WO2007015011A2

WO2007015011A2 - Detection method and device for a mimo system, mimo system, program and information medium

Info

Publication number: WO2007015011A2
Application number: PCT/FR2006/001883
Authority: WO
Inventors: Wladimir Bocquet
Original assignee: France Telecom
Priority date: 2005-08-01
Filing date: 2006-08-01
Publication date: 2007-02-08
Also published as: FR2889383A1; WO2007015011A3

Abstract

The invention relates to a reception method for a MIMO system. The aim of said method is to calculate, in the frequential domain, sub-carrier by sub-carrier, an extraction (1) of a desired signal for each signal emitted, from signals received on the different reception antennae. According to the invention, the extraction (1) is spatially carried out, i.e. for each pair of emission and reception antennae (RX0, RX Nr-1).

Description

DETECTION METHOD AND DEVICE FOR MIMO SYSTEM, MIMO SYSTEM, PROGRAM AND INFORMATION MEDIUM

The present invention relates generally to so-called digital communications, which are part of the telecommunications field. The digital communications include in particular the wireless communications of which the transmission channel is the air channel as well as the wired communications. Within this field, the invention relates to the reception methods and more particularly to the multipixed signal decoding techniques. by space division S DM, acronym for Space Division MultipIexing, in a multi-input and multi-input MIMO communication system, acronym for MultipIe Input MultipIe Output.

MIMO systems can be associated with different transmission techniques such as OFDM (Orthogonal Frequency Division MultipIexed) multi-carrier type OFDMA (Orthogonal Frequency Division MulfipIexed Access) or code type techniques. MC-CDMA (acronym for Multi Carrier Code Division MultipIe Access). A MlMO system includes Nt TX omission antennas and Nr RX receive antennas separated by a transmission channel for transmitting data. When a spatial multiplex technique is used on transmission, the coding is performed by branch, a technique better known by the acronym PAC of Per-Antenna-Coding. In reception, different detection techniques can be implemented,

Among the linear MIMO detection techniques, mention may be made of the ZF forcing technique and the technique based on a minimum square error criterion MMSE, the acronym for Minimum Mean Square Error. Figure 1 illustrates such detection in a MIMO reception chain. In the case of a linear detector F, the vector y corresponding to the received signal is multi by a matrix filter

which is a pseudo inverse of the answer

impulseIe H of the transmission channel:

(1) with + representing the inverse pseudo. The definition of an inverse pseudo is as follows:

In the case of an MMSE linear detector, the detection implemented consists of minimizing the mean square error between the transmitted symbols and the output of the linear detector, the expression of which is:

expression in which α is equal to the inverse of the sigual to noise ratio, 1 / SNR (Signal-Noise Ratio), I _Nr is the identity matrix of dimension Nr x Nr, and ^H represents the Hermitian transpose,

Although the compIexity of a linear detector such as ZF or MMSE is reasonable and these techniques can be implemented on hardware, however, a high signal-to-noise ratio is required and necessary to obtain a low packet error rate (Packct Error Rate); this rate being typically at least of the order of 10 ^-2 to 10 ^-3 for any type of wireless communication. With regard to a detector with a maximum likelihood criterion which is the optimal detector for MIMO systems, the latter is, by its structure, increasingly exponentially compatible with the number of transmitting antennas.

The article by Bocquet W. et al, "MlMO OFDM Visa transmits scheme for

2005 FEEE 61ST Stockholm, Sweden 30-01 May 2005, pages 1240-1244, XPO 10855609, ISBΝ: 0-7803-8887-9, discloses a detection method adapted to a particular frame; in which the pilot sequence is in TDMA mode which alone makes it possible to obtain a physical signal equal to zero which allows an algorithmic adaptation, of RLS type, and iterative of the element allowing the detection.

Thus, the object of the invention is to propose a reception method which makes it possible to improve the performance of the known linear detection reception methods without increasing the detection compiexity for a system.

MIMO.

The proposed method, which is a reception method, has the principle of calculating, under carrier subcarrier, a desired signal extraction for each signal transmitted from signals received on the different reception antennas; the extraction is therefore carried out spatially, that is to say for any cutting of transmit and receive antennas,

A reception method according to the invention is adapted for a system, with Nt transmit antennas and Nr receive antennas separated by a transmission channel, which transmits on N≥1 under carriers and on the Nt transmit antennas after a multip1exage by space division of a signal to be transmitted. The method according to the invention performs a decoding which comprises the step of: extracting, in the frequency domain, signals received on the Nr antennas receiving the signal transmitted by the transmission channel, by transmission antenna and by under carrier.

