Patent Publication Number: US-2022231734-A1

Title: Device and system characterized by measurement, report, and change procedure by terminal for changing transmission/reception point, and base station procedure for supporting same

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation application of prior application Ser. No. 16/321,612, filed on Jan. 29, 2019, which will be issued as U.S. Pat. No. 11,303,329 on Apr. 12, 2022, which is a U.S. National Stage application No. PCT/KR2017/008757, filed on Apr. 11, 2017, which is based on and claimed priority under 35 U.S.C. § 119(e) of a U.S. Provisional patent application No. 62/373,599, filed on Aug. 11, 2016, in the Korean Intellectual Property Office, the disclosure of which is incorporated by reference herein in its entirety. 
    
    
     TECHNICAL FIELD 
     The disclosure relates to a next-generation wireless communication system. More specifically, the disclosure relates to a measurement, report, and change procedure of a terminal for a system including one or more transmission and reception points, a method of transmitting a measurement reference signal for each transmission and reception point and a method of collecting reports by a base station for the measurement, report, and change procedure, and a method, procedure and system for changing a transmission and reception point of each terminal. 
     BACKGROUND ART 
     In order to satisfy a wireless data traffic demand that tends to increases after the 4G communication system commercialization, efforts to develop an improved 5G communication system or pre-5G communication system is being made. 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. In order to achieve a high data transfer rate, the 5G communication system is considered to be implemented in an mmWave band (e.g., 60 GHz band). In order to reduce a loss of electric waves and increase the transfer distance of electric waves in the mmWave band, beamforming, massive MIMO, full dimensional MIMO (FD-MIMO), array antenna, analog beamforming and large scale antenna technologies are being discussed in the 5G communication system. Furthermore, in order to improve the network of a system, technologies, such as an improved small cell, an advanced small cell, a cloud radio access network (cloud RAN), an ultra-dense network, device to device communication (D2D), wireless backhaul, a moving network, cooperative communication, coordinated multi-points (CoMP) and reception interference cancellation, are being developed in the 5G communication system. In addition, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) that are advanced coding modulation (ACM) schemes, improved filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) are being developed in the 5G system. 
     Meanwhile, the Internet evolves from a human-centered connection network over which human generates and consumes information to Internet of Things (IoT) in which information is exchanged and process between distributed elements, such as things. An Internet of Everything (IoE) technology in which a big data processing technology through a connection with a cloud server is combined with the IoT technology is emerging. In order to implement the IoT, technical elements, such as the sensing technology, wired/wireless communication and network infrastructure, service interface technology and security technology, are required. Accordingly, technologies, such as a sensor network, machine to machine (M2M) and machine type communication (MTC) for a connection between things, are recently researched. In the IoT environment, an intelligent Internet technology (IT) service in which a new value is created for human life by collecting and analyzing data generated from connected things may be provided. The 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 services, through convergence and composition between the existing information technology (IT) and various industries. 
     Accordingly, various attempts to apply the 5G communication system to the IoT are being made. For example, 5G communication technologies, such as a sensor network, machine to machine (M2M) and machine type communication (MTC), are implemented by schemes, such as beamforming, MIMO, and an array antenna. The application of a cloud wireless access network (cloud RAN) as the aforementioned big data processing technology may be said to be an example of convergence between the 5G technology and the IoT technology. 
     With the advent of smartphones, the amount of user data increases geometrically. The need for such data usage is further increasing. This means that a high bandwidth is necessary. To this end, a high frequency needs to be used. However, as a high frequency is used, a signal attenuation degree for each distance rises. That is, if a center frequency of 30 GHz or more is used, a coverage reduction of a base station attributable to signal attenuation is inevitable. Furthermore, there are problems in that many beams need to be used due to the coverage reduction and latency attributable to the use of many beams is increased. 
     In a wireless communication system, a structure is taken into consideration in which one base station including multiple transmission and reception points capable of transmission and reception supports a wide physical area in order to improve latency attributable to a frequent exchange of terminal information and for efficient resource utilization. Such a system has been researched in various ways in a conventional technology and has been implemented. 
     Representatively, the following systems may be taken as the existing technologies: 
     A distributed antenna system (DAS) in which different transmission and reception points under one base station are simply implemented as physical antennas and transmit or receive the same signal, 
     A remote radio head (RRH) system in which different transmission and reception points under one base station are implemented as a structure including an antenna and a simple RF stage and can transmit or receive different signals, 
     Furthermore, a coordinated multi-point transmission/reception (CoMP) system in which different transmission and reception points under one or different base stations transmit and receive the same information to and from one user at the same time through synchronization or the other transmission and reception point is silent while one transmission and reception point transmits and receives information. 
     In such a background, a measurement, report and change method of a terminal and an operation method of a base station supporting the same, for a transmission and reception point change are necessary. 
     Technical Problem 
     An embodiment of the disclosure proposes a method for a terminal to measure a reference signal for the selection of a beam and transmission and reception point, a method for the terminal to feed measured information back, and a method for the terminal to changing a beam and transmission and reception point in an environment in which transmission and reception points having different protocol structures are present in the same base station maintaining an RRC connected state with the terminal, and proposes a method for the base station to allocate a terminal-unique beam and transmission and reception point reference signal resource, a method for the base station to share allocated resource information with the terminal, a resource allocation and signaling method for receiving measured information through feedback, and a method for the base station to change a beam and transmission and reception point in a system configured with the base station and the transmission and reception points for the methods. 
     Furthermore, synchronization signals transmitted at a transmission point being used by a terminal as one reception beam and a transmission point not being used by the terminal as one reception beam cannot be received at the same time in a beamforming environment. In an embodiment of the disclosure, in order to solve the problem, there may be a method for a terminal to measure an adjacent transmission and reception point transmission reference signal while turning a dumb reception beam. In such a method, however, time is taken long, and a transmission and reception point maximum measurement time is very long, that is, the “number of transmission and reception points x the number of beams within transmission and reception point x the number of terminal beams.” There is proposed a method of efficiently measuring a transmission reference signal corresponding to only the “number of transmission and reception points x the number of beams within a transmission and reception point” using an effective terminal reception beam at the reference signal transmission times of different transmission and reception points based on information transmitted by a base station. 
     Solution to Problem 
     In accordance with an embodiment of the disclosure, an operation method of a terminal may provide a method, including receiving resource configuration information, including reference signal configuration information of a first transmission and reception point (TRP) and reference signal configuration information of a second TRP, from the first TRP; measuring a reference signal corresponding to the first TRP and a reference signal corresponding to the second TRP based on the resource configuration information; reporting the measurement information on the reference signal corresponding to the first TRP and the reference signal corresponding to the second TRP to the first TRP; receiving TRP change indication information from the first TRP; and changing a configuration for the second TRP based on the TRP change indication information. 
     In accordance with an embodiment of the disclosure, a terminal may provide a terminal, including a transceiver configured to transmit and receive signals and a controller configured to control to receive resource configuration information, including reference signal configuration information of a first transmission and reception point (TRP) and reference signal configuration information of a second TRP, from the first TRP, to measure a reference signal corresponding to the first TRP and a reference signal corresponding to the second TRP based on the resource configuration information, report the measurement information on the reference signal corresponding to the first TRP and the reference signal corresponding to the second TRP to the first TRP, to receive TRP change indication information from the first TRP, and to change a configuration for the second TRP based on the TRP change indication information. 
     In accordance with an embodiment of the disclosure, an operation method of a base station may provide a method, including transmitting resource configuration information, including reference signal configuration information of a first transmission and reception point (TRP) and reference signal configuration information of a second TRP, to a terminal through the first TRP; transmitting a reference signal corresponding to the first TRP and a reference signal corresponding to the second TRP based on the resource configuration information; receiving measurement information on the reference signal corresponding to the first TRP and the reference signal corresponding to the second TRP from the terminal; determining a TRP change for the terminal based on the measurement information; transmitting TRP change indication information to the terminal through the first TRP; and changing a configuration of the second TRP for the terminal in accordance with the TRP change indication information. 
     Advantageous Effects 
     In accordance with an embodiment of the disclosure, there can be provided a measurement, report, and change procedure of a terminal for a system including one or more transmission and reception points, a method for a base station to transmit a measurement reference signal and a method for a base station to collect reports for each transmission and reception point for the measurement, report, and change procedure, and a method, procedure and system for changing a transmission and reception point of each terminal. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram showing a TRP protocol structure according to an embodiment of the disclosure. 
         FIG. 2  is a diagram showing an environment including a multi-TRP and a multi-beam according to an embodiment of the disclosure. 
         FIG. 3  is a diagram showing a method of measuring a multi-TRP beam in a multi-beam, multi-TRP environment according to an embodiment of the disclosure. 
         FIG. 4  is a diagram showing a terminal initial access procedure in a multi-beam, multi-TRP environment according to an embodiment of the disclosure. 
         FIG. 5  is a diagram showing a terminal initial access procedure in a multi-beam, multi-TRP environment according to another embodiment of the disclosure. 
         FIG. 6  is a diagram showing a TRP change method according to an embodiment of the disclosure. 
         FIG. 7  is a diagram showing a TRP change method of a base station through the RS measurement of a terminal according to an embodiment of the disclosure. 
         FIG. 8  is a diagram showing a beam RS set change method of a base station through the RS measurement of a terminal in an embodiment of the disclosure. 
         FIG. 9  is a diagram showing a TRP change method when a base station controls the mobility of a terminal in an embodiment of the disclosure. 
         FIG. 10  is a diagram showing a procedure of changing a TRP after a grant in an embodiment of the disclosure. 
         FIG. 11  is a diagram showing a procedure of changing a TRP after a grant in another embodiment of the disclosure. 
         FIG. 12  is a diagram showing a procedure of changing a TRP based on an RRC message in another embodiment of the disclosure. 
         FIG. 13  is a diagram showing a method of exchanging terminal information between a TRP and a base station according to an embodiment of the disclosure. 
         FIG. 14  is a diagram showing a method of exchanging terminal information between a TRP and a base station according to another embodiment of the disclosure. 
         FIG. 15  is a diagram showing a method of sharing terminal information when a TRP change is requested in an embodiment of the disclosure. 
         FIG. 16  is a diagram showing a method of sharing terminal information when a TRP change is requested in another embodiment of the disclosure. 
         FIG. 17  is a diagram showing a method of sharing terminal information when a TRP change is requested in another embodiment of the disclosure. 
         FIG. 18  is a diagram showing a terminal feedback trigger and TRP change method according to an event in an embodiment of the disclosure. 
         FIG. 19  is a diagram showing a terminal feedback trigger and TRP change method according to an event in another embodiment of the disclosure. 
         FIG. 20  is a diagram showing a terminal according to an embodiment of the disclosure. 
         FIG. 21  is a diagram showing a base station according to an embodiment of the disclosure. 
     
