Notifying ue capability to support random access operation enhancements for 5g nr in unlicensed spectrum

Abstract

A method of notifying UE capability to support enhanced NR-U random access operation is proposed. A UE communicates UE capability information to a mobile communication network, the UE capability information including information indicating a capability of the UE for random access operation in unlicensed spectrum. The UE receives a configuration of an unlicensed cell from the mobile communication network. The UE performs a random access operation on the unlicensed cell according to the configuration.

Description

[0001] Cross Reference to Related Applications

[0002] This application is based on 35 U.S.C. § 119(e) of the priority of U.S. Patent Application No. 62 / 970,791, filed February 6, 2020, entitled “Methods for UE capability signaling,” and U.S. Patent Application No. 63 / 014,813, filed April 24, 2020, entitled “Methods for capability signaling,” the contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] Embodiments of the present application relate generally to wireless communication, and more specifically, to methods for signaling UE capabilities to support enhancements for random access operation of 5G New Radio (NR) in unlicensed spectrum (NR-U). BACKGROUND

[0004] Wireless communication networks have grown exponentially over the years. Long-Term Evolution (LTE) systems provide high peak data rates, low latency, improved system capacity, and low operating cost due to simplified network architecture. LTE systems, also referred to as 4G systems, also provide seamless integration with older wireless networks, such as GSM, CDMA, and Universal Mobile Telecommunications System (UMTS). In LTE systems, the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) includes multiple evolved Node-Bs (eNodeBs or eNBs) that communicate with multiple mobile stations referred to as user equipment (UE). Third Generation Partnership Project (3GPP) networks typically include a mix of 2G / 3G / 4G systems. As the network design is optimized, many improvements have evolved with the evolution of various standards. The Next Generation Mobile Network (NGMN) Board has decided to focus the future NGMN activity on defining the end-to-end requirements for the 5G New Radio (NR) system.

[0005] In 3GPP Release 16 specifications, support for 5G NR operating in unlicensed spectrum (this feature is also referred to as NR-U) was introduced in order to bring a variety of options for flexible use of unlicensed spectrum for 5G. NR-U supports the use of unlicensed spectrum with and without license assistance. In particular, standalone NR-U enables 5G to be deployed by small cells and operated by any vertical end user without the need for licensed spectrum. This new functionality will enable 5G NR to utilize the 5 GHz global band as well as the 6 GHz band, thereby significantly increasing the spectrum coverage for 5G.

[0006] In the case of unlicensed operation, transmissions are regulated by regional regulations such as Listen-Before-Talk (LBT), Occupied Channel Bandwidth (OCB), and Power Spectrum Density (PSD), etc. In order to meet the LBT / OCB / PSD requirements, enhancements to random access operation are proposed. However, depending on the region where the user equipment (UE) is used, these enhancements are not always needed. Furthermore, these enhancements can require additional UE implementation effort. Therefore, it is desirable to have a flexible way for the UE to support the enhancements to NR-U. SUMMARY

[0007] A method for informing a UE capability to support enhancements to random access operation of NR-U is proposed. The UE communicates UE capability information to a mobile communication network, wherein the UE capability information includes information indicating a capability of the UE for random access operation in unlicensed spectrum. The UE receives a configuration of an unlicensed cell from the mobile communication network. The UE performs random access operation on the unlicensed cell according to the configuration.

[0008] In one embodiment, the UE capability information includes a first indicator on whether the UE supports a physical random access channel (PRACH) transmission using a single long Zadoff-Chu (ZC) sequence, and the random access operation includes performing the PRACH transmission using the single long ZC sequence. The ZC sequence has a length value of 1151 or 571, and the configuration includes a PRACH sequence length of 1151 or 571. The unlicensed cell is configured by the mobile communication network as a secondary cell (SCell) for carrier aggregation, or as a primary SCell for dual connectivity (DC) operation, or as a target cell for handover.

