Reducing peak-to-average power ratio in cell communication systems

Abstract

According to one example aspect of the present invention, there is provided an apparatus comprising means for determining a first precoder for an uplink transmission comprising user data and / or an uplink reference signal and at least one second precoder for a peak cancellation signal, means for deciding whether to transmit the peak cancellation signal with the uplink transmission using one of the at least one second precoder, and means for transmitting at least the uplink transmission to the wireless network node using the first precoder in accordance with the decision.

Description

Technical Field

[0001] Various example embodiments relate generally to cellular communication systems, and more particularly to reducing peak-to-average power ratio (PAPR) in such systems. Background Art

[0002] Peak-to-average power ratio (PAPR) can occur, for example, in multi-carrier communication systems, where different subcarriers can be out of phase compared to each other, resulting in peaks in the output envelope. Therefore, reducing PAPR is important at least in various cell networks, such as in networks operating according to long-term evolution LTE and / or fifth-generation 5G radio access technology. 5G radio access technology may also be referred to as new radio (NR) access technology. The third generation partnership project 3GPP is still developing LTE as well as 5G / NR standards. Reducing PAPR may also be beneficial in other wireless communication networks in the future, such as in 6G networks. Summary of the invention

[0003] According to some aspects, the subject matter of the independent claims is provided. Some embodiments are defined in the dependent claims.

[0004] The independent claims define the scope of protection sought by various embodiments of the invention. Embodiments and features described in this specification that do not fall within the scope of the independent claims, if any, are to be construed as examples that aid in understanding the various embodiments of the invention.

[0005] According to a first aspect of the present invention, there is provided an apparatus, the apparatus comprising a component for determining a first precoder for uplink transmission and at least one second precoder for a peak elimination signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; a component for deciding whether to use one of the at least one second precoder to send the peak elimination signal together with the uplink transmission; and a component for sending at least the uplink transmission to a radio network node using the first precoder according to the above decision. The apparatus of the first aspect may be a user equipment UE or a device configured to control its function.

[0006] Embodiments of the first aspect may include at least one feature from the following bulleted list or any combination thereof:

[0007] The apparatus further comprises means for: if it is determined that the peak cancellation signal is to be sent using the one of the at least one second precoder, sending an uplink transmission to the radio network node using the first precoder and sending the peak cancellation signal using the one of the at least one second precoder;

[0008] Remove signal;

[0009] The peak elimination signal is transmitted via the user data and / or uplink reference signal

[0010] A subset of the frequency and / or time resources reserved for the signal is used for transmission;

[0011] wherein the at least one second precoder comprises at least two second precoders, and the apparatus further comprises means for selecting the one second precoder in the at least one second precoder for the peak removal signal from the at least two second precoders;

[0012] The apparatus further comprises means for: if it is determined that the peak cancellation signal is not to be sent using any of the at least one second precoder, sending an uplink signal to the wireless network node without sending the peak cancellation signal

[0013] transmission;

[0014] wherein the above determination is performed separately for each symbol, wherein the symbol is a cyclic prefix orthogonal frequency division multiplexing (OFDM CP)-OFDM symbol, a discrete Fourier transform spread (OFDMDFT-s)-OFDM symbol, or a known tail DFT-s-OFDM KT-DFT-s-OFDM symbol;

[0015] The apparatus further comprises means for receiving information about a first transmission rank and a second transmission rank from a radio network node, wherein the first transmission rank is used to send uplink transmissions without the peak cancellation signal and the second transmission rank is used to send uplink transmissions with the peak cancellation signal; and means for sending uplink transmissions to the radio network node using the first transmission rank or the second transmission rank based on the decision

[0016] Transmission components;

[0017] The apparatus further comprises means for receiving from a radio network node an indicator of the first precoder and at least one second precoder, or means for receiving from a radio network node an indicator of the first precoder and means for deriving the at least one second precoder from the indicator of the first precoder;

[0018] wherein the indicator is received in an uplink scheduling grant;

[0019] The apparatus further comprises means for receiving, from a radio network node, limits on an error vector magnitude, a power level and / or a power density associated with at least one second precoder; wherein the means for determining whether to use the one of the at least one second precoder to transmit the peak cancellation signal is based on the limits on the error vector magnitude, the power level and / or the power density of each of the at least one second precoder;

[0020] wherein the means for determining whether to use the one of the at least one second precoder to send the peak removal signal is based on at least one of the following:

[0021] o an evaluation of the efficiency of said one of the at least one second precoders;

[0022] o the space of applicability of the above one of the at least one second precoder; and / or

[0023] ○Channel measurement of the device;

[0024] The apparatus further comprises means for sending a notification to a radio network node about the one of the at least one second precoder and / or means for sending a notification to a radio network node about whether the apparatus has used the at least one second precoder;

[0025] wherein a cross-correlation between the first precoder and each of the at least one second precoder is substantially zero;

[0026] wherein the transmission rank of the first precoder is less than the number of antenna ports of the user equipment, wherein the antenna ports are configured for uplink transmission;

[0027] Wherein the uplink transmission is CP-OFDM transmission, DFT-s-OFDM transmission or KT-DFT-s-OFDM transmission.

[0028] According to a second aspect of the present invention, there is provided an apparatus comprising a component for determining, for a user equipment, a first precoder for uplink transmission and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; and a component for receiving the uplink transmission from the user equipment according to at least the first precoder. The apparatus of the second aspect may be a radio network node or a device configured to control its function.

[0029] Embodiments of the second aspect may include at least one feature from the following bulleted list or any combination thereof:

[0030] The apparatus further comprises receiving an uplink transmission from a user equipment according to a first precoder and transmitting the uplink transmission according to one of the at least one second precoder

[0031] A component for receiving a peak cancellation signal;

[0032] The peak elimination signal is transmitted via the user data and / or uplink reference signal

[0033] a subset of the frequency and / or time resources reserved for receiving a signal;

[0034] wherein the at least one second precoder comprises at least two second precoders;

[0035] The apparatus further comprises a method for receiving an uplink from a user equipment according to a first precoder

[0036] A component that transmits a signal through a channel but does not receive a peak cancellation signal;

[0037] The apparatus further comprises means for sending information about a first transmission rank and a second transmission rank to a user equipment, wherein the first transmission rank is used to send uplink transmissions without a peak removal signal, and the second transmission rank is used to send uplink transmissions with a peak removal signal; and means for receiving information from the user equipment according to the first transmission rank or the second transmission rank.

