Managing redirection of user equipment to a terrestrial-based network - Patents.com

Abstract

The present invention relates to a method for assisting relocation of a user equipment to an Earth-based network while the user equipment is connected to or camped on a satellite-based network, said method comprising, for a satellite-based network, obtaining and storing an Earth-based service preference indicator for the user equipment upon registration of the user equipment with the satellite-based network, then, when the user equipment at a given location proceeds to a subsequent operation with the satellite network to which it is connected or camped, receiving from the user equipment a location of the user equipment by means of an exchange related to the operation, reading the Earth-based service preference indicator by a relocation function of the satellite-based network, evaluating available Earth-based networks, and possibly sending to the user equipment an instruction to perform a redirection attempt to the appropriate Earth-based network if a suitable Earth-based network for setting up a service relationship of the user equipment is available at the given user equipment location while taking into account the Earth-based service preference indicator.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to a method for assisting in the relocation of user equipment to a terrestrial-based network while the user equipment is connected to or camped on a satellite-based network.

[0002] The present invention also relates to a satellite-based network infrastructure that includes a user equipment relocation function for managing the reselection of user equipment to an earth-based network while the user equipment is connected to or camped on the satellite-based network. [Background technology]

[0003] 2. Background of the Invention Regarding mobility, it is known that in 5G technology, mobility for NTN-IoT is considered as handover-based for eMTC and Radio Link Failure (RLF)-based for NB-IoT. NB-IoT and eMTC are standalone 5G technologies that do not interact with other technologies via handover or other technologies supported by the network.

[0004] In case of roaming, NB-IoT and eMTC user equipment (UE) performs in principle the same procedures as other UEs. This means that when roaming on another public land mobile network (VPLMN for visited-PLMN) than the home PLMN HPLMN or equivalent HPLMN EHPLMN, the UE periodically searches for its HPLMN. The search periodicity depends on some timer information retrieved from the SIM card with the relevant fields, i.e. timer information that interprets how often and with what period the HPLMN search is performed by the UE.

[0005] The importance of avoiding too frequent failures in the search for IoT devices has been recognized by 3GPP, and therefore different periodicities and parameters have been introduced in TS 23.122 Rel.-16. In addition, WO 2020239324 included further proposals on minimizing power consumption when performing HPLMN searches. However, when satellite connected, the satellite connection generally consumes more power due to the greater distance between the UE and the satellite-based base station (whether LEO, GEO, or MEO). It would therefore be beneficial for the UE to return to the Earth-based station as soon as possible if for no other reason than that it has lost connection or was previously out of range of Earth-based services. However, due to the large number of bands that may be used for NB-IoT or eMTC services, searching all the respective bands once without supporting information can take several minutes, quickly draining the battery.

[0006] A common problem encountered by user equipment during movement is the subsequent search attempt with a mode change to perform a quick relocation to a terrestrial-based service. In fact, a standard feature is to perform the search that is usually performed in roaming. In terrestrial-based networks, the current base station may provide additional information, namely the geographical location, whether an eMTC or NB-IoT cell is reachable or such information can be derived by knowing from which country the serving base station performs a "directional search". This means that if the UE is served by a roaming network, the UE can conclude some aspects from the information provided in the broadcast and by the Mobile Network Code (MNC) and Mobile Country Code (MCC) can conclude about the region / country in which the UE is located and therefore evaluate whether a HPLMN or EHPLMN is deployed in this country or a neighboring country and therefore perform some dedicated search. Furthermore, the device may also have a list of bands allocated in this country that have NB-Iot or eMTC from that HPLMN or EHPLMN. This means that the UE can incorporate some information that allows it to perform a dedicated search, i.e. a search for special operators that know where these HPLMNs have deployed the corresponding NB-IoT or eMTC bands.

[0007] Such information is static information transferred via broadcast since the location is fixed and the base station is not moving, and therefore the relationship between the current roaming base station and the higher ranked base station is also fixed. This means that if it knows that there is no higher ranked PLMN in said country, it does not need to start a corresponding search. If a higher ranked PLMN, e.g. HPLMN, is deployed, the UE will start searching at the specified time in the corresponding deployed frequency.

[0008] Furthermore, for Earth-based stations, in the broadcast there is a support mechanism consisting of a presence indication, i.e. an information element broadcasted in the current network / technology indicating that NB-IoT / eMTC or GSM is deployed in the area, so that a switch to said technology can be successful if desired by the device. The information is present in the NB-IoT or eMTC broadcast, respectively. Although NTN-IoT means that IoT connection via satellite can be performed via eMTC or NB-IoT, the situation is further aggravated because there is no information that can be derived from the broadcast, and therefore devices for Earth-based discovery may need to switch technology modes further.

[0009] In WO2020094451, the problem of hanging the core network or avoiding such a change is addressed in both technologies for NB-IoT. In the case of eMTC, such a problem should not occur since the network will perform the handover. However, if there is no corresponding cell with a suitable core network, the connection will fail and an RLF indication with the core network can also be performed upon re-establishment. However, in such a case, the desired core may not be present, which would have been a handover candidate if it was present. All these solutions are adapted to earth-based networks.

[0010] In the context of the Non-Terrestrial Network Internet of Things (NTN-IoT) research item update (RP-210868), it was reaffirmed that both Narrow-Band Internet of Things (NB-IoT) and enhanced Machine Type Communication (eMTC) on satellites are part of NTN-IoT, including both options of connection to the Evolved Packet Core (EPC) or to the 5th Generation Core (5GC). All these are options defined for the terrestrial IoT as well. Thus, the use of satellites is standardized for eMTC and NB-IoT, with both options connecting to the 4G or 5G core, EPC or 5GC respectively. As mentioned above, the terrestrial-based relocation or HPLMN search is an autonomous search of the UE, only the execution and periodicity are coordinated by the network side, providing the corresponding configuration. This is possible since, as mentioned above, the UE is able to obtain all relevant information, which can be further used for beneficial implementations resulting in power efficient behavior between terrestrial based networks and relocation / PLMN reselection processes.

