CN100359895C - Method for implementing full digital wireless communication system using fast Fourier transform - Google Patents

Abstract

The present invention relates to a method for implementing a full digital wireless communication system by fast Fourier transform. The transmitted data uses a burst structure based on a packet at the transmitting end, and symbol streams for transmission are formed by channel encoding, channel interleaving and a symbol mapping device. Serial symbolic streams are transformed into parallel symbol streams to be used as the input of an orthogonal modulator. The orthogonal modulator orthogonally modulates an N point input symbol sequence of each group for P times. Orthogonal modulation comprises the following steps that the input N point symbol sequence carries out frequency domain phase rotation, the reverse fast Fourier transform and time domain phase rotation; the input N point symbol sequence is ordered and is emitted after parallel-to-serial conversion, cyclic prefix addition and a digital-to-analog converter; at the receiving end, a signal received by a receiving antenna carries out analog-to-digital conversion, serial-to-parallel conversion, the phase rotation, the N point fast Fourier transform, channel estimation, frequency domain equalization, the parallel-to-serial conversion, symbol inverse mapping, communication channel interleaving release and channel decoding to obtain output data.

Description

Utilize fast fourier transform to realize full digital wireless communication system

Technical field

The present invention is a kind of middle and high fast wireless communication system that is applied to, and realizes the solution of full-digital broadband, the middle and high fast radio communication physical layer of ultra broadband, relates in particular to a kind of method of utilizing fast fourier transform to realize full digital wireless communication system.

Background technology

(Ultra-Wideband, UWB) technology is a revolutionary new technology of wireless communication field to ultra broadband.The characteristics of super-broadband tech are to utilize extremely wide frequency band to communicate, and can reach the wireless transmission rate above 1000M bps.In order other communication system in the service band not to be caused interference, the transmitting power of radio ultra wide band system has been subjected to strict restriction, and therefore, the distance of high speed ultra-wideband communications is generally in 10 meters at present.

At present, ultra-wideband communications has two kinds of basic implementations: a kind of is base band burst pulse mode, and another kind is the modulated carrier mode.Base band burst pulse mode utilizes base band burst pulse sequence to carry information, need not modulated carrier, generally is used for the system than low rate, low cost, low-power consumption.The modulated carrier mode is modulated at ultra-broadband signal on the sinusoidal carrier to be transmitted, and can realize very high message transmission rate, and has availability of frequency spectrum height, frequency band and use advantages such as flexible.

In the super broad band radio communication system of the modulated carrier that proposes at present, what generally adopt all is modulation, the demodulator of simulation.Promptly (Digital-to-Analog Conversion DAC) obtains base-band analog signal, then itself and analog carrier is multiplied each other, filtering, finishes carrier modulation by digital to analog conversion with digital signal at transmitting terminal; At receiving terminal, with bandpass signal and the analog carrier of receiving multiply each other, filtering, obtain base-band analog signal, finish carrier wave demodulation, again with this base-band analog signal by analog to digital conversion (Analog-to-Digital Conversion, ADC), obtain digital signal, and further handle.Adopt such method, need in the system to adopt the analog carrier modulator and demodulator, increased complexity, cost and power consumption that system realizes, and introduced noise, phase place lack of uniformity etc. in the analog-modulated, also can influence the performance of system.Simultaneously, the parameters such as centre frequency of analog-modulated, demodulator can't arbitrarily change, and have influenced the flexibility of system's use frequency spectrum.

On the other hand, also exist at present utilize Digital Up Convert (Digital-Up-Conversion, DUC) and Digital Down Convert (Digital-Down-Conversion, DDC) technology realizes the method for all-digital communication system.This method be utilize digital controlled oscillator (Numerically Controlled Oscillators NCO) produces digital carrier signal, with itself and digital signal multiply each other, filtering, finish carrier modulation and demodulation at numeric field.Because the message transmission rate of radio ultra wide band system is very high, if in radio ultra wide band system, utilize this method, realize that difficulty is very big, very high to hardware requirement.

Summary of the invention

The invention provides a kind of method that can in the super-broadband tech of modulated carrier, utilize fast fourier transform to realize full digital wireless communication system, the present invention can make system realize that cost is low, power consumption is little, easy of integration, have the stable advantage of systematic function.

The present invention adopts following technical scheme:

A kind of fast fourier transform of utilizing that is applied to middle and high fast wireless communication system realizes the method for full digital wireless communication system, comprise launching technique and method of reseptance, at transmitting terminal, data producer 1 produces and sends data, the The data that is produced is based on the burst structure of bag, the front end of each packet is bag detection, synchronizing sequence and a channel estimation sequence, is used to wrap detection, sign synchronization and channel estimating; Each packet at first through channel encoder 2 codings, has added the redundant information that is used for verification and error correction; Carry out channel interleaving by channel interleaver 3 after the chnnel coding, alleviate burst error in the Channel Transmission Effect on Performance; The output bit flow of channel interleaving forms the symbols streams that can be used for transmitting through symbol mapper 4; Then carry out serial to parallel conversion by serial-parallel converter 5, the symbols streams of serial is transformed into parallel symbols streams, as the input of quadrature modulator 6, quadrature modulator 6 carries out quadrature modulation P time to the N point incoming symbol sequence of each group, and the step of this quadrature modulation is as follows:

(a) the N point symbol sequence of input is carried out the rotation of frequency domain phase place, making the pairing time offset of N point sample value sequence of this quadrature modulation output is Δ n, this time offset Δ n is increased to P-1 successively from 0, and each quadrature modulation increases by 1, and above-mentioned frequency domain phase place rotates to be:

$X_{\mathrm{\&Delta;n}}(l,k)=X(l,k){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,k=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N-1),$

Wherein X (l, k), k=0,1 ..., (N-1) } and { X _{Δ n}(l, k), k=0,1 ..., (N-1) } and the N point symbol sequence that obtains after being respectively the N point symbol sequence of input and carrying out frequency domain phase place rotation;

(b) to { X _{Δ n}(l, k), k=0,1 ..., (N-1) } and carry out N point inverse fast fourier transformed, obtain N point sample value sequence { x _{1, Δ n}(l, n), n=0,1 ..., (N-1) };

(c) to { x _{1, Δ n}(l, n), n=0,1 ..., (N-1) } and carry out the rotation of time domain phase place, the signal of output is moved [(k ₀-1/2) Δ f, (k ₀+ N-1/2) Δ f] frequency band range within, Δ f is the subcarrier spacing of OFDM here, k ₀Be initial frequency deviation, set or change adaptively that above-mentioned time domain phase place rotates to be according to the requirement of system works frequency range:

$x_{2,\mathrm{\&Delta;n}}(l,n)=x_{1,\mathrm{\&Delta;n}}(l,n){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,n=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N-1),$

Here { x _{2, Δ n}(l, n), n=0,1 ..., (N-1) } and N point sample value sequence for obtaining after the time domain phase place rotation;

(d) with { x _{2, Δ n}(l, n), n=0,1 ..., (N-1) } and press M=log ₂N bit-binary inverted order is put in order preface, obtains { x _{Δ n}(l, n), n=0,1 ..., (N-1) }, the whole preface of above-mentioned M bit-binary inverted order is write the sample value sequence number in the former sequence as the M bit binary number, and bit sequence left and right sides inverted order that will this binary number of expression is arranged, again with the natural number of the new binary number correspondence new sequence number as former sample value;

(e) with sequence { x _{Δ n}(l, n), n=0,1 ..., (N-1) } and be placed on the position of [N Δ n ', the N Δ n '+N-1] of P * N point sequence { x ' (l, n) }, Δ n ' is the Q bit-binary inverted order of Δ n here, Q=log ₂P, above-mentioned Q bit-binary inverted order is write Δ n as the Q bit binary number, and bit sequence left and right sides inverted order that will this binary number of expression is arranged, again with the natural number of new binary number correspondence as Δ n ', each quadrature modulation obtains N the output sample that time offset is Δ n, obtain after P the quadrature modulation P * N point output sample sequence x ' (l, n), n=0,1,, (P * N-1) }, to { x ' (l, n) } carry out the whole preface of Q * M bit-binary inverted order, to the end the output sample sequence x (l, n), n=0,1,, (P * N-1) }

Data are carried out parallel serial conversion by parallel to serial converter 7 after quadrature modulator 6 is handled, and parallel data flow are transformed into the data flow of serial; Digital signal behind the parallel serial conversion adds Cyclic Prefix by OFDM symbol generator 8, generates OFDM (Orthogonal Frequency Division Multiplexing, OFDM) symbol; Then, produce the analog bandpass signal, behind amplifier 10 and band pass filter 11, by 12 emissions of transmitting terminal antenna through digital-to-analog converter 9;

At receiving terminal, the signal that reception antenna 13 receives is by interference signal and noise outside the band pass filter 14 filtering useful signal frequency bands, signal carries out analog to digital conversion by A-D converter 16 after amplifier 15 amplifies, after analog to digital conversion, in the receiving course of each packet, at first wrap and detect and sign synchronization 17, obtain the original position of each Frame, signal synchronously carries out serial to parallel conversion by serial-parallel converter 18, and carry out phase place by phase rotation device 19 and rotate, this phase place rotation is used for compensating the phase place rotation to time-domain signal that quadrature modulator 6 brings, and its method is:

$r_1(l,n)=r(l,n)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{nk}}_0/N},n=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N-1),$

Wherein r (l, n), n=0,1 ..., (N-1) } and be N point receiving data sequence, { r ₁(l, n), n=0,1, (N-1) } be the data after the phase place rotation, carry out N point fast Fourier conversion (FastFourier Transfer in phase place rotation back by fast fourier transformer 20, FFT), convert the signal into frequency domain, and carry out channel estimating by channel estimator 21 at this frequency domain, the estimated value of the channel frequency response that frequency-domain equalizer 22 usefulness channel estimating obtain is carried out frequency domain equalization to the reception data of back, data behind the frequency domain equalization are carried out parallel serial conversion by parallel to serial converter 23 successively, carry out the symbol inverse mapping by symbol inverse mapping device 24, carry out the channel deinterleaving by channel deinterleaver 25, and carry out channel decoding, obtain data output 27 by channel decoder 26.

