WO2020088736A1

WO2020088736A1 - Improving mobility in a wireless communication network

Info

Publication number: WO2020088736A1
Application number: PCT/EP2018/079574
Authority: WO
Inventors: Mikko SÄILY; Tommi Jokela; Elena Virtej
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2018-10-29
Filing date: 2018-10-29
Publication date: 2020-05-07
Anticipated expiration: 2021-04-29

Abstract

According to an example aspect of the present invention, there is provided a method comprising, receiving at least two first uplink transmissions from a wireless terminal, determining whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions and transmitting a second message to a central control unit, wherein the second message comprises information related to the at least two first uplink transmissions.

Description

IMPROVING MOBILITY IN A WIRELESS COMMUNICATION NETWORK

FIELD

[0001] Various example embodiments relate in general to wireless communication networks, and improving mobility in such networks.

BACKGROUND

[0002] Mobility of wireless terminals needs to be enabled in various wireless communication networks, such as, in cellular networks operating according to Long Term Evolution, LTE, and/or 5G radio access technology. 5G radio access technology may also be referred to as New Radio, NR, access technology. Since its inception, LTE has been widely deployed and 3rd Generation Partnership Project, 3GPP, still develops LTE. Similarly, 3GPP also develops standards for 5G/NR. One of the topics in the 3GPP discussions is related to mobility enhancements of wireless terminals. Similar enhancements may also be employed in other cellular networks and in several other wireless communication networks as well, such as, for example, in Wireless Local Area Networks, WLANs. In general, there is a need to provide methods, apparatuses and computer programs for improving mobility of wireless terminals.

SUMMARY

[0003] According to some aspects, there is provided the subject-matter of the independent claims. Some embodiments are defined in the dependent claims.

[0004] According to a first aspect of the present invention, there is provided a method for a distributed unit, comprising receiving at least two first uplink transmissions from a wireless terminal, determining whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions and transmitting a second message to a central control unit, wherein the second message comprises information related to the at least two first uplink transmissions.

[0005] In some embodiments of the first aspect, the method may further comprise determining statistics associated with the at least two first uplink transmissions and determining whether the wireless terminal is moving towards the distributed unit, or not, based on the statistics associated with the at least two first uplink transmissions.

[0006] In some embodiments of the first aspect, the method may further comprise determining a gradient of the at least two first uplink transmissions and determining whether the wireless terminal is moving towards the distributed unit, or not, based on the gradient of the at least two first uplink transmissions.

[0007] In some embodiments of the first aspect, the information related to the at least two first uplink transmissions comprises statistics associated with the at least two first uplink transmissions and/or a gradient of the at least two first uplink transmissions.

[0008] In some embodiments of the first aspect, the method may further comprise, upon determining that the wireless terminal is moving towards the distributed unit, transmitting the second message to the central control unit, wherein the second message comprises a request to be added to a list of candidate cells for a handover .

[0009] In some embodiments of the first aspect, the method may further comprise, upon determining that the wireless terminal is moving away from the distributed unit, transmitting the second message to the central control unit, wherein the second message comprises a request to be removed from a list of candidate cells for a handover.

[0010] In some embodiments of the first aspect, the method may further comprise, depending on the determination about whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions, transmitting the second message to the central control unit, wherein the second message comprises a request to modify a configuration of a cell in a list of candidate cells.

[0011] In some embodiments of the first aspect, the method may further comprise measuring received powers of the at least two first uplink transmissions and determining whether the wireless terminal is moving towards the distributed unit, or not, based on the measured received powers of the at least two first uplink transmissions.

[0012] In some embodiments of the first aspect, the information related to the at least two first uplink transmissions is formed depending on determining whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions.

[0013] In some embodiments of the first aspect, the method may further comprise determining a moving direction of the wireless terminal with respect to the distributed unit and transmitting the second message, wherein the second message comprises the determined moving direction.

[0014] In some embodiments of the first aspect, the method may further comprise receiving a handover command in response to the transmitted second message.

[0015] In some embodiments of the first aspect, the method may further comprise transmitting the second message to the central control unit based on the determination.

[0016] In some embodiments of the first aspect, the wireless terminal is a user equipment.

[0017] According to a second aspect of the present invention, there is provided a method comprising, receiving a second message from a distributed unit, wherein the second message comprises information related to at least two first uplink transmissions of a wireless terminal, determining whether a wireless terminal is moving towards the distributed unit, or not, based on the received information and adjusting a configuration of the distributed unit based on the determination.

[0018] In some embodiments of the second aspect, the information related to the at least two transmissions comprises statistics associated with the at least two first uplink transmissions and/or a gradient of the at least two first uplink transmissions.

[0019] In some embodiments of the second aspect, the method may further comprise, when the wireless terminal is moving towards the distributed unit, receiving the second message from the distributed unit, wherein the second message comprises a request to be added to a list of candidate cells.

[0020] In some embodiments of the second aspect, the method may further comprise, when the wireless terminal is moving away from the distributed unit, receiving the second message from the distributed unit, wherein the second message comprises a request to be removed from a list of candidate cells.

[0021] In some embodiments of the second aspect, the second message comprises a request to modify a configuration of a cell in a list of candidate cells.

[0022] In some embodiments of the second aspect, the method may further comprise determining a moving direction of the wireless terminal with respect to the distributed unit.

[0023] In some embodiments of the second aspect, the method may further comprise transmitting the handover command in response to the received second message. [0024] In some embodiments of the second aspect, the wireless terminal is a user equipment.

[0025] According to a third aspect of the present invention, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to perform a method according to the first aspect of the present invention.

[0026] According to a fourth aspect of the present invention, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to perform a method according to the second aspect of the present invention.

[0027] According to a fifth aspect of the present invention, there is provided an apparatus comprising means for performing a method according to the first aspect of the present invention.

[0028] According to a sixth aspect of the present invention, there is provided an apparatus comprising means for performing a method according to the second aspect of the present invention.

[0029] According to a seventh aspect of the present invention, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least perform a method according to the first aspect of the present invention.

[0030] According to an eighth aspect of the present invention, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least perform a method according to the second aspect of the present invention.

[0031] According to a ninth aspect of the present invention, there is provided computer program configured to perform a method according to the first aspect of the present invention.

