Distributed radio resource control

Abstract

Various example embodiments relate to radio resource control in a communication network. A method may include receiving, by a distributed unit of an access node from a central unit of the access node, a radio resource control identification of a device and an access stratum context associated with the radio resource control identification; configuring, based on the access stratum context, a radio resource control entity of a distributed unit of the access node for delivering radio resource control data to the device over a signaling radio bearer; generating radio resource control data for the device; and transmitting the radio resource control data to the device on the signaling radio bearer.

Description

Technical Field

[0001] Various example embodiments relate generally to the field of communication networks.Some example embodiments relate to distribution of radio resource control functionality between central and distributed units of an access node. Background Art

[0002] A wireless communication network may operate using a split access node architecture, in which the functionality of an access node, such as a fifth generation (5G) access node (gNB), is split between a central unit (CU) and one or more distributed units (DUs). For example, the CU may be responsible for the upper layers of the protocol stack, such as the service data adaptation protocol (SDAP), the packet data convergence protocol (PDCP), and the radio resource control (RRC). The distributed units may be responsible for the lower layers of the protocol stack, such as the radio link control (RLC), the medium access control (MAC), and the physical layer. The split access node architecture enables the de-aggregation of the radio access network (RAN). However, the functionality of the split access node architecture may be further improved. Summary of the invention

[0003] This Summary is provided to introduce some concepts in a simplified form that are further described in the Detailed Description below. 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 improve the efficiency and quality of radio resource control. This benefit 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, a method is disclosed. The method may include: receiving, by a distributed unit of an access node, a radio resource control identity of a device and an access layer context associated with the radio resource control identity from a central unit of the access node; configuring, based on the access layer context, a radio resource control entity of the distributed unit of the access node for delivering radio resource control data to the device via a signaling radio bearer; generating radio resource control data for the device; and sending the radio resource control data to the device on the signaling radio bearer.

[0006] According to an example embodiment of the first aspect, the radio resource control identity is independent of a serving cell of the device.

[0007] According to an example embodiment of the first aspect, the method may include sending a radio resource control identification to a device.

[0008] According to an example embodiment of the first aspect, the method may comprise: adding a signalling radio bearer to a dedicated radio bearer configuration; sending an indication of the signalling radio bearer to a central unit of the access node; and receiving a configuration of the signalling radio bearer from the central unit of the access node.

[0009] According to an example embodiment of the first aspect, the method may comprise receiving a configuration of a dedicated radio bearer from a central unit of the access node.

[0010] According to an example embodiment of the first aspect, the method may comprise sending a configuration of a signalling radio bearer or a configuration of a dedicated radio bearer to the device.

[0011] According to an example embodiment of the first aspect, the configuration of the signaling radio bearers or the configuration of the dedicated radio bearers is received from a central unit of the access node in a first radio resource control reconfiguration message, or the configuration of the signaling radio bearers or the configuration of the dedicated radio bearers is sent to the device in a second radio resource control reconfiguration message.

[0012] According to an example embodiment of the first aspect, the method may comprise: receiving an indication from a device that a radio resource control identifier is not available at the device; and forwarding the indication that the radio resource control identifier is not available at the device to a central unit of the access node.

[0013] According to an example embodiment of the first aspect, the method may include: receiving a first radio resource control reconnection message including a radio resource control identifier from a device; and in response to determining that a user equipment context of the device is unknown to a distributed unit of the access node, forwarding the radio resource control identifier to a central unit of the access node.

[0014] According to an example embodiment of the first aspect, the method may include: receiving a first radio resource control reconnection message including a radio resource control identifier from a device; and in response to determining that a user context of the device is known to a distributed unit of an access node, selecting an access layer context for configuration of a signaling radio bearer based on the radio resource control identifier.

[0015] According to an example embodiment of the first aspect, the method may comprise reactivating at least one security function for delivering radio resource control data to the device based on the access stratum context.

[0016] According to an example embodiment of the first aspect, the method may comprise: sending an indication of available capacity at a distributed unit of the access node to a central unit of the access node; and receiving an indication of a capacity share of a device from the central unit of the access node.

[0017] According to an example embodiment of the first aspect, an indication that a radio resource control identifier is not available at a device is received in a first radio resource control establishment request, the indication that the radio resource control identifier is not available at the device is forwarded to a central unit of the access node in a second radio resource control establishment request, the radio resource control identifier is forwarded to the central unit of the access node in a second radio resource control reconnection message, or an indication of available capacity at a distributed unit of the access node is sent to the central unit of the access node in a radio resource control establishment completion message or a second radio resource control reconnection message.

[0018] According to an example embodiment of the first aspect, at least one of the following is received from a central unit of the access node in a user equipment context setup message or a third radio resource control reconnect message: a radio resource control identity, an access stratum context, a configuration of a dedicated radio bearer, or an indication of a capability share of the device.

[0019] According to an example embodiment of the first aspect, at least one of the following is sent to the device in the fourth radio resource control reconnection message: configuration of a signaling radio bearer or configuration of a dedicated radio bearer.

[0020] According to a second aspect, a method is disclosed. The method may include: determining, by a central unit of an access node, an access stratum context for a device; determining a radio resource context identifier for the device, wherein the radio resource context identifier is associated with the access stratum context; and sending a radio resource control identifier and the access stratum context of the device to a distributed unit of the access node.

[0021] According to an example embodiment of the second aspect, the radio resource control identity is independent of a serving cell of the device.

[0022] According to an example embodiment of the second aspect, in response to receiving an indication from a distributed unit of an access node that a radio resource control identity is not available at the device, an access stratum context and a radio resource control identity are determined.

[0023] According to an example embodiment of the second aspect, the method may include: receiving an indication of a signaling radio bearer added by the distributed unit of the access node to a dedicated radio bearer for delivering radio resource control data to a device from a distributed unit of the access node; determining a configuration for the signaling radio bearer; and sending the configuration of the signaling radio bearer to the distributed unit of the access node.

[0024] According to an example embodiment of the second aspect, the method may comprise sending a configuration of a dedicated radio bearer to a distributed unit of the access node.

[0025] According to an exemplary embodiment of the second aspect, the configuration of the signalling radio bearer or the configuration of the dedicated radio bearer is sent to the distributed unit of the access node in a radio resource control reconfiguration message.

[0026] According to an example embodiment of the second aspect, the method may comprise reactivating at least one security function for delivering radio resource control data to the device based on the access stratum context.

[0027] According to an example embodiment of the second aspect, the method may include: receiving an indication of available capacity of a distributed unit of an access node from a distributed unit of an access node; allocating a capacity share of a device to the distributed unit of the access node; and sending an indication of the capacity share of a device to the distributed unit of the access node.

[0028] According to an example embodiment of the second aspect, an indication that a radio resource control identifier is unavailable at a device is received in a radio resource control establishment request, the radio resource control identifier is received in a radio resource control reconnection message, or an indication of available capacity of a distributed unit of an access node is received in a radio resource control establishment completion message or a radio resource control reconnection message.

[0029] According to an example embodiment of the second aspect, at least one of the following is sent to a distributed unit of an access node in a user equipment context setup message or another radio resource control reconnection message: a radio resource control identity, an access stratum context, a configuration of a dedicated radio bearer or an indication of a capability share of the device.

[0030] According to an example embodiment of the second aspect, the method may include: receiving an indication of a radio resource control reconnection of a device from a distributed unit of an access node; determining the validity of a radio resource control identifier of the device; in response to determining that the radio resource control identifier is invalid, determining an updated radio resource control identifier for the device; and sending the updated radio resource control identifier to the distributed unit of the access node.