[0009] In another embodiment, the UE capability information includes a second indicator of whether the UE supports an extension of a random access response (RAR) window. The extension of the RAR window includes extending the RAR window from 10 milliseconds to 40 milliseconds, and the configuration includes a RAR window greater than 10 milliseconds. The random access operation includes monitoring for a RAR from the mobile communication network for up to a duration of the RAR window, and decoding a 2-bit system frame number (SFN) indication in downlink control information (DCI) scheduling of the RAR.

[0010] In one example, the capability of the UE for random access operation in unlicensed spectrum is set and reported by the UE per band.

[0011] Other embodiments and advantages are described in the following detailed description and can be included in the summary of the application. This summary is not intended to define the application. The application is defined by the claims. BRIEF DESCRIPTION OF DRAWINGS

[0012] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0013] Figure 1 An example 5G New Radio (NR) network 100 that supports unlicensed spectrum is illustrated in accordance with one novel aspect.

[0014] Figure 2 A simplified block diagram of a wireless device in accordance with an embodiment of the application is illustrated.

[0015] Figure 3 A sequence flow between a UE 301 and a 5G NR network to inform UE capability in accordance with one novel aspect to support enhanced random access operation for NR-U is illustrated.

[0016] Figure 4 A sequence flow between a UE 401 and a 5G NR network to implement random access operation on unlicensed cells in accordance with one novel aspect is illustrated.

[0017] Figure 5 A flow diagram of a method to inform UE capability to support enhanced random access operation for NR-U in accordance with one novel aspect is illustrated. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to some embodiments of the application, examples of which are illustrated in the accompanying drawings.

[0019] Figure 1An exemplary 5G New Radio (NR) network 100 supporting unlicensed spectrum according to one novel aspect is illustrated. 5G NR network 100 includes a user equipment (UE) 110 communicatively connected to a gNB 121 operating in a licensed frequency band (e.g., 30 GHz to 300 GHz for mmWave) in an access network 120. Access network 120 is connected to a 5G core network 130 via an NG interface, more specifically, to a user plane function (UPF) via an NG user plane component (NG-u) and to a mobility management function (AMF) via an NG control plane component (NG-c). A gNB can be connected to multiple UPFs / AMFs for load sharing and redundancy.

[0020] In addition to gNB 121, UE 110 is surrounded by one or more gNBs (including gNB 101) operating in an unlicensed frequency band (e.g., 5 GHz or 6 GHz). gNB 101 may be deployed by the same operator as gNB 121, or may be deployed by a different operator than gNB 121. gNB 121 may form at least one cell, which may be referred to as an NR-based licensed cell (i.e., a cell operating in a 5G NR licensed frequency band). Similarly, gNB 101 may form at least one cell, which may be referred to as an NR-based unlicensed cell (i.e., a cell operating in an unlicensed frequency band).

[0021] UE 110 may be a smartphone, a wearable device, an Internet of Things (IoT) device, a tablet, etc., and may or may not support random access operations (e.g., contention-based random access and / or non-contention-based random access) on unlicensed cells.

[0022] According to one novel aspect, if UE 110 supports random access operations on unlicensed cells and resides on a cell (e.g., a PCell or PSCell) formed by gNB 121, UE 110 may transmit UE capability information regarding the UE's capability for random access operations in unlicensed spectrum to a serving cell during a UE Capability Transfer procedure. gNB 121 may then provide UE 110 with the configuration of the unlicensed cell, and UE 110 may perform random access operations on the unlicensed cell based on the configuration.

[0023] In one embodiment, the UE capability information includes a first indicator on whether the UE supports Physical Random Access Channel (PRACH) transmission using a single long Zadoff-Chu (ZC) sequence, and the random access operation includes performing the PRACH transmission using the single long ZC sequence. For example, the first indicator can be a “prach-Wideband-r16” information element (IE) to indicate whether the UE supports an enhanced PRACH design for shared spectrum channel access by employing a single long ZC sequence, where ZC sequence length = 1151 for 15KHz and ZC sequence length = 571 for 30KHz.

