WO2022208176A1

WO2022208176A1 - Methods and mechanisms for slice-based cell reselection

Info

Publication number: WO2022208176A1
Application number: PCT/IB2022/050961
Authority: WO
Inventors: Philippe Godin; Halit Murat Gürsu; György WOLFNER; Ömer BULAKCI; Muhammad NASEER-UL-ISLAM; Alessio Casati
Original assignee: Nokia Technologies Oy
Priority date: 2021-03-31
Filing date: 2022-02-03
Publication date: 2022-10-06
Also published as: JP2024512734A; EP4315997A1; CN117063531A

Abstract

Systems, methods, apparatuses, and computer program products for cell re-selection are provided. One method may include receiving radio mapping information between tracking area identifiers of tracking areas neighboring a served cell and a list of physical cell identifiers associated with each tracking area associated with physical cell identifiers corresponding to a neighbor cell of the served cell. Slice assistance information may be received from a network entity associated with the apparatus mapping one or more network slices and at least one of one or more tracking area identifiers of tracking areas in a user equipment registration area or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area supporting the one or more network slices. The radio mapping information and the slice assistance information may be used in a cell re-selection process.

Description

METHODS AND MECHANISMS FOR SLICE-BASED CELL RESELECTION TECHNICAL FIELD: [0001] Some example embodiments may generally relate to mobile or wireless telecommunication systems, such as Long Term Evolution (LTE), fifth generation (5G) radio access technology (RAT), new radio (NR) access technology, and/or other communications systems. For example, certain example embodiments may relate to systems and/or methods for cell re-selection. BACKGROUND: [0002] Examples of mobile or wireless telecommunication systems may include 5G RAT, the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), LTE Evolved UTRAN (E-UTRAN), LTE-Advanced (LTE-A), LTE-A Pro, NR access technology, and/or MulteFire Alliance.5G wireless systems refer to the next generation (NG) of radio systems and network architecture. A 5G system is typically built on a 5G NR, but a 5G (or NG) network may also be built on E-UTRA radio. It is expected that NR can support service categories such as enhanced mobile broadband (eMBB), ultra-reliable low-latency-communication (URLLC), and massive machine type communication (mMTC). NR is expected to deliver extreme broadband, ultra-robust, low latency connectivity, and massive networking to support the Internet of Things (IoT). The next generation radio access network (NG-RAN) represents the RAN for 5G, which may provide radio access for NR, LTE, and LTE-A. It is noted that the nodes in 5G providing radio access functionality to a user equipment (e.g., similar to the Node B in UTRAN or the Evolved Node B (eNB) in LTE) may be referred to as next-generation Node B (gNB) when built on NR radio, and may be referred to as next-generation eNB (NG-eNB) when built on E-UTRA radio. BRIEF DESCRIPTION OF THE DRAWINGS: [0003] For proper understanding of example embodiments, reference should be made to the accompanying drawings, wherein: [0004] FIG. 1 illustrates an example of a format of single-network slice selection assistance information. [0005] FIG.2 illustrates an example of a signaling diagram according to certain embodiments. [0006] FIG.3 illustrates an example of a flow diagram of a method according to various embodiments. [0007] FIG. 4 illustrates an example of a flow diagram of another method according to some embodiments. [0008] FIG. 5 illustrates an example of a flow diagram of another method according to certain embodiments. [0009] FIG.6 illustrates an example of various network devices according to some embodiments. [0010] FIG. 7 illustrates an example of a 5G network and system architecture according to certain embodiments. DETAILED DESCRIPTION: [0011] It will be readily understood that the components of certain example embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of some example embodiments of systems, methods, apparatuses, and computer program products for cell re-selection is not intended to limit the scope of certain embodiments, but is instead representative of selected example embodiments. [0012] An important function in Third Generation Partnership Project (3GPP) Fifth Generation (5G) is the ability to support different services using the same underlying mobile network infrastructure by way of network slices. Network slicing includes grouping devices with similar performance requirements, such as delay, throughput, and transmission rate. In this way, the physical infrastructure of a network can be divided into logically isolated virtual networks, such as according to ultra-reliable low latency communication (URLLC) and enhanced mobile broadband (eMBB). Each network slice can be uniquely identified by single-network slice selection assistance information (S-NSSAI), as illustrated in FIG.1. [0013] Currently, 3GPP allows a UE to connect to and be served by a maximum of eight single network slice selection assistance information (S-NSSAIs), while a single cell may support hundreds of S-NSSAIs, with a single tracking area (TA) able to support up to 1024 network slices. As illustrated in FIG. 1, each S-NSSAI may comprise slice service type (SST) and operator-defined slice differentiator (SD) fields (32-bit length), or just an SST field (8-bit length). The SST field may have standardized and non-standardized values, ranging from 0 to 127. For example, an SST value of 1 may indicate that the network slice is compatible with 5G eMBB, while an SST value of 2 may indicate that the network slice is compatible with URLLC. While network slices provide numerous benefits, some enterprise/industrial scenarios may require service continuity when the UE moves into neighboring cells where the network slice is unavailable. Thus, it would be beneficial for a UE to have uninterrupted service of on-going protocol data unit (PDU) sessions in order to provide service continuity. [0014] While in idle/inactive mode, the UE may perform periodic cell re-selection, and may camp on a cell while selecting a more suitable cell. During cell re-selection, the UE may detect neighboring cells, decode the master information block (MIB) from the detected neighboring cells, prioritize the detected neighboring cells, and select the best cell. The UE may then decode the system information block (SIB1) of the selected best cell to determine if the selected best cell is a suitable cell. If not, the UE may evaluate the second prioritized cell by decoding the SIB1 of the second prioritized cell until the UE finds a suitable cell. [0015] As noted above, UEs currently do not consider network slices supported in neighboring cells during cell re-selection. This results in active PDU sessions being dropped once the UE enters a connected state, breaking service continuity. In addition, even if each cell broadcasts its supported network slices, the UE would need to decode SIB1 for every cell, needlessly consuming network resources and delaying service continuity. Current cell re-selection techniques do not consider network slices supported in neighboring cells. Cell re-selection in network slicing deployments has