Post-failure network access control

Abstract

Embodiments include methods for controlling user equipment (UE) access to a communication network after a failure in the communication network.. Such methods include detecting a failure of an entity in the communication network. The failure of the entity causes at least one cell of the 5 communication network to become at least temporarily unavailable for UEs. Such methods include, in response to the detected failure, determining an access control configuration for one or more cells of the communication network. The access control configuration is different than a previous access control configuration for the one or more cells that was in use when the failure was detected. Such methods include applying the access control configuration in the one or more 0 cells, thereby controlling UE access to the one or more cells. Other embodiments include network equipment configured to perform such methods.

Description

[0001] POST-FAILURE NETWORK ACCESS CONTROL

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to wireless networks, and more specifically to techniques for controlling user equipment (UE) access to a communication network after detecting a failure that causes at least one cell of the communication network to become at least temporarily unavailable to UEs.

[0004] BACKGROUND

[0005] Currently the fifth generation (5G) of cellular systems, also referred to as New Radio (NR), is being standardized within the Third-Generation Partnership Project (3GPP). 5G / NR is developed for maximum flexibility to support multiple and substantially different use cases. These include enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device-to-device (D2D), and several other use cases. 5G / NR was initially standard in 3GPP Release 15 (Rel-15) and continues to evolve through subsequent releases, such as Rel-16 and Rel-17.

[0006] Seamless mobility is a key feature of 3GPP radio access technologies (RATs) including NR. In general, a serving radio access network (RAN) node (e.g., gNB) configures a user equipment (UE) to perform and report radio resource management (RRM) measurements to assist network-controlled mobility decisions, such as for handover (HO) from a serving cell to a target cell. Seamless handovers ensure that the UE moves around in the coverage area of different cells without excessive interruption to data transmission.

[0007] Two types of HOs are supported in 5G / NR networks: non-conditional, in which the RAN node informs the UE of the timing and the target cell for the HO; and conditional, in which the RAN node provides execution conditions based on which a UE determines the timing and the target cell for the HO. In either case, the UE must perform a random access (RA) to the target cell as part of the HO, similar to how the UE performs a RA to a particular cell when it initially establishes a connection to the network in that cell.

[0008] A 5G / NR network can control UE access to each cell in various ways and / or on various levels, based on a unified access control (UAC) framework. For example, access to a particular cell (or group of cells) can be barred for all UEs, a specific group of UEs, all except a specific group of UEs, etc. This done primarily based on Access Identities and Access Categories, as further defined in 3GPP TS 22.261 (v!9.6.0). Barring information for each cell is also broadcast in system information block 1 (SIB1) associated with the cell, as further defined in 3GPP TS 38.331 (V19.1.0). For example, UEs having certain access identities might be allowed on cells reserved by a network operator for its internal use, while all other UEs are barred from accessing these cells. As such, when a UE is camped (i. e. , in a non-connected state) on a particular cell, the UE may have selected that cell for camping because SIB1 broadcast in other nearby cells indicates the UE is barred from accessing these cells, even if they are otherwise preferrable (e.g., due to better signal strength). In addition, 3GPP specifications define some mechanisms to prioritize RA for different UEs based on RA configuration changes, including RA transmission power and back-off duration after a failed RA attempt.

[0009] Delivering connectivity services for business- or safety-critical applications is a significant opportunity for 5G networks. Such services usually have stringent performance requirements (e.g., for interruption time) that are formalized in a service level agreement (SLA) between a connectivity service provider (CSP, e.g., network operator) and a service consumer. Even so, these demanding services are only a small fraction of the services and users of a typical 5G network, thereby giving the CSP an opportunity to differentiate between services and optimize network resource usage per service and / or user type.

[0010] 5G standardization included a significant amount of work to bound packet delay for specific applications and users, resulting in features such as URLLC and quality of service (QoS) management. These features primarily address short-term impairments such as wireless channel fading and interference, and provide prioritization techniques for high traffic load scenarios. Even so, these features typically require a 5G network to be fully operational and / or functional.

[0011] However, a failure of a portion or subsystem of a 5G network may also affect the performance of critical applications. Such failures may include reduced performance or faults due to hardware component failures, software bugs, incorrect specifications, undesired control actions, incorrect configurations, and / or human interaction beyond what is specified for the network. Even so, it is desirable to prevent such failures from affecting critical application performance. Network techniques used to deliver a dependable service that is resilient to such failures are often referred to as Network Reliability, Availability, and Resilience (NRAR). NRAR techniques may be applied per service and / or user, specifically to the small fraction of the services and users who require them at any given time.

[0012] SUMMARY

[0013] When a RAN node (e.g., gNB) providing a cell that serves UEs fails, the served UEs are forced to reconnect to the RAN by performing RA, either to the same cell if the RAN node quickly re-starts or to a different cell if the RAN node does not quickly re-start. Since it simultaneously affects all UEs served by the cell, such a failure can produce a large RA load for which the affected cell has insufficient RA resources. Additionally, there may be an increased number of RA collisions between the many UEs attempting to access the affected cell. As such, high-priority users of critical applications with strict interruption time requirements will have the same difficulties accessing the cell as other users with less strict (or no) interruption time requirements. Existing RA prioritization techniques are based on lower RA loads experienced during normal network operating conditions rather than high RA loads experienced during exceptional conditions such as failures.

[0014] An object of embodiments of the present disclosure is to better control UE access to cells after a failure condition detected in a RAN, such as by providing, enabling, and / or facilitating solutions to exemplary problems summarized above and described in more detail below.

[0015] Embodiments include methods (e.g., procedures) for controlling UE access to a communication network after a failure in the communication network.

[0016] These exemplary methods include detecting a failure of an entity in the communication network (i.e., the “failed entity”). The failure of the entity causes at least one cell of the communication network to become at least temporarily unavailable for UEs. These exemplary methods also include, in response to the detected failure, determining an access control configuration for one or more cells of the communication network. Specifically, the access control configuration is different than a previous access control configuration for the one or more cells that was in use when the failure was detected. These exemplary methods also include applying the access control configuration in the one or more cells, thereby controlling UE access to the one or more cells.

[0017] In some embodiments, determining the access control configuration includes one of the following operations: modifying the previous access control configuration, generating the access control configuration, or selecting the access control configuration from a set of predefined access control configurations.

[0018] In some embodiments, the failure is detected by one of the following: the failed entity; a second unit or function of the failed entity, when the failure was in a first unit or function of the failed entity; or another entity of the communication network, of a same type or a different type as the failed entity.

[0019] In some of these embodiments, the other entity of a different type is a network management entity responsible for monitoring health and / or operational state of entities of the communication network. In some of these embodiments, the access control configuration is determined by one of the following: the failed entity, or a second entity of the communication network. In some variants of these embodiments, the second entity is one of the following: the second unit or function of the failed entity, when the failure was in the first unit or function of the failed entity; or the other entity of the same type or a different type as the failed entity.

[0020] In some variants of these embodiments, the failure is detected by the failed entity, the access control configuration is determined by the second entity, and these exemplary methods also include the failed entity sending one of the following to the second entity: an indication of the detected failure, or a request for modification of the previous access control configuration.

[0021] In some of these embodiments, the failed entity is one of the following:

[0022] • a radio access network (RAN) node that serves the at least one cell;

[0023] • one or more of the following units of the RAN node: centralized unit (CU), distributed unit (DU), baseband unit (BBU), radio unit (RU), and antenna unit;

[0024] • an Open-RAN (O-RAN) entity; or

[0025] • a control plane (CP) or user plane (UP) function in a core network of the communication network.

[0026] In some embodiments, the one or more cells, in which the access control configuration is applied, include one or more of the following: the at least one cell that becomes at least temporarily unavailable, and one or more neighbor cells proximate to the at least one cell. In some embodiments, the one or more cells, in which the access control configuration is applied, are provided by a backup entity to the failed entity. In some embodiments, applying the access control configuration in the one or more cells includes broadcasting, in the one or more cells, a system information block (SIB) that includes the access control configuration or an indication thereof.

[0027] Other embodiments and variants of the exemplary methods summarized above are described herein in more detail.

[0028] Other embodiments include network equipment (e.g, base stations, eNBs, gNBs, ng- eNBs, CUs / DUs, network management entities, etc.) configured to perform operations corresponding to any of the exemplary methods described herein. Other embodiments include non-transitory, computer-readable media storing program instructions that, when executed by processing circuitry, configure such network equipment to perform operations corresponding to any of the exemplary methods described herein.

[0029] These and other embodiments described herein may provide various advantages, benefits, and / or solutions to problems. For example, embodiments may improve performance for higher- priority users and / or services by prioritizing their access to a cell after a failure detected in the communication network, such as access to a new serving cell after failure of a RAN node that previously provided a serving cell for these and other users. Such improved performance may include reduced likelihood of a service outage, reduced service interruption time (e.g., if an outage occurs), and / or reduced probability of random access collision. These and other objects, features, and advantages of embodiments of the present disclosure will become apparent upon reading the following Detailed Description in view of the Drawings briefly described below.

[0030] BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figures 1-3 illustrate various aspects of an exemplary 5G / NR network architecture.

[0032] Figure 4 shows an exemplary Open RAN (O-RAN) architecture.

[0033] Figure 5 shows an exemplary configuration of NR user plane (UP) and control plane (CP) protocol stacks.

[0034] Figure 6 illustrates an exemplary conditional handover (CHO) procedure.

