WO2007032276A1 - Transport data assigning method and optical communication system - Google Patents

Abstract

[PROBLEMS] To provide an illumination light communication system and a transport data assigning method capable of assigning, in a short time, data to be transmitted by light sources in accordance with the correspondence of images of a light source group projected to a light receiving element group. [MEANS FOR SOLVING PROBLEMS] The light sources (11) of a transmitting end apparatus (1) sequentially emit respective light pilot signals, and the light receiving elements (21) of a receiving end apparatus (2) detect and hold the reception powers of the respective lights received from the light sources (11). For the light receiving elements (21), a D/U ratio is determined where D is a sum of k reception powers in decreasing order of value and U is a sum of the other reception powers. If the D/U ratio is greater than a predetermined value, an assignment of the same transport data is decided for the k light sources (11). As to the light receiving elements (21) for which the D/U ratio is equal to or smaller than the predetermined value, the number k is increased and the D/U ratio is then determined for retrial. In this way, the transport data can be assigned to the light sources (11) such that the light receiving elements (21) can receive the respective different data.

Description

 Specification

 Transmission data allocation method and optical communication system

 Technical field

 TECHNICAL FIELD [0001] The present invention relates to a visible light communication technique using visible light generated as a communication medium by a lighting apparatus using LD, LED, or the like.

 Background art

 [0002] With the development of LD and LED technology, visible light communication using visible light emitted from a lighting fixture or the like as a communication medium has attracted attention. Among them, in order to realize high-speed visible light communication, a parallel optical space communication system has been proposed in which different information is transmitted in parallel by multiple LEDs and received by a two-dimensional sensor. By transmitting in parallel, the transmission speed of the entire system is possible. High-speed communication is possible without depending on the response characteristics of SLEDs and 2D sensors. For example, Patent Document 1 describes that a two-dimensional flat display is used as a light source and parallel transmission is performed.

 [0003] In general, image sensors used in cameras and the like use a photodiode with tens of millions to millions of pixels. In parallel optical space communication systems, it is necessary to perform high-speed parallel processing. It is difficult to increase the number of photodiode arrays in the receiver due to the number constraints and thermal issues. Increasing transmitter parallelism is also impractical due to increased system complexity.

 [0004] In a situation where the number of elements of the image sensor is small, a plurality of LED images are projected onto one element, and thus interference between the LEDs of the transmitter becomes a problem. 8 to 10 are explanatory diagrams showing an example of the relationship between each pixel of the image sensor and the image of the LED array projected onto the image sensor. In the example shown in Fig. 8, each pixel of the image sensor is indicated by a rectangle, and the image of the LED array is indicated by a circle. As shown in Figure 8, multiple LED images may be projected onto one pixel of the image sensor. Therefore, if each LED transmits different data, the light from multiple LEDs will interfere, making it impossible to receive data.

[0005] Such a problem is not limited to the case where each LED transmits different data. Fig. 9 In the example shown in the figure, an example is shown in which the same data is transmitted for 2 X 2 LEDs. In Fig. 9, the same data is transmitted for the same pattern in the circle showing the LED image. In this case, the image of the LED that transmits the same data is projected on the upper left, upper right, lower left, lower right, and center of the 3 X 3 pixels shown in the image sensor. Can be received. However, for the other four pixels, images of LEDs that transmit different data are projected, and data cannot be received due to interference.

 [0006] On the other hand, in FIG. 10, the same data is transmitted for the same pattern in the circle indicating the LED image, and as shown in FIG. If done, all pixels of the image sensor have the same received signal from the LEDs projected into each pixel, and each pixel can receive separate data in parallel without interference. Therefore, high-quality communication with minimal influence of interference is possible, and high-throughput parallel communication can be performed.

 [0007] Except when receiving light from a constantly fixed LED array with an image sensor placed at a fixed position, the mutual position and distance between the LED array and the image sensor, image magnification, etc. Because of various factors, the relationship in Figure 10 is broken. In addition, even if it is used in a fixed state, it is necessary to set a relationship as shown in FIG. 10 in advance at the start of use. As described above, in order to enable high-throughput parallel communication in either case, each LED in the LED array has its own LED depending on the relationship between the image sensor and the image sensor and the LED array. It is necessary to determine the data to be transmitted.

