Managing network connectivity in a wireless communication system

Abstract

A method for use in managing connectivity of a first Radio Access Network, RAN, node, wherein the method comprises: establishing an Xn connection with a second RAN node based on the value of an Xn benefit parameter, the value of the Xn benefit parameter representing a benefit of establishing the Xn connection.

Description

[0001] MANAGING NETWORK CONNECTIVITY IN A WIRELESS COMMUNICATION SYSTEM

[0002] TECHNICAL FIELD

[0003] The present invention generally relates to managing network connectivity in a wireless communication system. Particularly, the present invention relates to managing network connectivity in a wireless communication system including at least one Wireless Access Backhaul, WAB, node. In an example, the wireless communication system includes at least one mobile Wireless Access Backhaul, WAB, node.

[0004] BACKGROUND

[0005] Wireless communication systems are largely deployed to address a wide range of applications, from mobile broadband, massive machine type communications to Ultra Reliable Low Latency Communications (URLLC). Such systems allow a plurality of user equipment (UE) or mobile terminals to share the wireless medium to exchange several types of data content (e.g., video, voice, messaging ...) over a radio access network (RAN) through one or more base stations. The base stations are conventionally wired-connected (e.g., through fiber) to a core network, forming an intermediate network, named backhaul (BH).

[0006] Examples of such wireless multiple-access communication systems include systems based on 3rd generation partnership project (3GPP - RTM) standards, such as fourth-generation (4G) Long Term Evolution (LTE) or recent fifth-generation (5G) New Radio (NR) systems, or systems-based IEEE 802.11 standards, such as WiFi.

[0007] The demand for network densification increases due to the rising number of users and higher throughput requirement.

[0008] Facing the issues of high deployment costs and time of the wired backhaul networks with network densification, 3GPP has proposed, in recent release 16 for 5G NR, a wireless backhaul, also known as Integrated Access and Backhaul, IAB, where part of the wireless (i.e., radio) spectrum is used for the backhaul connection of base stations instead of fiber. The wireless backhaul communications (between base stations) may use the same radio resources as access communications (between a base station and UEs).

[0009] IAB turns out to be a competitive alternative to the fiber-based backhauling in dense areas or areas difficult to cover, as it allows scalable and rapid installations without the burden of cabling the base stations.

[0010] IAB is most likely to operate in the millimeter wave (mmWave) band to achieve the required Gbps (gigabits per second) data rate.

[0011] Urban environments are usually characterized by a high density of users along with the presence of a significant number of vehicles (e.g., public / private passenger transportation, goods delivery, food trucks ...). The speed of some of the vehicles may be pretty low or at least similar to pedestrian speed and some of these vehicles may even be temporarily stationary. Some of these vehicles (e.g., buses, trains or trams), may have predictable routes and I or limited mobility areas (e.g., some vehicles, such as food trucks or promotional vehicles, may be located outside stadiums or show venues) while others may have predictable stationary locations (e.g., taxis).

[0012] 3GPP is considering that such vehicles could offer an opportunity to increase network coverage and connectivity to the UEs inside the vehicles, or even to UEs in proximity to the vehicles, by installing on these vehicles on-board base stations (or base station elements) that would act as relays. These relays would rely on 5G wireless backhaul (typically IAB, or Integrated Access & Backhaul) for connecting to a fixed donor device. Thus, based upon the fixed IAB foundations set out in Releases 16 and 17, 3GPP is now considering Mobile IAB systems and architecture, as a part of the Release 18 framework, in order to address scenarios focusing on mobile lAB-nodes mounted on vehicles (for example, a bus, a train, a taxi). In such scenarios, mobile lAB-nodes can also be referred to as Vehicle Mounted Relays (VMR), providing 5G coverage / capacity to on-board and / or surrounding UEs. The technical benefits of using vehicle relays include, among others, the ability of the relay vehicle to get better coverage than the nearby UE, thanks to better RF / antenna capabilities, thus providing the UE with a better link to the macro network. Additionally, a vehicle relay is expected to have less stringent power / battery constraints than the UEs.

[0013] Some enhancements of the existing wireless access backhauling, WAB, systems and architecture are further considered by 3GPP for Release 19. Such enhancements consider the need for 5G access for UEs onboard aircrafts, cruise ships, helicopters and vehicles in remote areas with limited sky visibility (e.g., where terrestrial cellular coverage or Wi-Fi coverage is not available), support for onboard / on-site mobile edge computing (MEC), local services, and direct local inter-UE communications or local Next Generation Node B (gNB) deployment in public safety or disaster recovery scenarios. The backhauling links for the base stations providing the 5G access in such scenarios would then be operated over either a terrestrial network (TN), or a non-terrestrial network (NTN), with a possibility to handover communications from a terrestrial network to a nonterrestrial network and vice-versa. Such base stations can be referred to as Wireless Access Backhaul (WAB) nodes, or mobile WAB (MWAB) nodes. As part of these wireless backhauling enhancements, 3GPP is also considering some evolution to the former LTE-based Femto framework, including a new 5G Femto or 5G Femtocell that would offer 5G indoor coverage improvement while allowing high bandwidth and throughput at home for new immersive applications such as AR / VR / MR gaming, e-sports, UHD 8K video, telepresence, etc.

[0014] A WAB node is made of a Mobile Termination, WAB-MT, part used for connecting to some fixed existing infrastructure and used to provide backhauling connectivity as previously discussed. The WAB node also embeds a base station or gNB, WAB-gNB, (also referred to as a gNB part) to serve UEs. WAB nodes may be referred to as mobile Wireless Access Backhaul (MWAB) nodes. This disclosure relates to WAB nodes and MWAB nodes and thus, references to MWAB nodes should be taken to refer to WAB nodes and vice versa. 3GPP TS 38.423 defines the Xn interface, which is a logical interface between two NG- RAN network nodes, or base stations, providing means for interconnecting these two NG-RAN nodes.

[0015] For instance, the Xn interface provides means for managing resource multiplexing between NG-RAN network nodes, or base stations, allowing NG-RAN network nodes (i.e., base stations, or gNBs) in proximity to coordinate their radio resources utilization so as to prevent the NG-RAN network nodes to mutually interfere. A need for resource multiplexing management also applies when considering a WAB-gNB and the NG-RAN network node serving the WAB-MT of the WAB node the WAB-gNB belongs to, as the WAB-gNB and the serving NG-RAN network node are likely to be close enough to interfere. Thus, having an Xn connection between the WAB-gNB of a WAB node and the NG-RAN network node serving the WAB-MT of the WAB node is desirable as it would at least facilitate managing resource multiplexing to avoid or minimize interference between the WAB-gNB and the serving NG-RAN network node.

[0016] Xn connections are systematically established between NG-RAN nodes. Upon detection of a new RAN node, an Xn Setup Request and Xn Setup Response message exchange takes place as part of an Xn connection establishment process.

[0017] Xn connection may also allow for faster UE handover process between a WAB-gNB and a surrounding NG-RAN network node (including the NG-RAN network node serving the WAB-MT collocated with the WAB-gNB), compared to an NG-level handover process, which is performed through the 5G core network, as defined in 3GPP TS 23.502 with N2 based handover.

[0018] Having faster handover may be particularly interesting when performed between two WAB-gNBs which respective WAB nodes are bound to a same vehicle, i.e., a train or cruise ship, in order to ensure service continuity at UE level. In this latter case, having a Xn connection would not only account for faster handover but would also allow for faster load balancing coordination between the several bound WAB nodes.

[0019] SUMMARY

[0020] The present disclosure provides methods for use in managing connectivity of a Radio Access Network, RAN, node. The disclosed methods provide mechanisms for selectively establishing or terminating an Xn connection between first and second RAN nodes (one or both of the first and second RAN nodes may be a Wireless Access Backhaul, WAB, node, a gNB component of a WAB node, or a Backhaul, BH, RAN node) in a network. The selective establishment or termination of the Xn connection is based on the determined benefit of establishing or maintaining the Xn connection, such that the Xn connection is only established if the determined benefit is sufficient and is terminated if the determined benefit is not sufficient. The determined benefit may be based on the ability of one or more UEs served by the first RAN node to connect to the second RAN node, the ability of a Mobile Termination, MT, component of the first RAN node (in a case where the first RAN node is a WAB node) to connect to the second RAN node, a measured connection quality (for example, a radio link quality) between the first and second RAN nodes, the presence of the second RAN node in a neighborhood of a third RAN node that is connected to the first RAN node via another Xn connection, the first and second RAN nodes being located in the same geographical area, and mobility characteristics of the first and / or second RAN nodes. Thus, the described mechanisms / methods avoid systematic Xn connection establishment between RAN nodes, thereby optimizing the usage of radio resources. Similarly, the described mechanisms / methods allow Xn connections that are no longer useful to be removed / terminated, freeing up radio resources. In other cases the Xn wireless link connecting a first RAN node to another RAN node may be subject to transient link degradation, which may lead to unnecessary removal of the Xn connection. The described mechanisms / methods can avoid unnecessary removal of the Xn connection, for example the Xn connection may not be removed even if the quality of the link degrades if, for example, the first and second RAN nodes are within the same neighbourhood, or a number of user equipments, UEs, served by the first RAN node are still able to connect to the second RAN node.

[0021] The described mechanisms / methods are particularly beneficial where one or both of the RAN nodes are WAB nodes. A WAB node, by its nature, is more likely to move relative to a second RAN / WAB node over time. Accordingly, it may be determined that there is little benefit to establishing an Xn connection with a particular RAN node if, for example, it is determined that the particular RAN node will only be in range fora limited period of time. Similarly, it may be determined to establish an Xn connection with a particular RAN node even if, for example, the radio link quality between the WAB node and the particular RAN node is poor, if the two nodes are operating in the same geographical area, or are expected to be collocated at a future point in time based on itinerary information and / or trajectory information relating to the two nodes. On the other hand, in some cases if the WAB node or the RAN node to which the WAB node is connected via an Xn connection moves after the Xn connection is established, the Xn connection may become useless shortly after being established, particularly when the WAB node is moving away from this RAN node at a fast pace. In such cases, the described mechanisms / methods allow the Xn connection to be terminated / removed to free up radio resources.

[0022] The present disclosure provides specific examples of criteria and certain factors that are used to determine the “benefit” of a particular Xn connection. It will be appreciated that the present invention is not limited to these specific examples and any suitable criteria / factor, and combinations thereof may be used to determine the benefit of a particular Xn connection. A criteria or factor that may be predictive of the long term utility, usefulness, or general functionality of an Xn connection may be used to determine the benefit of the Xn connection.

[0023] In general, the benefit of an Xn connection describes how useful said connection is, and / or will be, at a current time point or over a future time period. For example, there may be little benefit associated with an Xn connection that will become useless shortly after being established. Some embodiments described herein represent the benefit associated with a particular Xn connection using a parameter. In some embodiments, the parameter is an Xn benefit parameter. In some embodiments, the Xn benefit parameter may be a single value. Alternatively, the Xn benefit parameter may be a plurality of values, or may refer broadly to a set of criteria or conditions relating to the benefit of an Xn connection. It will be appreciated that use of a parameter to represent the benefit of the Xn connection is not essential. Any suitable alternative may be used to represent the benefit, which is broadly related to condition, criteria etc. Accordingly, the establishing and / or removal (termination) of an Xn connection may be based on the benefit associated with the Xn connection, or specifically the benefit of establishing and / or maintaining the Xn connection. The same applies to other uses of the term “parameter” herein, such as the served UE connectivity parameter, geographical area parameter etc. which may be a single value, or may be any suitable representation of the underlying conditions / criteria they are intended to represent.

[0024] According to a first aspect of the present invention, there is provided a method for use in managing connectivity of a first Radio Access Network, RAN, node, the method at the first RAN node including: establishing an Xn connection with a second RAN node based on the value of an Xn benefit parameter, the value of the Xn benefit parameter representing a benefit of establishing the Xn connection. As described above, by establishing the Xn connection based on the determined benefit of the Xn connection, the present invention can avoid systematic establishment of Xn connections that may not be beneficial, thus ensuring efficient use of radio resources. The Xn connection with the second RAN node may be established based on a determination that the benefit of establishing the Xn connection is sufficient. The Xn connection with the second RAN node may not be established based on a determination that the benefit of establishing the Xn connection is not sufficient.

[0025] According to a second aspect of the present invention, there is provided a method for use in managing connectivity of a first Radio Access Network, RAN, node, connected to a second RAN node via an Xn connection, the method at the first RAN node comprising: determining to remove (e.g. terminate) the Xn connection with the second RAN node based on the value of an Xn benefit parameter, the value of the Xn benefit parameter representing a benefit of maintaining the Xn connection. By deciding whether to terminate (e.g. remove) an established Xn connection based on the determined benefit of the Xn connection, the present invention can enable Xn connections that are not beneficial to be terminated, freeing up network resources. The present invention may also avoid terminating Xn connections that may, temporarily, have a poor connection quality (e.g. due to transient link degradation), but that would otherwise be beneficial connections. The Xn connection with the second RAN node may be terminated (e.g. removed) based on a determination that the benefit of establishing the Xn connection is not sufficient. The Xn connection with the second RAN node may not be terminated (e.g. may be maintained) based on a determination that the benefit of establishing the Xn connection is sufficient. According to a third aspect of the present invention there is provided a computer program comprising instructions which, when the program is executed by at least one processor unit, cause the at least one processor unit to carry out the method according to the first or second aspects.

[0026] According to a fourth aspect of the present invention there is provided a computer- readable medium carrying a computer program according to the third aspect.

[0027] According to a fifth aspect of the present invention there is provided an apparatus for a RAN node, the apparatus comprising one or more processing units configured to perform the method according to the first or second aspects.

[0028] As described above, the present disclosure (according to any one of the first to fifth aspects) advantageously enables an Xn connection to be selectively established and / or terminated (i.e. removed) based on the determined benefit associated with the Xn connection, thereby optimizing the usage of radio resources.

[0029] Optional features will now be set out. These are applicable singly or in any combination with any aspect of the disclosure.

[0030] The value of the Xn benefit parameter may be based on a served user equipment, UE, connectivity parameter, the value of the served UE connectivity parameter being representative of the ability of one or more UEs served by the first RAN node to connect to the second RAN node. Whether one or more UEs served by the first RAN node can connect to the second RAN node is an effective indication of the benefit of an Xn connection between the first and second RAN nodes because it indicates that the first and second RAN nodes may be within range and therefore indicate whether an Xn connection between the first and second RAN nodes can be established / maintained with an acceptable link quality.

