Transmission method for high-speed wireless communication networks

Abstract

A method (200; 400) is disclosed for exchange of data with one or more communication devices (UE) connected to a wireless communication network (100; 300). The method comprises: allocating (210; 410) time-frequency resources among a plurality of available time-frequency resources; exchanging (215-245; 415-445) data signals, which correspond to said data and exploit the allocated time-frequency resources, between a distributed unit (DU; DU') and a plurality of remote units (RU; RU') through a respective plurality of fronthaul links (FH1, FH2A, FH2B; FHX, FHY, FHZ) each one having a respective fronthaul capacity, and exchanging (250A, 250B;450X, 450Y, 450Z) radio frequency signals, corresponding to the data signals, between the plurality of remote units (RU; RU') and the one or more communication devices. Exchanging (215-245; 415-445) data signals comprises selectively controlling the exchange of the data signals between the distributed unit and the plurality of remote units by exchanging (240, 245; 440, 445), on each one of at least one fronthaul link (FH2A,FH2B; FHX, FHY, FHZ) of the plurality of fronthaul links, a respective portion of the data signals, wherein, for each one of the at least one fronthaul link, the portion of the data signals exchanged on the fronthaul link comprises a respective subset of the data signals exploiting a respective subset of the allocated time-frequency resources. For each one of the at least one fronthaul link, the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on at least one between the fronthaul capacity of the fronthaul link and an available capacity of the fronthaul link that is actually available for transmission, the available capacity of the fronthaul link being at least a portion of the respective fronthaul capacity.

Description

[0001] TRANSMISSION METHOD FOR HIGH-SPEED WIRELESS COMMUNICATION NETWORKS

[0002] DESCRIPTION

[0003] Background art

[0004] Technical field

[0005] The present disclosure generally relates to the field of the wireless communication networks. Particularly, the present disclosure relates to high-speed (or ultra-high speed) wireless communication networks (such as, for example, the future sixth generation (6G) mobile communication networks). More particularly, the present disclosure relates to a system for use in high-speed (or ultra-high speed) wireless communication networks.

[0006] Overview of the related art

[0007] Considering the benefits in terms costs, energy efficiency and performance that centralization may provide to the Radio Access Network (RAN), future high-speed (or ultra-high speed) wireless communication networks (such as the 6G mobile communication networks) are expected to be based on a centralized architecture including one or more Central Units (CUs) each one connected, on one side, to a plurality of Remote Units (RUs), preferably by means of fronthaul links (for example, optical fibre links), and, on the other side, to a core network of the telecommunication operator.

[0008] In a conventional centralized architecture, the CU implements the radio protocol operations of a traditional radio base station for the set of managed RUs, including the higher layer protocols (RRC / RLC / MAC) and possibly part of the physical layer (LI) signal processing operations. The exact functional split between CU and RUs may generally be a trade-off among required fronthaul capacity, maximum tolerated latency of the fronthaul links connecting the CU with the RUs, complexity of the RUs, and possibility to apply coordination algorithms for resource allocation and / or signal processing over the set of RUs managed by the same CU.

[0009] Recently, with the advent of 5G mobile communication networks, two main functional splits between CU and RU have been defined by 3 GPP (Third Generation Partnership Project) and O-RAN (Open RAN) Alliance respectively.

[0010] The first functional split, defined by 3 GPP and often referred to as functional split 2 in a set of possible split options, is a “High-Level Split” (HLS) between PDCP “Packet Data Convergence Protocol”) layer and RLC (‘Radio Link Control”) layer. Since only the PDCP layer and the layers above it are centralized, functional split 2 is less susceptible to latencies in the connection between CU and RU and its requirements in terms of fronthaul capacity are less stringent and approximately equivalent to the peak throughput at the radio interface.

[0011] The second functional split, defined by the O-RAN Alliance and often referred to as functional split 7-2x in said set of possible split options, is a “Lower Layer Split” (LLS) within the physical layer (LI). Since most part of the radio protocols is centralized, split option 7-2x is more susceptible to latencies in the connection between CU and RU and its requirements in terms of fronthaul capacity may be several times (e.g., up to 10 times) larger than the peak throughput at the radio interface.

[0012] According to O-RAN architecture, the eNB-DU / gNB-DU node defined by the 3 GPP NG- RAN architecture is further split into two sub-nodes denoted as O-RAN DU (0-DU) and O-RAN Radio Unit (0-RU). The fronthaul interface between 0-DU and 0-RU (O-FH interface) is an open interface specified by the O-RAN Alliance.

[0013] User-plane messages exchanged between the 0-DU and the O-RUs through the O-FH interface include data in the form of OFDM ^Orthogonal Frequency Division Multiplexing”) symbols. Control-plane messages exchanged between the 0-DU and the O-RUs through the O-FH interface include control information associated with the data transported on the user plane, such as for example the time / frequency resources (z.e., resource scheduling) on which the data are mapped.

[0014] The throughput at the O-FH interface is an important aspect on which deployment choices and transport network dimensioning depend.

[0015] Considering the functional split 7-2x, the throughput at the O-FH interface scales in proportion to the load on the radio interface, which is essentially represented by a number of allocated timefrequency blocks. This feature allows statistical multiplexing in the case of aggregation of traffic generated / received from multiple O-RUs, thereby increasing the efficiency of the transport network.

[0016] Regarding MIMO (^Multiple Input Multiple Output”) technique, since beamforming is performed in the O-RU, the throughput of the user plane scales proportionally to the number of MIMO layers, making it possible to use antennas with a large number of radiating elements (also known as massive MIMO) while maintaining reasonable transport requirements.

[0017] The throughput on the user plane depends on the number of used PRBs ("Physical Resource Blocks”), on the number of transmitted MIMO layers, and on the quantization level (which in turn depends on the used compression scheme), whereas the throughput on the control plane mainly depends on the number of communication devices (such as user equipment) served simultaneously and the used beamforming scheme.

[0018] The adoption of a centralized network architecture, like the one devised by the O-RAN Alliance, enables the implementation of coordinated transmission / reception schemes also known in literature as CoMP (Coordinated Multi Point). As the radio functionalities are split between (1) a centralized O-DU node that coordinates the operation and the signals transmitted / received by several O-RUs distributed over the coverage area and (2) the O-RUs, it becomes possible for a given user equipment to be simultaneously served by multiple O-RUs. The coordination among multiple transmission / reception points can be performed at different levels, like e.g., only in terms of resource allocation (z.e., at scheduling level) or also at physical layer level by jointly processing in the O-DU the signals transmitted or received by multiple O-RUs. In general, the coordination brings improvements in terms of spectrum efficiency and transmission reliability compared to the single point transmission, and this improvement is particularly significant for users located at the cell edge.

[0019] US 2021 / 0006944 discloses a C-RAN including a plurality of remote units (RUs), each being configured to exchange RF signals with at least one UE. The C-RAN also includes a central unit communicatively coupled to the plurality of RUs via a fronthaul interface. The central unit is configured to determine sets of data to be sent to a plurality of remote units across the fronthaul interface. The central unit is also configured to determine a mapping of each of the sets of data to at least one of the plurality of remote units. The central unit is also configured to add a respective indicator, based on the mapping, to each set of data, wherein each respective indicator indicates each remote unit that the respective set of data is intended for. The central unit is also configured to broadcast the sets of data, each with the respective indicator, to the plurality of remote units.

[0020] WO 2019 / 201963 discloses systems and methods for efficiently transmitting information over small cell networks. An exemplary method may include allocating wireless resources to a plurality of wireless endpoints by applying a network schedule using a centralized baseband unit, and transmitting, by the baseband unit, fronthaul data over wireless links to the plurality of wireless endpoints based on the allocated wireless resources and the network schedule.

[0021] Summary

[0022] The Applicant has understood that the fronthaul throughput will represent one of the potential bottlenecks for future wireless communication networks (such as 6G mobile communication networks), which are expected to use higher carrier frequencies in the mmWave or sub-THz frequency range, with carrier bandwidths in the order of up to several GHz.

[0023] The Applicant believes that, despite fronthaul capacity increases (e.g., up to 50 - 200 Gbit / s or more) that some solutions are expected to guarantee (e.g., non-coherent transmission techniques on optical fibres, 4-PAM (4 - 'Pulse-amplitude modulation”) modulation scheme, wavelength multiplexing techniques such as WDM (“Wavelength Division Multiplexing^) and DWDM (“ Dense WDM’), and multicore fibres), these fronthaul capacity increases may not be enough and / or may be available for a limited number of RUs (for example, for architecture and cost reasons).

[0024] Considering a hypothetical 6G carrier operating at millimeter or sub-THz (20-200 GHz) frequency (for example, with 1 GHz carrier bandwidth, 8 MIMO layers, 256-QAM modulation), the fronthaul throughput would be in the order of 130 Gbit / s in case of functional split 7-2x. The aggregated peak information bit rate for this hypothetical 6G carrier can be estimated in the order of 40-50 Gbit / s, which is still a very large value even assuming that the 6G mobile communication network uses a functional split higher than the functional split 7-2x, such as for example the functional split 6 between physical layer and MAC layer.

[0025] In addition, future wireless communication networks (such as the 6G mobile communication networks) will likely use Distributed MIMO (D-MIMO) techniques, to implement so called Cell-free MIMO networks. A Cell-free MIMO network refers to a network with many distributed RUs cooperatively serving multiple user equipment through joint transmission and reception using same time-frequency resources, wherein the set of serving RUs continuously changes as a function of the position of the user.

[0026] However, at millimeter or sub-THz frequencies each RU guarantees a limited coverage range (typically lower than or equal to 200 m). This results in the need for the operator to deploy a large number of RUs per km2in order to guarantee a continuous coverage. In this situation, due to a tradeoff between cost and complexity, especially for the extensive use of Wavelength-Division Multiplexing” (WDM) and “Dense WDM” (DWDM), the fronthaul capacity will be limited for many RUs, thus limiting the peak throughput that the radio interface could provide to a given user equipment.

