JP7178685B2 - Wireless base station and wireless communication method - Google Patents

Description

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

Conventional wireless communication systems, for example, LTE (Long Term Evolution) Release 8 (Rel-8), which is a wireless communication system standardized by 3GPP (3rd Generation Partnership Project), communicates using a maximum band of 20 MHz. It is possible to

Furthermore, in LTE-A (Long Term Evolution-Advanced), which is an advanced version of LTE, the bandwidth supported by LTE is the basic unit in order to achieve further high-speed transmission while ensuring backward compatibility with LTE. A carrier aggregation (CA) technology that bundles and simultaneously uses a plurality of component carriers (CCs) is adopted, and wideband transmission of 100 MHz width can be realized using a maximum of 5 CCs (100 MHz width). However, such carrier aggregation is transmission using different channels in adjacent frequency bands.

Despite efforts to increase the speed as described above, demand for mobile communication traffic has increased rapidly in recent years with the spread of highly functional mobile terminals such as smart phones.

As a result, in addition to the conventional expansion of the use of wireless LAN (Local Area Network), offloading to wireless LAN has progressed due to the increase in mobile data traffic due to the spread of smartphones, and unlicensed bands (2.4 GHz band, 5 GHz band) ) is seeing a surge in traffic.

In addition, due to the progress of the IoT (Internet Of Things) / M2M (Machine to Machine) society, there is concern that the above frequency band and the 920 MHz band will become even more tight, and improving the frequency utilization efficiency of these frequency bands has become an urgent issue. there is

Here, since the usage of radio resources varies depending on time, place, frequency band, radio channel, etc., a situation may occur in which only some frequency bands (or radio channels) are congested.

However, existing private wireless systems (for example, IEEE 802.11 wireless LAN) use a single frequency band or determine one band to be used in advance before performing communication. For example, IEEE802.11n is used after setting whether to use the 2.4 GHz band or the 5 GHz band. For this reason, even if there are free radio resources in the existing private radio system as a whole, congestion may occur.

Here, cognitive radio technology is attracting attention in order to effectively use radio communication resources. Cognitive wireless technology means that a wireless terminal recognizes the usage status of surrounding radio waves and changes the wireless communication resource to be used according to the status. Cognitive radio technology includes a heterogeneous type in which different radio communication standards are selected and used according to the situation, and a frequency sharing type in which a radio terminal searches for an available frequency and secures a necessary communication band.

In the heterogeneous type, cognitive radio recognizes multiple wireless systems operating in the vicinity, obtains information on the availability of each system and possible transmission quality, and connects to the appropriate wireless system. In other words, the heterogeneous cognitive radio indirectly increases the utilization efficiency of frequency resources by increasing the utilization efficiency of wireless systems existing in the vicinity.

On the other hand, in the frequency-sharing type, the cognitive radio device detects the presence of frequency resources (called white space) that are temporarily or locally unused in the frequency bands in which other radio systems are operated. is detected and used for signal transmission. In other words, frequency-sharing cognitive radio directly increases the utilization efficiency of frequency resources in a certain frequency band.

As a method to solve the problem of increased traffic in the unlicensed band as described above, a plurality of wireless LAN standards using different frequency bands (for example, 2.4 GHz band wireless LAN standard and 5 GHz band wireless LAN standard) are introduced. Heterogeneous cognitive radio approaches that are used selectively or in parallel are conceivable (for example, Patent Document 1 and Patent Document 2).

However, in this heterogeneous cognitive radio approach, it is necessary to divide transmission data as appropriate and sort in advance in which frequency band each data is to be transmitted. As a result, new problems arise, such as a large difference in transmission delay depending on the frequency band used depending on the degree of congestion in each frequency band, and a change in the order in which data arrives at the destination.

Therefore, it is desirable to realize cognitive wireless communication by sharing frequencies with existing systems in a plurality of frequency bands separated from each other, for example, a 2.4 GHz band wireless LAN and a 5 GHz band wireless LAN.

Japanese Patent Application Laid-Open No. 2011-211433 JP 2013-187561

However, wireless LANs are used in various places, and in an OBSS (Overlapping-Basic Service Set) environment where the communication areas of densely set wireless base stations (APs: Access Points) partially interfere, multiple The radio base stations will share the same channel. In such an OBSS environment, if the communication area can be efficiently shared, the overall communication efficiency can be improved.

Specifically, in a wireless LAN, interference signals are detected by carrier sense, and wireless communication is performed in an autonomous distributed manner. cannot be detected by the AP of the own cell by carrier sensing, and a hidden terminal problem arises for the terminal equipment (STA: Station) in the interference area. At this time, throughput decreases due to frame collisions in the interference area. Also, when each AP exists in the communication area of each other, it is possible to detect each other by carrier sense, but since a channel is shared by a plurality of APs, the throughput is lowered. On the other hand, if an attempt is made to avoid the occurrence of OBSS by lowering the transmission power, the transmission rate will also be lowered, and there is a possibility that the throughput will be lowered.

Further, for example, in LTE, etc., there is a SON (Self Organizing Network) technology that sets the power of a base station to the optimum power according to the installation position. However, this system can only be implemented in a form in which base stations are controlled under one network like mobile communications. Therefore, there is a problem that users can freely install base stations like a wireless LAN, and it is not possible to operate in a system with different networks.

In addition, this applies not only to wireless communication in which random access control is performed in each of a plurality of frequency bands separated from each other, but also to wireless communication in which random access control is performed in one frequency band.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a radio equipment station capable of improving overall communication efficiency in an OBSS environment in radio communication with random access control. and to provide a wireless communication method.

According to one aspect of the present invention, a radio base station is a radio base station for transmitting a signal using a radio channel on which random access control is performed, and A receiving unit for receiving an indicator indicating that a radio channel is heavily used, a transmission power determining unit for determining an increase or decrease in transmission power based on the reception of the indicator, and a transmission determined by the transmission power determining unit a transmitting unit for transmitting a signal to a terminal device in its own cell using a radio channel according to power.

Preferably, the receiving unit also receives other cell usage status, which is the usage status of radio channels related to other cells that may interfere with the own cell, from the terminal device of the own cell, and the radio base station is indicated by the other cell usage status. It further comprises an indicator transmission control section for controlling the transmission section so as to transmit an indicator to the radio base station of the other cell corresponding to the usage status of the other cell when the radio channel being used is frequently used.

Preferably, the indicator transmission control unit, when the utilization of the radio channel indicated by the received other cell utilization status is greater than the utilization of the radio channel indicated by the previously received other cell utilization status, the other cell The transmitter is controlled to transmit the indicator to the radio base station of the other cell corresponding to the usage situation.

Preferably, the transmit power determining unit increases the transmit power if no indicator is received, and reverses the previous increase or decrease in transmit power if the indicator is received.

Preferably, the usage status of other cells is the channel usage rate of other cells.

Preferably, the radio base station transmits signals using a plurality of radio channels on which random access control is performed in each of a plurality of frequency bands separated from each other, and the transmission unit transmits a plurality of transmission data. a digital signal processing unit for dividing into a plurality of partial data corresponding to each of the frequency bands and generating transmission packets for each frequency band; and a digital signal processing unit provided for each frequency band and generated by the A plurality of high-frequency processing units for converting the digital signal into a high-frequency signal for each corresponding frequency band, and a clock signal provided in common to the plurality of high-frequency processing units and used by the plurality of high-frequency processing units a local oscillator, a channel utilization observation unit that observes the utilization of a plurality of radio channels in a plurality of frequency bands, and predicts the channel utilization after a predetermined time based on the observed utilization and prediction information and the digital signal processing unit and the high frequency processing unit are controlled based on the prediction information. and an access control unit that transmits at the same timing.

According to another aspect of the present invention, a radio communication method is a radio communication method for transmitting a signal using a radio channel on which random access control is performed, wherein the radio channel related to the own cell transmitted from another cell a step of receiving an indicator indicating that there is a lot of use of, a step of determining an increase or decrease in transmission power based on the reception of the indicator, and a terminal of the own cell using the radio channel according to the determined transmission power and sending a signal to the device.

According to the present invention, it is possible to improve overall communication efficiency in the OBSS environment by determining whether to increase or decrease transmission power based on the reception of indicators from other cells.

1 is a schematic diagram showing the configuration of a radio communication system according to an embodiment of the present invention; FIG. 4 is a block diagram showing the configuration of a radio base station according to the same embodiment; FIG. 4 is a flow chart showing the operation of the radio base station according to the same embodiment; FIG. 4 is a diagram for explaining the timing of periodic sensing and periodic reporting according to the same embodiment; FIG. 10 is a conceptual diagram showing an arrangement situation of a plurality of BSSs in simulation in the same embodiment; It is a figure which shows the simulation result in the same embodiment. 1 is a conceptual diagram for explaining the configuration of a radio communication system according to this embodiment; FIG. FIG. 4 is a diagram for explaining a specific example for mapping transmission data to a plurality of bands, transmitting the data, and collectively receiving and integrating the data on the receiving side; 2 is a functional block diagram for explaining the configuration of transmission section 1000 of the present embodiment; FIG. 2 is a functional block diagram for explaining an example of a more detailed configuration of a transmission section 1000; FIG. FIG. 4 is a functional block diagram for explaining the configuration of a transmission section 1000′; FIG. 10 is a functional block diagram for explaining an example of a more detailed configuration of a transmission section 1000'; 4 is a timing chart for explaining the operations of channel usage status observation section 1060, channel usage status prediction section 1070, and access control section 1080. FIG. 2 is a functional block diagram for explaining the configuration of a receiving section 2000 according to an embodiment; FIG. FIG. 3 is a functional block diagram for explaining an example of a more detailed configuration of a receiving section 2000; FIG. FIG. 4 is a functional block diagram for explaining the configuration of a receiving section 2000'; FIG. 20 is a functional block diagram for explaining an example of a more detailed configuration of a receiving section 2000'; 10 is a flowchart for explaining the operations of a channel usage status observation section 1060, a channel usage status prediction section 1070, and an access control section 1080 of a transmission section 1000. FIG.

Hereinafter, a radio communication system and a radio base station according to the present invention will be described using embodiments. In the following embodiments, constituent elements and steps with the same reference numerals are the same or correspond to each other, and repetitive description may be omitted.

In the following, as an example for explaining the wireless communication of the present invention, a plurality of existing unlicensed bands (for example, the 920 MHz band used for IoT and the like, 2 4 GHz band and 5 GHz band).

