JP2008300989A - Communication control system and communication control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication control system and a communication control method, capable of adaptively avoiding interference between carriers in a plurality of cell layers including a macro-layer and a micro-layer superimposed on the macro-layer when the cell layers are used. <P>SOLUTION: The communication control device 100 is provided with: a cell layer communication demand collecting section 105 for acquiring communication demands in the cell layers; an operating section 107 for determining the frequency bandwidth of carriers used in the cell layers on the basis of the acquired communication demands; and a carrier setting information instructing section 109 for transmitting a bandwidth change notice for causing a radio base station to execute the change to the determined frequency bandwidth, to the radio base station. The carriers used in the cell layer include a common control channel commonly used for a plurality of mobile stations. The bandwidth change notice is used to notify the radio base station that the frequency bandwidth is changed while fixing a frequency used for transmission/reception of the common control channel. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication control system and a communication control method used in a mobile communication system provided with a plurality of cell layers that are a set of radio base stations having a common cell form.

  Conventionally, in a mobile communication system such as W-CDMA, the frequency bandwidth of a carrier used for transmission / reception of a radio signal is set with a cell layer as a unit of a set of radio base stations having a common cell form.

  In W-CDMA, in order to cover a service area, a “macro layer” that is a set of radio base stations constituting cells having the same size is provided. In addition, in W-CDMA, it is difficult to reach local areas where the communication demand is so large that only radio base stations included in the macro layer cannot handle or radio signals transmitted from the radio base stations included in the macro layer. A “microlayer” that covers a local area is provided (for example, Non-Patent Document 1). That is, the microlayer is provided so as to overlap the service area covered by the macrolayer.

For this reason, when a carrier using the same frequency band is assigned to the macro layer and the micro layer, interference between the carrier used in the macro layer and the carrier used in the micro layer, so-called inter-carrier interference occurs. Therefore, when a microlayer is newly provided, an engineer may appropriately redesign radio parameters related to a macrolayer that may cause inter-carrier interference, for example, a frequency bandwidth and transmission power allocated to the macrolayer. It is common.
Laiho, J., Wacker, A. and Novosad, T, “Radio Network Planning and Optimization for UMTS”, Jhon Wiley & Sons, pp 259-278, 2001

  By the way, the frequency bandwidth used for transmission / reception of radio signals, that is, a relatively new movement that can allocate carriers using the same frequency band in adjacent cells, such as OFDMA that can flexibly increase / decrease the frequency bandwidth of the carrier. In the body communication system, the following problems may occur.

  Specifically, since the communication demand increases and the area covered by each cell becomes more strict, the size of the cell constituted by the radio base stations included in the microlayer is further reduced. That is, the number of radio base stations configuring the cell increases dramatically.

  As described above, when the number of radio base stations included in the microlayer is drastically increased, it is no longer easy for engineers to redesign radio parameters related to a macrolayer that may cause inter-carrier interference. is there.

  The present invention has been made in view of such a situation, and in the case where a plurality of cell layers including a macro layer and a micro layer provided on the macro layer are used, inter-carrier interference in the cell layer is performed. It is an object of the present invention to provide a communication control system and a communication control method that can adaptively avoid the problem.

In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that a first cell layer (cell layer LY _A ) which is a set of radio base stations (for example, radio base stations 32A to 32C) having a common cell form, and the first cell layer Mobile communication system (mobile communication) having a plurality of cell layers including a second cell layer (cell layer LY _B ) provided in an area where radio communication with a mobile station (for example, mobile terminal 40A) can be performed A communication control system (communication control device 100) used in the system 10), and a communication demand acquisition unit (communication unit 101 and cell layer communication demand collection unit 105) that acquires communication demand (for example, transmission traffic amount) in the cell layer. And a key used in the cell layer based on the communication demand acquired by the communication demand acquisition unit. A bandwidth determination unit (arithmetic unit 107) that determines a frequency bandwidth (frequency bandwidth BW2) of the carrier (for example, carrier C13), and changes the frequency bandwidth determined by the bandwidth determination unit to the wireless A bandwidth change notification unit (carrier setting information instruction unit 109) that transmits a bandwidth change notification to be executed by the base station to the radio base station, and the carrier is commonly used for a plurality of the mobile stations. The bandwidth change notification includes a common control channel, and the gist is to notify that the frequency bandwidth is changed while fixing a frequency (for example, frequency F _C13 ) used for transmission / reception of the common control channel. .

  According to such a communication control system, the frequency bandwidth of the carrier used in the cell layer is determined based on the communication demand in the cell layer. Further, the frequency bandwidth of the carrier is changed while fixing the frequency used for transmission / reception of the common control channel.

  For this reason, the frequency bandwidth of the carrier according to communication demand can be set, avoiding the interference between cell layers. Further, since the frequency used for transmission / reception of the common control channel is fixed before and after the change of the frequency bandwidth, the mobile station can continue to receive the common control channel even after the change of the frequency bandwidth.

  That is, according to such a communication control system, when a plurality of cell layers including a macro layer and a micro layer provided on the macro layer are used, inter-carrier interference in the cell layer is adaptively avoided. can do.

