Downlink pdcch repetition

Abstract

The present disclosure provides a communication apparatus and method for Downlink Physical Downlink Control Channel (PDCCH) Repetition. A first communication apparatus comprises: circuitry, which in operation, determines a number of one or more repetitions of transmitted from a second communication apparatus, the number of one or more repetitions of PDCCH being determined based on a demodulation reference signal (DMRS) sequence transmitted from the second communication apparatus and / or based on a repetition common search space (CSS) associated with the one or more repetitions of PDCCH; and a receiver, which in operation, receives the one or more repetitions of PDCCH from the second communication apparatus based on the determination.

Description

[0001] DESCRIPTION

[0002] Title Of Invention: Downlink PDCCH Repetition

[0003] TECHNICAL FIELD

[0004] [1] The present disclosure relates to a communication apparatus and a communication method, and more particularly, a communication apparatus and a communication method for downlink Physical Downlink Control Channel (PDCCH) Repetition.

[0005] BACKGROUND

[0006] [2] In TR38.830, downlink coverage, particularly broadcast Physical Downlink Control Channel (PDCCH) is identified as a bottleneck channel. For the scenario of non-terrestrial networks (NTN), it is even more challenging because of the considerable distance between satellites and ground receivers. In this regard, third generation partnership project (3GPP) has a study item to enhance the downlink coverage enhancement of NTN, which is to study and specify if beneficial downlink coverage enhancements targeting support for additional reference satellite payload parameters covering both geosynchronous orbit (GSO) and non- geostationary orbit (NGSO) constellations operating in FR1-NTN or FR2-NTN e g., as described in [RAN1 , RAN2, RAN4], as well as to study and if needed specify solutions, including link level enhancements for FR1-NTN (e g. for PDCCH, physical downlink shared channel (PDSCH)) and / or system level enhancements for FR1-NTN and / or FR2-NTN, allowing dynamic and flexible power sharing between satellite beams or different satellite beam pattems / size (e g., wide or narrow) across the satellite footprint. Tn particular, the repetition mechanism has proven to be an effective method to improve downlink coverage.

[0007] [3] However, the legacy repetition indication mechanism has its limitations. For example, existing linkage mechanism is only able to link 2 search spaces, meaning that only 2 repetitions can be supported under current scheme which restricts communication through long distances. Further, existing linkage mechanism does not apply to broadcast PDCCH (other than Type3- PDCCH common search space (CSS)), and it only applies to user equipment (UE)-specific search spaces and Type3-PDCCH CSS.

[0008] [4] There is thus a need for a communication apparatus and a communication method for downlink PDCCH repetition to solve the above-mentioned issues. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background of the disclosure.

[0009] SUMMARY

[0010] |5| Non-limiting and exemplary embodiments facilitate providing communication apparatuses and communication methods for downlink PDCCH repetition.

[0011] [6] In a first aspect, the present disclosure provides a first communication apparatus comprising: circuitry, which in operation, determines a number of one or more repetitions of transmitted from a second communication apparatus, the number of one or more repetitions of PDCCH being determined based on a demodulation reference signal (DMRS) sequence transmitted from the second communication apparatus and / or based on a repetition common search space (CSS) associated with the one or more repetitions of PDCCH; and a receiver, which in operation, receives the one or more repetitions of PDCCH from the second communication apparatus based on the determination.

[0012] [7] In a second aspect, the present disclosure provides a second communication apparatus comprising: circuitry, which in operation, generates a demodulation reference signal (DMRS) sequence and / or configures a repetition common search space (CSS) based on a number of one or more repetitions of physical downlink control channel (PDCCH); and a transmitter, which in operation, transmits the one or more repetitions of PDCCH, and transmits the DMRS sequence and / or repetition CSS to a first communication apparatus

[0013] [8] In a third aspect, the present disclosure provides a communication method implemented by a first communication apparatus, the method comprising: determining a number of one or more repetitions of physical downlink control channel (PDCCH) transmitted from a second communication apparatus, the number of the one or more repetitions of PDCCH being determined based on a demodulation reference signal (DMRS) sequence transmitted from the second communication apparatus and / or a repetition common search space (CSS) associated with the one or more repetitions of PDCCH; and receiving the one or more repetitions of PDCCH from the second communication apparatus based on the determination.

[0014] [9] In a fourth aspect, the present disclosure provides a communication method implemented by a second communication apparatus, the method comprising: generating a demodulation reference signal (DMRS) sequence and / or configuring a repetition common search space (CSS) based on a number of one or more repetitions of physical downlink control channel (PDCCH); and transmitting the one or more repetitions of PDCCH and the DMRS and / or repetition CSS to a first communication apparatus.

[0015]

[0010] Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and / or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and / or advantages.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017]

[0011] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to illustrate various embodiments and to explain various principles and advantages in accordance with present embodiments.

[0018]

[0012] Figure 1 shows an exemplary architecture for a 3GPP new radio (NR) system to which exemplary embodiments of the present disclosure may be applied.

[0019]

[0013] Figure 2 shows an exemplary illustration of two search spaces linked via radio resource control (RRC) parameter according to Rel-17.

[0020]

[0014] Figure 3 shows a schematic diagram illustrating an example configuration of a communication apparatus in accordance with various embodiments of the present disclosure. [15J Figure 4 shows an exemplary flowchart illustrating a method according to various embodiments of the present disclosure.

[0021]

[0016] Figure 5 shows an exemplary flowchart illustrating another method according to various embodiments of the present disclosure.

[0022]

[0017] Figure 6 shows an exemplary illustration of parameters of demodulation reference signals (DMRS) sequence sets according to various embodiments of the present disclosure.

[0023]

[0018] Figure 7 shows an exemplary illustration of time division multiplexed (TDMed) broadcast PDCCH repetitions according to various embodiments of the present disclosure.

[0024]

[0019] Figure 8 shows an exemplary illustration of frequency division multiplexed (FDMed) broadcast PDCCH repetitions according to various embodiments of the present disclosure.

[0025]

[0020] Figure 9 shows an exemplary illustration of mixed division multiplexed (TDMed and FDMed) broadcast PDCCH repetitions according to various embodiments of the present disclosure.

[0026]

[0021] Figure 10 shows an exemplary illustration of multiple repetition common search space (CSS) in time domain according to various embodiments of the present disclosure.

[0027]

[0022] Figure 11 shows an exemplary illustration of a four repetition CSS according to various embodiments of the present disclosure.

[0023] Figure 12 shows an exemplary flow chart for base station (gNB) transmission of repeated broadcast PDCCHs and DMRS sequences according to various embodiments of the present disclosure.

[0028]

[0024] Figure 13 shows an exemplary flow chart for UE reception of repeated broadcast PDCCHs and DMRS sequences according to various embodiments of the present disclosure.

[0029]

[0025] Figure 14 shows an exemplary flow chart for gNB transmission of repeated broadcast PDCCHs in repetition CSSs according to various embodiments of the present disclosure.

[0030]

[0026] Figure 15 shows an exemplary flow chart for UE reception of repeated broadcast PDCCHs in repetition CSSs according to various embodiments of the present disclosure.

[0031]

[0027] Figure 16 shows exemplary functional split options in 5G open-radio access network (0-RAN) to which exemplary embodiments of the present disclosure may be applied.

[0032]

[0028] A person skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been depicted to scale. For example, the dimensions of some of the elements in the illustrations, block diagrams or flowcharts may be exaggerated in respect to other elements to help an accurate understanding of the present embodiments.

[0033] DETAILED DESCRIPTION

[0029] Some embodiments of the present disclosure will be described, by way of example only, with reference to the drawings. Like reference numerals and characters in the drawings refer to like elements or equivalents.

[0034]

[0030] 3GPP has been working at the next release for the 5thgeneration cellular technology, simply called 5G, including the development of a new radio access technology (NR) operating in frequencies ranging up to 100 GHz. The first version of the 5G standard was completed at the end of 2017, which allows proceeding to 5GNR standard-compliant trials and commercial deployments of smartphones.

[0035]

[0031] The second version of the 5G standard was completed in June 2020, which further expand the reach of 5Gto new services, spectrum and deployment such as unlicensed spectrum (NR-U), non-public network (NPN), time sensitive networking (TSN) and cellular-V2X.

[0036] 5GNR system architecture and protocol stacks

[0037]

[0032] 5G NR system architecture assumes an NG-RAN (Next Generation - Radio Access Network) that comprises gNBs, providing the NG-radio access user plane (SDAP / PDCP / RLC / MAC / PHY) and control plane (RRC) protocol terminations towards the UE. The gNBs are interconnected with each other by means of the Xn interface. The gNBs are also connected by means of the Next Generation (NG) interface to the NGC (Next Generation Core), more specifically to the AMF (Access and Mobility Management Function) (e g., a particular core entity performing the AMF) by means of the NG-C interface and to the UPF (User Plane Function) (e g., a particular core entity performing the UPF) by means of the NG- U interface. The NG-RAN architecture is illustrated in Figure 1 (see e.g., 3GPP TS 38.300

[0038] V15.6.0, section 4).

