EP2127092A2

EP2127092A2 - Dynamic time interleaving method and device therefor

Info

Publication number: EP2127092A2
Application number: EP07872019A
Authority: EP
Inventors: Isabelle Siaud; Anne-Marie Ulmer-Moll
Original assignee: France Telecom SA
Current assignee: Orange SA
Priority date: 2006-12-29
Filing date: 2007-12-21
Publication date: 2009-12-02
Also published as: CN101573871A; KR20090102840A; WO2008087351A2; US8351415B2; US20110002323A1; WO2008087351A3

Abstract

The invention relates to a time-interleaving method (1) and a time interleaver (ETS) for data. The data is intended to be sequentially transmitted by a baseband carrier of a single-carrier transmission device (EM). The method comprises interleaving a subsequent data block according to an interleaving law that is variable over time for a given transmission mode of the transmission device.

Description

DYNAMIC TIME INTERLACING METHOD AND DEVICE THEREFOR

The present invention relates to the field of telecommunications. Within this field, the invention relates more particularly to so-called digital communications. Digital communications include in particular wireless communications; they also include, for example, wire communications. The communications transmission medium is commonly referred to as the transmission or propagation channel, originally with reference to an overhead channel and by extension with reference to any channel.

The invention relates to interleaving techniques. These techniques are generally implemented to reduce the correlation introduced by a selective filtering operation inherent in the transmission channel.

The invention applies to any single-carrier transmission system, ie a system for which the baseband data symbols are transmitted sequentially in time, as opposed to a multi-carrier signal where N Data symbols previously modulated in baseband by the subcarriers of an Orthogonal Frequency Division Multiplexing (OFDM) are transmitted simultaneously to form a multi-carrier signal. In both cases, the transmitted data is then modulated by an RF (Radio Frequency) frequency. The baseband information is transmitted in the form of data symbols (QAM, QPSK, BPSK ... cells) around the zero frequency.

These symbols undergo a distortion due to the transmission channel which has the effect of filtering the transmitted signal and which is described by a baseband equivalent filter whose impulse response h (t, τ) depends on two variables t and τ where t represents the time variable and τ the delay variable associated with the coefficients of the filter at time t. The transmission channel, also called multipath channel, generates in reception a symbol correlation in the time domain over a period of the order of the coherence time of the transmission medium. The coherence time corresponds to the average value of the time difference necessary to ensure a decorrelation of the signal representative of the transmission medium with its time-shifted version.

This correlation limits the performance of the decision circuits in reception. It induces error packets after deciding on transmitted data symbols and decoding bits. These effects are encountered when the environment varies slowly and is multipath or more generally, when the transmission rate of the system is high vis-à-vis the Doppler frequency of the transmission medium. This is particularly the case for so-called Ultra Wide Band systems whose bandwidth greater than 500 MHz is intended to transmit very high data rates up to 1 Gbit / s in the band. 3.1-10.6} GHz in a weakly variable environment over time. An example of a UWB system is described in R. Fischer, R. Kohno, M. Mac Laughin, M. Wellborn, "DS-UWB Physical Layer Submission to 802.15 Task Group 3a", reference: IEEEP802.15- 04 / 137r3, July 2004.

This is also the case for the systems defined in the millimeter band, in particular at 60 GHz for which the target bit rates advanced by the IEEE802.15.3c standardization group are well above 1 Gbit / s. These systems are dedicated to indoor deployment of buildings. They are part of the so-called short-range systems whose radio coverage of flows is less than 10-15 m indoors. More generally, this correlation is disadvantageous for any transmission system whose transmission rate or modulation rate is high compared to the Doppler frequency of the transmission medium. Another example relates to the IEEE802.16 associated systems defined in the bands greater than 11 GHz and below 66 GHz for which the interleaving methods are static for a given transmission mode in a single carrier transmission. These systems are described in IEEE Std 802.16-2004, "IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems," June 2004.

