JP7398335B2 - Method for estimating communication distance in visible light communication - Google Patents

Description

The present invention relates to a method for estimating the communicable distance in visible light communication, and more specifically, the communicable distance at a desired communication speed when performing visible light communication between a transmitting device and a receiving device under target environmental conditions. The present invention relates to a method for easily estimating .

2. Description of the Related Art Visible light communication, in which data is wirelessly communicated using visible light, is used as a communication method in the air or underwater (for example, see Patent Document 1). Among these, visible light communication that uses light emitting diodes is safe for the human body and has low costs, making it highly versatile. However, since the visible light emitted by the light emitting diode is easily affected by water, suspended substances, etc., the communicable distance at a desired communication speed varies depending on the environmental conditions under which visible light communication is performed. For example, in the air, the communicable distance varies depending on environmental conditions such as the presence or absence of fog, the presence or absence of rain, and the intensity of external light. Underwater, the communication distance varies depending on environmental conditions such as water turbidity, salinity, and intensity of external light.

In the invention described in Patent Document 1, a visible light emitting device provided on an underwater vehicle emits visible light of multiple types of wavelengths. Then, by determining the wavelength of the visible light received by the visible light receiving section provided in the observation device by the wavelength determination section, the visible light communication device provided in the underwater moving object and the visible light communication device provided in the observation device are determined. We understand the wavelength of visible light that is optimal for visible light communication with. However, with this method, it is not possible to determine the communicable distance at a desired communication speed.

One way to determine the possible communication distance at a desired communication speed is, for example, to repeatedly conduct visible light communication tests while changing the distance between the transmitting device and the receiving device under the target environmental conditions, and to determine the desired communication speed. One possible method is to find the distance between the transmitting device and the receiving device that can be obtained. However, with this method, it is necessary to repeat the visible light communication test many times with the transmitting device and the receiving device separated from each other by several tens of meters to several hundred meters. Therefore, it takes a great deal of effort and time to align the transmitting device and the receiving device and to measure the separation distance between them.

JP2009-278455A

An object of the present invention is to provide a method that can easily estimate the communicable distance at a desired communication speed when performing visible light communication between a transmitting device and a receiving device under target environmental conditions.

In order to achieve the above object, the method of estimating the communication distance in visible light communication of the present invention enables communication at a desired communication speed when performing visible light communication between a transmitting device and a receiving device under target environmental conditions. A distance estimation method, wherein the visible light is emitted from the transmitting devices arranged at a distance from each other to the receiving device under an environmental condition in which the transmittance c of the visible light emitted by the transmitting devices is known in advance. Conduct a preliminary test to determine the transmittance c under the environmental conditions in the preliminary test, the separation distance L from the irradiation position of the transmitter to the light receiving position of the receiver, and the irradiance of visible light received by the receiver. A preliminary test step of calculating the light source intensity I of the transmitting device by substituting E into the following equation (1);
E=I・c ^L /L ² …(1)
an irradiance grasping step of grasping the irradiance E of the visible light received by the receiver corresponding to the desired communication speed when performing visible light communication between the transmitter and the receiver, and the target An on-site environmental test is conducted in which the visible light is irradiated from the transmitting devices placed apart from each other to the receiving device under environmental conditions or under environmental conditions that reproduce the target environmental conditions, and the on-site environmental test The separation distance L from the irradiation position of the transmitting device to the light receiving position of the receiving device, the irradiance E of the visible light received by the receiving device, and the light source intensity I of the transmitting device calculated in advance in the preliminary test step. and a transmittance grasping step of calculating the transmittance c of the visible light under the target environmental conditions by substituting the above into equation (1), and calculating the transmittance c under the target environmental conditions calculated in the transmittance grasping step. The transmittance c of the visible light at It is characterized in that the communicable distance L is estimated by substituting the irradiance E of visible light into the equation (1).

