Transmission window control

Abstract

Methods are provided for controlling transmission timing of sounding reference signal (SRS) data in wireless communication networks. A baseband unit or Distributed Unit (DU) configures or instructs a remote radio unit or Radio Unit (RU) with a transmission window during which SRS data or channel estimates should be sent from the RU to the DU. The transmission window relationship differs from that used for regular uplink data symbols. Three approaches are disclosed: (1) conveying complete transmission window information in Control-plane messages for dynamic control; (2) configuring transmission windows via Management-plane messages associated with specific SRS resource elements; and (3) a hybrid approach using Management-plane configuration with identifiers referenced in Control-plane messages. Different transmission windows may be configured for different SRS parts. The DU determines reception windows based on configured transmission windows and fronthaul delay profiles. This enables optimized resource utilization by providing predictable SRS data arrival timing while reducing fronthaul burst traffic in massive MIMO systems.

Description

TRANSMISSION WINDOW CONTROLTECHNICAL FIELDThe present application relates to the field of mobile communications networks, in particular to Open-RAN, O-RAN networks.BACKGROUNDMassive MIMO techniques were first adopted to practice in LTE. In 5G, it becomes one key technology component, which has been deployed in a much larger scale than in LTE. It features a large number of antennas used on the base-station side, where the number of antennas is typically much larger than the number of user layers, for example, 64 antennas serving 8 or 16 user layers in frequency range 1 (FR1), which comprises sub-6 GHz frequency bands, and 256 / 512 antennas serving 2 or 4 layers in FR2, which comprises frequency bands from 24.25 GHz to 71 GHz. A user layer when used herein means an independent downlink (DL) or uplink (UL) data stream intended for one user. One user or user equipment (UE) may have one or multiple user layers. User layer is often denoted as layer for simplicity reason. Massive MIMO is also referred to as massive beamforming, which is able to form narrow beams focusing on different directions to counteract the increased path loss at higher frequency bands. It also benefits multi-user MIMO (MU-MIMO) which allows for transmissions from / to multiple users simultaneously over separate spatial channels resolved by the massive MIMO technologies (e.g., by spatially nulling the interferences between users), while keeping high capacity for each user. Therefore, it can significantly increase the spectrum efficiency and cell capacity.At the base-station side, the interface between the distributed unit (DU) (also sometimes referred to as digital unit or baseband unit) and the radio unit (RU) is the fronthaul interface. The great benefits of massive MIMO at the air-interface also introduce new challenges at the base-station side. The legacy CPRI-type fronthaul transports timedomain in-phase and quadrature (IQ) samples per antenna branch. As the number of antennas scales up in massive MIMO systems, the required fronthaul capacity also increases proportionally, which significantly drives up the fronthaul costs. To address this challenge, the fronthaul interface evolved from CPRI to eCPRI, a packet-based fronthaul interface. In eCPRI, other functional split options between DU and RU are supported, referred to as different lower-layer split (LLS) options. In eCPRI terminologies, DU and RU are referred to as eREC (eCPRI Radio Equipment Control) and eRE (eCPRI Radio Equipment), respectively. The basic idea of LLS is to move the frequency-domain beamforming function from DU to RU so that frequency samples or data of user-layers are transported over the fronthaul interface. Note that the frequency-domain beamforming is sometimes also referred to as precoding in the DL direction and equalizing or preequalizing in UL direction. By doing this, the required fronthaul capacity and thereby the fronthaul costs are significantly reduced, as the number of user layers is typically much fewer than the number of antennas in massive MIMO. In O-RAN, DU is referred to as 0- DU while RU is referred to as O-RU, see e.g., [1],The great benefits and promising capacity that the modern wireless communication system can provide is built upon the fact that the base station has a correct understanding of the channel conditions between UEs and base station. Given the channel state information (CSI), the base station can conduct effective scheduling, resource allocation, link adaptation and beamforming. In the UL, sounding reference signal (SRS) is used to sound the channel for a certain bandwidth, e.g., the full bandwidth of a carrier. The SRS can occupy 1, 2 or 4 consecutive symbols in the last 6 symbols of a slot, e.g., the special slot between DL and UL slots. Each SRS symbol may contain the information of multiple SRS ports. One SRS port corresponds to the SRS signal sent from an antenna port from one UE. One antenna port can represent one antenna or an output of multiple antennas precoded with the same SRS signal. Each antenna port only uses part of the REs of SRS symbols in a comb structure. Current 3GPP specification supports comb 2, 4 and 8. For example, in the comb 2 setting, there are two sets of REs (even numbered REs and odd numbered REs) used for different SRS ports. Each comb set of REs can be used for multiple SRS ports as well. These SRS ports are coded with orthogonal sequences with different cyclic shifts and therefore they are orthogonal in code domain. Current 3GPP specification supports 8 cyclic shifts for comb 2, 12 cyclic shifts for comb 4, and 6 cyclic shifts for comb 8. SRS can be transmitted in a periodic, semi-persistent or aperiodic manner. Since SRS is used to sound the overall channel conditions, SRS symbols present typically over a much wider bandwidth comparing to the UL data signal (i.e.. Physical Uplink Shared Channel, PUSCH data), which is normally allocated with a portion of the bandwidth. The SRS signal is received per antenna at the RU. In some LLS designs, e.g., the current O-RAN open fronthaul specification [1], the SRS processing is in the DU. In this case, RU sends the IQ data of the SRS symbols of all antennas to the DU. It means that the number of FH spatial streams for transporting SRS IQ data equal to the number of antennas, while the number of FH spatial streams for transporting IQ data of PUSCH data equal to the number of the beamformed streams after RU beamforming which is much less than the number of antennas. As a result, the amount of the SRS IQ data per symbol is much more than that of the IQ data of PUSCH data symbol. For example, for 64 antennas and 8 spatial streams used for PUSCH, the IQ data of a fully loaded SRS symbol is 8 times more than that of a fully loaded PUSCH symbol. For PUSCH IQ data, it is sent symbol by symbol. The bit rate for sending PUSCH IQ data can be assumed as the amount of the PUSCH IQ data divided by a symbol period. If SRS IQ data is sent in the same way as the PUSCH IQ data, it will cause a high FH burst traffic for sending SRS IQ data as shown in Figure 1. In the previous example, the bit rate of SRS IQ data would be 8 times higher than that of PUSCH IQ data. This would dramatically increase the requirement of the FH bit rate and increase the FH cost. In the previous example, if we assume 100 MHz NR with 30 kHz subcarrier spacing, the FH bit rate required for PUSCH IQ data is close to 12.5 Gbps. However, the FH bit rate required for SRS IQ data is close to 100 Gbps. It means that it would require a 100 Gbit Ethernet link between DU and RU, though the PUSCH IQ data only consumes 12.5 Gbps.Handling high speeds, as well as processing data that arrives at high speed puts high demands on system capacity. Meeting such demands can be costly. There is always a desire to reduce cost, or increase capacity for a given cost.SUMMARYThis application relates, inter alia, to transmission window control for sounding reference signal (SRS) data in mobile communications networks, particularly Open-RAN (O-RAN) networks. The invention addresses the problem of high fronthaul burst traffic caused by SRS data transmission between radio units and baseband units in massive MIMO systems.In massive MIMO systems, the number of antennas is typically much larger than the number of user layers, which creates challenges for fronthaul capacity. When SRS data is sent using traditional methods, it creates high burst traffic because SRS symbols contain data from all antennas, whereas regular uplink data (PUSCH) contains data from fewer beamformed streams. For example, with 64 antennas and 8 spatial streams, SRS data can be 8 times larger than PUSCH data, potentially requiring 100 Gbps fronthaul capacity even when PUSCH only needs 12.5 Gbps.Current solutions use non delay-managed traffic to spread SRS transmission over longer periods, but this approach provides insufficient predictability for the Distributed Unit (DU), which cannot determine when SRS data will arrive and must reserve processing resources for extended periods.The present invention provides methods where the DU controls the transmission window during which the Radio Unit (RU) sends SRS data or channel estimates. Three main approaches are disclosed:Method 1 involves the DU conveying complete SRS transmission window information in Control-plane (C-Plane) messages. This provides full dynamic control and flexibility for the DU to specify exactly