Compared with prior art, the present invention has following advantage:

What adopt the present invention's proposition is the fully digital ultra-broadband wireless communication system scheme of core with " P * N point quadrature modulation ", can obtain following beneficial effect:

1. system adopts digital implementation, does not need analogue devices such as analog modulator, demodulator, makes the whole communication system cost reduce, and is easy to be integrated in the large scale integrated circuit of single-chip.

2. in ultra-wideband communication system, because the bandwidth of baseband signal is generally very big, the P value is less." P * N point quadrature modulation " further reduced the operand of P * N point IFFT again.So compare with existing digital modulation technique, communication system of the present invention has realized digital modulation with very little operand.

3. the digital implementation of system, it is very convenient to make adaptive spectrum move, and does not need extra hardware spending, noise and the phase place lack of uniformity of having avoided analog-modulated to bring simultaneously.

4. receiving terminal can adopt and owe Sampling techniques, thereby can use the ADC of low sampling rate, has reduced the realization cost of system.

5. utilize Reference Design method provided by the invention, the present invention can be used to realize to be with OFDM alliance (Multi-Band OFDM Alliance, many band-OFDM MBOA) (Multi-Band OFDM, MB-OFDM) scheme, and the update scheme of follow-up developments more.

Description of drawings

Fig. 1 is a theory diagram of the present invention.

Fig. 2 is the form of the packet that uses in the communication system of the present invention.

Fig. 3 is that the present invention proposes " P * N point quadrature modulation " schematic diagram.

Fig. 4 is the communication system schematic diagram of a specific embodiment of the present invention.

Embodiment

Embodiment 1

A kind of fast fourier transform of utilizing that is applied to middle and high fast wireless communication system realizes the method for full digital wireless communication system, comprise launching technique and method of reseptance, it is characterized in that: at transmitting terminal, data producer 1 produces and sends data, the The data that is produced is based on the burst structure of bag, the front end of each packet is bag detection, synchronizing sequence and a channel estimation sequence, is used to wrap detection, sign synchronization and channel estimating; Each packet at first through channel encoder 2 codings, has added the redundant information that is used for verification and error correction; Carry out channel interleaving by channel interleaver 3 after the chnnel coding, alleviate burst error in the Channel Transmission Effect on Performance; The output bit flow of channel interleaving forms the symbols streams that can be used for transmitting through symbol mapper 4; Then carry out serial to parallel conversion by serial-parallel converter 5, the symbols streams of serial is transformed into parallel symbols streams, as the input of quadrature modulator 6, quadrature modulator 6 carries out quadrature modulation P time to the N point incoming symbol sequence of each group, and the step of this quadrature modulation is as follows:

(a) the N point symbol sequence of input is carried out the rotation of frequency domain phase place, making the pairing time offset of N point sample value sequence of this quadrature modulation output is Δ n, this time offset Δ n is increased to P-1 successively from 0, and each quadrature modulation increases by 1, and above-mentioned frequency domain phase place rotates to be:

$X_{\mathrm{\&Delta;n}}(l,k)=X(l,k){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,k=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N-1),$

Wherein X (l, k), k=0,1 ..., (N-1) } and { X _{Δ n}(l, k), k=0,1 ..., (N-1) } and the N point symbol sequence that obtains after being respectively the N point symbol sequence of input and carrying out frequency domain phase place rotation;

(b) to { X _{Δ n}(l, k), k=0,1 ..., (N-1) } and carry out N point inverse fast fourier transformed, obtain N point sample value sequence { x _{1, Δ n}(l, n), n=0,1 ..., (N-1) };

(c) to { x _{1, Δ n}(l, n), n=0,1 ..., (N-1) } and carry out the rotation of time domain phase place, the signal of output is moved [(k ₀-1/2) Δ f, (k ₀+ N-1/2) Δ f] frequency band range within, Δ f is the subcarrier spacing of OFDM here, k ₀Be initial frequency deviation, set or change adaptively that above-mentioned time domain phase place rotates to be according to the requirement of system works frequency range:

$x_{2,\mathrm{\&Delta;n}}(l,n)=x_{1,\mathrm{\&Delta;n}}(l,n){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,n=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N-1),$

Here { x _{2, Δ n}(l, n), n=0,1 ..., (N-1) } and N point sample value sequence for obtaining after the time domain phase place rotation;

(d) with { x _{2, Δ n}(l, n), n=0,1 ..., (N-1) } and press M=log ₂N bit-binary inverted order is put in order preface, obtains { x _{Δ n}(l, n), n=0,1 ..., (N-1) }, the whole preface of above-mentioned M bit-binary inverted order is write the sample value sequence number in the former sequence as the M bit binary number, and bit sequence left and right sides inverted order that will this binary number of expression is arranged, again with the natural number of the new binary number correspondence new sequence number as former sample value;

(e) with sequence { x _{Δ n}(l, n), n=0,1 ..., (N-1) } and be placed on the position of [N Δ n ', the N Δ n '+N-1] of P * N point sequence { x ' (l, n) }, Δ n ' is the Q bit-binary inverted order of Δ n here, Q=log ₂P, above-mentioned Q bit-binary inverted order is write Δ n as the Q bit binary number, and bit sequence left and right sides inverted order that will this binary number of expression is arranged, again with the natural number of new binary number correspondence as Δ n ', each quadrature modulation obtains N the output sample that time offset is Δ n, obtain after P the quadrature modulation P * N point output sample sequence x ' (l, n), n=0,1,, (P * N-1) }, to { x ' (l, n) } carry out the whole preface of Q * M bit-binary inverted order, to the end the output sample sequence x (l, n), n=0,1,, (P * N-1) }

