Mobility procedures for on-demand SIB1 cells

Abstract

Methods, apparatuses, and systems are provided for a user equipment (UE) supporting on- demand system information block 1 (SIB1) mode operation and being served by a first cell, the methods, apparatuses, and systems supporting switching towards a second cell operating in an on-demand SIB1 mode. The UE receives from the first cell an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell, wherein the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell, performs measurements with respect to the frequency band deployed by the second cell based on the on-demand SIB1 reselection priority, and determines to switch to towards the second cell based on results of the measurements. Similar methods, apparatuses, and systems are provided for a cell.

Description

MOBILITY PROCEDURES FOR ON-DEMAND SIB1 CELLSTHECHNIC AL FIELD

[0001] The subject disclosure generally relates to wireless communication systems and, in particular, to mobility procedures for on-demand system information block 1 (SIB 1) cells or to enablers thereof. Yet more particularly, the subject disclosure provides methods and apparatuses for supporting switching towards a cell operating in on-demand SIB 1 mode.BACKGROUND

[0002] Wireless telecommunication systems, also referred to mobile communication systems, are under constant development. One crucial aspect in these mobile communication systems is energy saving. For user equipments (UEs), several techniques have been developed, such as discontinuous transmission and reception (DRT, DRX), energy saving in inactive and idle modes, etc., but many techniques for network energy savings (NES) are still in early phases of their development.

[0003] Usually, for example in the 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) mobile communication system, system information (SI) is broadcasted periodically over the entire cell area to inform UEs about parameters of the network in a continuous manner. The main drawback of this continuous broadcasting is a low energy efficiency, in particular, if a cell is faced with a low load or with no load in the cell (i.e., there are few or no UEs to benefit from the transmitted SI).

[0004] In the 3GPP 5th generation (5G) / New Radio (NR) mobile communication system, transmission of system information of other SI than minimum SI may be omitted. Minimum SI relates to information relating to master information block (MIB) and system information block 1 (SIB 1). The information of SIB2 to SIB19 may, additionally or alternatively to broadcasting, be provided on demand. MIB and SIB1 are currently still broadcasted regularly in NR to carry basic information required for initial access of the UEs.

[0005] A further enhancement of NES is to provide SIB1 information only on demand. This requires new processes, information elements, messages, etc. to be defined in new standard releases. Hence, legacy UE, i.e., UEs not supporting the new features of on-demand SIB1 mode operation, will not be able, e.g., to switch or, particularly, to reselect to cells operating in on- demand SIB1 mode because they are not able to obtain SIB1 of these cells. However, UEs supporting on-demand SIB1 mode operation should be able to switch to those cells operatingin on-demand SIB1 mode. Therefore, methods and apparatuses for supporting switching towards a second cell operating in an on-demand SIB 1 mode are required.SUMMARY

[0006] According to a first aspect of the subject disclosure, a method performed by a user equipment, UE, supporting on-demand system information block 1, SIB1, mode operation and being served by a first cell, is provided. The method supports switching towards a second cell operating in an on-demand SIB1 mode and comprises receiving from the first cell an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell, wherein the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell, performing measurements with respect to the frequency band deployed by the second cell based on the on-demand SIB 1 reselection priority, and determining to switch towards the second cell based on results of the measurements.

[0007] According to a second aspect of the subject disclosure, a method performed by a first cell in a mobile communication system supporting switching of a user equipment, UE, towards a second cell operating in an on-demand system information block 1, SIB1, mode, wherein the UE is supporting on-demand SIB1 mode operation and being served by the first cell, is provided. The method comprises transmitting an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell to the UE, wherein the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell, wherein the indication triggers, at the UE, measurements with respect to the frequency band deployed by the second cell based on the on-demand SIB1 reselection priority and a determination to switch towards the second cell based on results of the measurements.

[0008] According to a third aspect, an apparatus of a user equipment, UE, supporting on- demand system information block 1, SIB1, mode operation and being served by a first cell, is provided. The apparatus supports switching towards a second cell operating in an on-demand SIB1 mode and is configured to receive from the first cell an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell, wherein the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell, perform measurements with respect to thefrequency band deployed by the second cell based on the on-demand SIB1 reselection priority, and determine to switch towards the second cell based on results of the measurements.

[0009] According to a fourth aspect of the subject disclosure, an apparatus of a first cell in a mobile communication system supporting switching of a user equipment, UE, towards a second cell operating in an on-demand system information block 1, SIB1, mode, wherein the UE is supporting on-demand SIB1 mode operation and being served by the first cell, is provided. The apparatus is configured to transmit an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell to the UE, wherein the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell, wherein the indication triggers, at the UE, measurements with respect to the frequency band deployed by the second cell based on the on-demand SIB1 reselection priority and a determination to switchs towards the second cell based on results of the measurements.

[0010] In embodiments of all aspects, the UE is in in radio resource control, RRC, idle or inactive mode and camping on the first cell, wherein switching towards the second cell comprises cell reselection towards the second cell. In other embodiments of all aspects, the UE is in radio resource control, RRC, connected mode while receiving the indication of the on- demand SIB1 cell reselection priority and in RRC idle or inactive mode when performing measurements and determining to switch towards the second cell, wherein switching towards the second cell comprises cell reselection towards the second cell. In some embodiments of all aspects, the on-demand SIB 1 cell reselection priority of the second cell is different from a cell reselection priority of the second cell when not operating in SIB1 on-demand mode. In some further embodiments of all aspects, the indication of the on-demand SIB1 cell reselection priority is included in an on-demand SIB1 configuration message for the second cell.

[0011] In embodiments of all aspects, the on-demand SIB1 configuration message comprises the on-demand SIB1 cell reselection priority and at least one of a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell. In further embodiments of all aspects, the on-demand SIB1 configuration message further comprises an indication regarding the applicability of the on-demand SIB1 cell reselection priority. In yet further embodiments of all aspects, the indication regarding the applicability of the on-demand SIB1 cell reselection priority indicates applicability to the PCI of the second cell and / or the frequency band deployed by the second cell.

[0012] In embodiments of all aspects, the on-demand SIB1 configuration message comprises a Physical Cell ID, PCI, of the second cell and the frequency band deployed by thesecond cell, and wherein receiving the on-demand SIB1 configuration message is an implicit instruction to the UE to perform the measurements.

[0013] In embodiments of all aspects, the indication of the on-demand SIB1 cell reselection priority is included in a system information block, SIB, message including the on-demand SIB1 cell reselection priority. In further embodiments of all aspects, the SIB message comprises one or more SIB2 and / or SIB4 information elements defining the on-demand SIB1 cell reselection priority. In yet further embodiments of all aspects, the SIB message further comprises one or more SIB2 and / or SIB4 information elements defining a cell reselection priority for the second cell when not operating in SIB1 on-demand mode.

[0014] In embodiments of all aspects, the measurements triggered at the UE are cell reselection measurements concerning at least one of radio power and transmission quality of the second cell. In some embodiments of all aspects, the determination to switch towards the second cell is further based on whether the second cell operates in on-demand SIB1 mode or not

[0015] The above-noted aspects and features may be implemented in systems, apparatuses, methods, articles and non-transitory computer-readable media depending on the desired configuration. The subject disclosure may be implemented in and used with a number of different types of devices, including but not limited to cellular phones, tablet computers, wearable computing devices, portable media players, and any of various other computing devices.

[0016] This summary is intended to provide a brief overview of some of the aspects and features according to the subject disclosure. Accordingly, it will be appreciated that the abovedescribed features are merely examples and should not be construed to narrow the scope of the subject disclosure in any way. Other features, aspects, and advantages of the subject disclosure will become apparent from the following detailed description, drawings and claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A better understanding of the subject disclosure may be obtained when the following detailed description of various embodiments is considered in conjunction with the following drawings, in which:

[0018] FIG. 1 shows a schematic diagram of an example wireless network;

[0019] FIG. 2 shows a schematic diagram of an example wireless device;

[0020] FIG. 3 shows a schematic diagram of an example network node;

[0021] FIG. 4 shows a schematic diagram of mobility of a UE between coverage and capacity cells.

[0022] FIG. 5 presents a flow chart of a method performed by a user equipment according to the disclosure.

[0023] FIG. 6 presents different alternatives of a method performed by a cell according to the disclosure.

[0024] FIGs. 7 to 9 are illustrations of embodiments for providing an on-demand SIB1 cell reselection priority of a cell operating in on-demand SIB1 mode according to the disclosure.

[0025] FIG. 10 depicts a message flow diagram of providing the on-demand SIB1 cell reselection priority explicitly within an on-demand SIB1 configuration message according to the disclosure.

[0026] FIG. 11 depicts a message flow diagram of providing the on-demand SIB1 cell reselection priority implicitly within the on-demand SIB1 configuration message according to the disclosure.

[0027] FIG. 12 depicts a message flow diagram of providing the on-demand SIB1 cell reselection priority within another SIB message according to the disclosure.DETAILED DESCRIPTION

[0028] The examples and embodiments set forth below represent information to enable those skilled in the art to practice the subject disclosure. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the description and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the description.

[0029] In the following description, numerous specific details are set forth. However, it is understood that embodiments may be practiced without these specific details. In other instances, well-known circuits, structures, and techniques have not been shown in detail in order not to obscure the understanding of the description. Those of ordinary skill in the art, with the included description, will be able to implement appropriate functionality without undue experimentation.