[0038] A component of a user device receiving uplink transmissions;

[0039] The apparatus further comprises means for sending an indicator of the first precoder and at least one second precoder to the user equipment, or means for sending an indicator of the first precoder to the user equipment, wherein the at least one second precoder will be

[0040] derived from an indicator of the precoder;

[0041] · wherein the above indicator is sent in an uplink scheduling grant;

[0042] The apparatus further comprises means for sending to the user equipment a limit of an error vector magnitude, a power level and / or a power density associated with at least one second precoder;

[0043] The apparatus further comprises means for receiving a notification from the user equipment about the one of the at least one second precoder and / or means for receiving a notification from the user equipment about whether the user equipment has used the at least one second precoder.

[0044] According to a third aspect, a first method is provided, the first method comprising determining a first precoder for uplink transmission and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal, deciding whether to use one of the at least one second precoder to send the peak removal signal together with the uplink transmission, and sending at least the uplink transmission to a radio network node using the first precoder based on the decision. The first method may be performed by a user equipment UE or a device configured to control the function thereof.

[0045] According to a fourth aspect, a second method is provided, the second method comprising determining, for a user equipment, a first precoder for uplink transmission and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal, and receiving the uplink transmission from the user equipment according to at least the first precoder. The second method may be performed by a radio network node or a device configured to control its function.

[0046] According to a fifth aspect of the present invention, there is provided an apparatus, such as a wireless transmitter, comprising at least one processing core, at least one memory, the at least one memory comprising computer program code, the at least one memory and the computer program code being configured to cause the apparatus, together with the at least one processing core, to at least determine a first precoder for uplink transmission and at least one second precoder for peak elimination signal, wherein the uplink transmission comprises user data and / or uplink reference signal, decide whether to use one of the at least one second precoder to send the peak elimination signal together with the uplink transmission, and send at least the uplink transmission to the wireless network node using the first precoder according to the above decision. The apparatus of the fifth aspect may be a user equipment UE or a device configured to control its functions.

[0047] According to a sixth aspect of the present invention, there is provided an apparatus, such as a wireless receiver, comprising at least one processing core, at least one memory, the at least one memory comprising computer program code, the at least one memory and the computer program code being configured to cause the apparatus, together with the at least one processing core, to determine, at least for a user equipment, a first precoder for uplink transmission and at least one second precoder for a peak elimination signal, wherein the uplink transmission comprises user data and / or an uplink reference signal, and receiving the uplink transmission from the user equipment according to at least the first precoder. The apparatus of the sixth aspect may be a wireless network node or a device configured to control its functions.

[0048] According to a seventh aspect of the present invention, there is provided a non-transitory computer-readable medium having a computer-readable instruction set stored thereon, which, when executed by at least one processor, causes an apparatus to at least perform a first method. According to an eighth aspect of the present invention, there is provided a non-transitory computer-readable medium having a computer-readable instruction set stored thereon, which, when executed by at least one processor, causes an apparatus to at least perform a second method.

[0049] According to a ninth aspect of the present invention, there is provided a computer program, the computer program comprising instructions, when the program is executed by a device, the instructions cause the device to perform a first method. According to a tenth aspect of the present invention, there is provided a computer program, the computer program comprising instructions, when the program is executed by a device, the instructions cause the device to perform a second method. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 illustrates a network scenario according to at least some example embodiments;

[0051] Figure 2 illustrates a first signaling diagram according to at least some example embodiments;

[0052] Figure 3 illustrates a second signaling diagram according to at least some example embodiments;

[0053] Figure 4 illustrates example apparatus capable of supporting at least some example embodiments;

[0054] Figure 5 illustrates a flow chart of a first method according to at least some example embodiments; DETAILED DESCRIPTION

[0055] Through the process described in this article, the peak-to-average power ratio (PAPR) can be reduced in a cell communication system. Alternatively or additionally, other metrics other than PAPR, such as the cubic metric CM, can also be used. Finally, output backoff can be an important metric. For example, the output power backoff OBO can be defined based on the maximum power reduction, that is, what is the minimum power that the user equipment UE should provide in a specific scenario. PAPR and / or CM and other similar metrics can be used to approximate the OBO requirements of the UE's transmitter. However, the ultimate truth may only be obtained through simulations and / or measurements involving UE power amplifiers or UE power amplifier models, and related UE RF requirements, such as error vector magnitude EVM, in-band emission IBE, occupied channel bandwidth OCB, and adjacent channel leakage ratio ACLR.

[0056] More specifically, separate precoders can be selected for uplink transmission (such as transmission of user data and / or uplink reference signals) and for transmission of peak elimination signals PCS. That is, a first precoder can be selected for uplink transmission, and a second precoder can be selected for PCS. Therefore, tone selection and reservation of PCS can be performed in the spatial domain, so that the UE can transmit PCS without using additional spectrum. Typically, uplink transmission can cover one or more orthogonal frequency division multiplexing OFDM symbols. PCS can be sent via a subset of frequency and / or time resources reserved for the above-mentioned user data and / or uplink reference signals.

[0057] Figure 1 Network scenarios are illustrated according to at least some example embodiments. Figure 1 In an example network scenario, there may be a cell communication system including a UE 110, a radio network node 120, and a core network element 130. The UE 110 may be connected to the radio network node 120 via an air interface 115, and the radio network node 120 may also be connected to the core network element 130 via a wired interface 125. In some example embodiments, the air interface 115 may be a beam-based interface.

[0058] For example, UE 110 may include a smartphone, a cell phone, a machine-to-machine M2M node, a machine type communication MTC node, a RedCap UE (reduced capability UE) node, an Internet of Things IoT node, a car telemetry unit, a laptop, a tablet, or virtually any type of suitable wireless terminal, such as a relay. The radio network node 120 may be considered a serving node for the UE 110, and one cell of the radio network node 120 may be a serving cell for the UE 110.

