Method for sending and receiving a spread-spectrum wireless communication with high potential spectral efficiency and associated devices

Abstract

The invention relates to a method for sending a wireless communication, the method comprising: obtaining symbols through channel coding and digital modulation; DSSS spreading of each symbol obtained with a spreading code of period TDSSS applied with a spreading factor, the SF chips spreading a symbol being specific to the time of sending of the symbol; and obtaining, from each symbol, a set of SF chips that are spread according to the value of the symbol, these chips being separated by a period; implementing, on the chip, the steps of: - compressing the period between the chips at a compression rate that is strictly greater than 1, the period between the chips after this compression being equal to ξTc; - filtering by means of a shaping filter using square-root Nyquist filtering for orthogonality period Tc or a finite-length useful bandwidth.

Description

DESCRIPTION Title: Methods for transmitting and receiving spectrally spread wireless communication with high potential spectral efficiency and associated devices Technical field:

[0001] The invention lies in the field of spectrally spread wireless telecommunications as well as in that of high spectral efficiency systems. Previous technique:

[0002] DSSS (Direct Sequence Spread Spectrum) is a spectral spreading technique using "pseudo-noise" spreading codes over a frequency band larger than the minimum required (R. Pickholtz, D. Schilling, and L. Milstein, "Theory of spreadspectrum communications - a tutorial," IEEE Transactions on Communications, vol. 30, no. 5, pp. 855-884, 1982.).

[0003] In the case of spectrally spread radio transmission signals, a distinction is generally made between short codes whose period is less than the symbol duration (or by extension less than a few symbol durations), and long codes whose period corresponds at least to a high multiple of symbol durations.

[0004] In the civilian sector, this technique allows multiple users to employ orthogonal or near-orthogonal codes to simultaneously share the same frequency band while ensuring low interference (Code Division Multiple Access or CDMA [Kwang Soon Kim, Lickho Song, Yun Hee Kim, Yong Up Lee, and Jooshik Lee, “Analysis of quasi-ML multiuser detection of DS / CDMA systems in asynchronous channels,” IEEE Transactions on Communications, vol. 47, pp. 1875-1883, Dec. 1999]). In the military sector, its main advantage is its robustness to jammers (thanks to the spreading gain) and interception (thanks to the low power spectral density, which can be reduced to induce reception levels below the noise level).

[0005] A corollary to this application is that such so-called "discrete" communications are likely to be authorized to use allocated bands as a secondary user (SU). Indeed, this new user generates little interference (thanks to its low DSP) while being robust against the primary user's signal.

[0006] Unfortunately, spreading the signal spectrum significantly reduces spectral efficiency. This is one of the important criteria to consider when designing a waveform.

[0007] This problem has already been raised in the context of non-spread links. Examples of techniques that improve spectral efficiency include: Choosing the formatting filter: By using, for example, a raised cosine square root shaping filter, it is possible to reduce the bandwidth of the useful signal and thus increase spectral efficiency by adjusting a parameter called roll-off. Unfortunately, reducing the bandwidth also increases the filter's time support and therefore the complexity of reception. - The choice of modulation: Increasing the modulation order at constant band (and constant antenna output power) increases the number of bits transmitted per symbol and therefore spectral efficiency, but degrades performance in terms of bit error rate (BER). The use of Faster-Than-Nyquist (FTN) links The FTN involves transmitting at a higher baud rate than the so-called Nyquist rhythms. However, this benefit comes at the cost of the appearance of intrinsic inter-symbol interference (I ES I) from the moment of transmission, and of more complex receivers to process it.

