Forbidden tracking area list enhancements for radio access technology restriction

Abstract

Various example embodiments relate to devices, methods, apparatuses and computer readable media for forbidden tracking area list enhancements for radio access technology restriction A terminal device may be configured to transmit a registration request to a core network device, to receive a registration accept or reject message comprising first information and second information from the core network device, and to perform cell selection based on the first information and the second information. The first information indicates one or more radio access technologies that are restricted from being used for cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

Description

FORBIDDEN TRACKING AREA LIST ENHANCEMENTS FOR RADIO ACCESS TECHNOLOGY RESTRICTIONTECHNICAL FIELD

[0001] Various example embodiments described herein generally relate to communication technologies, and more particularly, to devices, methods, apparatuses and computer readable media for forbidden tracking area (TA) list enhancements for radio access technology (RAT) restriction.BACKGROUND

[0002] Certain abbreviations that may be found in the description and / or in the figures are herewith defined as follows:AMF Access and Mobility management FunctionAS Access StratumCN Core NetworkMME Mobility Management EntityNAS Non-Access StratumNTN Non-Terrestrial NetworkPLMN Public Land Mobile NetworkRAN Radio Access NetworkRAT Radio Access TechnologyRRC Radio Resource ControlTA Tracking AreaTAC Tracking Area CodeTAI Tracking Area IdentifierTAL Tracking Area List

[0003] In recent years, various radio access technologies (RATs) have been emerging to support diverse mobile services and wireless connections. Different RATs have their own advantages and disadvantages. An operator may deploy more than one RATs in a network, e.g., a cellular network, to meet different needs of users. Based on user’s subscription and / or operator’s preferences, user equipment may be restricted to utilize or not to utilize certain RAT(s).SUMMARY

[0004] A brief summary of exemplary embodiments is provided below to provide basic understanding of some aspects of various embodiments. It should be noted that this summary is not intended to identify key features of essential elements or define scopes of the embodiments, and its sole purpose is to introduce some concepts in a simplified form as a preamble for a more detailed description provided below.

[0005] In a first aspect, an example embodiment of a terminal device is provided. The terminal device may comprise at least one processor and at least one memory storing instructions. The instructions may, when executed by the at least one processor, cause the terminal device at least to transmit a registration request to a core network device, to receive a registration accept or reject message comprising first information and second information from the core network device, and to perform cell selection based on the first information and the second information. The first information indicates one or more radio access technologies that are restricted from being used for the cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

[0006] In an example embodiment, the second information comprises a list of forbidden tracking areas comprising the one or more tracking areas, and an indication of whether the list of forbidden tracking areas is allowed to be used for the cell selection.

[0007] In an example embodiment, the second information further indicates a cause associated with the list of forbidden tracking areas being allowed for or excluded from the cell selection.

[0008] In an example embodiment, the list of forbidden tracking areas is provided on a per radio access technology basis for at least one radio access technology other than the one or more radio access technologies restricted in the first information, with information indicating the radio access technology associated with the list of forbidden tracking areas.

[0009] In an example embodiment, the second information comprises a list of partially allowed tracking areas, the partially allowed tracking areas being deployed with at least one radio access technology other than the one or more radio access technologies restricted in the first information.

[0010] In an example embodiment, the second information comprises an indication of whether the list of partially allowed tracking areas is allowed for the cell selection.

[0011] In an example embodiment, the second information further comprises a list ofpartially restricted tracking areas that are forbidden for the cell selection.

[0012] In an example embodiment, performing the cell selection based on the first information and the second information comprises excluding a tracking area from the cell selection based on that the second information indicates that the tracking area is forbidden from being used for the cell selection, and performing the cell selection based on the first information in a tracking area based on that the second information indicates that the tracking area is allowed for being used for the cell selection.

[0013] In an example embodiment, performing the cell selection based on the first information comprises selecting a first cell operating with a first radio access technology, and accessing the first cell based on that the first radio access technology is not restricted in the first information, or selecting a second cell in the tracking area operating with a second radio access technology that is not restricted in the first information based on that the first radio access technology is indicated as restricted in the first information.

[0014] In a second aspect, an example embodiment of a core network device is provided. The core network device may comprise at least one processor and at least one memory storing instructions. The instructions may, when executed by the at least one processor, cause the core network device at least to receive a registration request from a terminal device, to retrieve context information of the terminal device, and to transmit a registration accept or reject message comprising first information and second information to the terminal device. The first information indicates one or more radio access technologies that are restricted from being used for cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

[0015] In an example embodiment, the second information comprises a list of forbidden tracking areas comprising the one or more tracking areas, and an indication of whether the list of forbidden tracking areas is allowed for being used for the cell selection.

[0016] In an example embodiment, the second information further indicates a cause associated with the list of forbidden tracking areas being allowed for or excluded from being used for the cell selection.

[0017] In an example embodiment, the list of forbidden tracking areas is provided on a per radio access technology basis for at least one radio access technology other than the one or more radio access technologies restricted in the first information, with information indicating the radio access technology associated with the list of forbidden tracking areas.

[0018] In an example embodiment, the second information comprises a list of partiallyallowed tracking areas, the partially allowed tracking areas being deployed with at least one radio access technology other than the one or more radio access technologies restricted in the first information.

[0019] In an example embodiment, the second information comprises an indication of whether the list of partially allowed tracking areas is allowed for the cell selection.

[0020] In an example embodiment, the second information further comprises a list of partially restricted tracking areas that are forbidden from being used for the cell selection.

[0021] In a third aspect, an example embodiment of a method is provided. The method comprises transmitting a registration request to a core network device, receiving a registration accept or reject message comprising first information and second information from the core network device, and performing cell selection based on the first information and the second information. The first information indicates one or more radio access technologies that are restricted from being used for cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

[0022] In an example embodiment, the second information comprises a list of forbidden tracking areas comprising the one or more tracking areas, and an indication of whether the list of forbidden tracking areas is allowed to be used for the cell selection.

[0023] In an example embodiment, the second information further indicates a cause associated with the list of forbidden tracking areas being allowed for or excluded from the cell selection.

[0024] In an example embodiment, the list of forbidden tracking areas is provided on a per radio access technology basis for at least one radio access technology other than the one or more radio access technologies restricted in the first information, with information indicating the radio access technology associated with the list of forbidden tracking areas.

[0025] In an example embodiment, the second information comprises a list of partially allowed tracking areas, the partially allowed tracking areas being deployed with at least one radio access technology other than the one or more radio access technologies restricted in the first information.

[0026] In an example embodiment, the second information comprises an indication of whether the list of partially allowed tracking areas is allowed for the cell selection.

[0027] In an example embodiment, the second information further comprises a list of partially restricted tracking areas that are forbidden for the cell selection.

[0028] In an example embodiment, performing the cell selection based on the firstinformation and the second information comprises excluding a tracking area from the cell selection based on that the second information indicates that the tracking area is forbidden from being used for the cell selection, and performing the cell selection based on the first information in a tracking area based on that the second information indicates that the tracking area is allowed for being used for the cell selection.

[0029] In an example embodiment, performing the cell selection based on the first information comprises selecting a first cell operating with a first radio access technology, and accessing the first cell based on that the first radio access technology is not restricted in the first information, or selecting a second cell in the tracking area operating with a second radio access technology that is not restricted in the first information based on that the first radio access technology is indicated as restricted in the first information.

[0030] In a fourth aspect, an example embodiment of a method is provided. The method comprises receiving a registration request from a terminal device, retrieving context information of the terminal device, and transmitting a registration accept or reject message comprising first information and second information to the terminal device. The first information indicates one or more radio access technologies that are restricted from being used for cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

[0031] In an example embodiment, the second information comprises a list of forbidden tracking areas comprising the one or more tracking areas, and an indication of whether the list of forbidden tracking areas is allowed for being used for the cell selection.

[0032] In an example embodiment, the second information further indicates a cause associated with the list of forbidden tracking areas being allowed for or excluded from being used for the cell selection.

[0033] In an example embodiment, the list of forbidden tracking areas is provided on a per radio access technology basis for at least one radio access technology other than the one or more radio access technologies restricted in the first information, with information indicating the radio access technology associated with the list of forbidden tracking areas.

