JP2010130603A - Visible light communication dedicated modem - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a visible light communication dedicated modem for realizing a system immune to a multipath and suitable for multiplexing, a structure of a visible light receiving section that considerably affects communication performance and a communication system, that does not limit a communication element of a communication protocol, while making a wide band of visible light effectively available. <P>SOLUTION: An OFDM modulation system and a reflection type receiver are adopted for a visible light communication dedicated modem to perform Internet communication, voice communication, video communication and various protocol-enabled 1-to-1, 1-to-n and n-to-n visible light communication. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a modem dedicated to visible light communication that enables wired communication including mobile communication and wireless communication.

Visible light communication is a communication method in which information is put on light by using blinking of light or modulation of the frequency of light. Focusing on the convenience of using a communication device simply by adding a modulation device to a familiar lighting fixture as a transmission device, research and usage methods of related devices have been sought.

When subcarrier inversion pulse phase modulation is used as a modulation method, a person does not notice flashing light. In addition, when an LED or the like that has been rapidly spreading in recent years is used as a light emitting element and a light receiving element, a signal can be converted at high speed between light and electricity, and visible light communication becomes possible.

Visible light range is safe for humans, wireless communication environment can be realized by using lighting equipment installed everywhere, and because it is not regulated by the Radio Law, it can be used freely in a wide frequency range Benefits can be enjoyed.

As described above, there are many proposals for visible light communication using communication using lighting equipment, but the vast bandwidth utilization of visible light communication has a wider range of utility values for future humanity. It is not limited to secondary use of lighting equipment.

Furthermore, visible light is expected to have a future potential as a third communication means, and is highly likely to be used not only for data communication but also for voice, image, and video communication.

On the other hand, visible light communication has a limited range in which light can reach, and there is a drawback that the distance is increased, interruption occurs if there is an obstruction, and speeding up becomes difficult. Therefore, relay technology for performing uninterrupted communication is indispensable, and in particular, provision of a modem dedicated to visible light communication is indispensable.

In addition, a communication method using visible light originally started with pulse modulation by blinking of a light source such as an LED (Patent Document 1). Thereafter, in order to increase transmission efficiency, QAM or the like that performs quadrature phase modulation of multi-value amplitude shift keying is adopted as a modulation method, and has become mainstream.
JP 2008-283446 A Japanese Patent Application No. 2008-185449 JP 2006-253528 A JP 2006-135123 A JP 2003-303977 A

However, the QAM modulation method is limited to the baseband method, and the implementation mechanism is simple. However, the QAM modulation method is not suitable for long-distance communication because it cannot perform a plurality of communications at the same time, and is vulnerable to noise. There is.

For this reason, it is necessary to adopt a modulation method that allows other communication methods and media to be carried in each other. As this modulation method, a wide band of visible light can be effectively used, a method that is strong against multipath generated and suitable for multiplexing is desired.

It is known to use a high-intensity LED that can be electrically controlled for the transmission light emitting part of a modem dedicated to visible light communication. However, a photodetector is used for the receiving light receiving unit that determines the performance of the modem. However, since sensitivity is particularly required, an efficient light receiving structure is required.
In addition, since visible light is closely related to daily life, it can be a carrier constituting a ubiquitous platform, and a method for wirelessly connecting peripheral devices via a visible light communication dedicated modem is desired.

In order to solve the above problems, the present invention has the following features.

The inventors previously proposed a relay method and a relay communication device (Patent Document 2) without interruption in visible light communication. The modem dedicated to visible light communication according to the present invention communicates based on the relay method and the transmission / reception method by data encapsulation.

In addition, the transmission light emitting unit is formed of an efficient reflection type light emitting diode unit (Patent Documents 3 and 4), and the reception light receiving unit includes a light receiving diode and a light emitting diode in the same unit. Therefore, it is integrated as a reflection type light emitting / receiving unit. With regard to the side-by-side reflection type light-receiving diode, Patent Document 5 describes a structure in which a plurality of diodes are provided side by side. Separation of light emission and light reception can be solved by a modulation method.

In addition, this light emitting / receiving diode is arranged in a structure facing the light emitting surface side of the light emitting element so that the light emitted by the element is directly received by the reflecting surface, and the light receiving element is arranged in parallel with the light emitting element, and the light is directly transmitted in the same manner. It can be received from the reflective surface. Patent Documents 3 and 4 describe that a plurality of light emitting elements and light receiving elements can be connected in series and parallel.