[0031] The ability of the one or more UEs served by the first RAN node to connect to the second RAN node may be determined based on a radio link quality between each of the one or more UEs and a cell managed by the second RAN node.

[0032] The value of the served UE connectivity parameter may be based on the number of served UEs that are able to connect to the second RAN node, or a ratio of the one or more UEs served by the first RAN node to the one or more UEs served by the first RAN node that are able to connect to the second RAN node.

[0033] The value of the served UE connectivity parameter may be representative of the ability of one or more UEs served by the first RAN node to connect to, and remain connected to, the second RAN node for at least a minimum time period. Whether one or more UEs served by the first RAN node can remain connected to the second RAN node for at least a minimum time period is an effective indication of the benefit of an Xn connection between the first and second RAN nodes because it indicates that, even if one of the RAN nodes is a mobile node such as a mobile WAB node, that the nodes are likely to remain in range for at least a minimum time period.

[0034] The first RAN node may be a gnB component of a first Wireless Access Backhaul, WAB, node comprising a Mobile Termination, MT, component, and the gNB component, and the value of the Xn benefit parameter may be based on a WAB-MT connectivity parameter, the value of WAB-MT connectivity parameter being representative of the ability of the MT component of the first WAB node to connect to the second RAN node. Whether the MT component of the first WAB node can connect to the second RAN node is an effective indication of the benefit of an Xn connection between the first and second RAN nodes because this indicates that the first and second RAN nodes are within range and therefore able to establish an effective Xn connection.

[0035] The value of the WAB-MT connectivity parameter may be representative of the ability of the MT component of the first WAB node to connect to, and remain connected to, the second RAN node for at least a minimum time period.

[0036] The value of the Xn benefit parameter may be based on an inter-RAN node connectivity parameter, the value of the inter-RAN node connectivity parameter being representative of a link quality between the first RAN node and the second RAN node.

[0037] The value of the Xn benefit parameter may be based on an Xn neighborhood parameter, the value of the Xn neighborhood parameter being representative of the second RAN node being present in a neighborhood of a third RAN node, the third RAN node being connected to the first RAN node via an Xn connection. The second RAN may be said to be in a neighborhood of a third RAN node when, for example, the second RAN is in the same geographical area, such as a Notification Area (RNA), Tracking Area (TA), and / or is in range of the third RAN node.

[0038] The value of the Xn benefit parameter may be based on a geographical area parameter, the value of the geographical area parameter being representative of the first RAN node and the second RAN node being located in the same geographical area. Whether the first RAN node and second RAN node are located in the same geographical area is an effective criterion upon which to determine the benefit associated with an Xn connection between the first and second RAN nodes. If the first and second RAN nodes are located within the same geographical area, this may be predictive that the two RAN nodes are within range of each other. For example, it may be determined that the benefit of establishing an Xn connection between the first and second RAN nodes is sufficient if they are located in the same geographical area even if the current connection quality between the first and second RAN nodes is poor.

[0039] The geographical area may be any one of a RAN-based Notification Area, RNA, a Tracking Area, TA, or a group of NR cells.

[0040] The value of the Xn benefit parameter is based on a mobility parameter, the value of the mobility parameter being representative of the mobility of the first RAN node. The mobility of the first RAN node is an effective criterion upon which to determine the benefit associated with an Xn connection between the first and second RAN nodes. The mobility of the first RAN node may be predictive of whether the first RAN node is likely to move out of range of the second RAN node within a time period (i.e. because the first RAN node is moving, expected to move, a distance away from the second RAN node that is too great to maintain an effective Xn connection therebetween). In some embodiments the mobility parameter may alternatively or additionally be based on the mobility of the second RAN node.

[0041] The value of the mobility parameter is based on one or more of: a minimum speed capability, an average speed capability, a maximum speed capability, range capability information, static period information indicating a duration of one or more time periods during which the first RAN node is expected to be stationary, and itinerary information indicating a sequence of time periods and further indicating whether the first RAN node is expected to be in motion or stationary during the respective indicated time periods.

[0042] The range capability information may comprise one or more of: information indicating an area in which the first RAN node may move, information indicating the size of the area in which the first RAN node may move, a distance that the first RAN node may move, and / or one or more cell Identifiers, IDs, corresponding to one or more cells that the first RAN node may be in range of or has been in range of previously.

[0043] The static period information may include information indicating one or more of: a minimum static period duration, an average static period duration, a maximum static period duration, and / or static position information indicating one or more locations at which the first RAN is expected to be stationary.

[0044] The itinerary information may include information indicating, for each of the time periods of the sequence of time periods, one or more of: the duration of the time period, the speed of the first RAN node if the first RAN node is expected to be in motion during the time period, and the location at which the first RAN node is expected to be stationary if the first RAN node is expected to be stationary during the time period. The use of static and / or stationary information may be particularly beneficial in scenarios wherein, for example, the first and / or second RAN nodes are installed on a vehicle such as a plane, train, or automobile. Itinerary information may be particularly applicable when the first / second RAN nodes are installed on a vehicle that is following a scheduled route with known stopping locations, such as a train or bus.

[0045] One or more scoring values corresponding to one or more of the served UE connectivity parameter, the WAB-MT connectivity parameter, the inter-RAN node connectivity parameter, the Xn neighborhood parameter, the geographical area parameter, and the mobility parameter may be determined.

[0046] The value of Xn benefit parameter may be the average of the determined one or more scoring values.

[0047] A weighting value may be associated with each of the determined one or more scoring values.

[0048] The value of the Xn benefit parameter may be a weighted average of the determined one or more scoring values, with each of the determined one or more scoring values being weighted according to its associated weighting value. Using a weighted average, or similar, may be particularly beneficial as it allows the influence of the various factors / criteria to be tuned depending on a particular application of the present invention.

[0049] Establishing the Xn connection may be based on a comparison of the Xn benefit parameter with a predetermined establishment threshold.

[0050] Establishing the Xn connection may comprise establishing the Xn connection if the value of the Xn benefit parameter is greater than or equal to (or greater than) the predetermined establishment threshold value.

[0051] Establishing the Xn connection may comprise establishing the Xn connection if the value of the Xn benefit parameter is greater than or equal to (or greater than) the predetermined establishment threshold value for a minimum time period.

[0052] The value of the predetermined establishment threshold may be set based on a configuration message received at the first RAN node, the configuration message including information specifying any one or more of: a minimum UE connectivity duration; a minimum WAB- MT connectivity duration; a minimum served UE connectivity value; one or more radio link quality threshold values.

[0053] The value of the predetermined establishment threshold may be set based on establishment threshold information included in a message received at the first RAN node, the message further including a request from the second RAN node to establish an Xn connection with the first RAN node. For example, the establishment threshold information may be included in a CONNECTION SETUP REQUEST message, as described below in relation to Figure 6. By adapting pre-existing messages sent between the first and second RAN nodes, this reduces the signalling overhead required to set the establishment threshold.

[0054] The establishment threshold information may include any one or more of: a minimum UE connectivity duration; a minimum WAB-MT connectivity duration; a minimum served UE connectivity value; one or more radio link quality threshold values.

[0055] Based on a comparison between the value of the Xn benefit parameter and the establishment threshold value, a response message may be transmitted to the second RAN node including an indication that the request to establish an Xn connection with the first RAN node is accepted.

[0056] Based on a comparison between the value of the Xn benefit parameter and the establishment threshold value, a failure message may be transmitted to the second RAN node including an indication that the request to establish an Xn connection with the first RAN node is rejected.

[0057] The failure message may further include failure cause information, the failure cause information comprising an indication that the value of the Xn benefit parameter is not sufficient.

[0058] The first RAN node may be a gNB component of a first Wireless Access Backhaul, WAB, node comprising a Mobile Termination, MT, component, and the gNB component; and the establishing an Xn connection with the second RAN node may be performed in response to the the first WAB node establishing a connection between the MT component of the first WAB node and the second RAN node.

[0059] The value of the Xn benefit parameter may be determined based on one or more messages received from a UE served by the first RAN node and / or, in a case where the second RAN node is a gNB component of a second WAB node, one or more messages received from an MT component of the second WAB node served by the first RAN node.

[0060] The value of the Xn benefit parameter may be determined on a periodic basis. The periodicity of the determination may be predetermined based on the particular application / scenario. For example, where the mobility of the first and / or second RAN nodes is greater, the value of the Xn benefit parameter may be expected to vary over a shorter timescale, and so may be determined more often (and vice versa).

[0061] The value of the Xn benefit parameter may be determined in response to any one or more of: one or more user equipments, UEs, served by the first RAN node being in range of the second RAN node; a quality of a radio link between one or more UEs served by the first RAN node, and the second RAN node, being above a predetermined quality threshold; a quality of the radio link between the first RAN node and the second RAN node being above another predetermined quality threshold; and / or a determination, by the first RAN node, that the first RAN node will be in range of the second RAN node within a period of time.

[0062] The determination, by the first RAN node, that the first RAN node will be in range of the second RAN node within a period of time may based on the current speed of the first RAN node and / or trajectory information of the first and / or second RAN nodes.

[0063] Determining the value of the Xn parameter in response to triggering events can unnecessary determination of the value of the Xn parameter, saving processing resources and the first and / or second RAN nodes.

[0064] The first RAN node may be a gNB component of a first wireless access backhaul, WAB, node, the first WAB node including a mobile termination, MT, component and the gNB component. As described above, the present invention may be particularly advantageous where the first RAN node (or second RAN node) is a gNB component of a WAB node. A WAB node, by its nature, is more likely to move relative to a second RAN / WAB node over time, and in such scenarios systematic establishment of Xn connections is more likely to result in unnecessary use of radio resources, such as when an Xn connection is established between a WAB node and another RAN node that will only be within range for a very short time period. It will be appreciated that in some embodiments, the first and / or second RAN nodes may be WAB nodes comprising an MT component and a gNB component.

[0065] Prior to establishing the connection, the second RAN node may be detected; wherein detecting the second RAN node may comprise any one or more of: the MT component of the first WAB node detecting a cell managed by the second RAN node; receiving, from a UE served by the first WAB node, an indication that the UE is in range of the second RAN node; and / or receiving, from a third RAN node, an indication that the second RAN node is in a neighborhood of the third RAN node.

[0066] The first RAN node may not be a gNB component of a WAB node, and the second RAN node may be a gNB component of a second WAB node, the second WAB node including a mobile termination, MT, component and the gNB component of the second WAB node.

[0067] Prior to establishing the connection, the gNB component of the second WAB node may be detected; wherein detecting the gNB component of the second WAB node may comprise any one or more of: receiving, from a UE served by the first RAN node, an indication that the UE is in range of the gNB component of the second WAB node; receiving, from a third RAN node, an indication that the second RAN node is a neighborhood of the third RAN node.

[0068] The first RAN node may be a Backhaul, BH, RAN node.

[0069] When determining whether to remove (e.g. terminate) an Xn connection previously established between the first and second RAN nodes, determining to remove the Xn connection to the second RAN node may based on a comparison of the Xn benefit parameter with a predetermined removal threshold.

[0070] Determining to remove an Xn connection previously established between the first and second RAN nodes may comprise determining to remove an Xn connection to the second RAN node may if the value of the Xn benefit parameter is less than the predetermined removal threshold value.

[0071] Determining to remove an Xn connection previously established between the first and second RAN nodes may comprise determining to remove an Xn connection to the second RAN node may if the value of the Xn benefit parameter is less than the predetermined removal threshold value for a minimum time period.

[0072] The value of the predetermined removal threshold may be set based on removal threshold information included in a message received at the first RAN node, the message further including a request from the second RAN node to remove the Xn connection with the first RAN node. For example, the removal threshold information may be included in a CONNECTION REMOVAL REQUEST, as described below in relation to Figure 6. By adapting pre-existing messages sent between the first and second RAN nodes, this reduces the signalling overhead required to set the removal threshold.

[0073] The removal threshold information may include any one or more of: a minimum UE connectivity duration; a minimum WAB-MT connectivity duration; a minimum served UE connectivity value; one or more radio link quality threshold values.

[0074] Based on a comparison between the value of the Xn benefit parameter and the removal threshold value, a response message may be transmitted to the second RAN node including an indication that the request to remove the Xn connection with the first RAN node is accepted. Based on a comparison between the value of the Xn benefit parameter and the removal threshold value, a failure message may be transmitted to the second RAN node including an indication that the request to remove the Xn connection with the first RAN node is rejected.

[0075] The failure message may further include failure cause information, the failure cause information comprising an indication that the value of the Xn benefit parameter is sufficient.

[0076] Determining to remove the Xn connection may be performed in response to a message received at the first RAN node, the message including a request to remove the Xn connection with the second RAN node. The message may be a message transmitted by the second RAN node, or may be a message transmitted by another network entity (i.e. a, or another, WAB-gNB, BH RAN node, or a surrounding NG-RAN node). For example, the message may be a CONNECTION REMOVAL REQUEST message, as described below in relation to Figure 6.

[0077] The message including a request to remove the Xn connection with the second RAN node may further include a cause parameter, the cause parameter indicating the reason for requesting to remove the Xn connection. An existing cause value such as “Action Desirable for Radio Reasons” may be used if the Xn link quality is too low or when the first and / or second RAN node is a WAB node moving out of range. Alternatively, the cause parameter may be a cause value such as a “WAB not authorized” value, indicating that a WAB-node authorization associated with the first and / or second RAN nodes (wherein one or both are WAB nodes) has changed.

[0078] The value of the Xn benefit parameter may be determined in response to any one or more of: one or more user equipments, UEs, served by the first RAN node being out of range of the second RAN node; a quality of a radio link between one or more UEs served by the first RAN node, and the second RAN node, being below a predetermined quality threshold; a quality of the radio link between the first RAN node and the second RAN node being below another predetermined quality threshold; and / or a determination, by the first RAN node, that the first RAN node will be out of range of the second RAN node within a period of time.

[0079] The determination, by the first RAN node, that the first RAN node will be out of range of the second RAN node within a period of time may be based on the current speed of the first RAN node and / or trajectory information of the first and / or second RAN nodes.

[0080] Any feature in one aspect of the disclosure may be applied to other aspects of the disclosure, in any appropriate combination. In particular, method aspects may be applied to apparatus / device / unit aspects, and vice versa.

