Patent Publication Number: US-2022239426-A1

Title: Controlling Data on a Full-Duplex Fronthaul Link

Description:
TECHNICAL FIELD 
     The present disclosure relates to the field of cellular networks, and in particular to an aggregator device and baseband device for controlling data on a full-duplex fronthaul link. 
     BACKGROUND 
     Cellular radio networks like LTE (Long-term Evolution) and NR (New Radio) can operate in different duplexing modes for supporting both UL (uplink) and DL (downlink), such as frequency division duplexing (FDD) and time division duplexing (TDD). In FDD, downlink and uplink carriers are separated in frequency, in which case the transmission in uplink and downlink can occur in parallel (full-duplex operation), and interference can be mitigated by filtering. 
     With TDD, downlink and uplink transmission are on the same frequency, but multiplexed in time. Switching transmission direction over time is called half-duplex operation as only one of DL and UL is active at a given point in time (except the guard period where direction switching is happening). UL data rate and DL data rate can be configured to be symmetric or asymmetric, depending on network support. 
     An aggregator device is provided between a baseband device and the radio devices to be an interface between a single fronthaul link and individual radio device links. The fronthaul link is full-duplex, supporting simultaneous transmission of the data received and transmitted by the radio devices. 
     Hence, cellular TDD radio systems can operate in half-duplex mode whereas the corresponding fronthaul links operate in full-duplex mode. Different asymmetry ratios as well as uplink or pure downlink transmission can occur. In NR, flexible mini-slot transmission as well as delayed listen-before-talk (LBT) operation are supported by the framing structure. 
     Fronthaul links are a costly resource and should be utilised as much as possible. In LTE and NR, the fronthaul links are mostly implemented using optical communication on dedicated fibre infrastructure. In order to support maximum radio throughput over TDD radio, the fronthaul links are often over-dimensioned, which is a costly network design. 
     SUMMARY 
     One objective is to improve utilisation of fronthaul links in TDD systems. 
     According to a first aspect, it is provided a method for controlling data on a full-duplex fronthaul link. The method is performed in an aggregator device and comprises the steps of: obtaining uplink data allocations per time period for at least two radio layers, the at least two radio layers being time-division duplex, TDD, radio layers, and the at least two radio layers being transmitted from at least one radio device; aggregating uplink data allocations per time period, yielding aggregated uplink TDD data; and when the uplink TDD data exceeds an uplink capacity of the full-duplex fronthaul link, shaping uplink data of at least one of the at least two radio layers for the full-duplex fronthaul link. 
     The method may further comprise the steps of: obtaining downlink data allocations per time period for each radio layer; aggregating downlink data allocations per time period, yielding aggregated downlink TDD data; and when the downlink TDD data exceeds a downlink capacity of the full-duplex fronthaul link, shaping downlink data for at least one of the at least two radio layers for the full-duplex fronthaul link. 
     The shaping may involve transmitting a shaping signal to a baseband device to reschedule data allocations between time periods. 
     The shaping may involve buffering data in the aggregator device. 
     The amount of data allocations may be based on modulation and coding schemes used on the at least two TDD radio layers. 
     The shaping may comprise redistributing data over time to, to the greatest extent possible, fit the data of the radio layers within the capacity of the full-duplex fronthaul link. 
     The method may further comprise the steps of: demultiplexing downlink data received over the full-duplex fronthaul link and forwarding the demultiplexed data to respective radio devices; and multiplexing uplink data received from the at least two radio devices and forwarding the data on the full-duplex fronthaul link. 
     According to a second aspect, it is provided an aggregator device for controlling data on a full-duplex fronthaul link. The aggregator device comprises: a processor; and a memory storing instructions that, when executed by the processor, cause the aggregator device to: obtain uplink data allocations per time period for at least two radio layers, the at least two radio layers being time-division duplex, TDD, radio layers, and the at least two radio layers being transmitted from at least one radio device; aggregate uplink data allocations per time period, yielding aggregated uplink TDD data; and when the uplink TDD data exceeds an uplink capacity of the full-duplex fronthaul link, shape uplink data of at least one of the at least two radio layers for the full-duplex fronthaul link. 