One method for correcting this correlation consists in implementing on the transmission an interleaving performed on the binary data or on the data symbols whose interleaving depth expressed in time must be greater than the coherence time of the transmission medium. In practice, the value of the coherence time is deduced from the autocovariance function Φ (Δt) of the signal associated with the transmission medium and corresponds to the time difference Δt necessary to obtain a statistical coefficient of autocorrelation less than one. value usually between 0.9 and 0.5. An estimate of this value is also given by the inverse of the Doppler frequency of the transmission medium. An interleaving depth greater than the coherence time is difficult to obtain in practice for very high speed systems because the latency time introduced by the interleaving operation on the system limits the available bit rate in real time. During a transmission, the data is transmitted in packet mode. The size of the packet is generally inversely proportional to the rate and each packet is transmitted independently, as a result of which the interleaving depth is limited by the size of the packet and is, in most cases, less than the coherence time of the medium of the packet. transmission. Interleaving techniques in a transmission system are therefore applied to the data to decorrelate the received data and improve the performance of the decision circuits.

At the bit level when the system comprises an error correcting coding device, the interleaving techniques applied after the encoding operation make it possible to reduce the size of the error packets in reception because the deinterleaving operation with the decoder input disseminates the high probability decision error bits and the decoder can correct these errors. Interleaving is said to be binary when it relates to coded bits or is designated by the Anglo-Saxon term "scrambling" if it is applied to the bits directly extracted from the source.

The symbol interleaving involves a block of complex value symbols of given size formed of complex signals (QPSK, x-QAM, BPSK ...) resulting from the binary coding operation usually designated by the terms digital modulation.

Interleaving may implement different laws for the in-phase and quadrature components (I, Q components) of the baseband modulated signal.

The interleaving is always carried out on the useful data of the transmission device with a static interleaving law for each transmission mode defined by the number of states of the modulation, the coding, etc. The data transmitted is referred to as the payload data. carrying an information message and lacking data dedicated to signaling and identification. In the rest of the document, the data designates the useful data, whether binary or in the form of data symbols.

All known single-carrier digital radio communications systems refer to a data permutation law that is clean and unique for a given transmission mode. The UWB-DS-CDMA system (Ultra Wide Band Direct Sequence Coded Division

Multiple Access) promoted in July 2004 as part of the IEEE802.15.3a standardization for short-range ultra-wideband systems does not involve symbol interleaving strictly speaking. The binary interleaving applied on the coded bits of the source can be likened to a symbol interleaving when a symbol is formed by a bit. The system, in one of the transmission modes, refers to a BPSK (Binary Phase Shift Keying) modulation resulting from a thresholding which transforms a bit taking its values in the bit space {0,1} into a binary symbol taking its values in a subspace taking its values in {-1,1}. This notion makes it possible to assimilate the implemented binary interleaver to a symbol interleaving. The interleaver of the UWB-DS-CDMA system is of convolutional type, its structure is unique for each mode of transmission and common to all modes of transmission. This interleaver is described in JL Ramsey's paper, "Realization of optimum interleavers", IEEE Tr. On Inf. Th., Vol. IT-16, May 1970, pp. 338-345. The system of transmission is illustrated by the scheme of FIG. 1. The transmitting EM device comprises a source data interleaving module ETBB, a channel coding module CC, a punching module PE, a binary interleaving module ETB, a FL emission filter. The transmission device implements so-called ternary spreading codes taking their values in the subspace {-1.0, 1}, of size Lc_24, denoted -24 (-l / 0/1).

The interleaving law implemented by the binary interleaver ETB does not vary with the length of the spreading sequence, nor with the modulation chosen, nor with the spreading sequence to generate a desired bit rate. The interleaving method applied to the bits associated with the BPSK symbols for the mandatory mode of the standard is a convolutional interleaver which generates a static and fixed dispersion between the symbols for the described transmission mode. However, this convolutional interleaver is not a block interleaver of size K defining a bijective law in the space of integers on the subset I = {0, .... K-1}. As its name indicates, the convolutional interleaver described by the Ramsey algorithm is a device that allows data to be stored in a buffer memory and to interleave the data by temporally shifting the data by a proportional delay. at an elementary delay Jo at each clock tick. The dispersion corresponding to the distance between the indices of the input-output data of the interleaving module is a multiple of Jo, the size of the elementary shift register of the interleaving system and is strictly less than the product of the number of branches by this elementary delay Jo. The interleaving method is illustrated by the scheme of Figure 2 which shows the multiple time lag of Jo between the interleaved coded bits bce and the coded bits bc before interleaving. Even if the interleaving is convolutional, the interleaving pattern is stationary in the broad sense and the law is constant whatever the moment considered.

