Time synchronization and coordination between radio units and baseband units

Abstract

Mechanisms are provided for enabling time synchronization and coordinated downlink transmission of data from a radio unit. A method is implemented by a network node. The method includes configuring at least two baseband units. The at least two baseband units are operatively connected to the radio unit for downlink transmission of data. The at least two baseband units are configured with time synchronization information for compensating for a difference in latency between the radio unit and each of the at least two baseband units for the downlink transmission of data. The at least two baseband units are configured with time scheduling information identifying which transmission slots of each frame are allowed to be used by the at least two baseband units for the downlink transmission of data.

Description

TECHNICAL FIELD

[0001] Embodiments presented herein relate to a method, a network node, a baseband unit, a computer program and a computer program product for enabling time synchronization and coordinated downlink transmission of data from a radio unit. BACKGROUND

[0002] In a communication network, there can be a challenge to obtain good performance and capacity for a given communication protocol, its parameters and the physical environment in which the communication network is deployed.

[0003] For example, all communication networks consume energy. Thus, increasing the size of a communication network and increasing the number of devices served by a communication network can result in an increase in energy consumption. Therefore, mechanisms and techniques have been designed aiming at reducing the energy consumption in a communication network.

[0004] Two non-limiting examples of mechanisms or techniques that can be deployed for reducing the energy consumption in a (radio) access network node in a communication network are micro-sleep transmission (MSTx) and low energy scheduling solution (LESS). In this regard, according to MSTx, the radio power amplifier is automatically turned off on a symbol time basis when there is no need to send signaling or user data on the downlink. MSTx enables discontinuous transmission on the downlink to save energy during low traffic. With LESS, downlink transmissions of non-critical data are rescheduled. Packets of time-sensitive services, such as voice services, are excluded, ensuring that the quality of service is not affected. LESS can be used in combination with MSTx to improve energy efficiency, since in LESS even more time slots are emptied and micro-sleep can be triggered.

[0005] However, there are scenarios in which the energy savings resulting from the use of LESS and MSTx are affected. Some examples of such scenarios are open radio access network, RAN, configurations in which different baseband units, possibly belonging to different operators, are connected to the same radio unit. One reason for this is that many radio units support variants of multi-band, multi-carrier and multi-RAT (where RAT is short for radio access technology) operation, and thus need to be configured in a very flexible manner.

[0006] Therefore, there is still a need for mechanisms and techniques that enable efficient energy savings in a communication network in general, and in particular in such communication networks in which different baseband units, possibly belonging to different operators, are connected to the same radio unit, without affecting the performance of the baseband units and the radio unit in terms of multi-band, multi-carrier and multi-RAT operation. SUMMARY

[0007] It is an object of embodiments herein to generally provide efficient energy saving in a communication network, and in particular in such a communication network where different baseband units, possibly belonging to different operators, are connected to the same radio unit.

[0008] According to a first aspect, a method for enabling time synchronized and coordinated downlink transmission of data from a radio unit is presented. The method is implemented by a network node. The method comprises configuring at least two baseband units. The at least two baseband units are operatively connected to the radio unit for downlink transmission of data. The at least two baseband units are configured with time synchronization information for compensating for a difference in time delay between the radio unit and each of the at least two baseband units for the downlink transmission of data. The at least two baseband units are configured with time scheduling information identifying which transmission slots per frame that are allowed to be used by the at least two baseband units for the downlink transmission of data.

[0009] According to a second aspect, a network node for enabling time synchronized and coordinated downlink transmission of data from a radio unit is presented. The network node comprises processing circuitry. The processing circuitry is configured to cause the network node to configure at least two baseband units. The at least two baseband units are operatively connected to the radio unit for downlink transmission of data. The at least two baseband units are configured with time synchronization information for compensating for a difference in time delay between the radio unit and each of the at least two baseband units for the downlink transmission of data. The at least two baseband units are configured with time scheduling information identifying which transmission slots per frame that are allowed to be used by the at least two baseband units for the downlink transmission of data.

[0010] According to a third aspect, a network node for enabling time synchronized and coordinated downlink transmission of data from a radio unit is presented. The network node comprises a configuration module configured to configure at least two baseband units. The at least two baseband units are operatively connected to the radio unit for downlink transmission of data. The at least two baseband units are configured with time synchronization information for compensating for a difference in time delay between the radio unit and each of the at least two baseband units for the downlink transmission of data. The at least two baseband units are configured with time scheduling information identifying which transmission slots per frame that are allowed to be used by the at least two baseband units for the downlink transmission of data.

[0011] According to a fourth aspect, a computer program for enabling time synchronized and coordinated downlink transmission of data from a radio unit is presented. The computer program comprises computer program code which, when run on processing circuitry of a network node, causes the network node to implement a method according to the first aspect.

[0012] According to a fifth aspect, a method for enabling time synchronized and coordinated downlink transmission of data from a radio unit is presented. The method is implemented by a baseband unit. The baseband unit is operatively connected to the radio unit for downlink transmission of data. The method comprises obtaining, from a network node, a configuration in terms of time synchronization information and time scheduling information, the time synchronization information being for compensating for a difference in time delay between the radio unit and the baseband unit for the downlink transmission of data, the time scheduling information identifying which transmission slots per frame that are allowed to be used by the baseband unit for the downlink transmission of data. The method comprises transmitting downlink data to the radio unit in accordance with the configuration.

[0013] According to a sixth aspect, a baseband unit for enabling time synchronized and coordinated downlink transmission of data from a radio unit is presented. The baseband unit is operatively connected to the radio unit for downlink transmission of data. The baseband unit comprises processing circuitry. The processing circuitry is configured to cause the baseband unit to obtain, from a network node, a configuration in terms of time synchronization information and time scheduling information, the time synchronization information being for compensating for a difference in time delay between the radio unit and the baseband unit for the downlink transmission of data, the time scheduling information identifying which transmission slots per frame that are allowed to be used by the baseband unit for the downlink transmission of data. The processing circuitry is configured to cause the baseband unit to transmit downlink data to the radio unit in accordance with the configuration.

[0014] According to a seventh aspect, a baseband unit for enabling time synchronized and coordinated downlink transmission of data from a radio unit is presented. The baseband unit is operatively connected to the radio unit for downlink transmission of data. The baseband unit comprises an obtaining module configured to obtain, from a network node, a configuration in terms of time synchronization information and time scheduling information, the time synchronization information being for compensating for a difference in time delay between the radio unit and the baseband unit for the downlink transmission of data, the time scheduling information identifying which transmission slots per frame that are allowed to be used by the baseband unit for the downlink transmission of data. The baseband unit comprises a transmitting module configured to transmit downlink data to the radio unit in accordance with the configuration.

[0015] According to an eighth aspect, there is presented a computer program for enabling time synchronization and coordinated downlink transmission of data from a radio unit 120, the computer program comprising computer program code which, when run on processing circuitry of a baseband unit, causes the baseband unit to implement the method according to the fifth aspect.

