Patent Application
20240365261
The disclosure relates to a method and a device for synchronizing and continuously tracking synchronization between a base station and a terminal in a wireless communication system.
To meet the increasing demand for wireless data traffic after the commercialization of the fourth generation (4G) communication system, efforts are being made to develop an improved fifth generation (5G) communication system or pre-5G communication system. For this reason, the 5G communication system or pre-5G communication system is called a ‘Beyond 4G Network’ communication system or a ‘Post LTE’ system. The 5G communication system set by 3GPP is called New Radio (NR) system. To achieve high data rates, the 5G communication system is considered for implementation in ultra-high frequency (mmWave) band (e.g., 60 GHz band). To alleviate path loss of radio wave in the ultra-high frequency band and increase transmission distance of radio wave, beamforming, massive MIMO, full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, and large scale antenna technologies were discussed in the 5G communication system and applied to the NR system. In addition, to improve the network of the system, evolved small cell, advanced small cell, cloud radio access network (cloud RAN), ultra-dense network, Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (COMP), and interference cancellation have been developed in the 5G communication system.
In addition, advanced coding modulation (ACM) method such as Hybrid FSK and QAM Modulation (FQAM) and Sliding Window Superposition Coding (SWSC), and advanced access technology such as Filter Bank Multi Carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) have been developed in the 5G system.
The Internet has evolved from a human-centered network in which humans create and consume information to an Internet of Things (IoT) network that exchanges and processes information between distributed components such as an object. Internet of Everything (IoE) technology, which combines IoT technology with big data processing technology through connection with a cloud server, and so on, is also emerging. In order to implement IoT, technology elements (such as sensing technology), wired and wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, sensor network, Machine to Machine (M2M), and Machine Type Communication (MTC) for connection between objects have been researched.
In the IoT environment, an intelligent Internet Technology (IT) service that creates new value in human life by collecting and analyzing data generated from connected objects may be provided. IoT may be applied to fields such as a smart home, a smart building, a smart city, a smart car or a connected car, a smart grid, health care, smart home appliances, and advanced medical service through convergence and combination of existing information technology (IT) and various industries.
Accordingly, various attempts have been made to apply the 5G communication system to the IoT network. For example, the sensor network, the M2M, and the MTC have been implemented by the 5G communication technology (such as the beam beamforming, MIMO, and array antenna). The application of cloud RAN as a big data processing technology described above may also be said to be an example of the convergence of the 5G technology and the IoT technology.
Provided are a method and a device for controlling and tracking uplink synchronization in a beamforming-based wireless communication system. Provided is a method of obtaining DL sync for each transmission (Tx) beam of a base station and reporting DL Sync difference information for each beam to the base station through beam-related reporting.
According to an aspect of the disclosure, a method performed by a terminal for aligning uplink synchronization in wireless communication system, includes: obtaining a difference value between: first downlink synchronization based on a synchronization signal/physical broadcast channel (SS/PBCH) block corresponding a first beam and second downlink synchronization based on the SS/PBCH block corresponding a second beam; based on a comparison between the second downlink synchronization and cyclic prefix (CP) length, transmitting, to a base station, reporting information comprising information associated with the difference value; and receiving, from the base station, information on a timing advance (TA) value derived based on the information associated with the difference value.
According to an aspect of the disclosure, a method performed by a base station in a wireless communication system, includes: based on a plurality of beams of the base station, transmitting, to a terminal, a plurality of synchronization signal/physical broadcast channel (SS/PBCH) blocks; receiving reporting information comprising information associated with a difference value between: first downlink synchronization based on a SS/PBCH block corresponding a first beam and second downlink synchronization based on the SS/PBCH block corresponding a second beam from the terminal; and transmitting information on a timing advance (TA) value derived based on the information associated with the difference value to the terminal, wherein based on comparison between the second downlink synchronization and cyclic prefix (CP) length, the reporting information comprises the information associated with the difference value.
According to an aspect of the disclosure, a terminal of a wireless communication system, includes: a transceiver configured to transmit and receive signals; and a processor configured to: control the transceiver, obtain a difference value between: first downlink synchronization based on a synchronization signal/physical broadcast channel (SS/PBCH) block corresponding a first beam and second downlink synchronization based on the SS/PBCH block corresponding a second beam, based on a comparison between the second downlink synchronization and cyclic prefix (CP) length, transmit, to a base station, reporting information comprising information associated with the difference value, and receive, from the base station, information on a timing advance (TA) value derived based on the information associated with the difference value.
Effects obtainable in the disclosure are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those having ordinary knowledge in the art to which the disclosure belongs from the description below.
Technical tasks to be achieved in the disclosure are not limited to the technical tasks mentioned above, and other technical tasks not mentioned will be clearly understood by those having ordinary knowledge in the art to which the disclosure belongs from the description below.
The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:
Hereinafter, an embodiment of the disclosure will be described in detail with reference to an accompanying drawing. In describing the embodiment of the disclosure below, a description of technical content well known in the technical field belonging to the disclosure and not directly related to the disclosure will be omitted. This is to convey the gist of the disclosure more clearly without obscuring it by omitting an unnecessary description.
For the same reason, some components in the accompanying drawing are exaggerated, omitted, or schematically illustrated. Additionally, a size of each component does not entirely reflect an actual size. In each drawing, identical or corresponding component is assigned the same reference number.