[0008] As a method of optimally allocating data to be transmitted to each LED, a method of measuring the throughput of all possible patterns of the LED array and selecting the best allocation pattern can be considered. However, investigating all possible LED array patterns requires a large number of trials, which is not practical. In addition, there is a problem that the characteristics depend on the correspondence between the image of the force LED and the image sensor. As described above, according to the correspondence of the image of the LED array projected onto the image sensor, each L There was a problem that data to be sent to ED could not be allocated in a short time.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-64465

 Disclosure of the invention

 Problems to be solved by the invention

The present invention has been made in view of the above-described circumstances, and assigns data to be transmitted by each light source in a short time according to the correspondence relationship between the images of the light source group projected onto the light receiving element group. It is an object of the present invention to provide a transmission data allocation method capable of performing the above and an illumination light communication system to which such a transmission data allocation method is applied.

 Means for solving the problem

[0011] The present invention includes an optical communication system having transmission side means including a plurality of light sources and reception side means including a plurality of light receiving elements, and transmitting a plurality of light source forces and a plurality of data in parallel by emitted light. The pilot signal is transmitted in order from each light source, and each pilot signal is received by each light receiving element, and the received power is held in correspondence with the light source that transmitted the pilot signal. And for each light receiving element, when the sum of k (k≥l) number of received powers is D and the other sum is U, the light receiving element has a DU ratio larger than a predetermined value. The light source corresponding to the maximum received power is assigned as data to be received by the light receiving element, and for light receiving elements having a DU ratio equal to or less than the predetermined value, k is increased and data is assigned. It is characterized by determining the DU ratio and assigning data to the light source, where D is the sum of the received power corresponding to the light source.

 The invention's effect

[0012] According to the present invention, according to the light reception result of the pilot signal of each light source power, the data to be transmitted by each light source is allocated so that each light receiving element can receive data satisfactorily. Can do. Thus, the data to be transmitted by each light source can be allocated so that high throughput can be obtained without depending on the correspondence between the light source and the light receiving element. In addition, since transmission data allocation can be determined simply by sending pilot signals from each light source, transmission can be done in a short time and with little effort. If the data can be assigned, there is an effect!

 BEST MODE FOR CARRYING OUT THE INVENTION

 FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a transmission side device, 2 is a reception side device, 11 is a light source, 12 is a light emission control unit, 21 is a light receiving element, and 22 is a light reception processing unit.

 The transmission-side device 1 includes a plurality of light sources 11 and a light emission control unit 12 that controls the light sources 11. The light source 11 includes, for example, various types of light sources that can be switched at high speed, such as LEDs and LDs. The light emission of these light sources 11 is controlled by the light emission control unit 12 every one or more. For example, it may be a light source for illumination.

 The light emission control unit 12 controls light emission for each of the plurality of light sources 11 from one to plural. At this time, data can be transmitted by the light emitted from the light source 11 by performing blinking or light amount control at such a high speed that it cannot be visually recognized. In addition, parallel transmission is possible by changing the data to be transmitted for each light source 11. When assigning data to be transmitted to each light source 11, control is performed so that a pilot signal is transmitted (emitted) in order from each light source 11. In this example, since the allocation result can be received from the receiving side device 2, data is allocated to each light source 11 accordingly, and actual data is transmitted.

[0016] The receiving-side device 2 includes a plurality of light receiving elements 21 and a light receiving processing unit 22 that detects received power when light is received by the light receiving elements 21 and performs data reception processing. . The plurality of light receiving elements 21 are image sensors, and may be, for example, CMOS sensors for high-speed communication. An optical system (not shown) such as a lens may be provided on the light receiving side of the light receiving element 21.

The light reception processing unit 22 detects the output signal force received light power from each light receiving element 21. During data communication, the signal is demodulated from the detected received light power to acquire data. Further, when assigning transmission data to each light source 11 of the transmission side device 1, the received light power when the pilot signal transmitted from each light source 11 of the transmission side device 1 is received is held. Then, the allocation of data to be transmitted is determined for each light source 11 of the transmission side device 1 by the process described later. Determined transmission data In this example, the assignment is returned from the reception side apparatus 2 to the transmission side apparatus 1. As a result, the transmission side device 1 can transmit data from each light source 11 according to the transmission data allocation for each light source 11 received from the reception side device 2.

 FIG. 2 is a flowchart showing an example of transmission data assignment processing for each light source according to the embodiment of the present invention. First, in S31, a pilot signal is emitted and transmitted in order from each light source 11 of the transmission side apparatus 1, and each received light source 11 is detected by each light receiving element 21 of the reception side apparatus 2 to detect and hold the received power of the light. .

 Next, in S32, initialization is performed assuming that different transmission data is assigned to all the light sources 11. In S33, a variable k for counting the number of repetitions is initialized to 1.

