JP2014155160A - Radio communication system and radio wave measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently measure a radio wave while suppressing the deterioration of throughput and a transmission delay in radio communication equipment.SOLUTION: When transmission data to be transmitted from an access point 100 are generated and another access point 100 is in a state of waiting for transmission of the transmission data, a centralized control station 300 performs control so that a transmission start time of the transmission data at the one access point 100 is simultaneous with the transmission start time at the other access point 100, and also, instructs an access point 100 for observing a radio wave to receive the radio wave at the transmission start time. The access point 100 that observes the radio wave receives a radio wave when the access point 100 waiting for transmission transmits the transmission data at the transmission start time, applies digitization to radio wave for conversion from analog signals to digital signals and outputs the digitized signals to the centralized control station 300. The centralized control station 300 obtains a radio wave measurement result from the digitized signals.

Description

  The present invention relates to a radio communication system and a radio wave measurement method.

  Frequency bands that are used for TV (television) broadcasts are not used in a specific region or time zone because the channel used varies from region to region and there is a broadcast suspension time. A band is formed. This is called TV white space. In TV white space, etc., distributed spectrum sensing has been proposed in which receivers are installed in multiple different locations and radio waves are observed as a means of grasping the presence or absence of a primary system and grasping available free frequency bands. (For example, refer nonpatent literature 1).

FIG. 4 is a diagram illustrating a configuration example of conventional distributed spectrum sensing.
The conventional distributed spectrum sensing includes a plurality of radio wave monitors 10-1 to 10-n and a radio wave information collecting unit 30. The plurality of radio wave monitors 10-1 to 10-n are installed in different places and connected to the radio wave information collection unit 30 via the core network 20. The core network 20 includes broadband transmission paths 20-1 to 20- (n + 1) such as optical fibers and wireless transmission paths, and the radio wave monitors 10-i (i = 1 to n) are connected to the broadband transmission path 20-. The radio wave information collection unit 30 is connected to the core network 20 via the broadband transmission path 20- (n + 1). The radio wave information collecting unit 30 collects radio wave reception statuses of the radio wave monitors 10-1 to 10-n. Here, since the operation of each of the radio wave monitors 10-1 to 10-n is the same, the operation of these radio wave monitors will be described using the radio wave monitor 10-1 as a representative.

  The broadband antenna 11 of the radio wave monitor 10-1 inputs the received radio wave to the receiving unit 12. The receiving unit 12 performs A / D (analog-digital) conversion on the received radio wave with time resolution corresponding to the frequency resolution, and then converts the received radio wave into a power value of each frequency band by fast Fourier transform or the like to the stream processing unit 13. input. The stream processing unit 13 converts the reception time with respect to the power value of each frequency band into a set of data. The converted data is transmitted as radio wave information from the network (NW) interface unit 14 to the radio wave information collecting unit 30 via the core network 20 based on the control of the control unit 15.

  The network (NW) interface unit 31 of the radio wave information collecting unit 30 inputs the radio wave information received from each of the radio wave monitors 10-1 to 10-n via the core network 20 to the database 32, and the database 32 is input. Accumulate radio wave information. The radio wave information stored in the database 32 is input to the statistical processing unit 33. The statistical processing unit 33 analyzes statistics such as the average value, maximum value, and cumulative distribution of the frequency usage time for a desired combination of radio wave monitors, and the display unit 35 displays the analysis result. Moreover, the control part 34 grasps | ascertains the electromagnetic wave utilization condition obtained by the statistical processing part 33 consolidating the electromagnetic wave information memorize | stored in the database 32, and in the range which installed the radio wave monitors 10-1 to 10-n. A free frequency band can be specified, and this free frequency band can be assigned to a certain transmission request.

Shunsuke Saruwatari, Junichi Naganawa, “Distributed Spectrum Sensing for Effective Use of Radio Resources”, Shingaku Techniques, USN 2011-6, May 2011

  In a wireless communication system using white space, it is possible to grasp the usable frequency band by measuring the interference / interference by measuring the radio wave over a wide band, expanding the use band, and operating multiple systems. Is possible.