More generally, for known single-carrier systems, the interleaving methods implemented for a given transmission mode are static and stationary in the broad sense. The static nature of the interleaving has advantages when estimating the transmission medium because it limits the insertion ratio of the training sequences intended to probe the transmission medium provided that the transmission medium varies slowly in the transmission medium. time relative to the transmission rate. On the other hand, the operations of interleaving of the data on the sending intended to decorrelate the data in reception have a limited efficiency because of the presence of fades of long duration due to the multipath channel varying slowly in the time.

Also, the technical problem to be solved by the object of the present invention is to propose a method for temporally interleaving data, data symbols or binary data, which is more efficient than the known methods for a single-carrier transmission device, particularly when the transmission medium varies slowly over time compared to the inverse of the modulation rate or the transmission rate. To this end, the present invention relates to a method of temporally interleaving symbols or data, intended to be transmitted sequentially by a baseband carrier of a single carrier transmission device, consisting of interleaving a block of symbols or data according to a determined time-varying interleaving law for a given transmission mode of the single-carrier transmission device.

In addition, the subject of the invention is a symbol or data interleaver intended to be transmitted sequentially by a baseband carrier of a single-carrier transmission device, for interleaving a block of symbols or data according to a law. defined interleaving device comprising a device for calculating the interleaving law able to vary in time the block interleaving law calculated for a given transmission mode of the single-carrier transmission device.

The invention furthermore relates to a transmission device comprising an interleaver according to a preceding object, as well as to a reception device comprising a deinterleaving module performing a deinterleaving of demodulated symbol blocks according to a law that is the inverse of a law of interleaving according to a previous object, the module being able to calculate the deinterleaving law at given times, the interleaving law varying with time for a given transmission mode.

Thus, a data block interleaving, corresponding to binary data or data symbols, according to the invention, of using a different interleaving law over time, for a given transmission mode, makes it possible to generate a variability dummy temporal transmission channel which has the effect of locally reducing the coherence time of the transmission medium in reception. This makes it possible to reduce the temporal correlation which affects the data of a transmission system and, consequently, to improve the reception decision-making; the efficiency of the system is thus improved. Unlike known methods for which the interleaving law is static for a given transmission mode, the interleaving law is dynamic, that is to say variable in time.

The fictitious variability of the transmission medium introduced may reduce the duration of the fast fading of the transmission medium and may make it possible to better take advantage of an interleaving operation performed on transmission, upstream of an interleaving according to the invention.

According to a particular embodiment, the temporal variation of the block interleaving law is obtained by means of a single basic mathematical algorithm integrated in a turbo structure which makes it possible, by an iterative method, to generate several laws of interleaving and to make a selection of the laws to be implemented according to a selection criterion. In particular, the variation is a function of the iteration chosen. This algorithm has been the subject of a French patent application No. FRO 04 141 13. Typically, after N blocks of K data symbols, the algorithm uses a different interleaving law by the number of iterations or by the selected interleaving parameters, selected according to a dispersion criterion of the interleaved data, a dedicated multiplexing of the data and the global constraints of the data. transmission system. A block interleaving law I (k) of size K is a bijective function which gives the following order to be read, at the output, an input sequence formed by K data indexed by an index k varying from 0 to KI . Let X (k) be an input sequence of an interleaving law interleaver I (k). Let Y (k) be the sequence at the output of the interleaver. Then Y (k) = X (I (k)): the kth data of the output sequence of the interleaver having the index of position k-1 corresponds to the index data I (kl) of the sequence of input X (O), ..., X (KI). The position of the input data to interleave and interleaved data is shown in the remainder of the document only by their position index k / I (k), unless otherwise indicated.

According to a particular embodiment, the variation of the interleaving law occurs every N blocks of K data, where K and N are integer values, N being a parameter determined according to the properties of the transmission channel and the screening of data, N ≥ \. In particular, N and / or K vary in time according to the screening of the data and at least one criterion associated with the overall performance of the transmission system, which makes it possible to adapt them to variations in the environment.

According to a particular embodiment, the temporal variation of the block interleaving law of size K depends on a temporal index n of data blocks.

An interleaving method according to the invention is particularly interesting for short-range systems delivering high data rates and indeed requiring low interleaving depths. This is the case of Ultra Wide Band systems, such as the UWB-DS-CDMA system defined by the 802.15.3a working group. The UWB-DS-CDMA system delivers a maximum useful bit rate of 1320 Mbps in the {3.1-4.85} GHz and {6.2-9.7} GHz bands by implementing direct-sequence time-domain symbol spreading to introduce a temporal diversity on the transmitted signal and transmit data symbols allocated to different users simultaneously.