    
    
     MODE FOR THE INVENTION 
     Hereinafter, preferred embodiments of the disclosure are described in detail with reference to the accompanying drawings. It is to be noted that the same reference numbers are used throughout the drawings to refer to the same elements. Furthermore, a detailed description of known functions or constructions that may make the gist of the disclosure vague is omitted. 
     In this specification, in describing the embodiments, a description of contents that are well known in the art to which the disclosure pertains and not directly related to the disclosure is omitted in order to make the gist of the disclosure clearer. 
     For the same reason, in the accompanying drawings, some elements are enlarged, omitted, or depicted schematically. Furthermore, the size of each element does not accurately reflect its real size. In the drawings, the same or similar elements are assigned the same reference numerals. 
     The merits and characteristics of the disclosure and a method for achieving the merits and characteristics will become more apparent from the embodiments described in detail in conjunction with the accompanying drawings. However, the disclosure is not limited to the disclosed embodiments, but may be implemented in various different ways. The embodiments are provided to only complete the disclosure of the disclosure and to allow those skilled in the art to understand the category of the disclosure. The disclosure is defined by the category of the claims. The same reference numerals will be used to refer to the same or similar elements throughout the drawings. 
     In the disclosure, it will be understood that each block of the flowchart illustrations and combinations of the blocks in the flowchart illustrations can be executed by computer program instructions. These computer program instructions may be mounted on the processor of a general purpose computer, a special purpose computer, or other programmable data processing apparatus, so that the instructions executed by the processor of the computer or other programmable data processing apparatus create means for executing the functions specified in the flowchart block(s). These computer program instructions may also be stored in computer-usable or computer-readable memory that can direct a computer or other programmable data processing equipment to function in a particular manner, such that the instructions stored in the computer-usable or computer-readable memory produce an article of manufacture including instruction means that implement the function specified in the flowchart block(s). The computer program instructions may also be loaded on a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-executed process, so that the instructions performing the computer or other programmable apparatus provide steps for executing the functions described in the flowchart block(s). 
     Furthermore, each block of the flowchart illustrations may represent a portion of a module, a segment, or code, which includes one or more executable instructions for implementing a specified logical function(s). It should also be noted that in some alternative implementations, the functions noted in the blocks may occur out of order. For example, two blocks shown in succession may in fact be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. 
     In this case, the term “unit”, as used in the embodiment means software or a hardware component, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), and the “unit” performs specific tasks. The “unit” may advantageously be configured to reside on an addressable storage medium and configured to operate on one or more processors. Accordingly, the “unit” may include, for example, components, such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, sub-routines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. The functionalities provided in the components and “units” may be combined into fewer components and “units” or may be further separated into additional components and “units.” Furthermore, the components and “units” may be implemented to operate on one or more CPUs within a device or a security multimedia card. 
     In an embodiment of the disclosure, a base station (BS) is a main agent communicating with a terminal, and may be referred to as a “BS, base transceiver station (BTS), nodeB (NB), eNodB (eNB), gNB, an access point (AP), etc. In an embodiment of the disclosure, the term called a base station or eNB is chiefly used, but is not limited thereto. The base station may be used as a gNB of a 5G NR system. 
     A terminal is a main agent communicating with a base station, and may be referred to as a “user equipment (UE), device, mobile station (MS), mobile equipment (ME), a terminal, etc. 
     In an embodiment of the disclosure, a transmission and reception point may refer to a transmission and reception point (TRP). 
       FIG. 1  is a diagram showing a TRP protocol structure according to an embodiment of the disclosure. 
     Referring to  FIG. 1 , a distributed unit structure configured with multiple transmission and reception points taken into consideration in an embodiment of the disclosure takes various candidates into consideration, and may include a centralized unit and a distributed unit. The centralized unit and the distributed unit may include an RF stage, a physical layer (L1 or PHY), and a higher layer (MAC stage, RLC stage, PDCP stage, and RRC stage). For example, referring to a combination of a CU and a DU1, the RRC, PDCP, RLC, MAC, and L1 layer are present in the CU, and only the RF stage is included in the DU. A combination of the CU and a DU6 is a case where the RRC, PDCP layer are present in the CU and the RLC, MAC, L1 layer and RF stage are present in the DU6. In an embodiment of the disclosure, various protocol stacks of various CUs and DUs illustrated in  FIG. 1  may be applied. 
     In an embodiment of the disclosure, a base station may be a concept including a CU and at least one DU. Furthermore, the base station may be a concept, including a CU, at least one DU, and at least one TRP. The TRP may correspond to the antenna of the base station. A different TRP may correspond to a different antenna of the base station. The TRP may correspond to at least one of the resource set, NR-SS resource set, beam set, or antenna configuration set of a channel state information-reference signal (CSI-RS). For example, if TRPs are different, CSI-RS resource sets, NR-SS resource sets, beam sets, and antenna configuration sets may be different. A TRP may manage a plurality of beams, and a plurality of beams managed by one TRP may be defined as a beam set. What a UE transmits a signal to a TRP may be construed as being what the UE transmits a signal to a base station connected to the TRP. What a UE receives a signal from a TRP may be construed as being what the UE receives a signal from a base station connected to the TRP. If a base station is construed as including a TRP, the transmission and/or reception of a signal, information, message between the base station and a TRP may be understood as being an internal operation of the base station. 
       FIG. 2  is a diagram showing an environment including a multi-TRP and a multi-beam according to an embodiment of the disclosure. Referring to  FIG. 2 , the environment including a multi-beam may include an eNB # 1 , an eNB # 2 , and a terminal. The eNB # 1  may include a plurality of TRPs TRP # 1  to the TRP #k. The eNB # 2  may include a plurality of TRPs TRP # 1  to the TRP #k. Each TRP may operate a plurality of beams. For example, each TRP may operate a beam # 1  to a beam #n. The n value may be different depending on the TRP. 
     In  FIG. 2 , it is assumed that the terminal moves while being served by the Beam # 1  of the TRP # 1  of the eNB # 1 . As the eNB # 1  moves, the beam of the TRP # 1  for the terminal may be changed. When the terminal is out of coverage of the TRP # 1  while moving by changing the serving beam of the TRP # 1 , a TRP change to another TRP (e.g., TRP #K) may occur. When the terminal moves from the TRP #K, a beam change may occur. When the terminal is out of coverage of the eNB # 1 , a serving eNB may be changed to the eNB # 2 . Likewise, when the terminal moves from the serving eNB # 2 , a beam change and a TRP change may occur. 
     A transmission and reception point taken into consideration in an embodiment of the disclosure may be a structure present at a location physically separated from any CU and another transmission and reception point having one of the protocol structures of  FIG. 1 . A terminal may perform wireless communication based on the same terminal ID (e.g., C-RNTI) as the CU using such different multiple transmission and reception points. 
     In this case, the corresponding terminal may communicate with the transmission and reception points or the CU using any ID (e.g., Cell ID) owned by a base station including all the multiple transmission and reception points or may communicate with the TRPs and the CU using a transmission and reception point ID (e.g., TRP ID) that is uniquely allocated and shared with the terminal or may communicate with the TRPs or the CU to which a corresponding protocol belongs using an ID (e.g., MAC ID, RLC ID, TCP ID, IP, . . . ) included in a protocol within each transmission and reception point. 
     In an embodiment of the disclosure, the following various methods are described in order to support a system in which multiple TRPs are managed. Each of the methods may be independently performed and a method of combining a plurality of methods may be performed.
         A method for a system to explicitly (additionally) transmit a unique TRP ID different from a Cell ID to a terminal   A method for a system to share an implicit rule by which terminals can distinguish between TRPs   A method for a base station within a system to transmit a measurement reference signals using multiple TRPs   A method for a terminal to receive the measured reference signals of multiple TRPs   A method for a terminal to feed measurement information from multiple TRPs back to a base station to which the terminal belongs   A method for a base station and terminal within a system to change a TRP       

     &lt;Method of Explicitly Transmitting Unique TRP ID to UE&gt; 
     1. a method of transmitting a TRP ID through a synchronization signal 
     A. a method of adding an additional TRP-SS—new synchronization signal for each TRP 
     : the existing synchronization signal (PSS, SSS, for Cell ID)+a new synchronization signal (new SS for a TRP ID) 
     a-1. Can identify a TRP as a new synchronization signal 
     a-2. Define a TRP ID as a new SS having a sequence identifier and transmit it. Reference is made to the following contents for a method of defining a new SS. 
     New SS Definition 
     A sequence d(0), . . . , d(K) used by a UE to obtain an extended synchronization signal is a length-K Zadoff-chu (ZC) sequence and is defined as follows. 
     
       
         
           
             
               
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     In this case, K is a maximum value of the sequence, and a TRP (or CSI-RS resource set, NR-SS resource set, beam set) number (e.g., 63) and M (e.g., 23) within each base station are root indices. 
     A sequence used to obtain an extended synchronization signal that may be obtained within an OFDM symbol l is defined as a d(n)cyclic shift and is as follows: 
     In this case, when l=0, . . . , 2·N symb   DL −1, a cyclic shift value Δ l  is defined in Table 1-A. 
     
       
         
           
               
             
               
                 TABLE 1-A 
               
             
            
               
                   
               
               
                 Cyclic shifts for the extended  
               
               
                 synchronization signal 
               
            
           
           
               
               
               
            
               
                   
                   
                 Cyclic shift 
               
               
                   
                 l 
                 Δ t   
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                  0 
                 0 
               
               
                   
                  1 
                 7 
               
               
                   
                  2 
                 14 
               
               
                   
                  3 
                 18 
               
               
                   
                  4 
                 21 
               
               
                   
                  5 
                 25 
               
               
                   
                  6 
                 32 
               
               
                   
                  7 
                 34 
               
               
                   
                  8 
                 38 
               
               
                   
                  9 
                 41 
               
               
                   
                 10 
                 45 
               
               
                   
                 11 
                 52 
               
               
                   
                 . . . 
                 . . . 
               
               
                   
                 K/4 
                 K-2 
               
               
                   
                   
               
            
           
         
       
     
     A sequence used to scramble an extended synchronization signal in a i∈{0,25} subframe is defined as follows: 
     
       
         
           
             
               
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     In this case, the pseudo-random sequence c(m) is defined as follows: 
     The pseudo-random sequence is defined as a length-31 Gold sequence. When n=0,1, . . . , K−1, an output sequence c(n), that is, a length M PN , is defined as follows: 
         c ( n )=( x   1 ( n+N   c )+ x   2 ( n+N   c ))mod 2 
         x   1 ( n +( K− 1)/2)=( x   1 ( n+ 3)+ x   1 ( n ))mod 2 
         x   2 ( n +( K− 1)/2)=( x   2 ( n+ 3)+ x   2 ( n+ 2)+ x   2 ( n+ 1)+ x   2 ( n ))mod 2 
     In this case, N c =1600, and the first m-sequence is initialized using x 1 (0)=1, x 1 (n)=0,n=1, 2, . . . , ((K−1)/2−1). The second m-sequence is initialized as c init =Σ i=0   (K-1)/2-1 x 2 (i)·2 i . In this case, the parameter value is determined depending on use of the sequence. 
     In the i-th subframe, a pseudo-random sequence generator needs to be initialized using c init =2 10 ·(i+1)·(2·N D   TRP +1)+2·N D   TRP +1. 
     A sequence d i (n) used in the extended synchronization signal is defined as follows. 
         d   i ( n )= r   1 ( n )· d   i ( n ),  n= 0, . . . , K− 1
 
     B. New SS Only—Method of Transmitting Only an SS for Synchronization for Each TRP without SS Including the Existing Cell ID 
     : SSs for a TRP ID only 
     C. Modified PSS/SSS—Method of Modifying the Existing SS and Including a TRP ID 
     : Method of transmitting a TRP ID in a PSS and SSS, that is, the existing synchronization signals in addition to a cell ID (PSS/SSS carry both Cell ID and the TRP ID) 
     c-1. Embodiment: A PSS is the same as that of LTE, and a scheme for modifying an SSS as follows. 
     n ID   (2) ∈{0,1,2} is a physical layer identifier (ID) and may be used in a cell and TRP (or CSI-RS resource set, NR-SS resource set, beam set). A sequence d(0), . . . , d(61) used for a second synchronization signal has a form of interleaved concatenation produced using two length-31 binary sequences. The concatenated sequence is a scrambled sequence given by the first synchronization signal. The second synchronization signal may be transmitted through the following port. p=300, . . . , 313. 
     The second synchronization signal defined as a combination of the two length-31 sequences may be differently defined as follows for each subframe: 
     
       
         
           
             
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     In this case, 0≤n≤30. S m     0    and S m     1    denote a physical layer cell ID group N ID   Cell(1)  and a physical layer TRP (or CSI-RS resource set, NR-SS resource set, beam set) ID group N ID   TRP(1) , respectively. 
     2. Method of Inclusion and Transmission in Reference Signal 
     A. Method of Using a Unique Sequence for a TRP (Unique Sequences for TRPs) 
     a-1. Method of Allocating a Unique Sequence for Each TRP 
     Method 1) Divide and Use the Existing Cell ID Space 
     A reference signal sequence η(m) is defined as follows: 
     
       
         
           
             
               
                 η 
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                   m 
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                 8 
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               - 
               1 
             
           
         
       
     
     In this case, 1=0, 1, . . . , 13 is an OFDM symbol number. The pseudo-random sequence c(i) is defined above, and the pseudo-random generator may be initialized using the following.
         1) c init =2 10 ·(7·(n 3 +1)+l′+1)·(2·N ID   cell ·N ID   TRP +1)+2·N ID   cell ·N ID   TRP +1   2) c init =2 10 ·(7·(n 2 +1)+l′+1)·(2·N ID   cell +2N ID   TRP +1)+2·N ID   cell +2·N ID   TRP +1   3) c init =2 10 ·(7·(n 1 +1)+l′+1)·(2·K+1)+2·K+1,       

         N   ID   cell =( K )mod( N   ID   cellmax /2), N   ID   TRP =(└ K /( N   ID   cellmax /2)┘+ N   ID   cell +1)mod( N   ID   cellmax /2)
         4) Or when       

     
       
         
           
             
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                 l 
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     and l′=l mod 7, any type of unique initialization code produced using different distinguishable N ID   cell  and N ID   TRP  at the early stage of an OFDM symbol 
     Method 2) New Sequence Design—Unique Sequence Design for Each Cell, Each TRP Including a N ID   Cell  and N ID   TRP    
     B. Method of Using a Different Resource for Each TRP (Different Resources for TRPs) 
     b-1. Allocated a different frequency (carrier, subcarrier, channel, a bandwidth, etc.) to a different TRP 
     b-2. Allocate a different time (slot, symbol, subframe, radio frame) to a different TRP 
     b-3. Allocate a radio resource (radio resource block), represented as a different frequency and time, to a different TRP 
     C. Different Resources &amp; Sequences for TRPs 
     c-1. Method of mixing different frequency/time/sequences and distinguishing between TRPs 
     3. Method of Inclusion and Transmission in Broadcasting Information 
     Share information for distinguishing between TRPs using broadcast information, such as a master information block (MIB), a broadcast channel (BCH), a system information block (SIB) 1 or 2 (BCH), a dedicated SIB. 
     &lt;Method of Sharing an Implicit TRP Classification Method with a UE&gt; 
     A base station may deliver a method by which a UE can distinguish between TRPs to the UE. 
     
