Method for operating user equipment using a cellular network base station

Abstract

The present invention relates to a method for operating a user equipment together with a base station, the base station being assigned to at least two core networks in a coexistence mode of a cellular network, the user equipment operating in a data communication mode with direct connection termination in the at least one core network, the method comprising the following steps for the user equipment: - camping on a base station having access rights to at least two core networks of different technical standards, - receiving from the base station a transmission indicating available radio resources of a first and a second core network, - selecting a core network appropriate for the envisaged connection, - sending to the base station a connection request for the envisaged connection using a portion of the indicated radio resources belonging to the selected core network, - receiving a response indication from the base station.

Description

Technical Field

[0001] The present invention relates to a method for operating a user equipment and also to a user equipment using said method.

[0002] The present invention further relates to a method for a base station to operate said user equipment. The present invention additionally relates to a base station using said method. Background Art

[0003] Generally, in the field of wireless cellular communications, it is known that user equipment is operating with one of a plurality of base stations with a cellular network. In the case of coexistence of multiple radio access networks for the corresponding cellular technology standard generations such as 2G (GSM), 3G (UMTS), 4G (LTE) today, user equipment accesses one of these radio access networks by camping on a base station assigned to the radio access network. The base station for 2G is called a base station (BS), the base station for 3G is called a nodeB, and the base station for 4G is called an eNodeB, and the base station for 5G is called a gNodeB. Depending on the various generations, the term base station covers various types of base stations.

[0004] However, in the advent of the next generation 5G (New Radio), it is foreseen that it is possible for one base station to access at least two radio access networks. This is due to the fact that the flavor of LTE, in particular for machine-type communications or IoT devices, is also backward compatible for 5G. This means that a user equipment capable of using the LTE variant LTE Cat Nb-IoT can access both a 4G eNodeB and a 5G gNodeB without changing the air interface protocol, both of which provide a common NB-IoT configuration on the air interface, in particular for the physical layer and the related lower level signaling of traditional user equipment. In addition, a base station can have access to one or two core networks. The problem is therefore that it is not unambiguously clear whether a user equipment is currently operating on 4G or 5G.

[0005] Furthermore, the issue is important because in the case of LTE Cat NB-IoT (short: NB-IoT), when the user equipment is using the so-called C-IoT optimization (Control Plane IoT Optimization), the access terminates its connection in the core network. C-IoT optimization means that the user data is encapsulated in a NAS bearer that terminates in the core network - respectively the MME in 4G and the AMF in 5G - while the network architecture for operating NB-IoT in 5G does not yet exist in detail. Therefore, the user equipment needs to have a means to select the core network it wants to access. This is particularly important when special services or slices (in 5G) are desired that are only provided by one of the available core networks.

[0006] In addition, the following situation may occur: due to special business reasons, it is expected that non-IP data such as non-IP data is contacted to 4G MME via NAS (C-IoT), and the 4G MME forwards the data to the corresponding SCEF (Service Control Exposure Function).

[0007] The same situation may apply to future generations.

[0008] Therefore, a solution is needed for ensuring that user equipment also gets access to the desired core network for NB-IoT. Therefore, further alternative and advantageous solutions would be desirable in the art. Summary of the invention

[0009] To this end, according to a first aspect of the present invention, a method for operating a user equipment is proposed. According to a second aspect of the present invention, a user equipment is further proposed.

[0010] According to a third aspect of the present invention, a method for operating a base station is proposed. According to a fourth aspect of the present invention, a base station is further proposed.

[0011] According to a first aspect of the invention, a method is proposed for operating a user equipment with a base station, the base station being assigned to at least two core networks in a coexistence mode of a cellular network, the user equipment operating in a data communication mode with direct connection termination in the at least one core network,

[0012] The method comprises the following steps for a user equipment:

[0013] - camping on a base station having access to at least two core networks of different technical standards,

[0014] - receiving a transmission from said base station indicating available radio resources of the first and second core networks,

[0015] - selecting an appropriate core network for the envisaged connection,

[0016] - sending a connection request for the envisaged connection to a base station using said indicated portion of radio resources belonging to the selected core network,

[0017] - Receive a response indication from the base station.

[0018] The method of the present invention relates to a user equipment capable of operating with a base station of a cellular network for wireless communications, particularly those cellular networks implementing 4G (LTE), 5G (New Radio) or higher wireless technology standards.

[0019] The method of the invention relates to such user equipment operating in a data communication mode with direct connection termination. This is particularly the case for LTE category NB-IoT (Narrowband Internet of Things), but may also be other modes, for example future modes of 5G or higher.

