CN1682508A - Iterative evaluation and equalization of asymmetry between in-phase and quadrature branches in multi-carrier transmission systems - Google Patents

Abstract

In an OFDM method, the distortion of the transmitted wireless signal in data blocks, which is caused by IQ asymmetry at the transmitter or receiver and by channel distortion, can be estimated and equalized by means of an iterative method. The method is used particularly advantageously in a direct mixing receiver.

Description

Asymmetric iteration assessment, equilibrium between homophase and orthogonal branches in the tds-ofdm transmission system

Technical field

The invention relates to a kind of method that is used to estimate with the correcting wireless distorted signals, wherein the wireless signal distortion is by reflector or receiver and IQ is asymmetric and by channel distortion and form, described wireless signal is with the emission of multicarrier launching technique, and the invention relates to the device that carries out described method.

Background technology

In European DVB (digital photography broadcasting) system, developed the digital transmission system that is used for satellite (DVB-S), wired (DVB-C) and is used for received terrestrial digital broadcasting emission (DVB-T), and existing well-designed corresponding specification.Because at the existing problematic launching condition of terrestrial wireless channel, so be OFDM launching technique (orthogonal frequency division multitask) in the launching technique of DVB-T specification defined, it can effectively resist the launching condition of difficulty.

Another important applied field of described OFDM launching technique is the high-speed radio transmit network, for example WLAN (wireless district network), particularly defined launching technique in standard IEEE 802.11a and 11g and HIPERLAN/2.

Described OFDM launching technique is a multicarrier launching technique, and wherein splitting traffic between many parallel (quadrature) subcarrier wherein is to adjust subcarrier by low relatively data speed.As shown in Figure 1, dispose (inferior) carrier frequency, thereby wear among the wide K in an emission, described (inferior) carrier frequency is each other at a distance of same distance.Described carrier frequency is the both sides that are symmetrically located at a centre frequency f.In time zone, the replacement of all k carrier frequencies forms the OFDM symbol.In frame form or breach (burst), finish described data transmission, a frame is the OFDM symbol that comprises similar number.

Based on the known reception notion of the heterodyne reception principle of mixing, can finish the reception and the demodulation of OFDM wireless signal with follow-up digital quadrature.Yet, suppress for image frequency, reduce power consumption and the main cause of avoiding chip-external filter, more and more useful reception notion is to use the method for directly mixing.Directly mixing in the receiver notion, receive with the wireless signal that amplifies by an antenna and to be divided into homophase (I) and quadrature (Q) branch, and mix with the output frequency of a regional oscillator in two branches, the oscillator frequency of described blender is delivered in reciprocal 90 degree skews by a phase deviation device.So, receive in the notion at this, use Analogical Circuit Technique, carry out described quadrature demodulation or reclaim described information-bearing baseband signal.

The incorrectness of joining known to stating in the processing procedure product and the imperfection of analog mixer and oscillator, and filter described in I and the Q branch and between error, cause the asymmetric or IQ distortion (distortion) of so-called IQ, that is the asymmetry of amplitude and phase place between the quadrature component.The real part of described complex base band signal and imaginary part are not actual each other phase deviation 90 degree, and the amplitude error between I branch and Q branch more takes place.In described reflector and described receiver, this IQ asymmetry all can take place.In described receiver, in system based on OFDM, described IQ asymmetry, in frequency field, that is in described receiver, FFT conversion (fast fourier transform; Fast Fourier Transform) afterwards, cause the reciprocal interference between two data symbols on the subcarrier, about the load frequency fc of described OFDM frequency spectrum, described sub-carrier frequencies be balanced configuration (after this be called subcarrier n with-n).Because added IQ asymmetry in time zone, each data symbol of being launched on described subcarrier n produces the subcarrier of a signal contribution in pointer-n (imaginary part frequency).Described replacement is formed on the distortion of position n and-n useful signal.

