WO2019088352A1

WO2019088352A1 - Polar coordinate modulation method and modulation apparatus, and optical wireless communication system using same

Info

Publication number: WO2019088352A1
Application number: PCT/KR2017/014671
Authority: WO
Inventors: 김정현; 김영우; 문성재; 사기동
Original assignee: 한국광기술원
Priority date: 2017-10-30
Filing date: 2017-12-13
Publication date: 2019-05-09
Also published as: KR102022289B1; KR20190048156A

Abstract

The present invention relates to a polar coordinate modulation apparatus and a polar coordinate modulation method. The polar coordinate modulation apparatus comprises: a quadrature amplitude modulation mapping unit for generating symbols having the same Euclidean distance; and a constellation rearranging unit for rearranging a constellation of the symbols generated from the quadrature amplitude modulation mapping unit, wherein the symbols of the constellation rearranged by the constellation rearranging unit are modulated by separating size and phase information. The modulation method comprises the steps of: mapping data to symbols by quadrature amplitude modulation (QAM); rearranging a constellation of the mapped symbols; and separating size and phase information in the rearranged symbols.

Description

Polar Coordination Modulation Method and Modulator, Wireless Optical Communication System Using It

The present invention relates to a polar modulation method and modulator, and a wireless optical communication system using the same. More particularly, the present invention relates to a polar coordinate modulation method and a modulator between symbols in a magnitude-phase plane, and a wireless optical communication system using the same.

Wireless LAN technology using visible broadband (400 ~ 700nm) in indoor LAN has been researched and developed due to advantages such as physical security and freedom of frequency interference.

In particular, light emitting diodes (LEDs) have long life, low power consumption and high quality of light, and can be used as a transmitter of data transmission, since LEDs can be controlled on / off and dimming.

The communication scheme to which this technique is applied is well known as Optical Wireless Communication (OWC).

In particular, since each transmit LED of the spatially multiplexed OWC multiple-input multiple-output (MIMO) transmission / reception system increases the transmission amount by transmitting different data without additional transmission power or frequency allocation, As a method of satisfying the requirements.

On the other hand, in the case of wireless optical communication, because of the characteristics of light, it is impossible to apply a modulation method using phase accuracy to an actual system. Therefore, wireless optical communication should use a structure that transmits and receives signals by intensity modulation and direct reception (IM / DD) method. (Fig. 1) Since the IM / DD system modulates a signal only by amplitude, a signal is transmitted only by real number information, not a signal including imaginary information. Therefore, a usable modulation method is limited. Therefore, in order to increase the transmission capacity, there has been a restriction that a modulation method that simultaneously uses amplitude and phase information can not be used.

Because of the way that only real numbers can be transmitted, various types of modulation schemes have been proposed for the modulation including the imaginary phase information, and M-QAM / OFDM modulation schemes such as those disclosed in FIG. 2 have been widely used. However, when OFDM is used, there is a problem in that the amount of computation is increased and there is a restriction in use.

To solve this problem, a Polar Coordinate Modulation (PCM) method of converting a signal into a polar coordinate and modulating a signal using polar coordinate information has been proposed. However, since PCM has a problem of poor reception performance, it has a small computational complexity and is easy to implement, but has a problem in practical use.

An object of the present invention is to propose a method and an apparatus for improving reception performance in a wireless optical communication system using modulation of a PCM scheme.

Another object of the present invention is to provide a wireless optical communication system having a low complexity and capable of high bit rate transmission.

According to an aspect of the present invention, there is provided a polar coordinate modulation method for a symbol having the same Euclidean distance in an embodiment, comprising the steps of: symbol-mapping data by quadrature amplitude modulation (QAM); Rearranging the constellation of the mapped symbol; And separating the size and phase information of the rearranged symbol.

The step of rearranging the constellation of the polar coordinate modulation method of a symbol having the same Euclidian distance in one embodiment includes the steps of obtaining a basis vector of size N, generating an NxN property store using the basis vector And transforming the constellation point into a complex plane and rearranging constellation diagrams.

The polar modulation method of a symbol having the same Euclidean distance in one embodiment includes the steps of generating an NxN property store using the basis vector and changing the generated property store to a complex plane to rearrange the constellation And determining whether or not the QAM is a square QAM.

