JP2012080509A - Management device, communication system, base station device and management method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a management device, a communication system, a base station device and a management method which can grasp synchronization status with other base station devices and perform processing to properly avoid interference according to the synchronization status.SOLUTION: A communication system comprises a plurality of femtocell base stations 1b, and a macro base station 1a with a function of a management device receiving and managing synchronization information transmitted from a plurality of base station devices 1 that concerns synchronization between base stations. The macro base station 1a comprises a management unit 27 for selecting whether to manage the synchronization information by own device or a management server 8.

Description

  The present invention relates to a management device, a communication system using the same, a base station device, and a management method.

  In a wireless communication system including a plurality of base station apparatuses, when communication areas (cells) set by the plurality of base station apparatuses overlap, a signal transmitted from a certain base station apparatus May arrive at a terminal device in the cell of the base station device and become an interference signal for the terminal device.

  It is well known that such interference can be suppressed by beam forming. That is, while directing a beam to a terminal device in its own cell (hereinafter also referred to as its own terminal device), to a terminal device (hereinafter also referred to as another terminal device) in a cell of another base station device. By performing the beam forming so that the null beam is directed, the signal (interference signal) from the own base station apparatus becomes difficult to reach other terminal apparatuses, and the interference is suppressed. 1).

Nobuyoshi Kikuma, "Adaptive signal processing by array antenna", Science and Technology Publishing, November 25, 1998

  By the way, in the said radio | wireless communications system, as a base station apparatus, the macro base station apparatus which forms the cell (macro cell) of the magnitude | size of several kilometers, for example, and the comparatively small cell (about several dozen meters installed in the said macro cell ( There is one provided with a femto base station apparatus that forms a femto cell) in the macro cell.

In the wireless communication system, a femto cell formed by a femto base station apparatus may be formed in a macro cell, and almost the entire area thereof may overlap with the macro cell. Furthermore, the femto base station apparatus may be installed at an arbitrary place in the macro cell by the user.
Therefore, the downlink signal of the femto base station apparatus interferes with the terminal apparatus connected to the macro base station apparatus, or the uplink signal transmitted by the terminal apparatus connected to the femto base station apparatus interferes with the macro base station apparatus. Or give.
In addition, a plurality of femto base station apparatuses that form femto cells adjacent to each other and terminal apparatuses connected thereto may interfere with each other.

  As described above, since there may be various cases in which interference occurs, even when the base station apparatus uses the beam forming, the interference can be suitably suppressed in various situations as described above. There were cases where it was difficult.

  Among the interferences described above, when the terminal device connected to the macro base station device is located in the vicinity of the femto base station device and receives interference from the downlink signal of the femto base station device, the macro base station device It is conceivable that the resource allocated to the terminal device connected to the terminal and the resource used by the femto base station device are different from each other in the frequency direction or the time direction. By setting in this way, it is possible to avoid that the downlink signals overlap each other and to avoid interference.

Here, when shifting the resources used in the frequency direction, the following inconvenience may occur. That is, for example, when the wireless communication system employs LTE, the control channel for storing the control signal and the like is arranged at the beginning of each downlink subframe and over the entire frequency of the subframe. Even if resource allocation is performed between one base station apparatus and the other base station apparatus in different frequency bands, there is a possibility that the control channels overlap each other and cause interference. If control signals transmitted using the control channel interfere with each other, a terminal device that receives the control signals may not normally recognize a data signal including user data included in a subframe.
Further, even if the data signal is allocated with a frequency band different from each other, both data signals overlap in the time domain, so that the reception power of one data signal is the same as the other data signal. If it is extremely smaller than that, it may be difficult to normally separate and receive one data signal.
As described above, when the resources to be used are shifted in the frequency direction, interference between the two base station apparatuses may not be completely suppressed. Therefore, the power of the transmission signal is relatively adjusted between the two base station apparatuses. It is also necessary.

On the other hand, when the resources used for each other are shifted in the time direction, duplication of both data signals in the time domain cannot occur. Also, with respect to the control signal, since the control signal is not substantially transmitted in the control channel of the subframe in which no resource is allocated, the power adjustment of the transmission signal is performed between both base station apparatuses. Without any interference to the other control signal.
However, in order to shift the resource allocation in the time direction, it is necessary that the transmission timings of the radio frames are synchronized between both base station apparatuses.

As described above, in order to suppress the interference received by the downlink signal from the femto base station device in the vicinity of the terminal device connected to the macro base station device, grasp the mutual synchronization state between the two base station devices. However, it can be said that it is necessary to perform appropriate processing according to the synchronization state.
However, for example, when there are a large number of femto base station devices in a cell of the macro base station device, the macro base station device grasps a synchronization state with the large number of femto base station devices and performs management. It is necessary to perform processing. For this reason, the processing load for managing the synchronization state may be excessive in the macro base station apparatus, and there is a possibility that the synchronization state cannot be appropriately managed.

  Therefore, an object of the present invention is to provide a management device, a communication system, a base station device, and a management method that can appropriately grasp and manage the synchronization state in the base station device.

(1) The present invention is a management device provided in a communication system including a plurality of base station devices, and receives a synchronization information related to synchronization between base stations transmitted from the plurality of base station devices; And a management unit that manages the synchronization information received by the reception unit.
According to the management apparatus having the above configuration, since the management unit that manages the synchronization information received by the reception unit is provided, the synchronization state of each base station apparatus can be grasped.
The synchronization state referred to here indicates condition settings and parameters in synchronization between base stations, such as a synchronization target serving as a reference for synchronization between base stations and an offset amount of a transmission timing of a radio frame with respect to the synchronization target.

(2) Preferably, the management device further includes an interference control unit that performs interference avoidance processing for avoiding interference between the plurality of base station devices based on the synchronization information managed by the device itself. .
In this case, the interference control unit can execute an appropriate interference avoidance process according to the synchronization state in each base station apparatus.

(3) In addition, the management apparatus may further include a function as a base station apparatus. In this case, exchange of synchronization information is facilitated.

(4) Moreover, the management device further includes a selection unit that selects whether the synchronization information is managed by the own device or another management device provided in the communication system other than the own device. Also good.
In this case, when the selection unit selects either the own device or another management device, the processing load related to management can be distributed between the own device and the other management device. As a result, it is possible to suppress an excessive load in performing the management process from acting on the own apparatus, and it is possible to appropriately manage the synchronization state in the base station apparatus.

(5) The selection unit may preferentially select either the own device or the other management device, and in this case, according to the processing capability of the own device or another management device. Thus, it is possible to select a device that can suitably manage synchronization information, and to more effectively suppress the load on the own device.

(6) (7) The synchronization information may include a clock synchronization target in which the plurality of base station apparatuses synchronize an internal clock of the own apparatus, and the synchronization information includes the plurality of synchronization information. A timing offset amount between the communication timing of one base station apparatus among the base station apparatuses and the communication timing of another base station apparatus other than the one base station apparatus may be included.

(8) Further, the present invention is a communication system including a plurality of base station apparatuses, and includes a management apparatus that receives and manages synchronization information related to synchronization between base stations transmitted from the plurality of base station apparatuses. It is characterized by being.

  According to the communication system configured as described above, since the management device that manages the synchronization information of a plurality of base station devices is provided, the synchronization state of each base station device can be grasped.

The management apparatus preferably includes an interference control unit that performs interference avoidance processing for avoiding interference between the plurality of base station apparatuses based on the synchronization information managed by the own apparatus.
In this case, the interference control unit can execute an appropriate interference avoidance process according to the synchronization state in each base station apparatus.
In the communication system, the management device may have a function as a base station device, and in this case, exchange of synchronization information is facilitated.