An advantage and feature of the disclosure, and a method of achieving them will become apparent with reference to the embodiments described in detail below with the accompanying drawing. However, the disclosure is not limited to the embodiments described below and may be implemented in various different forms, and the present embodiments are only to ensure that the disclosure is complete and to completely inform those having ordinary knowledge in the art to which the disclosure pertains to scope of the technical idea, and the disclosure is only defined by scope of the claims. Throughout the disclosure, the same reference numerals refer to the same components. In addition, in describing the disclosure, in case that it is determined that a detailed description of a related function or configuration may unnecessarily obscure the gist of the disclosure, the detailed description will be omitted. In addition, the terms described below are terms defined in consideration of the function in the disclosure, and may vary according to the intention or custom of a user or operator. Therefore, the definition should be made based on the content throughout the disclosure.
In this case, each block of the process flowchart drawings and combinations of the flowchart drawings may be performed by computer program instructions. Since these computer program instructions may be mounted on a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, the instructions, performed through the processor of the computer or other programmable data processing equipment, generate a means of performing functions described in flowchart block(s). Since these computer program instructions may also be stored in a computer-usable or computer-readable memory that may be directed toward a computer or other programmable data processing equipment to implement the function in a particular manner, the instructions stored in the computer-usable or computer-readable memory may also be capable of producing an article of manufacture involving the instruction means performing the function described in the flowchart block(s). Since the computer program instructions may also be mounted on the computer or other programmable data processing equipment, it is also possible for a series of operational steps to be performed on the computer or other programmable data processing equipment to generate a computer-executed process so that the instructions that perform the computer or other programmable data processing equipment provide steps for executing the functions described in the flowchart block(s).
In addition, each block may represent a portion of a module, segment, or a code including one or more executable instructions for executing a specified logical function(s). Additionally, it should be noted that in some alternative execution examples, it is also possible that functions mentioned in blocks occur out of order. For example, two blocks illustrated in succession may actually be performed substantially simultaneously, or the blocks may sometimes be performed in reverse order according to a corresponding function.
The term “couple” and the derivatives thereof refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with each other. The terms “transmit”, “receive”, and “communicate” as well as the derivatives thereof encompass both direct and indirect communication. The terms “include” and “comprise”, and the derivatives thereof refer to inclusion without limitation. The term “or” is an inclusive term meaning “and/or”. The phrase “associated with,” as well as derivatives thereof, refer to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, have a relationship to or with, or the like. The term “controller” refers to any device, system, or part thereof that controls at least one operation. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase “at least one of,” when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one item in the list may be needed. For example, “at least one of A, B, and C” includes any of the following combinations: A, B, C, A and B, A and C, B and C, and A and B and C, and any variations thereof. As an additional example, the expression “at least one of a, b, or c” may indicate only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof. Similarly, the term “set” means one or more. Accordingly, the set of items may be a single item or a collection of two or more items.
A 5G communication system should support a service that simultaneously satisfy various requirements so that the various requirements of a user and service provider may be freely reflected. Services considered for the 5G communication system include enhanced mobile broadband (eMBB), massive machine type communication (mMTC), ultra-reliability low latency communication (URLLC), and so on.
The eMBB aims to provide a more improved data transmission rate than the existing data transmission rate supported by LTE, LTE-A, or LTE-Pro. For example, in the 5G communication system, the eMBB should be able to provide a peak data rate of 20 Gbps in downlink and a peak data rate of 10 Gbps in uplink from a perspective of one base station. In addition, the 5G communication system should provide the peak data rate and at the same time provide an increased user perceived data rate of a terminal. To meet these requirements, improvement in various transmission and reception technologies may be required, including more advanced multiple-antenna (or multi input multi output (MIMO)) transmission technology. In addition, in LTE system, signals are transmitted by using a transmission bandwidth of up to 20 MHz in the 2 GHz band, while the 5G communication system may meet the data transmission rate required by the 5G communication system by using a wider frequency bandwidth than 20 MHz in the frequency band of 3 to 6 GHz or above 6 GHz.
At the same time, the mMTC is being considered to support an application service such as Internet of Thing (IoT) in the 5G communication system. In order to efficiently provide the IoT, the mMTC requires support for access to a large scale of terminal within a cell, improved coverage of the terminal, improved battery time, and reduced cost of the terminal. Since the IoT provides a communication function by being attached to various sensors and various devices, it should be able to support a large number of terminals (e.g., 1,000,000 terminals/km2) within the cell. In addition, due to the nature of the service, the terminal supporting the mMTC is likely to be located in a shaded area that cannot be covered by the cell, such as a basement of a building, and therefore require wider coverage compared than other services provided by the 5G communication system. The terminal supporting the mMTC should be configured as a low-cost terminal, and since it is difficult to frequently replace a battery of the terminal, a very long battery life time such as 10 to 16 years is required.
Lastly, in a case of the URLLC, it is a cellular-based wireless communication service used for a mission-critical. For example, a service used for remote control for robot or machinery, industrial automation, unmanned aerial vehicle, remote health care, emergency alert, and so on may be considered. Therefore, the communication provided by the URLLC should provide very low latency and very high reliability. For example, a service supporting the URLLC should meet an air interface latency of less than 0.5 milliseconds and at the same time meet a requirement of a packet error rate of 10-5 or less. Therefore, for the service supporting the URLLC, the 5G system should provide a smaller transmit time interval (TTI) than other services, and at the same time, it should allocate a wide range of resources in the frequency band to ensure the reliability of a communication link.
Three services of the 5G communication system (hereinafter may be used interchangeably with the 5G system), namely the eMBB, the URLLC, and the mMTC, may be multiplexed and transmitted in one system. In this case, different transmission/reception techniques and transmission/reception parameters may be used between services to satisfy different requirements of each service.
