JP2008271330A - Radio communication controller, and radio communication control method - Google Patents

Radio communication controller, and radio communication control method Download PDF

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JP2008271330A
JP2008271330A JP2007113368A JP2007113368A JP2008271330A JP 2008271330 A JP2008271330 A JP 2008271330A JP 2007113368 A JP2007113368 A JP 2007113368A JP 2007113368 A JP2007113368 A JP 2007113368A JP 2008271330 A JP2008271330 A JP 2008271330A
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channel
mobile terminal
radio
radio communication
mobile
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JP4989289B2 (en
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Hirotada Fujii
Junichiro Hagiwara
淳一郎 萩原
啓正 藤井
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Ntt Docomo Inc
株式会社エヌ・ティ・ティ・ドコモ
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication controller and a radio communication control method that can improve the throughput of a mobile terminal according to the system load of a mobile communication system. <P>SOLUTION: The radio communication controller is equipped with a system load decision section 111 which decides a system load determined based upon a traffic amount handled by the mobile communication system, and a channel allocation section 115 which allocates a radio communication channel to the mobile terminal according to channel retrieval order predetermined in the mobile communication system based upon a threshold set for the reception level of a radio signal received from the mobile terminal through the radio communication channel. The channel allocation section 115 increases the threshold set for the reception level of the radio signal received from the mobile terminal through at least some of radio communication channel according to a decrease in system load. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to wireless communication used in a mobile communication system that can increase the number of mobile terminals that can be accommodated at the same time by repeatedly using wireless communication channels that use the same wireless frequency at geographically distant locations. The present invention relates to a control device and a wireless communication control method.

  Conventionally, in a mobile communication system including a mobile terminal and a radio base station that performs radio communication with the mobile terminal, a method in which a plurality of radio base stations repeatedly use the same radio communication channel at geographically distant locations Is used. In particular, in the second generation mobile communication system, a dynamic channel allocation method based on the premise that voice communication is performed in an FDMA system is being studied.

  In the dynamic channel assignment method, generally, a wireless communication channel in which a predetermined condition, specifically, a signal-to-interference ratio (for example, CIR) exceeds a predetermined threshold is assigned to a mobile terminal. Here, when a plurality of radio communication channels satisfy the predetermined condition, the capacity of the entire mobile communication system changes depending on which radio communication channel is allocated to the mobile terminal.

  As one of such dynamic channel allocation methods, Autonomous Reuse Partitioning (ARP) is known (for example, Patent Document 1). According to ARP, the search order of radio communication channels in a mobile communication system (hereinafter referred to as channel search order) is unified. Each radio base station searches for a radio communication channel according to a unified channel search order, and first assigns a radio communication channel satisfying a predetermined condition to a mobile terminal.

  By assigning radio communication channels to mobile terminals in this way, the optimal “channel reuse distance” is autonomously set for each radio communication channel, so the number of mobile terminals that the mobile communication system can accommodate at the same time Can be increased.

That is, in a mobile communication system using ARP, a radio communication channel is assigned according to the reception level of a radio signal received from a mobile terminal. For this reason, a radio communication channel having a fast allocation order determined by the channel search order is frequently assigned to a mobile terminal located in the vicinity of the radio base station.
Japanese Patent No. 3376387 (pages 7-8, FIG. 2)

  By the way, in a mobile communication system in which ARP is used, when the traffic volume handled by each cell (wireless base station) is small and the system load of the mobile communication system is low, the mobile communication system is distributed by distributing assigned wireless communication channels. Increased throughput can be expected.

  However, even when the system load is low, in the above-described conventional mobile communication system, a mobile terminal with strong received radio signal strength, i.e., a mobile terminal located in the vicinity of a radio base station, has a fast allocation order. Communication channels are assigned frequently.

  For this reason, when a large number of mobile terminals are located in the vicinity of the radio base station, a throughput of the mobile terminal is selected by selecting a radio communication channel with an unnecessarily high amount of interference (specifically, interference power). There was a problem that did not improve.

  Therefore, the present invention has been made in view of such a situation, and provides a radio communication control apparatus and a radio communication control method capable of improving the throughput of a mobile terminal according to the system load of a mobile communication system. The purpose is to provide.

