KR101937560B1 - Image sensor communication system based on dimmable M-PSK - Google Patents

Abstract

Summary of the Invention The present invention is an image sensor communication system based on a hybrid communication of multiple phase shift keying (M-PSK) and multiple frequency shift keying (M-FSK).
An image sensor communication system based on a composite communication of a multi-phase shift keying (M-PSK) and a multiple frequency shift keying (M-FSK) according to the present invention includes a predetermined multi- A data coding unit for allocating a phase and a frequency corresponding to a data packet to be transmitted using an (M-FSK) coding table; A plurality of LEDs for transmitting data packets on / off corresponding to the data packets according to the allocated phase and frequency; A rolling shutter camera for capturing an on / off image of the LED by a rolling shutter method; A data processor for extracting a data packet corresponding to the assigned frequency using the predetermined M-PSK and M-FSK coding tables from on / off images of LEDs captured by the rolling shutter camera; Wherein at least one of the plurality of LEDs transmits a reference packet and the remainder transmits a data packet, wherein one bit per group set of LEDs is transmitted by the M-PSK scheme, If the phases of the groups are the same, they are set to bit 1, otherwise they are set to bit 0. Using the M-FSK technique, log ₂ M bits are transmitted.

Description

[0001] The present invention relates to an image sensor communication system based on dimmable M-PSK and a multi-frequency shift keying (M-PSK)

The present invention relates to an image sensor communication (ISC) system, and more particularly, to an image sensor communication system using multiple phase shift keying (M-PSK) and multiple frequency shift keying (M-FSK) To an image sensor communication (ISC) system that enables hybrid communication.

A recent standardization work related to optical wireless communication (OWC), well known for the revision of the well-known Visible Light Communication (VLC), was conducted in the IEEE 802.15.7r1 task group. According to this revision, optical wireless communication (OWC) can be classified as Image Sensor Communications (ISC), High Rate PD Communications and Low Rate PD Communications. Among them, image sensor communication (ISC) is an optical wireless communication using an image sensor as a receiver.

Recently, as the number of smart phones equipped with high-performance image sensors has surged, interest in image sensor communication (ISC) has increased. In particular, attempts have been made to apply a camera equipped with an image sensor of a global shutter system or a rolling shutter system to such an image sensor communication (ISC) system.

Most of cameras are electronic shutter cameras employing semiconductor image sensors. In the rolling shutter system, images are captured for each row of image sensors combined in a plurality of rows, .

However, the prior art discloses image sensor communication (ISC) only when the frame rate of the camera is fixed. In fact, when the frame rate of the camera changes unstably, image sensor communication can not be smoothly performed.

OOK signals that are rapidly modulated from LEDs in an image sensor communication (ISC) system should consider the following to be applied to a camera receiver (global shutter type) operating at 30 fps. That is, the unknown frequency signal and the unknown frequency signal can not be restored by only the LED state at the sampling time, and the frame rate of the camera is not fixed at 30 fps. And, assuming that the camera has a constant and variable frame rate, this problem may seem to make data recovery impossible with problems when an unknown frequency from the transmitter is received.

Korea Patent No. 1472583 Korean Patent Publication No. 2009-0016176 Korea Patent Publication No. 2010-0135683

It is an object of the present invention to provide an image sensor communication system in which a multi-phase shift keying (M-PSK) and a multi-frequency shift keying (M-FSK)

An image sensor communication system based on a composite communication of a multi-phase shift keying (M-PSK) and a multiple frequency shift keying (M-FSK) according to the present invention includes a predetermined multi- A data coding unit for allocating a phase and a frequency corresponding to a data packet to be transmitted using an (M-FSK) coding table; A plurality of LEDs for transmitting data packets on / off corresponding to the data packets according to the allocated phase and frequency; A camera for capturing an on / off image of the LED; A data processor for extracting a data packet corresponding to the assigned frequency using the predetermined M-PSK and M-FSK coding tables from on / off images of LEDs captured by the camera; Wherein at least one of the plurality of LEDs transmits a reference packet and the remainder transmits a data packet, wherein one bit per group set of LEDs is transmitted by the M-PSK scheme, If the phases of the groups are the same, they are set to bit 1, otherwise they are set to bit 0. Using the M-FSK technique, log ₂ M bits are transmitted.

In the image sensor communication system according to the present invention, there is compatibility with any OOK frequency received from the transmitter, and any visual field cutoff frequency and any camera cutoff frequency can be used for OOK illumination modulation.

Further, in the present invention, any global shutter camera having a variable frame rate, as well as a global shutter camera having a fixed frame rate and compatibility with any camera having a fixed frame rate or a variable frame rate, can be used as a receiver.

Also, in the present invention, the spatial MIMO design provides a significantly higher link rate for illumination services and can reduce the bit error rate (BER), which is an effect of long exposure.