[0081] It will be understood that features implemented in hardware may be implemented in software, and vice versa. Any reference to software and hardware features herein should be construed accordingly. For example, in accordance with other aspects of the disclosure, there are provided a computer program comprising instructions which, when the program is executed by one or more processing units, cause the one or more processing units to carry out the method of any aspect or example described above and a computer readable storage medium carrying the computer program. The preceding summary is provided for purposes of summarising some examples to provide a basic understanding of aspects of the subject matter described herein. Accordingly, the above-described features should not be construed to narrow the scope or spirit of the subject matter described herein in any way. Moreover, the above and / or proceeding examples may be combined in any suitable combination to provide further examples, except where such a combination is clearly impermissible or expressly avoided. Other features, aspects, and advantages of the subject matter described herein will become apparent from the following text and the accompanying drawings.

[0082] BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Different aspects of the invention will now be described, by way of example only, and with reference to the following drawings in which:

[0084] Figure 1 is a schematic diagram illustrating an example wireless communication system in which the present invention may be implemented according to one or more embodiments;

[0085] Figure 2 is a block schematic diagram illustrating an example wireless communication system (or Wireless Access Backhaul system) in which the present invention may be implemented according to one or more embodiments;

[0086] Figure 3 is a block schematic diagram illustrating an example wireless communication system (or Wireless Access Backhaul system) in which the present invention may be implemented according to one or more embodiments;

[0087] Figure 4 shows a block schematic representation of an example network node in accordance with one or more embodiments of the present invention;

[0088] Figure 5 is a block schematic diagram illustrating an example arrangement of a wireless communication system (or Wireless Access Backhaul system) in which the present invention may be implemented according to one or more embodiments;

[0089] Figure 6 is a schematic and simplified diagram illustrating example message flows for use in managing network connectivity in a wireless communication system including at least one Wireless Access Backhaul, WAB, node in accordance with one or more embodiments of the present invention and which may be used for managing Xn connection establishment and removal between a first NG-RAN network node and a second NG-RAN network node;

[0090] Figure 7 is a schematic and simplified diagram illustrating an example message flow for use in managing network connectivity in a wireless communication system including at least one Wireless Access Backhaul, WAB, node in accordance with one or more embodiments of the present invention and which may be used for configuring a WAB node;

[0091] Figure 8 is a flowchart of an example method for managing Xn connection establishment between a WAB-gNB and an NG-RAN network node according to one or more embodiments of the present invention; Figure 9 is a flowchart of an example method for managing Xn connection removal between a WAB-gNB and an NG-RAN network node according to one or more embodiments of the present invention.

[0092] Figure 10 is a flowchart of an example method for determining the benefit of an Xn connection between two NG-RAN network nodes according to one or more embodiments of the present invention.

[0093] DETAILED DESCRIPTION

[0094] Figure 1 illustrates an example communication system 100 in which the present invention may be implemented according to one or more embodiments.

[0095] As depicted, the example system 100 is a wireless communication system, in particular a mobile radio communication system such as a fifth-generation (5G) New Radio (NR) system including a Wireless Access Backhaul (WAB) communication system or network. Although in the following description, embodiments and examples of embodiments of the present invention will be described with respect to a 5G NR system, it will be appreciated that it is not intended that the present invention is necessarily limited to 5G NR systems and may be used in any wireless communication systems having wireless backhaul links.

[0096] The system 100 comprises a plurality of UEs (User Equipment) 111 , 112, 113, 121 , 122, 123, 131 , 132, 133, 134, 141 , 142, 143, 151 , 152, 153 and 154, a communication satellite 160, a satellite dish 101 , a remote core network 170, three fixed Base Stations 102, 103 and 104, a plurality of Wireless Access Backhaul (WAB) nodes, also referred to as mobile wireless access backhaul (MWAB) devices: such as MWAB node 110 (mounted on plane 161), MWAB nodes 120a and 120b (mounted on train 162), WAB node 130 (or Home gNB, mounted on a house 163), MWAB node 140 (mounted on a Unmanned Aerial Vehicle (UAV) 164) and MWAB node 150 (mounted on a backpack 165 or other carrier that can be carried by a user (e.g., in a disaster zone)).

[0097] In more general terms, the MWAB node may be mounted on or in a vehicle (such as a train, bus, taxi, tram, etc.) and / or an aircraft or flying vehicle (such as a plane, UAV, helicopter, etc. ) and / or a building (such as a house, enterprise / company / office building, hotel building, airport building, sports / event buildings, shopping center building, etc..) and / or a portable carrier that can be carried by a user, for example, in a disaster zone or for public safety (such as a backpack, bag, etc), and / or public infrastructure elements or units (such as lamp posts, traffic lights, etc.). In an example where the MWAB node is implemented in a 5G femto network, the MWAB node functions as a 5G femto node and may be mounted at a building (such as a house, enterprise / company / office building, hotel building, airport building, sports / event buildings, shopping center building, etc..) and / or public infrastructure elements or units (such as lamp posts, traffic lights, etc.). In some cases, particularly but not exclusively when a MWAB node 130 is mounted to a fixed structure, e.g., when the MWAB node is functioning as a 5G femto node, the MWAB node 130 may be considered a WAB node, which also may be referred to as a Home gNB, and is based on the same architecture as the MWAB node, i.e. the Home gNB comprising the Mobile Termination and gNB required to be a Wireless Access Backhaul node.

[0098] Some examples of UEs include smartphones / tablets (such as UEs 111 , 123, 134, 142, 152), extended Reality (XR) headsets (such as UEs 112, 122, 132), cameras (such as UEs 131 , 141 and 151), fixed video cameras (such as UEs 113, 121 , 133, 153) or mobile / wearable video cameras (such as UEs 143 and 154). In general, the UE may be any portable or handheld or mobile telephone, a smartphone, a tablet, a portable or fixed computer, fixed or mobile camera, portable television, other smart devices or other similar wireless communication device. In the following description, the term UE will be used and it is not intended to limit the description to any particular type of wireless communication device.

[0099] Base stations 102, 103 and 104 are interconnected through a wired link infrastructure 180, preferably based on optical fiber or any other wired means.

[0100] Base stations 102, 103 and 104 are also connected to the core network 170 through a wired link infrastructure 190, preferably based on optical fiber or any other wired means. In some implementations, base stations 102, 103 and 104 are 5G NR base stations (referred to as a gNB), as defined in 3GPP TS 38.300 v18.0.0 specification document.

[0101] Satellite dish 101 (e.g., satellite gateway) is also connected to wired link infrastructure 180 or 190, or to both infrastructures 180, 190. That is to say, the satellite dish 110 is connected to one or more of the wired link infrastructures 180, 190. While infrastructure 180 and 190 are referred to as separate, it should be understood that it may be the same infrastructure.

[0102] In order to extend the network coverage of base stations 102, 103 and 104 and reach the remote UEs 111 , 112, 113, 121 , 122, 123, 131 , 132, 133, 134, 141 , 142, 143, 151 , 152, 153 and 154, MWAB nodes, or MWAB-nodes, 110, 120a, 120b, 130, 140 and 150, have been installed on vehicles / mobile equipment / building 161 , 162, 163, 164 and 165. By acting as relaying nodes between the base stations 102, 103 and 104 and the UEs 111 , 112, 113, 121 , 122, 123, 131 , 132, 133, 134, 141 , 142, 143, 151 , 152, 153 and 154, MWAB-nodes 110, 120a, 120b, 130, 140 and 150 allow overcoming the reachability issue resulting from limited sky visibility while ensuring support for onboard / on-site mobile edge computing (MEC), local services, and direct local inter- UE communications. This allows further communication between base stations 102, 103 and 104 and the UEs 111 , 112, 113, 121 , 122, 123, 131 , 132, 133, 134, 141 , 142, 143, 151 , 152, 153 and 154 and / or communications between the UEs served by a same MWAB-node (e.g., UEs 151 , 152, 153 and 154 connected to MWAB node 150).

[0103] The base stations 102, 103 and 104, the MWAB nodes 110, 120a, 120b, 130, 140 and 150, the satellite 160, the satellite dish 101 are thus forming a backhaul network or WAB network (also referred to as WAB topology), or MWAB network (also referred to as MWAB topology), which accommodates UEs 111 , 112, 113, 121 , 122, 123, 131 , 132, 133, 134, 141 , 142, 143, 151 , 152, 153 and 154. The terms WAB network, MWAB network, WAB topology and MWAB topology will be used interchangeably in the following. The WAB network forms the Radio Access Network (RAN) or as referred to with respect to 5G, Next Generation (NG) RAN.

[0104] The WAB network forms the Radio Access Network (RAN) or as referred to with respect to 5G, the Next Generation (NG) RAN.

[0105] The base stations 102, 103 and 104, the MWAB nodes 110, 120a, 120b, 130, 140 and 150, the satellite 160, the satellite dish 101 , and the core network 170 are thus forming a WAB system, or MWAB system, which accommodates UEs 111 , 112, 113, 121 , 122, 123, 131 , 132, 133, 134, 141 , 142, 143, 151 , 152, 153 and 154.

[0106] The terms WAB system and MWAB system will be used interchangeably in the following. A base station, or gNB, such as base station 102, 103 or 104, is a logical node that provides the NR-connectivity, hosting both higher layer protocols, such as PDCP (Packet Data Convergence Protocol) and RRC (Radio Resource Control) protocols, and lower layer protocols, such as the RLC (Radio Link Control), MAC (Medium Access Control) and physical layer protocols.

[0107] The MWAB nodes 110, 120a, 120b, 130, 140 and 150, which may serve multiple radio sectors, are wireless backhauled to the base station 102, 103 or 104, via a single logical hop associated to a single radio link (i.e., radio links D1041a, D1041 b, D1031 , D1022, D1021), or split into two radio links in the case of satellite relaying (radio links D1601a and D1601 b). Although a single logical hop is shown in figure 1 , it will be appreciated that the MWAB nodes could be wireless backhauled to the base station over multiple logical hops (for example, similar to the multiple hops provided in an IAB network).

[0108] Each MWAB node consists of a gNB or RAN node or base station component or unit or part which is referred to as a MWAB / WAB gNB or MWAB / WAB-gNB, or also referred to as a MWAB base station, and a Mobile Termination (MT) component or unit or part which is referred to as an MWAB / WAB-MT, MWAB / WAB MT or MWAB / WAB-Mobile Termination. The MWAB-gNB functionality on an MWAB-node allows or enables the connection to a UE. The MWAB-MT functionality includes, e.g., physical layer, layer-2, RRC and Non-Access Stratum (NAS) functionalities and allows or enables connection to a base station, or gNB, such as base station 102, 103 or 104.

[0109] MWAB nodes 110, 120a, 120b, 140 and 150 are intended to be mobile devices that will move along with the vehicle they are mounted on. However, these MWAB nodes may remain at a fixed location for a significant duration when their associated vehicle is remaining still (e.g., a train may stop at a railway station, a plane may be parked at an airport for a while, a car / truck / fire engine, or similar appropriate vehicle may be parked, for example nearby a disaster area).

[0110] MWAB node 130 is likely to remain at fixed location and may be a 5G Femto node, which provides NR access at home or at enterprise premises. In such case, the 5G Femto node 130 may have a direct connection D1700 to the Core Network 170 through the wired link infrastructure 190, which is preferably based on optical fiber or any other wired means. Figure 2 is a simplified schematic diagram of a 5G system 200 in which the present invention may be implemented according to one or more embodiments. This figure illustrates the possible standardized interfaces between the various elements composing the system. First, it represents a User Equipment (UE) 201 having a Uu interface with the New Generation (NG) Radio Access Network (RAN or NG-RAN) 202, and a N1 interface with an Access and Mobility management Function (AMF) entity or AMF 212 in a 5G core network (5GC) 210. Each base station composing the RAN 202 has a N2 interface with one or more Access and Mobility management Function (AMF) entity or AMF, like AMF 212, and a N3 interface with one or more User Plane Function (UPF) entity or UPF, like UPF 211.

[0111] The N1 interface is used to convey Non-Access Stratum (NAS) protocol messages between a UE 201 and an AMF 212. NAS messages are used for the signaling between the UE and the core network for various procedures such as registration, session establishment, security, and mobility management. Actually, NAS messages are conveyed through the Uu interface between the UE 201 and the RAN 202, and the N2 interface between the RAN 202 and the AMF 212.

[0112] An AMF 212 is responsible for handling registration, authentication, connection and mobility management tasks for a UE. There may be several AMFs in a 5G core network, a standardized interface N14 enables the communications between AMFs. When a UE registers to the network through a serving base station, the serving base station will connect to an AMF suitable to handle the UE.

[0113] When the UE 201 is registered, one or more Protocol Data Unit (PDU) session(s) can be set up to transfer data flows between the UE 201 and the Data Network (DN) 220 providing internet access. A PDU session is established between a UE 201 and a User Plane Function (UPF) 211 in the 5G core network 210. In the user plane, the UPF 211 connects to the Data Network (DN) 220 through the interface N6, and it is responsible for data packets routing with the required Quality of Service (QoS). There may be several UPFs on the data path with a N9 interface between UPFs. The user data between a UE 201 and the Data Network 220 are thus conveyed through interfaces Uu, N3, N6 and potentially N9.

[0114] In the control plane, the setup of PDU sessions is handled through NAS messages involving the Session Management Function (SMF) entity or SMF 213 in the 5G core network 210. The NAS messages are still exchanged between the UE 201 and the AMF 212 through the N1 interface, but an additional interface N11 between an AMF 212 and the SMF 213 is used to reach the SMF 213. In a 5G core network, the SMF is responsible for the setup, modification, and release of PDU sessions for a UE, as well as the Internet Protocol (IP) address allocation for the UE. To manage a PDU session, the SMF 213 controls the UPF 211 (configuration) based on QoS policy defined for the PDU session. For this purpose, a N4 interface exists between the SMF 213 and the UPF 211. A base station in RAN 202 operating in a first Public Land Mobile Network (PLMN) may serve a UE having a subscription for a second PLMN (called home PLMN) different from the first PLMN (called visited PLMN). In such a roaming case, there are two options to provide the UE 201 with an access to the Data Network 220. In a first option called home routed, the UPF and its controlling SMF to access the Data Network 220 are located in the 5G core network for the home PLMN. However, the SMF of the visited PLMN controls the intermediate UPF(s) of the visited PLMN, and interacts with the SMF of the home PLMN. In a second option called local breakout, the UPF and its controlling SMF to access the Data Network 220 are located in the 5G core network for the visited PLMN. However, the SMF interacts with the home 5G core network to get QoS policies associated with the UE’s PDU session(s).

