WO2021160261A1

WO2021160261A1 - Energy efficient mobility management for dual-mode user equipment

Info

Publication number: WO2021160261A1
Application number: PCT/EP2020/053720
Authority: WO
Inventors: Sari Kaarina Nielsen; Jorma Johannes Kaikkonen; Timo Koskela; Antti Anton Toskala
Original assignee: Nokia Technologies Oy
Priority date: 2020-02-13
Filing date: 2020-02-13
Publication date: 2021-08-19

Abstract

Various example embodiments relate to energy efficient mobility management of dual-mode user equipment (UE). The dual-mode UE may be configured to monitor a paging channel with a first radio, for example an NB-IoT radio. While monitoring the paging channel, the UE may be located at a coverage area. In response to receiving a paging message from a first network node at the coverage area with the first radio, the UE may be configured to activate a second radio and transmit an access request with the second radio to a second network node. The first radio may comprise a power efficient radio such as for example an NB-IoT radio. The second radio may provide better communication capabilities and it may comprise for example an NR-Light radio. Apparatuses, methods, and computer programs are disclosed.

Description

ENERGY EFFICIENT MOBILITY MANAGEMENT FOR DUAL-MODE USER

EQUIPMENT

TECHNICAL FIELD

[0001] Various example embodiments generally relate to the field of wireless communications. In particular, some example embodiments relate to mobility management in a cellular communication network with dual-mode user equipment.

BACKGROUND

[0002] User equipment (UE), such as for example a mobile phone, may be configured with multiple radios for communicating with base stations or access points according to different standards, or profiles thereof. Different radios may be associated with different power consumption characteristics and in some applications it may be desired to reduce power consumption while still enabling sufficient communication capability .

SUMMARY

[0003] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0004] Example embodiments provide energy efficient mobility management of dual-mode user equipment capable of accessing network with different radio technologies. The benefits may be achieved by the features of the independent claims. Further implementation forms are provided in the dependent claims, the description, and the drawings.

[0005] According to an aspect, an apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: monitor, at a client node, a paging channel with a first radio at a coverage area; and in response to receiving a paging message from a first network node at the coverage area with the first radio, activate a second radio and transmit an access request with the second radio to a second network node.

[0006] According to an aspect, a method comprises monitoring, at a client node, a paging channel with a first radio at a coverage area; and in response to receiving a paging message from a first network node at the coverage area with the first radio, activating a second radio and transmit an access request with the second radio to a second network node.

[0007] According to an aspect, a computer program is configured, when executed by an apparatus, to cause the apparatus at least to: : monitor, at a client node, a paging channel with a first radio at a coverage area; and in response to receiving a paging message from a first network node at the coverage area with the first radio, activate a second radio and transmit an access request with the second radio to a second network node. [0008] According to an aspect, an apparatus comprises means for monitoring, at a client node, a paging channel with a first radio at a coverage area; and means for activating a second radio and transmit an access request with the second radio to a second network node, in response to receiving a paging message from a first network node at the coverage area with the first radio.

[0009] According to an aspect, an apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: transmit, by a first network node, a paging message to a client node, wherein the paging message comprises: an instruction to transmit a response to the paging message with a first radio of the client node, or an instruction to transmit the response to the paging message with a second radio of the client node.

[0010] According to an aspect, a method comprises transmitting, by a first network node, a paging message to a client node, wherein the paging message comprises: an instruction to transmit a response to the paging message with a first radio of the client node, or an instruction to transmit the response to the paging message with a second radio of the client node.

[0011] According to an aspect, a computer program is configured, when executed by an apparatus, to cause the apparatus at least to: transmit, by a first network node, a paging message to a client node, wherein the paging message comprises: an instruction to transmit a response to the paging message with a first radio of the client node, or an instruction to transmit the response to the paging message with a second radio of the client node.

[0012] According to an aspect, an apparatus comprises means for transmitting, by a first network node, a paging message to a client node, wherein the paging message comprises: an instruction to transmit a response to the paging message with a first radio of the client node, or an instruction to transmit the response to the paging message with a second radio of the client node.

[0013] Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and together with the description help to understand the example embodiments. In the drawings: [001 5] FIG. 1 illustrates an example of a network comprising network nodes and a client node, according to an example embodiment .

[0016] FIG. 2 illustrates an example of an apparatus configured to practice one or more example embodiments.

[0017] FIG. 3 illustrates an example of a procedure for energy efficient mobility management of dual-mode user equipment, according to an example embodiment;

[0018] FIG. 4 illustrates an example of using an NB-IoT radio as a host for an NR-Light radio, according to an example embodiment;

[0019] FIG. 5 illustrates an example of operations associated with paging through NB-IoT, according to an example embodiment; [0020] FIG. 6 illustrates an example of operations associated with a release of an NR-Light connection, according to an example embodiment;

[0021] FIG. 7 illustrates an example of operations associated with a user equipment originated connection, according to an example embodiment;

[0022] FIG. 8 illustrates an example of a method for efficient mobility management at a client node, according to an example embodiment .

[0023] FIG. 9 illustrates an example of a method for efficient mobility management at a network node, according to an example embodiment .

[0024] Like references are used to designate like parts in the accompanying drawings.

DETAILED DESCRIPTION

[0025] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0026] Technologies such as Narrowband (NB) IoT (Internet of Things), LTE-M (Long Term Evolution-Machine type communication), and eMTC (enhanced Machine Type Communication) as specified by the 3^rd Generation Partnership Project (3GPP) enable low power communication over cellular communication networks. However, low power technologies like NB-IoT, LTE-M, or met may not provide sufficient capacity for all present or future applications. 3GPP 5G NR (New Radio), or simply NR, provides another radio access technology, which is targeted for various types of services such as enhanced mobile broadband (eMBB) communications, ultra reliable low latency communications (URLCC), and massive machine type communications (mMTC). However, power consumption of NR user equipment may be too high for some IoT type of applications. [0027] It would be therefore desired to enable lower power consumption within the NR standard and for that purpose a low power profile of NR, e.g. NR-Light, may be provided. However, another concern is that heavily modifying the NR radio for NR- Light purposes would cause divergence in the chip set side and would not be attractive for chip set development. NR-Light is intended for addressing new use cases with IoT-type of requirements, which are not met with NB-IoT or LTE-M, such as higher data rate, higher reliability, and lower latency than eMTC or NB-IoT, but on the other hand lower cost and complexity and longer battery life than NR eMBB.