[0027] In view of the above, the Applicant has devised a transmission method capable of making transmission over the fronthaul links efficient and adapted to actual and real fronthaul link conditions, essentially regardless of the specific 0-DU / O-RUs topology or connection scheme.

[0028] One or more aspects of the present disclosure are set out in the independent claims, with advantageous features of the same disclosure that are indicated in the dependent claims, whose wording is enclosed herein verbatim by reference (with any advantageous feature being provided with reference to a specific aspect of the present disclosure that applies mutatis mutandis to any other aspect thereof).

[0029] An aspect of the present disclosure relates to a method for exchange of data with one or more communication devices connected to a wireless communication network. The method comprises: - allocating time-frequency resources among a plurality of available time-frequency resources;

[0030] - exchanging data signals, which correspond to said data and exploit the allocated timefrequency resources, between a distributed unit and a plurality of remote units through a respective plurality of fronthaul links each one having a respective fronthaul capacity, and

[0031] - exchanging radio frequency signals, corresponding to the data signals, between the plurality of remote units and the one or more communication devices.

[0032] Said exchanging data signals comprises selectively controlling the exchange of the data signals between the distributed unit and the plurality of remote units by exchanging, on each one of at least one fronthaul link of the plurality of fronthaul links, a respective portion of the data signals. For each one of the at least one fronthaul link, the portion of the data signals exchanged on the fronthaul link comprises a respective subset of the data signals exploiting a respective subset of the allocated time-frequency resources. For each one of the at least one fronthaul link, the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on at least one between the fronthaul capacity of the fronthaul link and an available capacity of the fronthaul link that is actually available for transmission. The available capacity of the fronthaul link is at least a portion of the respective fronthaul capacity.

[0033] According to an embodiment, for each one of the at least one fronthaul link and for each communication device of said one or more communication devices, the subset of the allocated timefrequency resources comprised in the portion of the data signals exchanged on the fronthaul link comprises a respective subset of the time-frequency resources allocated to that communication device.

[0034] According to an embodiment, for each one of the at least one fronthaul link and for each communication device of said one or more communication devices, the subset of the allocated timefrequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on an indication of a quality of a radio frequency link between the respective remote unit and the communication device.

[0035] According to an embodiment, the plurality of remote units comprises:

[0036] - a first remote unit connected to the distributed unit through a first fronthaul link, among the plurality of fronthaul links, having a first fronthaul capacity, the first remote unit being configured to exchange the data signals with the distributed unit through the first fronthaul link, and

[0037] - second remote units each one connected to the first remote unit through a respective second fronthaul link, among the plurality of fronthaul links, having a respective second fronthaul capacity lower than the first fronthaul capacity, the second remote units being configured to exchange the data signals with the distributed unit through the first remote unit, wherein the at least one fronthaul link comprises one or more of said second fronthaul links.

[0038] According to an embodiment, the first fronthaul capacity supports the exchange of data signals exploiting an amount of time-frequency resources equal to a totality of said available time-frequency resources, and each second fronthaul capacity supports the exchange of data signals exploiting an amount of time-frequency resources equal to a respective fraction of said available time-frequency resources.

[0039] Another aspect of the present disclosure relates to a system for use in a wireless communication network. The system is configured to exchange data with one or more communication devices connected to the wireless communication network. The system comprises:

[0040] - a central unit;

[0041] - a distributed unit communicably coupled to the central unit, and configured to allocate timefrequency resources among a plurality of available time-frequency resources, and to exchange data signals, corresponding to said data, exploiting the allocated time-frequency resources, and

[0042] - a plurality of remote units configured to exchange the data signals with the distributed unit through a respective plurality of fronthaul links each one having a respective fronthaul capacity, and radio frequency signals, corresponding to the data signals, with the one or more communication devices,

[0043] - a control arrangement configured to perform a selective control of the exchange of the data signals between the distributed unit and the plurality of remote units by allowing, on each one of at least one fronthaul link of said plurality of fronthaul links, the exchange of a respective portion of the data signals.

[0044] For each one of the at least one fronthaul link, the portion of the data signals exchanged on the fronthaul link comprises a respective subset of the data signals exploiting a respective subset of the allocated time-frequency resources.

[0045] For each one of the at least one fronthaul link, the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on at least one between the fronthaul capacity of the fronthaul link and an available capacity of the fronthaul link that is actually available for transmission.

[0046] The available capacity of the fronthaul link is at least a portion of the respective fronthaul capacity.

[0047] According to an embodiment, for each one of the at least one fronthaul link and for each communication device of said one or more communication devices, the respective subset of the allocated time-frequency resources comprises a respective subset of the time-frequency resources allocated to that communication device.

[0048] According to an embodiment, for each one of the at least one fronthaul link and for each communication device of said one or more communication devices, the subset of the allocated timefrequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on an indication of a quality of a radio frequency link between the respective remote unit and the communication device.

[0049] According to an embodiment, the plurality of remote units comprises:

[0050] - a first remote unit connected to the distributed unit through a first fronthaul link having a first fronthaul capacity, the first remote unit being configured to exchange the data signals with the distributed unit through the first fronthaul link, and

[0051] - second remote units each one connected to the first remote unit through a respective second fronthaul link having a respective second fronthaul capacity lower than the first fronthaul capacity, the second remote units being configured to exchange the data signals with the distributed unit through the first remote unit and the respective second fronthaul links.

[0052] The at least one fronthaul link comprises one or more of said second fronthaul link.

[0053] According to an embodiment, the first fronthaul capacity supports the exchange of data signals exploiting an amount of time-frequency resources equal to a totality of said available time-frequency resources, and each second fronthaul capacity supports the exchange of data signals exploiting an amount of time-frequency resources equal to a respective fraction of said available time-frequency resources.

[0054] Brief description of the drawings

[0055] These and other features and advantages of the disclosure will be made apparent by the following description of some exemplary and non-limitative embodiments thereof. For its better intelligibility, the following description should be read making reference to the attached drawings, wherein:

[0056] Figure 1 schematically shows a wireless communication network according to embodiments of the present disclosure;

[0057] Figure 2 shows a flow chart of a method implemented by a system of the mobile communication network of Figure 1 according to embodiments of the present disclosure;

[0058] Figure 3 schematically shows a wireless communication network according to other embodiments of the present disclosure, and Figure 4 shows a flow chart of a method implemented by a system of the mobile communication network of Figure 3 according to embodiments of the present disclosure.

[0059] Detailed description of embodiments of the present disclosure

[0060] With reference to the drawings, Figure 1 schematically shows a wireless communication network 100 (z.e., a portion thereof) according to embodiments of the present disclosure.

[0061] In the following, when one or more features of the wireless communication network 100 (and of a method implemented by it) are introduced by the wording “according to an embodiment”, they are to be construed as features additional or alternative to any features previously introduced, unless otherwise indicated and / or unless there is evident incompatibility among feature combinations that is immediately apparent to the person skilled in the art.

[0062] In the following, the terms “module” and “unit” are intended to emphasize functional (rather than implementation) aspects thereof. Without losing generality, each module and / or unit of the wireless communication network 100 may be implemented by software, hardware, and / or a combination thereof. In addition, each module and / or unit of the wireless communication network 100 (or at least a subset thereof) may also reflect, at least conceptually, physical structures of the wireless communication network 100 (or at least of one or more portions thereof).

[0063] According to an embodiment, the wireless communication network 100 may be a mobile communication network, such as a 4G mobile communication network, a 5G mobile communication network, or a 6G mobile communication network. However, the principles of the present disclosure may be applied to any wireless communication network.

[0064] According to an embodiment, the wireless communication network 100 comprises a system 105 (or more thereof). According to an embodiment, the system 105 is configured to exchange data (or information bits) with one or more communication devices connected to the wireless communication network 100 (the communication devices being not part of the system and being not part of the wireless communication network). Without losing generality, the system 100 implements a radio base station, or at least a portion thereof.

[0065] According to an embodiment, the communication devices comprise one or more user equipment, such as the user equipment UE. Data exchange between the system 105 and the user equipment UE may for example allow a respective user (for example, an owner of the user equipment UE) to access services delivered by the wireless communication network 100.

[0066] Without losing generality, the user equipment UE may comprise a mobile terminal. Examples of mobile terminal include, but are not limited to, portable devices (such as smartphones and tablets). According to an embodiment, the communication devices comprise one or more sensing devices (not shown). This could be the case of, for example, a 5G mobile communication network or a 6G mobile communication network (such as a 6G mobile communication network implementing “Integrated Sensing and Communication" (ISAC) and / or “Joint Sensing and Communication" (JSAC) frameworks). Examples of sensing devices include, but are not limited to, cameras and / or radars for vehicle-to-everything (V2X) applications.

[0067] In the following, reference will be made to the user equipment (such as the user equipment UE) as an example of communication device, it being understood that any features discussed in connection with the user equipment equivalently apply when considering communication devices additional or alternative to the user equipment (such as the sensing devices discussed above).

[0068] According to an embodiment, the wireless communication network 100 comprises a core network 110, for example the “Evolved Packet Core" (EPC) core network.

[0069] According to an embodiment, the wireless communication network 100 is based on the “Open Radio Access Network" (O-RAN) architecture, for example the O-RAN architecture disclosed in the O-RAN Alliance White Paper “O-RAN Use Cases and Deployment Scenarios, Towards Open and Smart RAN February 2020, available on the date of filing of the present application on https: / / www.o-ran.org / resources. However, the principles of the present disclosure may be adopted and / or adapted to other architectures, such as the “Centralized Radio Access Network" (C-RAN) architecture and the “Third Generation Partnership Project" (3 GPP) architecture.