[0033] The user plane protocol stack for NR (see e.g., 3GPP TS 38.300, section 4.4.1) comprises the PDCP (Packet Data Convergence Protocol, see section 6.4 of TS 38.300), RLC (Radio Link Control, see section 6.3 of TS 38.300) and MAC (Medium Access Control, see section 6.2 of TS 38.300) sublayers, which are terminated in the gNB on the network side. Additionally, a new access stratum (AS) sublayer (SDAP, Service Data Adaptation Protocol) is introduced above PDCP (see e.g., sub-clause 6.5 of 3GPP TS 38.300). A control plane protocol stack is also defined for NR (see for instance TS 38.300, section 4.4.2). An overview of the Layer 2 functions is given in sub-clause 6 of TS 38.300. The functions of the PDCP, RLC and MAC sublayers are listed respectively in sections 6.4, 6.3, and 6.2 of TS 38.300. The functions of the RRC layer are listed in sub-clause 7 of TS 38.300

[0039]

[0034] For instance, the Medium-Access-Control layer handles logical-channel multiplexing, and scheduling and scheduling-related functions, including handling of different numerologies.

[0040]

[0035] The physical layer (PHY) is for example responsible for coding, PHY hybrid automatic repeat request (HARQ) processing, modulation, multi-antenna processing, and mapping of the signal to the appropriate physical time-frequency resources. It 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 the set of timefrequency resources used for transmission of a particular transport channel, and each transport channel is mapped to a corresponding physical channel. For instance, the physical channels are PRACH (Physical Random Access Channel), PUSCH (Physical Uplink Shared Channel) and PUCCH (Physical Uplink Control Channel) for uplink, PDSCH (Physical Downlink Shared Channel), PDCCH (Physical Downlink Control Channel) and PBCH (Physical Broadcast Channel) for downlink, PRDCH (Physical Reader-to-Device Channel) and PDRCH (Physical Device-to-Reader Channel) for A-IoT, and PSSCH (Physical Sidelink Shared Channel), PSCCH (Physical Sidelink Control Channel) and Physical Sidelink Feedback Channel (PSFCH) for sidelink (SL).

[0041]

[0036] For XDD operation, the frequency domain (or frequency resource or frequency bandwidth) is divided into a plurality of frequency domains (also referred to as, for example, sub-bands, RB sets, sub-bandwidths, or sub-BWPs (Bandwidth parts)). The terminal performs transmission and reception in a direction (for example, a downlink or uplink direction) in units of subbands that are the divided domains. For SBFD symbols, the terminal may perform transmission / reception in one direction of uplink and downlink directions, and may not perform transmission / reception in the other direction. The base station, on the other hand, may be capable of performing both uplink and downlink transmissions / receptions simultaneously. SBFD symbols may have a fewer frequency domain usable for downlink compared to symbols for which only downlink transmission / reception is performed. Further, SBFD symbols may have a fewer frequency domain usable for uplink compared to symbol for which only uplink transmission / reception is performed.

[0042]

[0037] Further, for SBFD symbols, the terminal may perform uplink and downlink transmissions / receptions simultaneously. At this time, the frequency domain transmitted by the terminal and the frequency domain received by the terminal may not be adjacent and a frequency interval (also referred to as a frequency gap) may be provided therebetween.

[0043]

[0038] Further, sidelink transmission / reception may also be included as a transmission / reception direction in units of sub-bands which are the divided domains. |39] Use cases / deployment scenarios for NR could include enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC), massive machine type communication (mMTC), which have diverse requirements in terms of data rates, latency, and coverage. For example, eMBB is expected to support peak data rates (20Gbps for downlink and lOGbps for uplink) and user-experienced data rates in the order of three times what is offered by IMT- Advanced. On the other hand, in case of URLLC, the tighter requirements are put on ultra-low latency (0.5ms for UL and DL each for user plane latency) and high reliability (e.g., 1-10-5 within 1ms). Finally, mMTC may preferably require high connection density (e.g., 1,000,000 devices / km2 in an urban environment), large coverage in harsh environments, and extremely long-life battery for low-cost devices (e g., 15 years). f40] Therefore, the Orthogonal Frequency Division Multiplexing (OFDM) numerology (e.g., subcarrier spacing, OFDM symbol duration, cyclic prefix (CP) duration, number of symbols per scheduling interval) that is suitable for one use case might not work well for another. For example, low-latency services may preferably require a shorter symbol duration (and thus larger subcarrier spacing) and / or fewer symbols per scheduling interval (also known as transmission time interval (TTI)) than an mMTC service. Furthermore, deployment scenarios with large channel delay spreads may preferably require a longer CP duration than scenarios with short delay spreads. The subcarrier spacing should be optimized accordingly to retain the similar CP overhead. NR may support more than one value of subcarrier spacing. Correspondingly, subcarrier spacing of 15kHz, 30kHz, 60 kHz.. . . , etc are being considered at the moment. The symbol duration Tu and the subcarrier spacing Af are directly related through the formula Af = 1 / Tu. In a similar manner as in LTE systems, the term “resource element” can be used to denote a minimum resource unit being composed of one subcarrier for the length of one OFDM / SC-FDMA symbol.

[0044]

[0041] In the new radio system 5G-NR for each numerology and carrier a resource grid of subcarriers and OFDM symbols is defined respectively for uplink and downlink. Each element in the resource grid is called a resource element and is identified based on the frequency index in the frequency domain and the symbol position in the time domain (see 3GPP TS 38.211 V16.3.0).

[0045]

[0042] The existing (Rel-17) mechanism for indication of broadcast PDCCH repetitions utilized linkage to inform a user equipment (UE) about the repetitions For example, referring to illustration 200 of Figure 2, a linkage 202 is used to link 2 search spaces 204 and 206 via RRC configuration, where each of the search spaces 204 and 206 consists of one repetition. In order to cater the challenging conditions of non-terrestrial networks (NTNs), an improved repetition mechanism is required which can support beyond 2 repetitions.

[0046]

[0043] Further, the legacy repetition indication mechanism has its limitations. For example, existing linkage mechanism is only able to link 2 search spaces e.g., only 2 repetitions can be supported under current scheme. However, in a NTN scenario, the significant distance between users and satellites makes it inadequate to rely solely on two repetitions for achieving sufficient coverage gain. Furthermore, the existing linkage mechanism does not apply to broadcast PDCCH (other than Type3-PDCCH CSS), and it only applies to UE-specific search spaces and Type3-PDCCH CSS. Given the challenging scenario of NTN, a UE may not be able to establish connections without the repeated broadcast PDCCHs. It is also not specified in current technical specifications howto support the broadcast PDCCH (other than Type3-PDCCH CSS). 144] There is thus a need for a communication apparatus and a communication method for downlink PDCCH repetition to solve the above-mentioned issues. Furthermore, other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings.

[0047]

[0045] Figure 3 shows a schematic diagram illustrating an example configuration of a communication apparatus 300 in accordance with various embodiments of the present disclosure. The communication apparatus 300 may be utilized for downlink PDCCH repetition. The communication apparatus 300 may be implemented as a UE or a gNB in accordance with the present disclosure. It will be appreciated by a person skilled in the art that the communication apparatus 300 may be referred to as communication device 300 throughout the disclosure. As shown in Figure 3, the communication apparatus 300 may include circuitry 314, at least one radio transmitter 302, at least one radio receiver 304, and at least one antenna 312 (for the sake of simplicity, only one antenna is depicted in Figure 3 for illustration purposes). The circuitry 314 may include at least one controller 306 for use in software and / or hardware aided execution of tasks that the at least one controller 306 is designed to perform, including control of communications with one or more other communication apparatuses in a multiple input and multiple output (MIMO) wireless network. The circuitry 314 may further include at least one transmission signal generator 308 and at least one receive signal processor 310. The at least one controller 306 may control the at least one transmission signal generator 308 for generating an uplink signal, a downlink signal (e g., a downlink PDCCH repetition), a sidelink signal, or other similar signals to be sent through the at least one radio transmitter 302, and control the at least one receive signal processors 310 for processing an uplink signal, a downlink signal (e g., a downlink PDCCH repetition), a sidelink signal, or other similar signals received through the at least one radio receiver 304 from the one or more other communication apparatuses. The at least one transmission signal generator 308 and the at least one receive signal processor 310 may be stand-alone modules of the communication apparatus 300 that communicate with the at least one controller 306 for the above-mentioned functions, as shown in Figure 3. Alternatively, the at least one transmission signal generator 308 and the at least one receive signal processor 310 may be included in the at least one controller 306. It is appreciable to those skilled in the art that the arrangement of these functional modules is flexible and may vary depending on the practical needs and / or requirements. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and / or in chipsets. In various embodiments, when in operation, the at least one radio transmitter 302, at least one radio receiver 304, and at least one antenna 312 may be controlled by the at least one controller 306. Although not shown in Figure 3, it will be appreciated that the communication apparatus 300 may comprise at least one radio transceiver that is configured to perform the functions of the at least one radio transmitter 302 and the at least one radio receiver 304.

[0048]

[0046] The communication apparatus 300, when in operation, provides functions required for downlink PDCCH repetition. In one example, the communication apparatus 300 may be a UE (e.g., a first communication apparatus). Figure 4 shows a flowchart illustrating a method 400 according to various embodiments of the present disclosure. As shown in the exemplified method 400 for downlink PDCCH repetition in Figure 4, the communication apparatus 300, when in operation, is configured to perform the following steps:

[0049] Step 402: the circuitry 314 (or the at least one controller 306 of the circuitry 314) may determine a number of one or more repetitions of physical downlink control channel

[0050] (PDCCH) transmitted from a second communication apparatus, the number of one or more repetitions ofPDCCH being determined based on a demodulation reference signal (DMRS) sequence transmitted from the second communication apparatus and / or based on a repetition common search space (CSS) associated with the one or more repetitions ofPDCCH; and

[0051] Step 404: the at least one radio receiver 304 may receive the one or more repetitions of PDCCH from the second communication apparatus based on the determination.