According to the present invention, if the preliminary test process is performed, in the transmittance understanding process, an on-site environmental test is performed under the target environmental condition or an environmental condition that reproduces the target environmental condition, and the transmission in the on-site environmental test is performed. The distance L from the irradiation position of the device to the light receiving position of the receiver, the irradiance E of visible light received by the receiver, and the light source intensity I of the transmitter calculated in advance in the preliminary test process are expressed in equation (1). By simply substituting, the visible light transmittance c under the target environmental conditions can be easily calculated. Then, it corresponds to the visible light transmittance c under the target environmental conditions calculated in the transmittance understanding process, the light source intensity I of the transmitting device calculated in the preliminary test process, and the desired communication speed calculated in the irradiance understanding process. By simply substituting the irradiance E of the receiving device into equation (1), the communicable distance L at a desired communication speed under the target environmental conditions can be easily estimated.

The preliminary testing process and the irradiance understanding process do not need to be performed under the target environmental conditions, and can be easily performed indoors. In the on-site environment test in the transmittance understanding process, it is sufficient to set the distance L from the irradiation position of the transmitter to the light receiving position of the receiver to be approximately several meters, and the work of irradiating visible light from the transmitter to the receiver also requires 1. All you have to do is go around. Therefore, on-site environmental tests can be quickly completed with fewer man-hours.

FIG. 2 is an explanatory diagram illustrating, in plan view, a situation in which visible light communication is performed between a transmitting device and a receiving device. FIG. 2 is a graph diagram illustrating the relationship between the separation distance from the irradiation position of the transmitting device to the light receiving position of the receiving device and the illuminance of visible light received by the receiving device. FIG. 2 is a graph diagram illustrating a relationship between irradiance and illuminance of visible light received by a receiving device. FIG. 2 is a graph diagram illustrating the relationship between the illuminance of visible light received by a receiving device and communication speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for estimating a communicable distance in visible light communication according to the present invention will be described below based on the embodiment shown in the drawings.

As illustrated in FIG. 1, the present invention is a method for estimating the communicable distance at a desired communication speed when performing visible light communication between a transmitting device 1 and a receiving device 2 under target environmental conditions. . The transmitting device 1 includes a transmitting lens 3 that emits visible light V. The receiving device 2 includes a receiving lens 4 that receives visible light V emitted from the transmitting device 1.

In this embodiment, a case will be exemplified in which the target environmental condition is underwater in the ocean, and visible light communication is performed with the transmitting device 1 and the receiving device 2 each surrounded by an individual waterproof case 5. The waterproof case 5 may be made of, for example, acrylic resin or glass that has a high transmittance c of visible light V. When the target environmental condition is deep water, the waterproof case 5 may be formed of a combination of fiber-reinforced plastic (FRP), glass, etc., for example. The waterproof case 5 has an inner space that can accommodate the transmitting device 1 and the receiving device 2, and the material and dimensions are not particularly limited as long as the structure can withstand water pressure under the target environmental conditions. The waterproof case 5 can be used arbitrarily; for example, if the target environmental condition is not underwater, the waterproof case 5 may not be used. The target environmental conditions are not particularly limited as long as they allow visible light communication. Target environmental conditions include, for example, air that is affected by fog, rain, and extraneous light, underwater (sea, lake, etc.) that is affected by turbidity, salinity, and extraneous light, and liquids other than water. Can be mentioned.

In the present invention, a preliminary test step, an irradiance understanding step, and a transmittance understanding step are performed, and then the communicable distance at the desired communication speed described above is calculated.

FIG. 2 shows two patterns in which the transmitting device 1 and the receiving device 2 are of the same model, but different transmitting lenses 3 are attached to the transmitting device 1, and the light source intensity I (W/m ² ) of the transmitting device 1 is made different. Regarding (A, B), when visible light communication is performed in the atmosphere where the transmittance c of visible light V is approximately 1.0, from the irradiation position of the transmitting device 1 (the tip of the transmitting lens 3) to the receiving device 2 This is data graphing the relationship between the separation distance L (m) to the light receiving position (the tip of the receiving lens 4) and the illuminance (lux) of the visible light V received by the receiving device 2. As shown in FIG. 2, when the transmitting lenses 3 attached to the transmitting device 1 are different, the light source intensity I of the transmitting device 1 is different. Further, the light source intensity I of the transmitting device 1 also differs when the model of the transmitting device 1 is different. Therefore, by performing a preliminary test step, the light source intensity I of the transmitting device 1 (including the transmitting lens 3) used under the target environmental conditions is determined.

