CN104954311A - Method for generating leading signals of power line carrier communication systems on basis of OFDM (orthogonal frequency division multiplexing) modulation - Google Patents

Abstract

The invention discloses a method for generating leading signals of power line carrier communication systems on the basis of OFDM (orthogonal frequency division multiplexing) modulation. The method includes steps of S1, setting characteristic parameters of OFDM symbols; S2, designing a group of long binary pseudo random sequences PN (pseudo noise) <L> with the lengths of NL according to IFFT (inverse fast Fourier transformation) point numbers N; S3, primarily mapping BPSK (binary phase shift keying) symbols of the pseudo random sequences PN<L> to obtain BPSK modulation signals and filling corresponding effective sub-carriers with the BPSK modulation signals; S4, carrying out discrete fast Fourier inverse transformation on the BPSK modulation signals to obtain OFDM basic signals; S5, designing a group of binary short sequences PN<S> with the code lengths of NS; S6, carrying out BPSK modulation on the short sequences PN<S> to obtain short sequence symbols; S7, jointly modulating the OFDM basic signals by the aid of the short sequence symbols to obtain joint modulation signals of NS sections; S8, determining the leading signals according to the joint modulation signals of the NS sections. The characteristic parameters include the IFFT point numbers. The method has the advantage that the method is applicable to complicated multi-path channel environments of power lines.

Description

Based on the power-line carrier communication system targeting signal generation method of OFDM modulation

[technical field]

The present invention relates to digital information transmission technical field, particularly relate to the power-line carrier communication system targeting signal generation method based on OFDM modulation.

[background technology]

Power-line carrier communication is called for short PLC, refers to a kind of communication mode utilizing power line transmission data.The operating frequency of power line carrier communication is much larger than power frequency component 50Hz or 60Hz of electrical network, such high-frequency signal can transmit with electric energy simultaneously in power line, therefore, can make full use of existing low voltage power distribution network infrastructure, without the need to any wiring, be a kind of " No New Wires " technology, save resource, also save manpower simultaneously, saved cable investment, accelerate the network opening time.Particularly power-line carrier communication system can be applicable to automatic data logging (AMR), long-range throwing/field such as incision pass, energy/load management, equipment monitor and alarm for power-off, greatly can improve the safety and reliability of electrical network, improve service quality and economic benefit.

But, power line channel transmission environment very severe, exist Various Complex noise jamming, with being coupled of other business frequency band signals, severe frequency selectivity and time variation fast, these all cause the great obstruction to signal transmitting, need effective technology to ensure the effective robust of Signal transmissions.

OFDM (Orthogonal Frequency Division Multiplexing, be abbreviated as OFDM) technology has data transmission capabilities, the efficiently availability of frequency spectrum and anti-multipath jamming, opposing frequency selective fading channels ability at a high speed, is therefore well suited for being applied to field of power line communication.At present, G.9955 the narrow-band power line carrier communication standard formulated in the world, comprise ERDF G3 standard, PRIME standard and ITU, is all the narrow-band power line carrier communication technology standards supporting OFDM modulation.But external technical standard is also not suitable for China's national situation, therefore, need to develop corresponding ofdm communication system for the power line environment of China specially.

Because narrow-band power line carrier communication system belongs to the communication system of burst, it requires very strict to net synchronization capability, the error any time or in frequency, all can cause very large loss to the performance of power-line carrier communication system.Therefore, design good targeting signal, be convenient to transmitting terminal and receiving terminal obtains synchronously fast and accurately, significant to power-line carrier communication system.

In prior art, usually utilize the OFDM data of two or more repetition to design targeting signal, but transmitting terminal and receiving terminal are difficult to reach accurate synchronization, and noise immunity is lower.

In addition, country variant and area require it is different to the communications band of power line carrier communication, the CENELEC in Europe specifies A channel band 10kHz to 95kHz, B channel band 95kHz to 120kHz, C channel band 120kHz to 140kHz, the Federal Communications Commission FCC of the U.S. specifies to adopt 10kHz to 490kHz, and China's regulation power line carrier communication frequency range is 3kHz ~ 500kHz.Current targeting signal is difficult to adapt to the requirement of multiple countries and regions to frequency range.