  In order to solve the problems described above, the present invention has the following features. First, the first feature of the present invention is that a mobile terminal (mobile terminal 200A) that can be accommodated at the same time by repeatedly using a radio communication channel (radio communication channel CH) using the same radio frequency at geographically distant locations. ˜200C) is a radio communication control apparatus (for example, radio base station 100A) used in a mobile communication system (mobile communication system 1) capable of increasing the number of traffics handled in the mobile communication system A system load determining unit (system load determining unit 111) for determining a system load determined based on the amount, and a threshold set for a reception level of a radio signal received from the mobile terminal via the radio communication channel Based on a predetermined channel search order in the mobile communication system. A channel allocating unit (channel allocating unit 115) for allocating the radio communication channel to the mobile terminal, the channel allocating unit via at least some of the radio communication channels in response to a decrease in the system load. The gist is to raise the threshold set for the reception level of a radio signal received from the mobile terminal.

  According to such a radio communication control apparatus, the threshold of the reception level used for allocating the radio communication channel to the mobile terminal increases as the system load of the mobile communication system decreases.

  For this reason, when the system load of the mobile communication system is low, a radio communication channel with less interference is assigned to the mobile terminal due to an increase in the threshold of the reception level. That is, when the throughput of the mobile terminal can be improved by distributing the radio communication channels allocated to the mobile terminal, the amount of interference unnecessarily (specifically, interference power) according to the allocation order determined by the channel search order. By selecting a wireless communication channel having a high value, it is possible to solve the problem that the throughput of the mobile terminal is not improved.

  A second feature of the present invention relates to the first feature of the present invention, wherein the channel allocation unit is based on whether or not an allocation threshold value determined by an interference noise level, a required SINR and an allocation margin is exceeded. The gist of the present invention is to provide an allocation margin setting unit (allocation margin setting unit 116) that allocates a radio communication channel to the mobile terminal and increases the allocation margin in accordance with a decrease in the system load.

  A third feature of the present invention relates to the second feature of the present invention, and is summarized in that the allocation margin setting unit decreases the allocation margin in accordance with an increase in the system load.

  A fourth feature of the present invention relates to the second feature of the present invention, wherein the mobile terminal is equipped with a battery (battery 210), and information for acquiring battery status information indicating the status of the battery from the mobile terminal. The gist further includes an acquisition unit (information acquisition unit 112), wherein the allocation margin setting unit sets the allocation margin based on the battery state information acquired by the information acquisition unit.

  A fifth feature of the present invention relates to the fourth feature of the present invention, wherein the mobile terminal has a normal mode and a long life mode for extending the duration of the battery as compared with the normal mode, The battery status information includes operation mode information indicating whether the mobile terminal is operating in the normal mode or the long-life mode, and the allocation margin setting unit is configured so that the mobile terminal operates in the long-life mode. In this case, the gist is to make the allocation margin larger than that in the normal mode.

  A sixth feature of the present invention relates to the first feature of the present invention, and further comprises a modulation code set setting unit (MCS setting unit 114) for setting a modulation code set used for generating the radio signal, wherein the modulation The gist of the code set setting unit is to select the modulation code set that reduces the data rate after modulation in accordance with an increase in the system load.

  A seventh feature of the present invention is according to the sixth feature of the present invention, wherein the modulation code set setting section is configured such that the transmission rate of the radio signal transmitted by the mobile terminal is equal to or less than a transmission power threshold. The gist of the present invention is to stop the selection of the modulation code set having a low value.

  An eighth feature of the present invention relates to the seventh feature of the present invention, and is summarized in that the modulation code set setting unit decreases the transmission power threshold according to an increase in the system load.

  A ninth feature of the present invention is according to the first feature of the present invention, wherein the channel allocating unit uses an orthogonal channel that uses the radio signal in which symbols are orthogonal, or the radio signal in which the symbols are not completely orthogonal. A quasi-orthogonal channel that uses a channel can be assigned as the wireless communication channel, and includes a usage rate setting unit (a usage rate setting unit 117) that reduces the usage rate of the orthogonal channel in response to an increase in the system load. And

  A tenth feature of the present invention is a mobile communication system capable of increasing the number of mobile terminals that can be accommodated at the same time by repeatedly using radio communication channels using the same radio frequency at geographically distant locations. And determining a system load determined based on a traffic volume handled in the mobile communication system, and a radio signal received from the mobile terminal via the radio communication channel. Allocating a radio communication channel to the mobile terminal in accordance with a channel search order predetermined in the mobile communication system based on a threshold set for a reception level, and allocating the radio communication channel Then, according to the decrease in the system load, at least And summarized in that raising the threshold set for the reception level of a radio signal received from the mobile terminal through a portion of the wireless communication channel.

