JP2013038586A - Wireless base station, wireless terminal, signal measurement method, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless base station which can simply and properly measure reference signal reception intensity of neighboring cells.SOLUTION: Provided is a wireless base station comprising: an interference information acquisition unit for acquiring, from the outside, interference adjustment information about interference adjustment of a first base station for adjusting interference between the first base station and a second base station covering a smaller range than the first base station; and a reference signal measurement unit for measuring reference signals of neighboring cells by using the interference adjustment information acquired from the outside by the interference information acquisition unit.

Description

  The present disclosure relates to a radio base station, a radio terminal, a signal measurement method, and a computer program.

  With the spread of data communication terminals such as the UMTS (Universal Mobile Telecommunications System) system and the LTE (Long Term Evolution) system, data communication traffic is rapidly increasing. There is an urgent need for traffic countermeasures for indoor data communication, which accounts for a particularly large proportion.

  Indoor low-power base stations (femtocells) are connected to the Internet and operator core networks via broadband lines (hereinafter referred to as BB lines) such as ADSL (Asymmetric Digital Subscriber Line), FTTH (Fiber To The Home), and CATV. To do. A femtocell can be connected between a data communication terminal and the Internet without going through a core network, and is therefore expected as a countermeasure against the rapidly increasing traffic described above.

  Further, the femtocell is installed in a home or office by a user and can limit a usable user (terminal), and communicates with a data communication terminal at a short distance within a relatively small service area (coverage). Therefore, the femtocell provides a good communication quality and a high-throughput communication environment.

  In addition to femtocells, low-power base stations include picocells that do not limit the number of users that can be used. As with femtocells, they provide good communication quality and high-throughput communication environments, and traffic to the core network. Expected as a countermeasure, a technique for controlling the femtocell is also disclosed.

JP 2010-283756 A

  Since the femtocell needs to determine its maximum transmission power so as to avoid interference with other neighboring cells, it is necessary to measure the reference signal reception strength of the neighboring base stations at the time of startup or periodically. In the measurement of the reference signal reception strength by the conventional femtocell, it is assumed that the transmission power of the reference signal is always constant. Instantaneous radio waves are measured by measuring and averaging the reference signal in multiple subframes. Measurements were taken to avoid changes in the situation.

  However, when the interference adjustment method is taken between other base stations, if the transmission power differs depending on the subband within the downlink cell bandwidth, or there is a subframe that does not include the reference signal, There is a problem that the femtocell cannot stably measure with high accuracy.

  In addition, when there is a pico cell around the femto cell, and this pico cell receives a large amount of interference from the macro cell, in the subframe in which the macro cell reference signal or data is transmitted, the femto cell does not measure the pico cell reference signal. There is a problem that cannot be done accurately.

  Therefore, the present disclosure has been made in view of the above problems, and the object of the present disclosure is a novel and easy-to-accurate measurement of the reference signal reception strength of neighboring cells. An object is to provide an improved radio base station, radio terminal, signal measurement method, and computer program.

  According to the present disclosure, it relates to interference adjustment of the first base station for adjusting interference between the first base station and a second base station covering a narrower range than the first base station. A radio base comprising: an interference information acquisition unit that acquires interference adjustment information from outside; and a reference signal measurement unit that measures a reference signal of an adjacent cell using the interference adjustment information acquired from outside by the interference information acquisition unit. A station is provided.

  According to the present disclosure, the first base for adjusting the interference between the first base station and the second base station covering a range narrower than the first base station by the interference information acquisition unit. Interference adjustment information related to the interference adjustment of the station is acquired from the outside, and the reference signal measurement unit measures the reference signal of the adjacent cell using the interference adjustment information acquired from the outside by the interference information acquisition unit. This makes it possible to easily and accurately measure the reference signal reception strength of the neighboring cells.

  In addition, according to the present disclosure, the interference of the first base station for adjusting the interference between the first base station and the second base station covering a narrower range than the first base station. An interference information acquisition unit that acquires the interference adjustment information by specifying a cell identifier of a base station to a small base station management server that is notified of interference adjustment information related to adjustment, and the interference adjustment information acquired by the interference information acquisition unit. And a reference signal measurement unit that measures a reference signal of an adjacent cell.

  In addition, according to the present disclosure, the interference of the first base station for adjusting the interference between the first base station and the second base station covering a narrower range than the first base station. An interference information acquisition step of acquiring interference adjustment information related to adjustment from the outside, and a reference signal measurement step of measuring a reference signal of an adjacent cell using the interference adjustment information acquired from the outside in the interference information acquisition step. A signal measurement method is provided.

  In addition, according to the present disclosure, the first base for adjusting interference between the first base station and the second base station covering a range narrower than the first base station can be provided to a computer. An interference information acquisition step for acquiring interference adjustment information related to the interference adjustment of the station from the outside; a reference signal measurement step for measuring a reference signal of an adjacent cell using the interference adjustment information acquired from the outside in the interference information acquisition step; , A computer program is provided.

  As described above, according to the present disclosure, a new and improved radio base station, radio terminal, signal measurement method, and computer capable of easily and accurately measuring the reference signal reception strength of neighboring cells. A program can be provided.

It is explanatory drawing which shows the structural example of a general communication system. It is explanatory drawing which shows the example of the frame format of the downlink signal in the LTE system of frequency division multiplexing (FDD). It is explanatory drawing which shows the example of the interference avoidance by a base station. It is explanatory drawing which shows the example of the interference avoidance by a base station. It is explanatory drawing which shows the sub-frame (Almost Blank Subframe (ABS)) which does not insert data and CRS in the specific sub-frame of a macrocell. It is explanatory drawing which shows the example of the pattern of ABS. It is explanatory drawing which shows the whole structure of the data communication system which concerns on one Embodiment of this indication. It is explanatory drawing which shows the structure of the control part 22 contained in the femtocell 20 which concerns on one Embodiment of this indication. 5 is a flowchart showing an operation of the data communication system 1 according to an embodiment of the present disclosure. 5 is a flowchart showing an operation of the data communication system 1 according to an embodiment of the present disclosure. 5 is a flowchart showing an operation of the data communication system 1 according to an embodiment of the present disclosure. 5 is a flowchart showing an operation of the data communication system 1 according to an embodiment of the present disclosure. 5 is a flowchart showing an operation of the data communication system 1 according to an embodiment of the present disclosure. 3 is an explanatory diagram illustrating a configuration example of a wireless communication unit 24 in a femtocell 20 according to an embodiment of the present disclosure. FIG. 3 is an explanatory diagram illustrating a configuration example of a wireless communication unit 24 in a femtocell 20 according to an embodiment of the present disclosure. FIG.

  Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

The description will be made in the following order.
<1. Prior art and its problems>
<2. One Embodiment of the Present Disclosure>
[2-1. Overall configuration of data communication system]
[2-2. Operation of data communication system]
[2-2-1. First operation example]
[2-2-2. Second operation example]
[2-2-3. Third operation example]
[2-2-4. Fourth operation example]
[2-2-5. Fifth operation example]
[2-3. Configuration example of wireless communication unit]
<3. Summary>

<1. Prior art and its problems>
First, in describing a preferred embodiment of the present disclosure in detail, the related art and its problems will be described.

  FIG. 1 is an explanatory diagram illustrating a configuration example of a general communication system. The Internet, a core network A, and a core network B are connected to each other, and a macro cell and a pico cell are connected to the core networks A and B, respectively. FIG. 1 illustrates a macro cell terminal (Macro UE) communicating with a macro cell of the core network A and a pico cell terminal (Pico UE) communicating with a pico cell.

  FIG. 1 also shows a femtocell connected to the Internet and a femtocell terminal (Femto UE) that communicates with the femtocell. Further, FIG. 1 also shows a femtocell management server (SON server) for managing the femtocell.

