JP5696382B2 - Base station apparatus, radio resource allocation method, and program - Google Patents

Description

  The present invention relates to control of radio resources used for communication between a base station and a mobile station.

  With the spread of mobile phones in recent years, demand for voice communication and data communication by mobile phones is increasing not only outdoors but especially indoors, and now communication traffic from indoors reaches 70%. In response to such an increase in demand, the development of ultra-small base stations that can be installed indoors such as in user homes, small offices, and commercial facilities is underway. The range covered by such a base station is extremely small compared to the coverage of a base station installed outdoors, so it is called a femtocell. Hereinafter, this ultra-small base station is referred to as a femtocell base station. Since the femtocell base station can occupy a very small cell with a small number of people, the data communication speed can be dramatically increased. It can also be installed in places where radio waves are difficult to reach, such as high floors of buildings and underground malls, and has attracted attention as a means of expanding coverage (communication area satisfying required quality).

Femtocell base stations are installed so that they are overlaid on cells formed by neighboring base stations (for example, macro base stations, micro base stations and pico base stations that are smaller than macro base stations), or Installed in a blind area that does not cover. The femtocell base station is called Home NodeB (HNB) in W-CDMA (Wideband Code Division Multiple Access) and Home eNodeB (HeNB) in E-UTRA (Evolved Universal Terrestrial Radio Access). The femtocell base station is connected to an upper network (for example, a core network of a communication carrier) via a femto gateway (GW). The femto gateway is called Home NodeB Gateway in W-CDMA described later, and is called Home eNodeB Gateway in E- UTRA. When the mobile station is in the femtocell, the mobile station registered with the femtocell base station can connect to the network via the femtocell base station. On the other hand, a mobile station that is not registered in the femtocell base station cannot be connected to the network via the femtocell base station, or communication with the femtocell base station is restricted compared to a registered mobile station. The Hereinafter, a mobile station registered in advance with the femtocell base station is referred to as a “registered mobile station”. A mobile station that is not registered in advance with the femtocell base station is referred to as a “non-registered mobile station”. Further, hereinafter, a mobile station that communicates by connecting to a femtocell base station is referred to as a “femto mobile station”, and a mobile station that communicates by connecting to a macro base station is referred to as a “macro mobile station”.

  The femtocell base station is a system such as W-CDMA and E-UTRA (also called LTE: Long Term Evolution) in the wireless communication standard for mobile phones, and IEEE 802.16m in the wireless communication standard for wireless MAN (Wireless Metropolitan Area Network). It is considered to be used in such a system. When the femtocell base station is used in W-CDMA, CDMA (Code Division Multiple Access) is adopted as a wireless communication system, data transmission / reception using a dedicated channel for transmission power control in the uplink and downlink, Data transmission / reception is performed using a shared channel in the downlink. When the femtocell base station is used in E-UTRA, OFDMA (Orthogonal Frequency Division Multiple Access) and SC-FDMA (Single Carrier Frequency Division Multiple Access) are used as wireless communication systems, and multiple radio frequency bands are used. A scheduler that is divided into physical resource blocks (PRBs) and arranged in the base station allocates PRBs, and data transmission / reception is performed using the allocated PRBs. Furthermore, when a femtocell base station is used in IEEE 802.16m, OFDMA (Orthogonal Frequency Division Multiple Access) is used as a radio communication method, and the radio frequency band is divided into subcarriers and arranged in the base station. The scheduler assigns subcarriers, and data transmission / reception is performed using the assigned subcarriers. A bundle of a plurality of subcarriers corresponds to a resource block in terms of E-UTRA.

  The base station transmits a pilot signal toward the area covered by the base station. By receiving the pilot signal, the mobile station performs synchronization establishment, channel estimation, etc., and transmits / receives data to / from the base station. Therefore, enabling a mobile station to receive a pilot signal with good quality is a necessary condition for providing good communication quality. The same applies to the femtocell base station.

When operating a femtocell base station, a plurality of modes have been proposed regarding the frequency band of the femtocell base station and the presence or absence of transmission power control. For example, Non-Patent Document 1 illustrates four forms as shown in FIGS.
<Aspect A: FIGS. 19A and 19B>
The femtocell base station uses a frequency band different from that of the surrounding macro base station, and fixes the transmission power of the femtocell base station (transmission power control is not performed).
<Form B: FIGS. 20A and 20B>
The femtocell base station uses a frequency band different from that of the macro base station, and controls the transmission power of the femtocell base station.
<Form C: FIGS. 21A and 21B>
The femtocell base station uses the same frequency band as the macro base station, and controls the transmission power of the femtocell base station.
<Form D: FIGS. 22A and 22B>
The femtocell base station uses a frequency band that overlaps a part of the frequency band used by the macro base station. However, since the central frequency band R is for the control channel, the femtocell base station does not use the frequency band R.

  Among these, in the case of the form C shown in FIGS. 21A and 21B, that is, when the femtocell base station uses the same frequency band overlapping with the surrounding macro base stations, interference between the macrocell and the femtocell. (Hereinafter referred to as macro-femto interference) becomes prominent. In particular, when the macro mobile station is an unregistered mobile station that cannot connect to the femtocell base station, the macro mobile station located near the femtocell base station receives strong downlink interference from the femtocell base station. For this reason, it is necessary to control the downlink transmission power of the femtocell base station so as not to interfere with the macro mobile station communication (downlink communication) as much as possible. In addition, since the macro mobile station communicates with a relatively distant macro base station, the transmission power increases, and strong uplink interference is given to the femtocell base station.

  Patent Documents 1 and 2 show that a macro mobile station approaches a femtocell base station in a situation where the femtocell base station is operated in form C, in other words, in a situation where the femtocell and the macrocell use the same frequency band. In some cases, two methods for reducing macro-femto interference are disclosed. Specifically, the first method reduces the pilot signal transmission power of the femtocell base station when the macro mobile station is detected in the vicinity, and the uplink reception sensitivity of the femtocell base station (Input level necessary to maintain the required upstream quality) is slowed down. By doing so, the interference that the femtocell base station gives to the downlink communication of the macro mobile station is reduced, and the interference tolerance of the uplink communication of the femtocell base station is strengthened and the quality can be maintained.

  In the second method disclosed in Patent Documents 1 and 2, the frequency band used by the femtocell is changed to a frequency band different from the frequency band used by the macrocell when the macro mobile station is detected in the vicinity. In other words, the process shifts from form C shown in FIG. 21 to form B shown in FIG.

JP 2010-004187 A JP 2010-062951 A

3GPP TR 25.820 V8.2.0 (2008-09), 3rd Generation Partnership Project; Technical Specification Group Radio Access Networks; 3G Home NodeB Study Item Technical Report (Release 8), p14-17

  As shown in FIGS. 19 to 22, several modes have been proposed for the frequency band used by the femtocell base station and the transmission power control of the femtocell base station. Further, as shown in Patent Documents 1 and 2, a method of reducing macro-femto interference that occurs in Form C is also being studied. However, each form still has problems.

  Whether the frequency band different from the macro base station can be allocated to the femtocell base station as in the forms A and B greatly depends on the situation of the communication carrier. For example, due to the fact that the frequency band is tight due to the operation of the macro base station, or the frequency band that is allowed to be used in advance is small, a sufficient frequency band to be allocated exclusively to the femtocell base station is secured. It is a case where it cannot be done. In that case, as in form C or D, the macro base station and the femtocell base station need to share all or part of the frequency band.

