JP2010118853A - Band changing method, and radio base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a band controlling method and a radio base station for effectively using an up-stream frequency band and a down-stream frequency band. <P>SOLUTION: According to the band controlling method of a radio base station 20, each slot occupation rate is measured with an occupation rate measuring unit 21 and moreover a free bandwidth in the frequency band is measured with a bandwidth measuring unit 23. A frequency band control unit 24 respectively controls the assignment of frequency bands for communications of up-stream data and down-stream data based on the occupation rate of each slot and spare bandwidth. Accordingly, when an occupation rate of slot, for example, in the bandwidth of communication of the down-stream data is high and the free bandwidth is present, only the frequency band in the communication of down-stream data can be expanded. Therefore, the assignment of respective bandwidths can be controlled in accordance with the capacities of the up-stream data and the down-stream data. As a result, effective use of the up-stream frequency band and down-stream frequency band can be achieved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a band changing method and a radio base station.

Conventionally, FDD (Frequency Division Duplex) and TDD (Time Division Duplex) are known as a communication method between a mobile station and a radio base station. In the FDD scheme, an uplink line transmitted from the mobile station to the radio base station and a downlink line transmitted from the radio base station to the mobile station are separately provided between the mobile station and the radio base station. Thus, uplink communication and downlink communication are performed in synchronization with each other. In such an FDD system, various control methods have been conventionally known. For example, there is one described in Patent Document 1.
Japanese Patent Laid-Open No. 11-275625

  By the way, in recent years, demand for high-speed data communication has been increased with improvement of services for providing moving images and music data. In the future, when a service such as LTE (Long Term Evolution) is started, implementation with a bandwidth of 5 MHz is expected. When LTE is implemented, it is conceivable that the downlink communication capacity such as Web browsing is more important than the uplink communication capacity. For this reason, in realizing high-speed communication, there is a need for a bandwidth control method capable of effectively using the uplink frequency band and the downlink frequency band in consideration of the above-described assumptions.

  Therefore, the present invention has been made in view of such a problem, and an object thereof is to provide a band control method and a radio base station capable of effectively using an uplink frequency band and a downlink frequency band.

  In order to solve the above-described problem, the bandwidth control method of the present invention is a bandwidth that controls allocation of frequency bands for communication when uplink data and downlink data are transmitted and received by communication between a mobile station and a radio base station. A control method, an occupancy measurement step for measuring an occupancy ratio indicating the traffic status of each channel in a frequency band in units of channels, and a bandwidth measurement step for measuring an empty bandwidth including unused channels in the frequency band; Bands for controlling the allocation of frequency bands for uplink data and downlink data communication based on the channel occupancy measured in the occupancy measurement step and the free bandwidth measured in the bandwidth measurement step And a control step.

  Alternatively, the radio base station of the present invention is a radio base station that controls allocation of a frequency band for communication when transmitting and receiving uplink data and downlink data by communication with a mobile station, and in the frequency band Occupancy rate measuring means for measuring the occupancy rate indicating the traffic status of each channel in units of channels, bandwidth measuring means for measuring the free bandwidth including unused channels in the frequency band, and occupancy rate measuring means. Bandwidth control means for controlling the allocation of frequency bands for uplink data and downlink data communication based on the occupied ratio of the channel and the free bandwidth measured by the bandwidth measurement means, respectively. Features.

  According to such a band control method and a radio base station, the occupation ratio indicating the traffic status of each channel in the frequency band is measured, and the free bandwidth including unused channels in the frequency band is further measured. Then, allocation of frequency bands for uplink data and downlink data communication is controlled based on the occupancy rate and free bandwidth of each channel. Thereby, for example, when the occupation ratio of the channel in the downlink data communication band is high and there is a free bandwidth, only the frequency band in the downlink data communication can be expanded. Therefore, the allocation of each band can be controlled according to the capacities of uplink data and downlink data. As a result, it is possible to effectively use the upstream frequency band and the downstream frequency band.

  Further, it further includes an occupancy rate determining step for determining whether or not the channel occupancy rate measured in the occupancy rate measuring step is higher than a threshold value, and the bandwidth control step includes a channel occupancy rate that is higher than the threshold value in the occupancy rate determining step. If it is determined that the frequency is higher, it is preferable to allocate a frequency band for communication to the channel in the free bandwidth.

  In this way, only when it is determined that the channel occupancy rate is higher than the threshold value, the frequency band for communication is allocated to the channel in the free bandwidth, so the frequency band allocation is ensured when necessary. Can be controlled.