[0020] By providing a narrowband communication category, NB-IoT is foreseen to allow low-capability user equipment to access cellular networks. This is specifically called the category narrowband IoT, which consists in, for the assigned frequency band, accessing only a narrow subband, which in particular operates with another coding scheme than the rest of the assigned frequency band. This helps low-capability user equipment to communicate with base stations of the latest generation of cellular networks, preferably in both uplink and downlink, with much less effort in terms of processing power. It has been decided to maintain this category also for 5G. However, the present invention is not limited to 4G or 5G NB-IoT.

[0021] For NB-IoT in particular, the defining characteristic is that it terminates directly in the respective core network. The base stations involved act only as a passive air interface and make no decisions about routing received data.

[0022] The core network of a cellular network comprises cellular network components for ensuring connectivity between user equipments, either operating in the same cellular network or in different cellular networks, or establishing access to remote servers, in particular via the Internet. The core network typically comprises core components, servers and gateways, which include the Home Location Register (HLR) and other entities required for authentication and allow access and resource usage of user equipments in a specific cellular network of a specific cellular network operator. The communication of user equipments to the core network is called NAS (Non-Access Stratum), while the user equipment AS (Access Stratum) communication is terminated in the base station, i.e. the radio.

[0023] In other words, the core network is the entity to which the user equipment approaches using NAS signaling (in 4G EPC bearers) if needed, whereas the AS signaling (radio bearers / radio protocols) terminates in the eNodeB.

[0024] For 5G, the core network, or at least the main part of it, is called the 5G Next-Generation Core, and for 4G it is called the Evolved Packet Core.

[0025] In the case of a base station having access to at least two core networks of different technical standards, the user equipment will therefore have to decide which core network to access.

[0026] This is where the present invention comes in. It proposes an inventive method for the user equipment to implement the decision and the subsequent access to the corresponding core network.

[0027] The method of the invention starts when a user equipment is camped on a base station having access rights to at least two core networks of different technical standards. When the user equipment receives a transmission from the base station indicating available radio resources of the two core networks, the user equipment is informed of the latest situation.

[0028] Such radio resources are preferably dedicated in the time domain or frequency domain or in a new format, in particular for accessing the 5G core. In any case, for the user equipment, it is detectable which radio resources belong to which core network. So far, resources are assigned and can be indicated to the NB-IoT assumed to be used for accessing the system depending on the RSRP level, i.e., the reception level corresponding to a certain resource class. So far, this is defined as rsrp-ThresholdsPrachInfoList and provided as part of the broadcast system information (SIB).

[0029] Standard NB-IoT user equipment in Coverage Enhancement (CE) to select PRACH resources set to RSRP threshold 3 is signaled to determine the CE level of PRACH, see TS 36.213. The first element corresponds to RSRP threshold 1, the second element corresponds to RSRP threshold 2, and so on, see TS 36.321 [6].

[0030] In addition to the resources that can be used by NB-IoT user equipment to access the system depending on the RSRP level, a second set of resources is preferably introduced that indicates the resources used to access the new core network. In this regard, user equipment supporting both core networks is in a position to decide which one to access, and legacy user equipment can access directly by using the resources indicated in the rsrp-ThresholdsPrachInfoList in SIB2. The list for accessing the new core network can be defined as NextGenCore-rsrp-ThresholdsPrachInfoList in another SIB.

[0031] The information will be delivered to the user equipment in the PRACH configuration system information broadcast or in the corresponding extended container of the system information.

[0032] As a next step, the user equipment is foreseen to select radio resources belonging to the core network to which the user equipment is assumed to access. To make the selection, the user equipment respectively evaluates which of the core networks, whose resources are suitable for the envisaged connection, in particular the planned transmission or reception of data packets.

[0033] The selection may be driven in advance or in response to radio resource information received from the base station.With this, the user equipment has a means of determining whether the core network is suitable - meaning that it meets the requirements of the envisaged connection.

[0034] In a first embodiment, it is proposed that the selection of a core network includes considering the availability of core network capabilities.

[0035] This advantageous embodiment relates to pre-configuration of user equipment.

[0036] It considers at least one requirement that the user equipment has with respect to the selected core network for the selection of the core network. This is in particular provided by pre-configuration of the user equipment. Thus, when the user equipment is, for example, trying to access a certain desired, pre-configured service, such a service needs to be supported by the selected core network in order to be appropriately rated for it.