[0032] According to a tenth aspect of the present invention, there is provided computer program configured to perform a method according to the second aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIGURE 1 illustrates an exemplary network scenario in accordance with at least some embodiments;

[0034] FIGURE 2 illustrates a first exemplary process in accordance with at least some embodiments;

[0035] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments;

[0036] FIGURE 4 illustrates an exemplary signalling graph in accordance with at least some embodiments;

[0037] FIGURE 5 illustrates a flow graph of a first method in accordance with at least some embodiments;

[0038] FIGURE 6 illustrates a flow graph of a second method in accordance with at least some embodiments;

[0039] FIGURE 7 illustrates a second exemplary process in accordance with at least some embodiments.

EMBODIMENTS

[0040] Mobility of wireless terminals may be improved by the procedures described herein. For example, a wireless communication system may comprise a Central Unit, CU, and Distributed Units, DUs. A DU may receive uplink signals, i.e., first uplink transmissions, from a wireless terminal. The DU may then determine whether the wireless terminal is moving towards the DU, or not, based on the received first uplink transmissions. The DU may also transmit a report message, i.e., a second message, to the CU. The second message may comprise information related to the received first uplink transmissions. The CU may adjust a configuration of the DU based on the determination. In some embodiments, the DU may determine whether the wireless terminal is moving towards the distributed unit, or not, based on a gradient of the received first uplink transmissions. Some embodiments may be specifically related to a cloud Radio Access Network. [0041] FIGURE 1 illustrates an exemplary network scenario in accordance with at least some embodiments. The exemplary network scenario may refer to a cloud RAN. According to the example scenario of FIGURE 1 , there may be a wireless communication system, which comprises User Equipment, UE, 1 10, and three DUs 120a-c. DUs 120a-c may also comprise, or be associated with, cells. UE 1 10 may be connected to DUs 120a-c via air interface 1 15. The communication network may also comprise CU 130. In general, CU 130 may be referred to as a central control unit.

[0042] DUs 120a-c may be connected, directly or via at least one intermediate node, with CU 130 via wired interface 125. Interface 125 may be a front-haul, Fs, interface, for example a F1 interface. CU 130 may be, in turn, coupled to a core network via wired interface 135. The core network may be connected with another network (not shown in FIGURE 1 ), via which connectivity to further networks may be obtained, for example via a worldwide interconnection network. DUs 120a-c may also be connected with each other, or at least one other DU, via an inter-DU interface (not shown in FIGURE 1 ), even though in some embodiments the inter-DU interface may be absent.

[0043] UE 1 10 may comprise, for example, a smartphone, a cellular phone, a Machine-to-Machine, M2M, node, machine-type communications node, an Internet of Things, loT, node, a car telemetry unit, a laptop computer, a tablet computer or, indeed, another kind of suitable wireless terminal or mobile station. In the example system of FIGURE 1 , UE 1 10 may communicate wirelessly with a cell of DUs 120a-c via air interface 1 15. Air interface between UE 1 10 and DUs 120a-c may be configured in accordance with a Radio Access Technology, RAT, which both UE 1 10 and DUs 120a-c are configured to support. UE 1 10 may be referred to as wireless a terminal or a mobile station in general.

[0044] Examples of cellular RATs include Long Term Evolution, LTE, New Radio, NR, which may also be known as fifth generation, 5G, radio access technology and MulteFire. On the other hand, examples of non-cellular RATs include Wireless Local Area Network, WLAN, and Worldwide Interoperability for Microwave Access, WiMAX. In any case, embodiments are not restricted to any particular wireless technology. Instead, embodiments may be exploited in any wireless communication system which enables mobility of wireless terminals.

[0045] For instance, in the context of LTE, a Base Station, BS, may be referred to as eNB while in the context of NR, a base station may be referred to as gNB. Also, for example in the context of WLAN, a base station may be referred to as an access point. CU 130 may be a logical node and it may perform functions of a BS, such as, for example, transfer of user data, mobility control, radio access network sharing and session management. CU 130 may control actions, or operations, of DUs 120a-c via interface 125. In some embodiments, CU 130 may be referred to as a Baseband Unit, BBU. Moreover, DUs 120a-c may be logical nodes as well. DUs 120a-c may also perform some, i.e., a subset of, functions of a base station. In some embodiments, DUs 120a-c may be referred to as Remote Radio Heads, RRHs. That is to say, functions of a base station may be split between a DU and a CU.

[0046] Embodiments of the present invention provide uplink based mobility procedures. In some embodiments, at least one first uplink transmission of UE 1 10 may be received and measured by at least one DU 120a-c. The at least one first uplink transmission of UE 1 10 may be a physical uplink channel transmission, e.g., an uplink signal such as a reference signal. As an example, the at least one first uplink transmission may be an uplink signal specific for UE 1 10, such as, a sounding reference signal or a synchronization signal.

[0047] Said at least one DU 120a-c may control mobility of UE 1 10 using the measurements related to the at least one first uplink transmission of UE 1 10. According to the example of FIGURE 1 , UE 1 10 may be associated with DU 120a in the beginning. That is to say, a serving cell of DU 120a may be serving UE 1 10. The serving cell of DU 120a may be a source cell for a first handover. UE 1 10 may start moving towards DU 120b and at some point the first handover from the serving cell of DU 120a to a target cell of DU 120b may be needed. Hence, the mobility procedure in accordance with some embodiments may comprise, for example, the first handover from the serving cell of DU 120a to the target cell of DU 120b. A second handover from a cell of DU 120b to a cell of DU 120c may be needed as well, if UE 1 10 continues to move towards DU 120c as shown in FIGURE 1.

[0048] FIGURE 1 shows UE 1 10 configured to be in a wireless connection on one or more communication channels in a cell with DU 120a. It should be appreciated that functionalities of a base station may be implemented by using any node, host, server or access point, etc., entity suitable for such a usage. The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. However, the low latency applications and services, e.g., in 5G require bringing the content close to the radio which leads to local break out and Multi-access Edge Computing, MEC. 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content, host application instances, etc., in close proximity to cellular subscribers for faster response time. 5G (or NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and DUs 120a-c. It should be appreciated that MEC can be applied in LTE networks, and other networks as well.