In Andreas Schuchert paper " digital compensation method of hybrid analog-digital simulation quadrature asymmetry in the OFDM receiver " chapter 4 that Bergische Universit  t-Ges amthochschule Wuppertal electronic engineering and information technology system is accepted, propose the mathematical description of IQ asymmetry and be provided at institute to desire the video quantitative estimation of the interference contribution that frequency took place of signal.Chapter 6 in the above-mentioned paper proposes two kinds of diverse ways, by the frequency field equilibrium, and is used for the compensation of IQ mistake.The first method that is proposed is the individual frequencies independent compensation of IQ asymmetry.For detecting equalizing coefficient by an IQ error detector, also proposing to use pilot frequency carrier wave (pilot carrier), its emission is to estimate to believe that translation function becomes the purpose of training symbol in order to reach, and reaches the purpose of estimating I/Q distortion.Yet the circuit arrangement that is used for two method faults compensation has very many functional blocks and thereby has a high execution cost.

WO 02/056523 discloses another kind of method, and it can get rid of reflector and receiver end IQ asymmetry.The basis of the method is to produce compensating signal, is used in compensation corresponding to described IQ mistake and with it.

Summary of the invention

Therefore, the equalization methods that the purpose of this invention is to provide estimation approach and subsequent wireless signal distortion, it is by tds-ofdm transmission system, the reflector in the OFDM emission system or receiver end IQ asymmetry causes particularly, and provide and carry out the lower corresponding intrument of described method cost.

Reach purpose of the present invention by the feature in the claim independent entry, described claim advocates to estimate the method with correct transmission device end and receiver end IQ asymmetry respectively.Moreover the device of these methods is carried out in proposition.Favourable development of the present invention and modification are to be described in the described claim dependent claims.

The invention relates to the method that is used to estimate with the correcting wireless distorted signals, the distortion of described wireless signal caused by reflector or receiver end IQ asymmetry, be that wireless signal is the multicarrier emission in frame or breach formal approach and launching.Described method can be used in all spectra, in can use the multicarrier launching technique, that is in wireless data transmission network (WLAN) field or in the field of digital ground photography or voice signal emission.The frequency spectrum of described multicarrier launching technique comprises about centre frequency fc and the subcarrier n and the subcarrier-n of symmetrical spectrum configuration.

As mentioned above, the distortion of key of the present invention (distortion) is included in the interference between the monosymmetric subcarrier of multicarrier frequency spectrum centre frequency fc.By the asymmetry of reflector and receiver end IQ and form this distortion.Moreover the multipath propagation of described wireless channel (multipathpropagation) forms the linear distortion of subcarrier.Comprise the whole distortion of IQ distortion and channel distortion, can carry out emulation by following equation:

In described example,

Be the distorted symbols that is received in described subcarrier n at i, d _n(i) be undistorted emission symbol, A ^TXForm described emitter terminals IQ distortion matrix, A ^RXForm receiving terminal IQ distortion matrix, and C comprises the channel coefficients of multi-path channel.

Basis of the present invention is known described emitter terminals or described receiver end IQ asymmetry.So, if known described IQ distortion matrix (A ^RXOr A ^TX) one of them, but then iteration (iteratively) is estimated the coefficient and the channel coefficients C of another IQ distortion matrix, and simultaneously can be balanced and decision with the symbol that is received.In this example, in one, handle the multicarrier data symbol (for example OFDM symbol) that is received.As a result, in each iteration (iteration) loop, handle a data block that comprises OFDM symbol group, and channel coefficients and iteration are used for this groups of data symbols by the IQ distortion parameter that (iteration pass) end is determined.This groups of data symbols then is called data block, can be the inferior group of frame or breach (burst).Yet, depend on the definition of notch length in the acceptance criteria, well imagine that described data block is corresponding to described frame.

At first use emitter terminals IQ mistake (A ^TX) estimation with proofread and correct example, be described as follows.Estimate earlier and the described receiving terminal IQ distortion matrix (A of correction by suitable measurement ^RX).