[0030] References in the specification to "one embodiment," "an embodiment," "an example embodiment," etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0031] As used herein, "plurality" means two or more. As used herein, a "set" of items may include one or more of such items. As used herein, whether in the subject disclosure or the claims, the terms "comprising", "including", "carrying", "having", "containing", "involving", and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of and "consisting essentially of, respectively, are closed or semi-closed transitional phrases with respect to claims. Use of ordinal terms such as "first", "second", "third", etc., in the claims or the subject disclosure to modify an element does not by itself connote any priority, precedence, or order of one element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the elements. As used herein, "and / or" and "at least one of means that the listed items are alternatives, but the alternatives also include any combination of the listed items.

[0032] Before explaining the examples according to the subject disclosure in detail, certain general principles of a wireless communication system are briefly explained with reference to FIGS. 1 to 3 to assist in understanding the technology underlying the described examples.

[0033] FIG. 1 illustrates an example of a wireless network 100 that may be used for wireless communications. Wireless network 100 includes wireless devices, such as UEs 110 (e.g., 110A-110B), and network nodes, such as radio access nodes 120 (e.g., 120A-120B) (e.g., eNBs, gNBs, etc.), connected to one or more network nodes 130 over an interconnecting network 125. The network 100 may use any suitable deployment scenarios. UEs 110 within coverage area 115 may each be capable of communicating directly with radio access nodes 120 over a wireless or air interface. In some embodiments, UEs 110 may also be capable of communicating with each other via D2D communication.

[0034] As an example, UE 110A may communicate with radio access node 120A over a wireless or air interface. That is, UE 110A may transmit wireless signals to and / or receive wireless signals from radio access node 120A. The wireless signals may contain voice traffic, data traffic, control signals, and / or any other suitable information.

[0035] As used herein, the term "user equipment" (UE) has the full breadth of its ordinary meaning and may refer to any type of wireless device which may communicate with a networknode and / or with another UE in a cellular or mobile or wireless communication system. Examples of UE are target device, D2D UE, machine type UE or UE capable of machine-to- machine (M2M) communication, personal digital assistant, tablet, mobile terminal, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, ProSe UE, vehicle-to-vehicle (V2V) UE, V2X UE, MTC UE, eMTC UE, FeMTC UE, UE Cat 0, UE Cat Ml, narrow band loT (NB-IoT) UE, UE Cat NB1, etc. Example embodiments of a UE are described in more detail below with respect to FIG. 2.

[0036] In some embodiments, an area of wireless signal coverage 115 associated with a radio access node 120 may be referred to as a cell. However, particularly with respect to the 5thgeneration (5G) / New Radio (NR) mobile communication concepts, beams, such as the herein described multicast radio beams (MRBs) may be used within cells for communication. In some embodiments described herein, the UE 110 may be in an RRC inactive or idle mode and camp on a cell of radio access node 120 A, which be denoted as anchor or coverage cell, and may be in the coverage area 115 of radio access nodes 120A and 120B. The UE may alternatively also be in RRC connected mode and in communication with the cell of radio access node 120a. The cell of radio access node 120B may be denoted as non-anchor or capacity cell. Although not shown in FIG. 1, there may be more than one non-anchor cell provided by more than one other radio access node 120. The UE 100 may, in some embodiments, may want to switch the cells, i.e., transition to camp on a non-anchor cell or to be generally served by the non-anchor cell. Such situations are described later with respect to FIGs. 4 to 12.

[0037] With respect to a beam-based mobile communication system, the radio access node 120 (base station) may transmit a beamformed signal to the UE 110 in one or more transmit directions (transmission beam, Tx beam). The UE 110 may receive the beamformed signal from the base station 120 in one or more receive directions (reception beam, Rx beam). The UE 110 may also transmit a beamformed signal to the base station 120 in one or more directions and the base station 120 may receive the beamformed signal from the UE 110 in one or more directions. The base station 120 and the UE 110 may determine the best receive and transmit directions, e.g., best in the sense of these directions leading to the highest link quality or fulfilling other quality conditions in the most suitable manner, for each of the base station / UE pairs.

[0038] The interconnecting network 125 may refer to any interconnecting system capable of transmitting audio, video, signals, data, messages, etc., or any combination of the preceding. The interconnecting network 125 may include all or a portion of a public switched telephone network (PSTN), a public or private data network, a local area network (LAN), a metropolitanarea network (MAN), a wide area network (WAN), a local, regional, or global communication or computer network such as the Internet, a wireline or wireless network, an enterprise intranet, or any other suitable communication link, including combinations thereof.

[0039] In some embodiments, the network node 130 may be a core network node, managing the establishment of communication sessions and other various other functionalities for UEs 110. Examples of network node 130 may include mobile switching center (MSC), MME, serving gateway (SGW), packet data network gateway (PGW), operation and maintenance (O&M), operations support system (OSS), SON, positioning node (e.g., Enhanced Serving Mobile Location Center, E-SMLC), location server node, MDT node, etc. UEs 110 may exchange certain signals with the network node 130 using the non-access stratum (NAS) layer. In non-access stratum signaling, signals between UEs 110 and the network node 130 may be transparently passed through the radio access network. In some embodiments, radio access nodes 120 may interface with one or more network nodes 130 over an internode interface.

[0040] As used herein, the term "network node" has the full breadth of its ordinary meaning and may correspond to any type of radio access node (or radio network node) or any network node, which may communicate with a UE and / or with another network node in a cellular or mobile or wireless communication system. Examples of network nodes are NodeB, MeNB, SeNB, a network node may belonging to MCG or SCG, base station (BS), multi-standard radio (MSR) radio access node such as MSR BS, eNodeB, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission point, transmission node, RRU, RRH, node in distributed antenna system (DAS), core network node (e.g., MSC, MME, etc.), O&M, OSS, Self-organizing Network (SON), positioning node (e.g., E-SMLC), MDT, test equipment, etc. Example embodiments of a network node are described in more detail below with respect to FIG. 3.

[0041] In some embodiments, radio access node 120 may be a distributed radio access node. The components of the radio access node 120, and their associated functions, may be separated into two main units (or sub-radio network nodes) which may be referred to as the central unit (CU) and the distributed unit (DU). Different distributed radio network node architectures are possible. For instance, in some architectures, a DU may be connected to a CU via dedicated wired or wireless link (e.g., an optical fiber cable) while in other architectures, a DU may be connected a CU via a transport network. Also, how the various functions of the radio access node 120 are separated between the CU(s) and DU(s) may vary depending on the chosen architecture.

[0042] In some embodiments, radio access nodes 120 may communicate with each other over terrestrial or other connections. The communication between the radio access nodes 120 may, e.g., in a 5G / NR communication system may be achieved by using an Xn interface connecting the radio access nodes 120.

[0043] Exemplary wireless communication systems are architectures standardized by the 3rd Generation Partnership Project (3GPP). A latest 3GPP based development is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology (RAT). The various development stages of the 3GPP specifications are referred to as releases. More recent developments of the LTE are often referred to as LTE Advanced (LTE-A). The LTE (LTE-A) employs a radio mobile architecture known as the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and a core network known as the Evolved Packet Core (EPC). Base stations of such systems are known as evolved or enhanced Node Bs (eNBs) and provide E-UTRAN features such as user plane Packet Data Convergence / Radio Link Control / Medium Access Control / Physical layer protocol (PDCP / RLC / MAC / PHY) and control plane Radio Resource Control (RRC) protocol terminations towards the communication devices. Other RAT examples comprise those provided by base stations of systems that are based on technologies such as WLAN and / or Worldwide Interoperability for Microwave Access (WiMax). A base station may provide coverage for an entire cell or similar radio service area. Core network elements include Mobility Management Entity (MME), Serving Gateway (S-GW) and Packet Gateway (P-GW).

[0044] An example of a suitable communications system is the 5G or NR concept. Network architecture in NR may be similar to that of LTE-A. Base stations of NR systems may be known as next generation Node Bs (gNBs). Changes to the network architecture may depend on the need to support various radio technologies and finer Quality of Service (QoS) support, and some on-demand requirements for QoS levels to support Quality of Experience (QoE) of user point of view. Also network aware services and applications, and service and application aware networks may bring changes to the architecture. Those are related to Information Centric Network (ICN) and User-Centric Content Delivery Network (UC-CDN) approaches. NR may use multiple input-multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

[0045] Future networks may utilize network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into "buildingblocks" or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes, or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent.

[0046] An example 5G core network (CN) comprises functional entities. The CN is connected to a UE via the radio access network (RAN). An UPF (User Plane Function) whose role is called PSA (PDU Session Anchor) may be responsible for forwarding frames back and forth between the DN (data network) and the tunnels established over the 5G towards the UEs exchanging traffic with the data network (DN). The UPF is controlled by an SMF (Session Management Function) that receives policies from a PCF (Policy Control Function). The CN may also include an AMF (Access & Mobility Function).

[0047] Generally, all concepts disclosed herein may be applicable to different communication networks, comprising but not limited to LTE, LTE-A, 5G, 5G advanced, 6G, and other future or already implemented networks.

[0048] FIG. 2 is a schematic diagram of an apparatus for the UE. In an embodiment, the apparatus may comprise the UE, in yet another embodiment the apparatus is comprised in the UE, and in another embodiment the apparatus is the UE. The apparatus may comprise a wireless device. The apparatus may comprise at least one processor 220 and at least memory 230 storing computer program instructions that, when executed by the at least one processor 220, cause the apparatus to carry out the embodiments of the UE 110 described herein. UE 110 includes a transceiver 210, processor 220, memory 230, and a network interface 240. In some embodiments, the transceiver 210 facilitates transmitting wireless signals to and receiving wireless signals from radio access node 120 (e.g., via transmitter(s) (Tx), receiver(s) (Rx) and antenna(s)). The processor 220 executes instructions to provide some or all of the functionalities described herein as being provided by UE 110, and the memory 230 stores the instructions executed by the processor 220. In some embodiments, the processor 220 and the memory 230 form processing circuitry.