However, the wireless communication of the present invention is not necessarily limited to such a case, and more generally, using a plurality of frequency bands separated from each other, concurrently at the timing synchronized by the same wireless method It can be applied to wireless communication devices that perform communication. In addition, as will be described later, the wireless communication of the present invention can be applied to a wireless communication apparatus that uses a plurality of frequency bands separated from each other and performs simultaneous and parallel communication at synchronized timings in different wireless systems. It is possible. In addition, the wireless communication of the present invention uses a plurality of frequency bands separated from each other, and has a configuration for receiving signals transmitted simultaneously in parallel at synchronized timing by the same wireless system or different wireless systems. good too.

Moreover, the wireless communication of the present invention is not necessarily limited to wireless communication using a plurality of frequency bands separated from each other, and can be applied to wireless communication using a single frequency band.

FIG. 1 is a schematic diagram for explaining the configuration of a radio communication system according to this embodiment. Referring to FIG. 1, BSS 1 includes a radio base station 1-1 and a plurality of terminal devices 2-1 that perform radio communication with the radio base station 1-1. The BSS2 also includes a radio base station 1-2 and a plurality of terminal devices 2-2 that perform radio communication with the radio base station 1-2. Needless to say, the number of terminal devices in each BSS may be other than three. When the radio base stations 1-1 and 1-2 of the BSSs 1 and 2 are not distinguished, they are referred to as the radio base station 1, and when the terminal devices 2-1 and 2-2 are not distinguished, they are referred to as the terminal device 2. Sometimes. In FIG. 1, BSS1 and BSS2 are assumed to be OBSS. Therefore, when the terminal device 2 of BSS1 performs carrier sensing, the radio wave of BSS2 is also received, and when the terminal device 2 of BSS2 performs carrier sensing, the radio wave of BSS1 is similarly received. become. For example, when focusing on BSS1, BSS1 may be called the own cell, and BSSs other than BSS1 (BSS2 in FIG. 1) may be called other cells.

FIG. 2 is a block diagram showing the configuration of the radio base station 1. As shown in FIG. The radio base station 1 according to the present embodiment transmits a signal using a radio channel on which random access control is performed. and an indicator transmission control unit 14 . In particular, a case will be described where the radio base station 1 transmits signals using a plurality of radio channels on which random access control is performed in each of a plurality of frequency bands separated from each other. Although a plurality of channels may be used for each frequency band, the following description assumes that one channel is used for each frequency band. When multiple channels are used in each frequency band, the following processing is preferably performed for each radio channel used.

The receiving unit 11 receives an indicator, which is transmitted from another cell and indicates that the radio channel related to its own cell is frequently used. As will be described later, the high use of the radio channel may be, for example, that the use of the radio channel has increased or that the use of the radio channel is greater than a threshold. Here, if the receiving unit 11 is included in the radio base station 1-1 of BSS1 shown in FIG. is. Although not particularly limited, the indicator may be transmitted from the radio base station 1 of another cell, for example. In addition, when radio communication is performed using a plurality of frequency bands separated from each other in the own cell, the receiving unit 11 receives an indicator for the radio channel used by the own cell in each frequency band. is preferred. In that case, the indicators may be separate for each frequency band or a single one containing information about each frequency band.

The receiving unit 11 receives, from the terminal device 2 of the own cell, other cell usage status, which is the usage status of radio channels related to other cells that may interfere with the own cell. The number of other cells may be one, or two or more. When a plurality of other cells exist, it is preferable that the other cell usage status of each other cell is transmitted from the terminal device 2 to the radio base station 1 . The other cell usage status may be, for example, the channel usage rate of the other cell (channel occupancy rate (COR: Channel Occupancy Rate)), may be the throughput of the other cell, and other usage status related to the other cell It may be the information shown. In this embodiment, a case where the usage status of other cells is the channel usage rate of other cells will be mainly described. Also, the radio base station 1 normally performs transmission and reception with a WAN (Wide Area Network) side. Therefore, the receiving unit 11 may have a configuration for receiving information from the WAN side. Details of the configuration for performing wireless communication using a plurality of frequency bands separated from each other in the receiving unit 11 will be described later.

Here, a brief description will be given of a method by which the terminal device 2 acquires the usage status of other cells. Channel utilization can be calculated by dividing the busy period in the observation period (sensing period) by the observation period. In place of the channel utilization rate, for example, an idle rate obtained by dividing the idle state period in the observation period by the observation period, or an idle/idle rate obtained by dividing the idle state period in the observation period by the busy state period in the observation period The busy ratio or the like may be used as the other cell usage status. Also, the idle state is a state in which it is determined that communication is not being performed as a result of carrier sensing. The carrier sense may be, for example, physical carrier sense or virtual carrier sense. In the case of physical carrier sensing, the power spectrum corresponding to the received radio signal is compared with a preset threshold value, and it is determined that frequency bands with amplitudes greater than the threshold value are being used. , it may be determined that a frequency band whose amplitude is smaller than the threshold is not used. In the case of virtual carrier sense, in addition to physical carrier sense, it may be determined that communication is being performed during the planned use period (NAV period) of the radio signal included in the radio signal. Note that the NAV period will be described later.

When calculating the channel utilization rate for radio signals of other cells, it is necessary to distinguish whether the radio signals are those of the own cell or those of other cells. The terminal device 2, for example, demodulates the received radio signal and acquires the address of the radio base station 1 from the demodulated header information. The address may be, for example, a MAC address or another address. For example, the terminal device 2 may acquire the address of the wireless base station 1 from the header information of the wireless signal as follows. The terminal device 2 uses the header information of the radio signal to determine whether the radio signal is a downlink signal or an uplink signal. If the radio signal is a downlink signal, the address of the radio base station 1 can be obtained by obtaining the address of the transmission source included in the header information. On the other hand, if the radio signal is an uplink signal, the address of the radio base station 1 can be obtained by obtaining the destination address included in the header information. When the address of the radio base station 1 thus acquired is the same as the address of the radio base station 1 of the own cell, the terminal device 2 determines that the radio signal is the radio signal of the own cell. , otherwise, the terminal device 2 determines that the radio signal is a radio signal of another cell. Since there is a possibility of receiving radio signals from two or more other cells, the terminal device 2 preferably calculates the channel utilization rate for each other cell when calculating the channel utilization rate. Calculating the channel utilization rate for each other cell may be calculating the channel utilization rate for each address of the radio base station 1 of the other cell. Even if the other cell usage status is other than the channel usage rate, the terminal device 2 can similarly acquire the other cell usage status for each other cell. Further, when radio communication is performed using a plurality of frequency bands separated from each other in the own cell, the usage status of other cells is acquired for the radio channel used by the own cell in each frequency band. is preferred. The usage status of other cells for each frequency band acquired in the terminal device 2 in this manner may be transmitted to the radio base station 1 separately for each frequency band, or may be transmitted to the radio base station 1 collectively. may

FIG. 4 is a conceptual diagram showing an example of the relationship between periodic sensing in the terminal device 2 and periodic reporting (transmission of usage status of other cells to the radio base station 1). Referring to FIG. 4 , the length of time of the sensing period in each terminal device 2 is determined, and as an example, sensing in each terminal device 2 is started in response to an instruction from radio base station 1 . Therefore, the start point and the end point of each sensing period (for example, sensing period 1, sensing period 2, etc.) in each terminal device 2 are the same. The other cell usage status according to the radio channel observation in the sensing period 1 is transmitted to the radio base station 1 in the reporting period 1 . Since the reporting period corresponding to the sensing period starts after the sensing period ends, if the sensing period is synchronized in each terminal device 2, the reporting period is also synchronized in each terminal device 2. It will be. The transmission is performed according to the report timing (transmission time point) randomly selected in each terminal device 2 . The upward arrows in each reporting period in FIG. 4 indicate the transmission timing of other cell usage status. What the radio base station 1 wants to know in the report is information with a low degree of appropriateness indicating that the radio channel is suitable for use. This is because such information is considered to accurately indicate the actual communication situation. Therefore, each terminal device 2 may transmit to the radio base station 1 only information with a lower degree of appropriateness than other cell utilization states transmitted by other terminal devices 2 . By doing so, it is possible to reduce the consumption of radio resources according to the transmission of the other cell usage status. Note that when the other cell utilization is the channel utilization rate, the lower the channel utilization rate, the higher the appropriateness. Also, for such radio resource reduction techniques, see, for example, the following document.

Literature: Rui Teng, Kazuto Yano, Tomoaki Kumagai, "An Efficient Distributed-Reporting Approach for Cooperative Sensing in Wireless-LAN System", Proceedings of the 2017 IEICE Society Conference, 2017

Note that FIG. 4 shows the case where the sensing period and the reporting period are repeated continuously without an interval, but this need not be the case. At least one of the sensing period and the reporting period may be repeated continuously at intervals. For example, if the sensing period is P seconds, the reporting period is N seconds, and N seconds is less than P seconds (generally, the reporting period is assumed to be less than the sensing period), then each reporting period There may be an interval of (PN) seconds between.

When transmitting the other cell usage status to the radio base station 1 of the own cell, the terminal device 2 preferably transmits the other cell identification information corresponding to the other cell usage status. The identification information may be, for example, the address (for example, MAC address) of the radio base station 1 of another cell. Further, when acquisition of the other cell usage status is performed for a plurality of frequency bands, the terminal device 2, when transmitting the other cell usage status to the radio base station 1 of its own cell, does not know which frequency band the information is. It is preferable to send it so that it can be seen. Therefore, the terminal device 2 may transmit the other cell usage status together with information indicating the frequency band, for example.

The transmission power decision unit 12 decides to increase or decrease the transmission power based on the reception of the indicator. Determining whether to increase or decrease the transmission power based on the reception of the indicator means determining whether to increase or decrease the transmission power based on whether or not the indicator is received. The indicator, as described above, indicates that the radio channel associated with the own cell is heavily used. Therefore, the reception of the indicator can also be considered as a state of being pointed out (in other words, complained) by other neighboring cells about the high usage of the radio channel of the own cell. Therefore, when the indicator is not received for a certain frequency band, the transmission power determination unit 12 increases the transmission power with which the transmission unit 13 transmits the radio signal in that frequency band. This is because it is considered that the use of radio channels in a certain frequency band does not adversely affect other neighboring cells. On the other hand, when the indicator corresponding to a certain frequency band is received by the receiver 11, the transmission power of the transmitter 13 for that frequency band is changed opposite to the previous increase/decrease. That is, the transmission power determination unit 12 decreases the transmission power if the transmission power was increased immediately before, and increases the transmission power if the transmission power was decreased linearly. This is because the previous increase/decrease in transmission power adversely affected other neighboring cells, so it is considered better to restore it.