  According to the features of the present invention, it is possible to provide a radio communication control apparatus and a radio communication control method capable of improving the throughput of a mobile terminal according to the system load of a mobile communication system.

  Next, an embodiment of the present invention 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.

(Overall schematic configuration of mobile communication system)
FIG. 1 is an overall schematic configuration diagram of a mobile communication system according to the present embodiment. As shown in FIG. 1, the mobile communication system 1 includes a core network 10, radio base stations 100A and 100B, and mobile terminals 200A to 200C. The numbers of radio base stations and mobile terminals included in the mobile communication system 1 are not limited to the numbers shown in FIG.

  In the present embodiment, the mobile communication system 1 is compliant with a wireless communication system according to IEEE 802.16e (Mobile WiMAX). Further, in the mobile communication system 1, the number of mobile terminals that can be accommodated at the same time can be increased by repeatedly using the radio communication channel CH that uses the same radio frequency at geographically distant locations.

  Specifically, in the mobile communication system 1, Autonomous Reuse Partitioning (ARP, for example, Japanese Patent No. 3376387) is used. In ARP, when the signal-to-interference ratio (CIR) exceeds a predetermined threshold, the same radio frequency is reused in a plurality of radio base stations (radio communication control devices), that is, optimal for each radio communication channel CH. A “channel reuse distance” is set autonomously.

  The core network 10 connects the radio base station 100A and the radio base station 100B. The radio base stations 100A and 100B transmit and receive data by setting the radio communication channel CH with the mobile terminals 200A to 200C. The radio base station 100A forms a cell C1. Also, the radio base station 100B forms a cell C2. In the present embodiment, the radio base stations 100A and 100B constitute a radio communication control device.

  The mobile terminals 200A to 200C are movable wireless communication terminals. The mobile terminals 200A to 200C transmit and receive data using the radio communication channel CH. In addition, the mobile terminals 200A to 200C are equipped with a battery 210 that stores electric power necessary for the operation of the mobile terminal. The mobile terminal 200 </ b> A has a normal mode (normal mode) and a long life mode (long life mode) that extends the duration of the battery 210 as compared with the normal mode with respect to the operation of the battery 210.

(Functional block configuration of wireless communication control device)
Next, a functional block configuration of the radio base station 100A constituting the radio communication control apparatus in the present embodiment will be described. Note that the radio base station 100B has the same functional block configuration as the radio base station 100A.

(1) Overall Configuration FIG. 2 is an overall functional block configuration diagram of the radio base station 100A. Hereinafter, portions related to the present invention will be mainly described. Therefore, it should be noted that the radio base station 100A may include a functional block (such as a power supply unit) that is essential for realizing the function as the device and that is not illustrated or omitted.

  As illustrated in FIG. 2, the radio base station 100A includes a radio communication unit 101, a baseband signal processing unit 103, a network connection unit 105, and a communication control unit 110.

  The wireless communication unit 101 converts the baseband signal input from the baseband signal processing unit 103 into a wireless signal and transmits it. In addition, the wireless communication unit 101 converts the received wireless signal into a baseband signal and outputs the baseband signal to the baseband signal processing unit 103.

  The baseband signal processing unit 103 is connected to the wireless communication unit 101. The baseband signal processing unit 103 transmits data, specifically, baseband signals such as user data and control data to the wireless communication unit 101, and detects a control signal and an information signal from the input baseband signal. Or

  The network connection unit 105 is configured by a connection interface for connecting to the core network 10.

  The communication control unit 110 executes control related to a radio signal transmitted / received in the wireless communication unit 101 and a baseband signal transmitted / received via the baseband signal processing unit 103.

(2) Detailed Functional Block Configuration of Communication Control Unit 110 FIG. 3 is a detailed functional block configuration diagram of the communication control unit 110. As shown in FIG. 3, the communication control unit 110 includes a system load determination unit 111, an information acquisition unit 112, a received signal state measurement unit 113, an MCS setting unit 114, a channel allocation unit 115, an allocation margin setting unit 116, and a usage rate setting. Part 117.

  The system load determination unit 111 determines a system load determined based on the traffic amount handled in the mobile communication system 1.

  The system load determination unit 111 is information provided from the information acquisition unit, for example, the average frame usage rate in the past N frames in the neighboring cells in the mobile communication system 1, the average number of users waiting for transmission, and the amount of data stored in the transmission buffer. Alternatively, the system load of the mobile communication system 1 is determined based on information indicating an expected traffic volume based on a request for a transmission rate from a user.