when SRS data should be transmitted.Method 2 uses Management-plane (M-Plane) configuration where the DU configures a list of SRS transmission window configurations to the RU. Each configuration is associated with specific resource elements of SRS symbols. When the RU receives a C-Plane message matching configured resource elements, it applies the corresponding transmission window.Method 3 combines both approaches, where transmission window configurations are set up via M-Plane with associated identifiers, and C-Plane messages include these identifiers to indicate which configuration should be used for specific SRS resource elements.The invention allows different transmission windows for different parts of SRS symbols, enables the DU to optimize resource utilization by knowing when data will arrive, and can reduce SRS processing delay. The DU can consider factors such as TDD patterns, SRS patterns, resource planning, and fronthaul bit rate requirements when determining transmission windows, while also accommodating any constraints declared by the RU.The methods are applicable to both SRS IQ data transmission and SRS channel estimate transmission, and can be extended to other applications such as integrated sensing and communication (ISAC) systems that generate similar large amounts of data requiring controlled transmission timing.In an aspect, a method is provided performed by a baseband unit or part of a baseband unit, where the method includes setting up or telling a remote radio unit about a specific time period during which the remote radio unit should send sounding reference signal data or channel estimate data backto the baseband unit.The relationship between the transmission time period and when the sounding reference signal is received may be different from the relationship used for sending regular uplink data symbols from the remote radio unit to the baseband unit.The baseband unit may be an O-RAN Distributed Unit, O-DU and the remote radio unit may be an O-RAN Radio Unit, O-RU.An aspect provides a method that includes a Distributed Unit setting up a transmission time period for user data traffic on the communication link between the Distributed Unit and Radio Unit, where this time period is used by a Radio Unit for sending sounding reference signal data or channel estimate data to the Distributed Unit through the user data traffic.The setup or instruction may be done so that the transmission time period does not happen during uplink time division duplex traffic periods. Alternatively the setup or instruction may be done so that the transmission time period happens during uplink time division duplex traffic but only when there is no regular uplink shared channel data or partially scheduled uplink shared channel data to send on the communication link.The setup or instruction may be done so that the transmission time period does not happen in the time period during which regular uplink shared channel data are sent on the communication linkSetup or instruction may be done by including information that identifies the transmission time period in a Control plane message. Alternatively, or additionally, the setup or instruction may be done by including information in a management plane message that identifies the transmission time period relative to when the sounding reference signal is received from the radio interface.In an aspect, one or more configurations that identify a transmission time period relative to when the sounding reference signal is received from the air interface may be included in one or more management plane messages, with each configuration having an associated identifier, and where such an identifier is included in a Control plane message that provides scheduling information for the sounding reference signal resource elements requested by the Distributed Unit to indicate which particular configuration should be used to determine the transmission time period for the requested sounding reference signal resource elements.In an aspect, a control plane message referred to in preceding aspects may be a message that provides to the Radio Unit information about sounding reference signal resource elements requested by the Distributed Unit. Additionally, or alternatively, the Control plane message is a message that provides to the Radio Unit information about sounding reference signal resource elements for which a channel estimate is to be made by the Radio Unit.In an aspect, different transmission time periods may be set up for sending data from different parts of the sounding reference signal.In an aspect, the Distributed Unit determines a reception time period for the sounding reference signal data or channel estimate based on the configured transmission time period and a delay profile of the communication link.In an aspect, the Radio Unit may declare constraints regarding how transmission time periods may be set up or instructed.An aspect provides a Distributed Unit adapted to perform the method of any preceding aspect.Another aspect provides a Radio Unit adapted to receive from a Distributed Unit the setup or instruction of any preceding aspect. The Radio Unit may be adapted to send sounding reference signal data or a channel estimate in accordance with the setup or instruction received from the Distributed Unit.An aspect provides a computer program adapted to cause, when run, a Distributed Unit to perform the method of any preceding aspect.A further aspect provides a computer program adapted to cause, when run, a Radio Unit to receive from a Distributed Unit the setup or instruction of any previous aspect. The computer program may further cause the Radio Unit to send sounding reference signal data or a channel estimate in accordance with the setup or instruction received from the Distributed Unit.BRIEF DESCRIPTION OF THE DRAWINGSFigure 1 shows a diagram illustrating a high traffic burst for transporting SRS IQ data.Figure 2 shows a diagram illustrating an example of SRS transmission as non delaymanaged traffic.Figure 3 shows a flow chart of DU CU-plane operations in a method #1 where DU conveys complete SRS TC window information.Figure 4 shows a flow chart of RU CU-plane operations in method #1.Figure 5 shows a flow chart of M-plane operations in a method #2 where DU configures SRS TX windows via M-Plane.Figure 6 shows a flow chart of DU CU-Plane operations in method #2.Figure 7 shows a flow chart of RU CU plane operations in method #2.Figure 8 shows a flow chart of M-Plane operations in a method #3 which is a mix of C- Plane and M-Plane methods.Figure 9 shows a flow chart of DU CU-Plane operations in method #3.Figure 10 shows a flow chart of RU CU-Plane operations in method #3.Figure 11 shows a block diagram of a communications system in which methods, devices and computer programs of the present disclosure may be implemented.Figure 12 shows a block diagram of another communication system in which methods, devices and computer programs of the present disclosure may be implemented.Figure 13 shows a block diagram of a wireless device that may be used in the systems of figure 11 or 12.Figure 14 shows a block diagram of a network node that may be used in the systems of figure 11 or 12.Figure 15 shows a block diagram illustrating a virtualization environment in which functions implemented by some embodiments may be virtualized.DETAILED DESCRIPTIONThe issue of the high FH burst traffic caused by SRS IQ data is addressed in the current 0- RAN open fronthaul specification [1], Clause 4.4.7 describes how to use non delaymanaged U-plane traffic to reduce the bit rate for sending SRS IQ data. In this case, the SRS IQ data are sent in separate traffic flows from other delay-managed traffic, e.g., for sending PUSCH data. As mentioned before, the PUSCH data is sent symbol by symbol. Each symbol is sent within a transmission window relative to its arrival time at the antenna reference point over the air interface. The transmission window definition is declared by the RU to the DU. In this way, the DU knows the earliest and latest time when a symbol will be sent by the RU. Given the knowledge of the transport delay, the DU can also determine the earliest and latest time when a symbol will be received by the DU.When using non delay-managed traffic, the RU controls when to send the traffic. In this case, the SRS IQ data can utilize the non delay-managed traffic to spread its transmission to longer time to reduce the bit rate. As exemplified in Figure 2, part of SRS IQ data are sent before the UL slots and the rest of SRS IQ data are sent during the DL slots, where there is no other U-plane data in the UL direction.When RU controls when to transmit SRS IQ data the DU cannot derive the time window during which the SRS IQ data may be received by the DU. This is undesired from the perspective of DU processing. For any data processing task, DU needs to prepare the hardware resources. Then, the DU can release the resources for the benefit of other tasks once the processing task is done. If the DU doesn't know when the data would arrive, the DU has to reserve the resources for the time from the earliest possible time that the data may arrive until all data arrive and are processed. For example, memory to store the SRS IQ data have to be reserved. During this time, the resources cannot be released to be used by other processing tasks. Considering the example of Figure 2 where the RU may decide to send the remaining parts of SRS after PUSCH, and with a time-division duplex (TDD) pattern of 3 consecutive UL slots, the DU needs to wait for more than 3 slots to receive thesecond part