JP2012147193A - Base station system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station system where a radio communication disabled period is reduced.SOLUTION: A base station system 1 includes: multiple base band units (BBUs) 10; and radio frequency units (RFUs) 20 whose number is smaller than that of the BBUs 10. A common public radio interface (CPRI) switch 30 in the base station system 1 logically connects the multiple BBUs 10 to the multiple RFUs 20 by one-to-one relation, thereby to enable data transmission between the BBUs 10, a management system 16, and the RFUs 20. The CPRI switch 30 sets one BBU 10 as a preliminary BBU 10 which is not connected to any one of the RFUs 20.

Description

  The present invention relates to a base station system having a plurality of radio units and a plurality of radio control units.

  In 3GPP (Third Generation Partnership Project), a base station system such as LTE (Long Term Evolution) for which a standard has been established, a radio base station (LTE base station) performs BBU (Base Band Unit) processing at a baseband frequency. ) And an RFU (Radio Frequency Unit) that performs processing at a radio frequency. The BBU and the RFU are connected by a CPRI (Common Public Radio Interface) interface (see, for example, Patent Document 1). Moreover, as an installation form of the LTE base station, the BBU and the RFU may be remotely connected by an optical projection method.

JP 2010-226460 A

  In the LTE base station described above, when a failure occurs in a BBU, the RFU cannot operate until the BBU is restored. For this reason, wireless terminals in the wireless communication area corresponding to the RFU cannot perform wireless communication.

  In addition, for the purpose of securing a place for installing the communication apparatus including the BBU and RFU described above, the BBU is intensively arranged in the station building of the communication company or the line management company, and the RFU installed outside the station building In some embodiments, it is preferable to connect the BBU with a light projection method.

  In view of the above points, an object of the present invention is to provide a base station system that can efficiently connect a radio unit and a radio control unit.

  In order to solve the above-described problems, the present invention has the following features.

  A feature of the present invention is a base station system (base station system 1) having a plurality of radio units (RFU20) and a plurality of radio control units (BBU10), wherein the radio unit and the radio control unit The gist is to include a switch unit (CPRI switch 30) for switching connection.

  In such a base station system, the switch unit can appropriately perform a logical connection between the plurality of radio units and the plurality of radio control units. For this reason, an efficient connection between the wireless unit and the wireless control unit can be achieved.

  The gist of the present invention is that the radio unit waits for at least one unconnected spare radio control unit.

  In this case, when the wireless control unit stops operating due to a failure or the like, the wireless unit connected to the wireless control unit that has stopped operating can be connected to the standby wireless control unit by connection control of the switch unit. In this way, it is possible to reduce the period during which wireless communication is impossible.

  A feature of the present invention is that the switch unit logically connects the predetermined radio unit and the standby radio control unit when a failure occurs in the radio control unit to which the predetermined radio unit is connected. This is the gist.

  The gist of the present invention is that the switch unit performs a logical connection for transmitting user data.

  The gist of the present invention is that the switch unit performs logical connection for transmission of control data and management data.

  According to the present invention, it is possible to efficiently connect the radio unit and the radio control unit.

1 is an overall schematic configuration diagram of a base station system according to an embodiment of the present invention. It is a block diagram of the CPRI switch which concerns on embodiment of this invention. It is a figure which shows the 1st example of switch setting information which concerns on embodiment of this invention. It is a figure which shows the structure of the CPRI frame which concerns on embodiment of this invention. It is a figure which shows the 2nd example of switch setting information which concerns on embodiment of this invention. It is a flowchart which shows operation | movement of the CPRI switch which concerns on embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. Specifically, the configuration of the base station system, the operation of the CPRI switch, the operation / effect, and other embodiments will be described. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Configuration of Base Station System FIG. 1 is a schematic configuration diagram of a base station system according to the present embodiment. In the present embodiment, the base station system 1 is configured using LTE technology. A base station system 1 shown in FIG. 1 includes a BB (Base Band) module 15, a management system 16, and n RFUs (Radio Frequency Units) 20-1 to RFU20-n (hereinafter, RFU20-1 to RFU20-n). And an optical communication network 40 that performs multiplexed transmission by WDM (Wavelength Division Multiplexing), and a communication line 41 such as an optical fiber.

  In the present embodiment, the BB module 15, the management system 16, and the CPRI switch 30 are installed in a station building of a communication company or a line management company. On the other hand, the RFU 20-1 to RFU 20-n are installed at a remote location of the BB module 15, and are connected to the CPRI switch 30 via the optical communication network 40 by an optical projection method.

