New radio system physical downlink control channel design method, user equipment and memory

Abstract

Design methods of physical downlink control channel (PDCCH), user equipment and memory are proposed for next generation 5G new radio system. UE receives configuration of default control resource set (CORESET) in MIB / SIB from its serving base station. The default CORESET contains common search space and UE-specific search space for candidate PDCCH transmission. PDCCH in the default CORESET is mapped to physical resource in distributed or localized manner. Specifically, various REG-to-CCE mapping rules are proposed to improve frequency diversity gain or frequency selectivity gain, or to reduce latency of PDCCH processing. Furthermore, to facilitate analog beamforming in mmWave system, the default CORESET is transmitted in synchronization signal (SS) block associated with corresponding analog beam direction. The design methods of physical downlink control channel and related user equipment of the present invention can improve frequency diversity gain or frequency selectivity gain, or reduce latency of PDCCH processing.

Description

[0001] This application is a divisional application of application serial number "201880003628.3", titled "New Radio System Physical Downlink Control Channel Design Method, User Equipment and Memory", filed on March 22, 2018, which claims priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 62 / 474,696, titled "Physical Downlink Control Channel (PDCCH) Design", filed on March 22, 2017, the subject matter of which is incorporated by reference herein.

[0002] Cross Reference to Related Applications

[0003] This application claims priority under 35 U.S.C. § 119 to U.S. Provisional Application No. 62 / 474,696, titled "Physical Downlink Control Channel (PDCCH) Design", filed on March 22, 2017, the subject matter of which is incorporated by reference herein. TECHNICAL FIELD

[0004] The disclosed embodiments relate to Physical Downlink Control Channel (PDCCH) design, and more specifically, to PDCCH design and resource allocation in next generation 5G new radio (NR) mobile communication networks. BACKGROUND

[0005] A Long-Term Evolution (LTE) system provides high peak data rates, low latency, improved system capacity, and low operating cost due to simple network architecture. The LTE system also provides seamless integration with older wireless networks, such as GSM, CDMA, and Universal Mobile Telecommunication System (UMTS). In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node Bs (eNodeB or eNB) in communication with multiple mobile stations, referred to as user equipment (UE). Enhancements are considered to the LTE system so that they can meet or exceed the International Mobile Telecommunications Advanced (IMT-Advanced) fourth generation (4G) standards. Multiple access in the downlink is achieved by different sub-bands (i.e., groups of subcarriers, denoted as resource blocks (RBs)) of the system bandwidth based on the existing channel conditions for each user. In the LTE network, PDCCH is used for dynamic downlink scheduling.

[0006] A plurality of physical resource blocks (PRBs) are allocated for PDCCH transmission carrying downlink control information (DCI). In order to decode the PDCCH specifically intended for the UE, the UE needs to find out the location of its PDCCH. In a so-called "blind" decoding process, the UE has to try a number of candidate PDCCHs before knowing which PDCCH is for itself. The allocated radio resources where the candidate PDCCHs can be allocated or located. In addition, the PDCCHs can constitute a common search space (CSS) or a UE-specific search space (UESS). As a result, supporting distributed and localized PDCCH transmission in both common and UE-specific search spaces per UE can result in excessive control signaling and increased number of blind decodes.

[0007] For sub-6 GHz bands, the signal bandwidth of the next generation 5G NR system is estimated to increase up to hundreds of MHz and even to values of GHz in the case of millimeter wave (mmWave) bands. Moreover, the NR peak rate requirement can be as high as 20 Gbps, which is more than ten times that of LTE. Three main applications in the 5G NR system include enhanced Mobile Broadband (eMBB), Ultra-Reliable Low Latency Communications (URLLC), and massive Machine-Type Communication (MTC) based on mmWave technology, small cell access, and unlicensed spectrum transmission. Multiplexing eMBB and URLLC within a carrier is also supported. Specifically, the mmWave spectrum between 3 and 300 GHz is explored for the next generation wideband cellular communication networks. mmWave wireless networks use narrow-beam directional communication, which can support thousands of megabits per second data rates. Directional antennas can be implemented through phased-array antennas with many antenna elements. Analog beamforming and spatial multiplexing methods can be applied to multiple antenna systems.