[0037] Therefore, it is necessary to determine the core network capabilities. To this end, the base station provides information related to such core network capabilities. As an advantageous example of 5G, such a capability is particularly called slice discovery. With this, the user equipment determines which slices and therefore which services are available. Network slicing is a type of virtual networking architecture introduced for 5G, which allows a virtual end-to-end network to be customized for a certain application or service requirement. Preferably, in order not to affect the stability of the entire network with a certain highly occupied slice, different components are involved.

[0038] Alternatively, as further indicated above, the user equipment will receive rsrp-ThresholdsPrachInfoList via specified information related to performing RACH access on the cell from the base station, in particular the element PRACH-ConfigSIB and IE PRACH-Config for specifying the PRACH configuration in the system information, or, in the case where the 5G next generation core is also directly reachable for the NB-IoT device, also receive NextGenCore-rsrp-ThresholdsPrachInfoList.

[0039] Therefore, the user equipment can select or discard the available core networks at the base station.

[0040] According to a preferred embodiment, the core network capability is at least one of the following:

[0041] - Network sharding,

[0042] - Network services,

[0043] - expected power savings,

[0044] - desired QoS,

[0045] - special forms of communication,

[0046] -Roaming standards.

[0047] Network slicing - and corresponding network services - are available in particular via 5G networks, but may also be available in future networks.

[0048] The desired power saving involves network capabilities that provide the possibility to avoid signaling efforts, such as entering sleep modes like eDRX and the like.

[0049] In the case of expected QoS, it means a specific quality of service expected by the user equipment. The quality of service is defined in particular by attributes like availability, transmission delay, bandwidth, etc. It is usually expressed by traffic classes. The network is capable of providing a certain QoS, and when it does not adequately meet the user equipment requirements, it must decide whether another core network is more appropriate.

[0050] With special forms of communication, it is particularly foreseen that IP or non-IP network services are involved. The latter particularly involves certain types of non-IP network capabilities that terminate in MME to SCEF, which is now only available for 4G. In order to send data to applications, two optimizations of Cellular Internet of Things (CIoT) in Evolved Packet System (EPS) are defined - user plane CIoT EPS optimization and control plane CIoT EPS optimization. In general, NIDD / non-IP data is part of CIoT EPS optimization. PDN type "non-IP" is used for non-IP data. Non-IP data delivery via the control plane is done with the help of SCEF. By selecting PDN type non-IP, MME understands that this is non-IP data and forwards the relevant packets to SCEF. SCEF has relevant information or can retrieve information related to the recipient of the information from the home location register. SCEF uses this knowledge and then routes the packets accordingly. Simply put, it means that SCEF converts data suitable for routing in the core network. The advantage of this method is that the user equipment does not need to send a 40-byte IP header IPv6, and thus saves payload and power. SCEF adds the corresponding information to the data packet.

[0051] In the case of roaming standards, this means the situation where the user equipment is operating in the visited network and therefore needs to determine whether it can access a certain service - the corresponding slice. This means that the visited PLMN can accept NB-IoT user equipment via NB-IoT radio access, whether provided from a 4G or 5G base station, however, the core network behind may only accept roaming users of the traditional 4G core, where PLMN interworking has been established and provided. In addition, access to the slice may be limited to the operator's own user equipment or user equipment registered for an equivalent PLMN but without roaming users.

[0052] The selection of a core network may additionally be based on the availability of the respective core networks.

[0053] This comprises in particular in a first embodiment receiving a message from said base station indicating a high occupancy of one of said core networks and taking said occupancy indication into account for the step of selecting a core network.

[0054] This information indicates to the user equipment that the corresponding core network is already highly occupied and that the amount of resources potentially used for the pending connection session is not at hand. Such information is made available in particular with a transmission indicating available radio resources. In this sense, a core network that may not be accessed or hardly accessed is considered inappropriate for the user equipment.

[0055] Additionally, in another embodiment, a step of receiving a message from said base station indicating a blocking of one of said core networks and taking said blocking indication into account for selecting a core network is particularly foreseen.

[0056] This information indicates to the user equipment that the corresponding core network, in particular for the type of user equipment to which it belongs, is blocked.

[0057] The blocking is usually indicated by system information, in particular in SIB1. In case of device specific system information, in particular machine type (M-SIB), for user equipment belonging to that device type, (selective) blocking is applicable. This is particularly useful when many IoT devices try to access the network at the same time due to unfavorable signaling cycles.

[0058] Clearly, upon receipt of one of such messages, the user equipment will refrain from accessing the indicated core network. A blocked core network is deemed inappropriate for the user equipment.