Data are carried out parallel serial conversion by parallel to serial converter 7 after quadrature modulator 6 is handled, and parallel data flow are transformed into the data flow of serial; Digital signal behind the parallel serial conversion adds Cyclic Prefix by OFDM symbol generator 8, generates OFDM symbol; Then, produce the analog bandpass signal, behind amplifier 10 and band pass filter 11, by 12 emissions of transmitting terminal antenna through digital-to-analog converter 9;

At receiving terminal, the signal that reception antenna 13 receives is by interference signal and noise outside the band pass filter 14 filtering useful signal frequency bands, signal carries out analog to digital conversion by A-D converter 16 after amplifier 15 amplifies, after analog to digital conversion, in the receiving course of each packet, at first wrap and detect and sign synchronization 17, obtain the original position of each Frame, signal synchronously carries out serial to parallel conversion by serial-parallel converter 18, and carry out phase place by phase rotation device 19 and rotate, this phase place rotation is used for compensating the phase place rotation to time-domain signal that quadrature modulator 6 brings, and its method is:

$r_1(l,n)=r(l,n)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{nk}}_0/N},n=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N-1),$

Wherein r (l, n), n=0,1 ..., (N-1) } and be N point receiving data sequence, { r ₁(l, n), n=0,1, (N-1) } be the data after the phase place rotation, carry out the conversion of N point fast Fourier in phase place rotation back by fast fourier transformer 20, convert the signal into frequency domain, and carry out channel estimating by channel estimator 21 at this frequency domain, and the estimated value of the channel frequency response that frequency-domain equalizer 22 usefulness channel estimating obtain is carried out frequency domain equalization to the reception data of back, and the data behind the frequency domain equalization are carried out parallel serial conversion by parallel to serial converter 23 successively, carry out the symbol inverse mapping by symbol inverse mapping device 24, carry out the channel deinterleaving by channel deinterleaver 25, and carry out channel decoding by channel decoder 26, obtain data output 27.

Embodiment 2

The super broad band radio communication system of design according to the present invention is as a Reference Design of embodiment.The basic parameter of this communication system is as shown in table 1.In the system, the subcarrier spacing of OFDM modulation is Δ f=250 KHz, and sub-carrier number is N=128, wherein N _D=112 subcarriers transmit data.Reverse complex conjugate form is adopted in the input of IFFT.Adopt " 8 * 128 quadrature modulation " (to be P=8, N=128) frequency spectrum of baseband signal to be moved.The adaptive algorithm that does not comprise spectrum control in this example, k ₀Get fixed value 448, like this, in P * N=1024 point IFFT, the subcarrier sequence number that valid data take is 448-575, and baseband signal is shifted to [(k ₀-1/2) Δ f, (k ₀+ N-1/2) Δ f], promptly in the frequency range of 111.875-143.875 MHz.

Table 1: basic parameter

Parameter	Numerical value
		Subcarrier spacing Δ f	250KHz
The IFFT/FFT period T FFT＝1/Δf	4us
		Sub-carrier number N	128
Baseband signal bandwidth B=N * Δ f	32MHz
		The P value	8
" P * N point quadrature modulation " sub-carrier number P * N	1024
		Initial frequency deviation k 0	448
Reverse complex conjugate gain Q	2
		The Cyclic Prefix points N CP	32
Circulating prefix-length T CP	1us
		OFDM symbol lengths T SYM＝T FFT+T CP	5us
The transmission rate R of each subcarrier 0＝1/T SYM	200K OFDM Symbols/s
		The sub-carrier number N of transmission data D	112
The sub-carrier number N of transmission pilot tone P	0
		Modulation system (modulation factor MI)	QPSK(2)
The coded bit that every OFDM symbol carries is counted N CB＝ N D×MI/Q	112
		Total data rate R=R 0×N CB	22.4Mbps
Code rate R c	1/2
		Information data rate R Data＝R×R c	11.2Mbps

Fig. 4 is the schematic diagram of system for this reason.At transmitting terminal, it is 1/2 that chnnel coding adopts code rate, and constraint length is 7 convolution code.Block interleaving is adopted in channel interleaving, and the size of piece is 112 bits, and interleave depth is 14.Sign map adopts QPSK, per two bit b ₁b ₂Be mapped as a QPSK symbol s.Mapping mode is as shown in table 2.

Table 2:QPSK sign map mode

s	b1	b2
			1+j	0	0
1-j	0	1
			-1-j	1	1
-1+j	1	0

Transmit 56 QPSK symbols in each OFDM symbol, the QPSK symbolic representation that transmits in l OFDM symbol be s (l, k), k=0,1 ... 55}, these 56 QPSK symbols and reverse complex conjugate symbol thereof occupy 112 sub-carrier channels altogether, and other sub-carrier channels transmits 0.128 sub-carrier channels of each OFDM symbol are allocated as follows:

$X(l,k)=\left\{\begin{array}{cc}0,& k=0-7,\\ s(l,k-1),& k=8-63,\\ \mathrm{conj}\left[s(l,127-k)\right],& k=64-119,\\ 0,& k=120-127\end{array}l=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;\right.---\left(8\right)$

IFFT adopts 8 * 128 quadrature modulation, i.e. P=8, N=128.Behind the parallel serial conversion, add the Cyclic Prefix of 32 * 8=256 sample value before 128 * 8=1024 of each OFDM symbol sample value, form complete OFDM symbol.Then, produce the analog bandpass signal, behind band pass filter, launch by antenna through DAC.Here the input sample speed of DAC is 256M sample value/second, each sample value 8 bit quantization.

