WO2025113878A1

WO2025113878A1 - Configuration of multiple signaling radio bearer sets

Info

Publication number: WO2025113878A1
Application number: PCT/EP2024/078997
Authority: WO
Inventors: Janne Veikko Kaasalainen; Malgorzata Tomala; Daniyal Amir AWAN; Guillaume DECARREAU; Tero Henttonen
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2023-11-30
Filing date: 2024-10-15
Publication date: 2025-06-05
Anticipated expiration: 2026-05-30

Abstract

An access node may be configured to: transmit, to a device, configurations of a plurality of signaling radio bearer (SRB) sets for a radio resource control connection, wherein the plurality of SRB sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of SRB sets comprises at least a first SRB set assigned to a primary cell of the plurality of cells and a second SRB set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first SRB set comprises a primary cell specific SRB set configuration, wherein a configuration of the second SRB set comprises a secondary cell specific SRB set configuration, and wherein the configurations of the plurality of SRB sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

Description

CONFIGURATION OF MULTIPLE SIGNALING RADIO BEARER SETS

TECHNICAL FIELD

[0001] Various example embodiments generally relate to the field of wireless communication. Some example embodiments relate to configuration of multiple signaling radio bearer (SRB) sets for a radio resource control (RRC) connection.

BACKGROUND

[0002] In wireless communications, access nodes of a cellular radio network may be configured to provide communication services to devices, such as user equipment (UE), via multiple cells associated with aggregated carriers or links to different access nodes. A radio resource control (RRC) protocol may be configured to enable connection establishment between a UE and the network. A signaling radio bearer may be configured for exchanging RRC data between the UE and the network.

SUMMARY

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

[0004] Example embodiments of the present disclosure enable to avoid unnecessary suspension of an RRC connection. This and other benefits may be achieved by the features of the independent claims. Further example embodiments are provided in the dependent claims, the description, and the drawings.

[0005] According to a first aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the receiver at least to: receive, from an access node, a configuration of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, and wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a first cell and a second signaling radio bearer set assigned to a second cell; communicate with the access node via the first cell using the first signaling radio bearer set; switch to the second signaling radio bearer set, based on detecting an event causing the first signaling radio bearer set to become unavailable at the first cell; communicate with the access node via the second cell using the second signaling radio bearer set.

[0006] According to a second aspect, a method is disclosed. The method may comprise: receiving, from an access node, a configuration of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, and wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a first cell and a second signaling radio bearer set assigned to a second cell; communicating with the access node via the first cell using the first signaling radio bearer set; switching to the second signaling radio bearer set, based on detecting an event causing the first signaling radio bearer set to become unavailable at the first cell; communicating with the access node via the second cell using the second signaling radio bearer set.

[0007] According to a third aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the receiver at least to: transmit, to a device, a configuration of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells; communicate radio resource control data with the device using a first signaling radio bearer set of the plurality of signaling radio bearer sets via a first cell; and switch communication of the radio resource control data to a second cell configured to use a second set of the plurality of signaling radio bearer sets for communicating the radio resource control data.

[0008] According to a fourth aspect, a method is disclosed. The method may comprise: transmitting, to a device, a configuration of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells; communicating radio resource control data with the device using a first signaling radio bearer set of the plurality of signaling radio bearer sets via a first cell; and switching communication of the radio resource control data to a second cell configured to use a second set of the plurality of signaling radio bearer sets for communicating the radio resource control data.

[0009] According to a fifth aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the receiver at least to: receive, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells; store a configuration of a first signaling radio bearer set of the plurality of signaling radio bearer sets as an active signaling radio bearer set configuration for the radio resource control connection; store a configuration of a second signaling radio bearer set of the plurality of signaling radio bearer sets as a candidate signaling radio bearer set configuration for the radio resource control connection; communicate radio resource control data with the access node via a first cell of the plurality of cells using the first signaling radio bearer set; activate the configuration of the second signaling radio bearer set, based on detecting an event causing the first signaling radio bearer set to become unavailable at the first cell; and communicate the radio resource control data via a second cell of the plurality of cells using the second signaling radio bearer set.

[0010] According to a sixth aspect, a method is disclosed. The method may comprise: receiving, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells; storing a configuration of a first signaling radio bearer set of the plurality of signaling radio bearer sets as an active signaling radio bearer set configuration for the radio resource control connection; storing a configuration of a second signaling radio bearer set of the plurality of signaling radio bearer sets as a candidate signaling radio bearer set configuration for the radio resource control connection; communicating radio resource control data with the access node via a first cell of the plurality of cells using the first signaling radio bearer set; activating the configuration of the second signaling radio bearer set, based on detecting an event causing the first signaling radio bearer set to become unavailable at the first cell; and communicating the radio resource control data via a second cell of the plurality of cells using the second signaling radio bearer set.

[0011] According to a seventh aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the receiver at least to: receive, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, and wherein the configurations of the plurality of signaling radio bearer sets comprise a configuration of a first signaling radio bearer set configured for instant activation by the device and a configuration of a second signaling radio bearer set configured to be activated by the device at a configured time; store the configuration of the first signaling radio bearer set as an active signaling radio bearer set configuration for the radio resource control connection; store the configuration of the second signaling radio bearer set a candidate signaling radio bearer set configuration for the radio resource control connection; communicate radio resource control data with the access node via a first cell using the first signaling radio bearer set; activate the configuration of the second signaling radio bearer set based on reaching the configured time; communicate the radio resource control data via a second cell using the second signaling radio bearer set.

[0012] According to an eighth aspect, a method is disclosed. The method may comprise: receiving, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, and wherein the configurations of the plurality of signaling radio bearer sets comprise a configuration of a first signaling radio bearer set configured for instant activation by the device and a configuration of a second signaling radio bearer set configured to be activated by the device at a configured time; storing the configuration of the first signaling radio bearer set as an active signaling radio bearer set configuration for the radio resource control connection; storing the configuration of the second signaling radio bearer set a candidate signaling radio bearer set configuration for the radio resource control connection; communicating radio resource control data with the access node via a first cell using the first signaling radio bearer set; activating the configuration of the second signaling radio bearer set based on reaching the configured time; communicating the radio resource control data via a second cell using the second signaling radio bearer set.

[0013] According to a ninth aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the receiver at least to: transmit, to a device, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, wherein the configurations of the plurality of signaling radio bearer sets comprise a configuration of a first signaling radio bearer set configured for instant activation by the device and a configuration of a second signaling radio bearer set configured to be activated by the device at a configured time; communicate radio resource control data with the device using the first signaling radio bearer set via a first cell; and switch communication of the radio resource control data to a second cell configured to use the second signaling radio bearer set for communicating the radio resource control data.

[0014] According to a tenth aspect, a method is disclosed. The method may comprise: transmitting, to a device, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, wherein the configurations of the plurality of signaling radio bearer sets comprise a configuration of a first signaling radio bearer set configured for instant activation by the device and a configuration of a second signaling radio bearer set configured to be activated by the device at a configured time; communicating radio resource control data with the device using the first signaling radio bearer set via a first cell; and switching communication of the radio resource control data to a second cell configured to use the second signaling radio bearer set for communicating the radio resource control data. [0015] According to an eleventh aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the receiver at least to: transmit, to a device, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a primary cell of the plurality of cells and a second signaling radio bearer set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein a configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the configurations of the plurality of signaling radio bearer sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

[0016] According to a twelfth aspect, a method is disclosed. The method may comprise: transmitting, to a device, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a primary cell of the plurality of cells and a second signaling radio bearer set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein a configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the configurations of the plurality of signaling radio bearer sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

[0017] According to a thirteenth aspect, an apparatus is disclosed. The apparatus may comprise: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the receiver at least to: receive, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a primary cell of the plurality of cells and a second signaling radio bearer set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein a configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the configurations of the plurality of signaling radio bearer sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

[0018] According to a fourteenth aspect, a method is disclosed. The method may comprise: receiving, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a primary cell of the plurality of cells and a second signaling radio bearer set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein a configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the configurations of the plurality of signaling radio bearer sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

[0019] According to a fifteenth aspect, an apparatus is disclosed. The apparatus may comprise means for performing the method according to the second, fourth, sixth, eighth, tenth, twelfth, or fourteenth aspect, or any example embodiment(s) thereof, as provided in the description and/or the claims.

[0020] According to a sixteenth aspect, a computer program, a computer program product, or a (non-transitory) computer-readable medium is disclosed. The computer program, computer program product, or (non-transitory) computer- readable medium may comprise instructions, which when executed by an apparatus, cause the apparatus at least to perform the method according to the second, fourth, sixth, eighth, tenth, twelfth, or fourteenth aspect, or any example embodiment(s) thereof, as provided in the description and/or the claims.

[0021] Example embodiments of the present disclosure can thus provide apparatuses, methods, computer programs, computer program products, or computer readable media for improving various aspects of wireless tethering. Any example embodiment may be combined with one or more other example embodiments. These and other aspects of the present disclosure will be apparent from the example embodiment(s) described below. According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.

DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and, together with the description, help to explain the example embodiments. In the drawings:

[0023] FIG. 1 illustrates an example of a communication network;

[0024] FIG. 2 illustrates an example of an apparatus configured to practice one or more example embodiments;

[0025] FIG. 3 illustrates an example of signalling and operations for configuring a carrier aggregation (CA) or dual connectivity (DC) scheme;

[0026] FIG. 4 illustrates an example of division of a signaling radio bearer (SRB) set to multiple SRB sets;

[0027] FIGs. 5a, 5b, and 5c illustrate an example of signalling and operations for configuring a carrier aggregation scheme with multiple signaling radio bearers;

[0028] FIG. 6 illustrates an example of a structure of parameters and active configurations for primary and secondary link in association with carrier aggregation; and

[0029] FIGs. 7 to 13 illustrate examples of methods for radio resource control. [0030] Like references are used to designate like parts in the accompanying drawings.

DETAILED DESCRIPTION

[0031] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0032] FIG. 1 illustrates an example of a communication network. Communication network 100 may comprise one or more access nodes 120, 122, 124. Access node(s) 120, 122, 124 may be part of a radio access network (RAN) configured to enable a device, represented throughout the description by UE 110, to access communication services provided by core network 140. In connection with communication network 100, access node(s) 120, 122, 124 and core network 140 may be collectively referred to as the ‘network’. UE 110 may comprise a user device, a terminal apparatus, a terminal device, a mobile device, or the like. UE 110 may be configured to communicate with access node(s) 120, 122, 124 over a radio interface, which may be also referred to as an air interface. Access nodes 120, 22, 124 may be also referred to as network devices. A terminal device may comprise a device to which a connection from a communication network is terminated.

[0033] The radio interface may be configured for example based on the 5G NR (New Radio) standard defined by the 3^rd Generation Partnership Project (3 GPP), or any future standard or technology (e.g., 6G). Access nodes 120, 122, 124 may comprise, for example, 5^th generation access nodes (gNB). Transmission by an access node to UE 110 may be called downlink (DL) transmission. Transmission by UE 110 to an access node may be called uplink (UL) transmission. UE 110 may be therefore configured to operate as a transmitter for uplink transmissions and as a receiver for downlink transmissions. Access node(s) 120, 122, 124 may be configured to operate as a receiver for uplink transmissions and as a transmitter for downlink transmissions. Communication network 100 may comprise a wireless communication network or a mobile communication network, such as for example a cellular communication network.

[0034] Core network 140 may be implemented with various network functions (NF), including, for example, one or more user plane functions (UPF) and one or more access and mobility management functions (AMF). A UPF may be configured to handle user data part of a communication session. A UPF may thus provide an interconnect point between the radio access network and a data network configured to provide application services to UE 110 via core network 140 and the radio access network. For example, a UPF may be configured to handle encapsulation and decapsulation of user plane protocol(s), such as the GPRS (general packet radio service) tunnelling protocol for the user plane (GTP-U). An AMF may be configured to receive connection and session request related data from UE 110 (e.g., via an access node). An AMF may be configured to control connection and mobility management in communication network 100.