[0049] The processor 220 may include any suitable combination of hardware to execute instructions and manipulate data to perform some or all of the described functions of UE 110described herein. In some embodiments, the processor 220 may include, for example, one or more computers, one or more central processing units (CPUs), one or more microprocessors, one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs) and / or other logic.

[0050] The memory 230 is generally operable to store instructions, such as a computer program, software, an application including one or more of logic, rules, algorithms, code, tables, etc. and / or other instructions capable of being executed by a processor 220. Examples of memory 230 include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or or any other volatile or non-volatile, non- transitory computer-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processor 220 of UE 110. For example, the memory 230 includes computer program code causing the processor 220 to perform processing according to the methods described herein, e.g., the method of FIG. 5.

[0051] The network interface 240 is communicatively coupled to the processor 220 and may refer to any suitable device operable to receive input for UE 110, send output from UE 110, perform suitable processing of the input or output or both, communicate to other devices, or any combination thereof. The network interface 240 may include appropriate hardware (e.g., port, modem, network interface card, etc.) and software, including protocol conversion and data processing capabilities, to communicate through a network.

[0052] Other embodiments of UE 110 may include additional components beyond those shown in FIG. 2 that may be responsible for providing certain aspects of the wireless device’s functionalities, including any of the functionalities described herein and / or any additional functionalities (including any functionality necessary to support the mechanisms according to the subject disclosure). As an example, UE 110 may include input devices and circuits, output devices, and one or more synchronization units or circuits, which may be part of the processor 220. Input devices include mechanisms for entry of data into UE 110. For example, input devices may include input mechanisms, such as a microphone, input elements, a display, etc. Output devices may include mechanisms for outputting data in audio, video and / or hard copy format. For example, output devices may include a speaker, a display, etc.

[0053] In some embodiments, the wireless device UE 110 may comprise a series of modules configured to implement the functionalities of the wireless device described herein.Moreover, in some embodiments, the UE 110 may also comprise means for the functionalities described herein.

[0054] It will be appreciated that the various modules may be implemented as combination of hardware and software, for instance, the processor, memory, and transceiver(s) of UE 110 shown in FIG. 2. Some embodiments may also include additional modules to support additional and / or optional functionalities.

[0055] FIG. 3 is a schematic diagram of an example of an apparatus for a radio access node 120 or network node 130. The apparatus may comprise at least one processor 220 and at least memory 230 storing computer program instructions that, when executed by the at least one processor 220, cause the apparatus to carry out the embodiments of the network node 130 or radio access node 120 described herein. The example radio access node 120 or network node 130 may include one or more of a transceiver 310, processor 320, memory 330, and network interface 340. In some embodiments, the transceiver 310 facilitates transmitting wireless signals to and receiving wireless signals from wireless devices, such as UE 110 (e.g., via transmitter(s) (Tx), receiver(s) (Rx), and antenna(s)). The processor 320 executes instructions to provide some or all of the functionalities described herein as being provided by the radio access node 120 or the network node 130, the memory 330 stores the instructions executed by the processor 320. In some embodiments, the processor 320 and the memory 330 form processing circuitry. The network interface 340 may communicate signals to backend network components, such as a gateway, switch, router, Internet, Public Switched Telephone Network (PSTN), core network nodes or radio network controllers, etc.

[0056] The processor 320 may include any suitable combination of hardware to execute instructions and manipulate data to perform some or all of the described functions of the radio access node 120 or the network node 130, such as those described herein. In some embodiments, the processor 320 may include, for example, one or more computers, one or more central processing units (CPUs), one or more microprocessors, one or more application specific integrated circuits (ASICs), one or more field programmable gate arrays (FPGAs) and / or other logic.

[0057] The memory 330 is generally operable to store instructions, such as a computer program, software, an application including one or more of logic, rules, algorithms, code, tables, etc. and / or other instructions capable of being executed by a processor 320. Examples of memory 330 include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or or any othervolatile or non-volatile, non- transitory computer-readable and / or computer-executable memory devices that store information. For example, the memory 330 includes computer program code causing the processor 320 to perform processing according to the methods described herein, e.g., the method of FIG. 6.

[0058] In some embodiments, the network interface 340 is communicatively coupled to the processor 320 and may refer to any suitable device operable to receive input for the radio access node 120 or the network node 130, send output from the radio access node 120 or the network node 130, perform suitable processing of the input or output or both, communicate to other devices, or any combination of the preceding. The network interface 340 may include appropriate hardware (e.g., port, modem, network interface card, etc.) and software, including protocol conversion and data processing capabilities, to communicate through a network.

[0059] Other embodiments of the radio access node 120 or the network node 130 may include additional components beyond those shown in FIG. 3 that may be responsible for providing certain aspects of the node’s functionalities, including any of the functionalities described herein and / or any additional functionalities (including any functionality necessary to support the solutions described herein). The various different types of radio access nodes or network nodes may include components having the same physical hardware but configured (e.g., via programming) to support different radio access technologies, or may represent partly or entirely different physical components.

[0060] Processors, interfaces, and memory similar to those described with respect to FIG. 3 may be included in other nodes (such as UE 110, radio access node 120, etc.). Other nodes may optionally include or not include a wireless interface (such as the transceiver described in FIG. 3).

[0061] In some embodiments, the radio access node 120 or the network node 130 may comprise a series of modules configured to implement the functionalities of the radio access node 120 or the network node 130 described herein. Moreover, in some embodiments, the radio access node 120 or the network node 130 may also comprise means for the functionalities described herein.

[0062] It will be appreciated that the various modules may be implemented as combination of hardware and software, for instance, the processor, memory, and transceiver(s) of the radio access node 120 or the network node 130 shown in FIG. 3. Some embodiments may also include additional modules to support additional and / or optional functionalities.

[0063] Before referring to FIGs. 5 to 12 and describing methods supporting mobility for on-demand SIB1 cells according to the disclosure, some background information and aspectsrelated to the subject disclosure will be provided. It should be noted that all concepts described herein, although described, e.g., for one communication direction, e.g., for downlink communication, are applicable for the other direction as well, e.g., in the uplink (UL) communication. Moreover, concepts described for one entity, e.g., a UE 110, are applicable to another entity, e.g., a base station or network node 120, when considering for example another communication direction or another network setting as will be apparent to the skilled person.

[0064] Network energy saving plays an important role in modem communication networks. One approach as identified by the inventors to save energy is directed to transmission or non-transmission of system information (SI), which is usually broadcasted periodically over an entire cell area to inform UEs about parameters of the network in a continuous manner. The main drawback of this periodic broadcasting is a low energy efficiency, in particular, if a cell is faced with a low load or with no load in the cell (i.e., there are few or no UEs to benefit from the transmitted SI). In the 3GPP 5th generation (5G) / New Radio (NR) mobile communication system, transmission of system information of other SI than minimum SI may be omitted. Minimum SI relates to information of master information block (MIB) and system information block 1 (SIB1). The information of SIB2 to SIB 19, which carry non-essential SI, may, additionally or alternatively to broadcasting, be provided on demand. MIB and SIB1 are currently still broadcasted regularly in NR to carry basic information required for initial access of the UEs.

[0065] A further enhancement of NES is to also provide SIB1 only on demand. This requires new processes, information elements, messages, etc. to be defined in new standard releases. Hence, legacy UE, i.e., UEs not supporting the new features of on-demand SIB1 mode operation, will not be able, e.g., to switch to cells operating in on-demand SIB1 mode because they are not able to obtain SIB1 of these cells. However, UEs supporting on-demand SIB1 mode operation should be able to switch to those cells operating in on-demand SIB1 mode.

[0066] The assumption is that a capacity cell (also denoted in this disclosure as non-anchor cell, CapCell, or second cell) will not periodically broadcast the SIB1. Instead, the capacity cell will provide the SIB1 on demand, i.e., based on a request of the UE for transmission of SIB1. Hence, the UE will trigger a SIB1 transmission by sending a wake-up signal (WUS), more generally also referred to as on-demand SIB1 request in this disclosure, which could, e.g., be a random access preamble or any other suitable message. This requires that the UE is configured how to transmit the WUS, and, in order to save energy on the capacity cell, it is assumed that a WUS configuration, more generally also referred to on-demand SIB1 configuration, is provided by another cell, e.g. a coverage cell (also denoted in this disclosure as anchor cell, CovCell, orfirst cell). The coverage cell is regularly broadcasting the anchor cell’s SIB1, as per legacy operations. Moreover, according to embodiments of this disclosure, the UE is in an idle or inactive mode (RRC IDLE, RRC IN ACTIVE) and camping on the coverage cell. It is noted that the solutions provided herein also apply for UEs that are RRC connected mode with the coverage cell (RRC CONNECTED).

[0067] As explained above, the on-demand SIB1 transmission may be triggered by the on- demand SIB1 request from a UE, which may be similar to the on-demand SIB request for other SIBs based on physical random access channel (PRACH) in legacy specifications, e.g., as defined in 3GPP TS 38.331 Release 17 or 18. The configuration of the WUS / on-demand SIB1 request is provided by the network (NW), preferably, by the coverage cell.

[0068] Regarding on-demand SIB1 transmission from gNBs for RRC IDLE / INACTIVE UEs, two deployment cases may generally be considered:• Case-A: Co-located anchor and non-anchor cell in the same gNB, where the information exchange between the two cells is via internal interface. The RUs of anchor and non-anchor cells are physically located.• Case-B: Non-co-located anchor and non-anchor cell in different gNBs, e.g., in gNB 120 A and gNB 120B as described with respect to FIG. 1, where the information exchange between the two cells is via a backhaul interface, i.e. an Xn interface. The RUs of anchor and non-anchor cells are physically non-located.

