CN1809047A - Compatible single-carrier OFDMA signal transmitting method - Google Patents

Abstract

This invention relates to compatible single load wave crossing frequency multi-address signal sending method to generate base band by unit of block, wherein, the send method comprises the following steps: pre-modulating the transmission character vectors; discrete Fourier transformation; radio zone crossing displacement; radio zone signal expansion and shaping filter; loading wave and mapping; anti-discrete Fourier conversion; adding recycle front parts sliding and adopting recycle front parts technique to satisfy low peak proportion requirements and without interference between each user signal in ideal situation.

Description

Compatible single-carrier OFDMA signal transmitting method

Technical field

The present invention is a kind of Radio Transmission Technology method, belongs to the high-speed radiocommunication transmission technique field.

Background technology

OFDM (OFDM) technology, because its strong anti-multipath interference performance, simple discrete Fourier transform (DFT) (DFT) realize and are easy to adopt advantage such as multi-antenna transmitting transferring technology, obtain extensive studies and application, and become important candidate technologies following wireless and mobile communication system.In wireless communication system uplink link, be power efficiency and the expansion cell coverage area that improves portable terminal, the ratio (PAPR is called for short peak-to-average force ratio) that requires transmission signals to have low peak value and average power, and typical OFDM transmission signals has high peak-to-average force ratio.Reduce the peak-to-average force ratio of OFDM transmission signals, there is several different methods, wherein utilize DFT to carry out the method for signal extension, the ofdm signal that is produced has the peak-to-average force ratio performance close with single-carrier signal, produce the ofdm system scheme of DFT expansion and the ofdm system scheme of skew DFT expansion thus, abbreviate DFT-S-OFDM scheme and skew DFT-S-OFDM scheme respectively as, obtain extensive concern.The DFT-S-OFDM scheme is corresponding with the single-carrier system of quadrature amplitude modulation (QAM), its peak-to-average force ratio performance is identical, and skew DFT-S-OFDM scheme is corresponding with the single-carrier system of offset quadrature amplitude modulation(PAM) (OQAM), and its peak-to-average force ratio performance is identical and be better than the DFT-S-OFDM scheme.In DFT-S-OFDM scheme and skew DFT-S-OFDM scheme, when the shared sub carrier group of different user is not overlapping, can realize OFDM, obtain the single-carrier OFDMA scheme thus, be specially adapted to the mobile communication system uplink.

In mobile communication system, during above-mentioned two class single-carrier OFDMA technology co-existences, should adopt same implementation framework, to reduce implementation complexity, adopt different frequency domain molding filtrations, can further reduce the peak-to-average force ratio of transmission signals, make full use of the flexibility of system, can improve frequency diversity gain.

Summary of the invention

Technical problem: the single-carrier OFDMA signal transmitting method that the purpose of this invention is to provide a kind of compatibility, improve transmission signals peak-to-average force ratio performance, improve frequency diversity gain, satisfy wireless and mobile communication system, its uplink link particularly is to the requirement of transmission signals low peak average ratio and high diversity gain.

Technical scheme: in the single-carrier OFDMA signal transmitting method of compatibility of the present invention, producing baseband transmit signals is unit with the piece, and sending method may further comprise the steps:

1.1) premodulated of transmission symbol vector: promptly to k signal times coefficient w of n piece _Nb ^k,

1.2) discrete Fourier transform (DFT): promptly the signal to n piece carries out N _bThe discrete Fourier transform (DFT) of point,

1.3) the frequency domain quadrature shift: promptly according to the frequency-region signal vector after the following formula generation quadrature shift:

$x\left(n\right)=\frac{1}{2}(D\left(n\right)+J{D}^{*}\left(n\right))-\frac{j}{2}\mathrm{\Γ}(D\left(n\right)-{\mathrm{JD}}^{*}\left(n\right)),$

1.4) frequency-region signal expansion and molding filtration: frequency-region signal according to expansion of conjugation symmetry or cycle expansion, is generated the frequency-region signal after the expansion, and the frequency-region signal vector dot product frequency domain filtering function coefficients after will expanding again obtains the frequency-region signal behind the molding filtration,

