Coverage recovery in reduced capability wireless devices

Abstract

In addition to the main CORESET in a cellular communication system for control information transmission, an extended CORESET is defined in which a control channel can be transmitted. Candidates are defined and mapped together in both CORESETs.

Description

TECHNICAL FIELD

[0001] The following disclosure relates to wireless communications, and more specifically to coverage enhancements in reduced capability (REDCAP) wireless communication devices. BACKGROUND

[0002] Wireless communication systems, such as third generation (3G) mobile telephony standards and technologies, are well known. Such 3G standards and technologies have been developed by the Third Generation Partnership Project (3GPP) (RTM). Third generation wireless communications have been developed generally to support macro-cell mobile telephony communications. Communications systems and networks have evolved towards broadband and mobile systems.

[0003] In a cellular wireless communication system, User Equipment (UE) is connected to a Radio Access Network (RAN) over a wireless link. The RAN comprises a set of base stations providing wireless links to UEs located in cells covered by the base stations, and an interface to a Core Network (CN) providing overall network control. It will be appreciated that the RAN and CN each perform respective functions related to the overall network. For convenience, the term "cellular network" will be used to refer to the combined RAN and CN, and it will be appreciated that the term is used to refer to the respective systems for performing the disclosed functionality.

[0004] The Third Generation Partnership Project has developed a so-called Long Term Evolution (LTE) system, namely the Evolved Universal Mobile Telecommunication System Territorial Radio Access Network (E-UTRAN), for mobile access networks in which one or more macro cells are supported by base stations known as eNodeBs or eNBs (Evolved Node Bs). More recently, LTE is being further developed towards so-called 5G or NR (New Radio) systems in which one or more cells are supported by base stations known as gNBs. NR is proposed to use an Orthogonal Frequency Division Multiplexed (OFDM) physical transmission format.

[0005] The NR protocol aims to provide an option to operate in unlicensed radio bands, referred to as NR-U. When operating in unlicensed radio bands, gNBs and UEs must contend for physical medium / resource access with other devices. For example, Wi-Fi (RTM), NR-U, and LAA can use the same physical resources.

[0006] A trend in wireless communications is to provide lower latency and higher reliability services. For example, NR aims to support Ultra-reliable and low-latency communications (URLLC), while massive Machine-Type Communications (mMTC) aims to provide low latency and high reliability for small data packet sizes (typically 32 bytes). A user-plane latency of 1 ms with a reliability of 99.99999% is proposed, with a packet loss rate of 10 -5 or 10 -6 -1 at the physical layer.

[0007] mMTC services aim to support a large number of devices over a long life cycle through a highly energy-efficient communication channel, with occasional and infrequent data transfer with each device. For example, a cell can be expected to support thousands of devices.

[0008] The following disclosure relates to various improvements to cellular wireless communication systems. SUMMARY

[0009] The invention is defined by the claims, wherein there is provided a method of transmitting downlink control information from a base station to a UE in a cellular communications network using an OFDM transmission format, the method comprising: defining a primary 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.

[0010] The plurality of PDCCH candidates in the CORESET extension are mapped to a portion of the plurality of PDCCH candidates in the primary CORESET.

[0011] An offset parameter indicates an offset applied to the CORESET extension.

[0012] The main CORESET and the CORESET extension are interleaved before transmission.

[0013] The mapping step uses a configurable mapping or an implicit mapping.

[0014] The PDCCH candidates are encoded and mapped to CCEs, and wherein the UE decodes the PDCCH candidates using at least one CCE in the main CORESET and at least one CCE in the CORESET extension.

[0015] The method can further include determining an aggregation level and assigning the aggregation level to the UE; generating a DCI payload; appending a CRC to the DCI payload; encoding the DCI payload and the CRC to generate a codeword; rate matching the codeword using a demodulation reference signal to produce a channel coding; scrambling and mapping the channel coding as 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 main CORESET; and using the at least one CCE and the at least one REG in the main CORESET.

[0016] The at least one REG in the main CORESET can be indexed independently of at least one second REG used in the CORESET extension.

[0017] A base station configured to perform the methods described herein is also provided.

[0018] A UE configured to decode the main CORESET and the CORESET extension described herein is also provided.

[0019] The non-transitory computer readable medium can include at least one from a group consisting of a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read-Only Memory, a Programmable Read-Only Memory, an Erasable Programmable Read-Only Memory, an EPROM, an Electrically Erasable Programmable Read-Only Memory, and a flash memory. BRIEF DESCRIPTION OF DRAWINGS

[0020] Further details, aspects and embodiments of the application will be described, by way of example only, with reference to the drawings. The components in the drawings are schematically shown and not necessarily drawn to scale. Like reference numerals have been included in the respective drawings to facilitate understanding.

