CN108809885A - A kind of novel orthogonal space modulator approach based on indoor visible light communication - Google Patents

Abstract

The invention discloses a novel spatial quadrature modulation method based on indoor visible light communication. The steps are: based on the SQM scheme, according to the maximum likelihood estimation criterion, and under the condition of not considering the serial number of the activated LED, the demodulator is given a pair of sending signals. The estimated expression of BER; using PEP and UB technology, give the expression of SER under SQM mode; according to the expression of SER, give the expression of BER under the way of SQM; according to the expression of BER, define the upper limit expression of BER; establish Based on the SQM optimization problem of BER upper limit minimization, the optimization objective function and corresponding constraint conditions are given, so that the NSQM method based on the number of LEDs at the sending end is 4; based on the NSQM method, a 4-ary mapping signal set is designed, and an 8-ary system is given. The design process of the system mapping signal set is given, and the design idea of the hexadecimal mapping signal set is given. Finally, the 64 system mapping signal set is the superposition of 4‑NSQM and 16‑NSQM. This method improves the transmission reliability of the visible light signal by optimizing the mapping method of the transmitted light signal.

Description

A Novel Spatial Quadrature Modulation Method Based on Indoor Visible Light Communication

technical field

The present invention relates to a modulation method of a visible light signal in an indoor visible light communication scene, in particular to a novel spatial orthogonal modulation method based on indoor visible light communication.

Background technique

Visible light communication (VLC) has attracted much attention because of its significant advantages in energy efficiency and indoor wireless communication. The light signal is directly detected using a photodiode (PD) detector. However, it is worth noting that: based on the unipolar characteristics of the signal in the VLC system, there is a constraint problem that the signal adopts intensity modulation/direct detection. Therefore, in order to overcome the above-mentioned challenges and realize efficient and reliable information transmission, technologies such as spatial modulation (SM), multi-ary quadrature amplitude modulation (M-QAM) and spatial quadrature modulation (SQM) have become the mainstays of VLC modulation technology. important research content.

The basic principle of SQM technology is: convert the M-QAM signal to meet the requirements of the VLC system for the "real and positive" characteristics of the signal, and use the sending signal to activate the sending LED serial number, and send the information data through the LED; the receiving end is based on the maximum likelihood Criterion In the process of estimating the transmitted optical signal, it is necessary to consider the estimation of the serial number of the LED activated by the transmitting end. Therefore, in the indoor visible light communication scenario, based on SQM, how to optimize the mapping method of the transmitted optical signal to achieve efficient and reliable visible light signal transmission has always been the research focus of experts and scholars.

In order to obtain an efficient and reliable modulation method suitable for indoor visible light communication, this case came into being.

Contents of the invention

The purpose of the present invention is to provide a novel spatial quadrature modulation method based on indoor visible light communication, which improves the transmission reliability of visible light signals by optimizing the mapping method of transmitted optical signals.

In order to achieve the above object, the solution of the present invention is:

A novel spatial quadrature modulation method based on indoor visible light communication, comprising the following steps:

Step A, based on the SQM scheme, according to the maximum likelihood estimation criterion, without considering the serial number of the activated LED, give the estimated expression of the demodulator for the transmitted signal;

Step B, using PEP and UB technology, give the SER expression under the SQM mode;

Step C, according to the SER expression, by analyzing the characteristics of the sent signal, the BER expression under the SQM mode is given;

Step D, according to the expression of BER, define the upper limit expression of BER;

Step E, establishing an SQM optimization problem based on the minimization of the upper limit of the BER, providing an optimization objective function and corresponding constraint conditions, thereby obtaining an NSQM method based on the number of LEDs at the sending end N _t =4;

Step F, designing a 4-ary mapping signal set based on the NSQM method;

Step G, based on the NSQM method, the design process of the octal mapping signal set is given;

In step H, based on the NSQM method, the design idea of the hexadecimal mapping signal set is given;

In step I, based on the NSQM mode, the 64-ary mapping signal set is the superposition of 4-NSQM and 16-NSQM.

The concrete steps of above-mentioned step B are:

In step B1, using PEP and UB technology, the initial SER expression is given as: Among them, P(s _m →s _k ) means: when the transmitted symbol is s _m , the judgment is the PEP corresponding to the symbol s _k ; the number of modulation symbols is M;

Step B2, under the condition of visible light channel characteristic H, there is: P(s _m →s _k |H)=P(D(y,s _k )>D(y,s _m )|H), where D(y, s _m ) is the Euclidean distance between y and s _m , defined as: yl represents the optical signal detected by the l-th PD, N _r represents the number of PDs at the receiving end, and H _l represents the l-th row of H;

Step B3, get the SER expression:

in ^σ2 is the variance of Gaussian noise in the visible light channel, ρ is the average transmitted optical power of each symbol, and γ is the responsivity of the photodetector.