[0031] According to a third aspect, a method is disclosed. The method may include: receiving an indication of a radio resource control identity for a device from a distributed unit of an access node; receiving a configuration of a signaling radio bearer for delivering radio resource control data from the distributed unit of the access node, wherein the configuration of the signaling radio bearer is associated with the radio resource control identity; and receiving the radio resource control data on the signaling radio bearer.

[0032] According to an example embodiment of the third aspect, the radio resource control identifier is independent of a serving cell of the apparatus.

[0033] According to an example embodiment of the third aspect, the method may comprise sending an indication to a distributed unit of the access node that the radio resource control identifier is not available.

[0034] According to an exemplary embodiment of the third aspect, the indication that the radio resource control identity is not available is sent in the radio resource control setup request.

[0035] According to an example embodiment of the third aspect, the method may include sending a radio resource control reconnection message including a radio resource control identifier to a distributed unit of the access node.

[0036] According to an example embodiment of the third aspect, the method may comprise receiving a configuration of a dedicated radio bearer from a distributed unit of an access node.

[0037] According to an example embodiment of the third aspect, the configuration of the signalling radio bearer or the configuration of the dedicated radio bearer is received from the distributed unit of the access node in a radio resource control reconfiguration message or another radio resource control reconnection message.

[0038] According to a fourth aspect, an apparatus is disclosed. The apparatus may include means for performing the method according to the first aspect, the second aspect or the third aspect or any example embodiment thereof.

[0039] According to a fifth aspect, a computer program or a computer program product is disclosed. The computer program or the computer program product may include instructions, which when executed by an apparatus causes the apparatus to perform the method according to the first aspect, the second aspect or the third aspect or any example embodiment thereof.

[0040] According to a sixth aspect, an apparatus is disclosed. The apparatus may include: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, causes the apparatus to at least: receive, by a distributed unit of an access node, a radio resource control identifier of a device and an access layer context associated with the radio resource control identifier from a central unit of the access node; configure, based on the access layer context, a radio resource control entity of the distributed unit of the access node for delivering radio resource control data to the device via a signaling radio bearer; generate radio resource control data for the device; and send the radio resource control data to the device on the signaling radio bearer.

[0041] According to an example embodiment of the sixth aspect, the radio resource control identifier is independent of a serving cell of the device.

[0042] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause the apparatus to: send a radio resource control identification to a device.

[0043] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause the apparatus to: add a signaling radio bearer to a dedicated radio bearer configuration; send an indication of the signaling radio bearer to a central unit of an access node; and receive a configuration of the signaling radio bearer from the central unit of the access node.

[0044] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause an apparatus to: receive a configuration of a dedicated radio bearer from a central unit of an access node.

[0045] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause the apparatus to: send a configuration of a signaling radio bearer or a configuration of a dedicated radio bearer to a device.

[0046] According to an example embodiment of the sixth aspect, the configuration of the signaling radio bearer or the configuration of the dedicated radio bearer is received from a central unit of the access node in a first radio resource control reconfiguration message, or the configuration of the signaling radio bearer or the configuration of the dedicated radio bearer is sent to the device in a second radio resource control reconfiguration message.

[0047] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause the apparatus to: receive an indication from a device that a radio resource control identifier is not available at the device; and forward the indication that the radio resource control identifier is not available at the device to a central unit of an access node.

[0048] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause the apparatus to: receive a first radio resource control reconnection message including a radio resource control identifier from a device; and in response to determining that a user equipment context of the device is unknown to a distributed unit of the access node, forward the radio resource control identifier to a central unit of the access node.

[0049] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause the apparatus to: receive a first radio resource control reconnection message including a radio resource control identifier from a device; and in response to determining that a user context of the device is known to a distributed unit of an access node, select an access layer context for configuration of a signaling radio bearer based on the radio resource control identifier.

[0050] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause an apparatus to: reactivate at least one security function for delivering radio resource control data to a device based on an access stratum context.

[0051] According to an example embodiment of the sixth aspect, the instructions, when executed by at least one processor, cause the apparatus to: send an indication of available capacity at a distributed unit of the access node to a central unit of the access node; and receive an indication of a capacity share of a device from the central unit of the access node.

[0052] According to an example embodiment of the sixth aspect, an indication that a radio resource control identifier is unavailable at a device is received in a first radio resource control establishment request, the indication that the radio resource control identifier is unavailable at the device is forwarded to a central unit of the access node in a second radio resource control establishment request, the radio resource control identifier is forwarded to the central unit of the access node in a second radio resource control reconnection message, or an indication of available capacity at a distributed unit of the access node is sent to the central unit of the access node in a radio resource control establishment completion message or a second radio resource control reconnection message.

[0053] According to an example embodiment of the sixth aspect, at least one of the following is received from a central unit of the access node in a user equipment context establishment message or a third radio resource control reconnection message: a radio resource control identification, an access layer context, a configuration of a dedicated radio bearer, or an indication of a capability share of the device.

[0054] According to an example embodiment of the sixth aspect, at least one of the following is sent to the device in the fourth radio resource control reconnection message: configuration of a signaling radio bearer or configuration of a dedicated radio bearer.

[0055] According to a seventh aspect, an apparatus is disclosed. The apparatus may include: at least one processor; and at least one memory storing instructions, which when executed by the at least one processor causes the apparatus to at least: determine, by a central unit of an access node, an access layer context for a device; determine a radio resource context identifier for the device, wherein the radio resource context identifier is associated with the access layer context; and send a radio resource control identifier and the access layer context of the device to a distributed unit of the access node.

[0056] According to an example embodiment of the seventh aspect, the radio resource control identifier is independent of a serving cell of the device.

[0057] According to an example embodiment of the seventh aspect, in response to receiving an indication from a distributed unit of an access node that a radio resource control identity is not available at the device, an access stratum context and a radio resource control identity are determined.

[0058] According to an example embodiment of the seventh aspect, the instructions, when executed by at least one processor, cause the apparatus to: receive, from a distributed unit of an access node, an indication of a signaling radio bearer added by the distributed unit of the access node to a dedicated radio bearer, the dedicated radio bearer being used to deliver radio resource control data to a device; determine a configuration for the signaling radio bearer; and send the configuration of the signaling radio bearer to the distributed unit of the access node.

[0059] According to an example embodiment of the seventh aspect, the instructions, when executed by at least one processor, cause the apparatus to: send a configuration of a dedicated radio bearer to a distributed unit of an access node.

[0060] According to an exemplary embodiment of the seventh aspect, the configuration of the signalling radio bearer or the configuration of the dedicated radio bearer is sent to the distributed unit of the access node in a radio resource control reconfiguration message.

[0061] According to an example embodiment of the seventh aspect, the instructions, when executed by at least one processor, cause the apparatus to: reactivate at least one security function for delivering radio resource control data to the device based on the access stratum context.

[0062] According to an example embodiment of the seventh aspect, the instructions, when executed by at least one processor, cause the device to: receive an indication of available capacity of a distributed unit of an access node from a distributed unit of the access node; allocate a capacity share of a device to the distributed unit of the access node; and send an indication of the capacity share of a device to the distributed unit of the access node.

[0063] According to an example embodiment of the seventh aspect, an indication that a radio resource control identifier is unavailable at a device is received in a radio resource control establishment request, the radio resource control identifier is received in a radio resource control reconnection message, or an indication of available capacity of a distributed unit of an access node is received in a radio resource control establishment completion message or a radio resource control reconnection message.

[0064] According to an example embodiment of the seventh aspect, at least one of the following is sent to a distributed unit of an access node in a user equipment context establishment message or another radio resource control reconnection message: a radio resource control identifier, an access layer context, a configuration of a dedicated radio bearer, or an indication of a capability share of the device.