  Specifically, the system load determination unit 111 determines the system load of the mobile communication system 1 using information indicating the traffic amount acquired by the information acquisition unit 112 via the core network 10. Note that the system load determination unit 111 may acquire information indicating the level of the system load of the mobile communication system 1 instead of the information indicating the traffic volume.

  In addition, the system load determination unit 111 measures the system load in the own cell and transmits information indicating the measured system load to an information acquisition unit (not shown) of a radio base station configuring another cell.

  The information acquisition unit 112 acquires various information used for the operation of the communication control unit 110. In particular, in the present embodiment, as described above, information indicating the traffic volume handled in the mobile communication system 1 is acquired via the core network 10.

  Further, the information acquisition unit 112 acquires battery state information indicating the state of the battery 210 mounted on the mobile terminals 200A to 200C from the mobile terminals 200A to 200C. The battery state information includes operation mode information indicating whether the mobile terminals 200A to 200C are operating in the normal mode or the long life mode.

  The reception signal state measurement unit 113 measures the state of the wireless signal received by the wireless communication unit 101. Specifically, the reception signal state measurement unit 113 measures a signal-to-interference wave ratio (CIR), a signal-to-interference power / noise power ratio (SINR), and the like of a wireless signal received by the wireless communication unit 101.

  The MCS setting unit 114 sets a modulation code set (Modulation and Coding Scheme) used for generating a radio signal transmitted by the radio communication unit 101. In the present embodiment, the MCS setting unit 114 constitutes a modulation code set setting unit.

  The MCS setting unit 114 limits the use of a modulation code set having a high modulation multi-level number or a high coding rate in accordance with an increase in the system load determined by the system load determination unit 111.

  Further, the MCS setting unit 114 can cancel the selection of a modulation code set that lowers the data rate after modulation when the transmission power of radio signals transmitted by the mobile terminals 200A to 200C is equal to or lower than a predetermined transmission power threshold. . Furthermore, the MCS setting unit 114 can decrease the transmission power threshold according to an increase in system load.

  The channel allocation unit 115 allocates the radio communication channel CH to the mobile terminals 200A to 200C according to a channel search order determined in advance in the mobile communication system 1. Specifically, the channel allocation unit 115 searches for a radio communication channel CH according to a channel search order unified in the mobile communication system 1 based on ARP, and first selects a radio communication channel CH that satisfies a predetermined condition. Assigned to the mobile terminals 200A to 200C.

  In the present embodiment, the channel assignment unit 115 assigns the radio communication channel CH to the mobile terminals 200A to 200A based on a threshold set for the reception level of the radio signal received from the mobile terminals 200A to 200C via the radio communication channel CH. Assign to 200C.

  Specifically, the channel assignment unit 115 assigns the radio communication channel CH to the mobile terminals 200A to 200C based on the SINR threshold value of the radio signal received from the mobile terminals 200A to 200C.

  Here, FIG. 8 shows a frame configuration of a radio signal transmitted and received by the radio base station 100A. As shown in FIG. 8, a frame F of a radio signal transmitted / received by the radio base station 100A includes a preamble PA, a zone Z1, and a zone Z2. When the SINR of the radio signal received from the mobile terminal satisfies a predetermined threshold, the channel allocation unit 115 allocates the mobile terminal to the radio communication channel CH included in the zone Z1. Further, when the SINR of the radio signal does not satisfy the predetermined threshold but satisfies the threshold used for determining whether or not to allocate a mobile terminal to the zone Z2, the channel allocation unit 115 includes a radio communication channel included in the zone Z2. The mobile terminal is assigned to CH. If the threshold used for determining whether or not to allocate a mobile terminal to the zone Z2 is not satisfied, the channel allocation unit 115 blocks without allocating the radio communication channel CH to the mobile terminal.

  In the present embodiment, the channel allocation unit 115 allocates the radio communication channel CH to the mobile terminals 200A to 200C based on whether or not the allocation threshold value determined by the interference noise level, the required SINR, and the allocation margin is exceeded. Note that the allocation threshold value may be changed by controlling either the required SINR or the allocation margin.