[0034] In an example embodiment, the second information comprises a list of partially allowed tracking areas, the partially allowed tracking areas being deployed with at least one radio access technology other than the one or more radio access technologies restricted in the first information.

[0035] In an example embodiment, the second information comprises an indication ofwhether the list of partially allowed tracking areas is allowed for the cell selection.

[0036] In an example embodiment, the second information further comprises a list of partially restricted tracking areas that are forbidden from being used for the cell selection.

[0037] In a fifth aspect, an example embodiment of an apparatus is provided. The apparatus comprises means for transmitting a registration request to a core network device, means for receiving a registration accept or reject message comprising first information and second information from the core network device, and means for performing cell selection based on the first information and the second information. The first information indicates one or more radio access technologies that are restricted from being used for cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

[0038] In a sixth aspect, an example embodiment of an apparatus is provided. The apparatus comprises means for receiving a registration request from a terminal device, means for retrieving context information of the terminal device, and means for transmitting a registration accept or reject message comprising first information and second information to the terminal device. The first information indicates one or more radio access technologies that are restricted from being used for cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

[0039] In a seventh aspect, an example embodiment of a computer readable medium is provided. The computer readable medium comprises instructions that, when executed by at least one processor of an apparatus, cause the apparatus at least to transmit a registration request to a core network device, to receive a registration accept or reject message comprising first information and second information from the core network device, and to perform cell selection based on the first information and the second information. The first information indicates one or more radio access technologies that are restricted from being used for cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

[0040] In an eighth aspect, an example embodiment of a computer readable medium is provided. The computer readable medium comprises instructions that, when executed by at least one processor of an apparatus, cause the apparatus at least to receive a registration request from a terminal device, to retrieve context information of the terminal device, and to transmit a registration accept or reject message comprising first information and second information to the terminal device. The first information indicates one or more radio accesstechnologies that are restricted from being used for cell selection, the second information indicates whether one or more tracking areas are allowed for being used for the cell selection.

[0041] The above summary provides a basic understanding of some aspects of the present disclosure. This summary is not an extensive overview of the present disclosure. Nor is it intended to be used to limit the scope of the present disclosure. Other aspects and features of the present disclosure will become apparent to those of ordinary skill in the art upon review of the following description of example implementations in conjunction with the accompanying figures.BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Some example embodiments will now be described, by way of non-limiting examples, with reference to the accompanying drawings.

[0043] Fig 1 is a schematic diagram illustrating an example of a communication network in which example embodiments of the present disclosure can be implemented.

[0044] Fig 2 is a schematic diagram illustrating tracking areas (TAs) deployed with different radio access technologies (RATs).

[0045] Fig 3 is a message flow diagram illustrating a process in accordance with an example embodiment of the present disclosure.

[0046] Fig. 4A is a flowchart illustrating a method in accordance with an example embodiment of the present disclosure.

[0047] Fig 4B is a flowchart illustrating a method in accordance with an example embodiment of the present disclosure.

[0048] Fig 4C is a flowchart illustrating a method in accordance with an example embodiment of the present disclosure.

[0049] Fig 5 is a flowchart illustrating a method in accordance with an example embodiment of the present disclosure.

[0050] Fig 6A is a flowchart illustrating a method in accordance with an example embodiment of the present disclosure.

[0051] Fig 6B is a flowchart illustrating a method in accordance with an example embodiment of the present disclosure.

[0052] Fig 7 is a flowchart illustrating a method in accordance with an example embodiment of the present disclosure.

[0053] Fig 8 is a block diagram illustrating devices in a communication system inaccordance with an example embodiment of the present disclosure.

[0054] Throughout the drawings, same or similar reference numerals indicate same or similar elements. A repetitive description on the same elements would be omitted.DETAILED DESCRIPTION

[0055] The following embodiments are exemplary. Although the specification may refer to “an”, “one”, or “some” embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. Further, when a particular feature, structure, or characteristic is described in connection of an embodiment, it is within the knowledge of one skilled in the art to apply such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. It shall be understood that although the terms “first,” “second” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0056] For the purposes of the present disclosure, the phrases “at least one of A or B”, “at least one of A and B”, and “A and / or B” means (A), (B), or (A and B). For the purposes of the present disclosure, the phrase “A, B, and / or C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B, and C).

[0057] Example embodiments described may be implemented in a communication network, such as any of the following radio access technologies (RATs): Worldwide Interoperability for Micro-wave Access (WiMAX), Global System for Mobile communications (GSM, 2G), GSM EDGE radio access Network (GERAN), General Packet Radio Service (GRPS), Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced, and enhanced LTE (eLTE), 5G (also called NR), or any future RAT such as 6G. Moreover, communication within the communication network may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), and / or Discrete Fourier Transform spread OFDM (DFT-s-OFDM).

[0058] As used herein, the term “network device” or “network node” refers to a node in a communication network via which user equipment may access the network and / or which is capable of controlling radio communication and managing radio resources within a cell. The network node or network device may be referred to a node in a radio access network (RAN) (node), such as a base station (BS), an access point (AP) or an access node, or a node in a core network (CN). The RAN network device may be, depending on the applied technology, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio head (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, or an aircraft network device.

[0059] Moreover, in connection of split architecture, the RAN network device may refer to a centralized unit (CU) of a base station and / or a distributed unit (DU) of a base station. An interface between CU and DU may be referred to as an Fl interface in NR. In the split RAN architecture, node operations may be carried out, at least partly, in the central / centralized unit, CU, (e.g. server, host or node) operationally coupled to the DU, (e.g. a radio head / node). One CU may control one or more DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some embodiments, the DUs may comprise e.g. a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the CU may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layers. Other functional splits are possible too. In practice, any processing task may be performed in either the CU or the DU and the boundary where the responsibility is shifted between the CU and the DU may depend on the applied implementation.

[0060] A RAN network device may be connected to a CN network device via a backhaul network, which may comprise a fixed network, a satellite network, or a combination thereof. The core network may comprise for example Evolved Packet Core (EPC) that operates based on the 4th generation radio access technology (also known as Long Term Evolution, LTE), a 5G Core (5GC) that operate based on the 5th generation radio access technology (also known as New Radio, NR), or a future core network. The 5G Core or future core network may have a service-based architecture including a plurality of network functions (NFs), which may be implemented as a software running on dedicated hardware (e.g., one or morephysical computing devices, such as servers), as a virtualized network function (VNF) instantiated on a physical or virtual machine, or as a container provided by infrastructure of a cloud computing system. In 5GC, example network functions may comprise an access and mobility function (AMF), an authentication server function (AUSF), a network exposure function (NEF), a network repository function (NRF), a network slicing selection function (NSSF), a policy control function (PCF), a session management function (SMF), a user plane function (UPF), a united data repository (UDM), and a network data analytics function (NWDAF).

[0061] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example, a terminal device may be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), or a Mobile Station (MS). The terminal device may include a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, USB dongles, an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like.

[0062] A term “resource”, as used herein, may refer to radio resources in time domain, in frequency domain, in space domain, and / or in code domain. Some examples of resources include e.g. a physical resource block (PRB), a radio frame, a subframe, a time slot, a subband, a frequency region, a sub-carrier, a beam, etc. The term “transmission” and / or “reception” may refer to wirelessly transmitting and / or receiving via a wireless propagation channel on radio resources.

[0063] Fig 1 illustrates an example of a communication network 100 to which example embodiments disclosed herein may be applied. The communication network 100, e.g., a cellular communication network, may comprise an access node 120A providing one or more cells, such as a cell 101 A, and an access node 120B providing one or more other cells, such as a cell 101B. Each cell may be, e.g., a macro cell, a micro cell, a femto cell, or a pico cell, for example. The cell may define a coverage area or a service area of the correspondingaccess node.

[0064] The access node 120 A may provide user equipment (UE) 110A (one or more UEs) with wireless access to the communication network 100. The wireless access may comprise downlink (DL) communication from the access node 120 A to the UE HOAand uplink (UL) communication from the UE HOAto the access node 120A. Examples of uplink channels comprise physical uplink control channel (PUCCH) for transmitting control information and physical uplink shared channel (PUSCH) for transmitting data towards the network. Examples of downlink channels comprise physical downlink control channel (PDCCH) for transmitting control information and physical downlink shared channel (PDSCH) for transmitting data towards the user equipment.