 [0020] In S34, for each light receiving element 21, the sum of the received powers of the k powers with the larger pilot signal power is D, and the sum of the other received powers is U. The ratio of U (hereinafter referred to as DU ratio) is obtained. At this time, D indicates the signal power of the data, U indicates the power of the interference signal, and the DU ratio is the desired signal to interference signal power ratio. By using this DU ratio, it is possible to estimate the output of the light receiving element 21 as a relative value of the received power without estimating the absolute received power using the transmitted power of the light source 11 of the transmitting side device 1. In this example, the output of the light receiving element 21 at the time of receiving the pilot signal is also used as the relative received power.

 The processes of S35 to S38 are performed for each light receiving element 21. In S35, the DU ratio is compared with a predetermined threshold value THR for one light receiving element 21. If the DU ratio is greater than the threshold value THR, it is determined that sufficient data can be received with the light from k light sources 11, and in S36, the same transmission data is assigned to k light sources 11 having high received power. Confirm this. Note that the light receiving element 21 for which the assignment of transmission data has been confirmed is excluded from the subsequent processing targets.

[0022] If it is determined in S35 that the DU ratio is equal to or less than the predetermined threshold value THR, in S37, it is determined whether or not transmission data allocation is confirmed for the light source 11 having the k + 1st largest received power. If it is determined and confirmed, in S38, the received power from the light source 11 is set to be calculated as the power of the interference signal. [0023] In S39, it is determined whether or not all the light receiving elements 21 to be processed have been processed. If there are unprocessed light receiving elements 21, the process returns to S35 and the unprocessed light receiving elements 21 are processed. , Process.

 [0024] When all the light receiving elements 21 to be processed have been processed, it is determined in S40 whether or not the variable k is equal to or greater than a constant K indicating the maximum number of repetitions. Increase k by 1 and return to S34 to repeat the process.

 [0025] When k≥K, the assignment process ends. Here, as an example, in S42, the transmission data allocation result to each light source 11 determined so far is sent to the transmission side apparatus 1, and the processing is completed. Of course, for example, the user may refer to the allocation result, and the transmission side device 1 may be manually set based on the allocation result. Alternatively, configure the receiving device 2 so that the position and magnification are controlled so that the desired assignment result is obtained.

 Hereinafter, an example of the above-described operation will be described using specific examples. FIG. 3 is an explanatory diagram of an example of the relationship between the light receiving element and the image of the light source on the light receiving element and the received power after receiving the pilot signal. In the following specific example, as shown in FIG. 3, an image of nine light sources 11 is projected on four light receiving elements 21 and will be described. Each light source 11 is denoted by L 1 to L 9 and its image is shown. In addition, the respective light receiving elements 21 are denoted by symbols P1 to P4.

First, in S31 of FIG. 2, a pilot signal is transmitted from each light source 11, and the received power received by each light receiving element 21 is held. For example, only the light source L 1 is emitted to transmit a pilot signal, and each light receiving element 21 receives the light. In this example, the received power of 0.0005 is received at the light receiving element P1, and the received power of 0.040 power is acquired at the light receiving element P3. Similarly, pilot signals are sequentially transmitted to the light sources L2 to L9, and the received power received by the respective light receiving elements P1 to P4 is held at that time. As a result, as shown in FIG. 3, the light receiving element P1 acquires the received power 0.005, 0.080, and 0.0003 from the light sources LI, L2, and L3. In the light receiving element P2, received powers of 0.004 and 0.080 are obtained from the light sources L3 and L7, respectively. Similarly, in the light receiving element P3, the received power from the light sources LI, L4, L5, and L6 is 0.040, 0. 007, 0. 069, 0. 008 have been acquired. Further, the light receiving element P4 obtains the received power of 0.05, 0.070, 0.005 from the light sources L6, L8, L9. In FIG. 3, these received powers are rearranged in descending order until ί. Thus, the received power in each of the light receiving elements P1 to P4 when the pilot signals transmitted in order from the light sources L1 to L9 were received was obtained.

When moving to the next processing, different transmission data are allocated and initialized for each of the light sources L1 to L9 in S32 of FIG. In the example shown in FIG. 3, data D1 to D9 are temporarily assigned to the light sources L1 to L9, respectively. The variable k is initialized to 1 at S33 in Fig. 2.

 FIG. 4 is an explanatory diagram of a specific example of transmission data allocation by the first DU ratio. In S34 of Fig. 2, in each of the light receiving elements P1 to P4, one is extracted from the ones with large received power as D, and the sum of the other received power is set as U to obtain the DU ratio. Then, in S35, it is compared with a predetermined threshold value. Here, the predetermined threshold is 14 dB. For example, for the light receiving element P1, the received power 0.080 from the light source L2 is the maximum, so this is D. The sum of other received power (= 0.0008) is U. In this case, since the DU ratio is larger than 14 dB, it is determined that data D2 is assigned to the light source L2 in S36 of FIG. Note that the light receiving element P1 is excluded from the subsequent processing targets.

