Apparatus and method for physical random access channel retransmission

Abstract

A user equipment (UE) including a wireless transceiver and a controller is provided. The wireless transceiver performs wireless transmission and reception with a cellular station. The controller performs a first Physical Random Access Channel (PRACH) transmission or retransmission using a first PRACH resource and switches to perform a second PRACH retransmission using a second PRACH resource after the first PRACH transmission or retransmission.

Description

[0001] This application is a divisional application of the international application entering China, the original application date is May 11, 2018, the application number is 201880001926.9, the invention name is "Apparatuses and methods for physical random access channel retransmission" (the international application number is PCT / CN2018 / 086449, the invention name is "APPARATUSES AND METHODS FOR PHYSICAL RANDOM ACCESS CHANNEL (PRACH) RETRANSMISSION"). TECHNICAL FIELD

[0002] The present application relates generally to physical random access channel (PRACH) design, and more particularly, to apparatuses and methods for PRACH retransmission. BACKGROUND

[0003] The fifth generation (5G) new radio (NR) technology is an improvement over the fourth generation (4G) long term evolution (LTE) technology, which provides extremely high data speed and capacity for wireless broadband communication by utilizing higher unlicensed spectrum bands (e.g., above 30 GHz, commonly known as millimeter wave (mmWave)). Due to the huge path and penetration loss at millimeter wave wavelengths, a technique called "beamforming" is adopted, and the beamforming technique plays an important role in establishing and maintaining a robust communication link.

[0004] Beamforming generally requires one or more antenna arrays, each of which includes multiple antennas. By properly setting the antenna weights, which define the contribution of each antenna to the transmission or reception operation, the sensitivity of the transmission / reception can be formed to have a particularly high value in a specific beamforming direction. Different beam patterns can be achieved by applying different antenna weights, for example, different directive beams can be sequentially employed.

[0005] For transmit (Tx) operation, beamforming can direct a signal towards a receiver of interest. Likewise, during receive (Rx) operation, beamforming can provide high sensitivity when receiving a signal originating from a transmitter of interest. Since conventional practice does not employ beamforming and relies almost exclusively on isotropic transmission, while in beamforming transmission power can be focused anisotropically into, for example, a solid angle of interest, beamforming can provide better link budget than conventional practice due to its need for lower Tx power and higher received signal power.

[0006] For example, during a RACH procedure, a user equipment (UE) can apply beam switching or apply power ramping for PRACH retransmission according to 3GPP specification for 5G NR technology. For beam switching, the UE simply switches to a different Tx beam (or spatial domain transmission filter) to perform PRACH retransmission without increasing the transmission power. For power ramping, the UE increases the transmission power to perform PRACH retransmission on the same Tx beam (i.e., using the same spatial domain transmission filter) such that a power ramping counter is increased by 1. SUMMARY

[0007] In addition to beam switching and power ramping, it is proposed in this application that the UE can switch PRACH resources to perform PRACH retransmission, so that the frequency of applying power ramping can be reduced, and the interference to other UEs can be reduced.

[0008] According to a first aspect of the present application, there is provided a user equipment (UE) comprising a wireless transceiver and a controller. The wireless transceiver is configured to perform wireless transmission and reception with a cellular station. The controller is configured to perform a first PRACH transmission or retransmission using a first PRACH resource, and to switch to perform a second PRACH retransmission using a second PRACH resource after the first PRACH transmission or retransmission.

[0009] According to a second aspect of the present application, there is provided a method for PRACH retransmission, the method being performed by a UE wirelessly connected to a cellular station. The method comprises the steps of: performing a first PRACH transmission or retransmission using a first PRACH resource; and switching to perform a second PRACH retransmission using a second PRACH resource after the first PRACH transmission or retransmission.

[0010] Other aspects and features of the present application will become apparent to those ordinarily skilled in the art upon review of the description of specific embodiments of UE, cellular station, method for PRACH retransmission, and the accompanying figures. BRIEF DESCRIPTION OF DRAWINGS

[0011] The present application will be more fully understood and appreciated by reading the detailed description of the embodiments together with references to the drawings and examples. The following detailed description and examples are provided as further examples of and / or derivations for the present application.