       
         
           
               
            
               
                   
               
               
                 1. Table in which a Beam ID and  
               
               
                 a TRP ID are mapped 
               
            
           
           
               
               
               
            
               
                   
                 Beam ID 
                 TRP ID 
               
               
                   
                   
               
               
                   
                 0 
                 1 
               
               
                   
                 1 
                 2 
               
               
                   
                 . . . 
                 . . . 
               
               
                   
                 N 
                 K 
               
               
                   
                   
               
            
           
         
       
     
     2. Method of Calculating a TRP ID as a Beam ID 
     A. MSB K bits of Beam ID=TRP ID 
     B. (Beam ID)mod(K)=TRP ID 
     C. Floor(Beam ID/K)=TRP ID 
     D. ceiling(Beam ID/K)=TRP ID 
     E. Indication that the order of Beam RS transmission=TRP ID 
     3. Method of Classification Based on an RS Resource ID 
     A. Provide a UE with an associative relation between a sync signal resource ID, a CSI-RS resource ID and a TRP in a table/rule form 
     B. Provide a UE with an associative relation between a sync signal beam ID, a CSI-RS beam ID and a TRP in a table/rule form 
     4. Method of Classification Based on an RS Resource Set 
     A. A UE considers configured/scheduled RS resource sets as a different measurement subject and measure/change it. 
     B. A network may manage TRPs by differently allocating RS resource sets for each TRP. 
     C. A CSI-RS resource set, an NR-SS synch burst/burst set may be used. 
     The information may be provided to a UE in the following form. 
     1. Method of Inclusion and Transmission in Broadcast Information 
     May be transmitted using an MIB (BCH), an SIB 1 or 2 (BCH), and/or a Dedicated SIB. 
     2. Inclusion and Transmission in Dedicated (Unicast) Information 
     New MAC-CE use transmission, may be included in an RRC message (RRC Connection reconfiguration, RRC Connection Setup) as a new IE and transmitted, and may be transmitted as a PHY message and/or may be transmitted as a MAC message. 
     If the implicit TRP classification method is used, a base station includes a rule using the implicit classification method, instead of including a TRP ID, when it transmits resource configuration information of different TRPs or configures a resource based on an already set rule. This may be applied to step  713  of  FIG. 7A . 
     Furthermore, a UE may use a rule using the implicit classification method, included in a corresponding message when it distinguishes between different TRPs within received resource configuration information, or may distinguish between resources allocated by different TRPs based on an already set rule. This may be applied to step  716  of  FIG. 7A . 
     &lt;Method for a Base Station to Transmit a TRP-Measured Reference Signal (RS)&gt; 
     [Mobility Using an RS Transmitted by Base Station Allocation at a UE Unique Period/Time] 
     1. A TRP (or TRP-higher eNB) determines that each TRP transmits RSs for different Tx beams at the same time/frequency resource, and may notify a UE of corresponding scheduling information. 
     A. A known method uses a new IE within a PDCCH unicast, PDCCH sweeping broadcast/multicast, RRC connection reconfigure, 
     B. An RS may be determined as follows based on received feedback/report information with respect to one or multiple UEs 
     b-1. In the case of one UE target, allocation is performed in order of the best beam of beams reported to have reception performance (RSRP, RSRQ, CQI, SNR, SINR, RSSI) of a given threshold or more, which may be received by the corresponding UE 
     b.2. Transmit information to a higher eNB through front haul with respect to an adjacent TRP transmission beam or directly transmit the information to a corresponding TRP through an interface (X2, S1, . . . ) 
     b.3. Or determine to select given beams 
     b.4 Or Allocate adjacent beams (from the nearest beams) of the best beam for each TRP. 
     C. When a UE performs reception using each known TRP measurement value, the UE selects a better UE beam and measures a scheduling resource using the corresponding beam. 
     2. A TRP (or TRP-Higher eNB) May Determine that Each TRP Transmits an RS for a Different TRP at a Different Time (or Frequency) Resource and Notify a UE of Corresponding Scheduling Information. 
     &lt;Method for a UE to Measure a TRP&gt; 
       FIG. 3  is a diagram showing a method of measuring a multi-TRP beam in a multi-beam, multi-TRP environment according to an embodiment of the disclosure. 
     Referring to  FIG. 3 , a system may include a UE  300 , a TRP  1   301 , a TRP  2   302  and a base station  305 . The UE  300  is a UE belonging to the base station  305 , and exchanges information with the base station using the TRP 1   301 . In the embodiment of  FIG. 3 , different beams of different TRPs can be observed precisely and fast through two steps, such as a common beam measurement procedure and a UE dedicated beam measurement procedure. 
     A common beam measurement procedure  320  is to receive a common reference signal transmitted by TRPs, to search for a coarse (available) TRP beam and a UE beam pair, and to feed the measurement results of the common reference signal back. For example, the common reference signal may use a synchronization signal. The UE may perform the common beam measurement procedure using the synchronization signal. 
     A task of searching for the best beam using only the common reference signal requires a very long time in a system in which the number of beams is many (measurement corresponding to a maximum “number of transmission and reception points x the number of beams within a transmission and reception point x the number of UE beams” is necessary). Accordingly, a coarse beam direction is selected using the common reference signal, and UE-specific unique beam measurement is performed on fine beams adjacent to a selected beam using the coarse beam direction. 
     In this case, for the selection of a TRP to be transmitted by the base station and beam selection for each TRP, the UE need to feed back that it is better for different TRPs to transmit which beams and the best beam (or Best N beams) for each TRP (or best K TRP). 
     At operation  311 , the TRP  1   301  transmits information for common beam measurement to the UE. The information may be at least one of broadcast information, multicast information, or unicast system information. The information for the common beam measurement may include at least one of random access channel (RACH) subframe information, reception beam information in an RACN subframe, a system frame number (SFN), a physical hybrid-ARQ indicator channel (PHICH), a bandwidth, an antenna port, system information scheduling information, information on a cell ID, a TRP ID, or a beam ID. 
     At operation  312 , the TRP  2   302  may transmit information for common beam measurement to the UE  300 . For information included in the information for common beam measurement, reference is made to the contents described at operation  311 . 
     At operation  313 , the UE measures a common beam reference signal for the TRP  1   301 . At operation  314 , the UE measures a common beam reference signal for the TRP  2   302 . The UE  300  may measure the common reference signals while sweeping reception beams. 
     At operation  315 , the UE  300  may update the common beam measurement results. The UE  300  may update the common beam measurement results for each TRP. The UE  300  performs RS measurement on different TRPs, and updates measurement information for filtering purposes, for example, if necessary. 
     At operation  317 , the TRP  1   301  may indicate that the common beam measurement results should be reported. To report the best beam or N beams having good performance for each TRP may be indicated. Common beam measurement result report information may indicate that information on a TRP ID, a beam ID, beam quality should be reported. 
     At operation  318 , the UE  300  may report the common beam measurement results. The UE  300  may report the common beam measurement results to the TRP  1   301 . The common beam measurement results may be delivered to the CU of the base station  305 . 
     In UE dedicated beam measurement  340 , the base station  305  selects a transmission beam for each TRP, which will be transmitted to the UE  300 , using the feedback information. In this case, in general, UE beams capable of receiving beams transmitted by different TRPs may be different for each TRP (because TRP locations are different). Accordingly, if the UE  300  can receive a reference signal using only one beam at once, the UE may measure only a TRP present in one direction and only a beam belonging to the corresponding TRP at a given time. 
     Accordingly, the base station  305  needs to transmit corresponding TRP information (e.g., ID, TRP sequence) regarding when each TRP transmits information, while transmitting UE dedicated beam measurement transmission signal scheduling information so that the UE can receive reference signals transmitted by different TRPs using a given beam at a given time. In the UE dedicated beam measurement procedure, a UE dedicated beam may be used. The UE dedicated beam may use a CSI-RS, for example. 
     At operation  341  and operation  342 , the base station  305  selects transmission beams for each TRP using information, such as feedback information (e.g., common beam measurement results) of the UE. Furthermore, the base station  305  may schedule the reference signal of each TRP for UE dedicated beam measurement. The reference signal scheduling information for each TRP may be delivered to each TRP. The base station  305  may provide the TRP  1   301  with reference signal information for the TRP  2   302  in addition to reference signal information for the TRP  1   301 . In this case, the reference signal may be the UE dedicated reference signal of each TRP. 
     At operation  343 , the TRP  1   301  may provide the UE  300  with information on a TRP dedicated reference signal. The information on a TRP dedicated reference signal may include beam information, resource information related to a TRP ID. In addition to dedicated reference signal information of the TRP 1   301 , dedicated reference signal information of the TRP 2   302  may be provided to the UE  300 . 
     At operation  344 , the TRP  1   301  transmits a dedicated reference signal. At operation  345 , the TRP  2   302  transmits the dedicated reference signal. The UE  300  measures the dedicated reference signal transmitted by each TRP while sweeping reception beams. 
     At operation  346 , the UE  300  updates the measurement results of the dedicated reference signal for each TRP. 
     At operation  347 , the TRP 1   301  transmits, to the UE  300 , information indicating that the measurement results of the dedicated reference signal should be reported. 
     At operation  348 , the UE  300  reports the measurement results of the dedicated reference signal for each TRP. 
       FIG. 4  is a diagram showing a terminal initial access procedure in a multi-beam, multi-TRP environment according to an embodiment of the disclosure.  FIG. 4  is a diagram showing an initial access procedure when TRPs can be distinguished. 
     Referring to  FIG. 4 , a system may include a UE  400 , a TRP  1   401 , a TRP  2   402  and a base station  405 . The UE  400  is a UE belonging to the base station  405 , and exchanges information with the base station using the TRP 1   401 . 
     At operation  411  and operation  413 , the TRPs  401  and  401  may transmit information for initial access. The information may be at least one of broadcast, multicast, or unicast system information. The information may include at least one of random access channel (RACH) subframe information, reception beam information in an RACN subframe, a system frame number (SFN), a physical hybrid-ARQ indicator channel (PHICH), a bandwidth, an antenna port, system information scheduling information, information on a cell ID, a TRP ID, or a beam ID. 
     At operation  413 , the UE  400  measures a beam reference signal for the TRP  1   401 . At operation  414 , the UE  400  measures a beam reference signal for the TRP  2   402 . The reference signal may be a common reference signal. The UE  400  may measure a reference signal or common reference signal while sweeping reception beams. 
     At operation  415 , the UE  400  may update beam measurement results. The UE  400  may update the measurement results of the common reference signal. The UE  400  may update common beam measurement results for each TRP. The UE  400  performs RS measurement on different TRPs, and updates measurement information for filtering purposes, for example, if necessary. 
     At operation  417 , the UE may select a proper TRP for initial access based on the beam measurement result. For example, the UE may select a TRP having the best beam measurement results. In the embodiment, it is assumed that the TRP  1   401  has been selected. In the embodiment of  FIG. 4 , it is assumed that in the initial access results, the UE  400  may distinguish between TRPs based on beam measurement or common beam measurement. Accordingly, the UE  400  may distinguish between TRPs and select a proper TRP. 
     At operation  418 , the UE  400  transmits a radio resource control (RRC) connection request message to the TRP  1   401 . The UE  400  may transmit the RRC connection request message through a beam selected with respect to the selected TRP. 
     At operation  419 , the TRP  1   401  may deliver an RRC connection request message to the base station  405 . At operation  420 , the base station  405  may transmit an RRC connection setup message to the TRP  1   401 . The UE  400  may transmit the RRC connection request message using an RACH resource for the selected TRP or the selected beam. At operation  421 , the TRP  1   401  may transmit the RRC connection setup message to the UE  400 . The TRP 1   401  may transmit the RRC connection setup message to the UE  400  using a dedicated resource. 
       FIG. 5  is a diagram showing a terminal initial access procedure in a multi-beam, multi-TRP environment according to another embodiment of the disclosure.  FIG. 5  is a diagram showing an initial access procedure if TRPs cannot be distinguished. 
     Referring to  FIG. 5 , a system may include a UE  500 , a TRP  1   501 , a TRP  2   502  and a base station  505 . The UE  500  is a UE belonging to the base station  505 , and exchanges information with the base station using the TRP 1   501 . 
     At operation  511  and operation  513 , the TRPs  501  and  501  may transmit information for initial access. The information may include at least one of broadcast, multicast, or unicast system information. The information may include at least one of random access channel (RACH) subframe information, reception beam information in an RACN subframe, a system frame number (SFN), a physical hybrid-ARQ indicator channel (PHICH), a bandwidth, an antenna port, system information scheduling information, information on a cell ID, a TRP ID, or a beam ID. 