In this way, since it is necessary to change the transmission power in a manner opposite to the previous increase or decrease, the transmission power determining unit 12 displays the result of the transmission power change, that is, information indicating whether it is an increase or a decrease, for each frequency band. It may be stored on a recording medium that does not. The transmission power determining unit 12 may, for example, accumulate only the latest change result, or may accumulate change results within a predetermined period. Here, the transmission power is increased or decreased by the transmission power determination unit 12 within a predetermined range. That is, the transmission power determination unit 12 increases or decreases the transmission power within the range of the minimum value and the maximum value of the transmission power respectively set in advance. Therefore, for example, when the transmission power has already reached the maximum value, the transmission power determination unit 12 cannot increase the transmission power any further, and the transmission power has already reached the minimum value. In this case, the transmission power cannot be reduced any further. As such, even if the transmission power does not change as a result, the transmission power determination unit 12 stores information indicating the increase or decrease in transmission power determined based on the reception of the indicator in a recording medium (not shown). is preferred. Then, when the indicator corresponding to a certain frequency band is received by the receiving unit 11, the transmission power determining unit 12 preferably makes a change opposite to the content of the previous determination regarding the increase or decrease of the transmission power in that frequency band. is.

The absolute value of the increase when the transmission power determining unit 12 increases the transmission power and the absolute value of the decrease when the transmission power determining unit 12 decreases the transmission power may be the same. Or it may be different. In the latter case, for example, the absolute value of the increment may be smaller than the absolute value of the decrement. This is because, normally, when the transmission power is increased or decreased as described above, the number of operations for increasing the transmission power is greater. In addition, the transmission power determining unit 12 may determine that the other cell is not using the radio channel (for example, the channel utilization rate is 0, or the idle rate is 100 %), the transmission power may be increased regardless of the reception of the indicator. This is because no radio communication is performed in other cells, so it is considered that there is no problem in using the radio resources in the own cell regardless of whether the radio channel for the own cell is used frequently.

The transmission unit 13 transmits a signal to the terminal device 2 in its own cell using a radio channel according to the transmission power determined by the transmission power determination unit 12 . That is, the transmission unit 13 transmits a radio signal to the terminal device 2 in its own cell using the radio channel with the transmission power determined by the transmission power determination unit 12 . It is assumed that the transmission unit 13 transmits radio signals according to the transmission power thus determined for each frequency band. Also, the radio base station 1 normally performs transmission and reception with the WAN side. Therefore, the transmission unit 13 may have a configuration for transmitting information to the WAN side. Further, the details of the configuration for performing wireless communication using a plurality of frequency bands separated from each other in the transmission unit 13 will be described later.

When the radio channel indicated by the other cell usage status received by the receiving section 11 is frequently used, the indicator transmission control section 14 sends an indicator to the radio base station 1 of the other cell corresponding to the received other cell usage status. is controlled so that the transmission unit 13 transmits the The fact that the radio channel indicated by the received other cell usage status is frequently used means, for example, that the use of the radio channel indicated by the received other cell usage status is different from the previously received other cell usage of the same other cell. It may be that the utilization of the radio channel is greater than that indicated by the situation, or that the utilization of the radio channel that is indicated by the received other-cell utilization is greater than a predetermined threshold. In the former case, the indicator transmission control unit 14 transmits the indicator to the other cell corresponding to the other cell usage status when the usage of the radio channel indicated by the received other cell usage status increases. When the use of the radio channel indicated by the received other cell use status does not increase, control regarding the transmission of the indicator is not performed. The other cell usage status received previously may be, for example, the other cell usage status received one time before, or may be the previous other cell usage status. When the threshold is used to control the transmission of the indicator, the indicator transmission control unit 14, when the use of the radio channel indicated by the received other cell usage status is greater than the threshold, controls the radio channel indicated by the other cell usage status. Regardless of whether the use of the channel has increased, other cells corresponding to the other cell use state are controlled to transmit indicators, and the use of the radio channel indicated by the received other cell use state is the threshold When it is not greater than , there is no control over the transmission of the indicator. In the present embodiment, the indicator transmission control unit 14, when the use of the radio channel indicated by the received usage status of another cell is greater than the use of the radio channel indicated by the previously received usage status of another cell Next, the case of controlling to transmit the indicator to the radio base station 1 of the other cell corresponding to the other cell usage situation will be mainly described.

The indicator transmission control unit 14 receives from the receiving unit 11 the usage status of other cells transmitted from the terminal device 2 in a certain reporting period, and acquires the representative value of the usage status of the other cells for each other cell and for each frequency band. . The representative value obtained in this manner may be stored in a recording medium (not shown) for use in subsequent determination of indicator transmission. To which other cell the other cell usage status corresponds may be determined using the identification information of the other cell transmitted together with the other cell usage status from the terminal device 2 . In addition, it is possible to determine which frequency band the other cell usage status corresponds to by using the information indicating the frequency band transmitted together with the other cell usage status from the terminal device 2 . Also, the representative value of the usage status of other cells may be, for example, an average value, a median value, a maximum value, a minimum value, or the like. If the other cell utilization status is the channel utilization rate, its representative value is preferably an average value, a median value, a maximum value, or the like. From the viewpoint that a value with a low degree of appropriateness more accurately indicates the utilization status of other cells, it is preferable that the representative value of the channel utilization rate is the maximum value.

The indicator transmission control unit 14 determines whether or not the use of the radio channel indicated by the other cell usage status has increased, that is, whether the use of the radio channel indicated by the received other cell usage status has increased depending on the previously received other cell usage status. Whether or not the use of the radio channel is greater than the indicated radio channel is determined, for example, by whether the representative value of other cell utilization in a certain reporting period is greater than the representative value of other cell utilization in the previous reporting period. Alternatively, the representative value of the other cell usage situation in a certain reporting period is higher than the representative value of the other cell usage situation in the previous reporting period by a predetermined threshold (to distinguish from the above threshold, hereinafter, this (The threshold is sometimes called an “increase threshold”.). In the case of other cell utilization (e.g., in the case of the channel utilization rate), the value increases as the use of the radio channel increases, and by doing so, it is determined whether the use of the radio channel has increased. can be done. Note that the increase threshold is a real number equal to or greater than 0, and when the increase threshold is 0, it is the same as when no increase threshold is used. The determination is preferably made for each other cell and for each frequency band. Then, when it is determined that the use of the radio channel indicated by the other cell usage status has increased, the indicator transmission control unit 14 sends the indicator to the radio base station 1 of the other cell corresponding to the increased other cell usage status. Control the transmission unit 13 to transmit. In addition, when radio communication is performed using a plurality of frequency bands separated from each other in the own cell, and when the use of a radio channel indicated by the use status of other cells increases for a predetermined frequency band among them Alternatively, the indicator transmission control unit 14 may include, in the indicator to be transmitted, information indicating the frequency band in which the use of the radio channel indicated by the other cell usage status has increased.

On the other hand, in the case of the other cell usage status (for example, in the case of an idle rate) that becomes smaller as the radio channel usage increases, the indicator transmission control unit 14 determines that the radio channel usage indicated by the other cell usage status becomes smaller. Whether or not there has been an increase may be determined, for example, by determining whether the representative value of the usage status of other cells in a certain reporting period has become smaller than the representative value of the usage status of other cells in the previous reporting period.

When the transmission control of the indicator is performed using a threshold, the indicator transmission control unit 14 determines whether the usage of the radio channel indicated by the usage status of other cells is greater than the threshold. is a fixed value threshold (if the other cell utilization is the channel utilization rate of the other cell, the threshold may be, for example, 0.5 or 0.6). You can judge by whether In the case of other cell utilization (e.g., in the case of channel utilization), where the more the radio channel is used, the larger the value, by doing so, it is determined whether the radio channel is being used more than the threshold. be able to. The threshold, which is a fixed value, is stored, for example, in a recording medium (not shown), and the indicator transmission control unit 14 may read and use the threshold. On the other hand, in the case of the other cell usage status (for example, in the case of an idle rate) that becomes smaller as the radio channel usage increases, the indicator transmission control unit 14 determines that the radio channel usage indicated by the other cell usage status becomes smaller. Whether the number is greater than the threshold may be determined, for example, by determining whether a representative value of other cell usage states in a certain reporting period is less than the threshold.

The indicator transmission control unit 14, for example, transmits information to be transmitted (for example, information indicating a frequency band in which the usage status of other cells has increased) and information indicating a transmission destination (for example, identification information of other cells of the transmission destination). It may be passed to the transmission unit 13, and the transmission unit 13 may transmit the information to be transmitted to the transmission destination accordingly. Therefore, the transmission unit 13 may have a configuration that generates a radio signal corresponding to a desired indicator, for example, according to indicator transmission control by the indicator transmission control unit 14 . In addition, when the transmission unit 13 can directly perform wireless communication with the wireless base station 1 of the other cell of the transmission destination (for example, when the wireless base station 1 of the other cell of the transmission destination is within the communication area of the transmission unit 13, exist) or not (for example, the radio base station 1 of another cell as the destination does not exist within the communication area of the transmitting unit 13). In the former case, the transmitting unit 13 should directly transmit the indicator to the radio base station 1 of the other cell. On the other hand, when the transmitting unit 13 cannot directly communicate with the wireless base station 1 of the other cell, the transmitting unit 13 transmits an indicator, for example, the usage status of the other cell regarding the other cell of the destination. , may be transmitted to the terminal device 2 of the own cell, or the indicator may be transmitted to the terminal device 2 of the other cell. Then, the indicator may be transmitted to the radio base station 1 of another cell via the terminal device 2 . Further, when the terminal device 2 of the own cell cannot directly perform radio communication with the radio base station 1 of the other cell, the terminal device 2 transmits the received indicator to the terminal device 2 of the other cell, for example. You may send. Then, the indicator may be transmitted to the radio base station 1 of the other cell via the terminal device 2 of the other cell. Also, the radio base station 1 is usually considered to be connected to the WAN side. Therefore, the transmitter 13 may transmit the indicator to the target radio base station 1 via the WAN side. In this way, the transmitting unit 13 may directly transmit the indicator to the terminal device 2 in another cell, or may indirectly transmit the indicator via another device or the like. In the latter case, for example, the indicator may be relayed by the terminal device 2 of the own cell and/or the other cell performing ad-hoc mode communication.