The method includes discrete spectral analysis of the received signals providing frequency samples. The extraction consists in multiplying these samples, by subcarrier and by receiving antenna, independently, with coefficients of extraction of the transmission channel and to accumulate in a coherent way the result of the multiplication. The procedure is remarkable in this respect. that the extraction coefficients are determined by solving a system of equations obtained by decomposing the signals received by subcarrier on each receiving antenna into an expected signal and into unexpected components and forcing the unexpected components to zero. A method according to the invention can be considered as performing a low-complexity decoding because it does not require an inversion matrix which is generally the main source of compIexity. In fact, the extraction consists in multiplying the samples resulting from a discrete spectral analysis of the signals received in the spatial domain, by subcarrier and by transmit antenna, independently, with extraction coefficients of the transmission channel. and to accumulate in a coherent way the result of the multiplication. The extraction coefficients are determined by solving a system of equations obtained by decomposing the signals received by subcarrier on each receiving antenna into an expected signal and into unexpected components and forcing the unexpected components to zero. Extraction, which does not exist in the known linear detection methods which performs equalization in a global manner, makes it possible subsequently to process individually the different extracted signals corresponding to the different signals emitted. The individual character associated with the extraction thus makes it possible to associate a finer noise treatment than that which exists in the known linear detections which make a global treatment. A method according to the invention is particularly advantageous in that it does not require any particular frame structure.

Thus, this extraction is, according to a preferred mode, combined with an estimation of the transmission channel in the frequency domain to take account of the frequency seiectivity of this channel. This estimation takes into account the channel variations as well as the impact of the signal extraction on the received signal. According to this In combination, the method according to the invention equalizes in the frequency domain a distortion introduced by the transmission channel on the signal transmitted to each transmission antenna. This equalization is in particular a linear equalization.

According to a particular mode of implementation, the number Nr of receiving antennas is strictly greater than the number Nt of transmitting antennas. In this case, the preferred mode of implementation of the method takes into account the spatial diversity.

Thus, by transmission antenna, the method determines at most as many signals extracted as there are combinations of obtaining Nt signals among Nr received signals and combines, before demodulation, the extracted signals then equalized. After combination, the number of signals is equal to the number of transmitting antennas.

Other features and advantages of the invention will become apparent from the following description given with reference to the appended figures given as non-limiting examples,

FIG. 1 is a block diagram of a detection according to the prior art in a MlMO OFDM reception chain.

FIG. 1 is a block diagram of a MlMO OPDM transmission chain,

Fig. 3 is a frame example relating to the IEEE 802.11g standard.

FIG. 4 is an illustration of an IDFT applied to the frame of FIG. 3,

FIG. 5 is a block diagram of a MlMO OFDM reception chain. FIG. 6 is a first block diagram of a first particular embodiment of a reception method according to the invention.

FIG. 7 is a second block diagram of the first particular embodiment of a reception method according to the invention.

FIG. 8 is a block diagram of a second particular embodiment of a reception method according to the invention in the case where Nr> Nt

detailed description

A MlMO OFDM transmission channel is illustrated in FIG. 2. The chain comprises several branches each corresponding to an OFDM transmitter. The branches each typically comprise a channel encoder, CCo-CC _Nt-1 , an interleaver, E ₀ to E _Nt-1 , a modulator, M ₀ to M _Nt-1 , a driver insertion moduI, IP ₀ to IP _Nr-1 , an OFDM multiplexer, MXo to MX _Nt-1 , a header insertion mode and guard intervals, CPIo to CPI _Nt-1 , a DAo to DA _Nt-1 digital to analog converter, a frequency feeder, UCo to UC _Nr-1 , a transmitting antenna, TXo to

TX _Nt-1 . The bits of the input signal d are multiplexed at the input of the different branches by a serial / parallel converter CSPE.

By branch, the data symbols present at the output of the modulator are multiplexed by a frequency division obtained by means of an inverse discrete Fourier transform at N point IDFT. The resulting signal is composed of OFDM symbols. These symbols are converted into analog by a D / A digital converter of sampling frequency I / Ts with Ts the period of the samples, shifted in frequency by a frequency converter towards the RF emission band, emitted by an antenna. transmission and transmitted by the transmission channel, typically air.

