CN102624672B - Based on two conversion orthogonal frequency division multiplexing communication methods of piecemeal - Google Patents

Abstract

Based on two conversion orthogonal frequency division multiplexing communication methods of piecemeal, relate to a kind of frequency division multiplexing communication method.A kind of two conversion orthogonal frequency division multiplexing communication methods based on piecemeal considering the problem of height power ratio, frequency shift (FS) sensitivity and time varying channel poor performance that OFDM exists are provided.Digital modulation; Piecemeal FFT process; OFDM modulation converts; OFDM receives inverse transformation; The FFT conversion process of N point; Frequency domain equalization; The IFFT conversion process of piecemeal; Data demodulates.Owing to employing two conversion communication modes of FFT-IFFT, can be equivalent to and single-carrier modulated has been carried out to data symbol.At receiving terminal, in conjunction with frequency domain equalization process, comparatively legacy OFDM communication system, not only there is the advantage of multicarrier system itself, can anti-frequency domain Selective intensity well, and there is the advantage of single-carrier system process, anti-fast time variant performance is strong.

Description

Based on two conversion orthogonal frequency division multiplexing communication methods of piecemeal

Technical field

The present invention relates to a kind of frequency division multiplexing communication method, especially a kind of two conversion OFDM (Double Transform-Orthogonal Frequency Division Multiplexing, DT-OFDM) communication meanss based on piecemeal considering the problem of height power ratio, frequency shift (FS) sensitivity and time varying channel poor performance that OFDM exists.

Background technology

In recent years, OFDM (Orthogonal Frequency Division Multiplexing, OFDM) receives the concern of people as a kind of high-speed multi-carrier transmission technology effectively resisting ISI.At digital audio broadcasting (Digital AudioBroadcasting, DAB), high definition TV (High-definition Television, HDTV), WLAN (wireless local area network) (WirelessLocal Area Network, etc. WLAN) all to have succeeded in system application, in the mobile communication system after 3G, also will become core technology.But in OFDM conversion, due to the superposition of multi-carrier signal, there is higher peak-to-average force ratio, this just improves requirement to the linearity of amplifier in transmitter, when not meeting, probably brings the distortion of signal, thus cause the orthogonality of interchannel to be destroyed, make the penalty of system.In order to address this problem, someone proposes single carrier frequency domain equalization (Signal Carrier-Frequency Domain Equalization, SC-FDE) method, owing to there is not the problem of multiple carrier wave, therefore its peak-to-average force ratio also will be better than the OFDM modulation method of multiple independent sub-carriers superposition greatly.Meanwhile, its anti-carrier wave frequency deviation and the performance of phase noise are also better than OFDM modulation, but SC-FDE reduces expansion in relative time delay unlike OFDM by parallel transmission, and thus anti-fading ability is also just not as OFDM.After the analysis to OFDM and SC-FDE modulator approach, researcher proposes a kind of communication New System of two conversion OFDM (DT-OFDM) based on piecemeal, DT-OFDM is effective combination of traditional ofdm system and SC-FDE system, data symbol to be sent is first carried out the FFT conversion of piecemeal, after obtaining the data vector of frequency domain, IFFT conversion is being carried out in piecemeal integration, this two mapping modes based on FFT-IFFT, effectively can reduce peak-to-average force ratio, simultaneously, also multicarrier and single carrier advantage is separately remained, the choosing of anti-frequency and fast time variant strong.

Chinese patent CN101080892 discloses a kind of OFDM communication apparatus and orthogonal frequency division multiplexing communication method, to the most suitable repeat number of transmission data setting, thus can improve error rate characteristic, improve communication quality.In the apparatus, repeat number determining means (153), based on the quality information exported from quality information extraction unit (152), determines necessary repeat number.System bits repeat number determining means (154), based on the repeat number notified from repeat number determining means (153), determines most suitable repeat number to system bits.Parity check bit repeat number determining means (155) is also the same.Repetitive (103-1,103-2), according to the instruction from system bits repeat number determining means (154) and parity check bit repeat number determining means (155), repeats each bit.

Chinese patent CN102067637A discloses a kind of base station, travelling carriage and frequency division multiplexing communication method, base station comprises: the Multiplexing Unit being configured to frequency division multiplexing the 1st channel and the 2nd channel, wherein the 1st channel is for sending the 1st data sent multiple travelling carriage, and the 2nd channel is for sending the 2nd data sent a travelling carriage.