[0012] Figure 1 is a block diagram of a wireless communication environment in accordance with embodiments of the present application.

[0013] Figure 2 is a block diagram illustrating a UE 110 in accordance with embodiments of the present application.

[0014] Figure 3A and Figure 3B shows a flowchart of a method for PRACH retransmission in accordance with embodiments of the present application.

[0015] Figure 4 is a schematic diagram illustrating switching PRACH resources for PRACH retransmission in accordance with embodiments of the present application. DETAILED DESCRIPTION

[0016] In this description and the following claims, certain terms have been used for brevity, clarity and understanding. An ordinary artisan will recognize that elements under different names can be similar. As used throughout this description and in the claims, the term "comprising" is used in the sense of "including", and thus should be interpreted to cover the terms "consisting of", and "consisting essentially of" to the extent that the terms "consisting of" and "consisting essentially of" are synonymous with "comprising" under the doctrine of equivalents. In addition, the term "coupled" and variations thereof, as used throughout this description and in the claims, refers to any direct or indirect electrical, magnetic, or optical coupling or link between the elements that are connected in order to demodulate a signal. Therefore, if a first device is electrically connected to a second device, it is meant that the first device can be directly connected to the second device, or indirectly connected to the second device via other devices or connections.

[0017] Figure 1 is a block diagram of a wireless communication environment in accordance with embodiments of the present application. The wireless communication environment 100 includes a user equipment (UE) 110 and a 5G NR network 120, where the UE 110 is wirelessly connected to the 5G NR network 120.

[0018] The UE 110 can be a functional phone, a smart phone, a tablet personal computer (PC), a laptop, or any wireless communication device that supports cellular technology (i.e., 5G NR technology) used by the 5G NR network 120. In particular, the UE 110 can use beamforming technology for wireless transmission and / or reception.

[0019] 5G NR network 120 includes a Radio Access Network (RAN) 121 and a Next Generation Core Network (NG-CN) 122.

[0020] RAN 121 is responsible for processing radio signals, terminating radio protocols, and connecting UE 110 with NG-CN 122. In addition, RAN 121 is responsible for periodically broadcasting minimum SI, as well as providing other SI either through periodic broadcasting or based on UE 110’s request. RAN 121 can include one or more cellular stations (e.g., gNBs) that support high frequency bands (e.g., above 24 GHz), and each gNB can further include one or more Transmission Reception Points (TRPs), where each gNB or TRP can be referred to as a 5G cellular station. Some gNB functions can be distributed among different TRPs, while others can be centralized, thereby enabling flexibility and range of a particular deployment to meet requirements of a particular situation.

[0021] NG-CN 122 is generally composed of various network functions, including Access and Mobility Function (AMF), Session Management Function (SMF), Policy Control Function (PCF), Application Function (AF), Authentication Server Function (AUSF), User Plane Function (UPF), and User Data Management (UDM), where each network function can be implemented as a network component on a dedicated hardware, or as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, such as a cloud infrastructure.

[0022] The AMF provides UE-based authentication, authorization, mobility management, etc. The SMF is responsible for session management and allocates Internet Protocol (IP) addresses to the UE. It also selects and controls the UPF for data transmission. If the UE has multiple sessions, different SMFs can be assigned to each session to manage them individually, and different functionalities can be provided in each session. To support Quality of Service (QoS), the AF provides information about data packet flows to the PCF responsible for policy control. Based on this information, the PCF determines policies related to mobility and session management to enable the proper functioning of the AMF and SMF. The AUSF stores credentials for UE authentication, while the UDM stores the subscription information of the UE.

[0023] It should be noted that, Figure 1 The 5G NR network 120 depicted in FIG. 1 is for illustrative purposes only and is not intended to limit the scope of the present application. The present application can be applied to other cellular technologies, such as future enhancements of the 5G NR technology.

