KR20170131782A - Scheme and System for Fronthaul Interface of 5G RAN - Google Patents

Abstract

The present invention provides a method and a device for a fronthaul interface of a 5G base station having various base station separation structure shapes. According to an embodiment of the present invention, the device for a fronthaul interface of a 5G base station comprises: a central unit (CU) including a part of an independent network function realized in a virtual method; a distributed unit (DU) including the remaining of the independent network function realized in the virtual method; and a linkage interface of a fronthaul section between the CU and the DU.

Description

Technical Field [0001] The present invention relates to a front-end interface method and apparatus for a 5G base station,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for a front-hall interface of a 5G base station, and relates to a front-hall interface technology of a 5G radio access network base station.

One embodiment includes a CU that includes a portion of an independent network functionality implemented in a virtualization scheme, a DU that includes the remainder of the independent networking functionality implemented in a virtualization scheme, and an interface interface between the CU and the DUH It is possible to provide a front-hall interface device of a 5G base station.

FIG. 1 is a diagram illustrating a front hole configuration and interworking interface between a CU and a DU of a 5G wireless base station.
2 is a diagram showing an example of various separation structures between CU and DU of a 5G base station.
3 is a flowchart illustrating a handover of 5G DUs in the same 5G CU.
4 is a diagram illustrating a 5G DU handover procedure in the same 5G CU.
5 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.
6 is a diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference numerals even though they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

The wireless communication system in the present invention is widely deployed to provide various communication services such as voice, packet data and the like. A wireless communication system includes a user equipment (UE) and a base station (BS, or eNB). The user terminal in this specification is a comprehensive concept of a terminal in wireless communication. It is a comprehensive concept which means a mobile station (MS), a user terminal (UT), an SS (User Equipment) (Subscriber Station), a wireless device, and the like.

A base station or a cell generally refers to a station that communicates with a user terminal and includes a Node-B, an evolved Node-B (eNB), a sector, a Site, a BTS A base transceiver system, an access point, a relay node, a remote radio head (RRH), a radio unit (RU), and a small cell.

That is, the base station or the cell in this specification is interpreted as a comprehensive meaning indicating a partial region or function covered by BSC (Base Station Controller) in CDMA, NodeB in WCDMA, eNB in LTE or sector (site) And covers various coverage areas such as megacell, macrocell, microcell, picocell, femtocell and relay node, RRH, RU, and small cell communication range.

Since the various cells listed above exist in the base station controlling each cell, the base station can be interpreted into two meanings. i) the device itself providing a megacell, macrocell, microcell, picocell, femtocell, small cell in relation to the wireless region, or ii) indicating the wireless region itself. i indicate to the base station all devices that are controlled by the same entity or that interact to configure the wireless region as a collaboration. An eNB, an RRH, an antenna, an RU, an LPN, a point, a transmission / reception point, a transmission point, a reception point, and the like are exemplary embodiments of a base station according to a configuration method of a radio area. ii) may indicate to the base station the wireless region itself that is to receive or transmit signals from the perspective of the user terminal or from a neighboring base station.

Therefore, a base station is collectively referred to as a base station, collectively referred to as a megacell, macrocell, microcell, picocell, femtocell, small cell, RRH, antenna, RU, low power node do.

Herein, the user terminal and the base station are used in a broad sense as the two transmitting and receiving subjects used to implement the technical or technical idea described in this specification, and are not limited by a specific term or word. The user terminal and the base station are used in a broad sense as two (uplink or downlink) transmitting and receiving subjects used to implement the technology or technical idea described in the present invention, and are not limited by a specific term or word. Here, an uplink (UL, or uplink) means a method of transmitting / receiving data to / from a base station by a user terminal, and a downlink (DL or downlink) .