[0008] There is therefore a need for a spread-out transmission chain that can ensure a certain energy discretion while maintaining reasonable spectral efficiency. Summary of the invention:

[0009] To this end, according to a first aspect, the present invention describes a method for transmitting wireless communication, said method being implemented in a wireless telecommunications transmitting device receiving as input a signal to be transmitted, said method comprising the following steps implemented by the transmitting device: application of channel coding, including error-correcting coding and / or interleaving, to the signal to be transmitted, followed by digital modulation of said coded signal to obtain symbols; said method being characterized in that it further comprises the following steps implemented by the transmitting device: DSSS-type spreading of each symbol obtained by a TDSSS period spreading code applied with a spreading factor SF, the SF chips spreading a symbol being specific to the instant of the symbol's emission; and obtaining, from each symbol, a set of spread SF chips as a function of the symbol's value, these chips being separated by a period Te; implementation on the chips obtained after spreading of a treatment comprising: - the compression of the period between chips by a compression ratio strictly less than 1, the period between the chips after said compression being equal to - filtering by a formatting filter v e (t): - in Nyquist root of period of orthogonality T c ; Or - of a useful strip of finite length B = 1 / T C .

[0010] The invention thus proposes a new configurable waveform that increases the spectral efficiency of conventional DSSS links and provides a degree of energy discretion to conventional FTN links. Various reception schemes associated with different complexities are also proposed.

[0011] In some embodiments, such a process will further include at least one of the following features:

[0012] the signal s e (t) at the end of the filtering is defined by the following equation:

[0013] with : : the compression ratio, between 0 and 1; - the chips made from the displayed symbols; o in the case of a single-code spread: o in the case of a two-code spread: - T c : the time separating the uncompressed chips; SF: the spreading factor; - v e (t): the impulse response of the shaping filter. - has n : the symbol to be transmitted (output of the channel coding and digital modulation) with R e (has n ) the real part of the symbol and / m (has n ) the imaginary part of the symbol; - the single-code or double-code spreading used.

[0014] According to another aspect, the invention describes a computer program intended to be stored in the memory of a wireless telecommunications transmitting device further comprising a microcomputer, said computer program comprising instructions which, when executed on the microcomputer, implement the steps of the transmitting process described above.

[0015] According to another aspect, the invention describes a method for receiving wireless communication implemented in a wireless telecommunications receiving device comprising at least one receiving antenna receiving a transmitted signal as input, said method comprising the following steps implemented by the receiving device on a signal obtained via the receiving antenna(s): application of digital demodulation and channel decoding to the signal; said method being characterized in that it further comprises the following steps implemented by the receiving device: implementation of signal processing comprising filtering by a filter and at channel such as the filter is suitable for a formatting filter in Nyquist root of orthogonality period T c or a usable strip of finite length period sampling of the signal from the filter matched to the overall channel g*(-t) = The sampled signal is spread out according to the spreading code taken over a length equal to the spreading factor SF, the series of SF chips corresponding to the spreading code on a symbol being specific to the time of reception of said symbol, the SF chips being separated by a period, and obtaining symbols of duration

[0016] In some embodiments, such a receiving method shall further include at least one of the following features: in a SIMO receiver in which the channel h(t) and its matched filter are replaced by the vectors and ) with N the number of receiving antennas the process includes, after despreading, at least one of the following steps: an equalization of the despreaded symbols implemented by an equalizer block (28) of the receiving device; a selection of an element from a constellation of elements, according to the despreaded symbols, by the implementation of a Viterbi algorithm or by a decision block of said receiving device.

[0017] According to another aspect, the invention describes a computer program intended to be stored in the memory of a wireless telecommunications receiving device further comprising a microcomputer, said computer program comprising instructions which, when executed on the microcomputer, implement the steps of a receiving process as described above.

[0018] In another aspect, the invention describes a wireless communication transmission device adapted to receive as input a signal to be transmitted. The transmission device is adapted to apply channel coding, including error-correcting coding and / or interleaving, to the signal to be transmitted, and then to digitally modulate said coded signal to obtain symbols. The transmission device is characterized in that it is adapted to perform DSSS-type spreading of each symbol obtained by a spreading code of period T. DSSS applied with a spreading factor SF, the SF chips spreading a symbol being specific to the instant of the symbol's emission, and to obtain, from each symbol, a set of spread SF chips as a function of the symbol's value, these chips being separated by a period T c ; said emission device being adapted to implement on the chips obtained after spreading, a treatment comprising: - the compression of the period between chips by a compression ratio strictly less than 1, the period between the chips after said compression being equal to - filtering by a formatting filter v e (t): - in Nyquist root of period of orthogonality T c ; Or - of a useful strip of finite length B = 1 / T C .