  The maximum transmission power of the radio base station refers to an allowable value of the total power transmitted by the radio station within the allowed frequency band. For example, a downlink physical channel and signal transmitted from an LTE base station to a terminal include a physical downlink shared channel (PDSCH) that transmits data for individual users, and a physical downlink control channel (PDCCH) that transmits downlink control information. ), A physical broadcast channel (PBCH) for transmitting system information necessary for the terminal to access the network, and a physical hybrid ARQ notification channel for transmitting an acknowledgment for indicating whether the transport block should be retransmitted to the terminal (PHICH), a physical control format notification channel (PCFICH) for transmitting information necessary for PDCCH decoding, and a downlink reference signal (Reference) used for downlink channel estimation in order to perform synchronous detection in a downlink physical channel in which a terminal fluctuates. S gnal), and the like first synchronization signal (PSS) and a second synchronizing signal to be able to detect the physical layer cell ID (PCI) of the cell helps cell search terminal (SSS). The physical downlink shared channel and the like vary in power according to the number of users served by the base station, and the maximum transmission power indicates the maximum value allowed for the total power of all these channels.

  The terminal performs synchronization establishment and channel estimation by receiving the synchronization reference signal transmitted from the radio base station, and transmits and receives data to and from the radio base station. Therefore, it is necessary to enable the terminal to receive the synchronization reference signal with good reception quality in order to provide good communication quality. This synchronization reference signal refers to, for example, a common pilot channel (CPICH) in the UMTS scheme, and a cell-specific reference signal (CRS) that is one of the downlink reference signals in the LTE scheme. These synchronization reference signals are transmitted at a constant transmission power at a fixed power ratio (for example, maximum transmission power −10 dB) with respect to the maximum transmission power.

  A wide area base station (macrocell) that provides wide area coverage and large user capacity is a base station that determines the installation location and maximum transmission power after conducting a detailed field survey, unless there is a design change of the wireless network, Normally, the maximum transmission power of the wide area base station is not changed. On the other hand, the femtocell is a base station that is arbitrarily installed by the user, and since the operator cannot grasp when to start the operation, the femtocell has a function for autonomously setting radio parameters such as optimum maximum transmission power. Needed. In addition to the maximum transmission power, the radio parameters include, for example, a carrier frequency, a base station ID, and a scramble code in the case of the UMTS system.

  Interference is an important issue because femtocells have a mechanism to limit the number of users (terminals) that can be used. Avoiding interference between femtocells and macrocells operated at the same frequency is essential for femtocells. It becomes. A terminal that is served from a macro cell that is not allowed to access the femto cell (macro cell terminal) also moves to the femto cell even when the downlink signal from the femto cell becomes larger than the downlink signal from the macro cell when approaching the femto cell. The downlink signal transmitted from the femtocell cannot be handed over to the cell, and causes interference noise for the macrocell terminal. On the other hand, for a terminal served by a femtocell (femtocell terminal), a downlink signal transmitted from the macro cell becomes interference noise.

  When installing a femto cell, it is necessary to set radio parameters in the femto cell to avoid interference with the macro cell so that communication is not disabled due to interference from the femto cell when the macro cell terminal approaches the femto cell. Among the radio parameters, regarding the setting of the carrier frequency, base station ID, and UMTS scramble code, for example, the femtocell accesses the femtocell management server (SON server) at the time of activation and refers to a list operated by the same operator. There is a method of selecting so as not to overlap with the usage status of the surrounding base stations.

  On the other hand, with regard to the maximum transmission power among the radio parameters, the femtocell measures the strength of radio waves transmitted by neighboring base stations, and sets the maximum transmission power of the femtocell to suppress interference with these neighboring base stations as much as possible. It is necessary to set it independently.

  For example, 3GPP TR 36.992 provides guidelines regarding a method for determining transmission power of an LTE femtocell (HeNB). In this guideline, an example of a method for determining the maximum transmission power of a femtocell by measuring the power of a reference signal of a base station using the same frequency channel around the femtocell is shown by the following equation.

These parameters are: It can be given from the femtocell management server. If the femtocell does not detect another base station on the same channel, the value allowed by P _max may be adopted as the maximum transmission power.

  Further, the femtocell needs to limit the maximum transmission power of the femtocell in order to suppress interference with a base station using an adjacent frequency channel. In particular, when another operator is operating the adjacent frequency channel, the radio wave of the femtocell interferes with another operator's terminal using the adjacent channel, and does not interfere with the service of another operator. A method for limiting the maximum transmission power of the femtocell has been standardized.

  A femto cell having a downlink reception function, for example, as described below, performs a cell search for a neighboring base station in the same operation as a terminal, obtains frame synchronization with the neighboring base station, and requires a broadcast channel or the like. It becomes possible to decode the system information and measure the strength of the reference signal.

  FIG. 2 is an explanatory diagram illustrating an example of a frame format of a downlink signal in the frequency division multiplexing (FDD) LTE scheme. The femtocell detects PCI and frame timing by detecting a first synchronization signal (PSS) and a second synchronization signal (SSS) using a signal sequence corresponding to a physical layer cell ID (PCI) allocated to each base station. And detect. In addition, since the arrangement of the PSS and SSS in the radio frame is different between the frequency multiplexing method (FDD) and the time multiplexing method (TDD), the femtocell is simultaneously searched for the PSS and SSS, and the cell being searched is the same as the FDD system. It can also be determined which of the TDD systems is used. In order to enable simple cell search even if the system bandwidth of the base station is unknown, the synchronization signal is always arranged in the band of the central 6 resource blocks regardless of the service bandwidth.

  The system information is mapped to the physical broadcast channel (PBCH) and the physical downlink shared channel (PDSCH).

  A master information block (MIB) such as a downlink cell bandwidth, the number of transmission antennas, and a structure of control information is mapped to the PBCH. PDSCH includes information on whether the terminal can be in this cell, uplink bandwidth, random access channel parameters, parameters for uplink transmission power control, information on cell reselection, information on neighboring cells, etc. The system information block (SIB) is mapped. The femto cell that detects the frame timing decodes the MIB mapped to the PBCH, knows the downlink cell bandwidth from the MIB, knows the location of the PDSCH resource block to which the SIB is allocated after receiving the PDCCH, and responds Decode SIB information from PDSCH.

  As shown in FIG. 2, the cell-specific reference signal (CRS) is inserted into the first and last third OFDM symbol in the slot at intervals of 6 subcarriers in the frequency domain. There are several types of subcarrier positions where the cell-specific reference signal is initially arranged according to the physical layer cell ID (PCI), and FIG. 2 shows one of these patterns. Also, in the case of downlink multiple antenna transmission, an offset is added to the OFDM symbol and subcarrier for each antenna port so that the reference signals for each antenna do not overlap.

  Since the femtocell knows the position of the resource element in which the cell-specific reference signal (CRS) to be detected is inserted from the already detected PCI and the number of transmitting antennas, the received strength can be measured.

  A base station must suppress interference with other base stations in order to ensure its own coverage and communication quality. Between base stations operated at the same carrier center frequency, for example, in the LTE scheme, interference can be suppressed by resource block (or subband) separation and transmission power control. In addition, interference between base stations operated at different carrier center frequencies can be suppressed by separation based on filter frequency selectivity and transmission power control.

  3 and 4 are explanatory diagrams illustrating an example of interference avoidance by the base station. FIG. 3 shows a fractional frequency reuse in which subband frequencies allocated to users at a cell edge that may receive interference between macrocells operated at the same carrier center frequency do not overlap between adjacent base stations. FIG. 4 is an example of a method using Soft Frequency Reuse (SFR).

  The base station transmits information on the transmission power for each subband (relative narrowband transmit power (RNTP)) transmitted by the base station as information on the frequency reuse used by itself to other adjacent base stations. It can be notified by a message using the inter-backbone line (X2). Other base stations that receive this message can arrange the sub-band frequencies assigned to the cell edge users so that they do not overlap each other, thereby forming the entire network.