[0016] According to a ninth aspect, there is presented a computer program product comprising a computer program according to at least one of the fourth and eighth aspects and a computer readable storage medium on which the computer program is stored. The computer readable storage medium can be a non-transitory computer readable storage medium.

[0017] Advantageously, the methods, network nodes, baseband units, computer programs and computer program products provide efficient energy saving in a communication network where at least two baseband units are connected to the same radio unit.

[0018] Advantageously, the methods, network nodes, baseband units, computer programs and computer program products can be used to reduce heat generation in a radio unit.

[0019] In turn, reduced heat generation in a radio unit results in relaxed thermal design requirements for the radio unit, resulting in reduced product weight and volume.

[0020] Advantageously, the methods, network nodes, baseband units, computer programs and computer program products result in reduced energy related operational expenses for a mobile network operator.

[0021] Advantageously, the methods, network nodes, baseband units, computer programs and computer program products result in reduced environmental impact on a cellular communication network.

[0022] Other objects, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, the appended claims, and the accompanying drawings.

[0023] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined herein elsewhere. All references to a / an / the [element, device, apparatus, component, means, step, etc.] are to be interpreted openly as referring to at least one instance of said element, device, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed unless explicitly stated. BRIEF DESCRIPTION OF DRAWINGS

[0024] The concept of the present application will now be described more fully below with reference to the accompanying drawings, in which:

[0025] Figure 1 is a schematic diagram illustrating a communication system according to an embodiment;

[0026] Figure 2 is a schematic diagram illustrating an access node according to an embodiment;

[0027] Figure 3 and Figure 4 is a flowchart of a method according to an embodiment;

[0028] Figure 5 is a schematic illustration of a time / frequency resource grid according to an embodiment;

[0029] Figure 6 is a schematic diagram illustrating functional units of a network node according to an embodiment;

[0030] Figure 7 is a schematic diagram illustrating functional modules of a network node according to an embodiment;

[0031] Figure 8 is a schematic diagram illustrating functional units of a baseband unit according to an embodiment;

[0032] Figure 9 is a schematic diagram illustrating functional modules of a baseband unit according to an embodiment; and

[0033] Figure 10 shows one example of a computer program product comprising computer readable means according to an embodiment. DETAILED DESCRIPTION

[0034] The concept of the present application will now be described more fully below with reference to the accompanying drawings, in which:

[0035] Figure 1is a schematic diagram illustrating a communication system 100 in which embodiments presented herein can be applied. The communication system 100 includes a (radio) access node 110 and wireless devices 130a, 130b. The (radio) access node 110 can be any of a radio base station, a base transceiver station, a Node-B, an evolved Node-B, a gNB, an access point, an access node, an integrated access and backhaul node. Each wireless device 130a, 130b can be any of a portable wireless device, a mobile station, a mobile phone, a handset, a wireless local loop phone, a user equipment (UE), a smart phone, a laptop, a tablet computer, a wearable electronic device, a wireless modem, a wireless sensor device, a vehicle equipped with a network.

[0036] In turn, the (radio) access node 110 comprises a radio unit 120 and two baseband units 300a, 300b. In this regard, it can be understood that the (radio) access node 110 typically comprises at least two baseband units 300a, 300b, and thus can comprise a plurality of baseband units 300a, 300b. The baseband units 300a, 300b are utilized by one or more mobile network operators. Thus, each of the baseband units 300a, 300b can be associated with its own mobile network operator. But in other examples, two or more of the baseband units 300a, 300b are associated with the same same mobile network operator, possibly operating different radio access technologies from each other. The at least two baseband units 300a, 300b are operatively connected to the radio unit 120 for downlink transmission of data (towards the wireless devices 130a, 130b) and / or for uplink reception of data (from the wireless devices 130a, 130b).

[0037] In Figure 1 Examples, the (radio) access node 110 further comprises a network node 200. Thus, the network node 200 is shown as part of the (radio) access node 110. However, in other examples, the network node 200 is provided in, collocated with, or integrated with the radio unit 120. In yet other examples, the network node 200 is provided in, collocated with, or integrated with a central network node. Further aspects of the network node 200 will be disclosed below.

[0038] As disclosed above, there is still a need for efficient energy saving in a communication network in which different baseband units 300a, 300b are connected to the same radio unit 120.

[0039] In more detail, when the radio unit 120 is connected to several baseband units 300a, 300b, it cannot be guaranteed that the input signals from each baseband unit 300a, 300b to the radio unit 120 will contain simultaneous idle periods. This situation is schematically shown in Figure 2 . Figure 2 In more detail, a (radio) access network node 110 is schematically shown Figure 1 . As Figure 2 indicated, each baseband unit 300a, 300b has its own scheduler 340a, 340b, and each baseband unit 300a, 300b generates its own input signal to the radio unit 120 on a respective carrier. The input signals are shown at respective time / frequency resource grids 350a, 350b. According to the illustrative example of Figure 2 , the time / frequency resource grids 350a, 350b are out of time synchronization with respect to each other by At (corresponding to about half a time slot in duration), and occupy different frequency bands. The schedulers are responsible for the scheduling of transmission and reception time slots for their baseband units. Thus, in some aspects, the network node 200 is in communication with the schedulers in each baseband unit 300a, 300b. The input signals are combined at the radio unit 120 in a combiner 140 (which may, for example, be implemented as a summer), and transmitted on an antenna array represented by an antenna 150 (but where the antenna array can have multiple antennas or antenna elements).

[0040] The carriers of the different baseband units 300a, 300b are not active at different times. This results in a reduction in the efficiency of MSTx and LESS if performed separately for each baseband unit 300a, 300b. The time of energy saving with MSTx is even further reduced if there is no symbol synchronization and / or time slot synchronization between the carriers. This is shown at reference numeral 360, which shows the resulting output power at the radio unit 120 as a function of time on the same time scale as the time / frequency resource grids 350a, 350b (where the time scale is divided into units, where each unit corresponds to half a time slot). Although both baseband units 300a, 300b are silent in 5 out of 8 time slots (i.e., only 37.5% of the time is active), the radio unit 120 still needs to be active 62.5% of the time.

[0041] Further, in the absence of synchronization of radio frames, mandatory transmissions such as system information and synchronization signal broadcast can occur at different occasions on different carriers, further reducing the effect of energy saving using MSTx, as implemented using power amplifier controller 160 and power amplifier 170 at radio unit 120. Further, it can be difficult or even impossible to transfer information between baseband units 300a, 300b themselves. This is especially challenging if baseband units 300a, 300b belong to different mobile network operators. In summary, energy saving mechanisms and techniques such as symbol based power saving (SBPS) and LESS do not work well in multi-band / multi-RAT / multi-carrier / multi-operator / multi- baseband configurations.

