WO2018206011A1 - Apparatuses and methods for beam selection during a physical random access channel (prach) transmission or retransmission - Google Patents
Apparatuses and methods for beam selection during a physical random access channel (prach) transmission or retransmission Download PDFInfo
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- WO2018206011A1 WO2018206011A1 PCT/CN2018/086666 CN2018086666W WO2018206011A1 WO 2018206011 A1 WO2018206011 A1 WO 2018206011A1 CN 2018086666 W CN2018086666 W CN 2018086666W WO 2018206011 A1 WO2018206011 A1 WO 2018206011A1
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- prach
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W74/00—Wireless channel access
- H04W74/08—Non-scheduled access, e.g. ALOHA
- H04W74/0833—Random access procedures, e.g. with 4-step access
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0408—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas using two or more beams, i.e. beam diversity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0686—Hybrid systems, i.e. switching and simultaneous transmission
- H04B7/0695—Hybrid systems, i.e. switching and simultaneous transmission using beam selection
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0686—Hybrid systems, i.e. switching and simultaneous transmission
- H04B7/0695—Hybrid systems, i.e. switching and simultaneous transmission using beam selection
- H04B7/06952—Selecting one or more beams from a plurality of beams, e.g. beam training, management or sweeping
- H04B7/06966—Selecting one or more beams from a plurality of beams, e.g. beam training, management or sweeping using beam correspondence; using channel reciprocity, e.g. downlink beam training based on uplink sounding reference signal [SRS]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
- H04B7/0868—Hybrid systems, i.e. switching and combining
- H04B7/088—Hybrid systems, i.e. switching and combining using beam selection
Definitions
- the application generally relates to Physical Random Access Channel (PRACH) transmission/retransmission and, more particularly, to apparatuses and methods for beam selection during a PRACH transmission/retransmission.
- PRACH Physical Random Access Channel
- the fifth generation (5G) New Radio (NR) technology is an improvement over the fourth generation (4G) Long Term Evolution (LTE) technology, which provides extreme data speeds and capacity by utilizing higher, unlicensed spectrum bands (e.g., above 30 GHz, loosely known as millimeter Wave (mmWave) ) , for wireless broadband communications. Due to the huge path and penetration losses at millimeter wavelengths, a technique called “beamforming” is employed, and it assumes an important role in establishing and maintaining a robust communication link.
- 4G Long Term Evolution
- mmWave millimeter Wave
- Beamforming generally requires one or more antenna arrays, each comprising a plurality of antennas.
- antenna weights that define the contribution of each of the antennas to a transmission or reception operation, it becomes possible to shape the sensitivity of the transmission/reception to a particularly high value in a specific beamformed direction.
- different antenna weights By applying different antenna weights, different beam patterns can be achieved, e.g., different directive beams can be sequentially employed.
- beamforming may direct the signal towards a receiver of interest.
- beamforming may provide a high sensitivity in receiving a signal originating from a sender of interest. Since transmission power may be anisotropically focused, e.g., into a solid angle of interest, beamforming may provide better link budgets due to lower required Tx power and higher received signal power, when compared to conventional practice, which does not employ beamforming and relies on more or less isotropic transmission.
- a User Equipment may either apply beam switching or apply power ramping for a PRACH retransmission according to the 3GPP specifications for the 5G NR technology.
- beam switching the UE simply switches to a different beam to perform the PRACH retransmission, without increasing the transmission power.
- power ramping the UE stays on the same beam and increases the transmission power to perform the PRACH retransmission.
- the present application proposes UEs and methods for beam selection during a PRACH transmission/retransmission, allowing UEs to decide whether to apply beam switching (i.e., selects a different beam) or power ramping (i.e., selects the same beam) , and to decide which beam to switch to when applying beam switching.
- beam switching i.e., selects a different beam
- power ramping i.e., selects the same beam
- a User Equipment comprising a wireless transceiver and a controller.
- the wireless transceiver is configured to perform wireless transmission and reception to and from a cellular station.
- the controller is configured to initiate a RACH procedure with the cellular station via the wireless transceiver, and select a Transmission (Tx) beam for a PRACH transmission or a first PRACH retransmission during the RACH procedure according to at least one of the following: a beam correspondence capability indicating whether the UE is able to determine a correspondence between Reception (Rx) beams and Tx beams of the UE; results of measurements of downlink reference signals and Rx beams used for the measurements; a number of Tx beams of the UE; an estimated path loss to the cellular station; a maximum transmission power configured for the UE to perform the PRACH transmission or the first PRACH retransmission; a power ramping step configured for the UE to perform the PRACH transmission or the first PRACH retransmission; and a gain
- a method for beam selection during a PRACH transmission/retransmission executed by a UE wirelessly connected to a cellular station.