been considered for service continuity, which comprises retaining established PDU sessions on any slice, e.g., for RRC inactive UEs. This is not supported since the UE is unaware of the slice support of any neighbor cell. Thus, after cell re-selection, the UE may select a cell that does not support the network slice having a PDU session. As a result, the UE connects with the cell, and has to perform a registration area update procedure, after which the PDU session of the UE may be dropped as the network slice is not supported in that cell. This challenge also applies to RRC-idle UEs, i.e., when the UEs re-select a cell without the slice support for the intended slice of the UE, e.g., a slice from allowed NSSAI (or a new slice the UE has chosen to connect), the non-supported network slice in the TA of the cell will not be included in the allowed NSSAI in the registration accept message. [0016] Certain embodiments described herein may have various benefits and/or advantages to overcome at least the disadvantages described above, as well as other problems that may not be described herein. For example, certain embodiments may avoid transmitting duplicative identifiers, such as group ID. Some embodiments may also enable broadcasting of information that is limited in size, and enable fast cell re-selection. Various example embodiments may also enable PDU session continuity, enabling service continuity through slice supporting cell re-selection. Thus, certain embodiments discussed below are directed to improvements in computer-related technology. [0017] According to an embodiment, a fifth generation core (5GC) network may transmit, to a UE, a list of network slices in the UE-configured NSSAI and/or UE-allowed NSSAI supported by tracking areas (TAs) neighboring the current registration area (RA), and supported in TAs in the current RA. This list of network slices can allow the UE to select the best cell, if radio conditions allow, thereby maximizing the service continuity or the ability to accept the requested slices. [0018] FIG.2 illustrates an example of a signalling diagram depicting cell reselection, according to an embodiment. It is noted that, in some embodiments, NE 240 and NE 250 may be similar to NE 610 illustrated in Fig.6, and UE 230 may be similar to UE 620 illustrated in FIG.6. In addition, in some embodiments, 5GC 260 may be similar to the network illustrated in FIG.7. [0019] In one embodiment, at 201, NE 250 may transmit to 5GC 260 NG setup message(s) with similar information as described below for NE 240. At 203, for intra-frequency cell reselection information, NE 240 may transmit to UE 230 lists of PCIs per TAC for TACs neighboring the current UE RA and list of PCIs for the current UE RA or per TAC belonging to the current RA. At 205, for inter-frequency cell reselection information, NE 250 may transmit to UE 230 lists of frequency bands and/or a list of PCIs per frequency bands per TAC for TACs neighboring the current RA and list of frequency bands and/or a list of PCIs per frequency bands for the current RA or per TAC belonging to the current RA. At 207, NE 240 may transmit to 5GC 260 a NG setup message including the list of supported TACs and neighbor TACs of supported TACs, (such as TA1 and neighboring TA3), as well as a list of NSSAI(s) supported by the neighboring TACs. [0020] In various example embodiments, UE 230 may determine which network slices are supported by each neighbor cell. The prioritization of candidate cells during cell re-selection may also consider the information in any of the example embodiments described above. In some embodiments, the lists of S- NSSAI may be prioritized lists, and/or priority information may be assigned to different lists that UE 230 may consider during cell reselection. [0021] Furthermore, it is noted that TAC may be replaced by CAG identifiers in any of the example embodiments described herein. In addition, the exact encoding of the information may vary according to certain embodiments; for example, instead of sending a list of slices per TA or CAG, a list of TAs per slice in the allowed NSSAI or configured NSSAI may be transmitted. [0022] In a further embodiment, at 209, UE 230 may transmit at least one register request to 5GC 260. At 211, 5GC 260 may determine that a UE registration area (RA) includes a plurality of TAs, such as TA1 and TA2. At 213, 5GC 260 may transmit to UE 230 one or more register accept messages, such as a NAS Register Accept message during a register update procedure. In some embodiments, the register accept messages may include slice assistance information. In one embodiment, this slice assistance information may include allowed NSSAI, an indication of the UE RA including TA1 and TA2 with supported list of slices, and/or a third TA (TA3) indicating a list of slices. Alternatively, 5GC 260 may transmit the list of supported slices for all TAs of the RA per TA (such as TA1, TA2), as well as the list of supported slices for all TAs neighboring the RA (such as TA3). [0023] In some further embodiments, 5GC 260 may transmit in the slice assistance information those tracking area codes (TAC) and/or those network slices associated with allowed NSSAI and/or configured NSSAI of UE 230, or requested NSSAI of UE 230 (also for border TAC). For example, if just allowed NSSAI is of concern for service continuity, then just the network slices supported by the tracking areas neighboring the current RA may be sent. [0024] In various further example embodiments, 5GC 260 may transmit in the slice assistance information TAC border information for just those network slices which are not part of the allowed NSSAI (i.e., delta). As an example, the information may include a delta encoding instead of the allowed NSSAI. For example, an empty list of network slices provided for a border TAC or a TAC in the RA would mean that the same network slices are supported in the border TAs or the TA in current RA as in the allowed NSSAI. In some embodiments, a negative delta may also be used in the slice assistance information, e.g., with S-NSSAI SST = 15 delta indicating that it is the allowed NSSAI for TAC supporting all slices in the allowed NSSAI except the S-NSSAI SST=15. A similar consideration may apply for configured NSSAI deltas, wherein just negative deltas can apply on the configured NSSAI as there is no need to signal additional slices that are not in the configured NSSAI. [0025] In some embodiments, 5GC 260 may transmit indications of the trajectory of UE 230, for example, based on artificial intelligence (AI)/machine learning (ML) for a part of the TAC border information. Furthermore, in certain embodiments, TAC may be replaced by closed access group (CAG) identifiers. [0026] In a further embodiment, at 215, 5GC 260 may transmit to NE 240 NG context setup messages, such as a next generation application protocol (NGAP) initial context setup request or NGAP handover request. In various example embodiments, the above NG context setup messages may include the slice assistance information. In some embodiments, this slice assistance information may include UE RA with a list of S-NSSAI(s), or list of S-NSSAI(s) per TA of the RA and TA3 associated with a list of S- NSSAI. At 217, NE 240 may store the information received at 215. At 219, NE 240 may transmit a handover (HO) request to NE 250, which may include the UE RA with the list of S-NSSAI(s), or list of S-NSSAI(s) per TA of the RA, and indications of the TA3 (TA neighboring the RA) including the list of S-NSSAI(s). At 221, NE 250 may transmit to UE 230 a radio resource control (RRC) release message, which may include the slice assistance information. In some embodiments, this may include UE RA with the list of S-NSSAI(s), or list of S-NSSAI(s) per TA of the RA, and indications of the TA3 (TA neighboring the RA) including the list of S-NSSAI(s). In some embodiments, NE 250 may transmit the information to UE 230 during PDU session establishment/modification for the network slice associated with the PDU session. [0027] In some further embodiments, 5GC 260 may transmit at 215 just those TAC and/or just those network slices associated with allowed NSSAI and/or configured NSSAI of UE 230, or requested NSSAI of UE 230 (also for border TAC). For example, if just allowed NSSAI is of concern for service continuity, then just the network slices supported by the tracking areas neighboring the current RA may be sent. [0028] In various further example embodiments, 5GC 260 may transmit in the slice assistance information at TAC border information for just those network slices which are not part of the allowed NSSAI (i.e., delta). As an example, the information may include a delta encoding, instead of the allowed NSSAI, an empty list of network slices provided for a border TAC or a TAC in the RA. This would mean the same network slices supported in the border TAs and in TAC in the RA as there are in the allowed NSSAI. A negative delta may also be used in the slice assistance information, e.g., with S- NSSAI SST = 15 delta indicating that it is the allowed NSSAI for TAC supporting all slices in allowed NSSAI except the S-NSSAI SST=15. A similar consideration may apply for configured NSSAI deltas, wherein just negative deltas can apply on the configured NSSAI as there is no need to signal additional slices that are not in the configured NSSAI. [0029] In some further example embodiments, 5GC 260 may transmit indications of the trajectory of UE 230, for example, based on AI/ML for just a part of the TAC border information. Additionally or alternatively, in the slice assistance information border TA may be transmitted to UE 230 with an indication that all border TAs support the allowed NSSAI slices. Similarly, indications may be transmitted in the slice assistance information that all the network slices in the configured NSSAI are supported in the TAs of the RA and/or border TAs. UE 230 may receive the slice support of the border TAs around the RA, or the slice support of the TAs in the RA of UE 230 may also be provided. [0030] FIG.3 illustrates an example of a flow diagram of a method that may be performed by a UE, such as UE 620 illustrated in FIG. 6, according to various example embodiments. As illustrated in the example of FIG.3, at 301, the UE may receive radio mapping information between TA identifiers of TAs neighboring a served cell and a list of physical cell identifiers associated with each TA associated with physical cell identifiers corresponding to a neighbor cell of the served cell. [0031] At 303, the UE may receive radio mapping information comprising a mapping between the TA identifiers of TAs neighboring the served cell and the list of physical cell identifiers associated with each of the tracking areas with physical cell identifiers corresponding to at least one of the neighbor cells of the served cell configured for use by at least one frequency band neighboring the served cell. [0032] At 305, the UE may receive, from a network entity, slice assistance information associated with the apparatus mapping one or more network slices and at least one of one or more TA identifiers of tracking areas in a UE RA or one or more TA identifiers of tracking areas neighboring the UE RA supporting the one or more network slices. [0033] At 307, the UE may use the radio mapping information and the slice assistance information in a cell re-selection process. In some embodiments, the radio mapping information and the slice assistance information may be used in the cell re-selection process only when multiple neighbor cells are considered as suitable. Furthermore, the radio mapping information may be received via SIB by the served cell. Furthermore, the slice assistance information may be encoded reversely as the mapping between a list of tracking area identifiers and at least one network slice supported in each of the corresponding TAs, wherein the TAs may be at least one of a tracking area of the UE RA or a tracking area neighboring a TA of the UE RA. [0034] In various embodiments, the slice assistance information may indicate network slices corresponding to at least one of the list of slices requested by a UE during a registration update procedure, the list of requested slices which have been allowed by the network during a registration update procedure or the list of configured network slices which have been configured by the network to a user equipment. In addition, the slice assistance information may comprise only network slices which do not belong to the set of network slices reported as allowed by the network in a registration update procedure. In another embodiment, the tracking area identifiers may comprise closed access group identifiers. [0035] FIG. 4 illustrates an example of a flow diagram of a method that may be performed by a 5GC, such as the network illustrated in FIG. 7, according to various example embodiments. As illustrated in the example of FIG. 4, at 401, the 5GC may determine at least one tracking area in a UE RA. At 403, the 5GC may transmit slice assistance information comprising slices (of allowed NSSAI or configured NSSAI) associated with a UE indicating a mapping between one or more network slices and at least one of one or more TA identifiers of tracking areas in the UE RA, or one or more TA identifiers of tracking areas neighboring the UE RA that support the one or more network slices. [0036] In certain embodiments, each network slice included in the slice assistance information, may indicate at least one of SST and SD for each of the one or more network slices. Additionally or alternatively, the slice assistance information may be transmitted to at least one user equipment. Furthermore, the slice assistance information may be transmitted during a registration update procedure. [0037] In some embodiments, the slice assistance information may comprise at least one of a list of network slices requested by a user equipment during a registration update procedure, a list of requested network slices allowed by a network during a registration update procedure, and/or a list of network slices configured by the network to a user equipment. Furthermore, in an embodiment, the one or more tracking area identifiers of the slice assistance information may comprise just tracking area identifiers of tracking areas neighboring the user equipment registration area. The list of network slices in the slice assistance information may comprise a plurality of network slices allowed by the network during the registration update procedure. [0038] In various example embodiments, the slice assistance information may be encoded reversely as the