[0035] Figure 7 shows an exemplary ASN. 1 data structure for an exemplary system information block 1 (SIB 1 ) broadcast in a cell.

[0036] Figure 8 shows an exemplary ASN. 1 data structure for an exemplary uac- BarringlnfoSetList field included in SIB1.

[0037] Figure 9 shows an exemplary ASN. l data structure for an exemplary RA-Prioritization information element (IE).

[0038] Figures 10-12 show various example implementations involving two network entities, according to various embodiments of the present disclosure.

[0039] Figure 13 shows a flow diagram of an exemplary method for controlling UE access to a communication network after a failure in the communication network, according to various embodiments of the present disclosure.

[0040] Figure 14 shows a communication system according to various embodiments of the present disclosure.

[0041] Figure 15 shows a network node according to various embodiments of the present disclosure.

[0042] Figure 16 shows host computing system according to various embodiments of the present disclosure.

[0043] Figure 17 is a block diagram of a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized.

[0044] DETAILED DESCRIPTION

[0045] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided as examples to convey the scope of the subject matter to those skilled in the art. In general, all terms used herein are to be interpreted according to their ordinary meaning to a person of ordinary skill in the relevant technical field, unless a different meaning is expressly defined and / or implied from the context of use. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise or clearly implied from the context of use. The operations of any methods and / or procedures disclosed herein do not have to be performed in the exact order disclosed, unless an operation is explicitly described as following or preceding another operation and / or where it is implicit that an operation must follow or precede another operation. Any feature of any embodiment disclosed herein can apply to any other disclosed embodiment, as appropriate. Likewise, any advantage of any embodiment described herein can apply to any other disclosed embodiment, as appropriate.

[0046] Furthermore, the following terms are used throughout the description given below:

[0047] • Radio Access Node: As used herein, a “radio access node” (or equivalently “radio network node,” “radio access network node,” or “RAN node”) can be any node in a radio access network (RAN) that operates to wirelessly transmit and / or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g, gNB in a 3GPP 5G / NR network or an enhanced or eNB in a 3GPP LTE network), base station distributed components (e.g., CU and DU), a high-power or macro base station, a low-power base station (e.g., micro, pi co, femto, or home base station, or the like), an integrated access backhaul (IAB) node, a transmission point (TP), a transmission reception point (TRP), a remote radio unit (RRU or RRH), and a relay node.

[0048] • Core Network Node: As used herein, a “core network node” is any type of node in a core network. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a serving gateway (SGW), aPDN Gateway (P-GW), a Policy and Charging Rules Function (PCRF), an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), a Charging Function (CHF), a Policy Control Function (PCF), an Authentication Server Function (AUSF), a location management function (LMF), or the like.

[0049] • Wireless Device: As used herein, a “wireless device” (or “WD” for short) is any type of device that is capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other wireless devices. Communicating wirelessly can involve transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information through air. Unless otherwise noted, the term “wireless device” is used interchangeably herein with the term “user equipment” (or “UE” for short), with both of these terms having a different meaning than the term “network node”.

[0050] • Radio Node: As used herein, a “radio node” can be either a “radio access node” (or equivalent term) or a “wireless device.”

[0051] • Network Node: As used herein, a “network node” is any node that is either part of the radio access network (e.g, a radio access node or equivalent term) or of the core network (e.g., a core network node discussed above) of a cellular communications network. Functionally, a network node is equipment capable, configured, arranged, and / or operable to communicate directly or indirectly with a wireless device and / or with other network nodes or equipment in the cellular communications network, to enable and / or provide wireless access to the wireless device, and / or to perform other functions (e.g., administration) in the cellular communications network.

[0052] • Node: As used herein, the term “node” (without prefix) can be any type of node that can in or with a wireless network (including RAN and / or core network), including a radio access node (or equivalent term), core network node, or wireless device. However, the term “node” may be limited to a particular type (e.g., radio access node, IAB node) based on its specific characteristics in any given context.

[0053] The above definitions are not meant to be exclusive. In other words, various ones of the above terms may be explained and / or described elsewhere in the present disclosure using the same or similar terminology. Nevertheless, to the extent that such other explanations and / or descriptions conflict with the above definitions, the above definitions should control.

[0054] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system and can be applied to any communication system that may benefit from them.

[0055] Figure 1 illustrates a high-level view of an exemplary 5G network architecture, consisting of a Next Generation Radio Access Network (NG-RAN, 199) and a 5G Core (5GC, 198). The NG-RAN can include one or more gNodeB’s (gNBs) connected to the 5GC via one or more NG interfaces, such as gNBs (100, 150) connected via respective interfaces (102, 152). More specifically, the gNBs can be connected to one or more Access and Mobility Management Functions (AMFs) in the 5GC via respective NG-C interfaces and to one or more User Plane Functions (UPFs) in 5GC via respective NG-U interfaces. The 5GC can include various other network functions (NFs), such as Session Management Function(s) (SMF).

[0056] Although not shown, in some deployments the 5GC can be replaced by an Evolved Packet Core (EPC), which conventionally has been used together with a Long-Term Evolution (LTE) Evolved UMTS RAN (E-UTRAN). In such deployments, gNBs (e.g., 100, 150) can connect to one or more Mobility Management Entities (MMEs) in the EPC via respective Sl-C interfaces and to one or more Serving Gateways (SGWs) in EPC via respective NG-U interfaces.

[0057] In addition, the gNBs can be connected to each other via one or more Xn interfaces, such as Xn interface (140) between gNBs (100, 150). The radio technology for the NG-RAN is often referred to as “New Radio” (NR). With respect to the NR interface to UEs, each of the gNBs can support frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. Each of the gNBs can serve a geographic coverage area including one or more cells and, in some cases, can also use various directional beams to provide coverage in the respective cells. In general, a DL “beam” is a coverage area of a network-transmitted reference signal (RS) that may be measured or monitored by a UE.

[0058] NG-RAN logical nodes (e.g., gNB 100) include a Central Unit (CU or gNB-CU, e.g., 110) and one or more Distributed Units (DU or gNB-DU, e.g., 120, 130), which are connected via respective Fl logical interfaces (e.g., 122 and 132). CUs are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs. DUs are decentralized logical nodes that host lower layer protocols and can include, depending on the functional split option, various subsets of the gNB functions. Each DU can be connected to only a single CU. Each CU and DU can include various circuitry needed to perform their respective functions, including processing circuitry, communication interface circuitry (e.g., transceivers), and power supply circuitry.

[0059] Figure 2 shows a logical architecture for a gNB arranged in the split CU / DU architecture, such as gNB 100 in Figure 1. This logical architecture separates the CU into control plane (CP) and user plane (UP) functionality (CU-C and CU-U, respectively) that are connected by an El interface. Furthermore, each of the NG, Xn, and Fl interfaces is split into a CP interface (e.g., NG-C) and a UP interface (e.g., NG-U). Note that the terms “Central Entity” and “Distributed Entity” in Figure 2 refer to physical network nodes.

[0060] The functional split between CU and DU may also be referred to as a higher layer split (HLS). In addition, there may also be a lower layer split (LLS) of the DU functionality into a baseband unit (BBU) and one or more radio units (RUs) that produce the radio signals transmitted over the air. The LLS may use a proprietary interface, a standardized interface, or a mixture thereof. Figure 3 shows an exemplary partitioning of a RAN node (e.g., gNB) into a CU and two DUs, each of which includes a BBU and two RUs.

[0061] Open RAN (O-RAN) ALLIANCE is a community of mobile operators and RAN vendors working towards an open, intelligent, virtualized, operationally efficient, and fully interoperable RANs. To achieve these goals, the community has defined an O-RAN architecture with key functions and interfaces. Various specifications published by O-RAN work groups (WGs). For example, O-RAN WG1 is concerned with use cases and overall architecture. One general principle is that O-RAN architecture and interface specifications shall be consistent with 3GPP architecture and interface specifications, to the extent possible.

[0062] Figure 4 shows an exemplary O-RAN architecture. The Al, 01, and 02 interfaces connect the Service Management and Orchestration function (SMO, 410) to O-RAN network functions (NFs) and cloud infrastructure management (O-Cloud, 460). These O-RAN NFs include Near-Real Time RAN Intelligent Controller (RIC, 420), Open Centralized Units (O- CUs, 430), Open Distributed Units (O-DUs, 450), and Open Radio Units (O-RUs, 450). Additionally, there is an interface between SMO and external information sources.

[0063] The O-RAN Architecture also includes the following three control loops with respective latencies:

[0064] • Real Time (RT) Control Loop (<10 ms), typically in O-RU / O-DU;

[0065] • Near-RT RIC Control Loop (10-1000 ms), in Near-RT RIC; and

[0066] • Non-RT RIC Control Loop (>1000 ms), shown as sub-block 415 in SMO.

[0067] Use cases for Non-RT RIC and Near-RT RIC control loops are fully defined by O-RAN, but O- RAN only defines relevant interactions with other O-RAN nodes or functions for the RT control loop (which performs radio scheduling, HARQ, beamforming, etc.).

[0068] The Non-RT RIC provides the Al interface to the Near-RT RIC. One task of Non-RT RIC is to provide policy -based guidance, machine learning (ML) model management, and enrichment information to support intelligent RAN optimization by the Near-RT RIC (e.g., for radio resource management, RRM). The Non-RT RIC can also perform intelligent RRM in longer, non-RT intervals (e.g., greater than 1 second).