[0011] Changing connectivity from terrestrial-based to satellite coverage is quite clear, as it can be done in conjunction with coverage loss or other benefits considered for satellite connectivity. This means that if no terrestrial-based network capable of providing service is available, such as in a country without a reliable network or roaming partner, or simply located at sea, the device can switch its mode and service to satellite-based services to maintain connectivity and avoid service outages. However, even if avoiding loss of coverage is important for IoT applications, reverting to terrestrial-based coverage may lead to detrimental behavior of the user equipment's power and capacity.

[0012] Thus, the same problem of search attempts exists for connection / camping conversion from NTN-IoT to Earth. However, in this case, the aforementioned Earth-based solutions do not work. The reason is that the satellite beams have a diameter of up to 50 km and are moving, especially for the Low Earth Orbit (LEO) which is of most interest for IoT applications. Any information broadcasted therefore needs to be sub-sequentially updated, draining the battery of the listening device. Also, satellite-based and Earth-based networks are different networks, and therefore a particular user equipment may only access a particular Earth-based network, i.e. one whose owner / operator has a roaming agreement or is their HPLMN or EHPLMN. This means that the problem is even more substantially different here, since the UE can perform a PLMN change not only for its HPLMN or EHPLMN, but also to an Earth-based VPLMN, although such networks may be ranked higher than satellite networks. The advantage for the UE is in power saving.

[0013] In addition, certain UE types may access satellites generally or only for specific tasks, and any support on a dedicated basis from the satellite-based network also means that the UE needs to know if it wishes to be reassigned to Earth-based services.

[0014] In addition, in certain areas with poor coverage, many devices may end up roaming to the satellite-based network for service, but to prevent the satellite-based network from becoming overloaded, it may be beneficial to reconnect to the Earth-based network as soon as another possibility becomes available, so Earth-based relocation / connection may also be beneficial for the satellite-based network. Therefore, relocation to Earth is also an important measure for satellite networks for load balancing reasons. Therefore, there may be some importance in supporting the UE in an autonomous relocation determination process, if known or provided as a service by the satellite-based network.

[0015] Indeed, for the LEO satellites considered for IoT, nothing can be derived from the current serving satellite, and the satellite itself is moving, so it cannot receive broadcast assistance information. In that case, NB-Iot or eMTC will ignore what to search for. Moreover, switching from satellite to ground-based and back will drain the device's battery, especially considering the large number of bands that may require searching both frequencies.

[0016] Also, simple broadcast presence solutions for Earth-based technologies are not deployed.Furthermore, for satellite-based networks, it is unclear what networks the UE will be able to access while reconnecting on Earth if necessary or desired.

[0017] Thus, so far, a controlled reconnection to Earth can only be done by trial and error, since the satellites are moving and cannot provide any assistance broadcast information due to lack of knowledge for dedicated signaling. The device is also not aware that it can also connect to Earth NB-IoT / eMTC. Also, so far, the device has no possibility to control how to return to Earth. Also, if the switch to a satellite-based network was made for security reasons, for example, it may not want to return to Earth-based coverage.

[0018] So far, handover capabilities between different networks or PLMNs have relied on inter-Public Land Mobile Network (PLMN) capabilities.

[0019] As of today, HPLMN selection is a UE autonomous process. It is driven in periodicity and repeated attempts by information provided by the HPLMN on the SIM card. Roaming network information is used only as assistance information and generally there is no means to influence the HPLMN reselection process, whether it is performed or not. Only smart UE implementations perform directional searches using the general current information. However, the HPLMN search periodicity is configured by the HPLMN by values ​​provided on the SIM.

[0020] In the case of satellites, this process needs to be done directionally and, for power saving reasons, needs to be initiated whenever a preferred Earth-based service is reached in order to ensure early reconnection to the Earth-based service. That is, satellite connection and data transmission via satellite requires more energy than Earth-based. In addition, when connected to a satellite, the cell, especially a LEO satellite, can be changed quickly, necessitating a subsequent re-read of the SIB.

[0021] The solution of storing all the necessary information about potential roaming partners in the user equipment is disadvantageous because a larger user equipment storage is required to hold a global coverage map for checking coverage at relevant locations, and such material also needs to be kept physically. Maintaining such material physically requires subsequent updates, and therefore power costs, especially for tracking devices where power saving is important. The use of such service preference information stored inside the user equipment is limited to cases where it allows the user equipment to select a network that can provide a special service, i.e. voice service support corresponding to eMTC.

[0022] Also, the solution of signaling all potential cells to be selected when changing from an NTN-TN network to a TN network, i.e. from satellite-based to earth-based, is not an option due to the wide coverage of satellite beams and the huge number of terrestrial networks (TNs), whether dedicated or broadcast, as the signaling overhead would be too large.

[0023] Aspects related to the interaction and interworking of satellite-based networks and terrestrial-based coverage are not yet standardized at the level of redirection or corresponding reselection between different PLMNs. However, it is of interest to redirect the connection of devices to an appropriate terrestrial-based connection, in particular either eMTC or NB-IoT, as quickly and in an efficient manner as possible.

[0024] Therefore, there is a need for an efficient and advantageous solution for managing the mobility of devices between satellite-based networks and earth-based networks. Summary of the Invention [Means for solving the problem]

[0025] Summary of the Invention The present invention aims to provide a simple and efficient method for managing the reconnection of a communication device to a terrestrial-based network while connected to or camped on a satellite-based network.

[0026] The present invention, in its broadest sense, is defined as a method for assisting in the relocation of user equipment to a terrestrial based network while the user equipment is connected to or camped on a satellite based network, said method comprising, for the satellite based network: Upon registration of the user equipment to the satellite-based network, Obtaining a terrestrial-based service preference indicator for a user equipment; storing said obtained terrestrial-based service preference indicator for further use by a user equipment relocation function of the satellite-based network or by interacting with the satellite-based network, and thereafter When a user equipment at a given location proceeds to subsequent operation with the satellite network to which it is connected or camped, Receiving from the user equipment the location of the user equipment using an operation related exchange; reading an earth-based service preference indicator by a relocation function of a satellite-based network; Evaluating available Earth-based networks; and - sending an instruction to the user equipment to perform a relocation attempt to a suitable Earth-based network if a suitable Earth-based network for establishing a service relationship of the user equipment is available at a given user equipment location while taking into account an Earth-based service preference indicator.