[0035] An access node 120, 122, 124 may be configured to communicate with UE s via one or more cells. For example, access node 120 may be configured to serve UEs at cells 130-1 to 130- . Access node 122 may be configured to serve UEs at cells 132-1 to 132-Af. Access node 124 may be configured to serve UEs at cells 134-1 to 134-#. An access node may be configured to serve one or more cells so TV, M, and K may be positive integers. A cell may be configured to serve UEs at a certain geographical area at a certain radio frequency, or, a range of radio frequencies around a centre frequency of the cell.

[0036] Communication network 100 may be operated based on a protocol stack comprising a plurality of protocol layers. The protocol stack may be arranged based on the open systems interconnection (OSI) model or a layer model of a particular standard such as 3GPP 5G NR. As one example, the protocol stack may comprise a service data adaptation protocol (SDAP) layer, which may receive data from an application layer for transmission. The SDAP layer may be configured to exchange data with the packet data convergence (PDCP) layer. The PDCP layer may be responsible of generation of data bursts comprising one or more data packets, for example based on data obtained from the SDAP layer.

[0037] The PDCP layer may provide data to one or more instances of the radio link control (RLC) layer. For example, PDCP data may be transmitted on one or more RLC transmission legs. Each RLC instance may be associated with corresponding medium access control (MAC) instances of the MAC layer. The MAC layer may provide a mapping between logical channels of upper layer(s) and transport channels of the physical layer, handle multiplexing and demultiplexing of MAC service data units (SDU). Furthermore, the MAC layer may provide error correction functionality based on packet retransmissions, for example according to the hybrid automatic repeat request (HARQ) process. Physically separate transmission legs may be provided by the physical (PHY) layer, also known as Layer 1 (LI). Corresponding protocol stacks may be applied both at access nodes 120, 122, 124 and UE 110.

[0038] In a split access node architecture, part of the protocol layers may be implemented at a central unit (CU) of an access node, e.g., a gNB-CU, which may be configured to handle upper layers of the protocol stack, for example SDAP and PDCP layers. Furthermore, the central unit may be configured to handle radio resource control (RRC) operations. A central unit of an access node may be associated with, e.g., configured to control, one or more distributed units (DU) of the access node, e.g., gNB-DU, which may be configured to handle lower layers of the protocol stack, for example RLC, MAC, and LI. Radio unit(s) of the distributed unit(s) may be configured to transmit/receive data to/from UE(s) over the radio interface. A central unit may be referred to as a central node and a distributed unit may be referred to as a distributed node.

[0039] Radio resource control (RRC) of UE 110 may be implemented based on different radio resource control states. When UE 110 is powered up, it may be in a disconnected state or an idle state (e.g., RRC IDLE). UE 110 may enter or switch to a connected state (e.g., RRC CONNECTED) for example through connection establishment to the network. When UE 110 is in the connected state, UE 110 may have an RRC connection with the network and signaling radio bearer(s) may be configured to enable exchange of RRC data between UE 110 and the network. If UE 110 is not active for a certain time, UE 110 may suspend the RRC connection and change a state from the connected state to an inactive state (e.g., RRC INACTIVE). Suspending the RRC connection may therefore comprise transitioning from the connected state to the inactive state.

[0040] In the idle state, UE 110 may not be associated with an RRC context. From the network point of view there may not be a connection between the radio access network and core network 140 for UE 110. Therefore, UE 110 may not be able to communicate application data with the network. For example, UE 110 may be in a sleep-mode and only intermittently wake-up, for example for receiving paging messages. In the idle state, UE 110 may, however, perform cell re-selection and/or other idle state operations, for example.

[0041] In the connected state, UE 110 may be associated with an RRC context. In the connected state, UE 110 may communicate with core network 140 via the radio access network, for example access node 120. The RRC context may comprise parameters configured to enable UE 110 and the network, e.g., access node 120, to communicate RRC data. In the connected state, UE 110 may perform radio resource management (RRM) measurements, for example in relation to a mobility (handover) procedure. UE 110 may report its measurement results to the network (e.g., via access node 120). For example, the measurement results may be reported periodically and/or in response to detecting a reporting triggering criterion to be fulfilled.

[0042] In the inactive state, UE 110 may stay registered to the network, but the connection to the radio access network (e.g., access node 120) may be suspended. However, the radio access network may store the UE context, which enables the connection to be quickly resumed. The UE context may comprise parameters configured to enable UE 110 and the network, e.g., access node 120, to communicate user plane data (e.g., application data). Connection to the core network may be maintained.

[0043] RRC data may be configured to be delivered via signaling radio bearer(s) (SRB). SRB(s) may be specific type of a radio bearer(s) configured to carry signaling messages, e.g., RRC and/or non-access stratum (NAS) messages. Communication network 100 may be for example configured with the following SRBs:

- SRB0, which may be configured to carry RRC messages, for example using the common control channel (CCCH) logical channel.

- SRB1, which may be configured to carry RRC messages (e.g. including a piggybacked NAS message) and NAS messages prior to establishment of SRB2, for example using a downlink control channel (DCCH) logical channel.

- SRB2, which may be configured to carry NAS messages, for example using the DCCH logical channel. SRB2 may be associated with a lower priority than SRB1 and it may be configured by the network after security activation.

- SRB3, which may be configured to carry specific RRC messages when UE 110 is in EN-DC, referring to dual -connectivity between 5G NR and E-UTRA (evolved universal terrestrial radio access) access nodes, for example using the DCCH logical channel.

A combination of SRBs may be referred to as an SRB set. For example, the combination of SRB1 and SRB2 may be an SRB set. A set of SRB may however comprise a single SRB, such as SRB1.

[0044] Carrier Aggregation (CA) enables aggregating traffic to/from different radio frequency carriers. It enables UE 110 to transmit and/or receive combined data over multiple carriers, for example simultaneously. In carrier aggregation, there may be at least two serving cells between UE 110 and the network. One of the serving cells, e.g., cell 130-1, may be a primary cell (PCell) and the remaining cell(s), e.g., 13O-7V, may be secondary cell(s) (SCell). The serving cells (PCell, SCell) may share the same MAC entity, RLC entity and PDCP entity. A PCell may be tied with control plane related functionalities.

[0045] A cell-specific identifier, for example a cell radio network temporary identifier (C-RNTI), may be allocated to UE 110 in each of the serving cells. The C-RNTI may be a unique identifier used for identifying RRC connection and scheduling messages that are dedicated to a particular UE. Access node 120 may assign different C-RNTI values to different UEs. Access node 120 may use the C- RNTI to allocate UE 110 with uplink grants, downlink assignments, or the like. C- RNTI may be also used by access node 120 to distinguish uplink transmissions of UE 110 from transmissions of other UEs. C-RNTI is used throughout the description as an example of a cell-specific identifier of UE 110. The C-RNTI may be a physical layer identifier. For example, the C-RNTI may be configured to distinguish data of different users at a physical layer channel.

[0046] The radio resource control (RRC) layer of the PCell may be responsible for managing radio resources, for example the configuration and activation of carrier aggregation. The RRC layer may be configured to ensure that UE 110 is aware of the available carriers. The MAC layer may be configured to ensure that data is appropriately divided and scheduled across the different carriers, for example to maximize throughput and minimize latency.

[0047] In dual connectivity (DC), UE 110 may be configured to be simultaneously connected to two access nodes, for example access node 120 as a master node (MN) and access node 122 as a secondary node (SN). Cells served by the master node may belong to a master cell group (MCG), which may comprise a PCell and optionally one or more SCells of the carrier aggregation scheme. Cells served by the secondary node may belong to a secondary cell group (SCG), which may comprise another PCell (primary secondary cell, PSCell) and optionally one or more SCells of the carrier aggregation scheme. A cell-specific identifier (e.g., C- RNTI) may be allocated to UE 110 in each of the serving cells. In dual connectivity, UE 110 may be therefore configured to transmit/receive data via both access nodes, and optionally at multiple aggregated carriers at one access node or both of the access nodes. In general, aggregating data traffic in multiple carriers and/or allowing a multicarrier link for a UE in dual connectivity may be configured such that a primary connection (e.g., at PCell or MCG) is activated first. Additional cells may be then added on top of the primary connection.

[0048] In multi-connectivity, UE 110 may be configured to be simultaneously connected to two or more access nodes, for example access node 120 as a master node and access nodes 122, 124 as secondary nodes. UE 110 may be hence configured to communicate data via multiple cells served by different access nodes. Multi-connectivity may therefore comprise generalization of the dual connectivity scheme to more than two access nodes. Dual connectivity may be considered as an example of a multi -connectivity scheme. [0049] Communication network 100 may comprise other network function(s), network device(s), or protocol(s), in addition, or alternative to, those illustrated in FIG. 1. A network device may be configured to implement functionality of one or more network functions. Even though some embodiments have been described in the context of 5G, it is appreciated that embodiments of the present disclosure are not limited to this example network. Example embodiments may be therefore applied in any present or future communication networks. An apparatus, such as for example UE 110 or access node 120, may comprise, or be configured to implement, e.g., by means of software, one or more of the protocol layers described herein.

[0050] FIG. 2 illustrates an example of an apparatus configured to practice one or more example embodiments. Apparatus 200 may comprise a device such as UE 110, or an access node 120, 122, 124, an access point, a base station, a radio network node, or a split portion thereof (e.g., a central or distributed unit of an access node), a network device, a terminal device, or in general any apparatus configured to implement functionality described herein. Apparatus 200 may comprise at least one processor 202. The at least one processor 202 may comprise, for example, one or more of various processing devices, such as for example a co-processor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like.

[0051] Apparatus 200 may further comprise at least one memory 204. The memory 204 may be configured to store, for example, computer program code or the like, for example operating system software and application software. Memory 204 may comprise one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination thereof. For example, the memory may be embodied as magnetic storage devices (such as hard disk drives, magnetic tapes, etc.), optical magnetic storage devices, or semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.). Memory 204 is provided as an example of a (non-transitory) computer readable medium. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0052] Apparatus 200 may further comprise a communication interface 208 configured to enable apparatus 200 to transmit and/or receive information. Communication interface 208 may comprise an external communication interface, such as for example a radio interface between UE 110 and access node(s) 120, 122, 124, or a communication interface between a central unit and distributed unit(s) of an access node (e.g., an Fs-U and/or Fs-C interface). Communication interface 208 may comprise one or more radio transmitters or receivers, which may be coupled to one or more antennas or apparatus 200, or be configured to be coupled to one or more antennas external to apparatus 200.

[0053] Apparatus 200 may further comprise other components and/or functions such as a user interface (not shown) comprising at least one input device and/or at least one output device. The input device may take various forms such a keyboard, a touch screen, or one or more embedded control buttons. The output device may for example comprise a display, a speaker, or the like.

[0054] When apparatus 200 is configured to implement some functionality, some component and/or components of apparatus 200, such as for example the at least one processor 202 and/or the at least one memory 204, may be configured to implement this functionality. Furthermore, when the at least one processor 202 is configured to implement some functionality, this functionality may be implemented using program code 206 comprised, for example, in the at least one memory 204.

[0055] The functionality described herein may be performed, at least in part, by one or more computer program product components such as software components. According to an example embodiment, apparatus 200 comprises a processor or processor circuitry, such as for example a microcontroller, configured by the program code 206, when executed, to execute the embodiments of the operations and functionality described herein. Program code 206 is provided as an example of instructions which, when executed by the at least one processor 202, cause performance of apparatus 200.

[0056] Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include field-programmable gate arrays (FPGAs), applicationspecific integrated circuits (ASICs), application-specific standard products (ASSPs), system-on-a-chip systems (SOCs), complex programmable logic devices (CPLDs), graphics processing units (GPUs), or the like.