  A second feature of the present invention relates to the first feature of the present invention, and is a communication demand setting unit (communication demand) for setting at least one of the type and acquisition timing of the communication demand acquired by the communication demand acquisition unit. The gist is to include a setting unit 103).

  A third feature of the present invention relates to the first feature of the present invention, and is summarized in that the communication demand acquisition unit acquires the communication demand at a predetermined interval.

A fourth feature of the present invention relates to the first feature of the present invention, wherein priority is given to the plurality of cell layers, and the bandwidth determination unit is configured to use a priority cell layer (for example, a cell layer) having a high priority. LY _A ) is assigned a frequency band having a frequency bandwidth (for example, frequency bands BW12A, 12B) required according to the communication demand in the priority cell layer, and the priority is lower than that of the priority cell layer The gist is to assign a frequency band other than the frequency band assigned to the priority cell layer to a non-priority cell layer (for example, cell layer LY _B ).

  A fifth feature of the present invention relates to the fourth feature of the present invention, wherein the bandwidth determination unit is configured to use a maximum occupied bandwidth (for example, carrier C91, C92) used in the priority cell layer (for example, carriers C91 and C92). The gist is to define a frequency band BW12A) and assign a non-priority carrier (carrier C101) used in the non-priority cell layer to a frequency band other than the frequency band to which the priority carrier is assigned.

  A sixth feature of the present invention is that the first cell layer, which is a set of radio base stations having a common cell form, and an area where the first cell layer can perform radio communication with a mobile station are provided. A communication control method used in a mobile communication system having a plurality of cell layers including a second cell layer, wherein the mobile communication system determines a frequency bandwidth of a carrier used in the cell layer; The mobile communication system comprises a step of changing the carrier to the determined frequency bandwidth, wherein the carrier includes a common control channel commonly used for a plurality of the mobile stations, and the radio base The gist of the station is to change the frequency bandwidth while fixing a frequency used for transmission / reception of the common control channel. That.

  A seventh feature of the present invention relates to the sixth feature of the present invention, wherein the mobile communication system further comprises a step of acquiring a communication demand in the cell layer, and in the step of determining the frequency bandwidth, The gist is to determine the frequency bandwidth based on the communication demand acquired in the acquiring step.

  An eighth feature of the present invention relates to the seventh feature of the present invention, and is summarized in that the communication demand is acquired at predetermined intervals in the step of acquiring the communication demand.

  A ninth feature of the present invention relates to the seventh feature of the present invention, wherein priority is given to the plurality of cell layers, and in the step of determining the frequency bandwidth, a priority cell layer having a higher priority is assigned. On the other hand, a frequency band having a frequency bandwidth required according to the communication demand in the priority cell layer is assigned, and assigned to the priority cell layer for a non-priority cell layer having a lower priority than the priority cell layer The gist of the invention is that a frequency band other than the frequency band is allocated.

  A tenth feature of the present invention relates to the ninth feature of the present invention, wherein in the step of determining the frequency bandwidth, a maximum occupied bandwidth of a priority carrier used in the priority cell layer is defined, and the priority carrier is The gist is that a non-priority carrier used in the non-priority cell layer is allocated to a frequency band other than the allocated frequency band.

  According to the features of the present invention, when a plurality of cell layers including a macro layer and a micro layer provided to overlap the macro layer are used, inter-carrier interference in the cell layer can be adaptively avoided. A communication control system and a communication control method can be provided.

  Next, an embodiment of the present invention will be described. Specifically, (1) an overall schematic configuration of the mobile communication system, (2) a functional block configuration of the communication control system, and (3) an operation method of the mobile communication system using the communication control system will be described.

  In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(1) Overall Schematic Configuration of Mobile Communication System FIG. 1 is an overall schematic configuration diagram of a mobile communication system 10 according to the present embodiment. As shown in FIG. 1, the mobile communication system 10 includes a backbone network 20, radio base stations 31A and 31B, radio base stations 32A to 32C, and a mobile terminal 40A connected to the backbone network 20. The automobile 50 is equipped with mobile terminals 40B capable of performing wireless communication with the wireless base stations 31A and 31B and the wireless base stations 32A and 32B. In the present embodiment, the mobile terminal 40A constitutes a mobile station.

  The mobile communication system 10 forms a service area SA that can execute wireless communication with the mobile terminals 40A and 40B. Specifically, the service area SA is formed by the radio base stations 32A to 32C (macro cells). The radio base stations 31A and 31B (microcells) are provided so as to overlap the macrocell area.

In the present embodiment, the radio base stations 32A to 32C are included in a cell layer LY _A (not shown in FIG. 1, refer to FIG. 6), which is a set of radio base stations having a common cell form. In addition, the radio base stations 31A and 31B are included in the cell layer LY _B provided to overlap the cell layer LY _A.

That is, the cell layer LY _A is a macro layer, and the cell layer LY _B is a micro layer. The cell layer LY _B is provided so as to overlap the cell layer LY _A , that is, in an area where the radio base stations 32A to 32C can perform radio communication with the mobile terminal 40A.

