JP4547221B2 - Wireless base station equipment - Google Patents

Description

  The present invention relates to a radio base station apparatus used in a mobile communication system, and in particular, a radio communication function unit of a base station main body is arranged as a radio unit independently in a remote place, and the radio unit and base station main unit The present invention relates to a radio base station apparatus configured to perform signal transmission by connecting between them via, for example, an optical transmission path.

  Conventionally, a radio base station apparatus includes a wired transmission path function unit, a control function unit, a signal processing function unit, a modulation / demodulation and frequency conversion function unit, a transmission / reception amplification function unit, and the like, which are integrated. However, a system called RRH: Remote Radio Head has been proposed in order to reduce initial investment and operation costs in constructing a mobile communication system (see, for example, Patent Document 1).

  The RRH is a wireless base station device that is arranged in a remote place such as a tunnel or an underground shopping area with the wireless communication function unit including the modulation / demodulation and frequency conversion function unit and the transmission / reception amplification function unit as a wireless unit. The station main unit is connected using a wired transmission line such as an optical fiber.

  FIG. 5 is a configuration diagram showing an example of the RRH system. This RRH system includes base station main unit (BTS: Base Transceiver Station) 11 ', 12', 13 ', radio units (RRU: Remote Radio Unit) 21-29, a master station device 5, and a slave station device 6. ing. Each BTS 11 ′ to 13 ′ includes one IQ signal interface corresponding to transmission and reception of orthogonally modulated IQ signals, and is connected to the master station device 5 via optical cables C 11 to C 13, respectively. The RRUs 21 to 29 also have IQ signal interfaces, and are connected to the slave station devices 6 through optical cables C21 to C29, respectively. The master station device 5 and the slave station device 6 are connected by an optical cable C56, thereby enabling communication between the BTSs 11 'to 13' and the RRUs 21 to 29.

  Here, the operation of the wireless communication system will be described with reference to FIG. The BTSs 11 'to 13' transmit and receive IQ signals time-division multiplexed for 12 waves of 4 carriers and 3 sectors (4C3S), respectively. Therefore, IQ signals are transmitted / received in the optical cables C11 to C13 connected to the master station device 5 as data D10. In the optical cable C56 connecting the master station device 5 and the slave station device 6, IQ signals for 36 waves are time-division multiplexed and transmitted / received as data D10. Also, in the optical cables C21 to C29 connecting the slave station device 6 and the RRUs 21 to 29, IQ signals for four waves are time-division multiplexed and transmitted / received as data D20.

JP 2004-180220 A

  However, in the radio base station apparatus proposed in the related art, the master station apparatus 5 and the slave station apparatus 6 must each have a demultiplexing function for IQ signals according to the system configuration. That is, in communication from the BTSs 11 ′ to 13 ′ to the RRUs 21 to 29, the master station device 5 multiplexes the IQ signals for 12 waves received from the BTSs 11 ′ to 13 ′ into 36 waves to the slave station device 6. Send. Further, the slave station device 6 separates the IQ signals multiplexed in 36 waves received from the master station device 5 into 4 waves and transmits them to the RRUs 21 to 29. On the other hand, in communication from the RRUs 21 to 29 to the BTSs 11 ′ to 13 ′, the slave station device 6 multiplexes IQ signals for four waves received from the RRUs 21 to 29 into 36 waves, and the master station device 5 The IQ signals multiplexed into 36 waves need to be separated into 12 waves and transmitted to the BTSs 11 'to 13'. In addition, since the communication traffic of the mobile communication system varies greatly depending on the location, the introduction of a large-scale RRH system in a low-traffic area has a large burden as an initial investment.

  The present invention has been made paying attention to the above circumstances, and the purpose thereof is to reduce the burden of initial investment in system construction, and to be able to flexibly cope with the increase and decrease of system capacity at low cost. It is to provide a radio base station apparatus.

  In order to achieve the above object, a radio base station apparatus according to the present invention includes a base station main unit having a baseband processing function unit that performs processing related to connection and communication with a mobile station, and the base station main unit. And a plurality of wireless units including a wireless communication function unit that is connected via a transmission line and that transmits and receives a radio signal to and from a mobile station under the control of the baseband processing function unit. The base station main unit includes a plurality of communication interface function units corresponding to each of the plurality of radio units, and the communication interface function units independently transmit signals to the plurality of radio units. It is configured to send and receive.

  Therefore, according to the present invention, there is no need to provide a dedicated master station device and slave station device for performing demultiplexing in order to support the system. For example, the system capacity can be increased at low cost by using a commercially available WDM device. It is possible. Further, by providing the base station main unit with the communication interface for the number of sectors, it is possible to directly connect to the wireless unit. For this reason, it becomes possible to reduce the burden of the initial investment in system construction.