     At operation  513 , the UE  500  measures a beam reference signal for the TRP  1   501 . At operation  514 , the UE  500  measures a beam reference signal for the TRP  2   502 . The reference signal may be a common reference signal. The UE  500  may measure a reference signal or common reference signal while sweeping reception beams. 
     At operation  517 , the UE may select a proper beam for initial access based on the beam measurement results. For example, the UE may select a beam having the best beam measurement results. In the embodiment of  FIG. 5 , it is assumed that in initial access results, the UE  500  cannot distinguish between TRPs based on beam measurement or common beam measurement. 
     At operation  518 , the UE  400  transmits a radio resource control (RRC) connection request message to the TRP  1   501 . The UE  500  may transmit the RRC connection request message using an RACH resource for the selected beam. The UE  500  may transmit the RRC connection request message through the selected beam. The UE  500  may transmit information on the selected beam along with the RRC connection request message. 
     At operation  519 , the TRP  1   501  may deliver the RRC connection request message to the base station  505 . At operation  520 , the base station  505  may transmit an RRC connection setup message to the TRP  1   401 . At operation  521 , the TRP  1   501  may transmit the RRC connection setup message to the UE  500 . The TRP 1   501  may transmit the RRC connection setup message to the UE  500  using a dedicated resource. 
     &lt;Method for a Base Station and UE to Change a TRP&gt; 
     1. TRP change method using L1 beam feedback 
     A. Transparent method 
     i. UE beam quality measurement 
     ii. UE beam ID, beam quality report 
     iii. Distinguish between beams associated with base station-reported TRP 
     iv. A base station transmits beam change command to a UE 
     v. The UE changes a beam (at a designated time/frame after a lapse of an agreed time/frame) 
     vi. The base station changes a beam+a TRP (at a designated time/frame after a lapse of an agreed time/frame) 
     B. Method using an explicit TRP ID 
     i. Measure beam quality for each UE TRP 
     ii. A UE reports a TRP ID, a beam ID, beam quality 
     iii. A base station determines a beam/TRP change based on the reported beam and TRP 
     iv. The base station transmits a TRP change command to the UE 
     1. TRP ID only 
     2. TRP ID+beam ID 
     v. The UE changes a TRP 
     1. Change a TRP and use the best beam that has been implicitly previously reported 
     2. Use a TRP and beam ID as commanded 
     vi. The base station changes a beam+TRP 
     2. A beam/TRP change using MAC beam feedback 
     A. Change based on RACH msg 3 reception beam feedback 
     i. The base station transmits a TRP change command (msg 4 or a different PDCCH or mac msg) to the UE 
     1. TRP ID only 
     2. TRP ID+beam ID 
     ii. The UE changes a TRP 
     1. Change a TRP and use the best beam that has been implicitly previously reported 
     2. Use a TRP and beam ID as commanded 
     3. At a designated time/frame after a lapse of an agreed time/frame 
     iii. The base station changes a beam/TRP (at a designated time/frame after a lapse of an agreed time/frame) 
     B. Change based on MAC CE reception 
     i. The base station transmits a TRP change command (msg 4 or a different PDCCH or mac msg) to the UE 
     1. TRP ID only 
     2. TRP ID+beam ID 
     ii. The UE changes a TRP 
     1. Change a TRP and use the best beam that has been implicitly previously reported 
     2. Use a TRP and beam ID as commanded 
     3. At a designated time/frame after a lapse of an agreed time/frame 
     iii. The base station changes a beam/TRP (at a designated time/frame after a lapse of an agreed time/frame) 
     3. Method of changing a TRP feedback/change method based on an RRC configuration according to a base station/network configuration 
     A. If base station/network configurations are different, a TRP feedback/change method is fixed by transmitting an RRC message providing notification that the base station/network configurations are different 
     B. Define an RRC IE capable of transmitting the following 0˜3 Config 2 bits 
     C. Or define an RRC IE that transmits L1/MAC signaling and change=0, RRC signaling and chang=1 
     i. If it is 1, feed back and change only a beam 
     ii. If it is 1, perform measurement for each TRP, MR report, and change after receiving a base station RRC message 
     4. A TRP change using RRC control msg 
     A. The UE transmits measurement report based on a measurement trigger event for each TRP 
     B. MR triggering events 
     i. T1: measured quality of a TRP is higher than a threshold 
     ii. T2: measured quality of a TRP is lower than a threshold 
     iii. T3: measured quality of a neighbor TRP is offset higher than the measured quality of the serving the TRP 
     iv . . . . 
     C. A new RRC-connection reconfiguration IE for MR 
     i. TRP ID, TRP measurement, measurement ID, 
     An MR reception base station determines whether to change a TRP change and transmits it as an RRC message 
       FIG. 6  is a diagram showing a TRP change method according to an embodiment of the disclosure. 
     Referring to  FIG. 6 , a system may include a UE  600 , a TRP  1   601 , a TRP  2   602  and a base station  605 . 
     Referring to  FIG. 6 , the UE  600  is a UE belonging to the base station  605  and exchanges information with the base station using the TRP 1   601 . The UE  600  may have explicitly recognized that it uses the TRP 1   601  using the ID of the TRP 1   601  or may not explicitly recognize that it uses the TRP 1   601 , and may have recognized that it also performs communication with the base station using any beams belonging to the TRP 1   701 , for example, a CSI-RS resource set, an NR-SS resource set, a TRP antenna Tx/Rx configuration or any beam set. 
     At operation  611  and operation  612 , the base station  605  selects RSs to be transmitted by the TRP 1   601  and the TRP 2   602  the resources of the corresponding RSs so that the UE  600  can perform measurement, and delivers such information to the TRP 1   601  and the TRP 2   602  if the information needs to be provided to the TRPs. In this case, the TRP 1   601  needs to schedule RS information of the TRP 2   602  in addition to the RS of the TRP 1   601  with respect to the UE  600 . Accordingly, the base station  605  may provide the TRP 1   601  with both RS configuration information of the TRP 1   601  and configuration information of the TRP 2   602 . 
     At operation  613 , the TRP 1   601  provides the UE  600  with the configured resource configuration information of the TRP 1   601  and TRP 2   602  so that the UE  600  can measure each of the TRPs. In this case, a direct TRP ID associated with resource configuration information of a different TRP may be provided or any resource segmentation method of enabling the UE to indirectly distinguish between the TRPs, for example, a method of transmitting the RSs of different TRPs at time intervals may be used so that the UE  600  can recognize that the corresponding RSs are transmitted by different TRPs. 
     At operation  614 , the TRP 1   601  transmits an RS to the UE  600 , as allocated, for measurement. At operation  615 , the TRP 2   602  transmits the RS to the UE  600 , as allocated, for measurement. 
     At operation  616 , the UE  600  performs RS measurement on different TRPs, and updates measurement information for filtering purposes, for example, if necessary. 
     At operation  617 , the TRP  1   601  may indicate that beam measurement results should be reported. The TRP  1   601  may indicate that the best beam or N beams having good performance should be reported for each TRP. The beam measurement result report information may indicate that information on a TRP ID, beam ID, beam quality should be reported. 
     At operation  618 , the UE  600  may report beam measurement results. The UE  600  may report the beam measurement results to the TRP  1   601 . 
     At operation  619 , the TRP 1   601  may determine whether a TRP change is required. The TRP 1   601  may determine whether a TRP change is required based on the reported measurement results. The determination method may be the same as a measurement report transmission event. For example, when the measurement results of the reference signal of the TRP 2  are greater than the measurement results of the reference signal of the TRP 1  by a value of a preset offset, the TRP 1   601  may determine that a TRP change is required. 
     At operation  620 , if it is determined that a TRP change is not required, the process proceeds to operation  621 . If it is determined that a TRP change is required, the process proceeds to operation  622 . 
     At operation  621 , the TRP  601  does not need to provide the UE  600  with any information related to a TRP change. However, even in such a case, the UE  600  may need to change a beam being used within the same TRP. In such a case, the TRP 1   601  may enable the UE  600  to perform a beam change. 
     At operation  622 , the TRP 1   601  transmits information for requesting (e.g., TRP change indication information) a TRP change operation to the UE  600 . At operation  622 , the TRP 1   601  transmits information for requesting a TRP change operation to the UE  600 . The TRP change indication information (TRP change indication message) may be a physical layer message (PHY downlink control information), may be a MAC CE message, and may be an IE included in an RRE message, for example, an RRC connection reconfiguration message. For a detailed example that may be included in the corresponding TRP change signal, reference is made to the embodiment of  FIG. 7 . 
     At operation  623 , the TRP 1   601  provides a TRP change request and UE information to the base station  605 . A procedure of notifying the base station  605  of information indicating that a TRP change is necessary is necessary because the TRP 1   601  has determined a TRP change. The information may include at least one of a UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam/CSI-RS/NR-SS ID measured by a UE and a measured value of the TRP  2 , MAC information, RLC information, or TRP 2  timing advance measurement information of the UE, etc. 
     At operation  624 , the base station  605  may provide the TRP 2   602  with a TRP change request and UE information. The TRP 2   602  may prepare the joining of the UE based on the TRP change request and UE information. 
     At operation  625 , the UE  600  prepares to receive information of a target TRP, the TRP  2  included in the corresponding TRP change request message over a fixed time after the TRP change request message is received or until a scheduled resource is received. The UE  600  changes a reception configuration so that the reception beam of the UE  600  is suitable for the reception of the downlink resource of the TRP 2  included in the TRP change request message and a beam/CSI-RS/NR-SS having a beam association (QCL) relation with the corresponding resource. 
     At operation  626 , the TRP 1   601  flushes information on the UE  600 . 
     At operation  627 , the TRP 2   602  prepares to transmit a signal, included in the TRP change request message, to the UE over the fixed time after the TRP change request message is received. 
       FIG. 7  is a diagram showing a TRP change method of a base station through the RS measurement of a terminal according to an embodiment of the disclosure. 
     Referring to  FIG. 7 , a system may include a UE  700 , a TRP  1   701 , a TRP  2   702  and a base station  705 . 
     The UE  700  is a UE  700  belonging to the base station  705  and exchanges information with the base station using the TRP  701 . The UE  700  may have explicitly recognized that it uses the TRP  701  using the ID of the TRP  701  or may not explicitly recognized that it uses the TRP 1   701 , and may have recognized that it performs communication with the base station using any beams belonging to the TRP 1   701 , for example, a CSI-RS resource set, an NR-SS resource set, a TRP antenna Tx/Rx configuration or any beam set. 
     At operation  711  and operation  712 , the base station  705  selects RSs to be transmitted by the TRP 1   701  and the TRP 2   702  and the resources of the corresponding RSs so that the UE  700  can perform measurement, and delivers such information to the TRP 1   701  and the TRP 2   702  if the information needs to be provided to the TRPs. In this case, the TRP 1   701  needs to schedule RS information of the TRP 2   702  in addition to the RS of the TRP 1   701  with respect to the UE  700 . Accordingly, the base station  705  may provide the TRP  701  with both RS configuration information of the TRP 1   701  and RS configuration information of the TRP 2   702 . 
     At operation  713 , the TRP 1   701  provides the configured resource configuration information of the TRP 1   701  and TRP 2   702  to the UE  700  so that the UE  700  can measure each of the TRPs. The resource configuration information may include RS configuration information of the TRP 1   701  and RS configuration information of the TRP 2   702 . In this case, a direct TRP ID associated with resource configuration information of a different TRP may be provided or any resource segmentation method of enabling the UE to indirectly distinguish between the TRPs, for example, a method of transmitting the RSs of different TRPs at time intervals may be used so that the UE  700  can recognize that the corresponding RSs are transmitted by different TRPs. 
     At operation  714 , the TRP 1  transmits an RS to the UE  700 , as allocated, for measurement. At operation  715 , the TRP 2   702  transmits the RS to the UE  700 , as allocated, for measurement. 
     At operation  716 , the UE  700  performs RS measurement on different TRPs, and updates measurement information for filtering purposes, for example, if necessary. 
     At operation  717 , a network may configure RRM measurement by transmitting an RRC connection reconfiguration message for the TRP measurement and report of the UE, and may configure measurement report transmission. At operation  717 , the base station  705  may transmit the RRC connection reconfiguration message to the TRP 1   701 . At operation  718 , the TRP 1   701  may deliver the RRC connection reconfiguration message to the UE  700 . The message of operation  717  and operation  718  may have included the RS scheduling message of operation  713  or the measurement event configuration of operation  717  and operation  717  may have been included in the RS scheduling message of operation  713 . A measurement report transmission event of the UE that may be taken into consideration may be the A1˜A6 events of the LTE standard or may be the C1, C2 events or may be the following events of a form modified from the existing C1, C2 events.
         Event C1′: when a CSI-RS resource set (or TRP or NR-SS resource set or beam set or antenna configuration set) is greater than a set absolute threshold;   Event C2′: when a CSI-RS resource set (or TRP or NR-SS resource set or beam set or antenna configuration set) is better than a reference CSI-RS resource set (or TRP or NR-SS resource set or beam set or antenna configuration set) by a set offset or more   Event C1′ (when a CSI-RS resource set is greater than a set absolute threshold;       