  The mobile communication system 10 includes a communication control device 100. The communication control apparatus 100 controls the frequency and frequency bandwidth of the carrier (for example, carrier C13 shown in FIG. 4) transmitted and received by the radio base stations 31A and 31B and the radio base stations 32A to 32C.

(2) Functional Block Configuration of Communication Control System FIG. 2 is a functional block configuration diagram of the communication control device 100 configuring the communication control system in the present embodiment. As illustrated in FIG. 2, the communication control apparatus 100 includes a communication unit 101, a communication demand setting unit 103, a cell layer communication demand collection unit 105, a calculation unit 107, and a carrier setting information instruction unit 109.

  The communication unit 101 has a communication interface for connecting to the backbone network 20. The communication unit 101 is connected to a communication demand setting unit 103, a cell layer communication demand collection unit 105, and a carrier setting information instruction unit 109.

  The communication demand setting unit 103 sets the type of communication demand to be acquired by each wireless base station and the acquisition timing. In the present embodiment, the communication demand setting unit 103 sets at least one of the amount of generated traffic, the amount of transmission traffic, the communication quality, and the amount of radio resource usage generated in each radio base station or each mobile terminal as the communication demand.

  The generated traffic amount is, for example, the amount of data or the number of outgoing / incoming requests that stays in the buffer before being transmitted. The transmission traffic amount is the throughput of data to be transmitted and the number of communication lines set by the radio base station with the mobile terminal.

  The communication quality is, for example, data transmission delay time, call loss rate, forced disconnection rate, handover rate, and transmission error rate. The radio resource usage includes, for example, transmission power usage rate, interference power, spreading code usage rate, subcarrier usage rate, frequency bandwidth usage rate, and resource block usage rate.

  The communication demand setting unit 103 sets the type of communication demand to be acquired and the acquisition timing for all the radio base stations forming the service area SA. The communication demand setting unit 103 transmits communication demand acquisition information indicating the type of communication demand to be acquired and the acquisition timing to each radio base station via the communication unit 101.

  The cell layer communication demand collection unit 105 acquires the communication demand in each cell layer. In this embodiment, the communication unit 101 and the cell layer communication demand collection unit 105 constitute a communication demand acquisition unit. Specifically, the cell layer communication demand collection unit 105 receives the communication demand acquired by each radio base station from the radio base station, and collects the received communication demand for each cell layer.

  In the present embodiment, the cell layer communication demand collection unit 105 acquires communication demand at predetermined intervals. Note that the timing for acquiring the communication demand may be appropriately changed according to the time zone.

  The cell layer communication demand collecting unit 105 executes statistical processing (for example, averaging) of values indicating the acquired communication demand (for example, transmission traffic amount).

  The computing unit 107 is a carrier used in the cell layer based on the communication demand acquired by the cell layer communication demand collecting unit 105, specifically, the value of the communication demand subjected to statistical processing by the cell layer communication demand collecting unit 105. For example, the frequency bandwidth (frequency bandwidth BW2) of the carrier C13) shown in FIG. 4 is determined. In the present embodiment, the calculation unit 107 constitutes a bandwidth determination unit.

  Specifically, the calculation unit 107 determines a frequency bandwidth required according to the communication demand based on the value of the communication demand for which statistical processing has been executed by the cell layer communication demand collection unit 105.

When priority is given to a plurality of cell layers (cell layers LY _A , LY _B ), the arithmetic unit 107 responds to communication demand in the priority cell layer with respect to a priority cell layer (for example, the cell layer LY _A ) having a high priority. Accordingly, a frequency band having a required frequency bandwidth (for example, frequency bands BW12A and 12B shown in FIG. 13) can be allocated. Furthermore, the calculation unit 107 can assign a frequency band other than the frequency band assigned to the priority cell layer to a non-priority cell layer (for example, the cell layer LY _B ) having a lower priority than the priority cell layer.

  Further, the arithmetic unit 107 can define the maximum occupied bandwidth (for example, frequency band BW12A) of the priority carriers (for example, carriers C91 and C92 shown in FIG. 13) used in the priority cell layer. The computing unit 107 can assign a non-priority carrier (carrier C101) used in the non-priority cell layer to a frequency band other than the frequency band to which the priority carrier is assigned.

  Specifically, as illustrated in FIG. 13, the arithmetic unit 107 defines a priority carrier, that is, a frequency band BW12A of the carrier C91 and a frequency band BW12B of the carrier C92. The computing unit 107 assigns the carrier C101 having the frequency band BW13 as a non-priority carrier to the gap G formed between the frequency band to which the carrier C91 is assigned and the frequency band to which the carrier C92 is assigned.

  The computing unit 107 provides a predetermined threshold (for example, 90% radio resource usage (resource block usage rate)) for communication demand in the priority cell layer (or non-priority cell layer), and based on the threshold, the priority carrier A maximum occupied bandwidth may be defined. Note that the resource block usage rate is the ratio of resource blocks already allocated to communication among the total resource blocks (blocks defined by subcarriers and time slots) determined by the frequency bandwidth allocated to the radio base station. Is a value indicating

  Specifically, when the value of communication demand is larger than the threshold, the calculation unit 107 determines that a further expanded maximum occupied bandwidth is necessary.

