KR20200064907A - Method and apparatus for dynamic management of radio resource in communication system - Google Patents

Abstract

A method for operating a central processor (CP) included in a centralized/cloud-radio access network (C-RAN) in a communication system comprises: a step of transmitting a first message to a terminal through a plurality of access nodes (AN); a step of receiving a second message in response to the first message through the plurality of ANs from the terminal; a step of obtaining reception state information of the second message of each of the plurality of ANs; a step of constructing a cluster including at least one AN of the plurality of ANs based on the reception state information; and a step of transmitting a third message including resource information of the cluster and resource information of the at least one AN to the terminal through the at least one AN. Therefore, the performance of the communication system can be improved.

Description

METHOD AND APPARATUS FOR DYNAMIC MANAGEMENT OF RADIO RESOURCE IN COMMUNICATION SYSTEM in a communication system

The present invention relates to a method and apparatus for managing radio resources in a communication system, and more particularly, a communication node that manages radio resources to be allocated to a terminal in a communication system including a cloud-radio access network (C-RAN) and its It relates to a method of operation.

Recently, a mobile communication environment mainly consists of a technology such as LTE-A, which is called a 4th generation communication technology, and through this, a high capacity data can be exchanged with a wireless terminal. However, as consumers communicate more large amounts of data, a rapid increase in the amount of data traffic has been made, and various attempts are being made to increase the utilization of frequency resources to effectively process it. Recently, 5G communication technology has been developed.

As one of the 5G communication technologies, C-RAN (Cloud Radio Access Network) is a key node that is performed in a base station of an existing communication system as an edge node (or remote radio head (RRH)) and a central processor (or central processor) (or It can be performed by separating into a baseband processing unit pool.

In C-RAN, the link between the edge node and the central processor is called a fronthaul link, and the data capacity of the fronthaul channel is capable of supporting 1 Gbps or more in the case of optical cables, but the microwave fronthaul channel In the case of deterioration to a capacity of 10-100 Mbps may occur depending on the distance and weather conditions.

In order to solve the capacity problem of the front hole, a cache is installed in the edge node to store frequently requested data in advance, and when the terminal requests a file stored in the cache, the front node is not used, and the edge node uses the terminal. Cache cooperative communication can be performed to send data directly to.

Also, in C-RAN, instead of a wired front hole connecting wires between the edge nodes and the central processor in all cellular communication service areas, a wireless front hole connecting wirelessly between the edge nodes and the central processor is emerging.

In general, in cell deployment, a base station is fixedly disposed according to a cell deployment policy, and accordingly, an CP and AN are fixedly mapped to perform AN function, and an operating environment can be set. In an environment in which CP and AN are fixedly mapped, when a channel state of a terminal and a data transmission/reception state are changed or the terminal moves, the connection state between the base station and the terminal may rapidly deteriorate.

An object of the present invention for solving the above problems is to provide a method and apparatus for dynamically building a cell in a communication system including a Cloud Radio Access Network (C-RAN).

A method for operating a central processor (CP) included in a centralized/cloud-RAN (radio access network) (C-RAN) in a communication system according to an embodiment of the present invention for achieving the above object is a plurality of access nodes (AN) ) Through the first message to the terminal; Receiving a second message in response to the first message through a plurality of ANs from the terminal; Obtaining reception status information of the second message of each of the plurality of ANs; Configuring a cluster including at least one AN among a plurality of ANs based on the reception status information; And transmitting a third message including resource information of the cluster and resource information of the one or more ANs to the terminal through the one or more ANs.

According to the present invention, a centralized/cloud-RAN (radio access network) (C-RAN) dynamically manages a connection state with a terminal through distributed and constructed antennas, thereby efficiently performing data transmission and reception operations with the terminal. Can be.

According to the present invention, the C-RAN dynamically manages a cell using hardware resources and software resources of a central processor (CP) and an access node (CP) to manage mobility of the terminal, thereby efficiently transmitting and receiving data with the terminal. Can be done with

According to the present invention, when a different signal is received through a common resource from a plurality of terminals, the C-RAN detects collisions between signals and reallocates resources to each terminal, thereby efficiently transmitting and receiving data with the terminal. Can be done with

1 is a conceptual diagram showing an embodiment of a communication system.
2 is a block diagram showing an embodiment of a communication node constituting a communication system.
3 is a conceptual diagram illustrating an embodiment of a C/RAN (centralized/cloud-radio access network) structure.
4 is a conceptual diagram illustrating an embodiment of a radio resource of a C-RAN communication system.
5 is a flowchart illustrating an embodiment of an initial access procedure of a terminal in a communication system.
6 is a flowchart illustrating an embodiment of a signal transmission/reception procedure using beam-forming in a communication system.
7 is a conceptual diagram illustrating an embodiment of a beamforming result of communication nodes in a communication system.
8 is a conceptual diagram illustrating a first embodiment of cluster management in a communication system.
9 is a conceptual diagram illustrating a second embodiment of cluster management in a communication system.
10 is a flowchart illustrating an embodiment of a cluster management operation in a communication system.
11 is a conceptual diagram showing a first embodiment of resource management in a communication system.
12 is a flowchart illustrating a first embodiment of resource management in a communication system.
13 is a conceptual diagram showing a second embodiment of resource management in a communication system.
14 is a flowchart illustrating a second embodiment of resource management in a communication system.
15 is a flowchart illustrating a first embodiment of a method for managing mobility of a terminal in a communication system.
16 is a flowchart illustrating a second embodiment of a method for managing mobility of a terminal in a communication system.