[0028] One concern with NR is that its reference signals, for example synchronization signal block (SSB), may not enable energy efficient design of an NR radio, for example due to infrequent measurement opportunities. On the other hand, NB-IoT and LTE-M enable to reach lower power consumption due to: LTE's cell-specific reference signals (CRS), no impact of beamforming, and various UE power saving optimizations added on top of the LTE design. For example, because of the good CRS availability, a UE may wake up any time and quickly access the network. By contrast, in NR idle mode the UE may need to wait longer to accumulate enough energy due to the more infrequent CRSs, which results in waste of battery power. For example, idle power consumption has been estimated to be up to 45 % higher compared to LTE and difference to NB-IoT or eMTC would be even higher. [0029] It would be therefore desired to develop a system, which enables reasonable UE power consumption for reduced capability devices such as NR-Light devices or other low complexity devices, and which utilizes the NR physical layer (LI) without significant NR physical layer changes. Low UE power consumption is especially important in idle mode and in an in active state. NR radio is significantly less UE power consumption optimized than NB-IoT or LTE-M radios, or even a basic LTE radio. NR-Light devices are intended for IoT type of applications and therefore they are aimed at providing longer battery life than NR eMBB centric devices. However, NR-Light devices are intended to be more capable IoT centric devices than NB-IoT or LTE-M devices. Changing radically the NR system, for example the NR physical layer, could cause issues for legacy devices and therefore this may not be a desirable approach. Also, NR physical layer changes for UE power optimizations would need to be made at the cost of NR system performance. Changes would also incur cost to the device design.

[0030] According to an example embodiment, a dual-mode UE may be configured to monitor a paging channel with a first radio, for example an NB-IoT radio. While monitoring the paging channel, the UE may be located at a coverage area. In response to receiving a paging message from a first network node at the coverage area with the first radio, the dual-mode UE may be configured to activate a second radio and transmit an access request with the second radio to a second network node. The first radio may comprise a power efficient radio such as for example an NB-IoT radio. The second radio may provide better communication capabilities and it may comprise for example an NR-Light radio. In further example, the first or second radio may comprise of LTE, LTE-A, 3G, LTE-M, 802.11, Bluetooth, 5G NR (New Radio) or any derivative of these radios.

[0031] FIG. 1 illustrates an example embodiment of a network 100, according to an example embodiment. Network 100 may comprise at least one client node, which may be also referred to as a user node, user equipment (UE), mobile terminal, terminal, or the like. UE 110 may communicate with one or more base stations, such as for example NB-IoT node 120 and NR-Light node 130, over wireless radio channel(s). Base stations may be also called radio access network (RAN) nodes or just network nodes. A base station may comprise any suitable radio access point. For example, a base station may comprise a 4G radio access network node (eNB) or a 5G radio access network node (gNB). In general, a first network node may be configured to operate according to a first standard and a second network node may be configured to operate according to a second standard. A standard may be also understood as a profile or a subset of a certain specification or a group of specifications. According to an example embodiment, the first standard may comprise NB-IoT and the second standard may comprise NR-Light profile of the 5G NR standard. Even though example embodiments have been described using these particular standards as examples, it is appreciated that example embodiments may be applied to any suitable standards, or profiles thereof. For example, in one example embodiment a first network node may be configured to operate according to a wireless local area network standard such as for example specified by IEEE 802.11 series or Wi-Fi alliance and the second network node 130 may be configured to operate according to a cellular standard such as for example specified by 3GPP.

[0032] The network 100 may further comprise a core network 140. The core network 140 may functionally connect different types of base stations and thereby enable co-operation between RAN nodes. The core network 140 may be implemented by any suitable means. For example, the core network 140 may be configured according to the service based architecture (SBA) of 5G core network (CN) 144, which enables a plurality of interconnected network functions (NF) to access each other's service via a service based interface (SBI). The core network 140 may comprise one or more access and mobility management Functions (AMF) 145. An AMF 145 may be responsible for connection and mobility management. For example, an AMF 145 may receive and process connection and session request related information received from UE 110 via NB-IoT node 120 or NR-Light node 130. An AMF 145 may comprise a registration management function (RM) 146 configured to handle registration and deregistration of UEs to the network.

[0033] Additionally, the core network 140 may be configured to operate according to the Evolved Packet Core (EPC) 141 of 3GPP LTE standard. For example, the core network 140 may comprise one or more mobility management entities (MME) 142. MME 142 may comprise an EMM (Enhanced Packet Core Mobility Management) function 143 configured for example to manage service requests from UE 110, handle paging procedure for UE 110, and control mobility of UE 110. The EMM 143 may be for example configured to allocate a tracking area for UE 110. A tracking area may comprise a plurality of cells where the UE 110 may move without updating its location at MME 142. UE 110 may determine whether it has moved to a new tracking area based on comparing a tracking area code (TAC) received from the current cell to a group of tracking area codes included in a tracking area list.

[0034] Radio resource control (RRC) may refer to provision of radio resource related control data. Radio resource control messages may be transmitted on various logical control channels such as for example a common control channel (CCCH) or a dedicated control channel (DCCH). Logical control channels may be mapped to one to more signaling radio bearers (SRB). [0035] Although some example embodiments have been described using particular RRC messages as examples, it is appreciated that any suitable message(s) may be configured to carry the handover related signaling information described herein. Even though some example embodiments have been described using the 4G and/or 5G networks as examples, it is appreciated that example embodiments presented herein are not limited to these example networks and may be applied in any present or future communication networks, for example other type of cellular networks, short-range wireless networks, broadcast networks, or the like.

[0036] FIG. 2 illustrates an example embodiment of an apparatus 200, for example a client node such as for example UE 110, a network node such as for example a NB-IoT node 120, NR- Light node 130, or a core network device configured to implement one or more network functions. Apparatus 200 may comprise at least one processor 202. The at least one processor may comprise, for example, one or more of various processing devices, such as for example a co-processor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like.