[0052]

[0047] Additionally or alternatively, the circuitry 314 may be configured to determine the number of the one or more repetitions ofPDCCH based on an offset value added in a generation of the DMRS sequence. The offset value may be 0 when the number of the one or more repetitions of PDCCH is 1 , and the offset value may not be 0 when the number of the one or more repetitions ofPDCCH is more than 1. The offset value may be added to a cell identifier used for the generation of the DMRS sequence or may be added to a pseudo-random sequence used for the generation of the DMRS sequence.

[0053]

[0048] Additionally or alternatively, the circuitry 314 may be configured to determine the number of the one or more repetitions of PDCCH based on one or more sets of DMRS sequences. Each DMRS sequence within a same set of DMRS sequences indicates a same number of repetitions of PDCCH. Each set of DMRS sequences may indicate a different resource allocation, the resource allocation being a time division multiplexing (TDM), a frequency division multiplexing (FDM), or a mixed allocation comprising both TDM and FDM.

[0054]

[0049] Each DMRS sequence within a first set of DMRS sequences may indicate a number of repetitions of PDCCH that is different from that indicated by each DMRS sequence within a second set of DMRS sequences. A number of DMRS sequences in the first set may be equal to or larger than a number of DMRS sequences in the second set, and the number of the repetitions of PDCCH corresponding to the first set may be smaller than the number of the repetitions of PDCCH corresponding to the second set. A number of DMRS sequence in the first set may be equal to or larger than a number of DMRS sequence in the second set, and the number of the repetitions of PDCCH corresponding to the first set may be larger than the number of the repetitions of PDCCH corresponding to the second set.

[0055]

[0050] Additionally or alternatively, the circuitry 314 may be configured to determine a resource or a division multiplexing method of the one or more repetitions of PDCCH based on the DMRS sequence, wherein the resource of the one or more repetitions of PDCCH is different between a first set of one or more DMRS sequences and a second set of one or more DMRS sequences. The DMRS sequence may be predefined in technical specifications, and / or configured in a Master Information Block (MIB) or a System Information Block (SIB). The one or more repetitions of PDCCH may be time division multiplexed (TDMed), frequency division multiplexed (FDMed), or both TDMed and FDMed. The circuitry 314 may be further configured to perform a blind detection of the DMRS sequence on each candidate resource in the CSS, and combine the received one or more repetitions of PDCCH based on the determined number of repetitions from the detected DMRS sequence. The circuitry 314 may be further configured to determine the number of repetitions of PDCCH from a plurality of the repetition CSS, each repetition CSS carrying a repetition PDCCH. At least one repetition of PDCCH in one of the plurality of CSS may be larger than that in a user equipment specific search space (USS). The receiver 304 may be further configured to receive the DMRS sequence in a first resource and the one or more repetitions of PDCCH in a second resource. The receiver 314 may be further configured to receive a legacy CSS in a first resource and the repetition CSS in a second resource. [51 J In another example, the communication apparatus 300 may be a reader for a gNB (e g., a second communication apparatus). Figure 5 shows another exemplary flowchart illustrating a method 500 according to various embodiments of the present disclosure. As shown in the exemplified method 500 for downlink PDCCH repetition in Figure 5, the communication apparatus 300, when in operation, is configured to perform the following steps:

[0056] Step 502: the circuitry 314 (or the at least one controller 306 of the circuitry 314) may, in operation, generate a demodulation reference signal (DMRS) sequence and / or configures a repetition common search space (CSS) based on a number of one or more repetitions of physical downlink control channel (PDCCH); and

[0057] Step 504: the at least radio transmitter 302 may, in operation, transmit the one or more repetitions of PDCCH, and transmit the DMRS sequence and / or repetition CSS to a first communication apparatus.

[0058]

[0052] Additionally or alternatively, the circuitry 314 may be configured to determine an offset value to be added in the generation of the DMRS sequence based on the number of one or more repetitions of PDCCH. The offset value may be 0 when the number of the one or more repetitions of PDCCH is 1 , and the offset value may not be 0 when the number of the one or more repetitions of PDCCH is more than 1. The offset value may be added to a cell identifier used for the generation of the DMRS sequence or may be added to a pseudo-random sequence used for the generation of the DMRS sequence.

[0059]

[0053] Additionally or alternatively, the circuitry 314 may be configured to determine one or more sets of DMRS sequences based on the number of the one or more repetitions of PDCCH. Each DMRS sequence within a same set of DMRS sequences may indicate a same number of repetitions of PDCCH. Each set of DMRS sequences may indicate a different resource allocation, the resource allocation being a time division multiplexing (TDM), a frequency division multiplexing (FDM), or a mixed allocation comprising both TDM and FDM.

[0060]

[0054] The DMRS sequence may be predefined in technical specifications, and / or configured in a Master Information Block (MIB) or a System Information Block (SIB). The one or more repetitions of PDCCH are time division multiplexed (TDMed), frequency division multiplexed (FDMed), or both TDMed and FDMed. The circuitry 314 may further configure a plurality of the repetition CSS based on the number of repetition PDCCH, each repetition CSS carrying a repetition PDCCH. At least one repetition of PDCCH in one of the plurality of CSS may be larger than that in a user equipment specific search space (USS). The transmitter 302 may be further configured to transmit the DMRS sequence in a first resource and the one or more repetitions of PDCCH in a second resource. The transmitter 302 may be further configured to transmit a legacy CSS in a first resource and the repetition CSS in a second resource.

[0061]

[0055] According to the present disclosure, a gNB may be configured to transmit repeated PDCCHs (e.g., one or more repetitions of PDCCH) and indicate a number of repetitions used for the transmission. A UE may be configured to determine the number of repetitions and then receives the PDCCHs. The indication and determination of the repeated PDCCHs may be based on a demodulation reference signal (DMRS) sequence and / or a repetition common search space (CSS) e g., utilizing a specific DMRS sequence to indicate the number of repetitions, and / or utilizing a specific RRC parameter to indicate the number of repetitions in a repetition CSS. The repetition CSSs may be utilized in addition to legacy CSSs. Further, the repeated PDCCHs may be repeated broadcast PDCCHs that are transmitted in repetition CSSs, which are configured in addition to legacy CSSs. The number of repeated broadcast PDCCHs may be determined by a linkage configured by a new parameter e g., Repetition I Linked and virtual ID. It will be appreciated that the proposed high-level solution is not restricted to broadcast PDCCH only, and can be applied in a general PDCCH scenario. Further, a determination by a UE of a number of repetitions may be a detection or comprise a detection by the UE of the number of repetitions e.g., based on a DMRS sequence and / or a repetition CSS. Furthermore, a DMRS sequence may also be referred to herein as a sequence, and a repeated PDCCH or repeated broadcast PDCCH may also be referred to herein as a repetition. Advantageously, a UE is able to know the number of repetitions before reception of repeated broadcast PDCCHs and perform combined decoding for coverage gain improvement.

[0062]

[0056] In an implementation, a UE may be configured to determine the number of repeated broadcast PDCCHs based on a value (e g. an offset value added in a generation of a DMRS sequence, or a value of cyclic shifting) of DMRS sequences. The offset value or the value of cyclic shifting may be different for different numbers of repeated broadcast PDCCH. If one or more sets of DMRS sequences may be (pre-)defmed or (pre-)configured for a UE, the DMRS sequences within the same set may be for a same number of repeated broadcast PDCCH. In other words, the offset value or the value of cyclic shifting within a same set may be for a same number of repeated broadcast PDCCH.

[0063]

[0057] For example, the offset value or the cyclic shifting may be achieved by modifying a cell ID (e g , with an addition of a shift value (e.g., + “shift”). This modification will change the initialization value of the pseudo-random sequence generator, resulting in a new pseudorandom sequence e.g., a new DMRS sequence. The gNB generates and transmits the DMRS sequence generated by using the addition of a shift value. The UE receives the DMRS sequence and determines a number of repetition based on the DMRS sequence (i.e. the offset value or the shift value of the received DMRS sequence). Tn an example, an offset value may be added to a cell identifier used for a generation of a DMRS sequence.

[0064]

[0058] Further, a plurality of sets may be defined. For example, a set named as SetRepetition- 2t may contain the sequences indicating 2 repetitions in a TDM (e.g., sequence-21- 1 , sequence- 21-2, and other similar sequence). The sequence-21-1 may be used to indicate 2 broadcast PDCCH repetitions to advantageously avoid mis-detection with another 2 broadcast PDCCH repetitions indicated by, for example, sequence-2t-2.

[0065]

[0059] The sequences within a same set may be representing different resource allocation. A different set named as SetRepetition-4t may contain the sequences indicating 4 repetitions in a TDM

[0066]

[0060] Alternatively, one or more different sets of DMRS sequences may also be used for indicating different resource allocations. For example, one set may be used for sequences indicating 2 TDMed repetitions, and another set may be used for sequences indicating 2 FDMed repetitions. Further, a Radio Network Temporary Identifier (RNTI) may be used to further confirmation of their respective repeated broadcast PDCCHs.

[0067]

[0061] In an example, a number of sequences included in a set of 2 repetitions (e.g., SetRepetition-2f) may be larger than a number of sequences included in a set of 4 repetitions (e.g., SetRepetition-4t) In an example, a number of sequences included in a set of 2 repetitions (e.g., SetRepetition-2t) may be smaller than or equal to a number of sequences included in a set of 4 repetitions (e.g., SetRepetition-4t'). In an example, a number of sequences included in a set of 2 repetitions and / or 4 repetitions may be indicated by a higher layer signalling.