  The BB module 15 includes n + 1 BBUs (Base Band Units) 10-1 to BBU10-n + 1 (hereinafter, BBU10-1 to BBU10-n + 1 are collectively referred to as BBU10 as appropriate). In the present embodiment, the number of BBUs 10 is one more than the number of RFUs 20.

  The BBU 10 performs baseband frequency band processing. Specifically, the BBU 10 receives user data from an S-GW (Serving-Gate Way) (not shown) and generates IQ data that is a baseband frequency signal. Further, the BBU 10 transmits IQ data to the CPRI switch 30. The IQ data is given identification information (for example, an IP address) of the source BBU 10. Further, the BBU 10 receives the IQ data from the CPRI switch 30 and generates user data. The IQ data is given identification information (for example, an IP address) of the destination BBU 10.

  The management system 16 transmits control & management (C & M) data to the CPRI switch 30. The C & M data is given identification information (for example, an IP address) of the RFU 20 as a transmission destination.

  The RFU 20 performs radio frequency band processing. Specifically, the RFU 20 receives the CPRI frame obtained by converting IQ data transmitted by the BBU 10 and C & M data transmitted by the management system 16 via the CPRI switch 30. Further, the RFU 20 acquires IQ data and C & M data from the CPRI frame, modulates the data into a radio frequency band signal, and transmits the radio signal to a radio terminal (UE) (not shown) by radio communication.

  Also, the RFU 20 receives a radio frequency band signal from the UE. Further, the RFU 20 converts the received radio frequency band signal into a baseband frequency band signal to obtain IQ data. Further, the RFU 20 converts the IQ data into a CPRI frame and transmits it to the CPRI switch 30.

  The CPRI switch 30 switches logical connections between the BBUs 10-1 to BBU10-n + 1 and the RFUs 20-1 to RFU20-n. The CPRI switch 30 may switch the physical connection between the BBU 10-1 to BBU 10-n + 1 and the RFU 20-1 to RFU 20-n.

  FIG. 2 is a diagram showing the configuration of the CPRI switch 30. As shown in FIG. The CPRI switch 30 illustrated in FIG. 2 includes a communication control unit 31, a memory 32, a network 33, buffers 34-1 to 34-n (hereinafter, the buffers 34-1 to 34-n are collectively referred to as a buffer 34 as appropriate). CPRI port 35-1 through CPRI port 35-n (hereinafter, CPRI port 35-1 through CPRI port 35-n are collectively referred to as CPRI port 34 as appropriate). The buffers 34-1 to 34-n and the CPRI ports 35-1 to 35-n correspond one-to-one with the RFU 20-1 to RFU 20-n.

  The CPRI switch 30 and the BB module 15 are connected by a single communication line 41.

  The communication control unit 31 is configured by a CPU, for example. The communication control unit 31 logically connects the BBU 10 and the RFU 20 one to one. Specifically, the communication control unit 31 generates connection setting information in which the identification information of the BBU 10 that is a combination of logical connections and the identification information are associated with the RFU 20.

  FIG. 3 is a first example of connection setting information. The connection setting information shown in FIG. 3 associates the identification information of the BBU 10-1 and the identification information of the RFU 20-1, for example. This association indicates that the BBU 10-1 and the RFU 20-1 are logically connected. The connection between the BBU 10 and the RFU 20 is not limited to the connection between the BBU 10 and the RFU 20 owned by one communication company, and the connection between the BBU 10 and the RFU 20 when a plurality of communication companies use the BBU 10 and the RFU 20 separately. Can be.

  In the present embodiment, the number of BBUs 10 is one more than the number of RFUs 20. For this reason, the CPRI switch 30 logically connects the BBU 10 and the RFU 20 on a one-to-one basis, and sets one BBU 10 to a state where it is not connected to any RFU 20. The BBU 10 that is not connected to any of the RFUs 20 becomes a spare BBU 10.

  In FIG. 3, BBU10-n + 1 does not have an RFU 20 as a connection partner, and becomes a backup BBU10. The communication control unit 31 stores the generated connection setting information in the memory 32.

  Further, the communication control unit 31 monitors the BBU 10 logically connected to the RFU 20 among the BBUs 10-1 to BBU10-n + 1. For example, the communication control unit 31 transmits a monitoring signal to the BBU 10 at a predetermined cycle. When the BBU 10 receives a monitoring signal, it returns a response signal. The communication control unit 31 determines that the corresponding BBU 10 is normal when the response signal is received, and determines that a failure has occurred in the corresponding BBU 10 when the response signal is not received.

  When a failure occurs in the BBU 10, the communication control unit 31 switches the connection partner of the RFU 20 that is logically connected to the failed BBU 10 to the spare BBU 10.