[0019] In one embodiment, the signal s e (t), obtained by said emission device after filtering, is defined by the following equation:

[0020] with : - : the compression ratio, between 0 and 1; - : the chips resulting from the spread symbols; in the case of a single-code spread: in the case of a two-code spread: - T c: the time separating the uncompressed chips; - SF: the spreading factor; - v e (t): the impulse response of the shaping filter. - has n : the symbol to be transmitted (output of the channel coding and digital modulation) with R e (.has n ) the real part of the symbol and / m (has n ) the imaginary part of the symbol; - : the single or double spreading code used.

[0021] According to another aspect, the invention describes a wireless communication receiving device adapted to receive a transmitted signal as input via one or more receiving antennas. This receiving device is adapted to apply digital demodulation and channel decoding to the signal obtained via the receiving antenna(s). The device is characterized in that it is adapted to implement signal processing comprising filtering by a filter and to the channel such that the filter is adapted to a formatting filter v e (t) in Nyquist root of period of orthogonality T c or of a useful strip of finite length B = 1 / T C ; said device is adapted to perform period sampling of the signal from of the filter adapted to the global channel The device is adapted to perform despreading of the sampled signal according to the spreading code taken over a length equal to the spreading factor SF, the series of SF chips corresponding to the spreading code on a symbol being specific to the instant of reception of said symbol, the SF chips being separated by a period ; and to obtain duration symbols Brief description of the figures:

[0022] The invention will be better understood and other features, details and advantages will become clearer from the following description, given by way of non-limiting reason, and from the accompanying figures, given by way of example.

[0023] [Fig. 1] Figure 1 is an illustration of a transmitting device in an embodiment implemented by the invention;

[0024] [Fig. 2] Figure 2 is a diagram representing the steps of the emission process according to one embodiment of the present invention;

[0025] [Fig. 3] Figure 3 is a diagram of a receiving device according to an embodiment of the present invention;

[0026] [Fig. 4] Figure 4 is a diagram representing the steps of the process according to another embodiment of the invention.

[0027] Identical references may be used in different figures when they refer to identical or comparable elements. Detailed description:

[0028] A wireless telecommunications system implementing the invention, in one embodiment, comprises a wireless telecommunications transmitting device 10, hereinafter referred to as transmitter 10, and a wireless telecommunications receiving device 20, hereinafter referred to as receiver 20.

[0029] The wireless telecommunications transmitting device 10 according to the invention is adapted to determine, as a function of a source signal supplied to it as input, symbols modulated by a digital modulation in a known way, then to apply to said symbols a direct sequence spread spectrum, called DSSS (for Direct Sequence Spread Spectrum), and finally to apply a Faster-than-Nyquist type processing, called FTN, in transmission.

[0030] The wireless telecommunications receiver 20 is adapted to receive a communication signal transmitted by the transmitter 10, and then to apply to the received signal Faster-than-Nyquist (FTN) spread processing, followed by despadding processing. The characteristics of the FTN processing at the receiver correspond to the characteristics of the FTN processing performed in the transmitter 10. The characteristics used for the despadding performed by the receiver 20 are similar to the characteristics of the spreading performed by the transmitter 10.

[0031] In one embodiment of the invention, the transmitter 10 comprises, with reference to Figure 1, a coding block 11, an interlacing block 12, a modulation block 13, a DSSS spreading block 14, a compression block 15, a filtering block 16 and a radio frequency (RF) transmitting antenna 17.