  The macro cells are cover areas of the same size, and are arranged as shown in FIG. 3, which covers a wide area with a plurality of macro cells. On the other hand, the pico cell has a smaller cover area than the macro cell, and is arranged to overlay the macro cell as shown in FIG. 1 for the purpose of covering a local area. Therefore, the interference between the macro cell and the pico cell becomes very severe.

  Accordingly, in order to protect the control channel used by the user of the pico cell from interference from the macro cell, a subframe (Almost Blank Subframe (ABS)) in which no data or CRS is inserted into a specific subframe of the macrocell is used as shown in FIG. Used, the pico cell can transmit important signals to the terminal at this time.

  The macro cell notifies the subframe number of the Almost Blank Subframe (ABS) used by the macro cell to the pico cell in the coverage area of the macro cell by a message (ABS information) using the inter-base station backbone line (X2). Can do. The pico cell that has received this message can avoid interference by assigning important information to the user of the pico cell to this subframe.

  Due to the relationship of the period of the retransmission confirmation response of the LTE transport block, the subframe pattern using the ABS is repeated at 40 ms. FIG. 6 is an explanatory diagram showing an example of an ABS pattern. FIG. 6 shows examples of four types of ABS patterns according to the required frequency of ABS. For example, in the case of FDD, a retransmission confirmation response (ACK / NACK) from the pico cell for uplink data transmitted from the terminal is issued every 8 subframes (8 ms), so that ACK / NACK is protected from severe interference from the macro cell. It is desirable for ABS to occur in 8 ms. Since subframe # 5 is a subframe for transmitting a system information block, it cannot be set in the ABS. As shown in FIG. 6, a bit map indicating whether or not 40 individual subframes for 40 ms are ABSs is reported between base stations as ABS information.

  The terminal must measure and report the reference signal reception strength of the serving cell and the reference signal reception strength of the adjacent cell to a base station (serving cell) such as a macro cell or a pico cell in which the terminal is located. This is because the cellular system helps the terminal to select the optimal base station as the terminal moves, and supports the terminal to continue data communication while moving. Information on neighboring cells is reported to the system information block of the serving cell, and the terminal can easily obtain neighboring cell information. In addition, a terminal that uses a base station in which interference adjustment is performed as a serving cell can receive information on a subband and a subframe to be measured (measurement target information) from the serving cell through higher layer signaling. For example, an ABS pattern used by the base station is shown in the measurement target information.

  Since the femtocell needs to determine its maximum transmission power so as to avoid interference with other neighboring cells, it is necessary to measure the reference signal reception strength of the neighboring base stations at the time of startup or periodically. In the measurement of the reference signal reception strength by the conventional femtocell, it is assumed that the transmission power of the reference signal is always constant. Instantaneous radio waves are measured by measuring and averaging the reference signal in multiple subframes. Measurements were taken to avoid changes in the situation.

  However, when the interference adjustment method is taken between other base stations, if the transmission power differs depending on the subband within the downlink cell bandwidth, or there is a subframe that does not include the reference signal, There is a problem that the femtocell cannot stably measure with high accuracy.

  In addition, when a pico cell exists in the vicinity of the femto cell and the pico cell receives a large amount of interference from the macro cell, the measurement of the reference signal of the pico cell by the femto cell is accurate in the subframe in which the macro cell reference signal and data are transmitted. There is a problem that can not be done.

  The number of femtocells in a macro cell is enormous, and because the femtocell is installed and activated by the user, the operator cannot grasp the detailed existence of the femtocell, and a high-speed backbone line is also provided between the macrocell and the femtocell. For example, it is difficult to notify the femtocell of information related to interference adjustment from the macrocell when the femtocell is activated.

  In addition, special messages that are not standardized cannot be exchanged between different operators of adjacent frequency channels, and it is difficult to notify the femtocell of information related to interference adjustment from a macrocell of another operator.

  The usage status of Frequency Reuse (spatial reuse of the same frequency) in a macro cell can be understood if the femto cell closely measures the reference signal strength for each resource block, but this work increases overhead. In order to measure a reference signal with high accuracy with an appropriate overhead, a method is required in which the femtocell obtains information on the power and subframe of the reference signal of the neighboring base station (information on interference adjustment).

  Therefore, the present disclosure has been made in such a background, and not only transmits information related to interference adjustment between base stations and terminals that cause interference or interference, but also does not directly relate to interference adjustment. The station and the terminal can detect information related to interference adjustment used by the neighboring base stations so that the intensity measurement of the neighboring base stations can be accurately performed.

  For example, the femtocell obtains information on the transmission power of the reference signal for the resource block in the neighboring cell and information on the subframe number including the reference signal via the femtocell management server, so that the reference of the neighboring cell by the femtocell is obtained. It is characterized in that the signal reception intensity can be measured easily and accurately.

  The prior art, its problems, and features of the present disclosure have been described above. Next, the overall configuration of the data communication system according to an embodiment of the present disclosure will be described.

<2. One Embodiment of the Present Disclosure>
[2-1. Overall configuration of data communication system]
FIG. 7 is an explanatory diagram illustrating an overall configuration of a data communication system according to an embodiment of the present disclosure. Hereinafter, the overall configuration of the data communication system according to an embodiment of the present disclosure will be described with reference to FIG.

  The data communication system 1 shown in FIG. 7 is a data communication system including femtocells. As shown in FIG. 7, the data communication system 1 according to an embodiment of the present disclosure includes data communication terminals 10a, 10b, and 10c, a femtocell (indoor small base station) 20, the Internet 31, and a femtocell gateway. 32, a core network 33, a BB line modem 34, a macro cell (outdoor base station) 35, a pico cell 36, a subscriber information server 37, and a femto cell management server 40.

  The macro cell (outdoor base station) 35 is a base station that covers a relatively wide range with a cell radius of several hundreds to several tens of kilometers. The femtocell (indoor small base station) 20 is a base station with a small transmission power having a cell radius of about several tens of meters. The femtocell 20 can be installed and used indoors where the radio wave of the macrocell is difficult to reach. The femtocell 20 is connected to the core network 33 via, for example, the BB line modem 34, the BB line, the Internet 31, and the femtocell gateway 32.

  A communication interface between the femtocell 20 and the femtocell gateway 32 is defined by a standard interface such as Iuh (3GPP TS 25.467), for example.

  The femtocell 20 includes a wireless communication unit 24 that performs wireless communication with the data communication terminal 10a, an IP communication unit 25 that performs wired communication with the femtocell management server 40 and the femtocell gateway 32, and measurement of downlink radio waves of neighboring base stations. Control unit 22 for performing frequency switching control of the wireless communication unit and measurement control of the reference signal, and the address of the femtocell management server 40, the address of the femtocell gateway 32, and the terminal that can access the femtocell 20 And a storage unit 26 storing ID (Allowed CSG List) and the like. The storage unit 26 also stores radio parameters of the femtocell 20 such as a carrier frequency and maximum transmission power.

  The femtocell management server 40 is a server that performs preparations and maintenance of femtocells handled by one operator, and includes an IP communication unit 42 that performs communication with a plurality of femtocells, a storage unit 41, and the like. , Including. The storage unit 41 stores a physical cell ID, a carrier frequency, neighboring cell information, location information, and the like used by the femtocell managed by the femtocell management server 40. Although FIG. 7 shows only one femtocell management server 40 operated by a certain business operator (for example, business operator A), other business operators operate similar servers. In the present disclosure, femtocells managed by a plurality of operators may be managed by one femtocell management server.

  The femtocell 20 operated by the operator A is connected to the core network 33 via the femtocell gateway 32. Similarly, the macro cell 35 is a macro cell operated by the operator A, and the pico cell 36 is a pico cell operated by the operator A. The operator A operates the downlink carrier frequency A, and the macro cell 35, the pico cell 36, and the femto cell 20 transmit the carrier frequency A on the downlink.

  The data communication terminals 10a, 10b, and 10c are terminals that have contracted with the operator A that operates the core network 33, the data communication terminal 10a is indoors where the femtocell 20 can be used, and the data communication terminal 10b is Communication is performed via the pico cell 36, and the data communication terminal 10 c is communicating via the macro cell 35.

