KR20110063379A - Vlc device and method for processing visible light signal - Google Patents

Abstract

PURPOSE: A visible light signal transmit-receive device and method thereof are provided to solve power different of a receiving signal which is generated due to a difference of incoming angle. CONSTITUTION: A photo detector(201) receives an optical signal transmitted from a visible light emitting element of a base station. A measuring unit(209) measures a received power of distance with the visible light emitting device and an optical signal. A determining unit(211) produces an incident angle of an optical signal by using distance and received power.

Description

Visible light signal transmission and reception apparatus and its method {VLC DEVICE AND METHOD FOR PROCESSING VISIBLE LIGHT SIGNAL}

The present invention relates to an apparatus for transmitting and receiving visible light signals and a method thereof.

Visible light communication (VLC) system is a system that communicates using visible light, and utilizes the advantages of visible light to build a communication network and has both a role such as lighting and a communication system.

This visible light communication system is a communication technology that transmits information using visible light (400-700 nm) and flashes visible light of a light emitted from a fluorescent lamp or a light emitting diode (LED) used in a display device at an invisible speed. High speed communication is possible by sending technology.

In addition, visible light communication is more complementary than wireless LAN because there is no fear of information leaking to the outside when light is blocked.

However, when it is assumed that the signal is transmitted at the same power, the performance is drastically reduced as the incident angle is reduced according to the position of the base station and the terminal. Due to this problem, if the location of the terminal is changed, the same QoS cannot be provided.

1 is a view schematically showing a configuration of a conventional visible light communication system.

Referring to FIG. 1, visible light emitted from a light emitting diode (LED) light source of a base station (not shown) is received by each terminal device M1, M2, and M3.

Here, the distance between the terminal device M1 and the LED light source is 'd1', the distance between the terminal device M2 and the LED light source is 'd2', and the distance between the terminal device M3 and the LED light source is 'd3'.

At this time, the optical signal incident angle between the terminal device M1 and the LED light source is 'α', and the power of the received signal is very strong. On the other hand, the light signal incident angle between the terminal device M2 and the LED light source is 'β' and the light signal incident angle between the terminal device M3 and the LED light source is 'γ', and the power of the received signal is relatively weak.

Further, if the distance is d3> d2> d1, the received power of the signal received at each terminal device M1, M2, M3 is M1> M2> M3.

As such, it can be seen that the reception power varies according to the distance between the terminal devices M1, M2, and M3 and the LED light source and the incident angle.

Therefore, when the visible light of the same power is emitted, the difference in the received power occurs according to the position of each terminal device (M1, M2, M3).

Accordingly, an aspect of the present invention is to provide an apparatus and method for transmitting and receiving visible light signals capable of resolving power differences of received signals caused by differences in incident angles.

In addition, the present invention provides an apparatus and method for transmitting and receiving visible light signals capable of satisfying the same QoS regardless of the location of each user terminal by applying AMC (Adaptive Modulation and Coding) and TPC (Transmit Power Control) technology.

According to one aspect of the invention there is provided a visible light signal receiving apparatus. The apparatus includes a photo-detector for receiving an optical signal transmitted by a visible light emitting element of a base station; A measuring unit measuring a distance from the visible light emitting device and a received power of the optical signal; And a determination unit configured to calculate an incident angle of the optical signal using the distance and the received power, determine whether to compensate the transmission power of the optical signal according to the incident angle, and request transmission power compensation to the base station through a feedback channel. Include.

According to another feature of the invention there is provided a visible light signal transmission apparatus. This apparatus comprises: a visible light emitting element for emitting an optical signal; And a power controller for compensating for transmission power when receiving transmission power compensation request from the terminal device receiving the optical signal through a feedback channel.

According to another feature of the invention there is provided a visible light signal receiving method. The method includes the steps of receiving an optical signal emitted by the visible light emitting device; Measuring the received power of the optical signal; Measuring a distance from the light emitting device; Calculating an incident angle using the received power and the distance; Determining whether to compensate for transmission power of the optical signal using the incident angle; And when transmission power compensation is determined, requesting transmission power compensation to the visible light emitting device.