[0032] The function of the blocks is indicated below and is further completed later, with reference to figure 2.

[0033] The three blocks 11, 12, 13 thus perform channel coding and source coding, by methods known to those skilled in the art.

[0034] The coding block 11 is suitable for receiving a source signal consisting of a series of bits and is suitable for performing channel coding.

[0035] The interleaving block 12 is adapted to receive the bits from the channel coding block 11, to interleave the received bits together in order to introduce temporal diversity, in order to protect the signal from the phenomenon known as fading.

[0036] The modulation block 13 is adapted to apply digital modulation to the bit sequences output from the interleaver block 12, i.e., to assign each bit sequence a state (or symbol), corresponding to the bit sequence, from among the M possible states in the constellation associated with the chosen modulation. The digital modulation is, for example, of the ASK, mQAM, mPSK, mAPSK type.

[0037] The DSSS 14 spreading block is adapted to implement a direct sequence spreading (DSSS) technique, which is a well-known spreading technique: the input signal to the DSSS 14 block is combined with arbitrary modulation spreading codes, which may differ in the real and imaginary parts of the symbol and have a higher rate than the useful symbols, thus dividing the signal data according to a spreading ratio: cf. R. Pickholtz, D. Schilling and L. Milstein, "Theory of Spread-Spectrum Communications - A Tutorial," IEEE Transactions on Communications, vol. 30, no. 5, pp. 855-884, May 1982. c is the period separating the chips from the spreading code.

[0038] The compression block 15 and the filtering block 16 are adapted to implement the FTN technique in transmission. This FTN technique is described in detail, notably in J. Mazo, "Faster-Than-Nyquist signaling," Bell System Tech Journal, vol. 54, no. 8, pp. 1451–1462, October 1975. According to an embodiment of the present invention, the Faster-Than-Nyquist (FTN) technique is implemented with a shaping filter, for example, of the root-raised cosine (RRC) type. In a Another embodiment of the invention is the use of the FTN technique coupled with any other frequency-bounded (B-band) shaping filter.

[0039] Compression block 15 is adapted to modify the period separating spread symbols according to a fixed compression ratio Exiting the block compression 15, the spread symbols are therefore each made up of SF pulses (chips) separated this time by a period

[0040] According to one embodiment of the present invention, the filter block 16 is considered as a Nyquist root filter with orthogonality time T c : it applies, to the received input signal, a filter adapted to the filter v e (t) such that either a Nyquist filter for the period T c that is to say, such that all the If the formatting filter is in RRC, v e (t) is associated with a roll-off parameter β, between 0 and 1, a compromise between spectral efficiency and the temporal support of the filter (the lower the roll-off, the smaller the band, the better the spectral efficiency but the more the temporal support of the filter increases, which complicates reception).

[0041] For more details on the FTN link, see the publication by J. Fan, S. Guo, X. Zhou, Y. Ren, GY Li and X. Chen, "Faster-Than-Nyquist Signaling: An Overview," in IEEE Access, vol. 5, pp. 1925-1940, 2017, doi: 10.1109 / ACCESS.2017.2657599. This filter limits the signal band to B (where B is the band of the shaping filter) and is defined so that, when i, = 1, transmitter 10 corresponds to a conventional DSSS transmitter.

[0042] Faster-Than-Nyquist (FTN) transmission involves transmitting information faster than the limit imposed by the orthogonality time (T c) of the shaping filter 16. Exceeding this limit has the advantage of increasing the data rate while maintaining the same B band (there is an increase in spectral efficiency), but the disadvantage of introducing intrinsic inter-symbol interference (IESI). In the specific case of an FTN-DSSS link according to the invention, the transmission time of the chips is compressed. This means that intrinsic inter-chip interference will be introduced, associated not only with the current symbol, but also potentially with the preceding and following symbols.

