CN115834314A - Arrangement in a base station - Google Patents

Abstract

An apparatus for use in a base station, comprising a processor circuit configured to cause the base station to: mapping Physical Downlink Control Channel (PDCCH) candidates for one or more User Equipments (UEs) to time and frequency resources of a control resource set (CORESET); mapping a demodulation reference signal (DMRS) sequence shared to the PDCCH candidate to a time resource of CORESET and a frequency resource of CORESET or a bandwidth part (BWP) associated with CORESET; and transmitting the PDCCH candidates and the DMRS sequences to the one or more UEs by using CORESET, wherein the PDCCH candidates and the DMRS sequences are time-division multiplexed, and frequency resources for PDCCH candidates having a non-maximum Aggregation Level (AL) are entirely included in frequency resources for PDCCH candidates having a maximum AL.

Description

Arrangement in a base station

Cross Reference to Related Applications

This application is based on and claims priority from U.S. application No.63/245,137, filed 9/16/2021, the entire contents of which are incorporated herein by reference.

Technical Field

Embodiments of the present disclosure relate generally to the field of wireless communications, and more particularly, to an apparatus for use in a base station.

Background

Mobile communications have evolved from early speech systems to today's highly sophisticated integrated communication platforms. A 5G or New Radio (NR) wireless communication system will provide access to information and sharing of data by various users and applications anytime and anywhere.

Drawings

Embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings in which like reference numerals refer to similar elements.

Fig. 1 shows a flow diagram of a PDCCH transmission method according to some embodiments of the present disclosure.

Fig. 2A-2C illustrate diagrams of multiplexing DMRS sequences and PDCCH candidates within different DFT-s-OFDM symbols in a TDM manner when DFT-s-OFDM waveforms are used for PDCCH transmission according to some embodiments of the present disclosure.

Fig. 2D illustrates a schematic diagram of multiplexing DMRS sequences and PDCCH candidates within the same DFT-s-OFDM symbol in a TDM manner when a DFT-s-OFDM waveform is used for PDCCH transmission according to some embodiments of the present disclosure.

Fig. 3A-3C illustrate diagrams of pre-configured DMRS patterns when DMRS sequences and PDCCH candidates are TDM-multiplexed and DFT-s-OFDM symbols are used for PDCCH transmission, according to some embodiments of the present disclosure.

Fig. 4 shows a schematic diagram of a network according to various embodiments of the present disclosure.

Fig. 5 shows a schematic diagram of a wireless network in accordance with various embodiments of the present disclosure.

Fig. 6 illustrates a block diagram of components capable of reading instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and performing any one or more of the methodologies discussed herein, in accordance with various embodiments of the present disclosure.

Detailed Description

Various aspects of the illustrative embodiments will be described using terms commonly employed by those skilled in the art to convey the substance of the disclosure to others skilled in the art. It will be apparent, however, to one skilled in the art that many alternative embodiments can be practiced using portions of the described aspects. For purposes of explanation, specific numbers, materials, and configurations are set forth in order to provide a thorough understanding of the illustrative embodiments. It will be apparent, however, to one skilled in the art that alternative embodiments may be practiced without these specific details. In other instances, well-known features may be omitted or simplified in order not to obscure the illustrative embodiments.

Further, various operations will be described as multiple discrete operations in turn, in a manner that is most helpful in understanding the illustrative embodiments; however, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.

The phrases "in an embodiment," "in one embodiment," and "in some embodiments" are used repeatedly herein. Such phrases are generally not referring to the same embodiment; however, they may also refer to the same embodiment. The terms "comprising," "having," and "including" are synonymous, unless the context dictates otherwise. The phrases "A or B" and "A/B" mean "(A), (B), or (A and B)".

Currently, system designs for 5G wireless communication systems target carrier frequencies up to 52.6GHz and have the following waveform choices: cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) is employed for Downlink (DL) and Uplink (UL); in addition, discrete Fourier transform spread OFDM (DFT-s-OFDM) is employed for the UL. However, for carrier frequencies above 52.6GHz, the need for a single-carrier based waveform is anticipated in order to address issues including low Power Amplifier (PA) efficiency and large phase noise.

In a 5G wireless communication system, a control resource set (CORESET) is defined as a set of one, two, or three OFDM symbols and Resource Element Groups (REGs), where one or more User Equipments (UEs) may attempt to blind decode downlink control information in CORESET, REGs are defined as a Physical Resource Block (PRB) and one OFDM symbol, and 6 REGs form a Control Channel Element (CCE) used as a resource allocation unit for Physical Downlink Control Channel (PDCCH) candidates. Furthermore, a set of CCEs may be used for transmission of a certain PDCCH candidate, and the number of CCEs used for transmission of the PDCCH candidate is defined as an Aggregation Level (AL) for the PDCCH candidate.

In a 5G wireless communication system, the control search space is defined as a set of PDCCH candidates with a particular AL. Each control search space is associated with a single CORESET, and multiple control search spaces may be associated with the same CORESET. In this case, different control search spaces associated with a given CORESET may have different periodicities for monitoring by a User Equipment (UE). The UE needs to monitor PDCCH candidates with different aggregation levels transmitted from a next generation node B (gNB) to detect and receive the PDCCH, and PDCCH decoding relies only on demodulation reference signal (DMRS) sequences associated with the PDCCH candidates transmitted from the gNB. From a UE processing perspective, channel estimation sharing between PDCCH candidates with different ALs may be beneficial.

Fig. 1 shows a flow diagram of a PDCCH transmission method 100 according to some embodiments of the present disclosure. As shown in fig. 1, a PDCCH transmission method 100 includes: s102, mapping PDCCH candidates for one or more UEs to time and frequency resources of CORESET; s104, mapping a demodulation reference signal (DMRS) sequence shared to the PDCCH candidates to time resources of CORESET and frequency resources of CORESET or a bandwidth part (BWP) associated with CORESET; and S106, transmitting the PDCCH candidates and DMRS sequences to one or more UEs by using CORESET, wherein the PDCCH candidates and DMRS sequences are time division multiplexed, and frequency resources for PDCCH candidates with non-maximum AL are completely included in frequency resources for PDCCH candidates with maximum AL.

In the PDCCH transmission method 100, since DMRS sequences are shared by PDCCH candidates and frequency resources for PDCCH candidates having non-maximum AL are entirely included in frequency resources for PDCCH candidates having maximum AL, channel estimation sharing between PDCCH candidates having different AL can be achieved, and thus channel estimation complexity can be reduced. In other words, since the channel estimation for the PDCCH candidate with the largest AL may be repeated for all other PDCCH candidates with non-largest AL, and the channel estimation for the PDCCH candidates with non-largest AL may be repeated for the part of the PDCCH candidates with larger AL, the channel estimation complexity may be reduced.