[0057] Apparatus 200 may be configured to perform, or cause performance of, method(s) described herein or comprise means for performing method(s) described herein. In one example, the means comprises the at least one processor 202, the at least one memory 204 including instructions (e.g., program code 206) configured to, when executed by the at least one processor 202, cause apparatus 300 to perform the method(s). In general, computer program instructions may be executed on means providing generic processing functions. Such means may be embedded for example in a personal computer, a smart phone, a network device, or the like. The method(s) may be thus computer-implemented, for example based algorithm(s) executable by the generic processing functions, an example of which is the at least one processor 202. The means may comprise transmission or reception means, for example one or more radio transmitters or receivers, which may be coupled or be configured to be coupled to one or more antennas. Apparatus 200 may comprise, for example, a network device, for example, an access node, an access point, a base station, or a central/distributed unit thereof. Although apparatus 200 is illustrated as a single device, it is appreciated that, wherever applicable, functions of apparatus 200 may be distributed to a plurality of devices.

[0058] FIG. 3 illustrates an example of signalling and operations for configuring carrier aggregation or dual connectivity in communication network 100. RRC procedures and operations may be configured on a cell level basis. Carrier aggregation and dual connectivity, which may be configured to be activated by RRC configurations, may be therefore configured to operate based on this principle. Carrier aggregation and dual connectivity may be therefore configured on cell level. Use of RRC procedures may be therefore tied to a cell identifier (cell id). This implies that even if UE 110 has multicarrier uplink or downlink configuration and UE 110 may be connected to multiple radios of different access nodes, it may still be configured with one primary/master RRC connection determining the success or failure of the logical RRC connection establishment. The RRC connection, also referred to as an RRC link, may be configured to apply the primary/master physical cell identifier (PCI) as a reference parameter, for example for RRC security, mobility, measurements, and/or failure detection.

[0059] In some cases the multiple carriers or links might have equal communication capabilities, but this may not be the case in general. Upon radio link failure (RLF) detection on the primary link, UE 110 may be configured to suspend operation (e.g., transition from the RRC connected state to the RRC inactive state) and report the failure to the network. When the multicarrier configuration is split to a master/primary cell and secondary cells, a handover or a release of primary cell(s) may lead to reconfiguration of the other cells associated with the primary cell(s). In this kind of setup, the RRC connection for UE 110 may be unnecessarily disconnected. After reconfiguration, UE 110 might be even configured again with the same carrier configuration, at least partially. This situation is illustrated in FIG. 3, where access node 120 (e.g., a gNB) is configured to serve Cells 1 to 3.

[0060] At operation 301, UE 110 may transmit, to access node 120 via Cell 1, a request for establishing an RRC connection to the network, for example as an RRC setup request.

[0061] At operation 302, access node 120 may transfer necessary messages with AMF 142 for establishing the RRC connection.

[0062] At operation 303, access node 120 may transmit a configuration of SRB1 to UE 110 via Cell 1, for example in an RRC setup message.

[0063] At operation 304, access node 120 and AMF 142 may perform UE context setup, in order to setup a UE context for UE 110.

[0064] At operation 305, access node 120 and UE 110 may perform a security setup via Cell 1.

[0065] At operation 306, access node 120 and UE 110 may perform RRC reconfiguration via Cell 1 to configure SRB2 for UE 110. In this example, UE 110 is configured with at least SRB1 and SRB2. UE 110 is configured with SRB set. In the example of FIG. 3, one SRB set comprising SRB1 and SRB2 may be configured, by the access node, for the RRC connection. [0066] At operation 307, access node 120 may perform transfer of messages with AMF 142.

[0067] At operation 308, access node 120 may trigger carrier aggregation or dual connectivity for UE 110, resulting in addition of another carrier aggregated cell and/or a cell served by another access node (e.g., access node 122) for UE 110.

[0068] At operation 309, access node 120 and UE 110 may perform RRC reconfiguration via Cell 1 to add PSCell(s) and/or a secondary cell group (SCG) for UE 110.

[0069] At operation 310, UE 110 may detect a radio link failure (RLF) for Cell 1. UE 110 may be for example configured to detect the radio link failure based on measurements. For example, UE 110 may be configured to detect the RLF based on at least one of detecting measured reference signal received power (RSRP) to be below a threshold, failing to decode the physical downlink control channel (PDCCH), or failing to decode the physical downlink shared channel (PDSCH).

[0070] At operation 311, UE 110 may suspend the SRB(s) and synchronize to Cell 1.

[0071] At operation 312, UE 110 may detect the PCell or MCS. There may be however some recovery time for reconfigurations before detecting the PCell or MCG.

[0072] At operation 313, UE 110 may transmit an RRC re-establishment request to access node 120 via Cell 1 using SRB1.

[0073] Since UE 110 is configured with a single connection for handling the RRC connection, UE 110 may need perform a synchronized reconfiguration procedure to re-establish the RRC connection, resulting in interruption of the communication between UE 110 and the network. Example embodiments of the present disclosure enable multiple carriers or links to handle the same RRC connection, for example in order to enable changing the RRC connection to another (physical) cell or to use another cell (e.g., physical cell) for the RRC connection without a synchronized reconfiguration procedure. This provides the benefit of enabling to avoid unnecessary RRC connection interruptions, for example during radio link failures or intra-access node handovers, as will be further described below. [0074] FIG. 4 illustrates an example of division of a signaling radio bearer (SRB) set to multiple SRB sets. In this example, SRB1 and SRB2 are used as an example of an SRB set, but it is noted that an SRB set may generally include any number of SRBs. Both SRB1 and SRB2 may be configured to carry data. In general, SRB1 and SRB2 may be configured to be communicated via a primary connection (e.g., via PCell or PSCell). The SRBs may be however split to different cells configured for UE 110, for example due to carrier aggregation and/or dual connectivity, in order to generate a robust multicarrier RRC connection. For example, the SRB set comprising SRB1 and SRB2 may be split into two SRB sets, where a first SRB set (SRB set “a”) comprises SRB la and SRB2a and a second SRB set (SRB set “b”) comprises SRB lb and SRB2b. These split SRBs may be referred to as sub-SRBs. Note that a sub-SRB (e.g., SRBla) may be configured to carry all data of the respective SRB (e.g., SRB1) when that sub-SRB is active. The sub-SRBs may be therefore configured to provide alternative routes for delivering the SRB data. The sub-SRBs may be associated with dedicated C-RNTIs. The sub-SRBs may be however associated with the same logical channel identifier. A logical channel may comprise a MAC layer channel.

[0075] RRC may be associated to a per-carrier SRB (e.g., one SRB per carrier), which may be configured to carry the data using any radio resources (e.g., physical resources such as time-frequency resources) configured for UE 110 for that carrier. This may be enabled by the split of the SRB(s) to the per-carrier sub-SRBs, where each sub-SRB may be associated with one carrier. Note that the carriers may be provided by different access nodes, for example in case of dual connectivity or multi -connectivity. The sub-SRBs may be also re-associated between carriers. For example, a particular sub-SRB may be first configured for a first carrier (e.g., a first aggregated carrier of a first cell) and then re-associated to another carrier (e.g., a second aggregated carrier of a second cell). Re-associating an SRB set may comprise releasing the SRB set from one carrier and assigning it to another carrier. The RRC connection may be maintained continuously. For example, when reassociating the SRB set a first carrier to third carrier a second carrier having an SRB set may be used for the RRC connection. Each sub-SRB may be associated with a C-RNTI. Even if using the term ‘sub-SRB’, the SRBs configured at the different cells may be considered to be separate SRBs configured to be activated when needed.

[0076] Configuring multiple SRB sets for a single RRC connection at different cells provides various benefits. When UE 110 has an RRC connection established with the network, UE 110 may be initially linked to access node 120 through a single SRB set. Example embodiments of the present disclosure enable establishing separate SRB sets, also referred to as sub-SRBs, for different carriers, for example with dedicated UE identifiers such as C-RNTIs. Note that the RRC connection may be active on one of the SRB sets. Access node 120 (e.g., the user plane) may be configured to scramble the RRC data using the C-RNTI mapped to that SRB set. A current RRC connection, which may be associated with one of the SRB sets (e.g. SRB la and SRB2a), can be retained and transferred to a new indicated SRB set (e.g., SRB lb & SRB2b), without suspending the RRC connection. This may be enabled by switching the RRC context from the currently active SRB set to another SRB set. The other SRB set or the new SRB set (e.g., SRB lb & SRB2b) may be configured to serve as RRC connection back-up for the currently active SRB set (e.g., SRBla & SRB2a). The C-RNTIs of the SRB sets may be also the same until it is changed due to security reasons. The switch to the other SRB set may be configured to be triggered by a radio link failure at the cell associated with the currently active SRB set, or triggered by an intra-access node inter-cell handover. Both UE 110 and the network may be configured with information about the SRB sets (e.g., their existence or parameters). The PDCP configuration for both UE and access node 120 may remain unchanged, but the logical channel (LCH) and/or logical channel group (LCG) configurations (e.g., at MAC/RLC) may be different. This enables the change in the serving cell due to radio link failure or handover to be done without a synchronized RRC reconfiguration procedure. This enables UE 110 to handle radio link failures and mobility without UE-network connection interruptions. Note that when the RRC connection is configured to be carried over multiple carriers and both the old (previous) and the new configurations are associated with RRC connection capable carriers, and when the RRC connection handling entity (e.g., gNB or gNB-CU) does not change, there is no need for UE 110 to perform any synchronized reconfiguration procedures. [0077] For example, when a central unit (CU) of access node 120 (e.g., gNB-CU) configures PDCP for UE message, it may use a control plane security key to configure the needed security. The security anchor point may however remain in the central unit, even if the serving cell for UE 110 were to change due to an intraaccess node handover. Therefore, the security configuration may be configured not to change at the central unit. In some approaches, UE 110 may be configured with one set of SRBs, such as SRB1 and SRB2 , which may be, for example, assigned to a primary cell. Each of the SRB sets may have their own PDCP entity and RLC bearer. In this case, UE 110 could use the primary cell to monitor quality of the SRB connection and to trigger a radio link failure, resulting in suspension of the RRC connection due to quality of the primary radio link not being sufficient. A drawback of such an approach might be that the RRC connection could get unnecessarily suspended, if the other carriers still had sufficient radio link quality. [0078] In contrast to such approaches, example embodiments of the present disclosure enable UE 110 to be configured with multiple sets of SRBs for a single RRC connection. UE 110 may be also configured to use the multiple SRB sets for radio link failure monitoring. An SRB set may be assigned to one carrier, e.g., one cell. UE 110 may be configured to consider the multiple SRB sets as equivalent in terms of radio link failure monitoring. UE 110 may be therefore configured to perform radio link failure monitoring based on evaluation of the available SRB sets such that a connection failure for one SRB set triggers switch to another SRB set and not declaration of a radio link failure to the network. Hence, if one of the SRB sets fails, UE 110 may be configured to use another, or any, of the remaining sets for communicating RRC data using the same RRC connection (e.g., non-suspended RRC connection).

[0079] Evaluation of the quality of the RRC connection may be therefore extended to preconfigured equivalent sets of SRBs. Therefore, a radio link failure for one SRB set does not lead to UE configuration suspension. Instead, UE 110 may be configured to switch communication associated with the RRC connection to another SRB set, which may be preconfigured by the network, without communicating the failure to the network. Triggering of a recovery procedure for the RRC connection at the network side may be hence avoided. [0080] The same approach may be used also during intra-access node handovers. During a handover to a new cell, UE 110 may be configured to switch to a secondary SRB set and continue communicating the RRC data on the second SRB set. Internal mobility within an access node may be therefore handled via carrier additions and removals without interruption of the UE-network connection (e.g., the RRC connection). Based on signaling the configurations of the SRB sets to UE 110, both UE 110 and network may be made aware of the possibility to communicate data of the RRC connection via multiple links (e.g., SRB sets of different cells). UE 110 may therefore stay connected to the network even if only one of the SRB sets is available.