[0024] Figure 2 is a block diagram illustrating a UE 110 according to an embodiment of the present application. The UE 110 includes a wireless transceiver 10, a controller 20, a storage device 30, a display device 40, and an input / output (I / O) device 50.

[0025] The wireless transceiver 10 is configured to perform wireless transmission and reception with the RAN 121. Specifically, the wireless transceiver 10 includes a radio frequency (RF) device 11, a baseband processing device 12, and an antenna 13, which can include one or more antennas for beamforming. The baseband processing device 12 is configured to perform baseband signal processing and control communication between a subscriber identity module (not shown) and the RF device 11. The baseband processing device 12 can contain a plurality of hardware components to perform baseband signal processing, such as Analog-to-Digital Conversion (ADC) / Digital-to-Analog Conversion (DAC), gain adjustment, modulation / demodulation, encoding / decoding, etc. The RF device 11 can receive an RF wireless signal via the antenna 13, convert the received RF wireless signal to a baseband signal processed by the baseband processing device 12, or receive a baseband signal from the baseband processing device 12 and convert the received baseband signal to an RF wireless signal that is later transmitted by the antenna 13. The RF device 11 can also include a plurality of hardware devices to perform radio frequency conversion. For example, the RF device 11 can include a mixer to multiply a baseband signal with a carrier oscillating at a radio frequency of a supported cellular technology, which can be any frequency used in the 5G NR technology (e.g., 28 GHz for millimeter wave, 39 GHz for millimeter wave, 60 GHz for millimeter wave, 700 MHz for sub-6 GHz, etc.), 2.1 GHz for Long Term Evolution (LTE) technology, etc. ) or other frequency modulation, depending on the cellular technology used.

[0026] The controller 20 can be a general-purpose processor, a Micro Control Unit (MCU), an application processor, a Digital Signal Processor (DSP), or the like, which includes various circuits for providing data processing and calculation, controlling the wireless transceiver 10 to perform wireless communication with the RAN 121, storing data to and retrieving data from the storage device 30 (e.g., program codes), transmitting a series of frame data (e.g., text messages, graphics, images, etc.) to the display device 40, and receiving signals from the I / O device 50. In particular, the controller 20 coordinates the aforementioned operations of the wireless transceiver 10, the storage device 30, the display device 40, and the I / O device 50 for performing the method of PRACH retransmission.

[0027] In another embodiment, the controller 20 can be incorporated into the baseband processing device 12 to function as a baseband processor.

[0028] As will be appreciated by one of ordinary skill in the art, the circuitry of the controller 20 generally includes transistors configured to control the operation of the circuitry in accordance with the functions and operations described herein. As will be further appreciated, the particular structure or interconnection of the transistors will typically be determined by a compiler, such as a Register Transfer Language (RTL) compiler. The RTL compiler can operate on a script to compile the script into a form that is loaded into the configuration or fabrication equipment to configure or fabricate the final circuitry. Indeed, the role and use of RTL in the design of electronic and digital systems is well known.

[0029] The storage device 30 is a non-transitory machine-readable storage medium that includes a memory such as a FLASH memory or a Non-Volatile Random Access Memory (NVRAM), or a magnetic storage device such as a hard disk or a magnetic tape, or an optical disk, or any combination thereof, to store application programs, communication protocols, and / or instructions and / or program codes for the method of PRACH retransmission.

[0030] The display device 40 can be a Liquid Crystal Display (LCD), a Light Emitting Diode (LED) display, or an Electronic Paper Display (EPD), or the like, for providing a display function. Alternatively, the display device 40 can further include one or more touch sensors disposed thereon or thereunder for sensing a touch, contact, or proximity of an object such as a finger or a stylus.

[0031] The I / O device 50 can include one or more buttons, a keyboard, a mouse, a touchpad, a camera, a microphone, and / or a speaker, etc. that are used as a Man-Machine Interface (MMI) to interact with a user.