[0115] Figure 3 is a simplified schematic diagram of a 5G system 300 involving a Wireless Access Backhaul (WAB) node (or a MWAB node), and in which the present invention may be implemented according to one or more example embodiments. This figure first represents a User Equipment (UE) 301 served by a WAB node 310 through the Uu interface. The WAB node 310 is composed of or includes a MT or WAB-MT or MWAB-MT unit / component / entity 311 (also called WAB-UE), and a gNB or RAN node or WAB-gNB, or MWAB-gNB unit / component / entity 312. Through the WAB-gNB 312, a WAB node acts as a gNB for UEs providing access to the 5G network, i.e. providing a NR access link to the UEs that can be located inside or outside the entity, such as a vehicle, equipped with the WAB node 310 (e.g. on entering / leaving the vehicle). In other words, the WAB-gNB 312 includes full base station or gNB function (including both Central Unit (CU) and distributed unit (DU)) and MT function, where the gNB function is used to communicate with UEs for access service and the MT function is used to communicate with another gNB for backhauling purpose. The WAB node 310 wirelessly connects to the 5G Core Network (using NR Uu interface) through an IP connectivity provided by PDU session(s) established by the WAB-MT 311 via a gNB 320, which can be called a backhaul RAN node or BH RAN node, backhaul base station, backhaul gNB or BH gNB. Acting as a legacy UE, the WAB-MT 311 connects via a NG- RAN cell of the BH gNB 320, through a backhaul link that may be a direct link or via a satellite (e.g. when the WAB node 310 is embedded in an airplane). Thus, a PDU session is provided either by a Terrestrial Network (TN) or by a Non-Terrestrial Network (NTN). In addition, the WAB node 310 may embed some core network functions, like a UPF 313, to enable local services to the served UEs. The traffic associated to these local services does not need to use the links to / from the core network via the BH gNB 320, which has the advantages to reduce the load on these links and to run applications having very low latency requirements. For example, where the WAB node 310 includes a UPF 313, the WAB node can connect to one or more local servers (e.g. mounted at the same entity as the WAB 310) enabling a UE served by the WAB access to local services provided by the local servers with no traffic required outside of the WAB node / server environment. The BH gNB 320 provides N3 and N2 interfaces so that the WAB-MT 311 can access to the functions of its 5G core network 330. Indeed, a WAB-MT 311 may have access to some or several PLMNs through the appropriate subscriptions, and it may connect in a non-roaming manner to one PLMN, e.g. PLMN1 supported by the BH gNB 320, and may then have access to the corresponding 5G core network 330. In particular the WAB-MT 311 interacts with the AMF 332, which can be called the WAB AMF, and establishes PDU session(s) with the UPF 331 , which can be called the WAB UPF. The WAB UPF 331 is controlled by the SMF 333 (through N4 interface), which can be called the WAB SMF, and which also interacts with the WAB AMF 332 (through N11 interface). There may be one or several intermediate UPFs between the BH gNB 320 and the WAB UPF 331 as mentioned in the Figure 2.

[0116] An interface internal to the WAB node 310 exists between the WAB-gNB 312 and the WAB-MT 311 , which may be implemented on different or the same hardware resources. For instance, these two functions are implemented on the same processing unit 402 of Figure 4, and interactions exist between the two functions.

[0117] Once the WAB-MT 311 has established a PDU session with the WAB UPF 331 , the WAB node is ready to serve UEs and the WAB-gNB 312 can start operating as a legacy gNB. The WAB- gNB may support various PLMNs and the UE 301 connects to one PLMN, e.g. PLMN2, which may be different from the PLMN1 the WAB-MT 311 connects to. In the case where PLMN1 and PLMN2 are different, the UE 301 connects to the 5G core network 340, including a UPF 341 , which can be called the UE UPF, an AMF 342, which can be called the UE AMF, and a SMF 343, which can be called the UE SMF. The UE SMF 343 interacts with the UE AMF 342 (through N11 interface) and the UE UPF 341 (through N4 interface). In the case where the PLMN1 and the PLMN2 are the same, the UE UPF 341 , the UE AMF 342, the UE SMF 343, the WAB UPF 331 , the WAB AMF 332, and the WAB SMF 333 belong to the same 5G core network 350. In addition, the UE UPF 341 and the WAB UPF 331 may be the same UPF, the UE AMF 342 and the WAB AMF 332 may be the same AMF, the UE SMF 343 and the WAB SMF 333 may be the same SMF.

[0118] The connections between the UE 301 to the UE UPF 341 and to the UE AMF 342 are possible thanks to the N6 interface between the UE UPF 341 and the WAB UPF 331 , and thanks to the N6 interface between the WAB UPF 331 and the UE AMF 342. These N6 interfaces enable the establishment of N2 interface between the WAB-gNB 312 and the UE AMF 342, and the establishment of N3 interface between the WAB-gNB 312 and the UE UPF 341 , which allows the UE 301 to access the Data Network 360.

[0119] In case the WAB-MT 311 connects to the 5G network in a roaming manner corresponding to the home routed option, then the PLMN1 is the visited PLMN and the WAB UPF 331 connects to another UPF not represented in the Figure 3 in the home PLMN through a N9 interface. It is this other UPF that provides the connection to the UE UPF 341 and the UE AMF 342 through N6 interfaces. In case the WAB-MT 311 connects to the 5G network in a roaming manner corresponding to the local breakout option, then the PLMN1 is the visited PLMN and the WAB UPF 331 directly connects to the UE UPF 341 and the UE AMF 342 through N6 interfaces as shown in the Figure 3.

[0120] Finally, the WAB-gNB 312 may use the backhaul link between the WAB-MT 311 and the BH-gNB 320 and a PDU session established by the WAB-MT 311 to setup a Xn connection with another RAN node. In another embodiment, the WAB-gNB 312 may use a dedicated network interface to directly connect to another RAN node (e.g. the network interface 432 of figure 4).

[0121] For instance, a Xn connection may be established between the WAB-gNB 312 and the BH-gNB 320.

[0122] Figure 4 is a block schematic diagram of an example RAN node or network node or base station 400, such as base stations or gNBs or MWAB nodes shown in Figure 1 or WAB nodes, in accordance with one or more embodiments of the invention. Each of a MWAB node 110, 120a, 120b, 130, 140, or 150 of figure 1 may comprise the elements of the base station of figure 4. In the following description, the network node 400 will be referred to generally as a base station. As will be apparent to a skilled person, Figure 4 is a simplified schematic diagram and shows only some of the functional components of an example base station 400 for use in describing the one or more embodiments of the invention.

[0123] The base station 400 includes components for transmitting and receiving communications. As shown in Figure 4, the base station 400 includes a processing unit 402, a wireless interface 404, one or more antennas 410, a network interface 432, and memory 418.

[0124] The network interface 432 manages communications of the base station 400 with the core network, other base stations, local network functions (like UPF), or local servers. It may provide a standardized interface, wired (e.g., fiber) or wireless, to support these communications. Through this network interface 432, the base station 400 may implement the standardized interfaces N2 (based on NGAP protocol) and N3 (based on GPRS tunneling protocol) with the core network, and the standardized interface Xn (based on XnAP protocol) with other base stations of the Radio Access Network (RAN), all defined by the 3GPP standard. The network interface 432 may not be present or active in case the base station 400 is a MWAB node that does not support local services, that is not used as a legacy base station like base station 102, 104 in Figure 1 , and / or that is not used as a home base station providing Femto cells like base station 130 in Figure 1.

[0125] The wireless interface 404 is configured to provide wireless communication via communication links (414) with other wireless devices, such as one or more UEs, e.g., link D1041 b between base station 104 and the MT / UE unit of MWAB node 120b, or link D1202 between the gNB unit of MWAB node 120b and the UE 122. In case of MWAB node, the wireless interface 410 may then be used both for the wireless backhaul link(s) with backhaul base station(s) and for the wireless link(s) with the UE(s) served by the MWAB node. The wireless interface 404 may be compliant with a fifth-generation (5G) New Radio (NR) system and thus implementing the Uu interface defined by 3GPP standard, or with other wireless communication system. The wireless interface 404 is coupled to the processing unit 402 and typically includes one or more antennas (such as the antenna 410), a receiving unit 406 and a transmitting unit 408. The configuration of the wireless interface 404 may be limited to connect to one antenna, but preferably several antennas are used, in order to provide beamforming capability. Although not shown in Figure 4, the receiving unit 406 typically includes elements such as a receiver, demodulator, decoder, and the transmitting unit 408 typically includes elements such as a transmitter, modulator, coder. The receiving unit 406 and transmitting unit 408 may together be referred to as a transceiver.

[0126] The processing unit 402 is configured to carrying out processing for operation of the base station 400. The processing unit 402 may be a single processor (e.g., Central Processing Unit) or may comprise two or more processors. The number of processors and the allocation of processing functions to the processors is a matter of design choice for a skilled person. The base station 400 includes memory 418 for storing data and computer programs containing instructions for the operation of the base station 400. Memory 418 includes RAM (Random Access Memory), ROM (Read Only Memory), or combination of both or as a non-limiting example a mass storage device such as a disk or a Solid-State Drive. Memory 418 includes a program memory in which are stored programs containing processor instructions for operation of the base station 400 and for implementing the methods in accordance with one or more embodiments of the invention. The programs may contain a number of different program elements or sub-routines containing processor instructions for a variety of different tasks, for example, for: establishing, controlling and releasing communications with the UEs (e.g., implementing the Uu interface); processing data and signalling received at the receiving unit 406; processing signalling (e.g., paging messages, System Information Blocks) and data for transmission by the transmitting unit 408.

[0127] Memory 418 may further include memory (e.g., RAM) for storing information. For example, information stored in memory 418 may further include information associated with the mobile WAB node, such as information elements 420 related to a MWAB node, including MWAB information. The information elements may be static information elements and / or dynamic information elements. The information elements 420 may be associated to the base station 400 (when the base station is a MWAB node), and may be communicated to any network node or entity when necessary. The information elements may also be related to a MWAB node (which is not the base station 400), and stored after reception from the MWAB node or from another network node or entity. Other nodes or entities described, such as the gNB, AMF and UPF, may comprise information elements stored in their own respective memories. These information elements being related to a MWAB node (including WAB-MT connection information, WAB connection information, WAB neighbouring information, neighbour WAB cells list information, femto capability information, WAB co-location information, WAB group information, etc. as discussed below) or their capability to serve a MWAB node.

[0128] Specific program elements / sub-routines stored in program memory may include one or more of the following: elements for performing connection setup to establish a Xn connection between the gNB component of a WAB node and a RAN node (e.g. neighbour RAN node) based on information shared between the WAB node and the RAN node. The information shared may include information for identifying a relationship between the WAB node and the RAN node: such a relationship may be a connection has been established between the MT component of the WAB node and the RAN node or in the case where the RAN node is another WAB node, the WAB node and the other WAB node belong or are part of the same group of WAB nodes. The elements may include one or more of: an element for sending a request to initiate establishment of a Xn connection between the gNB component of the WAB node and the RAN node; an element for receiving a response to the request; and / or an element for receiving a request to initiate establishment of a Xn connection between the gNB component of the WAB node and the RAN node; an element for sending a response to the request. Other elements that may be included will be apparent from the description of the example message flows and example methods set out below.

[0129] In an example arrangement, a communication bus 424 provides communication and interoperability between the various elements included in the base station 400 or connected to it. The representation of the bus is not limiting and in particular, the processing unit 402 is operable to communicate instructions to any element of the base station 400 directly or by means of another element of the base station 400.

[0130] In an example implementation, the base station 400 may be or may include an apparatus comprising one or more processing units or processors for performing or implementing the methods in accordance with one or more embodiments of the invention. In other words, the apparatus may be capable of performing one or more functions of the base station including performing the methods in accordance with one or more embodiments of the invention by means of the one or more processing units. For example, the one or more processing units use software to implement the one or more embodiments of the invention as described above with reference to the processing unit 402 of Figure 4. Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, a CPU of a microcontroller Unit (MCU), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or other equivalent integrated (e.g., on an Integrated Circuit) or discrete logic circuitry. However, alternatively, the one or more processing units for performing or implementing the methods may be implemented in hardware: for example, in the form of an Application Specific Integrated Circuit or ASIC or other hardware comprising logic element (s). Accordingly, the term “processing unit” as used herein may refer to any of the foregoing structures or any other structure suitable for implementation of the techniques described herein. Figure 5 illustrates an example of a wireless communication system 500, including a WAB network or WAB network system, according to some embodiments. The WAB network or WAB network system may be considered a mobile WAB network or a mobile WAB network system.

[0131] A WAB network will also be referred to as a WAB network system, WAB topology, WAB system, topology or system and so in this application, the terms WAB network system, WAB network, WAB topology, WAB system, topology or system will be used interchangeably.

[0132] The WAB network system of Figure 5, is composed of or comprises three base stations 501 , 502 and 503, also referred to as Backhaul base stations, or backhaul gNBs (also referred to as BH-gNB) or backhaul RAN node (also referred to as BH RAN node), two core networks 510 and 520, with the respective AMF entities 511 a and 511 b (for Core Network 510) and 521a and 521 b (for Core Network 520) and the respective UPF entities 512a and 512b (for Core Network 510) and 522a and 522b (for Core Network 520), and two WAB nodes 530 and 540.

[0133] A wired backhaul IP network 590 interconnects the base stations 501 , 502 and 503 and the Core Networks 510 and 520. For instance, this wired link consists of optical fiber cable(s).

[0134] As discussed above, each WAB node comprises a Mobile Termination (MT) part or unit or component (WAB-MT 531 for WAB node 530 and WAB-MT 541 for WAB node 540) and a base station part or unit or component (WAB-gNB 532 for WAB node 530 and WAB-gNB 542 for WAB node 540).

[0135] WAB node 530 and WAB node 540 may also embed a UPF entity, respectively UPF entity 533 and UPF 543, as previously discussed in relation to figure 3, allowing WAB-node 530 to provide UEs 551 , 552 and 561 with at least some local services, such as for instance inter-UE communication where the user data exchanged between the two UEs would be routed through UPF entity 533 instead of being routed through a UPF entity belonging to Core Network 510 or 520. In some implementations, the UPF entity of the WAB node may be configured for one or more local services.

