The present disclosure pertains to the field of wireless communications. The present disclosure relates to a transmitter node, a receiver node, and methods for reducing peak to average power ratio.

BACKGROUND

Achieving a low PAPR may be seen as a challenge for systems that deploy linear modulation schemes (e.g. in systems such as Enhanced GPRS, EDGE, Wideband Code- Division Multiple Access, WCDMA, Orthogonal Frequency Division Multiplexing, OFDM). To not deteriorate the information carried by the signal or cause spectral regrowth, the analog signal path needs to be operated in its linear regime. In particular, the power amplifier, PA, needs to be biased with a back-off that ensures linear operation. This severely limits the power-added-efficiency, PAE, to far below 50%.

For example, with a system requiring total-rad iated-power, TRP, of about 24 dBm, both the total power consumption and heat dissipation becomes problematic. There is therefore a need for techniques to reduce the PAPR.

SUMMARY

There is need for more efficient techniques in that less resources and less capacity of the wireless link are used for PAPR reduction. Accordingly, there is a need for devices and methods for reducing Peak to Average Power Ratio, PAPR , which can mitigate, alleviate or address the shortcomings existing and can reduce the usage of resources and the usage of the capacity of the wireless link.

Disclosed is a transmitter node for reducing Peak to Average Power Ratio, PAPR. The transmitter node comprises an antenna array. The antenna array comprises a plurality of antenna elements. Each antenna element is configured to communicate using a plurality of N subcarriers (e.g. OFDM). The transmitter node comprises circuitry configured to cause the transmitter node to transmit, using a first antenna element, a first signal on the N subcarriers. The first signal is configured to carry a first data signal and a first PAPR reduction signal on respectively different subcarriers of the N subcarriers. The transmitter node comprises circuitry configured to cause the transmitter node to transmit, using a second antenna element, a second signal on the N subcarriers. The second signal is configured to carry a second data signal and a second PAPR reduction signal on respectively different subcarriers of the N subcarriers. The first PAPR reduction signal and the second PAPR reduction signal are carried on respectively different subcarriers of the N subcarriers.

Disclosed is a method, performed by a transmitter node for reducing Peak to Average Power Ratio, PAPR. The transmitter node comprises an antenna array. The antenna array comprises a plurality of antenna elements. Each antenna element is configured to communicate using a plurality of N subcarriers. The method comprises transmitting, using a first antenna element, a first signal on the N subcarriers. The first signal is configured to carry a first data signal and a first PAPR reduction signal on respectively different subcarriers of the N subcarriers. The method comprises transmitting, using a second antenna element, a second signal on the N subcarriers. The second signal is configured to carry a second data signal and a second PAPR reduction signal on respectively different subcarriers of the N subcarriers. The first PAPR reduction signal and the second PAPR reduction signal are carried on different subcarriers of the N subcarriers.

Advantageously, the disclosed transmitter node and related method can reduce the usage of resources and the usage of the capacity of the wireless link. The disclosed technique enables transmitting the same amount of data as if no PAPR reduction signal were used, for example when the number of antenna elements used is sufficient. The disclosed technique enables obtaining an improved data rate.

Disclosed is a receiver node . The receiver node comprises an antenna configuration. The antenna configuration comprises at least one antenna element. The receiver node is configured to communicate using a plurality of N subcarriers. The receiver node comprising circuitry configured to cause the receiver node to receive, from a transmitter node, control signalling indicative of a scheme for PAPR reduction for upcoming communication.

Disclosed is a method, performed by a receiver node for adapting to a scheme for PAPR reduction. The receiver node comprises an antenna configuration. The antenna configuration comprises a at least one antenna element. Each antenna element is configured to communicate using a plurality of N subcarriers. The method comprises receiving, from a transmitter node, control signalling indicative of a scheme for PAPR reduction for upcoming communication.

It is an advantage of the present disclosure that the disclosed receiver node and related method can optimize reception by being informed of which subcarriers are used for PAPR reduction. As the foreseen interference level on subcarriers, SCs, carrying PAPR signal depends on the number of antennas in the transmit antenna array that carry a PAPR reducing signal at the SCs (and may differ from SCs not carrying PAPR signal), knowledge about the foreseen interference level enables the receiver to optimize the estimation of the received signals and thus may enhance the Bit Error Rate and/or Block Error Rate (BER/BLER). The information may further include which SC are exposed to PAPR signals (e.g. which SC may have different interference) and the data-signal to PAPR-signal ratio (e.g. SINR), defined by the array gain of the data signal.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present disclosure will become readily apparent to those skilled in the art by the following detailed description of examples thereof with reference to the attached drawings, in which:

Fig. 1 is a diagram illustrating an example wireless communication system comprising an example network node and an example wireless device according to this disclosure,

Figs. 2A-2B are diagrams illustrating example transmitter nodes according to this disclosure,

Fig. 3 is a block diagram illustrating an example transmitter node according to this disclosure,

Fig. 4 is a block diagram illustrating an example receiver node according to this disclosure,