[0042] Accordingly, embodiments disclosed herein relate to mechanisms for enabling time synchronized and coordinated downlink transmission of data from radio unit 120. To obtain such mechanisms, a network node 200, a method implemented by a network node 200, a computer program product comprising code, e.g. in the form of a computer program, which when run on processing circuitry of the network node 200, causes the network node 200 to implement the method, are provided. To obtain such mechanisms, further a baseband unit 300a, 300b, a method implemented by a baseband unit 300a, 300b, and a computer program product comprising code, e.g. in the form of a computer program, which when run on processing circuitry of the baseband unit 300a, 300b, causes the baseband unit 300a, 300b to implement the method, are provided.

[0043] Reference is now made to Figure 3 , Figure 3 A method for enabling time synchronized and coordinated downlink transmission of data from radio unit 120 as implemented by a network node 200 according to embodiments is shown.

[0044] S102: Network node 200 configures at least two baseband units 300a, 300b. The at least two baseband units 300a, 300b are operatively connected to radio unit 120 for downlink transmission of data.

[0045] Network node 200 configures the at least two baseband units 300a, 300b with time synchronization information for compensating for a difference in latency between radio unit 120 and each of the at least two baseband units 300a and 300b for downlink transmission of data.

[0046] The network node 200 configures the at least two baseband units 300a, 300b with time scheduling information identifying which transmission slots per frame are allowed to be used by the at least two baseband units 300a and 300b for downlink transmission of data.

[0047] In some aspects, the time synchronization information and the time scheduling information are provided to a scheduler in each baseband unit 300a, 300b.

[0048] The method coordinates transmissions from multiple baseband units 300a, 300b connected to the same radio unit 120 in order to ensure efficient energy saving, e.g. with LESS and MSTx.

[0049] Embodiments relating to further details of implementing time synchronization and coordination of downlink transmissions of data from a radio unit 120 as implemented by a network node 200 will now be disclosed.

[0050] In some aspects, the at least two baseband units 300a, 300b are not time synchronized with each other. Hence, in some embodiments, the time synchronization information relates to a time synchronization difference between the at least two baseband units 300a, 300b.

[0051] There can be one or more levels of time synchronization between the baseband units 300a, 300b. In some embodiments, the time synchronization information relates to symbol level time synchronization, slot level time synchronization or frame level time synchronization for compensating for latency differences. That is, when the radio unit 120 receives multiple signals from the baseband units 300a, 300b, one or more levels of time synchronization between these baseband units 300a, 300b is ensured. For example, symbol level synchronization can be created in the radio unit 120, e.g. by delaying the input signal(s) by a fraction of a symbol (in case of different subcarrier spacing, in steps of the smallest common numerology). For example, slot level synchronization can be created in the radio unit 120, e.g. by delaying the input signal(s) by a fraction of a slot (depending on subcarrier spacing). For example, system frame number (SFN) level synchronization can be created in the radio unit 120, e.g. by ensuring a common start of radio frame counters in the attached baseband units 300a, 300b.

[0052] Furthermore, in this regard, the baseband units 300a, 300b are only roughly time synchronized in the sense that the transmission time slot boundaries do not exactly match. In the case of the New Radio (NR) air interface in the fifth generation (5G) telecommunication system, it is possible to schedule transmissions that do not start and stop at the time slot boundaries. To address this issue, one of the schedulers (e.g., the scheduler with the smallest subcarrier spacing) can have a preferential scheduling window that starts slightly after the time slot boundary (e.g., 1 Orthogonal Frequency-Division Multiplexing (OFDM) symbol after the time slot boundary) and / or ends slightly before the time slot boundary (e.g., 1 OFDM symbol before the time slot boundary).

[0053] Time synchronization on the SFN level or the radio frame level can require that the radio unit (or some other network unit such as the network node 200) is configured to control the timing of the SFN counter start. This will ensure that the synchronization signal block (SSB) and system information (SI) transmissions approximately occur at the same time in the different signal components received by the radio unit 120 (at least where possible).

[0054] By allowing the radio unit 120 or the network node 200 to provide a time correction term to the baseband units 300a, 300b, different levels of time synchronization can be created. The time correction term can be provided in terms of an absolute time reference (e.g., with a GPS receiver in the radio unit 120) or a relative time reference (e.g., a message indicating the start of a clock can be sent from the radio unit 120 or the network node 200 to all connected baseband units 300a, 300b). That is, in some embodiments, the network node 200 configures the at least two baseband units 300a, 300b with time synchronization information as an absolute time reference or as a relative time reference.

[0055] In a further aspect, periodic compensation of timing drift between the attached baseband units 300a, 300b can be required. That is, in some embodiments, the network node 200 periodically configures the at least two baseband units 300a, 300b with time synchronization information.

[0056] In a further aspect, one of the baseband units 300a, 300b acts as a master time keeper, and the radio unit 120 or the network node 200 informs the other connected baseband units 300a, 300b to synchronize their timing relative to the master unit. That is, in some embodiments, the network node 200 uses time information from one of the at least two baseband units 300a, 300b as a time reference for the time synchronization information.

[0057] By defining overlapping priority transmission slots for the baseband units 300a, 300b, the non-transmission time periods of different baseband units 300a, 300b can be highly correlated. This also applies to cases where the numerologies between the baseband units 300a, 300b differ. That is, in some embodiments, at least two of the at least two baseband units 300a, 300b use different numerologies with respect to each other for the downlink transmission of data, and the time scheduling information is adapted to each numerology. In this regard, the time scheduling information can be adapted such that the priority transmission slots or allowed transmission slots in the different numerologies at least partially overlap. The following described embodiments are applicable to both cases, i.e. where the numerologies between the baseband units 300a, 300b are the same and where the numerologies between the baseband units 300a, 300b differ. Figure 5 Examples are given.

[0058] In some aspects, the radio unit 120 or the network node 200 informs the baseband units 300a, 300b of the priority transmission slots or priority low bandwidth slots. In other aspects, the priority transmission slots are defined as a static or semi-static configuration for each baseband unit 300a, 300b. In some examples, there are multiple levels of priority slots. That is, in some embodiments, the time synchronization information specifies an order of priority of the transmission slots of each frame that are allowed to be used by the at least two baseband units 300a, 300b for the downlink transmission of data. For example, according to the order of priority, the baseband units 300a, 300b should attempt to only utilize the highest priority transmission slots when scheduling the downlink transmission of data. When all of the highest priority transmission slots have been filled, the baseband units 300a, 300b should attempt to only utilize the second highest priority transmission slots when scheduling the downlink transmission of data, etc.

[0059] The indication of which transmission slots are considered priority can be dynamically adjusted. The network node 200 can make such dynamic adjustments with the assistance of or by means of input from a central network management node, e.g. an Operations Support System (OSS) node or a Self-Optimizing Network (SON) node, etc. The adjustment can be based on, for example, the amount of time sensitive traffic in the network or in a particular cell. That is, in some embodiments, the data to be transmitted is associated with a level of time sensitivity, and the network node 200 accesses the information of the time sensitivity for dynamically updating the time scheduling information. In other embodiments, each of the at least two baseband units 300a, 300b is configured with the same transmission slots of each frame that are allowed to be used for the downlink transmission of data.