1 is a configuration diagram of a demultiplexing multi-phase shift keying (M-PSK) -based image sensor communication system according to an embodiment of the present invention;
FIG. 2 is a diagram illustrating a design example of a 2-PSK and M-FSK LED lighting system using a dual LED tube according to an embodiment of the present invention.
3 is a structural diagram of an LED group receiver using a 2-PSK and M-FSK complex modulation scheme according to an embodiment of the present invention.
4 is a design example of a LED lighting system for 2-PSK and M-FSK using a 3-LED tube set according to another embodiment of the present invention,
FIG. 5 is a diagram showing one of the LEDs in the 2-PSK using the 3-LED in FIG. 4 for the reference for mitigating the rolling effect,
6 is a structural diagram of an LED group receiver using a 2-PSK and M-FSK complex modulation scheme according to an embodiment of the present invention.
FIG. 7 is a diagram illustrating a design example of an LED lighting system for 4-PSK and M-FSK using a 4-LED tube set according to another embodiment of the present invention;
FIG. 8 is a view showing one of the LEDs in the 2-PSK using the 4-LED in FIG. 7 as a reference for mitigating the rolling influence; FIG.

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the embodiments of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the difference that the embodiments of the present invention are not conclusive.

In describing the components of the embodiment of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected or connected to the other component, Quot; may be "connected," "coupled," or "connected. &Quot;

1 is a configuration diagram of an image sensor communication system based on a multi-phase shift keying (M-PSK) and a multiple frequency shift keying (M-FSK) hybrid communication according to an embodiment of the present invention.

1, an image sensor communication system 100 (hereinafter, referred to as an ISC system) based on a hybrid communication of multiple phase shift keying (M-PSK) and multiple frequency shift keying (M- The LED 120, the camera 130, and the data processing unit 140. The data coding unit 110 includes a data coding unit 110, an LED 120, a camera 130,

The data coding unit 110 allocates a frequency corresponding to a data packet to be transmitted using a preset M-PSK and a M-FSK coding table. By allocating the frequency corresponding to the transmission data packet in this way, the transmission data packet is output as a signal in the frequency domain.

At least one LED 120 is provided. The LED 120 serves as a transmitter for transmitting data in the optical camera communication system 100 according to the present invention. The LED 120 recognizes that the on / off state can not be distinguished from the on / off state of the human eye when the pulse rate is 110 or more per second. This pulse rate can of course be adjusted. In the present invention, the LED 120 is typically described as a transmitter for transmitting data by irradiating light. However, the present invention is not limited to this, and any light source capable of transmitting data through on / In the present invention, all such light sources are represented by LEDs.

The camera 130 captures an on / off image of the LED 120 in a rolling shutter manner. The camera 130 includes an image sensor (not shown) that supports either a global shutter mode or a rolling shutter mode. The image sensor of the rolling shutter camera 130 captures and captures an on / off image of the LED 120 for each of a plurality of rows during one capture time. At this time, image capturing for each row is performed by a nonlinear scanning method at predetermined time intervals. That is, each row of the image sensor of the rolling shutter type in the rolling shutter camera 130 is sequentially exposed for a preset exposure time, and each row is exposed at a predetermined time interval. In this case, the last exposure time of the first row and the last exposure time of the last row are referred to as a frame time, and the exposure time and the frame time are the capturing time. The rolling shutter camera 130 photographs the LED 120 while the LED 120 is turned on / off. The image captured during the capture time is displayed as a white band when the LED 120 is on and displayed as a black band when the LED 120 is off. Of course, the brightness values of the white band W and the black band B are different in the process of the LED 120 being turned on or off. Such a rolling shutter camera 130 serves as a receiver for receiving data in the OCC system 100. As such an image sensor 131, for example, a CMOS semiconductor sensor may be used.

The data processing unit 140 extracts data packets corresponding to the assigned phases and frequencies from the on / off images of the LED 120 captured by the camera 130 using the preset M-PSK and M-FSK coding tables do. The extraction of such a data packet is to identify the phase and frequency assigned to the LED 120 and extract the transmission data packet corresponding to these corresponding phases and frequencies in the preset M-PSK and M-FSK coding tables.

2 is a diagram illustrating a design example of a 2-PSK and M-FSK LED lighting system using a dual LED tube according to an embodiment of the present invention.

2, since the M-FSK can support a plurality of transmitters (LEDs) and the frequency allocation is based on the M-FSK to share the band of all the LEDs, the M-FSK technology can effectively There is an advantage to be avoided. In addition, M-FSK is effectively supported on rolling shutter receivers, and frequency detection is also much easier with rolling effects.

In addition, when the M-PSK is used in combination with the M-FSK, it is possible to obtain a data rate several times better than that in the case of only the M-FSK, and it is possible to additionally support the claus shutter receiver.