     The aggregator device may further comprise instructions that, when executed by the processor, cause the aggregator device to: obtain downlink data allocations per time period for each radio layer; aggregate downlink data allocations per time period, yielding aggregated downlink TDD data; and when the downlink TDD data exceeds a downlink capacity of the full-duplex fronthaul link, shape downlink data for at least one of the at least two radio layers for the full-duplex fronthaul link. 
     The shaping may involve transmitting a shaping signal to a baseband device to reschedule data allocations between time periods. 
     The shaping may involve buffering data in the aggregator device. 
     The amount of data allocations may be based on modulation and coding schemes used on the at least two TDD radio layers. 
     The shaping may comprise redistributing data over time to, to the greatest extent possible, fit the data of the radio layers within the capacity of the full-duplex fronthaul link. 
     The aggregator device may further comprise instructions that, when executed by the processor, cause the aggregator device to: demultiplex downlink data received over the full-duplex fronthaul link and forwarding the demultiplexed data to respective radio devices; and multiplex uplink data received from the at least two radio devices and forwarding the data on the full-duplex fronthaul link. 
     According to a third aspect, it is provided a computer program for controlling data on a full-duplex fronthaul link. The computer program may comprise computer program code which, when run on a aggregator device causes the aggregator device to: obtain uplink data allocations per time period for at least two radio layers, the at least two radio layers being time-division duplex, TDD, radio layers, and the at least two radio layers being transmitted from at least one radio device; aggregate uplink data allocations per time period, yielding aggregated uplink TDD data; and when the uplink TDD data exceeds an uplink capacity of the full-duplex fronthaul link, shape uplink data of at least one of the at least two radio layers for the full-duplex fronthaul link. 
     According to a fourth aspect, it is provided a computer program product comprising a computer program according to the third aspect and a computer readable means on which the computer program is stored. 
     According to a fifth aspect, it is provided a method for controlling data on a full-duplex fronthaul link. The method is performed in a baseband device and comprises the steps of: obtaining downlink data allocations per time period for at least two radio layers, the at least two radio layers being time-division duplex, TDD, radio layers, and the at least two radio layers being transmitted from at least one radio device; aggregating downlink data allocations per time period, yielding aggregated downlink TDD data; and when the downlink TDD data exceeds a downlink capacity of a full-duplex fronthaul link, shaping downlink data from the radio layers of the at least two radio layers for the full-duplex fronthaul link. 
     The method may further comprise the steps of: receiving a shaping signal from an aggregator device to reschedule data allocations between time periods; and rescheduling data allocations between time periods. 
     According to a sixth aspect, it is provided a baseband device for controlling data on a full-duplex fronthaul link. The baseband device comprises: a processor; and a memory storing instructions that, when executed by the processor, cause the baseband device to: obtain downlink data allocations per time period for at least two radio layers, the at least two radio layers being time-division duplex, TDD, radio layers, and the at least two radio layers being transmitted from at least one radio device; aggregate downlink data allocations per time period, yielding aggregated downlink TDD data; and when the downlink TDD data exceeds a downlink capacity of a full-duplex fronthaul link, shape downlink data from the radio layers of the at least two radio layers for the full-duplex fronthaul link. 
     The baseband device may further comprise instructions that, when executed by the processor, cause the baseband device to: receive a shaping signal from an aggregator device to reschedule data allocations between time periods; and reschedule data allocations between time periods. 
     According to a seventh aspect, it is provided a computer program for controlling data on a full-duplex fronthaul link. The computer program comprises computer program code which, when run on a baseband device causes the baseband device to: obtain downlink data allocations per time period for at least two radio layers, the at least two radio layers being time-division duplex, TDD, radio layers, and the at least two radio layers being transmitted from at least one radio device; aggregate downlink data allocations per time period, yielding aggregated downlink TDD data; and when the downlink TDD data exceeds a downlink capacity of a full-duplex fronthaul link, shape downlink data from the radio layers of the at least two radio layers for the full-duplex fronthaul link. 
     According to an eighth aspect, it is provided a computer program product comprising a computer program according to the seventh aspect and a computer readable means on which the computer program is stored. 
     Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to “a/an/the element, apparatus, component, means, step, etc.” are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects and embodiments are now described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematic diagram illustrating a cellular network  8  in which embodiments presented herein can be applied; 
         FIGS. 2A-C  are schematic diagrams illustrating how traffic shaping can improve the throughput on the fronthaul link of  FIG. 1 ; 
         FIGS. 3 and 4  are schematic diagrams illustrating how shaping of traffic can be employed for better throughput over the fronthaul link; 
         FIGS. 5A-C  are flow charts illustrating embodiments of methods performed in the aggregator device for controlling data on a full-duplex fronthaul link; 
         FIGS. 6A-B  are flow charts illustrating embodiments of methods performed in the baseband device for controlling data on a full-duplex fronthaul link; 
         FIG. 7  is a schematic diagram showing functional modules of the aggregator device of  FIG. 1  according to one embodiment; 
         FIG. 8  is a schematic diagram showing functional modules of the baseband device of  FIG. 1  according to one embodiment; and 
         FIG. 9  shows one example of a computer program product comprising computer readable means. 
     
    
    
     DETAILED DESCRIPTION 
     The aspects of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the invention are shown. These aspects may, however, be embodied in many different forms and should not be construed as limiting; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and to fully convey the scope of all aspects of invention to those skilled in the art. Like numbers refer to like elements throughout the description. 
       FIG. 1  is a schematic diagram illustrating a cellular network  8  in which embodiments presented herein can be applied. The cellular communication network  8  may e.g. comply with any one or a combination of 5G NR (New Radio), LTE (Long Term Evolution), LTE Advanced, W-CDMA (Wideband Code Division Multiplex), EDGE (Enhanced Data Rates for GSM (Global System for Mobile communication) Evolution), GPRS (General Packet Radio Service), CDMA2000 (Code Division Multiple Access 2000), or any other current or future wireless network, as long as the principles described hereinafter are applicable. 
     A number of radio devices  14   a - c  comprise respective transmitters and receivers for communicating with one or more user devices, e.g. in the form of any one or more a mobile communication terminal, user equipment (UE), mobile terminal, user terminal, user agent, wireless terminal, machine-to-machine device etc., and can be, for example, what today are commonly known as a mobile phone, smart phone or a tablet/laptop with wireless connectivity. Communication in a direction towards the user devices is denoted downlink (DL) and communication in a direction towards more centrally located equipment is denoted uplink (UL). 
     The first radio device  14   a  and the second radio device  14   b  are configured to use TDD (Time Division Duplex) and their antennas  15   a - b  are each used for both DL and UL, where DL and UL are in the same frequency band, but are allocated different time periods. The third radio device  14   c  is configured to use FDD (Frequency Division Duplex) where DL and UL are separated into different frequency bands, and can thus be active simultaneously. The third radio device  14   c  can be provided with multiple antennas  15   c  for simultaneous use of the different frequency bands. It is to be noted that any radio device  14   a - c  can have one or multiple antennas (regardless if FDD or TDD is used). The different antennas can be used for UL/DL diversity, MIMO (Multiple-Input and Multiple-Output)/beamforming (in same frequency band), or multiple carriers in different frequency bands (with and without carrier aggregation). The structure shown in  FIG. 1  is just an example. 
     One or more baseband devices  3  are used for baseband processing in the cellular network, as known in the art per se. The baseband device  3  comprises a processor  70 , which is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions  77  stored in a memory  74 , which can thus be a computer program product. The processor  70  could alternatively, or additionally, be implemented using an application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc. The processor  70  can be configured to execute the methods described with reference to  FIGS. 6A-B  below. 
     The memory  74  can be any combination of random-access memory (RAM) and/or read-only memory (ROM). The memory  74  also comprises persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid-state memory or even remotely mounted memory. The memory  74  can also comprise a data memory for reading and/or storing data during execution of software instructions in the processor  70 . 