  The bandwidth control step preferably reduces the number of channels used in the frequency band when it is determined in the occupation rate determination step that the channel occupation rate is lower than the threshold.

  In this way, when the channel occupancy is low, the number of channel usage can be reduced by shifting the user connected to the channel with the low occupancy to another channel. As a result, the free bandwidth increases, so that the free bandwidth can be supplemented as a communication bandwidth with an increased capacity.

  In addition, in a case where communication is performed with a wide bandwidth by allocating a frequency band for communication to a channel with an empty bandwidth and expanding the bandwidth of the channel, the bandwidth control step is performed with a wide bandwidth at the occupation rate determination step. When it is determined that the occupation ratio of the channel in communication is lower than the threshold value, it is preferable to narrow the channel bandwidth.

  In this way, when communication is performed with a wide bandwidth even though the channel occupancy is low, the free bandwidth can be increased by narrowing the bandwidth of the channel. This makes it possible to supplement the available bandwidth as a communication bandwidth with an increased capacity.

  Further, the bandwidth control step is performed when there is a free bandwidth having a bandwidth of two or more channels in at least one of the frequency bands for transmitting / receiving uplink data and downlink data when a new communication request is made. It is preferable to allocate a frequency band for uplink data and downlink data communication to a channel in the free bandwidth.

  In this way, when the occupancy rate of downlink data is high, for example, uplink data and downlink data of a user who requests new communication can be allocated to a band for uplink data communication. As a result, even when the communication capacity of one of the bands increases, it is possible to perform communication of uplink data and downlink data for which a new communication request has been made in the other band with a small communication capacity. Therefore, further effective utilization of the upstream frequency bandwidth and the downstream frequency bandwidth can be achieved.

  In the bandwidth control step, when two or more channels are adjacent to each other on the frequency axis, the transition is performed so that the channels are not adjacent to each other, and communication of uplink data and downlink data to a channel with an empty bandwidth is performed. Is preferably assigned.

  In this way, the transition is performed so that the channels are not adjacent to each other on the frequency axis, so that interference between uplink data and downlink data can be avoided.

  In addition, in the case where two or more channels are used for transmission / reception of uplink data or downlink data, the bandwidth control step is determined in the occupancy determination step that the occupancy of the two or more channels is lower than the threshold value In some cases, it is preferable to transfer a user connected to one channel to the other channel.

  In this way, when the channel occupancy rate decreases due to a decrease in the number of users, the user of one channel is shifted to the other channel, so that free bandwidth can be efficiently created. This makes it possible to supplement the available bandwidth as a communication bandwidth with an increased capacity.

  According to the present invention, it is possible to effectively use the upstream frequency band and the downstream frequency band.

  Hereinafter, preferred embodiments of a bandwidth control method and a radio base station according to the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a schematic configuration diagram of a radio communication system according to a preferred embodiment of the present invention. As shown in the figure, the wireless communication system 1 according to the present embodiment includes a mobile station 10 and a wireless base station 20, and uses frequency division duplex (FDD). Wireless communication is performed between the mobile station 10 and the wireless base station 20. FDD is one of the methods for realizing simultaneous transmission / reception (duplex communication) in wireless communication and the like, and as shown in FIGS. 2A and 2B, the frequency band of the communication path is halved (Uplink and Downlink). And transmitting and receiving at the same time. The radio communication system 1 includes a plurality of radio base stations 20 and a plurality of mobile stations 10. Hereinafter, each component of the radio | wireless communications system 1 is demonstrated in detail.

  The mobile station 10 is a mobile communication terminal that performs uplink communication to the radio base station 20. The mobile station 10 can communicate with the radio base station 20 by being in a radio cell formed by the radio base station 20. Although not shown, the mobile station 10 physically stores data between the main storage device such as a CPU, ROM, and RAM, an input device such as an operation button, an output device such as a display, and the radio base station 20. It includes an auxiliary storage device such as a communication module and a memory device for performing transmission and reception.