[0037] The apparatus may further comprise at least one memory 204. The memory may be configured to store, for example, computer program code or the like, for example operating system software and application software. The memory may comprise one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination thereof. For example, the memory may be embodied as magnetic storage devices (such as hard disk drives, floppy disks, magnetic tapes, etc.), optical magnetic storage devices, or semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

[0038] Apparatus 200 may further comprise communication interface 208 configured to enable apparatus 200 to transmit and/or receive information to/ from other devices. In one example, apparatus 200 may use communication interface 208 to transmit or receive signaling information and data in accordance with at least one cellular communication protocol. The communication interface may be configured to provide at least one wireless radio connection, such as for example a 3GPP mobile broadband connection (e.g. 3G, 4G, 5G) . However, the communication interface may be configured to provide one or more other type of connections, for example a wireless local area network (WLAN) connection such as for example standardized by IEEE 802.11 series or Wi-Fi alliance; a short range wireless network connection such as for example a Bluetooth, NFC (near field communication), or RFID connection; a wired connection such as for example a local area network (LAN) connection, a universal serial bus (USB) connection or an optical network connection, or the like; or a wired Internet connection. Communication interface 208 may comprise, or be configured to be coupled to, at least one antenna to transmit and/or receive radio frequency signals. One or more of the various types of connections may be also implemented as separate communication interfaces, which may be coupled or configured to be coupled to a plurality of antennas.

[0039] Apparatus 200 may further comprise a user interface 210 comprising an input device and/or an output device. The input device may take various forms such a keyboard, a touch screen, or one or more embedded control buttons. The output device may for example comprise a display, a speaker, a vibration motor, or the like.

[0040] When the apparatus is configured to implement some functionality, some component and/or components of the apparatus, such as for example the at least one processor and/or the memory, may be configured to implement this functionality. Furthermore, when the at least one processor is configured to implement some functionality, this functionality may be implemented using program code 206 comprised, for example, in the memory 204.

[0041] The functionality described herein may be performed, at least in part, by one or more computer program product components such as software components. According to an embodiment, the apparatus comprises a processor or processor circuitry, such as for example a microcontroller, configured by the program code when executed to execute the embodiments of the operations and functionality described. Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), application-specific Integrated Circuits (ASICs), application-specific Standard Products (ASSPs), System- on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), Graphics Processing Units (GPUs).

[0042] The apparatus comprises means for performing at least one method described herein. In one example, the means comprises the at least one processor, the at least one memory including program code configured to, when executed by the at least one processor, cause the apparatus to perform the method.

[0043] Apparatus 200 may comprise for example a computing device such as for example a base station, a server, a mobile phone, a tablet computer, a laptop, an internet of things (IoT) device, or the like. Examples of IoT devices include, but are not limited to, consumer electronics, wearables, sensors, and smart home appliances. In one example, apparatus 200 may comprise a vehicle such as for example a car. Although apparatus 200 is illustrated as a single device it is appreciated that, wherever applicable, functions of apparatus 200 may be distributed to a plurality of devices, for example to implement example embodiments as a cloud computing service.

[0044] FIG. 3 illustrates an example of a procedure for energy efficient mobility management of dual-mode user equipment, according to an example embodiment. The procedure describes various operations performed at UE 110, generally referred to as a client node, and NB-IoT node 120 and NR-Light node 130, generally referred to as first and second network nodes, respectively. Even though the procedure is illustrated as a single figure, it is appreciated that example embodiments may relate to subsets of the operations. It is also understood that references to particular technologies such as NB-IoT or NR-Light are provided only as examples and the example embodiments may be applied in any present or future communication system.

[0045] At 301, the UE 110 may transmit indication of a dual mode capability. The indication may comprise an indication of at least two supported radio technologies. For example, the UE 110 may indicate that it has both NB-IoT and NR-Light radios. The indication of the dual-mode capability may be included in any suitable control message, for example a radio resource control (RRC) message.

[0046] At 302, the UE 110 may transmit an indication of a hosting capability. The indication may comprise an indication of a first radio technology that has capability to operate as a host for a second radio technology. The first radio technology may comprise NB-IoT. The second radio technology may comprise NR or NR-Light Thus, the UE 110 may indicate that its NB-IoT radio is capable of hosting its NR-Light radio. As discussed above, hosting another radio technology may refer to handling one or more functions, for example access functions, on behalf of the other radio technology. The indication of the hosting capability may be included in any suitable control message, for example a radio resource control (RRC) message. The indications of the dual-mode capability and the hosting capability may be included in same or separate control messages. [0047] The NB-IoT node 120 may forward the information about the dual-mode capability and/or the hosting capability of the UE 110 to the core network, for example the enhanced packet core (EPC) 141 to enable the core network to divide functionality of the hosted NR-Light technology between the NB-IoT node 120 and the NR-Light node 130.

[0048] At 303, the EPC 141 may communicate with 5G CN 144 to enable the hosting functionality at the core network side. For example, information about the hosting capability of the UE 110 may be delivered to the 5G CN 144, which may provide the EPC 141 and NB-IoT node 120 with necessary information to facilitate the hosted functionalities, for example paging via NB-IoT node 120. [0049] FIG. 4 illustrates an example of a dual mode operation between two radios, according to an example embodiment. UE 110 may be a dual-mode UE comprising NB-IoT and NR-Light radios. The NB-IoT radio may be configured to operate as a host for the NR- Light radio. The NR-Light and NB-IoT capable UE may be registered to the core network through NB-IoT. This enables the UE 110 to keep its NR radio inactive, which significantly reduces power consumption at UE 110 compared to the NR radio being active. As discussed above, UE 110 may indicate through NB-IoT, or alternatively over NR that it has both NB-IoT and NR-Light radios and it supports needed hosting functionalities. Ability of hosting NR-Light with NB-IoT may be regarded as a UE capability. When hosting NR-Light with NB-IoT, the NB-IoT radio may provide necessary radio and core network functions also for NR-Light when the NB-IoT radio is in idle mode. Therefore, the NR-Light radio does not need to be active and UE power can be saved by exploiting the highly power consumption optimized NB-IoT radio. While the NB-IoT radio operates as a host for the NR-Light radio, the UE 110 may indicate its NR-Light capabilities to the core network 140, which enables a higher data rate with the more capable NR-Light radio instead of NB-IoT radio, which may have limited data transmission capabilities. The NR-light radio may be activated whenever higher data rate is needed. Instead of NB- IoT, other radio technologies such as LTE-M or other LTE UE categories, for example category 4, may be used. As illustrated in FIG. 4, the indication of the hosting capability may be for example delivered to an MME 142 and/or EMM 143 of the core network 140 over the NB-IoT connection. Alternatively, the hosting indication may be delivered to an AMF 145 and/or RM 146 of the 5G CN 144. At this phase the NB-IoT radio may be active while the NR-Light radio may be powered off or kept in a low power state. Necessary information for initiating communication over NR-Light may be provided over the NB-IoT connection. However, while the NR-Light radio of the UE 110 is powered off or in the low power state, UE context associated with NR-Light may be maintained at the core network, for example at an instance of the AMF 145.