  On the other hand, when the value of the communication demand is smaller than the threshold value, the arithmetic unit 107 determines that the maximum occupied bandwidth of the assigned priority carrier is excessive. In this case, a part of the frequency band assigned to the priority carrier is assigned to the non-priority carrier.

  When it is determined that the expanded maximum occupied bandwidth is necessary, the arithmetic unit 107 reduces the frequency bandwidth allocated to the non-priority carrier and increases the frequency bandwidth (maximum occupied bandwidth) allocated to the priority carrier. . Note that, when the frequency bandwidth allocated to the non-priority carrier is reduced, the calculation unit 107 may determine a minimum frequency bandwidth so as not to fall below the frequency bandwidth.

  The carrier setting information instructing unit 109 generates broadcast information including information indicating the carrier frequency bandwidth determined by the computing unit 107. Specifically, the carrier setting information instruction unit 109 generates broadcast information indicating the center frequency and frequency bandwidth of the carrier determined by the calculation unit 107.

  Carrier setting information instructing section 109 transmits broadcast information generated via communication section 101 to each radio base station.

  Further, the carrier setting information instruction unit 109 transmits a bandwidth change notification that causes the radio base station to execute the change to the frequency bandwidth determined by the computing unit 107 to the corresponding radio base station. In the present embodiment, the carrier setting information instruction unit 109 constitutes a bandwidth change notification unit.

The bandwidth change notification is included in the broadcast information and is a frequency used for transmission / reception of a common control channel commonly used for a plurality of mobile terminals (mobile terminals 40A and 40B) (for example, frequency F _C13 shown in FIG. 4). Is used to change the frequency bandwidth of the carrier (carrier C13).

(3) Operation Method of Mobile Communication System Using Communication Control System Next, an operation method of the mobile communication system 10 using the communication control apparatus 100 constituting the communication control system in the present embodiment will be described. Specifically, (3.1) General operation flow of communication control system, (3.2) Basic example of carrier allocation, (3.3) Configuration of cell layer, (3.4) Frequency bandwidth allocated to cell layer An example of change, (3.5) Example of change of frequency bandwidth when OFDMA is used, and (3.6) Setting of priority cell layer will be described.

(3.1) Schematic Operation Flow of Communication Control System FIG. 3 shows a schematic operation flow of the communication control device 100. Specifically, FIG. 3 shows an operation flow in which the communication control apparatus 100 instructs to change the frequency bandwidth of the carrier transmitted and received by the radio base station based on the communication demand.

  In step S10, the communication control apparatus 100 sets the type of communication demand and the acquisition timing that each radio base station should acquire. Specifically, the communication control apparatus 100 transmits, to each radio base station, communication demand acquisition information indicating the type of communication demand (for example, transmission traffic amount) to be acquired by each radio base station and the acquisition timing.

  In step S20, the communication control apparatus 100 receives the communication demand acquired by each radio base station from the radio base station, and collects the received communication demand for each cell layer.

  In step S30, the communication control apparatus 100 executes statistical processing (for example, averaging) of communication demand collected for each cell layer.

  In step S40, the communication control apparatus 100 determines whether or not the value of communication demand for which statistical processing has been executed exceeds a predetermined threshold value.

  When the value of communication demand exceeds a predetermined threshold (YES in step S40), in step S50, the communication control apparatus 100 determines that the radio base station is in response to a radio base station whose communication demand value exceeds the predetermined threshold. Instruct to change the frequency bandwidth of the carrier to be transmitted. Specifically, the communication control apparatus 100 transmits, to the radio base station, a bandwidth change notification that causes the radio base station to expand the frequency bandwidth of the carrier.

  In addition, the communication control apparatus 100 performs the process of step S40 and S50 for every cell layer.

  On the other hand, when the value of the communication demand does not exceed the predetermined threshold (NO in step S40), the communication control device 100 repeats the process from step S20. When the communication demand value does not exceed the predetermined threshold, the communication control apparatus 100 may transmit a bandwidth change notification that causes the radio base station to reduce the frequency bandwidth of the carrier to the radio base station. Good.

(3.2) Basic Example of Carrier Allocation FIG. 4 and FIG. 5 show a basic example of carrier allocation in the mobile communication system 10. In the present embodiment, a spectrum having a frequency bandwidth that enables operation by a radio access method used in the mobile communication system 10 is referred to as a “carrier”.

  In a time division duplex (TDD) scheme in which a downlink transmitted from a radio base station to a mobile terminal and an uplink transmitted from the mobile terminal to the radio base station are allocated to the same frequency band, Corresponds to the physical frequency bandwidth. On the other hand, in the frequency division duplex (FDD) scheme in which the downlink and uplink are assigned to different frequency bands, the carrier means a pair of frequency bands assigned to the downlink and uplink. Hereinafter, a transmission frequency band of a radio base station, that is, a downlink will be described as an example.