mapping between a list of tracking area identifier(s) and the network slices which are supported in each of the corresponding tracking areas. The tracking areas may comprise one or more tracking areas of the user equipment registration area and/or one or more tracking areas neighboring a tracking area of the user equipment registration area. In addition, according to some embodiments, the slice assistance information may comprise just network slices which do not belong to the set of network slices reported as allowed by the network in a registration update procedure. In some embodiments, the slice assistance information may be associated with a trajectory of the user equipment. In some embodiments, the mapping information (both radio mapping and slice assistance information) may comprise at least one closed access group identifier(s) in replacement of the tracking area identifiers. [0039] FIG. 5 illustrates an example of a flow diagram of a method that may be performed by a network entity, such as NE 610 illustrated in FIG.6, according to various example embodiments. As illustrated in the example of FIG. 5, at 501, the NE may receive slice assistance information associated with a user equipment indicating a mapping between one or more network slices and one or more TA identifiers of TAs in a UE RA and/or one or more tracking area identifiers of tracking areas neighboring the UE RA that support the one or more network slices. [0040] At 503, the NE may store the slice assistance information. At 505, the NE may transmit a radio resource control release message comprising the slice assistance information to a UE. At 507, the NE may transfer the stored slice assistance information to a network entity in response to at least one handover procedure. [0041] In some embodiments, the method may further comprise transferring the stored slice assistance information to a network entity in response to at least one handover procedure. Furthermore, the radio resource control release message may be configured to cause the user equipment to enter a radio resource control inactive state. Additionally or alternatively, each network slice included in the slice assistance information may indicate at least one of SST and SD. [0042] In certain embodiments, the slice assistance information may be received from a core network. Furthermore, in some embodiments, the slice assistance information may be received in a NGAP initial context setup request message or a NGAP handover request message. [0043] In various example embodiments, the method may further comprise transmitting, to a user equipment, radio mapping information comprising mapping information between tracking area identifiers of tracking areas neighboring a served cell and a list of physical cell identifiers associated with each tracking area associated with physical cell identifiers corresponding to a neighbor cell of the served cell, and/or radio mapping information of a mapping between the tracking area identifiers of tracking areas neighboring the served cell and the list of physical cell identifiers associated with each of the tracking areas with physical cell identifiers corresponding to at least one of the neighbor cells of the served cell configured for use by at least one frequency band neighboring the served cell. Furthermore, in some embodiments, the radio mapping information may be transmitted via system information broadcast by the served cell. [0044] FIG. 6 illustrates an example of a system according to certain example embodiments. In one example embodiment, a system may include one or more devices, such as, for example, NE 610 and/or UE 620. [0045] NE 610 may be one or more of a base station, such as an eNB or gNB, a serving gateway, a server, an access point, a transmission-reception point (TRP), citizens broadband radio service device (CBSD), and/or any other access or radio node or combination thereof. [0046] In an embodiment where NE 610 may be a gNB, NE 610 may further comprise at least one gNB-CU, which may be associated with at least one gNB-DU. The at least one gNB-CU and the at least one gNB-DU may be in communication via at least one F1 interface, at least one X_n-C interface, and/or at least one NG interface via a 5GC. [0047] UE 620 may include one or more of a mobile device, such as a mobile phone, smart phone, personal digital assistant (PDA), tablet, or portable media player, digital camera, pocket video camera, video game console, navigation unit, such as a global positioning system (GPS) device, desktop or laptop computer, IoT device, single-location device, such as a sensor or smart meter, or any combination thereof. [0048] NE 610 and/or UE 620 may include at least one processor, respectively indicated as 611 and 621. Processors 611 and 621 may be embodied by any computational or data processing device, such as a central processing unit (CPU), application specific integrated circuit (ASIC), or comparable device. The processors may be implemented as a single controller, or a plurality of controllers or processors. [0049] At least one memory may be provided in one or more of the devices, as indicated at 612 and 622. The memory may be fixed or removable. The memory may include computer program instructions or computer code contained therein. Memories 612 and 622 may independently be any suitable storage device, such as a non-transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate from the one or more processors. Furthermore, the computer program instructions stored in the memory, and which may be processed by the processors, may be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. [0050] Processors 611 and 621, memories 612 and 622, and any subset thereof, may be configured to provide means corresponding to the various blocks of FIGS.2-5. Although not shown, the devices may also include positioning hardware, such as GPS or micro electrical mechanical system (MEMS) hardware, which may be used to determine a location of the device. Other sensors are also permitted, and may be configured to determine location, elevation, velocity, orientation, and so forth, such as barometers, compasses, and the like. [0051] As shown in FIG.6, transceivers 613 and 623 may be provided, and one or more devices may also include at least one antenna, respectively illustrated as 614 and 624. The device may have many antennas, such as an array of antennas configured for multiple input multiple output (MIMO) communications, or multiple antennas for multiple RATs. Other configurations of these devices, for example, may be provided. Transceivers 613 and 623 may be a transmitter, a receiver, both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception. [0052] The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus, such as UE or NE, to perform any of the processes described above (i.e., FIGS. 2-5). Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, perform a process such as one of the processes described herein. Alternatively, certain embodiments may be performed entirely in hardware. [0053] In certain embodiments, an apparatus may include circuitry configured to perform any of the processes or functions illustrated in FIGS. 2-5. For example, circuitry may be hardware-only circuit implementations, such as analog and/or digital circuitry. In another example, circuitry may be a combination of hardware circuits and software, such as a combination of analog and/or digital hardware circuitry with software or firmware, and/or any portions of hardware processors with software (including digital signal processors), software, and at least one memory that work together to cause an apparatus to perform various processes or functions. In yet another example, circuitry may be hardware circuitry and or processors, such as a microprocessor or a portion of a microprocessor, that includes software, such as firmware, for operation. Software in circuitry may not be present when it is not needed for the operation of the hardware. [0054] FIG. 7 illustrates an example of a 5G network and system architecture according to certain embodiments. Shown are multiple network functions that may be implemented as software operating as part of a network device or dedicated hardware, as a network device itself or dedicated hardware, or as a virtual function operating as a network device or dedicated hardware. The NE and UE illustrated in FIG.7 may be similar to NE 610 and UE 620, respectively. The user plane function (UPF) may provide services such as intra-RAT and inter-RAT mobility, routing and forwarding of data packets, inspection of packets, user plane quality of service (QoS) processing, buffering of downlink packets, and/or triggering of downlink data notifications. The application function (AF) may primarily interface with the core network to facilitate application usage of traffic routing and interact with the policy framework. [0055] The features, structures, or characteristics of example embodiments described throughout this specification may be combined in any suitable manner in one or more example embodiments. For example, the usage of the phrases “various embodiments,” “certain embodiments,” “some embodiments,” or other similar language throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with an example embodiment may be included in at least one example embodiment. Thus, appearances of the phrases “in various embodiments,” “in certain embodiments,” “in some embodiments,” or other similar language throughout this specification does not necessarily all refer to the same group of example embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments. [0056] Additionally, if desired, the different functions or procedures discussed above may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the described functions or procedures may be optional or may be combined. As such, the description above should be considered as illustrative of the principles and teachings of certain example embodiments, and not in limitation thereof. [0057] One having ordinary skill in the art will readily understand that the example embodiments discussed above may be practiced with procedures in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although some embodiments have been described based upon these example embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the example embodiments. [0058] According to a first embodiment, a method may include receiving radio mapping information between tracking area identifiers of tracking areas neighboring a served cell and a list of physical cell identifiers associated with each tracking area associated with physical cell identifiers corresponding to a neighbor cell of the served cell. The method may further include receiving radio mapping information comprising a mapping between the tracking area identifiers of tracking areas neighboring the served cell and the list of physical cell identifiers associated with each of the tracking areas with physical cell identifiers corresponding to at least one of the neighbor cells of the served cell configured for use by at least one frequency band neighboring the served cell. The method may further include receiving, from a network entity, slice assistance information associated with the apparatus mapping one or more network slices and at least one of one or more tracking area identifiers of tracking areas in a user equipment registration area or one and more tracking area identifiers of tracking areas neighboring the user equipment registration area supporting the one or more network slices. The method may further include using the radio mapping information and the slice assistance information in a cell re-selection process. [0059] In a variant, the radio mapping information and the slice assistance information may be used in the cell re-selection process only when multiple neighbor cells are considered as suitable. [0060] In a variant, the radio mapping information may be received via system information broadcast by the served cell. [0061] In a variant, the slice assistance information may be encoded reversely as the mapping between a list of tracking area identifiers and at least one network slice(s) supported in each of the corresponding tracking areas, wherein the tracking areas are at least one of a tracking area of the user equipment registration area or a tracking area neighboring a tracking area of the user equipment registration area. [0062] In a variant, the slice assistance information may indicate network slices corresponding to at least one of the list of slices requested by a user equipment during a registration update procedure, the list of requested slices which have been allowed by the network during a registration update procedure and the list of configured network slices which have been configured by the network to a user equipment. [0063] In a variant, the slice assistance information may comprise only network slices which do not belong to the set of network slices reported as allowed by the network in a registration update procedure. [0064] In a variant, the tracking area identifiers may comprise closed access group identifiers. [0065] According to a second embodiment, a method may include determining at least one tracking area in a user equipment registration area. The method may further include transmitting slice assistance information associated with a user equipment indicating a mapping between one or more network slices and at least one of one or more tracking area identifiers of tracking areas in the user equipment registration area, or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area that support the one or more network slices. [0066] In a variant, each network slice may be included in the slice assistance information indicates at least one of slice service type and slice differentiator for each of the one or more network slices. [0067] In a variant, the slice assistance information may be transmitted to at least one user equipment. [0068] In a variant, the slice assistance information may be transmitted during a registration update procedure. [0069] In a variant, the slice assistance information may comprise at least one of a list of network slices requested by a user equipment during a registration update procedure, a list of requested network slices allowed by a network during a registration update procedure, and a list of network slices configured by the network to a user equipment. [0070] In a variant, the one or more tracking area identifiers of the slice assistance information may only comprise tracking area identifiers of tracking areas neighboring the user equipment registration area, wherein