     An aggregator device  1  is used for multiplexing and demultiplexing between a fronthaul link  21  to the baseband device  3  and individual links to the radio devices. The aggregator device comprises a physical interface (PHY)  10  for interfacing with the fronthaul link  21  on one side and supporting transmission (Tx) and reception (Rx) connections on the other side. Corresponding physical interfaces (not shown) are provided towards the radio devices  14   a - c . The fronthaul link  21  is a full-duplex fronthaul link and can e.g. be based on CPRI (Common Public Radio Interface), evolved CPRI (eCPRI) or any other suitable standard, such as a packet network based on Ethernet, IP (Internet Protocol), multiprotocol label switching (MPLS) or similar. The fronthaul link can be based on an optical, electrical, or wireless transmission medium such as microwave. The full-duplex operation of the fronthaul link can e.g. be achieved using echo cancellation (near-end/far-end crosstalk mitigation) on electrical interfaces or by duplex fibred (one fibre per direction) or on single fibre utilising bi-directional optics, separating downlink from uplink by using different wavelengths. It is to be noted that the fronthaul link  21  can be based on a network between the aggregator device  1  and the baseband device  3 . In any case, the fronthaul link  21  supports high-capacity full-duplex communication between the baseband device  3  and the aggregator device  1  either directly or as a segment of a fronthaul network. 
     A framer  11  establishes the fronthaul transmission framing used on the fronthaul link  21 . An aggregator core  12  is provided for the multiplexing and demultiplexing for the links with the individual radio devices  14   a - c.    
     The aggregator device  1  further comprises a processor  60 , which is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions  67  stored in a memory  64 , which can thus be a computer program product. The processor  60  could alternatively, or additionally, be implemented using an application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc. The processor  60  can also communicate with the baseband device  3  over a control link  24 . This allows the processor  60  of the aggregator device  1  to obtain allocation and scheduling information such as UL/DL framing parameters, radio resource and medium access scheduling, modulation and coding schemes (MCS) and similar, used by the radio devices  14   a - c . The allocation and scheduling information can be used to determine when there is a risk for insufficient capacity on the fronthaul link  21 . The processor  60  can be configured to execute the methods described with reference to  FIGS. 5A-C  below. 
     The memory  64  can be any combination of random-access memory (RAM) and/or read-only memory (ROM). The memory  64  also comprises persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid-state memory or even remotely mounted memory. The memory  64  can also comprise a data memory for reading and/or storing data during execution of software instructions in the processor  60 . 
       FIGS. 2A-C  are schematic diagrams illustrating how traffic shaping can improve the throughput on the fronthaul link  21  of  FIG. 1 . In this example, there are three time periods  30   a - c  shown, a first time period  30   a , a second time period  30   b  and a third time period  30   c . Whenever the term time period is used herein, the time period can be different for different implementations, but is consistent for embodiments presented herein of the same implementation. For instance, the time period can be (multiples of) radio frames, sub-frames, slots, modulation symbol periods (e.g. OFDM (Orthogonal Frequency-Division Multiplexing) symbol periods) etc. 
     Looking first at  FIG. 2A , there is a first TDD schedule  22   a  for a radio layer of the first radio device ( 14   a  of  FIG. 1 ). There is also a second TDD schedule  22   b  for a radio layer of the second radio device ( 14   b  of  FIG. 1 ). Each radio layer can represent a carrier, a MIMO layer, a beam-forming layer, etc. It is to be noted that the different layers can be for separate radio devices or different layers of the same radio device. 
     The first TDD schedule  22   a  is transmitted can be transmitted on a first frequency and the second TDD schedule  22   b  can be transmitted on a second frequency. The first frequency and the second frequency should not be adjacent to minimise interference due to leakage. Alternatively, the TDD schedules  22   a - b  can be transmitted in different MIMO layers on the same frequency. 
     The first TDD schedule  22   a  contains first downlink periods DL 1  and first uplink periods UL 1 . The second TDD schedule  22   b  contains second downlink periods DL 2  and second uplink periods UL 2 . If these two TDD schedules  22   a - b  are aggregated on a single fronthaul link, there are significant time spans where there are both first downlink periods DL 1  and second downlink periods DL 2 , as well as other time spans where there are both first uplink periods UL 1  and second uplink periods UL 2 . If these TDD schedules are aggregated according to what is shown in  FIG. 2A , the capacity requirements will be accumulated for the different TDD schedules, leading to excessive capacity usage on the fronthaul link, which should be avoided if possible. 