  In short, according to the present invention, it is possible to provide a radio base station apparatus that can reduce the burden of initial investment in system construction, and can flexibly cope with an increase or decrease in system capacity at a low cost. it can.

  FIG. 1 is a configuration diagram showing an embodiment of a radio base station system including a radio base station apparatus according to the present invention. This system integrates a plurality of radio base station apparatuses, and each radio base station apparatus includes one base station main unit (BTS) 11-13 and a plurality of radio units (RRU) 21-29. I have. Each of the RRUs 21 to 29 is arranged corresponding to a radio area called a sector. The BTSs 11 to 13 and the radio units (RRU) 21 to 29 are connected via optical wavelength division multiplexing (WDM) devices 31 and 32.

  The BTSs 11 to 13 include a baseband processing unit including a wired transmission path function unit, a control function unit, a signal processing function unit, and the like. The RRUs 21 to 29 include a wireless communication function unit including an antenna 4, a modulation / demodulation and frequency conversion function unit, a transmission / reception amplifier, and the like, and perform wireless communication with a mobile station (not shown). The WDM devices 31 and 32 are optical transmission devices that perform wavelength multiplexing and separation, and commercially available WDM devices can also be used. In this embodiment, it is assumed that 9 wavelengths can be multiplexed and separated.

  Each of the BTSs 11 to 13 includes three IQ signal interfaces corresponding to each sector. A wired transmission path is used for the connection between the BTSs 11 to 13 and the WDM device 31, and is configured by an optical fiber capable of communicating at an optical level, for example. Each of the BTSs 11 to 13 is connected to the WDM device 31 via the optical cables C11a, C11b, C11c, C12a, C12b, C12c and C13a, C13b, C13c by the IQ signal interface. The WDM device 31 and the WDM device 32 are connected by an optical cable C33 to perform wavelength multiplexing transmission.

  On the other hand, each of the RRUs 21 to 29 includes one IQ signal interface. The IQ signal interface is connected to the WDM device 32 through optical cables C21 to C29 formed of, for example, optical fibers. With such a connection configuration, transmission / reception of IQ signals between the BTSs 11 to 13 and the RRUs 21 to 29 is performed via the WDM devices 31 and 32.

The operation in the information transmission of the RRH system configured as described above will be described with reference to FIG. Note that information transmission between the BTSs 11 to 13 and the RRUs 21 to 29 is performed in four carriers and three sectors (4C3S).
First, an operation for transmitting IQ signals from the BTSs 11 to 13 to the RRUs 21 to 29 will be described. The BTSs 11 to 13 transmit IQ signals for four waves indicated by the data D1 to the WDM device 31 via the IQ signal interface corresponding to each sector. The WDM device 31 receives four-wave IQ signals corresponding to the sectors transmitted from the BTSs 11 to 13, and uses the wavelengths λ1 to λ9 previously associated with the sectors of the BTSs to store the data D3. Thus, the data is transmitted to the WDM device 32 via the optical cable C33. Based on the wavelengths λ1 to λ9 corresponding to each sector, the WDM device 32 separates the signals into four waves indicated by the data D2 corresponding to each sector and transmits the signals to the RRUs 21 to 29. Thus, IQ signals corresponding to the sectors transmitted by the BTSs 11 to 13 in the RRUs 21 to 29 can be received.

  Next, an operation in which the BTSs 11 to 13 receive IQ signals transmitted from the RRUs 21 to 29 will be described. The RRUs 21 to 29 transmit the IQ signals for four waves indicated by the data D2 to the WDM device 32 via the IQ signal interface corresponding to each sector. The WDM device 32 receives four-wave signals corresponding to the sectors of the RRUs 21 to 29, and uses the wavelengths λ1 to λ9 associated with the sectors of the BTSs 11 to 13 in advance to indicate the data D3. Then, wavelength multiplexing is performed, and transmission is performed toward the WDM apparatus 31 using an optical fiber. Based on the wavelengths λ1 to λ9 corresponding to each sector, the WDM apparatus 31 separates the signals into four waves indicated by data D1 corresponding to each sector and transmits the signals to the BTSs 11 to 13. Thus, the IQ signals corresponding to the sectors transmitted by the RRUs 21 to 29 in the BTSs 11 to 13 can be received.

  Next, the configuration of the RRH system according to communication traffic using the above-described radio base station apparatus will be described. FIG. 3 shows a configuration example of the RRH system at the time of low traffic. This system includes a BTS 11 and RRUs 21 and 22, and the BTS 11 and the RRUs 21 and 22 are connected via optical cables C112a and C112b, respectively. As described above, since the IQ signal interface corresponding to each sector is provided in the BTS 11, it is possible to directly connect to the RRUs 21 and 22, respectively. For this reason, it is not necessary to arrange a master station device and a slave station device having a demultiplexing function, and it is possible to provide an inexpensive system with a minimum configuration in a low traffic area.