[summary of the invention]

Because the correlation of the OFDM data simply repeated is not strong, cause the synchronous accuracy of generated targeting signal not high, noise immunity is not strong yet.In power-line carrier communication system, power line channel is the channel of very severe, and various interference noise is complicated, and impedance transformation is large, and decay is comparatively large, there is the problems such as serious interference, severe impedance mismatch and multipath fading be serious.Therefore, the targeting signal that the said method of prior art generates makes the requirement that transmitting terminal and receiving terminal accurate synchronization and noise immunity are strong when cannot meet application.

In order to overcome the deficiencies in the prior art, the invention provides a kind of power-line carrier communication system targeting signal generation method based on OFDM modulation, improving synchronization accuracy and noise robustness.

Based on the power-line carrier communication system targeting signal generation method of OFDM modulation, comprise the steps:

S1, arranges the characterisitic parameter of OFDM symbol, and described characterisitic parameter comprises IFFT and counts;

S2, according to described IFFT points N, designs a group leader binary pseudo-random sequence PN _l, described pseudo random sequence PN _llength be NL;

S3, to described pseudo random sequence PN _lcarry out a BPSK sign map, obtain BPSK modulation signal, and described BPSK modulation signal is filled on corresponding effective subcarrier;

S4, does discrete fast Fourier inverse transformation to described BPSK modulation signal, obtains OFDM baseband signal;

S5, designs one group of binary system short data records PN _s, described short data records PN _scode length be NS;

S6, to described short data records PN _sdo BPSK modulation, obtain short data records symbol;

S7, utilizes described short data records symbol to carry out combined modulation to described OFDM baseband signal, obtains the combined modulation signal of NS section;

S8, according to the combined modulation signal determination targeting signal of described NS section, described targeting signal comprises described combined modulation signal.

In one embodiment, also comprise the steps: in step S8

Intercept prefix signal and suffix signal, before being positioned over the first paragraph of described combined modulation signal respectively and after final stage; Wherein, described prefix signal is taken at the first paragraph of described combined modulation signal, and described suffix signal is taken at the final stage of described combined modulation signal;

Using the entirety of described prefix signal, combined modulation signal and suffix signal as described targeting signal.

In one embodiment, described prefix signal is taken at the data of RI backmost of the first paragraph of described combined modulation signal, and described suffix signal is taken at a foremost RI data of the final stage of combined modulation signal.

In one embodiment, described step S2 comprises the steps:

S21, described pseudo random sequence PN _llength NL meet:

$\mathrm{NL}\&GreaterEqual;\frac{N}{2}-1;$

S22, chooses described pseudo random sequence PN _lm ₁rank primitive polynomial G ₁(x), wherein m ₁meet:

$\mathrm{NL}=2^{m_1}-1;$

S23, according to the m chosen ₁rank primitive polynomial G ₁x (), arranges initial phase value, generating length is the pseudo random sequence PN of NL _l.

In one embodiment, described step S3 comprises the steps:

S31, by described pseudo random sequence PN _lbe mapped to BPSK modulation signal X _l:

X _L(k)＝[1-2×PN _L(k)]+j[1-2×PN _L(k)]；

Wherein, X _lk () represents a kth BPSK modulation signal X _l, PN _lk () represents pseudo random sequence PN _lkth value;

S32, by described BPSK modulation signal X _lk () is filled on OFDM subcarrier one by one;

Wherein, X _bk () represents a kth OFDM subcarrier.

In one embodiment, by sequence number be on subcarrier be set to invalid subcarrier.

In one embodiment, described step S4 comprises the steps:

Again real part is got to the result that described BPSK modulation signal does inverse fast fourier transform, obtains OFDM baseband signal:

$x_b\left(n\right)=\mathrm{real}\left\{\mathrm{IFFT}\right[X_b\left(k\right)\left]\right\}=\mathrm{read}\left\{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{X}_b\left(k\right)e^{j\frac{2\mathrm{\&pi;nk}}{N}}\right\},0\&le;n\&le;N-1;$

Wherein, x _bn () represents OFDM baseband signal, IFFT [] represents inverse fast fourier transform handling function, and real [] expression gets real part handling function to complex signal.

In one embodiment, described step S6 comprises the steps:

In the following way to described short data records PN _sdo BPSK modulation:

x _s(i)＝[1-2×PN _S(i)],0≤i≤NS；

Wherein, x _si () represents i-th symbol in short data records symbol, PN _si () represents short data records PN _sin i-th value.