[0060] In further aspects, the radio unit 120 or network node 200 informs the baseband unit 300a, 300b how many priority transmission slots the radio unit 120 is able to handle during a certain time unit, such as a radio frame. The number of priority transmission slots can be adjusted dynamically and can be based on, for example, the current load in the radio unit 120, the temperature of a certain component or subsystem. Accordingly, in some aspects, instead of specifying which transmission slots are prioritized for transmission, instead, transmission slots are specified that are prioritized to be empty.

[0061] In some aspects, the radio unit 120 is configured to dynamically adjust its mode of operation by inspecting the input signals from the baseband unit 300a, 300b. In particular, in some embodiments, the radio unit 120 comprises a power amplifier (PA) 170 and a PA controller 160, and the network node 200 provides input to the PA controller 160 for dynamically adjusting the PA 170 according to the maximum power or data rate required for the downlink transmission of data. In some examples, the PA bias can be dynamically determined by inspecting the peak power of each data stream and the peak data rate (or modulation order) from the baseband unit 300a, 300b. In terms of PA bias, the peak power of all attached signals can be determined, for example, by adding the side information provided in each data stream. In terms of peak data rate or modulation bias, the maximum data rate or modulation order in all attached signals can be determined, and the PA backoff can be adjusted accordingly; lower data rates or modulation orders result in less PA backoff. Furthermore, after combining all input component signals, digital processing can adapt to the requirements of the sum signal. The radio unit 120 can activate digital processing resources based on a predetermined function of the scheduled bandwidth, the number of branches, the number of wireless devices 130a, 130b, the number of layers, etc., in all attached input signal components.

[0062] In some aspects, the one or more other baseband units 300a, 300b can use temporary excess radio capacity (e.g. caused by a cool outdoor temperature, or one or more of the baseband units 300a, 300b not operating in full throughput mode, etc.). In particular, in some embodiments, the network node 200 obtains information of the temporary excess radio capacity at the radio unit 120, and according to the information of the temporary excess radio capacity, the network node 200 dynamically updates the time scheduling information by allocating further transmission slots per frame allowed to be used by the at least two baseband units 300a, 300b for data downlink transmission. This can be achieved by feedback from the radio unit 120 or the network node 200 to one or more of the baseband units 300a, 300b regarding availability of excess radio unit capacity. In particular, in some embodiments, the network node 200 obtains information of downlink traffic load at each of the baseband units 300a, 300b, and according to the information of the downlink traffic load, the network node 200 dynamically updates the time scheduling information by allocating further transmission slots per frame not used by one of the at least two baseband units 300a, 300b to another of the at least two baseband units 300a, 300b.

[0063] In some aspects, a priority of scheduling bandwidth of the baseband units 300a, 300b is deployed. Thus, the network node 200 can configure the baseband units 300a, 300b with frequency scheduling information. In particular, in some embodiments, the network node 200 is configured to implement (optional) step S104:

[0064] S104: The network node 200 configures the at least two baseband units 300a, 300b with frequency scheduling information identifying which frequency bands per frame are allowed to be used by the at least two baseband units 300a and 300b for data downlink transmission.

[0065] In some aspects, the frequency scheduling information is provided to a scheduler in each of the baseband units 300a, 300b.

[0066] This means that, where possible, the baseband units 300a, 300b should try to reduce the scheduling bandwidth in a particular step. This can e.g. be used in the radio unit 120 to reduce the number of digital processing resources that need to be activated for data downlink transmission.

[0067] Generally, any of the above disclosed embodiments can be applied to uplink reception of data. That is, data for the baseband units 300a, 300b is received from the wireless devices 130a, 130b in a reception time slot by the radio unit 120. This means that the baseband units 300a, 300b are operatively connected to the radio unit 120 for uplink reception of data. In particular, in some embodiments, the network node 200 is configured to implement (optional) step S106:

[0068] S106: The network node 200 configures the at least two baseband units 300a, 300b with time scheduling information identifying possible reception time slots per frame for uplink reception of data at the at least two baseband units 300a, 300b.

[0069] In some aspects, the time scheduling information is provided to a scheduler in each baseband unit 300a, 300b.

[0070] In some examples, each baseband unit 300a, 300b signals information of scheduled uplink activity to the radio unit 120 or the network node 200. The radio unit 120 or the network node 200 can then inform other ones of the baseband units 300a, 300b of the planned uplink activity in order to co-locate uplink activity of two or more baseband units 300a, 300b. In turn, this can result in an increased number of unused reception time slots at the radio unit 120.

[0071] The network node 200 can have different ways of configuring the at least two baseband units 300a, 300b with the time synchronization information and the time scheduling information in step S102 (and with the frequency scheduling information in step S104 and the time scheduling information in step S106). In some examples, the at least two baseband units 300a, 300b are configured with the time synchronization information and the time scheduling information by step S102 (and the frequency scheduling information in step S104 and the time scheduling information in step S106), wherein the time synchronization information and the time scheduling information are provided in control messages sent on an interface between the network node 200 and each of the at least two baseband units 300a, 300b or piggybacked with uplink data. One example of such an interface is Common Public Radio Interface (CPRI).

[0072] Reference is now made to Figure 4 , Figure 4A method for enabling time-synchronized and coordinated downlink transmission of data from a radio unit 120 as implemented by one of the baseband units 300a, 300b according to an embodiment is shown. The baseband unit 300a, 300b is operatively connected to the radio unit 120 for downlink transmission of data.

[0073] S202: The baseband unit 300a, 300b acquires a configuration regarding time synchronization information for compensating for a time delay difference between the radio unit 120 and the baseband unit 300a, 300b for downlink transmission of data and time scheduling information identifying which transmission slots per frame are allowed to be used by the baseband unit 300a, 300b for downlink transmission of data.

[0074] In some aspects, the configuration is acquired by a scheduler in the baseband unit 300a, 300b.

[0075] S206: The baseband unit 300a, 300b transmits downlink data to the radio unit 120 according to the configuration.

[0076] In some aspects, the transmission of downlink data is scheduled by a scheduler in the baseband unit 300a, 300b according to the configuration.

[0077] Embodiments relating to further details of enabling time-synchronized and coordinated downlink transmission of data from a radio unit 120 as implemented by the baseband unit 300a, 300b will now be disclosed.

[0078] Generally, the embodiments disclosed above relating to the operation of the network node 200 also apply to the operation of each baseband unit 300a, 300b.

[0079] As disclosed above, at least two baseband units 300a, 300b are operatively connected to the radio unit 120 for downlink transmission of data and the at least two baseband units 300a, 300b are not time-synchronized with each other. Thus, in some embodiments, the time synchronization information relates to a time synchronization difference between the baseband unit 300a, 300b and another baseband unit 300a, 300b.

