CN100583866C - Multi-carrier spread spectrum communication method based on discrete Fourier transform sequence - Google Patents

Abstract

The invention relates to one multi-load frequency expansion communication method based on discrete Fourier exchange sequence, which is characterized by the following: the system transmission data uses one special sequence expansion by use of one certain discrete exchange on multiple load wave; due to this cross property, the user data can be divided and sent to ensure data transmission rate and frequency spectrum efficiency.

Description

A kind of multi-carrier spread spectrum communication method based on discrete Fourier transform sequence

Technical field

The present invention relates to a kind of multi-carrier spread spectrum communication method, belong to the broad band multicarrier transmission technique field of wireless communication technology based on discrete Fourier transform sequence.

Background technology

OFDM (OFDM) is as a kind of transmission technology of broad band multicarrier efficiently, it is advantageous that higher band efficiency, outstanding to ability of anti-multipath and be suitable for high speed data transfer.Its core concept is with low-rate signal, uses different carrier frequencies, carries out parallel transmission in same broad-band channel, thereby improves transmission rate.Because the message transmission rate on the single sub-carrier greatly reduces, and the OFDM character added Cyclic Prefix as protection at interval, makes the OFDM transmission to disturb and frequency selective fading anti-multipath effectively.But, because the subcarrier of OFDM only could effectively transmit data under the situation of carrier wave strict orthogonal, the inter-carrier interference that frequency shift (FS) causes (ICI) causes systematic function sharply to descend, and especially can't resist sizable Doppler frequency expansion in the high-speed mobile environment.At present, the carrier wave interference OFDM (CI-OFDM) that has proposed has improved the performance of OFDM under frequency-selective channel to a great extent, and has reduced peak-to-average power ratio significantly.Yet traditional CI sign indicating number still can't resist the Doppler frequency expansion effectively.

At present, in based on the system of OFDM, existed certain methods can estimate and eliminate ICI to a certain extent.Yet the problem of these methods is:

(1) system complexity height;

(2) availability of frequency spectrum reduces.

Based on above background, at the Doppler frequency scaling problem in the high-speed mobile environment, we have proposed a kind of availability of frequency spectrum that neither reduces, the multi-carrier spread spectrum communication method based on discrete Fourier transform sequence that is easy to simultaneously realize.The data of the present invention transmission are with a kind of specific for transmission simultaneously on a plurality of subcarriers behind the sequence spread spectrum of discrete Fourier transform (DFT), because the orthogonality of this frequency expansion sequence, user data can be distinguished and be sent simultaneously, has guaranteed the transfer rate and the spectrum efficiency of data.In addition, utilize the odd even reverse characteristic of this sequence, eliminate the Doppler frequency expansion that brings owing to the portable terminal high-speed motion significantly and disturb.

Summary of the invention

The objective of the invention is to propose a kind of multi-carrier spread spectrum communication method, provide the ability of high transfer of data, satisfy the demand that system high-speed communicates in moving the portable terminal of high-speed motion based on discrete Fourier transform sequence.It is characterized in that,, adopted the transmission means of OFDM for high data rate is provided; For the multipath that can reduce in the transmission disturbs, adopted along the mode of subcarrier direction spread spectrum; In order to resist time selective fading and the Doppler frequency expansion interference that high-speed mobile is brought effectively, adopted the reverse characteristic of frequency expansion sequence odd even.

The transmitting terminal based on the multi-carrier spread spectrum communication method of discrete Fourier transform sequence that the present invention proposes may further comprise the steps:

(1) transmitting terminal is according to customer requirements, and producing length is the frequency expansion sequence of M, and wherein M is any positive even numbers;

(2) digital baseband signal is carried out symbol-modulated, to produce modulation signal;

(3) above-mentioned modulation signal is entered the serial to parallel conversion module, to produce M parallel symbol;

(4) frequency expansion sequence that produces according to transmitting terminal, with each symbol with corresponding frequency expansion sequence spread spectrum after addition:

(5) the parallel symbol of the M after the above-mentioned addition is carried out the zero padding computing, mends N-M zero, promptly at the two ends of M data symbol each to mend (N-M)/2 zero, M≤N=2 wherein ⁿ, n is any positive integer.When M=N, the chip of all frequency expansion sequences sends on N way carrier wave; When M＜N, all frequency expansion sequences only send on M way carrier wave, and all the other subcarriers are not for passing the zero carrier of data;

(6) N the data symbol that obtains carried out the IDFT computing, and export after adding Cyclic Prefix;

(7) output signal of above-mentioned steps (6) is carried out digital to analog conversion, obtain analog signal;

(8) produce carrier frequency by the transmitting terminal frequency synthesizer, and above-mentioned analog signal is modulated on this carrier frequency.

The receiving terminal based on the multi-carrier spread spectrum communication method of discrete Fourier transform sequence that the present invention proposes may further comprise the steps:

(1) reception antenna receives above-mentioned signal, and is undertaken obtaining corresponding baseband signal after the demodulation by the output signal of receiving terminal frequency synthesizer;

(2) above-mentioned signal obtains digital signal corresponding through after the analog to digital conversion;

(3) above-mentioned digital signal is removed Cyclic Prefix;

(4) N the data symbol that obtains carried out exporting after the DFT computing;

(5) to the computing of zero-suppressing of above-mentioned output symbol, remove N-M zero, promptly at the two ends of N data symbol each to remove (N-M)/2 zero;

(6) enter the matched filter of each frequency expansion sequence, behind parallel serial conversion, export again through merging after the coupling;

(7) above-mentioned serial output signal is carried out obtaining user data behind the symbol demodulation.

Generation length of the present invention is the method for the frequency expansion sequence of M, may further comprise the steps;

(1) generation M * M discrete Fourier matrix is as follows:

Wherein $W_M=\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{M}\right)$ , rewrite matrix F _MCapable vector be $A_i=({\mathrm{\&alpha;}}_0^{\left(i\right)},{\mathrm{\&alpha;}}_1^{\left(i\right)},...,{\mathrm{\&alpha;}}_{M..1}^{\left(i\right)});$

(2) in matrix F _MIn since first row, odd column is constant, even column oppositely (promptly multiply by-1) obtains matrix S, its capable vector representation is $S_i=({\mathrm{\&beta;}}_0^{\left(i\right)},{\mathrm{\&beta;}}_1^{\left(i\right)},...,{\mathrm{\&beta;}}_{M-2}^{\left(i\right)},{\mathrm{\&beta;}}_{M-1}^{\left(i\right)})=({\mathrm{\&alpha;}}_0^{\left(i\right)},-{\mathrm{\&alpha;}}_1^{\left(i\right)},...,{\mathrm{\&alpha;}}_{M-2}^{\left(i\right)},-{\mathrm{\&alpha;}}_{M-1}^{\left(i\right)}),$ Promptly ${\mathrm{\&beta;}}_k^{\left(i\right)}={(-1)}^k{\mathrm{\&alpha;}}_k^{\left(i\right)},0\&le;k\&le;(M-1).$ The vectorial S of row _i, 0≤i≤(M-1) is the frequency expansion sequence of asking required for the present invention.

According to this method, the invention provides a kind of multi-carrier spread spectrum communication method based on discrete Fourier transform sequence, system hardware and software is simple in structure, implementation complexity is very low, is easy to realize in the software systems of the hardware system of programmable logic array (FPGA) at the scene or digital signal processor (DSP).

Show by the checking of software emulation and real system: do not reduce under the situation of data transmission rate simultaneously not increasing system complexity, the present invention has played very big inhibitory action to Doppler frequency expansion, makes the supported rate travel of system compare with traditional CI-OFDM system to double above.

Description of drawings

Fig. 1 is the system bandwidth schematic diagram.

Fig. 2 is each subcarrier transmission schematic diagram data (M=N) of system.

Fig. 3 is system's each subcarrier transmission schematic diagram data (M＜N).