     One solution to this problem is to reschedule the second TDD schedule  22   b  to a time shifted second TDD schedule  22   b ′ as shown in  FIG. 2B  by applying a time shift  23 . By shifting the second TDD schedule, at any one point in time, there is now only one of the downlink periods DL 1 /DL 2  and only one of the uplink periods UL 1 /UL 2 . The rescheduling can be implemented by the baseband module or by buffering in the aggregator device. 
       FIG. 2C  is the equivalent to  FIG. 2B  in time, but here the downlink periods DL 1 , DL 2  are aggregated on a downlink aggregation  24   a  and the uplink periods UL 1 , UL 2  are aggregated on an uplink aggregation  24   b . The downlink aggregation  24   a  can then be transmitted over the downlink channel of the fronthaul link and the uplink aggregation  24   b  can be transmitted over the uplink channel of the fronthaul link. 
     In the scenario illustrated in  FIGS. 2A-C , the UL and DL of the two radio layers match perfectly, so that the UL allocation of one radio layer matches the DL allocation of the other radio layer in time. In this case, the time shift achieves perfect matching, which minimises capacity requirements on the fronthaul link. The same situation occurs if there are two radio layers with symmetric UL and DL. 
       FIGS. 3 and 4  are schematic diagrams illustrating how shaping of traffic can be employed for better throughput over the fronthaul link as an extension of the concept in  FIG. 2A-C . This shaping will now be described with reference to both  FIG. 3  and  FIG. 4 , with corresponding time periods  30   a ,  30   b  and  30   c.    
     In each of the time periods of  FIG. 3 , it is shown the scheduled data rate (in data units per time period) in DL and UL in radio for the first radio device  14   a , the second radio device  14   b  and the third radio device  14   c . In the third time period  30   c , there is only DL data for the second radio device  14   b , e.g. due to licence-assisted access, LAA. LAA implies DL-only sharing in unlicensed spectrum, using listen-before-talk. Also, supplementary uplink (SUL) and/or supplementary downlink (SDL) could be in the mix of radio layers. SUL and SDL are used in the same way s LAA but in licensed band and thus without LBT (which can cause possible delays). SUL and SDL are UL or DL only radio layers, and carrier-aggregated to an anchor primary carrier. Both the first and second radio devices  14   a - b  utilise TDD and the third radio device  14   c  utilises FDD. 
     Looking now to  FIG. 4 , the DL data and UL data is separately accumulated in each time period  30   a - c  for the fronthaul link (schematically shown as a pipe, even though there is separate capacity for DL and UL). The capacity  27  (e.g. in Gbit/s) of the fronthaul link is illustrated as the size of the pipe and can be different for UL and DL. 
     In the first time period  30   a , the aggregated DL data exceeds the capacity  27 . However, there is spare DL capacity in the second time period  30   b . Hence, some or all of the excess DL data from the first time period is moved  28   a  to the second time period  30   b . This allows all (or at least more of) the DL data to be transferred over the fronthaul link within its capacity  27 . Similarly, in the second time period  30   b , the aggregated UL data exceeds the capacity  27 . However, there is spare UL capacity in the third time period  30   c . Hence, some or all of the excess UL data from the second time period is moved  28   b  to the third time period  30   b . Excess DL data in the third period  30   c  can be moved  28   c  to the next period, etc. 
     The moving of data can be achieved by the aggregator device signalling to the baseband device, or by the aggregator buffering data between time periods. In other words, the data can be buffered, stored and delayed to achieve better throughput over the fronthaul link. It is to be noted that moving of both DL data and UL data can be performed in the aggregator device. Alternatively, the aggregator device moves UL data and the baseband device moves DL data. The moving of data can be implemented between adjacent time periods only, to reduce latency issues. Alternatively, data can be moved more freely across multiple time periods (larger processing window) to improve throughput and reduce the risk of having to discard data, at the price of possibly increased latency. 
     Data that can not be fit within the capacity  27  even when moved, has to be discarded, which higher layers will need to manage with retransmissions, etc. 