[0065] According to an example embodiment of the seventh aspect, the instructions, when executed by at least one processor, cause the apparatus to: receive an indication of a radio resource control reconnection of a device from a distributed unit of an access node; determine the validity of a radio resource control identifier of the device; in response to determining that the radio resource control identifier is invalid, determine an updated radio resource control identifier for the device; and send the updated radio resource control identifier to the distributed unit of the access node.

[0066] According to an eighth aspect, an apparatus is disclosed. The apparatus may include: at least one processor; and at least one memory storing instructions, which when executed by the at least one processor causes the apparatus to at least: receive an indication of a radio resource control identity for the apparatus from a distributed unit of an access node; receive a configuration of a signaling radio bearer for delivering radio resource control data from the distributed unit of the access node, wherein the configuration of the signaling radio bearer is associated with the radio resource control identity; and receive the radio resource control data on the signaling radio bearer.

[0067] According to an example embodiment of the eighth aspect, the radio resource control identifier is independent of a serving cell of the apparatus.

[0068] According to an example embodiment of the eighth aspect, the instructions, when executed by at least one processor, cause the apparatus to: send an indication to a distributed unit of the access node that a radio resource control identifier is not available.

[0069] According to an example embodiment of the eighth aspect, the indication that the radio resource control identity is not available is sent in the radio resource control setup request.

[0070] According to an example embodiment of the eighth aspect, the instructions, when executed by at least one processor, cause the apparatus to: send a radio resource control reconnection message including a radio resource control identifier to a distributed unit of an access node.

[0071] According to an example embodiment of the eighth aspect, the instructions, when executed by at least one processor, cause an apparatus to: receive a configuration of a dedicated radio bearer from a distributed unit of an access node.

[0072] According to an example embodiment of the eighth aspect, the configuration of the signalling radio bearer or the configuration of the dedicated radio bearer is received from a distributed unit of the access node in a radio resource control reconfiguration message or another radio resource control reconnection message.

[0073] According to a ninth aspect, a (non-transitory) computer-readable medium is disclosed. The (non-transitory) computer-readable medium may include program instructions, which, when executed by an apparatus, cause the apparatus to perform the method according to the first aspect, the second aspect, or the third aspect, or any exemplary embodiment thereof.

[0074] Therefore, the example embodiments of the present disclosure may provide an apparatus, method, computer program, computer program product, or computer-readable medium for improving radio resource control in the context of a distributed network architecture. 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 embodiments described below. According to some aspects, the subject matter of independent claims is provided. Some additional aspects are defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] The accompanying drawings, which are included to provide a further understanding of example embodiments and constitute a part of this specification, illustrate example embodiments and together with the description help explain example embodiments. In the drawings:

[0076] Figure 1 An example of a split access node architecture is shown;

[0077] Figure 2 Examples of implementations of various protocols in a split access node architecture are shown;

[0078] Figure 3 An example of an apparatus configured to practice one or more example embodiments is shown;

[0079] Figure 4 An example of implementation of various protocols in a split access node architecture with split RRC functionality is shown;

[0080] Figure 5 An example of message sequence and operations for initial establishment when the gNB does not have UE context is shown;

[0081] Figure 6 An example of message sequence and operations for RRC reconnection establishment when the gNB-DU has UE context is shown;

[0082] Figure 7 An example of message sequence and operations for RRC reconnection establishment when the gNB-DU does not have UE context is shown;

[0083] Figure 8 Examples of message sequences and operations for different RRC reconnection options are shown;

[0084] Fig. 9 An example of a method for radio resource control at a distributed unit of an access node is shown;

[0085] Fig.10 An example of a method for radio resource control at a central unit of an access node is shown; and

[0086] Fig.11 An example of a method for radio resource control at a device is shown.

[0087] In the drawings, the same reference numerals are used to denote the same components. DETAILED DESCRIPTION

[0088] 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 conjunction with the drawings is intended as a description of the present example and is not intended to represent the only form 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 implemented by different examples.

[0089] Figure 1 An example of a split access node architecture is shown. The access node represented by the gNB 120 may be functionally and / or physically separated into a central unit (CU) 128 and one or more distributed units (DUs) 122-1, 122-2, 122-N. The CU 128 may also be referred to as a gNB-CU, and the DU may also be referred to as a gNB-DU. The CU 128 may include a control plane (CP) and a user plane (UP) entity represented by a gNB-CU-CP 124 and a gNB-CU-UP 126, respectively. The gNB-CU-CP 124 may be configured to control the communication of signaling data that enables the transmission of user / application data at the user plane. User plane communications may be provided by one or more gNB-CU-UPs 126 associated with the gNB-CU-CP 124. The CU 128 and the DU may be configured to provide radio access network (RAN) services to a device represented by a user equipment (UE) 110 at one or more cells 112.

[0090] The control and user plane entities of CU 128 may communicate via a communication interface (e.g., an E1 interface). CU 128 may communicate with DU 122-n (n=1...N) via a communication interface (e.g., an F1 interface). The F1 interface may include a control plane interface and a user plane interface (F1-C, F1-U) between the control plane entity and the user plane entity of DU 122-n and CU 128, respectively. DU 122-1 to 122-N may be collectively referred to as DU 122, where N is a positive integer ranging, for example, from 1 to 100. However, higher values ​​(such as up to 2 36 -1) is also possible.

[0091] The CU / DU split architecture enables RAN deaggregation, enabling operators to leverage different vendors for different network nodes, and also enables network vendors to decouple their network implementations for scalability purposes. For example, the control plane and user plane may be separated into their own entities, enabling the control plane and user plane functions to be dimensioned separately. However, the separation may be (almost) invisible to the user equipment (UE), so on the UE side, the protocol layers may be (mostly) unaware of the separation, except for a small part that the UE may implicitly determine from the associated RRC configuration.

[0092] Figure 2 An example of protocol layers in a communication network using a split access node architecture is shown. UE 110 may access application services via a radio access network (RAN) including one or more gNBs 120. UE 110 may communicate with gNB 120 via a radio interface, which may be configured based on the 5G NR (New Radio) standard defined by the Third Generation Partnership Project (3GPP), for example. Thus, communication network 100 may include a wireless communication network.

[0093] The core network of the communication network can be implemented with various network functions, including, for example, a user plane function (UPF) 130 and an access and mobility management function (AMF) 132. UPF 130 can be configured to handle the user data portion of a communication session. Therefore, UPF 130 can provide an interconnection point between a radio access network and a data network. For example, UPF 130 can be configured to handle encapsulation and decapsulation of a user plane protocol (e.g., GPRS (General Packet Radio Service) Tunneling Protocol (GTP-U) for the user plane). Therefore, UPF 130 can be configured to communicate with CU-UP 126. AMF 132 can be configured to receive connection and session request related data from UE 110 (via gNB). AMF 132 can be configured to control connection and mobility management in a wireless communication network. Therefore, AMF 132 can be configured to communicate with CU-CP 124.

[0094] The communication network 100 can operate based on a protocol stack including multiple protocol layers. The protocol stack can be arranged based on an open system interconnection (OSI) model or a layer model of a specific standard. In one example, the protocol stack can include a service data adaptation protocol (SDAP) layer, which can receive data from the application layer for transmission. The SDAP layer can be configured to exchange data with a packet data convergence (PDCP) layer. The PDCP layer can be responsible for generating a data burst including one or more data packets, for example, based on data obtained from the SDAP layer.

[0095] The PDCP layer may provide data to one or more instances of the radio link control (RLC) layer. For example, PDCP data may be sent on one or more RLC transmission branches. Each RLC instance may be associated with a corresponding MAC instance of the MAC layer. The MAC layer may provide mapping between logical channels of the upper layer and transmission channels of the physical layer, and handle multiplexing and demultiplexing of MAC service data units (SDUs). In addition, the MAC layer may provide error correction functions based on packet retransmissions, for example, according to a hybrid automatic repeat request (HARQ) process. Physically separated transmission branches may be provided by a physical (PHY) layer, also referred to as layer 1 (L1). The RLC, MAC, and L1 functions may reside on the DU 122. The corresponding protocol stack may be applied at the gNB 120 and the UE 110.