  However, if radio waves are transmitted from a wireless communication device during measurement of radio waves for grasping available frequencies, there is a problem in the detection power accuracy due to the influence of leakage power in the adjacent frequency band or the next adjacent frequency band. It will occur. For this reason, during the measurement of radio waves, it is necessary to stop the transmission of radio waves outside the measurement target from the radio communication devices that constitute the radio communication system. For example, when the radio wave monitor is a wireless communication device such as an access point, in order to monitor the radio wave while transmission is performed randomly from another wireless communication device, the transmission stops at the other wireless communication device every time measurement is performed. Is required. Therefore, as the number of adjacent wireless communication devices increases, the transmission opportunity of the own device is lost, and there is a concern that throughput may deteriorate.

  The present invention has been made in view of the circumstances as described above, and provides a radio communication system and a radio wave measurement method for accurately measuring radio waves while suppressing deterioration in wireless communication throughput and transmission delay.

  In order to solve the above-described problem, the present invention is a wireless communication system having a centralized control device and a plurality of wireless communication devices, wherein the centralized control device generates transmission data to be transmitted by the wireless communication device. If another wireless communication device is waiting to transmit transmission data, the transmission start time of transmission data in the wireless communication device and the other wireless communication device is controlled at the same time, and radio waves are observed. A processing unit that instructs the radio communication device to receive radio waves at the transmission start time, and a measurement unit that measures radio waves to be observed received by the radio communication device that observes radio waves at the transmission start time. The wireless communication device includes a transmission unit that wirelessly transmits transmission data at the transmission start time according to control of the control processing unit, and the wireless communication device that observes radio waves. Apparatus includes a receiving unit, for receiving a radio wave to be observed on the transmission start time in accordance with the control of the control processing unit, a wireless communication system, characterized in that.

  The present invention is the above-described wireless communication system, wherein the control processing unit waits for transmission of transmission data when the transmission data to be transmitted is generated by the wireless communication device. And when there exists time more than predetermined by the said transmission start time, it controls so that the transmission start time of the transmission data in the said radio | wireless communication apparatus and the said other radio | wireless communication apparatus may become simultaneous.

  Further, the present invention is the above-described wireless communication system, wherein the control processing unit instructs each of the plurality of wireless communication devices having the same transmission start time to use different frequencies, and the transmitting unit includes the control processing unit. Transmitting the transmission data by radio of the frequency instructed to be used by the reception unit, and the receiving unit collectively receives the radio waves of the different frequencies used by the plurality of wireless communication devices having the same transmission start time. Features.

  Further, the present invention is the above-described wireless communication system, wherein the wireless communication apparatus that observes radio waves transmits wirelessly to a radio station under the wireless communication apparatus at a time when the observation target radio waves are received. It further has a control part which controls to suppress.

  Further, the present invention is the above-described wireless communication system, wherein the centralized control device further includes a traffic measurement unit that measures traffic of the plurality of wireless communication devices, and the control processing unit is measured by the traffic measurement unit A plurality of the wireless communication devices are grouped based on the received traffic, and when the transmission data to be transmitted is generated by the wireless communication device and another wireless communication device is waiting to transmit the transmission data, It is characterized in that processing for controlling the transmission start time of transmission data in the communication device and the other wireless communication device to be performed simultaneously is performed for each group.

  The present invention is also the above-described wireless communication system, wherein the control processing unit groups the wireless communication devices using different frequencies, and transmits other wireless data when transmission data to be transmitted is generated by the wireless communication device. When the communication device is waiting for transmission of transmission data, a process for controlling the transmission start time of transmission data in the wireless communication device and the other wireless communication device to be performed simultaneously is performed for each group. .

  The present invention is also a radio wave measurement method executed by a wireless communication system having a control device and a plurality of wireless communication devices, wherein the central control device generates transmission data to be transmitted by the wireless communication device. When the other wireless communication device is waiting for transmission of transmission data, the wireless communication device controls the transmission start time of transmission data in the wireless communication device and the other wireless communication device to be simultaneous and observes radio waves. An instruction process for instructing a device to receive radio waves at the transmission start time, a transmission process in which the wireless communication apparatus transmits transmission data wirelessly at the transmission start time according to control by the instruction process, and the radio observation A wireless communication device receiving a radio wave to be observed at the transmission start time according to the control by the instruction process; and the centralized control device There is a radio wave measuring method characterized by having a measurement process of measuring a radio wave of the observed object received in said receiving step.