In the preliminary test process, under environmental conditions in which the transmittance c of the visible light V emitted by the transmitting device 1 is known in advance, visible light V is irradiated from the transmitting devices 1 spaced apart from each other to the receiving device 2. A test is conducted, and the irradiance E (W/m ² ) of the visible light V received by the receiving device 2 at that time is determined. The place where the preliminary test is performed is not particularly limited as long as it is under environmental conditions where the transmittance c of visible light V is known in advance. Since the transmittance c of visible light V in the normal atmosphere, which is not affected by fog, rain, gas, etc., is about 1.0, it is preferable to conduct the preliminary test in the atmosphere, such as indoors. For example, a preliminary test may be conducted in a water tank or the like containing a liquid (such as pure water) whose transmittance c of visible light V is known.

As in this embodiment, when it is assumed that visible light communication is performed using the waterproof case 5 under target environmental conditions, the transmitting device 1 and the receiving device 2 are each surrounded by the waterproof case 5 in the same way. It is preferable to conduct a preliminary test under the condition that the The irradiance E of the visible light V received by the receiving device 2 can be measured using a power meter or the like.

FIG. 3 shows two patterns (A, B) in which the transmitting device 1 and the receiving device 2 are of the same model, but different transmitting lenses 3 are attached to the transmitting device 1, and the light source intensity I of the transmitting device 1 is made different. , is data graphing the relationship between the irradiance E of the visible light V received by the receiving device 2 and the illuminance. As shown in FIG. 3, regardless of the difference in the light source intensity I of the transmitting device 1, the irradiance E of the visible light V received by the receiving device 2 and the illuminance have a linear relationship. Therefore, when determining the irradiance E of the visible light V received by the receiving device 2, it is also possible to measure the illuminance of the visible light V received by the receiving device 2 and convert the measured illuminance to the irradiance E. can. The illuminance of the visible light V received by the receiving device 2 can be measured using an illuminance meter or the like.

The separation distance L from the irradiation position of the transmitting device 1 to the light receiving position of the receiving device 2 when performing the preliminary test can be set as appropriate depending on the environmental conditions in which the preliminary test is performed, but if the separation distance L is too short, Since the irradiance E and illuminance of the visible light V received by the receiving device 2 are extremely high, it is difficult to accurately measure the irradiance E and illuminance. Furthermore, the separation distance L set in the preliminary test only needs to be within the range that can measure the irradiance E or illuminance of the visible light V received by the receiving device 2, so there is no need to set the separation distance L excessively long. . Therefore, the separation distance L from the irradiation position of the transmitting device 1 to the light receiving position of the receiving device 2 in the preliminary test is preferably set within a range of 1 m or more and 10 m or less, for example.

In the preliminary test process, next, the transmittance c under the environmental conditions in the preliminary test, the separation distance L from the irradiation position of the transmitter 1 to the light receiving position of the receiver 2, and the amount of visible light V received by the receiver 2 are determined. By substituting the irradiance E into the following equation (1), the light source intensity I of the transmitter 1 is calculated. Equation (1) is a known theoretical equation based on the inverse square law regarding light attenuation.
E=I・c ^L /L ² …(1)

FIG. 4 shows two patterns (A, B) in which the transmitting device 1 and the receiving device 2 are of the same model, but different transmitting lenses 3 are attached to the transmitting device 1, and the light source intensity I of the transmitting device 1 is made different. , the relationship between the illuminance of the visible light V received by the receiving device 2 and the communication speed (Mbps) performed between the transmitting device 1 and the receiving device 2 when visible light communication is performed under different environmental conditions. This is graphed data. As shown in FIG. 4, when the specifications of the transmitting device 1 and the receiving device 2 differ, the illuminance and irradiance E of visible light V received by the receiving device 2 corresponding to the desired communication speed also differ.