the list of network slices comprise a plurality of network slices allowed by the network during the registration update procedure. [0071] In a variant, the slice assistance information may be encoded reversely as the mapping between a list of tracking area identifier(s) and the network slices which are supported in each of the corresponding tracking areas, wherein the tracking areas comprise at least one of one or more tracking areas of the user equipment registration area or one or more tracking areas neighboring a tracking area of the user equipment registration area. [0072] In a variant, the slice assistance information may comprise only network slices which do not belong to the set of network slices reported as allowed by the network in a registration update procedure. [0073] In a variant, the slice assistance information may be associated with a trajectory of the user equipment. [0074] In a variant, the mapping information may comprise at least one closed access group identifier in replacement of the tracking area identifiers. [0075] According to a third embodiment, a method may include transmitting at least one of radio mapping information to a user equipment comprising mapping information between tracking area identifiers of tracking areas neighboring a served cell and a list of physical cell identifiers associated with each tracking area associated with physical cell identifiers corresponding to a neighbor cell of the served cell, and radio mapping information of a mapping between the tracking area identifiers of tracking areas neighboring the served cell and the list of physical cell identifiers associated with each of the tracking areas with physical cell identifiers corresponding to at least one of the neighbor cells of the served cell configured for use by at least one frequency band neighboring the served cell. [0076] In a variant, the method may further comprise transferring the stored slice assistance information to a network entity in response to at least one handover procedure. [0077] In a variant, the radio resource control release message may be configured to cause the user equipment to enter a radio resource control inactive state. [0078] In a variant, each network slice may be included in the slice assistance information comprises at least one of slice service type and slice differentiator. [0079] In a variant, the slice assistance information may be received from a core network. [0080] In a variant, the slice assistance information may be received in a next generation application protocol initial context setup request message or a next generation application protocol handover request message. [0081] In a variant, the method may further comprise receiving slice assistance information associated with a user equipment indicating a mapping between one or more network slices and at least one of one or more tracking area identifiers of tracking areas in a user equipment registration area or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area that support the one or more network slices. The method may further comprise storing the slice assistance information. The method may further comprise transmitting a radio resource control release message comprising the slice assistance information to a user equipment. [0082] In a variant, the radio mapping information may be transmitted via system information broadcast by the served cell. [0083] According to a fourth, fifth, and sixth embodiment, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus at least to perform a method according to the first embodiment and any of its variants. [0084] According to a third embodiment, an apparatus may include means for performing the method according to the first embodiment and any of its variants. [0085] According to a seventh, eighth, and ninth embodiment, a computer program product may be encoded with instructions for performing a process including a method according to the first embodiment and any of its variants. [0086] According to a tenth, eleventh, and twelfth embodiment, a non-transitory, computer- readable medium may have instructions stored thereon that, when executed in hardware, perform a process including a method according to the first embodiment and any of its variants. [0087] According to a thirteenth, fourteenth, and fifteenth embodiment, computer program code may include instructions for performing a method according to the first embodiment and any of its variants. [0088] According to a sixteenth, seventeenth, and eighteenth embodiment, an apparatus may include circuitry configured to perform a process including a method according to the first embodiment and any of its variants. [0089] Partial Glossary [0090] 3GPP Third Generation Partnership Project [0091] 5G Fifth Generation [0092] 5GC Fifth Generation Core [0093] 5GS Fifth Generation System [0094] 5QI Fifth Generation Quality of Service Indicator [0095] AI Artificial Intelligence [0096] AMF Access and Mobility Management Function [0097] ASIC Application Specific Integrated Circuit [0098] BS Base Station [0099] CAG Closed Access Group [0100] CBSD Citizens Broadband Radio Service Device [0101] CN Core Network [0102] CPU Central Processing Unit [0103] DL Downlink [0104] DMRS Demodulation Reference Signal [0105] DRB Data Radio Bearer [0106] eMBB Enhanced Mobile Broadband [0107] eMTC Enhanced Machine Type Communication [0108] eNB Evolved Node B [0109] eOLLA Enhanced Outer Loop Link Adaptation [0110] EPS Evolved Packet System [0111] gNB Next Generation Node B [0112] GPS Global Positioning System [0113] HDD Hard Disk Drive [0114] HO Handover [0115] LTE Long-Term Evolution [0116] LTE-A Long-Term Evolution Advanced [0117] MAC Medium Access Control [0118] MBS Multicast and Broadcast Systems [0119] MCS Modulation and Coding Scheme [0120] MEMS Micro Electrical Mechanical System [0121] MIB Master Information Block [0122] MIMO Multiple Input Multiple Output [0123] ML Machine Learning [0124] MME Mobility Management Entity [0125] mMTC Massive Machine Type Communication [0126] NAS Non-Access Stratum [0127] NB-IoT Narrowband Internet of Things [0128] NE Network Entity [0129] NG Next Generation [0130] NGAP Next Generation Application Protocol [0131] NG-eNB Next Generation Evolved Node B [0132] NG-RAN Next Generation Radio Access Network [0133] NR New Radio [0134] NR-U New Radio Unlicensed [0135] OFDM Orthogonal Frequency Division Multiplexing [0136] OLLA Outer Loop Link Adaptation [0137] PBR Prioritized Bit Rate [0138] PCI Physical Cell Identifier [0139] PDA Personal Digital Assistance [0140] PDU Protocol Data Unit [0141] PRACH Physical Random Access [0142] RA Registration Area [0143] RACH Random Access Channel [0144] RAM Random Access Memory [0145] RAN Radio Access Network [0146] RAT Radio Access Technology [0147] RRC Radio Resource Control [0148] SD Slice Differentiator [0149] SIB System Information Block [0150] S-NSSAI Single Network Slice Assistance Information [0151] SST Slice Service Type [0152] TAC Tracking Area Code [0153] TR Technical Report [0154] TS Technical Specification [0155] UE User Equipment [0156] UL Uplink [0157] UMTS Universal Mobile Telecommunications System [0158] URLLC Ultra-Reliable and Low-Latency Communication [0159] UTRAN Universal Mobile Telecommunications System Terrestrial Radio Access Network [0160] WLAN Wireless Local Area Network

