RA-RNTI Calculation for Multi-PRACH Transmission

Abstract

The present disclosure provides a communications apparatus and a communications method for Random Access Radio Network Temporary Identifier (RA-RNTI) calculation for multiple Physical Random Access Channel (multiple PRACH) transmissions, the communications apparatus including: a transmitter configured, in operation, to transmit a preamble in at least one of a plurality of Random Access Channel Opportunities (ROs) of a first RO group; and a receiver configured, in operation, to receive downlink control information (DCI) having a cyclic redundancy check (CRC) scrambled with one or more Random Access Radio Network Temporary Identifier (RA-RNTI) candidates determined based on at least one of the plurality of ROs.

Description

[Technical Field]

[0001] The present disclosure relates to a communications apparatus and method for Random Access Radio Network Temporary Identifier (RA-RNTI) calculation for multi-Physical Random Access Channel (multi-PRACH) transmissions. [Background technology]

[0002] The Random Access Radio Network Temporary Identifier (RA-RNTI) is used to determine Random Access Response (RAR) data (e.g., Msg2) during the random access procedure (see Table 7.1-2 of NRTL 1 for the use of RNTI). In the current technical specifications, a user equipment (UE) transmits a preamble (e.g., Msg1) to a base station (gNB) via a Physical Random Access Channel (PRACH) to obtain uplink (UL) synchronization in a single PRACH transmission scenario. The gNB then transmits an RAR (Msg2) to the UE in response to the preamble transmission sent by the UE. The UE then attempts to detect downlink control information (DCI) with a cyclic redundancy check (CRC) scrambled by the RA-RNTI calculated within the RAR window. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP TS 38.321 [Non-patent document 2] 3GPP TS 38.300 v16.3.0 [Non-patent document 3] 3GPP TS 38.211 v16.3.0 [Non-patent document 4] 3GPP TS 23.502 [Non-Patent Document 5] 3GPP TS 23.122 [Non-patent document 6] ITU-R M.2083 [Non-Patent Document 7] 3GPP TS 23.287 v16.4.0 Summary of the Invention

[0004] In practical deployments, uplink (UL) channel performance can be a challenge in many scenarios, and new vertical use cases requiring heavy UL traffic, such as video upload and camera surveillance, are emerging. In terms of coverage performance in 5G New Radio (NR), the PRACH has been identified as one of the bottleneck channels. Due to the limited scope of Coverage Enhancement (CovEnh) in Release 17 (Rel. 17), PRACH coverage has not been extended. Therefore, in Rel. 18, a new NR CovEnh working item (WI) was approved, with one of its main objectives being to improve PRACH coverage using multiple physical random access channel (multi-PRACH) transmissions.

[0005] However, there has been no discussion yet on a communication device and a communication method for RA-RNTI calculation for multi-PRACH transmission.

[0006] Therefore, what is needed is a communication device and a communication method that provide a feasible technical solution for RA-RNTI calculation for multiple PRACH transmissions in order to successfully decode corresponding RARs of the multiple PRACH transmissions while improving the coverage performance of the PRACH. Furthermore, other desirable features and characteristics will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the background art of this disclosure.

[0007] Non-limiting examples are provided to provide a communications apparatus and method for RA-RNTI calculation for multi-PRACH transmission.

[0008] According to a first embodiment of the present disclosure, there is provided a communication device comprising: a transmitter that, in operation, transmits a preamble in at least one of a plurality of Random Access Channel Occasion (RO) of a first RO group; and a receiver that, in operation, receives Downlink Control Information (DCI) having a Cyclic Redundancy Check (CRC) scrambled by one or more Random Access Radio Network Temporary Identifier (RA-RNTI) candidates determined based on at least one of the plurality of ROs.

[0009] According to a second embodiment of the present disclosure, there is provided a base station comprising: a receiver that, during operation, receives a preamble in at least one of a plurality of ROs in a first RO group from a communication device; a circuit that, during operation, determines one or more RA-RNTI candidates based on the at least one of the plurality of ROs in the first RO group and generates a DCI having a CRC scrambled by the one or more RA-RNTI candidates; and a transmitter that, during operation, transmits the DCI to the communication device.

[0010] 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 selective combination thereof.

[0011] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, but not all of them necessarily need to be provided to obtain one or more identical features.

[0012] Embodiments of the present disclosure, by way of example only, will be better understood and readily apparent to those skilled in the art from the following description and in conjunction with the drawings in which: [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 illustrates an example architecture of a 3GPP NR Radio Access Network (NR-RAN) to which exemplary embodiments of the present disclosure may be applied. [Figure 2] FIG. 1 is a schematic diagram illustrating the division of functions between an NG-RAN and a 5G Core Network (5GC) to which exemplary embodiments of the present disclosure are applied. [Figure 3] FIG. 1 is a sequence diagram of a radio resource control (RRC) connection setup / reconfiguration procedure to which an exemplary embodiment of the present disclosure is applied. [Figure 4] 1 is a schematic diagram illustrating usage scenarios of enhanced Mobile BroadBand (eMBB), massive Machine Type Communications (mMTC), and Ultra Reliable and Low Latency Communications (URLLC), to which exemplary embodiments of the present disclosure are applied. [Figure 5]FIG. 1 is a block diagram illustrating an example 5G system architecture for V2X communications in a non-roaming scenario to which example embodiments of the present disclosure may be applied. [Figure 6] FIG. 1 is an example diagram of a random access response (RAR) being transmitted to a user equipment (UE) in response to a preamble transmission in a single PRACH transmission according to the current technical specification. [Figure 7] 1 is an example diagram of RA-RNTI calculation in a random access channel opportunity (RO) UE group based on a first solution according to various embodiments of the present disclosure. [Figure 8] FIG. 10 is an example diagram of RA-RNTI candidate calculation for a group of RO UEs based on the first option according to various embodiments of the present disclosure. [Figure 9] FIG. 10 is an example diagram of RA-RNTI candidate calculation for a group of RO UEs based on the second option according to various embodiments of the present disclosure. [Figure 10] FIG. 10 is an example diagram of RA-RNTI candidate calculation for a group of RO UEs based on the third option according to various embodiments of the present disclosure. [Figure 11] FIG. 1 is an illustrative diagram of two RA-RNTI candidates for a short RAR window and a long RAR window, respectively, according to various embodiments of the present disclosure. [Figure 12] 1 is an example diagram of N RA-RNTI candidates for N ROs in an RO UE group according to various embodiments of the present disclosure. [Figure 13] FIG. 1 is an example diagram of selecting one of multiple RA-RNTI candidates to determine RAR data for a multi-PRACH transmission according to various embodiments of the present disclosure. [Figure 14] FIG. 10 is an illustrative diagram of selecting one of the RA-RNTI candidates based on options 4a, 4b, and 4c for a UE according to various embodiments of the present disclosure. [Figure 15] FIG. 1 illustrates an example of selecting RA-RNTI candidates based on Solution 5 and Option 5a according to various embodiments of the present disclosure. [Figure 16] FIG. 1 is an example diagram of determining two RA-RNTI candidates for a UE according to various embodiments of the present disclosure. [Figure 17] FIG. 10 is another example diagram of determining two RA-RNTI candidates for a UE according to various embodiments of the present disclosure. [Figure 18] 1 is a flowchart for a UE according to various embodiments of the present disclosure; [Figure 19] Another flowchart for a UE according to various embodiments of the present disclosure. [Figure 20] 1 is a flowchart illustrating a communication method according to various embodiments of the present disclosure. [Figure 21] 1 is a schematic block diagram of an exemplary communication device according to various embodiments of the present disclosure. [Figure 22] 1 is a schematic block diagram of another exemplary communication device with multiple antennas according to various embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Those skilled in the art will appreciate that the elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures, block diagrams, or flowcharts may be exaggerated relative to other elements to help improve understanding of the embodiments.

[0015] Some embodiments of the present disclosure will now be described, by way of example, with reference to the drawings in which like reference numbers and letters indicate similar or equivalent elements.

[0016] In particular, the overall system architecture assumes an NG-RAN (Next Generation Radio Access Network) with gNBs, which terminate NG radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocols for user equipment (UE). The gNBs are interconnected with each other via an Xn interface. The gNBs are also connected to an NGC (Next Generation Core) via an NG interface, more specifically to an AMF (Access and Mobility Management Function) (e.g., a specific core entity that runs the AMF) via an NG-C interface, and to a UPF (User Plane Function) (e.g., a specific core entity that runs the UPF) via an NG-U interface. The NG-RAN architecture 100 is shown in Figure 1 (see, for example, Section 4 of Non-Patent Document 2).

[0017] The user plane protocol stack in NR (see, for example, Section 4.4.1 of Non-Patent Document 2) includes a PDCP (Packet Data Convergence Protocol) sublayer, an RLC (Radio Link Control) sublayer, and a MAC (Medium Access Control) sublayer, which are terminated at the gNB on the network side. In addition, a new access stratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) is introduced above PDCP (see, for example, Section 6.5 of Non-Patent Document 2). NR also defines a control plane protocol stack (see, for example, Section 4.4.2 of Non-Patent Document 2). An overview of Layer 2 functions is provided in Section 6 of Non-Patent Document 2. The functions of the PDCP, RLC, and MAC sublayers are described in Sections 6.4, 6.3, and 6.2 of 3GPP TS 2.0, respectively. The functions of the RRC layer are described in Section 7 of 3GPP TS 2.0, also in Section 7 of 3GPP TS 2.0. Furthermore, sidelink communication is introduced in 3GPP TS 2.0. Sidelink supports direct communication between UEs using sidelink resource allocation modes, physical layer signals / channels, and physical layer procedures (see, for example, Section 5.7 of 3GPP TS 2.0).

[0018] For example, the Medium-Access-Control (MAC) layer handles scheduling and scheduling-related functions, including multiplexing logical channels and handling various numerologies.

[0019] 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 transmitting a specific transport channel, and each transport channel is mapped to a corresponding physical channel. For example, physical channels are the Physical Random Access Channel (PRACH), the Physical Uplink Shared Channel (PUSCH), and the Physical Uplink Control Channel (PUCCH) in the uplink, and the Physical Downlink Shared Channel (PDSCH), the Physical Downlink Control Channel (PDCCH), and the Physical Broadcast Channel (PBCH) in the downlink. Furthermore, the physical sidelink channels include a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), a physical sidelink feedback channel (PSFCH), and a physical sidelink broadcast channel (PSBCH).