[0096] In a split access node architecture, a portion of the protocol layer may be implemented at the CU 128. Figure 2 In the example of , CU 128 (e.g., CU-UP 126) can be configured to process upper layers of the protocol stack, such as SDAP and PDCP layers. In addition, CU128 (e.g., CU-CP 124) can be configured to process radio resource control (RRC) operations. DU 122 can be configured to process lower layers of the protocol stack, such as RLC, MAC, and L1. The user plane (U-plane) control function can interact with the MAC layer to encapsulate RRC data received from CU-CP 124 in MAC packets and / or decapsulate RRC data from MAC packets, and provide RRC data to CU-CP 124. The radio unit of DU 122 can send data to / receive data from the UE via a radio interface.

[0097] When UE 110 is powered on, it may be in a disconnected state or an idle state (e.g., RRC_IDLE). UE 110 may move to a connected state (e.g., RRC_CONNECTED), for example, by connection establishment to a network. UE 110 may move from a connected state to an inactive state (e.g., RRC_INACTIVE) if UE 110 is inactive for a certain period of time.

[0098] In the idle state, UE 110 may not be associated with an RRC context. From the network's perspective, there may be no connection between the radio access network and the core network for UE 110. Therefore, UE 110 may not communicate application data with the network. UE 110 may also be in sleep mode and only wake up intermittently, for example, to receive paging messages. However, UE 110 may perform cell reselection and other idle state operations. In the connected state, UE 110 may be associated with an RRC context. In the connected state, UE 110 may communicate with the core network via the radio access network (e.g., gNB 120).

[0099] In the inactive state, the UE 110 may remain registered to the network, but the connection to the radio access network may be suspended. However, the radio access network may store the UE context, which enables a quick restoration of the connection. The connection to the core network may be maintained.

[0100] In the connected state, UE 110 may perform radio resource management (RRM) measurements, e.g., with respect to mobility (handover) procedures. UE 110 may report its measurement results to the network (e.g., via gNB 120), e.g., periodically and / or in response to detecting a reporting trigger criterion to be met. Although some example embodiments have been described using the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED states of a 5G system as examples, it should be understood that the example embodiments may be applied to other types of idle states, inactive states, or connected states (e.g., having similar characteristics to the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED states). RRC states may also be referred to as RRC modes.

[0101] As described above, a CU may include several DUs. In addition, a DU may serve multiple cells, such as dozens of cells. Providing the RRC layer in CU 128 may enable good control of the mobility of UE 110 and also enable it to operate as a centralized resource manager for UE 110. However, a problem in this architecture is that all RRC signaling may need to be routed through CU 128, which does not actually define most of the content of the RRC messages, for example, because the most frequently changed configuration parameters may be related to the L1 features controlled by DU 122.

[0102] DU 122 may include a resource manager that controls the use of lower-layer radio parameters (e.g., periodic physical uplink control channel (PUCCH) resources), as well as some centralized computing unit (CPU) computing resources. These may have complex connections with radio resource usage. It may be difficult to make it visible via an open multi-vendor interface (e.g., F1-C) between the central unit and the distributed units. On the other hand, when the responsibility for constructing an RRC message toward the UE 100 lies only at CU 128, the lack of required information at CU 128 may result in low gain or additional delay in RRC message processing. Therefore, an example embodiment of the present disclosure implements a split RRC architecture in which an RRC connection may be identified with a CU-specific RRC identifier (ID), which may not be associated with a specific cell. Therefore, an RRC anchor-based RRC may be used instead of a cell-specific RRC.

[0103] Apart from Figure 2 In addition to or alternatively to those shown in , the communication network 100 may include other network functions, network devices, or protocols. Although some embodiments have been described in the context of 5G, it should be understood that the embodiments of the present disclosure are not limited to this example network. Therefore, the example embodiments may be applied to any current or future communication network. The device may include or be configured to implement one or more protocol layers described herein, for example, by software.

[0104] Figure 3 An example of an apparatus configured to practice one or more example embodiments is shown. Apparatus 300 may include an access node, an access point, a base station, a radio network node, or a separate portion thereof, or generally include a device configured to implement the functionality described herein. Apparatus 300 may include at least one processor 302. At least one processor 302 may include, for example, one or more of a variety of processing devices, such as a coprocessor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuit with or without an accompanying DSP, or various other processing devices including integrated circuits (such as application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), microcontroller units (MCUs), hardware accelerators, dedicated computer chips, etc.).

[0105] The apparatus 300 may also include at least one memory 304. The memory 304 may be configured to store, for example, computer program code, such as operating system software and application software. The memory 304 may include one or more volatile memory devices, one or more non-volatile memory devices, and / or a combination thereof. For example, the memory may be implemented as a magnetic storage device (such as a hard disk drive, a magnetic tape, etc.), an optical magnetic storage device, or a semiconductor memory (such as a mask ROM, a PROM (programmable ROM), an EPROM (erasable PROM), a flash ROM, a RAM (random access memory), etc.). The memory 304 is provided as an example of a (non-transitory) computer-readable medium. As used herein, the term "non-transitory" is a limitation of the medium itself (i.e., tangible, not a signal), not a limitation on data storage persistence (e.g., RAM versus ROM).

[0106] The apparatus 300 may also include a communication interface 308, which is configured to enable the apparatus 300 to send and / or receive information. The communication interface 308 may include an internal or external communication interface, such as an E1, F1, F1-C, and / or F2-C interface. The apparatus 300 may also include other components and / or functions, such as a user interface (not shown) including at least one input device and / or at least one output device. The input device may take various forms, such as a keyboard, a touch screen, or one or more embedded control buttons. The output device may, for example, include a display, a speaker, etc.

[0107] When the device 300 is configured to implement some functions, a certain component and / or some components (e.g., at least one processor 302 and / or at least one memory 304) of the device 300 may be configured to implement the function. In addition, when the at least one processor 302 is configured to implement some functions, the function may be implemented using, for example, a program code 306 included in the at least one memory 304.

[0108] The functions 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, the apparatus 300 includes a processor or processor circuit (e.g., a microcontroller) configured by program code 306, which, when executed, performs embodiments of the operations and functions described herein. The program code 306 is provided as an example of an instruction that, when executed by at least one processor 302, causes the performance of the apparatus 300.

[0109] Alternatively or additionally, the functions described herein may be performed at least in part by one or more hardware logic components. For example, but not limited to, illustrative types of hardware logic components that may be used include field programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), application specific standard products (ASSPs), systems on chips (SOCs), complex programmable logic devices (CPLDs), graphics processing units (GPUs), etc.

[0110] The device 300 may be configured to perform the methods described herein or include components for performing the methods described herein. In one example, the components include at least one processor 302, and at least one memory 304 includes program code 306, which is configured to cause the device 300 to perform the method when executed by the at least one processor 302.

[0111] The apparatus 300 may include, for example, a network device such as an access node, access point, base station or a central / distributed unit thereof. Although the apparatus 300 is shown as a single device, it should be understood that the functionality of the apparatus 300 may be distributed to multiple devices wherever applicable.