In some embodiments, to preserve the low peak-to-average power ratio (PAPR) characteristic of PDCCH transmissions, DFT-s-OFDM waveforms are used for transmission of PDCCH candidates. In this case, the PDCCH candidates may be multiplexed within different DFT-s-OFDM symbols or the same DFT/s-OFDM symbol in a Time Division Multiplexing (TDM) manner.

In some embodiments, the PDCCH candidates are all mapped to frequency resources in the CORESET starting from a common frequency resource starting point, and the common frequency resource index associated with the common frequency resource starting point may be obtained according to a randomization distribution function.

In some embodiments, DMRS sequences for PDCCH candidates with non-maximum AL are always part of the DMRS sequences for PDCCH candidates with maximum AL.

In some embodiments, the starting point of the frequency resource for the frequency resource of the PDCCH candidate with non-maximum AL is different from the starting point of the frequency resource for the frequency resource of the PDCCH candidate with maximum AL.

In some embodiments, the association between the AL for PDCCH candidates is configured by higher layers via Radio Resource Control (RRC) signaling, e.g., as part of the search space configuration associated with CORESET.

Fig. 2A illustrates a schematic diagram of multiplexing DMRS sequences and PDCCH candidates within different DFT-s-OFDM symbols in a TDM fashion when DFT-s-OFDM waveforms are used for PDCCH transmission, according to some embodiments of the present disclosure. As shown in fig. 2A, different PDCCH candidates for the same UE or different PDCCH candidates for different UEs are transmitted in different DFT-s-OFDM symbols, and frequency resources for the PDCCH candidates are the same. The same AL may be used for PDCCH candidatesAnd (5) transmitting. Alternatively, a different AL may be used for transmission of PDCCH candidates, but to allow the same frequency allocation to PDCCH candidates, the AL for one PDCCH candidate may be 2 of the AL for another PDCCH candidate ^N And N is an integer greater than 0. Any association between the ALs for PDCCH candidates may be configured by higher layers and may help reduce the number of blind decoding attempts and channel estimation burden for a given UE.

Fig. 2B-2C also illustrate schematics of multiplexing DMRS sequences and PDCCH candidates within different DFT-s-OFDM symbols in a TDM manner when DFT-s-OFDM waveforms are used for PDCCH transmission, according to some embodiments of the present disclosure. As shown in fig. 2B to 2C, different PDCCH candidates for the same UE or different PDCCH candidates for different UEs are transmitted in different DFT-s-OFDM symbols, and frequency resources for the PDCCH candidates are different. For example, the frequency resources for a first PDCCH candidate may comprise frequency resources for a second PDCCH candidate. In this case, the frequency resource for the DMRS sequence may be the same as or may include the frequency resource for the first PDCCH candidate. For example, the frequency resources used for DMRS sequences may span the entire frequency domain of CORESET.

For the TDM option shown in fig. 2A to 2C, PDCCH candidates require separate Discrete Fourier Transform (DFT) or Inverse Discrete Fourier Transform (IDFT) operations. Frequency-first mapping may be used for transmission of PDCCH candidates. Since the frequency domain allocation for different PDCCH candidates is the same and there is no difference in DMRS sequences between different DFT-s-OFDM symbols in the time domain, the frequency domain channel estimation burden does not increase proportionally with the number of PDCCH candidates. In particular, one frequency domain channel estimate may be reused for different PDCCH candidates located in different time resources.

Fig. 2D illustrates a schematic diagram of multiplexing DMRS sequences and PDCCH candidates within the same DFT-s-OFDM symbol in a TDM manner when a DFT-s-OFDM waveform is used for PDCCH transmission according to some embodiments of the present disclosure. As shown in fig. 2D, different PDCCH candidates for the same UE or different PDCCH candidates for different UEs are multiplexed in a TDM manner before the DFT operation. This means that different PDCCH candidates can be multiplexed within one DFT-s-OFDM symbol even in a TDM manner. The DFT size for a PDCCH candidate may be configured by higher layers (where the association between the ALs for different PDCCH candidates may be configured by higher layers via RRC signaling, e.g., as part of the search space configuration), or determined according to the AL for different PDCCH candidates (e.g., the union of the ALs for different PDCCHs may be used for DFT sizes) or the frequency domain size of CORESET. For example, the DFT size for a PDCCH candidate is equal to the frequency domain size of CORESET, and in order to multiplex the PDCCH candidate in the same CORESET in a TDM manner, a wideband DMRS sequence may be inserted in the CORESET, wherein frequency resources for the DMRS sequence span the entire frequency domain of the CORESET. The DMRS sequence may then be used for channel estimation of PDCCH candidates in the same CORESET. In this case, the frequency domain allocations for different PDCCH candidates are the same, and since there is no difference in DMRS sequences between CCEs in the time domain, the channel estimation burden may not scale with the number of CCEs. In particular, one channel estimate in the frequency domain may be reused for different PDCCH candidates located in different time resources.

It should be noted that while it may be feasible to multiplex different PDCCH candidates for the same UE in a TDM manner before the DFT operation from the perspective of a single UE, the TDM option shown in fig. 2D may be complex for the case of multiplexing PDCCH candidates for different UEs, particularly for high-band operation. In particular, since different UEs may be located in different cell locations experiencing different channel conditions, different beamforming needs to be performed for the different UEs. This complicates the multiplexing of TDM fashion from a power control perspective. Also, the TDM option shown in fig. 2D may be practical for a single UE with different PDCCH candidates, or for the case where multiple UEs are physically close enough and have similar transmit power. The AL of different PDCCH candidates for the same UE may be correlated together to reduce blind decoding attempts.

Fig. 3A illustrates a schematic diagram of a pre-configured DMRS pattern when DMRS sequences and PDCCH candidates are TDM-multiplexed and DFT-s-OFDM waveforms are used for PDCCH transmission, according to some embodiments of the present disclosure. As shown in fig. 3A, DMRS sequences are dedicated to PDCCH candidates, frequency resources for PDCCH candidates are different, and the frequency resources for DMRS sequences include the frequency resource for the PDCCH candidate with the largest AL. For example, the frequency resources used for DMRS sequence splitting may span the entire frequency domain of CORESET, and the UE only needs to generate DMRS sequences and perform channel estimation once for all PDCCH candidates.

Fig. 3B also shows a schematic diagram of a pre-configured DMRS pattern when DMRS sequences and PDCCH candidates are TDM-multiplexed and DFT-s-OFDM waveforms are used for PDCCH transmission, according to some embodiments of the present disclosure. As shown in fig. 3B, DMRS sequences are dedicated to PDCCH candidates, the frequency resources used for PDCCH candidates are the same, and the frequency resources used for DMRS sequences and the frequency resources used for PDCCH candidates are the same. In this case, the UE may generate a DMRS sequence and perform channel estimation once for all PDCCH candidates.