Fig. 4 is a sender baseband architecture schematic diagram.

Fig. 5 is a receiver baseband architecture schematic diagram.

Fig. 6 is the performance comparison curves of the inventive method and traditional C I-OFDM method:

(a) be the performance curve that adopts equal gain combining (EGC);

(b) be to adopt least mean-square error to merge the performance curve of (MMSEC);

dop＝0.2，CI-OFDM

dop＝0.2，new?system

dop＝0.1，Cl-OF?DM

dop＝0.1，new?system

dop＝0.02，CI-OFDM

dop＝0.02，new?sy?st?em。

Embodiment

Embodiment is a received signal with the mobile communication signal, and its characteristics and implementation are described in detail in detail.

In order to explain concrete structure of the present invention and function, at first sketch ofdm system.Ofdm system sends user data through walking abreast behind the serial to parallel conversion on the plurality of sub carrier wave of a frequency band (being labeled as W), the parallel data cell that sends is the OFDM character, and subcarrier bandwidth is Δ F, and the OFDM character data is partly long to be T _d, the Cyclic Prefix of adding is long to be T _a, the character total length is designated as T.At receiving terminal, the demodulation of OFDM character becomes the user data of reception behind parallel serial conversion.

The present invention is based on a kind of multi-carrier spread spectrum communication method of OFDM.Be located at N way carrier wave f is arranged in the frequency band that bandwidth is W ₀, f ₁..., f _N-1, satisfy N * Δ F=W.In addition, the frequency expansion sequence S that M length is arranged is M _i, 0≤i≤(M-1)≤(N-1) }, and $S_i=({\mathrm{\&beta;}}_0^{\left(i\right)},{\mathrm{\&beta;}}_1^{\left(i\right)},...,{\mathrm{\&beta;}}_{M-1}^{\left(i\right)}),$ β _k ⁽ⁱ⁾Be plural number.At transmitting terminal, user data d _i, 0≤i≤(M-1), with frequency expansion sequence S _iOn M way carrier wave, send after multiplying each other, promptly at subcarrier f _kLast transmission d _iβ _k ⁽ⁱ⁾At receiving terminal, the signal parallel on each way carrier wave enters S _iMatched filter $S_i^{*}=({\mathrm{\&beta;}}_0^{{\left(i\right)}^{*}},{\mathrm{\&beta;}}_1^{{\left(i\right)}^{*}},...,{\mathrm{\&beta;}}_{M-1}^{{\left(i\right)}^{*}}),$ Dateout d _i, 0≤i≤(M-1).

Referring to Fig. 1, be system bandwidth schematic diagram of the present invention.System bandwidth is W, is divided into N subcarrier, and each subcarrier width is Δ F, and the carrier frequency of each sub-band is f ₀, f ₁..., f _N-1

Referring to Fig. 2, be each subcarrier transmission schematic diagram data of system of the present invention.The situation of having represented M=N among the figure.According to the symbol definition of front, at subcarrier f ₀, f ₁..., f _N-1Distinguish transmitting user data d above _iChip d _iβ _k ⁽ⁱ⁾, 0≤k≤(N-1).

Referring to Fig. 3, be each subcarrier transmission schematic diagram data of system of the present invention.The situation of having represented M＜N among the figure.According to the symbol definition of front, at subcarrier f _(N-M)/2, f _(N-M)/2+1..., f _(N+M)/2-1Distinguish transmitting user data d above _iChip d _iβ _k ⁽ⁱ⁾, 0≤k≤(M-1).

Following emphasis is told about frequency expansion sequence $S_i=({\mathrm{\&beta;}}_0^{\left(i\right)},{\mathrm{\&beta;}}_1^{\left(i\right)},...,{\mathrm{\&beta;}}_{M-1}^{\left(i\right)})$ Building method, embodiment is with M=6, N=8 describes.