[0136] WAB node 530 is connected to the serving backhaul base station BH-BS1 , also referred to as BH-gNB1 , 501 through BH link 5011 .

[0137] WAB node 540 may be connected to the serving backhaul base station referred to as BH-gNB2, 502 through BH link 5021 or to the serving backhaul base station referred to as BH- gNB3, 503 through BH link 5031 or, in case of dual connectivity, to both the serving backhaul base station BH-gNB2, 502 through BH link 5021 and the serving backhaul base station BH-gNB3, 503 through BH link 5031.

[0138] WAB-gNB 532 of WAB node 530 is also connected to UE 551 through communication link or radio link 5301 and to UE 552 through communication link or radio link 5302.

[0139] Similarly, WAB-gNB 542 of WAB node 540 is also connected to UE 561 through communication link or radio link 5401 . Although Figure 5 shows only one UE 561 connected to WAB node 540, it will be appreciated that there may be a plurality of UEs connected to WAB nodes of the wireless communication system. Similarly, Figure 5 shows a plurality of UEs 551 , 552, connected to WAB node 530 but it will be appreciated that there may be one UE connected.

[0140] WAB-gNB 532 and WAB-MT 531 may be connected to a same AMF entity (e.g., AMF 511a) or to different AMF entities belonging to the same Core Network (e.g., AMF 511a and AMF 511 b) or to different Core Networks (e.g., AMF 511 a and AMF 521a).

[0141] Some AMF entities may be implementing WAB-specific features for managing a WAB node (e.g., advanced mobility features). Some AMF entities may not implement such features but may still be capable of serving a WAB node with a limited set of basic features. Some AMF entities may not be capable of serving a WAB node.

[0142] Processes or methods for managing one or more network connections in a wireless communication system including one or more WAB (WAB) nodes, including managing the setup of an Xn communication connection and removal between a WAB-gNB and a RAN node such as a base station or gNB, oranother WAB-gNB of another WAB node, will now be described according to one or more examples of embodiments of the present invention.

[0143] Figure 8 is a flowchart of an example method 800 for managing Xn connection establishment between a first and a second NG-RAN network nodes according to one or more embodiments of the present invention.

[0144] The method 800 as illustrated in Figure 8 is performed at the first RAN node. It will be appreciated that the method 800 could be performed at the second RAN node or at some other network entity. In some embodiments processing steps, such as the determination of an Xn benefit parameter, of the method 800 may be performed at the first RAN node (or second RAN node). In alternative embodiments, such processing steps may be performed outside of the first RAN node (or second RAN node) for example where the method 800 is performed at the first RAN node, the determination of the Xn benefit parameter may be performed by the second RAN node, or another network entity, and communicated to the first RAN node.

[0145] In one embodiment, one or both of the first RAN node and the second RAN node are Wireless Access Backhaul, WAB, nodes, each WAB node comprising a Mobile Termination, MT, component and a gNB component.

[0146] In one embodiment, at least one out of the two NG-RAN nodes may be the gNB component (or part or unit), or WAB-gNB, of a Wireless Access Backhaul, WAB, node, while the other NG-RAN node may be a Backhaul RAN node, or the gNB component (or part or unit), or WAB-gNB, of a Wireless Access Backhaul, or any NG-RAN node in the network.For example, with reference to the wireless communication system shown in and described with respect to Figure 5, a WAB node performing the method 800 may be the MWAB-node 530, which comprises MWAB- MT 531 and MWAB-gNB 532, of WAB system 500, while a Backhaul RAN node performing the invention may be the NG-RAN node 501 or 502.

[0147] The method 800 as shown in and described with respect to Figure 8 may be performed by software elements and / or hardware elements. The NG-RAN node performing the invention may be implemented in a communication device 400 as shown in and described with reference to Figure 4 with the method as shown in and described with respect to Figure 8 being performed by one or more processing units, such as the processing unit 402.

[0148] Optionally, in a first step 801 , a first RAN node may determine the benefit of establishing an Xn connection with the second RAN node. In other embodiments, the benefit may be determined by the second RAN node, or determined by another network entity, and communicated to the first RAN node.

[0149] In one embodiment, the first RAN node may determine the benefit of establishing an Xn connection with a second RAN by performing the method 1000, defined in relation with Figure 10.

[0150] In one embodiment, when the first RAN node is a WAB node, it may detect the second RAN node based on one of the following methods: the WAB-MT part of the first RAN node detects a cell managed by the second RAN node.

[0151] In one example, the WAB-MT of the first RAN node may perform such detection when receiving some information broadcast by the second RAN node. This information may for instance be broadcast using the SIB1 message, as defined in 3GPP TS 38.331. In one embodiment, the information broadcast by the second RAN node includes some information indicating if this second RAN node is a WAB node; a UE served by the first RAN node reports to the first RAN node that it is in range of the second RAN node. In one example, the first RAN node may detect the second RAN node when receiving a measurement report, such as, for instance, the MeasurementReport message defined in TS 38.331 ; the first RAN node is informed by a third RAN node, through an existing Xn connection previously established between the first and third RAN nodes, that the second RAN node is in the neighborhood of the third RAN node, e.g. the second RAN node is in a same geographical area, such as a Notification Area (RNA), Tracking Area (TA), or is in range of the third RAN node.

[0152] In one embodiment, when the first RAN node is not a WAB node, e.g., a Backhaul RAN node, while the second RAN node is a WAB node, it may detect the second RAN node based on one of the following methods: a UE served by the first RAN node reports to the first RAN node that it is in range of the second RAN node. In one example, the first RAN node may detect the second RAN node when receiving a measurement report, such as, for instance, the MeasurementReport message defined in TS 38.331 ; the first RAN node is informed by a third RAN node, through an existing Xn connection previously established between the first and third RAN nodes, that the second RAN node is in the neighborhood of the third RAN node.

[0153] In one embodiment, the method 800 includes detecting, by the first RAN node, the second RAN node prior to determining whether to establish the Xn connection with the second RAN node based on the determined benefit of establishing the Xn connection. In other embodiments, the second RAN node has already been detected prior to determining whether to establish the Xn connection.

[0154] In one embodiment, the first RAN node may determine the benefit of establishing a an Xn connection with a second RAN node upon one of the following triggering events:

[0155] One or more UEs served by the first RAN node are in range of the second RAN node;

[0156] The quality of the radio link between one or more UEs served by the first RAN node and the second RAN node is above a predefined quality threshold or has been above a predefined quality threshold for a predefined period of time;

[0157] The quality of the radio link between the first RAN node and the second RAN node is above a predefined quality threshold or has been above a predefined quality threshold for a predefined period of time;

[0158] The first RAN node determines that it will be in range with the second RAN node within a certain period of time (e.g., 10s, 1 minute ...). The first RAN node may perform such determination based on its current speed and / or some known trajectory- related information.

[0159] At step 802, the first RAN node establishes an Xn connection with the second RAN node based on the determined benefit of establishing the Xn connection. In the illustrated embodiment of method 800, the determined benefit of establishing the Xn connection is represented by the value of an Xn benefit parameter. The first RAN node decides to establish an Xn connection with the second RAN node if it determines that the benefit of establishing an Xn connection with the second RAN node is sufficient. In particular, the first RAN node decides to establish the Xn connection based on the value of the Xn benefit parameter. The first RAN node may determine not to establish an Xn connection with the second RAN node if it determines that the benefit of establishing an Xn connection with the second RAN node is not sufficient.

[0160] In one example, the first RAN node may establish an Xn connection with the second RAN node according to one of method 600 of Figure 6, method 700 of Figure 7 or method 800 of Figure 8.

[0161] In one embodiment, the first RAN node may determine that the benefit of establishing an Xn connection with the second RAN node is sufficient if the benefit value determined in step 801 is greater or equal to an establishment threshold.

[0162] In one embodiment, the first RAN node may determine that the benefit of establishing an Xn connection with the second RAN node is sufficient if the benefit value determined in step 801 is greater than or equal to an establishment threshold for a minimum time period. In some embodiments, the first RAN node may start a timer when it is determined that the benefit value (e.g. the XR benefit parameter value) is greater than or equal to the establishment threshold value, and the establishment of an Xn connection may be triggered after the timer value exceeds the predetermined minimum period.

[0163] In embodiments wherein the benefit of establishing an Xn connection with the second RAN node is represented by an Xn benefit parameter, the establishment threshold may be represented by an establishment threshold parameter. The first RAN node (or second RAN node) may compare the value of the Xn benefit parameter to the value of the establishment threshold parameter. The first RAN node (or second RAN node) may determine that the benefit of establishing an Xn connection is sufficient based on the value of the Xn benefit parameter being greater than (or greater than or equal to) the value of the establishment threshold parameter. The first RAN node (or second RAN node) may determine that the benefit of establishing an Xn connection is not sufficient based on the value of the Xn benefit parameter being less than (or less than or equal to) the value of the establishment threshold parameter.

[0164] In one embodiment, the establishment threshold may be configured at first RAN node by one of the following: the Network, through an Operations, Administration and Maintenance (OAM) procedure, or by the AMF entity serving the first RAN node, through the CONFIGURATION message 702 or 703, as defined in relation with Figure 7; the Backhaul RAN node, BH RAN node, serving the first RAN node through the CONFIGURATION message 701 , as defined in relation with Figure 7, when the first RAN node is a WAB node.

[0165] The second RAN node, when the second RAN node initiates the establishment of an Xn connection with the first RAN node. In one example, a RAN node may initiate an Xn connection establishment by sending a CONNECTION SETUP REQUEST message 601 , as defined in Figure 6.

[0166] Figure 9 is a flowchart of an example method 900 for managing Xn connection establishment between a first and a second NG-RAN network nodes according to one or more embodiments of the present invention.

[0167] The method 900 of Figure 9 is performed at the first RAN node. It will be appreciated that the method 900 could be performed at the second RAN node or at some other network entity. In some embodiments processing steps, such as the determination of an Xn benefit parameter, of the method 900 may be performed at the first RAN node (or second RAN node). In alternative embodiments, such processing steps may be performed outside of the first RAN node (or second RAN node) for example where the method 900 is performed at the first RAN node, the determination of the Xn benefit parameter may be performed by the second RAN node, or another network entity, and communicated to the first RAN node. In one embodiment, one or both of the first RAN node and the second RAN node are Wireless Access Backhaul, WAB, nodes, each WAB node comprising a Mobile Termination, MT, component and a gNB component.

[0168] In one embodiment, at least one out of the two NG-RAN nodes may be the gNB component (or part or unit), or WAB-gNB, of a Wireless Access Backhaul, WAB, node, while the other NG-RAN node may be a Backhaul RAN node, or the gNB component (or part or unit), or WAB-gNB, of a Wireless Access Backhaul, or any NG-RAN node in the network.

[0169] For example, with reference to the wireless communication system shown in and described with respect to Figure 5, a WAB node performing the method 900 may be the MWAB- node 530, which comprises MWAB-MT 531 and MWAB-gNB 532, of WAB system 500, while a Backhaul RAN node performing the invention may be the NG-RAN node 501 or 502.

[0170] The method 900 as shown in and described with respect to Figure 9 may be performed by software elements and / or hardware elements. The NG-RAN node performing the invention may be implemented in a communication device 400 as shown in and described with reference to Figure 4 with the method as shown in and described with respect to Figure 9 being performed by one or more processing units, such as the processing unit 402.

[0171] At step 902, the first RAN node may decide to terminate (remove) the Xn connection with the second RAN node based on the determined benefit of maintaining the Xn connection. In the illustrated embodiment of method 900, the determined benefit of maintaining the Xn connection is represented by the value of an Xn benefit parameter. The first RAN node determines to terminate the Xn connection with the second RAN node if it determines that the benefit of maintaining an Xn connection with the second RAN node is not sufficient. In particular, the first RAN node determines to terminate the Xn connection based on the value of the Xn benefit parameter.

[0172] In one example, the first RAN node may remove (terminate) an Xn connection with the second RAN node according to one of method 600 of Figure 6, method 700 of Figure 7 or using any of the processing steps described with respect to method 800 of Figure 8.

[0173] Optionally, in a first step 901 , a first RAN node may determine the benefit of maintaining a previously established Xn connection with a second RAN node. In other embodiments, the benefit may be determined by the second RAN node, or determined by another network entity, and communicated to the first RAN node.

[0174] In one embodiment, the first RAN node may determine the benefit of maintaining a previously established Xn connection with a second RAN node on a periodic basis, e.g., every second.

[0175] In one embodiment, the first RAN node may determine the benefit of maintaining a previously established Xn connection with a second RAN node upon one of the following triggering events:

[0176] One or more UEs served by the first RAN node are no longer in range of the second RAN node; The quality of the radio link between one or more UEs served by the first RAN node and the second RAN node has been decreasing for a certain period of time (e.g., 100ms, 1s, 10s ...), or is below a predefined quality threshold;

[0177] The quality of the radio link between the first RAN node and the second RAN node has been decreasing for a certain period of time (e.g., 100ms, 1 s, 10s ...), or is below a predefined quality threshold;

[0178] The first RAN node determines that it will be out of range with the second RAN node within a certain period of time (e.g., 10s, 1 minute ...). The first RAN node may perform such determination based on its current speed and / or some know trajectory-related information.

[0179] In one embodiment, the first RAN node may determine the benefit of maintaining an Xn connection with a second RAN by performing the method 1000, defined in relation with Figure 10.

[0180] In one embodiment, the first RAN node may determine that the benefit of maintaining an Xn connection with the second RAN node is not sufficient if the benefit value determined in step 901 is lower than a removal threshold.

[0181] In one embodiment, the first RAN node may determine that the benefit of maintaining an Xn connection with the second RAN node is not sufficient if the benefit value determined in step 901 is lower than (or lower than or equal to) a removal threshold for a minimum time period. In some embodiments, the first RAN node may start a timer when it is determined that the benefit value (e.g. the XR benefit parameter value) is lower than the removal threshold value, and the removal of an Xn connection may be triggered after the timer value exceeds the predetermined minimum period.

[0182] In one embodiment, the removal threshold of method 900 is equal to the establishment threshold of method 800.

[0183] In one embodiment, the removal threshold of method 900 is different from the establishment threshold of method 800.

[0184] In one embodiment, the removal threshold may be configured at first RAN node by one of the following: the Network, through an Operations, Administration and Maintenance (OAM) procedure, or by the AMF entity serving the first RAN node, through the CONFIGURATION message 702 or 703, as defined in relation with Figure 7; the Backhaul RAN node, BH RAN node, serving the first RAN node through the CONFIGURATION message 701 , as defined in relation with Figure 7, when the first RAN node is a WAB node.