[0008] A solution is sought that improves the design of PDCCH structure and supports analog beamforming, COMP, and MU-MIMO in PDCCH design. SUMMARY

[0009] A new design for PDCCH is proposed for the next generation 5G new radio system. Each PDCCH is associated with a set of control channel elements (CCEs) for PDCCH transmission. Each CCE consists of multiple resource element groups (REGs) based on REG-to-CCE mapping rules, and each REG is indexed by frequency-first REG indexing manner or by time-first REG indexing manner. A UE receives the configuration of a default control resource set (CORESET) in master information block (MIB) / system information block (SIB) from its serving base station. The default CORESET contains common search space and UE-specific search space. PDCCHs in the default CORESET are mapped to physical resources in a distributed or localized manner. Specifically, various REG-to-CCE mapping rules are proposed to improve frequency diversity gain or frequency selectivity gain, or to reduce the latency of PDCCH processing. Furthermore, to facilitate analog beamforming in mmWave systems, the default CORESET is transmitted in a synchronization signal (SS) block associated with a corresponding analog beam direction. A UE reads the configuration of the default CORESET in the SS block of its preferred analog beam direction and derives physical random-access channel (PRACH) resources for channel access.

[0010] In one embodiment, a UE receives a control signal from a base station to determine a set of received physical resource blocks (PRBs) and a set of OFDM symbols carrying downlink control information. The UE determines a set of candidate PDCCHs within the set of PRBs. Each PDCCH is associated with a set of CCEs for PDCCH transmission. The UE collects multiple REGs for each CCE. Each CCE consists of multiple REGs based on REG-to-CCE mapping, and each REG is indexed by frequency-first REG indexing manner or by time-first REG indexing manner. The UE decodes downlink control information mapped to the collected REGs.

[0011] In another embodiment, the UE receives one or more SS blocks from a base station. Each SS block is associated with a respective analog beam direction. The UE obtains a default CORESET in the SS block and determines a respective UE favored analog beam direction. The default CORESET includes a set of PRBs, a set of OFDM symbols, numerology, periodicity, and reference signal (RS) configuration. The UE obtains a PRACH resource associated with the default CORESET. The UE performs an access procedure on the obtained PRACH resource.

[0012] The design method of the physical downlink control channel and the related user equipment of the present application can improve the frequency diversity gain or the frequency selectivity gain, or reduce the delay of PDCCH processing.

[0013] Other embodiments and advantages are described in the following detailed description. This summary is not intended to define the application. The application is defined by the claims. BRIEF DESCRIPTION OF DRAWINGS

[0014] In the drawings, like numerals refer to like components, illustrating embodiments of the application.

[0015] Figure 1 A next generation NR mobile communication network with control channel design is shown according to one novel aspect.

[0016] Figure 2 A simplified block diagram of a base station and a user equipment according to embodiments of the present application is shown.

[0017] Figure 3A A first embodiment of a PDCCH structure with frequency-first REG indexing and distributed REG-to-CCE mapping is shown.

[0018] Figure 3B A second embodiment of a PDCCH structure with frequency-first REG indexing and localized REG-to-CCE mapping is shown.

[0019] Figure 3C A third embodiment of a PDCCH structure with time-first REG indexing and distributed REG-to-CCE mapping is shown.

[0020] Figure 3D A fourth embodiment of a PDCCH structure with time-first REG indexing and localized REG-to-CCE mapping is shown.

[0021] Figure 4 CORESETs and search spaces configured for different UEs according to one novel aspect of the present application are shown.

[0022] Figure 5 Support of analog beamforming in PDCCH design is shown.

[0023] Figure 6 is a flowchart of a method PDCCH structure according to a novel aspect.

[0024] Figure 7 is a flowchart of a method PDCCH transmission with analog beamforming according to a novel aspect. DETAILED DESCRIPTION

[0025] Reference will now be made in detail to some embodiments of the application, examples of which are illustrated in the accompanying drawings.

[0026] Figure 1 A next generation NR mobile communication network 100 with PDCCH design according to a novel aspect is shown. The mobile communication network 100 is an OFDM / OFDMA system comprising a serving base station BS 101 and a plurality of user equipments UEs 102 and 103. When there is a downlink packet to be transmitted from the BS to the UEs, each UE gets a downlink assignment, e.g. a set of radio resources in the physical downlink shared channel (PDSCH). When a UE needs to transmit a packet in the uplink to the BS, the UE gets a grant from the BS which allocates the physical uplink shared channel (PUSCH) consisting of a set of uplink radio resources. The UE gets the downlink or uplink scheduling information from the PDCCH dedicated to this UE. In addition, broadcast control information is also transmitted in the PDCCH. The downlink and uplink scheduling information and the broadcast control information carried by the PDCCH are together referred to as DCI.