- the method comprises the steps of: initiating a RACH procedure with the cellular station; and selecting a Tx beam for a PRACH transmission or a first PRACH retransmission during the RACH procedure according to at least one of the following: a beam correspondence capability indicating whether the UE is able to determine a correspondence between Rx beams and Tx beams of the UE; results of measurements of downlink reference signals and Rx beams used for the measurements; a number of Tx beams of the UE; an estimated path loss to the cellular station; a maximum transmission power configured for the UE to perform the PRACH transmission or the first PRACH retransmission; a power ramping step configured for the UE to perform the PRACH transmission or the first PRACH retransmission; and a gain of the selected Tx beam.
- Fig. 1 is a block diagram of a wireless communication environment according to an embodiment of the application
- Fig. 2 is a block diagram illustrating the UE 110 according to an embodiment of the application
- Fig. 3 is a flow chart illustrating the method for beam selection during a PRACH transmission/retransmission according to an embodiment of the application
- Fig. 4 is a schematic diagram illustrating the beam selection for a UE with full beam correspondence according to an embodiment of the application
- Fig. 5 is a schematic diagram illustrating the beam selection for a UE with partial beam correspondence according to another embodiment of the application
- Fig. 6 is a schematic diagram illustrating the beam selection for a UE without beam correspondence according to another embodiment of the application.
- Fig. 7 is a schematic diagram illustrating the beam selection for a cell-centered UE according to another embodiment of the application.
- Fig. 8 is a schematic diagram illustrating the beam selection for a cell-edge UE according to another embodiment of the application.
- Fig. 1 is a block diagram of a wireless communication environment according to an embodiment of the application.
- the wireless communication environment 100 includes a User Equipment (UE) 110 and a 5G NR network 120, wherein the UE 110 is wirelessly connected to the 5G NR network 120.
- UE User Equipment
- the UE 110 may be a feature phone, a smartphone, a panel Personal Computer (PC) , a laptop computer, or any wireless communication device supporting the cellular technology (i.e., the 5G NR technology) utilized by the 5G NR network 120.
- the UE 110 employs the beamforming technique (i.e., supports beam switching) for wireless transmission and/or reception.
- the 5G NR network 120 includes a Radio Access Network (RAN) 121 and a Next Generation Core Network (NG-CN) 122.
- RAN Radio Access Network
- NG-CN Next Generation Core Network
- the RAN 121 is responsible for processing radio signals, terminating radio protocols, and connecting the UE 110 with the NG-CN 122. In addition, the RAN 121 is responsible for periodically broadcasting the minimum SI, and providing the other SI by periodic broadcasting or at the request of the UE 110.
- the RAN 121 may include one or more cellular stations, such as gNBs, which support high frequency bands (e.g., above 24GHz) , and each gNB may further include one or more Transmission Reception Points (TRPs) , wherein each gNB or TRP may be referred to as a 5G cellular station.
- TRPs Transmission Reception Points
- Some gNB functions may be distributed across different TRPs, while others may be centralized, leaving the flexibility and scope of specific deployments to fulfill the requirements for specific cases.
- the NG-CN 122 generally consists 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) , wherein each network function may be implemented as a network element on a dedicated hardware, or as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure.
- AMF Access and Mobility Function
- SMF Session Management Function
- PCF Policy Control Function
- AF Application Function
- AUSF Authentication Server Function
- UPF User Plane Function
- UDM User Data Management
- the AMF provides UE-based authentication, authorization, mobility management, etc.
- the SMF is responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF for data transfer. If a UE has multiple sessions, different SMFs may be allocated to each session to manage them individually and possibly provide different functions per session.
- the AF provides information on the packet flow to PCF responsible for policy control in order to support Quality of Service (QoS) . Based on the information, the PCF determines policies about mobility and session management to make the AMF and the SMF operate properly.
- the AUSF stores data for authentication of UEs, while the UDM stores subscription data of UEs.
- the 5G NR network 120 depicted in Fig. 1 is for illustrative purposes only and is not intended to limit the scope of the application.