[0020] NR use cases / deployment scenarios include enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and / or massive machine-type communications (mMTC), which have diverse requirements for 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 Finally, mMTC preferably requires high connection density (1,000,000 devices / km in urban environments). 2 ), wide coverage in adverse environments, and extremely long battery life (15 years) for low-cost devices may be desired.

[0021] Therefore, an OFDM numerology (e.g., subcarrier spacing, OFDM symbol length, cyclic prefix (CP) length, 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 length (and therefore a larger subcarrier spacing) and / or fewer symbols per scheduling interval (also called TTI) than mMTC services. Furthermore, deployment scenarios with large channel delay spreads may preferably require a longer CP length than scenarios with small delay spreads. To maintain a similar 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. Therefore, subcarrier spacings of 15 kHz, 30 kHz, 60 kHz, etc. are currently considered. The symbol length T u and the subcarrier spacing Δf is given by the formula Δf=1 / Tu 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.

[0022] In the new wireless system 5G-NR, a resource grid of subcarriers and OFDM symbols is defined for each numerology and carrier in the uplink and downlink. Each element of 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 3).

[0023] The schematic diagram 200 in Figure 2 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 Access and Mobility Management Function (AMF), User Plane Function (UPF), and Session Management Function (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 allocation (scheduling) of resources to UEs in both uplink and downlink; - IP header compression, encryption, and integrity protection of data; - AMF selection at UE attach time when routing to an AMF cannot be determined from information provided by the UE; - Routing of user plane data towards UPF; - Routing of control plane information towards AMF; - Setting up and tearing down connections; - scheduling and sending of paging messages; - Scheduling and transmission of system broadcast information (AMF or OAM origin); - setting up measurements and measurement reporting for mobility and scheduling; - Transport-level packet marking in the uplink; - Session management; - Support for network slicing; - QoS flow management and mapping to data radio bearers; - Support for UEs in RRC_INACTIVE state; - Non-Access Stratum (NAS) message delivery function; - Sharing of radio access networks; - Dual connectivity; - Close collaboration between NR and E-UTRA.

[0025] The Access and Mobility Management Function (AMF) handles the following main functions: - Terminating Non-Access Stratum (NAS) signaling; - NAS signaling security; - Access Stratum (AS) security control; - 3GPP Core Network (CN) inter-node signaling for mobility between access networks; - Reachability to idle mode UEs (including control and execution of paging retransmissions); - Managing the registration area; - Support for intra-system and inter-system mobility; - Access authentication; - Access authorization, including checking roaming privileges; - Mobility management control (subscription and policy); - Support for network slicing; - Select the Session Management Function (SMF).

[0026] Furthermore, the User Plane Function (UPF) handles the following main functions: - anchor points for intra-RAT mobility / inter-RAT mobility (if applicable); - External PDU (Protocol Data Unit) session points for interconnection with data networks; - packet routing and forwarding; - Packet inspection and user plane policy rule enforcement; - Traffic usage reporting; - uplink classifier that supports routing of traffic flows to the data network; - Branching Point to support multi-homed PDU sessions; - QoS processing for the user plane (e.g., packet filtering, gating, UL / DL rate enforcement); - Uplink traffic validation (mapping of SDF to QoS flows); - Downlink packet buffering and downlink data notification triggering functions.

[0027] Finally, the Session Management Function (SMF) handles the following major functions: - Session management; - IP address allocation and management for UE; - Selection and control of UPF; - The ability to configure traffic steering in the User Plane Function (UPF) to route traffic to the appropriate destination; - Policy enforcement and QoS in the control section; - Notification of downlink data.

[0028] The sequence diagram 300 in Figure 3 shows some of the interactions between the UE, gNB, and AMF (5GC entity) when the UE transitions from RRC_IDLE to RRC_CONNECTED in the NAS part (see Non-Patent Document 2). The transition steps are as follows:

[0029] 1. The UE requests to set up a new connection from the RRC_IDLE state. 2 / 2a. The gNB completes the RRC setup procedure. Note: Scenarios in which the gNB rejects the request are described below. 3. The first NAS message from the UE, sent piggyback in RRCSetupComplete, is sent to the AMF. 4 / 4a / 5 / 5a. Additional NAS messages may be exchanged between the UE and the AMF, see reference

[22] of 3GPP TS 26.210 ("Non-Access Stratum (NAS) Functions Associated with Mobile Station in Idle Mode"). 6. The AMF prepares and sends UE context data (including PDU session context, security keys, UE radio capabilities, and UE security capabilities, etc.) to the gNB. 7 / 7a. The gNB activates AS security with the UE. 8 / 8a. The gNB performs reconfiguration to set up SRB2 and DRB. 9. The gNB notifies the AMF that the setup procedure is complete.

[0030] RRC is a higher layer signaling protocol used to configure the UE and the gNB. Specifically, in this transition, the AMF creates UE context data (including, for example, PDU session context, security keys, UE radio capabilities, and UE security capabilities) and sends it to the gNB via an INITIAL CONTEXT SETUP REQUEST. The gNB then activates AS security with the UE by sending a SecurityModeCommand message to the UE, and the UE responds with a SecurityModeComplete message. The gNB then performs reconfiguration to establish signaling radio bearer 2 (SRB2) and data radio bearers (DRBs) by sending an RRCReconfiguration message to the UE and receiving an RRCReconfigurationComplete message from the UE in response. For signaling-only connections, the RRCReconfiguration step is omitted because SRB2 and DRBs are not set up. Finally, the gNB notifies the AMF that the establishment procedure is complete via an INITIAL CONTEXT SETUP RESPONSE.

[0031] The schematic diagram 400 in Figure 4 illustrates several use cases for 5G NR. The 3GPP NR (3rd Generation Partnership Project New Radio) considers three use cases envisioned for IMT-2020 to support a wide variety of services and applications. Phase 1 technical specifications for enhanced mobile broadband (eMBB) have been finalized. Current and future work includes standardization for ultra-reliable and low-latency communications (URLLC) and massive machine-type communications (mMTC), in addition to further extending eMBB support. Figure 4 illustrates some examples of IMT usage scenarios envisioned for 2020 and beyond (see, for example, Figure 2 in Non-Patent Document 6).

[0032] URLLC use cases have stringent requirements for capabilities such as throughput, latency, and availability, and are envisioned as one of the enablers for 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. URLLC's ultra-high reliability is supported by identifying technologies to meet the requirements set by TR 38.913. For NR URLLC in Release 15, key requirements include a user plane target latency of 0.5 ms for the uplink (UL) and 0.5 ms for the downlink (DL). A typical URLLC requirement for a single packet transmission is a block error rate (BLER) of 1E-5 for a 32-byte packet size with a 1-ms user plane latency.

[0033] From a physical layer perspective, there are several possible ways to improve reliability. Current scope for improving reliability includes defining a separate CQI table for URLLC, a more compact DCI format, PDCCH repetition, etc. However, as NR becomes more stable and developed (a key requirement for NR URLLC), the scope for achieving ultra-high reliability may expand. Specific use cases for NR URLLC in Release 15 include augmented reality / virtual reality (AR / VR), e-health, e-safety, and mission-critical applications.

[0034] Furthermore, technology enhancements targeted at NR URLLC target latency improvement and reliability enhancement. Technology enhancements for latency improvement include configurable numerology, minislot-based scheduling with flexible mapping, grant-free (configured grant) uplink, minislot-level repetition in the data channel, and preemption in the downlink. Preemption means that a transmission for which resources have already been allocated is aborted and the allocated resources are used for another transmission requested later with smaller latency / higher priority requirements. Thus, a previously granted transmission is preempted by a later transmission. Preemption applies regardless of the specific service type. For example, a transmission of service type A (URLLC) can be preempted by a transmission of service type B (e.g., eMBB). Technology enhancements for reliability improvement include dedicated channel quality indicator (CQI) / modulation and coding scheme (MCS) tables for a target BLER of 1E-5.

[0035] 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 latency sensitive. 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, enabling long battery life.

[0036] As mentioned above, it is expected that the reliability range in NR will expand. 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 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 the frequency, time, and / or spatial domains. These areas are generally applicable to reliability, regardless of the specific communication scenario.

[0037] Additional use cases with more stringent requirements are envisioned for NR URLLC, such as factory automation, transportation, and power distribution. The more stringent requirements include higher reliability (up to 10 times faster), depending on the use case. -6 level), higher availability, packet size up to 256 bytes, time synchronization on the order of a few microseconds (values ​​range from 1 to a few microseconds depending on the frequency range), and short latency on the order of 0.5 to 1 ms (target latency for the user plane in particular is 0.5 ms).

[0038] Furthermore, for NR URLLC, several technology enhancements are possible from the perspective of the physical layer. In particular, enhancements related to the PDCCH (Physical Downlink Control Channel) include compact DCI, PDCCH repetition, and increased PDCCH monitoring. Also, enhancements related to the UCI (Uplink Control Information) include 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 comprises 14 symbols).

[0039] The 5G Quality of Service (QoS) model is based on QoS flows and supports both QoS flows that require a guaranteed flow bit rate (GBR QoS flows) and QoS flows that do not require a guaranteed flow bit rate (non-GBR QoS flows). Therefore, 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 ID (QFI) carried in the encapsulation header over the NG-U interface.

[0040] 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 along with the PDU session, and can then configure additional DRBs for the QoS flows of that PDU session (as determined by the NG-RAN, e.g., as described above with reference to Figure 3). 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.

[0041] Block diagram 500 in FIG. 5 shows the non-roaming reference architecture for 5G NR (see Section 4.2.1.1 of Non-Patent Document 7). Application Functions (AFs) (e.g., external application servers handling 5G services as exemplified in FIG. 4) 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) deemed trusted by the operator can be allowed to interact directly with the associated Network Functions. Application Functions not permitted by the operator to directly access Network Functions interact with the associated Network Functions using an external exposure framework via the NEF.

[0042] Figure 5 further illustrates additional functional units of the 5G architecture for V2X communication, namely, Unified Data Management (UDM), Policy Control Function (PCF), Network Exposure Function (NEF), Application Function (AF), Unified Data Repository (UDR), Access and Mobility Management Function (AMF), Session Management Function (SMF), and User Plane Function (UPF) in 5G, as well as a V2X Application Server (V2AS) and Data Network (DN; e.g., operator-provided services, internet access, or third-party services). All or part of the core network functions and application services may be located and executed in a cloud computing environment.