[0069] In the embodiments described herein, the uplink (UL) on-demand SIB1 request, also called wake-up-signal (WUS), may be received either by the anchor cell, although it may, in specific scenarios also be received by the non-anchor cell. The following different scenarios are generally conceivable for each of cases A and B.

[0070] Scenario 1 : The backhaul signaling of on-demand SIB1 request / WUS configuration may be exchanged between anchor cells 120-2 and non-anchor cells 120-1 (via backhaul for non-co-located case or via internal interface for collocated case). The anchor cell 120-2 may handle the on-demand SIB1 request configuration, herein also denoted as configuration information, to the RRC IDLE / RRC INACTIVE UEs as well as the on-demand SIB1 request reception from the RRC IDLE / RRC INACTIVE UEs. In the meanwhile, the anchor cell 120- 2 may also handle the delivery of on-demand non-anchor cell SIB1 to the RRC IDLE / RRC INACTIVE UEs based on the exchanged information via backhauling. From network energy saving perspective, in this case, the non-anchor cell 120-1 could achieve the best network side energy saving performance because of the only network side energy consumption is for information exchange of backhauling. This case does not require UE 110switching between anchor cell 120-2 and non-anchor cell 120-1 for acquiring the on-demand SIB1.

[0071] Scenario-2: The anchor cell 120-2 may trigger the non-anchor cell 120-1 to send the on-demand SIB1 by non-anchor cell 120-1 itself. The anchor cell 120-2 may then handle the transmission of on-demand SIB1 request configuration to the RRC IDLE / RRC IN ACTIVE UEs as well as the on-demand SIB1 request reception from the RRC IDLE / RRC INACTIVE UEs. This case requires UE 110 switching between anchor cell 120-2 and non-anchor cell 120-1 for acquiring the on-demand SIB1 since the non-anchor cell's SIB1 is transmitted from the non-anchor cell 120-1 itself.

[0072] Scenario-3: The anchor cell 120-2 only handles the on-demand configuration to the RRC IDLE / RRC INACTIVE UEs, e.g. the information of on-demand SIB1 request configuration may be exchanged via backhauling beforehand for non-collocated case. And the non-anchor cell 120-1 may then handle the on-demand reception from the RRC IDLE / RRC INACTIVE UEs as well as the transmission of on-demand SIB1 by itself. This case requires the non-anchor cell 120-1 to monitor for on-demand SIB1 request / WUS reception, which increases the energy consumption for non-anchor cell 120-1 compared to scenarios 1 and 2. This case requires UE 110 switching between anchor cell 120-2 and non- anchor cell 120-1 for acquiring the on-demand SIB1.

[0073] Scenario-4: The operation of on-demand SIB1 is independent from the anchor cell 120-2. The non-anchor cell 120-1 may handle the on-demand SIB1 request configuration to the RRC IDLE / RRC INACTIVE UEs as well as the on-demand SIB1 request reception from the RRC IDLE / RRC INACTIVE UEs. In the meanwhile, the non-anchor cell 120-1 will also handle the delivery of on-demand SIB1 to the RRC IDLE / RRC INACTIVE UEs. This case requires a mechanism to point to UE 110 the on-demand SIB1 request / WUS. This case requires UE 110 switching between anchor cell 120-2 and non-anchor cell 120-1 for acquiring the on- demand SIB1. This case seems not as promising as the other scenarios. Hence, the preferred embodiments described in this disclosure consider one of the scenarios 1 to 3, in which the on- demand SIB1 configuration (message) is transmitted via the coverage celE

[0074] Practically, it may be assumed in some embodiments that the anchor cell provides the IDLE mode functions for camping and initial access. The common signals / channels including synchronization signal block (SSB) / SIB / paging / random access channel (RACH) may be transmitted to or received from the RRC IDLE / RRC INACTIVE UEs camping on this cell. Thus, the anchor cell may be used also to transmit the on-demand SIB1 WUS configuration to UE. The on-demand SIB1 request configuration may be added as part of system information,in MIB, SIB1, any of SIB 2 to SIB 19, or any other, possibly newly defined SIB of the anchor cell.

[0075] Generally, in legacy operations, a first message for RRC IDLE / INACTIVE UEs to communicate with NW is sending of UL PRACH signal. In addition, in legacy operations for RRC IDLE / RRC IN ACTIVE UEs requesting the on-demand SIB(s) other than SIB1 information, it is also required for the RRC IDLE / RRC INACTIVE UEs to perform PRACH transmission as requesting indication to receive on-demand SIBs. To align with the legacy operation for on-demand SIB operation, PRACH may be used as on-demand SIB 1 request for triggering of on-demand SIB1 transmission for RRC IDLE / RRC INACTIVE UEs.

[0076] As already indicated above, UEs may camp on the coverage cell (or, in some embodiments, alternatively being in RRC connected mode with the coverage cell) and may - continuously or triggered by information transmitted from the coverage cell - also search for another cell to switch to, e.g., to camp on. For deciding whether to reselect towards another cell, the UE obtains cell reselection priorities, also denoted as frequency priorities, and performs measurements on the neighboring cells having a higher cell reselection priority than the current serving cell, i.e., higher than the coverage cell. The UE decides, based on the measurements (and the cell reselection priority, which depends on whether the cell is in on-demand SIB 1 mode or not), whether to switch, e.g., reselect to another cell. One parameter controlling reselection of a cell is, thus, the cell reselection priority.

[0077] This disclosure addresses how a UE would acquire the WUS configuration from a coverage cell to trigger the on-demand SIB1 transmission on a capacity cell. Particularly, it addresses the UE mobility scenarios where the UE acquires WUS configuration from the coverage cell and has to do cell reselection towards the capacity cell, when the capacity cell is in an on-demand SIB1 mode (i.e., not transmitting SIB1 regularly).

[0078] An example situation of UE mobility is depicted in Fig. 4. A UE 110 camps either on coverage cell 120-A of, e.g., gNB 120A, or on coverage cell 120-C of, e.g. gNB 120B. It may be advantageous for the UE to reselect to capacity cell 120-B. Therefore, two situations are conceivable:(a) The UE 110 is camping in the coverage cell 120-A deploying frequency Fl. The network would prefer the UE 110 to move (reselect) to the capacity cell 120-B deploying frequency F2.(b) The UE 110 is camping in the coverage cell 120-C deploying frequency Fl. The network would prefer the UE 110 to move (reselect) to the capacity cell 120-B deploying frequency F2.

[0079] If the network configures F2 to have higher priority than Fl using legacy SIB2- SIB4 (in cells 120-A and / orl20- C), the legacy UEs (Release 18 and earlier) will also obtain the configuration and attempt to reselect to cell 120-B. However, the legacy UEs will fail to do so because cell 120-B (F2) is not broadcasting SIB1 and the legacy UEs are not able to request the SIB1 from cell 120-B.

[0080] The network may address this by providing frequency priority configurations of cell 120-B to the Release 19 UEs in a dedicated manner. This, however, is a complicated solution, because the signaling is then required to be done per UE 110, i.e., each UE 110 needs to be in RRC CONNECTED state to receive the configuration. Furthermore, the network may not be aware that a Release 19 (or later) UE 110 in RRC IDLE or RRC INACTIVE state has moved from a certain cell to cell 120-A (as long as they are in the same tracking area). Therefore, the UE 110 may be subject to offloading to the capacity cell 120-B but the network will not configure the frequency priority for the UE 110.

[0081] This disclosure addresses the issue of how to configure cell reselection priorities (or, in other words, frequency priorities for cell reselection) such that, based on those frequency priorities, only Release 19 (and later) UEs 110 are attempting to reselect to a capacity cell, which operates in on-demand SIB1 mode. Now turning to FIG. 5, which presents a flow chart of a method performed by a user equipment 110 for supporting switching (e.g., reselection or handover) towards an on-demand SIB1 cell, e.g., capacity cell 120-B of FIG. 4, according to the disclosure. The UE 110 supports on-demand system information block 1, SIB1, mode operation (e.g., is a Release 19 UE of NR or later), and is served by a first cell, e.g., coverage cell 120-A or coverage cell 120-B of FIG. 4. The UE may be in radio resource control, RRC, idle (RRC IDLE) or inactive (RRC INACTIVE) mode or also in some embodiments in RRC connected mode (RRC CONNECTED).

[0082] The UE 100 receives (as shown in box 610) from the first cell 120-A, 120-C an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell 120-B. We assume here, that the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell 120-A, 120-C. If the on-demand SIB1 reselection priority of the second cell 120- B is lower than the reselection priority, i.e., the reselection priority given to the frequency of the first cell 120-A, 120-C, the UE 110 may in some examples also receive the on-demand SIB1 reselection priority as described below but may then not perform the next processes as described below, i.e., may not perform measurements as, e.g., defined in 3GPP TS 38.304, Release 17 or 18, clause 5.2.4.2.

[0083] The UE 110 then, i.e., if the on-demand SIB1 reselection priority of the second cell is higher than the reselection priority of the first cell 120-A, 120-C, performs (as shown in box 620) measurements with respect to the frequency band deployed by the second cell 120-B based on the on-demand SIB1 reselection priority. The measurements may, e.g., be cell reselection measurements concerning at least one of reference signal received power (RSRP) and reference signal received quality (RSRQ) of the second cell 120-B.