The present invention can be applied to various changes and can have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from other components. For example, the first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may be referred to as a first component. The term and/or includes a combination of a plurality of related described items or any one of a plurality of related described items.

When an element is said to be "connected" or "connected" to another component, it is understood that other components may be directly connected to or connected to the other component, but there may be other components in between. It should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that no other component exists in the middle.

The terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, terms such as “include” or “have” are intended to indicate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, one or more other features. It should be understood that the existence or addition possibilities of fields or numbers, steps, operations, components, parts or combinations thereof are not excluded in advance.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person skilled in the art to which the present invention pertains. Terms such as those defined in a commonly used dictionary should be interpreted as having meanings consistent with meanings in the context of related technologies, and should not be interpreted as ideal or excessively formal meanings unless explicitly defined in the present application. Does not.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In order to facilitate the overall understanding in describing the present invention, the same reference numerals are used for the same components in the drawings, and duplicate descriptions for the same components are omitted.

Referring to Figure 1, the communication system 100 is a plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Here, the communication system may be referred to as a "communication network". Each of the plurality of communication nodes may support at least one communication protocol. For example, each of the plurality of communication nodes is a communication protocol based on code division multiple access (CDMA), a communication protocol based on wideband CDMA (WCDMA), a communication protocol based on time division multiple access (TDMA), and a frequency division multiple access) based communication protocol, OFDM (orthogonal frequency division multiplexing) based communication protocol, OFDMA (orthogonal frequency division multiple access) based communication protocol, SC (single carrier)-FDMA based communication protocol, NOMA (non-orthogonal multiple) access) based communication protocol, SDMA (space division multiple access) based communication protocol, and the like. Each of the plurality of communication nodes may have the following structure.

2 is a block diagram showing an embodiment of a communication node constituting a communication system.

Referring to FIG. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. In addition, the communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, and the like. Each of the components included in the communication node 200 may be connected by a bus 270 to communicate with each other. However, each component included in the communication node 200 may be connected through a separate interface or a separate bus centered on the processor 210, not the common bus 270. For example, the processor 210 may be connected to at least one of the memory 220, the transceiver 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor in which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may be configured as at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be configured as at least one of read only memory (ROM) and random access memory (RAM).

Referring back to FIG. 1, the communication system 100 includes a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2), and a plurality of terminals (user equipment). ) (130-1, 130-2, 130-3, 130-4, 130-5, 130-6). Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong to the coverage of the third base station 110-3. . The first terminal 130-1 may belong to the coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the coverage of the fifth base station 120-2.

Here, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) g node B (gNB; next generation Node B), Node B (NodeB), upgraded Node B (evolved NodeB), base transceiver station (BTS), radio base station, radio transceiver, access point, access node, road side unit (RSU), Referred to as a digital unit (DU), cloud digital unit (CDU), radio remote head (RRH), radio unit (RU), transmission point (TP), transmission and reception point (TRP), relay node, etc. Can be. Each of the plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) is a terminal, an access terminal, a mobile terminal, It may be referred to as a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, or the like.

Multiple communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6) Each may support cellular communication (for example, long term evolution (LTE), LTE-A (advanced), 5G NR (new RAT), etc., which are defined in a 3rd generation partnership project (3GPP) standard). Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other through an ideal backhaul or a non-ideal backhaul, and the ideal backhaul Alternatively, information can be exchanged with each other through a non-ideal backhaul. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to a core network (not shown) through an ideal backhaul or a non-ideal backhaul. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) receives a signal received from the core network corresponding to the terminal (130-1, 130-2, 130-3, 130) -4, 130-5, 130-6), and the core network receives signals received from the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, 130-6 Can be transferred to.

Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) can support OFDMA-based downlink transmission, and SC-FDMA-based uplink (uplink) ) Can support transmission. In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 transmits multiple input multiple output (MIMO) (eg, single user (SU)-MIMO, Multi user (MU)-MIMO, massive MIMO, etc., COMP (coordinated multipoint) transmission, carrier aggregation (carrier aggregation) transmission, transmission in an unlicensed band, device-to-device (D2D) ) Communication (or ProSe (proximity services), etc.), where a plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) each base station (110-1, 110-2, 110-3, 120-1, 120-2) and corresponding operation, by the base station (110-1, 110-2, 110-3, 120-1, 120-2) Supported operations can be performed.

3 is a conceptual diagram illustrating an embodiment of a C/RAN (centralized/cloud-radio access network) structure.

Referring to FIG. 3, the communication network may include a core network 310 and a C-RAN 320. C-RAN 320 may include a base station network configured in a centralized (centralized) structure. Specifically, the C-RAN 320 may include a baseband unit (BBU), which is a processing unit related to modulation and demodulation and connection to a core network, and an RRH (or RF, TRP), which is a transmission/reception device associated with an antenna, among base station devices. Can be. The BBU of the C-RAN 320 may be centrally located and deployed in the communication network, and the RRH may be distributed and installed in an area that is easy to provide communication services to users. BBU and RRH are connected by wire to transmit and receive data and control information.

The processing device including the BBU of the C-RAN 320 may be represented by a central processor (CP) 321, and the transmitting and receiving device including the RRH may be represented by an access node (AN) 322. In the standard specification, CP 321 may be represented by a central unit (CU), and AN 322 may be represented by a distributed unit (DU). CP 321 may perform a higher layer (L2, L3) function or a physical layer function in the mobile communication layer structure. The AN 322 may perform an RF function or a physical layer function.