[0049] Some embodiments may be related to conditional handovers. In case of conditional handovers, a first critical step for a successful handover may be associated with detection of a candidate target cell. In more detail, the first critical step may be related to timing of the detection of the candidate target cell. Then, a second critical step may be associated with addition of the detected candidate target cell to a list of candidate cells of UE 1 10. For example, if the detection and addition of the candidate target cell is done too early, preparations for a handover may incur overhead because some cells may be prepared for the handover for nothing. Thus, in the beginning it may not be necessary to prepare a cell of DU 120c for a handover, even though it may needed later on if UE 1 10 moves towards DU 120c as demonstrated in FIGURE 1.

[0050] Handover preparations may comprise, e.g., reservation of resources for UE 1 10 at DU 120c, but if UE 1 10 does not move towards DU 120c after all, the reserved resources at DU 120c may not be used. Unnecessary reservation of resources should be thus avoided. Handover preparations may be done for nothing if for example a moving direction of UE 1 10 changes or measured time variant radio conditions between UE 1 10 and a distributed unit indicated a wrong cell. On the other hand, if the handover preparations are done too late, benefits of a conditional handover may be lost, e.g., for robust handover.

[0051] It is noted that measurements done by UE 1 10 may not represent full availability of DUs 120a-c, or cells of DUs 120a-c, always. Thus, measurements of DUs 120a-c may be needed. For example, if cells of DUs 120a-c are small and deployed densely in an area, feasible number of cells of DUs 120a-c that UE 1 10 can report may be limited and/or propagation conditions between UE 1 10 and various cells may be rather similar because distance between the cells of DUs 120a-c may be small. Also, in case of dense deployment the cells of DUs120a-c may have rather similar propagation characteristics. Such issues may lead to multiple handover commands to add/modify/remove cells from a candidate list, i.e., a conditional handover configuration, of UE 1 10. The handover commands may be transmitted over air interface to UE 1 10 which would cause signalling overhead. Therefore, unnecessary handover commands should be also avoided.

[0052] In some embodiments of the present invention, UE 1 10 may transmit uplink signals, i.e., first uplink transmissions. The first uplink transmissions may be received and measured by one or more of DUs 120a-c. One or more DUs 120a-c may comprise a target cell for a handover. Moreover, each of DUs 120a-c may compute a gradient of uplink measurements of said first uplink transmissions. The gradient associated with a DU may represent mobility of UE 1 10 relative to said DU, i.e., a target cell of the DU.

[0053] In general, a gradient may be seen as a generalized function compared to a derivative. The gradient may be associated with functions that have multiple variables and the functions may be vector-valued. On the other hand, a derivative may be associated with functions of single variables and it may be scalar-valued.

[0054] Gradient may be seen similar as a derivative, because the gradient may also represent a slope of a function. The gradient may point to a direction of a greatest increase rate of the function. Moreover, a magnitude of the gradient may refer to the slope of the function in said direction. As an example, if standard unit vectors in directions of x, y and z coordinates are denoted by i, j and k, respectively, in the three-dimensional coordinate system the gradient V/ may be calculated using the following equation

[0055] In some embodiments, the gradient may be used at a DU for evaluating whether an UE is moving towards, or away from, a cell of the DU. The gradient may be calculated in terms of uplink radio signals, i.e., first uplink transmissions, from the UE. For example, the gradient may be calculated in terms of received powers of the first uplink transmissions. In some embodiments, the gradient may be calculated for each cell of each DU. [0056] Depending on the gradient of first uplink transmissions received by a cell of a

DU, the DU may transmit a second message to a serving CU. The second message may comprise an indication, e.g., whether the cell of the DU should be added to, or removed from, a potential configuration. For example, in a centralized cloud radio access network deployment the information about the potential configuration may be readily available in the CU. Hence, the CU may adjust operations related to a potential conditional handover configuration of the UE. Said adjustment of a DU may comprise adding, modifying or removing operations of candidate target cells, e.g., adding a cell to, or removing a cell from, a list of candidate cells for a conditional handover. Modifying a cell in the list of candidate cells may refer to modifying at least one of handover evaluation and execution parameters associated with the conditional handover.

[0057] Thus, in general the potential configuration may refer to a list of candidate cells of DUs and said candidate cells may be potential target cells for a handover. The candidate cells may be prepared by the serving CU and the UE may perform the handover to one of the candidate cells later on. The potential configuration may be sent in a handover command to DUs which are associated with the listed candidate cells. Listed candidate cells may be prepared with UE context.

[0058] FIGURE 2 illustrates a first exemplary process in accordance with at least some embodiments. The exemplary process may be associated with a conditional handover in a cloud RAN. On the vertical axes are disposed, from left to right, UE 1 10, first DU 120a, second DU 120b, DUs 120c-n, and CU 130 of FIGURE 1. First DU 120a may be associated with a source cell for a handover, i.e., first DU 120a may comprise the source cell. Second DU 120b may be associated with a target cell for the handover, i.e., second DU 120b may comprise the target cell. All DUs 120b-n may be in a candidate set of UE 1 10 for a handover.

[0059] At step 1 of FIGURE 2, CU 130 may start the exemplary process by transmitting a first context modification request message to DU 120a. The first context modification request message may be, for example, a UE Context Modification Request. In addition, or alternatively, the first context modification request message may comprise information related to a connection reconfiguration for UE 1 10, e.g., Radio Resource Control , RRC, Connection Reconfiguration information. The information related to the connection reconfiguration may further comprise reference signal configuration, such as, Uplink- Reference Signal, UL-RS, configuration. Alternatively, UE 1 10 may be configured with a specific Random Access Channel, RACH, preamble. The information related to the connection reconfiguration may be referred to as a configuration of a first uplink transmission. Hence, DU 120a may be configured for receiving the first uplink transmission upon receiving the first context modification request message.

[0060] Upon receiving the first context modification request message, DU 120a may transmit, at step 2, a first connection reconfiguration message to UE 1 10. The first connection reconfiguration message may comprise said information related to the connection reconfiguration. Hence, UE 1 10 may be configured for transmitting the first uplink transmissions upon receiving the first connection reconfiguration message.

