CN116250202A - Coverage recovery in reduced capability wireless devices - Google Patents

Abstract

In addition to the primary CORESET for control information transmission in a cellular communication system, an extended CORESET is defined in which control channels may be transmitted. Candidates are defined in two coreses and mapped together.

Description

Coverage recovery in reduced capability wireless devices

Technical Field

The following disclosure relates to wireless communications, and more particularly to coverage enhancement (coverage enhancements) in reduced capability (reduced capability, REDCAP) wireless communication devices.

Background

Wireless communication systems, such as third generation (3G) mobile telephone standards and technologies are well known. Such 3G standards and techniques have been developed by the third generation partnership project (Third Generation PartnershipProject,3 GPP) (RTM). Third generation wireless communications have been commonly developed to support macro-cellular (macro-cell) mobile phone communications. Communication systems and networks have evolved towards broadband and mobile systems.

In a cellular wireless communication system, a User Equipment (UE) is connected to a radio access network (Radio Access Network, RAN) by a wireless link. The RAN includes a set of base stations that provide radio links to UEs located in a cell covered by the base stations, and an interface that provides overall Network control to a Core Network (CN). It should be appreciated that the RAN and CN each perform a respective function related to the overall network. For convenience, the term "cellular network" will be used to refer to the RAN and CN in combination, and it should be understood that the term is used to refer to the corresponding system for performing the disclosed functions.

The third generation partnership project has developed a so-called long term evolution (Long Term Evolution, LTE) system, an evolved universal mobile telecommunications system territory radio access network (Evolved Universal MobileTelecommunication System Territorial Radio Access Network, E-UTRAN), for mobile access networks in which one or more macro cells are supported by base stations called enodebs or enbs (evolved nodebs). Recently, LTE is further evolving towards so-called 5G or NR (new radio) systems, where one or more cells are supported by a base station called a gNB. NR is proposed to use an orthogonal frequency division multiplexing (Orthogonal Frequency Division Multiplexed, OFDM) physical transport format.

The NR protocol is intended to provide an option to operate in an unlicensed radio band (unlicensed radio bands), referred to as NR-U. While operating in the unlicensed radio band, the gNB and UE must compete for physical media/resource access with other devices. For example, wi-Fi (RTM), NR-U, and LAA may use the same physical resources.

The trend in wireless communication is to provide lower latency (lower latency) and higher reliability (higher reliability) services. For example, NR is intended to support Ultra-reliable and low-latency communication (URLLC), while large-scale Machine-type communication (mMTC) is intended to provide low latency and high reliability for small packet sizes (typically 32 bytes). User plane delay (user) of 1ms with a reliability of 99.99999%-plane latency) is proposed, 10 at the physical layer ^-5 Or 10 ^-6 Packet loss rate (packet loss rate).

The mctc service aims to support a large number of devices over a long lifecycle through an energy efficient communication channel, with occasional and infrequent data transmissions with each device. For example, one cell may be expected to support thousands of devices.

The following disclosure relates to various improvements to cellular wireless communication systems.

Disclosure of Invention

The present invention is defined by the claims, wherein a method of transmitting downlink control information from a base station to a UE in a cellular communication network using an OFDM transmission format is provided, the method comprising: defining a master CORESET comprising a plurality of PDCCH candidates; defining a CORESET extension comprising a plurality of PDCCH candidates; and mapping at least one of the plurality of PDCCH candidates in the CORESET extension to at least one of the plurality of PDCCH candidates in the primary CORESET extension.

The plurality of PDCCH candidates in the core extension are mapped to a portion of the plurality of PDCCH candidates in the master core.

The offset parameter indicates the offset applied to the CORESET extension.

The main CORESET and CORESET extensions are interleaved prior to transmission.

The mapping step uses a configurable image or an implicit image.

The PDCCH candidates are encoded and mapped to CCEs, and wherein the UE decodes the PDCCH candidates using at least one CCE in the primary core and at least one CCE in the core extension.

The method may further comprise: determining an aggregation level and assigning the aggregation level to the UE; generating a DCI payload; appending the CRC to the DCI payload; encoding the DCI payload and the CRC to generate a codeword; rate matching the codeword using the demodulation reference signal to produce a channel code; scrambling and mapping the channel codes into a plurality of QPSK symbols; mapping the QPSK symbols to at least one CCE and at least one REG using a mapping scheme defined in the primary CORESET; and using at least one CCE and at least one REG in the primary CORESET.

