WO2019137601A1

WO2019137601A1 - Network access node and methods thereof

Info

Publication number: WO2019137601A1
Application number: PCT/EP2018/050473
Authority: WO
Inventors: Bengt Lindoff; Wenquan HU; Stefan Recknagel
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2018-01-09
Filing date: 2018-01-09
Publication date: 2019-07-18

Abstract

The invention relates to a network access node (100) for a wireless communication system (500). The network access node (100) selects a first centre frequency resource for a set of symbols to be transmitted to a client device (300), wherein the first centre frequency resource is frequency offset in relation to a modulation frequency resource of the network access node (100) and selected such that a resulting phase shift between two consecutive symbols of the set of symbols when modulated with a modulation frequency corresponding to the modulation frequency resource and demodulated at a first centre frequency corresponding to the first centre frequency resource is less than a threshold value. The network access node (100) further modulates the set of symbols with the modulation frequency so as to obtain a set of modulation symbols and transmits the set of modulation symbols around the first centre frequency to a client device (300). Furthermore, the invention also relates to corresponding methods and a computer program.

Description

NETWORK ACCESS NODE AND METHODS THEREOF

Technical Field

The invention relates to a network access node. Furthermore, the invention also relates to corresponding methods and a computer program.

Background

The 5G wireless communication system, also called new radio (NR), is currently being standardized. NR is targeting radio spectrum from below 1 GHz up to and above 60 GHz. To allow for such diverse radio environments not only different system bandwidths will be supported, but also different numerologies, such as different subcarrier-spacings (SCS).

When a user equipment (UE) is switched on in a wireless communication system an initial cell search is performed to find a cell to connect to. During the initial cell search the UE will search for synchronisation signal blocks (SSBs) by scanning potential carrier frequencies. In NR, the system bandwidth may be up to 100-200 MHz, compared to 20 MHz in Long Term Evolution (LTE). Furthermore, there may be multiple SSBs in the system bandwidth of a NR base station.

Summary

An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the present invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a network access node for a wireless communication system, the network access node being configured to

select a first centre frequency resource for a set of symbols to be transmitted to a client device, wherein the first centre frequency resource is frequency offset in relation to a modulation frequency resource of the network access node and selected such that a resulting phase shift between two consecutive symbols of the set of symbols when modulated with a modulation frequency corresponding to the modulation frequency resource and demodulated at a first centre frequency corresponding to the first centre frequency resource is less than a threshold value; modulate the set of symbols with the modulation frequency so as to obtain a set of modulation symbols;

transmit the set of modulation symbols around the first centre frequency to a client device.

The first centre frequency resource can in this disclosure be understood to mean a subcarrier or a subband, e.g. selected by a baseband processor, which results in the first centre frequency after modulation. Furthermore, a modulation frequency resource can in this disclosure be understood to mean a subcarrier or subband, whose frequency is equal to the centre frequency of the frequency range or corresponding system bandwidth of the network access node.

An advantage of the network access node according to the first aspect is that the set of modulation symbols transmitted to the client device can be demodulated by the client device without having to perform phase shift compensation. Thereby, the implementation of the client device can be made simpler.

In an implementation form of a network access node according to the first aspect, the network access node is further configured to

modulate and up-convert the set of symbols to a carrier frequency fo being the modulation frequency so as to obtain the set of modulation symbols.

An advantage with this implementation form is that the network access node transmits information using its own modulation frequency, thereby simplifying the implementation in the network access node.

transmit the set of modulation symbols in a first frequency range centred around the first centre frequency.

An advantage with this implementation form is that information transmitted from the network access node to the client device is within the receiver bandwidth of the client device, hence the client device can demodulate and decode all the transmitted information.

In an implementation form of a network access node according to the first aspect, the first frequency range is a bandwidth part configured for the client device. An advantage with this implementation form is that the client device can derive the first frequency range from the configured bandwidth part. Thereby, a method with low complexity is provided for determining the first frequency range.

In an implementation form of a network access node according to the first aspect, the first frequency range is associated with at least one of synchronization signal block, remaining system information, and other system information.

An advantage with this implementation form is that the client device knows where the synchronization signal block, the remaining system information and other system information are within the system bandwidth of the network access node.

In an implementation form of a network access node according to the first aspect, the set of modulation symbols comprises at least one of a synchronization signal block, a CORESET of remaining system information, a CORESET of other system information, and a CORESET of a bandwidth part configured for the client device.