[0027] In Figure 1In the example, BS 101 transmits DCI to UE 102 and UE 103 using PDCCH 110 and PDCCH 120, respectively. In a 3GPP LTE system based on OFDMA downlink, radio resources are divided into subframes, each consisting of two time slots, and each time slot has seven OFDMA symbols along the time domain. Each OFDMA symbol also includes multiple OFDMA subcarriers along the frequency domain, depending on the system bandwidth. The basic unit of the resource grid is called an RE, which spans OFDMA subcarriers on an OFDMA symbol. A PRB occupies one time slot and twelve subcarriers, while a PRB pair occupies two consecutive time slots in a subframe. Each candidate PDCCH is associated with a set of CCEs to potentially carry DCI. The base station maps multiple REGs to each CCE based on REG-to-CCE mapping rules. If the DCI is intended for the UE, the base station encodes downlink control information on the set of CCEs to be transmitted to the UE.

[0028] Compared to the LTE parameter sets (subcarrier spacing and OFDM symbol length), next-generation 5G NR systems support multiple parameter sets, and the radio frame structure differs slightly depending on the type of parameter set. Additionally, PDCCH transmission supports analog beamforming. However, the general operation of PDCCH transmission remains the same as in LTE. To decode a PDCCH specifically for a UE, the UE needs to locate its PDCCH. In this so-called "blind" decoding process, the UE must try multiple candidate PDCCHs before knowing which PDCCH is for itself. PDCCHs can form a CSS for multiple UEs or a UESS for a single UE.

[0029] exist Figure 1 In the example, each UE receives the configuration of the default CORESET from the serving base station in the MIB / SIB. On the time-frequency radio resource grid, UE 102 receives default CORESET#1, and UE 103 receives default CORESET#2. The default CORESET contains a common search space and a UE-specific search space. PDCCHs in the default CORESET are mapped to physical resources in a distributed or localized manner. Specifically, various REG-to-CCE mapping rules are proposed to improve frequency diversity gain or frequency selectivity gain, or to reduce the latency of PDCCH processing. Furthermore, to facilitate analog beamforming in the mmWave system, the default CORESET is transmitted in the SS block associated with the corresponding analog beam direction. For example, CORESET#1 is transmitted in SSB#1 associated with the first beam direction of UE 102, and CORESET#2 is transmitted in SSB#2 associated with the second beam direction of UE 103.

[0030] Figure 2 A simplified block diagram of a base station 201 and a user equipment 211 according to embodiments of the application is shown. For the base station 201, an antenna 207 transmits and receives radio signals. An RF transceiver 206 coupled with the antenna receives RF signals from the antenna, converts them to baseband signals and sends them to a processor 203. The RF transceiver 206 also converts baseband signals received from the processor into RF signals and sends them to the antenna 207. The processor 203 processes the received baseband signals and invokes different functional modules to perform features in the base station 201. A memory 202 stores program instructions and data 209 to control the operation of the base station.

[0031] A similar configuration exists in the UE 211, where an antenna 217 transmits and receives RF signals. An RF transceiver 216 coupled with the antenna receives RF signals from the antenna, converts them to baseband signals and sends them to a processor 213. The RF transceiver 216 also converts baseband signals received from the processor into RF signals and sends them to the antenna 217. The processor 213 processes the received baseband signals and invokes different functional modules to perform features in the UE 211. A memory 212 stores program instructions and data 219 to control the operation of the UE.

[0032] The base station 201 and the UE 211 also include several functional modules and circuits to implement some embodiments of the application. The different functional modules and circuits can be implemented by software, firmware, hardware, or any combination thereof. In one example, each functional module or circuit includes a processor and a corresponding program code. When executed by the processors 203 and 213 (e.g., by executing the program instructions and data 209 and 219), the functional modules and circuits allow the base station 201 to encode and transmit downlink control information to the UE 211, and allow the UE 211 to receive and decode the downlink control information accordingly.