[0059] This embodiment is particularly advantageous because it allows the user equipment, in the event that such a message is received from the core network to which it originally planned to access, to decide ad hoc if it makes sense to select the resources of another network, regardless of its original plan. The user equipment may prefer to at least use the available services at another core network to avoid having no connection at all, as long as the other core network can support the desired service or any similar service at all.

[0060] This is particularly comprised in the prioritization of user equipment's requirements to available core networks. Such prioritization governs in particular whether a connection to a core network can be requested when a certain requirement is not available at the core network.

[0061] Once the selection has been made, the user equipment according to the method of the invention sends a connection request to the base station, the connection request indicating the desired radio resources. With this indication, the base station forwards the request via the radio resources to the corresponding core network depicted.

[0062] When the connection request is successful, the user equipment then expects to receive a response indication from the base station, information about the status of the connection request, in particular whether the connection has been established or rejected.

[0063] In a preferred embodiment, it is proposed that for a user equipment operating non-stationary and capable of selecting a new serving base station in case of detecting a radio link failure of the communication with the previous serving base station, the method further comprises the following steps:

[0064] -Select the new base station,

[0065] - Sending a connection request to the new base station indicating that the core network is operating with the previous serving base station.

[0066] This embodiment mainly relates to mobile user equipment. As is known, many NB-IoT user equipment are fixedly installed, for example as electricity meters, as part of vending machines, etc. In this sense, fixed means non-mobile, at least for the foreseeable time. Nevertheless, it may happen that the NB-IoT user equipment is moving and therefore needs to be handed over from one base station to another.

[0067] To reduce overhead and within the expectations of user equipment with primarily fixed operations, the mobility handling of NB-IoT is greatly reduced compared to normal operation, especially for mobile phones.

[0068] As a result, handover / reselection is replaced by a simple detection of a radio link failure (RLF) on the current serving base station. Once this occurs, the user equipment searches for the most suitable base station and attempts to continue operation.

[0069] Since time and uninterrupted connection are not the top priorities for NB-IoT user equipment, this is decided to have a low impact, but save a lot of power and resources. However, for the problem solved by the present invention, it presents the following difficulty: when operating with the core network once selected on the first base station and then accessing the next base station, there is a need to ensure that the user equipment selects, and in particular is allowed to select, the same core network as it used before. Although NB-IoT mobility is based on radio link failure, that is, maintaining the connection until it is disconnected, establishing a new connection and requesting to retrieve the communication session from the previous base station, the communication session is kept uninterrupted in this way, that is, the transmission can be completed. Now there is not only a base station from which to retrieve the communication session, but also information related to the previously used core network with the following correlation: that is, accessing the same core for the continuity of the communication session. This is particularly relevant when the core network will not allow the new user equipment to establish a new connection due to lack of free resources.

[0070] To solve this problem, the preferred embodiment proposes that the user equipment indicates with a connection request to a new base station that it is active on a certain core network to a previous serving base station.

[0071] For this purpose, the UE uses resources on the radio associated with the previously used core network on the new base station, if provided.

[0072] In more advanced cases, corresponding indications may also be included, which may however cause additional signaling load and bring only limited benefit, especially when relying on the fact that a newly accessed user equipment will follow the corresponding overload indication and not select the corresponding core if not absolutely necessary, i.e. it already had a connection to said core network earlier and the communication session has not yet ended.

[0073] It is envisaged that the core network then assigns the resources previously allocated to the user equipment to the user equipment also via the new base station.

[0074] This ensures that the desired core network is selected again and furthermore the user equipment can continue to access the core network even though it will appear fully occupied to new connection requests.

[0075] For the core network, this embodiment has the following advantages: when terminating a communication session, the previously reserved resources are then used by the user equipment and potentially released regularly. Compared to the proposed embodiment, in the case of a radio link failure, no such regular termination occurs and the assigned resources are available to other user equipment only much later with a high probability.

[0076] According to a second aspect of the present invention, a user equipment is proposed for operating in a coexistence mode of a cellular network with a base station assigned to at least two core networks, the user equipment operating in a mode with direct connection termination in at least one core network, wherein the user equipment is configured to:

[0077] - camping on a base station having access to at least two core networks of different standards,

[0078] - receiving from said base station a transmission indicating resources of the first and second core networks,

[0079] - selecting an appropriate core network for the envisaged connection,

[0080] - sending a connection request for the envisaged connection to a base station comprising said indicated resources belonging to the selected core network.