Fig. 5 is a flow-chart illustrating an example method, performed by a transmitter node for reducing Peak to Average Power Ratio, PAPR according to this disclosure, and Fig. 6 is a flow-chart illustrating an example method, performed by a receiver node for reducing Peak to Average Power Ratio, PAPR according to this disclosure. DETAILED DESCRIPTION

Various examples and details are described hereinafter, with reference to the figures when relevant. It should be noted that the figures may or may not be drawn to scale and that elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are only intended to facilitate the description of the examples. They are not intended as an exhaustive description of the disclosure or as a limitation on the scope of the disclosure. In addition, an illustrated example needs not have all the aspects or advantages shown. An aspect or an advantage described in conjunction with a particular example is not necessarily limited to that example and can be practiced in any other examples even if not so illustrated, or if not so explicitly described.

The figures are schematic and simplified for clarity, and they merely show details which aid understanding the disclosure, while other details have been left out. Throughout, the same reference numerals are used for identical or corresponding parts.

Fig. 1 is a diagram illustrating an example wireless communication system 1 comprising an example receiver node 400 and an example transmitter node 300 according to this disclosure.

As discussed in detail herein, the present disclosure relates to a wireless communication system 1 comprising a cellular system, for example, a 3GPP wireless communication system. The wireless communication system 1 comprises a transmitter node 300 and/or a receiver node 400.

A transmitter node may be seen as a node or a device configured to act as a transmitter. A received node may be seen as a node or a device configured to act as a receiver.

The transmitter node may be a wireless device and/or a network node. The receiver node may be a wireless device and/or a network node. A network node disclosed herein refers to a radio access network, RAN, node operating in the radio access network, such as a base station, an evolved Node B, eNB, or gNB in NR. In one or more examples, the RAN node is a functional unit which may be distributed in several physical units. A wireless device may refer to a mobile device and/or a user equipment, UE.

In Fig. 1 , the transmitter node 300 acts as a wireless device while the receiver node acts as a network node, such as a RAN node.

The wireless communication system 1 described herein may comprise one or more transmitter nodes and/or one or more receiver nodes, such as one or more of: a base station, an eNB, a gNB and/or an access point. Optionally, the wireless communication system 1 may comprise an additional transmitter node 300A.

The transmitter node 300, 300A may be configured to communicate with the receiver node 400 via a wireless link (or radio access link) 10, 10A.

Approaches for PAPR reduction include tone injection, tone-reservation, constellation extension, partial transmit sequence, selective mapping, companding transform, and block coding. The PAPR reduction techniques can be broadly classified into three varieties namely (1) clip effect transformations (clipping), (2) block coding techniques and (3) probabilistic approaches.

Clip effect transformations proposes that large peaks are simply not transmitted.

However, this causes some spectral growth and associated bit errors and possibly retransmissions.

Block coding techniques include reserving resources for PAPR reduction. This can be implemented by allocating sub-carriers, SC, or symbols for injection of non-information carrying signals that only reduce the PAPR, or by constellation modifications where some transitions are avoided. However, in the block coding approach, resources are sacrificed to enable a lower back off at the PA and to obtain a net gain.

The probabilistic approaches relate to reduction of the probability of large amplitude peaks by selecting codewords optimally (i.e. to avoid fast phase transitions). However, this also involves designing codewords that avoids such fast phase transitions. Figs. 2A-2B are diagrams, such as diagram 2 illustrating an example transmitter node 300 according to this disclosure. The transmitter node 300 comprises an antenna array 303A comprising a plurality of M antenna elements 31 , 32, 33 to communicate using a plurality of N subcarriers, such as N orthogonal subcarriers. The subcarriers may be seen as OFDM subcarriers. Each antenna element 31, 32, 33 is configured to communicate using a plurality of N subcarriers. In other words, the N subcarriers may be mutually orthogonal in the example implementation. The subcarriers may not be mutually orthogonal in some other examples. The disclosed technique may be applied to subcarriers which are not mutually orthogonal. Stated differently, any one subcarrier of the N subcarriers may be orthogonal to any of the other subcarriers in some examples. The plurality of subcarriers comprises a first subcarrier and a second subcarrier, wherein the first subcarrier can be orthogonal to the second subcarrier.

The subcarriers may be obtained using a standard block coding technique with tone injection.

The transmitter node comprises circuitry, such as a plurality of a digital-to-analog converters, DAC, a plurality of variable capacitors and a plurality of power amplifiers, PA. The variable capacitors are shown for illustrative purpose (for example, applicable for hybrid / analog beamforming, BF). Physical capacitors may not be needed when fully digital BF is used. This may be seen as a transmit chain or a transmit path. Fig. 2 shows an example of a fully digital beamforming architecture where each transmit path needs its dedicated DAC (for example, in that baseband signals are different at each antenna element).

The subcarriers may be seen as being indexed from 1 to N. Fig. 2 illustrates the signals transmitted on corresponding subcarriers in a graph illustrating the subcarrier index vs time where in black the PAPR reduction signals 4, 5, 6 are illustrated. In Fig. 2, two transmissions are illustrated over the N subcarriers.

