Compander method with domain conversion for low-papr transmission

Abstract

A method, in a transmitter, comprises applying an invertible compression function to a first modulation signal, to produce a first compressed modulation signal, and generating a radio- frequency (RF) signal for transmission from the first compressed modulation signal, using Orthogonal Frequency Division Multiplexing (OFDM) modulation. A corresponding method, in a receiver, comprises performing OFDM demodulation on a received signal, to obtain an OFDM-demodulated signal; and applying an inverse-compression function to the OFDM-demodulated signal, to produce a first modulation signal. The performing of these methods may be preceded by an exchange of signaling to establish compression / decompression configurations for carrying out these techniques, in some embodiments.

Description

[0001]      COMPANDER METHOD WITH DOMAIN CONVERSION FOR LOW-PAPR TRANSMISSION TECHNICAL FIELD This disclosure is generally related to wireless communications and is more particularly related to techniques for reducing peak-to-average-power ratio (PAPR) in transmitted signals. BACKGROUND Due to their multicarrier structure, traditional Orthogonal Frequency Division Multiplexing (OFDM) signals have an inherently high peak-to-average-power ratio (PAPR), i.e., a high probability of high instantaneous signal magnitude peaks in relation to the average magnitude of the waveform. This is problematic for power-efficient power amplifier (PA) operations, since the peaks may drive the PA to its non-linear input / output mapping region, which will distort the output by attenuating or clipping the corresponding peaks and causing spectral widening whereby adjacent channel interference is created, degrading the adjacent channel leakage ratio (ACLR). To avoid this, the PA needs to be operated in its shallow linear region so that the peaks do not drive it into the non-linear part of the transfer curve. However, this results in low power efficiency since, on average, a moderate fraction of the full power capability is utilized. Operating with such a PA strategy is costly, since PAs with higher peak power need to be used, and the related energy consumption is also high, since the PAs need to be driven at a higher bias voltage. Minimizing energy consumption in wireless networks, in both UEs and NW nodes is a necessity for supporting constantly increasing bandwidths and data rates with maintained time between charging. PA energy consumption is a major contributor to both user equipment (UE) and network (NW) energy consumption. Numerous approaches have been used for PAPR reduction, e.g., discrete Fourier Transform-spread OFDM (DFTS-OFDM), crest factor reduction (CFR), tone reservation (TR), digital pre-distortion (DPD), and digital post-distortion (DPoD). Some of these techniques, such as DPD and DPoD, have been proposed as a way for 3rd-generation Partnership Project (3GPP) networks to save energy, particularly in higher-load scenarios. The basic building blocks of DFTS-OFDM, also referred to as Single Carrier Frequency- Division Multiple Access (SC-FDMA), are illustrated in Figure 1. As seen in Figure 1, a baseband input signal, which may be referred to as a “modulation symbol,” e.g., comprising       quadrature-phase-shift keying (QPSK), 16-quadrature-amplitude modulation (16QAM), or 64QAM modulation symbols, and which may be regarded as being in the frequency-domain (F-domain), with respect to the inverse Fast Fourier Transform (IFFT) operation to be performed later, is input to a discrete Fourier Transform (DFT) operation, to “spread” the input baseband signal across the frequency bins output from the DFT. This is shown in Figure 1 as the DFTS block. An IFFT operation is then performed on the DFTS block’s output. The resulting time-domain signal is then provided to the radio frequency (RF) circuitry, shown as RF FE (front-end) + PA in Figure 1, for upconversion, amplification, and transmission. At the receiver end, the reverse processes are performed. After passing through the radio channel, the RF signal is received with a receiver’s RF circuitry, shown as LNA (low-noise amplifier) + RF FE in Figure 1. This block amplifies and downconverts the received radio signal. A Fast Fourier Transform (FFT) is performed, to reverse the IFFT operation performed in the transmitter. Optionally, the output is equalized, to compensate for channel distortions. The DFTS process is reversed, using an inverse DFT. This produces an output signal, again in the “F-domain” with respect to the IFFT and FFT operations, which can be demodulated. For the purposes of the present disclosure, DFTS-OFDM is regarded as one form of OFDM. Cyclic-prefix OFDM (CP-OFDM), which is used by base stations in LTE networks and which does not include the DFTS step shown in Figure 1, is another. Several mitigation approaches may reduce the PAPR or non-linear effects, but each has respective shortcomings. For example, with DFT-spread OFDM, the multi-carrier OFDM signal is converted to single-carrier signal by applying a DFT prior to conversion to the time domain. The resulting signal has a lower PAPR, but the PAPR reduction is moderate and is not robust with respect to channel dispersion. As a consequence, equalization needs to be applied prior to the inverse DFT in the receiver. Crest factor reduction (CFR) is another example. With CFR, the individual signal peaks are reduced before feeding the signal into the PA, e.g., by soft or hard clipping. Uncontrolled spectral spreading is avoided but considerable signal distortion remains. With tone reservation (TR), another approach, some OFDM subcarriers are reserved and an additive signal component is inserted into the reserved tones, to produce a time-domain contribution that reduces the individual high peaks. However, for a sufficiently strong effect, a large number of       reserved tones is required, reducing carrier capacity, and the computation complexity of deriving a suitable additive waveform is high. Digital pre-distortion (DPD) is another technique. With DPD, the PA input signal is pre- distorted so that the aggregate effect of the pre-distortion and PA distortion is approximately linear. Although overall distortion at the receiver is reduced or eliminated, the PA non-linearity, when relying solely on DPD, can still generate excessive spectral leakage. Digital-Post Distortion (DPoD), which is a receiver-side technique, can be used to reduce the impact of non- linearity in the PA, but not clipping, and the inverse processing in the RX amounts to a high- complexity iterative process since the residual non-linearity function may not be known or not easily invertible, and it only works in cases where the TX (PA output) and RX (LNA input) signals are exactly the same signals; to maintain manageable complexity, the signal needs to be single-layer. There is thus a need for a method to improve PA efficiency and / or received signal fidelity without causing noticeable compression / clipping or spectral leakage in the PA, to ensure relatively simple RX processing, and to also allow non-linearity protection for signal components that are transmitted together with additional signals not seen at a particular receiver. SUMMARY Embodiments of the techniques, apparatuses, and systems described herein may address this need, by providing a technique whereby a signal is pre-processed (compressed) in the transmit (TX) baseband (i.e., before transmission), using a predetermined compression function, where the function generates a reduced-PAPR image of the desired signal that does not lead to significant additional clipping / memory effects in the PA. The process is reversed at the receiver (RX) end. Together, this compression and inverse-compression (or decompression) may be understood as providing a compander function, i.e., a combination of a compressor operation and an expander operation. The techniques herein may utilize at least one predetermined compression function. In some embodiments, multiple predetermined compression functions may be available for selection and use. Applying the compression function at the transmitter may include converting the baseband (or early / late digitized) signal from the F-domain to the time-domain (T-domain), applying the function, and converting back. The compression may be applied in two (or more)       steps, for example, converting first at nominal sample timing and applying the function and converting back, after which time-shifting in F-domain by ½-sample and repeating the procedure. The compressed signal may then be transmitted. With proper selection and application of the compression function, it may have a low-PAPR property, causing negligible distortion / spectral leakage at the PA. Multiple separately compressed single-layer signals may be summed and transmitted simultaneously, subject to conservative summing / scaling constraints. In some embodiments, the transmitted signal may include a scaling reference (RS), e.g., as part of each compressed signal layer. At the receiver (RX) end, the receiver may extract its desired F-domain BB signal component, may apply equalization, and apply the inverse (decompression) function. The receiver may then perform conventional demodulation. In various embodiments, the TX and RX may exchange capability and processing / configuration signaling. For instance, for uplink compression, the UE may signal the network with compression capability info (which function(s), parameter ranges, …), receive a compression activation order from the gNB (and optionally a specific function configuration, or a configuration change), and may request a preferred function type or parameter value, in various instances or embodiments. For downlink compression, the UE may provide the network with decompression capability info, receive a decompression activation order from the gNB (and optional configuration info), and may request a preferred function type or parameter value, in various instances or embodiments. According to the present invention, there is provided a method, in a transmitter, for transmitting a radio-frequency (RF) signal. The method comprises sending, to a receiver of the RF signal, an indication of supporting use of an invertible compression function. The receiver of the RF signal may also be referred to as a target of the RF signal. The method further comprises receiving, from the receiver of the RF signal, an indication that the receiver supports use of the invertible compression function. The method further comprises applying the invertible compression function to a first modulation signal, to produce a first compressed modulation signal, and generating a radio-frequency (RF) signal for transmission from the first compressed modulation signal, using Orthogonal Frequency Division Multiplexing (OFDM) modulation.       In some embodiments, the transmitter may be a User Equipment, UE. In these embodiments, the receiver, or target of the RF signal, may be a network node. Alternatively, for example in sidelink operation, the receiver may be a second UE. In these embodiments, the indication of supporting use of an invertible compression function may be sent in UE capability signaling and / or UE assistance or preference information. Further, the indication that the receiver supports use of the invertible compression function may be received in configuration information. For example, the configuration information may comprise one or more parameters of the invertible compression function and / or information indicating usage of the invertible compression function. The configuration information may be received in higher layer signaling, for example Radio Resource Control, RRC, signaling. In addition, or alternatively, the indication that the receiver supports use of the invertible compression function may comprise an activation order to apply the invertible compression function. The activation order may be received in Layer 1, L1, or Layer 2, L2 signaling, for example in a Medium Access Control Element, MAC CE, or in a Dynamic Control Information, DCI. In an embodiment, the indication of supporting use of an invertible compression function is sent to the receiver as part of a Scheduling Request, SR. In this case, the indication that the receiver supports use of the invertible compression function may be part of a corresponding scheduling grant received from the receiver. In particular, the scheduling grant may indicate whether the UE may or should apply the invertible compression function in respect to an uplink, UL, signal scheduled by the scheduling grant. According to some embodiments, the method may further comprise indicating in the RF signal that the invertible compression function has been applied, for example in a bitfield of the payload of the RF signal. In some embodiments, the transmitter may be a network node. In this case, the receiver may be a UE.       