WO2017213561A1

WO2017213561A1 - Inter-carrier interference cancellation in a wireless multi-carrier system

Info

Publication number: WO2017213561A1
Application number: PCT/SE2016/050550
Authority: WO
Inventors: Shashi Kant; Fredrik Huss; Eric NORDSTRÖM; Vidit SAXENA; Amit Singh
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-06-09
Filing date: 2016-06-09
Publication date: 2017-12-14

Abstract

There is provided a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system. The method comprises obtaining (S1) a time-domain carrier aggregation involving at least two different carriers, wherein the at least two 5 different carriers include a first carrier and a second carrier. The method further comprises performing (S2), for the first carrier, precoding for inter-carrier interference cancellation by precoding (S22) transmit symbols of the first carrier based on information representing inter-carrier interference of the second carrier relative to the first carrier, wherein the information representing inter-carrier interference of the 10 second carrier relative to the first carrier is based on the time-domain carrier aggregation and information representing the first carrier.

Description

INTER-CARRIER INTERFERENCE CANCELLATION

IN A WIRELESS MULTI-CARRIER SYSTEM

TECHNICAL FIELD

The proposed technology generally relates to wireless communication systems and more particularly to a method and arrangement for enabling inter-carrier interference cancellation in a wireless multi-carrier system, and a communication unit comprising such an arrangement and a network device configured to support inter-carrier interference cancellation as well as a corresponding computer program and computer- program product, and also an apparatus for supporting inter-carrier interference cancellation in a wireless multi-carrier system.

BACKGROUND

One of the multifaceted challenges of network operators is to achieve efficient spectrum utilization and efficient coexistence among similar or dissimilar systems. By way of example, it is desirable to provide efficient coexistence among different multi-standard Radio Access Technologies (RATs), such as New Radio (NR), Long Term Evolution (LTE), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications (GSM), and spectrum compatibility even among similar systems.

In one of the potential use-cases of the future 5th Generation (5G) systems, it is important to have more efficient spectrum utilization, providing coexistence that is nearly optimal in terms of Adjacent Channel Interference (ACI), also referred to as adjacent channel leakage, among systems sharing the spectrum/band and radio. The coexistence should preferably meet channel raster requirement without penalizing spectral efficiency but maximizing spectrum utilization.

FIG. 1 is a simplified schematic diagram illustrating an example of relevant parts of a wireless communication system, involving multi-carrier transmission from the same baseband/digital unit and/or radio of a network node 210 to one or more wireless communication devices 220, or vice versa.

For example, filtering and windowing techniques are widely employed to achieve better coexistence. However, these spectrum shaping techniques still necessitate some guard-band between different carriers.

Furthermore, the general known technique to achieve spectrum compatibility even among similar systems, e.g. for intra-band contiguous carrier aggregation of multiple LTE carriers, is to have some appropriate frequency guard-band, as illustrated for two LTE carriers in FIGs. 2A-B.

FIG. 2A is a schematic diagram illustrating an example of ideal/desired LTE intra-band contiguous carrier aggregation considering 100 KHz channel raster requirement. FIG. 2B is a schematic diagram illustrating an example of practical LTE contiguous intra- band carrier aggregation with integer multiple of 300 KHz channel placement to maintain frequency orthogonality.

In order to have no or at least negligible adjacent channel interference among intra- band LTE carriers, the frequency guard-band not only considers the 1 00 KHz channel raster requirement but also attempts to maintain the orthogonality between the carriers by considering the 15 KHz subcarrier spacing of the LTE system. This leads to placement of intra-band LTE carriers by a multiple of 300 KHz which can fulfill both the channel raster requirement and maintain orthogonality for optimal co- existence. Thus, placement of LTE carriers by an integer multiple of 300 KHz apparently wastes extremely expensive frequency resource besides the guard-band within an LTE system bandwidth.

If two or more dissimilar systems are sharing the spectrum within a band and sharing radio unit, e.g., LTE/NR and GSM/WCDMA carrier aggregation, then the non- orthogonal carriers are normally placed far apart from each other in frequency in order to minimize the adjacent channel interference. Hence, these large frequency guard-bands between similar or dissimilar RATs apparently waste extremely scarce and expensive frequency resource. For example, in order to utilize scarce low frequency band (e.g. < 2 GHz band), some operators deploy GSM within LTE/NR guard/in-band. However, they need to penalize the spectral efficiency of LTE/NR by restricting the allocation of the data within smaller bandwidths than the standard discrete LTE/NR system bandwidths such that there is an appropriate frequency guard-band among GSM and LTE/NR.

FIG. 3A is a schematic diagram illustrating an example of desired LTE/NR and GSM coexistence without any frequency guard-band.

As illustrated in FIG. 3A, if one GSM and/or NarrowBand Internet of Things (NB-loT) carrier is allocated non-orthogonally right next to the LTE/NR edge Physical Resource Block (PRB) and sharing the same power amplifier or radio unit, then at least 1 -2 or more adjacent PRBs of LTE/NR need to be completely deactivated in order to have minimal Inter-Carrier Interference (ICI) to LTE depending on the support of higher Multiple Input Multiple Output (MIMO) rank or larger modulation alphabet. After deactivating some LTE/NR PRBs when GSM/NB-loT is deployed within guard-band of LTE/NR, the increased frequency guard-band avoids penalizing the LTE/NR DL performance; GSM/NB-loT Downlink (DL) performance is not really affected since the transmit power spectral density of GSM/NB-loT is much higher than the LTE/NR power spectral density.

FIG. 3B is a schematic diagram illustrating an example of prior art allocating GSM within LTE/NR system bandwidth by deactivating some LTE/NR PRBs.

In order to avoid deactivating some PRBs/resource units, prior art simply allocates the NB-loT carrier orthogonal to LTE/NR (i.e. LTE/NR and NB-loT carriers are allocated a multiple m of 300KHz) as illustrated in FIG. 3B, but it consumes expensive frequency by having larger guard-band.

Similarly, FIG. 4A and FIG. 4B illustrate the ideal and practical (with frequency guard band) coexistence, respectively, of non-orthogonal NB-loT/GSM in-band deployment within LTE/NR system bandwidth. FIG. 4A is a schematic diagram illustrating an example of desired LTE/NR and NB- loT/GSM coexistence without any frequency guard-band.

FIG. 4B is a schematic diagram illustrating an example of deployment of NB-loT/GSM within LTE/NR system bandwidth by deactivating some neighbouring PRBs.

On the other hand, it is worth to mention that by deactivating some edge LTE/NR PRBs for DL and over-dimensioning Physical Uplink Control Channel (PUCCH) for Uplink (UL), some channels can only be protected, e.g., Physical Downlink Shared Channel (PDSCH), Enhanced Physical Downlink Control Channel (EPDCCH), Physical Uplink Control Channel (PUSCH) and PUCCH, and so forth. However, some cell-specific Physical Downlink Control Channel (PDCCH), Physical Control Format Indicator Channel (PCFICH), Physical channel Hybrid ARQ Indicator Channel (PHICH) are not really possible to be protected by deactivating LTE/NR edge PRBs. Unfortunately this frequency guard-band effectively penalizes the spectral efficiency of LTE/NR by restricting available frequency resource allocation even though it avoids penalizing the LTE/NR throughput or other quality of service.

There is thus a general need for improvements relating to efficient spectrum utilization in wireless multi-carrier systems and coexistence among multiple carrier waveforms sharing the spectrum.

SUMMARY It is a general object to enable improvements of the spectrum utilization in wireless multi- carrier systems.

It is an object to provide a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system.

Another object is to provide an arrangement configured to enable inter-carrier interference cancellation in a wireless multi-carrier system. It is also an object to provide a communication unit comprising such an arrangement.