  In form C, the occurrence of macro-femto interference cannot be avoided. Interference can be avoided to some extent by reducing the transmission power of the femtocell base station when the macro mobile station and the femtocell base station approach each other as in the first method described in Patent Documents 1 and 2 . However, there is a limit to avoiding interference by this method. For example, there is a case where there is a macro mobile station that cannot be connected to the femtocell base station in the same room where the femtocell base station is installed. In this case, according to the first method described in Patent Documents 1 and 2, the transmission power of the femtocell base station is reduced when there is a macro mobile station in the vicinity. However, there is a lower limit on the transmission power of the femtocell base station because of restrictions on specifications and the necessity of continuing communication with the mobile stations under its control. If there are no walls that shield each other between the macro mobile station and the femtocell base station, the propagation loss between the macro mobile station and the femtocell base station is the same as that between the macro mobile station and the macro mobile station. It is much smaller than that between base stations (for example, about several tens of dB). As a result, even if the femtocell base station transmits with the minimum power, the power of the interference wave from the femtocell base station to the macro mobile station is relatively stronger than the power of the desired wave from the macro base station. . In some cases, the macro mobile station may not be able to communicate. In addition, the above-described second methods described in Patent Documents 1 and 2 cannot be adopted unless the frequency band allocated to the communication carrier is sufficient.

  In the form D, the frequency band of the femtocell base station is limited to a part of the use frequency band of the macro base station. As a result, since the interference given to the macro mobile station can be limited to a part of the band, the communication quality can be maintained by the macro mobile station receiving the interference not using the band. However, the frequency band that can be allocated by the femtocell base station always decreases, and the communication quality such as the throughput of the femto mobile station deteriorates. For example, if the bandwidth is limited to half, the achievable peak rate is halved and the throughput is also greatly reduced.

  As described above, forms C and D, as well as patent documents, except when a frequency band dedicated to femtocells can be secured (that is, forms A and B and the second method described in Patent Documents 1 and 2). In any case of the first method described in 1 and 2, interference suppression when the macro mobile station and the femtocell base station approach each other is not sufficient, and depending on the situation, the communication quality of at least one of the macrocell and the femtocell is May deteriorate.

  The present invention has been made on the basis of the above-described knowledge, and an object of the present invention is to provide an operation mode in which a macro base station and a femtocell base station use the same frequency band, and a macro mobile station By providing a base station apparatus, a radio communication system, a radio resource allocation method, and a program capable of maintaining both the communication quality of a macro mobile station and the communication quality of a femto mobile station even in an extreme situation such as being near a station is there.

  A first aspect of the present invention is a base station apparatus. The base station apparatus includes a radio communication unit and a resource allocation unit. The wireless communication unit performs first wireless communication with at least one first mobile station. The resource allocation unit allocates a radio resource including a radio frequency to the first radio communication. Further, the resource allocating unit performs the first wireless communication before the approach when the approach to the second mobile station that performs the second wireless communication with the neighboring base station is estimated. A radio frequency to be allocated to the first radio communication is determined from a second frequency band limited to a part of the first frequency band that can be allocated.

  A second aspect of the present invention is a wireless communication system. The radio communication system includes a first base station and a resource allocation unit. The first base station performs first wireless communication with at least one first mobile station. The resource allocation unit allocates a radio resource including a radio frequency to the first radio communication. Further, the resource allocating unit performs the first wireless communication before the approach when the approach to the second mobile station that performs the second wireless communication with the neighboring base station is estimated. A radio frequency to be allocated to the first radio communication is determined from a second frequency band limited to a part of the first frequency band that can be allocated.

A third aspect of the present invention is a radio resource allocation method. The method includes the following steps (a) and (b).
Approach between a first base station that performs first wireless communication with at least one first mobile station and a second mobile station that performs second wireless communication with the second base station And a second limited to a portion of a first frequency band that could be assigned to the first wireless communication prior to the approach when the approach is estimated. Determining a radio frequency to be allocated to the first radio communication from a frequency band (b);

  A fourth aspect of the present invention is a program that causes a computer to perform the radio resource allocation method according to the third aspect of the present invention described above.

According to the present invention, in an operation mode in which the macro base station and the femtocell base station use the same frequency band, even in an extreme situation where the macro mobile station is in the vicinity of the femtocell base station, the communication quality of the macro mobile station And a base station apparatus, a radio communication system, a radio resource allocation method, and a program capable of maintaining both the communication quality of the Femto mobile station.
Can provide.

It is a figure which shows the structural example of the radio | wireless communications system which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structural example of the femtocell base station which concerns on Embodiment 1 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structural example of the femtocell base station which concerns on Embodiment 2 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 2 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 3 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 4 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 5 of this invention. It is a block diagram which shows the structural example of the femtocell base station which concerns on Embodiment 6 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 6 of this invention. It is a block diagram which shows the structural example of femto GW which concerns on Embodiment 7 of this invention. It is a flowchart which shows the specific example of the process sequence by femto GW which concerns on Embodiment 6 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 7 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 8 of this invention. It is a block diagram which shows the structural example of the femtocell base station which concerns on Embodiment 9 of this invention. It is a flowchart which shows the specific example of the radio | wireless resource allocation procedure performed by the femtocell base station which concerns on Embodiment 9 of this invention. It is a figure which shows an example of the time change of the uplink received power in the femtocell base station which concerns on Embodiment 1 of this invention. It is a figure which shows an example of the frequency and time resource allocation with respect to the data channel and control channel at the time of applying Embodiment 1 of this invention to LTE. It is a figure which shows the 1st example of the operation | use form of the frequency band of the femtocell base station which concerns on background art, and transmission power control. It is a figure which shows the 2nd example of the operation | use form of the frequency band of the femtocell base station which concerns on background art, and transmission power control. It is a figure which shows the 3rd example of the operation | use form of the frequency band of the femtocell base station which concerns on background art, and transmission power control. It is a figure which shows the 4th example of the operation | use form of the frequency band of the femtocell base station which concerns on background art, and transmission power control.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted as necessary for the sake of clarity.

<Embodiment 1 of the Invention>
FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to the present embodiment. The radio communication system according to the present embodiment includes a femtocell base station 1, a registered mobile station 2-1, an unregistered mobile station 2-2, and a peripheral base station 3 (for example, a macro base station, a micro base station, or a pico base station). )including. The femtocell base station 1 forms a femtocell 6. The femtocell base station 1 is connected to the network 5 via a femto gateway (GW) 4. The peripheral base station 3 forms a peripheral cell 7 (for example, a macro cell, a micro cell, or a pico cell). The femtocell 6 may be at least partially overlaid in the peripheral cell 7 or may be positioned so as not to overlap the peripheral cell 7. The registered mobile station 2-1 is a mobile station that is permitted to connect to the femtocell base station 1. The unregistered mobile station 2-2 is a mobile station that is not permitted to connect to the femtocell base station 1. In the following description, it is assumed that the neighboring base station 3 is a macro base station, the neighboring cell 7 is a macro cell, and the unregistered mobile station 2-2 is a macro mobile station. The registered mobile station 2-1 is called a femto mobile station.

  FIG. 2 is a block diagram illustrating a configuration example of the femtocell base station 1 according to the present embodiment. The femtocell base station 1 includes a radio communication unit 10 and a radio resource allocation unit 11. The wireless communication unit 10 receives an uplink signal from a mobile station via a reception antenna. The received data is transmitted to the femto GW4. Further, the wireless communication unit 10 generates a downlink signal including control data and user data received from the femto GW 4 and wirelessly transmits the downlink signal via the transmission antenna. The wireless communication unit 10 may be a communication unit on the base station side adapted to a wireless system such as W-CDMA, E-UTRA, or IEEE 802.16m. Here, the description regarding the detail of the structure of the radio | wireless communication part 10 is abbreviate | omitted.