- the application may also be applied to other cellular technologies, such as a future enhancement of the 5G NR technology.
- Fig. 2 is a block diagram illustrating the UE 110 according to an embodiment of the 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.
- I/O Input/Output
- the wireless transceiver 10 is configured to perform wireless transmission and reception to and from the RAN 121.
- the wireless transceiver 10 includes a Radio Frequency (RF) device 11, a baseband processing device 12, and antenna (s) 13, wherein the antenna (s) 13 may include one or more antennas for beamforming.
- the baseband processing device 12 is configured to perform baseband signal processing and control the communications between subscriber identity card (s) (not shown) and the RF device 11.
- the baseband processing device 12 may contain multiple hardware components to perform the baseband signal processing, including Analog-to-Digital Conversion (ADC) /Digital-to-Analog Conversion (DAC) , gain adjusting, modulation/demodulation, encoding/decoding, and so on.
- ADC Analog-to-Digital Conversion
- DAC Digital-to-Analog Conversion
- the RF device 11 may receive RF wireless signals via the antenna (s) 13, convert the received RF wireless signals to baseband signals, which are processed by the baseband processing device 12, or receive baseband signals from the baseband processing device 12 and convert the received baseband signals to RF wireless signals, which are later transmitted via the antenna (s) 13.
- the RF device 11 may also contain multiple hardware devices to perform radio frequency conversion.
- the RF device 11 may include a mixer to multiply the baseband signals with a carrier oscillated in the radio frequency of the supported cellular technologies, wherein the radio frequency may be any radio frequency (e.g., 30GHz ⁇ 300GHz for mmWave) utilized in the 5G NR technology, or another radio frequency, depending on the cellular technology in use.
- the controller 20 may 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 the functions of data processing and computing, controlling the wireless transceiver 10 for wireless communications with the RAN 121, storing and retrieving data (e.g., program code) to and from the storage device 30, sending a series of frame data (e.g. representing text messages, graphics, images, etc. ) to the display device 40, and receiving/outputting signals from/to the I/O device 50.
- 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 for beam selection during a PRACH transmission/retransmission.
- controller 20 may be incorporated into the baseband processing device 12, to serve as a baseband processor.
- the circuits of the controller 20 will typically include transistors that are configured in such a way as to control the operation of the circuits in accordance with the functions and operations described herein.
- the specific structure or interconnections of the transistors will typically be determined by a compiler, such as a Register Transfer Language (RTL) compiler.
- RTL compilers may be operated by a processor upon scripts that closely resemble assembly language code, to compile the script into a form that is used for the layout or fabrication of the ultimate circuitry. Indeed, RTL is well known for its role and use in the facilitation of the design process of electronic and digital systems.
- the storage device 30 is a non-transitory machine-readable storage medium, including 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 disc, or any combination thereof for storing instructions and/or program code of applications, communication protocols, and/or the method for beam selection during a PRACH transmission/retransmission.
- NVRAM Non-Volatile Random Access Memory
- the display device 40 may be a Liquid-Crystal Display (LCD) , a Light-Emitting Diode (LED) display, or an Electronic Paper Display (EPD) , etc., for providing a display function.
- the display device 40 may further include one or more touch sensors disposed thereon or thereunder for sensing touches, contacts, or approximations of objects, such as fingers or styluses.
- the I/O device 50 may include one or more buttons, a keyboard, a mouse, a touch pad, a video camera, a microphone, and/or a speaker, etc., to serve as the Man-Machine Interface (MMI) for interaction with users, such as receiving user inputs, and outputting prompts to users.
- MMI Man-Machine Interface
- the UE 110 may include more components, such as a power supply, or a Global Positioning System (GPS) device, wherein the power supply may be a mobile/replaceable battery providing power to all the other components of the UE 110, and the GPS device may provide the location information of the UE 110 for use of some location-based services or applications.
- a power supply may be a mobile/replaceable battery providing power to all the other components of the UE 110
- GPS device may provide the location information of the UE 110 for use of some location-based services or applications.
- Fig. 3 is a flow chart illustrating the method for beam selection during a PRACH transmission/retransmission according to an embodiment of the application.
- the method for beam selection during a PRACH transmission/retransmission is executed by a UE (e.g., the UE 110) which is wirelessly connected to a cellular station (e.g., a gNB or TRP of the RAN 121) , and the PRACH transmission/retransmission may refer to transmission/retransmission of the message-1 (i.e., random access preamble) of a RACH procedure.