In addition, when wireless communication is performed using a plurality of frequency bands separated from each other in the own cell, the other cell usage status and indicators may be transmitted and received using the plurality of frequency bands, for example. , or may be transmitted and received in one predetermined frequency band. If control signals and the like are to be transmitted and received between the radio base station 1 and the terminal device 2 using a 2.4 GHz band control channel, for example, the other cell usage status is The indicator may be transmitted/received only in the band, and the indicator may be transmitted/received only in the 2.4 GHz band between the plurality of radio base stations 1 .

Also, when it is determined whether to transmit the indicator as described above, the A decision will be made. Therefore, the transmission power determining unit 12 determines whether to transmit the indicator for a period of time equal to or longer than the period (this period is a predetermined period in step S1006 described later). ), it is preferable to decide to increase or decrease the transmission power based on the reception of the indicator.

Referring to FIG. 1, in each BSS, the other cell usage status is transmitted from the terminal device 2 to the radio base station 1, and the radio base station 1 uses the other cell usage status transmitted from the terminal device 2 to generate an indicator to other cells. Then, when the indicator is transmitted, the indicator is transmitted from the radio base station 1 to the radio base station 1 of the other cell (double arrow). Also, the radio base station 1 of each BSS increases or decreases the downlink transmission power in its own cell based on the reception of indicators from other cells. As a result, communication efficiency in the OBSS environment can be improved as a whole. This will be described later using simulation results.

In general, when there is a large overlap between multiple cells (that is, when multiple cells exist at substantially the same position), it is better to shorten the transmission time by increasing the transmission power of each radio base station 1. , the plurality of cells as a whole is considered to be more efficient in communication (that is, the overall throughput is improved). On the other hand, when the overlap of a plurality of cells is small, the transmission power of each radio base station 1 is suppressed to the level at which OBSS occurs, so that the efficiency of communication is improved for the plurality of cells as a whole. Conceivable. In the present embodiment, it is considered that such control is achieved by issuing indicators according to the usage status of other cells and increasing or decreasing transmission power based on the reception of indicators from other cells.

Note that the indicator may include information indicating the timing of the sensing period corresponding to the other cell usage status used in determining whether to transmit the indicator. The information indicating the timing of the sensing period may be, for example, information indicating the start time of the sensing period. More specifically, in FIG. 4, when it is decided to issue an indicator according to the usage status of other cells reported in reporting period 1, the start of sensing period 1 corresponding to reporting period 1 is included in the indicator. may include information indicating the time of Then, the transmission power determination unit 12 of each radio base station 1 stores the time at which the transmission power was determined to be increased or decreased, together with the content of the determination. The transmission power may be changed inversely to the increase/decrease in transmission power performed immediately before the included time. For example, the period from the control of the transmission power increase/decrease in the own cell to the timing of issuing the indicator in the other cell may be longer than expected, and the transmission power may be increased/decreased multiple times during that period. could be. Even in such a case, in response to the reception of the indicator, the transmission power is changed in the opposite direction to that which caused the indicator to be issued by increasing or decreasing the transmission power immediately before the time included in the indicator. It is considered that it is possible to change the transmission power of 1, and to realize control that has an appropriate causal relationship.

Also, by using only indicators received within a predetermined period to increase or decrease the transmission power, the causal relationship between the control of the transmission power and the reception of the indicators can be made appropriate. good. For example, even if the transmission power is increased or decreased in the own cell, sensing is performed in other cells regarding the use of radio resources in the own cell according to the result, and the sensing results are transmitted to the radio base station 1 of the other cell. A predetermined period of time is required before the indicator is transmitted. Therefore, the transmission power determination unit 12, for example, starts at the time T _start from the time of increase or decrease in the transmission power performed in the own cell, and ends at the time T _end from the time of increase or decrease. A decision to increase or decrease transmission power may be made based on the reception of the indicator. However, _Tstart and _Tend are predetermined values, and _Tend is larger than _Tstart . When the transmission power is increased or decreased in this way, it is preferable that the sensing period, the transmission timing of the indicator, etc. are synchronized in each cell. Therefore, for example, the radio base station 1 of each cell may perform control for such synchronization.

Next, the operation of the radio base station 1 according to this embodiment will be explained using the flowchart of FIG. This flowchart describes a case where the other cell utilization status is the channel utilization rate of the other cell.

(Step S1001) The receiving unit 11 determines whether or not the indicator transmitted from another cell and the usage status of another cell transmitted from the terminal device 2 of its own cell have been received. If so, the process proceeds to step S1002; otherwise, the process proceeds to step S1003.

(Step S1002) When receiving an indicator transmitted from another cell, the receiving section 11 stores the indicator in a recording medium (not shown). Further, when the reception unit 11 receives the other cell usage status from the terminal device 2 of its own cell, it stores the other cell usage status in a recording medium (not shown). In addition, when receiving information indicating the frequency band, identification information of other cells, etc. together with the indicator and the other cell usage status, the receiving unit 11 stores such information in association with the indicator and the other cell usage status. It is preferable to Then, the process returns to step S1001.

(Step S1003) The transmission power determining unit 12 determines whether or not to determine transmission power. If the transmission power is determined, the process proceeds to step S1004; otherwise, the process proceeds to step S1008. The transmission power determining unit 12 may, for example, periodically determine to determine the transmission power. The cycle of this determination may be, for example, approximately the same as the cycle of determination in step S1008, or may be longer than that cycle.

(Step S1004) The transmission power determining unit 12 determines whether or not the channel utilization rate of the other cell indicated by the other cell utilization status received from the terminal device 2 in the latest reporting period is zero. Then, if the channel utilization rate of the other cell is 0, the process proceeds to step S1005; otherwise, the process proceeds to step S1006.

(Step S1005) The transmission power determination unit 12 increases transmission power. As a result, the transmitting unit 13 transmits the radio signal to the terminal device 2 in its own cell with the increased transmission power. The transmission power determination unit 12 may store information indicating that the transmission power has been increased in a recording medium (not shown) as the latest change result. Then, the process returns to step S1001.

(Step S1006) The transmission power determining unit 12 determines whether or not an indicator has been received from another cell within a predetermined period. Then, if the indicator is received from another cell within the predetermined period, the process proceeds to step S1007, and if the indicator is not received from the other cell within the predetermined period, the process proceeds to step S1005.

(Step S1007) The transmission power determination unit 12 changes the transmission power in the direction opposite to the previous increase/decrease. As a result, the transmitting unit 13 transmits the radio signal to the terminal device 2 in its own cell with the changed transmission power. The transmission power determination unit 12 may store the change result (that is, increase or decrease) of the transmission power in a recording medium (not shown) as the latest change result. Then, the process returns to step S1001.

Note that when wireless communication is performed using a plurality of frequency bands separated from each other in the own cell, the processing of steps S1004 to S1007 is preferably performed for each of the plurality of frequency bands. For example, when wireless communication is performed by a 2.4 GHz band wireless LAN and a 5 GHz band wireless LAN in the own cell, the processing of steps S1004 to S1007 is performed in the 2.4 GHz band, and also in the 5 GHz band. , steps S1004 to S1007 are preferably performed.

(Step S1008) The indicator transmission control unit 14 determines whether to make a determination regarding indicator transmission. Then, if the transmission of the indicator is to be determined, the process proceeds to step S1009; otherwise, the process returns to step S1001. The indicator transmission control unit 14 may, for example, periodically determine to make a determination regarding indicator transmission. Since the determination regarding the transmission of the indicator cannot be made unless the other cell usage status is received, for example, the cycle for determining whether to perform the determination regarding the transmission of the indicator is, for example, the length of the reporting period and the interval between the reporting periods It may be as long as the period plus the length of the interval of , or it may be longer.

(Step S1009) The indicator transmission control unit 14 determines whether the representative value of the channel utilization rate of other cells indicated by the other cell utilization status received from the terminal device 2 in the most recent reporting period has increased. If so, the process proceeds to step S1010; otherwise, the process returns to step S1001.

(Step S1010) The indicator transmission control unit 14 controls the transmission unit 13 so as to transmit indicators to other cells in which the representative value of the channel utilization rate has increased. As a result, the indicator is transmitted from the transmitter 13 to the radio base station 1 of the other cell. Then, the process returns to step S1001.

It should be noted that the processes of steps S1009 and S1010 are preferably performed for each other cell corresponding to the other cell usage status. Further, when wireless communication is performed using a plurality of frequency bands separated from each other in the own cell, the processing of steps S1009 and S1010 is preferably performed for each of the plurality of frequency bands. For example, when wireless communication is performed by a 2.4 GHz band wireless LAN and a 5 GHz band wireless LAN in the own cell, the processing of steps S1009 and S1010 is performed in the 2.4 GHz band, and also in the 5 GHz band. , steps S1009 and S1010 are preferably performed. Note that when indicators are transmitted to the same other cell for a plurality of frequency bands, one indicator may be transmitted, or a plurality of indicators may be transmitted for each frequency band. In both the former case and the latter case, the indicator preferably contains information indicating the corresponding frequency band.

Further, since the flowchart in FIG. 3 shows only main processing in the radio base station 1, the radio base station 1 may perform processing other than that shown in the flowchart in FIG. For example, the radio base station 1 may relay information received from the terminal device 2 of its own cell to the WAN side, or may relay information received from the WAN side to the terminal device 2 of its own cell. Also, the radio base station 1 may perform processing such as routing and NAT (Network Address Translation) during the relay. Further, the order of processing in the flowchart of FIG. 3 is an example, and the order of each step may be changed as long as the same result can be obtained. Further, in the flowchart of FIG. 3, if Yes is determined in step S1003, the process may proceed to step S1006. By doing so, whenever an indicator is received, the transmit power will be changed in the opposite direction. On the other hand, in the flowchart of FIG. 3, even if the indicator is received, the transmission power is increased when the channel utilization rate of the other cell is 0. In addition, in the flowchart of FIG. 3, the processing ends when the power is turned off or an interrupt for processing end occurs.