In one embodiment, combined modulation signal S (n) of described NS section is:

$\begin{array}{cc}S\left(n\right)=\underset{i=0}{\overset{\mathrm{NS}-1}{\mathrm{\&Sigma;}}}{x}_s\left(i\right)\&CenterDot;R_N(n-i\&CenterDot;N)\&CenterDot;x_b(n-i\&CenterDot;N),& 0\&le;n\&le;(N\&CenterDot;\mathrm{NS}-1);\end{array}$

Wherein, R _n[] represents the rectangular window function based on length N:

In one embodiment, also comprise the steps:

Carry out windowing process by raised cosine window to described targeting signal, wherein, windowed function win (n) is:

$\mathrm{win}\left(n\right)=\left\{\begin{array}{cc}0.5+0.5\cos (\mathrm{\&pi;}+\frac{n\&CenterDot;\mathrm{\&pi;}}{\mathrm{RI}}),& 0\&le;n\&le;\mathrm{RI}-1\\ 1.0,& \mathrm{RI}\&le;n\&le;N\&CenterDot;\mathrm{NS}-1+\mathrm{RI}\\ 0.5+0.5\cos \left[\frac{(n-N\&CenterDot;\mathrm{NS}-\mathrm{RI})\&CenterDot;\mathrm{\&pi;}}{\mathrm{RI}}\right],& N\&CenterDot;\mathrm{NS}+\mathrm{RI}\&le;n\&le;N\&CenterDot;\mathrm{NS}-1+2\&CenterDot;\mathrm{RI}\end{array}\right..$

The present invention's beneficial effect is compared with prior art:

One aspect of the present invention makes full use of the good autocorrelation performance of pseudo random sequence, makes the targeting signal generated also have good correlation, namely can be and synchronously provide accurate and reliable timing position, to adapt to complicated power line multi-path channel environment.

On the other hand, make full use of the flexibility of the effective sub-carrier configuration of OFDM, the band limits of targeting signal is facilitated adjustable, the requirement to power line carrier frequency range with satisfied adaptation country variant and area.

Meanwhile, the subcarrier-modulated of targeting signal makes full use of the stochastic behaviour of pseudo random sequence, makes generated targeting signal have the feature of low peak average ratio.

In addition, by the windowing process to whole targeting signal, reduce further out-of-band radiation power, ensure the good Electro Magnetic Compatibility of system.

[accompanying drawing explanation]

Fig. 1 is that a kind of targeting signal that the specific embodiment of the invention provides generates method flow diagram;

Fig. 2 is a kind of embodiment of effective subcarrier and virtual subnet distribution of carriers in ofdm system;

Fig. 3 is long pseudo-random sequence PN in the specific embodiment of the invention _lgenerating structure figure;

Fig. 4 be in the specific embodiment of the invention generate targeting signal structural representation;

Fig. 5 is the targeting signal waveform schematic diagram generated in the specific embodiment of the invention;

Fig. 6 be in the specific embodiment of the invention generate the spectrum diagram of targeting signal;

Fig. 7 is the correlation peak schematic diagram of targeting signal under the state of signal-to-noise of-3dB that in the specific embodiment of the invention, receiving terminal receives.

[embodiment]

Below the preferred embodiment of invention is described in further detail.

As shown in Fig. 1 to 7, a kind of power-line carrier communication system targeting signal generation method based on OFDM modulation of embodiment, for generating the targeting signal of OFDM power-line carrier communication system.

Step S1: the OFDM symbol characterisitic parameter arranging system, comprises working band, subcarrier spacing and IFFT and counts.

First, the OFDM symbol characterisitic parameter of define system, shown in table specific as follows:

Table 1 OFDM narrow-band power line carrier communication system parameter

Index	Value
		Operating frequency (kHz)	250
IFFT points N	512
		Working band (kHz)	41.992～88.867
Subcarrier spacing Δ f	488.28125Hz

Wherein, operating frequency is total frequency range that all effective subcarriers and invalid subcarrier occupy.

Then, based on working band and subcarrier spacing, effective total number of sub-carriers (N of real work is calculated _v=97) and corresponding effective subcarrier sequence number from 86 ~ 182.Therefore, as shown in Figure 2, in Fig. 2, W1 represents effective subcarrier, and W2 represents invalid subcarrier in the distribution of its subcarrier.