[0043] In current technical specifications, a user equipment (UE) transmits a preamble (e.g., Msg1) to a base station (gNB) via a physical random access channel (PRACH) to acquire uplink (UL) synchronization in a single PRACH transmission scenario, as shown in example diagram 600 of Fig. 6. Each preamble transmission (e.g., RACH opportunity (RO)) is associated with an RA-RNTI candidate, which is calculated based on the RO of the single PRACH transmission (e.g., RO 602) according to the following formula in Non-Patent Document 1:

[0044] RA-RNTI=1+s_id+14×t_id+14×80×f_id+14×80×8×ul_carrier_id

[0045] where s_id is the index of the first OFDM symbol of the PRACH opportunity (0≦s_id<14), t_id is the index of the first slot of the PRACH opportunity within the system frame (0≦t_id<80), f_id is the index of the PRACH opportunity in the frequency domain (0≦f_id<8), and ul_carrier_id is the UL carrier used for PRACH preamble transmission (0 for normal uplink (NUL) carrier and 1 for supplementary uplink (SUL) carrier). s_id, t_id, and f_id are referred to herein as multiple indices of resources (e.g., time and frequency resources) of the RO. The gNB then transmits an RAR (e.g., Msg2) to the UE in response to the preamble transmission sent by the UE. The UE attempts to detect the DCI with a cyclic redundancy check (CRC) scrambled by the RA-RNTI calculated above within the RAR window 604 (e.g., the length of the RAR window is configurable by the upper layer parameter ra-ResponseWindow). If the UE successfully decodes the DCI, it decodes the PDSCH containing the RAR. The calculation of the RA-RNTI candidates is known by both the UE and the gNB. In Release 18 (Rel. 18), a new work item (WI) for further New Radio (NR) coverage enhancements (CovEnh) was approved, with one of the main objectives being to study and, if justified, identify (1) multiple PRACH transmissions on the same beam in a four-stage RACH procedure and (2) PRACH transmissions on different beams in a four-stage RACH procedure, and to specify PRACH coverage extensions (RAN1, RAN2) [RP-221858]. The PRACH enhancements target Frequency Range 2 (FR2) and, if applicable, can also be applied to Frequency Range 1 (FR1). Furthermore, these PRACH extensions are targeted at short PRACH formats and may be applied to other formats if applicable. The calculation method for the RA-RNTI for multi-PRACH transmissions has not yet been specified, which is important for successful decoding of the corresponding RARs of multi-PRACH transmissions.

[0046] In the present disclosure, for a specific number N of PRACH transmissions, one or more RA-RNTI candidates can be calculated within a RO UE group. Here, N is 1 or more and is based on one of the following solutions. (Solution 1) A single RA-RNTI candidate is calculated based on a plurality of indexes of the resources of the first, nth, or last RO within the RO UE group (e.g., the s_id, t_id, f_id of the first, nth, or last RO within the RO UE group are used in an equation for calculating a single RA-RNTI candidate) (where 1 < n < N). (Solution 2) The RO UE group can be divided into two sub-groups, the first RA-RNTI candidate is calculated based on a plurality of indexes of the resources of the first RO included in the first sub-group, and the second RA-RNTI is calculated based on a plurality of indexes of the resources of the nth or last RO included in the second sub-group. (Solution 3) Each of one or more RA-RNTI candidates is calculated based on a plurality of indexes of the resources of each of the N ROs included in the RO UE group. For example, referring to the exemplary diagram 700 of FIG. 7, the RA-RNTI calculation in each of the RO UE groups 702, 704, and 706 is based on Solution 1 where a plurality of indexes of the resources of the first RO of each RO UE group are used to calculate the RA-RNTI candidate for each UE (e.g., RA-RNTI candidate #0 determined based on RO 708 of RO UE group 702 for UE#0, RA-RNTI candidate #1 determined based on RO 710 of RO UE group 704 for UE#1, and RA-RNTI candidate #2 determined based on RO 712 of RO UE group 706 for UE#2). In one implementation, the first RA-RNTI candidate can be calculated based on a plurality of indexes of the resources of any RO included in the first sub-group. With these solutions, the UE can successfully decode the corresponding RAR for multi-PRACH transmissions. The RO UE group can be referred to as a first RO group including a plurality of ROs, and each of the plurality of ROs within the RO group is used for the PRACH transmission in multi-PRACH transmissions.The ROs included in a RO UE group may be the same as or different from the ROs included in another RO UE group used by another communication device.

[0047] An RO UE group includes N ROs for N specific PRACH transmissions, which may be transmitted in one PRACH attempt, for example. One preamble may be transmitted on each of the N ROs of the RO UE group. If a synchronization signal block (SSB)-based beam is used to transmit a preamble on each of the N ROs of the RO UE group, the RO UE group may be associated with one or more SSB indices, or may be associated with at least two SSB indices. Furthermore, if a channel state information reference signal (CSI-RS)-based beam is used to transmit a preamble on each of the N ROs of at least one RO UE group, the RO UE group may be associated with one or more CSI-RS indices. The SSB-based and / or CSI-RS-based beams may be configured for the UEs by the gNB.

[0048] In one implementation, an RO UE group includes ROs for N PRACH transmissions. N PRACH transmissions are also referred to as multiple PRACH transmissions, multi-PRACH transmissions, or one PRACH attempt. If a UE is capable of multiple PRACH transmissions, the UE can perform N PRACH transmissions in one PRACH attempt based on the ROs in the RO UE group, and one PRACH attempt is also referred to as a process of transmitting N PRACH transmissions. Furthermore, the first, nth, or last RO in an RO UE group can be defined based on: first, ascending order of frequency resource index for frequency-multiplexed PRACH opportunities; second, ascending order of time resource index for time-multiplexed PRACH opportunities within a logical / physical PRACH slot; or third, ascending order of logical / physical PRACH slot index. There may be other possibilities for defining the order of ROs within a RO UE group (e.g., first, ascending order of time resource index for time-multiplexed PRACH opportunities within a logical / physical PRACH slot, second, ascending order of logical / physical PRACH slot index, and third, ascending order of frequency resource index for frequency-multiplexed PRACH opportunities), and the solution is applicable to any of these other possibilities. Furthermore, the solution is applicable to all UE capabilities (e.g., reduced capability (RedCap) UEs, non-RedCap UEs / legacy UEs, and other similar types of UEs).

[0049] When a UE transmits a preamble to a gNB based on the RO in a RO UE group in a multi-PRACH transmission, the gNB sends an RAR to the UE in response, called Message 2 (Msg2). The UE monitors to receive the RAR within the RAR window (e.g., reception window). The RAR includes a timing advance command, an uplink grant, and the TC-RNTI for the subsequent uplink data transmission (e.g., Message 3 (Msg3)). To do this, the UE needs to receive and decode downlink control information (DCI) with a CRC scrambled by the RA-RNTI in order to decode the PDSCH containing the RAR. The calculation of the RA-RNTI is known by both the UE and the gNB.

[0050] In Solution 1, the UE calculates a single RA-RNTI candidate based on one of the N ROs in the RO UE group based on one of the following options, and receives a DCI with a CRC scrambled by the single RA-RNTI within the RAR window: In Option 1, multiple indices (e.g., s_id, t_id, f_id) of the resources of the first RO in the RO UE group are used in a formula to calculate a single RA-RNTI candidate (e.g., RA-RNTI=1+s_id+14×t_id+14×80×f_id+14×80×8×ul_carrier_id). The RAR window may start at least one OFDM symbol after the last OFDM symbol of the first RO and end at least one OFDM symbol after the last OFDM symbol of the last RO in the RO UE group. For example, the RAR window may start at an OFDM symbol determined based on the first RO of the RO UE group and end at an OFDM symbol determined based on the determined length and the last RO of the RO UE group, and the single RA-RNTI candidate used in the RAR window may be determined based on the first RO of the RO group. The determined length may be indicated by higher layer signaling, MAC signaling, or downlink control information.

[0051] In option 2, the resources (of multiple indices, e.g., s_id, t_id, f_id) of the nth RO in the RO UE group are used in a formula to calculate a single RA-RNTI candidate. The RAR window may start at least one OFDM symbol after the last OFDM symbol of the nth RO and end at least one OFDM symbol after the last OFDM symbol of the last RO in the RO UE group. For example, the RAR window may start at an OFDM symbol determined based on the nth RO of the RO UE group and end at an OFDM symbol determined based on the determined length and the last RO of the RO UE group, and the single RA-RNTI candidate used in the RAR window may be determined based on the nth RO of the RO group. The determined length may be indicated by higher layer signaling, MAC CE signaling, or downlink control information.

[0052] In option 3, multiple resource indices (e.g., s_id, t_id, f_id) of the last RO in the RO UE group are used in a formula to calculate a single RA-RNTI candidate. The RAR window may start at least one OFDM symbol after the last OFDM symbol of the last RO and end at least one OFDM symbol after the last OFDM symbol of the last RO in the RO UE group. For example, the RAR window may start at an OFDM symbol determined based on the last RO in the RO UE group and end at an OFDM symbol determined based on the determined length and the last RO in the RO UE group, and the single RA-RNTI candidate used in the RAR window may be determined based on the last RO in the RO group. The determined length may be indicated by higher layer signaling, MAC CE signaling, or downlink control information.

[0053] For Option 1, Option 2, or Option 3, in order to receive the RAR for multi-PRACH transmission, the UE may receive and decode a DCI with a CRC scrambled by a single RA-RNTI candidate, and decode a PDSCH containing the RAR.

[0054] In Option 1, when the UE successfully receives the RAR, it is advantageously possible to terminate the multi-PRACH transmission early to save the UE's effort, such as terminating the next PRACH transmission in advance. In Option 3, the conventional length of the RAR window can be advantageously reused to minimize the impact on the specification.

[0055] In Solution 1, the UE can be set to determine any of the three options for calculating the RA-RNTI candidate by implicit notification according to a rule (for example, use Option 1 when N = 1, use Option 2 when 1 < N < threshold, and use Option 3 otherwise. For example, the threshold can be set or predefined as 3. Use Option 2 when N = 2. Use Option 3 when N = 3.), or explicit notification by upper layer signaling, MAC CE signaling, or downlink control information.