  As shown in FIG. 4, in the frequency band on the transmitting side in the radio base station (specifically, a predetermined frequency band having a frequency bandwidth BW1), a plurality of carriers ( Carriers C11-C16) are assigned. The frequency bandwidth (maximum occupied bandwidth) of each carrier is adjusted within a range allowed in the radio access scheme. Of course, the frequency bandwidth of the carrier (for example, the frequency bandwidth BW2 of the carrier C13) can be adjusted to a different value for each carrier.

In this embodiment, each carrier includes a common control channel that is commonly used for a plurality of mobile terminals. The transmission frequency (frequency F _{C11 to} F _C16 ) of the common control channel may be located at the center or other than the center of the carrier spectrum. The frequency bandwidth of the carrier can be adaptively changed according to changes in communication demand (see the lower part of the figure). Even when the carrier frequency bandwidth is changed, the transmission frequency of the common control channel is not changed.

The carrier spectrum is assigned to continuous frequency bands. Further, as shown in FIG. 5, the carrier spectrum may be dispersed within a range allowed by the wireless access scheme (see carrier C21 in FIG. 5). Even in this case, the transmission frequency (frequency F _C21 ) of the common control channel may be located at the center or other than the center of the carrier spectrum.

(3.3) Configuration of Cell Layer FIG. 6 shows a configuration example of a plurality of cell layers that can be used in the mobile communication system 10. As shown in FIG. 6, in the mobile communication system 10, a service area SA is formed by the radio base stations 32A to 32C (macro cells). In addition, wireless base stations 31A and 31B (micro cells) are provided in the service area SA, that is, in the area of the macro cell.

In FIG. 6, a cell layer LY _A including radio base stations 32A to 32C (macro cells) and a cell layer LY _B including radio base stations 31A and 31B (micro cells) are illustrated.

  Here, when focusing on a specific part of the area (shaded area in the figure), a radio base station (radio base station 32A to 32A to set a communication line with the mobile terminal 40B mounted on the automobile 50 having a high moving speed. 32C) requires increasing the cell size. This is because when the cell size is small, the number of handovers per unit time increases and the control load in the mobile communication system 10 increases, resulting in unstable communication quality.

  On the other hand, the radio base stations (radio base stations 31A and 31B) that establish a communication line with the mobile terminal 40A used by a pedestrian or the like whose movement speed is low need to reduce the cell size. This is because if the cell size is small, a large number of radio base stations (microcells) can be installed, and the system capacity of the mobile communication system 10 as a whole increases.

  That is, by using a plurality of cell layers according to the moving speed, communication lines with various mobile terminals can be set efficiently.

Moreover, since the communication demand in each cell layer changes from time to time, the system bandwidth BW _SYS allocated to the mobile communication system 10 is appropriately selected for each cell layer according to the change in the communication demand in each cell layer. Distributes frequency bandwidth. For example, the frequency bandwidth BW3 is distributed to the cell layer LY _A , and the frequency bandwidth BW4 is distributed to the cell layer LY _B. Note that the frequency bandwidth BW3 and the frequency bandwidth BW4 do not necessarily have to be continuous on the frequency axis.

(3.4) Example of Changing Frequency Band Allocation to Cell Layer FIGS. 7A, 7B, 8A, and 8B show examples of changing carrier allocation to the cell layer. Comparing FIG. 7 (a) and FIG. 7 (b), in FIG. 7 (a), the frequency bandwidth of the carriers (carriers C31 and C32) included in the cell layer LY _A is expanded in the system bandwidth BW _SYS. Has been. That is, the frequency bandwidth allocated to the carriers C31 and 32 included in the cell layer LY _A and the frequency bandwidth allocated to the carrier C41 included in the cell layer LY _B are changed.

Here, before and after the change of the frequency bandwidth, the transmission frequency (frequency F _C31 , F _C32 , F _C41 ) of the common control channel in each carrier does not change.

FIG. 8A is the same as FIG. In FIG. 8B, the frequency bandwidth allocated to the cell layer LY _A is reduced compared to the case shown in FIG. As shown in FIG. 8B, the carrier C41 included in the cell layer LY _B may be allocated separately to the center portion and both end portions (shaded portions in the drawing) of the system bandwidth BW _SYS .

(3.5) Example of changing frequency bandwidth when OFDMA is used Next, an example of changing the frequency bandwidth when OFDMA is used is shown. Specifically, in evolved universal terrestrial radio access (evolved UTRA), which is a radio access standard defined in 3GPP, an example of changing the frequency bandwidth when using a radio access system in which OFDMA is applied to the downlink Indicates. The applicable radio access method is not limited to OFDMA, and radio access that can flexibly change the frequency bandwidth (system bandwidth BW _SYS ) or the carrier frequency bandwidth during operation of the mobile communication system. The system (CDMA, FDMA, TDMA, IDMA, etc.) may be used.

  In OFDMA, the upper limit value of the carrier frequency bandwidth can be set to 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz by increasing or decreasing the number of subcarriers. The frequency bandwidth setting information is transmitted from the radio base station as broadcast information in the cell via a common control channel assigned to a band near the center frequency of the carrier. The mobile terminal is configured to receive the broadcast information and follow the setting of the radio base station. For this reason, the frequency bandwidth can be changed on the radio base station side. The frequency bandwidth can be changed when the radio base station is restarted and during operation.