[0080] As disclosed above, there can be one or more levels of time synchronization between the baseband units 300a, 300b. Thus, in some embodiments, the time synchronization information relates to symbol-level time synchronization, slot-level time synchronization or frame-level time synchronization for compensating for a time delay difference.

[0081] As disclosed above, by allowing the radio unit 120 or the network node 200 to provide the baseband unit 300a, 300b with a time correction term in terms of absolute time reference or relative time reference, different levels of time synchronization can be created. Thus, in some embodiments, the baseband unit 300a, 300b is configured with time synchronization information as absolute time reference or as relative time reference.

[0082] As disclosed above, periodic compensation of timing drift between attached baseband units 300a, 300b can be required. Thus, in some embodiments, the baseband unit 300a, 300b periodically acquires said configuration.

[0083] As disclosed above, the network node 200 can use time information from one of said at least two baseband units 300a, 300b as time reference for the time synchronization information. Thus, in some embodiments, time information from the baseband unit 300a, 300b is used as time reference for the time synchronization information.

[0084] As disclosed above, the network node 200 can inform the baseband unit 300a, 300b of a preferred transmission slot or a preferred low-bandwidth slot. Thus, in some embodiments, the time synchronization information specifies a priority order of transmission slots per frame that are allowed to be used by the baseband unit 300a, 300b for downlink transmission of data.

[0085] As disclosed above, the network node 200 can configure the baseband unit 300a, 300b with frequency scheduling information, as in (optional) step S104. Thus, in some embodiments, the baseband unit 300a, 300b is configured to implement (optional) step S204:

[0086] S204: The baseband unit 300a, 300b acquires from the network node 200 a configuration regarding frequency scheduling information, said frequency scheduling information identifying which frequency bands per frame that are allowed to be used by the baseband unit 300a, 300b for downlink transmission of data.

[0087] In some aspects, said configuration is acquired by a scheduler in the baseband unit 300a, 300b.

[0088] Downlink transmission of data from the baseband unit 300a, 300b is then adapted according to the frequency scheduling information.

[0089] As disclosed above, in some aspects, the baseband units 300a, 300b are operatively connected to the radio unit 120 for uplink reception of data, and the network node 200 configures the baseband units 300a, 300b with time scheduling information identifying possible reception time slots per frame for uplink reception of data, as in (optional) step S106. Thus, in some embodiments, the baseband units 300a, 300b are configured to implement (optional) step S208 and step S210:

[0090] S208: The baseband units 300a, 300b obtain configuration from the network node 200 in terms of time scheduling information identifying possible reception time slots per frame for uplink reception of data at the baseband units 300a, 300b.

[0091] In some aspects, the configuration is obtained by a scheduler in the baseband units 300a, 300b.

[0092] S210: The baseband units 300a, 300b receive uplink data from the radio unit 120 according to the configuration.

[0093] In some aspects, the reception of uplink data is scheduled by a scheduler in the baseband units 300a, 300b according to the configuration.

[0094] As disclosed above, the network node 200 can have different ways of configuring the baseband units 300a, 300b with the time synchronization information and time scheduling information as received in step S202 (and the frequency scheduling information as received in step S204 and the time scheduling information as received in step S208). That is, in some embodiments, the baseband units 300a, 300b are configured with the time synchronization information and time scheduling information (and the frequency scheduling information as received in step S204 and the time scheduling information as received in step S208) by obtaining it from control messages sent on an interface between the network node 200 and the baseband units 300a, 300b or piggybacked with the uplink data. One example of such an interface is the Common Public Radio Interface (CPRI).

[0095] Figure 5 An example of the schedulers of the two baseband units 300a, 300b using different numerologies from each other is schematically illustrated in the form of time / frequency (t / f) resource grids. The time / frequency resource grid for the baseband unit 300a is as illustrated in Figure 5 (a) and Figure 5 (b), while the time / time resource grid for the baseband unit 300b is as illustrated in Figure 5 (c) and Figure 5(d) are shown. It is assumed that two baseband units 300a, 300b are connected to the radio unit 120 for downlink transmission of data (and / or uplink reception of data). Thus, the time slot numbering is different for the two baseband units 300a, 300b; the time slot numbering for baseband unit 300a goes from 0 to 7, while the time slot numbering for baseband unit 300b goes from 0 to 15. According to the time scheduling information, baseband unit 300a prioritizes time slots 3 and 7, while baseband unit 300a prioritizes time slots 6, 7, 14 and 15. Due to the use of different numerologies, time slot 3 of baseband unit 300a overlaps with time slots 6 and 7 of baseband unit 300b, while time slot 7 of baseband unit 300a overlaps with time slots 14 and 15 of baseband unit 300b. Thus, as shown in Figure 5 (a) and Figure 5 (c) are shown) how the scheduled time / frequency resources (before configuration, as shown in Figure 5 (a) and Figure 5 (c) are shown) how the scheduled time / frequency resources (before configuration, as shown in Figure 5 (a) and

[0096] Figure 6 The components of the network node 200 according to an embodiment are schematically shown in the form of a number of functional units. The processing circuitry 210 is provided using any combination of one or more of a multitude of Figure 10 processing units, such as CPUs, microprocessors, microcontrollers, digital signal processors (DSPs), etc. capable of executing software instructions stored in a computer program product 1010a (as shown in

[0097] In particular, the processing circuitry 210 is configured to cause the network node 200 to perform a set of operations or a set of steps as disclosed above. For example, the storage medium 230 can store a set of instructions, and the processing circuitry 210 can be configured to retrieve the set of instructions from the storage medium 230 to cause the network node 200 to perform the set of instructions. The set of instructions can be provided as a set of executable instructions. Thus, the processing circuitry 210 is thereby arranged to perform the methods as herein disclosed.

[0098] The storage medium 230 can further include a persistent memory, e.g. the persistent memory can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0099] The network node 200 can further include a communication interface 220 for communicating with at least the radio unit 120 and the baseband unit 300a, 300b. As such, the communication interface 220 can comprise one or more transmitters and receivers, comprising analog and digital components.

[0100] The processing circuitry 210 controls the general operation of the network node 200, e.g. by sending data and control signals to the communication interface 220 and the storage medium 230, by receiving data and reports from the communication interface 220, and by retrieving data and instructions from the storage medium 230. Other components and their related functionality, of the network node 200, are omitted in order to not

[0101] Figure 7 The components of the network node 200 according to embodiments are schematically shown in the form of a number of functional modules. Figure 7 The network node 200 of the first aspect comprises a configuration module 210a configured to perform step S102. Figure 7 The network node 200 of the first aspect can further comprise a number of optional functional modules, such as any one of a configuration module 210b configured to perform step S104 and a configuration module 210c configured to perform step S106. In general terms, each functional module 210a: 210c can be implemented in hardware or in software. Preferably, one or more or all functional modules 210a: 210c can be implemented by the processing circuitry 210, possibly in cooperation with the communication interface 220 and / or the storage medium 230. Thus, the processing circuitry 210 can be arranged to fetch instructions provided by a functional module 210a: 210c from the storage medium 230 and to execute these instructions, thereby performing any steps of the network node 200 as herein disclosed.