According to an aspect of the present invention, there is provided a polar modulation apparatus comprising: a quadrature amplitude modulation mapping unit for generating a symbol having the same Euclidean distance; A constellation rearranging unit for rearranging the constellation of the symbol generated from the quadrature amplitude modulation mapping unit; And the constellation rearrangement unit rearranges the symbols of the constellation diagram by modulating the size and phase information.

In one embodiment, the constellation rearranging unit of the polar coordinate modulating apparatus further includes a basis vector generating unit.

According to an aspect of the present invention, there is provided a wireless optical communication system including: a quadrature amplitude modulation mapping unit for generating symbols having the same Euclidean distance; A constellation rearranging unit for rearranging the constellation of the symbol generated from the quadrature amplitude modulation mapping unit; A polar coordinate modulating unit for modulating a symbol of constellation rearranged by the constellation rearranging unit by separating magnitude and phase information; A plurality of light sources for dividing a signal modulated by the polar modulation unit into a magnitude and a phase to transmit a corresponding intensity of light; And a receiver for receiving the light of the plurality of emitted light sources and receiving the data.

In one embodiment, the receiver of the wireless optical communication system includes a plurality of photodiodes for receiving light of the transmitted plurality of light sources, a channel estimator for estimating a channel using light received from the plurality of photodiodes, A MIMO interference cancellation signal detector for detecting a symbol based on the determined channel, a polarity demodulator for demodulating polar coordinates of the determined symbol to generate a quadrature amplitude modulated symbol, a quadrature amplitude modulation for demapping the quadrature amplitude modulated symbol, And a demapper portion.

The effect of the present invention is that it is possible to configure the Euclidean distance to be the same without the nonlinear characteristic even if the PCM modulation is used.

Also, the size of the symbol is smaller than that of the conventional PCM method, and the power consumption can be reduced.

Figure 1 Concept of IM / DD

2 shows a conventional M-QAM / OFDM modulation apparatus

Fig. 3 Representation of signals in the complex plane

Figure 4 illustrates the performance of the present invention and models the geometric channel between the transmitting LED and the receiving PD of the system for verification.

5 is a block diagram of an OWC-MIMO system using a general PCM modulation scheme.

FIG. 6 shows a simulation result in which a complex plane M-QAM signal is mapped to a magnitude-phase plane using PCM

Figure 7 Simulation of intersymbol interference in AWGN environment after SNR = 40dB after polar modulation

Figure 8 Simulation of intersymbol interference in AWGN environment with SNR = 55dB after polar modulation

Figure 9 is a configuration diagram of the OWC-MIMO system using the modulated PCM modulation

10 and 11 The constellation rearrangement method algorithm of the present invention

FIG. 12 is a schematic diagram illustrating a general PCM and a proposed PCM in the case of 4QAM, 16QAM, and 64QAM.

Fig. 13 Performance of bit error rate (BER) of polar modulation scheme with coordinate modulation and constellation rearrangement

Figure 14 Results for PCM energy gain for QAM size

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terms first, second, A, B, etc. may be used to describe various elements, but the elements should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. And / or < / RTI > includes any combination of a plurality of related listed items or any of a plurality of related listed items.

It is to be understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, . On the other hand, when an element is referred to as being "directly connected" or "directly connected" to another element, it should be understood that there are no other elements in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. It is to be understood that the term "comprises" or "having" in the present application does not preclude the presence or addition of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification .

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, a polar modulation method and a modulation apparatus according to the present invention and a wireless optical communication system using the same will be described in detail with reference to the accompanying drawings.

When a signal is modulated with QAM, the symbol of the modulated signal has a complex number form. The shape of the complex number may be expressed in the form of s = a + jb as shown in FIG. 3, but it may be defined as a shape having a predetermined size and angle.

4 is a diagram for modeling a geometric channel between a transmitting LED and a receiving PD of a system for explaining and verifying the performance of the present invention.

The system modeling considered OWC channels consisting of NT transmit LEDs and NR receive PDs.

5 is a configuration diagram of an OWC-MIMO system that uses a modulation of a general PCM scheme.

The system includes a transmitting unit 100 and a receiving unit 200.

The transmitter 100 maps the input DATA to a symbol of a predetermined quadrature amplitude modulation type in a quadrature amplitude modulation mapper (QAM mapper) 110. [ The symbols mapped in the quadrature amplitude modulation mapper 110 may have a constellation having a square shape or a constellation having a non-square shape. The mapped symbol is obtained by obtaining the size and phase information of the symbol using the size information extracting unit 121 and the phase information extracting unit 122 in the polar coordinate modulating unit 120, (141 to 144).