Summary of the invention

The object of the present invention is to provide a kind of two conversion OFDM (Double Transform-Orthogonal FrequencyDivision Multiplexing, DT-OFDM) communication meanss based on piecemeal considering the problem of height power ratio, frequency shift (FS) sensitivity and time varying channel poor performance that OFDM exists.

The present invention includes following steps:

1) digital modulation, concrete grammar is: carry out sign map to information source data, obtains data symbol s;

2) piecemeal FFT process, concrete grammar is:

(1) data that will send are carried out sign map and are become s, become (s) by serioparallel exchange _{lM × N}, wherein l is block count, and M is the FFT transform length that piecemeal carries out;

(2) data of each piecemeal are carried out M point FFT and are converted, and obtain the data symbol vector X of frequency domain _k, namely

$X_k=\underset{i=0}{\overset{M-1}{\mathrm{\Σ}}}{s}_i{e}^{-j2\mathrm{\πik}/M},k=\mathrm{0,1},\·\·\·,M-1---\left(1\right)$

(3) carry out N point IFFT after the domain data information that piecemeal process obtains being integrated to convert, complete OFDM modulation;

3) OFDM modulation conversion, concrete grammar is: to step 2) the block data sign integration of gained frequency domain becomes the data vector of N point, and add pilot tone in the data, converted by N point IFFT, the data symbol vector that IFFT transforms to time domain is x _n, namely

$x_n=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{X}_k{e}^{j2\mathrm{\πnk}/N},n=\mathrm{0,1},\·\·\·,N-1---\left(2\right)$

Then add cyclic prefix CP, send after up-sampling, digital to analog conversion and upward frequency conversion process;

4) OFDM receives inverse transformation, and concrete grammar is: carry out down-conversion, analog to digital conversion, down-sampling process first to received signal, after serioparallel exchange, remove cyclic prefix CP, the receiving symbol vector r obtained _k, because there is channel effect, noise and inter-sub-carrier interference, remove the Received signal strength symbolic vector r of Cyclic Prefix _kcan be write as:

$r_k=\underset{i=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{\hat{s}}_{i}h(k-i)+n_k+{\mathrm{ie}}_k,k=\mathrm{0,1},...,N-1---\left(3\right)$

Wherein for the data symbol vector received, h is the time domain parameter of channel, n _kbe average be 0, variance is independent same distribution white Gaussian noise, ie _kfor carrier-in-interference, noise n and channel h impact are to received signal separate;

5) the FFT conversion process of N point, concrete grammar is: the data symbol vector after interference is converted by the FFT of N point, and its conversion process is consistent with transmitting terminal, obtains the data vector of frequency domain namely

${\hat{X}}_k=H_{k,n}{S}_{k,n}+N_{k,n}+I_{k,n}---\left(4\right)$

Wherein H _{k, n}, S _{k, n}, N _{k, n}, I _{k, n}represent the frequency coefficient of kth point corresponding in n symbol;

6) frequency domain equalization, concrete grammar is: to step 5) in signal vector after N point FFT converts, estimate channel information by pilot tone, utilize zero forcing equalization or linear mean squared error equalization criterion to carry out frequency domain equalization process, the data vector X ' obtained _k; That is:

Zero forcing equalization: $X_k^{\′}={\hat{X}}_k/H_k---\left(5\right)$

Linear mean squared error is balanced: $X_k^{\′}={\hat{X}}_k\·\frac{H_k^{*}}{{\left|H_k\right|}^2+{\mathrm{\γ}}^{-1}}---\left(6\right)$

Wherein H _kbe the estimated value of channel, γ=E/N is the signal to noise ratio of Received signal strength;

7) the IFFT conversion process of piecemeal, concrete grammar is: to step 6) data symbol vector X ' after the equilibrium of gained _kcarry out piecemeal IFFT conversion, obtain the data of time domain, the data of each piecemeal are that is:

${\hat{r}}_k=\underset{i=0}{\overset{M-1}{\mathrm{\Σ}}}{\hat{X}}_i^{\′}{e}^{j2\mathrm{\πki}/M},k=\mathrm{0,1},...,M-1---\left(7\right)$

8) data demodulates, concrete grammar is: to step 7) in data carry out symbol de-maps, obtain stay of two nights Bit data.