[0033] In one embodiment, the base station 201 configures a set of radio resources for PDCCH transmission via the control module 208 and maps the downlink control information to the configured REGs via the mapping module 205. The downlink control information carried in the PDCCH is then modulated and encoded via the encoder 204, passed through the beamforming circuit 231 for transmission by the transceiver 206 via the antenna 207. The beamforming circuit 231 can belong to the part of the RF transceiver 206. The UE 211 receives the downlink control information by the transceiver 216 through the antenna 217. Optionally, the UE 211 can perform beamforming via the beamforming circuit 241, which can belong to the part of the RF transceiver 216. The UE 211 determines the configured radio resources for PDCCH transmission via the control module 218 and collects the configured REGs via the collector 215. The UE 211 then demodulates and decodes the downlink information from the collected REGs via the decoder 214. After successfully decoding the downlink control information and the PDCCH, the UE 211 can determine its preferred UE analog beam direction and PRACH resource and perform channel access through the channel access processing circuit 242.

[0034] The design of PDCCH resource allocation is decomposed into two steps. First, the base station maps multiple REGs to each CCE based on the REG-to-CCE mapping rule. The physical units are indexed by REG, where a set of REs is predefined for each REG. The logical units are created by CCE, where a set of REGs is predefined or configured for each CCE by higher layers. The REG indexing can be done in frequency-first manner or in time-first manner over the CORESET. The REG-to-CCE mapping can be distributed or localized. Second, the CCE-to-PDCCH candidate mapping is defined in the search space. For distributed transmission of PDCCH, a CCE is composed of several REGs distributed in multiple non-contiguous PRBs across the whole channel frequency, so that the distributed CCE structure can be used to maximize the frequency diversity gain. For localized transmission of PDCCH, a CCE is composed of several REGs uniformly distributed in a single PRB, so that it helps to uniformly utilize the reference signal within one PRB for better robustness in channel estimation.

[0035] Figure 3A A first embodiment of PDCCH structure with frequency-first REG indexing and distributed REG-to-CCE mapping is shown. In this embodiment, the REGs are indexed in frequency-first manner, and the REG-to-CCE mapping is distributed. The REGs are indexed in frequency-first manner, and the REG-to-CCE mapping is distributed. Figure 3AIn the example of FIG. 2, each unit block represents a REG. The CORESET has 24 PRBs in the frequency domain and two OFDM symbols in the time domain. One CCE has six REGs. The physical REGs are labeled with physical REG indices. Since the mapping is frequency-first, the REG indices follow a frequency-first manner. For each REG, the physical REG index is converted to a logical REG index. The conversion is done by an interleaver. The purpose of the interleaver is to achieve a distributed mapping within a CCE. The interleaver has a scope of the entire CORESET in the frequency and time domains. The interleaved REGs are then grouped into CCEs according to the logical indices. For example, the REGs with logical indices 0 to 5 are grouped to form CCE #0, and the REGs with logical indices 6 to 11 are grouped to form CCE #1. This distributed REG-to-CCE mapping is used with the frequency-first REG indices to achieve frequency diversity gain, e.g., the physical REGs of one CCE are located in different subcarriers in the frequency domain, respectively.

[0036] Figure 3B A second embodiment of PDCCH structure with frequency-first REG indices and localized REG-to-CCE mapping is shown in FIG. 3. In the example of FIG. 3, each unit block represents a REG. The CORESET has 24 PRBs in the frequency domain and two OFDM symbols in the time domain. One CCE has six REGs. The physical REGs are labeled with physical REG indices. Since the mapping is frequency-first, the REG indices follow a frequency-first manner. An interleaver is not needed. The REGs are then grouped into CCEs according to the logical indices. For example, the REGs with logical indices 0 to 5 are grouped to form CCE #0, and the REGs with logical indices 6 to 11 are grouped to form CCE #1. This localized REG-to-CCE mapping is used with the frequency-first REG indices to reduce latency of PDCCH processing, e.g., the physical REGs of one CCE are located within one OFDM symbol. Figure 3B