  Furthermore, the channel allocation unit 115 can increase the threshold set for the reception level in accordance with a decrease in the system load of the mobile communication system 1. Specifically, the channel allocation unit 115 increases the threshold value set for the reception level of the radio signal received via the radio communication channel CH that has a higher allocation order determined by the channel search order. Note that the channel assignment unit 115 assigns the radio communication channel CH to the mobile terminal so that the radio communication channel CH with the lower allocation order is not used when the radio communication channel CH with the higher allocation order is empty.

  Further, according to the state of a plurality of mobile terminals (users) allocated in the zone, a resource, specifically, a predetermined number of subchannels CHs included in the zone may be allocated to the mobile terminals. For example, the channel assignment unit 115 can determine the number of subchannels CHs or the number of mobile terminals assigned to a zone based on the transmission and reception bit rates of each mobile terminal.

  Further, the channel allocation unit 115 may fix the unit (allocation unit) of the subchannel CHs allocated to the mobile terminal and allocate the subchannel CHs that can be allocated to the mobile terminal for each allocation unit. For example, the channel allocating unit 115 can allocate a plurality of subchannels CHs to mobile terminals according to the number of mobile terminals performing wireless communication in the sector SC1 (to SC3).

  Further, the channel allocation unit 115 can allocate, as the radio communication channel CH, an orthogonal channel using radio signals whose symbols are orthogonal or a quasi-orthogonal channel using radio signals whose symbols are not completely orthogonal.

  In this embodiment, the channel assignment unit 115 assigns a quasi-orthogonal channel with priority to a mobile terminal located in the area A1 (see FIG. 1) close to the radio base station. Specifically, the channel assignment unit 115 assigns the radio communication channel CH to the mobile terminal so that the usage rate of the quasi-orthogonal channel in the area A1 is about 90%.

  Further, the channel allocation unit 115 allocates the radio communication channel CH to the mobile terminal so that the usage rate of the quasi-orthogonal channel in the area A2 located outside the area A1 is about 60%, and the area located outside the area A2 The radio communication channel CH is allocated to the mobile terminal so that the usage rate of the quasi-orthogonal channel in A3 is about 30%. The area A3 is located on the outermost side in the cell (for example, the cell C2) and has a portion that overlaps with the adjacent cell (for example, the cell C1).

  The allocation margin setting unit 116 sets an allocation margin. Specifically, the allocation margin setting unit 116 sets an allocation margin according to the table shown in FIG. As shown in FIG. 9, the allocation margin setting unit 116 increases the allocation margin in accordance with a decrease in system load of the mobile communication system 1. Further, the allocation margin setting unit 116 decreases the allocation margin in accordance with the increase in the system load.

  Further, the allocation margin setting unit 116 can set an allocation margin based on the battery state information acquired by the information acquisition unit 112. Specifically, the allocation margin setting unit 116 sets an allocation margin according to the table shown in FIG. As shown in FIG. 10, when the mobile terminals 200A to 200C operate in the long life mode, the allocation margin setting unit 116 makes the allocation margin larger than that in the normal mode normal mode.

  The usage rate setting unit 117 sets the usage rate of the orthogonal channel or the quasi-orthogonal channel. In the present embodiment, the usage rate setting unit 117 decreases the usage rate of the orthogonal channel in accordance with an increase in the system load of the mobile communication system 1.

(Operation of wireless communication control device)
Next, the operation of the radio base station 100A constituting the radio communication control apparatus in the present embodiment will be described. Specifically, an operation in which the radio base station 100A allocates the radio communication channel CH to the mobile terminal 200A will be described.

(1) Operation example 1
In FIG. 4, the radio base station 100A sets an allocation margin according to the system load of the mobile communication system 1, and based on the threshold of the reception level of the radio signal received from the mobile terminal 200A and the set allocation margin. The operation | movement which allocates radio | wireless communication channel CH to 200 A of mobile terminals is shown.

  As illustrated in FIG. 4, in step S <b> 10, the radio base station 100 </ b> A determines the system load of the mobile communication system 1 based on information indicating the system load in the mobile communication system 1.

  In step S20, the radio base station 100A sets an allocation margin. Specifically, radio base station 100A sets an allocation margin according to the table shown in FIG.

  In step S30, the radio base station 100A assigns the radio communication channel CH to the mobile terminal 200A according to a channel search order determined in advance in the mobile communication system 1. Specifically, the radio base station 100A searches for the radio communication channel CH according to the channel search order unified in the mobile communication system 1 based on the ARP, and is determined by the interference noise level, the required SINR, and the allocation margin. A radio communication channel CH exceeding the allocation threshold is allocated to the mobile terminal 200A.