[0065] There may be a plurality of UEs 110A, HOB in the communication network, each of them may be served by the same or by different access nodes 120 A, 120B. UE may be configured with dual connectivity (DC), wherein the UE, e.g. UE HOB, may be connected to multiple access nodes 120 A, 120B. The UEs 110A, HOB may communicate with each other, in case device-to-device (D2D) communication interface is established between them via a so-called sidelink (SL). Such D2D communications may be referred to as machine-to-machine, peer-to-peer (P2P) communications, or vehi cl e-to- vehicle (V2V), for example.

[0066] In the case of multiple access nodes in the communication network, the access nodes may be connected to each other via an interface. LTE specifications call such an interface as X2 interface. An interface between an LTE node and a 5G node, or between two 5G nodes may be called Xn interface.

[0067] The access nodes 120 A and 120B may be further connected via another interface to a core network 130 of the communication network 100. The LTE specifications specify the core network as an evolved packet core (EPC), and the core network may comprise e.g. a mobility management entity (MME) and a gateway node. The MME may handle mobility of terminal devices in a tracking area (TA) encompassing a plurality of cells and handle signaling connections between the terminal devices and the core network. The gateway node may handle data routing in the core network and to / from the terminal devices. The 5G specifications specify the core network as a 5G Core (5GC). The 5G Core may comprise e.g. an access and mobility management function (AMF), a user plane function / gateway (UPF), a united data repository (UDM) and other functions. The AMF may handle termination of non-access stratum (NAS) signaling, NAS ciphering & integrity protection, registration management, connection management, mobility management, access authentication andauthorization, and security context management. The UPF node may support packet routing and forwarding, packet inspection and quality of service (QoS) handling, for example. The UDM node may perform authentication procedures, stores and manages user data, including such as subscriber profiles, authentication credentials, and authorization policies, implements security mechanisms to protect user data and resources of the communication network (e.g., the core network 130) from unauthorized access attacks and vulnerabilities, and interacts with other network functions of the core network 130 to enforce access control policies, Quality of Service (QoS) parameters, and service restrictions based on user profiles and subscription plans. The UDM is also responsible for managing the registration of network functions that serve UE.

[0068] In some example embodiments, the core network 130 comprises a core network device / node comprising at least one network function (e.g., AMF, UPF, UDM, ... etc.). The core network device / node comprising a network function refers to a device / node performing and / or configured to perform at least part of functionalities of the network function.

[0069] The communication network 100 may be deployed with multiple radio access technologies (RATs) such as 3G, 4G, 5G and 6G to meet different needs of users. Fig. 2 shows an example scenario 200 where a first tracking area TAI comprises cells with radio access technologies RATI, RAT2, and a second tracking area TA2 comprises cells with radio access technologies RATI, RAT2 and RAT3. The network, e.g., an access and mobility management function in the core network, may be able to restrict UE from accessing certain RATs by delivering RAT utilization restriction information in association with a public land mobile network (PLMN) list to the UE in a registration procedure. The PLMN list may indicate one or more PLMNs, i.e., operators, that are allowed for the UE to use. The RAT utilization restriction information (or “RAT restriction information” for short) may indicate one or more RATs that the UE is allowed or not to use for access to the network. For example, in the example scenario 200 shown in Fig. 2, the network can prevent UE from accessing cells configured with RAT2 and RAT3 and allow the UE to access cells configured with RATI by configuring and sending proper RAT restriction information (e.g., RAT utilization control information element (IE)) to the UE.

[0070] Another way to restrict the UE from accessing to certain networks is using a forbidden TA list. Specifically, the network may provide to the UE a forbidden TA list which indicates one or more TAs that the UE is not allowed to access. In the forbidden area, the UE is prohibited to initiate any communication with the network for this PLMN. The UEbehavior in terms of PLMN selection, RAT selection and cell selection depends on the network response that informs the UE of the forbidden area. For example, in the example scenario 200 shown in Fig. 2, the network can prevent the UE from accessing the tracking areas TAI and TA2 by sending to the UE a forbidden TA list indicating that the tracking areas TAI and TA2 are not allowed for the UE to access.

[0071] To manage UE mobility in a flexible way, it would be desirable to be able to configure both the RAT utilization restriction and the forbidden TA list for UEs. However, these two concepts may not work together. That is the RAT utilization restriction and the forbidden TA list may conflict with each other if they are both configured for UEs. In addition, a tracking area may be configured with more than one RTA. The use of the forbidden TA list may penalize a RAT that is not supposed to be restricted just because the operator has configured two or more RATs in the same TA. For example, referring to Fig. 2, the operator wants to forbid RAT2 and RAT3 and to allow RATI for UEs. If the network configures and sends a forbidden TA list containing both TAI and TA2 to UEs, it ends up forbidding also RATI.

[0072] Some example embodiments of the present disclosure propose various forbidden TA list enhancements so that the enhanced forbidden TA list can be used in combination with RAT restriction for UE access and mobility management. In some examples, the network may indicate to UEs, implicitly or explicitly, whether or not a forbidden TA list is allowed to be used for RAT restriction, or the indication may be included as a part of the forbidden TA list. The indication may be provided on a per TA list basis or on a per TA basis. The network may also indicate a cause for allowing or forbidding the forbidden TA list to be used for RAT restriction. In some examples, more than one TA list may be provided to UEs. For example, the network may provide the forbidden TA list per RAT, including a RAT that is currently used to serve UE and other RATs that are supported at the UE. In another example, the network may provide to UE one or more overlapping TA lists including TAs that belong to different RATs, including restricted RATs and non-restricted RATs, and indicate whether the one or more overlapping TA lists are allowed for or forbidden from being used for RAT restriction. Optionally, the network may also indicate RAT information relating to each tracking area indicated in the overlapping TA list. In some examples, the network may indicate whether the forbidden TA list or respective tracking areas indicated in the forbidden TA list are allowed for or excluded from cell selection, and optionally one or more RATs that are allowed for the forbidden TA list or the respective tracking areas to use in the cellselection. It would be appreciated that examples of the forbidden TA list enhancements described in the present disclosure may be combined in any way to produce new examples.

[0073] Fig 3 is a message flow diagram illustrating a process 300 in accordance with some example embodiments of the present disclosure. The process 300 may be implemented at UE 110, one or more RAN nodes 120 (e.g., gNB 120A and gNB 120B as shown) and a core network node 130. The core network node 130 may refer to a node that is responsible for mobility management, e.g., the MME in EPC, the AMF in 5GC, or an equivalent mobility management entity or network function in a future core network.

[0074] Referring to Fig. 3, the UE 110 may transmit at 302 a registration request message to the network to initiate a registration process. The registration request message is a non-access stratum (NAS) layer message and contains information about the UE 110, to register the UE 110 with the core network. The UE 110 may transmit the registration request message via the RAN node 120Ato the core network node 130 once an RRC connection is established between the UE 110 and the RAN node 120A.

[0075] In response to the registration request, the core network node 130 may retrieve at 304 UE context from another core network node (not shown), e.g., the UDM in 5GC. The UE context may comprise subscription profile of the UE 110.

[0076] At 306, the core network node 130 may determine that it has configured one or more tracking areas (TAs) that contain cells operating with more than one radio access technologies (RATs). In such case, if both RAT restriction and forbidden TA list are configured in a legacy way for the UE 110, a RAT that is not supposed to be restricted may be unexpectedly forbidden in a TA that involves more than one RATs, as discussed above with respect to Fig. 2. Then, the core network node 130 may decide to configure an enhanced forbidden TA list for the UE 110, which will be described below in detail.