[0027] The indication is provided in connection with the completion of an exchange related to an operation between the user equipment and the satellite-based network.

[0028] In addition, the instructions not only take into account the appropriate operator, but also the device capabilities such as technology support, and the frequency bands supported by the device, whether NB-IoT or eMTC, the technology currently used in conjunction with satellite networks.

[0029] The method of the present invention allows the user equipment to return to Earth-based coverage in a timely manner, which brings power and capacity advantages. It allows for efficient switching from satellite to Earth-based coverage areas, especially when the switch is forced by leaving the Earth-based coverage area. It avoids subsequent searches of the Earth-based network, which may drain the battery if based on periodic searches, or may result in long delays in the change if the periodicity is too large. In addition, it may prevent subsequent technology mode switching of the device, i.e., from NB-Iot to eMTC, depending on which technology is used in the satellite network and which technology is used in the Earth-based network, or the preferred technology depending on the use case of the UE.

[0030] Network selection and indication by the satellite is signalled in a dedicated manner and the selection process involves information received by the roaming PLMN from the HPLMN to which the user equipment belongs, i.e. a list of suitable or acceptable networks.

[0031] In any case, the device needs to report its geographical location for regulatory purposes, i.e. national laws, and associated satellite processing. The determination is made in the satellite-based network on the basis of a known and verified user equipment location as regulated received by the satellite-based network. This transmission of the user equipment location is standardized, so it is not part of the present invention to explain how this knowledge is obtained with the corresponding reliability.

[0032] The present invention avoids knowing about all possible UE terrestrial based UE roaming networks and HPLMN / EHPLMN to evaluate whether one of the networks in the vicinity of the UE location will accept the UE for service. In the present invention, such information is provided by the UE HPLMN when entering the satellite network as a roaming UE.

[0033] In addition to loss of coverage, the UE may also have entered the satellite network for other reasons, namely because it is more secure to exchange data via satellite than via earth-based networks. As a result, the server also needs to have an indication of whether the UE intends or wants to be redirected to an earth-based network in order to avoid the ping-pong effect. The present invention provides a solution to this problem.

[0034] Thus, when the user equipment reaches a corresponding coverage area verified by its location by the satellite-based network, the satellite-based network indicates said situation to the user equipment. The indication can be made, for example, at the end of the communication session or during it, when sending a disconnect to the user equipment, including an indication regarding the technology and frequency of the respective appropriate terrestrial-based network.

[0035] The satellite-based network evaluates whether terrestrial-based coverage is reachable for every communication exchange, including simple regulatory receipt of the user equipment's location, for all UEs that have indicated that terrestrial-based service is preferred, and where additional information regarding suitable roaming / PLMN networks is available.

[0036] According to the method of the present invention, the Earth-based service preference indicator can be forwarded by the Earth-based current PLMN or the user equipment itself, but additional information is advantageously exchanged between the core networks other than the "Earth-based service preference indicator" directly. Thus, satellite core network and UE HPLM signaling resources on the air interface are saved. Thus, the present invention includes an exchange of these additional information between the core networks that avoids the signaling and involvement of the user equipment, except for the provision of the user equipment's location and, if applicable, the Earth-based service preference indicator. This means that all the remaining information can be received from the core network. It should also be noted here that most of the information is not even important for the satellite network, but only for the reselection function. This also means that the user equipment does not need to signal any capabilities other than the actual satellite communication. This means that the UE advantageously transmits all UE capabilities that are important to the satellite network, but not more.

[0037] In this case, since the satellite network is based on a single technology, i.e. NB-IoT in a single frequency band, the indication on the support of an additional technology not used by the satellite network, in this example eMTC in GSM, and the frequency band not used by the satellite network, is not beneficial for the communication between the user equipment and the satellite network, but is important for the return to Earth support function.

[0038] The complete set of technologies and frequency bands supported by the UE is important for assessing the appropriate PLMN, in addition to the question of whether the UE is allowed on the network, since it is also necessary to clarify whether the UE can access or connect to the network based on its capabilities.

[0039] In particular, the present invention optimizes connection changes from a satellite-based network to a terrestrial-based network by introducing a support function / server into the network that optimizes connection changes based on:

[0040] - The actual UE location, which is evaluated and forwarded every time the UE initiates communication with a satellite-based network (this is necessary for regulatory reasons) - Knowledge of potential Earth-based roaming / HPLMN networks, and -Preferences of Earth-served UEs are used to optimize the redirection / guidance for reselection to Earth.

[0041] This means that when the UE is in a position where terrestrial-based services based on the frequency bands and technologies supported by the UE can be reached, the satellite-based network indicates to said frequency or terrestrial network the information provided by the relocation server, respectively, when terminating a current communication opportunity with the satellite network.

[0042] Based on the UE's location, supported technologies and frequency bands, and knowledge of potential roaming PLMNs or HPLMNs / EHPLMNs, the server infers whether a terrestrial-based network willing to serve the UE is reachable, and the UE can attempt to register with said network.

[0043] According to the present invention, the user equipment is informed that it can only connect to a terrestrial-based network while it is connected to a satellite-based network. Thus, in advance for the next scheduled communication session, the device can start searching based on the information provided in the optimal format. Once the UE discovers a terrestrial-based network, it will try to register accordingly by the well-known PLMN selection procedure in case of roaming involving network communication with the HPLMN. However, said registration itself is not part of the present invention, but can include additional inferences such as terrestrial-based relocation when performing cell selection, which can give some indication that the UE was previously connected to a satellite-based network, and the respective core entity can inform the satellite-based network or the HPLMN that the device has been relocated. Said indication to the satellite network can be beneficial to avoid resource retention in said network. In addition, some of the context or UE related information can also be obtained.

[0044] Based on the user equipment location and the terrestrial based service preference indicator, which advantageously includes the user equipment capabilities also related to the inactive technologies (i.e. eMTC or NB-Iot EPC / 5GC or vice versa) and the MNO, the user equipment can connect to the appropriate PLMN when roaming becomes clear. This uses only the user equipment location and capabilities related to the global coverage map of the MNO and technology. If so, it indicates this and also indicates whether there is a need to change MNO and technology. It is considered advantageous if the indications regarding the satellite based networks and the corresponding frequency bands as well as the unused technologies by the potential operator roaming partners are transferred directly between the UE HPLMN and the relocation service center / function. Since the relocation service center / function relies on the information of the home network and is important for the device, it may also be the HPLMN running said service engine. This means that the 5G core network of the satellite based network is connected in its service oriented architecture with the relocation function.