[0021] Figure 1 Selected elements of a cellular communications network are shown;

[0022] Figures 2 to 7 Various CORESET examples are shown that can be used in a cellular communications network. Figure 1 DETAILED DESCRIPTION ​

[0023] Those skilled in the art will recognize and appreciate that the details of the described examples are illustrative only and that the teachings provided herein are applicable to a variety of alternative settings.

[0024] Figure 1 A schematic diagram showing three base stations (e.g. eNBs or gNBs depending on the particular cellular standard and terminology) forming a cellular network is shown. Typically, each base station will be deployed by a cellular network operator to provide geographical coverage for UEs in the area. The base stations form a 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 a core network by an S1 interface. It will be appreciated that only basic details are shown for the purpose of illustrating key features of a cellular network. A PC5 interface is provided between UEs for sidelink communication. The relevant interfaces and component names are used only as examples, different systems operating on the same principles can use different nomenclature. Figure 1

[0025] Each base station comprises hardware and software to implement the functionality of the RAN, including communication with the core network and other base stations, control and data signal transmission between the core network and UEs, and maintaining wireless communication with UEs associated with each base station. The core network comprises hardware and software to implement network functions, such as overall network management and control, and routing of calls and data.

[0026] The base stations transmit a physical downlink control channel (PDCCH) on a pre-configured region of the time frequency grid (called a control resource set (CORESET)). A search space provides a configuration associated with a given CORESET and specifies symbols and physical resource blocks (PRBs) that a UE uses to attempt PDCCH decoding. Modern telecommunication standards include functionality for reduced capability (REDCAP) devices that operate with reduced bandwidth and reduced number of receive chains (1RX or 2RX).

[0027] ​Compared to standard UE devices, REDCAP devices have a fixed coverage loss due to reduced hardware complexity, reduced physical downlink control channel (PDCCH) monitoring capability, and reduced bandwidth reception capability for PDCCH. Coverage recovery solutions that require a larger PDCCH bandwidth or increase the number of blind decoding attempts are not suitable.

[0028] Solutions that can increase PDCCH coverage can reduce the Downlink Channel Information (DCI) size, providing a smaller payload, which would result in the same number of resources with a higher coding rate. Other solutions can include larger aggregation levels (ALs), which would result in a higher coding rate but also require more resources, which in turn would result in PDCCH blocking. That is, there are not enough resources available to schedule other UEs. Additionally, solutions can include repetition of the PDCCH, which is repeated multiple times in the time and / or frequency domain. However, for REDCAP, only time-domain repetition can be an option because the bandwidth is limited. Repetition in time would result in larger delays and increased power consumption.

[0029] Transmitting a PDCCH requires transmitting the DCI payload at the base station (gNB) side following the general steps 1 to 7 below:

[0030] Step 1 - Determine aggregation level: The gNB determines the AL according to the link adaptation algorithm. Typically, UEs with poor coverage conditions get assigned a larger AL than UEs with good coverage conditions.

[0031] Step 2 - Generate DCI payload: The gNB generates the DCI according to the UE configuration and the control information it wants to transmit.

[0032] Step 3 - Append 24-bit cyclic redundancy check (CRC): A 24-bit CRC is generated from the DCI payload and scrambled with the appropriate radio network temporary identifier (RNTI).

[0033] Step 4 - Channel coding: Polar coding is used to encode the payload and CRC.

[0034] Step 5 - Rate matching: From the generated codeword, only those bits that fit the allocated resources are transmitted, taking into account the demodulation reference signal (DMRS). In addition, taking into account the demodulation reference signal (DMRS), an interleaving is applied to transmit only those bits that fit the allocated resources.

[0035] Step 6 - PDCCH encoding: The bits from the channel coding are scrambled and mapped to quadrature phase shift keying (QPSK) symbols. The gNB can apply a transmit diversity scheme and precoding for the control data and DMRS.

[0036] Step 7 - Resource mapping: The QPSK symbols are mapped to control channel elements (CCEs) and resource element groups (REGs) according to the CCE-to-REG mapping defined in the CORESET.