In the LTE system, the 5G system, and so on, an orthogonal frequency division multiplexing (OFDM) method is adopted as one of the multiple access methods, and time-frequency resource for carrying data or control information for each user are usually allocated and operated so that they do not overlap, that is, orthogonality is established, so that each user's data or control information is distinguished.
Hereinafter, the LTE, LTE-A, or new radio (NR) (i.e., 5G) system will be described as an example, but an embodiment of the disclosure may also be applied to other communication systems having a similar technical background or channel type. In addition, the disclosure may be applied to other communication systems through some modifications without significantly departing from the scope of the disclosure at the discretion of a person with skilled technical knowledge.
In the disclosure, a base station is a subject that performs resource allocation of the terminal, and may be at least one of gNode B, eNode B, Node B, Base Station (BS), a wireless access unit, a base station controller (processor), or a node on a network. The terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function.
In the disclosure, downlink (DL) is a wireless transmission path of a signal transmitted by the base station to the terminal, and uplink (UL) refers to a wireless transmission path of a signal transmitted by the terminal to the base station. In order to transmit and receive a signal between the base station and the terminal, it is necessary to synchronize the base station and the terminal.
In
The ‘reference synchronization’ may refer to synchronization that is a reference of a base station. Transmit/receive signals of the base station may be encoded/decoded based on the corresponding reference synchronization.
The ‘DL synchronization’ may refer to synchronization that is a reference of DL operation of a terminal (e.g., user equipment (UE)). The terminal may detect a radio boundary (i.e., the exact timing when a radio frame starts) and an OFDM symbol boundary (i.e., the exact timing when the OFDM symbol starts) through the DL synchronization process. The DL synchronization may mean synchronization (reference Sync+DL path delay) in which propagation delay of the DL path is added to the reference synchronization. Herein, the propagation delay may be interpreted as a path delay of a corresponding path.
Through the UL synchronization process, the terminal may identify the exact timing at which uplink data (e.g., PUSCH/PUCCH) should be transmitted. The UL synchronization may be defined as how fast UL transmission is performed compared to the DL synchronization (i.e., terminal synchronization). For example, the UL synchronization may be described by {DL Sync-Timing Advance value}. In addition, the UL synchronization may finally be defined as indicating how fast UL should be transmitted to meet reference synchronization (i.e., base station synchronization) compared to the DL synchronization (i.e., terminal synchronization), and the quantitative value of how fast UL should be transmitted may be defined as the propagation delay of the UL path as in DL (e.g., DL Sync-UL path delay). Herein, the UL path delay may be interpreted as a propagation delay of the UL path.
In long term evolution (LTE) and fifth generation (5G) system that uses an orthogonal frequency-division multiple access (OFDMA) method, cyclic prefix (CP) is inserted in front of each orthogonal frequency-division multiplexing (OFDM) symbol to reduce interference between symbols. That is, a signal of a last section of a valid symbol section is copied and inserted in front of the valid symbol.
A transmitted signal is in a form of a sine wave in which amplitude and phase change from one symbol to the next. With CP insertion, the amplitude and phase at the beginning of each symbol are the same as the amplitude and phase at the end. In a multi-path environment, receiving-end receives signals transmitted through a plurality of paths with different arrival times. In this case, when CP length is longer than delay spread, the receiving-end may still read information from one symbol at a time. However, when the CP is shorter than the longest path delay, some power of the previous OFDM symbol and transition to the current symbol are included in a symbol Fast Fourier Transform (FFT), breaking subcarrier orthogonality and increasing error vector magnitude (EVM). That is, when the propagation delay (i.e., path delay) is longer than the CP length, the problem of broken DL sync/UL sync may occur.
Hereinafter, how the DL synchronization and the UL synchronization are obtained and tracked in a 3GPP 5G NR standard will be described in detail.
The terminal may obtain and track the DL Sync based on synchronization signal/physical broadcast channel (SS/PBCH) block transmitted by the base station. Specifically, the terminal obtains the DL Sync by measuring the SS/PBCH block transmitted by the base station by itself, and continuously measure the difference from the previous DL Sync by measuring the SS/PBCH block transmitted periodically, and reflecting this in the DL Sync to track it. Herein, the SS/PBCH block refers to a physical layer channel block configured with Primary SS (PSS), Secondary SS (SSS), and PBCH, and is specifically as follows.
Master information block (MIB) information transmitted through the PBCH may include information such as system frame number (SFN), most significant bit (MSB) of the SS/PBCH block index, half frame timing, subcarrier spacing for common control, SS/PBCH subcarrier offset, SIB1 PDCCH configuration, and total payload size. In particular, the MSB of the SS/PBCH block index enables transmission of a plurality of SS/PBCH blocks by providing MSB information of the SS/PBCH block index to support the plurality of SS/PBCH blocks. By securing such an SS/PBCH block index, the terminal may proceed with random access procedure required for initial access by transmitting a beam-based physical random access channel (PRACH) to a base station by using PRACH resource allocated for each SS/PBCH block.
The terminal may obtain DL synchronization by detecting the SS/PBCH block and decode system information. The terminal may identify a structure of an SS/PBCH block burst set based on the detected SS/PBCH block index, and may detect a symbol/slot/half-frame boundary accordingly. The number of a frame/half-frame to which the detected SS/PBCH block belongs may be identified by using SFN information and half-frame indication information.
Specifically, the terminal may obtain 10-bit SFN information from the PBCH. Among the 10-bit SFN information, 6 bits are obtained from the MIB, and the remaining 4 bits are obtained from PBCH Transport Block (TB).