An advantage with this implementation form is that these are control channels which the client device has to monitor in order to be able to detect a cell and decode system information associated with the cell, or to monitor for determination of dedicated data to the client device.

select the first centre frequency based on at least one of a cyclic prefix length, a subcarrier spacing, and a chip duration of symbols of the set of modulation symbols.

An advantage with this implementation form is that the network access node can select a first centre frequency such that a desired negligible phase shift between symbols can be achieved.

In an implementation form of a network access node according to the first aspect, the threshold value is dependent on N number of symbols in the set of modulation symbols.

An advantage with this implementation form is that the network access node can select a first centre frequency such that a desired negligible phase shift between symbols can be achieved. In an implementation form of a network access node according to the first aspect, the threshold value is dependent on N number of symbols in the set of modulation symbols and total phase shift p over symbols of the set of modulation symbols.

The total phase shift p over symbols of the set of modulation symbols gives a measure of allowed phase shift and may for instance be 45 degrees.

An advantage with this implementation form is that the network access node can select a threshold value which gives a phase shift at the client device between adjacent symbols of the set of modulation symbols which is small enough to be neglectable.

In an implementation form of a network access node according to the first aspect, the threshold value is given as p/N.

An advantage with this implementation form is that the network access node can select a threshold value which gives a phase shift between adjacent symbols of the set of modulation symbols which is small enough to be neglectable. Furthermore, in this implementation form a closed form expression is given.

In an implementation form of a network access node according to the first aspect, the threshold value is pre-defined.

An advantage with this implementation form is that the network access node does not need to compute the threshold value on-the-fly, and hence a low complexity solution is achieved.

According to a second aspect of the invention, the above mentioned and other objectives are achieved with a method for a network access node, the method comprises

selecting a first centre frequency resource for a set of symbols to be transmitted to a client device, wherein the first centre frequency resource is frequency offset in relation to a modulation frequency resource of the network access node and selected such that a resulting phase shift between two consecutive symbols of the set of symbols when modulated with a modulation frequency corresponding to the modulation frequency resource and demodulated at a first centre frequency corresponding to the first centre frequency resource is less than a threshold value;

modulating the set of symbols with the modulation frequency so as to obtain a set of modulation symbols; transmitting the set of modulation symbols around the first centre frequency to a client device.

The method according to the second aspect can be extended into implementation forms corresponding to the implementation forms of the network access node according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the network access node.

The advantages of the methods according to the second aspect are the same as those for the corresponding implementation forms of the network access node according to the first aspect.

The invention also relates to a computer program, characterized in program code, which when run by at least one processor causes said at least one processor to execute any method according to embodiments of the present invention. Further, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

Further applications and advantages of the embodiments of the present invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the present invention, in which:

- Fig. 1 shows a network access node according to an embodiment of the invention;

- Fig. 2 shows a method according to an embodiment of the invention;

- Fig. 3 shows a wireless communication system according to an embodiment of the invention;

- Fig. 4 shows selection of a first centre frequency according to an embodiment of the invention.

Detailed Description

In NR the bandwidth of the gNB and the bandwidth of the UE may be separated from each other. Hence, the UE can connect and receive signals from the gNB even in cases where the bandwidth of the UE is smaller than the system bandwidth of the gNB. Furthermore, in order to optimize the system bandwidth the UE can be configured to operate on a smaller bandwidth part (BWP) with a centre frequency which is not aligned with the gNB centre frequency.

According to the 5G/New Radio (NR) specification in TS 38.21 1v15.0.0, the time-continuous signal ^^{f) on antenna port p and subcarrier spacing configuration m for orthogonal frequency division multiplexing (OFDM) symbol / in a subframe for any physical channel or physical signal except physical random access channel (PRACH) is defined by

where o £ ί < (/n^ + /v^_{p ;})r_c and m is the subcarrier spacing configuration. Furthermore, a[^r{^m) is the modulation symbol / on sub-carrier k, NRB is the number of physical resource blocks, and N_Sc is the number of sub-carriers per resource block (RB). Hence, the product N_RB ^*N_Sc corresponds to the next generation eNode B (gNB) fast Fourier transform (FFT) size. Furthermore, Af denotes the sub-carrier spacing, T_c is the chip duration and the k₀ is an offset parameter. The function exp(j^*x) in the above expression is the complex valued exponential function and hence

is the complex-valued baseband representation of the transmitted signal. Modulation and up-conversion to the carrier frequency fo of the complex-valued OFDM baseband signal for antenna port p and subcarrier spacing configuration m is given by