(9) Moreover, the base station apparatus of this invention is provided with the transmission part which transmits the synchronous information regarding the synchronization between base stations toward the management apparatus which manages the said synchronous information.
According to the base station apparatus having the above configuration, since the transmission unit that transmits the synchronization information to the management apparatus that manages the synchronization information is provided, the management apparatus can be made to know the synchronization state of each base station apparatus.

(10) A management method for managing synchronization information related to synchronization between base stations in a communication system including a base station device, wherein the base station device is directed to a management device that manages the synchronization information. And the management device that has received the synchronization information manages the synchronization information.
According to the management method having the above configuration, the management apparatus that has received the synchronization information manages the synchronization information, so that the management apparatus can grasp the synchronization state of each base station apparatus.

  According to the present invention, it is possible to appropriately grasp and manage the synchronization state in the base station apparatus.

It is the whole structure of the radio | wireless communications system provided with the base station apparatus which concerns on embodiment of this invention. It is a figure which shows the aspect of the communication network of each BS. 1 is a schematic diagram of a structure of an LTE downlink radio frame (DL frame). FIG. It is a block diagram which shows the structure of a macro base station apparatus. It is a flowchart which shows the process in which a macro base station apparatus sets the management mode of a femto base station apparatus. It is a figure which shows the process sequence regarding the management of the synchronous state of the synchronization between base stations performed between a macro base station apparatus and the femto base station apparatus set to the direct management mode. It is a figure which shows the content of the request message contained in a synchronous request. It is a figure which shows the content of the report message contained in synchronous information. It is a figure which shows the process sequence regarding the management of the synchronous state of the synchronization between base stations when the detected femto base station apparatus is set to indirect management mode. It is a figure which shows the process sequence regarding the interference avoidance process which a macro base station apparatus performs between the femto base station apparatuses set to the direct management mode. It is a figure for demonstrating the process in which a macro base station apparatus detects the terminal device located in the femto base station apparatus vicinity from the terminal devices connected to an own apparatus. It is a figure which shows an example of the measurement result transmitted to the said macro base station apparatus when a macro base station apparatus requests | requires measurement with respect to the some terminal device connected to an own apparatus in FIG. (A) is a figure which shows an example of the resource allocation which both base station apparatuses perform when the timing synchronization of a radio | wireless frame is not taken between the macro base station apparatus and femto base station apparatus in FIG. FIG. 3 is a diagram illustrating an example of resource allocation performed by both base station apparatuses when the radio frame timing is synchronized between the base station apparatus and the femto base station apparatus in FIG. 1. It is a figure which shows the process sequence regarding the interference avoidance process which a macro base station apparatus performs between the femto base station apparatuses set to the indirect management mode.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
[1. Configuration of communication system]
FIG. 1 is an overall configuration of a wireless communication system including a base station apparatus according to an embodiment of the present invention. The radio communication system according to the present embodiment is a system for mobile phones to which, for example, LTE (Long Term Evolution) is applied, and communication based on LTE is performed between each base station device and a terminal device. . However, the communication method is not limited to LTE.

  This wireless communication system includes a plurality of base station devices 1 and a terminal device 2 (mobile station) that can perform wireless connection to any one of the base station devices 1 and perform communication. .

  The base station apparatus 1 provided in the wireless communication system includes, for example, a macro base station 1a that forms a communication area (macrocell) MC having a size of several kilometers, as well as a number installed in the macrocell MC. A plurality of femto base station apparatuses (Femto Base Stations) 1b forming a relatively small femtocell FC of about 10 meters are provided. In the illustrated example, only the femto base station apparatus 1b (FBS1) installed in the macro cell MC of the macro base station apparatus 1a (MBS1) is shown as the femto base station apparatus 1b for ease of explanation. Yes.

A macro base station apparatus (hereinafter also referred to as “macro BS”) 1a can perform wireless communication with a terminal apparatus 2 in its own macro cell MC.
Further, the femto base station apparatus (hereinafter also referred to as “femto BS”) 1b is disposed, for example, in a place where it is difficult to receive the radio wave of the macro BS 1a, for example, indoors, and forms the femto cell FC.

  The femto BS 1b can perform wireless communication with a terminal device (hereinafter also referred to as “MS”) 2 in the femto cell FC formed by the femto BS 1b. In this system, even in a place where it is difficult to receive the radio wave of the macro BS 1a, a service with sufficient throughput is provided to the MS 2 by installing the femto BS 1b that forms a relatively small femto cell FC in the place. Enable.

In FIG. 1, it is assumed that MS2a, MS2b, and MS2c are connected to a macro BS1a (MBS1), and MS2d is connected to a femto BS1b (FBS1).
Here, in order for the MS 2 to connect to the femto BS 1b, it is necessary to be registered in advance in the femto BS 1b. If the MS 2 is not registered, the MS 2 in the femto cell FC as shown in FIG. Even if it is located, it cannot be connected to the femto BS 1b, but is connected to the macro BS 1a.

FIG. 2 is a diagram illustrating an aspect of a communication network of each BS. Each macro BS 1a is connected to a communication network 4 of the wireless communication system via an MME (Mobility Management Entity) 3. The MME 3 is a node that manages the location and the like of each MS 2 and performs a process for movement management of each MS 2.
Each femto BS 1b is connected to the MME 3 via the gateway 5 (GW). The MME 3 and each macro BS 1a, the MME 3 and the gateway 5, and the gateway 5 and the femto BS 1b are connected by lines 6 using communication interfaces called S1 interfaces, respectively.

Further, each macro BS 1a is connected by a line 7 by a communication interface between base stations called an X2 interface, and communication for information exchange can be directly performed between base station apparatuses. The gateway 5 is also connected to the macro BS 1a via a line 7 with an X2 interface.
This X2 interface is provided for the purpose of exchanging information about mobility management such as handover in each MS 2 that moves between base station apparatuses. Such a function overlaps with the function of the MME 3, but if the MME 3 centrally performs the mobility management for the MS 2 connected to each macro BS 1a, the processing becomes a huge amount of processing, and the mobility management. Therefore, an X2 interface for performing communication between base station apparatuses is provided because it is more efficient to perform the process between base station apparatuses.

In the present embodiment, the macro BS 1a and the femto BS 1b are each connected to the management server 8. This management server 8 is a device for intensively managing the movement management of the MS 2 in the femto BS 1b located in the cell of each macro BS 1a and the situation related to the synchronization between base stations, and as necessary for each macro BS 1a. Installed. The management server 8 is connected to the macro BS 1a and the femto BS 1b so that IP communication is possible.
When the femto BS 1b existing in the cell of the macro BS 1a increases, the management server 8 increases the amount of processing such as mobility management performed with the femto BS 1b in the macro BS 1a. It is provided to process part or all in a complementary manner in place of the macro BS 1a. Therefore, when the femto BS 1b existing in the own cell is relatively small and can be processed with the processing capability of the macro BS 1a, it is not necessary to install the management server 8.

  In FIG. 2, the macro BS 1a directly connected to the MME 3 may be referred to as an eNB (Evolved Node B), the gateway 5 may be referred to as a Home-eNB Gateway, and the femto BS 1b may be referred to as a Home-eNB.

[2. LTE frame structure]
In LTE applied in this radio communication system, a frequency division duplex (FDD) scheme is adopted, and an uplink signal (a transmission signal from a terminal device to a base station device) and a downlink signal (a base station device to a terminal device). Uplink communication and downlink communication can be performed at the same time by assigning different use frequencies to each other.

  FIG. 3 shows an outline of the structure of an LTE downlink radio frame (DL frame). One DL frame is configured by arranging 10 subframes in the time axis direction (FIG. 3 shows a part of one DL frame). One subframe has a length of 14 OFDM symbols in the time axis direction (= 1 msec), and has a maximum frequency bandwidth of 20 MHz.