[0062] In an example, it is assumed that Njo11= 10 and shift=l (e.g., assume this shift ! is to generate a “sequence-2t-f"). A pseudo-random sequence may be initialized using Cinitwith the following equation: Cinit= (217 + 1) + 2NlD)mod231wherein a modified initialization with shift is NID= + shift = 10+1 =11. A different pseudo-random sequence c(i) is generated based on a new Cinitby computing Cinitwith the N,D= 11 using the equation above. Using a new pseudo-random sequence c(i) will then provide a new DMRS sequence based on the following equation: r^m) = ^=(1—2 ■ c(2m)) + j -= (1 — 2 ■ c(2m + 1)) In an example, an offset value may be added to a pseudorandom sequence used for the generation of the DMRS sequence.

[0068]

[0063] Alternatively, different DMRS sequences may also be achieved by varying the initialization index, Cini[. This index may be calculated using parameters like the cell ID NID. For example, changing the cell ID NID±to NID2may result in different Cini[values, which in turn generate distinct pseudo-random sequences, and ultimately producing different DMRS sequences for different UEs. In an example, an offset value may be added to the initialization index used for a generation of a DMRS sequence.

[0069]

[0064] In an example, a sequence of no repetition may be generated with shift=O. In an example, sequences in a set of 2 repetitions may be related to non-consecutive shift values (e.g. shift=O, 3). In an example, sequences in a set of 2 repetitions may be related to consecutive shift values (e.g. shift=O, 1). In an example, adding “shift” to e.g., Cinitor other is also possible, instead of adding “shift” In an example, an offset value may be added to a cell identifier, a pseudo-random sequence, an initialization index, and / or other similar parameters used for generation of a DMRS sequence.

[0070]

[0065] In an example, signalling to a UE may be predefined in the technical specifications. A set of sequences may be representing a number of repetitions, e.g., SetRepetition-2t includes sequences indicating 2 repetitions in TDM mode, SetRepelition-4f includes sequences indicating 4 repetitions in FDM mode. In an example, signalling to a UE may be configured in a Master Information Block (MIB) or a System Information Block (SIB). One or more parameters in the MIB / SIB may be utilized to configure the set of sequences. The indication (letters ‘t’, ‘f and ‘m’ representing TDM, FDM and mixed mode respectively) may be as follows: “ sequence-2 t-T may represent a 1 st sequence indicating 2 TDMed repetitions, “ sequence-2f-2” may represent a 2nd sequence indicating 2 FDMed repetitions, and “ sequence- 4m-121-r may represent a 1st sequence indicating 4 mixed FDM / TDM repetitions with resource allocation pattern ‘ 1-2-T . Considering a broadcast PDCCH that serves many UEs in a cell, several UEs may require the same repetitions. For example, 4 UEs in a cell may require 4 repetitions. Hence, there may be 4 DMRS sequences for the 4 UEs e.g., sequence-41- 1, sequence-4t-2, sequence-41- 3, and sequence-4t-4 respectively. A further example of parameters of DMRS sequence sets is as shown in illustration 600 of Figure 6.

[0071]

[0066] In an example, the allocation of broadcast PDCCHs may not be necessary to be in same frequency. Different set of sequences may indicate multiplexing methods of the repeated broadcast PDCCH, e.g. TDM, FDM and mixed In another example, the underlying pseudorandom sequence c(i) for repetition and actual sets of specific DMRS sequence may be the same. Further, the search spaces may be configured in an overlapping manner so that the increase of the number of monitored broadcast PDCCH candidates may be minimised, and not exceed a maximum number of monitored broadcast PDCCH candidates agreed on Section 10.1 of TS38.213.

[0072]

[0067] In an implementation, resource allocation may be configured by a gNB and may be one or a combination of options 1, 2 and 3 as will be further described in the following paragraphs, and the UE may be configured to receive and detect broadcast PDCCHs with DMRS sequence based on a predefined sequence, a SIB or a MIB. In a first option, time division multiplexed (TDMed) broadcast PDCCH repetitions may be utilized. For example, referring to illustration 700 of Figure 7, TDMed broadcast PDCCH repetitions may comprise a sequence-2t-l (see reference 702) indicating 2 repetitions for PDCCH 7; sequence-2t-2 indicating 2 repetitions for PDCCH 2 (see reference 704), and sequence-4t-l indicating 4 repetitions for PDCCH 3 (see reference 706). Both sequence-2t-l 702 and sequence-2t-2 704 are categorised in SetRepetition-2t, which represent sequences for 2 repetitions. Sequence-4t-l 706 is categorised in SetRepetition-4t representing 4 repetitions. There may also be legacy PDCCH (see reference 708) without any repetitions. It will be appreciated that the allocation of broadcast PDCCHs may begin in any search space and span across the time domain in a consecutive manner, and the example of illustration 700 is for illustration purpose only. Further, the PDCCH need not be a broadcast PDCCH and other types of PDCCH are also applicable. Advantageously, gain improvement can be achieved from time diversity.

[0073]

[0068] In an option 2, frequency division multiplexed (FDMed) broadcast PDCCH repetitions may be utilized. For example, referring to illustration 800 of Figure 8, FDMed broadcast PDCCH repetitions may comprise sequence-2f-l (see reference 802) indicating 2 repetitions for PDCCH 7; sequence-2f-2 (see reference 804) indicating 2 repetitions for PDCCH 3 and sequence-4f-l (see reference 806) indicating 4 repetitions for PDCCH 2. Both sequence-2f-l 802 and sequence-2f-2 804 are categorised in SetRepetition-2f representing sequences for 2 repetitions, and sequence-4f-l 806 is categorised in SetRepetition-4f representing 4 repetitions. It may not be necessary for the repetitions to be contiguous in frequency domain. It will be appreciated that the PDCCH need not be a broadcast PDCCH and other types of PDCCH are also applicable. Advantageously, low latency delay may be achieved as the repetitions occur in a same occasion.

[0074]

[0069] In an option 3, mixed (e.g., including both FDM and TDM) broadcast PDCCH repetitions may be utilized. For example, referring to illustration 900 of Figure 9, 4 repetitions with a mixed allocation (e g., categorised as SetRepetition-4m may comprise a sequence-4m- 121-1 (see reference 902) having repetitions with a resource allocation pattern ‘ 1-2-R , and a sequence-4m-211-1 (see reference 904) having repetitions with a resource allocation pattern ‘2-1-1" . IT will be appreciated that the allocation of PDCCHs may begin in any search space, and span across time domain in consecutive manner, and the example as shown in illustration 900 is not exhaustive. Further, the term “121” with a value more than 1 in sequence-4m-121-l 902 (and other sequence indicator) may be used to indicate FDM allocation. For example, the third part of the term "sequence-4m-121-l" (after the second hyphen in the term) may indicate the type of resource allocation, specifying whether it is TDM or FDM within a search space. The value " 121" may denote that the repeated PDCCHs are distributed across three search spaces: for example one PDCCH in the first search space, two PDCCHs in the second search space in FDM manner, and one PDCCH in the third search space A value greater than one may signify FDM resource allocation. The PDCCH also need not be a broadcast PDCCH and other types of PDCCH are also applicable. Advantageously, gain improvement can be achieved from frequency diversity gain and time diversity gain.

[0070] Tn an example, UE may be configured to perform a blind detection of DMRS sequence on each candidate resource in CSS and receive a broadcast PDCCH using the detected DMRS with repetition combining. The UE may not need to perform broadcast PDCCH blind decoding with CRC checking. For example, if the UE detects a DMRS sequence oi“sequence-2t-l" on a Repetition #1 of a broadcast PDCCH in a first slot, the UE will know the number of repetitions (which is 2) based on the detected DMRS sequence. Then, the UE may be configured to receive Repetition #1 and Repetition #2 of the broadcast PDCCH and perform a soft combining of the received repetitions accordingly. In soft combining, the receiver may combine the repetitions to make a more accurate estimation of the transmitted data. The combined information can result in a higher probability of correctly decoding the signal, especially in scenarios with poor signal conditions or high interference. UE blind detection may be based on DMRS detection because DMRS resources are embedded within broadcast PDCCH resources.