[0077] Based on the UE context and the network configuration and / or status, the core network node 130 may configure RAT restriction and enhanced forbidden TAlist for the UE 110, and transmit information or configuration of the RAT restriction and enhanced forbidden TAlist in a registration accept or reject message to the UE 110 at 308, depending on whether or not the registration procedure is successfully performed. It would be appreciated that some registration messages are omitted in Fig. 3 in order not to obscure the present disclosure. The registration accept message and the registration reject message both are NAS messages and they are transmitted via the serving gNB 120Ato the NAS layer of the UE 110. Either of them can be used to convey the RAT restriction information and theenhanced forbidden TA list information. In an example embodiment, the RAT restriction information may be contained in for example a RAT utilization control information element (IE), and the enhanced forbidden TA list information may be contained in for example an enhanced Forbidden TA List IE. The RAT restriction information may indicate one or more RATs that are restricted from being used at the UE 110 for cell selection. Additionally or alternatively, the RAT restriction information may indicate one or more RATs that are allowed to be used at the UE 110 for cell selection. For example, the RAT restriction information may contain a bit map in association with a RAT list. A bit “1” may indicate a corresponding RAT in the RAT list is allowed to be used at the UE 110, and a bit “0” may indicate the corresponding RAT is restricted from being used at the UE 110. The enhanced forbidden TAlist information may comprise one or more forbidden TAlists and an indication of whether or not the respective forbidden TA lists or respective TAs in each list are allowed to be used for RAT restriction. Some examples of the enhanced forbidden TAlist information and subsequent cell selection will be discussed below. It is worth noting that, throughout the present disclosure, reference to cell selection also covers cell re-selection.

[0078] If / Based on the registration accept message is received, the UE 110 successfully registers with the core network and can receive service provided by the network. If the registration reject message is received, the UE 110 can find a cause code in the registration reject message indicating a specific reason for the rejection. The UE 110 can take appropriate actions in response to the rejection cause, including for example re-attempting the registration or notifying the user. For instance, if the registration request is rejected due to forbidden TA, the UE 110 is not allowed to access the network with this PLMN. The UE 110 may proceed to PLMN selection and cell selection and then re-send the registration request with a new PLMN. If the registration request is rejected due to RAT restriction, the UE 110 may proceed to cell selection with the same PLMN and re-send the registration request with a new cell operating in a new RAT. In either case, the RAT restriction information and the enhanced forbidden TAlist information received in the registration accept or reject message will be considered for the cell selection.

[0079] At 310, the UE 110 may turn to an RRC idle state for any possible reason.

[0080] In order to make sure that the UE 110 would not select or latch on to any of the restricted RATs and forbidden TAs, the UE 110 may send from the NAS layer to the access stratum (AS) layer the RAT restriction information and the enhanced forbidden TA list information at 312. Then the UE AS layer can use the RAT restriction information and theenhanced forbidden TA list information to manage / handle the cell selection.

[0081] The UE 110 may perform in the AS layer a cell selection based on the RAT restriction information and the enhanced forbidden TA list information at 314. If the registration reject message is received at 308 indicating a rejection cause of forbidden TA, the UE 110 may also carry out PLMN selection before the cell selection, based on a PLMN list received in the registration reject message indicating one or more PLMNs that are allowed for the UE 110 to use. Based on the RAT restriction information and the enhanced forbidden TA list information, the UE 110 can select a cell served with a non-restricted RAT in a non-forbidden tracking area. Some examples of the cell selection will be discussed below in detail. In the example show in Fig. 3, it is assumed that the UE 110 selects a cell with RAT2 supported by the gNB 120B.

[0082] Then the UE 110 may access the selected cell by for example a random access channel (RACH) procedure at 316.

[0083] Optionally, if the registration reject message is received at 308, the UE 110 may reinitiate the registration procedure at 318. For instance, the UE 110 may transmit a registration request with new PLMN and / or RAT to the network.

[0084] In some example embodiments, the NAS layer in the UE may be a NAS entity and the AS layer in the UE may be an AS entity.

[0085] Some examples of the enhanced forbidden TA list information provided from the network to the UE will be described hereinafter. In an example, the enhanced forbidden TA list information may contain a list of forbidden TAs, and an indication of whether or not the list of forbidden TAs is allowed to be used for RAT restriction, or in other words, whether or not the list of forbidden TAs is to be used for cell selection. The list may contain one or more tracking area codes (TACs) or tracking area identities / identifiers (TAIs). The indication, namely a flag or notification, may comprise for example one bit with a value “0” indicating that the list of forbidden TAs is allowed to be used for RAT restriction, or a value “1” indicating that the list of forbidden TAs is not allowed to be used for RAT restriction. In case the list of forbidden TAs is allowed to be used for RAT restriction, the UE 110 is prohibited to access cells belonging to the forbidden TAs indicated in the list, and it would exclude the forbidden TAs in the cell selection procedure. In case the list of forbidden TAs is not used for RAT restriction, the UE 110 is allowed to access one or more cells belonging to the forbidden TAs indicated in the list if the one or more cells are served with a radio access technology that is not restricted in the RAT restriction information. Then the UE mayconsider the forbidden TAs indicated in the list in the cell selection procedure. For instance, referring to Fig. 2, assume a scenario where the RAT restriction information indicates that RTA1 is allowed and RAT2, RAT3 are restricted, and the list of forbidden TAs includes both TAI and TA2. If the enhanced forbidden TA list information indicates that the forbidden TA list is used for RAT restriction (i.e., not used for cell selection), the UE will exclude TAI and TA2 from the cell selection. As a result, the UE cannot access cells in TAI and TA2, including cells with RATI. If the enhanced forbidden TA list information indicates that the forbidden TA list is not used for RAT restriction (i.e., used for cell selection), the UE will consider cells with non-restricted RATs in TAI and TA2 for the cell selection. As a result, the UE can still access cells with RATI in TAI and TA2.

[0086] In an example, the enhanced forbidden TAlist information may also indicate a cause, e.g. by including a cause code, of allowing or not allowing the forbidden TA list to be used for the cell selection. For instance, an example cause for allowing the forbidden TAlist to be used for the cell selection may be that the forbidden TA list contains TAIs that are deployed with non-restricted RATs. Example causes for not allowing the forbidden TA list to be used for the cell selection may include for example user subscription limits or security requirements not satisfied or congestion.

[0087] In an example, the enhanced forbidden TA list information may provide the forbidden TA list on a per RAT basis. For instance, the enhanced forbidden TA list information may provide one or more forbidden TA lists for at least one or more nonrestricted RATs, respectively. The enhanced forbidden TAlist information may also indicate the non-restricted RAT relating to the respective forbidden TA lists. For example, in the example scenario 200 shown in Fig. 2, in case RATI is allowed while RAT2 and RAT3 are restricted, the enhanced forbidden TA list information may provide a first forbidden TA list including TAI and TA2 and indicate that the first forbidden TA list is related to RATI . If the first forbidden TA list is indicated to be used for cell selection, then the UE can select cells with RATI in TAI and TA2. It would be beneficial for access and mobility management in connection with a specific RAT.

[0088] In another example, the enhanced forbidden TA list information may provide the forbidden TA list on a per RAT basis for one or more RATs supported at the UE, including non-restricted and restricted RATs. For instance, in the example scenario 200 shown in Fig.2, in case that the UE supports RATI, RAT2 and RAT3, that the enhanced forbidden TA list information may provide a first forbidden TA list including TAI and TA2 for RATI, that asecond forbidden TA list including TAI and TA2 for RAT2, and that a third forbidden TA list including TA2 for RAT3. The enhanced forbidden TA list information may also indicate that the first forbidden TA list (TAI, TA2) and the second forbidden TA list (TAI, TA2) are used for the cell selection, and the third forbidden TA list (TA2) is not used for the cell selection. If the RAT restriction information indicates that RATI is allowed and RAT2, RAT3 are restricted, then the UE can select cells with RATI in TAI and TA2 because the first forbidden TA list is used for the cell selection. It is noted that the UE cannot select cells with RAT2 in TAI and TA2 indicated in the second forbidden TA list because RAT2 is restricted in the RAT restriction information. If the network updates the RAT restriction information configured to the UE such that RATI, RAT3 are restricted and RAT2 is allowed, then the UE can select cells with RAT2 in TAI and TA2 because the second forbidden TA list is used for the cell selection. Since the forbidden TA lists for all UE supported RATs have been provided to the UE, the network does not need to update the enhanced forbidden TA list information at every RAT restriction change, thereby preventing extra signaling load resulting from the RAT restriction change.