The CP 321 may perform a control plane (CP) function and a user plane (UP) function, and may include an entity performing a control plane function and an entity performing a user plane function. . Also, the CP 321 may include function split entities according to layers, and may be divided into entities that perform the functions of the L3 and L2 layers and entities that perform the functions of the L1 layer. The C-RAN 320 may be connected to the core network 310 through the CP 321. The connection between the CP 321 and the core network 310 may be a backhaul network, and the connection between the CP 321 and the AN 322 may be a fronthaul network. Communication between the CP 321 and the AN 322 may be connected by a digital communication method, and the AN 322 may convert analog signals to digital or digital signals to analog signals.

4 is a conceptual diagram illustrating an embodiment of a radio resource of a C-RAN communication system.

4, the C-RAN can perform one cell function, and all the ANs 421, 422, 423, 424, and 425 connected to one CP 410 each perform one cell function. It can be configured to. The radio resource of the cell may include common resources, cluster resources, AN resources, and terminal resources. The common resource may mean a radio resource commonly used throughout the cell. The cluster resource may refer to a radio resource used only by a terminal having one cluster information. The AN resource may refer to a radio resource used by one antenna or AN (for example, one of 421 to 425). The terminal resource may refer to a radio resource used by one terminal 430.

Each radio resource can be classified using frequency, time, code, and space. For example, each communication node classifies the entire frequency bandwidth into physical resources (eg, physical resource block (PRB)) according to frequency and time, and wirelessly based on code using an identifier to identify each physical resource. The signal can be modulated or classified according to space using an antenna.

The CP 410 may perform functions according to the hierarchical structure of the base station. Specifically, the CP 410 performs radio resource control (RRC), packet data convergence protocol (PDCP), radio link control (RLC), media access control (MAC), and physical (physical) layer functions for one cell. can do.

Each of the ANs 421 to 425 may broadcast a wireless signal and system information channel using one cell identifier. The identifier used to distinguish a cell, a terminal, etc. may include a cell identifier, a cluster identifier (eg, cluster ID, or sector ID), an AN identifier, and a terminal identifier. The cell identifier may be an identifier indicating a cell, the cluster identifier may be an identifier for managing resources allocated to the terminal, and an AN identifier or an identifier for distinguishing AN (eg, AN ID, TRP ID, etc.) ), and the terminal identifier may be an identifier (eg, UE ID, C-RNTI, TMSI) for distinguishing the terminal.

5 is a flowchart illustrating an embodiment of an initial access procedure of a terminal in a communication system.

Referring to FIG. 5, the communication system may include a C-RAN 510 including a CP 511 and an AN 512 and a user equipment (UE) 520. CP 511 and AN 512 of FIG. 5 may be configured the same or similar to CP and AN shown in FIGS. 3 to 4. And, unlike shown in Figure 5, C-RAN may include a CP and a plurality of AN. In addition, the terminal of FIG. 5 may be configured the same or similar to the terminals described in FIG. 1.

The terminal 520 illustrated in FIG. 5 may be located within communication coverage of a plurality of ANs, and thus the terminal 520 may transmit and receive signals to and from the C-RAN 510 using a plurality of antennas. . The terminal 520 may perform an initial access procedure to the C-RAN 510 by performing the following procedure.

The CP 511 can configure and set system information. The CP 511 may transmit the set system information to the AN 512. The AN 512 may generate a radio signal including system information obtained from the CP 511. The AN 512 may transmit a downlink signal including system information to the terminal 520 (S520). The downlink signal may include a synchronization signal (synchronization signal (SS), physical broadcast channel (SS/PBCH), etc.) and a system information channel (system information block (SIB), master information block (MIB), etc.).

The terminal 520 may receive a downlink signal (eg, SS/PBCH block) including system information from the AN 512 (S510). The terminal 520 may acquire time and frequency synchronization based on the received downlink signal. In addition, the terminal 520 may acquire system information by receiving system information from the received downlink signal. The terminal 520 may receive the same signal from a plurality of ANs 512 (S510), and may demodulate data based on the signals received from the plurality of ANs 512.

The terminal 520 may generate Msg1 based on the system information obtained from the AN 512, and the terminal may configure a physical random access channel (pRACH) parameter included in Msg1. For example, the terminal 520 determines the transmission time of the pRACH channel, the location of the frequency resource, the pRACH preamble, and the identifier of the pRACH channel (for example, pRACH ID or pRACH preamble sequence ID) based on the system information. Can be configured. The terminal 520 may transmit the Msg1 generated based on the configured pRACH parameter to the C-RAN 512 base station (eg, AN 512) to request access to the C-RAN 512 (S520). . The terminal 520 may transmit Msg1 using a common resource (S520).

The C-RAN 510 may receive Msg1 from the terminal 520, and specifically, a plurality of AN 512 may receive Msg1 from the terminal 520 (S520 ). The CP 511 may acquire Msg1 from the AN 512 (at least one AN 512), and when successfully receiving the Msg1 obtained from the AN 512, check the access request of the terminal 520 Can be.

However, since the terminal 520 transmits Msg1 using a common resource, the C-RAN 512 may not identify the terminal 520 that has transmitted Msg1. For example, C-RAN 512 may receive Msg1 transmitted by one terminal 520 through a plurality of ANs 512, and C-RAN 512 may also be different terminals 520. Since they can receive the same random access identifier and Msg1 transmitted through a common resource, it may be difficult to distinguish the relationship between the RACH and the terminal 520.