[0070] According to an embodiment, the system 105 comprises disaggregated or split units or components.

[0071] According to an embodiment, the system 105 comprises a central unit, a distributed unit, and a plurality of (i.e., two or more) remote units.

[0072] In the considered embodiment in which the wireless communication network 100 is compliant with the O-RAN architecture, the central unit comprises an O-RAN Central Unit (O-CU)) CU, the distributed unit comprises an O-RAN Distributed Unit (0-DU)) DU, and the plurality of remote units comprise a plurality of O-RAN Radio Units (O-RUs)) RU.

[0073] Although explicit reference is made to an O-CU, an 0-DU and O-RUs, the principles of the present disclosure also apply to disaggregated or split units or components provided by architectures other than the O-RAN architecture.

[0074] Just as an example, the principles of the present disclosure also apply when considering central units, distributed units and remote units provided by the C-RAN architecture or the 3 GPP architecture. Considering for example the 3 GPP architecture, the 3 GPP architecture defines Distributed Units (DUs), such as eNB-DU and gNB-DU, for possible use intermediate between central units (gNB-CUs) and remote units (RUs). Particularly, according to the 3GPP architecture, the gNB-DU is a logical node hosting RLC, MAC and PHY layers of the gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. The gNB-DU terminates the Fl interface connected with the gNB-CU.

[0075] According to an embodiment, the O-CU CU comprises a logical node hosting RRC ("Radio Resource Control”), SDAP (“Service Data Adaptation Protocol”) and PDCP protocols. Without losing generality, the O-CU CU may be based on any protocols or future protocols additional or alternative to one or more among RRC, SDAP and PDCP protocols. Without losing generality, the O-CU CU may comprise a physical unit or a virtualized unit.

[0076] According to an embodiment, the O-CU CU and the core network 110 are connected to each other through a backhaul link BH.

[0077] According to an embodiment, the 0-DU DU comprises a logical node hosting RLC / MAC / High-PHY layers based on a lower layer functional split (e.g., the lower layer functional split 7-2x). Without losing generality, the 0-DU DU may be based on any layers or future layers additional or alternative to one or more among RLC / MAC / High-PHY layers. Without losing generality, the O-DU DU may comprise a physical unit or a virtualized unit.

[0078] According to an embodiment, the O-DU DU is communicably coupled to the O-CU CU. According to an embodiment, the O-DU DU and the O-CU CU are connected to each other through a midhaul link MH (for example, the Fl interface described in 3GPP TS 38.401).

[0079] According to an embodiment, each O-RU RU comprises a logical node hosting Low-PHY layer and RF processing based on a lower layer functional split (e.g., the lower layer functional split 7-2x), and an antenna radiating system (illustrated in the figure by a schematic representation thereof). Without losing generality, each O-RU RU may be based on any layers or future layers additional or alternative to Low-PHY layer. Without losing generality, the O-RUs RU (or at least a subset thereof) comprise physical units or virtualized units. Without losing generality, the antenna radiating system of each O-RU RU comprises a plurality of co-located antennas (for example, in order to perform radio frequency signal exchanges according to one or more MIMO techniques, as better discussed in the following).

[0080] Although explicit reference is made to functional split 7-2x, the principles of the present disclosure also apply to different functional splits, such as the functional split 6 between PHY and MAC layers specified by the Small Cell Forum (SCF), and also known as “Functional Application Platform Interface" (https: / / www.smallcellforum.org / work-items / fapi / , “5G FAPI: PHY APT" specification, document number SCF222, Introduction, pages 1-3).

[0081] According to an embodiment, the 0-DU DU is configured to exchange data signals with the 0-RUs RU (or a subset thereof). According to an embodiment, the exchange of data signals comprises transmission of the data signals from the 0-DU DU to one or more of the 0-RUs RU (downlink transmission) and reception of the data signals at the 0-DU DU from one or more of the 0-RUs RU (uplink transmission).

[0082] According to an embodiment, the data signals correspond to the data. By data signals corresponding to the data, it is herein meant that the data signals are obtained by proper processing of the data, the data signals thus containing the data (or a processed version thereof).

[0083] According to an embodiment, the data signals comprise OFDM (f Orthogonal Frequency Division Multiplexing") symbols, i.e., symbols generated (from the data) based on an OFDM technique.

[0084] According to OFDM technique, the data are split into data sequences, thereafter the data sequences are modulated by separate and reciprocally orthogonal sub-carriers and multiplexed into corresponding OFDM symbols for transmission.

[0085] OFDM technique is based on radio resources allocation in time / frequency domain. Considering, just as an example, the 3GPP LTE / LTE-Advanced standard, in time domain radio resources are distributed every Transmission Time Interval (TTI), each one lasting 1 ms (sub-frame) and comprising two time slots of 0.5 ms each, whereas in frequency domain the whole bandwidth is divided into a plurality of 180-kHz sub-channels (each one corresponding to N=12 adjacent and equally spaced sub-carriers). A time-frequency resource comprising a certain number of OFDM symbols (e.g., seven) spanning over one time slot in time domain and twelve adjacent sub-carriers in frequency domain is referred to as “Physical Resource Block" (PRB) and corresponds to the smallest time-frequency resource that can be allocated to a user equipment (or, more generally, to a communication device) for transmission. In the considered example of 3GPP LTE / LTE-Advanced standard, each PRB comprises twelve sub-carriers spaced in frequency by 15 kHz over one OFDM symbol.

[0086] According to an embodiment, the 0-DU DU is configured to allocate time-frequency resources among a plurality of available time-frequency resources (the plurality of available timefrequency resources identifying a so-called time-frequency resource grid), and to exchange the data signals, corresponding to the data, exploiting the allocated time-frequency resources. According to an embodiment, time-frequency resource allocation is performed at the MAC layer (for example, at a scheduling unit thereof, not shown) of the O-DU DU.

[0087] According to an embodiment, the data signals may comprise a compressed version of the OFDM symbols, for example based on “ Block Floating Point” (BFP) compression scheme defined by the O-RAN Alliance.

[0088] According to an embodiment, the O-RUs RU are configured to exchange the data signals with the distributed unit DU, and radio frequency signals, corresponding to the data signals, with the user equipment UE (and, possibly, with additional user equipment, not shown).

[0089] According to an embodiment, the O-RUs RU are configured to exchange the radio frequency signals with user equipment UE based on one or more MIMO (^Multiple Input Multiple Output”) techniques. According to a conventional MIMO technique, multiple data streams including the OFDM symbols (also referred to as MIMO layers) are transmitted / received via multiple antennas at both O-RU and user equipment sides, the MIMO layers logically representing mutually separated information flows.

[0090] According to an embodiment, the O-RUs RU comprise a primary O-RU RUi connected to the O-DU DU through a primary fronthaul link FHi, the primary O-RU RUi being configured to exchange the data signals with the O-DU DU through the primary fronthaul link FHi.

[0091] According to an embodiment, a capacity of the primary fronthaul link FHi (hereinafter referred to as primary fronthaul capacity Ci) allows the primary O-RU RUi and the O-DU DU to exchange data signals exploiting an amount of allocated time-frequency resources up to a totality of the available time-frequency resources (or, otherwise stated, the primary fronthaul link FHi supports the exchange of data signals exploiting all the available time-frequency resources, z.e., the full timefrequency resource grid). Thus, the primary fronthaul capacity Ci represents a nominal or maximum or theoretical capacity of the primary fronthaul link FHi.

[0092] According to an embodiment, the first fronthaul link FHi comprises a fiber optic link based on “ Wavelength Division Multiplexing" (WDM) techniques.

[0093] According to an embodiment, the first fronthaul link FHi is a digital fronthaul link over which the OFDM-based data signals (functional split 7-2x) or the data (functional split 6) are transmitted.

[0094] According to an embodiment (as illustrated), the primary O-RU RUi is implemented as a separate entity being physically separated from the O-DU DU.

[0095] According to an embodiment (not illustrated), the primary O-RU RUi (or at least part thereof) and the O-DU DU are integrated in a same apparatus. In this embodiment, the first fronthaul link FHi may be or comprise an internal interface of the apparatus. In this embodiment, integration (in the O- DU DU) of one or more among the Low-PHY layer of the primary O-RU RUi, the RF processing of the primary O-RU RUi, and the antenna radiating system of the primary O-RU RUi, may be omitted.

[0096] According to an embodiment, the primary O-RU RUi and the O-DU DU are configured to exchange the data signals through a respective interface. According to an embodiment, the primary O-RU RUi and the O-DU DU are configured to exchange the data signals through the Open Fronthaul (O-FH) interface specified by the O-RAN alliance. According to an embodiment, the primary O-RU RUi and the O-DU DU are configured to exchange the data signals through any interface where the time-frequency resources are transmitted in the frequency domain over a packet transport network and where the frequency resources (e.g., the PRBs) and the time resources (e.g., the time slots) can be separately addressed, selected and processed.

[0097] According to an embodiment, the O-RUs RU comprise a plurality of (z.e., two or more) secondary O-RUs RU2A, RUIB. According to an embodiment, each secondary O-RU RU2A, RUIB is connected to the primary O-RU RUi through a respective secondary fronthaul link FH2A, FH2B.

