WO2023117151A1

WO2023117151A1 - Interference Measurement Technique

Info

Publication number: WO2023117151A1
Application number: PCT/EP2022/056979
Authority: WO
Inventors: Karl Werner; David Astely; Rikke APELFRÖJD; Antonios PITAROKOILIS
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-12-22
Filing date: 2022-03-17
Publication date: 2023-06-29

Abstract

A technique for compensating a varying distortion level at a network node for an interference measurement, IM, at a radio device is described. A method aspect of the technique is performed by the network node serving the radio device using resource elements, REs (406), in orthogonal frequency-division multiplexing, OFDM, symbols (404). Power for the compensating of the varying distortion level is injected at the network node on IM REs (412) associated with the IM.

Description

Interference Measurement Technique

Technical Field

The present disclosure relates to an interference measurement technique. More specifically, and without limitation, methods and devices are provided for compensating a varying distortion level at a network node for an interference measurement at a radio device.

Background

The mobile connectivity of wireless communication systems is influenced by the position of a user equipment (UE) within a cell of a radio access network (RAN) relative to a network node serving the UE, the environment of the UE which may absorb or obstruct radio propagation, and an interference level at the UE which may be caused by neighboring network nodes of the RAN. Therefore, the performance of wireless communication systems dependents on the channel quality at the UE. Furthermore, wireless communication systems according to the Fourth Generation (4G) such as Long Term Evolution (LTE) or the Fifth Generation (5G) such as New Radio (5G NR) specified by the 3rd Generation Partnership Project (3GPP) use Orthogonal Frequency-Division Multiple Access (OFDMA) to share available radio resources in time and frequency among the UEs, wherein a scheduler of the serving network node allocates the radio resources to the UEs. Therefore, the performance of wireless communication systems also dependents on the network load.

For reporting the channel quality at the UE, 3GPP has defined several channel indicators such as a rank indicator (Rl), a precoding matrix indicator (PMI), and channel quality indicator (CQ.I ), which the network node uses for scheduling and link adaptation, e.g. in channel state information. Theses channel indicators are influenced by all three main factors for the mobile connectivity including the position of the UE within the cell, the interference level at the UE, and the data traffic of all UEs in the same cell. The network node receives channel state information (CSI) reports from the UEs and controls modulation, channel coding and scheduling of the data traffic based on the CSI reports to ensure the network performance. Therefore, the measurement of the interference level at the UE plays an important role in the CSI reports for improving reliability and data rate. Network nodes can cause a distortion level on radio resources used to perform an interference measurement (IM, e.g., a CSI-IM) which depends on signals and channels transmitted on the same orthogonal frequency-division multiplexing (OFDM) symbol that is configured for the IM, i.e., the OFDM symbol to which radio resources of the IM are mapped, or previous OFDM symbols. The distortion level caused by a crest factor reduction (CFR) such as clipping or by heating up of a transmit processing chain is typically greater if power transmitted in the respective or previous OFDM symbols is greater. However, if the distortion level on OFDM symbols for interference measurement is different from the distortion levels in OFDM symbols used for data transmission (e.g., later in time), the interference measurement is not representative of the channel state at the future data transmission.

Summary

Accordingly, there is a need for a more representative interference measurement technique. Alternatively or more specifically, there is a need for a technique that compensates a varying distortion level at a network node for a representative interference measurement at a radio device, which is relevant for a data transmission in a future OFDM symbol.

At least some embodiments can be based on the insight that OFDM symbols associated with an IM, i.e., OFDM symbols comprising resource elements (REs) for the IM) may be protected from a too high distortion level caused (e.g., by clipping) at the network node due to the blanked resources associated with the IM (i.e., the IM REs) and the correspondingly lower transmit power of the respective OFDM symbol. That is, those resource elements (REs) used for the IM conventionally experience significantly less interference (e.g., intra-carrier or inter-carrier interference) than typical REs in other OFDM symbols not associated with the IM, e.g., REs of a physical downlink shared channel (PDSCH). Further concrete examples for the varying distortion level are mentioned in the detailed description.

Same or further embodiments can prevent a biased IM, if the distortion level on the resources associated with the IM, i.e., the IM REs (e.g., REs associated with a CSI-IM) is lower than the distortion which is targeted by the network node (e.g., a gNB) given a scheduling hypothesis to which the IM (e.g., a CSI-IM) and/or the corresponding CSI report is associated. The injected power of the embodiments can compensate for a too low distortion level in the IM REs (that would conventionally bias the IM) so that the radio device does not underestimate the combined effect of the distortion level caused by the serving network node and by other sources of noise and interference at the radio device. Hence, the embodiments can prevent that the radio device potentially reports a too optimistic CSI, e.g. in terms of a channel quality indicator (CQI) and/or rank indicator (Rl).

Same or further embodiments of the technique can be beneficially applied in any scenario when a too low distortion level may appear at the IM, because the distortion level on the IM REs (e.g., REs associated with the CSI-IM) is less than the distortion level expected or measured on REs hypothetically scheduled according to a CSI report derived using the IM on the IM REs.

In a first exemplary scenario, at least one subcarrier in the at least one OFDM symbol associated with the IM (e.g., CSI-IM) may be blanked, e.g., because the IM REs (e.g., CSI-IM resource elements) itself are usually void of a PDSCH, so that the (e.g., output) power in those OFDM symbols is lower (e.g., systematically less than an average power of the OFDM symbols), which leads to less distortion in the IM.

In a second exemplary scenario, the distortion level of the network node (e.g., a gNB) varies for other reasons, e.g., because a state of the network node changes such as at least one of (e.g., transmit) power, operating temperature, modulation order, and number of multiple-input multiple-output (MIMO) layers (i.e., spatial streams).

In a third exemplary scenario, a bandwidth in term of number of resource blocks scheduled for the PDSCH is less in a slot including the IM (e.g., the CSI-IM), e.g., due to a varying network load at the network node or in the wireless communication system (optionally maintaining a constant transmit power per physical resource block, PRB, at the network node). In such a third exemplary scenario, a conventional network node could cause a performance loss of the wireless communication system due to a biased (e.g., too positive) CSI report, whereas an embodiment can achieve a network performance that is only limited by the shared radio resources. As to a method aspect, a method of compensating a varying distortion level at a network node for an interference measurement (IM) at a radio device is provided. The method is performed by the network node serving the radio device using resource elements (REs) in orthogonal frequency-division multiplexing (OFDM) symbols. The method comprises or initiates the step of injecting power for the compensating of the varying distortion level at the network node on IM REs associated with the IM.

The varying distortion level may be due to a distortion of the OFDM symbols at the network node. More specifically, the distortion may be varying since the symbol power in the OFDM symbol with the IM can be different from the symbol power in a later OFDM symbol where data is transmitted.

Each of the REs may correspond to a single subcarrier in a single OFDM symbol.

The network node may be an access node of a radio access network (RAN), e.g. a cellular RAN. The network node may provide radio access (e.g., to the radio device or a plurality of radio devices including the radio device) in one or more cells of the RAN. Alternatively or in addition, the network node may be or comprise at least one of a base station, radio unit, and radio node.

The power of any one of the OFDM symbols may be referred to as a symbol power (e.g., a total power) of the respective one of the OFDM symbols, e.g., the sum of the power of the REs in the respective one of the OFDM symbols or based on an integral of energy over a symbol length of the respective one of the OFDM symbols divided by the symbol length.

The distortion level may be varying because the distortion level depends on at least one of a symbol power (e.g., an instant symbol power) of the respective one of the OFDM symbols and a state of the network node, e.g., at least one of a temperature, a bandwidth of the OFDM symbols, a number of subcarriers used by the OFDM symbols, a number of spatial layers for transmitting the OFDM symbols, and a number of active antenna elements. Alternatively or in addition, the distortion level (e.g., the distortion level that depends on the symbol power of the respective one of the OFDM symbols) may be due to at least one of a non-linearity of a power amplifier (PA) at the network node and a reduction of a peak-to- average-power-ratio (PAPR) performed at the network node and/or a digital pre- distortion performed at the network node before the PA to linearize the PA (i.e., to reduce the distortion caused by the PA). Alternatively or in addition, the distortion level may vary solely because the distortion level depends on an (e.g., instant) power of the OFDM symbols.

The distortion level may be a relative measure of a distortion of the respective one of the OFDM symbols, e.g. a distortion power of the distortion of the respective one of the OFDM symbols divided by (or in units of) a symbol power of the respective one of the OFDM symbols. The distortion level may be a measure of the distortion relative to the symbol power of the respective OFDM symbol or relative to a transmit power of a transmitted signal of the OFDM symbol. For example, the distortion level may be an error vector magnitude (EVM), optionally averaged over all REs (or all subcarriers of a physical resource block) in the respective OFDM symbol.

Alternatively or in addition, the distortion level may be an absolute measure of a distortion of the respective one of the OFDM symbols, e.g. a distortion power of the distortion or EVM x symbol power (i.e., the EVM multiplied by the symbol power) of the respective one of the OFDM symbols.

The IM may be a channel state information (CSI) IM, or CSI-IM. The network node may receive a report (e.g., a CSI report) indicative of a result of the IM from the radio device.

The injected power may also be referred to as a compensating power. The injected power may be injected in a frequency domain and/or a digital domain of a first OFDM symbol comprising the IM REs.

The first OFDM symbol (e.g., according to the method or a device aspect) may comprise the IM REs. The injected power may depend on a second distortion level at the network node for a second OFDM symbol other than the first OFDM symbol. Alternatively or in addition, a first distortion level at the network node for the first OFDM symbol may be neglected for determining the injected power.

Optionally, the distortion level in the first OFDM symbol may be neglected, e.g., assumed to be zero, for determining the injected power. The second distortion level may be an example of the varying distortion level at the network node, e.g., due to a varying symbol power. Referring to the second distortion level may or may not imply the usage of a first distortion level at the network node for the first OFDM symbol.

The PA may be a power amplifier of the network node for transmitting the OFDM symbols to the radio device, e.g., in the second OFDM symbol. The network node may have multiple power amplifiers (e.g., when the network node has multiple antennas).

The injected power on the IM REs (e.g., according to the method or device aspect) may be or may be determined from, the difference between a first distortion level at the network node for a first OFDM symbol comprising the IM REs and a second distortion level at the network node for a second OFDM symbol other than the first OFDM symbol.

In any embodiment, the symbol power of the first OFDM symbol may be referred to as a first symbol power. The symbol power of the second OFDM symbol may be referred to as a second symbol power. Herein, the first distortion level and second distortion level may be examples of the varying distortion levels, i.e., the first and second distortion levels may be different, because the distortion level is varying.

The first distortion level may be a first value of the varying distortion level in the first OFDM symbol. The second distortion level may be a second value of the varying distortion level in the second OFDM symbol. The first distortion level and/or the second distortion level may be a measure for the varying distortion level of the respective OFDM symbol. Alternatively or in addition, the first distortion level and/or the second distortion level may be a measure for the varying distortion level as a power of the distortion per RE in the respective OFDM symbol, e.g., an average for the respective OFDM symbol. For example, the average of the power of the distortion per RE may be the power of the distortion in the OFDM symbol divided by the number of REs in the respective OFDM symbol.

Herein, a quantity comprising the expression "level" (e.g., in power level, varying distortion level, first or second distortion level, or interference level) may or may not be represented on a logarithmic scale. A difference between such quantities, e.g., a difference between the first distortion level and the second distortion level, may refer to the difference between the respective quantities, e.g. instead of a difference between logarithms of the respective quantities.

In any example or embodiment, the first and/or second distortion level may be an example (e.g., an instantaneous value) of the varying distortion level at the network node.

In one example, the first distortion level may be a power of the varying distortion level per RE in the first OFDM symbol averaged over the first OFDM symbol. The second distortion level may be a power of the varying distortion level per RE in the second OFDM symbol averaged over the second OFDM symbol. The injected power that is injected on the IM REs may be the difference (i.e., the second distortion level minus the first distortion level) multiplied by the number of IM REs Alternatively or in addition, the injected power that is injected on the IM REs may be the difference (i.e., the second distortion level minus the first distortion level), wherein the step of injecting the injected power is performed for each of the IM REs.

In another example, the first distortion level may be a power of the varying distortion level in the first OFDM symbol. The second distortion level may be a power of the varying distortion level in the second OFDM symbol. The injected power that is injected on the IM REs may be the difference (i.e., the second distortion level minus the first distortion level) multiplied by the fraction of the number of IM REs over the number of REs in the first OFDM symbol. Alternatively or in addition, the injected power that is injected on the IM REs may be the difference (i.e., the second distortion level minus the first distortion level) divided by the number of REs in the first OFDM symbol, wherein the step of injecting the injected power is performed for each of the IM REs.