Reducing peak-to-average-power-ratio, PAPR, of signals in transmitters may be seen as avoiding sacrificing valuable resources by spatially filtering the injected PAPR reduction signal from the desired communication beam. The disclosed technique involves the spatial dimension. The transmitter node 300 can inject a signal for PAPR reduction. The injected signal may be treated or processed differently than the data signal so as to achieve a lower array gain. The disclosed technique may apply to systems with beamforming, BF, and where an array of antenna elements is used at the transmitter node (e.g. at least two antennas, or larger number of antenna elements which may lead to array gain and a larger Signal to Interference and Noise Ratio, SINR, at the receiver node). Examples of implements of the disclosed technique can depend on the hardware, HW, implementation, for example, if full digital BF or hybrid BF is used.

The transmitter node 300 transmits, using a first antenna element 31 , a first signal on the first N subcarriers. The first signal is configured to carry a first data signal and a first PAPR reduction signal 4 (illustrated in black in Fig. 2) on respectively different subcarriers of the N subcarriers.

The transmitter node 300 transmits, using a second antenna element 32, a second signal on the first N subcarriers. The second signal is configured to carry a second data signal and a second PAPR reduction signal 5 on respectively different subcarriers of the N subcarriers.

The first PAPR reduction signal 4 and the second PAPR reduction signal 5 are carried on different subcarriers of the N subcarriers, and hence no array gain is obtained for the PAPR reducing signals. For example, tone reservation can be used as a PAPR reduction technique. As illustrated in Fig. 2A, on every X:th subcarrier, no data signal is transmitted while a PAPR reduction signal (such as PAPR reduction signal 4, 5, 6) is introduced on every X:th SCs and fed to the antenna element.

For example, for each antenna element, a different subcarrier is selected for transmitting the PAPR reduction signal. In some examples, as the subcarriers are all orthogonal, the array gain for the data signal on subcarriers subject to PAPR reduction on any of the antenna elements will be reduced with one antenna element. In other words, for each subcarrier, all antennas except one may transmit the same signal (e.g. referred to as data signal) at a time. For example, each antenna element also carries the PAPR reduction signal on every X:th SC, where X is an integer less than N. For example, for each subcarrier, there may be only one antenna element carrying that specific PAPR reduction signal, and the array gain may be therefore 1 (or 0 dB). In the far field, the received ratio between the data signal and the PAPR reducing signal may become (M-D)/D on the subcarriers carrying the PAPR reducing signal, (for example SINR has an upper limit) where D elements carry PAPR reducing signal at a certain subcarrier and M is the number of antenna elements.

The transmitter node 300 transmits, using an M:th antenna element 33, an M:th signal on the N subcarriers. The M:th signal is configured to carry an M:th data signal and an M:th PAPR reduction signal 6 on respectively different subcarriers of the N subcarriers.

In Fig. 2A, the first PAPR reduction signal 4 and the M:th PAPR reduction signal 6 are carried on different subcarriers of the N subcarriers. The second PAPR reduction signal 5 and the M:th PAPR reduction signal 6 are carried on different subcarriers of the N subcarriers.

Fig. 2A shows the beam 7 associated with the M-1 coherently added data signals, such as the first data signal, the second data signal and/or the M:th data signal. Fig. 2A shows the beam 8 associated with the M PAPR reduction signals, such as the first PAPR reduction signal, the second PAPR reduction signal and/or the M:th PAPR reduction signal.

In one or more example transmitter nodes, the transmitter node is configured, for each antenna element, to determine subcarriers to use for PAPR reduction signals based on a spreading parameter. As illustrated in Fig. 2A, the Mth PAPR reduction signals 4 or 5 or 6 are separated based on spreading parameter.

For example, the first PAPR reduction signal 4 and/or the second PAPR reduction 5 are signals configured to reduce PAPR. For example, the first and second PAPR reduction signals 4, 5 are configured to reduce PAPR by applying tone reservation with different tones at different antenna elements and different subcarriers.

An example implementation of the transmitter node may use one of the block coding on each transmit chain (as illustrated in Fig. 2 by DAC, capacitor, PA and antenna element) in combination with the disclosed PAPR reduction signal. In other words, the disclosed PAPR reduction signal can be injected (or absent, e.g. in case no signal needs to be injected due to low PAPR for a symbol) so as to achieve a lower array gain. Stated differently, a resulting “low PAPR” signal transmitted by each antenna element may be seen as comprising or containing two components. The first component may correspond to the disclosed data signal, DS (such as data carrying signal). The second component may correspond to the PAPR reduction signal, PS. For example, the disclosed data signal, DS, may be the same for the M antenna elements and create a beam that relates to the relative phases and/or amplitudes and antenna configurations (for example, the DS adds coherently to shape a spatial filter a.k.a. a beam).