According to another feature of the invention there is provided a visible light signal transmission method. The method includes the steps of: emitting an optical signal through a visible light emitting device at a base station; Receiving transmission power compensation request from a terminal device receiving the optical signal through a feedback channel; Compensating for the transmission power of the optical signal according to the incident angle of the optical signal received in the requesting step; And transmitting the optical signal, the transmission power of which has been compensated, to the terminal device.

According to an embodiment of the present invention, if a difference occurs in the reception power of the optical signal according to the incident angle, by applying the AMC (Adaptive Modulation and Coding) and TPC (Transmit Power Control) technology to compensate for the transmission power to maintain a constant power Can ensure the stability of the communication service.

1 is a view schematically showing a configuration of a conventional visible light communication system.
2 shows a receiver model of a visible light signal according to an embodiment of the present invention.
3 is a graph illustrating an optical filter gain according to an incident angle according to an exemplary embodiment of the present invention.
4 is a configuration of an incident angle table according to an embodiment of the present invention.
5 is a block diagram showing an internal configuration of a visible light signal transmitting and receiving device according to an embodiment of the present invention.
6 is a flowchart illustrating a visible light signal transmission and reception method according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, except to exclude other components unless specifically stated otherwise.

In the present specification, a terminal device may include a mobile station (MS), a terminal, a mobile terminal (MT), a subscriber station (SS), a portable subscriber station (PSS), a user. A device may be referred to as a user equipment (UE), an access terminal (AT), or the like, and may include all or some functions of a mobile terminal, a subscriber station, a portable subscriber station, a user device, and the like.

In the present specification, a base station (BS) is an access point (AP), a radio access station (Radio Access Station, RAS), a Node B (Node B), a base transceiver station (Base Transceiver Station, BTS), MMR ( Mobile Multihop Relay) -BS and the like, and may include all or part of functions such as an access point, a radio access station, a Node B, a base transceiver station, and an MMR-BS.

Hereinafter, an apparatus and method for transmitting and receiving visible light signal according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

2 illustrates a receiver model of a visible light signal according to an exemplary embodiment of the present invention, and FIG. 3 is a graph illustrating an optical filter gain according to an incident angle according to an exemplary embodiment of the present invention.

First, referring to FIG. 2, the LED light source emits visible light at a position having an angle of Ψ.

Then, visible light is collected by a hemispherical concentrator, and the visible light passes through a bandpass optical filter and received by a photo-detector.

In this case, the visible light is received at an incident angle 'θ' based on the C axis on the A-B axis.

Here, the distance from the LED light source is the same, but the graph shows the wideband transmission filter gain of visible light received by changing the incident angle 'θ', as shown in FIG. 3.

Referring to FIG. 3, the value of the broadband pass filter gain varies according to the value of the incident angle 'θ'. A graph of a predetermined level of gain continues and then drops rapidly at a specific point. In other words, when 'θ = 0', the maximum wideband pass filter gain is 0.96 and remains substantially constant until 'θ = 60 Hz'. The broadband pass filter gain drops sharply from the point where &thetas; = 60 Hz.

Here, the pilot signal, the preamble signal, and the postamble signal may be used for measuring the incident angle of the visible light signal.

On the other hand, Figure 4 is a configuration of the angle of incidence table according to an embodiment of the present invention, is generated based on the graph of FIG.

Referring to FIG. 4, the angle of incidence table 100 is paired with the angle of incidence by pairing a 'wideband frequency filter gain' and a 'distance with an LED light source'.

In other words, the horizontal field contains the wideband frequency filter gain 101, and the vertical field contains the distance (d) 103 from the LED light source.

In the case where the distance is d1, when the wideband frequency filter gain is 0.96, the incident angle θ = 0m is mapped, and when the wideband frequency filter gain is 0.91, the incident angle θ = 60 Hz 105 is mapped.

A configuration for solving the difference in the received power of the visible light signal according to the incident angle using the incident angle table will be described below.

5 is a block diagram showing an internal configuration of a visible light signal transmitting and receiving device according to an embodiment of the present invention.