Fig. 3C also shows a schematic diagram of a pre-configured DMRS pattern when DMRS sequences and PDCCH candidates are TDM-multiplexed and DFT-s-OFDM waveforms are used for PDCCH transmission, according to some embodiments of the present disclosure. As shown in fig. 3C, DMRS sequences are shared to PDCCH candidates and a Physical Downlink Shared Channel (PDSCH), frequency resources for PDCCH candidates partially overlap or do not overlap with frequency resources for PDSCH, and frequency resources for DMRS sequences include frequency resources for both PDCCH candidates and PDSCH. In this case, the frequency resources for the DMRS sequence may span the entire frequency domain of a bandwidth part (BWP) associated with CORESET.

Fig. 4-5 illustrate various systems, devices, and components that can implement aspects of the disclosed embodiments.

Fig. 4 shows a schematic diagram of a network 400 according to various embodiments of the present disclosure. The network 400 may operate in accordance with 3GPP technical specifications for Long Term Evolution (LTE) or 5G/NR systems. However, the exemplary embodiments are not limited in this respect and the described embodiments may be applied to other networks that benefit from the principles described herein, such as future 3GPP systems and the like.

Network 400 may include a UE 402, which may include any mobile or non-mobile computing device designed to communicate with a Radio Access Network (RAN) 404 via an over-the-air connection. The UE 402 may be, but is not limited to, a smart phone, a tablet computer, a wearable computer device, a desktop computer, a laptop computer, an in-vehicle infotainment device, an in-vehicle entertainment device, a dashboard, a heads-up display device, an on-board diagnostic device, a dashboard mobile device, a mobile data terminal, an electronic engine management system, an electronic/engine control unit, an electronic/engine control module, an embedded system, a sensor, a microcontroller, a control module, an engine management system, a network device, a machine-to-machine (M2M) or device-to-device (D2D) device, an internet of things (IoT) device, and/or the like.

In some embodiments, network 400 may include multiple UEs directly coupled to each other through a sidelink interface. The UE may be an M2M/D2D device that communicates using a physical sidelink channel (e.g., without limitation, a Physical Sidelink Broadcast Channel (PSBCH), a Physical Sidelink Discovery Channel (PSDCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Fundamental Channel (PSFCH), etc.).

In some embodiments, the UE 402 may also communicate with an Access Point (AP) 406 over an over-the-air connection. The AP 406 may manage Wireless Local Area Network (WLAN) connections that may be used to offload some/all network traffic from the RAN 404. The connection between the UE 402 and the AP 406 may be in accordance with any IEEE 802.11 protocol, where the AP 406 may be wireless fidelity

A router. In some embodiments, the UE 402, RAN 404, and AP 406 may utilize cellular WLAN aggregation (e.g., LTE-WLAN aggregation (LWA)/lightweight IP (LWIP)). Cellular WLAN aggregation may involve configuration by the RAN 404 of the UE 402 to utilize both cellular radio resources and WLAN resources.

The RAN 404 may include one or more access nodes, such as AN Access Node (AN) 408. The AN 408 may terminate air interface protocols of the UE 402 by providing access stratum protocols including a Radio Resource Control (RRC) protocol, a Packet Data Convergence Protocol (PDCP), a Radio Link Control (RLC) protocol, a Medium Access Control (MAC) protocol, and AN L1 protocol. In this manner, AN 408 may enable a data/voice connection between Core Network (CN) 420 and UE 402. In some embodiments, AN 408 may be implemented in a discrete device or as one or more software entities running on a server computer (as part of a virtual network, for example, which may be referred to as a distributed RAN (CRAN) or virtual baseband unit pool). AN 408 may be referred to as a Base Station (BS), a next generation base station (gNB), a RAN node, AN evolved node B (eNB), a next generation eNB (ng-eNB), a node B (NodeB), a roadside unit (RSU), a transmit receive point (TRxP), a transmit point (TRP), etc. AN 408 may be a macrocell base station or a low power base station that provides for microcells, picocells, or other similar cells having smaller coverage areas, smaller user capacities, or higher bandwidths than macrocells.

In embodiments where the RAN 404 comprises multiple ANs, the ANs may be coupled to each other over AN X2 interface (if the RAN 404 is AN LTE RAN) or AN Xn interface (if the RAN 404 is a 5G RAN). In some embodiments, the X2/Xn interface, which may be separated into a control/user plane interface, may allow the AN to communicate information related to handover, data/context transfer, mobility, load management, interference coordination, and the like.

The AN of the RAN 404 may each manage one or more cells, groups of cells, component carriers, etc., to provide the UE 402 with AN air interface for network access. The UE 402 may be simultaneously connected with multiple cells provided by the same or different ANs of the RAN 404. For example, the UE 402 and the RAN 404 may use carrier aggregation to allow the UE 402 to connect with multiple component carriers, each corresponding to a primary cell (PCell) or a secondary cell (SCell). In a dual connectivity scenario, the first AN may be a master node providing a Master Cell Group (MCG) and the second AN may be a secondary node providing a Secondary Cell Group (SCG). The first/second AN can be any combination of eNB, gNB, ng-eNB, etc.

The RAN 404 may provide an air interface over a licensed spectrum or an unlicensed spectrum. To operate in unlicensed spectrum, a node may use a License Assisted Access (LAA), enhanced LAA (eLAA), and/or further enhanced LAA (feLAA) mechanism based on the Carrier Aggregation (CA) technology of PCell/Scell. Prior to accessing the unlicensed spectrum, the node may perform a medium/carrier sensing operation based on, for example, a Listen Before Talk (LBT) protocol.

In a vehicle-to-everything (V2X) scenario, the UE 402 or AN 408 may be or act as a Road Side Unit (RSU), which may refer to any transport infrastructure entity for V2X communication. The RSU may be implemented in or by AN appropriate AN or stationary (or relatively stationary) UE. An RSU implemented in or by a UE may be referred to as a "UE-type RSU"; an RSU implemented in or by an eNB may be referred to as an "eNB-type RSU"; an RSU implemented in or by a next generation NodeB (gNB) may be referred to as a "gNB-type RSU" or the like. In one example, the RSU is a computing device coupled with radio frequency circuitry located at the curb side that provides connection support to passing vehicle UEs. The RSU may also include internal data storage circuitry for storing intersection map geometry, traffic volume statistics, media, and applications/software for sensing and controlling ongoing vehicle and pedestrian traffic. The RSU may provide very low latency communications required for high speed events (e.g., collision avoidance, traffic warnings, etc.). Additionally or alternatively, the RSU may provide other cellular/WLAN communication services. The components of the RSU may be enclosed in a weatherproof enclosure suitable for outdoor installation and may include a network interface controller to provide a wired connection (e.g., ethernet) to a traffic signal controller or backhaul network.