The main difference of a synchronization signal transmission between NR and LTE is that in NR the central subcarrier of a SSB will not be aligned with the up-conversion carrier frequency fo for a gNB. The carrier frequency fo is the centre frequency of the FFT spanning the entire gNB system bandwidth (BW). Typically, the gNB system bandwidth is up to 20 MHz in LTE, while for NR the system bandwidth can be up to 100-200 MHz. Furthermore, in NR there can be multiple SSBs in the gNB system bandwidth. Moreover, the SSB in NR consists of the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) as well as the physical broadcast channel (PBCH), which includes the master information block (MIB). In the MIB, information such that whether a cell is allowed for initial connection or not is found as well as information about the subframe number (SFN). The eNB centre frequency in LTE is indirectly detected using the knowledge that the PSS, SSS and PBCH always are transmitted in the central 6 RBs centred around the carrier frequency. Therefore, once a UE have determined the PSS and SSS it has also determined the centre frequency of the eNB system bandwidth, and hence the centre frequency used in the receiver FFT processing.

The NR PBCH does not contain much information, instead there will be a pointer to where the remaining system information (RMSI) control resource set (CORESET) can be found. From this pointer, the UE gets information about a frequency range where the UE should monitor the CORESET, i.e. time-frequency resources in a control channel where indication of RMSI information is sent. In the RMSI further system information is given including random access channel (RACH) parameters for initial connection setup, and information and/or pointer to other system information (OSI). For SSB symbols in NR, the baseband signal at a gNB transmitter can be written as:

(Equation 1 ) where 0

l = 0,1,2... . a_{k l} is the modulated symbol of a SSB, and wherein the SSB occupies only part of subcarriers in the system bandwidth, herein labelled as the FFT size of the SSB, i.e. NSSB. The parameter M is the offset in sub-carriers between the centre frequency of the gNB system bandwidth and the centre frequency of the SSB bandwidth.

The relationship between the frequency offset f_m, the sub-carrier offset M and the subcarrier spacing Af is given as f_m=M*Af. The lower frequency of the SSB bandwidth starts at carrier frequency according to

According to the current status of NR specification, up-conversion to the carrier frequency fo of the SSB part of the baseband signal is given by

(Equation 2).

In initial cell search in NR, a UE will search for SSBs. In principle the UE will adapt its down- conversion frequency to a hypothetical down conversion frequency f_x and adapt its receiver bandwidth to cover the SSB signal, and down-convert the received signal and trying to detect the PSS and SSS. As long as the hypothetical down conversion frequency f_x is different from the frequency fo +†M the UE will not detect the SSB and will scan for further potential carrier frequencies.

Assuming an ideal channel, the received baseband signal after down-conversion by a receiver local oscillator at frequency fo +†M, i.e. the correct carrier frequency at the UE for detecting the SSB in an OFDM symbol without cyclic prefix (CP) length, can be expressed as

0 £ t < (N_a + N_CPJ )T_c,l = 0,l, 2. (Equation 3)

where†M=MA† is an unknown subcarrier offset between the carrier frequency at the receiver and the carrier frequency at the transmitter at the initial cell search phase for a UE. Hence, upon switching on a UE and performing an initial cell search in NR, the UE will be affected by an unknown phase shift between the symbols of the SSB, where the phase shift among other things is dependent on the length of the cyclic prefix as well as the frequency offset between the gNB centre (carrier) frequency and the SSB centre frequency as can be seen from the expression in Equation 3, i.e.

where / is the symbol number. It can be noted that if M=0, i.e. no frequency offset between the SSB and the gNB offset, then ph(l)=J

In fact, the above mentioned phase shift between consecutive OFDM symbols is not only present in the SSB case, but in all cases where the UE is configured to monitor a BWP whose centre frequency is not aligned with the gNB centre frequency. The frequency offset may be estimated but the estimate will however be uncertain and will degrade the decoding performance especially in high throughput scenarios. Furthermore, due to the phase shift wrap around, the UE cannot estimate the exact gNB centre frequency, but only a set of centre frequency candidates and hence optimized decoding performance cannot be achieved. Consequently, there is a need for a method and a device to mitigate this phase shift problem and thus optimize the decoding performance. The following disclosure presents a network access node and a corresponding method providing such a solution.