[0037] At the receiving end, the UE searches for PDCCH candidates in the 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 assignment DCI format 0_0 or 0_1 or DL assignment DCI format 1_0 or 1_1. The UE is also (pre-)configured with the payload size of each DCI. However, when the UE does not have the exact configuration information of the DCI format, AL, and related resources in the CORESET, it has to blindly try all possible combinations. The necessary steps can be summarized as follows:

[0038] Step 1 - Select DCI format: The payload of the DCI is known by pre-configuration.

[0039] Step 2 - Select an AL: The AL defines the number of resources (i.e., CCEs) used for decoding the attempt.

[0040] Step 3 - Attempt decoding: For all possible resource allocations of that AL, attempt to decode the PDCCH. If the CRC is correct, the decoding is successful, i.e., the CRC corresponds to the target RNTI. If not successful, go back to step 2 and try a different AL.

[0041] Repeat the above procedure for each DCI format with a different payload. If the payload is the same, the DCI format is distinguished by a flag within the payload to indicate the format.

[0042] The apparatuses, systems, and methods described herein extend CORESETs beyond 3 symbol duration by introducing a CORESET extension that directly maps to resources in a regular CORESET. Thus, a UE decodes PDCCH candidates to utilize resources in the CORESET and the CORESET extension to improve reliability / coverage. This results in reduced decoding latency because the extended CORESET is contiguous, reduced power consumption because the RF can be turned off after successful reception, and reduced memory consumption because there are fewer repetitions to buffer and combine before attempting to decode. In addition, the number of blind decoding attempts is the same as previous systems, but the diversity gain is increased because the CORESET and its extension can be configured with different CCE-to-REG mappings.

[0043] For example, a CORESET with 4 symbols can be configured as a 3 symbol CORESET duration and 1 symbol extension, a 2 symbol CORESET duration and 2 symbol extension, or a 1 symbol CORESET duration and 3 symbol extension. Figure 2 An example of a 3 symbol CORESET and an additional 3 symbol extension is shown. This CORESET is referred to as an extended CORESET and the additional symbols are referred to as a CORESET extension.

[0044] The CORESET extension can also be dynamically configured by dedicated DCI, which can enable or disable the extension or reconfigure it. The extension can span the same frequency resources as the CORESET or different frequency resources.

[0045] The PDCCH candidate that the CORESET extension is implicitly linked (or mapped) to the CORESET. This avoids treating the extension together with the CORESET as a normal large CORESET, which increases the PDCCH search space and thus the number of blind decoding attempts, which is undesirable for REDCAP UEs with reduced PDCCH decoding capability.

[0046] Not all resources in the CORESET need to be linked to the CORESET extension. For example, a PDCCH candidate with CCE indices from 0 to 7 is not linked to the CORESET extension, while a PDCCH candidate with CCE indices from 8 to 15 is linked to the CORESET extension. This will allow the gNB to reserve a portion of the CORESET for UEs with good coverage and no need for large ALs, and concentrate the extra resources in the extension to UEs with lower coverage. Figure 3One example where the REGs 36 to 53 are independent of the CORESET extension, while the REGs 0 to 35 are associated with the CORESET extension. The associated resources can be indicated in REGs, CCEs or physical resource blocks (PRBs).

[0047] The association of resources in the CORESET with resources in the CORESET extension can be configured in multiple ways. One approach is to configure a bit string indicating which resources are associated. In Figure 3 In the example of frequencyDomainResources being configured by the bit string 01111111111111111110, where the leftmost zero corresponds to PRBs 0 to 5. The frequencyDomainResources of the associated resources are then given by 01111111111110000000. Equivalently, the non-associated resources can be indicated.

[0048] The configuration by bit string allows for maximum flexibility, but consumes signaling bandwidth. Therefore, a more compact form can be to introduce possible fractions of the relevant CORESET resources, e.g. 1 / 2, 3 / 4, 2 / 3, 1 / 3, 1 / 4, etc., e.g. only the first half of the resources in the CORESET are associated with the extension. Additionally, an offset parameter can be introduced to increase flexibility. Likewise, in the example of Figure 3 In the example of frequencyDomainResources being configured by the bit string 01111111111111111110, where the leftmost zero corresponds to PRBs 0 to 5. The frequencyDomainResources of the associated resources are then given by 01111111111110000000. Equivalently, the non-associated resources can be indicated.

[0049] Furthermore, to maximize frequency diversity, the CORESET and the CORESET extension can be interleaved separately. That can be achieved by using all interleaving parameters reg-BundleSize, interleaverSize and shiftIndex or only some of them, e.g. shiftIndex. This will ensure that the resources in the CORESET and the CORESET extension do not occupy the same frequency resources, to maximize robustness to frequency selective fading.