[0089] An example representing a possible impact of providing the forbidden TA list on a per RAT basis for more than one RATs on 3rd Generation Partnership Project Technical Specification (3GPP TS) 24.501 is shown below.Table 9.11.3.9.1: Tracking area identity list information element Value part of the Tracking area identity list information element (octets 3 to n) The value part of the Tracking area identity list information element consists of one or several partial tracking area identity lists. The length of each partial tracking area identity list can be determined from the 'type of list' field and the 'number of elements' field in the first octet of the partial tracking area identity list.The UE shall store the complete list received. If more than 16 TAIs are included in this information element, the UE shall store the first 16 TAIs and ignore the remaining octets of the information element.Partial tracking area identity list:Type of list (octet 1)Bits7 60 0 list of TACs belonging to one PLMN or SNPN, with non-consecutive TAC values0 1 list of TACs belonging to one PLMN or SNPN, with consecutive TAC values 1 0 list of TAIs belonging to different PLMNs (see NOTE)1 1 list of TAIs belonging to different RATs (see NOTE 2)NOTE 1: If the "list of TAIs belonging to different PLMNs" is used, the PLMNs included in the list need to be present in the list of "equivalent PLMNs". This type of list is not applicable in an SNPN.NOTE 2: If the "list of TAIs belonging to different RATs" is used, the RAT information is included in the list.

[0090] In an example, in addition to or as an alternative of the above-mentioned forbidden TA list, the enhanced forbidden TA list information may provide a list of partially allowed TAs. The list of partially allowed TAs may include one or more overlapping tracking areas that are deployed with more than one RATs, including not only the restricted RAT(s), but also one or more non-restricted RATs. The enhanced forbidden TA list information may include a list type field associated with each list indicating what list is provided, e.g., a forbidden TA list, a partially allowed TA list, or others. Inclusion of the list of partially allowed TAs may implicitly indicate that the list of partially allowed TAs is used for the cell selection, or the enhanced forbidden TA list information may further comprise an indication (or as a part of the list) of whether or not the list of partially allowed TAs is used for the cell selection. The UE may be allowed to access at least a part of the respective overlapping TAs with the non-restricted RATs. This is where the name “partially allowed TA” comes from. For instance, in the example scenario 200 shown in Fig. 2, if RATI is allowed and RAT2, RAT3 are restricted, the enhanced forbidden TA list information may provide a list of partially allowed TAs comprising TAI and TA2, and the UE may be allowed to select and access cells with RATI in TAI and TA2.

[0091] In an example, the enhanced forbidden TAlist information may further provide RAT information related to the list of partially allowed TAs. For instance, the enhanced forbidden TA list information may indicate which RAT(s) is allowed for the list of partially allowed TAs, and optionally which RAT(s) is not allowed for the list of partially allowed TAs. The RAT information may be provided per tracking area or per list. For example, in the example scenario 200 shown in Fig. 2, if RATI, RAT3 are allowed and RAT2 is restricted, the enhanced forbidden TA list information may provide a list of partially allowed TAs comprising TAI, TA2, and indicate that RATI, RAT3 are allowed for the list, or indicate that RATI is allowed for TAI, and RATI, RAT3 are allowed for TA2. It can facilitate UE’s ability to select an appropriate cell with allowed RAT in a tracking area.

[0092] In an example, the enhanced forbidden TA list information may provide complementary information of the list of partially allowed TAs, e.g., a list of partiallyrestricted TAs. The list of partially restricted TAs may include one or more overlapping tracking areas that are excluded from the cell selection. In other words, the list of partially restricted TAs is equivalent to a list of partially allowed TAs that is indicated not to be used for the cell selection. For the list of partially restricted TAs, no cell / RAT can be used at UE.

[0093] In the above-described examples, applicability of the forbidden TA list (including the partially allowed TA list) for the cell selection is indicated on a per list basis. It can save signaling overhead. In some other examples, the enhanced forbidden TA list information may provide an indication for each or at least one tracking area contained in the forbidden TA list regarding whether or not the tracking area is allowed to be used for the cell selection with a non-restricted RAT(s). The indication may comprise for example a flag bit with a value “1” indicating that the tracking area is allowed to be used for the cell selection or a value “0” indicating that the tracking area is not allowed to be used for the cell selection. It can achieve precise access and mobility management over specific tracking areas. For instance, in the example scenario 200 shown in Fig. 2, if RATI is allowed and RAT2, RAT3 are restricted, the enhanced forbidden TA list information may indicate that TAI is allowed for the cell selection and TA2 is not allowed for the cell selection. Then the UE is allowed to select and access cells with RATI in TAI, but it is not allowed to select or access cells with RATI in TA2 even though TA2 also includes one or more cells with RATI.

[0094] In some examples, the enhanced forbidden TA list information may indicate whether each or at least one tracking area contained in the forbidden TA list is fully or partially forbidden for the UE. If the tracking area is fully forbidden, the UE is not allowed to access any cell in the tracking area. If the tracking area is partially forbidden, the UE is allowed to access one or more cells with a non-restricted RAT(s) in the tracking area. Optionally, in case a tracking area is indicated as a partially forbidden tracking area, the enhanced forbidden TA list information may further indicate whether the partially forbidden tracking area is allowed for or excluded from the cell selection.

[0095] The enhanced forbidden TA list information may also provide a cause code and / or RAT-related information for each or at least one tracking area in the forbidden TA list (including the partially allowed TA list). As described above, the cause code may indicate a cause of the tracking area being allowed or not allowed for the cell selection, the RAT-related information may indicate one or more RATs that are allowed and / or not allowed for the tracking area. Since some examples of the cause code and the RAT-related information have been discussed above in detail, a repetitive description thereof is omitted here forconvenience.

[0096] As mentioned above, the UE 110 may carry out cell selection based on the RAT restriction information and the enhanced forbidden TA list information at 314. Cell selection refers to a procedure by which UE acquires time and frequency synchronization with a cell and detects system information of the cell. Even though the detailed mechanism of cell selection varies a little bit depending on specific radio access technology, the basic concept and purpose is substantially same. Take the cell selection procedure in the 5G NR network as an example. The UE 110 may detect synchronization signal block (SSB) on synchronization raster and try to decode master information block (MIB) on a physical broadcast channel (PBCH). Based on the MIB, the UE 110 may decode system information block 1 (SIB1) on physical downlink shared channel (PDSCH). The MIB and SIB1 contain system information of the cell which is needed for the UE 110 to initiate a random access channel (RACH) procedure towards the cell. In other radio access technologies, the UE 110 can also obtain such system information of a cell in a similar way during the cell selection. Then the UE 110 can establish an RRC connection with the cell by initiating the RACH procedure.

[0097] During the cell selection, the system information received from the cell includes a PLMN identity, a tracking area code (TAC) and radio access technology related information of the cell. For example, such information may be included in the SIB1 received from a NR cell. The tracking area code indicates which tracking area the cell belongs to, and the radio access technology related information indicates which radio access technology is used at the cell. The PLMN identity and the tracking area code constitute a tracking area identity (TAI) which identifies a tracking area globally. The UE 110 may evaluate whether it is allowed to access the detected cell based on the system information received from the cell, before initiating the RACH procedure. In an example, if the enhanced forbidden TA list information indicates that the tracking area to which the cell belongs is not allowed to be used for the cell selection, the UE 110 may exclude the tracking area from the cell selection. In this case, the UE 110 may proceed to select a new PLMN and perform the cell selection again. If there are no available PLMNs, the UE 110 may pop up a window notifying the user that there are no available networks.

[0098] If the enhanced forbidden TA list information indicates that the tracking area to which the detected cell belongs is allowed to be used for the cell selection, the UE 110 may evaluate whether or not the cell operates with a non-restricted radio access technology, i.e.,a radio access technology that is not restricted in the RAT restriction information. If the cell operates with a non-restricted radio access technology, the UE 110 may access the cell by for example initiating a RACH procedure. If the cell operates with a radio access technology that is restricted in the RAT restriction information, the UE 110 may abandon the cell and perform the cell selection again to select a new cell. The UE 110 may perform the process repeatedly until it finds a cell operating with a non-restricted radio access technology in the tracking area or it determines that there are no available cells in the tracking area. In the latter case, the UE 110 may proceed to select a new PLMN and attempt the cell selection again. If there are no available PLMNs, the UE 110 may pop up a window notifying the user that there are no available networks.