[0037] A third embodiment of PDCCH structure with time-first REG indices and distributed REG-to-CCE mapping is shown in FIG. 4. In the example of FIG. 4, each unit block represents a REG. The CORESET has 24 PRBs in the frequency domain and two OFDM symbols in the time domain. One CCE has six REGs. The physical REGs are labeled with physical REG indices. Since the mapping is time-first, the REG indices follow a time-first manner. An interleaver is not needed. The REGs are then grouped into CCEs according to the logical indices. For example, the REGs with logical indices 0 to 5 are grouped to form CCE #0, and the REGs with logical indices 6 to 11 are grouped to form CCE #1. This distributed REG-to-CCE mapping is used with the time-first REG indices to achieve time diversity gain, e.g., the physical REGs of one CCE are located in different OFDM symbols in the time domain, respectively. Figure 3C Figure 3C ​In the example of FIG. 6, each unit block represents a REG. The CORESET has 24 PRBs in the frequency domain and two OFDM symbols in the time domain. One CCE has six REGs. The physical REGs are labeled with physical REG indices. Since the mapping is time-first, the REG indices follow a time-first manner. For each REG, the physical REG index is converted to a logical REG index. The conversion is done by an interleaver. The purpose of the interleaver is to achieve a distributed mapping within a CCE. The interleaver has a scope of the entire CORESET in the frequency and time domain. The REGs are then grouped into CCEs according to the logical indices. For example, the REGs with logical indices 0 to 5 are grouped to form CCE #0 and the REGs with logical indices 6 to 11 are grouped to form CCE #1.

[0038] Figure 3D A fourth embodiment of a PDCCH structure with time-first REG indexing and localized REG-to-CCE mapping is shown. In the example of FIG. 7, each unit block represents a REG. The CORESET has 24 PRBs in the frequency domain and two OFDM symbols in the time domain. One CCE has six REGs. The physical REGs are labeled with physical REG indices. Since the mapping is time-first, the REG indices follow a time-first manner. An interleaver is not needed. The REGs are then grouped into CCEs according to the logical indices. For example, the REGs with logical indices 0 to 5 are grouped to form CCE #0 and the REGs with logical indices 6 to 11 are grouped to form CCE #1. This localized REG-to-CCE mapping is used together with time-first REG indexing to improve the frequency-selective gain, e.g., the physical REGs of one CCE are located within nearby subcarriers. Figure 3D

[0039] Figure 4 CORESETs and search spaces configured for different UEs according to a novel aspect of the present application are shown. A UE receives the configuration of a default CORESET in the MIB or SIB. The CORESET configuration includes a set of PRBs in the frequency domain and a set of OFDM symbols in the time domain. In addition, the CORESET configuration includes a numerology of the radio resource grid, a periodicity of the control signals, and a RS configuration. In one example, as shown in FIG. 8, the CORESET configuration includes a set of PRBs in the frequency domain and a set of OFDM symbols in the time domain. The CORESET configuration also includes a numerology of the radio resource grid, a periodicity of the control signals, and a RS configuration. The UE receives the configuration of a search space in the MIB or SIB. The search space configuration includes a set of PRBs in the frequency domain and a set of OFDM symbols in the time domain. In addition, the search space configuration includes a numerology of the radio resource grid, a periodicity of the control signals, and a RS configuration. In one example, as shown in FIG. 9, the search space configuration includes a set of PRBs in the frequency domain and a set of OFDM symbols in the time domain. The search space configuration also includes a numerology of the radio resource grid, a periodicity of the control signals, and a RS configuration. Figure 4 ​A REG contains 12 REs along the frequency domain and occupies one OFDM symbol, as shown in 410, and the reference signal (e.g., DMRS is self-contained in the REG). A default CORESET contains common search space and UE-specific search space. PDCCH in the default CORESET is mapped to physical resources in a distributed manner, e.g., REG to CCE mapping is distributed. This is because PDCCH can be for all UEs in the cell and frequency diversity is desired. The physical resources of the default CORESET can be contiguous or non-contiguous in the frequency domain. The default CORESET can not be present in every slot. This is because paging and system information appear periodically and random access response appears within a window of PRACH resources.

[0040] After obtaining the UE ID from the base station, e.g., after its C-Radio Network Temporary Identifier (RNTI) is available, the UE can be additionally configured by higher layers with additional CORESETs, e.g., receiving additional CORESETs through higher layer signaling. Similar to the default CORESET, the additional CORESET configuration includes the numerology of the radio resource grid, periodicity of the control signal, and RS configuration. The additional CORESET contains UE-specific search space because it is typically for that UE. REG to CCE mapping of PDCCH in the additional CORESET is localized or distributed. The default CORESET and the additional CORESET can overlap in time domain and / or frequency domain for the UE. The properties of the default CORESET and the additional CORESET can be different, e.g., physical resource allocation (time-first or frequency-first; localized or distributed), transmission scheme, RS pattern, PRB bundling size, etc. There are two types of PDCCH, i.e., broadcast / multicast PDCCH and unicast PDCCH. Broadcast / multicast PDCCH and unicast PDCCH should have different REG to PDCCH candidate mapping, i.e., time-first or frequency-first, localized or distributed. Therefore, REG to PDCCH candidate mapping is a parameter of search space, not a parameter of CORESET.