- a UE e.g., the UE 110
- a cellular station e.g., a gNB or TRP of the RAN 121
- the PRACH transmission/retransmission may refer to transmission/retransmission of the message-1 (i.e., random access preamble) of a RACH procedure.
- the UE initiates a RACH procedure with the cellular station (step S310) .
- the RACH procedure is also called a random access procedure which is initiated on the Random Access Channel.
- the RACH procedure may be initiated when the UE requires uplink synchronization with the cellular station for uplink data transfer, or when the cellular station receives downlink data for the UE but the uplink synchronization with the UE is lost, or when the UE does not have an uplink grant to transmit uplink data and the Physical Uplink Control Channel (PUCCH) resources for transmission of Scheduling Request (SR) are released or not configured for the UE.
- PUCCH Physical Uplink Control Channel
- the UE selects a Transmission (Tx) beam for a PRACH transmission or a first PRACH retransmission during the RACH procedure according to at least one of: the beam correspondence capability, the results of measurements of downlink reference signals and the Rx beams used for the measurements, the number of Tx beams of the UE, the estimated path loss to the cellular station, the maximum transmission power, the power ramping step, and the potential beam gain (i.e., the potential gain of the selected Tx beam) (step S320) .
- Tx Transmission
- the beam correspondence capability indicates whether the UE is able to determine a correspondence between Reception (Rx) beams and Tx beams of the UE.
- the downlink reference signal may refer to a Channel State Information-Reference Signal (CSI-RS) , a Synchronization Signal Block (SSB) , or a Physical Broadcast Channel (PBCH) block.
- CSI-RS Channel State Information-Reference Signal
- SSB Synchronization Signal Block
- PBCH Physical Broadcast Channel
- the maximum transmission power and the power ramping step are configured by the cellular station for the UE to perform the PRACH transmission or the first PRACH retransmission, wherein the maximum transmission power indicates the maximum transmission power that the UE is allowed to use for the PRACH transmission or the first PRACH retransmission, and the power ramping step is used to increase the transmission power after every failed PRACH transmission/retransmission.
- the UE may use a transmission power to perform the PRACH transmission, increase the transmission power to perform the first PRACH retransmission, and increment the power ramping counter by one in response to performing the PRACH transmission and the first PRACH retransmission.
- the UE may use the same transmission power to perform the PRACH transmission on a first beam and to perform the first PRACH retransmission on a second beam.
- the UE increments the power ramping counter by one in response to performing the PRACH transmission and does not increment the power ramping counter by one in response to performing the first PRACH retransmission.
- Fig. 4 is a schematic diagram illustrating the beam selection for a UE with full beam correspondence according to an embodiment of the application.
- beam selection is performed according to at least the beam correspondence capability, the measurement results of downlink reference signals, and the Rx beams used for the measurements, wherein the beam correspondence capability indicates that the UE is able to determine the full correspondence between the Rx beams and the Tx beams of the UE, and the measurement results of downlink reference signals indicate that the downlink reference signal received on an Rx beam corresponding to the second Tx beam (denoted with the number ‘2’ in Fig. 4) has the best signal quality.
- full beam correspondence refers to that each Rx beam corresponds a Tx beam explicitly.
- the second Tx beam is considered most probable Tx beam
- the neighboring Tx beams i.e., the first and third Tx beams
- the rest Tx beam i.e., the fourth Tx beam
- the UE stays on the most probable beam (i.e., the second Tx beam) to perform the PRACH retransmissions until the maximum transmission power is reached, and after that, the UE switches to the probable beams first and then the least probable beam for the following PRACH retransmissions.
- the UE selects the second Tx beam and increments the power ramping counter (denoted as “PRC” in Fig. 4) by one.
- PRC power ramping counter
- the UE stays on the same beam, increases the transmission power, and increments the power ramping counter by one.
- the UE stays on the same beam, increases the transmission power, and increments the power ramping counter by one.
- the UE switches from the most probable Tx beam (i.e., the second Tx beam) to one of the probable Tx beams (e.g., the first Tx beam) , and keeps the transmission power and the power ramping counter unchanged.
- the UE switches to another probable Tx beams (e.g., the third Tx beam) , and keeps the transmission power and the power ramping counter unchanged.
- the UE switches to the least probable Tx beam (i.e., the fourth Tx beam) , and keeps the transmission power and the power ramping counter unchanged.