Because approximation a _n ^TX, a _n ^TX, equation (1) becomes

$\left[\begin{array}{c}{\hat{d}}_n^{\&prime;}\left(i\right)\\ {\hat{d}}_{-n}^{\&prime;*}\left(i\right)\end{array}\right]=\left[\begin{array}{cc}{\mathrm{<figure-callout\; id="0"\; label="C\; n"\; filenames="A0382137800161.png"\; state="\{\{state\}\}">C</figure-callout>}}_n& 0\\ 0& C_{-n}^{*}\end{array}\right]\&CenterDot;\left[\begin{array}{cc}1& b_n^{\mathrm{TX}}\\ b_{-n}^{\mathrm{TX}*}& 1\end{array}\right]\&CenterDot;\left[\begin{array}{c}{d}_n\left(i\right)\\ d_{-n}^{*}\left(i\right)\end{array}\right]---\left(2.1\right)$

By described channel coefficients C _n, C _-nKnowledge, described IQ distortion matrix A ^TXThe decision of surplus variable can by

${\hat{b}}_n^{\mathrm{TX}}=\frac{{\hat{d}}_n^{\&prime;}\left(i\right)-C_n\&CenterDot;d_n\left(i\right)}{C_n\&CenterDot;d_{-n}^{*}\left(i\right)}$

${\hat{b}}_{-n}^{\mathrm{TX}}=\frac{{\hat{d}}_{-n}^{\&prime;}\left(i\right)-C_{-n}\&CenterDot;d_{-n}\left(i\right)}{C_{-n}\&CenterDot;d_n^{*}\left(i\right)}---\left(2.2\right)$

According to the present invention, be used on this basis estimate and the first method of proofreading and correct described emitter terminals IQ asymmetry.According to the present invention, described first method common form, at first be method step a, with from the channel coefficients that previous data block was determined, and with the received data symbol equilibrium of first data block.In method step b, follow-up by the temporary transient IQ distortion parameter that previous data block determined, and with described data symbol equilibrium.In this mode, then in step c, will be provided to the symbol determination procedure by the data symbol of equilibrium.In steps d, reference signal that is provided by described symbol determination procedure and the symbol that is received are to be used for channel estimating, are used to produce new signal coefficient.At last, in method step e, estimate reference symbol and the new channel coefficients that data symbol was determined that is received, estimate new IQ distortion parameter to state signal.

As the data block of the specified received data symbol of first data block, be the arbitrary data piece (arbitrary data block) that is defined as wireless signal transmission.Designing first data block only distinguishes as language idendification and from second data block of temporary connection.

Being actually the described wireless transmission data block of first data block according to the time, is to be designed to the initial data piece.In the example of this initial data piece, owing to do not have the data block of temporary transient processing, so can't initially carry out the method according to this invention in the identical mode of all subsequent data blocks.Can be in step a and b, the data symbol equilibrium that is received in the described initial data piece will be included in, therefore on the basis of pilot signal (pilot signal), carry out a channel estimating, normally be contained in the front portion (preamble) of the affiliated corresponding data breach of described initial data piece.In described method step a,,, and in step b, described IQ distortion parameter setting is equalled zero the data symbol equilibrium that is received with from the channel coefficients that described channel estimating was determined.

In described method step d and e, determined after new channel coefficients and the new IQ distortion parameter, in the method according to this invention, can carry out another iteration (iteration) step, wherein by described new channel coefficients and described new IQ distortion parameter, for temporary connection is the received data symbol of second data block of first data block, repeating step a to e (method step f), and with the new channel coefficients that determined among the method step f and new IQ distortion parameter, and with the received data symbol equilibrium (method step g) of described first data block.

In addition, in step f, also can be provided at the new channel coefficients and new IQ distortion parameter that determine among method step d and the e, for the received data symbol of first data block, repetition methods step a to e.Thereby, based on first data block or the data block of temporary connection, optionally carry out this iterative step and other iterative step, be used to upgrade described channel coefficients and described IQ distortion parameter.

Aforesaid iteration is used to upgrade described channel coefficients and IQ distortion parameter with method step f and g, if suitably, then then passes through other iterative step of method step a to e.After last iterative step terminal is provided, by the channel coefficients and the IQ distortion parameter that have upgraded at last, and with the data symbol equilibrium that is received, and provide to described symbol determination procedure, and the data symbol that is determined is next processing unit that is output to described receiver.