[0084] The UE 110 further determines (as shown in box 630) whether to reselect to towards the second cell 120-B based on results of the measurements. For example, if the signal received power and / or signal received quality of the second cell 120-B are above a threshold (or a threshold for each), the UE 110 may determine to reselect towards the second cell 120-B. Further conditions as described in 3GPP TS 38.304, Release 17 or 18, clause 5.2.4.2, may apply, too. Moreover, the UE 110 may also take the cell reselection priority (either the on-demand SIB1 cell reselection priority or the usual / legacy cell reselection priority of the second cell 120- B depending on the mode the cell is operating in) into account for the decision to switch to the second cell 120-B.

[0085] The on-demand SIB1 cell reselection priority of the second cell 120-B may be different from a cell reselection priority of the second cell 120-B when not operating in SIB1 on-demand mode. The "usual" cell reselection priority of the second cell 120-B may, e.g., be defined by the frequency priority of the frequency (e.g., F2) deployed by the second cell 120- B. Hence, frequency F2 may have been given a priority of 5, which is provided to the UE 110, e.g., in system information block, SIB, information of the first cell 120-A, 120-C within the information element (IE) CellReselectionPriority - and in some examples also additionally within the IE CellReselectionSubPriority - as defined in 3GPP TS 38.3331, Release 17 or 18. However, if the second cell 120-B is operating in on-demand SIB1 mode, the on-demand SIB1 cell reselection priority with, e.g., a value of 7 may be provided by the first cell 120-A, 120-C to non-legacy UEs 110 in order to force reselection towards the second cell 120-B.

[0086] In some embodiments, the indication of the on-demand SIB1 cell reselection priority may be included in an on-demand SIB1 configuration message for the second cell 120- B. The on-demand SIB1 configuration message may comprise on-demand SIB1 configuration information for transmitting a SIB1 request, for receiving a SIB1 response, and / or for receiving the on-demand SIB1 information from the second cell 120-B. The on-demand SIB1 configuration message may also or additionally comprise other information related to the acquisition of the on-demand SIB1 information from the second cell 120-B.

[0087] The on-demand SIB1 configuration message may, in some examples, comprise the on-demand SIB1 cell reselection priority, i.e., the indication of the on-demand SIB1 cell reselection priority relates to an explicit value of the priority, and at least one of a Physical Cell ID, PCI, of the second cell 120-B and the frequency band deployed by the second cell 120-B. In these examples, the on-demand SIB1 configuration message may further comprise an indication regarding the applicability of the on-demand SIB1 cell reselection priority. Such an indication regarding the applicability of the on-demand SIB1 cell reselection priority may indicate applicability to the PCI of the second cell 120-B and / or to the frequency band deployed by the second cell 120-B. In other words, the on-demand SIB1 cell reselection priority can be defined for a specific cell or for all on-demand cells that operate in a frequency.

[0088] In some further embodiments, the on-demand SIB1 configuration message may comprise a Physical Cell ID, PCI, of the second cell 120-B and the frequency band deployed by the second cell 120-B. In these embodiments, the indication of the on-demand SIB1 cell reselection priority relates to an implicit indication of a highest or predefined value for the on- demand SIB1 cell reselection priority by receiving the on-demand SIB1 configuration message. This means, receiving the on-demand SIB1 configuration message may be an implicit instruction to the UE 110 to perform the measurements.

[0089] In some further examples, the indication of the on-demand SIB1 cell reselection priority may be included in a system information block, SIB, message including the on-demand SIB1 cell reselection priority. In this example, the indication is again an explicit value of the priority. In some further examples, the SIB message may comprise one or more SIB2 and / or SIB4 information elements defining the on-demand SIB1 cell reselection priority. In yet further examples, the SIB message may also comprise one or more SIB2 and / or SIB4 information elements defining a cell reselection priority for the second cell 120-B when not operating in SIB1 on-demand mode.

[0090] It is noted that although the embodiments described for FIG. 5 and in the following for FIGs 6 to 12 mostly assume that the UE 110 is in RRC IDLE or RRC INACTIVE mode, the solutions described also apply likewise for UEs in RRC CONNECTED mode. For example, the UE 110 may be in RRC CONNECTED mode while receiving the indication of the on-demand SIB 1 cell reselection priority and in RRC idle or inactive mode when performing measurements and determining to switch, i.e., reselect towards the second cell. In other embodiments, the UE 110 may switch directly from RRC connected mode in the first cell to RRC idle / inactive mode in the second cell (i.e., skipping being in idle / inactive in the first cell).

[0091] Similar processes as described with respect to FIG. 5 for the UE 110 are performed on the network side, e.g., for the first cell 120-A, 120-C as now described with respect to FIG. 6. FIG: 6 presents different alternatives of a method performed by a first cell, such as coverage cell 120-A, 120-B of FIG. 4, in a mobile communication system supporting reselection of a user equipment, UE 110, towards a second cell, such as capacity cell 120-B of FIG. 4, operating in an on-demand system information block 1, SIB1, mode, according to the disclosure. The UE 110 is supporting on-demand SIB1 mode operation and camping on the first cell in radio resource control, RRC, idle or inactive mode.

[0092] The method of FIG: 6 comprises one process, which depicted in box 610 and corresponds to the process of box 510 of FIG. 5 for the UE 100. The first cell 120-A, 120-C transmits (as shown in box 610) an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell 120-B to the UE 110. The on- demand SIB1 reselection priority is again assumed to be higher than the reselection priority associated with the frequency band deployed by the first cell 120-A, 120-C.

[0093] The indication triggers, at the UE, measurements with respect to the frequency band deployed by the second cell 120-B based on the on-demand SIB1 reselection priority and triggers a determination to reselect to towards the second cell 120-B based on results of the measurements. The measurements may, e.g., be cell reselection measurements concerning at least one of reference signal received power (RSRP) and reference signal received quality (RSRQ) of the second cell 120-B.

[0094] The determination of the UE 110 whether to reselect to towards the second cell 120- B is based on results of the measurements. For example, if the signal received power and / or signal received quality of the second cell 120-B are above a threshold (or a threshold for each), the UE 110 may determine to reselect towards the second cell 120-B. Further conditions as described in 3GPP TS 38.304, Release 17 or 18, clause 5.2.4.2, may apply, too.

[0095] The on-demand SIB1 cell reselection priority of the second cell 120-B may be different from a cell reselection priority of the second cell 120-B when not operating in SIB1 on-demand mode. The "usual" cell reselection priority of the second cell 120-B may, e.g., be defined by the frequency priority of the frequency (e.g., F2) deployed by the second cell 120- B. Hence, frequency F2 may have been given a priority of 5, which is provided to the UE 110, e.g., in system information block, SIB, information of the first cell 120-A, 120-C within the information element (IE) CellReselectionPriority - and in some examples also additionally within the IE CellReselectionSubPriority - as defined in 3GPP TS 38.3331, Release 17 or 18. However, if the second cell 120-B is operating in on-demand SIB1 mode, the on-demand SIB1cell reselection priority with, e.g., a value of 7 may be provided by the first cell 120-A, 120-C to non-legacy UEs 110 in order to force reselection towards the second cell 120-B.

[0096] In some embodiments, the indication of the on-demand SIB1 cell reselection priority may be included in an on-demand SIB1 configuration message for the second cell 120- B, which is shown in box 611. The on-demand SIB1 configuration message may comprise on- demand SIB1 configuration information for transmitting a SIB1 request, for receiving a SIB1 response, and / or for receiving the on-demand SIB1 information from the second cell 120-B. The on-demand SIB1 configuration message may also or additionally comprise other information related to the acquisition of the on-demand SIB1 information from the second cell 120-B.

[0097] The on-demand SIB1 configuration message may, in some examples, comprise the on-demand SIB1 cell reselection priority, i.e., the indication of the on-demand SIB1 cell reselection priority relates to an explicit value of the priority (as shown in box 612), and at least one of a Physical Cell ID, PCI, of the second cell 120-B and the frequency band deployed by the second cell 120-B. In these examples, the on-demand SIB1 configuration message may further comprise an indication regarding the applicability of the on-demand SIB1 cell reselection priority. Such an indication regarding the applicability of the on-demand SIB1 cell reselection priority may indicate applicability to the PCI of the second cell 120-B and / or to the frequency band deployed by the second cell 120-B. In other words, the on-demand SIB1 cell reselection priority can be defined for a specific cell or for all on-demand cells that operate in a frequency.

[0098] In some further embodiments, the on-demand SIB1 configuration message may comprise a Physical Cell ID, PCI, of the second cell 120-B and the frequency band deployed by the second cell 120-B. In these embodiments, the indication of the on-demand SIB1 cell reselection priority relates to an implicit indication (as shown in box 613) of, e.g., a highest or predefined value for the on-demand SIB1 cell reselection priority by receiving the on-demand SIB1 configuration message. This means, receiving the on-demand SIB1 configuration message may be an implicit instruction to the UE 110 to perform the measurements.

[0099] In some further examples, the indication of the on-demand SIB1 cell reselection priority may be included in a system information block, SIB, message including the on-demand SIB1 cell reselection priority, which is shown in box 614. In this example, the indication is again an explicit value of the priority. In some further examples, the SIB message may comprise one or more SIB2 and / or SIB4 information elements defining the on-demand SIB1 cell reselection priority. In yet further examples, the SIB message may also comprise one or moreSIB2 and / or SIB4 information elements defining a cell reselection priority for the second cell 120-B when not operating in SIB1 on-demand mode.