  The downlink signal transmitted by the macro cell 35 is interference noise for the data communication terminal 10b. Therefore, interference adjustment is performed between the macro cell 35 and the pico cell 36, and information on the ABS used by the macro cell 35 is notified to the pico cell 36. The pico cell 36 assigns and transmits an important downlink signal to the data communication terminal 10b to the downlink subframe of the pico cell 36 corresponding to the time of the subframe designated by the macro cell 35 as the ABS.

  When the power of the femtocell 20 is turned on, the femtocell 20 searches the radio waves of the surrounding base stations including the macrocell 35, measures the received power, and receives and obtains base station broadcast information. Further, the femtocell 20 is connected to the femtocell management server 40, obtains information on base stations around the pre-registered position information, confirms the position by collating with the measurement result of the femtocell 20, and The optimum radio parameters are selected so as not to overlap with the radio parameters used by the station.

  The downlink signal transmitted by the femtocell 20 is interference noise for the data communication terminal 10c, and the femtocell periodically sets the maximum of the femtocell so as to minimize interference according to the measurement result of the reference signal strength of the neighboring base stations. Determine the transmission power.

  The overall configuration of the data communication system according to the embodiment of the present disclosure has been described above with reference to FIG. Next, the configuration of the control unit 22a included in the femtocell 20a according to an embodiment of the present disclosure will be described.

  FIG. 8 is an explanatory diagram illustrating a configuration of the control unit 22 included in the femtocell 20 according to an embodiment of the present disclosure. Hereinafter, the configuration of the control unit 22 included in the femtocell 20 according to an embodiment of the present disclosure will be described with reference to FIG.

  As illustrated in FIG. 8, the control unit 22 included in the femtocell 20 according to an embodiment of the present disclosure includes an interference information acquisition unit 51, a reference signal measurement unit 52, and a power setting unit 53. Composed.

  The interference information acquisition unit 51 requests the femtocell management server 40 for interference adjustment information that is information related to interference adjustment notified from the macrocell 55, thereby acquiring interference adjustment information. When there is a request for interference adjustment information from the interference information acquisition unit 51, the femtocell management server 40 returns interference adjustment information to the femtocell 20.

  The reference signal measurement unit 52 measures the reference signal of the adjacent cell using the interference adjustment information acquired from the femtocell management server 40 by the interference information acquisition unit 51. The power setting unit 53 determines the transmission power of the femtocell 20 using the reference signal of the adjacent cell measured by the reference signal measurement unit 52. The method for measuring the reference signal of the adjacent cell using the interference adjustment information by the reference signal measuring unit 52 and the method for determining the transmission power of the femtocell 20 by the power setting unit 53 will be described in detail later.

  The configuration of the control unit 22 included in the femtocell 20 according to an embodiment of the present disclosure has been described above with reference to FIG. Note that the control unit 22 can have a functional configuration as illustrated in FIG. 8, for example, when the control unit 22 reads and executes a computer program stored in the storage unit 26.

  Next, the operation of the data communication system including the femtocell 20 according to an embodiment of the present disclosure will be described.

[2-2. Operation of data communication system]
[2-2-1. First operation example]
As a first operation example, a method will be described in which a macro cell notifies RNTP information and ABS information to neighboring SON servers. Specifically, the femtocell management server (SON server) 40 that manages the installation and maintenance of the plurality of femtocells 20, the neighboring cell information that the femtocell 20 broadcasts in the system information block, and the macrocell 35 appropriately update each The interference adjustment information of the macro cell 35 is held. When the femtocell 20 inquires of the femtocell management server 40 about interference adjustment information of neighboring base stations, the femtocell management server 40 notifies the femtocell 20 of interference adjustment information of the macrocell 35 around the femtocell 20. The operation will be described below.

  Information on neighboring cells is broadcast in the system information block of the serving cell, and the terminal can easily obtain neighboring cell information. In addition, information on neighboring cells that the terminal needs to measure is notified from the serving cell to the terminal through higher layer signaling. The neighboring cell information is associated with the carrier frequency of the neighboring base station, the physical layer cell ID (PCI) of the base station, an offset value when comparing the measured values and determining the rank, and the terminal obtains neighboring cell information. Thus, it is possible to efficiently measure peripheral cells. The neighboring cell information broadcast by the macro cell cannot include information on many femto cells existing in the same area. However, neighboring macro cell information reported by the femto cell can be loaded with neighboring macro cell information.

  The femtocell management server (SON server) 40 manages a plurality of femtocells 20 such as setting, management, and maintenance of radio parameters of the femtocell 20. The femtocell 20 stores the address of the femtocell management server 40, and can access the femtocell management server 40 at the time of activation to obtain necessary information. Neighboring cell information notified by the femtocell 20 is also stored in the femtocell management server 40, and the femtocell management server 40 knows which macrocell exists around a certain femtocell.

  FIG. 9 is a flowchart showing an operation of the data communication system 1 according to the embodiment of the present disclosure. For example, when the macro cell 35 starts an interference adjustment function to reduce interference with a pico cell terminal or changes interference adjustment information (step S101), the macro cell 35 transmits interference adjustment information to a pico cell that is a target of interference adjustment. Not only is notified (step S102), but also information related to interference adjustment is notified to the femtocell management server 40 (step S103). It is difficult for the macro cell 35 to notify the interference adjustment information to a large number of femto cells 20 in the same base station area. However, since the number of femtocell management servers 40 is small and the addresses are known in advance, the macro cell 35 can notify the femtocell management server 40 of information relating to interference adjustment.

  The femtocell 20 requests interference adjustment information of neighboring cells from the femtocell management server 40 at the time of activation (step S104). The femtocell management server 40 extracts interference adjustment information related to the macrocell held for the femtocell (step S105), and returns the extracted information to the requested femtocell 20 (step S106). When the femtocell 20 acquires the interference adjustment information related to the macro cell, the femtocell 20 performs measurement of the neighboring cell (step S107), and updates the maximum transmission power based on the measurement result of the neighboring cell (step S108).

  When the interference adjustment information obtained by the femtocell 20 from the femtocell management server 40 is, for example, transmission power information (RNTP information) for a subband, the femtocell 20 uses the subband reference measured for the downlink of the macrocell 35. The propagation loss (path loss) between the macro cell 35 and the femto cell 20 is obtained from the signal strength and the transmission power of the same subband in the RNTP information, and the position of the femto cell 20 is determined from the cell site in the macro cell area. Determine if it is an edge. Then, the femtocell 20 can select a subband corresponding to this, and can determine the maximum transmission power based on the measured value of the reference signal of the selected subband.

  When the interference adjustment information obtained by the femtocell 20 from the femtocell management server 40 is, for example, information of subframe numbers (ABS information) in which no data or CRS is inserted, the femtocell 20 is not set to ABS (that is, CRS). Only the reference signal of the downlink subframe of the macro cell is measured. The femtocell 20 can determine the maximum transmission power based on this measurement value.

  When the femtocell 20 is activated for the first time and there is no neighboring cell information in the femtocell management server 40, the femtocell 20 performs a cell search, detects the PCI of the neighboring base station, and requests interference adjustment information for this PCI. By doing so, it becomes possible to obtain corresponding information.

  FIG. 10 is a flowchart showing an operation of the data communication system 1 according to the embodiment of the present disclosure. For example, when the macro cell 35 starts an interference adjustment function to reduce interference with a pico cell terminal or changes interference adjustment information (step S111), the macro cell 35 transmits interference adjustment information to a pico cell that is a target of interference adjustment. In addition to notifying (step S112), the femtocell management server 40 is also notified of information relating to interference adjustment (step S113).

  When the femtocell 20 is activated for the first time and there is no neighboring cell information in the femtocell management server 40, the femtocell 20 performs a cell search (step S114), detects the PCI of the neighboring base station, and It requests the femtocell management server 40 for interference adjustment information for PCI (step S115).