In these embodiments, the indication of supporting use of an invertible compression function may be sent in a configuration carried in one or more of RRC signaling, MAC-CE, or downlink, DL, scheduling signaling. The indication that the receiver supports use of the inconvertible compression function may be received in one or more of UE capability signaling, UE assistance information and UE preference signaling. The indication of supporting use of an invertible compression function may be in respect of respective DL scheduled data. For example, the indication of supporting use of an invertible compression function may be sent in a downlink, DL, data assignment. The DL data assignment may comprise configuration parameters of the inconvertible compression function. In some embodiments, the method may comprise sending the indication of supporting use of an invertible compression function to the receiver before receiving the indication that the receiver supports use of the inconvertible compression function. In other embodiments, the method may comprise sending the indication of supporting use of an invertible compression function to the receiver after receiving the indication that the receiver supports use of the inconvertible compression function. In some embodiments, the method comprises selecting the invertible compression function from a plurality of invertible compression functions. As detailed above, the indication of supporting use of an invertible compression function may thus comprise an indication that the invertible compression function is being or will be applied to the first modulation signal. According to some embodiments, the compression function may be applied to the first modulation signal prior to an inverse Fourier transform operation performed to generate an OFDM signal. The method may further comprise transmitting the RF signal.       In some embodiments the method may further comprise applying an invertible compression function to a second modulation signal, to produce a second compressed modulation signal and combining the first compressed modulation signal and the second compressed modulation signal prior to the OFDM modulation. In some embodiments, generating the RF signal comprises including a scaling reference signal, the scaling reference signal being indicative of a pre-compression amplitude of the first modulation signal. According to the present invention, there is further provided a method, in a receiver, for receiving a Radio Frequency, RF, signal. The method comprises receiving, from the transmitter of the RF signal, an indication that the transmitter supports use of an invertible compression function. The method further comprises sending, to the transmitter of the RF signal, an indication of supporting use of the invertible compression function. The method further comprises performing OFDM demodulation on a received signal, to obtain an OFDM- demodulated signal; and applying an inverse-compression function to the OFDM-demodulated signal, to produce a first modulation signal. In some embodiments, the method may comprises receiving, from the transmitter of the RF signal, an indication that the transmitter supports use of an invertible compression function before sending, to the transmitter of the RF signal, an indication of supporting use of the invertible compression function. In other embodiments, the method may comprise receiving, from the transmitter of the RF signal, an indication that the transmitter supports use of an invertible compression function after sending, to the transmitter of the RF signal, an indication of supporting use of the invertible compression function. In some embodiments, the receiver may be a network node. In this case, the transmitter may be a UE. In these embodiments, the indication that the transmitter supports use of the invertible compression function may be received in UE capability signaling and / or UE assistance or preference information.       Further, the indication of supporting use of the invertible compression function may be sent in configuration information. The configuration information may comprise one or more parameters of the invertible compression function and / or information indicating usage of the invertible compression function. The configuration information may be sent in Radio Resource Control, RRC, signaling. In some embodiments, sending the indication of supporting use of the invertible compression function may comprise sending an activation order to apply the invertible compression function, to the transmitter of the RF signal. The activation order may be sent in Layer 1, L1, or Layer 2, L2 signaling, for example in a Medium Access Control Element, MAC CE, or in a Dynamic Control Information, DCI. In some embodiments, the indication that the transmitter supports use of an invertible compression function may be received in a Scheduling Request, SR from the transmitter; and the indication of supporting use of the invertible compression function may be sent, to the transmitter, in a corresponding scheduling grant. The scheduling grant may indicate whether the UE may or should apply the invertible compression function in respect to an uplink, UL, signal scheduled by the scheduling grant. The method may comprise receiving an indication in the RF signal that the transmitter has applied the invertible compression function, for example in a bitfield of the payload of the RF signal. In other embodiments, the receiver may be a UE, and the transmitter may be a network node or a second UE. In these embodiments, the indication that the transmitter supports use of an invertible compression function may be received in a configuration carried in one or more of RRC signaling, MAC-CE, or downlink, DL, scheduling signaling. Further, the indication of supporting use of the inconvertible compression function may be sent in one or more of UE capability signaling, UE assistance information and UE preference signaling. The indication that the transmitter supports use of an invertible compression function may be in respect of respective DL scheduled data. The indication that the transmitter supports use of       an invertible compression function may be received in a downlink, DL, data assignment. The DL data assignment may comprise configuration parameters of the inconvertible compression function. The method may comprise selecting the invertible compression function from a plurality of invertible compression functions. According to the present invention, there is further provided a transmitter comprising processing circuitry configured to carry out the above method in a transmitter. The transmitter may be a user equipment, UE, or a network node. According to the present invention, there is further provided a receiver comprising processing circuitry configured to carry out the method above in a receiver. The receiver may be a user equipment, UE, or a network node. Using the techniques described herein, spectral leakage in the PA and ACLR impact may be avoided or reduced. RX processing complexity may be moderate, and the processing may advantageously be limited to BaseBand BB only. The methods can be applied to individual single-layer signals, even if multiple such signals are transmitted simultaneously. The end-to- end signal properties may advantageously be relatively independent of actual PA / LNA properties. The lowering of the PAPR by the compander methods described herein may make DPD redundant, or make the DPD simpler since the dynamic range of the compressed signals can be smaller. BRIEF DESCRIPTION OF THE FIGURES Some embodiments of the present invention will now be described in more detail, by way of example only, with reference to the drawings, in which: Figure 1 illustrates Discrete-Fourier-Transform-spread OFDM. Figure 2 is a block diagram illustrating functional blocks of a system implementing techniques described herein, according to some embodiments.       Figure 3 is a process flow diagram illustrating steps carried out by a transmitter and a receiver, according to some embodiments. Figure 4 shows the use of techniques described herein on multiple signal layers. Figure 5 illustrates an extension of the techniques described herein to apply the compression function to time-shifted version(s) of the input signal. Figure 6 is a process flow diagram illustrating an example method carried out in a transmitter circuit, according to some embodiments. Figure 7 is a process flow diagram illustrating an example method carried out in a receiver circuit, according to some embodiments. Figure 8 is a further process flow diagram illustrating a method in a transmitter according to some embodiments. Figure 9 is a further process flow diagram illustrating a method in a receiver according to some embodiments. Figure 10a shows a transmitter according to some embodiments. Figure 10b shows a receiver according to some embodiments. Figure 11 illustrates an example communication system, according to some embodiments. Figure 12 shows an example user equipment (UE) in which the techniques described herein may be implemented, in some embodiments. Figure 13 shows an example network node which the techniques described herein may be implemented, in some embodiments. DETAILED DESCRIPTION Described herein are compander (compression-expansion) methods for low-PAPR transmission of an OFDM signal. These techniques may be applied by a UE and a gNB (a 3GPP base station), for example, on either or both uplink (UL) and downlink (DL) transmissions in a wireless communication system. The concept will first be described generally and then specifics related to its application in the specific directions will be elaborated.       The techniques herein may utilize at least one predetermined compression function. In some embodiments, multiple predetermined compression functions may be available for selection and use. The compression function (or each compression function, when there are multiple functions) may be an instantaneous non-linear amplitude modification. This function is invertible, which for the purposes of the present disclosure means that the function can be reversed, within a set input signal magnitude range. The compression function is non-linear. This latter property follows from the requirement that the compression function reduces the PAPR, of course, as a simple linear scaling of the input signal, for instance, reduces the signal amplitudes, but the peak-to-average power remains the same. A key step in several embodiments described herein is to compress a single-layer signal in the baseband, before performing OFDM, i.e., before converting it to a time-domain signal using an IFFT, by applying a non-linear compression function so that the power amplifier’s transfer function (input-output characteristic) will not cause additional distortion, or will create distortion below a tolerable threshold. This is achieved by reducing the magnitude of instantaneous signal peaks so that the non-linear range of the PA’s input-output characteristic is not exercised significantly. At the receiver side, the signal is de-compressed by applying the inverse of the compression function, repeating the transmitter steps in the reverse order, and the original signal is recovered within a tolerable fidelity margin. The OFDM signal to be transmitted may be a CP-OFDM (multi-carrier) or DFTS-OFDM (single-carrier) signal. Note that all domain conversion and OFDM IFFT / FFT examples described herein are provided as non-limiting. In particular, IFFT and FFT operations are specific digital implementations of frequency-to-time domain transforms and time-to- frequency domain transforms - alternative and mathematically equivalent or well- approximated signal processing sequences may be applied that result in similar functionality being achieved. Thus, where the terms IFFT and FFT are used herein, they should be understood as simply exemplifying frequency-to-time and time-to-frequency domain conversions. A block diagram of several functional blocks in an example transmitter and receiver is shown in Figure 2. A high-level process flow of some embodiments of the techniques described herein, including both transmitter and receiver operations, is illustrated in Figure 3.       