For example, the PAPR reduction signal can be designed to be different at each antenna element or each antenna element of a group of antennas (e.g. an antenna port, e.g. if hybrid BF), with properties that make them orthogonal in the sense that the array gain for that group becomes 1 (0 dB) between groups of antenna elements (e.g. so that they do not add coherently) in the direction of the beam of the first component. Groups of antennas (with G antenna ports) may be envisaged to support a scenario where the number of orthogonal resources or subcarriers is fewer than the number of antenna elements. If hybrid BF is used, the number of orthogonal signals is effectively reduced to G. A grouping of antenna elements may be envisaged to support a scenario where the number of orthogonal subcarriers, N, is less (e.g. when the PS is needed on every N:th SC in a larger set of N’ SCs) than the number of antenna elements. The DS may show an array gain of G ^* M, and hence, SINR may be still limited to M-1 , for SC carrying PS.

For example, the PAPR reduction signals are different in that different SCs are used, and the values carried on each subcarriers are different among all antennas.

In other words, Fig. 2A may also illustrate the case where orthogonality between the injected PAPR signals is achieved by the use of different subcarriers for each antenna element or antenna port (31 , 32, 33) feeding one group of antennas. Stated differently, the disclosed technique proposes orthogonal PAPR resources for the signals fed to each antenna element or antenna port associated with a sub-set of an antenna array of a transmitter node where the antenna elements may be interleaved (i.e. may be located in any relative order). With the disclosed technique, less resources dedicated to PAPR reduction need to be allocated, and hence, all SCs carry DS as seen from the receiver node.

Fig. 2B shows grouping of antenna elements. For example, Fig.2B shows a first grouping 40, and a second grouping 41. Grouping 40 shows groups 42, 43. Each of the groups of antenna elements are fed with the same signals, for example same PS signals and same DS signals. Grouping 41 shows groups 44, 45, 46. Each antenna element in the group 42 is fed with orthogonal PS. Each group 44, 45 may have a single antenna port and receive the same PS signal. Grouping 41 applies to hybrid BF, but can also be a description of grouping 40 according to re-arrangement of the antenna elements shown by the arrows.

Fig. 3 shows a block diagram of an example transmitter node 300, e.g. for reducing Peak to Average Power Ratio, PAPR, according to the disclosure. The transmitter node 300 comprises an antenna array 303A which comprises a plurality of antenna elements, such as a first antenna element 31, and a second antenna element 32. The second antenna element may be different from the first antenna element. Each antenna element 31 , 32 is configured to communicate using a plurality of N subcarriers, such as N orthogonal subcarriers. For example, the first antenna element 31 is configured to communicate using a plurality of N orthogonal subcarriers. For example, the second antenna element 32 is configured to communicate using a plurality of N subcarriers, such as N orthogonal subcarriers. In one or more examples, the N subcarriers are mutually orthogonal. Stated differently, any one subcarrier of the N subcarriers can be orthogonal to any of the other subcarriers. The plurality of subcarriers comprises a first subcarrier and a second subcarrier, wherein the first subcarrier can be orthogonal to the second subcarrier.

The antenna array may have one or two dimensions.

The transmitter node 300 may comprise an antenna port associated with one or more antenna elements, i.e. group of antennas. The antenna port may be seen as an antenna configuration associated with a gain pattern related to at least one antenna element. The transmitter node may comprise an antenna assembly which may comprise two or more antenna elements, wherein the antenna port may be associated with at least one of the antenna elements, and may be associated with a beam configuration. The antenna port may be a virtual antenna port in one or more examples. In one or more examples, both an antenna element and an antenna port have a single feed, while the antenna port may be associated with multiple antenna elements.

The transmitter node 300 comprises circuitry, such as memory circuitry 301, processor circuitry 302, and a wireless interface 303. The wireless interface 303 comprises the antenna array 303A which comprises a plurality of antenna elements, such as a first antenna element 31 , and a second antenna element 32. The plurality of antenna elements may comprise a third antenna element, a fourth antenna element, and an M:th antenna element etc.

The term “antenna element” may be used interchangeably with the term “antenna port”. The wireless interface 303 is configured for wireless communications via a wireless communication system, such as a 3GPP system, such as a 3GPP system supporting one or more of: New Radio, NR, EDGE, WCDMA, OFDM and Long Term Evolution.

The transmitter node 300 comprises circuitry (such as via the wireless interface 303) configured to cause the transmitter node 300 to transmit, using a first antenna element 31, a first signal on the N subcarriers. The first signal is configured to carry a first data signal and a first PAPR reduction signal on respectively different subcarriers of the N subcarriers, such as N orthogonal subcarriers. In other words, the transmitter node 300 is configured transmit (such as via the wireless interface 303), using the first antenna element 31, a first signal on the N subcarriers. The first signal is configured to carry a first data signal and a first PAPR reduction signal on respectively different subcarriers of the N subcarriers. In other words, a part of the N subcarriers may be reserved for PAPR reduction, for example transmitting PAPR reduction signals, such as the first PAPR reduction signal.