Accordingly, in receiving the Msg1, the CP 511 may obtain the Msg1 reception state information through the AN 512. For example, the CP 511 may acquire information about the AN 512 successfully demodulating Msg1 based on the Msg1 obtained from each AN 512. For example, the CP 511 further acquires Msg reception status information (eg, signal to noise ration (SNR), SINR, quality of service (QoS), etc.) obtained from each of the AN 512, , It is possible to obtain information about ANs 512 having a signal strength equal to or greater than a preset threshold.

CP 511 may generate a response channel for Msg1 (eg, Msg2). Msg2 may include response channel information for Msg1, and response channel information for Msg1 may further include an identifier (eg, RACH identifier) of Msg1 and an AN 512 identifier. The identifier of Msg1 (eg, RACH identifier) and the AN 512 identifier may be included in the data of Msg2, or may be implicitly expressed by time, code, and spatial resources of Msg2. In addition, Msg2 may further include information on resources to be allocated to the terminal 520. The resource information may include temporary C-RNTI, radio resource information for transmitting uplink data (eg, uplink grant, etc.) and synchronization information. CP 511 generates different response channel information (eg, AN 512 identifier, temporary C-RNTI, radio resource information and time synchronization information) according to AN 512 for transmitting a response channel. Can be. For example, when the CP 511 wants to transmit response channel information through a plurality of ANs 512, the CP 511 can generate a plurality of response channel information, and each generated response channel information. It can be transmitted through different AN (512).

The CP 511 may transmit response channel information to the AN 512, specifically, AN (which successfully demodulates the RACH from the terminal 520 (or the received signal strength of the RACH exceeds a preset threshold)) 512) RACH response channel information. The AN 512 may generate an RACH response channel based on the obtained response channel information, and may transmit the RACH response channel to the terminal 520 (S530).

The terminal 520 may receive the RACH response channel from the AN 512 (S530), and demodulate the received RACH response channel. The UE 520 can demodulate the RACH response channel and identify a node that has transmitted the RACH based on the RACH indicator of the RACH response channel. In addition, the terminal 520 can demodulate the RACH response channel to check the identifier of the AN 512 that has transmitted the RACH. The terminal 520 may measure and store the signal reception strength of the RACH response channel. The terminal 520 may acquire allocated UL resource information by demodulating the RACH response channel, and the UL resource information may be set differently according to the AN 512.

The terminal 520 may generate data to transmit uplink to the C-RAN 512 based on the information obtained from the RACH response channel. The uplink data may include an identifier (or temporary C-RNTI) of the terminal 520, information about the AN 512, and information about the RACH (for the purpose of transmitting the message, etc.). The information about the AN 512 included in the uplink data includes a list of identifiers of the AN 512 and reception strength information of a downlink signal (eg, RACH response channel) received from each AN 512. can do. The terminal 520 may transmit a signal (eg, Msg3) including uplink data to the C-RAN 512 to the C-RAN 512. The terminal 520 may transmit Msg3 to one AN 512 (S540).

The C-RAN 512 (eg, AN 512) may receive Msg3 from the terminal 520 (S540). The C-RAN 512 (eg, CP 511) may map the RACH channel and the identifier of the terminal 520 based on the information of Msg3 received from the terminal 520. In addition, the C-RAN 512 (eg, CP 511) may determine the AN 512 to be mapped to the terminal 520 based on the information related to the AN 512 included in Msg3. For example, the CP 511 is based on the list of identifiers of the AN 512 and the reception strength information of the downlink signal (eg, RACH response channel) received from each AN 512, the terminal 520 A cluster may be allocated to the terminal 520 by setting a plurality of ANs 512 to be connected with. The CP 511 selects AN 512 having a good channel state among a plurality of AN 512 to map the cluster identifier for the terminal 520.

The C-RAN 512 (eg, CP 511) may generate data related to Msg4. The C-RAN 512 may transmit the generated data to the AN 512. The AN 512 may configure Msg4 based on the data, and may transmit Msg4 to the terminal 520 (S550). Msg4 may include a control channel and a data channel. The control channel may include information necessary for demodulation of the data channel, and may include AN 512 identification information (or a list of identification information) of the data channel, data size information, and radio resource information of the data channel. In addition, the data channel of Msg4 may include AN 512 resource information and cluster resource information for the terminal 520 to use for data communication. The resource information of the AN 512 may be information required for the terminal 520 to receive a control channel (eg, PDCCH), and the cluster resource information may include the terminal 520 having a data channel (eg, PDSCH). And information required to receive the reference signal.

In transmitting the control channel and data channel of the Msg4, the C-RAN 512 may transmit through different resources. For example, the C-RAN 512 may transmit the control channel of Msg4 through the AN 512 resource that has received Msg3 (S550). Further, the C-RAN 512 may transmit the data channel of Msg4 through the AN 512 resource or the cluster resource (S550).

The terminal 520 may receive Msg4 from the C-RAN 512 and access the C-RAN 512 base station (S550). The terminal 520 may receive a control channel of Msg4 and obtain location information of a downlink radio resource for receiving a data channel of Msg4. In addition, the terminal 520 may receive a data channel of Msg4 based on the location information of the downlink radio resource and set a wireless communication environment with the C-RAN 512. In addition, the terminal 520 may obtain information necessary for uplink data transmission from Msg4. For example, the terminal 520 may obtain AN 512 (or cluster) resource information for use in uplink data transmission, radio resource information required for transmission of uplink data, and uplink data size information. . The terminal 520 may transmit an uplink signal and/or an uplink channel to the C-RAN 512 based on the obtained information on the uplink data transmission (S560).

6 is a flowchart illustrating an embodiment of a signal transmission/reception procedure using beamforming in a communication system, and FIG. 7 is a conceptual diagram illustrating an embodiment of beamforming results of communication nodes in a communication system.