As shown at block 100 of Figure 3, the TX and RX, which may correspond respectively to the UE and gNB, for example, may perform control signaling to establish one or more of: matching capability of compression and decompression functionality, supported compression functions and parameter ranges, capability to perform the function in specific operating scenarios, preferred compression settings for the current operating scenario, etc. As a result of this step, the TX and RX will be configured for aligned compander operation regarding the compression function, parameters, and to which signals or in which transmission resources the compander operation is applied. The capability and preference signaling may be updated over time, and the configuration may be correspondingly updated. More details of signaling aspects are provided in a separate section below. As shown at block 110 of Figure 3, the TX applies the compression function with previously determined settings to a single-layer signal component in digital baseband representation. ^ In some embodiments, the function is applied by converting the F-domain signal to T-domain, applying the function defined in the T-domain, and converting back to the F-domain. Note that this is performed before the IFFT that forms part of the OFDM modulation (e.g., DFTS-OFDM or CP-OFDM). ^ In some embodiments, the compression may be applied in two steps, e.g., sequentially applying the compression function to 0- and ½-sample-shifted signal representations. This sample-shifting extension may also be used at a higher resolution, e.g. ¼ or 1 / 8- sample, in cases where maximum compression efficiency is desired, at expense of additional processing. More details of compression function application are provided in a separate section below. In some embodiments, the input signal may be assumed to be scaled in a predetermined manner or nominally, as per routine OFDM signal power allocation in the time-frequency grid resource elements (REs). The compression function may then be scaled or otherwise configured so as to achieve a predetermined effect on the properly scaled signal. In another embodiment, the input signal may be normalized or scaled to a predetermined power level prior to applying a predetermined compression function configuration. To facilitate scaling alignment of compression / decompression, the compressed signal may contain an RS for scaling reference purposes (ScRS), in some embodiments. Its       structure / mode and parameters may also be defined via the configuration / negotiation steps shown at block 100 of Figure 3, or via other configuration operations. ^ In some embodiments, a non-compressed F-domain ScRS is added to the compressed signal. The SCRS is scaled in relation to the compressed signal level / power, where the total power of the ScRS is low compared to the compressed signal power and the PAPR impact is negligible. The ScRS amplitude in the received signal may then be directly estimated without distortion. ^ In other embodiments, a F-domain ScRS may be included in the input signal prior to compression, so that the effective power reduction due to compression will affect the ScRS proportionally and in a known manner. (It may be assumed that the T-domain waveform shape change due to non-linear distortion appears in the F-domain as low- level additive noise that may be ignored.) The ScRS may be an existing RS, e.g., the demodulation reference symbols (DMRS). ^ In yet other embodiments, a T-domain ScRS may be added before or after applying T-domain compression but before converting back to the F-domain. The ScRS may be a pseudo-noise-like sequence with low cross-correlation to the desired signal, e.g., a Gold sequence, m-sequence, ZC-sequence, etc. The application of the compression function shown at block 110 of Figure 3 may be applied in different points in the digital baseband signal flow in the lower-layer processing split, but preferably prior to the application of the IFFT (OFDM modulator). For example, it may be applied at the same signal flow stage as used for DFTS (including its relation to equalization at the receiver). Applying the compression function generally reduces the total power of the output signal if no corrections are applied. In some embodiments, a power expansion factor (e.g., a beta- factor) may be applied to ensure that the output signal from the compression has the same average power as the input functions. In other embodiments, the compression function may be modified, effectively shifting the compression curve, so that it is not unity in the linear region but applies a suitable power expansion across the signal magnitude ranges. Returning to Figure 3, as shown at block 130, the TX may apply an IFFT to the compressed signal component, convert it to analog RF, and transmits it via a PA. Preferably, the signal compression has reduced the signal peaks to that non-linear distortion at the PA and associated spectral leakage is below a threshold.       In some embodiments, multiple single-layer signal components, one or more of them from respective processing instances corresponding to step 110, may be summed prior to performing step 120. An example of this, involving two signal layers, is shown in Figure 4. The multiple components may be summed after applying component-specific precoding weights (e.g., signals to multiple MU-MIMO users, or a mix of broadcast and dedicated signals) or they may be multiplexed in frequency (e.g., MU scheduling in frequency or transmitting multiple MC component carriers). The compression parameters and / or summing coefficients may be selected conservatively so that the sum signal peaks remain below the non-linear region of the PA with a sufficiently high probability. In some embodiments, for single-user multiple-input multiple-output (SU-MIMO) transmission, joint compression among the layers may be applied, since the receiver has full information about all layers. Since the compression is unaware of the precoder weights in antenna space, it needs to compress for worst case. The joint compression is a simple extension of the general method above. At transmission, the compression is applied to the sum of the layer amplitudes: ^^^^ ^^^ ^ ^^ଶ^ ^^^ ^⋯^ ^^ே^ ^^^ and at reception the procedure is inverted. This gives a compression that works in worst case scenarios, but it may reduce the PA utilization. As shown at block 130, the RX receives the signal compressed transmitted at step 120. It is down-converted in the RF font and sampled, and FFT (OFDM demodulation) may be applied. In some embodiments, the received signal may contain multiple signal components (not necessarily the same composition as in the TX signal), e.g., a gNB receiving UL signals from multiple UEs. The compressed signal components may then be separated, e.g., via spatial filtering / RX beamforming, prior to performing the step shown at block 140 of Figure 3. As shown at block 140, the RX applies the inverse of the compression function, with agreed / aligned parameters, to a single-layer signal component in digital baseband representation. The reverse process includes the mirror-image domain conversion, including, for example, the optional combination of 0- and ½-sample offset signal versions. In practice, this inversion is done in the presence of interference, and the transform effecting the inverse function may be further designed to suppress the interference or avoid noise enhancement, e.g., by minimizing the total noise, interference, and distortion component. This may also be designed to be robust near the compression function truncation, e.g., when the function slope becomes zero or small.       In dispersive environments, equalization may be applied to the received signal before performing the decompression step. Also, power expansion factors applied in step 110 may be reversed to maintain proper nominal scaling. If a ScRS was included in the transmitted signal, it may be extracted in accordance with the insertion format (as described above for block 110). The obtained ScRS power or magnitude estimate may then be used to re-scale the total received signal appropriately prior to applying the inverse function at predetermined scaling. Alternatively, the UE may determine the appropriate scaling based on the received signal power, and optionally apply additional scaling factors to remove the scaling impact due to other signal components based on the estimated received signal SINR. If the received signal SINR is below a threshold, the RX may omit the inverse function application step to avoid noise-plus-interference enhancement. After inverting the compression function, the received signal may be processed according to known techniques for signal demodulation, decoding, etc. Compression-decompression processing In some embodiments, the following sequence of steps may be applied in the step shown at block 110 of Figure 3 to achieve compression by applying a compression function ^^^ ^^^. If the function is invertible for only a subset of the support x, the input values need to be restricted to that region where the function is invertible. This may be done by applying clipping, for example. The example detailed here uses two levels, with sample offsets of 0 and 1 / 2. The technique can be applied using only the first level, however, or with additional, finer-grained offsets. The two-level processing described here is illustrated in Figure 5. Level 1: 1. Take as input ^^ input an OFDM BB signal for one layer, of length N, N may be the same as, or smaller than, the size of the IFFT subsequently used for generating the OFDM signal, in some embodiments. 2. Go to time domain with an N-IFFT: ^^ 3. Apply the function ^^ ൌ ^^^ ^^^ (with truncation) 4. Go back to the frequency domain with an N-FFT: X´= FFT( ^^)       Level 2 (adds ½-sample offset representation): ഏ^^ 1. ^^‘ is shifted half a sample in time domain ^^^′^ ൌ ^^′^ ^^ಿ. Note that this is a shift of half of the sample interval. 2. Repeat Level 1: ^^^′^ ൌ ^^ ^^ ^^ ^^^ ^^^′^ ^, ^^^′^ ൌ ^^^ ^^^′^ ^, ^^^′^ ൌ ^^ ^^ ^^^ ^^^′^ ^ 3. Shift back to ^ ൌ ^ಿresult.Applying the compression function via level 1 processing to both 0- and1 / 2-sample offset signal versions ensures that the choice of sampling instants does not miss continuous signal trajectory points with high peak values. Additionally, a finer sampling grid (e.g. ¼- and ¾- sample shifts) may similarly be included if more strict control of PAPR is desired, at the cost of additional processing of 4 or 8 levels, respectively. In one embodiment, the compression functions f(x) for the different levels may be different. The compression stage as a whole may be seen as being performed in the frequency domain. Only for the purposes of applying the compression function, the relevant signal is converted to the time domain and then back. In an alternative embodiment, more steps may be performed in the time domain, e.g., the ½- sample-shifting operation may be obtained via up-sampling and interpolation, etc. Various functions ^^^^^^may be used. In one non-limiting example, the function ^^^^^^ൌ ^^ െ ^^|^^|ଶ^^may be used where ^^ is a tunable / configurable parameter. Other functions or function categories may be used, e.g., hyperbolic tangent, sigmoid, etc. The decompression process shown at block 140 of Figure 4 executes the above sequence in the reverse order and applies the inverse of the function ^^^ ^^^, obtaining ^^^ ൌ ^^ି^^ ^^^. The inverse may be predetermined or computed analytically or numerically for the chosen value of ^^. Control signaling The following signaling aspects may be used in both UL and DL (unless indicated). Likewise, similar signaling to coordinate device-to-device (D2D) transmissions between two UEs can be used.       