Yet another object is to provide a network device configured to support inter-carrier interference cancellation in a wireless multi-carrier system.

Still another object is t provide a computer program for supporting, when executed by a processor, inter-carrier interference cancellation in a wireless multi-carrier system.

It is also an object to provide a corresponding computer-program product.

Yet another object is to provide an apparatus for supporting inter-carrier interference cancellation in a wireless multi-carrier system.

These and other objects are met by embodiments of the proposed technology.

According to a first aspect, there is provided a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system. The method comprises obtaining a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier. The method also comprises performing, for the first carrier, precoding for inter-carrier interference cancellation by precoding transmit symbols of the first carrier based on information representing inter-carrier interference of the second carrier relative to the first carrier, wherein the information representing inter-carrier interference of the second carrier relative to the first carrier is based on the time-domain carrier aggregation and information representing the first carrier.

In this way, efficient spectrum utilization can be achieved in wireless multi-carrier systems. The proposed technology makes it possible to send multiple similar/dissimilar carrier waveforms closer together in frequency, while maintaining good performance. Efficient coexistence can be ensured, which not only optimizes the spectrum utilization but also improves the spectral efficiency. According to a second aspect, there is provided an arrangement configured to enable inter-carrier interference cancellation in a wireless multi-carrier system. The arrangement is configured to obtain a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier. The arrangement is also configured to perform, for the first carrier, precoding for inter-carrier interference cancellation by determining, based on the time-domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier, and precoding transmit symbols of the first carrier based on the determined information representing inter-carrier interference of the second carrier relative to the first carrier.

According to a third aspect, there is provided a communication unit comprising such an arrangement.

According to a fourth aspect, there is provided a network device configured to support inter-carrier interference cancellation in a wireless multi-carrier system. The network device is configured to obtain a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier. The network device is configured to determine, based on the time- domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier to enable inter-carrier interference cancellation. According to a fifth aspect, there is provided a computer program for supporting, when executed by a processor, inter-carrier interference cancellation in a wireless multi- carrier system. The computer program comprises instructions, which when executed by the processor, causes the processor to:

obtain a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier; and

determine, based on the time-domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier to enable inter-carrier interference cancellation.

According to a sixth aspect, there is provided a corresponding computer-program product comprising a computer-readable medium having stored thereon such a computer program.

According to a seventh aspect, there is provided an apparatus for supporting inter- carrier interference cancellation in a wireless multi-carrier system. The apparatus comprises an input module for obtaining a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier. The apparatus comprises a determination module for determining, based on the time-domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier to enable inter-carrier interference cancellation.

Other advantages will be appreciated when reading the detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments, together with further objects and advantages thereof, may be understood by making reference to the following description taken together with the accompanying drawings, in which:

FIG. 1 is a schematic diagram illustrating an example of relevant parts of a wireless communication system.

FIG. 2A is a schematic diagram illustrating an example of ideal/desired LTE intra-band contiguous carrier aggregation considering 100 KHz channel raster requirement. FIG. 2B is a schematic diagram illustrating an example of practical LTE contiguous intra-band carrier aggregation with integer multiple of 300 KHz channel placement to maintain frequency orthogonality. FIG. 3A is a schematic diagram illustrating an example of desired LTE/NR and GSM coexistence without any frequency guard-band.

FIG. 4A is a schematic diagram illustrating an example of desired LTE/NR and NB- loT/GSM coexistence without any frequency guard-band.

FIG. 4B is a schematic diagram illustrating an example of deployment of NB-loT/GSM within LTE/NR system bandwidth by deactivating some neighbouring

FIG. 5 is a schematic flow diagram illustrating an example of a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system. FIG. 6 is a schematic flow diagram illustrating another example of a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system.

FIG. 7 is a schematic flow diagram illustrating yet another example of a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system.

FIG. 8 is a schematic flow diagram illustrating an example of an extension of the method for enabling inter-carrier interference cancellation also for the second carrier.

FIG. 9 is a schematic flow diagram illustrating a particular example of an extension of the method for enabling inter-carrier interference cancellation also for the second carrier. FIG. 10 is a schematic diagram illustrating an example of the use of a precoding concept to combat inter-carrier interference on a carrier of a first RAT due to a non- orthogonal adjacent carrier of a second RAT. FIG. 1 1 is a schematic diagram illustrating an example of the use of a precoding concept in a successive or iterative scheme to achieve even better performance according to an embodiment.

FIG. 12 is a schematic diagram illustrating an example of the ICI computation .

FIG. 13 is a schematic diagram illustrating an example of the precoding ICI self- cancellation.

FIG. 14 and FIG. 15 are schematic block diagrams that together illustrate an example of the overall signal processing of transport blocks all the way to antenna transmission.

FIG. 16A is a schematic curve diagram illustrating an example of the spectrum sharing of two non-orthogonal OFDM signals of equal effective bandwidth (BW) of 4.5 MHz, but with different subcarrier spacing.

FIG. 16B is a schematic curve diagram illustrating the signal-to-ICI power for both RATs before and after precoding for both method#1 and method#2. FIG. 17A is a schematic curve diagram illustrating an example where a 6dB PSD boosted narrowband RAT2 (OFDM signal with 3.75 KHz subcarrier spacing) in the guard-band of RATI (OFDM signal with 15 KHz subcarrier spacing).

FIG. 17B is a schematic curve diagram illustrating the signal-to-ICI power for both RATI and RAT2 before and after precoding for both methods.

FIG. 18 is a schematic curve diagram illustrating an example of the performance when deploying a non-orthogonal NB signal adjacent to the edge PRB of an LTE signal. FIG. 19 is a schematic curve diagram illustrating an example of LTE PDSCH link-level performance of the proposed precoding method#1 in terms of normalized throughput versus SNR. FIG. 20 is a schematic block diagram illustrating an example of an arrangement, based on a processor-memory implementation according to an embodiment.

FIG. 21 is a schematic block diagram illustrating an example of a communication unit comprising an arrangement as described herein.

FIG. 22 is a schematic diagram illustrating an example of a computer-implementation according to an embodiment.

FIG. 23 is a schematic diagram illustrating an example of an apparatus for supporting inter-carrier interference cancellation in a wireless multi-carrier system.

FIG. 24 is a schematic diagram illustrating an example of a network device configured to support inter-carrier interference cancellation in a wireless multi-carrier system. FIG. 25 is a schematic diagram illustrating an example of a network infrastructure for supporting a wireless communication system.

DETAILED DESCRIPTION

Throughout the drawings, the same reference designations are used for similar or corresponding elements.

As used herein, the non-limiting terms "wireless communication device", "station", "User Equipment (UE)", and "terminal" may refer to a mobile phone, a cellular phone, a Personal Digital Assistant (PDA), equipped with radio communication capabilities, a smart phone, a laptop or Personal Computer (PC), equipped with an internal or external mobile broadband modem, a tablet with radio communication capabilities, a target device, a device to device UE, a machine type UE or UE capable of machine to machine communication, Customer Premises Equipment (CPE), Laptop Embedded Equipment (LEE), Laptop Mounted Equipment (LME), USB dongle, a portable electronic radio communication device, a sensor device equipped with radio communication capabilities or the like. In particular, the term "wireless communication device" should be interpreted as non-limiting terms comprising any type of wireless device communicating with a network node in a wireless communication system and/or possibly communicating directly with another wireless communication device. In other words, a wireless communication device may be any device equipped with circuitry for wireless communication according to any relevant standard for communication.