(2) Operation example 2
FIG. 5 shows that in addition to the system load of the mobile communication system 1, the radio base station 100A allocates a radio communication channel CH to the mobile terminal 200A based on the operation mode (normal mode normal mode or long life mode) of the mobile terminal 200A. The operation is shown.

  As shown in FIG. 5, in step S110, the radio base station 100A determines the system load of the mobile communication system 1.

  In step S120, the radio base station 100A acquires the operation mode of the mobile terminal 200A. Specifically, the radio base station 100A acquires battery status information indicating the status of the battery 210 mounted on the mobile terminal 200A from the mobile terminal 200A. The battery state information includes operation mode information indicating whether the mobile terminal 200A is operating in the normal mode or the long life mode.

  In step S130, the radio base station 100A sets an allocation margin based on the acquired operation mode. Specifically, radio base station 100A sets an allocation margin according to the table shown in FIG.

  In step S140, the radio base station 100A searches for the radio communication channel CH in accordance with the channel search order unified in the mobile communication system 1 based on the ARP, and the allocation determined by the interference noise level, the required SINR, and the allocation margin. A radio communication channel CH exceeding the threshold is allocated to the mobile terminal 200A.

(3) Modification 1
FIG. 6 shows a modification example of the operation of the radio base station 100A applicable to the operation example 1 shown in FIG. 4 and the operation example 2 shown in FIG.

  The operation flow shown in FIG. 6 is executed between step S10 and step S20 shown in FIG. 4 or between step S110 and step S120 shown in FIG.

  In step S11, the radio base station 100A determines whether or not the system load of the mobile communication system 1 is higher than a predetermined threshold value.

  When the system load of the mobile communication system 1 is higher than a predetermined threshold (YES in step S11), in step S12, the radio base station 100A uses a modulation code set (used to generate a radio signal to be transmitted to the mobile terminal 200A). Sets the upper limit of (Modulation and Coding Scheme).

  Specifically, the radio base station 100A selects a modulation code set that lowers the data rate after modulation as the system load increases. Also, the radio base station 100A sets an upper limit value of the modulation code set when the system load is higher than a predetermined threshold.

(4) Modification 2
FIG. 7 shows a modification example of the operation of the radio base station 100A applicable to the operation example 1 shown in FIG. 4 and the operation example 2 shown in FIG.

  The operation flow shown in FIG. 7 is executed between step S10 and step S20 shown in FIG. 4 or between step S110 and step S120 shown in FIG.

  In step S11A, the radio base station 100A determines whether or not the system load of the mobile communication system 1 is higher than a predetermined threshold value.

  When the system load of the mobile communication system 1 is higher than a predetermined threshold (YES in step S11A), in step S12A, the radio base station 100A indicates that the transmission power of the radio signal transmitted from the mobile terminal 200A is a predetermined transmission power threshold. It is determined whether or not.

  When the transmission power of the radio signal transmitted by the mobile terminal 200A is equal to or less than a predetermined transmission power threshold (YES in Step S12A), the radio base station 100A is used to generate a radio signal to be transmitted to the mobile terminal 200A in Step S13A. Sets the upper limit of the modulation code set (Modulation and Coding Scheme).

  Specifically, the radio base station 100A can cancel the selection of a modulation code set that lowers the data rate after modulation.

(Action / Effect)
According to the radio base station 100A (100B), the threshold of the reception level (SINR) of radio signals received from the mobile terminals 200A to 200C increases as the system load of the mobile communication system 1 decreases.

  In the present embodiment, the channel allocation unit 115 performs radio communication based on whether or not the reception level of the radio signal received from the mobile terminals 200A to 200C exceeds the total value of the threshold and the allocation margin added to the threshold. The communication channel CH is allocated to the mobile terminals 200A to 200C. Further, the allocation margin setting unit 116 increases the allocation margin in accordance with a decrease in system load.

  For this reason, when the system load of the mobile communication system 1 is low, the radio communication channel CH with less interference becomes mobile terminals 200 </ b> A to 200 </ b> A <b> A by increasing the threshold of the reception level, specifically, the total value of the threshold and the allocation margin. Assigned to 200C.

  That is, in the case where the throughput of the mobile terminals 200A to 200C can be improved by distributing the radio communication channels CH allocated to the mobile terminals 200A to 200C, unnecessarily interfered according to the allocation order determined by the channel search order based on the ARP. By selecting a radio communication channel CH with a high amount (specifically, interference power), it is possible to solve the problem that the throughput of the mobile terminals 200A to 200C is not improved. In addition, since the radio communication channel CH with less interference is allocated to the mobile terminals 200A to 200C, the transmission power of the mobile terminals 200A to 200C can be suppressed.