[0045] The presence of the relocation function may be indicated in a network repository function that acts as a network discovery function, maintains network functions and services that are available from the network, and is indicated to users by a network exposure function, which provides a means of exposing the services offered by 3GPP network functions to users.

[0046] Thus, instructions for suitable earth-based services can be provided by such a connected service center, and also instructions regarding suitable earth-based networks that can be reached can be provided in the data stream by such a service center. In that sense, the present invention is comparable to a data center that executes the service. It is therefore original and advantageous to operate the relocation function as a service that is part of or interworks with a satellite network and thus has access to or utilizes the essential information provided in the signaling / control plane and uses the device's positioning information provided in the communication setup for the relocation function. While not part of a satellite network or connected to a service function, there is no way to access said information used in the signaling plane and there is a need / repetition of additional communication via the user data plane.

[0047] According to an advantageous feature, the method comprises a preliminary step of storing and updating, for each user equipment, a terrestrial-based service preference indicator in a central server accessible to the satellite-based network, said terrestrial-based service preference indicators of the user equipment being subsequently obtained by the satellite-based network from this central server.

[0048] If the server is hosted by an HPLMN, there may be multiple servers, or at least one virtualization architecture, in which there may be different virtual servers for devices from different HPLMNs, receiving information from their respective HPLMNs.

[0049] With this functionality, the central server is connected to the satellite network, either being part of the satellite network or connected via a redirect service function. However, being part of a satellite-based network makes it easier to obtain indicators, UE location and provide information via the signaling plane. However, being a pure HPLMN service connected to the 5G service architecture of the satellite network also works, but the information needs to be transferred in a different way, i.e. in the data stream.

[0050] In the present invention, it is the user equipment that wakes up to perform the connection service and triggers the main steps of the invention by transmitting its location. Thus, the user equipment monitors the timing of the invention but does not monitor the knowledge. So far it was a periodic timer provided by the HPLMN. That is, the HPLMN service center is triggered when the UE wakes up. Also, the introduction of a maximum wake-up time for the HPLMN could be an add-on. In this case, such a timer is in the UE and the UE wakes up when the timer value is reached further, regardless of the normal service needs. However, such an additional wake-up to transmit data (empty packets) to stimulate the relocation center / function can only be advantageous in very rare cases. To avoid the UE getting stuck on the satellite network when the relocation function is faulty, the UE can perform an autonomous search with a very large timer value. However, this is aligned with the state of the art and has the aforementioned drawbacks. The method of the present invention itself does not imply any extra wake-up or activity in the user equipment. While the user equipment transmits data to the satellite-based network, the central server evaluates whether the user equipment can be reassigned to Earth. Advantageously, the available terrestrial networks are then indicated at the connection termination.

[0051] The terrestrial based service preference indicator is information exchanged between the UE and the satellite based network, or between components of the PLMN, two core networks where corresponding actions and information exchanges need to take place. However, receiving said terrestrial based preference indicator from the UE in its capacity may have the advantage that, depending on security needs, the UE may preferably actively camp in a specific area on the satellite network and receive over said network information for reliability and security reasons. For example, in Europe, the UE may want to quickly return to terrestrial based services if a change to satellite is caused by a coverage hole, whereas in certain parts of Africa where there are unreliable / non-functioning networks, the device may actively remain on or have changed to a satellite based network. The terrestrial based preference indicator here may be information / distinction that can only be made by the UE and its integrated capabilities.

[0052] Advantageously, the central server is connected to the home location register of the user equipment, which makes it possible to obtain further information not used in conjunction with the satellite network, i.e. supported technologies or additional frequency bands.

[0053] Advantageously, the storing of the terrestrial based service preference indicator is performed when the user equipment is accepted as a roaming user equipment by the satellite based network from a previously connected public land mobile network.

[0054] This functionality allows the satellite-based network to have information available directly to the satellite-based network.

[0055] Advantageously, the terrestrial based service indicator is obtained directly from the user equipment and the additional user equipment capability information is obtained from a previously connected public land mobile network or a home public land mobile network.

[0056] This is particularly advantageous where the UE's capabilities in terms of technology, frequency bands and features are not described as being used in conjunction with satellite communications.

[0057] In accordance with an advantageous embodiment, acquisition of the terrestrial-based service indicator is performed when the user equipment begins to camp on the satellite-based network.

[0058] Thus, said information may be exchanged by the UE at connection setup time or using a function in the UE, ensuring that the user equipment is redirected to the terrestrial-based network as soon as possible while camping.

[0059] According to an advantageous feature, the relocation function obtains a list of Earth-based roaming networks suitable for the Earth-based services of the user equipment.

[0060] Such direct acquisition of a suitable Earth-based roaming network allows for easy selection and detection of the presence of a suitable Earth-based network for presenting same to user equipment in accordance with the present invention.

[0061] Advantageously, said list of suitable terrestrial-based roaming networks is obtained from a home location register of the user equipment whilst camped on a satellite-based network.

[0062] Receiving said information from the user equipment itself could be a potential solution, but considering the maintenance and signaling effort to transfer such a list and keep it up to date, it is more advantageous according to the invention to receive the list from the HLR of the user equipment where the list is stored and maintained.

[0063] In addition to maintaining such a list by the UE's HLR, the satellite-based network may also maintain a list of suitable Earth-based networks for all satellite-connected UEs and activate an Earth-based service preference indicator. In this situation, it is the satellite-based network that attempts to redirect the UE to another VPLMN on Earth, e.g., for offloading purposes.

[0064] According to an advantageous feature, a list of suitable Earth-based networks is established based on an offloading agreement of the Earth-based networks to accept redirection of the user equipment from the satellite-based network.

[0065] This feature allows the satellite-based network to negotiate directly with the Earth-based network for offloading of user equipment in a particular area. In practice, this list can be the same list obtained from the HLR or a second list.