According to a particular embodiment, the data symbols can be interleaved by data blocks of size K which is a multiple of the length Ko of the spreading sequence according to a time-varying block interleaving law. The size spreading sequence Ko spreads a data symbol over Ko samples designated by 'chips'. According to the spreading algorithm chosen, the system can use KB spreading sequences different in size KO to simultaneously transmit Ko data symbols allocated at most to KO users.

Other features and advantages of the invention will become apparent from the following description given with reference to the accompanying figures given by way of non-limiting examples. FIG. 1 is a diagram illustrating a static data interleaving method according to the prior art in a particular case where a data symbol is formed by 1 bit for a single carrier system.

FIG. 2 is a detailed diagram illustrating the interleaving method implemented by a convolutional interleaver of a transmission system of the prior art illustrated by FIG.

Figure 3 is a diagram of a transmission system implementing a dynamic symbol block interleaving according to a particular embodiment of the invention.

FIG. 4 is a schematic representation of various embodiments of an interleaving method according to the invention.

FIG. 5 is a block diagram of an interleaving device implementing an iterative interleaving algorithm making it possible to obtain a time-varying interleaving law for a method according to the invention.

FIG. 6 is a diagram illustrating an exemplary implementation of a particular embodiment of an interleaving according to the invention in a particular single-carrier transmission / reception system implementing a method of spreading the symbols by direct sequence.

Between the different figures, the same references and symbols are used to designate the same things. FIG. 3 is a diagram of an example of a transmission system SY implementing an interleaving method 1 according to the invention. The transmission system SY comprises a single carrier transmitting EM device and a receiving RE device. The transmitting EM device comprises a source data generation module SE, a channel coding module CC, a bit interleaving module ETB, a symbol-to-symbol coding module CBS, an ETS time interleaver of the data symbols, a MT framing device, a FL emission filter.

The symbol ETS temporal interleaver comprises in particular a device for calculating the interleaving law I _n (k) such that the calculated block interleaving law is variable in time, according to a time index n, for a mode of given transmission of the EM transmission device. The rasterizer MT distributes the interleaved data symbols Set and the symbols dedicated to channel estimation and synchronization. At the output of filter FL, the transmitted signal Is transmitted by the propagation channel CN and assigned a Gaussian additive white noise BBAG. This schematic representation is the baseband equivalent of a real transmission on an RF carrier. The receiving device RE comprises an equalizing filter FLE, a despreading module DMT, a de-interleaving module DETS, a decision module DCBS, a deinterlining module DETB, a decoding module DCC. The symbol de-interleaving module DETS performs de-interleaving of demodulated symbols according to an inverse law to the interleaving law used on transmission. This deinterlacing module is capable of calculating, at given times, the deinterlacing law which varies with time for a given transmission mode. A method 1 of interleaving according to the invention is implemented by the interleaver

Time ETS of the transmitting EM device. It applies according to the example on the data symbols Sd resulting from the binary coding to symbol.

Process 1 interleaves successive data symbols Sd according to an interleaving law I _n (k) determined. According to the invention, the interleaving law is variable in time according to the index n for a given transmission mode.

The baseband data symbols Sd, consisting of m coded bits, are converted into complex value signals, are partitioned and interleaved according to method 1 into blocks of K contiguous symbols. According to one embodiment, the blocks of K symbols are grouped by N. According to the illustration, N is equal to three. In each block of K symbols, the position of the data symbols is indexed by the integer k varying from 0 to KI. An interleaving law I _n (k) of K time index size n varying from 0 to 1 NN'-, where NN corresponds to the number of different interleaving laws implemented, is applied on each block of 2 K symbols.

According to one embodiment, the temporal variation of the interleaving law occurs every N blocks of K symbols.

