User Equipment Involved in Executing the Random Access Procedure

Abstract

The present disclosure relates to a user equipment (UE) having a receiver that receives multiple random access type thresholds. Processing circuitry in the UE determines a random value and then selects a type of random access procedure to be performed by the UE. The selecting includes at least selecting one from the multiple random access type thresholds, comparing the determined random value with the selected random access type threshold, and selecting a type of random access procedure based on a result of the comparison. The UE then performs the selected type of random access procedure.

Description

[Technical field]

[0001] The present disclosure is directed to methods, apparatus, and articles in communication systems, such as 3GPP communication systems. [Background technology]

[0002] Currently, the 3rd Generation Partnership Project (3GPP) is working on technical specifications for the next generation of cellular technology, also known as the fifth generation (5G).

[0003] One objective is to provide a single technical framework that addresses all usage scenarios, requirements, and deployment scenarios (see, for example, Section 6 of Non-Patent Document 1), including at least enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), and massive machine type communication (mMTC). For example, deployment scenarios for eMBB may include indoor hotspots, dense urban areas, suburban areas, urban areas, and high-speed. Deployment scenarios for URLLC may include industrial control systems, mobile health management (remote monitoring, remote diagnosis, and remote treatment), real-time control of vehicles, and wide-area monitoring and control systems for smart grids. Deployment scenarios for mMTC may include scenarios using a large number of devices with low latency data transmission, such as smart wearables and sensor networks. eMBB and URLLC services are similar in that both require extremely high bandwidth, but differ in that URLLC services preferably require extremely low latency.

[0004] A second objective is to achieve forward compatibility: backward compatibility to Long Term Evolution (LTE, LTE-A) cellular systems is not required, which will facilitate the design of entirely new systems and / or the introduction of new features. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] TR 38.913 version 15.0.0 [Non-Patent Document 2] 3GPP TS 38.300 v15.6.0 [Non-Patent Document 3] 3GPP TR 38.801 v14.0.0 [Non-Patent Document 4] 3GPP TS 38.300 [Non-Patent Document 5] 3GPP TS 38.211 v15.6.0 [Non-Patent Document 6] TS 23.501 v16.1.0 [Non-Patent Document 7] 3GPP TS 22.261 v16.8.0 [Non-Patent Document 8] 3GPP TS 24.501 v16.1.0 [Non-Patent Document 9] 3GPP TS 38.331 v15.6.0 [Non-Patent Document 10] 3GPP TS 38.321 v15.6.0 [Non-Patent Document 11] 3GPP Technical Report TR 36.889,version 13.0.0 Summary of the Invention

[0006] One non-limiting and exemplary embodiment facilitates providing procedures that facilitate improving random access procedures performed by a UE.

[0007] In one embodiment, the techniques disclosed herein feature a user equipment (UE) having a receiver that, during operation, receives a plurality of random access type thresholds. The UE also has processing circuitry that, during operation, determines a random value. The processing circuitry, during operation, selects a type of random access procedure to be performed by the UE, the selection comprising at least: - selecting one from among the plurality of random access type thresholds; - comparing the determined random value to the selected random access type threshold; and - selecting a type of random access procedure based on a result of said comparison; Then, the UE performs a random access procedure of the selected type.

[0008] It should be noted that the general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any combination thereof.

[0009] Further benefits and advantages of the disclosed embodiments and various implementations will become apparent from the specification and drawings. These benefits and / or advantages may be obtained individually by the various embodiments and features of the specification and drawings, however, they need not all be present in order to obtain one or more of such benefits and / or advantages. [Brief description of the drawings]

[0010] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings.

[0011] [Figure 1] FIG. 1 illustrates an example architecture of a 3GPP NR system. [Diagram 2] FIG. 1 illustrates an example user and control plane architecture for LTE eNB, gNB, and UE. [Diagram 3] Schematic diagram showing the division of functions between NG-RAN and 5GC [Figure 4] Sequence diagram of RRC connection setup / reconfiguration procedure [Diagram 5] Schematic showing the usage scenarios for Enhanced Mobile Broadband (eMBB), Massive Machine Type Communications (mMTC), and Ultra-Reliable Low Latency Communications (URLLC) [Figure 6] Block diagram illustrating an exemplary 5G system architecture for a non-roaming scenario [Figure 7] Diagram showing messages exchanged between eNB and UE when performing a contention-based RACH procedure [Figure 8] Diagram showing messages exchanged between eNB and UE when performing a contention-free RACH procedure [Figure 9] FIG. 1 illustrates an exemplary simplified structure of a UE and a gNB. [Figure 10] FIG. 1 illustrates a structure of a UE according to an exemplary implementation of an improved random access procedure. [Figure 11] FIG. 1 is a flow diagram of the operation of a UE according to an exemplary implementation of an improved solution; [Figure 12] Flow diagram of the operation of a gNB according to an exemplary implementation of the improved solution [Figure 13] FIG. 1 is a flow diagram of the operation of a UE according to an exemplary implementation of an improved solution; [Figure 14] FIG. 1 is a flow diagram of the operation of a UE according to an exemplary implementation of an improved solution; [Figure 15] Flow diagram of the operation of a gNB according to an exemplary implementation of the improved solution DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 5G NR System Architecture and Protocol Stack

[0013] 3GPP is working on the next release of fifth-generation cellular technology (known simply as 5G), which includes the development of a new radio access technology (NR) that will operate in frequencies up to 100 GHz. The first version of the 5G standard will be completed at the end of 2017, which will allow smartphones compliant with the 5G NR standard to proceed to testing and commercial deployment.

[0014] In particular, the overall system architecture envisages an NG-RAN (Next Generation - Radio Access Network) with gNBs terminating NG radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocols. The gNBs are interconnected with each other by an Xn interface. The gNBs are also connected to an NGC (Next Generation Core) by a Next Generation (NG) interface, more specifically to an AMF (Access and Mobility Management Function) (e.g., a specific core entity that runs the AMF) by an NG-C interface, and to a UPF (User Plane Function) (e.g., a specific core entity that runs the UPF) by an NG-U interface. The NG-RAN architecture is shown in Figure 1 (see, for example, Section 4 of Non-Patent Document 2).

[0015] Various different deployment scenarios can be supported (see, for example, Non-Patent Document 3). In this document, for example, a decentralized deployment scenario is presented (for example, in Non-Patent Document 3, a base station supporting 5G NR can be deployed. Figure 2 shows an exemplary decentralized deployment scenario (for example, see Figure 5.2.-1 in Non-Patent Document 3), and further shows an LTE eNB and a user equipment (UE), which is connected to both the gNB and the LTE eNB. The new eNB of NR 5G can be exemplarily called a gNB. The eLTE eNB is an evolution of the eNB and supports connectivity to the EPC (Evolved Packet Core) and NGC (Next Generation Core).

[0016] The user plane protocol stack in NR (see, for example, Section 4.4.1 of Non-Patent Document 4) includes a PDCP (Packet Data Convergence Protocol, see Section 6.4 of Non-Patent Document 4) sublayer, an RLC (Radio Link Control, see Section 6.3 of Non-Patent Document 4) sublayer, and a MAC (Medium Access Control, see Section 6.2 of Non-Patent Document 4) sublayer, which are terminated at the gNB on the network side. In addition, a new sublayer (SDAP, Service Data Adaptation Protocol) of the access stratum (AS) is introduced on top of the PDCP (see, for example, Section 6.5 of Non-Patent Document 4). A control plane protocol stack is also defined in NR (see, for example, Section 4.4.2 of Non-Patent Document 4). An overview of the functions of Layer 2 is described in Section 6 of Non-Patent Document 4. The functions of the PDCP sublayer, the RLC sublayer and the MAC sublayer are described in clauses 6.4, 6.3 and 6.2, respectively, of 3GPP TS 215.221. The functions of the RRC layer are described in clause 7 of 3GPP TS 215.221.

[0017] For example, the medium access control layer handles scheduling and scheduling-related functions, including multiplexing of logical channels, as well as handling of various numerologies.

[0018] The physical layer (PHY) is responsible for, for example, coding, PHY HARQ processing, modulation, multi-antenna processing, and mapping of signals to appropriate physical time-frequency resources. The physical layer also handles mapping of transport channels to physical channels. The physical layer provides services to the MAC layer in the form of transport channels. A physical channel corresponds to a set of time-frequency resources used for the transmission of a particular transport channel, and each transport channel is mapped to a corresponding physical channel. One physical channel is the PRACH (Physical Random Access Channel), which is used for random access.

[0019] NR use cases / deployment scenarios include enhanced Mobile Broadband (eMBB), ultra-reliable and low latency communications (URLLC), and massive machine type communications (mMTC), which have diverse requirements in terms of data rates, latency, and coverage. For example, eMBB is expected to support peak data rates (20 Gbps downlink and 10 Gbps uplink) and user-perceived data rates on the order of three times those offered by IMT-Advanced. In contrast, URLLC has more stringent requirements, including extremely low latency (user plane latency of 0.5 ms for UL and DL, respectively) and high reliability (1-10 Mbps within 1 ms). -5 ) and mMTC requires high connection density (1 km 2 1,000,000 devices per second), wide coverage in harsh environments, and extremely long battery life (15 years) to lower device costs may be preferably required.

[0020] Thus, an OFDM numerology (e.g., subcarrier spacing, OFDM symbol duration, cyclic prefix (CP) duration, number of symbols per scheduling interval) suitable for one use case may not work well for another use case. For example, low latency services may preferably require a shorter symbol duration (and therefore a larger subcarrier spacing) and / or fewer symbols per scheduling interval (also referred to as TTI) than mMTC services. Furthermore, deployment scenarios with large channel delay spreads may preferably require a longer CP duration than scenarios with small delay spreads. To maintain a comparable CP overhead, the subcarrier spacing should be optimized depending on the delay spread. In NR, more than one value of subcarrier spacing may be supported. Thus, currently, subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, ... are considered. Symbol duration T u and the subcarrier spacing Δf is expressed by the formula (Δf=1 / T u ), as in LTE systems, the term "resource element" can be used to denote the smallest resource unit consisting of one subcarrier for the length of one OFDM / SC-FDMA symbol.