[0066] Advantageously, the relocation function of the satellite-based network is located in or connected to the access and mobility management function of the satellite-based network, since data received via the UE function is stored / available in the AMF.

[0067] This feature allows direct and rapid access to indicators corresponding to each user equipment currently in communication with the satellite-based network.

[0068] Advantageously, at the end of the method, the indications transmitted to the user equipment are inserted into the connection termination. When the user equipment receives the connection termination, it starts searching for a suitable PLMN. The user equipment finds it because the satellite-based network knows if such a suitable PLMN is available. The present invention avoids any previous attempts by the user equipment to search for a suitable terrestrial-based network, but none of such suitable terrestrial-based networks are available.

[0069] Advantageously, the connection termination is an RRC connection release with an indication that a suitable terrestrial based network is available for redirection.

[0070] Such connection termination provides additional information to the user equipment. According to one embodiment, the indication is transmitted to the user equipment by use of a paging message.

[0071] This may be of value in cases where the assessment is not finalized while the UE is connected to the satellite network and the UE is paged to perform the relocation.

[0072] According to an advantageous feature, while receiving a paging message, the user equipment ignores said paging message relating to the satellite-based network and performs relocation instead.

[0073] According to an optional embodiment, the method further includes transmitting the earth information to an appropriate Earth-based network indicated in the Earth-based service preference indicator to facilitate redirection of the user equipment to the Earth-based network.

[0074] This optional feature allows for easier connection of user equipment to a selected appropriate Earth-based network, and eliminates the need for further resource considerations when the satellite network is notified of successful relocation.

[0075] More specifically and advantageously, the terrestrial based service preference indicator includes at least information on whether the user equipment UE prefers to be operated on a terrestrial basis, and information on the technologies supported by the user equipment including frequency bands supported by the UE, roaming networks to which the UE can connect, PLMN and EHPLMN information.

[0076] This gives the satellite-based network the possibility to evaluate whether it should search for a suitable Earth-based network.

[0077] Advantageously, in addition to the indicator, the relocation function also receives information regarding a list of friendly earth-based roaming networks.

[0078] This allows for more accurate and personalized notification of user equipment.

[0079] Advantageously, in addition to the indicator, the relocation function also receives information regarding frequency bands and technologies that are supported by the device but are not used in conjunction with the satellite network.

[0080] This will allow for a greater variety of Earth-based networks to choose from. The present invention also relates to a satellite based network infrastructure comprising a user equipment relocation function for managing redirection of a user equipment to a terrestrial based network while the user equipment is connected to or camped on the satellite based network, said user equipment relocation function comprising: Upon registration of the user equipment to the satellite-based network, Obtaining an Earth-based service preference indicator for the user equipment; storing said obtained Earth-based service preference indicator for further use, and thereafter When a user equipment at a given location proceeds to subsequent operation with the satellite network to which it is connected or camped, Receiving from the user equipment the location of the user equipment using an operation related exchange; ○ Reading Earth-Based Service Preference Indicators; o configured to send an instruction to a user equipment to perform a relocation attempt to a suitable Earth-based network, as indicated by the Earth-based service preference indicator, if a suitable Earth-based network for establishing a service relationship of said user equipment is available at a given user equipment location, taking into account the Earth-based service preference indicator.

[0081] Such an infrastructure implementing the method of the present invention ensures that any user equipment connected to the satellite-based network is redirected to the Earth-based network as soon as possible, taking into account the capabilities of the user equipment as well as the nature of the communication established with the satellite-based network.

[0082] In addition, the satellite-based network infrastructure preferably receives from the UE HPLMN information regarding earth-based networks that are potential roaming / relocation networks, and UE capabilities regarding unused technologies or the device's capabilities in conjunction with satellite communications. Using this additional information, the satellite infrastructure and associated relocation functions can optimally function to evaluate suitable roaming networks.

[0083] A device that is normally served by an Earth-based network may intentionally, i.e., for security reasons, prefer to be connected to a satellite network instead of being connected to another Earth-based roaming network. Thus, the device or its application needs a means to indicate whether it is interested in relocating to an Earth-based network or whether it is interested in remaining on the satellite network as a preference.

[0084] The present invention also describes the characteristics of user equipment that is roaming into a satellite network as being out of Earth-based coverage and indicates that the user equipment wishes to be served again by an Earth-based station or the device reselects satellite service for other reasons, i.e., security reasons.

[0085] To the accomplishment of the foregoing and related ends, the one or more embodiments comprise the features hereinafter fully described and particularly pointed out in the claims.

[0086] BRIEF DESCRIPTION OF THE DRAWINGS The following description and the annexed drawings set forth in detail certain illustrative aspects and illustrate some of the various ways in which the principles of the embodiments may be employed. Other advantages and novel features will become apparent from the following detailed description when considered in conjunction with the drawings, and the disclosed embodiments are intended to include all such aspects and their equivalents. [Brief description of the drawings]

[0087] [Figure 1] FIG. 2 is a time diagram of the method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0088] Detailed Description of the Invention Embodiments In order to more fully understand the present invention, the present invention will be described in detail with reference to the accompanying drawings. The detailed description illustrates and describes what are considered to be preferred embodiments of the present invention. It should be understood, of course, that various modifications and changes in form or details can be easily made without departing from the scope of the present invention. Therefore, the present invention may not be limited to the exact forms and details shown and described herein, and is not intended to be limited to less than the entirety of the invention disclosed herein and claimed below. The same elements are indicated by the same reference numerals in different drawings. For clarity, only those elements and steps that are useful for understanding the present invention are shown and described in the drawings.

[0089] FIG. 1 is a time diagram of the method of the present invention. First, the user equipment UE is connected to or camped on a first earth-based network EBN_A, as indicated by step S0, and then the user equipment UE loses coverage to the earth-based network EBN_A in step S1.