The transmitter node 300 comprises circuitry configured to cause the transmitter node 300 to transmit (such as via the wireless interface 303), using a second antenna element, a second signal on the N subcarriers. The second signal is configured to carry a second data signal and a second PAPR reduction signal on respectively different subcarriers of the N subcarriers. In other words, the transmitter node 300 is configured to transmit (such as via the wireless interface 303), using a second antenna element, a second signal on the N subcarriers. The second signal is configured to carry a second data signal and a second PAPR reduction signal on respectively different subcarriers of the N subcarriers.

The first data signal and the second data signal are the same on subcarriers not carrying PS. In other words, data signals transmitted by the two antenna elements (such as two antenna ports) on the subcarriers carrying data on both antenna elements are the same. Stated differently, the data signals on subcarriers not carrying PAPR reduction signal are the same at different antenna ports.

In one or more example transmitter nodes, the first data signal and the second data signal are the same signals. In other words, the data signals (such as the first data signal and the second data signal) on subcarriers not carrying PAPR reduction signal are the same at the two or more antenna elements or antenna ports.

In one or more example transmitter nodes, the first and second PAPR reduction signals are configured to reduce PAPR by applying tone reservation with different tones at different subcarriers and at different antenna elements. In other words, tone reservation may be applied, the reserved tones are used to transmit the disclosed first and/or second PAPR reducing signal.

In one or more example transmitter nodes, the first PAPR reduction signal and the second PAPR reduction signal are carried on different subcarriers of the N subcarriers. In other words, transmission of the second PAPR reduction signal is orthogonal to transmission of the first PAPR reduction signal.

In one or more example transmitter nodes, the transmitter node is configured, for each antenna element, to determine subcarriers to use for PAPR reduction signals based on one or more spreading parameters, such as a first spreading parameter and/or a second spreading parameter. In other words, for a given antenna element, the subcarriers selected for PAPR reduction may need to be sufficiently spread out. In other words, the subcarriers selected for PAPR reduction for any two antenna elements (such as two antenna ports) may need to be sufficiently spread out. For example, the first spreading parameter may be based on an offset X between the subcarriers reserved for PAPR reduction for an antenna element, such as antenna port, e.g. every X:th subcarrier is reserved for PAPR reduction. For example, the second spreading parameter may be based on an offset Y between two reserved subcarriers of two antenna elements, such as antenna ports. For example, for an antenna element, such as an antenna port 31 , the subcarriers reserved for PAPR reduction are the 1 ^st , 11 ^th , 21 ^st , 31 ^st while for antenna element (such as antenna port) 32, the subcarriers reserved for PAPR reduction are 1+Y,

11 +Y, 21 +Y, 31 +Y where Y is in an integer. In one or more example transmitter nodes, the first PAPR reduction signal and/or the second PAPR reduction are signals configured to reduce PAPR. The first signal comprises the first data signal and the first PAPR reduction signal. For example, the first PAPR reduction signal s2(t) can carry values that are selected based on the values in the first data signal s1(t). The aggregate time domain signal s(t) forming the first signal can be expressed as s1 (t)+s2(t). The values of s2(t) may be selected in such a way that s(t) never has any large peaks, thereby reducing the PAPR. For example, in some scenarios, PAPR reduction signals (e.g. the first PAPR reduction signal and/or the second PAPR reduction) may be blanked (e.g. s2(t)=0).

In one or more example transmitter nodes, the transmitter node comprises circuitry configured to further cause the transmitter node to transmit, to a receiver node, control signalling indicative of a PAPR reducing scheme.

In one or more example transmitter nodes, the first PAPR reduction signal is transmitted using K orthogonal subcarriers. K denotes an integer. In one or more example transmitter nodes, K is equal or larger than one. In one or more example transmitter nodes, K is less than N. It may be envisaged to have more than one orthogonal subcarrier reserved for PAPR reduction.

In one or more example transmitter nodes, the first data signal is transmitted using P orthogonal subcarriers. In one or more example transmitter nodes, P is equal to N minus K, e.g.: P = N - K

In one or more example transmitter nodes, each P subcarriers is different from each of the K subcarriers, e.g. for an antenna element. In other words, any of the P subcarriers for transmission of the data signal is different than the K subcarriers for transmission of the PAPR reduction signal.

The transmitter node 300 may be configured to perform any of the methods disclosed in Fig. 5.

The transmitter node 300 is optionally configured to perform any of the operations disclosed in Fig. 5 (such as any one or more of S101, S102). The operations of the wireless device 300 may be embodied in the form of executable logic routines (for example, lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (for example, memory circuitry 301) and are executed by processor circuitry 302).

Furthermore, the operations of the transmitter node 300 may be considered a method that the transmitter node 300 is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may also be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and/or software.

Memory circuitry 301 may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable device. In a typical arrangement, memory circuitry 301 may include a non-volatile memory for long term data storage and a volatile memory that functions as system memory for processor circuitry 302. Memory circuitry 301 may exchange data with processor circuitry 302 over a data bus. Control lines and an address bus between memory circuitry 301 and processor circuitry 302 also may be present (not shown in Fig. 3). Memory circuitry 301 is considered a non-transitory computer readable medium.

