CN1466291A - OFDM transmitter for raising transfer rate and signal compressing method - Google Patents

Abstract

An OFDM transmitter capable of improving a transmission rate of OFDM signals and a method for compressing signals thereof are provided to increase a transmission rate of whole data by reducing the length of one OFDM symbol. An inverse fourier transform unit(200) transforms OFDM(Orthogonal Frequency Division Multiplexing) signals of a frequency domain into OFDM signals of a time domain through inverse fourier transform. An even function extracting unit(210) extracts an even function signal symmetrical to a y axis from the OFDM signals of the time domain. An odd function extracting unit(230) extracts an odd function signal symmetrical to the origin from the OFDM signals of the time domain. The even function signal is formed of the sum of a first even function signal and a second even function signal. A first selecting unit(213) selects anyone of the first even function signal and the second even function signal. The odd function signal is formed of the sum of a first odd function signal and a second odd function signal. A second selecting unit(233) selects anyone of the first odd function signal and the second odd function signal. A first cutting unit(215) takes one half signal of the selected even function signal. A second cutting unit(235) takes one half signal of the selected odd function signal.

Description

Be used to improve the OFDM transmitter and the compression method of transmission rate

Technical field

(orthogonal frequency divisionmultiplexing, OFDM) transmitter relate in particular to a kind of by even function that uses ofdm signal and the transmitter that odd function improves transmission rate to the present invention relates to a kind of OFDM.

Background technology

In general, the broadcasting system of high definition TV (HDTV) can be divided into image encoding unit and modulating unit roughly.The image encoding unit becomes the digital data compression of the about 1Gbps that imports from the high-definition image source data of 15～18Mbps.The frequency band passage of modulating unit by approximate 6～8MHzd sends to receiving terminal with the numerical data of tens Mbps.Distribute to the very high frequency(VHF)/hyperfrequency (VHF/UHF) of general television broadcasting mode by use, digital HDTV broadcasting mode has adopted the synchronous broadcasting method in land.The modulator approach that is used for the broadcasting system of HDTV must satisfy following condition because land broadcasts environment synchronously.

At first, be used for the demanding spectrum efficiency of modulation of the broadcasting system of HDTV, so that send the numerical data of tens Mbps by the limited frequency band passage of 6～8MHz.Secondly, because close to buildings or certain facility and multipath fading takes place often, the modulator approach that is used for the broadcasting system of HDTV should be antifading.The 3rd, the modulator approach that is used for the broadcasting system of HDTV should be able to resist co-channel interference, because the interference of the channel of this feature takes place often because of general anolog TV signals.In addition, the digital modulation signals in the broadcasting system of HDTV should be able to reduce to minimum to the interference in the general simulated television receiver.

As transmission rate that can improve the per unit bandwidth and pre-anti-tampering Ditital modulation method, in Europe, the synchronous broadcasting method in land that OFDM (OFDM) method is used as follow-on HDTV uses.

The symbol sebolic addressing that ofdm system is come in serial is converted into the modular unit parallel data, then these parallel symbol multichannels is distributed on different subcarrier (sub-carrier) frequency.Different with the conventional method that uses single carrier, ofdm system uses multicarrier (multiple carrier).In this multicarrier, mutually orthogonal between each carrier wave.Orthogonality means that the product of two carrier waves is zero, and this is to use one of necessary condition of multicarrier.Ofdm system realizes that by fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) this can directly obtain by the definition of orthogonality between the carrier wave and fast Fourier transform (FFT).

Fig. 1 is the functional-block diagram that explanation is used for the general TDS-OFDM transmitter of transmission OFDM signal.The input data are encoded so that receiving element (not marking) can be by (forwarderror correcting, FEC) error detection method of unit 10 settings detects and correction error by the forward direction adjuster.N point IFFT unit 20 is transformed to N time-domain sampling data to coded data.Here, N represents the frequency domain call number, simultaneously also vice carrier index number.

GI inserts unit 50 and personal distance (GI) is inserted into the OFDM symbol that is for conversion into N time-domain sampling data.Being inserted into N the GI in the sampled data unit is the data that obtain by the sampled data of partly duplicating N sampled data rear end.