The concrete steps of above-mentioned step F are:

Step F1, according to the SQM method, the 4-ary signal set of NSQM is defined as:

Step F2, without considering the influence of H _l , give all possible forms of Euclidean distance:

Step F3, according to the optimization objective function and corresponding constraint conditions, in the case of α=1 and β=0, all possible Euclidean distances after optimization are obtained as:

In step F4, the 4-ary signal set of NSQM is obtained as follows:

The concrete steps of above-mentioned step G are:

In step G1, the octal NSQM signal set is recorded as:

And define η=α/β;

Step G2, without considering the influence of H _l , give all possible Euclidean distances:

This formula is related to η;

In step G3, according to the optimization objective function and the corresponding constraint conditions, the optimization design of the modulation is realized by calculating the optimization factor η _opt .

The concrete steps of above-mentioned step H are:

In step H1, two 4-ary NSQM signal sets are given:

Define η=α/β;

In step H2, the hexadecimal NSQM signal set is: The signal operation is the superposition operation of complex numbers;

Step H3, according to the optimization objective function and the corresponding constraint conditions, by calculating the optimization factor η _opt to realize the optimization design of the modulation.

After adopting the above scheme, the present invention aims at the problem of high signal transmission BER in the existing SQM method in indoor visible light communication. Compared with the existing SQM technology, the present invention provides a method based on The signal estimation expression of the maximum natural criterion, and focus on establishing the optimization problem of minimizing the upper limit of the error based on the SQM method, giving the optimization objective function and constraint conditions, and further designing the signal mapping method of the multi-ary NSQM, which effectively improves the signal transmission The BER performance improves the information transmission quality in the indoor visible light communication scene, and the present invention is applicable to user nodes in the indoor visible light communication.

Description of drawings

Fig. 1 is the BER performance comparison curve figure of 4-NSQM and 8-NSQM proposed by the present invention and existing 4-SQM and 8-SQM;

Fig. 2 is a comparison curve of bit error rate performance between 16-NSQM and 64-NSQM proposed by the present invention and existing 16-SQM and 64-SQM.

Detailed ways

The technical solutions and beneficial effects of the present invention will be described in detail below in conjunction with the accompanying drawings.

The present invention provides a novel spatial quadrature modulation method based on indoor visible light communication, which includes the following steps:

Step A): Based on the existing spatial quadrature modulation (SQM) scheme, according to the maximum likelihood estimation criterion, without considering the serial number of the activated LED, the demodulator is given an estimation expression for the transmitted signal;

Step B): Utilize Paired Error Probability (PEP) and Uniform Bound (UB) technology to give the Symbol Error Rate (SER) expression under the SQM mode;

Step C): According to the SER expression, by analyzing the characteristics of the transmitted signal, the bit error rate (BER) expression under the SQM mode is given;

Step D): according to the expression of BER, define the upper limit expression of BER;

Step E): Establishing an SQM optimization problem based on the minimization of the upper limit of BER, providing the optimization objective function and corresponding constraint conditions, thereby obtaining a novel spatial quadrature modulation (NSQM) method based on the number of LEDs at the sending end N _t =4;

Step F): Under the NSQM mode, design a 4-ary mapping signal set;

Step G): Based on the NSQM method, the design process of the octal mapping signal set is given.

Step H): Based on the NSQM method, the design idea of the hexadecimal mapping signal set is given.

Step I): Based on the NSQM mode, the 64-ary system mapping signal set is the superposition of 4-NSQM and 16-NSQM.

Wherein, the concrete steps of described step B are:

Step B1): Using PEP and UB technology, the initial SER expression is given as:

Among them, P(s _m →s _k ) means: when the transmitted symbol is s _m , the judgment is the PEP corresponding to the symbol s _k ; the number of modulation symbols is M;

Step B2): Under the condition of visible light channel characteristic H, there is: P(s _m →s _k |H)=P(D(y,s _k )>D(y,s _m )|H), where D(y ,s _m ) is the Euclidean distance between y and s _m , defined as: yl represents the optical signal detected by the l-th PD, N _r represents the number of PDs at the receiving end, and H _l represents the l-th row of H;

Step B3): get the SER expression: in ^σ2 is the variance of Gaussian noise in the visible light channel, ρ is the average transmitted optical power of each symbol, and γ is the responsivity of the photodetector.

The concrete steps of described step F are:

Step F1): According to the SQM method, the 4-ary signal set of NSQM is defined as:

Step F2): Without considering the influence of H _l , give all possible forms of Euclidean distance:

Step F3): According to the optimization objective function and corresponding constraint conditions, in the case of α=1 and β=0, all possible Euclidean distances after optimization are:

Step F4): Obtain the 4-ary signal set of NSQM as:

The concrete steps of described step G are:

Step G1): The octal NSQM signal set can be written as:

And define η=α/β;

Step G2): Without considering the influence of H _l , give all possible Euclidean distances:

This formula is related to η;

Step G3): According to the optimization objective function and the corresponding constraint conditions, the optimization design of the modulation can be realized by calculating the optimization factor η _opt .

The concrete steps of described step H are:

Step H1): Two 4-ary NSQM signal sets are given:

Define η=α/β

Step H2): The hexadecimal NSQM signal set is: The signal operation is the superposition operation of complex numbers.