At first, generation 6 * 6 discrete Fourier matrixes are as follows:

${\mathrm{<figure-callout\; id="6"\; label="F"\; filenames="C2007100638240014H1.png"\; state="\{\{state\}\}">F</figure-callout>}}_6={\left[W_6^{i-k}\right]}_{\underset{0\&le;k\&le;5}{0\&le;i\&le;5}}\left[\begin{array}{cccccc}1& 1& 1& 1& 1& 1\\ 1& e^{j\frac{\mathrm{\&pi;}}{3}}& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& -1& -e^{j\frac{\mathrm{\&pi;}}{3}}& -e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}\\ 1& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& {-e}^{j\frac{\mathrm{\&pi;}}{3}}& 1& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& {-e}^{j\frac{\mathrm{\&pi;}}{3}}\\ 1& -1& 1& -1& 1& -1\\ 1& {-e}^{j\frac{\mathrm{\&pi;}}{3}}& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& 1& -e^{j\frac{\mathrm{\&pi;}}{3}}& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}\\ 1& {-e}^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& -e^{j\frac{\mathrm{\&pi;}}{3}}& -1& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& e^{j\frac{\mathrm{\&pi;}}{3}}\end{array}\right]$

Then, in matrix F ₆In since first row, odd column is constant, even column reverse (promptly multiply by-1) obtains matrix S, is expressed as:

$S=\left[\begin{array}{cccccc}1& -1& 1& -1& 1& -1\\ 1& {-e}^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& 1& -e^{j\frac{\mathrm{\&pi;}}{3}}& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}\\ 1& {-e}^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& {-e}^{j\frac{\mathrm{\&pi;}}{3}}& -1& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& e^{j\frac{\mathrm{\&pi;}}{3}}\\ 1& 1& 1& 1& 1& 1\\ 1& e^{j\frac{\mathrm{\&pi;}}{3}}& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& -1& {-e}^{j\frac{\mathrm{\&pi;}}{3}}& -e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}\\ 1& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& {-e}^{j\frac{\mathrm{\&pi;}}{3}}& 1& e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{3}}& -e^{j\frac{\mathrm{\&pi;}}{3}}\end{array}\right]$

The vectorial S of row _i, 0≤i≤5 are the frequency expansion sequence of asking required for the present invention.

Referring to Fig. 4, be sender baseband architecture schematic diagram of the present invention, may further comprise the steps:

(1) transmitting terminal is according to customer requirements, and generation length is 6 frequency expansion sequence S _i, 0≤i≤5, as mentioned above;

(2) digital baseband signal is carried out symbol-modulated, the modulation signal D=(d that exports in proper order with generation ₀, d ₁, d ₂, d ₃, d ₄, d ₅);

(3) above-mentioned modulation signal is entered the serial to parallel conversion module, to produce 6 parallel symbol d _i, i=0,1 ... 5;

(4) the frequency expansion sequence S that produces according to transmitting terminal _i, 0≤i≤5 obtain each symbol after the addition after with corresponding frequency expansion sequence spread spectrum $G=(\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_0^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_1^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_2^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_3^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_4^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_5^{\left(i\right)});$

(5) 6 parallel symbols after the above-mentioned addition are carried out the zero padding computing, obtain after mending 2 zero, $H=(0,\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_0^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_1^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_2^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_3^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_4^{\left(i\right)},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_5^{\left(i\right)},0);$

(6) 8 data symbols that obtain are carried out exporting Y=HF ' after the IDFT computing ₈, F ' ₈It is 8 * 8 discrete contrary Fourier matrix;

(7) baseband digital signal that obtains is added the laggard line number modular transformation of Cyclic Prefix and be sent to the radio frequency transmission then.