[0081] Considering internal communication within units of an access node (e.g., CU-to-DU communication), the central unit may be configured to indicate the used (e.g., active) SRB set to the distributed unit. Based on this indication the distributed unit, which may be configured to process lower protocol layers of the access node, may perform cyclic redundancy check (CRC) code scrambling of data transmitted to UE 110 with the correct C— RNTI. UE 110 may be configured to either listen to multiple (e.g., all) configured C-RNTIs at corresponding cells, or, to listen to a specific C-RNTI per cell. Based on the C-RNTI, UE 110 may be configured to determine whether it is receiving a SRB. Example embodiments of the present disclosure will be further described with reference to FIGs 5a, 5b, and 5c.

[0082] FIGs. 5a, 5b, and 5c illustrate an example of signalling and operations for configuring a carrier aggregation scheme with multiple signaling radio bearers. It is noted that even though the procedure is described using carrier aggregation as an example of establishing multiple SRB sets at respective cells, similar functionality may be applied also whenever a single RRC connection is associated with multiple cells, for example in case of dual connectivity or multi -connectivity. Even though certain operations have been described to be performed by central unit (CU) 120-1 or a distributed unit (DU) 120-2 or of access node 120 (cf., gNB-CU and gNB-DU), it is understood that similar functionality may be performed by any suitable network device, or a unit thereof. Access node 120 may be configured to collectively perform operations of CU 120-1 and DU 120-2. Alternatively, an access node may be configured to perform operations of either CU 120-1 or DU 120-2. [0083] At operation 501, UE 110 may transmit, to DU 120-2 via Cell 1, a request for establishing an RRC connection to the network, for example as an RRC setup request.

[0084] At operation 502, DU 120-2 may transmit information about the received request to establish the RRC connection to CU 120-1, for example by initial uplink (UL) RRC message transfer.

[0085] At operation 503, CU 120-1 may transmit a configuration of a first SRB (‘SRBla’) to DU 120-2, for example by downlink (DL) RRC message transfer. SRB la may be associated with Cell 1. SRBla may be associated with a first C— RNTI, or in general, an identifier of UE 110 at Cell 1. CU 120-1 may configure SRBla, cell, and C-RNTI mapping to the RRC Setup message. At this point, SRBla may be referred to as the first SRB set. Further SRB(s), for example SRB lb, may be then added to the first SRB set.

[0086] At operation 504, DU 120-2 may transmit the configuration of SRBla to UE 110 via Cell 1, for example in an RRC setup message. DU 120-1 may transmit the configuration of SRBla as a configuration of the first SRB set to UE 110 via SRB1, using the first C-RNTI. UE 110 may therefore receive the configuration of SRBla. UE 110 may also receive the first C-RNTI as an identifier of SRBla. A configuration message, e.g. RRC message, e.g. RRC setup message, may comprise or be indicative of a mapping between sub-SRBs and C-RNTIs per carrier.

[0087] At operation 505, UE 110 may store the configuration of SRBla as a configuration of the first SRB set. An SRB set may comprise one or a plurality of SRBs. UE 110 may store the configuration of SRBla as an active SRB set configuration. For example, UE 110 may store the configuration of SRBla in an RRC active context.

[0088] At operation 506, UE 110 may transmit, to DU 120-2, an indication of completion of the configuration of SRBla, for example as an indication of completion of the RRC setup in general. UE 110 may transmit the indication by, for example, an RRC setup complete message (e.g., initial message).

[0089] At operation 507, UE 110 may inform CU 120-1 about the completion of the RRC setup, for example by UL RRC message transfer. [0090] At operation 508, CU 120-1 may transmit an initial context setup request to AMF 142. AMF 142 may establish a UE context for UE 110 accordingly.

[0091] At operation 509, AMF 142 may transmit an initial context setup message to CU 120-1. The initial context setup message may be provided to add a second SRB, e.g. SRB2a, to the first SRB set and to associate it with Cell 1. CU 120-1 may determine to add SRB2a to the first SRB set, in response to receiving the initial context setup message.

[0092] At operations 510 and 511, CU 120-1 and DU 120-2 may perform a UE context setup, for example by exchanging UE context setup request 510 and UE context setup response 511 messages.

[0093] At operations 512 and 513, DU 120-2 and UE 110 may perform a security setup via Cell 1, for example by exchanging RRC security mode command 512 and RRC security mode complete 513 messages.

[0094] At operation 514, DU 120-2 may inform CU 120-1 about completion of the security setup, for example by UL RRC message transfer.

[0095] At operation 515, CU-120-1 may transmit an indication of mapping of SRB2a to the first SRB set associated with Cell 1, for example by DL RRC message transfer.

[0096] At operation 516, DU 120-2 may transmit a reconfiguration of the first SRB set indicative of the addition of SRB2a to the first SRB set. DU 120-2 may transmit the reconfiguration via SRB la, for example as an RRC reconfiguration (DBR) message.

[0097] At operation 517, UE 110 may store the configuration of SRB2a in the configuration of the first SRB set. For example, UE 110 may append SRB2a to the RRC active context as part of the first SRB set. The stored configuration of the first SRB set (SRB set “a”) may therefore comprise configurations of SRB la and SRB2a, which may be configured for Cell 1. SRB la and SRB2a may be therefore associated with same C-RNTI.

[0098] Continuing the procedure with reference to FIG. 5b, at operation 518 UE 110 may transmit, to DU 120-2, an indication of completion of the configuration of SRB2a, for example as an RRC reconfiguration complete message. UE 110 may transmit the indication using SRB 1 a. UE 110 may transmit the indication via Cell 1. [0099] At operation 519, DU 120-2 may inform CU 120-1 about the completion of the configuration of SRB2a at UE 110, for example by UL RRC message transfer.

[0100] At operation 520, carrier aggregation may be triggered. Carrier aggregation for UE 110 may be triggered by access node 120, for example CU 120- 1. CU 120-1 may determine to add the new carrier (e.g., Cell 2). When the added carrier(s) have the needed capability for uplink and downlink, e.g., to carry independent RRC connection, CU 120-1 may allocate a second C-RNTI and map the second C-RNTI to SRBlb and SRB2b as a second SRB set (SRB set ‘b’). CU 120-1 may map the associated configuration message to SRB la of the first SRB set (SRB set ‘a’), which is to be transmitted using the C-RNTI of UE 110 at Cell 1 (first C-RNTI) on the lower layers of user plane protocols.

[0101] At operation 521, CU 120-1 may transmit, to DU 120-2, a request to add a new carrier (e.g., Cell 2) for UE 110 with addition of the second SRB set (SRB set ‘b’), for example as a UE context setup request. The request may include the configuration of the second SRB set (SRBlb, SRB 2b).

[0102] At operation 522, DU 120-2 may acknowledge the request to add the new carrier (e.g., Cell 2) and the second SRB set for UE 110, for example by transmitting a UE context setup response message to CU 120-1.

[0103] At operation 523, CU 120-1 may transmit the configuration of the second SRB set to DU 120-2, for example by DL RRC message transfer. CU 120-1 may be configured to indicate, e.g., in the same message, that the configuration of the second SRB set is to be delivered via the first SRB set (SRB set ‘a’).

[0104] At operation 524, DU 120-2 may transmit the configuration of the second SRB set to UE 110, for example as an RRC reconfiguration request. The configuration may comprise mapping of the second SRB set (SRBlb, SRB2b) to Cell 2. DU 120-2 may transmit the configuration of the second SRB set using the first SRB set, for example SRB la. DU 120-2 may therefore transmit the configuration of the second SRB set via Cell 1, using the C-RNTI of UE 110 at Cell 1 (first C-RNTI) For example, DU 120-2 may scramble the associated CRC code(s) with the first C-RNTI. This enables UE 110 to identify data addressed to UE 110 at Cell 1. [0105] UE 110 may therefore receive the configuration of the second SRB set from DU 120-2 via Cell 1. UE 110 may identify data addressed to it by descrambling CRC(s) of the received data by the C-RNTI of UE 110 at Cell 1 (first C-RNTI). Considering operations 504 and/or 516, UE 110 may receive configurations of a plurality of SRB sets, e.g., the first SRB set comprising SRB la and SRB2a (SRB set ‘a’) and the second SRB set comprising SRBlb and SRB2b (SRB set ‘b’). The different SRB sets may be associated with different cells. The different SRB sets may be associated with different C-RNTIs, as defined by the SRB set configurations. UE 110 may therefore receive, from DU 120-2, identifiers of the SRB sets. Each of the identifiers may be associated with one of the SRB sets. [0106] In this example, the first SRB set is associated with Cell 1 (e.g., allocated with radio transmission resources at Cell 1) and the second SRB set is associated with Cell 2 (e.g., allocated with radio transmission resources at Cell 2). UE 110 may be associated with a first C-RNTI at Cell 1 and a second C-RNTI at Cell 2. The second C-RNTI may be different from the first C-RNTI. Considering, for example, operations 516, 518, and/or 524, UE 110 may be configured to communicate (e.g., transmit and/or receive) RRC data with DU 120-2 using the first SRB set (e.g., SRB la). In case of carrier aggregation, Cell 1 may be a PCell (or PSCell) and Cell 2 may be an SCell. The SRB set of a PCell may be called a primary SRB set. Even though two SRB sets associated with two cells have been described in this example, it is understood that UE 110 may be generally configured with a plurality (e.g., two, three, four,. . .) of SRB sets associated with a plurality of cells (e.g., one SRB set for each cell).

[0107] In one example, access node 120 may be configured to change the C— RNTI with a polling, uplink grant, or with a timer. Access node 120 may be for example configured to reconfigure a second prime (e.g., an SRB set of a second primary cell) to be taken into use after particular time and to start polling UE 110 until UE 110 responds via access node 120 with a new C-RNTI. In this case, the RRC layer of UE 110 may be configured to start using the second SRB set for RRC messaging when reaching the particular time. Access node 120 and UE 110 may be configured to repeat the RRC message(s) after the change until both sides use the new C— RNTI. One of the configurations of the SRB sets may be therefore configured for instant activation by UE 110. Instant activation of a new SRB configuration may comprise activation of the new SRB set configuration substantially upon reception of the new configuration, for example before activating any other SRB configurations. It is however noted that RRC data may be momentarily communicated with a current SRB set between reception of the new SRB configuration and completion of the instant activation of the new SRB set. For example, RRC data already configured for transmission with the current SRB set may still be communicated with the current SRB set, until the instant activation of the new SRB set is effected by generation of RRC for transmission on the new SRB set. Other configuration(s) of the SRB set(s) may be configured to be activated by a configured time (e.g., after a configured time period from receiving the configuration), which may be indicated in the configuration of the SRB set. For example, the configuration of the first SRB set may be configured for instant activation by UE 110. The configuration of the second SRB set may be configured to be activated by UE 110 at the configured time. UE 110 may be configured to activate the configuration of the second SRB set based on reaching the configured time, for example in response to determining that the configured time period has lapsed from reception of the configuration. The configured time may therefore comprise an absolute time or a relative time, for example with respect to reception time of the configuration.

[0108] Access node 120 may be configured to transmit a polling request to UE 110, in order to request UE 110 to indicate an identifier (e.g., C-RNTI) of the SRB set that is currently active at UE 110. UE 110 may be configured to respond to the polling request. UE 110 may be for example configured to transmit an indication of the currently active SRB set to access node 120. UE 110 may be for example configured to transmit RRC data to access node 120 with the currently active C- RNTI. Access node 120 may be configured to switch communication to a cell associated with the new C-RNTI. Access node 120 may be for example configured to switch communication of the RRC data to Cell 2, in response to receiving from UE 110 RRC data with the C-RNTI of the second SRB set as a response to the polling request. [0109] The polling mechanism enables access node 120 to change the C-RNTI associated with an SRB set (e.g., sub-SRB). The polling mechanism may comprise the network (e.g., access node 120) sending an uplink grant associated with the new C-RNTI to UE 110. Access node 120 may be configured to prompt a response from UE 110 or configure UE 110 with a timer. In the latter case, UE 119 may be configured with a timer associated with the C-RNTI change. Upon expiry of the timer, UE 110 is required to be ready for operation with the new C-RNTI. No additional procedures may be required. Also, a combination of the prompting and timer based approaches may be used. For example, access node 120 may be configured to poll UE 110 even before expiry of the timer. UE 110 might however respond by an indication of not being ready if the change of C-RNTI is still underway.

