WO2019225914A1

WO2019225914A1 - Method and apparatus for handling strongest cell not supporting selected core network in wireless communication system

Info

Publication number: WO2019225914A1
Application number: PCT/KR2019/005948
Authority: WO
Inventors: Taehun Kim
Original assignee: Lg Electronics Inc.
Priority date: 2018-05-20
Filing date: 2019-05-17
Publication date: 2019-11-28

Abstract

A method and apparatus for handling a strongest cell not supporting a selected core network in a wireless communication system is provided. A wireless network (i.e. non-access stratum (NAS) layer) selects a core network upon public land mobile network (PLMN) selection. When a strongest cell supporting the selected core network is not a strongest cell on a current frequency, the wireless device (i.e. AS layer) informs the NAS layer that there is no cell supporting the selected core network, and the wireless device (i.e. NAS layer) performs PLMN selection based on the information that there is no cell supporting the selected core network.

Description

METHOD AND APPARATUS FOR HANDLING STRONGEST CELL NOT SUPPORTING SELECTED CORE NETWORK IN WIRELESS COMMUNICATION SYSTEM

The present invention relates to wireless communications, and more particularly, to a method and apparatus for handling a strongest cell not supporting a selected core network in a wireless communication system.

3rd generation partnership project (3GPP) long-term evolution (LTE) is a technology for enabling high-speed packet communications. Many schemes have been proposed for the LTE objective including those that aim to reduce user and provider costs, improve service quality, and expand and improve coverage and system capacity. The 3GPP LTE requires reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure, an open interface, and adequate power consumption of a terminal as an upper-level requirement.

Work has started in international telecommunication union (ITU) and 3GPP to develop requirements and specifications for new radio (NR) systems. 3GPP has to identify and develop the technology components needed for successfully standardizing the new RAT timely satisfying both the urgent market needs, and the more long-term requirements set forth by the ITU radio communication sector (ITU-R) international mobile telecommunications (IMT)-2020 process. Further, the NR should be able to use any spectrum band ranging at least up to 100 GHz that may be made available for wireless communications even in a more distant future.

The NR targets a single technical framework addressing all usage scenarios, requirements and deployment scenarios including enhanced mobile broadband (eMBB), massive machine-type-communications (mMTC), ultra-reliable and low latency communications (URLLC), etc. The NR shall be inherently forward compatible.

When a user equipment (UE) is in a radio resource control (RRC) idle state (RRC_IDLE) and/or RRC inactive state (RRC_INACTIVE), the UE performs public land mobile network (PLMN) selection and/or cell (re-)selection.

It has been discussed that a specific core network will be selected upon performing PLMN section when the UE is in RRC_IDLE and/or RRC_INACTIVE. However, there may be a case that the selected cell corresponding to the selected core network is not the strongest cell on a current frequency. In this case, user performance can be reduced and/or inter-cell interference can be increased.

In an aspect, a method performed by a wireless device in a wireless communication system is provided. The method includes selecting a core network, when a strongest cell supporting the selected core network is not a strongest cell on a current frequency: informing a non-access stratum (NAS) layer that there is no cell supporting the selected core network, and performing a public land mobile network (PLMN) selection based on the information that there is no cell supporting the selected core network.

In another aspect, a wireless device in a wireless communication system is provided. The wireless device includes a memory, a transceiver, a processor, operably coupled to the memory and the transceiver. The processor is configure to select a core network, and when a strongest cell supporting the selected core network is not a strongest cell on a current frequency, the processor is configure to, inform a non-access stratum (NAS) layer that there is no cell supporting the selected core network, and perform a public land mobile network (PLMN) selection based on the information that there is no cell supporting the selected core network.

In another aspect, a processor for a wireless device in a wireless communication system is provided. The processor is configured to select a core network, when a strongest cell supporting the selected core network is not a strongest cell on a current frequency, inform a non-access stratum (NAS) layer that there is no cell supporting the selected core network, and perform a public land mobile network (PLMN) selection based on the information that there is no cell supporting the selected core network.

When a strongest cell on a carrier does not support a selected core network, the UE can perform PLMN selection and/or core network selection quickly.

FIG. 1 shows examples of 5G usage scenarios to which the technical features of the present invention can be applied.

FIG. 2 shows an example of a wireless communication system to which the technical features of the present invention can be applied.

FIG. 3 shows an example of a wireless communication system to which the technical features of the present invention can be applied.

FIG. 4 shows another example of a wireless communication system to which the technical features of the present invention can be applied.

FIG. 5 shows a block diagram of a user plane protocol stack to which the technical features of the present invention can be applied.

FIG. 6 shows a block diagram of a control plane protocol stack to which the technical features of the present invention can be applied.

FIG. 7 shows an example of selecting/re-selecting non-optimal cells upon PLMN selection and core network selection.

FIG. 8 shows an example of a method for handling a strongest cell not supporting a selected core network according to an embodiment of the present invention.

FIG. 9 shows a UE to which the technical features of the present invention can be applied.

FIG. 10 shows an example of an AI device to which the technical features of the present invention can be applied.

FIG. 11 shows an example of an AI system to which the technical features of the present invention can be applied.

The technical features described below may be used by a communication standard by the 3rd generation partnership project (3GPP) standardization organization, a communication standard by the institute of electrical and electronics engineers (IEEE), etc. For example, the communication standards by the 3GPP standardization organization include long-term evolution (LTE) and/or evolution of LTE systems. The evolution of LTE systems includes LTE-advanced (LTE-A), LTE-A Pro, and/or 5G new radio (NR). The communication standard by the IEEE standardization organization includes a wireless local area network (WLAN) system such as IEEE 802.11a/b/g/n/ac/ax. The above system uses various multiple access technologies such as orthogonal frequency division multiple access (OFDMA) and/or single carrier frequency division multiple access (SC-FDMA) for downlink (DL) and/or uplink (UL). For example, only OFDMA may be used for DL and only SC-FDMA may be used for UL. Alternatively, OFDMA and SC-FDMA may be used for DL and/or UL.

In this document, the term "/" and "," should be interpreted to indicate "and/or." For instance, the expression "A/B" may mean "A and/or B." Further, "A, B" may mean "A and/or B." Further, "A/B/C" may mean "at least one of A, B, and/or C." Also, "A, B, C" may mean "at least one of A, B, and/or C."

Further, in the document, the term "or" should be interpreted to indicate "and/or." For instance, the expression "A or B" may comprise 1) only A, 2) only B, and/or 3) both A and B. In other words, the term "or" in this document should be interpreted to indicate "additionally or alternatively."

The 5G usage scenarios shown in FIG. 1 are only exemplary, and the technical features of the present invention can be applied to other 5G usage scenarios which are not shown in FIG. 1.

Referring to FIG. 1, the three main requirements areas of 5G include (1) enhanced mobile broadband (eMBB) domain, (2) massive machine type communication (mMTC) area, and (3) ultra-reliable and low latency communications (URLLC) area. Some use cases may require multiple areas for optimization and, other use cases may only focus on only one key performance indicator (KPI). 5G is to support these various use cases in a flexible and reliable way.

eMBB focuses on across-the-board enhancements to the data rate, latency, user density, capacity and coverage of mobile broadband access. The eMBB aims ~10 Gbps of throughput. eMBB far surpasses basic mobile Internet access and covers rich interactive work and media and entertainment applications in cloud and/or augmented reality. Data is one of the key drivers of 5G and may not be able to see dedicated voice services for the first time in the 5G era. In 5G, the voice is expected to be processed as an application simply using the data connection provided by the communication system. The main reason for the increased volume of traffic is an increase in the size of the content and an increase in the number of applications requiring high data rates. Streaming services (audio and video), interactive video and mobile Internet connectivity will become more common as more devices connect to the Internet. Many of these applications require always-on connectivity to push real-time information and notifications to the user. Cloud storage and applications are growing rapidly in mobile communication platforms, which can be applied to both work and entertainment. Cloud storage is a special use case that drives growth of uplink data rate. 5G is also used for remote tasks on the cloud and requires much lower end-to-end delay to maintain a good user experience when the tactile interface is used. In entertainment, for example, cloud games and video streaming are another key factor that increases the demand for mobile broadband capabilities. Entertainment is essential in smartphones and tablets anywhere, including high mobility environments such as trains, cars and airplanes. Another use case is augmented reality and information retrieval for entertainment. Here, augmented reality requires very low latency and instantaneous data amount.

mMTC is designed to enable communication between devices that are low-cost, massive in number and battery-driven, intended to support applications such as smart metering, logistics, and field and body sensors. mMTC aims ~10 years on battery and/or ~1 million devices/km2. mMTC allows seamless integration of embedded sensors in all areas and is one of the most widely used 5G applications. Potentially by 2020, internet-of-things (IoT) devices are expected to reach 20.4 billion. Industrial IoT is one of the areas where 5G plays a key role in enabling smart cities, asset tracking, smart utilities, agriculture and security infrastructures.