  The radio base station 20 transmits / receives uplink data and downlink data to / from the mobile station 10. In addition, the radio base station 20 transmits and receives uplink data and downlink data to and from the user's mobile station 10 of a plurality of communication systems (“SYSTEM (hereinafter“ SysA ”) and“ SYSTEM B (hereinafter “SysB”)). The plurality of communication systems show communication systems with different communication methods or different service providing methods of the same communication method, where FIG. 3, the radio base station 20 physically includes a CPU 31, a RAM 32 and a ROM 33 as main storage devices, an auxiliary storage device 34 such as a hard disk device, a keyboard and a mouse as input devices, and the like. Input device 35, an output device 36 such as a display, a communication module 37, etc. Radio base station 2 to be described later. Each function of 0 is operated with the communication module 37, the input device 35, and the output device 36 under the control of the CPU 31 by reading predetermined software on the hardware such as the CPU 31 and the RAM 32 shown in FIG. This is realized by reading and reading data in the RAM 33 and the auxiliary storage device 34.

  Next, the functional configuration of the radio base station 20 will be described in detail.

  As shown in FIG. 1, the radio base station 20 includes an occupancy rate measurement unit (occupancy rate measurement unit) 21, an occupancy rate determination unit 22, a bandwidth measurement unit (bandwidth measurement unit) 23, and a bandwidth control unit (bandwidth control). Means) 24. The radio base station 20 includes a transmission / reception unit (not shown) that transmits / receives uplink data and downlink data to / from the mobile station 10.

  The occupancy rate measuring unit 21 measures the occupancy rate of each slot in the uplink and downlink frequency bands in slot units. Further, the occupation rate determination unit 21 measures the number of users connected to the slot. Here, the slot indicates a channel whose frequency band is divided into a predetermined bandwidth. FIG. 4 is a diagram illustrating an exemplary arrangement of slots on the frequency axis. As shown in the figure, for example, when the frequency bandwidth of Uplink and Downlink is 2 GHz, the slot has a frequency bandwidth of 5 MHz allocated by dividing it into four. Any number of slots may be used. In the present embodiment, it is assumed that the frequency band of m MHz is divided into four and each bandwidth of the first to fourth slots is n MHz (4 n MHz = m MHz).

  Occupancy rate indicates how much each slot that can be transmitted and received in the frequency band is occupied within a certain period of time, that is, the traffic situation that varies depending on the number of connected users communicating in each slot and the throughput. Is. Specifically, the slot occupancy rate is, for example, when the frequency bandwidth of the slot is 5 MHz, even if one user uses 5 Mbps or 100 users use 50 kbps each. 100%. The occupancy rate measuring unit 21 outputs occupancy rate data indicating the measured occupancy rate of each slot or the number of users to the occupancy rate determining unit 22.

  The occupancy rate determination unit 22 determines, based on the occupancy rate data output from the occupancy rate measurement unit 21, whether or not the occupancy rate indicated by the occupancy rate data is higher than a threshold value for each slot being used for communication. To do. In addition, the occupancy rate determination unit 22 determines, based on the occupancy rate data, whether or not the number of users indicated by the occupancy rate data is greater than or less than a threshold value for each slot being used for communication. . The occupation rate determination unit 22 outputs determination data indicating the determination result to the bandwidth control unit 24.

  The bandwidth measuring unit 23 measures an empty bandwidth including unused slots in the frequency band. The bandwidth measurement unit 23 measures the frequency bandwidth of an unused slot that is not used for communication in the uplink frequency band (Uplink) and the downlink frequency band (Downlink) as an empty bandwidth. The bandwidth measuring unit 23 outputs bandwidth data indicating the free bandwidth in the measured frequency band to the bandwidth control unit 24.

  The bandwidth control unit 24 controls allocation of frequency bands for communication when the mobile station 10 transmits and receives uplink and downlink data based on the data output from the occupation rate determination unit 22 and the bandwidth measurement unit 23. To do. More specifically, a description will be given with reference to FIGS. 5 (a) to 5 (c). FIG. 5A to FIG. 5C are diagrams showing the states of slots before and after control of frequency band assignment by the band control unit 24. 5A to 5C show that the shaded portion in the slot is used for communication.

  As shown in FIG. 5 (a), the bandwidth control unit 24 uses, for example, the occupancy rate (U-Ocp) of the first frequency band in the uplink frequency band in the determination data output from the occupancy rate determination unit 22. U-thre1) is higher than (U-Ocp> U-thre1), based on the bandwidth data output from the bandwidth measurement unit 23, the unused slot adjacent on the frequency axis A frequency band for communication is allocated to the frequency band, and the frequency bandwidth of the first slot is expanded to widen the band.