[0112] Figure 4 An example of implementation of various protocols in a split access node architecture with split RRC functionality is shown. Example embodiments of the present disclosure provide solutions for current and next generation networks (such as 6G networks) in which radio resource control is separated between a central unit and a distributed unit, in other words, deaggregated according to CU / DU separation. This enables CU 128 and DU 122 to exchange RRC messages with UE 110. Therefore, the RRC protocol can be disconnected from the cell dependency so that UE 110 can retain a portion of the RRC protocol even between state transitions. A radio connection may not be required to retain (a portion of) the RRC protocol. Therefore, UE 110 can be in a state of an RRC inactive type and is ready to resume the RRC connection without a separate state transition. This provides the benefit of simplifying RRC state processing after completing initial network registration. For example, the signaling overhead caused by the exchange of unnecessary information between CU 128 and DU 122 can be reduced. This also enables more efficient radio resource control because DU 122 can have more information about parameters that affect certain aspects of RRC.

[0113] In addition, on the network side, the roles of the central unit and the distributed unit are clarified by dividing the RRC into two parts (e.g., RRC-hi(gh) which can be anchored at the CU 128 (e.g., CU-CP 124) and RRC-lo(w) which can be anchored at the DU 122). RRC-hi can be configured to be responsible for QoS flow resource management, UE capability sharing, and / or act as an RRC connection anchor towards the core network (e.g., AMF 132). The RRC-lo at the DU 122 can be configured to be responsible for radio connection related configuration (e.g., physical layer configuration). RRC-lo can be configured to interact with the MAC layer, such as including RRC data (RRC-lo or both RRC-hi / lo) to / extracting RRC data (RRC-lo or both RRC-hi / lo) from the MAC packet. However, towards the UE 110, the RRC protocol can still appear as one RRC. The UE 110 can process the RRC messages as if the RRC layer is a single entity. Therefore, some PDCP functions (PDCP'") may be included at the DU 122 instead of or in addition to the PDCP layer (PDCP") of the CU 128.

[0114] For example, the separation between RRC-lo / hi can be implemented so that the cell group configuration (CellGroupConfig) parameter of the RRC reconfiguration information element is included in RRC-lo. This enables DU122 to transmit the cell group configuration parameter directly to UE 110. RRC-hi may include a parameter of the radio bearer configuration (RadioBearerConfig), which enables CU 128 to centrally process the radio bearer configuration. The cell group configuration may include a configuration for a group of cells (e.g., two, three or more cells), which may be identified by a cell group identifier (CellGroupID) in the cell group information. The cell group configuration may include, for example, a physical layer or MAC layer configuration for a cell group.

[0115] To achieve separation of RRC from CU 128, CU 128 may define an RRC ID, for example during RRC establishment, that is independent of a cell identifier (cell_id) of a serving cell of UE 110. The RRC ID may be used to configure RRC transmissions, for example for deriving security keys. The RRC ID may be used for this purpose in addition to or instead of a cell identifier (e.g., a physical cell identifier PCI) received from a serving cell. gNB 120 may define a validity period for the RRC ID. In response to detecting expiration of the validity period, UE 110 may perform a connection reestablishment, wherein UE 110 may indicate unavailability of a (valid) RRC ID. This may be done as if starting without any stored RRC configuration.

[0116] In one example, CU 128 may share an access stratum (AS) context with DU 122. This allows DU 122 to establish an independent RRC entity for UE 110. Thus, RRC-lo may have a separate RRC entity for ciphering and integrity protection of the signaling radio bearers (SRBs) used toward UE 110. This may also be achieved via separate SRBs for DU 122 within RRC. The AS context may include a set of parameters that enable UE security and integrity verification.

[0117] In another example, the CU 128 and the DU 122 may be configured to establish independent RRC message contexts. In this case, the CU 128 may provide integrity protection and security keys for RRC data to the DU 122 along with the AS context. In this way, the DU 122 may add content to the RRC message and may also generate their own RRC messages using the same SRB used on the CU 128. The consistency of integrity protection and security keys may be maintained with a key update procedure.

[0118] In another example, CU 128 may provide the RRC ID in a non-RRC message (e.g., an F1 message) to DU 122. CU 128 may protect the RRC ID using integrity and security algorithms and provide it to DU 122. The F1 message may also include parameters from CU 128. DU 122 may generate a final RRC message, but append the RRC ID container received from CU 128 to the message.

[0119] With any of the above examples, whenever UE 110 needs an RRC connection, UE 110 can be enabled to access an RRC connection associated with an RRC ID from any radio point that has been established with DU 122. If UE 110 has an RRC ID that is immediately available when an RRC connection starts, the rest of the RRC connection process can be simplified. UE 110 can also be configured with multiple radio connections. In the case where some radio connections are not needed, DU 122 can release the radio connection it has. If all radio connections from all DU 122 are released, UE 110 is in a state similar to "RRC inactive" without any additional configuration. CU 128 can, for example, keep the context within a limited time and be ready to quickly resume the RRC connection. Therefore, the concept of RRC can be enhanced so that DU 122 can use any method to establish a radio connection with UE 100 because there is no cell dependency. The radio interface of DU 122 can be based on a transmit-receive point (TRP), a cell or a cell-free concept.

[0120] Once the DU 122 receives the RRC ID from the UE 110, it can verify the RRC ID with the CU 128, receive a share of the UE capabilities, an AS context, or an indication / configuration of a data connection that may already exist. The UE 110 can establish multiple radio connections in the DU 122, and the CU 128 can be configured to separate the data in the DU 122 and also (fully) control the mobility of the UE 110 within the DU 122. If the UE 110 is capable of multiple uplinks, it can also transparently establish radio connections with multiple DUs 122. Therefore, the UE 110 can operate without seeing any DU boundaries.

[0121] The disclosed method enables the UE 110 to always use the best configured uplink for RRC message transmission. Any DU 122-n can be configured to be responsible for mobility within its cell and also apply any RRC reconfiguration triggered therein. Since the UE 110 is continuously ready to resume the RRC connection, the disclosed method can also clearly reduce the need for handover. In many cases, the UE 110 can immediately resume data transmission in any radio access point in the gNB area. In handover, the UE 110 can send an indication of whether it has separation capability (e.g., capable of receiving data from the source cell and the target cell or only from the target cell) so that the UE requests additional resources or resource handover. For example, the UE 110 can be configured to have multiple DU RRC connections, for example, one with the source cell and one with the target cell. In this case, handover may not be required because the UE 110 can be configured with a secondary (target) DU. Once the secondary DU has been configured, the source DU can be released. The target configuration may be initiated by the network (e.g., by sending a request for a new DU (cell) while continuing to receive data from the source cell (DU)), or directly by the UE 110. As disclosed herein, an RRC ID, which may also be referred to as an AS context ID, may be defined for and provided to the UE 110 and for the DU 122. The RRC ID may include parameters that replace a cell-based UE ID (e.g., ue-Identitu).

[0122] Figure 5 An example of a message sequence and operations for initial establishment when the gNB does not have a UE context is shown. Although the figures show functionality based on certain messages, it should be understood that different types of messages may be utilized to implement similar functionality. However, using the messages described herein may be beneficial for implementing the example embodiments in the context of the 3GPP specifications. Even though operations between a CU 128 and a single DU 122-n have been shown, it should be understood that similar operations may be performed between a CU 128 and multiple DUs 122, such as to allocate different shares of UE capabilities to different DUs.

[0123] At operation 501, UE 110 may send an RRC setup request to DU 122-n. At this point, UE 110 may not have an RRC connection to the network. UE 110 may not be associated with an RRC ID. The RRC setup request may include an indication of the unavailability of the RRC ID at UE 110 ("no RRC ID"). The RRC setup request may, for example, include an information element (IE) indicating that UE 110 does not have an RRC connection in the network. Therefore, the indication of the unavailability of the RRC ID may be sent as an indication of not having an RRC connection to the network, which also means that UE 110 does not have an RRC ID. The indication of the unavailability of the RRC ID may be provided as an RRC setup request that does not include an RRC ID.