URLLC will make it possible for devices and machines to communicate with ultra-reliability, very low latency and high availability, making it ideal for vehicular communication, industrial control, factory automation, remote surgery, smart grids and public safety applications.　URLLC aims ~1ms of latency. URLLC includes new services that will change the industry through links with ultra-reliability / low latency, such as remote control of key infrastructure and self-driving vehicles. The level of reliability and latency is essential for smart grid control, industrial automation, robotics, drones control and coordination.

Next, a plurality of use cases included in the triangle of FIG. 1 will be described in more detail.

5G can complement fiber-to-the-home (FTTH) and cable-based broadband (or DOCSIS) as a means of delivering streams rated from hundreds of megabits per second to gigabits per second. This high speed can be required to deliver TVs with resolutions of 4K or more (6K, 8K and above) as well as virtual reality (VR) and augmented reality (AR). VR and AR applications include mostly immersive sporting events. Certain applications may require special network settings. For example, in the case of a VR game, a game company may need to integrate a core server with an edge network server of a network operator to minimize delay.

Automotive is expected to become an important new driver for 5G, with many use cases for mobile communications to vehicles. For example, entertainment for passengers demands high capacity and high mobile broadband at the same time. This is because future users will continue to expect high-quality connections regardless of their location and speed. Another use case in the automotive sector is an augmented reality dashboard. The driver can identify an object in the dark on top of what is being viewed through the front window through the augmented reality dashboard. The augmented reality dashboard displays information that will inform the driver about the object's distance and movement. In the future, the wireless module enables communication between vehicles, information exchange between the vehicle and the supporting infrastructure, and information exchange between the vehicle and other connected devices (e.g. devices accompanied by a pedestrian). The safety system allows the driver to guide the alternative course of action so that he can drive more safely, thereby reducing the risk of accidents. The next step will be a remotely controlled vehicle or self-driving vehicle. This requires a very reliable and very fast communication between different self-driving vehicles and between vehicles and infrastructure. In the future, a self-driving vehicle will perform all driving activities, and the driver will focus only on traffic that the vehicle itself cannot identify. The technical requirements of self-driving vehicles require ultra-low latency and high-speed reliability to increase traffic safety to a level not achievable by humans.

Smart cities and smart homes, which are referred to as smart societies, will be embedded in high density wireless sensor networks. The distributed network of intelligent sensors will identify conditions for cost and energy-efficient maintenance of a city or house. A similar setting can be performed for each home. Temperature sensors, windows and heating controllers, burglar alarms and appliances are all wirelessly connected. Many of these sensors typically require low data rate, low power and low cost. However, for example, real-time high-definition (HD) video may be required for certain types of devices for monitoring.

The consumption and distribution of energy, including heat or gas, is highly dispersed, requiring automated control of distributed sensor networks. The smart grid interconnects these sensors using digital information and communication technologies to collect and act on information. This information can include supplier and consumer behavior, allowing the smart grid to improve the distribution of fuel, such as electricity, in terms of efficiency, reliability, economy, production sustainability, and automated methods. The smart grid can be viewed as another sensor network with low latency.

The health sector has many applications that can benefit from mobile communications. Communication systems can support telemedicine to provide clinical care in remote locations. This can help to reduce barriers to distance and improve access to health services that are not continuously available in distant rural areas. It is also used to save lives in critical care and emergency situations. Mobile communication based wireless sensor networks can provide remote monitoring and sensors for parameters such as heart rate and blood pressure.

Wireless and mobile communications are becoming increasingly important in industrial applications. Wiring costs are high for installation and maintenance. Thus, the possibility of replacing a cable with a wireless link that can be reconfigured is an attractive opportunity in many industries. However, achieving this requires that wireless connections operate with similar delay, reliability, and capacity as cables and that their management is simplified. Low latency and very low error probabilities are new requirements that need to be connected to 5G.

Logistics and freight tracking are important use cases of mobile communications that enable tracking of inventory and packages anywhere using location based information systems. Use cases of logistics and freight tracking typically require low data rates, but require a large range and reliable location information.

Referring to FIG. 2, the wireless communication system may include a first device 210 and a second device 220.

The first device 210 includes a base station, a network node, a transmitting UE, a receiving UE, a wireless device, a wireless communication device, a vehicle, a vehicle equipped with an autonomous driving function, a connected car, a drone, an unmanned aerial vehicle (UAV), an artificial intelligence (AI) module, a robot, an AR device, a VR device, a mixed reality (MR) device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a fin-tech device (or, a financial device), a security device, a climate/environmental device, a device related to 5G services, or a device related to the fourth industrial revolution.

The second device 220 includes a base station, a network node, a transmitting UE, a receiving UE, a wireless device, a wireless communication device, a vehicle, a vehicle equipped with an autonomous driving function, a connected car, a drone, a UAV, an AI module, a robot, an AR device, a VR device, an MR device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a fin-tech device (or, a financial device), a security device, a climate/environmental device, a device related to 5G services, or a device related to the fourth industrial revolution.

For example, the UE may include a mobile phone, a smart phone, a laptop computer, a digital broadcasting terminal, a personal digital assistant (PDA), a portable multimedia player (PMP), a navigation device, a slate personal computer (PC), a tablet PC, an ultrabook, a wearable device (e.g. a smartwatch, a smart glass, a head mounted display (HMD)) . For example, the HMD may be a display device worn on the head. For example, the HMD may be used to implement AR, VR and/or MR.

For example, the drone may be a flying object that is flying by a radio control signal without a person boarding it. For example, the VR device may include a device that implements an object or background in the virtual world. For example, the AR device may include a device that implements connection of an object and/or a background of a virtual world to an object and/or a background of the real world. For example, the MR device may include a device that implements fusion of an object and/or a background of a virtual world to an object and/or a background of the real world. For example, the hologram device may include a device that implements a 360-degree stereoscopic image by recording and playing stereoscopic information by utilizing a phenomenon of interference of light generated by the two laser lights meeting with each other, called holography. For example, the public safety device may include a video relay device or a video device that can be worn by the user's body. For example, the MTC device and the IoT device may be a device that do not require direct human intervention or manipulation. For example, the MTC device and the IoT device may include a smart meter, a vending machine, a thermometer, a smart bulb, a door lock and/or various sensors. For example, the medical device may be a device used for the purpose of diagnosing, treating, alleviating, handling, or preventing a disease. For example, the medical device may be a device used for the purpose of diagnosing, treating, alleviating, or correcting an injury or disorder. For example, the medical device may be a device used for the purpose of inspecting, replacing or modifying a structure or function. For example, the medical device may be a device used for the purpose of controlling pregnancy. For example, the medical device may include a treatment device, a surgical device, an (in vitro) diagnostic device, a hearing aid and/or a procedural device, etc. For example, a security device may be a device installed to prevent the risk that may occur and to maintain safety. For example, the security device may include a camera, a closed-circuit TV (CCTV), a recorder, or a black box. For example, the fin-tech device may be a device capable of providing financial services such as mobile payment. For example, the fin-tech device may include a payment device or a point of sales (POS). For example, the climate/environmental device may include a device for monitoring or predicting the climate/environment.

The first device 210 may include at least one or more processors, such as a processor 211, at least one memory, such as a memory 212, and at least one transceiver, such as a transceiver 213. The processor 211 may perform the functions, procedures, and/or methods of the present invention described below. The processor 211 may perform one or more protocols. For example, the processor 211 may perform one or more layers of the air interface protocol. The memory 212 is connected to the processor 211 and may store various types of information and/or instructions. The transceiver 213 is connected to the processor 211 and may be controlled to transmit and receive wireless signals.

The second device 220 may include at least one or more processors, such as a processor 221, at least one memory, such as a memory 222, and at least one transceiver, such as a transceiver 223. The processor 221 may perform the functions, procedures, and/or methods of the present invention described below. The processor 221 may perform one or more protocols. For example, the processor 221 may perform one or more layers of the air interface protocol. The memory 222 is connected to the processor 221 and may store various types of information and/or instructions. The transceiver 223 is connected to the processor 221 and may be controlled to transmit and receive wireless signals.