[0021] In the new radio system 5G-NR, for each numerology and carrier, a resource grid of subcarriers and OFDM symbols is defined in the uplink and downlink, respectively. Each element in the resource grid is called a resource element and is identified based on a frequency index in the frequency domain and a symbol position in the time domain (see Non-Patent Document 5).

[0022] Split of 5G NR functions between NG-RAN and 5GC

[0023] Figure 3 shows the division of functions between NG-RAN and 5GC. The logical nodes of NG-RAN are gNB or ng-eNB. The logical nodes of 5GC are AMF, UPF, and SMF.

[0024] In particular, the gNB and ng-eNB handle the following key functions: - Radio Resource Management functions, such as Radio Bearer Control, Radio Admission Control, Connection Mobility Control, dynamic resource allocation (scheduling) to UEs in both uplink and downlink directions - IP header compression, encryption, and data integrity protection - Selection of AMF at UE attach time when routing to AMF cannot be determined from information provided by the UE - Routing user plane data to the UPF - Routing control plane information to AMF - Establishing and releasing connections - Scheduling and sending paging messages - Scheduling and transmission of system broadcast information (sent from AMF or OAM) - Configuring measurements and measurement reporting for mobility and scheduling - Transport-level packet marking in the uplink - Session Management - Network slicing support - QoS flow management and mapping to data radio bearers - Support for UEs in RRC_INACTIVE state - NAS message delivery function - Wireless Access Network Sharing - Dual Connectivity - Tight interworking between NR and E-UTRA

[0025] The Access and Mobility Management Function (AMF) handles the following main functions: - Termination of Non-Access Stratum (NAS) signalling - NAS signaling security - Access Stratum (AS) security control - Core Network (CN) inter-node signaling for mobility between 3GPP access networks - Reachability for idle mode UEs (including control and execution of paging retransmissions) - Registration Area Management - Support for intra-system and inter-system mobility - Access Authentication - Access authentication, including roaming rights checks - Mobility management controls (subscriptions and policies) - Network slicing support - Selection of Session Management Function (SMF)

[0026] In addition, the User Plane Function (UPF) handles the following main functions: - Anchor points for intra-RAT / inter-RAT mobility (when applicable) - External PDU session points for interconnection with data networks - Packet routing and forwarding - User plane part of packet inspection and policy rule enforcement - Traffic usage reports - An uplink classifier to support routing of traffic flows to the data network. - Branching points to support multi-homed PDU sessions - User plane QoS processing (e.g. packet filtering, gating, UL / DL rate enforcement) - Validation of uplink traffic (mapping of SDF to QoS flows) - Downlink packet buffering and downlink data notification triggering

[0027] Finally, the Session Management Function (SMF) handles the following major functions: - Session Management - UE IP address allocation and management - UP function selection and control - Configuring traffic steering in the User Plane Function (UPF) to route traffic to the correct destination - Policy enforcement and QoS control - Downlink data notification

[0028] RRC connection establishment and reconfiguration procedures

[0029] Figure 4 shows the interactions between the UE, gNB, and AMF (5GC entities) in the NAS part when the UE transitions from RRC_IDLE to RRC_CONNECTED (see Non-Patent Document 2)

[0030] RRC is a higher layer signaling (protocol) used for the configuration of the UE and the gNB. In particular, in this transition, the AMF prepares UE context data (including, for example, PDU session context, security keys, UE radio capabilities, and UE security capabilities, etc.) and sends it to the gNB by an INITIAL CONTEXT SETUP REQUEST. The gNB then activates AS security with the UE, which is performed by the gNB sending a SecurityModeCommand message to the UE and the UE responding with a SecurityModeComplete message to the gNB. The gNB then performs a reconfiguration to establish a signaling radio bearer 2 (SRB2) and a data radio bearer (DRB), which is performed by the gNB sending an RRCReconfiguration message to the UE and the gNB receiving an RRCReconfigurationComplete from the UE in response. In the case of a signaling-only connection, these steps related to RRCReconfiguration are skipped since SRB2 and DRB are not established. Finally, the gNB informs the AMF that the establishment procedure is complete via an INITIAL CONTEXT SETUP RESPONSE.

[0031] Therefore, in the present disclosure, a fifth generation core (5GC) entity (e.g., AMF, SMF, etc.) is provided that has a control circuit that, in operation, establishes a next generation (NG) connection with a gNodeB, such that a signaling radio bearer is established between the gNodeB and a user equipment (UE), and a transmitter that, in operation, transmits an initial context setup message to the gNodeB via the NG connection. In particular, the gNodeB transmits radio resource control (RRC) signaling including a resource allocation setting information element to the UE via the signaling radio bearer. The UE then performs uplink transmission or downlink reception based on the resource allocation setting.

[0032] Usage scenarios for IMT-2020 and beyond

[0033] Figure 5 shows some of the use cases for 5G NR. The 3rd generation partnership project new radio (3GPP NR) considers three use cases that are envisaged to support a wide variety of services and applications by IMT-2020. The specifications for Phase 1 of enhanced mobile broadband (eMBB) have been finalized. Current and upcoming work will include standardization for ultra-reliable and low latency communications (URLLC) and large-scale machine-type communications, in addition to further extending eMBB support. Figure 5 shows some examples of usage scenarios envisaged for IMT beyond 2020.

[0034] URLLC use cases have stringent requirements on capabilities such as throughput, latency and availability, and are envisioned as one of the enablers of future vertical applications such as wireless control of industrial manufacturing or production processes, remote medical surgery, power distribution automation in smart grids, and transportation safety. The ultra-high reliability of URLLC is supported by identifying technologies to meet the requirements set by NR URLLC in Release 15. For NR URLLC in Release 15, key requirements include a user plane target latency of 0.5 ms for UL (uplink) and 0.5 ms for DL ​​(downlink). A typical URLLC requirement for a single transmission of a packet is a BLER (block error rate) of 1E-5 for a packet size of 32 bytes with a user plane latency of 1 ms.

[0035] From the RAN1 perspective, reliability can be improved in many possible ways. Current scope for improving reliability includes defining separate CQI tables for URLLC, more compact DCI formats, PDCCH repetition, etc. However, as NR becomes more stable and developed (for a key requirement of NR URLC), the scope for achieving ultra-high reliability can be broadened. Specific use cases for NR URLCC in Release 15 include augmented reality / virtual reality (AR / VR), e-health, e-safety, and mission-critical applications.

[0036] Furthermore, technology enhancements targeted by NR URLCC target latency improvement and reliability improvement. Technology enhancements for latency improvement include configurable numerology, non-slot-based scheduling with flexible mapping, grant-free (configured grant) uplink, slot-level repetition of data channel, and preemption for downlink. Preemption means that a transmission for which resources are already allocated is aborted and the already allocated resources are used for another transmission with smaller latency / higher priority requirement requested later. Thus, an already granted transmission is preempted by a later transmission. Preemption applies regardless of the specific service type. For example, a transmission of service type A (URLCC) can be preempted by a transmission of service type B (eMBB, etc.). Technology enhancements for reliability improvement include dedicated CQI / MCS tables for a target BLER of 1E-5.

[0037] The mMTC (Massive Machine Type Communication) use case is characterized by a very large number of connected devices transmitting relatively small amounts of data that are generally not sensitive to latency. The devices need to be low cost and have extremely long battery life. From an NR perspective, utilizing very narrow bandwidth portions is one possible solution to achieve power savings from the UE perspective to enable long battery life.

[0038] As mentioned above, it is expected that the range of reliability in NR will increase. One key requirement for all cases, especially for URLLC and mMTC, is high or ultra-high reliability. Several mechanisms can be considered to improve reliability from a radio perspective and from a network perspective. In general, there are several key areas that can help improve reliability. These areas include compact control channel information, data channel / control channel repetition, and diversity related to frequency, time, and / or spatial domains. These areas are generally applicable to reliability, regardless of the specific communication scenario.

[0039] For NR URLC, further use cases with more stringent requirements have been identified, e.g. in factory automation, the transport industry, power supply, etc. Depending on the use case, the more stringent requirements are higher reliability (up to the level of 10-6), higher availability, packet sizes up to 256 bytes, time synchronization on the order of a few μs (values ​​range from 1 to a few μs depending on the frequency range), and low latency on the order of 0.5 to 1 ms (in particular the target latency for the user plane is 0.5 ms).

[0040] Furthermore, for NR URLLC, several technology enhancements are recognized from the RAN1 perspective. In particular, PDCCH (Physical Downlink Control Channel) enhancements related to compact DCI, PDCCH repetition, and increased PDCCH monitoring. Furthermore, UCI (Uplink Control Information) enhancements related to HARQ (Hybrid Automatic Repeat Request) enhancements and CSI feedback enhancements. Also, PUSCH enhancements related to minislot level hopping and retransmission / repetition are recognized. The term "minislot" refers to a Transmission Time Interval (TTI) that contains fewer symbols than a slot (a slot containing 14 symbols).

[0041] QoS Control

[0042] The 5G Quality of Service (QoS) model is based on QoS flows and supports both QoS flows that require guaranteed flow bitrates (GBR QoS flows) and QoS flows that do not require guaranteed flow bitrates (non-GBR QoS flows). Thus, at the NAS level, QoS flows are the finest granularity of QoS differentiation in a PDU session. Within a PDU session, QoS flows are identified by a QoS Flow Identifier (QFI) that is conveyed in the encapsulation header over the NG-U interface.

[0043] The 5GC establishes one or more PDU sessions for each UE. The NG-RAN establishes at least one Data Radio Bearer (DRB) for each UE together with the PDU sessions, and can then configure additional DRBs for the QoS flows of that PDU session (NG-RAN decides when to do so), e.g. as described above with reference to FIG. 4. The NG-RAN maps packets belonging to different PDU sessions to different DRBs. NAS-level packet filters in the UE and 5GC associate UL and DL packets with QoS flows, and AS-level mapping rules in the UE and NG-RAN associate UL and DL QoS flows with DRBs.