[0050] Referring back to FIG. 3, at 304 the first network node may transmit dual-mode configuration data to the client node, which may receive the dual-mode configuration data. The first network node may comprise the NB-IoT node 120. The dual mode configuration data may in general comprise any information associated with the dual-mode and/or hosting functionality between at least two radio technologies, for example NB-IoT and NR-Light. According to an example embodiment, the dual-mode configuration data may comprise an instruction to transmit a response to a paging message with a second radio. The second radio may comprise the NR-Light radio. Alternatively, the dual mode configuration data may comprise an instruction to transmit a response to the paging message with a first radio. The first radio may comprise the NB-IoT radio. It is however possible that no information regarding a preferred or requested radio technology for responding to paging messages is provided by the NB-IoT node 120 to the UE 110. For example, the UE 110 may be configured to determine which radio to use based on various conditions associated with the UE 110 or the radio link to the NB-IoT node 120, as will be further described below. [0051] According to an example embodiment, the dual-mode configuration data may comprise an indication of a default radio for responding to paging messages from the first network node. For example, the core network may determine that UE 110 should respond to paging messages with the NB-IoT radio or the NR-Light radio. A default configuration of the radio may be communicated to UE 110 and the default radio may be used at UE 110 for responding to paging messages unless otherwise instructed. The UE 110 may assign a default radio based on the received indication of the default radio for responding to paging messages. Alternatively, assignment of the default radio may be preconfigured at the client node.

[0052] According to an example embodiment, the dual-mode configuration data may comprise assistance information for accessing the network with the second radio. For example, the assistance information may comprise radio resource management (RRM) information to support accelerated access of UE 110 to the NR-Light node 130. According to an example embodiment, the UE 110 may receive the radio resource management information from the first network node. The radio resource management information may comprise at least one of: a random access configuration for the second network node accessible with the second radio, synchronization information associated with the second network node, at least one cell identifier for at least one neighboring or co-located cell of the target cell accessible with the second radio, cell broadcast information associated with the target cell, or beam level information associated with the second target cell.

[0053] The assistance information may comprise information for performing radio resource management measurements and/or initial access to NR-Light node 130. As an example, the assistance information may comprise at least one of: contention free random access (CFRA) configuration or contention based random access (CBRA) configuration, which may enable quick initial access to NR-Light cell; synchronization relation, e.g. timing difference or offset(s); cell-ID(s) of neighbouring or co-located NR cells; Physical cell-ID(s) of neighbouring or co located NR cells; partial or full cell broadcast information; or beam level assistance information such as for example synchronization signal / physical broadcast channel block (SS/PBCH), or synchronization signal block (SSB) time locations. [0054] Operations 301 to 304 may be performed at any suitable time to initiate the dual-mode and/or hosting functionality. It is however appreciated that, wherever applicable, similar operations may be performed after initiating the dual-mode and/or hosting functionality. For example, the dual-mode configuration data, or portions thereof, may be updated or new dual-mode configuration data may be added and communicated to UE 110 any time throughout the procedure.

[0055] At 305, the NB-IoT radio of UE 110 may enter an idle state or an inactive state, for example an RRC-IDLE or an RRC- INACTIVE state according to NB-IoT. In the idle or inactive state the UE 110 may monitor one or more cell reselection criteria, for example by measuring signal quality of one or more neighboring cells. The UE 110 may further receive cell broadcast information, monitor paging channel(s),and exchange control information with the NB-IoT node 120.

[0056] At 306, the UE 110 may initiate cell reselection to a target cell with the first radio. The UE 110 may further determine whether the target cell or carrier supports the second radio. Determining whether the target cell supports the second radio may be based on cell-specific information of the target cell. The UE 110 may receive the cell-specific information of the target cell with the first radio at the current (source) cell or the second radio at the current (source) cell. Alternatively, the cell-specific information may be preconfigured at the UE 110. For example, UE 110 may monitor cell reselection criteria in NB-IoT and when UE 110 determines to reselect a cell, the UE 110 may check from system information of NB-IoT cell, LTE cell, or NR Cell, whether NR-Light is available in the selected cell or carrier. The cell reselection may be performed with the NB-IoT radio while NR-Light radio is still inactive.

[0057] Determining whether the target cell supports the second radio may be based on cell-specific information of the target cell. The cell-specific information may for example include an indication of availability of the second radio technology at the target cell. The availability information may be provided to UE in dedicated signaling (e.g. RRC) or provided in the broadcast information. The availability information may be provided by the first radio technology or the second radio technology. The UE 110 may determine to perform cell reselection to the target cell, for example in response to determining that the target cell supports NR-Light.

[0058] According to an example embodiment, the cell-specific information may further comprise at least one of: at least one candidate reselection cell associated with the target cell for the second radio, at least one preferred reselection cell associated with the target cell for the second radio, or at least one cell supporting a profile associated with the second radio. For example, the cell-specific information received over NB-IoT may include the above information for the NR or NR-Light radio. Based on the cell-specific information the UE 110 may determine whether a target cell is associated with one or more cells that can be accessed with the NR or NR-Light radio. This information may be used by UE 110 when performing the cell reselection. UE 110 may determine to perform cell reselection to the target cell, for example in response to determining that the target cell is associated with candidate cell(s), preferred cell(s), and/or other type of cell(s) that support NR or the NR-Light profile. [0059] According to an example embodiment, the UE 110 may transmit a request for the cell-specific information of the target cell with the second radio. The request for the cell- specific information may be transmitted in response to determining that sufficient cell-specific information of the target cell is not available at the UE 110. For example, the UE 110 may be preconfigured with NB-IoT cell-specific information and upon cell reselection at NB-IoT, the UE 110 may determine whether it has up to date record of NR cells associated with the reselected NB-IoT cell. Determining that the UE 110 does not have a record, or an up to date record, of NR cells available may trigger transmission of the information request over NR- Light.