Below follows an example of long-term scale type of signaling such as capability exchange, configuration parameters, semi-statically turning on / off (until further reconfiguration) etc. Note that “NB” refers to “Node B,” i.e., the network base station. Type Directio Contents Decision basis Signaling n mechanism s Capability UE - > Supported Fixed by RRC, NB compression implementation capability functions, parameter reporting ranges framework Preferences UE - Preferred function and PA operating mode RRC, UAI >NB parameter selection (UL), required RX framework quality / tolerable EVM (DL), active / signal BW, power consumption status, computational / proce ssing status… Configurati NB - > ^ configured UE preference and RRC, MAC on UE function capability, PA CE parameters (f(x), a) operating mode ^ applied to which (DL), required RX physical signals quality / tolerable (PDCCH / PDSCH) EVM (UL), active / signal BW, power consumption status, computational / proce ssing status… Dynamic NB - > ^ Dynamic feature UE preference and MAC CE, activation UE on / off capability, PA DCI ^ applied to which operating mode temporal resources (DL), required RX (symbols, slots) quality / tolerable EVM (UL), active / signal BW Dynamic RX - > Dynamic function or RX signal DCI, UCI, feedback TX parameter / power quality / properties, MAC-CE feedback for required RX signal immediate adjustment fidelity       Table 1 As seen in the table, the signaling may include short-term scale (dynamic) type of signaling as well for the compression. In the downlink, the gNB can indicate, per scheduling (e.g., in a DCI), whether the scheduled transmission is compressed, type of compression (configuration), etc. Furthermore, in the DL but for an UL scheduling grant, the gNB can indicate whether the UL transmission by the UE shall be compressed and type of compression. In some embodiments, the UE can explicitly indicate to the gNB whether the decompressed data quality is below a certain level (e.g., the error vector magnitude exceeds a certain level). The gNB may then, based on the received indication, choose to stop the compression process. The gNB may however decide to stop the compression for other reasons, such as when the UE negatively acknowledges (NACK) compressed data reception more than a certain level. The compression function (or indicator) and / or compression usage(on / off) and / or parameters may be indicated to the UE using higher layer signaling, e.g., RRC signaling. In one example, one or more of these indicators or parameters can be indicated to the UE using RRC, and then L1 / L2 signaling can be used in order to indicate which one is activated / deactivated. In one example, the UE may indicate, e.g., as part of the scheduling request (SR), its capability or preference to apply compression, and may then receive a grant, e.g., from gNB for example within downlink control information, which indicates to the UE that it can / should use compression while transmitting the signal. In one example, the UE indicates in UL signal, e.g., using a bitfield in the payload that it has applied compression in the UL signal. The bitfield can be pre-configured, or that the UE receives a configuration through higher layer signaling of e.g., its presence, size, and starting point. It can also be different location or configuration in different UL signals, e.g., PUCCH / PUSCH. Note also that the signaling steps described above may also be applied to other two-sided PA optimization and non-linearity suppression schemes, e.g., combinations of DPD / DPoD, including approaches where some form of NL-compensation, e.g., a DPD, may be applied after the IFFT in the transmitter, and DPoD is not applied on a per-layer basis or may be applied after the FFT in the receiver.       Sidelink aspects As indicated, the proposed method can also be applied to sidelink transmissions, where the transmitter and receiver are both UEs. The principles as outlined in the table above are also valid for the sidelink operation. In sidelink communications, a network gNB may still be coordinating the communication e.g. via scheduled resource allocation of the sidelink. Hence, in some examples it may be reasonable that all or parts of the signaling for configuration may still be communicated between UEs and gNB, where gNB may act as a coordinating node for the compression control. As an example, the capability, preferences and configuration information in the table above may be signaled and controlled in-between UEs network gNB also for sidelink operation. The dynamic activation and feedback may however at least in some examples be handled in-between UEs directly, e.g., utilizing sidelink control information (SCI) within Sidelink PDCCH (S-PDCCH) signaling. Other examples may be envisioned, e.g., in fully UE-autonomous sidelink mode, where all coordination of compression may be done in- between UEs without gNB interaction. Figure 6 and Figure 7 are process flow diagrams illustrating, respectively, example methods performed in a transmitter circuit and receiver circuit. These are intended to be generalizations of and to encompass many of the techniques described above. Thus, where the terminology used to describe Figures 6 and 7 differs from that used above, the terms used below should be interpreted to encompass or be synonymous with similar or clearly related terms used above. Note that the methods shown in Figure 6 and Figure 7 complement each other, such that both (or various variations of both) may be used together, at respective ends of a communication link. Figure 6 illustrates a method carried out in a transmitter circuit, which may be found in a UE or in a base station (e.g., a 5G gNB), in various embodiments or instances. At the heart of the illustrated method, as shown at block 640, is the step of applying an invertible compression function to a first modulation signal, to produce a first compressed modulation signal. Note that “invertible” as used herein means that the function is reversible within at least a defined range of signal amplitudes. The output of the compression function is a signal having a reduced peak-to-average power ratio, compared to the input. The inverse of the compression function, which amounts to an expansion function, can be applied to this output to reproduce the input signal. As was described above, the input signal may be a baseband signal, e.g., comprising a digital representation of QPSK- or QAM-modulated control data and / or user data.       As shown at block 650, the method further comprises generating a radio-frequency (RF) signal for transmission from the first compressed modulation signal, using Orthogonal Frequency Division Multiplexing (OFDM) modulation. This signal is subsequently transmitted, as shown at block 660. In some embodiments or instances, the method may comprise selecting the compression function from a plurality of predetermined compression functions. This is shown at block 620, in Figure 3. The method may comprise, in some embodiments, sending, to at least one target of the RF signal, an indication that the compression function is being or will be applied to the first modulation signal and / or an indication of the compression function, as shown at block 630. The latter may be used, for example, when multiple compression functions are available for use, where this indication identifies the compression function actually used to the receiving end. In some embodiments, the method comprises exchanging, with at least one target of the RF signal, an indication of one or more capabilities and / or configuration parameters regarding use of the compression function. This is shown at block 610. Examples of these capabilities and / or configuration parameters were described above, e.g., in Table 1. This exchange may take the form of “handshake” or “negotiation” signaling, in some embodiments or instances. In others, one or more of the parameters may be broadcast, or signaled as a directive, e.g., in RRC signaling. Note that in some embodiments or instances, this exchange of capabilities and / or configuration parameters may comprise the providing of multiple possible values for one or more parameters, or one or more configurations of the compression, decompression, in such a way that a particular one of the values and / or configurations can be subsequently identified in dynamic signaling. This dynamic signaling might be understood as “activating” a configuration established in the exchange shown at block 610, for example. In various embodiments or instances, the compression function is applied to the first modulation signal prior to an inverse Fourier transform operation performed to generate an OFDM signal. Generating the RF signal may comprise cyclic-prefix OFDM (CP-OFDM) modulation or discrete Fourier Transform-spread OFDM (DFTS-OFDM) modulation, in various embodiments or instances. In some embodiments or instances, applying the compression function may comprise transforming the first modulation signal using a first frequency-domain-to-time-domain       transform, applying a time-domain representation of the compression function to the resulting time-domain representation of the first modulation signal, and transforming the resulting compressed signal using a first time-domain-to-frequency-domain transform to obtain the first compressed modulation signal. In some of these embodiments, this process may be repeated for one or more shifts of the input signal. Thus, applying the compression function may further comprise shifting samples of the output of the first time-domain-to-frequency-domain transform by a pre-determined fraction of a sample interval to obtain a shifted modulation signal, transforming the shifted modulation signal using a first frequency-domain-to-time- domain transform, applying the time-domain representation of the compression function to the resulting time-domain representation of the shifted modulation signal, transforming the resulting compressed shifted signal using a first time-domain-to-frequency-domain transform to obtain a shifted compressed modulation signal, and shifting samples of the shifted compressed modulation signal back by the pre-determined fraction of the sample interval, to obtain the first compressed modulation signal. An example of this was illustrated in Figure 5, as discussed above. In this example, the pre- determined fraction of the sample interval is 1 / 2. In other embodiments, the pre-determined fraction of the sample interval is 1 / 4 and the shifting, transforming, and applying steps discussed immediately above are repeated for shifts of 1 / 2 and 3 / 4. The compression function may be applied to a single-layer signal, in some embodiments or instances. In others, the method may further comprise applying a compression function to a second modulation signal, to produce a second compressed modulation signal and combining the first compressed modulation signal and the second compressed modulation signal prior to the OFDM modulation. This is shown at blocks 642 and 644 in Figure 6. As noted above, this combining may comprise a summing of weighted versions of the compressed signals, in some instances or embodiments, or frequency multiplexing, in other instances or embodiments. In some embodiments or instances, generating the RF signal comprises including a scaling reference signal, the scaling reference signal being indicative of a pre-compression amplitude of the first modulation signal. This may be done in several different ways. For example, the method may comprise applying the compression function to a scaling reference symbol along with the first modulation signal. Alternatively, including the scaling reference signal may comprise adding a scaling reference symbol to the first compressed modulation signal, prior to the OFDM modulation.       