The at least one REG in the master CORESET may be indexed independently of the at least one second REG used in the CORESET extension.

A base station configured to perform the methods described herein is also provided.

A UE configured to decode the primary CORESET and CORESET extensions described herein is also provided.

The non-transitory computer readable medium may include at least one from the group consisting of: hard disks, CD-ROMs, optical storage devices, magnetic storage devices, read-only memory, programmable read-only memory, erasable programmable read-only memory, EPROM, electrically erasable programmable read-only memory, and flash memory.

Drawings

Further details, aspects and embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings. The components in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. Like reference numerals have been included in the respective drawings for ease of understanding.

Fig. 1 shows selected elements of a cellular communication network;

fig. 2-7 illustrate various CORESET examples that may be used in the cellular communication network of fig. 1.

Detailed Description

Those skilled in the art will recognize and appreciate that the specifics of the examples described are merely illustrative of some embodiments and that the teachings set forth herein are applicable in a variety of alternative settings.

Fig. 1 shows a schematic diagram of three base stations (e.g., enbs or gnbs depending on the particular cellular standard and terminology) forming a cellular network. Typically, each base station will be deployed by one cellular network operator to provide geographic coverage for UEs in that area. The base stations form a radio area network (Radio Area Network, RAN). Each base station provides wireless coverage for UEs in its area or cell. The base stations are interconnected by an X2 interface and connected to the core network by an S1 interface. It should be understood that only basic details are shown for the purpose of illustrating key features of a cellular network. The PC5 interface is provided between UEs for side-link communication. The interface and component names associated with fig. 1 are for example only, and different systems operating on the same principles may use different nomenclature.

Each base station includes hardware and software to implement the functions of the RAN, including communication with the core network and other base stations, control and data signaling between the core network and UEs, and UEs associated with each base station remain in wireless communication. The core network includes hardware and software that implements network functions such as overall network management and control, and routing of calls and data.

The base station transmits a physical downlink control channel (physical downlink control channel, PDCCH) on a pre-configured region (pre-configured region of the time frequency grid) of the time frequency grid, known as the control resource set (CORESET). The search space (search space) provides the configuration associated with a given CORESET and specifies the symbols and physical resource blocks (physical resource blocks, PRBs) that the UE uses to attempt PDCCH decoding. Modern telecommunication standards include the functionality of means for reduced capability (REDCAP) operating with reduced bandwidth and a reduced number of receive chains (1 RX or 2 RX).

The REDCAP device has a fixed coverage loss due to reduced hardware complexity compared to a standard UE device, which reduces physical downlink control channel (physical downlink control channel, PDCCH) monitoring capability and reduces bandwidth reception capability of the PDCCH. Coverage recovery schemes that require greater PDCCH bandwidth or increase the number of blind decoding attempts (blind decoding attempts) are unsuitable.

A solution that can increase PDCCH coverage may reduce the downlink channel information (Downlink Channel Information, DCI) size, providing a smaller payload (payload), which may result in the same number of resources with a higher coding rate. Other solutions may include a larger aggregation level (aggregation levels, AL), which may result in a higher coding rate, but also require more resources, which in turn may result in PDCCH blocking. That is, there are not enough resources available for scheduling other UEs. In addition, the solution may include repetition of the PDCCH, which is repeated multiple times in the time and/or frequency domain. However, for REDCAP, only time domain repetition may be an option because bandwidth is limited. The repetition in time will result in greater delay and increased power consumption.

Transmitting PDCCH requires transmitting DCI payload at base station (gNB) side according to the following general steps 1 to 7:

step 1-determining the aggregation level: the gNB determines AL from the link adaptation algorithm. In general, UEs with poor coverage conditions obtain a larger AL allocated than UEs with good coverage conditions.

Step 2-generating DCI payload: the gNB generates DCI according to the UE configuration and the control information to be transmitted by the gNB.

Step 3-additional 24-bit cyclic redundancy check (cyclic redundancy check, CRC): a 24-bit CRC is generated from the DCI payload and scrambled using an appropriate radio network temporary identifier (scrambled with the appropriate radio network temporary identifier, RNTI).

Step 4-channel coding: polar coding (Polar coding) is used to encode the payload and CRC.