For reliable detection on reception, it is typically necessary for the receiver to know the transmission channel and follow its phase and amplitude variations. To allow estimation of the transmission channel on reception, the transmitter of each branch occasionally transmits known learning symbols, in particular pilot symbols. MlMO OFDM transmits sequences of N symboIes

_t modulated during the i th OFDM symbol period by means of N subcarriers. The OFDM signal transmitted in baseband corresponding to the ith symbolic period, is expressed in the form:

Expression in which is the symbol of data of the jth symbo

OFDM corresponding to the p-th transmit antenna and the n-th subcarrier. To combat Inter Symbol Interference (ISI) and Inter Carrier Interference (ICI), OFDM symbols are added to Guard Interval (Gl). ) such as a cyclic prefix (Cyclic Prefix (CP)) or Zero Padding (ZP). In the case of a cyclic prefix CP, the last Ng samples of each OFDM symbol are copied and added to the header. The signal transmitted in baseband and then transmitted can be expressed in the following form:

Generally, the samples of the input signal are grouped into frames. A frame is a temporal representation of a sequence transmitted by the transmit antennas and transmitted by the transmission channel. A frame example relating to the IEEE 802. 1 1g standard is illustrated in FIG. 3. This TR frame comprises two pilot symbols, SP ₁ and SP ₂ , and J OFDM symbols, S ₁ to S _j . Each OFDM symbol is the output of a discrete inverse Fourier transform IDFT, for example sixty-four points, to which a GI guard interval is added. For equation (4), this means that j varies between one and J, that n and k vary between zero and sixty three. FIG. 4 illustrates an IDFT applied to the frame of FIG. 3. FIG. 5 illustrates a reception channel of an OFDM MIMO receiver with Nr receiving antennas RX ₀ to RX _Nr-1 . On reception, the received signal y ₀ to Y _Nr-1 by the receiving antennas is shifted into baseband by a DC ₀ to DC _Nr-1 frequency converter and digitally converted by an AD / _O converter AD ₀ at AD _Nr-1 with a frequency l / T s. The guard intervals are extracted by a CPD ₀ to CPD _Nr-1 slot extraction modulus and a DFT discrete Fourier transform DFT is performed by OFDM DMX ₀ to DMX _Nr-1 demultipulator. Since the parameters of the transmission channel are assumed to be frequency selective, the detection must be done by OFDM subcarrier. Therefore, to recover the Nt signal data transmitted by subcarrier, the signals received from the subcarrier i are routed to the i th MIMO detector, DE ₀ to DE _N-1 . Then, the receiver performs a demodulation with a demodulator DM ₀ to DM _N-1 , a deinterlacing with a deinterleaver BDI ₀ to BDI _N-1 and a channel decoding with a channel decoder DD ₀ to DD _N-1 for the N parallel data and the resulting data are combined by a CPSR series parallel converter to obtain the original binary sequence

The following temporal and frequency signal model is related to the foregoing description of the OFDM MIMO system with reference to FIGS. 2 to 5. Assuming that the system comprises Nt TX and Nr RX antennas, a system denoted Nt * Nr, that The transmitter emits at time intervals r a vector compiexe i ( _r ) of dimension Nt, the receiver receives a compIexe vector p {τ) of dimension Nr. The model assumes that the system operates in an environment with a selective RayIeigh fading. in frequency and that the transmission channel remains constant during transmission of a sequence. Furthermore, the faded channel is assumed to be baseband modelable by a finite impulse response FIR filter (LI) in which L represents the duration of samples corresponding to the maximum delay spread. In addition, the model takes into account an additive Gaussian white noise (AWGN) of mean zero and variance.

When the maximum lag time does not exceed the GI guard interval, there is no inter-symbol interference (ISI) between OFDM MlMO symbols. Therefore, after the suppression of the GI guard interval, the expression in the frequency domain of the OFDM MlMO signal is as follows:

with

The signal received on the nth sub-carrier by the q-th receiving antenna, for the ith OFDM symbiont and for the nth subcarrier, with Ie

AWGN noise present on the nth subcarrier for the qth receiver antenna, for the fth OFDM symbol, and with the channel response between the fth

transmitting antenna and the q-th receiving antenna that composes the channel matrix

Thus, by subcarrier, the channel is fading. For each subcarrier during transmission of a frame, the variation is considered constant (the duration of a frame is assumed to be less than the coherence time).