[0041] In Figure 4In an example, consider a PDCCH structure with frequency-first REG indexing and localized REG-to-CCE mapping. A serving base station configures CORESET #1 for UE #1 and CORESET #2 for UE #2. Assume that the CORESET duration for UE #1 is OFDM symbol 1 and the CORESET duration for UE #2 is OFDM symbols 1 and 2. When a CORESET contains an integer number of CCEs in the frequency domain, e.g., four CCEs, the CCEs for UE #1 and the CCEs for UE #2 are aligned in the second OFDM symbol. In this way, the blocking rate for PDCCH scheduling is low. Therefore, in the frequency domain, a CORESET contains an integer number of CCEs.

[0042] Figure 5 Support of analog beamforming in PDCCH design is shown. When a UE powers on, it starts cell search and selects an appropriate cell to perform the following behaviors. First, the UE reads the MIB in the SS block, where the MIB contains the configuration of the default CORESET. Second, the UE reads the DCI of the basic SIB in the default CORESET. The DCI is delivered by PDCCH in the common search space contained in the default CORESET. The basic SIB is delivered by PDSCH, which carries the configuration of PRACH resources. Third, the UE performs random access based on the PRACH resource configuration to enter RRC connected mode and obtain a C-RNTI. Fourth, after entering RRC connected mode, the UE can be signaled about the configuration of additional CORESETs through dedicated RRC.

[0043] When analog beamforming is used, the above behaviors need to be considered with a beam management procedure. For example, in mmWave systems, control beams associated with different beamforming weights are defined for periodically broadcasting control information to all UEs in the cell. As Figure 5As shown, assume there are two DL TX analog beam directions. BS 501 transmits SS block #1, default CORESET #1 and SIB #1 via the first DL TX analog beam direction. BS 501 transmits SS block #2, default CORESET #2 and SIB #2 via the second DL TX analog beam direction. For UE #1 that prefers the first DL TX analog beam direction in the cell search procedure, UE #1 reads MIB #1 and obtains the configuration of default CORESET #1 in SS block #1. For UE #2 that prefers the second DL TX analog beam direction in the cell search procedure, UE #2 reads MIB #2 and obtains the configuration of default CORESET #2 in SS block #2. Through SIB #1, UE #1 knows the resource configuration #1 of PRACH resources and transmits PRACH preamble based on PRACH #1 resources. Through SIB #2, UE #2 knows the resource configuration #2 of PRACH resources and transmits PRACH preamble based on PRACH #2 resources.

[0044] The network knows which analog beam direction the UE prefers (or which default CORESET the UE is monitoring) from the PRACH resource the UE adopts. The random-access response (RAR) is transmitted with the DL TX analog beam direction the UE prefers. To transmit unicast PDCCH, the network needs to know the analog beam direction the UE prefers. Broadcast or multicast PDCCH is transmitted in the default CORESET in all analog beam directions. After its C-RNTI is available, the UE can be additionally configured with an additional CORESET by higher layers. Because PDSCH can not occur after the CORESET, the starting symbol of PDSCH can be carried in the unicast PDCCH transmission.

[0045] For coordinated multi-point (COMP) transmission, when different transmission points (TRPs) use the same cell ID, the UE cannot distinguish the SS blocks transmitted from different TRPs. Downlink COMP can be performed by multiple TRPs or multiple transmit beam directions in mmWave systems. The transmit beam direction can be an aggregation of the transmit beams of multiple TRPs. For each transmit beam, the UE knows which receive beam should be used through the beam management procedure or channel state information (CSI) measurement procedure. If each TRP (or each group of TRPs) uses a different DMRS sequence for PDCCH, the UE can distinguish the signals from different TRPs (or a group of TRPs). For MU-MIMO transmission, PDCCHs for different UEs can be transmitted through MU-MIMO. The PDCCHs can come from different TRP groups. The PDCCHs can come from the same TRP group. The PDCCHs can have different beam directions.