[0061] UE 1 10 may transmit a first reconfiguration complete message to DU 120a. The first reconfiguration complete message may be a positive acknowledgement to the first connection reconfiguration message. The first reconfiguration complete message may be referred to as a RRC Reconfiguration Complete. Thus, in some embodiments RRC Reconfiguration Complete may be a positive acknowledgement to RRC Connection Reconfiguration message. In general, the first reconfiguration complete message may be sent upon reception of the first connection reconfiguration message. [0062] At step 3 of FIGURE 2, DU 120a may transmit a first modification response to CU 130 upon receiving the first reconfiguration complete message from UE 1 10. The first modification response message may be, e.g., a UE Context Modification Response.

[0063] After performing steps 1 -3 of FIGURE 2, UE 1 10 may be configured for a transmission of an UE-specific uplink signal, i.e., first uplink transmission. For example, UE 1 10 may be configured for a transmission of Sounding Reference Signal, SRS, transmission or a RACH preamble. UE-specific SRS may be referred to as UE-SRS as well. Thus, the first uplink transmissions may comprise SRS or RACH preamble.

[0064] Transmission of a UE-SRS may require time and frequency synchronization to at least one target cell of a DU, which may be expected to receive the UE-SRS transmission. However, it is noted that accurate time and frequency synchronization for a first uplink transmission may not be needed in certain networks, for example, in case of dense networks which comprise small cells because a difference between propagation times from UE 1 10 to different target cells of DUs may be within a Cyclic Prefix, CP. The target cells may be synchronized with each other anyway. On the other hand, requirements related to time synchronization may be eased, for example, in large networks or in networks that comprise target cells which are unsynchronized in time, by configuring a RACH preamble for UE 1 10 for first uplink transmissions.

[0065] At step 4 of FIGURE 2, CU 130 may transmit a setup request message to DUs 120b-n to configure DUs 120b-n for measuring the first uplink transmissions, e.g., UE-SRS or RACH preamble. In some embodiments, distributed units 120b-n may be under same CU 130, i.e., served by same CU 130.

[0066] The setup request message may be referred to as an UE Context Setup Request. In addition, or alternatively, the setup request message may comprise a measurement configuration for measuring the first uplink transmission, i.e., the uplink signal which is specific for UE 1 10. In some embodiments, the measurement configuration may be referred to as a DU Measurement Configuration. In addition, or alternatively, the measurement configuration may comprise a first threshold. The first threshold may indicate to DUs 120b-n when measurement results should be reported CU 130. Thus, the first threshold may indicate when a second message, i.e., a report message, should be transmitted to CU 130. In one example, a DU may report the measurements to CU if at least one e.g. Reference Signal Received Power, RSRP, Reference Signal Received Quality, RSRQ, Block Error Rate, BLER, Received Signal Strength Indicator, RSSI, or Channel Quality Indication, CQI, is higher than a corresponding threshold. The threshold may be understood as, for example, corresponding to a RSRP threshold_1 or RSRQ threshold_2, or BLER threshold_3. For instance, BLER threshold_3 may refer to a signal quality corresponding to 10% BLER for a hypothetical Primary Downlink Control Channel, PDCCH, transmission.

[0067] In response to receiving the setup request message, one or more DUs 120b- n may, at step 5, transmit a setup response message to CU 130. In some embodiments, the setup response message may be referred to as an UE Context Setup Response.

[0068] At step 7, UE 1 10 may start transmitting UE-specific uplink signals, i.e., first uplink transmissions. In some embodiments, UE 1 10 may start transmitting UE-specific uplink signals, e.g., UE-SRS or RACH preamble, immediately. That is to say, UE 1 10 may start transmitting the UE-specific uplink signals upon receiving the first connection reconfiguration message at step 2.

[0069] Alternatively, UE 1 10 may be configured with a criterion, which is used to trigger the transmission of UE-specific uplink signals. Thus, UE 1 10 may start transmitting UE-specific uplink signals when the criterion is met. The criterion may be referred to as a second threshold, such as, a RSRP, RSRQ, RSSI, BLER or CQI threshold. In some embodiments, the criterion may be associated with a reporting event, e.g., denoted as Event 1 for example. The reporting event may be referred to as a trigger event as well.

[0070] DUs 120b-n may be associated with candidate cells for a handover and at step 8, DUs 120b-n may measure UE-specific uplink signals transmitted by UE 1 10. Moreover, DUs 120b-n may compute statistics for each cell based on one or more received UE-specific uplink signals individually, i.e., each DUs 120b-n may compute the statistics based on its own measurements. DUs 120b-n may compute, e.g., a gradient of the uplink measurements at step 9 for each of their cells. The gradient may indicate a direction of UE 1 10. As an example, the gradient may indicate whether UE 1 10 is moving towards a cell of DU 120b, or not.

[0071] For example, DU 120b may determine that UE 1 10 is moving towards one of its cells and consequently transmit, at step 10, a report message to CU 130. The report message may comprise an indication that a cell of DU 120b may be added to a potential configuration. That is to say, in some embodiments the cell of DU 120b may not be in a list of candidate cells before it is determined that UE 1 10 is moving towards the cell in question.

[0072] Alternatively, DU 120b may determine that UE 1 10 is moving away from one of its cells and consequently transmit, at step 10, a report message to CU 130, the report message possibly comprising an indication that a cell of DU 120b may be removed from the potential configuration. Alternatively, or in addition, the report message may comprise the computed gradient and/or a measurement report. In some embodiments, alternatively or in addition, the report message may comprise also an indication about addition to, or removal from, the potential candidate target cell list made by CU. In some embodiments, the report message may be referred to as an UE Context Modification Required message. CU 130 may transmit, at step 1 1 , a context modification confirm message to DU 120b in response to receiving the report message. In some embodiments, the report message may be referred to as a second message.

[0073] Upon receiving a report message from at least one DUs 120b-n, CU 130 may, at step 12, add, modify or remove operations on cells of DUs 120b-n based on the report messages, or the information therein, received from DUs 120b-n. That is to say, CU 130 may add one or more of cells of DUs 120b-n to a list of candidate cells and/or remove one or more cells of DUs 120b-n from the list of candidate cells. In some embodiments, DUs 120b-n may be associated with candidate cells, which may be configured by CU 130.

[0074] CU 130 may prepare at least one handover command at step 13. The at least one handover command may be based on a received report message, which may comprise, e.g., uplink measurements or statistics about uplink measurements related to the first uplink transmissions. For example, the uplink measurement statistics, such as, a gradient, may indicate which cells of DUs have the most potential for a handover of UE 1 10.