[0032] It should be appreciated that Figure 2 The components described in the embodiments of the UE 110 are for illustration only and are not intended to limit the scope of the present application. For example, the UE 110 can include more components, such as a power supply, which can be a mobile / replaceable battery that supplies power to all other components of the UE 110, or a Global Positioning System (GPS) device that provides location information of the UE 110 for some location-based services or applications.

[0033] Figure 3A And Figure 3B A flowchart of a method for PRACH retransmission is shown according to an embodiment of the present application. In this embodiment, the method for PRACH retransmission is applied to a UE (e.g., the UE 110) that is wirelessly connected to a cellular station (e.g., a gNB or a TRP of the RAN 121), and the PRACH transmission / retransmission refers to the transmission / retransmission of message-1 (i.e., a random access preamble) of a RACH procedure.

[0034] First, the UE performs a first PRACH transmission or retransmission using a first PRACH resource (step S310). In one embodiment, the UE can initiate a RACH procedure by performing the first PRACH transmission. In another embodiment, the UE can perform the first PRACH retransmission during a RACH procedure.

[0035] Each first PRACH resource can include one or more PRACH preambles and / or one or more RACH occasions, where each RACH occasion refers to a time-frequency resource that transmits message-1 of a RACH procedure with a single specific Tx beam (or referred to as a spatial domain transmission filter) in a configured PRACH preamble format.

[0036] Next, for a second PRACH retransmission after the first PRACH transmission or retransmission, the UE determines whether at least one of the following conditions is satisfied (step S320).

[0037] Specifically, these conditions include: (1) a measurement result of a downlink reference signal associated with the first PRACH resource is better than a measurement result of a downlink reference signal associated with the second PRACH resource, where the downlink reference signal can include a Channel State Information-Reference Signal (CSI-RS) or a Synchronization Signal / Physical Broadcast Channel block (SSB); (2) a next occurrence time of the second PRACH resource is closer to a current time than a next occurrence time of the first PRACH resource (i.e., the second PRACH resource is earlier than the first PRACH resource); (3) a transmission power used for the first PRACH transmission or retransmission is equal to a maximum transmission power of the UE (which can be configured by the cellular station and / or the UE), while a total number of PRACH transmissions or retransmissions has not reached a maximum number of transmissions configured by the cellular station; (4) a Transmission Configuration Indication (TCI) state associated with a search space has changed, where the TCI state is used to monitor a response to the first PRACH transmission or retransmission.

[0038] After step S320, if at least one of the above conditions is satisfied, the UE switches to perform a second PRACH retransmission using the second PRACH resource (step S330), which is associated with a different downlink reference signal (e.g., a CSI-RS or a SSB) than the first PRACH resource. Next, the UE increments a preamble transmission counter (i.e., PREAMBLE_TRANSMISSION_COUNTER in 3GPP specification TS 38.321) by 1 and does not increment a power ramping counter (i.e., PREAMBLE_POWER_RAMPING_COUNTER in 3GPP specification TS 38.321) in response to the second PRACH retransmission (step S340), after which the method ends. That is, by switching to a PRACH resource associated with a different downlink reference signal than the previously selected downlink reference signal, the UE does not need to increase the transmission power for the second retransmission.

[0039] Note that in this application, when the UE transmits a PRACH preamble and the PRACH preamble is detected by the UE, the association between the downlink reference signal and the PRACH resource can indicate the downlink reference signal selected by the UE to the cellular station.

[0040] After step S320, if none of the above conditions are met, the UE switches to performing a second PRACH retransmission using a third PRACH resource, the downlink reference signal associated with the third PRACH resource is the same as the downlink reference signal associated with the first PRACH resource (step S350). Next, in response to the second PRACH retransmission, the UE increments the preamble transmission counter by 1 (step S360), and determines whether the first PRACH transmission or retransmission and the second PRACH retransmission are performed on the same beam (i.e., using the same spatial domain transmission filter) or different beams (step S370).