  In the present embodiment, the allocation margin setting unit 116 decreases the allocation margin as the system load increases. When the allocation margin decreases, the radio communication channel CH with much interference is allocated to the mobile terminals 200A to 200C. That is, the usage rate of the radio communication channel CH with the fast allocation order determined by the channel search order is high, and the usage rate of the radio communication channel CH with the slow allocation order is low. For this reason, when ARP is used, user data and the like can be efficiently transmitted even when the system load is low.

  In the present embodiment, the allocation margin setting unit 116 sets the allocation margin based on the battery state information acquired by the information acquisition unit 112, specifically, the operation mode. When the mobile terminals 200A to 200C operate in the long life mode, the allocation margin becomes larger than when the mobile terminals 200A to 200C operate in the normal mode. For this reason, it can suppress that radio | wireless communication channel CH which requires high transmission power with respect to the mobile terminal which is operate | moving by long life mode can be suppressed.

  In the present embodiment, the MCS setting unit 114 selects a modulation code set (MCS) in which the data rate after modulation decreases as the system load increases. When a modulation code set that reduces the data rate after modulation is selected, radio communication channels CH with much interference are allocated to the mobile terminals 200A to 200C. That is, the usage rate of the radio communication channel CH with the fast allocation order determined by the channel search order is high, and the usage rate of the radio communication channel CH with the slow allocation order is low.

  For this reason, even when the received power value of the radio signal transmitted by the mobile terminal is low, it is possible to increase the transmission frequency at a high rate when the system load is low, as compared with the method of always searching with the required SINR of the lowest rate. System throughput is increased. Also, compared to a method that always searches from a required SINR at a high rate, some users can transmit at high speed when the system load is high, but it is possible to prevent the occurrence of users who cannot communicate.

  Further, when the transmission power of the radio signal transmitted by the mobile terminal is equal to or lower than the transmission power threshold, the MCS setting unit 114 stops selecting a modulation code set that reduces the data rate after modulation. Furthermore, the MCS setting unit 114 can decrease the transmission power threshold according to an increase in system load. For this reason, when a modulation code set that increases the data rate after modulation can be used without requiring high transmission power, the throughput of the mobile terminal can be improved.

  In the present embodiment, the usage rate setting unit 117 decreases the usage rate of the orthogonal channel according to an increase in system load. For this reason, the usage rate of the quasi-orthogonal channel increases, and interference with adjacent cells can be reduced. That is, when the usage rate of the quasi-orthogonal channel increases, interference is gradually received from other interfering radio communication channels CH, so that the total amount of interference received by the specific radio communication channel CH is higher than when the orthogonal channel is used. Can be suppressed. For this reason, the throughput of the entire mobile communication system 1 is improved.

(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, when the radio base station 100A includes a plurality of sectors, specifically, the sectors SC1 to SC3 (see FIG. 1), the content of the above-described operation may be changed depending on the position of the sector. Specifically, the sector SC1 that is close to the sea or the like and does not have an adjacent cell (sector) on the sea side has little interference with other cells (sectors). Also good.

  In the above-described embodiment, the battery state information includes the operation mode. However, the battery state information may include battery remaining amount information indicating the remaining amount of the battery 210.

  Further, in the above-described embodiment, the radio communication channel CH is allocated according to the allocation order determined by the channel search order according to the ARP. However, the radio communication is not performed according to the ARP but simply according to the predetermined channel search order. A channel CH may be assigned.

