KR20170084708A - Image sensor communication system based on dimmable M-PSK - Google Patents

Abstract

The present invention relates to an image sensor communication (ISC) system in which dimming characteristics are supported.
The demultiplexing multi-phase shift keying (M-PSK) based image sensor communication system according to the present invention allocates a frequency corresponding to a data packet to be transmitted using a predetermined M-PSK coding table A data coding unit; N LEDs turned on / off corresponding to the data packet according to the allocated frequency; A rolling shutter camera for capturing on / off images of the N LEDs in a rolling shutter manner; A data processor for extracting a data packet corresponding to the assigned frequency using the predetermined M-PSK coding table from on / off images of LEDs captured by the rolling shutter camera; And the on / off states of the N LEDs have a time delay of T / N, respectively.

Description

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

The present invention relates to an image sensor communication (ISC) system, in which a dimming characteristic is provided between an LED and a rolling shutter camera in an image sensor communication based on multiple phase shift keying (M-PSK) Supported image sensor communication (ISC) system.

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 image sensor communication (ISC) systems must consider the following to be applied to camera receivers (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

However, in most situations dimming characteristics must be supported. In the conventional M-PSK technique, dimmign needs to be specifically proposed as a new feature.

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

An object of the present invention is to provide an image sensor communication system in which a dimming characteristic is supported in an image sensor communication (ISC) of a multi-phase shift keying (M-PSK) scheme.

The demosaile multi-phase shift keying (M-PSK) -based image sensor communication system according to the present invention allocates a phase corresponding to a data packet to be transmitted using a preset multi-phase shift keying (M-PSK) coding table A data coding unit; N LEDs turned on / off corresponding to the data packet according to the assigned phase; A camera for capturing on / off images of the N LEDs; A data processor for extracting a data packet corresponding to a corresponding allocated phase from the ON / OFF image of the LED captured by the camera using the preset M-PSK coding table; And the on / off states of the N LEDs have a time delay of T / N, respectively.

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 illustrates a mapping process for generating a discrete waveform according to an exemplary embodiment of the present invention and detecting a phase and a dimming level,
3 is a graph showing delay differences between dimming signals for controlling LEDs according to the present invention,
4 is a diagram illustrating a design example of an LED tube for M-PSK according to an embodiment of the present invention.

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 block diagram of a demultiplexing multi-phase shift keying (M-PSK) based image sensor communication system according to an embodiment of the present invention.

1, a demultiplexing multi-phase shift keying (M-PSK) based image sensor communication system 100 (hereinafter referred to as an ISC system) according to an embodiment of the present invention includes a data coding unit 110, an LED 120, A rolling shutter camera 130, and a data processing unit 140.

The data coding unit 110 allocates a phase corresponding to a data packet to be transmitted using a preset M-PSK coding table. By thus allocating the phase corresponding to the transmission data packet, the transmission data packet is outputted as the signal of the phase region.

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 a data packet corresponding to the assigned phase from the ON / OFF image of the LED 120 captured by the rolling shutter camera 130 using the predetermined M-PSK coding table. The extraction of such data packets is to identify the frequencies assigned to the LEDs 120 and to extract the transmission data packets corresponding to these corresponding phases in a predetermined M-PSK coding table.

Hereinafter, the demodulation M-PSK technique will be described using an example of the Dimmable 8-PSK.

MIMO LED-The transmitter consists of many LED groups. Each LED group is made up of 8-LEDs. It is assumed that there are two kinds of LED groups. One transmits a reference signal as a reference group and the other transmits a data group. Because the LEDs in each group are synchronized with each other, if the first LED is delayed by T / 8 cycles, the other LEDs are also delayed by T / 8 cycles. The signals from the LEDs change together over time and are referred to as the Phase_Shift value. The signal for controlling the LED is a dimmed square signal. That is, it is a dimmed OOK signal. The phase-shift value of the reference group does not change from 0. The phase-shift value of the data group is changed to transmit the data.

The signal transmission of the group according to the time variable t is shown as (1), and the received state of the LED at the specific time value t0 appears as (2).

...... (1)

...... (One)

...... (2)

...... (2)

Thus, a discontinuous waveform is created through the received 8-state of the 8-LED in the group and the phase of the group is detected. Such a descrete waveform is shown as an example as shown in FIG.

FIG. 2 shows a mapping process for generating a discrete waveform according to an embodiment of the present invention and detecting a phase and a dimming level.