A particular embodiment of a reception method according to the invention is illustrated by FIGS. 6 and 7. The reception chain which makes it possible to implement the reception method has been described with regard to FIG. 5; it is not re-described.

Hereinafter is described the detection part implemented by a detector DEK, according to the invention, of a receiver RE. The detection takes place after the suppression of the guard intervals and the discrete Fourier transform DFT at N point of the data. sampled which carries out sub-carrier data reduction for each receiving antenna.

The method comprises a first step 1 during which the signal is extracted spatially and a second step 2 during which the distortion effects of the channel are compensated. To extract the signal transmitted by each transmitting antenna spatially, on each subcarrier, the samples are multiplied independently with channel extraction coefficients and accumulated consistently.

The channel distortion effects are compensated for in the frequency domain using a known method such as one-dimensional forcing-type equalization zero, ID-ZF (One Dimension zero forcing), a minimum squared error criterion 1D-MMSE or a maximum likelihood criterion ID-MLD.

In the case of an Nt * Nr system, the received signal can be expressed by the relation

(6). The extraction is carried out by extraction methods illustrated more particularly by FIG. 7. There are typically as many extraction modules, EX ₀ , ₀ to EX _NI , _Nt-I , as transmit antenna and than subcarriers. However, during the implementation, the extraction can just as easily be done by a single moduIe that groups the NtxN moduIes. The output of the uth extraction model which performs a weighted multiplication followed by a coherent accumulation can be expressed as:

Expression in which

represents the weighting coefficient of the eighth moduIe to extract, for each symbol j, the signal received by the q-th receiving antenna on the n-th subcarrier, {w} represents the set of coefficients necessary to extract the different transmitted signals.

By referring the expression of y (equation (6)) in z (equation (8)), z is expressed as:

The method according to the invention consists in forcing the various components which do not correspond to the expected signal to zero, which amounts to writing that the signal z depends only on the signal X:

therefore :

The solution of this equation (14) must be independent of the different signals emitted, Thus, this equation can be decomposed an Nt-1 following independent equations:

To calculate the different coefficients, the equation. (15) can be expressed as:

The method consists in arbitrarily setting the value of a coefficient which does not modify the overall performance of the BER. For example, the fixed process:

A complementary standardization step;

allows to simplify and to determine the number K. Typically K can be chosen equal to one then normalizes from the equation

(18). Thus the system of equations to be solved becomes:

To solve this system of equations and to determine the coefficients w, there are various techniques known to those skilled in the art: analytical calculation, matrix inversion, Gaussian elimination, LU or QR decomposition. The last three techniques are more particularly described in the reference book "Numerical Rectpes in C, The Art of Scientific Computing, Second Edition" of WH Press, SATcukolsky, WTVetterling, BPFlannery, Cambridge University Press. In a second step 2, to compensate for the distortion effects of the channel, an equalization of, for example, a zero forcing or Zero Forcing (1D-ZF) dimension is performed on the extraction output data. The output after equalization is expressed as:

expression in which are respectively the output of the equalizer

and the equalization coefficient for the uth transmitted sequence of the fth symbol on the nth subcarrier.

The equalization is carried out by equalization models illustrated more particularly by FIG. 7. There are typically as many types of extraction,

EG ₀ , ₀ to EG _N-1 , _N1-1 , as transmitting antenna and as subcarriers. However, during the implementation, the equalization can equally well be carried out by a single moduIe which groups the NtxN moduIes.

The following example corresponds to the particular case where Nt = Nr = 2, ie a system with two transmitting antennas and two receiving antennas. The index j corresponding to the symbol number does not appear in the relations which follow. In this case the received signal is expressed as:

The AWGN noise terms have been omitted because only signal extraction is considered.

The conditions for estimating the extraction coefficients can be defined from the set of equations, for the signal received on the first reception antenna noted.

and for the signal received on the second reception antenna denoted 1:

The fading compensation is described by:

To determine the equalization coefficients, various techniques known to those skilled in the art are applicable.