of the SRS IQ data. Then, the resources for processing the second part of the SRS IQ data are occupied for more than 3 slots until the processing is done, since DU doesn't know when the second part will arrive. Therefore, if SRS is sent as non delaymanaged traffic as specified in the current O-RAN WG4 specification, it is not possible for DU to plan and optimize the resource usage for SRS processing. For example, if DU would know that SRS will not be sent during PUSCH slots, DU can use the resources to process other tasks.Another consideration is that if the RU sends SRS too slow, it will also increase the delay for SRS processing.Sending of SRS at fronthaul using legacy delay management where transmission is tightly coupled to radio reception thus gives rise to transmission spikes.Legacy non delay-managed transmission gives too little predictability of SRS arrival at DU which requires resources allocated for an unnecessarily long time.A solution is to provide an intermediate level of delay management where the tight and static connection between symbol arrival at RU radio interface and its transmission on fronthaul to DU is loosened to allow sending at later times where fronthaul load is low, as well as allowing different timing for different parts of SRS, and put the timing in control of DU, either dynamically per scheduling of SRS or semi-statically by M-plane configuration, or a combination of the two.This disclosure provides methods in which the DU determines and informs the RU of a time window during which RU shall send the IQ data of an SRS symbol received from an antenna or from a beam formed using multiple antennas. SRS symbols from different antennas or beams can have the same time window or different time windows. In this document, this time window is referred to as SRS transmission (TX) window.The first method (Method #1) is that the DU conveys complete SRS TX window information in C-Plane messages, e.g. indications of the start and the end of the TX window, such as a TX window offset and a TX window size..In O-RAN open fronthaul specification, C-Plane messages are sent per slot. A C-Plane message for UL U-Plane data is sent from DU to RU, and provides the description of which REs in a slot are requested by the DU and additional information for RU to process these REs, e.g., beam weights that RU will apply on the REs.For example, a legacy C-Plane message that requests a comb set of an SRS symbol for a spatial stream (e.g., data received by an antenna or a beam formed using multiple antennas) contains the information regarding the locations of the REs used in the requested comb set in the frequency-time grid of a slot. If the spatial stream represents a beamformed stream, the C-Plane message also provides the information regarding beamforming weights that will be used to perform beamforming for these REs.In method #1, the SRS TX window information is added in the C-Plane message(s) that provide the description of requested SRS REs. After receiving the C-Plane message(s) the RU will receive the SRS on the radio interface and send the resource elements (REs) of SRS symbol(s) described in the C-plane messages to DU during the SRS TX windowdescribed in the C-plane message. This method is fully dynamic and flexible to control the SRS TX window from the DU perspective.The second method (Method #2) is to configure SRS TX windows via M-Plane. A list of SRS TX window configurations is configured to O-RU endpoint(s) by the O-DU. In the list, each SRS TX window configuration is associated to certain REs of a range of SRS symbol(s) from one or more antennas or beams. The location in the time-frequency resource grid of SRS symbol(s) or part of the SRS symbol(s) (i.e., some REs of the SRS symbol(s)) is provided. When an O-RU endpoint receives a C-Plane message specifying REs that match the REs of an SRS TX window configured for the endpoint (e.g. a C-plane message for SRS), it will apply the corresponding TX window for sending the REs to the 0- DU. The same mechanism may also be used to specify TX windows for other data than SRS.Hence, when receiving the C-Plane message for SRS (or for symbols with configured TX windows), the RU will know the requested IQ data is SRS (or just know the symbols with configured TX windows) and know its corresponding SRS TX window, from the SRS TX window configuration in M-Plane. Then, the RU will send the requested SRS IQ data in one or multiple SRS TX windows according to the configuration. This method is a static configuration of SRS TX window. It is easier for RU to implement without the need to support dynamically changed SRS TX windows.The third method (Method #3) is mixing of C-Plane and M-Plane methods. A list of SRS TX windows is configured via M-Plane. Each SRS TX window configuration may be associated with an SRS window ID. For certain SRS REs, DU sends an indicator (e.g., SRS window ID or the list index) to identify an SRS TX window configuration in the M-Plane list in a C-Plane message which provides the information of the SRS REs. After receiving the C-Plane message, the RU will know the SRS time window information from the indicator received in the C-Plane message. Then, the RU will send the REs of SRS symbol(s) described in the C-plane messages during the SRS TX window indicated by the received SRS window ID or the list index. This method is semi-static for SRS TX window control. Compared to the second method, RU doesn't need to detect if an M-Plane configured TX window should be applied as this information is inferred from the TX window information in the C-Plane message (as is true also for the first method).Compared to the first method, it is more deterministic for RU since it only needs to support a few windows configured by the DU.Individual features of the three methods, as well as features disclosed elsewhere in this disclosure may be applied to other methods than the one it is disclosed with, as well as otherwise combined.With the methods of this disclosure, the DU controls the SRS TX window for RU to send SRS and thus controls when the SRS IQ data arrive. In this way, DU can optimize the processing resource planning and scheduling for different tasks to increase resource utilization. For example, only making the resource available when needed, e.g., when the data is ready for buffering and processing. Comparing to the legacy method using non delay managed traffic to send SRS under RU control, the proposed methods would significantly improve the DU resource utilization and therefore increase system capacity.Also, DU can consider the RU constraints declared by the RU and therefore there is no impact to the RU.The proposed methods also provide the way to configure different TX windows for different sets of SRS symbols, PRBs and REs. For example, the first SRS symbol can be sent with less delay than the second SRS symbol (e.g., send the first SRS symbol immediately in UL slot time when the first available slot is free while RU is performing e.g DMRS-based beamforming for PUSCH and delay the second SRS symbol to the DL slot time). When there are two SRS symbols, each of which only use equal to or less than half of the REs of a full SRS symbol (e.g., each symbol only uses one comb set of REs in comb 2), Method #1 and Method #3 can let RU send the REs also of the second SRS symbol earlier (e.g., send these REs immediately since the REs of the first symbol don't use up the available FH bandwidth in the UL slot). Therefore, this can also reduce the delay for SRS processing. It can be also used to change the window size to control the bit rate for sending SRS IQ data. For example, increasing the window size for a symbol indicates that the symbol can be sent in longer time and thereby RU can send the messages less frequently to reduce the overall bit rate.In current O-RAN open fronthaul specification, the SRS transmissions are handled by RU endpoints which support non delay-managed traffic. Each RU end point represents a logical processing point in the RU which handles the data flow of one spatial stream or one layer, i.e., receiving the C-plane message of the scheduling information of a spatial stream or a layer from the DU, processes the spatial stream or the layer of the UE data according to the scheduling information in the received C-plane message, and send the corresponding processed U-Plane data of the spatial stream or the layer back to O-DU for UL traffic. (Even though not independent on one another, scheduling here refers to transmission on fronthaul, as opposed to scheduling on the radio interface.) For the endpoint used for SRS, each endpoint may handle one antenna or one beam. These endpoints are declared via M-Plane. To be more compatible to the current specification and make it easier for RUs to support sending SRS in legacy and new ways, we propose to introduce a new feature (e.g., DU-CONFIG-SRS-TX-WINDOW) for the endpoints that support non delay managed traffic. If an RU endpoint is declared to support the new feature (e.g., DU-CONFIG-SRS-TX-WINDOW-SUPPORTED), the endpoint can support DU controlled SRS TX window with at least one of the methods that are described below, i.e.. Method #1, #2 and #3. If the RU supports more than one method, it is up to the DU to decide which method to configure. If DU configures the endpoint to use the new feature, the endpoint will send SRS symbol(s) during the SRS TX window(s) determined by the DU. For the non delay-managed U-Plane data other than SRS, the endpoint may still treat them as non delay-managed traffic and send them in best effort.Another way is that the RU uses delay managed