FIG. 9 shows an operation example of the radio base station when the frequency bandwidth is changed when the radio base station is restarted (reboot). When changing the frequency bandwidth when the radio base station is restarted, the communication control device sets the upper limit value of the frequency bandwidth (frequency bandwidths BW5 and BW6) of the carrier (carrier C51) to be set at the next start of the radio base station. After 100 is determined, the radio base station is restarted in the normal procedure. After the restart, the notification information is automatically set. Note that the transmission frequency (frequency F _C51 ) of the common control channel does not change before and after the change of the frequency bandwidth.

  FIG. 10 shows an operation example of the radio base station when the frequency bandwidth is changed during operation of the radio base station. When changing the frequency bandwidth during operation of the radio base station, when expanding the upper limit value of the frequency bandwidth of the carrier (carrier C61) (when changing from the frequency bandwidth BW8 to BW7 in the figure), the communication control device The radio base station may update the content of the broadcast information in accordance with 100 determinations.

  On the other hand, when the upper limit value of the carrier frequency bandwidth is reduced (when the frequency bandwidth is changed from BW8 to BW9 in the figure), the radio base station communicates with the mobile terminal using the frequency band to be reduced. The communication line is shifted within the reduced frequency bandwidth.

Alternatively, the upper limit value of the frequency bandwidth of the carrier may be reduced after the use of the subcarrier assigned to the frequency band to be reduced by the radio base station is prohibited. In this case, the broadcast information may be updated simultaneously with the reduction of the upper limit value of the frequency bandwidth. Note that the transmission frequency (frequency F _C61 ) of the common control channel does not change before and after the change of the frequency bandwidth.

  FIG. 11 shows an operation example of the radio base station when the frequency bandwidth is virtually changed regardless of the actual upper limit value of the frequency bandwidth. When the frequency bandwidth (frequency bandwidth BW10) is virtually reduced, the radio base station maintains the upper limit value of the actual frequency bandwidth without changing the content of the broadcast information to the mobile terminal. Use of the frequency bandwidth is prohibited.

  On the other hand, when expanding the frequency bandwidth, the radio base station cancels the prohibition of use of the frequency band previously executed for the mobile terminal while maintaining the upper limit value of the actual frequency bandwidth. The radio base station performs the above-described operation based on control from the communication control device 100.

In addition, what is necessary is just to update alerting | reporting information similarly to FIG. 10, when expanding a frequency bandwidth beyond the upper limit of the present frequency bandwidth (frequency bandwidth BW10). Further, the transmission frequency (frequency F _C71 ) of the common control channel does not change before and after the change of the frequency bandwidth.

  By virtually changing the frequency bandwidth in this way, the carrier bandwidth is not constrained by the upper limit of the frequency bandwidth that can take discontinuous values such as 1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz. The frequency bandwidth can be changed continuously.

Also, as shown in FIG. 12, the radio base station sets the frequency bandwidth (frequency bandwidth BW11) in units of subcarriers so that the transmission frequency (frequency F _C81 ) of the common control channel is at the center of the carrier spectrum. Carriers (carriers C81, C81 ′) that are not located in the lower side may be realized (low frequency side arrangement and high frequency side arrangement in the figure). Further, the radio base station may realize discontinuous spectrum carriers (subcarriers C81a to C81c) (distributed arrangement in the figure).

(3.6) Setting of priority cell layer As described above, in the present embodiment, when priority is given to a plurality of cell layers (cell layers LY _A , LY _B ), a priority cell layer having a high priority (for example, The frequency bandwidth required according to the communication demand can be preferentially assigned to the cell layer LY _A ).

  The priority cell layer can be set so as to be continuous in the service area SA. By setting the priority cell layers so as to be continuous in plane, the mobile terminal 40B mounted on the automobile 50 and having a high moving speed can be positioned in the priority cell layer over a wide area.

  Furthermore, when a wireless base station other than the wireless base station used to set the priority cell layer to be continuous in a plane is included in the non-priority cell layer and there is little communication demand in the priority cell layer, many frequencies are added to the non-priority cell layer. Bandwidth may be allocated. In this case, a radio base station that is a discontinuous area but also includes a non-priority cell layer can more reliably set a communication line with a mobile terminal.

Further, as shown in FIG. 13, the communication control apparatus 100 uses the center frequency (frequency F _C91 ) of the carrier _C91 and the carrier so that the frequency band BW12A of the carrier C91 and the frequency bandwidth BW12B of the carrier C92 do not overlap. The center frequency of C92 (frequency F _C92 ) is determined. Carrier C91 and carrier C92 are assigned as priority carriers.

  Furthermore, in the communication control apparatus 100, the carrier C101 having the frequency band BW13 is allocated as a non-priority carrier to the gap G formed between the carrier C91 and the carrier C92.

  According to such carrier allocation, even if the cell formed by the radio base station included in the priority cell layer and the cell formed by the radio base station included in the non-priority cell layer are installed close to each other, the carrier There is no duplication of spectrum. For this reason, it can prevent that the common control channel of a non-priority cell layer receives interference.