[0043] Even if the formatting filter does not correspond to a Nyquist root filter (the autocorrelation of the Nyquist root formatting filter which must cancel each other out (k # 0) to respect the so-called Nyquist criterion), it is possible to define TJ = 1 / B from the finite useful bandwidth B of the filter (for example, with an upper limit at the -3dB point, or the cutoff frequency...). By setting T c = TJ, the results of the invention as described below can be extended to any useful band-shaping filter B: cf. L. Mounsif and D. Roque, "Optimal Pilot Sequences for Timing Estimation in Faster-Than-Nyquist Systems," in IEEE Communications Letters, vol. 25, no. 4, pp. 1236-1240, April 2021, doi: 10.1 109 / LCOMM.2020.304551.

[0044] Figure 2 illustrates the steps of a method 100 for emitting a wireless communication signal in one embodiment of the invention.

[0045] Blocks 11 to 16 of transmitter 10 are adapted to implement those steps, described below with reference to Figure 2, which are their responsibility. In one embodiment, these blocks (or at least one of them) include a microprocessor and memory storing software instructions, which, when executed on the block's microprocessor, implement the steps of process 100 that are the responsibility of said block.

[0046] In step 101, the coding block 11 receives the digital signal s n to transmit and implements first on this signal s n an error detection or correction coding of any kind, with efficiency R (turbocodes, convolutional code ...), in order to protect the signal from noise during its transmission.

[0047] In a step 102, the 12π interleaver interleaves the received bits and provides identically distributed resulting useful bits.

[0048] In step 103, modulation block 13 delivers symbols a n depending on the constellation states corresponding to bit sequences provided by the interleaver 12. The symbols a n delivered by modulation block 13 each have the same duration equal to T.

[0049] In a subsequent step 104, each symbol has nis spread by the spreading block 14: the spreading block 14 modulates each of the symbols supplied to it as input by a set of SF chips called a spreading code. This spreading code can be identical for each symbol (short codes) or different from one symbol to another (long codes). The length of a short code is therefore the symbol duration, while that of a long code can be several centuries. Spreading consists of multiplying the symbols (separated by a period T) that we wish to spread by spreading codes (pseudo-random sequences) made up of SF chips separated by a smaller period (with SF being the factor). (spreading). The length L DSSS and the period T DSSS = L DSSS . T c The code varies depending on the application: the value of T DSSS can range from the duration of a symbol (T DSSS =T: short-term codes) to several centuries (long-term codes). The longer the T DSSSThe larger and more arbitrary the DSSS code, the more difficult it is to recover the spreading code and despread the signal, and the more discrete the transmission. The spreading code can be real or complex (of any modulation) and may be identical or different for the real and imaginary parts of the symbols.

[0050] The spreading factor (SF) is the ratio between the transmission frequency of the chips (1 / T C ) and symbols (1 / 7').

[0051] The spreading code associated with the symbol a n is a long code: the The spreading code changes every time the symbols change, i.e., it is different for each symbol. n and is therefore also a function of n. These SF chips spreading a symbol are specific to the constitution of said spreading code, its initial synchronization and the instant of emission of the symbol.

[0052] For example SF = 3 and the same spreading code (long: different symbol all times) is used on the real and imaginary part of the symbol.

[0053] With S being the Dirac delta function, the DSSS symbol that we wish to transmit (at time nT = nSFT) c ) East :

[0054]

[0055] The associated spreading code is:

[0056]

[0057] The spread symbol is therefore:

[0058]

[0059] Depending on the spreading code used, different needs can be met:

[0060] If you want a connection with high energy discretion, you must: Use an independent and identically distributed (iid) long code on each symbol with a large spreading factor (SF); or Use a shortcode with the addition of a scrambler for each symbol (transforms the shortcode into a longcode) with a large SF spreading factor.

[0061] If we want a connection with improved spectral efficiency and performance, we should: - Choose a spreading code or subset of a spreading code that minimizes interference introduced by the transmitting FTN; and / or - Choose the constellation used by the spreading code to limit intrinsic reception errors (pathological cases) and those introduced by the FTN

[0062] Using a short code, phase modulation, or a sufficiently large spreading factor can reduce the complexity of reception.