Referring to FIG. 6, the communication system may include a C-RAN 610 including a CP 611 and an AN 612 and a terminal. CP 611 and AN 612 of FIG. 6 may be configured to be the same or similar to CP 611 and AN 612 illustrated in FIGS. 3 to 4. And, unlike shown in Figure 6, C-RAN 610 may include a single CP (611) and a plurality of AN (612). In addition, the terminal 620 of FIG. 6 may be configured identically or similarly to the terminals described in FIG. 1.

The communication nodes of FIG. 6 (eg, CP 611, AN 612, UE, etc.) may be communication nodes of a communication network using beamforming technology. For example, the C-RAN 610 controls the direction and region of a signal transmitted from the AN 612 using a beam-forming vector to determine the strength of the signal received from the terminal 620 and the like. Interference between signals can be minimized by controlling.

The C-RAN 610 (eg, CP 611) may extract beamforming vector information to be used by each AN 612 through channel state information of the pre-stored terminal 620 (S610). The C-RAN 610 may acquire channel state information from the terminal 620, and may be downlink channel state measurement information measured by the terminal 620 or measurement information of an uplink signal transmitted by the terminal 620. Can be. The CP 611 may generate beamforming vector information for the AN 612 to transmit the downlink signal and beamforming vector information for the UE 620 to transmit the uplink signal from the channel state information (S610). . The CP 611 may transmit antenna control information including the extracted beamforming vector information to the AN 612 (S620).

The AN 612 may acquire antenna control information from the CP 611 (S620), and may transmit a downlink signal and/or a downlink channel to the terminal 620 with a beam indicated by the antenna control information. (S630). The terminal 620 may receive a downlink signal and/or a downlink channel using one beam or a plurality of beams (S630). For example, the terminal 620 receives a downlink signal and/or a downlink channel through one beam as shown in FIG. 7(a), or two beams as shown in FIG. 7(b). Through this, a downlink signal and/or a downlink channel may be received (S630). The terminal 620 may obtain beamforming vector information for transmitting an uplink signal from the downlink signal.

The terminal 620 may transmit an uplink signal and/or an uplink channel to the AN 612 based on the set beamforming vector information (S640). For example, the terminal 620 may transmit an uplink signal and/or an uplink channel through two different beams as shown in FIG. 7(c), or illustrated in FIG. 7(d) As described above, an uplink signal and/or an uplink channel may be transmitted through one beam (S640).

The AN 612 may receive an uplink signal and/or an uplink channel from the terminal 620 through a beam indicated by the beamforming vector information (S650). According to an embodiment, the C-RAN 610 may receive an uplink signal and/or an uplink channel through a plurality of ANs 612 (S650). Each AN 612 performs a cooperative reception function to improve the uplink data demodulation performance of the CP 611. The CP 611 may acquire an uplink signal and/or an uplink channel from the AN 612, and demodulate and transmit the uplink signal and/or the uplink channel to the upper layer.

8 is a conceptual diagram showing a first embodiment of cluster management in a communication system, FIG. 9 is a conceptual diagram showing a second embodiment of cluster management in a communication system, and FIG. 10 is one embodiment of a cluster management operation in a communication system It is a flowchart showing an example.

8 to 10, the communication system may include a C-RAN and a terminal including CP and AN. CP and AN of FIGS. 8 to 10 may be configured the same or similar to CP and AN shown in FIGS. 3 to 4. And, unlike shown in Figure 10, C-RAN may include a CP and a plurality of AN. In addition, the terminals of FIGS. 8 to 10 may be configured the same or similar to the terminals described in FIG. 1.

8 to 9, the CP 811 of the communication system may acquire information from the terminal and allocate a cluster to the terminal. Specifically, referring to FIG. 8, CP 811 may be connected to a plurality of ANs 812-1 to 812-4, and each AN 812-1 to 812-4 may have the same cell identifier. . The terminal 820 may be located in one cluster generated by the CP 811. And, referring to Figure 9, CP 811 may be connected to a plurality of AN (812-1 to 812-4), each AN (812-1 to 812-4) may have a different cell ID have. And each of the terminals (821, 822) may be located in different clusters generated by the CP (811).

Referring to FIG. 10, the CP 811 of the communication system may transmit system information to the AN (S1010). System information may include a cell ID. Specifically, in the case of FIG. 8, the CP 811 may transmit system information including the same cell ID to the plurality of ANs 812-1 to 812-4 (S1010). In addition, in the case of FIG. 9, the CP 811 may transmit system information including different cell IDs to a plurality of ANs (S1010). Accordingly, the CP 811 may assign different cell IDs to the respective ANs 812-1 to 812-4.

The AN, which has obtained the cell ID from the CP 811, may transmit a downlink signal (eg, a reference signal or a data signal) to the terminal (S1020). In the case of FIG. 9, the plurality of ANs 812-1 to 812-4 may transmit a downlink signal using different cell identifiers (S1020).

The terminal 820 may receive a downlink signal and/or a downlink channel (S1020), and may transmit an uplink signal and/or an uplink channel including channel measurement information to the AN (S1030). The terminal 820 may transmit an uplink signal and/or an uplink channel through a single beam or an uplink signal and/or an uplink channel through a plurality of beams (S1030). 9, the terminal 820 performs a cell search procedure based on each downlink signal and/or downlink channel received through a plurality of ANs 812-1 to 812-4. Can be. The terminal 820 may transmit an uplink signal and/or an uplink channel including channel measurement information to an AN through an uplink resource corresponding to a downlink signal and/or a downlink channel successfully demodulated as a result of cell search. There is (S1030). The AN may acquire channel measurement information from an uplink signal and/or an uplink channel, and may transmit the acquired channel measurement information to the CP 811 (S1040).