[0056] FIG. 8 shows an example 800 of RA-RNTI candidate calculation for the RO UE group 802 based on Option 1. The RA-RNTI candidate is calculated based on multiple indexes (for example, s_id, t_id, f_id) of the resources of the first RO (for example, RO 804) of the RO UE group 802. The RAR window 808 starts from at least one OFDM symbol after the last OFDM symbol of RO 804 and ends at at least one OFDM symbol after the last OFDM symbol of the last RO 806 of the RO UE group 802.

[0057] 9 shows an example 900 of RA-RNTI candidate calculation for a RO UE group 902 based on Option 2, where the RA-RNTI candidate is calculated based on multiple indices (e.g., s_id, t_id, f_id) of resources of the nth RO (e.g., RO 904) of the RO UE group 902. The RAR window 908 may start at least one OFDM symbol after the last OFDM symbol of RO 904 and end at least one OFDM symbol after the last OFDM symbol of the last RO 906 of the RO UE group 902.

[0058] 10 shows an example 1000 of RA-RNTI candidate calculation for a RO UE group 1002 based on Option 3, where the RA-RNTI candidate is calculated based on multiple indices (e.g., s_id, t_id, f_id) of the resources of the last RO (e.g., RO 1004) of the RO UE group 1002. The RAR window 1006 may start at least one OFDM symbol after the last OFDM symbol of the RO 1004 and end at least one OFDM symbol after the last OFDM symbol of the RO 1004 of the RO UE group 1002.

[0059] In Solution 2, the ROU E group can be divided into two sub - groups. The first sub - group (e.g., including N ROs) includes at least the first RO of the ROU E group, and the second sub - group includes the remaining ROs of the ROU E group (1 < n ≤ N). A short RAR window can be set for the first sub - group. The short RAR window starts from at least one OFDM symbol after the last OFDM symbol of the first PRACH transmission and may end at at least one OFDM symbol after or before the last OFDM symbol of the nth RO. Further, a long RAR window can be set for the second sub - group. The long RAR window starts from at least one OFDM symbol after the last OFDM symbol of the nth RO of the ROU E group and ends at at least one OFDM symbol after the last OFDM symbol of the last RO of the ROU E group. In an implementation, a long RAR window can be set for the first sub - group and a short RAR window can be set for the second sub - group. Further, the ROU E group can be divided into at least two sub - groups. The first sub - group includes at least the first RO of the ROU E group, and the second or subsequent sub - groups include the remaining ROs of the ROU E group. RAR windows corresponding to each of the at least two sub - groups are set. Further, instead of the long RAR window and the short RAR window, it is possible to set RAR windows of the same length for the first sub - group and the second sub - group. Further, it is also possible to divide the ROU E group into three or more sub - groups.

[0060] 11 , a first RA-RNTI candidate is calculated based on multiple indices of resources of a first RO (e.g., RO 1108) of a first subgroup (e.g., subgroup 1104) of an RO UE group (e.g., RO UE group 1102) within a short RAR window (e.g., RAR window 1112), while a second RA-RNTI candidate is calculated based on multiple indices of resources of an nth or last RO of a second subgroup (e.g., subgroup 1106) within a long RAR window (e.g., RAR window 1114). In example 1100, assuming n=2 is set, the second RA-RNTI candidate is calculated based on multiple indices of resources of a second RO (e.g., RO 1110) of RO UE group 1102. To receive the RAR of a multi-PRACH transmission within the short RAR window 1112, the UE receives DCI with a CRC scrambled with the first RA-RNTI candidate and decodes the PDSCH including the RAR. To receive the RAR of a multi-PRACH transmission within the long RAR window 1114, the UE receives DCI with a CRC scrambled with the second RA-RNTI candidate and decodes the PDSCH including the RAR. When the density of the ROs of a multi-PRACH transmission varies in the time domain, it is beneficial to provide a flexible configuration of the RAR window so that the multi-PRACH transmission can be terminated early to save the UE effort if the UE successfully receives the RAR.

[0061] In some implementations, there may be one or more short RAR windows and one or more long RAR windows. These RAR windows may overlap each other in the time domain depending on the configuration. Therefore, RA-RNTI candidates are calculated for each of the one or more short RAR windows and one or more long RAR windows. When RAR windows overlap each other in the time domain, only one of the RA-RNTI candidates associated with one of the two RAR windows may be available in the overlapping portion of the RAR window. For example, only the RA-RNTI candidate associated with the short RAR window may be available, and the RA-RNTI candidate associated with the long RAR window may not be available in the overlapping portion of the RAR window.

[0062] In Solution 3, each of N RA-RNTI candidates is calculated based on multiple resource indices for each of the N ROs in the RO UE group. The N RA-RNTI candidates are associated with corresponding N RAR windows. Each of the N RAR windows may start at least one OFDM symbol after the last OFDM symbol of the corresponding PRACH transmission in the multi-PRACH transmission and end at least one OFDM symbol after or before the last OFDM symbol of the next PRACH transmission in the multi-PRACH transmission (e.g., the PRACH transmission after the corresponding PRACH transmission). The N RAR windows may overlap each other in the time domain depending on the configuration. To receive the RAR for the multi-PRACH transmission, within each of the N RAR windows, the UE receives DCI with a CRC scrambled with the corresponding RA-RNTI candidate and attempts to detect the DCI to decode the PDSCH containing the RAR.

[0063] For example, referring to example 1200 of Figure 12, when N = 3, three RA-RNTI candidates (e.g., RA-RNTI candidates #0, #1, and #2) are calculated based on multiple indices of resources for each of three ROs (e.g., ROs 1204, 1206, and 1208 corresponding to PRACH transmissions) in RO UE group 1202. Thus, each of the three RA-RNTI candidates is associated with a corresponding RAR window (e.g., RA-RNTI candidates #0, #1, and #2 are associated with RAR windows 1210, 1212, and 1214, respectively).

[0064] There may be multiple RARs for the N PRACH transmissions. In some implementations, less effort may be required from the UE if the N RAR windows do not overlap each other in the time domain, or if the N RAR windows overlap each other in the time domain and the application period of the RA-RNTI candidates is limited from the start of the associated RAR window to the start of the subsequent RAR window. For example, in FIG. 12, the UE may decode the RAR using only RA-RNTI candidate #0 until the start of RAR window 1212, and may decode the RAR using only RA-RNTI candidate #1 from the start of RAR window 1212 to the start of RAR window 1214. Alternatively, the UE may decode the RAR using only RA-RNTI candidate #0 until the end of the RAR window 1210, may decode the RAR using only RA-RNTI candidate #1 from the end of the RAR window 1210 until the end of the RAR window 1212, and may decode the RAR using only RA-RNTI candidate #2 from the end of the RAR window 1212 until the end of the RAR window 1214. Advantageously, solution 3 allows for early termination of multi-PRACH transmission to save UE effort.

[0065] In a variation of Solution 3 (e.g., Solution 3.1), N RA-RNTI candidates may be calculated based on the ROs of the multi-PRACH transmissions within multiple RAR windows. Each of the N RAR windows may begin at least one OFDM symbol after the last OFDM symbol of the corresponding multi-PRACH transmission and end at least one OFDM symbol after the last OFDM symbol of the last RO. For example, referring to example 1300 of FIG. 13 , when N=3, RA-RNTI candidates #0, #1, and #2 are associated with RAR windows 1308, 1310, and 1312, respectively. RAR window 1308 begins at least one OFDM symbol after the last OFDM symbol of RO 1302 and ends at least one OFDM symbol after the last OFDM symbol of the last RO 1306. The RAR window 1310 begins at least one OFDM symbol after the last OFDM symbol of the RO 1304 and ends at least one OFDM symbol after the last OFDM symbol of the last RO 1306. Additionally, the RAR window 1312 begins at least one OFDM symbol after the last OFDM symbol of the RO 1306 and ends at least one OFDM symbol after the last OFDM symbol of the RO 1306.

[0066] To receive the RAR for a multi-PRACH transmission, the UE receives a DCI with a CRC scrambled with only one of the N RA-RNTI candidates within the entire length of the N RAR windows. For example, referring to FIG. 13, the UE receives a DCI with a CRC scrambled with only one of the RA-RNTI candidates #0, #1, or #2. The UE attempts to detect the DCI to decode the PDSCH containing the RAR. The RA-RNTI candidate is selected from the N RA-RNTI candidates by the gNB based on one of the following options: (Option 3.1a) The RA-RNTI candidate is selected based on the first RO of the multi-PRACH transmission. (Option 3.1b) The RA-RNTI candidate is selected based on the last RO of the multi-PRACH transmission. (Option 3.1c) The RA-RNTI candidate is selected based on the nth RO of the multi-PRACH transmission, where the nth RO is different from the first and last ROs. Solution 3.1 implemented with Option 3.1b is similar to Solution 1 implemented with Option 3, where there can be only one RAR for N PRACH transmissions.

[0067] In an alternative implementation, instead of one or more RA-RNTI candidates being calculated based on an RO UE group (as shown in Solutions 1 to 3 for example), they can be calculated based on each of M (where M is 1 or more) RO cell groups for a specific number of PRACH transmissions. This alternative implementation can be carried out based on any of the following solutions. (Solution 4) A single RA-RNTI candidate for each of the M RO cell groups is calculated based on a plurality of indices of the resources of the first, the t-th (1 < t < T), or the last RO among the T ROs included in each of the M RO cell groups. (Solution 5) A single RA-RNTI candidate for each of the M RO cell groups is calculated based on the index of each of the M RO cell groups in the time domain. (Solution 6) Each of the M RO cell groups is divided into two sub-groups, a first RA-RNTI candidate is calculated based on the index of the first sub-group, and a second RA-RNTI is calculated based on the index of the second sub-group in the time domain. This implementation enables successful decoding of the corresponding RAR for multi-PRACH transmissions. An RO cell group includes a plurality of ROs and may be referred to as a second RO group associated with at least one PRACH transmission in a multi-PRACH transmission from a UE, and at least one of the plurality of ROs in the second RO group corresponds to at least one PRACH transmission in the multi-PRACH transmission. An RO cell group may include one or more ROs used among one or more communication devices. An RO cell group is a kind of cell-specific group within a serving cell, and an RO UE group is a kind of UE-specific group within a serving cell.