The

memory

212, 222 may be connected internally or externally to the

processor

211, 212, or may be connected to other processors via a variety of technologies such as wired or wireless connections.

The first device 210 and/or the second device 220 may have more than one antenna. For example, antenna 214 and/or antenna 224 may be configured to transmit and receive wireless signals.

Specifically, FIG. 3 shows a system architecture based on an evolved-UMTS terrestrial radio access network (E-UTRAN). The aforementioned LTE is a part of an evolved-UTMS (e-UMTS) using the E-UTRAN.

Referring to FIG. 3, the wireless communication system includes one or more user equipment (UE) 310, an E-UTRAN and an evolved packet core (EPC). The UE 310 refers to a communication equipment carried by a user. The UE 310 may be fixed or mobile. The UE 310 may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, etc.

The E-UTRAN consists of one or more evolved NodeB (eNB) 320. The eNB 320 provides the E-UTRA user plane and control plane protocol terminations towards the UE 10. The eNB 320 is generally a fixed station that communicates with the UE 310. The eNB 320 hosts the functions, such as inter-cell radio resource management (RRM), radio bearer (RB) control, connection mobility control, radio admission control, measurement configuration/provision, dynamic resource allocation (scheduler), etc. The eNB 320 may be referred to as another terminology, such as a base station (BS), a base transceiver system (BTS), an access point (AP), etc.

A downlink (DL) denotes communication from the eNB 320 to the UE 310. An uplink (UL) denotes communication from the UE 310 to the eNB 320. A sidelink (SL) denotes communication between the UEs 310. In the DL, a transmitter may be a part of the eNB 320, and a receiver may be a part of the UE 310. In the UL, the transmitter may be a part of the UE 310, and the receiver may be a part of the eNB 320. In the SL, the transmitter and receiver may be a part of the UE 310.

The EPC includes a mobility management entity (MME), a serving gateway (S-GW) and a packet data network (PDN) gateway (P-GW). The MME hosts the functions, such as non-access stratum (NAS) security, idle state mobility handling, evolved packet system (EPS) bearer control, etc. The S-GW hosts the functions, such as mobility anchoring, etc. The S-GW is a gateway having an E-UTRAN as an endpoint. For convenience, MME/S-GW 330 will be referred to herein simply as a "gateway," but it is understood that this entity includes both the MME and S-GW. The P-GW hosts the functions, such as UE Internet protocol (IP) address allocation, packet filtering, etc. The P-GW is a gateway having a PDN as an endpoint. The P-GW is connected to an external network.

The UE 310 is connected to the eNB 320 by means of the Uu interface. The UEs 310 are interconnected with each other by means of the PC5 interface. The eNBs 320 are interconnected with each other by means of the X2 interface. The eNBs 320 are also connected by means of the S1 interface to the EPC, more specifically to the MME by means of the S1-MME interface and to the S-GW by means of the S1-U interface. The S1 interface supports a many-to-many relation between MMEs / S-GWs and eNBs.

Specifically, FIG. 4 shows a system architecture based on a 5G NR. The entity used in the 5G NR (hereinafter, simply referred to as "NR") may absorb some or all of the functions of the entities introduced in FIG. 3 (e.g. eNB, MME, S-GW). The entity used in the NR may be identified by the name "NG" for distinction from the LTE/LTE-A.

Referring to FIG. 4, the wireless communication system includes one or more UE 410, a next-generation RAN (NG-RAN) and a 5th generation core network (5GC). The NG-RAN consists of at least one NG-RAN node. The NG-RAN node is an entity corresponding to the eNB 320 shown in FIG. 3. The NG-RAN node consists of at least one gNB 421 and/or at least one ng-eNB 422. The gNB 421 provides NR user plane and control plane protocol terminations towards the UE 410. The ng-eNB 422 provides E-UTRA user plane and control plane protocol terminations towards the UE 410.

The 5GC includes an access and mobility management function (AMF), a user plane function (UPF) and a session management function (SMF). The AMF hosts the functions, such as NAS security, idle state mobility handling, etc. The AMF is an entity including the functions of the conventional MME. The UPF hosts the functions, such as mobility anchoring, protocol data unit (PDU) handling. The UPF an entity including the functions of the conventional S-GW. The SMF hosts the functions, such as UE IP address allocation, PDU session control.

The gNBs 421 and ng-eNBs 422 are interconnected with each other by means of the Xn interface. The gNBs 421 and ng-eNBs 422 are also connected by means of the NG interfaces to the 5GC, more specifically to the AMF by means of the NG-C interface and to the UPF by means of the NG-U interface.

A protocol structure between network entities described above is described. On the system of FIG. 3 and/or FIG. 4, layers of a radio interface protocol between the UE and the network (e.g. NG-RAN and/or E-UTRAN) may be classified into a first layer (L1), a second layer (L2), and a third layer (L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system.

FIG. 5 shows a block diagram of a user plane protocol stack to which the technical features of the present invention can be applied. FIG. 6 shows a block diagram of a control plane protocol stack to which the technical features of the present invention can be applied.

The user/control plane protocol stacks shown in FIG. 5 and FIG. 6 are used in NR. However, user/control plane protocol stacks shown in FIG. 5 and FIG. 6 may be used in LTE/LTE-A without loss of generality, by replacing gNB/AMF with eNB/MME.

Referring to FIG. 5 and FIG. 6, a physical (PHY) layer belonging to L1. The PHY layer offers information transfer services to media access control (MAC) sublayer and higher layers. The PHY layer offers to the MAC sublayer transport channels. Data between the MAC sublayer and the PHY layer is transferred via the transport channels. Between different PHY layers, i.e., between a PHY layer of a transmission side and a PHY layer of a reception side, data is transferred via the physical channels.

The MAC sublayer belongs to L2. The main services and functions of the MAC sublayer include mapping between logical channels and transport channels, multiplexing/de-multiplexing of MAC service data units (SDUs) belonging to one or different logical channels into/from transport blocks (TB) delivered to/from the physical layer on transport channels, scheduling information reporting, error correction through hybrid automatic repeat request (HARQ), priority handling between UEs by means of dynamic scheduling, priority handling between logical channels of one UE by means of logical channel prioritization (LCP), etc. The MAC sublayer offers to the radio link control (RLC) sublayer logical channels.

The RLC sublayer belong to L2. The RLC sublayer supports three transmission modes, i.e. transparent mode (TM), unacknowledged mode (UM), and acknowledged mode (AM), in order to guarantee various quality of services (QoS) required by radio bearers. The main services and functions of the RLC sublayer depend on the transmission mode. For example, the RLC sublayer provides transfer of upper layer PDUs for all three modes, but provides error correction through ARQ for AM only. In LTE/LTE-A, the RLC sublayer provides concatenation, segmentation and reassembly of RLC SDUs (only for UM and AM data transfer) and re-segmentation of RLC data PDUs (only for AM data transfer). In NR, the RLC sublayer provides segmentation (only for AM and UM) and re-segmentation (only for AM) of RLC SDUs and reassembly of SDU (only for AM and UM). That is, the NR does not support concatenation of RLC SDUs. The RLC sublayer offers to the packet data convergence protocol (PDCP) sublayer RLC channels.

The PDCP sublayer belong to L2. The main services and functions of the PDCP sublayer for the user plane include header compression and decompression, transfer of user data, duplicate detection, PDCP PDU routing, retransmission of PDCP SDUs, ciphering and deciphering, etc. The main services and functions of the PDCP sublayer for the control plane include ciphering and integrity protection, transfer of control plane data, etc.

The service data adaptation protocol (SDAP) sublayer belong to L2. The SDAP sublayer is only defined in the user plane. The SDAP sublayer is only defined for NR. The main services and functions of SDAP include, mapping between a QoS flow and a data radio bearer (DRB), and marking QoS flow ID (QFI) in both DL and UL packets. The SDAP sublayer offers to 5GC QoS flows.

A radio resource control (RRC) layer belongs to L3. The RRC layer is only defined in the control plane. The RRC layer controls radio resources between the UE and the network. To this end, the RRC layer exchanges RRC messages between the UE and the BS. The main services and functions of the RRC layer include broadcast of system information related to AS and NAS, paging, establishment, maintenance and release of an RRC connection between the UE and the network, security functions including key management, establishment, configuration, maintenance and release of radio bearers, mobility functions, QoS management functions, UE measurement reporting and control of the reporting, NAS message transfer to/from NAS from/to UE.