Memory circuitry 301 may be configured to store information related to the subcarriers, spreading parameter(s), and/or PAPR reduction scheme in a part of the memory.

Fig. 4 shows a block diagram of an example receiver node 400 according to the disclosure. The receiver node 400 comprises an antenna configuration, such as an antenna array 403A which comprises at least one antenna element 41 A. In one or more examples, the receiver node 400 comprises an antenna array 403A which comprises a plurality of antenna elements. The receiver node 400 is configured to communicate, for example using a wireless interface 403, using a plurality of N subcarriers, such as N orthogonal subcarriers, such as N mutually orthogonal subcarriers.

The receiver node 400 comprises circuitry, such as memory circuitry 401, processor circuitry 402, and a wireless interface 403. The wireless interface 403 comprises the antenna array 403A which comprises at least one antenna element 41 A.The network node 400 may be configured to perform any of the methods disclosed in Fig. 6. The receiver node 400 comprises circuitry (such as via the wireless interface 403) configured to cause the receiver node 400 to receive, from a transmitter node, control signalling indicative of a scheme for PAPR reduction for upcoming communication. In other words, the receiver node 400 is configured to receive (such as via the wireless interface 403), from a transmitter node, control signalling indicative of a scheme for PAPR reduction for upcoming communication.

In one or more example receiver nodes, the control signalling is indicative of the presence or absence of a PAPR reduction signal.

In one or more example receiver nodes, the control signalling is indicative of subcarrier positions of the PAPR reduction signal in the plurality of N subcarriers. The position may be seen as the location of the PAPR reduction signal in the plurality of N subcarriers, such as subcarrier 1 , subcarrier 2 etc.

The position may also be indicated by the spreading factor (X, Y) based on a default start position that may optionally be explicitly indicated.

The wireless interface 403 is configured for wireless communications via a wireless communication system, such as a 3GPP system.

In one or more examples, the antenna array may comprise a plurality of antenna elements, and the receiver node 400 may be configured to receive PAPR reducing signals on different subcarriers at each antenna element, such as a first PAPR reduction signal using a first antenna element and a second PAPR reduction signal using a second antenna element wherein the first PAPR reduction signal and the second PAPR reduction signal are carried on different subcarriers of the N subcarriers.

The receiver node 400 may be configured to receive and demodulate data signals on respective subcarriers of the N subcarriers, such a first data signal received using the first antenna element and the second data signal using the second antenna element.

In one or more example receiver nodes, the first data signal and the second data signal are the same signals. In other words, the data signals (such as the first data signal and the second data signal) on subcarriers not carrying PAPR reduction signal are the same at the two or more antenna elements or antenna ports. Processor circuitry 402 is optionally configured to perform any of the operations disclosed in Fig. 6 (such as S202). The operations of the receiver node 400 may be embodied in the form of executable logic routines (for example, lines of code, software programs, etc.) that are stored on a non-transitory computer readable medium (for example, memory circuitry 401 ) and are executed by processor circuitry 402.

Furthermore, the operations of the receiver node 400 may be considered a method that the receiver node 400 is configured to carry out. Also, while the described functions and operations may be implemented in software, such functionality may also be carried out via dedicated hardware or firmware, or some combination of hardware, firmware and/or software.

Memory circuitry 401 may be one or more of a buffer, a flash memory, a hard drive, a removable media, a volatile memory, a non-volatile memory, a random access memory (RAM), or other suitable device. In a typical arrangement, memory circuitry 401 may include a non-volatile memory for long term data storage and a volatile memory that functions as system memory for processor circuitry 402. Memory circuitry 401 may exchange data with processor circuitry 402 over a data bus. Control lines and an address bus between memory circuitry 401 and processor circuitry 402 also may be present (not shown in Fig. 4). Memory circuitry 401 is considered a non-transitory computer readable medium.

Memory circuitry 401 may be configured to store information related to of a scheme for PAPR reduction in a part of the memory.

Fig. 5 shows a flow diagram of an example method 100, performed by a transmitter node (such as transmitter node 300 in any of Fig. 1, Fig. 2A, and Fig. 3), for reducing Peak to Average Power Ratio, PAPR according to this disclosure. The transmitter node comprises an antenna array which comprises a plurality of antenna elements. Each antenna element is configured to communicate using a plurality of N subcarriers, such as N orthogonal subcarriers.

The method 100 comprises transmitting S104, using a first antenna element, a first signal on the N subcarriers. The first signal is configured to carry a first data signal and a first PAPR reduction signal on respectively different subcarriers of the N subcarriers. The method 100 comprises transmitting S106, using a second antenna element, a second signal on the N subcarriers. The second signal is configured to carry a second data signal and a second PAPR reduction signal on respectively different subcarriers of the N subcarriers.

In one or more example methods, the first PAPR reduction signal and the second PAPR reduction signal are carried on different subcarriers of the N subcarriers.