There are no restrictions on multiple access schemes applied to wireless communication systems. Various multiple access schemes such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), OFDM-FDMA, OFDM- Can be used. An embodiment of the present invention can be applied to asynchronous wireless communication that evolves into LTE and LTE-advanced via GSM, WCDMA, and HSPA, and synchronous wireless communication that evolves into CDMA, CDMA-2000, and UMB. The present invention should not be construed as limited to or limited to a specific wireless communication field and should be construed as including all technical fields to which the idea of the present invention can be applied.

A TDD (Time Division Duplex) scheme in which uplink and downlink transmissions are transmitted using different time periods, or an FDD (Frequency Division Duplex) scheme in which they are transmitted using different frequencies can be used.

In systems such as LTE and LTE-advanced, a standard is constructed by configuring uplink and downlink based on a single carrier or carrier pair. The uplink and the downlink are divided into a Physical Downlink Control Channel (PDCCH), a Physical Control Format Indicator CHannel (PCFICH), a Physical Hybrid ARQ Indicator CHannel, a Physical Uplink Control CHannel (PUCCH), an Enhanced Physical Downlink Control Channel (EPDCCH) Transmits control information through the same control channel, and is configured with data channels such as PDSCH (Physical Downlink Shared CHannel) and PUSCH (Physical Uplink Shared CHannel), and transmits data.

On the other hand, control information can also be transmitted using EPDCCH (enhanced PDCCH or extended PDCCH).

In this specification, a cell refers to a component carrier having a coverage of a signal transmitted from a transmission point or a transmission point or transmission / reception point of a signal transmitted from a transmission / reception point, and a transmission / reception point itself .

The wireless communication system to which the embodiments are applied may be a coordinated multi-point transmission / reception system (CoMP system) or a coordinated multi-point transmission / reception system in which two or more transmission / reception points cooperatively transmit signals. antenna transmission system, or a cooperative multi-cell communication system. A CoMP system may include at least two multipoint transmit and receive points and terminals.

The multi-point transmission / reception point includes a base station or a macro cell (hereinafter referred to as 'eNB'), and at least one mobile station having a high transmission power or a low transmission power in a macro cell area, Lt; / RTI >

Hereinafter, a downlink refers to a communication or communication path from a multipoint transmission / reception point to a terminal, and an uplink refers to a communication or communication path from a terminal to a multiple transmission / reception point. In the downlink, a transmitter may be a part of a multipoint transmission / reception point, and a receiver may be a part of a terminal. In the uplink, the transmitter may be a part of the terminal, and the receiver may be a part of multiple transmission / reception points.

Hereinafter, a situation in which a signal is transmitted / received through a channel such as PUCCH, PUSCH, PDCCH, EPDCCH, and PDSCH is expressed as 'PUCCH, PUSCH, PDCCH, EPDCCH and PDSCH are transmitted and received'.

In the following description, an indication that a PDCCH is transmitted or received or a signal is transmitted or received via a PDCCH may be used to mean transmitting or receiving an EPDCCH or transmitting or receiving a signal through an EPDCCH.

That is, the physical downlink control channel described below may mean a PDCCH, an EPDCCH, or a PDCCH and an EPDCCH.

Also, for convenience of description, the PDCCH, which is an embodiment of the present invention, may be applied to the PDCCH, and the PDCCH may be applied to the portion described with the EPDCCH.

Meanwhile, the High Layer Signaling described below includes RRC signaling for transmitting RRC information including RRC parameters.

The eNB performs downlink transmission to the UEs. The eNB includes a physical downlink shared channel (PDSCH) as a main physical channel for unicast transmission, downlink control information such as scheduling required for reception of a PDSCH, A physical downlink control channel (PDCCH) for transmitting scheduling grant information for transmission in a Physical Uplink Shared Channel (PUSCH). Hereinafter, the transmission / reception of a signal through each channel will be described in a form in which the corresponding channel is transmitted / received.

The existing LTE radio base stations can be separated into DU and RU. DU, which is mainly installed in the concentrated country, performs the physical layer, MAC, RLC, and RRC functions, and the RU installed at the cell site performs RF functions.