[0068] To determine the RO cell group, if M=1, one RO cell group can be determined by including all ROs available for multiple PRACH transmissions. If M>1, each of the M RO cell groups can be commonly determined within the serving cell based on one of the following methods 1 to 5. (Method 1) Each of the M RO cell groups can be determined by clustering one or more ROs located closely in the time domain. (Method 2) Each of the M RO cell groups can be determined by clustering one or more ROs located in the same time unit including the same slot / subframe / frame or the same configuration period for a specific number of multiple PRACH transmissions. (Method 3) Each of the M RO cell groups can be determined by clustering one or more ROs located closely in the frequency domain. (Method 4) Each of the M RO cell groups can be determined by clustering one or more ROs located in the same frequency resource allocation. (Method 5) Each of the M RO cell groups can be determined by clustering one or more ROs located closely in the frequency domain and the time domain. The one or more ROs may be separate or common ROs, respectively, that are separate from or common to a single PRACH transmission. Each of the one or more ROs in methods 1 to 5 above may have a specific time and frequency resource allocation. The M RO cell groups may be determined based on cell-specific (pre-) configuration. On the gNB side, the gNB may be configured to receive N PRACH transmissions and perform combined detection of the preambles.

[0069] In an alternative implementation, M RO cell groups are commonly defined among UEs in a serving cell. The first, t-th, or last RO in an RO cell group may be defined based on an order of: first, ascending frequency resource index for frequency-multiplexed PRACH opportunities; second, ascending time resource index for time-multiplexed PRACH opportunities within a logical or physical PRACH slot; or third, ascending logical or physical PRACH slot index.

[0070] In Solution 4, a single RA-RNTI candidate is calculated for each of the M RO cell groups, and the RA-RNTI candidate is associated with an RAR window. Options 1, 2, and 3 of Solution 1 above can be adapted to calculate a single RA-RNTI candidate based on one or more RO cell groups (rather than based on one or more RO UE groups as required in Solutions 1, 2, and 3), and define a corresponding associated RAR window. There may be M RA-RNTI candidates for the M RO cell groups. The UE may be configured to select one of the M RA-RNTI candidates based on one of the following options: In Option 4a, the selection is based on the association of the first RO in the RO UE group with its corresponding RO cell group; in Option 4b, the selection is based on the association of the nth RO in the RO UE group with its corresponding RO cell group; and in Option 4c, the selection is based on the association of the last RO (out of N ROs) in the RO UE group with its corresponding RO cell group.

[0071] 14 shows an example 1400 illustrating selection of an RA-RNTI candidate (e.g., from four RA-RNTI candidates #0, #1, #2, and #3) based on options 4a, 4b, and 4c for a UE (e.g., RO UE group 1402 for the UE's four PRACH transmissions) according to solution 4, where the first RO in each RO cell group is used to calculate the corresponding RA-RNTI candidate. Based on option 4a, the UE selects the first RO (e.g., RO 1412) of RO cell group 1404 as RA-RNTI candidate #0 (because RO cell group 1404 is associated with the first RO (e.g., RO 1428) of RO UE group 1402). Based on option 4b (when the nth RO is the second RO), the UE selects the first RO (e.g., RO 1414) of RO cell group 1406 as RA-RNTI candidate #1 (because RO cell group 1406 is associated with the second RO (e.g., RO 1430) of RO UE group 1402). Based on option 4b (when the nth RO is the third RO), the UE selects the first RO (e.g., RO 1416) of RO cell group 1408 as RA-RNTI candidate #2 (because RO cell group 1408 is associated with the third RO (e.g., RO 1432) of RO UE group 1402). Further, based on option 4c, the UE selects the first RO (e.g., RO 1418) of the RO cell group 1410 as RA-RNTI candidate #3 (because the RO cell group 1410 is associated with the last RO (e.g., RO 1434) of the RO UE group 1402). To receive the RAR of the multi-PRACH transmission, the UE then receives DCI having a CRC scrambled with the selected single RA-RNTI candidate and decodes the PDSCH containing the RAR. Because the M RO cell groups are cell-specific configurations, the M RA-RNTI candidates are also cell-specific candidates, advantageously minimizing the gNB's effort to calculate all possible RA-RNTI candidates.

[0072] In Solution 5, a single RA-RNTI candidate for each of the M RO cell groups is calculated based on the index of each M RO cell group (e.g., the index in the formula for calculating a single RA-RNTI candidate: "RA-RNTI=1+s_id+14×t_id+14×80×f_id+14×80×8×ul_carrier_id"). The indexes s_id and t_id can be derived based on the index of each M RO cell group in the time domain, and the index f_id can be derived based on one of the following options in the frequency domain: In Option 5a, the index f_id can be derived based on the index of a frequency hop in each M RO cell group; In Option 5b, the index f_id can be derived based on the index of the frequency resource of the first, t, or last RO in each M RO cell group. The UE can be configured to select one of the M RA-RNTI candidates based on Options 4a, 4b, and 4c of Solution 4. Options 1, 2, and 3 of Solution 1 above can be adapted to calculate RA-RNTI candidates based on M RO cell groups (rather than based on one or more RO UE groups as required in Solutions 1, 2, and 3) and define corresponding associated RAR windows. To receive the RAR of the multi-PRACH transmission, the UE then receives DCI with a CRC scrambled with the selected single RA-RNTI candidate and decodes the PDSCH containing the RAR. Because the M RO cell groups are cell-specific, the M RA-RNTI candidates are also cell-specific, advantageously minimizing the gNB's effort to calculate all possible RA-RNTI candidates. The index of the RO cell group in the time domain can be implicitly indicated based on rules from the included RO or explicitly indicated by the gNB.

[0073] 15 illustrates an example 1500 of selecting RA-RNTI candidates for a UE (e.g., RO UE group 1502 for four PRACH transmissions of the UE) based on Solution 5 and Option 5a in accordance with various embodiments of the present disclosure. For example, s_id and t_id are derived based on the index of each RO cell group (e.g., each of RO cell groups 1504, 1506, 1508, and 1510) in the time domain, and f_id is derived based on the index of the third frequency hop of each RO cell group in the frequency domain (e.g., ROs 1512, 1514, 1516, and 1518 of RO cell groups 1504, 1506, 1508, and 1510).

[0074] In solution 6, each of the M RO cell groups may be divided into two subgroups, for example, a first subgroup and a second subgroup. The first RA-RNTI candidate is calculated based on the index of the first subgroup (e.g., in the formula for calculating the first RA-RNTI candidate). The indexes s_id and t_id can be derived based on the index of the first subgroup in the time domain, and the index f_id can be derived based on one of the following options: In option 6a, the index f_id can be derived based on the index of the frequency hopping in the first subgroup. In option 6b, the index f_id can be derived based on the index of the frequency resource of the first, nth, or last RO in the first subgroup. The second RA-RNTI candidate is calculated based on the index of the second subgroup (i.e., in the formula for calculating the second RA-RNTI candidate). The indexes s_id and t_id can be derived based on the index of the second subgroup in the time domain, and f_id can be derived based on either option 6a or option 6b for the second subgroup.

[0075] The UE may be configured to select two RA-RNTI candidates from 2M RA-RNTI candidates for two subgroups (because there are M RO cell groups) based on Option 4a, 4b, or 4c of Solution 4. Options 1, 2, and 3 of Solution 1 described above can be adapted to define corresponding associated RAR windows based on M RO cell groups (rather than based on one or more RO UE groups as required by Solutions 1, 2, and 3). To receive the RAR of a multi-PRACH transmission, the UE receives a DCI with a CRC scrambled by a single selected RA-RNTI candidate to decode the PDSCH containing the RAR. When an RO cell group is defined by clustering one or more ROs located in the same frequency resource allocation and the density of ROs within an RO cell group varies in the time domain, this solution enables early termination of the multi-PRACH transmission, thereby saving the UE effort if the UE successfully receives the RAR. In Solution 6, each of the M RO cell groups may be divided into two or more subgroups, and the calculation of each RA-RNTI candidate is accordingly based on the index of each corresponding subgroup.

[0076] 16 shows an example 1600 for determining two RA-RNTI candidates for a UE (e.g., RO UE group 1602 for UEs) according to Solution 6, where RO cell group 1604 is divided into two subgroups 1606 and 1608. A first RA-RNTI candidate is calculated based on a first RO (e.g., RO 1610) of subgroup 1606, and a second RA-RNTI candidate is calculated based on a first RO (e.g., RO 1612) of subgroup 1608.

[0077] 17 shows another example 1700 for determining two RA-RNTI candidates for a UE (e.g., RO UE group 1702 for UEs) according to Solution 6, where RO cell group 1704 is divided into two subgroups 1706 and 1708. A first RA-RNTI candidate is calculated based on a first RO (e.g., RO 1710) of subgroup 1706, and a second RA-RNTI candidate is calculated based on a first RO (e.g., RO 1712) of subgroup 1708.

[0078] In one implementation, all RAR windows in Solutions 1-6 are sliding windows. Furthermore, the length of the RAR window in any of Solutions 1-6 is configurable, and the lengths of each RAR window can be the same or different from each other.

[0079] In one implementation, when multi-PRACH transmissions are applied to different coverage levels and a subset of PRACH transmissions from the multi-PRACH transmissions exists for each different coverage level, one or more RA-RNTI candidates for each coverage level may be calculated based on solutions 1 to 6 and their variations.

[0080] In some implementations, the contents of the multiple RARs of Solution 2 or Solution 3 may be identical. In Solution 6, the first RA-RNTI candidate is calculated based on multiple indexes of resources of the first RO included in the first subgroup, and the second RA-RNTI is calculated based on multiple indexes of resources of the t-th or last RO included in the second subgroup.

[0081] In Solution 1, variations of Options 1, 2, and 3 may be implemented as follows: In Option 1, the RAR window may start at least one OFDM symbol after the last OFDM symbol of the first RO and end L OFDM symbols long (or the RAR window length) from the last OFDM symbol of the last RO in the RO UE group, where L is greater than or equal to 1. In Option 2, the RAR window may start at least one OFDM symbol after the last OFDM symbol of the nth RO and end L OFDM symbols long (or the RAR window length) from the last OFDM symbol of the last RO in the RO UE group. In Option 3, the RAR window may start at least one OFDM symbol after the last OFDM symbol of the last RO and end L OFDM symbols long (or the RAR window length) from the last OFDM symbol of the last RO in the RO UE group.