1.5) the carrier wave mapping: with the length behind the molding filtration be N _bThe frequency-region signal vector to be mapped to length be N _IFFTSignal phasor, the insufficient section zero padding,

1.6) anti-discrete Fourier transform (DFT): the frequency-region signal after will shining upon carries out N _IFFTThe anti-discrete Fourier transform (DFT) of point,

1.7) add Cyclic Prefix and time-domain windowed is level and smooth: the time-domain signal vector after the anti-discrete Fourier transform (DFT) is added Cyclic Prefix, in that to carry out time-domain windowed level and smooth, generate the base band discrete-time signal then;

Adopting all above-mentioned steps, and step 1.4) baseband transmit signals of the ofdm system of generation skew discrete Fourier expansion when the frequency domain signal extension adopts the expansion of conjugation symmetry; Remove step 1.1 in employing) and step 1.3) outside two steps in steps and step 1.4) generate the baseband transmit signals of the ofdm system of discrete Fourier expansion during frequency domain signal extension employing cycle expansion.

Step 1.4) molding filtration adopts discrete generalized root-raised cosine frequency domain molding filtration, and the parameter of filtering can be optimized according to the modulator approach that adopts and rolloff-factor and choose.

When step 1.5) carrier wave shone upon, different user took one group of different subcarriers in the same signal phasor, and each user can take different sub carrier group according to the frequency hopping pattern of setting in the unlike signal vector.

Beneficial effect: the present invention has provided compatible single-carrier OFDMA scheme, can expand the several modules that increase under the framework that the ofdm system base band sends structure and revise minority at DFT and just can realize that skew DFT expands the base band transmission of ofdm system, has kept good compatibility.With the skew DFT expansion ofdm system that this scheme realizes, to compare with DFT expansion OFDM scheme, transmission signals has lower peak-to-average force ratio, can satisfy wireless better and mobile communication system, particularly up link.The broad sense root raised cosine frequency domain molding filtration that the present invention provides can further reduce the peak-to-average force ratio of transmission signals under the situation that does not increase complexity.Multi-user's frequency hopping frequency division multiple access method that the present invention provides is compared with traditional single-carrier OFDMA scheme, can obtain extra frequency diversity gain, thereby obtains better transmission property.

Description of drawings

Fig. 1 is compatible single-carrier OFDMA signal transmitting method schematic diagram.

Fig. 2 is a premodulated step schematic diagram.

Fig. 3 is a frequency domain quadrature shift step schematic diagram.

Fig. 4 is multi-user's frequency hopping frequency division multiple access method schematic diagram.

Embodiment

Figure 1 shows that compatible single-carrier OFDMA transmission technology scheme of the present invention.Transmission information bit stream is through the symbols streams of encoding, interweaving and the modulation symbol mapping being produced, pass through deserializer, generate the vector signal sequence, carry out DFT conversion and frequency domain migration processing after each signal phasor premodulated, carry out the IDFT conversion after then the vector that produces being passed through continuation and frequency domain molding filtration, obtain the transmission signal of each signal phasor, convert serial to through parallel-to-serial converter again and send signal, and insert Cyclic Prefix and carry out time-domain windowed level and smooth, obtain sending baseband signal.Ofdm system for the DFT expansion need not premodulated and frequency domain migration processing, and for the ofdm system that is offset the DFT expansion, these two links need.The signal continuation method that adopts in two type systematics is respectively periodic extension and is total to the volume symmetric extension.The frequency domain molding filtration can adopt the root-raised cosine filter function, but for further improving the peak-to-average force ratio performance of transmission signals, the present invention adopts the form of its expansion, i.e. broad sense root-raised cosine filter function, and under different roll-off factors and modulation system, it is optimized selection.When the shared sub carrier group of different user is not overlapping, can realize each user's quadrature multiple access transmission, for improving each user's frequency diversity performance, shared sub carrier group can be different on different OFDM symbols for each user, carry out the frequency hopping transmission by predefined frequency hopping pattern.Below generative process and the broad sense root-raised cosine function that sends signal specifically described.