Synchronizing information is inserted unit 40 and is inserted synchronizing information, is used for forecasting regularly synchronizing information and channel, and the PN sequence was for example arranged before GI.Then, 50 pairs of ofdm signal filtering of filter cell, RF unit 60 then carries out radio frequency processing to the signal of filtering and a signal that obtains is transmitted on certain channel.

As mentioned above, traditional IFFT unit 20 uses the OFDM method to make each subcarrier quadrature, simultaneously described subcarrier is inserted into the frequency range of appointment.This OFDM method is adjusted (align) data in each subcarrier of frequency domain, carry out inverse Fourier transform, and modulate this data.IFFT multiplies each other with each OFDM data and these quadrature subcarriers.The ofdm signal that is modulated in the time domain is sent to transmission channel.As shown in Figure 2, the signal by 20 modulation of IFFT unit does not need special processing just to be divided into a real signal real_data and an empty signal img_data.That is, the time domain OFDM signal S (n) by the IFFT cells modulate is expressed by following formula 1:

＜formula 1 〉 $S\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k{e}^{\mathrm{j\φk}}{e}^{\mathrm{jk}{\mathrm{\ω}}_{d}n}n=\mathrm{0,1,2,3},...,N-1$ Here, α _ke ^{J φ k}Expression is applied to the OFDM data of each subcarrier, ω _dThe interval of vice carrier wave.In addition, n represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

Therefore, IFFT unit 20 usefulness subcarriers and OFDM data multiply each other respectively, have reduced the hardware spending of system for this reason.

Yet because IFFT unit 20 can send the modulated signal of making in the time domain without any need for just handling, modulated time-domain signal just must distribute a large amount of time to give the OFDM symbol.As a result, the data transfer rate that sends of signal is lower than possible.

Summary of the invention

Therefore, an object of the present invention is to provide a kind of OFDM transmitter, it presses the data transfer rate of the time domain OFDM signal raising ofdm signal of OFDM method modulation by compression.

In order to reach the aforesaid purpose of the present invention, a kind of OFDM transmitter is provided, it comprises: the inverse fast Fourier transform unit is used for a frequency domain ofdm signal inverse fast Fourier transform and becomes time domain OFDM signal; The even function extraction unit is used for extracting the even function signal that has symmetric property about Y-axis in time domain OFDM signal; The odd function extraction unit is used for extracting the odd function signal that has symmetric property about initial point in time domain OFDM signal; First selected cell, be used for selecting the first and second even function signals one of at least, the even function signal by the first and second even function signals and form; Second selected cell, be used for selecting the first and second odd function signals one of at least, the odd function signal by the first and second odd function signals and form; First interception unit is used to intercept half of even function signal that first selected cell selects; Second interception unit is used to intercept half of odd function signal that second selected cell selects.In addition, the OFDM transmitter also comprises personal distance insertion unit, be used for inserting by the front end signal of half signal of first interception unit intercepting as the personal distance of even function signal with by the initial point symmetric signal of the front end signal of half signal of second interception unit intercepting personal distance as the odd function signal.

Preferable is that the odd function signal of being selected by the even function signal and second selected cell of the selection of first selected cell satisfies Hilbert transform.

Another aspect of the present invention, the compression method that is provided for the OFDM transmitter comprises the steps: that a frequency domain ofdm signal inverse fast Fourier transform becomes time domain OFDM signal; Be extracted in even function signal that the first and second even function signal sums by have symmetric property about Y-axis in the time domain OFDM signal form and by in time domain OFDM signal, having the odd function signal that the first and second odd function signal sums of symmetric property are formed about initial point; Select in the first and second even function signals one of at least with the first and second odd function signals at least one signal; Selecteed even function signal and selecteed odd function signal are respectively intercepted half.

In addition, the compression method that is used for the OFDM transmitter also comprises as next procedure: the front end signal that is inserted in half signal of intercepting of intercepting step as the personal distance of even function signal and as described in the initial point symmetric signal of front end signal of half signal as the personal distance of odd function signal.