[0060] Alternatively, the UE 110 may transmit the request for the cell-specific information of the target cell based on a preconfigured or received instruction to transmit the request for the cell-specific information with the second radio upon the cell reselection with the first radio. This enables the network to configure the UE 110 to request for additional assistance information for dual-mode operation whenever performing reselection of an NB-IoT cell. The second network node may be configured to transmit the cell-specific information to the client node, for example in response to receiving the request for the cell-specific information from the client node.

[0061] During operations 305 and 306, the UE 110 may monitor a paging channel with the first radio. While monitoring the paging channel the UE 110 may be located at a coverage area. The coverage area may comprise any preconfigured or signaled area. For example, the coverage area may comprise one or more cells. The coverage area, or cells belonging to the coverage area, may be associated with a tracking area or a notification area. A cell may be identified based on a cell identifier, a tracking area may be identified based on a tracking area identifier, and notification area may be identified based on a notification area identifier .In a further example, a coverage area may comprise of one or more cells or RAN notification area (e.g. configured set of cells where UE context is known for INACTIVE state mobility). In one example the coverage area may be a specific part of the cell determined by detection of reference signals or based on the geographical location information. [0062] At 307, NB-IoT node 120 may transmit a paging message to the UE 110, for example on the paging channel. The UE 110 may receive the paging message with the first radio. The UE 110 may be located at the first tracking area when receiving the paging message.

[0063] According to an example embodiment, the UE 110 may determine whether to send a response to the paging message with the first radio or the second radio. Determining whether to use the first or second radio may be based on at least one criterion. For example, the UE 110 may determine to respond to the paging message with the second radio if the UE 110 is within the coverage area and/or if the paging message comprises a request to respond with the second radio.

[0064] Alternatively, or additionally, determining whether to send the response to the paging message with the first radio or the second radio may be based on at least one of: a latency requirement for a service associated with the paging message, a traffic volume of the service associated with the paging message, a type of the service associated with the paging message, an identifier the service associated with the paging message, a default radio assigned to responding to paging messages, or a cell identifier, a tracking area identifier, or a notification area identifier of a cell associated with the paging message. For example, a service associated with the paging message may require low latency, which may not be possible to achieve with the NB-IoT radio. The UE 110 may be configured with a threshold latency for deciding whether to use NB-IoT or NR-Light radio. If a required latency, which may be indicated in the paging message, is lower than the threshold latency, the UE 110 may determine to use NR-Light radio for subsequent communication. The threshold latency may be received from the network, for example as part of the dual-mode configuration data sent at 304. If the required latency, is higher than the threshold latency, the UE 110 may determine to use the NB-IoT radio for subsequent communication. In one alternative example, for the UE initiated communication (i.e. it is not paged), the above conditions (e.g. service based, latency, traffic volume etc.) may be used by UE 110 for the selection of radio access technology. For example, the UE 110 may be configured to initiate UE initiated communication based on one or more of the criteria provided for responding to paging messages. As an example, in the UE initiated case, the UE 110 may determine the arrival of uplink (UL) data to the transmission buffer (s) or the UE 110 may otherwise determine that it needs to communicate with network.

[0065] Another criterion may comprise the traffic volume, for example the amount or an estimate of an amount of data to be communicated. The UE 110 may be configured with a threshold volume for deciding whether to use NB-IoT or NR-Light radio. If a traffic volume, which may be indicated in the paging message, is higher than the threshold volume, the UE 110 may determine to use the NR-Light radio for subsequent communication. The threshold volume may be received from the network, for example as part of the dual-mode configuration data sent at 304. If the traffic volume is lower than the threshold volume, the UE 110 may determine to use the NB-IoT radio for subsequent communication .

[0066] Another criterion may comprise a type of service or an identifier of a service. The UE 110 may be configured with an allocation of one or more service types, or service identifiers, to the NB-IoT radio or the NR-Light radio. The service type and/or identifier may be indicated in the paging message. Based on the service type and/or identifier the UE 110 may determine whether to use the NR-Light or NB-IoT radio for subsequent communication. The mapping between the service type and/or identifier and the preferred or requested radio may be preconfigured or received from the network, for example as part of the dual-mode configuration data sent at 304.

[0067] Another criterion may comprise information at the UE 110. Based on the internal information the UE 110 may determine which radio to use for subsequent communication. The internal information may include information about whether the UE 110 is connected to power supply or whether it is operating on battery, or, other device battery power level related information internal to the UE 110. In one example, the UE 110 may determine to operate (e.g. monitor paging, communicate, initiate communication) on second radio (such as NR-Light, LTE, NR that may have higher performance with cost of energy consumption) when it is connected to power supply. When the UE 110 is not connected to power supply, e.g. when it operates on battery, it may operate as described herein e.g. monitor paging on the first radio. In yet another example, the UE 110 may indicate or provide information to network whether is currently connected to power supply (or operates on battery) and/or whether its battery power level is above specific threshold value (e.g. UE battery above 80% charge level). Network may configure the UE 110 to operate (e.g. receive paging, initiate communication) on first or second radio, for example based on the provided information. In one example, if the UE 110 is connected to power supply it may be configured not to switch the paging monitoring to the first radio and operate on the second radio, for example initiate communication on the second radio. In one alternative, the UE 110 may be configured to monitor paging on the first radio based on provided information. These are non-limiting examples.

[0068] Another criterion may comprise assignment of a default radio for responding to paging messages. For example, the UE 110 may determine to transmit a response to the paging message with the second radio, if the second radio has been assigned as a default radio for responding to paging messages. Alternatively, or additionally, a default radio may be assigned for UE initiated connection establishment. This may be network configurable, and different or same radio may be assigned for default radio for paging reception and/or UE initiated case.