[0063] In another embodiment, the long spreading code is obtained by scrambling a short code, thus making it specific to the symbol to which it will be multiplied.

[0064] In step 105, the compression block 15 then compresses, according to the compression ratio, the period T c separating the chips from the spread symbols 1). On exit From compression block 15, the spread symbols are therefore made up of SF pulses linked to the spreading code separated by a period. In one embodiment, is chosen strictly less than 1.

[0065] Thus, using the example above, the FTN-DSSS signal at the output of compression block 15 is:

[0066]

[0067] Note: the factor allows us to obtain an average emission power constant regardless of the value of

[0068] In step 106, these spread symbols consisting of SF pulses separated by a period ejc are then filtered by the shaping filter, which can be a Nyquist root of orthogonality time T c or any finite useful band B = 1 / T C .

[0069] In step 107, the resulting signal s e (t) FTN-DSSS constant power transmission is then emitted via RF antenna 17.

[0070] In general:

[0071] with : - : the compression ratio, between 0 and 1; - : the chips from the displayed symbols; - T c : the time separating the chips; SF: the spreading factor; - v e (t): the impulse response of the shaping filter.

[0072] We can consider a spreading code (i.e., a bi-code) with arbitrary and different modulation on the real and imaginary parts of the symbol. In this case, the expression of the c nSF+q is given by:

[0073] with: a n : the transmitted symbol ui,nsF+q : I e coc the spreading on the real part, S e (has n ), of the symbol u2,nsF+q : I e c ° of spreading over the imaginary part, / m(a n ), of the symbol In such a case, of course, there are symbols with a non-zero real part and symbols with a non-zero imaginary part.

[0074] Equivalently, the above equation can be rewritten as:

[0075] with :

[0076] : the spreading code associated with the symbol a n

[0077] : The spreading code associated with the conjugate symbol

[0078] If we consider the special case where the spreading code on the real part is identical to the code on the imaginary part, then we have and the equation giving e (t) becomes:

[0079] with : - : the compression ratio - has n : the symbols obtained after modulation: I e spreading code associated with the symbol a n - T c : the uncompressed chip period SF: the spreading factor - v e (t): the formatting filter.

[0080] Specifically, continuing with the example outlined above:

[0081]

[0082] From the equation giving s e(t), we note that the proposed FTN-DSSS signal does indeed depend on eight main transmission parameters: - : the compression ratio SF: the spreading factor - B: the occupied band, the formatting filter, the constellation symbol - the error-correcting code used, the interleaver used - : The two spreading codes

[0083] In one embodiment of the invention, with reference to Figure 3, the wireless telecommunications receiver 20 comprises an RF receiving antenna 21, a filtering block 24 for receiving shaping, a channel synchronization and estimation module 50 and a demodulation and decoding module 51.

[0084] The channel synchronization and estimation module 50 includes a frame synchronization block 40, a fine synchronization block 41, and a channel estimation block 42. The demodulation and decoding module 51 includes a filtering block adapted to the estimated channel 25, a sampler block 26, a despreading block 27, an equalization block 2 (optional), a decision block 29, a demodulation block 30, a deinterlacing block 31, and a decoding block 32.

[0085] These receiver blocks 20 are adapted to implement the steps, described below with reference to Figure 4, which are their responsibility.

[0086] In one embodiment, the receiver blocks 20 (or at least one of them) include a microprocessor and a memory storing software instructions, which, when executed on the block's microprocessor, implement the steps of process 100 that are the responsibility of said block.

[0087] With reference to Figure 4, the steps of a method for receiving a wireless communication signal implemented in an embodiment using receiver 20 are described.

[0088] One difference between an FTN-DSSS reception according to the invention and a (Nyquist-)DSSS reception stems from the sampling, which is performed every both in the channel synchronization and estimation part and in the demodulation and decoding part, as described below.