- Fig. 5 is a schematic diagram illustrating the beam selection for a UE with partial beam correspondence according to another embodiment of the application.
- beam selection is performed according to at least the beam correspondence capability and the measurement results of downlink reference signals, wherein the beam correspondence capability indicates that the UE is able to determine partial correspondence between the Rx beams and the Tx beams of the UE, and the measurement results of downlink reference signals indicate that the downlink reference signal received on an Rx beam corresponding to either the first or second Tx beam (denoted with the number ‘1’ and ‘2’ in Fig. 5) has the best signal quality.
- partial beam correspondence refers to that the correspondence between the Tx beams and the Tx beams may be rough (i.e., an Rx beam may correspond more than one Tx beam.
- the first and second Tx beams are considered more probable Tx beams, and the rest Tx beams (i.e., the third and fourth Tx beams) are considered less probable beams.
- the UE switches between the more probable beams (i.e., the first and second Tx beams) to perform the PRACH retransmissions until the maximum transmission power is reached, and after that, the UE sweeps from the first Tx beam to the fourth Tx beam for the following PRACH retransmissions.
- the UE selects one of the more probable beams (e.g., the first Tx beam) and increments the power ramping counter (denoted as “PRC” in Fig. 5) by one.
- the UE switches to another more probable beam (e.g., the second Tx beam) , and keeps the transmission power and the power ramping counter unchanged.
- the UE stays on the same beam, increases the transmission power, and increments the power ramping counter by one.
- the UE switches to another more probable Tx beam (i.e., the first Tx beam) , and keeps the transmission power and the power ramping counter unchanged.
- the UE stays on the same beam, increases the transmission power, and increments the power ramping counter by one.
- the UE switches from the first Tx beam to the second Tx beam, from the second Tx beam to the third Tx beam, and then from the third Tx beam to the fourth Tx beam, while keeping the transmission power and the power ramping counter unchanged.
- Fig. 6 is a schematic diagram illustrating the beam selection for a UE without beam correspondence according to another embodiment of the application.
- beam selection is performed according to at least the beam correspondence capability which indicates that the UE is unable to determine a correspondence between the Rx beams and the Tx beams of the UE. Since there is no beam correspondence, it may be preferred to conduct beam sweeping before applying power ramping. To further clarify, power ramping may be applied after each round of beam sweeping.
- the UE selects the first Tx beam and increments the power ramping counter (denoted as “PRC” in Fig. 6) by one.
- PRC power ramping counter
- the UE switches from the first Tx beam to the second Tx beam, from the second Tx beam to the third Tx beam, and then from the third Tx beam to the fourth Tx beam, while keeping the transmission power and the power ramping counter unchanged.
- each Tx beam has been tried (i.e., the first round of beam sweeping is completed) with the same transmission power.
- the UE stays on the same beam, further increases the transmission power, and increments the power ramping counter by one.
- the UE switches from the fourth Tx beam to the first Tx beam, from the first Tx beam to the second Tx beam, and then from the second Tx beam to the third Tx beam, while keeping the transmission power and the power ramping counter unchanged.
- each Tx beam has been tried (i.e., the second round of beam sweeping is completed) with the increased transmission power.
- the UE stays on the same beam, increases the transmission power, and increments the power ramping counter by one.
- the UE switches from the third Tx beam to the fourth Tx beam, from the fourth Tx beam to the first Tx beam, and then from the first Tx beam to the second Tx beam, while keeping the transmission power and the power ramping counter unchanged.
- each Tx beam has been tried (i.e., the third round of beam sweeping is completed) with the further increased transmission power.
- the present application may increase the number of PRACH retransmissions without violating the PRACH power ramping regulation defined by the 3rd Generation Partnership Project (3GPP) for the 5G NR technology. Also, by increasing the number of PRACH retransmissions, the successful rate of the UE accessing the cellular station may be improved.
- 3GPP 3rd Generation Partnership Project
- Fig. 7 is a schematic diagram illustrating the beam selection for a cell-centered UE according to another embodiment of the application.
- beam selection is performed according to at least one or more of: the estimated path loss, the maximum transmission power, the power ramping step, and the beam gain of the selected Tx beam, wherein the estimated path loss is less than a predetermined threshold (i.e., the UE may be relatively near the cell center) , and/or the power ramping step is less than the beam gain, and/or the number of times to ramp up to the maximum transmission power for the power ramping step and the estimated path loss is greater than the number of Tx beams.