[0069] Another criterion may comprise an identifier of the coverage area. The coverage area may be associated with one or more cells. The cell(s) may be associated with a tracking area and/or a notification area. Determining whether to send the response to the paging message with the first or the second radio may be based on an identifier of the cell, an identifier of the tracking area, or an identifier of the notification area. For example, the UE 110 may be configured with a list of cell identifiers, tracking area identifiers, and/or notification area identifiers. Before responding to the paging message, the UE 110 may determine whether the identifier of the current cell, current tracking area, or current notification area is on the list. If the corresponding cell identifier is determined to be on the list, the UE 110 may determine to send the response to the paging message with the second radio, for example via NR-Light. If the corresponding cell identifier is determined not to be on the list, the UE 110 may determine to send the response to the paging message with the first radio, for example via NB-IoT. The list may be received for example from the first network node with the first radio.

[0070] At 308, the UE 110 may activate the second radio, for example in response to receiving the paging message from the first network node. Furthermore, the second radio may be activated based on the any of the above criteria for using the second radio. In case of hosting NR-Light radio with NB-IoT, the NR-Light radio may be kept inactive before operation 308 and necessary information for initiating communication with NR-Light may be advantageously provided through the power efficient NB- IoT radio.

[0071] At 309, the UE 110 may establish a connection to the second network node with the second radio. For example, the UE 110 may transmit an access request with the second radio to the second network node. The second network node may comprise the NR-Light node 130. The access request may for example comprise a random access (RA) preamble. The RA preamble may be transmitted on a random access channel (RACH), for example a physical random access channel (PRACH). The RA preamble may be used to obtain uplink synchronization between UE 110 and NR-Light node 130 and to obtain resources for transmitting further signalling messages and data. In response to receiving the access request, the NR- Light node 130 may respond with a RACH response (not shown). The access request may alternatively, or additionally comprise a paging response message. In response to receiving the access request from UE 110 at the NR-Light node 130, UE MM/SM context transfer may be performed at the core network, for example between EPC 141 and 5G CN 144, at operation 311.

[0072] FIG. 5 illustrates an example of operations associated with paging through NB-IoT. Monitoring paging messages with NR consumes more power than NB-IoT for the same purpose. Also, when NR coverage is limited, UE 110 may often perform reselection between NB-IoT and NR. This may further increase the power consumption at UE 110. To enable lower power consumption at UE 110, the paging may be performed using NB-IoT. However, the network may request UE 110 to respond through NR-Light, or the UE 110 may autonomously decide to respond through NR-Light, as discussed above. Following the response to the paging message, the network may perform the context transfer and subsequently data may be communicated between the UE 110 and the NR-Light node 130.

[0073] Referring back to FIG. 3, at operation 310 the NR- Light radio of UE 110 may transition to a connected state with respect to the NR-Light node 130. At 312, data may be communicated between the UE 110 and the NR-Light node 130.

[0074] At 313, the UE 110 may detect a release of the connection to the second network node, or, detect a radio link failure associated with the second network node. The connection release may be due to inactivity, a network triggered release, or a UE requested or indicated release.

[0075] At 313, the UE 110 may further initiate a timer, for example in response to detecting the connection release. The UE 110 may maintain the connection to the second network node until expiry of the timer. For example, while the timer is running, the UE 110 may stay in NR-Light, monitor paging, and perform mobility. While the timer is running the UE 110 may refrain from performing reselection to NB-IoT. However, the UE 110 may still perform cell reselection within NR-Light.

[0076] According to an example embodiment, the UE 110 may restart the timer upon the cell reselection if the target cell is associated with the first tracking area. For example, if the target NR-Light cell belongs to the same tracking are as the current NR-Light cell, the timer may be restarted when reselecting the target NR-Light cell. The timer may be restarted with the same initial value as earlier, or the initial value may be adjusted. For example, scaling the initial value to a smaller value enables to limit the time spent at NR-Light in case of one or more cell reselections after a connection release.

[0077] According to an example embodiment, UE 110 may cause expiry of the timer upon the cell reselection. The UE 110 may cause expiry of the timer for example if the target cell is associated with a second tracking area. Therefore, the UE 110 may be configured to stay in NR-Light while moving within the same tracking area. However, when moving to a new tracking area, the UE 110 may be configured to switch to NB-IoT. This enables further paging messages over NB-IoT to be routed to the current cell of UE 110.

[0078] FIG. 6 an example of operations associated with a release of an NR-Light connection. NB-IoT may use longer DRX (discontinuous reception) cycles for paging than NR. Therefore, if UE 110 moves to NB-IoT immediately after detecting a connection release, it may take longer time for the network to re-activate the UE 110 via NB-IoT. Therefore, when transitioning to idle mode in NR-Light, for example due to a connection release of the NR-Light connection, the network may indicate to the UE 110 to stay in NR-Light for a time period before moving to NB- IoT idle mode. Once the timer expires, the UE 110 may switch to NB-IoT. A tracking area update may be performed in case the NB- IoT node 120 is connected to the EPC 141. If the NR-Light node 130 and the NB-IoT node 120 are connected to the 5G CN 144, the switch may take place without further registration, because UE context is already available in the 5G CN 144. Alternatively, a registration message may be provided to confirm the switch. This enables the network to control how long UE 110 stays in NR, for example depending on application activity.

[0079] As discussed above, at 313 the UE 110 may also detect a radio link failure. According to an example embodiment, the UE 110 may initiate a timer and refrain from switching to the first network node until expiry of the timer, for example in response to detecting the radio link failure. The initial value of the timer may be preconfigured at UE 110 or it may be received from the first network node with the first radio. For example, in case of radio link failure in NR-Light, UE 110 may be configured to stay in NR-Light for recovery until the recovery is successful or the timer expires. Therefore, when the timer is running the UE 110 may be configured not to switch to NB-IoT for recovery. [0080] Use of the timer, the initial value, and/or adjusting of the initial value upon cell reselection may be configurable by the network. According to an example embodiment, the first network node or the second network node may transmit an instruction to switch to the first network node with the first radio upon detecting a release or a radio link failure of a connection to a the second network node with the second radio. For example, the NB-IoT node 120 may be configured to transmit this information to UE 110, for example as part of the dual-mode configuration data provided at operation 304, or another signaling message. Alternatively, the NR-Light node 130 may be configured to provide this information to UE 110, for example after UE 110 has accessed the NR-Light node 130 at 309.