1, sends the generative process of signal

At first we do as giving a definition system parameters: establishing α is roll-off factor, N _bBe the size of DFT, N _IFFTBe anti-DFT size, the clock frequency behind the anti-DFT is F _s, N _sFor the sub-carrier number of continuation half, single CU number of sub carrier wave is N _b=N _b+ 2N _sThe transmitting terminal complex baseband signal generates according to following steps:

(1) premodulated step: establishing d (n) is the baseband modulation signal phasor later of n piece, and block length is N _b, promptly

$d\left(n\right)={[d_1\left(n\right),d_2\left(n\right),...,d_{N_b}\left(n\right)]}^T$

D wherein _k(n) k symbol in n piece of expression.The signal after the premodulated then By formula

$\tilde{d}\left(n\right)=\mathrm{\Λd}\left(n\right)$ Calculate, wherein $\mathrm{\Λ}=\mathrm{diag}(w_{N_b}^0,w_{N_b}^1,...,w_{N_b}^{N_b-1}),$ $w_{N_b}^k=\exp (-2\mathrm{\πjk}/N_b),$

Here, the step of one diagonal matrix is lined up the element in the bracket in diag () expression.For the ofdm system of DFT expansion, send the signal generation and need not this step, at this moment, d (n) is the input vector of DFT conversion.

(2) DFT step: the signal D (n) behind the generation DFT, $D\left(n\right)=\mathrm{DFT}\left(\tilde{d}\left(n\right)\right).$

(3) frequency domain quadrature shift step: in this step, generate complex baseband signal x (n) after the frequency domain skew according to DFT, $x\left(n\right)=\frac{1}{2}(D\left(n\right)+{\mathrm{JD}}^{*}\left(n\right))-\frac{j}{2}\mathrm{\Γ}(D\left(n\right)-{\mathrm{JD}}^{*}\left(n\right)),$ The * operation table conjugation of giving instructions in reply here, $\mathrm{\Γ}=\mathrm{diag}(w_{N_b}^{0.5},w_{N_b}^{1.5},...,w_{N_b}^{N_b-0.5}),$ J represents anti-unit matrix.For the ofdm system of DFT expansion, send the signal generation and need not this step, directly get x (n)=D (n).

(4) signal extension and frequency domain forming step: in this step,, signal is carried out continuation, the signal after the continuation earlier according to roll-off factor α $\underset{\‾}{x}={\left[x_{\mathrm{left}}^T\left(n\right)x_{\min }^T\left(n\right)x_{\mathrm{right}}^T\left(n\right)\right]}^T.$ In DFT expansion ofdm system, the signal continuation is a periodic extension, at this moment

$x_{\mathrm{left}}\left(n\right)=[x_{N_b-N_s}\left(n\right)x_{N_b-N_s+1}\left(n\right)...x_{N_b-1}]$

x _mid(n)＝x(n)

$x_{\mathrm{right}}\left(n\right)=[x_0\left(n\right)x_1\left(n\right)...x_{N_s-1}]$

In skew DFT expansion ofdm system, the signal continuation is the conjugation symmetric extension, at this moment

$x_{\mathrm{left}}\left(n\right)=[x_{N_s-1}^{*}\left(n\right)x_{N_s-2}^{*}\left(n\right)...x_0^{*}]$

x _mid(n)＝x(n)

$x_{\mathrm{right}}\left(n\right)=[x_{N_b-1}^{*}\left(n\right)x_{N_b-2}^{*}\left(n\right)...x_{N_b-N_s}^{*}]$

If frequency domain becomes the type function vector to be

The frequency domain vectors after the frequency-domain shaping then For:

$\underset{\‾}{\overset{~}{x}}=\underset{\‾}{x}\left(n\right).*\tilde{w}.$

2, broad sense root-raised cosine frequency domain moulding

In the ofdm system of DFT expansion and skew DFT expansion, the frequency domain moulding in the step (4) all has certain influence to the peak-to-average force ratio that sends signal, and the molding filtration function that chooses can further reduce the peak-to-average force ratio that sends signal.But in order to make the receiver of matched filtering satisfy no intersymbol interference condition under Gaussian channel, the molding filtration function need satisfy Nyquist criterion, and the root-raised cosine function is exactly wherein comparatively use always a kind of.In the present invention, we have introduced a kind of function that satisfies Nyquist criterion, and promptly broad sense root raised cosine frequency-domain function is used as frequency domain and becomes type function.Broad sense root raised cosine function can be divided into two big classes, and a class is a convex broad sense root raised cosine function, and another kind of is spill broad sense root raised cosine function.Order