[0050] The UEs that do not support the extended CORESETs can still receive control information in the normal CORESET. The extended resources can be considered and signaled as reserved resources in order for those UEs to calculate the correct amount of data resources.

[0051] In order to use the additional resources in the CORESET extension for PDCCH transmission, all resources can be used to encode the PDCCH with as high a code rate as possible. All candidate resources in the CORESET and the CORESET extension are used to try to decode the PDCCH. For example, a UE tries to decode AL 4 in the CORESET and is pre-configured to recognize the location of another 4 CCEs 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.

[0052] Thus, the UE will consider the combined resources when determining the AL to search for PDCCH candidates. For example, if 1 CCE in the CORESET is associated with 1 CCE of the extension, the UE will not search for AL 1, since the minimum AL is 2. That also means that ALs of e.g. 5 or 12 are possible. However, there is no increase in blind decoding attempts.

[0053] The ratio of CORESET resources to resources in the CORESET extension can also be configurable. For example, this can be achieved by configuring resources that are independent of the CORESET extension.

[0054] Alternatively, the PDCCH can be repeated in the CORESET extension and combined with the PDCCH in the CORESET. Thus, the UE can combine the two transmissions and subsequently decode the PDCCH candidate.

[0055] The number of repetitions can be configurable and given by the resource mapping between the CORESET and the CORESET extension. For example, if for AL 2, 2 CCEs in the CORESET are associated with 4 CCEs in the CORESET extension, the PDCCH on the 2 CCEs is repeated twice in the extension.

[0056] The apparatuses, systems, and methods described herein can use implicit mapping of resources indicated in the CORESET extension. CCEs in the CORESET can be mapped to another set (possibly different) of CCEs in the CORESET extension. Furthermore, the mapping can be fixed and only semi-statically changeable.

[0057] REGs can be individually indexed for a CORESET and a CORESET extension. Thus, a simple mapping rule is used to associate N CCEs with index n = 0, 1,..., N-1 to N CCEs in the CORESET extension having the same index n. Figure 4 One example of 4 CCEs of a CORESET mapping to 4 CCEs of an extension, i.e. only REGs 0 to 23 are associated with the CORESET extension. In this example, assuming PDCCH encoding across all resources, the UE would start decoding PDCCH candidates with AL 2, i.e. 1 CCE from the CORESET and 1 CCE from the extension, resulting in 4 PDCCH candidates. Similarly, the UE decodes PDCCH candidates with AL 4 spanning CCE0 / CCE1 and CCE2 / CCE3. Finally, one PDCCH candidate with AL 8 spanning all 8 CCEs.

[0058] A CORESET and a CORESET extension can have different CCE-to-REG mappings. Figure 5 An example of an extended CORESET with 2-symbol extension is shown, where the CORESET and the CORESET extension have different CCE-to-REG mappings. More precisely, the REG bundle size of the CORESET is 6, while the REG bundle size of the CORESET extension is 2. The interleaver depth of both is 3, i.e. the CORESET bandwidth is divided into 3 parts.

[0059] The same mapping rule can be applied, i.e. CCEs 0 to 3 in the CORESET are associated with CCEs 0 to 3 in the CORESET extension. However, due to interleaving, they correspond to different REGs.

[0060] There can be configurations where the number of resources in a CORESET and a CORESET extension is different. Consider Figure 6 an example where 2 CCEs are associated with 4 CCEs in the extension. In this case, 1 CCE in the CORESET is associated with 2 CCEs in the CORESET extension.

[0061] For example, CCE 0 is associated with CCE 0 / 1, CCE 1 is associated with CCE 2 / 3. The general mapping rule can be defined as follows: and N CCE,p denote the number of associated CCEs in the CORESET extension and the CORESET p, respectively. If CCE n in CORESET p is associated with CCE m in the CORESET extension by the following, where n = 0, 1,..., N CCE,p :

[0062] m = R CCE,p · n + i (1)

[0063] Similarly, if then CCE m in the CORESET extension is associated with CCE n in CORESET p by the following, where m = 0, 1,..., N CCE,p :

[0064] n = R CCE,p · m + i (2)

[0065] where

[0066]

[0067] When the number of CCEs in the CORESET extension is less than the number of CCEs in the associated CORESET, then multiple CCEs in the CORESET are associated with one CCE in the CORESET extension. Figure 7 An extended CORESET with 1 symbol extension is shown, where 4 CCEs in the CORESET are associated with 2 CCEs in the CORESET extension. Using this example and according to the above equation (2), 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 try to decode 4 times AL 2, 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) means CCEs x in the CORESET and CCEs y in the CORESET extension.