  Further, as shown in FIG. 5B, when the bandwidth control unit 24 performs communication using a plurality of first to fourth slots, the determination data output from the occupation rate determination unit 22 is For example, if the slot occupancy (U-Ocp) indicates that it is lower than the threshold (U-Thre1) (U-Ocp <U-Thre1), the frequency of the user connected to the slot with the lower occupancy A band is handed over (transitioned) to another slot adjacent on the frequency axis. Thereby, the band control unit 24 reduces the number of slots used for communication. Note that the bandwidth control unit 24 does not perform handover between two different radios (SysA and SysB).

  Further, as shown in FIG. 5 (c), the band control unit 24 allocates a frequency band of an unused slot in response to an increase in the slot occupancy rate, and the frequency bandwidth is expanded to increase the bandwidth. When the determination data output from the occupancy rate determination unit 22 indicates a decrease in the occupancy rate of the slot, the slot with the increased bandwidth is narrowed. In addition, the bandwidth control unit 24 indicates that the occupation rate data output from the occupation rate determination unit 22 indicates that the number of users connected to the line has increased and the frequency bandwidth of unused slots has decreased. Narrows the bandwidth-enhanced slot as necessary.

  Furthermore, the bandwidth control unit 24, when there are a plurality of different wireless users and a communication request (user increase) is made from a new user, the bandwidth data output from the bandwidth measurement unit 23 When it is indicated that there are two or more unused slots in at least one of the frequency bands (Uplink and Downlink) for transmitting and receiving data, new user uplink data and downlink data are stored in the unused slots. Allocate a frequency band for communication. More specifically, description will be made with reference to FIGS. 6 (a) to 6 (c). FIG. 6A to FIG. 6C are diagrams showing the states of slots before and after control of frequency band allocation by the band control unit 24. In FIG. 6A to FIG. 6C, the hatched portion in the slot indicates that it is used for communication.

  As shown in FIG. 6A, the bandwidth control unit 24 determines that the determination data output from the occupation rate determination unit 22 exceeds, for example, the number of connections of SysA users (SysA simultaneous connection number> SysA band expansion determination). Threshold value Th_SysA), indicating that the band for SysA is insufficient, at least one frequency band in the uplink direction and the downlink direction having two or more unused slots (three in FIG. 6A) (Uplink frequency band having unused slots of (3 MHz)) is assigned a frequency band for uplink data and downlink data communication. At this time, when two or more unused slots are adjacent to each other on the frequency axis, the band control unit 24 changes the frequency band of the already communicating user as shown in FIG. The slot is shifted so that the added uplink data and downlink data slots are not adjacent to each other after the addition. Note that the bandwidth controller 24 performs similar control for SysB.

  Further, as shown in FIG. 6C, the bandwidth control unit 24, from the occupation rate determination unit 22 in the case where, for example, a SysA user is communicating in two slots each in the upstream and downstream frequency bands. When the output determination data indicates that the number of users connected to the two slots S1 and S2 has decreased, the frequency band of the connected user to one slot S2 having a low occupation rate is Hard handover to slot S1. Thereby, the band control unit 24 reduces the number of slots used for communication.

  Next, the bandwidth control method of the radio base station 20 will be described in detail with reference to FIGS. 7 to 10 are flowcharts showing the bandwidth control operation in the radio base station 20.

  First, with reference to FIG. 7, control for expanding the frequency bandwidth according to the occupation ratio when there is an empty band will be described. In the following description, it is assumed that the SysB user is already communicating with a bandwidth of nHHz. Further, in the following description, an uplink frequency band is shown, but a downlink frequency band is the same.

  First, when a communication request is made from a SysB user, the occupation rate measuring unit 21 measures the occupation rate (U_Ocp) of the slot (step S01). Next, whether or not the slot occupancy is higher than the threshold 1 (U_thre1) (U_Ocp> U_thre1) is determined by the occupancy determination unit 22 (step S02). If the slot occupancy is higher than threshold 1, the process proceeds to step S03. On the other hand, if the slot occupancy is lower than threshold 1, the process returns to step S01.

  In step S03, the bandwidth measuring unit 23 measures a vacant band in the upstream frequency band. Next, the bandwidth control unit 24 determines whether there is an unused slot that can be secured for SysB communication in the free bandwidth (step S04). If the frequency band of the unused slot can be secured, the band control unit 24 allocates the frequency band for communication of the SysB user to the unused slot (step S05). Specifically, when the bandwidth of the unused slot that can be used for communication of the SysB user is 3 nMHz, the bandwidth of the first slot is expanded to 4 nMHz, and when the bandwidth of the unused slot is 2 nMHz, the first When the bandwidth of the slot is expanded to 3 nMHz and the bandwidth of the unused slot is n MHz, the bandwidth of the first slot is expanded to 2 nMHz to increase the bandwidth. As described above, the frequency bandwidth for communication of the SysB user is allocated.