Step 5-rate matching: considering demodulation reference signals (demodulation reference signal, DMRS), only those bits suitable for the allocated resources are transmitted from the generated codeword. Further, considering demodulation reference signals (DMRS), interleaving is applied to transmit only those bits that fit into the allocated resources.

Step 6-PDCCH encoding: bits from the channel coding are scrambled and mapped to quadrature phase shift keying (quadrature phase shift keying, QPSK) symbols. The gNB may apply a transmit diversity scheme (transmit diversity scheme) and precoding control data and DMRS.

Step 7-resource mapping: QPSK symbols are mapped to Control Channel Elements (CCEs) and resource element groups (resource element groups, REG) according to a CCE-to-REG mapping (CCE-to-REG mapping) defined in CORESET.

At the receiving end, the UE searches for PDCCH candidates in a configured set of search spaces (configured search space sets). In each search space set, the UE is configured to search for a specific DCI. For example, in a UE-specific search space set, the UE will look for UL allocation DCI format 0_0 or 0_1 or DL allocation DCI format 1_0 or 1_1. The UE also (pre) configures the payload size of each DCIs. However, when the UE does not have the exact DCI format, AL and configuration information of the relevant resources in CORESET, it must blindly try all possible combinations. The necessary steps can be summarized as follows:

step 1-selecting a DCI format: the payload of DCI is known by pre-configuration.

Step 2-select one AL: AL defines the number of resources (i.e., CCEs) used for decoding attempts.

Step 3-attempt decoding: for all possible resource allocations for this AL, an attempt is made to decode the PDCCH. If the CRC is correct, the decoding is successful, i.e., the CRC corresponds to the target RNTI. If not, return to step 2 and try a different AL.

The above procedure is repeated for each DCI format having a different payload. If the payloads are identical, the DCI format is distinguished by a flag (flag) within the payload to indicate the format.

The apparatus, systems, and methods described herein extend CORESET to durations exceeding 3 symbols by introducing CORESET extensions that directly map to resources in conventional CORESET. Thus, the UE decodes the PDCCH candidates to utilize resources in CORESET and CORESET extensions (CORESET extension) to improve reliability/coverage. This results in reduced decoding delay, reduced power consumption because the extended CORESET is continuous, reduced power consumption because the RF can be turned off after successful reception, and reduced memory consumption because the number of repetitions of buffering and combining before decoding is attempted. Furthermore, the number of blind decoding attempts is the same as in previous systems, but the diversity gain (diversity gain) increases because CORESET and its extensions can configure different CCE-to-REG images.

For example, a CORESET with 4 symbols may be configured as a CORESET duration of 3 symbols and 1 symbol extension (symbol extension), a CORESET duration of 2 symbols and 2 symbol extension, or a CORESET duration of 1 symbol and 3 symbol extension. Fig. 2 shows an example of a CORESET of 3 symbols and an extension of the other 3 symbols. The CORESET is referred to as an extended CORESET and the appended symbol (additional symbols) is referred to as a CORESET extension.

The CORESET extension may also be dynamically configured by a dedicated DCI, which may enable or disable the extension or reconfigure it. The extension may span the same frequency resource as CORESET or a different frequency resource.

The CORESET extension implicitly links (implicitly linked) (or maps) to the PDCCH candidates of CORESET. This avoids treating the extension as a normal large CORESET with CORESET, thereby increasing the PDCCH search space and thus the number of blind decoding attempts, which is undesirable for REDCAP UEs with reduced PDCCH decoding capability.

Not all resources in CORESET need be linked to CORESET extensions. For example, PDCCH candidates with CCE indexes from 0 to 7 are not linked to the CORESET extension, while PDCCH candidates with CCE indexes from 8 to 15 are linked to the CORESET extension. This would allow the gNB to reserve a portion of the CORESET for UEs that are well covered and do not require large ALs, and concentrate additional resources in extension to UEs that are lower in coverage. Fig. 3 shows one example where REGs 36 through 53 are independent of CORESET extensions, while REGs 0 through 35 are associated with CORESET extensions. The associated resources may be indicated with REGs, ccs, or Physical Resource Blocks (PRBs).

The association of resources in CORESET with resources in CORESET extensions can be configured in a number of ways. One approach is to configure a bit string indicating which resources are associated. In the example of fig. 3, frequencydomain resources are configured by a bit string 01111111111111111110, with the leftmost zeros corresponding to PRBs 0 through 5. The frequencydomalnresource of the associated resource is then given by 01111111111110000000. Equivalently, non-associated resources may be indicated.