     The UE confirms: 
     1&gt; whether the following specified condition C1-1′ is satisfied by taking into consideration the following specified condition C1-1′ as the entry condition of an event; 
     1&gt; Whether the following specified condition C1-2′ is satisfied by taking into consideration the following specified condition C1-2′ as the escape condition of an event; 
         Mcr+Ocr−Hys &gt;Thresh  Inequality C1-1′ (entry condition)
 
         Mcr+Ocr+Hys &lt;Thresh  Inequality C1-2′ (escape condition)
 
     The variables of the equation are defined as follows: 
     Mcr is a measured value of a CSI-RS resource set in which any offset is not taken into consideration. 
     NOTE: In this case, Mcr may be derived through a measured value of one or one or more CSI-RS resources included in the CSI-RS resource set, and may have included multiple CSI-RS measurement values. The UE may derive one Mcr using the multiple CSI-RS measurement values. 
     An example of methods that may be used to derive Mcr is as follows:
         After filtering, the best N CSI-RS measurement values are averaged in order of measured values   After filtering, measured values included in any condition among the best N CSI-RS measurement values, for example, within a counterpart value offset in an absolute value or more or the best measurement value are averaged in order of the measured values   After filtering, the best N CSI-RS measurement values are added in order of measured values   After filtering, measured values included in any condition among the best N CSI-RS measurement values, for example, within a counterpart value offset in an absolute value or more or the best measurement value are added in order of the measured values.       

     ※ Filtering may be performed in various layers, for example, L1 or L2 or L3. A method, such as weight averaging by applying an arithmetic average, a geometric average or weight set by a network to measured value ordering, may be used as a method for averaging. 
     Ocr is a CSI-RS resource set unique offset. Hys is a hysteresis parameter for a corresponding event, and Thresh is a threshold for the corresponding event. 
     Mcr, Thresh is represented in dBm. 
     Ocr, Hys is represented in dB. 
     Event C2′ (when a CSI-RS resource set is better than a reference CSI-RS resource set by an offset or more) 
     The UE confirms: 
     1&gt; whether the following specified condition C2-1′ is satisfied by taking into consideration the following specified condition C2-1′ as the entry condition of an event; 
     1&gt; whether the following specified condition C2-2′ is satisfied by taking into consideration the following specified condition C2-2′ as the escape condition of an event; 
         Mcr+Ocr−Hys&gt;Mref+Oref+Ofj   Inequality C2-1′ (entry condition)
 
         Mcr+Ocr+Hys&lt;Mref+Oref+Ofj   Inequality C2-2′ (escape condition)
 
     The variables in the formula are defined as follows: 
     Mcr is a measured value of a CSI-RS resource set in which any offset is not taken into consideration. 
     NOTE: In this case, Mcr may be derived through a measured value of one or one or more CSI-RS resources included in a CSI-RS resource set, and may have included multiple CSI-RS measurement values. The UE may derive one Mcr using the multiple CSI-RS measurement values. 
     An example of methods that may be used to derive Mcr is described in the event C1′. 
     Ocr is a CSI-RS resource set unique offset 
     Mref is a measured value of a reference CSI-RS resource set. 
     Oref is a unique offset value of a reference CSI-RS resource set. 
     Hys is a hysteresis parameter for a corresponding event, and Thresh is a threshold for the corresponding event. 
     Off is the parameter of the corresponding event 
     Mcr, Mref is represented in dBm. 
     Ocr, Oref, Hys, Off are represented in dB. 
     In an embodiment of the disclosure, an event that was a reference has been written in the form of a CSI-RS resource set change event because is a CSI-RS-based event. A method for a UE to calculate the measurement results (Mcr) of one CSI-RS resource set has various possibilities, and methods that may be taken into consideration are as follows:
         The mean or sum of measured values satisfying a given condition (e.g., having a relative/absolute threshold or more) among N best CSI-RS measurement values (L1/or L2/or L3 filtered)       

     The mean may be weighted averaging. A base station may transmit such weight, N, filtering coefficient, etc. to a UE while transmitting a measurement configuration. 
     Operation  719  and operation  720  are a procedure for the UE  700  to report measurement to the base station  705  based on the preset condition. At operation  719 , when the preset event condition is satisfied, the UE  700  reports the measurement results to the measurement TRP  1   701 . At operation  720 , the TRP  1   701  reports the measurement results, received from the UE  700 , to the base station  705 . The corresponding measurement report may be transmitted from the UE  700  to the base station  705  when any condition (event) set by the base station  705  is satisfied or when set periodicity is satisfied. 
     At operation  720 , the base station  705  determines whether the UE  700  needs to change a TRP based on the reported measurement information. The determination method may be the same as the measurement report transmission event of the UE  700  or may be a base station implementation. 
     If a TRP change is not required at operation  722 , the process proceeds to operation  724 . At operation  724 , the base station  705  does not need to provide the UE  700  with any information related to a TRP change. However, even in such a case, the UE  700  may need to change a beam being used within the same TRP. In such a case, the base station  705  may enable the UE  700  to perform a beam change. 
     If a TRP change is required at operation  722 , the process proceeds to operation  723 . At operation  723  and operation  725 , the base station  705  transmits information for requesting a TRP change operation to the UE  705 . At operation  723 , the base station  705  transmits the information for requesting (e.g., TRP change indication information) a TRP change operation to the TRP 1   701 . At operation  725 , the TRP 1   701  delivers the information for requesting a TRP change operation to the UE  700 . 
     TRP change indication information (TRP change indication message) may be a physical layer message (PHY downlink control information), may be a MAC CE message, may be an IE included in an RRE message, for example, an RRC connection reconfiguration message. A corresponding TRP change signal may include some or all of the following information.
         TRP ID   CSI-RS resource set ID   NR-SS resource set ID   Beam set ID   Beam ID(s)   CSI-RS ID(s)   NR-SS ID(s)   Downlink resource scheduling including the CSI-RS, NR-SS of a TRP being used or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association, providing notification that a base station will transmit information using which beam as a corresponding resource   a CSI RS ID having a QCL relation with a corresponding resource   an NR-SS ID having a QCL relation with a corresponding resource   
           Downlink resource scheduling including the CSI-RS, NR-SS of a target TRP to be changed in the future or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association, providing notification that a base station will transmit information using which beam as a corresponding resource   a CSI RS ID having a QCL relation with a corresponding resource   an NR-SS ID having a QCL relation with a corresponding resource   
           Uplink resource scheduling including the CSI-RS, NR-SS of a target TRP to be changed in the future or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association providing notification that a base station will receive information using what beam as a corresponding resource   a CSI RS ID having a QCL relation with a corresponding resource   an NR-SS ID having a QCL relation with a corresponding resource   
               

     At operation  726 , the TRP 1   701  transmits UE information to the central unit of the base station  705 . If all contents have been previously included in the measurement report at operation  720 , operation  726  is an operation that may be omitted. The UE information that may be transmitted at operation  726  or operation  720  may be some or all of the followings. 
     A UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam of the TRP  2  measured by the UE/CSI-RS/NR-SS ID and a measured value, MAC information, RLC information, TRP 2  timing advance measurement information of the UE, etc. 
     Operation  727  is an operation for the base station  705  to prepare the TRP 2   702  for the joining of the UE  700 , and is an operation that may be omitted if the TRP 2   702  includes only a simple RF stage or antenna. UE information that may be transmitted at operation  727  may be some or all of the followings.
         A UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam of the TRP  2  measured by the UE/CSI-RS/NR-SS ID and a measured value, MAC information, RLC information, TRP 2  timing advance measurement information of the UE, etc.       

     At operation  731 , the UE  700  prepares to receive information of a target TRP, the TRP  2 , included in the corresponding TRP change indication information, over a fixed time after the TRP change indication information is received at operation  725  or until a scheduled resource is received. The UE  700  changes a reception configuration so that the reception beam of the UE  700  is suitable for the reception of the downlink resource of the TRP 2  included in the TRP change indication information and a beam/CSI-RS/NR-SS having a beam association (QCL) relation with the corresponding resource. 
     At operation  732 , the TRP 2   702  prepares to transmit a signal to a UE, included in the TRP change indication information, over a fixed time after the TRP change indication information is received. 
     At operation  733 , the TRP 1   701  flushes information on the UE  700 . 
     At operation  734 , the TRP 2  prepares downlink transmission as already allocated to the UE. A method for the base station to determine downlink information to be transmitted and transmitted information, and the operation of the UE may include some or all of the following operations and transmission information. 
     Information 1) an RACH Execution Indicator or an RACH Resource Allocation Method 
     If a given UE needs to change a given TRP (or CSI-RS resource set, or NR-SS resource set, or beam set), the TRP 2  (or base station) may transmit both or one or more of an indicator indicative of RACH execution in order to obtain new TRP uplink synchronization or a dedicated RACH configuration through a downlink signal that transmits a corresponding change to the UE. 
     The corresponding RACH configuration may have included some or all of types of information of a target TRP (or CSI-RS resource set, or NR-SS resource set, or beam set) to be changed, for example, a TRP ID, a TRP transmission CSI-RS ID, an NR-SS ID. 
     The base station measures the signal (UL SRS, UL CSI-RS, UL SR, . . . ), transmitted by the UE, through a different beam/TRP/beam belonging to a TRP. If one or more of the following conditions are satisfied, the base station may determine that RACH execution is necessary for a TRP change for the corresponding UE. The base station may include an indicator in a downlink signal in order to denote the execution of an RACH, may transmit the indicator and an RACH configuration or may simply transmit the RACH configuration or may transmit only a difference between an RACH configuration being used and an RACH configuration to be changed. 
     i. When a probability that the uplink synchronization of the UE will be broken is a given threshold or more if the UE changes a current uplink transmission beam pair (UE beam—base station beam) to a new transmission beam pair 
     ii. If the UE changes an uplink transmission beam pair (UE beam—base station beam) being used to a new transmission beam pair, when the uplink synchronization timing advance (timing advance difference) value between the two different beam pairs is a given threshold or more 
     The UE that has received RACH-related information transmitted by the base station may immediately perform information transmission to a new TRP using the corresponding RACH information or after a given time set by the base station elapses. 
     Information 2) TA modification request information and modification value 
     If a given UE needs to change a given TRP (or CSI-RS resource set, or NR-SS resource set, or beam set), a base station may check a difference between a timing advance value, measured using a target TRP (or CSI-RS resource set, or NR-SS resource set, or beam set) that may change a given signal (e.g., SRS signal, UL RS signal) transmitted by the corresponding UE, and a TRP (or CSI-RS resource set, or NR-SS resource set, or beam set) value being used in a conventional technology in order to obtain uplink synchronization, and may transmit the corresponding timing advance difference or the timing advance value of the TRP through a downlink signal in which a corresponding change is transmitted to the UE. The base station may include an indicator in the downlink signal in order to indicate that a TA should be modified, may transmit the indicator and a TA value or may simply transmit the TA value or may transmit a difference between a TA value being used and a TA value to be changed. 
     Target TRP (or CSI-RS resource set, or NR-SS resource set, or beam set) information to be changed, for example, some or all of the following information may have been included in the corresponding timing advance configuration value.
         TRP ID   beam RS set ID   CSI-RS resource set ID   NR-SS resource set ID   beam ID(s))   CSI-RS ID(s)   NR-SS ID(s)   Downlink resource scheduling including the CSI-RS, NR-SS of a beam RS set being used or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association, providing notification that a base station will transmit information using what beam as a corresponding resource   CSI RS ID having a QCL relation with a corresponding resource   NR-SS ID having a QCL relation with a corresponding resource   
           Downlink resource scheduling including the CSI-RS, NR-SS of a target beam RS set to be changed in the future or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association, providing notification that a base station will transmit information using what beam as a corresponding resource   CSI RS ID having a QCL relation with a corresponding resource   NR-SS ID having a QCL relation with a corresponding resource   
           Uplink resource scheduling including the CSI-RS, NR-SS of a target beam RS set to be changed in the future or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association, providing notification that a base station will receive information using what beam as a corresponding resource   CSI RS ID having a QCL relation with a corresponding resource   NR-SS ID having a QCL relation with a corresponding resource   
               