  Next, the control for reducing the number of slots used in the frequency band will be described in detail with reference to FIG.

  First, the bandwidth control unit 24 determines whether or not there is a user addition notification (step S11). If there is a user addition notification, the process proceeds to step S12. On the other hand, if there is no user addition notification, the same processing is repeated.

  In step 12, the occupancy rate determination unit 22 determines whether the number of users of SysA and SysB that are simultaneously connected to the uplink and downlink frequency bands is equal to or less than a predetermined value. Specifically, it is determined whether or not the number of SysA simultaneous connection users is equal to or less than the SysA band expansion determination threshold (Th_SysA). In addition, it is determined whether the number of SysB simultaneous connection users is equal to or less than the SysB band expansion determination threshold (Th_SysB). When the number of users of SysA and SysB is equal to or less than the predetermined value, the process proceeds to step S13. On the other hand, when the number of users of at least one of SysA and SysB exceeds a predetermined value, the process proceeds to step S23.

  In step S13, the occupation rate measuring unit 21 measures the occupation rate of the slot occupation rate (U-Ocp) in the upstream frequency band and the occupation rate of the slot (D-Ocp) in the downstream frequency band. Then, the occupancy rate determination unit 22 determines whether or not U−Ocp ≦ U−thre1 and D−Ocp> D−thre1 (step S14). If U-Ocp ≦ U-thre1 and D-Ocp> D-thre1, the process proceeds to step S15. On the other hand, if U-Ocp ≦ U-thre1 and D-Ocp> D-thre1, the process proceeds to step S17.

  In step S15, the bandwidth controller 24 determines whether or not two or more slots are used for uplink data communication (UL). When two or more slots are used for uplink data communication, the band control unit 24 causes the uplink data to be handed over to the other slot by handing over the frequency band for user communication connected to one slot. The number of slots used for communication is reduced (step 16). On the other hand, if two or more slots are not used for uplink data communication, the process is terminated.

  In step S17, the occupancy rate determination unit 22 determines whether U-Ocp> U-thre1 and D-Ocp ≦ D-thre1. If U-Ocp> -thre1 and D-Ocp ≦ D-thre1, the process proceeds to step S18. On the other hand, if U-Ocp> -thre1 and D-Ocp ≦ D-thre1, the process proceeds to step S20.

  In step S18, the bandwidth controller 24 determines whether or not two or more slots are used for downlink data communication (DL). When two or more slots are used for downlink data communication, the band control unit 24 causes the frequency band for communication of the user connected to one slot to be handed over to another slot, thereby downlink data. The number of communication slots used is reduced (step 19). On the other hand, if two or more slots are not used for downlink data communication, the process is terminated.

  In step 20, the occupation rate determination unit 22 determines whether or not U−Ocp ≦ U−thre <b> 1 and D−Ocp ≦ D−thre <b> 1. When U-Ocp ≦ U-thre1 and D-Ocp ≦ D-thre1, the process proceeds to step S21. On the other hand, if U-Ocp ≦ U-thre1 and D-Ocp ≦ D-thre1, the process is terminated.

  In step S21, the bandwidth control unit 24 determines whether or not two or more slots are used for uplink and downlink data communications (UL and DL). When two or more slots are used for uplink and downlink data communication, the band control unit 24 causes the frequency band for user communication connected to one of the slots to be handed over to the other slot. As a result, the number of slots used for uplink and downlink data communication is reduced (step 22). On the other hand, if two or more slots are not used for uplink and downlink data communication, the process is terminated.

  In step S23, a bandwidth control process is performed. The bandwidth control process in step S23 will be described in detail with reference to FIG. In the following description, the number of SysA simultaneous connection users exceeds the SysA bandwidth expansion determination threshold (Th_SysA), but the number of SysB simultaneous connections users exceeds the SysB bandwidth expansion determination threshold (Th_SysB). The same applies to the case where

  When the band control process is started, first, the band control unit 24 determines whether or not there are unused slots of n MHz in the upstream and downstream frequency bands (step S31). When there is an unused slot of n MHz, the slot is reserved by the bandwidth control unit 24 for communication of uplink and downlink data for SysA, and a frequency band for communication is assigned to each slot (step S32). On the other hand, if there is no unused slot by n MHz, the process proceeds to step S33.