In method step d, produce described channel coefficients, since from a channel estimating the channel coefficients that determined, its basis is that described symbol determination procedure reference symbol that provides and the data symbol that is received are to be used for and the old numerical value weighted average of channel coefficients, thereby, can reappraise IQ mistake according to equation (2.2) based on the data symbol that is received among average channel coefficients, reference symbol and the method step e.(IQ tracking)

More can in method step, provide and produce new IQ distortion parameter, because the new channel coefficients that the basis of the described IQ distortion parameter of decision is in channel estimation process to be determined, average described reference symbol and the data symbol that received and previous iterative step in the IQ distortion parameter of one or more steps decisions.

If before another advantage is that the channel estimating in method step is carried out,, carry out the IQ predistortion (predistortion) of the reference symbol that provided by the symbol determination procedure based on the IQ distortion parameter that upgrades.This EQ predistortion of described reference symbol makes and can significantly reduce misjudgment owing to described IQ distortion.

According to second method of the present invention, as the estimation and the correction of described receiver end IQ asymmetry.Carry out from equation (1) once more, suppose to have estimated by suitable measurement in advance and proofreaied and correct described emitter terminals IQ distortion matrix (A ^TX).

By approximation a _n ^TX, a _n ^TXAnd known channel coefficients C _n, C _-n, described IQ distortion matrix A ^RXSurplus variable can be by the decision of following equation

${\hat{b}}_n^{\mathrm{RX}}=\frac{{\hat{d}}_n^{\&prime;}\left(i\right)-C_n\&CenterDot;d_n\left(i\right)}{C_{-n}\&CenterDot;d_{-n}^{*}\left(i\right)}$

${\hat{b}}_{-n}^{\mathrm{RX}}=\frac{{\hat{d}}_{-n}^{\&prime;}\left(i\right)-C_{-n}\&CenterDot;d_{-n}\left(i\right)}{C_n\&CenterDot;d_n^{*}\left(i\right)}---\left(3.1\right)$

Second method according to the present invention is on this basis, carries out the estimation and the correction of described receiver end IQ asymmetry.According to the present invention in the prevailing form of second method, at first, in method step a, by the IQ distortion parameter that data block determined from a temporary connection, and the data symbol equilibrium that first data block is received.Then provide data symbol to be used for channel estimating, be used for producing new channel coefficients, then in method step c, by the channel coefficients that is determined and with described data symbol equilibrium at method step b.Then, with in this way balanced data symbol symbol determination procedure to the method step d is provided.Then, in method step e,, carry out IQ and estimate, and provide correcting circuit to IQ with the IQ distortion parameter that is determined based on the reference symbol that provided by the symbol determination procedure and by the channel coefficients that described channel estimating was provided.

Description of drawings

According to the present invention, carry out described method and the embodiment that carries out the corresponding intrument of described method, as described below, and see also the accompanying drawing of being attached.

Fig. 1 is the frequency spectrum of explanation OFDM launching technique.

Fig. 2 is explanation one a receiver end block circuit arrangement, is used to carry out the method according to this invention, is used for the estimation and the correction of emitter terminals IQ asymmetry.

Fig. 3 is explanation one a receiver end block circuit arrangement, is used to carry out the method according to this invention, is used for the estimation and the correction of receiver end IQ asymmetry.

Embodiment

In the embodiment shown in Figure 2, wherein employed variable is about the estimation of an emitter terminals IQ asymmetry and correction, described channel coefficients C _n, C _-n, and determine described IQ distortion parameter

With

Needed emission symbol d _n(i) and d _-n(i) (equation (2.2)).

Be contained in the receiver and device as shown in Figure 2, present the data symbol that is received

Described data symbol is included in the data block.A plurality of data blocks form a frame, and each frame has anterior symbol

By the formed data symbol of OFDM among the embodiment, be to be fed to the impartial device 2 of a channel, wherein be with by channel coefficients that described previous data block was determined and with its equilibrium.