The first and/or second distortion level may be caused (e.g., exclusively) at (or by) the network node, e.g. by a radio unit of the network node. For example, the first and/or second distortion level or the difference may be caused by a transmit processing chain of the network node, e.g., by a non-linearity of the PA of the network node and/or the reduction of the PAPR and/or a change in the state (e.g., temperature) of the PA between the first OFDM symbol and the second OFDM symbol. The second distortion level may be greater than the first distortion level. The difference between the first distortion level and the second distortion level may be the power of the second distortion level minus the power of the first distortion level.

The first distortion level may be estimated for the IM REs in the first OFDM symbol, i.e., for the subcarriers of the IM REs in the first OFDM symbol. The second distortion level may be determined for the same subcarriers (i.e., the subcarriers corresponding to the IM REs in the first OFDM symbol) in the second OFDM symbol or for all subcarriers in the second OFDM symbol. The REs in the second OFDM symbol may comprise (e.g., exclusively) REs of a data channel, e.g., a physical downlink shared channel (PDSCH). Alternatively or in addition, the first distortion level may be estimated as a power density of the varying distortion level in the first OFDM symbol. The second distortion level may be determined as a power density of the varying distortion level in the second OFDM symbol.

Herein, referring to the first OFDM symbol may comprise referring to each of at least one first OFDM symbol. Each of the at least one first OFDM symbol may be associated with the IM (e.g., the CSI-IM) and/or may comprise at least one of the IM REs.

The first OFDM symbol and the second OFDM symbol may be in the same subframe or the same slot or in different subframes or different slots. Each subframe may correspond to 1 millisecond (1 ms). There may be one or more slots in each subframe.

The IM REs (e.g., according to the method or device aspect) may be allocated to a zero-power reference signal for the IM. Alternatively or in addition, the first OFDM symbol further comprises a non-zero-power reference signal for a channel estimation at the radio device. Alternatively or in addition, the second OFDM symbol comprises no IM REs or is not used for the IM.

The zero-power reference signal (ZP RS) and/or the non-zero-power reference signal (NZP RS) may be examples of CSI reference signals (CSI-RS) and/or may be defined according to the 3GPP document TS 38.211, version 16.7.0, clause 7.4.1.5 or 7.4.1.5.1. For example, the ZP RS may be a zero-power (ZP) CSI-RS. Alternatively or in addition, the NZP RS may be a non-zero-power (NZP) CSI-RS. For a NZP CSI-RS configured by a NZP-CSI-RS-Resource Information Element (IE) or by a CSI-RS- Resource-Mobility field in a CSI-RS-ResourceConfigMobility IE, a sequence may be generated according to clause 7.4.1.5.2 of the 3GPP document TS 38.211, version 16.7.0 and mapped to REs according to clause 7.4.1.5.3 of the 3GPP document TS 38.211, version 16.7.0. For a ZP CSI-RS configured by a ZP-CSI-RS-Resource IE, the radio device may assume that the REs defined in clause 7.4.1.5.3 of the 3GPP document TS 38.211, version 16.7.0 are not used for PDSCH transmission subject to clause 5.1.4.2 of the 3GPP document TS 38.214, version 16.7.0. The radio device may perform the same measurement or reception on channels or signals except PDSCH regardless of whether they collide with the ZP CSI-RS or not.

The NZP RS may or may not be in the IM symbol (i.e., the same OFDM symbol as the ZP REs, i.e., the resource for the IM). For example, ZP REs for the IM may be in one or more first OFDM symbols other than (i.e., that are different from) OFDM symbols comprising the NZP RS for channel estimation.

The IM REs may be muted (i.e., silent or blanked), e.g., a ZP CSI-RS, at the network node, e.g., except for the injecting of the injected power. The IM REs may be allocated to the radio device for the IM at the radio device. The radio device may be unaware of the injected power in the IM REs. The injected power in the IM REs may be received at the radio device indistinguishably from noise and/or interference at the radio device.

Herein, the NZP RS (e.g., the NZP CSI-RS) may be briefly referred to as RS (e.g., CSI- RS). That is, when referring to a RS (e.g., a CSI-RS), without indicating ZP, may refer to the NZP RS (e.g., the NZP CSI-RS).

The first OFDM symbol may be associated with a CSI measurement. The first OFDM symbol may further comprise a CSI reference signal (CSI-RS), e.g., for each of a plurality of antenna ports. The CSI-RS may be defined for a certain number of antenna ports.

Alternatively or in addition, the CSI-RS (e.g., the ZP CSI-RS used for the IM and/or the NZP CSI-RS) may comprise REs from one or several (e.g., consecutive) OFDM symbols. The ZP CSI-RS and the NZP CSI-RS may or may not be in the at least one first OFDM symbol (i.e., in the same set of OFDM symbols). For example, the ZP CSI-RS and the NZP CSI-RS may comprise different numbers of OFDM symbols). For example, the ZP CSI-RS and the NZP CSI-RS may be in the different slots.

Alternatively or in addition, the network node may receive a report (e.g., a CSI report) from the radio device. The report may be indicative of a result of both a channel estimation based on the (e.g., CSI) reference signal and the IM.

Optionally, the second OFDM symbol does not comprise IM REs or REs associated with the IM or the CSI or the CSI-IM. Alternatively or in addition, the second OFDM symbol may relate to a future transmission from the network node to the radio device, e.g., a transmission of data or control signaling.

The first distortion level (e.g., according to the method or device aspect) may comprise power spread into the IM REs of the first OFDM symbol.

The power that is spread into the IM REs may be power that is leaking within the first OFDM symbol from REs other than the IM REs to the IM REs. In other words, the power may spread from REs other than the IM REs in the first OFDM symbol. The other REs may comprise CSI reference signals (RS), e.g., non-zero power (NZP) CSI RS, and/or REs carrying at least one of physical downlink control channel (PDCCH) and physical downlink shared channel (PDSCH).

Herein, power may refer to input power or output power at any component of the transmit processing chain at the network node or a transmit power of the network node transmitting the respective OFDM symbol.

The varying distortion level may be the power that spreads into (i.e., that is leaking into) one RE in the respective OFDM symbol, optionally averaged over all REs of the respective OFDM symbol. The first distortion level may be the power that spreads into (i.e., that is leaking into) one RE in the first OFDM symbol, optionally averaged over all REs of the first OFDM symbol. The second distortion level may be the power that spreads into (i.e., that is leaking into) one RE in the second OFDM symbol, optionally averaged over all REs of the second OFDM symbol.

The first distortion level (e.g., according to the method or device aspect) may be assumed to be constant for a plurality of first OFDM symbols each comprising IM REs and/or is averaged over a plurality of first OFDM symbols each comprising IM REs.

Alternatively or in addition, the (e.g., estimated) first distortion level may be constant over one or more slots of the OFDM symbols. For example, each of the slots may comprise one or two first OFDM symbols each comprising IM REs. This can enable consistent distortion levels for multiple CSI reports.

A CSI-IM may use REs (e.g., ZP REs and/or NZP REs) in one, two or more first OFDM symbols. The radio device may average over the REs used in the CSI-IM to obtain a result of the IM. For example, the radio device may use a CSI-IM which uses two subcarriers per physical resource block (PRB) in two consecutive OFDM symbols, wherein a result of the CSI-IM comprises one IM per PRB and/or per slot. The radio device may use the result for a single CSI report.

The second distortion level (e.g., according to the method or device aspect) may be assumed to be constant for a plurality of second OFDM symbols other than the first OFDM symbol and/or is averaged over a plurality of second OFDM symbols other than the first OFDM symbol.

Alternatively or in addition, the (e.g., determined) second distortion level may be constant over one or more slots of the OFDM symbols. For example, each of the slots may comprise multiple second OFDM symbols other than the first OFDM symbol. For example, the second OFDM symbols may comprise all OFDM symbols available in a slot and/or all OFDM symbols other than the at least one IM symbol and/or all OFDM symbols scheduled for a PDSCH transmission and/or REs.

For example, the second symbol power may correspond to an averaged or typical load level (e.g., a typical transmission load level) in the second OFDM symbol.

Alternatively or in addition, the second distortion level may depend on a (e.g., transmission load level of the) network node, optionally wherein the transmission load level is determined from historical data or statistics of transmissions from the network node.

For example, both the first distortion and the second (i.e., target) distortion may be independent of an (e.g., estimated) channel state of a channel for the OFDM symbols. I.e., both the first distortion and the second (i.e., target) distortion may be sole properties of the network node (e.g., the non-linearity in the transmit processing chain).

In any embodiment, the symbol power of the respective one of the first OFDM symbol and the second OFDM symbol may vary (i.e., the first symbol power may be different from the second symbol power) due to different numbers of muted REs in different OFDM symbols. Alternatively or in addition, the symbol power of the respective one of the first OFDM symbol and the second OFDM symbol may vary due to different loads (e.g., in a physical downlink shared channel, PDSCH) in different OFDM symbols. Alternatively or in addition, the symbol power of the respective one of the first OFDM symbol and the second OFDM symbol may vary due to different scaling of the power or different states of the PA in different OFDM symbols. Alternatively or in addition, the symbol power of the respective one of the first OFDM symbol and the second OFDM symbol may vary due to different operating temperatures of the PA in different OFDM symbols. Alternatively or in addition, the symbol power of the respective one of the first OFDM symbol and the second OFDM symbol may vary due to different bandwidths used in transmitting in different OFDM symbols. For example, different bandwidths and/or different number of REs may be allocated or used for the radio device in the first OFDM symbol and in the second OFDM symbols, optionally if there is not enough data to fill the entire bandwidth.

The method may further comprise or initiate a step of estimating the first distortion level for the first OFDM symbol. Alternatively or in addition, the first distortion level may be estimated based on a first symbol power of the first OFDM symbol.

The method may further comprise or initiate a step of determining the second distortion level for the second OFDM symbol other than the first OFDM symbol, alternatively or in addition, the second distortion level may be determined based on a second symbol power of the second OFDM symbol.

Referring to the first symbol power may or may not imply the existence or need for the second symbol power. Alternatively or in addition, referring to the second symbol power may or may not imply the existence or need for the first symbol power. The first symbol power (e.g., according to the method or device aspect) may be or may comprise a sum of the power of REs in the first OFDM symbol. Alternatively or in addition, the first symbol power (e.g., according to the method or device aspect) may be or may comprise an average of the power of a plurality of first OFDM symbols each comprising IM REs.

The second symbol power (e.g., according to the method or device aspect) may be or may comprise a hypothesis of the power of the second OFDM symbol. Alternatively or in addition, the second symbol power (e.g., according to the method or device aspect) may be or may comprise an average of the power of a plurality of second OFDM symbols other than the first OFDM symbol.

Since a transmission of the second OFDM symbol may be after the determining of the second distortion level, the power of the second OFDM symbol may be a hypothesis of the power (i.e., a hypothesized power) of the second OFDM symbol.

Alternatively or in addition, the hypothesis of the power of the second OFDM symbol may correspond to one of at least two hypotheses of the power. The network node may transmit a CSI reference signal (CSI-RS) using a first hypothesis of the power (e.g., in the first OFDM symbol or one of the first OFDM symbols) resulting in a first CSI report from the radio device, and may transmit a CSI-RS using a second hypothesis of the power (e.g., in another one of the first OFDM symbols) resulting in a second CSI report from the radio device. The first hypothesis of the power and the second hypothesis of the power may use different power (e.g., different output power or different transmit power or different symbol power) and, hence, may experience different (e.g., first) distortion levels (e.g., in the respective first OFDM symbol) at the network node.

The hypothesis of the power of the second OFDM symbol may be selected out of the first hypothesis and second hypothesis based on the first CSI report and the second CSI report. For example, the network node may compare the CSI reports for all hypotheses in order to select the best way (e.g., in terms of maximum bit rate or highest reliability) to transmit in the second OFDM symbol.

The first distortion level (e.g., according to the method or device aspect) may be a function of the first symbol power of the first OFDM symbol. Alternatively or in addition, the second distortion level (e.g., according to the method or device aspect) may be a function of the second symbol power of the second OFDM symbol. Optionally, the same function may be used for the estimating of the first distortion level and the determining of the second distortion level.