endpoints for SRS transmissions by declaring support for the new feature for delay managed endpoints for SRS. However, if the RU wants to support both legacy and new ways, the drawback is that RU has to provide twice times of the endpoints for SRS, i.e., one set of non delay-managed end points to support the legacy way and the other set of delay-managed end points to support the new way.Note that declaring support of the feature can be done by declaring support for certain section extensions, e.g.. Section Extension 18.In addition to all methods above, the DU may configure the RU to uniformly distribute (with the best effort) the transmission of SRS within the transmission window.In all these methods, RU can also declare to DU some constraints about the possible window configurations. Then, DU will schedule the SRS and configure the SRS TX windows considering these constraints. For example, RU may declare to DU how many SRS REs or physical resource blocks (PRBs) it can buffer and the longest transmission window size for sending all SRS REs of one or more symbols. These constraints can also be discussed and agreed between RU and DU vendors during the system integration phase. If RU and DU are from the same vendor, these constraints are already known in the product design phase.Further, DU may determine the SRS TX window considering one or more of TDD pattern, SRS pattern, DU resource planning and FH bit rate, in addition to the RU constraints if any. With the proposed methods, DU is able to optimize its resource utilization for different TDD pattern and SRS pattern (hence providing reduced hardware costs and / or increased capacity) and reduce the SRS FH delay, also fulfill the RU constraints for SRS buffering and transmission.Method #1:In this method, DU conveys complete SRS TX window information (e.g., indication of start and end of the TX window or start and duration of the TX window) in C-Plane messages. As shown in Figure 3, the DU determines one or more SRS TX windows considering TDD pattern, SRS pattern, as well as RU constraints if provided. DU sends the C-Plane messages containing SRS configuration / scheduling information and SRS TX window information to the RU. Information of different TX windows associated with different subgroups of REs of a range of SRS symbol(s) may be sent in different C-Plane messages. The benefit of indicating REs is enabling configuring different TX windows for the REs of different comb set, for example, to make it possible to prioritize certain comb set(s). Based on the determined TX window and delay profile of transport interface, the DU determines the reception (RX) window(s) for the upcoming SRS symbols or SRS REs. Then the DU can receive U-Plane SRS IQ data from RU applying the determined RX window(s) and continue processing the received SRS IQ data.The second step (sending C-plane message) and third step (determine SRS reception window) could be performed in parallel, or the order could be switched.As indicated in Figure 4, RU receives C-Plane messages from DU containing information of SRS TX window(s). Accordingly, it prepares the corresponding REs of SRS symbol(s) which are also described in the C-plane messages and sends the REs during the configured SRS TX window(s).This method is fully dynamic and flexible to control the SRS TX window from the DU perspective.Method #2In this method, DU configures SRS TX windows via M-Plane. Specifically, as shown in Figure 5, DU determines an M-Plane list of SRS TX window configurations considering TDD pattern, SRS pattern, as well as RU constraints if provided. In the list, each SRS TX window configuration (indication of start and end of the TX window or start and duration of the TX window) is associated to certain REs of one or more SRS symbol(s) from one or more antennas or beams. The location of SRS symbol(s) or part of the SRS symbol(s) is provided by, for example, slot number (subframeld and slotld in O-RAN WG4 specification), symbol range, PRB range, RE mask (indicating certain SRS REs), etc. The configuration list and the corresponding RE association is configured by the DU to the RU via M-Plane messages.Figure 6 shows the DU operations in Control- and User-Plane. The DU sends scheduling information for SRS to the RU via C-Plane messages. Given the configured M-Plane list of SRS TX window, the DU can determine the reception window for certain SRS REs based on the corresponding TX window configuration and the knowledge of the transport network delay related to transport topology (the delay can be also measured). Then the SRS IQ data can be received during the determined SRS reception window and forwarded for further processing.Reception windows can be determined from the scheduling information, so can be determined also before or during the sending of the C-Plane message..Figure 7 shows the RU operations in Control- and User-Plane. When RU receives the C- Plane message with scheduling information for SRS, it will know the requested IQ data is SRS and determine, according to the configured M-Plane SRS TX window list, the corresponding SRS TX window for the SRS IQ data described by the received C-Plane messages. Then, the RU will send the requested SRS IQ data in one or multiple SRS TX windows according to the configuration. This method is a static configuration of SRS TX window. It is easier for RU to implement without the need to support dynamically changed SRS TX windows.Method #3The third method is a mixing of C-Plane and M-Plane methods. Similar to Method # 2, a list of SRS TX windows is configured by the DU to the RU via M-Plane. Certain REs of a range of SRS symbol(s) from one or more antennas or beams may be associated to one or multiple SRS TX window configuration. Additionally, each SRS TX window configuration may be associated with an SRS window ID or identified by its list index. The M-Plane related process is shown in Figure 8.In this method, as described in Figure 9 and Figure 10, for certain SRS REs, DU sends an indicator (e.g., the SRS window ID or the list index) to identify an SRS TX window configuration in the M-Plane list in a C-Plane message which provides the scheduling information for the SRS REs. The indicator is thereby associated to the certain REs of one or more SRS symbol(s) from one or more antennas or beams described by the C-Plane message. After receiving the C-Plane message, the RU determines the SRS TX window by referring the indicator received in the C-Plane message to the configured M-Plane SRS TX window list. Then, the RU will send the REs of SRS symbol(s) described in the C-planemessages during the SRS TX window indicated. This method is semi-static for SRS TX window control. Comparing to the second method, RU doesn't need to detect the SRS location and associate between REs and the corresponding TX window itself. Comparing to the first method, it is more deterministic for the RU since it only needs to support the windows statically configured by the DU.Further embodiments:In the descriptions above, it assumes that RU sends SRS IQ data to DU and DU performs SRS channel estimation. There may be another implementation in which the RU performs SRS channel estimation and then send the SRS channel estimates back to the DU. The methods described above are also applicable for controlling the TX windows for RU to send SRS channel estimates in this implementation. In this case, RU may declare some more constraints. For example, RU may have a further constraint when SRS channel estimates will be available.For 6G, there is a lot of interest in industry and academia regarding integrated sensing and communication (ISAC) where a base station can, in addition to communicate with UEs, also be used for sensing applications such as radar. Depending on type of sensing, number of RU antennas, and amount of processing done in the RU, sensing could create large amounts of data, e.g., in form of IQ data, channel estimates, or impulse responses per antenna, group of antennas, or per direction. This does not necessarily involve any SRS but since the amount of data might be similar to that of SRS, and since the DU or another node might need to reserve resources also for ISAC processing, the methods described above can be beneficial also for ISAC.A DU may be a baseband unit, BBU, or a part thereof. An RU may be a remote radio unit, RRU.A DU is typically an O-RAN O-DU, but may be any kind of DU. An RU is typically an O-RAN O-RU but may be any kind of RU.The O-DU can be implemented as virtualized O-DU in a Cloud environment.SRS data may be in the form of IQ data. It may be the data contained in a complete SRS transmission or a subset thereof, for example only for particular resource elements, antennas, beams or ports.The terms air interface and radio interface are used interchangeably.C-plane messages referred to herein may be C-plane messages according to O-RAN Lower Layer Split Control-plane (LLS-C): Lower Layer Split Control-plane: logical interface (for real-time control and reporting measurements) between O-DU and O-RU when using a lower layer functional split.U-plane messages referred to herein may be U-plane messages according to 0 RAN Lower Layer Split User-plane (LLS-U): Lower Layer Split User-plane: logical interface (for IQ data) between O-DU and O-RU when using a lower layer functional split.Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Embodiments described above may be implemented in settings as described below. Embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.Figure 11 shows an example of a communication system 100 in accordance with some embodiments.