Then the data symbol of equilibrium being delivered to an IQ Error-Correcting Circuit 3, wherein is with the IQ distortion parameter b by described previous data block was determined _n ^TX, b _-n ^TXAnd carry out an IQ error correction.

The data symbol that then described equilibrium and IQ proofread and correct is sent to symbol decision unit 4, and it has two inputs.After described symbol decision, there is new reference symbol to be used for all subcarrier n/-n, and first output that exports described symbol decision unit 4 to.

At the received data symbol In the channel estimator of being delivered to 6,, carry out new channel estimating based on these reference symbols.The reference symbol of described symbol decision 4 confessions in unit is delivered to an IQ predistorter 5, the IQ distortion parameter b that is wherein upgraded ^TXBe to be sent to described IQ predistorter 5.Because described IQ distortion, described IQ predistortion reduces misjudgment.

Be provided at the channel coefficients that is calculated in the channel estimator 6, and with old numerical value weighted average, thereby on the basis of these average channel coefficients, reference symbol and reception value, can in an IQ tracking cell 7, reappraise described IQ mistake, wherein receiving symbol

Be to deliver to described IQ tracking cell 7.Estimating for each subcarrier that can get

With Afterwards, can in time orientation (by an iteration piece), carry out the average of these values, to reach the purpose that reduces noise.Then, with the value average (weighted average) of previous iteration in the value of these estimations and the averaging unit 8.

Then, carry out new iteration (iteration) by delivering to the impartial device 2 of described channel and the described channel coefficients of described IQ correcting circuit 3 and the updating value of IQ distortion parameter.Can use the data block of the reception OFDM symbol of the present data block of temporary connection, carry out described iteration.Yet available identical reception data block is the basis, improves estimated value by multiple iteration.

For initial described parameter, in first iteration (it=0) before, based on reference data, the symbol of in a front portion (preamble), being launched for example As shown in Figure 2, finish the OFDM channel estimating.Suppose $b_n^{\mathrm{TX}},b_{-n}^{\mathrm{TX}}=0$ Be the initial value of the IQ distortion parameter of IQ correcting circuit 3, thereby described IQ correction (with described IQ predistortion) keep invalid in described first iteration.Yet, also can be by the suitable estimated initial of described IQ distortion parameter, and improve the of short duration reaction of control.

Embodiment shown in Fig. 3 and employed variable wherein are estimation and the corrections about a receiver end IQ asymmetry, With

Equation (3.1) is as the basis of the described IQ distortion parameter of decision.

The device that is included in the receiver end shown in Fig. 3 is received data symbol

At first described data symbol is delivered to an IQ correcting circuit 10, wherein carrying out the basis that an IQ proofreaies and correct is to be the IQ distortion parameter, and the basis of its decision is the previous iteration passed through based on more preceding groups of data symbols.

Then described IQ correction data symbol is delivered to a channel estimator 11, be used to determine channel coefficients, and quilt equilibrium in the impartial device 12 of a channel then, its basis is the channel coefficients that described channel estimator 22 is determined.

Then, the receiving symbol of channel equalization is delivered to a symbol decision-making circuit 13, wherein the data symbol for described equilibrium carries out a symbol determination procedure.Described symbol decision-making circuit 13 has two outputs.After described symbol decision, there is new reference symbol to can be used for all subcarrier n/-n, described reference symbol is exported to first output of described symbol decision unit 13.

Described reference symbol to IQ estimator 14 is provided, and wherein the channel coefficients that is provided based on described reference symbol and described channel estimator 11 carries out the estimation of described IQ distortion parameter.To provide by the IQ distortion parameter that described IQ estimator 14 is reappraised, therefore based on present data block or next data block, the iteration of upgrading to described IQ correcting circuit 10.