[0081] The user equipment provides several components for conducting wireless communications. This includes at least processing circuits for executing operating software, in particular those processing circuits implementing the method of the first aspect of the invention.

[0082] Furthermore, the user equipment comprises transmitting and receiving circuits connected to at least one antenna, typically a transceiver for exchanging wireless communication signals with a base station of a cellular network. Furthermore, a memory unit for volatile and / or permanent storage of executable software, configuration data and measurement data, for example before receiving a transmission from a serving base station.

[0083] The second aspect of the present invention shares the advantages of the first aspect of the present invention.

[0084] According to a third aspect of the present invention, a method for operating a base station assigned to at least two core networks in a coexistence mode of a cellular network is proposed, thereby providing at least one user equipment camped on the base station with direct connection terminating access to one of the core networks, the method comprising the following steps:

[0085] - sending a resource indication transmission to at least one of the resident user equipments, wherein the resource indication transmission indicates available resources of at least two of the at least two core networks,

[0086] - receiving a connection request including an indication of resources of a selected core network,

[0087] - establishing a connection with the selected core network, including indicating the selected resources to the selected core network,

[0088] - Sending a connection setup indication to the requesting user equipment.

[0089] This aspect of the invention relates to a base station as a counterpart on the air interface of a user equipment according to the second aspect of the invention for achieving the proposed problem.Thus, in order to solve the proposed problem, it is expected that the base station also supports the user equipment in its efforts.

[0090] A base station is one of multiple base stations of a cellular network and is configured to implement the technical standards of 4G or 5G. In addition, it is capable of operating in the narrowband communication category, which is NB-IoT.

[0091] Since NB-IoT is a continuation of 5G, user equipment operating in NB-IoT may reside on a 5G or 4G base station. Therefore, one base station has access to the core components of the cellular network that supports 4G and 5G in parallel or any other combination. The base station therefore has communication connections to at least two core networks. Such communication connections are usually wired connections.

[0092] Usually the base station not only supports NB-IoT, but also supports other categories of 4G, corresponding 5G or higher versions.

[0093] However, for NB-IoT access to a specific core network, the user equipment does not make the decision of which core network to access. However, it performs steps to support the user equipment by making this decision and implementing it.

[0094] This is accomplished by sending a resource indication transmission to the user equipment served by the base station in question. The resource indication transmission comprises at least two resource indications accessible to the core network.

[0095] When the base station receives a connection request message from a resident user equipment containing a resource indication, it is up to the base station to decide to which core network it will perform the connection setup. The connection request message typically comprises an indication of a communication endpoint, in particular a server URL or any other type of indication.

[0096] The base station preferably takes defined steps for setting up a connection for the user equipment and reserves selected resources at the core network from which the resources originated.

[0097] When this is successfully carried out, the base station sends a connection setup indication to the requesting user equipment, which then operates accordingly in a connected mode to the depicted communication endpoint through the selected core network.

[0098] Otherwise, a connection rejection indication is sent to the user equipment.

[0099] Such a rejection is sent in particular in the event of a high occupancy rate of the corresponding core network.

[0100] This is the case when one or all accessible core networks have reached a given occupancy level as determined by the base station in conjunction with the core networks.

[0101] By this, the user equipment is informed of the shortage of resources in the accessible core network. This is advantageous because it helps the user equipment to consider delaying the data transmission to another point in time. Preferably, the user equipment has means for adjusting the data transmission schedule, for example for metering applications. When it is found that the desired core network is usually occupied at a certain predefined time, which is indicated by the rejection message, the user equipment can adjust its transmission schedule to a later time.

[0102] According to another preferred embodiment, it is proposed that the base station is further configured to retrieve a connection request from a user equipment having a selected core network, the method comprising the following steps:

[0103] - determining whether the user equipment has previously operated with a neighboring base station in said selected core network,

[0104] - Allowing access to the selected core network regardless of occupancy level.

[0105] This embodiment supports mobility of user equipment. It involves a base station receiving a connection request from a user equipment that it has not previously served. Therefore, if a core network indicates full occupancy, it will typically be necessary to reject a user equipment connection request to the core network.

[0106] This is not the case when a user equipment, in particular a non-fixed (that means mobile) user equipment sets up its connection on another base station, in particular a neighbouring base station. As indicated above, in this set-up process the neighbouring base station supports the user equipment in deciding which accessible core network to set up the connection to.

[0107] When the user equipment is moving towards the base station in question it will request the base station to access the core network.To ensure that no rejection occurs, in particular due to resource unavailability, the base station receives an indication that the user equipment has previously operated with a neighbouring base station in said selected core network.