Preferable is that even function signal and the odd function signal selected in described selection step satisfy Hilbert transform.

As a result, by in the ofdm signal that inverse fast Fourier transform is crossed, extracting even function signal and odd function signal respectively and utilizing the even function signal, send signal and can be compressed half about Y-axis symmetric property and odd function signal character about former point symmetry.

Description of drawings

When with reference to following detailed description and and accompanying drawing when considering together, to the more complete correct evaluation of the present invention and subsidiary wherein advantage can be healed by understanding better obvious in vain.Similar reference symbol in the accompanying drawing is represented same or analogous element.

Fig. 1 is the principle block diagram of the traditional OFDM transmitter of explanation;

Fig. 2 is the more detailed block diagram of the explanation IFFFT unit of Fig. 1;

Fig. 3 is the principle block diagram of OFDM transmitter in the explanation embodiments of the invention;

Fig. 4 is that explanation is inserted processed signal flow graph in the unit in the personal distance of Fig. 3; With

Fig. 5 is the flow chart of series of steps that is presented at the signal processing method of the OFDM transmitter among Fig. 3.

Embodiment

OFDM transmitter and compression method wherein according to the embodiment of the invention are made following detailed description with reference to the accompanying drawings.

Fig. 3 is the principle block diagram of OFDM transmitter in the explanation embodiments of the invention.What especially will say is, Fig. 3 is the more detailed block diagram of an explanation TDS-OFDM transmitter, is used for explaining a kind of processing procedure that the frequency-domain OFDM data-modulated is become time domain OFDM signal and compress this ofdm signal.

That is, the data that are input to the OFDM transmitter are passed through a FEC unit 10 by error coding, and are modulated into time domain OFDM signal by IFFT unit 20.Subsequently, ofdm signal by 20 modulation of IFFT unit passes through even function extraction unit 210, odd function extraction unit 230, first and second selected cells 213 and 233, be compressed into a predetermined transmission signal with first and second interception unit 215 and 235, again by GI insert unit 300 insert a personal distance (guard interval, GI).

Even function extraction unit 210 extract with from the corresponding signal of the even function in the time domain OFDM signal of IFFT unit 200.This even function is always about the Y-axis symmetry.For example, the ofdm signal S (n) from IFFT unit 200 is expressed by following formula 2:

＜formula 2 〉 $S\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k{e}^{\mathrm{j\φk}}{e}^{\mathrm{jk}{\mathrm{\ω}}_{d}n}n=\mathrm{0,1,2,3},...,N-1$ Here, α _ke ^{J φ k}Expression is applied to the OFDM data of each subcarrier, ω _dThe interval of vice carrier wave.In addition, n represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

When ofdm signal S (n) is expressed by following formula 2, express by following formula 3 corresponding to the signal of this even function:

＜formula 3 〉 $E\left(n\right)=0.5\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}({\mathrm{\α}}_k{e}^{\mathrm{j\φk}}{e}^{\mathrm{jk}{\mathrm{\ω}}_{d}n}+{\mathrm{\α}}_k{e}^{\mathrm{j\φk}}{e}^{-\mathrm{jk}{\mathrm{\ω}}_{d}n})$ $=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k{e}^{\mathrm{j\φk}}\cos \left({\mathrm{k\ω}}_{d}n\right)$ $=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)...........e1\left(n\right)$ $+\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{j\α}}_k\sin \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)...........e2\left(n\right)$

Odd function extraction unit 230 extract with from the corresponding signal of odd function among the time domain OFDM signal S (n) of IFFT unit 200.This odd function is about former point symmetry.And express by following formula 4:

＜formula 4 〉 $O\left(n\right)=0.5\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}({\mathrm{\α}}_k{e}^{\mathrm{j\φk}}{e}^{\mathrm{jk}{\mathrm{\ω}}_{d}n}-{\mathrm{\α}}_k{e}^{\mathrm{j\φk}}{e}^{-\mathrm{jk}{\mathrm{\ω}}_{d}n})$ $=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k{e}^{\mathrm{j\φk}}j\sin \left({\mathrm{k\ω}}_{d}n\right)$ $=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_{k}j\cos \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)...........o1\left(n\right)$ $-\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)...........o2\left(n\right)$ That is, even function E (n) and odd function O (n) have following relation:

Cos (φ _k) cos (k ω _dN) Hilbert transform is cos (φ _k) sin (k ω _dN),

-sin (φ _k) sin (k ω _dN) Hilbert transform is sin (φ _k) cos (k ω _dN), here, cos (φ _k) and sin (φ _k) all be constant, they are constant in the OFDM symbol.