  Specifically, the communication control unit 31 determines connection setting information including the identification information of the BBU 10 in which the failure has occurred from the connection setting information stored in the memory 32, and the RFU 20 included in the connection setting information. Delete identification information. Further, the communication control unit 31 generates new connection setting information in which the deleted identification information of the RFU 20 and the identification information of the backup BBU 10 are associated with each other, and stores them in the memory 32.

  FIG. 5 is a second example of connection setting information. Initially, it is assumed that a failure has occurred in the BBU 10-3 in a state where the connection setting information shown in FIG. In this case, the communication control unit 31 determines connection setting information including the identification information of the BBU 10-3, and deletes the identification information of the RFU 20-3 included in the connection setting information. Furthermore, the communication control unit 31 generates new connection setting information in which the deleted identification information of the RFU 20-3 is associated with the identification information of the backup BBU 10-n + 1. As a result, the connection setting information is updated from that shown in FIG. 3 to that shown in FIG.

  When data transmission from the BBU 10 to the RFU 20 is performed, the CPRI switch 30 performs the following first process. When data transmission from the RFU 20 to the BBU 10 is performed, the CPRI switch 30 performs the following second process. .

(First process)
The communication control unit 31 receives IQ data (downlink IQ data) from the BBU 10-1 to BBU 10-n + 1. The communication control unit 31 extracts the identification information of the source BBU 10 attached to the downlink IQ data. The communication control unit 31 reads the identification information of the RFU 20 from the connection setting information including the extracted identification information of the BBU 10 of the transmission source among the connection setting information stored in the memory 32. The read identification information of the RFU 20 is the identification information of the RFU 20 that is the transmission destination of the downlink IQ data.

  Next, the communication control unit 31 converts the downlink IQ data into a CPRI frame (downlink CPRI frame). FIG. 4 is a diagram illustrating a CPRI protocol. As shown in FIG. 4, the CPRI protocol defines electrical signal transmission (Electrical Transmission), optical signal transmission (Optical Transmission), and time division multiplexing (Time Division Multiplexing). In layer 2, IQ data, Vender Specific, Ethernet (registered trademark), HDLC, and L1 Inband Protocol are defined.

  The communication control unit 31 stores the downstream CPRI frame in the buffer 34 corresponding to the RFU 20 determined by the read identification information of the RFU 20.

  The communication control unit 31 receives C & M data from the management system 16. The communication control unit 31 extracts the identification information of the destination RFU 20 attached to the C & M data. Next, the communication control unit 31 converts the C & M data into a CPRI frame (downlink CPRI frame). The communication control unit 31 stores the downlink CPRI frame in the buffer 34 corresponding to the RFU 20 determined by the extracted identification information of the RFU 20.

  The communication control unit 31 transmits the downlink CPRI frame stored in the buffer 34 to the RFU 40 via the CPRI port 35 and the optical communication network 40 at a predetermined timing.

(Second process)
The communication control unit 31 stores the CPRI frame (upstream CPRI frame) transmitted from the RFU 20 via the optical communication network 40 and the CPRI port 35 in the corresponding buffer 34. Thereafter, the communication control unit 31 reads the upstream CPRI frame stored in the buffer 34 at a predetermined timing. Next, the communication control unit 31 converts the uplink CPRI frame into IQ data (uplink IQ data).

  Next, the communication control unit 31 determines the transmission destination of the uplink IQ data based on the identification information of the transmission destination BBU 10 included in the uplink IQ data. Further, the communication control unit 31 transmits the uplink IQ data to the BBU 10 that is the transmission destination.

(2) Operation of CPRI Switch FIG. 6 is a flowchart showing the operation of the CPRI switch 30.

  In step S101, the CPRI switch 30 logically connects the BBU 10 and the RFU 20 one to one. At this time, the CPRI switch 30 sets one BBU 10 as a spare BBU 10.

  In step S <b> 102, the CPRI switch 30 receives the downlink IQ data from the BBU 10 and the C & M data from the management system 16.

  In step S103, the CPRI switch 30 converts the received downlink IQ data and C & M data into a downlink CPRI frame.

  In step S104, the CPRI switch 30 stores the downlink CPRI frame in the buffer 34 corresponding to the transmission destination RFU 20.

  In step S105, the CPRI switch 30 transmits the downlink CPRI frame stored in the buffer 34 to the transmission destination RFU 20.

  In parallel with the operations from Step S102 to Step S105, the operations from Step S106 to Step S109 are performed.

  In step S <b> 106, the CPRI switch 30 receives the upstream CPRI frame from the RFU 20.