As used herein, the non-limiting term "network node" may refer to base stations, access points, network control nodes such as network controllers, radio network controllers, base station controllers, access controllers, and the like. In particular, the term "base station" may encompass different types of radio base stations including standardized base station functions such as Node Bs, or evolved Node Bs (eNBs), and also macro/micro/pico radio base stations, home base stations, also known as femto base stations, relay nodes, repeaters, radio access points, Base Transceiver Stations (BTSs), and even radio control nodes controlling one or more Remote Radio Units (RRUs), or the like. In the following, the general non-limiting term "communication unit" includes network nodes and/or associated wireless devices.

As used herein, the term "network device" may refer to any device located in connection with a communication network, including but not limited to devices in access networks, core networks and similar network structures. The term network device may also encompass cloud-based network devices.

As previously mentioned, it is desirable to improve the spectrum utilization in wireless multi-carrier systems and ensure efficient coexistence among multiple carrier waveforms sharing the spectrum.

In communications technology, a carrier may be defined as a carrier wave, carrier waveform or carrier signal, sometimes also simply referred to as a waveform, used for the purpose of conveying information, usually based on modulation and/or coding, or other forms of signal modification or processing. The carrier is generally characterized by a center frequency and a bandwidth, and is normally associated with a unique modulation, coding and/or sub-carrier spacing. FIG. 5 is a schematic flow diagram illustrating an example of a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system.

Basically, the method comprises the following steps: S1 : obtaining a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier; and

S2: performing, for the first carrier, precoding for inter-carrier interference cancellation by:

S22: precoding transmit symbols of the first carrier based on information representing inter-carrier interference of the second carrier relative to the first carrier, wherein the information representing inter-carrier interference of the second carrier relative to the first carrier is based on the time-domain carrier aggregation and information representing the first carrier. In this way, efficient spectrum utilization can be achieved in wireless multi-carrier systems. The proposed technology makes it possible to send multiple similar/dissimilar carrier waveforms closer together in frequency, while maintaining good performance. Efficient coexistence can be ensured, which not only optimizes the spectrum utilization but also improves the spectral efficiency.

The proposed technology is generally applicable to any multi-carrier system(s). However, the proposed technology is especially applicable for, but not limited to spectrally efficient co-existence among dissimilar or non-orthogonal systems, such as NX (with different subcarrier spacing) and LTE, LTE/NR and also non-LTE/non- NR systems, e.g. EC-GSM/GSM.

By way of example, the step of obtaining a time-domain carrier aggregation could imply generating an aggregated or composite carrier waveform or signal from at least two different carrier waveforms or signals. Alternatively, the step of obtaining a time- domain carrier aggregation could simply imply receiving such an aggregated or composite carrier waveform.

Taking a simple example to illustrate carrier-aggregation in time-domain per se. For example, assume there are two GSM signals and one LTE signal, and they all share the same radio and/or power amplifier, then these three signals could be aggregated in a given so-called Instantaneous Bandwidth (IBW) of, e.g., 40 MHz, supported by the given radio.

LTE signal has a different baseband sampling frequency (for 20 MHz LTE BW, say it is 30.72 MHz), while GSM (GMSK) signal has something like 270.833 KHz. If one wants to combine all these three signals in a given IBW (e.g., 40 MHz), then all these three signals should have a Nyquist sampling frequency according to the considered IBW (which is still in complex baseband). Accordingly, these signals are up-sampled (and thereby filtered to remove aliases) according to the desired sampling frequency meeting the Nyquist condition of the considered IBW, then each individual signal is allocated at the desired frequency; and thereafter all the signals are combined or summed.

In other words, a time-domain carrier aggregation of at least two different carriers can be seen as an aggregated or composite carrier waveform, where the at least two different carriers are combined in a selected Instantaneous Bandwidth to form the aggregated waveform.

Information representing Inter-Carrier Interference (ICI) could be the determined ICI or a representation thereof, as will be exemplified later on. Information representing a carrier could be the carrier waveform or signal or a suitable representation thereof, such as one or more (complex) symbols of the carrier, as will be exemplified later on.

Precoding generally implies some form of processing or coding of a considered signal, and can be for example be regarded as a multiplication of a signal vector x by a precoding matrix W. In a particular example, as will be outlined in detail later on, the proposed precoding involves subtracting ICI from (or equivalent^ adding a negated ICI to) the original transmit symbol. FIG. 6 is a schematic flow diagram illustrating another example of a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system.

In this particular example, the overall step of performing (S2), for the first carrier, precoding for inter-carrier interference cancellation optionally comprises the step (S21 ) of determining the information representing inter-carrier interference of the second carrier relative to the first carrier based on the time-domain carrier aggregation and the information representing the first carrier. By way of example, the step of performing (S2), for the first carrier, precoding for inter- carrier interference cancellation may be performed at least partly in the frequency domain. FIG. 7 is a schematic flow diagram illustrating yet another example of a method for enabling inter-carrier interference cancellation in a wireless multi-carrier system.

In this example, the step of determining (S21 ) information representing inter-carrier interference of the second carrier relative to the first carrier comprises:

- performing (S21 1 ) demodulation of at least part of the time-domain carrier aggregation with respect to the first carrier to obtain, per subcarrier, a demodulated complex symbol in the frequency domain;

estimating (S212), per subcarrier, inter-carrier interference based on subtracting a complex symbol of the first carrier from a corresponding demodulated complex symbol in the frequency domain.

In this example, the step of precoding (S22) transmit symbols of the first carrier comprises subtracting (S221 ), per subcarrier, the inter-carrier interference from the corresponding complex symbol of the first carrier to generate updated complex symbols of the first carrier in the frequency domain.

FIG. 8 is a schematic flow diagram illustrating an example of an extension of the method for enabling inter-carrier interference cancellation also for the second carrier. In this example, the method further comprises performing (S3), for the second carrier, precoding for inter-carrier interference cancellation by precoding (S32) transmit symbols of the second carrier based on information representing inter-carrier interference of the first carrier relative to the second carrier, wherein the information representing inter-carrier interference of the first carrier relative to the second carrier is based on the time-domain carrier aggregation and information representing the second carrier. Optionally, the step of performing (S3), for the second carrier, precoding for inter- carrier interference cancellation comprises the step (S31 ) of determining the information representing inter-carrier interference of the first carrier relative to the second carrier based on the time-domain carrier aggregation and the information representing the second carrier.

By way of example, the step of performing (S3), for the second carrier, precoding for inter-carrier interference cancellation is performed at least partly in the frequency domain.

FIG. 9 is a schematic flow diagram illustrating a particular example of an extension of the method for enabling inter-carrier interference cancellation also for the second carrier. In this example, the step of determining (S31 ) information representing inter-carrier interference of the first carrier relative to the second carrier comprises:

performing (S31 1 ) demodulation of at least part of the time-domain carrier aggregation with respect to the second carrier to obtain, per subcarrier, a demodulated complex symbol in the frequency domain;

- estimating (S312), per subcarrier, inter-carrier interference based on subtracting a complex symbol of the second carrier from a corresponding demodulated complex symbol in the frequency domain.

In this example, the step of precoding (S32) transmit symbols of the second carrier comprises subtracting (S321 ), per subcarrier, the inter-carrier interference from the corresponding complex symbol of the second carrier to generate updated complex symbols of the second carrier in the frequency domain.

The updated complex symbols may then be modulated to obtain discrete updated time-domain samples, as will be exemplified later on.

For example, the steps of performing (S2), for the first carrier, precoding for inter- carrier interference cancellation and performing (S3), for the second carrier, precoding for inter-carrier interference cancellation may be executed in parallel, successively and/or iteratively, as will be exemplified below.