[0001] In the example, the communication system 100 includes a telecommunications network 102 that includes an access network 104, such as a radio access network (RAN), and a core network 106, which includes one or more core network nodes 108. The access network 104 includes one or more access network nodes or base stations of various types, access network nodes 110A and 110B are depicted (which may be collectively referred to as network nodes 110), or any other similar 3rdGeneration Partnership Project (3GPP) access nodes or non-3GPP access points (APs). Some embodiments of the access network 104 may include more than one access network technology. The network nodes 110 of access network 104 facilitate direct or indirect connection of wireless devices, also referred to as user equipments (UEs), such as by connecting UEs 112A, 112B, 112C, and 112D (one or more of which may be generally referred to as UEs 112) to the core network 106 over one or more wireless connections.

[0002] Moreover, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, the telecommunications network 102 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a network node in the telecommunications network 102 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other network nodes to implement one or more functionalities of any network node in the telecommunications network 102, including one or more access network nodes 110 and / or core network nodes 108.

[0003] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (0- CU-CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or anycombination thereof (the adjective "open" designating support of an ORAN specification). An ORAN network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN network node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an 0-2 interface defined by the 0- RAN Alliance or comparable technologies.

[0004] The network nodes 110 facilitate direct or indirect connection of one or more UEs 112 to the core network 106 over one or more wireless connections. Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 100 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. The communication system 100 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0005] The UEs 112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with the network nodes 110 and other communication devices. Similarly, the network nodes 108, 110 are arranged, capable, configured, and / or operable to communicate directly or indirectly (e.g., via other devices of telecommunications network 102) with the UEs 112 and / or with other network nodes or equipment in the telecommunications network 102 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in the telecommunications network 102. More specifically, UEs 112 may send messages, data, and / or other signals to network nodes 108, 110 or other elements of the telecommunications network 102 by transmitting such signals to the relevant device directly without the signals passing through any intervening devices or by transmitting such signals to the relevant device indirectly through an intervening device (or multiple intervening devices) that then transmit the signal to the relevant device.Similarly, network nodes 108, 110 may send messages, data, and other signals to UEs 1122, other network nodes 108, 110, and other devices in telecommunications network 102 directly or indirectly. As one specific example, a core network node 108 may transmit a particular message to a UE 112 by transmitting the message to an access network node 110 that will then transmit the message to the intended UE 112. Similarly, a core network node 108 may receive a particular message from a UE 112 by receiving the message from an access network node 110 that itself received the message from the UE 112.

[0006] In the depicted example, the core network 106 connects elements of the access network 104 (e.g., one or more of the network nodes 110) to one or more host computing systems, such as host 116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 106 includes one or more core network nodes (e.g., core network node 108) of various types, one or more of which may be generally referred to as network nodes 108. Network nodes 108 are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, access network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 108. Example core network nodes provide functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0007] The host 116 may be under the ownership or control of a service provider other than an operator or provider of the access network 104 and / or the telecommunications network 102. The host 116 may be operated by the service provider or on behalf of the service provider. The host 116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0008] As a whole, the communication system 100 of Figure 1 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system 100may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (Wi-Fi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (Wi-Max), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, Li-Fi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox. Moreover, the communication system 100 may be configured to support multiple different standards, protocols, or other rule sets, with individual components supporting all of the relevant rule sets or with different components or sub-systems within the communication system 100 supporting different standards, protocols, or rule sets.

[0009] As one example, in certain embodiments, access network 104 may contain some access network nodes 110 that support 3GPP radio access technologies (RAT), such as LTE or NR, while other access network nodes 110 support (or the same access network nodes 110 additionally support) non-3GPP RATs, such as Wi-Fi or a proprietary RAT. As another example, telecommunications network 102 may support multiple generations of related communication standards (e.g., 4G and 5G 3GPP communication standards) and, as a result, may include an access network 104 and / or a core network 106 that supports multiple different standard generations or may include multiple access networks 104 and / or multiple core networks 106 with individual networks 104, 106 supporting different standard generations.

[0010] Telecommunications network 102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunications network 102. For example, the telecommunications network 102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive loT services to yet further UEs.

[0011] In some examples, one or more of the UEs 112 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 104. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[0012] In the example, the hub 114 communicates with the access network 104 to facilitate indirect communication between one or more UEs (e.g., UE 112C and / or 112D) and network nodes (e.g., network node 110B). In some examples, the hub 114 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 114 may be a broadband router enabling access to the core network 106 for the UEs. As another example, the hub 114 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 110, or by executable code, script, process, or other instructions in the hub 114.

[0013] As another example, the hub 114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 114 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, the hub 114 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0014] The hub 114 may have a constant / persistent or intermittent connection to the network node 110B. The hub 114 may also allow for a different communication scheme and / or schedule between the hub 114 and UEs (e.g., UE 112C and / or 112D), and between the hub 114 and the core network 106. In other examples, the hub 114 is connected to the core network 106 and / or one or more UEs via a wired connection. Moreover, the hub 114 may be configured to connect to an M2M service provider over the access network 104 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 110 while still connected via the hub 114 via a wired or wireless connection. In some embodiments, the hub 114 may be a dedicated hub- that is, a hub whose primary function is to route communications to / from the UEs from / to the network node 110B. In other embodiments, the hub 114 may be a non-dedicated hub- that is, a device which is capable of operating to route communications between the UEsand network node 110B, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0015] Figure 12 is another example of a communication system 200 according to some embodiments. As used herein, the communication system 200 includes multiple access points (APs) 210 (with four exemplary APs 210A, 210B, 210C, and 210D being depicted) and multiple wireless devices, referred to in the context of communication system 200 as stations (STAs) 212 (referred to individually as STA 212A, STA 212B, STA 212C, STA 212D, and STA 212 E). STA 212A is served by AP 210A in a first basic service set (BSS) 220A. STA 210B and STA 210C are served by AP 210B in a second BSS, BSS 220B. STA 212D is served by AP 210C in a third BSS, BSS 220C. STA 212E is served by AP 210D in a fourth BSS, BSS 220D. Stations 212 may be non-AP STAs and correspond to various kinds of wireless devices, for example, user terminals, such as mobile or stationary computing devices like smartphones, laptop computers, desktop computers, tablet computers, gaming devices, head-mounted displays (HMDs) for Augmented Reality (AR) or Virtual Reality (VR), or the like. Further, stations 212 could, for example, correspond to other kinds of equipment like smart home devices, printers, multimedia devices, data storage devices, or the like.