[0110] For the case when the change occurs for a primary SRB (e.g., SRB la), the procedure may be configured as follows:

[OHl] Access node 120 may reconfigure UE 110 with an additional primary SRB set (e.g., SRBla’) for a carrier, e.g., by transmission of a reconfiguration message comprising a configuration of the primary SRB set. The configuration may contain a timer, after which the procedure (e.g., the change of C-RNTI) is required to be ready and/or instructions on how to treat the current primary SRB after the procedure. In one example, UE 110 may be configured to change the previous SRBla to become SRB lb and SRBla’ to become becomes SRBla. The previous primary SRB may therefore becomes a sub-SRB (e.g., a non-active SRB). UE 110 may be configured just to changes the configuration. In one example, UE 110 may be configured to drop the previous SRBla and change SRBla’ to become SRBla. UE 110 may change primary SRB and drop the previous configuration of the primary SRB.

[0112] RRC layer of UE 110 may then apply the new sub-SRB configuration and start to use it for RRC messaging.

[0113] The network (e.g., access node 120) may then start polling UE 110 (e.g. based on expiry of the timer), for example by sending uplink grants associated with the new C-RNTI. Once UE 110 replies to the uplink grant associated with the new C-RNTI (e.g., addressed to the new primary SRB), the network (e.g., access node 120) may determine that the new primary SRB has been taken into use. Both access node 120 and UE 110 may be configured to repeat the message. For example, the network (e.g., access node 120) may be configured to repeat the polling. UE 110 may be configured to repeat transmission of the polling response after the change until both sides are using the new C-RNTI.

[0114] In one example, the RRC configuration for the primary RRC connection may be activated in later phase, e.g., as described above. In this case, UE 110 may be configured to keep one RRC connection active but have a second RRC connection waiting for lower layer activation.

[0115] At operation 525, UE 110 may store the configuration of the second SRB set (SRB lb, SRB 2b). UE 110 may store the configuration of SRB lb and SRB2b as a candidate SRB set configuration for the same RRC connection, e.g., as established in operations 501 to 504. For example, UE 110 may store the configuration of SRB lb and SRB2b in an RRC candidate context. The RRC candidate context may be also referred to as a pending RRC context or a fallback RRC context. If UE 110 receives further configurations of SRB sets for further cell(s), e.g., Cell 3, UE 110 may store such SRB set configurations as other candidate SRB set configurations. In general, UE 110 may store a plurality of SRB set configurations. UE 110 may store one of the SRB set configurations as an active configuration and the other SRB set configurations as candidate configurations. For example, UE 110 may store the first SRB set as an active SRB set and the second SRB set, optionally with further SRB sets, as candidate SRB set(s).

[0116] At operation 526, UE 110 may initiate radio link failure monitoring of the cells associated with the active SRB set configuration and the candidate SRB set configuration(s). Initiating the radio link failure monitoring of the cells may be based on (e.g., in response to) receiving the configurations of the SRB sets. Radio link failure monitoring may comprise evaluating radio link quality of the active SRB set and the candidate SRB set(s). For example, based on receiving the configuration of the second SRB set, UE 110 may initiate radio link failure monitoring for the carrier of the second SRB set at Cell 2 similar to the carrier of the first SRB set at Cell 1. The radio link failure monitoring, also referred to as radio link monitoring (RLM), may be configured as follows. [0117] If the radio link quality of Cell 1, which is in this example the serving cell associated with the first SRB set, does not meet predetermined condition(s), UE 110 may determine that there is a radio link failure for the first SRB set (e.g., a primary SRB set). The predetermined condition(s) may include, for example, minimum requirements to classify the radio link as usable or acceptable (e.g., UE 110 not detecting to be out of synchronization or detecting downlink radio link quality on configured radio resources to be above a predefined threshold, for example within an evaluation period).

[0118] The determination of the radio link failure may however remain internal to UE 110. For example, UE 110 may be configured to not to communicate radio link failures associated with individual cells to the network. Hence, triggering an RRC connection re-establishment or recovery procedure may be avoided, if UE 110 has other SRB sets configured in addition to the SRB set for which the radio link failure was detected. In this case, UE 110 may be configured not to suspend operation. Instead, UE 110 may be configured to switch to another configured SRB set, e.g., the second SRB set previously configured as a candidate SRB set. Switching from the first SRB set to the second SRB set may be therefore without suspending the RRC connection. Suspension of the RRC connection may comprise any operation that requires UE 110 to perform a synchronized reconfiguration procedure in order to re-establish the RRC connection. When switching to the second SRB set, UE 110 may be configured to activate the second SRB set configuration. UE 110 may be further configured to deactivate the first SRB set configuration.

[0119] UE 110 may be configured to select the second SRB set configuration for activation from the candidate SRB configurations based on a configured order (e.g., sequence) of SRB sets. UE 110 may receive the configuration of the order of SRBs from DU 120-2. The order may define a priority order for selecting the SRB set configuration to be activated from the candidate SRB set configurations. UE 110 may be therefore configured to switch between preconfigured SRB sets according to a preconfigured sequence defined by the network. The sequence may for example indicate the second SRB set to be replaced by the first SRB set, if the first SRB set becomes unavailable to UE 110. [0120] Optionally, UE 110 may be configured to determine whether the radio link quality (e.g., downlink radio link quality) for the second SRB set, or in general any of the candidate SRB sets, is acceptable before switching to it. If there is any candidate SRB set for which the evaluation is passed positively (e.g., no radio link failure is detected), UE 110 may switch to that candidate SRB set, for example start using it as a primary SRB set.

[0121] Evaluating the radio link quality of the candidate SRB sets may comprise determining whether the radio link quality for UE 110 (e.g., downlink radio link quality) on radio transmission resources configured for a particular candidate SRB set exceeds a predefined threshold, for example within a certain evaluation period. UE 110 may be configured to evaluate radio link quality of the candidate SRB sets and select one (e.g., the one with best radio link quality) of the candidate SRB configurations to be activated. UE 110 may be configured to perform the evaluation and/or the selection based on detecting the radio link failure at Cell 1. UE 110 may be configured to perform activation of the second SRB set configuration, or in general one of the candidate SRB set configurations, based on detecting the radio link failure at Cell 1.

[0122] Alternatively, if the evaluation of the radio link quality fails for the SRBs sets configured for UE 110 for the RRC connection, UE 110 may be configured to declare the radio link failure to the network, for example by transmitting an indication of the radio link failure to DU 120-2. UE 110 may be therefore configured to transmit the indication of the radio link failure to DU 120-2, in response to determining that radio link quality of none of the SRBs configured for UE 110 meet the condition(s).

[0123] In general, UE 110 may be configured to switch to the second SRB set based on detecting an event causing the first SRB set to become unavailable at the first cell. Radio link failure at Cell 1 is one example of such an event. Other examples of such an event include handover of UE 110 from Cell 1 (e.g., an intraaccess node handover among cells served by DU 120-2 or other DUs associated with CU 1201) or a release of Cell 1 for UE 110. UE 110 may be configured to perform the evaluation of the radio link quality of the candidate SRB sets and/or the selection of the candidate SRB set configuration to be activated based on detecting the event (e.g., radio link failure, intra-access node handover, or release). UE 110 may be configured to activate the second SRB set configuration, or in general one of the candidate SRB set configurations, based on detecting the event. [0124] At operation 527, UE 110 may transmit, to DU 120-2, an indication of completion of the configuration of the second SRB set (SRB lb, SRB 2b), for example as an RRC reconfiguration complete message. UE 110 may transmit the indication using SRB la. In this case, UE 110 may transmit the indication via Cell 1 using the first C-RNTI. Alternatively, UE 110 might transmit the indication using SRBlb. In this case, UE 110 may transmit the indication via Cell 2 using the second C-RNTI.

[0125] At operation 528, DU 120-2 may inform CU 120-1 about the completion of the configuration of the second SRB set at UE 110, for example by UL RRC message transfer.

[0126] At operation 529, access node 120 (e.g., CU 120-1 and/or DU 120-2) may trigger a handover type of function, where one SRB set, which may be also referred to as an RRC carrying carrier, is removed and another SRB set is added, for example by a single reconfiguration message. Since UE 110 is configured with multiple SRB sets, this change may be done without a synchronized handover procedure. UE 110 may therefore continuously maintain the RRC connection to the network.

[0127] At operation 530, CU 120-1 may transmit to DU 120-2 a request to add a new aggregated carrier, in this example Cell 3, for UE 110 with addition of a third SRB set (SRB set ‘c’), for example as a UE context setup request. The request may also indicate removal of the first SRB set. The request may therefore comprise a request to replace the first SRB set with the third SRB set.

[0128] At operation 531, DU 120-2 may acknowledge the request received at operation 530, for example as a UE context setup response message.

[0129] Continuing the procedure with reference to FIG. 5c, at operation 532, CU 120-1 may transmit the configuration of the third SRB set and the request to remove the first SRB set to DU 120-2, for example by DL RRC message transfer. CU 120-1 may be configured to indicate, e.g., in the same message, that the configuration of the third SRB set and the removal of the first SRB set are to be indicated via the second SRB set (SRB set ‘b’) and Cell 2. [0130] At operation 533, DU 120-2 may transmit the configuration of the third SRB set and the request to remove the first SRB set to UE 110, for example as an RRC reconfiguration request. The configuration of the third SRB set may comprise mapping of the third SRB set to Cell 3 and a respective C-RNTI. DU 120-2 may transmit the configuration of the third SRB set and the request to remove the first SRB set using the second SRB set, for example SRBlb. DU 120-2 may therefore transmit the configuration of the third SRB set and the request to remove the first SRB set via Cell 2 using the C-RNTI of UE 110 at Cell 2 (second C-RNTI).

[0131] As an alternative to adding the third SRB set and removing the first SRB set, the configuration may comprise an indication of re-association of the first SRB set with Cell 3. The first SRB set may be therefore configured to be associated with a third C-RNTI applicable for UE 110 at Cell 3. SRBs may be therefore reassociated between carriers and each carrier may be associated with a different C— RNTI. In this case, the configuration may comprise a request to remove Cell 1 from the first SRB set and to add Cell 3 for the first SRB set (SRB la, SRB2a).

[0132] UE 110 may therefore receive, from DU 120-2 via Cell 2, one or more of the following: the configuration of the third SRB set, the request to remove of the first SRB set, or the configuration comprising the re-association of the first SRB set from Cell 1 to Cell 3. UE 110 may identify data addressed to it at Cell 2 by descrambling CRC(s) of the received data by the C-RNTI of UE 110 at Cell 2 (second C-RNTI).

[0133] When receiving RRC data on the SRB sets, UE 110 may be configured to apply the C-RNTIs configured for the different SRB sets to receive RRC data on the active SRB set. For example, UE 110 may be configured to apply both the first and the second C-RNTI (e.g., as associated with Cell 1 and Cell 2), to identify data addressed to UE 110 at the first SRB set. Similarly, UE 110 may be configured to apply both the first and the second C-RNTI to identify data addressed to UE 110 at the second SRB set. In general, UE 110 may be configured to receive the RRC data on the first SRB set by applying multiple identifiers to the first SRB set, for example, to descramble CRC(s) of the RRC data with multiple C-RNTIs (e.g., all C-RNTIs configured for the different SRB sets). UE 110 may be configured to receive the RRC data on the second SRB set by applying the multiple identifiers to the second SRB set. UE 110 may be for example configured to read all configured C-RNTIs on each SRB set. This enables UE 110 to read the RRC data without considering the allocation on the C-RNTIs to specific carriers, which simplifies operation ofUE 110.