[0082] FIG. 18 shows a flowchart 1800 for a UE according to various embodiments of the present disclosure. In step 1802, the UE determines one or more RA-RNTI candidates in the RO UE group for specific N PRACH transmissions based on any of Solutions 1 to 3. In step 1804, the UE performs N PRACH transmissions using the N ROs of the RO UE group in one PRACH attempt. The N PRACH transmissions may be performed on the same beam. The N PRACH transmissions are associated with one or more RA-RNTI candidates. In step 1806, the gNB transmits an RAR (e.g., Msg2) to the UE in response to the N PRACH transmissions transmitted by the UE. In step 1808, to receive the RAR for the multi-PRACH transmission, the UE receives DCI having a CRC scrambled by one or more RA-RNTI candidates to decode the PDSCH containing the RAR. Flowchart 1800 is applicable to the different beam case, where a UE makes N PRACH transmissions using N ROs of an RO UE group in one PRACH attempt on different beams.

[0083] FIG. 19 shows an alternative flowchart 1900 for a UE according to various embodiments of the present disclosure. In step 1902, the UE calculates multiple RA-RNTI candidates in M ​​RO cell groups for specific N PRACH transmissions based on any of solutions 4 through 6. In step 1904, the UE determines one or more RA-RNTI candidates from the multiple RA-RNTI candidates based on any of options 4a, 4b, and 4c. In step 1906, the UE performs N PRACH transmissions using the N ROs in the RO UE group in one PRACH attempt on the same beam. The N PRACH transmissions are associated with one or more RA-RNTI candidates calculated by the UE. In step 1908, the gNB transmits an RAR (e.g., Msg2) to the UE in response to the N PRACH transmissions sent by the UE. In step 1910, to receive the RAR of the multi-PRACH transmission, the UE receives DCI having a CRC scrambled by one or more R-RNTI candidates to decode the PDSCH including the RAR.

[0084] 20 shows a flowchart illustrating a communication method according to various embodiments of the present disclosure. In step 2002, a preamble may be transmitted in at least one of a plurality of random access channel opportunities (ROs) of a first RO group. In step 2004, downlink control information (DCI) having a cyclic redundancy check (CRC) scrambled with one or more random access radio network temporary identifier (RA-RNTI) candidates determined based on at least one of the plurality of ROs may be received.

[0085] In one implementation, a preamble may be received at at least one of a plurality of ROs in a first RO group from a communication device, one or more RA-RNTI candidates may be determined based on the at least one of the plurality of ROs in the first RO group, a DCI having a CRC scrambled by the one or more RA-RNTI candidates may be generated, and the DCI may be transmitted to the communication device. In another implementation, a preamble may be received at at least one of a plurality of ROs in a first RO group from a communication device, one or more RA-RNTI candidates may be determined based on an association of the at least one RO of the plurality of ROs in the first RO group with one or more second RO groups, a DCI having a CRC scrambled by the one or more RA-RNTI candidates may be generated, and the DCI may be transmitted to the communication device.

[0086] Figure 21 illustrates a schematic partial cross-sectional view of a communications device 2100 that may be implemented in accordance with various embodiments and examples shown in Figures 1-20. The communications device 2100 may be implemented as a UE or a base station in accordance with various embodiments.

[0087] The various functions and operations of the communications device 2100 are arranged in layers according to a hierarchical model, in which lower layers report to and receive instructions from higher layers according to 3GPP technical specifications, and for the sake of brevity, the details of the hierarchical model will not be described in this disclosure.

[0088] As shown in FIG. 21 , the communications device 2100 may include a circuit 2114, at least one wireless transmit (Tx) chain 2102 (also referred to herein as a transmitter 2102), at least one wireless receive (Rx) chain 2104 (also referred to herein as a receiver 2104), and at least one antenna 2112 (for simplicity, only one antenna is depicted in FIG. 21 for illustrative purposes). The circuit 2114 may include at least one controller 2106. The controller 2106 is used to perform tasks that the at least one controller 2106 is designed to perform with the assistance of software and hardware, including controlling communications with one or more other communications devices in a wireless network. The circuit 2114 may further include at least one transmit signal generator 2108 and at least one receive signal processor 2110. The at least one control unit 2106 can control, under the control of the at least one control unit 2106, at least one transmit signal generator 2108 for generating a signal (e.g., a baseband signal) to be transmitted to one or more other communication devices (e.g., a base communication device) via the at least one wireless transmitter 2102, and at least one receive signal processor 2110 for processing a signal (e.g., a baseband signal) received from one or more other communication devices via the at least one wireless receiver 2104, under the control of the at least one control unit 2106. The at least one transmit signal generator 2108 and the at least one receive signal processor 2110 may be standalone modules of the communication device 2100 that communicate with the at least one control unit 2106 for the above-mentioned functions, as shown in FIGS. 1 to 20 . Alternatively, the at least one transmit signal generator 2108 and the at least one receive signal processor 2110 may be included in the at least one control unit 2106. It will be apparent to those skilled in the art that the arrangement of these functional modules is flexible and may vary according to actual needs and / or requirements. Data processing, virtual memory, and other related controls may be provided on appropriate circuit boards and / or within chipsets.In various embodiments, in operation, the at least one wireless transmitter 2102, the at least one wireless receiver 2104, and the at least one antenna 2112 may be controlled by the at least one controller 2106. It will be appreciated that the communications device 2100 may include multiple antennas 2212, for example, as shown in communications device 2200 of FIG. 22. Each of the multiple antennas 2212 may include a corresponding Tx chain 2202 and Rx chain 2204.

[0089] The communications device 2100, in operation, provides functionality necessary for RA-RNTI calculation for multi-PRACH transmission. For example, the communications device 2100 may be a UE, and the transmitter 2102, in operation, may transmit a preamble on at least one of a plurality of random access channel opportunities (ROs) of a first RO group. The receiver 2104, in operation, may receive downlink control information (DCI) having a cyclic redundancy check (CRC) scrambled by one or more random access radio network temporary identifier (RA-RNTI) candidates determined based on at least one of the plurality of ROs.

[0090] The ROs included in the first RO group may be the same as or different from the ROs included in other RO groups used by other communication devices. A single RA-RNTI candidate may be determined based on multiple indices of resources of the first, nth, or last RO of the first RO group. The multiple indices may include an index of a first OFDM symbol of a PRACH opportunity, an index of a first slot of the PRACH opportunity in a system frame, and an index of the PRACH opportunity in the frequency domain. The receiver 2102 may be configured to receive the DCI within a random access response (RAR) window. The RAR window may start at least one OFDM symbol after the last OFDM symbol of the first RO, the nth RO, or the last RO, respectively, and end at least one OFDM symbol after the last OFDM symbol of the last RO of the first RO group. The RAR window starts at an OFDM symbol determined based on the first RO of the first RO group and ends at an OFDM symbol determined based on the determined length and the last RO of the first RO group, and a single RA-RNTI candidate used in the RAR window is determined based on the first RO of the first RO group. The determined length may be indicated by higher layer signaling, MAC CE signaling, or downlink control information.

[0091] In operation, the circuit 2114 may divide a first RO group into at least two subgroups: a first subgroup including at least one RO of the first RO group and a second or subsequent subgroup including the remaining ROs of the first RO group; determine a first RA-RNTI candidate among the one or more RA-RNTI candidates based on a plurality of indexes of resources of the first RO; and determine a second RA-RNTI candidate among the one or more RA-RNTI candidates based on a plurality of indexes of resources of the ROs of the second subgroup. The circuit 2114 may be further configured to determine at least one short RAR window for the first subgroup and at least one long RAR window for the second subgroup, wherein the at least one short RAR window has a length shorter than the at least one long RAR window. The at least one short RAR window and the at least one long RAR window may overlap each other in the time domain.

[0092] The circuit 2114 may be configured to determine one or more RA-RNTI candidates based on each of the plurality of ROs in the first RO group. The circuit 2114 may be configured to determine an RAR window for each of the plurality of ROs, where the RAR window starts at least one OFDM symbol after the last OFDM symbol of the PRACH transmission and ends before or after the last OFDM symbol of the next PRACH transmission. The circuit 2114 may be configured to determine at least one first RAR window for a first RO of the plurality of ROs and a second RAR window for a second RO of the plurality of ROs, where the first RAR window starts at an OFDM symbol determined based on the first RO and ends at an OFDM symbol determined based on the start of the second RAR window, and where the length of the first RAR window is shorter than the determined length. Each of the one or more RA-RNTI candidates may be associated with a corresponding RAR window.

[0093] The circuit 2114, during operation, may determine one or more second RO groups, where the one or more second RO groups are commonly determined in the serving cell based on clustering one or more ROs located proximate to each other in the time domain or the frequency domain, or both the time domain and the frequency domain. The plurality of ROs in the first RO group are determined from the one or more second RO groups. The circuit 2114, during operation, may also determine one or more RA-RNTI candidates based on association of at least one RO among the plurality of ROs in the first RO group with the one or more second RO groups. The circuit 2114 may be further configured to determine the one or more RA-RNTI candidates based on indices of resources of the clustered ROs in the one or more second RO groups in addition to the association. The circuit 2114 may divide each of the one or more second RO groups into at least two subgroups: a first subgroup including at least a first RO of each of the one or more second RO groups and a second or subsequent subgroup including the remaining ROs of each of the one or more second RO groups; determine a first RA-RNTI candidate among the one or more RA-RNTI candidates based on the association plus multiple indexes of the resources of the first subgroup; and determine a second RA-RNTI candidate among the one or more RA-RNTI candidates based on the association plus multiple indexes of the resources of the second subgroup.

[0094] The circuit 2114, in operation, may determine one or more RA-RNTI candidates for each of the one or more coverage levels. The receiver 2104 may be further configured to receive one or more DCIs having a cyclic redundancy check (CRC) scrambled by the one or more RA-RNTI candidates, and the communications device further comprises circuitry, in operation, for decoding each DCI to obtain a PDSCH including an RAR.

[0095] The communications device 2100 may be a base station, and the receiver 2104, upon operation, may receive a preamble from the communications device on at least one of a plurality of ROs in a first RO group. The circuit 2114, upon operation, may determine one or more RA-RNTI candidates based on the at least one of the plurality of ROs in the first RO group and generate a DCI having a CRC scrambled by the one or more RA-RNTI candidates. The transmitter 2104, upon operation, may transmit the DCI to the communications device.