At receiving terminal, the output signal of antenna is at first passed through band pass filter, carries out ADC after the amplification.The ADC sampling rate is 64 M sample value/second, each sample value 8 bit quantization.Carry out back phase place rotation synchronously behind bag detection and the symbol, carry out 128 FFT then, transform to frequency domain, and carry out channel estimating and frequency domain equalization at frequency domain.The algorithm of phase place rotation, channel estimating and frequency domain equalization is as indicated above.After the equilibrium,, the output symbol of FFT is merged, that is: according to the reverse complex conjugate characteristics of being input as of transmitting terminal IFFT

$\hat{y}(l,k)=\frac{1}{2}(\tilde{y}(l,k)+\mathrm{conj}[\tilde{y}(l,111-k)\left]\right),k=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;55---\left(9\right)$

Here $\{\tilde{y}(l,k),k=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,111\}$ Be the output of l OFDM symbol equilibrium.

Carry out the QPSK inverse mapping behind the parallel serial conversion, and then, obtain dateout through deinterleaving and Viterbi decoding.

Embodiment 3

The present invention adopts OFDM (Orthogonal Frequency Division Multiplexing in base band, OFDM) coding modulation technique, and utilize FFT/IFFT to realize the frequency spectrum shift of base band ultra-broadband signal, thereby realize the fully digital ultra-broadband wireless communication system.

The theory diagram of the fully digital ultra-broadband wireless communication system that the present invention proposes as shown in Figure 1.At transmitting terminal, the transmission The data that data producer 1 produces is based on the burst structure of bag, with the requirement of the flexible use transfer resource that adapts to the high-speed radio multimedia communication.As shown in Figure 2, the front end of each packet is bag detection, synchronizing sequence and a channel estimation sequence, is used to wrap detection, sign synchronization and channel estimating.The channel estimation sequence back is the data sequence that will send.Each packet at first passes through channel encoder 2, adds the redundant information that is used for verification and error correction.Chnnel coding can adopt multiple mode, as convolution code, Turbo code, low-density checksum (Low Density Parity Check, LDPC) sign indicating number etc.Carry out channel interleaving by channel interleaver 3 after the chnnel coding, to alleviate burst error in the Channel Transmission to Effect on Performance.Channel interleaving can be adopted various ways such as block interleaving, convolutional interleave.The output bit flow of channel interleaving forms the symbols streams of suitable transmission through symbol mapper 4.Sign map can adopt binary phase shift keying (Binary Phase-Shift Keying, BPSK), quarternary phase-shift keying (QPSK) (Quadriphase-Shift Keying, QPSK), 8 system phase shift keyings (8-ary Phase-Shift Keying, 8PSK) and 16 ary quadrature amplitude (16-ary Quadrature-Amplitude Modulation, multiple mode such as 16QAM).Then carry out serial to parallel conversion by serial-parallel converter 5.Serial to parallel conversion is transformed into parallel bit stream with the bit stream of serial, as the input of back quadrature modulator 6.6 pairs of data of quadrature modulator are carried out P * N point quadrature modulation, handle N point input data at every turn, the l time input be expressed as X (l, k), k=0,1 ..., (N-1) }, l=0,1 ...If each N point input data satisfy reverse complex conjugate condition, that is:

X(l，k)＝conj(X(l，N-1-k))，k＝0，1，…，(N/2-1)， (1)

Wherein conjugate operation is got in conj () expression, then the imaginary part of its output sequence is 0, can finish transmission and reception to the output sequence real part this moment with one tunnel communication channel, otherwise need to adopt emptyly divide, the time method of grading, send respectively and receive with the real part and the imaginary part of two-way communication channel output sequence.

The present invention proposes with P * N point quadrature modulation realization N point IFFT, and finish after the IFFT conversion method simultaneously the frequency spectrum shift of baseband signal.IFFT and fast fourier transform are a pair of inverse transformations.Can be at transmitting terminal IFFT, receiving terminal FFT also can be conversely.According to custom, we have adopted preceding a kind of mode, to embody the physical significance of transmitting terminal from the frequency domain transform to the time domain.The present invention is applicable to the situation of " P * N point FFT " too.