Herein, the first OFDM symbol may be at least one first OFDM symbol. The first distortion level may be a function of the (e.g. constant, i.e., equal) first symbol power of each of the at least one first OFDM symbol.

Furthermore, herein, the second OFDM symbol may be at least one second OFDM symbol. The second distortion level may be a (or the) function of the (e.g. constant, i.e., equal) second symbol power of each of the at least one second OFDM symbol.

The function may indicate the respective distortion level (e.g., power spread across REs) in the respective OFDM symbol at an output of a component of the transmit processing chain of the network node as a function of the symbol power of the respective OFDM symbol at an input of the component.

The function (e.g., according to the method or device aspect) may be monotonically increasing. The function (i.e., the varying distortion level) may be a (e.g., strictly) monotonically increasing function of the respective symbol power (i.e., the power of a respective one of the OFDM symbols).

Since the first OFDM symbol comprises the IM REs, which may be absent (i.e., used for transmission of data or control signaling) in the second OFDM symbol, the first symbol power may be less than the second symbol power. As a result, the second distortion level may be greater than first distortion level. Therefore, without the injected power, a conventional network node could cause a systematic underestimation of the interference level in the IM at the radio device. The injected power can compensate for the varying distortion level at the network node so that the IM at the radio device is accurately indicative of the interference level (e.g., including a contribution from the second distortion level) for the second OFDM symbol.

The function (e.g., according to the method or device aspect) may comprise a characteristic of one or more components of a transmit processing chain of the network node. Alternatively or in addition, the function may comprise a characteristic of a PA of the network node or a characteristic of a PAPR reduction unit for reducing a peak to average power ratio (PAPR) of the OFDM symbols. The function may be stored at the network node based on at least one of measuring the varying distortion level of one or more components of a transmit processing chain of the network node; and receiving a configuration message that is indicative of the function.

The characteristic may comprise a non-linear characteristic (briefly: a non-linearity, e.g., a non-linear relation between input power and output power) of the one or more components of the transmit processing chain and/or a dependency on a state of the one or more components of the transmit processing chain (e.g., an operating temperature).

Alternatively or in addition, the function may be determined (e.g., measured) by generating an OFDM symbol (e.g., up until the point in the transmit processing chain to which the respective (e.g., first or second) symbol power pertains) for a plurality of different values of the respective (e.g., first or second) symbol power, and measuring the respective (e.g., first or second) distortion level in the generated OFDM symbol. The function may be stored by storing the value of the symbol power and the value of the distortion level may be stored in pairs.

The function (e.g., according to the method or device aspect) may be stored at the network node using at least one of a look-up table, a fitted piecewise linear function, and a polynomial function.

The at least one of the first symbol power of the first OFDM symbol, the second symbol power of the second OFDM symbol, the first distortion level, and the second distortion level (e.g., according to the method or device aspect) may be pertaining to one of a baseband signal of the network node; a signal output of a baseband processor of the network node; a digital domain of the network node; a signal input of a PAPR reduction unit for reducing a PAPR at the network node; and a signal input of a PA of the network node.

Herein, the power of the respective one of the first OFDM symbol and the second OFDM symbol (i.e., the first symbol power and/or the second signal power) and/or the distortion level of the respective one of the first OFDM symbol and the second OFDM symbol (i.e., the first distortion level and/or the second distortion level) may be an instantaneous power, e.g., sampled or averaged over one symbol duration of the respective OFDM symbol. The symbol duration may be a length of the respective OFDM symbol or the inverse of a subcarrier spacing.

Herein, any power (e.g., the injected power, the first or second symbol power, or the first or second distortion level) may also be referred to as an energy. For example, the energy may correspond to the power multiplied by the symbol duration.

Alternatively or in addition, the power of the respective one of the first OFDM symbol and the second OFDM symbol (i.e., the first symbol power and/or the second signal power) may be the sum of the power of all REs in the respective one of the first OFDM symbol and the second OFDM symbol. Alternatively or in addition, the power of the respective one of the first OFDM symbol and the second OFDM symbol (i.e., the first symbol power and/or the second signal power) may be the sum of the power in subcarriers other than the subcarriers of the IM REs in the respective one of the first OFDM symbol and the second OFDM symbol.

In any example or embodiment, the respective symbol power (e.g., the first symbol power of the first OFDM symbol and/or the second symbol power of the second OFDM symbol) may be substituted by a respective power back-off (e.g., a first power back-off of the first OFDM symbol and/or a second power back-off of the second OFDM symbol). The respective power back-off may be defined as the ratio between a nominal power (e.g., a full power level) of an OFDM symbol and the respective symbol power. For example, the function may be a function of the power back-off (e.g., instead of the symbol power), wherein an infinite power back-off may correspond to zero symbol power and/or wherein a maximum power back-off may correspond to minimum symbol power.

The first symbol power and/or the second symbol power (e.g., according to the method or device aspect) may be determined based on counting a number of scheduled non-zero power REs (NZP REs) in the first OFDM symbol and/or the second OFDM symbol, respectively. Alternatively or in addition, the first symbol power and/or the second symbol power (e.g., according to the method or device aspect) may be determined based on summing up the power on scheduled NZP REs in the first OFDM symbol and/or the second OFDM symbol, respectively. At least one or each of the first distortion level, the second distortion level, the injected power, and the output power of the PA may be determined for each antenna branch (e.g., associated with a single PA and/or with a single antenna) at the network node. Alternatively or in addition, at least one or each of the first distortion level, the second distortion level, the injected power, and the output power of the PA may be determined as a sum or an average over multiple antenna branches.

The power in NZP REs may be assumed constant power. Therefore, the power on the scheduled REs may be determined by counting the NZP REs.

The first and/or second distortion level may be represented by an error vector magnitude (EVM).

The first distortion level (e.g., according to the method or device aspect) may further depend on at least one of an operating temperature of one or more components of the network node when processing the first OFDM symbol; a PAPR of a signal transmitted from the network node in the first OFDM symbol; and a spatial precoding or a number of spatial layers of a signal transmitted from the network node in the first OFDM symbol.

The second distortion level (e.g., according to the method or device aspect) may further depend on at least one of characteristics of a signal transmitted from the network node in the second OFDM symbol; an operating temperature of one or more components of the network node when processing the second OFDM symbol; a PAPR of a signal transmitted from the network node in the second OFDM symbol; and a spatial precoding or a number of spatial layers of a signal transmitted from the network node in the second OFDM symbol.

The second distortion level (e.g., according to the method or device aspect) may depend on a scheduling hypothesis in which a result of the IM, optionally a channel state information (CSI) report derived from the IM, is applied.

The injecting of the injected power (e.g., according to the method or device aspect) may comprise injecting a compensation signal, optionally a pseudo random signal, on the IM REs. A power level (or energy level) of the compensation signal may correspond to injected power.

The compensation signal (e.g., according to the method or device aspect) may be a function of at least one of a time index, a subcarrier index, and a spatial precoding index or an antenna index.

The subcarrier index may be a RE index of the respective RE. Alternatively or in addition, the time index may be a symbol index of the respective OFDM symbol. For example, two or multiple consecutive first OFDM symbols may comprise the IM RE. Alternatively or in addition, the spatial precoding index may correspond to a direction of a beamformed transmission from the network node. For example, the spatial precoding index may be indicative of a spatial layer or a beam or a spatial precoder for a transmission from the network node to the radio device.

Alternatively or in addition, the compensation signal may be a white noise (e.g., a noise signal without correlation w.r.t at least one of the time index, the subcarrier index, and the spatial precoding index) or a compensation signal with color (e.g., a noise signal with correlation w.r.t at least one of the time index, the subcarrier index, and the spatial precoding index or the antenna index).

The injecting may comprise controlling a spatial color (i.e., a spatial correlation) of the compensation signal. The spatial color may be the correlation between the compensation signals for different antenna indices (e.g., different antenna ports) in the same OFDM subcarrier 402 (e.g., the same subcarrier index) and the same OFDM symbol 404 (e.g., the same symbol index).

As an example, second order statistics of the injected compensation signal may be matched to a function of second order statistics of a signal transmitted in the one or more first OFDM symbols comprising the IM REs. This is to reflect the correlation (e.g., the spatial color) of the distortions (e.g. the correlation between distortions of different antennas for the same RE).

The compensation signal (e.g., according to the method or device aspect) may be configured to cancel amplitude peaks in a time domain of a signal transmitted on the first OFDM symbol. The compensation signal may be configured to cancel (i.e., may cancel by design) amplitude peaks in an overall waveform (e.g., the signal in the time domain) of the first OFDM symbol.

The injected power may be the power of the compensation signal transmitted on the IM REs in the first OFDM symbol. Alternatively or in addition, the injected power may be a function of the signal transmitted on all REs in the one or more first OFDM symbols, i.e., the OFDM symbols associated with the IM (e.g., on which the CSI-IM is mapped).

The network node (e.g., according to the method or device aspect) may comprise a plurality of antennas or antenna ports for transmitting at least one of the first OFDM symbol and the second OFDM symbol. Alternatively or in addition, the injected power may be injected for each antenna or each antenna port of the network node.

Each antenna port may correspond to a (e.g., disjoint) subset of the plurality antennas.

As to a further aspect, a computer program product comprising program code portions for performing any one of the steps of the method or device aspect when the computer program product is executed on one or more computing devices is provided. Optionally, the computer program product may be stored on a computer-readable recording medium.

As to a device aspect, a network node for compensating a varying distortion level at the network node for an IM at a radio device is provided. The network node is configured to serve the radio device using REs in OFDM symbols and to inject power for the compensating of the varying distortion level at the network node on IM REs associated with the IM.

The network node (e.g., according to the device aspect) may further be configured to perform any of the steps of the method aspect.

As to a further device aspect, a network node for compensating a varying distortion level at the network node for an IM at a radio device is provided. The network node comprising memory operable to store instructions and processing circuitry operable to execute the instructions, such that the network node is operable to serve the radio device using REs in OFDM symbols and to inject power for the compensating of the varying distortion level at the network node on IM REs associated with the IM.

The network node (e.g., according to the further device aspect) may further be configured to perform any of the steps of the method aspect.

As to a still further device aspect, a communication system including a host computer provided. The communication system comprises processing circuitry configured to provide user data (e.g., transmitted in the second OFDM symbol). The communication system further comprises processing circuitry configured to forward user data to a cellular radio network or an ad hoc radio network for transmission from a network node to a radio device. The network node comprises a radio interface and processing circuitry, the processing circuitry of the network node being configured to execute any of the steps of the method aspect.

The communication system (e.g., according to the still further device aspect) may further include the UE. Alternatively or in addition, the radio network (e.g., according to the further device aspect) may further comprise a base station, or a radio device functioning as a gateway, which is configured to communicate with the UE and/or embodies the network node. The base station, or the radio device functioning as a gateway, may comprise processing circuitry, which is configured to execute any one of the steps of the method aspect.

The processing circuitry of the host computer (e.g., according to the further device aspect) may be configured to execute a host application, thereby providing the user data. The processing circuitry of the network node (e.g., according to the further device aspect) may be configured to execute a client application associated with the host application.

Without limitation, for example in a 3GPP implementation, any "radio device" may be a user equipment (UE).

The network node, the radio device, and/or the RAN may form, or may be part of, a radio network, e.g., according to the Third Generation Partnership Project (3GPP) or according to the standard family IEEE 802.11 (Wi-Fi). The method aspect may be performed by one or more embodiments of the network node (e.g., a base station or any node of the RAN or the wireless communication system).

The RAN may comprise one or more base stations, e.g., each performing the method aspect. Alternatively or in addition, the radio network may be a vehicular, ad hoc and/or mesh network comprising two or more radio devices, e.g., acting as a remote radio device, a relay radio device, and/or a further remote radio device.

Any of the radio devices may be a 3GPP user equipment (UE) or a Wi-Fi station (STA). The radio device may be a mobile or portable station, a device for machinetype communication (MTC), a device for narrowband Internet of Things (NB-loT) or a combination thereof. Examples for the UE and the mobile station include a mobile phone, a tablet computer and a self-driving vehicle. Examples for the portable station include a laptop computer and a television set. Examples for the MTC device or the NB-loT device include robots, sensors and/or actuators, e.g., in manufacturing, automotive communication and home automation. The MTC device or the NB-loT device may be implemented in a manufacturing plant, household appliances and consumer electronics.

Whenever referring to the RAN, the RAN may be implemented by one or more network nodes (e.g., base stations).