[0059] The air interface 115 between the UE 110 and the radio network node 120 may be configured according to a radio access technology RAT, and both the UE 110 and the radio network node 120 are configured to support the RAT. Examples of cell RATs include long term evolution LTE, new radio NR (also known as fifth generation 5G radio access technology), and MulteFire. For example, in the context of LTE, the radio network node 120 may be referred to as an eNB, and in the context of NR, the radio network node 120 may be referred to as a gNB. In some example embodiments, the radio network node 120 may be referred to as a transmission reception point (TRP), or may control multiple TRPs, which may be co-located or non-co-located. In some example embodiments, the radio network node 120 may be a relay. In any case, the example embodiments of the present disclosure are not limited to any particular wireless technology. On the contrary, the example embodiments may be used in any wireless communication network where it is necessary to reduce the PAPR.

[0060] The radio network node 120 may be connected to the core network element 130 via an interface 125 directly or via at least one intermediate node. The core network element 130 may also be connected to another network ( Figure 1 The radio network node 120 may be coupled to the core network element 130 or another core network directly or via at least one intermediate node, through which a connection to other networks may be obtained, for example, via a global interconnected network.

[0061] In some example embodiments, the network scenario may include a relay node as an alternative or in addition to UE 110 and / or radio network node 120. For example, when operating on millimeter wave frequencies, a relay may be used. An example of a relay node may be an integrated access and backhaul IAB node. An IAB node may also be referred to as a self-backhaul relay. Another example of a relay may be an out-of-band relay. In general, a relay node may include two parts:

[0062] 1) A distributed unit DU portion, which may facilitate the functionality of a radio network node 120, such as a gNB. Thus, in some example embodiments, the DU portion of the relay may be referred to as a radio network node 120, and the DU may perform the tasks of a radio network node 120;

[0063] 2) A mobile terminal MT part, which can facilitate the functions of UE 110, i.e., a backhaul link, which can be a communication link between a parent node (DU) (such as the DU part of radio network node 120) and a relay (such as an IAB node). In some example embodiments, the MT part can be called UE 110 and perform the tasks of UE 110.

[0064] Embodiments of the present disclosure take into account precoding and spectrum utilization for uplink transmissions, such as for 5G / NR. On the UE 110 side, the high PAPR of the OFDM waveform can be one of the limiting factors in the utilization of efficient power amplifiers PA. In order to maintain the quality of the waveform quality, such as with respect to EVM, PA back-off can be introduced. However, due to the reduced output power, PA back-off will limit the potential coverage of the uplink transmission of UE 110. Another way to mitigate the PAPR may be to apply a larger PA, which may also linearly amplify the peak. However, the problem with this approach is that the power consumption of UE 110 and the PA cost will increase accordingly.

[0065] For example, frequency reused tone reservation signals may be used to reduce PAPR, but such signals will require additional frequency resources and reduce spectral efficiency. Therefore, embodiments of the present disclosure provide precoding-based PAPR reduction and related signaling between, for example, UE 110 and radio network node 120, at least for codebook-based uplink transmissions and non-codebook-based uplink transmissions. Thus, the PAPR statistics of the transmitted waveform may be improved without incurring a direct loss of spectral efficiency due to the allocation of additional PCS time-frequency resources as in the case of tone reservation signals.

[0066] In some example embodiments, a first spatial precoder may be selected for uplink transmissions, such as for transmission of user data for UE 110, and a second spatial precoder may be selected for PCS. For example, for a UE performing codebook-based transmissions in a PAPR-limited scenario, such as at a cell edge, in addition to scheduling UE 110 with the first precoder for uplink transmissions, radio network node 120 may schedule UE 110 with at least one second precoder for transmission of PCS. The at least one second precoder may be selected in such a manner that the at least one second precoder does not significantly interfere with the uplink transmissions, such as by spanning a null space of a channel. For example, when selecting the at least one second precoder for PCS, radio network node 120 may take into account interference of transmitted PCS energy at different devices.

[0067] The radio network node 120 may send an indicator of the selected first precoder and the at least one second precoder to the UE 110. For example, the above indicators of the selected first precoder and the at least one second precoder may be sent in an uplink scheduling grant. The at least one second precoder for the PCS may be selected from the same codebook as the first precoder for the user data, or from a separate codebook.

[0068] Alternatively or additionally, the radio network node 120 may send information about a first transmission rank and a second transmission rank to the UE 110, possibly also in an uplink scheduling grant, wherein the first transmission rank is used for sending uplink transmissions without PCS and the second transmission rank is used for sending uplink transmissions with PCS. The radio network node 120 may define the first transmission rank and the second transmission rank, i.e. the number of layers, for transmissions of uplink transmissions without PCS and for transmissions of uplink transmissions without PCS, respectively.

[0069] In some example embodiments, UE 110 may therefore determine the first precoder for uplink transmission and the at least one second precoder for PCS based on the indicator received from radio network node 120. Alternatively, UE 110 may receive an indicator of the first precoder from radio network node 120 and derive the at least one second precoder from the indicator of the first precoder. UE 110 may then decide whether to use one of the at least one second precoder to send the PCS with the uplink transmission. UE 110 may perform the above decision separately for each symbol, which may be a cyclic prefix orthogonal frequency division multiplexing OFDM (CP-OFDM) symbol, a discrete Fourier transform spread OFDM (DFT-s-OFDM) symbol, or a known tail DFT-s-OFDM (KT-DFT-s-OFDM) symbol. UE 110 may decide whether to use the at least one second precoder and send the PCS based on the allocation of the at least one second precoder and the relevant network configuration.

[0070] For UEs performing non-codebook based transmission, for example, in PAPR limited situations, UE 110 may also utilize at least one second precoder for PCS transmission. BS 120 may configure UE 110 with multiple sounding reference signal SRS ports, for example, using radio resource control (RRC) signaling. UE 110 may then use at least one second precoder for PCS transmission for each SRS port based on a downlink signal, such as a channel state information reference signal CSI-RS.

[0071] For example, UE 110 may use at least one second precoder for PCS transmission together with the first precoder when setting up an uplink data transmission, ie, when sending an uplink reference signal, such as a layer-by-layer SRS for an upcoming uplink data transmission of user data.

[0072] In some example embodiments, UE 110 may determine at least one second precoder for PCS transmission based on SRS port(s) indicated for uplink data (such as Physical Uplink Shared Channel (PUSCH) data) with or without separate feedback from BS 120 .