[0099] In the example embodiments described here, the forbidden TA list information is enhanced to include one or more lists of tracking areas with additional information indicating whether the one or more lists or respective tracking areas are allowed for UE to access. The enhanced forbidden TA list information may further provide information about a cause for allowing or forbidding UE to access a list or a tracking area, and radio access technologies related to the list or the tracking area. As such, the enhanced forbidden TA list information can be used in combination with the RAT restriction information. It can provide flexible and precise control over access and mobility of UEs.

[0100] Fig 4 A illustrates a method 400 according to an example embodiment of the present disclosure. The method 400 may be implemented at user equipment (UE), such as the UE 110 discussed above.

[0101] Referring to Fig. 4, the method 400 may comprise transmitting at 410 a registration request to a core network device such as the core network node 130 discussed above, receiving at 420 a registration accept or reject message comprising first information and second information from the core network device, and performing at 430 cell selection based on the first information and the second information. The first information may indicate one or more radio access technologies (RATs) that are restricted from being used for the cell selection. In an example embodiment, the first information may comprise the RAT restriction information described above. The second information may indicate whether or not one or more tracking areas (TAs) are allowed to be used for the cell selection. In an example embodiment, the second information may comprise the enhanced forbidden TA list information described above.

[0102] In an example embodiment, the second information may comprise a list offorbidden tracking areas and an indication of whether or not the list of forbidden tracking areas is allowed to be used for the cell selection. For instance, the indication may be a flag bit with a value “0” or “1” indicating whether or not the list of forbidden tracking areas is to be used for the cell selection.

[0103] In an example, the second information may further indicate a cause associated with the list of forbidden tracking areas being allowed for or excluded from the cell selection. For instance, an example cause for the list of forbidden tracking areas being allowed to be used for the cell selection may include that the list contains at least one tracking area deployed with a non-restricted radio access technology(ies).

[0104] In an example, the list of forbidden tracking areas is provided on a per radio access technology basis for one or more non-restricted radio access technologies, i.e., one or more radio access technologies different from the one or more radio access technologies restricted in the first information. The second information may comprise one or more lists of forbidden tracking areas for the one or more non-restricted radio access technologies, respectively. The second information may further indicate the radio access technology associated with each list of forbidden tracking areas.

[0105] In an example, the second information may comprise a list of partially allowed tracking areas. The partially allowed tracking areas each is deployed with at least one nonrestricted radio access technology. The second information may include a list type field associated with each list indicating what list is provided, e.g., a forbidden TA list, a partially allowed TA list, or others. Inclusion of the list of partially allowed TAs may implicitly indicate that the list of partially allowed TAs is used for the cell selection, or the second information may further comprise an indication of whether or not the list of partially allowed TAs is allowed to be used for the cell selection.

[0106] In an example, the second information may further comprise a list of partially restricted tracking areas, as complementary information of the list of partially allowed tracking area. The partially restricted tracking areas each is also deployed with at least one non-restricted radio access technology, but the list of partially restricted TAs is not allowed to be used for the cell selection.

[0107] The UE may perform the cell selection based on the first information and the second information. Generally, the UE may detect a cell in the cell selection procedure. If the cell operates with a radio access technology that is not restricted in the first information, and the cell belongs to a tracking area that is allowed for the cell selection as indicated in the secondinformation, the UE may select the cell to access. If the cell operates with a radio access technology that is restricted in the first information, or the cell belongs to a tracking area that is not allowed for the cell selection as indicated in the second information, the UE may ignore / abandon the cell and perform the cell selection procedure to detect a new cell.

[0108] Fig 4B illustrates operations carried out at user equipment (UE) such as the UE 110 described above for the cell selection. Referring to Fig. 4B, the UE may exclude at 432 a tracking area from the cell selection based on that the second information indicates that the tracking area is forbidden from being used for the cell selection, and perform at 434 the cell selection based on the first information in a tracking area based on that the second information indicates that the tracking area is allowed for being used for the cell selection.

[0109] For example, the UE may receive system information of a cell by monitoring synchronization signal block (SSB) during the cell selection. The system information indicates, among others, a PLMN identity of the cell, a tracking area which the cell belongs to, and a radio access technology used in the cell. If the second information indicates that the tracking area to which the cell belongs is not allowed for the cell selection, i.e., not allowed for the UE to access, the UE may exclude the tracking area from the cell selection. In this case, the UE may proceed to select a new PLMN and perform the cell selection with the new PLMN. If the second information indicates that the tracking area to which the cell belongs is allowed for the cell selection, i.e., allowed for the UE to access, the UE can proceed with the cell selection based on the first information.

[0110] Fig 4C illustrates operations carried out at the UE for performing the cell selection based on the first information in a tracking area that is indicated in the second information as being allowed for the cell selection. Referring to Fig. 4C, the UE may select at 435 a first cell operating with a first radio access technology, and determine at 436 whether the first radio access technology is restricted for the UE to use based on the first information. If the first radio access technology is not restricted in the first information, the UE may proceed to access the selected first cell with the first radio access technology at 437, e.g., by initiating a RACH procedure towards the first cell. If the first information indicates that the first radio access technology is restricted for the UE, i.e., not allowed for the UE to use, the UE may proceed to select at 438 a second cell in the tracking area operating with a second radio access technology that is not restricted in the first information.

[0111] Fig 5 illustrates a method 500 according to an example embodiment of the present disclosure. The method 500 may be implemented at a core network device, such as the corenetwork node 130 discussed above. The core network device may be the MME in EPC, the AMF in 5GC, or an equivalent mobility management entity or network function in other core networks.

[0112] Referring to Fig. 5, the method 500 may comprise receiving at 510 a registration request from UE such as the UE 110 described above, retrieving at 520 UE context of the UE in response to the registration request, and transmitting at 530 a registration accept or reject message to the UE depending on whether the registration procedure is successfully performed or not. In either case, the registration accept or reject message may contain, among others, first information indicating one or more radio access technologies that are restricted from being used for cell selection, and second information indicating whether one or more tracking areas are allowed for being used for the cell selection. In an example embodiment, the first information and the second information may be determined based at least in part on the UE context, e.g., based on a subscription profile included in the UE context. In an example embodiment, the first information may comprise the RAT restriction information described above, the second information may comprise the enhanced forbidden TA list information described above. Some examples of the first information and the second information have been described above with respect to Figs. 4A-4C, a repetitive description thereof is omitted here for convenience.

[0113] Fig 6 A illustrates a method 600 according to an example embodiment of the present disclosure. The method 600 may be implemented at user equipment (UE), such as the UE 110 discussed above.

[0114] Referring to Fig. 6, the method 600 may comprise transmitting at 610 a registration request to a core network device such as the core network node 130 discussed above, receiving at 620 a registration accept or reject message comprising first information and second information from the core network device, and performing at 630 cell selection based on the first information and the second information. The first information may indicate one or more radio access technologies (RATs) that are restricted from being used for the cell selection. In an example embodiment, the first information may comprise the RAT restriction information described above. The second information may indicate whether or not one or more tracking areas (TAs) are respectively allowed for at least one non-restricted radio access technology, i.e., at least one radio access technology other than the one or more radio access technologies restricted in the first information. In an example embodiment, the second information may comprise the enhanced forbidden TA list information described above.

[0115] In an example embodiment, the second information may comprise a list of forbidden tracking areas and an indication for each or at least one tracking area in the list indicating whether or not the tracking area is allowed for the at least one non-restricted radio access technology. For instance, the indication may be a flag bit with a value “0” or “1” indicating whether or not the corresponding tracking area is allowed for one or more nonrestricted radio access technologies.

[0116] In an example, the list of forbidden tracking areas may be provided per nonrestricted radio access technology with information of the radio access technology associated with the list of forbidden tracking areas. If there are multiple non-restricted radio access technologies, the second information may provide multiple lists of forbidden tracking areas for the multiple non-restricted radio access technologies, respectively.