[0041] After step S370, if the first PRACH transmission or retransmission and the second PRACH retransmission are performed on different beams, the UE does not increment the power ramping counter (step S380). That is, by beam switching and PRACH resource switching (switching to using a PRACH resource associated with the same downlink reference signal as the previously selected downlink reference signal), the UE does not need to increase the transmission power for the second retransmission. Otherwise, if the first PRACH transmission or retransmission and the second PRACH retransmission are performed on the same beam, the UE increments the power ramping counter by 1 (step S390), and the method ends. That is, despite switching to using a PRACH resource associated with the same downlink reference signal as the previously selected downlink reference signal, the UE needs to increase the transmission power for the second retransmission because it remains on the same beam.

[0042] Likewise, each of the second and third PRACH resources can comprise one or more PRACH preambles and / or one or more RACH occasions, where each RACH occasion refers to a time-frequency resource with a single specific Tx beam (or referred to as a spatial domain transmission filter) to transmit message-1 of a RACH procedure in a configured PRACH preamble format.

[0043] Figure 4 FIG. 3 is a schematic diagram illustrating switching PRACH resources for PRACH retransmission according to embodiments of the present application.

[0044] In this embodiment, there is an association between the downlink reference signals and the PRACH resources. For example, a first SSB is associated with a first PRACH resource, a second SSB is associated with a second PRACH resource, a third SSB is associated with a third PRACH resource, and a fourth SSB is associated with a fourth PRACH resource.

[0045] As Figure 4As shown, during the RACH procedure, the UE performs PRACH transmission / retransmission (e.g., message-1 (Msg 1) transmission) on a Tx beam (or referred to as a spatial domain transmission filter) using the third PRACH resource, but no response (e.g., Radom Access Response (RAR)) to the PRACH transmission / retransmission is received. Subsequently, the UE switches to perform PRACH retransmission on the same Tx beam (i.e., using the same spatial domain transmission filter) using the first PRACH resource, and the RACH procedure ends when the response to the PRACH retransmission is received.

[0046] In view of the foregoing embodiments, it should be appreciated that the present application provides an alternative for the UE to perform PRACH retransmission. In addition to the conventional options such as beam switching and power ramping, the UE can switch PRACH resources to perform PRACH retransmission. Advantageously, the frequency of applying power ramping can be reduced, and interference to other UEs can be reduced. Moreover, since the UE is allowed to switch PRACH resources during PRACH retransmission, access latency of the UE can be reduced.

[0047] Although the present application has been described by way of example and in terms of preferred embodiments, it should be appreciated that the present application is not limited thereto. Various changes and modifications can be made by those skilled in the art without departing from the scope and spirit of the present application. Therefore, the scope of the present application should be limited by the claims and their equivalents.

[0048] In the claims, the use of ordinal numbers such as "first", "second", etc. to distinguish claim components does not by itself imply any priority, precedence or order of one claim component over another claim component, nor a time order of the method steps performed, but is only used as a marker to distinguish one claim component having a certain name from another component having the same name (using ordinal numbers) to distinguish claim components.

Claims

1. A method for retransmission of a Physical Random Access Channel (PRACH), the method being performed by a User Equipment (UE) wirelessly connected to a cellular station, wherein, The method includes: The first PRACH transmission or retransmission is performed using a first spatial domain transmission filter on a first PRACH resource, wherein the first PRACH resource is associated with a first downlink reference signal; After the first PRACH transmission or retransmission, a second PRACH transmission or retransmission is performed using a second spatial domain transmission filter on a second PRACH resource, wherein the second PRACH resource is associated with a second downlink reference signal; and In response to the UE selecting a second spatial domain transmission filter different from the first spatial domain transmission filter, the power ramp counter is not incremented; or, in response to the UE selecting a second downlink reference signal different from the first downlink reference signal, the power ramp counter is not incremented. In response to the UE selecting the same second spatial domain transmission filter as the first spatial domain transmission filter and the same second downlink reference signal as the first downlink reference signal, the power ramp counter is incremented by 1.