[0075] In an example embodiment, CU 130 may use uplink measurements, measured by multiple cells of one or more DUs 120b-n, to improve results related to use of measurement gradients. This way, CU 130 may reduce noisiness of individual measurement gradients, as CU 130 may determine the overall direction of movement of the UE based on several measurements, i.e., observations, of cells of multiple DUs.

[0076] At step 14 of FIGURE 2, CU 130 may transmit a second context modification request message to DU 120a. The second context modification request message may be, for example, a UE Context Modification Request. In addition, or alternatively, the second context modification request message may comprise information related to a connection reconfiguration for UE 1 10, e.g., Radio Resource Control, RRC, Connection Reconfiguration information. The information related to the connection reconfiguration may further comprise a handover command.

[0077] Upon receiving the second context modification request message, DU 120a may transmit, at step 15, a second connection reconfiguration message to UE 1 10. The second connection reconfiguration message may be for example RRC Connection Reconfiguration message. The second configuration message may comprise the handover command, wherein the handover command may comprise at least one condition for triggering a handover to a target cell of DU 120b. The condition may be associated with a handover event, e.g., denoted as Event 2 for example. The handover may be a conventional conditional handover, wherein UE 1 10 initiates the handover when the at least one condition for triggering the handover is met.

[0078] At step 16 of FIGURE 2, DU 120a may transmit a second context modification response to CU 130. The second context modification response may be, e.g., an UE Context Modification Response.

[0079] At step 17, UE 1 10 may detect that the condition for triggering the handover to the target cell of DU 120b, has been met. UE 1 10 may therefore trigger the handover to to the target cell of DU 120b. Upon detecting that the condition has been met, UE 1 10 may perform a random access procedure with DU 120b, i.e., the target cell of DU 120b at step 18.

[0080] Once the random access procedure has been completed, UE 1 10 may transmit, at step 19, a second connection reconfiguration complete message to DU 120b. The second connection reconfiguration complete message may be for example a RRC Connection Reconfiguration Complete message.

[0081] At step 20, DU 120b may transmit an uplink transfer message to CU 130. The uplink transfer message may be for example an Uplink Transfer message, i.e., a RRC Connection Reconfiguration Complete message.

[0082] Upon receiving the uplink transfer message, CU 130 may release unnecessary target configurations, i.e., configurations of DUs 120c-n. CU 130 may release unnecessary target configurations by transmitting, at step 21 , a context release command, e.g., UE Context Release Command. DUs 120c-n may respond to the context release command by transmitting, at step 22, a context release complete message, e.g., an UE Context Release Complete message.

[0083] After the handover, UE 1 10 may, at step 23, continue transmitting first uplink transmissions, e.g., UE-SRS, due to potential a ping-pong handover back to a source cell of DU 120a. In case of a ping-pong handover the radio conditions may change and the source cell may become the best serving cell again at some point. Hence, a handover back to the source cell may be needed later on, after the first handover.

[0084] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments. The example apparatus may be suitable for operation in a cloud RAN. Illustrated is device 300, which may comprise, for example, UE 1 10, or wireless terminals in general, DU 120a-n, or CU 130. Comprised in device 300 is processor 310, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 310 may comprise, in general, a control device. Processor 310 may comprise more than one processor. Processor 310 may be a control device. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core produced by Advanced Micro Devices Corporation. Processor 310 may comprise at least one Qualcomm Snapdragon and/or Intel Atom processor. Processor 310 may comprise at least one application-specific integrated circuit, ASIC. Processor 310 may comprise at least one field-programmable gate array, FPGA. Processor 310 may be means for performing method steps in device 300. Processor 310 may be configured, at least in part by computer instructions, to perform actions.

[0085] A processor may comprise circuitry, or be constituted as circuitry or circuitries, the circuitry or circuitries being configured to perform phases of methods in accordance with embodiments described herein. As used in this application, the term“circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of hardware circuits and software, such as, as applicable: (i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0086] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0087] Device 300 may comprise memory 320. Memory 320 may comprise random- access memory and/or permanent memory. Memory 320 may comprise at least one RAM chip. Memory 320 may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory 320 may be at least in part accessible to processor 310. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be means for storing information. Memory 320 may comprise computer instructions that processor 310 is configured to execute. When computer instructions configured to cause processor 310 to perform certain actions are stored in memory 320, and device 300 overall is configured to run under the direction of processor 310 using computer instructions from memory 320, processor 310 and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be at least in part external to device 300 but accessible to device 300.

[0088] Device 300 may comprise a transmitter 330. Device 300 may comprise a receiver 340. Transmitter 330 and receiver 340 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. T ransmitter 330 may comprise more than one transmitter. Receiver 340 may comprise more than one receiver. Transmitter 330 and/or receiver 340 may be configured to operate in accordance with Global System for Mobile communication, GSM, Wideband Code Division Multiple Access, WCDMA, 5G, Long Term Evolution, LTE, IS-95, Wireless Local Area Network, WLAN, Ethernet and/or Worldwide Interoperability for Microwave Access, WiMAX, standards, for example.

[0089] Device 300 may comprise a Near-Field Communication, NFC, transceiver 350. NFC transceiver 350 may support at least one NFC technology, such as Bluetooth, Wibree or similar technologies.

[0090] Device 300 may comprise User Interface, Ul, 360. Ul 360 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 300 to vibrate, a speaker and a microphone. A user may be able to operate device 300 via Ul 360, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory 320 or on a cloud accessible via transmitter 330 and receiver 340, or via NFC transceiver 350, and/or to play games.

[0091] Device 300 may comprise or be arranged to accept a user identity module 370. User identity module 370 may comprise, for example, a Subscriber Identity Module, SIM, card installable in device 300. A user identity module 370 may comprise information identifying a subscription of a user of device 300. A user identity module 370 may comprise cryptographic information usable to verify the identity of a user of device 300 and/or to facilitate encryption of communicated information and billing of the user of device 300 for communication effected via device 300.

[0092] Processor 310 may be furnished with a transmitter arranged to output information from processor 310, via electrical leads internal to device 300, to other devices comprised in device 300. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 320 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 310 may comprise a receiver arranged to receive information in processor 310, via electrical leads internal to device 300, from other devices comprised in device 300. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 340 for processing in processor 310. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver.