  Note that the number of carriers assigned to the priority cell layer and the non-priority cell layer is not limited to the number shown in FIG.

(Action / Effect)
According to the communication control apparatus 100, the frequency bandwidth of the carrier used in the cell layer is determined based on the communication demand in the cell layers LY _A and LY _B. Further, the frequency bandwidth of the carrier is changed while fixing the frequency used for transmission / reception of the common control channel.

  For this reason, the frequency bandwidth of the carrier according to communication demand can be set, avoiding the interference between cell layers. In addition, since the frequency used for transmission / reception of the common control channel is fixed before and after the change of the frequency bandwidth, the mobile terminals 40A and 40B continue to transmit the common control channel transmitted by the radio base station after the change of the frequency bandwidth. Can be received.

That is, according to the communication control apparatus 100, when a plurality of cell layers including a macro layer (cell layer LY _A ) and a micro layer (cell layer LY _B ) provided to overlap the macro layer are used, Inter-carrier interference can be adaptively avoided.

  The communication control device 100 is particularly effective in the following cases. That is, only the macro layer is generally used at the start of service by the mobile communication system 10. Thereafter, in order to cope with an increase in communication demand and a stricter area covered by each cell, a micro layer is provided on the macro layer.

  When a microlayer is newly provided, it is unlikely that unused carriers are left around the radio base station included in the microlayer. For this reason, in general, a carrier used by an existing radio base station included in the macro layer is reused. It is also assumed that a general user or the like installs a radio base station using the same frequency band in the vicinity of the radio base station included in the mobile communication system 10.

  Even in such a case, according to the communication control apparatus 100, since the frequency bandwidth of the carrier is changed while fixing the frequency used for transmission / reception of the common control channel, the frequency band assigned to the mobile communication system 10 is changed. Inter-carrier interference can be adaptively avoided while being used efficiently.

  In this embodiment, communication demand is acquired at predetermined intervals. For this reason, even if the communication demand changes with the passage of time, a new radio base station is installed, or even if the installation location of the radio base station is changed, the engineer must redesign the radio parameters. There is no need to do.

  In the present embodiment, a frequency band having a frequency bandwidth required according to communication demand in the priority cell layer is allocated to the priority cell layer, and a frequency band other than the frequency band allocated to the priority cell layer is allocated to the non-priority cell layer. A frequency band is assigned.

  For this reason, specific communication demand (for example, communication demand regarding a mobile terminal with a high moving speed) can be satisfied more reliably. Moreover, when the communication demand in a priority cell layer is low, the frequency band utilization efficiency can be improved as the mobile communication system 10 as a whole by assigning a large frequency bandwidth to the non-priority cell layer.

  In the present embodiment, the maximum occupied bandwidth of the carrier is defined, and the non-priority carrier is assigned to a frequency band other than the frequency band to which the priority carrier is assigned. For this reason, the use efficiency of the frequency band can be further improved as the entire mobile communication system 10 while avoiding interference between the priority carrier and the non-priority carrier.

(Other embodiments)
As described above, the contents of the present invention have been disclosed through one embodiment of the present invention. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments will be apparent to those skilled in the art.

  For example, in the above-described embodiment of the present invention, the communication control device 100 is assumed to have each functional block realized on the same hardware (for example, a server computer). The functional block may be realized in different hardware. For example, the function of the communication demand setting unit 103 and the function of the cell layer communication demand collection unit 105 may be realized on separate hardware.

  In the above-described embodiment, two cell layers have been described as an example, but the number of cell layers may be three or more. The cell layer is not the cell size, but the transmission power of the radio base station, the owner of the radio base station (communication carrier, local government or general user), and the communication target of the radio base station (public, specific group or specific individual) The wireless base station may be classified according to the installation location of the wireless base station (outdoor, indoor, public space or private space), the characteristics of the mobile terminal with which the wireless base station performs communication (mobile phone terminal or PC), or a combination thereof.

  In the above-described embodiment, the carrier frequency bandwidth is determined based on the communication demand such as the amount of transmission traffic in each radio base station or each mobile terminal. However, the carrier frequency bandwidth is not necessarily based on the communication demand. Does not have to be determined. For example, the frequency bandwidth of the carrier may be changed according to the time zone.

  As described above, the present invention naturally includes various embodiments that are not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