[0068] Although not shown in detail, any apparatus or device forming part of the network can comprise at least a processor unit, a storage unit and a communication interface, wherein the processor unit, the storage unit and the communication interface are configured to perform the method of any aspect of the application. Further options and choices are described below.

[0069] The signal processing functionality of embodiments of the application, particularly the gNB and the UE, can be implemented using computing systems or architectures known to those of skill in the art in view of the teachings herein. For example, a computing system, such as a desktop, laptop or notebook computer, hand-held computing device (PDA, cell phone, palmtop, etc.), mainframe, server, client, or any other type of special or general purpose computing device as can be desirable or appropriate for a given application or environment can be used. The computing system can include one or more processors, as described above, which can be implemented using a general or special purpose processing engine such as a microprocessor or microcontroller, or other control module.

[0070] The computing system can further include a main memory, such as random access memory (RAM) or other dynamic storage devices, for storing information and instructions to be executed by the processor. Such main memory also can be used for storing temporary variables or other intermediate information during execution of instructions to be executed by the processor. The computing system can likewise include a read only memory (ROM) or other static storage device for storing static information and instructions for the processor.

[0071] The computing system can further include an information storage system, which can include, for example, a media drive and a removable storage interface. The media drive can include a drive or other mechanism to support fixed or removable storage media, such as a hard disk drive, a floppy disk drive, a magnetic tape drive, an optical drive, a Compact Disc (CD) or Digital Video Drive (DVD) (R or RW), a read or write drive (R or RW), or other removable or fixed media drive. Storage media can include, for example, a 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 the media drive. Storage media can include a computer-readable storage medium, having stored therein particular computer software or data.

[0072] In alternative embodiments, the information storage system can include other similar components for allowing computer programs or other instructions or data to be loaded into the computing system. Such components can include, for example, a removable storage unit and an interface, such as a program cartridge and cartridge interface, a removable memory (for example, a flash memory or other removable memory module) and memory slot, and other removable storage units and interfaces that allow software and data to be transferred from the removable storage unit to the computing system.

[0073] A computing system can also include a communications interface. Such a communications interface can be used to allow software and data to be transferred between computing system and external devices. Examples of communications interface can include a modem, a network interface (such as an Ethernet or other NIC card), a communications port (such as a Universal Serial Bus (USB) port), a PCMCIA slot and card, etc. Software and data transferred via communications interface are in the form of signals which can be electronic, electromagnetic, and optical or other signals capable of being received by a communications interface.

[0074] In this document, the terms "computer program product," "computer-readable medium," and the like can be used to generally refer to tangible media such as memory, storage devices, or storage units. These, and other forms of computer-readable media, can store one or more instructions for use by a processor including a computer system to cause the processor to perform a certain operation. Such instructions, generally referred to as "computer program code" (which can be grouped in the form of computer processes or other grouping) when executed, enable a computing system to perform functions of embodiments of the present application. Note that the code can directly cause a processor to perform specified operations, be compiled to

[0075] A non-transitory computer readable medium can include at least one from among the group consisting of a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a read-only memory, a programmable read-only memory, an erasable programmable read-only memory, an EPROM, an electrically erasable programmable read-only memory, and a flash memory. In embodiments where components are implemented using software, the software can be stored in a computer readable medium and loaded into the computing system using, for example, a removable storage drive. The control modules, in this example software instructions or executable computer program code, when executed by a processor in the computing system, cause the processor to perform the functions of the present application as described herein.

[0076] Furthermore, the inventive concept can be applied to any circuitry for performing signal processing functions within a network component. It is further envisaged that, for example, a semiconductor manufacturer can employ the inventive concept in the design of a microcontroller of a stand-alone device, such as a Digital Signal Processor (DSP), or an Application-Specific Integrated Circuit (ASIC), and / or any other sub-system element.

[0077] It should be appreciated that the above description for clarity has described embodiments of the application with reference to individual functional units and processors. However, the modularity and scope of the application is not to be interpreted as having a limited scope or scope attached only to a certain number of functions or units. Rather, it is considered that modules can have novel combinations and assemblages other than those discussed and the preferred embodiments should not be construed while limited to the certain combination or assemblage of units presented and set forth.

[0078] Aspects of the application can be implemented in any suitable form including hardware, software, firmware or any combination of these. The application can 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, such as FPGA devices.