In some embodiments, the RAN 404 may be an LTE RAN 410, including an evolved node B (eNB), e.g., eNB 412. The LTE RAN 410 may provide an LTE air interface with the following characteristics: subcarrier spacing (SCS) of 15 kHz; a single carrier frequency division multiple access (SC-FDMA) waveform for Uplink (UL) and a cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) waveform for Downlink (DL); turbo codes for data and tail-biting convolutional codes (TBCC) for control, etc. The LTE air interface may rely on channel state information reference signals (CSI-RS) for CSI acquisition and beam management; performing Physical Downlink Shared Channel (PDSCH)/Physical Downlink Control Channel (PDCCH) demodulation by relying on a DMRS for PDSCH/PDCCH demodulation; and relying on Cell Reference Signals (CRS) for cell search and initial acquisition, channel quality measurements, and channel estimation, and on channel estimation for coherent demodulation/detection at the UE. The LTE air interface may operate on the 6GHz sub-band.

In some embodiments, RAN 404 may be a Next Generation (NG) -RAN 414 with a gNB (e.g., gNB 416) or gn-eNB (e.g., NG-eNB 418). The gNB416 may connect with 5G-enabled UEs using a 5G NR interface. The gNB416 may be connected to the 5G core through an NG interface, which may include an N2 interface or an N3 interface. The NG-eNB 418 may also be connected with the 5G core over the NG interface, but may be connected with the UE over the LTE air interface. The gNB416 and ng-eNB 418 may be connected to each other through an Xn interface.

In some embodiments, the NG interface may be divided into two parts, a NG user plane (NG-U) interface, which carries traffic data between the UPF448 and the nodes of the NG-RAN 414 (e.g., an N3 interface), and a NG control plane (NG-C) interface, which is a signaling interface between the access and mobility management function (AMF) 444 and the nodes of the NG-RAN 414 (e.g., an N2 interface).

NG-RAN 414 may provide a 5G-NR air interface with the following characteristics: variable SCS; cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) for DL, CP-OFDM and DFT-s-OFDM for UL; polarity, repetition, simplex, and reed-muller codes for control; and low density parity check codes (LDPC) for the data. The 5G-NR air interface may rely on channel state reference signals (CSI-RS), PDSCH/PDCCH demodulation reference signals (DMRS), similar to the LTE air interface. The 5G-NR air interface may not use Cell Reference Signals (CRS), but may use Physical Broadcast Channel (PBCH) demodulation reference signals (DMRS) for PBCH demodulation; performing phase tracking of the PDSCH using a Phase Tracking Reference Signal (PTRS); and time tracking using the tracking reference signal. The 5G-NR air interface may operate over the FR1 band, which includes the 6GHz sub-band, or the FR2 band, which includes the 24.25GHz to 52.6GHz band. The 5G-NR air interface may include synchronization signals and PBCH blocks (SSBs), which are regions of a downlink resource grid including Primary Synchronization Signals (PSS)/Secondary Synchronization Signals (SSS)/PBCH.

In some embodiments, the 5G-NR air interface may use a bandwidth portion (BWP) for various purposes. For example, BWP may be used for dynamic adaptation of SCS. For example, UE 402 may be configured with multiple BWPs, where each BWP configuration has a different SCS. When the BWP is indicated to the UE 402 to change, the SCS of the transmission also changes. Another use case for BWP relates to power saving. In particular, the UE 402 may be configured with multiple BWPs with different numbers of frequency resources (e.g., PRBs) to support data transmission in different traffic load scenarios. BWPs containing a smaller number of PRBs may be used for data transmission with smaller traffic load while allowing power savings at UE 402 and, in some cases, at gNB 416. BWPs containing a large number of PRBs may be used in scenarios with higher traffic loads.

The RAN 404 is communicatively coupled to a CN 420, which includes network elements, to provide various functions to support data and telecommunications services to customers/subscribers (e.g., users of the UEs 402). The components of CN 420 may be implemented in one physical node or in different physical nodes. In some embodiments, network Function Virtualization (NFV) may be used to virtualize any or all functions provided by the network elements of CN 420 onto physical computing/storage resources in servers, switches, and the like. Logical instances of CN 420 may be referred to as network slices, and logical instances of a portion of CN 420 may be referred to as network subslices.

In some embodiments, CN 420 may be LTE CN 422, which may also be referred to as Evolved Packet Core (EPC). LTE CN 422 may include a Mobility Management Entity (MME) 424, a Serving Gateway (SGW) 426, a serving General Packet Radio Service (GPRS) support node (SGSN) 428, a Home Subscriber Server (HSS) 430, a Proxy Gateway (PGW) 432, and a policy control and charging rules function (PCRF) 434, which are coupled to each other by an interface (or "reference point") as shown. The functions of the elements of LTE CN 422 may be briefly introduced as follows.

The MME 424 may implement mobility management functions to track the current location of the UE 402 to facilitate paging, bearer activation/deactivation, handover, gateway selection, authentication, and the like.

The SGW 426 may terminate the S1 interface towards the RAN and route data packets between the RAN and the LTE CN 422. The SGW 426 may be a local mobility anchor for inter-RAN node handovers and may also provide an anchor for inter-3 GPP mobility. Other responsibilities may include lawful interception, billing, and some policy enforcement.

The SGSN 428 can track the location of the UE 402 and perform security functions and access control. In addition, the SGSN 428 may perform EPC inter-node signaling for mobility between different Radio Access Technology (RAT) networks; PDN and S-GW selection specified by MME 424; MME selection for handover, etc. An S3 reference point between the MME 424 and the SGSN 428 may enable user and bearer information exchange for inter-3 GPP access network mobility in idle/active state.

HSS 430 may include a database for network users that includes subscription-related information that supports network entities handling communication sessions. HSS 430 may provide support for routing/roaming, authentication, authorization, naming/addressing resolution, location dependency, etc. The S6a reference point between HSS 430 and MME 424 may enable the transmission of subscription and authentication data for authenticating/authorizing user access to LTE CN 420.

PGW 432 may terminate the SGi interface towards a Data Network (DN) 436 that may include an application/content server 438. PGW 432 may route data packets between LTE CN 422 and data network 436. PGW 432 may be coupled with SGW 426 via an S5 reference point to facilitate user plane tunneling and tunnel management. PGW 432 may also include nodes (e.g., PCEFs) for policy enforcement and charging data collection. Additionally, the SGi reference point between PGW 432 and data network 436 may be, for example, an operator external public, private PDN, or an operator internal packet data network for providing IP Multimedia Subsystem (IMS) services. PGW 432 may be coupled with PCRF 434 via a Gx reference point.