[0044] Figure 6 shows the 5G NR non-roaming reference architecture (see section 4.23 of 3GPP RFC3266-2). Application Functions (AFs) (e.g., external application servers handling 5G services exemplarily described in Figure 5) interact with the 3GPP Core Network to provide services. For example, they support application influence on traffic routing, access Network Exposure Functions (NEFs), or interact with a policy framework (see Policy Control Function PCF) for policy control (e.g., QoS control). Based on the operator's deployment, application functions (AFs) that are considered trusted by the operator can be allowed to interact directly with the relevant network functions. Application functions (AFs) that are not allowed by the operator to directly access network functions interact with the relevant network functions using an external exposure framework via the NEF.

[0045] Figure 6 shows further functional units of the 5G architecture: Network Slice Selection Function (NSSF), Network Repository Function (NRF), Unified Data Management (UDM), Authentication Server Function (AUSF), Access and Mobility Management Function (AMF), Session Management Function (SMF), and Data Network (DN) (e.g. operator services, internet access or third party services).

[0046] Unified Access Control (UAC)

[0047] In an exemplary 5G scenario, different criteria may be used when deciding which access attempts should be allowed or blocked, depending for example on operator policies, deployment scenarios, subscriber profiles, and available services (see Section 6.22 of Non-Patent Document 7 and Section 4.5 of Non-Patent Document 8). These different access control criteria may be associated with an Access Identity and an Access Category. 5G systems currently offer a single unified access control where operators control access based on these two criteria.

[0048] In the unified access control, each access attempt is classified into one or more access identities and one access category. The UE performs a test of whether the actual access attempt can be made based on the access control information applicable to the corresponding access identity and access category of the access attempt.

[0049] The unified access control supports extensibility to allow for the inclusion of additional standardized access identities and access categories, as well as flexibility to allow operators to define operator-defined access categories using their own criteria (e.g., network slicing, applications, and application servers).

[0050] The following table provides an overview of the various access identities that may be defined in 3GPP.

[0051] [Table 1]

[0052] The following table gives an overview of the various access categories that may be defined by 3GPP.

[0053] [Table 2]

[0054] As is evident from the table above, Access Category 0 is unrestricted, regardless of Access Identity.

[0055] Based on the operator's policy, the 5G system can prevent the UE from accessing the network using associated regulatory parameters that vary depending on the access identity and the access category. The access identity is configured in the UE as shown in the table above. The access category is defined by a combination of a condition related to the UE and a type of access attempt as shown in the table above. For an access attempt, one or more access identities and exactly one access category are selected and tested.

[0056] 5G networks may broadcast regulatory control information (i.e., lists of regulatory parameters associated with access identities and access categories) in one or more regions of the RAN.

[0057] The UE may determine whether a particular new access attempt is allowed or not based on the broadcasted barring control information and the barring parameters received from the UE's configuration. The unified access control framework may be applicable to UEs in RRC Idle, RRC Inactive, and RRC Connected states when initiating a new access attempt (e.g., a new session request).

[0058] In particular, the purpose of the UAC procedure is to perform access barring checks on access attempts related to a granted access category and one or more access identities, eg, upon request from higher layers.

[0059] An access control check is performed for access attempts of certain events, for example as defined in 3GPP TS 21.2006.02, section 4.5.1. When the UE initiates an access attempt for one of these events, it can determine one or more access identities associated with the access attempt from the relevant standardized access identities (see table above) and an access category from a set of standardized and possibly operator-defined access categories (see for example section 4.5.3 of 3GPP TS 21.2006.02, section 4.5.3).

[0060] In one exemplary 3GPP implementation, the following steps are performed by the UE for the Unified Access Control (UAC) procedure (see section 5.3.14.5 of 3GPP TS 2010-010621):

[0061] [Table 3]

[0062] Some parameters of the UAC procedure are provided to the UE by System Information, for example in SIB1 (eg SIB1, see section 6.2.2 of 3GPP TS 2010-010521).

[0063] [Table 4-1] [Table 4-2] [Table 4-3] [Table 4-4]

[0064] The parameter UAC-BarringInfoSetList of SIB1 can be defined as follows, and carries the above parameter UAC-BarringFactor in the UAC procedure:

[0065] [Table 5]

[0066] The above UAC procedure can be summarized as follows: An access attempt can be associated with one access category and one or more access identities. First, the UE checks whether the access attempt is allowed based on the associated access identity broadcasted by the system information and the configured access identity (e.g., SIB1, see section 6.2.2 of 3GPP TS 21.110626). Then, if the UE determines that it is allowed to perform an access attempt with the cell based on the access identity, the UE performs the access attempt. On the other hand, if the UE determines that it is not allowed to perform an access attempt with the cell based on the access identity, the UE determines whether the access attempt is allowed based on the access category. This includes, for example, taking a random value and comparing it with a certain probability threshold for an access category-based access attempt (a uac-BarringFactor associated with the access category; the information is known to the UE, for example, by the system information). If the random value is less than the access attempt probability threshold, the UE is allowed to access the cell. However, if the random value is equal to or greater than the access attempt probability threshold, the UE is not allowed to access the cell.

[0067] One important further procedure performed by the UE, closely related to the Unified Access Control, is the Random Access Procedure (also called the RACH procedure). The UAC allows the UE to test whether it should perform an access attempt with a particular gNB. If the UE positively decides to perform an access attempt, the UE can, for example, perform a random access procedure to access the radio cell. In other words, the access attempt includes performing a random access procedure.

[0068] As explained below, the random access procedure can be performed for many different reasons. From the RACH procedure point of view, the execution of the random access procedure may or may not necessarily be preceded by the execution of a UAC check by the UE as described above.

[0069] Random Access Procedure

[0070] Like LTE, 5G NR provides a Random Access Channel (RACH) procedure (or simply random access procedure). For example, the RACH procedure can be used by a UE to access a cell that the UE has found. The RACH procedure is not related to other contexts in NR, e.g. In case of handover, when establishing synchronization with a new cell, Re-establishing uplink synchronization to the current cell if synchronization is lost due to too long a period of time without uplink transmission from the device; Requesting uplink scheduling when a dedicated scheduling request resource is not configured for the device; It can also be used in

[0071] There are a number of events that may cause the UE to perform a random access procedure, for example (see section 9.2.6 of 3GPP TS 2010-010366): - Initial access from RRC_IDLE - RRC Connection Re-establishment procedure - DL or UL data arrival during RRC_CONNECTED when UL synchronization state is "asynchronous" - UL data arrival during RRC_CONNECTED when no PUCCH resources for SR are available - SR disorder - Requested by RRC during synchronization reconfiguration (e.g. handover) - Transition from RRC_INACTIVE - Establishing time alignment when adding SCells - other SI requirements (see section 7.3) - Beam Damage Recovery

[0072] The RACH procedure is described in more detail below with reference to Figures 7 and 8. A mobile terminal can be scheduled for uplink transmission if its uplink transmission is time synchronized. Thus, the Random Access Channel (RACH) procedure serves as an interface between an unsynchronized mobile terminal (UE) and an orthogonal transmission of uplink radio access. For example, random access is used to achieve uplink time synchronization for user equipment that has not yet acquired or lost uplink synchronization. Once the user equipment achieves uplink synchronization, the base station can schedule uplink transmission resources for it. One scenario related to random access is when a user equipment in RRC_CONNECTED state that hands over from its current serving cell to a new target cell performs a random access procedure to achieve uplink time synchronization in the target cell.

[0073] There may be two types of random access procedures that allow access to be either contention-based, ie, implying an inherent risk of collision, or contention-free (non-contention-based).

[0074] An exemplary definition of the random access procedure can be found in section 5.1 of 3GPP TS 2010-010521.

[0075] The contention-based random access procedure is described in more detail below with respect to Fig. 7. This procedure consists of four "steps" and can therefore also be called a four-step RACH procedure. First, the user equipment transmits a random access preamble to the base station on the Physical Random Access Channel (PRACH) (i.e., message 1 of the RACH procedure). After detecting the RACH preamble, the base station transmits a Random Access Response (RAR) message (message 2 of the RACH procedure) on the Physical Downlink Shared Channel (PDSCH) addressed on the PDCCH with a (Random Access) RA-RNTI that identifies the time-frequency and slot where the preamble was detected. If multiple user equipments transmit the same RACH preamble on the same PRACH resource (also called collision), they will receive the same random access response message. The RAR message may convey the detected RACH preamble, a Timing Alignment Command (TA command) for synchronization of subsequent uplink transmissions based on the timing of the received preamble, an initial uplink resource allocation (grant) for transmitting the first scheduled transmission, and an allocation of a Temporary Cell Radio Network Temporary Identifier (T-CRNTI) that is used by the base station to address the mobile station for which the RACH preamble was detected until the RACH procedure is finished, since the "real" identity of the mobile station at this point in time is not yet known by the base station.

[0076] The user equipment monitors the PDCCH to receive a random access response message within a given time window (e.g., called the RAR reception window), which can be set by the base station. In response to the RAR message received from the base station, the user equipment first transmits a scheduled uplink transmission on the radio resources allocated by the grant in the random access response. This scheduled uplink transmission carries the actual random access procedure message, such as, for example, an RRC Connection Request, an RRC Resume Request, or a buffer status report.

[0077] If a preamble collision occurs in the first message of the RACH procedure, i.e., multiple user equipments transmit the same preamble on the same PRACH resource, the colliding user equipments receive the same T-CRNTI in the random access response and also collide on the same uplink resource when transmitting their scheduled transmissions in the third step of the RACH procedure. If the base station successfully decodes the scheduled transmission from one user equipment, the contention remains unresolved for the other user equipment. To resolve this type of contention, the base station transmits a contention resolution message (fourth message) addressed to the C-RNTI or Temporary C-RNTI. This ends the procedure.

[0078] Figure 8 shows a contention-free random access procedure, which is simplified compared to the contention-based random access procedure. In a first step, the base station provides the user equipment with a preamble to be used for random access, so that there is no risk of collision, i.e. no risk of multiple user equipments transmitting the same preamble. The user equipment then transmits the preamble signaled by the base station in the uplink on the PRACH resource. Since contention-free random access avoids the case where multiple UEs are transmitting the same preamble, essentially the contention-free random access procedure is terminated after successful reception of the random access response by the UE.