FIG. 4 illustrates various embodiments of an interleaving method according to the invention, for which the temporal variation of the interleaving law occurs every N blocks of K symbols, with N and K possibly being variable in time. Block 4.1 illustrates the case where N and K are constant. According to the illustration N is equal to three (N = 3) and the interleaving law changes all three blocks of K symbols. According to the illustrated case, the interleaving law for the first three blocks is Io (k), the law for the following N blocks is Ii (k), and so on up to the maximum number of different laws NN'-1 Block 4.2 illustrates the case where N is variable, noted N _n , and K constant. Block 4.3 illustrates the case where N and K are variable and described by the variables N _n and K _n of time index n. Thus, according to the embodiments, the value N _n of the number of blocks of K symbols interleaved by the same interleaving law I _n (k) is variable or constant, or the value N _n of the number of blocks and the size of block interleaving K _n are variable, and this on a motive constituted by NT symbol blocks implementing NN 'different interleaving laws, with n varying between 0 and NN'-1. FIG. 5 gives a schematic diagram of FIG. an interleaving device AND implementing an iterative interleaving algorithm making it possible to obtain a time-varying interleaving law. The interleaving device AND makes it possible to obtain laws interleaving variables varying in time by modifying the parameters of the algorithm and / or the number of iterations of the algorithm, for an interleaving method according to the invention.

The interleaving AND device implementing the algorithm comprises as many basic cells I as there are iterations. The output of the jth base cell I, I _j which corresponds to the ith iteration, provides an interleaving pattern which is expressed as:

where p and q are two integer parameters describing the basic function I and the iteration associated with I. The implementation of the algorithm makes it possible to carry out block interleaving of size K with J index iterations j, J being greater than or equal to 1, of input digital data indexed by a variable k = OJ, ...., AT - 1}.

Each basic cell I of the AND device interleaver has the same structure: two inputs, one output and two unit cells, denoted _{Lo, p} and Li _{iP> q.} The integers p and q are two parameters of the law of interlacing which make it possible to generate the desired law. Each elementary cell Lo, _p and Li, _pq comprises two inputs and one output. One of the two inputs of the two cells Lo, _p and Li _{, p, q} is identical for these two functions and corresponds to the index variation of the samples before interleaving. The two inputs of the elementary cell Lo, _p correspond to the two inputs of the basic cell I to which it belongs, the output of the elementary cell Li _pq corresponds to the output of the basic cell I to which it belongs. The output of the elementary cell Lo, _p is connected to a first input of the elementary cell h _{\ ΦA} . The second input of the elementary cell Li _{, p, q} is connected to a first input of the basic cell I to which it belongs; this input of the base cell I being fed by the indices k to be interlaced which are generally in the form of a ramp from 0 to KI. The second input of the base cell I is connected to the output of the base cell I above, except for the first basic cell, for which the two inputs are connected to each other and correspond to the index k.

The interleaving algorithm Ij] ₁ (£) thus rests on an iterative structure for which the interleaving law depends on three parameters (K, p, q) and the iteration considered j. K corresponds to the size of the block to be interleaved, p and q are two parameters that modify the properties of the interleaving device, in particular the interleaving law and the dispersion denoted Δ _{ç I} y y y (s). The dispersion corresponds to the minimum distance after interleaving of the position indices of the input data separated by s-1 output. The choice of the iteration makes it possible to modify the law of interlacing and the dispersion while preserving a pattern of size p. The variation in time of the interleaving law is obtained by modifying either the iteration, or one of the parameters p and q of the interleaver according to a criterion of optimization of the law or of a constraint associated with the system. of transmission.

This interleaving, which is based on the combination of two algebraic functions Lo _{, p} and L], _p , _q with a 'turbo' structure, has the property of preserving a pattern, that is to say, of preserving the order of multiplexing p data flow after interleaving, p being a parameter of the interleaving algorithm sub-multiple of the size K of the block interleaving, q is an integer parameter that makes it possible to vary the interleaving law and the dispersion . In a typical embodiment, q is arbitrarily set to two for simplicity and sets the size of the pattern.

This property of preservation of a pattern is very interesting to preserve optimization operations based on a multiplexing of p data made upstream or downstream of the interleaving operation.