In other words, the RRC layer controls logical channels, transport channels, and physical channels in relation to the configuration, reconfiguration, and release of radio bearers. A radio bearer refers to a logical path provided by L1 (PHY layer) and L2 (MAC/RLC/PDCP/SDAP sublayer) for data transmission between a UE and a network. Setting the radio bearer means defining the characteristics of the radio protocol layer and the channel for providing a specific service, and setting each specific parameter and operation method. Radio bearer may be divided into signaling RB (SRB) and data RB (DRB). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

An RRC state indicates whether an RRC layer of the UE is logically connected to an RRC layer of the E-UTRAN. In LTE/LTE-A, when the RRC connection is established between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is in the RRC connected state (RRC_CONNECTED). Otherwise, the UE is in the RRC idle state (RRC_IDLE). In NR, the RRC inactive state (RRC_INACTIVE) is additionally introduced. RRC_INACTIVE may be used for various purposes. For example, the massive machine type communications (MMTC) UEs can be efficiently managed in RRC_INACTIVE. When a specific condition is satisfied, transition is made from one of the above three states to the other.

A predetermined operation may be performed according to the RRC state. In RRC_IDLE, public land mobile network (PLMN) selection, broadcast of system information (SI), cell re-selection mobility, core network (CN) paging and discontinuous reception (DRX) configured by NAS may be performed. The UE shall have been allocated an identifier (ID) which uniquely identifies the UE in a tracking area. No RRC context stored in the BS.

In RRC_CONNECTED, the UE has an RRC connection with the network (i.e. E-UTRAN/NG-RAN). Network-CN connection (both C/U-planes) is also established for UE. The UE AS context is stored in the network and the UE. The RAN knows the cell which the UE belongs to. The network can transmit and/or receive data to/from UE. Network controlled mobility including measurement is also performed.

Most of operations performed in RRC_IDLE may be performed in RRC_INACTIVE. But, instead of CN paging in RRC_IDLE, RAN paging is performed in RRC_INACTIVE. In other words, in RRC_IDLE, paging for mobile terminated (MT) data is initiated by core network and paging area is managed by core network. In RRC_INACTIVE, paging is initiated by NG-RAN, and RAN-based notification area (RNA) is managed by NG-RAN. Further, instead of DRX for CN paging configured by NAS in RRC_IDLE, DRX for RAN paging is configured by NG-RAN in RRC_INACTIVE. Meanwhile, in RRC_INACTIVE, 5GC-NG-RAN connection (both C/U-planes) is established for UE, and the UE AS context is stored in NG-RAN and the UE. NG-RAN knows the RNA which the UE belongs to.

NAS layer is located at the top of the RRC layer. The NAS control protocol performs the functions, such as authentication, mobility management, security control.

The physical channels may be modulated according to OFDM processing and utilizes time and frequency as radio resources. The physical channels consist of a plurality of orthogonal frequency division multiplexing (OFDM) symbols in time domain and a plurality of subcarriers in frequency domain. One subframe consists of a plurality of OFDM symbols in the time domain. A resource block is a resource allocation unit, and consists of a plurality of OFDM symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific OFDM symbols (e.g. first OFDM symbol) of the corresponding subframe for a physical downlink control channel (PDCCH), i.e. L1/L2 control channel. A transmission time interval (TTI) is a basic unit of time used by a scheduler for resource allocation. The TTI may be defined in units of one or a plurality of slots, or may be defined in units of mini-slots.

The transport channels are classified according to how and with what characteristics data are transferred over the radio interface. DL transport channels include a broadcast channel (BCH) used for transmitting system information, a downlink shared channel (DL-SCH) used for transmitting user traffic or control signals, and a paging channel (PCH) used for paging a UE. UL transport channels include an uplink shared channel (UL-SCH) for transmitting user traffic or control signals and a random access channel (RACH) normally used for initial access to a cell.

Different kinds of data transfer services are offered by MAC sublayer. Each logical channel type is defined by what type of information is transferred. Logical channels are classified into two groups: control channels and traffic channels.

Control channels are used for the transfer of control plane information only. The control channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH) and a dedicated control channel (DCCH). The BCCH is a DL channel for broadcasting system control information. The PCCH is DL channel that transfers paging information, system information change notifications. The CCCH is a channel for transmitting control information between UEs and network. This channel is used for UEs having no RRC connection with the network. The DCCH is a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. This channel is used by UEs having an RRC connection.

Traffic channels are used for the transfer of user plane information only. The traffic channels include a dedicated traffic channel (DTCH). The DTCH is a point-to-point channel, dedicated to one UE, for the transfer of user information. The DTCH can exist in both UL and DL.

Regarding mapping between the logical channels and transport channels, in DL, BCCH can be mapped to BCH, BCCH can be mapped to DL-SCH, PCCH can be mapped to PCH, CCCH can be mapped to DL-SCH, DCCH can be mapped to DL-SCH, and DTCH can be mapped to DL-SCH. In UL, CCCH can be mapped to UL-SCH, DCCH can be mapped to UL- SCH, and DTCH can be mapped to UL-SCH.

UE procedures in RRC_IDLE and/or RRC_INACTIVE are described. It may be referred to as Section 5 of 3GPP TS 38.304 V1.0.1 (2018-04).

First, PLMN selection is described. In the UE, the AS shall report available PLMNs to the NAS on request from the NAS or autonomously.

During PLMN selection, based on the list of PLMN identities in priority order, the particular PLMN may be selected either automatically or manually. Each PLMN in the list of PLMN identities is identified by a PLMN identity. In the system information on the broadcast channel, the UE can receive one or multiple PLMN identity in a given cell. The result of the PLMN selection performed by NAS is an identifier of the selected PLMN.

On request of the NAS, the AS shall perform a search for available PLMNs and report them to NAS.

The UE shall scan all radio frequency (RF) channels in the NR bands according to its capabilities to find available PLMNs. On each carrier, the UE shall search for the strongest cell and read its system information, in order to find out which PLMN(s) the cell belongs to. If the UE can read one or several PLMN identities in the strongest cell, each found PLMN shall be reported to the NAS as a high quality PLMN (but without the reference signal received power (RSRP) value), provided that the following high quality criterion is fulfilled: for a NR cell, the measured RSRP value shall be greater than or equal to X dBm.

Found PLMNs that do not satisfy the high quality criterion but for which the UE has been able to read the PLMN identities are reported to the NAS together with the RSRP value. The quality measure reported by the UE to NAS shall be the same for each PLMN found in one cell.

The search for PLMNs may be stopped on request of the NAS. The UE may optimize PLMN search by using stored information, e.g. carrier frequencies and optionally also information on cell parameters from previously received measurement control information elements.

Once the UE has selected a PLMN, the cell selection procedure shall be performed in order to select a suitable cell of that PLMN to camp on.

Second, cell selection and reselection is described. Cell selection is applicable in RRC_IDLE while cell reselection is applicable in both RRC_IDLE and RRC_INACTIVE.

The UE shall perform measurements for cell selection and reselection purposes.

The NAS can control the RAT(s) in which the cell selection should be performed, for instance by indicating RAT(s) associated with the selected PLMN, and by maintaining a list of forbidden registration area(s) and a list of equivalent PLMNs. The UE shall select a suitable cell based on RRC_IDLE measurements and cell selection criteria.

In order to expedite the cell selection process, stored information for several RATs may be available in the UE.

When camped on a cell, the UE shall regularly search for a better cell according to the cell reselection criteria. If a better cell is found, that cell is selected. The change of cell may imply a change of RAT.

The NAS is informed if the cell selection and reselection result in changes in the received system information relevant for NAS.

For normal service, the UE shall camp on a suitable cell, tune to that cell's control channel(s) so that the UE can:

1) Receive system information from the PLMN; and

- receive registration area information from the PLMN, e.g., tracking area information; and

- receive other AS and NAS Information; and

2) if registered:

- receive paging and notification messages from the PLMN; and

- initiate transfer to RRC_CONNECTED.

For cell reselection in multi-beam operations, using a maximum number of beams to be considered and a threshold which are provided in system information, measurement quantity of a cell is derived amongst the beams corresponding to the same cell based on synchronization signal (SS)/physical broadcast channel (PBCH) block as follows:

1> if the highest beam measurement quantity value is below the threshold:

2> derive a cell measurement quantity as the highest beam measurement quantity value;

1> else:

2> derive a cell measurement quantity as the linear average of the power values of up to the maximum number of highest beam measurement quantity values above the threshold.