[0073] In some example embodiments, UE 110 may suggest or notify radio network node 120 to use at least one second precoder for PCS transmission when establishing uplink data transmission, i.e., when sending an uplink reference signal. UE 110 may, for example, send a notification about at least one second precoder to the radio network node. That is, UE 110 may suggest or notify radio network node 120 of a second precoder or multiple candidate precoders that it is using.

[0074] For both codebook-based transmission and non-codebook-based transmission, there may be an upper limit on the maximum power that can be used for PCS transmission (i.e., use of at least one second precoder for PCS). The maximum power that can be used for PCS transmission may be predefined in a specification, such as in the 3GPP standard, or the maximum power that can be used for PCS transmission may be controlled by a parameter configured by the radio network node 120, using, for example, RRC signaling.

[0075] Embodiments of the present disclosure may be applied to both multi-carrier transmissions such as OFDM and single-carrier transmissions such as DFT-s-OFDM. For example, embodiments of the present disclosure may be applied to at least OFDM transmissions (such as CP-OFDM) and single-carrier transmissions defined according to frequency domain signal generation (such as DFT-s-OFDM and KT-DFT-s-OFDM).

[0076] In some example embodiments of the present disclosure, all frequency resources may be available for uplink transmission, such as transmission of user data or uplink reference signals, because PCS may be multiplexed with uplink transmission in the spatial domain. At any selected subcarrier, the transmission signal x including uplink transmission and PCS may be written as

[0077] x=αVs+βWr, (1)

[0078] Where V is N for uplink transmission TX *N S The size of the precoder matrix, where N TX is the number of transmit antenna ports, N S is the number of layers (rank), s is the N of data symbols S *1 vector, W is the precoder array for PCS, and r is the vector of PCS values. In addition, α and β are the power scaling factors for uplink transmission and PCS, respectively. The size of the vector term Wr can be fixed to N TX *1, but the individual sizes of the matrix W and the vector r may vary depending on the selected transmission rank and PCS configuration. To enable spatial multiplexing of PCS, the transmission rank of the uplink transmission (i.e., the first transmission) may need to be less than the number of transmit antenna ports of UE 110, i.e., N S<N TX , wherein the above-mentioned antenna port is configured for uplink transmission.

[0079] In order to minimize the interference caused by the PCS to uplink transmissions (such as user data or uplink reference signals), at least one second precoder for the PCS may be designed to span the null space of the channel between the UE 110 and the radio network node 120. However, using a codebook-based approach, precoding may only be applied to the channel with limited resolution due to the limited set of available precoder options.

[0080] Figure 2 A first signaling diagram is illustrated according to at least some example embodiments. More specifically, Figure 2 Signaling is illustrated in the case of codebook based transmission using precoding based PAPR reduction, for example after UE 110 has signaled its PCS generation capability in the spatial domain. In the case of codebook based transmission, the uplink transmission may include user data.

[0081] At step 210, UE 110 may perform channel sounding, for example, by sending an uplink reference signal, such as an SRS, to radio network node 120. Alternatively or additionally, UE 110 may perform a demodulation reference signal, DMRS, transmission. At step 215, radio network node 120 may decide a first precoder for uplink transmission, at least one second precoder for PCS, and possibly a first transmission rank and a second transmission rank, wherein the first transmission rank is used to send uplink transmissions without PCS, and the second transmission rank is used to send uplink transmissions with PCS. In some example embodiments, radio network node 120 may set limits for EVM, power level, and / or power density of PCS transmissions.

[0082] At step 220, radio network node 120 may send indicators of the first precoder and at least one second precoder, and possibly information about the first transmission rank and the second transmission rank, to UE 110, possibly in an uplink scheduling grant. The indicators may include, for example, a transmitted precoding matrix indicator TPMI for the first precoder and a TPMI for each second precoder. In some example embodiments, radio network node 120 may send limits on the EVM, power level, and / or power density of PCS transmissions to UE 110. These limits may also be sent in an uplink scheduling grant.

[0083] That is, the transmission rank(s) and the uplink precoder(s) may be defined by the network (such as the radio network node 120) from a codebook and further signaled to the UE 110 as part of an uplink scheduling grant or in another message (e.g., a control message). The precoder(s) identifier(s) may be based on the TPMI(s). Thus, if PAPR reduction is required in uplink transmission, for example due to coverage enhancement, the network (i.e., the radio network node 120) may be able to notify the UE 110 of the uplink transmission rank(s) and the precoder(s), as well as related configuration parameters, such as EVM, power level, and / or power density limits for PCS transmissions. For example, the total power available for at least one second precoder and / or the power spectral density of at least one second precoder may be capped at a predefined value (such as a value specified in a 3GPP standard), or a configuration value configured by the radio network node 120.

[0084] The at least one second precoder selected by the network may match the number of transmission ports of UE 110. The at least one second precoder for the PCS may, but need not necessarily, be selected from a set of precoders of the same rank used with uplink transmissions (such as user data). For example, when considering a rank 2 transmission with 4 antenna ports, the first precoder may be selected as one of the 4×2 precoder matrices available in the codebook, but the at least one second precoder may be selected as one of the remaining precoders of the same set for uplink transmissions, or alternatively one or more precoders from an arbitrary rank codebook with 4 antenna ports.

[0085] At step 225, UE 110 may determine a first precoder for uplink transmission and at least one second precoder for PCS based on the received indicator. UE 110 may also decide whether to use one of the at least one second precoder to send PCS with the uplink transmission. That is, UE 110 may decide to use or not use PAPR reduction using the provided at least one second precoder based on the received scheduling grant.

[0086] In some example embodiments, the decision may be based on an evaluation of the efficiency of the one of the at least one second precoder, the spatial applicability of the one of the at least one second precoder, and / or an associated power constraint. When the at least one second precoder does not sufficiently span the same space as the best PCS, ignoring the PCS and the associated at least one second precoder may be more energy efficient. That is, due to power inefficiency, the UE 110 may decide not to use any of the at least one second precoder to send the PCS. Similarly, if the at least one second precoder includes at least two second precoders, the UE 110 may select one of the at least one second precoder for the peak elimination signal from the at least two second precoders based on an evaluation of the efficiency of the one of the at least one second precoder, the spatial applicability of the one of the at least one second precoder, and / or an associated power constraint.

[0087] Depending on the network configuration, UE 110 may signal whether it has used one of the at least one second precoder by sending a notification about the use. The notification about whether UE 110 has used the one of the at least one second precoder may be included in each uplink transmission with a PCS opportunity. Another option may be to include the notification about whether UE 110 has used the one of the at least one second precoder in another signal, such as a power headroom report.