[0016] Each of STAs 212 may connect through a radio link to one of APs 210. For example, depending on location or channel conditions experienced by a given STA 212, the STA may select an appropriate AP a nd BSS for establishing the radio link. The radio link may be based on one or more orthogonal frequency-division multiplexing (OFDM) carriers from a frequency spectrum that is shared on the basis of a contention-based mechanism, e.g., an unlicensed or license exempt band like 2.4 GHz Industrial, Scientific, and Medical (ISM) band, the 5 GHz band, the 6 GHz band, or the 60 GHz band.

[0017] Each AP 210 may provide data connectivity to STAs 212 connected to a particular AP 210. As illustrated, APs 210 may be connected to a data network 230. In this way, APs 210 may also provide data connectivity between STAs 212 and other entities, e.g., to one or more servers, service providers, data sources, data sinks, user terminals, or the like. Accordingly, the radio link established between a given STA 212 and its serving AP 210 may be used for providing various kinds of services to STA 212, e.g., a voice service, a multimedia service, or other data service. Such services may be based on applications that are executed on STA 212 and / or on a device linked to STA 212. By way of example. Figure 2 illustrates an application service platform 232 provided in data network 230. The a pplication(s) executed on STA 212 and / or on one or more other devices linked to STA 212 may use the radio link for data communication with one or more other STA 212 and / or the applicationservice platform 232, thereby enabling utilization of the corresponding service(s) at STA 212.

[0018] Figure 13 shows a wireless device 300, which may be configured to operate in communication system 100 of Figure 1 or in communication system 200 of Figure 20. The wireless device 300 may be alternatively referred to as a UE 300, like a UE 112 within the context of communication system 100, or as a station (STA) 300 or as a non-access-point station (non-AP STA) 300, like a STA 212 within the context of the communication system 200, in accordance with respective embodiments. As used herein, a wireless device refers to a device capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other wireless devices. Examples of a wireless device include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle, vehicle-mounted or vehicle embedded / integrated wireless device, and wireless terminal. Other examples include any type of UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and / or an enhanced MTC (eMTC) UE.

[0019] A wireless device 300 may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication. Dedicated Short- Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle-to-everything (V2X). In other examples, wireless device 300 may not necessarily have a user in the sense of a human user who owns and / or operates the relevant device. Instead, wireless device 300 may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, wireless device 300 may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).

[0020] In particular embodiments, wireless device 300 includes processing circuitry 302 that is operatively coupled via a bus 304 to an input / output interface 306, a power source 308, a memory 310, a communication interface 312, and / or any other component, or any combination thereof. Certain embodiments of wireless device 300 may include all or a subset of the components shown in Figure 3. The level of integration between thecomponents may vary from one embodiment of wireless device 300 to another. In general, in a particular embodiment of wireless device 300, processing circuitry 302, input / output interface 306, power source 308, memory 310, and communication interface 312 may, in whole or in part, represent or include physical components common to or shared by one or more of the other elements of wireless device 300. Further, certain embodiments of wireless devices 300 may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.

[0021] The processing circuitry 302 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 310. The processing circuitry 302 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 302 may include multiple central processing units (CPUs).

[0022] In the example, the input / output interface 306 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and / or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into wireless device 300. Examples of an input device include a touch-sensitive or presencesensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.

[0023] In some embodiments, the power source 308 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used to supply power to circuitry or tocharge an associated battery. The power source 308 may further include power circuitry for delivering power from the power source 308 itself, and / or an external power source, to the various parts of wireless device 300 via input circuitry or an interface such as an electrical power cable. Power source 308 may perform any formatting, converting, or other modification to make accessible power suitable for the respective components of the wireless device 300 to which power is supplied.

[0024] The memory 310 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 310 includes one or more programs 314, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 316. The memory 310 may store, for use by wireless device 300, any of a variety of various operating systems or combinations of operating systems.

[0025] The memory 310 may be configured to include a numberof physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD- DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and / or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as 'SIM card.' The memory 310 may allow wireless device 300 to access instructions, programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 310, which may be or comprise a device-readable storage medium.

[0026] The processing circuitry 302 may be configured to communicate with an access network or other network via or using the communication interface 312. The communication interface 312 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 322. The communicationinterface 312 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another wireless device ora network node in an access network). Each transceiver may include a transmitter 318 and / or a receiver 320 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 318 and receiver 320 may be coupled to one or more antennas (e.g., antenna 322) and may share circuit components, software or firmware, or alternatively be implemented separately.

[0027] In the illustrated embodiment, communication functions of the communication interface 312 may include cellular communication, Wi-Fi communication (e.g., according to an IEEE 802.11 family standard), LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.

[0028] In particular embodiments, wireless device 300 may provide an output of data captured via a sensor, through its communication interface 312, via a wireless connection to a network node, and / or in any appropriate manner. Data captured by sensors of a wireless device 300 can be communicated through a wireless connection to a network node via another wireless device 300. In particular embodiments, such output may be periodic (e.g., once every 15 minutes if it reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient).

[0029] As another example, wireless device 300 comprises an actuator, a motor, ora switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, wireless device 300 may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according tothe received input or to a robotic arm performing a medical procedure according to the received input.

[0030] Wireless device 300, when in the form of an Internet of Things (loT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, wearable technology, extended industrial application and healthcare. Nonlimiting examples of such an loT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door / window sensor, a flood / moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. In particular embodiments, wireless device 300 represents an loT device that comprises circuitry and / or software in dependence of the intended application of the loT device in addition to other components as described in relation to the example embodiment of wireless device 300 shown in Figure 3.

[0031] As yet another specific example, in an loT scenario, wireless device 300 may represent a machine or other device that performs monitoring and / or measurements, and transmits the results of such monitoring and / or measurements to another wireless device and / or a network node. Wireless device 300 may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, wireless device 300 may implement the 3GPP NB-IoT standard. In other scenarios, wireless device 300 may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and / or reporting on its operational status or other functions associated with its operation.

[0032] In practice, any number of wireless devices 300 may be used together with respect to a single use case. For example, a first wireless device 300 might be or be integrated in a drone and provide the drone's speed information (obtained through a speed sensor) to a second wireless device 300 that is a remote controller operating the drone. When a user makes changes from the remote controller, the first wireless device 300 may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone'sspeed. The first and / or the second wireless device 300 can also include more than one of the functionalities described above. For example, wireless device 300 might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators.