[0185] The second RAN node, when the second RAN node initiates the removal of an Xn connection with the first RAN node. In one example, a RAN node may initiate an Xn connection removal by sending a CONNECTION REMOVAL REQUEST message 601 , as defined in Figure 6. Figure 10 is a flowchart of an example method 1000, at a RAN node, for determining the benefit of an Xn connection between two NG-RAN network nodes according to one or more embodiments of the present invention.

[0186] In one embodiment, the NG-RAN node performing method 1000 may be a Wireless Access Backhaul, WAB, node, or a Backhaul RAN node or any NG-RAN node in the network.

[0187] For example, with reference to the wireless communication system shown in and described with respect to Figure 5, a WAB node performing the method 1000 may be the MWAB- node 530 of WAB system 500, while a Backhaul RAN node performing the invention may be the NG-RAN node 501 or 502.

[0188] The method 1000 as shown in and described with respect to Figure 10 may be performed by software elements and / or hardware elements. The NG-RAN node performing the invention may be implemented in a communication device 400 as shown in and described with reference to Figure 4 with the method as shown in and described with respect to Figure 10 being performed by one or more processing units, such as the processing unit 402.

[0189] Briefly, in a first step 1001 , a first NG-RAN node may determine the benefit of an Xn connection with a second NG-RAN node.

[0190] In one embodiment, the NG-RAN node may determine the benefit of an Xn connection which has not been established yet.

[0191] In one embodiment, the NG-RAN node may determine the benefit of an Xn connection which has already been established.

[0192] In one example, the benefit of an Xn connection with a second NG-RAN node, as determined by the first NG-RAN node, is a function of at least one of the following criteria:

[0193] Served UE connectivity criterion. This criterion refers to the ability for one or more UEs served by the first RAN node to connect to the second RAN node.

[0194] In one example, a UE served by the first RAN node may be able to connect to the second RAN node if the radio link quality resulting from signal strength measurements performed by the UE and associated to a cell managed by the second RAN node is above a predefined threshold radio link quality.

[0195] In one example, a UE served by the first RAN node may report to the first RAN node the radio link quality between this UE and the second RAN node by sending to the first RAN node a measurement reporting message, such as the MeasurementReport message, as defined in TS 38.331.

[0196] In one example, the Served UE connectivity criterion may be related to the number of served UEs that are able to connect to the second RAN node. For instance, the Served UE connectivity criterion may be related to the number of served UEs that are able to connect to the second RAN node compared to a predefined Served UE connectivity threshold.

[0197] In one example, the Served UE connectivity criterion may be related to the ratio of served UEs that are able to connect to the second RAN node. For instance, the Served UE connectivity criterion may be related to the ratio of served UEs that are able to connect to the second RAN node compared to a predefined Served UE connectivity ratio threshold.

[0198] In one example, the Served UE connectivity criterion may be related to the ability for one or more UEs served by the first RAN node to connect to the second RAN node for a minimum duration, or Minimum UE Connectivity Duration threshold. In one example, to assess the Served UE connectivity criterion, the first RAN node may rely on a dedicated timer, or Minimum UE Connectivity Duration Timer.

[0199] In one example, the first RAN node may derive a score, or UE connectivity score, from the Served UE connectivity criterion. In one example, this score may be an integer value.

[0200] WAB-MT connectivity criterion. In case the first NG-RAN node is a WAB node, this criterion refers to the ability for the WAB-MT part of the first RAN node to connect to the second RAN node.

[0201] In one example, a WAB-MT may be able to connect to the second RAN node if the radio link quality resulting from signal strength measurements performed by the WAB-MT and associated to a cell managed by the second RAN node is above a predefined radio link quality threshold.

[0202] In one example, the WAB-MT connectivity criterion may be related to the ability for the WAB-MT of the first RAN node to connect to the second RAN node for a minimum duration, or Minimum WAB-MT Connectivity Duration threshold. In one example, to assess the WAB-MT connectivity criterion, the first RAN node may rely on a dedicated timer, or Minimum WAB-MT Connectivity Duration Timer.

[0203] In one example, the first RAN node may derive a score, or WAB-MT connectivity score, from the WAB-MT connectivity criterion. In one example, this score may be an integer value.

[0204] Direct connectivity criterion. This criterion refers to radio link quality between the first and the second RAN node. This criterion may be related to the signal strength measurements performed by the first RAN node and associated to a cell managed by the second RAN node.

[0205] In one example, to assess the Direct connectivity criterion, the first RAN node may compare the signal strength measurements to one or more predefined radio link quality thresholds.

[0206] In one example, the first RAN node may derive a score, or Direct connectivity score, from the Direct connectivity criterion. In one example, this score may be an integer value.

[0207] Xn neighborhood criterion. This criterion refers to the presence of the second RAN node in the neighborhood of a third RAN node having Xn connectivity with the first RAN node. In one example, the third RAN node may establish a list of the neighbor cells belonging to RAN nodes neighboring or in the vicinity of the third RAN node. In one example, the third RAN node may share all or part of this list upon Xn connection establishment.

[0208] In one example, the first RAN node may derive a score, orXn neighborhood score, from the Xn neighborhood criterion. In one example, this score may be an integer value. Geographical area criterion. This criterion refers to the presence of the first and second RAN nodes in a same geographical area.

[0209] In one example, the considered geographical area may be any one of: RAN-based Notification Area (RNA), Tracking Area (TA), a group of NR Cells.

[0210] In one example, the first RAN node may derive a score, or Geographical area score, from the Geographical area criterion. In one example, this score may be an integer value.

[0211] Mobility criterion. This criterion refers to impact of the mobility of the first RAN nodes on being present in one same geographical area as the second RAN node.

[0212] In one example, the Mobility criterion may be based all or part of the following: speed information indicating a speed capability of the first RAN node, range information indicating a mobility area of the first RAN node, static information indicating a duration of one or more static periods the first RAN node may experience, itinerary information indicating a sequence of mobility and static periods for an itinerary the first RAN node may follow.

[0213] The speed information may include information indicating one or more of a minimum speed capability of the first RAN node, average speed capability of the first RAN node, maximum speed capability of the first RAN node.

[0214] The range information may include information indicating an area in which the first RAN node may move or range of movement of the first RAN node. For example, the range information may include a type or category of the mobility area in which the first RAN node may move and which can be an indication of the size or nature of the geographical area in which the first RAN node may move. For example, the type (or category) of mobility area may indicate the geographical area is a plane route, a train route, or a car route. As an example, a car route may be an expected navigation route determined by a satellite navigation system, or similar.

[0215] The range information additionally or alternatively may include a size of the area (i.e., mobility area) in which the first RAN node may move and / or a list of the cell Identifiers (IDs) of the cells that the first RAN node may visit or has visited previously. The range information additionally or alternatively may include a distance by which the first RAN node may move.

[0216] The static information may include static time information indicating one or more of minimum static period duration, average static period duration or maximum static period duration. The static information may also include static position information indicating the location where the first RAN will be static.

[0217] The itinerary information may include information indicating, for each of the mobility and static periods, the duration of the period, the speed of the first RAN node during one or more of the mobility periods, the location of the first RAN node during one or more of the static periods.

[0218] In one example, the first RAN node may derive a score, or Mobility score, from the Mobility criterion. In one example, this score may be an integer value. According to one embodiment of the invention, the aforementioned signal strength measurements may include all or part of the following metrics:

[0219] Reference Signal Received Power (RSRP), which provides a measure of the received power of the strongest reference signal from the considered cell.

[0220] Reference Signal Received Quality (RSRQ), which provides a measure of the quality of the received reference signal from the considered cell, relative to the interference level in the cell.

[0221] Signal-to-Noise Ratio (SNR), which provides a measure of the signal quality relative to the noise level in the cell and can be used to determine the strength of the signal from the considered cell.

[0222] Channel Quality Indicator (CQI), which provides a measure of the quality of a received signal.

[0223] In addition to the above metrics, other measurements such as cell identity, beamforming quality, and channel state information may also be considered for signal strength measurements.

[0224] In one embodiment, the first RAN node may derive the benefit of an Xn connection from all or part of the above scores. The first RAN node may represent the derived benefit of an Xn connection as a parameter, such as an Xn benefit parameter.

[0225] In one example, the benefit value of an Xn connection (e.g. the value of the Xn benefit parameter) may be the average of the considered score values.

[0226] In one example where some of the above criteria are considered more important than others, the benefit value of an Xn connection (e.g. the value of the Xn benefit parameter) may be a weighted average of the considered score values.

[0227] In one example, the benefit value of an Xn connection (e.g. the value of the Xn benefit parameter) may be an integer value (e.g., an integer value ranging from 0 to 8).

[0228] Considering the above criteria in order to estimate the benefit of establishing an Xn connection, as also discussed in relation with Figure 8, may allow preventing systematic Xn connection establishment, which would cause unnecessary radio resources usage and device processing. Moreover, systematic Xn connection establishment would result in an increase of Xn connection removals, which would also cause unnecessary radio resources usage and device processing.

[0229] Referring now also to Figure 6, which is a schematic and simplified diagram 600 illustrating example message flows for use in managing network connectivity in a wireless communication system including at least one Wireless Access Backhaul, WAB, node in accordance with one or more embodiments of the present invention and which may be used for managing Xn connection establishment between a first RAN node 620 and a second RAN node 630, is shown. In one embodiment, at least one out of the two NG-RAN nodes 620 and 630 may be the gNB component (or part or unit), or WAB-gNB, of a Wireless Access Backhaul, WAB, node, while the other NG-RAN node may be a Backhaul RAN node, or the gNB component (or part or unit), or WAB-gNB, of a Wireless Access Backhaul, or any NG-RAN node in the network.

[0230] The mobile termination part (or component or unit), WAB-MT, of the NG RAN node being a Wireless Access Backhaul, WAB, node (which may correspond to WAB node 120a of Figure 1 and WAB node 530 of Figure 5 as described above, or correspond to other descriptions of WAB node discussed herein), may perform RRC connection setup process with the other NG-RAN network node.

[0231] For example, an NG RAN node being a WAB node may perform a MT connection setup or MT connection setup process (as shown by the dotted box 604 in figure 6) to establish a connection between the WAB-MT of the WAB node and the other NG-RAN network node. In an example, the process of section 5.3.3 of TS38.331 may be performed to establish a connection between the MT component of the WAB node and the NG-RAN network node.

[0232] Once the WAB-MT connection setup process has completed, RAN node 620 may start determining the benefit of establishing an Xn connection with RAN node 630.

[0233] In one embodiment, the determining of the benefit of establishing an Xn connection with RAN node 630 may be initiated by RAN node 620 once the NG setup process, as described in 3GPP TS 38.413 has completed.

[0234] In one embodiment, RAN node 620 may determine the benefit of establishing an Xn connection with RAN node 630 by performing the method 1000 of Figure 10.

[0235] In order to perform method 1000 of Figure 10, the RAN node 620 may rely on some measurement reporting received through MEASUREMENT REPORT message 605a issued by a served UE 640, or through MEASUREMENT REPORT message 605b issued by a served WAB- MT in case RAN NODE 630 is a WAB node.

[0236] In one embodiment, RAN node 620 may determine the benefit of establishing an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 on a periodic basis.

[0237] In one embodiment, RAN node 620 may determine the benefit of establishing an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 upon reception of a MEASUREMENT REPORT message 605a indicating that UE 640 is in range of RAN node 630. In one example, RAN node 620 may determine the benefit of establishing an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 upon reception of a plurality of successive MEASUREMENT REPORT messages 605a indicating that UE 640 is in range of RAN node 630.

[0238] In one embodiment, RAN node 620 may determine the benefit of establishing an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 upon reception of a MEASUREMENT REPORT message 605b indicating that RAN node 630 is in range of RAN node 620. In one example, RAN node 620 may determine the benefit of establishing an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 upon reception of a plurality of successive MEASUREMENT REPORT messages 605b indicating that RAN node 630 is in range of RAN node 620.

[0239] In one embodiment, RAN node 620 may determine the benefit of establishing an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 when the radio link measurements between the UE 640 and the RAN node 630 in a received MEASUREMENT REPORT message 605a, or in a plurality of successive MEASUREMENT REPORT messages 605a, are above a predefined threshold.

[0240] In one embodiment, RAN node 620 may determine the benefit of establishing an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 when the radio link measurements between the UE 630 and the RAN node 620 in a received MEASUREMENT REPORT message 605b, or in a plurality of successive MEASUREMENT REPORT messages 605b, are above a predefined threshold.

[0241] If it determines that the benefit of establishing an Xn connection with RAN node 630 is sufficient, the RAN node 620 may initiate a connection setup process to establish a Xn connection with the RAN node 630 by sending a CONNECTION SETUP REQUEST message 601 to the RAN node 630.

[0242] In one example, this connection setup process may be the Xn Setup procedure, as defined in 3GPP TS 38.423.

[0243] In one example, the CONNECTION SETUP REQUEST message 601 may be the XN SETUP REQUEST message, as specified in 3GPP TS 38.423.

[0244] The RAN node 630 may further respond to the CONNECTION SETUP REQUEST message 601 by sending a CONNECTION SETUP RESPONSE message 602 to the RAN node 620.

[0245] In one example, the CONNECTION SETUP RESPONSE message 602 may be the XN SETUP RESPONSE message, as specified in 3GPP TS 38.423.

[0246] In one embodiment of the invention, the RAN node 620 may add to the CONNECTION SETUP REQUEST message 601 some information related to the Xn connection benefit value it previously computed when performing the method 1000 of Figure 10.

[0247] In one example, in case the Xn connection benefit value received from RAN node 620 is below a predefined threshold, RAN node 630 may reject the connection request by sending a connection failure message to RAN node 620. In such case, the CONNECTION SETUP RESPONSE message 602 may be the XN SETUP FAILURE message, as specified in 3GPP TS 38.423. In one example, RAN node 630 may provide in the connection failure message a failure cause information, which would indicate that the Xn connection benefit value is too low.

[0248] In one embodiment of the invention, the RAN node 620 may add to the CONNECTION SETUP REQUEST message 601 an Xn setup threshold value information.