The present invention includes following basic process:

(1) digital modulation is carried out to information source data, generate the data symbol after a digital modulation;

(2) by the Fourier transform of M point piecemeal, the data symbol after modulation is transformed into the data vector of frequency domain;

(3) again gained block data symbolic vector is integrated into the data vector of N point, is converted by N point FFT, obtain the data symbol vector of time domain; N/4 the data at OFDM symbol end are added to before symbol as Cyclic Prefix (Cyclic Prefix, CP) and are used as protection interval, through up-sampling, after digital to analog conversion and upconversion process, are sent by signal;

(4) after receiving, signal is carried out to the inverse process process of transmitting terminal, remove CP the data received before data symbol, obtained the data of frequency domain by the Fourier transform of N point, this receives as OFDM;

(5) after receiving OFDM, signal carries out equilibrium, in equilibrium, first utilizes the pilot tone added to obtain channel information, adopts zero forcing equalization or linear mean squared error equalization criterion to carry out frequency domain equalization process.

(6) by the Fourier inversion of M point piecemeal, demodulation is carried out to the data symbol after equilibrium, obtain the data message of time domain;

(7) symbol de-maps is carried out to the estimated value of described data symbol, obtain stay of two nights Bit data.

The invention provides two conversion OFDM (DT-OFDM) communication meanss of piecemeal, owing to employing two conversion communication modes of FFT-IFFT, can be equivalent to and single-carrier modulated has been carried out to data symbol.At receiving terminal, in conjunction with frequency domain equalization process, comparatively legacy OFDM communication system, the present invention not only has the advantage of multicarrier system itself, can anti-frequency domain Selective intensity well, and has the advantage of single-carrier system process, and anti-fast time variant performance is strong.

Accompanying drawing explanation

Fig. 1 is the flow chart of two conversion OFDM (DT-OFDM) communication meanss that the present invention is based on piecemeal.

Fig. 2 is the analysis process of two conversion OFDM (DT-OFDM) communication meanss considered based on piecemeal.

Embodiment

Following examples will the present invention is further illustrated by reference to the accompanying drawings.

Based on two conversion OFDM (DT-OFDM) communication meanss of piecemeal, comprise the following steps:

Step 1: digital modulation;

Sign map is carried out to information source data, obtains data symbol s;

Step 2: piecemeal FFT process;

To the data symbol s after the digital modulation of step 1 gained, after serial to parallel conversion, carry out l piecemeal, the data symbol of each piecemeal is { s _i, i=0,1 ..., M-1}, carries out M point FFT to data and converts, and obtains the data symbol vector X of frequency domain _k, namely

$X_k=\underset{i=0}{\overset{M-1}{\mathrm{\Σ}}}{s}_i{e}^{j2\mathrm{\πik}/M},k=\mathrm{0,1},...M-1---\left(1\right)$

Step 3:OFDM modulating transformation;

The block data sign integration of step 2 gained frequency domain is become to the data vector of N point, add pilot tone in the data, when being converted by N point IFFT, need to add N-lM data zero.The data symbol vector that IFFT transforms to time domain is x _n, namely

$x_n=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{X}_k{e}^{-j2\mathrm{\πnk}/N},n=\mathrm{0,1},...,N-1---\left(2\right)$

Then add cyclic prefix CP, send after up-sampling, digital to analog conversion and upconversion process;

Step 4:OFDM receives inverse transformation;

First carry out to received signal down-conversion, analog to digital conversion, down-sampling process, after serioparallel exchange, remove cyclic prefix CP, the receiving symbol vector r obtained _k, because there is channel effect, noise and inter-sub-carrier interference, remove the Received signal strength symbolic vector r of Cyclic Prefix _kcan be write as:

$r_k=\underset{i=-\∞}{\overset{+\∞}{\mathrm{\Σ}}}{\hat{s}}_{i}h(k-i)+n_k+{\mathrm{ie}}_k,k=\mathrm{0,1},...,N-1---\left(3\right)$

Wherein for the data symbol vector received, h is the time domain parameter of channel, n _kbe average be 0, variance is independent same distribution white Gaussian noise, ie _kfor carrier-in-interference, noise n and channel h impact are to received signal separate;

The FFT conversion process of step 5:N point

Data symbol vector after interference is converted by the FFT of N point, and its conversion process is consistent with transmitting terminal, obtains the data vector of frequency domain namely

${\hat{X}}_k=H_{k,n}{S}_{k,n}+N_{k,n}+I_{k,n}---\left(4\right)$

Wherein H _{k, n}, S _{k, n}, N _{k, n}, I _{k, n}represent the frequency coefficient of kth point corresponding in n symbol.