PCRF 434 is the policy and charging control element of LTE CN 422. PCRF 434 can be communicatively coupled to application/content server 438 to determine appropriate quality of service (QoS) and charging parameters for a service flow. The PCRF 432 can provide relevant rules to the PCEF (via the Gx reference point) with appropriate Traffic Flow Templates (TFTs) and QoS Class Identifiers (QCIs).

In some embodiments, CN 420 may be a 5G core network (5 GC) 440. The 5GC 440 may include an authentication server function (AUSF) 442, an access and mobility management function (AMF) 444, a Session Management Function (SMF) 446, a User Plane Function (UPF) 448, a Network Slice Selection Function (NSSF) 450, a network open function (NEF) 452, an NF storage function (NRF) 454, a Policy Control Function (PCF) 456, a Unified Data Management (UDM) 458, and an Application Function (AF) 460, which are coupled to each other by an interface (or "reference point") as shown. The function of the elements of the 5GC 440 can be briefly described as follows.

The AUSF 442 may store data for authentication of the UE 402 and handle authentication related functions. The AUSF 442 may facilitate a common authentication framework for various access types. The AUSF 442 may exhibit a Nausf service based interface in addition to communicating with other elements of the 5GC 440 through the reference points as shown.

The AMF 444 may allow other functions of the 5GC 440 to communicate with the UE 402 and the RAN 404 and subscribe to notifications regarding mobility events for the UE 402. The AMF 444 may be responsible for registration management (e.g., registering the UE 402), connection management, reachability management, mobility management, lawful interception of AMF related events, and access authentication and authorization. AMF 444 may provide for the transmission of Session Management (SM) messages between UE 402 and SMF446 and act as a transparent proxy for routing SM messages. The AMF 444 may also provide for the transmission of SMS messages between the UE 402 and the SMSF. The AMF 444 may interact with the AUSF 442 and the UE 402 to perform various security anchoring and context management functions. Further, the AMF 444 may be a termination point for the RAN CP interface, which may include or be an N2 reference point between the RAN 404 and the AMF 444; the AMF 444 may serve as a termination point for NAS (N1) signaling and perform NAS ciphering and integrity protection. The AMF 444 may also support NAS signaling communications with the UE 402 over the N3 IWF interface.

SMF446 may be responsible for SM (e.g., tunnel management between UPF448 and AN 408, session establishment); UE IP address assignment and management (including optional authorization); selection and control of the UP function; configuring flow control at the UPF448 to route the traffic to the appropriate destination; termination of the interface to the policy control function; controlling a portion of policy enforcement, charging, and QoS; lawful interception (for SM events and interface to the LI system); terminate the SM portion of the NAS message; a downlink data notification; initiating AN-specific SM message (sent to AN 408 over N2 via AMF 444); and determining an SSC pattern for the session. SM may refer to the management of PDU sessions, and a PDU session or "session" may refer to a PDU connection service that provides or enables the exchange of PDUs between the UE 402 and the data network 436.

The UPF448 may serve as an anchor point for intra-RAT and inter-RAT mobility, an external PDU session point to interconnect with the data network 436, and a branch point to support multi-homed PDU sessions. The UPF448 may also perform packet routing and forwarding, perform packet inspection, perform the user plane part of policy rules, lawful intercepted packets (UP collection), perform traffic usage reporting, perform QoS processing for the user plane (e.g., packet filtering, gating, UL/DL rate enforcement), perform uplink traffic verification (e.g., SDF to QoS flow mapping), transport level packet marking in uplink and downlink, and perform downlink packet buffering and downlink data notification triggering. The UPF448 may include an uplink classifier to support routing of traffic flows to the data network.

NSSF 450 may select a set of network slice instances that serve UE 402. NSSF 450 may also determine allowed Network Slice Selection Assistance Information (NSSAI) and a mapping to a single NSSAI (S-NSSAI) of the subscription, if desired. The NSSF 450 may also determine a set of AMFs to use for serving the UE 402, or determine a list of candidate AMFs, based on a suitable configuration and possibly by querying the NRF 454. The selection of a set of network slice instances for the UE 402 may be triggered by the AMF 444 (with which the UE 402 registers by interacting with the NSSF 450), which may result in a change in the AMF. NSSF 450 may interact with AMF 444 via the N22 reference point; and may communicate with another NSSF in the visited network via an N31 reference point (not shown). Further, NSSF 450 may expose an interface based on the NSSF service.

NEF452 may securely expose services and capabilities provided by 3GPP network functionality for third parties, internal exposure/re-exposure, AF (e.g., AF 460), edge computing or fog computing systems, and the like. In these embodiments, NEF452 may authenticate, authorize, or limit AF. NEF452 may also translate information exchanged with AF 460 and information exchanged with internal network functions. For example, the NEF452 may translate between the AF service identifier and the internal 5GC information. NEF452 may also receive information from other NFs based on the public capabilities of the other NFs. This information may be stored as structured data at NEF452 or at data storage NF using a standardized interface. NEF452 may then re-expose the stored information to other NFs and AFs, or for other purposes such as analysis. In addition, NEF452 may expose an interface based on the Nnef service.

NRF 454 may support a service discovery function, receive NF discovery requests from NF instances, and provide information of discovered NF instances to NF instances. NRF 454 also maintains information on available NF instances and their supported services. As used herein, the terms "instantiate," "instance," and the like may refer to creating an instance, "instance" may refer to a specific occurrence of an object, which may occur, for example, during execution of program code. Further, NRF 454 may expose an interface based on the nrrf service.

PCF 456 may provide policy rules to control plane functions to enforce these policy rules and may also support a unified policy framework to manage network behavior. PCF 456 may also implement a front end to access subscription information related to policy decisions in the UDR of UDM 458. In addition to communicating with functions through reference points as shown, PCF 456 also presents an Npcf service-based interface.

UDM 458 may process subscription-related information to support network entities handling communication sessions, and may store subscription data for UE 402. For example, subscription data may be transmitted via an N8 reference point between UDM 458 and AMF 444. UDM 458 may include two parts: application front end and User Data Record (UDR). The UDR may store policy data and subscription data for UDM 458 and PCF 456, and/or structured data and application data for NEF452 for exposure (including PFD for application detection, application request information for multiple UEs 402). The UDR may expose an interface based on the nurr service to allow UDM 458, PCF 456, and NEF452 to access a particular collection of stored data, as well as to read, update (e.g., add, modify), delete, and subscribe to notifications of relevant data changes in the UDR. The UDM may include a UDM-FE (UDM front end) that is responsible for handling credentials, location management, subscription management, and the like. Several different front ends may serve the same user in different transactions. The UDM-FE accesses subscription information stored in the UDR and performs authentication credential processing, user identification processing, access authorization, registration/mobility management, and subscription management. UDM 458 may expose a numm service based interface in addition to communicating with other NFs through reference points as shown.