Next, the terminal may obtain 1-bit half-frame indication information. In case that carrier frequency is less than or equal to 3 GHZ, the half-frame indication information may be implicitly signaled by using PBCH DeModulation Reference Signal (DMRS). The PBCH DMRS indicates 3-bit information by using one of eight PBCH DMRS sequences. Therefore, in a case of L=4, among the 3 bits that may be indicated by using eight PBCH DMRS sequences, the 1 bit remaining after indicating an SSB index may be used for half-frame indication.
Lastly, the terminal may obtain the SS/PBCH block index based on DMRS sequence and PBCH payload. An SS/PBCH block candidate is indexed from 0 to L−1 according to time order within the SS/PBCH block burst set (i.e., half-frame). In a case where L=8 or 64, least significant bit (LSB) 3 bits of the SS/PBCH block index may be indicated by using eight different PBCH DMRS sequences. In a case of L=64, MSB 3 bits of the SS/PBCH block index are indicated through the PBCH. In a case of L=2, LSB 2 bits of the SS/PBCH block index may be indicated by using four different PBCH DMRS sequences. In a case of L=4, among the 3 bits that may be indicated by using eight PBCH DMRS sequences, the 1 bit remaining after indicating the SS/PBCH block index may be used for half-frame indication.
Next, a process of obtaining and tracking UL synchronization is described in detail.
Initial UL synchronization may be obtained during a RACH process of initial access.
In
By calculating UL path delay based on the Msg1 received from the terminal, the base station may transmit a corresponding timing advance value to the terminal by including it in the Msg2. Through this operation, the terminal may obtain initial UL synchronization. Thereafter, the terminal informs the base station that the corresponding Msg2 has been successfully received by transmitting Msg3 (hereinafter, interchangeable with ‘scheduled transmission’) to the base station (S330), and thereafter, the base station informs that contention has been resolved by transmitting a contention resolution message on PDSCH (S340).
The base station may control the terminal to track UL Sync by transmitting an appropriate timing advance value to the terminal when the terminal connects or moves for the first time, especially when the beam changes in a beamforming-based system, and this may be referred to as ‘UL Sync tracking’ throughout the disclosure.
By having the base station measure a timing offset from DMRS of a UL signal (e.g., PUSCH), the UL Sync tracking after the initial UL synchronization may allow the terminal to track UL synchronization by calculating the timing advance (TA) value, and transmitting it to the terminal through a timing advance command medium access control (MAC) control element (CE).
A method of controlling timing advance through MAC CE is examined in more detail.
The timing advance command MAC CE may be indicated for a timing advance group (TAG).
The timing advance group (TAG) may mean a serving cell group configured by RRC and uses the same timing reference cell and the same timing advance value for a cell in which UL is configured. A TAG including SpCell of MAC entity is referred to as a primary timing advance group (PTAG), while the term secondary timing advance group (STAG) refers to another TAG.
The timing advance command MAC CE may be identified by a MAC subheader having logical channel identity (LCID). It may have a fixed size and may be configured as a single octet, defined as follows:
The terminal may be provided with a value NTA,offset of the timing advance offset for the serving cell by n-TimingAdvanceOffset for the serving cell. In a case where the terminal is not provided with the n-TimingAdvanceOffset for the serving cell, the terminal may determine a default value. In a case where two UL carriers for the serving cell are configured in the terminal, the same timing advance offset value NTA,offset may be applied to both carriers.
The terminal that has received the timing advance command for the TAG may adjust uplink timing for PUSCH/SRS/PUCCH transmission in all serving cells of the TAG based on i) the value NTA,offset that the terminal expects to be the same for all serving cells of the TAG, and ii) the received timing advance command where the uplink timing for PUSCH/SRS/PUCCH transmission is the same for all serving cells of the TAG.
For SCS at 2μ·15 kHz, the timing advance command for the TAG may indicate a change in UL timing relative to the current uplink timing for the TAG as a multiple of 16·64·Te/2μ.
In a case of a random access response or an absolute timing advance command MAC CE, the timing advance command TA for the TAG may indicate NTA values by an index value of TA=0, 1, 2, . . . , 3846. Herein, the amount of timing alignment for a TAG having the SCS of 2μ·15 kHz is NTA=TA·16·64/2μ. NTA is relative to the SCS of a first uplink transmission from the UE after receiving the random access response or the absolute timing advance command MAC CE.
In other cases, the timing advance command TA for the TAG indicates adjusting NTA_old, which is the current NTA value, to NTA_new, which is the new NTA value, by an index value of TA=0, 1, 2, . . . , 63. Herein, for the SCS of 2μ·15 kHz, it is NTA_new=NTA_old+(TA−31)·16·64/2μ.
Adjusting the NTA value to a positive or negative number means advancing or delaying the uplink transmission timing for the TAG by the corresponding amount, respectively.
The base station processes multiple terminals and needs to ensure that a UL signal from all terminals must be aligned with a common receiver timer of the base station. Therefore, it is necessary to adjust Tx timing (UL timing) of each terminal. When UL synchronization is not properly set by the base station, not only the reception quality of the UL signal transmitted from the terminal decrease significantly, but the link between the base station and the terminal may be disconnected.
Since the base station may communicate with an omni-directional radiation pattern in LTE or 5G NR band below 6 GHz, a difference in path delay compared to the initial path occurs only when the terminal moves. Even when the difference in path delay occurs, the difference in path delay caused by the terminal movement may not be significant. In this case, it may not be a problem to use the existing timing advance control method that measures the timing offset in the UL signal (e.g., PUSCH) and updates the TA value for UL Sync through the timing advance command MAC CE.
However, in a network using a directional beam, such as in a high frequency band above 6 GHz of 5G NR, a large path delay may occur not only by the movement of the terminal but also by beam change.