[0096] (control signal) In the present disclosure, the downlink control signal (information) according to the present disclosure may be a signal (information) transmitted via a PDCCH of a physical layer, or may be a signal (information) transmitted via a MAC Control Element (CE) of a higher layer or an RRC. The downlink control signal may be a predefined signal (information).

[0097] The uplink control signal (information) according to the present disclosure may be a signal (information) transmitted via a PUCCH of a physical layer, or may be a signal (information) transmitted via a MAC CE of a higher layer or RRC. The uplink control signal may also be a predefined signal (information). The uplink control signal may be uplink control information (UCI), first-stage sidelink control information (SCI), or second-stage SCI.

[0098] (base station) In the present disclosure, a base station may be, for example, a Transmission Reception Point (TRP), a cluster head, an access point, a Remote Radio Head (RRH), an eNodeB (eNB), a gNodeB (gNB), a Base Station (BS), a Base Transceiver Station (BTS), a base unit, or a gateway. Furthermore, in sidelink communication, a terminal may be used instead of a base station. The base station may be a relay device that relays communication between an upper node and a terminal. The base station may be a roadside unit.

[0099] (Uplink / Downlink / Sidelink) The present disclosure may be applied to any of the uplink, downlink, and sidelink.

[0100] For example, the present disclosure may be applied to uplink channels such as PUSCH, PUCCH, and PRACH, downlink channels such as PDSCH, PDCCH, and PBCH, and sidelinks such as PSSCH (Physical Sidelink Shared Channel), PSCCH (Physical Sidelink Control Channel), and PSBCH (Physical Sidelink Broadcast Channel).

[0101] The PDCCH, PDSCH, PUSCH, and PUCCH are examples of a downlink control channel, a downlink data channel, an uplink data channel, and an uplink control channel, respectively. The PSCCH and PSSCH are examples of a sidelink control channel and a sidelink data channel, respectively. The PBCH and PSBCH are examples of a broadcast channel, and the PRACH is an example of a random access channel.

[0102] (Data channel / Control channel) The present disclosure may be applied to both data channels and control channels. The channels in this disclosure may be replaced with data channels including PDSCH, PUSCH, and PSSCH, and / or control channels including PDCCH, PUCCH, PBCH, PSCCH, and PSBCH.

[0103] (reference signal) In this disclosure, a reference signal is a signal known to both a base station and a mobile station, and each reference signal may be referred to as a reference signal (RS) or a pilot signal. A reference signal may be any of a demodulation reference signal (DMRS), a channel state information - reference signal (CSI-RS), a tracking reference signal (TRS), a phase tracking reference signal (PTRS), a cell-specific reference signal (CRS), and a sounding reference signal (SRS).

[0104] (time interval) In the present disclosure, the time resource unit is not limited to one or a combination of a slot and a symbol, and may be a time resource unit such as a frame, a superframe, a subframe, a slot, a subslot of a time slot, a minislot, or a symbol, an Orthogonal Frequency Division Multiplexing (OFDM) symbol, a Single Carrier-Frequency Division Multiplexing Access (SC-FDMA) symbol, or other time resource unit. The number of symbols included in one slot is not limited to the number of symbols exemplified in the above-mentioned embodiments, and may be other numbers of symbols.

[0105] (frequency band) The present disclosure may be applied to both licensed and unlicensed bands.

[0106] (communication) The present disclosure may be applied to communication between a base station and a terminal (Uu link communication), communication between terminals (sidelink communication), and vehicle-to-everything (V2X) communication. The channels in the present disclosure may be replaced with PSCCH, PSSCH, Physical Sidelink Feedback Channel (PSFCH), PSBCH, PDCCH, PUCCH, PDSCH, PUSCH, and PBCH.

[0107] The present disclosure may also be applied to a terrestrial network or a non-terrestrial network (NTN: Non-Terrestrial Network) that uses a satellite or a High Altitude Pseudo Satellite (HAPS). The present disclosure may also be applied to a network with a large cell size or a terrestrial network in which the delay is large compared to the symbol length or slot length, such as an ultra-wideband transmission network.

[0108] (antenna port) An antenna port refers to a logical antenna (antenna group) formed by one or more physical antennas (multiple antennas are possible). That is, an antenna port does not necessarily refer to one physical antenna, but may refer to an array antenna formed by multiple antennas. For example, the number of physical antennas forming an antenna port is not defined. Instead, an antenna port is defined as the smallest unit by which a terminal can transmit a reference signal. An antenna port may also be defined as the smallest unit for multiplying a weight of a precoding vector.

[0109] As described above, embodiments of the present disclosure provide an improved communication system, communication method, and communication device that advantageously performs RA-RNTI calculation for multi-PRACH transmissions.

[0110] The present disclosure can be implemented by software, hardware, or software cooperating with hardware. Each functional block described in the above embodiments may be partially or entirely realized as an LSI, which is an integrated circuit. Each process described in the above embodiments may be partially or entirely controlled by a single LSI or a combination of LSIs. The LSI may be formed as an individual chip, or a single chip may be formed to include some or all of the functional blocks. The LSI may include a data input / output unit coupled to it. Depending on the degree of integration, the LSI may be referred to as an IC, system LSI, super LSI, or ultra LSI. However, the technology for implementing an integrated circuit is not limited to LSI, and may be implemented using dedicated circuits, general-purpose processors, or dedicated processors. Furthermore, FPGAs (field programmable gate arrays), which can be programmed after LSI fabrication, and reconfigurable processors, which can reconfigure the connections and settings of circuit cells located within the LSI, may also be used. The present disclosure can be implemented using digital or analog processing. If, as a result of advances in semiconductor technology or other derivative technologies, LSI is replaced by future integrated circuit technologies, these future integrated circuit technologies can be used to integrate functional blocks. Biotechnology can also be applied.

[0111] The present disclosure may be implemented by any type of apparatus, device, or system having communication capabilities (collectively referred to as communication apparatus).

[0112] Non-limiting examples of such communication devices include telephones (e.g., mobile phones, smartphones), tablets, personal computers (PCs) (e.g., laptops, desktops, netbooks), cameras (e.g., digital still cameras / video cameras), digital players (e.g., digital audio players / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices), game consoles, digital book readers, telehealth / telemedicine (remote healthcare / medicine prescription) devices, and vehicles (e.g., cars, airplanes, ships) that provide communication capabilities, in various combinations.

[0113] Communications equipment is not limited to portable or mobile equipment, but also includes non-portable or fixed equipment, devices, and systems of any kind, such as smart home devices (appliances, lighting equipment, smart meters or metering devices, control panels, etc.), vending machines, and any other "things" that may exist on an Internet of Things (IoT) network.

[0114] Communications include data communications via cellular systems, wireless LAN systems, communications satellite systems, etc., as well as data communications via combinations of these.

[0115] A communications device may include devices such as controllers and sensors coupled to the communications device to perform the communications functions described in this disclosure, including, for example, controllers and sensors that generate control and data signals used by the communications device to perform the communications functions of the communications device.

[0116] The communications apparatus may further include infrastructure facilities, such as base stations, access points, and any other apparatus, device, or system that communicates with or controls the apparatus in the above non-limiting examples.

[0117] Although some features of the various embodiments are described with reference to the apparatus, it will be understood that the corresponding features also apply to the methods of the various embodiments, and vice versa.

[0118] The present disclosure may refer to the following statements:

[0119] Statement 1. a transmitter that, during operation, transmits a preamble on at least one of a plurality of Random Access Channel Occasion (RO) of a first RO group; a receiver that, during operation, receives Downlink Control Information (DCI) having a Cyclic Redundancy Check (CRC) scrambled with one or more Random Access Radio Network Temporary Identifier (RA-RNTI) candidates determined based on at least one of a plurality of ROs; Communication equipment.

[0120] Statement 2. 10. The communications device of statement 1, wherein the plurality of ROs included in the first RO group are the same as or different from the plurality of ROs included in other RO groups used by other communications devices.

[0121] Statement 3. 3. The communications device of statement 1 or 2, wherein the single RA-RNTI candidate is determined based on a plurality of indexes of resources of the first, nth, or last RO in the first RO group.

[0122] Statement 4. 4. The communications apparatus of statement 3, wherein the plurality of indices includes an index of a starting OFDM symbol of the PRACH opportunity, an index of a starting slot of the PRACH opportunity within a system frame, and an index of the PRACH opportunity in the frequency domain.

[0123] Statement 5. 4. The communications device of any one of statements 1 to 3, wherein the receiver is configured to receive the DCI within a Random-Access Response (RAR) window.

[0124] Statement 6. The communications device of statement 5, wherein the RAR window starts at least one OFDM symbol after the last OFDM symbol of each of the first RO, the nth RO, or the last RO, and ends at least one OFDM symbol after the last OFDM symbol of the last RO in the first RO group.

[0125] Statement 7. 6. The communications device of claim 5, wherein the RAR window starts at an OFDM symbol determined based on the first RO of the first RO group and ends at an OFDM symbol determined based on the determined length and the last RO of the first RO group, and a single RA-RNTI candidate used in the RAR window is determined based on the first RO of the first RO group.

[0126] Statement 8. 8. The communications device of statement 7, wherein the determined length is indicated by higher layer signaling, MAC CE signaling, or downlink control information.

[0127] Statement 9. 3. The communications device of statement 1 or 2, further comprising: circuitry that, during operation, divides a first RO group into at least two subgroups, a first subgroup including at least a first RO of the first RO group and a second or subsequent subgroup including the remaining ROs of the first RO group; determines a first RA-RNTI candidate among the one or more RA-RNTI candidates based on a plurality of indexes of resources of the first RO; and determines a second RA-RNTI candidate among the one or more RA-RNTI candidates based on a plurality of indexes of resources of the ROs of the second subgroup.

[0128] Statement 10. 10. The communication device of claim 9, wherein the circuitry is further configured to determine at least one short RAR window for the first subgroup and at least one long RAR window for the second subgroup, the at least one short RAR window having a length shorter than the at least one long RAR window.

[0129] Statement 11. 10. The communication device of statement 9, wherein the at least one short RAR window and the at least one long RAR window overlap each other in the time domain.

[0130] Statement 12. 3. The communications device of statement 1 or 2, further comprising: circuitry that, during operation, determines each of one or more RA-RNTI candidates based on each RO of a plurality of ROs in the first RO group.