[0093] Device 300 may comprise further devices not illustrated in FIGURE 4. For example, where device 300 comprises a smartphone, it may comprise at least one digital camera. Some devices 300 may comprise a back-facing camera and a front-facing camera, wherein the back-facing camera may be intended for digital photography and the front- facing camera for video telephony. Device 300 may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device 300. In some embodiments, device 300 lacks at least one device described above. For example, some devices 300 may lack a NFC transceiver 350 and/or user identity module 370.

[0094] Processor 310, memory 320, transmitter 330, receiver 340, NFC transceiver 350, Ul 360 and/or user identity module 370 may be interconnected by electrical leads internal to device 300 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 300, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the embodiments.

[0095] FIGURE 4 illustrates an exemplary signalling graph in accordance with at least some embodiments of the present invention. The exemplary signalling graph may describe operation for a conditional handover in a cloud RAN. On the vertical axes are disposed, from left to right, UE 1 10, DU 120b and CU 130. With reference to FIGURE 2, the setup phase of FIGURE 4 may comprise steps 1 - 6 of FIGURE 2 and the reconfiguration and handover phase may comprise steps 14 - 23 of FIGURE 2. [0096] Step 410 of FIGURE 4 may correspond to step 7 of FIGURE 2. Thus, UE 1 10 may start transmitting first uplink transmissions, such as, UE-specific uplink signals, e.g., UE-SRS or RACH preamble, at step 410. Consequently, DU 120b may receive at least two first transmissions from UE 1 10. DU 120b may determine whether UE 1 10 is moving towards DU 120b, or not, based on the received at least two first transmissions.

[0097] Step 420 of FIGURE 4 may comprise steps 8 and 9 of FIGURE 2. For instance, upon reception of the at least two first transmissions from UE 1 10, DU 120b may measure received powers of the at least two first transmissions. DU 120b may also determine whether UE 1 10 is moving towards DU 120b, or not, based on the measured received powers of the at least two first transmissions.

[0098] The determination may be based on statistics associated with the at least two first transmissions. For example, DU 120b may determine a gradient of the at least two first transmissions and then determine whether the wireless terminal is moving towards DU 120b, or not, based on the gradient of the at least two first transmissions.

[0099] In one example, the gradient could be understood as a difference between at least two consecutive measurements. The at least two measurements may be done in a certain time window and a difference between the at least two measurements may be calculated, e.g., by computing S(t+1) - S(t), wherein S(t+1) denotes a measurement done at time t+1 and S(t) denotes a measurement done at time t. If the difference is positive, i.e., signal strength S at time t+1 is higher than signal strength S at time f, it would indicate that the UE is moving towards a DU. In another example, the gradient may be computed using a derivation, e.g., [S(t+dT) - S(t)] / dT, where dT is the time between the at least two measurements. Furthermore, the computation of the gradient may be based on more than two measurement samples. In that case, a rate of change in signal strength may be estimated based on the multiple measurement samples.

[00100] That is to say, DU 120b may determine a direction of UE 1 10. The direction of UE 1 10 may be determined relative to DU 120b, i.e., with respect to a location of DU 120b. The direction of UE 1 10 may be referred to as a direction of movement of UE 1 10, i.e., a moving direction.

[00101] Upon determining whether UE 1 10 is moving towards DU 120b, or not, DU 120b may transmit a second message, i.e., a report message, to CU at step 430. Step 430 of FIGURE 4 may correspond to step 10 of FIGURE 2. The report message may comprise information related to the at least two first uplink transmissions. For example, the report message may comprise information about statistics associated with the at least two first uplink transmissions and/or a gradient of the at least two transmissions. Alternatively, or in addition, the report message may comprise a measurement report, the measurement report comprising for example measured received powers of the at least two first uplink transmissions.

[00102] In some embodiments, DU 120b may, upon determining that UE 1 10 is moving towards DU 120b, transmit at step 430 an indication to CU 130. The indication may comprise a request to be added to a potential configuration of UE 1 10 to CU 130. On the other hand, in some embodiments, DU 120b may, upon determining that UE 1 10 is moving away from DU 120b, transmit at step 430 an indication comprising a request to be removed from the potential configuration of UE 1 10 to DU 130. The report message may comprise the request or the request may be transmitted separately, e.g., in a context modification required message.

[00103] CU 130 may confirm reception of the report message and/or the request to be added/removed to/from the potential configuration by transmitting a confirm message at step 440. The confirm message may be for example a context modification confirm message, e.g., an UE Context Modification Confirm message. Step 440 may correspond to step 1 1 of FIGURE 2.

[00104] Step 450 of FIGURE 4 may correspond to step 12 of FIGURE 2. At step 450, CU 130 may configure operations of DU 120b. For example, CU 130 may add DU 120b to a list of candidate cells of UE 1 10. CU 130 may also modify operations of DU 120b associated with UE 1 10. Alternatively, CU 130 may remove DU 120b from the list of candidate cells of UE 1 10. The configuration of operations of DU 120b may be performed by CU 130 based on the received report message. Hence, CU 130 may configure operations of DU120b based on, for example, statistics associated with the at least two first transmissions, a gradient of the at least two first transmissions and/or the indication (i.e., a request to be added/removed).

[00105] Step 460 of FIGURE 4 may correspond to step 13 of FIGURE 2. At step 460, CU 130 may prepare at least one handover command. The at least one handover command may be prepared based on statistics associated with the at least two first transmissions, a gradient of the at least two first transmissions and/or the indication (i.e., a request to be added/removed) as well. That is to say, at step 460, CU 130 may also determine whether UE 1 10 is moving towards DU 120b, or not, and prepare the at least one handover command accordingly. The determination at CU 130 may be done similarly as at DU 120b. The handover command may be communicated to DU 120b and UE 1 10 during the reconfiguration and handover phase of FIGURE 4, e.g., as shown in steps 14 and 15 of FIGURE 2. In some embodiments, CU 130 may compare measurements of DU 120b to measurements of other DUs for the handover command, to ensure that DU 120b is indeed the best option for the handover.