Cell selection is performed by one of the following two procedures:

a) Initial cell selection (no prior knowledge of which RF channels are NR carriers);

1. The UE shall scan all RF channels in the NR bands according to its capabilities to find a suitable cell.

2. On each carrier frequency, the UE need only search for the strongest cell.

3. Once a suitable cell is found this cell shall be selected.

b) Cell selection by leveraging stored information;

1. This procedure requires stored information of carrier frequencies and optionally also information on cell parameters, from previously received measurement control information elements or from previously detected cells.

2. Once the UE has found a suitable cell the UE shall select it.

3. If no suitable cell is found, the initial cell selection procedure shall be started.

Absolute priorities of different NR frequencies or inter-RAT frequencies may be provided to the UE in the system information, in the RRC connection release message, or by inheriting from another RAT at inter-RAT cell (re)selection. In the case of system information, a NR frequency or inter-RAT frequency may be listed without providing a priority (i.e. the field cellReselectionPriority is absent for that frequency). If priorities are provided in dedicated signaling, the UE shall ignore all the priorities provided in system information.

The UE shall only perform cell reselection evaluation for NR frequencies and inter-RAT frequencies that are given in system information and for which the UE has a priority provided.

The UE shall delete priorities provided by dedicated signaling when:

- the UE enters RRC_CONNECTED; or

- a PLMN selection is performed on request by NAS.

The UE shall not consider any black listed cells as candidate for cell reselection.

The UE shall inherit the priorities provided by dedicated signaling at inter-RAT cell (re)selection.

The network may assign dedicated cell reselection priorities for frequencies not configured by system information.

UE domain selection is described. It may be referred to as Section 4.3 of 3GPP TS 24.501 V1.1.1 (2018-05).

The UE's usage setting applies to voice capable UEs in 5GS and indicates whether the UE has preference for voice services over data services or vice-versa, where:

a) voice services include IP multimedia core network subsystem (IMS) voice; and

b) data services include any kind of user data transfer without a voice media component.

The UE's usage setting can be set to:

a) "voice centric"; or

b) "data centric".

If the UE is capable of S1 mode, there is a single UE's usage setting at the UE which applies to both 5GS and EPS. S1 mode is a mode of a UE allowing access to the EPC via the E-UTRAN.

The The behavior of the UE for domain selection is determined by:

a) the UE usage setting;

b) the availability of IMS voice; and

c) whether the UE operates in single-registration mode or dual-registration mode.

"IMS voice not available" is determined per access type independently, i.e. 3GPP access or non-3GPP access.

"IMS voice not available" refers to one of the following conditions:

a) the UE does not support IMS voice;

b) the UE supports IMS voice, but the network indicates in the REGISTRATION ACCEPT message that IMS voice over packet-switched (PS) sessions are not supported; or

c) the UE supports IMS voice, the network indicates in the REGISTRATION ACCEPT message that IMS voice over PS sessions are supported, but the upper layers:

1) provide no indication that the UE is available for voice call in the IMS within a manufacturer determined period of time; or

2) indicate that the UE is not available for voice calls in the IMS.

If conditions　a and b evaluate to false, the upper layers need time to attempt IMS registration. In the event an indication from the upper layers that the UE is available for voice calls in the IMS takes longer than the manufacturer determined period of time (e.g. due to delay when attempting IMS registration or due to delay in obtaining a QoS flow for SIP signalling), the NAS layer assumes the UE is not available for voice calls in the IMS.

"IMS voice available" applies when "IMS voice not available" does not apply.

When IMS voice is not available over 3GPP access, if the UE's usage setting is "voice centric" and the UE operates in single-registration mode, the UE shall disable the N1 mode radio capabilities, and attempt to select an E-UTRA cell connected to EPC. N1 mode is a mode of a UE allowing access to the 5G core network via the 5G access network. If such a cell is found, the UE shall then perform voice domain selection procedures.

If the UE operates in single-registration mode, whenever the UE's usage setting changes, the UE shall execute procedures according to Table 1.

UE's usage setting change	Procedure to execute
From "data centric" to "voice centric" and "IMS voice not available" over 3GPP access	Disable the N1 mode radio capabilities
From "voice centric" to "data centric" and the N1 mode radio capabilities are disabled at the UE	Re-enable the N1 mode radio capabilities

If the UE operates in single-registration mode, whenever the IMS voice availability is determined or changes, the UE shall execute procedures according to Table 2.

Change of IMS voice available condition	Procedure to execute
IMS voice not available over 3GPP access and the UE's usage setting is "voice centric"	Disable the N1 mode radio capabilities

Interworking with E-UTRAN connected to EPC is described. It may be referred to as Section 4.8 of 3GPP TS 24.501 V1.1.1 (2018-05). In order to interwork with E-UTRAN connected to EPC, the UE supporting both S1 mode and N1 mode can operate in single-registration mode or dual-registration mode. Support of single-registration mode is mandatory for UEs supporting both S1 mode and N1 mode.

During the attach procedure or initial registration procedure, the mode for intersystem interworking is selected if the UE supports both S1 mode and N1 mode, and the network supports intersystem interworking.

If the UE is capable of both N1 mode and S1 mode, when the UE needs to use one or more functionalities not supported in 5GS but supported in EPS and the UE is in 5GMM-IDLE mode, the UE may disable the N1 mode radio capabilities.

If the UE is capable of both N1 mode and S1 mode and lower layers provide an indication that the current E-UTRA cell is connected to both EPC and 5GCN, the UE shall select a core network type (EPC or 5GC) based on the PLMN selection procedures and provide the selected core network type information to the lower layer during the initial registration procedure.

Disabling and re-enabling of UE's N1 mode radio capability is described. It may be referred to as Section 4.9 of 3GPP TS 24.501 V1.1.1 (2018-05). When the UE supporting both N1 mode and S1 mode is disabling the N1 mode radio capability, it should proceed as follows:

a) select an E-UTRA cell connected to EPC of the registered PLMN or a PLMN from the list of equivalent PLMNs;

b) if an E-UTRA cell connected to EPC of the registered PLMN or a PLMN from the list of equivalent PLMNs cannot be found, the UE may select another RAT of the registered PLMN or a PLMN from the list of equivalent PLMNs that the UE supports;

c) if another RAT of the registered PLMN or a PLMN from the list of equivalent PLMNs cannot be found, or the UE does not have a registered PLMN, then perform PLMN selection; or

d) if no other allowed PLMN and RAT combinations are available, then the UE may re-enable the N1 mode capability and remain camped in NG-RAN of the registered PLMN, and may periodically scan for another PLMN and RAT combination which can provide non-5GS services.

When the UE supporting both N1 mode and S1 mode needs to stay in E-UTRA connected to EPC (e.g. due to the domain selection for UE originating sessions), in order to prevent unwanted handover or cell reselection from E-UTRA connected to EPC to NG-RAN connected to 5GC, the UE operating in single-registration mode shall disable the N1 mode radio capability and:

a) shall set the N1 mode bit to "N1 mode not supported" in the UE network capability IE of the ATTACH REQUEST message and the TRACKING AREA UPDATE REQUEST message in EPC; and

b) the UE NAS layer shall indicate the access stratum layer(s) of disabling of the N1 mode radio capability.

The UE can only disable the N1 mode radio capability when in 5GMM-IDLE mode.

The UE shall re-enable the N1 mode radio capability when:

a) the UE performs PLMN selection; or

b) the UE powers off and powers on again or the universal subscription identification module (USIM) is removed.

If the disabling of N1 mode radio capability was due to IMS voice is not available over 3GPP access and the UE's usage setting is "voice centric", the UE shall re-enable the N1 mode radio capability when the UE's usage setting is changed from "voice centric" to "data centric" or when the IMS voice becomes available in 5GS.

The UE may start a timer for re-enabling N1 mode radio capability, after the N1 mode radio capability is disabled. On the expiry of this timer, the UE should enable the N1 mode radio capability.

The UE should memorize the identity of the PLMN where N1 mode radio capability was disabled and should not consider this PLMN in subsequent PLMN selections.

As mentioned above, an important principle for mobility in RRC_IDLE and/or RRC_INACTIVE is that the UE should always camp on the strongest cell within a carrier. The rationale for this principle is that it results in the best user performance and minimizes inter-cell interference. Meanwhile, as also mentioned above, the core network may be selected as part of the PLMN selection. In this case, there may be a risk that the above principle is violated. The reason is that cells with the wrong core network type are excluded in the cell selection/re-selection which may cause the UE to end up on a non-optimal cell.