The interleaving law l _p ° _q (k) given by the output of the interleaving module I for the iteration (j) results from the combination of two algebraic functions with two inputs and an output Lo _p and Li _pq . described below:

L _Op (k, k \) = [-kk _r p] _k k = {0, ...., K- \}

L _{] pq} (k, k ₂ ) = [Kp + k + qpk ₂ ] _κ , k = {0, ...., K- \} (I)

I _pq (k, k \) = _Lpq (k, L _Op (k, kl))

For the iteration j = l, the inputs k and kl of the function Lo _{, p} are identical and correspond to the position indices of the data at the input of the interleaving method. The following expressions result for a pattern of size p and a parameter q:

_Piq I (k) = L _{1 <Pιq} (k, Jk L ₀₎₎ = [Kp + k + QPL _(Kp (k)] _κ k = {θ, Kl} (2)

I _Pιg (k) = [Kp + k + qp - [- kpk] _κ ] _κ k = {0, ...., Kl}

The outputs of algebraic functions Lo and L _p _{\ fA} for iteration (j) are given respectively by the laws LLJ _p (k, _j k) and L ^(/ ^ _q (k, k _^) for which variables kl and k ₂ are fed respectively by the interleaving law of the previous iteration I '' ^~ '' (k) and the output of the function Lo ₄ , for the current iteration (j), for the iteration j , the block of equations (2) is of the form:

li _l f _p (k) = [-kpI _p ^< _'q ^l> (k)} _k k = {0, ^} -7

I _p ^<j : (k) {0, KI) (3)

IJ ^<> (k) ^K - *}

The sequence of the interlaced output data Y (k) is related to the sequence of the input data before interleaving X (k) by the relation: Y (k) = X (I ^ k)). The pseudo periodic and algebraic structure of the algorithm makes it possible to pre-calculate the dispersion Min between data separated by s-1 data.

The dispersion corresponds to the minimum distance after interleaving, between the position indices of the input data when the output data of the interleaver are separated by s-1 data.

The dispersion Δ _{e / f} I _p ⁽ 'J (s) for the iteration (j) of the interleaving law I _p ^(J ^ (k) is determined by

P _{j M}

Affi _p _{q (^ = MinΛ s- [q -p (s + pP _j ^ Jk _q))] s- K- [q- p- (pP + _S _j _ _M Jk))

This algebraic function P _{j, p} , q, _s (k) depends on the parameters p and q of the interleaving, where p corresponds to the largest size of the preserved pattern, q is a parameter which modifies the interleaving law and j) is the iteration considered.

According to a particular embodiment, a method according to the invention comprises such an iterative interleaving algorithm and an ETS time interleaver according to the invention comprises such an interleaving device AND, with a size K corresponding to the number of symbols per block. . The interleaving law varies temporally, for example all the M symbols, by modifying either the number of iterations or one of the parameters p and q of the interleaving device AND for a given transmission mode. The parameters of the iterative interleaving algorithm are then indexed by a time index n which is incremented every N blocks of K symbols and whose minimum value is zero and the maximum value corresponds to the number of different interleaving laws decreased by 1, or NN'-1, with M = KxN.

The law of interlacing given by the blocks of equations (2) and (3) is modified to take into account the dynamic character of this law as follows: p _n , q _n and j _n are the parameters chosen for the law I _n (k) of time index n and NN 'corresponds to the number of laws considered. I (k) = l ^(jn) (k)

l ⁽ in ^} (k) = K - p _{n +} k ₊ q _n - p _n - [- k - _Pn - I _p ^{(J "} - _n ^l} (k) (5) Pn A KK k = {0 K - I)

The following example, to which FIG. 6 corresponds, illustrates an optimization of a particular embodiment of an interleaving method according to the invention in the case of an implementation with a UWB-DS type system. -CDMA. Interleaving is performed on blocks of data symbols before spreading the data using spreading sequences as described in Table I in Appendix 1.

The optimization of the method consists in a first step in defining the sizes of possible interleaving blocks K _n for the block interleaving laws I _n (k). K _n is determined according to the number of spreading codes implemented corresponding to the number of users and according to the number of data symbols per user to be transmitted. K _n is, for example, multiple of the number of user Nu and a number of data symbols per user greater than 1.

A second optimization step consists in determining the NN 'interleaving laws I _n (k) to be implemented as well as the number of blocks N _n for which the block interleaving law I _n (k) of size K _n is applied according to the iterative algorithm described with reference to FIG.