Here, the visible light signal receiving device 200 is mounted on a terminal device (not shown), and the visible light signal transmitting device 300 is mounted on a base station (not shown).

Referring to FIG. 5, the visible light signal receiver 200 includes a photo detector 201, a reception filter 203, a demultiplexer 205, a demodulator 207, a measurement unit 209, and a determination unit 211. , A storage unit 213, and a weight selection unit 215.

For example, the optical signal emitted from the LED light source is received by the photo detector 201 through the optical wireless channel. The detection is performed through the reception filter 203, the demultiplexer 205, and the demodulator 207.

At this time, the determination unit 211 determines whether the transmission power is compensated using the incident angle table 100 stored in the storage unit 213.

On the other hand, the apparatus 300 for transmitting visible light includes an adaptive modulation and coding (AMC) controller 301, an AMC processor 303, a multiplexer 305, a power controller 307, and a transmitter 309.

The visible light signal processing method of the visible light transmitting and receiving apparatus 200 and 300 will be described in detail with reference to FIG. 6.

6 is a flowchart illustrating a visible light signal processing method according to an embodiment of the present invention.

Referring to FIG. 6, the apparatus 300 for transmitting visible light broadcasts the visible light signal (S101).

Then, the photodetector 201 of the visible light source receiving apparatus 200 receives the optical signal (S103). In addition, the measurement unit 209 measures the distance to the visible light emitting device, that is, the visible light signal transmission apparatus 300 and the received power of the optical signal (S105 and S107) and transmits the measured power to the determination unit 211.

In this case, as described above, the reception power of the visible light signal is used with a wideband frequency filter gain.

In addition, the distance measuring method with the visible light emitting device is a technique well known to those skilled in the art, it may be employed in a variety of techniques.

Then, the determination unit 211 extracts an incident angle mapped with the distance received from the measuring unit 209 and the received power from the incident angle table 100 (S109).

For example, if the distance is' d1 'and the broadband frequency filter gain is' 0.91', then the mapped incidence angle [theta] = '60 Hz '105.

At this time, the determination unit 211 determines whether the incident angle extracted in the step S109 is greater than or equal to a predetermined threshold angle (S111). In other words, it is checked whether the broadband pass filter gain of FIG.

If not greater than the critical angle, it starts again from step S101.

On the other hand, if the threshold angle or more, check the compensation method (S113), the determination unit 211 determines whether to proceed with the compensation in the AMC method or TPC method (S115). This compensation method is previously defined in the determination unit 211.

In this case, when the compensation is performed by the AMC method, the determination unit 211 requests the transmission power compensation to the visible light signal transmitting apparatus 300 together with the incident angle (S117).

Then, the AMC control unit 301 of the visible light signal transmitting apparatus 300 determines the modulation order and the channel coding rate according to the incident angle received in step S117 (S119). 3, the modulation order and the channel coding rate are determined to compensate for the decrease in the wideband pass filter gain corresponding to the incident angle.

Then, the AMC processor 303 performs adaptive modulation and channel coding using the modulation order and the channel coding rate determined by the AMC controller 301 (S121). The adaptive modulated and channel coded signal is input to the multiplexer 305, the power controller 307, and the transmitter 309 and transmitted to the optical wireless channel.

In addition, when the compensation is performed by the TPC method, the determination unit 211 transmits the incident angle to the weight selection unit 215. The weight selector 215 determines the weight of the transmission power according to the incident angle (S125) and requests the visible power signal transmission apparatus 300 to compensate for the transmission power together with the weight (S127).

Then, the power control unit 307 receives the weight to compensate for the transmission power (S129), and then transmits to the optical wireless channel through the transmission unit 309 (S131).