[0100] FIGs. 7 to 9 now present illustrations of embodiments for providing an on-demand SIB1 cell reselection priority of a cell operating in on-demand SIB1 mode according to the disclosure. In FIG. 7, abase station 120 provides a coverage cell 120-A and an on-demand SIB1 capacity cell 120-B. The coverage cell 120-A (also known as anchor cell) transmits the WUS configuration, i.e., the on-demand SIB1 configuration message (or messages), to the UE 110. The WUS configuration may be defined per PCI and may be used by the UE to send an UL- WUS, i.e., an on-demand SIB1 request, to trigger the SIB1 transmission by the second cell 120- B with the given PCI.

[0101] The WUS configuration includes at least an indication of a frequency priority for the frequency layer or for each of the frequency layers, in which the second cell 120-B and / or other on-demand SIB1 cells operate. These frequency priorities, i.e., corresponding to on- demand SIB1 cell reselection priorities, are to be used by the UE 110 to perform cell reselection to an on-demand SIB1 cell (e.g., to the capacity cell 120-B) deploying the corresponding frequency carrier. The indication of the frequency priority may be given explicitly and overwrite any legacy frequency priorities for the same frequency layer of the capacity cell 120- B (as provided per legacy SIBs) or may be provided explicitly as an offset, which the UE applies to the frequency priority of the legacy SIBs for the respective frequency.

[0102] The frequency priority included in the WUS configuration may be provided for the PCI of the capacity cell 120-B, for which the WUS configuration is defined. Alternatively or additionally, the frequency priority included in the WUS configuration may be provided for the (or one) frequency layer of the second cell 120-B (i.e., the frequency priority may be applicable for any cell deploying the respective frequency layer). A flag could indicate whether the frequency priority is applicable to the PCI(s) and / or frequency layer(s).

[0103] As indicated above, after the UE 110 received the WUS configuration indicating the frequency priority of the capacity cell 120-B (i.e., the on-demand SIB1 cell reselection priority), the UE 110 performs measurements of the capacity cell 120-B (if the frequency priority of the capacity cell 120-B is higher / equal than / to the frequency priority of the serving coverage cell 120-A). If the UE 110 then determines to reselect towards the capacity cell 120- B, the UE 110 transmits a SIB1 request to the second cell 120-B, in order to then receive the SIB1 of the second cell 120-B (which is only transmitted on-demand).

[0104] The setup of FIG. 8 is similar to FIG. 7. The base station 120 provides a coverage cell 120-A and an on-demand SIB1 capacity cell 120-B. The coverage cell 120-A transmits theWUS configuration, i.e., the on-demand SIB1 configuration message (or messages), to the UE 110. The WUS configuration may be defined per PCI and may be used by the UE to send an UL-WUS, i.e., an on-demand SIB1 request, to trigger the SIB1 transmission by the second cell 120-B with the given PCI.

[0105] In this example, the WUS configuration includes not only the PCI of the capacity cell 120-B, but also the frequency layer of the PCI, i.e., of the capacity cell 120-B. When the UE 110 receives the WUS configuration including the frequency layer information, the UE 110 is triggered to search for the PCI on the frequency layer and perform measurements of the respective capacity cell 120-B. This means, the trigger to measure power / quality (e.g., RSRP / RSRQ) of the second cell 120-B is independent of the frequency priority configuration provided in SIB2 / 4. In other words, the UE is pushed to perform cell search of the PCI and attempt cell reselection to the PCI without receiving an explicit value for the frequency priority but receives an implicit indication by receiving the WUS configuration, which includes the frequency layer information of the capacity cell 120-B.

[0106] For this embodiments, the 3GPP TS 38.304, Release 17 or 18, clause 5.2.4.2 may be amended, for Release 19 or later, such that a further condition for a UE being triggered to perform cell search may be added, which reads "If the UE is operating in radio resource control, RRC, idle or inactive mode and receives an on-demand SIB1 configuration information for requesting acquisition of SIB1 information from a cell operating in on-demand SIB1 mode, the UE shall perform measurements of such NR inter-frequency cells of equal or lower priority, or such inter-RAT frequency cells of lower priority according to TS 38.133 [8]" or similar.

[0107] As indicated above, after the UE 110 received the WUS configuration implicitly indicating the frequency priority (a high / predefined etc. priority) of the capacity cell 120-B (i.e., the on-demand SIB1 cell reselection priority), the UE 110 performs measurements of the capacity cell 120-B (if the frequency priority of the capacity cell 120-B is higher / equal than / to the frequency priority of the serving coverage cell 120-A). If the UE 110 then determines to reselect towards the capacity cell 120-B, the UE 110 transmits a SIB1 request to the second cell 120-B, in order to then receive the SIB1 of the second cell 120-B (which is only transmitted on-demand).

[0108] In FIG. 9, the base station 120 again provides a coverage cell 120-A and an on- demand SIB1 capacity cell 120-B. The coverage cell 120-A transmits the WUS configuration, i.e., the on-demand SIB1 configuration message (or messages), to the UE. The WUS configuration may be defined per PCI and may be used by the UE 110 to send an UL-WUS,i.e., an on-demand SIB1 request, to trigger the SIB1 transmission by the second cell 120-B with the given PCI.

[0109] In this example, the WUS configuration does not include information with respect to the frequency priority but only the PCI of the capacity cell 120-B. The SIB2 and / or SIB4 of the coverage cell 120-B includes an additional information element with specific on-demand SIB1 frequency priority or frequency priorities. For example, SIB2 and / or SIB4 may comprise IE CellReselectionPriority - and in some examples also additionally IE CellReselectionSubPriority - as defined in 3GPP TS 38.3331, Release 17 or 18. These IES may define the legacy cell reselection priority for a frequency. Additionally, SIB2 and / or SIB4 may comprise further IEs that define specific on-demand SIB1 frequency priorities, i.e., for cells operating in on-demand SIB1 mode, e.g., IEs CellReseletionSIBlondemandPriority and / or CellReselectionSIBlondemandSubPriority. Alternatively, the cell reselection priority of the on-demand SIB1 cells may be included in a new IE InterFreqNeighCellList-vl910, similar to the legacy IE InterFreqNeighCellList-vl610 or -vl710 but with a new IE InterFreqNeighCelllnfo, which comprises the on-demand SIB1 frequency priority as parameter / IE, e.g., cellReselectionSIBlondemandPriority or the like.

[0110] The Release 19 UEs 110 may apply the additional information element IEs (i.e., the on-demand SIB1 specific frequency priority) as soon as WUS configuration is received. The UEs 110 may apply the additional IEs to the PCI(s) included in the WUS configuration only and not to the entire frequency layer, i.e., other cells operating in legacy SIB1 mode on the same frequency. The legacy UEs, in contrast, do not understand the additional IEs and will only apply the legacy cell reselection IEs and the respective frequency priorities.[OHl] As indicated above, after the UE 110 received the WUS configuration indicating the frequency priority of the capacity cell 120-B is to be taken from the SIB2 / SIB4 additional IE (i.e., which corresponds to the on-demand SIB1 cell reselection priority), the UE 110 performs measurements of the capacity cell 120-B (if the frequency priority of the capacity cell 120-B is higher / equal than / to the frequency priority of the serving coverage cell 120-A). If the UE 110 then determines to reselect towards the capacity cell 120-B, the UE 110 transmits a SIB1 request to the second cell 120-B, in order to then receive the SIB1 of the second cell 120- B (which is only transmitted on-demand).

[0112] In some embodiments, there may be multiple capacity cells on multiple different frequency layers and that some, but not all those cells, may be utilizing the WUS triggered SIB1 on-demand transmission features. Therefore, the WUS configuration may be configured per PCI. However, the WUS configuration may also be per frequency layer, and not including PCIsat all, meaning that any PCI deploying the frequency layer is operating with on-demand SIB 1 In some embodiments, the WUS configuration may apply to a set of PCIs or a set of frequencies. Generally, when the UE 110 has received the indication of the on-demand SIB1 cell reselection priority, the UE 110 it will be able to determine whether to start measurements on the frequency layer of the capacity cell(s), while the legacy UEs will not start the search.

[0113] Before going into further detail with respect to FIGs. 10 to 12, it is noted that although most embodiments described herein assume the UE 110 is in RRC IDLE or RRC IN ACTIVE and camp on the coverage cell 120-A when receiving the WUS configuration, the UE 110 may in alternative embodiments be in RRC CONNECTED mode in the coverage cell 120-A, such that the UE 110 can receive the WUS configuration and / or frequency priority information via a dedicated RRC signalling, e.g. as part of an RRC Release message.

[0114] FIG. 10 now depicts a message flow diagram of providing the on-demand SIB1 cell reselection priority explicitly within an on-demand SIB1 configuration message according to the disclosure. The UE 110 camps on the coverage cell 120-A, which has PCI A and operates on frequency Fl. The UE 110 receives (arrow 1001) the SIBs as defined, e.g., for Release 17 and / or 18 of NR from the coverage cell 120-A, which comprise cell reselection priority for different frequency layers. In this example, frequency Fl has a higher priority than frequency F2. Since capacity cell 120-B with PCI B operates in frequency F2, a legacy UE only receiving the legacy SIB information will not perform cell search and measurements towards capacity cell 120-B.

[0115] The UE 110 also receives (arrow 1002) an on-demand SIB1 configuration message (or messages) from the coverage cell 120-A, which comprises information with respect to the capacity cell 120-B. This is indicated by the PCI B. Moreover, the on-demand SIB1 configuration message also comprises an on-demand SIB1 cell reselection priority for F2. In this example, the cell reselection priority is defined be per PCI but may also be defined per frequency. The on-demand SIB1 cell reselection priority indicated that the frequency F2 now has a higher priority than frequency Fl.