Optimization consists in selecting the laws that maximize the dispersion between adjacent symbols allocated to distinct users spread by different codes and transmitted on the same RF subcarrier or neighboring RF subcarriers. For this configuration, the parameter s to be considered is between 1 and Nu. The values of p _n , q _n and j _n are selected to generate a maximum dispersion A JJr, / p ⁷ _n ", q ^ _n (s) for the chosen values of s The interleaving algorithm generates a law interleaving index n less than or equal to 1 NN'- the one hand according to a parameter p _n _n K submultiple of that preserves a pattern and changes the dispersion, and on the other hand according to a q parameter _n and an iteration j _n which modify the dispersion The number NN 'of different laws is arbitrarily chosen for the example equal to two, ie n = {0, l} The number N _n is variable for a periodic pattern constituted by three blocks of Ko symbols for the law Io (k) (N _o = 3) and two blocks of Ki data symbols for the law Ii (k) (N i = 2) The interleaving sizes considered are Ko = 576 and Ki = 432 multiples of 24 and 12 corresponding to the size Lc of the sequence spreading codes Assuming that the spreading sequences result from rapid unit transformations, The different sequences may be used for simultaneous transmission of data symbols allocated to different Lc users. For these two interleaving sizes, where the symbols allocated to Lc users are interleaved by the law I _n (k), Nc symbols per user are integrated in the interleaving process as follows: N, -, 6)

The parameters chosen p _n , j _n to define the laws I ₀ (k) and Ii (k) are those which provide the maximum dispersion ^ rA "" ^Jn '(s) (n = {0, l}) between symbols of adjacent and inter-symbol data separated by a value of s less than the size of the spreading code Lc (1 <s <L _1. ) so as to optimize the dispersion between symbols allocated to different users and transmitted simultaneously. The parameter q _n is chosen arbitrarily equal to two. For a sequence size of Lc = I 2 or Lc = 24, the method selects four values for s, s = {l, 2, 6, 12} less than the spread length of the codes, are less than the potential number of codes that can be allocated to different users.

Interleaving is performed on the symbol blocks of size Ko = 432 and Ki = 576. These sizes are multiples of the spreading lengths of the sequences and allow, in the case where the number of users Nu is equal to the length of the spreading sequence, to allocate the same number of data symbols to each user by interleaved data block. In the implementation mode considered, two adjacent data symbols are considered as allocated to different users. For these two sizes of interleaving, the dispersions Δ _ç I _{p p} J ^J '(s) calculated using the equation blocks (3) are given in Appendix 2. For each block size, the process selects the values of p _n , q _n and j _n at maximum dispersion for all the values of s considered, as well as the values of p _n , q _n and j _n such that the dispersion for s = 1 has no sub- multiple common with the size of the block K _n considered. The values selected for each interleaving size are given in Appendix 2. Preferably, if an optimized multi-user multiplexing of the data symbols is performed upstream of an interleaving according to the invention, then it is preferable to choose p multiple of number of user Nu.

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

For a wired implementation, the ETS time interleaver or some of the elements of the ETS time interleaver used (for example the AND interleaver) to perform the different steps at the transmitter may be integrated into one or more circuits. specific integrated systems (ASICs), in signal processors (DSPs, DSPDs), in programmable logic circuits (PLDs, FPGAs), in controllers, microcontrollers, microprocessors, or any other electronic component designed to perform the previously described functions.

For a software implementation, some or all of the steps of an interleaving method according to the invention can be implemented by modules 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 desirable form 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 medium, for example a floppy disk or a disk. hard.

On the other hand, the information medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed 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.

ANNEX 1

Table I

ANNEX 2

Selection of interleaving matrices of size Ko = 432, law Io (k)

Interlacing parameters selected according to the dispersion maximization criterion for the values of s = {1, 2, 6, 12}. These values make it possible to generate four different matrices of size Ko for the law Io (k), only one is implemented according to the given example.

Selection of interleaving parameters of interleaving matrices of size Ki = 576, law Ii (k)

Table IΙI (continued): Possible values of the parameters {p, q, j} for the interleaving matrices of size Ki = 576 s = {6,12} Interlacing parameters selected for the law Ii (k) of size Ki according to the criterion of maximization of the dispersion for the values of s = {1, 2, 6, 12}.

Claims

A method (1) for temporally interleaving data, to be sequentially transmitted by a baseband carrier of a single carrier transmitting device (EM), comprising interleaving (2) a data block in accordance with a determined interleaving law, characterized in that the block interleaving law is variable in time for a given transmission mode of the single-carrier transmission device (EM).