Fig. 1 shows a network access node 100 according to an embodiment of the invention. In the embodiment shown in Fig. 1 , the network access node 100 comprises at least one processor 102, an internal or external memory 104, and a transceiver 106. The processor 102 can be coupled to the memory 104 and the transceiver 106 by communication means 108 known in the art. The network access node 100 may further comprise a plurality of processors 102. The memory 104 may store program code that, when being executed, causes the processor(s) 102 of the network access node 100 to performing the functions and actions described herein. The network access node 100 further comprises an antenna or antenna array 1 10 coupled to the transceiver 106, which means that the network access node 100 is configured for wireless communications in a wireless communication system. That the network access node 100 is configured to perform certain actions should in this disclosure be understood to mean that the network access node 100 comprises suitable means, such as e.g. the processor 102 and the transceiver 106, configured to perform said actions. In embodiments, the processor 102 may e.g. be a baseband processor.

The network access node 100 herein is configured to select a first centre frequency resource for a set of symbols to be transmitted to a client device 300. The first centre frequency resource is frequency offset in relation to a modulation frequency resource of the network access node 100. Furthermore, the first centre frequency resource is selected such that a resulting phase shift between two consecutive symbols of the set of symbols when modulated with a modulation frequency corresponding to the modulation frequency resource at the network access node and when afterwards demodulated at a first centre frequency corresponding to the first centre frequency resource e.g. at a client device 300 is less than a threshold value. In other words, the network access nodes 100 modulates the set of symbols based on the first centre frequency resource. Then when a client device 300 receives the modulated symbols and demodulates them based on the first centre frequency a resulting phase shift between the symbols at the client device 300 is below a threshold. The network access node 100 is further configured to modulate the set of symbols with the modulation frequency so as to obtain a set of modulation symbols and transmit the set of modulation symbols around the first centre frequency to a client device 300. By transmitting the set of modulation symbols around the first centre frequency the network access node 100 can ensure that the client device 300 detects the set of modulation symbols around the first centre frequency. Correspondingly the client device 300 demodulates the set of modulation symbols based on the first centre frequency. Due to the above mentioned smart choosing of the first centre frequency resource, the client device 300 does not need to apply a phase shift correction to the modulated symbols.

Fig. 2 shows a flow chart of a corresponding method 200 which may be executed in a network access node 100, such as the one shown in Fig. 1. The method 200 comprises selecting 202 a first centre frequency resource for a set of symbols to be transmitted to a client device 300. The first centre frequency resource is frequency offset in relation to a modulation frequency resource of the network access node 100 and selected such that a resulting phase shift between two consecutive symbols of the set of symbols when modulated with a modulation frequency corresponding to the modulation frequency resource and demodulated at a first centre frequency corresponding to the first centre frequency resource is less than a threshold value. The method 200 further comprises modulating 204 the set of symbols with the modulation frequency so as to obtain a set of modulation symbols and transmitting 206 the set of modulation symbols around the first centre frequency to a client device 300.

Fig. 3 shows a wireless communication system 500 according to an implementation. The wireless communication system 500 comprises a client device 300 and a network access node 100 configured to operate in the wireless communication system 500. For simplicity, the wireless communication system 500 shown in Fig. 3 only comprises one client device 300 and one network access node 100. However, the wireless communication system 500 may comprise any number of client devices 300 and any number of network access nodes 100 without deviating from the scope of the invention.

In the wireless communication system 500, the network access node 100 transmits sets of modulation symbols MSs to the client device 300. The network access node 100 obtains a set of modulation symbols MS by modulating a set of symbols with the modulation frequency of the network access node 100. In embodiments of the invention, the modulation frequency used by the network access node 100 for modulation of symbols for transmission to the client device 300 may be the frequency used by the network access node 100 for performing the (inverse (I)) FFT and/or (I) discrete Fourier transform (DFT) processing of OFDM symbols. The (l)FFT and/or (l)DFT may be the corresponding Fourier transforms associated to the entire system bandwidth of the network access node 100, i.e. the total amount of transmitted physical resource blocks (PRBs). Thus, the network access node 100 may in embodiments modulate and up-convert the set of symbols to a carrier frequency fo being the modulation frequency so as to obtain the set of modulation symbols MS.