As illustrated in
Therefore, a method of controlling timing advance (that is, UL sync) is needed to compensate for the path delay that may occur due to the beam change. However, in the current 3GPP 5G NR standard has a problem in that it cannot respond to a large Sync error that may occur due to the beam change.
Before describing a method and/or embodiment proposed in the disclosure, a beam feedback operation defined in the conventional standard will be described.
In
A terminal may measure SSB received from a base station (S610). The base station may transmit a plurality of SSBs to the terminal through different transmission (Tx) beams.
Configuration for a beam report by using the SSB may be performed in an RRC connected state. SSB resources (used for beam management) may be set based on configuration information (e.g., CSI-ResourceConfig IE) transmitted from the base station. The configuration information may include a list (e.g., CSI-SSB-ResourceSetList) of the SSB resources used for beam management and reporting in one resource set. Herein, an SSB resource set may be set to {SSBx1, SSBx2, SSBx3, SSBx4, . . . }. SSB index may be defined from 0 to 63. For example, the SSB index 0, SSB index 1, . . . , and SSB index 63 may correspond to different Tx beams (e.g., beam #0, beam #1, . . . , and beam #63) of the base station, respectively.
The terminal may measure RSRP for the SSB resources and obtain DL Sync (S620).
The terminal may determine whether a feedback request has been received from the base station (S630). For example, in case that a reportQuantity of CSI report configuration information (e.g., CSI-reportConfig) is set as a parameter (e.g., ssb-Index-RSRP) that indicates reporting on SSB resource indicator (SSBRI) and reference signal received power (RSRP), the terminal may determine that the feedback request has been received.
In case that the terminal receives the feedback request from the base station, the terminal may transmit feedback information to the base station (S640). The feedback information may include a beam ID (e.g., SSBRI) and RSRP Pair corresponding thereto.
As described in
In an example of
Hereinafter, in the disclosure, a method for updating/tracking UL synchronization (i.e., a method for controlling timing advance) while preventing wireless link disconnection in a multi-path environment where path delay values of each path may be different is proposed. In addition, a method is proposed to utilize a beam with good RSRP even if the path delay is long. Specifically, the disclosure proposes a method in which a terminal measures a DL Sync difference between the serving beam and the neighbor beam, and reports information on the DL Sync difference to a base station through beam-related feedback (e.g., beam CSI reporting). In addition, a method is proposed in which the base station may respond to a rapid UL Sync error experienced when changing the beam by transmitting a timing advance value determined based on the reported value to the terminal along with a beam change request.
In
A terminal may receive SSB from a base station and measure the received SSB (S910). Herein, the SSB may mean an SS/PBCH block, and each SSB (SS/PBCH block) may include a SS and a PBCH. Also, each SSB may correspond to different beams of the base station. That is, the base station may transmit the SSB to the terminal through different Tx beams.
The terminal may obtain DL synchronization and measure RSRP based on the SSB (S920).
The terminal may determine whether the current beam is a serving beam (e.g., first beam) (S930).
In case that the current beam is a serving beam, DL Sync information of the serving beam may be obtained and stored (S941). In an embodiment, in case that the current beam is not a serving beam (e.g., second beam), a difference between the DL Sync of the previously stored serving beam and the DL Sync of the current beam may be calculated and stored (S942). In other words, a difference value between the DL Sync (e.g., first DL Sync) based on the SSB corresponding to the serving beam and the DL Sync (e.g., second DL Sync) based on the SSB corresponding to the current beam (e.g., second beam, not the serving beam) may be obtained and stored.
For example, the operation of S910 to S942 may be performed repeatedly as many times as the set number of SSB resources. That is, the terminal may receive a plurality of SSBs based on a plurality of beams of the base station, and each SSB may correspond to a different Tx beam. In addition, the terminal may measure DL Sync and RSRP value for each SSB.
The terminal may determine whether a feedback request has been received from the base station (S950).
For example, the terminal may receive configuration information (e.g., CSI-reportConfig IE) associated with feedback reporting from the base station, and in a case where “reportQuantity” included in the configuration information is set as a parameter (e.g., ssb-Index-RSRP) representing reporting on SSBRI and RSRP (Reference Signal Received Power), the terminal may determine that the feedback request has been received.
For another example, a new “reportQuantity” value may be defined to explicitly indicate feedback reporting (e.g., information associated with DL Sync difference value) related to the DL Sync. For an example, in “reportQuantity” within the configuration information (e.g., CSI-ReportConfig IE) associated with the feedback reporting obtained from the base station, a parameter (e.g., ssb-Index-RSRP-DLSyncdelta) indicating reporting of information associated with SSBRI, RSRP, and DL Sync difference value may be set, and in this case, the terminal may determine that the feedback request has been received.
In case that the terminal receives the feedback request from the base station, the terminal may transmit feedback information (i.e., reporting information) to the base station (S960). The feedback information may be transmitted based on an uplink channel (e.g., PUCCH and PUSCH). The feedback information may include Beam ID (e.g., SSBRI), RSRP, and information (e.g., DL Sync Delta Tuple) associated with the difference value between the DL Sync of the serving beam and the DL Sync of the current beam. By transmitting the information (e.g., DL Sync Delta Tuple) associated with the difference value between the DL Sync of the serving beam and the DL Sync of the current beam, it may tell how many UL Sync errors may occur when the base station applies the beam.
For example, the information (e.g., DL Sync Delta Tuple) associated with the difference value may be configured as the difference value (i.e., delta) between the DL sync of the serving beam and the DL sync of the neighbor beam. For an example, the difference value may be expressed as |(DL path delay of serving beam)−(DL path delay of neighbor beam)|.