Simulations were performed to evaluate the transmission power control based on the issuance of the indicator and the reception of the indicator as described above. In this simulation, the evaluation was performed using only one frequency band for simplicity. In this simulation, as shown in FIG. 5, the three BSS1 to BSS3 are arranged such that the distance between the access point (radio base station) AP1 of BSS1 and the access point AP2 of BSS2 is 350 m, and the access point of BSS2 is The distance between AP2 and the access point AP3 of BSS3 was arranged to be 350 m. Also, in this simulation, the transmission power was increased or decreased in the range of 1 to 20 dBm. It is also assumed that each of BSS1 to BSS3 has 10 STAs (terminal devices), and the STAs are randomly arranged. Also, in this simulation, each STA was randomly arranged 30 times, and a Monte Carlo simulation was performed in which the results for each arrangement were aggregated. In addition, the usage status of other cells is the channel usage rate of other cells, and if the average value of the channel usage rate increases even a little, it is set to issue an indicator (that is, the increase threshold in the above description is set to "0" set). It is also assumed that there is no uplink traffic in each BSS. In each BSS, the downlink transmission power is increased or decreased every 5 seconds, and the amount of power change is set to "+1 dBm" when increasing and "-3 dBm" when decreasing.

FIG. 6 shows the results of this simulation. FIG. 6(a) shows temporal changes in the throughputs (AP1 to AP3) of each access point and temporal changes in their total throughput (Total). FIG. 6(b) shows temporal changes in the average transmission power (AP1 to AP3) of each access point. In this simulation, OBSS occurs when the transmission power of each access point is approximately 4 dBm. Therefore, referring to FIG. 6(b), the transmission power increases until OBSS occurs, and after OBSS occurs, the transmission power decreases due to the issuance of the indicator, and thereafter the indicator is not received. It can be seen that an increase in transmission power in response to , and a decrease in transmission power in response to reception of the indicator are repeated. With such control, the overall throughput (Total) of the three BSSs is lower than the throughput without power control, i.e., the simulation time near 0 seconds, which is indicated by the dashed line, at most of the time. It has a higher value. Thus, it can be seen that, as a whole, the three BSSs can achieve more efficient wireless communication by controlling the transmission power according to this embodiment.

As described above, according to the radio base station 1 according to the present embodiment, an indicator is issued according to the other cell usage status received from the terminal device 2 of the own cell, and the indicator transmitted from the other cell is received. By determining whether to increase or decrease transmission power based on , it is possible to achieve overall efficient wireless communication in multiple cells in an OBSS environment. In addition, even when the traffic volume or the number of terminals changes, such control makes it possible to achieve optimum channel sharing with high throughput. In this embodiment, only the transmission power on the downlink side of the radio base station 1 is controlled. Through such control, the BSS as a whole can also appropriately control the transmission power.

In this embodiment, a case where wireless communication is performed using a plurality of frequency bands separated from each other has been mainly described, but this need not be the case. The radio base station 1 and the terminal device 2 according to this embodiment may perform radio communication using a single frequency band. As such, in a radio communication system that performs radio communication using a single frequency band, when an indicator is transmitted and received, the indicator does not have to include information indicating the corresponding frequency band. This is because the frequency band corresponding to the indicator can be specified without the information.

Further, in this embodiment, a case will be described in which, in each cell, the radio base station 1 collects the usage status of other cells from the terminal device 2, and the radio base station 1 transmits an indicator to the radio base station 1 of the other cell. but it doesn't have to be. For example, in each cell, an information collection device different from the radio base station 1 collects the usage status of other cells from the terminal device 2, and the information collection device, like the radio base station 1 described above, An indicator may be sent to station 1 . In that case, the radio base station 1 does not have to include the indicator transmission control unit 14, the receiving unit 11 does not need to receive the other cell usage status, and the transmitting unit 13 transmits the indicator. It doesn't have to be.

Next, wireless communication using a plurality of frequency bands separated from each other will be described. FIG. 7 is a conceptual diagram for explaining the configuration of a radio communication system that performs radio communication using a plurality of frequency bands separated from each other.

Referring to FIG. 7, on the premise that the transmitting side uses three frequency bands of 920 MHz band, 2.4 GHz band, and 5 GHz band, one radio channel is used in each band. configure.

Although a plurality of channels may be used for each frequency band, the following description assumes that one channel is used for each frequency band.

In this embodiment, radio access control having the following features is performed.

That is, first, the transmitting side observes the usage status of multiple frequency bands (the availability status of each radio channel, etc.) by a method to be described later.

Subsequently, the transmitting side simultaneously transmits radio packets (frames) in one or more unused frequency bands/radio channels at a certain timing. At this time, the transmission data is mapped to a plurality of bands and transmitted.

On the other hand, the receiving side collectively receives multiple bands and integrates the data.

In transmission and reception, if such a configuration is adopted, transmission opportunities can be secured even if there is unevenness in congestion between bands, so improvement in frequency utilization efficiency and reduction in transmission delay can be expected. No problem.

FIG. 8 is a diagram for explaining a specific example for mapping transmission data to a plurality of bands, transmitting the data, and collectively receiving and integrating the data on the receiving side.

As shown in FIG. 8, transmission data is divided by the number of symbols proportional to the transmission rate Ri of each band using the transmission sequence and assigned to each band by serial/parallel conversion.

For example, if (5 GHz band transmission rate: 2.4 GHz band transmission rate: 920 MHz band transmission rate)=(R1:R2:R3)=(3:2:1), the transmission data sequence is divided every 6 symbols, 3 symbols, 2 symbols, and 1 symbol are assigned to the 5 GHz band (ch1), 2.4 GHz band (ch2), and 920 MHz band (ch3). In addition, when the transmission sequence is divided and assigned, it is not limited to such a case, and more generally, when m frequency bands are used, the ratio of the transmission rates of the frequency bands is set to (R1:R2 : ...: Rm) (the ratio is expressed irreducibly), the transmission sequence is divided into (R1 + R2 + ... + Rm) × n (m, n: natural number) symbols, and each channel has ( R1×n) symbols, (R2×n) symbols, . . . , (Rm×n) symbols may be assigned.

After such allocation, a physical header is attached to the transmission symbols for each band to form packets, and these packets are transmitted simultaneously and in parallel at the same timing.

The number of symbols assigned to each band on the transmitting side is stored as information in this physical header.

The receiving side uses the physical header on each band to perform synchronization and demodulation processing. Each demodulated series is combined by parallel/serial conversion in the reverse process of the transmission side, and the frame is decoded.

[Sender configuration]
FIG. 9 is a functional block diagram for explaining the configuration of transmitting section 1000 in a transmitting-side device relating to wireless communication using a plurality of frequency bands separated from each other according to this embodiment. When the transmission unit 13 of the radio base station 1 and the transmission unit (not shown) of the terminal device 2 perform transmission by wireless communication using a plurality of frequency bands separated from each other, the same configuration as that of the transmission unit 1000 may be

Referring to FIG. 9, transmission section 1000 includes serial/parallel conversion (hereinafter referred to as S/P conversion) section 1010 for assigning a transmission sequence to each frequency band as described in FIG. A radio frame (packet) is formed for communication by a predetermined radio communication method, such as addition of a physical header, addition of an error correction code, interleave processing, etc., for each frequency band to the data after P conversion. Radio frame generation units 1020.1 to 1020.3 for executing digital processing, and digital signals from radio frame generation units 1020.1 to 1020.3 are subjected to digital-to-analog conversion processing and a predetermined modulation method, respectively. high-frequency processing units (RF units) 1040.1 to 1040.3 that perform modulation processing (for example, quadrature modulation processing for a predetermined multilevel modulation method), up-conversion processing, power amplification processing, etc., and an RF unit and antennas 1050.1 to 1050.3 for transmitting high frequency signals of 1040.1 to 1040.3, respectively. The operations of RF sections 1040.1 to 1040.3 are controlled based on a clock from local oscillator 1030 provided in common to them.

Furthermore, the transmission unit 1000 includes a channel usage status observation unit 1060 that observes the usage status (such as availability of each wireless channel) of each frequency band (one or more wireless channels in each frequency band), and a channel usage status Based on the observation by observation unit 1060, channel usage prediction unit 1070 predicts the channel usage at a predetermined timing; and an access control unit 1080 for controlling transmission timing in .3 so that radio packets are simultaneously transmitted in unused frequency bands and radio channels for a predetermined period at the same controlled transmission timing.

As described with reference to FIG. 7, the transmitting unit 1000 having such a configuration maps data to a plurality of bands and transmits the data, and the receiving side collectively receives the plurality of bands and integrates the data.

FIG. 10 is a functional block diagram for explaining an example of a more detailed configuration of transmission section 1000. As shown in FIG.

The functional block diagram shown in FIG. 10 shows, as an example, the configuration of a transmitting section that conforms to a wireless communication system similar to the wireless communication standard 802.11a.

That is, although the wireless communication standard 802.11a is a wireless LAN communication method in the 5 GHz band, in FIG. shall use a receiver that complies with

Therefore, in each frequency band, the configuration of the preamble portion of a packet, etc. shall be common to a plurality of frequency bands.

However, it is not essential that the wireless communication methods of each frequency band have the same configuration, and even if the wireless communication method (signal format, symbol length, subcarrier interval, etc.) differs for each frequency band, good. In this case, at least a single transmission sequence is divided into each band and transmitted simultaneously. (preamble length, etc.) may be different for multiple frequency bands.

FIG. 10 exemplarily shows a configuration related to transmission in the 5 GHz band. Since a wireless communication system similar to the wireless communication standard 802.11a is assumed, signals to be transmitted shall be OFDM (orthogonal frequency division multiplex) modulated.

Referring to FIG. 10, radio frame generation section 1020.3 receives transmission data distributed from S/P conversion section 1010, and error correction coding section 1110 performs error correction coding. An interleaving/mapping unit 1120 for performing interleaving and mapping processing on the output of the converting unit 1110, an IFFT unit 1130 for performing inverse Fourier transform processing, and a GI addition unit for adding a guard interval part. 1140 and a digital-to-analog converter (DAC) 1150 for converting the digital signal to analog signals of I and Q components. As shown in FIG. 10, radio frame generation section 1020.3 can also be called a baseband processing section. Further, since digital signal processing is performed in S/P conversion section 1010 and radio frame generation sections 1020.1 to 1020.3, they are collectively referred to as digital signal processing sections.

High-frequency processing section 1040.3 includes quadrature modulator 1210 for modulating the signal from DAC 1150 into a predetermined multilevel modulated signal, upconverter 1220 for upconverting the output of quadrature modulator 1210, and the output of upconverter 1220. and a power amplifier 1230 for power amplifying and transmitting from antenna 1050.3.

As a result, RF section 1040.3 converts the baseband OFDM signal to a carrierband OFDM signal.