[0090] Typically, the user equipment UE is a multi-mode terminal capable of operating on NB-IoT, eMTC or GSM. As both are completely independent, the device can switch between technologies, which requires a re-registration. Whether further downtime occurs depends on the resources available on the device. Some devices have enough flash memory to switch between stacks, while others need to unpack an unused version before operation. Anyway, the switch can be made in a fairly short time, which is also important for optimized search times. However, if no suitable terrestrial-based network is found, meaning that the UE has searched in the broadcast of network EBN_A, or there is no indication on any other suitable network, the UE may decide to relocate to a satellite-based network.

[0091] It is advantageous for an indication to be given by the Earth-based network to the user equipment indicating whether satellite coverage is available and for which technology, i.e. eMTC or NB-IoT, in areas with spare Earth-based coverage. This information provisioning of the EBN_A provides satellite coverage information with an indication to the technology eMTC or NB-IoT and the corresponding frequency. This information is particularly valuable when satellite coverage is not always present and thus said information includes timing relations or is only available when the satellite is in reach. However, the presence of said information along with the absence of an Earth-based alternative indication, since no suitable network is indicated, can also be used by the UE to directly search for satellites without performing an Earth-based search, even though the EBN_A generally supports such indications as seen by the satellite presence indication.

[0092] A central server, which is an integral part of the network, here a satellite-based network, can reassign UEs towards the Earth-based network based on specific capabilities and knowledge.

[0093] The UE location needs to be known, this is not an issue with regard to national regulations, the GPS location of the UE is known when doing dedicated signalling exchange with the network.

[0094] The invention advantageously implements a central server assisted if it also has a connection to or is part of the Home Public Land Mobile Network (HPLMN) or at least the Home Location Register (HLR), so that the Home Public Land Mobile Network (HPLMN) controls the reselection process. The central server can be connected to the satellite network as a service and controlled by the HPLMN / MNO of the UE. In this way, the central server also has the knowledge of being a terrestrial-based roaming partner. So it can only instruct the user equipment when it has reached an accessible network. This means that it is a UE-executed process, i.e. by the UE performing a search and reselection to a terrestrial-based network, assisted directly from a central server or function, i.e. the HPLMN reselection assistance server, which can also be part of the HPLMN or part of the satellite network when under shared control.

[0095] Moreover, this is a new type of indication, since it is an indication on a different PLMN to avoid longer lasting coverage losses. In certain areas, the entire Earth-based deployment does not make sense. For example, Canada only has radio stations along the 150 km US border, in cities and some other areas, but on the roads in the north. In such cases, the last coverage base station is advantageously equipped to give an indication to switch to a satellite-based network for any NB-IoT-supported user equipment. This means that for those Earth-based nodes, the static broadcast indication is close to the existing one, simply referring to the mode used on the satellite, reflecting the mode from the satellite operator, which is a different Public Mobile Network (PMN).

[0096] In a situation where coverage is no longer available, the user equipment UE typically attempts to reach the satellite-based network SBN, either under instruction or on its own, in step S2. If successful, roaming information and negotiation is performed in step S3 between the device's earth-based home network (also EBN_A in this case for simplicity) and the satellite-based network SBN. Such roaming negotiation is known from the prior art.

[0097] According to the invention, i.e. when the UE reaches outside the satellite-based network according to the first option, in step S4a the UE provides an indication EB_SPI to the satellite network that it prefers Earth-based services, i.e. that it has roamed to the satellite network for coverage reasons and wishes to return when Earth-based coverage becomes available again.

[0098] Alternatively, according to a second option, in parallel with or subsequent to the roaming negotiation, the satellite based network SBN obtains from the Earth based network EBN_A an Earth based service preference indicator EB_SPI corresponding to this user equipment S4b.

[0099] Thus, the relocation function described above obtains UE capability information from the UE HPLMN, and in particular, the UE capabilities with respect to technology, frequency bands, and features are described as not being used in conjunction with satellite communications.

[0100] This Earth-based service preference indicator EB_SPI is stored in step S5 by a user equipment relocation function ReLF located in or connected to the satellite-based network SBN.

[0101] The indicator is received by the satellite-based network SBN for any roaming device that prefers to return to terrestrial-based service, i.e. any device that has a different HPLMN than the satellite-based network. Said indicator is forwarded / obtained when roaming to the satellite network, preferably only if roaming is done for coverage reasons.

[0102] The indicator can be received in two possible ways: the first way is directly from the user equipment UE when registering with the satellite network.

[0103] The second method is from the device's land-based home public land mobile network HPLMN when the satellite-based network SBN negotiates access with the HPLMN.

[0104] The indicator is then received by the satellite network. The reception may occur via the HPLMN towards the satellite-based network when roaming and access of the user equipment is permitted. Alternatively, the indicator may be part of the user equipment capability information, i.e. information on the set of supported capabilities, said set may be limited to capabilities required for the UE communication exchange with the satellite-based network.

[0105] The set of commonly supported technologies and supported frequency bands may be received in step 5a from the HPLMN, in this case EBN_A, which contains a list of potential terrestrial-based roaming networks, identifiable by their MNC, to which the device may roam. It may not be desirable to provide all said information from the UE.

[0106] Typically, once the indicator is received by the terrestrial-based network from which the user equipment UE originates, during roaming communication, communication between the networks is accordingly defined, i.e., beyond pure roaming negotiation, but also including communication over the appropriate terrestrial-based network and inactive technologies supported by the user equipment UE.

[0107] Regardless of the reception method, the indicator is stored together with an identifier of the user equipment UE in the MME (LTE), AMF (5G) of the satellite based network SBN, respectively.

[0108] The Earth-based service preference indicator EB_SPI contains information to be known by the satellite-based network to assist the user equipment UE in switching from a satellite to an Earth-based connection or for related assistance.

[0109] The indicator EB_SPI also contains information whether the user equipment UE prefers terrestrial-based operation, which informs the satellite-based network whether the user equipment UE wants to change.

[0110] Other information may also be included in the indicator EB_SPI, such as information about the technologies supported by the user equipment UE, in particular the technology in use. Indeed, satellite-based networks may implement NB-IoT, but in certain areas only NB-IoT or eMTC is deployed in terrestrial-based networks. It is therefore important for the satellite-based network to know whether the user equipment supports eMTC technology or not.