The radio device may be wirelessly connected or connectable (e.g., according to a radio resource control, RRC, state or active mode) with the network node.

The network node may encompass any station (e.g., a base station) that is configured to provide radio access to any of the radio devices. The network node may also be referred to as cell, transmission and reception point (TRP), radio access node or access point (AP). The network node and/or the radio device may provide a data link to a host computer providing the user data to the remote radio device or gathering user data from the remote radio device. Examples for the base stations may include a 3G base station or Node B (NB), 4G base station (gNB) or eNodeB (eNB), a 5G base station or gNodeB (gNB), a Wi-Fi AP and a network controller (e.g., according to Bluetooth, ZigBee or Z-Wave). The RAN may be implemented according to the Global System for Mobile Communications (GSM), the Universal Mobile Telecommunications System (UMTS), 3GPP Long Term Evolution (LTE) and/or 3GPP New Radio (NR).

Any aspect of the technique may be implemented on a Physical Layer (PHY), a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, a packet data convergence protocol (PDCP) layer, and/or a Radio Resource Control (RRC) layer of a protocol stack for the radio communication.

Herein, referring to a protocol of a layer may also refer to the corresponding layer in the protocol stack. Vice versa, referring to a layer of the protocol stack may also refer to the corresponding protocol of the layer. Any protocol may be implemented by a corresponding method.

Any one of the network node (e.g., gNB), the radio device (e.g., UE), the communication system or any node or station for embodying the technique may further include any feature disclosed in the context of the method aspect, and vice versa. Particularly, any one of the units and modules disclosed herein may be configured to perform or initiate one or more of the steps of the method aspect.

Brief Description of the Drawings

Further details of embodiments of the technique are described with reference to the enclosed drawings, wherein:

Fig. 1 shows a schematic block diagram of an embodiment of a device for compensating a varying distortion level for an interference measurement at a radio device;

Fig. 2 shows a flowchart for a method of compensating a varying distortion level for an interference measurement at a radio device, which method may be implementable by the device of Fig. 1;

Fig. 3 schematically illustrates a first example of a radio network comprising an embodiment of the device of Fig. 1 performing the method of Fig. 2; Fig. 4 schematically illustrates a first example of a physical resource block of a slot comprising at least one OFDM symbol associated with a CSI-IM;

Fig. 5 schematically illustrates a second example of physical resource blocks of a slot comprising at least one OFDM symbol associated with a CSI-IM;

Fig. 6 shows an example of a varying distortion level in terms of error vector magnitude depending on symbol power;

Fig. 7 shows an example of a varying distortion level in terms of error vector magnitude depending on power back-off;

Fig. 8 shows a flowchart for a method of controlling a distortion by controlling a power for an interference measurement in a radio transmission, which method may be implementable by the device of Fig. 1;

Fig. 9 shows a schematic block diagram of a network node embodying the device of Fig. 1;

Fig. 10 schematically illustrates an example telecommunication network connected via an intermediate network to a host computer;

Fig. 11 schematically illustrates an example telecommunication network connected via an intermediate network to a host computer; and

Figs. 12 and 13 show flowcharts for methods implemented in a communication system including a host computer, a base station or radio device functioning as a gateway and a user equipment.

Detailed Description

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as a specific network environment in order to provide a thorough understanding of the technique disclosed herein. It will be apparent to one skilled in the art that the technique may be practiced in other embodiments that depart from these specific details. Moreover, while the following embodiments are primarily described for a New Radio (NR) or 5G implementation, it is readily apparent that the technique described herein may also be implemented for any other radio communication technique, including a Wireless Local Area Network (WLAN) implementation according to the standard family IEEE 802.11, 3GPP LTE (e.g., LTE-Advanced or a related radio access technique such as MulteFire), for Bluetooth according to the Bluetooth Special Interest Group (SIG), particularly Bluetooth Low Energy, Bluetooth Mesh Networking and Bluetooth broadcasting, for Z-Wave according to the Z-Wave Alliance or for ZigBee based on IEEE 802.15.4.

Moreover, those skilled in the art will appreciate that the functions, steps, units and modules explained herein may be implemented using software functioning in conjunction with a programmed microprocessor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP) or a general purpose computer, e.g., including an Advanced RISC Machine (ARM). It will also be appreciated that, while the following embodiments are primarily described in context with methods and devices, the invention may also be embodied in a computer program product as well as in a system comprising at least one computer processor and memory coupled to the at least one processor, wherein the memory is encoded with one or more programs that may perform the functions and steps or implement the units and modules disclosed herein.

Fig. 1 schematically illustrates a block diagram of an embodiment of a device for compensating a varying distortion level at a network node 100 for an interference measurement (IM) at a radio device 120 according to the device aspect. The device is generically referred to by reference sign 100.

Optionally, the device 100 comprises an estimation module 102 that estimates a first distortion level. The first distortion level may be estimated for the IM REs in the first OFDM symbol, i.e., for the subcarriers of the IM REs in the first OFDM symbol. The first distortion level may be estimated as a power density of the varying distortion level in the first OFDM symbol.

Optionally, the device 100 comprises a determination module 104 that determines a second distortion level. The second distortion level may be determined at the network node 100 for a second OFDM symbol other than the first OFDM symbol, e.g., according to a scheduling hypothesis. The second distortion level may be determined as a power density of the varying distortion level in the second OFDM symbol.

The device 100 comprises an injection module 106 that injects power for compensating a varying distortion level at a network node 100. The injecting of the power may part of a step of transmitting at least the first OFDM symbol comprising the IM REs from the network node to the radio device.

Any of the modules of the device 100 may be implemented by units configured to provide the corresponding functionality.

The modules 102 and 104 may be configured to perform the optional steps (e.g., the steps 202 and 204, respectively, described below) of the method aspect. The module 106 may be configured to perform the step (e.g., the step 206 described below) of the method aspect.

The device 100 may also be referred to as, or may be embodied by, the network node (or briefly: NN), e.g., a base station (briefly: BS). Each of the at least one radio device may be embodied by below device 120, e.g., user equipment device (UE).

Alternatively or in addition, the network node 100 and the at least one radio device 120 may be in direct radio communication, e.g., at least when the network node transmits the first and/or second OFDM symbol from the network node to the radio device.

Herein, any radio device may be a mobile or portable station and/or any radio device wirelessly connectable to the network node (e.g., a base station) or RAN, or to another radio device. For example, the radio device may be a user equipment (UE), a device for machine-type communication (MTC) or a device for (e.g., narrowband) Internet of Things (loT). Two or more radio devices may be configured to wirelessly connect to each other, e.g., in an ad hoc radio network or via a 3GPP sidelink (SL) connection. Furthermore, any base station may be a station providing radio access, may be part of a radio access network (RAN) and/or may be a node connected to the RAN for controlling the radio access. For example, the base station may be an access point, for example a Wi-Fi access point. Fig. 2 shows an example flowchart for a method 200 of compensating a varying distortion level at a network node 100 for an interference measurement (IM), e.g., according to the method aspect or the claim 1 of the list of claims. The method 200 may be implementable by the device of Fig. 1 (e.g., the network node 100).

In a step 202 of the method 200, the network node 100 may estimate a first distortion level for the first OFDM symbol 410. The first distortion level may be estimated based on a first symbol power of the first OFDM symbol. For example, the level of distortion noise affecting the IM REs (e.g., the CSI-IM resource elements) due to a transmission on other REs in the same time instance (i.e., in the same OFDM symbol), given the instantaneous output power and set of scheduled signals and/or channels, is estimated.

In step 204 of the method 200, the network node 100 may determine a second distortion level for the second OFDM symbol other than the first OFDM symbol. The second distortion level may be determined based on a second symbol power of the second OFDM symbol. The second distortion level may also be referred to as target distortion level and may depend on the scheduling hypothesis for which the CSI (e.g., in the CSI report) derived from the IM (e.g., a CSI-IM) is applied.

In step 206 of the method 200, the network node 100 may inject power for the compensating of the varying distortion level at the network node 100 on IM REs associated with the IM. A compensation signal is added to the IM REs (e.g., all REs associated with the CSI-IM) to make up for the difference between the target distortion level and the distortion noise already created.

The power injected in the step 206 may add extra noise and/or a signal to the IM REs (e.g., the REs of the CSI-IM resource elements) to reach a target distortion level that corresponds to the scheduling hypothesis that the CSI derived from the CSI-IM is assumed to be used for.

Herein, whenever referring to noise or a signal-to-noise ratio (SNR), a corresponding step, feature or effect is also disclosed for noise and/or interference or a signal-to-interference-and-noise ratio (SINR).

While the technique is described primarily for a downlink (DL) from the network node to the radio device, the technique may also be applied to an uplink (UL), wherein the network node is a mobile terminal and the radio device is a base station. Alternatively or in addition, the technique may also be applied to a direct communications between radio devices, e.g., device-to-device (D2D) communications or sidelink (SL) communications, wherein the network node is a mobile terminal.

The network node 100 may be a base station. Herein, any radio device may be a mobile or portable station and/or any radio device wirelessly connectable to a base station or RAN, or to another radio device. For example, the radio device may be a user equipment (UE), a device for machine-type communication (MTC) or a device for (e.g., narrowband) Internet of Things (loT). Two or more radio devices may be configured to wirelessly connect to each other, e.g., in an ad hoc radio network or via a 3GPP SL connection. Furthermore, any base station may be a station providing radio access, may be part of a radio access network (RAN) and/or may be a node connected to the RAN for controlling the radio access. For example, the base station may be an access point, for example a Wi-Fi access point.

Fig. 3 schematically illustrates a wireless communication system 300 comprising a radio access network (RAN) 110. The RAN comprises at least one network node 100 (e.g., a base station). Each network node 100 provides radio access to one or more radio devices 120 in a respective cell 101.

The radio device 120 may be in the cell 101 of the network node 100, e.g., either in a central area of the cell 101 or close to an edge of the cell 101.

Fig. 4 schematically illustrates a grid of resource elements (REs) 406 in the frequency domain, e.g., measured in subcarriers 402, and in time, e.g., measured in orthogonal frequency-division multiplexing (OFDM) symbols 404.

Furthermore, Fig. 4 schematically illustrates an example of a resource block (RB, e.g., a physical resource block, PRB) of slot. The PRB 12 subcarriers 402 in frequency and the slot comprises 14 OFDM symbols 404 in time. The smallest addressable unit in 4G and 5G systems using OFDM is one subcarrier in one OFDM symbol, and this is referred to as one RE 406.

Each of the REs 406 may be allocated to a certain physical downlink channel (e.g., a physical downlink control channel, PDCCH, or a physical downlink shared channel, PDSCH) and/or a reference signal (RS), e.g., a zero-power RS (ZP-RS) for the IM, a channel state information RS (CSI-RS) or a demodulation RS (DM-RS) according to a radio access technologies (RAT) such as 3GPP LTE or 3GPP NR. The ZP-RS may be considered as a special case of the CSI-RS for the CSI-IM.

The slot comprises at least one IM symbol 410 as the first OFDM symbol. The IM symbol 410 is an OFDM symbol that is associated with the IM (e.g., the CSI-IM). That is, the IM symbol 410 comprises REs 412 associated with or allocated for the IM (e.g., the CSI-IM) at the radio device 120. The REs 412 associated with the IM are briefly referred to as IM REs 412. The ZP-RS (e.g., a ZP-CSI-RS) may correspond to a set of the IM REs 412.

The second OFDM symbol 408 is an OFDM symbol 404 that is not associated with the IM, i.e., an OFDM symbol 404 that does not comprise REs 412 allocated for the IM (or IM REs 412).

The scheduling and link adaptation functionalities between network node 100 and radio device 120 require knowledge about the instantaneous channel condition. Such knowledge is referred to as channel state information (CSI) and the radio device 120 may determine CSI by performing measurements on so-called CSI reference signals (CSI-RS) which are transmitted in the downlink.

The CSI-RS resources are multiplexed on the time-frequency grid with other transmission such as data transmission on the physical downlink shared channel (PDSCH) and its associated demodulation reference signals (DM-RS).

In 3GPP NR, the network node 100 instructs the radio device 120 to measure the channel state on a certain set of CSI-RSs, and each CSI-RS is mapped to a set of REs which the network node 100 uses for transmission of the respective reference signals (RSs).

The REs of the CSI-RS are multiplexed on the time-frequency grid with data transmission on the physical downlink shared channel (PDSCH) and there are different types of CSI-RSs.