  In step S <b> 33, the band control unit 24 determines whether there is an unused slot of n MHz in one of the upstream and downstream frequency bands and a slot in which a broadband operation of 2 n MHz or more is in the other. If there is an unused slot of n MHz on one side and a slot operating in a wide band of 2 n MHz or more on the other side, the process proceeds to step S34. On the other hand, if there is no unused slot of n MHz on one side and no slot in which a broadband operation of 2 n MHz or higher is on the other side, the process proceeds to step S36.

  In step S34, the bandwidth controller 24 hands over an existing user connected to a slot operating in a wide band of 2n MHz or more, whereby the 2n MHz slot is narrowed to an n MHz slot. Then, an unused slot of n MHz newly created by the narrowing of the band and another unused slot of n MHz are secured as frequency bands for communication. A frequency band is assigned (step S35).

  In step S36, the band control unit 24 determines whether there is an unused slot of 2n MHz or higher in any of the upstream and downstream frequency bands. If there is an unused slot of 2nMHz or higher in any of the upstream and downstream frequency bands, the process proceeds to step S37, while an unused slot of 2nMHz or higher is present in either the upstream or downstream frequency band. If not, the process proceeds to step S39.

  In step S37, in the upstream or downstream frequency band having an unused slot of 2n MHz or higher, the bandwidth control unit 24 changes the frequency band of the existing user to another slot so that the slot is not adjacent on the frequency axis. Make a hard handover. Then, the frequency band for uplink and downlink data communication is allocated by the band control unit 24 to the two slots of nHHz secured so as not to be adjacent to each other (step S38).

  In step 39, the band control unit 24 determines whether or not a frequency band of 4 nMHz or higher is used in the frequency bands in the uplink and downlink directions of the SysB user. If the SysB user uses a frequency band of 4 nMHz or higher, the process proceeds to step S40. On the other hand, if the SysB user is not using a frequency band of 4 nMHz or higher, the process ends.

  In step S40, the occupation rate determination unit 22 determines whether or not the number of SysB users in the frequency band of 4 nMHz or higher is tight. When the number of SysB users is not tight, the bandwidth control unit 24 reduces the frequency band of users connected to slots of 2 nMHz or higher in the uplink and downlink frequency bands to n MHz by hard handover, or By narrowing the band, slots of n MHz are secured in the upstream and downstream frequency bands, respectively (step S41). Then, the bandwidth control unit 24 assigns frequency bands for uplink and downlink data communication to the two reserved slots of nHHz (step S42). The band control process is performed as described above.

  Next, with reference to FIG. 10, control for creating a free band when the number of users decreases will be described. In the following description, for example, SysA (first and second slots) and SysB (third and fourth slots) perform downlink data communication in all slots (first to fourth slots) in the downlink frequency band. This is a case where a free band is created by making the first or second slot of SysA an unused slot.

  First, the number of users a (Act_usr_a) connected to the first slot is measured by the occupation rate measuring unit 21 (step S51). Next, whether or not the measured number of users a is smaller than the connection number threshold 2 (Act_thre2) (Act_usr_a <Act_thre2) is determined by the occupation rate determination unit 22 (step S52). The connection number threshold 2 is set to, for example, 30% of the number of users that can be simultaneously connected to one slot (sector). If the number of users a is less than the connection number threshold 2, the process proceeds to step 53. On the other hand, if the number of users a is greater than the connection number threshold 2, the process returns to step S51.

  In step S <b> 53, the occupation rate measuring unit 21 measures the number of users b (Act_usr_b) connected to the second slot. Then, whether or not the measured number of users b is smaller than the connection number threshold 2 (Act_thre2) (Act_usr_b <Act_thre2) is determined by the occupation rate determination unit 22 (step S54). When the number of users b is smaller than the connection number threshold 2, the process proceeds to step 55. On the other hand, if the number of users b is greater than the connection number threshold 2, the process returns to step S51.

  In step S55, it is determined by the occupation rate determination 22 whether or not the number of users a + b (Act_usr_ (a + b)) connected to the first and second slots is smaller than the connection number threshold 3 (Act_thre3). The connection number threshold 3 is set to, for example, 50% of the number of users that can be simultaneously connected to one slot. When the number of users a + b is smaller than the connection number threshold 3, the process proceeds to step 56. On the other hand, when the number of users a + b is larger than the connection number threshold 3, the process returns to step S51.