[0081] According to an example embodiment, the instruction to switch to the first network node may comprise the initial value for the timer. The timer may be associated with delaying the switch to the first network node. The initial value of the timer may be zero. This enables the network to configure UE 110 to switch to NB-IoT instantly upon detection of the connection release or the radio link failure. The UE 110 may receive the instruction to switch to the first network node with the first radio upon detecting a release or a radio link failure of a connection to a the second network node with the second radio. In response to receiving the instructions, the UE 110 may for example set the initial value of the timer according to the received value and/or determine to switch to the first network node accordingly. Alternatively, the timer may be preconfigured at UE 110. The preconfigured timer may be overridden by a value provided by the network, for example in an RRC Release message. This value may temporarily or permanently (until again reconfigured) override the configured/preconfigured value. For example, when the timer value is temporarily overridden, the UE 110 may start timer/use the timer value once and the again use the previously configured value. In one example, in case of occurrence of UE initiated communication to network while the timer is running, the UE 110 may use default radio for the UL access (e.g. RACH) or the UE 110 may use the second radio.

[0082] At 314, the UE 110 may detect expiry of the timer. In response to detecting the expiry of the timer, the UE 110 may switch to the first network node. The UE 110 may further transmit an indication of the switch to the network, for example to the first network node.

[0083] FIG. 7 illustrates an example of operations associated with a user equipment originated connection, according to an example embodiment. The UE 110 may be configured to determine whether to use the first radio or the second radio for data transmission based on at least one condition comprising at least one of: a latency requirement for associated with the data transmission, an amount of data associated with the data transmission, an amount of data in an uplink data buffer associated with the data transmission, a type of the service associated with the data transmission, or an identifier of the service associated with the data transmission. [0084] In general, the NB-IoT system may be more power efficient than the NR system. For example, if the UE 110 has already registered to NB-IoT, there may be less steps to be completed to get a data packet transmitted. However, NB-IoT may not provide sufficient capacity or quality of service (QoS) for some applications.

[0085] Conditions for determining whether the UE initiates the connection with the first or second radio may be similar to the criteria for determining whether to respond to the paging message with the first or second radio or in case of UE initiated communication. For example, the UE 110 may determine to use the NR-Light radio if a latency requirement associated with for a service can not be satisfied with NB-IoT. Another condition may comprise the amount of data to be transmitted. If data volume is large, the NB-IoT transmission may take a long time which increases the power consumption of the otherwise power efficient NB-IoT system. Therefore, the UE 110 may check the amount of data to be transmitted, for example the amount of data in its uplink data buffer. If the amount of data is below a threshold, the UE 110 may determine to initiate connection with NB-IoT. If the amount of data exceeds a threshold, the UE 110 may determine to initiate a connection with the NR-Light radio. The threshold may be preconfigured or it may be received form the network, for example from the NB-IoT node 120 or the NR-Light node 130.

[0086] Another condition may comprise a type of service or an identifier of a service associated with a data transmission. For example, the UE 110 may be configured to initiate data transmission associated with particular service(s) with the NB- IoT radio or the NR-Light radio. Applying one or more of the above conditions enables a UE initiated connection with appropriate power consumption and quality of service.

[0087] FIG. 8 illustrates an example of a method 800 for efficient mobility management at a client node.

[0088] At 801, the method may comprise monitoring, at a client node, a paging channel with a first radio at a coverage area. [0089] At 802, the method may comprise, in response to receiving a paging message from a first network node at the coverage area with the first radio, activating a second radio and transmit an access request with the second radio to a second network node.

[0090] FIG. 9 illustrates an example of a method 900 for efficient mobility management at a network node.

[0091] At 901, the method may comprise transmitting, by a first network node, a paging message to a client node, wherein the paging message comprises: an instruction to transmit a response to the paging message with a first radio of the client node, or an instruction to transmit the response to the paging message with a second radio of the client node.

[0092] Further features of the methods directly result for example from functionalities of the client node such as UE 110, or the network node(s) such as the NB-IoT node 120 or the NR- Light node 130, as described throughout the specification and in the appended claims, and are therefore not repeated here. Different variations of the methods may be also applied, as described in connection with the various example embodiments. [0093] An apparatus, for example a client node such as a UE

110, or a network node such as NB-IoT node 120 and NR-Light node 130 may be configured to perform or cause performance of any aspect of the method (s) described herein. Further, a computer program may comprise instructions for causing, when executed, an apparatus to perform any aspect of the method (s) described herein. Further, an apparatus may comprise means for performing any aspect of the method (s) described herein. According to an example embodiment, the means comprises at least one processor, and memory including program code, the at least one processor, and program code configured to, when executed by the at least one processor, cause performance of any aspect of the method (s). [0094] Any range or device value given herein may be extended or altered without losing the effect sought.Also, any embodiment may be combined with another embodiment unless explicitly disallowed .

[0095] Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0096] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

[0097] The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the embodiments described above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the effect sought.

[0098] The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[0099] Although subjects may be referred to as 'first' or 'second' subjects, this does not necessarily indicate any order or importance of the subjects. Instead, such attributes may be used solely for the purpose of making a difference between subjects. [00100] As used in this application, the term 'circuitry' may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor (s), such as a microprocessor (s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims.

[00101] As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[00102] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.

Claims

1.An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: monitor, at a client node, a paging channel with a first radio at a coverage area; and in response to receiving a paging message from a first network node at the coverage area with the first radio, activate a second radio and transmit an access request with the second radio to a second network node.

2. The apparatus according to claim 1, wherein the paging message comprises an instruction to transmit a response to the paging message with the first radio or the second radio.

3. The apparatus according to claim 1, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: determine whether to send the response to the paging message with the first radio or the second radio, or determine whether to initiate client node initiated communication with the first radio or the second radio, based on at least one of: a latency requirement for a service associated with the paging message; a traffic volume of the service associated with the paging message; a type of the service associated with the paging message; an identifier the service associated with the paging message; information on whether the client node is connected to a power supply or whether the client node operates on battery; a default radio assigned to responding to paging messages; or a cell identifier, a tracking area identifier, or a notification area identifier of a cell associated with the paging message.