AF 460 may provide application impact on traffic routing, provide access to NEF, and interact with the policy framework for policy control.

In some embodiments, the 5GC 440 may enable edge computation by selecting an operator/third party service that is geographically close to the point where the UE 402 connects to the network. This may reduce delay and load on the network. To provide an edge calculation implementation, the 5GC 440 may select a UPF448 near the UE 402 and perform traffic steering from the UPF448 to the data network 436 over the N6 interface. This may be based on UE subscription data, UE location, and information provided by AF 460. In this way, the AF 460 may affect UPF (re-) selection and traffic routing. Based on operator deployment, the network operator may allow AF 460 to interact directly with the relevant NFs when AF 460 is considered a trusted entity. In addition, AF 460 may expose a Naf service based interface.

The data network 436 may represent various network operator services, internet access, or third party services that may be provided by one or more servers, including, for example, an application/content server 438.

Fig. 5 illustrates a wireless network 500 in accordance with various embodiments. The wireless network 500 may include a UE 502 in wireless communication with AN 504. The UE 502 and the AN 504 may be similar to and substantially interchangeable with like-named components described elsewhere herein.

The UE 502 may be communicatively coupled with the AN 504 via a connection 506. Connection 506 is shown as an air interface to enable communication coupling and may operate at millimeter wave or below 6GHz frequencies according to a cellular communication protocol, such as an LTE protocol or a 5G NR protocol.

UE 502 may include a host platform 508 coupled with a modem platform 510. Host platform 508 can include application processing circuitry 512, which can be coupled with protocol processing circuitry 514 of modem platform 510. The application processing circuitry 512 may run various applications for the UE 502 that obtain/receive its application data. Application processing circuitry 512 may also implement one or more layers of operations to send/receive application data to/from a data network. These layer operations may include transport (e.g., UDP) and internet (e.g., IP) operations.

Protocol processing circuitry 514 may implement one or more layers of operations to facilitate the sending or receiving of data over connection 506. Layer operations implemented by the protocol processing circuit 514 may include, for example, medium Access Control (MAC), radio Link Control (RLC), packet Data Convergence Protocol (PDCP), radio Resource Control (RRC), and non-access stratum (NAS) operations.

Modem platform 510 may further include digital baseband circuitry 516, which digital baseband circuitry 516 may implement one or more layer operations "below" the layer operations performed by protocol processing circuitry 514 in the network protocol stack. These operations may include, for example, PHY operations including one or more of HARQ-ACK functions, scrambling/descrambling, encoding/decoding, layer mapping/demapping, modulation symbol mapping, received symbol/bit metric determination, multi-antenna port precoding/decoding, wherein these functions may include one or more of space-time, space-frequency, or spatial coding, reference signal generation/detection, preamble sequence generation and/or decoding, synchronization sequence generation/detection, control channel signal blind decoding, and other related functions.

Modem platform 510 may further include transmit circuitry 518, receive circuitry 520, RF circuitry 522, and RF front end (RFFE) circuitry 524, which may include or be connected to one or more antenna panels 526. Briefly, the transmit circuit 518 may include digital-to-analog converters, mixers, intermediate Frequency (IF) components, and the like; the receive circuitry 520 may include analog-to-digital converters, mixers, IF components, and the like; RF circuitry 522 may include low noise amplifiers, power tracking components, and the like; the RFFE circuitry 524 may include filters (e.g., surface/bulk acoustic wave filters), switches, antenna tuners, beam forming components (e.g., phased array antenna components), and so on. The selection and arrangement of components of transmit circuitry 518, receive circuitry 520, RF circuitry 522, RFFE circuitry 524, and antenna panel 526 (collectively, "transmit/receive components") may be specific to details of the particular implementation, e.g., whether the communication is Time Division Multiplexed (TDM) or Frequency Division Multiplexed (FDM), at mmWave or below 6GHz frequencies, etc. In some embodiments, the transmit/receive components may be arranged in a plurality of parallel transmit/receive chains, and may be arranged in the same or different chips/modules, etc.

In some embodiments, the protocol processing circuitry 514 may include one or more instances of control circuitry (not shown) to provide control functionality for the transmit/receive components.

UE reception may be established by and via antenna panel 526, RFFE circuitry 524, RF circuitry 522, receive circuitry 520, digital baseband circuitry 516, and protocol processing circuitry 514. In some embodiments, antenna panel 526 may receive transmissions from AN 504 by receiving beamformed signals received by multiple antennas/antenna elements of one or more antenna panels 526.

UE transmissions may be established via and through protocol processing circuitry 514, digital baseband circuitry 516, transmit circuitry 518, RF circuitry 522, RFFE circuitry 524, and antenna panel 526. In some embodiments, a transmit component of UE 502 may apply spatial filtering to data to be transmitted to form a transmit beam transmitted by the antenna elements of antenna panel 526.

Similar to the UE 502, the AN 504 may include a host platform 528 coupled with a modem platform 530. Host platform 528 may include application processing circuitry 532 coupled with protocol processing circuitry 534 of modem platform 530. The modem platform may also include digital baseband circuitry 536, transmit circuitry 538, receive circuitry 540, RF circuitry 542, RFFE circuitry 544, and antenna panel 546. The components of AN 504 may be similar to, and substantially interchangeable with, the synonymous components of UE 502. In addition to performing data transmission/reception as described above, the components of AN 504 may perform various logical functions including, for example, radio Network Controller (RNC) functions such as radio bearer management, uplink and downlink dynamic radio resource management, and data packet scheduling.

Fig. 6 is a block diagram illustrating components capable of reading instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and performing any one or more of the methodologies discussed herein, according to some example embodiments. In particular, fig. 6 shows a schematic diagram of hardware resources 600, hardware resources 600 including one or more processors (or processor cores) 610, one or more memory/storage devices 620, and one or more communication resources 630, where each of the processors, memory/storage devices, and communication resources may be communicatively coupled via a bus 640 or other interface circuitry. For embodiments utilizing node virtualization (e.g., network Function Virtualization (NFV)), hypervisor 602 may be executed to provide an execution environment for one or more network slices/subslices to utilize hardware resources 600.

Processor 610 may include, for example, a processor 612 and a processor 614. The processor 610 may be, for example, a Central Processing Unit (CPU), a Reduced Instruction Set Computing (RISC) processor, a Complex Instruction Set Computing (CISC) processor, a Graphics Processing Unit (GPU), a Digital Signal Processor (DSP) such as a baseband processor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Radio Frequency Integrated Circuit (RFIC), another processor (including those discussed herein), or any suitable combination thereof.