The relaxation of rolling effects is complex. This is because the receiver has many steps: First, the LED position is detected to identify the correct state of the LED. Second, the reference phase is compared to detect the reception_phase. Third, the transmission_phase is estimated from the reception_phase. In the present invention, a new M-PSK design scheme for a transmitter is considered in which a combination of M-PSK and M-FSK is considered in order to simplify the rolling shutter ISC system.

Referring to FIG. 2, one bit per 2-LED group set may be transmitted by the 2-PSK scheme. If two LED groups are in the same phase, bit 1 can be set, and if the phase is opposite, bit 0 can be set. The M-FSK technique uses log ₂ M (bits) are transmitted.

3 is a structural diagram of an LED group receiver using a 2-PSK and M-FSK combined modulation technique according to an embodiment of the present invention.

Referring to FIG. 3, the LED 1 and the LED 2 transmit the time information of the data packet through the phase using the 2-PSK technique and transmit the data through the frequency encoder using the M-FSK technique.

The decoding algorithm of 2-PSK and M-FSK is as follows.

First, when a dual LED tube is detected, the phases of the two LEDs in the tube are compared. If the phases are the same, the asynchronous bit is set to 1; otherwise, the asynchronous bit is set to 0. At this time, the asynchronous bit is the time information of the data packet. Then, the common frequency of the dual LED is detected. The data is decoded using M-FSK.

4 is a diagram illustrating a design example of an LED lighting system for 2-PSK and M-FSK using a 3-LED tube set according to another embodiment of the present invention.

Referring to FIG. 4, two bits per set of 3-LED groups are transmitted using the 2-PSK scheme. One LED is for reference and two for data (see FIG. 5). If the LED is the same phase as the reference LED, transmit bit 1, otherwise transmit bit 0. The M-FSK technique uses log ₂ M bits to be transmitted.

 6 is a structural diagram of an LED group receiver using a 2-PSK and M-FSK combined modulation technique according to an embodiment of the present invention. LED 1, LED 2 or LED 3 transmits time information of the data packet. The reference LED, LED 1, transmits a reference phase (always phase = 0) so that the receiver can mitigate the rolling effect in 2-PSK technology. It also transmits data through the frequency as the other two LEDs. LED 2 and LED 3 are data LEDs that transmit information in the phase and frequency of the signal.

FIG. 7 is a diagram illustrating a design example of an LED lighting system for 4-PSK and M-FSK using a 4-LED tube set according to another embodiment of the present invention.

As shown in the figure, three bits per set of 4-LED groups are transmitted using the 2-PSK scheme by using 2-PSK and M-FSK together with the 4-LED tube group in the present invention. At this time, one LED is for reference and three for data as shown in Fig. If the LED is the same phase as the reference LED, transmit bit 1, otherwise transmit bit 0. The M-FSK technique uses log ₂ M bits to be transmitted. Thus, the 4-PSK transmits 2 bits / LED, and the reference LED helps mitigate the rolling influence of the receiver. All three other LEDs transmit 2 X 3 = 6 bits.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them. Furthermore, the terms "comprises", "comprising", or "having" described above mean that a component can be implanted unless otherwise specifically stated, But should be construed as including other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

110: LED coding unit 120: LED
130: Rolling shutter camera 140: Data processing unit

Claims (5)

Generating a phase encoded signal in which data packets are encoded according to a 2-PSK (Phase Shift Keying) scheme;
Generating a first frequency-encoded signal and a second frequency-encoded signal in which the data packets are encoded according to a multiple frequency shift keying (M-FSK) scheme;
Modulating the phase encoded signal and the first frequency encoded signal to generate a first signal;
Modulating the phase encoded signal and the second frequency encoded signal to generate a second signal;
Flickering the first light source according to the M-FSK scheme according to the first signal; And
And blinking a second light source at the same frequency as the first light source in accordance with the second signal,
Wherein the first light source and the second light source are arranged such that,
And flickers in the same or opposite phase according to asynchronous bits which are time information of the data packets. The method according to claim 1,
Wherein the asynchronous bit comprises:
Wherein 0 and 1 are alternately repeated. delete Generates a phase encoded signal obtained by encoding data packets according to a 2-PSK (Phase Shift Keying) scheme,
Generates a first frequency-encoded signal and a second frequency-encoded signal obtained by coding the data packets according to a multiple frequency shift keying (M-FSK) scheme,
Generating a phase-coded signal and a first signal modulating the first frequency-encoded signal,
Generating a phase-coded signal and a second signal by modulating the second frequency-
The first light source is blinked by the M-FSK method according to the first signal,
And a processor for blinking a second light source at the same frequency as the first light source in accordance with the second signal,
Wherein the first light source and the second light source are arranged such that,
And flickers in the same or opposite phase according to asynchronous bits which are time information of the data packets. delete

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