[0116] Therefore, a search for the capacity cell 120-B with PCI B is started (box 1003) according to the now updated cell reselection priority, i.e., because the on-demand SIB1 cell reselection priority for Fl is higher than the cell reselection priority of frequency Fl.

[0117] The UE 110 obtains (arrow 1004) an SSB from the coverage cell 120-A and performs cell measurements. The UE 110 also obtains (arrow 1005) an SSB from the capacity cell 120-B and performs cell measurements as well. Depending on the results of themeasurements, the UE may then determine that the capacity cell 120-B is a suitable candidate for cell reselection (box 1006), e.g., because it has a higher / equal priority and the measurement results fulfill threshold(s) defined the in the 3 GPP standards.

[0118] If so, the UE 110 sends (arrow 1007) an on-demand SIB1 request to the capacity cell 120-B, e.g., a random access preamble indicating that the UE 110 requires the SIB1 of the capacity cell 120-B. The capacity cell 120-B then transmits (arrow 1008) the SIB1 information to the UE, e.g., by turning broadcast of SIB1 on, by sending a dedicated RRC message with the SIB 1 information, or the like.

[0119] FIG. 11 depicts a message flow diagram of providing the on-demand SIB1 cell reselection priority implicitly within the on-demand SIB1 configuration message according to the disclosure. The UE 110 again camps on the coverage cell 120-A, which has PCI A and operates on frequency Fl. The UE 110 receives (arrow 1001, i.e., similar as in FIG. 10) the SIBs as defined, e.g., for Release 17 and / or 18 of NR from the coverage cell 120-A, which comprise cell reselection priority for different frequency layers. In this example, frequency Fl has a higher priority than frequency F2. Since capacity cell 120-B with PCI B operates in frequency F2, a legacy UE only receiving the legacy SIB information will not perform cell search and measurements towards capacity cell 120-B.

[0120] The UE 110 also receives (arrow 1102, i.e., different from FIG. 10) an on-demand SIB1 configuration message (or messages) from the coverage cell 120-A, which comprises information with respect to the capacity cell 120-B. This is indicated by the PCI B as described with respect to FIG. 10. However, contrary what was explained with respect to FIG: 10, the on- demand SIB1 configuration message does not comprises an on-demand SIB1 cell reselection priority for F2 but only indicates that the capacity cell 120-B with PCI B operating on frequency F2.

[0121] In this example, the UE 110 interprets the reception of the on-demand SIB1 configuration message as instruction to perform cell search and measurements towards the capacity cell 120-B with PCI B. Hence, a search for the capacity cell 120-B with PCI B is started (box 1103) and the legacy priorities received with SIB information in arrow 1001 are ignored.

[0122] The UE 110 obtains (arrow 1004) an SSB from the coverage cell 120-A and performs cell measurements. The UE 110 also obtains (arrow 1005) an SSB from the capacity cell 120-B and performs cell measurements as well. Depending on the results of the measurements, the UE may then determine that the capacity cell 120-B is a suitable candidatefor cell reselection (box 1006), e.g., because it has a higher / equal priority and the measurement results fulfill threshold(s) defined the in the 3 GPP standards.

[0123] If so, the UE 110 sends (arrow 1007) an on-demand SIB1 request to the capacity cell 120-B, e.g., a random access preamble indicating that the UE 110 requires the SIB1 of the capacity cell 120-B. The capacity cell 120-B then transmits (arrow 1008) the SIB1 information to the UE, e.g., by turning broadcast of SIB1 on, by sending a dedicated RRC message with the SIB 1 information, or the like.

[0124] FIG. 12 depicts a message flow diagram of providing the on-demand SIB1 cell reselection priority within another SIB message according to the disclosure. The UE 110 again camps on the coverage cell 120-A, which has PCI A and operates on frequency Fl. The UE 110 receives (arrow 1201, i.e., different from FIG. 10) SIB2 / SIB4 which have been amended compared to, e.g., Release 17 and / or 18 of NR. SIB2 / SIB4 now comprise the legacy cell reselection priorities for different frequency layers but also additional specific on-demand SIB1 cell reselection priorities. For example, considering only the legacy cell reselection priorities, frequency Fl has a higher priority than frequency F2. This applies for legacy UEs. However, specific new IES are defined for the on-demand SIB1 cell reselection priorities, which may in this example indicate that, for on-demand SIB1 cell, i.e., capacity cell 120-B, the cell reselection priorities are different, e.g., frequency F2 having a higher priority than frequency Fl. This in turn also means that capacity cell 120-B may have different cell reselection priorities depending on whether it is in on-demand SIB1 mode or not, e.g., the higher priority for F2 only applies in on-demand SIB1 mode.

[0125] The UE 110 also receives (arrow 1202) an on-demand SIB1 configuration message (or messages) from the coverage cell 120-A, which comprises information with respect to the capacity cell 120-B but do not affect the priority of the frequency of the capacity cell 120-B but only define other parameters needed to obtain SIB1 from capacity cell 120-B (which may be required later). The UE 110 already knows that frequency F2 has a higher cell reselection priority than Fl for on-demand SIB1 cells (from the SIB2 / SIB4) and now also knows that capacity cell 120-B operates in on-demand SIB1 mode. Therefore, a cell search and measurements are triggered at the UE 110 (box 1203) according to the on-demand SIB1 cell reselection priority received in SIB2 and / or SIB4.

[0126] The UE 110 obtains (arrow 1004) an SSB from the coverage cell 120-A and performs cell measurements. The UE 110 also obtains (arrow 1005) an SSB from the capacity cell 120-B and performs cell measurements as well. Depending on the results of the measurements, the UE may then determine that the capacity cell 120-B is a suitable candidatefor cell reselection (box 1006), e.g., because it has a higher / equal priority and the measurement results fulfill threshold(s) defined the in the 3 GPP standards.

[0127] If so, the UE 110 sends (arrow 1007) an on-demand SIB1 request to the capacity cell 120-B, e.g., a random access preamble indicating that the UE 110 requires the SIB1 of the capacity cell 120-B. The capacity cell 120-B then transmits (arrow 1008) the SIB1 information to the UE, e.g., by turning broadcast of SIB1 on, by sending a dedicated RRC message with the SIB 1 information, or the like.

[0128] The herein described procedures may be applied per model or per functionality level (identified by an identifier) or across models or functionalities of a given entity, e.g., as a UE feature. It should be understood that the apparatuses described herein may comprise or be coupled to other units or modules etc., such as radio parts or radio heads, used in or for transmission and / or reception. Although the apparatuses have been described as one entity, different modules and memory may be implemented in one or more physical or logical entities.

[0129] It is noted that whilst embodiments have been described in relation to LTE and 5G NR, similar principles may be applied in relation to other networks and communication systems where enforcing fast connection re-establishment is required. Therefore, although certain embodiments were described above by way of example with reference to certain example architectures for wireless networks, technologies and standards, embodiments may be applied to any other suitable forms of communication systems than those illustrated and described herein.

[0130] It is also noted herein that while the above describes exemplary embodiments, there are several variations and modifications which may be made to the disclosed solution without departing from the scope of the subject disclosure.

[0131] In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects of the subject disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the subject disclosure is not limited thereto. While various aspects of the subject disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0132] Example embodiments of the subject disclosure may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and / or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computerexecutable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

[0133] Further in this regard it should be noted that any blocks of the logic flow as in the figures may represent program processes, or interconnected logic circuits, blocks and functions, or a combination of program processes and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

[0134] The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), FPGA, gate level circuits and processors based on multicore processor architecture, as non-limiting examples.

[0135] Example embodiments of the subject disclosure may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate.

[0136] The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of the subject disclosure. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this disclosure will still fall within the scope of the subject disclosure as defined in the appendedclaims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

Claims:

1. A method performed by a user equipment, UE, supporting on-demand system information block 1, SIB1, mode operation and being served by a first cell, the method supporting switching towards a second cell operating in an on-demand SIB1 mode and comprising:- receiving from the first cell an indication of an on-demand SIB 1 cell reselection priority associated with a frequency band deployed by the second cell, wherein the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell;- performing measurements with respect to the frequency band deployed by the second cell based on the on-demand SIB1 reselection priority; and- determining to switch towards the second cell based on results of the measurements.

2. The method of claim 1, wherein the UE is in radio resource control, RRC, idle or inactive mode and camping on the first cell, wherein switching towards the second cell comprises cell reselection towards the second cell.

3. The method of claim 1, wherein the UE is in radio resource control, RRC, connected mode while receiving the indication of the on-demand SIB 1 cell reselection priority and in RRC idle or inactive mode when performing measurements and determining to switch towards the second cell, wherein switching towards the second cell comprises cell reselection towards the second cell.

4. The method of any one of claims 1 to 3, wherein the on-demand SIB1 cell reselection priority of the second cell is different from a cell reselection priority of the second cell when not operating in SIB1 on-demand mode.

5. The method of any one of claims 1 to 4, wherein the indication of the on-demand SIB1 cell reselection priority is included in an on-demand SIB 1 configuration message for the second cell.

6. The method of claim 5, wherein the on-demand SIB1 configuration message comprises the on-demand SIB 1 cell reselection priority and at least one of a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell.

7. The method of claim 6, wherein the on-demand SIB1 configuration message further comprises an indication regarding the applicability of the on-demand SIB1 cell reselection priority.

8. The method of claim 7, wherein the indication regarding the applicability of the on- demand SIB 1 cell reselection priority indicates applicability to the PCI of the second cell and / or the frequency band deployed by the second cell.

