of linear phase and phase offset that lead to a PAPR reduction with respect to linear phase and phase offset valid values as given in example above