The CP 811 may configure a cluster to be allocated to the terminal 820 based on the channel measurement information obtained from the terminal 820 (S1050). For example, referring to FIG. 8, the CP 811 may configure a cluster including AN1 to AN3 (812-1 to 812-3) and allocate it to the terminal 820 (S1050). In addition, referring to FIG. 9, the CP 811 may be assigned to the first terminal 821 by configuring a first cluster including AN1 to AN3 (812-1 to 812-3), and AN2 to AN4 (812-). 2 to 812-4) may be configured and assigned to the second terminal 822 (S1050). The CP 811 may transmit data, a reference signal, and an antenna control signal to the AN to transmit a signal to the terminal through only the configured cluster (S1060). The AN may transmit a downlink signal and/or a downlink channel to the terminal based on the antenna control signal obtained from the CP (S1070).

11 is a conceptual diagram illustrating a first embodiment of resource management in a communication system, and FIG. 12 is a flowchart illustrating a first embodiment of resource management in a communication system.

11 to 12, a communication system may include a C-RAN and a terminal 1120 including a CP 1111 and an AN 1112. CP 1111 and AN 1112 of FIGS. 11 to 12 may be configured the same or similar to CP 1111 and AN 1112 shown in FIGS. 3 to 4. And, unlike shown in Figure 2, C-RAN 1120 may include a single CP (1111) and a plurality of AN (1112). And the terminal 1120 of FIGS. 11 to 12 may be configured the same or similar to the terminals described in FIG. 1.

The terminal 1120 may communicate with the C-RAN 1120 by transmitting a reference signal and a data channel to the AN 1112 in the cluster. However, when the terminal 1120 moves, a resource for transmitting a reference signal (eg, SRS, RACH, etc.) to an adjacent AN 1112 located outside the current cluster may be changed. The C-RAN 1120 may select an AN 1112 to be added to the cluster of the terminal 1120 by measuring a reference signal obtained through the neighboring AN 1112. To perform mobility and connection management of the terminal 1120, the C-RAN 1120 may manage resources through a control plane of a cluster that is currently connected by performing the following operations.

The terminal 1120 may be connected to the control plane of the CP 1111 through the AN 1112 in the cluster. The control plane of the terminal 1120 may exist in the CP 1111. The CP 1111 may manage resources used for transmission of reference signals (SRS, RACH) of all terminals 1120 in the cluster.

The CP 1111 may transmit resource information for transmission of a reference signal to be used in a cluster to which the terminal 1120 belongs (S1210). The CP 1111 may provide resource information for transmitting a reference signal to each terminal 1120 in a periodic or request-response manner. Resource information for reference signal transmission may include bandwidth, hopping bandwidth, frequency location, configuration index, and cyclic shift information.

The resource for transmitting the reference signal may be dedicated resources for each terminal 1120, or may be a resource commonly used by all terminals 1120 in a cluster, and all terminals 1120 in a plurality of clusters are common. It may be a resource used as a.

The CP 1111 may provide information for transmitting a reference signal to the terminal 1120 by referring to the geographical location of the cluster to which the terminal 1120 belongs. Specifically, the CP 1111 may identify the AN 1112 adjacent to the terminal 1120 and provide resources for transmitting different reference signals for each of the adjacent AN 1112 to the terminal 1120.

The terminal 1120 may transmit the reference signal using the resource indicated by the resource information for transmitting the reference signal received from the CP 1111 (S1220). The terminal 1120 that transmits the reference signal has its own identification information (eg, identification information having uniqueness within the coverage of the C-RAN 1120) and reference signal transmission information (eg, the reference signal transmission time ( Frame or subframe) information, transmission power, and the like) may be additionally transmitted to the CP 1111 (S1220).

The C-RAN 1120 may receive a reference signal through the AN 1112 (S1220). The AN 1112 may measure the received reference signal to obtain reception information of the reference signal, and may transmit the received reference signal reception information to the CP 1120. The CP 1120 may obtain reception information of a reference signal from the AN 1112 (S1220). The received information may include information that can identify the AN 1112 that received the reference signal, information obtained as a result of receiving the reference signal at the physical layer, such as the strength of the received signal of the reference signal.

When the transmission resource used by the terminal 1120 to transmit the reference signal is not a dedicated resource for each terminal 1120, the CP 1111 crashes the reference signal, which is a situation where a plurality of terminals 1120 simultaneously transmit the reference signal. It can be determined whether or not (S1230).

When the CP 1111 detects a reference signal collision, the CP 1111 may request the terminals 1120 to retransmit the reference signal. Alternatively, the CP 1111 may change resources for transmitting reference signals to be allocated to the terminals 1120.

13 is a conceptual diagram illustrating a second embodiment of resource management in a communication system, and FIG. 14 is a flowchart illustrating a second embodiment of resource management in a communication system.

13 to 14, the communication system may include a C-RAN 1320 and a terminal 1330 including CP and AN, and may further include a macro base station 1310. CP and AN of FIGS. 11 to 12 may be configured the same or similar to CP and AN shown in FIGS. 3 to 4. In addition, the terminals 1330 of FIGS. 11 to 12 may be configured to be the same or similar to the terminals described in FIG. 1.