 [0030] Also, for example, for the light receiving element P2, the received power 0.080 from the light source L7 is the maximum, so this is D. The sum of other received power (= 0.014) is U. In this case, the DU ratio is 14 dB or less. In this case, in S37 of FIG. 2, it is determined whether or not the allocation is confirmed for the light source corresponding to the k + 1st, that is, the second largest received power, in this example, the light source L3. In this case, the light source L3 has not yet been assigned. In this case, the first process for the light receiving element P2 is finished. For the light receiving elements P3 and P4, the DU ratio is 14 dB or less, and the allocation of the light source corresponding to the second largest received power is confirmed, so even with these light receiving elements, the first processing is performed. End. After increasing the variable k by 1 in S41 of Fig. 2, return to S34.

FIG. 5 is an explanatory diagram of a specific example of transmission data allocation by the second DU ratio. In S34 in Fig. 2, each of the light receiving elements P2 to P4 has the two that have the highest received power. Obtain the DU ratio by taking the sum of each and letting D be the sum of the other received power and U. Then, in S35, it is compared with a predetermined threshold (14dB here). For example, for the light receiving element P2, the sum 0.094 of the received power from the light sources L7 and L3 is D. The sum of other received power is 0, which is U. In this case, since the DU ratio is greater than 14 dB, it is determined in S36 of FIG. 2 that the same data is assigned to the light sources L7 and L3. In this example, it is determined that the data D7 is assigned to the light source L7 and the light source L3.

 Similarly, for the light receiving element P4, the sum of received power from light source L8 and light source L6, 0.127, is D, and the other received power sum, 0.005, is U. Also in this case, since the DU ratio is larger than 14 dB, it is determined in S36 of FIG. 2 that the same data (data D8) is assigned to the light source L8 and the light source L6. Since the data assignment for the light receiving elements P2 and P4 has been determined, they are excluded from the subsequent processing.

 [0033] For the light receiving element P3, if the sum of received power from light source L5 and light source L1 0.129 is D, and the sum of other received power 0.015 is U, the DU ratio is 14 dB or less. In this case, in S37 of FIG. 2, it is determined whether or not the assignment is confirmed for the light source corresponding to the k + 1st, that is, the third largest received power, in this example, the light source L6. In this case, the assignment of the light source L6 is determined by the processing of the light receiving element P4. Therefore, in S38 of FIG. 2, the received power of the third largest light source L6 is included in the interference signal U in the subsequent processing. Then, after the second process is completed, the variable k is incremented by 1 in S41 of FIG. 2, and the process returns to S34.

FIG. 6 is an explanatory diagram of a specific example of transmission data allocation by the third DU ratio. In S34 of Fig. 2, in the light receiving element P3, three are extracted from the ones with large received power, the sum is set as D, and the sum of the other received power is set as U, and the DU ratio is obtained. At this time, since the received power corresponding to the third light source L6 is actually included in the interference signal U, the received power corresponding to the light source L4 is extracted as the third. Therefore, D is the sum of the received power from the light sources L5, LI, and L4, 0.136, and U is 0.008. Since the DU ratio in this case is greater than 14 dB, it is determined in S36 in FIG. 2 that the same data is assigned to the light sources L5, LI, and L4. In this example, data D5 is allocated for light sources L5, LI, and L4. It is decided to hit.

 FIG. 7 is an explanatory diagram of a specific example of the allocation result. As described above, data D2 is assigned to light source L2, data D7 is assigned to light sources L3 and L7, data D8 is assigned to light sources L6 and L8, and data D5 is assigned to light sources LI, L4, and L5. You can decide to hit. By assigning the data to be transmitted for each light source in this way, each light receiving element can reliably receive each data.

[0036] Such an allocation result can be transmitted from the receiving side device 2 to the transmitting side device 1, for example. This transmission method is arbitrary. For example, in the same way as transmission from the transmission side device 1 to the reception side device 2, light is transmitted by a light emitting element and a light receiving element, infrared rays or radio waves are used, or power line or communication is used. You may transmit via a cable. Alternatively, the assignment result may be set manually in the transmission side apparatus 1 by referring to the assignment result. Furthermore, the received power data of each light receiving element 21 when the pilot signal performed at S 31 in FIG. 2 is received is sent to the transmitting side device 1, and the processing after S 32 in FIG. You may go.