Referring to Fig. 5, be receiver baseband architecture schematic diagram of the present invention, may further comprise the steps:

(1) receiving terminal received RF signal, and by down-conversion, analog to digital conversion obtains corresponding baseband digital signal Y '=α Y+I behind the removal Cyclic Prefix _Noise, wherein α has represented subcarrier decline and frequency shift (FS), I _NoiseBe noise;

(2) modulation symbol that obtains is carried out exporting H '=Y ' F after the DFT computing ₈, F wherein ₈It is 8 * 8 discrete Fourier matrix;

(3) to the computing of zero-suppressing of above-mentioned output signal, remove 2 zero, after the two ends of 8 data symbols are respectively removed 1 zero, obtain G '=(g ' ₀, g ' ₁, g ' ₂, g ' ₃, g ' ₄, g ' ₅)=(h ' ₁, h ' ₂, h ' ₃, h ' ₄, h ' ₅, h ' ₆);

(4) enter the matched filter of each frequency expansion sequence, merge after the coupling and obtain $D^{\&prime;}=(\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_0^{{\left(i\right)}^{*}},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_1^{{\left(i\right)}^{*}},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_2^{{\left(i\right)}^{*}},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_3^{{\left(i\right)}^{*}},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_4^{{\left(i\right)}^{*}},\underset{i=0}{\overset{5}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_5^{{\left(i\right)}^{*}}),$ ω wherein _iDetermine by the merging mode;

(5) the gained signal is carried out parallel serial conversion, carry out symbol demodulation then and just obtain user data.

Enumerate a design example below, so that further specify the function of system.

System adopts 128 way carrier waves, and every way carrier bandwidths is 10KHz, and overall system bandwidth is 1.28MHz.Frequency expansion sequence when the frequency expansion sequence that adopts is M=100 has 100.The system data transmission takies No. 14 to the 113rd work song carrier wave, and No. 0 to No. 13, and be zero carrier to the 127th work song allocation of carriers No. 14, so that serve as protection at interval.

More than be of the present invention specifying.

The present invention has passed through the checking of computer simulation fully, and with M=32, N=32 describes.

At first produce frequency expansion sequence $S_i=({\mathrm{\&beta;}}_0^{\left(i\right)},{\mathrm{\&beta;}}_1^{\left(i\right)},...,{\mathrm{\&beta;}}_{31}^{\left(i\right)}),$ Method is as follows:

(1) produces 32 * 32 discrete Fourier matrixes $F_{32}={\left[W_{32}^{i\&CenterDot;k}\right]}_{0\&le;i,k\&le;31};$

(2) in matrix F ₃₂In since first row, odd column is constant, even column oppositely (promptly multiply by-1) obtains matrix S, its capable vector representation is $S_i=({\mathrm{\&beta;}}_0^{\left(i\right)},{\mathrm{\&beta;}}_1^{\left(i\right)},...,{\mathrm{\&beta;}}_{30}^{\left(i\right)},{\mathrm{\&beta;}}_{31}^{\left(i\right)})=({\mathrm{\&alpha;}}_0^{\left(i\right)},-{\mathrm{\&alpha;}}_1^{\left(i\right)},...,{\mathrm{\&alpha;}}^{30},-{\mathrm{\&alpha;}}_{31}^{\left(i\right)}),$ Promptly ${\mathrm{\&beta;}}_k^{\left(i\right)}={(-1)}^k{\mathrm{\&alpha;}}_k^{\left(i\right)},0\&le;k\&le;31.$ The vectorial S of row _i, 0≤i≤31 are the frequency expansion sequence of asking required for the present invention.

Sender may further comprise the steps:

(1) transmitting terminal is according to customer requirements, and generation length is 32 frequency expansion sequence S _i, 0≤i≤31, as mentioned above;

(2) digital baseband signal is carried out symbol-modulated, the modulation signal D=(d that exports in proper order with generation ₀, d ₁..., d ₃₁);

(3) above-mentioned modulation signal is entered the serial to parallel conversion module, to produce 32 parallel symbol d _i, i=0,1 ..., 31;

(4) the frequency expansion sequence S that produces according to transmitting terminal _i, 0≤i≤31 obtain each symbol after the addition after with corresponding frequency expansion sequence spread spectrum $G=(\underset{i=0}{\overset{31}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_0^{\left(i\right)},\underset{i=0}{\overset{31}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_1^{\left(i\right)},...,\underset{i=0}{\overset{31}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_{31}^{\left(i\right)});$