  In step S56, a new connection (communication request) is accepted to a slot having a smaller number of user connections, that is, a lower occupancy ratio among the first and second slots for which the number of user connections is determined in steps S52 and S54. Is stopped by the bandwidth controller 24. Then, the occupancy rate determination unit 22 determines whether the number of users connected to the low occupancy rate slot is less than the HHO threshold (Force threshold) (Act_usr_ (a or b) <Force threshold) (step S57). If the number of users (aor b) is less than the HHO threshold, go to step 58. On the other hand, when the number of users (a or b) is larger than the HHO threshold, the same process is repeated.

  In step S58, the bandwidth control unit 24 performs a hard handover of the frequency band of the user currently connected to the slot with a low occupancy rate to the other slot. Then, after the hard handover is completed, the stop of accepting a new connection is released by the bandwidth control unit 24 (step S59). A free band is created as described above. In the above processing, it is preferable that the slot occupancy is determined by the number of users, but the slot occupancy may be determined by the data capacity (throughput).

  According to the band control method by the radio base station 20 described above, the occupancy measuring unit 21 measures the occupancy indicating the traffic status of each slot in the frequency band, and the bandwidth measuring unit 23 further uses the unused frequency band. Measure the free bandwidth including the slots. Then, the bandwidth control unit 24 controls allocation of frequency bands for uplink data and downlink data communication based on the occupancy rate of each slot and the free bandwidth. As a result, for example, when the slot occupancy is high in the downlink data communication band and there is a free bandwidth, only the frequency band in the downlink data communication can be expanded. Therefore, the allocation of each band can be controlled according to the capacities of uplink data and downlink data. As a result, it is possible to effectively use the upstream frequency band and the downstream frequency band.

  In addition, the bandwidth control unit 24 is unused when the occupancy rate determination unit 22 determines that the slot occupancy rate (U-Cop, D-Cop) is higher than the threshold value (U-Thre1, D-Thre1). A frequency band for communication is assigned to the slots. As a result, only when it is determined that the slot occupancy is higher than the threshold, the frequency band for communication is allocated to the slot in the vacant bandwidth, so that the frequency band allocation control is surely performed when necessary. It can be carried out.

  The bandwidth control unit 24 reduces the number of slots used in the frequency band when the occupation rate determination unit 22 determines that the slot occupation rate is lower than the threshold (U-Thre1, D-Thre1). Accordingly, when the slot occupancy is low, the number of used slots can be reduced by handing over a user connected to a slot with a low occupancy to another slot. As a result, the free bandwidth increases, so that the free bandwidth can be supplemented as a communication bandwidth with an increased capacity.

  In addition, in the case where communication is performed with a wide bandwidth by allocating a frequency band for communication to a slot with an empty bandwidth and expanding the bandwidth of the slot, the bandwidth control unit 24 uses the occupation rate determination unit 22 to When it is determined that the occupation ratio of the slot communicating with the width is lower than the threshold, the slot bandwidth is narrowed. As a result, when communication is performed with a wide bandwidth even though the slot occupancy is low, the free bandwidth can be increased by narrowing the bandwidth of the slot. This makes it possible to supplement the available bandwidth as a communication bandwidth with an increased capacity.

In addition, when a new communication request is made, the bandwidth control unit 24 has a free bandwidth having a bandwidth of two or more slots in at least one of the frequency bands for transmitting and receiving uplink data and downlink data. Allocates a frequency band for uplink data and downlink data communication to a slot in the free bandwidth. As a result, for example, when the downlink data occupancy is high and there is a surplus band of 2 slots or more in the uplink frequency band, the uplink data and downlink data of the user requesting new communication are transferred to the uplink data communication. Can be allocated to the band for. Therefore, even when the communication capacity of one of the bands is increased, it is possible to perform communication of uplink data and downlink data for which a new communication request is made in the other band having a small communication capacity. Therefore, further effective utilization of the upstream frequency bandwidth and the downstream frequency bandwidth can be achieved.

  Further, when two or more slots are adjacent to each other on the frequency axis, the bandwidth control unit 24 performs a transition so that the slots are not adjacent to each other. Assign a frequency band for As a result, handover is performed so that slots are not adjacent to each other on the frequency axis, and interference between uplink data and downlink data can be avoided.