For example, the terminal may report up to four SSBRI and RSRP pairs. Therefore, each DL sync difference value of SSBs corresponding to the reported SSBRI may be reported to the base station. For example, when the number of reported SSBRIs is n, the information associated with the difference value may include DL Sync delta 1 between the serving beam and a neighbor beam #1, DL Sync delta 2 between the serving beam and a neighbor beam #2, . . . , and DL Sync delta n between the serving beam and a neighbor beam #n.
For example, based on the DL sync of the serving beam, a range of the difference value (i.e., Delta) may be divided into N sections, and an index corresponding to each section may be pre-defined. For an example, the corresponding relationship between the index and Delta range may be pre-defined as illustrated in Table 1. Alternatively, the corresponding relationship of the Table 1 may be set to higher layer signaling (e.g., RRC). Additionally, an index corresponding to the obtained difference value may be included and reported in the reporting information. The Table 1 is only an example and does not limit the technical scope of the disclosure. Therefore, the range of the difference value may be further subdivided and may be fed back to 3 bits or more, or resolution of the range may be lowered and the range of the difference value may be fed back to less than 2 bits. Through this, the number of bits required for feedback may be reduced by comparing the DL Sync delta value feedback method.
For another example, instead of directly reporting the difference value to the base station, the terminal may determine that new TA control is necessary based on the measured difference value and explicitly request that the base station send a new TA value by using 1-bit signaling. In this case, the feedback information may include 1-bit information indicating that a SS/PBCH block index corresponding to a second beam, the RSRP value, and the TA value need to be updated. The base station may know that the new TA value should be transmitted to the terminal when changing to the second beam through the 1-bit information. The terminal may compare the DL sync of a beam (e.g., second beam) other than the serving beam with the CP length, and based on this, report feedback information including information (e.g., difference value, index corresponding to the difference value, and the like) associated with the difference value to the base station.
For example, the terminal may select an SSB resource having the best RSRP value among SSB resources. In case that the DL Sync value obtained based on the selected SSB resource exceeds the CP length, information associated with the difference value may be reported to the base station. In other words, the terminal may transmit feedback information including i) a beam ID (e.g., SSB resource identifier) corresponding to the selected SSB resource, ii) an RSRP value measured based on the selected SSB resource, and iii) information associated with a difference value between DL Sync obtained based on the selected SSB resource and DL Sync obtained based on the SSB corresponding to the serving beam to the base station. For an example, the information associated with the difference value may include the difference value itself, a value converted from the difference value to a specific time unit, or an index corresponding to the difference value. When the DL Sync value obtained based on the selected SSB resource does not exceed the CP length, only SSBRI and RSRP may be reported as in a conventional method.
For example, the terminal may report up to four SSBRI and RSRP pairs. The reported SSBRI may be determined according to the RSRP measured based on the SSB resource. Therefore, up to four pieces of information associated with the DL sync difference value corresponding to the reported SSBRI may also be reported. Even in this case, information associated with the DL sync difference value may be reported only for a beam having DL Sync exceeding the CP length. For example, it is assumed that SSB #1, SSB #2, SSB #3, and SSB #4 are reported. Among these, DL sync of a beam associated with SSB #2 and SSB #3 may exceed the CP length, and DL sync of a beam associated with SSB #1 and SSB #4 may not exceed the CP length. In this case, the terminal may report {SSB #1 and RSRP for SSB #1}, {SSB #2, RSRP for SSB #2, and DL sync delta #2}, {SSB #3, RSRP for SSB #3, and DL sync delta #3}, and {SSB #4 and RSRP for SSB #4} to the base station.
For example, the terminal may select one or more candidate beams among a plurality of beams of the base station based on the RSRP value measured for the SSB. In other words, the terminal may select SSB candidates having an RSRP value greater than or equal to a specific value based on the measured RSRP value. The specific value may be pre-defined or set through higher layer signaling. That is, in order to select a beam of good quality, the SSB candidates may be selected based on the RSRP value. And among the SSB candidates (i.e., candidate beams), SSBs having a smaller value in the DL Sync difference with the serving beam may be selected. For an example, in case that one SSBRI is reported, the terminal may select an SSB (i.e., a beam corresponding to the SSB) having the smallest value in the DL Sync difference with the serving beam among the SSB candidates, and report an index (e.g., SSBRI) corresponding to the selected SSB, RSRP, and information (e.g., a difference value, a value converted from the difference value to a specific time unit, or an index corresponding to the difference value, and the like) associated with the DL Sync difference value. For an example, in case that a plurality of SSBRIs are reported, the terminal may select the SSB among the SSB candidates in order of having a smaller value in the DL Sync difference with the serving beam. Through this, it is possible to report on a beam with good RSRP while maintaining the DL sync of the serving beam similar.
For example, in case that a fast uplink transmission is required, in order to filter a beam with a path delay exceeding the CP length, beams exceeding a threshold value for path delay may be first filtered (excluded) and SSBRI and RSRP for a beam with the best RSRP value among the remaining beams may be reported. In addition, information associated with the difference value corresponding to the corresponding beam may be reported together. For an example, the threshold value for the path delay may be pre-defined or set through higher layer signaling (e.g., RRC). In addition, the threshold value may be set/defined as a CP length or a percentage (%) (e.g., 90%) of the CP length.
The terminal may receive information on a TA value derived based on information (e.g., DL Sync Delta Tuple) associated with the difference value from the base station, and track/update UL sync by using the TA value. For example, information on the TA value may be transmitted by being included in a MAC (medium access control) CE (control element) command including information indicating a change from the serving beam to another beam.
A base station may transmit a beam-related feedback request to a terminal (S1010).