  The radio resource allocating unit 11 determines a radio resource used for radio communication between the radio communication unit 10 and the femto mobile station 2-1, and instructs the radio communication unit 10 to determine the radio resource. Hereinafter, wireless communication between the wireless communication unit 10 and the femto mobile station 2-1 is referred to as “femto wireless communication” for convenience. Femto radio communication includes uplink radio communication and downlink radio communication. The radio resource determined by the radio resource allocation unit 11 includes at least one of a radio frequency used for downlink radio communication and a radio frequency used for uplink radio communication.

  More specifically, when the approach between the macro mobile station 2-2 and the femtocell base station 1 is estimated, the radio resource allocator 11 can allocate frequencies to the femto radio communication before this approach. A radio frequency to be allocated to femto radio communication is determined from a frequency band (hereinafter, second frequency band FB2) limited to a part of the band (hereinafter, first frequency band FB1). The restriction from FB1 to FB2 may be performed on either the downlink signal or the uplink signal, or may be performed on both the downlink signal and the uplink signal. By narrowing the use frequency band of the downlink signal, downlink interference from the femtocell base station 1 to the macro mobile station 2-2 can be reduced. On the other hand, uplink interference from the macro mobile station 2-2 to the femtocell base station 1 can be reduced by narrowing the use frequency band of the uplink signal. The radio resource allocation unit 11 may broadcast information on the frequency band FB2 after being limited to the femto mobile station 2-1, as necessary.

  Various specific modes can be considered as to how to select the usable frequency band FB2 after the approach from the usable frequency band FB1 before the approach. For example, a predetermined ratio (for example, 50%, 40%, etc.) of FB1 may be set as FB2. The frequency range selected as FB2 from FB1 may be determined in advance, or may be determined dynamically when performing the restriction. Further, for example, in the case of E-UTRA, both the frequency band used for the control channel and the frequency band used for the data channel for transmitting user data in one subframe may be reduced at the same ratio. Further, the reduction rate may be changed between the frequency band used for the control channel and the frequency band used for the data channel. For example, the frequency band used for the control channel may be maintained in FB2 and the frequency band used for the data channel may be reduced.

The approach determination between the macro mobile station 2-2 and the femtocell base station 1 may be performed by the femtocell base station 1 or other devices (for example, the macro base station 3, the femto GW4, and devices arranged in the network 5). , Femto mobile station 2-1, or macro mobile station 2-2). The approach between the macro mobile station 2-2 and the femtocell base station 1 can be determined using, for example, at least one of the following indices (1) to (5).
(1) Increase in uplink received power at the femtocell base station 1;
(2) Increase in downlink received power from the femtocell base station 1 in the macro mobile station 2-2;
(3) Reduction of the distance between these two devices calculated using the position information of the femtocell base station 1 and the position information of the macro mobile station 2-2;
(4) reception of a connection request from the macro mobile station 2-2 in the femtocell base station 1;
(5) Reception of the handover request of the macro mobile station 2-2 via the network 5 in the femtocell base station 1.

  FIG. 3 is a flowchart showing a specific example of the radio resource allocation procedure performed by the radio resource allocation unit 11. When the macro mobile station 2-2 is not approaching the femtocell base station 1 (NO in step S11), the radio resource allocation unit 11 maintains the frequency band that can be allocated for femto radio communication as FB1 ( Step S12). On the other hand, when the macro mobile station 2-2 approaches the femtocell base station 1 (YES in step S11), the radio resource allocation unit 11 narrows the frequency band that can be allocated for femto radio communication to FB2 (step S13). ). In step S14, the radio resource allocating unit 11 determines a radio frequency to be specifically allocated to radio communication (data channel and control channel) with the currently connected femto mobile station 2-1 from the FB2, This is instructed to the wireless communication unit 10. In the case of E-UTRA, step S14 corresponds to resource block scheduling by the scheduler.

  As described above, the femtocell base station 1 according to the present embodiment uses the entire frequency band (FB1) for femto radio communication unless the macro mobile station 2-2 and the femtocell base station 1 are close to each other. it can. On the other hand, when the approach between the macro mobile station 2-2 and the femtocell base station 1 is estimated, the femtocell base station 1 sets the frequency band (FB2) that can be used for femto radio communication before approaching. Narrow to a part of the usable frequency band (FB1).

  For example, in the case of E-UTRA, the downlink frequency band in which the macro mobile station 2-2 receives strong interference from the femtocell base station 1 is reduced from the entire FB1 to FB2 by narrowing the frequency band used for downlink femto radio communication. To do. The macro mobile station 2-2 reports to the macro base station 3 that the reception quality of the band FB2 has deteriorated by transmitting quality information (for example, CQI: Channel Quality Indication). When the macro base station 3 schedules radio resources to the macro mobile station 2-2, the macro base station 3 allocates resource blocks based on the quality information received from the macro mobile station 2-2. Specifically, the scheduler of the macro base station 3 allocates a resource block that uses a frequency other than FB2 to the macro mobile station 2-2 with poor reception quality in the band FB2. As a result, the femtocell base station 1 and the macro mobile station 2-2 that approaches the femtocell base station 1 use a different frequency range in the entire band FB1. That is, the femtocell base station 1 uses FB2, and the macro mobile station 2-2 uses other frequencies excluding FB2.

  That is, the base station 1 according to the present embodiment is configured such that the macro mobile station 2-2 is in the vicinity of the femtocell base station 1 in the operation mode in which the macro base station 3 and the femtocell base station 1 use the same frequency band FB1. When approaching, the use frequency band of the femtocell base station 1 is narrowed to a part of the band (FB2) included in the FB1. Thereby, even in an extreme situation where the macro mobile station 2-2 is in the vicinity of the femtocell base station 1, both the communication quality of the macro mobile station 2-2 and the communication quality of the femto mobile station 2-1 can be maintained. .

  Further, the band limiting process by the radio resource allocating unit 11 described in the present embodiment is ASIC (Application Specific Integrated Circuit), DSP (Digital Signal Processor), MPU (Micro Processing Unit) or CPU (Central Processing Unit) or these. It is realizable using the computer system containing the combination of these. Specifically, it is sufficient to cause a computer system to execute a program including a group of instructions related to these processing procedures.

  These programs can be stored using various types of non-transitory computer readable media and supplied to a computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / W and semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)) are included. The program may also be supplied to the computer by various types of transitory computer readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

  Modifications of the femtocell base station 1 described in the present embodiment will be described in detail in Embodiments 2 to 9 of the invention described below.

<Embodiment 2 of the Invention>
In the present embodiment, an example in which the femtocell base station 1 performs the approach determination between the femtocell base station 1 and the macro mobile station 2-2 will be described. Furthermore, in the present embodiment, an example will be described in which the proximity determination is performed using an increase in uplink reception power in the femtocell base station 1 as an index. Furthermore, in the present embodiment, a configuration example of a radio resource allocation unit 11 suitable for a multiple access scheme that performs dynamic allocation of radio resources including frequency and time as in E-UTRA will be described.

  A configuration example of the wireless communication system according to the present embodiment is the same as that shown in FIG. FIG. 4 is a block diagram showing a configuration example of the femtocell base station 1 according to the present embodiment. In FIG. 4, the approach determination unit 12 determines the approach between the macro mobile station 2-2 and the femtocell base station 1. The approach between the macro mobile station 2-2 and the femtocell base station 1 may be determined based on a spatial distance or may be determined based on a radio wave distance based on a propagation loss. In this embodiment, the reception power P_ul of the uplink received by the wireless communication unit 10 is measured, and the approach is determined by comparing the reception power P_ul with a threshold value.