Figure 7 shows a corresponding and complementary method performed in a receiver circuit, which may also be found in a UE or in a base station (e.g., a 5G gNB), in various embodiments or instances. At the heart of this illustrated method are the inverse operations to those shown at blocks 640 and 650 in Figure 6. Thus, as shown at block 740 of Figure 7, the method comprises performing OFDM demodulation on a received signal, to obtain an OFDM- demodulated signal. As shown at block 750, the method further comprises applying an inverse- compression function to the OFDM-demodulated signal, to produce a first modulation signal. Assuming that the inverse-compression function is the exact inverse of the compression function used at the transmitter, the output first modulation signal here is the same as the modulation signal input to the compression function at the transmitter, subject to distortion by the radio channel. In dispersive environments, equalization may be applied to the received signal before performing the decompression step – this is shown at block 745 in Figure 7. In some embodiments or instances, the method shown in Figure 7 comprises selecting the inverse-compression function from a plurality of predetermined inverse-compression functions. This is shown at block 730. As shown at block 720, the method may further comprise receiving, from a transmitting source of the received signal, an indication that a compression function is being or will be applied to the first modulation signal prior to transmission and / or an indication of the compression function. The selection shown in block 730 may be responsive to signaling received as shown at block 720, in some embodiments. In others, the receiver circuit may indicate a preference for a particular compression / decompression function, and / or signal a command for a particular compression / decompression function, such that the selection of a particular function from a set of predetermined functions is controlled by the receiver. In some embodiments or instances, the method comprises exchanging, with a transmitting source of the received signal, an indication of one or more capabilities and / or configuration parameters regarding use of the inverse-compression function. This is shown at block 710, which corresponds to block 610 of Figure 6. The same variations and considerations discussed above apply here. In some embodiments or instances, demodulating the RF signal comprises cyclic-prefix OFDM (CP-OFDM) demodulation or discrete Fourier Transform-spread OFDM (DFTS-OFDM) demodulation. In some embodiments or instances, applying the inverse-compression function comprises transforming the OFDM-demodulated signal using a first frequency-domain-to- time-domain transform, applying a time-domain representation of the inverse-compression       function to the resulting time-domain representation of the OFDM-demodulated signal, and transforming the resulting de-compressed signal using a first time-domain-to-frequency- domain transform, to obtain the first modulation signal. In some of these embodiments or instances, applying the inverse-compression function may further comprise shifting samples of the output of the first time-domain-to-frequency-domain transform by a pre-determined fraction of a sample interval to obtain a shifted modulation signal, transforming the shifted modulation signal using a first frequency-domain-to-time-domain transform, applying the time-domain representation of the inverse-compression function to the resulting time-domain representation of the shifted modulation signal, transforming the resulting de-compressed shifted signal using a first time-domain-to-frequency-domain transform to obtain a shifted de- compressed modulation signal, and shifting samples of the shifted de-compressed modulation signal back by the pre-determined fraction of the sample interval, to obtain the first modulation signal. This pre-determined fraction of the sample interval is 1 / 2, in some instances or embodiments. In other examples, the pre-determined fraction of the sample interval is 1 / 4 and wherein the shifting, transforming, and applying steps of example embodiment 21 are repeated for shifts of 1 / 2 and 3 / 4. In some embodiments or instances, the method comprises determining a scaling reference signal from the received signal, the scaling reference signal being indicative of a pre- compression amplitude of the first modulation signal, and scaling the first modulation signal based on the scaling reference signal. The techniques described herein may be applied in point-to-point communication link scenarios, or in cellular networks, such as those defined by 3GPP. In view of the detailed examples and explanation provided above, it will be appreciated that the list below lists core aspects of some embodiments of the presently disclosed techniques, on the TX side. Subsets of the aspects listed below apply to UE-based and network node-based implementations, respectively. 1. A method in a wireless transmitter for OFDM signal transmission with limited distortion, comprising: transmitting to a receiver an indication of supporting baseband PAPR compression using one or more predefined signal compression functions,     prior, or after said signaling, receiving an indication from the receiver that a compatible compression function is supported, transmitting to the receiver a compressed signal where the compression function is applied to a signal before IFFT processing, according to the indicated capability. 2. + the signal is a single-layer signal. [If TX is UE:] 3. + the transmitting of the indication of support is comprised in a capability signaling or in UE assistance info / preference signaling to the gNB and receiving the indication of support is comprised in configuration from the gNB. 4. + receiving from the receiver a compression configuration, and the transmitted signal is compressed according to that configuration. a) + the compression configuration comprises one or more of on / off switch, a compression function, or a parameter (e.g., an index) indicative of a compression function, and parameters, etc. b) + the compression function (or indicator), and / or compression usage(on / off), and / or parameters are dynamically indicated to the UE by the gNB or another UE per UL allocation. c) + the compression function (or indicator), and / or compression usage(on / off), and / or parameters are semi-statically indicated to the UE by the gNB or another UE, e.g., using L1 / L2 signaling such as DCI or MAC- CE whereby the compression and its configuration remains valid until further configuration. d) the compression function (or indicator), and / or compression usage(on / off), and / or parameters are indicated to the UE using higher layer signaling, e.g., RRC signaling. In one example, one or more of this can be indicated to the UE, and then L1 / L2 signaling can be used in order to indicate which one is activated / deactivated. e) In one example, the UE as part of the scheduling request (SR) can indicate its capability or preference to apply compression, and then it may receive a grant e.g., from gNB for example within downlink control information     which indicates to the UE that it can / should use compression while transmitting the signal. f) In one example, the UE indicates in UL signal, e.g., using a bitfield in the payload that it has applied compression in the UL signal. The bitfield can be pre-configured, or that the UE receives a configuration through higher layer signaling of e.g., its presence, size, and starting point. It can also be different location or configuration in different UL signals, e.g., PUCCH / PUSCH. [If TX is gNB:] 5. + the transmitting the indication of support is comprised in a configuration carried in one or more of dedicated RRC signaling, MAC-CE, DL scheduling signaling , and the and receiving the indication of support is comprised in the capability signaling or in UE assistance info / preference signaling to the gNB. a) + the indication per DL assignment (e.g., DCI 1_1) of whether the DL scheduled data (PDSCH) is compressed b) + the indication per DL assignment of configuration parameters necessary for the receiver decompression of the scheduled data. [Internal processing:] 6. + generating the compressed signal in baseband by applying the compression function in time domain a) + generating compressed versions of zero- and one or more fractional- sample-shifted transformed signals 7. + embedding a RS for scaling reference [for applying the inverse function in the RX] [Multiple signal components] 8. + transmitted signal is sum of two or more signal components where each component is individually processed according to 4.       Similarly, the list below lists core aspects of some embodiments of the presently disclosed techniques, on the RX side. Subsets of the aspects listed below apply to UE-based and network node-based implementations, respectively. 9. A method in a wireless receiver for OFDM signal transmission with limited distortion, comprising: signaling to a transmitter an indication of supporting baseband PAPR compression using one or more predefined signal compression functions, prior, or after said signaling, receiving an indication from the transmitter that a compatible compression function is supported, receiving from the transmitter a compressed signal where the compression function has been applied to a signal before IFFT processing, according to the indicated capability. 10. + the signal is a single-layer signal. [If RX is UE:] 11. + the signaling of the indication of support is comprised in a capability signaling or in UE assistance info / preference signaling to the gNB and receiving the indication of support is comprised in configuration from the gNB. 12. + receiving from the transmitter a compression configuration, and the received signal is compressed according to that configuration. 13. + the compression configuration comprises one or more of on / off switch, a compression function, or a parameter (e.g., an index) indicative of a compression function and parameters, etc. [If RX is gNB:] 14. + the signaling the indication of support is comprised in a configuration carried in one or more of dedicated RRC signaling, MAC-CE, DL scheduling signaling, and DL control channel signaling, and the and receiving the indication of support is comprised in the capability signaling or in UE assistance info / preference signaling to the gNB.       [Internal processing:] 15. + extracting a desired signal from the compressed signal in baseband by applying an inverse of the compression function in time domain a) + summing decompressed versions of zero- and half-sample-shifted transformed signals 16. + using an embedded RS for scaling reference when applying the inverse function. Figures 8 and 9 are further process flow diagrams illustrating, respectively, methods performed in a transmitter and receiver according to some embodiments of the present invention. Figure 8 illustrates a method, in a transmitter, for transmitting a radio-frequency (RF) signal. The method comprises, at 800, sending, to a receiver of the RF signal, an indication of supporting use of an invertible compression function. The receiver of the RF signal may also be referred to as a target of the RF signal. The method further comprises, at 810, receiving, from the receiver of the RF signal, an indication that the receiver supports use of the invertible compression function. These steps may be performed simultaneously or in any order. The method further comprises, at 820, applying the invertible compression function to a first modulation signal, to produce a first compressed modulation signal. The method further comprises, at 830, generating a radio-frequency (RF) signal for transmission from the first compressed modulation signal, using Orthogonal Frequency Division Multiplexing (OFDM) modulation. In some embodiments, the transmitter may be a User Equipment, UE. In this case, the receiver, or target of the RF signal, may be a network node. Alternatively, for example in sidelink operation, the receiver may be a second UE. In step 800, the indication of supporting use of an invertible compression function may be sent to the receiver of the RF signal in UE capability signaling and / or UE assistance or preference information. In step 810, the indication that the receiver supports use of the invertible compression function may be received in configuration information. For example, the configuration information may       comprise one or more parameters of the invertible compression function and / or information indicating usage of the invertible compression function. The configuration information may be received in higher layer signaling, for example Radio Resource Control, RRC, signaling. In addition, or alternatively, the indication that the receiver supports use of the invertible compression function may comprise an activation order to apply the invertible compression function. The activation order may be received in Layer 1, L1, or Layer 2, L2 signaling, for example in a Medium Access Control Element, MAC CE, or in a Dynamic Control Information, DCI. In an embodiment, in step 800, the indication of supporting use of an invertible compression function is sent to the receiver as part of a Scheduling Request, SR. In this case, in step 810, the indication that the receiver supports use of the invertible compression function may be part of a corresponding scheduling grant from the receiver. In particular, the scheduling grant may indicate whether the UE may or should apply the invertible compression function in respect to an uplink, UL, signal scheduled by the scheduling grant. According to some embodiments, the method may further comprise indicating in the RF signal that the invertible compression function has been applied, for example in a bitfield of the payload of the RF signal. Further, in some embodiments, the transmitter may be a network node, and the receiver may be a UE. In this case, in step 800, the indication of supporting use of an invertible compression function may, for example, be sent in a configuration carried in one or more of RRC signaling, MAC- CE, or downlink, DL, scheduling signaling. Further, in step 810, the indication that the receiver supports use of the inconvertible compression function may be received in one or more of UE capability signaling, UE assistance information and UE preference signaling. In some embodiments, in step 800, the indication of supporting use of an invertible compression function may be in respect of respective DL scheduled data. For example, the indication of supporting use of an invertible compression function may be sent in a downlink,       DL, data assignment. The DL data assignment may comprise configuration parameters of the inconvertible compression function. More generally, in some embodiments, the method may further comprise selecting the invertible compression function from a plurality of invertible compression functions. In some embodiments, the indication of supporting use of an invertible compression function may comprise an indication that the invertible compression function is being or will be applied to the first modulation signal. According to some embodiments, the compression function may be applied to the first modulation signal prior to an inverse Fourier transform operation performed to generate an OFDM signal. The method may further comprise transmitting the RF signal. In some embodiments the method may further comprise applying an invertible compression function to a second modulation signal, to produce a second compressed modulation signal and combining the first compressed modulation signal and the second compressed modulation signal prior to the OFDM modulation. In some embodiments, generating the RF signal comprises including a scaling reference signal, the scaling reference signal being indicative of a pre-compression amplitude of the first modulation signal. Figure 9 illustrates a method, in a receiver, for receiving a Radio Frequency, RF, signal. The method comprises, at 900, receiving, from the transmitter of the RF signal, an indication that the transmitter supports use of an invertible compression function. The method further comprises, at 910, sending, to the transmitter of the RF signal, an indication of supporting use of the invertible compression function. The method further comprises, at 920, performing OFDM demodulation on a received signal, to obtain an OFDM-demodulated signal; and, at 930, applying an inverse-compression function to the OFDM-demodulated signal, to produce a first modulation signal. Again, at least steps 900 and 910 may be performed simultaneously or in any order.       In some embodiments, the receiver may be a network node, and the transmitter may be a UE. In step 900 the indication that the transmitter supports use of the invertible compression function may be received in UE capability signaling and / or UE assistance or preference information. In step 910 the indication of supporting use of the invertible compression function may be sent in configuration information. The configuration information may comprise one or more parameters of the invertible compression function and / or information indicating usage of the invertible compression function. The configuration information may be sent in Radio Resource Control, RRC, signaling. In some embodiments, step 910 may comprise sending an activation order to apply the invertible compression function, to the transmitter of the RF signal. The activation order may be sent in Layer 1, L1, or Layer 2, L2 signaling, for example in a Medium Access Control Element, MAC CE, or in a Dynamic Control Information, DCI. In some embodiments, in step 900, the indication that the transmitter supports use of an invertible compression function may be received in a Scheduling Request, SR from the transmitter; and, in step 910, the indication of supporting use of the invertible compression function may be sent, to the transmitter, in a corresponding scheduling grant. The scheduling grant may indicate whether the UE may or should apply the invertible compression function in respect to an uplink, UL, signal scheduled by the scheduling grant. The method may comprise receiving an indication in the RF signal that the transmitter has applied the invertible compression function, for example in a bitfield of the payload of the RF signal. In some embodiments, the receiver may be a UE, and the transmitter may be a network node or a second UE. In step 900, the indication that the transmitter supports use of an invertible compression function may be received in a configuration carried in one or more of RRC signaling, MAC- CE, or downlink, DL, scheduling signaling.       In step 910 the indication of supporting use of the inconvertible compression function may be sent in one or more of UE capability signaling, UE assistance information and UE preference signaling. The indication that the transmitter supports use of an invertible compression function may be in respect of respective DL scheduled data. For example, in step 900, the indication that the transmitter supports use of an invertible compression function may be received in a downlink, DL, data assignment. The DL data assignment may comprise configuration parameters of the inconvertible compression function. The method may comprise selecting the invertible compression function from a plurality of invertible compression functions. Figure 10 shows a transmitter 1000 according to some embodiments. The transmitter 1000 may comprise processing circuitry configured to carry out any of the methods described above as being performed in a transmitter. The transmitter may be a user equipment, UE, or a network node. Figure 11 shows a receiver 1100 according to some embodiments. The receiver 1100 may comprise processing circuitry configured to carry out any of the methods described above as being performed in a receiver. The receiver may be a user equipment, UE, or a network node. Using the techniques described herein, advantageously, spectral leakage in the PA and ACLR impact may be avoided or reduced. RX processing complexity may be moderate, and the processing may advantageously be limited to BaseBand BB only. The methods can be applied to individual single-layer signals, even if multiple such signals are transmitted simultaneously. The end-to-end signal properties may advantageously be relatively independent of actual PA / LNA properties. The lowering of the PAPR by the compander methods described herein may make DPD redundant, or make the DPD simpler since the dynamic range of the compressed signals can be smaller. Figure 11 shows an example of a communication system QQ100 in accordance with some embodiments. The techniques and apparatuses described above may be implemented in such a system, or variations thereof. In this example, the communication system QQ100 includes a       telecommunication network QQ102 that includes an access network QQ104, such as a radio access network (RAN), and a core network QQ106, which includes one or more core network nodes QQ108. The access network QQ104 includes one or more access network nodes, such as network nodes QQ110a and QQ110b (one or more of which may be generally referred to as network nodes QQ110), or any other similar 3rd Generation Partnership Project (3GPP) access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunication network QQ102 includes one or more Open- RAN (ORAN) network nodes. An ORAN network node is a node in the telecommunication network QQ102 that supports an ORAN specification (e.g., a specification published by the O- RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication network QQ102, including one or more network nodes QQ110 and / or core network nodes QQ108. Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU-CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an A1, F1, W1, E1, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. The network nodes QQ110 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs QQ112a, QQ112b, QQ112c, and QQ112d (one or more of which may be generally referred to as UEs QQ112) to the core network QQ106 over one or more wireless connections.       Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system QQ100 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. The communication system QQ100 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system. The UEs QQ112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with the network nodes QQ110 and other communication devices. Similarly, the network nodes QQ110 are arranged, capable, configured, and / or operable to communicate directly or indirectly with the UEs QQ112 and / or with other network nodes or equipment in the telecommunication network QQ102 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in the telecommunication network QQ102. In the depicted example, the core network QQ106 connects the network nodes QQ110 to one or more hosts, such as host QQ116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network QQ106 includes one more core network nodes (e.g., core network node QQ108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node QQ108. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF). The host QQ116 may be under the ownership or control of a service provider other than an operator or provider of the access network QQ104 and / or the telecommunication network       QQ102, and may be operated by the service provider or on behalf of the service provider. The host QQ116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server. As a whole, the communication system QQ100 of Figure QQ1 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox. In some examples, the telecommunication network QQ102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network QQ102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network QQ102. For example, the telecommunications network QQ102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive IoT services to yet further UEs. In some examples, the UEs QQ112 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network QQ104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network QQ104. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being       configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio – Dual Connectivity (EN-DC). In the example, the hub QQ114 communicates with the access network QQ104 to facilitate indirect communication between one or more UEs (e.g., UE QQ112c and / or QQ112d) and network nodes (e.g., network node QQ110b). In some examples, the hub QQ114 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub QQ114 may be a broadband router enabling access to the core network QQ106 for the UEs. As another example, the hub QQ114 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes QQ110, or by executable code, script, process, or other instructions in the hub QQ114. As another example, the hub QQ114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub QQ114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub QQ114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub QQ114 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub QQ114 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy IoT devices. The hub QQ114 may have a constant / persistent or intermittent connection to the network node QQ110b. The hub QQ114 may also allow for a different communication scheme and / or schedule between the hub QQ114 and UEs (e.g., UE QQ112c and / or QQ112d), and between the hub QQ114 and the core network QQ106. In other examples, the hub QQ114 is connected to the core network QQ106 and / or one or more UEs via a wired connection. Moreover, the hub QQ114 may be configured to connect to an M2M service provider over the access network QQ104 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes QQ110 while still connected via the hub QQ114 via a wired or wireless connection. In some embodiments, the hub QQ114 may be a dedicated hub – that is, a hub whose primary function is to route communications to / from the UEs from / to the network node QQ110b. In other embodiments, the hub QQ114 may be a non-dedicated hub – that is, a device which is capable of operating to route communications between the UEs and       network node QQ110b, but which is additionally capable of operating as a communication start and / or end point for certain data channels. Figure 12 shows a UE QQ200 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE. A UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter). The UE QQ200 includes processing circuitry QQ202 that is operatively coupled via a bus QQ204 to an input / output interface QQ206, a power source QQ208, a memory QQ210, a communication interface QQ212, and / or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in Figure QQ2. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.       The processing circuitry QQ202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory QQ210. The processing circuitry QQ202 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry QQ202 may include multiple central processing units (CPUs). In the example, the input / output interface QQ206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE QQ200. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device. In some embodiments, the power source QQ208 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source QQ208 may further include power circuitry for delivering power from the power source QQ208 itself, and / or an external power source, to the various parts of the UE QQ200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source QQ208. Power circuitry may perform any formatting, converting, or other modification       to the power from the power source QQ208 to make the power suitable for the respective components of the UE QQ200 to which power is supplied. The memory QQ210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory QQ210 includes one or more application programs QQ214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data QQ216. The memory QQ210 may store, for use by the UE QQ200, any of a variety of various operating systems or combinations of operating systems. The memory QQ210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM card.’ The memory QQ210 may allow the UE QQ200 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory QQ210, which may be or comprise a device- readable storage medium. The processing circuitry QQ202 may be configured to communicate with an access network or other network using the communication interface QQ212. The communication interface QQ212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna QQ222. The communication interface QQ212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another       UE or a network node in an access network). Each transceiver may include a transmitter QQ218 and / or a receiver QQ220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter QQ218 and receiver QQ220 may be coupled to one or more antennas (e.g., antenna QQ222) and may share circuit components, software or firmware, or alternatively be implemented separately. In the illustrated embodiment, communication functions of the communication interface QQ212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth. Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface QQ212, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient). As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.       A UE, when in the form of an Internet of Things (IoT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an IoT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an IoT device comprises circuitry and / or software in dependence of the intended application of the IoT device in addition to other components as described in relation to the UE QQ200 shown in Figure QQ2. As yet another specific example, in an IoT scenario, a UE may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another UE and / or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation. In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and / or the second UE can also include more than one of the       functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators. Figure 13 shows a network node QQ300 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with a UE and / or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)), O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU). Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS). Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs). The network node QQ300 includes a processing circuitry QQ302, a memory QQ304, a communication interface QQ306, and a power source QQ308. The network node QQ300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node QQ300 comprises       multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node QQ300 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory QQ304 for different RATs) and some components may be reused (e.g., a same antenna QQ310 may be shared by different RATs). The network node QQ300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node QQ300, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node QQ300. The processing circuitry QQ302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other network node QQ300 components, such as the memory QQ304, to provide network node QQ300 functionality. In some embodiments, the processing circuitry QQ302 includes a system on a chip (SOC). In some embodiments, the processing circuitry QQ302 includes one or more of radio frequency (RF) transceiver circuitry QQ312 and baseband processing circuitry QQ314. In some embodiments, the radio frequency (RF) transceiver circuitry QQ312 and the baseband processing circuitry QQ314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry QQ312 and baseband processing circuitry QQ314 may be on the same chip or set of chips, boards, or units. The memory QQ304 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other       volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processing circuitry QQ302. The memory QQ304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions capable of being executed by the processing circuitry QQ302 and utilized by the network node QQ300. The memory QQ304 may be used to store any calculations made by the processing circuitry QQ302 and / or any data received via the communication interface QQ306. In some embodiments, the processing circuitry QQ302 and memory QQ304 is integrated. The communication interface QQ306 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, the communication interface QQ306 comprises port(s) / terminal(s) QQ316 to send and receive data, for example to and from a network over a wired connection. The communication interface QQ306 also includes radio front-end circuitry QQ318 that may be coupled to, or in certain embodiments a part of, the antenna QQ310. Radio front-end circuitry QQ318 comprises filters QQ320 and amplifiers QQ322. The radio front-end circuitry QQ318 may be connected to an antenna QQ310 and processing circuitry QQ302. The radio front-end circuitry may be configured to condition signals communicated between antenna QQ310 and processing circuitry QQ302. The radio front-end circuitry QQ318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry QQ318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters QQ320 and / or amplifiers QQ322. The radio signal may then be transmitted via the antenna QQ310. Similarly, when receiving data, the antenna QQ310 may collect radio signals which are then converted into digital data by the radio front-end circuitry QQ318. The digital data may be passed to the processing circuitry QQ302. In other embodiments, the communication interface may comprise different components and / or different combinations of components. In certain alternative embodiments, the network node QQ300 does not include separate radio front-end circuitry QQ318, instead, the processing circuitry QQ302 includes radio front-end circuitry and is connected to the antenna QQ310. Similarly, in some embodiments, all or some of the RF transceiver circuitry QQ312 is part of the communication interface QQ306. In still other embodiments, the communication interface QQ306 includes one or more ports or       terminals QQ316, the radio front-end circuitry QQ318, and the RF transceiver circuitry QQ312, as part of a radio unit (not shown), and the communication interface QQ306 communicates with the baseband processing circuitry QQ314, which is part of a digital unit (not shown). The antenna QQ310 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna QQ310 may be coupled to the radio front-end circuitry QQ318 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna QQ310 is separate from the network node QQ300 and connectable to the network node QQ300 through an interface or port. The antenna QQ310, communication interface QQ306, and / or the processing circuitry QQ302 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, the antenna QQ310, the communication interface QQ306, and / or the processing circuitry QQ302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment. The power source QQ308 provides power to the various components of network node QQ300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source QQ308 may further comprise, or be coupled to, power management circuitry to supply the components of the network node QQ300 with power for performing the functionality described herein. For example, the network node QQ300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source QQ308. As a further example, the power source QQ308 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail. Embodiments of the network node QQ300 may include additional components beyond those shown in Figure 13 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, the network node QQ300 may include user       interface equipment to allow input of information into the network node QQ300 and to allow output of information from the network node QQ300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node QQ300. Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments may comprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software or firmware and computationally intensive functions may be implemented in hardware. In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device- readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing       circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.