$w_{1,k}=\sqrt{1+q\cos \left(\frac{\mathrm{\π}}{d}(\frac{d-1}{2}+\frac{k+0.5}{{2N}_s})\right)}$

$w_{2,k}=\sqrt{3-\frac{2(k+0.5)}{N_s}+q\cos \left(\frac{\mathrm{\π}}{d}(\frac{d-1}{2}+\frac{k+0.5}{{2N}_s})\right)}$

K=0 here ..., 2N _s-1, d is a broad sense root raised cosine function parameters, q=1/cos (π (d-1)/(2d)).Then discrete generalized root-raised cosine frequency domain becomes type function to be

${\tilde{w}}_{j,k}=\left\{\begin{array}{cc}{w}_{j,{2N}_s-k+1};& 0\&le;k<2N_s\\ 1;& 2N_s\&le;k<N_b\\ w_{j,k-N_b;}& N_b\&le;k<N_b+{2N}_s\end{array}\right.$

Be that convex broad sense root-raised cosine frequency domain becomes type function during j=1 wherein, and be that spill broad sense root-raised cosine frequency domain becomes type function during j=2.By above expression formula, know that easily when d=1, convex broad sense root-raised cosine function is traditional root raised cosine function.

Under the condition of different modulation and roll-off factor, can further reduce the peak-to-average force ratio that sends signal by being optimized to the selection of broad sense raised cosine type and to parameter d.

3, multi-user's frequency hopping frequency division multiple access method

In the single-carrier OFDMA multi-user system, different user is modulated to different frequency ranges, is used for each other differentiation.In skew DFT expansion ofdm system, OFDM can adopt centralized and distributed two kinds between the existing user.In Centralized Mode, same CU plurality of adjacent subcarrier, and in distributed mode, the subcarrier of one group of pectination of same CU.These two kinds of multi-access modes respectively have pluses and minuses, and distributed multiple access pattern is compared with centralized multiple access pattern because frequency spectrum more disperses, and has higher frequency diversity, under especially more in number of users and/or the condition that frequency selective fading is serious.And the performance of distributed multiple access pattern is more responsive to the synchronous and channel estimating of system, promptly exists synchronous error or channel estimation errors can make that the performance of distributed multiple access pattern is poorer between the user, even is inferior to Centralized Mode.

Provided a kind of multiple access solution of multi-user's frequency hopping frequency division multiple access among the present invention, in this programme, between the user according to the centralized OFDM of carrying out.And the shared subcarrier of different user changes over time, and promptly each user takies different sub-carrier section in the different moment.Figure 3 shows that traditional centralized, distributed and frequency hopping time-frequency sending method schematic diagram, as we can see from the figure, in the hopping scheme that provides, different users on sometime according to centralized realization OFDM, and in the different moment, the sub-carrier section of certain CU changes.Can see that thus compare the fixing centralized OFDM of subcarrier number, multi-user's frequency hopping frequency division multiple access scheme can obtain extra frequency diversity gain; And compare with distributed multiple access scheme, multi-user's frequency hopping frequency division multiple access scheme has been avoided user's orthogonality sensitive issue.The subcarrier that different user takies can distribute according to the frequency hopping pattern of setting.

The invention provides a kind of single-carrier OFDMA signal transmitting method of compatibility of low peak average ratio, satisfy wireless and mobile communication system, its uplink link particularly is to the requirement of transmission signals low peak average ratio.

Embodiment is as follows:

(1) determines system parameters: under given system bandwidth, general standard according to the ofdm system design, determine subcarrier number in the system according to Doppler frequency deviation and implementation complexity, the IDFT transform size, the shared subcarrier of configure user arbitrarily, and the size of definite DFT conversion and roll-off factor etc.Determine that system adopts skew DFT expansion OFDM mode or DFT expansion OFDM mode.According to transmission mode, modulation system and roll-off factor are determined broad sense root-raised cosine moulding function parameters d.