It should also be understood that although the proposed technology is applicable to any set of different carriers, it may be used with benefit to eliminate or at least reduce inter-carrier interference between carriers of different radio access technologies. By way of example, the first carrier may be a carrier of a first radio access technology and the second carrier may be a carrier of a second, different radio access technology. For a better understanding, the proposed technology will now be described with reference to a number of non-limiting examples.

In a first aspect, the proposed technology may be seen as a way of determining information representing inter-carrier interference of a given carrier relative to another carrier to enable inter-carrier interference cancellation.

In another complementary aspect, the proposed technology may be regarded as a precoding technique adapted for ICI self-cancellation for multi-carrier RATs/systems sharing the spectrum and the same baseband and/or radio unit in order to utilize the spectrum efficiently and thereby maximize the spectral efficiency of the considered system or systems by suppressing ICI effectively.

For more information on the theoretical foundations of this type of precoding, reference can be made, e.g. to [1 ].

In a particular example, the precoding with respect to ICI self-cancellation may involve combining a pre-corrective complex symbol with the initial complex symbol to be transmitted such that the inter-carrier interference and/or inter-symbol interference rendered due to non-orthogonal multiple component carriers/RATs can be suppressed/mitigated effectively when combining/aggregating/bonding the multiple non-orthogonal component carriers. According to the proposed technology, there are numerous approaches to obtain a precoder that self-cancels ICI of interest herein. Some practical precoding variants for ICI self-cancellation include, but are not limited to, (a) parallel ICI self-cancellation based precoding, (b) serial ICI self-cancellation based precoding, (c) parallel with serial ICI self-cancellation.

The proposed technology makes it possible to send multiple similar/dissimilar waveforms closer together in frequency, while maintaining good performance. The proposed technology also enables maximization of the spectrum utilization efficiency and consequently the attainable cell/site throughput.

The proposed technology allows efficient coexistence among multiple waveforms sharing the spectrum which not only maximizes the spectrum utilization but also improves the spectral efficiency. Coexistence is one of the major challenges and the current focus of R&D across the industry due to the clearly important commercial implications.

The proposed technology also offers the possibility to maximize the peak data rate.

In the following, the proposed technology will be exemplified with reference to carriers of different RATs. The proposed technology is not limited thereto, but may be generally applied to any set of carriers. As mentioned previously, in order to share spectrum among two or more different RATs even though they are sharing the same baseband and/or radio unit, the general concept is to have some minimum frequency guard-band among the RATs to avoid penalizing the performance of each individual RAT - this frequency separation is apparently a waste of extremely expensive resource. In order to have optimal spectrum utilization for coexistence and sharing the same baseband and/or radio unit, it is desirable to have as small frequency guard-band between the RATs as possible (or even no frequency guard band), while still not penalizing the performance of each RAT.

In other words, there is provided a precoding technique for ICI self-cancellation in order to have efficient spectrum utilization among similar/different radio access technologies sharing the same baseband and/or radio unit and offer better coexistence among them without penalizing the vulnerable system performance.

In a particular example, it is proposed to use a precoding technique to the symbols to be transmitted by obtaining knowledge of the ICI due to adjacent non -orthogonal component carriers/RATs/systems sharing the spectrum and radio. The proposed precoding then performs ICI self-cancellation when combining/aggregating the waveforms which maximizes the spectrum utilization and also the spectral efficiency of the systems by suppressing ICI effectively.

There are numerous approaches to obtain a precoder that self-cancels ICI of interest herein. Two empirical/practical techniques to obtain precoding symbols include, but are not limited to.

Example - Method#1 : Two-step Precoding Approach

FIG. 10 is a schematic diagram illustrating an example of the use of a precoding concept to combat inter-carrier interference on a carrier of a first RAT due to a non- orthogonal adjacent carrier of a second RAT.

Below, the first RAT is simply referred to as "RATI " and the second RAT is simply referred to as "RAT2".

Precoding per considered RAT in this approach can be shown as a two-step approach exemplified in FIG. 10, for a RATI waveform (for example OFDM based LTE/NR signal) that coexists with another RAT2 waveform. In the computations below, RATI transmit symbols are precoded for ICI self- cancellation caused by RAT2 towards RATI : Step-1 : ICI computation (per sub-carrier)

An example of determining information representing inter-carrier interference may include one or more of the following: · Aggregate the multiple (non-orthogonal) carriers/waveforms in the time- domain within the supported aggregated bandwidth (either in baseband or radio unit). Note that the aggregate signal is a linear combination of the time- domain waveforms of RATI and RAT2.

• Perform OFDM demodulation of the aggregate signal as per the RATI numerology, i.e. , CP removal and performing FFT appropriately, and obtain the received complex symbols per subcarrier.

• Compute ICI at k-th subcarrier of RATI by subtracting the received complex symbol Y[k] with the original RATI complex symbols X[k] prior to carrier aggregation, i.e. , ICI[k] = Y[k] - X[k] . One could vectorize the set of the ICI symbols per OFDM symbol based on the energy of the computed ICI symbol.

If the energy of the ICI symbol is below some given threshold, then ignore the candidate ICI symbol from the list.

In the above example, information representing the first carrier may thus include the original RATI complex symbols X[k] .

FIG. 1 2 is a schematic diagram illustrating an example of the ICI computation, as described above, per antenna port. A transmitter today combines waveforms from internal source(s) , such as baseband units, before sending the composite waveform on air. Often these sources represent different RATs, but it can be different carriers and numerologies of the same RAT. The waveforms may be placed closer in frequency than what a standard might suggest to get specified performance. In this particular example, by demodulating at least parts of the aggregated or composite waveform before transmission, knowledge of how the close-in-frequency placement will cause errors to the transmitted symbols in the composite signal can be obtained. This knowledge can then be used to perform suitable compensation in a "reiterated" modulation process.

Step-2: Precoding transmit symbols for ICI self-cancellation

• After computing the set of ICI symbols for RATI , we simply propose the addition of negated ICI symbols to the original RATI symbols, i.e., X[k] =

X[k] - ICI [k] .

• Perform the OFDM modulation, i.e., IFFT and CP addition followed by appropriate spectrum shaping, utilizing updated RATI symbols X[k] . FIG. 1 3 is a schematic diagram illustrating an example of the precoding ICI self- cancellation, as described above, per antenna port.

Similarly, the RAT2 signal may, if desired, be precoded in parallel (as illustrated as an option in FIG. 1 0) and/or successively (as will be exemplified in FIG. 1 1 ). Thereafter, it is possible to re-aggregate the precoded RATI and RAT2 signals in the time-domain to suppress ICI effectively on the individual signals.

As indicated, the precoding of RATI and RAT2 waveforms can be performed successively and/or in parallel. In the following, an example of a successive scheme will be described with reference to FIG. 1 1 . The successive scheme can be regarded as an iterative approach, as will be discussed below. In addition, the successive or iterative scheme can optionally be performed in a parallel manner, as also illustrated in FIG. 1 1 . Example - Method#2: Successive (Iterative) Precoding Approach

FIG. 1 1 is a schematic diagram illustrating an example of the use of a precoding concept in a successive or iterative scheme to achieve even better performance according to an embodiment. As mentioned previously, there can be numerous approaches to obtain ICI symbols. FIG. 1 1 exemplifies an iterative or successive scheme to perform precoding on each RAT waveform. For RATI waveform, we perform the following iterations (corresponding to the top flow of FIG. 1 1 ) in order to perform precoding on RATI .

In the first iteration, iteration#1 , firstly perform the aforementioned method#1 precoding on RAT2 and aggregate the RATI and precoded RAT2 signals in the time- domain.

In the second iteration, iteration#2, perform the method#1 precoding on RATI .