A first type of CSI-RSs comprises non-zero-power CSI-RS (NZP-CSI-RS), which are used to measure a gain of the channel (e.g., including amplitude gain and phase for each port-antenna pair). In these REs, the network node 100 will transmit RSs, i.e. a sequence of symbols known by both transmitter (e.g., the network node 100) and receiver (e.g., the radio device 120). The NZP-CSI-RS has typically not been altered by the transmitter (e.g., through a precoding filter).

A second type of CSI-RSs (e.g., CSI-RS resources) comprises zero-power CSI resources (ZP CSI resources, also referred to as: ZP CSI-RS resources or ZP CSI-RS) to perform the IM (e.g., the CSI-IM) at the radio device 120. The CSI-IM may be used to estimate an interference level and/or a noise level and/or any impairments at the radio device 120. The ZP CSI-RS may be allocated to ZP REs. Herein, the OFDM symbols 404 comprising the ZP CSI-RS may be referred to as the first OFDM symbol 410, or briefly, IM symbol 410.

The CSI-IM is associated with a set of IM REs 412. These IM REs 412 are used primarily to measure the interference (i.e., for the IM). The set of IM REs may comprise four adjacent REs 404 (e.g., in each PRB over the entire bandwidth of the OFDM symbol) in one OFDM symbol. The latter arrangement of IM REs 412 is symbolically referred to by "4x1". Other arrangements include two subcarriers 402 and two neighboring IM symbols 402 per PRB and slot comprising the set of IM REs 412, which arrangement is symbolically referred to as "2x2".

Fig. 4 schematically illustrates a single PRB of a slot comprising the IM REs 412. Alternatively, each PRB over the bandwidth (e.g., within one IM symbol 410) comprises the set of IM REs 412, e.g., as schematically illustrated in Fig. 5 for two PRBs 403.

Fig. 5 schematically illustrates an example of two physical resource blocks (PRB)

403 of a slot. In NR, a set of REs 406 over twelve adjacent subcarriers 402 is referred to as physical resource block (PRB) 403. Fourteen adjacent OFDM symbols

404 constitute a slot. Fig. 5 schematically illustrates an example of multiple PRBs comprising one IM symbol 410, e.g. over the bandwidth of the radio device 120.

The serving network node 100 typically transmits nothing in the resource elements (REs) used for the IM, i.e. the subcarriers are blanked and/or empty and/or muted (e.g., except for the spurious distortion level). This is realized by configuring a zero power CSI-RS (ZP-CSI-RS), which is indicative to the radio device 120 that a PDSCH is not mapped to those REs, i.e. the set of IM REs 412. Typically, network nodes serving neighboring cells (e.g., neighboring network node of the network node 100) use the IM REs 412 in a way that corresponds to normal activity, thereby allowing the radio device 120 to measure a reliable estimate of the interference from other cells, which is also referred to as inter-cell interference.

Herein, the IM REs 412 in an OFDM symbol associated with IM (i.e., in the IM symbol 410) may synonymously be referred to as zero power CSI-RS (ZP-CSI-RS) or ZP REs.

The REs 406 in the first OFDM symbol (i.e., the IM symbol) 410 and the second OFDM symbol 408 (i.e., an OFDM symbol 404 other than the at least one IM symbol 410) may have a symbol power (e.g., a power spectral density or spectral power) from zero power to a nominal power (e.g., a maximum power).

For simplicity, Figs. 4 and 5 show an arbitrary one of the one or more second symbols 408 that are not associated with the IM, i.e., OFDM symbols 404 other than the IM symbol 410. For example, while Figs. 4 and 5 only show one second OFDM symbol 408, the second symbol power may be based on a plurality of second OFDM symbols 408 (e.g., by computing the average over a plurality of second OFDM symbols 408). Alternatively or in addition, while the second OFDM symbol 408 is illustrated within the same slot comprising the IM symbol 410 and/or prior to the IM symbol 410, the scheduling hypothesis (e.g., for a data transmission from the network node 100 to radio device 120) may use at least one second OFDM symbol 408 (e.g., the same temporal position relative to the PRB 413) in another PRB 413 after the PRB 413 comprising the IM symbol 410.

For brevity and not limitation, the radio device 120 is below referred to as UE 120.

For evaluating the channel quality at the UE 120, any embodiment may use (i.e., measure on) the CSI-RS such as NZP CSI-RS and ZP CSI-RS 412 in the IM symbol 410 to derive the channel quality, e.g., to derive at least one of the indicators CQI, Rl, and PMI.

For reporting the channel quality from the UE 120 to the network node 100, any embodiment may use any one of several channel indicators defined by the 3rd Generation Partnership Project (3GPP). This includes at least one of the indicators Rl, PMI and CQI, which may be used at the network node 100 for at least one of scheduling and link adaption (e.g., including selecting how many spatial layer are to be used by the UE 120).

RATs using OFDM, such as the 3GPP LTE or 3GPP NR, share the available channel bandwidth between multiple UEs 100. This can be done by multiplexing UEs in time and frequency utilizing different time slots (e.g., comprising 7 or 14 OFDM symbols 404) and subcarriers 402. The smallest addressable unit is one subcarrier 402 in one OFDM symbol 404, and this is referred to as resource element (RE) 406. A set of REs 406 over twelve adjacent subcarriers 402 is referred to as physical resource block (PRB) 403. Multiplexing in time is done using time slots, where each time slot has room for up to 14 adjacent OFDM symbols 402.

Any embodiment of the network node 100 may perform at least one of dynamic scheduling and link adaptation (e.g., including coding and/or modulation scheme) for the UE 120 based on the CSI report derived from the IM and received from the UE 120, which is briefly referred to as scheduling and link adaptation functionalities.

Dynamic scheduling and link adaptation are used to take instantaneous traffic demands and channel conditions into account with an update rate equal slot level (e.g., equal to or less than 1 ms). This means that UEs 120 with high signal to interference and noise ratio (SINR) may use several multiple-input-multiple- output (MIMO) layers and/or modulation and coding schemes with high modulation orders (e.g., 256-QAM) and high code rates (up to 0.95), whereas a UE 120 at low SINR may use a single layer with a Quadrature Phase Shift Keying (QPSK) and low code rate (e.g., 0.1).

In the absence of distortions caused by non-linearities, sources of interference include downlink transmissions by neighboring base stations (i.e., inter-cell interference) or even from the serving base station in the case of multiple-use MIMO (MU-MIMO) (i.e., intra-cell interference). Furthermore, there is a distortion level caused by a non-linearity in the signal processing at the network node 100 (e.g., in the transmit processing chain) when power of one RE 406 spreads into other REs 406 due to the non-linearity (i.e., non-linear operations). This distortion varies between the OFDM symbols 404 because the symbol power (e.g., the total power of the respective OFDM symbol in the baseband or the total transmit power of the respective OFDM symbol) is varying.

The distortion level introduced by non-linear operations at the network node 100 contributes to the interference measured at the UE 120. Examples of non-linear operations comprise a crest factor reduction (CFR) such as clipping and a nonlinearity of a power amplifier (PA), e.g., due to heating up of a transmit processing chain.

To be able to achieve (e.g. very) high peak data rates (at least in the cell center and/or at low network load when there is little inter-cell interference), the maximum average power must be allocated. However, since the non-linear distortions (i.e., the varying distortion level due to a non-linearity) increase with the symbol power (e.g., transmission power), it is required that they are kept adequately low, e.g. around 3.5%, for corresponding maximum average power. This in turn drives a requirement for a relatively high PAPR, e.g. around 7.5 dB. In other words, for cell center UEs 120 it may be possible to achieve very high data rates since the noise and intercell interference may be low. However, for such UEs 120 the distortions may be large, e.g. relative to the noise and intercell interference and thus limit the achievable SINR (which includes the distortions). The level of distortion may depend on the total power and how for example the CFR is configured. The CFR may be configured so that the PAPR is around 7.5dB corresponding to a distortion level in terms of EVM of around 3.5% for maximum transmit power. The CFR can also be configured so that the PAPR may be smaller, and the distortion level may be higher (e.g., 17.5% at maximum transmit power or higher). For transmit powers lower than the maximum transmit power, the level of distortions may be less and the corresponding PAPR greater.

Any embodiment of the network node 100 may use dynamic scheduling and/or link adaptation to take instantaneous traffic demands and/or channel conditions into account, e.g. with an update rate equal to the slot rate (e.g. equal to or less than 1 ms). This means that a UE 120 with high signal to interference and noise ratio (SINR) can use (i.e., may be controlled by the network node 100 to use) several multiple-input-multiple-output (MIMO) layers and/or modulation and coding schemes with high modulation (e.g., quadrature amplitude modulation (QAM) orders such as 64QAM or 256QAM) and/or high code rates (e.g., up to 0.9 or 0.95 or higher). A UE 120 at low SINR may use (i.e., may be controlled by the network node 100 to use) a single layer with quadrature phase shift keying (QPSK) and low code rate (e.g., 0.1 or less).

For OFDM, data is transmitted in parallel on many subcarriers 402. This may be implemented using OFDM symbols 404 (in the frequency domain) and generating a time domain sequence through an inverse fast Fourier transformation (IFFT). An advantage of ODFM is its robustness to multipath propagation, but a disadvantage is a relatively high peak-power to average-power ratio (PAPR). Therefore, there is a need for the network node 100 using CFR to reduce the PAPR at the cost of introducing distortions to the (e.g., baseband or transmitted) signal.

The PAPR may be the relation between a maximum power (e.g., of a sample) in a given OFDM symbol 402 divided by the average power of the respective OFDM symbol 402. In other words, the PAPR may be the ratio of peak power to average power of a signal.

For brevity and not limitation, the network node 100 is below referred to as gNB 100.

The gNB 100 may configure the UE 120 to report the CSI (i.e., in the CSI reports) back to the gNB 100. Such a report (i.e., the CSI report) may comprise or may be indicative of one or more of the following: a rank indicator (Rl), a precoding matrix indicator (PMI), and channel quality indicator (CQ.I). The CQI can be viewed as a quantization of the SINR that is obtained conditioned on the reported number of layers as indicated by the Rl and the precoding weights as indicated by the PMI.

The CSI report is obtained (i.e., derived) by the UE 120 with the combination of at least one channel measurement (e.g., from NZP-CSI-RS) and the at least one IM, e.g. the CSI-IM, in the IM REs 412.

At the gNB 100, there may be a delay of several slots between measurement (i.e., when the IM symbol 410 is transmitted from the gNB 100 to the UE 120) and transmission of the CSI report from the UE 120 and/or a further delay due to the gNB 100 processing for demodulation of the CSI report and (link) adaptation of the subsequent transmissions based on it (e.g., including the transmission of the second OFDM symbol 408 in a subsequent or later PRB 403). Alternatively or in addition, the gNB 100 may determine which UE 120 to schedule and which transmission parameters to select, e.g., comprising at least one of bandwidth, number of layers, precoding, modulation order and channel coding rate.

The gNB 100 may determine a combination of a CSI-IM (i.e., IM RE 412) and NZP- CSI-RS (e.g., other RE 406 in the IM symbol 410) as a hypothesis of a future scheduling by the gNB 100. It is desirable that the combination of measured channel (e.g., the channel gain as measured on NZP CSI-RS) and the measured interference (as measured in the CSI-IM on the IM RE 412) be similar to the measured channel and measured interference, respectively, when the next (or a future) data transmission is scheduled, e.g. because then the associated CSI or the transmission parameter derived from the CSI will be sufficiently close to the optimal transmission parameters.

In any embodiment, the gNB 100 may configure the UE 120 with a combination of multiple NZP-CSI-RSs and/or multiple CSI-IMs (i.e., multiple sets of IM RE 412 for multiple IMs) and/or with multiple (e.g., CSI) reports.

In any embodiment of the gNB 100, the UE 120 may be triggered and/or configured by the gNB 100 to measure interference levels (i.e., to perform the IM) for CSI reporting (i.e., for the gNB 100 to receive a CSI report from the UE 120) on specific REs referred to as IM REs 412, i.e., combinations of OFDM symbols 402 and subcarrier 404) assigned by the gNB 100. These are typically blanked (i.e., left empty) by the gNB 100 (e.g., except for the varying distortion level).

In any embodiment, the varying distortion level caused by the gNB 100 may depend on the symbol power (e.g., an output power used by the gNB 100). More specifically, the varying distortion level may be greater if the symbol power (e.g., output power) is greater (i.e., the function relating symbol power and varying distortion level may be (e.g., strictly) monotonic.