Memory/storage device 620 may include a main memory, a disk storage device, or any suitable combination thereof. The memory/storage 620 may include, but is not limited to, any type of volatile, non-volatile, or semi-volatile memory, such as Dynamic Random Access Memory (DRAM), static Random Access Memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, solid-state memory, and the like.

The communication resources 630 may include interconnection or network interface controllers, components, or other suitable devices to communicate with one or more peripherals 604 or one or more databases 606 or other network elements via the network 608. For example, communication resources 630 can include wired communication components (e.g., for coupling via USB, ethernet, etc.), cellular communication components, near Field Communication (NFC) components, a network interface component, and/or a network interface component,

(or

Low energy) assembly,

Components, and other communication components.

The instructions 650 may include software, programs, applications, applets, applications, or other executable code for causing at least any one of the processors 610 to perform any one or more of the methods discussed herein. The instructions 650 may reside, completely or partially, within at least one of the processor 610 (e.g., in a cache of the processor), the memory/storage 620, or any suitable combination thereof. Further, any portion of instructions 650 may be communicated to hardware resource 600 from any combination of peripherals 604 or database 606. Thus, the memory of the processor 610, the memory/storage 620, the peripherals 604, and the database 606 are examples of computer-readable and machine-readable media.

The following paragraphs describe examples of various embodiments.

Example 1 includes an apparatus for use in a base station, wherein the apparatus comprises a processor circuit configured to cause the base station to: mapping Physical Downlink Control Channel (PDCCH) candidates for one or more User Equipments (UEs) to time and frequency resources of a control resource set (CORESET); mapping a demodulation reference signal (DMRS) sequence shared to the PDCCH candidate to time resources of the CORESET and frequency resources of the CORESET or a bandwidth part (BWP) associated with the CORESET; and transmitting the PDCCH candidates and the DMRS sequences to the one or more UEs by using the CORESET, wherein the PDCCH candidates and the DMRS sequences are time division multiplexed, and frequency resources for PDCCH candidates having a non-maximum Aggregation Level (AL) are entirely included in frequency resources for PDCCH candidates having a maximum AL.

Example 2 includes the apparatus of example 1, wherein a discrete fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) waveform is used for transmission of the PDCCH candidates.

Example 3 includes the apparatus of example 2, wherein the PDCCH candidates are all mapped to frequency resources in the CORESET starting from a common frequency resource starting point.

Example 4 includes the apparatus of example 3, wherein the common frequency resource index associated with the common frequency resource starting point is obtained according to a randomized distribution function.

Example 5 includes the apparatus of example 3, wherein the DMRS sequence for the PDCCH candidate with non-maximum AL is always part of the DMRS sequence for the PDCCH candidate with maximum AL.

Example 6 includes the apparatus of example 2, wherein a starting point of a frequency resource for the frequency resource of the PDCCH candidate with non-maximum AL is different from a starting point of a frequency resource for the frequency resource of the PDCCH candidate with maximum AL.

Example 7 includes the apparatus of example 1, wherein an association between the ALs for the PDCCH candidates is configured by higher layers via Radio Resource Control (RRC) signaling.

Example 8 includes the apparatus of example 1, wherein an association between ALs for the PDCCH candidates is configured as part of a search space configuration associated with the CORESET.

Example 9 includes the apparatus of example 2, wherein the PDCCH candidates are multiplexed within different DFT-s-OFDM symbols.

Example 10 includes the apparatus of example 2, wherein the PDCCH candidates are multiplexed within the same DFT-s-OFDM symbol.

Example 11 includes the apparatus of example 9, wherein, when the DMRS sequence is dedicated to the PDCCH candidate, a frequency resource for the DMRS sequence is the same as or includes a frequency resource for the PDCCH candidate with the largest AL.

Example 12 includes the apparatus of example 11, wherein the frequency resources for the DMRS sequence span an entire frequency domain of the CORESET.

Example 13 includes the apparatus of example 9, wherein, when the DMRS sequence is shared to the PDCCH candidate and a Physical Downlink Shared Channel (PDSCH) and frequency resources for the PDCCH candidate partially overlap or do not overlap with frequency resources for the PDSCH, the frequency resources for the DMRS sequence include frequency resources for both the PDCCH candidate and the PDSCH.

Example 14 includes the apparatus of example 13, wherein the frequency resources for the DMRS sequence span an entire frequency domain of the BWP associated with the CORESET.

Example 15 includes a method for use in a base station, wherein the method comprises: mapping Physical Downlink Control Channel (PDCCH) candidates for one or more User Equipments (UEs) to time and frequency resources of a control resource set (CORESET); mapping a demodulation reference signal (DMRS) sequence shared to the PDCCH candidate to time resources of the CORESET and frequency resources of the CORESET or a bandwidth part (BWP) associated with the CORESET; and transmitting the PDCCH candidates and the DMRS sequences to the one or more UEs by using the CORESET, wherein the PDCCH candidates and the DMRS sequences are time division multiplexed, and frequency resources for PDCCH candidates having a non-maximum Aggregation Level (AL) are entirely included in frequency resources for PDCCH candidates having a maximum AL.

Example 16 includes the method of example 15, wherein a discrete fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) waveform is used for transmission of the PDCCH candidates.

Example 17 includes the method of example 16, wherein the PDCCH candidates are all mapped to frequency resources in the CORESET starting from a common frequency resource starting point.

Example 18 includes the method of example 17, wherein the common frequency resource index associated with the common frequency resource starting point is obtained according to a randomized distribution function.

Example 19 includes the method of example 17, wherein the DMRS sequence for the PDCCH candidate with non-maximum AL is always part of the DMRS sequence for the PDCCH candidate with maximum AL.

Example 20 includes the method of example 16, wherein a starting point of a frequency resource for the frequency resource of the PDCCH candidate with non-maximum AL is different from a starting point of a frequency resource for the frequency resource of the PDCCH candidate with maximum AL.

Example 21 includes the method of example 15, wherein the association between the ALs for the PDCCH candidates is configured by higher layers via Radio Resource Control (RRC) signaling.

Example 22 includes the method of example 15, wherein the association between the ALs for the PDCCH candidates is configured as part of a search space configuration associated with the CORESET.

Example 23 includes the method of example 16, wherein the PDCCH candidates are multiplexed within different DFT-s-OFDM symbols.

Example 24 includes the method of example 16, wherein the PDCCH candidates are multiplexed within the same DFT-s-OFDM symbol.

Example 25 includes the method of example 23, wherein, when the DMRS sequence is dedicated to the PDCCH candidate, a frequency resource for the DMRS sequence is the same as or includes a frequency resource for the PDCCH candidate with the largest AL.