  The radio resource allocation unit 11 illustrated in FIG. 4 includes a radio resource control unit 111, a resource scheduling unit 113, and an own cell quality information acquisition unit 112. The radio resource control unit 111 determines radio resource adjustment based on the determination result of the approach determination unit 12. Specifically, the radio resource control unit 111 sets the frequency band that can be used for femto radio communication to the entire band FB1 according to whether the macro mobile station 2-2 and the femtocell base station 1 are close to each other. Or to limit to a part (FB2) thereof.

  The own cell quality information acquisition unit 112 is in the femtocell 6 and acquires a measurement report including quality information indicating the reception quality of the downlink signal of the femtocell base station 1 measured by the femto mobile station 2-1. In the case of W-CDMA, the received power (RSCP: Received Signal Code Power) or received quality (SINR: Signal-to-Interference plus Noise power Ratio, Ec / Io etc.). In the case of E-UTRA, the reception quality of the downlink signal is the received power (RSRP: Reference Signal Received Power) or the reception quality (RSRQ: Reference Signal Received) when receiving a reference signal sent using a predetermined downlink resource element. Quality). The setting of items to be actually measured, report cycle, etc. may be notified from the upper network 5 to the femtocell base station 1. The measurement report is discretized into CQI (Channel Quality Indicator) and transmitted from the femto mobile station 2-1 to the femtocell base station 1 using the uplink control channel. The CQI creation method may be appropriately selected from a plurality of methods, such as a method of making one for the entire band and a method of making a unit of divided frequencies.

  The resource scheduling unit 113 performs radio resource scheduling for radio communication (femto radio communication) between the femto mobile station 2-1 and the radio communication unit 10. In this scheduling, the quality information of the downlink reception quality acquired by the own cell quality information acquisition unit 112 and the band limitation result by the radio resource control unit 111 are reflected. By referring to the downlink reception quality, the resource scheduling section 113 determines a communication rate that can be transmitted using each resource unit (eg, E-UTRA resource block) divided by frequency and time. When a plurality of femto mobile stations 2-1 are connected to the femtocell base station 1, the resource scheduling unit 113 assigns to each mobile station based on the quality information reported from the plurality of mobile stations 2-1. Determine resources.

  FIG. 5 is a flowchart showing a specific example of a radio resource allocation procedure performed by the femtocell base station 1 according to the present embodiment. Comparing FIG. 5 and FIG. 3, the flowchart of FIG. 5 includes steps S20 and S21 instead of step S11. Steps S20 and S21 relate to the approach determination between the macro mobile station 2-2 and the femtocell base station 1.

  In step S20, the approach determination unit 12 measures the uplink received power P_ul. The uplink received power P_ul may be measured for each resource block, or may be an integrated value or an average value over the entire frequency band. The uplink received power P_ul varies with time as the femto mobile station 2-1 and the macro mobile station 2-2 located around the femtocell base station 1 transmit uplink signals, and also varies on the frequency axis. To do. When measuring P_ul, especially when the femto mobile station 2-1 and the macro mobile station 2-2 are transmitting data, the uplink from the macro mobile station 2-2 is removed except for the contribution of the femto mobile station 2-1. The received power of the signal may be P_ul. Instead of this, the received power measured in a state where the femto mobile station 2-1 is not transmitting may be P_ul. Further, P_ul may be an instantaneous value at a certain time, or may be a statistical value such as an average value, median value, representative value, or X% value from the top of a plurality of samples measured over a certain period (X is a positive value). Integer).

  In step S21, the approach determination unit 12 compares P_ul with a predetermined threshold A. The threshold A may be set according to the definition of P_ul measurement. That is, whether P_ul is a measurement result for each resource block, a measurement result in the entire frequency band, a measurement result of contribution of only the macro mobile station 2-2, or a contribution of the femto mobile station 2-1 An appropriate value may be set as the threshold value A depending on whether it is a measurement result of the total received power included.

  Other steps S12 to 14 shown in FIG. 5 are the same as steps S12 to 14 shown in FIG.

<Third Embodiment of the Invention>
In the present embodiment, an example of how to determine the restricted radio frequency band FB2 when the femtocell base station 1 and the macro mobile station 2-2 approach each other will be described. More specifically, in this embodiment, when limiting the frequency band that can be allocated to femto wireless communication, the frequency band for the data channel is preferentially narrowed.

A configuration example of the wireless communication system according to the present embodiment is the same as that shown in FIG. Moreover, the structural example of the femtocell base station 1 concerning this Embodiment is the same as that of FIG. 2 or FIG. FIG. 6 is a flowchart showing a specific example of a radio resource allocation procedure performed by the femtocell base station 1 according to the present embodiment. As shown in step S33, in the present embodiment, the radio resource control unit 111, upon approach of the macro mobile station 2-2, while maintaining the bandwidth for the control channel, reducing the bandwidth for data channel To do.

  Compared with the case where the frequency band is limited for both the data channel and the control channel, this embodiment can reduce the influence on the overall configuration of the radio communication system.

<Embodiment 4 of the Invention>
In the present embodiment, another example of how to determine the restricted radio frequency band FB2 when the femtocell base station 1 and the macro mobile station 2-2 approach each other will be described. More specifically, in the present embodiment, when the frequency band that can be allocated to femto radio communication is limited, the frequency band is limited according to the number of femto mobile stations 2-1 connected to the femtocell base station 1. Determine the bandwidth.

  A configuration example of the wireless communication system according to the present embodiment is the same as that shown in FIG. Moreover, the structural example of the femtocell base station 1 concerning this Embodiment is the same as that of FIG. 2 or FIG. FIG. 7 is a flowchart showing a specific example of a radio resource allocation procedure performed by the femtocell base station 1 according to the present embodiment. As shown in step S43, in the present embodiment, the radio resource control unit 111 sets the bandwidth of the limited frequency band FB2 according to the number of femto mobile stations 2-1 connected to the femtocell base station 1. To decide. For example, when the number of connected femto mobile stations 2-1 is small (such as one), there are few mobile stations that are affected by restricting the frequency band, so the bandwidth of the restricted frequency band FB2 is relatively Should be narrowed. On the other hand, when the number of connected femto mobile stations 2-1 is large (such as 5), there are many mobile stations that are affected by limiting the frequency band. What is necessary is just to make a bandwidth comparatively wide. It should be noted that priority indicating which band is to be limited when performing band limitation is set in advance, and in accordance with the increase in the number of connections of the femto mobile station 2-1, the band cannot be used in descending order of priority. A band to be selected may be selected.

  In the present embodiment, the bandwidth of the limited frequency band FB2 is determined according to the number of femto mobile stations 2-1 connected to the femtocell base station 1. For this reason, the influence on the communication quality (for example, throughput) of the femto mobile station 2-1 can be considered.

<Embodiment 5 of the Invention>
In the present embodiment, another example of how to determine the restricted radio frequency band FB2 when the femtocell base station 1 and the macro mobile station 2-2 approach each other will be described. More specifically, in the present embodiment, the limited bandwidth is determined according to the QoS (Quality of service) of the bearer used by the connected femto mobile station 2-1.

  A configuration example of the wireless communication system according to the present embodiment is the same as that shown in FIG. Moreover, the structural example of the femtocell base station 1 concerning this Embodiment is the same as that of FIG. 2 or FIG. FIG. 8 is a flowchart showing a specific example of a radio resource allocation procedure performed by the femtocell base station 1 according to the present embodiment. As shown in step S53, in this embodiment, the radio resource control unit 111 determines the bandwidth of the restricted frequency band FB2 according to the QoS of the bearer used by the connected femto mobile station 2-1. To do.