[0069] The Non-RT RIC can use data analytics and ML model training / inference to determine RAN optimizations, for which it can leverage SMO services such as data collection from and provisioning to the O-RAN nodes. These actions are performed by Non-RT RIC RAN Applications (rApps, e.g., 411), which are exposed to Non-RT RIC functionality and services via the R1 interface in SMO.

[0070] Figure 5 shows an exemplary configuration of NR user plane (UP) and control plane (CP) protocol stacks between a UE (510), a gNB (520), and an AMF (530). Physical (PHY), Medium Access Control (MAC), Radio Link Control (RLC), and Packet Data Convergence Protocol (PDCP) layers between the UE and the gNB are common to UP and CP. PDCP provides ciphering / deciphering, integrity protection, sequence numbering, reordering, and duplicate detection for both CP and UP. In addition, PDCP provides header compression and retransmission for UP data. On the UP side, Internet protocol (IP) packets arrive to PDCP as service data units (SDUs), and PDCP creates protocol data units (PDUs) to deliver to RLC. The Service Data Adaptation Protocol (SDAP) layer handles quality-of-service (QoS) including mapping between QoS flows and Data Radio Bearers (DRBs) and marking QoS flow identifiers (QFI) in UL and DL packets. RLC transfers PDCP PDUs to MAC through logical channels (LCH). RLC provides error detection / correction, concatenation, segmentation / reassembly, sequence numbering, reordering of data transferred to / from the upper layers. MAC provides mapping between LCHs and PHY transport channels, LCH prioritization, multiplexing into or demultiplexing from transport blocks (TBs), hybrid ARQ (HARQ) error correction, and dynamic scheduling (in gNB). PHY provides transport channel services to MAC and manages transfer over the NR radio interface, e.g., via modulation, coding, antenna mapping, and beam forming.

[0071] On the CP side, the non-access stratum (NAS) layer between UE and AMF handles UE / gNB authentication, mobility management, and security control. RRC sits below NAS in the UE but terminates in the gNB rather than the AMF. RRC controls communications between UE and gNB at the radio interface as well as the mobility of a UE between cells in the NG-RAN. RRC also broadcasts system information (SI) and performs establishment, configuration, maintenance, and release of DRBs and Signaling Radio Bearers (SRBs) and used by UEs. Additionally, RRC controls addition, modification, and release of carrier aggregation (CA) and dual-connectivity (DC) configurations for UEs, and performs various security functions such as key management.

[0072] After a UE is powered ON it will be in the RRC ..IDLE state until an RRC connection is established with the network, at which time the UE will transition to RRC CONNECTED state (e.g., where data transfer can occur). The UE returns to RRC DLE after the connection with the network is released. In RRC IDLE state, the UE’s radio is active on a discontinuous reception (DRX) schedule configured by upper l yers. During DRX active periods (also referred to as “DRX On durations”), an RRCJDLE UE receives SI broadcast in the cell where the UE is camping, performs measurements of neighbor cells to support cell reselection, and monitors a paging channel on PDCCH for pages from 5GC via gNB.

[0073] An NR UE in RRC JDLE state is not known to the gNB serving the cell where the UE is camping. The UE must perform a random-access (RA) procedure to move from RRC JDLE to RRC CONNECTED state, where the cell serving the UE is known and an RRC context is established for the UE in the serving gNB, such that the UE and gNB can communicate. As part of (or in conjunction with) the RA procedure, the UE also transmits an RRCSetupRequest message to the serving gNB. NR RRC also includes an RRC INACTIVE state in which a UE is known (e.g., via UE context) by the serving gNB. RRCJNACTIVE has some properties similar to a “suspended” condition used in LTE. As mentioned above, seamless mobility is a key feature of 3GPP RATs including NR. When a UE moves between the coverage areas of two cells, a serving cell change needs to be performed at some point. A UE in RRC CONNECTED state can be configured to perform and report measurements of its serving cell(s) and neighbor cells to its serving RAN node. Upon the reported measurements meeting a certain condition or threshold, the serving RAN node may send a handover (HO) command to the UE, indicating a target cell for the handover. In NR, the handover command is an RRCReconflguration message with a reconflgurationWithSync field. The procedure to perform a handover is sometimes also referred to as “L3 mobility”, as it is controlled by layer 3 (L3, i.e., RRC) and the messages exchanged are part of L3.

[0074] Even so, HO can have various robustness problems. For example, a HO command is normally sent when the radio conditions for the UE are already quite bad, such as at or near cell borders. As such, the HO command may need to be segmented (e.g., to allow for redundancy to protect against errors) and / or retransmitted one or more times before it reaches the UE. In such case, the HO command may not reach the UE in time (or at all) before the degraded connection with the source node (e.g., the node hosting the UE’s current serving cell) is dropped. Failure of handover to a target cell may lead to the UE declaring radio link failure (RLF) in the source cell and attempting to reestablish its connection in another target cell.

[0075] Conditional handover (CHO) was introduced in 3GPP Rel-16 to improve robustness of UE mobility. The key idea in CHO is separation of transmission and execution of the handover command. This allows the handover command to be sent to a UE earlier when the radio conditions are still good, thus increasing the likelihood that the message is successfully transferred. The execution of the handover command is done later in time based on an associated execution condition.

[0076] The execution condition is typically based on a threshold. For example, a signal strength of candidate target cell becomes X dB better than the serving cell (so called “A3 event ”). A preceding measurement reporting event could use a threshold Y that is selected to be lower than X used as the HO execution condition. This allows the serving RAN node to prepare the HO upon reception of an early measurement report and to send an RRCReconflguration message with either a reconflgurationWithSync or a CellGroupConfig at a time when the radio link between the serving cell and the UE is still relatively stable.

[0077] In 3GPP terminology, a cell for which conditional HO is configured may be called a “candidate target cell” while a RAN node controlling a candidate target cell may be called a “candidate target node.” Once the conditional HO execution condition has been fulfilled for a candidate target cell and mobility execution towards this cell has been triggered, this cell is no longer a “candidate” since it is now certain that the HO will be executed towards it. Rather, the candidate target cell is then referred to as the “target cell”.

[0078] Figure 6 illustrates an exemplary CHO procedure between a UE (610), a source RAN node (620), and a target RAN node (630). For example, the source and target nodes can be gNBs and / or components of gNBs, such as CUs and / or DUs.

[0079] This procedure involves two different measurement thresholds: a low threshold and a high threshold. The two thresholds can be expressed as different levels of a particular metric, e.g., signal strength, signal quality, etc. For example, the high threshold could be that the quality of the mobility reference signal (MRS) of the target cell or beam becomes X dB stronger than the MRS of the UE’s serving cell (e.g., provided by the source RAN node), with the low threshold being less than the high threshold (i.e., target exceeds source by lower amount). As used in this context, MRS denotes a reference signal used for any mobility-related purpose. For example, in NR, MRS can be either SSB (SS / PBCH block) or CSI-RS. As a further example, for NR operating in unlicensed spectrum (referred to as NR-U), MRS can be a discovery reference signal (DRS) in addition to any of the signals mentioned above.

[0080] The UE can be provided with a measurement configuration including the low threshold (not shown in the figure). Upon performing measurements that meet the low threshold, the UE can send a measurement report to the serving node (operation 1). While performing the measurements and evaluating the low threshold, the UE continues operating in its current RRC configuration. In operation 2, based on this report, the source RAN node can decide to request an early handover of the UE to the target RAN node (e.g., to a cell indicated in the measurement report). For example, this early handover request can include a HandoverPreparationlnformation IE such as described above.

[0081] The target RAN node performs admission control for the UE and responds with a CHO request acknowledgement (operation 5) that includes RRC configuration, similar to conventional handover. In operation 6, the source RAN node then sends the UE a RRCReconfiguration message that includes a “CHO Configuration”, which can include the high threshold. After responding with an RRCReconfigurationComplete message (operation 7), the UE continues to perform measurements and whenever the high threshold condition is met for a target cell, it can detach from the source cell and, after performing a RA procedure and synchronizing with the target cell, send the target RAN node an RRCReconfigurationComplete message (e.g., operations 8-9). Even so, the UE can remain in the source cell for an extended amount of time in case the high threshold condition is not fulfilled.

[0082] In operation 10, the target RAN node sends a HANDOVER SUCCESS message to the source gNB indicating the UE has successfully established the target connection. Upon reception of the handover success indication, the source RAN node stops scheduling any further DL or UL data to the UE and sends an SN STATUS TRANSFER message to the target RAN node indicating the latest PDCP SN transmitter and receiver status (operation 11). The source RAN node now also starts to forward User Data to the target RAN node (operation 12). Upon receiving the handover complete message (operation 9), the target RAN node can start exchanging user data with the UE. The target RAN node also requests the AMF to switch the DL data path from the UPF from the source RAN node to the target RAN node (not shown). Once the path switch is completed the target RAN node sends the UE CONTEXT RELEASE to the source RAN node (operation 13).

[0083] As noted above, the UE must perform a RA to the target cell in both conditional and nonconditional HO, similar to how the UE performs a RA to a particular cell when it initially establishes a connection to that cell when moving from RRC IDLE to RRC CONNECTED state.