[0079] 3GPP is also considering a two-step (contention-based) RACH procedure for 5G NR, in which message 1 (which may also be referred to as msgA), corresponding to message 1 and message 3 in the four-step LTE RACH procedure, is transmitted first. The gNB then responds with message 2 (which may also be referred to as msgB), corresponding to message 2 and message 4 in the LTE RACH procedure. This msgB may include, for example, a Success Random Access Response (RAR), a Fallback RAR, and optionally a backoff indication. For the two-step RACH procedure, some further assumptions are made, for example, that after the UE determines the RACH type (e.g., two-step RACH), it keeps retrying the same RACH type until failure. However, it may be possible that the UE can fall back to the four-step RACH procedure after a certain time.

[0080] Furthermore, the network may semi-statically determine the mutually exclusive radio resources used to perform the two-step RACH procedure and the four-step RACH procedure. The radio resources used to transmit the first message in the RACH procedure include at least a RACH occasion and a preamble. For example, in the two-step RACH procedure, the first message msgA uses not only the PRACH resource (e.g., the RACH occasion and the preamble) but also the associated PUSCH resource.

[0081] Due to the reduced message exchange, the latency of the two-step RACH procedure may be reduced compared to the four-step RACH procedure, whereas the two-step RACH procedure may consume more radio resources than the four-step RACH procedure because additional PUSCH resources are required for the first message transmitted in the two-step RACH procedure.

[0082] The network may configure the UE, for example, to use only a 4-step RACH or a 2-step RACH, or to use both a 4-step RACH and a 2-step RACH.

[0083] So, a UE may support both 4-step and 2-step RACH procedures. The selection of the appropriate type of RACH procedure (e.g., 2-step vs. 4-step) may be based on an indication provided to all UEs by system information, or may be based separately on a UE-specific configuration for each UE, e.g., using an RRC configuration message.

[0084] The present inventors have identified shortcomings with the current preliminary agreement on how a UE should select the type of RACH procedure to perform.

[0085] For example, if the gNB uses system information to instruct all UEs to perform a type of RACH procedure, the radio resources of the instructed RACH type (e.g., 2-step) may become very congested, while the radio resources of other RACH types (e.g., 4-step) are hardly utilized, which will have a negative impact on the radio resource management as well as on the successful execution of the random access procedure.

[0086] On the one hand, instructing UEs in a dedicated way, for example using dedicated RRC messages, may not suffer from the drawbacks mentioned above when using system information. On the other hand, it may only be applicable to UEs in RRC_CONNECTED state that are actually connected to the network and can receive such RRC messages. Other UEs (e.g. in RRC idle state) may not be able to receive such information at all. Such dedicated communication may further result in a large signaling overhead.

[0087] The inventors have therefore identified a possibility to improve the random access procedure performed between a UE and a base station, particularly in the case where there are several different types of random access procedures.

[0088] In the following, UEs, base stations, and procedures that meet such needs are described for new radio access technologies envisioned for 5G mobile communication systems, but which may also be used in LTE mobile communication systems. Various implementations and variations are also described. The following disclosure has been facilitated by, and may be based, for example, at least in part on, the above discussion and discoveries.

[0089] In general, it should be noted that many assumptions are made herein to allow the principles underlying the present disclosure to be explained in a clear and understandable manner. However, these assumptions should be understood as merely examples made herein for illustrative purposes, without limiting the scope of the present disclosure. Those skilled in the art will recognize that the principles of the following disclosure and claims can be applied to various scenarios and in ways not explicitly described herein.

[0090] Furthermore, some of the terms such as procedures, entities, layers, etc. used below are closely related to the terms used in the LTE / LTE-A system or in the current 3GPP 5G standardization, even though the specific terms used in the context of new radio access technologies for the upcoming 3GPP 5G communication system have not yet been fully determined or may eventually change. Therefore, the terms may be changed in the future without affecting the functionality of the embodiments. Therefore, those skilled in the art will recognize that the embodiments and their scope of protection should not be limited to the specific terms used illustratively in this specification due to the lack of other more recent or finally agreed upon terms, but should be more broadly understood in terms of the functions and concepts underlying the functions and principles of the present disclosure.

[0091] For example, a mobile station or mobile node or user terminal or user equipment (UE) is a physical entity in a communication network. A node may have several functional entities. A functional entity refers to a software or hardware module that implements and / or provides a given set of functions to other functional entities of the same or other nodes or networks. A node may have one or more interfaces that connect the node to communication facilities or media that allow the node to communicate. Similarly, a network entity may have logical interfaces that connect functional entities to communication facilities or media that allow the node to communicate with other functional entities or corresponding nodes.

[0092] The term "base station" or "radio base station" as used herein refers to a physical entity in a communication network. Similar to a mobile station, a base station may have several functional entities. A functional entity refers to a software or hardware module that implements and / or provides a given set of functions to other functional entities of the same or other nodes or networks. The physical entity performs several control tasks for the communication devices, including one or more scheduling and configuration. It should also be noted that base station functions and communication device functions may be integrated in a single device. For example, a mobile terminal may also implement the functions of a base station for other terminals. The term used in LTE is eNB (or eNodeB), while the term currently used in 5G NR is gNB.

[0093] 9 shows a general, simplified, exemplary block diagram of a user equipment (also called a communication device) and a scheduling device (here, illustratively assumed to be located in a base station, e.g., in an eLTE eNB (alternatively called ng-eNB) or in a gNB in ​​5G NR). The UE and the eNB / gNB communicate with each other over (radio) physical channels using their respective transceivers.

[0094] A communication device may have a transceiver and a processing circuit. The transceiver may then have a receiver and a transmitter and / or function as a receiver and a transmitter. The processing circuit may be one or more hardware, such as, for example, one or more processors or any LSI. Between the transceiver and the processing circuit, there are input / output points (or nodes) through which the processing circuit can control the transceiver during operation, i.e., control the receiver and / or the transmitter and exchange receive / transmit data. The transceiver may include, as a transmitter and receiver, an RF (radio frequency) front including one or more antennas, amplifiers, RF modulators / demodulators, etc. The processing circuit may implement control tasks such as controlling the transceiver to transmit user data and control data provided by the processing circuit and / or to receive user data and control data that are further processed by the processing circuit. The processing circuit may also be involved in performing other processes, such as, for example, judging, deciding, calculating, measuring, etc. The transmitter may be involved in performing the process of transmitting and other processes related thereto. The receiver may be responsible for performing the receiving process and other processes related thereto (eg, monitoring the channel, etc.).

[0095] In the following, an improved procedure on how to perform the random access procedure is described.

[0096] Figure 10 shows a simplified exemplary UE structure according to one solution of the improved procedure, which can be implemented based on the general UE structure described in relation to Figure 9. The various structural elements of the UE shown in this figure can be interconnected with each other, for example, by means of corresponding input / output nodes (not shown), for example, to exchange control and user data and other signals. Although not shown for purposes of illustration, the UE may include further structural elements.

[0097] As can be seen from FIG. 10, the UE may include a random access type threshold receiver, a random value determining circuit, a random access type threshold selecting circuit, a value comparing circuit, a random access procedure type selecting circuit, and a random access procedure executing circuit.

[0098] As will become apparent from the disclosure below, in this case the processing circuitry may thus be exemplarily configured to at least partially perform one or more of: determining a random value; selecting one among a plurality of random access type thresholds; comparing said random value with said one random access type threshold; selecting a random access procedure type; performing a random access procedure; determining whether an access attempt to the radio cell can be made as part of an access control procedure; etc.

[0099] Thus, the receiver may be exemplarily configured to at least partially perform one or more of: receiving a plurality of random access type thresholds; receiving a message as part of a random access procedure; receiving information regarding an association between the random access type thresholds and other criteria (e.g., RACH triggers, access categories, channel quality, radio cells, etc.);

[0100] Thus, the transmitter may be illustratively configured to at least partially perform one or more of: transmitting messages as part of a random access procedure;

[0101] FIG. 11 is a sequence diagram of an example UE operation with an improved RACH procedure, which is described in more detail below.

[0102] The UE is assumed to support several types of random access procedures, such as the two-step and four-step RACH (here contention-based) procedures mentioned above. In the following, for illustrative purposes, there are only two different types of random access procedures that the UE needs to select from. However, the improved RACH procedures are not limited to this and the UE may equally select from three or more different RACH procedures.

[0103] Further, exemplarily, the UE shall be involved in making the final decision as to which type of RACH procedure to perform, for example, to access a radio cell, which decision may be controlled to some extent by the network operator (e.g., gNB) by providing appropriate parameters that the UE uses to arrive at the type of RACH procedure.

[0104] Accordingly, the UE may receive multiple threshold parameters (which may also be referred to as random access type thresholds or simply RACH type thresholds) to use for selecting a RACH type. As will be described in more detail later, by providing multiple RACH type thresholds (e.g., instead of one probability threshold), the network may exercise accurate and precise control of how different UEs select a RACH type, e.g., by allowing it to take into account the RACH trigger, the access category associated with the RACH procedure to be performed, the channel quality of the radio link over which the RACH procedure is performed, or the radio cell over which the RACH procedure is performed (e.g., PCell vs. SCell).

[0105] Although here and below it is assumed to use multiple RACH type thresholds, it is also possible to use only one RACH type threshold to control the selection of the RACH type in the UE. In this case, the control of the RACH type selection may be less accurate. On the other hand, not only can the selection of the RACH type in the UE be simplified, but also the parameters to be configured by the network side (e.g. to be transmitted by the gNB) can be reduced.

[0106] According to the improved RACH procedure, a selection of a RACH type is performed based on a random value and a received RACH type threshold. In response, the UE determines a random value. Furthermore, the UE selects one among a plurality of random access type thresholds and compares the previously determined random value with the selected random access type threshold. Based on the result of the comparison, the UE selects a type of random access procedure. The UE then performs the random access procedure according to the selected type.

[0107] By using this mechanism of comparing a UE selected random value with a network defined threshold, the network can control the loading of the 2-step and / or 4-step RACH resources in an appropriate manner. Moreover, this mechanism facilitates that no specific UE needs to be configured to perform the 2-step or 4-step RACH procedure.