  Each subframe has a control area in which control information (Control Information) is stored at the head of each subframe, and then a PDSCH (Physical Downlink Shared Channel) in which user data is stored. . The control area is secured over the entire frequency bandwidth of each subframe in the frequency axis direction up to 3 symbols in the time axis direction.

  In the control area, a downlink control channel (PDCCH: Physical Downlink Control Channel) for transmitting downlink and uplink allocation information and the like is secured. In addition to the allocation information, the PDCCH includes information on an uplink transmission power limit value, a report instruction for a downlink CQI (Channel Quality Indicator), and the like. Note that the size of the PDCCH changes according to the size of the control information.

  In addition to the PDCCH, a control channel configuration indication channel (PCFICH: Physical Control Indicator Channel) for notifying PDCCH, and a hybrid automatic repeat request (HARQ: Hybrid Automatic Repeat) reception request for the PUSCH are included in the control region. A hybrid ARQ indication channel (PHICH: Physical Hybrid-ARQ Indicator Channel) for transmitting a notification of success (ACK: Acknowledgment) and a notification of reception failure (NACK: Negative Acknowledgment) is also assigned.

The PDSCH in which user data and the like are stored is an area that is shared and used by a plurality of terminal apparatuses, and stores control information and the like for each terminal apparatus in addition to user data.
The PDSCH includes a plurality of resource blocks (RBs) that are basic unit areas (minimum units for radio resource allocation) in data transmission. The resource block has a size of 12 subcarriers in the frequency axis direction and 7 OFDM symbols in the time axis direction.

  When the frequency bandwidth of the DL frame is set to 10 MHz, 600 subcarriers are arranged. Therefore, 50 resource blocks are arranged in the frequency axis direction in one subframe, and two resource blocks in the time axis direction are arranged in one subframe.

  In addition, a synchronization signal including a known signal is assigned to predetermined positions of the first (first) subframe and the sixth subframe among the ten subframes constituting one DL frame.

  The base station apparatus 1 has a function of allocating resource blocks, which are radio resources, to terminal apparatuses and determining a transmission power value for each resource block. Similarly to the DL frame, the LTE uplink radio frame (UL frame) also has a plurality of resource blocks, and the base station apparatus 1 also determines allocation of the DL frame resource blocks to the terminal device. Is done.

  The downlink and uplink resource block allocations determined by the base station apparatus 1 are stored in the PDCCH as allocation information and transmitted from the base station apparatus 1 to the terminal apparatus 2. The base station apparatus 1 and the terminal apparatus 2 perform communication using resource blocks according to the determined allocation information.

[3. Configuration of base station apparatus]
FIG. 4 is a block diagram showing a configuration of the macro BS 1a. Here, the configuration of the macro BS 1a will be described, but the configuration of the femto BS 1b also basically has the same configuration as the macro BS 1a.

  The macro BS 1a performs transmission / reception between the antenna 11, the transmission / reception unit (RF unit) 10 to which the antenna 11 is connected, and the RF unit 10. And a signal processing unit 20 that performs comprehensive management such as processing for suppressing interference to other base station devices or terminal devices, and synchronization status of other base station devices (particularly, femto BS 1b). Note that the femto BS 1b is not necessary for the function of performing comprehensive management of other base station apparatuses, and therefore may not be provided.

  The RF unit 10 includes an upstream signal receiver 12, a downstream signal receiver 13, and a transmitter 14. The uplink signal receiving unit 12 is for receiving an uplink signal from the MS 2. The downlink signal receiving unit 13 is for receiving a downlink signal from another macro BS 1a or another femto BS 1b. The transmission unit 14 is for transmitting a downlink signal to the MS 2.

  In the present embodiment, the downlink signal receiving unit 13 is used for intercepting downlink signals of other base station apparatuses 1 and observing (measurement) of the downlink signals. The downlink reception signal output from the downlink signal reception unit 13 is given to the signal processing unit 20 and processed by the measurement unit 21 or a demodulation unit (not shown).

The signal processing unit 20 is configured by a processor (microcomputer) that can generate various types of information, and functionally includes a measurement unit 21 that performs measurement, a resource allocation unit 22, and a synchronization processing unit 23.
The measurement unit 21 periodically performs measurement, and based on the downlink reception signal of the other base station device 1 received by the downlink signal reception unit 13, the transmission power, the use frequency, the radio frame in the other base station device 1 A synchronization signal indicating the timing is acquired. Also, it has a function of acquiring a cell ID or the like that is a unique ID assigned to another base station apparatus 1 and specifying the other base station apparatus 1.

  The resource allocation unit 22 allocates a resource block to each MS 2 that is wirelessly connected to the own device for each of the uplink and downlink subframes of the own device. The resource allocation unit 22 also has a function of setting the transmission power of the downlink transmission signal of the own device and the transmission power of the uplink transmission signal of the terminal device 2 connected to the own device 1 for each resource block.

  The resource allocation unit 22 is used by the own device or the control unit 24 (described later) of the other base station device 1 or the own device determined by the management server 8 according to the synchronization state with the other base station device 1. Using resources within the possible range, resource allocation is performed for each MS 2 connected to the device itself.

The synchronization processing unit 23 has a function of performing a synchronization process for achieving synchronization between base stations for wireless communication of other base station devices. Specifically, the synchronization processing unit 23 corrects its own internal clock with respect to a predetermined reference clock to adjust the time direction length of its own radio frame, and the communication timing of its own radio frame. It has a function to adjust.
The synchronization processing unit 23 synchronizes the length of its own radio frame in accordance with the reference clock given from the control unit 24 so that the length of the radio frame is determined by the reference clock (clock synchronization).
Further, the synchronization processing unit 23 synchronizes the timing of its own radio frame so as to coincide with the timing of the reference radio frame given from the control unit 24 (timing synchronization).

  The synchronization processing unit 23 acquires the radio frame timing of the downlink signal of the other base station device using the synchronization signal included in the downlink signal of the other base station device acquired by the measurement unit 21, and performs the synchronization described above. Processing (air synchronization) can be performed, and the above-described synchronization processing can also be performed based on information obtained by communication via the IP interface 29 or the X2 interface 30 described later.

  The signal processing unit 20 further includes a control unit 24 that controls processing related to synchronization with other base station devices 1 and interference avoidance, and a storage unit 25 that stores information about other base station devices 1 and the like. A detection unit 26 that detects the MS 2 located in the vicinity of the other base station device 1 to the extent that there is a risk of interference from the downlink signal of the other base station device 1 among the MSs 2 connected to the own device, and a storage unit 25, the management unit 27 that comprehensively manages the information of the other base station apparatus 1 stored in 25, and IP communication with the management server 8 via the IP interface 29 and other base station apparatus via the X2 interface 30 1 and a transmission / reception unit 28 for performing communication between base stations.

Note that communication between base station apparatuses using the X2 interface may be performed in a plurality of ways, such as a method in which base station apparatuses are directly connected or a method in which base station apparatuses are connected via a gateway. It is done.
In the femto BS 1b of the present embodiment, as shown in FIG. 2, a communication line using an X2 interface is not directly installed with another base station apparatus 1. For this reason, the femto BS 1b according to the present embodiment does not directly perform communication between base station apparatuses using the X2 interface, but passes through the communication line 6 and the gateway 5 using the S1 interface that connects to the gateway 5, and other base station apparatuses. 1 is used to perform communication between base station apparatuses using the X2 interface. In the following, although not specifically described, in the case of the femto BS 1b, the transmission / reception units 27 and 28 for performing communication between base station apparatuses are connected to another base station apparatus 1 via the gateway 5 by the X2 interface. A description will be given on the assumption that intercommunication is performed.