Claims

WE CLAIM: 1. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: receive radio mapping information between tracking area identifiers of tracking areas neighboring a served cell and a list of physical cell identifiers associated with each tracking area associated with physical cell identifiers corresponding to a neighbor cell of the served cell; receive radio mapping information comprising a mapping between the tracking area identifiers of tracking areas neighboring the served cell and the list of physical cell identifiers associated with each of the tracking areas with physical cell identifiers corresponding to at least one of the neighbor cells of the served cell configured for use by at least one frequency band neighboring the served cell; receive, from a network entity, slice assistance information associated with the apparatus mapping one or more network slices and at least one of one or more tracking area identifiers of tracking areas in a user equipment registration area or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area supporting the one or more network slices; and use the radio mapping information and the slice assistance information in a cell re-selection process.

2. The apparatus of claim 1, wherein the radio mapping information and the slice assistance information are used in the cell re-selection process when multiple neighbor cells are considered as suitable.

3. The apparatus of claim 1, wherein the radio mapping information is received via system information broadcast by the served cell.

4. The apparatus of claim 1, wherein the slice assistance information is encoded reversely as the mapping between a list of tracking area identifiers and at least one network slice supported in each of the corresponding tracking areas, wherein the tracking areas are at least one of a tracking area of the user equipment registration area or a tracking area neighboring a tracking area of the user equipment registration area.

5. The apparatus of claim 1, wherein the slice assistance information indicates network slices corresponding to at least one of the list of slices requested by a user equipment during a registration update procedure, the list of requested slices which have been allowed by the network during a registration update procedure or the list of configured network slices which have been configured by the network to a user equipment.

6. The apparatus of claim 4, wherein the slice assistance information comprises only network slices which do not belong to the set of network slices reported as allowed by the network in a registration update procedure.

7. The apparatus of claim 1, wherein the tracking area identifiers comprise closed access group identifiers.

8. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: determine at least one tracking area in a user equipment registration area; and transmit slice assistance information associated with a user equipment indicating a mapping between one or more network slices and at least one of one or more tracking area identifiers of tracking areas in the user equipment registration area, or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area that support the one or more network slices.

9. The apparatus of claim 8, wherein each network slice included in the slice assistance information indicates at least one of slice service type or slice differentiator for each of the one or more network slices.

10. The apparatus of claim 8, wherein the slice assistance information is transmitted to at least one user equipment.

11. The apparatus of claim 8, wherein the slice assistance information is transmitted during a registration update procedure.

12. The apparatus of claim 8, wherein the slice assistance information comprises at least one of: a list of network slices requested by a user equipment during a registration update procedure; a list of requested network slices allowed by a network during a registration update procedure; or a list of network slices configured by the network to a user equipment.

13. The apparatus of claim 11, wherein the one or more tracking area identifiers of the slice assistance information comprise tracking area identifiers of tracking areas neighboring the user equipment registration area, wherein the list of network slices comprise a plurality of network slices allowed by the network during the registration update procedure.

14. The apparatus of claim 8, wherein the slice assistance information is encoded reversely as the mapping between a list of tracking area identifier(s) and the network slices which are supported in each of the corresponding tracking areas, wherein the tracking areas comprise at least one of one or more tracking areas of the user equipment registration area or one or more tracking areas neighboring a tracking area of the user equipment registration area.

15. The apparatus of claim 14, wherein the slice assistance information comprises only network slices which do not belong to the set of network slices reported as allowed by the network in a registration update procedure.

16. The apparatus of claim 8, wherein the slice assistance information is associated with a trajectory of the user equipment.

17. The apparatus of claim 8, wherein the mapping information comprises at least one closed access group identifier.

18. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: transmit at least one of: radio mapping information to a user equipment comprising mapping information between tracking area identifiers of tracking areas neighboring a served cell and a list of physical cell identifiers associated with each tracking area associated with physical cell identifiers corresponding to a neighbor cell of the served cell; or radio mapping information of a mapping between the tracking area identifiers of tracking areas neighboring the served cell and the list of physical cell identifiers associated with each of the tracking areas with physical cell identifiers corresponding to at least one of the neighbor cells of the served cell configured for use by at least one frequency band neighboring the served cell.

19. The apparatus of claim 18, wherein the radio mapping information is transmitted via system information broadcast by the served cell.

20. The apparatus of claim 18, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: receive slice assistance information associated with a user equipment indicating a mapping between one or more network slices and at least one of one or more tracking area identifiers of tracking areas in a user equipment registration area or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area that support the one or more network slices; store the slice assistance information; and transmit a radio resource control release message comprising the slice assistance information to a user equipment.

21. The apparatus of claim 20, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: transfer the stored slice assistance information to a network entity in response to at least one handover procedure.

22. The apparatus of claim 20, wherein the radio resource control release message is configured to cause the user equipment to enter a radio resource control inactive state.

23. The apparatus of claim 20, wherein each network slice included in the slice assistance information comprises at least one of slice service type or slice differentiator.