  The bearer is a traffic transmission line set to provide services such as voice and data between a base station and a mobile station. QoS defines the priority for providing services such as voice and data, and target values for achieving predetermined quality. In general, voice has higher QoS than data (FTP, Web, mail, etc.). Therefore, for example, when the bearer of the connected femto mobile station 2-1 is for data, the required QoS is relatively low, and therefore the bandwidth of the restricted frequency band FB2 may be relatively narrowed. Conversely, when the bearer of the connected femto mobile station 2-1 is for voice, the required QoS is relatively high, and therefore the bandwidth of the restricted frequency band FB2 may be made relatively wide. In addition, when the priority indicating which band is limited when performing the band limitation is set in advance and the QoS of the bearer used by the connected femto mobile station 2-1 is low, the band with the higher priority. Bands that cannot be used may be selected in order.

  In the present embodiment, the bandwidth of the restricted frequency band FB2 is determined according to the QoS of the bearer of the femto mobile station 2-1 connected to the femtocell base station 1. For this reason, the influence on the communication quality (for example, throughput) of the femto mobile station 2-1 can be considered.

<Sixth Embodiment of the Invention>
In the present embodiment, another example of how to determine the restricted radio frequency band FB2 when the femtocell base station 1 and the macro mobile station 2-2 approach each other will be described. Specifically, in the present embodiment, the femto mobile station 2-1 or the femtocell base station 1 measures the reception quality of the downlink signal from the macro base station 3, and receives the downlink signal from the macro base station 3. Based on the quality, it is determined which frequency (frequency band) included in the entire FB1 before the restriction is not used.

  A configuration example of the wireless communication system according to the present embodiment is the same as that shown in FIG. FIG. 9 is a block diagram illustrating a configuration example of the femtocell base station 1 according to the present embodiment. In FIG. 9, the other cell quality information acquisition unit 114 acquires the measurement result of the reception quality of the downlink signal from the macro base station 3 measured by the femto mobile station 2-1. In the case of W-CDMA, the downlink reception quality is the reception power (RSCP) or reception quality (SINR, Ec / Io, etc.) when receiving the pilot signal transmitted using the entire frequency band. Good. In the case of E-UTRA, the reception quality of the downlink signal may be reception power (RSRP) or reception quality (RSRQ) when receiving a reference signal transmitted using a predetermined downlink resource element. The setting of items to be actually measured, report cycle, etc. may be notified from the upper network 5 to the femtocell base station 1 or the femto mobile station 2-1.

  The radio resource control unit 111 illustrated in FIG. 9 determines which frequency (frequency band) included in the entire FB1 before the restriction is not used based on the reception quality of the downlink signal from the macro base station 3.

  FIG. 10 is a flowchart showing a specific example of a radio resource allocation procedure performed by the femtocell base station 1 according to the present embodiment. 10 is compared with FIG. 5, the flowchart of FIG. 10 includes step S63 instead of step S13. Furthermore, step S60 is added to FIG. In step S60, the other cell quality information acquisition unit 114 receives the measurement result of the reception quality of the downlink signal from the macro base station 3 from the femto mobile station 2-1. The reception quality of the downlink signal from the macro base station 3 may be a report value at a predetermined time, an average value of a plurality of samples acquired during a predetermined period, a median value, a representative value, or a value of X% from the top Or the like (X is a positive integer).

In step S63, the radio resource control unit 111 sets the frequency band FB2 after restriction, in other words, the unused band in the band FB1 before restriction based on the measurement result of the reception quality of the downlink signal from the macro base station 3. To decide. Specifically, the radio resource control unit 111 preferentially selects a frequency band in which the reception quality of the downlink signal from the macro base station 3 is lower than the reference as the restricted frequency band FB2. This is because the macro base station 3 sends radio resources (such as resource blocks) that use a band in which the reception quality of the downlink signal from the macro base station 3 by the macro mobile station 2-2 is low to the macro mobile station 2-2. This is because the possibility of assignment to the user is small. That is, for the macro mobile station 2-2 located in the vicinity of the femtocell base station 1 and the femto mobile station 2-1, the frequency at which the reception quality of the macro base station 3 measured by the femto mobile station 2-1 is low. It can be estimated that it is difficult to allocate the bandwidth. Therefore, even when the femtocell base station 1 uses this band, interference with the macro mobile station 2-2 is reduced.

  As described above, the present embodiment preferentially selects the frequency band estimated to have little influence on the macro mobile station 2-2 as the restricted frequency band FB2, and therefore, between the macro and femto. Interference can be reduced more effectively.

<Seventh Embodiment of the Invention>
In the present embodiment, an example will be described in which the same frequency band is used as the restricted frequency band FB2 among the plurality of femtocell base stations 1 under the femto GW4. A configuration example of the wireless communication system according to the present embodiment is the same as that shown in FIG. Moreover, the structural example of the femtocell base station 1 concerning this Embodiment is the same as that of FIG. However, the radio resource control unit 111 included in the femtocell base station 1 according to the present embodiment exchanges information with the femto GW4. Specifically, the radio resource control unit 111 determines the restricted frequency band FB2 as in the previous embodiments, but reports information on the determined frequency band FB2 to the femto GW4. The femto GW 4 acquires similar information from the plurality of femto cell base stations 1, determines a band to be used as the frequency band FB2, and uses the determined band information (hereinafter referred to as band designation information) to each femto cell base station. 1 to send. The radio resource control unit 111 resets the restricted frequency band FB2 according to the band designation information received from the femto GW4.

  FIG. 11 is a block diagram illustrating a configuration example of the femto GW 4 according to the present embodiment. The femtocell base station information acquisition unit 41 acquires information on the frequency band determined by the femtocell base station 1 as FB2. The band designation information creation unit 42 compares the information of the frequency band FB2 acquired from the femtocell base station 1 with the information of the frequency band FB2 that has already been received from the other adjacent femtocell base station 1. Then, the band designation information creating unit 42 creates band designation information that designates a band to be used as the frequency band FB2 after the restriction by the plurality of femtocell base stations 1 that are adjacent to each other. The band designation information transmission unit 43 transmits the band designation information to the femtocell base station 1.

  The operation of the femto GW 4 in this embodiment will be described with reference to the flowchart of FIG. In step S701, the femtocell base station information acquisition unit 41 acquires information on the frequency band FB2 in order from the plurality of femtocell base stations 1. Specifically, the femtocell base station information acquisition unit 41 acquires information indicating a band to be used as the frequency band FB2.

  In step S702, based on the information acquired in step S701, the band designation information creating unit 42 uses the same frequency band as the limited frequency band FB2 among the plurality of femtocell base stations 1 that are adjacent to each other. Create bandwidth specification information as follows. Specifically, the band designation information creation unit 42, when a certain femtocell base station 1 has reported the frequency band FB2, if there is no other femtocell base station 1 adjacent to the reporting base station, Band designation information for permitting the reported frequency band FB2 may be created. On the other hand, if there is another femtocell base station 1 adjacent to the reporting base station, and the other femtocell base station 1 has not yet restricted the frequency band, it is reported. Band designation information indicating that the frequency band FB2 is permitted may be created. Further, when there is another femtocell base station 1 adjacent to the reporting base station, and the other femtocell base station 1 has already restricted the frequency band, the reported frequency band Band designation information for refusing FB 2 and designating use of the same frequency band as that of another adjacent femtocell base station 1 may be created.