The present invention can be used for the receiver notion, wherein is preferably the receiving inputted signal branch between I and the Q[, still is the analog circuit part of described receiver.Most important applications of the present invention is about so-called direct mixing receiver, as paper the 3.5th figure of the Schuchert that quotes in the background of invention.Yet the present invention can be used for the known heterodyne receiver with direct mixing second stage in principle, shown in the 3.6th figure in the above-mentioned related article.This has the modification of heterodyne receiver formula one heterodyne receiver of direct mixing second stage, and wherein said second mix stages is to be embodied as direct hybrid analog-digital simulation quadrature receiver.Also can occur in this receiver in the IQ mistake described in the background of invention, and can be estimated with balanced by the method according to this invention.

Claims (20)

1. A method for estimating and correcting the distortion of a radio signal formed by in-phase and quadrature branch (IQ) asymmetry and channel distortion at the transmitter, the radio signal being transmitted over a multi-carrier Transmitting in the method, it has sub-carrier n and sub-carrier-n symmetrically arranged respectively with respect to a center frequency f _c , it is characterized in that: a. First, the channel coefficients determined by the previous data block will be equalized according to the received data symbols of the first data block; b. Then, equalize the data symbols with the IQ distortion parameter determined by temporarily processing the data block; c. then providing said equalized data symbols to a symbol decision process; d. using the reference symbols provided by the symbol decision procedure and the received data symbols for a channel estimation to generate new channel coefficients; and e. Generating said new IQ distortion parameters based on said new channel coefficients, said reference symbols and said received data symbols determined during said channel estimation process. 2. The method according to claim 1, characterized in that At the beginning of the method, in method steps a and b, the data symbols contained in the initial data block are equalized, a signal estimation is thus carried out on the basis of pilot signals, and in step a using The received data symbols are equalized by channel parameters determined by said channel frequency estimate, and in method step b, said IQ distortion parameter is set equal to zero. 3. The method according to claim 1 or 2, characterized in that f. repeating method steps a to e with said new channel coefficients and new IQ distortion parameters determined in method steps d and e for received data symbols of a second data block temporarily subsequent to said first data block; and g. Equalizing the received data symbols of the first blocks with the new channel coefficients and the new IQ distortion parameters determined in method step f. 4. The method according to claim 1 or 2, characterized in that f. repeating method steps a to e for the received data symbols of said first data block with said new channel coefficients and new IQ distortion parameters determined in method steps d and e; and g. Equalizing the received data symbols of the first blocks with the new channel coefficients and the new IQ distortion parameters determined in method step f. 5. The method of claim 1, characterized in that In method step d, said new channel coefficients are generated due to said channel estimate determined from a channel estimate on the basis of reference symbols provided by said symbol decision procedure and received data symbols being provided at Weighted average with old values of the channel coefficients. 6. The method of claim 1, wherein In method step e, the new IQ distortion parameters are generated, because the determined IQ distortion parameters, the reference symbols are based on the new channel coefficients determined in the channel estimation process The received data symbols are averaged with the IQ distortion parameters determined in one or more previous iteration steps. 7. The method of claim 1, wherein Before method step d, an IQ predistortion of the reference symbols provided by the symbol decision procedure is performed on the basis of the updated IQ distortion parameters. 8. The method of claim 1, wherein In method step e, the basis for generating the new IQ distortion parameters lies in the following formula ${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; b</span>}}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; TX</span>}}<span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; d</span>}}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}$ ${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; b</span>}}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; TX</span>}}<span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; d</span>}}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span>$ 9. A method for estimating and correcting distortion of a wireless signal formed by in-phase and quadrature branch (IQ) asymmetry and channel distortion at the receiver, the wireless signal being transmitted over a multi-carrier Transmitting in the method, it has sub-carrier n and sub-carrier-n symmetrically arranged respectively with respect to a center frequency f _c , it is characterized in that: a. said IQ distortion parameters determined by temporarily processing data blocks will be equalized according to the received data symbols of the first data block; b. Then, sending the IQ equalized data symbols to a channel estimation to determine channel coefficients; c. Then, equalize the data symbols with the channel coefficients; d. providing said channel equalized data symbols to a symbol decision procedure; and e. Generating said new IQ distortion parameters based on said reference symbols provided by said symbol decision procedure and said channel coefficients provided by said channel estimation. 10. The method of claim 9, characterized in that f. repeating method steps a to e for received data symbols of a second data block temporally succeeding said first data block with said new IQ distortion parameter determined in method step e; and g. Equalizing the received data symbols of the first blocks with the new channel coefficients and the new IQ distortion parameters determined in method step f. 11. The method of claim 9, characterized in that f. repeating method steps a to e for the received data symbols of said first data block with said new IQ distortion parameters determined in method step e; and g. Equalizing the received data symbols of the first blocks with the new channel coefficients and the new IQ distortion parameters determined in method step f. 12. A method according to any one of claims 9 to 11, characterized in that In method step e, the basis for generating the new IQ distortion parameters lies in the following formula ${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; b</span>}}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; RX</span>}}<span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; d</span>}}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}$ ${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; b</span>}}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; RX</span>}}<span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; d</span>}}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; \&CenterDot;</span>{\mathrm{<span\; class="notranslate">\; d</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; .</span>$ 13. A method of using any preceding claim in a direct mixing receiver. 14. A method of using any one of the preceding claims 1 to 12 in a heterodyne receiver with a direct mixing second stage. 15. An apparatus for performing the method of any one of claims 1 to 8, comprising: a channel equalizer (2) for equalizing received data symbols of a data block; an in-phase and quadrature-branch (IQ) correction circuit (3) for said IQ equalization of said data symbols provided by said channel equalizer (2); a symbol decision unit (4) for performing a symbol decision procedure by means of said data symbols provided by said IQ correction circuit (3); a channel estimator (6) for generating new channel coefficients based on said reference symbols and said received data symbols fed by said symbol decision unit (4); an IQ tracking unit (7) for generating said new IQ distortion parameters based on said new channel coefficients provided by said channel estimator (6), said reference symbols and said received data symbol; and The output of the IQ tracking unit (7) is connected to an input of the IQ correction circuit (3). 16. The apparatus of claim 15, wherein an IQ predistortion unit (5), configured to perform an IQ predistortion on the reference symbols provided by the symbol decision unit (4) based on the updated IQ distortion parameters; and The IQ predistortion unit (5) has a first input connected to the output of the symbol decision unit (4), and a second input connected to the IQ tracking unit (7) An output, and an output connected to said channel estimator (6). 17. Apparatus according to claim 15 or 16, characterized in that An averaging unit (8), used for averaging the IQ distortion parameters, the basis for determining the IQ distortion parameters is the new channel coefficients determined in the channel estimation process, the reference symbols and the received data symbols for said IQ distortion parameters determined in one or more previous iterative steps; and An input of the averaging unit (8) is connected to an output of the IQ tracking unit (7), and an output of the averaging unit (8) is connected to an input of the IQ correction circuit (3) and an input of the IQ predistortion unit (5). 18. Apparatus according to any one of claims 13 to 15, characterized in that A channel estimator (1) to whose input said received data symbols are fed and at whose output said channel coefficients determined by said channel estimate are provided. 19. The apparatus of claim 18, wherein a changeover switch whereby said input of said channel equalizer (2) is connected to said input of said channel estimator (1) or to said input of said channel estimator (6) the output. 20. An apparatus for performing the method of any one of claims 9 to 12, comprising: an in-phase and quadrature-branch (IQ) correction circuit (10) for IQ equalization of said received data symbols; a channel estimator (11) for generating channel coefficients and which is connected to said output of said IQ correction circuit (10); a channel equalizer (12) for equalizing said received data symbols based on said channel coefficients provided by said channel estimator (11); a symbol decision unit (13) for performing a symbol decision procedure with said data symbols provided by said channel equalizer (12); and an IQ estimator (14) for generating IQ distortion parameters based on said reference symbols provided by said symbol decision circuit (13), said channel provided by said channel estimator (11) coefficients, said reference symbols and said received data symbols; an output of said IQ estimator (14) is connected to an input of said IQ correction circuit (10).

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