[0075]

[0071] In an implementation, one or more CSSs for repeated broadcast PDCCHs (e.g., referred to herein as repetition CSS) may be configured for a UE. If one or more repetition CSSs are configured, it means there are repeated broadcast PDCCHs. The UE may be able to determine the number of repetitions from the existence of repetition CSS and / or the associated information / parameter (e g., virtual ID, Repetition ID Linked) . Repetition CSSs may be FDMed with legacy CSSs as sets, and virtual ID may be assigned to each repetition CSS Each of the repetition CSS may carry one repeated broadcast PDCCH for a UE and a new information element (IE) such as Repetition J D Linked may be introduced to indicate the linked virtual IDs. Repetition CSSs may be TDMed with legacy CSSs, where repetition CSSs and legacy CSSs can be allocated within a slot (which might be referred as intra-slot repetitions) or across multiple slots (which might be referred as inter-slot repetition). For inter-slot repetition, it is possible that (1) repetition CSSs and legacy CSSs can be located in consecutive slots, wherein each slot includes one of repetition CSSs and legacy CSSs; or (2) repetition CSSs and legacy CSSs can be located in non-consecutive slots, wherein there is time gap between 2 consecutive CSSs (e.g., a time gap between repetition CSS and legacy CSS, or a time gap between repetition CSSs) and a unit of time gap can be based on one or more slots. For either (1) or (2), it is expected that there is a PDCCH repetition per CSS which is either repetition or legacy CSS. If repetition CSS(s) is / are configured in addition to legacy CSS by gNB, a legacy UE might decode a PDCCH in legacy CSS and skip PDCCH monitoring in repetition CSS(s). On the other hand, a UE with capable of PDCCH repetition, it might monitor a PDCCH over repetition CSS(s) and legacy CSS in order to decode the PDCCH by using a soft combining method. An example to realise TDMed repetition CSS is shown in illustration 1000 of Figure 10, in which an IE Repetition ID Linked ={2,3, 5, 6} may be used to link 4 repetition CSSs 1002, 1004, 1006 and 1008 with virtual_ID=2, 3, 5 and 6 respectively, where each of the repetition CSSs contains a repeated broadcast PDCCH. When a length of CSS is one or 2 OFDM symbols, for instance, these 4 repetition CSSs can be located within a slot depending on a configuration of gNB. Another instance, 4 repetition CSSs can be configured to be located across 4 consecutive slots such as n, n+1, n+2, n+3 slots, where n is equal to or greater than 0. It would be appreciated that PDCCH repetitions can be interchangeably used in this application as repeated broadcast PDCCHs, broadcast PDCCH repetitions, repetition CSSs, repeated PDCCH candidates, and repeated PDCCHs. Further, a number of the repetitions in a CSS may be larger than that in a user equipment specific search space (USS)

[0076] 172] In an implementation, a set of virtual ID may be utilized to represent a number of repeated broadcast PDCCHs in a repetition CSS. For example, virtual ID 1-10 may be utilized to represent 2 repetitions, virtual ID 11-20 may be utilized to represent 4 repetitions and so on. When 8 repetitions are required, Repetition I D I inked may link, for example, repetition CSSs with virtual ID =2, 3 and 11 (e.g., comprising 2 repetitions, 2 repetitions, and 4 repetitions respectively) or repetition CSSs with virtual ID = 12 and 15 (e.g., comprising 4 repetitions and 4 repetitions respectively). Illustration 1100 of Figure 11 shows an example comprising 4 broadcast PDCCH repetitions (e.g., reference 1108 indicating 2 broadcast PDCCH repetitions for repetition CSS 1104 and reference 1110 indicating 2 broadcast PDCCH repetitions for repetition CSS 1106) in 2 repetition CSSs. The two repetition CSSs are indicated by virtual ID = 2 & 4 respectively, and linked by Repetition ID Linked - {2, 4} (see reference 1102). Further, repetition CSS can be mapped on an extended (or additional) CORESET (based on a proposed next update to increase the number of CORESET symbols for the enhancement of PDCCH coverage) for repetition.

[0077]

[0073] Alternatively, gNB can indicate to a UE that there are PDCCH repetitions by using an explicit indication, instead of using implicit indication as linkage. The explicit indication can be based on (a) a spare bit in MIB, (b) reserved bit in PBCH payload, or (c) codepoint in PBCH payload. By receiving the explicit indication in advance, the UE monitors PDCCH repetitions to decode DCI accordingly.

[0078]

[0074] In an implementation, if DMRS resources and broadcast PDCCH resources are decoupled (e g., DMRS resource for repetition indication and broadcast PDCCH resource to be decoded are independent), a UE may be configured to perform a blind decoding of broadcast PDCCH on the candidate resources, assuming repetitions are indicated by the DMRS. For example, a gNB may be configured to transmit 1 resource for DMRS (referring as “#a”) and 1 resource for broadcast PDCCH (referring as #b). The UE may first detect #a to determine whether there is repetition. If the UE detects #a with sequences (e.g., DMRS sequences) that T1 indicates repetition (e g. sequence-4t-l), the UE may then perform a blind decoding of broadcast PDCCH on #b. In another example, #a can be transmitted in a legacy CSS and #b may be transmitted in a repetition CSS. If the UE detected #a with DMRS sequences that indicate repetition, UE may then perform a blind decoding at repetition CSS for #b. Advantageously, the DMRS used for broadcast PDCCH demodulation can also be used by a legacy UE.

[0079]

[0075] Figure 12 shows an exemplary flow chart 1200 for base station (gNB) transmission of repeated broadcast PDCCHs and DMRS sequences according to various embodiments of the present disclosure. In step 1202, one or more sets of specific DMRS sequences may be configured by a gNB. In step 1204, the gNB may be configured to decide the number of repetitions for one or more PDCCH transmission. In step 1206, the gNB may be configured to select the DMRS sequence corresponding to the number of repetitions. In step 1208, the gNB may be configured to transmit repeated broadcast PDCCHs with a selected DMRS sequence.

[0080]

[0076] Figure 13 shows an exemplary flow chart 1300 for UE reception of repeated broadcast PDCCHs and DMRS sequences according to various embodiments of the present disclosure. In step 1302, one or more sets of specific DMRS sequences may be configured or specified to a UE. In step 1304, the UE may be configured to receive broadcast PDCCHs with DMRS sequences In step 1306, the UE may be configured to detect a specific DMRS sequence of the received broadcast PDCCHs to determine the number of repetitions. In step 1308, the UE may be configured to decode the received broadcast PDCCHs (e g., soft combining of the number of repetitions).

[0077] Figure 14 shows an exemplary flow chart 1400 for gNB transmission of repeated broadcast PDCCHs in repetition CSSs according to various embodiments of the present disclosure. In step 1402, a gNB may be configured to decide a number of repetitions for broadcast PDCCHs transmission. In step 1404, the gNB may configure repetition CSSs for repeated broadcast PDCCHs transmission, and a linkage to link the repetition CSSs. For example, each of the repetition CSSs may be identified by a parameter virtual ID, and the linkage which links the CSSs is by a parameter Repetition ID Linked. In step 1406, the gNB may be configured to transmit repeated broadcast PDCCHs in the repetition CSSs.

[0081]

[0078] Figure 15 shows an exemplary flow chart 1500 for UE reception of repeated broadcast PDCCHs in repetition CSSs according to various embodiments of the present disclosure. In step 1502, the UE may be configured to receive signalling of a parameter Repetition ID Linked. In step 1504, the UE may be configured to determine a number of repetitions from the parameter Repetition ID Linked. In step 1506, the UE may be configured to identify the broadcast PDCCHs based on DMRS sequences and perform a soft combining for repeated broadcast PDCCHs (e g., based on the determined number of repetitions) in the linked repetition CSSs. In step 1508, the UE may be configured to decode the received broadcast PDCCHs.

[0082]

[0079] In the following paragraphs, certain exemplifying embodiments are explained with reference to terms related to 5G core network and the present disclosure, namely:

[0083] RRC connection setup and reconfiguration procedures

[0080] Interactions between a UE, gNB, and AMF (an 5GC entity) in the context of a transition of the UE from RRC IDLE to RRC CONNECTED for the NAS part are described (see TS 38.300 vl5.6.0).

[0084]

[0081] RRC is a higher layer signaling (protocol) used for UE and gNB configuration. In particular, this transition involves that the AMF prepares the UE context data (including e.g. PDU session context, the Security Key, UE Radio Capability and UE Security Capabilities, etc.) and sends it to the gNB with the INITIAL CONTEXT SETUP REQUEST. Then, the gNB activates the AS security with the UE, which is performed by the gNB transmitting to the UE a SecurityModeCommand message and by the UE responding to the gNB with the SecurityModeComplete message. Afterwards, the gNB performs the reconfiguration to setup the Signaling Radio Bearer 2, SRB2, and Data Radio Bearer(s), DRB(s) by means of transmitting to the UE the RRCReconfiguration message and, in response, receiving by the gNB the RRCReconfigurationComplete from the UE. For a signalling-only connection, the steps relating to the RRCReconfiguration are skipped since SRB2 and DRBs are not setup. Finally, the gNB informs the AMF that the setup procedure is completed with the INITIAL CONTEXT SETUP RESPONSE.

[0085]

[0082] In the present disclosure, thus, an entity (for example AMF, SMF, etc.) of a 5th Generation Core (5GC) is provided that comprises control circuitry which, in operation, establishes a Next Generation (NG) connection with a gNodeB, and a transmitter which, in operation, transmits an initial context setup message, via the NG connection, to the gNodeB to cause a signaling radio bearer setup between the gNodeB and a user equipment (UE). In particular, the gNodeB transmits a Radio Resource Control, RRC, signaling containing a resource allocation configuration information element to the UE via the signaling radio bearer. The UE then petforms an uplink transmission or a downlink reception based on the resource allocation configuration.

[0086]

[0083] The 5G QoS (Quality of Service) model is based on QoS flows and supports both QoS flows that require guaranteed flow bit rate (GBR QoS flows) and QoS flows that do not require guaranteed flow bit rate (non-GBR QoS Flows). At NAS level, the QoS flow is thus the finest granularity of QoS differentiation in a PDU session. A QoS flow is identified within a PDU session by a QoS flow ID (QFI) carried in an encapsulation header over NG-U interface.

[0087]

[0084] For each UE, 5GC establishes one or more PDU Sessions. For each UE, the NG-RAN establishes at least one Data Radio Bearers (DRB) together with the PDU Session, and additional DRB(s) for QoS flow(s) of that PDU session can be subsequently configured (it is up to NG-RAN when to do so). The NG-RAN maps packets belonging to different PDU sessions to different DRBs. NAS level packet filters in the UE and in the 5GC associate UL and DL packets with QoS Flows, whereas AS-level mapping rules in the UE and in the NG- RAN associate UL and DL QoS Flows with DRBs.