[0046] Figure 6 is a flowchart of a method PDCCH structure according to one novel aspect. In step 601, a UE receives a control signal from a base station to determine a set of received PRBs and a set of OFDM symbols carrying downlink control information. In step 602, the UE determines a set of candidate PDCCHs within the set of PRBs. Each PDCCH is associated with a set of CCEs for PDCCH transmission. In step 603, the UE collects a plurality of REGs for each CCE. Each CCE consists of a plurality of REGs based on REG-to-CCE mapping, and each REG is indexed by frequency-first REG indexing or by time-first REG indexing. In step 604, the UE decodes the downlink control information mapped to the collected plurality of REGs.

[0047] Figure 7 is a flowchart of a method of PDCCH transmission with analog beamforming according to one novel aspect. In step 701, a UE receives one or more SS blocks from a base station. Each SS block is associated with a respective analog beam direction. In step 702, the UE obtains a default CORESET in the SS block and determines a respective UE preferred analog beam direction. The default CORESET includes a set of PRBs, a set of OFDM symbols, a numerology, a periodicity, and an RS configuration. In step 703, the UE obtains a PRACH resource associated with the default CORESET. In step 704, the UE performs an access procedure on the obtained PRACH resource.

[0048] While the application has been described above in connection with certain specific embodiments for instructional purposes, the application is not limited to this. Therefore, various modifications in form and detail can be made without departing from the scope of the application as set forth in the following claims.

Claims

1. A method for physical downlink control channel design of a new radio system, comprising: receiving, by a user equipment, one or more synchronization signal blocks from a base station, wherein each synchronization signal block is associated with a corresponding beam direction; acquiring a default control resource set in a synchronization signal block and determining a corresponding user equipment preferred beam direction, wherein the default control resource set comprises a set of physical resource blocks and a set of OFDM symbols; acquiring a physical random access channel resource associated with the default control resource set; and performing an access procedure on the acquired physical random access channel resource; wherein the user equipment receives an additional control resource set on higher layer signaling after the user equipment obtains a user equipment ID from the base station. The default control resource set contains common search space and user equipment specific search space for physical downlink control channel transmission. 2.The method of designing a physical downlink control channel of a new radio system of claim 1, wherein, The user equipment receives broadcast or multicast physical downlink control channel transmitted in the default control resource set in all analog beam directions. 3.The method of physical downlink control channel design for new radio system of claim 2, wherein, The user equipment receives unicast physical downlink control channel transmitted in the additional control resource set using the user equipment preferred analog beam direction. 4.The method of physical downlink control channel design for new radio system of claim 1, wherein, Each physical downlink control channel is associated with a set of control channel elements, and wherein the additional control resource set and the default control resource set contain an integer number of control channel elements in frequency domain. 5.The method of physical downlink control channel design for new radio system of claim 1, wherein, 6.A user equipment for physical downlink control channel design of a new radio system, comprising: a radio frequency receiver configured to receive one or more synchronization signal blocks from a base station, wherein each synchronization signal block is associated with a corresponding beam direction; a control circuit configured to acquire a default control resource set in a synchronization signal block and determine a corresponding user equipment preferred beam direction, wherein the default control resource set comprises a set of physical resource blocks and a set of OFDM symbols; and a channel access processing circuit configured to acquire a physical random access channel resource associated with the default control resource set and perform an access procedure on the acquired physical random access channel resource; wherein the user equipment receives an additional control resource set on higher layer signaling after the user equipment obtains a user equipment ID from the base station. The default control resource set contains common search space and user equipment specific search space for physical downlink control channel transmission.

7. The user equipment for new radio system physical downlink control channel design of claim 6, wherein, The user equipment receives broadcast or multicast physical downlink control channel transmitted in the default control resource set in all analog beam directions.

8. The user equipment for new radio system physical downlink control channel design of claim 7, wherein, The user equipment receives unicast physical downlink control channel transmitted in the additional control resource set using the user equipment preferred analog beam direction. 9.The user equipment for a physical downlink control channel design of a new radio system of claim 6, wherein, Each physical downlink control channel is associated with a set of control channel elements, and wherein the additional control resource set and the default control resource set contain an integer number of control channel elements in frequency domain. 10.The user equipment for a physical downlink control channel design of a new radio system of claim 6, wherein, 11.A user equipment for physical downlink control channel design of a new radio system, comprising: ​ A processor coupled to the transceiver and the memory, which when executing a program stored in the memory, causes the user equipment to perform operations recited in any of claims 1-5.

12. A memory storing a program which, when executed by a processor of a user equipment for physical downlink control channel design of new radio systems, causes the user equipment to perform operations recited in any of claims 1-5.

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