In one or more example methods, the method 100 comprises, for each antenna element, determining S102 subcarriers to use for PAPR reduction signals based on a spreading parameter.

In one or more example methods, the first PAPR reduction signal and/or the second PAPR reduction are signals configured to reduce PAPR.

In one or more example methods, the first and second PAPR reduction signals are configured to reduce PAPR by applying tone reservation with different tones at different antenna elements.

In one or more example methods, the method 100 comprises transmitting S101, to a receiver node, control signalling indicative of a PAPR reducing scheme.

In one or more example methods, the N subcarriers are mutually orthogonal.

In one or more example methods, the first PAPR reduction signal is transmitted using K orthogonal subcarriers.

In one or more example methods, K is equal or larger than one and less than N.

In one or more example methods, the first data signal is transmitted using P orthogonal subcarriers.

In one or more example methods, P is equal to N minus K.

In one or more example methods, each P subcarriers is different from each of the K subcarriers.

In one or more example methods, the first data signal and the second data signal are the same, for example on subcarriers of the N subcarriers. Fig. 6 shows a flow diagram of an example method 200, performed by a receiver node (such as receiver node 400 in any of Fig. 1 , and Fig. 4) for adapting to a scheme for Peak to Average Power Ratio, PAPR reduction, such as for reducing Peak to Average Power Ratio, PAPR according to this disclosure. The receiver node comprises an antenna array which comprises at least one antenna element. For example, the receiver node comprises an antenna array which comprises a plurality of antenna elements. The antenna element is configured to communicate using a plurality of N subcarriers, such as N orthogonal subcarriers.

The method 200 comprises receiving S202, from a transmitter node (such as transmitter node 300 of Fig. 1 , Fig. 2A, and Fig. 3), control signaling indicative of a scheme for PAPR reduction for upcoming communication.

In one or more example methods, the control signaling is indicative of the presence or absence of a PAPR reduction signal.

In one or more example methods, the control signaling is indicative of subcarrier positions of the PAPR reduction signal in the plurality of N subcarriers.

In one or more example methods, the N subcarriers are mutually orthogonal.

The method 200 may comprise receiving, from the transmitter node, a first signal on the N subcarriers transmitted using a first antenna element. The first signal is configured to carry a first data signal and a first PAPR reduction signal on respectively different subcarriers of the N subcarriers according to the scheme for PAPR reduction.

The method 200 may comprise receiving, from the transmitter node, a second signal on the N subcarriers transmitted using a second antenna element. The second signal is configured to carry a second data signal and a second PAPR reduction signal on respectively different subcarriers of the N subcarriers according to the scheme for PAPR reduction. The first PAPR reduction signal and the second PAPR reduction signal are carried on different subcarriers of the N subcarriers.

The terms “PAPR reduction signal” and “PAPR reducing signal” may be used interchangeably in the present disclosure.

Examples of methods and products (transmitter node and receiver node) according to the disclosure are set out in the following items: Item 1.A transmitter node for reducing Peak to Average Power Ratio, PAPR, the transmitter node comprising an antenna array comprising a plurality of antenna elements, wherein each antenna element is configured to communicate using a plurality of N subcarriers, the transmitter node comprising circuitry configured to cause the transmitter node to: transmit, using a first antenna element, a first signal on the N subcarriers, wherein the first signal is configured to carry a first data signal and a first PAPR reduction signal on respectively different subcarriers of the N subcarriers; and transmit, using a second antenna element, a second signal on the N subcarriers, wherein the second signal is configured to carry a second data signal and a second PAPR reduction signal on respectively different subcarriers of the N subcarriers; and wherein the first PAPR reduction signal and the second PAPR reduction signal are carried on different subcarriers of the N subcarriers.

Item 2. The transmitter node according to item 1, wherein the transmitter node is configured, for each antenna element, to determine subcarriers to use for PAPR reduction signals based on a spreading parameter.

Item 3. The transmitter node according to any of the previous items, wherein the first PAPR reduction signal and/or the second PAPR reduction are signals configured to reduce PAPR.

Item 4. The transmitter node according to any of the previous items, wherein the first and second PAPR reduction signals are configured to reduce PAPR by applying tone reservation with different tones at different antenna elements.

Item 5. The transmitter node according to any of the previous items, the transmitter node comprising circuitry configured to further cause the transmitter node to: transmit, to a receiver node, control signaling indicative of a PAPR reducing scheme. Item 6. The transmitter node according to any of the previous items, wherein the N subcarriers are mutually orthogonal.

Item 7. The transmitter node according to any of the previous items, wherein the first data signal and the second data signal are the same signals.

Item 8. The transmitter node according to any of the previous items, wherein the first PAPR reduction signal is transmitted using K orthogonal subcarriers, where K is equal or larger than one and less than N; wherein the first data signal is transmitted using P orthogonal subcarriers, wherein P is equal to N minus K, and wherein each P subcarriers is different from each of the K subcarriers.