The DU and RU devices are connected via the CPRI-based front-hall interface, but it is difficult to ensure compatibility if the equipment manufacturer is different. In addition, 5G requires a large number of virtual server-based base stations to reliably provide various transmission speeds, reliability, delay requirements, and various services. Therefore, it is necessary to design the front-hall interface inside the virtual base station as open as possible have.

It is an object of the present invention to provide a method and apparatus for a front-end interface of a 5G base station having various base station isolation structure shapes.

The 5G radio access network (RAN) is mainly divided into 5G CU (Central Unit) installed at the national office and 5G DU (Distributed Unit) installed at the cell site. However, the 5G DU may include RF or antenna functions, or it may be separated, and if it is separate, it may be designed as a three-stage separation structure of CU, DU, and RF / antenna. Here, the interfacing interface of the front hall section between 5G CU and 5G DU is defined as Xf. In some cases, the front hall is sometimes referred to as Midhaul.

The 5G baseband baseband function is implemented as a virtualization method by independent network function (NF) of PHY, MAC, RLC, PDCP, and RRC type, and the upper protocol and lower protocol functions are appropriately separated and arranged to CU and DU respectively . Of course, the performance of NF-specific functions may vary.

In particular, 5G operators want to optimally build and operate various types of 5G base stations depending on wireless data traffic / coverage demand, equipment price, and cell site environment. In addition, when a base station is used in the case of using a millimeter wave frequency, there is a burden of building a large number of small cells. Therefore, in order to secure flexibility through multi-vendor compatibility, the frontal hall interface should be standardized as an open type.

FIG. 1 shows an open front hole configuration and interworking interface capable of inter-vendor interoperability between a CU and a DU of a 5G wireless base station.

In 5G, various base station functions and base station separated structure can be used according to the scenario of establishing the wireless network of the operator.

Figure 2 shows an example of various 5G base station internal isolation structures. Of course, other types of separate structures depending on the arrangement of the base stations NF are possible, but they are omitted here. Here, the Type 1 base station (PDCP-RLC separation structure) is a case where the RRC / PDCP NF is allocated to the CU and the RLC / MAC / PHY NF is allocated to the DU. Type 2 (MAC-PHY separation structure) The base station is a case where RRC / PDCP / RLC / MAC NF is allocated to CU and PHY NF is allocated to DU.

Type 1 base stations will be more suitable for mmWave base stations for broadband transmission because they can be easily interworked between 5G and LTE / WiFi base station equipment through PDCP and require small capacity front hole data transmission. Type 2 base stations are expected to have short transmission delay, Scheduling is possible, but it will be more suitable for base stations using 6GHz band frequency because large capacity front hole data transmission is required.

On the other hand, in DU, a radio resource management (RRM) function is added to support the mobility and the like, or an NF (eg, RRC) corresponding to the RAN control plane (CP) They will be deployable.

Thus, 1) another vendor's CU and DU may be configured with the same NF deployment, or 2) another vendor's CU and DU may be configured with different NFs. 1) is a case where both connected CUs and DUs are Type 1. 2), if the connection is changed to another DU, it will be necessary to change the transmission data according to the NF configuration information of the DU which is changed in the CU. The CU must include all base station NFs for interworking with other types of DUs, and the NF that is configured and required must be dynamically configurable via base station virtualization.

The front-hall interface Xf is a point-to-point logical interface between the CU and the DU, exchanging signaling information and performing data transfer. UP data may be transmitted through GTP-U, and CP Xf AP through SCTP.

The main features of the Xf interface are as follows:

- NF virtualization management of CU and DU

- Inter-DU Mobility Management

- Transmission control and management signaling between CU and DU

- User plane bearer or flow control between CU and DU

- Packet mapping and format conversion

- Load management

- Error handling

Here, an example in which handover occurs due to movement of UEs through different interfaces via the Xf interface will be described. The flow chart and the procedure of the handover between 5G DUs connected in the same 5G CU are shown in FIG. 3 and FIG. 4, respectively.