FIG. 7 shows an example of selecting/re-selecting non-optimal cells upon PLMN selection and core network selection. Referring to FIG. 7, a UE moves from an EPC coverage area to 5GC coverage area. However, if the N1 mode radio capability of the UE is disabled due to the UE's usage setting set to "voice centric" and/or "IMS voice not available", the UE cannot select/re-select NR cells in the 5GC coverage area, because the 5GC cannot be selected upon PLMN selection. The UE may select/re-select LTE cells in the EPC coverage area, which may cause interference to NR cells.

On the contrary, if the UE selects a specific PLMN in the PLMN selection and LTE/5GC in the core network selection and then moves from the LTE/5GC area into the LTE/EPC only area within the specific PLMN, the UE may select a weak LTE/5GC cell instead of a strong LTE/EPC cell. If the LTE/5GC cell and LTE/EPC cell are using the same carrier, the UE will cause unnecessary interference to the LTE/EPC cell.

In other words, if the core network type is set during PLMN selection and is used as cell suitability criterion, the UE may select/re-select to a cell which is not the strongest cell on the carrier, causing additional inter-cell interference.

To address the problem described above, the following two options have been proposed.

(1) Option 1: The option 1 is to only allow the UE to select/re-select to the LTE/5GC cell if it is the strongest cell on the carrier. That is, the UE shall discard all weaker cells on a carrier whenever the strongest cell is discarded. Therefore, no suitable E-UTRA cell with the given core network type can be found. In this case, the UE will search for suitable cells on other RATs and if also this fails, the UE will enter "Any cell selection state" where it will try to find an acceptable cell of any PLMN to camp on, trying all RATs supported by the UE. Since the goal of this search is to find a cell where the UE can obtain limited service, it is reasonable to allow the UE to remove the core network restriction and camp on cells with any type of core network. Once an acceptable cell is found, the UE enters the "Camped on Any cell state" where it will regularly search for a suitable cell.

(2) Option 2: The option 2 is to select the core network as part of the cell selection/re-selection instead of during the PLMN selection. Basically, every time the AS layer selects/re-selects to a new cell, the supported core network types are reported to the NAS layer which then selects one of them. If this is the first time a core network type is selected or if the core network type changes, the NAS layer will also trigger a registration request to register the UE onto the new core network. Since the core network type is no longer part of the cell suitability criterion, this approach ensures that the UE always camps on the best cell on a given carrier. Unlike in the option 1, it is no longer possible to restrict the cell search to a given core network type. For example, the AS layer may select/re-select to a LTE/EPC only cell which would force the NAS layer to select EPC, even though it is preferred that the UE to continue the cell search for LTE/5GC cells.

The two options described above do not give clear solution for the problem described above. For the option 1, it can be a burden to the UE to perform cell search continuously. For the option 2, since the core network selection is responsible to the NAS layer based on upper layer information (e.g. which service the UE intends to use is supported by specific core network and/or UE's usage setting (i.e. data centric or voice centric)), it is not desired that the AS layer is allowed to change core network during cell (re)-selection.

FIG. 8 shows an example of a method for handling a strongest cell not supporting a selected core network according to an embodiment of the present invention. This embodiment may be performed by a UE/wireless device. The UE/wireless device may be in communication with at least one of a user equipment, a network, and/or autonomous vehicles other than the UE/wireless device.

In step S800, the UE (i.e. NAS layer) selects a core network. The UE may select the core network upon PLMN selection. The UE may select EPC, and the UE may stay in (i.e. camp on) LTE cells connected to EPC. For example, when the UE supporting both N1 mode and S1 mode disables the N1 mode radio capability, the UE may select EPC. Or, the NAS layer may select EPC (e.g. based on PLMN selection) and provide information on the selected core network (i.e. EPC) to the AS layer. Alternatively, the UE may select 5GC. The NAS layer indicate the selected core network to the AS layer. The AS layer may consider cells supporting the EPC as candidates for cell (re)-selection.

In step S810, when a strongest cell supporting the selected core network is not a strongest cell on a current frequency, the UE (i.e. AS layer) informs the NAS layer that there is no cell supporting the selected core network. In step S820, the UE (i.e. NAS layer) performs PLMN selection based on the information that there is no cell supporting the selected core network. The UE (i.e. NAS layer) may select a new core network upon the PLMN selection.

More specifically, if the strongest cell supporting the selected core network is not the strongest cell operating on the current carrier, and if the UE has the E-UTRAN frequency and/or inter-RAT frequency, other than the current frequency, the UE (i.e. AS layer) may select at least one frequency other than the current frequency before informing the NAS layer that there is no cell supporting the selected core network. Information on the E-UTRAN frequency and/or inter-RAT frequency for cell re-selection may be obtained from the network via system information and/or dedicated signaling. The UE may select the at least one frequency based on a frequency priority, which may be provided from the network via system information (i.e. cellReselectionPriority) and/or dedicated signaling. The UE attempts to find a cell on the selected at least one frequency. The cell the UE wants to find may support the selected core network, and may be the strongest cell on the selected at least one frequency, and may be a suitable cell.

If the UE find the cell on the selected at least one frequency, the UE (i.e. AS layer) may select the cell and camp on the cell normally. The UE may always consider the selected at least one frequency to be the highest priority frequency (i.e. higher than any of the network configured values), irrespective of any other frequency priority allocated to the selected at least one frequency while the cell is the strongest cell on the selected at least one frequency and suitable cell. In this case, that there is no cell supporting the selected core network may not be informed to the NAS layer, and the PLMN selection may not be performed.

Else if, the UE cannot find the cell and/or the UE does not have the E-UTRAN frequency and/or inter-RAT frequency, other than the current frequency, the UE (i.e. AS layer) informs the NAS layer that there is no cell connected to the selected core network of the registered PLMN and/or a PLMN from the list of equivalent PLMNs. Upon receiving the information, the NAS layer may perform PLMN selection, and then, core network selection.

Alternatively, the UE cannot find the cell and/or the UE does not have the E-UTRAN frequency and/or inter-RAT frequency, other than the current frequency, the UE (i.e. AS layer) may memorize the following conditions.

- There is no cell connected to the selected core network of the registered PLMN and/or a PLMN from the list of equivalent PLMNs; and/or

- For all frequencies provided by system information and/or dedicated signaling, there is no cell supporting the selected core network which is the strongest cell on the corresponding frequency and the suitable cell; and/or

- The strongest cell supporting the selected core network is not the strongest cell operating on the current carrier.

If RRC signaling is triggered in RRC_IDLE (e.g. mobile-originating (MO) signaling/data is generated and/or mobile-terminating (MT) signaling (paging) is received) while the above conditions are kept, the UE (i.e. AS layer) may inform the NAS layer that there is no cell connected to the selected core network of the registered PLMN and/or a PLMN from the list of equivalent PLMNs, and perform PLMN selection. In this case, the UE does not transmit the RRC signaling.

While no RRC signaling is triggered in RRC_IDLE, if the above conditions are changed (e.g. the cell supporting the selected core network becomes suitable cell and the strongest cell on the frequency which belongs to frequencies provided by system information and/or dedicated signaling), the UE (i.e. AS layer) may remove the memorized conditions. The UE may select the strongest cell on the frequency which supports the selected core network and camp on the cell normally. The UE may always consider the frequency to be the highest priority frequency (i.e. higher than any of the network configured values), irrespective of any other frequency priority allocated to the frequency while the cell is the strongest cell on the selected at least one frequency and suitable cell.

Furthermore, a network (e.g. cell connected to EPC and/or 5GC) may provide information used for cell re-selection to the UE as follows via system information and/or dedicated signaling. The information may be provided to the UE with information that the UE supports only the selected core network. A cell connected to the selected core network (e.g. EPC) may provide information on whether or not neighbor cell supports only the other core network (e.g. 5GC) and/or the neighbor cell ID (e.g. Physical cell ID). A cell connected to EPC and/or 5GC (in boundary area) may provide a list of frequencies which is used (or not used) in the cell supporting only the other core network (e.g. 5GC), and/or a list of frequencies the UE can use with (without) interference to the cell supporting only the other core network (e.g. 5GC).