[0088] Open-RAN

[0089]

[0085] The base station described in each exemplary embodiment (for example, a 5G NR base station called gNB) may be formed of three functional modules: Centralized Unit (CU), Distributed Unit (DU), and Radio Unit (RU).

[0090]

[0086] CU may also be referred as, for example, a centralized node, an aggregated node, a centralized station, an aggregated station, or a central unit. DU may also be referred as, for example, O-DU (O-RAN Distributed Unit), a distributed node, a distributed station, or a distributed unit. RU may also be referred as, for example, O-RU (O-RAN Radio Unit), a radio apparatus, a radio node, a radio station, an antenna unit, or a radio unit.

[0091]

[0087] Several split options are defined for the functional split configuration (or functional split point) between CU, DU, and RU. The term “functional split point” may also be referred to as “split”, “option”, or “split option”.

[0092]

[0088] Examples of the “split option” include the following split options 1 to 8. The functionality of the base station described in each exemplary embodiment may be split into functions as CU, DU, and RU by one of the following split options 1 to 8. For example, each of CU, DU, and RU may be subjected to functional splitting or functional splitting only between CU and DU or only between DU and RU is possible.

[0093] (1) Split Option 1: between RRC (radio resource control) and PDCP

[0094] (2) Split Option 2: between PDCP and RLC (High-RLC)

[0095] (3) Split Option 3: between High-RLC and Low-RLC

[0096] (4) Split Option 4: between RLC (Low-RLC) and MAC (High-MAC)

[0097] (5) Split Option 5: between High-MAC and Low-MAC

[0098] (6) Split Option 6: between MAC (Low-MAC) and PHY (High-PHY)

[0099] (7) Split Option 7: between High-PHY and Low-PHY

[0100] (8) Split Option 8: between PHY (Low-PHY) and RF

[0101]

[0089] The functional split point between CU and O-DU may be Split Option 2. The link between CU and O-DU is referred to as midhaul and the Fl interface is defined by the 3GPP. Further, the link between O-DU and O-RU is referred to as fronthaul and its functional split point may be Split Option 7-2x adopted as the 0-RAN fronthaul specifications.

[0102]

[0090] FIG. 16 illustrates an example in which the base station functionality of the gNB is subjected to functional splitting into CU, O-DU, 0-RU by Split Option 2 and Split Option 7- 2x.

[0103]

[0091] CU may include, for example, an RRC (radio resource control) function, an SDAP (service data adaptation protocol) function, and a PDCP (packet data convergence protocol) function.

[0104]

[0092] O-DU may include, for example, an RLC (radio link control) function, a MAC function, and a higher physical layer (HIGH-PHY) function. Further, the HIGH-PHY function may include an encoding function, a scrambling function, a modulation function, a layer mapping function, a precoding function, and an RE (resource element) mapping function for downlink (DL) transmission. The HIGH-PHY function may also include a decoding function, a descrambling function, a demodulation function, a layer demapping function, and an RE (resource element) demapping function for uplink (UL) reception.

[0105]

[0093] 0-RU may include, for example, a LOW-PHY function and an RF function. Further, the LOW-PHY function may include a beamforming function, IFFT (Inverse First Fourier Transform) + CP (Cyclic Prefix) addition functions, and a D / A (Digital to Analog) conversion function for downlink transmission. Further, the LOW-PHY function may include an A / D (Analog to Digital) conversion function, CP removal + FFT (First Fourier Transform) functions, and a beamforming function for uplink reception. [94J Note that, in a case where O-DU does not include the precoding function, O-RU may include the precoding function.

[0106]

[0095] O-RU may include an LBT (listen before Talk)-related function.

[0107]

[0096] eCPRI (Evolved Common Public Radio Interface) is defined as a communication scheme between O-DU and O-RU in Split Option 7-2x.

[0108]

[0097] In Split Option 7-2x, a sampling sequence of the in-phase (I) and quadrature (Q) components of an OFDM signal in the frequency domain as well as information used for beamforming in the antenna, a time synchronization signal, and the like are transmitted and received by eCPRI.

[0109]

[0098] Information transmitted by signals (PDCCH, PUCCH, PDSCH, PUSCH, MAC CE, RRC, and the like) described in each exemplary embodiment may be transmitted by using the User Plane (U-Plan) or Control Plane (C -Plane) of eCPRI between O-DU and O-RU.

[0110]

[0099] In a case where a function described in each exemplary embodiment is executed in O- RU by function splitting, O-DU may control O-RU by transmitting information for controlling the function by means of a control signal (for example, eCPRI) between O-DU and O-RU.

[0111]

[0100] In a case where a function described in each exemplary embodiment is executed by function splitting in O-DU, O-RU may receive a result of the execution of the function in O- DU by means of a control signal (for example, eCPRT) and may control O-RU based on the received result.

[0112]

[0101] CU, 0-DU, and O-RU may be deployed in physically different apparatuses, the respective functions of which are connected by optical fibers or the like, or some or all of the functions may be deployed in a physically identical apparatus.

[0113]

[0102] CU and 0-DU may be logical entities implemented as software operating on a server, such as a cloud, as a virtual Radio Access Network (vRAN). Further, some or all of the functions of CU and O-DU may be provided as services of a Network Functions Virtualization (NFV) function.

[0114]

[0103] The transceiver may not be a radio transceiver and may be, for example, a network transceiver, an optical transceiver, or the like. The radio resource allocated by 0-DU may be a resource for radio communication between O-RU and the UE.

[0115] SBFD

[0116]

[0104] Operations on uplink, downlink, and sidelink symbols in one exemplary embodiment of the present disclosure may be applied to symbols (for example, SBFD (Subband nonoverlapping full duplex) symbols, Subband full duplex) on which an SBFD operation or control is performed. For SBFD symbols, the frequency domain (or frequency resource or frequency bandwidth) is divided into a plurality of frequency domains (also referred to as, for example, sub-bands, RB sets, sub-bandwidths, or sub-BWPs (Bandwidth parts)). The terminal performs transmission and reception in a direction (for example, a downlink or uplink direction) in units of sub-bands that are the divided domains. For SBFD symbols, the terminal may perform transmission / reception in one direction of uplink and downlink directions, and may not perform transmission / reception in the other direction. The base station, on the other hand, may be capable of performing both uplink and downlink transmissions / receptions simultaneously. SBFD symbols may have a fewer frequency domain usable for downlink compared to symbols for which only downlink transmission / reception is performed. Further, SBFD symbols may have a fewer frequency domain usable for uplink compared to symbol for which only uplink transmission / reception is performed.

[0117]

[0105] Further, for SBFD symbols, the terminal may perform uplink and downlink transmissions / receptions simultaneously. At this time, the frequency domain transmitted by the terminal and the frequency domain received by the terminal may not be adjacent and a frequency interval (also referred to as a frequency gap) may be provided therebetween.

[0118]

[0106] Further, sidelink transmission / reception may also be included as a transmission / reception direction in units of sub-bands which are the divided domains.

[0119] XDD: Cross Division Duplex

[0120]

[0107] Operations on uplink, downlink, and sidelink symbols in one exemplary embodiment of the present disclosure may be applied to symbols (for example, Full duplex symbols) on which a Full duplex operation or control is performed. For Full duplex symbols, both the terminal and the base station are capable of performing uplink and downlink transmissions / receptions simultaneously. For Full duplex symbols, the terminal and the base station may operate to perform transmission / reception simultaneously in available frequency domains (or frequency resources or frequency bandwidths) or may operate to perform transmission / reception simultaneously in one or some of frequency domains (that is, may operate to perform transmission or reception in the other frequency domains). At this time, the frequency domain transmitted by the base station or the terminal and the frequency domain received by the base station or the terminal may not be adjacent and a frequency interval (also referred to as a frequency gap) may be provided therebetween. Further, for example, for the purpose of reduction in interference or the like, one of the terminal and the base station may operate to perform transmi ssion / reception simultaneously (that is, the other may operate to perform transmission or reception).

[0121]

[0108] Further, the Full duplex operation may be applied to an operation in which the terminal is capable of performing sidelink transmission / reception simultaneously. Further, the Full duplex operation may be applied to an operation in which the terminal is capable of performing sidelink transmission / reception and uplink or downlink transmission / reception simultaneously.

[0122] Control Signals

[0123]

[0109] In the present disclosure, the downlink control signal (information) related to the present disclosure may be a signal (information) transmitted through PDCCH of the physical layer or may be a signal (information) transmitted through a MAC Control Element (CE) of the higher layer or the RRC. The downlink control signal may be a pre-defined signal (information).

[0124] [HO] The uplink control signal (information) related to the present disclosure may be a signal (information) transmitted through PUCCH of the physical layer or may be a signal (information) transmitted through a MAC CE of the higher layer or the RRC Further, the uplink control signal may be a pre-defined signal (information). The uplink control signal may be replaced with uplink control information (UCT), the 1 st stage sidelink control information

[0125] (SCI) or the 2nd stage SCI.

[0126] Base Station

[0127] |111| In the present disclosure, the base station may be a Transmission Reception Point (TRP), a clusterhead, an access point, a Remote Radio Head (RRH), an eNodeB (eNB), a gNodeB (gNB), aBase Station (BS), aBase Transceiver Station (BTS), a base unit or a gateway, for example. Further, in sidelink communication, a terminal may be adopted instead of a base station. The base station may be a relay apparatus that relays communication between a higher node and a terminal. The base station may be a roadside unit as well. sure may be applied to any of uplink, downlink and sidelink.