For example, the base station may transmit configuration information (e.g., CSI-reportConfig IE) associated with feedback reporting to the terminal, and transmit “reportQuantity” included in the configuration information to the terminal by being configured as a parameter (e.g., ssb-Index-RSRP) representing reporting on SSBRI and RSRP (Reference Signal Received Power).
For example, a new “reportQuantity” value may be defined to explicitly indicate feedback reporting related to DL Sync (e.g., information associated with DL Sync difference value). For an example, the base station may configure a parameter (e.g., ssb-Index-RSRP-DLSyncdelta) indicating reporting on information associated with SSBRI, RSRP, and DL Sync difference value in “reportQuantity” within configuration information (e.g., CSI-ReportConfig IE) associated with feedback reporting and transmit it to the terminal.
The base station may receive feedback information (i.e., reporting information) from the terminal in response to the feedback request (S1020). The feedback information may be received based on an uplink channel (e.g., PUCCH and PUSCH). The feedback information may include Beam ID (e.g., SSBRI), RSRP, and information (e.g., DL Sync Delta Tuple) associated with a difference value between DL Sync of a serving beam and DL Sync of the current beam.
For example, the information (e.g., DL Sync Delta Tuple) associated with the difference value may be configured as the difference value (i.e., delta) between the DL sync of the serving beam and DL sync of a neighbor beam. The difference value may be expressed as |(DL path delay of serving beam)−(DL path delay of neighbor beam)|.
For example, the information (e.g., DL Sync Delta Tuple) associated with the difference value may include an index corresponding to the difference value (i.e., delta) between the DL sync of the serving beam and the DL sync of the neighbor beam. The range of the difference value (i.e., delta) is divided into N sections based on the DL sync of the serving beam, and the index corresponding to each section may be pre-defined as in the example in Table 1 above. Alternatively, a corresponding relationship of Table 1 may be set to higher layer signaling (e.g., RRC).
For example, the information (e.g., DL Sync Delta Tuple) associated with the difference value may be configured as 1-bit information indicating that the TA value needs to be updated. In this case, the feedback information may include 1-bit information indicating that an index of a SS/PBCH block corresponding to a second beam, an RSRP value, and the TA value need to be updated.
The information associated with the difference value may be included in the feedback information based on a comparison between DL sync of a beam (e.g., second beam) other than the serving beam and a CP length. For example, in case that the DL sync (e.g., second DL sync) of the beam (e.g., second beam) other than the serving beam exceeds the CP length, the information associated with the difference value may be included in the feedback information.
For example, an SSB resource having the best RSRP value may be selected among a plurality of SSB resources, and in case that the DL Sync value obtained based on the selected SSB resource exceeds the CP length, the information associated with the difference value may be included in the feedback information. That is, the base station may receive feedback information including i) a beam ID (e.g., SSB resource identifier) corresponding to the selected SSB resource, ii) an RSRP value measured based on the selected SSB resource, and iii) information associated with a difference value between DL Sync based on the selected SSB resource and DL Sync based on the SSB corresponding to the serving beam from the terminal. For example, the information associated with the difference value may include the difference value itself, a value converted from the difference value to a specific time unit, or an index corresponding to the difference value.
For example, one or more candidate beams among a plurality of beams of the base station may be determined based on a RSRP value corresponding to each of a plurality of SS/PBCH blocks transmitted by the base station. In other words, SSB candidates having an RSRP value greater than or equal to a specific value may be selected based on the measured RSRP value. The specific value may be pre-defined or configured through higher layer signaling. SSBs (i.e., beam corresponding to SSB) having a smaller value among difference values between DL sync associated with each of the one or more candidate beams and the DL Sync of the serving beam may be selected. For an example, an index (e.g., SSBRI) corresponding to an SSB with the smallest value in the DL Sync difference, RSRP, and information associated with the DL Sync difference value (e.g., a difference value, a value converted from the difference value to a specific time unit, or an index corresponding to the difference value) may be received.
The base station may determine whether the beam needs to be changed based on the received feedback information (S1030). For example, it may be determined whether a beam change is necessary based on the RSRP. For an example, in case that the received RSRP value is smaller than a specific threshold value, it may be determined that the beam change is necessary.
When it is determined that the beam change is necessary, the base station may transmit a beam change request to the terminal (S1040). In this case, the base station may transmit information on the TA value calculated/derived based on the information (e.g., DL Sync Delta Tuple) associated with the difference value of the DL Sync, together with the beam change request.
For example, the beam change request may be transmitted by using TCI state activation/deactivation MAC CE. In this case, the TCI state activation/deactivation MAC CE may include a new TCI state and a TA value (index) corresponding to the TCI state. In addition, the TCI state activation/deactivation MAC CE may further include a serving cell ID and a BWP ID.
When receiving HARQ feedback for the corresponding beam change request from the terminal (S1050), the base station may perform the beam switch (change) after a certain time (e.g., 3 ms) (S1060).
The terminal may adjust UL synchronization by reflecting the TA included in the beam change request and may apply the adjusted UL synchronization to UL transmission, thereby preventing UL Sync error from occurring due to the beam change.
As described above, in
Compared to
In
The transmit/receive unit 1201 (or the transceiver 1201) may be configured as a transmit unit and a receive unit according to another embodiment. The transmit/receive unit 1201 (or the transceiver 1201) may transmit and receive a signal to and from a base station. The signal may include control information and data. To this end, the transmit/receive unit 1201 (or the transceiver 1201) may be configured with an RF transmitter that up-converts and amplifies frequency of a transmitted signal, and an RF receiver that amplifies the received signal with low noise and down-converts the frequency. In addition, the transmit/receive unit 1201 (or the transceiver 1201) may output a signal by receiving it through a wireless channel to the processor 1202, and transmit the signal outputted from the processor 1202 through the wireless channel.