  The femtocell management server 40 extracts interference adjustment information corresponding to the PCI requested from the femtocell 20 in step S115 (step S116), and returns the extracted information to the requested femtocell 20 (step S117). ). When the femtocell 20 acquires the interference adjustment information related to the macrocell, the femtocell 20 performs measurement of the neighboring cell (step S118), and sets the maximum transmission power based on the measurement result of the neighboring cell (step S119).

  Since many femtocells 20 exist in the area of one macrocell 35, interference adjustment information of one macrocell 35 is shared by many femtocells 20. That is, the femtocell management server 40 mediates the interference adjustment information of the macrocell 35, so that it is possible to share information efficiently without requiring a huge amount of signaling in the core network.

  The address of the femtocell management server 40 and the method for requesting interference adjustment information are disclosed on the Internet, so that it is possible to respond to inquiries about interference adjustment information from femtocells of other operators of adjacent frequencies. Even a terminal (for example, a positioning terminal) can accurately measure the reference signal by detecting the PCI of the neighboring base station and inquiring the interference adjustment information to the femtocell management server 40. That is, a terminal other than the cellular terminal (for example, a positioning terminal) has the configuration of the control unit 22 as shown in FIG. 8, thereby detecting the PCI of the neighboring base station and transmitting the interference adjustment information to the femtocell management server 40. By inquiring, it is possible to accurately measure the reference signal.

[2-2-2. Second operation example]
As a second operation example, a method of notifying transmission power information for each subband and subframe information not including a reference signal using a broadcast channel will be described. In this method, transmission power information (RNTP information) for each subband transmitted by the base station, subframes (Almost Blank Subframe (ABS)) in which data and CRS are not inserted are used for which subframe number. This is a method of broadcasting information relating to interference adjustment such as information on whether or not it is present (ABS information) as system information using the broadcast channel of the base station.

  The femtocell 20 having a downlink reception function detects a first synchronization signal (PSS) and a second synchronization signal (SSS) of a base station to be measured using a cell search procedure, and performs PCI. Frame timing is detected, and a master information block (MIB) such as a downlink cell bandwidth, the number of transmission antennas, and a structure of control information mapped to the physical broadcast channel (PBCH) is detected. The femtocell 20 receives the PDCCH, knows the position of the PDSCH resource block to which the system information block (SIB) including RNTP information and ABS information is assigned, and decodes the system information block from the corresponding PDSCH. Information regarding interference adjustment can be obtained.

  That is, the femtocell 20 can obtain information related to interference adjustment by providing the femtocell 20 with a reception function for performing the above procedure without registering a location as a terminal and receiving signaling. Using the information related to interference adjustment, the femtocell 20 can accurately measure the reference signals of the neighboring base stations, as in the first operation example described above. A configuration example of the femtocell 20 having a downlink reception function will be described in detail later.

[2-2-3. Third operation example]
As a third operation example, a method in which the femtocell has a UE function and temporarily obtains measurement target information from the macrocell will be described. This method has a communication function as a minimum terminal necessary for the femtocell 20 to obtain information (measurement target information) of subbands and subframes to be measured by signaling of the macrocell 35. 35 is a method of temporarily accessing the terminal 35 as a terminal and receiving the measurement target information from the macro cell through higher layer signaling. Then, the femtocell 20 performs accurate measurement of the reference signal of the macrocell 35 based on the measurement object information, stores the measurement value, turns off the function of the terminal, and uses the measurement value to determine the maximum transmission power. It is a method to do.

  FIG. 11 is a flowchart showing an operation of the data communication system 1 according to the embodiment of the present disclosure. When the terminal function is turned on (step S121), the femtocell starts a cell search (step S122) and synchronizes with the downlink of the nearest macro cell. When the terminal function of the femto cell 20 transmits a random access preamble to the macro cell 35 using an uplink physical random access channel (PRACH) (step S123), the macro cell 35 responds to the random access response (step S124) with a femto cell terminal. Returns the function's transmission timing adjustment value and the next uplink resource allocation.

  The femtocell 20 sends a terminal identifier to the network using an RRC connection request (step S125) using the terminal function. The macro cell 35 returns an acknowledgment that succeeds in random access (step S126). If the macro cell 35 performs interference adjustment with another base station, the macro cell 35 notifies the information of the subband and subframe (measurement target information) to be measured by the terminal function of the femtocell 20 using the RRC message. (Step S127).

  The femtocell 20 uses the terminal function to measure the neighboring cells according to the measurement target information notified in step S127 (step S128), and stores the measurement target information and measurement values in the storage unit 26 of the femtocell 20. (Step S129). Thereafter, the femtocell 20 turns off the terminal function and sets the maximum transmission power based on the previously stored measurement values of the neighboring cells (step S130).

  The femtocell 20 may notify the femtocell management server 40 of information related to macro cell interference adjustment obtained by this method. The femtocell management server 40 can collect information notified from these femtocells 20 and share information related to macro cell interference adjustment among a plurality of femtocells.

[2-2-4. Fourth operation example]
As a fourth operation example, a method for detecting an ABS pattern by measuring a femto cell will be described. This method is a method in which a femtocell having a downlink reception function measures a reference signal of a subframe that is not set in the ABS according to the ABS pattern.

  The femtocell 20 having a downlink reception function detects a first synchronization signal (PSS) and a second synchronization signal (SSS) of a base station to be measured using a cell search procedure, and performs PCI. Frame timing is detected, and a master information block (MIB) such as a downlink cell bandwidth, the number of transmission antennas, and a structure of control information mapped to the physical broadcast channel (PBCH) is detected. The femtocell 20 measures the reference signal reception strength for each subframe of the downlink transmitted by the macrocell 35 a plurality of times, and detects the pattern of the subframe number in which the ABS is implemented. Due to the relationship of the period of the retransmission confirmation response of the LTE transport block, the pattern of the ab frame using the ABS is repeated at 40 ms as shown in FIG. Therefore, the ABS pattern can be determined by measuring the reference signal strength for each subframe for 40 ms.

  Assuming that this ABS pattern is repeatedly used for a certain time, the femtocell 20 detects the ABS pattern, and then detects a reference signal of a subframe not set in the ABS according to the ABS pattern for a predetermined period of time. Measure.

  The femtocell 20 may notify the femtocell management server 40 of information related to macro cell interference adjustment obtained by this method. The femtocell management server 40 can collect information notified from these femtocells 20 and share information related to macro cell interference adjustment among a plurality of femtocells.

  It takes time to detect the ABS pattern because it is necessary to make several measurements for 40 ms. On the other hand, it is not known from the femtocell 20 whether the macro cell 35 continues to use the detected ABS pattern. In the ABS pattern shown in FIG. 5, since the subframe # 5 for transmitting system information is not set to the ABS, the femtocell 20 detects that the ABS is being used by the above measurement. Alternatively, a method may be used in which only a specific subframe in which no ABS is set, such as frame # 5, is to be measured for the reference signal strength. Further, the femtocell 20 may use a method of measuring the reference signal of the radio frame of the macro cell 36 corresponding to the radio frame not including the reference signal of the macro cell 35 with reference to the ABS pattern shown in FIG.

[2-2-5. Fifth operation example]
As a fifth operation example, a method for obtaining interference adjustment information by temporarily moving a femto cell terminal to a macro cell will be described. The femtocell 20 is a base station that can restrict accessible terminals. Whether or not a terminal can access the femtocell 20 is controlled by a list of terminals that can access the femtocell 20 (Allowed CSG List). The Allowed CSG List (ACL) is stored in the subscriber information server 37 connected to the core network 33 as the relationship of the cell ID (PCI) of the femtocell accessible to the user for the user's subscriber information. . Information stored in the subscriber information server 37 is copied to the UIM of each node, femtocell, and terminal connected to the core network 33 as necessary, and used for access control. Management of the Allowed CSG List, such as addition or deletion of PCI, can be performed by the operator or by the femtocell owner.