Step S2: count according to IFFT, designs group leader's binary pseudo-random sequence, is called long sequence PN _l, length is NL.

First, be 512 according to IFFT points N, determine the area requirement of the length NL of binary pseudo-random sequence, namely

$\mathrm{NL}\&GreaterEqual;\frac{N}{2}-1$

Then, based on long sequence PN _llength requirement, i.e. NL>=255, choose the m of described long pseudo-random sequence ₁rank primitive polynomial G ₁(x), wherein m ₁meet:

$\mathrm{NL}=2^{m_1}-1,$ I.e. m ₁=8

Then, according to the 8 rank primitive polynomial G chosen ₁(x)=x ⁸+ x ⁴+ x ³+ x ²+ 1, the rational initial phase value of optimal design-aside is 10101011b, generates the described long sequence PN that length is NL=255 _l, its generating structure as shown in Figure 3;

Step S3: to long sequence PN _lcarry out BPSK sign map, obtain its modulation signal and be filled on corresponding effective subcarrier;

First, by described long sequence PN _lbe mapped to BPSK modulation signal X _l, wherein mapping ruler is:

X _L(k)＝[1-2×PN _L(k)]+j[1-2×PN _L(k)]；

Wherein, X _l(k) kth BPSK modulation signal, PN _lk () represents pseudo random sequence PN _lkth value;

Secondly, by BPSK modulation signal X _lk () is filled into IFFT one by one to count is 512, subcarrier spacing is Δ f and effectively subcarrier number is on the OFDM modulation carrier wave of 97, namely;

Preferably, in order to realize the transmission of base band real number signal on power line, the subcarrier on 256≤k≤511 is all set to invalid subcarrier.

Step S4: discrete fast Fourier inverse transformation (IFFT) is done to the modulation signal after mapping, obtains OFDM baseband signal.

Result modulation signal being done to inverse fast fourier transform gets real part again, obtains OFDM baseband signal, that is:

$x_b\left(n\right)=\mathrm{real}\left\{\mathrm{IFFT}\right[X_b\left(k\right)\left]\right\}=\mathrm{read}\left\{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{X}_b\left(k\right)e^{j\frac{2\mathrm{\&pi;nk}}{N}}\right\},0\&le;n\&le;N-1;$

Wherein, x _bn () represents OFDM baseband signal.IFFT [] represents inverse fast fourier transform handling function.Real [] expression gets real part handling function to complex signal.

Step S5: introduce other one group of short binary pseudo-random sequence or Barker code or their truncated code, be referred to as short data records PN _s, code length is NS;

Due to short data records PN _sbe that therefore its Design of length will take into account net synchronization capability and efficiency of transmission usually in order to carry out entirety modulation to whole OFDM baseband signal, its code length of design is between 10 ~ 20 usually.In the preferred embodiment, the Barker code with excellent correlated performance of NS=13bit is chosen as short data records, namely

PN _S＝[1,1,1,1,1,0,0,1],。1,0,1,0,1

Step S6: to short data records PN _sdo BPSK modulation, obtain short data records symbol;

Short data records PN _sdoing BPSK modulation is positive negatively-modulated in order to realize whole OFDM baseband signal, and therefore, its BPSK modulating rule is:

x _s(i)＝[1-2×PN _S(i)],0≤i≤NS；

Wherein, X _lk () represents a kth BPSK modulation signal X _l, PN _lk () represents pseudo random sequence PN _lkth value.

By above formula, realize binary system short data records from " 0 " to+1 value and " 1 " to the sign map of-1 value, obtain corresponding short data records symbol.

Step S7: utilize short data records symbol to carry out combined modulation to OFDM baseband signal, obtains NS section combined modulation signal;

Utilize short data records symbol to carry out combined modulation to OFDM baseband signal, the combined modulation signal that total length is NNS can be obtained, that is:

$\begin{array}{cc}S\left(n\right)=\underset{i=0}{\overset{\mathrm{NS}-1}{\mathrm{\&Sigma;}}}{x}_s\left(i\right)\&CenterDot;R_N(n-i\&CenterDot;N)\&CenterDot;x_b(n-i\&CenterDot;N),& 0\&le;n\&le;(N\&CenterDot;\mathrm{NS}-1).\end{array}$

Wherein, R _n[] represents the rectangular window function based on length N, namely

So far, can according to the combined modulation signal determination targeting signal of described NS section, using combined modulation signal as targeting signal.But the spectral band due to this combined modulation signal such as to harass outward at the poor-performing, also needs the further process of step S8 to S9, could improve correlated performance further.