[00106] For example, in a cloud RAN a (e.g. centralized) CU may have information available related to uplink measurements. The information may be provided by DUs which may be associated with target cells, and configured by the CU. Embodiments may therefore provide lower latency and reduced signalling load compared to conventional solutions. A UE may trigger a handover, as in case of conventional conditional handover, thereby enabling same benefits in terms of robustness. Moreover, preparation of target cells of DUs for a handover may be done almost in real-time, especially in dense networks.

[00107] In some embodiments, a gradient of at least two uplink transmissions may be used for indicating whether the UE is moving towards a certain DU, or not. Nevertheless, there is no need to update the candidate set of the UE unless there is a clear indication that some of the targets cells of DUs are coming less potential and some new target cells of DUs are becoming likely next serving cells.

[00108] FIGURE 5 is a flow graph of a first method in accordance with at least some embodiments. The phases of the illustrated first method may be performed by DU 120b or by a control device configured to control the functioning thereof, possibly when installed therein. The phases of the first method may be suitable for a conditional handover in a cloud RAN.

[00109] The first method may comprise, at step 510, receiving at least two first uplink transmissions from a wireless terminal. The first method may also comprise, at step 520, determining whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions. In addition, the first method may comprise, at step 530, transmitting a second message to a central control unit, wherein the second message comprises information related to the at least two first uplink transmissions.

[00110] FIGURE 6 is a flow graph of a second method in accordance with at least some embodiments. The phases of the illustrated second method may be performed by CU 130, MEC node 140 or by a control device configured to control the functioning thereof, possibly when installed therein. The phases of the second method may be suitable for a conditional handover in a cloud RAN.

[00111] The second method may comprise, at step 610, receiving a second message from a distributed unit, wherein the second message comprises information related to at least two first uplink transmissions of a wireless terminal. The second method may also comprise, at step 620, determining whether a wireless terminal is moving towards the distributed unit, or not, based on the received information. In addition, the second method may comprise, at step 630, adjusting a configuration of the distributed unit based on the determination. In some embodiments, adjusting the configuration of the distributed unit may comprise adding a cell of the distributed unit to a list of candidate cells for a handover or removing a cell of the distributed unit from the list of candidate cells.

[00112] FIGURE 7 illustrates a second exemplary process in accordance with at least some embodiments. In FIGURE 7, A MEC node is denoted by 140. In general, MEC node 140 may be referred to as a central control unit. With reference to FIGURE 2, steps 1 - 6 from FIGURE 7 may be similar compared to steps 6 - 8 of FIGURE 2. However, according to the second exemplary process of FIGURE 7, DUs 120a and 120b may forward measurement results to CUs 130a and 130b, respectively (steps 6 and 8 in FIGURE 7). Moreover, CUs 130a and 130b may forward the measurement results to MEC node 140 (steps 7 and 9 in FIGURE 7). The measurement results may also comprise assistance data, such as, location of DUs 120a and 120b, traffic load of DUs 120a and 120b, beam measurements and beam indexes of beamformed access of DUs 120a and 120b, mobility info (speed, history, time of stay in each cell, etc.).

[00113] Upon receiving the measurement results, MEC node 140 may, at step 10, perform centralized processing of UE SRSs and mobility information. Also, MEC node 140 may optimize a new conditional handover configuration of multiple target cells in a CU-DU deployment at step 1 1. Deploying the new conditional handover configuration may be performed at step 12.

[00114] That is to say, MEC node 140 may perform similar operations as CUs. For example, MEC node 140 may receive a second message from a distributed unit, wherein the second message comprises information related to at least two first uplink transmissions of a wireless terminal, determine whether a wireless terminal is moving towards the distributed unit, or not, based on the received information and adjust a configuration of the distributed unit based on the determination. Mobile edge computing may be thus seen as as one option to coordinate (add, remove, modify) the target cell candidate selection, i.e., list of candidate cells.

[00115] The second exemplary process of FIGURE 7 may be useful, e.g., in a controlled environment, such as, in a large industrial area. FIGURE 7 describes a process for distributed - centralized processing where the optimization may be done using a centralized machine learning algorithm and the centralized machine learning algorithm may exploit data collected from more than one CU. Nevertheless, CUs may perform local decision about configuration for conditional handovers, and the configuration given by the centralized machine learning algorithm may be complemented with the real-time local measurement data.

[00116] In general, embodiments of the present invention may be related to a cloud RAN and implementation using a processor and a computer program may also cover selection of target cell candidates using machine learning or artificial intelligence. For example, decision making may be proactive based machine learning algorithms. In case of proactive decision making, the machine learning algorithm may use at least two previous first uplink transmissions of a wireless terminal and coordinate (add, remove, modify) the target cell selection. In case of proactive decision making, the machine learning algorithm may use at least two previous first uplink transmissions of a wireless terminal and coordinate (add, remove, modify) the target cell selection.

[00117] It is to be understood that the embodiments disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[00118] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases“in one embodiment” or“in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[00119] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations. [00120] In an exemplary embodiment, an apparatus, such as, for example, a DU or a CU, may comprise means for carrying out the embodiments described above and any combination thereof.

[00121] In an exemplary embodiment, a computer program may be configured to cause a method in accordance with the embodiments described above and any combination thereof. In an exemplary embodiment, a computer program product, embodied on a non- transitory computer readable medium, may be configured to control a processor to perform a process comprising the embodiments described above and any combination thereof.

[00122] In an exemplary embodiment, an apparatus, such as, for example, a DU or a CU, may comprise at least one processor, and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform the embodiments described above and any combination thereof.

[00123] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[00124] While the forgoing examples are illustrative of the principles of the embodiments in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[00125] The verbs“to comprise” and“to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality. INDUSTRIAL APPLICABILITY

[00126] At least some embodiments find industrial application in wireless communication networks, wherein it is desirable to enable mobility of wireless terminals. For example, some embodiments find industrial application in a cloud RAN, for a conditional handover.