[0249] In one example, in case the benefit value computed by RAN node 630 for the Xn connection between RAN node 620 and RAN node 630, is greater than or equal to the Xn setup threshold value received in the CONNECTION SETUP REQUEST message 601 from RAN node 620, RAN node 630 may accept the connection setup request by sending a CONNECTION SETUP RESPONSE message 602 to RAN node 620.

[0250] In one example, in case the benefit value computed by RAN node 630 for the Xn connection between RAN node 620 and RAN node 630, is lower than the Xn setup threshold value received in the CONNECTION SETUP REQUEST message 601 from RAN node 620, RAN node 630 may reject the connection setup request by sending a connection failure message to RAN node 620. In such case, the CONNECTION SETUP RESPONSE message 602 may be the XN SETUP FAILURE message, as specified in 3GPP TS 38.423. In one example, RAN node 630 may provide in the connection failure message a failure cause information, which would indicate that the Xn connection benefit value is too low.

[0251] Once the Xn connection setup process between RAN node 620 and RAN node 630 has completed, RAN node 620 may start determining the benefit of maintaining an Xn connection with RAN node 630.

[0252] In one embodiment, RAN node 620 may determine the benefit of maintaining an Xn connection with RAN node 630 by performing the method 1000 of Figure 10.

[0253] In order to perform method 1000 of Figure 10, the RAN node 620 may rely on some measurement reporting received through MEASUREMENT REPORT message 605a issued by a served UE 640, or through MEASUREMENT REPORT message 605b issued by a served WAB- MT in case RAN node 630 is a WAB node.

[0254] In one embodiment, RAN node 620 may determine the benefit of maintaining an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 on a periodic basis.

[0255] In one embodiment, RAN node 620 may determine the benefit of maintaining an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 upon reception of a MEASUREMENT REPORT message 605a indicating whether UE 640 is still in range of RAN node 630. In one example, RAN node 620 may determine the benefit of maintaining an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 upon reception of a plurality of successive MEASUREMENT REPORT messages 605a indicating whether UE 640 is still in range of RAN node 630.

[0256] In one embodiment, RAN node 620 may determine the benefit of maintaining an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 upon reception of a MEASUREMENT REPORT message 605b indicating that RAN node 630 whether UE 640 is still in range of RAN node 620. In one example, RAN node 620 may determine the benefit of maintaining an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 upon reception of a plurality of successive MEASUREMENT REPORT messages 605b indicating that RAN node 630 is in range of RAN node 620. In one embodiment, RAN node 620 may determine the benefit of maintaining an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 when the radio link measurements between the UE 640 and the RAN node 630 in a received MEASUREMENT REPORT message 605a, or in a plurality of successive MEASUREMENT REPORT messages 605a, are below a predefined threshold.

[0257] In one embodiment, RAN node 620 may determine the benefit of maintaining an Xn connection with RAN node 630 by performing the method 1000 of Figure 10 when the radio link measurements between the UE 630 and the RAN node 620 in a received MEASUREMENT REPORT message 605b, or in a plurality of successive MEASUREMENT REPORT messages 605b, are below a predefined threshold.

[0258] If it determines that the benefit of maintaining an Xn connection with RAN node 630 is not sufficient, the RAN node 620 may initiate a connection removal process to remove the Xn connection with the RAN node 630 by sending a CONNECTION REMOVAL REQUEST message 606 to the RAN node 630.

[0259] In one example, this connection setup process may be the Xn Removal procedure, as defined in 3GPP TS 38.423.

[0260] In one example, the CONNECTION REMOVAL REQUEST message 606 may be the XN REMOVAL REQUEST message, as specified in 3GPP TS 38.423.

[0261] The RAN node 630 may further respond to the CONNECTION REMOVAL REQUEST message 606 by sending a CONNECTION REMOVAL RESPONSE message 607 to the RAN node 620.

[0262] In one example, the CONNECTION REMOVAL RESPONSE message 607 may be the XN REMOVAL RESPONSE message, as specified in 3GPP TS 38.423.

[0263] In one embodiment of the invention, the RAN node 620 may add to the CONNECTION REMOVAL REQUEST message 606 some information related to the Xn connection benefit value it previously computed when performing the method 1000 of Figure 10. In one example, RAN node 620 may provide in the CONNECTION REMOVAL REQUEST message 606 a failure cause information, which would indicate that the Xn connection benefit value is too low.

[0264] In one embodiment of the invention, the RAN node 620 may add to the CONNECTION REMOVAL REQUEST message 606 an Xn removal threshold value information.

[0265] In one example, in case the benefit value computed by RAN node 630 for the Xn connection between RAN node 620 and RAN node 630, is lower than the Xn removal threshold value received in the CONNECTION REMOVAL REQUEST message 606 from RAN node 620, RAN node 630 may accept the connection request by sending a CONNECTION REMOVAL RESPONSE message 607 to RAN node 620.

[0266] In one example, in case the benefit value computed by RAN node 630 for the Xn connection between RAN node 620 and RAN node 630, is greater than the Xn removal threshold value received in the CONNECTION REMOVAL REQUEST message 606 from RAN node 620, RAN node 630 may reject the connection removal request by sending a connection failure message to RAN node 620. In such case, the CONNECTION REMOVAL RESPONSE message 602 may be the XN REMOVAL FAILURE message, as specified in 3GPP TS 38.423. In one example, RAN node 630 may provide in the connection failure message a failure cause information, which would indicate that the Xn connection benefit value is sufficient.

[0267] With respect to Xn connection removal for WAB, in case the benefit of maintaining an Xn connection is considered as not sufficient (e.g., Xn link quality is too low, WAB-gNB is moving away, WAB-node authorization status has changed ...) by a WAB-gNB or a BH RAN node or a surrounding NG-RAN node, this WAB-gNB I BH RAN node I surrounding NG-RAN node may initiate the removal of the Xn connection by sending an XN REMOVAL REQUEST message. In such case, a cause value information indicating the reason for initiating the Xn connection removal may be included in the XN REMOVAL REQUEST message. The existing cause value “Action Desirable for Radio Reasons” may be appropriate when the Xn link quality is too low or when the WAB-node is moving away, but a new cause value may be introduced, for instance “WAB not authorized”, when the reason is that the WAB-node authorization has changed.

[0268] Thus, it is proposed that the XN REMOVAL REQUEST message may include a cause value indicating the reason for requesting the Xn connection removal.

[0269] In one example, the Xn setup threshold value information and / or the Xn removal threshold value information may be shared between two RAN nodes, such as RAN node 620 and RAN node 630, when performing the Xn-C TNL address discovery procedure, as defined in 3GPP TS 38.300. In such case, the Xn setup threshold value information and / or the Xn removal threshold value information may be carried by the UPLINK RAN CONFIGURATION TRANSFER message, the DOWNLINK RAN CONFIGURATION TRANSFER message, UPLINK RAN CONFIGURATION TRANSFER message and the DOWNLINK CONFIGURATION TRANSFER message, as defined in 3GPP TS 38.300.

[0270] Referring now also to Figure 7, which is a schematic and simplified diagram 700 illustrating example message flows for use in managing network connectivity in a wireless communication system including at least one Wireless Access Backhaul, WAB, node in accordance with one or more embodiments of the present invention and which may be used for managing Xn connection establishment between a first RAN node and a second RAN node, is shown.

[0271] NG-RAN node 720 may be a Backhaul RAN node, such as BH node 502 of Figure 5, or the gNB component (or part or unit), or WAB-gNB, of a Wireless Access Backhaul, WAB, node, such as WAB node 540 of Figure 5, or any NG-RAN node in the network.

[0272] In one embodiment where RAN node 720 is a WAB node served by BH gNB 710, BH gNB 710 may configure the RAN node 720 so that RAN node 720 may further evaluate the benefit of establishing an Xn connection with some other RAN nodes. BH gNB 710 may configure RAN node 720 by sending a CONFIGURATION message 701 to RAN node 720.

[0273] In one example, the CONFIGURATION message 701 may be the RRCReconfiguration message, as specified in 3GPP TS 38.331.

[0274] In one embodiment where RAN node 720 is a WAB node served by BH gNB 710 or is a BH gNB, a Network entity 730 may configure RAN node 720 so that RAN node 720 may further evaluate the benefit of establishing an Xn connection with some other RAN nodes. Network entity 730 may configure RAN node 720 by sending a CONFIGURATION message 702 to RAN node 720.

[0275] In one example, the CONFIGURATION message 701 may be part of an Operations, Administration and Maintenance (OAM) procedure.

[0276] In one example, the CONFIGURATION message 702 may be the AMF CONFIGURATION UPDATE message or the NG SETUP RESPONSE message, as specified in 3GPP TS 38.413.

[0277] In one example, the BH gNB 710 may include in the CONFIGURATION message 702 some Xn benefit configuration information.

[0278] The Xn benefit configuration information may include at least one of:

[0279] In one embodiment, a Network entity 730 may configure by BH gNB 710 so that by BH gNB 710 may further evaluate the benefit of establishing an Xn connection with some WAB nodes. Network entity 730 may configure BH gNB 710 by sending a CONFIGURATION message 703 to BH gNB 710.

[0280] In one example, the CONFIGURATION message 703 may be the AMF CONFIGURATION UPDATE message or the NG SETUP RESPONSE message, as specified in 3GPP TS 38.413.

[0281] In one example, the CONFIGURATION messages 701 , 702 and 703 may include some Xn benefit configuration information.

[0282] The Xn benefit configuration information may include at least one of:

[0283] Minimum WAB-MT Connectivity Duration threshold, as defined in relation with Figure 10;

[0284] Minimum UE Connectivity Duration threshold, as defined in relation with Figure 10;

[0285] Served UE connectivity ratio threshold, as defined in relation with Figure 10;

[0286] Served UE connectivity threshold, as defined in relation with Figure 10;

[0287] Radio link quality thresholds to be used to determine whether a UE is in range of a RAN node, or whether a RAN node is in range of another RAN node, as discussed in relation with Figure 10. Reference to MWAB node / device, or mobile WAB node / device, throughout the description should be considered to also refer to WAB node / device. Typically, a WAB node may be understood to refer particularly but not exclusively to the node / device being non-mobile, i.e., disposed to a fixed, i.e., static, structure, for example, MWAB node 130 may be considered a WAB node 130 because it is mounted to a building. In most cases, as is understood from the forgoing, mobile may be understood to mean capable of moving, i.e., capable of changing geographical location, and still operating. For example, by being attached to a vehicle or person which is capable of moving.

[0288] While the present invention has been described with reference to examples and embodiments, it is to be understood that the invention is not limited to the disclosed examples and embodiments. It will be appreciated by those skilled in the art that various changes and modification might be made without departing from the scope of the invention, as defined in the appended claims. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

[0289] In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that different features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be advantageously used.

[0290] In the preceding description, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over, as one or more instructions or code, a computer-readable medium and executed by a hardware-based processing unit.

[0291] Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium. By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave may be included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transient media, but are instead directed to non-transient, tangible storage media. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

Claims

1. CLAIMS1. A method for use in managing connectivity of a first Radio Access Network, RAN, node, the method at the first RAN node including: establishing an Xn connection with a second RAN node based on the value of an Xn benefit parameter, the value of the Xn benefit parameter representing a benefit of establishing the Xn connection.

2. The method of claim 1 , wherein the value of the Xn benefit parameter is based on a served user equipment, UE, connectivity parameter, the value of the served UE connectivity parameter being representative of the ability of one or more UEs served by the first RAN node to connect to the second RAN node.

3. The method of claim 2, wherein the ability of the one or more UEs served by the first RAN node to connect to the second RAN node is determined based on a radio link quality between each of the one or more UEs and a cell managed by the second RAN node.

4. The method of claim 2 or claim 3, wherein the value of the served UE connectivity parameter is based on the number of served UEs that are able to connect to the second RAN node, or a ratio of the one or more UEs served by the first RAN node to the one or more UEs served by the first RAN node that are able to connect to the second RAN node.

5. The method of any one of claims 2 to 4, wherein the value of the served UE connectivity parameter is representative of the ability of one or more UEs served by the first RAN node to connect to, and remain connected to, the second RAN node for at least a minimum time period.

6. The method of any one of claims 1 to 5, wherein the first RAN node is a gNB component of a Wireless Access Backhaul, WAB, node comprising a Mobile Termination, MT, component, and the gNB component; wherein the value of the Xn benefit parameter is based on a WAB-MT connectivity parameter, the value of WAB-MT connectivity parameter being representative of the ability of the MT component of the first WAB node to connect to the second RAN node.

7. The method of claim 6, wherein the value of the WAB-MT connectivity parameter is representative of the ability of the MT component of the first WAB node to connect to, and remain connected to, the second RAN node for at least a minimum time period.

8. The method of any one of claims 1 to 7, wherein the value of the Xn benefit parameter is based on an inter-RAN node connectivity parameter, the value of the inter-RAN node connectivityparameter being representative of a link quality between the first RAN node and the second RAN node.

9. The method of any one of claims 1 to 8, wherein the value of the Xn benefit parameter is based on an Xn neighborhood parameter, the value of the Xn neighborhood parameter being representative of the second RAN node being present in a neighborhood of a third RAN node, the third RAN node being connected to the first RAN node via an Xn connection.

10. The method of any one of claims 1 to 9, wherein the value of the Xn benefit parameter is based on a geographical area parameter, the value of the geographical area parameter being representative of the first RAN node and the second RAN node being located in the same geographical area.

11. The method of claim 10, wherein the geographical area is any one of a RAN-based Notification Area, RNA, a Tracking Area, TA, or a group of NR cells.

12. The method of any one of claims 1 to 11 , wherein the value of the Xn benefit parameter is based on a mobility parameter, the value of the mobility parameter being representative of the mobility of the first RAN node.

13. The method of claim 12, wherein the value of the mobility parameter is based on one or more of: a minimum speed capability, an average speed capability, a maximum speed capability, range capability information, static period information indicating a duration of one or more time periods during which the first RAN node is expected to be stationary, and itinerary information indicating a sequence of time periods and further indicating whether the first RAN node is expected to be in motion or stationary during the respective indicated time periods.

14. The method of claim 13, wherein the range capability information comprises one or more of: information indicating an area in which the first RAN node may move, information indicating the size of the area in which the first RAN node may move, a distance that the first RAN node may move, and / or one or more cell Identifiers, IDs, corresponding to one or more cells that the first RAN node may be in range of or has been in range of previously.