Upon the above information, the UE may use the information to perform cell reselection. For example, the UE may consider the list of frequencies which is not used in the cell supporting only the other core network (e.g. 5GC) as candidates for cell reselection.

According to the embodiment of the present invention shown in FIG. 8, when the strongest cell on a carrier does not support a selected core network, the UE can perform PLMN selection and/or core network selection quickly. Therefore, it can be avoided that the UE causes interference to other cells.

A UE includes a processor 910, a power management module 911, a battery 912, a display 913, a keypad 914, a subscriber identification module (SIM) card 915, a memory 920, a transceiver 930, one or more antennas 931, a speaker 940, and a microphone 941.

The processor 910 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor 910. The processor 910 may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The processor 910 may be an application processor (AP). The processor 910 may include at least one of a digital signal processor (DSP), a central processing unit (CPU), a graphics processing unit (GPU), a modem (modulator and demodulator). An example of the processor 910 may be found in SNAPDRAGON^TM series of processors made by Qualcomm^®, EXYNOS^TM series of processors made by Samsung^®, A series of processors made by Apple^®, HELIO^TM series of processors made by MediaTek^®, ATOM^TM series of processors made by Intel^® or a corresponding next generation processor.

The processor 910 may be configured to select a core network. The processor 910 may be configured to select the core network upon PLMN selection. The processor 910 may be configured to select EPC, and the UE may stay in (i.e. camp on) LTE cells connected to EPC. For example, when the UE supporting both N1 mode and S1 mode disables the N1 mode radio capability, the processor 910 may be configured to select EPC. Or, the NAS layer may select EPC (e.g. based on PLMN selection) and provide information on the selected core network (i.e. EPC) to the AS layer. Alternatively, the processor 910 may be configured to select 5GC. The NAS layer indicate the selected core network to the AS layer. The AS layer may consider cells supporting the EPC as candidates for cell (re)-selection.

When a strongest cell supporting the selected core network is not a strongest cell on a current frequency, the processor 910 may be configured to inform the NAS layer that there is no cell supporting the selected core network. The processor 910 may be configured to perform PLMN selection based on the information that there is no cell supporting the selected core network. The processor 910 may be configured to select a new core network upon the PLMN selection.

More specifically, if the strongest cell supporting the selected core network is not the strongest cell operating on the current carrier, and if the UE has the E-UTRAN frequency and/or inter-RAT frequency, other than the current frequency, the processor 910 may be configured to select at least one frequency other than the current frequency before informing the NAS layer that there is no cell supporting the selected core network. Information on the E-UTRAN frequency and/or inter-RAT frequency for cell re-selection may be obtained from the network via system information and/or dedicated signaling. The processor 910 may be configured to select the at least one frequency based on a frequency priority, which may be provided from the network via system information (i.e. cellReselectionPriority) and/or dedicated signaling. The processor 910 may be configured to attempt to find a cell on the selected at least one frequency. The cell the UE wants to find may support the selected core network, and may be the strongest cell on the selected at least one frequency, and may be a suitable cell.

If the UE find the cell on the selected at least one frequency, the processor 910 may be configured to select the cell and camp on the cell normally. The processor 910 may be configured to always consider the selected at least one frequency to be the highest priority frequency (i.e. higher than any of the network configured values), irrespective of any other frequency priority allocated to the selected at least one frequency while the cell is the strongest cell on the selected at least one frequency and suitable cell. In this case, that there is no cell supporting the selected core network may not be informed to the NAS layer, and the PLMN selection may not be performed.

Else if, the UE cannot find the cell and/or the UE does not have the E-UTRAN frequency and/or inter-RAT frequency, other than the current frequency, the processor 910 may be configured to inform the NAS layer that there is no cell connected to the selected core network of the registered PLMN and/or a PLMN from the list of equivalent PLMNs. Upon receiving the information, the processor 910 may be configured to perform PLMN selection, and then, core network selection.

The power management module 911 manages power for the processor 910 and/or the transceiver 930. The battery 912 supplies power to the power management module 911. The display 913 outputs results processed by the processor 910. The keypad 914 receives inputs to be used by the processor 910. The keypad 914 may be shown on the display 913. The SIM card 915 is an　integrated circuit　that is intended to　securely store the　international mobile subscriber identity　(IMSI) number and its related　key, which are used to identify and authenticate subscribers on　mobile telephony　devices (such as　mobile phones　and　computers). It is also possible to store contact information on many SIM cards.

The memory 920 is operatively coupled with the processor 910 and stores a variety of information to operate the processor 910. The memory 920 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in the memory 920 and executed by the processor 910. The memory 920 can be implemented within the processor 910 or external to the processor 910 in which case those can be communicatively coupled to the processor 910 via various means as is known in the art.

The transceiver 930 is operatively coupled with the processor 910, and transmits and/or receives a radio signal. The transceiver 930 includes a transmitter and a receiver. The transceiver 930 may include baseband circuitry to process radio frequency signals. The transceiver 930 controls the one or more antennas 931 to transmit and/or receive a radio signal.

The speaker 940 outputs sound-related results processed by the processor 910. The microphone 941 receives sound-related inputs to be used by the processor 910.

According to the embodiment of the present invention shown in FIG. 9, when the strongest cell on a carrier does not support a selected core network, the UE can perform PLMN selection and/or core network selection quickly. Therefore, it can be avoided that the UE causes interference to other cells.

The present invention may be applied to various future technologies, such as AI.

<AI>

AI refers to artificial intelligence and/or the field of studying methodology for making it. Machine learning is a field of studying methodologies that define and solve various problems dealt with in AI. Machine learning may be defined as an algorithm that enhances the performance of a task through a steady experience with any task.

An artificial neural network (ANN) is a model used in machine learning. It can mean a whole model of problem-solving ability, consisting of artificial neurons (nodes) that form a network of synapses. An ANN can be defined by a connection pattern between neurons in different layers, a learning process for updating model parameters, and/or an activation function for generating an output value. An ANN may include an input layer, an output layer, and optionally one or more hidden layers. Each layer may contain one or more neurons, and an ANN may include a synapse that links neurons to neurons. In an ANN, each neuron can output a summation of the activation function for input signals, weights, and deflections input through the synapse. Model parameters are parameters determined through learning, including deflection of neurons and/or weights of synaptic connections. The hyper-parameter means a parameter to be set in the machine learning algorithm before learning, and includes a learning rate, a repetition number, a mini batch size, an initialization function, etc. The objective of the ANN learning can be seen as determining the model parameters that minimize the loss function. The loss function can be used as an index to determine optimal model parameters in learning process of ANN.

Machine learning can be divided into supervised learning, unsupervised learning, and reinforcement learning, depending on the learning method. Supervised learning is a method of learning ANN with labels given to learning data. Labels are the answers (or result values) that ANN must infer when learning data is input to ANN. Unsupervised learning can mean a method of learning ANN without labels given to learning data. Reinforcement learning can mean a learning method in which an agent defined in an environment learns to select a behavior and/or sequence of actions that maximizes cumulative compensation in each state.

Machine learning, which is implemented as a deep neural network (DNN) that includes multiple hidden layers among ANN, is also called deep learning. Deep learning is part of machine learning. In the following, machine learning is used to mean deep learning.

The AI device 1000 may be implemented as a stationary device or a mobile device, such as a TV, a projector, a mobile phone, a smartphone, a desktop computer, a notebook, a digital broadcasting terminal, a PDA, a PMP, a navigation device, a tablet PC, a wearable device, a set-top box (STB), a digital multimedia broadcasting (DMB) receiver, a radio, a washing machine, a refrigerator, a digital signage, a robot, a vehicle, etc.

Referring to FIG. 10, the AI device 1000 may include a communication part 1010, an input part 1020, a learning processor 1030, a sensing part 1040, an output part 1050, a memory 1060, and a processor 1070.

The communication part 1010 can transmit and/or receive data to and/or from external devices such as the AI devices and the AI server using wire and/or wireless communication technology. For example, the communication part 1010 can transmit and/or receive sensor information, a user input, a learning model, and a control signal with external devices. The communication technology used by the communication part 1010 may include a global system for mobile communication (GSM), a code division multiple access (CDMA), an LTE/LTE-A, a 5G, a WLAN, a Wi-Fi, Bluetooth^TM, radio frequency identification (RFID), infrared data association (IrDA), ZigBee, and/or near field communication (NFC).