The principle of P * N point quadrature modulation is to finish the IFFT computing of the N point being imported data with P * N point IFFT, and N, P are the positive integer greater than 2 here, generally get N=2 ^M, P=2 ^Q, M and Q are positive integer.The appropriate location of the input by this N point data being placed on P * N point IFFT is finished the frequency spectrum shift to the IFFT output signal simultaneously, (has omitted data block sequence number l among the figure) as shown in Figure 3.If the l time of quadrature modulator 6 (or P * N point IFFT) be input as X ' (l, k), k=0,1 ..., (P * N-1) }, then:

$X^{\&prime;}(l,k)=\left\{\begin{array}{cc}0,& k=0,\&CenterDot;\&CenterDot;\&CenterDot;,(k_0-1),\\ X(l,k-k_0),& k=k_0,\&CenterDot;\&CenterDot;\&CenterDot;,(k_0+N-1),\\ 0,& k=(k_0+N),\&CenterDot;\&CenterDot;\&CenterDot;,(P\&times;N-1),\end{array}---\left(2\right)\right.$

0≤k wherein ₀≤ (P * N-N) is called initial frequency deviation for the original position of N point input data sequence { X (l, k) } in P * N point input data sequence { X ' (l, k) }.Initial frequency deviation has been represented the position of frequency spectrum shift, and promptly the frequency spectrum of output signal has been shifted to [(k ₀-1/2) Δ f, (k ₀+ N-1/2) Δ f] scope within, Δ f is the subcarrier spacing of OFDM here.

IFFT is different with directly carrying out P * N point, have in the P * N point quadrature modulation utilization input continuous (being divided into one or two) (individual 0 the characteristics of P * N-N) by P N point IFFT, are finished P * N point IFFT, make total operand from Inferior complex multiplication and PN log ₂(PN) inferior complex addition has reduced to respectively Inferior complex multiplication and PNlog ₂N complex addition.Its algorithm is described below.

Step (1)-(5) that algorithm at first circulates below carrying out are total to P time, and Δ n value difference in each circulation is incremented to (P-1) from 0 successively.Deviation post in the P * N point sequence of the output that the N point time series that on behalf of this circulation, Δ n export is in the end total is called time offset.

(2) with sequence { X _{Δ n}(l, k) } for input, carry out N point IFFT, obtain N point time series { X _{1, Δ n}(l, n), n=0,1 ..., (N-1) };

$\left(3\right)---{\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">x</figure-callout>}}_{2,\mathrm{\&Delta;n}}(l,n)=x_{1,\mathrm{\&Delta;n}}(l,n){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">e</figure-callout>}}^j,n=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N-1);$

(4) with { x _{2, Δ n}(l, n), n=0,1 ..., (N-1) } and put in order preface by M bit-binary inverted order, obtain { x _{Δ n}(l, n), n=0,1 ..., (N-1) }, that is:

x _Δn(l，n)＝x _2，Δn(l，Or(M，n))，n＝0，1，…，(N-1)， (3)

Wherein function Or (M n) is write natural number n as the M bit binary number, and bit sequence left and right sides inverted order that will this binary number of expression is arranged, again with the output of the natural number of new binary number correspondence as function, such as M=3,

N=3 (Binary Zero 11), Or (M, n)=6 (binary one 10);

(5) establish Δ n '=Or (Q, Δ n), with sequence { x _{Δ n}(l, n) } be placed on the position of [N Δ n ', the N Δ n '+N-1] of P * N point sequence { x ' (l, n) }.

After circulating through P time, with obtain a complete P * N point sequence x ' (l, n), n=0,1 ..., (P * N-1) }, incite somebody to action at last x ' (l, n) } put in order preface by Q * M bit-binary, and multiply by the factor

The output sequence that gets final product to the end x (l, n), n=0,1 ..., (P * N-1) }, that is:

$x(l,k)=\frac{x^{\&prime;(l,\mathrm{Or}(Q\&times;M,n))}}{\sqrt{P}},n=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(P\&times;N-1)---\left(4\right)$

Can prove that the output sequence that obtains like this { x (l, n) } is with directly to carry out the output sequence that P * N point IFFT obtains just the same for input with { X ' (l, k) }, but operand from $\frac{\mathrm{<figure-callout\; id="2"\; label="PN"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">PN</figure-callout>}}{2}{\log }_2\left(\mathrm{PN}\right)$ Inferior complex multiplication and PN log ₂(PN) inferior complex addition has reduced to respectively $(\frac{\mathrm{<figure-callout\; id="2"\; label="PN"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">PN</figure-callout>}}{2}{\log }_{2}N+2N)$ Inferior complex multiplication and PNlog ₂N complex addition.

In P * N point quadrature modulation, change initial frequency deviation k ₀Value, can realize frequency spectrum shift easily at numeric field.System can adopt the operating position and the quality of various existent method detection communication channels, determines the best transmission frequency range of signal, and corresponding k is set then ₀Value can be moved [(k with signal ₀-1/2) Δ f, (k ₀+ N-1/2) Δ f] frequency range in, wherein Δ f is the subcarrier spacing that adopts among the OFDM.Carry out parallel serial conversion by parallel to serial converter 7 after P * N point quadrature modulation, parallel data flow is transformed into the data flow of serial.Digital signal behind the parallel serial conversion adds that by OFDM symbol generator 8 (Cyclic Prefix, CP) (Guard Interval GI) (protects the interval also can not have) to Cyclic Prefix, generation OFDM symbol at interval with protection.Then, produce the analog bandpass signal, behind amplifier 10 and band pass filter 11, by 12 emissions of transmitting terminal antenna through digital-to-analog converter 9.