[0108] FIG. 12 is a sequence diagram of an exemplary gNB operation with an improved RACH procedure, which is described in more detail below. The gNB can transmit information regarding multiple random access type thresholds to the UE, which the UE can use to perform RACH type selection as described above and below. After the UE determines the type of RACH, it can initiate the RACH procedure, and the gNB can participate in the UE-initiated RACH procedure accordingly, e.g., receive the first and third messages and transmit the second and fourth messages of a four-step RACH (see FIG. 7 and the relevant paragraphs above), or receive the first message and transmit the second message of a two-step RACH.

[0109] The values ​​of the random value and the received RACH type threshold should be adjusted to allow a meaningful comparison. For example, the RACH type threshold and the random value can be defined as probabilities, e.g., their values ​​can be between 0 and 1 (non-integer values) or between 0 and 100. Accordingly, if the probability threshold is defined as 0 or 1, the network ensures that a particular RACH type is always or never used by a UE in a radio cell.

[0110] The RACH type threshold may be associated with one of the types of RACH procedures (e.g., a two-step RACH procedure), so that the above-mentioned RACH type selection can determine whether to select that type of RACH procedure (e.g., a two-step RACH). For example, if the random value is smaller than the first type-related RACH threshold, the UE determines that the first type of RACH procedure should be selected. If the random value is equal to or larger than the first type-related RACH threshold, the UE determines that the first type of RACH procedure should not be selected, but should select the second type of RACH procedure. Here, since it is exemplarily assumed that there are only two different RACH procedures (see above 2-step RACH vs. 4-step RACH), there is no need to perform any other RACH type selection procedure, because the UE can directly decide to use one RACH type or the other RACH type (e.g., 4-step) based on the single RACH type selection.

[0111] It is likewise possible to distinguish between two or more different RACH procedures, in which case it may be necessary, for example, to provide different RACH type thresholds and / or for the UE to perform more than one RACH type selection.

[0112] As already mentioned above, the UE may be provided with multiple random access type thresholds, each associated with a particular parameter or criterion that may be taken into account for the RACH type selection. For example, the network may differentiate RACH type selection per RACH trigger, and / or per access category, and / or per channel quality, and / or per radio cell used, and / or any other suitable criterion.

[0113] More specifically, the RACH procedure can be triggered by different events, e.g., as described above for the exemplary 3GPP standard implementation. For some or all of these different RACH trigger events, different RACH type thresholds can be defined by the network and provided to the UE. Accordingly, when performing RACH type selection, the UE decides to perform the RACH type threshold associated with the RACH trigger that triggered the current RACH. It then compares the previously generated random value with the RACH trigger-specific RACH type threshold to decide to perform with the type of RACH.

[0114] Which particular value to associate with each RACH trigger can be decided by the network based on considerations such as, for example, how important or urgent the RACH trigger is. For example, the RACH trigger "Request for Other SI" is less urgent than the "RRC Connection Re-establishment procedure" because the latency requirement for acquiring "Other SI" is less restrictive than the latency requirement for resuming from a dropped RRC connection. In this sense, the network can configure the RACH type threshold such that the UE is more likely to perform a 2-step RACH procedure if its RACH trigger is "RRC Connection Re-establishment" and more likely to perform a 4-step RACH procedure if its RACH trigger is "Request for Other SI".

[0115] Furthermore, the RACH procedure is closely related to the access categories mentioned above in relation to the unified access control (UAC) procedure. For example, it was exemplarily assumed that most every RACH is preceded by an access attempt under the control of the UAC procedure executed in the UE. Therefore, a RACH trigger can be associated with a particular access category. In the following, an exemplary association between a RACH trigger and possible access categories is presented.

[0116] [Table 6]

[0117] Thus, for example, a UE performing a RACH procedure triggered due to initial access from RRC_IDLE will select a RACH type threshold associated with access category 2 or 8 (the following excerpt is from the table further above), since the RACH attempt is the result of RRC level signaling.

[0118] [Table 7]

[0119] For other RACH triggers, several access categories are possible and the UE may determine the access category of the access attempt by referring to previously performed UAC procedures.

[0120] For the purposes of the present invention, some RACH triggers (e.g. beam failure recovery, time alignment when adding a SCell, DL data arrival during asynchrony, etc.) do not necessarily need to be associated with an access category, since they are performed as contention-free RACH procedures and therefore do not require a type selection (since it is exemplarily assumed that there is only one type of contention-free RACH procedure).

[0121] Which particular value to associate with each access category can be decided by the network based on considerations such as how important or urgent the access category is. For example, access category 2 (emergency) is more urgent than access category 7 (MO data not belonging to other access categories), because obviously the latency requirements for emergency calls must be much more restrictive than those of low priority uplink traffic. In this sense, the network can set the RACH type threshold such that the UE is more likely to perform a 2-step RACH procedure if the RACH procedure is triggered by access category 2, and more likely to perform a 4-step RACH procedure if the RACH procedure is triggered by access category 7.

[0122] Another possibility is that each RACH type threshold can be associated with a value or range of a channel quality (e.g., RSRP / RSRQ). As a result, the UE can thus determine (measure) the quality of the channel through which the RACH procedure is performed (e.g., RSRP and / or RSRQ of a beam) and then determine the RACH type threshold associated with the determined channel quality. This determined channel quality specific RACH type threshold can then be used to compare the random value.

[0123] Which particular value to associate with each channel quality can be determined by the network based on considerations such as resource utilization efficiency. Since using a two-step RACH procedure consumes more radio resources (PUCCH+PUSCH), failing a two-step RACH procedure is more detrimental than failing a four-step RACH procedure. In this sense, the network may want the success rate of performing a two-step RACH procedure to be higher than the success rate of performing a four-step RACH procedure. As a result, the network may set the RACH type threshold such that the UE is more likely to perform a two-step RACH procedure when the link quality between the UE and the gNB is good, and the UE is more likely to perform a four-step RACH procedure when the link quality between the UE and the gNB is poor.

[0124] Yet another possibility is that each RACH type threshold can be associated to a specific radio cell (e.g., the PCell, or one of the SCells, etc.) on which the RACH procedure is performed. Until now, no distinction has been made regarding the radio cell on which the RACH procedure is performed. For example, it is usually assumed that the contention-based RACH procedure is always performed on the PCell. Nevertheless, for example, in future 3GPP releases, it may be possible that the contention-based RACH procedure is performed on one of the configured SCells. In such a scenario, the network may be interested in separately controlling the use of the 2-step and 4-step RACH procedures on the PCell and on the SCell. Correspondingly, the network may define different RACH type thresholds for the PCell and one or more SCells. For example, if the RACH procedure is performed on one of the SCells, the UE first determines the RACH type threshold associated with that SCell and compares the previously determined random value with the SCell-specific RACH type threshold.

[0125] Which specific value to associate with each radio cell can be decided by the network based on the consideration that a RACH procedure performed on a PCell should have a higher priority than a RACH procedure performed on a SCell. This is because if a UE is performing a RACH procedure on a SCell, some other UEs may also want to perform a RACH procedure on the same cell, which is the PCell for them. By assuming that a RACH procedure performed on a PCell is more urgent / important than a RACH procedure performed on a SCell, the network can configure the RACH type threshold such that the UE is more likely to perform a 2-step RACH procedure if the RACH procedure is performed on a PCell and more likely to perform a 4-step RACH procedure if the RACH procedure is performed on a SCell.

[0126] Furthermore, some or all of the above criteria (RACH trigger, access category, channel quality, radio cell) can be taken into account for RACH type selection by providing RACH type thresholds associated therewith. For example, it may be beneficial to provide RACH type thresholds associated with access categories and types of radio cells. However, other combinations are possible as well, depending on the interests of the network operator.

[0127] Said association between RACH type thresholds and different criteria can be provided to the UEs in different ways. One exemplary solution is to broadcast such association in the system information (e.g. SIB1). In this way, all UEs in the radio cell will be able to determine the association and keep it up to date through the already established system information update mechanism in case of any changes to the association by the network.

[0128] According to one particular example implementation, where RACH type thresholds are associated with different access categories, information about such association can be transmitted together with the access attempt threshold information. For this purpose, when using a 3GPP standard specific implementation, the corresponding information element carried by SIB1 and containing information about the access attempt threshold of one particular access category (UA-BarringInfoSetList in SIB1, see Non-Patent Document 9) can be extended, for example, as follows to carry information about the association between the RACH type threshold (here, as used to decide whether to use 2-step RACH or not, e.g. 2stepRACH-ProbThres) and the access category:

[0129] [Table 8]

[0130] Different values ​​for the RACH type threshold can be defined (here, for example, in 10 percent steps from 0 to 100), where p00 may mean that only a 4-step RACH is configured for the access category, and p100 may mean that only a 2-step RACH is configured for this access category. In this respect, it is exemplarily assumed that any random value below the 2-step RACH specific threshold leads to the use of a 2-step RACH, whereas any random value equal to or greater than the 2-step RACH specific threshold leads to the use of only the other RACH type (i.e., a 4-step RACH) without using a 2-step RACH.

[0131] Above we have described the association between different RACH type thresholds and access categories, carried by the UAC-BarringInfoSetList information element. Similarly, the association between RACH type thresholds and other criteria (e.g. RACH trigger, channel quality, PCell / SCell) can be transmitted in corresponding information elements, e.g. as presented below. All such information elements can be transmitted, e.g., by system information (e.g. SIB1).

[0132] In particular, the Trigger-RACHTypeSelect information element associates a particular RACH trigger event (herein identified by "RACH-TriggerEvent") with a particular RACH type threshold (herein identified by 2stepRACH-ProbThres).

[0133] [Table 9]

[0134] The ChannelQ-RACHTypeSelect information element associates different channel qualities (here identified by channel-Quality-UpperBound and channel-Quality-LowerBound) with specific RACH type thresholds (here identified by 2stepRACH-ProbThres).

[0135] [Table 10]

[0136] The Cell-RACHTypeSelect information element associates different radio cells (here identified by cell-Type) with specific RACH type thresholds (here identified by 2stepRACH-ProbThres).