Step S8: intercept prefix signal and suffix signal, is positioned over the foremost and backmost of combined modulation signal respectively;

Described prefix signal is taken at the data of RI backmost of the 1st section (sequence number i equals 0) of combined modulation signal, and suffix signal is taken at a foremost RI data of the NS-1 section (that is final stage, sequence number i equals [NS-1]) of combined modulation signal.Preferably, arranging RI value is 124.Its implementation is modulated shown in schematic diagram as the targeting signal of Fig. 4, T _rIrepresent the length of prefix signal and suffix signal.

Step S9: carry out windowing process to prefix signal and suffix signal, obtains the prefix signal after using windowing and suffix signal and combined modulation signal as the final targeting signal of system.

In order to the spectral band reducing system is further harassed outward, carry out windowing process by design raised cosine window to targeting signal, the final targeting signal waveform obtained as shown in Figure 5.Concrete windowed function is expressed as:

$\mathrm{win}\left(n\right)=\left\{\begin{array}{cc}0.5+0.5\cos (\mathrm{\&pi;}+\frac{n\&CenterDot;\mathrm{\&pi;}}{\mathrm{RI}}),& 0\&le;n\&le;\mathrm{RI}-1\\ 1.0,& \mathrm{RI}\&le;n\&le;N\&CenterDot;\mathrm{NS}-1+\mathrm{RI}\\ 0.5+0.5\cos \left[\frac{(n-N\&CenterDot;\mathrm{NS}-\mathrm{RI})\&CenterDot;\mathrm{\&pi;}}{\mathrm{RI}}\right],& N\&CenterDot;\mathrm{NS}+\mathrm{RI}\&le;n\&le;N\&CenterDot;\mathrm{NS}-1+2\&CenterDot;\mathrm{RI}\end{array}\right.$

As can be seen from the final targeting signal spectrum diagram of Fig. 6, the signal spectrum generated is at 41.992 ~ 88.867kHz, and attenuation outside a channel can reach more than 30dB, can meet common EMC Requirements well.

And be illustrated in figure 7 under the state of signal-to-noise of-3dB, the correlation peak schematic diagram of the targeting signal that receiving terminal receives.As can be seen from Figure 7, even if under the severe communication environment of-3dB, still clearly, show that targeting signal noise immunity is very strong, performance is fine for the correlation peak of receiving terminal targeting signal.

Simultaneously, as can be seen from described method, by simple modification working band, any frequency range of system works in the special frequency range of the power line carrier of 40kHz ~ 500kHz can be guaranteed, thus China Power line carrier-specific frequency range can be supported well, and European CENELEC A/B/C/D frequency range and extended frequency band.

Above content is in conjunction with concrete preferred implementation further description made for the present invention, can not assert that specific embodiment of the invention is confined to these explanations.For general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, some simple deduction or replace can also be made, all should be considered as belonging to the scope of patent protection that the present invention is determined by submitted to claims.

Claims (10)

1., based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that, comprise the steps:

S1, arranges the characterisitic parameter of OFDM symbol, and described characterisitic parameter comprises IFFT and counts;

S2, according to described IFFT points N, designs a group leader binary pseudo-random sequence PN _l, described pseudo random sequence PN _llength be NL;

S3, to described pseudo random sequence PN _lcarry out a BPSK sign map, obtain BPSK modulation signal, and described BPSK modulation signal is filled on corresponding effective subcarrier;

S4, does discrete fast Fourier inverse transformation to described BPSK modulation signal, obtains OFDM baseband signal;

S5, designs one group of binary system short data records PN _s, described short data records PN _scode length be NS;

S6, to described short data records PN _sdo BPSK modulation, obtain short data records symbol;

S7, utilizes described short data records symbol to carry out combined modulation to described OFDM baseband signal, obtains the combined modulation signal of NS section;

S8, according to the combined modulation signal determination targeting signal of described NS section, described targeting signal comprises described combined modulation signal.