Furthermore, high-frequency processing section 1040.3 includes clock frequency conversion section 1310 for converting the reference frequency signal from local oscillator 1030 into a reference clock signal of a corresponding frequency band, and clock frequency conversion section 1310 based on the reference clock from clock frequency conversion section 1310. a clock generation unit 1320 for generating a clock used for modulation processing in a quadrature demodulator 1210; and a clock generator 1340 that

That is, the reference frequency signal from local oscillator 1030 is used as a clock signal in such a conversion from baseband OFDM signal to carrier band OFDM signal. More generally, even if the wireless communication system is different, basically the reference frequency signal from the local oscillator 1030 is used as the clock signal in the conversion from the baseband signal to the carrierband signal.

[Other configurations on the sending side]
An example of the configuration of the transmission section 1000 has been described with reference to FIGS. 9 and 10 .

9 and 10, the transmission data is distributed to each frequency band by the S/P conversion section 1010, and then error correction coding processing and interleaving processing are performed.

However, the configuration of transmission section 1000 is not limited to such a case.

FIG. 11 is a functional block diagram for explaining the configuration of a transmission section 1000' having such another configuration.

In the transmission section 1000′ of FIG. 11, the transmission data is distributed to each frequency band by the S/P conversion section 1010 after performing error correction coding processing and interleaving processing. Radio frame generation sections 1020.1 to 1020.3 perform mapping processing, IFFT processing, addition of guard intervals, and digital-to-analog conversion processing.

FIG. 12 is a functional block diagram for explaining an example of a more detailed configuration of such a transmitting section 1000'. The configuration of FIG. 12 corresponds to the configuration of FIG.

The functional block diagram shown in FIG. 12 also shows, as an example, the configuration of a transmission unit that complies with the wireless communication method similar to the wireless communication standard 802.11a.

As shown in FIG. 12, after the error correction coding processing by the error correction coding processing unit 1110 and the interleaving processing by the interleaving unit 1112 are performed, the S/P conversion unit 1010 distributes to each frequency band. A stronger frequency diversity effect can be obtained.

FIG. 13 is a timing chart for explaining the operations of channel usage observation section 1060 , channel usage prediction section 1070 and access control section 1080 .

Referring to FIG. 13, channel usage status observing section 1060 observes the usage status of each frequency band (for example, the availability status and busy probability of each radio channel), and channel usage forecasting section 1070 monitors the usage status of each frequency band. The access control unit 1080 predicts the most recent usage status, and based on the result, determines transmission parameters such as transmission timing, frequency band to be used, and radio channel so that good communication can be performed.

That is, as will be described in detail later, for example, when communication is performed using three frequency bands, channel usage prediction section 1070 uses the current time as a reference, for example, at time t2, uses two bands. If it is time t3, it is predicted that 3 bands can be used. In order to perform efficient transmission, the access control unit 1080 determines the transmission start timing and the frequency band to be used based on the prediction result of the usage status.

For example, in random access control in a conventional wireless LAN or the like, transmission is performed immediately when a transmission opportunity is obtained by CSMA/CA and random backoff, which will be described later.

On the other hand, the access control unit 1080 of the present embodiment waits for transmission until a plurality of frequency bands/radio channels can be used simultaneously even if a transmission opportunity is obtained in some radio channels as necessary. , is controlled.

[Receiving side configuration]
The configuration of the receiving side used in the radio communication system as described with reference to FIG. 7 will be described below.

FIG. 14 is a functional block diagram for explaining the configuration of receiving section 2000 in a device on the receiving side relating to wireless communication using a plurality of mutually separated frequency bands according to this embodiment. When the receiving unit 11 of the radio base station 1 and the receiving unit (not shown) of the terminal device 2 perform reception by wireless communication using a plurality of frequency bands separated from each other, the configuration is the same as that of the receiving unit 2000. may be

14, receiving unit 2000 includes antennas 2010.1 to 2010.3 for receiving signals of a plurality of frequency bands (920 MHz band, 2.4 GHz band, 5 GHz band), antenna 2010.1 Common to reception processing sections 2100.1 to 2100.3 for executing reception processing such as down-conversion processing, demodulation/decoding processing, etc. of signals from 1 to 2010.3 and reception processing sections 2100.1 to 2100.3 Local oscillator 2020 for generating a reference frequency signal, which is a clock serving as a reference for the operation of reception processing units 2100.1 to 2100.3, and each series of signals from reception processing units 2100.1 to 2100.3 are combined by parallel/serial conversion in a process opposite to that on the transmission side. The integrated frame output from the parallel/serial (P/S) converter 2700 is passed to upper layers.

Receiving section 2000 detects the frequency offset of local oscillator 2020 from the preamble signal of the received signal, generates a signal (oscillation frequency control signal) for controlling the oscillation frequency of local oscillator 2020, and performs carrier frequency synchronization processing. and also includes a synchronization processing unit 2600 that generates a signal (synchronization timing signal) for timing synchronization in digital signal processing from the received signal.

Reception processing section 2100.1 receives a signal from antenna 2010.1, performs low-noise amplification processing, down-conversion processing, demodulation processing for a predetermined modulation scheme (for example, quadrature demodulation processing for a predetermined multilevel modulation scheme), A high-frequency processing unit (RF unit) 2400.1 for executing analog-to-digital conversion processing, etc., and a base for executing baseband processing such as demodulation/decoding processing on the digital signal from the RF unit 2400.1 It includes a band processor 2500.1.

Reception processing section 2100.2 also includes high frequency processing section (RF section) 2400.2 and baseband processing section 2500.2 for performing similar processing for the corresponding frequency band. Reception processing section 2100.3 also includes high frequency processing section (RF section) 2400.3 and baseband processing section 2500.3 for performing similar processing for the corresponding frequency band.

Baseband processing units 2500.1 to 2500.3 and parallel/serial (P/S) conversion unit 2700 are collectively referred to as digital signal processing unit 2800. FIG.

FIG. 15 is a functional block diagram for explaining an example of a more detailed configuration of receiving section 2000 shown in FIG.

The functional block diagram shown in FIG. 15 also shows, as an example, the configuration of a receiving section conforming to a wireless communication system similar to the wireless communication standard 802.11a.

Therefore, the configuration of the receiving section corresponds to the configuration of the transmitting section shown in FIG.

FIG. 15 also exemplifies the configuration of reception processing section 2100.3 for the 5 GHz band as a representative.

Referring to FIG. 15, RF section 2400.3 of reception processing section 2100.3 includes low-noise amplifier 3010 for amplifying the signal received from antenna 2010.3, and frequency-converts the output of low-noise amplifier 3010. a downconverter 3020, an automatic gain controller 3030 for controlling the output of the downconverter 3020 to have a predetermined amplitude, a quadrature demodulator 3040 for demodulating a predetermined multilevel modulated signal, and a quadrature demodulator and an analog-to-digital converter (ADC) 3050 for converting the I and Q component outputs of unit 3040, respectively, to digital signals.

RF section 2400.3 further includes clock frequency conversion section 3060 for converting the reference frequency signal from local oscillator 2020 into a reference clock signal of a corresponding frequency band, and based on the reference clock from clock frequency conversion section 3060, , a clock generation unit 3070 for generating a clock used for down-conversion processing in the down converter 3020, and a clock used for demodulation processing in the quadrature demodulator 3040 based on the reference clock from the clock frequency conversion unit 3060. and a clock generator 3080 .

Since a wireless communication system similar to the wireless communication standard 802.11a is assumed, the transmitted signal is OFDM (orthogonal frequency division multiplex) modulated. As a result, RF section 2400.3 converts the carrier band OFDM signal to a baseband OFDM signal.

The reference frequency signal from the local oscillator 2020 is then used for carrier frequency synchronization in such conversion from carrierband OFDM signals to baseband OFDM signals. More generally, even if the wireless communication system is different, basically the reference frequency signal from the local oscillator 2020 is used for carrier frequency synchronization in the conversion from the carrier band signal to the base band signal.

Returning to FIG. 15 again, baseband processing section 2500.3 receives the signal from ADC 3050, performs GI removal section 4010 for removing the guard interval portion, and the signal from which the guard interval has been removed, It includes an FFT section 4020 for performing a fast Fourier transform, a demapping/deinterleaving section 4030 for performing demapping and deinterleaving processing on the output of the FFT section 4020, and an error correction section 4040.

Here, the synchronization timing signal output from synchronization processing section 2600 is used for symbol timing synchronization and the like for detecting the beginning of an OFDM symbol.

More generally, the synchronization timing signal output from synchronization processing section 2600 is basically used as a synchronization signal in baseband processing, even if the wireless communication system is different.

[Other Configurations on the Receiving Side]
An example of the configuration of the receiving section 2000 has been described with reference to FIGS. 14 and 15 .

In the configurations of FIGS. 14 and 15, corresponding to the configuration of the transmission side of FIGS. It was a configuration that combined signals from each frequency band by

However, the configuration of receiving section 2000 is not limited to such a case.

FIG. 16 is a functional block diagram for explaining the configuration of the receiving section 2000' having such another configuration.

The receiving section 2000′ in FIG. 16 is configured to perform deinterleave processing and error correction processing on the received data after the P/S conversion section 2700 combines the signals of each frequency band. Baseband processing sections 2500.1 to 2500.3 perform guard interval removal, FFT processing, and demapping processing.

Therefore, the receiving section 2000' in FIG. 16 corresponds to receiving the signal from the transmitting section 1000' in FIG.

FIG. 17 is a functional block diagram for explaining an example of a more detailed configuration of such a receiving section 2000'. The configuration of FIG. 17 corresponds to the configuration of FIG.

The functional block diagram shown in FIG. 17 also shows, as an example, the configuration of a transmitting section that complies with the wireless communication method similar to the wireless communication standard 802.11a.

As shown in FIG. 17, for each frequency band, after removal of guard intervals by guard interval removal section 4010, FFT processing by FFT section 4020, and demapping processing by demapping section 4032, P/S conversion section 2700 performs each frequency Combining band signals. After combining by P/S conversion section 2700, deinterleaving processing by deinterleaving section 4042 and error correction processing by error correction section 4040 are executed.

FIG. 18 is a flowchart for explaining the operations of the channel usage status observation section 1060, the channel usage status prediction section 1070, and the access control section 1080 of the transmission section 1000 explained in FIG. 9 or the transmission section 1000′ explained in FIG. be.

Referring to FIG. 18, first, channel usage observation section 1060 performs carrier sense in a plurality of bands, and updates usage information stored in a storage device (not shown) (S100).

That is, the channel usage status observation unit 1060 determines the busy/idle state of each radio channel to be used in a plurality of frequency bands, and measures the duration of these states.