A first technique corresponds to the so-called zero or zero forcing method. According to this technique, the equalization coefficients are expressed in the form:

A second technique known as 1D-MMSE, which stands for Minimum Mean Square Error Detection, allows the expression of equalization coefficients in the form:

(22.a)

(22.b) A third technique resulting in an optimal solution implements a maximum likelihood criterion 1 D-MLD ei makes it possible to directly express the signal at the output of equalization in the form:

FIG. 8 relates to a preferred mode of implementation of the method in the case where the system comprises a number Nr of receiving antenna s strictly greater than the number Nt of transmitting antennas. According to this preferred embodiment, the method takes into account the spatial diversity. For each emitted signal to be reconstructed, and therefore by transmitting antenna, the method determines in a first step 1 at most as many signals extracted as there are combinations of obtain signals from among Nr received signals. The number of signals may be less than or equal to the number of combinations; The number of signals is typically determined during the learning phase. In a second step 2, the method equalizes the extracted signals.

In a third step 3, the method combines, before demodulation, the equalized signals. At the output of the combination, the number of signals is equal to the number of transmitting antennas. The combination is performed for example according to a technique called MRC, acronym for Maximum Ratio Combining or MMS technique

The following description refers to the particular case where Nt = 2 and Nr = 3. The index corresponding to the symbol number does not appear in the relations which follow. The signal received by each reception antenna can be expressed in the form;

In relation to equation (19), the method calculates for each combination the extraction coefficients making it possible to extract the different signals z:

For the reconstituted signal

and corresponding to the signal transmitted by the transmit antenna denoted 0 (i = 0), the coefficients are given by the following relations;

The reconstituted signal x ^® * is given by the combination which is expressed in the form:

techniques known to those skilled in the art and recalled previously with reference to FIGS. 6 and 7,

For the reconstituted signal

and corresponding to the signal emitted by the transmitting antenna denoted 1 (i ^ 1), the coefficients are given by the following relations:

The reconstituted signal is given by the combination which is expressed in the form;

The method that has been described for an OFDM MTMO system can be implemented in various communication systems, typically wireless but not exclusively, including multi-carrier MC-CDMA or OFDMA or single carrier systems. The method applies to all pilot structures including in particular structures with time, frequency or code multiplex, or structures combining the various previous multiplexing techniques.

The method according to the invention can be implemented by various means. For example, the method may be implemented in hardware form, in software form, or a combination of both.

For a wired implementation, the elements used or some of the elements (extractors referenced EXo ₁ O to EX _N-1 , _Nt-1 , equalizers referenced EG _0.0 to EG _NI , _Nt-1 , etc.) to execute the various steps at the receiver level can be integrated into one or more specific integrated circuits (ASlCs), signal processors (DSPs, DSPDs), programmable logic circuits (PLDs, FPGAs), controllers, microprocessors, microprocessors, or any other electronic component. designed to perform the functions previously described.

For a software implementation, some or all of the reception stages (referenced 1 to 3) can be implemented by moduIs that perform the previously described functions. The software code can be stored in a memory and executed by a processor. The memory may be part of the processor or external to the processor and coupled thereto by means known to those skilled in the art. Accordingly, the invention also relates to a computer program, including a computer program on or in an information carrier or memory, adapted to implement the invention. This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code such as in a partially compiled form, or in any other form desirable for implementing a method according to the invention.

The information carrier may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording means, for example a floppy disk or a disk. hard,

On the other hand, the information medium may be a transmissive medium such as an electrical or optical signal, which may be routed via an electrical or optical cable, by radio or by other means. The program according to the invention can be downloaded in particular on an Internet type network.

Claims

1, Reception method for a system with Nt transmit antennas (TX ₀ , TX _Nr-1 ) and Nr receive antennas (RX ₀ , RX _Nr-1 ) separated by a transmission channel, signals transmitted by the channel transmitting after a space division multip1exage of a signal to be omitted over N ≥1 under carriers and on Nt transmit antennas, performing a decoding which comprises the step of:

to extract (1), in the frequency domain, the signal transmitted by the transmission channel of the signals received on the Nr receiving antennas, by transmitting antenna and by subcarrier, the said method comprising a discrete processed analysis (DFT) received signals providing frequency samples

), the extraction (1) of multiplying these samples, by receiving antenna sub-gate, independently, with extraction coefficients

transmission channel and to accumulate in a coherent manner the result of the multiplication, characterized in that the extraction coefficients

are determined by solving a system of equations obtained by decomposing the signals received by subcarrier on each receiving antenna into an expected signal and into unexpected components and forcing the unexpected components to zero.