- the estimated path loss may be used to determine the initial transmission power
- the initial transmission power and the power ramping step may be used to determine the number of times to ramp up to the maximum transmission power.
- the UE selects the first Tx beam, uses the initial transmission power to perform the PRACH transmission, and increments the power ramping counter by one.
- the UE switches from the first Tx beam to the second Tx beam, from the second Tx beam to the third Tx beam, and then from the third Tx beam to the fourth Tx beam, while keeping the transmission power and the power ramping counter unchanged.
- each Tx beam has been tried (i.e., the first round of beam sweeping is completed) with the initial transmission power.
- the UE stays on the same beam, increases the transmission power, and increments the power ramping counter by one.
- the UE switches from the fourth Tx beam to the third Tx beam, from the third Tx beam to the second Tx beam, and then from the second Tx beam to the first Tx beam (i.e., the beams are swept backward) , while keeping the transmission power and the power ramping counter unchanged.
- Fig. 7 prioritizes beam switching over power ramping, especially when the estimated path loss is less than a predetermined threshold, or when the power ramping step is less than the beam gain, or when the number of times to ramp up to the maximum transmission power for the power ramping step and the estimated path loss is greater than the number of Tx beams.
- the RACH procedure may continue with more PRACH retransmissions until the maximum transmission power is reached.
- Fig. 8 is a schematic diagram illustrating the beam selection for a cell-edge UE according to another embodiment of the application.
- beam selection is performed according to at least one or more of: the estimated path loss, the maximum transmission power, the power ramping step, and the beam gain of the selected Tx beam, wherein the estimated path loss is greater than a predetermined threshold (i.e., the UE may be relatively near the cell edge) , and/or the power ramping step is greater than the beam gain, and/or the number of times to ramp up to the maximum transmission power for the power ramping step and the estimated path loss is smaller than the number of Tx beams.
- the estimated path loss may be used to determine the initial transmission power
- the initial transmission power and the power ramping step may be used to determine the number of times to ramp up to the maximum transmission power.
- the UE selects the first Tx beam, uses the initial transmission power to perform the PRACH transmission, and increments the power ramping counter by one.
- the UE stays on the same beam, increases the transmission power by the power ramping step, and increments the power ramping counter by one.
- the UE switches from the first Tx beam to the second Tx beam, from the second Tx beam to the third Tx beam, and then from the third Tx beam to the fourth Tx beam for the following three PRACH retransmissions, while keeping the transmission power and the power ramping counter unchanged.
- the embodiment of Fig. 8 prioritizes power ramping over beam switching, especially when the estimated path loss is greater than a predetermined threshold, or when the power ramping step is greater than the beam gain, or when the number of times to ramp up to the maximum transmission power for the power ramping step and the estimated path loss is smaller than the number of Tx beams, except when the UE has reached the maximum transmission power.
- the present application allows the UE to access the cellular station as soon as it can without violating the PRACH power ramping regulation defined by the 3GPP for the 5G NR technology, by providing different beam selection patterns for the cell-centered UE and the cell-edge UE.
- the beam selection pattern indicates the UE to apply beam switching before power ramping.
- the beam selection pattern indicates the UE to apply power ramping before beam switching.
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Abstract
Description
Claims (24)
- A User Equipment (UE) , comprising:a wireless transceiver, configured to perform wireless transmission and reception to and from a cellular station; anda controller, configured to initiate a Random Access Channel (RACH) procedure with the cellular station via the wireless transceiver, and select a Transmission (Tx) beam for a Physical Random Access Channel (PRACH) transmission or a first PRACH retransmission during the RACH procedure according to at least one of the following:a beam correspondence capability indicating whether the UE is able to determine a correspondence between Reception (Rx) beams and Tx beams of the UE;results of measurements of downlink reference signals and Rx beams used for the measurements;a number of Tx beams of the UE;an estimated path loss to the cellular station;a maximum transmission power of the UE to perform the PRACH transmission or the first PRACH retransmission;a power ramping step configured for the UE to perform the PRACH transmission or the first PRACH retransmission; anda gain of the selected Tx beam.
- The UE of claim 1, wherein, when the same Tx beam is selected for the PRACH transmission and the first PRACH retransmission, the controller is further configured to use a transmission power to perform the PRACH transmission via the wireless transceiver, increase the transmission power to perform the first PRACH retransmission via the wireless transceiver, and increment a power ramping counter by one in response to performing the first PRACH retransmission.