The control unit 24 has a function of determining a synchronization target serving as a reference for achieving clock synchronization and timing synchronization of the device itself, and outputting the reference clock and reference timing to the synchronization processing unit 23.
In addition, the control unit 24 generates a synchronization request for requesting another base station device 1 to synchronize between base stations with the own device as a synchronization target, and transmits the other request via the management unit 27 and the transmission / reception unit 28. It has the function to transmit toward the base station apparatus 1.

  Further, when the synchronization target is determined and synchronization is performed with the synchronization target, or in response to a request from another device such as another base station device 1, the control unit 24 synchronizes itself. The synchronization information regarding the state is output to the management unit 27 and also transmitted to the other base station device 1 or the management server 8 via the management unit 27 and the transmission / reception unit 28.

The control unit 24 has a function of performing interference avoidance processing for avoiding interference with other base station apparatuses 1.
The control unit 24 requests the other base station device 1 to provide a free resource for avoiding interference, and the own device allocates a resource corresponding to the free resource to the other base station device 1. Interference avoidance processing that can avoid mutual interference is performed by assigning to MS2 that may cause interference between the two.
The control unit 24 generates a processing request for requesting provision of the free resource so that the other base station device 1 provides the free resource, and the other base station device via the management unit 27 and the transmission / reception unit 28 1 to send.

When generating the processing request, the control unit 24 determines whether or not the timing of the other base station device 1 is synchronized with the own device based on the synchronization information of the other base station device 1. . The control unit 24 determines the requested free resource mode according to the determination result.
The control unit 24 acquires the synchronization information of the other base station apparatus 1 from the management unit 27.

  More specifically, when the control unit 24 determines that the other base station apparatus 1 does not synchronize timing with itself, a part of the frequency direction by the other base station apparatus 1 is determined. The use of resources belonging to the bandwidth is prohibited, and a determination is made so that free resources are continuously present in the time direction.

  On the other hand, when the other base station apparatus 1 determines that the timing is synchronized with itself, the control unit 24 uses the other base station apparatus 1 for resources belonging to a predetermined range in the time direction. The use is prohibited, the free resources are secured in predetermined time units, and the free resources are determined to be scattered in the time direction.

As described above, the control unit 24 generates a processing request for requesting execution of the interference avoidance processing based on the synchronization information of the other base station apparatus, and transmits the other base via the management unit 27 and the transmission / reception unit 28. It has a function of transmitting to the station device.
In addition to the above information, various information output from the control unit 24 is output to the management unit 27 and transmitted to another base station apparatus 1 or the management server 8 via the management unit 27 and the transmission / reception unit 28. Is done.

  The storage unit 25 stores a neighbor list 25a in which information such as a cell ID for specifying another base station device 1 located in the vicinity of the own device is registered. In this neighbor list 25a, the base station device 1 specified to be located in the vicinity of the own device 1a can be input and registered in advance, or another base station specified by the measurement unit 21 of the own device 1a can be registered. The base station device 1 specified by the measurement (described later) of the neighboring cell can also be registered in the device 1 or a terminal device connected to the device 1a.

The management unit 27 manages the neighbor list 25a stored in the storage unit 25 and information related to the other base station device 1, thereby managing the movement and synchronization of the terminal device in the other base station device 1 (particularly the femto BS 1b). It has a function to perform comprehensive management such as status. In the following description, only the management of the synchronization state will be described while focusing on the management process performed by the management unit 27.
When the other base station apparatus 1 is specified (detected) by external input or measurement or the like, the management unit 27 registers the other base station apparatus 1 in the neighbor list 25a. When the other base station device 1 (hereinafter, the identified other base station device is also referred to as the specific base station device 1) is registered in the neighbor list 25a, the management unit 27 indicates the synchronization state related to the specific base station device 1. For management, it is selected whether the device 1a manages (direct management mode) or the management server 8 manages (indirect management mode). Note that the management server 8 also has a comprehensive management function related to another base station apparatus 1 similar to the management unit 27, as will be described later.

For example, when the direct management mode is selected for the specific base station device 1, the management unit 27 outputs the above-described synchronization request or processing request output from the control unit 24 to the specific base station device 1 to the X2 interface 30. Is transmitted to the specific base station apparatus 1 via In this case, the management unit 27 transmits a notification to the specific base station apparatus 1 that the specific base station apparatus 1 is selected to be managed by the own apparatus 1a.
The specific base station device 1 that has received the notification transmits synchronization information to the macro BS 1a through inter-base station communication via the X2 interface.
When the management unit 27 acquires the synchronization information transmitted by the specific base station device 1 in response to the notification, the management unit 27 associates the synchronization information with information for specifying the specific base station device 1 in the neighbor list 25a and the like. 25 and manage.

On the other hand, when the indirect management mode is selected for the specific base station apparatus 1, the management unit 27 transmits a notification to the specific base station apparatus 1 that the specific base station apparatus 1 is selected to be managed by the management server 8.
The specific base station apparatus 1 that has received the notification transmits synchronization information to the management server 8 by communication via the IP interface.

  The management server 8 includes a management list for managing the synchronization information and the like of the plurality of base station devices 1. When receiving the synchronization information from the specific base station device 1 for which the indirect management mode is selected, Information for specifying the specific base station apparatus 1 such as the cell ID of the specific base station apparatus 1 and the synchronization information are registered and managed in association with the management list.

  As described above, the macro BS 1a includes the management unit 27 and the storage unit 25, thereby configuring a management device that receives and manages the synchronization information transmitted from the femto BS 1b. The management server 8 also constitutes a management device that receives and manages synchronization information from the base station device 1. In addition, the management unit 27 of the macro BS 1a has a function as a selection unit that selects whether the synchronization information of the other base station device 1 is managed by the own device 1a or the management server 8.

  Note that the femto BS 1b does not need the management function of the other base station device 1 described above, and therefore may not include the management unit 27. In this case, the control unit 24 performs processing related to management of various types of information stored in the storage unit 25 and transmission / reception of synchronization information and synchronization requests.

  The detection unit 26 requests each MS2 connected to its own device to measure neighboring cells (downlink signal observation), and based on the measurement result of the received power as a result of the measurement transmitted from each MS2, Ascertaining the positional relationship between each MS 2 and other base station devices 1 around it, the MS 2 located in the vicinity of the other base station device 1 to the extent that there is a risk of being interfered by the downlink signal of the other base station device 1 To detect.

[4. About Management Server]
The management server 8 is a device composed of a processor that can perform various types of information processing, a storage unit that can store information related to processing, and the like, and is located in the cell of each macro BS 1a as described above. The femto BS 1b has a function of centrally managing the status of MS2 movement management and inter-base station synchronization. In particular, as described above, a management list for managing synchronization information and the like of a plurality of base station devices 1 is provided, and synchronization status management is performed by registering the synchronization information of each base station device 1 Can do.
As described above, the management server 8 is a device whose purpose is to perform part or all of the processing performed by the macro BS 1a in place of the macro BS 1a, and is generally higher than the base station device 1. Has processing capacity.

  The management server 8 also has a function of performing transmission / reception of information regarding synchronization processing and interference avoidance processing by IP communication between the femto BS 1b for which the indirect management mode is selected and the macro BS 1a. Furthermore, the management server 8 can also relay information transmission / reception between the macro BS 1a and the femto BS 1b.

  Furthermore, the management server 8 has a function of performing interference avoidance processing similar to the function of the control unit 24 of the macro BS 1a. That is, the management server 8 is set to avoid interference between the macro BS 1a and the base station apparatus 1 managed by the management server 8 based on the interference avoidance process execution request transmitted from the macro BS 1a. In addition, it has a function of determining a free resource mode according to whether or not timing synchronization is taken, and generating a processing request for requesting interference avoidance processing and transmitting it to the target base station apparatus 1. Yes.