(2) sending method: the method that transmitting terminal provides according to technical scheme and Fig. 1-4 produces and sends baseband signal, and sends after carrier modulation.Concrete steps are:

(2.1) signal after will modulating carries out serial to parallel conversion.

(2.2) signal behind the serial to parallel conversion is carried out premodulated according to the method that Fig. 2 provides.

(2.3) signal phasor after the premodulated is carried out N _bThe DFT conversion of point.

(2.4) the frequency-region signal vector after the DFT conversion is carried out quadrature shift.

(2.5) signal after the frequency domain quadrature shift is expanded and frequency domain moulding and subcarrier mapping, adopted the broad sense root-raised cosine function of describing in the technical scheme 2 during the frequency domain moulding.And multi-user's frequency modulation subcarrier distribution scheme of when subcarrier shines upon, describing in the employing technical scheme 3.

(2.6) signal after will shining upon is N _IFFTThe anti-DFT of point.

(2.7) signal after the anti-DFT conversion is carried out parallel serial conversion, and insert Cyclic Prefix, carry out the level and smooth windowing of time domain then, obtain sending baseband signal.

(3) method of reseptance: receiving terminal can adopt DFT territory single-point balancing technique to carry out input, deciphers afterwards, recovers the information transmitted bit, also can adopt the iterative detection decoding technology to recover the information transmitted bit.

In the uplink link was used, the input of different user and decoding can be adopted same DFT conversion and carry out at transform domain, also can carry out the DFT conversion independently and detect decoding.

Claims (3)

1, a kind of single-carrier OFDMA signal transmitting method of compatibility, it is characterized in that producing baseband transmit signals is unit with the piece, sending method may further comprise the steps:

1.1) premodulated of transmission symbol vector: promptly to k signal times coefficient w of n piece _Nb ^k,

1.2) discrete Fourier transform (DFT): promptly the signal to n piece carries out N _bThe discrete Fourier transform (DFT) of point,

1.3) the frequency domain quadrature shift: promptly according to the frequency-region signal vector after the following formula generation quadrature shift:

$x\left(n\right)=\frac{1}{2}(D\left(n\right)+{\mathrm{JD}}^{*}\left(n\right))-\frac{j}{2}\mathrm{\&Gamma;}(D\left(n\right)-{\mathrm{JD}}^{*}\left(n\right)),$

1.4) frequency-region signal expansion and molding filtration: frequency-region signal according to expansion of conjugation symmetry or cycle expansion, is generated the frequency-region signal after the expansion, and the frequency-region signal vector dot product frequency domain filtering function coefficients after will expanding again obtains the frequency-region signal behind the molding filtration,

1.5) the carrier wave mapping: with the length behind the molding filtration is N _bThe frequency-region signal vector to be mapped to length be N _IFFTSignal phasor, the insufficient section zero padding,

1.6) anti-discrete Fourier transform (DFT): the frequency-region signal after will shining upon carries out N _IFFTThe anti-discrete Fourier transform (DFT) of point,

1.7) add Cyclic Prefix and time-domain windowed is level and smooth: the time-domain signal vector after the anti-discrete Fourier transform (DFT) is added Cyclic Prefix, in that to carry out time-domain windowed level and smooth, generate the base band discrete-time signal then;

Adopting all above-mentioned steps, and step 1.4) baseband transmit signals of the ofdm system of generation skew discrete Fourier expansion when the frequency domain signal extension adopts the expansion of conjugation symmetry; Remove step 1.1 in employing) and step 1.3) outside two steps in steps and step 1.4) generate the baseband transmit signals of the ofdm system of discrete Fourier expansion during frequency domain signal extension employing cycle expansion.

2, the single-carrier OFDMA signal transmitting method of compatibility according to claim 1, it is characterized in that step 1.4) molding filtration adopt discrete generalized root-raised cosine frequency domain molding filtration, the parameter of filtering can be optimized according to the modulator approach that adopts and rolloff-factor and choose.

3, according to the single-carrier OFDMA signal transmitting method of right 1 described compatibility, it is characterized in that step 1.5) when carrier wave shines upon, different user takies one group of different subcarriers in the same signal phasor, and each user can take different sub carrier group according to the frequency hopping pattern of setting in the unlike signal vector.

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