If beamforming transmission is supported at the 5G terminal and the base station, a number of beam information and measurements within the DU will be additionally required.

1. The 5G terminal reports the results of beam and cell measurements to the serving and neighboring DUs to the CU. CU ID and DU ID, which are unique identifiers of CU and DU, are used. The exchange of messages between CU and DU is transmitted through the front-hall interface Xf AP.

2. The CU determines that a DU handover is required depending on the beam and cell measurement results.

3. The CU selects the beam and cell of the target DU for optimal connection (eg, the best cell, the candidate cell, the optimal beam and beam pair, the candidate beam and beam pair, the cell ID, the beam ID, Beam Pair ID, etc.).

4. Based on the NF information of the collected target DU, the CU can configure the CU NF if necessary and change the transmission data accordingly. The RAN NF ID and the NF Set ID of the CU and DU that can identify the RAN NF can be used.

5. The CU requests a handover between the DUs (using the RRC Connection Reconfiguration message). Here, the handover includes cell and / or beam-to-beam handover.

6. The terminal performs a random access procedure (RACH) on the CU via the target DU. For example, a RACH Preamble message is used.

7. The CU sends a response to the random access procedure (RACH) to the terminal via the target DU.

8. When a data bearer and / or flow change is required, the CU makes a data bearer and / or flow modification request to the target DU. Radio bearer and wireless flow information and an identifier (ID). If additional bearer-to-flow conversions and mappings are required, the CU will do so.

9. The target DU responds to the data bearer and / or flow modification request to the CU.

10. Target DU performs radio resource allocation required for the corresponding terminal.

11. The UE informs the CU of the completion of the DU-to-DU handover via the target DU (using the RRC Connection Reconfiguration Complete message).

12. Release the radio resource of the terminal connected to the source DU.

As described above, according to the present invention, a large number of virtual server-based base stations will be utilized in order to stably provide various transmission speeds, reliability, delay requirements, and various services in the 5G. Through efficient interworking between other vendor 5G CU and DU base stations, it provides more stable connectivity and can reduce construction / operation costs.

5 is a diagram illustrating a configuration of a base station according to another embodiment of the present invention.

5, a base station 1000 according to another embodiment includes a control unit 1010, a transmission unit 1020, and a reception unit 1030.

The control unit 1010 includes a CU including a part of the independent network functions implemented by the virtualization method according to the present invention described above, a DU including the remainder of the independent network functions implemented in a virtualization manner, a front hole interval between the CU and DU Lt; RTI ID = 0.0 > BS < / RTI >

The transmitting unit 1020 and the receiving unit 1030 are used to transmit and receive signals, messages, and data necessary for carrying out the present invention to and from the terminal.

6 is a diagram illustrating a configuration of a user terminal according to another embodiment of the present invention.

6, a user terminal 1100 according to another embodiment includes a receiving unit 1110, a control unit 1120, and a transmitting unit 1130.

The receiving unit 1110 receives downlink control information, data, and messages from the base station through the corresponding channel.

In addition, the controller 1120 includes a CU including a part of independent network functions implemented by the virtualization method according to the present invention, a DU including the rest of the independent network functions implemented in a virtualization manner, a front hole between the CU and DU And controls the overall operation of the terminal necessary to perform the function of the interworking interface of the section.

The transmitter 1130 transmits uplink control information, data, and a message to the base station through the corresponding channel.

The standard content or standard documents referred to in the above-mentioned embodiments constitute a part of this specification, for the sake of simplicity of description of the specification. Therefore, it is to be understood that the content of the above standard content and some of the standard documents is added to or contained in the scope of the present invention, as falling within the scope of the present invention.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims (1)

A CU that includes some of the independent networking features implemented in a virtualized manner;
A DU comprising the remainder of the independent network functionality implemented in the virtualization scheme; And
The interlocking interface between the CU and the DU
Gt; 5G < / RTI > base station.

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