The same methodology may be performed on RAT2 in parallel (corresponding to the bottom flow of FIG. 1 1 ); and thereafter both precoded signals may be aggregated in the time domain.

It is worth to highlight that this precoding framework can be employed with any spectrum shaping techniques (e.g., filtering, windowing, etc.). On the other hand, employing this proposed precoding technique to other systems like WCDMA involve some approximations which would render suboptimal solution, but the negative impact of ICI can still be combated without penalizing the performance significantly of such vulnerable system. In general, OFDM/multi-carrier based waveforms are known to be susceptible to non-linear RF distortions causing both in-band and out-of-band distortions. In practice, linearization techniques (e.g., digital pre-distortion methods, feed-forward, etc.) are widely employed in order to linearize the non-linear RF distortions (mainly emanating from power amplifiers) and thereby minimize both in-band and out-of- band distortions on (aggregated) waveforms. Nonetheless, the proposed precoding methods are expected to harvest the gain by minimizing the ICI with or without any linearization techniques. For a better understanding of a possible use-case context, reference can be made to the schematic block diagrams of FIG. 14 and FIG. 1 5. Together, the block diagrams of FIG. 14 and FIG. 15 illustrate an example of the overall signal processing of transport blocks all the way to antenna transmission. In this example, the signal processing includes channel encoding, scrambling, modulation mapper, layer mapper, precoding for layer-to-logical antenna port-to physical antenna port mapping, resource element mapper, OFDM modulation and carrier aggregation and the novel proposed precoding for self-ICI cancellation and the radio processing for transmission via a set of one or more antennas and/or antenna elements.

By way of example, this may correspond to LTE PDSCH processing as RATI processing with the addition of the proposed precoding for self-ICI cancellation, and with another RAT such as OFDM-based 5G-NR as RAT2. In the following some numerical results will be presented to show the efficacy of the proposed precoding scheme for better coexistence.

The Power Spectrum Density (PSD) of RATI is 4 dB higher than RAT2. Both RATs are not spectrum shaped (no filtering/windowing). RATI is an OFDM signal having LTE numerology, i.e., 15 KHz subcarrier spacing. RAT2 is an OFDM signal having 3.75 KHz subcarrier spacing.

FIG. 16B is a schematic curve diagram illustrating the signal-to-ICI power for both RATs before and after precoding for both method#1 and method#2. As can easily be construed from FIG. 16B, the gain in terms of reduction of ICI power is more than 12 dB and 20 dB due to the proposed precoding method#1 and method#2, respectively. FIG. 17A is a schematic curve diagram illustrating an example where a 6dB PSD boosted narrowband RAT2 (OFDM signal with 3.75 KHz subcarrier spacing) in the guard-band of RATI (OFDM signal with 15 KHz subcarrier spacing). FIG. 17B is a schematic curve diagram illustrating the signal-to-ICI power for both RATI and RAT2 before and after precoding for both methods. As can easily be construed from FIG. 17B, method#1 and method#2 have similar performance on RATI , which is more than 20 dB reduction in ICI power. For RAT2, method#2 renders better performance gain in terms of reduction of ICI power than method#1 . However, RAT2 power was boosted so signal-to-ICI power was already quite high before and after precoding for method#1 itself.

FIG. 18 is a schematic diagram illustrating an example of the performance when deploying a non-orthogonal NB signal adjacent to the edge PRB of an LTE signal. This example depicts the considered system model to evaluate the impact of non- orthogonal NB interferer (filtered OFDM system with 3.75 KHz subcarrier spacing) on the LTE-FDD link-level performance, where the 12 dB PSD boosted NB interferer having 180 KHz bandwidth is placed right next to the edge PRB of LTE 10 MHz - full 50 PRB allocation. The considered test scenario to evaluate LTE-FDD PDSCH link- level performance is 2x2 MIMO with open-loop spatial multiplexing scheme, 64QAM modulation with 0.8 coding-rate, EPA5 propagation channel, HARQ enabled and considering 3% TX-EVM.

FIG. 19 is a schematic curve diagram showing the corresponding performance in terms of throughput versus SNR. As evident from the simulation, without any precoding technique, the LTE performance is extremely poor, with the high ICI causing the poor performance. An example of the proposed precoding method (herein method#1 is employed) renders nearly ICI-free signal and thereby the performance of the proposed method is as good as the reference LTE signal.

It will be appreciated that the methods and arrangements described herein can be implemented, combined and re-arranged in a variety of ways. For example, embodiments may be implemented in hardware, or in software for execution by suitable processing circuitry, or a combination thereof.

The steps, functions, procedures, modules and/or blocks described herein may be implemented in hardware using any conventional technology, such as discrete circuit or integrated circuit technology, including both general-purpose electronic circuitry and application-specific circuitry.

Alternatively, or as a complement, at least some of the steps, functions, procedures, modules and/or blocks described herein may be implemented in software such as a computer program for execution by suitable processing circuitry such as one or more processors or processing units.

Examples of processing circuitry includes, but is not limited to, one or more microprocessors, one or more Digital Signal Processors (DSPs), one or more Central Processing Units (CPUs), video acceleration hardware, and/or any suitable programmable logic circuitry such as one or more Field Programmable Gate Arrays (FPGAs), or one or more Programmable Logic Controllers (PLCs). It should also be understood that it may be possible to re-use the general processing capabilities of any conventional device or unit in which the proposed technology is implemented. It may also be possible to re-use existing software, e.g. by reprogramming of the existing software or by adding new software components. According to an aspect of the proposed technology there is provided an arrangement configured to enable inter-carrier interference cancellation in a wireless multi-carrier system. The arrangement is configured to obtain a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier. The arrangement is also configured to perform, for the first carrier, precoding for inter-carrier interference cancellation by a) determining, based on the time-domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier, and b) precoding transmit symbols of the first carrier based on the determined information representing inter-carrier interference of the second carrier relative to the first carrier.

By way of example, the arrangement is configured to determine information representing inter-carrier interference of the second carrier relative to the first carrier and precode transmit symbols of the first carrier at least partly in the frequency domain. In a particular example, the arrangement is configured to determine information representing inter-carrier interference of the second carrier relative to the first carrier by a) performing demodulation of at least part of the time-domain carrier aggregation with respect to the first carrier to obtain, per subcarrier, a demodulated complex symbol in the frequency domain, and b) estimating, per subcarrier, inter-carrier interference based on subtracting a complex symbol of the first carrier from a corresponding demodulated complex symbol in the frequency domain .

In this example, the arrangement is further configured to precode transmit symbols of the first carrier by subtracting, per subcarrier, the inter-carrier interference from the corresponding complex symbol of the first carrier to generate updated complex symbols of the first carrier in the frequency domain.

Optionally, the arrangement may be configured to perform, for the second carrier, precoding for inter-carrier interference cancellation by a) determining, based on the time-domain carrier aggregation and information representing the second carrier, information representing inter-carrier interference of the first carrier relative to the second carrier, and b) precoding transmit symbols of the second carrier based on the determined information representing inter-carrier interference of the first carrier relative to the second carrier.

As an example, the arrangement is configured to determine information representing inter-carrier interference of the first carrier relative to the second carrier and precode transmit symbols of the second carrier at least partly in the frequency domain. In a particular example, the arrangement is configured to determine information representing inter-carrier interference of the first carrier relative to the second carrier by a) performing demodulation of at least part of the time-domain carrier aggregation with respect to the second carrier to obtain, per subcarrier, a demodulated complex symbol in the frequency domain, and b) estimating, per subcarrier, inter-carrier interference based on subtracting a complex symbol of the second carrier from a corresponding demodulated complex symbol in the frequency domain.

