JP6068613B2 - Base station equipment - Google Patents

Description

  The present invention relates to a mobile communication base station apparatus.

  Conventionally, when a mobile station located in its own cell in mobile communication (hereinafter also referred to as “user equipment” (UE: User Equipment) as appropriate) moves to a cell of an adjacent base station while continuing data communication or the like. A base station apparatus that performs a handover (HO) process is known. Identification information for identifying the own station (own cell) and the adjacent base station (cell) from each other when this HO process is performed is assigned to each base station. For example, in a LTE (Long Term Evolution) mobile communication system, physical cell identifiers (PCI: Physical Cell Identifier) are assigned to each base station so as not to overlap each other in the range of 0 to 503 (for example, see Non-Patent Document 1). ).

  In addition, a small cell base station (hereinafter, referred to as a “small cell base station” as appropriate) having a smaller size than a macro cell is known. A macro cell base station (hereinafter referred to as a “macro cell base station” as appropriate) is systematically installed. On the other hand, small cell base stations are not installed systematically, and are installed in places where radio waves are weak, for example.

  The macro cell base station and the small cell base station overlap with adjacent base stations (cells) in order to share the PCI between the macro cell base station and the small cell base station in the very small range 0 to 503 that can be assigned by the PCI. PCI that cannot be assigned cannot be allocated, and handover (HO) processing may fail. In particular, when a plurality of small cell base stations are installed in the macro cell, each small cell base station must be assigned a PCI that is different from the PCI of the macro cell base station and does not overlap between the plurality of small cell base stations. Therefore, it is difficult to install a small cell base station. Further, the small cell base station has a short wireless communication distance, and only a mobile station that is very close to the small cell base station can be present.

In order to solve the above problem, a base station apparatus according to an aspect of the present invention is a base station apparatus provided in a small cell base station that performs radio communication with a mobile station in a mobile communication system, and a frequency used in the own station. A physical cell identifier that can be allocated in a frequency bandwidth different from that of the macro cell base station, comprising frequency bandwidth selection means for selecting a frequency bandwidth different from that of the macro cell base station installed around the own station as the bandwidth From this range, the physical cell identifier of the own station is assigned regardless of the physical cell identifier used by the macro cell base station.
Further, in the base station apparatus, priority information may be set for each frequency bandwidth usable in the mobile station so that the mobile station is preferentially located in the small cell of the own station. For example, the priority may be set for each frequency bandwidth so that the frequency bandwidth used in the local station is preferentially used in the mobile station over the frequency bandwidth used in the macrocell base station. Good. The priority information may be notified from the small cell base station to the mobile station and used when selecting a frequency bandwidth during connection processing in which the mobile station connects to the base station. In addition, the priority for each frequency bandwidth is also set in the macro cell base station, is notified to the mobile station from the macro cell base station, and is used to select the frequency bandwidth at the time of connection processing in which the mobile station connects to the base station. It may be used when.
In the base station apparatus, the physical cell identifier may be allocated autonomously by the base station apparatus or based on a control command received from a server provided on the mobile communication network side.
In the base station apparatus, the frequency bandwidth used in the macro cell base station may be 15 MHz or 20 MHz, and the frequency bandwidth used in the own station may be 10 MHz. The frequency bandwidth is an example and is not limited thereto.

  According to the present invention, there is an effect that physical cell identifiers that do not overlap with other neighboring base stations can be reliably assigned to the small cell base station.

Explanatory drawing which shows schematic structure of the mobile communication system by which the base station which has a base station apparatus which concerns on one Embodiment of this invention is arrange | positioned. FIG. 2A is a functional block diagram illustrating an example of a schematic configuration of a main part of a user apparatus that can communicate with the mobile communication system according to the present embodiment. (B) is a functional block diagram showing an example of a schematic configuration of a main part of a base station apparatus constituting the small cell base station of the present embodiment. Explanatory drawing which shows an example of PCI allocation in the case of additionally installing the small cell base station which concerns on this embodiment in a macrocell. Explanatory drawing which shows an example of PCI allocation in the case of newly installing the small cell base station which concerns on this embodiment in a macrocell.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory diagram showing a schematic configuration of a mobile communication system in which a base station having a base station apparatus according to an embodiment of the present invention is arranged. In FIG. 1, the mobile communication system according to the present embodiment is a communication system compliant with LTE specifications, and within a macro cell 10 </ b> A that is a radio communication area of the macro cell base stations 10, 11, and 12 and the one macro cell base station 10. A small cell base station 20 located in A small cell 20A that is a radio communication area of the small cell base station 20 is included inside the macro cell 10A. In the illustrated example, the user equipment (UE) 30 that is a mobile station is located in the small cell 20A, and is in a state in which wireless communication for telephone or data communication can be performed with the small cell base station 20. . Moreover, since the user apparatus 30 is located inside the macro cell 10A and at the outer edge of the small cell 20A (the boundary with the macro cell 10A), the radio signal emitted from the user apparatus 30 reaches the macro cell base station 10. Or a radio signal emitted from the macrocell base station 10 reaches the user apparatus 30. In addition to the macro cell base station 10, there are macro cell base stations 11 and 12 as base stations located around the small cell base station 20.