     In addition to the method for the TRP to directly provide the UE with (dedicated signal) information, a base station may provide that transmission and reception between TRPs needs to be changed as a network common signal. 
     In an embodiment, a base station includes information in a reference signal (RS), transmitted by a different TRP, in the form of an indicator (or group ID). A UE may read the RS and perform a TA change or RACH only when transmission and reception between corresponding TRPs (or TRPs belonging to a different group) is changed. 
     In another embodiment, a base station may transmit an indicator, indicating that a TA change or RACH execution is necessary, through a broadcasting signal (or multicasting signal) only when UE transmission and reception between different TRPs is changed. 
     At operation  735 , the UE  700  starts communication with the TRP 2   702  based on the TRP change indication information and the message received from the TRP 2   702 . In this case, transmittable information may have various form, and may include a response message or acknowledge message for the downlink transmission of the TRP  2  or RACH preamble signal transmission. 
     The TRP 1   701  and the TRP 2   702  may be substituted with CSI-RS resource set1 and set2, NR-SS resource set1 and 2, or beam set1 and set2, or base station antenna configuration set1 and set2 and applied and used. 
       FIG. 8  is a diagram showing a method for a base station to change a beam RS set (CSI/RS resource set/NR-SS resource set/beam resource set/antenna configuration set) through the RS measurement of a terminal in an embodiment of the disclosure. 
     Referring to  FIG. 8 , a system may include a UE  800  and a base station  805 . First, the UE  800  is a UE belonging to the base station  805 , and exchanges information with the base station  805  using a beam RS sett. The UE  800  may have explicitly recognized that it uses the beam RS set1 using the ID of the beam RS set1 or may not explicitly recognize that it uses the beam RS set1 or may have recognized that it performs communication with the base station using any beams belonging to the beam RS sett, for example, a CSI-RS resource set, an NR-SS resource set, a TRP antenna Tx/Rx configuration or any beam set. The beam RS set1 may correspond to a TRP  1 . 
     At operation  811 , the base station  805  selects RSs to be transmitted by the beam RS set1 and a beam RS set2 and the resources of the corresponding RSs so that the corresponding UE  800  can perform measurement, and schedules a resource in which the corresponding RSs will be transmitted in advance with respect to the UE. 
     At operation  812  and operation  813 , the base station  805  transmits the RSs to the corresponding UE  802 , as allocated, for measurement. At operation  812 , the base station may transmit the RS corresponding to the beam RS set 1. At operation  813 , the base station may transmit the RS corresponding to the beam RS set 2. The beam RS set 2 may correspond to a TRP  2 . 
     At operation  814 , the UE  800  performs RS measurement on the different beam RS sets, and updates measurement information for filtering purposes, for example, if necessary. 
     At operation  815 , a network may configure RRM measurement by transmitting an RRC connection reconfiguration message for the beam RS set measurement and report of the UE, and may configure measurement report transmission. The message of operation  815  may include the RS scheduling message of operation  811 . The measurement event configuration of operation  815  may be included in the RS scheduling message of operation  811 . A measurement report transmission event of the UE that may be taken into consideration may be the A1˜A6 events of the LTE standard or may be the C1, C2 events or may be the C1′ and C2′ events modified from the existing C1 and C2 events and described in  FIG. 7 . 
     Operation  816  is a procedure for the UE  800  to report measurement to the base station based on a condition configured at operation  815 . The corresponding measurement report may be transmitted from the UE to the base station when any condition (event) configured by the base station is satisfied or set periodicity is satisfied. 
     At operation  817 , the base station determines whether the UE needs to change a beam RS set based on the reported measurement information. The determination method may be the same as the measurement report transmission event of the UE or may be a base station implementation. 
     If a beam RS set change is not required at operation  818 , the base station  805  does not need to provide the UE  800  with any information related to the beam RS set change. However, even in such a case, the UE  800  may need to change a beam being used within the same beam RS set. In such a case, the base station  805  may enable the UE  800  to perform a beam change. 
     If it is determined that a beam RS set change is required at operation  818 , the process proceeds to operation  819 . At operation  819 , the base station  805  transmits information for requesting a beam RS set change operation to the UE  800  as the beam RS set change is changed. The beam RS set change signal (beam RS set change indication message) may be a physical layer message (PHY downlink control information), may be a MAC CE message, may be an IE included in an RRE message, for example, an RRC connection reconfiguration message. The corresponding beam RS set change signal may include some or all of the following information.
         beam RS set ID   CSI-RS resource set ID   NR-SS resource set ID   beam ID(s)   CSI-RS ID(s)   NR-SS ID(s)   Downlink resource scheduling including the CSI-RS, NR-SS of a beam RS set being used or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association, providing notification that a base station will transmit information using what beam as a corresponding resource   CSI RS ID having a QCL relation with a corresponding resource   NR-SS ID having a QCL relation with a corresponding resource   
           Downlink resource scheduling including the CSI-RS, NR-SS of a target beam RS set to be changed in the future or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association, providing notification that a base station will transmit information using what beam as a corresponding resource   CSI RS ID having a QCL relation with a corresponding resource   NR-SS ID having a QCL relation with a corresponding resource   
           Uplink resource scheduling including the CSI-RS, NR-SS of a target beam RS set to be changed in the future or some or all of the following information having an association relation with any beam or any antenna configuration
           Quasi-co location (QCL) ID representing a beam association, providing notification that a base station will receive information using what beam as a corresponding resource   CSI RS ID having a QCL relation with a corresponding resource   NR-SS ID having a QCL relation with a corresponding resource   
               

     At operation  820 , the UE  800  changes a reception configuration so that the reception beam of the UE is suitable for the reception of the downlink resource of the beam RS set2 included in the beam RS set change indication information and a beam/CSI-RS/NR-SS having a beam association (QCL) relation with the corresponding resource in order to prepare to receive information of the target beam RS set2 included in the corresponding beam RS set change indication information over a fixed time after the beam RS set change indication information is received at operation  819  or a scheduled resource. 
     At operation  821 , the beam RS set2 prepares downlink transmission as already allocated to the UE  800 . Transmittable downlink information may have included some or all of the following information.
         A beam RS set2 connection grant, timing Advance change information, RACH request information, etc.       

     At operation  822 , the UE  800  starts communication using some or all of the beams of the beam RS set2 based on the beam RS set change indication information and the message received from the beam RS set2. In this case, transmittable information may have various form, and may include a response message or acknowledge message or RACH preamble signal transmission for the downlink transmission of the beam RS set2. 
     The beam RS set1 and the beam RS set2 may be substituted with CSI-RS resource set1 and set2, NR-SS resource set1 and 2, beam set1 and set2, a TRP 1  and a TRP 2 , or base station antenna configuration set1 and set2 and applied and used. 
       FIG. 9  is a diagram showing a TRP change method when a base station controls the mobility of a terminal in an embodiment of the disclosure. 
     Referring to  FIG. 9 , a system may include a UE  900 , a TRP  1   901 , a TRP  2   902  and a base station  905 . 
     The UE  900  is a UE belonging to the base station  905  and exchanges information with the base station using the TRP 1   901 . The UE  900  may have explicitly recognized that it uses the TRP  901  using the ID of the TRP  901  or may not explicitly recognize that it uses the TRP 1   901  and may recognize that it performs communication with the base station using any beams belonging to the TRP 1   901 , for example, a CSI-RS resource set, an NR-SS resource set, a TRP antenna Tx/Rx configuration or a given beam set. 
     At operation  911  and operation  912 , the base station  905  selects RSs to be transmitted by the TRP 1   901  and the TRP 2   902  and the resources of the corresponding RSs so that the UE  900  can perform measurement, and delivers such information to the TRP 1   901  and the TRP 2   902  if the information needs to be provided to the TRPs. In this case, the TRP 1   901  needs to schedule RS information of the TRP 2   902  with respect to the UE  900  in addition to the RS of the TRP 1   901 . Accordingly, the base station  905  may provide the TRP 1   901  with both RS configuration information of the TRP 1   901  and configuration information of the TRP 2   902 . 
     At operation  913 , the TRP 1   901  provides the UE  900  with the configured resource configuration information of the TRP 1   901  and the TRP 2   902  so that the UE  900  can measure each of the TRPs. In this case, a direct TRP ID associated with resource configuration information of a different TRP may be provided or any resource segmentation method of enabling the UE to indirectly distinguish between the TRPs, for example, a method of transmitting the RS s of different TRPs at time intervals may be used so that the UE  900  can recognize that the corresponding RSs are transmitted by different TRPs. 
     At operation  914 , the TRP 1   901  transmits the RS to the UE  900 , as allocated, for measurement. At operation  915 , the TRP 2   902  transmits the RS to the UE  900 , as allocated, for measurement. 
     At operation  916 , the UE  900  performs RS measurement on different TRPs, and updates measurement information for filtering purposes, for example, if necessary. 
     At operation  917 , the TRP  1   901  may indicate that beam measurement results should be reported. The TRP  1   901  may indicate that the best beam or N beams having good performance should be reported for each TRP. The beam measurement result report information may indicate that information on a TRP ID, a beam ID, beam quality should be reported. 
     At operation  918 , the UE  900  may report beam measurement results. The UE  900  may report the beam measurement results to the TRP  1   901 . The beam measurement results may include the best beam for each TRP or N beams having good performance for each TRP, and may also include ID information of the UE. 
     At operation  919 , the TRP 1   901  transmits the feedback information, received from the UE  900 , to the base station  905 . The TRP 1   901  may transmit the ID information of the UE and information on the best beam for each TRP or the N beams having good performance for each TRP to the base station  905 . 
     At operation  920 , the base station  905  may determine whether a TRP change is required. The base station  905  may determine whether a TRP change is required based on information received from the TRP 1   901 . The determination method may be the same as a measurement report transmission event. For example, when the measurement results of the reference signal of the TRP 2  is greater than the measurement results of the reference signal of the TRP 1  by a value of a preset offset, the base station may determine that a TRP change is required. 
     If it is determined that a TRP change is not required at operation  921 , the process proceeds to operation  922 . If it is determined that a TRP change is required, the process proceeds to operation  923 . 
     At operation  922 , the base station  905  does not need to provide the UE  900  with any information related to a TRP change. However, even in such a case, the UE  900  may need to change a beam being used within the same TRP. In such a case, the TRP 1   901  may enable the UE  900  to perform a beam change. 
     At operation  923 , the base station  905  transmits information for requesting (e.g., TRP change indication information) a TRP change operation to the TRP 1   901 . At operation  924 , the TRP 1   901  transmits the information for requesting a TRP change operation to the UE  900 . TRP change indication information (TRP change indication message) may be a physical layer message (PHY downlink control information), may be a MAC CE message, may be an IE included in an RRE message, for example, an RRC connection reconfiguration message. For a detailed example that may be included in the corresponding TRP change signal, reference is made to the embodiment of  FIG. 7 . 
     At operation  926 , the TRP 1   901  transmits UE information to the central unit of the base station  905 . If all contents have been previously included in the measurement report at operation  919 , operation  926  is an operation that may be omitted. The UE information that may be transmitted at operation  926  or operation  919  may be some or all of the followings. 
     A UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam of the TRP  2  measured by the UE/CSI-RS/NR-SS ID and a measured value, MAC information, RLC information, TRP 2  timing advance measurement information of the UE, etc. 
     Operation  927  is an operation for the base station  905  to prepare the TRP 2   902  for the joining of the UE  900 , and is an operation that may be omitted if the TRP 2   902  includes only a simple RF stage or antenna. At operation  927 , UE information that may be transmitted may be some or all of the followings.
         A UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam of the TRP  2  measured by the UE/CSI-RS/NR-SS ID and a measured value, MAC information, RLC information, TRP 2  timing advance measurement information of the UE, etc.       