[5. About management mode settings]
The macro BS 1a performs processing for managing the synchronization state of synchronization between base stations in the other base station device 1 in order to perform interference avoidance processing with the other base station device 1 (particularly the femto BS 1b). .
The macro BS 1a selects and sets the management mode described above when performing processing for managing the synchronization state of the other base station apparatus 1.
FIG. 5 is a flowchart illustrating processing in which the macro BS 1a sets the management mode of the femto BS 1b.
First, the macro BS 1a (the management unit 27) determines whether or not the femto BS 1b as another base station device 1 is detected by the measurement unit 21 or the like in and around the cell of the own device 1a (step S1). .
If the femto BS 1b is not detected, the macro BS 1a repeats the determination in step S1 again.

  If it is determined in step S1 that the femto BS 1b has been detected, the macro BS 1a refers to the neighbor list 25a stored in the storage unit 25 and confirms whether or not the cell ID of the detected femto BS 1b is registered. To do. When the femto BS 1b is not registered in the neighbor list 25a, the macro BS 1a registers the femto BS 1b in the neighbor list 25a.

Next, the macro BS 1a determines whether or not the management server 8 connected to the own device 1a exists (step S2).
When determining that the management server 8 does not exist, the macro BS 1a sets the management mode of the detected femto BS 1b to the direct management mode (step S3).
On the other hand, when determining that the management server 8 exists, the management unit 27 of the macro BS 1a determines whether or not the management server 8 can manage the detected femto BS 1b (step S4).
If it is determined that management is possible, the macro BS 1a sets the management mode of the detected femto BS 1b to the indirect management mode (step S5).
If it is determined that management is not possible, the macro BS 1a sets the management mode of the detected femto BS 1b to the direct management mode (step S3).

  Note that once the macro BS 1a determines that the management server 8 exists, the macro BS 1a performs processing from step S1 to step S4. When the macro BS 1a confirms the existence of the management server 8, the macro BS 1a transmits synchronization information regarding the synchronization state of the own device 1a to the management server 8. As a result, the macro BS 1a is registered and managed in the management list of the management server 8 together with the synchronization information.

Further, in step S4, the macro BS 1a determines whether the management server 8 can manage the detected femto BS 1b. The macro BS 1a inquires the management server 8 about the management status of the management server 8, and manages the management. Judged according to the situation. For example, if the management server 8 has reached a quantity that the base station apparatus 1 cannot be managed beyond, the macro BS 1a determines that it cannot be managed by the management server 8 and directly determines the management mode.
By making the determination in step S4 as described above, the macro BS 1a causes the management server 8 to preferentially manage the detected femto BS 1b.

  As described above, the macro BS 1a sets the management mode for the detected femto BS 1b. The macro BS 1a stores the determined management mode in association with the detected cell ID of the femto BS 1b in the neighbor list 25a of the storage unit 25.

[6. About synchronization status management]
Next, management of the synchronization state of inter-base station synchronization performed between the macro BS 1a and the femto BS 1b will be described.
[6.1 Management of femto base station apparatus in direct management mode]
FIG. 6 is a diagram illustrating a processing procedure regarding management of synchronization state of synchronization between base stations performed between the macro base station apparatus and the femto base station apparatus. FIG. 6 illustrates a case where the femto BS 1b (FBS1) is installed in the macro cell MC of the macro BS 1a (MBS1) in FIG. 1 and the management mode of the femto BS 1b is set to the direct management mode.

First, when the femto BS 1b is installed and activated (step S101), the femto BS 1b forms a femto cell FC around its own device.
The macro BS 1a receives the downlink signal started by the femto BS 1b being activated by the measurement of the downlink signal of the other base station apparatus 1 by the measurement unit 21. Based on the downlink signal, the macro BS 1a acquires the cell ID of the femto BS 1b and specifies (detects) the femto BS 1b. The macro BS 1a sets the management mode for the detected femto BS 1b. Here, it is assumed that the direct management mode is set for the detected femto BS 1b (step S102).

  Next, in response to the detection of the femto BS 1b, the macro BS 1a generates a synchronization request for requesting the femto BS 1b to synchronize with the own device 1a as a synchronization target, via the X2 interface. The synchronization request is transmitted by communication between base station apparatuses (step S103). Further, the macro BS 1a notifies the fact that the indirect management mode is selected together with the synchronization request, that is, that the management of the synchronization state of the femto BS 1b is performed by the macro BS 1a by inter-base station communication.

FIG. 7 is a diagram showing the contents of a request message included in the synchronization request. The synchronization request is composed of request messages shown in FIG.
Among each request message, “Synchronization Target” is a message for designating a synchronization target in clock synchronization. As a mode of the message, “lte” (when the own apparatus 1a is designated as a synchronization target), “gps”. "(When GNSS (GPS, Galileo, GLONASS) is designated as a synchronization target)," ieee 1588 "(when synchronized using IEEE 1588)," ntp "(when an NTP server is designated as a synchronization target)," tv " (When a television signal is designated as a synchronization target) is provided, and one of these is designated.

“Timing Offset” is a message indicating an offset amount in timing synchronization of a radio frame between the macro BS 1a as a synchronization target and the femto BS 1b as another base station device. The mode of the message is an integer, and the unit is expressed by time (μs), symbol, subframe, or radio frame.
Upon receiving this message, the femto BS 1b can perform synchronization processing based on the offset amount indicated in the message when it is determined to synchronize timing with the macro BS 1a.
The macro BS 1a can recognize the frame timing of the femto BS 1b from the synchronization signal included in the downlink signal of the femto BS 1b received using its own downlink signal receiving unit 13, and can obtain the offset amount.

  “Timing Accuracy” is a message indicating the required accuracy for timing synchronization, and its mode is an integer (unit: time (μs)).

When the femto BS 1b performs synchronization using the timing of the radio frame of the other base station device obtained from the downlink signal of the other base station device received using its own downlink signal receiving unit 13 (air synchronization) Includes “Target Cell ID” classified as “Air Synchronization Information” and “Received Power Threshold” as a request message.
“Target Cell ID” is a message for specifying a synchronization target of frame timing synchronization, and is basically a cell ID of the device 1a. Further, “Received Power Threshold” is a threshold value for determining whether to perform air synchronization with respect to the received power from the base station apparatus specified by “Target Cell ID”. If the received power is larger than this threshold, it indicates that air synchronization is allowed.

The macro BS 1a can request inter-base station synchronization after designating the synchronization target by transmitting the synchronization request as described above to the femto BS 1b.
In FIG. 7, the synchronization target (particularly “Target Cell ID”) is indicated by the cell ID, but the method for indicating the synchronization target is not limited to the one explicitly specified by the cell ID. For example, the address to be synchronized may be used, and the synchronization target may be indicated by a numerical number, a symbol, or the like assigned to each of a plurality of preset synchronization targets.

Returning to FIG. 6, the femto BS 1b that has received the notification regarding the management mode recognizes that the management of the own device 1b is performed by the macro BS 1a.
Further, the femto BS 1b that has received the synchronization request determines whether to synchronize between the base stations with the macro BS 1a as a synchronization target based on the request message included therein.
When the femto BS 1b determines to perform synchronization between base stations with the macro BS 1a as a synchronization target and adjusts its own frame timing using the “Timing Offset” or performs synchronization processing by air synchronization (step S104). ), The synchronization information related to its own synchronization state is transmitted to the macro BS 1a (step S105).
The femto BS 1b performs communication between base station apparatuses via the X2 interface via the gateway 5 (FIG. 2) to the macro BS 1a, and transmits the synchronization information.