  In step S <b> 703, the band designation information transmitting unit 43 transmits band designation information to the report source femtocell base station 1.

  FIG. 13 is a flowchart showing a specific example of a radio resource allocation procedure performed by the femtocell base station 1 according to the present embodiment. Comparing FIG. 13 with FIG. 5, the flowchart of FIG. 13 includes steps S731 to S733 instead of step S13. In step S731, the radio resource control unit 111 determines the restricted frequency band FB2, and transmits information on the band selected as FB2 to the femto GW4. In step S732, the radio resource control unit 111 receives band designation information notified from the femto GW4. In step S733, the radio resource control unit 111 resets the restricted frequency band FB2 so as to match the frequency band indicated in the received band designation information.

  As described above, in the present embodiment, the plurality of femtocell base stations 1 that are adjacent to each other use the same frequency band as the limited frequency band FB2. Therefore, even when a plurality of femtocell base stations 1 are arranged in close proximity to each other, it is possible to create a free band for use by the macro mobile station 2-2.

  In the above description, the example in which the femto GW 4 generates band designation information has been described. However, the band designation information may be generated by another device arranged in the network 5.

<Embodiment 8 of the Invention>
In the present embodiment, a specific example of a procedure for returning from the restricted frequency band FB2 to the original frequency band FB1 will be described. A configuration example of the wireless communication system according to the present embodiment is the same as that shown in FIG. Moreover, the structural example of the femtocell base station 1 concerning this Embodiment is the same as that of FIG.

  FIG. 14 is a flowchart showing a specific example of a radio resource allocation procedure performed by the femtocell base station 1 according to the present embodiment. In step S80, the radio resource allocation unit 11 limits the frequency band that can be allocated to the femto radio communication from FB1 to FB2 as in any of the second to seventh embodiments. In this case, the frequency band assigned to femto wireless communication may be rapidly switched from FB1 to FB2.

  In step S81, the approach determination unit 12 measures the uplink received power P_ul. In step S <b> 82, the approach determination unit 12 compares P_ul with a predetermined threshold B. The threshold value B may be the same as the threshold value A when determining approach, but may be a different value. For example, the threshold value B may be set to a value smaller than the threshold value A.

  When it is determined that the uplink received power P_ul is still higher than the threshold value B (YES in step S82), the radio resource control unit 111 continues to limit the frequency band (step S83). This is because it is estimated that the macro mobile station 2-2 is still in the vicinity of the femtocell base station 1.

  On the other hand, when it is determined that the uplink received power P_ul is equal to or less than the threshold value B (NO in step S82), the radio resource control unit 111 releases the restriction on the frequency band (step S84). When canceling the restriction on the frequency band, it is preferable to gradually increase the frequency band to be used instead of suddenly returning from FB2 to FB1. For example, it is good to return to FB1 slowly in the order of several seconds to several minutes.

  As described above, according to the present embodiment, the frequency band that can be allocated to femto wireless communication is suddenly reduced from FB1 to FB2 when the frequency band that can be allocated to femto radio communication is reduced, and when the restriction is released, the frequency band can be reduced compared to the restriction time. The bandwidth that can be allocated slowly and gradually increases from FB2 to FB1. As a result, it is possible to avoid suddenly giving large interference to the macro mobile station 2-2.

<Ninth Embodiment of the Invention>
In this embodiment, a modified example of the approach determination between the femtocell base station 1 and the macro mobile station 2-2 will be described. A configuration example of the wireless communication system according to the present embodiment is the same as that shown in FIG. FIG. 15 is a block diagram illustrating a configuration example of the femtocell base station 1 according to the present embodiment.

  The radio resource control unit 111 illustrated in FIG. 15 receives information (hereinafter referred to as approach determination information) used for approach determination from the macro base station 3 or a device arranged in the network 5. And the radio | wireless resource control part 111 implements the zone | band limitation from FB1 to FB2, when approach determination information shows the approach of the femtocell base station 1 and the macro mobile station 2-2.

  An example of the approach determination information is reception quality of the downlink signal from the femtocell base station 1 measured by the macro mobile station 2-2. The femtocell base station 1 may receive the measurement result from the macro base station 3. When the macro base station 3 detects that the macro mobile station 2-2 receives strong interference from the specific femtocell base station 1, the macro base station 3 may transfer the measurement result to the corresponding femtocell base station 1. In the case of W-CDMA, the reception quality of the downlink signal from the femtocell base station 1 is the reception power (RSCP) when receiving the pilot signal transmitted using the entire frequency band, or the reception quality (SINR, Ec / Io etc.). In the case of E-UTRA, reception power (RSRP) or reception quality (RSRQ) when receiving a reference signal transmitted using a predetermined downlink resource element may be used.

  Another example of the approach determination information is distance information between these two devices calculated using the position information of the femtocell base station 1 and the position information of the macro mobile station 2-2. This distance calculation may be performed by a device that knows the position of the femtocell base station 1, for example, an OAM (Operation and Maintenance) server disposed in the macro base station 3 or the network 5. As the position information of the macro mobile station 2-2, for example, position information obtained by a GPS (Global Positioning System) receiver mounted on the mobile station 2-2 may be used. Further, the position information of the macro mobile station 2-2 may be estimated by using downlink signal measurement information reported by the macro mobile station 2-2.

  For example, the case where the macro base station 3 estimates the distance between the femtocell base station 1 and the macro mobile station 2-2 will be described. In this case, the macro base station 3 refers to the position information of the femtocell base station 1 arranged in the macro cell 7. The location information of the femtocell base station 1 may be set in advance in the macro base station 3 by the operator, or may be automatically supplied from the OAM server to the macro base station 3, or the macro base station 3 accesses the OAM server or the like. You may acquire by doing. The macro base station 3 acquires the position information of the macro mobile station 2-2 in the macro cell 7 from the measurement information reported by the macro mobile station 2-2, and compares it with the position information of the femtocell base station 1. What is necessary is just to estimate a distance.

  Still another example of the approach determination information is a notification indicating that the approach between the femtocell base station 1 and the macro mobile station 2-2 is determined. In this case, the device arranged in the macro base station 3 or the network 5 may determine the approach between the femtocell base station 1 and the macro mobile station 2-2 and notify the femtocell base station 1 of the determination result. . The approach determination may be performed using any of the methods already described in the first to eighth embodiments and the present embodiment.

  For example, if the macro base station 3 detects that the macro mobile station 2-2 is located in the vicinity (for example, about 10 m) of the specific femtocell base station 1 by calculation using the position information, the macro base station 3 A notification indicating that the macro mobile station 2-2 is in the vicinity may be generated and transmitted to the specific femtocell base station 1.

  FIG. 16 is a flowchart showing a specific example of a radio resource allocation procedure performed by the femtocell base station 1 according to this embodiment. 16 is compared with FIG. 5, the flowchart of FIG. 16 includes step S91 instead of steps S20 and S21. In step S91, the radio resource control unit 111 determines whether or not the approach determination information has been received. When the access determination information is received, or when the content of the access determination information indicates an approach between the femtocell base station 1 and the macro mobile station 2-2 (YES in step S91), the radio resource control unit 111 performs femto radio communication. The usable frequency band is limited to FB2 (step S13).

<Other embodiments>
In the above-described first to ninth embodiments of the invention, the case where the present invention is applied to the wireless communication system of the W-CDMA system or the E-UTRA system has been described. However, the wireless communication system to which the present invention is applied is not particularly limited. For example, the present invention can also be applied to a wireless communication system (for example, WiMAX, IEEE 802.16m) that employs a TDD (Time Division Duplex) method in which the same radio frequency is used in the uplink and downlink. .