[0098] According to an embodiment, a capacity of each secondary fronthaul link FFUA, FFUB (hereinafter referred to as secondary fronthaul capacity ('22, C22, respectively) is lower than the primary fronthaul capacity Ci. According to an embodiment, each secondary fronthaul capacity C2A,C2B is a fraction or a respective fraction of the primary fronthaul capacity Ci. Thus, each secondary fronthaul capacity ('22, C2B represents a nominal or maximum or theoretical capacity of the respective secondary fronthaul link FFUA, FH211

[0099] According to an embodiment, each secondary fronthaul capacity C22, C2B allows the primary O-RU RUi and the respective secondary O-RU RU2A, RU2B to exchange data signals exploiting an amount of time-frequency resources equal to a fraction or a respective fraction of the available timefrequency resources (or, otherwise stated, each secondary fronthaul link FFUA, FFUB supports the exchange of data signals exploiting a fraction or a respective fraction of the available time-frequency resources, i.e., a fraction or respective fraction of the time-frequency resource grid).

[0100] According to an embodiment, the secondary O-RUs RU2A, RU2B are configured to exchange the data signals with the O-DU DU through the primary O-RU RUi and the respective secondary fronthaul links FFUA, FH211 Particularly, according to an embodiment, each secondary O-RU RU2A, RU2B is configured to exchange one or more portions or respective portions of the data signals (hereinafter, data signal portions) with the primary O-RU RUi.

[0101] For the purposes of the present disclosure, the exchange of data signal portions comprises transmission of the data signal portions from the primary O-RU RUi to the secondary O-RUs RU2A, RUIB (downlink transmission), and transmission of the data signal portions from the secondary O- RUs RU2A, RU2B to the primary O-RU RUi (uplink transmission).

[0102] For the purposes of the present disclosure, the data signal portions exchanged by the secondary O-RU RU2A, RU2B may comprise partially redundant data signal portions (z.e., data signal portions comprising redundant data and / or being transmitted exploiting partially redundant time-frequency resources), or totally different data signal portions (z.e., data signal portions comprising no redundant data and / or being transmitted exploiting no redundant time-frequency resource).

[0103] According to an embodiment, each secondary fronthaul link FH2A, FH2B (or at least a subset thereof) comprises a fiber optic link based on “Single Wavelength Transmission" (SWT) techniques.

[0104] According to an embodiment, the primary O-RU RUi and each secondary O-RU RU2A, RU2B, are configured to exchange the data signal portions through a respective interface.

[0105] According to an embodiment, the primary O-RU RUi and each secondary O-RU RU2A, RU2B, are configured to exchange the data signal portions through the O-FH interface specified by O-RAN Alliance. According to an embodiment, the primary O-RU RUi and each secondary O-RU RU2A, RU2B, are configured to exchange the data signal portions through any interface where the timefrequency resources are transmitted in the frequency domain over a packet transport network and where the frequency resources (e.g., the PRBs) and the time resources (e.g., the time slots) can be separately addressed, selected and processed.

[0106] According to an embodiment, the wireless communication network 100 comprises a control arrangement configured to implement a selective transmission allowing each secondary O-RU RU2A, RU2B (or a subset thereof) to exchange a respective data signal portion with the primary O-RU RUi through the respective secondary fronthaul link FH2A, FH2B.

[0107] According to an embodiment, the control arrangement comprises one or more control modules of the primary O-RU RUi and / or of one or more of the secondary O-RUs RU2A, RU2B. In the exemplary considered embodiment, the control arrangement comprises a control module 115i of (or associated with) the primary O-RU RUi, a control module 1152A of (or associated with) the secondary O-RU RU2A, and a control module 1152B of (or associated with) the secondary O-RU RU2B.

[0108] The primary O-RU RUi and the secondary O-RUs RU2A, RU2B discussed above define a hierarchical topology (z.e., a hierarchical connection scheme) that may find advantageous (although not exclusive) application in future 6G mobile communication networks, where a high or relatively high number of O-RUs are expected to be deployed. Particularly, the hierarchical topology allows avoiding (or at least strongly reducing) long or relatively long direct fronthaul links between the O- RUs and the O-DU, thus increasing the number of O-RUs that can be deployed. With reference now to Figure 2, it shows an activity diagram of a method 200 (implementing the selective transmission) according to embodiments of the present disclosure. Particularly, Figure 2 shows a flow chart which describes the flow of activities relating to exemplary embodiments of the present disclosure. In this respect, each step of the activity diagram may correspond to one or more executable instructions for implementing the specified logical function(s) on a relevant software component of a respective actor. Without losing generality, the following actors are exemplary considered as being involved in the selective transmission: the O-DU DU, the primary O-RU RUi, the secondary O-RUs RU2A, RUIB, and the user equipment UE (or other communication device(s)).

[0109] Without losing generality, selective transmission may be implemented through an equivalent method (e.g., by using similar steps, removing some steps being not essential, or adding further optional steps); moreover, at least some of the steps may be performed in different order, concurrently or in an interleaved way (at least partly).

[0110] The method 200 is discussed with reference to a downlink transmission (z.e., transmission from the O-CU CU to the user equipment UE). However, as better discussed in the following, analogous considerations apply when considering an uplink transmission (z.e., transmission from the user equipment UE to the O-CU CU).

[0111] According to an embodiment, the method steps may be implemented by respective computer program products loadable into a digital memory of the actors (z.e., a digital memory of computational resources where the actors are implemented). According to an embodiment, each computer program product comprises software code means for performing the method steps when the computer program product is run on the corresponding actor.

[0112] Broadly speaking, the method 200 comprises allocating the time-frequency resources among the plurality of available time-frequency resources, selectively controlling the exchange of the data signals (exploiting the allocated time-frequency resources) between the O-DU DU and the O-RUs RU, and exchanging the radio frequency signals, corresponding to the data signals, between the O- RUs RU and the user equipment UE (or, more generally, to the communication device(s)), wherein said selectively controlling the exchange of the data signals between the O-DU DU and the O-RUs RU comprises exchanging, on each one of at least one of the fronthaul links, a respective portion of the data signals. In the hierarchical topology herein considered to which the method 200 (preferably, although not exclusively) applies, said selectively controlling the exchange of the data signals between the O-DU DU and the O-RUs RU comprises exchanging a respective portion of the data signals on each one of one or more of the secondary fronthaul link FHIA, FHIB. According to the general principles of the method 200, for each secondary fronthaul link FHIA, FHIB, the portion of the data signals exchanged on the secondary fronthaul link FH2A, FHIB comprises a respective subset of the data signals exploiting a respective subset of the allocated time-frequency resources, and the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the secondary fronthaul link is based on at least one between the fronthaul capacity of the secondary fronthaul link FHIA, FHIB (z.e., the secondary fronthaul capacity ('22, C2B) and an available capacity of the secondary fronthaul link FHIA, FHIB that is actually available for transmission, the available capacity of the secondary fronthaul link FHIA, FHIB being at least a portion of the respective secondary fronthaul capacity C 4,C2B.

[0113] According to an embodiment, the method 200 comprises, at the 0-DU DU, upon reception of the data from the O-CU CU (action node 205) and allocation of time-frequency resources among the available time-frequency resources (action node 210), generating (from the data) the corresponding data signals (e.g., the OFDM symbols or the OFDM-based data signals) according to the allocated time-frequency resources, and transmitting the data signals to the primary 0-RU RUi through the primary fronthaul link FHi (action node 215).

[0114] Without losing generality, the allocated time-frequency resources may comprise the totality of the available time-frequency resources or a part thereof.

[0115] According to an embodiment (which may correspond to a practical use case scenario), the data signals may comprise both data signals associated with the user equipment UE (z.e., data signals comprising data for the user equipment UE) and data signals associated with one or more additional user equipment, not shown (z.e., data signals comprising data for additional user equipment other than the user equipment UE). Otherwise stated, the allocated time-frequency resources may comprise both time-frequency resources that have been allocated to the user equipment UE, and time-frequency resources that have been allocated to the additional user equipment.

[0116] According to an embodiment, determination of the data signal portions to be exchanged between the primary 0-RU RUi and the secondary O-RUs RU2A, RUIB (nodes 220-245) is performed on a per user equipment basis (or, more generally, on a per communication device basis). Otherwise stated, the data signal portions to be exchanged between the primary 0-RU RUi and the secondary O-RUs RU2A, RU2B may comprise both data signal portions associated with (z.e., for or directed to) the user equipment UE and data signal portions associated with (z.e., for or directed to) additional user equipment.

[0117] In the following, operations aimed at determining the data signal portions associated with the user equipment UE will be considered for the sake of conciseness, it being understood that similar operations may be adopted or adapted for determining the data signal portions associated with any additional user equipment (multi-user equipment scenario). Just as an example, in a multi-user equipment scenario, a scheduling unit (not shown), e.g., located at the O-DU DU, may be adopted or adapted to handle, according to any proper criteria, two or more user equipment competing for data signal portion exchanges on same secondary fronthaul links. Without losing generality, examples of criteria for handling two or more competing user equipment comprise, but not limited to, fronthaul capacities of the secondary fronthaul links and / or quality of the radio frequency links between each user equipment and the secondary fronthaul links (nonetheless, any criterion and / or algorithm may be devised without departing from the principles of the present disclosure).

[0118] According to an embodiment, the method 200 comprises, at the primary 0-RU RUi, determining one or more parameters of the secondary fronthaul link of each secondary 0-RU identified as serving secondary 0-RU for the user equipment UE (action node 220).

[0119] In the following, the secondary O-RUs RU2A, RUIB are assumed to act as serving secondary O-RUs for the user equipment UE (although this should not be construed limitatively). Therefore, in the following, whenever the secondary O-RUs RU2A, RUIB (and the respective secondary fronthaul links FH2A,FH2B and the associated fronthaul capacities ('2.2 C2B) are cited, they are intended to refer to any secondary O-RUs identified as serving (or potentially serving) secondary O-RUs for the user equipment UE (and the respective secondary fronthaul links and the associated secondary fronthaul capacities). Moreover, as better understood from the following discussion, although two secondary O-RUs (z.e., the secondary O-RUs RU2A, RU2B) are assumed to act as serving secondary O-RUs for the user equipment UE, the number of secondary O-RUs identified as serving secondary O-RUs for the user equipment UE (and, hence, the number of secondary O-RUs required for transmission of the data signal portions) may dynamically change as a result of time / frequency resource partitioning.