The transmitted signal is received by a plurality of photodiodes 211 to 214 through a predetermined channel H, the channel estimating unit 220 estimates a channel using the received signal, The MIMO interference cancellation signal detector 230 removes the interference signal and determines a symbol of the received signal. The determined symbol finally decodes the data through the polar coordinate demodulator 240 and the quadrature amplitude demodulator 250. [

FIG. 6 is a simulation result in which a complex plane M-QAM signal is mapped to a magnitude-phase plane using PCM. In the case of QPSK, the Euclidean distance between symbols in the magnitude-phase plane is constant even if the plane is changed. However, as shown in FIG. 6, since a general polar coordinate modulation scheme does not have a linearity when a QAM symbol is converted into a polar coordinate symbol, when the plane is changed in 16QAM and 64QAM, the Euclidean distance between symbols is constant not. In this size-phase plane, the Euclidean distance between polar coordinate symbols is non-uniform, resulting in BER performance degradation.

FIGS. 7 and 8 show the result of simulating the intersymbol interference phenomenon in the AWGN environment after SNR = 40 dB and 55 dB after the polar modulation, and it is confirmed that the interference increases in a specific symbol due to a uniform Euclidean distance, The required SNR is also high in order to obtain a desired BER for inter-interference.

The present invention proposes a modified polar coordinate modulation method and apparatus for eliminating features with nonuniform Euclidean distance by applying a PCM to change the symbol from a complex plane to a magnitude-phase plane.

9 is a configuration diagram of an OWC-MIMO system using the modified PCM modulation of the present invention.

The system of the present invention includes a constellation rearrangement (CR) 160, whose position is located between the quadrature amplitude modulation mapper 110 and the polar coordinate modulator 120. When the quadrature amplitude modulation mapper 110 generates a symbol having a predetermined constellation, the constellation rearranging unit 160 rearranges the constellation. Using the rearranged constellation diagram, the polar coordinate modulation unit extracts the size and phase information of the symbol, modulates the signal, and transmits the signal using the plurality of LEDs 141 to 144. The constellation rearranging unit 160 may be constituted by a single apparatus together with the polar coordinate modulating unit 120. The constellation rearranging unit 160 may be configured as shown in FIG.

The constellation rearranging unit 160 rearranges the constellation diagrams according to the algorithm disclosed in Figs.

Cal (x) is a function to obtain the size of the base vector for reconstructing the constellation, and N is the result of the function satisfying x = N ² . P _{k, l} means the constellation point, and round (x) is a function that rounds x.

The method of rearranging the constellation is to use the number of syllable points included in the constellation (

Calculating a size (N) of a basis vector for constellation reconstruction, generating a basis vector (vec), generating an NxN property store using the vector, Changing the store to a complex plane and rearranging the constellation.

The step of rearranging the constellation based on the generated basis vector is divided into the case of the square QAM and the case of the non-square QAM, and the case of the case of the square QAM

, There is no need for additional steps, but for non-square QAM (

)

In this order, the steps of removing and reconstructing the constellation are performed.

The step of generating the basis vectors may be computed as a function of N such as that shown in Fig.

In order to understand the step of rearranging the constellation, the constellation rearrangement process for the square QAM will be described based on the square 16-QAM in FIG. 11 as follows.

The input of the CR function is the magnitude of the required constellation

, And the output is a newly reordered set of 16-QAM property stores.

cal (16) function is used to calculate the size value 4 of the basis vector for generating a new constellation, and as a result, a base vector vec having a size of 4 is generated. The plane of the generated basis vector is the polar coordinate magnitude-phase plane.

The maximum value of the phase of the polar modulation symbol is 2pi, and round (2pi) = 6, which is within the range not exceeding the maximum value, is set to max, and then evenly distributed by 2N and then the constellation coordinates, Value. For example, a basis vector of size 4 is vec = {6/8, 18/8, 30/8, 42/8}.

Completes the constellation using the basis vector vec and transforms the generated constellation point into a complex plane. The C _QAM generated after the transformation is 16 in size and is a set of homogeneous complex planar constellations for polar modulation.

Based on the rearranged property store set, the polar modulation unit 120 performs PCM modulation.

12 is a constellation diagram in which 4QAM, 16QAM, and 64QAM are performed in a general PCM and a proposed PCM.