[0088] At step 230, UE 110 may send at least an uplink transmission to radio network node 120 using the first precoder according to the above decision at step 225. If UE 110 decides that the PCS is to be sent using the above one of the at least one second precoder, UE 110 may send the uplink transmission to radio network node 120 using the first precoder and may send the PCS to radio network node 120 using the above one of the at least one second precoder, which may use the second transmission rank. On the other hand, if UE 110 decides that the PCS is not to be sent using any of the at least one second precoder, UE 110 may send the uplink transmission to radio network node 120 without sending the PCS, which may use the first transmission rank. Therefore, according to the above decision at step 225, UE 110 may send the uplink transmission to radio network node 120 using the first transmission rank or the second transmission rank.

[0089] Figure 3 A second signaling diagram is illustrated according to at least some example embodiments. More specifically, Figure 3 Signaling in the case of non-codebook based transmission using precoding based PAPR reduction is illustrated.In the case of non-codebook based transmission, the uplink transmission may include an uplink reference signal (such as SRS) or user data.

[0090] At step 310, the radio network node 120 may transmit a downlink reference signal, such as a CSI-RS. The UE 110 may acquire uplink channel information based on the received downlink reference signal by assuming channel reciprocity. At step 315, the UE 110 may then determine a first precoder for an uplink transmission, wherein the uplink transmission includes an uplink reference signal, such as an SRS. The UE 110 may also determine at least one second precoder for the PCS and decide whether to use one of the at least one second precoder to transmit the PCS together with the uplink transmission.

[0091] That is, in some example embodiments, UE 110 may decide whether to use one of the at least one second precoder to send the peak cancellation signal together with the uplink transmission based on the channel measurement of UE 110. Similarly, if the at least one second precoder includes at least two second precoders, UE 110 may select one of the at least one second precoder from the at least two second precoders for the peak cancellation signal based on the channel measurement of UE 110.

[0092] At step 320, UE 110 may send at least an uplink transmission to radio network node 120 using the first precoder according to the above decision. The uplink transmission may be a layer-by-layer SRS transmission using at least one second precoder selected by UE 110. If UE 110 decides that the PCS is to be transmitted using the above one of the at least one second precoder, UE 110 may send the uplink transmission to radio network node 120 using the first precoder and may send the PCS to radio network node 120 using the at least one second precoder, which may use the second transmission rank. On the other hand, if UE 110 decides that the PCS is not to be transmitted using any of the at least one second precoder, UE 110 may send the uplink transmission to radio network node 120 without sending the PCS, which may use the first transmission rank. Therefore, according to the above decision, UE 110 may send the uplink transmission to radio network node 120 using the first transmission rank or the second transmission rank. UE 110 may perform transmission on each selected beam. UE 110 may send a notification about the one of the at least one second precoder and / or a notification about whether it has used the at least one second precoder to the radio network node.

[0093] At step 325, radio network node 120 may determine which second precoder of at least one second precoder selected by UE 110 may be used for a subsequent uplink transmission, wherein the subsequent uplink transmission includes user data. Radio network node 120 may decide a first precoder for uplink transmission, at least one second precoder for PCS, and possibly a first transmission rank and a second transmission rank, wherein the first transmission rank is used to send uplink transmissions without PCS, and the second transmission rank is used to send uplink transmissions with PCS. In some example embodiments, radio network node 120 may set limits on the EVM, power level, and / or power density of PCS transmissions.

[0094] At step 330, the radio network node 120 may send indicators of the first precoder and at least one second precoder for subsequent uplink transmissions and possibly information about the first transmission rank and the second transmission rank to the UE 110, possibly in an uplink scheduling grant.

[0095] At steps 335 and 340, UE 110 may respectively perform the same Figure 2 Steps 225 and 230 are the same steps.

[0096] To enable efficient peak removal performance, the first precoder for uplink transmission (such as user data) and at least one second precoder for PCS may be selected in such a way that their cross-correlation is zero, i.e., V H W = 0. Note that the cross-correlation may be substantially zero, since it is difficult or even impossible to achieve zero in practice. This operation is not channel dependent and therefore does not require any channel knowledge.

[0097] In order to maximize the signal-to-interference ratio (SIR) between the uplink transmission (such as user data) and the PCS at the receiver, the SIR can be evaluated for each combination of the first precoder and each of the at least one second precoder that satisfies the above-mentioned zero correlation condition. Thereafter, the precoder combination that maximizes the SIR can be selected for the transmission. The SIR evaluation can be based on the complete combined channel effect including the wireless channel and the precoder, and therefore requires the use of channel estimation.

[0098] Therefore, the exemplary embodiments of the present disclosure provide considerable potential for improving power efficiency. In addition, unused channel ranks can be utilized instead of additional resource elements to improve spectral efficiency. Codebook-based transmission scenarios and non-codebook-based transmission scenarios can be supported. The exemplary embodiments of the present disclosure can be applied to at least frequency range 1 (FR1) and FR2 scenarios and higher frequency bands, such as above 71 GHz and below THz.

[0099] Figure 4 An example apparatus capable of supporting at least some embodiments is illustrated. Device 400 is illustrated, which may be referred to as, for example, UE 110 or wireless network node 120, or a device configured to control the functions of the device is illustrated. A processor 410 is included in device 400, which may include, for example, a single-core or multi-core processor, wherein a single-core processor includes one processing core and a multi-core processor includes more than one processing core. Processor 410 may generally include a control device. Processor 410 may include more than one processor. Processor 410 may be a control device. For example, the processing core may include a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core produced by Advanced Micro Devices Corporation. Processor 410 may include at least one Qualcomm Snapdragon and / or Intel Atom processor. Processor 410 may include at least one application-specific integrated circuit ASIC. Processor 410 may include at least one field programmable gate array FPGA. Processor 410 may be a component for performing method steps in device 400. Processor 410 may be configured at least in part by computer instructions to perform actions.