  In FIG. 1, three macro cell base stations 10, 11, 12, one small cell base station 20, and one user apparatus 30 are illustrated, but the macro cell base station is 2 or less or 4 or more. There may be a plurality of small cell base stations and a plurality of user apparatuses. In the following embodiments, the case where the small cell base station 20 performs processing and control described later will be described, but similar processing and control may be performed by another base station such as the macrocell base station 10. Further, a part common to the three macro cell base stations 10, 11, 12 will be described as the macro cell base station 10.

  The macrocell base station 10 is a wide-area base station that covers a macrocell that is a wide area having a radius of about several hundred m to several km that is installed outdoors in a mobile communication network. Sometimes referred to as “Macro e-Node B”, “MeNB” or the like. The macrocell base station 10 is connected to other base stations via a wired communication line, for example, and can communicate with a predetermined communication interface. Further, the macrocell base station 10 is connected to the core network of the mobile communication network via a line terminating device and a dedicated line, and can communicate with various nodes in the mobile communication network through a predetermined communication interface. Yes.

  The small cell base station 20, unlike a macro cell base station in a wide area, has a wireless communication range of several meters to several hundred meters, and can be installed indoors such as a general home, a store, an office, etc. It is a good base station. Since the small cell base station 20 is provided so as to cover an area smaller than the area covered by the wide-area macro cell base station in the mobile communication network, it is called a “femto base station” or “Home e-Node B”. Or “Home eNB”. The small cell base station 20 is also connected to the core network of the mobile communication network via a line terminating device and a broadband public communication line such as an ADSL (Asymmetric Digital Subscriber Line) line or an optical line, Can communicate with each other via a predetermined communication interface.

  Each of the macro cell base station 10 and the small cell base station 20 is assigned a physical cell identifier (PCI) for identifying each base station in the handover process of the user apparatus 30 or the like. This PCI is selected from a predetermined assignable range (for example, 0 to 503) independently set for each frequency bandwidth (for example, 20 MHz, 15 MHz, and 10 MHz) used in wireless communication with the user apparatus 30. Assigned. Therefore, for example, for a base station using 20 MHz as a frequency bandwidth, a base station using 15 MHz as a frequency bandwidth, and a base station using 10 MHz as a frequency bandwidth, overlapping PCIs are mutually used. Can be assigned. PCI allocation may be performed autonomously by the macro cell base station 10 and the small cell base station 20, or from each of the servers provided on the mobile communication network side of the macro cell base station 10 and the small cell base station 20. You may perform based on the received control command. PCI information assigned to each of the base stations 10 and 20 is also stored in the base station apparatus of the own station, and can be used for a handover process of the user apparatus 30 and the like.

  In addition, each frequency bandwidth has an index of priority that makes it easy to be in the service area. This priority can be set independently for each frequency bandwidth. Therefore, a priority can be set for each of the macro cell base station 10 using 15 MHz or 20 MHz as the frequency bandwidth and the small cell base station 20 using 10 MHz as the frequency bandwidth. In the present embodiment, for example, the priority is set to “high” for a frequency bandwidth of 10 MHz, and set to “low” for a frequency bandwidth of 15 MHz or 20 MHz. The priority information set in this way is notified to the mobile station and used when the frequency bandwidth is selected during the connection process in which the user apparatus 30 connects to the base station. Thereby, the user apparatus 30 can be easily located in the small cell 20A that uses the frequency bandwidth of 10 MHz.