[0084] A 5G / NR network can control UE initial access to each cell in various ways and / or on various levels, based on a unified access control (UAC) framework. For example, access to a particular cell (or group of cells) can be barred for all UEs, a specific group of UEs, all except a specific group of UEs, etc. For example, UEs having certain access identities might be allowed on cells reserved by a network operator for its internal use, while all other UEs are barred from accessing these cells. As such, when a UE is camped (e.g., in RRC IDLE) on a particular cell, the UE may have selected that cell for camping because the UE is barred from accessing other nearby cells, even if they are otherwise preferrable (e.g., due to better signal strength).

[0085] A UE in RRC IDLE wanting to move to RRC CONNECTED initially acquires essential SI from cell broadcast, including the master information block (MIB) and SI block 1 (SIB1), the latter of which provides relevant access control information. Figure 7 shows an ASN.l data structure for an exemplary SIB1 broadcast in a cell, as further defined in 3GPP TS 38.331 (vl8.1.0). The most relevant information is in the field uac-Barringlnfo, which includes barring information that is public land mobile network (PLMN)-specific (field uac-BarringPerPLMN- Lisf) and common barring information (field uac-BarringForCommo ) that is only applicable for PLMNs (or standalone non-public networks) with no PLMN-specific barring information.

[0086] This field also includes a uac-BarringlnfoSetList field, which provides a list of access control parameter sets. An access category can be configured with one of the access control parameter sets identified by the uac-BarringlnfoSetList field. Figure 8 shows an ASN. l data structure for an exemplary uac-BarringlnfoSetList. The following table defines the field and sub- fields shown in Figure 8.

[0087] 3GPP TS 22.261 (vl8.6.0) Table 6.22.2.2-1 (repeated below) defines the Access Identities referred to in various sub-fields of the uac-BarringlnfoSetList field of SIB 1 :

[0088] 3GPP TS 22.261 (vl8.6.0) Table 6.22.2.3-1 (repeated below) defines the Access Categories referred to in the uac-BarringlnfoSetList sub-field of the uac-BarringlnfoSetList field of SIB 1:

[0089] The UE then initiates RRC connection establishment including performing UAC as described in 3GPP TS 38.331 (vl8.1.0) section 5.3.14. In particular, UAC may bar UE access to the cell based on Access Identity and Access Category information. If access is barred, the UE stops the access procedure but if access is not barred, the UE continues the access procedure to the cell in accordance with the UAC, including performing RA.

[0090] In addition, 3GPP specifications define some mechanisms to prioritize RA for different UEs based on RA configuration changes, including RA transmission power and back-off duration after a failed RA attempt. Figure 9 shows an ASN.l data structure for a RA-Prioritization IE that may be used for this purpose. The powerRampingStepHighPrioritiy field defines a power ramping step applied for prioritized random access procedure, while the scalingFactorBI field defines scaling factor for the backoff indicator (BI) for the prioritized random access procedure.

[0091] A UE transmits its initial message (i. e. , preamble) during RA on a physical random-access channel (PRACH). Prior to initiation of RA, the UE lower layers (e.g., PHY) receives the following information from the higher layers (e.g., RRC):

[0092] • Configuration of PRACH transmission parameters such as preamble format, time resources, and frequency resources; and

[0093] • Parameters for determining a PRACH preamble sequence set, such as index to logical root sequence table, cyclic shift (CS N), set type (e.g., unrestricted, restricted set A, or restricted set B), etc.

[0094] The UE higher layers obtain this information from the RACH-ConflgCommon IE broadcast in SIB1. Individual fields of the RACH-ConflgCommon IE are defined in 3GPP TS 38.331 (vl8.1.0). The RAN node configures the set of random-access preamble sequences the UE is allowed to use, generated from one or several root Zadoff-Chu sequences with zero correlation zone. In an NR cell, there are up to two sets of up to 64 preamble sequences available, where set 1 corresponds to higher-layer PRACH configuration using prach-Conflgurationlndex and prach- FrequencyOffset, and set 2 (if configured) corresponds to higher-layer PRACH configuration using prach-ConflgurationlndexHighSpeed and prach-FrequencyOffsetHighSpeed.

[0095] A UE determines the set of (up to) 64 preamble sequences in a cell by including, in the order of increasing cyclic shift, all the available cyclic shifts of a root Zadoff-Chu sequence with the logical index rootSequencelndexHighSpeed (for Set 2, if configured) or with the logical index RACH_ROOT_SEQUENCE (for Set 1), where both rootSequencelndexHighSpeed (if configured) and RACH ROOT SEQUENCE are broadcast as SI for the cell. In case the number of allowed preamble sequences cannot be generated from a single root Zadoff-Chu sequence, the UE obtains additional ones from root sequences with consecutive logical indices until all allowed preamble sequences are found.

[0096] A RAN node can modify SI that it broadcasts in a cell according to a broadcast control channel (BCCH) modification period defined as modiflcationPeriodCoeff* defaultPagingCycle, where modiflcationPeriodCoeff can be configured to be {2, 4, 8, 16} and defaultPagingCycle can be configured to be {32, 64, 128, or 256} radio frames, with each radio frame being 10 ms. These parameters are included in the servingCellConflgCommon IE of SIB1, as shown in Figure 7. A typical BCCH modification period is 2*128 radio frames, which results in a BCCH modification period of 2.56 seconds. A UE must monitor SI accordingly to detect any changes.

[0097] As briefly mentioned above, delivering connectivity services for business or safety critical applications is a significant opportunity for 5G networks. Such services usually have stringent performance requirements (e.g., for interruption time) that are formalized in an SLA between a connectivity service provider (CSP, e.g., network operator) and a service consumer. 5G standardization included a significant amount of work to bound packet delay for such critical applications and users, resulting in features such as URLLC and QoS management. These features primarily address short-term impairments such as wireless channel fading and interference, and provide prioritization techniques for high traffic load scenarios. Even so, these features typically require a 5G network to be fully operational and / or functional.

[0098] However, a failure of a portion or subsystem of a 5G network may also affect the performance of critical applications. Such failures may include reduced performance or faults due to hardware component failures, software bugs, incorrect specifications, undesired control actions, incorrect configurations, and / or human interaction beyond what is specified for the network. Even so, it is desirable to prevent such failures from affecting critical application performance. When a RAN node (e.g., gNB) providing a cell that serves UEs fails, the served UEs are forced to reconnect to the RAN by performing RA, either to the same cell if the RAN node quickly re-starts or to a different cell if the RAN node does not quickly re-start. Since it simultaneously affects all UEs served by the cell, such a failure can produce a large RA load for which the affected cell has insufficient RA resources. Additionally, there may be an increased number of RA collisions between the many UEs attempting to access the affected cell. As such, high-priority users of critical applications with strict interruption time requirements will have the same difficulties accessing the cell as other users with less strict (or no) interruption time requirements.

[0099] In principle, access control may be configured to prioritize the access of high-priority users, such as by barring the access of other users. However, this approach may unnecessarily penalize non-high-priority users when the network is operating normally and should be able to cope with the corresponding load. Although an operator may configure access control as desired in accordance with 3GPP specifications, a typical configuration does not provide mechanisms for preventing sudden access to a cell of a large group of UEs due to the failure of another cell. Moreover, existing RA prioritization techniques are based on lower RA loads experienced during normal network operating conditions rather than high RA loads experienced during exceptional conditions such as failures.

[0100] Embodiments of the present disclosure address these and related problems, issues, and / or difficulties by flexible and efficient techniques for setting up and / or modifying access (or admission) control procedures for cells in response to a failure detected in a communication network. Accordingly, embodiments may improve performance for higher-priority users and / or services by prioritizing their access to a cell after a failure detected in the communication network, such as access to a new serving cell after failure of a RAN node that previously provided a serving cell for these and other users. Such improved performance may include reduced likelihood of a service outage, reduced service interruption time (e.g., if an outage occurs), and / or reduced probability of RA collision.

[0101] In general, embodiments involve detecting a failure in the communication network. The detected failure may be of a RAN node (e.g., gNB), a unit of a RAN node (e.g., CU, DU, BBU, RU) or portion thereof (e.g., CU-CP, CU-UP), an O-RAN entity (e.g., O-CU, O-DU, O-RU, Near-RT RIC, Non-RT RIC), a hardware element (e.g., antenna array), an instance of a network function (e.g., UPF), etc. More generically, “failed entity” will be used to refer to the entity in which the detected failure occurred. In various embodiments, the failure detection may be performed by any of the following:

[0102] • the failed entity (e.g., gNB); • a second unit or function of the failed entity (e.g., a CU of a gNB), when the failure was detected in a first unit or function of the failed entity (e.g., a DU of the gNB);

[0103] • another network entity of the same type as the failed entity (e.g., a second gNB);

[0104] • a network management entity (e.g., operations / administration / maintenance (OAM) function, SMO, etc.) responsible for monitoring health, operational state, etc. of other network entities including the failed entity.

[0105] In general, the detected failure causes at least one serving cell for UEs to become unavailable, at least temporarily. In response to detecting the failure, an access control configuration for one or more cells is modified to ensure that high-priority UEs (e.g., having users with NRAR-grade service) have higher priority when accessing the one or more cells after the failure. The one or more cells for which the access control configuration is modified may be referred to as “affected cells”, and may include at least one neighbor cell proximate to the at least one serving cell and / or any of the at least one serving cell (if subsequently becoming available again).

[0106] Note that “modify” when applied to access control configurations does not necessarily mean that some parameters, etc. of an existing access control configuration are adjusted. Rather, it may also mean determining an access control configuration that is different than the one currently in use when the failure was detected, such as generating the access control configuration (e.g., from scratch) or selecting one of a set of predefined access control configurations. In this broader sense, “modifications” may be understood as “differences” between new and previous access control configurations.