- The UE of claim 1, wherein, when different Tx beams are selected for the PRACH transmission and the first PRACH retransmission, the controller is further configured to use a transmission power to perform the PRACH transmission on a first beam and to perform the first PRACH retransmission on a second beam, and not increment a power ramping counter by one in response to performing the first PRACH retransmission.
- The UE of claim 3, wherein, when the beam correspondence capability indicates that the UE is unable to determine a correspondence between the Rx beams and the Tx beams of the UE, the UE is further configured to select the second TX beam different from the first TX beam, and the second Tx beam is subsequent to the first Tx beam in a sequential order of beam sweeping or is selected randomly from the Tx beams of the UE.
- The UE of claim 3, wherein, when the beam correspondence capability indicates that the UE is able to determine a correspondence between the Rx beams and the Tx beams of the UE, the second Tx beam is selected according to the correspondence and the results of the measurements of the downlink reference signals.
- The UE of claim 1, wherein, when the estimated path loss is greater than a predetermined threshold, the controller is further configured to select the same beam for the PRACH transmission and the first PRACH retransmission, increase a transmission power which is used for the PRACH transmission to perform the first PRACH retransmission via the wireless transceiver, select a different beam for a second PRACH retransmission, and use the increased transmission power to perform the second PRACH retransmission via the wireless transceiver.
- The UE of claim 1, wherein, when the estimated path loss is less than a predetermined threshold, the controller is further configured to select different beams for the PRACH transmission and the first PRACH retransmission, use the same transmission power to perform the PRACH transmission and the first PRACH retransmission via the wireless transceiver, select the same beam for the first PRACH retransmission and a second PRACH retransmission, and increase the transmission power to perform the second PRACH retransmission via the wireless transceiver.
- The UE of claim 1, wherein, when the power ramping step is less than the beam gain, the controller is further configured to select different Tx beams for the PRACH transmission and the first PRACH retransmission, and use the same transmission power to perform the PRACH transmission and the first PRACH retransmission via the wireless transceiver.
- The UE of claim 1, wherein, when the power ramping step is greater than the beam gain, the controller is further configured to select the same Tx beam for the PRACH transmission and the first PRACH retransmission, and increase a transmission power which is used for the PRACH transmission to perform the first PRACH retransmission via the wireless transceiver.
- The UE of claim 1, wherein, when the number of times to ramp up to the maximum transmission power for the power ramping step and the estimated path loss is greater than the number of Tx beams, the controller is further configured to select different Tx beams for the PRACH transmission and the first PRACH retransmission, and use the same transmission power to perform the PRACH transmission and the first PRACH retransmission via the wireless transceiver.
- The UE of claim 1, wherein, when the number of times to ramp up to the maximum transmission power for the power ramping step and the estimated path loss is smaller than the number of Tx beams, the controller is further configured to select the same Tx beam for the PRACH transmission and the first PRACH retransmission, and increase a transmission power which is used for the PRACH transmission to perform the first PRACH retransmission via the wireless transceiver.
- The UE of claim 1, wherein, when the UE has reached the maximum transmission power, the controller is further configured to select different Tx beams for the PRACH transmission and the first PRACH retransmission, and use the same transmission power to perform the PRACH transmission and the first PRACH retransmission via the wireless transceiver.
- A method for beam selection during a PRACH transmission or retransmission, executed by a UE wirelessly connected to a cellular station, the method comprising:initiating a RACH procedure with the cellular station; andselecting a Tx beam for a PRACH transmission or a first PRACH retransmission during the RACH procedure according to at least one of the following:a beam correspondence capability indicating whether the UE is able to determine a correspondence between Rx beams and Tx beams of the UE;results of measurements of downlink reference signals and Rx beams used for the measurements;a number of Tx beams of the UE;an estimated path loss to the cellular station;a maximum transmission power of the UE to perform the PRACH transmission or retransmission;a power ramping step configured for the UE to perform the PRACH transmission or retransmission; anda gain of the selected Tx beam.
- The method of claim 13, further comprising:when determining to increase the transmission power for the first PRACH retransmission,using a transmission power to perform the PRACH transmission;increasing the transmission power to perform the first PRACH retransmission; andincrementing a power ramping counter by one in response to performing the first PRACH retransmission.