Referring to FIG. 2, in order to generate a discrete waveform, a sampled state of a 4-LED is obtained in a group, and a process of mapping the discrete waveform to a decoding table to find a phase in an LED group is performed.

3 is a graph showing delay differences between dimming signals for controlling LEDs according to the present invention.

Referring to FIG. 3, the dimmable M-PSK technique uses an M LED to transmit the phase of an LED group. For example, in the case of 8-PSK, there are 8 LEDs in the group together as shown in FIG. For example, if a group of 8 LEDs is used, then N = 8 phases, and 3 bits can be transmitted at each time. At this time, the dimming step is 0.125. Here, the dimming level AB% = (Sigma "1") / 8. The eight states of the LED are 10000011, and the dimming level AB% = 3/8 = 37.5%.

Table 1 shows the encoding table through phase comparison, and Table 2 shows the decoding table from D (phase).

Encoding table 3-bits input Phase output 000 One 001 2 010 3 011 4 100 5 101 6 110 7 111 8

Decoding table D (phase) 3-bits output One 0001 2 012 3 103 4 114 5 005 6 016 7 107 8 118

The dimmed M-PSK decoding algorithm according to the embodiment of the present invention is as follows.

First, the dimming level is detected. The dimming level AB% = (Sigma "1") / 8.

Second, it maps to one of the phase encoding tables. This is determined by the dimming level. Eight groups of reference LEDs are decoded to provide one reference phase. 8 groups of data LEDs are decoded to provide one data phase.

Finally, the decoding is performed using the decoding table from the phase D. This phase D can be determined by subtracting the reference phase from the data phase.

Table 3 and Table 4 show the phase decoding table according to the T / 8 dimming signal.

1/8 Dimmed Signal 2/8 Dimmed Signal 3/8 Dimmed Signal 4/8 Dimmed Signal 8-States Input Phase Output 8-States Input Phase Output 8-States Input Phase Output 8-States Input Phase Output 1000 0000 One 1000 0001 One 1000 0011 One 1000 0111 One 0100 0000 2 1100 0000 2 1100 0001 2 1100 0011 2 0010 0000 3 0110 0000 3 1110 0000 3 1110 0001 3 0001 0000 4 0011 0000 4 0111 0000 4 1111 0000 4 0000 1000 5 0001 1000 5 0011 1000 5 0111 1000 5 0000 0100 6 0000 1100 6 0001 1100 6 0011 1100 6 0000 0010 7 0000 0110 7 0000 1110 7 0001 1110 7 0000 0001 8 0000 0011 8 0000 0111 8 0000 1111 8

5/8 Dimmed Signal 6/8 Dimmed Signal 7/8 Dimmed Signal 8-States Input Phase Output 8-States Input Phase Output 8-States Input Phase Output 1000 1111 One 1001 1111 One 1011 1111 One 1100 0111 2 1100 1111 2 1101 1111 2 1110 0011 3 1110 0111 3 1110 1111 3 1111 0001 4 1111 0011 4 1111 0111 4 1111 1000 5 1111 1001 5 1111 1011 5 0111 1100 6 1111 1100 6 1111 1101 6 0011 1110 7 0111 1110 7 1111 1110 7 0001 1111 8 0011 1111 8 0111 1111 8

4 is a diagram illustrating a design example of an LED tube for M-PSK according to an embodiment of the present invention.

Referring to FIG. 4, a plurality of LEDs according to the present invention constitute one LED tube. These LED tubes are implemented as shown in the drawing for M-PSK.

The left side of FIG. 4 (a) is a design example of an 8 × 8 LED transmitter for the Dimmer 8-PSK, and the right side is a design example of the design of a Dimmable 2-PSK LED transmitter. 4 (b) and 4 (c) are illustrations of an LED-tube design for Dimmable 2-PSK, and FIG. 4 (d) . In the drawing, green indicates a data LED, and red indicates a reference LED.

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 (1)

A data coding unit for allocating a frequency corresponding to a data packet to be transmitted using a predetermined M-PSK coding table;
N LEDs turned on / off corresponding to the data packet according to the allocated frequency;
A rolling shutter camera for capturing on / off images of the N LEDs in a rolling shutter manner;
A data processor for extracting a data packet corresponding to the assigned frequency using the predetermined M-PSK coding table from on / off images of LEDs captured by the rolling shutter camera; Lt; / RTI >
Wherein the on / off of the N LEDs has a time delay of T / N, respectively.

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