ACRONYMS LIST

3GPP 3rd Generation Partnership Project

BBU Baseband Unit

BLER Block Error Ratio

BS Base Station

CP Cyclic Prefix

CQI Channel Quality Indication

CU Central Unit

DU Distributed Unit

GSM Global System for Mobile communication IEEE Institute of Electrical and Electronics Engineers loT Internet of Things

LTE Long-Term Evolution

M2M Machine-to-Machine

MAC Media Access Control

MEC Multi-access Edge Computing

NFC Near-Field Communication

NR New Radio

PDCCH Primary Downlink Control Channel

RACH Random Access Channel

RAN Radio Access Network

RAT Radio Access Technology RRH Remote Radio Head

RSRP Reference Signal Receive Power

RSRQ Reference Signal Received Quality

RSSI Reference Signal Strength Indicator

SIM Subscriber Identity Module

SRS Sounding Reference Signal

UE User Equipment

Ul User Interface

UL-RS Uplink-Reference Signal

WCDMA Wideband Code Division Multiple Access WiMAX Worldwide Interoperability for Microwave Access WLAN Wireless Local Area Network

REFERENCE SIGNS LIST

Claims

CLAIMS:

1. A method for a distributed unit, comprising:

- receiving at least two first uplink transmissions from a wireless terminal;

- determining whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions; and

- transmitting a second message to a central control unit, wherein the second message comprises information related to the at least two first uplink transmissions.

2. A method according to claim 1 , further comprising:

- determining statistics associated with the at least two first uplink transmissions; and

- determining whether the wireless terminal is moving towards the distributed unit, or not, based on the statistics associated with the at least two first uplink transmissions.

3. A method according to claim 1 or claim 2, further comprising:

- determining a gradient of the at least two first uplink transmissions; and

- determining whether the wireless terminal is moving towards the distributed unit, or not, based on the gradient of the at least two first uplink transmissions.

4. A method according to any of the preceding claims, wherein the information related to the at least two first uplink transmissions comprises statistics associated with the at least two first uplink transmissions and/or a gradient of the at least two first uplink transmissions.

5. A method according to any of the preceding claims, further comprising:

- upon determining that the wireless terminal is moving towards the distributed unit, transmitting the second message to the central control unit, wherein the second message comprises a request to be added to a list of candidate cells for a handover

6. A method according to any of the preceding claims, further comprising:

- upon determining that the wireless terminal is moving away from the distributed unit, transmitting the second message to the central control unit, wherein the second message comprises a request to be removed from a list of candidate cells for a handover.

7. A method according to any of the preceding claims, further comprising: - depending on the determination about whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions, transmitting the second message to the central control unit, wherein the second message comprises a request to modify a configuration of a cell in a list of candidate cells.

8. A method according to any of the preceding claims, further comprising:

- measuring received powers of the at least two first uplink transmissions; and

- determining whether the wireless terminal is moving towards the distributed unit, or not, based on the measured received powers of the at least two first uplink transmissions.

9. A method according to any of the preceding claims, wherein the information related to the at least two first uplink transmissions is formed depending on determining whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions.

10. A method according to any of the preceding claims, further comprising:

- determining a moving direction of the wireless terminal with respect to the distributed unit; and

- transmitting the second message, wherein the second message comprises the determined moving direction.

1 1. A method according to any of the preceding claims, further comprising:

- receiving a handover command in response to the transmitted second message.

12. A method according to any of the preceding claims, further comprising:

- transmitting the second message to the central control unit based on the determination.

13. A method according to any of the preceding claims, wherein the wireless terminal is a user equipment.

14. A method for a central control unit, comprising: - receiving a second message from a distributed unit, wherein the second message comprises information related to at least two first uplink transmissions of a wireless terminal;

- determining whether a wireless terminal is moving towards the distributed unit, or not, based on the received information; and

- adjusting a configuration of the distributed unit based on the determination.

15. A method according to claim 14, wherein the information related to the at least two transmissions comprises statistics associated with the at least two first uplink transmissions and/or a gradient of the at least two first uplink transmissions.

16. A method according to claim 14 or claim 15, further comprising:

- when the wireless terminal is moving towards the distributed unit, receiving the second message from the distributed unit, wherein the second message comprises a request to be added to a list of candidate cells.

17. A method according to any of claims 14 - 16, further comprising:

- when the wireless terminal is moving away from the distributed unit, receiving the second message from the distributed unit, wherein the second message comprises a request to be removed from a list of candidate cells.

18. A method according to any of claims 14 - 17, wherein the second message comprises a request to modify a configuration of a cell in a list of candidate cells.

19. A method according to any of claims 14 - 18, further comprising:

- determining a moving direction of the wireless terminal with respect to the distributed unit.

20. A method according to any of claims 14 - 19, further comprising:

- transmitting the handover command in response to the received second message.

21 . A method according to any of claims 14 - 20, wherein the wireless terminal is a user equipment.

22. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to perform:

- receive at least two first uplink transmissions from a wireless terminal;

- determine whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions; and

- transmit a second message to a central control unit, wherein the second message comprises information related to the at least two first uplink transmissions.

23. An apparatus according to claim 22, wherein the at least one memory and the computer program code are further configured to, with the at least one processing core, cause the apparatus at least to perform a method according to any of claims 2 - 13.

24. An apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to perform:

- receive a second message from a distributed unit, wherein the second message comprises information related to at least two first uplink transmissions of a wireless terminal;

- determine whether a wireless terminal is moving towards the distributed unit, or not, based on the received information; and

- adjust a configuration of the distributed unit based on the determination.

25. An apparatus according to claim 24, wherein the at least one memory and the computer program code are further configured to, with the at least one processing core, cause the apparatus at least to perform a method according to any of claims 14 - 21 .

26. An apparatus comprising:

- means for receiving at least two first uplink transmissions from a wireless terminal;

- means for determining whether the wireless terminal is moving towards the distributed unit, or not, based on the received at least two first uplink transmissions; and

- means for transmitting a second message to a central control unit, wherein the second message comprises information related to the at least two first uplink transmissions.

27. An apparatus according to claim 26, further comprising means for performing a method according to any of claims 2 - 13.

28. An apparatus comprising:

- means for receiving a second message from a distributed unit, wherein the second message comprises information related to at least two first uplink transmissions of a wireless terminal;

- means for determining whether a wireless terminal is moving towards the distributed unit, or not, based on the received information; and

- means for adjusting a configuration of the distributed unit based on the determination.

29. An apparatus according to claim 28, further comprising means for performing a method according to any of claims 14 - 21.

30. A non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least perform a method according to any of claims 1 - 13 or 14 - 21.

31. A computer program configured to perform a method according to any of claims 1 - 13 or 14 - 21.