  FIG. 8 is a diagram showing the contents of the report message included in the synchronization information. The synchronization information includes each report message shown in FIG. Each report message and its mode are the same as the synchronization request shown in FIG. 7, and show the state after the femto BS 1 b performs the synchronization process, such as the synchronization target for which the synchronization process has been performed and the current timing offset amount. Yes.

The macro BS 1a can grasp the synchronization target when the femto BS 1b performs inter-base station synchronization based on the synchronization information transmitted from the femto BS 1b.
In FIG. 8, the synchronization target (particularly “Target Cell ID”) is indicated by the cell ID. However, the synchronization target address may be used, and a numerical number assigned to each of a plurality of preset synchronization targets may be used. The synchronization target can also be indicated by a symbol or the like.

  Returning to FIG. 6, the macro BS 1 a that has received the synchronization information associates the received synchronization information with the cell ID of the femto BS 1 b in the neighbor list 25 a and stores it in its storage unit 25. Thereby, the macro BS 1a can manage the synchronization state of the femto BS 1b (step S106).

  Even if the femto BS 1b does not set the macro BS 1a as the synchronization target in step S104, and performs synchronization between base stations with another base station device other than the macro BS 1a as the synchronization target, for example, the femto BS 1b is in the current synchronization state. Is sent to the macro BS 1a. That is, the femto BS 1b transmits synchronization information to the macro BS 1a to the base station apparatus that has received the synchronization request regardless of whether or not synchronization between base stations is performed in response to the synchronization request.

[6.2 Management of femto base station device in indirect management mode]
Next, a case where the management mode of the femto BS 1b is set to the indirect management mode will be described.
FIG. 9 is a diagram illustrating a processing procedure regarding management of synchronization state of synchronization between base stations when the detected femto BS 1b is set to the indirect management mode.

  In FIG. 9, when the femto BS 1b is installed and activated (step S110), the macro BS 1a sets the management mode for the detected femto BS 1b as in the case of FIG. Here, it is assumed that the indirect management mode is set for the detected femto BS 1b (step S111).

  Next, the macro BS 1a confirms that the indirect management mode is selected for the femto BS 1b by the inter-base station communication via the X2 interface, that is, the management server 8 manages the synchronization state of the femto BS 1b. Notice. Further, in response to the detection of the femto BS 1b, the macro BS 1a generates a synchronization request for requesting synchronization between the base stations to the femto BS 1b, and transmits the generated synchronization request together with the notification through inter-base station communication. (Step S112). This synchronization request is the same as that shown in FIG.

The femto BS 1b that has received the notification regarding the management mode recognizes that the management server 8 manages the own device 1a.
Further, the femto BS 1b that has received the synchronization request determines whether to synchronize between the base stations with the macro BS 1a as a synchronization target based on the request message included therein.
When the femto BS 1b determines to perform inter-base station synchronization with the macro BS 1a as a synchronization target, the femto BS 1b adjusts its own frame timing using the “Timing Offset” or performs synchronization processing by air synchronization (step S113). .
Next, the femto BS 1b transmits synchronization information about the synchronization state of the own device 1b to the management server 8 that recognizes that the own device 1a is managed by communication using the IP interface (step S114). The synchronization information is the same as that shown in FIG.

The management server 8 that has received the synchronization information registers and stores the received synchronization information in its own management list in association with the cell ID of the femto BS 1b. Thereby, the management server 8 can manage the synchronization state of the femto BS 1b (step S115).
Further, the management server 8 transmits to the macro BS 1a that the femto BS 1b has synchronized the macro BS 1a as a synchronization target (step S116). Thereby, macro BS1a can recognize that detected femto BS1b synchronized with the own apparatus 1a.

  Even when the femto BS 1b does not set the macro BS 1a as a synchronization target in step S113 and performs synchronization between base stations with a base station apparatus other than the macro BS 1a as a synchronization target, for example, the femto BS 1b is in the current synchronization state. Is sent to the management server 8. That is, the femto BS 1b transmits synchronization information to the management server 8 regardless of whether or not synchronization between base stations is performed in response to the synchronization request to the base station apparatus that has received the synchronization request.

  As described above, according to the macro BS 1a of the present embodiment, the macro BS 1a as the management device that manages the synchronization information of each base station device 1 such as the femto BS 1b and the management server 8 are provided. The synchronization status can be grasped and managed.

  Further, since the macro BS 1a of the present embodiment includes the management unit 27 as a selection unit that selects whether the synchronization information is managed by the own device 1a or the management server 8, the own device 1a, The management server 8 can distribute the processing load related to management. As a result, it is possible to suppress an excessive load in performing the management process from acting on the own apparatus 1a, and it is possible to appropriately manage the synchronization state in the other base station apparatus 1 such as the femto BS 1b.

  Further, in the present embodiment, in step S4 in FIG. 5, the macro BS 1a preferentially selects the management server 8 having generally higher processing capability than the macro BS 1a for the management of the femto BS 1b. The load on the device itself can be effectively suppressed.

[7. Interference avoidance process]
Next, interference avoidance processing performed by the macro BS 1a with the femto BS 1b will be described.
[7.1 Interference avoidance process with femto base station apparatus in direct management mode]
FIG. 10 is a diagram illustrating a processing procedure related to interference avoidance processing performed by the macro BS 1a with the femto BS 1b set in the direct management mode. 10, similarly to FIG. 6, the case where the femto BS 1b (FBS1) is installed in the macro cell MC of the macro BS 1a (MBS1) in FIG. 1 will be described.

  Macro BS1a detects whether MS2 located in the vicinity of femto BS1b exists among MS2 connected to the own apparatus 1a (step S201).

FIG. 11 is a diagram for explaining processing in which the macro BS 1a detects MS 2 located in the vicinity of the femto BS 1b from the MS 2 connected to the own device 1a.
First, the macro BS 1a requests each MS 2 connected to the own device 1a to measure a neighboring cell (observation of a downlink signal) (step S301).
This request includes the above-described neighbor list 25a possessed by the macro BS 1a. Receiving this measurement request, each MS 2 attempts to receive a downlink signal from each base station apparatus in the neighbor list 25a and measures the received power.
Each MS 2 transmits the measurement result of the received power of each base station device to the macro BS 1a (step S303).

FIG. 12 shows the measurement results transmitted to the macro BS 1a (MBS1) when the macro BS 1a (MBS1) in FIG. 1 requests the MS 2a, MS 2b, and MS 2c connected to the own device 1a for measurement. It is a figure which shows an example. The measurement result is indicated by associating the cell ID of the base station apparatus in the neighbor list 25a with the measured received power.
The cell ID of each base station apparatus 1 is shown as “MBS2” and “FBS1” attached to each base station apparatus 1 in FIG. In FIG. 1, the distance from MS2a to macro BS1a (MBS2) and the distance from MS2b to macro BS1a (MBS2) are substantially the same, and the distance from MS2c to femto BS1b (FBS1) is MS2b. It is assumed that the distance is larger than the distance from Femto BS1b (FBS1).

  FIG. 12A shows an example of measurement results of MS2a in FIG. Since this MS 2a is located in the cell of the femto BS 1b (FBS 1), the received power of the femto BS 1b (FBS 1) appears greatly, and since the MS 2a is close to the macro cell of the macro BS 1a (MBS 2), the macro BS 1a The received power of (MBS2) is also detected.

  FIG.12 (b) has shown the example of a measurement result of MS2b in FIG. Although this MS 2b is located outside the cell of the femto BS 1b (FBS 1), the reception power of the femto BS 1b (FBS 1) is slightly detected because it is in the vicinity of the cell. Further, since the distance to the macro BS 1a (MBS2) of the MS 2b is substantially the same as that of the MS 2a, the reception power of the macro BS 1a (MBS 2) is detected as a value (10 dB) similar to that in the MS 2a.