[0033] Figure 14 shows a network node 400 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and / or operable to communicate directly or indirectly with a UE and / or with other network nodes or equipment, in a telecommunications network. In accordance with respective embodiments, network node 400 may be configured to operate in communication system 100 of Figure 1, like network nodes 108 or 110, or in communication system 200 of Figure 2, like an AP 210 or a station 212. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations. Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)), O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU).

[0034] Network nodes 400 may be categorized based on the amount of coverage they provide (or, stated differently, theirtransmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. Network node 400 may be a relay node or a relay donor node controlling a relay. Network nodes 400 may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0035] Other examples of network nodes 400 include multiple transmission point (multi- TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes. Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g.. Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0036] In particular embodiments, network node 400 includes a processing circuitry 402, a memory 404, a communication interface 406, and a power source 408. In general, in aparticular embodiment of network node 400, processing circuitry 402, memory 404, communication interface 406, and power source 408 may, in whole or in part, represent or include physical components common to or shared by one or more of the other elements of network node 400.

[0037] The network node 400 may be composed of multiple distinct network entities (e.g., a NodeB entity and a RNC entity, or a BTS entity and a BSC entity, etc.), which may each have or utilize their own respective physical components. In certain scenarios in which the network node 400 comprises multiple such entities (e.g., BTS and BSC), one or more of the separate entities may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 400 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memories 404 or portions of memory 404 for different RATs) and some components may be reused (e.g., a same antenna 410 may be shared by different RATs). The network node 400 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 400, for example GSM, WCDMA, LTE, NR, Wi-Fi (e.g., according to an IEEE 802.11 family standard). Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 400.

[0038] The processing circuitry 402 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other components, such as the memory 404, to provide network node 400 functionality.

[0039] In some embodiments, the processing circuitry 402 includes a system on a chip (SOC). In some embodiments, the processing circuitry 402 includes one or more of radio frequency (RF) transceiver circuitry 412 and baseband processing circuitry 414. In some embodiments, the RF transceiver circuitry 412 and the baseband processing circuitry 414 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 412 and baseband processing circuitry 414 may be on the same chip or set of chips, boards, or units.

[0040] The memory 404 may comprise any form of volatile or non-volatile computer- readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processing circuitry 402. The memory 404 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions capable of being executed by the processing circuitry 402 and utilized by the network node 400. The memory 404 may be used to store any calculations made by the processing circuitry 402 and / or any data received via the communication interface 406. In some embodiments, the processing circuitry 402 and memory 404 is integrated.

[0041] The communication interface 406 is used in wired or wireless communication of signaling and / or data with UEs, other network nodes, and / or any other network equipment. In the illustrated embodiment, communication interface 406 comprises port(s) / terminal(s) 416 to send and receive data, for example to and from a network over a wired connection. In particular embodiments, network node 300 may be capable of wireless communication and communication interface 406 may also include radio front-end circuitry 418 that may be coupled to, or in certain embodiments a part of, an antenna 410. Particular embodiments of radio front-end circuitry 418 include filter(s) 420 and amplifier(s) 422. The radio frontend circuitry 418 may be connected to an antenna 410 and processing circuitry 402. The radio front-end circuitry may be configured to condition signals communicated between antenna 410 and processing circuitry 402. The radio front-end circuitry 418 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 418 may convert the digital data into a radio signal(s) having the appropriate channel and bandwidth parameters using a combination of filters 420 and / or amplifiers 422. The radio signal(s) may then be transmitted via the antenna 410. Similarly, when receiving data, the antenna 410 may collect radio signals which are then converted into digital data by the radio front-end circuitry 418. The digital data may be passed to the processing circuitry 402. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0042] In certain alternative embodiments, network node 400 may be capable of wireless communication but does not include separate radio front-end circuitry 418, instead, the processing circuitry 402 includes radio front-end circuitry and is connected to the antenna 410. Similarly, in some embodiments, all or some of the RF transceiver circuitry 412 is part of the communication interface 406. In still other embodiments, the communication interface 406 includes one or more ports orterminals 416, the radio front-end circuitry 418, and the RF transceiver circuitry 412, as part of a radio unit (not shown), and the communication interface 406 communicates with the baseband processing circuitry 414, which is part of a digital unit (not shown).

[0043] The antenna 410 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signa Is. The antenna 410 may be coupled to the radio frontend circuitry 418 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 410 is separate from the network node 400 and connectable to the network node 400 through one or more interfaces or ports.

[0044] The antenna 410, communication interface 406, and / orthe processing circuitry 402 may be configured to perform some or all of the receiving operations and / or obtaining operations described herein as being performed by the network node 400. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, the antenna 410, the communication interface 406, and / or the processing circuitry 402 may be configured to perform some or all of the transmitting or sending operations described herein as being performed by the network node 400. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment.

[0045] The power source 408 provides power to the various components of network node 400 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 408 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 400 with power for performing the functionality described herein. For example, the network node 400 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 408. As a further example, the power source 408 may comprise a source of power in the form of abattery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0046] Embodiments of the network node 400 may include additional components beyond those shown in Figure 4 for providing certain aspects of the network node's functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, the network node 400 may include user interface equipment to allow input of information into the network node 400 and to allow output of information from the network node 400. This may allow a user to perform diagnostic, maintenance, repair, and otheradministrative functions forthe network node 400.

[0047] Figure 15 is a block diagram illustrating a virtualization environment 500 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 500 hosted by one or more of hardware nodes, such as a hardware computing device that operates as an access network node, UE, core network node, or host. Further, in embodiments in which a virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 500 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an 0-2 interface.

[0048] Applications 502 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 0400 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0049] Hardware 504 includes processing circuitry, memory that stores software and / or instructions executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 506 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VM 508Aand VM 508B (which may be collectively referred to as VMs 508), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. The virtualization layer 506 may present a virtual operating platform that appears like networking hardware to one or more of the VMs 508.

[0050] The VMs 508 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by virtualization layer 506. Different embodiments of the instance of a virtual appliance 502 may be implemented on one or more of VMs 508, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0051] In the context of NFV, each of the VMs 508 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, nonvirtualized machine. Each of the VMs 508, and that part of hardware 504 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more of the VMs 508 on top of the hardware 504 and corresponds to an application 502.

[0052] Hardware 504 may be implemented in a standalone network node with generic or specific components. Hardware 504 may implement some functions via virtualization. Alternatively, hardware 504 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 510, which, among others, oversees lifecycle management of applications 502. In some embodiments, hardware 504 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 512 which may alternatively be used for communication between hardware nodes and radio units.

[0053] Although the computing devices described herein (e.g., UEs, network nodes, hosts) may include the illustrated combination of hardware components, other embodiments maycomprise computing devices with different combinations of components. It is to be understood that these computing devices may comprise any suitable combination of hardware and / or software needed to perform the tasks, features, functions and methods disclosed herein. Determining, calculating, obtaining or similar operations described herein may be performed by processing circuitry, which may process information by, for example, converting the obtained information into other information, comparing the obtained information or converted information to information stored in the network node, and / or performing one or more operations based on the obtained information or converted information, and as a result of said processing making a determination. Moreover, while components are depicted as single boxes located within a larger box, or nested within multiple boxes, in practice, computing devices may comprise multiple different physical components that make up a single illustrated component, and functionality may be partitioned between separate components. For example, a communication interface may be configured to include any of the components described herein, and / or the functionality of the components may be partitioned between the processing circuitry and the communication interface. In another example, non-computationally intensive functions of any of such components may be implemented in software orfi rmware and computationally intensive functions may be implemented in hardware.