  FIG. 12 is a flowchart showing an operation of the data communication system 1 according to the embodiment of the present disclosure. FIG. 12 shows a sequence example in which the femtocell terminal (data communication terminal 10a) temporarily moves to the macrocell 35 and obtains measurement target information. In FIG. 12, the case where the femtocell terminal is in the connected mode during data communication is illustrated. However, even in the idle mode (the state where data communication is not in progress), the same operation is performed except that the handover operation is cell reselection. The effect can be expected.

  When the femtocell 20 notifies the subscriber information server 37 of a message regarding editing of the Allowed CSG List (step S131), the subscriber information server 37 executes ACL correction (step S132), and the femtocell 20 and data communication are performed. The updated ACL is transmitted to the terminal 10a (steps S133 and S134). As a result, the data communication terminal 10 a that is within the femtocell 20 and receives a service from the femtocell 20 is temporarily not allowed to access the femtocell 20.

  The data communication terminal 10a is instructed to move from the femtocell 20 to the adjacent base station (macrocell 35). The data communication terminal 10a temporarily moves to the macro cell 35 by the handover procedure, and continuously receives communication services from the macro cell 35. Specifically, when the data communication terminal 10a transmits a measurement report to the femtocell 20 (step S135), the femtocell 20 transmits a handover request to the macro cell 35 (step S136). Then, the macro cell 35 transmits a handover approval to the femto cell 20 (step S137), and the femto cell 20 transmits a handover command to the data communication terminal 10a (step S138). The data communication terminal 10a that has received the handover command from the femtocell 20 establishes downlink synchronization with the macrocell 35 (step S139).

  When the data communication terminal 10a transmits a connection request to the macro cell 35 (step S140), the macro cell 35 returns a connection permission to the data communication terminal 10a (step S141). Then, the data communication terminal 10a receives information (measurement target information) on subbands and subframes to be measured by the data communication terminal 10a from the macro cell 35 by upper layer signaling (step S142), and stores the measurement target information. deep.

  After a certain period of time, the femtocell 20 notifies the subscriber information server 37 of a message regarding editing of the Allowed CSG List so as to add the data communication terminal 10a to the Allowed CSG List (step S143). The access to the femtocell 20 is returned to the permission. The subscriber information server 37 corrects the ACL (step S144), and transmits the updated ACL to the femtocell 20 and the data communication terminal 10a (steps S145 and S146).

  Originally, the data communication terminal 10a is located within the femtocell 20 and in a place where the femtocell 20 has high radio field intensity. Therefore, when the data communication terminal 10a performs neighboring cell measurement (step S147) and sends a measurement report to the macro cell 35 (step S148), the macro cell 35 refers to the cell ID of the femto cell indicated in the measurement report, and A handover to the cell 20 is determined (HO determination, step S149).

  When a handover request is sent from the macro cell 35 to, for example, the subscriber information server 37 (step S150), the subscriber information server 37 collates the cell ID, terminal identification ID, and subscriber information of the Femto cell of the Allowed CSG List. (Access check, step S151), the handover request is transferred to the femtocell 20 (step S152).

  When the femtocell 20 transmits a handover approval to the macrocell 35 (step S153), the macrocell 35 transmits a handover command to the femtocell 20 to the data communication terminal 10a (step S154). The data communication terminal 10a that has received the handover command hands over to the femtocell again. Specifically, the data communication terminal 10a establishes downlink synchronization with the femtocell 20 (step S155), and transmits a connection request to the femtocell 20 (step S156), the femtocell 20 transmits to the data communication terminal 10a. A connection permission is returned (step S157).

  The femtocell 20 requests the measurement target information from the data communication terminal 10a (step S158). The data communication terminal 10a transfers the macro cell measurement target information received from the macro cell 35 in step S142 to the femto cell 20 (step S159). This measurement target information corresponds to interference adjustment information of the macro cell 35, and can be easily converted into interference adjustment information by the femto cell. Then, the femtocell 20 updates the maximum transmission power (step S160).

  As described above, the femtocell 20 can accurately measure the reference signals of the neighboring base stations using the information related to the interference adjustment, similarly to the above-described operation example 1 and the like. When the data communication terminal 10a transfers the measurement target information of the macro cell 35 received from the macro cell 35 to the femto cell 20, the measurement values of the neighboring cells by the data communication terminal 10a may be transferred at the same time. When the data communication terminal 10a transfers the neighboring cell measurement value, the femtocell 20 can determine the maximum transmission power using the measurement value of the data communication terminal 10a without performing the neighboring cell measurement.

  FIG. 13 is a flowchart showing an operation of the data communication system 1 according to the embodiment of the present disclosure. FIG. 13 shows a sequence in which the femtocell terminal (data communication terminal 10a) temporarily moves to the macrocell 35, triggers an interference adjustment function from the macrocell 35 to the femtocell 20, and the femtocell 20 obtains measurement target information. An example is shown.

  When the femtocell 20 notifies the subscriber information server 37 of a message regarding editing of the Allowed CSG List (step S161), the subscriber information server 37 executes ACL correction (step S162), and the femtocell 20 and data communication are performed. The updated ACL is transmitted to the terminal 10a (steps S163 and S164). As a result, the data communication terminal 10 a that is within the femtocell 20 and receives a service from the femtocell 20 is temporarily not allowed to access the femtocell 20.

  The data communication terminal 10a is instructed to move from the femtocell 20 to the adjacent base station (macrocell 35). The data communication terminal 10a temporarily moves to the macro cell 35 by the handover procedure, and continuously receives communication services from the macro cell 35. Specifically, when the data communication terminal 10a transmits a measurement report to the femtocell 20 (step S165), the femtocell 20 transmits a handover request to the macro cell 35 (step S166). Then, the macro cell 35 transmits a handover approval to the femto cell 20 (step S167), and the femto cell 20 transmits a handover command to the data communication terminal 10a (step S168). The data communication terminal 10a that has received the handover command from the femtocell 20 establishes downlink synchronization with the macro cell 35 (step S169).

  When the data communication terminal 10a transmits a connection request to the macro cell 35 (step S170), the macro cell 35 returns a connection permission to the data communication terminal 10a (step S171). Then, the data communication terminal 10a receives information (measurement target information) of subbands and subframes to be measured by the data communication terminal 10a from the macro cell 35 by higher layer signaling (step S172). In this sequence, the data communication terminal 10a need not store the measurement target information.

  Originally, the data communication terminal 10a is in a femtocell area and is in a place where the femtocell has a strong radio wave intensity. Therefore, the data communication terminal 10a performs a peripheral cell measurement (step S173), and sends a measurement report (PCI) to the macrocell 35. (Step S174), the macro cell 35 refers to the cell ID of the femto cell indicated in the measurement report, and determines handover to the femto cell (HO determination, step S175).

  When a handover request is sent from the macro cell 35 to, for example, the subscriber information server 37 (step S176), the subscriber information server 37 checks the cell ID, terminal identification ID, and subscriber information of the Femto cell of the Allowed CSG List. (Access check, step S177). At this point, since access to the femtocell 20 by the data communication terminal 10a is not permitted, the subscriber information server 37 replies to the macrocell 35 that access is not permitted (step S178).

  Since the access to the femtocell 20 of the data communication terminal 10a is not permitted, the handover request of the macrocell 35 is rejected, and the macrocell 35 notifies the femtocell 20 of an interference adjustment request for using the ABS ( Step S179). The interference adjustment request transmitted by the macro cell 35 includes interference adjustment information such as ABS information used by the macro cell 35. The femtocell 20 that has received the interference adjustment information measures the reference signal of the neighboring cell (macrocell 35) (step S180), and updates the setting of the maximum transmission power based on the measurement result (step S181). The femtocell 20 can accurately measure the reference signal of the neighboring cell (macrocell 35) using the interference adjustment information.

  After a certain period, the femtocell 20 notifies the subscriber information server 37 of a message regarding editing of the Allowed CSG List so as to add the data communication terminal 10a to the Allowed CSG List (step S182). Access to the femtocell 20 is returned to permission. The subscriber information server 37 corrects the ACL (step S183), and transmits the updated ACL to the femtocell 20 and the data communication terminal 10a (steps S184 and S185).