[0107] In some embodiments, the access control configuration may be modified on a network entity basis. For example, the access control configuration may be modified for the failed entity (e.g., if expected to recover quickly) or another network entity that is configured to replace the failed entity. As a more specific example, in a cloud RAN deployment, a backup instance of the failed entity may be in stand-by prior to the detected failure and placed into operation in response to detecting the failure.

[0108] In other embodiments, the access control configuration may be modified on a network slice basis. Network slicing allows the operator to partition a PLMN into different logical end- to-end slices of functionality that minimize impact between groups of users sharing a pool of network resources (e.g., radio resources). Each slice can have a different configuration in terms of protocols, resource usage policies, access criteria, etc. Different slices can also be realized with independent logical or physical instances of the various network functions. For example, it is possible to use separate dedicated core network (CN) instances for different slices. In some embodiments, the access control configuration may include UAC mechanisms such as access barring features described above. In such embodiments, the modifications may restrict or limit access by certain users or services in the affected cells, such as by preventing one or more access identities and / or access categories from accessing the affected cells. Alternately or in addition, the modifications may providing a lower probability of access success for one or more access identities and / or access categories in the affected cells, such as by appropriate setting of the uac-BarringFactor parameters discussed above.

[0109] In some embodiments, the access control configuration may be modified for a specific PLMN or standalone non-public network (SNPN), such as by modifications to the uac- BarringPerPLMN-List field discussed above. In other embodiments, the access control configuration modifications may be common to all PLMNs / SNPNs (or to all except one or more specific PLMNs / SNPNs), such as modifications to the uac-BarringForCommon field discussed above.

[0110] In some embodiments, the access control configuration may identify resources used for accessing the affected cells (e.g., PRACH preambles, time / frequency resources, etc.), such that the modifications identify a different set of resources than before the failure was detected. For example, the modification may increase the resources available for accessing to cope with the sudden increase in access attempts to the affected cells due to the failure. The additional resources may be configured for all UEs (i.e., providing increased capacity for all users) or only for high- priority UEs (i.e., providing increased capacity for high-priority users).

[0111] In some embodiments, the modifications to the access control configuration may include changes to a RA prioritization for high-priority users, such as applying or modifying a RA- Prioritization IE such as discussed above. As more specific examples, the powerRampingStepHighPrioritiy field can be modified to increase the power ramping step applied for prioritized RA, and / or the scalingFactorBI field can be modified to change the scaling factor for the backoff indicator (BI) for prioritized RA.

[0112] In some embodiments, the modifications to the access control configuration may include changes to the modiflcationPeriodCoeff and / or defaultPagingCycle fields in the servingCellConfigCommon IE of SIB1, which define the BCCH modification period as discussed above. For example, the BCCH modification period may be reduced to facilitate timely UE acquisition of other modifications to the access control configuration broadcast in SIB1, thereby improving the effectiveness of the modifications.

[0113] In some embodiments, the access control configuration may be modified subsequently (i.e., a second time) to its pre-failure settings or to different settings altogether. This subsequent modification may be performed after a duration of using the modified settings after the failure. The duration may be determined based on expiration of timer initiated upon the modification, a predetermined number of RA occasions, a predetermined number of RA attempts, when all high- priority users have accessed the affected cells, etc.

[0114] Some examples are given below to further illustrate embodiments of the present disclosure. In a first example, a first UE (UE1) is connected to a first cell (cell-A). During normal operation, UE1 received a CHO configuration from cell-A, specifying that UE1 will HO to a second cell (cell-B) if a quality measurement for cell-B is better than a quality measurement for cell-A. A second UE (UE2) is also connected to cell-A. UE1 and UE2 have different access control parameters, such as different access identities or use different services that are associated with different access categories. As a specific example, UE1 may use services with NRAR requirements while UE2 uses services that do not have such requirements.

[0115] At some point, a network failure that affects cell-A is detected. For example, a failure is detected in a DU that provides cell-A, such that cell-A is (at least temporarily) unavailable to UE1 and UE2. In response to this failure, the access control configuration for cell-B is modified to prioritize access to RA resources by UE1 over UE2.

[0116] For example, cell-B may use an access control configuration that (at least temporarily) bars UE2 from using RACH resources, based on an access identity and / or an access category associated with UE2 being barred. As another example, cell-B may use an access control configuration that (at least temporarily) lowers the probability that UE2 uses RA resources in cell- B, such as increasing a barring factor that applies to an access category associated with UE2. Based on its CHO configuration and measurements of failed cell-A, UE1 attempts HO to cell-B. Based on the modified access control configuration, UE1 performs RA and completes HO of its connection to cell-B.

[0117] UE2 also attempts to change its connection to cell-B, either due to having a CHO configuration similar to UE1 or after declaring radio link failure (RLF) in cell-A and performing re-selection of cell-B. Based on the modified access control configuration, however, UE2 is temporarily barred from accessing cell-B. In this way, a potential collision between UE1 and UE2 during RA is avoided. The barring of UE2 access to cell-B may be removed after some duration, such that UE2 and other lower priority users / services are then able to access cell-B.

[0118] In a second example, cell-B is configured as a fallback for cell-A. In other words, it is expected that users served by cell-A will switch to cell-B if / when cell-A fails. During normal operation, cell-B broadcasts an access control configuration that allows access for the following:

[0119] Access identities AI-1 and AI-2; and

[0120] Access categories AC-1 and AC-2. Based on this configuration, UEs using access identity AI-1 or AI-2 can access cell-B. After a failure for cell-A is detected, cell-B broadcasts a modified access control configuration that includes one or more of the following modifications:

[0121] • Access allowed for AI-1 but not for AI-2 (i.e., for any access category); and

[0122] • Access allowed for AC-1 but not for AC-2 (i.e., for any access identity).

[0123] Based on the first modification above, UEs using AI-1 may access the cell but not UEs using AI- 2. Based on the second modification above, UEs using any access identity (including AI-1 and AI-2) may access cell-B so long that the access category is AC-1, but all access identities are prohibited for AC -2.

[0124] Figures 10-12 show various example implementations involving two network entities, according to various embodiments of the present disclosure. For example, the two network entities may be integrated / standalone nodes or virtualized entities in a cloud environment.

[0125] In a first example shown in Figure 10, the first network entity (1010) fails, and the failure is detected by the first network entity, the second network entity (1020), or a third network entity (e.g., 0AM function) responsible for monitoring operational status of other network entities. The second network entity modifies the access control configuration for one or more cells in response to the detected failure.

[0126] For example, the first network entity may be a first gNB or the CU of a first gNB, while the second network entity may be a second gNB or the CU of a second gNB. For example, in a cloud environment, the second network entity may be configured as a backup for the first network entity, such that the second network entity is activated upon the detected failure.

[0127] In a second example shown in Figure 11, the first network entity (1010) explicitly notifies the second network entity (1020) about the detected failure. The first network entity may directly detect the failure or detect it based on a notification received from a third network entity (e.g., 0AM function) responsible for monitoring operational status of other network entities. The detected failure may be within the first network entity or within a domain for which the first network entity is responsible (e.g., a CU associated with a failed DU). The second network entity modifies the access control configuration for one or more cells in response to the detected failure, in a similar manner as shown in Figure 10.

[0128] In a third example shown in Figure 12, instead of explicitly notifying the second network entity (1020) about the detected failure, the first network entity (1010) requests an action from the second network entity in response to the detected failure. For example, the first network entity may request modification of the access control configuration for one or more cells, which causes the second network entity to perform such a modification. In some embodiments, the operations discussed above for various embodiments may be performed by one or more network entities of a ORAN architecture, such as shown in Figure 4 described above. For example, detecting a failure in the communication network may be performed by an SMO (410), a Near-RT RIC (420), an O-CU (430), an O-DU (440), an O-RU (450), and / or an O-Cloud (460). Likewise, modifying an access control configuration may be performed by the SMO, the Near-RT RIC, the O-CU, the O-DU, the O-RU, and / or the O-Cloud. Likewise, applying the modified access control configuration in one or more cells (e.g., by broadcasting) may be performed by the SMO, the Near-RT RIC, the O-CU, the O-DU, the O-RU, and / or the O-Cloud

[0129] Various embodiments may be defined as procedures, messages, etc. in 3GPP specifications. For example, a new message may be defined for various interfaces (e.g., Fl, Xn, NG, El, 01, etc.) between network entities to indicate network entity failure, such as DU failure, CU failure, gNB failure, etc. Alternately, existing messages over these various interfaces may be modified to include an indication of network entity failure.

[0130] Similarly, new messages may be defined (or existing messages modified) to provide a modified access control configuration after a detected failure, such as in the RRC protocol defined in 3GPP TS 38.331 (vl8.1.0). Likewise, new access identities and / or new access categories may be defined (e.g., in 3GPP TS 22.261 V18.6.0) for users requiring a high degree of resiliency or a short service interruption time, such that these may be used as part of a modified access control configuration after a detected failure in a network entity.

[0131] Various features of the embodiments described above correspond to various operations illustrated in Figure 13, which shows an exemplary method (e.g., procedure) for controlling UE access to a communication network after a failure in the communication network, according to various embodiments of the present disclosure. In other words, various features of the operations described below correspond to various embodiments described above. The exemplary method can be performed by any appropriate network equipment (e.g., one or more network entities) such as described elsewhere herein. Although Figure 13 shows specific blocks in a particular order, the operations of the exemplary method can be performed in different orders than shown and can be combined and / or divided into blocks having different functionality than shown. Optional blocks or operations are indicated by dashed lines.