  In step S107, the CPRI switch 30 stores the uplink CPRI frame in the buffer 34 corresponding to the transmission source RFU 20.

  In step S108, the CPRI switch 30 converts the uplink CPRI frame stored in the buffer 34 into uplink IQ data.

  In step S109, the CPRI switch 30 transmits the uplink IQ data to the destination BBU 10.

  After the operation in step S105 or the operation in step S109, in step S110, the CPRI switch 30 determines whether or not a failure has occurred in the BBU 10 logically connected to the RFU 20.

  If there is no failure in the BBU 10 logically connected to the RFU 20, the operation after the reception of the downlink IQ data and C & M data in step S102 and the operation after the reception of the uplink CPRI frame in step S106 are performed. Repeated.

  On the other hand, when a failure occurs in the BBU 10 logically connected to the RFU 20, the CPRI switch 30 logically connects the RFU 20 connected to the failed BBU 10 and the spare BBU 10. Thereafter, the operation after step S102 and the operation after step S106 are repeated.

(3) Operation / Effect In this embodiment, the base station system 1 includes a plurality of BBUs 10 and a smaller number of RFUs 20 than the BBUs 10. The CPRI switch 30 in the base station system 1 logically connects the plurality of BBUs 10 and the plurality of RFUs 20 on a one-to-one basis, and enables data transmission between the BBU 10 and the management system 16 and the RFU 20. The CPRI switch 30 sets one BBU 10 as a spare BBU 10 that is not connected to any RFU 20.

  Further, when a failure occurs in the BBU 10 connected to the RFU 20, the CPRI switch 30 connects the RFU 20 connected to the failed BBU 10 and the spare BBU 10.

  For this reason, when the BBU 10 stops operating due to a failure, it is possible to reduce the period during which wireless communication between the RFU 20 and the UE cannot be performed.

  Further, by providing one spare BBU 10 for a plurality of BBUs 10 logically connected to the RFU 20, a one-to-one ratio between the BBU 10 logically connected to the RFU 20 and the spare BBU 10 is provided. The cost can be reduced compared to the case prepared in.

  In addition, since the plurality of BBUs 10 are installed in one place as the BB module 15, the cost of maintenance is reduced. In addition, since a plurality of BBUs 10 are aggregated, it is easy to secure an installation location, and costs associated with installation are reduced.

  Further, since the BB module 15 composed of a plurality of BBUs 10 and the CPRI switch 30 are connected by a single communication line 41, the line cost is reduced.

  Further, since the CPRI switch 30 also converts the C & M data from the management system 16 into a CPRI frame and transmits it to each RFU 20, the management system 16 and each RFU 20 can directly communicate on the IP layer. And the RFU 20 can be monitored using a management protocol.

(4) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  In the above-described embodiment, the case has been described in which the BB module 15 is configured by a plurality of BBUs 10 and one of the BBUs 10 is the spare BBU 10. However, the configuration of the BB module 15 and the ratio of the spare BBU 10 are not limited to this.

  For example, when one cell is composed of six sectors, the BB module 15 is composed of seven BBUs 10, and one of the seven BBUs 10 may be a spare BBU 10. When one cell is composed of three sectors, the BB module 15 may be configured by four BBUs 10, and one of the four BBUs 10 may be a spare BBU 10.

  In the above-described embodiment, the LTE base station system 1 has been described. However, the present invention is similarly applied to a base station system in which a radio control unit and a radio unit are connected by a CPRI interface. Can do.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  The base station system of the present invention can reduce the period during which wireless communication is impossible, and is useful as a base station system.

  DESCRIPTION OF SYMBOLS 1 ... Base station system, 10-1 thru | or 10-n + 1 ... BBU, 15 ... BB module, 16 ... Management system, 20-1 thru | or 20-n ... RFU, 30 ... CPRI switch, 31 ... Communication control part, 32 ... Memory 33 ... Network, 34-1 to 34-n ... Buffer, 35-1 to 35-n ... CPRI port, 40 ... Optical communication network, 41 ... Communication line

Claims (5)

A base station system having a plurality of radio units and a plurality of radio control units,
A base station system comprising a switch unit that switches connection between the radio unit and the radio control unit.   The base station system according to claim 1, wherein at least one standby radio control unit that is not connected to the radio unit waits.   The switch unit logically connects the predetermined radio unit and the standby radio control unit when a failure occurs in the radio control unit to which the predetermined radio unit is connected. The base station system described.   The base station system according to claim 1, wherein the switch unit performs a logical connection for transmitting user data.   The base station system according to claim 1 or 2, wherein the switch unit performs a logical connection for transmission of control data and management data.

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