[0120] According to an embodiment, the parameter(s) of the secondary fronthaul links FH2A, FH2B of the secondary O-RUs RU2A, RU2B (hereinafter, fronthaul param eter(s)) comprise, for each secondary 0-RU RU2A, RU2B, the respective fronthaul capacity ('2.2 C2B.

[0121] According to an embodiment, the fronthaul capacity of each secondary fronthaul link FH2A, FH2B (or an indication thereof) is stored at the respective secondary 0-RU RU2A, RU2B, and communicated to the primary 0-RU RUi (action nodes 225A, 225B). According to an embodiment, for each secondary 0-RU RU2A, RU2B, communication of the respective fronthaul capacity may take place on a periodic basis (for example, at each predetermined time interval), and / or on an aperiodic basis (for example, on request by the primary 0-RU RUi, e.g., upon reception of the data).

[0122] According to an alternative embodiment, the fronthaul capacity of each secondary fronthaul link FH2A,FH2B(or an indication thereof) is stored at the primary 0-RU RUi at a configuration phase of the system 105 and / or of the wireless communication network 100.

[0123] According to an embodiment, the fronthaul parameter(s) comprise, for each secondary O-RU RUIA, RUIB, an available capacity of the respective secondary fronthaul link FHIA, FHIB that is actually available for transmission (hereinafter, available fronthaul capacity). As should be understood, the available fronthaul capacity may differ from one secondary O-RU RUIA, RUIB to another, for example depending on a current load or congestion of the respective secondary fronthaul link FHIA, FHIB (e.g., in that each secondary O-RU RUIA, RUIB may meanwhile act as a serving secondary O-RU for additional user equipment other than the user equipment UE). Therefore, for each secondary fronthaul link FHIA, FHIB, the respective available fronthaul capacity is lower than (or at most equal to) the respective secondary fronthaul capacity ('22, C2B.

[0124] According to an embodiment, the available fronthaul capacity of each secondary fronthaul link FHIA, FHIB is determined according to a level of occupation of the transmission buffer of the respective secondary O-RU RU2A, RU2B. According to an embodiment, determination of the available fronthaul capacity of each secondary fronthaul link FH2A, FH2B takes place at the primary O-RU RUi (downlink transmission), or at the respective O-RU RU2A, RU2B and communicated to the primary O-RU RUi (uplink transmission). -According to an embodiment, for each secondary O-RU RU2A, RU2B, determination and / or communication of the respective available fronthaul capacity may take place on a periodic basis (for example, at each predetermined time interval), and / or on an aperiodic basis (for example, on request by the primary O-RU RUi, e.g., upon reception of the data).

[0125] According to an embodiment, the method 200 further comprises, at the primary O-RU RUi, determining one or more parameters of the radio links between the user equipment UE and any O- RUs identified as serving (or potentially serving) O-RU for the user equipment UE (action node 220). According to an embodiment, the serving (or potentially serving) O-RUs may comprise both secondary O-RUs RU2A, RU2B (such as the secondary O-RUs RU2A, RU2B) and primary O-RUs (such as the primary O-RU RUi).

[0126] According to an embodiment, the one or more parameters of the radio links of the serving O- RUs (hereinafter, concisely referred to as radio link parameter(s)) comprise, but are not limited to, metrics and / or measurements reported by the user equipment UE (action node 230). According to an embodiment, the metrics and / or measurements reported by the user equipment UE may be contained in and / or derivable from control information transmitted by the uplink control channels. According to an embodiment, the control information may be extracted (to determine or derive the radio link parameter(s)) at the primary O-RU RUi (as conceptually represented in the figure by connection between action node 230 and action node 220). Examples of radio link parameters include, but are not limited to, “Received Signal Strength Indicator" (RS SI), “Reference Signals Received Row er" (RSRP), “Reference Signal Received Quality' (RSRQ), “Signal to Interference plus Noise Ratio ' (SINR), and “Channel Quality Indicator" (CQI).

[0127] According to an embodiment, the method 200 comprises, at the primary 0-RU RUi, if (exit branch Y of decision node 235) at least one of the secondary O-RUs RUIA, RUIB has one or more constraints to full data signal transmission, determining the data signal portion to be transmitted over each secondary fronthaul link FHIA, FHIB (action node 240) - or, more generally, to each secondary fronthaul link of each secondary 0-RU identified as serving secondary 0-RU for the user equipment UE. By full data signals, it is herein meant the data signals (associated with the user equipment UE) exploiting the totality of the time-frequency resources allocated to the user equipment UE.

[0128] According to an embodiment, constraints may comprise capacity constraints.

[0129] According to an embodiment, a capacity constraint for the secondary 0-RU RUIA, RUIB may arise in case of low or relatively low secondary fronthaul capacity C2A,C2B, for example when the respective secondary fronthaul capacity C2A,C2B is a fraction or a respective fraction of the primary fronthaul capacity Ci (such as in the hierarchical topology of Figure 1). In this embodiment, the data signal portion to be transmitted over each secondary fronthaul link FHIA, FHIB may comprise a respective subset of the data signals exploiting a respective subset of the time-frequency resources allocated to the user equipment UE (so that the data signal portion transmitted over each secondary fronthaul link FHIA, FHIB does not exceed the respective secondary fronthaul capacity C2A,C2B).

[0130] Just as an example of data signal portion in presence of capacity constraint resulting from a low or relatively low secondary fronthaul capacity (i.e., limited fronthaul capacity), when the secondary fronthaul capacity C2A,C2B is a fraction of the primary fronthaul capacity Ci the data signal portion to be transmitted over each secondary fronthaul link FHIA, FHIB may comprise a respective MIMO layer (or a portion thereof) of a plurality of MIMO layers (e.g., so as to implement a transmission based on “Distrihuted-MIMO" (D-MIMO) technique). In a first example, transmission of a MIMO layer or of a portion thereof over a secondary fronthaul link only depends on a ratio between the respective secondary fronthaul capacity and the primary fronthaul capacity (for example, a whole MIMO layer may be transmitted to any secondary fronthaul link having secondary fronthaul capacity equal to a first fraction (for example, 1 / 4) of the primary fronthaul capacity, whereas respective portions of a MIMO layer may be transmitted to secondary fronthaul links having secondary fronthaul capacities equal to a second fraction of the primary fronthaul capacity lower than the first fraction (for example, 1 / 8)). In a second example, as better discussed in the following, each MIMO layer or each MIMO layer portion (z.e., the respective time and frequency resources) may be partitioned among the secondary O-RUs according to available fronthaul capacities of the respective secondary fronthaul links.

[0131] According to an embodiment, a capacity constraint for a secondary O-RU RUIA, RUIB may arise when the respective available fronthaul capacity is lower than a fronthaul capacity requested for full data signal transmission over the respective secondary fronthaul link FHIA, FHIB (hereinafter, requested fronthaul capacity). In this embodiment, the data signal portion (which may also be a MIMO layer portion in a D-MIMO scenario) to be transmitted over each secondary fronthaul link FHIA, FHIB may be determined based on the respective available fronthaul capacity, the data signal portion for example comprising a respective subset of the data signals exploiting a respective subset of the time-frequency resources allocated to the user equipment UE (so that the data signal portion transmitted over each secondary fronthaul link FHIA, FHIB does not exceed the respective available fronthaul capacity).

[0132] Therefore, in this embodiment, time and / or frequency resource partitioning into the respective subsets of the time-frequency resources (and, hence, the distribution of the resources in terms of PRBs and time slots on the secondary O-RUs) depends on an instantaneous or current load on the secondary fronthaul links.

[0133] In the following, for the sake of conciseness, the subset of the allocated time-frequency resources of the data signal portion to be transmitted over a secondary fronthaul link will be also denoted as subset of the allocated time-frequency resources associated with the secondary fronthaul link.

[0134] Just as an example of time and / or frequency resource partitioning in presence of capacity constraint resulting from a low o relatively low available fronthaul capacity, in case that the available fronthaul capacity of both (or, more generally, of all) the secondary O-RUs RUIA, RUIB is lower than the requested fronthaul capacity, the subsets of the allocated time-frequency resources associated with the secondary fronthaul links FHIA, FHIB may be proportional to the respective available fronthaul capacities, or, more generally, may be proportional to a ratio between the respective available fronthaul capacities. Just as a numerical example, assuming that the secondary fronthaul capacity ( '22 is equal to the secondary fronthaul capacity C2 / 1, and the available fronthaul capacities of the secondary O-RUs RUIA and RUIB are 1 / 3 and 2 / 3 of the secondary fronthaul capacity, respectively, the subset of the allocated time-frequency resources associated with each secondary fronthaul link FHIA, FHIB may be 1 / 3 and 2 / 3, respectively, of the totality of the time-frequency resources allocated to the user equipment UE (provided that each corresponding data signal portion does not exceed the available fronthaul capacity of the respective secondary fronthaul link FHIA, FHIB), or, more generally, the subset of the allocated time-frequency resources associated with the secondary fronthaul link FHIA may be half of the subset of the allocated time-frequency resources associated with the secondary fronthaul link FHIB.