[0102] Network node 200 can be provided as a standalone device or as part of at least one other device. For example, network node 200 can be provided in a node of a radio access network or in a node of a core network. Optionally, the functionality of network node 200 can be distributed among at least two devices or nodes. These at least two nodes or devices can be part of the same network component (such as a radio access network or a core network), or can be distributed among at least two such network components. Generally, instructions that need to be implemented in real time can be implemented in devices or nodes that are operationally closer to the cell than instructions that do not need to be implemented in real time.

[0103] Therefore, the first portion of the instructions implemented by network node 200 can be executed in a first device, while the second portion of the instructions implemented by network node 200 can be executed in a second device; the embodiments disclosed herein are not limited to any particular number of devices on which the instructions implemented by network node 200 can be executed. Therefore, the method according to the embodiments disclosed herein is suitable for implementation by network node 200 residing in a cloud computing environment. Therefore, although Figure 6 A single processing circuit 210 is shown, but processing circuits 210 can be distributed across multiple devices or nodes. This also applies to... Figure 7 Functional modules 210a: 210c and Figure 10 Computer program 1020a.

[0104] Figure 8 The components of the baseband units 300a and 300b according to the embodiment are schematically shown in the form of multiple functional units. The processing circuitry 310 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., which is capable of executing a computer program product 1010b (such as...) Figure 10 The software instructions (shown) are provided, for example, in the form of storage medium 330. The processing circuitry 310 may further be provided as at least one application-specific integrated circuit (ASIC) or field-programmable gate array (FPGA).

[0105] Specifically, the processing circuit 310 is configured to cause the baseband units 300a and 300b to perform a set of operations or steps, as disclosed above. For example, the storage medium 330 may store the set of operations, and the processing circuit 310 may be configured to retrieve the set of operations from the storage medium 330 to cause the baseband units 300a and 300b to perform the set of operations. The set of operations may be provided as a set of executable instructions. Thus, the processing circuit 310 is thereby arranged to perform the methods disclosed herein.

[0106] The storage medium 330 can also include persistent memory, e.g., which can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory.

[0107] The baseband units 300a, 300b can further include a communication interface 320 for communicating with at least the network node 200 and the radio unit 120. As such, the communication interface 320 can comprise one or more transmitters and receivers, comprising analog and digital components.

[0108] The processing circuitry 310 controls the general operation of the baseband unit 300a, 300b e.g. by sending data and control signals to the communication interface 320 and the storage medium 330, by receiving data and reports from the communication interface 320, and by retrieving data and instructions from the storage medium 330. Other components and their related functionality in the baseband unit 300a, 300b have been omitted in order to not obscure the concepts presented herein.

[0109] Figure 9 The components of the baseband unit 300a, 300b according to embodiments are schematically shown in the form of a number of functional modules. Figure 9 The baseband unit 300a, 300b comprises a number of functional modules; an obtaining module 310a configured to implement step S202 and a transmitting module 310c configured to implement step S206. Figure 9 The baseband unit 300a, 300b can further comprise a number of optional functional modules, such as any one of an obtaining module 310b configured to implement step S204, an obtaining module 310d configured to implement step S206 and a receiving module 310d configured to implement step S210. In general terms, each functional module 310a:310e can be implemented in hardware or in software. Preferably, one or more or all functional modules 310a:310e can be implemented by the processing circuitry 310, possibly in cooperation with the communication interface 320 and / or the storage medium 330. Thus, the processing circuitry 310 can be arranged to, from the storage medium 330, retrieve instructions provided by a functional module 310a:310e and perform these instructions, thereby implementing any steps of the baseband unit 300a, 300b as disclosed herein.

[0110] Figure 10One example of a computer program product 1010a, 1010b comprising computer readable means 1030 is shown. In this computer readable means 1030, a computer program 1020a can be stored, which computer program 1020a can cause the processing circuitry 210, and thereto operatively coupled entities and devices such as the communications interface 220 and the storage medium 230, to execute methods according to embodiments described herein. As such, the computer program 1020a and / or computer program product 1010a can provide means for implementing any steps of methods of the network node 200 as disclosed herein. In this computer readable means 1030, a computer program 1020b can be stored, which computer program 1020b can cause the processing circuitry 310, and thereto operatively coupled entities and devices such as the communications interface 320 and the storage medium 330, to execute methods according to embodiments described herein. As such, the computer program 1020b and / or computer program product 1010b can provide means for implementing any steps of methods of the baseband unit 300a, 300b as disclosed herein.

[0111] In Figure 10 In the example of Fig. 10, the computer program product 1010a, 1010b is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 1010a, 1010b could also be embodied as a memory such as a random access memory (RAM), a read only memory (ROM), an erasable programmable read only memory (EPROM) or an electrically erasable programmable read-only memory (EEPROM), and more particularly as a non-volatile storage medium of a device, such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. As such, although the computer program 1020a, 1020b is here schematically illustrated as a track on the depicted disc, the computer program 1020a, 1020b can be stored in any way which is appropriate for the computer program product 1010a, 1010b.

[0112] The concepts of the present application have mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the concepts of the present application, as defined by the appended patent claims.

Claims

1. A method for enabling time synchronized and coordinated arrival of downlink data from at least two baseband units (300a, 300b) at a radio unit (120), the method being implemented by a network node (200), the method comprising: configuring (S102) the at least two baseband units (300a, 300b) operatively connected to the radio unit (120) for downlink transmission of data with: - time synchronization information for compensating for a difference in latency between the radio unit (120) and each of the at least two baseband units (300a, 300b) for the downlink transmission of data, wherein the time synchronization information specifies a priority order of transmission slots per frame allowed by the at least two baseband units (300a, 300b) for the downlink transmission of data, and - time scheduling information identifying which transmission slots per frame are allowed by the at least two baseband units (300a, 300b) for the downlink transmission of data, wherein the at least two baseband units (300a, 300b) are configured with overlapping priority transmission slots using the time scheduling information such that the at least two baseband units (300a, 300b) scheduled time / frequency resources before the configuration are mapped to new scheduled time / frequency resources after the configuration, and the at least two baseband units (300a, 300b) have more identical transmission free periods after the configuration compared to before the configuration.

2. The method of claim 1, wherein, The time synchronization information relates to symbol level time synchronization, slot level time synchronization or frame level time synchronization for compensating for the difference in latency.

3. The method of any one of claims 1-2, wherein, The network node (200) configures the at least two baseband units (300a, 300b) with the time synchronization information as an absolute time reference or as a relative time reference.

4. The method of any one of claims 1 to 2, wherein, The time synchronization information relates to a time synchronization difference between the at least two baseband units (300a, 300b).

5. The method of any one of claims 1 to 2, wherein, The network node (200) periodically configures the at least two baseband units (300a, 300b) with the time synchronization information.