[0100] The processor may include a circuit system, or be constructed as one or more circuit systems, which are configured to perform the various stages of the method according to the embodiments described herein. As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) a pure hardware circuit implementation, such as an implementation in analog and / or digital circuit systems only, and (b) a combination of hardware circuits and software, such as, if applicable: (i) a combination of (multiple) analog and / or digital hardware circuits with software / firmware, and (ii) any portion of (multiple) hardware processors with software (including (multiple) digital signal processors), software and (multiple) memories, which work together to cause an apparatus such as UE 110 or radio network node 120 or a device configured to control its functions to perform various functions), and (c) (multiple) hardware circuits and / or (multiple) processors, such as (multiple) microprocessors or (multiple) microprocessor parts, which require software (e.g., firmware) for operation, but when software is not required for operation, the software may not be present.

[0101] This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cell network device, or other computing or network device.

[0102] Device 400 may include memory 420. Memory 420 may include random access memory and / or permanent memory. Memory 420 may include at least one RAM chip. Memory 420 may include, for example, solid-state, magnetic, optical and / or holographic memory. Memory 420 may be at least partially accessible by processor 410. Memory 420 may be at least partially included in processor 410. Memory 420 may be a component for storing information. Memory 420 may include computer instructions that processor 410 is configured to execute. When computer instructions configured to cause processor 410 to perform certain actions are stored in memory 420, and device 400 as a whole is configured to run under the guidance of processor 410 using computer instructions from memory 420, processor 410 and / or at least one of its processing cores may be considered to be configured to perform certain actions described above. Memory 420 may be at least partially included in processor 410. Memory 420 may be at least partially located outside device 400, but device 400 may access the memory.

[0103] The device 400 may include a transmitter 430. The device 400 may include a receiver 440. The transmitter 430 and the receiver 440 may be configured to send and receive information according to at least one cell or non-cell standard, respectively. The transmitter 430 may include more than one transmitter. The receiver 440 may include more than one receiver. The transmitter 430 and / or the receiver 440 may be configured to operate according to, for example, the Global System for Mobile Communications GSM, Wideband Code Division Multiple Access WCDMA, 5G / NR, 5G Advanced (i.e., NRRe1-18 and later), Long Term Evolution LTE, IS-95, Wireless Local Area Network WLAN, Ethernet, and / or Worldwide Interoperability for Microwave Access WiMAX standards.

[0104] The device 400 may include a near field communication NFC transceiver 450. The NFC transceiver 450 may support at least one NFC technology, such as NFC, Bluetooth, Wibree, or similar technology.

[0105] Device 400 may include a user interface UI 460. UI 460 may include at least one of a display, a keyboard, a touch screen, a vibrator arranged to signal a user by causing vibration of device 400, a speaker, and a microphone. The user may be able to operate device 400 via UI 460, such as accepting an incoming phone call, making a phone call or video call, browsing the Internet, managing digital files stored in memory 420 or on a cloud accessible via transmitter 430 and receiver 440 or via NFC transceiver 450, and / or playing games.

[0106] The device 400 may include or be arranged to accept a user identity module 470. The user identity module 470 may include, for example, a subscriber identity module SIM card that may be installed in the device 400. The user identity module 470 may include information identifying a subscription of a user of the device 400. The user identity module 470 may include cryptographic information that may be used to verify the identity of the user of the device 400 and / or facilitate encryption of communication information and billing of the user of the device 400 for communications effected via the device 400.

[0107] The processor 410 may be equipped with a transmitter that is arranged to output information from the processor 410 to other devices included in the device 400 via electrical conductors inside the device 400. Such a transmitter may include a serial bus transmitter that is arranged to output information to the memory 420 for storage therein, for example, via at least one electrical conductor. As an alternative to the serial bus, the transmitter may include a parallel bus transmitter. Similarly, the processor 410 may include a receiver that is arranged to receive information in the processor 410 from other devices included in the device 400 via electrical conductors inside the device 400. Such a receiver may include a serial bus receiver that is arranged to receive information from the receiver 440, for example, via at least one electrical conductor, for processing in the processor 410. As an alternative to the serial bus, the receiver may include a parallel bus receiver.

[0108] The device 400 may include Figure 4 Other devices not shown in the figure. For example, where the device 400 includes a smartphone, it may include at least one digital camera. Some devices 400 may include a rear camera and a front camera, wherein the rear camera may be used for digital photography and the front camera is used for video calls. The device 400 may include a fingerprint sensor that is arranged to at least partially authenticate a user of the device 400. In some embodiments, the device 400 lacks at least one of the above devices. For example, some devices 400 may lack an NFC transceiver 450 and / or a user identity module 470.

[0109] The processor 410, the memory 420, the transmitter 430, the receiver 440, the NFC transceiver 450, the UI 460 and / or the user identity module 470 may be interconnected in a variety of different ways via electrical conductors inside the device 400. For example, each of the above devices may be individually connected to a main bus inside the device 400 to allow the devices to exchange information. However, those skilled in the art will appreciate that this is just an example, and that various ways of interconnecting at least two of the above devices may be selected according to the embodiment without departing from the scope of the present invention.

[0110] Figure 5 is a flow chart of a first method according to at least some embodiments. The stages of the illustrated first method may be performed by the UE 110, or by a control device configured to control its functions (perhaps when installed therein).

[0111] The first method may include determining a first precoder for an uplink transmission and at least one second precoder for a peak cancellation signal at step 510, wherein the uplink transmission includes user data and / or an uplink reference signal. The first method may also include deciding whether to use one of the at least one second precoder to send the peak cancellation signal with the uplink transmission at step 520. Finally, the first method may include sending at least an uplink transmission to a radio network node using the first precoder based on the decision at step 530.

[0112] It should be understood that the disclosed embodiments are not limited to the specific structures, process steps or materials disclosed herein, but can be extended to equivalents that will be recognized by those of ordinary skill in the relevant art. It should also be understood that the terminology used herein is only for the purpose of describing specific embodiments and is not intended to be limiting.

[0113] References to one embodiment or embodiments throughout this specification indicate that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in at least one embodiment. Thus, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily all refer to the same embodiment. When terms such as about or substantially are used to reference values, the exact value is also disclosed.

[0114] As used herein, for convenience, multiple items, structural elements, constituent elements and / or materials can be presented in a common list. However, these lists should be interpreted as each member in the list is individually identified as a separate and unique member. Therefore, any individual member in such a list should not be interpreted as the de facto equivalent of any other member in the same list only based on its presentation in a common group (without contrary indication). In addition, various embodiments and examples and alternatives of various components thereof can be referenced herein. It should be understood that these embodiments, examples and alternatives should not be interpreted as de facto equivalents to each other, but should be regarded as separate and autonomous representations.