[0089] In step 201, the filter adapted to the formatting filter v e (t) is applied by the filter block 24 to the signal x(t) supplied via the antenna 21. More precisely, corresponds to the conjugate of v e (t) returned temporally.

[0090] In step 202, the frame synchronization block 40 performs frame synchronization of the signal delivered by the shaping filter 24 (synchronization can, for example, be done via a dedicated channel or by using a preamble before data transmission or directly on a specific pilot spreading code): the frequency shift and the delays are thus estimated by the synchronization block Frame 40 and delivered by the frame 40 synchronization block to the fine synchronization block 41 and the channel estimation block 42. The signal filtered with the filter adapted to the shaping filter is, for example, frequency-shifted in parallel for different frequency shifts. Subsequently, the received signal is sampled on each parallel branch at times (where a is the oversampling factor). Thus, on each branch, we obtain a succession of samples which we will correlate with the preamble (known spread symbols present in a frame), then we select the signal with the highest A large envelope is used before comparing the correlation of the sectioned signal to a threshold. If the latter exceeds the set threshold, a path is detected. The estimated delay and frequency shift that caused the threshold to be exceeded are then retrieved.

[0091] In a step 203, the channel estimation block 42 estimates the transmission channel parameters representing the artifacts brought by the channel (e.g., from pilot sequences appearing in the signal frame).

[0092] In step 204, the fine synchronization block 41, based on the received frequency offsets and delays, performs the fine synchronization to improve the estimation of delays

[0093] These two steps 203 and 204 are for example carried out simultaneously as is classically the case in DSSS receiving processes.

[0094] Then in a step 205, the filtering block adapted to the estimated channel 25 applies to the signal delivered by the filtering block 24 the filter h * (-t) adapted to the propagation channel determined, where appropriate, according to the estimates of the transmission channel parameters made in step 203.

[0095] In a subsequent step 206, the sampler block 26 applies period sampling to the coefficients delivered by the filtering block adapted to the estimated channel 25. Indeed, as at transmission T was compressed c from a factor to find what one has transmitted to the receiver, it is necessary to sample all (the compression rate to (sending and receiving are identical).

[0096] Next, in step 207, the signal samples as delivered by the sampler block 26 are despreaded by the despreading block 27, which thus determines symbol sequences of duration by cross-correlation of the received signal with the respective sequences of SF chips separated by a period function of the code of spreading and the symbol. In an example where SF = 3, at the output of step 205, we obtain the signal z(t), then we sample every 26. We therefore obtain the signal sampled:

[0097]

[0098] The despadding step from the samples {z nSF+0 ,z nSF+1 , z nSF+2 This is done by multiplying these by the conjugate spreading codes (used in transmission and associated with the symbol n) and summing them (for a single code):

[0099]

[0100] Unlike a (Nyquist-)DSSS bond, the sample z nSF+q no longer depends solely on the current chip (a n u nSF+q ) but also the preceding and following chips and symbols: In the case of a classic single-code DSSS connection, we would have in the "perfect" case (perfect channel + no noise)

[0101]

[0102] Whereas in the FTN-DSSS case we have:

[0103]

[0104] with interference from the spreading code associated with the current symbol and the interference of spreading codes associated with the following and preceding symbols.

[0105] In the case of a SISO connection with a flat channel And assuming perfect synchronization and the same code for the real and imaginary parts, we obtain the following signal after despadding:

[0106] with: a n : the contribution of the spreading code associated with the current symbol i n : the interference associated with the preceding and following symbols (if the SF is greater than or equal to the inverse of the compression ratio - 1). b n : the noise received. : the amplitude of the channel

[0107] We therefore obtain symbols with varying degrees of interference. The optimal reception, according to the MLSE (Maximum Likelihood Sequence Estimation) criterion, is given using on the received symbols, a decision box implementing the Viterbi algorithm with a non-classical branch metric.