6. The method of any one of claims 1 to 2, wherein, The network node (200) uses time information from one of the at least two baseband units (300a, 300b) as a time reference for the time synchronization information.

7. The method of any one of claims 1 to 2, wherein, Each of the at least two baseband units (300a, 300b) is configured with identical transmission slots per frame allowed for the downlink transmission of data.

8. The method of any one of claims 1 to 2, wherein, The data to be transmitted is associated with a level of time sensitivity, and wherein the network node (200) accesses the time sensitivity information for dynamically updating the time scheduling information.

9. The method of any one of claims 1 to 2, wherein, At least two of the at least two baseband units (300a, 300b) use different sets of parameters relative to each other for the downlink transmission of data, and wherein the time scheduling information is adapted to each of the sets of parameters.

10. The method of any one of claims 1 to 2, wherein, The radio unit (120) comprises a power amplifier (170) and a power amplifier controller (160), and wherein the network node (200) provides input to the power amplifier controller (160) for dynamically adjusting the power amplifier (170) according to a maximum power or data rate required for the downlink transmission of data.

11. The method of any one of claims 1 to 2, wherein, The network node (200) obtains information of temporary excess radio capacity at the radio unit (120), and wherein the network node (200) dynamically updates the time scheduling information by allocating further transmission slots per frame that are allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data according to the information of temporary excess radio capacity.

12. The method of any one of claims 1 to 2, wherein, The network node (200) obtains information of downlink traffic load at each of the baseband units (300a, 300b), and wherein the network node (200) dynamically updates the time scheduling information by allocating further transmission slots per frame that are not used by one of the at least two baseband units (300a, 300b) to another one of the at least two baseband units (300a, 300b) according to the information of downlink traffic load.

13. The method of any one of claims 1 to 2, wherein, The method further comprises: configuring (S104) the at least two baseband units (300a, 300b) with frequency scheduling information that identifies which frequency bands per frame are allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data.

14. The method of any one of claims 1 to 2, wherein, The method further comprises: configuring (S106) the at least two baseband units (300a, 300b) with time scheduling information that identifies possible reception slots per frame for uplink reception of data at the at least two baseband units (300a, 300b).

15. The method of any one of claims 1 to 2, wherein, The at least two baseband units (300a, 300b) are configured by the time synchronization information and the time scheduling information being provided in control messages sent on an interface between the network node (200) and each of the at least two baseband units (300a, 300b) or piggybacked with uplink data.

16. The method of any one of claims 1 to 2, wherein, The network node (200) is provided in, collocated with, or integral to any of: the radio unit (120), a central network node.

17. A method for time synchronization and coordination of downlink transmissions of data arriving at a radio unit (120) from a first baseband unit (300a, 300b) and downlink transmissions of data arriving at the radio unit (120) from at least a second baseband unit, the method being implemented by the first baseband unit (300a, 300b) operatively connected to the radio unit (120) for downlink transmissions of data, the method comprising: obtaining (S202), from a network node (200), a configuration regarding: - time synchronization information for compensating for a difference in latency between the radio unit (120) and the first baseband unit (300a, 300b) for the downlink transmissions of data, wherein the time synchronization information specifies a priority order of transmission slots per frame allowed to be used by the first baseband unit (300a, 300b) for the downlink transmissions of data, and - time scheduling information identifying which transmission slots per frame are allowed to be used by the first baseband unit (300a, 300b) for the downlink transmissions of data, wherein the first baseband unit (300a, 300b) and the second baseband unit are configured with overlapping priority transmission slots using the time scheduling information, such that the scheduled time / frequency resources of the first baseband unit (300a, 300b) and the second baseband unit before the configuration are mapped to new scheduled time / frequency resources after the configuration, and the first baseband unit (300a, 300b) and the second baseband unit have more identical non-transmission periods after the configuration compared to before the configuration; and transmitting (S206) downlink data to the radio unit (120) in accordance with the configuration. The time synchronization information relates to symbol-level time synchronization, slot-level time synchronization or frame-level time synchronization for compensating for the difference in latency. The first baseband unit (300a, 300b) is configured with the time synchronization information as an absolute time reference or as a relative time reference.

18. The method of claim 17, wherein, The time synchronization information relates to a difference in time synchronization between the first baseband unit (300a, 300b) and the second baseband unit (300a, 300b).

19. The method of any one of claims 17-18, wherein, The first baseband unit (300a, 300b) periodically obtains the configuration.

20. The method of any one of claims 17-18, wherein, Time information from the first baseband unit (300a, 300b) is used as a time reference for the time synchronization information.

21. The method of any one of claims 17-18, wherein, The method further comprises:

22. The method of any one of claims 17-18, wherein, obtaining (S204), from the network node (200), a configuration regarding frequency scheduling information identifying which frequency bands per frame are allowed to be used by the first baseband unit (300a, 300b) for the downlink transmissions of data.

23. The method of any one of claims 17-18, wherein, The method further comprises: ​ 24. The method of any one of claims 17-18, wherein, ​ obtaining (S208), from the network node (200), a configuration regarding time scheduling information, the time scheduling information identifying possible reception time slots per frame for uplink reception of data at the first baseband unit (300a, 300b); and receiving (S210) uplink data from the radio unit (120) according to the configuration.

25. The method of any one of claims 17-18, wherein, configuring the first baseband unit (300a, 300b) by the time synchronization information and the time scheduling information, the time synchronization information and the time scheduling information being obtained in control messages sent on an interface between the network node (200) and the first baseband unit (300a, 300b) or piggybacked with uplink data.

26. A network node (200) for enabling time synchronized and coordinated arrival of downlink data from at least two baseband units (300a, 300b) at a radio unit (120), the network node (100) comprising processing circuitry (210), the processing circuitry being configured to cause the network node (20) to: configure the at least two baseband units (300a, 300b) operatively connected to the radio unit (120) for downlink transmission of data with: - time synchronization information for compensating for a difference in time delay between the radio unit (120) used for the downlink transmission of data and each of the at least two baseband units (300a, 300b), wherein, the time synchronization information specifying a priority order of transmission time slots per frame allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data, and time scheduling information identifying which transmission time slots per frame are allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data, wherein the at least two baseband units (300a, 300b) are configured with overlapping prioritized transmission time slots by the time scheduling information to cause the at least two baseband units (300a, 300b) to scheduled time / frequency resources prior to the configuration are mapped to new scheduled time / frequency resources after the configuration, and the at least two baseband units (300a, 300b) have more same transmission free periods after the configuration compared to prior to the configuration.