The processor 1202 may control a series of processes in which the terminal 1200 may operate according to the above-described embodiment of the disclosure. For example, according to an embodiment of the disclosure, the processor 1202 may control a process in which the terminal obtains DL sync for each TX beam of the base station, calculates a DL sync difference value between a serving beam and neighbor beams, and reports this to the base station. To this end, the processor 1202 may include at least one processor. For example, the processor 1202 may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls a higher layer such as an application program.
The memory 1203 may store a DL sync difference value between the serving beam and the neighbor beam calculated by the terminal 1200 and/or information related to the DL sync difference, and may have an area for storing data required for controlling the processor 1202 and data generated when the processor 1202 controls.
In
The transmit/receive unit 1301 (or the transceiver 1301) may be configured as a transmit unit and a receive unit according to another embodiment. The transmit/receive unit 1301 (or the transceiver 1301) may transmit and receive a signal to and from a terminal. The signal may include control information and data. To this end, the transmit/receive unit 1301 (or the transceiver 1301) may be configured with an RF transmitter that up-converts and amplifies frequency of a transmitted signal, and an RF receiver that amplifies the received signal with low noise and down-converts the frequency. In addition, the transmit/receive unit 1301 (or the transceiver 1301) may output a signal by receiving it through a wireless channel to the processor 1302, and transmit the signal outputted from the processor 1302 through the wireless channel.
The processor 1302 may control a series of processes (functions or operations) so that the base station 1300 may operate according to the above-described embodiment of the disclosure. For example, the processor 1302 may calculate a TA value based on DL sync difference value included in the beam-related reporting received from the terminal according to an embodiment of the disclosure, and may control to transmit beam change request information including information (e.g., TCI state) on a new beam and the TA value to the terminal. To this end, the processor 1302 may include at least one processor. For example, the processor 1302 may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls a higher layer such as an application program.
The memory 1303 may store the DL sync difference value, beam-related reporting information, and the like received from the terminal, and may have an area for storing data required for control of the processor 1302 and data generated when the processor 1302 controls.
In
In
The base station 1300 may include a reception unit (beam-based DL sync delta receiver 1410) configured to receive the beam feedback transmitted from the terminal 1200, a calculation unit (sync delta based TA calculator 1412) configured to calculate the Timing Advance (TA) based on the received DL Sync Delta, a determination unit (beam change decision circuit 1414) configured to determine whether to change the beam, and a transmission unit (beam change request circuit w/TA 1416) configured to transmit a beam change request by including calculation TA when requesting the beam change when the beam change is determined.
In
According to an embodiment, a terminal of a wireless communication system may comprise a transceiver configured to transmit and receive signals, memory including one or more storage media, storing instructions, and at least one processor including processing circuitry. The instructions, when being executed by the at least one processor individually or collectively, may cause the terminal to obtain a difference value between first downlink synchronization based on a synchronization signal/physical broadcast channel (SS/PBCH) block corresponding a first beam and second downlink synchronization based on the SS/PBCH block corresponding a second beam, based on a comparison between the second downlink synchronization and cyclic prefix (CP) length, transmit, to a base station, reporting information comprising information associated with the difference value, and receive, from the base station, information on a timing.
The term ‘˜unit’ used in the above-described embodiment of the disclosure refers to software or hardware components such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC), and ‘˜unit’ performs certain roles. However, the ‘˜unit’ does not mean limited to software or hardware. The ‘˜unit’ may be configured to be in an addressable storage medium or may be configured to reproduce one or more processors. Therefore, as an example, the ‘˜unit’ includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, procedures, sub-routines, segments of program code, drivers, firmware, microcode, circuit, data, database, data structures, tables, arrays, and variables. A function provided within the components and the ‘˜units’ may be combined into a smaller number of components and ‘˜units’ or further divided into additional components and ‘˜units.’ Additionally, the components and the ‘˜units’ may be implemented to reproduce one or more CPUs within a device or a secure multimedia card. In addition, in an embodiment, the ‘˜unit’ may include one or more processors.
In the disclosure, the processor (the processor 1202, the processor 1302) may correspond to one or more processors. The processor of the disclosure may include or correspond to circuitry like a central processing unit (CPU), a microprocessor unit (MPU), an application processor (AP), a coprocessor (CP), a system-on-chip (SoC), or an integrated circuit (IC). In the disclosure, the memory (the memory 1203, the memory 1204) may correspond to one or more memories (memory devices).
The embodiments disclosed in the disclosure and drawings are merely provided as a specific example to easily explain the technical content of the disclosure and to aid understanding of the disclosure, and are not intended to limit the scope of the disclosure. In other words, it is obvious to those having ordinary knowledge in the art that other modification examples based on the technical idea of the disclosure may be implemented. In addition, each of the above embodiments may be operated in combination with each other as needed.
No claim element is to be construed under the provisions of 35 U.S.C. § 112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or “means.”
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0002689 | Jan 2022 | KR | national |
| 10-2022-0046847 | Apr 2022 | KR | national |
This application is a by-pass continuation application of International Application No. PCT/KR2022/018829, filed on Nov. 25, 2022, which is based on and claims priority to Korean Patent Application Nos. 10-2022-0002689, filed on Jan. 7, 2022, and 10-2022-0046847, filed on Apr. 15, 2022, in the Korean Intellectual Property Office, the disclosures of which are incorporated by reference herein their entireties.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/KR2022/018829 | Nov 2022 | WO |
| Child | 18764859 | US |