9. The method of claim 5, wherein the on-demand SIB1 configuration message comprises a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell, and wherein receiving the on-demand SIB1 configuration message is an implicit instruction to the UE to perform the measurements.

10. The method of any one of claims 1 to 4, wherein the indication of the on-demand SIB1 cell reselection priority is included in a system information block, SIB, message.

11. The method of claim 10 wherein the SIB message comprises one or more SIB2 information elements and / or one or more SIB4 information elements defining the on- demand SIB1 cell reselection priority.

12. The method of claim 11, wherein the SIB message further comprises one or more SIB2 information elements and / or one or more SIB4 information elements defining a cell reselection priority for the second cell when not operating in SIB 1 on-demand mode.

13. The method of any one of claims 1 to 12, wherein the measurements are cell reselection measurements concerning at least one of signal received power and signal received quality of the second cell.

14. The method of any one of claims 1 to 13, wherein the determination to switch towards the second cell is further based on whether the second cell operates in on-demand SIB1 mode or not.

15. A method performed by a first cell in a mobile communication system supporting switching of a user equipment, UE, towards a second cell operating in an on-demand system information block 1, SIB1, mode, wherein the UE is supporting on-demand SIB1 mode operation and being served by the first cell, the method comprising:- transmitting an indication of an on-demand SIB 1 cell reselection priority associated with a frequency band deployed by the second cell to the UE, wherein the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell; wherein the indication triggers, at the UE, measurements with respect to the frequency band deployed by the second cell based on the on-demand SIB 1 reselection priority and a determination to switch towards the second cell based on results of the measurements.

16. The method of claim 15, wherein the UE is in in radio resource control, RRC, idle or inactive mode and camping on the first cell, wherein switching towards the second cell comprises cell reselection towards the second cell.

17. The method of claim 15, wherein the UE is in radio resource control, RRC, connected mode while receiving the indication of the on-demand SIB 1 cell reselection priority and in RRC idle or inactive mode when performing measurements and determining to switch towards the second cell, wherein switching towards the second cell comprises cell reselection towards the second cell.

18. The method of any one of claims 15 to 17, wherein the on-demand SIB1 cell reselection priority of the second cell is different from a cell reselection priority of the second cell when not operating in SIB1 on-demand mode.

19. The method of any one of claims 15 to 18, wherein the indication of the on-demand SIB1 cell reselection priority is included in an on-demand SIB 1 configuration message for the second cell.

20. The method of claim 19, wherein the on-demand SIB1 configuration message comprises the on-demand SIB 1 cell reselection priority and at least one of a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell.

21. The method of claim 20, wherein the on-demand SIB1 configuration message further comprises an indication regarding the applicability of the on-demand SIB1 cell reselection priority.

22. The method of claim 21, wherein the indication regarding the applicability of the on- demand SIB 1 cell reselection priority indicates applicability to the PCI of the second cell and / or the frequency band deployed by the second cell.

23. The method of claim 19, wherein the on-demand SIB1 configuration message comprises a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell, and wherein receiving the on-demand SIB1 configuration message is an implicit instruction to the UE to perform the measurements.

24. The method of any one of claims 15 to 18, wherein the indication of the on-demand SIB1 cell reselection priority is included in a system information block, SIB, message.

25. The method of claim 24, wherein the SIB message comprises one or more SIB2 and / or SIB4 information elements defining the on-demand SIB1 cell reselection priority.

26. The method of claim 25, wherein the SIB message further comprises one or more SIB2 and / or SIB4 information elements defining a cell reselection priority for the second cell when not operating in SIB1 on-demand mode.

27. The method of any one of claims 15 to 26, wherein the measurements triggered at the UE are cell reselection measurements concerning at least one of signal received power and signal received quality of the second cell.

28. The method of any one of claims 15 to 27, wherein the determination to switch towards the second cell is further based on whether the second cell operates in on-demand SIB1 mode or not.

29. An apparatus of a user equipment, UE, supporting on-demand system information block 1, SIB1, mode operation and being served by a first cell, the apparatus supporting switching towards a second cell operating in an on-demand SIB1 mode and being configured to:- receive from the first cell an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell, wherein the on-demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell;- perform measurements with respect to the frequency band deployed by the second cell based on the on-demand SIB1 reselection priority; and- determine to switch towards the second cell based on results of the measurements.

30. The method of claim 29, wherein the UE is in in radio resource control, RRC, idle or inactive mode and camping on the first cell, wherein switching towards the second cell comprises cell reselection towards the second cell.

31. The method of claim 25, wherein the UE is in radio resource control, RRC, connected mode while receiving the indication of the on-demand SIB 1 cell reselection priority and in RRC idle or inactive mode when performing measurements and determining to switchtowards the second cell, wherein switching towards the second cell comprises cell reselection towards the second cell.

32. The apparatus of any one of claims 29 to 31, wherein the on-demand SIB1 cell reselection priority of the second cell is different from a cell reselection priority of the second cell when not operating in SIB1 on-demand mode.

33. The apparatus of any one of claims 29 to 32, wherein the indication of the on-demand SIB1 cell reselection priority is included in an on-demand SIB1 configuration message for the second cell.

34. The apparatus of claim 33, wherein the on-demand SIB1 configuration message comprises the on-demand SIB 1 cell reselection priority and at least one of a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell.

35. The apparatus of claim 34, wherein the on-demand SIB1 configuration message further comprises an indication regarding the applicability of the on-demand SIB1 cell reselection priority.

36. The apparatus of claim 35, wherein the indication regarding the applicability of the on- demand SIB 1 cell reselection priority indicates applicability to the PCI of the second cell and / or the frequency band deployed by the second cell.

37. The apparatus of claim 33, wherein the on-demand SIB1 configuration message comprises a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell, and wherein receiving the on-demand SIB1 configuration message is an implicit instruction to the UE to perform the measurements.

38. The apparatus of any one of claims 29 to 32, wherein the indication of the on-demand SIB1 cell reselection priority is included in a system information block, SIB, message.

39. The apparatus of claim 38, wherein the SIB message comprises one or more SIB2 and / or SIB4 information elements defining the on-demand SIB1 cell reselection priority.

40. The apparatus of claim 39, wherein the SIB message further comprises one or more SIB2 and / or SIB4 information elements defining a cell reselection priority for the second cell when not operating in SIB1 on-demand mode.

41. The apparatus of any one of claims 29 to 40, wherein the measurements are cell reselection measurements concerning at least one of signal received power and signal received quality of the second cell.

42. The method of any one of claims 29 to 41, wherein the determination to switch towards the second cell is further based on whether the second cell operates in on-demand SIB1 mode or not.

43. An apparatus of a first cell in a mobile communication system supporting switching of a user equipment, UE, towards a second cell operating in an on-demand system information block 1, SIB1, mode, wherein the UE is supporting on-demand SIB1 mode operation and being served by the first, the apparatus being configured to:- transmit an indication of an on-demand SIB1 cell reselection priority associated with a frequency band deployed by the second cell to the UE, wherein the on- demand SIB1 reselection priority is higher than the reselection priority associated with the frequency band deployed by the first cell; wherein the indication triggers, at the UE, measurements with respect to the frequency band deployed by the second cell based on the on-demand SIB 1 reselection priority and a determination to switch to towards the second cell based on results of the measurements.

44. The method of claim 43, wherein the UE is in in radio resource control, RRC, idle or inactive mode and camping on the first cell, wherein switching towards the second cell comprises cell reselection towards the second cell.

45. The method of claim 43, wherein the UE is in radio resource control, RRC, connected mode while receiving the indication of the on-demand SIB 1 cell reselection priority and in RRC idle or inactive mode when performing measurements and determining to switch towards the second cell, wherein switching towards the second cell comprises cell reselection towards the second cell.

46. The apparatus of any one of claims 43 to 45, wherein the on-demand SIB1 cell reselection priority of the second cell is different from a cell reselection priority of the second cell when not operating in SIB1 on-demand mode.

47. The apparatus of any one of claims 43 to 46, wherein the indication of the on-demand SIB1 cell reselection priority is included in an on-demand SIB1 configuration message for the second cell.

48. The apparatus of claim 47, wherein the on-demand SIB1 configuration message comprises the on-demand SIB 1 cell reselection priority and at least one of a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell.

49. The apparatus of claim 48, wherein the on-demand SIB1 configuration message further comprises an indication regarding the applicability of the on-demand SIB1 cell reselection priority.

50. The apparatus of claim 49, wherein the indication regarding the applicability of the on- demand SIB 1 cell reselection priority indicates applicability to the PCI of the second cell and / or the frequency band deployed by the second cell.

51. The apparatus of claim 47, wherein the on-demand SIB1 configuration message comprises a Physical Cell ID, PCI, of the second cell and the frequency band deployed by the second cell, and wherein receiving the on-demand SIB1 configuration message is an implicit instruction to the UE to perform the measurements.

52. The apparatus of any one of claims 43 to 46, wherein the indication of the on-demandSIB1 cell reselection priority is included in a system information block, SIB, message.

53. The apparatus of claim 52, wherein the SIB message comprises one or more SIB2 and / or SIB4 information elements defining the on-demand SIB1 cell reselection priority.

54. The apparatus of claim 53, wherein the SIB message further comprises one or more SIB2 and / or SIB4 information elements defining a cell reselection priority for the second cell when not operating in SIB1 on-demand mode.

55. The apparatus of any one of claims 43 to 54, wherein the measurements triggered at the UE are cell reselection measurements concerning at least one of signal received power and signal received quality of the second cell.

56. The method of any one of claims 43 to 54, wherein the determination to switch towards the second cell is further based on whether the second cell operates in on-demand SIB1 mode or not.

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