Therefore, in the irradiance understanding process, for the transmitting device 1 and receiving device 2 used under the target environmental conditions, reception corresponding to the desired communication speed when performing visible light communication between the transmitting device 1 and the receiving device 2 is performed. The irradiance E of the visible light V received by the device 2 is determined.

In the irradiance understanding step, the transmitting device 1 and the receiving device 2 are placed apart from each other, and the communication speed between the transmitting device 1 and the receiving device 2 is set to a desired communication speed for estimating the communicable distance. . Then, visible light communication is performed between the transmitting device 1 and the receiving device 2, and the irradiance E of the visible light V received by the receiving device 2 at that time is grasped. The separation distance L from the irradiation position of the transmitting device 1 to the light receiving position of the receiving device 2 when performing the irradiance determining step can be appropriately set according to the environmental conditions in which the irradiance determining step is performed.

As shown in FIG. 4, when using a transmitter 1 and a receiver 2 with the same specifications, even if the environmental conditions for visible light communication are different, the illuminance of the visible light V received by the receiver 2 and the communication speed The relationship with Japan remains largely unchanged. Therefore, like the preliminary test process, the irradiance understanding process does not need to be performed under the target environmental conditions, and can be performed indoors or the like.

In this way, by performing the preliminary test process, it is possible to understand the light source intensity I of the transmitting device 1 used under the target environmental conditions, and by performing the irradiance determining process, the receiving device 2 that corresponds to the desired communication speed can be determined. The irradiance E of the received visible light V can be grasped.

In the transmittance understanding process, on-site environmental tests are conducted. In the on-site environmental test, visible light V is irradiated from the transmitting devices 1 placed apart from each other to the receiving device 2 under the target environmental conditions for estimating the communicable distance or under the environmental conditions that reproduce the target environmental conditions. At this time, the irradiance E of the visible light V received by the receiving device 2 is determined. That is, the on-site environmental test can be conducted at the actual site under the target environmental conditions, or it can be conducted indoors or outdoors where the target environmental conditions other than the site are reproduced.

For example, if the target environmental condition is underwater in the ocean, as in this embodiment, an aquarium, lighting equipment, etc. can be used to adjust the water quality (salt concentration, turbidity, etc.) and brightness (external water) of the target environmental condition. Reproduce environmental conditions close to (e.g., light illuminance). As a preparation before conducting an on-site environmental test, by collecting water under the target environmental conditions and measuring the illuminance under the target environmental conditions, it is possible to accurately reproduce the target environmental conditions indoors or outdoors. It is preferable that the water tank used in the field environment test be provided with marks, scales, etc. so that the separation distance L between the transmitting device 1 and the receiving device 2 can be easily understood.

The separation distance L from the irradiation position of the transmitter 1 to the light reception position of the receiver 2 when performing field environmental tests can be set as appropriate depending on the target environmental conditions, but if the separation distance L is too short, the receiver Since the irradiance E and illuminance of the visible light V received by the device 2 become extremely high, it is difficult to accurately measure the irradiance E and illuminance. In addition, the separation distance L set in the field environment test only needs to be within the range that can measure the irradiance E or illuminance of the visible light V received by the receiving device 2, so there is no need to set the separation distance L excessively long. do not have. Therefore, the separation distance L from the irradiation position of the transmitting device 1 to the light receiving position of the receiving device 2 in the field environment test is preferably set within a range of 1 m or more and 10 m or less, for example.

Next, the distance L from the irradiation position of the transmitting device 1 to the light receiving position of the receiving device 2 in the on-site environmental test and the irradiance E of the visible light V received by the receiving device 2 are calculated in advance in the pre-test process. By substituting the light source intensity I of the transmitting device 1 into the above-mentioned equation (1), the transmittance c of visible light V under the target environmental condition is calculated. With the above steps, the transmittance grasping process is completed.