15. The method of claim 13 or claim 14, wherein the static period information includes information indicating one or more of: a minimum static period duration, an average static period duration, a maximum static period duration, and / or static position information indicating one or more locations at which the first RAN is expected to be stationary.

16. The method of any one of claims 13 to 15, wherein the itinerary information includes information indicating, for each of the time periods of the sequence of time periods, one or more of: the duration of the time period, the speed of the first RAN node if the first RAN node is expected to be in motion during the time period, and the location at which the first RAN node is expected to be stationary if the first RAN node is expected to be stationary during the time period.

17. The method of any of claims 2 to 16, wherein one or more scoring values corresponding to one or more of the served UE connectivity parameter, the WAB-MT connectivity parameter, the inter-RAN node connectivity parameter, the Xn neighborhood parameter, the geographical area parameter, and the mobility parameter are determined.

18. The method of claim 17, wherein the value of Xn benefit parameter is the average of the determined one or more scoring values.

19. The method of claim 17 or claim 18, wherein a weighting value is associated with each of the determined one or more scoring values.

20. The method of claim 19, wherein the value of the Xn benefit parameter is a weighted average of the determined one or more scoring values, with each of the determined one or more scoring values being weighted according to its associated weighting value.21 . The method of any one of claims 1 to 20, wherein establishing the Xn connection is based on a comparison of the Xn benefit parameter with a predetermined establishment threshold.

22. The method of claim 21 , wherein establishing the Xn connection comprises establishing the Xn connection if the value of the Xn benefit parameter is greater than or equal to the predetermined establishment threshold value.

23. The method claim 21 or claim 21 , wherein establishing the Xn connection comprises establishing the Xn connection if the value of the Xn benefit parameter is greater than or equal to the predetermined establishment threshold value for a minimum time period.

24. The method of any one of claims 21 to 23, wherein the value of the predetermined establishment threshold is set based on a configuration message received at the first RAN node, the configuration message including information specifying any one or more of: a minimum UE connectivity duration; a minimum WAB-MT connectivity duration; a minimum served UE connectivity value;44one or more radio link quality threshold values.

25. The method of any one of claims 21 to 23, wherein the value of the predetermined establishment threshold is set based on establishment threshold information included in a message received at the first RAN node, the message further including a request from the second RAN node to establish an Xn connection with the first RAN node.

26. The method of claim 25, wherein the establishment threshold information includes any one or more of: a minimum UE connectivity duration; a minimum WAB-MT connectivity duration; a minimum served UE connectivity value; one or more radio link quality threshold values.

27. The method of claim 25 or claim 26, further comprising transmitting, based on a comparison between the value of the Xn benefit parameter and the establishment threshold value, a response message to the second RAN node including an indication that the request to establish an Xn connection with the first RAN node is accepted.

28. The method of claim 25 or claim 26, further comprising transmitting, based on a comparison between the value of the Xn benefit parameter and the establishment threshold value, a failure message to the second RAN node including an indication that the request to establish an Xn connection with the first RAN node is rejected.

29. The method of claim 28, wherein the failure message further includes failure cause information, the failure cause information comprising an indication that the value of the Xn benefit parameter is not sufficient.

30. The method of any one of claims 1 to 29, wherein the first RAN node is a gNB component of a first Wireless Access Backhaul, WAB, node comprising a Mobile Termination, MT, component, and the gNB component; and wherein the establishing of an Xn connection with the second RAN node is performed in response to the first WAB node establishing a connection between the MT component of the first WAB node and the second RAN node.31 . The method of any one of claims 1 to 30, wherein the value of the Xn benefit parameter is determined based on one or more messages received from a UE served by the first RAN node and / or, in a case where the second RAN node is a second gNB component of a second WAB node,one or more messages received from an MT component of the second WAB node served by the first RAN node.

32. The method of any one of claims 1 to 31 , wherein the value of the Xn benefit parameter is determined on a periodic basis.

33. The method of any one of claims 1 to 32, wherein the value of the Xn benefit parameter is determined in response to any one or more of: one or more user equipments, UEs, served by the first RAN node being in range of the second RAN node; a quality of a radio link between one or more UEs served by the first RAN node, and the second RAN node, being above a predetermined quality threshold; a quality of the radio link between the first RAN node and the second RAN node being above another predetermined quality threshold; and / or a determination, by the first RAN node, that the first RAN node will be in range of the second RAN node within a period of time.

34. The method of claim 33, wherein the determination, by the first RAN node, that the first RAN node will be in range of the second RAN node within a period of time is based on the current speed of the first RAN node and / or trajectory information of the first and / or second RAN nodes.

35. The method of any one of claims 1 to 34, wherein the first RAN node is a gNB component of a first WAB node, the first WAB node including a mobile termination, MT, component and the gNB component.

36. The method of claim 35 further comprising, prior to establishing the connection, detecting the second RAN node; wherein detecting the second RAN node comprises any one or more of: the MT component of the first WAB node detecting a cell managed by the second RAN node; receiving, from a UE served by the first WAB node, an indication that the UE is in range of the second RAN node; and / or receiving, from a third RAN node, an indication that the second RAN node is in a neighborhood of the third RAN node.

37. The method of any one of claims 1 to 33, wherein the first RAN node is not a gNB component of a WAB node, and the second RAN node is a gNB component of a second WAB node, the second WAB node including a mobile termination, MT, component and the gNB component of the second WAB node.

38. The method of claim 37, further comprising, prior to establishing the connection, detecting the gNB component of the second WAB node; wherein detecting the gNB component of the second WAB node comprises any one or more of: receiving, from a UE served by the first RAN node, an indication that the UE is in range of the second gNB component of the second WAB node; receiving, from a third RAN node, an indication that the second RAN node is in a neighborhood of the third RAN node.

39. The method of claim 1 , wherein the first RAN node is a Backhaul, BH, RAN node.

40. A method for use in managing connectivity of a first Radio Access Network, RAN, node, connected to a second RAN node via an Xn connection, the method at the first RAN node comprising: determining to remove the Xn connection with the second RAN node based on the value of an Xn benefit parameter, the value of the Xn benefit parameter representing a benefit of maintaining the Xn connection.

41. The method of claim 40, wherein the value of the Xn benefit parameter is based on a served user equipment, UE, connectivity parameter, the value of the served UE connectivity parameter being representative of the ability of one or more UEs served by the first RAN node to connect to the second RAN node.

42. The method of claim 41 , wherein the ability of the one or more UEs served by the first RAN node to connect to the second RAN node is determined based on a radio link quality between each of the one or more UEs and a cell managed by the second RAN node.

43. The method of claim 41 or 42, wherein the value of the served UE connectivity parameter is based on the number of served UEs that are able to connect to the second RAN node, or a ratio of the one or more UEs served by the first RAN node to the one or more UEs served by the first RAN node that are able to connect to the second RAN node.

44. The method of any one of claims 41 to 43, wherein the value of the served UE connectivity parameter is representative of the ability of one or more UEs served by the first RAN node to connect to, and remain connected to, the second RAN node for at least a minimum time period.

45. The method of any one of claims 40 to 44, wherein the first RAN node is a gNB component of a first Wireless Access Backhaul, WAB, node comprising a Mobile Termination, MT, component, and the gNB component; wherein the value of the Xn benefit parameter is based on a WAB-MT connectivity parameter, the value of WAB-MT connectivity parameter being representative of the ability of the MT component of the first WAB node to connect to the second RAN node.

46. The method of claim 45, wherein the value of the WAB-MT connectivity parameter is representative of the ability of the MT component of the first WAB node to connect to, and remain connected to, the second RAN node for at least a minimum time period.

47. The method of any one of claims 40 to 46, wherein the value of the Xn benefit parameter is based on an inter-RAN node connectivity parameter, the value of the inter-RAN node connectivity parameter being representative of a link quality between the first RAN node and the second RAN node.

48. The method of any one of claims 40 to 47, wherein the value of the Xn benefit parameter is based on an Xn neighborhood parameter, the value of the Xn neighborhood parameter being representative of the second RAN node being present in a neighborhood of a third RAN node, the third RAN node being connected to the first RAN node via an Xn connection.

49. The method of any one of claims 40 to 48, wherein the value of the Xn benefit parameter is based on a geographical area parameter, the value of the geographical area parameter being representative of the first RAN node and the second RAN node being located in the same geographical area.

50. The method of claim 49, wherein the geographical area is any one of a RAN-based Notification Area, RNA, a Tracking Area, TA, or a group of NR cells.51 . The method of any one of claims 40 to 50, wherein the value of the Xn benefit parameter is based on a mobility parameter, the value of the mobility parameter being representative of the mobility of the first RAN node.

52. The method of claim 51 , wherein the value of the mobility parameter is based on one or more of: a minimum speed capability, an average speed capability, a maximum speed capability, range capability information, static period information indicating a duration of one or more time periods during which the first RAN node is expected to be stationary, and itinerary informationindicating a sequence of time periods and further indicating whether the first RAN node is expected to be in motion or stationary during the respective indicated time periods.

53. The method of claim 52, wherein the range capability information comprises one or more of: information indicating an area in which the first RAN node may move, information indicating the size of the area in which the first RAN node may move, a distance that the first RAN node may move, and / or one or more cell Identifiers, IDs, corresponding to one or more cells that the first RAN node may visit or has visited previously.

54. The method of claim 52 or claim 53, wherein the static period information includes information indicating one or more of: a minimum static period duration, an average static period duration, a maximum static period duration, and / or static position information indicating one or more locations at which the first RAN is expected to be stationary.

55. The method of any one of claims 52 to 54, wherein the itinerary information includes information indicating, for each of the time periods of the sequence of time periods, one or more of: the duration of the time period, the speed of the first RAN node if the first RAN node is expected to be in motion during the time period, and the location at which the first RAN node is expected to be stationary if the first RAN node is expected to be stationary during the time period.

56. The method of any of claims 41 to 55, wherein one or more scoring values corresponding to one or more of the served UE connectivity parameter, the WAB-MT connectivity parameter, the inter-RAN node connectivity parameter, the Xn neighborhood parameter, the geographical area parameter, and the mobility parameter are determined.

57. The method of claim 56, wherein the value of Xn benefit parameter is the average of the determined one or more scoring values.

58. The method of claim 56 or claim 57, wherein a weighting value is associated with each of the determined one or more scoring values.

59. The method of claim 58, wherein the value of the Xn benefit parameter is a weighted average of the determined one or more scoring values, with each of the determined one or more scoring values being weighted according to its associated weighting value.

60. The method of any one of claims 40 to 59, wherein determining to remove the Xn connection to the second RAN node is based on a comparison of the Xn benefit parameter with a predetermined removal threshold.

61. The method of claim 60, wherein determining to remove the Xn connection comprises determining to remove the Xn connection if the value of the Xn benefit parameter is less than the predetermined removal threshold value.

62. The method of claim 60 or claim 61 , wherein determining to remove the Xn connection comprises determining to remove the Xn connection if the value of the Xn benefit parameter is less than the predetermined removal threshold value for a minimum time period.

63. The method of any one of claims 60 to 62, wherein the value of the predetermined removal threshold is set based on a configuration message received at the first RAN node, the configuration message including any one or more of: a minimum UE connectivity duration; a minimum WAB-MT connectivity duration; a minimum served UE connectivity value; one or more radio link quality threshold values.

64. The method of any one of claims 60 to 62, wherein the value of the predetermined removal threshold is set based on removal threshold information included in a message received at the first RAN node, the message further including a request from the second RAN node to remove the Xn connection with the first RAN node.

65. The method of claim 64, wherein the removal threshold information includes any one or more of: a minimum UE connectivity duration; a minimum WAB-MT connectivity duration; a minimum served UE connectivity value; one or more radio link quality threshold values.

65. The method of claim 64 or claim 65, further comprising transmitting, based on a comparison between the value of the Xn benefit parameter and the removal threshold value, a response message to the second RAN node including an indication that the request to remove the Xn connection with the first RAN node is accepted.

65. The method of claim 64 or claim 65, further comprising transmitting, based on a comparison between the value of the Xn benefit parameter and the removal threshold value, a failure message to the second RAN node including an indication that the request to remove the Xn connection with the first RAN node is rejected.

66. The method of claim 65, wherein the failure message further includes failure cause information, the failure cause information comprising an indication that the value of the Xn benefit parameter is sufficient.

67. The method of any one of claims 40 to 66, further comprising receiving a message including a request to remove the Xn connection with the second RAN node, and wherein determining to remove the Xn connection is in response to the received message.

68. The method of claim 67, wherein the message further includes a cause parameter, the cause parameter indicating the reason for requesting to remove the Xn connection.

69. The method of any one of claims 40 to 68, wherein the value of the Xn benefit parameter is determined based on one or more messages received from a UE served by the first RAN node and / or, in a case where the second RAN node is a gNB component of a second WAB node, one or more messages received from an MT component of the second WAB node served by the first RAN node.

70. The method of any one of claims 40 to 69, wherein the value of the Xn benefit parameter is determined on a periodic basis.71 . The method of any one of claims 40 to 70, wherein the value of the Xn benefit parameter is determined in response to any one or more of: one or more user equipments, UEs, served by the first RAN node being out of range of the second RAN node; a quality of a radio link between one or more UEs served by the first RAN node, and the second RAN node, being below a predetermined quality threshold; a quality of the radio link between the first RAN node and the second RAN node being below another predetermined quality threshold; and / or a determination, by the first RAN node, that the first RAN node will be out of range of the second RAN node within a period of time.

72. The method of claim 71 , wherein the determination, by the first RAN node, that the first RAN node will be out of range of the second RAN node within a period of time is based on the current speed of the first RAN node and / or trajectory information of the first and / or second RAN nodes.

73. The method of any one of claims 40 to 72, wherein the first RAN node is a gNB component of a first wireless access backhaul, WAB, node, the first WAB node including a mobile termination, MT, component and the gNB component.

74. The method of any one of claims 40 to 72, wherein the first RAN node is not a WAB node, and the second RAN node is a second WAB node, the second WAB node including a mobile termination, MT, component and a gNB component.

75. The method of claim 40, wherein the first RAN node is a Backhaul, BH, RAN node.

76. A computer program comprising instructions which, when the program is executed by at least one processor unit, cause the at least one processing unit to carry out the method according to any one of claims 1 to 75.

77. A computer-readable medium carrying a computer program according to claim 76.

78. An apparatus for a Radio Access Network, RAN, node, the apparatus comprising one or more processing units configured to perform the method as recited in any one of claims 1 to 75.52

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