  FIG.12 (c) has shown the example of a measurement result of MS2c in FIG. Since this MS2c is located at a position away from the cell of the femto BS1b (FBS1) and the macro cell of the macro BS1a (MBS2) as compared to the other MS2a and MS2b, the received power of the femto BS1b (FBS1), The received power of the macro BS 1a (MBS2) is not detected.

Thus, although the received power of each base station apparatus 1 measured by each MS 2 depends on the transmission power of each base station apparatus 1, it means that the larger the power is, the closer to the target base station apparatus 1 is. In general, the positional relationship between the MS 2 and each base station apparatus 1 is shown.
Therefore, the macro BS 1a determines whether or not each MS 2 may receive interference due to the downlink signal of each base station device 1 by grasping the received power of each base station device 1 measured by each MS 2. be able to.

Returning to FIG. 11, when the macro BS 1a receives the measurement result of the reception power of each base station apparatus 1 transmitted by each MS 2 in step S303, the macro BS 1a selects the MS 2 from the MS 2 based on the measurement result. MS2 located in the vicinity of femto BS1b is detected (step S304).
For example, when the received power of the neighboring base station apparatus in MS2 is equal to or higher than a predetermined threshold, the macro BS 1a is located in the vicinity of the neighboring base station apparatus to some extent that the base station apparatus may receive interference due to the downlink signal. Detect as MS2. In the detection process performed in step S304, the received power of the other macro BS 1a is not considered. This is because there is little possibility of interference between macro base station apparatuses.

  For example, if the predetermined threshold is 10 dB or more, MS2a is detected as MS2 located in the vicinity of femto BS1b (FBS1) in the measurement result shown in FIG.

  As described above, the macro BS 1a detects the MS 2 located in the vicinity of the femto BS 1b to a certain extent from the MS 2 connected to the own device 1a.

Returning to FIG. 10, when the MS 2a is detected as the MS 2 located in the vicinity of the femto BS 1b from the MS 2 connected to the own apparatus 1a in step S201, the macro BS 1a refers to the storage unit 25. Then, referring to the synchronization state of the detected femto BS 1b in the vicinity of the MS 2a, the femto BS 1b determines whether or not the radio frame timing is synchronized with the own device 1a.
In order to perform the above-described interference avoidance process, the macro BS 1a determines, based on the determination result, an aspect of the free resource that is requested to the femto BS 1b to avoid the interference (step S202).

  In step S201, when the MS 2 located in the vicinity of the femto BS 1b is not detected, the macro BS 1a does not perform the following interference avoidance process, and again returns to the vicinity of the femto BS 1b after a predetermined period. The MS2 that is located is detected.

  Next, the macro BS 1a generates a processing request for realizing the free resource mode determined according to the determination result, and transmits the processing request to the femto BS 1b (step S203).

  In response to the processing request, the femto BS 1b receives the processing request and performs resource allocation for the MS 2d connected to the own device 1b in a resource range other than the range where the use of the own device 1b is prohibited (free resource). . Thereby, interference avoidance processing on the femto BS 1b side is performed (step S204).

  When the femto BS 1b performs the above process by performing resource allocation as described above, the femto BS 1b transmits a notification that the process has been executed to the macro BS 1a (step S205).

When the macro BS 1a receives the notification from the femto BS 1b, the macro BS 1a allocates a resource (free resource) in a range where the use of the femto BS 1b is prohibited to the MS 2a detected as the MS 2 located in the vicinity of the femto BS 1b. Thereby, interference avoidance processing on the macro BS 1a side is performed (step S206).
As a result, since the resources allocated to the MS 2a that may interfere with the femto BS 1b are not used by the femto BS 1b, it is possible to avoid interference with the femto BS 1b.
Since the other MS 2b and MS 2c are less likely to cause interference with the femto BS 1b, other resources can be allocated.

  Here, in step S202, when the femto BS 1b determines that the radio frame timing is not synchronized with the own device 1a, the macro BS 1a is a resource belonging to a part of the bandwidth in the frequency direction by the femto BS 1b. Is determined to be in a mode in which free resources are continuously present in the time direction. The macro BS 1a transmits a processing request corresponding to this to the femto BS 1b.

In this case, resource allocation performed by both base station apparatuses is as follows.
FIG. 13A shows an example of resource allocation performed by both base station apparatuses when the radio frame timing is not synchronized between the macro BS 1a (MBS1) and the femto BS 1b (FBS1) in FIG. FIG.
As shown in the figure, the femto BS 1b allocates resources other than a part of the bandwidth that is prohibited to be used to the MS 2d connected to the own device 1b. Thereby, free resources exist continuously in the time direction.

The macro BS 1a allocates resources in a range corresponding to the above-described free resources to the MS 2a that may cause interference with the femto BS 1b, and the MS 2b and MS 2c that are less likely to cause interference with the femto BS 1b have other Allocate resources.
In this case, since the free resources exist continuously in the time direction, even if the radio frame timing is not synchronized between the macro BS 1a and the femto BS 1b, the femto BS 1b has resource resources in a predetermined bandwidth. Use can be prohibited and free resources can be provided, and mutual interference can be avoided.

However, since a control region (control channel) in which a control signal or the like is stored is arranged at the beginning of each downlink subframe and over the entire frequency of the subframe, between the macro BS 1a and the femto BS 1b, Even if resources are allocated in different frequency bands, there is a possibility that the control area overlaps with each other in the frequency range used and causes interference. If control signals transmitted using the control region interfere with each other, a terminal device that receives the control signals may not normally recognize a data signal including user data included in the subframe.
Furthermore, even if data signals are allocated to different frequency bands on both sides, both data signals overlap each other in the time domain, so that the reception power of one data signal is the same as the other data signal. If it is extremely smaller than that, it may be difficult to normally separate and receive one data signal.
As described above, when the resources to be used are shifted in the frequency direction, interference between the two base station apparatuses may not be completely suppressed. Therefore, the power of the transmission signal is relatively adjusted between the two base station apparatuses. It will be necessary.

On the other hand, when the femto BS 1b determines that the radio frame timing is synchronized with the own device 1a in step S202, the macro BS 1a uses the resources belonging to the predetermined range in the time direction by the femto BS 1b. It is prohibited and free resources are secured in predetermined time units, and the free resources are determined to be scattered in the time direction. The macro BS 1a transmits a processing request corresponding to this to the femto BS 1b.
Note that the processing request in this case can be specified by a parameter that can specify a section in the time direction such as a subframe number in a downlink signal of the macro BS 1a, for example, when securing a free resource in units of subframes. It is also possible to specify a section in the time direction such as a subframe number in the downlink signal of the femto BS 1b by a parameter that can be specified. Since the macro BS 1a and the femto BS 1b recognize the offset amount between the radio frames, the parameter of the processing request parameter is set in advance so that it can be set on either the macro BS 1a side or the femto BS 1b side. Also good.

In this case, resource allocation performed by both base station apparatuses is as follows.
FIG. 13B shows an example of resource allocation performed by both base station apparatuses when the radio frame timing is synchronized between the macro BS 1a (MBS1) and the femto BS 1b (FBS1) in FIG. FIG.
As shown in the figure, the femto BS 1b is prohibited from using every other subframe, and resources are allocated to the MS 2d connected to the own apparatus 1b using a subframe other than the subframe that is prohibited from being used. It is carried out. Thereby, free resources are scattered in the time direction in units of subframes.