[0132] The exemplary method includes the operations of block 1310, where the network equipment detects a failure of an entity in the communication network (i.e., the “failed entity”). The failure of the entity causes at least one cell of the communication network to become at least temporarily unavailable for UEs. The exemplary method also includes the operations of block 1330, where in response to the detected failure, the network equipment determines an access control configuration for one or more cells of the communication network. Specifically, the access control configuration is different than a previous access control configuration for the one or more cells that was in use when the failure was detected. The exemplary method also includes the operations of block 1340, where the network equipment applies the access control configuration in the one or more cells, thereby controlling UE access to the one or more cells.

[0133] In some embodiments, determining the access control configuration in block 1330 includes one of the following operations, labelled with corresponding sub-block numbers:

[0134] • (1331) modifying the previous access control configuration (e.g., changing one or more parameters);

[0135] • (1332) generating the access control configuration, or

[0136] • (1333) selecting the access control configuration from a set of predefined access control configurations (which may also include the previous access control configuration).

[0137] In some embodiments, the failure is detected in block 1310 by one of the following:

[0138] • the failed entity;

[0139] • a second unit or function of the failed entity, when the failure was in a first unit or function of the failed entity; or

[0140] • another entity of the communication network, of a same type or a different type as the failed entity.

[0141] In some of these embodiments, the other entity of a different type is a network management entity responsible for monitoring health and / or operational state of entities of the communication network. In some of these embodiments, the access control configuration is determined in block 1330 by one of the following: the failed entity, or a second entity of the communication network. In some variants of these embodiments, the second entity is one of the following: the second unit or function of the failed entity, when the failure was in the first unit or function of the failed entity; or the other entity of the same type or a different type as the failed entity.

[0142] In some variants of these embodiments, the failure is detected by the failed entity, the access control configuration is determined by the second entity, and the exemplary method also includes the operations of block 1320, where the failed entity sends one of the following to the second entity: an indication of the detected failure, or a request for modification of the previous access control configuration.

[0143] In some of these embodiments, the failed entity is one of the following:

[0144] • a radio access network (RAN) node that serves the at least one cell;

[0145] • one or more of the following units of the RAN node: centralized unit (CU), distributed unit (DU), baseband unit (BBU), radio unit (RU), and antenna unit; • an Open-RAN (O-RAN) entity; or

[0146] • a control plane (CP) or user plane (UP) function in a core network of the communication network.

[0147] In some embodiments, the one or more cells, in which the access control configuration is applied in block 1340, include one or more of the following: the at least one cell that becomes at least temporarily unavailable, and one or more neighbor cells proximate to the at least one cell. For example, the proximate neighbor cells may have overlapping, adjacent, or nearby coverage areas to the at least one unavailable cell. Moreover, proximate neighbor cells may have coverage areas that are overlapping, adjacent, or nearby to each other. Note that the proximity of the neighbor cells may be independent of the locations of RAN nodes serving the neighbor cells and the at least one unavailable cell.

[0148] In some embodiments, the one or more cells, in which the access control configuration is applied in block 1340, are provided by a backup entity to the failed entity. In some embodiments, applying the access control configuration in the one or more cells in block 1340 includes the operations of sub-block 1341, where the network equipment broadcasts, in the one or more cells, a system information block (SIB) that includes the access control configuration or an indication thereof. Note that a “SIB” in this context refers not only to the specific SIB data structure used in 5G and earlier 3GPP-specified networks, but also to data structures (which may be called SIBs or other names) containing similar information that are used in other present- or future-generation networks.

[0149] In some of these embodiments, the previous access control configuration identifies a cell broadcast modification period for the one or more cells, and determining the access control configuration in block 1330 includes the operations of sub-block 1334, where the network equipment reduces the cell broadcast modification period to facilitate faster UE acquisition of the SIB that includes the access control configuration. For example, this can involve changes to the modificationPeriodCoeff and / or defaultPagingCycle fields in the servingCellConfigCommon IE of SIB1, as discussed above.

[0150] In some of these embodiments, the access control configuration is included in one or more of the following of the SIB: a first IE carrying access control information or access barring information, and a second IE carrying serving cell configuration information. In some variants of these embodiments, the first IE is a uac-Barringlnfo IE and the second IE is a servingCellConfigCommon IE, e.g., as specified in 3GPP TS 38.331.

[0151] In some embodiments, the previous access control configuration includes or identifies access control parameter sets for respective access categories. Each access category is associated with one or more services or applications used by the UEs. In some of these embodiments, each access control parameter set includes or identifies the following for the corresponding access category:

[0152] • a probability that access attempts to a cell, by UEs associated with the access category, will be allowed during access barring checks;

[0153] • a duration after barring of an access attempt to a cell by a UE associated with the access category, until a new access attempt by the UE is allowed; and

[0154] • respective indications of whether access attempts are allowed for each of a plurality of access identities.

[0155] In some variants of these embodiments, determining the access control configuration for one or more cells in block 1330 includes one or more of the following operations, labelled with corresponding sub-block numbers:

[0156] • (1335) increasing the probability that access attempts to the one or more cells by UEs associated with a first access category will be allowed;

[0157] • (1336) reducing the probability that access attempts to the one or more cells by UEs associated with a second access category will be allowed; and

[0158] • (1337) changing one or more of the indications to indicate that access attempts are barred for the corresponding access identities.

[0159] In some of these embodiments, differences between the access control configuration and the previous access control configuration relate to one of the following: all public land mobile network (PLMN) and standalone non-public network (SNPN) identities, or only one or more specific PLMN and / or SNPN identities. In other of these embodiments, differences between the access control configuration and the previous access control configuration relate to one of the following: all network slices of the communication network, or only one or more specific network slices of the communication network.

[0160] In some embodiments, the previous access control configuration identifies random access (RA) resources available in the one or more cells, and the access control configuration identifies additional RA resources available in the one or more cells after the detected failure. In some of these embodiments, the additional RA resources in the one or more cells are available to one of the following: all UEs, or only high-priority UEs or UEs associated with high-priority services.

[0161] In some embodiments, the previous access control configuration includes a configuration for prioritized RA, and determining the access control configuration in block 1330 includes one or more of the following operations, labelled with corresponding sub-block numbers:

[0162] • (1338) increasing a power ramping step used for prioritized RA, and

[0163] • (1339) reducing a scaling factor used to determine a power backoff for prioritized RA. For example, these operations can involve increasing the value of powerRampingStepHighPrioritiy field to increase the power ramping step applied for prioritized RA, and / or reducing the value of the scalingFactorBI field to reduce the scaling factor for the backoff indicator (BI) for prioritized RA.

[0164] In some embodiments, the exemplary method also includes the following operations, labelled with corresponding block numbers:

[0165] • (1350) determining a further access control configuration that is different than the access control configuration; and

[0166] • (1360) at the end of a duration after applying the access control configuration, applying the further access control configuration in the one or more cells.

[0167] In some of these embodiments, the further access control configuration is same as the previous access control configuration. In some of these embodiments, the duration after applying the access control configuration is based on one of the following:

[0168] • expiration of a timer initiated upon applying the access control configuration;

[0169] • a predetermined number of access attempts by UEs in the one or more cells;

[0170] • a predetermined number of random access (RA) occasions in the one or more cells;

[0171] • a determination that one or more of the following have accessed the one or more cells after the failure: high-priority UEs, and UEs associated with high-priority services.

[0172] Although various embodiments are described above in terms of methods, techniques, and / or procedures, the person of ordinary skill will readily comprehend that such methods, techniques, and / or procedures can be embodied by various combinations of hardware and software in various systems, communication devices, computing devices, control devices, apparatuses, non-transitory computer-readable media, computer program products, etc.

[0173] Figure 14 shows an example of a communication system 1400 in accordance with some embodiments. In this example, communication system 1400 includes a telecommunication network 1402 that includes an access network 1404 (e.g., RAN) and a core network 1406, which includes one or more core network nodes 1408. Access network 1404 includes one or more access network nodes, such as network nodes 1410a-b (one or more of which may be generally referred to as network nodes 1410), or any other similar 3GPP access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, telecommunication network 1402 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in telecommunication network 1402 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in telecommunication network 1402, including one or more network nodes 1410 and / or core network nodes 1408.

[0174] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU- CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e. g. , r App), or any combination thereof (the adj ective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an 0-2 interface defined by the O-RAN Alliance or comparable technologies. Network nodes 1410 facilitate direct or indirect connection of UEs, such as by connecting UEs 1412a-d (one or more of which may be generally referred to as UEs 1412) to core network 1406 over one or more wireless connections.

[0175] In some embodiments, telecommunication network 1402 can also include one or more Network Management (NM) nodes 1418, which can be part of an operation support system (OSS), a business support system (BSS), and / or an operation / administration / maintenance (0AM) system. The NM nodes can monitor and / or control operations of other nodes in access network 1404 and core network 1406. Although not shown in Figure 14, NM node 1418 is configured to communicate with other nodes in access network 1404 and core network 1406 for these purposes.