     At operation  931 , the UE  900  prepares to receive information of a target TRP, the TRP  2  included in the corresponding TRP change indication information over a fixed time after the TRP change indication information is received at operation  924  or until a scheduled resource is received. The UE  900  changes a reception configuration so that its own reception beam is suitable for the reception of the downlink resource of the TRP 2   902  included in the TRP change indication information and a beam/CSI-RS/NR-SS having a beam association (QCL) relation with the corresponding resource. 
     At operation  932 , the TRP 2   902  prepares to transmit a signal to the UE  900 , included in the TRP change indication information, over a fixed time after the TRP change indication information is received. 
     At operation  933 , the TRP 1   901  flushes information on the UE  900 . 
     Thereafter, the UE  900  and the TRP 2   902  may perform communication. 
       FIG. 10  is a diagram showing a procedure of changing a TRP after a grant in an embodiment of the disclosure. 
     Referring to  FIG. 10 , a system may include a UE  1000 , a TRP  1   1001 , a TRP  2   1002  and a base station  1005 . The UE  1000  is a UE belonging to the base station  1005 , and exchanges information with the base station using the TRP 1   1001 . 
     Operation  1011  to operation  1023  of  FIG. 10  correspond to the contents of operation  911  to operation  923  of  FIG. 9 . For them, reference is made to the related contents of  FIG. 9 . 
     At operation  1023 , the base station  1005  transmits information for requesting (e.g., TRP change indication information) a TRP change operation to the TRP 1   1001 . At operation  1024 , the TRP 1   1001  transmits UE information to the central unit of the base station  1005 . If all the contents have been previously included in the measurement report at operation  1019 , operation  1024  is an operation that may be omitted. At operation  1024  or operation  1019 , the UE information that may be transmitted may be some or all of the followings. 
     A UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam of the TRP  2  measured by the UE/CSI-RS/NR-SS ID and a measured value, MAC information, RLC information, TRP 2  timing advance measurement information of the UE, etc. 
     Operation  1025  is an operation for the base station  1005  to prepare the TRP 2   1002  for the joining of the UE  1000 , and is an operation that may be omitted if the TRP 2   1002  includes only a simple RF stage or antenna. UE information that may be transmitted at operation  1025  may be some or all of the followings.
         A UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam of the TRP  2  measured by the UE/CSI-RS/NR-SS ID and a measured value, MAC information, RLC information, TRP 2  timing advance measurement information of the UE, etc.       

     At operation  1026 , the TRP 2   1002  may transmit a response message for a TRP change request to the base station  1005 . The TRP 2   1002  may transmit information indicative of a TRP change grant or a TRP change denial. 
     At operation  1027 , the base station  1005  may deliver a response message for a TRP change request to the TRP 1   1001 . The response message may include information for granting a TRP change or information for denying a TRP change depending on whether the TRP 2   1002  grants a TRP change. 
     When information to grant a TRP change is received, at operation  1028 , the TRP 1   1001  transmits information for requesting (e.g., TRP change indication information) a TRP change operation to the UE  1000 . The TRP change indication information (TRP change indication message) may be a physical layer message (PHY downlink control information), may be a MAC CE message, may be an IE included in an RRE message, for example, an RRC connection reconfiguration message. 
     Operation  1031  to operation  1033  of  FIG. 10  correspond to operation  931  to operation  933  of  FIG. 9 . For them, reference is made to the description of  FIG. 9 . 
       FIG. 11  is a diagram showing a procedure of changing a TRP after a grant in another embodiment of the disclosure. 
     Referring to  FIG. 11 , a system may include a UE  1100 , a TRP  1   1101 , a TRP  2   1102  and a base station  1105 . The UE  1100  is a UE belonging to the base station  1105 , and exchanges information with the base station using the TRP 1   1101 . 
     Operation  1111  to operation  1118  of  FIG. 11  correspond to operation  1011  to operation  1018  of  FIG. 10 . For them, reference is made to the related contents of  FIG. 10 . 
     At operation  1119 , the TRP 1   1101  transmits feedback information, received from the UE  1100 , to the base station  1105 . The TRP 1   1101  may transmit ID information of the UE and information on the best beam for each TRP or N beams having good performance for each TRP to the base station  1105 . 
     At operation  1119 - 2 , the TRP 1   1101  transmits the UE information to the central unit of the base station  1105 . If all the contents have been previously included in the measurement report at operation  1119 , operation  1119 - 2  is an operation that may be omitted. UE information that may be transmitted at operation  1119  or operation  1119 - 2  may be some or all of the followings.
         A UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam of the TRP  2  measured by the UE/CSI-RS/NR-SS ID and a measured value, MAC information, RLC information, TRP 2  timing advance measurement information of the UE, etc.       