[0054] In certain embodiments, some or all of the functionality described herein may be provided by processing circuitry executing instructions stored on in memory, which in certain embodiments may be a computer program product in the form of a non-transitory computer-readable storage medium. In alternative embodiments, some or all of the functionality may be provided by the processing circuitry without executing instructions stored on a separate or discrete device-readable storage medium, such as in a hard-wired manner. In any of those particular embodiments, whether executing instructions stored on a non-transitory computer-readable storage medium or not, the processing circuitry can be configured to perform the described functionality. The benefits provided by such functionality are not limited to the processing circuitry alone or to other components of the computing device, but are enjoyed by the computing device as a whole, and / or by end users and a wireless network generally.Numbered embodiments1. A method performed by a baseband unit, BBU, or part thereof comprising the step of configuring or instructing a remote radio unit, RRU, with a time window during which sounding reference signal(s), SRS, or channel estimate data should be sent from the RRU to the BBU.2. A method according to embodiment 1 wherein the relation of the time window to the time of reception of the SRS is different from a relation of a time window used for sending physical uplink shared channel, PUSCH, symbols from the RRU to the BBU to the time of reception of the symbols.3. A method comprising configuring or instructing, by an O-RAN Digital Unit, DU, a transmission, TX, window for a user plane, U-plane, traffic flow of a fronthaul link between the DU and an O-RAN Radio Unit, RU, the TX window to be used by the RU for transmitting sounding reference signal, SRS, data or channel estimate data to the DU in the U-plane traffic flow.4. A method according to embodiment 3 wherein the configuring or instructing is made so that the TX window does not occur during uplink time division duplex, TDD, traffic.5. A method according to embodiment 3 wherein the configuring or instructing is made so that the TX window occurs during uplink TDD traffic at a time when there is no regular PUSCH data or partially scheduled PUSCH data to send on fronthaul.6. A method according to any of the embodiments 3-5 wherein the configuring or instructing is made by including information identifying the TX window in a Control plane, C-Plane, message.7. A method according to any of the embodiments 3-6 wherein the configuring or instructing is made by including in a management plane, M-plane, message information identifying the TX window relative to a time of reception of SRS from the radio interface.8. A method according to any of the embodiments 3-7 wherein one or more configurations identifying a TX window relative to a time of reception of SRS from air interface are included in one or more M-plane messages, each configuration being associated with an identifier, and wherein such an identifier is included in a C-plane message that provides the scheduling information of the SRS REs requested by DU to the RU to indicate that the particular configuration associated with the identifier is to be used to determine the TX window for the requested SRS REs.9 A method according to embodiment 6 or 8 wherein the C-Plane message is a message that provides to the RU information on SRS resource elements, REs, requested by the DU10 A method according to embodiment 6 or 8 wherein the C-Plane message is a message that provides to the RU information on SRS REs for which a channel estimate is to be made by the RU.11. A method according to any of the embodiments 3-10 wherein different TX windows are configured for sending data from different parts of SRS.12. A method according to any of the embodiments 3-11 wherein the DU determines a reception window for the SRS data or channel estimate based on the configured TX window and a delay profile of the fronthaul link.13. A method according to any of the embodiments 3-12 wherein the RU declares constraints regarding how TX windows may be configured or instructed.14. A method according to any combination of the preceding embodiments.15. A DU adapted to perform the method of any preceding embodiment.16. An RU adapted to receive from a DU the configuration or instruction of any preceding method embodiment.17. An RU according to embodiment 16 adapted to send SRS or a channel estimate in accordance with the configuration or instruction received from the DU.18. A computer program adapted to cause a DU to perform the method of any preceding method embodiment.19. A computer program adapted to cause an RU to receive from a DU the configuration or instruction of any preceding method embodiment.20. A computer program according to embodiment 19 adapted to cause an RU to send SRS or a channel estimate in accordance with the configuration or instruction received from the DU.bbreviations

Claims

CLAIMS1. A method performed by a baseband unit, BBU, or part thereof comprising the step of configuring or instructing a remote radio unit, RRU, with a time window, TX window, during which sounding reference signal(s), SRS, or channel estimate data should be sent from the RRU to the BBU.

2. A method according to claim 1 wherein the relation of the TX window to the time of reception of the SRS is different from a relation of a TX window used for sending physical uplink shared channel, PUSCH, symbols from the RRU to the BBU to the time of reception of the symbols.

3. A method according to any preceding claim wherein the BBU orthe part thereof is an 0- RAN Distributed Unit, O-DU, and the RRU is an O-RAN Radio Unit, O-RU.

4. A method according to claim 3 comprising configuring or instructing, by the O-DU, a transmission, TX, window for a user plane, U-plane, or control plane, C-Plane, traffic flow of a fronthaul link between the O-DU and the O-RU, the TX window to be used by the 0- RU for transmitting sounding reference signal, SRS, data in the U-plane traffic flow or channel estimate data to the DU in the C-plane traffic flow.

5. A method according to any preceding claim wherein the configuring or instructing is made so that the TX window does not occur during uplink time division duplex, TDD, traffic.

6. A method according to any preceding claim except claim 5 wherein the configuring or instructing is made so that the TX window optionally occurs during uplinkTDD traffic and at a time when there is no regular PUSCH data or at a time when there are partially scheduled PUSCH data to send on fronthaul,.

7. A method according to any preceding claim wherein the configuring or instructing is made by including information identifying the TX window in a Control plane, C-Plane, message.

8. A method according to any preceding claim wherein the configuring or instructing is made by including in a management plane, M-plane, message information identifying the TX window relative to a time of reception of SRS from the radio interface.

9. A method according to any preceding claim when dependent on claim 3 wherein one or more configurations identifying a TX window relative to a time of reception of SRS from air interface are included in one or more M-plane messages, each configuration being associated with an identifier, and wherein such an identifier is included in a C-plane message that provides the scheduling information of the SRS REs requested by the O-DU to the O-RU to indicate that the particular configuration associated with the identifier is to be used to determine the TX window for the requested SRS REs.

10. A method according to claim 7 or 9 when dependent on claim 3 wherein the C-Plane message is a message that provides to the O-RU information on SRS resource elements, REs, requested by the O-DU11. A method according to claim 7 or 9 when dependent on claim 3 wherein the C-Plane message is a message that provides to the O-RU information on SRS REs for which a channel estimate is to be made by the O-RU.

12. A method according to any preceding claim wherein different TX windows are configured for sending data from different parts of SRS.

13. A method according to any preceding claim when dependent on claim 3 wherein the O-DU determines a reception window for the SRS data or channel estimate based on the configured TX window and a delay profile of the fronthaul link.

14. A method according to any preceding claim when dependent on claim 3 wherein the RU declares constraints regarding how TX windows may be configured or instructed.

15. A DU adapted to perform the method of any preceding claim.

16. An RU adapted to receive from a DU the configuration or instruction of any preceding method claim.

17. An RU according to claim 16 adapted to send SRS or a channel estimate in accordance with the configuration or instruction received from the DU.

18. A computer program adapted to cause, when run, a DU to perform the method of any preceding method claim.

19. A computer program adapted to cause, when run, an RU to receive from a DU the configuration or instruction of any preceding method claim.

20. A computer program according to claim 19 adapted to cause, when run, an RU to send SRS or a channel estimate in accordance with the configuration or instruction received from the DU.

Images