[0128]

[0113] The present disclosure may be applied to, for example, uplink channels, such as PUSCH, PUCCH, and PRACH, downlink channels, such as PDSCH, PDCCH, and PBCH, and side link channels, such as Physical Sidelink Shared Channel (PSSCH), Physical Sidelink Control Channel (PSCCH), and Physical Sidelink Broadcast Channel (PSBCH).

[0129] 1114 ] 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. PSCCH and PSSCH are examples of a sidelink control channel and a sidelink data channel, respectively. PBCH and PSBCH are examples of broadcast channels, respectively, and PRACH is an example of a random access channel.

[0130] Data Channels / Control Channels

[0131] |115| The present disclosure may be applied to any of data channels and control channels. The channels in the present disclosure may be replaced with data channels including PDSCH, PUSCH and PSSCH and / or control channels including PDCCH, PUCCH, PBCH, PSCCH, and PSBCH.

[0132] Reference Signals

[0133]

[0116] In the present disclosure, the reference signals are signals known to both a base station and a mobile station and each reference signal may be referred to as a Reference Signal (RS) or sometimes a pilot signal. The reference signal may be any of a 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).

[0134] Time Intervals

[0135]

[0117] In the present disclosure, time resource units are not limited to one or a combination of slots and symbols, and may be time resource units, such as frames, super-frames, subframes, slots, time slot sub-slots, mini-slots, or time resource units, such as symbols, OFDM symbols,

[0136] Single Carrier-Frequency Division Multiplexing Access (SC-FDMA) symbols, or other time resource units. The number of symbols included in one slot is not limited to any number of symbols exemplified in the embodiment(s) described above, and may be other numbers of symbols.

[0137] Bands

[0138] [US] The present disclosure may be applied to any of a licensed band and an unlicensed band.

[0139] Communication

[0140]

[0119] The present disclosure may be applied to any of communication between a base station and a terminal (Uu-link communication), communication between a terminal and a terminal (Sidelink communication), and Vehicle to Everything (V2X) communication, and communication between Ambient loT Reader and Ambient loT Device. The channels in the present disclosure may be replaced with PSCCH, PSSCH, Physical Sidelink Feedback Channel (PSFCH), PSBCH, Physical Reader-to-Device Channel (PRDCH), Physical Device-to-Reader Channel (PDRCH), PDCCH, PUCCH, PDSCH, PUSCH, and PBCH. Control information in the present disclosure may be referred to as DCI, UCI, Sidelink control infromation (SCI), R2D control information or D2R control information.

[0141]

[0120] Tn addition, the present disclosure may be applied to any of a terrestrial network or a network other than a terrestrial network (NTN: Non-Terrestrial Network) using a satellite or a High Altitude Pseudo Satellite (HAPS). In addition, the present disclosure may be applied to a network having a large cell size, and a terrestrial network with a large delay compared with a symbol length or a slot length, such as an ultra-wideband transmission network.

[0142] Antenna Ports

[0143] |121| An antenna port refers to a logical antenna (antenna group) formed of one or more physical antenna(s). That is, the antenna port does not necessarily refer to one physical antenna and sometimes refers to an array antenna formed of multiple antennas or the like. For example, it is not defined how many physical antennas form the antenna port, and instead, the antenna port is defined as the minimum unit through which a terminal is allowed to transmit a reference signal. The antenna port may also be defined as the minimum unit for multiplication of a precoding vector weighting.

[0144]

[0122] The present disclosure can be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of each embodiment described above can be partly or entirely realized by an LSI such as an integrated circuit, and each process described in each embodiment may be controlled partly or entirely by the same LSI or a combination of LSIs. The LSI may be individually formed as chips, or one chip may be formed so as to include a part or all of the functional blocks. The LSI may include a data input and output coupled thereto. The LSI here may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI depending on a difference in the degree of integration. However, the technique of implementing an integrated circuit is not limited to the LSI and may be realized by using a dedicated circuit, a general -purpose processor, or a special -purpose processor. In addition, a FPGA (Field Programmable Gate Array) that can be programmed after the manufacture of the LSI or a reconfigurable processor in which the connections and the settings of circuit cells disposed inside the LSI can be reconfigured may be used. The present disclosure can be realized as digital processing or analogue processing. If future integrated circuit technology replaces LSIs as a result of the advancement of semiconductor technology or other derivative technology, the functional blocks could be integrated using the future integrated circuit technology. Biotechnology can also be applied.

[0145]

[0123] The present disclosure can be realized by any kind of apparatus, device or system having a function of communication, which is referred to as a communication apparatus.

[0146]

[0124] The communication apparatus may comprise a transceiver and processing / control circuitry The transceiver may comprise and / or function as a receiver and a transmitter The transceiver, as the transmitter and receiver, may include an RF (radio frequency) module including amplifiers, RF modulators / demodulators and the like, and one or more antennas.

[0147]

[0125] Some non-limiting examples of such a communication apparatus include a phone (e.g., cellular (cell) phone, smart phone), a tablet, a personal computer (PC) (e.g., laptop, desktop, netbook), a camera (e.g., digital still / video camera), a digital player (digital audio / video player), a wearable device (e.g., wearable camera, smart watch, tracking device), a game console, a digital book reader, a telehealth / telemedicine (remote health and medicine) device, and a vehicle providing communication functionality (e g., automotive, airplane, ship), and various combinations thereof.

[0148]

[0126] The communication apparatus is not limited to be portable or movable, and may also include any kind of apparatus, device or system being non-portable or stationary, such as a smart home device (e g., an appliance, lighting, smart meter, control panel), a vending machine, and any other “things” in a network of an “Internet of Things (loT)”.

[0149]

[0127] The communication may include exchanging data through, for example, a cellular system, a wireless LAN system, a satellite system, etc., and various combinations thereof.

[0150]

[0128] The communication apparatus may comprise a device such as a controller or a sensor which is coupled to a communication device performing a function of communication described in the present disclosure. For example, the communication apparatus may comprise a controller or a sensor that generates control signals or data signals which are used by a communication device performing a communication function of the communication apparatus.

[0151]

[0129] The communication apparatus also may include an infrastructure facility, such as a base station, an access point, and any other apparatus, device or system that communicates with or controls apparatuses such as those in the above non-limiting examples.

[0152]

[0130] According to the present disclosure, various examples below have been described:

[0153] 1. A first communication apparatus comprising: circuitry, which in operation, determines a number of one or more repetitions of physical downlink control channel (PDCCH) transmitted from a second communication apparatus, the number of one or more repetitions of PDCCH being determined based on a demodulation reference signal (DMRS) sequence transmitted from the second communication apparatus and / or based on a repetition common search space (CSS) associated with the one or more repetitions of PDCCH; and a receiver, which in operation, receives the one or more repetitions of PDCCH from the second communication apparatus based on the determination.

[0154] 2. The first communication apparatus of example 1, wherein the circuitry is configured to determine the number of the one or more repetitions of PDCCH based on an offset value added in a generation of the DMRS sequence.

[0155] 3. The first communication apparatus of example 2, wherein the offset value is 0 when the number of the one or more repetitions of PDCCH is 1, and the offset value is not 0 when the number of the one or more repetitions of PDCCH is more than 1.

[0156] 4. The first communication apparatus of example 2, wherein the offset value is added to a cell identifier used for the generation of the DMRS sequence or is added to a pseudo-random sequence used for the generation of the DMRS sequence.

[0157] 5. The first communication apparatus of example 1, wherein the circuitry is further configured to determine the number of the one or more repetitions of PDCCH based on one or more sets of DMRS sequences.

[0158] 6. The first communication apparatus of example 5, wherein each DMRS sequence within a same set of DMRS sequences indicates a same number of repetitions of PDCCH.

[0159] 7. The first communication apparatus of example 1, wherein each DMRS sequence within a first set of DMRS sequences indicates a number of repetitions of PDCCH that is different from that indicated by each DMRS sequence within a second set of DMRS sequences. 8. The first communication apparatus of example 7, wherein a number of DMRS sequences in the first set is equal to or larger than a number of DMRS sequences in the second set, and the number of the repetitions of PDCCH corresponding to the first set is smaller than the number of the repetitions of PDCCH corresponding to the second set.

[0160] 9. The first communication apparatus of example 7, wherein a number of DMRS sequence in the first set is equal to or larger than a number of DMRS sequence in the second set, and the number of the repetitions of PDCCH corresponding to the first set is larger than the number of the repetitions of PDCCH corresponding to the second set.

[0161] 10. The first communication apparatus of example 5, wherein each set of DMRS sequences indicates a different resource allocation, the resource allocation being a time division multiplexing (TDM), a frequency division multiplexing (FDM), or a mixed allocation comprising both TDM and FDM.

[0162] 11. The first communication apparatus of example 1, wherein the circuitry is further configured to determine a resource or a division multiplexing method of the one or more repetitions of PDCCH based on the DMRS sequence, wherein the resource of the one or more repetitions of PDCCH is different between a first set of one or more DMRS sequences and a second set of one or more DMRS sequences.

[0163] 12. The first communication apparatus of example 1, wherein the DMRS sequence is predefined in technical specifications, and / or configured in a Master Information Block (MIB) or a System Information Block (SIB). 13. The first communication apparatus of example 1, wherein the one or more repetitions of

[0164] PDCCH are time division multiplexed (TDMed), frequency division multiplexed (FDMed), or both TDMed and FDMed.