  When a user apparatus (UE) 30 as a mobile station used by a user is located in the macro cell 10A or the small cell 20A, the user apparatus (UE) 30 is located between the macro cell base station 10 or the small cell base station 20 corresponding to the cell in which the user apparatus (UE) 30 is located. Wireless communication can be performed using a predetermined communication method and resource.

  FIG. 2A is a functional block diagram showing an example of a schematic configuration of a main part of the user device 30 that can communicate with the mobile communication system of the present embodiment. Moreover, FIG.2 (b) is a functional block diagram which shows an example of schematic structure of the principal part of the base station apparatus 200 which comprises the small cell base station 20 of this embodiment. In addition, since the base station apparatus of the macrocell base station 10 located in the periphery of the small cell base station 20 can be comprised similarly to the small cell base station 20, description is abbreviate | omitted.

  The user device 30 is configured using hardware such as a computer device having a CPU, a memory, etc., an external communication interface unit for the core network, a wireless communication unit, and the like, and the base stations 10 and 20 are executed by executing predetermined programs. Wireless communication and the like can be performed. The base station device 200 is configured using hardware such as a computer device having a CPU, a memory, and the like, an external communication interface unit for the core network, a wireless communication unit, and the like, and will be described later by executing a predetermined program. Performs various processes and controls such as storing and updating the list of neighboring base stations adjacent to the small cell base station 20 to be controlled, controlling downlink transmission power, measuring the interference level from neighboring cells, and suppressing interference. Or wireless communication with the user apparatus 30 can be performed.

  2A, the user device 30 includes a control unit 301, a duplexer (DUP) 302, a radio reception unit 303, an OFDM (Orthogonal Frequency Division Multiplexing) demodulation unit 304, a reception quality measurement unit 305, and broadcast information. And an extraction unit 306. Further, the user apparatus 30 includes a P-CQI (Periodic-Channel Quality Indicator) generation unit 307, an SC-FDMA (Single-Carrier Frequency-Division Multiple Access) modulation unit 308, and a radio transmission unit 309.

  The control unit 301 is configured by, for example, a computer device, controls each unit based on the broadcast information extracted by the broadcast information extraction unit 306, and transmits information on downlink signal reception quality measured by the reception quality measurement unit 305 to P- It functions as a means for passing to the CQI generation unit 307.

The radio reception unit 303 receives a radio signal modulated by the OFDM system for downlink defined in LTE from the base stations 10 and 20 via the antenna and duplexer 302.
The OFDM demodulator 304 demodulates a radio signal modulated by the OFDM method to obtain a received signal.
Reception quality measurement section 305 measures downlink reception quality (for example, field strength, reception level, etc.) when receiving a downlink radio signal from the reception signal demodulated by OFDM demodulation section 304, and measures the downlink reception quality measured. Information (CQI: Channel Quality Indicator) is passed to the control unit 301.
The broadcast information extraction unit 306 transmits broadcast information transmitted from the base stations 10 and 20 (for example, cell identification information such as CGI and cell ID, location registration area information such as TAC, etc.) from the reception signal demodulated by the OFDM demodulation unit 304. Control channel information, network version information, and the like), and the extracted broadcast information is passed to the control unit 301.
The P-CQI generating unit 307, based on the downlink reception quality information (CQI) and broadcast information received from the control unit 301, transmits a P-CQI as a measurement report (Measurement Report) periodically transmitted from the user apparatus 30. A transmission signal is generated.
The SC-FDMA modulation unit 308 modulates various baseband transmission signals using an SC-FDMA (single carrier frequency division multiple access) scheme for uplink defined in LTE. In particular, in this example, the SC-FDMA modulation unit 308 modulates the P-CQI transmission signal generated by the P-CQI generation unit 307 using the SC-FDMA method.
Radio transmission section 309 transmits a transmission signal such as P-CQI modulated by SC-FDMA modulation section 308 to base stations 10 and 20 via duplexer 302 and an antenna.

  Here, the P-CQI is a transmission signal including downlink reception quality information (CQI) periodically reported to the base stations 10 and 20 by the user apparatus 30 and cell identification information such as CGI and cell ID. In addition to the P-CQI, the user apparatus 30 may also periodically transmit a reference signal (SRS) used for measuring uplink reception quality at the base stations 10 and 20. As a physical channel for P-CQI transmission, for example, PUCCH (Uplink Control Channel) format 2 which is an uplink control channel defined by LTE is used. In addition, radio resources (time and frequency) used for transmission of P-CQI and SRS are designated by the base stations 10 and 20.