  Originally, the data communication terminal 10a is located within the femtocell 20 and in a place where the femtocell 20 has high radio field intensity. Therefore, when the data communication terminal 10a performs neighboring cell measurement (step S186) and sends a measurement report to the macro cell 35 (step S187), the macro cell 35 refers to the cell ID of the femto cell indicated in the measurement report, and A handover to the cell 20 is determined (HO determination, step S188).

  When a handover request is sent from the macrocell 35 to, for example, the subscriber information server 37 (step S189), the subscriber information server 37 collates the cell ID, terminal identification ID, and subscriber information of the Femtocell of the Allowed CSG List. (Access check, step S190), the handover request is transferred to the femtocell 20 (step S191).

  When the femtocell 20 transmits a handover approval to the macrocell 35 (step S192), the macrocell 35 transmits a handover command to the femtocell 20 to the data communication terminal 10a (step S193). The data communication terminal 10a that has received the handover command hands over to the femtocell again. Specifically, the data communication terminal 10a establishes downlink synchronization with the femtocell 20 (step S194), and transmits a connection request to the femtocell 20 (step S195). The femtocell 20 then transmits to the data communication terminal 10a. A connection permission is returned (step S196).

  The operation of the data communication system including the femtocell 20 according to an embodiment of the present disclosure has been described above. As described above, when the data communication system including the femtocell 20 according to the embodiment of the present disclosure operates, the femtocell 20 according to the embodiment of the present disclosure can easily measure the reference signal of the macrocell. And can be done accurately. And the femtocell 20 which concerns on one Embodiment of this indication can determine maximum transmission power so that interference may be suppressed to the minimum by measuring the reference signal of a macrocell.

[2-3. Configuration example of wireless communication unit]
Next, a configuration example of the wireless communication unit 24 in the femtocell 20 according to an embodiment of the present disclosure will be described. FIG. 14 is an explanatory diagram illustrating a configuration example of the wireless communication unit 24 in the femtocell 20 according to an embodiment of the present disclosure. As shown in FIG. 14, the wireless communication unit 24 includes an antenna 101, a duplexer 102, a downlink reception antenna 103, a downlink reception RF filter 104, a reception processing unit 110, a transmission processing unit 120, A baseband processing unit 130, a downlink receiving unit 140, a crystal oscillator 150, and a frequency synthesizer 160 are configured.

  The reception processing unit 110 includes a reception amplifier 111, a reception RF filter 112, and a quadrature demodulator 113. The transmission processing unit 120 includes a quadrature modulator 121, a transmission variable gain amplifier 122, a transmission RF filter 123, a transmission power amplifier 124, and an isolator 125. The downlink reception unit 140 includes a reception amplifier 141, a downlink reception RF filter 142, and a quadrature demodulator 143.

  A signal received by the antenna 101 is sent to the reception processing unit 110 via the duplexer 102. The reception processing unit 110 amplifies the signal transmitted from the duplexer 102 with the reception amplifier 111, executes predetermined filtering with the reception RF filter 112, and demodulates with the quadrature demodulator 113. The demodulated signal is sent to the baseband processing unit 130.

  The signal transmitted from the baseband processing unit 130 to the transmission processing unit 120 is modulated by the quadrature modulator 121, amplified by the transmission variable gain amplifier 122, subjected to predetermined filtering by the transmission RF filter 123, and transmitted. Amplified by the power amplifier 124 and sent to the duplexer 102 via an isolator 125 that prevents backflow of the signal. The signal sent to the duplexer 102 is transmitted from the antenna 101.

  The femtocell 20 according to an embodiment of the present disclosure includes the wireless communication unit 24 as illustrated in FIG. 14, so that it can receive a downlink signal from the macrocell 35 and measure a reference signal of the macrocell. The maximum transmission power can be determined so as to minimize interference.

  FIG. 15 is an explanatory diagram illustrating a configuration example of the wireless communication unit 24 in the femtocell 20 according to an embodiment of the present disclosure. As illustrated in FIG. 15, the wireless communication unit 24 includes the antennas 101 and 201, the duplexers 102 and 202, the reception processing unit 110, the transmission processing unit 120, the baseband processing unit 130, the crystal oscillator 150, The frequency synthesizers 160 and 260, the downlink reception unit 210, and the uplink transmission unit 220 are configured.

  The reception processing unit 110 includes a reception amplifier 111, a reception RF filter 112, and a quadrature demodulator 113. The transmission processing unit 120 includes a quadrature modulator 121, a transmission variable gain amplifier 122, a transmission RF filter 123, a transmission power amplifier 124, and an isolator 125.

  The downlink unit 210 includes a reception amplifier 211, a downlink reception RF filter 212, and a quadrature demodulator 213. The uplink transmission unit 220 includes a quadrature modulator 221, a transmission variable gain amplifier 222, an uplink transmission RF filter 223, a transmission power amplifier 224, and an isolator 225.

  A signal received by the antenna 101 is sent to the reception processing unit 110 via the duplexer 102. The reception processing unit 110 amplifies the signal transmitted from the duplexer 102 with the reception amplifier 111, executes predetermined filtering with the reception RF filter 112, and demodulates with the quadrature demodulator 113. The demodulated signal is sent to the baseband processing unit 130.

  The signal transmitted from the baseband processing unit 130 to the transmission processing unit 120 is modulated by the quadrature modulator 121, amplified by the transmission variable gain amplifier 122, subjected to predetermined filtering by the transmission RF filter 123, and transmitted. Amplified by the power amplifier 124 and sent to the duplexer 102 via an isolator 125 that prevents backflow of the signal. The signal sent to the duplexer 102 is transmitted from the antenna 101.

  A downlink signal from the macro cell 35 received by the antenna 201 is sent to the downlink unit 210 via the duplexer 102. The downlink unit 210 amplifies the signal received by the antenna 201 with the reception amplifier 211, executes predetermined filtering with the reception RF filter 212, and demodulates with the quadrature demodulator 213. The demodulated signal is sent to the baseband processing unit 230.

  The uplink signal transmitted from the baseband processing unit 130 to the uplink transmission unit 220 is modulated by the quadrature modulator 221, amplified by the transmission variable gain amplifier 222, and subjected to predetermined filtering by the transmission RF filter 223. The signal is amplified by the transmission power amplifier 224 and sent to the duplexer 202 via an isolator 225 that prevents backflow of the signal. Then, the uplink signal sent to the duplexer 202 is transmitted from the antenna 201.

  The femtocell 20 according to an embodiment of the present disclosure includes the wireless communication unit 24 as illustrated in FIG. 15, so that the downlink signal from the macrocell 35 can be received and the reference signal of the macrocell is measured. The maximum transmission power can be determined so as to minimize interference.

  The configuration example of the wireless communication unit 24 in the femtocell 20 according to an embodiment of the present disclosure has been described above.

<3. Summary>
As described above, according to an embodiment of the present disclosure, the femtocell 20 measures the downlink reference signal power of the neighboring base station (for example, the macro cell 35), and reduces the interference with the neighboring base station. The appropriate maximum transmit power of the cell is determined autonomously. In such a method, the femtocell 20 can easily and accurately perform measurement by the femtocell by knowing in advance the subframe pattern including the reference signal in the neighboring base station and the transmission power pattern for each radio resource in the neighboring base station. Is possible.

  Further, according to an embodiment of the present disclosure, the femtocell 20 can accurately measure the downlink reference signal of another base station that performs inter-cell interference control with the neighboring base stations.

  According to an embodiment of the present disclosure, the adjustment to the interference of the entire network is quickly and stable, and the capacity of the entire network is improved. That is, every time a large number of femtocells are activated, it is not necessary for neighboring base stations to notify each femtocell of interference adjustment information, etc., and it is possible to efficiently perform interference adjustment of the entire network without increasing overhead due to signaling. Can be done. In addition, the measurement accuracy of a terminal (for example, a positioning terminal) that measures downlink reference signal power other than the femtocell is increased.