[0134] Alternatively, UE 110 may be configured to apply the C-RNTIs configured for the SRB sets on a per-carrier basis. For example, UE 110 may be configured to determine, e.g., based on the mapping between the first C-RNTI and the first SRB set, as indicated in operation 504, to read RRC data in the first SRB based on the carrier specific C-RNTI of Cell 1, in this example the first C-RNTI. Similarly, UE 110 may be configured to read RRC data on the second SRB set based on the carrier specific C-RNTI of Cell 2, in this case the second C-RNTI. UE 110 may be therefore configured to receive the radio resource control data based on applying one of the C-RNTIs to the active SRB set (e.g., first SRB set or the second SRB set). This provides the benefit of simplifying monitoring of an SRB set, because application of multiple C-RNTIs may be avoided.

[0135] At operation 534, UE 110 may replace the currently active SRB set, in this example the second SRB set, with another SRB set from the candidate SRB set(s). UE 110 may adjust used radio transmission resources according to the new SRB set.

[0136] At operation 535, UE 110 may transmit, to DU 120-2, an indication of completion of the configuration of the third SRB set or the re-association of the first SRB set with Cell 3, for example as an RRC reconfiguration complete message. UE 110 may transmit the indication using SRBlb via Cell 2. UE 110 may therefore communicate RRC data via Cell 2 using the second SRB set. Communication of the RRC data via Cell 2 may be subsequent to switching from the first SRB set to the second SRB set. For example, at operation 533 UE 110 may receive RRC data (e.g., RRC reconfiguration request) using the second SRB set. At operation 535, UE 110 may transmit RRC data (e.g., RRC reconfiguration complete message) via the second SRB set. The data communicated via the second SRB set may be associated with the same RRC connection as the RRC data communicated using the first SRB set (cf., operations 516, 518, 524, 527).

[0137] At operation 536, UE 110 may detect a radio link failure for Cell 2. [0138] At operation 537, UE 110 may transmit, to DU 120-2, measurement results of Cell 2. The measurement report may comprise measurement result data, for example included in one or more information elements (IE) of the measurement report. The measurement report may comprise an indication of an SRB set that is not working (e.g., unavailable to UE 110), for example in another information element. The measurement report may comprise indication of Cell 2, which may be configured as a second primary cell, not being available to UE (e.g., out of use). UE 110 may therefore indicate to the network that the RRC connection is not working via the second SRB set connected to Cell 2. UE 110 may therefore switch to using the SRB set connected to Cell 3 (e.g., the first SRB set, if re-associated to Cell 3, or the third SRB set). UE 110 may continue to use the SRB set connected to Cell 3 for any SRB communication without any breaks or need for reconfigurations.

[0139] At operation 538, DU 120-2 may remove Cell 2 as a non-working cell. Even though Cell 2 is removed from the configuration, DU 120-2 may continue to use the SRB set connected to Cell 3 to communicate RRC data with UE 110.

[0140] FIG. 6 illustrates an example of a structure of parameters and active configurations for primary and secondary links in association with carrier aggregation. UE 110 may be configured to store and manage the SRB set configuration by separating the SRB set configurations that may need synchronization from other configurations. For example, UE 110 may be configured to assign activated contexts (e.g., SRB sets) a primary or secondary connection (e.g., PCell or SCell) and append them with a carrier aggregation context. The carrier aggregation context may be common for different SRB sets. The carrier aggregation context or carrier aggregation configuration may comprise parameters configured for communicating via aggregated carriers.

[0141] On the left, there are role-specific parts of the configurations, for which a role change does not change synchronization. A role may refer to the role of a particular cell in the carrier aggregation scheme (e.g., primary or secondary cell). The role-specific configurations may include configurations for primary (PCell) and secondary cells (SCell) of the carrier aggregation scheme. On the right, there is the carrier configuration of the carrier aggregation scheme, which may be common for the primary and secondary cells. UE 110 may be configured to synchronize to this part of the configuration. The common part of the configuration may be configured not to change if the role of the cell changes.

[0142] For example, the configuration of the first SRB set may comprise a primary cell specific SRB set configuration, which may be a role-specific configuration. The configuration of the second SRB set may comprise a secondary cell specific SRB set configuration, which may be another role-specific configuration. The configurations of the first and second SRB sets may however comprise a common configuration of the carrier scheme, which may not be specific to the role of the cell as a primary or secondary cell. When activating the configuration of the second SRB set, UE 110 may be configured to activate the secondary cell specific SRB set configuration and maintain the common configuration of the CA scheme. This provides the benefit of simplifying implementation of switching between different SRBs configured for the same RRC connection.

[0143] Using the above format of the SRB set specific configurations for a carrier in RRC context, it is possible to separate SRB specific configuration that needs synchronization from the remaining configurations. Therefore, when UE 110 performs internal synchronization for a secondary cell (e.g., second SRB set), the role-specific primary carrier configuration may be replaced by the role-specific part of the SRB set configuration of the second SRB set. UE 110 may be configured to perform cell synchronization with a non-role-specific configuration. When performing a role change, UE 110 may take the role configuration into use, which may be different from an actual synchronization procedure. Internal synchronization may comprise UE 110 configuring lower protocol layers with the role specific configuration.

[0144] Access node 120 may be configured to transmit, e.g., at operations 504 and/or 516, a configuration of a first SRB set, which may be assigned to the primary cell (e.g., Cell 1). This configuration may comprise a primary cell specific SRB set configuration for UE 110. Access node 120 may be further configured to transmit, e.g., at operation 524 a configuration of a second SRB set, which may be assigned to a secondary cell (e.g., Cell 2). This configuration may comprise a secondary cell specific SRB set configuration for UE 110. As carrier aggregation is a configured at this point, this configuration may further comprise a common configuration of the carrier aggregation scheme for the primary cell and the secondary cell. UE 110 and access node 120 may be configured to switch between different SRB set, as described above. However, switching the communication of the RRC data form one cell and SRB set to another (e.g., from the primary cell to the secondary cell) may comprise activating the new SRB set configuration (e.g., the secondary cell specific SRB set configuration) and maintaining the common configuration of the carrier aggregation scheme.

[0145] The RRC configuration may be split to a common carrier configuration part that may be kept the same in case of role activation (e.g., activating communication of RRC data at a particular SRB set). When UE 110 makes the synchronization for the common carrier configuration part, it does not need to perform resynchronization or random access channel (RACH) procedure when a secondary cell is changing its role to carry the RRC connection. When the above activation is used, UE 110 may take the role specific configuration (e.g., primary cell or secondary cell specific configuration) into use and can still keep the previous configuration in case the role is changed back.

[0146] FIG. 7 illustrates an example of a method 700 for radio resource control, according to Example embodiment 1 of method 700. Method 700 may be performed by a device, e.g., UE 110, or by a control apparatus configured to control the functioning thereof, when installed therein.

[0147] At operation 701, the method may comprise receiving, from an access node, a configuration of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, and wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a first cell and a second signaling radio bearer set assigned to a second cell.

[0148] At operation 702, the method may comprise communicating with the access node via the first cell using the first signaling radio bearer set.

[0149] At operation 703, the method may comprise switching to the second signaling radio bearer set, based on detecting an event causing the first signaling radio bearer set to become unavailable at the first cell. [0150] At operation 704, the method may comprise communicating with the access node via the second cell using the second signaling radio bearer set.

[0151] Method 700 may be performed, for example, according to any of the following example embodiments:

[0152] Example embodiment 2: Method 700 according to Example embodiment 1, wherein receiving the configuration of the plurality of signaling radio bearer sets comprises: receiving a configuration of the second signaling radio bearer set via the first signaling radio bearer set.

[0153] Example embodiment 3: Method 700 according to Example embodiment 1 or 2, wherein the switching to the second signaling radio bearer set is without suspension of the radio resource control connection.

[0154] Example embodiment 4: Method 700 according to any of Example embodiments 1 to 3, wherein the instructions are configured to, when executed by the at least one processor, cause the device to: receive, from the access node, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

[0155] Example embodiment 5: Method 700 according to Example embodiment 4, further comprising: receiving radio resource control data based on applying the plurality of identifiers to the first signaling radio bearer set; and/or receiving radio resource control data based on applying the plurality of identifiers to the second signaling radio bearer set.

[0156] Example embodiment 6: Method 700 according to Example embodiment 4, further comprising: receiving radio resource control data based on applying one of the plurality of identifiers to the first signaling radio bearer set or the second signaling radio bearer set.

[0157] Example embodiment 7: Method 700 according to any of Example embodiments 4 to 6, wherein the plurality of identifiers comprise cellspecific physical layer identifiers of the device.

[0158] Example embodiment 8: Method 700 according to any of Example embodiments 1 to 7, wherein the plurality of identifiers comprise cell radio network temporary identifiers of the device. [0159] Example embodiment 9: Method 700 according to any of Example embodiments 1 to 8, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

[0160] Example embodiment 10: Method 700 according to any of Example embodiments 1 to 9, wherein the first cell comprises a primary cell of a carrier aggregation scheme and the second cell comprises a secondary cell of the carrier aggregation scheme

[0161] Example embodiment 11 : Method 700 according to any of Example embodiments 1 to 10, wherein the plurality of cells comprise cells served by different access nodes.

[0162] Example embodiment 12: Method 700 according to any of Example embodiments 1 to 11, wherein the first cell comprises a master cell of a dual -connectivity or multi -connectivity and the second cell comprises a secondary cell of the dual -connectivity or multi -connectivity scheme, wherein the dualconnectivity or multi -connectivity scheme comprises connections between the device and a plurality of access nodes.

[0163] Example embodiment 13: Method 700 according to any of Example embodiments 1 to 12, further comprising: initiating radio link monitoring of the plurality of cells based on receiving the configuration of the plurality of signaling radio bearer sets for the radio resource control connection or based on receiving a configuration of the second signaling radio bearer set via the first signaling radio bearer set.

[0164] Example embodiment 14: Method 700 according to any of Example embodiments 1 to 13, wherein the event comprises a radio link failure associated with the first cell, an intra-access node handover from the first cell, or a release of the first cell.

[0165] Example embodiment 15: Method 700 according to any of Example embodiments 1 to 13, further comprising: receiving an indication of a reassociation of the first signaling radio bearer set with a third cell of the plurality of cells; and re-associating the first signaling radio bearer set with the third cell of the plurality of cells. [0166] Example embodiment 16: Method 700 according to any of Example embodiments 1 to 14, further comprising: transmitting, to the access node, a request for establishing the radio resource control connection.

[0167] FIG. 8 illustrates an example of a method 800 for radio resource control, according to Example embodiment 17. Method 800 may be performed by an access node, a unit thereof, or by a control apparatus configured to control the functioning thereof, when installed therein.

[0168] At operation 801, the method may comprise transmitting, to a device, a configuration of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells.

[0169] At operation 802, the method may comprise communicating radio resource control data with the device using a first signaling radio bearer set of the plurality of signaling radio bearer sets via a first cell.

[0170] At operation 803, the method may comprise switching communication of the radio resource control data to a second cell configured to use a second set of the plurality of signaling radio bearer sets for communicating the radio resource control data.

[0171] Method 800 may be performed, for example, according to any of the following example embodiments:

[0172] Example embodiment 18: Method 800 according to Example embodiment 17, wherein the second cell is configured to be served by the access node, and wherein the switching of the communication of the radio resource control data to the second cell comprises initiating, by the access node, the communication of the radio resource control data via the second cell.

[0173] Example embodiment 19: Method 800 according to Example embodiment 17, wherein the second cell is configured to be served by another access node, and wherein the switching of the communication of the radio resource control data to the second cell comprises transferring, by the access node, a radio resource control context of the device to the other access node.