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

100: incident angle table 200: visible light receiving device
201: Photodetector 203: Receive filter
205: demultiplexer 207: demodulator
209: measuring unit 211: determining unit
213: storage unit 215: weight selection unit
300: visible light transmitting device 301: AMC control unit
303: AMC processing unit 305: Multiplexing unit
307: power control unit 309: transmission unit

Claims (14)

A photo-detector for receiving an optical signal transmitted by the visible light emitting device of the base station;
A measuring unit measuring a distance from the visible light emitting device and a received power of the optical signal; And
A determination unit configured to calculate an incident angle of the optical signal using the distance and the received power, determine whether to compensate the transmission power of the optical signal according to the incident angle, and request transmission power compensation to the base station through a feedback channel.
Visible light signal receiving device comprising a. The method of claim 1,
The angle of incidence table generated by measuring the received power of the optical signal received at a plurality of different angles of incidence at the same distance, wherein the angle of incidence table is paired with distance and received power, and the angle of incidence is mapped for each received power based on the same distance. A storage for storing the present;
The determination unit,
And a visible light signal receiving device extracting an incident angle mapped to the received power and the distance from the incident angle table. The method according to claim 1 or 2,
The determination unit,
Visible light for comparing the incident angle with a predetermined threshold angle, wherein the threshold angle is defined as the incident angle at the time when the reception power of the optical signal is weakened in the incident angle table, and determines compensation of transmission power when the incident angle is a value greater than or equal to the threshold angle. Signal receiving device. The method of claim 3,
Further comprising a weight selection unit for determining a weight in accordance with the incident angle received from the determination unit,
The determination unit,
And transmitting the weight along with a transmission power compensation request to the base station through a feedback channel. Visible light emitting device for emitting an optical signal; And
Power control unit for compensating for transmission power when receiving the transmission power compensation request through the feedback channel from the terminal device receiving the optical signal
Visible light signal transmission device comprising a. The method of claim 5,
An adaptive modulation and coding (AMC) control unit that determines a modulation order and a channel coding rate defined according to the incidence angle when a transmission power compensation request is received together with the incidence angle of the optical signal from the terminal device; And
An AMC processor that performs adaptive modulation and channel coding of transmission power according to the determined modulation order and channel coding rate and provides the power control unit to the power control unit
Visible light signal transmission device further comprising. The method of claim 5,
The power control unit,
And a transmission power compensation request received from the terminal device with a weight determined using the incident angle of the optical signal, and applying the weight to the transmission power. Receiving an optical signal transmitted by a visible light emitting device;
Measuring the received power of the optical signal;
Measuring a distance from the light emitting device;
Calculating an incident angle using the received power and the distance;
Determining whether to compensate for transmission power of the optical signal using the incident angle; And
When transmission power compensation is determined, requesting transmission power compensation to the visible light emitting device
Visible light signal receiving method comprising a. The method of claim 8,
Prior to the receiving step,
The angle of incidence table generated by measuring the received power of the optical signal received at a plurality of different angles of incidence at the same distance, wherein the angle of incidence table is paired with distance and received power, and the angle of incidence is mapped for each received power based on the same distance. Storing the present;
The calculating step,
And extracting the incident angle mapped to the received power and the distance from the incident angle table. The method according to claim 8 or 9,
The determining step,
Comparing the incident angle with a predetermined threshold angle, wherein the threshold angle is defined as the incident angle at the time when the reception power of the optical signal is weakened in the incident angle table; And
Determining compensation of transmission power when the incident angle is a value greater than or equal to the threshold angle
Visible light signal receiving method comprising a. The method of claim 10,
Between the determining step and the requesting step
Selecting a weight according to the incident angle;
The requesting step,
And transmitting the weight when requesting transmission power compensation to the visible light emitting device. Emitting an optical signal through a visible light emitting device at a base station;
Receiving transmission power compensation request from a terminal device receiving the optical signal through a feedback channel;
Compensating for the transmission power of the optical signal according to the incident angle of the optical signal received in the requesting step; And
Transmitting an optical signal having a transmission power compensated to the terminal device;
Visible light signal transmission method comprising a. The method of claim 12,
Compensating step,
Determining a modulation order and a channel coding rate defined according to the incident angle; and
Performing adaptive modulation and channel coding of transmit power according to the determined modulation order and channel coding rate
Visible light signal transmission method comprising a. The method of claim 12,
The requesting step,
Receiving a weight determined according to an angle of incidence of the optical signal,
Compensating step,
The visible light signal transmission method of applying the weight to the transmission power.

Images