  Further, when two or more slots are used for transmission / reception of uplink data or downlink data, the bandwidth control unit 24 determines the number of users (Act_usr_a, Act_usr_b) connected to the two slots by the occupation rate determination unit 22, respectively. When it is determined that the frequency is smaller than the threshold (Act_thre2), the frequency band of the user connected to one slot is handed over to the other slot. As a result, when the occupancy rate of the slot becomes low due to a decrease in the number of users, the user in one slot is shifted to the other slot, so that a free bandwidth can be efficiently created. This makes it possible to supplement the available bandwidth as a communication bandwidth with an increased capacity.

  Although the present invention has been specifically described above based on the embodiment, the present invention is not limited to the above embodiment, and various modifications can be made.

1 is a schematic configuration diagram of a radio communication system according to a preferred embodiment of the present invention. It is a figure which shows the frequency band of FDD. It is a hardware block diagram of a radio base station. It is a figure which shows the example of arrangement | sequence of the slot on a frequency axis. It is a figure which shows the state of the slot before and after control of the allocation of the frequency band by a band control part. It is a figure which shows the state of the slot before and after control of the allocation of the frequency band by a band control part. It is a flowchart which shows the band control operation | movement in a radio base station. It is a flowchart which shows the band control operation | movement in a radio base station. It is a flowchart which shows the band control operation | movement in a radio base station. It is a flowchart which shows the band control operation | movement in a radio base station.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Mobile station, 20 ... Radio base station, 21 ... Occupancy rate measurement part (occupancy rate measurement means), 23 ... Bandwidth measurement part (bandwidth measurement means), 24 ... Bandwidth control part (bandwidth control means).

Claims (8)

When transmitting and receiving uplink data and downlink data by communication between a mobile station and a radio base station, a band control method for controlling allocation of frequency bands for the communication,
An occupancy measurement step of measuring an occupancy indicating the traffic status of each channel in the frequency band in units of channels;
A bandwidth measuring step for measuring a free bandwidth including an unused channel in the frequency band;
Allocation of the frequency band for communication of the uplink data and downlink data based on the occupation ratio of the channel measured in the occupation ratio measurement step and the free bandwidth measured in the bandwidth measurement step Bandwidth control step for controlling each of
A bandwidth control method comprising: An occupancy determination step of determining whether the occupancy of the channel measured in the occupancy measurement step is higher than a threshold;
The bandwidth control step assigns the frequency band for communication to a channel in the free bandwidth when it is determined in the occupation rate determination step that the channel occupation rate is higher than the threshold value. The bandwidth control method according to claim 1.   The bandwidth control step decreases the number of channels used in the frequency band when it is determined in the occupancy determination step that the occupancy of the channel is lower than a threshold value. 2. The bandwidth control method according to 2. In the case of performing communication with a wide bandwidth by allocating the frequency band for the communication to the channel of the free bandwidth and expanding the bandwidth of the channel,
The bandwidth control step is to narrow the bandwidth of the channel when the occupation rate of the channel performing communication with the wide bandwidth is determined to be lower than a threshold value in the occupation rate determination step. The bandwidth control method according to claim 1 or 2, characterized in that:   In the bandwidth control step, when a new communication request is made, at least one of the frequency bands for transmitting and receiving the uplink data and the downlink data has a free bandwidth having a bandwidth of two or more channels. 5. The bandwidth control method according to claim 2, wherein a frequency band for communication of the uplink data and the downlink data is allocated to a channel in the vacant bandwidth.   In the bandwidth control step, when the two or more channels are adjacent on the frequency axis, the transition is performed so that the channels are not adjacent to each other, and the uplink data and the downlink data are transferred to the channel of the free bandwidth. 6. The band control method according to claim 5, wherein a frequency band for communication is allocated. In the case where two or more channels are used for transmission / reception of the uplink data or downlink data,
In the bandwidth control step, when it is determined in the occupancy rate determination step that the occupancy rate of the two or more channels is lower than the threshold, the user connected to one of the channels is shifted to the other channel. 7. The bandwidth control method according to claim 2, wherein A radio base station that controls allocation of frequency bands for communication when transmitting and receiving uplink data and downlink data by communication with a mobile station,
Occupancy rate measuring means for measuring an occupancy rate indicating the traffic status of each channel in the frequency band in units of channels;
Bandwidth measuring means for measuring a free bandwidth including unused channels in the frequency band;
Allocation of the frequency band for communication of the uplink data and downlink data based on the occupation ratio of the channel measured by the occupation ratio measuring means and the free bandwidth measured by the bandwidth measurement means Bandwidth control means for controlling each of them,
A radio base station comprising:

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