Next, the transmittance c of visible light V under the target environmental conditions calculated in the transmittance understanding process, the light source intensity I of the transmitting device 1 calculated in the preliminary test process, and the desired communication speed calculated in the irradiance understanding process are calculated. By substituting the irradiance E of the corresponding receiving device 2 into equation (1), the communicable distance L at the desired communication speed under the target environmental condition is estimated.

In this way, in the present invention, if the preliminary test process is performed, the on-site environmental test is performed under the target environmental conditions or under the environmental conditions that reproduce the target environmental conditions, and the on-site environmental test is performed in the transmittance understanding process. The distance L from the irradiation position of the transmitting device 1 to the light receiving position of the receiving device 2, the irradiance E of the visible light received by the receiving device 2, and the light source intensity I of the transmitting device 1 calculated in advance in the preliminary test process. , (1), the transmittance c of visible light V under the target environmental conditions can be easily calculated. Then, the transmittance c of visible light V under the target environmental conditions calculated in the transmittance understanding process, the light source intensity I of the transmitter 1 calculated in the preliminary test process, and the desired communication speed calculated in the irradiance understanding process are determined. By simply substituting the irradiance E of the corresponding receiving device 2 into equation (1), the communicable distance L at a desired communication speed under the target environmental condition can be easily estimated.

The preliminary testing process and the irradiance understanding process do not need to be performed under the target environmental conditions, and can be easily performed indoors. In the field environment test of the transmittance understanding process, the distance L from the irradiation position of the transmitter 1 to the light receiving position of the receiver 2 may be set to about several meters, and the visible light V is transmitted from the transmitter 1 to the receiver 2. The irradiation work only needs to be done once. That is, under the target environmental conditions, it is not necessary to separate the transmitting device 1 and the receiving device 2 by several tens of meters to several hundred meters, and it is possible to change the distance L between the transmitting device 1 and the receiving device 2 to transmit the visible light V. There is no need to repeat the irradiation process over and over again. Therefore, on-site environmental tests can be completed quickly with fewer man-hours. Furthermore, since equation (1) is a simple formula and the amount of calculation required to calculate the communicable distance L is small, the communicable distance L can be easily calculated in the field using a simple calculator such as a scientific calculator. Therefore, the present invention is very convenient.

As in this embodiment, when the target environmental condition is underwater such as the ocean, if an on-site environmental test is performed under environmental conditions that reproduce the target environmental condition, it is possible to connect the transmitter 1 to the receiver under the target environmental condition. There is no need to perform the work of irradiating the visible light V to the object 2, and it is only necessary to perform the work of collecting water and measuring the illuminance under the target environmental conditions. Therefore, if the on-site environmental test is conducted under environmental conditions that reproduce the target environmental conditions, compared to the case where the on-site environmental test is conducted under the target environmental conditions, the work time under the target environmental conditions can be reduced and the worker This is more advantageous for reducing labor costs.

As mentioned above, in the on-site environment test in the transmittance understanding process, it is only necessary to irradiate the visible light V from the transmitter 1 to the receiver 2 once, but from the irradiation position of the transmitter 1 to the receiver 2 By performing the task of irradiating visible light V multiple times while changing the separation distance L to the position, the transmittance c of visible light V under the target environmental conditions can be grasped more accurately, and the communicable distance L can be estimated. This is useful for increasing accuracy.

Measuring devices such as illuminance meters that measure illuminance are relatively susceptible to external light such as sunlight. Therefore, when the target environmental condition is one in which the influence of external light is large, such as in shallow water or in dense fog, when the irradiance E of the visible light V received by the receiving device 2 is directly measured, the irradiance This is advantageous for accurately grasping E. On the other hand, measuring instruments such as illumination meters that measure illuminance are relatively inexpensive compared to precise measuring instruments such as power meters that directly measure irradiance E, and illuminance can be measured relatively easily than irradiance E. can. Therefore, when the target environmental condition is an environment where the influence of external light is small, such as deep water, the illuminance of the visible light V received by the receiving device 2 is measured, and the measured illuminance is converted into the irradiance E. It is best to convert it to .