In any embodiment, the instantaneous symbol power, i.e., the power per OFDM symbol (e.g., the power of an OFDM symbol in the digital domain or the output power of an OFDM symbol) varies across slots (e.g., due to a varying load or utilization, of the PDSCH and/or the PDCCH) and/or across OFDM symbols 404 (e.g., due to blanked resources such as the IM RE 412).

In any embodiment, the CSI reports received from the UE 120 may be used by the gNB 100 for link adaptation and/or scheduling. The accurate CSI reports enable an efficient operation of the wireless communication system 300.

Fig. 6 schematically illustrates the varying distortion level 602 as a function 600 of the (e.g., instantaneous) symbol power 604. In other words, Fig. 6 shows a relationship 600 between the symbol power 604 and the varying distortion level 602, e.g., relative to the symbol power 604 and/or in terms of an error vector magnitude (EVM). The symbol power 604 (e.g., an OFDM symbol) may be for example a total power in the OFDM symbol 408 and/or 410.

The vertical line 606 in Fig. 6 schematically illustrates the nominal power as a reference value for the symbol power. In a first example, the nominal power may be a maximum power (e.g., of the power amplifier). In a second example, the nominal power may correspond to a clipping threshold of the PAPR reduction unit. In a third example, the nominal power may correspond to a maximum power of a single RE 406 (i.e., a single subcarrier in the OFDM symbol) multiplied by the number of subcarriers 402 (e.g., in the bandwidth of the UE 120).

Fig. 4 shows an exemplary value of the second symbol power 608 (i.e., the symbol power of the second OFDM symbol 408 (also referred to as non-IM symbol 408), e.g. as illustrated in the Figs. 4 and 5. The second symbol power 608 may cause a second distortion level 618 (e.g., a second value of the EVM).

Fig. 4 further shows an exemplary value of the first symbol power 610 (i.e., the symbol power of the first OFDM symbol 410 (also referred to as IM symbol 410), e.g. as illustrated in the Figs. 4 and 5. The first symbol power 610 may cause a first distortion level 620 (e.g., a first value of the EVM).

In an embodiment, the second symbol power 608 is greater than the first symbol power 610 so that the first distortion level 620 is less than the second distortion level 618 because the function 600 is monotonically increasing. Optionally, the nominal power 606 is greater than the second symbol power 608. As the PAPR of signals of OFDM symbols 404 is relatively high, the PAPR reduction unit may implement a so-called crest factor reduction (CFR) of the PAPR to reduce the peaks of the baseband signal that is input to the power amplifier (PA). By reducing the peaks, the average power of the signal can be increased for the same PA. Thus, the received signal to noise ratio (SNR) will be higher. Effectively, the amplitude range in which the PA needs to be linear can be reduced. The cost for this improvement in energy efficiency is that the varying distortion level 602 is introduced or increased at the gNB 100.

The CFR is a technique to reduce the PAPR of a waveform to a desired value.

Alternatively or in conjunction with the CFR, the PAPR reduction unit or another unit may comprise a digital pre-distortion (DPD) that is configured to improve the overall linearization or overall linearity of the gNB 100 or the transmit processing chain of the gNB 100 or the combination of the DPD and the PA of the gNB 100.

Basic techniques for CFR include iterative clip-and-filtering and peak cancellation. Alternatively or in addition, more advanced techniques (e.g. applicable to a gNB 100 comprising multiple antennas) include a convex reduction of amplitudes (CRAM). The varying distortion level can remain or result from the PAPR reduction unit, e.g. for conventional techniques operating independently on the signal to each antenna. Alternatively or in addition, the distortions due to clipping lead to inter-carrier interference, and will hence affect also carriers with no data mapped, e.g., the IM REs 412.

There is a trade-off between the varying distortion level created by the CFR and the power efficiency of the power amplifier (PA). When a high level of distortion can be tolerated, then the signal power distribution can be brought closer to the efficient region of the PA, e.g., closer towards the nominal power 606.

Assuming that CFR is used to limit the signal peak power to a certain value (e.g., corresponding to the nominal power 606) so that the PA is operating in the linear region of the PA (e.g., below the nominal power 606), there is a dependency between the level of distortion 602 and the symbol power 604 (which may also be represented as a dependency on the output power). The varying distortion level 602 (briefly referred to as the distortions 602) are commonly quantified in terms of the error vector magnitude (EVM), e.g., in percent, i.e., as a relative quantity (e.g. relative to the symbol power 604). Even though there are also other imperfections in the transmit processing chain (e.g., in the radio signal path) such as phase noise, the CFR may often be the dominating source of the distortions 602.

Alternatively or in addition, a non-linear power amplifier (PA) of the gNB 100 may also introduce distortions 602 not only within the frequencies reserved by the desired signal but also at frequencies adjacent to it (which is also referred to as spreading of power in the frequency domain or adjacent channel leakage). To avoid generating this kind of interference to signals using other frequencies, the signal can be pre-distorted (e.g., using the DPD) to compensate for distortion that would be generated otherwise. This may or may not impact the general relation 600, i.e. a dependency between the symbol power 604 (e.g., the output power) and the level of distortions 602.

In one embodiment, the estimated distortion 602 is a function of the output power 604 in the OFDM symbols 404 that are associated with the IM (e.g., the CSI-IM), i.e., the first OFDM symbols 410 (also referred to as IM symbols 410). Note that the determined output power 604 may be pertaining to a single carrier or to multiple carriers.

The function 600 of the output power 604 may be derived from characterization (e.g., technical specifications) of components of the transmit processing chain and/or from measurements. Alternatively or in addition, the function 600 may be represented (e.g., stored) in the form of a lookup table (LUT), a fitted piecewise linear function, and/or a polynomial.

An alternate representation of such a function 600 is schematically illustrated in Fig. 7, wherein a power back-off 704 is the ratio between the nominal power 606 and the symbol power of the respective OFDM symbol (e.g., an output power). In other words, on a logarithmic scale or in units of dB, the power back-off 704 may be a difference between the nominal power 606 and the symbol power 604 (e.g., output power), e.g. in OFDM symbols associated with CSI-IM for the first symbol power. The varying distortion level 602 may be an EVM. Fig. 7 shows a relationship 700 between the power back-off 704 and the varying distortion level 602 in terms of an error vector magnitude (EVM). Fig. 7 shows an example of how the distortions 602 (e.g., in terms of EVM) vary based on the power back-off 704, optionally assuming that CFR is used to ensure that the power amplifier (PA) is operating within its linear region (e.g., below or close to the nominal power 606).

A power back-off 704 of an OFDM symbol 404 may refer to a ratio between a nominal power and the symbol power of the OFDM symbol. Alternatively or in addition, the power back-off may refer to a reduction of power at the network node, e.g., relative to the nominal power. The power reduced according to the power back-off may be an input power of a power amplifier (PA) at the network node 100 for the radio transmission.

Alternatively or in addition, the symbol power that is set or reduced (e.g., compared to the nominal power 606) according to the power back-off may be an input power of a PAPR reduction unit at the gNB 100 for a radio transmission from the gNB 100 to the radio UE 120. Alternatively or in addition, the symbol power that is set or reduced according to the power back-off may be a symbol power (e.g., an output power) of a baseband signal (e.g., in the digital domain and/or generated by a signal processor of the gNB 100, or in the analog domain and/or generated by a modem) for the radio transmission.

One of the main source of distortion of the signal is distortion due to PA. When PA is working in non-linear region (or close to non-linear region), it causes a distortion level in in-band or out-band. When symbol power 604 is close to non-linear region 606 (e.g., reference power in Fig. 6), PA is working most efficiently.

Distortions are commonly quantified in terms of EVM in percent. Fig. 7 illustrates how the EVM of the distortions 602 per antenna varies with the (input) signal power back-off 704. The power back-off 704 in a PA can be understood as a power level below the saturation point at which the PA will continue to operate in the linear region even if there is a slight increase in the input power level. Even though there are also other imperfections in the radio signal path, such as phase noise, the CFR is often the dominating source of the distortions and this a reason for why the EVM can be reduced by reducing the transmit power. The vertical line 710 shows an exemplary power back-off according to the symbol power 610 in Fig. 6. The higher power back-off 704 it results the lower distortion level 802. The vertical line 708 shows an exemplary power back-off according to the input power 608 in Fig. 6. Therefore, the first distortion level 620 due to the power back-off 710 is lower than the second distortion level 618 due to the power back-off 708.

There is a fundamental tradeoff between increasing symbol power 604 (e.g., for a power-efficient operation of the power amplifier) and decreasing the distortion 602. For example, the maximum average symbol power may be chosen so that the distortions 602 allow high data peak rates (e.g., a predefined data rate and/or for at least UEs 120 at the cell center not limited by thermal noise or inter-cell interference). This leads to a requirement on a large enough PAPR, which in turn leads to a requirement of a sufficiently high power back-off 704.

On the other hand, if less PAPR is enforced, less power back-off 704 may be applied, which increases the power-efficiency and/or the maximum average symbol power, which in turn improves the coverage, e.g. in terms of data rates, that can be offered to the UEs 120 at the cell edge whose performance is limited by noise or inter-cell interference. The drawback is that the distortions 602 increase and this in turn limits the achievable peak data rates if the same PAPR threshold is applied uniformly to the UEs 120 across the cell 101.

The symbol power (e.g., the output power) may be determined from counting the number of scheduled NZP resource elements, or from summing powers on the scheduled REs 406. This can be done either per branch associated with a single power amplifier and antenna, or a sum or average over multiple antenna branches could be used.

In another embodiment, the gNB 100 obtains the function 600 or 700 (e.g., the dependency 600 or 700 of the distortion 602 to symbol power 604 or power back-off 704, respectively) from another node (e.g., another radio unit, another gNB or an operations support system, OSS) in the wireless communication system 300 using a communication protocol, e.g., according to an open radio access network (O-RAN). In another embodiment, the estimated distortion 620 (i.e., the first distortion level 620 in the IM symbol 410) is constant. Any dependency on a scheduled transmission power may be ignored or the transmission power may be constant in the step 202 of estimating the first distortion level 620.

In another embodiment, the injected power may depend on further characteristics of the transmitted signal (i.e., the signal to be transmitted based on the CSI report), e.g., a spatial precoding.

In another embodiment, the symbol power (e.g., the output power) per resource element is considered in at least one of the first symbol power 610 and the second symbol power 608.

In one embodiment, the temperature of a radio component is considered, e.g., as a parameter of the function 600 or 700.

Fig. 8 shows an exemplary flowchart of an implementation of the method 200. The method 200 may be implemented for controlling a power for an IM in a radio transmission.

The method 200 may be implementable by the network node 100, which is referred to using the example of a gNB 100 below. In other words, the steps in the Fig. 2 and/or Fig. 8 may be performed by the device gNB 100 (e.g., the gNB 100 of the Fig. 1).

In the step 202, the gNB 100 estimates a first distortion level 620 at the gNB 100 for the first OFDM symbol 610 (i.e., the IM symbol 610 comprising the IM REs 412, e.g., partly or completely). The first OFDM symbol 610 may comprise IM REs 412 scheduled for an IM (e.g., a CSI-IM). The first distortion level 610 (which may also be referred to as distortion noise created on the IM REs) may be estimated based on at least one of the instantaneous symbol (e.g., output) power, and the set of scheduled signals or channels in the one or more IM symbols 610 (e.g., the one or more OFDM symbols 610 associated with the CSI-IM).

In the step 204, the gNB 100 determines a second distortion level 618 at the network node 100 for the second OFDM symbol 408 other than the first OFDM symbol 410. The determined second distortion level 618 may also be referred to as target distortion level. The target distortion level 618 may be determined based on the scheduling hypothesis in which the CSI derived from the CSI-IM is applied.

The target distortion level 618 may be determined similarly to the determination (i.e., the estimation 202) of the first distortion level 620 and/or by using the same function 600 or 700 used for the estimation 202, wherein input is the scheduled signal given the hypothesis (e.g., the second symbol power 608).

In a basic example, the target distortion level 618 is determined in the step 204 from an expected distortion at a typical load level as the second symbol power 608. The typical load level 608 may in turn be determined from historical data (e.g., an average over the second symbol power 608 of a plurality of second OFDM symbols 408).

In another embodiment, the target distortion level 618 is constant. This can lead to consistent distortion levels for multiple CSI reports, which may be beneficial for selecting a transmit power (e.g., in a step of scaling the power) based on the CSI report and/or selecting transmit power out of a set hypotheses of the transmit power (e.g., as part of the scheduling hypothesis).