  In addition, the configuration of the femtocell base station according to the embodiment of the invention described above is an example, and other configurations are possible. For example, the function of limiting the frequency band may be executed by a device arranged in the network 5 such as a high-order femto GW 4, an RNC (Radio Network Controller), or an OAM server. For example, the radio resource control unit 111 may be arranged in the RNC. In this case, the RNC may receive the approach determination result from the femtocell base station 1 and limit the frequency band. Further, the RNC may transmit the frequency band restriction result to the femtocell base station 1. Thus, the function of the radio resource control unit 111 can be arbitrarily shared between the femtocell base station 1 and the upper network 5 to which the femtocell base station 1 is connected.

  Moreover, Embodiment 1-9 of invention demonstrated the case where this invention was applied to the femtocell base station 1. FIG. However, the present invention is not limited to the femtocell base station 1 but can be applied to a pico base station, a micro base station, and a macro base station that cover a wider area than the femtocell base station 1. Furthermore, the present invention is applicable not only for avoiding interference between a macro base station and a femtocell base station but also for avoiding interference between femtocell base stations.

  Further, Embodiments 1 to 9 of the invention detect that the macro mobile station 2-2 as an unregistered mobile station is in the vicinity of the femtocell base station 1. However, the macro mobile station 2-2 may be a registered mobile station that can communicate with the femtocell base station 1. For example, it is assumed that the registered mobile station communicates with the macro base station 3 before handing over to the femtocell base station 1. In order to reduce the interference given to the macro mobile station 2-2 as the registered mobile station, it may be detected that the macro mobile station 2-2 as the registered mobile station is in the vicinity of the femtocell base station 1.

Further, Embodiment 6 of the invention has shown a specific example in which a registered mobile station that communicates with the femtocell base station 1 measures reception quality of a downlink signal from the macro base station 3. However, the femtocell base station 1 itself may measure this. Specifically, a downlink reception power measurement function such as a mobile station may be arranged in the femtocell base station 1 so that the femtocell base station 1 measures the reception quality of the downlink signal of the macro base station 3. This function is called Network Listening Mode (NLM) and is a function installed in the recent femtocell base station 1. The NLM is normally used for power setting when the femtocell base station 1 is activated, but other timing, for example, when not communicating with a registered mobile station, or when stopping transmission during communication with a registered mobile station ( It may be measured during the transmission gap period.

  Moreover, Embodiment 7 of the invention showed the specific example which exchanges the restriction | limiting information of the use frequency band of the femtocell base station 1 via femto GW4. However, the restriction information of the used frequency band may be directly exchanged between the plurality of femtocell base stations 1 that are adjacent to each other. In this case, when a certain femtocell base station 1 limits the frequency band to be used, the information may be transmitted to another adjacent femtocell base station 1. When the other femtocell base station 1 detects that there is a macro mobile station 2-2 that causes interference in the vicinity, the femtocell base station 1 limits the same band as the femtocell base station 1 that is the information transmission source based on the received information. What is necessary is just to use as subsequent frequency band FB2.

  Hereinafter, some application examples corresponding to the above-described embodiments will be described in detail with reference to the drawings.

<Application example 1>
This application example is an example of approach determination between the femtocell base station 1 and the macro mobile station 2-2 described in the first to eighth embodiments. Specifically, an example will be described in which the approach between the femtocell base station 1 and the macro mobile station 2-2 is determined using the uplink received power P_ul as an index. An example of the time change of P_ul is shown in FIG. FIG. 17 illustrates an example of a temporal change in the uplink received power P_ul. In FIG. 17, the horizontal axis represents time, and the vertical axis represents uplink received power P_ul. The threshold A shown in FIG. 17 is a threshold (see Embodiments 2 to 7 of the invention) used when determining the approach between the femtocell base station 1 and the macro mobile station 2-2. The threshold value B shown in FIG. 17 is a threshold value (see Embodiment 8 of the invention) used when determining that the femtocell base station 1 and the macro mobile station 2-2 are separated.

  Since the uplink received power is equal to or lower than the threshold A until time T1, it is considered that the macro mobile station 2-2 is relatively far from the femtocell base station 1. This is because the uplink reception power P_ul is small because the propagation loss between the femtocell base station 1 and the macro mobile station is large. Therefore, the femtocell base station 1 does not determine the approach of the macro mobile station 2-2.

  As the macro mobile station 2-2 approaches the femtocell base station 1, the uplink received power P_ul increases and exceeds the threshold A at time T1. The femtocell base station 1 determines that the macro mobile station 2-2 is in the vicinity when P_ul exceeds the threshold A for a time TTT1 (Time To Trigger) or more, and can be assigned to femto radio communication. Implement restrictions. The reason why the predetermined time TTT1 is provided to determine whether the macro mobile station 2-2 is in the vicinity is to ensure the stability of the system. If the frequency limit is immediately performed when P_ul exceeds the threshold A, the start and stop of the frequency limit operation of the femtocell base station 1 may frequently occur when the P_ul fluctuates around the threshold A. High nature. Therefore, in order to avoid this instability, the time TTT1 may be provided.

  When it is determined that the macro mobile station 2-2 is in the vicinity of the femtocell base station 1 and a time T2 is reached after a while, P_ul becomes the threshold value B or less. At this time, the femtocell base station 1 recognizes that the macro mobile station 2-2 is moving away, and if this state continues for a time TTT2, it determines that the macro mobile station 2-2 has moved far enough and releases the restriction on the frequency. To do. Although the threshold value B may be the same value as the threshold value A, the threshold value B is made smaller than the threshold value A in FIG.

  As described in the second embodiment of the invention, there are various variations in the method for measuring the uplink received power Pul. P_ul may be a physical quantity expressed in dB as a ratio to thermal noise, such as noise rise or IoT (Interference over Thermal noise). Further, in terms of correspondence with the wireless communication system, the uplink received power for all frequency bands is measured in the W-CDMA system, and the uplink received power is measured for each resource block in the E-UTRA system. In particular, in the case of the E-UTRA scheme, the total value or average value of the uplink received power for each resource block may be used, but the uplink received power for each resource block is compared with the threshold A (actually, the value obtained by dividing the threshold A by the number of resource blocks). May be. In this case, when the number of resource blocks whose uplink received power exceeds the threshold A exceeds the threshold, it can also be determined that the macro mobile station 2-2 is in the vicinity of the femtocell base station 1.

<Application example 2>
In this application example, a case where the frequency band limiting operation described in the first to ninth embodiments is applied to LTE (Long Term Evolution) will be described as an example.

  FIG. 18 shows how resource blocks are allocated to main channels in LTE. FIG. 18 shows PDSCH (Physical Downlink Shared Channel), PDCCH (Physical Downlink Control Channel), P-SCH (Primary Synchronization Channel), S-SCH (Secondary Synchronization Channel), and BCH (Broadcast Channel) in a subframe of 1 msec. ) Indicates the allocation of resource blocks to which the resource blocks are allocated. PDSCH is a shared data channel for transmitting downlink user data. PDCCH is a control channel for transmitting downlink scheduling information such as frequency allocation, modulation scheme, data amount, retransmission information, and the like. P-SCH and S-SCH are control channels used for cell search. BCH is a control channel for transmitting broadcast information. PDSCH and PDCCH are transmitted using the entire frequency band in each subframe when there is user data to be transmitted. The SCH is transmitted using 6 RBs at the center of the frequency band at a period of 5 msec. The BCH is transmitted using 6 RBs in the center of the frequency band in 4 subframes in a 40 msec cycle.