Here, the items observed and measured by channel usage status observation section 1060 include the following.

i) the status of each radio channel (busy or idle, which is the physical carrier sense result)
ii) busy duration of each radio channel iii) frame length described in the physical header of the frame being received iv) NAV value described in the MAC header of the frame being received (virtual carrier sense result )

Here, NAV is Network Allocation Vector (transmission prohibited period).

In order to explain terms, a general method for avoiding transmission collisions from terminals in a wireless LAN will be briefly described below.

In a wireless LAN channel, a method called "CSMA (Carrier Sense Multiple Access)" is adopted because packets collide and efficient communication cannot be established unless they mutually wait for transmission.

In the case of wireless, it is not possible to tell whether a collision will occur simply by monitoring the strength of the radio waves. This is because radio waves are greatly attenuated by distance, so it is possible that the radio waves cannot be detected if the opponent causing the collision is far away.

Therefore, a "waiting time (DIFS: Distributed Access Inter Frame Space)" is always provided before transmission, and the transmission is performed after confirming that there are no other transmission signals. Such a method is called “CA (Collision Avoidance)”.

After transmission, it always waits for "ACK (ACKnowledgement, arrival confirmation response)", and if ACK is not returned, it judges that a collision has occurred and retransmits.

In addition to this, there is, for example, "RTS/CTS (Request to Send/Clear to Send)" devised as a countermeasure against hidden terminals as an access control mechanism unique to wireless LANs. Here, a hidden terminal is a terminal that is outside the radio wave range of itself but is within the radio wave range of the communication partner. Its existence cannot be known directly, but it causes interference.

Assuming that the reach of radio waves is Lm, consider a situation where a communication partner B (access point) of wireless terminal A is Lm ahead, and another wireless terminal C is Lm ahead.

At this time, since the radio wave from terminal C does not reach terminal A, even if terminal A checks whether other terminals are transmitting signals (even if it carries out carrier sensing), terminal C does not know the existence of terminal C. It becomes a hidden terminal of terminal A. If no measures are taken, even if terminal C is transmitting to access point B, terminal A will also transmit data to access point B. This causes collisions at the access point B and becomes a factor that lowers the throughput.

RTS/CTS is a mechanism in which all wireless devices issue an "RTS (transmission request)" packet before transmission, and the receiving side responds with "CTS (receivable)" if reception is possible. In the above example, terminal C sends an RTS to access point B first. However, this RTS does not reach terminal A.

Access point B notifies terminal C that reception is possible by transmitting CTS. Since this CTS also reaches terminal A, terminal A perceives that communication will be performed and postpones transmission. The RTS/CTS packet describes the expected channel occupation period, during which communication is suspended. This period is called "NAV (Network Allocation Vector, transmission prohibited period)".

The usage statistics of each radio channel calculated and predicted by the channel usage prediction unit 1070 from the results of observation and measurement by the channel usage observation unit 1060 are as follows.

a) Probability of being busy (temporal utilization rate)
b) Probability distribution of duration of busy state and idle state c) Duration of idle/busy state relative to previous busy/idle state duration Occurrence probability distribution (e.g. probability density function (PDF) or cumulative distribution function (CDF))
d) Occurrence pattern of busy state and idle state (period and duty ratio: when background traffic is periodic)

A specific example of the prediction information calculated by channel usage prediction section 1070 will be described below.

1) Calculation method of "occurrence probability distribution of duration of idle state" The probability density function (PDF) p(τ) of the frame arrival interval τ of the wireless LAN is the Pareto (Pareto) distribution is known to follow (see Document 1 below).

Reference 1: Dashdorj Yamkhin and Youjip Won, "Modeling and analysis of wireless LAN traffic," Journal of Information Science and Engineering, vol. 25, no. 6, pp. 1783-1801, Nov. 2009.

ここで、ａは分布形状を決定する係数、τ_mは最小フレーム到来間隔である。

Here, a is a coefficient that determines the distribution shape, and τ _m is the minimum frame arrival interval.

Also, when a and τ _m are given, the mean μ and variance σ ² of τ are given by the following equations (2) and (3).

例えばIEEE 802.11 DCF規格の場合、データフレームの最小到来間隔は、上述したＤＩＦＳであるため、τ_m＝ＤＩＦＳと設定する。アイドル（idle）状態の継続時間をフレーム到来間隔とし、キャリアセンス結果からμやσ²を計測すれば、上の式を用いて、チャネル利用状況予測部１０７０は、ａの値を推定できる。

For example, in the case of the IEEE 802.11 DCF standard, the minimum arrival interval of data frames is DIFS as described above, so set τ _m =DIFS. If μ and σ ² are measured from the carrier sense result with the duration of the idle state as the frame arrival interval, the channel usage prediction unit 1070 can estimate the value of a using the above equation.

Then, when the value of a is obtained, channel usage prediction section 1070 obtains the occurrence probability distribution represented by the following equation as the probability C(τ) that the idle state continues for τ time or longer.

使用予定の無線チャネルがアイドル（idle）状態となった場合、その時点からt後までアイドル（idle）状態が継続する確率は、Ｃ（τ）から求めることができる。

When the radio channel to be used becomes an idle state, the probability that the idle state will continue for t after that time can be obtained from C(τ).

2) As a result of carrier sense, idle (idle) duration time and busy (busy) duration time are almost the same each time, and when channel usage prediction section 1070 determines that the traffic is periodic, idle ( As the occurrence probability distribution of the duration of the idle state, for example, the idle state from the start of the idle state to the average value of the duration of the idle state (it may be the median value or the minimum value) ) A step function may be used in which the continuation probability is set to 100% and thereafter set to 0%.

3) On the other hand, if the wireless channel to be used is in a busy state, decode the frame length described in the physical header of the incoming packet (frame) and the NAV value described in the MAC frame. By doing so, channel usage prediction section 1070 can acquire the duration of the busy state and predict the duration of the busy state.

Returning to FIG. 18 again, the access control unit 1080 determines whether there is data to be transmitted (S102), and if there is no data to be transmitted (N in S102), the process returns to S100.

On the other hand, when there is data to be transmitted (Y in S102), the access control unit 1080 first determines whether or not the wireless channel on which the transmission opportunity is obtained satisfies the "immediate transmission condition" described below. .

That is, originally, the access control unit 1080 determines whether or not the transmission timing has arrived based on the prediction result of the channel usage state prediction unit 1070, but actually the busy/idle state is reached. Since there is a risk that an error will occur in the prediction of the occurrence of a transmission, the transmission opportunity may not be obtained as expected. control to immediately start transmission (S104). That is, in this case, when the access control unit 1080 determines that a predetermined communication quality can be achieved by performing transmission on a wireless channel that has a transmission opportunity, the access control unit 1080 does not wait for the transmission timing based on the prediction result, and immediately control the wireless transmission of

a1) The total transmission rate is equal to or greater than a predetermined value a2) If the transmission is started immediately, the transmission delay of the transmission data is equal to or less than the predetermined value a3) If the transmission is started immediately, the throughput increases by a predetermined amount or more a4) A transmission opportunity has been secured When transmission is performed on wireless channels, the variance and/or average of the usage rate between wireless channels becomes smaller. a5) When transmission is performed on wireless channels for which transmission opportunities have been secured, the energy consumption required for transmission is less than a predetermined amount. a6) A transmission opportunity has been obtained on a given radio channel a7) When loss of transmission opportunity is not allowed

If any one of the conditions a1) to a7) as described above is satisfied, or if a predetermined combination (combination of two or more conditions) of the conditions a1) to a7) holds, the access control unit 1080 immediately starts transmission using a radio channel for which a transmission opportunity has been secured. That is, access control section 1080 determines transmission parameters and maps transmission data (S108), controls S/P conversion section 1010 and radio frame generation sections 1020.1 to 1020.3, and controls the selected frequency. The frame is transmitted by the band and radio channel (S110), and the process returns to step S100.

Here, "transmission parameters" include "used band and used radio channel", "transmission rate used in each radio channel", "transmission power of each radio channel (each subcarrier is also possible in the case of OFDM)", etc. There is

It should be noted that if a predetermined condition is satisfied, it may be possible to perform transmission using only some wireless channels instead of all available frequency band wireless channels.

Also, for determining the transmission rate and transmission power, an existing technique such as that described in Document 2 below can be used.

Document 2: Tomoaki Yoshiki, Seiichi Sampei, Norihiko Morinaga, "OFDM adaptive modulation scheme using multi-level transmission power control for high-speed data transmission," Transactions of the Institute of Electronics, Information and Communication Engineers (B), J84-B, 7 , pp. 1141-1150, Jul. 2001

Also, channel information necessary for determining the transmission rate and transmission power can be obtained by, for example, the following method.

• Utilize the results of channel estimation performed when receiving frames received in reverse communication.

・Use the channel feedback method specified in IEEE 802.11 wireless LAN.

Subsequently, if the “immediate transmission condition” is not satisfied (N in S104), access control section 1080 determines whether or not the transmission timing has arrived based on the prediction result of channel usage prediction section 1070 as described above. It judges (S106).

For determination of the transmission start timing, prediction information based on usage information is used as follows.

b1) Prediction of the time required for a busy radio channel to become idle (prediction of "How long should I wait?")

For this, by using the following information, it is possible to predict "how long should we wait?"

b1-1) Length of frame or NAV that is a busy factor (if already known)

b1-2) Whether or not a busy state occurs in each radio channel after an arbitrary time (in the case of periodic background traffic, from the cycle and duty of the busy state and idle state predictable)

b1-3) Idle occurrence probability for future waiting time based on past busy duration (can be calculated from CDF of busy state and idle state)

b2) Prediction of the time required for an idle radio channel to become busy (prediction of "how long can you wait?")

b2-1) Presence or absence of occurrence of a busy state in each radio channel after an arbitrary time (periodic background traffic can be predicted from the period and duty of the busy state and idle state)

b2-2) Probability of occurrence of busy for future waiting time based on past idle duration (can be calculated from CDF of busy state and idle state)

The access control unit 1080 performs the above-described "prediction of the time required until a radio channel in a busy state becomes an idle state" and By combining this with the prediction of the time required until the transmission speed reaches the maximum, the transmission timing that maximizes the expected value of the transmission speed is calculated.

In other words, by combining the above two predictions, the access control unit 1080 assumes that the transmission rate of each radio channel has a predetermined value, and in a predetermined time range from the current time, at each time timing, the idle state It is possible to predict the maximum amount of data that can be transmitted by the radio channel. If the predicted amount of data that can be transmitted (transmission rate) exceeds a value corresponding to a predetermined transmission rate, the data is transmitted at that transmission timing.