1 is an overall schematic configuration diagram of a mobile communication system 10 according to an embodiment of the present invention. It is a functional block block diagram of the communication control apparatus 100 which concerns on embodiment of this invention. It is a figure which shows the schematic operation | movement flow of the communication control apparatus 100 which concerns on embodiment of this invention. It is a figure which shows the basic example of the carrier allocation in the mobile communication system 10 which concerns on embodiment of this invention. It is a figure which shows the basic example of the carrier allocation in the mobile communication system 10 which concerns on embodiment of this invention. It is a figure which shows the structural example of the some cell layer which can be used in the mobile communication system 10 which concerns on embodiment of this invention. It is a figure which shows the example of a change of the carrier allocation to the cell layer which concerns on embodiment of this invention. It is a figure which shows the example of a change of the carrier allocation to the cell layer which concerns on embodiment of this invention. It is a figure which shows the operation example of the radio base station in the case of changing a frequency bandwidth at the time of restart (reboot) of the radio base station which concerns on embodiment of this invention. It is a figure which shows the operation example of the radio base station in the case of changing a frequency bandwidth during operation of the radio base station according to the embodiment of the present invention. It is a figure which shows the operation example of the radio base station in the case of changing the said frequency bandwidth virtually irrespective of the actual upper limit of the frequency bandwidth which concerns on embodiment of this invention. It is a figure which shows the example of the carrier in which the transmission frequency of the common control channel which concerns on embodiment of this invention is not located in the center part of a carrier spectrum. It is a figure which shows the example of allocation of the priority carrier and non-priority carrier which concern on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Mobile communication system, 20 ... Backbone network, 31A, 31B, 32A, 32B ... Wireless base station, 40A, 40B ... Mobile terminal, 50 ... Automobile, 100 ... Communication control apparatus, 101 ... Communication part, 103 ... Communication demand Setting unit 105 ... Cell layer communication demand collecting unit 107 ... Calculation unit 109 ... Carrier setting information instruction unit, BW1 to BW11, BW12A, BW12B, BW13 ... Frequency bandwidth, BW _SYS ... System bandwidth, C11 to C16, C21 , C31, C32, C41C51, C61 , C71 ... career, C81a~C81c ... sub-carrier, C91, C92, C101 ... _{career, F C11 ~F C16, F C21} , F C31, F C32, F C41, F C51, F _{C61, F C71, F C81,} F C91, F C92 F _{C101 ...} frequency, G ... gap, _LY A, _LY B _... cell layer, SA ... Service Area

Claims (10)

A plurality of cells including a first cell layer that is a set of radio base stations that share a common cell form, and a second cell layer that is provided in an area where the first cell layer can perform radio communication with a mobile station. A communication control system used in a mobile communication system having a cell layer of
A communication demand acquisition unit for acquiring communication demand in the cell layer;
Based on the communication demand acquired by the communication demand acquisition unit, a bandwidth determination unit that determines a frequency bandwidth of a carrier used in the cell layer;
A bandwidth change notification unit that transmits to the radio base station a bandwidth change notification that causes the radio base station to perform a change to the frequency bandwidth determined by the bandwidth determination unit;
The carrier includes a common control channel commonly used for a plurality of the mobile stations,
The said bandwidth change notification is a communication control system which notifies changing the said frequency bandwidth, fixing the frequency used for transmission / reception of the said common control channel.   The communication control system according to claim 1, further comprising a communication demand setting unit that sets at least one of a type and an acquisition timing of the communication demand acquired by the communication demand acquisition unit.   The communication control system according to claim 1, wherein the communication demand acquisition unit acquires the communication demand at a predetermined interval. Priorities are given to the plurality of cell layers,
The bandwidth determination unit
For the priority cell layer having a high priority, a frequency band having a frequency bandwidth required according to the communication demand in the priority cell layer is allocated,
The communication control system according to claim 1, wherein a frequency band other than the frequency band allocated to the priority cell layer is allocated to a non-priority cell layer having a lower priority than the priority cell layer. The bandwidth determination unit
Defining a maximum occupied bandwidth of a priority carrier used in the priority cell layer;
The communication control system according to claim 4, wherein a non-priority carrier used in the non-priority cell layer is allocated to a frequency band other than the frequency band to which the priority carrier is allocated. A plurality of cells including a first cell layer that is a set of radio base stations that share a common cell form, and a second cell layer that is provided in an area where the first cell layer can perform radio communication with a mobile station. A communication control method used in a mobile communication system having a cell layer of
The mobile communication system determining a frequency bandwidth of a carrier used in the cell layer;
The mobile communication system comprises changing the carrier to the determined frequency bandwidth;
The carrier includes a common control channel commonly used for a plurality of the mobile stations,
The communication control method, wherein the radio base station changes the frequency bandwidth while fixing a frequency used for transmission / reception of the common control channel. The mobile communication system further comprises the step of acquiring communication demand in the cell layer,
The communication control method according to claim 6, wherein in the step of determining the frequency bandwidth, the frequency bandwidth is determined based on the communication demand acquired in the acquiring step.   The communication control method according to claim 7, wherein in the step of acquiring the communication demand, the communication demand is acquired at a predetermined interval. Priorities are given to the plurality of cell layers,
In the step of determining the frequency bandwidth,
A frequency band having a frequency bandwidth required according to the communication demand in the priority cell layer is allocated to the priority cell layer having a high priority,
The communication control method according to claim 7, wherein a frequency band other than the frequency band allocated to the priority cell layer is allocated to a non-priority cell layer having a lower priority than the priority cell layer. In the step of determining the frequency bandwidth,
A maximum occupied bandwidth of a priority carrier used in the priority cell layer is defined,
The communication control method according to claim 9, wherein a non-priority carrier used in the non-priority cell layer is allocated to a frequency band other than the frequency band to which the priority carrier is allocated.

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