At receiving terminal, the output signal of reception antenna 13 is at first passed through band pass filter 14, as far as possible interference signal and the noise outside the filtering useful signal frequency band.Amplifier amplifies the back to 15 signals and carries out analog to digital conversion by A-D converter 16.Analog to digital conversion comprises sampling, quantizes two key steps.Here adopt and owe Sampling techniques, promptly use 2 to 4 times sampling rate, rather than use the desired higher sampling rate of bandpass signal with respect to equivalent baseband signal bandwidth.After analog to digital conversion, in the receiving course of each packet, at first wrap and detect and sign synchronization 17.Signal synchronously carries out serial to parallel conversion by serial-parallel converter 18, carries out the phase place rotation by phase rotation device 19 again.

The phase place rotation is used for compensating the phase place rotation to time-domain signal that P * N point quadrature modulation is brought.If the l time (l=0,1 ...) N receive data be r (l, n), n=0,1 ..., (N-1) }, the data after the phase place rotation are { r ₁(l, n), n=0,1 ..., (N-1) }, then have:

$r_1(l,n)=r(l,n)e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C20041006567200181.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{\mathrm{nk}}_0/N},n=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N-1)\&CenterDot;---\left(5\right)$

Carry out N point FFT in phase place rotation back by fast fourier transformer 20, convert the signal into frequency domain, and carry out channel estimating by channel estimator 21 at frequency domain.In the communication system of the present invention, various existing channel estimation methods can be adopted, but initial frequency deviation k in P * N point quadrature modulation must be comprised in the estimated result of the method that is adopted ₀The phase place rotation that is brought with the time offset Δ n of the unknown

Provide the channel estimation methods that adopts zero forcing algorithm herein.

In zero forcing algorithm, before the data sequence of each packet, a channel estimation sequence is arranged, as shown in Figure 2.Channel estimation sequence is by L _cIndividual OFDM symbol constitutes, L _cSize decide according to the performance requirement of system.In each channel estimating OFDM symbol, the pseudo random sequence that transmission is fixed c (k)=± 1, and k=0,1 ..., (N _D-1) }, N _DIt is the data symbol number that sends in the OFDM symbol.Channel estimation sequence and data sequence send at frequency domain together.

At receiving terminal, establish the frequency domain received (be FFT after) channel estimation sequence and be { y _c(l, k), l=0,1 ..., (L _c-1), k=0,1 ..., (N _D-1) }, y wherein _c(l k) is the pairing reception sample value of k sample value of l channel estimation symbol, and then the estimated value of the frequency response of channel is:

$\hat{H}\left(k\right)=\frac{1}{L_c}\underset{l=0}{\overset{L_c-1}{\mathrm{\&Sigma;}}}\frac{y_c(l,k)}{c\left(k\right)},k=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;(N_D-1)\&CenterDot;---\left(6\right)$

The estimated value of the channel frequency response that frequency-domain equalizer 22 usefulness channel estimating obtain is carried out frequency domain equalization to the reception data of back.If the data sequence of receiving is { y _d(l, k), l=0,1 ..., (L _d-1), k=0,1 ..., (N _D-1) }, L _dBe the OFDM symbol numbers that data sequence comprises, the balanced data sequence is $\{{\tilde{y}}_d(l,k),l=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(L_d-1),k=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N_D-1)\},$ Then have:

${\tilde{y}}_d(l,k),=y_d(l,k)/\hat{H}\left(k\right),l=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(L_d-1),k=\mathrm{0,1},\&CenterDot;\&CenterDot;\&CenterDot;,(N_D-1)\&CenterDot;---\left(7\right)$

Data after the frequency domain equalization are carried out parallel serial conversion, are carried out the symbol inverse mapping, carried out the channel deinterleaving by channel deinterleaver 25 by symbol inverse mapping device 24 by parallel to serial converter 23, and carry out channel decoding by channel decoder 26, obtain data output 27.The implementation method that symbol inverse mapping, channel deinterleaving and channel decoding adopt is decided according to method that transmitting terminal sign map, channel interleaving and chnnel coding adopted.

Claims (1)

1, a kind of fast fourier transform of utilizing that is applied to middle and high fast wireless communication system realizes the method for full digital wireless communication system, comprise launching technique and method of reseptance, it is characterized in that: at transmitting terminal, data producer (1) produces and sends data, the The data that is produced is based on the burst structure of bag, the front end of each packet is bag detection, synchronizing sequence and a channel estimation sequence, is used to wrap detection, sign synchronization and channel estimating; Each packet at first passes through channel encoder (2) coding, has added the redundant information that is used for verification and error correction; Carry out channel interleaving by channel interleaver (3) after the chnnel coding, alleviate burst error in the Channel Transmission Effect on Performance; The output bit flow of channel interleaving forms the symbols streams that can be used for transmitting through symbol mapper (4); Then carry out serial to parallel conversion by serial-parallel converter (5), the symbols streams of serial is transformed into parallel symbols streams, as the input of quadrature modulator (6), quadrature modulator (6) carries out quadrature modulation P time to the N point incoming symbol sequence of each group, and the step of this quadrature modulation is as follows:

(a) the N point symbol sequence of input is carried out the rotation of frequency domain phase place, making the pairing time offset of N point sample value sequence of this quadrature modulation output is Δ n, this time offset Δ n is increased to P-1 successively from 0, and each quadrature modulation increases by 1, and above-mentioned frequency domain phase place rotates to be:

$X_{\mathrm{\&Delta;n}}(l,k)=X(l,k)e^{j2\mathrm{\&pi;}\frac{\mathrm{\&Delta;nk}}{\mathrm{PN}}},k=\mathrm{0,1},...,(N-1),$

Wherein X (l, k), k=0,1 ..., (N-1) } and { X _{Δ n}(l, k), k=0,1 ..., (N-1) } and the N point symbol sequence that obtains after being respectively the N point symbol sequence of input and carrying out frequency domain phase place rotation;

(b) to { X _{Δ n}(l, k), k=0,1 ..., (N-1) } and carry out N point inverse fast fourier transformed, obtain N point sample value sequence { x _{1, Δ n}(l, n), n=0,1 ..., (N-1) };

(c) to { x _{1, Δ n}(l, n), n=0,1 ..., (N-1) } and carry out the rotation of time domain phase place, the signal of output is moved [(k ₀-1/2) Δ f, (k ₀+ N-1/2) Δ f] frequency band range within, Δ f is the subcarrier spacing of OFDM here, k ₀Be initial frequency deviation, set or change adaptively that above-mentioned time domain phase place rotates to be according to the requirement of system works frequency range:

$x_{2,\mathrm{\&Delta;n}}(l,n)=x_{1,\mathrm{\&Delta;n}}(l,n)e^{j2\mathrm{\&pi;}\frac{(\mathrm{nP}+\mathrm{\&Delta;n})k_0}{\mathrm{PN}}},n=\mathrm{0,1},...,(N-1),$

Here { x _{2, Δ n}(l, n), n=0,1 ..., (N-1) } and N point sample value sequence for obtaining after the time domain phase place rotation;

(d) with { x _{2, Δ n}(l, n), n=0,1 ..., (N-1) } and press M=1og ₂N bit-binary inverted order is put in order preface, obtains { x _{Δ n}(l, n), n=0,1 ..., (N-1) }, the whole preface of above-mentioned M bit-binary inverted order is write the sample value sequence number in the former sequence as the M bit binary number, and bit sequence left and right sides inverted order that will this binary number of expression is arranged, again with the natural number of the new binary number correspondence new sequence number as former sample value;

(e) with sequence { x _{Δ n}(l, n), n=0,1 ..., (N-1) } and be placed on the position of [N Δ n ', the N Δ n '+N-1] of P * N point sequence { x ' (l, n) }, Δ n ' is the Q bit-binary inverted order of Δ n here, Q=log ₂P, above-mentioned Q bit-binary inverted order is write Δ n as the Q bit binary number, and bit sequence left and right sides inverted order that will this binary number of expression is arranged, again with the natural number of new binary number correspondence as Δ n ', each quadrature modulation obtains N the output sample that time offset is Δ n, obtain after P the quadrature modulation P * N point output sample sequence x ' (l, n), n=0,1,, (P * N-1) }, to { x ' (l, n) } carry out the whole preface of Q * M bit-binary inverted order, to the end the output sample sequence x (l, n), n=0,1,, (P * N-1) }

Data are carried out parallel serial conversion by parallel to serial converter (7) after quadrature modulator (6) is handled, and parallel data flow are transformed into the data flow of serial; Digital signal behind the parallel serial conversion adds Cyclic Prefix by OFDM symbol generator (8), generates OFDM (Orthogonal Frequency Division Multiplexing, OFDM) symbol; Then, produce the analog bandpass signal, behind amplifier (10) and band pass filter (11), launch by transmitting terminal antenna (12) through digital-to-analog converter (9);

At receiving terminal, the signal that reception antenna (13) receives is by interference signal and noise outside band pass filter (14) the filtering useful signal frequency band, signal carries out analog to digital conversion by A-D converter (16) after amplifier (15) amplifies, after analog to digital conversion, in the receiving course of each packet, at first wrap and detect and sign synchronization (17), obtain the original position of each Frame, signal synchronously carries out serial to parallel conversion by serial-parallel converter (18), and carry out phase place by phase rotation device (19) and rotate, this phase place rotation is used for compensating the phase place rotation to time-domain signal that quadrature modulator (6) brings, and its method is:

$r_1(l,n)=r(l,n)e^{-j2\mathrm{\&pi;n}{k}_0/N},n=\mathrm{0,1},...,(N-1),$

Wherein r (l, n), n=0,1 ..., (N-1) } and be N point receiving data sequence, { r ₁(l, n), n=0,1, (N-1) } be the data after the phase place rotation, carry out the conversion of N point fast Fourier in phase place rotation back by fast fourier transformer (20), convert the signal into frequency domain, and carry out channel estimating by channel estimator (21) at this frequency domain, frequency-domain equalizer (22) carries out frequency domain equalization with the estimated value of the channel frequency response that channel estimating obtains to the reception data of back, data behind the frequency domain equalization are carried out parallel serial conversion by parallel to serial converter (23) successively, carry out the symbol inverse mapping by symbol inverse mapping device (24), carry out the channel deinterleaving by channel deinterleaver (25), and carry out channel decoding by channel decoder (26), obtain data outputs (27).

Images