That is, when access control section 1080 determines that such a transmission timing has arrived (Y in S106), access control section 1080 determines transmission parameters and maps transmission data (S108), and performs S/P conversion. Controls section 1010 and radio frame generation sections 1020.1 to 1020.3 to transmit frames in the selected frequency band and radio channel (S110), and returns the process to step S100.

If the access control unit 1080 determines in step S106 that the predicted amount of data that can be transmitted (transmission rate) does not exceed the value corresponding to the predetermined transmission rate, the access control unit 1080 waits for transmission, thereby (N in step S106), and the process returns to step S100. This is because it is considered possible to improve frequency utilization efficiency, reduce transmission delay, and the like by performing such a standby operation.

The access control unit 1080 may employ the following criteria for determining whether or not the transmission timing has arrived.

c1) Minimize the time it takes to complete the transmission of transmission data (because the faster the transmission ends, the more frames can be transmitted and the less resources are wasted).
c2) Minimize the amount of free resources generated until transmission is completed c3) Maximize the amount of data that can be transmitted within a predetermined time c4) Minimize the dispersion and average of the usage rate of each wireless channel in order to eliminate extremely congested channels.)
c5) Minimize the required transmission energy under the condition that the transmission of transmission data is completed within a certain period of time c6) Transmission outage (transmission failure/loss of transmission opportunity) probability is a predetermined value or less c7) Use of a specific radio channel by itself rate is less than a predetermined value (in order to keep the time utilization rate of the frequency band within the limit in a frequency band with a transmission time limit such as the 920 MHz band).

Here, as a specific example, c1) a technique for minimizing the time until transmission of transmission data is completed will be further described.

For example, radio channels ch1, ch2, and ch3 are assumed as radio channels to be used, and available transmission rates there are R ₁ , R ₂ , and R ₃ [b/s]. Let Ci(τ) be the expected idle duration time probability of radio channel i. Also, let I [bit] be the amount of data to be transmitted from now on.

i) If we get a transmission opportunity on a certain radio channel (let's say ch1), calculate:

i-1) The time required to transmit data using only channel ch1 is as follows.

ｉ－２）次に送信機会が得られる無線チャネルを仮にｃｈ２とし、そこで送信機会を得るのに必要な時間τ₂(例えばビジー（busy）継続時間＋DIFS)を算出する。

i-2) Assuming that the radio channel on which the next transmission opportunity is obtained is ch2, calculate the time τ ₂ (eg, busy duration + DIFS) required to obtain the transmission opportunity there.

i-3) Since the expected probability that ch1 will be available after waiting for τ ₂ is C ₁ (τ ₂ ), when attempting to use channel ch2, simultaneous use with channel ch1 is possible with a probability of C ₁ (τ ₂ ). can. When transmission is started after τ ₂ , the expected value T ₂ of the time until data transmission ends is as follows.

ｉ－４）同様に、チャネルｃｈ３が利用可能になるまでの時間をτ₃とすると、τ₃後に伝送を開始した場合、データ伝送が終わるまでの時間の期待値Ｔ₃は、以下のようになる。

i-4) Similarly, if the time until channel ch3 becomes available is τ ₃ , and if transmission is started after τ ₃ , the expected value T ₃ of the time until data transmission ends is as follows: Become.

以上の計算をもとに、時間Ｔ₁，Ｔ₂，Ｔ₃を比較し、時間Ｔ₂が最小ならば、τ₂待機後に、時間Ｔ₃が最小ならばτ₃待機後に送信する。そうでなければ、チャネルｃｈ１の送信機会を得た時点で送信する。

Based on the above calculations, the times T ₁ , T ₂ and T ₃ are compared, and if the time T ₂ is the shortest, the signal is transmitted after waiting τ ₂ , and if the time T ₃ is the shortest, the transmission is made after waiting τ ₃ . Otherwise, it will be transmitted when a transmission opportunity for channel ch1 is obtained.

With the configuration as described above, it is possible to map each piece of transmission data to a plurality of frequency bands, adjust the transmission timing, and perform data transmission.

As described above, the receiving unit 11 and the transmitting unit 13 of the radio base station 1 according to the present embodiment, and the receiving unit and the transmitting unit of the terminal device 2 perform random access control in each of a plurality of frequency bands separated from each other. radio communication may be performed using multiple radio channels that perform random access control, or radio communication may be performed using a radio channel that performs random access control in a single frequency band. There may be. In the latter case, the transmitting section and the receiving section may have a configuration related to wireless communication in the predetermined frequency band described above. For example, the transmitter and receiver may have a configuration for wireless communication in the 2.4 GHz band.

The embodiments disclosed this time are examples of configurations for specifically implementing the present invention, and do not limit the technical scope of the present invention. The technical scope of the present invention is indicated by the scope of claims rather than the description of the embodiments, and includes changes within the scope of the claims and their equivalent meanings. is intended.

1 radio base station (AP), 2 terminal device (STA), 11 receiving unit, 12 transmission power determining unit, 13 transmitting unit, 14 indicator transmission control unit, 1000 transmitting unit, 1010 S/P conversion unit, 1020.1 ~ 1020.3 radio frame generation unit, 1030 local oscillator, 1040.1 to 1040.3 RF unit (high frequency processing unit), 1050.1 to 1050.3 antenna, 1060 channel usage observation unit, 1070 channel usage prediction unit, 1080 access control unit, 2000 reception unit, 2010.1 to 2010.3 antenna, 2020 local oscillator, 2100.1 to 2100.3 reception processing unit, 2400.1 to 2400.3 RF unit (high frequency processing unit), 2500. 1 to 2500.3 baseband processing unit, 2700 P/S conversion unit, 2600 synchronization processing unit, 2800 digital signal processing unit

Claims (7)

A radio base station for transmitting signals using a radio channel that performs random access control,
An indicator indicating that the use of the radio channel related to the own cell has increased, which is transmitted from another cell, and the usage status of the radio channel related to the other cell that may interfere with the own cell is received from the terminal device of the own cell. a receiver for receiving cell usage;
a transmission power determination unit for determining an increase or decrease in transmission power based on the reception of the indicator;
a transmission unit for transmitting a signal to a terminal device of its own cell using the radio channel according to the transmission power determined by the transmission power determination unit;
When the use of the radio channel indicated by the received other cell usage status is greater than the use of the radio channel indicated by the previously received other cell usage status, the other cell corresponding to the other cell usage status a radio base station, comprising an indicator transmission controller for controlling the transmitter to transmit an indicator to the radio base station. A radio base station for transmitting signals using a radio channel that performs random access control,
a receiving unit for receiving an indicator transmitted from another cell indicating that a radio channel related to the own cell is frequently used;
A transmit power decision unit for determining an increase or decrease in transmit power by increasing the transmit power if no indicator is received and by making a change opposite to the previous increase or decrease in transmit power if an indicator is received. When,
A radio base station, comprising: a transmitting section for transmitting a signal to a terminal device in its own cell using the radio channel according to the transmission power determined by the transmission power determining section. A radio base station for transmitting signals using a plurality of radio channels in which random access control is performed in each of a plurality of frequency bands separated from each other,
a receiving unit for receiving an indicator transmitted from another cell indicating that a radio channel related to the own cell is frequently used;
a transmission power determination unit for determining an increase or decrease in transmission power based on the reception of the indicator;
a transmission unit for transmitting a signal to a terminal device of the own cell using the radio channel according to the transmission power determined by the transmission power determination unit;
The transmission unit
a digital signal processing unit for dividing transmission data into a plurality of partial data corresponding to each of the plurality of frequency bands and generating transmission packets for each of the frequency bands;
a plurality of high-frequency processing units provided for each of the frequency bands for converting the digital signal generated by the digital signal processing unit into a high-frequency signal for each of the corresponding frequency bands;
a local oscillator provided in common to the plurality of high-frequency processing units for generating a clock signal used by the plurality of high-frequency processing units;
a channel usage status observation unit that observes the usage status of the plurality of radio channels in the plurality of frequency bands;
a channel usage prediction unit that predicts the channel usage after a predetermined time period and generates prediction information according to the observed usage;
Based on the prediction information, the digital signal processing unit and the high frequency processing unit are controlled, and each of the partial data is processed as a packet for each of the plurality of frequency bands by the plurality of radio channels at the same timing in synchronization. a transmitting access control unit. 2. The radio base station according to claim 1 , wherein said other cell utilization status is a channel utilization rate of the other cell. A wireless communication method for transmitting a signal using a wireless channel on which random access control is performed,
receiving an indicator transmitted from another cell indicating increased utilization of a radio channel associated with the own cell;
determining an increase or decrease in transmit power based on receiving the indicator;
a step of transmitting a signal to a terminal device of the own cell using the radio channel according to the determined transmission power;
a step of receiving, from a terminal device of the own cell, another cell usage status, which is the usage status of a radio channel related to another cell that may interfere with the own cell;
When the use of the radio channel indicated by the received other cell usage status is greater than the use of the radio channel indicated by the previously received other cell usage status, the other cell corresponding to the other cell usage status and transmitting an indicator to a radio base station. A wireless communication method for transmitting a signal using a wireless channel on which random access control is performed,
receiving an indicator transmitted from another cell indicating that the radio channel for the own cell is heavily used;
determining an increase or decrease in transmit power by increasing the transmit power if the indicator is not received and by making a change opposite to the previous increase or decrease in transmit power if the indicator is received;
and transmitting a signal to a terminal device in the own cell using the radio channel according to the determined transmission power. A wireless communication method for transmitting signals using a plurality of wireless channels in which random access control is performed in each of a plurality of frequency bands separated from each other,
receiving an indicator transmitted from another cell indicating that the radio channel for the own cell is heavily used;
determining an increase or decrease in transmit power based on receiving the indicator;
transmitting a signal to a terminal device of the own cell using the radio channel according to the determined transmission power;
The step of transmitting the signal includes:
dividing transmission data into a plurality of partial data corresponding to each of the plurality of frequency bands, and generating transmission packets for each of the frequency bands;
Using a clock signal generated by a local oscillator provided in common to the plurality of frequency bands, the digital signal of the transmission packet generated for each of the frequency bands is converted into a high-frequency signal for each of the corresponding frequency bands. and
observing the usage status of the plurality of radio channels in the plurality of frequency bands;
a step of predicting a channel utilization state after a predetermined time period and generating prediction information according to the observed utilization state;
and transmitting each of the partial data as packets for each of the plurality of frequency bands synchronously at the same timing through the plurality of radio channels based on the prediction information.

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