[0165] 14. The first communication apparatus of example 1, wherein the circuitry is further configured to perform a blind detection of the DMRS sequence on each candidate resource in the CSS, and combine the received one or more repetitions of PDCCH based on the determined number of repetitions from the detected DMRS sequence.

[0166] 15. The first communication apparatus of example 1 , wherein the circuitry is further configured to determine the number of repetitions of PDCCH from a plurality of the repetition CSS, each repetition CSS carrying a repetition PDCCH.

[0167] 16. The first communication apparatus of example 1, wherein at least one repetition of PDCCH in one of the plurality of CSS is larger than that in a user equipment specific search space (USS).

[0168] 17. The first communication apparatus of example 1, wherein the receiver is further configured to receive the DMRS sequence in a first resource and the one or more repetitions of PDCCH in a second resource.

[0169] 18. The first communication apparatus of example 1 , wherein the receiver is further configured to receive a legacy CSS in a first resource and the repetition CSS in a second resource.

[0170] 19. A second communication apparatus comprising: circuitry, which in operation, generates a demodulation reference signal (DMRS) sequence and / or configures a repetition common search space (CSS) based on a number of one or more repetitions of physical downlink control channel (PDCCH); and a transmitter, which in operation, transmits the one or more repetitions of PDCCH, and transmits the DMRS sequence and / or repetition CSS to a first communication apparatus.

[0171] 20. The second communication apparatus of example 19, wherein the circuitry is configured to determine the number of the one or more repetitions of PDCCH based on an offset value added in the generation of the DMRS sequence.

[0172] 21. The second communication apparatus of example 20, wherein the offset value is 0 when the number of the one or more repetitions of PDCCH is 1, and the offset value is not 0 when the number of the one or more repetitions of PDCCH is more than 1.

[0173] 22. The second communication apparatus of example 21, wherein the offset value is added to a cell identifier used for the generation of the DMRS sequence or is added to a pseudo-random sequence used for the generation of the DMRS sequence.

[0174] 23. The second communication apparatus of example 19, wherein the circuitry is further configured to determine one or more sets of DMRS sequences based on the number of the one or more repetitions of PDCCH.

[0175] 24. The second communication apparatus of example 23, wherein each DMRS sequence within a same set of DMRS sequences indicates a same number of repetitions. 25. The second communication apparatus of example 23, wherein each set of DMRS sequences indicates a different resource allocation, the resource allocation being a time division multiplexing (TDM), a frequency division multiplexing, or a mixed allocation comprising both TDM and FDM.

[0176] 26. The second communication apparatus of example 19, wherein the DMRS sequence is predefined in technical specifications, and / or configured in a Master Information Block (MIB) or a System Information Block (SIB).

[0177] 27. The second communication apparatus of example 19, wherein the one or more repetitions ofPDCCH are time division multiplexed (TDMed), frequency division multiplexed (FDMed), or both TDMed and FDMed.

[0178] 28. The second communication apparatus of example 19, wherein the circuitry further configures a plurality of the repetition CSS based on the number of repetition PDCCH, each repetition CSS carrying a repetition PDCCH.

[0179] 29. The second communication apparatus of example 19, wherein at least one repetition of PDCCH in one of the plurality of CSS is larger than that in a user equipment specific search space (USS).

[0180] 30. The second communication apparatus of example 19, wherein the transmitter is further configured to transmit the DMRS sequence in a first resource and the one or more repetitions ofPDCCH in a second resource. 31. The second communication apparatus of example 19, wherein the transmitter is further configured to transmit a legacy CSS in a first resource and the repetition CSS in a second resource.

[0181] 32. A communication method implemented by a first communication apparatus comprising: determining a number of one or more repetitions of physical downlink control channel (PDCCH) transmitted from a second communication apparatus, the number of the one or more repetitions of PDCCH being determined based on a demodulation reference signal (DMRS) sequence transmitted from the second communication apparatus and / or a repetition common search space (CSS) associated with the one or more repetitions of PDCCH; and receiving the one or more repetitions of PDCCH from the second communication apparatus based on the determination.

[0182] 33. A communication method implemented by a second communication apparatus comprising: generating a demodulation reference signal (DMRS) sequence and / or configuring a repetition common search space (CSS) based on a number of one or more repetitions of physical downlink control channel (PDCCH); and transmitting the one or more repetitions of PDCCH and the DMRS and / or repetition CSS to a first communication apparatus.

[0183]

[0131] It will be appreciated by a person skilled in the art that numerous variations and / or modifications may be made to the present disclosure as shown in the specific embodiments without departing from the spirit or scope of the disclosure as broadly described. The present embodiments are, therefore, to be considered in all respects illustrative and not restrictive.

Claims

CLAIMS1. A first communication apparatus comprising: circuitry, which in operation, determines a number of one or more repetitions of physical downlink control channel (PDCCH) transmitted from a second communication apparatus, the number of one or more repetitions of PDCCH being determined based on a demodulation reference signal (DMRS) sequence transmitted from the second communication apparatus and / or based on a repetition common search space (CSS) associated with the one or more repetitions of PDCCH; and a receiver, which in operation, receives the one or more repetitions of PDCCH from the second communication apparatus based on the determination.

2. The first communication apparatus of claim 1, wherein the circuitry is configured to determine the number of the one or more repetitions of PDCCH based on an offset value added in a generation of the DMRS sequence.

3. The first communication apparatus of claim 2, wherein the offset value is 0 when the number of the one or more repetitions of PDCCH is 1, and the offset value is not 0 when the number of the one or more repetitions of PDCCH is more than 1.

4. The first communication apparatus of claim 2, wherein the offset value is added to a cell identifier used for the generation of the DMRS sequence or is added to a pseudo-random sequence used for the generation of the DMRS sequence.

5. The first communication apparatus of claim 1 , wherein the circuitry is further configured to determine the number of the one or more repetitions of PDCCH based on one or more sets of DMRS sequences.

6. The first communication apparatus of claim 5, wherein each DMRS sequence within a same set of DMRS sequences indicates a same number of repetitions of PDCCH.

7. The first communication apparatus of claim 1, wherein each DMRS sequence within a first set of DMRS sequences indicates a number of repetitions of PDCCH that is different from that indicated by each DMRS sequence within a second set of DMRS sequences.

8. The first communication apparatus of claim 7, wherein a number of DMRS sequences in the first set is equal to or larger than a number of DMRS sequences in the second set, and the number of the repetitions of PDCCH corresponding to the first set is smaller than the number of the repetitions of PDCCH corresponding to the second set.

9. The first communication apparatus of claim 7, wherein a number of DMRS sequence in the first set is equal to or larger than a number of DMRS sequence in the second set, and the number of the repetitions of PDCCH corresponding to the first set is larger than the number of the repetitions of PDCCH corresponding to the second set.

10. The first communication apparatus of claim 5, wherein each set of DMRS sequences indicates a different resource allocation, the resource allocation being a time division multiplexing (TDM), a frequency division multiplexing (FDM), or a mixed allocation comprising both TDM and FDM.

11. The first communication apparatus of claim 1, wherein the circuitry is further configured to determine a resource or a division multiplexing method of the one or more repetitions of PDCCH based on the DMRS sequence, wherein the resource of the one or more repetitions of PDCCH is different between a first set of one or more DMRS sequences and a second set of one or more DMRS sequences.

12. A second communication apparatus comprising: circuitry, which in operation, generates a demodulation reference signal (DMRS) sequence and / or configures a repetition common search space (CSS) based on a number of one or more repetitions of physical downlink control channel (PDCCH) ; and a transmitter, which in operation, transmits the one or more repetitions of PDCCH, and transmits the DMRS sequence and / or repetition CSS to a first communication apparatus.

13. The second communication apparatus of claim 12, wherein the circuitry is configured to determine an offset value to be added in the generation of the DMRS sequence based on the number of the one or more repetitions of PDCCH.

14. The second communication apparatus of claim 13, wherein the offset value is 0 when the number of the one or more repetitions of PDCCH is 1, and the offset value is not 0 when the number of the one or more repetitions of PDCCH is more than 1 .

15. The second communication apparatus of claim 16, wherein the offset value is added to a cell identifier used for the generation of the DMRS sequence or is added to a pseudorandom sequence used for the generation of the DMRS sequence.

16. The second communication apparatus of claim 12, wherein the circuitry is further configured to determine one or more sets of DMRS sequences based on the number of the one or more repetitions of PDCCH.

17. The second communication apparatus of claim 16, wherein each DMRS sequence within a same set of DMRS sequences indicates a same number of repetitions of PDCCH.

18. The second communication apparatus of claim 16, wherein each set of DMRS sequences indicates a different resource allocation, the resource allocation being a time division multiplexing (TDM), a frequency division multiplexing, or a mixed allocation comprising both TDM and TDM.

19. A communication method implemented by a first communication apparatus comprising: determining a number of one or more repetitions of physical downlink control channel (PDCCH) transmitted from a second communication apparatus, the number of the one or more repetitions of PDCCH being determined based on a demodulation reference signal (DMRS) sequence transmitted from the second communication apparatus and / or a repetition common search space (CSS) associated with the one or more repetitions of PDCCH; and receiving the one or more repetitions of PDCCH from the second communication apparatus based on the determination.

20. A communication method implemented by a second communication apparatus comprising:generating a demodulation reference signal (DMRS) sequence and / or configuring a repetition common search space (CSS) based on a number of one or more repetitions of physical downlink control channel (PDCCH); and transmitting the one or more repetitions of PDCCH and the DMRS and / or repetition CSS to a first communication apparatus.

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