  According to the present invention, a radio communication system can accurately measure radio waves while suppressing deterioration in radio communication throughput and transmission delay.

It is a figure which shows the data transmission timing of the radio | wireless communications system in one Embodiment of this invention. It is a functional block diagram of the radio | wireless communications system in the embodiment. It is a figure which shows the processing flow of the centralized control station in the same embodiment. It is a figure which shows the structural example of the conventional distributed spectrum sensing. It is a figure which shows the data transmission timing of the radio | wireless communications system by a prior art.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Hereinafter, a case will be described in which a plurality of wireless communication devices in the wireless communication system of the present embodiment are access points such as a wireless LAN (Local Area Network).

  FIG. 5 is a diagram showing the data transmission timing of each access point in the wireless communication system of the prior art. This figure shows a case where the access point D observes (monitors) the radio waves of the access points A, B, and C in the conventional wireless communication system.

At time t _ra, when the data transmission request to the access point A occurs, DIFS (Distributed interframe space) and the total time of a random backoff time BO _rnd access point A is set as the transmission waiting time of the access point A The DIFS is a time required to determine that the radio wave is in an idle state in which no radio wave is used, and if no signal power is detected during this time, it is determined to be in the idle state. Random backoff time is used to reduce the probability that communication data collision will occur when a plurality of wireless communication devices start transmission at the same time when radio waves are idle. Random time to wait for transmission at the device. The minimum value of the random back-off time is BO _min , and the difference between (DIFS + BO _rnd ) and (DIFS + BO _min ) corresponds to the coordinated transmission adjustment interval. Access point A, if the idle state from the time t _ra data transmission request is generated to the time t _sa of after transmission standby time has continued, transmits the data by the frequency f1.

Subsequently, when a data transmission request is made to the access point B at the time t _rb when the access point A is waiting for data transmission, the total time of the DIFS and the random backoff time BO _rnd of the access point B is It is set as the transmission waiting time of. When the idle state continues from the time t _rb when the data transmission request is generated to the time t _sb after the transmission standby time has elapsed, the access point B transmits data at the frequency f2.

Further, when a data transmission request is generated at the access point C at the time t _rc when the access points A and B are waiting for data transmission, the total time of the DIFS and the random back-off time BO _rnd of the access point C is C is set as the transmission waiting time. The access point C, when the idle state from the time t _r3 data transmission request is generated to the time t _sc after lapse transmission standby time has continued, transmits the data by frequency f3.
The access point D stops wireless transmission at time t _sb , time t _sa , and time t _sc and receives radio waves to be observed. The available frequency band can be grasped from the measurement result of the radio wave received by the access point D.

  FIG. 1 is a diagram showing the data transmission timing of each access point in the wireless communication system of this embodiment. In the figure, the case where the access point D observes the radio waves of the access points A, B, and C in the wireless communication system of the present embodiment is shown.

At time t _ra, when the data transmission request to the access point A occurs, the total time of a random backoff time BO _rnd the DIFS and the access point A is set as the transmission waiting time of the access point A. When an idle state from the time t _ra to time t _sa of after transmission standby time has continued, the access point A transmits data by frequency f1.

Subsequently, it is assumed that a data transmission request is issued to the access point B at the time _trb when the access point A is waiting for data transmission. When the time from time t _rb to time t _sa is longer than (DIFS + backoff minimum time CW _min ), the time from time t _rb to time t _{sa is set as} the transmission standby time of access point B. That is, the time (t _{rb −tra} ) elapsed from the time _tra when the data transmission request is generated at the access point A to the time _trb when the data transmission request is generated at the access point B is the transmission waiting time of the access point A. The time obtained by subtracting from is the transmission standby time of the access point B (= DIFS + random backoff time BO _{rnd of the} access point B). The minimum back-off time CW _min may be the same as or different from the minimum back-off time BO _min in the conventional wireless communication system. When the idle state continues from time t _rb to time t _sa after the transmission standby time elapses, access point B transmits data at frequency f2.