 In any case, in the specific example described above, according to the assignment result as described above, the light source L2 transmits data D2, the light sources L3 and L7 transmit data D7, and the light sources LI, L4, and L5 transmit data. D5 is transmitted, and light sources L6 and L8 transmit data D8, so that data D2 is received by light receiving element P1, data D7 is received by light receiving element P2, data D5 is received by light receiving element P3, and data D8 is received by light receiving element P4. Can be received in parallel.

 In this way, by determining the assignment of data to be transmitted by each light source by the processing of the present invention, each light receiving element 21 is not affected by interference by different data and is predetermined in a state. Data can be received, parallel transmission can be performed efficiently, and high throughput can be obtained.

[0039] In the above-described example, when obtaining D indicating the signal power of data, k sums are calculated for the respective light receiving elements 21 to be processed from the higher received power, and data that can be determined at that time. Are determined sequentially. In addition to this method, for example, paying attention to one light receiving element, select a direction with a large received power until the DU ratio reaches a predetermined value or more, and obtain the minimum k for which the DU ratio becomes a predetermined value or more. The light source corresponding to the k received power. It is also possible to configure the assignment so that the same data is transmitted for reception by the light receiving element. In this case, adjustment of data may be necessary later because there is a possibility that data allocation may overlap between adjacent light receiving elements.

 Brief Description of Drawings

 [0040] FIG. 1 is a block diagram showing an embodiment of the present invention.

 FIG. 2 is a flowchart showing an example of transmission data assignment processing for each light source in the embodiment of the present invention.

 FIG. 3 is an explanatory diagram of an example of a relationship between a light receiving element and an image of a light source on the light receiving element and received power after receiving a pilot signal.

 FIG. 4 is an explanatory diagram of a specific example of transmission data allocation by the first DU ratio.

 FIG. 5 is an explanatory diagram of a specific example of transmission data allocation by the second DU ratio.

 FIG. 6 is an explanatory diagram of a specific example of transmission data allocation by the third DU ratio.

 FIG. 7 is an explanatory diagram of a specific example of an allocation result.

 FIG. 8 is an explanatory diagram showing an example of a relationship between each pixel of the image sensor and an image of the LED array projected onto the image sensor.

 FIG. 9 is an explanatory diagram showing an example of the relationship between each pixel of the image sensor and an image of the LED array when transmission data is fixedly assigned to the LED.

 FIG. 10 is an explanatory diagram showing an example of the relationship between each pixel of the image sensor and an image of the LED array when transmission data is optimally assigned to the LED.

 Explanation of symbols

 [0041] 1 ... Transmission side device, 2 ... Reception side device, 11 ... Light source, 12 ... Light emission control unit, 21 ... Light receiving element, 22 ... Light reception processing unit.

Claims

The scope of the claims  [1] In an optical communication system having a transmission side means including a plurality of light sources and a reception side means including a plurality of light receiving elements, and transmitting a plurality of light source powers and a plurality of data in parallel by emitted light. A transmission data allocation method for allocating data to be transmitted, in which pilot signals are transmitted in order from each light source power, and each pilot signal is received by each light receiving element and associated with the light source that transmitted the pilot signal. Receiving power is held, and for each light receiving element, when the sum of the k receiving powers is D, and D is the other sum, U is the maximum for light receiving elements with a DU ratio greater than the specified value. A light source corresponding to the received power of the receiver is assigned to transmit data for reception by the light receiving element, and k is increased for light receiving elements having a DU ratio equal to or less than the predetermined value. The transmission data allocation method is characterized in that the DU ratio is determined and the data is allocated to the light source, where D is the sum of received power corresponding to the light source and D is allocated. [2] A transmission-side device including a plurality of light sources and a control unit that controls the light sources, and a processing unit that detects received power at the plurality of light receiving elements and the light receiving elements and assigns transmission data to the light sources. An optical communication system having a receiving side device including the transmitting side device, wherein the control means of the transmitting side device transmits a pilot signal in order of each light source power, and each of the receiving side devices is controlled by each pilot signal. The received power is held in correspondence with the light source that has received the light by the light receiving element and transmitted the pilot signal, and the processing means sets the sum of k from the largest received power to D for each light receiving element. When the other sum is U, for a light receiving element having a DU ratio larger than a predetermined value, the light source corresponding to the maximum received power is assumed to be transmitted as data for receiving by the light receiving element. For a light-receiving element with a DU ratio equal to or less than the predetermined value, k is increased and data is assigned. If the sum of received power corresponding to the light source is D, the determination of the DU ratio and the light source are performed. An optical communication system characterized by performing data allocation.