[0115] In some example embodiments, an apparatus such as, for example, UE 110 or radio network node 120, or a device configured to control the functions thereof may include means for performing the above-described embodiments and any combination thereof.

[0116] In some example embodiments, the computer program may be configured to cause methods according to the above embodiments and any combination thereof. In an example embodiment, a computer program product embodied on a non-transitory computer readable medium may be configured to control a processor to perform a process including the above embodiments and any combination thereof.

[0117] In some example embodiments, an apparatus, such as, for example, UE 110 or radio network node 120, or a device configured to control the functionality thereof may include at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, together with the at least one processor, cause the apparatus to at least perform the above-described embodiments and any combination thereof.

[0118] In addition, the described features, structures or characteristics can be combined in any suitable manner in one or more embodiments. In the foregoing description, many specific details, such as examples of length, width, shape, etc., are provided to provide a thorough understanding of embodiments of the present invention. However, those skilled in the relevant art will recognize that the present invention can be practiced without one or more specific details, or practiced using other methods, components, materials, etc. In other cases, in order to avoid obscuring aspects of the present invention, well-known structures, materials or operations are not shown or described in detail.

[0119] Although the above examples illustrate the principles of the embodiments in one or more specific applications, it will be apparent to those skilled in the art that many modifications may be made to the form, usage and details of implementation without exercising creative ability and without departing from the principles and concepts of the invention. Therefore, the present invention is not intended to be limited except as set forth above.

[0120] In this document, the verbs "comprise" and "include" are used as open limitations, neither excluding nor requiring the presence of unrecited features. Unless explicitly stated otherwise, the features recited in the dependent claims may be freely combined with each other. Furthermore, it should be understood that the use of "a" or "an" (i.e., the singular) throughout this document does not exclude a plurality.

[0121] Industrial Applicability

[0122] At least some embodiments of the present invention find industrial application in cellular communication systems where it is desirable to reduce PAPR, such as in systems operating according to 3GPP standards.

[0123] List of abbreviations

[0124] 3GPP: Third Generation Partnership Project

[0125] ACLR: Adjacent Channel Leakage Ratio

[0126] ASIC: Application-Specific Integrated Circuit

[0127] BS: Wireless network node

[0128] CP-OFDM: Cyclic Prefix OFDM

[0129] CSI-RS: Channel State Information Reference Signal

[0130] D2D: Device to Device

[0131] DFT-s-OFDM: Discrete Fourier Transform Extended OFDM

[0132] DMRS: Demodulation Reference Signal

[0133] DU: Distributed Unit

[0134] EVM: Error Vector Magnitude

[0135] FPGA: Field Programmable Gate Array

[0136] FR: Frequency range

[0137] GSM: Global System for Mobile Communications

[0138] IAB: Integrated Access and Backhaul

[0139] IBE: In-Band Emission

[0140] IoT: Internet of Things

[0141] LTE: Long Term Evolution

[0142] KT-DFT-s-OFDM: Known Tail DFT-s-OFDM

[0143] M2M: Machine to Machine

[0144] MT: Mobile Terminal

[0145] MTC: Machine Type Communication

[0146] NFC: Near Field Communication

[0147] NR: New Radio

[0148] OBO: Output power back-off

[0149] OCB: Occupied Bandwidth

[0150] OFDM: Orthogonal Frequency Division Multiplexing

[0151] PA: Power Amplifier

[0152] PAPR: Peak to Average Power Ratio

[0153] PCS: Peak Cancellation Signal

[0154] PUSCH: Physical Uplink Shared Channel

[0155] RAN: Radio Access Network

[0156] RAT: Radio Access Technology

[0157] RRC: Radio Resource Control

[0158] SIM: Subscriber Identity Module

[0159] SIR: Signal to Interference and Noise Ratio

[0160] SRS: Sounding Reference Signal

[0161] TPMI: Transmitted Precoding Matrix Indicator

[0162] TRP: Transmission Reception Point

[0163] UE: User Equipment

[0164] UI: User Interface

[0165] WCDMA: Wideband Code Division Multiple Access

[0166] WiMAX: Worldwide Interoperability for Microwave Access

[0167] WLAN: Wireless Local Area Network

[0168] Reference numerals list

[0169] 110 User Equipment 115、125、135 interface 120 Wireless network node 130 Core network components 210-230 Figure 2 Steps in 310-340 Figure 3 Steps in 400-470 Figure 4 The structure of the device 510-530 Figure 5 The stages of the first method

Claims

1. A device comprising: - means for determining a first precoder for an uplink transmission, and at least one second precoder for a peak cancellation signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; - means for deciding whether to use one of said at least one second precoder to transmit said peak cancellation signal together with said uplink transmission; as well as - means for sending at least the uplink transmission to a radio network node using the first precoder in dependence on the decision.

2. The apparatus according to claim 1, further comprising: - means for sending the uplink transmission to the radio network node using the first precoder and sending the peak cancellation signal using the one second precoder of the at least one second precoder if it is decided that the peak cancellation signal is to be sent using the one second precoder of the at least one second precoder.

3. The apparatus according to claim 2, wherein the peak cancellation signal is sent via a subset of frequency and / or time resources reserved for the user data and / or the uplink reference signal.

4. The apparatus according to any one of the preceding claims, wherein the at least one second precoder comprises at least two second precoders, and the apparatus further comprises: - means for selecting said one of said at least one second precoder for said peak removal signal from among said at least two second precoders.

5. The device according to any one of the preceding claims, further comprising: - means for sending the uplink transmission to the radio network node without sending the peak cancellation signal if it is decided that the peak cancellation signal is not to be sent using any of the at least one second precoder.

6. The apparatus according to any of the preceding claims, wherein the determining is performed separately for each symbol, wherein the symbol is a cyclic prefix orthogonal frequency division multiplexing OFDM (CP)-OFDM symbol, a discrete Fourier transform spread OFDM (DFT-s)-OFDM symbol, or a known tail DFT-s-OFDM (KT-DFT-s-OFDM) symbol.