The input part 1020 can acquire various kinds of data. The input part 1020 may include a camera for inputting a video signal, a microphone for receiving an audio signal, and a user input part for receiving information from a user. A camera and/or a microphone may be treated as a sensor, and a signal obtained from a camera and/or a microphone may be referred to as sensing data and/or sensor information. The input part 1020 can acquire input data to be used when acquiring an output using learning data and a learning model for model learning. The input part 1020 may obtain raw input data, in which case the processor 1070 or the learning processor 1030 may extract input features by preprocessing the input data.

The learning processor 1030 may learn a model composed of an ANN using learning data. The learned ANN can be referred to as a learning model. The learning model can be used to infer result values for new input data rather than learning data, and the inferred values can be used as a basis for determining which actions to perform. The learning processor 1030 may perform AI processing together with the learning processor of the AI server. The learning processor 1030 may include a memory integrated and/or implemented in the AI device 1000. Alternatively, the learning processor 1030 may be implemented using the memory 1060, an external memory directly coupled to the AI device 1000, and/or a memory maintained in an external device.

The sensing part 1040 may acquire at least one of internal information of the AI device 1000, environment information of the AI device 1000, and/or the user information using various sensors. The sensors included in the sensing part 1040 may include a proximity sensor, an illuminance sensor, an acceleration sensor, a magnetic sensor, a gyro sensor, an inertial sensor, an RGB sensor, an IR sensor, a fingerprint recognition sensor, an ultrasonic sensor, an optical sensor, a microphone, a light detection and ranging (LIDAR), and/or a radar.

The output part 1050 may generate an output related to visual, auditory, tactile, etc. The output part 1050 may include a display unit for outputting visual information, a speaker for outputting auditory information, and/or a haptic module for outputting tactile information.

The memory 1060 may store data that supports various functions of the AI device 1000. For example, the memory 1060 may store input data acquired by the input part 1020, learning data, a learning model, a learning history, etc.

The processor 1070 may determine at least one executable operation of the AI device 1000 based on information determined and/or generated using a data analysis algorithm and/or a machine learning algorithm. The processor 1070 may then control the components of the AI device 1000 to perform the determined operation. The processor 1070 may request, retrieve, receive, and/or utilize data in the learning processor 1030 and/or the memory 1060, and may control the components of the AI device 1000 to execute the predicted operation and/or the operation determined to be desirable among the at least one executable operation. The processor 1070 may generate a control signal for controlling the external device, and may transmit the generated control signal to the external device, when the external device needs to be linked to perform the determined operation. The processor 1070 may obtain the intention information for the user input and determine the user's requirements based on the obtained intention information. The processor 1070 may use at least one of a speech-to-text (STT) engine for converting speech input into a text string and/or a natural language processing (NLP) engine for acquiring intention information of a natural language, to obtain the intention information corresponding to the user input. At least one of the STT engine and/or the NLP engine may be configured as an ANN, at least a part of which is learned according to a machine learning algorithm. At least one of the STT engine and/or the NLP engine may be learned by the learning processor 1030 and/or learned by the learning processor of the AI server, and/or learned by their distributed processing. The processor 1070 may collect history information including the operation contents of the AI device 1000 and/or the user's feedback on the operation, etc. The processor 1070 may store the collected history information in the memory 1060 and/or the learning processor 1030, and/or transmit to an external device such as the AI server. The collected history information can be used to update the learning model. The processor 1070 may control at least some of the components of AI device 1000 to drive an application program stored in memory 1060. Furthermore, the processor 1070 may operate two or more of the components included in the AI device 1000 in combination with each other for driving the application program.

Referring to FIG. 11, in the AI system, at least one of an AI server 1120, a robot 1110a, an autonomous vehicle 1110b, an XR device 1110c, a smartphone 1110d and/or a home appliance 1110e is connected to a cloud network 1100. The robot 1110a, the autonomous vehicle 1110b, the XR device 1110c, the smartphone 1110d, and/or the home appliance 1110e to which the AI technology is applied may be referred to as AI devices 1110a to 1110e.

The cloud network 1100 may refer to a network that forms part of a cloud computing infrastructure and/or resides in a cloud computing infrastructure. The cloud network 1100 may be configured using a 3G network, a 4G or LTE network, and/or a 5G network. That is, each of the devices 1110a to 1110e and 1120 consisting the AI system may be connected to each other through the cloud network 1100. In particular, each of the devices 1110a to 1110e and 1120 may communicate with each other through a base station, but may directly communicate with each other without using a base station.

The AI server 1100 may include a server for performing AI processing and a server for performing operations on big data. The AI server 1100 is connected to at least one or more of AI devices constituting the AI system, i.e. the robot 1110a, the autonomous vehicle 1110b, the XR device 1110c, the smartphone 1110d and/or the home appliance 1110e through the cloud network 1100, and may assist at least some AI processing of the connected AI devices 1110a to 1110e. The AI server 1100 can learn the ANN according to the machine learning algorithm on behalf of the AI devices 1110a to 1110e, and can directly store the learning models and/or transmit them to the AI devices 1110a to 1110e. The AI server 1100 may receive the input data from the AI devices 1110a to 1110e, infer the result value with respect to the received input data using the learning model, generate a response and/or a control command based on the inferred result value, and transmit the generated data to the AI devices 1110a to 1110e. Alternatively, the AI devices 1110a to 1110e may directly infer a result value for the input data using a learning model, and generate a response and/or a control command based on the inferred result value.

Various embodiments of the AI devices 1110a to 1110e to which the technical features of the present invention can be applied will be described. The AI devices 1110a to 1110e shown in FIG. 11 can be seen as specific embodiments of the AI device 1000 shown in FIG 10.

In view of the exemplary systems described herein, methodologies that may be implemented in accordance with the disclosed subject matter have been described with reference to several flow diagrams. While for purposed of simplicity, the methodologies are shown and described as a series of steps or blocks, it is to be understood and appreciated that the claimed subject matter is not limited by the order of the steps or blocks, as some steps may occur in different orders or concurrently with other steps from what is depicted and described herein. Moreover, one skilled in the art would understand that the steps illustrated in the flow diagram are not exclusive and other steps may be included or one or more of the steps in the example flow diagram may be deleted without affecting the scope of the present disclosure.

Claims

A method performed by a wireless device in a wireless communication system, the method comprising:

selecting a core network;

when a strongest cell supporting the selected core network is not a strongest cell on a current frequency:

informing a non-access stratum (NAS) layer that there is no cell supporting the selected core network; and

performing a public land mobile network (PLMN) selection based on the information that there is no cell supporting the selected core network.
The method of claim 1, further comprising selecting at least one frequency other than the current frequency, before informing the NAS layer that there is no cell supporting the selected core network.
The method of claim 2, further comprising obtaining information on frequencies including the at least one frequency from a network via system information and/or a dedicated signaling.
The method of claim 2, further comprising attempting to find a cell on the selected at least one frequency,

wherein the cell supports the selected core network, and is a strongest cell on the selected at least one frequency.
The method of claim 4, wherein the cell is not found.
The method of claim 4, further comprising camping on the cell and considering the selected at least one frequency as a highest priority when the cell is found.
The method of claim 6, wherein that there is no cell supporting the selected core network is not informed to the NAS layer, and

Wherein the PLMN selection is not performed.
The method of claim 1, further comprising selecting a new core network upon the PLMN selection.
The method of claim 1, wherein the selected core network is an evolved packet core (EPC).
The method of claim 9, wherein the wireless devices disables an N1 mode radio capability.
The method of claim 1, wherein the selected core network is a 5G core network (5GC).
The method of claim 1, further comprising indicating the selected core network to an AS layer.
The method of claim 1, wherein the wireless device is in communication with at least one of a user equipment, a network, and/or autonomous vehicles other than the wireless device.
A wireless device in a wireless communication system, the wireless device comprising:

a memory;

a transceiver; and

a processor, operably coupled to the memory and the transceiver,

wherein the processor is configure to select a core network,

when a strongest cell supporting the selected core network is not a strongest cell on a current frequency:

wherein the processor is configure to, inform a non-access stratum (NAS) layer that there is no cell supporting the selected core network, and

wherein the processor is configure to perform a public land mobile network (PLMN) selection based on the information that there is no cell supporting the selected core network.
A processor for a wireless device in a wireless communication system, wherein the processor is configured to:

select a core network,

when a strongest cell supporting the selected core network is not a strongest cell on a current frequency:

inform a non-access stratum (NAS) layer that there is no cell supporting the selected core network, and

perform a public land mobile network (PLMN) selection based on the information that there is no cell supporting the selected core network.