The modulation method employs OFDM (Orthogonal Frequency Division Multiplexing). OFDM is a multiplexing scheme in which a part of carrier bands are overlapped so that phases are orthogonal between adjacent carriers. Subcarriers, which are a large number of carriers, do not interfere with other subcarriers, and thus have an advantage of being strong against multipath and being able to use the band very effectively. By using these subcarriers, bidirectional transmission / reception, n-to-n communication, and transmission / reception of various media and data can be performed at once.

Therefore, the modem dedicated to visible light communication according to the present invention is a modem having a wireless or wired communication relay function, and includes a reflection type light emitting / receiving device in which a light emitting unit and a light receiving unit are integrated, and a visible light communication control device using an OFDM modulation method. It is characterized by having.

In addition, the reflection type light emitting / receiving device of the modem dedicated to visible light communication according to the present invention has a structure in which at least one light emitting element and at least one light receiving element are arranged to face each other so as to be directly received by a reflection surface. It is characterized by that.

Visible light communication modem, data received from existing network, etc. are encapsulated in accordance with visible light communication protocol and relayed to devices capable of visible light communication. Similarly, it receives data transmitted from devices capable of visible light communication,
The capsule is removed and transmitted to an external network that is not visible light communication.

In an environment where visible light can reach between devices capable of visible light communication, communication is possible only by visible light communication. Further, when visible light cannot reach due to an obstacle or a long distance, communication is possible by repeating relaying. Thus, the relay function realizes n-to-n and 1-to-n communication.

Adopting wireless visible light communication is advantageous when managing a system connected to a cable such as a PC and a printer, or home appliances that originally exist separately by remote control.

Furthermore, convenience can be improved by separating the part of the device that is originally integrated and performing visible light communication between the main body and the parts. Visible light is a ubiquitous communication system that allows wireless connection over a very short distance. In extreme cases, communication in the nano range is also possible with terahertz-class frequencies. In this way, the relay function realizes one-to-one or one-to-n communication.

Therefore, the visible light communication control device of the modem dedicated to visible light communication according to the present invention encapsulates information in information transmission / reception with a network that does not use visible light by wireless communication or wired communication, and follows a predetermined visible light communication protocol. It is characterized by enabling communication with a base in a visible light communication network.

Further, the modem dedicated to visible light communication according to the present invention has a feature that at least one communication partner can be limited by defining a certain visible light band.

In addition, the visible light communication control device of the modem dedicated to visible light communication according to the present invention has a feature that communication can be limited for each purpose of use by defining a certain visible light band.

ADVANTAGE OF THE INVENTION According to this invention, there exists an effect which can utilize effectively a vast band of visible light by employ | adopting an OFDM modulation system for visible light communication. Further, other communication methods and media can be carried in each other, and there is an effect of enabling 1 to n and n to n multiplexed communication in both directions. In addition, it is strong against multipath and has the effect of being able to perform optimal control even in a noisy environment.

In addition, in the transmission and reception of visible light, there is an effect that the reflection type light emitting and receiving device in which the light receiving and light emitting diodes are integrated can be efficiently made into a compact device.

In addition, there is an effect that enables communication between extremely narrow distances using the frequency of visible light. Furthermore, there is an effect that the communication frequency band can be determined and the communication partner can be limited. Furthermore, there is an effect that the communication frequency band can be determined and the purpose of use can be limited.

This effect adds the effect of becoming a carrier that constitutes a ubiquitous platform using visible light that is in close contact with daily life, for example, leading to the effect of wirelessly connecting connection devices.

FIG. 1 is a diagram showing a configuration of a modem dedicated to visible light communication according to the present invention. The visible light communication-dedicated modem can be freely configured such as a structure having only a visible light communication function or a structure having a wireless communication function or a wired communication function added thereto. In some cases, a dedicated modem for visible light communication is attached to the main device or an independent relay device. For this reason, this figure shows the core visible light communication function part, and other parts are not shown.

The visible light communication control device 100 is responsible for executing communication and controlling the visible light protocol based on the OFDM modulation scheme. In transmission, information on an electric signal is carried on a visible light carrier wave and transferred to the reflective light emitting and receiving device 101. For reception, a visible light carrier wave is received from the reflective light emitting and receiving device 101 and converted into an electrical signal.

The reflection type light emitting / receiving device 101 employs a high-intensity LED as the light emitting element 105 and a photodetector as the light receiving element 102, and has both of them coexist in the same unit to efficiently receive and emit light through the reflecting mirror. . Originally, in order to avoid multipath, the light emitting unit and the light receiving unit are separated from each other. However, the OFDM modulation method has a strong feature in multipath, and the information capsule in the information capsule adopted by the present invention for visible light communication. Since the transmission / reception can be identified by the destination identification function and the frequency designation function of the information packet, a structure that integrates light reception and emission is possible.