[0124] At operation 502, DU 122-n may send an RRC setup request including an indication of unavailability of the RRC ID at UE 110 to CU 128. Thus, the indication of unavailability may be forwarded to CU 128. The RRC setup request may include an initial configuration. For example, DU 122-n may include the received RRC setup request message in an initial UL (uplink) RRC message transmission message, and if UE 110 is granted, include the corresponding low-layer configuration for UE 110, and transmit the message to CU 128. The initial UL RRC message transmission message may include a cell radio network temporary identifier (C-RNTI) assigned to UE 110 by DU 122-n.

[0125] At operation 503, CU 128 may send an RRC setup message to DU 122. For example, CU 128 may assign a gNB-CU UE F1AP (F1 Application Protocol) ID to UE 110 and include it in the RRC setup message. The RRC setup message may be encapsulated in a DL (downlink) RRC message transport message. The gNB-CU UE F1AP ID may uniquely identify UE 110 via an F1 interface within CU 128.

[0126] At operation 504 , DU 122 - n may send an RRC setup message to UE 110 .

[0127] At operation 505, UE 110 may send an RRC (connection) setup complete message to DU 122-n. The RRC setup complete message may include an initial message, which may be the first message from UE 110 to the core network (e.g., AMF 132). Once the RRC connection has been established, UE 110 may initiate communication with AMF 132.

[0128] At operation 506, the DU 122-n may send an RRC setup complete message to the CU 128, for example, via an F1 interface. The RRC setup complete message may include an initial message. The RRC setup complete message may include an indication of available capacity at the DU 122-n. The available capacity may be indicated, for example, as a percentage of available capacity, for example, via an information element capacity value, which indicates, for example, an integer value between 0 and 100, an amount of resources per cell and per synchronization signaling block (SSB) region available relative to the total resources of the DU 122-n.

[0129] At operation 507, the CU 128 may send an initial UE message to the AMF 132, for example as an NGAP (Next Generation Application Protocol) message.

[0130] At operation 508, the CU 128 may send an initial context setup message to the DU 122-n, for example, as an NGAP protocol message.

[0131] At operation 509 , the CU 128 may determine an access stratum (AS) context for the UE 110 .

[0132] At operation 510 , the CU 128 may send a SecurityModeCommand to the UE 110 via the DU 122 - n .

[0133] At operation 511, UE 110 may send a SecurityModeCommand to CU 128 via DU 122-n.

[0134] At operation 512, CU 128 may send a UE capability query to UE 110 via DU 122-n.

[0135] At operation 513, UE 110 may send UE capability information to CU 128 via DU 122-n. The UE capability information may include an indication of whether UE 110 supports the use of RRC ID.

[0136] At operation 514, CU 128 may store the UE capability information and allocate a share for DU 122-n to allow direct RRC (uplink) communication with UE 110. This means that CU 128 allows its own signaling radio bearer (SRB) for DU 122-n. CU 128 may determine its share of UE capability to allocate to DU 122-n based on the UE capability information and the available capacity of DU 122-n.

[0137] At operation 515, CU 128 may send a UE context setup message to DU 122-n. The UE context setup message may include at least one of the following: an AS context, a configuration of a dedicated radio bearer (DRB), a UE capability share, or an RRC ID. The RRC ID may be associated with the AS context or the DRB configuration or both. In other words, the AS context or the DRB configuration may be applicable to a UE with a specific RRC ID. The RRC ID may be independent of the serving cell of UE 110. This enables UE 110 to use the RRC ID for subsequently resuming the RRC connection in another cell.

[0138] The UE context may include a block of information maintained by a RAN node (e.g., CU 128 or DU 122-n) associated with one UE. The block of information may include information used to maintain RAN services toward an active UE. The UE context may be established when a transition to an RRC connected state is completed for the corresponding UE, or in a target RAN node after handover resource allocation is completed during handover preparation. The UE context may include UE state information, security information, UE capability information, or an identification of a logical network connection associated with the UE.

[0139] At operation 516, DU 122-n may store the AS context. The AS context may be subsequently used to deliver RRC data to UE 110. To this end, an RRC entity may be configured (e.g., established) at DU 122-n. This enables DU 122-n to communicate RRC data directly with UE 110 without routing the data to CU 128. When stored, the AS context may be associated with the RRCID.

[0140] At operation 517, DU 122-n may add an SRB (SRB_DU) for DU 122-n. The SRB may be added to the DRB configuration.

[0141] At operation 518, DU 122-n may send a UE context setup response to CU 128. The UE context setup response may include at least one of the following: a radio configuration or an indication of an added SRB (SRB_DU). In response to receiving the indication of the added SRB, CU 128 may determine a configuration for the SRB. The radio configuration may include a cell group configuration.

[0142] At operation 519, CU 128 may send an RRC reconfiguration message to DU 122-n. The RRC reconfiguration message may include at least one of the following: configuration of a dedicated radio bearer, configuration of a signaling radio bearer (SRB_DU), or an RRC ID. Providing the RRC ID at the UE context establishment of operation 515 enables configuration of DU 122-n. Providing the RRC ID at the RRC reconfiguration message of operation 519 enables configuration of UE 110 via DU 122-n. The content of the RRC reconfiguration may be transparent (unreadable) to DU 122-n. In this case, the SRB_DU configuration may include parameters for opening subsequent SRB_DU messages. Similarly, providing the RRC ID in the UE context establishment of operation 515 enables configuration of DU 122-n, because the content of the RRC reconfiguration of operation 519 may be transparent to DU 122-n.

[0143] At operation 520, DU 122-n may send an RRC reconfiguration message to UE 110. The RRC reconfiguration message may include at least one of the following: configuration of a dedicated radio bearer, SRB_DU, radio configuration modification, or RRC ID. UE 110 may store the received information. The radio configuration may include a cell group configuration, such as a frequency configuration, information about a reference signal, etc. SRB configuration (e.g., SRB_DU) may include parameters for reading and using SRB data.

[0144] At operation 521, UE 110 may send an RRC reconfiguration complete message to DU 122-n.

[0145] At operation 522, the DU 122-n may send an RRC reconfiguration complete message to the CU 128. The DU 122-n may use the signaling radio bearer to send RRC data to the UE 110. Note that the DU 122-n may generate the RRC data, and thus the DU 122-n may be able to communicate the RRC data with the UE 110 independently of the CU 128. The DU 122-n may also add the RRC data to the RRC message received from the CU 128.

[0146] Figure 6 An example of the message sequence and operations for RRC reconnection establishment when the gNB-DU has a UE context is shown. In this example, for example, based on Figure 5, UE 110 may have previously had an RRC connection to the network, and UE 110 may have stored an RRPID for resuming the RRC connection. Subsequently, the RRC connection may have been terminated, for example due to a handover or a lost radio connection. However, UE 110 may resume the RRC connection based on the stored RRC_ID, as will be further described below.

[0147] At operation 601, UE 110 may send an RRC reconnection message (eg, an RRC reconnection request) to DU 122-n. The RRC reconnection message may include an RRC ID.

[0148] At operation 602, the DU 122-n may determine whether the UE 110 is known. If the DU 122-n has a UE context for the UE 110, the DU 122-n may determine that the UE 110 is known.

[0149] At operation 603, in response to determining that UE 110 is unknown, DU 122-n may send an RRC reconnection message to CU 128, for example, via an F1 interface. The RRC reconnection message may include an RRC ID. The RRC reconnection message may include an indication of the capacity available at the DU, for example, similar to operation 506. Thus, the RRC ID may be forwarded to CU 128. When UE 110 is known, the system may be as described in reference to Figure 7 Generally, the RRC reconnection / reconfiguration message may be included in the corresponding F1 message. For example, the RRC reconnection message of operation 603 may be included in the RRC_MESSAGE_TRANSFER message of the F1 interface. The RRC message may not be used directly at the F1 interface.