27. A network node (200) for enabling time synchronized and coordinated arrival of downlink data from at least two baseband units (300a, 300b) at a radio unit (120), the network node (100) comprising: a configuration module (210a) configured to configure the at least two baseband units (300a, 300b) operatively connected to the radio unit (120) for downlink transmission of data with: the time synchronization information specifying a priority order of transmission time slots per frame allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data, and time scheduling information identifying which transmission time slots per frame are allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data, wherein the at least two baseband units (300a, 300b) are configured with overlapping prioritized transmission time slots by the time scheduling information to cause the at least two baseband units (300a, 300b) to - time synchronization information for compensating for a difference in latency between the radio unit (120) used for the downlink transmission of data and each of the at least two baseband units (300a, 300b), wherein the time synchronization information specifies a priority order of transmission slots per frame that are allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data, and - time scheduling information identifying which transmission slots per frame are allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data, wherein the at least two baseband units (300a, 300b) are configured with overlapping priority transmission slots using the time scheduling information, such that the at least two baseband units (300a, 300b) scheduled time / frequency resources before the configuration are mapped to new scheduled time / frequency resources after the configuration, and the at least two baseband units (300a, 300b) have more identical non-transmission periods after the configuration compared to before the configuration.

28. The network node (200) according to claim 26 or 27, further configured to implement the method according to any one of claims 2 to 16.

29. A first baseband unit (300a, 300b) for enabling time synchronization and coordination of downlink transmissions of data from the first baseband unit (300a, 300b) arriving at a radio unit (120) with downlink transmissions of data from at least a second baseband unit arriving at the radio unit (120), the first baseband unit (300a, 300b) being operably connected to the radio unit (120) for downlink transmission of data and comprising processing circuitry (310) configured to cause the first baseband unit (300a, 300b) to: obtain from a network node (200) a configuration regarding: - time synchronization information for compensating for a difference in latency between the radio unit (120) used for the downlink transmission of data and the first baseband unit (300a, 300b), wherein the time synchronization information specifying a priority order of transmission slots per frame that are allowed to be used by the first baseband unit (300a, 300b) for the downlink transmission of data, and - time scheduling information identifying which transmission slots per frame are allowed to be used by the first baseband unit (300a, 300b) for the downlink transmission of data, wherein the first baseband unit (300a, 300b) and the second baseband unit are configured with overlapping priority transmission slots using the time scheduling information, such that the first baseband unit (300a, 300b) ​ - the scheduled time / frequency resources of the first baseband unit (300a, 300b) and the second baseband unit prior to the configuration are mapped to new scheduled time / frequency resources after the configuration, and the first baseband unit (300a, 300b) and the second baseband unit have more identical non-transmission time periods after the configuration than prior to the configuration; and transmitting downlink data to the radio unit (120) in accordance with the configuration.

30. A first baseband unit (300a, 300b) for enabling time synchronization and coordination of downlink transmissions of data from the first baseband unit (300a, 300b) arriving at a radio unit (120) with downlink transmissions of data from at least a second baseband unit arriving at the radio unit (120), the first baseband unit (300a, 300b) being operatively connected to the radio unit (130) for downlink transmission of data and comprising: - time synchronization information for compensating for a difference in latency between the radio unit (120) and the first baseband unit (300a, 300b) for the downlink transmission of data, wherein the time synchronization information specifies a priority order of transmission slots per frame that are allowed to be used by the first baseband unit (300a, 300b) for the downlink transmission of data, and - time scheduling information identifying which transmission slots per frame that are allowed to be used by the first baseband unit (300a, 300b) for the downlink transmission of data, wherein the first baseband unit (300a, 300b) and the second baseband unit are configured with overlapping priority transmission slots using the time scheduling information, such that the scheduled time / frequency resources of the first baseband unit (300a, 300b) and the second baseband unit prior to the configuration are mapped to new scheduled time / frequency resources after the configuration, and the first baseband unit (300a, 300b) and the second baseband unit have more identical non-transmission time periods after the configuration than prior to the configuration; and a transmitting module (310b) configured to transmit downlink data to the radio unit (120) in accordance with the configuration.

31. The first baseband unit (300a, 300b) of claim 29 or 30, further configured to implement the method of any one of claims 18 to 25.

32. A computer program (1020a) for enabling time synchronization and coordination of arrival of downlink data from at least two baseband units (300a, 300b) at a radio unit (120), the computer program comprising computer code which, when run on processing circuitry (210) of a network node (200), causes the network node (200) to: - the scheduled time / frequency resources of the first baseband unit (300a, 300b) and the second baseband unit prior to the configuration are mapped to new scheduled time / frequency resources after the configuration, and the first baseband unit (300a, 300b) and the second baseband unit have more identical non-transmission time periods after the configuration than prior to the configuration; and transmitting downlink data to the radio unit (120) in accordance with the configuration. ​ The at least two baseband units (300a, 300b) are configured (S102) with the following information, the at least two baseband units (300a, 300b) being operatively connected to the radio unit (120) for downlink transmission of data: - time synchronization information for compensating for a difference in time delay between the radio unit (120) used for the downlink transmission of data and each of the at least two baseband units (300a, 300b), wherein, the time synchronization information specifies a priority order of transmission slots per frame that are allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data, and - time scheduling information identifying which transmission slots per frame that are allowed to be used by the at least two baseband units (300a, 300b) for the downlink transmission of data, wherein the at least two baseband units (300a, 300b) are configured with the time scheduling information with overlapping priority transmission slots such that the scheduled time / frequency resources of the at least two baseband units (300a, 300b) before the configuration are mapped to new scheduled time / frequency resources after the configuration, and the at least two baseband units (300a, 300b) have more same transmission free periods after the configuration compared to before the configuration.

33. A computer program (1020b) for enabling time synchronization and coordination of downlink transmission of data from a first baseband unit (300a, 300b) arriving at a radio unit (120) with downlink transmission of data from at least a second baseband unit arriving at the radio unit (120), the computer program comprising computer code which, when run on processing circuitry (310) of the first baseband unit (300a, 300b), causes the first baseband unit (300a, 300b) to: obtain (S202), from a network node (200), a configuration regarding: - time synchronization information for compensating for a difference in latency between the radio unit (120) and the first baseband unit (300a, 300b) for the downlink transmission of data, wherein, the time synchronization information specifies a priority order of transmission slots per frame that are allowed to be used by the first baseband unit (300a, 300b) for the downlink transmission of data, and - time scheduling information identifying which transmission slots per frame that are allowed to be used by the first baseband unit (300a, 300b) for the downlink transmission of data, wherein the first baseband unit (300a, 300b) and the second baseband unit are configured with the time scheduling information with overlapping priority transmission slots such that the scheduled time / frequency resources of the first baseband unit (300a, 300b) before the configuration are mapped to new scheduled time / frequency resources after the configuration, and the first baseband unit (300a, 300b) has more same transmission free periods after the configuration compared to before the configuration. ​ 300b) and the second baseband unit have more same non-transmission periods after the configuration than before the configuration; and transmit (S206) downlink data to the radio unit (120) according to the configuration.

34. A computer program product (1010a, 1010b) comprising a computer program (1020a, 1020b) according to at least one of the claims 32 and 33, and a computer readable storage medium (1030) on which the computer program is stored.

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