Further, it is assumed that a data transmission request is issued to the access point C at the time _trc when the access points A and B are waiting for data transmission. When the time from time t _rc to time t _sa is longer than (DIFS + backoff minimum time CW _min ), the time from time t _rc to time t _{sa is set as} the transmission standby time of access point C. That is, the time (t _rc −t _ra ) elapsed from the time _tra when the data transmission request is generated at the access point A to the time _trc when the data transmission request is generated at the access point C is the transmission waiting time of the access point A. The time obtained by subtracting from is the transmission standby time of the access point C (= DIFS + random backoff time BO _{rnd of the} access point C). When an idle state from the time t _rc to time t _sa of after transmission standby time has continued, the access point C transmits data by frequency f3.

The access point D stops wireless transmission at time _tsa and receives the radio wave to be observed. Based on the measurement result of the radio wave received by the access point D, the usable frequency band can be grasped.

  As described above, in this embodiment, when a transmission request is generated in the other access points B and C in a period from when a transmission request is issued to the access point A until data is transmitted at the access point A, these access points The points A, B, and C are adjusted so that the data transmission times are the same. As a result, all of the access points A, B, and C can comply with the wireless LAN time rules, and can establish transmission time synchronization between access points without causing an excessive delay time. In addition, it is possible to monitor the usage status of the radio band (channel) efficiently, and the time during which the access point D stops transmitting radio waves is shorter than before, so that deterioration in throughput can be suppressed.

  FIG. 2 is a configuration diagram of a wireless communication system according to an embodiment of the present invention. As shown in the figure, the wireless communication system includes a plurality of access points 100-1 to 100-n and a centralized control station 300. The access points 100-1 to 100-n are connected to the central control station 300 via the core network 200. The centralized control station 300 collects transmission / reception data at the access points 100-1 to 100-n. The core network 200 includes broadband transmission paths 200-1 to 200- (n + 1) such as optical fibers, and the access points 100-i (i = 1 to n) are connected to the core network by the broadband transmission path 200-i. The centralized control station 300 is connected to the core network 200 via a broadband transmission path 200- (n + 1). Hereinafter, the access points 100-1 to 100-n are also collectively referred to as the access point 100.

  The access point 100 includes a network (NW) interface unit 101, a control unit 102, a transmission buffer 103, a transmission unit 104, a transmission / reception changeover switch (SW) 105, a broadband antenna 106, a reception unit 107, and a reception buffer 108. The

The network interface unit 101 transmits and receives data via the core network 200.
Upon receiving an instruction from the central control station 300, the control unit 102 instructs the transmission buffer 103 to output the stored transmission data to the transmission unit 104. In addition, the control unit 102 receives an instruction from the centralized control station 300, and receives a radio wave of an observation target frequency at the transmission start time when another access point 100 transmits transmission data by radio to the reception unit 107. Instruct. Further, the control unit 102 instructs the reception buffer 108 to output the stored reception signal, and outputs the reception signal output from the reception buffer 108 to the central control station 300 to the network interface unit 101. Instruct.

  The transmission buffer 103 temporarily stores transmission data to be transmitted to wireless terminals (wireless stations) under its own access point. The transmission unit 104 converts the transmission data received from the central control station 300 via the network interface unit 101 into a radio frequency band and inputs the converted data to the transmission buffer 103. The transmission unit 104 transmits the transmission data output from the transmission buffer 103 from the broadband antenna 106 by a radio signal.

The transmission / reception selector switch 105 switches between reception and transmission of radio waves by the broadband antenna 106. The broadband antenna 106 transmits and receives radio waves. The broadband antenna 106 can simultaneously receive radio waves from a plurality of wireless channels.
The receiving unit 107 digitizes the radio wave received by the wideband antenna 106 from an analog signal to a digital signal. The reception buffer 108 temporarily stores a reception signal obtained by the reception unit 107 digitizing radio waves.