As previously described, the network access node 100 transmits the set of modulation symbols MS to the client device 300 around a first centre frequency, where the first centre frequency may correspond to a first centre frequency resource selected by the network access node 100. The first centre frequency resource and hence the first centre frequency may be selected such that consecutive symbols are affected with a phase shift between symbols smaller than a threshold value when the client device 300 demodulates the received set of modulation symbols MS using the first centre frequency as centre frequency for the demodulation, e.g. in the IFFT process. In this way, the client device 300 may demodulate the set of modulation symbols MS without performing phase compensation. Thereby, the decoding of the set of modulation symbols MS in the client device 300 is simplified.

According to embodiments of the invention, the network access node 100 may transmit the set of modulation symbols MS in a first frequency range centred around the first centre frequency. The first frequency range may e.g. be a bandwidth part (BWP) configured for the client device 300. For example, the network access node 100 may configure a BWP for the client device 300, where the first centre frequency is the centre frequency of the BWP. The BWP configured for the client device 300 may be signalled from the network access node 100 to the client device 300 in control signalling, e.g. in a control message. Hence, the client device 300 may be configured to receive a control message from the network access node 100, wherein the control message indicates the BWP configured for the client device 300. The network access node 100 further transmits the set of modulation symbols MS in the BWP centred around the first centre frequency.

Furthermore, the first frequency range may also be associated with at least one of synchronization signal block, remaining system information, and other system information. In this case, the set of modulation symbols may comprise at least one of a synchronization signal block, comprising primary and secondary synchronization signals as well as a physical broadcast channel, a CORESET of remaining system information, a CORESET of other system information, and a CORESET of a bandwidth part configured for the client device 300. The remaining system information and other system information may include information relevant for the client device 300 to connect to the network access node 100. According to embodiments of the invention, the network access node 100 may select the first centre frequency resource and hence the first centre frequency based on at least one of a cyclic prefix length, a subcarrier spacing, and a chip duration of symbols of the set of modulation symbols, as will now be described with reference to Fig. 4. In the embodiment shown in Fig. 4, the network access node 100 has a centre frequency f_c and has configured the client device 300 with a BWP with a centre frequency f_m(BWP). The subcarrier offset M between the centre frequency f_c of the network access node 100 and the centre frequency f (BWP) of the BWP is equal to f_m(BWP)IAf, where Af is the subcarrier spacing. Furthermore, the client device 300 is configured to monitor a control resource set indicating whether data is allocated to the client device 300 in the BWP with the centre frequency f_m(BWP) and to use the centre frequency f_m(BWP) as a centre frequency for the IFFT processing. As previously described at the beginning of the detailed description (see Equation 3) the phase shift can be determined using the following expression:

Hence, the client device 300 in the embodiment shown in Fig. 4 is affected by a phase shift f which is a function of among other things the CP length of the set of modulation symbols N_cp, the subcarrier spacing Af, and the chip duration of the set of modulation symbols T_c.

Utilizing the fact that the phase shift f wraps around every 2TT, subcarriers kV, k2’, ... may be determined where f~2p^*h, where n is an integer. Subcarriers kV, k2’, ... where f~2p^*h may be determined based on the following condition

f=2p ^* (M-K') ^*N_cp ^*Af^*T_c ~ 2p^*h (Equation 4)

When the client device 300 uses a centre frequency corresponding to one of the determined subcarriers kV, k2’, ..., the client device 300 will not be affected by a phase shift or at least a phase shift between symbols that is smaller than a threshold value and may therefore be neglected. Hence, the network access node 100 may select the first centre frequency to correspond to a subcarrier kV, k2’, ... where f~2p*h, where n is an integer. In Fig. 4, the first centre frequency is selected to correspond to the subcarrier k2^'. It can be noted that the CP length may be different for different symbols in the set of modulation symbols and as the phase shift depends on the CP length it may not be possible to select a first centre frequency such that the resulting phase shift between all consecutive symbols of the set of modulation symbols is less than the threshold value. Therefore, when the CP length is different for different symbols in the set of modulation symbols, the first centre frequency may be selected such that the phase shift between at least a subset of the set of modulation symbols is below the threshold value.