7. The device according to any one of the preceding claims, further comprising: - means for receiving, from the radio network node, information about a first transmission rank for sending the uplink transmission without the peak cancellation signal and a second transmission rank for sending the uplink transmission with the peak cancellation signal; and - means for sending the uplink transmission to the radio network node using the first transmission rank or the second transmission rank in dependence on the decision.

8. The device according to any one of the preceding claims, further comprising: - means for receiving, from the radio network node, an indicator of the first precoder and the at least one second precoder; or - means for receiving an indicator of the first precoder from the radio network node, and means for deriving the at least one second precoder from the indicator of the first precoder.

9. The apparatus of any preceding claim, wherein the indicator is received in an uplink scheduling grant.

10. The device according to any one of the preceding claims, further comprising: - means for receiving from the radio network node a limitation of an error vector magnitude, a power level and / or a power density associated with the at least one second precoder; in - said means for deciding whether to use said one of said at least one second precoder for transmitting said peak cancellation signal is based on said limits on said error vector magnitude, power level and / or power density of each of said at least one second precoder.

11. The apparatus of any one of the preceding claims, wherein the means for deciding whether to use the one of the at least one second precoder to transmit the peak cancellation signal is based on at least one of: - an evaluation of the efficiency of said one of said at least one second precoder; - a space of applicability of said one of said at least one second precoder; and - Channel measurement of the device.

12. The apparatus according to any one of the preceding claims, further comprising: - means for sending a notification about said one of said at least one second precoder to said radio network node; and / or - means for sending a notification to the radio network node as to whether the apparatus has used the at least one second precoder.

13. The apparatus of any preceding claim, wherein a cross-correlation between the first precoder and each of the at least one second precoder is substantially zero.

14. The apparatus according to any of the preceding claims, wherein the transmission rank of the first precoder is less than the number of antenna ports of the user equipment, wherein the antenna ports are configured for uplink transmission.

15. The apparatus of any preceding claim, wherein the uplink transmission is a CP-OFDM transmission, a DFT-s-OFDM transmission, or a KT-DFT-s-OFDM transmission.

16. An apparatus comprising: - means for determining, for a user equipment, a first precoder for uplink transmissions comprising user data and / or uplink reference signals, and at least one second precoder for a peak removal signal; as well as - means for receiving an uplink transmission from said user equipment according to at least said first precoder.

17. The apparatus according to claim 16, further comprising: - means for receiving said uplink transmission from said user equipment according to said first precoder and receiving said peak removal signal according to one of said at least one second precoder.

18. The apparatus of claim 17, wherein the peak cancellation signal is received via a subset of frequency and / or time resources reserved for the user data and / or the uplink reference signal.

19. The apparatus according to any one of claims 16 to 18, wherein the at least one second precoder comprises at least two second precoders.

20. The device according to any one of claims 16 to 19, further comprising: - means for receiving said uplink transmission from said user equipment according to said first precoder without receiving said peak cancellation signal.

21. The apparatus according to any one of claims 16 to 20, further comprising: - means for sending information about a first transmission rank and a second transmission rank to the user equipment, wherein the first transmission rank is used to send the uplink transmission without the peak cancellation signal and the second transmission rank is used to send the uplink transmission with the peak cancellation signal; and - means for receiving the uplink transmission from the user equipment according to the first transmission rank or the second transmission rank.

22. The apparatus according to any one of claims 16 to 21, further comprising: - means for sending an indicator of the first precoder and the at least one second precoder to the user equipment; or - means for sending an indicator of said first precoder to said user equipment, wherein said at least one second precoder is to be derived from said indicator of said first precoder.

23. The apparatus of claim 22, wherein the indicator is sent in an uplink scheduling grant.

24. The apparatus according to any one of claims 16 to 23, further comprising: - means for sending to said user equipment a limitation of an error vector magnitude, a power level and / or a power density associated with said at least one second precoder.

25. The apparatus according to any one of claims 16 to 24, further comprising: - means for receiving a notification about said one of said at least one second precoder from said user equipment; and / or - means for receiving a notification from said user equipment as to whether said user equipment has used said at least one second precoder.

26. A method comprising: - determining a first precoder for an uplink transmission, and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; -determining whether to use one of the at least one second precoder to send the peak cancellation signal together with the uplink transmission; as well as - Based on the decision, sending at least the uplink transmission to a radio network node using the first precoder.

27. A method comprising: - determining, for a user equipment, a first precoder for uplink transmission and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; as well as - receiving an uplink transmission from the user equipment according to at least the first precoder.

28. An apparatus comprising at least one processing core, at least one memory, the at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processing core, cause the apparatus to at least perform: - determining a first precoder for an uplink transmission, and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; -determining whether to use one of the at least one second precoder to send the peak cancellation signal together with the uplink transmission; as well as - Based on the decision, sending at least the uplink transmission to a radio network node using the first precoder.

29. An apparatus comprising at least one processing core, at least one memory, the at least one memory comprising computer program code, the at least one memory and the computer program code being configured to, together with the at least one processing core, cause the apparatus to at least perform: - determining, for a user equipment, a first precoder for uplink transmission and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; and - receiving an uplink transmission from the user equipment according to at least the first precoder.

30. A non-transitory computer readable medium having a set of computer readable instructions stored thereon, which when executed by at least one processor causes an apparatus to at least perform: - determining a first precoder for an uplink transmission, and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; -determining whether to use one of the at least one second precoder to send the peak cancellation signal together with the uplink transmission; as well as - Based on the decision, sending at least the uplink transmission to a radio network node using the first precoder.

31. A non-transitory computer readable medium having a set of computer readable instructions stored thereon, the set of computer readable instructions, when executed by at least one processor, causing an apparatus to at least perform: - determining, for a user equipment, a first precoder for uplink transmission and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; and - receiving an uplink transmission from the user equipment according to at least the first precoder.

32. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus to perform: - determining a first precoder for an uplink transmission, and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; -determining whether to use one of the at least one second precoder to send the peak cancellation signal together with the uplink transmission; as well as - Based on the decision, sending at least the uplink transmission to a radio network node using the first precoder.

33. A computer program comprising instructions which, when executed by a device, cause the device to perform: - determining, for a user equipment, a first precoder for uplink transmission and at least one second precoder for a peak removal signal, wherein the uplink transmission comprises user data and / or an uplink reference signal; and - receiving an uplink transmission from the user equipment according to at least the first precoder.

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