In this example, the arrangement is further configured to precode transmit symbols of the second carrier by subtracting, per subcarrier, the inter-carrier interference from the corresponding complex symbol of the second carrier to generate updated complex symbols of the second carrier in the frequency domain.

Preferably, the arrangement may also be configured to modulate the updated complex symbols to obtain discrete updated time-domain samples.

By way of example, the arrangement may be configured to perform, for the first carrier, precoding for inter-carrier interference cancellation and perform, for the second carrier, precoding for inter-carrier interference cancellation in parallel, successively and/or iteratively.

As previously mentioned, the proposed technology may be well suited for use with carriers of different radio access technologies. For example, the first carrier may be a carrier of a first radio access technology and the second carrier may be a carrier of a second, different radio access technology.

FIG. 20 is a schematic block diagram illustrating an example of an arrangement 100, based on a processor-memory implementation according to an embodiment. In this particular example, the arrangement 100 comprises at least one processor 1 10 and memory 120, the memory 120 comprising instructions, which when executed by the at least one processor (1 10), cause the at least one processor (1 10) to enable inter- carrier interference cancellation. Optionally, the arrangement/system 100 may also include a communication circuit 130. The communication circuit 130 may include functions for wired and/or wireless communication with other devices and/or network nodes in the network. In a particular example, the communication circuit 130 may be based on radio circuitry for communication with one or more other nodes, including transmitting and/or receiving information. The communication circuit 130 may be interconnected to the processor 1 10 and/or memory 120. By way of example, the communication circuit 130 may include any of the following: a receiver, a transmitter, a transceiver, input/output (I/O) circuitry, input port(s) and/or output port(s).

It is also possible to provide a solution based on a combination of hardware and software. The actual hardware-software partitioning can be decided by a system designer based on a number of factors including processing speed, cost of implementation and other requirements.

FIG. 21 is a schematic block diagram illustrating an example of a communication unit 200 comprising an arrangement 100 as described herein.

For example, the communication unit 200 may be a network node 210 or a wireless communication device 220.

FIG. 22 is a schematic diagram illustrating an example of a computer-implementation 400 according to an embodiment. In this particular example, at least some of the steps, functions, procedures, modules and/or blocks described herein are implemented in a computer program 425; 435, which is loaded into the memory 420 for execution by processing circuitry including one or more processors 410. The processor(s) 410 and memory 420 are interconnected to each other to enable normal software execution. An optional input/output device 440 may also be interconnected to the processor(s) 410 and/or the memory 420 to enable input and/or output of relevant data such as input parameter(s) and/or resulting output parameter(s). The term 'processor' should be interpreted in a general sense as any system or device capable of executing program code or computer program instructions to perform a particular processing, determining or computing task. The processing circuitry including one or more processors 410 is thus configured to perform, when executing the computer program 425, well-defined processing tasks such as those described herein.

The processing circuitry does not have to be dedicated to only execute the above- described steps, functions, procedure and/or blocks, but may also execute other tasks.

In a particular embodiment, there is provided a computer program 425; 435 for supporting, when executed by a processor 410, inter-carrier interference cancellation in a wireless multi-carrier system. The computer program comprises instructions, which when executed by the processor 410, causes the processor 410 to:

In a particular example, the computer program further comprises instructions, which when executed by the processor 410, causes the processor 410 to precode transmit symbols of the first carrier based on the determined information representing inter- carrier interference of the second carrier relative to the first carrier.

The proposed technology also provides a carrier comprising the computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium. By way of example, the software or computer program 425; 435 may be realized as a computer program product, which is normally carried or stored on a computer-readable medium 420; 430, in particular a non-volatile medium. The computer-readable medium may include one or more removable or non-removable memory devices including, but not limited to a Read-Only Memory (ROM), a Random Access Memory (RAM), a Compact Disc (CD), a Digital Versatile Disc (DVD), a Blu-ray disc, a Universal Serial Bus (USB) memory, a Hard Disk Drive (HDD) storage device, a flash memory, a magnetic tape, or any other conventional memory device. The computer program may thus be loaded into the operating memory of a computer or equivalent processing device for execution by the processing circuitry thereof.

The flow diagram or diagrams presented herein may be regarded as a computer flow diagram or diagrams, when performed by one or more processors. A corresponding apparatus may be defined as a group of function modules, where each step performed by the processor corresponds to a function module. In this case, the function modules are implemented as a computer program running on the processor.

The computer program residing in memory may thus be organized as appropriate function modules configured to perform, when executed by the processor, at least part of the steps and/or tasks described herein.

FIG. 23 is a schematic diagram illustrating an example of an apparatus 500 for supporting inter-carrier interference cancellation in a wireless multi-carrier system. The apparatus 500 comprises an input module 510 for obtaining a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier. The apparatus also comprises a determination module 520 for determining, based on the time-domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier to enable inter- carrier interference cancellation.

In a particular example, the apparatus 500 further comprises an optional precoding module 530 for precoding transmit symbols of the first carrier based on the determined information representing inter-carrier interference of the second carrier relative to the first carrier.

Alternatively it is possible to realize the module(s) in FIG. 23 predominantly by hardware modules, or alternatively by hardware, with suitable interconnections between relevant modules. Particular examples include one or more suitably configured digital signal processors and other known electronic circuits, e.g. discrete logic gates interconnected to perform a specialized function, and/or Application Specific Integrated Circuits (ASICs) as previously mentioned. Other examples of usable hardware include input/output (I/O) circuitry and/or circuitry for receiving and/or sending signals. The extent of software versus hardware is purely implementation selection.

According to yet another aspect, at least part of the proposed technology is implemented in a network device. The network device may be any suitable network device in the wireless communication system, or a network device in connection with the wireless communication system. By way of example, the network device may be a suitable network node such a base station or an access point. However, the network device may alternatively be a cloud-implemented network device.

By way of example, there is provided a network device configured to support inter- carrier interference cancellation in a wireless multi-carrier system. The network device may be configured to obtain a time-domain carrier aggregation involving at least two different carriers, wherein the at least two different carriers include a first carrier and a second carrier. The network device may also be configured to determine, based on the time-domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier to enable inter-carrier interference cancellation. For example, the network device may be configured to precode transmit symbols of the first carrier based on the determined information representing inter-carrier interference of the second carrier relative to the first carrier. FIG. 24 is a schematic diagram illustrating an example of a network device configured to support inter-carrier interference cancellation in a wireless multi-carrier system. In the example of FIG. 24, the network device 300 comprises at least one processor 310 and memory 320, the memory 320 comprising instructions, which when executed by the at least one processor 310, cause the at least one processor 310 to enable inter- carrier interference cancellation.

For example, the network device 300 may be a network node or a cloud-based network device.

FIG. 25 is a schematic diagram illustrating an example of a network infrastructure for supporting a wireless communication system, including a radio access network 610 and/or a core network 620 and/or an Operations and Support System (OSS), 630 and/or a cloud-based network environment 640.

In the example of FIG. 14, the network device 300 may be provided for location in the radio access network 610, the core network 620, the OSS system 630 and/or the cloud-based network environment 640, with suitable transfer of information to support inter-carrier interference cancellation.

It is becoming increasingly popular to provide computing services (hardware and/or software) in network devices such as network nodes and/or servers where the resources are delivered as a service to remote locations over a network. By way of example, this means that functionality, as described herein, can be distributed or re- located to one or more separate physical nodes or servers. The functionality may be re-located or distributed to one or more jointly acting physical and/or virtual machines that can be positioned in separate physical node(s), i.e. in the so-called cloud. This is sometimes also referred to as cloud computing, which is a model for enabling ubiquitous on-demand network access to a pool of configurable computing resources such as networks, servers, storage, applications and general or customized services.