The terminal 1330 may communicate with the C-RAN 1320 by transmitting a reference signal and a data channel to an AN in the cluster. And when the terminal 1330 moves, the macro base station 1310 and the C-RAN 1320 may change resources for transmitting a reference signal (for example, SRS, RACH, etc.) other than the cluster in which the current terminal is located. . The macro base station 1310 and the C-RAN 1320 may select an AN to be newly included in the cluster of the terminal 1330 by measuring a reference signal received through the adjacent AN. The operation method of the macro base station 1310 and C-RAN 1320 managing the mobility and connection of the terminal 1330 through the control plane of the cluster currently being accessed is as follows.

The terminal 1330 is a macro base station 1310 (or a master base station) and a C-RAN 1320 base station (secondary base station) corresponding to the ANs and CPs in the cluster where the terminal 1330 of FIG. 13 is connected to a data plane. ) And dual connectivity (DC).

In a double connection, the user plane of the terminal 1330 may be connected to the macro base station 1310 and the C-RAN 1320, respectively. The control plane of the terminal 1330 may be connected only to the macro base station 1310. That is, the radio resource management layer of the terminal 1330 (eg, radio resource control (RRC)) may exist only in the macro base station 1310. An entity of a core (for example, a mobility management entity (MME) of 4G or an access and mobility management function (AMF) of 5G) that manages mobility of the terminal 1330 is a C-RAN (1320). ), and may be connected only to the macro base station 1310. The macro base station 1310 may manage macro-wide resources used for transmitting reference signals (SRS, RACH) of all terminals 1330 within macro coverage.

The macro base station 1310 may transmit resource information for transmission of a reference signal to be used in the cluster to which the terminal 1330 belongs (S1410). The macro base station 1310 may provide resource information for transmitting a reference signal to each terminal 1330 in a periodic or request-response manner (S1410). In the case of SRS, resource information for reference signal transmission may include bandwidth, hopping bandwidth, frequency location, configuration index, and cyclic shift information.

The resource for transmitting the reference signal may be dedicated resources for each terminal 1330, or may be a resource commonly used by all terminals 1330 in a cluster, and all terminals 1330 in a plurality of clusters are common. It may be a resource used as a.

The terminal 1330 may transmit a reference signal using the resource indicated by the resource information for transmitting the reference signal received from the macro base station 1310 (S1420). The terminal 1330 transmitting the reference signal has its own identification information (eg, identification information having uniqueness within the coverage of the macro base station 1310) and reference signal transmission information (eg, reference signal transmission time (frame Alternatively, subframe information, transmission power, and the like) may be additionally transmitted to the macro base station 1310 (S1420).

The C-RAN 1320 may receive a reference signal through AN (S1420). The AN may measure the received reference signal to obtain the reception information of the reference signal, and may transmit the received reference signal reception information to the CP. The CP may obtain reception information of a reference signal from AN. The received information may include information that can identify the AN that received the reference signal, information obtained as a result of receiving the reference signal at the physical layer, such as the received signal strength of the reference signal. The CP may transmit the received information to the macro base station 1310 through an inter-base station interface (eg, X2 interface) (S1430).

If the transmission resource used by the terminal 1330 to transmit the reference signal is not a dedicated resource for each terminal 1330, the macro base station 1310 is a reference signal that is a situation where a plurality of terminals 1330 simultaneously transmit the reference signal. A collision may be determined (S1430).

When the macro base station 1310 detects a reference signal collision, the macro base station 1310 may request the terminals 1330 to retransmit the reference signal. Alternatively, the macro base station 1310 may change resources for transmitting a reference signal to be allocated to the terminals 1330.

15 is a flowchart illustrating a first embodiment of a method for managing mobility of a terminal in a communication system.

Referring to FIG. 15, the communication system may include a C-RAN 1510 including CP and AN and a terminal 1520. In addition, the communication system may further include a general base station 1530 adjacent to the C-RAN 1510. CP and AN of FIG. 15 may be configured the same or similar to CP and AN shown in FIGS. 3 to 4. And unlike shown in Figure 15, C-RAN 1510 may include a CP and a plurality of AN. In addition, the terminal 1520 of FIG. 15 may be configured the same or similar to the terminals described in FIG. 1.

The general base station 1530 adjacent to a cell composed of a C-RAN 1510 base station may configure a separate cell to perform communication with terminals 1520 located in a separate cell. The base station adjacent to the C-RAN 1510 in the communication system may include a general (eg, HetNet, etc.) base station (eg, gNB, eNB, femtocell, macro cell, small cell, pico cell, etc.).

The terminal 1520 that transmits and receives data by accessing the C-RAN 1510 (S1510) may periodically receive a control signal from the general base station 1530 (S1520). The terminal 1520 may receive a signal and/or a channel including a synchronization signal, a reference signal, and system information from the general base station 1530 (S1520). The terminal 1520 may acquire channel control information of a neighbor cell from a control signal/and/or control channel, and may measure control signal strength such as a synchronization signal and a reference signal to obtain control signal measurement information.

The terminal 1520 may transmit channel control information and control signal measurement information obtained from the general base station 1530 to the C-RAN 1510 (S1530 ). The channel control information and control signal measurement information may include signal strength information and a cell identifier generated by a neighboring base station. In addition, the C-RAN 1510 may manage control signal measurement information transmitted by the terminal 1520.

The C-RAN 1510 may receive control signal measurement information from the terminal 1520 (S1530), and may determine whether the terminal is handed over based on the control signal measurement information (S1540). When the cell identifier included in the control signal measurement information is different from the cell identifier of the C-RAN 1510 base station, the C-RAN 1510 may start a handover procedure. The C-RAN 1510 may compare the antenna signal strength in the cluster of the terminal 1520 and the AN signal strength value around the cluster (S1540), and set a timer based on the comparison result to perform a handover procedure of the terminal 1520 Prepare.