Step H3): According to the optimization objective function and the corresponding constraint conditions, the optimization design of the modulation can be realized by calculating the optimization factor η _opt .

To sum up the above, the present invention is a novel spatial quadrature modulation method based on indoor visible light communication. Aiming at the characteristics of transmission signals in visible light communication, under the condition that the serial number estimation of activated LEDs is omitted, by analyzing the bit error rate performance in the SQM mode, the establishment of The optimization problem of minimizing the upper limit of the error, the optimized objective function and constraints are given, so as to optimize the mapping form of the transmitted signal, and the multi-ary signal mapping form of the NSQM method is given, which improves the bit error rate performance of information transmission . It can be seen from Figure 1 that, under certain simulation parameters, when the bit error rate is 10 ^-4 , the proposed 4-NSQM and 8-NSQM schemes are about 4.5dB and 1.5dB performance gain; as can be seen from Figure 2, under certain simulation parameters, when the bit error rate is 10 ^-5 , the proposed 16-NSQM and 64-NSQM schemes are compared with the existing corresponding SQM schemes. There are performance gains of about 2.3dB and 1.0dB respectively; in addition, it can be obtained from Figure 1 and Figure 2 that: under the condition of high signal-to-noise ratio, the derived error upper limit can be used to accurately describe the corresponding bit error rate performance.

The above embodiments are only to illustrate the technical ideas of the present invention, and can not limit the protection scope of the present invention with this. All technical ideas proposed in accordance with the present invention, any changes made on the basis of technical solutions, all fall within the protection scope of the present invention. Inside.

Claims (5)

1. a kind of novel orthogonal space modulator approach based on indoor visible light communication, it is characterised in that include the following steps：

Step A is based on SQM schemes, is provided under conditions of not considering activated LED serial numbers according to maximal possibility estimation criterion Estimated expression of the demodulator to transmission signal；

Step B provides the SER expression formulas under SQM modes using PEP and UB technologies；

Step C provides the BER expression formulas under SQM modes according to SER expression formulas；

Step D defines the upper limit expression formula of BER according to the expression formula of BER；

Step E establishes the SQM optimization problems minimized based on the BER upper limits, provides optimization object function and corresponding constraints, To obtain being based on transmitting terminal LED number Ns_t=4 NSQM modes；

Step F designs 4 system mapping signal collection based under NSQM modes；

Step G provides the design cycle of 8 system mapping signal collection based under NSQM modes；

Step H provides the mentality of designing of 16 system mapping signal collection based under NSQM modes；

Step I, based under NSQM modes, 64 system mapping signals integrate being superimposed as 4-NSQM and 16-NSQM.

2. a kind of novel orthogonal space modulator approach based on indoor visible light communication as described in claim 1, feature exist In：The step B's comprises the concrete steps that：

Step B1, using PEP and UB technologies, providing initial SER expression formulas is：Wherein P (s_m→s_k) indicate：Transmission symbol is s_mWhen, and it is symbol s to adjudicate_kCorresponding PEP；Modulation symbol number is M；

Step B2 has based under the conditions of visible light channel characteristic H：P(s_m→s_k| H)=P (D (y, s_k)>D(y,s_m) | H), wherein D (y,s_m) it is y and s_mBetween Euclidean distance, be defined as：y_lIndicate the light that first of PD is detected Signal, N_rIndicate the number of receiving terminal PD, H_lIndicate the l rows of H；

Step B3 obtains SER expression formulas：

Whereinσ²For the variance of Gaussian noise in visible light channel, ρ is the average hair of each symbol It is the responsiveness of photoelectric detector to send luminous power, γ.

3. a kind of novel orthogonal space modulator approach based on indoor visible light communication as described in claim 1, feature exist In：The step F's comprises the concrete steps that：

Step F1, according to SQM modes, the 4 binary signal collection of NSQM are defined as：

Step F2 is not considering H_lUnder conditions of influence, all Euclidean distance forms that may be present are provided：

Step F3, it is all after being optimized in α=1 and β=0 according to optimization object function and corresponding constraints Possible Euclidean distance is：

Step F4, the 4 binary signal collection for obtaining NSQM are：

4. a kind of novel orthogonal space modulator approach based on indoor visible light communication as described in claim 1, feature exist In：The step G's comprises the concrete steps that：

Step G1,8 system NSQM signal collection are denoted as：

And define η=α/ β；

Step G2 is not considering H_lUnder conditions of influence, all Euclidean distances that may be present are provided：

The formula is related to η；

Step G3 optimizes factor η according to optimization object function and corresponding constraints by calculating_optRealize the optimization of modulation Design.

5. a kind of novel orthogonal space modulator approach based on indoor visible light communication as described in claim 1, feature exist In：The step H's comprises the concrete steps that：

Step H1 provides two 4 system NSQM signal collection：

Define η=α/β；

Step H2,16 system NSQM signal collection are：Signal operation is the superposition of plural number；

Step H3 optimizes factor η according to optimization object function and corresponding constraints by calculating_optRealize the optimization of modulation Design.