[0024] In another embodiment, the UE capability information includes a second indicator on whether the UE supports an extension of a Random Access Response (RAR) window. For example, the second indicator can be an “extendedRAR-Window-r16” IE to indicate whether the UE supports RAR extension from 10ms to 40ms by decoding a 2-bit System Frame Number (SFN) indication in a Downlink Control Information (DCI) format 1_0.

[0025] Figure 2 A simplified block diagram of a wireless device (e.g., UE 201 and gNB 211) according to an embodiment of the application is illustrated. The gNB 211 has an antenna 215 for transmitting and receiving radio signals. A radio frequency (RF) transceiver module 214 coupled to the antenna 215 receives RF signals from the antenna 215, converts them to baseband signals and sends them to the processor 213. The RF transceiver 214 also converts baseband signals received from the processor 213 to RF signals and sends them to the antenna 215. The processor 213 processes the received baseband signals and invokes different functional modules to perform the functions in the gNB 211. The memory 212 stores program instructions and data 220 to control the operation of the gNB 211. In Figure 2In the example of FIG. 2, the gNB 211 also includes a protocol stack 280 and a set of control functions and circuits 290. The protocol stack 280 can include a Non-Access-Stratum (NAS) layer for communication with an AMF / SMF / MME entity connected to a core network, a Radio Resource Control (RRC) layer for high layer configuration and control, a Packet Data Convergence Protocol / Radio Link Control (PDCP / RLC) layer, a Media Access Control (MAC) layer, and a Physical (PHY) layer. In one example, the control functions and circuits 290 include a UE capability information query circuit 291 for querying UE 201 for UE capability information, and a Random Access (RA) configuration circuit 292 for preparing configuration of random access parameters for unlicensed cells.

[0026] Similarly, the UE 201 has a memory 202, a processor 203, and a radio frequency (RF) transceiver module 204. The RF transceiver 204 is coupled with an antenna 205, receives RF signals from the antenna 205, converts them to baseband signals and sends them to the processor 203. The RF transceiver 204 also converts baseband signals received from the processor 203 to RF signals and sends them to the antenna 205. The processor 203 processes the received baseband signals and invokes different function modules and circuits for performing features in the UE 201. The memory 202 stores data and program instructions 210 executed by the processor 203 to control the operation of the UE 201. Suitable processors include, for example, application specific processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors in association with a DSP core, controllers, micro-controllers, application specific integrated circuits (ASICs), field programmable gate array (FPGA) circuits, and other types of integrated circuits (ICs) and / or state machines. A processor associated with software can be used to implement and configure the features of the UE 201.

[0027] UE 201 also includes a protocol stack 260 and a set of control functional modules and circuits 270. Protocol stack 260 may include a NAS layer for communicating with the AMF / SMF / MME entity connected to the core network, an RRC layer for high-level configuration and control, a PDCP / RLC layer, a MAC layer, and a PHY layer. The control functional modules and circuits 270 may be implemented and configured using software, firmware, hardware, and / or a combination thereof. When executed by processor 203 using program instructions contained in memory 202, the control functional modules and circuits 270 may interact with each other to enable UE 201 to perform the embodiments and functional tasks and features in the network.

[0028] In one example, the control function module and circuit 270 includes a transmitter circuit 271, a receiver circuit 272, and a random access (RA) processing circuit 273. The transmitter circuit 271 is used to transmit the UE's capability information of random access operation in unlicensed spectrum to the gNB 211, the receiver circuit 272 is used to receive the configuration of the unlicensed cell from the gNB 211, and the random access processing circuit 273 is used to perform random access operation on the unlicensed cell according to the received configuration.