[0108] This gives a sufficient indication that the user equipment has been connected previously. Therefore, the occupancy level of the core network can be ignored in order to set up and accordingly continue the connection via the new serving base station.

[0109] This is an important step because for NB-IoT, common mobility measures, especially handover, are not supported. Therefore, when a radio link failure of the base station previously camped on is detected, the mobile user equipment performs a handover to another base station.

[0110] According to a fourth aspect of the present invention, there is proposed a base station of a cellular network assigned to at least two core networks in a coexistence mode of the cellular networks, thereby providing at least one user equipment camped on the base station with direct connection terminating access to one of the core networks,

[0111] The base station is configured as:

[0112] - sending a resource indication transmission to at least one of the resident user equipments, wherein the resource indication transmission indicates available resources of at least two of the at least two core networks,

[0113] - receiving a connection request including an indication of resources of a selected core network,

[0114] - establishing a connection with the selected core network, including indicating the selected resources to the selected core network,

[0115] - Sending a connection setup indication to the requesting user equipment.

[0116] The base station according to this aspect of the invention comprises receiving and transmitting circuits and at least one antenna. It is further communicatively coupled to at least two core networks of different technical standards. In addition, it comprises processing circuits for controlling the operation of the base station. Additionally, it comprises volatile and / or permanent memory at least for storing configuration and operating software.

[0117] The base station according to this aspect of the invention shares the advantages of the third aspect of the invention.

[0118] As shown, the present invention advantageously solves the depicted problem and proposes a solution in which user equipment and base stations operate in a manner that matches the new cellular network topology without investing too much additional effort on the user equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0119] The following description and drawings set forth certain illustrative aspects in detail and are indicative of only a few of the various ways in which the principles of the embodiments may be employed. The characteristics and advantages of the present invention will become apparent when reading the following description and drawings of advantageous embodiments given as illustrative and non-limiting examples.

[0120] Figure 1 represents a user equipment of the type to which the present invention is applied as an embodiment in combination with a base station according to the fourth aspect of the present invention;

[0121] Figure 2 A sequence diagram showing a preferred embodiment of the method of the present invention;

[0122] Figure 3 In another exemplary embodiment, a user equipment is shown that operates non-stationarily with two base stations.

[0123] Figure 1 A user equipment UE of the type to which the present invention is applied as an embodiment is schematically shown. The user equipment UE is residing on a base station eNB supporting the NB-IoT category. Therefore, the base station eNB according to this embodiment can be a 4G or 5G base station, because NB-IoT is at least backward compatible with both technical standards defined.

[0124] The base station is connected to at least two core networks - in this case, a core network CON1 supporting 5G (New Radio) and a core network CON2 supporting 4G (LTE). The core networks of the corresponding technical standards are called 4G Evolved Packet Core (EPC) and 5G Next Generation Core.

[0125] Each core network provides different capabilities. For example, the 5G core network CON1 may have the capability to support certain slices, for example, for ultra-reliable communication or dedicated to machine-type communication.

[0126] However, in the case of a user equipment UE operating in NB-IoT together with a base station eNB, it is the case that the connection is terminated directly in the core network. Therefore, in the scenario shown, the user equipment UE needs to make a selection decision to which core network it wants to connect to.

[0127] To do this, Figure 2 The method of the present invention is illustrated in the exemplary embodiment of FIG. This is a sequence diagram showing the main steps of the exemplary embodiment.

[0128] The sequence starts with the user equipment UE camping on the base station eNB with a message M1. This is usually done based on measurements by the user equipment UE to find the best suitable base station.

[0129] The step of camping may usually take more sub-steps, including activities from the base station, but for simplicity, it is depicted with one message M1. At this point, the user equipment is expected to camp on the base station eNB in ​​idle mode, i.e. no connection is established. It is assumed that both the user equipment and the base station communicate in the category NB-IoT.

[0130] The base station has access to two core networks CON1 (5G, next generation core) and CON2 (LTE, EPC).

[0131] When camped on a base station, the user equipment monitors the broadcast signals from the base station eNB.One of the broadcast transmissions M2 comprises an indication of available resources at both the core network CON1 and the core network CON2.

[0132] Two results are shown below. In the first option with message M3, the user equipment sends a connection request including the selected resources indicated in the broadcast of message M2. With this option, the user equipment indicates to the base station to which core network it wants to establish a connection. In the first option, this is the 5G core network CON1, so the base station forwards the connection request directly to the core network with message M4. Specific core network components are usually designated to handle such requests.