The configuration by bitmap (bitmap) allows maximum flexibility but consumes signaling bandwidth (signaling bandwidth). Thus, a more compact form may be a possible portion of the introduction of relevant CORESET resources, e.g., 1/2, 3/4, 2/3, 1/4, etc., e.g., only the first half of the resources in CORESET are associated with an extension. In addition, an offset parameter (offset parameter) may be introduced to increase flexibility. Also, taking the example of FIG. 3 as an example, only 2/3 of the CORESET resources are associated with an extension, i.e., 12 out of 18 REGs. In this example, the offset parameter is 0 REG, but may be any integer between 0 and 6. For example, if the offset is 3 REGs, the PRBs 24 through 95 will be associated with the extension.

In addition, to maximize frequency diversity (frequency diversity), CORESET and CORESET extensions may be used separately by interleaving (interleaved separately). That may be achieved by using all interleaving parameters (interleaving parameters) reg-BundleSize, interleaverSize and shiftIndex or using only some parameters, such as shiftIndex. This will ensure that the resources in CORESET and CORESET extensions do not occupy the same frequency resources to maximize robustness to frequency selective fading (frequency selective fading).

A UE that does not support extended CORESETs may still receive control information in the normal CORESET. The extended resources may be considered and signaled as reserved resources so that those UEs calculate the correct amount of data resources.

In order to use the additional resources in the CORESET extension for PDCCH transmission, the PDCCH may be encoded with as high a code rate as possible using all the resources. All candidate resources in CORESET and CORESET extensions are used to attempt to decode PDCCH. For example, the UE attempts to decode AL 4 in CORESET and is preconfigured to identify the locations of the other 4 ccs in the CORESET extension. Thus, in order to try to decode the PDCCH candidate, it uses all 8 CCEs, which is effectively an AL of 8.

Thus, the UE will search for PDCCH candidates in consideration of the combined resources when determining AL. For example, if 1 CCE in CORESET is associated with an extended 1 CCE, the UE will not search for AL 1 because the smallest AL is 2. That also means that an AL of e.g. 5 or 12 is possible. However, blind decoding attempts are not increased.

The ratio of CORESET resources to resources in CORESET extensions may also be configurable. This may be achieved, for example, by configuring resources that are not related to CORESET extensions.

Alternatively, the PDCCH may be repeated in the CORESET extension and combined with the PDCCH in CORESET. Thus, the UE may combine the two transmissions and then decode the PDCCH candidates.

The number of repetitions may be configurable and given by a resource mapping between CORESET and CORESET extensions. For example, if 2 ccs in CORESET are associated with 4 ccs in CORESET extension for AL 2, the PDCCH on 2 ccs is repeated twice in extension.

The apparatus, systems, and methods described herein may use implicit mapping (mapping) of resources indicated in the CORESET extension. The ccs in CORESET may be mapped to another (possibly different) set of ccs in the CORESET extension. Furthermore, the mapping may be fixed and may only change semi-statically.

REGs may be indexed separately for CORESET and CORESET extensions. Thus, N ccs are associated with index n=0, 1 using a simple mapping rule. Fig. 4 shows an example where 4 ccs of CORESET map to 4 ccs of the extension, i.e. only REGs 0 to 23 are associated with CORESET extension. In this example, assuming PDCCH encoding across all resources, the UE will start decoding PDCCH candidates with AL 2, i.e. 1 CCE from CORESET and 1 CCE from extension, resulting in 4 PDCCH candidates. Similarly, the UE decodes AL 4 with PDCCH candidates spanning CCE0/CCE1 and CCE2/CCE 3. Finally, one PDCCH candidate with AL 8 spanning all 8 ccs.

The CORESET and CORESET extensions may have different CCE-to-REG mappings. Fig. 5 shows an extended CORESET with a 2 symbol extension, where CORESET and CORESET extensions have different CCEREG mappings. More precisely, the REG bundle size (bundle size) of CORESET is 6, while the CORESET expanded REG bundle size is 2. Both interleaver depths (interleaver depth) were 3, i.e., the CORESET bandwidth was divided into 3 parts.

The same mapping rule may be applied, i.e. ccs 0 to 3 in CORESET are associated with ccs 0 to 3 in CORESET extension. However, due to interleaving, they correspond to different REGs.