2., as claimed in claim 1 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that, also comprise the steps: in step S8

Intercept prefix signal and suffix signal, before being positioned over the first paragraph of described combined modulation signal respectively and after final stage; Wherein, described prefix signal is taken at the first paragraph of described combined modulation signal, and described suffix signal is taken at the final stage of described combined modulation signal;

Using the entirety of described prefix signal, combined modulation signal and suffix signal as described targeting signal.

3., as claimed in claim 2 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that,

Described prefix signal is taken at the data of RI backmost of the first paragraph of described combined modulation signal, and described suffix signal is taken at a foremost RI data of the final stage of combined modulation signal.

4., as claimed in claim 1 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that, described step S2 comprises the steps:

S21, described pseudo random sequence PN _llength NL meet:

$\mathrm{NL}\&GreaterEqual;\frac{N}{2}-1;$

S22, chooses described pseudo random sequence PN _lm ₁rank primitive polynomial G ₁(x), wherein m ₁meet:

$\mathrm{NL}=2^{m_1}-1;$

S23, according to the m chosen ₁rank primitive polynomial G ₁x (), arranges initial phase value, generating length is the pseudo random sequence PN of NL _l.

5., as claimed in claim 4 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that, described step S3 comprises the steps:

S31, by described pseudo random sequence PN _lbe mapped to BPSK modulation signal X _l:

X _L(k)＝[1-2×PN _L(k)]+j[1-2×PN _L(k)]；

Wherein, X _lk () represents a kth BPSK modulation signal X _l, PN _lk () represents pseudo random sequence PN _lkth value;

S32, by described BPSK modulation signal X _lk () is filled on OFDM subcarrier one by one;

Wherein, X _bk () represents a kth OFDM subcarrier.

6., as claimed in claim 5 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that,

By sequence number be on subcarrier be set to invalid subcarrier.

7., as claimed in claim 6 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that, described step S4 comprises the steps:

Again real part is got to the result that described BPSK modulation signal does inverse fast fourier transform, obtains OFDM baseband signal:

$x_b\left(n\right)=\mathrm{real}\left\{\mathrm{IFFT}\right[X_b\left(k\right)\left]\right\}=\mathrm{real}\left\{\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\&Sigma;}}}{X}_b\left(k\right)e^{j\frac{2\mathrm{\&pi;nk}}{N}}\right\},0\&le;n\&le;N-1;$

Wherein, x _bn () represents OFDM baseband signal, IFFT [] represents inverse fast fourier transform handling function, and real [] expression gets real part handling function to complex signal.

8., as claimed in claim 7 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that, described step S6 comprises the steps:

In the following way to described short data records PN _sdo BPSK modulation:

x _s(i)＝[1-2×PN _S(i)],≤0i≤NS；

Wherein, x _si () represents i-th symbol in short data records symbol, PN _si () represents short data records PN _sin i-th value.

9., as claimed in claim 8 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that, combined modulation signal S (n) of described NS section is:

$S\left(n\right)=\underset{i=0}{\overset{\mathrm{NS}-1}{\mathrm{\&Sigma;}}}{x}_s\left(i\right)\&CenterDot;R_N(n-i\&CenterDot;N)\&CenterDot;x_b(n-i\&CenterDot;N),0\&le;n\&le;(N\&CenterDot;\mathrm{NS}-1);$

Wherein, R _n[] represents the rectangular window function based on length N:

10., as claimed in claim 3 based on the power-line carrier communication system targeting signal generation method of OFDM modulation, it is characterized in that, also comprise the steps:

Carry out windowing process by raised cosine window to described targeting signal, wherein, windowed function win (n) is:

$\mathrm{win}\left(n\right)=\left\{\begin{array}{cc}0.5+0.5\cos (\mathrm{\&pi;}+\frac{n\&CenterDot;\mathrm{\&pi;}}{\mathrm{RI}}),& 0\&le;n\&le;\mathrm{RI}-1\\ 1.0,& \mathrm{RI}\&le;n\&le;N\&CenterDot;\mathrm{NS}-1+\mathrm{RI}\\ 0.5+0.5\cos \left[\frac{(n-N\&CenterDot;\mathrm{NS}-\mathrm{RI})\&CenterDot;\mathrm{\&pi;}}{\mathrm{RI}}\right],& N\&CenterDot;\mathrm{NS}+\mathrm{RI}\&le;n\&le;N\&CenterDot;\mathrm{NS}-1+2\&CenterDot;\mathrm{RI}\end{array}\right..$