[0131] Statement 13. 13. The communications device of statement 12, wherein the circuitry is configured to determine an RAR window for each RO of the plurality of ROs, the RAR window starting at least one OFDM symbol after the last OFDM symbol of the PRACH transmission and ending before or after the last OFDM symbol of the next PRACH transmission.

[0132] Statement 14. 13. The communications device of statement 12, wherein the circuitry is configured to determine a first RAR window for at least a first RO of the plurality of ROs and a second RAR window for a second RO of the plurality of ROs, the first RAR window starting at an OFDM symbol determined based on the first RO and ending at an OFDM symbol determined based on the start of the second RAR window, and the length of the first RAR window is less than the determined length.

[0133] Statement 15. 13. The communications device of any one of statements 5, 9, and 12, wherein each of the one or more RA-RNTI candidates is associated with an RAR window corresponding to the RA-RNTI candidate.

[0134] Statement 16. 3. The communications device of statement 1 or 2, further comprising: circuitry that, during operation, determines one or more second RO groups commonly determined in a serving cell based on clustering one or more ROs located proximate to each other in the time domain or the frequency domain, or both the time domain and the frequency domain, wherein the plurality of ROs in the first RO group are determined from the one or more second RO groups; and determines one or more RA-RNTI candidates based on association of at least one RO among the plurality of ROs in the first RO group with the one or more second RO groups.

[0135] Statement 17. 17. The communications device of statement 16, wherein the circuitry is further configured to determine one or more RA-RNTI candidates based on a plurality of indexes of resources of the clustered ROs in the one or more second RO groups in addition to the association.

[0136] Statement 18. The circuit is Dividing each of the one or more second RO groups into at least two subgroups: a first subgroup including at least a first RO of each of the one or more second RO groups and a second or subsequent subgroup including the remaining ROs of each of the one or more second RO groups; and determining a first RA-RNTI candidate from the one or more RA-RNTI candidates based on the plurality of indexes of the resources of the first subgroup in addition to the association, and determining a second RA-RNTI candidate from the one or more RA-RNTI candidates based on the plurality of indexes of the resources of the second subgroup in addition to the association. Statement 16 communication device.

[0137] Statement 19. The circuit is Dividing each of the one or more second RO groups into at least two subgroups: a first subgroup including at least a first RO of each of the one or more second RO groups and a second or subsequent subgroup including the remaining ROs of each of the one or more second RO groups; and determining a first RA-RNTI candidate among the one or more RA-RNTI candidates based on an index of the first subgroup in the time domain and an index of frequency hopping of the first subgroup in the frequency domain in addition to the association, and determining a second RA-RNTI candidate among the one or more RA-RNTI candidates based on an index of the second subgroup in the time domain and an index of frequency hopping of the second subgroup in the frequency domain in addition to the association. Statement 16 communication device.

[0138] Statement 20. 10. The communications device of statement 1, further comprising circuitry that, during operation, determines one or more RA-RNTI candidates for each of one or more coverage levels.

[0139] Statement 21. The communications device of statement 1, wherein the receiving unit is further configured to receive one or more DCIs having a cyclic redundancy check (CRC) scrambled by one or more RA-RNTI candidates, and the communications device further comprises circuitry that, in operation, decodes each DCI to obtain a PDSCH including an RAR.

[0140] Statement 22. a receiver that, during operation, receives a preamble at at least one of a plurality of ROs of a first RO group from a communication device; a circuit that, during operation, determines one or more RA-RNTI candidates based on at least one of a plurality of ROs of a first RO group, and generates a DCI having a CRC scrambled with the one or more RA-RNTI candidates; a transmitter that, when operational, transmits DCI to a communication device; A base station comprising:

[0141] Statement 23. Transmitting a preamble in at least one of a plurality of random access channel opportunities (ROs) of a first RO group; receiving downlink control information (DCI) having a CRC scrambled with one or more random access radio network temporary identifier (RA-RNTI) candidates determined based on at least one of a plurality of ROs; Communication method.

[0142] Statement 24. receiving a preamble at at least one of a plurality of ROs of a first RO group from the communication device; determining one or more RA-RNTI candidates based on at least one of the plurality of ROs of the first RO group; generating a DCI having a CRC scrambled by one or more RA-RNTI candidates; transmitting the DCI to the communication device; Communication method.

[0143] Statement 25. receiving a preamble at at least one of a plurality of ROs of a first RO group from the communication device; determining one or more RA-RNTI candidates based on an association of at least one RO among the plurality of ROs in the first RO group with one or more second RO groups; generating a DCI having a CRC scrambled by one or more RA-RNTI candidates; transmitting the DCI to the communication device; Communication method.

[0144] Those skilled in the art will appreciate that numerous variations and / or modifications may be made to the present disclosure as set forth in the specific embodiments without departing from the spirit or scope of the disclosure as broadly described, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. a transmitter that, in operation, transmits a preamble in at least one of a plurality of Random Access Channel Occasion (RO) opportunities of a first RO group; a receiver that, during operation, receives Downlink Control Information (DCI) having a Cyclic Redundancy Check (CRC) scrambled with one or more Random Access Radio Network Temporary Identifier (RA-RNTI) candidates determined based on at least one of the plurality of ROs. Communication equipment.

2. The ROs included in the first RO group are the same as or different from the ROs included in other RO groups used by other communication devices; The communication device according to claim 1 .

3. a single RA-RNTI candidate is determined based on a plurality of indices of resources of the first, nth or last RO in the first RO group; 3. The communication device according to claim 1 or 2.

4. the plurality of indices include an index of a starting OFDM symbol of a PRACH opportunity, an index of a starting slot of the PRACH opportunity within a system frame, and an index of the PRACH opportunity in the frequency domain. The communication device according to claim 3 .

5. the receiver is configured to receive the DCI within a Random-Access Response (RAR) window. A communication device according to any one of claims 1 to 3.

6. the RAR window starts at least one OFDM symbol after the last OFDM symbol of the first RO, the nth RO or the last RO, and ends at least one OFDM symbol after the last OFDM symbol of the last RO in the first RO group; The communication device according to claim 5 .

7. the RAR window starts at an OFDM symbol determined based on a first RO of the first RO group and ends at an OFDM symbol determined based on a determined length and a last RO of the first RO group, and a single RA-RNTI candidate to be used in the RAR window is determined based on the first RO of the first RO group; The communication device according to claim 5 .

8. the determined length is indicated by higher layer signaling, MAC CE signaling, or the downlink control information; The communication device according to claim 7.

9. When in operation, Dividing the first RO group into at least two subgroups, a first subgroup including at least a first RO of the first RO group and a second or subsequent subgroup including the remaining ROs of the first RO group; determining a first RA-RNTI candidate from among one or more RA-RNTI candidates based on a plurality of indexes of resources of the first RO, and determining a second RA-RNTI candidate from among the one or more RA-RNTI candidates based on a plurality of indexes of resources of the ROs of the second subgroup; further comprising a circuit, 3. The communication device according to claim 1 or 2.

10. the circuitry is further configured to determine at least one short RAR window for the first subgroup and at least one long RAR window for the second subgroup, the at least one short RAR window having a length shorter than the at least one long RAR window; The communication device according to claim 9.

11. the at least one short RAR window and the at least one long RAR window overlap each other in the time domain; The communication device according to claim 9.

12. and further comprising a circuit that, during operation, determines each of the one or more RA-RNTI candidates based on each RO of the plurality of ROs of the first RO group.

3. The communication device according to claim 1 or 2.

13. the circuitry is configured to determine an RAR window for each RO of the plurality of ROs, the RAR window starting at least one OFDM symbol after the last OFDM symbol of a PRACH transmission and ending before or after the last OFDM symbol of a next PRACH transmission. The communication device of claim 12.

14. the circuitry is configured to determine a first RAR window for at least a first RO of the plurality of ROs and a second RAR window for a second RO of the plurality of ROs, the first RAR window starting at an OFDM symbol determined based on the first RO and ending at an OFDM symbol determined based on a start of the second RAR window, and a length of the first RAR window being shorter than the determined length; The communication device of claim 12.

15. Each of the one or more RA-RNTI candidates is associated with an RAR window corresponding to the RA-RNTI candidate.

13. A communication device according to any one of claims 5, 9 and 12.

16. When in operation, determining one or more second RO groups commonly determined in a serving cell based on clustering one or more ROs located close to each other in a time domain or a frequency domain, or both the time domain and the frequency domain, wherein the ROs of the first RO group are determined from the one or more second RO groups; determining the one or more RA-RNTI candidates based on an association of at least one RO among the plurality of ROs of the first RO group with the one or more second RO groups; further comprising a circuit, 3. The communication device according to claim 1 or 2.

17. the circuitry is further configured to determine the one or more RA-RNTI candidates based on the association as well as a plurality of indexes of resources of clustered ROs in the one or more second RO groups.

17. The communication device of claim 16.

18. The circuit comprises: Dividing each of the one or more second RO groups into at least two subgroups: a first subgroup including at least a first RO of each of the one or more second RO groups, and a second or subsequent subgroup including the remaining ROs of each of the one or more second RO groups; and determining a first RA-RNTI candidate from the one or more RA-RNTI candidates based on a plurality of indexes of resources of the first subgroup in addition to the association, and determining a second RA-RNTI candidate from the one or more RA-RNTI candidates based on a plurality of indexes of resources of the second subgroup in addition to the association.

17. The communication device of claim 16.

19. The circuit comprises: Dividing each of the one or more second RO groups into at least two subgroups: a first subgroup including at least a first RO of each of the one or more second RO groups, and a second or subsequent subgroup including the remaining ROs of each of the one or more second RO groups; and determining a first RA-RNTI candidate among the one or more RA-RNTI candidates based on an index of the first subgroup in the time domain and a frequency hopping index of the first subgroup in the frequency domain in addition to the association, and determining a second RA-RNTI candidate among the one or more RA-RNTI candidates based on an index of the second subgroup in the time domain and a frequency hopping index of the second subgroup in the frequency domain in addition to the association.

17. The communication device of claim 16.

20. a receiver configured, in operation, to receive a preamble in at least one of a plurality of ROs of a first RO group from a communication device; a circuit for, during operation, determining one or more RA-RNTI candidates based on the at least one of a plurality of ROs of a first RO group, and generating a DCI having a CRC scrambled by the one or more RA-RNTI candidates; a transmitter configured, in operation, to transmit the DCI to the communication device; A base station comprising:

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