2, receiving method for a system with Nt transmission antennas and Nr receiving antennas separated by a transmission channel according to the preceding claim, wherein the decoding further comprises the step of;

to equalize (2) in the frequency domain a distortion introduced by the transmission channel onto the transmitted signal,

3. Reception method for a system with Nt transmission antennas and Nr receiving antennas separated by a transmission channel according to the preceding claim, with Nr> Nt, in which the method extracts (1) at the same time as many signals as there are combinations of obtaining Nt signals from Nr received signals and combines (3) the signals extracted after equalization (2) and before demodulation.

4. Reception method for a system with Nt receiving antennas and Nr receiving antennas separated by a transmission channel according to Claim 2 or 3, in which the equalization is a linear equalization (ZF),

5. Detector for reception device (RE) of signals transmitted by a transmission channel, after multiplexing by space division of a signal to be transmitted on N ≥ 1 under carriers and on Nt transmit antennas and received by Nr receiving antennas (RX ₀ , RX _Nr-1 ) coupled to the receiving device, the receiving device comprising discrete spectral analysis means (DMXO, ... DMX _Nr-1 ) of the signals

receivers providing frequency samples), said detector comprising:

a detection means (DHB) for extracting, in the frequency domain, signals received on the Nr receiving antennas (RXo, RX _Nr-1 ), a signal transmitted between the transmitting and receiving antennas via the transmission channel; transmission, by transmit antenna and by subcarrier, the extraction (1) of multiplying the frequency samples, by sub-carrier and by receiving antenna, independently, with transmission channel extraction coefficients and accumulate

coherently the result of the multiplication, characterized in that the detection means determines the extraction coefficients by solving a system of equations obtained by decomposing the signals received by subcarrier on each receiving antenna into an expected signal and into unexpected components and forcing unprescribed components to zero,

Receiver (RE) characterized in that it comprises a detector according to the preceding claim,

7. Transmission system comprising Nt transmit antennas, Nr receive antennas (RXo, RX _NI -I), a transmission channel between the transmitting and receiving antennas and comprising a receiver (RB) of signals transmitted by Ie transmission channel after a space division multip1exage of a signal to be transmitted on N ≥i under carriers and on Nt transmit antennas and received by the Nr receiving antennas (RXo, RX _Nr-1 ) coupled to the receiver (RF), characterized in that the receiver comprises: a discrete spectral analysis means O ... DMX _Nr-1 ) of the received signals providing frequency samples

detection means (DEE) for extracting a transmitted signal from signals received on the Nr receiving antennas (RXo, RX _Nr-1 ), in the frequency domain, by transmission antenna (TXo, TX _Nr-1) ) and by subcarrier, the extraction (1) of multiplying the frequency samples, by subcarrier and by antenna of the reception, independently, with coefficients of extraction of the channel of

transmits and accumulates coherently the result of the multiplication, characterized in that the detecting means determines the extraction coefficients (by solving a system of equations obtained by decomposing the signals, received by subcarrier on each receiving antenna in an expected signal and expected noo components and forcing the unexpected components to zero.

8. Computer program on an information carrier, said program comprising program instructions adapted to the implementation of a reception procedure for a system with Nt transmit antennas (TXo, TX _Nr-1 ) and Nr receive antennas (RXo, RX _Nr-1 ) separated by a transmission channel, according to any one of claims 1 to 4, when said program is loaded and executed in an electronic device.

9. Digital signal intended to be used in a receiver adapted to receive a signal transmitted on N≥l under carriers and Nt transmit antennas after a space division multipIexage of a signal to be omitted, the digital signal comprising at least codes for the execution by the receiver of the following steps: - extraction, in the frequency domain, of the signal transmitted by the transmission channel of the signals received on the Nr receiving antennas, by transmission antenna and by subcarrier analysis s discrete (DFT) received signals providing

frequency samples), the extraction consisting in multiplying these samples, by subcarrier and by receiving antenna, independently, with extraction coefficients

of the transmission channel and to accumulate coherently

result of multiplication, the extraction coefficients being determined in solving a system of equations obtained by decomposing the signals received by subcarrier on each receiving antenna into an expected signal and into unexpected components and forcing the unexpected components to zero.

An information carrier having program instructions adapted to implement a reception method for a system with N transmit antennas and Nr receive antennas separated by a transmission channel, according to any one of Claims 1 to 4, when said program is loaded and executed in a receiver.