  The centralized control station 300 includes a network (NW) interface unit 301, an upper layer processing unit 302, a MAC (Medium Access Control) layer processing unit 303, a modulation unit 304, a demodulation unit 305, a database 306, and a traffic measurement unit 307. Composed.

  The network interface unit 301 transmits and receives data via the core network 200. The upper layer processing unit 302 performs processing of an upper layer than the MAC layer in the OSI (Open Systems Interconnection) reference model. When transmission data to the wireless terminal is generated, the upper layer processing unit 302 outputs a transmission request to the access point 100 to which the wireless terminal belongs to the MAC layer processing unit 303 and converts the transmission data into a frame to perform MAC layer processing. The data is output to the unit 303.

  The MAC layer processing unit 303 performs MAC layer processing. When a transmission request is input from the upper layer processing unit 302, the MAC layer processing unit 303 sets a transmission standby time to the access point 100 that has generated the transmission request, that is, the access point 100 to which the wireless terminal that is the destination of transmission data belongs. Set and output transmission data. The MAC layer processing unit 303 instructs the access point 100 to transmit transmission data when the transmission standby time set while the radio wave is in an idle state has elapsed. In addition, the MAC layer processing unit 303 notifies the access point 100 that observes the radio wave of the transmission data transmission time and the frequency used for transmission at the access point 100 where the transmission request is generated.

  Modulator 304 converts transmission data addressed to the wireless terminal into a wireless signal. Demodulation section 305 demodulates the received signal at access point 100 to obtain the power value of each frequency band. The demodulator 305 writes measurement data such as average power and time series data of each frequency band obtained from the demodulation result in the database 306. Further, the demodulation unit 305 demodulates the reception signal received from the wireless terminal under the control of the reception unit 107 of the access point 100, and outputs the reception data obtained by the demodulation to the MAC layer processing unit 303. The received data output to the MAC layer processing unit 303 is input to the upper layer processing unit 302. The database 306 stores measurement data obtained by the demodulator 305. The available channel (frequency band) can be grasped from the measurement result of the interference / interference of the radio wave indicated by the measurement data.

  The traffic measurement unit 307 transmits the transmission data addressed to the wireless terminal under the access point 100 output from the upper layer processing unit 302 to the MAC layer processing unit 303, and the access point output from the MAC layer processing unit 303 to the upper layer processing unit 302. Based on data received from wireless terminals under 100, the traffic statistics of each access point 100 are measured.

  Next, the operation of the wireless communication system according to this embodiment will be described. Hereinafter, a case where the access point 100-n observes radio waves transmitted by the access points 100-1 to 100- (n-1) will be described as an example.

First, transmission data for a wireless terminal connected to the access point 100-1 is input to the upper layer processing unit 302 via the network interface unit 301 of the centralized control station 300. The upper layer processing unit 302 issues a transmission request to the MAC layer processing unit 303. The MAC layer processing unit 303 sets the transmission standby time T1 (= DIFS + random backoff) of the access point 100-1 when the transmission request is issued. The time when a transmission request to a wireless terminal under the access point 100-1 is issued is t _r1 , and the time when the transmission standby time T1 set for the access point 100-1 has elapsed from the time t _r1 is t _s1 . When the idle state continues from the time _tr1 when the transmission request is issued until the transmission standby time T1 elapses, the MAC layer processing unit 303 sets the core network 200 to transmit data to the subordinate wireless terminals. To the control unit 102 of the access point 100-1. The transmission data is framed by the MAC layer processing unit 303 of the centralized control station 300 during the transmission standby time, converted into a radio signal by the modulation unit 304, and transmitted to the access point 100-1 via the core network 200. The Transmission data transmitted to the access point 100-1 is subjected to frequency conversion to a radio frequency band, band limitation, and the like by the transmission unit 104, and is accumulated in the transmission buffer 103.