[0135] Just as another example of time and / or frequency resource partitioning in presence of capacity constraints resulting from a low o relatively low available fronthaul capacity, in case that the available fronthaul capacity of one of the secondary O-RUs (for example, the secondary O-RU RUIA) is lower than the requested fronthaul capacity and the available fronthaul capacity of the other one(s) of the secondary O-RUs (for example, the secondary O-RU RUIB) is higher than the requested fronthaul capacity, the subset of the allocated time-frequency resources associated with the secondary fronthaul link FHIA may be proportional to the respective available fronthaul capacity (for example, as discussed above), whereas the subset of the allocated time-frequency resources associated with the secondary fronthaul link FHIB (which has no capacity constraints) may comprise all the timefrequency resources allocated to the user equipment UE (or, otherwise stated, the full data signals associated with the user equipment UE are transmitted over the secondary fronthaul link FHIB). Full data signal transmission over one or more secondary fronthaul links supporting it improves spatial diversity when one or more MIMO techniques are used for radio frequency exchanges between the secondary O-RUs and the user equipment UE.

[0136] Just as a practical example of time and / or frequency resource partitioning, let it be considered the case that a set of frequency resources (z.e., PRBs) numbered from Nl to N2 (with N2 > Nl) and a set of time resources (z.e., time slots) numbered from T1 to T2 (with T2 > 77) are allocated to the user equipment UE.

[0137] Let it be assumed that a single MIMO layer is transmitted, but the principle can be simply extended to the case of multiple MIMO layer transmission (z.e., Spatial Multiplexing). Indeed, as mentioned above, it may be assumed that different MIMO layers are transmitted on the primary fronthaul link FHi as logically separated information flows, as it occurs in the O-FH interface specified by the O-RAN Alliance. It follows that the different MIMO layers can be separately processed in the primary O-RU RUi, and each MIMO layer or group of MIMO layers can be transmitted over a respective secondary fronthaul link.

[0138] In case of limitations in the available fronthaul capacity of the secondary fronthaul links FHIA, FHIB, the primary O-RU RUi may partition the set of time-frequency resources (of the respective MIMO layer(s)) and apply the selective transmission towards the secondary O-RUs RUIA, RUIB. For example, a first data signal portion exploiting a first subset of the PRBs (e.g., from Nl to Nm, with Nm < N2) and a first subset of the time slots (e.g, from T1 to Tm, with Tm < 72) may be transmitted to the secondary O-RU RUIA, and a second data signal portion exploiting a second (e.g., remaining) subset of the PRBs (e.g., from Nm to A2) and a second (e.g., remaining) subset of the time slots (e.g., from Tm to 72) may be transmitted to the secondary O-RU RUIB. In this way, even if the secondary fronthaul links FHIA, FHIB have not sufficient available fronthaul capacity for the full data signal transmission, it is possible to transmit all the information even though a lower level of spatial diversity is experienced at the user equipment UE.

[0139] Thus, in case of limited fronthaul capacity and / or limited available fronthaul capacity, selective transmission on a per user equipment basis is performed by partitioning the allocated timefrequency resources among the (serving and / or potentially serving) secondary O-RUs (“throttling”), in order to remain within the limit of the capacity of the respective secondary fronthaul links. Hence, a macro diversity level for a user equipment is determined according to the load status of the secondary fronthaul links, thus guaranteeing a soft “ Quality of Service'' (QoS) degradation as the load increases.

[0140] In the above examples of determination of the data signal portions (action node 240), the subset of the allocated time-frequency resources associated with each secondary fronthaul link FHIA, FHIB is based on at least one between the respective secondary fronthaul capacity ('22, C2B and the respective available capacity.

[0141] As mentioned in the foregoing, all the above examples of time / frequency resource partitioning may involve (i.e., consider), in addition to the secondary O-RUs actually and currently serving the user equipment UE (such as the secondary O-RUs RUIA, RUIB), further secondary O-RUs potentially serving the user equipment UE (i.e., secondary O-RUs that actually are not serving the user equipment UE but that are capable of doing it).

[0142] According to an embodiment, constraints may comprise radio link constraints. According to an embodiment, a radio link constraint for the secondary O-RU RUIA, RUIB may arise when quality degradation of the respective radio link is experienced, which limits an amount of radio frequency signals that can be transmitted over the radio link with at least a minimum quality (which in turns sets a limit on a size of the data signal portion that can be transmitted over the respective secondary fronthaul link FHIA, FHIB). In this embodiment, the data signal portion may be determined according to the indication of the quality of the corresponding radio frequency link.

[0143] Just as an example, in case that the quality of the radio link of a secondary O-RU RUIA, RUIB sets a limit on the size of the data signal portion that can be handled by that secondary O-RU RUIA, RUIB, the subset of the allocated time-frequency resources associated with the respective secondary fronthaul link FH2A,FHIB may be based on the smallest one between the subset of the allocated timefrequency resources meeting the capacity constraints and the subset of the allocated time-frequency resources meeting the radio link constraints.

[0144] Back to the activity diagram, according to an embodiment, the method 200 comprises, at the primary 0-RU RUi, if (exit branch N of decision node 235) none of the secondary O-RUs RUIA, RUIB has constraints to full data signal transmission, performing full data signal transmission over each secondary fronthaul link FH2A, FHIB (action node 245).

[0145] Although not shown, the selective transmission, and particularly the time / frequency resource partitioning, equivalently applies when the primary 0-RU RUi also acts as a serving 0-RU for the user equipment UE. In this case, if no radio link constraint is determined between the primary 0-RU RUi and the user equipment UE, transmission of the full data signal (z.e., of the corresponding RF signals) may take place from the primary 0-RU RUi, otherwise transmission of a respective data signal portion (z.e., of the corresponding RF signals) meeting the radio link constraints may take place from the primary 0-RU RUi.

[0146] According to an embodiment, after transmission of the data signal portions (or of the data signals, as the case may be) to the secondary O-RUs RU2A, RU2B over the respective secondary fronthaul links FH2A,FH2B (action nodes 240 and 245), the method 200 comprises, at each secondary 0-RU RU2A, RU2B, generating the corresponding radio frequency signals and transmitting them to the user equipment UE (action nodes 250A, 250B).

[0147] Without losing generality, in embodiments (not shown) in which the serving O-RUs comprise both the secondary O-RUs RU2A, RU2B and the primary 0-RU RUi, and the primary 0-RU RUi is also selected, according to selective transmission, to transmit the data signals or a respective data signal portion, radio frequency signals corresponding to the data signals or the respective data signal portion may be generated at the primary 0-RU RUi and transmitted to the user equipment UE.

[0148] According to an embodiment, the method 200 comprises, at the user equipment UE, processing the radio frequency signals (corresponding to the data signals and / or the data signal portions) to obtain the corresponding data (action node 255).

[0149] According to an embodiment, radio frequency signal processing may comprise data demodulation and radio channel coefficient estimates (also referred to as channel estimates).

[0150] According to an embodiment, data demodulation is based on dedicated pilot signals, preferably pilot signals experiencing same channel conditions as the associated data (spatial colocation of Type D), such as the “DeModulation Reference Signals’" DMRS foreseen by 5G or 6G mobile communication networks. According to an embodiment, channel estimates comprise a combined channel estimate for each time-frequency resource exploited for transmission to / from multiple (serving) O-RUs. According to an embodiment, the combined channel estimate is based on averaging the channel estimates in frequency or time domain. According to an embodiment, the combined channel estimate is based on averaging the channel estimates in frequency or time domain, and on real-time control signaling aimed at communicating changes in the number of serving O-RUs and / or on aligning mechanisms aimed at aligning a granularity of the channel estimation averaging at the user equipment UE and a granularity of the selective transmission performed by the primary O-RU RUi (for example, in order to address possible channel discontinuity issues arising from averaging in correspondence of a point where the number of serving O-RUs changes due to the selective transmission). Just as an example, in order to avoid the channel discontinuity issues, the granularity of the selective transmission may be equal to, or an integer multiple of, the granularity of the channel estimation.

[0151] According to an embodiment, the selective transmission discussed above in connection with data transmission may also be adopted or adapted to data retransmission within the ''Hybrid Automatic Repeat Request” (HARQ) procedure, for example upon data reception with errors (NACK reporting).

[0152] As mentioned above, the method 200 discussed above with reference to a downlink transmission also applies to uplink transmission. Particularly, for uplink transmission the control modules 115IA, 115IB of the secondary O-RUs RUIA, RUIB may monitor the respective fronthaul links FHIA, FHIB, and determine which part of the time-frequency resources can be exploited for transmission by each secondary O-RU RUIA, RUIB on the respective secondary fronthaul link FHIA, FHIB towards the primary O-RU RUi, by “cutting” the time-frequency resources that exceed the fronthaul capacity or the available fronthaul capacity. In uplink transmission, coordination among the secondary O-RUs RUIA, RUIB may be envisaged to guarantee that all the time-frequency resources allocated to the user equipment UE are selected for transmission to the primary O-RU RUi by at least one of the secondary O-RU RUIA, RUIB. Different coordination schemes may be envisaged, such as static and / or dynamic coordination schemes, preferably through the support of proper control information.

[0153] The selective transmission discussed above is compatible with the 7-2x functional split selected by the 0-RAN Alliance, but is applicable to all LLS ('' ower Layer Splits” functional splits up to functional split 6 (MAC -PHY functional split), provided that FFT / IFFT operations are performed at the O-RUs and that the data signals are in the form of OFDM symbols (or other possible multi carrier variants). The selective transmission discussed above may find advantageous (although not exclusive) application in future 6G mobile communication networks operating at mmWave or sub-THz frequencies, where a high or relatively high number of O-RUs with fronthaul links having fronthaul capacities lower than the peak throughput per single user equipment at the radio interface are reasonably expected to be deployed, and where, due to a high or relatively high number of simultaneous users equipment (or, more generally, communication devices) to be served and / or to applications requiring very high bit rates, the fronthaul links will likely represent a bottleneck that limits the peak throughput that the radio interface can provide.

[0154] However, the Applicant believes that the selective transmission discussed above may find application also in systems based on one or more conventional topologies (or, more generally, based on topologies other than the hierarchical topology of Figure 1).