As a result, the design with a view to miniaturization of the light emitting / receiving unit becomes free, leading to miniaturization of mobile terminals, mobile phones, public communication equipment, broadcast communication equipment, voice communication equipment, and information communication equipment. The spread to wired cable networks and wireless network networks is also promoted, and it can be expected as a foothold for future ubiquitous networks.

In reception, the amplifying unit 103 receives a visible light OFDM signal, increases the signal strength, performs timing adjustment, carrier frequency synchronization, and the like, and passes the signal to the OFDM demodulating unit 104. The OFDM demodulator 104 performs Fourier transform on the serial-parallel converted signal to extract subcarriers, demodulates the signal for each subcarrier, performs parallel-serial conversion, integrates received data, and passes the data to the visible light communication interface 108.

In transmission, transmission data is transmitted from the visible light communication interface 108 to the OFDM modulation unit 107. The OFDM modulation unit 107 performs serial / parallel conversion and divides transmission data into subcarriers. Next, inverse Fourier transform is performed to change the subcarrier into a multicarrier signal. This is converted from parallel to serial and the OFDM signal is passed to the LED driver 106. The LED driving unit 106 converts an electric signal into a visible light carrier wave and sends the visible light carrier wave to the reflective light emitting and receiving device 101.

The communication control unit 109 performs visible light communication protocol, frequency selection, and the like. Also, the control of the visible light communication in general is performed such that the encapsulated data is decapsulated and communication analysis is performed, and transmission data transmitted from the main device or relayed is encapsulated and transmitted.

FIG. 2 is a diagram showing the structure of the reflective light emitting / receiving device 101 which is a component of the modem dedicated to visible light communication according to the present invention.

The lead wire frames a and b mount the light emitting elements 105 a and b and the light receiving elements 102 a and b at positions where the concave reflecting plate 201 has a reflection effect. The light receiving element connecting gold wire 202 and the light emitting element connecting gold wire 203 are conductive between the elements or up to the opposing lead wire frame. Usually, the number of elements is one, but since a plurality of elements are connected in parallel or in series and structured in a reflective type, a very powerful light collecting effect is exhibited. The reflection type light emitting / receiving device 101 has a structure in which this diode is fixed with a transparent epoxy resin or a transparent silicon resin 207.

FIG. 3 is a diagram showing a usage form of a screen-separated mobile phone equipped with a modem dedicated to visible light communication according to the present invention. The best mode of a modem dedicated to visible light communication can be explained by a screen-separated type mobile phone, but at the same time, an effective usage mode of the present invention is also described in this figure, and various functions will be explained below.

A normal mobile phone is compact because the screen is folded on the mobile phone. When viewing the screen, the mobile phone is connected to the screen, so the screen is expanded or the front and back screens are rotated. Since communication using light can freely use light, if there is a visible light communication modem function, communication is easy. Using this freedom, we assumed a mode in which the mobile phone and the screen were separated and used wirelessly.

The mobile phone main body 301 is usually connected to the separation-type mobile screen 302 by a joint portion 303. When calling while watching the screen or using a mobile phone as a mobile terminal, it is convenient to separate the screen and the main body. The separation-type mobile screen 302 is opened to the left and right to enlarge the screen. Signal exchange and information exchange between the mobile phone main body 301 and the separation-type mobile screen 302 are performed by visible light communication via the mobile main body light emitting / receiving device 304 and the screen light emitting / receiving device 305. In this portable main body / screen one-to-one visible light communication 340, one communication partner is fixed. A similar case is the server-to-printer one-to-one visible light communication 341 between the server 310 and the printer 311. Visible light communication is performed via the server light emitting / receiving device 312 and the printer light emitting / receiving device 313.

The cellular phone network is wireless communication. Of course, the mobile phone body 301 can also communicate with the other party wirelessly via the mobile phone network. This is n-to-n wireless communication 363 between mobiles. Also, it must be able to connect to the Internet 332. This is the one-to-n wireless communication 351 between the mobile phone and the Internet.