[0029] Figure 3 A sequence flow for notifying UE capabilities between UE 301 and a 5G NR network to support enhancements to random access operations for NR-U according to a novel aspect is illustrated. In step 311, UE 301 receives a UECapabilityEnquiry message from the 5G NR network. When the 5G NR network requires (additional) UE radio access capability information, it may initiate this procedure to the RRC_CONNECTED UE. The 5G NR network shall obtain UE capabilities only after AS security activation. In step 321, UE 301 prepares UE capability information, which includes information indicating the UE's ability to perform random access operations in unlicensed spectrum. Specifically, the UE capability information may include a first indicator (e.g., "prach-Wideband-r16" IE) regarding whether the UE supports PRACH transmission using a single long ZC sequence and / or a second indicator (e.g., "extendedRAR-Window-r16" IE) regarding whether the UE supports RAR window extension. In step 331, UE 301 sends a UECapabilityInformation message including UE capability information to the 5G NR network.

[0030] Figure 4A sequence flow between a UE 401 and a 5G NR network for implementing random access operation on an unlicensed cell is illustrated according to one novel aspect. In step 411, the UE 401 receives a RRCReconfiguration message whose configuration includes random access parameters (e.g., PRACH sequence length = 1151 / 571, and / or a RAR window larger than 10 ms) of an unlicensed cell. In step 421, the UE 401 sends a RRCReconfigurationComplete message to the 5G NR network. In step 431, the UE 401 performs a PRACH transmission on the unlicensed cell by employing a single long ZC sequence with length 1151 / 571. In step 441, the UE 401 monitors a RAR from the unlicensed cell for up to the duration of the RAR window. In step S451, the UE 401 decodes a 2-bit SFN indication in the DCI scheduling of the RAR.

[0031] If the random access operation is based on a contention-based random access, the random access operation ends in step S411 when the UE 401 receives and successfully decodes a RAR for the UE 401. Alternatively, if the random access operation is based on a contention-based random access, the UE 401 can perform an uplink scheduling transmission (i.e., Msg-3) and contention resolution (i.e., Msg-4) after step S441.

[0032] Figure 5 A flow chart of a method for informing UE capability to support random access operation enhancements of NR-U according to one novel aspect. In step 501, a UE communicates its UE capability information to a mobile communication network, wherein the UE capability information includes information indicating the UE’s capability for random access operation in unlicensed spectrum. In step 502, the UE receives a configuration of an unlicensed cell from the mobile communication network. In step 503, the UE performs a random access operation on the unlicensed cell according to the configuration.

[0033] In one embodiment, the UE capability information includes a first indicator of whether the UE supports PRACH transmission using a single long ZC sequence, and the random access operation includes performing a PRACH transmission using a single long ZC sequence. The ZC sequence has a length value of 1151 or 571, and the configuration includes a PRACH sequence length of 1151 or 571. The unlicensed cell is configured by the mobile communication network as a Secondary Cell (SCell) of carrier aggregation, or a Primary SCell (PSCell) of Dual Connectivity (DC) operation, or as a target cell of handover.

[0034] In another embodiment, the UE capability information includes a second indicator of whether the UE supports RAR window extension. The UE capability information includes the second indicator of whether the UE supports RAR window extension, the configuration including a RAR window greater than 10 milliseconds. The random access operation includes monitoring for a RAR from the mobile communication network for up to a duration of the RAR window, decoding a 2-bit SFN indication in a DCI schedule of the RAR.

[0035] In one example, the capability of the UE for random access operation in unlicensed spectrum is set and reported by the UE per band.

[0036] Although the present application is described in connection with certain specific embodiments, this is not intended to limit the application. Various modifications, alterations, and permutations of the described embodiments are possible and within the scope of the application, as set forth in the following claims, in which

Claims

1. A method of informing user equipment (UE) capability information, comprising: transmitting, by a user equipment (UE), UE capability information to a mobile communication network, wherein the UE capability information comprises information indicating a capability of the UE to operate random access in unlicensed spectrum; receiving, by the UE, a configuration of an unlicensed cell from the mobile communication network; and performing, by the UE, a random access operation on the unlicensed cell according to the configuration; wherein the UE capability information comprises a first indicator on whether the UE supports a physical random access channel (PRACH) transmission using a single long Zadoff-Chu (ZC) sequence, and the random access operation comprises performing a PRACH transmission using the single long ZC sequence, wherein a length value of the ZC sequence is 1151 or 571.