[0176] Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, communication system 1400 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. Communication system 1400 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system. UEs 1412 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with network nodes 1410 and other communication devices. Similarly, network nodes 1410 are arranged, capable, configured, and / or operable to communicate directly or indirectly with UEs 1412 and / or with other network nodes or equipment in telecommunication network 1402 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in telecommunication network 1402.

[0177] In the depicted example, core network 1406 connects network nodes 1410 to one or more hosts, such as host 1416. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. Core network 1406 includes one or more core network nodes (e.g., 1408) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of core network node 1408. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and / or a User Plane Function (UPF).

[0178] Host 1416 may be under the ownership or control of a service provider other than an operator or provider of access network 1404 and / or telecommunication network 1402, and may be operated by the service provider or on behalf of the service provider. Host 1416 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0179] In some embodiments, access network 1404 can include a service management and orchestration (SMO) system or node 1420, which can monitor and / or control operations of the access network nodes 1410. This arrangement can be used, for example, when access network 1404 utilizes an O-RAN architecture. SMO system 1420 can be configured to communicate with core network 1406 and / or host 1416, as shown in Figure 14.

[0180] In some embodiments, one or more of core network node 1408, host 1416, NM node 1418, and SMO system 1420 can be configured to perform various operations of exemplary methods (e.g, procedures) for controlling UE access to a communication network after a failure in the communication network, such as described above in relation to other figures.

[0181] As a whole, communication system 1400 of Figure 14 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

[0182] In some examples, telecommunication network 1402 is a cellular network that implements 3GPP standardized features. Accordingly, telecommunication network 1402 may support network slicing to provide different logical networks to different devices that are connected to telecommunication network 1402. For example, telecommunication network 1402 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC) / Massive loT services to yet further UEs.

[0183] In some examples, UEs 1412 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to access network 1404 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from access network 1404. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[0184] In the example, hub 1414 communicates with access network 1404 to facilitate indirect communication between one or more UEs (e.g., 1412c and / or 1412d) and network nodes (e.g., network node 1410b). In some examples, hub 1414 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, hub 1414 may be a broadband router enabling access to core network 1406 for the UEs. As another example, hub 1414 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1410, or by executable code, script, process, or other instructions in hub 1414. As another example, hub 1414 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, hub 1414 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, hub 1414 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which hub 1414 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, hub 1414 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0185] Figure 15 shows a network node 1500 in accordance with some embodiments. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (e.g., radio base stations, Node Bs, eNBs, gNBs), and O-RAN nodes or components of an O-RAN node (e.g., O-RU, O-DU, O-CU).

[0186] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0187] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, and positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs))).

[0188] In some embodiments, network node 1500 can be configured to perform various operations of exemplary methods (e.g., procedures) for controlling UE access to a communication network after a failure in the communication network, such as described above in relation to other figures.

[0189] Network node 1500 includes processing circuitry 1502, memory 1504, communication interface 1506, and power source 1508. Network node 1500 may be composed of multiple physically separate components (e.g., a NodeB component and an RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which network node 1500 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, network node 1500 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1504 for different RATs) and some components may be reused (e.g., a same antenna 1510 may be shared by different RATs). Network node 1500 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 1500, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 1500.

[0190] Processing circuitry 1502 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other network node 1500 components, such as memory 1504, to provide network node 1500 functionality.

[0191] In some embodiments, processing circuitry 1502 includes a system on a chip (SOC). In some embodiments, processing circuitry 1502 includes radio frequency (RF) transceiver circuitry 1512 and / or baseband processing circuitry 1514. In some embodiments, RF transceiver circuitry 1512 and baseband processing circuitry 1514 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1512 and / or baseband processing circuitry 1514 may be on the same chip or set of chips, boards, or units.

[0192] Memory 1504 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by processing circuitry 1502. Memory 1504 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions (collected denoted computer program 1504a, which may be in the form of a computer program product) capable of being executed by processing circuitry 1502 and utilized by network node 1500. Memory 1504 may be used to store any calculations made by processing circuitry 1502 and / or any data received via communication interface 1506. In some embodiments, processing circuitry 1502 and memory 1504 is integrated.

[0193] Communication interface 1506 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, communication interface 1506 comprises port(s) / terminal(s) 1516 to send and receive data, for example to and from a network over a wired connection. Communication interface 1506 also includes radio frontend circuitry 1518 that may be coupled to, or in certain embodiments a part of, antenna 1510. Radio front-end circuitry 1518 comprises filters 1520 and amplifiers 1522. Radio front-end circuitry 1518 may be connected to an antenna 1510 and processing circuitry 1502. The radio front-end circuitry may be configured to condition signals communicated between antenna 1510 and processing circuitry 1502. Radio front-end circuitry 1518 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. Radio front-end circuitry 1518 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1520 and / or amplifiers 1522. The radio signal may then be transmitted via antenna 1510. Similarly, when receiving data, antenna 1510 may collect radio signals which are then converted into digital data by radio front-end circuitry 1518. The digital data may be passed to processing circuitry 1502. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0194] In certain alternative embodiments, network node 1500 does not include separate radio front-end circuitry 1518, instead, processing circuitry 1502 includes radio front-end circuitry and is connected to antenna 1510. Similarly, in some embodiments, all or some of RF transceiver circuitry 1512 is part of communication interface 1506. In still other embodiments, communication interface 1506 includes one or more ports or terminals 1516, radio front-end circuitry 1518, and RF transceiver circuitry 1512, as part of a radio unit (not shown), and communication interface 1506 communicates with baseband processing circuitry 1514, which is part of a digital unit (not shown).

[0195] Antenna 1510 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. Antenna 1510 may be coupled to radio front-end circuitry 1518 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, antenna 1510 is separate from network node 1500 and connectable to network node 1500 through an interface or port.

[0196] Antenna 1510, communication interface 1506, and / or processing circuitry 1502 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, antenna 1510, communication interface 1506, and / or processing circuitry 1502 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment.

[0197] Power source 1508 provides power to the various components of network node 1500 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 1508 may further comprise, or be coupled to, power management circuitry to supply the components of network node 1500 with power for performing the functionality described herein. For example, network node 1500 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of power source 1508. As a further example, power source 1508 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0198] Embodiments of network node 1500 may include additional components beyond those shown in Figure 15 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, network node 1500 may include user interface equipment to allow input of information into network node 1500 and to allow output of information from network node 1500. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 1500.

[0199] Figure 16 is a block diagram of a host 1600, which may be an embodiment of host 1416 of Figure 14, in accordance with various aspects described herein. Host 1600 may be or comprise various combinations hardware and / or software, including a standalone server, a blade server, a cloud-implemented server, a distributed server, a virtual machine, container, or processing resources in a server farm.

[0200] Host 1600 includes processing circuitry 1602 that is operatively coupled via a bus 1604 to an input / output interface 1606, a network interface 1608, a power source 1610, and a memory 1612. Other components may be included in other embodiments. Features of these components may be substantially similar to those described with respect to the devices of previous figures, such as Figure 18, such that the descriptions thereof are generally applicable to the corresponding components of host 1600.

[0201] Memory 1612 may include one or more computer programs including one or more host application programs 1614 and data 1616, which may include user data, e.g., data generated by a UE for host 1600 or data generated by host 1600 for a UE. Embodiments of host 1600 may utilize only a subset or all of the components shown. Host application programs 1614 may be implemented in a container-based architecture and may provide support for video codecs (e.g., Versatile Video Coding (VVC), High Efficiency Video Coding (HEVC), Advanced Video Coding (AVC), MPEG, VP9) and audio codecs (e.g., FLAC, Advanced Audio Coding (AAC), MPEG, G.711), including transcoding for multiple different classes, types, or implementations of UEs (e.g., handsets, desktop computers, wearable display systems, heads-up display systems). Host application programs 1614 may also provide for user authentication and licensing checks and may periodically report health, routes, and content availability to a central node, such as a device in or on the edge of a core network. Accordingly, host 1600 may select and / or indicate a different host for over-the-top services for a UE. Host application programs 1614 may support various protocols, such as the HTTP Live Streaming (HLS) protocol, Real-Time Messaging Protocol (RTMP), Real- Time Streaming Protocol (RTSP), Dynamic Adaptive Streaming over HTTP (MPEG-DASH), etc.

[0202] In some embodiments, host 1600 can be configured to perform various operations of exemplary methods (e.g., procedures) for controlling UE access to a communication network after a failure in the communication network, such as described above in relation to other figures.

[0203] Figure 17 is a block diagram illustrating a virtualization environment 1700 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1700 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 1700 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an O-2 interface. Applications 1702 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1700 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein. In some embodiments, one or more applications 1702 can be configured to perform various operations of exemplary methods (e.g., procedures) for controlling UE access to a communication network after a failure in the communication network, such as described above in relation to other figures.

[0204] Hardware 1704 includes processing circuitry, memory that stores software and / or instructions (collected denoted computer program 1704a, which may be in the form of a computer program product) executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1706 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1708a-b (one or more of which may be generally referred to as VMs 1708), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. Virtualization layer 1706 may present a virtual operating platform that appears like networking hardware to VMs 1708.

[0205] VMs 1708 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1706. Different embodiments of the instance of a virtual appliance 1702 may be implemented on one or more of VMs 1708, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0206] In the context of NFV, each VM 1708 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each VM 1708, and that part of hardware 1704 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1708 on top of hardware 1704 and corresponds to application 1702.