There may be configurations in which the number of resources in the CORESET and CORESET extensions are different. Consider the example of fig. 6, where 2 ccs are associated with 4 ccs in the extension. In this case, 1 CCE in CORESET is associated with 2 CCEs in CORESET extension.

For example, CCE0 is associated with CCE0/1, and CCE1 is associated with CCE 2/3. The general mapping rule may be defined as follows:

and N _CCE,p Representing the number of associated CCEs in the CORESET extension and CORESET p, respectively. If it is

CCE N in CORESET p is associated with CCE m in CORESET extension by the following formula, where n=0, 1, …, N _CCE,p :

m＝R _CCE,p ·n+i (1)

Similarly, if

CCE m in the CORESET extension is then associated with CCE N in CORESET p by the following equation, where m = 0,1, …, N _CCE,p :

n＝R _CCE,p ·m+i (2)

Wherein the method comprises the steps of

When the ccs in the CORESET extension are less than the ccs in the associated CORESET,

then a plurality of CCEs in the CORESET are associated with one CCE in the CORESET extension. Fig. 7 shows an extended CORESET with a 1 symbol extension, where 4 ccs in the CORESET are associated with 2 ccs in the CORESET extension. Using this example and according to equation (2) above, CCE0 and CCE1 in the CORESET extension are associated with CCE0/1 and CCE2/3, respectively. For PDCCH candidate decoding, this means that the UE will attempt to decode AL 24 times, i.e. CCEs 0/(0), 1/(0), 2/(1) and 3/(1) 2,2 times AL 3, i.e.CCEs 0/1/(0) and 2/3/(1), once AL 6, i.e., CCEs 0/1/2/3/(0/1), where CCEs x/(y) represents CCEs x in CORESET and CCEs y in CORESET extension.

Although not shown in detail, any apparatus or device forming part of a network may comprise at least a processor, a storage unit, and a communication interface, wherein the processor unit, the storage unit, and the communication interface are configured to perform the methods of any aspect of the invention. Further options and selections are described below.

The signal processing functions of embodiments of the present invention, particularly the gNB and UE, may be implemented using computing systems or architectures known to those skilled in the relevant art. It may be desirable or appropriate to use a computing system, such as a desktop, laptop or notebook computer, handheld computing device (PDA, cell phone, palmtop, etc.), mainframe, server, client, or any other type of special or general purpose computing device for a given application process or environment. A computing system may include one or more processors, which may be implemented using a general-purpose or special-purpose processing engine, such as a microprocessor, microcontroller, or other control module.

The computing system may also include a main memory, such as Random access memory (Random AccessMemory, RAM) or other dynamic memory, for storing information and instructions to be executed by the processor. Such main memory may also be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor. The computing system may also include Read Only Memory (ROM) or other static storage device for storing static information and instructions for the processor.

The computing system may also include an information storage system, which may include, for example, a media drive and a removable storage interface. The media drive may include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, floppy disk drive, magnetic tape drive, optical disk drive, compact Disc (CD) or digital video drive (Digital Video Drive, DVD) (RTM), read or write drive (Read or Write Drive, R or RW), or other removable or fixed media drive. Storage media may include, for example, hard disk, floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed or removable medium that is read by and written to by a media drive. The storage medium may include a computer-readable storage medium having stored therein specific computer software or data.

In alternative embodiments, the information storage system may include other similar components for allowing computer processes or other instructions or data to be loaded into the computing system. Such components may include, for example, removable storage units and interfaces such as process cartridge and cartridge interfaces, removable memory (e.g., flash memory or other removable memory modules) and memory slots, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage units to the computing system.

The computing system may also include a communication interface. Such a communication interface may be used to allow software and data to be transferred between the computing system and external devices. Examples of communication interfaces may include modems, network interfaces (e.g., ethernet or other NIC cards), communication ports (e.g., universal Serial Bus (USB) ports), PCMCIA slots and cards, etc. Software and data transferred via the communications interface are in the form of signals which may be electronic, electromagnetic and optical or other signals capable of being received by the communications interface medium.

In this document, the terms "computer process product," "computer-readable medium," and the like may be used to generally refer to tangible media, such as memory, storage devices, or storage units. These and other forms of computer-readable media may store one or more instructions for use by a processor, including a computer system, to cause the processor to perform specified operations. Such instructions, commonly referred to as "computer process code" (which may be grouped in the form of computer processes or other groupings), when executed, enable a computing system to perform functions of embodiments of the present invention. Note that the code may directly cause the processor to perform the specified operation, be compiled to do so, and/or be combined with other software, hardware, and/or firmware elements (e.g., libraries for performing standard functions) to do so.