The present invention can also be applied to the case where visible light communication is performed between visible light communication devices having both a transmitting lens 3 and a receiving lens 4. In that case, the visible light communication device on the transmitting side becomes the transmitting device 1, and the visible light communication device on the receiving side becomes the receiving device 2. In the embodiment described above, the irradiation position of the transmitting device 1 is the tip of the transmitting lens 3, and the light receiving position of the receiving device 2 is the tip of the receiving lens 4. However, the irradiating position of the transmitting device 1 and the light receiving position of the receiving device 2 can be set as appropriate according to the specifications of the transmitting device 1 and receiving device 2.

In the embodiment illustrated above, the pre-test process, the irradiance understanding process, and the transmittance understanding process are carried out in this order, but if the conditions for performing the pre-test process before the transmittance understanding process are met, , the pre-test step, the irradiance understanding step, and the transmittance understanding step are not particularly limited in the order of implementation. That is, for example, the irradiance grasping step, the preliminary test step, and the transmittance grasping step can be carried out in this order, or the pretesting step, the transmittance grasping step, and the irradiance grasping step can be carried out in this order. Further, for example, the preliminary test step and the irradiance understanding step can be performed in parallel, and the irradiance understanding step and the transmittance understanding step can also be performed in parallel. Further, the irradiance understanding step, like the transmittance understanding step, can also be performed under environmental conditions that reproduce the target environmental conditions or under target environmental conditions.

1 Transmitting device 2 Receiving device 3 Transmitting lens 4 Receiving lens 5 Waterproof case V Visible light L Distance (from the irradiation position of the transmitting device to the light receiving position of the receiving device)

Claims (5)

A method for estimating a communicable distance at a desired communication speed when performing visible light communication between a transmitting device and a receiving device under target environmental conditions, the method comprising:
Under environmental conditions in which the transmittance c of the visible light emitted by the transmitting devices is known in advance, a preliminary test is conducted in which the transmitting devices arranged at a distance from each other irradiate the receiving device with the visible light; The transmittance c under the environmental conditions in the test, the separation distance L from the irradiation position of the transmitting device to the light receiving position of the receiving device, and the irradiance E of visible light received by the receiving device are determined by the following (1). a preliminary test step of calculating the light source intensity I of the transmitting device by substituting it into a formula;
E=I・c ^L /L ² …(1)
an irradiance determining step of determining the irradiance E of the visible light received by the receiving device corresponding to the desired communication speed when performing visible light communication between the transmitting device and the receiving device;
Conducting an on-site environmental test in which the visible light is irradiated from the transmitting devices spaced apart from each other to the receiving device under the target environmental conditions or under environmental conditions reproducing the target environmental conditions, and performing the on-site environmental test. The separation distance L from the irradiation position of the transmitting device to the light receiving position of the receiving device, the irradiance E of the visible light received by the receiving device, and the light source of the transmitting device calculated in advance in the preliminary test step. and a transmittance understanding step of calculating the transmittance c of the visible light under the target environmental conditions by substituting the intensity I into the equation (1),
The transmittance c of the visible light under the target environmental conditions calculated in the transmittance understanding step, the light source intensity I of the transmitting device calculated in the preliminary test step, and the desired desired value ascertained in the irradiance understanding step. The communicable distance L is estimated by substituting the irradiance E of the visible light received by the receiving device corresponding to the communication speed into the equation (1). How to estimate distance. 2. The method for estimating a communicable distance in visible light communication according to claim 1, wherein the illuminance of the visible light received by the receiving device is measured, and the measured illuminance is converted into the irradiance E. The method for estimating a communicable distance in visible light communication according to claim 1, wherein the irradiance E of the visible light received by the receiving device is directly measured. The method for estimating a communicable distance in visible light communication according to any one of claims 1 to 3, wherein the target environmental condition is underwater, and the preliminary test is performed in the atmosphere. Visible light communication according to any one of claims 1 to 4, wherein the separation distance L from the irradiation position of the transmitting device to the light receiving position of the receiving device in the field environment test is set within a range of 1 m or more and 10 m or less. A method for estimating the communicable distance.

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