[0117] In an example, in case at least one first tracking area in the one or more tracking areas (e.g., in the list of forbidden tracking areas) is allowed for at least one non-restricted radio access technology, the second information may further indicate whether the at least one first tracking area is allowed for or excluded from the cell selection.

[0118] In an example, in case at least one second tracking area in the one or more tracking areas (e.g., in the list of forbidden tracking areas) is allowed for at least one non-restricted radio access technology, the second information may further indicate the at least one radio access technology that the at least one second tracking area is allowed for.

[0119] The UE may perform the cell selection based on the first information and the second information. Generally, the UE may detect a cell in the cell selection procedure. If the cell operates with a radio access technology that is not restricted in the first information, and the cell belongs to a tracking area that is allowed for the radio access technology as indicated in the second information, the UE may select the cell to access. If the cell operates with a radio access technology that is restricted in the first information, or the cell belongs to a tracking area that is not allowed for the radio access technology as indicated in the second information, the UE may ignore / abandon the cell and perform the cell selection procedure to detect a new cell.

[0120] Fig 6B illustrates operations carried out at user equipment (UE) such as the UE 110 described above for the cell selection. Referring to Fig. 6B, the UE may select at 632 a first cell operating with a first radio access technology in a tracking area that is indicated in the second information as being allowed for non-restricted radio access technologies. The UE may determine at 634 whether the first radio access technology is restricted or not in the firstinformation. If the first radio access technology is not restricted in the first information, the UE may proceed to access the selected first cell with the first radio access technology at 636, e.g., by initiating a RACH procedure towards the first cell. If the first information indicates that the first radio access technology is restricted for the UE, i.e., not allowed for the UE to use, the UE may proceed to select at 638 a second cell in the tracking area operating with a second radio access technology that is not restricted in the first information. Then the UE can access the second cell in the tracking area.

[0121] Fig 7 illustrates a method 700 according to an example embodiment of the present disclosure. The method 700 may be implemented at a core network device, such as the core network node 130 discussed above. The core network device may be for example the MME in EPC, the AMF in 5GC, or an equivalent mobility management entity or network function in other core networks.

[0122] Referring to Fig. 7, the method 700 may comprise receiving at 710 a registration request from UE such as the UE 110 described above, retrieving at 720 UE context of the UE in response to the registration request, and transmitting at 730 a registration accept or reject message to the UE depending on whether the registration procedure is successfully performed or not. In either case, the registration accept or reject message may contain, among others, first information indicating one or more radio access technologies that are restricted from being used for cell selection, and second information indicating whether or not one or more tracking areas are respectively allowed for at least one non-restricted radio access technology, i.e., at least one radio access technology different from the one or more radio access technologies restricted in the first information. In an example embodiment, the core network node may determine / configure the first information and the second information for the UE based at least in part on the UE context, e.g., based on a subscription profile included in the UE context. In an example embodiment, the first information may comprise the RAT restriction information described above, the second information may comprise the enhanced forbidden TA list information described above. Some examples of the first information and the second information have been described above with respect to Figs. 6A-6B, a repetitive description thereof is omitted here for convenience.

[0123] Fig 8 is a schematic block diagram illustrating devices in a communication system 800 in which example embodiments of the present disclosure can be implemented. As shown in Fig. 8, the communication system 800 may comprise a terminal device 810 which may be implemented as the UE 110 discussed above, a RAN device 820 which may be implementedas the RAN node 120 discussed above, and a core network device 830 which may be implemented as the core network node 130 discussed above.

[0124] Referring to Fig. 8, the terminal device 810 may comprise one or more processors 811, one or more memories 812 and one or more transceivers 813 interconnected through one or more buses 814. The one or more buses 814 may be address, data, or control buses, and may include any interconnection mechanism such as series of lines on a motherboard or integrated circuit, fiber, optics or other optical communication equipment, and the like. Each of the one or more transceivers 813 may comprise a receiver and a transmitter, which are connected to one or more antennas 816. The terminal device 810 may wirelessly communicate with the RAN device 820 through the one or more antennas 816. The one or more memories 812 may include computer program code or instructions 815. The one or more memories 812 and the computer program code / instructions 815 may be configured to, when executed by the one or more processors 811, cause the terminal device 810 to perform operations, methods and processes relating to the UE 110 as described above.

[0125] The RAN device 820 may comprise one or more processors 821, one or more memories 822, one or more transceivers 823 and one or more network interfaces 827 interconnected through one or more buses 824. The one or more buses 824 may be address, data, or control buses, and may include any interconnection mechanism such as a series of lines on a motherboard or integrated circuit, fiber, optics or other optical communication equipment, and the like. Each of the one or more transceivers 823 may comprise a receiver and a transmitter, which are connected to one or more antennas 826. The RAN device 820 may operate as a base station and wirelessly communicate with the terminal device 810 through the one or more antennas 826. The one or more network interfaces 827 may provide wired or wireless communication links through which the RAN device 820 may communicate with other network devices, entities, elements or functions. For example, the RAN device 820 may communicate with the core network device 830 via a connection 828. The one or more memories 822 may include computer program code or instructions 825. The one or more memories 822 and the computer program code / instructions 825 may be configured to, when executed by the one or more processors 821, cause the RAN device 820 to perform operations, methods and processes relating to RAN nodes 120 (e.g., 120A, 120B) as described above.

[0126] The core network device 830 may comprise one or more processors 831, one or more memories 832, and one or more network interfaces 837 interconnected through one ormore buses 834. The one or more buses 834 may be address, data, or control buses, and may include any interconnection mechanism such as a series of lines on a motherboard or integrated circuit, fiber, optics or other optical communication equipment, and the like. The core network device 830 may communicate with the RAN device 820 through one or more links. The one or more network interfaces 837 may provide wired or wireless communication links through which the core network device 830 may communicate with other network devices, entities, elements or functions. The one or more memories 832 may include computer program code or instructions 835. The one or more memories 832 and the computer program code / instructions 835 may be configured to, when executed by the one or more processors 831, cause the core network device 830 to perform operations, methods and processes relating to the core network node 130 as described above.

[0127] The one or more processors 811, 821 and 831 discussed above may be of any appropriate type that is suitable for the local technical network, and may include one or more of general purpose processors, special purpose processor, microprocessors, a digital signal processor (DSP), one or more processors in a processor based multi-core processor architecture, as well as dedicated processors such as those developed based on Field Programmable Gate Array (FPGA) and Application Specific Integrated Circuit (ASIC). The one or more processors 811, 821 and 831 may be configured to control other elements of the terminal or network devices and operate in cooperation with them to implement the operations, methods or processes discussed above.

[0128] The one or more memories 812, 822 and 832 may include at least one storage medium in various forms, such as a volatile memory and / or a non-volatile memory. The volatile memory may include but not limited to for example a random access memory (RAM) or a cache. The non-volatile memory may include but not limited to for example a read only memory (ROM), a hard disk, a flash memory, and the like. Further, the one or more memories 812, 822 and 832 may include but not limited to an electric, a magnetic, an optical, an electromagnetic, an infrared, or a semiconductor system, apparatus, or device or any combination of the above.

[0129] In some example embodiments, at least some of the processes, methods and operations described herein may be carried out by an apparatus comprising means for carrying out at least some of the described processes, methods and operations. Means for performing the processes, methods and operations as disclosed herein may include software and / or hardware components of the apparatus. For example, the at least one processor, theat least one memory, and the computer program code / instructions may form means for carrying out the processes, methods and operations as disclosed herein, and any of the embodiments thereof. As used herein the term “means” is to be construed in singular form, i.e. referring to a single element, or in plural form, i.e. referring to a combination of single elements. Therefore, terminology “means for [performing A, B, C]”, is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C. Further, terminology “means for performing A, means for performing B, means for performing C” is to be interpreted to cover an apparatus in which there is only one means for performing A, B and C, or where there are separate means for performing A, B and C, or partially or fully overlapping means for performing A, B, C.