[0155] With reference to Figure 3, it schematically shows a wireless communication network 300 according to embodiments of the present disclosure. Particularly, the wireless communication network 300 comprises a system 305, based on a conventional topology, which may benefit of selective transmission. In the following, features, implementations, generalizations, examples, and variants of modules or units of the wireless communication network 300 and of the system 305 that are same or similar to those of the wireless communication network 100 and of the system 305, will not be discussed again for the sake of conciseness.

[0156] According to an embodiment, the wireless communication network 300 comprises the core network 110.

[0157] According to an embodiment, the wireless communication network 300 comprises the O-CU CU connected to the core network 110 through the backhaul link BH.

[0158] According to an embodiment, the wireless communication network 300 comprises an O-DU DU’. Similar to the O-DU DU, the O-DU DU’ comprises a logical node hosting RLC / MAC / High- PHY layers based on a lower layer functional split (e.g. , the lower layer functional split 7-2x). Without losing generality, the O-DU DU’ may be based on any layers or future layers additional or alternative to one or more among RLC / MAC / High-PHY layers.

[0159] According to an embodiment, the O-DU DU’ and the O-CU CU are connected to each other through the midhaul link MH (for example, the Fl interface described in 3GPP TS 38.401).

[0160] According to an embodiment, the system 305 comprises a plurality of O-RUs RUx, RUY, RUz (globally denoted also as RU’) each one connected to the O-DU DU’ through a respective fronthaul link FHx, FHY, FHZ (the connection between the O-RUs RUx, RUY, RUZ and the O-DU DU’ thus identifying a star topology of the system). According to an embodiment, each O-RU RUx, RUY, RUZ is configured to exchange the data signals with the O-DU DU’ through the respective fronthaul link FHx, FHY, FHZ.

[0161] Similarly to the above, although explicit reference is made to an O-CU, an O-DU and O-RUs, the principles of the present disclosure also apply to disaggregated or split units or components provided by architectures other than the O-RAN architecture. Just as an example, the principles of the present disclosure also apply when considering central units, distributed units and remote units provided by the C-RAN architecture or the 3 GPP architecture.

[0162] According to an embodiment, the wireless communication network 300 comprises a control arrangement configured to implement the selective transmission allowing each 0-RU RUx, RUY, RUz (or a subset thereof) to exchange a respective data signal portion with the O-DU DU’ through the respective fronthaul link FHx, FHY, FHZ.

[0163] According to an embodiment, the control arrangement comprises one or more control modules of the O-DU DU’ and / or of one or more of the O-RUs RUx, RUY, RUZ. In the exemplary considered embodiment, the control arrangement comprises a control module 315’ of (or associated with) the O- DU DU’, a control module 315x of (or associated with) the O-RU RUx, a control module 315Y of (or associated with) the O-RU RUY, and a control module 315z of (or associated with) the O-RU RUz.

[0164] Figure 4 shows an activity diagram of a method 400 (implementing the selective transmission performed by the system 305) according to embodiments of the present disclosure. According to an embodiment, selective transmission (and / or retransmission within the HARQ procedure) discussed in connection with Figure 2 for the system 105, as well as the corresponding features, implementations, generalizations, examples, and variants thereof, equivalently apply to selective transmission (and / or retransmission within the HARQ procedure) discussed in connection with Figure 4 for the system 305 (with the O-DU DU’, particularly the control module 315' thereof, that implements the method steps performed at the O-DU DU and at the primary O-RU RUi, and with the O-RUs RUx, RUY, RUZ that implement the method steps performed at the secondary O-RUs RUIA, RUIB). In the following, features, implementations, generalizations, examples, and variants of the method steps of the activity diagram of Figure 4 that are same or similar to those of Figure 2, will not be discussed again for the sake of conciseness.

[0165] Broadly speaking, the method 400 comprises allocating the time-frequency resources among the plurality of available time-frequency resources, selectively controlling the exchange of the data signals (exploiting the allocated time-frequency resources) between the O-DU DU’ and the O-RUs RU’, and exchanging the radio frequency signals, corresponding to the data signals, between the O- RUs RU’ and the communication devices, wherein said selectively controlling the exchange of the data signals between the O-DU DU’ and the O-RUs RU’ comprises exchanging, on each fronthaul link FHx, FHY, FHZ (or a subset thereof, such as one or more thereof) a respective portion of the data signals. According to the general principles of the method 400, said selectively controlling the exchange of the data signals between the O-DU DU and the O-RUs RU comprises exchanging a respective portion of the data signals on each fronthaul link FHx, FHY, FHZ (or on each one of one or more of the fronthaul links FHx, FHY, FHZ), wherein the portion of the data signals exchanged on each fronthaul link FHx, FHY, FHZ comprises a respective subset of the data signals exploiting a respective subset of the allocated time-frequency resources, and the subset of the allocated timefrequency resources comprised in the portion of the data signals exchanged on each fronthaul link FHx, FHY, FHZ is based on at least one between a fronthaul capacity of the fronthaul link FHx, FHY, FHz (hereinafter referred to as fronthaul capacity Cx, CY, CZ) and an available capacity of the fronthaul link FHx, FHY, FHZ that is actually available for transmission (the available capacity of each fronthaul link FHx, FHY, FHZ being at least a portion of the respective fronthaul capacity fronthaul capacity Cx, CY, CZ).

[0166] According to an embodiment, the method 400 comprises, at the O-DU DU’, upon reception of the data from the O-CU CU (action node 405) and allocation of time-frequency resources among the available time-frequency resources (action node 410), generating (from the data) the corresponding data signals (action node 415). Method steps 405, 410, 415 essentially correspond to method steps 205, 210, 215, respectively, thus features, implementations, generalizations, examples, and variants discussed in connection with method steps 205, 210, 215 equivalently apply to method steps 405, 410, 415.

[0167] According to an embodiment, the method 400 comprises, at the O-DU DU’, determining one or more parameters of the fronthaul link of each O-RU identified as serving O-RU for the user equipment UE (action node 420).

[0168] In the following, the O-RUs RUx, RUY, RUZ are assumed to act as serving O-RUs for the user equipment UE (although this should not be construed limitatively). Therefore, in the following, whenever the O-RUs RUx, RUY, RUZ (and the respective fronthaul links FHx, FHY, FHZ and the associated fronthaul capacities Cx, CY, CZ) are cited, they are intended to refer to any O-RUs identified as serving (or potentially serving) O-RUs for the user equipment UE (and the respective fronthaul links and the associated fronthaul capacities). Moreover, although three O-RUs (i.e., the O-RUs RUx, RUY, RUZ) are assumed to act as serving O-RUs for the user equipment UE, the number of O-RUs identified as serving O-RUs for the user equipment UE (and, hence, the number of O-RUs required for transmission of the data signal portions) may dynamically change as a result of time / frequency resource partitioning.

[0169] According to an embodiment, the fronthaul parameter(s) of the fronthaul links FHx, FHY, FHz of the O-RUs RUx, RUY, RUZ comprise, for each O-RU RUx, RUY, RUZ, the respective fronthaul capacity Cx, CY, CZ.

[0170] According to an embodiment, the fronthaul capacity of each fronthaul link FHx, FHY, FHZ (or an indication thereof) is stored at the respective O-RU RUx, RUY, RUZ, and communicated to the O-DU DU’ (action nodes 425x, 425Y, 425z).

[0171] According to an embodiment, the fronthaul parameter(s) comprise, for each O-RU RUx, RUY, RUz, the available capacity of the respective fronthaul link FHx, FHY, FHZ that is actually available for transmission. As should be understood, the available fronthaul capacity may differ from one O- RU RUx, RUY, RUZ to another, for example depending on a current load or congestion of the respective fronthaul link FHx, FHY, FHZ (e.g., in that each O-RU RUx, RUY, RUZ may meanwhile act as a serving O-RU for additional user equipment other than the user equipment UE). Therefore, for each fronthaul link FHx, FHY, FHZ, the respective available fronthaul capacity is lower than (or at most equal to) the respective fronthaul capacity Cx, CY, CZ.

[0172] According to an embodiment, the available fronthaul capacity of each secondary fronthaul link FHx, FHY, FHZ is determined according to a level of occupation of the corresponding transmission buffer. According to an embodiment, determination of the available fronthaul capacity of each secondary fronthaul link FHx, FHY, FHZ takes place at the O-DU DU’ (downlink transmission), or at the respective O-RU RUx, RUY, RUZ and communicated to the O-DU DU’ (uplink transmission).

[0173] According to an embodiment, the method 400 comprises, at the O-DU DU’, determining one or more radio link parameter(s)) of the radio links between the user equipment UE and any O-RUs identified as serving (or potentially serving) O-RU for the user equipment UE (action node 420).

[0174] According to an embodiment, the radio link parameter(s)) comprise, but are not limited to, metrics and / or measurements reported by the user equipment UE (action node 430).

[0175] Method step 420, method steps 425x, 425Y, 425Z, and method step 430 essentially correspond to method step 220, method steps 225A, 225B, and method step 230, respectively, thus features, implementations, generalizations, examples, and variants discussed in connection with method steps 220, 225A, 225B, 230 equivalently apply to method steps 420, 425x, 425Y, 425Z, 430.

[0176] According to an embodiment, the method 400 comprises, at the O-DU DU’, if (exit branch Y of decision node 435) at least one of the O-RUs RUx, RUY, RUZ has one or more constraints to full data signal transmission, determining the data signal portion to be transmitted over each fronthaul link FHx, FHY, FHZ (action node 440) - or, more generally, over each fronthaul link of each O-RU identified as serving O-RU for the user equipment UE.