       FIGS. 5A-C  are flow charts illustrating embodiments of methods for controlling data on a full-duplex fronthaul link. These embodiments are performed in an aggregator device. 
     In an obtain UL allocations step  40   a , the aggregator device obtains uplink data allocations per time period for at least two radio layers. The at least two radio layers are TDD radio layers. Furthermore, the at least two radio layers are transmitted from at least one radio device. 
     In an aggregate UL allocations step  42   a , the aggregator device aggregates uplink data allocations per time period. This yields aggregated uplink TDD data with a time-period granularity. 
     In a conditional exceeds UL capacity on FH step  43   a , the aggregator device determines when the uplink TDD data exceeds an uplink capacity of the full-duplex fronthaul link (in at least one time period). When this is the case, the method proceeds to a shape UL data step  44   a . Otherwise, the method returns to the obtain Ul allocations step  40   a.    
     In the shape UL data step  44   a , the aggregator device shapes uplink data of at least one of the at least two radio layers for the full-duplex fronthaul link. 
     Looking now to  FIG. 5B , only new or modified steps compared to the steps of  FIG. 5A  will be described. In  FIG. 5B , the shaping determination for the uplink of  FIG. 5A  is also applied in corresponding steps for the downlink. 
     In an optional obtain DL allocations step  40   b , the aggregator device obtains downlink data allocations per time period for each radio layer. 
     In an optional aggregate DL allocations step  42   b , the aggregator device aggregates downlink data allocations per time period. This aggregation yields aggregated downlink TDD data, with a time-period granularity. 
     In an optional conditional exceeds DL capacity on FH step  43   b , the aggregator device determines when the downlink TDD data exceeds a downlink capacity of the full-duplex fronthaul link. When this is the case, the method proceeds to an optional shape DL data step  44   b . Otherwise, the method returns to the obtain DL allocations step  40   b.    
     In the optional shape DL data step  44   b , the aggregator device shapes downlink data for at least one of the at least two radio layers for the full-duplex fronthaul link. 
     It is to be noted that steps  40   b ,  42   b ,  43   b  and  44   b  can be performed in a different execution sequence (e.g. different processor core, process, thread, etc) in the aggregation device than the steps of  FIG. 5A . 
     The shaping in steps  44   a  and  44   b  can occur in different ways, e.g. as exemplified in  FIGS. 2-4  and described above. The shaping can contain buffering data, aggregating data and discarding data if necessary. 
     In one embodiment, the shaping involves transmitting a shaping signal to a baseband device to reschedule data allocations between time periods. 
     In one embodiment, the shaping involves buffering data in the aggregator device. 
     The amount of data allocations (which is used in steps  44   a  and  44   b ), e.g. expressed in Gbit/s, can be based on modulation and coding schemes used on the at least two TDD radio layers. 
     In one embodiment the shaping comprises redistributing data over time to, to the greatest extent possible, fit the data of the radio layers within the capacity of the full-duplex fronthaul link. 
     The obtaining of allocations in steps  40   a  and  40   b , can be implemented by the aggregator device requesting this information from the baseband device and/or the radio device(s). Furthermore, MCS can be used to determine the number of data units (e.g. bits or bytes) which are allocated in each time period. 
     Looking now to  FIG. 5C  this illustrates the multiplexing and demultiplexing which can optionally be performed by the aggregator device. 
     In an optional demultiplex step  46 , the aggregator device demultiplexes downlink data received over the full-duplex fronthaul link and forwards the demultiplexed data to respective radio layers in one or more radio devices. 
     In an optional multiplex step  48 , the aggregator device multiplexes uplink data received from at least two radio layers of one or more radio devices and forwards the data on the full-duplex fronthaul link. 
     It is to be noted that steps  46  and  48  can be performed in a different hardware or execution sequence in the aggregation device than the steps of  FIG. 5A  and/or  FIG. 5B . 
       FIGS. 6A-B  are flow charts illustrating embodiments of methods for controlling data on a full-duplex fronthaul link. The embodiments are performed in a baseband device. 
     In an obtain DL allocations step  50 , the baseband device obtains downlink data allocations per time period for at least two radio layers. The at least two radio layers are TDD radio layers. The at least two radio layers are transmitted from at least one radio device. 