24. The apparatus of claim 20, wherein the slice assistance information is received from a core network.

25. The apparatus of claim 20, wherein the slice assistance information is received in a next generation application protocol initial context setup request message or a next generation application protocol handover request message.

26. A method, comprising: receiving radio mapping information between tracking area identifiers of tracking areas neighboring a served cell and a list of physical cell identifiers associated with each tracking area associated with physical cell identifiers corresponding to a neighbor cell of the served cell; receiving radio mapping information comprising a mapping between the tracking area identifiers of tracking areas neighboring the served cell and the list of physical cell identifiers associated with each of the tracking areas with physical cell identifiers corresponding to at least one of the neighbor cells of the served cell configured for use by at least one frequency band neighboring the served cell; receiving, from a network entity, slice assistance information associated with the apparatus mapping one or more network slices and at least one of one or more tracking area identifiers of tracking areas in a user equipment registration area or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area supporting the one or more network slices; and using the radio mapping information and the slice assistance information in a cell re-selection process.

27. The method of claim 26, wherein the radio mapping information and the slice assistance information are used in the cell re-selection process when multiple neighbor cells are considered as suitable.

28. The method of claim 26, wherein the radio mapping information is received via system information broadcast by the served cell.

29. The method of claim 26, wherein the slice assistance information is encoded reversely as the mapping between a list of tracking area identifiers and at least one network slice supported in each of the corresponding tracking areas, wherein the tracking areas are at least one of a tracking area of the user equipment registration area or a tracking area neighboring a tracking area of the user equipment registration area.

30. The method of claim 26, wherein the slice assistance information indicates network slices corresponding to at least one of the list of slices requested by a user equipment during a registration update procedure, the list of requested slices which have been allowed by the network during a registration update procedure or the list of configured network slices which have been configured by the network to a user equipment.

31. The method of claim 29, wherein the slice assistance information comprises only network slices which do not belong to the set of network slices reported as allowed by the network in a registration update procedure.

32. The method of claim 26, wherein the tracking area identifiers comprise closed access group identifiers.

33. A method, comprising: determining at least one tracking area in a user equipment registration area; and transmitting slice assistance information associated with a user equipment indicating a mapping between one or more network slices and at least one of one or more tracking area identifiers of tracking areas in the user equipment registration area or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area that support the one or more network slices.

34. The method of claim 33, wherein each network slice included in the slice assistance information indicates at least one of slice service type or slice differentiator for each of the one or more network slices.

35. The method of claim 33, wherein the slice assistance information is transmitted to at least one user equipment.

36. The method of claim 33, wherein the slice assistance information is transmitted during a registration update procedure.

37. The method of claim 36, wherein the slice assistance information comprises at least one of: a list of network slices requested by a user equipment during a registration update procedure; a list of requested network slices allowed by a network during a registration update procedure; or a list of network slices configured by the network to a user equipment.

38. The method of claim 36, wherein the one or more tracking area identifiers of the slice assistance information comprise tracking area identifiers of tracking areas neighboring the user equipment registration area, wherein the list of network slices comprise a plurality of network slices allowed by the network during the registration update procedure.

39. The method of claim 33, wherein the slice assistance information is encoded reversely as the mapping between a list of tracking area identifier(s) and the network slices which are supported in each of the corresponding tracking areas, wherein the tracking areas comprise at least one of one or more tracking areas of the user equipment registration area or one or more tracking areas neighboring a tracking area of the user equipment registration area.

40. The method of claim 39, wherein the slice assistance information comprises only network slices which do not belong to the set of network slices reported as allowed by the network in a registration update procedure.

41. The method of claim 33, wherein the slice assistance information is associated with a trajectory of the user equipment.

42. The method of claim 33, wherein the mapping information comprises at least one closed access group identifier.

43. A method, comprising: transmitting at least one of: radio mapping information to a user equipment comprising mapping information between tracking area identifiers of tracking areas neighboring a served cell and a list of physical cell identifiers associated with each tracking area associated with physical cell identifiers corresponding to a neighbor cell of the served cell; or radio mapping information of a mapping between the tracking area identifiers of tracking areas neighboring the served cell and the list of physical cell identifiers associated with each of the tracking areas with physical cell identifiers corresponding to at least one of the neighbor cells of the served cell configured for use by at least one frequency band neighboring the served cell.

44. The method of claim 43, wherein the radio mapping information is transmitted via system information broadcast by the served cell.

45. The method of claim 43, further comprising: receiving slice assistance information associated with a user equipment indicating a mapping between one or more network slices and at least one of one or more tracking area identifiers of tracking areas in a user equipment registration area or one or more tracking area identifiers of tracking areas neighboring the user equipment registration area that support the one or more network slices; storing the slice assistance information; and transmitting a radio resource control release message comprising the slice assistance information to a user equipment.

46. The method of claim 43, further comprising: transfer the stored slice assistance information to a network entity in response to at least one handover procedure.

47. The method of claim 43, wherein the radio resource control release message is configured to cause the user equipment to enter a radio resource control inactive state.

48. The method of claim 43, wherein each network slice included in the slice assistance information comprises at least one of slice service type or slice differentiator.

49. The method of claim 43, wherein the slice assistance information is received from a core network.

50. The method of claim 43, wherein the slice assistance information is received in a next generation application protocol initial context setup request message or a next generation application protocol handover request message.

51. An apparatus, comprising: means for performing the method of any of claims 26-50.

52. A non-transitory, computer-readable medium comprising program instructions stored thereon for performing the method of any of claims 26-50.

53. An apparatus comprising circuitry configured to cause the apparatus to perform the method of any of claims 26-50.

54. A computer program product encoded with instructions for performing the method of any of claims 26-50.