After the time _{t r1} transmission request under the wireless terminals access point 100-1 is issued, from the time _{t s1} after the lapse transmission wait time set in the access point 100-1 (DIFS + backoff minimum time In the period up to the time of subtracting (CW _min ), a transmission request to the wireless terminal under the access point 100-j (j = 2 to n-1) is issued from the upper layer processing unit 302 to the MAC layer processing unit 303 To do. The time at which the transmission request is issued to the wireless terminal under the access point 100-j is assumed to be _trj . In this case, the MAC layer processing unit 303 determines the time (t _rj) elapsed from the time t _r1 when the transmission request for the access point 100-1 is issued to the time t _rj when the transmission request for the access point 100-j is issued. _-Tr1 ) is calculated. The MAC layer processing unit 303 sets a time obtained by subtracting the calculated elapsed time (t _rj −t _r1 ) from the transmission waiting time T1 set for the access point 100-1 as the transmission waiting time Tj for the access point 100-j. To do. When the idle state continues until the transmission waiting time Tj elapses, the MAC layer processing unit 303 transmits the data to the subordinate wireless terminal via the core network 200 to the access point 100-j. Request to the control unit 102.

  Note that the channels used in each access point 100 may be set to be different from each other by presetting, and the MAC layer processing unit 303 of the centralized control station 300 may be set between the access points 100 from which transmission requests are issued. Therefore, the control units 102 of the access points 100 may be set to use different channels. The control unit 102 of the access point 100 instructs the transmission unit 104 to transmit a signal through the channel set by the central control station 300.

Further, the MAC layer processing unit 303 of the centralized control station 300 groups only the access points 100 having different channels used for wireless communication with subordinate wireless terminals, and adjusts the transmission time for each group as described above. good. The MAC layer processing unit 303 of the centralized control station 300 instructs the control unit 102 of the access point 100 that observes radio waves to collectively receive radio waves of these different channels.
Further, the MAC layer processing unit 303 groups access points 100 having similar traffic characteristics based on the traffic statistics measured by the MAC layer processing unit 303 for each access point 100, and for each group as described above. The transmission time may be adjusted.

  The MAC layer processing unit 303 of the centralized control station 300 transmits access data to the control unit 102 of the access point 100-n that observes radio waves transmitted by the access points 100-1 to 100- (n-1). 100 identification information, the frequency of the channel to be observed, and the transmission start time of transmission data are notified. Under the control of the control unit 102, the access point 100-n transmits a plurality of channels transmitted by other access points 100 using the notified frequency of the channel to be observed at the transmission start time notified from the central control station 300. Radio waves are collectively received by the broadband antenna 106. Note that the control unit 102 of the access point 100-n transmits a NAV (Network Allocation Vector) to a wireless terminal subordinate to the access point 100-n at the time of receiving radio waves transmitted by other access points 100 for observation. ) May be set to instruct suppression of signal transmission.

  The radio wave data received by the broadband antenna 106 of the access point 100-n is digitized by the receiving unit 107, accumulated in the receiving buffer 108, and then controlled by the control unit 102, so that the communication band of the core network 200 is obtained. Is transmitted to the centralized control station 300 so as not to be tight. The radio wave data collected by the centralized control station 300 is converted into measurement data such as average power and time series data in each frequency band by the demodulator 305 and stored in the database 306. The MAC layer processing unit 303 uses these measurement data stored in the database 306 for determination of transmission timing control of a plurality of access points 100 in consideration of the amount of interference.

  FIG. 3 is a diagram showing a processing flow of the centralized control station 300 of the present embodiment. Note that the MAC layer processing unit 303 of the centralized control station 300 determines whether the channel state is busy or idle based on the result of the demodulation unit 305 demodulating the radio wave data received from the access point 100 during the execution of this processing flow. Judgment is always performed. The MAC layer processing unit 303 continues the following processing when the channel state is idle, but stops when it is determined to be busy. In addition, when the channel state shifts from busy to idle and the central control station 300 resumes processing, parameter resetting or changing is performed as appropriate.

  The MAC layer processing unit 303 of the centralized control station 300 selects an access point 100-i (i is any integer between 1 and N) from which a transmission request is first issued from a plurality of access points 100 at random. (Step S100). The MAC layer processing unit 303 sets the transmission waiting time of the selected access point 100-i by (DIFS + random backoff BOnd) (step S110), and starts subtraction of the set transmission waiting time (step S120).