(5) 32 data symbols that obtain are carried out exporting Y=GF after the IDFT computing ₃₂'=(y ₀, y ₁..., y ₃₁), F ₃₂' be 32 * 32 discrete contrary Fourier matrix;

(6) will obtain Q=(q behind four Cyclic Prefix of baseband digital signal adding that obtain ₀, q ₁..., q ₃₅)=(y ₂₈..., y ₃₁, y ₀..., y ₃₁), carry out digital to analog conversion then and be sent to the radio frequency transmission then.Receiver may further comprise the steps:

(1) receiving terminal received RF signal, and by down-conversion, analog to digital conversion obtain corresponding baseband digital signal Q '=α Q+N=(q ' ₀, q ' ₁..., q ' ₃₅), wherein α has represented subcarrier decline and frequency shift (FS), N is a noise:

(2) remove obtain behind four Cyclic Prefix Y '=(y ' ₀, y ' ₁..., y ' ₃₁)=(q ' ₄, q ' ₅..., q ' ₃₅);

(3) modulation symbol that obtains is carried out exporting G '=Y ' F after the DFT computing ₃₂=(g ' ₀, g ' ₁..., g ' ₃₁), F wherein ₃₂It is 32 * 32 discrete Fourier matrix;

(4) data that obtain are entered the matched filter of each frequency expansion sequence, merge after the coupling and obtain $D^{\&prime;}=(\underset{i=0}{\overset{31}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_0^{{\left(i\right)}^{*}},\underset{i=0}{\overset{31}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_1^{{\left(i\right)}^{*}},...,\underset{i=0}{\overset{31}{\mathrm{\&Sigma;}}}{\mathrm{\&omega;}}_i{g}_i^{\&prime;}{\mathrm{\&beta;}}_{31}^{{\left(i\right)}^{*}}),$ ω wherein _iDetermine by the merging mode;

(5) the gained signal is carried out parallel serial conversion, carry out symbol demodulation then and just obtain user data.

Fig. 6 provided that the present invention under the multipath Rayleigh channel condition proposes based on the multi-carrier spread spectrum communication method of discrete Fourier transform sequence and the performance comparison curves of traditional C I-OFDM, that (a) adopt is equal gain combining (EGC), and what (b) adopt is that least mean-square error merges (MMSEC).Wherein, system signal noise ratio is defined as $\mathrm{SNR}={\mathrm{\&sigma;}}_s^2/{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="C2007100638240012H2.png"\; state="\{\{state\}\}">n</figure-callout>}}^2,$ That is the ratio of the average power of transmitting terminal time-domain signal and white Gaussian noise average power.Normalization carrier wave frequency deviation (with the ratio of subcarrier spacing) dop value is respectively: 0.2,0.1 and 0.02.Can see that the normalization carrier wave frequency deviation equals to adopt communication system of the present invention at 0.2 o'clock, its error code is flat to be equaled to adopt the error code of CI-OFDM system flat roughly the same at 0.1 o'clock with the normalization carrier wave frequency deviation.Proof thus adopts the multi-carrier spread spectrum communication system the present invention is based on discrete Fourier transform sequence to make the supported rate travel of system compare with traditional CI-OFDM system can to double above.

Claims (1)

1. the multi-carrier spread spectrum communication method based on discrete Fourier transform (DFT) is characterized in that, described method realizes according to the following steps successively:

At transmitting terminal, carry out according to the following steps with digital integrated circuit chip:

It is the frequency expansion sequence of M that step (1) frequency expansion sequence produces circuit generation length, and M is any positive even numbers;

Step (1.1) produces following M * M discrete Fourier matrix F _M:

Wherein $W_M=\exp \left(j\frac{2\mathrm{\&pi;}}{M}\right),$ Ik represents the capable k row of i, and i is the line number of M * Metzler matrix, and 0≤i≤(M-1), k is the columns of M * Metzler matrix, 0≤k≤(M-1),