Because the cos (φ that even function extraction unit 210 is selected _k) and sin (φ _k) all become constant, even function signal E (n) comprise e1 (n) and e2 (n) and, they all are cosine functions, the odd function signal O (n) that odd function extraction unit 230 is selected comprise o1 (n) and o2 (n) with, they all are SIN function.

Therefore, first selected cell 213 is selected an even function signal E (n) with e1 (n) and e2 (n) from even function extraction unit 210.

In addition, second selected cell 233 is selected an odd function signal O (n) with o1 (n) and o2 (n) from odd function extraction unit 230.Here, under the requirement of Hilbert transform, first and second selected cells 213 and 233 must be selected described signal.Correspondingly, receiving terminal is demodulated to even function signal E (n) and odd function signal O (n) to the even function signal e1 (n) and the odd function signal o2 (n) that select by Hilbert transform from first and second selected cells 213 and 233.When first selected cell 213 was selected e1 (n), second selected cell 233 must select to have with e1 (n) o2 (n) of Hilbert transform relation.On the contrary, when first selected cell 213 was selected e2 (n), second selected cell 233 must select to have with e2 (n) o1 (n) of Hilbert transform relation.

For example, can select respectively by first and second selected cells 213 and 233 with following formula 5 and 6 even function signal e1 (n) and the odd function signal o2 (n) that express:

＜formula 5 〉 $e1\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$

＜formula 6 〉 $o2\left(n\right)=-\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$

Shown in the explanation of Fig. 3, in even function signal e1 (n) and odd function signal o2 (n) from first and second selected cells 213 and 233, when n=0,1,2,3 ..., when the condition of N-1 satisfies, even function signal e1 (n) is about the Y-axis symmetry, and odd function signal o2 (n) is long-pending symmetrical about bearing, and promptly initial point is at the N/2-1 place.

By utilizing symmetric property, 215 interceptings of first interception unit are about half of the even function signal e1 (n) of Y-axis symmetry, and 235 interceptings of second interception unit are about half of the odd function signal o2 (n) of described former point symmetry.

In Fig. 3, (n) (n) express by following formula 7 and formula 8 with odd function signal o2 ' from first and second interception unit 215 and the 235 even function signal e1 ' that export:

＜formula 7 〉 $e1\text{'}\left(n\right)=\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$

＜formula 8 〉 $o2\text{'}\left(n\right)=-\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$ That is, because even function signal e1 ' (n) (n) has symmetry characteristic with odd function signal o2 ', the previous section of signal is intercepted and is sent in the passage, and the signal aft section does not need to be sent out.Even function signal e1 ' (n) previous section and the signal previous section addition result that received about the Y-axis symmetry, and odd function signal o2 ' (n) previous section and the signal previous section addition result that received about former point symmetry, thus, (n) carry out demodulation at receiving terminal dual function signal e1 ' with odd function signal o 2 ' (n).

GI inserts unit 50 GI is inserted in from the even function signal e1 ' of first and second interception unit 215 and 235 (n) and odd function signal o2 ' front (n).GI is the data that obtain by the rear end sampled data of partly duplicating the OFDM symbol.

(n) (n) the GI eGI and the oGI of front have the relation of following formula 9 and 10 according to the principle of Fig. 4 with odd function signal o2 ' to be inserted in even function signal e1 ' from first and second interception unit 215 and 235 respectively.