[0111] The indicator EB_SPI also contains information whether the user equipment UE can optionally communicate with unused cores, i.e. 5GC or EPC, since NB-IoT and eMTC can be deployed in either core network, and it is important to know whether the UE also understands the legacy EPC core in particular. It also indicates whether the user equipment UE supports additional unused technologies, i.e. NB-IoT or GSM as supported core network types.

[0112] The indicator EB_SPI also includes a terrestrial based network / PLMN that accepts said user equipment UE together with a terrestrial based preference, which provides for example friendly network coverage.

[0113] The indicator EB_SPI, together with the location of the user equipment UE, which is provided periodically by default to the satellite-based network by the user equipment UE, allows the satellite-based network to manage the redirection of the user equipment UE to a suitable Earth-based network. In an advantageous embodiment, the satellite network receives the EB_SPI directly from the UE and indicates the preference supported for relocation to Earth-based services (step S4a) and all additional information regarding potential roaming Earth-based partners from the HPLMN for supported technologies, in particular technologies, frequencies, and devices not used in satellite. In step S5a, such an approach minimizes signaling over the air interface and the satellite network can indicate that the UE has already indicated its Earth-based preference in roaming negotiations with the HPLMN and the HPLMN delivers the additional information to the satellite network.

[0114] Once the aforementioned indicators are available, as will appear below, the satellite-based network may indicate a preferred candidate for Earth-based communications for the user equipment UE to perform a search or, later, when possible, to perform a redirection directly to Earth-based communications, i.e., when an Earth-based network is detected as available at the user equipment's location.

[0115] Most advantageously, a presence indication would be included in the communication termination so that the UE could perform the well known cell selection process in a directed search fashion.

[0116] Network assisted relocation to Earth as a service provided by satellite based networks is a new aspect. Currently, the return to the HPLMN / EHPLMN is done by a periodic timer search which is inefficient and battery draining in such cases. The periodic search performed by the device drains the battery or leads to long delays. Provisioning satellite services or camping on a satellite network consumes more power than camping on an Earth based network, since the satellites providing the service / camping can change very frequently, especially in LEO scenarios which require reacquisition of some BCH information.

[0117] In addition to such periodic searches of PLMNs, the information for assistance cannot be obtained from the satellites, and if it is intended to serve as assistance information for more dedicated searches, the technology must be changed and the information material must actually be maintained in the user equipment. Such a burden is avoided by the new satellite return to earth services of the present invention. This new service model increases acceptance. The present invention also avoids the user equipment having to store operator coverage material based on location, which requires additional memory, and having to keep this material up to date.

[0118] The roaming negotiation is completed in step S6 by sending a roaming accept ACK to the user equipment UE.

[0119] Thereafter, the user equipment UE is served by the satellite based network in step S7, which means that the user equipment registers and camps on the satellite based network SBN.

[0120] The invention then benefits from a default reporting by the device of its geographical location for the relevant satellite processing. Indeed, national laws require such functionality to be implemented in the user equipment and in any case the location of the user equipment must be periodically evaluated. Such reporting of the geographical location of the user equipment GP_UE is done in step S8 in conjunction with a UE service request by the user equipment UE. This allows the user equipment UE to be processed in accordance with national regulations. It should be noted here that step S8 may also be a UE connection request. Thus, in a satellite-based network, the country is known and said information can be used by the satellite-based network for coverage assessment.

[0121] Each time the satellite-based network receives such a geographical position GP_UE of this user equipment UE, it checks in step S9 for any suitable earth-based network EBN_B. For this purpose, the satellite-based network advantageously has access to information about the user's potential roaming partners on the user equipment position GP_UE or exchanges information with the HPLMN. Typically, the coverage areas of the networks are available in the Internet or are received as a global map by the corresponding operator, since they are also interested in early user equipment UE handback to earth. This means that the relocation service center / function stores and maintains such coverage map.

[0122] If a suitable Earth-based network EBN_B is found, an instruction to relocate to Earth is sent to the user equipment UE in step S10. Thus, typically, when the user equipment UE reaches such a roaming coverage provision area, the satellite-based network SBN includes an instruction in the Radio Resource Control (RRC) signaling related to the available Earth-based coverage if the location is up-to-date for the current session provided or at the time of the next user equipment activity. Such an instruction can also be provided in a special paging message by the satellite-based network if it is not evaluated in time before terminating the connection and the next connection setup may last long and therefore the assistance information is no longer accurate. Typically, the relocation instruction is encapsulated in the paging message.

[0123] Thus, according to the present invention, a user equipment UE connected to a satellite-based network SBN is typically associated with an earth-based service preference indicator indicating that earth-based services are preferred, as temporarily out of range of the earth-based network. As the connecting satellite exchanging information with the user equipment UE is always in position, the satellite-based network, in cooperation with a mobility management entity (MME) or an access and mobility management function (AMF), can evaluate a match between the earth-based service preference indicator and the available earth-based networks at the current location of the user equipment. If there is a match, the user equipment UE receives corresponding assistance information to perform the relevant cell selection procedure. The earth-based preference indicator is advantageously decoupled from the user equipment's capabilities and its compatibility with the various different sub-networks / sub-technologies present in 5G technology, and such information can be advantageously received from the HPLMN during roaming negotiations performed between core networks.

[0124] Optionally, the user equipment reconfigures itself in step S11. Again optionally, the satellite-based network SBN transmits information RC_I to the first terrestrial-based network in step S12 that the user equipment UE has been relocated to the terrestrial-based network. Said information can also be optimally transmitted in the other direction following step S14, transmitted when the UE has been relocated to EBN_B, so that the core network does not require further resources on said UE.

[0125] Following known procedures, the user equipment UE then connects to the appropriate terrestrial based network EBN_B in step S13 and performs roaming negotiation in step S14.

[0126] Preferably, based on the same core 5GC or EPC, the selection based on the same core is considered better than the same RAT and is advantageous as one redirection rule. This implies a certain burden for the user equipment, i.e. changing the RAT, but is overall advantageous, especially since such user equipment may have enough resources to change the RAT during operation, i.e. without downtime. Therefore, it helps to minimize interruptions in service time, since re-registration to a different core 5GC / EPC takes more time and signaling effort and causes a larger downtime / out-of-service time than simply changing the RAT and maintaining the type of core to allow context fetching.