The group local visible light communication network 330 is a communication network between limited communicators by visible light communication. Of course, it is also possible to enter this network via an external network. The cellular phone 322 with a modem dedicated to visible light communication communicates from a place where visible light does not reach directly. In this case, the visible light communication relay device 321 relays and enters the group local visible light communication network 330. Similarly, communication from other group local visible light communication networks and external networks by radio is also possible by the visible light communication relay device. The visible light communication relay device performs carrier conversion or the like to enable communication. Therefore, communication is possible regardless of differences in media, communication protocol, and communication method. The mobile phone 322 with a dedicated modem for visible light communication communicates with the portable main body 301 by the n-to-n visible light communication 362 via the relay device. The visible light communication relay device 321 and the portable main body 301 communicate with each other between the portable / relay devices n: n. Visible light communication 361 is performed. In addition, the mobile phone 320 with a modem dedicated to visible light communication performs mobile-to-mobile n-to-n visible light communication 360 and the server 310 performs server-to-mobile 1-to-n visible light communication.

The portable main body / screen one-to-one visible light communication 340 and the server / printer one-to-one visible light communication 341 are cases where a frequency band is specified and only a fixed partner communicates. The visible light communication protocol has a structure of an encapsulated packet frame, and has a function capable of fixing the other party by group information in the header. Either may be selected. Similarly, the group local visible light communication network 330 can also limit communication partners by fixing the frequency band or using header information.

The present invention employs a method of utilizing the wide band of visible light communication and the multiplexing of OFDM and utilizing the frequency band according to the purpose of use. For example, a detection band is allocated near the communication band, and in the detection band, a fixed sampling carrier wave is transmitted, and the frequency used is avoided or changed by the distortion, or the distortion of the weekly carrier wave is set in advance. There are methods that can be used to correct. Applications can be used for simultaneous requests to nodes and for monitoring inappropriately used nodes.

Also, from a visible light frequency of about 400 to 800 terahertz, a wavelength of about 800 to 400 nanometers can be converted, and if it is longer than one symbol of communication distance, communication is theoretically possible, so communication with future micromachines Is also applicable.
The microfabrication of the devices in the present invention must wait for a future technology, but it is optimal as an idea.

It is a figure which shows the structure of the modem only for visible light communications which is this invention. It is a figure which shows the structure of the reflection type light receiving and emitting apparatus which is a component of the modem only for visible light communication of this invention. It is a figure which shows the utilization form of a screen separation type | mold mobile phone equipped with the modem only for visible light communications of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Visible light communication control apparatus 101 Reflection type light receiving and emitting apparatus 102 Light receiving element 103 Amplifying part 104 OFDM demodulation part 105 Light emitting element 106 LED drive part 107 OFDM modulation part 108 Visible light communication interface 109 Communication control part 201 Concave reflector 202 Light receiving element connection Gold wire 203 Light emitting element connection gold wire 206a Lead wire frame a
206b Lead wire frame b
207 Transparent Epoxy Resin 301 Mobile Phone Body 302 Separable Mobile Screen 303 Joint 304 Mobile Body Light Emitting Device 305 Screen Light Emitting Device 310 Server 311 Printer 312 Server Light Emitting Device 313 Printer Light Emitting Device 320, 322 With Modem for Visible Light Communication Mobile phone 321 Visible light communication relay device 330 Group local visible light communication network 331 Mobile phone network 332 Internet 340 One-to-one visible light communication between mobile unit / screen 341 One-to-one visible light communication between server / printer 350, 352 Server / mobile 1-to-n visible light communication between 351 mobile / Internet 1-to-n wireless communication 360 n-to-n visible light communication between mobiles 361 n-to-n visible light communication between mobile / relay devices 362 n-to-n visible light communication between mobiles via relay device 363 n-to-n wireless communication between mobile phones

Claims (5)

  A modem having a wireless or wired communication relay function, comprising a reflective light emitting / receiving device in which a light emitting portion and a light receiving portion are integrated, and a visible light communication control device using an OFDM modulation method. The reflection type light emitting and receiving device has a structure in which at least one light emitting element and at least one light receiving element are arranged to face each other so as to be directly received by a reflection surface. A modem dedicated to visible light communication. The visible light communication control device encapsulates information in communication with a network that does not use visible light by wireless communication or wired communication, and communicates with a base in the visible light communication network according to a defined visible light communication protocol. The modem for exclusive use in visible light communication according to claim 1 or 2, characterized in that it is made possible. 4. The visible light communication dedicated modem according to claim 1, wherein the visible light communication control device can limit at least one communication partner by determining a certain visible light band. 5. The visible light communication dedicated modem according to claim 1, wherein the visible light communication control device is capable of limiting communication for each purpose of use by determining a certain visible light band. 6.

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