Claims

CLAIMS 1. A method, in a transmitter, for transmitting a radio-frequency (RF) signal, the method comprising: sending (800), to a receiver of the RF signal, an indication of supporting use of an invertible compression function; receiving (810), from the receiver of the RF signal, an indication that the receiver supports use of the invertible compression function; applying (820) the invertible compression function to a first modulation signal, to produce a first compressed modulation signal; and generating (830) a radio-frequency (RF) signal for transmission from the first compressed modulation signal, using Orthogonal Frequency Division Multiplexing (OFDM) modulation.

2. The method of claim 1, wherein the transmitter is a User Equipment, UE.

3. The method of claim 2, wherein the receiver is a network node.

4. The method of claim 2, wherein the receiver is a second UE.

5. The method of any of claims 2 to 4, wherein the indication of supporting use of an invertible compression function is sent in UE capability signaling and / or UE assistance or preference information.

6. The method of claim 3 or 4, wherein the indication that the receiver supports use of the invertible compression function is received in configuration information.

7. The method of claim 6, wherein the configuration information comprises one or more parameters of the invertible compression function and / or information indicating usage of the invertible compression function.

8. The method of claim 6 or 7, wherein the configuration information is received in Radio Resource Control, RRC, signaling.

9. The method of claim 3 or 4, wherein the indication that the receiver supports use of the invertible compression function comprises an activation order to apply the invertible compression function received from the receiver.

10. The method of claim 9, wherein the activation order is received in Layer 1, L1, or Layer 2, L2 signaling, for example in a Medium Access Control Element, MAC CE, or in a Dynamic Control Information, DCI.

11. The method of claim 3, wherein the indication of supporting use of an invertible compression function is sent to the receiver as part of a Scheduling Request, SR; and wherein the indication that the receiver supports use of the invertible compression function is part of a corresponding scheduling grant received from the receiver.

12. The method of claim 11, wherein the scheduling grant indicates whether the UE may or should apply the invertible compression function in respect to an uplink, UL, signal scheduled by the scheduling grant.

13. The method of any of claims 2 to 12, further comprising indicating in the RF signal that the invertible compression function has been applied, for example in a bitfield of the payload of the RF signal.

14. The method of claim 1, wherein the transmitter is a network node.

15. The method of claim 14, wherein the receiver is a UE.

16. The method of claim 14, wherein the indication of supporting use of an invertible compression function is sent in a configuration carried in one or more of RRC signaling, MAC-CE, or downlink, DL, scheduling signaling.

17. The method of claim 15, wherein the indication that the receiver supports use of the inconvertible compression function is received in one or more of UE capability signaling, UE assistance information and UE preference signaling.

18. The method of any of claims 14 to 17, wherein the indication of supporting use of an invertible compression function is in respect of respective DL scheduled data.

19. The method of claim 18, wherein the indication of supporting use of an invertible compression function is sent in a downlink, DL, data assignment.

20. The method of claim 19, wherein the DL data assignment comprises configuration parameters of the inconvertible compression function.

21. The method of any preceding claim, wherein the method comprises sending (800) the indication of supporting use of an invertible compression function to the receiver before receiving (810) the indication that the receiver supports use of the inconvertible compression function.

22. The method of any of claims 1 to 20, wherein the method comprises sending (800) the indication of supporting use of an invertible compression function to the receiver after receiving (810) the indication that the receiver supports use of the inconvertible compression function.

23. The method of any preceding claim, wherein the method comprises selecting the invertible compression function from a plurality of invertible compression functions.

24. The method of any preceding claim, wherein the indication of supporting use of an invertible compression function comprises an indication that the invertible compression function is being or will be applied to the first modulation signal.

25. The method of any preceding claim, wherein the compression function is applied to the first modulation signal prior to an inverse Fourier transform operation performed to generate an OFDM signal.

26. The method of any preceding claim, further comprising transmitting the RF signal.

26. The method of any preceding claim, wherein the method further comprises applying an invertible compression function to a second modulation signal, to produce a second compressed modulation signal and combining the first compressed modulation signal and the second compressed modulation signal prior to the OFDM modulation.

27. The method of any preceding claim, wherein generating the RF signal comprises including a scaling reference signal, the scaling reference signal being indicative of a pre-compression amplitude of the first modulation signal.

28. A method, in a receiver, for receiving a Radio Frequency, RF, signal, the method comprising: receiving (900), from the transmitter of the RF signal, an indication that the transmitter supports use of an invertible compression function; sending (910), to the transmitter of the RF signal, an indication of supporting use of the invertible compression function; performing (920) OFDM demodulation on a received signal, to obtain an OFDM- demodulated signal; and applying (930) an inverse-compression function to the OFDM-demodulated signal, to produce a first modulation signal.

29. The method of claim 28, wherein the receiver is a network node.

30. The method of claim 29, wherein the transmitter is a UE.

31. The method of claim 30, wherein the indication that the transmitter supports use of the invertible compression function is received in UE capability signaling and / or UE assistance or preference information.

32. The method of claim 29, wherein the indication of supporting use of the invertible compression function is sent in configuration information.

33. The method of claim 32, wherein the configuration information comprises one or more parameters of the invertible compression function and / or information indicating usage of the invertible compression function.

34. The method of any of claims 29 to 31, wherein sending the indication of supporting use of the invertible compression function comprises sending an activation order to apply the invertible compression function, to the transmitter of the RF signal.

35. The method of claim 28, wherein the receiver is a UE.

36. The method of claim 35, wherein the transmitter is a network node.

37. The method of claim 36, wherein the indication that the transmitter supports use of an invertible compression function is received in a configuration carried in one or more of RRC signaling, MAC-CE, or downlink, DL, scheduling signaling.

38. The method of any of claims 35 to 37, wherein the indication of supporting use of the inconvertible compression function is sent in one or more of UE capability signaling, UE assistance information and UE preference signaling.

39. A transmitter comprising processing circuitry configured to carry out a method according to any of claims 1 to 27.

40. The transmitter of claim 39, wherein the transmitter is a user equipment, UE (QQ200).

41. The transmitter of claim 39, wherein the transmitter is a network node (QQ300).

42. A receiver comprising processing circuitry configured to carry out a method according to any of claims 28 to 38.

43. The receiver of claim 42, wherein the receiver is a user equipment, UE (QQ200).

44. The receiver of claim 42, wherein the receiver is a network node (QQ300).

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