     Operation  1119  and Operation  1119 - 2  may be formed of one transmission operation. 
     Operation  1120  to operation  1123  of  FIG. 11  correspond to operation  1020  to operation  1023  of  FIG. 10 . For them, reference is made to the related description of  FIG. 10 . In  FIG. 11 , an operation corresponding to operation  1024  of  FIG. 10  has been omitted. An operation corresponding to operation  1024  has been performed at operation  1119 - 2 . 
     Operation  1125  to operation  1133  of  FIG. 11  correspond to operation  1025  to operation  1033  of  FIG. 10 . For them, reference is made to the related operations of  FIG. 10 . 
       FIG. 12  is a diagram showing a procedure of changing a TRP based on an RRC message in another embodiment of the disclosure. 
     Referring to  FIG. 12 , a system may include a UE  1200 , a TRP  1   1201 , a TRP  2   1202  and a base station  1205 . The UE  1200  is a UE belonging to the base station  1205 , and exchanges information with the base station using the TRP 1   1201 . 
     Operation  1211  to operation  1233  of  FIG. 12  correspond to operation  711  to operation  733  of  FIG. 7 . For them, reference is made to the related contents of  FIG. 7 . 
     At operation  1234 , the UE  1200  transmits an RRC connection request message to the TRP 2   1202 . That is, the UE  1200  receives TRP change indication information from the base station  1205  or the TRP 1   1201 , and transmits the RRC connection request message to a TRP (TRP 2   1202  in the embodiment of  FIG. 12 ) for which a TRP change has been indicated in response thereto. 
     At operation  1235 , the TRP 2   1202  transmits an RRC connection response message to the UE  1200  in response to the reception of the RRC connection request. A TRP change using the RRC message may be performed depending on operation  1234  and operation  1235 . 
     &lt;Information Exchange Method Between TRP-CU&gt; 
     1. A TRP may exchange and share UE information (MAC context, RLC context, timer information, buffer information, . . . ) with a CU and other TRPs in real time. 
     A. Information sharing between TRPs may be performed through a CU using an interface between the CU and the TRP. 
     B. Information sharing between TRPs may be performed using an interface between TRPs directly connected between the TRPs. 
     2. A CU may receive UE information from one TRP and manage the UE information, and may share it with other TRPs when the TRPs require the UE information (when a TRP change is necessary). 
       FIG. 13  is a diagram showing a method of exchanging UE information between a TRP and a base station according to an embodiment of the disclosure. 
     Referring to  FIG. 13 , a system may include a UE  1300 , a TRP 1   1301 , a TRP 2   1302 , a TRP k  1303 , and a base station  1305 . The UE  1300  is a UE belonging to the base station  1305 , and exchanges information with the base station  1305  using the TRP 1   1301 . 
     At operation  1311 , the UE  1300  transmits feedback information to the TRP 1   1301 . The feedback information may include TRP information, beam information, RACH information, SR information, etc. Furthermore, the feedback information may include UE information (MAC context, RLC context, timer information, buffer information, . . . ). 
     At operation  1312 , the TRP 1   1301  may transmit UE information to the base station  1305 . The UE information may be UE context information. The UE information may include MAC context, RLC context, timer information, buffer information, . . . . 
     At operation  1313 , the base station  1305  may transmit the UE information, received from the TRP 1   1301 , to the TRP 2   1302 . At operation  1314 , the base station  1305  may transmit the UE information, received from the TRP 1   1301 , to the TRP k  1303 . 
     As described above, UE information may be delivered to another TRP using an interface between the base station  1305  and the TRP. 
       FIG. 14  is a diagram showing a method of exchanging UE information between a TRP and a base station according to another embodiment of the disclosure. 
     Referring to  FIG. 14 , a system may include a UE  1400 , a TRP 1   1401 , a TRP 2   1402 , a TRP k  1403 , and a base station  1405 . The UE  1400  is a UE belonging to the base station  1405 , and exchanges information with the base station  1405  using the TRP 1   1401 . 
     At operation  1411 , the UE  1400  transmits feedback information to the TRP 1   1401 . The feedback information may include TRP information, beam information, RACH information, SR information, etc. Furthermore, the feedback information may include UE information (MAC context, RLC context, timer information, buffer information, . . . ). 
     At operation  1412 , the TRP 1   1401  may transmit UE information to the base station  1405 . The UE information may be UE context information. The UE information may include MAC context, RLC context, timer information, buffer information, . . . . 
     At operation  1413 , the TRP 1   1401  may transmit the UE information to the TRP 2   1402 . At operation  1414 , the TRP 1   1401  may transmit the UE information to the TRP k  1403 . 
     As described above, information sharing between TRPs may be performed using an interface between TRPs directly connected between the TRPs. 
       FIG. 15  is a diagram showing a method of sharing UE information when a TRP change is requested in an embodiment of the disclosure. 
     Referring to  FIG. 15 , a system may include a UE  1500 , a TRP 1   1501 , a TRP 2   1502 , a TRP k  1503 , and a base station  1505 . The UE  1500  is a UE belonging to the base station  1505 , and exchanges information with the base station  1505  using the TRP 1   1501 . 
     At operation  1511 , the UE  1500  transmits feedback information to the TRP 1   1501 . The feedback information may include TRP information, beam information, RACH information, SR information, etc. Furthermore, the feedback information may include UE information (MAC context, RLC context, timer information, buffer information, . . . ). 
     At operation  1512 , the TRP 1   1501  determines whether a TRP change is required. For a method of determining a TRP change, reference is made to the determination methods described in the previous embodiments. 
     If a TRP change is not required, at operation  1513 , the TRP 1   1501  does not need to provide the UE  1500  with any information related to a TRP change. However, even in such a case, the UE  1500  may need to change a beam being used within the same TRP. In such a case, the TRP 1   1501  or the base station  1505  may enable the UE  1500  to perform a beam change. 
     At operation  1514 , the TRP 1   1501  transmits information for requesting a TRP change operation to the base station  1505 . The information for requesting (e.g., TRP change indication information) a TRP change operation may be a physical layer message (PHY downlink control information), may be a MAC CE message, may be an IE included in an RRE message, for example, an RRC connection reconfiguration message. For the contents of information that may be included in the TRP change indication information, reference is made to the embodiment of  FIG. 7 . 
     At operation  1515 , the base station  1505  transmits the information for requesting a TRP change operation to the TRP  2   1502 , that is, the subject of a TRP change. In the embodiment, the base station  1505  transmits the information for requesting a TRP change operation to the TRP 2   1502  because it is assumed that a TRP for the UE  1500  is changed from the TRP 1   1501  to the TRP 2   1502 . 
       FIG. 16  is a diagram showing a method of sharing UE information when a TRP change is requested in another embodiment of the disclosure. 
     Referring to  FIG. 16 , a system may include a UE  1600 , a TRP 1   1601 , a TRP 2   1602 , a TRP k  1603 , and a base station  1605 . The UE  1600  is a UE belonging to the base station  1605 , and exchanges information with the base station  1605  using the TRP 1   1601 . 
     At operation  1611 , the UE  1600  transmits feedback information to the TRP 1   1601 . The feedback information may include TRP information, beam information, RACH information, SR information, etc. Furthermore, the feedback information may include UE information (MAC context, RLC context, timer information, buffer information, . . . ). 
     At operation  1612 , the TRP 1   1601  determines whether a TRP change is required. For a method of determining a TRP change, reference is made to the determination methods described in the previous embodiments. 
     If a TRP change is not required, at operation  1613 , the TRP 1   1601  does not need to provide the UE  1600  with any information related to a TRP change. However, even in such a case, the UE  1600  may need to change a beam being used within the same TRP. In such a case, the TRP 1   1601  or the base station  1605  may enable the UE  1600  to perform a beam change. 
     At operation  1614 , the TRP 1   1601  transmits information for requesting a TRP change operation to the base station  1605 . The information (e.g., TRP change indication information) for requesting a TRP change operation may be a physical layer message (PHY downlink control information), may be a MAC CE message, may be an IE included in an RRE message, for example, an RRC connection reconfiguration message. For the contents of information that may be included in the TRP change indication information, reference is made to the embodiment of  FIG. 7 . 
     At operation  1615 , the TRP 1   1601  transmits the information for requesting a TRP change operation to the TRP  2   1602 , that is, the subject of a TRP change. In the embodiment, the TRP 1   1601  transmits the information for requesting a TRP change operation to the TRP 2   1602  because it is assumed that a TRP for the UE  1600  is changed from the TRP 1   1601  to the TRP 2   1602 . 
       FIG. 17  is a diagram showing a method of sharing UE information when a TRP change is requested in another embodiment of the disclosure. 
     Referring to  FIG. 17 , a system may include a UE  1700 , a TRP 1   1701 , a TRP 2   1702 , a TRP k  1703 , and a base station  1705 . The UE  1700  is a UE belonging to the base station  1705 , and exchanges information with the base station  1705  using the TRP 1   1701 . 
     At operation  1711 , the UE  1700  transmits feedback information to the TRP 1   1701 . The feedback information may include TRP information, beam information, RACH information, SR information, etc. Furthermore, the feedback information may include UE information (MAC context, RLC context, timer information, buffer information, . . . ). 
     At operation  1712 , the TRP 1   1701  may transmit UE information to the base station  1705 . The UE information may be UE context information. The UE information may include MAC context, RLC context, timer information, buffer information, . . . . 
     At operation  1713 , the base station  1705  determines whether a TRP change is required. For a method of determining a TRP change, reference is made to the determination methods described in the previous embodiments. 
     If a TRP change is not required, at operation  1714 , the base station  1705  does not need to provide the UE  1700  with any information related to a TRP change. However, even in such a case, the UE  1700  may need to change a beam being used within the same TRP. In such a case, the base station  1705  may enable the UE  1700  to perform a beam change. 
     If a TRP change is required, at operation  1715 , the base station  1705  transmits information for requesting a TRP change operation to the TRP 2   1602 . The information (e.g., TRP change indication information) for requesting a TRP change operation may be a physical layer message (PHY downlink control information), may be a MAC CE message, may be an IE included in an RRE message, for example, an RRC connection reconfiguration message. For the contents of information that may be included in the TRP change indication information, reference is made to the embodiment of  FIG. 7 . 
       FIG. 18  is a diagram showing a UE feedback trigger and TRP change method according to an event in an embodiment of the disclosure. 
     Referring to  FIG. 18 , a system may include a UE  1800 , a TRP  1   1801 , a TRP  2   1802  and a base station  1805 . 
     The UE  1800  is a UE  1800  belonging to the base station  1805 , and exchanges information with the base station using the TRP 1   1801 . 
     At operation  1811  and operation  1812 , the base station  1805  selects RSs to be transmitted by the TRP 1   1801  and the TRP 2   1802  and the resources of the corresponding RSs so that the UE  1800  can measure the TRPs, and delivers such information to the TRP 1   1801  and the TRP 2   1802  if the information needs to be provided to the TRPs. In this case, the TRP 1   1801  has to schedule RS information of the TRP 2   1802  in addition to the RS of the TRP 1   1801  with respect to the UE  1800 . Accordingly, the base station  1805  may provide the TRP 1   1801  with both RS configuration information of the TRP 1   1801  and configuration information of the TRP 2   1802 . 
     At operation  1813 , the TRP 1   1801  provides the UE  1800  with the configured resource configuration information of the TRP 1   1801  and the TRP 2   1802  so that the UE  1800  can measure each of the TRPs. In this case, the TRP  1   1801  may provide a direct TRP ID associated with resource configuration information of a different TRP or any resource segmentation method of enabling the UE to indirectly distinguish between the TRPs, for example, a method of transmitting the RSs of different TRPs at time intervals may be used so that the UE  1800  can recognize that the corresponding RSs are transmitted by different TRPs. 
     At operation  1814 , the TRP 1   1801  transmits the RS to the UE  1800 , as allocated, for measurement. At operation  1815 , the TRP 2   1802  transmits the RS to the UE  1800 , as allocated, for measurement. 
     At operation  1816 , the UE  1800  performs RS measurement on different TRPs, and updates measurement information for filtering purposes, for example, if necessary. 
     At operation  1817 , the TRP 1   1801  may indicate that beam measurement results should be reported. The TRP  1   1801  may indicate that the best beam or N beams having good performance should be reported for each TRP. The beam measurement result report information may indicate that information on a TRP ID, a beam ID, beam quality should be reported. 
     At operation  1818 , the UE  1800  checks whether a feedback event has been triggered. If a feedback event has not been triggered, at operation  1819 , the UE  1800  does not perform an operation for feedback. If a feedback event has been triggered, at operation  1820 , the UE  1800  transmits feedback information to the TRP 1   1801 . The information may be transmitted using a pre-scheduled resource, RACH resource, SR resource, other possible resource, etc. 
     At operation  1821 , the TRP 1   1801  may determine whether a TRP change is required. The TRP 1   1801  may determine whether a TRP change is required based on reported measurement results. For example, if the measurement results of the reference signal of the TRP 2  is greater than the measurement results of the reference signal of the TRP 1  by a value of a preset offset, the TRP 1   1801  may determine that a TRP change is required. 
     If it is determined that a TRP change is not required at operation  1822 , the process proceeds to operation  1823 . If it is determined that a TRP change is required, the process proceeds to operation  1824 . 
     At operation  1823 , the TRP 1   1801  does not need to provide the UE  1800  with any information related to a TRP change. However, even in such a case, the UE  1800  may need to change a beam being used within the same TRP. In such a case, the TRP 1   1801  may enable the UE  1800  to perform a beam change. 
     At operation  1824 , the TRP 1   1801  transmits information (e.g., TRP change indication information) for requesting a TRP change operation to the UE  1800 . At operation  1824 , the TRP 1   1801  transmits the information for requesting a TRP change operation to the UE  1800 . 
     At operation  1825 , the TRP 1   1801  provides a TRP change request and UE information to the base station  1805 . There is a need for a procedure of notifying the base station  1805  of information indicating that a TRP change is necessary because the TRP 1   1801  has determined the TRP change. The information may include at least one of a UE ID, a UE best beam/CSI-RS/NR-SS ID, the best beam of the TRP  2  measured by the UE/CSI-RS/NR-SS ID and a measured value, MAC information, RLC information, or TRP 2  timing advance measurement information of the UE. 
     At operation  1826 , the base station  1805  may provide the TRP 2   1802  with the TRP change request and UE information. The TRP 2   1802  may prepare the joining of the UE based on the TRP change request and UE information. 
     At operation  1831 , the UE  1800  prepares to receive information of a target TRP, the TRP  2  included in a corresponding TRP change request message over a fixed time after the TRP change request message is received or until a scheduled resource is received. The UE  1800  changes a reception configuration so that the reception beam of the UE is suitable for the reception of the downlink resource of the TRP 2  included in the TRP change request message and a beam/CSI-RS/NR-SS having a beam association (QCL) relation with the corresponding resource. 
     At operation  1832 , the TRP 1   1801  flushes information on the UE  1800 . 
     At operation  1833 , the TRP 2   1802  prepares to transmit a signal to a UE, included in the TRP change request message, over a fixed time after the TRP change request message is received. 
       FIG. 19  is a diagram showing a terminal feedback trigger and TRP change method according to an event in another embodiment of the disclosure. 
     Referring to  FIG. 19 , a system may include a UE  1900 , a TRP  1   1901 , a TRP  2   1902  and a base station  1905 . The UE  1900  is a UE  1900  belonging to the base station  1905 , and exchanges information with the base station using the TRP 1   1901 . 
     Operation  1911  to operation  1917  of  FIG. 19  correspond to operation  1811  to operation  1817  of  FIG. 18 . For them, reference is made to the related description of  FIG. 18 . 
     At operation  1918 , the UE  1900  determines whether a TRP change event has been triggered. If a TRP change event has not been triggered, at operation  1919 , the UE  1900  does not perform an operation for a TRP change. 
     If a TRP change event has been triggered, at operation  1920 , the UE  1900  may transmit TRP change request information to the TRP 2   1902 . The UE  1900  may transmit at least one of a TRP change request, a TRP reallocation request, or a TRP reconfiguration request. The request of the UE  1900  may be transmitted through a common channel or an RACH channel or an allocated another uplink resource. 
     At operation  1921 , the TRP 2   1902  requests UE context from the base station  1905 . At operation  1922 , the base station  1905  requests the UE context from the TRP 1   1901 . 
     At operation  1923 , the TRP 1   1901  transmits the UE context to the base station  1905 . The UE context may include beam information, best beam information, MAC context, RLC context, timer information, buffer information, etc. 
     At operation  1924 , the base station  1905  may transmit TRP change request information to the TRP 2   1902 . 
     At operation  1925 , the TRP 2   1902  transmits TRP change response information to the UE  1900 . 
     At operation  1931 , the UE  1900  prepares to receive information of a target TRP, the TRP  2 , included in the corresponding TRP change request message, over a fixed time after the TRP change request message is received or until a scheduled resource is received. The UE  1900  changes a reception configuration so that the reception beam of the UE is suitable for the reception of the downlink resource of the TRP 2  included in the TRP change request message and a beam/CSI-RS/NR-SS having a beam association (QCL) relation with the corresponding resource. 
     At operation  1932 , the TRP 1   1901  flushes information on the UE  1800 . 
     At operation  1933 , the TRP 2   1902  prepares to transmit a signal to a UE, included in the TRP change request message, over a fixed time after the TRP change request message is received. 
       FIG. 20  is a diagram showing a terminal according to an embodiment of the disclosure. 
     Referring to  FIG. 20 , the UE may include a transceiver  2010  and a controller  2030 . The UE transmits and/or receives a signal, information, data, a message, etc. through the transceiver  2010 . The controller  2030  may include at least one processor. The controller  2030  may control an overall operation of the UE. 
     In accordance with an embodiment of the disclosure, the controller  2030  may control to receive resource configuration information, including reference signal configuration information of a first TRP and reference signal configuration information of a second TRP, from a first transmission and reception point (TRP), to measure a reference signal corresponding to the first TRP and a reference signal corresponding to the second TRP based on the resource configuration information, to report the measurement information on the reference signal corresponding to the first TRP and the reference signal corresponding to the second TRP to the first TRP, to receive TRP change indication information from the first TRP, and to change a configuration for the second TRP based on the TRP change indication information. The TRP change indication information may be included in a medium access control (MAC) control element (CE) message. The TRP change indication information may include a channel state information-reference signal (CSI-RS) for the second TRP. 
     Furthermore, the controller  2030  may control to receive at least one of connection grant information, timing advance (TA) information or random access channel (RACH) request information from the TRP 2 . 
     An operation of the controller  2030  is not limited thereto. In an embodiment of the disclosure, the controller  2030  may control the operation of the UE described through the embodiments of  FIGS. 1 to 19  of the disclosure. 
       FIG. 21  is a diagram showing a base station according to an embodiment of the disclosure. 
     Referring to  FIG. 21 , the base station may include a transceiver  2110  and a controller  2130 . The transceiver  2110  of the base station may be a concept including at least one TRP and or at least one antenna. The controller  2130  of the base station may be a concept including at least one CU and at least one DU. The base station may transmit and/or receive a signal, information, data, a message, etc. through the transceiver  2110 . The controller  2130  may include at least one processor. The controller  2130  may control an overall operation of the base station. 
     In accordance with an embodiment of the disclosure, the transceiver  2110  includes a first transmission and reception point (TRP) and a second TRP. The controller  2130  may perform control to transmit resource configuration information including reference signal configuration information of the first TRP and reference signal configuration information of the second TRP, to receive measurement report information transmitted by a UE, to determine whether the transceiver  2110  transmitting and receiving information to and from the UE will be changed from the first TRP to the second TRP, to transmit TRP change indication information to the UE using the first TRP, to provide additional information enabling the UE to easily access the second TRP if necessary, and to resume communication with the UE through the second TRP. The TRP change indication information may be included in a medium access control (MAC) control element (CE) message. The TRP change indication information may include a channel state information-reference signal (CSI-RS) for the second TRP. 
     Furthermore, the controller  2130  may control to transmit at least one of connection grant information, timing advance (TA) information or random access channel (RACH) request information from the TRP 2  to the UE using the TRP 1 . 
     An operation of the controller  2130  is not limited thereto. In an embodiment of the disclosure, the controller  2130  may control the operations of the base station described through the embodiments of  FIGS. 1 to 19  of the disclosure. 
     Furthermore, the embodiments disclosed in the specification and drawings have proposed only specific examples in order to easily describe the contents of the disclosure and help understanding of the disclosure, and are not intended to restrict the scope of the disclosure. Accordingly, the scope of the disclosure should be construed as including all the changes or modified forms derived based on the technical spirit of the disclosure in addition to the disclosed embodiments.