In the step 206, the gNB 100 injects power on the IM REs depending on the first distortion level 620 and the second distortion level 618. A signal is added to the IM RE 412 associated with the IM (e.g., the CSI-IM) to make up for the difference between the target distortion level 618 and the distortion noise 620 already created.

The power of the interference (i.e., the power of the step 206) to be injected is determined from the difference between the interference power 620 on the CSI- IM (estimated in the step 202), and the target distortion level 618 (determined from step 204).

The interference (i.e., the power of the step 206) may be injected in the frequency domain, specifically on the IM REs 412 associated with the CSI-IM. The values of the IM REs 412 (i.e., the complex-valued components in the frequency domain) may comprise a pseudo-random signal, optionally which is a function of a time index and a subcarrier index and an antenna index. In another embodiment, the injected signal is designed to cancel peaks in the overall waveform. In this case the injected signal is a function of the signal transmitted on all REs in the one or more first OFDM symbols 410 (i.e., the IM symbols 410) on which CSI-IM is mapped. Potentially, the injected signal on a given antenna (or a subset of antennas) is a function of the signal on the REs on the same antenna (or a subset of antennas).

In another embodiment, the spatial color (e.g., correlation) of the injected interference (i.e., the injected signal conveying the injected power in the step 206) is controlled. As an example, second order statistics of the injected signal is a function of the second order statistics of the overall transmitted signal (i.e., of the signal transmitted in the downlink from the gNB 100 to the UE 120) chosen to match the second order statistics of the distortions that would be generated by such signals. Such second order statistics can include spatial color, i.e. correlations between different antennas.

If the network node 100 comprise N antennas, the correlation may be represented by a correlation matrix of size NxN. "Spatial color" refers to this correlation, wherein a diagonal correlation matrix would mean that the antennas are uncorrelated, i.e. "white" in terminological analogy to the characterization of a correlation of noise in the frequency domain.

The injected interference can have spatial color that is chosen to reflect spatial color (e.g., dependency) of the distortions. The spatial color of distortions refers to the correlation between the distortions for different antennas for the same RE 406, i.e. the same subcarrier 402 and the same OFDM symbol 404.

In the step 208, the gNB 100 transmits (e.g., at least the second OFDM symbol 408) based on the CSI report received from the UE 120, which in turn is based on measuring at least the first OFDM symbol 410 (i.e., based on at least the IM).

Fig. 9 shows a schematic block diagram for an embodiment of a device for compensating a varying distortion level 602 at a network node 100 for IM at a radio device 120. The device is generically referred to by reference sign 100. The device 100 comprises an interface 902 (e.g., antenna interface) modularly coupled with the device 100 for radio communication with one or more other devices 100 (e.g., network node or base station) or with one or more radio devices 120 (e.g., user equipments (UEs) 120). The device 100 comprises a power amplifier 908 that modularly coupled to the device 100.

The device 100 comprises PAPR reduction unit 910. The PAPR reduction unit 910 may be an up-conversion unit, a peak-to-average-power ratio (PAPR) reduction unit (e.g., implemented in a digital domain or analog domain of the network node).The PAPR reduction unit 910 may be modularly coupled to the device 100. The device 100 may comprise at least one memory 906 modularly coupled with the device 100. For example, the memory 906 may be encoded with instructions that implement at least one of the modules 102, 104, and 106.

The device 100 may comprise at least one processor 904 for performing the method 200. The one or more processors 904 may be in 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, microcode and/or encoded logic operable to provide either alone or in conjunction with other components of the device 100, such as the memory 906, network node functionality. For example, the one or more processors 904 may execute instructions stored in the memory 906. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device 100 being configured to perform the action.

According to some embodiments, the network node 100 may comprise a radio unit (RU) or a transmit processing chain 920. The RU or transmit processing chain 920 may comprise at least one of the interface 902, a power amplifier (PA) 908, a PAPR reduction unit 910, one or more signal processors 904, and memory 906.

The memory 906 may be encoded with instructions embodying at least one of the estimation module 102, determination module 104, and the injection module 106. The modules may be modularly coupled to each other, e.g., according to interfaces defined for the O-RAN. That is, the modules (or units) of device 100 may be in communication with each other.

The PA 908 and the interface 902 may be part of an analog domain of the transmit processing chain 920. The PAPR reduction unit 910 may be implemented in a digital domain of the transmit processing chain 920, e.g., a further module encoded in the memory 906, or in the analog domain, e.g., as part of the PA 908.

According to some embodiments, the network node 100 may comprise one or more processors 904 and memory 906. The memory 906 may comprise the estimation module 102, the determination module 104 and the injection module 106, modularly coupled to each other. At least some of the modules may be implemented in a computer network (also referred to as a cloud) and/or in centralized unit (CU). The cloud or CU may be a central network or an intermediate network or a host computer, as described below.

The CU may be in communication with a distributed unit (DU). The DU may comprise at least one of the radio unit (RU), the radio interface 902, the PA 908, and the PAPR reduction unit 910.

With reference to Fig. 10, in accordance with an embodiment, a communication system 1000 includes a telecommunication network 1010, such as a 3GPP-type cellular network, which comprises an access network 1011, such as a radio access network, and a core network 1014. The access network 1011 comprises a plurality of base stations 1012a, 1012b, 1012c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 1013a, 1013b, 1013c. Each base station 1012a, 1012b, 1012c is connectable to the core network 1014 over a wired or wireless connection 1015. A first user equipment (UE) 1091 located in coverage area 1013c is configured to wirelessly connect to, or be paged by, the corresponding base station 1012c. A second UE 1092 in coverage area 1013a is wirelessly connectable to the corresponding base station 1012a. While a plurality of UEs 1091, 1092 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 1012.

Any of the base stations 1012 and the UEs 1091, 1092 may embody the network node 100 and the radio device 120, respectively.

The telecommunication network 1010 is itself connected to a host computer 1030, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 1030 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 1021, 1022 between the telecommunication network 1010 and the host computer 1030 may extend directly from the core network 1014 to the host computer 1030 or may go via an optional intermediate network 1020. The intermediate network 1020 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 1020, if any, may be a backbone network or the Internet; in particular, the intermediate network 1020 may comprise two or more sub-networks (not shown).

The communication system 1000 of Fig. 10 as a whole enables connectivity between one of the connected UEs 1091, 1092 and the host computer 1030. The connectivity may be described as an over-the-top (OTT) connection 1050. The host computer 1030 and the connected UEs 1091, 1092 are configured to communicate data and/or signaling via the OTT connection 1050, using the access network 1011, the core network 1014, any intermediate network 1020 and possible further infrastructure (not shown) as intermediaries. The OTT connection 1050 may be transparent in the sense that the participating communication devices through which the OTT connection 1050 passes are unaware of routing of uplink and downlink communications. For example, a base station 1012 need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 1030 to be forwarded (e.g., handed over) to a connected UE 1091. Similarly, the base station 1012 need not be aware of the future routing of an outgoing uplink communication originating from the UE 1091 towards the host computer 1030.

By virtue of the method 200 being performed by any one of the base stations 1012 (i.e., network node 100), the performance or range of the OTT connection 1050 can be improved, e.g., in terms of increased throughput and/or reduced latency and/or increased reliability. More specifically, the host computer 1030 may indicate to the RAN 110 or the network node 100 or 1012 (e.g., on an application layer) at least one of the estimated first distortion level, the determined second distortion level, and the injection power to be injected for compensating a varying distortion level. Alternatively or in addition, the host computer 1030 may transmit to the RAN 110 or the network node 100 or 1012 (e.g., on an application layer) a trigger (e.g., a Quality of Service, QoS, requirement) that triggers performing the method 200. Example implementations, in accordance with an embodiment of the UE, base station and host computer discussed in the preceding paragraphs, will now be described with reference to Fig. 11. In a communication system 1100, a host computer 1110 comprises hardware 1115 including a communication interface 1116 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 1100. The host computer 1110 further comprises processing circuitry 1118, which may have storage and/or processing capabilities. In particular, the processing circuitry 1118 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 1110 further comprises software 1111, which is stored in or accessible by the host computer 1110 and executable by the processing circuitry 1118. The software 1111 includes a host application 1112. The host application 1112 may be operable to provide a service to a remote user, such as a UE 1130 connecting via an OTT connection 1150 terminating at the UE 1130 and the host computer 1110. In providing the service to the remote user, the host application 1112 may provide user data, which is transmitted using the OTT connection 1150. The user data may depend on the location of the UE 1130. The user data may comprise auxiliary information or precision advertisements (also: ads) delivered to the UE 1130. The location may be reported by the UE 1130 to the host computer, e.g., using the OTT connection 1150, and/or by the base station 1120, e.g., using a connection 1160.

The communication system 1100 further includes a base station 1120 provided in a telecommunication system and comprising hardware 1125 enabling it to communicate with the host computer 1110 and with the UE 1130. The hardware 1125 may include a communication interface 1126 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 1100, as well as a radio interface 1127 for setting up and maintaining at least a wireless connection 1170 with a UE 1130 located in a coverage area (not shown in Fig. 11) served by the base station 1120. The communication interface 1126 may be configured to facilitate a connection 1160 to the host computer 1110. The connection 1160 may be direct, or it may pass through a core network (not shown in Fig. 11) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 1125 of the base station 1120 further includes processing circuitry 1128, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 1120 further has software 1121 stored internally or accessible via an external connection.

The communication system 1100 further includes the UE 1130 already referred to. Its hardware 1135 may include a radio interface 1137 configured to set up and maintain a wireless connection 1170 with a base station serving a coverage area in which the UE 1130 is currently located. The hardware 1135 of the UE 1130 further includes processing circuitry 1138, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 1130 further comprises software 1131, which is stored in or accessible by the UE 1130 and executable by the processing circuitry 1138. The software 1131 includes a client application 1132. The client application 1132 may be operable to provide a service to a human or non-human user via the UE 1130, with the support of the host computer 1110. In the host computer 1110, an executing host application 1112 may communicate with the executing client application 1132 via the OTT connection 1150 terminating at the UE 1130 and the host computer 1110. In providing the service to the user, the client application 1132 may receive request data from the host application 1112 and provide user data in response to the request data. The OTT connection 1150 may transfer both the request data and the user data. The client application 1132 may interact with the user to generate the user data that it provides.

It is noted that the host computer 1110, base station 1120 and UE 1130 illustrated in Fig. 11 may be identical to the host computer 1030, one of the base stations 1012a, 1012b, 1012c and one of the UEs 1091, 1092 of Fig. 10, respectively. This is to say, the inner workings of these entities may be as shown in Fig. 11, and, independently, the surrounding network topology may be that of Fig. 10.

In Fig. 11, the OTT connection 1150 has been drawn abstractly to illustrate the communication between the host computer 1110 and the UE 1130 via the base station 1120, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 1130 or from the service provider operating the host computer 1110, or both. While the OTT connection 1150 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

The wireless connection 1170 between the UE 1130 and the base station 1120 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE 1130 using the OTT connection 1150, in which the wireless connection 1170 forms the last segment. More precisely, the teachings of these embodiments may reduce the latency and improve the data rate and thereby provide benefits such as better responsiveness and improved QoS.

A measurement procedure may be provided for the purpose of monitoring data rate, latency, QoS and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 1150 between the host computer 1110 and UE 1130, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 1150 may be implemented in the software 1111 of the host computer 1110 or in the software 1131 of the UE 1130, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 1150 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 1111, 1131 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 1150 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 1120, and it may be unknown or imperceptible to the base station 1120. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer's 1110 measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software 1111, 1131 causes messages to be transmitted, in particular empty or "dummy" messages, using the OTT connection 1150 while it monitors propagation times, errors etc. Fig. 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figs. 10 and 11. For simplicity of the present disclosure, only drawing references to Fig. 12 will be included in this paragraph. In a first step 1210 of the method, the host computer provides user data. In an optional substep 1211 of the first step 1210, the host computer provides the user data by executing a host application. In a second step 1220, the host computer initiates a transmission carrying the user data to the UE. In an optional third step 1230, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth step 1240, the UE executes a client application associated with the host application executed by the host computer.

Fig. 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figs. 10 and 11. For simplicity of the present disclosure, only drawing references to Fig. 13 will be included in this paragraph. In a first step 1310 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In a second step 1320, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step 1330, the UE receives the user data carried in the transmission.