With reference to Fig. 4, insert even function signal e1 ' GI eGI (n) and become from rear end (A) signal of the original even function signal e1 (n) of first selected cell, 213 outputs.Promptly by using the characteristic about the Y-axis symmetry, the signal e1 ' of first interception unit, 215 interceptings (n) front end (A ') has become the rear end (A) of signal e1 (n).Correspondingly, inserting even function signal e1 ' GI eGI (n) is expressed as follows by formula 9:

＜formula 9 〉 $\mathrm{eGI}\left(n\right)=\underset{n=-G}{\overset{-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$

In addition, inserting odd function signal o1 ' GI oGI (n) becomes from rear end (B) signal of the original odd function signal o1 (n) of second selected cell, 233 outputs.Promptly by using the characteristic about former point symmetry, the signal o1 ' of second interception unit, 235 interceptings (n) front end (B ') has become the rear end (B) of signal o1 (n).Therefore, inserting odd function signal o1 ' GI oGI (n) is expressed as follows by formula 10:

＜formula 10 〉 $\mathrm{oGI}\left(n\right)=-\underset{n=-G}{\overset{-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$

Therefore, ofdm signal Xe (n) and Xo (n) are expressed by following formula 11 and 12, wherein, GIeGI and oGI be inserted into even function signal e1 ' (n) and odd function signal o1 ' (n).

＜formula 11 〉 $\mathrm{Xe}\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}[\underset{n=-G}{\overset{-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)+\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)]$

＜formula 12 〉 $\mathrm{Xo}\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}[-\underset{n=-G}{\overset{-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)-\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)]$

As mentioned above, even function signal and odd function signal be from extracting through the ofdm signal of IFFT unit 20 modulation, so that by using the even function signal can be compressed about the characteristic of Y-axis symmetry and the odd function signal characteristic OFDM signal about former point symmetry.

That is, the length of even function signal and odd function signal has reduced half, thereby so ofdm signal length be reduced and improved whole data transfer rate.

Fig. 5 is the flow chart that shows according to the series of steps of the signal processing method of TDS-OFDM transmitter in the embodiments of the invention.

At first, the data that are input to transmitter are carried out error coding and are modulated into time domain OFDM signal (S10) by IFFT unit 200 by FEC unit 10.

Even function extraction unit 210 and odd function extraction unit 230 extract the characteristic even function signal and the odd function signal (S20) that has about the characteristic of former point symmetry that has about the Y-axis symmetry respectively in from the time domain OFDM signal of IFFT unit 200.

The even function signal E (n) that is extracted by even function extraction unit 210 is made up of two cosine function e1 (n) and e2 (n) sum, and the odd function signal O (n) that is extracted by odd function extraction unit 230 is made up of two SIN function o1 (n) and o2 (n) sum.

Secondly, first selected cell 213 and second selected cell 233 are selected an even function signal, for example select e1 (n) from the E (n) that comprises e1 (n) and e2 (n) sum.In addition, second selected cell 233 is selected odd function signal o2 (n) in the odd function signal O (n) that is made of o1 (n) and o2 (n) sum, this odd function signal o2 (n) with select even function signal e1 (n) to have Hilbert transform relation (S30) by first selected cell 213.

First interception unit 215 is by using the relevant Y-axis symmetry characteristic of even function signal e1 (n), and half of intercepting even function signal e1 (n) is e1 ' (n) (S40).Second interception unit 235 is by using the relevant initial point symmetry characteristic of odd function signal o2 (n), and half of intercepting odd function signal o2 (n) is o2 ' (n) (S40).

GI inserts unit 50 and respectively GI eGI and oGI is inserted into from the even function signal e1 ' of first and second interception unit 215 and 235 (n) and odd function signal o2 ' (n) (S50).

Still with reference to Fig. 4, the GI eGI that (n) inserts before at even function signal e1 ' becomes from rear end (A) signal of the original even function signal e1 (n) of first selected cell, 213 outputs.In addition, the GI oGI that (n) inserts before at odd function signal o1 ' becomes from rear end (B) signal of the original odd function signal o1 (n) of second selected cell, 233 outputs.That is, by using characteristic about former point symmetry, with respect to from the signal o1 ' of second interception unit, 235 interceptings (n) the initial point symmetric signal of front end (B ') be the rear end (B) of signal o1 (n).