Step 6: frequency domain equalization

To the signal vector in step 5 after N point FFT converts, estimate channel information by pilot tone, utilize zero forcing equalization or linear mean squared error equalization criterion to carry out frequency domain equalization process, the data vector X ' obtained _k; That is:

Zero forcing equalization: $X_k^{\′}={\hat{X}}_k/H_k---\left(5\right)$

Linear mean squared error is balanced: $X_k^{\′}={\hat{X}}_k\·\frac{H_k^{*}}{{\left|H_k\right|}^2+{\mathrm{\γ}}^{-1}}---\left(6\right)$

Wherein H _kbe the estimated value of channel, γ=E/N is the signal to noise ratio of Received signal strength;

Step 7: the IFFT conversion process of piecemeal

To the data symbol vector X ' after the equilibrium of step 6 gained _kcarry out piecemeal IFFT conversion, obtain the data of time domain, the data of each piecemeal are that is:

${\hat{r}}_k=\underset{i=0}{\overset{M-1}{\mathrm{\Σ}}}{\hat{X}}_i^{\′}{e}^{j2\mathrm{\πki}/M},k=\mathrm{0,1},...,M-1---\left(7\right)$

Step 8: data demodulates

Symbol de-maps is carried out to the data in step 7, obtains stay of two nights Bit data.

Consideration piecemeal FFT process in step 2, its detailed process is:

Step 2-1: the data that will send are carried out sign map and become s, becomes (s) by serioparallel exchange _{lM × N}, wherein l is block count, and M is the FFT transform length that piecemeal carries out;

Step 2-2: the data of each piecemeal are carried out M point FFT and converted, obtains the data symbol vector X of frequency domain _k;

Step 2-3: domain data information piecemeal process obtained is carried out N point IFFT after integrating and converted, and completes OFDM modulation;

Fig. 1 is two conversion OFDM (DT-OFDM) communication meanss based on piecemeal.As shown in Figure 1, at transmitting terminal, information source data are carried out Data Modulation, serioparallel exchange, the FFT conversion of piecemeal, the piecemeal data to be transmitted obtained carries out integration and pilot data carries out data-reusing process according to blocked format, then carries out IFFT conversion, then adds Cyclic Prefix, through up-sampling, send after digital to analog conversion and upconversion process.The signal received is carried out down-converted by receiving terminal, and complete digitlization by analog-to-digital conversion, then through down-sampling and go cyclic prefix CP process, send into FFT unit, the data obtained through frequency domain equalization, then pass through the IFFT conversion process of piecemeal, obtain effective data, respectively through parallel-serial conversion, data demodulates, obtains stay of two nights Bit data.

As shown in Figure 2, FFT-IFFT communication mode of the present invention, first carry out the FFT process of piecemeal, obtain the data vector of frequency domain, then by Data Integration, by IFFT unit, convert time domain data to, sent by up-conversion, complete the inverse process of transmission in receiving end, and frequency domain equalization process is carried out to signal.

Method described in the embodiment of the present invention is adopted to carry out emulation testing, its simulation result shows: having white Gaussian noise, under the channel model of multidiameter delay and Doppler frequency shift, adopt two conversion OFDM (DT-OFDM) communication systems comparatively legacy OFDM communication system based on piecemeal of QPSK modulation and MMSE frequency domain equalization processing method, peak-to-average force ratio is reduced, simultaneously, when different frequency offseting values, the peak-to-average ratio of DT-OFDM communication system all changes at about 8dB, and that is system is insensitive to frequency shift (FS).Under perfect channel estimation, the error rate is 10 ^-2time, when maximum doppler frequency is 200Hz, the ofdm system that DT-OFDM communication system is more traditional has the gain of 5dB; When maximum doppler frequency is 45Hz, the ofdm system that DT-OFDM communication system is more traditional has the gain being greater than 10dB, visible, and this system has stronger robustness.

In sum, the invention provides a kind of two conversion orthogonal frequency division multiplexing communication methods based on piecemeal, due to the FFT process of piecemeal, the peak-to-average force ratio that the superposition of sub-carrier signal is formed is reduced, and can improve the sensitiveness of traditional ofdm system for frequency shift (FS) simultaneously.Owing to employing two conversion of FFT-IFFT at transmitting terminal, the communication mode of whole system is equivalent to and carries out single-carrier modulated to data symbol, has the advantage of multicarrier and single-carrier modulated, the performance enhancement of anti-multipath jamming and fast time variant interference.