When the remaining transmission waiting time is longer than DIFS + backoff minimum time CW _min (step S130: NO), the MAC layer processing unit 303 determines that another access point 100-j (j is an integer between 1 and N, It is determined whether or not a transmission request is issued for j ≠ i) (step S140). If the transmission request for the other access point 100-j has not been issued (step S140: NO), the MAC layer processing unit 303 returns to step S120 and continues to subtract the transmission waiting time.

  On the other hand, when the transmission request for the access point 100-j has been issued (step S140: YES), the MAC layer processing unit 303 sets the transmission waiting time of the access point 100-j to the selected access point 100-i. The remaining transmission waiting time at the present time is set (step S150). Thereby, the MAC layer processing unit 303 adjusts the transmission time of the selected access point 100-i to be the same as that of the other access point 100-j to which a transmission request is newly issued, and returns to step S120. Continue to subtract the transmission wait time.

When the remaining transmission waiting time of the selected access point 100-i is equal to or less than DIFS + back-off minimum time CW _min (step S130: NO), the MAC layer processing unit 303 transmits the transmission time to other access points 100. For the access point 100-k (k is an integer not smaller than 1 and not larger than N, k ≠ i, j) without adjustment, the time when the transmission waiting time becomes zero as the radio wave observation start time, and the monitoring The frequency band to be notified is notified and radio wave observation is instructed (step S160). At this time, the access point 100-j may be zero, one, or a plurality of access points 100. As frequency bands to be monitored, information on channels used by all access points 100 scheduled to transmit data is notified. At this time, the access point 100-k that monitors the radio wave may be set to suppress transmission from the subordinate radio terminal with the radio wave observation time as the NAV section.

  The MAC layer processing unit 303 of the centralized control station 300 instructs the access points 100-i and 100-j to transmit transmission data at the time when the transmission waiting time becomes zero as time elapses. As a result, radio waves are transmitted at the target access points 100-i and 100-j, and reception is performed at the access point 100-k that monitors (observes) the radio waves at the adjusted time. With the transmission / reception of radio waves at the access points 100-i and 100-j, the central control station indicates that transmission is completed from the control unit 102 of the access points 100-i and 100-j and reception is completed from the control unit 102 of the access point 100-k 300 is notified. The MAC layer processing unit 303 of the centralized control station 300 grasps the access points 100 that have mutually performed radio wave environment observations by comparing these pieces of information (step S170). After the process of step S170, the MAC layer processing unit 303 returns to the selection of the access point 100 from which the first transmission request is issued.

  As described above, according to the present embodiment, the channels are set so that the frequencies are different between the access points, and the data is transmitted at the same time so as not to cause a delay by providing a cooperative transmission section. Radio waves can be observed by batch reception. In addition, since the transmission stop time required for observation, which observes radio waves by collective reception of radio waves, can be reduced, it is possible to suppress a decrease in throughput of the monitored access point.

  Each functional unit of the access point 100 and the centralized control station 300 described above may be realized by dedicated hardware (for example, wired logic), and a computer-readable recording of a program for realizing each functional unit. The function may be realized by recording in a medium, reading the program recorded in the recording medium into a computer system, and executing the program. Here, the “computer system” includes an OS and hardware such as peripheral devices. The “computer system” includes a WWW system having a homepage providing environment (or display environment). The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Further, the “computer-readable recording medium” refers to a volatile memory (RAM) in a computer system that becomes a server or a client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. In addition, those holding programs for a certain period of time are also included.

  The program may be transmitted from a computer system storing the program in a storage device or the like to another computer system via a transmission medium or by a transmission wave in the transmission medium. Here, the “transmission medium” for transmitting the program refers to a medium having a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing a part of the functions described above. Furthermore, what can implement | achieve the function mentioned above in combination with the program already recorded on the computer system, and what is called a difference file (difference program) may be sufficient.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and includes designs and the like that do not depart from the gist of the present invention.

10-1, 10-2, 10-n Radio wave monitor 11, 106 Broadband antenna 12, 107 Receiver 13 Stream processor 14, 31, 101, 301 Network interface 15, 34, 102 Controller 20-1, 20- 2, 20-n, 20- (n + 1), 200-1, 200-2, 200-n, 200- (n + 1) Broadband transmission line 20, 200 Core network 30 Radio wave information collection unit 32, 306 Database 33 Statistical processing unit 35 Display unit 100, 100-1, 100-2, 100-n Access point 103 Transmission buffer 104 Transmission unit 105 Transmission / reception switch 108 Reception buffer 300 Centralized control station (centralized control device)
302 Upper layer processing unit 303 MAC layer processing unit (control processing unit)
304 Modulation unit 305 Demodulation unit (measurement unit)
307 Traffic measurement unit

Claims (7)

A wireless communication system having a centralized control device and a plurality of wireless communication devices,
The central control device is:
When transmission data to be transmitted by the wireless communication device is generated and another wireless communication device is waiting for transmission data, the transmission start time of transmission data in the wireless communication device and the other wireless communication device is A control processing unit that controls the radio communication device to simultaneously monitor the radio communication device that observes radio waves, and instructs the radio communication device to receive radio waves at the transmission start time;
A measurement unit that measures the radio waves to be observed received by the wireless communication device that observes radio waves at the transmission start time;
With
The wireless communication device
A transmission unit that wirelessly transmits transmission data at the transmission start time according to the control of the control processing unit;
With
The wireless communication device for observing radio waves is:
A receiving unit that receives the radio wave to be observed at the transmission start time according to the control of the control processing unit;
Comprising
A wireless communication system. The control processing unit waits for transmission of transmission data when the transmission data to be transmitted by the wireless communication device is generated, and has a predetermined time or more before the transmission start time The transmission start time of the transmission data in the wireless communication device and the other wireless communication device is controlled simultaneously,
The wireless communication system according to claim 1. The control processing unit instructs the use of different frequencies for each of the plurality of wireless communication devices having the same transmission start time,
The transmission unit transmits the transmission data by radio of the frequency instructed to be used by the control processing unit,
The receiving unit collectively receives radio waves of the different frequencies used by the plurality of wireless communication devices having the same transmission start time;
The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system. The wireless communication device that observes radio waves further includes a control unit that controls radio stations under the radio communication device to suppress radio transmission in a time for receiving the radio waves to be observed.
The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system. The central control device is:
A traffic measurement unit that measures traffic of the plurality of wireless communication devices;
The control processing unit groups a plurality of the wireless communication devices based on the traffic measured by the traffic measurement unit, and when other wireless communication devices generate transmission data to be transmitted by the wireless communication device, When waiting for transmission of transmission data, a process for controlling the transmission start time of transmission data in the wireless communication apparatus and the other wireless communication apparatus to be performed simultaneously is performed for each group.
The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system. The control processing unit groups the wireless communication devices using different frequencies, and when another wireless communication device is waiting for transmission of transmission data when transmission data to be transmitted is generated by the wireless communication device, A process for controlling the transmission start time of transmission data in the wireless communication apparatus and the other wireless communication apparatus to be performed simultaneously is performed for each group.
The wireless communication system according to claim 1, wherein the wireless communication system is a wireless communication system. A radio wave measurement method executed by a wireless communication system having a centralized control device and a plurality of wireless communication devices,
When the central control device is waiting for transmission of transmission data when transmission data to be transmitted is generated by the wireless communication device, transmission between the wireless communication device and the other wireless communication device An instruction process for instructing the wireless communication device that observes radio waves to receive radio waves at the transmission start time, while controlling the transmission start times of data to be simultaneous,
A transmission process in which the wireless communication device wirelessly transmits transmission data at the transmission start time according to control by the instruction process;
The wireless communication device for observing radio waves, receiving a radio wave to be observed at the transmission start time according to control by the instruction process,
A measurement process in which the centralized control device measures the radio wave of the observation object received in the reception process;
A radio wave measuring method characterized by comprising:

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