  2B, the base station apparatus 200 includes a radio signal path switching unit 201, a duplexer (DUP) 202, a downlink radio reception unit 203, an OFDM demodulation unit 204, a broadcast information extraction unit 205, and an uplink radio reception. Unit 206, SC-FDMA demodulation unit 207, and reception power measurement unit 208. Furthermore, the base station apparatus 200 includes a control unit 209 that controls transmission power and the like, a downlink signal generation unit 210, an OFDM modulation unit 211, and a downlink radio transmission unit 212. Note that the base station apparatus 200 may include an antenna.

The downlink radio reception unit 203 transmits a radio signal including broadcast information modulated by a downlink OFDM scheme stipulated in LTE via the antenna, the radio signal path switching unit 201, and the duplexer 202 via the macro cell base Receive from station 10.
The OFDM demodulator 204 demodulates a radio signal modulated by the OFDM method to obtain a received signal.
The broadcast information extraction unit 205 extracts broadcast information (for example, information of SIB2: System Information Block type 2) transmitted from the macrocell base station 10 from the reception signal demodulated by the OFDM demodulation unit 204, and extracts the extracted broadcast information. It passes to the control unit 209.
These downlink radio reception unit 203, OFDM demodulation unit 204, and broadcast information extraction unit 205 are information acquisition means for acquiring information on the electric field strength of the transmission signal transmitted from the macrocell base station 10 located in the vicinity of the own station, Also, it functions as a measuring means for measuring the interference level from the macro cell 10A located in the vicinity of the own station.

The uplink radio reception unit 206 receives an uplink radio signal transmitted from the user apparatus 30 communicating with the base station 200 via the radio signal path switching unit 201 and the duplexer 202. This radio signal includes a noise signal such as white noise generated by the uplink radio reception unit 206 or the like, and a radio signal in a predetermined radio resource and physical channel set for transmission of the above-described P-CQI and SRS. Further, when there is a user apparatus (MUE) communicating with the macro cell base station 10 adjacent to the small cell base station 20, the radio signal is transmitted from the user apparatus (MUE). Includes signal.
SC-FDMA demodulator 207 performs SC-FDMA demodulation processing on the received signal received by uplink radio receiver 206.

  The received power measuring unit 208 is configured to receive the predetermined radio resource and physical data obtained by the demodulation process in the SC-FDMA demodulation unit 207 based on the broadcast information from the neighboring macro cell base station 10 extracted by the broadcast information extraction unit 205. The power of the received signal in the channel is measured every single or multiple subframes. The received power measuring unit 208 is a predetermined frequency assigned to a signal (P-CQI or SRS) periodically transmitted from the user apparatus (MUE) to the macro cell base station 10 located in the vicinity of the own station. It functions as a measuring means for measuring power in the band.

  Further, the control unit 209 has a memory such as a RAM and a ROM, and stores storage means for storing PCI information assigned to the own station and a list of PCIs of peripheral base stations located around the own station, and the frequency It functions as a storage means for storing priority information for each bandwidth. Further, the control unit 209 selects a frequency bandwidth selection unit that selects a frequency bandwidth different from that of the macrocell base station 10 in which the own station is installed as a frequency bandwidth used by the own station for wireless communication with the user apparatus 30. Also works. For example, when 15 MHz or 20 MHz is used as the frequency bandwidth in the macro cell base station 10, 10 MHz different from 15 MHz or 20 MHz is selected as the frequency bandwidth. Also, the control unit 209 selects its own PCI from a range of physical cell identifiers (for example, 0 to 503) that can be allocated in a frequency bandwidth (for example, 10 MHz) different from that of the macrocell base station 10, and information on the PCI May function as a means for storing in the memory or the like.

The downlink signal generation unit 210 generates a downlink signal to be transmitted to the user apparatus 30 residing in the cell 20A of the own station.
The OFDM modulation unit 211 modulates the downlink signal generated by the downlink signal generation unit 210 using the OFDM method so that the downlink signal is transmitted with the transmission power determined by the control unit 209.
The downlink radio transmission unit 212 transmits the transmission signal modulated by the OFDM modulation unit 211 via the duplexer 202, the radio signal path switching unit 201, and the antenna.