[0079] Accordingly, components and assemblies of embodiments of the application can be implemented in any suitable form, including hardware, software, firmware or any combination of these. The functionality can be implemented in a single unit, in multiple units, or as part of other functional units. Although the application has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the scope of the appended claims. In the claims, the term "comprising" does not exclude the presence of elements or steps other than those listed in a claim. In the claims, the term "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. It is further noted that specific features, objects and / or effects can be implemented independently from each other and can be combined in any order.

[0080] Furthermore, features implemented in different embodiments as separate features can be combined and / or structures implemented as a combined structure can be separated, into separate features. In addition, certain features can be enabled or disabled, depending on the configuration or implementation or the like. Furthermore, any combination of two or more features can be enabled or disabled, depending on the configuration or implementation or the like. In the claims, any reference signs placed between two different points represent that a combination of features enabling the use of such reference signs is appreciated. Furthermore, it is to be understood that the features can be implemented by hardware, software, firmware or any combination of them, and preferably any combination of hardware, software and firmware.

[0081] Furthermore, the order of the features in the claims do not mean that these features must be performed in that exact order, unless the claims state in other words that a certain feature is performed subsequently to another feature. In particular, unless the claims state in other words that a certain step is performed subsequently to another step, the order of the steps in the claims does not mean that these steps must be performed in that exact order. Rather, these steps can be performed in any suitable order. Furthermore, singular references do not exclude a plurality. Thus references to "a", "an", "the" are generally considered to be referring to a single aspect. However, some aspects can employ a plurality of these single aspects to implement the features of the application. For instance, reference to "one aspect" can include a plurality of that aspect, unless the context clearly indicates otherwise. The word "comprise" and variations of the word, such as "comprising", "comprises" and "comprised", as well as "include", "including" and "includes" when used in this document are not used in the theoretical or the abstract sense, but are used in a practical sense to describe one embodiment of the application.

[0082] Although the present application has been described in connection with some embodiments, it is not intended to be limited to the particular form set forth herein. Rather, the scope of the present application is limited only by the claims. Furthermore, although features can have been described in conjunction with a particular embodiment, one of ordinary skill in the art will recognize that variations and / or modifications of these features can be implemented in accordance with the application. In the claims, the term "comprising" or "including" does not exclude the presence of elements or steps other than those listed in a claim.

Claims

1. A method for transmitting downlink control information from a base station to a UE in a cellular communication network using OFDM transmission format, the method comprising: Define a main CORESET that includes multiple PDCCH candidates; The definition includes a CORESET extension for multiple PDCCH candidates; as well as Mapping at least one of the multiple PDCCH candidates in the CORESET extension to at least one of the multiple PDCCH candidates in the extension to the main CORESET, characterized in that: The number of control channel elements (CCEs) associated with the CORESET extension The number N of control channel elements (CCEs) associated with the main CORESET CCE,p It has the following mapping relationship, when The CCE n in the main CORESET is associated with the CCE m in the CORESET extension, where m = R CCE,p ·n+i and n=0,1,…,N CCE,p , when The CCE n in the main CORESET is associated with the CCE m in the CORESET extension, where n = R CCE,p ·m+i and m=0,1,…,N CCE,p , in 2. The method according to claim 1, characterized in that, Multiple PDCCH candidates in the CORESET extension are mapped to a subset of multiple PDCCH candidates in the main CORESET.

3. The method according to claim 1, characterized in that, The main CORESET and CORESET extension are interleaved before transmission.

4. The method according to claim 1, characterized in that, The mapping step uses either configurable mapping or implicit mapping.

5. The method according to claim 1, characterized in that, PDCCH candidates are encoded and mapped to CCEs, and the UE uses at least one CCE in the main CORESET and at least one CCE in the CORESET extension to decode the PDCCH candidates.

6. The method according to claim 1, characterized in that, The method further includes: Determine the aggregation level and assign it to the UE; Generate DCI payload; Attach CRC to the DCI payload; The DCI payload and CRC are encoded to generate codewords; The demodulation reference signal is used to rate-match the codewords to generate channel coding; The channel is scrambled and mapped to multiple QPSK symbols; Using the mapping scheme defined in the main CORESET, map QPSK symbols to at least one CCE and at least one REG; and Use at least one CCE and at least one REG in the main CORESET.

7. A base station, characterized in that, It includes: Memory, which stores computer-readable instructions; and The processor reads computer-readable instructions stored in the memory to perform the method of any one of the preceding claims.

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