     In an aggregate DL allocations step  52 , the baseband device aggregates downlink data allocations per time period. This yields aggregated downlink TDD data with a time-period granularity. 
     In a conditional exceeds DL capacity on FH step  53 , the baseband device determines when the downlink TDD data exceeds a downlink capacity of a full-duplex fronthaul link. 
     In a shape DL data step  54 , the baseband device shapes downlink data from the radio layers of the at least two radio layers for the full-duplex fronthaul link. 
     Looking now to  FIG. 6B , only new or modified steps compared to those illustrated in  FIG. 6A  will be described. 
     In a receive shaping signal step  56 , the baseband device receives a shaping signal from an aggregator device to reschedule data allocations between time periods. 
     In a reschedule step  58 , the baseband device reschedules data allocations between time periods, in accordance with the shaping signal received in step  56 . 
     Adjusting the timing in baseband device or buffering data in the aggregator device give different results, but these embodiments can be combined as described above. 
     Buffering is limited by the maximum allowed fronthaul latency (typically below 100 us) but does not have any problems with adjacent TDD bands since the timing alignment at the antenna is not impacted. Due to the strict latency requirements for fronthaul, buffering would work best when the TDD period is short (e.g. 5G NR on millimetre wave bands where subcarrier spacing is large and slots are short). 
     Adjusting the timing in the baseband device does not have the same latency restrictions, but it changes the timing alignment at the antenna reference point. If adjacent TDD bands have different timing, there can be near-far problems caused by spectral leakage and non-ideal filters. Timing adjustment could be used for any TDD period size. 
       FIG. 7  is a schematic diagram showing functional modules of the aggregator device  1  of  FIG. 1  according to one embodiment. The modules are implemented using software instructions such as a computer program executing in the aggregator device  1 . Alternatively or additionally, the modules are implemented using hardware, such as any one or more of an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or discrete logical circuits. The modules correspond to the steps in the methods illustrated in  FIGS. 5A-5C . 
     An UL allocation obtainer  60   a  corresponds to step  40   a . A DL allocation obtainer  60   b  corresponds to step  40   b . An UL allocation aggregator  62   a  corresponds to step  42   a . A DL allocation aggregator  62   b  corresponds to step  42   b . An UL capacity determiner  63   a  corresponds to step  43   a . A DL capacity determiner  63   b  corresponds to step  43   b . An UL data shaper  64   a  corresponds to step  44   a . A DL data shaper  64   b  corresponds to step  44   b . A demultiplexer  66 , corresponds to step  46 . A multiplexer  68  corresponds to step  48 . 
       FIG. 8  is a schematic diagram showing functional modules of the baseband device  3  of  FIG. 1  according to one embodiment. The modules are implemented using software instructions such as a computer program executing in the baseband device  3 . Alternatively or additionally, the modules are implemented using hardware, such as any one or more of an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or discrete logical circuits. The modules correspond to the steps in the methods illustrated in  FIGS. 6A and 6B . 
     A DL allocation obtainer  80  corresponds to step  50 . A DL allocation aggregator  82  corresponds to step  52 . A DL capacity determiner  83  corresponds to step  53 . A DL data shaper  84  corresponds to step  54 . A signal receiver  86  corresponds to step  56 . A rescheduler  88  corresponds to step  58 . 
       FIG. 9  shows one example of a computer program product comprising computer readable means. On this computer readable means, a computer program  91  can be stored, which computer program can cause a processor to execute a method according to embodiments described herein. In this example, the computer program product is an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. As explained above, the computer program product could also be embodied in a memory of a device, such as the computer program products  64 ,  74  of  FIG. 1 . While the computer program  91  is here schematically shown as a track on the depicted optical disk, the computer program can be stored in any way which is suitable for the computer program product, such as a removable solid-state memory, e.g. a Universal Serial Bus (USB) drive. 
     By shaping traffic as presented herein, the fronthaul link can be better utilised. Peaks in capacity requirements can be reduced, resulting in lower capacity requirements on the fronthaul link, which leads to significantly reduced cost. 
     The aspects of the present disclosure 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 invention, as defined by the appended patent claims. Thus, while various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims.