JP7687435B2 - Radio signal measurement system, radio signal measurement method, and control device - Google Patents

Description

The present invention relates to a technology for measuring interference conditions of channels used in a wireless communication system.

When multiple wireless communication systems share the same frequency band, wireless signals of various standards are mixed in the same frequency band. In such a wireless environment, selecting and using a channel with less interference is effective in improving throughput and communication capacity. Since the interference situation is not constant, it is preferable to properly grasp the interference situation and reselect a channel.

Non-Patent Document 1 discloses a beacon signal transmitted by a wireless LAN access point. By referring to the information written in the field in the beacon signal, the wireless signal of the system itself can be distinguished from other wireless signals. This makes it possible to check the usage status of the channel used in the system itself.

"Wi-Fi Technology Lecture No. 2: Beacons are Notification Signals", January 15, 2018 (https://www.wlan-business.org/archives/12421)

To understand the interference situation of a channel used in a wireless communication system, it is considered to measure the radio signals of that channel and surrounding channels. When multiple wireless communication systems share the same frequency band, wireless signals of various standards are mixed in the same frequency band. Therefore, it is possible to use a spectrum analyzer or software radio that can measure wireless signals regardless of the wireless signal standard. In this case, the frequency band of the channel used by the wireless communication system to be measured and the surrounding channels are scanned. However, while the wireless communication system to be measured is using the channel, it is difficult to determine whether the wireless signal measured by the scan is the wireless communication system's own wireless signal or an interference signal. This leads to a decrease in the accuracy of recognition of the interference situation.

One object of the present invention is to provide a technology that can accurately measure the interference situation of channels used in a wireless communication system.

The first aspect relates to a wireless signal measurement system.
The wireless signal measurement system includes a measurement device and a control device.
The measurement device measures the interference situation of a channel used in a wireless communication system.
The control device controls the wireless communication system so as to stop signal transmission at least during a measurement period during which the measurement device measures the interference situation.

The second aspect relates to a method for measuring a radio signal.
The wireless signal measurement method is
A process of measuring an interference state of a channel used in a wireless communication system;
and controlling the wireless communication system to stop signal transmission at least during a measurement period in which the interference situation is measured.

The third aspect relates to a control device for controlling a radio signal measurement system that measures an interference situation of a channel used in a radio communication system.
The control device is configured to control the wireless communication system to stop signal transmission at least during a measurement period in which the interference situation is measured.

According to the present invention, when the interference situation of a channel used in a wireless communication system is measured, the wireless communication system being measured is controlled to stop signal transmission. In other words, the interference situation is measured while the wireless communication system being measured stops signal transmission. Therefore, the wireless signal of the wireless communication system being measured itself is prevented from interfering with the measurement of the interference situation. As a result, it becomes possible to more accurately measure (recognize) the interference situation that changes over time. In addition, even if the wireless communication system being measured is in an operating state, it is possible to accurately measure the interference situation of the channel.

1 is a schematic diagram illustrating a configuration example of a wireless communication system according to an embodiment; 1 is a block diagram showing an example of the configuration of a wireless signal measurement system according to an embodiment; FIG. 11 is a block diagram showing another example configuration of the wireless signal measurement system according to the embodiment. 1 is a conceptual diagram for explaining a wireless signal measurement process performed by a wireless signal measurement system according to an embodiment. FIG. FIG. 2 is a conceptual diagram for explaining a first example of a wireless signal measurement process according to an embodiment. 5 is a flowchart illustrating a first example of a wireless signal measurement process according to the embodiment. 5 is a flowchart illustrating a first example of a wireless signal measurement process according to the embodiment. FIG. 11 is a conceptual diagram for explaining a second example of a wireless signal measurement process according to an embodiment. 11 is a flowchart illustrating a second example of a wireless signal measurement process according to the embodiment.

An embodiment of the present invention will be described with reference to the attached drawings.

1 is a schematic diagram showing a configuration example of a wireless communication system 1 according to the present embodiment. The wireless communication system 1 includes a plurality of wireless communication devices 10 that configure a wireless communication network. In the example shown in FIG. 1, the wireless communication system 1 includes wireless communication devices 10-1 to 10-4.

For example, the multiple wireless communication devices 10 include a base station (parent device) and one or more wireless terminals (child devices). The base station and the one or more wireless terminals form a wireless communication network and perform wireless communication with each other.

For example, the wireless communication system 1 is a wireless LAN (Local Area Network) system. In that case, the base station is an access point of the wireless LAN. In the example shown in FIG. 1, the wireless communication device 10-1 is an access point (AP) of the wireless LAN. The wireless communication devices 10-2 to 10-4 are wireless terminals (STAs) that communicate with the access point. A cell consisting of an access point and one or more wireless terminals is called a BSS (Basic Service Set).

There may be cases where multiple wireless communication systems share the same frequency band. In such cases, wireless signals of various standards are mixed in the same frequency band. In such a wireless environment, selecting and using a channel with minimal interference is effective in improving throughput and communication capacity. Since the interference situation is not constant, it is preferable to grasp the interference situation and reselect a channel even while the system is operating.

Below, we consider measuring radio signals to understand the interference situation of channels used in wireless communication system 1.

2 is a block diagram showing an example of the configuration of a wireless signal measurement system 100 according to the present embodiment. The wireless signal measurement system 100 measures the interference state of a channel used in a wireless communication system 1 by measuring a wireless signal. The wireless signal measurement system 100 includes a wireless communication device 10, a measurement device 20, and a control device 30. The wireless communication device 10 is included in the wireless communication system 1 to be measured.

The measuring device 20 measures the interference situation of the channel used in the wireless communication system 1 by measuring the wireless signal. For example, the measuring device 20 includes a spectrum analyzer. As another example, the measuring device 20 may be configured with a wireless interface, wireless software, and a processor that executes the wireless software. This measuring device 20 can measure the wireless signal without depending on the wireless signal standard. For example, the measuring device 20 scans the frequency bands of the channel and surrounding channels used in the wireless communication system 1 to be measured. Note that the measuring device 20 may be included in the wireless communication device 10.

The control device 30 controls the wireless signal measurement system 100. That is, the control device 30 controls the wireless communication device 10 and the measurement device 20. The control device 30 may be a control device included in the wireless communication device 10. As shown in FIG. 3, the wireless communication device 10 may include the measurement device 20 and the control device 30.

The control device 30 may be a computer having one or more processors 31 (hereinafter simply referred to as "processor 31") and one or more storage devices 32 (hereinafter simply referred to as "storage device 32"). For example, the processor 31 includes a CPU (Central Processing Unit). The storage device 32 stores various information required for processing by the processor 31. Examples of the storage device 32 include a volatile memory, a non-volatile memory, a HDD (Hard Disk Drive), an SSD (Solid State Drive), etc.

Program 33 is a computer program executed by processor 31. The functions of control device 30 are realized as a result of processor 31 executing program 33. Program 33 is stored in storage device 32. Program 33 may be recorded on a computer-readable recording medium. Program 33 may be provided to control device 30 via a network.

3. Radio Signal Measurement Processing As described above, the measurement device 20 measures the interference situation of the channel used in the wireless communication system 1 by measuring the wireless signal. At this time, the measurement device 20 scans the frequency band of the channel used in the wireless communication system 1 to be measured and the surrounding channels. However, while the wireless communication system 1 to be measured is using the channel, it is difficult to determine whether the wireless signal measured by the scan is the wireless communication system 1's own wireless signal or an interference signal. This leads to a decrease in the accuracy of recognition of the interference situation. Therefore, the wireless signal measurement system 100 according to the present embodiment executes the wireless signal measurement processing as follows.

Figure 4 is a conceptual diagram for explaining the radio signal measurement processing by the radio signal measurement system 100 according to this embodiment. The measurement period PM is a period during which the measurement device 20 measures the interference situation of the channel used in the wireless communication system 1. The control device 30 controls the wireless communication system 1 to stop signal transmission at least during the measurement period PM. That is, the control device 30 stops signal transmission in the wireless communication system 1 in conjunction with the measurement by the measurement device 20.

More specifically, the control device 30 controls the wireless communication device 10 included in the wireless communication system 1 that is the measurement target, thereby causing the wireless communication system 1 to stop transmitting signals. In other words, the control device 30 controls the wireless communication device 10 included in the wireless communication system 1 so that the wireless communication system 1 stops transmitting signals at least during the measurement period PM.

The transmission prohibition period PX is a period during which signal transmission in the wireless communication system 1 is prohibited. The transmission prohibition period PX is set to include the measurement period PM. Each wireless communication device 10 included in the wireless communication system 1 stops signal transmission during the transmission prohibition period PX. The control device 30 controls the measurement device 20 to perform measurement during the transmission prohibition period PX.

Thus, according to this embodiment, when the interference situation of a channel used in the wireless communication system 1 is measured, the wireless communication system 1 to be measured is controlled to stop signal transmission. In other words, the measurement of the interference situation is performed while the wireless communication system 1 to be measured stops signal transmission. Therefore, the wireless signal of the wireless communication system 1 to be measured itself is prevented from interfering with the measurement of the interference situation. As a result, it is possible to more accurately measure (recognize) the interference situation that changes over time. Furthermore, according to this embodiment, it is possible to accurately measure the interference situation of the channel even if the wireless communication system 1 to be measured is in an operating state.

Below, a specific example of radio signal measurement processing by the radio signal measurement system 100 of this embodiment is described.

3-1. First Example In the first example, the wireless communication system 1 is a wireless LAN system (see FIG. 1). In wireless LANs, the RTS (Request To Send)/CTS (Clear To Send) method is known as a technique for efficiently avoiding collisions. Before transmitting data, a wireless terminal (STA) transmits an RTS frame, which is a transmission request, to an access point (AP). The RTS frame includes information on the length of data to be transmitted. The access point that receives the RTS frame returns a CTS frame to the requesting wireless terminal. The CTS frame transmitted from the access point is received not only by the requesting wireless terminal, but also by other wireless terminals in the network. The CTS frame includes information on the channel occupancy period (Network Allocation Vector, NAV). By receiving the CTS frame, wireless terminals other than the requesting wireless terminal recognize that the other wireless terminals will start transmitting data. Then, wireless terminals other than the requesting wireless terminal refrain from transmitting data during the channel occupancy period indicated by the CTS frame.

Figure 5 is a conceptual diagram for explaining a first example of wireless signal measurement processing. In the first example, the above-mentioned CTS frame is used. The channel occupation period indicated by the CTS frame corresponds to the transmission prohibition period PX. When the wireless communication device 10 (access point) included in the wireless communication system 1 transmits a CTS frame, it becomes possible to set the transmission prohibition period PX in the wireless communication system 1. The transmission prohibition period PX is a maximum of 37 msec.

The control device 30 determines the timing at which the measuring device 20 measures the channel interference situation. Based on the determined measurement timing, the control device 30 controls the wireless communication device 10 and the measuring device 20 to work together. The wireless communication device 10 and the measuring device 20 operate as follows under the control of the control device 30.

Figure 6 is a flowchart showing a first example of a wireless signal measurement process. Here, the wireless communication device 10 is an access point (AP) of a wireless LAN.

The wireless communication device 10 empties the transmission queue near the measurement timing (step S110). The measurement device 20 also completes parameter setting by the measurement timing (step S111). The maximum value of the transmission prohibition period PX (channel occupancy period) is approximately 37 msec. Since it is necessary to secure a margin of 1 msec or more before the start of scanning, the measurement period PM (scan period) is set to 35 msec or less.

Then, in step S112A, the wireless communication device 10 (access point) transmits a "CTS-to-self frame." The CTS-to-self frame is a CTS frame addressed to the access point itself. The CTS-to-self frame transmitted from the access point is received by each wireless communication device 10 in the wireless communication system 1. Therefore, a transmission prohibition period PX can be set for each wireless communication device 10 in the wireless communication system 1.

After step S112A, the measuring device 20 starts scanning after the random access time swing (about 1 msec) (step S113). The measuring device 20 scans the frequency bands of the channels and surrounding channels used in the wireless communication system 1 to be measured (step S114). Then, the measuring device 20 completes the scan (step S115).

After step S115, the wireless communication device 10 performs normal data transmission (step S116).

Figure 7 shows the processing flow when the wireless communication device 10 is a wireless terminal (STA). In the example shown in Figure 7, step S112A described above is replaced with step S112B. Otherwise, the processing flow is the same as that shown in Figure 6.

In step S112B, the wireless communication device 10 (STA) transmits an RTS frame to the access point, thereby causing the access point to transmit a CTS frame. The CTS frame transmitted from the access point is received by each wireless communication device 10 in the wireless communication system 1. Therefore, a transmission prohibition period PX can be set for each wireless communication device 10 in the wireless communication system 1.

3-2. Second Example FIG. 8 is a conceptual diagram for explaining a second example of the wireless signal measurement process according to the present embodiment. In the second example, a "notification frame" that specifies a transmission prohibition period PX including a measurement period PM is used. The wireless communication device 10 transmits the notification frame in advance to the other wireless communication devices 10 included in the wireless communication system 1. This allows each wireless communication device 10 included in the wireless communication system 1 to know the transmission prohibition period PX in advance. Each wireless communication device 10 stops signal transmission during the transmission prohibition period PX specified in the notification frame.

The control device 30 determines the timing at which the measurement device 20 measures the interference status of the channel. The control device 30 sets the transmission prohibition period PX to include the measurement period PM. If accurate time synchronization is possible between the wireless communication devices 10 included in the wireless communication system 1, the transmission prohibition period PX may be set in absolute time. If accurate time synchronization is not possible, a well-known time timing such as TBTT (Target Beacon Transmit Time) is used. The control device 30 controls the wireless communication device 10 and the measurement device 20 to cooperate based on the set transmission prohibition period PX. The wireless communication device 10 and the measurement device 20 operate as follows according to the control of the control device 30.

Figure 9 is a flowchart showing a second example of wireless signal measurement processing.

In step S120, the wireless communication device 10 transmits a notification frame specifying the transmission prohibition period PX in advance to the other wireless communication devices 10 included in the wireless communication system 1. This allows each wireless communication device 10 included in the wireless communication system 1 to know the transmission prohibition period PX in advance.

The measuring device 20 completes parameter setting by the measurement timing (step S121).

When the start time of the transmission prohibition period PX arrives, each wireless communication device 10 included in the wireless communication system 1 stops signal transmission (step S122). In other words, each wireless communication device 10 stops signal transmission during the transmission prohibition period PX specified in the notification frame.

After step S122, the measuring device 20 starts scanning after the time synchronization swing (about 10 msec) (step S123). The measuring device 20 scans the frequency bands of the channels and surrounding channels used in the wireless communication system 1 to be measured (step S124). Then, the measuring device 20 completes the scan (step S125).

After step S125, the wireless communication device 10 performs normal data transmission (step S126).

According to the second example, transmission can be stopped adaptively, making it possible to efficiently utilize time other than measurement.

4. Effects According to this embodiment, when the interference situation of a channel used in the wireless communication system 1 is measured, the wireless communication system 1 to be measured is controlled to stop signal transmission. In other words, while the wireless communication system 1 to be measured stops signal transmission, the interference situation is measured. Therefore, the wireless signal of the wireless communication system 1 to be measured itself is prevented from interfering with the measurement of the interference situation. As a result, it is possible to measure (recognize) the interference situation that changes over time with higher accuracy. Furthermore, according to this embodiment, even if the wireless communication system 1 to be measured is in an operating state, it is possible to measure the interference situation of the channel with higher accuracy.

Reference Signs List 1 Wireless communication system 10 Wireless communication device 20 Measurement device 30 Control device 31 Processor 32 Storage device 33 Program 100 Wireless signal measurement system

Claims (7)

A wireless signal measurement system that is applied to an environment in which multiple wireless communication systems share the same frequency band and wireless signals of multiple standards coexist in the same frequency band,
a measuring device configured to measure radio wave intensity and frequency usage status of a wireless signal without depending on a standard, the measuring device measuring an interference status of a channel used in a target wireless communication system among the plurality of wireless communication systems;
A control device that controls the target wireless communication system so as to stop signal transmission at least during a measurement period in which the measurement device measures the interference situation. 2. The wireless signal measurement system according to claim 1,
The target wireless communication system further includes a wireless communication device,
The control device controls the wireless communication device included in the target wireless communication system to stop the signal transmission to the target wireless communication system. 3. The wireless signal measurement system according to claim 2,
the wireless communication device is a base station of a wireless LAN,
The control device controls the base station to transmit a CTS-to-self frame before the measurement period. 3. The wireless signal measurement system according to claim 2,
the wireless communication device is a wireless terminal that communicates with a base station of a wireless LAN;
The control device controls the wireless terminal to transmit an RTS frame to the base station before the measurement period. 3. The wireless signal measurement system according to claim 2,
the control device controls the wireless communication device to transmit a notification frame specifying a transmission inhibition period including the measurement period to another wireless communication device included in the target wireless communication system;
Each wireless communication device included in the target wireless communication system stops signal transmission during the transmission prohibition period specified in the notification frame. 6. The wireless signal measurement system according to claim 1 ,
The wireless signal measurement system, wherein the measurement device includes a spectrum analyzer. A radio signal measurement method applicable to an environment in which a plurality of radio communication systems share the same frequency band and radio signals of a plurality of standards coexist in the same frequency band, comprising:
measuring an interference state of a channel used in a target wireless communication system among the plurality of wireless communication systems by using a measuring device configured to be able to measure the radio wave intensity and frequency usage state of a wireless signal without depending on a standard;
and controlling the target wireless communication system to stop signal transmission at least during a measurement period during which the interference situation is measured.

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