[0150] At operation 604, CU 128 may check the AS context of UE 110. CU 128 may, for example, determine that the AS context of UE 110 is stored at CU 128. When CU 128 knows the available UE capabilities and an estimate of the available capacity of DU 122-n, CU 128 may determine the share of the UE capabilities it gives to DU 122-n.

[0151] At operation 605, CU 128 may send an RRC reconnection message (e.g., via an F1 interface). The RRC reconnection message may include at least one of the following: an AS context, a configuration of a dedicated radio bearer, and a capability share allocated to DU 122-n. The message may be sent as a response to the RRC reconnection message of operation 603.

[0152] At operation 606 , the DU 122 - n may store the AS context, eg, similar to operation 516 .

[0153] At operation 607, DU 122-n may reactivate security. For example, DU 122-n may reactivate security functions for delivering RRC data to UE 110. The security functions may include, for example, encryption of RRC data. The security functions may be based on the AS context of UE 110 received at operation 605.

[0154] At operation 608 , similar to operation 517 , DU 122 - n may add an SRB for DU 122 - n (SRB_DU).

[0155] At operation 609, DU 122-n may send an RRC reconnection message to UE 110. The RRC reconnection message may include at least one of the following: configuration of a dedicated radio bearer, configuration of a signaling radio bearer, or a radio configuration modification. DU 122-n may then use the signaling radio bearer to send RRC data to UE 110, as described with reference to operation 522. UE 110 may reestablish SRB_DU. However, other previously used signaling radio bearers (e.g., SRB1 and SRB2) may also be active. SRB0 may be configured for RRC messages using a common control channel (CCCH) logical channel. SRB1 may be configured for RRC messages that may include piggybacked non-access stratum (NAS) messages, as well as NAS messages for establishing SRB2 before, for example, using a downlink control channel (DCCH) logical channel. SRB2 may be used for NAS messages and RRC messages including logged measurement information (e.g., using a DCCH logical channel). SRB2 may have a lower priority than SRB1 and may be configured by the network after AS security activation. When UE 110 is known to DU 122-n, Figure 6 The operation enables fast recovery of the RRC connection. Since the RRC ID is independent of the serving cell of the UE 110, the RRC connection can be recovered in any cell within the DU 122 of the CU 128.

[0156] Figure 7 An example of message sequence and operations for RRC reconnection establishment when the gNB-DU does not have UE context is shown. Figure 7 The example of is similar to in the sense that UE 110 may have previously had an RRC connection to the network. Figure 6 However, in this example, DU 122-n is known to UE 110, which accelerates the RRC reconnection process due to the available RRC ID.

[0157] At operation 701 , UE 110 may send an RRC reconnection message to DU 122 - n , similar to operation 601 .

[0158] At operation 702 , the DU 122 - n may determine that the UE 110 is known, for example, based on the availability of a corresponding UE context at the DU 122 - n , as described with reference to operation 602 .

[0159] At operation 703 , in response to determining that UE 110 is known, DU 122 - n may select a stored AS context of UE 110 based on the RRC ID for configuring a signaling radio bearer (SRB_DU).

[0160] At operation 704 , the DU 122 - n may reactivate security similar to operation 607 , but using the stored AS context of the UE 110 .

[0161] At operation 705, DU 122-n may send an RRC reconnection message to UE 110. The RRC reconnection message may include at least one of the following: configuration of a dedicated radio bearer, configuration of a signaling radio bearer (SRB_DU), and a radio configuration modification. DU 122-n may then use the signaling radio bearer to send RRC data to UE 110, as described with reference to operation 522. When UE 110 is unknown to DU 122-n, Figure 7 The example enables fast recovery of the RRC connection. Again, since the RRCID is independent of the serving cell of the UE 110, the RRC connection can be recovered in any cell within the DU(s) 122 of the CU 128 even if the relevant DU is not aware of the UE context.

[0162] At operation 706, DU 122-n may send an indication of an RRC reconnection of UE 110 to CU 128. This may indicate to CU 128 that UE 110 has made an RRC reconnection to the network.

[0163] At operation 707, CU 128 may determine whether to change the RRC ID. CU 128 may determine the validity of the RRC ID, for example, in response to receiving an indication of an RRC reconnection. CU 128 may, for example, determine whether the validity period of the RRC ID is still in progress. In response to detecting the expiration of the validity period, CU 128 may update the RRC ID. CU 128 may send the updated RRC ID to DU 122-n, and DU 122-n may forward the updated RRC ID to UE 110. The updated RRC ID may be sent to DU 122-n similar to the initial RRC ID. UE 110 may use the updated RRC ID in a subsequent RRC reconnection.

[0164] Figure 8 Examples of message sequences and operations for different RRC reconnection options are shown. Also in this example, UE 110 may have previously had an RRC connection to the network, but DU 122-n is known to UE 110.

[0165] At operation 801, UE 110 may send an RRC reconnection message, similar to operation 701. However, the RRC reconnection message may include an information element indicating the AS context ID. Figure 8 In the example embodiment, the AS context ID can be replaced by the RRPID.

[0166] At operation 802 , the DU 122 - n may determine that the UE 110 is unknown, similar to operation 802 .

[0167] At operation 803, the DU 122-n may send an RRC reconnection message, for example, over an F1 interface, to the CU 128. The RRC reconnection message may include an indication of available capacity at the DU 122-n.

[0168] At operation 804 , the CU 128 may check the AS context, similar to operation 604 .

[0169] At operation 805 , the CU 128 may reactivate security, such as described with reference to operation 607 for the DU 122 - n .

[0170] At operation 806, the CU 128 may send an RRC reconnection message. The RRC reconnection message may include at least one of the following: an AS context, a configuration of a dedicated radio bearer, and a capability share allocated to the DU 122-n for the UE 110.

[0171] At operation 807 , the DU 122 - n may store the AS context, similar to operation 606 .

[0172] At operation 808 , the DU 122 - n may reactivate security, similar to operation 607 .

[0173] At operation 809, DU 122-n may send an RRC reconnection message to UE 110. The RRC reconnection message may include at least one of the following: AS context ID, configuration of dedicated radio bearers, radio configuration modification. This enables a non-handover-ready UE to resume the RRC connection in the case of intra-DU and inter-DU mobility or after a radio connection drop at the same or different DU.

[0174] At operation 810, the DU 122-n and the UE 110 may define a handover condition. In response to detecting the defined condition, a handover of the UE 110 may be performed, for example, between cells of the DU 122-n.

[0175] At operation 811, UE 110 may transmit another RRC reconnection message including the AS context ID. At operation 801, the message may be transmitted from a different cell as a corresponding message.

[0176] At operation 812, DU 122-n may determine that UE 110 is known because it has the AS context of UE 110 (received at operation 806). Therefore, DU 122-n may proceed directly to operation 813 without unnecessary messaging with CU 128. RRC reconnection of UE 110 may be due to intra-DU mobility or loss of a radio connection within DU 122-n. This also applies to inter-DU mobility or loss when CU 128 has delivered the AS context to DU 122-n. Allocation of transmission resources (e.g., time / frequency resources) may not need to be performed in advance.

[0177] At operation 813 , DU 122 - n may send an RRC reconnection message, similar to operation 809 .

[0178] At operation 814, DU 122-n and UE 110 may activate measurements. The measurements may include handover measurements. For example, in the case of intra-DU mobility, DU 122-n may configure measurements for UE 110 instead of CU 128.

[0179] At operation 815, the DU 122-n may report the measurements to the DU 122-n.

[0180] At operation 816, the DU 122-n may send an RRC reconfiguration message. The RRC reconfiguration message may include at least one of: an AS context ID, configuration of a dedicated radio bearer, or a radio configuration modification.