2. The method of claim 1, wherein each of the first PRACH resource and the second PRACH resource comprises one or more PRACH preambles, one or more RACH timings, or a combination of the PRACH preambles and the RACH timings.

3. The method as described in claim 1, wherein, The downlink reference signals include Channel State Information Reference Signal (CSI-RS), Synchronization Signal Block (SSB), or Physical Broadcast Channel (PBCH) block.

4. The method of claim 1, wherein the method further comprises: Regardless of whether the second downlink reference signal is the same as or different from the first downlink reference signal, the preamble transmission counter is incremented by 1.

5. The method of claim 1, wherein the method further comprises: In response to the second PRACH transmission or retransmission, the preamble transmission counter is incremented by 1.

6. The method of claim 1, wherein the step of selecting a second downlink reference signal different from the first downlink reference signal is performed under at least one of the following conditions, the at least one condition including: The measurement results of the second downlink reference signal are better than those of the first downlink reference signal; The next occurrence time of the second PRACH resource associated with the second downlink reference signal is closer to the current time than the next occurrence time of the first PRACH resource associated with the first downlink reference signal; The first transmission power used for the first PRACH transmission or retransmission is equal to the maximum transmission power of the UE, while the total number of PRACH transmissions or retransmissions does not reach the maximum number of transmissions configured for the cellular station. as well as The transport configuration indication (TCI) state associated with the search space has changed, wherein the transport configuration indication state is used to monitor the response to the first PRACH transport or retransmission.

7. A user equipment (UE), comprising: A wireless transceiver is configured to perform wireless transmission and reception with a cellular station; as well as The controller is configured to perform a first PRACH transmission or retransmission using a first spatial domain transmission filter on a first PRACH resource, wherein the first PRACH resource is associated with a first downlink reference signal; and after the first PRACH transmission or retransmission, to perform a second PRACH transmission or retransmission using a second spatial domain transmission filter on a second PRACH resource, wherein the second PRACH resource is associated with a second downlink reference signal. The controller is further configured to not increment the power ramp counter in response to the second spatial domain transmission filter being different from the first spatial domain transmission filter or the second downlink reference signal being different from the first downlink reference signal; The controller is further configured to increment the power ramp counter by 1 in response to the second spatial domain transmission filter being the same as the first spatial domain transmission filter and the second downlink reference signal being the same as the first downlink reference signal.

8. The user equipment (UE) as described in claim 7, wherein, Each of the first PRACH resource and the second PRACH resource includes one or more PRACH preambles, one or more RACH timings, or a combination of the PRACH preambles and the RACH timings.

9. The user equipment (UE) as claimed in claim 7, wherein, The downlink reference signals include Channel State Information Reference Signal (CSI-RS), Synchronization Signal Block (SSB), or Physical Broadcast Channel (PBCH) block.

10. The user equipment (UE) as claimed in claim 7, wherein, The controller is also configured to increment the preamble transmission counter by 1 regardless of whether the second downlink reference signal is the same as or different from the first downlink reference signal.

11. The user equipment (UE) as claimed in claim 7, wherein, The controller is also configured to increment the preamble transmission counter by 1 in response to the second PRACH transmission or retransmission.

12. The user equipment (UE) as claimed in claim 7, wherein, The controller selects a second downlink reference signal that is different from the first downlink reference signal under at least one of the following conditions: The measurement results of the second downlink reference signal are better than those of the first downlink reference signal; The next occurrence time of the second PRACH resource associated with the second downlink reference signal is closer to the current time than the next occurrence time of the first PRACH resource associated with the first downlink reference signal; The first transmission power used for the first PRACH transmission or retransmission is equal to the maximum transmission power of the UE, while the total number of PRACH transmissions or retransmissions does not reach the maximum number of transmissions configured for the cellular station. as well as The transport configuration indication (TCI) state associated with the search space has changed, wherein the transport configuration indication state is used to monitor the response to the first PRACH transport or retransmission.

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