Rewrite matrix F again _MCapable vector be $A_i=({\mathrm{\&alpha;}}_0^{\left(i\right)},{\mathrm{\&alpha;}}_1^{\left(i\right)},...,{\mathrm{\&alpha;}}_{M-1}^{\left(i\right)});$

Step (1.2) is asked frequency expansion sequence:

In described matrix F _MIn, since first row, odd column is constant, and even column multiply by-1, and is promptly reverse, obtains matrix S, the vectorial S of its row _iFor: $S_i=({\mathrm{\&beta;}}_0^{\left(i\right)},{\mathrm{\&beta;}}_1^{\left(i\right)},...,{\mathrm{\&beta;}}_{M-1}^{\left(i\right)})=({\mathrm{\&alpha;}}_0^{\left(i\right)},-{\mathrm{\&alpha;}}_1^{\left(i\right)},...,-{\mathrm{\&alpha;}}_{M-1}^{\left(i\right)}),$ Wherein ${\mathrm{\&beta;}}_k^{\left(i\right)}={(-1)}^k{\mathrm{\&alpha;}}_k^{\left(i\right)},$ 0≤k≤M-1, the vectorial S of row _i, 0≤i≤M-1 is required frequency expansion sequence;

Step (2) modulation circuit carries out symbol-modulated to digital baseband signal, produces modulation signal D=(d ₀, d ₁..., d _M-1);

Serial to parallel conversion circuit of the described modulation signal of step (3) input produces M parallel symbol, wherein, described M quantitatively with the equal in length of frequency expansion sequence described in the step (1);

The frequency expansion sequence that step (4) produces according to step (1), each symbol in the described parallel symbol of step (3) with corresponding frequency expansion sequence spread spectrum after addition, that is: phase adduction output behind the frequency expansion sequence spread spectrum that each symbol that is produced by step (3) is produced with step (1.2), the M of output parallel symbol is

$G=(\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_0^{\left(i\right)},\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_1^{\left(i\right)},...,\underset{i=0}{\overset{M-1}{\mathrm{\&Sigma;}}}{d}_i{\mathrm{\&beta;}}_{M-1}^{\left(i\right)});$

The M of step (5) after to an above-mentioned addition parallel symbol carries out the zero padding computing, mends N-M zero, promptly at the two ends of M data symbol each to mend (N-M)/2 zero, M≤N=2 wherein ⁿ, n is the M≤N=2 that satisfies condition arbitrarily ⁿPositive integer, when M=N, the chip of all frequency expansion sequences sends on N way carrier wave; When M＜N, the chip of all frequency expansion sequences only sends on M way carrier wave, and all the other subcarriers are not for passing the zero carrier of data;

Step (6) is carried out the IDFT computing to N the data symbol that step (5) obtains, and by exporting behind figure place of setting and the form adding Cyclic Prefix;

Step (7) is carried out digital to analog conversion to the signal that step (6) obtains, and obtains analog signal;

Step (8) produces carrier frequency by frequency synthesizer, and the analog signal that step (7) is obtained is modulated on this carrier frequency;

At receiving terminal, carry out according to the following steps with another digital integrated circuit chip:

The signal of step (1 ') reception antenna receiving step (8) emission, and obtain corresponding baseband signal behind the output signal demodulation by frequency synthesizer;

The signal of step (2 ') step (1 ') obtains digital signal corresponding after analog to digital conversion;

Step (3 ') is removed Cyclic Prefix to the digital signal of step (2 ') output;

Step (4 ') carries out exporting after the DFT computing to N the data symbol that step (3 ') obtains;

Step (5 ') is to the computing of zero-suppressing of the output symbol of step (4 '), removes N-M zero, promptly at the two ends of N data symbol each to remove (N-M)/2 zero;

Step (6 ') step (5 ') obtain zero-suppress after symbol import the matched filter of each frequency expansion sequence, behind parallel serial conversion, export again through merging after the coupling;

Step (7 ') carries out obtaining user data behind the symbol demodulation to the serial output signal of step (6 ').

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