12 (a) has a non-uniform Euclidian distance, as described above, when a symbol having a constellation shown in FIG. 12 (a) is converted to an amplitude-phase plane by a general PCM. 12 (b) can be obtained by rearranging the constellation proposed in the present invention by the constellation having the same constellation as that of FIG. 12. Although the Euclidean distance between symbols on the complex plane is not the same, - In terms of the phase plane, it has a uniform Euclidean distance (Fig. 12 (d)).

Simulation was performed to verify the performance of the polar modulation method and apparatus using the proposed constellation rearrangement.

In the simulation environment, four LEDs and a PD are used as a transmitting end and a receiving end respectively, and QPSK, 16QAM, 64QAM modulation and polar modulation are used for modulation. It is assumed that the receiver of the MIMO channel is aware of the value of the MIMO channel, and Zero Forcing (ZF) detection is applied to remove interference from the multiplexed MIMO stream. The following table summarizes the simulation environment.

FIG. 13 compares the bit error rate (BER) performance of the polar modulation scheme using the coordinate modulation scheme and the constellation rearrangement in 4QAM, 16QAM, and 64QAM. Compared with the general polar modulation method, the BER performance is shown to be about 5dB for 4QAM, about 8dB for 16QAM, and about 9dB for 64QAM in polar modulation schemes using constellation rearrangement. It can be seen that, in a general polar coordinate modulation scheme, as the number of stores increases, the number of interference areas increases, which means that the number of symbols affected by the interference increases and the BER performance decreases. For this reason, as the degree of modulation of QAM increases, the performance of the polar modulation method applied with CR is further improved.

14 shows the results of the PCM energy gain for the QAM size for measuring the power consumption efficiency. If the energy gain is 0dB or more, the power consumption efficiency is good. If the energy gain is 0dB or less, the power consumption efficiency is bad. It can be confirmed that the performance is improved since 16QAM is used. This is because, when the proposed polar modulation is performed, the average symbol size of the polar modulation symbols becomes smaller than that of a general polar modulation.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Therefore, the spirit of the present invention should not be construed as being limited to the above-described embodiments, and all of the equivalents or equivalents of the claims, as well as the following claims, I will say.

Claims

In a polar coordinate modulation method of a symbol having the same Euclidean distance,

Performing symbol mapping on the data by quadrature amplitude modulation (QAM);

Rearranging the constellation of the mapped symbol;

Separating the rearranged symbols from the magnitude and phase information

And a polar coordinate modulation method.
The method according to claim 1,

The step of rearranging the constellation includes:

Obtaining a basis vector of size N

Generating an NxN property store using the basis vector;

And transforming the constellation point to a complex plane to rearrange the constellation.
3. The method of claim 2,

Further comprising the step of determining whether or not the square QAM exists between the step of generating the NxN property store using the basis vector and the step of rearranging the constellation by changing the generated property point to the complex plane Polar coordinate modulation method.
In a polar coordinate modulation apparatus,

A quadrature amplitude modulation mapping unit for generating a symbol having the same Euclidean distance;

A constellation rearranging unit for rearranging the constellation of the symbol generated from the quadrature amplitude modulation mapping unit;

Wherein the constellation rearrangement unit modulates symbols of constellation rearranged by the constellation rearranging unit by separating size and phase information from each other

Polar modulation device.
5. The method of claim 4,

Wherein the constellation rearranging unit further comprises a basis vector generating unit.
In a wireless optical communication system,

A quadrature amplitude modulation mapping unit for generating a symbol having the same Euclidean distance;

A constellation rearranging unit for rearranging the constellation of the symbol generated from the quadrature amplitude modulation mapping unit;

A polar coordinate modulating unit for modulating a symbol of constellation rearranged by the constellation rearranging unit by separating magnitude and phase information;

A plurality of light sources for dividing a signal modulated by the polar modulation unit into a magnitude and a phase to transmit a corresponding intensity of light;

And a receiver for receiving light of the plurality of transmitted light sources and receiving data.
The method of claim 6, wherein

The receiver may further comprise:

A plurality of photodiodes for receiving light of the plurality of emitted light sources,

A channel estimator for estimating a channel using light received from the plurality of photodiodes,

A MIMO interference cancellation signal detector for detecting a symbol based on the estimated channel,

A polar coordinate demodulator for demodulating the polar coordinates of the determined symbol to generate a quadrature amplitude modulated symbol,

And a quadrature amplitude modulation demapper section for demapping the quadrature amplitude modulated symbols.