[0177] According to an embodiment, constraints may comprise capacity constraints (similarly to the above, a capacity constraint for the O-RU RUx, RUY, RUZ may arise in case of low or relatively low fronthaul capacity Cx, CY, CZ, and / or when the respective available fronthaul capacity is lower than the requested fronthaul being requested for full data signal transmission over the respective fronthaul link FHx, FHY, FHZ)

[0178] Thus, in case of limited fronthaul capacity and / or limited available fronthaul capacity, selective transmission is performed by partitioning the allocated time-frequency resources among the (serving and / or potentially serving) O-RUs (“throttling”), in order to remain within the limit of the capacity of the respective fronthaul links.

[0179] Method steps 435, 440 essentially correspond to method steps 235, 240, respectively, thus features, implementations, generalizations, examples, and variants discussed in connection with method steps 235, 240 equivalently apply to method steps 435, 440. Particularly, at action node 440, in order to determine the data signal portions, the subset of the allocated time-frequency resources associated with each fronthaul link FHx, FHY, FHZ is based on at least one between the respective fronthaul capacity Cx, CY, CZ and the respective available capacity.

[0180] According to an embodiment, the method 400 comprises, at the 0-DU DU’, if (exit branch N of decision node 435) none of the O-RUs RUx, RUY, RUZ has constraints to full data signal transmission, performing full data signal transmission over each fronthaul link FHx, FHY, FHZ (action node 445).

[0181] According to an embodiment, after transmission of the data signal portions (or of the data signals, as the case may be) to the O-RUs RUx, RUY, RUZ over the respective fronthaul links FHx, FHY, FHZ (action nodes 440 and 445), the method 400 comprises, at each O-RU RUx, RUY, RUZ, generating the corresponding radio frequency signals and transmitting them to the user equipment UE (action nodes 450x, 450Y, 450Z).

[0182] According to an embodiment, the method 400 comprises, at the user equipment UE, processing the radio frequency signals (corresponding to the data signals and / or the data signal portions) to obtain the corresponding data (action node 455).

[0183] Thanks to selective transmission applied to a system based on a conventional topology (such as the system 305 based on the star topology), the fronthaul capacity Cx, CY, CZ may advantageously be lower than the fronthaul capacity required to support full data signal transmission (typically, 25 Gbit / s using a single wavelength, in conventional Centralized RAN (C-RAN) architectures).

[0184] Naturally, in order to satisfy local and specific requirements, a person skilled in the art may apply to the disclosure described above many logical and / or physical modifications and alterations. More specifically, although the present disclosure has been described with a certain degree of particularity with reference to preferred embodiments thereof, it should be understood that various omissions, substitutions and changes in the form and details as well as other embodiments are possible. In particular, different embodiments of the disclosure may even be practiced without the specific details set forth in the preceding description for providing a more thorough understanding thereof; on the contrary, well-known features may have been omitted or simplified in order not to encumber the description with unnecessary details. Moreover, it is expressly intended that specific elements and / or method steps described in connection with any disclosed embodiment of the disclosure may be incorporated in any other embodiment.

[0185] More specifically, similar considerations apply if the system (and, more generally, the wireless communication network) has a different structure, comprises equivalent components or it has other operative characteristics. In any case, every component thereof may be separated into more elements, or two or more components may be combined together into a single element; moreover, each component may be replicated to support the execution of the corresponding operations in parallel. Moreover, unless specified otherwise, any interaction between different components generally does not need to be continuous, and it may be either direct or indirect through one or more intermediaries.

Claims

CLAIMS1. A method (200; 400) for exchange of data with one or more communication devices (UE) connected to a wireless communication network (100; 300), the method comprising:- allocating (210; 410) time-frequency resources among a plurality of available timefrequency resources;- exchanging (215-245; 415-445) data signals, which correspond to said data and exploit the allocated time-frequency resources, between a distributed unit (DU; DU’) and a plurality of remote units (RU; RU’) through a respective plurality of fronthaul links (FHi, FHIA, FHIB; FHX, FHY, FHZ) each one having a respective fronthaul capacity, and- exchanging (250A, 250B; 450X, 450Y, 450Z) radio frequency signals, corresponding to the data signals, between the plurality of remote units (RU; RU’) and the one or more communication devices, wherein said exchanging (215-245; 415-445) data signals comprises selectively controlling the exchange of the data signals between the distributed unit and the plurality of remote units by exchanging (240, 245; 440, 445), on each one of at least one fronthaul link (FHIA, FHIB; FHX, FHY, FHz) of the plurality of fronthaul links, a respective portion of the data signals, wherein, for each one of the at least one fronthaul link, the portion of the data signals exchanged on the fronthaul link comprises a respective subset of the data signals exploiting a respective subset of the allocated timefrequency resources, and wherein for each one of the at least one fronthaul link, the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on at least one between the fronthaul capacity of the fronthaul link and an available capacity of the fronthaul link that is actually available for transmission, the available capacity of the fronthaul link being at least a portion of the respective fronthaul capacity.

2. The method (200; 400) according to claim 1, wherein, for each one of the at least one fronthaul link (FHIA, FHIB; FHX, FHY, FHZ) and for each communication device (UE) of said one or more communication devices, the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the fronthaul link comprises a respective subset of the time-frequency resources allocated to that communication device (UE).

3. The method (200; 400) according to any of the preceding claims, wherein, for each one of the at least one fronthaul link (FHIA, FHIB; FHX, FHY, FHZ) and for each communication device(UE) of said one or more communication devices, the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on an indication of a quality of a radio frequency link between the respective remote unit (RU; RU’) and the communication device (UE).

4. The method (200) according to any of the preceding claims, wherein the plurality of remote units (RU) comprises:- a first remote unit (RUi) connected to the distributed unit (DU) through a first fronthaul link (FHi), among the plurality of fronthaul links, having a first fronthaul capacity, the first remote unit being configured to exchange the data signals with the distributed unit through the first fronthaul link, and- second remote units (RUIA, RUIB) each one connected to the first remote unit through a respective second fronthaul link (FHIA, FHIB), among the plurality of fronthaul links, having a respective second fronthaul capacity lower than the first fronthaul capacity, the second remote units being configured to exchange the data signals with the distributed unit through the first remote unit, wherein the at least one fronthaul link (FHIA, FHIB; FHX, FHY, FHZ) comprises one or more of said second fronthaul links (FHIA, FHIB).

5. The method (200) according to claim 4, wherein the first fronthaul capacity supports the exchange of data signals exploiting an amount of time-frequency resources equal to a totality of said available time-frequency resources, and each second fronthaul capacity supports the exchange of data signals exploiting an amount of time-frequency resources equal to a respective fraction of said available time-frequency resources.

6. A system (105; 305) for use in a wireless communication network (100; 300), wherein the system is configured to exchange data with one or more communication devices (UE) connected to the wireless communication network, the system comprising:- a central unit (CU);- a distributed unit (DU; DU’) communicably coupled to the central unit, and configured to allocate time-frequency resources among a plurality of available time-frequency resources, and to exchange data signals, corresponding to said data, exploiting the allocated time-frequency resources, and- a plurality of remote units (RU; RU’) configured to exchange the data signals with thedistributed unit through a respective plurality of fronthaul links (FHi, FHIA, FHIB; FHX, FHY, FHZ) each one having a respective fronthaul capacity, and radio frequency signals, corresponding to the data signals, with the one or more communication devices,- a control arrangement (115i, 115IA, 115IB; 315’, 315x, 315Y, 315Z) configured to perform a selective control of the exchange of the data signals between the distributed unit and the plurality of remote units by allowing, on each one of at least one fronthaul link (FHIA, FHIB; FHX, FHY, FHZ) of said plurality of fronthaul links, the exchange of a respective portion of the data signals, wherein, for each one of the at least one fronthaul link, the portion of the data signals exchanged on the fronthaul link comprises a respective subset of the data signals exploiting a respective subset of the allocated time-frequency resources, and wherein for each one of the at least one fronthaul link, the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on at least one between the fronthaul capacity of the fronthaul link and an available capacity of the fronthaul link that is actually available for transmission, the available capacity of the fronthaul link being at least a portion of the respective fronthaul capacity.

7. The system (105; 305) according to claim 6, wherein, for each one of the at least one fronthaul link (FHIA, FHIB; FHX, FHY, FHZ) and for each communication device (UE) of said one or more communication devices, the respective subset of the allocated time-frequency resources comprises a respective subset of the time-frequency resources allocated to that communication device (UE).

8. The system (105; 305) according to claim 6 or 7, wherein, for each one of the at least one fronthaul link (FHIA, FHIB; FHX, FHY, FHZ) and for each communication device (UE) of said one or more communication devices, the subset of the allocated time-frequency resources comprised in the portion of the data signals exchanged on the fronthaul link is based on an indication of a quality of a radio frequency link between the respective remote unit (RU; RU’) and the communication device (UE).

9. The system (105) according to any claim from 6 to 8, wherein the plurality of remote units comprises:- a first remote unit (RUi) connected to the distributed unit through a first fronthaul link (FHi) having a first fronthaul capacity, the first remote unit being configured to exchange the data signals with the distributed unit through the first fronthaul link, and- second remote units (RUIA, RUIB) each one connected to the first remote unit through a respective second fronthaul link (FHIA, FHIB) having a respective second fronthaul capacity lower than the first fronthaul capacity, the second remote units being configured to exchange the data signals with the distributed unit through the first remote unit and the respective second fronthaul links, wherein the at least one fronthaul link (FHIA, FHIB; FHX, FHY, FHZ) comprises one or more of said second fronthaul link (FHIA, FHIB).

10. The system (105) according to claim 9, wherein the first fronthaul capacity supports the exchange of data signals exploiting an amount of time-frequency resources equal to a totality of said available time-frequency resources, and each second fronthaul capacity supports the exchange of data signals exploiting an amount of time-frequency resources equal to a respective fraction of said available time-frequency resources.

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