[0127] Said option is especially important in case of a scenario, where the UE or the owner of the respective UE only wants to ensure that it is continuously connected and attached, and therefore he only wants to reach one roaming partner, i.e. a satellite that is reachable everywhere.

[0128] The UE changes to the satellite network when it is out of coverage of the terrestrial-based serving network. The satellite network itself also has some roaming partners to offload UEs of its network. Thus, a UE that has indicated a preference to be terrestrial-based may be roamed to another network by the satellite network accordingly. This can be interpreted as a kind of sub-roaming agreement for traffic offloading in the satellite network.

[0129] In general, the present invention provides a user equipment autonomous PLMN reselection function periodically controlled by parameters provided by the HPLMN to the SIM / USIM card, a network supported relocation to Earth function. The user equipment can indicate an Earth-based service preference indicator when registering with the satellite-based network. Thus, whenever the user equipment exchanges data with the satellite-based network, it evaluates whether relocation to Earth makes sense for the UE, whether searching for a network to relocate to makes sense for the UE, or whether it is better.

[0130] Additional information for evaluating the best Earth-based roaming PLMN is provided by the HPLMN to the relocation evaluation function, including roaming partners and frequencies / technologies supported by the device that are not used by the UE when communicating with the satellite network and thus are not included in the UE capabilities. Furthermore, the periodic relocation search is reduced to a network search opportunity based on a network indication received when signaling is terminated or via additional paging. This indication is provided only if a suitable Earth-based roaming network has been reached. Thus, the present invention provides a new opportunity-driven search approach from periodic searches for the HPLMN, since searching is anyway battery-costly. Also, staying connected or camped on a satellite for too long incurs high energy costs compared to Earth-based camping.

[0131] In the above detailed description, reference is made to the accompanying drawings which show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Accordingly, the above detailed description is not to be taken in a limiting sense, and the scope of the invention is defined only by the appended claims, appropriately interpreted.

Claims

1. 1. A method for assisting in relocation of user equipment to a terrestrial-based network while the user equipment is connected to or camped on a satellite-based network, the method comprising: upon registration of the user equipment with the satellite-based network, Obtaining a terrestrial-based service preference indicator for said user equipment; storing said obtained terrestrial-based service preference indicator for further use by a user equipment relocation function connected to said satellite-based network; and thereafter when the user equipment at a given location proceeds to subsequent operation with the satellite-based network to which it is connected or camped, receiving from said user equipment a location of said user equipment using an exchange related to said operation; reading said terrestrial-based service preference indicator by said relocation function of a satellite-based network; Evaluating available Earth-based networks; and sending an instruction to the user equipment to perform a redirection attempt to a suitable terrestrial-based network for establishing a service relationship of the user equipment, if the suitable terrestrial-based network is available at the given user equipment location, taking into account the terrestrial-based service preference indicator; A method comprising:

2. 2. The method of claim 1, wherein the method includes a preliminary step of storing and updating, for each user equipment, a terrestrial-based service preference indicator in a central server accessible to the satellite-based network, the terrestrial-based service preference indicators of the user equipment being subsequently retrieved by the satellite-based network from this central server.

3. 3. The method of claim 2, wherein the storing of the terrestrial-based service preference indicator is performed when the user equipment is accepted as roaming user equipment by the satellite-based network from a previously connected public land mobile network.

4. 2. The method of claim 1, wherein the terrestrial-based service preference indicator is obtained directly from the user equipment, and additional user equipment capability information is obtained from the previously connected public land mobile network or a home public land mobile network.

5. The method of claim 1 , wherein the obtaining of the terrestrial-based service preference indicator is performed when the user equipment begins camping on a satellite-based network.

6. The method of claim 1 , wherein the relocation function obtains a list of terrestrial-based roaming networks suitable for terrestrial-based service of the user equipment.

7. 7. The method of claim 6, wherein the list of suitable terrestrial-based roaming networks is obtained from a home location register of the user equipment while camped on the satellite-based network, or from the user equipment itself.

8. 8. The method of claim 6, wherein the list of suitable terrestrial-based roaming networks is established based on an offloading agreement of the terrestrial-based network to accept redirection of the user equipment from a satellite-based network.

9. The method of claim 1 , wherein the relocation function of the satellite-based network is located in an access and mobility management function of the satellite-based network.

10. The method of claim 1 , wherein the indication is sent to the user equipment in a connection termination message.

11. The method of claim 1 , wherein the connection termination is an RRC connection release with an indication that a suitable terrestrial-based network is available for relocation.

12. The method of claim 1 , wherein the indication is transmitted to the user equipment by use of a paging message.

13. 13. The method of claim 12, wherein while receiving the paging message, the user equipment ignores the paging message associated with the satellite-based network and instead performs relocation.

14. 10. The method of claim 1, further comprising: facilitating the redirection of the user equipment to the appropriate Earth-based network indicated in the Earth-based service preference indicator by transmitting earth information to the appropriate Earth-based network.

15. 2. The method of claim 1, wherein the terrestrial-based service preference indicator includes at least information about whether the user equipment UE prefers to be operated on a terrestrial basis, and any kind of information about technologies supported by the user equipment including frequency bands supported by the UE, roaming networks the UE can connect to, PLMN and EHPLMN information.

16. 1. A satellite-based network infrastructure comprising a user equipment relocation function that manages redirection of user equipment to a terrestrial-based network while the user equipment is connected to or camped on a satellite-based network, the user equipment relocation function comprising: upon registration of the user equipment with the satellite-based network, obtaining a terrestrial-based service preference indicator for said user equipment; storing said obtained Earth-based service preference indicator for further use; when the user equipment at a given location proceeds to subsequent operation with the satellite-based network to which it is connected or camped, receiving from said user equipment a location of said user equipment using an exchange related to said operation, reading said Earth-based service preference indicator; Evaluate available Earth-based networks; - if a suitable terrestrial-based network for establishing a service relationship for the user equipment is available at the given user equipment location, taking into account the terrestrial-based service preference indicator, sending to the user equipment an instruction to perform a redirection attempt to the suitable terrestrial-based network, as indicated by the terrestrial-based service preference indicator; A satellite-based network infrastructure that is configured to:

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