The macro BS 1a allocates resources in a range corresponding to the above-described free resources to the MS 2a that may cause interference with the femto BS 1b, and the MS 2b and MS 2c that are less likely to cause interference with the femto BS 1b have other Allocate resources.
In this case, since the radio frame timing is synchronized between the macro BS 1a and the femto BS 1b, the femto BS 1b is provided with free resources secured in predetermined time units and scattered in the time direction. A range of free resources that can be requested and scattered in the time direction can be specified. For this reason, macro BS1a can allocate the resource corresponding to an empty resource to MS2a with a possibility of interference with femto BS1b, and can avoid mutual interference.

  In addition, as shown in FIG. 13B, when the free resources are secured in a predetermined time unit so that the resources to be used do not overlap in the time direction, duplication of both data signals occurs in the time domain. No. Also, regarding the control signal, since a substantial control signal is not allocated to the control region of the subframe in which no resource is allocated, it is possible to suppress interference with the other control signal.

As described above, when the radio frame timing is synchronized between the own apparatus 1a and the femto BS 1b, the macro BS 1a can avoid duplication of resources in the time direction and avoid duplication of resources in the frequency direction. Problems such as duplication of control signals and data signals in the time direction can be solved.
As described above, since the macro BS 1a transmits a processing request according to the determination as to whether or not synchronization is achieved by the synchronization information, appropriate interference avoidance according to the synchronization state in the femto BS 1b which is another base station apparatus. Processing can be executed.

[7.2 Interference avoidance process with femto base station apparatus in indirect management mode]
FIG. 14 is a diagram illustrating a processing procedure related to interference avoidance processing performed by the macro BS 1a with the femto BS 1b set in the indirect management mode. Also in FIG. 14, the case where the femto BS 1b (FBS 1) is installed in the macro cell MC of the macro BS 1a (MBS 1) in FIG. 1 will be described.

  The macro BS 1a detects whether or not there is an MS 2 located in the vicinity of the femto BS 1b to a certain degree from the MS 2 connected to the own device 1a (step S211). The processing in step S211 is the same as that in step S201 in FIG.

  When MS2a is detected as MS2 located in the vicinity of femto BS1b from MS2 connected to its own device in step S211, macro BS1a transmits an execution request for interference avoidance processing to management server 8 (step S211). S212). The execution request for the interference avoidance process includes the cell ID of the macro BS 1a that is the request source and the cell ID of the femto BS 1b that is the interference target, and the management server 8 uses the cell IDs to execute the execution request. It is possible to recognize the macro BS 1a (MBS1) that is the request source and the femto BS 1b (FBS1) that is the interference target.

  In step S211, when the MS 2 located in the vicinity of the femto BS 1b is not detected, the macro BS 1a does not transmit the execution request, and after a predetermined period, the macro BS 1a is again located in the vicinity of the femto BS 1b. Detecting MS2 is performed.

The management server 8 that has received the request to execute the interference avoidance process refers to the management list of its own device 8 and determines whether the radio frame timing is synchronized between the requesting macro BS 1a and the interference target femto BS 1b. Determine whether.
The management server 8 requests the femto BS 1b to perform interference avoidance processing, and determines whether or not the free resource mode provided for the macro BS 1a to avoid interference is synchronized with the timing of the radio frame. The determination is made according to the determination result (step S213).

  Next, the management server 8 generates a processing request for realizing the free resource mode determined according to the determination result, and transmits the processing request to the macro BS 1a and the femto BS 1b (step S214).

  In response to the processing request, the femto BS 1b receives the processing request and performs resource allocation for the MS 2d connected to the own device 1b in a resource range other than the range where the use of the own device 1b is prohibited (free resource). . Thereby, the interference avoidance process on the femto BS 1b side is performed (step S215).

  On the other hand, the macro BS 1a that similarly received the processing request, in response to the processing request, detects a resource (empty resource) in a range in which the use of the femto BS 1b is prohibited as an MS 2a that is located in the vicinity of the femto BS 1b. Assign to. Thereby, interference avoidance processing on the macro BS 1a side is performed (step S216).

When the macro BS 1a and the femto BS 1b perform the interference avoidance process by performing resource allocation as described above, the macro BS 1a and the femto BS 1b transmit a notification that the process has been performed to the management server 8 (steps S217 and S218).
The management server 8 that has received the notification that the processing has been executed from the macro BS 1a and the femto BS 1b transmits a notification that the interference avoidance processing has been completed to the macro BS 1a (step S219). The macro BS 1a that has received the notification recognizes that the interference avoidance process with the requested femto BS 1b has been completed.

  As a result, since the resources allocated to the MS 2a that may interfere with the femto BS 1b are not used by the femto BS 1b, it is possible to avoid interference with the femto BS 1b.

  As described above, since the management server 8 transmits a processing request according to the determination as to whether synchronization is achieved by the synchronization information, as in the macro BS 1a, the synchronization state in the femto BS 1b that is another base station device It is possible to execute an appropriate interference avoidance process according to the above.

  In the present embodiment, the interference avoidance process for the femto BS 1b is performed by either the own apparatus 1a that manages the synchronization information of the femto BS 1b selected by the management unit 27 or the management server 8. Can be distributed. As a result, it is possible to suppress an excessive processing load from acting on the device 1a.

  The present invention is not limited to the above embodiment. In the above embodiment, the management unit 27 of the macro BS 1a is configured to preferentially select the management server 8 in step S4 in FIG. 5, but for example, the management by the own device 1a is given priority and the own device 1a is selected. The management server 8 may be selected at the stage where the management by the server cannot be performed, or the management server 27 of the own apparatus 1a and the management server 8 may be allocated to both according to the relative ratio of the processing capabilities. You can also choose.

  FIG. 13B shows the case where the femto BS 1b provides empty resources in units of subframes. However, empty resources are provided in units of radio frames, slots in subframes, and units of resource blocks. Also good.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive.
In the above embodiment, the case where the present invention is applied to a system for a mobile phone to which LTE is applied has been exemplified, but the communication method is not limited to LTE.
The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 Base station apparatus 1a Macro base station apparatus (management apparatus)
1b Femto base station device 2 Terminal device 8 Management server (management device)
24 Control unit (interference control unit)
27 Manager (Selector)
28 Transceiver

Claims (10)

A management device provided in a communication system including a plurality of base station devices,
A receiving unit that receives synchronization information regarding synchronization between base stations transmitted from the plurality of base station devices;
And a management unit that manages the synchronization information received by the reception unit.   The management apparatus according to claim 1, further comprising an interference control unit that performs interference avoidance processing for avoiding interference between the plurality of base station apparatuses based on the synchronization information managed by the own apparatus.   The management apparatus according to claim 1, further comprising a function as a base station apparatus.   4. The apparatus according to claim 1, further comprising a selection unit that selects whether the synchronization information is managed by the own device or another management device provided in the communication system other than the own device. The management apparatus as described in.   The management device according to claim 4, wherein the selection unit preferentially selects either one of the own device or the other management device.   The management apparatus according to any one of claims 1 to 5, wherein the synchronization information includes a clock synchronization target in which the plurality of base station apparatuses synchronize an internal clock of the own apparatus.   The synchronization information includes a timing offset amount between a communication timing of one base station apparatus among the plurality of base station apparatuses and a communication timing of another base station apparatus other than the one base station apparatus. Item 6. The management device according to any one of Items 1 to 5. A communication system comprising a plurality of base station devices,
A communication system comprising: a management device that receives and manages synchronization information related to synchronization between base stations transmitted from the plurality of base station devices.   A base station apparatus comprising a transmission unit that transmits synchronization information related to synchronization between base stations to a management apparatus that manages the synchronization information. A management method for managing synchronization information related to synchronization between base stations in a communication system including a base station device,
The base station device transmitting the synchronization information to a management device that manages the synchronization information;
A management method comprising: the management device receiving the synchronization information managing the synchronization information.

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