[0137] [Table 11]

[0138] Instead of defining the thresholds for a two-step RACH procedure, it is also possible to use a four-step RACH procedure and define the thresholds for using it in RACH type selection in a corresponding manner. The following is an example of such a four-step RACH threshold setting:

[0139] [Table 12]

[0140] In this case, for example, any random value less than the 4-step RACH specific threshold will lead to the use of a 4-step RACH, while any random value greater than or equal to the 4-step RACH specific threshold will lead to the use of only the other RACH type (i.e., 2-step RACH) without using a 4-step RACH.

[0141] In the following, variants of the improved RACH procedure are described in detail. For example, some of these variants revolve around the interrelationship between the UAC procedure and the RACH procedure. The UAC is currently specified in 3GPP and introduced above. To avoid repetition, we refer to those detailed descriptions and only provide a brief overview. In summary, the UE performs an access control procedure (UAC) to determine whether an access attempt should be made to a radio cell. The UAC check is based on one or more access identities of the access attempt, and if the access attempt is not allowed based on the access identity, the UAC check continues based on the access category of the access attempt. As described above, the UE determines a random value and compares this random value with an access attempt threshold (UAC-BarringFactor) associated with the access category. For example, if the random value is equal to or greater than the threshold, the UE is barred from accessing the cell, and if the random value is less than the threshold, the UE can perform the access attempt.

[0142] A positive access attempt check (i.e., the UE can perform an access attempt) may be followed by a RACH procedure, for example, according to one of the improved RACH procedures described above. According to one exemplary implementation, the UAC procedure and the improved RACH procedure may be performed consecutively, but independently of each other. For example, the UE first performs a UAC procedure, including deriving a random value, if necessary, and comparing the random value to an appropriate access attempt threshold (e.g., UAC-BarringFactor). Thereafter, as part of the improved RACH type selection solution described above, the UE derives another random value and compares the another random value to an appropriate RACH type threshold to select the type of RACH procedure to perform.

[0143] This solution is illustrated in Figure 13, which is a sequence diagram of an exemplary UE operation with an improved RACH procedure. According to the above description, the UE may have to derive a random number twice, one random number A during UAC check (based on access category) and another random number B for RACH type selection. Then, each check is performed based on each random number.

[0144] Separating the two procedures from each other facilitates that the UAC procedures do not need to be modified, and furthermore, the RACH type selection is independent of the UAC procedures, which allows the RACH type selection to be independently controlled by the network.

[0145] According to another example implementation, instead of deriving the random number twice, e.g. as done in the above solution described in Fig. 13, the UAC procedure and the RACH type selection procedure are inter-related to facilitate that the random number only needs to be derived once. In particular, if a random number has already been derived as part of the UAC procedure, the UE may reuse that random number for RACH type selection as well and will not derive another random number (random number B in the solution of Fig. 13). Otherwise, if a random number is not derived as part of the UAC procedure (e.g. because an access attempt has already been authorized based on one of the access identities), the UE shall derive a random number for selecting a RACH type.

[0146] Furthermore, it should be noted that the RACH type threshold and the access attempt threshold work together to determine how many UEs will access a cell based on a particular type of RACH procedure. For example, if the RACH type threshold is set higher than the access attempt threshold, the network may achieve that the random value is always lower than the RACH type threshold, because only UEs for which the exemplary random value<access attempt threshold perform an access attempt and therefore perform RACH type selection. This results in all UEs always selecting the same type of RACH procedure.

[0147] An example sequence of checks is shown below: If as a result of the uac-BarringForAccessIdentity based check the UE needs to further check based on uac-BarringFactor, the UE fetches a random value (RAN_value, 0-99).

[0148] [Table 13]

[0149] If, as a result of the uac-BarringForAccessIdentity based check, the UE is allowed access to the cell, the UE retrieves a random value (RAND_value, 0 to 99).

[0150] [Table 14]

[0151] One exemplary implementation of the above solution, where only one random value needs to be determined, is shown in Fig. 14, a sequence diagram of an exemplary UE operation with an improved RACH procedure. As is evident from the figure, the UE needs to determine in each case only one random number A. The RACH type selection is then performed based on said random number A, which may have already been derived and used for the access attempt check performed based on the access category.

[0152] These exemplary implementations have the advantage that only one random number needs to be derived in the UE in any case. Determining the random value is processor consuming and increases the complexity of the UE, and it is generally preferable to avoid these drawbacks. Furthermore, the UAC check can remain exactly the same as currently defined, since no changes are actually required. For example, an additional process of deriving the random number A if the access attempt is allowed with a matching access identity can be part of the RACH type selection.

[0153] FIG. 14 further illustrates an optional step of normalizing the RACH type threshold, which may be performed if the access attempt is allowed based on the access identity. More specifically, assume for example that the access attempt threshold is set to 0.8. This means that 80% of the UEs are allowed to perform an access attempt to the cell (based on the random number A, see FIG. 14). Furthermore, assume exemplarily that the RACH type threshold is 0.4. Bearing in mind that only UEs with random value A between 0 and 0.8 will attempt access, this RACH type selection will result in 50% of the UEs actually attempting access (i.e., 0.4 / 0.84) using, for example, a two-step RACH. However, when the random number A needs to be derived in the case of the access attempt being allowed based on the access identity, the range of the random value for the UEs performing the RACH type selection is 0 to 1. This will result in 40% of the UEs actually attempting access (0.4 / 1) using, for example, a two-step RACH. Therefore, the control of RACH type selection depends on how the access decision is granted for the UE: based on access identity or based on access category.

[0154] To allow a unified control of RACH type selection, for example when access attempts are allowed based on an access identity, a normalization step can be optionally introduced. In particular, the normalization step adapts the value of the RACH type threshold such that the probability of selecting a certain type of RACH procedure is the same when access to a cell is allowed based on an access identity as when access to a cell is allowed based on an access category. Furthermore, the normalization depends on the value of the access attempt threshold. For example, in the exemplary scenario used above, the RACH type threshold may be normalized to 0.5. In general, the normalized RACH type threshold can be calculated by "old RACH type threshold" / "access attempt threshold", which in the above case is 0.4 / 0.8=0.5.

[0155] As explained before, the information on the association may be transmitted together with the access attempt threshold information. For this purpose, when using a 3GPP standard specific implementation, the corresponding information element carried by SIB1 and containing information on the access attempt threshold of one particular access category (UA-BarringInfoSetList in SIB1, see 3GPP 38.331) may be extended, for example, as follows to carry information on the association between a RACH type threshold (here, as used to decide whether to use 2-step RACH or not, e.g., 2stepRACH-ProbThres) and an access category:

[0156] [Table 15]

[0157] In this exemplary solution, the specific value of 2stepRACH-ProbThres is the same as the value of uac-BarringFactor to allow the network to define the same threshold for policing and RACH type selection. In particular, when selecting the same RACH type threshold as the access attempt threshold, the network can control the UE to perform RACH according to only one type.

[0158] According to a further solution, the network (e.g., a gNB) can dynamically change the value of the RACH type threshold (optionally also the value of the access attempt threshold) and then transmit the updated RACH type threshold (optionally also the updated access attempt threshold) to the UE, e.g., in system information.

[0159] The network may consider various criteria for dynamically adapting the threshold. Such criteria may include, for example, the load of the radio cell or the availability of uplink radio resources. For example, the load of the radio cell may be determined at the gNB to determine an appropriate value of the RACH type threshold (and optionally the access attempt threshold). In one exemplary implementation, when the cell load is high (e.g., above a certain threshold, such as 1000 active UEs in RRC_CONNECTED mode), the RACH type threshold may be adapted such that fewer UEs can use the two-step RACH procedure. The two-step RACH procedure will consume more radio resources due to the transmission of the combined PRACH and PUSH in the first message, so that in a high-load situation, the available radio resources may not be sufficient to support the two-step RACH procedure, but may still be able to support the four-step RACH procedure. Conversely, when the cell load is low (e.g., below that same certain threshold), the RACH type threshold may be adapted such that more UEs can use the two-step RACH procedure. The same or similar dynamic adaptation may also be made to the access attempt threshold (eg, uac-barringfactor) based on cell load.

[0160] On the other hand, the availability of uplink resources may vary significantly from time to time. This is true in general, but it is especially true for unlicensed radio cells (e.g., NR-U scenarios). The use of unlicensed bands is the focus of the new 5G-NR development. In NR, Listen-Before-Talk is performed on unlicensed carriers. In particular, the transmitting entity performs LBT, and channel occupancy is only allowed after a successful LBT Clear channel Assessment (CCA) in order to facilitate coexistence with other systems, e.g., Wi-Fi (IEEE 802.11) systems operating in such unlicensed bands (see, for example, Non-Patent Document 11).

[0161] Accordingly, resources may be repeatedly blocked by other terminals or WIFI nodes, resulting in low availability of uplink resources for UEs controlled by the gNB. On the other hand, if there are few other UEs or WiFi nodes using unlicensed carriers, the availability of uplink resources for UEs controlled by the gNB is high. The gNB may also perform its own CCA to determine the availability of uplink resources of its radio cell, but may adapt the RACH type threshold to the changing availability. For example, if uplink resources are scarce (e.g., below a certain threshold, such as when the channel occupancy time is less than 30% of the total time), the gNB may adapt the RACH type threshold so that fewer UEs can use the two-step RACH procedure. Considering that the two-step RACH procedure consumes more radio resources than the four-step RACH procedure, if the gNB can hardly acquire the channel, the available radio resources will not be enough to support the two-step RACH, but it may still be able to support the four-step RACH. On the other hand, if uplink resources are sufficiently available (e.g., above a certain threshold, such as when the channel occupancy time is more than 90% of the total time), the RACH type threshold may be adapted to allow more UEs to use the two-step RACH procedure.

[0162] The same or similar dynamic adaptation may also be made to the access attempt threshold (eg, uac-barringfactor) based on cell load.