Example 26 includes the method of example 25, wherein the frequency resources for the DMRS sequence span an entire frequency domain of the CORESET.

Example 27 includes the method of example 23, wherein when the DMRS sequence is shared to the PDCCH candidate and a Physical Downlink Shared Channel (PDSCH) and frequency resources for the PDCCH candidate partially overlap or do not overlap with frequency resources for the PDSCH, the frequency resources for the DMRS sequence include frequency resources for both the PDCCH candidate and the PDSCH.

Example 28 includes the apparatus of example 27, wherein the frequency resources for the DMRS sequence span an entire frequency domain of the BWP associated with the CORESET.

Example 29 includes a computer-readable storage medium having computer-executable instructions stored thereon, wherein the computer-executable instructions, when executed by processor circuitry of a base station, cause the base station to perform the method of any of examples 15 to 28.

Example 30 includes an apparatus for use in a base station, comprising means for performing the method of any of examples 15-28.

Example 31 includes a base station comprising means for performing the method of any of examples 15 to 28.

Although certain embodiments have been illustrated and described herein for purposes of description, a wide variety of alternate and/or equivalent embodiments or implementations calculated to achieve the same purposes may be substituted for the embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the embodiments discussed herein. Therefore, it is manifestly intended that the embodiments described herein be limited only by the claims and the equivalents thereof.

Claims (25)

1. An apparatus for use in a base station, wherein the apparatus comprises a processor circuit configured to cause the base station to:

mapping Physical Downlink Control Channel (PDCCH) candidates for one or more User Equipments (UEs) to time and frequency resources of a control resource set (CORESET);

mapping a demodulation reference signal (DMRS) sequence shared to the PDCCH candidate to time resources of the CORESET and frequency resources of the CORESET or a bandwidth part (BWP) associated with the CORESET; and

transmitting the PDCCH candidate and the DMRS sequence to the one or more UEs by using the CORESET, wherein

The PDCCH candidates and the DMRS sequences are time division multiplexed, and frequency resources for PDCCH candidates having a non-maximum Aggregation Level (AL) are entirely included in frequency resources for PDCCH candidates having a maximum AL.

2. The apparatus of claim 1, wherein a discrete fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) waveform is used for transmission of the PDCCH candidates.

3. The apparatus of claim 2, wherein the PDCCH candidates are all mapped to frequency resources in the CORESET starting from a common frequency resource starting point.

4. The apparatus of claim 3, wherein a common frequency resource index associated with the common frequency resource starting point is obtained according to a randomized distribution function.

5. The apparatus of claim 3, wherein the DMRS sequence for the PDCCH candidate with non-maximum AL is always part of the DMRS sequence for the PDCCH candidate with maximum AL.

6. The apparatus of claim 2, wherein a starting point of a frequency resource for a frequency resource of the PDCCH candidate with non-maximum AL is different from a starting point of a frequency resource for a frequency resource of the PDCCH candidate with maximum AL.

7. The apparatus of claim 1, wherein an association between AL's for the PDCCH candidates is configured by higher layers via Radio Resource Control (RRC) signaling.

8. The apparatus of claim 1, wherein an association between AL's for the PDCCH candidates is configured as part of a search space configuration associated with the CORESET.

9. The apparatus of claim 2, wherein the PDCCH candidates are multiplexed within different DFT-s-OFDM symbols.

10. The apparatus of claim 2, wherein the PDCCH candidates are multiplexed within the same DFT-s-OFDM symbol.

11. The apparatus of claim 9, wherein, when the DMRS sequence is dedicated to the PDCCH candidate, a frequency resource for the DMRS sequence is the same as or includes a frequency resource for the PDCCH candidate with the largest AL.

12. The apparatus of claim 11, wherein frequency resources for the DMRS sequence span an entire frequency domain of the CORESET.

13. The apparatus of claim 9, wherein, when the DMRS sequence is shared to the PDCCH candidate and a Physical Downlink Shared Channel (PDSCH) and frequency resources for the PDCCH candidate partially overlap or do not overlap with frequency resources for the PDSCH, the frequency resources for the DMRS sequence comprise frequency resources for both the PDCCH candidate and the PDSCH.

14. The apparatus of claim 13, wherein frequency resources for the DMRS sequence span an entire frequency domain of the BWP associated with the CORESET.

15. A computer-readable storage medium having computer-executable instructions stored thereon, wherein the computer-executable instructions, when executed by a processor circuit of a base station, cause the base station to:

mapping Physical Downlink Control Channel (PDCCH) candidates for one or more User Equipments (UEs) to time and frequency resources of a control resource set (CORESET);

mapping a demodulation reference signal (DMRS) sequence shared to the PDCCH candidate to a time resource of the CORESET and a frequency resource of the CORESET or a bandwidth part (BWP) associated with the CORESET; and

transmitting the PDCCH candidate and the DMRS sequence to the one or more UEs by using the CORESET, wherein

The PDCCH candidates and the DMRS sequences are time division multiplexed, and frequency resources for PDCCH candidates having a non-maximum Aggregation Level (AL) are entirely included in frequency resources for PDCCH candidates having a maximum AL.

16. The computer-readable storage medium of claim 15, wherein a discrete fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM) waveform is used for transmission of the PDCCH candidates.

17. The computer-readable storage medium of claim 16, wherein the PDCCH candidates are all mapped to frequency resources in the CORESET starting from a common frequency resource starting point.

18. The computer-readable storage medium of claim 17, wherein the common frequency resource index associated with the common frequency resource starting point is obtained according to a randomized distribution function.

19. The computer-readable storage medium of claim 17, wherein the DMRS sequence for the PDCCH candidate with non-maximum AL is always part of the DMRS sequence for the PDCCH candidate with maximum AL.

20. The computer-readable storage medium of claim 16, wherein a starting point of a frequency resource for a frequency resource of the PDCCH candidate with a non-maximum AL is different from a starting point of a frequency resource for a frequency resource of the PDCCH candidate with a maximum AL.

21. The computer-readable storage medium of claim 15, wherein an association between ALs for the PDCCH candidates is configured by higher layers via Radio Resource Control (RRC) signaling.

22. The computer-readable storage medium of claim 15, wherein an association between AL for the PDCCH candidates is configured as part of a search space configuration associated with the CORESET.

23. The computer-readable storage medium of claim 16, wherein the PDCCH candidates are multiplexed within different DFT-s-OFDM symbols.

24. The computer-readable storage medium of claim 16, wherein the PDCCH candidates are multiplexed within the same DFT-s-OFDM symbol.

25. The computer-readable storage medium of claim 23, wherein, when the DMRS sequence is dedicated to the PDCCH candidate, a frequency resource for the DMRS sequence is the same as or includes a frequency resource for the PDCCH candidate with the largest AL.

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