[0174] Example embodiment 20: Method 800 according to any of Example embodiments 17 to 19, wherein the switching of the communication of the radio resource control data to the second cell is without suspension of the radio resource control connection.

[0175] Example embodiment 21 : Method 800 according to any of Example embodiments 17 to 20, further comprising: transmitting, to the device, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

[0176] Example embodiment 22: Method 800 according to Example embodiment

21, wherein the plurality of identifiers comprise cell-specific physical layer identifiers of the device.

[0177] Example embodiment 23 : Method 800 according to Example embodiment

22, wherein the plurality of identifiers comprise cell radio network temporary identifiers of the device.

[0178] Example embodiment 24: Method 800 according to any of Example embodiments 17 to 23, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

[0179] Example embodiment 25: Method 800 according to any of Example embodiments 17 to 24, wherein the first cell comprises a primary cell of a carrier aggregation scheme and the second cell comprises a secondary cell of the carrier aggregation scheme

[0180] Example embodiment 26: Method 800 according to any of Example embodiments 16 to 25, wherein the plurality of cells comprise cells served by different access nodes.

[0181] Example embodiment 27: Method 800 according to any of Example embodiments 17 to 26, wherein the first cell comprises a master cell of a dualconnectivity or multi -connectivity and the second cell comprises a secondary cell of the dual -connectivity or multi -connectivity scheme, wherein the dualconnectivity or multi -connectivity scheme comprises connections between the device and a plurality of access nodes

[0182] Example embodiment 28: Method 800 according to any of Example embodiments 17 to 27, further comprising: transmitting, to the device, an indication of a re-association of the first signaling radio bearer set with a third cell of the plurality of cells, in response to determining the first cell to become unavailable to the device.

[0183] Example embodiment 29: Method 800 according to any of Example embodiments 17 to 28, wherein the access node comprises a distributed access node unit, the method further comprising: receiving, form a central access node unit, an indication of the re-association of the first signaling radio bearer set with a third cell of the plurality of cells; and transmitting an indication of the re-association of the first signaling radio bearer set with a third cell of the plurality of cells to the device. [0184] Example embodiment 30: Method 800 according to any of Example embodiments 17 to 29, further comprising: receiving, from the device, a request for establishing the radio resource control connection.

[0185] Example embodiment 31 : Method 800 according to any of Example embodiments 17 to 30, wherein transmitting the configurations of the plurality of signaling radio bearer sets comprises: transmitting a configuration of the second signaling radio bearer set via the first signaling radio bearer set.

[0186] FIG. 9 illustrates an example of a method 900 for radio resource control, according to Example embodiment 1 of method 900. Method 900 may be performed by a device, e.g., UE 110, or by a control apparatus configured to control the functioning thereof, when installed therein.

[0187] At operation 901, the method may comprise receiving, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells.

[0188] At operation 902, the method may comprise storing a configuration of a first signaling radio bearer set of the plurality of signaling radio bearer sets as an active signaling radio bearer set configuration for the radio resource control connection.

[0189] At operation 903, the method may comprise storing a configuration of a second signaling radio bearer set of the plurality of signaling radio bearer sets as a candidate signaling radio bearer set configuration for the radio resource control connection. [0190] At operation 904, the method may comprise communicating radio resource control data with the access node via a first cell of the plurality of cells using the first signaling radio bearer set.

[0191] At operation 905, the method may comprise activating the configuration of the second signaling radio bearer set, based on detecting an event causing the first signaling radio bearer set to become unavailable at the first cell.

[0192] At operation 906, the method may comprise communicating the radio resource control data via a second cell of the plurality of cells using the second signaling radio bearer set.

[0193] Method 900 may be performed, for example, according to any of the following example embodiments:

[0194] Example embodiment 2: Method 900 according to Example embodiment 1, further comprising: deactivating the configuration of the first signaling radio bearer set, based on detecting the event causing the first signaling radio bearer set to become unavailable at the first cell.

[0195] Example embodiment 3 : Method 900 according to Example embodiment 1 or 2, further comprising: storing a plurality of candidate signaling radio bearer sets comprising the second signaling radio bearer set as candidate signaling radio bearer sets for the radio resource control connection; evaluating radio link quality of the plurality of candidate signaling radio bearer sets; and activating the second signaling radio bearer set based on the evaluation of the radio link quality of the plurality of candidate signaling radio bearer sets.

[0196] Example embodiment 4: Method 900 according to Example embodiment 3, further comprising: evaluating radio link quality of the plurality of signaling radio bearer sets; and transmitting, to the access node, an indication of a radio link failure, in response to determining that radio link quality of none of the plurality of signaling radio bearer sets meets a condition.

[0197] Example embodiment 5: Method 900 according to any of Example embodiments 1 to 4, wherein the deactivation of the first signaling radio bearer set and the activation of the second signaling radio bearer set is without suspension of the radio resource control connection. [0198] Example embodiment 6: Method 900 according to any of Example embodiments 1 to 5, wherein the plurality of signaling radio bearer sets are associated with same logical channel identifier.

[0199] Example embodiment 7: Method 900 according to any of Example embodiments 1 to 6, further comprising: receiving, from the access node, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

[0200] Example embodiment 8: Method 900 according to Example embodiment 7, further comprising: receiving the radio resource control data based on applying the plurality of identifiers to the first signaling radio bearer set; and/or receiving the radio resource control data based on applying the plurality of identifiers to the second signaling radio bearer set.

[0201] Example embodiment 9: Method 900 according to Example embodiment 7, further comprising: receiving the radio resource control data based on applying one of the plurality of identifiers to the first signaling radio bearer set or the second signaling radio bearer set.

[0202] Example embodiment 10: Method 900 according to any of Example embodiments 7 to 9, wherein the plurality of identifiers comprise cell-specific physical layer identifiers of the device.

[0203] Example embodiment 11: Method 900 according to any of Example embodiments 7 to 9, wherein the plurality of identifiers comprise cell radio network temporary identifiers of the device.

[0204] Example embodiment 12: Method 900 according to any of Example embodiments 1 to 11, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

[0205] Example embodiment 13: Method 900 according to any of Example embodiments 1 to 12, wherein the first cell comprises a primary cell of a carrier aggregation scheme and the second cell comprises a secondary cell of the carrier aggregation scheme.

[0206] Example embodiment 14: Method 900 according to Example embodiment 13, wherein the configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein the configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the plurality of configurations comprise a common configuration of the carrier aggregation scheme for the primary cell and the secondary cell.

[0207] Example embodiment 15: Method 900 according to any of Example embodiments 1 to 14, wherein the activation of the configuration of the second signaling radio bearer set comprises activating the secondary cell specific signaling radio bearer set configuration and maintaining the common configuration of the carrier aggregation scheme.

[0208] Example embodiment 16: Method 900 according to any of Example embodiments 1 to 15, wherein the plurality of cells comprise cells served by different access nodes.

[0209] Example embodiment 17: Method 900 according to any of Example embodiments 1 to 16, wherein the first cell comprises a master cell of a dualconnectivity or multi -connectivity scheme and the second cell comprises a secondary cell of the dual -connectivity or multi -connectivity scheme, wherein the dual -connectivity or multi-connectivity scheme comprises connections between the device and a plurality of access nodes.

[0210] Example embodiment 18: Method 900 according to any of Example embodiments 1 to 17, further comprising: initiating radio link monitoring of the plurality of cells based on receiving the configurations of the plurality of signaling radio bearer sets for the radio resource control connection.

[0211] Example embodiment 19: Method 900 according to any of Example embodiments 1 to 18, wherein the event comprises a radio link failure associated with the first cell, an intra-access node handover from the first cell, or a release of the first cell.

[0212] Example embodiment 20: Method 900 according to any of Example embodiments 1 to 19, further comprising: receiving an indication of a re-association of the first signaling radio bearer set with a third cell of the plurality of cells; and re-associating the first signaling radio bearer set with the third cell of the plurality of cells. [0213] Example embodiment 21: Method 900 according to any of Example embodiments 1 to 20, further comprising: transmitting, to the access node, a request for establishing the radio resource control connection.

[0214] Example embodiment 22: Method 900 according to any of Example embodiments 1 to 21, wherein the radio resource control connection is associated with a single radio resource control entity at the device.

[0215] Example embodiment 23: Method 900 according to any of Example embodiments 1 to 22, wherein the device is a user equipment.

[0216] Example embodiment 24: Method 900 according to any of Example embodiments 1 to 23, wherein the user equipment comprises at least one antenna for communicating the radio resource control data with the access node.

[0217] FIG. 10 illustrates an example of a method 1000 for radio resource control, according to Example embodiment 1 of method 1000. Method 1000 may be performed by an access node, a unit thereof, or by a control apparatus configured to control the functioning thereof, when installed therein.

[0218] At operation 1001, the method may comprise receiving, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, and wherein the configurations of the plurality of signaling radio bearer sets comprise a configuration of a first signaling radio bearer set configured for instant activation by the device and a configuration of a second signaling radio bearer set configured to be activated by the device at a configured time.

[0219] At operation 1002, the method may comprise storing the configuration of the first signaling radio bearer set as an active signaling radio bearer set configuration for the radio resource control connection.

[0220] At operation 1003, the method may comprise storing the configuration of the second signaling radio bearer set a candidate signaling radio bearer set configuration for the radio resource control connection.

[0221] At operation 1004, the method may comprise communicating radio resource control data with the access node via a first cell using the first signaling radio bearer set. [0222] At operation 1005, the method may comprise activating the configuration of the second signaling radio bearer set based on reaching the configured time.

[0223] At operation 1006, the method may comprise communicating the radio resource control data via a second cell using the second signaling radio bearer set.

[0224] Method 1000 may be performed, for example, according to any of the following example embodiments:

[0225] Example embodiment 2: Method 1000 according to Example embodiment

1, further comprising: deactivating the configuration of the first signaling radio bearer set based on reaching the configured time.

[0226] Example embodiment 3: Method 1000 according to Example embodiment

2, wherein the deactivation of the first signaling radio bearer set and the activation of the second signaling radio bearer set is without suspension of the radio resource control connection.

[0227] Example embodiment 4: Method 1000 according to any of Example embodiments 1 to 3, further comprising: receiving, from the access node, a polling request for indicating an identifier of a currently active signaling radio bearer set; and responding to the polling request by transmitting radio resource control data with the identifier of the currently active signaling radio bearer set.

[0228] Example embodiment 5: Method 1000 according to Example embodiment 4, wherein the identifier of the currently active signaling radio bearer set comprises a cell-specific physical layer identifier of the device.

[0229] Example embodiment 6: Method 1000 according to Example embodiment 4 or 5, wherein the identifier of the currently active signaling radio bearer set comprises a cell radio network temporary identifier of the device.

[0230] Example embodiment 7: Method 1000 according to Example embodiments 1 to 6, further comprising: receiving, from the access node, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

[0231] Example embodiment 8: Method 1000 according to Example embodiment 7, wherein the plurality of identifiers comprise cell-specific physical layer identifiers of the device. [0232] Example embodiment 9: Method 1000 according to Example embodiment 7 or 8, wherein the plurality of identifiers comprise cell radio network temporary identifiers of the device.

[0233] Example embodiment 10: Method 1000 according to any of Example embodiments 1 to 9, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

[0234] Example embodiment 11: Method 1000 according to any of Example embodiments 1 to 10, wherein the first cell comprises a primary cell of a carrier aggregation scheme and the second cell comprises a secondary cell of the carrier aggregation scheme.

[0235] Example embodiment 12: Method 1000 according to any of Example embodiments 1 to 12, wherein the plurality of cells comprise cells served by different access nodes.

[0236] Example embodiment 13: Method 1000 according to any of Example embodiments 1 to 12, wherein the first cell comprises a master cell of a dualconnectivity or multi -connectivity and the second cell comprises a secondary cell of the dual -connectivity or multi -connectivity scheme, wherein the dualconnectivity or multi -connectivity scheme comprises connections between the device and a plurality of access nodes

[0237] FIG. 11 illustrates an example of a method 1100 for radio resource control, according to Example embodiment 14 of method 1100. Method 1100 may be performed by an access node, a unit thereof, or by a control apparatus configured to control the functioning thereof, when installed therein.