In order to predict regularly synchronizing signal and certain channel, synchronizing information is inserted unit 40 and inserted synchronizing information before GI eGI and oGI is inserted into, and PN sequence for example is in ofdm signal Xe (n) and the Xo (n) (S60).

Then, 60 pairs of ofdm signals of filter unit 50 and radio frequency unit carry out filtering and radio frequency processing and ofdm signal are sent to transmission channel (S70).

Therefore, even function signal and odd function signal are extracted from the time domain OFDM signal of crossing through inverse fast Fourier transform to be used for compressing described ofdm signal, have therefore improved message transmission rate.

According to the present invention,, send signal and can be compressed half by in by the adjusted ofdm signal in IFFT unit, extracting even function signal and odd function signal respectively and utilizing the even function signal about Y-axis symmetric property and odd function signal character about former point symmetry.

As a result, thus the length of OFDM symbol is reduced the transmission rate that has improved whole data.

Because the present invention can implement under the situation that does not break away from its essence spirit and substantive characteristics in a variety of forms, therefore should be understood that, aforesaid embodiment is not limited by previously described any details, unless be specifically noted in addition, within the invention spirit and scope of appending claims definition, should broadly explain, therefore all changes and revision all should drop on these claims in the fixed scope, therefore the description that perhaps is equal to this scope also should be at these additional claims contains.

Claims (16)

1. OFDM transmitter comprises:

The inverse fast Fourier transform unit is used for a frequency domain ofdm signal inverse fast Fourier transform and becomes time domain OFDM signal;

The even function extraction unit is used for extracting the even function signal that has symmetric property about Y-axis in time domain OFDM signal;

The odd function extraction unit is used for extracting the odd function signal that has symmetric property about initial point in time domain OFDM signal;

First selected cell, be used for selecting the first and second even function signals one of at least, the even function signal by the first and second even function signals and form;

Second selected cell, be used for selecting the first and second odd function signals one of at least, the odd function signal by the first and second odd function signals and form;

First interception unit is used to intercept half of even function signal that first selected cell selects;

Second interception unit is used to intercept half of odd function signal that second selected cell selects; With

Personal distance is inserted the unit, be used for inserting by the front end signal of half signal of first interception unit intercepting as the personal distance of even function signal with by the initial point symmetric signal of the front end signal of half signal of second interception unit intercepting personal distance as the odd function signal.

2. according to the OFDM transmitter of claim 1, wherein, the even function signal of being selected by first selected cell satisfies Hilbert transform, and the odd function signal of being selected by second selected cell also satisfies Hilbert transform.

3. according to the OFDM transmitter of claim 1, wherein, the inverse fast Fourier transform unit becomes following time domain OFDM signal to the frequency domain ofdm signal inverse fast Fourier transform $S\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k{e}^{\mathrm{j\φk}}{e}^{\mathrm{jk}{\mathrm{\ω}}_{d}n}n=\mathrm{0,1,2,3},...,N-1$ Here, α _ke ^{J φ k}Expression is applied to the OFDM data of each subcarrier, ω _dThe interval of vice carrier wave, n represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

4. according to the OFDM transmitter of claim 1, wherein, the even function signal E (n) that the even function extraction unit extracts is as e1 (n) and e2's (n) and press following formulate: $E\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)...........e1\left(n\right)$ $+\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}j{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\cos \left({k\mathrm{\ω}}_{d}n\right)...............e2\left(n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

5. according to the OFDM transmitter of claim 1, wherein, the odd function signal O (n) that the odd function extraction unit extracts is as o1 (n) and o2's (n) and press following formulate: $O\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_{k}j\cos \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)................o1\left(n\right)$ $-\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)............o2\left(n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

6. according to the OFDM transmitter of claim 2, wherein, when the even function signal e1 (n) that selects by first selected cell by following formula $e1\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$ During expression, the odd function signal o2 (n) that is selected by second selected cell is by following equation expression: $o2\left(n\right)=-\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

7. according to the OFDM transmitter of claim 1, wherein, when half of the even function signal of first interception unit intercepting is that e1 ' is (n) by following formula $e1\text{'}\left(n\right)=\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$ During expression, the personal distance eGI (n) that is inserted into selected even function signal e1 (n) is by following equation expression: $\mathrm{eGI}\left(n\right)=\underset{n=-G}{\overset{-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