[0163] Instead of broadcasting the updated RACH type threshold (and optionally also the updated access attempt threshold) in the system information as described above, the gNB can also provide the updated values ​​to the UE in or together with a Channel Occupation Time indication (COT indication), which is sent by the gNB (on the CO-PDCCH) to indicate to the UE that the channel is now available. This COT indication can be further extended to carry information about updated values ​​of one or both of the RACH type threshold and the access attempt threshold. If the UE receives the updated values ​​via the CO-PDCCH, the previous values ​​received via the system information are overwritten with the new values.

[0164] FIG. 15 shows a sequence diagram of an exemplary operation of a gNB updating a RACH type threshold according to an exemplary implementation. As is evident from the figure, the gNB shall set multiple RACH type thresholds and access attempt thresholds according to one of the above solutions. Information about these thresholds is then transmitted to the UE (e.g., by system information) to be used for RACH type selection and UAC procedures, respectively. As mentioned above, to update the thresholds, the gNB may monitor the cell load and uplink resource availability (referred to as RACH resource congestion and RACH resource free in the example of FIG. 15). If there is a significant change in any of the monitored criteria, the gNB may decide to adapt either or both of the RACH type threshold and the access attempt threshold and transmit the updated values ​​to the UE (e.g., broadcast again in the system information or COT, or in a dedicated manner as described below).

[0165] According to further exemplary implementations, the RACH type threshold can be provided to the UE in yet other ways, for example in a dedicated way. More specifically, the gNB can send a dedicated RRC message to the UE, for example in case of handover or conditional handover scenarios. Specifically, the UE exchanges several RRC messages with the old and new gNBs during handover. One of these RRC messages can be adapted and used by the UE to determine the type of contention-based RACH during or immediately after handover. In one exemplary implementation, this RACH type threshold is applicable to all access categories and can be valid until the UE acquires the RACH type threshold of the target radio cell, for example by system information.

[0166] Another way to transmit the RACH type threshold to the UE is to use a message of the RACH procedure, for example, if the RACH procedure fails (e.g., due to a contention). In one implementation, the second or fourth message carrying the back-off indicator can additionally carry the (updated) RACH type threshold. Thus, the UE can perform a new RACH type selection (after a failed RACH procedure) using a different value for subsequent RACH attempts. In one exemplary implementation, this RACH type threshold is applicable to all access categories and may be valid until the UE acquires the RACH type threshold of the radio cell, for example, by system information.

[0167] These solutions are beneficial when the network needs to relieve 2-step or 4-step RACH radio resources in a short time. Updating the RACH type threshold using system information can be done in parallel to reach all UEs in the radio cell, but updating the system information can take more time since it is usually performed at the next system information change period.

[0168] Further Aspects

[0169] According to a first aspect, there is provided a user equipment (UE) having a receiver for receiving a plurality of random access type thresholds, the UE further comprising a processing circuit for determining a random value, the processing circuit for selecting a type of random access procedure to be performed by the UE, the selecting comprising at least: - selecting one from among the plurality of random access type thresholds; - comparing the determined random value to the selected random access type threshold; and - selecting a type of a random access procedure based on a result of the comparison, wherein the UE performs the random access procedure of the selected type.

[0170] According to a second aspect provided in addition to the first aspect, the processing circuitry determines whether an access attempt can be made to a wireless cell. In an optional implementation, the access attempt includes performing the random access procedure. In a further optional implementation, the access attempt is associated with one or more access identities and an access category, and the processing circuitry determines the access attempt to the wireless cell as: first determining whether or not the one or more access identities can be accessed; Then, if the access attempt cannot be made based on the one or more access identities, determining whether the access attempt can be made based on the access category, wherein determining whether the access attempt can be made based on the access category includes determining an access attempt threshold associated with the access category of the access attempt.

[0171] According to a third aspect provided in addition to the second aspect, determining whether the access attempt can be made includes determining a second random value and comparing the second random value to the access attempt threshold.

[0172] According to a fourth aspect provided in addition to the second aspect, determining whether the access attempt can be made includes comparing the same random value to be used to select the random access procedure type to the access attempt threshold. In an optional implementation, if determining that the access attempt can be made based on the one or more access identities, selecting the random access procedure type includes, for example, normalizing the random access type threshold based on the access attempt threshold such that a probability of performing one type of random access procedure when an attempt based on the access identity is successful is the same as or close to a probability of performing the same type of random access procedure when an attempt based on the access category is successful.

[0173] According to a fifth aspect provided in addition to one of the first to fourth aspects, the random access type thresholds are associated with the use of one of different types of random access procedures, such as a two-step random access procedure or a four-step random access procedure. In an optional implementation, the random value smaller than the random access type threshold is associated with a first type of the random access procedure, and the random value larger than or equal to the random access type threshold is associated with a second type of the random access procedure. In an optional implementation, the random value is a non-integer value determined between 0 and 1, and the random access type threshold is also a non-integer value between 0 and 1.

[0174] According to a sixth aspect provided in addition to one of the first to fifth aspects, among the random access type thresholds, there are respective random access type thresholds associated with different random access trigger events that cause the UE to perform a random access procedure, and selecting the respective random access type thresholds comprises determining the random access type threshold associated with the random access trigger that caused the random access procedure to be performed. Additionally or alternatively, among the random access type thresholds, there are respective random access type thresholds associated with different access categories of an access attempt, and selecting the respective random access type thresholds comprises determining the random access type threshold associated with the access category of the access attempt. Additionally or alternatively, among the random access type thresholds, there are respective random access type thresholds associated with different sets of channel qualities, and selecting the respective random access type thresholds comprises 1) determining the channel quality of a radio link between the UE and a base station by which the random access procedure is to be performed, and 2) determining the random access type threshold associated with the determined channel qualities. Additionally or alternatively, among the plurality of random access type thresholds there are respective random access type thresholds associated with different radio cells of a base station, and selecting the respective random access type thresholds comprises determining the random access type thresholds associated with the radio cells through which the random access procedure is to be performed, optionally the different radio cells being a primary radio cell and one or more secondary radio cells.

[0175] According to a seventh aspect provided in addition to the sixth aspect, the receiver, in operation, receives system information broadcasted from a base station in a radio cell, the system information comprising: information regarding an association between the random access type threshold and the random access trigger event; information about an association between said random access type thresholds and said access categories, optionally and information about an association between said access attempt thresholds and said access categories; information regarding an association between said random access type threshold and said channel quality; information about an association between the random access type threshold value and the radio cell through which the random access procedure should be performed, Contains one or more of the following:

[0176] According to an eighth aspect provided in addition to one of the first to seventh aspects, the receiver receives from a base station in a radio cell a single random access threshold to be used for selecting a type of random access procedure instead of using one of the multiple random access type thresholds. In an optional implementation, the single random access threshold is received in a message of a failed random access procedure performed between the base station and the UE, and optionally in a random access response of the failed random access procedure or in a message of a handover procedure performed by the UE together with a source base station and a target base station.

[0177] According to a ninth aspect provided in addition to one of the first to eighth aspects, the random access procedure is one of a two-step random access procedure and a four-step random access procedure. In one optional implementation, in the case of the two-step random access procedure, at least a transmitter of the UE, during operation, transmitting a random access preamble and uplink data to a base station; The receiver, during operation, receives a random access response and at least information relating to contention resolution.

[0178] In the case of the four-step random access procedure, at least a transmitter of the UE, during operation, transmitting a random access preamble to a base station; receiving, by the receiver, a random access response indicating radio resources to be used by the UE during operation; the transmitter, during operation, transmitting uplink data using the indicated radio resources; The receiving includes receiving, during operation, information related to conflict resolution.

[0179] According to a tenth aspect, there is provided a method, executed by a user equipment (UE), comprising the steps of: receiving a plurality of random access type thresholds; determining a random value; Selecting a type of random access procedure to be performed by the UE, the selecting step comprising at least: - selecting one from among the plurality of random access type thresholds; - comparing the determined random value to the selected random access type threshold; and - selecting a type of random access procedure based on a result of the comparison; performing a random access procedure of the selected type; and A method is provided comprising:

[0180] According to an eleventh aspect provided in addition to the tenth aspect, the method further comprises a step of determining whether an access attempt to a radio cell can be made. In an optional implementation, the access attempt includes performing the random access procedure. In an optional implementation, the access attempt is associated with one or more access identities and an access category, and the determining step includes determining the access attempt to the radio cell as: first determining whether or not the one or more access identities can be accessed; Then, if the access attempt cannot be made based on the one or more access identities, determining whether the access attempt can be made based on the access category, wherein determining whether the access attempt can be made based on the access category includes determining an access attempt threshold associated with the access category of the access attempt.

[0181] According to a twelfth aspect provided in addition to the eleventh aspect, determining whether the access attempt can be made includes determining a second random value and comparing the second random value to the access attempt threshold.

[0182] According to a thirteenth aspect provided in addition to the eleventh aspect, determining whether the access attempt can be made includes comparing the same random value to be used for selecting the random access procedure type to the access attempt threshold. In an optional implementation, if determining that the access attempt can be made based on the one or more access identities, selecting the random access procedure type includes, for example, normalizing the random access type threshold based on the access attempt threshold such that a probability of performing one type of random access procedure when an attempt based on the access identity is successful is the same as or close to a probability of performing the same type of random access procedure when an attempt based on the access category is successful.

[0183] According to a fourteenth aspect provided in addition to any of the tenth to thirteenth aspects, the plurality of random access type thresholds are associated with the use of one of various types of random access procedures, such as a two-step random access procedure or a four-step random access procedure. In an optional implementation, the random value smaller than the random access type threshold is associated with a first type of the random access procedure, and the random value larger than or equal to the random access type threshold is associated with a second type of the random access procedure. In an optional implementation, the random value is a non-integer value determined between 0 and 1, and the random access type threshold is also a non-integer value between 0 and 1.

[0184] According to a fifteenth aspect provided in addition to any of the tenth to fourteenth aspects, among the plurality of random access type thresholds, a respective random access type threshold is associated with a different random access trigger event that causes the UE to perform a random access procedure, and selecting the respective random access type thresholds comprises determining the random access type threshold associated with the random access trigger that caused the random access procedure. Additionally or alternatively, among the plurality of random access type thresholds, a respective random access type threshold is associated with a different access category of an access attempt, and selecting the respective random access type threshold comprises determining the random access type threshold associated with the access category of the access attempt.