The non-transitory computer readable medium may include at least one from the group consisting of: hard disks, CD-ROMs, optical storage devices, magnetic storage devices, read-only memory, programmable read-only memory, erasable programmable read-only memory, EPROM, electrically erasable programmable read-only memory, and flash memory. In embodiments where the components are implemented using software, the software may be stored in a computer readable medium and loaded into a computing system using, for example, a removable storage drive. The control module (in this example, software instructions or executable computer process code) when executed by a processor in a computer system causes the processor to perform the functions of the invention as described herein.

Furthermore, the concepts of the present invention may be applied to any circuit for performing signal processing functions within a network component. It is further contemplated that the inventive concept may be employed by, for example, a semiconductor manufacturer in the design of a stand-alone device, such as a microcontroller of a digital signal processor (Digital Signal Processor, DSP), or an Application-specific integrated circuit (ASIC), and/or any other subsystem element.

It should be appreciated that for clarity, the above description has described embodiments of the invention with reference to a single processing logic. However, the inventive concept may equally be implemented by a number of different functional units and processors to provide signal processing functionality. Thus, references to specific functional units are only to be seen as references to suitable means for providing the described functionality rather than indicative of a strict logical or physical structure or organization.

Aspects of the invention may be implemented in any suitable form including hardware, software, firmware or any combination of these. The invention may optionally be implemented at least partly as computer software running on one or more data processors and/or digital signal processors or configurable module components of e.g. FPGA devices.

Thus, the components and assemblies of embodiments of the invention can be physically, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term "comprising" does not exclude the presence of other elements or steps.

Furthermore, although individually listed, a plurality of means, components or method steps may be implemented by e.g. a single unit or processor. Furthermore, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Furthermore, the inclusion of a feature in one category of claims does not imply a limitation to this category but rather indicates that the feature is equally applicable to other claim categories as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed, and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. Furthermore, singular references do not exclude a plurality. Thus, references to "a," "an," "the first," "the second," etc. do not exclude a plurality.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the invention is limited only by the appended claims. Furthermore, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in accordance with the invention. In the claims, the term "comprising" or "comprises" does not exclude the presence of other elements.

Claims (10)

1. A method of transmitting downlink control information from a base station to a UE in a cellular communication network using an OFDM transmission format, the method comprising:

defining a master CORESET comprising a plurality of PDCCH candidates;

defining a CORESET extension comprising a plurality of PDCCH candidates; and

at least one of the plurality of PDCCH candidates in the CORESET extension is mapped to at least one of the plurality of PDCCH candidates in the primary CORESET extension.

2. The method of claim 1 wherein a plurality of PDCCH candidates in a CORESET extension are mapped to a portion of a plurality of PDCCH candidates in a master CORESET.

3. The method of claim 2, wherein the offset parameter indicates an offset applied to the CORESET extension.

4. The method of claim 1, wherein the primary CORESET and CORESET extensions are interleaved prior to transmission.

5. The method according to any of the preceding claims, wherein the mapping step uses a configurable mapping or an implicit mapping.

6. The method of any of the preceding claims, wherein the PDCCH candidates are encoded and mapped to CCEs, and wherein the UE decodes the PDCCH candidates using at least one CCE in a primary CORESET and at least one CCE in a CORESET extension.

7. The method of any one of claims 1 to 6, wherein the method further comprises:

determining an aggregation level and assigning the aggregation level to the UE;

generating a DCI payload;

appending the CRC to the DCI payload;

encoding the DCI payload and the CRC to generate a codeword;

rate matching the codeword using the demodulation reference signal to produce a channel code;

scrambling and mapping the channel codes into a plurality of QPSK symbols;

mapping the QPSK symbols to at least one CCE and at least one REG using a mapping scheme defined in the primary CORESET; and

at least one CCE and at least one REG are used in the primary core.

8. The method of claim 7, wherein at least one REG in the master CORESET is indexed independently of at least one second REG used in the CORESET extension.

9. A base station configured to perform the method of any of the preceding claims.

10. A UE configured to decode the master CORESET and CORESET extensions of any one of claims 1 to 8.

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