  FIG. 3 is an explanatory diagram illustrating an example of PCI allocation when the small cell base station 20 according to the present embodiment is additionally installed in the macro cell 10A. In the example of FIG. 3, the small cell base station 20 has five small cell base stations 21 to 25 installed in the macro cell 10 </ b> A in which a frequency bandwidth of 15 MHz or 20 MHz is used for wireless communication with the user apparatus 30. It is an example in the case of installing additionally. The frequency bandwidth used in the existing small cell base stations 21 to 25 is 10 MHz, and 1 to 5 are assigned as PCIs to the small cell base stations 21 to 25, respectively.

  In FIG. 3, when the base station apparatus 200 of the small cell base station 20 searches for neighboring base stations, for example, information received from the macro cell base station 10, information received from a user apparatus in the area, mobile communication network If it is determined that the frequency bandwidth used in the macrocell base station 10 is 15 MHz or 20 MHz based on information received from a server provided on the side, the frequency bandwidth used for wireless communication with the user apparatus 30 10 MHz, which is different from 15 MHz or 20 MHz, is selected. Moreover, the base station apparatus 200 of the small cell base station 20 is based on, for example, information received from the existing small cell base stations 21 to 25 or the user apparatus 30, information received from a server provided on the mobile communication network side, or the like. Instead of selecting the PCI of the local station from the PCIs (1 to 5) allocated to the existing small cell base stations 21 to 25, the frequency does not depend on the PCI used by the macrocell base station 10. From the PCI range (0 to 503) that can be allocated when the bandwidth is 10 MHz, a PCI (for example, 6) that does not overlap with the PCI of the existing small cell base stations 21 to 25 is selected and allocated to the own station. This PCI allocation is not performed autonomously but may be performed based on a control command received from a server provided on the mobile communication network side.

  As described above, according to the example of FIG. 3, even when the small base station device 20 is additionally installed in a state where the plurality of small base station devices 21 to 25 are already installed in the macro cell 10 </ b> A, the other base stations 10 and 21 in the vicinity are provided. PCIs that do not overlap with each other can be reliably assigned to the additionally installed small base station apparatus 20.

  FIG. 4 is an explanatory diagram showing an example of PCI allocation when the small cell base station 20 according to the present embodiment is newly installed in the macro cell 10A. The example of FIG. 4 is an example in which the small cell base station 20 is newly installed in the boundary area between the macro cells 10A and 11A in which a frequency bandwidth of 15 MHz or 20 MHz is used for wireless communication with the user apparatus 30.

  In FIG. 4, when the base station apparatus 200 of the small cell base station 20 searches for neighboring base stations, for example, information received from the macro cell base station 10, information received from the user apparatus in the area, mobile communication network If it is determined that the frequency bandwidth used in the macrocell base station 10 is 15 MHz or 20 MHz based on information received from a server provided on the side, the frequency bandwidth used for wireless communication with the user apparatus 30 10 MHz, which is different from 15 MHz or 20 MHz, is selected. Then, regardless of the PCI used by the macrocell base station 10, one PCI (for example, 1) is arbitrarily selected from the PCI range (0 to 503) that can be allocated when the frequency bandwidth is 10 MHz. Assign to your station. This PCI allocation is not performed autonomously but may be performed based on a control command received from a server provided on the mobile communication network side.

  As described above, according to the example of FIG. 4, when a small cell base station 20 is newly installed in the boundary region between the macro cells 10 </ b> A and 11 </ b> A, a small base station device in which PCIs that do not overlap with the neighboring macro base stations 10 and 11 are newly installed. 20 can be reliably assigned.

10, 11 Macrocell base station (neighboring base station)
10A Macrocell 20 Small cell base station 20A Small cell 21-25 Small cell base station 30 User equipment (mobile station)

3GPP TS 36.211 "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical channels and modulation" V9.1.0

Claims (1)

A base station apparatus provided in a small cell base station that performs radio communication with a mobile station in a mobile communication system,
As a frequency bandwidth used by the own station, comprising a frequency bandwidth selection means for selecting a frequency bandwidth different from the macro cell base station installed around the own station,
From the range of physical cell identifiers that can be allocated in a frequency bandwidth different from that of the macro cell base station, the physical cell identifier of the own station is allocated regardless of the physical cell identifier used by the macro cell base station,
The priority is set for each frequency bandwidth so that the frequency bandwidth used in the local station is preferentially used in the mobile station over the frequency bandwidth used in the macrocell base station. Base station equipment .

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