There are different forms of virtualization that can be useful in this context, including one or more of: • Consolidation of network functionality into virtualized software running on customized or generic hardware. This is sometimes referred to as network function virtualization.

• Co-location of one or more application stacks, including operating system, running on separate hardware onto a single hardware platform. This is sometimes referred to as system virtualization, or platform virtualization. · Co-location of hardware and/or software resources with the objective of using some advanced domain level scheduling and coordination technique to gain increased system resource utilization. This is sometimes referred to as resource virtualization, or centralized and coordinated resource pooling. Although it may often desirable to centralize functionality in so-called generic data centers, in other scenarios it may in fact be beneficial to distribute functionality over different parts of the network.

A Network Device (ND) may generally be seen as an electronic device being communicatively connected to other electronic devices in the network.

By way of example, the network device may be implemented in hardware, software or a combination thereof. For example, the network device may be a special-purpose network device or a general purpose network device, or a hybrid thereof.

A special-purpose network device may use custom processing circuits and a proprietary operating system (OS), for execution of software to provide one or more of the features or functions disclosed herein. A general purpose network device may use common off-the-shelf (COTS) processors and a standard OS, for execution of software configured to provide one or more of the features or functions disclosed herein. By way of example, a special-purpose network device may include hardware comprising processing or computing resource(s), which typically include a set of one or more processors, and physical network interfaces (Nls), which sometimes are called physical ports, as well as non-transitory machine readable storage media having stored thereon software. A physical Nl may be seen as hardware in a network device through which a network connection is made, e.g. wirelessly through a wireless network interface controller (WNIC) or through plugging in a cable to a physical port connected to a network interface controller (NIC). During operation, the software may be executed by the hardware to instantiate a set of one or more software instance(s). Each of the software instance(s), and that part of the hardware that executes that software instance, may form a separate virtual network element.

By way of another example, a general purpose network device may for example include hardware comprising a set of one or more processor(s), often COTS processors, and network interface controller(s) (NICs), as well as non-transitory machine readable storage media having stored thereon software. During operation, the processor(s) executes the software to instantiate one or more sets of one or more applications. While one embodiment does not implement virtualization, alternative embodiments may use different forms of virtualization - for example represented by a virtualization layer and software containers. For example, one such alternative embodiment implements operating system-level virtualization, in which case the virtualization layer represents the kernel of an operating system (or a shim executing on a base operating system) that allows for the creation of multiple software containers that may each be used to execute one of a sets of applications. In an example embodiment, each of the software containers (also called virtualization engines, virtual private servers, or jails) is a user space instance (typically a virtual memory space). These user space instances may be separate from each other and separate from the kernel space in which the operating system is executed; the set of applications running in a given user space, unless explicitly allowed, cannot access the memory of the other processes. Another such alternative embodiment implements full virtualization, in which case: 1 ) the virtualization layer represents a hypervisor (sometimes referred to as a Virtual Machine Monitor (VMM)) or the hypervisor is executed on top of a host operating system; and 2) the software containers each represent a tightly isolated form of software container called a virtual machine that is executed by the hypervisor and may include a guest operating system.

A hypervisor is the software/hardware that is responsible for creating and managing the various virtualized instances and in some cases the actual physical hardware. The hypervisor manages the underlying resources and presents them as virtualized instances. What the hypervisor virtualizes to appear as a single processor may actually comprise multiple separate processors. From the perspective of the operating system, the virtualized instances appear to be actual hardware components.

A virtual machine is a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine; and applications generally do not know they are running on a virtual machine as opposed to running on a "bare metal" host electronic device, though some systems provide para-virtualization which allows an operating system or application to be aware of the presence of virtualization for optimization purposes.

The instantiation of the one or more sets of one or more applications as well as the virtualization layer and software containers if implemented, are collectively referred to as software instance(s). Each set of applications, corresponding software container if implemented, and that part of the hardware that executes them (be it hardware dedicated to that execution and/or time slices of hardware temporally shared by software containers), forms a separate virtual network element(s). The virtual network element(s) may perform similar functionality compared to Virtual Network Element(s) (VNEs). This virtualization of the hardware is sometimes referred to as Network Function Virtualization (NFV)). Thus, NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which could be located in data centers, NDs, and Customer Premise Equipment (CPE). However, different embodiments may implement one or more of the software container(s) differently. For example, while embodiments are illustrated with each software container corresponding to a VNE, alternative embodiments may implement this correspondence or mapping between software container-VNE at a finer granularity level; it should be understood that the techniques described herein with reference to a correspondence of software containers to VNEs also apply to embodiments where such a finer level of granularity is used.

According to yet another embodiment, there is provided a hybrid network device, which includes both custom processing circuitry/proprietary OS and COTS processors/standard OS in a network device, e.g. in a card or circuit board within a network device ND. In certain embodiments of such a hybrid network device, a platform Virtual Machine (VM), such as a VM that implements functionality of a special- purpose network device, could provide for para-virtualization to the hardware present in the hybrid network device.

The embodiments described above are merely given as examples, and it should be understood that the proposed technology is not limited thereto. It will be understood by those skilled in the art that various modifications, combinations and changes may be made to the embodiments without departing from the present scope as defined by the appended claims. In particular, different part solutions in the different embodiments can be combined in other configurations, where technically possible.

REFERENCES

[1 ] Writing on Dirty Paper, by Max H.M. Costa, IEEE Transactions on information Theory, Vol. IT-29, NO. 3, May 1983

Claims

1 . A method for enabling inter-carrier interference cancellation in a wireless multi- carrier system, wherein the method comprises:

- obtaining (S1 ) a time-domain carrier aggregation involving at least two different carriers, wherein said at least two different carriers include a first carrier and a second carrier; and

performing (S2), for the first carrier, precoding for inter-carrier interference cancellation by precoding (S22) transmit symbols of the first carrier based on information representing inter-carrier interference of the second carrier relative to the first carrier, wherein the information representing inter-carrier interference of the second carrier relative to the first carrier is based on the time-domain carrier aggregation and information representing the first carrier.

2. The method of claim 1 , wherein the step of performing (S2), for the first carrier, precoding for inter-carrier interference cancellation is performed at least partly in the frequency domain.

3. The method of claim 1 or 2, wherein the step of performing (S2), for the first carrier, precoding for inter-carrier interference cancellation further comprises the step (S21 ) of determining the information representing inter-carrier interference of the second carrier relative to the first carrier based on the time-domain carrier aggregation and the information representing the first carrier.

4. The method of claim 3, wherein the step of determining (S21 ) information representing inter-carrier interference of the second carrier relative to the first carrier comprises:

performing (S21 1 ) demodulation of at least part of the time-domain carrier aggregation with respect to the first carrier to obtain, per subcarrier, a demodulated complex symbol in the frequency domain;

estimating (S212), per subcarrier, inter-carrier interference based on subtracting a complex symbol of the first carrier from a corresponding demodulated complex symbol in the frequency domain; and wherein the step of precoding (S22) transmit symbols of the first carrier comprises subtracting (S221 ), per subcarrier, the inter-carrier interference from the corresponding complex symbol of the first carrier to generate updated complex symbols of the first carrier in the frequency domain.

5. The method of any of the claims 1 to 4, wherein the method further comprises performing (S3), for the second carrier, precoding for inter-carrier interference cancellation by precoding (S32) transmit symbols of the second carrier based on information representing inter-carrier interference of the first carrier relative to the second carrier, wherein the information representing inter-carrier interference of the first carrier relative to the second carrier is based on the time-domain carrier aggregation and information representing the second carrier.