[0185] Additionally or alternatively, among the plurality of random access type thresholds there are respective random access type thresholds associated with respective different sets of channel qualities, and selecting the respective random access type thresholds comprises: 1) determining the channel quality of a radio link between the UE and a base station, through which the random access procedure is to be performed, and 2) determining the random access type threshold associated with the determined channel quality. Additionally or alternatively, among the plurality of random access type thresholds there are respective random access type thresholds associated with respective different radio cells of a base station, and selecting the respective random access type thresholds comprises determining the random access type threshold associated with the radio cell through which the random access procedure is to be performed, optionally the different radio cells being a primary radio cell and one or more secondary radio cells.

[0186] Hardware and Software Implementations of the Disclosure

[0187] The present disclosure can be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of each embodiment above can be realized, in part or in whole, by an LSI such as an integrated circuit, and each process described in each embodiment can be controlled, in part or in whole, by the same LSI or a combination of LSIs. The LSI may be formed as an individual chip, or one chip may be formed to include some or all of the functional blocks. The LSI may include a data input and a data output connected thereto. Here, the LSI may be called an IC, a system LSI, a super LSI, or an ultra LSI depending on the degree of integration. However, the technology for realizing the integrated circuit is not limited to the LSI, and may be realized using a dedicated circuit, a general-purpose processor, or a dedicated processor. In addition, a field programmable gate array (FPGA) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connection and settings of the circuit cells arranged inside the LSI may be used. The present disclosure can be realized as digital processing or analog processing. If future integrated circuit technologies replace LSI as a result of advances in semiconductor technology or other derived technologies, the future integrated circuit technologies can be used to integrate the functional blocks. Biotechnology is also applicable.

[0188] The present disclosure may be implemented by any type of apparatus, device, or system having communication capabilities, referred to as a communications apparatus.

[0189] Some non-limiting examples of such communications devices include telephones (e.g., cell phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, notebooks), cameras (e.g., digital still / video cameras), digital players (digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), game consoles, digital book readers, telehealth / telemedicine devices, vehicles (e.g., automobiles, airplanes, ships) that provide communications capabilities, and various combinations thereof.

[0190] Communications devices are not limited to being portable or mobile, but may include any type of equipment, device, or system that is non-portable or fixed, such as, for example, smart home devices (e.g., appliances, lighting, smart meters, control panels), vending machines, or any other "things" in an "Internet of Things" network.

[0191] Communications may include, for example, the exchange of data via cellular systems, wireless LAN systems, satellite systems, and the like, as well as various combinations thereof.

[0192] A communications device may include devices such as controllers and sensors connected to the communications device to perform the communications functions described in this disclosure. For example, a communications device may include a controller or a sensor that generates control or data signals used by the communications device to perform the communications functions of the communications device.

[0193] Communications equipment may also include infrastructure facilities, such as base stations, access points, or any other equipment, device, or system that communicates with or controls the equipment in the non-limiting examples above.

[0194] Furthermore, the various embodiments may be implemented by means of software modules, which are executed by a processor or directly in hardware. Also a combination of software modules and hardware implementation is possible. The software modules can be stored on any kind of computer-readable storage medium, for example RAM, EPROM, EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc. It should be noted further that individual features of the different embodiments may be the subject of another embodiment, individually or in any combination.

[0195] It will be apparent to those skilled in the art that various changes and / or modifications may be made to the present disclosure as set forth in the specific embodiments, and the present embodiments are therefore to be considered in all respects as illustrative and not restrictive.

Claims

1. A communication device, comprising: a receiver for receiving, during operation, a plurality of random access type thresholds; and a processing circuit for determining a random value during operation; the plurality of random access type thresholds includes a first random access type threshold associated with a first type of random access procedure; The processing circuitry, in operation, selecting said first random access type threshold; comparing said determined random value with said first random access type threshold; selecting said first type of random access procedure if, as a result of said comparison, said random value is less than said first random access type threshold; The communication device performs the first type random access procedure. Communications equipment.

2. The processing circuitry, during operation, determines whether an access attempt to a wireless cell can be made; the access attempt includes performing the first type random access procedure; The access attempt is associated with one or more access identities and an access category, and the processing circuitry is configured to process the access attempt to the wireless cell by: first determining whether or not it is possible to do so based on said one or more access identities; then, if the access attempt cannot be made based on the one or more access identities, determining whether the access attempt can be made based on the access category, wherein determining whether the access attempt can be made based on the access category includes determining an access attempt threshold associated with the access category of the access attempt. The communication device according to claim 1 .

3. determining whether the access attempt may be made includes determining a second random value and comparing the second random value to the access attempt threshold. The communication device according to claim 2 .

4. the plurality of random access type thresholds are associated with the use of one of a two-step random access procedure and a four-step random access procedure; the random value is a non-integer value determined between 0 and 1, and the random access type threshold is also a non-integer value between 0 and 1. The communication device according to claim 1 .

5. and / or wherein among the plurality of random access type thresholds, there are respective random access type thresholds associated with different random access triggering events that cause the communications device to perform a random access procedure, and selecting each random access type threshold comprises determining the random access type threshold associated with the random access triggering event that caused the communications device to perform the random access procedure; and / or wherein among the plurality of random access type thresholds, there are respective random access type thresholds associated with different access categories of an access attempt, and selecting the respective random access type thresholds includes determining the random access type thresholds associated with the access categories of the access attempt; Among the plurality of random access type thresholds, each random access type threshold is associated with a different set of channel qualities, and selecting each random access type threshold comprises: 1) determining the channel quality of a radio link between the communication device and a base station, over which the random access procedure is performed; and 2) determining the random access type threshold associated with the determined channel quality; and / or Among the plurality of random access type thresholds there are respective random access type thresholds associated with different radio cells of a base station, and selecting the respective random access type thresholds comprises determining the random access type thresholds associated with the radio cells through which the random access procedure is performed, the different radio cells being a primary radio cell and one or more secondary radio cells. The communication device according to claim 1 .

6. In operation, the receiver receives system information broadcast from a base station in a radio cell, the system information comprising: - information regarding an association between the random access type threshold and the random access trigger event; - information regarding the association between the random access type threshold and the access category, and information regarding the association between the access attempt threshold and the access category; - information regarding an association between the random access type threshold and the channel quality; - information regarding an association between the random access type threshold and the radio cell through which the random access procedure is performed, including one or more of: The communication device according to claim 5.

7. wherein, during operation, the receiver receives a single random access threshold instead of receiving the multiple random access type thresholds; The single random access threshold is received in a message of a failed random access procedure performed between a base station and the communication device; Received in a random access response of the failed random access procedure or in a message of a handover procedure performed by the communication device together with the source base station and the target base station; The communication device according to claim 1 .

8. The random access procedure is either a two-step random access procedure or a four-step random access procedure, and in the case of the two-step random access procedure, at least a transmitter of the communication device, in operation, transmitting a random access preamble and uplink data to a base station; The receiver, during operation, receives a random access response and at least information related to contention resolution; In the case of the four-step random access procedure, at least a transmitter of the communication device, in operation, transmitting a random access preamble to a base station; receiving, by the receiver, a random access response indicating radio resources to be used by the communications device during operation; transmitting uplink data using the indicated radio resource, during operation of the transmitter; receiving, during operation, information regarding conflict resolution; The communication device according to claim 1 .

9. A method comprising the steps of: receiving a plurality of random access type thresholds, the plurality of random access type thresholds including a first random access type threshold associated with a first type of random access procedure; determining a random value; selecting the first random access type threshold; comparing the determined random value to the first random access type threshold; selecting the first type of random access procedure if the random value is less than the first random access type threshold as a result of the comparison; performing the first type random access procedure; and The method comprising:

10. The method further comprises the step of determining whether an access attempt to the radio cell can be made, the access attempt includes performing the first type random access procedure; The access attempt is associated with one or more access identities and an access category, and the determining step comprises classifying the access attempt to the wireless cell as: first determining whether or not it is possible to do so based on said one or more access identities; then, if the access attempt cannot be made based on the one or more access identities, determining whether the access attempt can be made based on the access category, wherein determining whether the access attempt can be made based on the access category includes determining an access attempt threshold associated with the access category of the access attempt.

10. The method of claim 9.

11. determining whether the access attempt may be made includes determining a second random value and comparing the second random value to the access attempt threshold. The method of claim 10.

12. the plurality of random access type thresholds are associated with the use of one of a two-step random access procedure and a four-step random access procedure; the random value is a non-integer value determined between 0 and 1, and the random access type threshold is also a non-integer value between 0 and 1.

10. The method of claim 9.

13. and / or wherein among the plurality of random access type thresholds, there are respective random access type thresholds associated with different random access triggering events that cause the communications device to perform a random access procedure, and selecting each random access type threshold comprises determining the random access type threshold associated with the random access triggering event that caused the communications device to perform the random access procedure; and / or wherein among the plurality of random access type thresholds, there are respective random access type thresholds associated with different access categories of an access attempt, and selecting the respective random access type thresholds includes determining the random access type thresholds associated with the access categories of the access attempt; Among the plurality of random access type thresholds, each random access type threshold is associated with a different set of channel qualities, and selecting each random access type threshold comprises: 1) determining the channel quality of a radio link between the communication device and a base station, over which the random access procedure is performed; and 2) determining the random access type threshold associated with the determined channel quality; and / or Among the plurality of random access type thresholds there are respective random access type thresholds associated with different radio cells of a base station, and selecting the respective random access type thresholds comprises determining the random access type thresholds associated with the radio cells through which the random access procedure is performed, the different radio cells being a primary radio cell and one or more secondary radio cells.

10. The method of claim 9.

14. An integrated circuit for controlling processing of a communication device, the processing comprising: receiving a plurality of random access type thresholds, the plurality of random access type thresholds including a first random access type threshold associated with a first type of random access procedure; determining a random value; selecting the first random access type threshold; comparing the determined random value to the first random access type threshold; selecting the first type of random access procedure if the random value is less than the first random access type threshold as a result of the comparison; performing the first type random access procedure; 4. An integrated circuit comprising:

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