4. The apparatus according to claim 3, wherein the assignment of the default radio is preconfigured at the client node.

5. The apparatus according to claim 3, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: receive an indication of the default radio for responding to paging messages from the first network node; and assign the default radio based on the received indication of the default radio.

6. The apparatus according to any preceding claim, wherein the access request comprises a random access preamble.

7. The apparatus according to any preceding claim, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: initiate cell reselection to a target cell with the first radio; determine whether the target cell supports the second radio.

8. The apparatus according to claim 7, wherein determining whether the target cell supports the second radio is based on cell-specific information of the target cell, wherein the cell- specific information of the target cell is preconfigured at the client node, received with the first radio at a source cell, or received with the second radio at the source cell.

9. The apparatus according to claim 8, wherein the cell- specific information further comprises at least one of: at least one candidate reselection cell associated with the target cell for the second radio; at least one preferred reselection cell associated with the target cell for the second radio; at least one cell supporting a profile associated with the second radio.

10. The apparatus according to claim 8 or claim 9, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: transmit a request for the cell-specific information of the target cell with the second radio.

11. The apparatus according to claim 10, wherein the request for the cell-specific information of the target cell is transmitted in response to determining that sufficient cell- specific information of the target cell is not available at the client node, or wherein the request for the cell-specific information of the target cell is transmitted based on a preconfigured or received instruction to transmit the request for the cell-specific information of the target cell with the second radio upon the cell reselection with the first radio.

12. The apparatus according to any preceding claim, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: establish a connection to the second network node with the second radio; receive, from the first network node with the first radio or the second network node with the second radio, an instruction to switch to the first network node with the first radio upon detecting a release of the connection to the second network node; in response to detecting the release of the connection to the second network node, initiate a timer and maintain the connection to the second network node until expiry of the timer.

13. The apparatus according to any of claims 1 to 11, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: establish a connection to the second network node with the second radio; detect a radio link failure associated with the second network node; in response to detecting the radio link failure, initiate a timer and refrain from switching to the first network node until expiry of the timer.

14. The apparatus according to claim 13, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: in response to detecting expiry of the timer, switch to the first network node and transmit an indication of the switch to the first network node.

15. The apparatus according to any of claims 1 to 11, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: establish a connection to the second network node with the second radio; in response to detecting a release of the connection to the second network node, initiate a timer and maintain the connection to the second network node until expiry of the timer.

16. The apparatus according to claim 15, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: restart the timer upon the cell reselection if the target cell is associated with a first tracking area; or cause expiry of the timer upon the cell reselection if the target cell is associated with a second tracking area.

17. The apparatus according to any of claims 12 to 16, wherein an initial value of the timer is preconfigured, or wherein the initial value of the timer is received from the first network node with the first radio.

18. The apparatus according to claim 17, wherein the initial value of the timer is zero.

19. The apparatus according to any preceding claim, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: receive, from the first network node with the first radio, radio resource management information comprising at least one of: a random access configuration for the second network node; synchronization information associated with the second network node; at least one cell identifier for at least one neighboring or co-located cell of the target cell accessible with the second radio; cell broadcast information associated with the target cell; or beam level information associated with the target cell.

20. The apparatus according to any preceding claim, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: determine whether to use the first radio or the second radio for data transmission based on at least one of: a latency requirement associated with the data transmission; an amount of data associated with the data transmission; an amount of data in an uplink data buffer associated with the data transmission; a type of the service associated with the data transmission; or an identifier of the service associated with the data transmission .

21. The apparatus according to any preceding claim, wherein the first radio comprises an NB-IoT radio and the second radio comprises a 5G NR-Light radio.

22.An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: transmitting, by a first network node, a paging message to a client node, wherein the paging message comprises: an instruction to transmit a response to the paging message with a first radio of the client node, or an instruction to transmit the response to the paging message with a second radio of the client node.

23. The apparatus according to claim 22, wherein the paging message comprises an indication of a default radio for responding to paging messages.

24. The apparatus according to claim 22 or claim 23, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: transmit cell-specific information for a target cell accessible with the second radio, wherein the cell-specific information comprises at least one of: at least one candidate reselection cell associated with the target cell accessible with the second radio; at least one preferred reselection cell associated with the target cell accessible with the second radio; at least one cell supporting a profile associated with the second radio.

25. The apparatus according to any of claims 22 to 24, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: transmit, an instruction to switch to the first network node with the first radio upon detecting a release or a radio link failure of a connection to a second network node with the second radio.

26. The apparatus according to claim 25, wherein the instruction to switch to the first network node upon detecting the release or the radio link failure of the connection to the second network node comprises an initial value for a timer associated with delaying the switch to the first network node.

27. The apparatus according to claim 26, wherein the initial value of the timer is zero.

28. The apparatus according to claim any of claims 25 to 27, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: receive, from the client node, an indication of the switch to the first network node.

29. The apparatus according to any preceding claim, wherein the at least one memory and the computer code are further configured to, with the at least one processor, cause the apparatus to: transmit radio resource management information comprising at least one of: a random access configuration for a second network node accessible with the second radio; synchronization information associated with the second network node; at least one cell identifier for at least one neighboring or co-located cell of a target cell accessible with the second radio; cell broadcast information associated with the target cell; or beam level information associated with the target cell.

30. The apparatus according to any preceding claim, wherein the first radio comprises an NB-IoT radio and the second radio comprises a 5G NR-Light radio.

31.A method, comprising: monitoring, at a client node, a paging channel with a first radio at a coverage area; and in response to receiving a paging message from a first network node at the coverage area with the first radio, activating a second radio and transmit an access request with the second radio to a second network node.

32.A method, comprising: transmitting, by a first network node, a paging message to a client node, wherein the paging message comprises: an instruction to transmit a response to the paging message with a first radio of the client node, or an instruction to transmit the response to the paging message with a second radio of the client node.

33. A computer program comprising program code configured to cause an apparatus at least to: monitor, at a client node, a paging channel with a first radio at a coverage area; and in response to receiving a paging message from a first network node at the coverage area with the first radio, activate a second radio and transmit an access request with the second radio to a second network node.

34. A computer program comprising program code configured to cause an apparatus at least to: transmit, by a first network node, a paging message to a client node, wherein the paging message comprises: an instruction to transmit a response to the paging message with a first radio of the client node, or an instruction to transmit the response to the paging message with a second radio of the client node.