[0133] With message M5, the core network responds to the requesting user equipment via the base station with a connection setup message or a connection rejection.Technically, the user equipment receives the message transmitted from the base station, but is directly triggered by the core network CON1.

[0134] In another alternative (below the dashed line), the resources selected by the user equipment with the connection request message M6 belong to the core network CON2, in this example LTE. Therefore, the base station eNB forwards the request to the core network CON2 with a message M7. In a response message M8, the user equipment is informed whether the connection can be established.

[0135] The choice of the two options is driven by the question of which core networks are appropriate for the envisaged connection. This takes into account in particular the availability and capabilities of the respective core networks. If a core network is blocked, then at least for NB-IoT user equipment, the user equipment will most likely choose another core network. However, if it is appropriate to require that it has a high priority, this means that only core networks that provide the capabilities to support the respective requirements will be selected. In extreme cases, this may mean selecting none.

[0136] This applies in particular, for example, when the 5G core network includes a remote provisioning slice that unprovisioned user equipment can access. However, if the 5G core network is blocked, the user equipment will not access the 4G core network, which does not have anything like that available.

[0137] If the connection setup is successful after message M5 or M8, the user equipment is operating in connected mode with the respective core network.Now, data transmission is possible in both uplink and downlink directions, in particular to a remote server accessible via the respective core network.

[0138] The exemplary embodiment shown relates to the initial setup of a connection. It shows in what sense a base station is involved (which is primarily a data pipe), a decision is made at the user equipment addressed by the core network, and if a connection is established, a decision is made at the corresponding core network.

[0139] use Figure 3, in another exemplary embodiment, subsequent communications after a connection is established are shown. For the case of a fixed user equipment that does not move, once a connection is established, it may be advantageous to stay on the base station where it originally resides.

[0140] However, if Figure 3 The user equipment UE shown in is in non-stationary operation, which means that it is moving. In the example shown, after camping on the base station eNB1 and setting up a connection with a selected one of the core networks CON1, CON2 at time t1, the user equipment UE moves away from the base station eNB1.

[0141] At time t2, it is found that the signal reception from the base station eNB1 is so poor that a radio link failure (RLF) occurs. This indicates to the user equipment UE operating in NB-IoT that it cannot continue to operate with the current serving base station.

[0142] Therefore, the user equipment UE selects a more suitable base station, in this case the base station eNB2.

[0143] The base station eNB2 also has access to both core networks CON1 and CON2. The user equipment therefore receives a broadcast from the base station eNB2 which resources of the two core networks are available. It then sends a connection request with the selected resources to the base station.

[0144] There may be a situation where the selected core network is fully occupied at the same time, at least for NB-IoT user equipment. Since the user equipment UE simply wants to continue the existing connection with the new base station eNB2 established via the base station eNB1, the user equipment sends an indication to the base station together with the connection request informing that a connection is in place. Therefore, the addressed core network can therefore decide to continue the connection with the user equipment.

[0145] With this embodiment, it is ensured that a persistent connection for the NB-IoT user equipment UE is ensured. Once a connection is in place, it will generally be privileged compared to user equipment that wants to establish a new connection. This is solved with this embodiment of the method of the invention.

[0146] In the above detailed description, reference is made to the accompanying drawings, which illustrate by way of illustration specific embodiments in which the present invention can be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention. It is to be understood that the various embodiments of the present invention, although different, are not necessarily mutually exclusive. For example, without departing from the scope of the present invention, the specific features, structures or characteristics described herein in conjunction with one embodiment may be implemented in other embodiments. In addition, it is to be understood that the position or arrangement of the various elements in each disclosed embodiment may be modified without departing from the scope of the present invention. Therefore, the above detailed description should not be considered in a restrictive sense, and the scope of the present invention is limited only by the appended claims properly interpreted together with the full scope of equivalents given by the claims.

Claims

1. A method for operating a user equipment (UE) with a base station (eNB), the base station (eNB) being assigned to at least two core networks (CON1, CON2) in a cellular network (CN) coexistence mode, the user equipment operating in a data communication mode with direct connection termination in at least one core network, The method comprises the following steps for a user equipment (UE): - resides on a base station (eNB) having access to at least two core networks (CON1, CON2) of different technical standards, - receiving from said base station (eNB) a transmission indicating available radio resources of the first and second core networks (CON1, CON2), - select the appropriate core network (CON1) for the envisaged connection, - sending a connection request for the envisaged connection to the base station (eNB) using said indicated portion of radio resources belonging to the selected core network (CON1), - receiving a response indication from a base station (eNB), in, For a user equipment (UE) that is mobile in operation and is able to select a new serving base station (eNB2) upon detecting a radio link failure for communication with a previous serving base station (eNB1), the method further comprises the steps of: -Select the new base station (eNB2), - Sending a connection request to the new base station (eNB2), the connection request indicating that the core network (CON1, CON2) is operating with the previous serving base station.