[0238] At operation 1101, the method may comprise transmitting, to a device, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells, wherein the configurations of the plurality of signaling radio bearer sets comprise a configuration of a first signaling radio bearer set configured for instant activation by the device and a configuration of a second signaling radio bearer set configured to be activated by the device at a configured time. [0239] At operation 1102, the method may comprise communicating radio resource control data with the device using the first signaling radio bearer set via a first cell.

[0240] At operation 1103, the method may comprise switching communication of the radio resource control data to a second cell configured to use the second signaling radio bearer set for communicating the radio resource control data.

[0241] Method 1100 may be performed, for example, according to any of the following example embodiments:

[0242] Example embodiment 15: Method 1100 according to Example embodiment 14, further comprising: transmitting, to the device, a polling request for indicating an identifier of a currently active signaling radio bearer set at the device; and switching communication of the radio resource control data to the second cell, in response to receiving, from the device, radio resource control data associated with an identifier of the second signaling radio bearer set as a response to the polling request.

[0243] Example embodiment 16: Method 1100 according to Example embodiment 15, wherein the identifier of the currently active signaling radio bearer set comprises a cell-specific physical layer identifier of the device.

[0244] Example embodiment 17: Method 1100 according to Example embodiment 15 or 16, wherein the identifier of the currently active signaling radio bearer set comprises a cell radio network temporary identifier of the device.

[0245] Example embodiment 18: Method 1100 according to any of Example embodiments 14 to 17, further comprising: transmitting, to the device, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

[0246] Example embodiment 19: Method 1100 according to Example embodiment 18, wherein the plurality of identifiers comprise cell-specific physical layer identifiers of the device.

[0247] Example embodiment 20: Method 1100 according to Example embodiment 18 or 19, wherein the plurality of identifiers comprise cell radio network temporary identifiers of the device. [0248] Example embodiment 21: Method 1100 according to any of Example embodiments 14 to 20, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

[0249] Example embodiment 22: Method 1100 according to any of Example embodiment 14 to 21, wherein the first cell comprises a primary cell of a carrier aggregation scheme and the second cell comprises a secondary cell of the carrier aggregation scheme.

[0250] Example embodiment 23: Method 1100 according to any of Example embodiments 14 to 22, wherein the plurality of cells comprise cells served by different access nodes.

[0251] Example embodiment 24: Method 1100 according to any of Example embodiments 14 to 23, wherein the first cell comprises a master cell of a dualconnectivity or multi -connectivity and the second cell comprises a secondary cell of the dual -connectivity or multi -connectivity scheme, wherein the dualconnectivity or multi -connectivity scheme comprises connections between the device and a plurality of access nodes

[0252] FIG. 12 illustrates an example of a method 1200 for radio resource control, according to Example embodiment 1 of method 1200. Method 1200 may be performed by an access node, a unit thereof, or by a control apparatus configured to control the functioning thereof, when installed therein.

[0253] At operation 1201, the method may comprise transmitting, to a device, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a primary cell of the plurality of cells and a second signaling radio bearer set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein a configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the configurations of the plurality of signaling radio bearer sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

[0254] Method 1200 may be performed, for example, according to any of the following example embodiments:

[0255] Example embodiment 2: Method 1200 according to Example embodiment

1, further comprising: communicating radio resource control data with the device using the first signaling radio bearer set via the primary cell; and switching communication of the radio resource control data to the secondary cell configured to use the second signaling radio bearer set for communicating the radio resource control data.

[0256] Example embodiment 3: Method 1200 according to Example embodiment

2, wherein switching the communication of the radio resource data to the secondary cell comprises activating the secondary cell specific signaling radio bearer set configuration and maintaining the common configuration of the carrier aggregation scheme.

[0257] Example embodiment 4: Method 1200 according to any of Example embodiments 1 to 3, further comprising: transmitting, to the device, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

[0258] Example embodiment 5: Method 1200 according to Example embodiment 4, wherein the plurality of identifiers comprise cell-specific physical layer identifiers of the device.

[0259] Example embodiment 6: Method 1200 according to Example embodiment 4 or 5, wherein the plurality of identifiers comprise cell radio network temporary identifiers of the device.

[0260] Example embodiment 7: Method 1200 according to any of Example embodiments 1 to 6, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

[0261] Example embodiment 8: Method 1200 according to any of Example embodiments 1 to 7, wherein transmitting the configurations of the plurality of signaling radio bearer sets comprises: transmitting the configuration of the second signaling radio bearer set via the first signaling radio bearer set.

[0262] FIG. 13 illustrates an example of a method 1300 for radio resource control, according to Example embodiment 9 of method 1300. Method 1300 may be performed by an access node, a unit thereof, or by a control apparatus configured to control the functioning thereof, when installed therein.

[0263] At operation 1301, the method may comprise receiving, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a primary cell of the plurality of cells and a second signaling radio bearer set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein a configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the configurations of the plurality of signaling radio bearer sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

[0264] Method 1300 may be performed, for example, according to any of the following example embodiments:

[0265] Example embodiment 10: Method 1300 according to Example embodiment 9, further comprising communicating radio resource control data with the access node using the first signaling radio bearer set via the primary cell; and switching communication of the radio resource control data to the secondary second cell configured to use the second signaling radio bearer set for communicating the radio resource control data, based on detecting an event causing the first signaling radio bearer set to become unavailable at the primary cell.

[0266] Example embodiment 11: Method 1300 according to Example embodiment 10, wherein the switching of the communication of the radio resource data to the secondary cell comprises activating the secondary cell specific signaling radio bearer set configuration and maintaining the common configuration of the carrier aggregation scheme.

[0267] Example embodiment 12: Method 1300 according to Example embodiment 10 or 11, wherein the switching of the communication of the radio resource data to the secondary cell is without suspension of the radio resource control connection.

[0268] Example embodiment 13: Method 1300 according to any of Example embodiments 9 to 12, further comprising: deactivating the configuration of the first signaling radio bearer set, based on detecting the event causing the first signaling radio bearer set to become unavailable at the primary cell.

[0269] Example embodiment 14: Method 1300 according to any of Example embodiments 9 to 13, further comprising: receiving, from the access node, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

[0270] Example embodiment 15: Method 1300 according to Example embodiment 14, wherein the plurality of identifiers comprise cell-specific physical layer identifiers of the device.

[0271] Example embodiment 16: Method 1300 according to Example embodiment 14 or 15, wherein the plurality of identifiers comprise cell radio network temporary identifiers of the device.

[0272] Example embodiment 17: Method 1300 according to any of Example embodiments 9 to 16, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

[0273] Example embodiment 18: Method 1300 according to any of Example embodiments 9 to 17, further comprising: transmitting, to the access node, a request for establishing the radio resource control connection.

[0274] Example embodiment 19: Method 1300 according to any of Example embodiments 9 to 18, wherein the radio resource control connection is associated with a single radio resource control entity at the device.

[0275] Example embodiment 20: Method 1300 according to any of Example embodiments 9 to 19, wherein the device is a user equipment. [0276] Example embodiment 21: Method 1300 according to Example embodiment 20, wherein the user equipment comprises at least one antenna for communicating the radio resource control data with the access node.

[0277] Further features of the methods directly result for example from functionality of UE 110, or access node(s) 120, 122, 124, as described throughout the description, claims, and drawings, and are therefore not repeated here. An apparatus, for example a device such as UE 110, or an access node, may be configured to perform or cause performance of any aspect of the method(s) described herein. Further, a computer program, a computer program product, or a (non-transitory) computer-readable medium may comprise instructions for causing, when executed by an apparatus, the apparatus to perform any aspect of the method(s) described herein. Further, an apparatus may comprise means for performing any aspect of the method(s) described herein. According to an example embodiment, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform any aspect of the method(s).

[0278] Any range or device value given herein may be extended or altered without losing the effect sought. Also, any embodiment may be combined with another embodiment unless explicitly disallowed.

[0279] Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[0280] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

[0281] The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the example embodiments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought.

[0282] The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements. [0283] As used herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0284] Although subjects may be referred to as ‘first’ or ‘second’ subjects, this does not necessarily indicate any order or importance of the subjects. Instead, such attributes may be used solely for the purpose of making a difference between subjects.

[0285] As used in this application, the term ‘circuitry’ may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable) :(i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor(s), such as a microprocessor s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims.

[0286] As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device. [0287] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.

Claims

1. An access node, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the access node at least to: transmit, to a device, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a primary cell of the plurality of cells and a second signaling radio bearer set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein a configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the configurations of the plurality of signaling radio bearer sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

2. The access node according to claim 1, wherein the instructions are configured to, when executed by the at least one processor, cause the access node to: communicate radio resource control data with the device using the first signaling radio bearer set via the primary cell; and switch communication of the radio resource control data to the secondary cell configured to use the second signaling radio bearer set for communicating the radio resource control data.

3. The access node according to claim 2, wherein switching the communication of the radio resource data to the secondary cell comprises activating the secondary cell specific signaling radio bearer set configuration and maintaining the common configuration of the carrier aggregation scheme.

4. The access node according to any of claims 1 to 3, wherein the instructions are configured to, when executed by the at least one processor, cause the access node to: transmit, to the device, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

5. The access node device according to claim 4, wherein the plurality of identifiers comprise cell-specific physical layer identifiers of the device.

6. The access node device according to any of claims 1 to 5, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

7. The access node according to any of claims 1 to 6, wherein transmitting the configurations of the plurality of signaling radio bearer sets comprises: transmitting the configuration of the second signaling radio bearer set via the first signaling radio bearer set.

8. A device, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the device at least to: receive, from an access node, configurations of a plurality of signaling radio bearer sets for a radio resource control connection, wherein the plurality of signaling radio bearer sets are associated with a plurality of cells configured to be served by the access node, wherein the plurality of signaling radio bearer sets comprises at least a first signaling radio bearer set assigned to a primary cell of the plurality of cells and a second signaling radio bearer set assigned to a secondary cell of the plurality of cells, wherein a configuration of the first signaling radio bearer set comprises a primary cell specific signaling radio bearer set configuration, wherein a configuration of the second signaling radio bearer set comprises a secondary cell specific signaling radio bearer set configuration, and wherein the configurations of the plurality of signaling radio bearer sets comprise a common configuration of a carrier aggregation scheme for the primary cell and the secondary cell.

9. The device according to claim 8, wherein the instructions are configured to, when executed by the at least one processor, cause the device to: communicate radio resource control data with the access node using the first signaling radio bearer set via the primary cell; and switch communication of the radio resource control data to the secondary second cell configured to use the second signaling radio bearer set for communicating the radio resource control data, based on detecting an event causing the first signaling radio bearer set to become unavailable at the primary cell.

10. The device according to claim 9, wherein the switching of the communication of the radio resource data to the secondary cell comprises activating the secondary cell specific signaling radio bearer set configuration and maintaining the common configuration of the carrier aggregation scheme.

11. The device according to claim 9 or 10, wherein the switching of the communication of the radio resource data to the secondary cell is without suspension of the radio resource control connection.

12. The device according to any of claims 8 to 11, wherein the instructions are configured to, when executed by the at least one processor, cause the device to: receive, from the access node, a plurality of identifiers of the plurality of signaling radio bearer sets, wherein each of the plurality of identifiers is associated with one of the plurality of signaling radio bearer sets.

13. The device according to claim 12, wherein the plurality of identifiers comprise cell-specific physical layer identifiers of the device.

14. The device according to any of claims 8 to 13, wherein the plurality of signaling radio bearer sets are configured to be carried on a plurality of aggregated carriers.

15. The device according to any of claims 8 to 14, wherein the radio resource control connection is associated with a single radio resource control entity at the device.