  For LTE using data channel and control channel resource allocation as shown in FIG. 18, the frequency band limiting operation performed by the femtocell base station 1 may have several variations. An example is shown below. First, there is a method of obtaining the restricted band FB2 by compressing the entire frequency band FB1 before the approach for both the control channel RB and the data channel RB at an equal ratio. For example, when narrowing from the 10 MHz band FB1 to the 5 MHz band FB2, the control channel RB and the data channel RB may be compressed by 50%. By doing so, interference to the control channel arranged in the central RB can be avoided as interference given to the macro mobile station 2-2, and interference given to the PDSCH and PDCCH can be limited to a half frequency band. The macro base station 3 in the vicinity of the femtocell base station 1 preferentially allocates 5 MHz not used by the femtocell base station 1 to the macro mobile station 2-2.

  In another band limiting method, the femtocell base station 1 and the macro base station 3 shift the timing so that the time timing for assigning the central RB to the control channel (SCH, BCH) does not match while maintaining the entire band FB1. Scheduling method. In LTE, a subframe to which a control channel in a central RB is assigned is defined. Therefore, the femtocell base station 1 recognizes the transmission timing of the control channel (that is, the transmission subframe) by the macro base station 3, and the P-SCH, S in a subframe different from the subframe used by the macro base station 3. -Send SHC and BCH. For example, the macro base station 3 may transmit the timing or subframe for transmitting these control channels using broadcast information. Further, the femtocell base station 1 does not assign PDSCH and PDCCH to the subframe to which the macro base station 3 assigns the control channel. By doing so, it is possible to avoid interference from the femtocell base station 1 with respect to the SCH and BCH transmitted by the macro base station.

  Furthermore, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention described above.

For example, a part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.
(Appendix 1)
Wireless communication means for performing first wireless communication with a first mobile station;
Resource allocating means for allocating a radio resource including a radio frequency to the first radio communication;
With
The resource allocating means can be allocated to the first radio communication before the approach when the approach to the second mobile station that performs the second radio communication with a neighboring base station is estimated. Determining a radio frequency to be allocated to the first radio communication from the second frequency band limited to a part of the first frequency band.
Base station device.

(Appendix 2)
The base station apparatus according to supplementary note 1, wherein the resource allocating unit determines the second frequency band based on reception quality of a downlink radio signal transmitted from the neighboring base station.

(Appendix 3)
The base station apparatus according to supplementary note 2, wherein the resource allocation unit selects, as the second frequency band, a frequency band in which the reception quality is lower than a reference among the first frequency band.

(Appendix 4)
The base station apparatus according to appendix 2 or 3, wherein the resource allocating unit determines the second frequency band based on the reception quality measured by the first mobile station.

(Appendix 5)
The base station apparatus according to appendix 1, wherein the resource allocating unit dynamically determines a bandwidth of the second frequency band according to communication quality of the first wireless communication.

(Appendix 6)
6. The apparatus according to any one of appendices 1 to 5, further comprising a determination unit that determines an approach between the second mobile station and the radio station apparatus based on reception power of an uplink signal received from the second mobile station. Base station equipment.

(Appendix 7)
The first wireless communication includes a data channel and a control channel;
The base station apparatus according to any one of appendices 1 to 6, wherein the resource allocation unit limits at least one of a frequency band that can be allocated to the data channel and a frequency band that can be allocated to the control channel.

(Appendix 8)
The base station apparatus according to any one of appendices 1 to 7, wherein the approach estimation is performed based on a relative distance between the second mobile station and the base station apparatus.

(Appendix 9)
The resource is exchanged by exchanging information related to bandwidth limitation with a plurality of base station apparatuses including the base station apparatus and other base station apparatuses, or with the other base station apparatus. The base station apparatus according to any one of appendices 1 to 8, wherein the allocating unit makes the second frequency band after restriction the same as that of the other base station apparatus.

(Appendix 10)
A first base station that performs first wireless communication with a first mobile station;
Resource allocating means for allocating a radio resource including a radio frequency to the first radio communication;
With
The resource allocating unit may determine whether the second mobile station that performs the second wireless communication with the neighboring second base station is close to the first base station when the second mobile station is estimated to approach the first base station. Determining a radio frequency to be allocated to the first radio communication from a second frequency band limited to a part of the first frequency band that could be allocated to the first radio communication.
Wireless communication system.

(Appendix 11)
Estimating an approach between a first base station that performs first wireless communication with a first mobile station and a second mobile station that performs second wireless communication with a second base station And, when the approach is estimated, the second frequency band limited to a part of the first frequency band that could be allocated to the first wireless communication before the approach Determining a radio frequency to be assigned to the first radio communication;
A radio resource allocation method comprising:

(Appendix 12)
A program for causing a computer to perform a radio resource allocation method,
The method
Estimating an approach between a first base station that performs first wireless communication with a first mobile station and a second mobile station that performs second wireless communication with a second base station And, when the approach is estimated, the second frequency band limited to a part of the first frequency band that could be allocated to the first wireless communication before the approach Determining a radio frequency to be assigned to the first radio communication;
A program comprising:

1 Femtocell base station 2-1 Registered mobile station (Femto mobile station)
2-2 Unregistered mobile station (macro mobile station)
3 Peripheral base stations (macro base stations)
4 Femto Gateway (Femto GW)
5 Network 6 Femtocell 7 Peripheral cell (macro cell)
DESCRIPTION OF SYMBOLS 10 Radio communication part 11 Radio resource allocation part 12 Approach determination part 111 Radio resource control part 112 Own cell quality information acquisition part 113 Resource scheduling part 114 Other cell quality information acquisition part

Claims (6)

Wireless communication means for performing first wireless communication with at least one first mobile station;
Resource allocating means for allocating a radio resource including a radio frequency to the first radio communication;
Other cell quality information acquisition means for acquiring reception quality of downlink radio signals from base stations installed in the vicinity of the own device;
With
The resource allocation means preferentially determines a frequency band whose reception quality is lower than a reference as a frequency band that can be allocated to the first radio communication, and the first radio is selected from the allocatable frequency bands. determining the radio frequency to be assigned to the communication,
The resource allocating means further exchanges information on the allocable frequency band between a cell formed by a base station installed in the periphery and another base station forming a cell at least partially overlapping, Making the allocatable frequency band the same with the other base stations;
Base station device. A second mobile station that performs second wireless communication with a base station installed in the vicinity of the own device, and a determination unit that determines an approach between the own device and the second mobile station;
When the second mobile station and the own device is determined to be approaching to determine the assignable frequency band, the base station apparatus according to claim 1. Said determining means, on the basis of the received power of the second uplink signal received from the mobile station of said second mobile station determines the approach of the own apparatus, the base station apparatus according to claim 2. The base station apparatus according to any one of claims 1 to 3 , wherein information on the assignable frequency band is exchanged with the other base station via a host apparatus. Obtaining the reception quality of at least one first second downlink radio signal from a base station installed near the first base station for a first wireless communication with the mobile station, and the A frequency band whose reception quality is lower than a reference is preferentially selected as a frequency band that can be allocated to the first radio communication, and a radio frequency to be allocated to the first radio communication is determined from the allocatable frequency band. To do,
With
The determination includes exchanging information on the assignable frequency band between a cell formed by the second base station and another base station forming a cell at least partially overlapping, and the assignable Including making the frequency band the same between the other base stations,
Radio resource allocation method. Program for executing a method of allocating radio resources according to the computer to claim 5.

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