One of ordinary skill in the art will appreciate that, the all or part of step realized in above-described embodiment method is that the hardware that can carry out instruction relevant by program completes, described program can be stored in computer-readable recording medium, such as read-only memory (being called for short ROM), random access memory (being called for short RAM), disk, CD etc.

The above; be only the present invention's preferably embodiment, but protection scope of the present invention is not limited thereto, is anyly familiar with those skilled in the art in the technical scope that the present invention discloses; the change that can expect easily or replacement, all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claim.

Claims (1)

1., based on two conversion orthogonal frequency division multiplexing communication methods of piecemeal, it is characterized in that comprising the following steps:

1) digital modulation, concrete grammar is: carry out sign map to information source data, obtains data symbol s;

2) piecemeal FFT process, concrete grammar is:

(1) to step 1) data symbol s after gained digital modulation, after serial to parallel conversion, carry out l piecemeal, the data symbol of each piecemeal is { s _i, i=0,1 ..., M-1}, M are the FFT transform length that piecemeal carries out;

(2) data of each piecemeal are carried out M point FFT and are converted, and obtain the data symbol vector X of frequency domain _k, namely

$X_k=\underset{i=0}{\overset{M-1}{\Σ}}{s}_i{e}^{-j2\mathrm{\π}ik/M},k=0,1,...,M-1---\left(1\right);$

3) OFDM modulation conversion, concrete grammar is: to step 2) the block data sign integration of gained frequency domain becomes the data vector of N point, and add pilot tone in the data, converted by N point IFFT, the data symbol vector that IFFT transforms to time domain is x _n, namely

$x_n=\underset{k=0}{\overset{N-1}{\Σ}}{X}_k{e}^{j2\mathrm{\π}nk/N},n=0,1,...,N-1---\left(2\right)$

Then add cyclic prefix CP, send after up-sampling, digital to analog conversion and upward frequency conversion process;

4) OFDM receives inverse transformation, and concrete grammar is: carry out down-conversion, analog to digital conversion, down-sampling process first to received signal, after serioparallel exchange, remove cyclic prefix CP, the receiving symbol vector r obtained _k, because there is channel effect, noise and inter-sub-carrier interference, remove the Received signal strength symbolic vector r of Cyclic Prefix _kwrite as:

$r_k=\underset{i=-\mathrm{\∞}}{\overset{+\mathrm{\∞}}{\Σ}}\widehat{s_i}h(k-i)+n_k+{\mathrm{ie}}_k,k=0,1,...,N-1---\left(3\right)$

Wherein for the data symbol vector received, h is the time domain parameter of channel, n _kbe average be 0, variance is independent same distribution white Gaussian noise, ie _kfor carrier-in-interference, noise n _kseparate with channel h impact to received signal;

5) the FFT conversion process of N point, concrete grammar is: the data symbol vector after interference is converted by the FFT of N point, and its conversion process is consistent with transmitting terminal, obtains the data vector of frequency domain namely

${\hat{X}}_k=H_{k,n}{S}_{k,n}+N_{k,n}+I_{k,n}---\left(4\right)$

Wherein H _k,n, S _k,n, N _k,n, I _k,nrepresent the frequency coefficient of kth point corresponding in n symbol;

6) frequency domain equalization, concrete grammar is: to step 5) in signal vector after N point FFT converts, estimate channel information by pilot tone, utilize zero forcing equalization or linear mean squared error equalization criterion to carry out frequency domain equalization process, the data vector X' obtained _k; That is:

Zero forcing equalization: $X_k^{\′}={\hat{X}}_k/H_k---\left(5\right)$

Linear mean squared error is balanced: $X_k^{\′}={\hat{X}}_k\·\frac{H_k^{*}}{{\left|H_k\right|}^2+{\mathrm{\γ}}^{-1}}---\left(6\right)$

Wherein H _kbe the estimated value of channel, γ=E/N is the signal to noise ratio of Received signal strength;

7) the IFFT conversion process of piecemeal, concrete grammar is: to step 6) data symbol vector X' after the equilibrium of gained _kcarry out piecemeal IFFT conversion, obtain the data of time domain, the data of each piecemeal are that is:

${\hat{r}}_k=\underset{i=0}{\overset{M-1}{\Σ}}{\hat{X}}_i^{\′}{e}^{j2\mathrm{\π}ki/M},k=0,1,...,M-1---\left(7\right)$

8) data demodulates, concrete grammar is: to step 7) in data carry out symbol de-maps, obtain stay of two nights Bit data.