[0130] It would be understood that blocks in the drawings may be implemented in various manners, including software, hardware, firmware, or any combination thereof. In some embodiments, one or more blocks may be implemented using software and / or firmware, for example, machine-executable instructions stored in the storage medium. In addition to or instead of machine-executable instructions, parts or all of the blocks in the drawings may be implemented, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application-Specific Standard Products (ASSPs), System-on-Chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), etc.

[0131] Some exemplary embodiments further provide computer program code or instructions which, when executed by one or more processors, may cause a device or apparatus to perform the procedures described above. The computer program code or instructions for carrying out procedures of the example embodiments may be written in any combination of one or more programming languages. The computer program code or instructions may be provided to one or more processors or controllers of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a standalone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0132] Some example embodiments further provide a computer program product or a computer readable medium having the computer program code or instructions stored therein. The computer readable medium may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but is not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0133] Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

[0134] Although the subject matter has been described in a language that is specific to structural features and / or method actions, it is to be understood the subject matter defined in the appended claims is not limited to the specific features or actions described above. On the contrary, the above-described specific features and actions are disclosed as an example of implementing the claims.

Claims

CLAIMS:

1. A terminal device comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the terminal device at least to perform:transmitting, to a core network device, a registration request;receiving, from the core network device, a registration accept or reject message comprising first information indicating one or more radio access technologies that are restricted from being used for cell selection, and second information indicating whether one or more tracking areas are allowed for being used for the cell selection; and performing the cell selection based on the first information and the second information.

2. The terminal device of claim 1, wherein the second information comprises a list of forbidden tracking areas comprising the one or more tracking areas and an indication of whether the list of forbidden tracking areas is allowed to be used for the cell selection.

3. The terminal device of claim 2, wherein the second information further indicates a cause associated with the list of forbidden tracking areas being allowed for or excluded from the cell selection.

4. The terminal device of claim 2 or 3, wherein the list of forbidden tracking areas is provided on a per radio access technology basis for at least one radio access technology other than the one or more radio access technologies restricted in the first information, with information indicating the radio access technology associated with the list of forbidden tracking areas.

5. The terminal device of any of claims 1 to 4, wherein the second information comprises a list of partially allowed tracking areas, the partially allowed tracking areas being 32deployed with at least one radio access technology other than the one or more radio access technologies restricted in the first information.

6. The terminal device of claim 5, wherein the second information comprises an indication of whether the list of partially allowed tracking areas is allowed for the cell selection.

7. The terminal device of claim 5 or 6, wherein the second information further comprises a list of partially restricted tracking areas that are forbidden for the cell selection.

8. The terminal device of any of claims 1 to 7, wherein performing the cell selection based on the first information and the second information comprises:excluding a tracking area from the cell selection based on that the second information indicates that the tracking area is forbidden from being used for the cell selection; and performing the cell selection based on the first information in a tracking area based on that the second information indicates that the tracking area is allowed for being used for the cell selection.

9. The terminal device of claim 8, wherein performing the cell selection based on the first information comprises:selecting a first cell operating with a first radio access technology; andaccessing the first cell based on that the first radio access technology is not restricted in the first information, orselecting a second cell in the tracking area operating with a second radio access technology that is not restricted in the first information based on that the first radio access technology is indicated as restricted in the first information.

10. A core network device comprising:at least one processor; andat least one memory storing instructions that, when executed by the at least oneprocessor, cause the core network device at least to perform:receiving, from a terminal device, a registration request;retrieving context information of the terminal device; andtransmitting, to the terminal device, a registration accept or reject message comprising first information indicating one or more radio access technologies that are restricted from being used for cell selection, and second information indicating whether one or more tracking areas are allowed for being used for the cell selection.

11. The core network device of claim 10, wherein the second information comprises a list of forbidden tracking areas comprising the one or more tracking areas and an indication of whether the list of forbidden tracking areas is allowed for being used for the cell selection.

12. The core network device of claim 11, wherein the second information further indicates a cause associated with the list of forbidden tracking areas being allowed for or excluded from being used for the cell selection.

13. The core network device of claim 11 or 12, wherein the list of forbidden tracking areas is provided on a per radio access technology basis for at least one radio access technology other than the one or more radio access technologies restricted in the first information, with information indicating the radio access technology associated with the list of forbidden tracking areas.

14. The core network device of any of claims 10 to 13, wherein the second information comprises a list of partially allowed tracking areas, the partially allowed tracking areas being deployed with at least one radio access technology other than the one or more radio access technologies restricted in the first information.

15. The core network device of claim 14, wherein the second information comprises an indication of whether the list of partially allowed tracking areas is allowed for the cell selection.

16. The core network device of claim 14 or 15, wherein the second information further comprises a list of partially restricted tracking areas that are forbidden from being used for the cell selection.

17. A method comprising:transmitting, to a core network device, a registration request;receiving, from the core network device, a registration accept or reject message comprising first information indicating one or more radio access technologies that are restricted from being used for cell selection, and second information indicating whether one or more tracking areas are allowed for being used for the cell selection; and performing the cell selection based on the first information and the second information.

18. The method of claim 17, wherein the second information comprises a list of forbidden tracking areas comprising the one or more tracking areas and an indication of whether the list of forbidden tracking areas is allowed to be used for the cell selection.

19. The method of claim 18, wherein the second information further indicates a cause associated with the list of forbidden tracking areas being allowed for or excluded from the cell selection.

20. The method of claim 18 or 19, wherein the list of forbidden tracking areas is provided on a per radio access technology basis for at least one radio access technology other than the one or more radio access technologies restricted in the first information, with information indicating the radio access technology associated with the list of forbidden tracking areas.

21. The method of any of claims 17 to 20, wherein the second information comprises a list of partially allowed tracking areas, the partially allowed tracking areas being deployed with at least one radio access technology other than the one or more radio access technologies restricted in the first information.

22. The method of claim 21, wherein the second information comprises an indication of whether the list of partially allowed tracking areas is allowed for the cell selection.

23. The method of claim 21 or 22, wherein the second information further comprises a list of partially restricted tracking areas that are forbidden for the cell selection.

24. The method of any of claims 17 to 23, wherein performing the cell selection based on the first information and the second information comprises:excluding a tracking area from the cell selection based on that the second information indicates that the tracking area is forbidden from being used for the cell selection; and performing the cell selection based on the first information in a tracking area based on that the second information indicates that the tracking area is allowed for being used for the cell selection.

25. The method of claim 24, wherein performing the cell selection based on the first information comprises:selecting a first cell operating with a first radio access technology; andaccessing the first cell based on that the first radio access technology is not restricted in the first information, orselecting a second cell in the tracking area operating with a second radio access technology that is not restricted in the first information based on that the first radio access technology is indicated as restricted in the first information.

26. A method comprising:receiving, from a terminal device, a registration request;retrieving context information of the terminal device; andtransmitting, to the terminal device, a registration accept or reject message comprising first information indicating one or more radio access technologies that are restricted from being used for cell selection, and second information indicating whether one or moretracking areas are allowed for being used for the cell selection.

27. The method of claim 26, wherein the second information comprises a list of forbidden tracking areas comprising the one or more tracking areas and an indication of whether the list of forbidden tracking areas is allowed for being used for the cell selection.

28. The method of claim 27, wherein the second information further indicates a cause associated with the list of forbidden tracking areas being allowed for or excluded from being used for the cell selection.

29. The method of claim 27 or 28, wherein the list of forbidden tracking areas is provided on a per radio access technology basis for at least one radio access technology other than the one or more radio access technologies restricted in the first information, with information indicating the radio access technology associated with the list of forbidden tracking areas.

30. The method of any of claims 26 to 29, wherein the second information comprises a list of partially allowed tracking areas, the partially allowed tracking areas being deployed with at least one radio access technology other than the one or more radio access technologies restricted in the first information.

31. The method of claim 30, wherein the second information comprises an indication of whether the list of partially allowed tracking areas is allowed for the cell selection.

32. The method of claim 30 or 31, wherein the second information further comprises a list of partially restricted tracking areas that are forbidden from being used for the cell selection.

33. An apparatus comprising means for performing the method of any of claims 17 to 32.3734. A computer readable medium comprising instructions that, when executed by at least one processor of an apparatus, cause the apparatus at least to perform the method of any of claims 17 to 32.38

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