  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 according to an embodiment of the present invention. It is a whole functional block block diagram of the radio | wireless communication control apparatus which concerns on embodiment of this invention. It is a detailed functional block block diagram of the communication control part which concerns on embodiment of this invention. It is an operation | movement flow of the radio | wireless communication control apparatus which concerns on embodiment of this invention. It is an operation | movement flow of the radio | wireless communication control apparatus which concerns on embodiment of this invention. It is an operation | movement flow of the radio | wireless communication control apparatus which concerns on the example of a change of this invention. It is an operation | movement flow of the radio | wireless communication control apparatus which concerns on the example of a change of this invention. It is a frame block diagram of the radio signal which the radio | wireless communication control apparatus which concerns on embodiment of this invention transmits / receives. It is a table which shows the correspondence of the system load and allocation margin which are used in embodiment of this invention. It is a table which shows the correspondence of the system load used in embodiment of this invention, and an allocation margin (an operation mode of a mobile terminal is included).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Mobile communication system, 10 ... Core network, 100A, 100B ... Wireless base station, 101 ... Wireless communication part, 103 ... Baseband signal processing part, 105 ... Network connection part, 110 ... Communication control part, 111 ... System load Determination unit 112 ... Information acquisition unit 113 ... Received signal state measurement unit 114 114 MCS setting unit 115 115 Channel allocation unit 116 ... Allocation margin setting unit 117 117 Usage rate setting unit 200A to 200C Mobile terminal 210: Battery, A1 to A3 ... Area, C1, C2 ... Cell, CH ... Wireless communication channel, CHs ... Subchannel, F ... Frame, PA ... Preamble, SC1-SC3 ... Sector

Claims (10)

  1. A wireless communication control apparatus used in a mobile communication system that can increase the number of mobile terminals that can be accommodated at the same time by repeatedly using wireless communication channels that use the same radio frequency at geographically distant locations. And
    A system load determination unit for determining a system load determined based on a traffic amount handled in the mobile communication system;
    Based on a threshold set for a reception level of a radio signal received from the mobile terminal via the radio communication channel, the radio communication channel is set according to a channel search order determined in advance in the mobile communication system. A channel assignment unit assigned to the mobile terminal,
    The channel allocation unit is configured to increase the threshold set for a reception level of a radio signal received from the mobile terminal via at least a part of the radio communication channel in response to a decrease in the system load. Control device.
  2. The channel allocation unit allocates the radio communication channel to the mobile terminal based on whether or not an allocation threshold determined by an interference noise level, a required SINR, and an allocation margin is exceeded.
    The radio communication control apparatus according to claim 1, further comprising an allocation margin setting unit that increases the allocation margin in accordance with a decrease in the system load.
  3.   The radio communication control apparatus according to claim 2, wherein the allocation margin setting unit decreases the allocation margin in accordance with an increase in the system load.
  4. The mobile terminal is equipped with a battery,
    An information acquisition unit that acquires battery state information indicating the state of the battery from the mobile terminal;
    The radio communication control apparatus according to claim 2, wherein the allocation margin setting unit sets the allocation margin based on the battery state information acquired by the information acquisition unit.
  5. The mobile terminal has a normal mode and a long life mode for extending the duration of the battery than the normal mode,
    The battery status information includes operation mode information indicating whether the mobile terminal is operating in the normal mode or the long life mode,
    The radio communication control apparatus according to claim 4, wherein the allocation margin setting unit increases the allocation margin as compared to the normal mode when the mobile terminal is operating in the long life mode.
  6. A modulation code set setting unit for setting a modulation code set used for generating the radio signal;
    The radio communication control apparatus according to claim 1, wherein the modulation code set setting unit selects the modulation code set that decreases a data rate after modulation according to an increase in the system load.
  7.   The radio according to claim 6, wherein the modulation code set setting unit cancels the selection of the modulation code set that lowers the data rate when the transmission power of the radio signal transmitted by the mobile terminal is equal to or lower than a transmission power threshold. Communication control device.
  8.   The radio communication control apparatus according to claim 7, wherein the modulation code set setting unit decreases the transmission power threshold according to an increase in the system load.
  9. The channel allocating unit can allocate, as the wireless communication channel, an orthogonal channel that uses the radio signal in which symbols are orthogonal, or a quasi-orthogonal channel that uses the radio signal in which the symbol is not completely orthogonal,
    The radio communication control apparatus according to claim 1, further comprising a usage rate setting unit that reduces the usage rate of the orthogonal channel in accordance with an increase in the system load.
  10. This is a radio communication control method used in a mobile communication system that can increase the number of mobile terminals that can be accommodated at the same time by repeatedly using radio communication channels that use the same radio frequency at geographically distant locations. And
    Determining a system load determined based on a traffic volume handled in the mobile communication system;
    Wireless communication according to a channel search order determined in advance in the mobile communication system based on a reception level threshold set with respect to a reception level of a wireless signal received from the mobile terminal via the wireless communication channel Assigning a channel to the mobile terminal,
    In the step of allocating the wireless communication channel, the threshold set for the reception level of a wireless signal received from the mobile terminal via at least a part of the wireless communication channel is increased in accordance with a decrease in the system load. A wireless communication control method.
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