[0207] Hardware 1704 may be implemented in a standalone network node with generic or specific components. Hardware 1704 may implement some functions via virtualization. Alternatively, hardware 1704 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration function 1710, which, among others, oversees lifecycle management of applications 1702. In some embodiments, hardware 1704 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1712 which may alternatively be used for communication between hardware nodes and radio units.

[0208] The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art.

[0209] The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and / or electronic devices and can include, for example, electrical and / or electronic circuitry, devices, modules, processors, memories, logic solid state and / or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and / or displaying functions, and so on, as such as those that are described herein.

[0210] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for performing one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure. As described herein, device and / or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and / or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person.

[0211] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0212] In addition, certain terms used in the present disclosure, including the specification and drawings, can be used synonymously in certain instances (e.g., “data” and “information”). It should be understood, that although these terms (and / or other terms that can be synonymous to one another) can be used synonymously herein, there can be instances when such words can be intended to not be used synonymously.

Claims

CLAIMS1. A method for controlling user equipment, UE, access to a communication network after a failure in the communication network, the method comprising: detecting (1310) a failure of an entity in the communication network, wherein the failure of the entity causes at least one cell of the communication network to become at least temporarily unavailable for UEs; in response to the detected failure, determining (1330) an access control configuration for one or more cells of the communication network, wherein the access control configuration is different than a previous access control configuration for the one or more cells that was in use when the failure was detected; and applying (1340) the access control configuration in the one or more cells, thereby controlling UE access to the one or more cells.

2. The method of claim 1, wherein determining (1330) the access control configuration comprises one of the following: modifying (1331) the previous access control configuration, generating (1332) the access control configuration, or selecting (1333) the access control configuration from a set of predefined access control configurations.

3. The method of any of claims 1-2, wherein the failure is detected by one of the following: the failed entity; a second unit or function of the failed entity, when the failure was in a first unit or function of the failed entity; or another entity of the communication network, of a same type or a different type as the failed entity.

4. The method of claim 3, wherein the other entity of a different type is a network management entity responsible for monitoring health and / or operational state of entities of the communication network.

5. The method of any of claims 3-4, wherein the access control configuration is determined by one of the following: the failed entity, or a second entity of the communication network.

6. The method of claim 5, wherein:the failure is detected by the failed entity and the access control configuration is determined by the second entity; and the method further comprises the failed entity sending (1320) one of the following to the second entity: an indication of the detected failure, or a request for modification of the previous access control configuration.

7. The method of any of claims 5-6, wherein the second entity is one of the following: the second unit or function of the failed entity, when the failure was in the first unit or function of the failed entity; or the other entity of the same type or a different type as the failed entity.

8. The method of any of claims 3-7, wherein the failed entity is one of the following: a radio access network, RAN, node that serves the at least one cell; one or more of the following units of the RAN node: centralized unit, CU; distributed unit, DU; baseband unit, BBU; radio unit, RU; and antenna unit; an Open-RAN, O-RAN, entity; or a control plane, CP, or user plane, UP, function in a core network of the communication network.

9. The method of any of claims 1-8, wherein the one or more cells, in which the access control configuration is applied, include one or more of the following: the at least one cell that becomes at least temporarily unavailable; and one or more neighbor cells proximate to the at least one cell.

10. The method of any of claims 1-9, wherein the one or more cells, in which the access control configuration is applied, are provided by a backup entity to the failed entity.

11. The method of any of claims 1-10, wherein applying (1340) the access control configuration in the one or more cells comprises broadcasting (1341), in the one or more cells, a system information block, SIB, that includes the access control configuration or an indication thereof.

12. The method of claim 11, wherein the previous access control configuration identifies a cell broadcast modification period for the one or more cells, and determining (1330) the accesscontrol configuration comprises reducing (1334) the cell broadcast modification period to facilitate faster UE acquisition of the SIB that includes the access control configuration.

13. The method of any of claims 11-12, wherein the access control configuration is included in one or more of the following of the SIB: a first information element, IE, carrying access control information or access barring information; and a second IE carrying serving cell configuration information.

14. The method of claim 13, wherein the first IE isa uac-Barringlnfo IE and the second IE is a servingCellConfigCommon IE.

15. The method of any of claims 1-14, wherein the previous access control configuration includes or identifies access control parameter sets for respective access categories, wherein each access category is associated with one or more services or applications used by the UEs.

16. The method of claim 15, wherein each access control parameter set includes or identifies the following for the corresponding access category: a probability that access attempts to a cell, by UEs associated with the access category, will be allowed during access barring checks; a duration after barring of an access attempt to a cell by a UE associated with the access category, until a new access attempt by the UE is allowed; and respective indications of whether access attempts are allowed for each of a plurality of access identities.

17. The method of claim 16, wherein determining (1330) the access control configuration for one or more cells includes one or more of the following: increasing (1335) the probability that access attempts to the one or more cells by UEs associated with a first access category will be allowed; reducing (1336) the probability that access attempts to the one or more cells by UEs associated with a second access category will be allowed; and changing (1337) one or more of the indications to indicate that access attempts are barred for the corresponding access identities.

18. The method of any of claims 15-17, wherein differences between the access control configuration and the previous access control configuration relate to one of the following: allpublic land mobile network, PLMN, and standalone non-public network, SNPN, identities; or only one or more specific PLMN and / or SNPN identities.

19. The method of any of claims 15-17, wherein differences between the access control configuration and the previous access control configuration relate to one of the following: all network slices of the communication network, or only one or more specific network slices of the communication network.

20. The method of any of claims 1-19, wherein the previous access control configuration identifies random access, RA, resources available in the one or more cells, and the access control configuration identifies additional RA resources available in the one or more cells after the detected failure.

21. The method of claim 20, wherein the additional RA resources in the one or more cells are available to one of the following: all UEs; or only high-priority UEs or UEs associated with high-priority services.

22. The method of any of claims 1-21, wherein the previous access control configuration includes a configuration for prioritized random access, RA, and determining (1330) the access control configuration comprises one or more of the following: increasing (1338) a power ramping step used for prioritized RA, and reducing (1339) a scaling factor used to determine a power backoff for prioritized RA.

23. The method of any of claims 1-22, further comprising: determining (1350) a further access control configuration that is different than the access control configuration; and at the end of a duration after applying (1340) the access control configuration, applying (1360) the further access control configuration in the one or more cells.

24. The method of claim 23, wherein the duration after applying the access control configuration is based on one of the following: expiration of a timer initiated upon applying the access control configuration; a predetermined number of access attempts by UEs in the one or more cells; a predetermined number of random access (RA) occasions in the one or more cells;a determination that one or more of the following have accessed the one or more cells after the failure: high-priority UEs, and UEs associated with high-priority services25. The method of any of claims 23-24, wherein the further access control configuration is same as the previous access control configuration.

26. Network equipment (410-460, 520, 1010, 1020, 1408, 1410, 1416, 1418, 1420, 1500, 1600, 1700) configured to control user equipment, UE (510, 1412) access to a communication network (1402) after a failure in the communication network, the network equipment comprising: communication interface circuitry (1506, 1608, 1704) configured to communicate with one or more entities of the communication network; and processing circuitry (1502, 1602, 1704) operably coupled to the communication interface circuitry, wherein the processing circuitry and the communication interface circuitry are configured to: detect a failure of an entity in the communication network, wherein the failure of the entity causes at least one cell of the communication network to become at least temporarily unavailable for UEs; in response to the detected failure, determine an access control configuration for one or more cells of the communication network, wherein the access control configuration is different than a previous access control configuration for the one or more cells that was in use when the failure was detected; and apply the access control configuration in the one or more cells, thereby controlling UE access to the one or more cells.

27. The network equipment of claim 26, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to any of the methods of claims 2-25.

28. Network equipment (410-460, 520, 1010, 1020, 1408, 1410, 1416, 1418, 1420, 1500, 1600, 1700) configured to control user equipment, UE (510, 1412) access to a communication network (1402) after a failure in the communication network, the network equipment being further configured to:detect a failure of an entity in the communication network, wherein the failure of the entity causes at least one cell of the communication network to become at least temporarily unavailable for UEs; in response to the detected failure, determine an access control configuration for one or more cells of the communication network, wherein the access control configuration is different than a previous access control configuration for the one or more cells that was in use when the failure was detected; and apply the access control configuration in the one or more cells, thereby controlling UE access to the one or more cells.

29. The network equipment of claim 28, being further configured to perform operations corresponding to any of the methods of claims 2-25.

30. The network equipment of any of claims 26-29, wherein the network equipment includes one or more of the following: the failed entity; and another entity of the communication network, of the same type or a different type as the failed entity.

31. A non-transitory, computer-readable medium (1504, 1612, 1704) storing computerexecutable instructions that, when executed by processing circuitry (1502, 1602, 1704) of network equipment (410-460, 520, 1010, 1020, 1408, 1410, 1416, 1418, 1420, 1500, 1600, 1700) configured to control user equipment, UE (510, 1412) access to a communication network (1402) after a failure in the communication network, configure the network equipment to perform operations corresponding to the methods of any of claims 1-25.

32. A computer program product (1504a, 1614, 1704a) comprising computer-executable instructions that, when executed by processing circuitry (1502, 1602, 1704) of network equipment (410-460, 520, 1010, 1020, 1408, 1410, 1416, 1418, 1420, 1500, 1600, 1700) configured to control user equipment, UE (510, 1412) access to a communication network (1402) after a failure in the communication network, configure the network equipment to perform operations corresponding to the methods of any of claims 1-25.

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