Item 9. A receiver node, the receiver node comprising an antenna configuration comprising at least one antenna element, wherein the receiver node is configured to communicate using a plurality of N subcarriers, the receiver node comprising circuitry configured to cause the receiver node to:

- receive, from a transmitter node, control signaling indicative of a scheme for PAPR reduction for upcoming communication.

Item 10. The receiver node according to item 9, wherein the control signaling is indicative of the presence or absence of a PAPR reduction signal.

Item 11. The receiver node according to any of items 9-10, wherein the control signaling is indicative of subcarrier positions of the PAPR reduction signal in the plurality of N subcarriers.

Item 12. A method, performed by a transmitter node, for reducing Peak to Average Power Ratio, PAPR, the transmitter node comprising an antenna array comprising a plurality of antenna elements, wherein each antenna element is configured to communicate using a plurality of N subcarriers, the method comprising: transmitting (S104) using a first antenna element, a first signal on the N subcarriers, wherein the first signal is configured to carry a first data signal and a first PAPR reduction signal on respectively different subcarriers of the N subcarriers; and transmitting (S106), using a second antenna element, a second signal on the N subcarriers, wherein the second signal is configured to carry a second data signal and a second PAPR reduction signal on respectively different subcarriers of the N subcarriers; and wherein the first PAPR reduction signal and the second PAPR reduction signal are carried on different subcarriers of the N subcarriers.

Item 13. The method according to item 12, the method comprising, for each antenna element, determining (S102) subcarriers to use for PAPR reduction signals based on a spreading parameter. Item 14. The method according to any of items 12-13, wherein the first PAPR reduction signal and/or the second PAPR reduction are signals configured to reduce PAPR.

Item 15. The method according to any of items 12-14, wherein the first and second PAPR reduction signals are configured to reduce PAPR by applying tone reservation with different tones at different antenna elements.

Item 16. The method according to any of items 12-15, the method comprising transmitting (S101), to a receiver node, control signalling indicative of a PAPR reducing scheme.

Item 17. The method according to any of items 12-16, wherein the N subcarriers are mutually orthogonal. Item 18. The method according to any of items 12-17, wherein the first data signal and the second data signal are the same signals.

Item 19. The method according to any of items 12-18, wherein the first PAPR reduction signal is transmitted using K orthogonal subcarriers, where K is equal or larger than one and less than N; wherein the first data signal is transmitted using P orthogonal subcarriers, wherein P is equal to N minus K, and wherein each P subcarriers is different from each of the K subcarriers.

Item 20. A method, performed by a receiver node, the receiver node comprising an antenna array comprising at least one antenna element, wherein the antenna element is configured to communicate using a plurality of N subcarriers, the method comprising: receiving (S202), from a transmitter node, control signalling indicative of a scheme for PAPR reduction for upcoming communication. Item 21. The method according to item 20, wherein the control signalling is indicative of the presence or absence of a PAPR reduction signal.

Item 22. The method according to any of items 20-21 , wherein the control signalling is indicative of subcarrier positions of the PAPR reduction signal in the plurality of N subcarriers.

Item 23. The method according to any of items 20-22, wherein the N subcarriers are mutually orthogonal. The use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. does not imply any particular order, but are included to identify individual elements. Moreover, the use of the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. does not denote any order or importance, but rather the terms “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. are used to distinguish one element from another. Note that the words “first”, “second”, “third” and “fourth”, “primary”, “secondary”, “tertiary” etc. are used here and elsewhere for labelling purposes only and are not intended to denote any specific spatial or temporal ordering. Furthermore, the labelling of a first element does not imply the presence of a second element and vice versa.

The use of a letter and “:th” may correspond to an arbitrary integer number, e.g. N:th.

It may be appreciated that Figs. 1-6 comprise some circuitries or operations which are illustrated with a solid line and some circuitries or operations which are illustrated with a dashed line. Circuitries or operations which are comprised in a solid line are circuitries or operations which are comprised in the broadest example. Circuitries or operations which are comprised in a dashed line are examples which may be comprised in, or a part of, or are further circuitries or operations which may be taken in addition to circuitries or operations of the solid line examples. It should be appreciated that these operations need not be performed in order presented. Furthermore, it should be appreciated that not all of the operations need to be performed. The example operations may be performed in any order and in any combination.

It is to be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed.

It is to be noted that the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements.

It should further be noted that any reference signs do not limit the scope of the claims, that the examples may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware.

The various example methods, devices, nodes and systems described herein are described in the general context of method steps or processes, which may be implemented in one aspect by a computer program product, embodied in a computer- readable medium, including computer-executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), etc. Generally, program circuitries may include routines, programs, objects, components, data structures, etc. that perform specified tasks or implement specific abstract data types. Computer-executable instructions, associated data structures, and program circuitries represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

Although features have been shown and described, it will be understood that they are not intended to limit the claimed disclosure, and it will be made obvious to those skilled in the art that various changes and modifications may be made without departing from the scope of the claimed disclosure. The specification and drawings are, accordingly, to be regarded in an illustrative rather than restrictive sense. The claimed disclosure is intended to cover all alternatives, modifications, and equivalents.