8. according to the OFDM transmitter of claim 1, wherein, when being that o2 ' is (n) by following formula by half of the odd function signal of second interception unit intercepting $o2\text{'}\left(n\right)=-\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$ During expression, be inserted into selected odd function signal o2 ' personal distance oGI (n) (n) by following equation expression: $\mathrm{oGI}\left(n\right)=-\underset{n=-G}{\overset{-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

9. a compression method that is used for the OFDM transmitter comprises the steps:

The frequency domain ofdm signal inverse fast Fourier transform is become time domain OFDM signal;

Be extracted in even function signal that the first and second even function signal sums by have symmetric property about Y-axis in the time domain OFDM signal form and by in time domain OFDM signal, having the odd function signal that the first and second odd function signal sums of symmetric property are formed about initial point;

Select in the first and second even function signals one of at least with the first and second odd function signals at least one signal; With

Selecteed even function signal and selecteed odd function signal are respectively intercepted half;

The front end signal that is inserted in half signal that intercepting intercepts in the step is as the initial point symmetric signal of the front end signal of the personal distance of even function signal and half signal of intercepting in the intercepting step personal distance as the odd function signal.

10. according to the method for claim 9, wherein, even function signal and the odd function signal selected in described selection step satisfy Hilbert transform.

11. according to the method for claim 9, wherein, the time domain OFDM signal in the inverse fast Fourier transform step is by following equation expression: $S\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k{e}^{\mathrm{j\φk}}{e}^{\mathrm{jk}{\mathrm{\ω}}_{d}n}n=\mathrm{0,1,2,3},...,N-1$ Here, α _ke ^{J φ k}Expression is applied to the OFDM data of each subcarrier, ω _dThe interval of vice carrier wave, n represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

12. according to the method for claim 9, wherein, the even function signal E (n) in extraction step is as e1 (n) and e2's (n) and by following formulate: $E\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)...........e1\left(n\right)$ $+\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}j{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\cos \left({k\mathrm{\ω}}_{d}n\right)...............e2\left(n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

13. according to the method for claim 9, wherein, the odd function signal O (n) that is extracted in extraction step is as o1 (n) and o2's (n) and by following formulate: $O\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_{k}j\cos \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)................o1\left(n\right)$ $-\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)............o2\left(n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

14. according to the method for claim 10, wherein, when the even function signal e1 (n) that is selecting to select in the step by following formula: $e1\left(n\right)=\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$ During expression, selected odd function signal o2 (n) is by following equation expression: $o2\left(n\right)=-\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

15. according to the method for claim 9, wherein, in the personal distance inserting step, when half of the even function signal that intercepts in the step in intercepting be e1 ' (n) by following formula: $e1\text{'}\left(n\right)=\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$ During expression, the personal distance eGI (n) that is inserted into selected even function signal e1 (n) is by following equation expression: $\mathrm{eGI}\left(n\right)=\underset{n=-G}{\overset{-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\cos \left({\mathrm{\φ}}_k\right)\cos \left({\mathrm{k\ω}}_{d}n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

16. according to the method for claim 9, wherein, in the personal distance inserting step, when half of the odd function signal that intercepts in the step in intercepting is that o2 ' is (n) by following formula $o2\text{'}\left(n\right)=-\underset{n=0}{\overset{N/2-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$ During expression, be inserted into selected odd function signal o2 ' personal distance oGI (n) (n) by following equation expression: $\mathrm{oGI}\left(n\right)=-\underset{n=-G}{\overset{-1}{\mathrm{\Σ}}}{\mathrm{\α}}_k\sin \left({\mathrm{\φ}}_k\right)\sin \left({\mathrm{k\ω}}_{d}n\right)$ Here, ω _dThe interval of vice carrier wave, n=0,1,2,3 ..., N-1 represents the call number of each time-domain sampling data, and k is illustrated in the call number of the subcarrier that is loaded with the OFDM data in the frequency domain.

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