As has become apparent from above description, at least some embodiments of the technique allow for an improved and more accurate CSI report to the network node from the radio device. If the distortion level measured on terminal side more accurately reflects the distortion experienced when being scheduled with PDSCH, the CSI report will be more accurate (i.e. predict performance better) and this will improve performance in terms of spectral efficiency and other key performance indicators (KPIs) such as reliability and/or latency.

For example, if an interference measurement is done in a slot in which no or less data is scheduled so that the transmission power is zero or very low, the interference measurement will not include any self-distortion contribution. On the other hand, such self-interference will indeed be present when the data is scheduled for transmission to the radio device (e.g., over a large bandwidth using high power).

Embodiments of the technique can prevent under-estimating the total interference level, or equivalently over-estimating the data rate supported by the channel state. Same or further embodiments allows consistent levels of distortion across all instances of CSI report. This enables better scheduling and/or link adaptation.

Many advantages of the present invention will be fully understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the units and devices without departing from the scope of the invention and/or without sacrificing all of its advantages. Since the invention can be varied in many ways, it will be recognized that the invention should be limited only by the scope of the following claims.

Claims

1. A method (200) of compensating a varying distortion level (602) at a network node (100; 1012; 1120) for an interference measurement, IM, at a radio device (120; 1091; 1092; 1130), the method (200) being performed by the network node (100; 1012; 1120) serving the radio device (120; 1091; 1092; 1130) using resource elements, REs (406), in orthogonal frequency-division multiplexing, OFDM, symbols (404), the method (200) comprising or initiating the step of: injecting (206) power for the compensating of the varying distortion level (602) at the network node (100; 1012; 1120) on IM REs (412) associated with the IM.

2. The method (200) of claim 1, wherein a first OFDM symbol (410) comprises the IM REs (412), and wherein the injected power depends on a second distortion level (618) at the network node (100; 1012; 1120) for a second OFDM symbol (408) other than the first OFDM symbol (410), optionally wherein a first distortion level (620) at the network node (100; 1012; 1120) for the first OFDM symbol (410) is neglected for determining the injected power.

3. The method (200) of claim 1 or 2, wherein the injected power on the IM REs (412) is, or is determined from, the difference between a first distortion level (620) at the network node (100; 1012; 1120) for a first OFDM symbol (410) comprising the IM REs (412) and a second distortion level (618) at the network node (100; 1012; 1120) for a second OFDM symbol (408) other than the first OFDM symbol (410).

4. The method (200) of claim 2 or 3, wherein the IM REs (412) are allocated to a zero-power reference signal for the IM, and/or wherein the first OFDM symbol (410) further comprises a non-zero-power reference signal for a channel estimation at the radio device (120; 1091; 1092; 1130), and/or wherein the second OFDM symbol (408) comprises no IM REs (412) or is not used for the IM.

5. The method (200) of any one of claims 2 to 4, wherein the first distortion level (620) comprises power spread into the IM REs (412) of the first OFDM symbol (410). 6. The method (200) of any one of claims 2 to 5, wherein the first distortion level (620) is assumed to be constant for a plurality of first OFDM symbols (410) each comprising IM REs (412) and/or is averaged over a plurality of first OFDM symbols (410) each comprising IM REs (412).

7. The method (200) of any one of claims 2 to 6, wherein the second distortion level (618) is assumed to be constant for a plurality of second OFDM symbols (408) other than the first OFDM symbol (410) and/or is averaged over a plurality of second OFDM symbols (408) other than the first OFDM symbol (410).

8. The method (200) of any one of claims 2 to 7 , further comprising or initiating at least one of the steps of: estimating (202) the first distortion level (620) for the first OFDM symbol (410), optionally wherein the first distortion level (620) is estimated (202) based on a first symbol power (610) of the first OFDM symbol (410); and determining (204) the second distortion level (618) for the second OFDM symbol (408) other than the first OFDM symbol (410), optionally wherein the second distortion level (618) is determined (204) based on a second symbol power (608) of the second OFDM symbol (408).

9. The method (200) of claim 8, wherein the first symbol power (610) is or comprises at least one of: a sum of the power of REs (406) in the first OFDM symbol (410); and an average of the power of a plurality of first OFDM symbols (410) each comprising IM REs (412).

10. The method (200) of claim 8 or 9, wherein the second symbol power (608) is or comprises at least one of: a hypothesis of the power of the second OFDM symbol (408); and an average of the power of a plurality of second OFDM symbols (408) other than the first OFDM symbol (410).

11. The method (200) of any one of claims 8 to 10, wherein the first distortion level (620) is a function (600) of the first symbol power (610) of the first OFDM symbol (410) and the second distortion level (618) is a function (600) of the second symbol power (608) of the second OFDM symbol (408), optionally wherein the same function (600) is used for the estimating (202) of the first distortion level (620) and the determining (204) of the second distortion level (618). 12. The method (200) of claim 11, wherein the function (600) is monotonically increasing.

13. The method (200) of claim 11 or 12, wherein the function (600) comprises a characteristic of one or more components (904; 908; 910) of a transmit processing chain (920) of the network node (100; 1012; 1120), optionally a characteristic of a PA (908) of the network node (100; 1012; 1120) or a characteristic of a PAPR reduction unit (910) for reducing a peak to average power ratio, PAPR, of the OFDM symbols (404), and/or wherein the function (600) is stored at the network node (100; 1012; 1120) based on at least one of: measuring the varying distortion level (602) of one or more components (904; 908; 910) of a transmit processing chain (920) of the network node (100; 1012; 1120); and receiving a configuration message that is indicative of the function (600).

14. The method (200) of any one of claims 11 to 13, wherein the function (600) is stored at the network node (100; 1012; 1120) using at least one of: a look-up table; a fitted piecewise linear function; and a polynomial function,

15. The method (200) of any one of claims 2 to 14, wherein at least one of the first symbol power (610) of the first OFDM symbol (410), the second symbol power (608) of the second OFDM symbol (408), the first distortion level (620), and the second distortion level (618) is pertaining to one of: a baseband signal of the network node (100; 1012; 1120); a signal output of a baseband processor (904; 1128) of the network node (100; 1012; 1120); a digital domain of the network node (100; 1012; 1120); a signal input of a PAPR reduction unit (910) for reducing a PAPR at the network node (100; 1012; 1120); and a signal input of a PA (908) of the network node (100; 1012; 1120).

16. The method (200) of any one of claims 8 to 15, wherein the first symbol power (610) and/or the second symbol power (608) is determined based on at least one of: counting a number of scheduled non-zero power REs, NZP REs, in the first OFDM symbol (410) and/or the second OFDM symbol (408), respectively; and summing up the power on scheduled NZP REs in the first OFDM symbol (410) and/or the second OFDM symbol (408), respectively.

17. The method (200) of any one of claims 2 to 16, wherein the first distortion level (620) further depends on at least one of: an operating temperature of one or more components (904; 908; 910) of the network node (100; 1012; 1120) when processing the first OFDM symbol (410); a PAPR of a signal transmitted from the network node (100; 1012; 1120) in the first OFDM symbol (410); and a spatial precoding or a number of spatial layers of a signal transmitted (208) from the network node (100; 1012; 1120) in the first OFDM symbol (410).

18. The method (200) of any one of claims 2 to 17, wherein the second distortion level (618) further depends on at least one of: characteristics of a signal transmitted (208) from the network node (100; 1012; 1120) in the second OFDM symbol (408); an operating temperature of one or more components (904; 908; 910) of the network node (100; 1012; 1120) when processing the second OFDM symbol (408); a PAPR of a signal transmitted (208) from the network node (100; 1012; 1120) in the second OFDM symbol (408); and a spatial precoding or a number of spatial layers of a signal transmitted (208) from the network node (100; 1012; 1120) in the second OFDM symbol (408).

19. The method (200) of any one of claims 1 to 18, wherein the second distortion level (618) depends on a scheduling hypothesis in which a result of the IM, optionally a channel state information, CSI, report derived from the IM, is applied.

20. The method (200) of any one of claims 1 to 19, wherein the injecting (206) of the injected power comprises injecting a compensation signal, optionally a pseudo random signal, on the IM REs (412).

21. The method (200) of claim 20, wherein the compensation signal is a function of at least one of a time index (404), a subcarrier index (402), and a spatial precoding index. 22. The method (200) of claim 20 or 21, wherein the compensation signal is configured to cancel amplitude peaks in a time domain of a signal transmitted (208) on the first OFMD symbol (410).

23. The method (200) of any one of claims 1 to 22, wherein the network node (100; 1012; 1120) comprises a plurality of antennas or antenna ports (902; 1127) for transmitting at least one of the first OFDM symbol (410) and the second OFDM symbol (408), optionally wherein the injected power is injected for each antenna or each antenna port (902; 1127) of the network node (100; 1012; 1120).

24. A computer program product comprising program code portions for performing the steps of any one of the claims 1 to 23 when the computer program product is executed on one or more computing devices (904; 1128), optionally stored on a computer-readable recording medium (906).

25. A network node (100; 1012; 1120) for compensating a varying distortion level (602) at the network node (100; 1012; 1120) for an interference measurement, IM, at a radio device (120; 1091; 1092; 1130), the network node (100; 1012; 1120) comprising memory (906) operable to store instructions and processing circuitry (904; 1128) operable to execute the instructions, such that the network node (100; 1012; 1120) is operable to serve the radio device (120; 1091; 1092; 1130) using resource elements, REs (406), in orthogonal frequency-division multiplexing, OFDM, symbols (404) and to: inject (206) power for the compensating of the varying distortion level (602) at the network node (100; 1012; 1120) on IM REs (412) associated with the IM.

26. The network node (100; 1012; 1120) of claim 25, further operable to perform any one of the steps of any one of claims 2 to 23. 1. A network node (100; 1012; 1120) for compensating a varying distortion level (602) at the network node (100; 1012; 1120) for an interference measurement, IM, at a radio device (120; 1091; 1092; 1130), the network node (100; 1012; 1120) being configured to serve the radio device (120; 1091; 1092; 1130) using resource elements, REs (406), in orthogonal frequency-division multiplexing, OFDM, symbols (404) and to: inject (206) power for the compensating of the varying distortion level (602) at the network node (100; 1012; 1120) on IM REs (412) associated with the IM. 28. The network node (100; 1012; 1120) of claim 27 , further configured to perform the steps of any one of claim 2 to 23.

29. A base station (100; 1012; 1120) configured to communicate with a user equipment, UE (120; 1091; 1092; 1130), the base station (100; 1012; 1120) comprising a radio interface (902; 1127) and processing circuitry (904; 1128) configured to serve the radio device (120; 1091; 1092; 1130) using resource elements, REs (406), in orthogonal frequency-division multiplexing, OFDM, symbols (404) and to: inject (206) power for the compensating of the varying distortion level (602) at the network node (100; 1012; 1120) on IM REs (412) associated with the IM.

30. The base station (100; 1012; 1120) of claim 33, wherein the processing circuitry (1204; 1428) is further configured to execute the steps of any one of claims 2 to 28.

31. A communication system (1000; 1100) including a host computer (1030; 1110) comprising: processing circuitry (1118) configured to provide user data; and a communication interface (1116) configured to forward user data to a cellular or ad hoc radio network (1010) for transmission from a network node (100; 1012; 1120) to a radio device (120; 1091; 1092; 1130) wherein the network node (100; 1012; 1120) comprises a radio interface (902; 1127) and processing circuitry (904; 1128), the processing circuitry (904; 1128) of the network node (100; 1012; 1120) being configured to execute the steps of any one of claims 1 to 23.

32. The communication system (1000; 1100) of claim 31, further including the UE (120; 1091; 1092; 1130).

33. The communication system (1000; 1100) of claim 31 or 32, wherein the network node (100; 1012; 1120) is implemented as a base station (100; 1012; 1120), or a radio device (120; 1091; 1092; 1130) functioning as a gateway, which is configured to communicate with the UE (120; 1091; 1092; 1130).

34. The communication system (1000; 1100) of claim 33, wherein the base station (100; 1012; 1120), or the radio device (120; 1091; 1092; 1130) functioning as a gateway, comprises processing circuitry (904; 1128), which is configured to execute the steps of claim 1 to 23. 35. The communication system (1000; 1100) of any one of claims 31 to 34, wherein: the processing circuitry (1118) of the host computer (1030; 1110) is configured to execute a host application (1112), thereby providing the user data; and the processing circuitry (904; 1128) of the network node (100; 1012; 1120) is configured to execute a client application (1132) associated with the host application (1112).