2. The method of claim 1, wherein, the configuration comprises a PRACH sequence length of 1151 or 571.

3. The method of claim 1, wherein, the unlicensed cell is configured by the mobile communication network as a secondary cell (SCell) for carrier aggregation, or as a primary SCell for dual connectivity (DC) operation, or as a target cell for handover.

4. The method of claim 1, wherein, the capability of the UE to operate random access in unlicensed spectrum is set and reported by the UE per frequency band. 5.A method of informing user equipment (UE) capability information, comprising: transmitting, by a user equipment (UE), UE capability information to a mobile communication network, wherein the UE capability information comprises information indicating a capability of the UE to operate random access in unlicensed spectrum; receiving, by the UE, a configuration of an unlicensed cell from the mobile communication network; and performing, by the UE, a random access operation on the unlicensed cell according to the configuration, wherein the UE capability information comprises a second indicator on whether the UE supports an extension of a random access response (RAR) window, wherein the extension of the RAR window comprises extending the RAR window from 10 milliseconds to 40 milliseconds.

6. The method of claim 5, wherein, the configuration comprises a RAR window larger than 10 milliseconds.

7. The method of claim 5, wherein, the random access operation comprises: monitoring for a RAR from the mobile communication network for at most a duration of the RAR window; and decoding a 2-bit system frame number (SFN) indication in downlink control information (DCI) scheduling of the RAR.

8. The method of claim 5, wherein, the capability of the UE to operate random access in unlicensed spectrum is set and reported by the UE per frequency band.

9. The method of claim 5, wherein, the unlicensed cell is configured by the mobile communication network as a secondary cell (SCell) for carrier aggregation, or as a primary SCell for dual connectivity (DC) operation, or as a target cell for handover. 10.A user equipment (UE), comprising: a transmitter configured to transmit UE capability information to a mobile communication network, wherein the UE capability information comprises information indicating a capability of the UE to operate random access in unlicensed spectrum; a receiver configured to receive a configuration of an unlicensed cell from the mobile communication network; and a random access processing circuitry configured to perform a random access operation on the unlicensed cell according to the configuration. The UE capability information includes a first indicator on whether the UE supports PRACH transmission using a single long Zadoff-Chu (ZC) sequence, and the random access operation includes performing PRACH transmission using the single long ZC sequence; and the length of the ZC sequence is 1151 or 571.

11. The UE of claim 10, wherein the configuration includes a PRACH sequence length of 1151 or 571.

12. The UE of claim 10, wherein, The unlicensed cell is configured by the mobile communication network as an SCell for carrier aggregation, or as a primary SCell for DC operation, or as a target cell for handover.

13. The UE of claim 10, wherein, The capability of the UE for random access operation in unlicensed spectrum is set and reported by the UE per frequency band.

14. A user equipment (UE), comprising: a transmitter configured to transmit UE capability information to a mobile communication network, wherein the UE capability information includes information indicating a capability of the UE for random access operation in unlicensed spectrum; a receiver configured to receive a configuration of an unlicensed cell from the mobile communication network; and a random access processing circuitry configured to perform a random access operation on the unlicensed cell according to the configuration; The UE capability information includes a second indicator on whether the UE supports extension of a RAR window, wherein the extension of the RAR window includes extending the RAR window from 10 milliseconds to 40 milliseconds.

15. The UE of claim 14, wherein, The configuration includes a RAR window greater than 10 milliseconds.

16. The UE of claim 14, wherein, The random access operation includes: monitoring for a RAR from the mobile communication network for up to a duration of the RAR window; and decoding a 2-bit SFN indication in DCI scheduling of the RAR.

17. The UE of claim 14, wherein, The capability of the UE for random access operation in unlicensed spectrum is set and reported by the UE per frequency band.

18. The UE of claim 14, wherein, The unlicensed cell is configured by the mobile communication network as an SCell for carrier aggregation, or as a primary SCell for DC operation, or as a target cell for handover.

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