6. The method of claim 5, wherein the step of performing (S3), for the second carrier, precoding for inter-carrier interference cancellation is performed at least partly in the frequency domain.

7. The method of claim 5 or 6, wherein the step of performing (S3), for the second carrier, precoding for inter-carrier interference cancellation comprises the step (S31 ) of determining the information representing inter-carrier interference of the first carrier relative to the second carrier based on the time-domain carrier aggregation and the information representing the second carrier.

8. The method of claim 7, wherein the step of determining (S31 ) information representing inter-carrier interference of the first carrier relative to the second carrier comprises:

- estimating (S312), per subcarrier, inter-carrier interference based on subtracting a complex symbol of the second carrier from a corresponding demodulated complex symbol in the frequency domain; and wherein the step of precoding (S32) transmit symbols of the second carrier comprises subtracting (S321 ), per subcarrier, the inter-carrier interference from the corresponding complex symbol of the second carrier to generate updated complex symbols of the second carrier in the frequency domain.

9. The method of claim 4 or 8, wherein the updated complex symbols are modulated to obtain discrete updated time-domain samples.

10. The method of any of the claims 5 to 9, wherein the steps of performing (S2), for the first carrier, precoding for inter-carrier interference cancellation and performing

(S3), for the second carrier, precoding for inter-carrier interference cancellation are executed in parallel, successively and/or iteratively.

1 1 . The method of any of the claims 1 to 10, wherein the first carrier is a carrier of a first radio access technology and the second carrier is a carrier of a second, different radio access technology.

12. An arrangement (100) configured to enable inter-carrier interference cancellation in a wireless multi-carrier system,

wherein the arrangement (100) is configured to obtain a time-domain carrier aggregation involving at least two different carriers, wherein said at least two different carriers include a first carrier and a second carrier; and

wherein the arrangement (100) is configured to perform, for the first carrier, precoding for inter-carrier interference cancellation by determining, based on the time- domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier, and precoding transmit symbols of the first carrier based on the determined information representing inter-carrier interference of the second carrier relative to the first carrier.

13. The arrangement of claim 12, wherein the arrangement (100) is configured to determine information representing inter-carrier interference of the second carrier relative to the first carrier and precode transmit symbols of the first carrier at least partly in the frequency domain.

14. The arrangement of claim 12 or 13, wherein the arrangement (100) is configured to determine information representing inter-carrier interference of the second carrier relative to the first carrier by performing demodulation of at least part of the time- domain carrier aggregation with respect to the first carrier to obtain, per subcarrier, a demodulated complex symbol in the frequency domain, and estimating, per subcarrier, inter-carrier interference based on subtracting a complex symbol of the first carrier from a corresponding demodulated complex symbol in the frequency domain, and wherein the arrangement (100) is configured to precode transmit symbols of the first carrier by subtracting, per subcarrier, the inter-carrier interference from the corresponding complex symbol of the first carrier to generate updated complex symbols of the first carrier in the frequency domain.

15. The arrangement of any of the claims 12 to 14, wherein the arrangement (100) is configured to perform, for the second carrier, precoding for inter-carrier interference cancellation by determining, based on the time-domain carrier aggregation and information representing the second carrier, information representing inter-carrier interference of the first carrier relative to the second carrier, and precoding transmit symbols of the second carrier based on the determined information representing inter- carrier interference of the first carrier relative to the second carrier.

16. The arrangement of claim 15, wherein the arrangement (100) is configured to determine information representing inter-carrier interference of the first carrier relative to the second carrier and precode transmit symbols of the second carrier at least partly in the frequency domain.

17. The arrangement of claim 15 or 16, wherein the arrangement (100) is configured to determine information representing inter-carrier interference of the first carrier relative to the second carrier by performing demodulation of at least part of the time- domain carrier aggregation with respect to the second carrier to obtain, per subcarrier, a demodulated complex symbol in the frequency domain, and estimating, per subcarrier, inter-carrier interference based on subtracting a complex symbol of the second carrier from a corresponding demodulated complex symbol in the frequency domain, and

wherein the arrangement (100) is configured to precode transmit symbols of the 5 second carrier by subtracting, per subcarrier, the inter-carrier interference from the corresponding complex symbol of the second carrier to generate updated complex symbols of the second carrier in the frequency domain.

18. The arrangement of claim 14 or 17, wherein the arrangement (100) is configured 10 to modulate the updated complex symbols to obtain discrete updated time-domain samples.

19. The arrangement of any of the claims 15 to 18, wherein the arrangement (100) is configured to perform, for the first carrier, precoding for inter-carrier interference

15 cancellation and perform, for the second carrier, precoding for inter-carrier interference cancellation in parallel, successively and/or iteratively.

20. The arrangement of any of the claims 12 to 19, wherein the first carrier is a carrier of a first radio access technology and the second carrier is a carrier of a second,

20 different radio access technology.

21 . The arrangement of any of the claims 12 to 20, wherein the arrangement (100) comprises at least one processor (1 10) and memory (120), the memory (120) comprising instructions, which when executed by the at least one processor (1 10),

25 cause the at least one processor (1 10) to enable inter-carrier interference cancellation.

22. A communication unit (200) comprising the arrangement (100) of any of the claims 12 to 21 .

30 23. The communication unit of claim 22, wherein the communication unit (200) is a network node (210) or a wireless communication device (220).

24. A network device (300) configured to support inter-carrier interference cancellation in a wireless multi-carrier system, wherein the network device (300) is configured to obtain a time-domain carrier aggregation involving at least two different carriers, wherein said at least two different carriers include a first carrier and a second carrier; and

wherein the network device (300) is configured to determine, based on the time- domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier to enable inter-carrier interference cancellation.

25. The network device of claim 24, wherein the network device (300) is configured to precode transmit symbols of the first carrier based on the determined information representing inter-carrier interference of the second carrier relative to the first carrier.

26. The network device of claim 24 or 25, wherein the network device (300) comprises at least one processor (310) and memory (320), the memory (320) comprising instructions, which when executed by the at least one processor (310), cause the at least one processor (310) to enable inter-carrier interference cancellation.

27. The network device of any of the claims 24 to 26, wherein the network device (300) is a network node or a cloud-based network device.

28. A computer program (425; 435) for supporting, when executed by a processor (410), inter-carrier interference cancellation in a wireless multi-carrier system, wherein the computer program comprises instructions, which when executed by the processor (410), causes the processor (410) to:

- obtain a time-domain carrier aggregation involving at least two different carriers, wherein said at least two different carriers include a first carrier and a second carrier; and

29. The computer program of claim 28, wherein the computer program further comprises instructions, which when executed by the processor (410), causes the processor (410) to precode transmit symbols of the first carrier based on the determined information representing inter-carrier interference of the second carrier

5 relative to the first carrier.

30. A computer-program product comprising a computer-readable medium (420; 430) having stored thereon a computer program (425; 435) of claim 28 or 29.

10 31 . An apparatus (500) for supporting inter-carrier interference cancellation in a wireless multi-carrier system, wherein the apparatus comprises:

an input module (510) for obtaining a time-domain carrier aggregation involving at least two different carriers, wherein said at least two different carriers include a first carrier and a second carrier; and

15 - a determination module (520) for determining, based on the time-domain carrier aggregation and information representing the first carrier, information representing inter-carrier interference of the second carrier relative to the first carrier to enable inter-carrier interference cancellation.

20 32. The apparatus of claim 31 , wherein the apparatus (500) further comprises a precoding module (530) for precoding transmit symbols of the first carrier based on the determined information representing inter-carrier interference of the second carrier relative to the first carrier.

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