2. The method according to claim 1, The selection of the core network (CON1, CON2) includes consideration of the availability of the core network capabilities.

3. The method according to claim 2, The core network capability is at least one of the following: - Network sharding, - Network services, - expected power savings, - desired QoS, - special forms of communication, -Roaming standards.

4. The method according to claim 1, further The following steps are involved: receiving a message from the base station (eNB) indicating high occupancy of one of the core networks (CON1, CON2), and taking into account said indication of high occupancy for the step of selecting a core network.

5. The method according to one of claims 1 to 3, further comprising the method step of receiving a message from said base station (eNB) indicating blocking of one of said core networks (CON1, CON2), and considering said indication of blocking for the step of selecting a core network.

6. A user equipment (UE) for operating in a coexistence mode of a cellular network (CN) with a base station (eNB) assigned to at least two core networks (CON1, CON2), the user equipment (UE) operating in a mode with direct connection termination in at least one core network, in, The user equipment (UE) is configured to: - resides on a base station (eNB) having access to at least two core networks (CON1, CON2) of different standards, - receiving from said base station (eNB) a transmission indicating resources of the first and second core networks (CON1, CON2), - select the appropriate core network for the envisaged connection, - sending a connection request for the envisaged connection to a base station comprising said indicated resources belonging to the selected core network, wherein the user equipment (UE) is further mobile operated and is configured to select a new serving base station (eNB2) upon detecting a radio link failure associated with communications with a previous serving base station (eNB1), and The user equipment (UE) is configured as -Select the new base station (eNB2), - Send a connection request to the new base station (eNB2), indicating that the core network (CON1, CON2) is being used with the previous serving base station (eNB1).

7. The user equipment (UE) according to claim 6, is further configured to receive a message from said base station (eNB) indicating a high occupancy of one of said core networks (CON1, CON2), and taking into account said indication of high occupancy for the step of selecting a core network.

8. A method for operating a base station (eNB) assigned to at least two core networks (CON1, CON2) in a cellular network (CN) coexistence mode, thereby providing at least one user equipment (UE) camped on the base station (eNB) with direct connection terminating access to one of the core networks, The method The following steps are involved: - sending a resource indication transmission to at least one of the resident user equipments (UEs), wherein the resource indication transmission indicates available resources of at least two of the at least two core networks (CON1, CON2), - receiving a connection request including an indication of resources of a selected core network, - establishing a connection with the selected core network, including indicating the selected resources to the selected core network, - sending a connection setup indication to the requesting user equipment (UE), wherein the base station (eNB) is further configured to retrieve a connection request to the selected core network from a user equipment (UE), The method comprises the following steps: - determining whether the user equipment (UE) has previously operated with a neighboring base station (eNB1) in said selected core network, - Allowing access to the selected core network regardless of occupancy level.

9. The method according to claim 8, further comprising the step of determining whether a given occupancy level is reached for at least one of the core networks (CON1, CON2), In response, a high occupancy message is sent to at least one user equipment (UE).

10. A base station (eNB) of a cellular network (CN) assigned to at least two core networks (CON1, CON2) in a coexistence mode of the cellular networks, thereby providing at least one user equipment (UE) camped on the base station (eNB) with direct connection terminating access to one of the core networks, The base station is configured as: - sending a resource indication transmission to at least one of the resident user equipments (UEs), in, The resource indication transmission indicates available resources of at least two of the at least two core networks (CON1, CON2), - receiving a connection request including an indication of resources of a selected core network, - establishing a connection with the selected core network, including indicating the selected resources to the selected core network, - sending a connection setup indication to the requesting user equipment (UE), wherein the base station is further configured to retrieve a connection request indicating the selected core network from a user equipment (UE), to determine whether the user equipment has previously operated with a neighboring base station in the selected core network, and Access to the selected core network is allowed regardless of occupancy level.

11. The base station (eNB) according to claim 10, The method is further configured to determine, for at least one of the core networks (CON1, CON2), whether a given occupancy level is reached and, in response, to send a high occupancy message to at least one user equipment (UE).

Images