When the signal strength of the control signal measurement information obtained from the terminal 1520 is greater than a preset threshold, the C-RAN 1510 may perform a handover operation. The C-RAN 1510 base station may transmit a handover request message of the terminal 1520 to the general base station 1530 (S1550). The general base station 1530 may check the terminal 1520 information and deliver a handover approval message to the base station of the C-RAN 1510 when the predetermined criteria are satisfied (S1560). The handover approval message may include control information necessary for communication of the terminal 1520. The C-RAN 1510 base station may initiate a handover of the terminal 1520 by transmitting a handover indication message to the terminal 1520 (S1570 ). The terminal 1520 may transmit an access request message requesting access by transmitting an uplink signal (eg, RACH, uplink data channel) to the general base station 1530 (S1580). The general base station 1530 may receive a connection request message and transmit a connection approval message to the terminal 1520 (S1590). The terminal 1520 may access the cell of the general base station 1530 to perform communication with the general base station 1530 and release the connection with the base station of the C-RAN 1510.

16 is a flowchart illustrating a second embodiment of a method for managing mobility of a terminal in a communication system.

Referring to FIG. 16, the communication system may include a C-RAN 1630 including a CP and AN and a terminal 1620. In addition, the communication system may further include a general base station 1610 adjacent to the C-RAN 1630. CP and AN in FIG. 16 may be configured the same or similar to CP and AN shown in FIGS. 3 to 4. And unlike the one shown in FIG. 16, the C-RAN 1630 may include one CP and a plurality of ANs. In addition, the terminal 1620 of FIG. 15 may be configured to be the same or similar to the terminals described in FIG. 1.

The general base station 1610 neighboring a cell composed of a C-RAN 1630 base station may configure a separate cell to communicate with terminals 1620 located in a separate cell. The base station adjacent to the C-RAN 1630 in the communication system may include a general (eg, HetNet, etc.) base station (eg, gNB, eNB, femtocell, macro cell, small cell, pico cell, etc.).

The terminal 1620 that transmits and receives data by connecting to the general base station 1610 (S1610) may periodically receive a control signal from the C-RAN 1630 (S1620). The terminal 1620 may receive a control signal including a synchronization signal, a reference signal, and system information (S1620). The terminal 1620 may acquire channel control information of a cell generated by the C-RAN 1630 from the control signal, and obtain control signal measurement information by measuring signal strengths such as a synchronization signal and a reference signal. .

The terminal 1620 may transmit channel control information and control signal measurement information obtained from the C-RAN 1630 to the general base station 1610 (S1630). The channel control information and the control signal measurement information may include signal strength information and a cell identifier generated by the C-RAN 1630. Also, the general base station 1610 may manage control signal measurement information transmitted by the terminal 1620.

The general base station 1610 may receive control signal measurement information from the terminal 1620 (S1630), and may determine whether the terminal is handed over based on the control signal measurement information (S1640). If the cell identifier included in the control signal measurement information is different from the cell identifier of the general base station 1610, a handover procedure may be started. The general base station 1610 may compare the antenna signal strength in the cluster of the terminal 1620 and the AN signal strength value around the cluster (S1640), and set a timer based on the comparison result to perform a handover procedure of the terminal 1620. Can be initiated.

When the signal strength of the control signal measurement information obtained from the terminal 1620 is greater than a preset threshold, the general base station 1610 may perform a handover operation. The general base station 1610 may transmit a handover request message of the terminal 1620 to the C-RAN 1630 (S1650). The C-RAN 1630 may check the terminal 1620 information and deliver a handover approval message to the general base station 1610 when the predetermined criteria are satisfied (S1660). The handover approval message may include control information required for communication of the terminal 1620. The general base station 1610 may initiate a handover of the terminal 1620 by transmitting a handover indication message to the terminal 1620 (S1670). The terminal 1620 may receive an access request message requesting access by transmitting an uplink signal (eg, RACH, uplink data channel) to the C-RAN 1630 (S1680). The C-RAN 1630 may receive a connection request message and transmit a connection approval message to the terminal 1620 (S1690). The terminal 1620 may access a cell of the C-RAN 1630 to perform communication with the C-RAN 1630 and release connection with the general base station 1610.

example The methods according to the invention are implemented in the form of program instructions that can be executed through various computer means and can be recorded on a computer readable medium. Computer-readable media may include program instructions, data files, data structures, or the like alone or in combination. The program instructions recorded on the computer-readable medium may be specially designed and configured for the present invention or may be known and usable by those skilled in computer software.

Examples of computer-readable media include hardware devices specially configured to store and execute program instructions, such as roms, rams, flash memories, and the like. Examples of program instructions include high-level language codes that can be executed by a computer using an interpreter, etc., as well as machine language codes such as those produced by a compiler. The above-described hardware device may be configured to operate with at least one software module to perform the operation of the present invention, and vice versa.

Although described with reference to the above embodiments, those skilled in the art understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. Will be able to.

Claims (1)

In the operating method of the central processor (CP) included in the centralized / cloud-RAN (radio access network) in the communication system,
Transmitting a first message to a terminal through a plurality of access nodes (ANs);
Receiving a second message in response to the first message through a plurality of ANs from the terminal;
Obtaining reception status information of the second message of each of the plurality of ANs;
Configuring a cluster including at least one AN among a plurality of ANs based on the reception status information; And
And transmitting a third message including resource information of the cluster and resource information of the one or more ANs to the terminal through the one or more ANs.

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