  Note that a series of control processing by each device described in this specification may be realized using any of software, hardware, and a combination of software and hardware. For example, a program constituting the software is stored in advance in a storage medium provided inside or outside each device. Each program is read into the RAM at the time of execution and executed by the processor, for example.

  The preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, but the present disclosure is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present disclosure belongs can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present disclosure.

In addition, this technique can also take the following structures.
(1)
Interference adjustment information related to interference adjustment of the first base station for adjusting interference between the first base station and a second base station covering a narrower range than the first base station is externally provided. An interference information acquisition unit to acquire;
A reference signal measurement unit that measures a reference signal of an adjacent cell using the interference adjustment information acquired from the outside by the interference information acquisition unit;
A wireless base station comprising:
(2)
The radio base station according to (1), wherein the interference information acquisition unit acquires the interference adjustment information from a small base station management server to which the interference adjustment information is notified from the first base station.
(3)
The radio base station according to (1) or (2), wherein the interference information acquisition unit temporarily accesses the first base station to acquire the interference adjustment information from the first base station. .
(4)
The interference information acquisition unit broadcasts interference adjustment information related to interference adjustment of the first base station as system information for adjusting interference between the first base station and the second base station. The radio base station according to any one of (1) to (3), wherein the interference adjustment information is acquired from a broadcast channel of the first base station.
(5)
A downlink receiver for receiving a downlink from the first base station;
The reference signal measurement unit measures the reference signal for each radio frame in a predetermined period of the first base station in the downlink received by the downlink reception unit, (1) to (4) A radio base station according to any one of the above.
(6)
When the reference signal measurement unit detects that the first base station uses a radio frame that does not include a reference signal, the reference signal measurement unit detects only a specific radio frame that is known in advance to include a reference signal. The radio base station according to (5), which is a measurement target.
(7)
The interference information acquisition unit temporarily disables access to the radio base station by a terminal connected to the radio base station, connects the terminal to the first base station, and connects the first base station to the first base station. Any of (1) to (6), wherein after obtaining the interference adjustment information from the base station, the access to the radio base station is returned to permission, and the interference adjustment information obtained by the terminal is obtained from the terminal. The radio base station according to the above.
(8)
The reference signal measurement unit measures a reference signal of a radio frame of the second radio base station corresponding to a radio frame not including the reference signal of the first base station, (1) to (7) A radio base station according to any one of the above.
(9)
The radio base station according to any one of (1) to (8), wherein the interference adjustment information is information indicating a position of a radio frame that does not include a reference signal.
(10)
The interference adjustment information according to any one of (1) to (9), wherein the interference adjustment information is information indicating transmission power of a reference signal for a partial frequency band in a transmission frequency band of the first base station. Radio base station.
(11)
Interference adjustment information related to interference adjustment of the first base station for adjusting interference between the first base station and the second base station covering a narrower range than the first base station is notified. An interference information acquisition unit that acquires the interference adjustment information by designating a cell identifier of the base station to the small base station management server,
A reference signal measurement unit that measures a reference signal of an adjacent cell using the interference adjustment information acquired by the interference information acquisition unit;
A wireless terminal comprising:
(12)
Interference adjustment information related to interference adjustment of the first base station for adjusting interference between the first base station and a second base station covering a narrower range than the first base station is externally provided. An interference information acquisition step to be acquired;
A reference signal measurement step of measuring a reference signal of an adjacent cell using the interference adjustment information acquired from the outside in the interference information acquisition step;
A signal measurement method comprising:
(13)
On the computer,
Interference adjustment information related to interference adjustment of the first base station for adjusting interference between the first base station and a second base station covering a narrower range than the first base station is externally provided. An interference information acquisition step to be acquired;
A reference signal measurement step of measuring a reference signal of an adjacent cell using the interference adjustment information acquired from the outside in the interference information acquisition step;
A computer program that executes

DESCRIPTION OF SYMBOLS 1 Data communication system 10a, 10b, 10c Data communication terminal 20 Femtocell 31 Internet 32 Femtocell gateway 33 Core network 34 BB line modem 35 Macrocell 40 Femtocell management server 51 Interference information acquisition part 52 Reference signal measurement part 53 Power setting part Reference Signs List 101 antenna 102 duplexer 103 downlink reception antenna 110 reception processing unit 111 reception amplifier 112 reception RF filter 113 orthogonal demodulator 120 transmission processing unit 121 orthogonal modulator 122 transmission variable gain amplifier 123 transmission RF filter 124 transmission power amplifier 125 isolator 130 base Band processing unit 150 Crystal oscillator 160 Frequency synthesizer

Claims (13)

Interference adjustment information related to interference adjustment of the first base station for adjusting interference between the first base station and a second base station covering a narrower range than the first base station is externally provided. An interference information acquisition unit to acquire;
A reference signal measurement unit that measures a reference signal of an adjacent cell using the interference adjustment information acquired from the outside by the interference information acquisition unit;
A wireless base station comprising:   The radio base station according to claim 1, wherein the interference information acquisition unit acquires the interference adjustment information from a small base station management server to which the interference adjustment information is notified from the first base station.   The radio base station according to claim 1, wherein the interference information acquisition unit temporarily accesses the first base station to acquire the interference adjustment information from the first base station.   The interference information acquisition unit broadcasts interference adjustment information related to interference adjustment of the first base station as system information for adjusting interference between the first base station and the second base station. The radio base station according to claim 1, wherein the interference adjustment information is acquired from a broadcast channel of the first base station. A downlink receiver for receiving a downlink from the first base station;
2. The radio base according to claim 1, wherein the reference signal measurement unit measures a reference signal for each radio frame in a predetermined period of the first base station in the downlink received by the downlink reception unit. Bureau.   When the reference signal measurement unit detects that the first base station uses a radio frame that does not include a reference signal, the reference signal measurement unit detects only a specific radio frame that is known in advance to include a reference signal. The radio base station according to claim 5, which is a measurement target.   The interference information acquisition unit temporarily disables access to the radio base station by a terminal connected to the radio base station, connects the terminal to the first base station, and connects the first base station to the first base station. The radio base station according to claim 1, wherein after obtaining the interference adjustment information from a base station, access to the radio base station is returned to permission, and the interference adjustment information obtained by the terminal is obtained from the terminal.   2. The radio base according to claim 1, wherein the reference signal measurement unit measures a reference signal of a radio frame of the second radio base station corresponding to a radio frame not including the reference signal of the first base station. Bureau.   The radio base station according to claim 1, wherein the interference adjustment information is information indicating a position of a radio frame that does not include a reference signal.   The radio base station according to claim 1, wherein the interference adjustment information is information indicating transmission power of a reference signal for a partial frequency band in a transmission frequency band of the first base station. Interference adjustment information related to interference adjustment of the first base station for adjusting interference between the first base station and the second base station covering a narrower range than the first base station is notified. An interference information acquisition unit that acquires the interference adjustment information by designating a cell identifier of the base station to the small base station management server,
A reference signal measurement unit that measures a reference signal of an adjacent cell using the interference adjustment information acquired by the interference information acquisition unit;
A wireless terminal comprising: Interference adjustment information related to interference adjustment of the first base station for adjusting interference between the first base station and a second base station covering a narrower range than the first base station is externally provided. An interference information acquisition step to be acquired;
A reference signal measurement step of measuring a reference signal of an adjacent cell using the interference adjustment information acquired from the outside in the interference information acquisition step;
A signal measurement method comprising: On the computer,
Interference adjustment information related to interference adjustment of the first base station for adjusting interference between the first base station and a second base station covering a narrower range than the first base station is externally provided. An interference information acquisition step to be acquired;
A reference signal measurement step of measuring a reference signal of an adjacent cell using the interference adjustment information acquired from the outside in the interference information acquisition step;
A computer program that executes

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