2. Method (2) of temporal interleaving according to the preceding claim wherein the time-varying interleaving law is obtained by means of an iterative interleaving algorithm generating a variable interleaving law as a function of the iteration. .

The time interleaving method (2) according to claim 1 wherein the time-varying interleaving law is obtained by selecting one of a plurality of interleaving laws generated by means of an interleaving algorithm. iterative generating a variable interleaving law according to the iteration.

4. Method (2) of temporal interleaving according to one of claims 1 to 3, wherein the temporal variation of the interleaving law occurs as a function of the value of a temporal index of data blocks.

5. Method (2) of temporal interleaving according to the preceding claim, wherein the variation of laws occurs all N blocks of K data, N being a parameter determined according to the properties of the transmission channel and the screening of the data, TV > 1.

6. Method (2) temporal interleaving according to the preceding claim, wherein N varies over time.

7. Method (2) temporal interleaving according to one of the preceding claims, wherein K varies in time.

Data temporal interleaver (ETS), intended to be transmitted sequentially by a baseband carrier of a single-carrier transmission device (EM), for interleaving a data block according to a determined interleaving law, characterized in that it comprises a device for calculating the interleaving law capable of varying in time the block interleaving law calculated for a given transmission mode of the single-carrier transmission device (EM).

9. Interleaver (ETS) time according to the preceding claim wherein the computing device comprises a block interleaving device (ET) of size K with J iterations of index j, J being greater than or equal to 1, of data of input indexed by a variable k = {0, ...., K - I], comprising J cells (I ⁽¹⁾ , I ⁽¹ ') of base I with two inputs and an output, such that each cell (I ^(I) , I * ^) of base I is formed of two elementary cells Lo, _p and L], _p , _q which each comprise two inputs and one output and which respectively implement two algebraic functions modulo K with two inputs and an output, of parameters p and q, L _op {k, k \) and L _x (k, k ₂ ), the first inputs of the elementary cells and of the basic cells I being common and corresponding to the index k, the output of the cell (I (I ⁾ , 1 ^) of base I corresponding to the output of the elementary cell Li, _p , _q , the two inputs of the cell (I ⁽¹⁾ , 1 ^) of base I corresponding to the two inputs of the elementary cell Lo _{> p} , the output of the elementary cell Lo, _p corresponding to the other input of the elementary cell L | _ήP , _q , and in that the two inputs of the first cell (I _t ) of base I are connected to each other, and in that the output of each basic cell I is connected to the second input of the basic cell I of the next iteration, and in that the output of the Jth cell determines the interleaving function I (k). .

10. time interleaver (ETS) according to the preceding claim wherein the two modulo K algebraic functions with two inputs and an output, of parameters p and q, respectively have for expression:

_Op (k, k \) = [-k -k _r p) _{κ and} t L _lpq (k, k ₂ ) = [K - p + k + q - p - k ₂ ] _κ .

1 1. Use of a temporal interleaver (ETS) of position index data k, performing the interleaving of a data block according to a determined interleaving law I (k), comprising an interleaver ( AND) a block of size K, of parameters p and q determined for a given dispersion, composed of index iterations j of a two-input turbo base structure and an output cascading a first modulo K algebraic function with two entries ^ / ^ ^ whose entry is equal to the position index k of the data before interleaving and a second input k1 is fed by the output of the previous iteration, and a second algebraic function modulo K with two inputs Z _{1 pq} (k, k ₂ ) whose second input k ₂ is connected to the output of the first algebraic function, the output of the iteration J determining the interleaving function I (k) for the iteration J as being the combination of the two algebraic functions with k _x = k when j equals a, J being greater than or equal to 1, to vary the temporal interleaving in the data time as a function of the choice in time of the values of J, p, q or K.

12. Transmission device comprising a temporal interleaver (ETS) according to one of claims 8 to 10.

13. Receiving device (RE) comprising a deinterleaving module performing a data de-interleaving according to an inverse law to an interleaving law, characterized in that the module is able to calculate the de-interlacing law at determined times, the law of deinterlacing. interleaving over time for a given transmission mode.

An information carrier having program instructions adapted to implement a time interleaving method (2) according to any one of claims 1 to 7 when said program is loaded and executed in a electronic device.

A computer program product loadable directly into the internal memory of an electronic device, comprising portions of software code for executing the steps of a method (2) of time interleaving data according to one of the claims

1 to 7, when the program is executed by the electronic device.