  FIG. 4 shows a configuration example of the RRH system at the time of high traffic. In this system, WDM devices 31 and 32 are added between the BTS 11 and the RRUs 21 and 22, respectively. Then, the BTS 11 and the WDM device 31 are connected via optical cables C11a and C11b, respectively, the WDM device 31 and the WDM device 32 are connected via optical cable C33, and the WDM device 32 and the RRUs 21 and 22 are connected. Are connected via optical cables C21 and C22, respectively. With this configuration, it is possible to add more BTSs and RRUs without changing the configuration of each device, and the system capacity can be flexibly increased or decreased according to the state of communication traffic.

  As described above, in the above embodiment, each BTS 11 to 13 is provided with an IQ signal interface corresponding to each sector, that is, RRU 21 to 23, 24 to 26, 27 to 29, and these IQ signals are provided. The BTSs 11 to 13 are configured to transmit signals in a one-to-one relationship with the RRUs 21 to 23, 24 to 26, and 27 to 29 using the interface.

  Therefore, when the system operation mode is low traffic, it is possible to transmit IQ signals by directly connecting the BTS 11 and the RRUs 21 and 22 using the optical cables C112a and C112b as shown in FIG. . On the other hand, when the system operation mode is high traffic, as shown in FIG. 4, WDM devices 31 and 32 are arranged between the BTS 11 and the RRUs 21 and 22, and an optical cable C33 is connected between these WDM devices 31 and 32. Connect through. The IQ signals transmitted between the BTS 11 and the RRUs 21 and 22 are wavelength-multiplexed by the WDM apparatuses 31 and 32 and transmitted. By doing so, it is possible to efficiently transmit IQ signals even in a high traffic system.

  For this reason, there is no need to provide a dedicated master station device 5 and slave station device 6 for performing demultiplexing in order to correspond to the system configuration as in the prior art, leading to a reduction in development cost in the radio base station system. In addition, as shown in FIG. 3, in a low traffic area, the BTS 11 and the RRUs 21 and 22 can be directly connected to transmit and receive IQ signals, so that it is possible to reduce the burden of initial investment and operation costs. .

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, a four-carrier three-sector wireless base station system has been described as an example. However, the functional configuration, connection mode, and number of apparatuses can be variously modified without departing from the scope of the present invention. .

  In the above-described embodiment, the case where an optical cable is used as a transmission path for connecting between a BTS and an RRU has been described as an example. However, a metallic cable that transmits an electrical signal may be used, and a radio wave such as a microwave may be used. It is also possible to use a line. However, when this wireless line is used, consideration must be given so as not to adversely affect the wireless communication between the RRU and the mobile station.

  In short, the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

The block diagram which shows one Embodiment of a wireless base station system provided with the wireless base station apparatus concerning this invention. The figure which shows the operation | movement of the information transmission in the wireless base station system shown in FIG. The schematic block diagram of the system at the time of the low traffic using the wireless base station apparatus shown in FIG. The schematic block diagram of the system at the time of the high traffic using the radio base station apparatus shown in FIG. The block diagram which shows an example of a wireless base station system provided with the wireless base station apparatus by a prior art. The figure which shows the operation | movement of the information transmission in the wireless base station system shown in FIG.

Explanation of symbols

  11-13 ... BTS, 21-29 ... RRU, 31,32 ... WDM device, 4 ... antenna, C11a-C11b, C12a-C12b, C13a-C13b, C21-C29, C33, C112a, C112b ... optical cable, D1-D3 …data.

Claims (1)

A base station unit having a baseband processing function unit for performing processing related to connection and communication with a mobile station;
A plurality of radio units including a radio communication function unit that is connected to the base station main unit via an optical transmission line and that transmits and receives radio signals to and from the mobile station under the control of the baseband processing function unit In a radio base station apparatus comprising:
The base station main unit includes a plurality of communication interface function units corresponding to the plurality of radio units , and the first optical wavelength multiplex transmission is performed for each signal corresponding to the plurality of radio units by the communication interface function units. Output to the device,
The first optical wavelength division multiplexing transmission device converts the wavelength corresponding to each signal into a wavelength multiplexed signal, and outputs the wavelength multiplexed signal to the second optical wavelength multiplexing transmission device via the optical transmission line.
The second optical wavelength division multiplex apparatus separates and outputs a signal input via the optical transmission line based on a wavelength associated with each signal corresponding to the plurality of wireless units. ,
The radio base station apparatus , wherein the radio unit outputs a radio signal to the mobile station based on a signal input from the second optical wavelength division multiplex apparatus.

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