[0181] At operation 817, UE 110 may send an RRC reconfiguration complete message to DU 122-n. This enables UE 110 to restore the RRC connection in the event of a network-controlled handover.

[0182] Fig. 9 An example of a method for radio resource control at a distributed unit of an access node is shown.

[0183] At 901 , the method may include receiving, by a distributed unit of an access node from a central unit of the access node, a radio resource control identifier of a device and an access stratum context associated with the radio resource control identifier.

[0184] At 902, the method may include configuring, based on the access stratum context, a radio resource control entity of a distributed unit of an access node for delivering radio resource control data to a device over a signaling radio bearer.

[0185] At 903, the method may include generating radio resource control data for the device.

[0186] At 904, the method may include sending radio resource control data to a device on a signaling radio bearer.

[0187] Fig.10 An example of a method for radio resource control at a central unit of an access node is shown.

[0188] At 1001 , the method may include determining, by a central unit of an access node, an access stratum context for a device.

[0189] At 1002, the method may include determining a radio resource context identification for a device, wherein the radio resource context identification is associated with an access stratum context.

[0190] At 1003, the method may include sending a radio resource control identity and an access stratum context of the device to a distributed unit of the access node.

[0191] Fig.11 An example of a method for radio resource control at a central unit of an access node is shown.

[0192] At 1101 , the method may include receiving an indication of a radio resource control identity for a device from a distributed unit of an access node.

[0193] At 1102, the method may include receiving, from a distributed unit of an access node, a configuration of a signaling radio bearer for delivering radio resource control data, wherein the configuration of the signaling radio bearer is associated with a radio resource control identity.

[0194] At 1103, the method may include receiving radio resource control data on a signaling radio bearer.

[0195] As described throughout the specification, claims, and drawings, other features of the method result directly from the functionality of the DU 122, CU 128, or UE 110, and are therefore not repeated here. The device may be configured to perform or cause the performance of any aspect of the method described herein. In addition, the computer program or computer program product may include instructions for causing the device to perform any aspect of the method described herein when executed by the device. In addition, the device may include a component for performing any aspect of the method described herein. According to an example embodiment, the component includes: at least one processor; and at least one memory storing instructions that, when executed by at least one processor, cause the device to perform at least any aspect of the method.

[0196] Any range or device value given herein may be expanded or changed without losing the effect sought. Furthermore, unless explicitly not permitted, any embodiment may be combined with another embodiment.

[0197] Although the subject matter has been described in language specific to structural features and / or acts, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Instead, the specific features and acts described above are disclosed as examples of implementing the claims, and other equivalent features and acts are intended to fall within the scope of the claims.

[0198] 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 embodiments that solve any or all of the stated problems or embodiments that have any or all of the stated benefits and advantages. It will also be understood that references to "an" may refer to one or more of those items.

[0199] The steps or operations of the methods described herein may be performed in any suitable order, or simultaneously where appropriate. In addition, individual blocks may be deleted from any method 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 other example embodiments described to form additional example embodiments without losing the effects sought.

[0200] The term "comprising" is used herein to mean including the identified methods, blocks, or elements, but such blocks or elements do not include an exclusive list and the method or apparatus may contain additional blocks or elements.

[0201] As used herein, “at least one of: ” and “at least one of ” and similar expressions (wherein a list of two or more elements is connected by “and” or “or”) refer to at least any one of the elements, or at least any two or more of the elements, or at least all of the elements.

[0202] Although a subject may be referred to as the "first" or "second" subject, this does not necessarily indicate any order or importance of the subjects. Instead, such an attribute may serve the sole purpose of creating a distinction between subjects.

[0203] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) hardware circuit implementations only (e.g., implementations only in analog and / or digital circuitry), and (b) combinations of hardware circuitry and software, such as (where applicable): (i) a combination of analog and / or digital hardware circuitry with software / firmware, and (ii) any portion of a hardware processor with software (including a digital signal processor, software, and memory that work together to enable a device such as a mobile phone or server to perform various functions), and (c) hardware circuitry and / or processors, such as a microprocessor or a portion of a microprocessor, that require software (e.g., firmware) for operation, but where the software may not be present when not required for operation. This definition of circuitry applies to all uses of the term in this application (including any claims).

[0204] As another example, as used in this application, the term circuitry also encompasses an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. For example and if applicable to the particular claim element, the term circuitry also encompasses a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0205] It will be understood that the above description is given as an example only, and various modifications may be made by those skilled in the art. The above description, 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 separate embodiments, those skilled in the art may make many changes to the disclosed embodiments without departing from the scope of this specification.

Claims

1. A method comprising: Receiving, by a distributed unit of an access node, a radio resource control identifier of a device and an access layer context associated with the radio resource control identifier from a central unit of the access node; configuring, based on the access stratum context, a radio resource control entity of the distributed unit of the access node for delivering radio resource control data to the device via a signaling radio bearer; generating radio resource control data for the device; as well as The radio resource control data is sent to the device on the signaling radio bearer. 2 . The method of claim 1 , wherein the radio resource control identifier is independent of a serving cell of the device.

3. The method according to claim 1 or 2, further comprising: The radio resource control identifier is sent to the device.

4. The method according to any one of the preceding claims, further comprising: receiving, from the device, an indication that the radio resource control identifier is not available at the device; as well as The indication that the radio resource control identifier is not available at the device is forwarded to the central unit of the access node.

5. The method according to any one of the preceding claims, further comprising: receiving, from the device, a first radio resource control reconnection message including the radio resource control identifier; as well as In response to determining that a user equipment context of the device is unknown to the distributed unit of the access node, the radio resource control identification is forwarded to the central unit of the access node.

6. The method according to any one of claims 1 to 4, further comprising: receiving, from the device, a first radio resource control reconnection message including the radio resource control identifier; as well as In response to determining that a user context of the device is known to the distributed unit of the access node, the access stratum context for configuration of the signaling radio bearer is selected based on the radio resource control identification.

7. The method according to claim 5 or 6, further comprising: At least one security function is reactivated based on the access stratum context for delivering the radio resource control data to the device.

8. The method according to any one of the preceding claims, further comprising: sending an indication of available capacity at the distributed unit of the access node to the central unit of the access node; as well as An indication of a capacity share of the device is received from the central unit of the access node.

9. A method comprising: determining, by a central unit of the access node, an access stratum context for the device; determining a radio resource context identifier for the device, wherein the radio resource context identifier is associated with the access stratum context; as well as The radio resource control identifier and the access layer context of the device are sent to a distributed unit of the access node.

10. The method according to claim 9, further comprising: receiving, from the distributed unit of the access node, an indication of available capacity of the distributed unit of the access node; allocating a capacity share of the device to the distributed unit of the access node; as well as An indication of the capability share of the device is sent to the distributed unit of the access node.

11. The method according to claim 9 or 10, further comprising: receiving, from the distributed unit of the access node, an indication of a radio resource control reconnection of the device; determining validity of the radio resource control identifier of the device; In response to determining that the radio resource control identifier is invalid, determining an updated radio resource control identifier for the device; as well as The updated radio resource control identifier is sent to the distributed unit of the access node.

12. A method comprising: receiving an indication of a radio resource control identity for the device from a distributed unit of the access node; receiving, from the distributed unit of the access node, a configuration of a signaling radio bearer for delivering radio resource control data, wherein the configuration of the signaling radio bearer is associated with the radio resource control identity; and The radio resource control data is received on the signaling radio bearer.

13. The method according to claim 12, further comprising: A radio resource control reconnection message including the radio resource control identifier is sent to the distributed unit of the access node.

14. An apparatus comprising means for performing the method according to any one of claims 1 to 13.

15. A computer program comprising instructions which, when executed by a device, cause the device to perform the method according to any one of claims 1 to 13.

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