- The method of claim 13, further comprising:when different Tx beams are selected for the PRACH transmission and the first PRACH retransmission,using a transmission power to perform the PRACH transmission on a first beam and to perform the first PRACH retransmission on a second beam; andnot incrementing a power ramping counter by one in response to performing the first PRACH retransmission.
- The method of claim 15, further comprising: when the beam correspondence capability indicates that the UE is unable to determine a correspondence between the Rx beams and the Tx beams of the UE, selecting the second TX beam different from the first TX beam, wherein the second Tx beam is subsequent to the first Tx beam in a sequential order of beam sweeping or is selected randomly from the Tx beams of the UE.
- The method of claim 15, wherein, when the beam correspondence capability indicates that the UE is able to determine a correspondence between the Rx beams and the Tx beams of the UE, the second Tx beam is selected according to the correspondence and the results of the measurements of the downlink reference signals.
- The method of claim 13, further comprising:when the estimated path loss is greater than a predetermined threshold,selecting the same beam for the PRACH transmission and the first PRACH retransmission;increasing a transmission power which is used for the PRACH transmission to perform the first PRACH retransmission;selecting a different beam for a second PRACH retransmission; andusing the increased transmission power to perform the second PRACH retransmission.
- The method of claim 13, further comprising:when the estimated path loss is less than a predetermined threshold,selecting different beams for the PRACH transmission and the first PRACH retransmission;using the same transmission power to perform the PRACH transmission and the first PRACH retransmission;selecting the same beam for the first PRACH retransmission and a second PRACH retransmission; andincreasing the transmission power to perform the second PRACH retransmission.
- The method of claim 13, further comprising:when the power ramping step is less than the beam gain,selecting different Tx beams for the PRACH transmission and the first PRACH retransmission; andusing the same transmission power to perform the PRACH transmission and the first PRACH retransmission.
- The method of claim 13, further comprising:when the power ramping step is greater than the beam gain,selecting the same Tx beam for the PRACH transmission and the first PRACH retransmission; andincreasing a transmission power which is used for the PRACH transmission to perform the first PRACH retransmission.
- The method of claim 13, further comprising:when the number of times to ramp up to the maximum transmission power for the power ramping step and the estimated path loss is greater than the number of Tx beams,selecting different Tx beams for the PRACH transmission and the first PRACH retransmission, andusing the same transmission power to perform the PRACH transmission and the first PRACH retransmission.
- The method of claim 13, further comprising:when the number of times to ramp up to the maximum transmission power for the power ramping step and the estimated path loss is smaller than the number of Tx beams,selecting the same Tx beam for the PRACH transmission and the first PRACH retransmission, andincreasing a transmission power which is used for the PRACH transmission to perform the first PRACH retransmission.
- The method of claim 13, further comprising:when the UE has reached the maximum transmission power,selecting different Tx beams for the PRACH transmission and the first PRACH retransmission, andusing the same transmission power to perform the PRACH transmission and the first PRACH retransmission.
Priority Applications (3)
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EP18798006.5A EP3616463A4 (en) | 2017-05-12 | 2018-05-14 | Apparatuses and methods for beam selection during a physical random access channel (prach) transmission or retransmission |
BR112019023400-4A BR112019023400A2 (en) | 2017-05-12 | 2018-05-14 | APPLIANCES AND METHODS FOR SELECTING BEAM DURING A TRANSMISSION OR RETRANSMISSION OF RANDOM ACCESS PHYSICAL CHANNEL (PRACH) |
CN201880003889.5A CN109845391A (en) | 2017-05-12 | 2018-05-14 | The apparatus and method of beam selection during Physical Random Access Channel transmission or re-transmission |
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US15/977,080 US20180332625A1 (en) | 2017-05-12 | 2018-05-11 | Apparatuses and methods for beam selection during a physical random access channel (prach) transmission or retransmission |
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WO2022178829A1 (en) * | 2021-02-26 | 2022-09-01 | Qualcomm Incorporated | Indication of a beam direction associated with a beam application time |
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US11445561B2 (en) * | 2019-02-27 | 2022-09-13 | Qualcomm Incorporated | Techniques for retransmitting random access messages in wireless communications |
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EP3616463A4 (en) | 2021-01-13 |
EP3616463A1 (en) | 2020-03-04 |
US20180332625A1 (en) | 2018-11-15 |
TW201947892A (en) | 2019-12-16 |
CN109845391A (en) | 2019-06-04 |
BR112019023400A2 (en) | 2020-06-16 |
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