A threshold value giving a neglectable phase shift may be dependent on N number of symbols in the set of modulation symbols. Moreover, the threshold value may be dependent on N number of symbols in the set of modulation symbols and total phase shift p over symbols of the set of modulation symbols. For example, the threshold value may be given as p/N. In this case, a 45 degrees phase shift over a span of N number of (maximum) expected symbols may be acceptable, i.e. the threshold value may be set to 45/N degrees. However, what may be considered an acceptable phase shift may depend on the coding and modulation alphabet used. A phase shift between two symbols of up to 60-70 degrees will generally not degrade performance for robust QPSK/BPSK signalling. For 16-QAM 45 degrees may give acceptable degradation. For high performance 64 QAM or 256 QAM phase shift thresholds around 15-20 may be acceptable.

According to embodiments of the invention, the threshold value may be pre-defined, e.g. in a wireless communication system standard. The network access node 100 may hence be configured with the pre-defined threshold value. However, the threshold value may in embodiments instead be determined by the network access node 100, e.g. based on the N number of symbols in the set of modulation symbols and total phase shift p over symbols of the set of modulation symbols, as previously described. In either case, to cater for different coding and modulation alphabets, the threshold value may comprise a set of threshold values, where each threshold value in the set of threshold values are valid for a specific coding and/or modulation scheme.

The client device 300 herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a Station (STA), which is any device that contains an IEEE 802.1 1 - conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth generation wireless technologies, such as New Radio.

The network access node 100 herein may also be denoted as a radio network access node, an access network access node, an access point, or a base station, e.g. a Radio Base Station (RBS), which in some networks may be referred to as transmitter,“gNB”,“gNodeB”,“eNB”, “eNodeB”,“NodeB” or“B node”, depending on the technology and terminology used. The radio network access nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network access node can be a Station (STA), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The radio network access node may also be a base station corresponding to the fifth generation (5G) wireless systems.

Furthermore, any method according to embodiments of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, it is realized by the skilled person that embodiments of the client device 300 and the network access node 100 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the present solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the present solution.

Especially, the processor(s) of the client device 300 and the network access node 100 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression“processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1. A network access node (100) for a wireless communication system (500), the network access node (100) being configured to

select a first centre frequency resource for a set of symbols to be transmitted to a client device (300), wherein the first centre frequency resource is frequency offset in relation to a modulation frequency resource of the network access node (100) and selected such that a resulting phase shift between two consecutive symbols of the set of symbols when modulated with a modulation frequency corresponding to the modulation frequency resource and demodulated at a first centre frequency corresponding to the first centre frequency resource is less than a threshold value;

modulate the set of symbols with the modulation frequency so as to obtain a set of modulation symbols;

transmit the set of modulation symbols around the first centre frequency to a client device

(300).

2. The network access node (100) according to claim 1 , configured to

3. The network access node (100) according to claim 1 or 2, configured to

4. The network access node (100) according to claim 3, wherein the first frequency range is a bandwidth part configured for the client device (300).

5. The network access node (100) according to claim 3 or 4, wherein the first frequency range is associated with at least one of synchronization signal block, remaining system information, and other system information.

6. The network access node (100) according to claim 5, wherein the set of modulation symbols comprises at least one of a synchronization signal block, a CORESET of remaining system information, a CORESET of other system information, and a CORESET of a bandwidth part configured for the client device (300).

7. The network access node (100) according to any of the preceding claims, configured to select the first centre frequency based on at least one of a cyclic prefix length, a subcarrier spacing, and a chip duration of symbols of the set of modulation symbols.

8. The network access node (100) according to any of the preceding claims, wherein the threshold value is dependent on N number of symbols in the set of modulation symbols.

9. The network access node (100) according to claim 8, wherein the threshold value is dependent on N number of symbols in the set of modulation symbols and total phase shift p over symbols of the set of modulation symbols.

10. The network access node (100) according to claim 9, wherein the threshold value is given as p/N.

1 1. The network access node (100) according to any of the preceding claims, wherein the threshold value is pre-defined.

12. A method (200) for a network access node (100), the method (200) comprising

selecting (202) a first centre frequency resource for a set of symbols to be transmitted to a client device (300), wherein the first centre frequency resource is frequency offset in relation to a modulation frequency resource of the network access node (100) and selected such that a resulting phase shift between two consecutive symbols of the set of symbols when modulated with a modulation frequency corresponding to the modulation frequency resource and demodulated at a first centre frequency corresponding to the first centre frequency resource is less than a threshold value;

modulating (204) the set of symbols with the modulation frequency so as to obtain a set of modulation symbols;

transmitting (206) the set of modulation symbols around the first centre frequency to a client device (300).

13. A computer program with a program code for performing a method according to claim 12 when the computer program runs on a computer.