[0108] From the optimal scheme, we can deduce suboptimal receiver configurations by optionally adding an equalizer (Minimum Mean Square Error (MMSE), Expected Propagation (EP) ...), performed by the equalization block 28.

[0109] Then, in step 208, decision block 29 decides, based on the symbol sequences from step 207, which symbols of the constellation have been received (Viterbi or symbol-by-symbol decision).

[0110] Then, during step 209, the reverse operations of those performed during transmission are carried out, including: symbol demodulation, deinterlacing, and finally channel decoding: - thus, the demodulation of the symbol is carried out by the demodulation block 30, which provides for each symbol the bits corresponding to the symbol in accordance with the type of modulation chosen; - the deinterlacing block 31 performs the reverse processing of the interlacing performed in step 102. - and finally, channel decoding is performed by decoding block 32, to identify any errors, correct them, and ultimately deliver a bit estimate transmitted.

[0111] The receiver 20 described above with reference to figure 2 implements switching demodulation, but of course the application of the invention is not limited to this type of receiver.

[0112] The invention thus proposes the combined use of DSSS and FTN techniques (with an RRC shaping filter or other), in order to ensure a certain degree of energy discretion and robustness to interference for sufficient SF, while limiting the loss in spectral efficiency compared to a conventional DSSS link, and while seeking to achieve good reception performance at reasonable complexity. The combination of the two techniques, DSSS and FTN, makes it possible to both take advantage of their complementary strengths and reduce their drawbacks.

[0113] Indeed, in terms of spectral efficiency: - FTN increases spectral efficiency (especially when the compression ratio is low), - while the DSSS reduces it (all the more so as the spreading factor is large); and at the level of inter-symbol interference: - FTN adds intrinsic IES (especially when the compression ratio is low), - while the DSSS reduces the IES (especially as the SF spreading factor is large). Thus, with this combination of the spreading factor and the compression ratio, compression limits the spectral efficiency loss induced by spreading, and the reduced spreading reduces the intrinsic ES generated by compression, potentially enabling very good performance from receivers with reduced complexity. The behavior and performance of the FTN-DSSS coupling depend on the combination of values ​​assigned to eight parameters, defining at least partially the configuration of the communication system: - the spreading factor; - the compression ratio; - gang occupation; - the link balance in reception. - the formatting filter - the symbolic constellation - the error-correcting code used - the interlacing machine used.

[0114] This combination makes it possible to generate a configurable FTN-DSSS waveform, which, depending on the configurations: greatly improves spectral efficiency; - induces energy discretion - limits the complexity of the receptor; - or even in some cases, improves performance (at constant spectral efficiency).

[0115] Depending on the eight parameters defined above, it is possible, for example, to: implement a CDMA network implementing the invention, resulting in increased system spectral efficiency compared to a conventional CDMA network; or - to design an energy-efficient discrete IoT system

[0116] The optimal combinations of values ​​for these parameters are determined, for example, by system simulation; they will depend on the application in which The invention is implemented and the signal band. In general, the waveform according to the invention makes it possible to increase the spectral efficiency of the transmission. The choice of values ​​for the various parameters indicated and the spreading code used makes it possible either to improve performance at constant spectral efficiency or to improve energy discretion.

[0117] Wireless telecommunications according to the invention can be implemented more generally in all applications, civil or military, where the notion of energy discretion is desired, for example civil applications relating to loT or 5G-6G networks, but also applications relating to CDMA networks with increased spectral efficiency.

[0118] The invention can be implemented in the context of: simplex links (in one direction only) with the FOP (Parameterizable Waveform) associated with specific parameters and various synchronization / delay estimation processes (MMSE, etc.), particularly in radionavigation applications; simplex links with the FOP associated with specific parameters and various reception, demodulation, and decoding processes (RAKE, EP, MLSE, etc.), particularly in broadcasting applications; duplex links (transmits and receives) with the FOP associated with specific parameters and various demodulation and decoding processes (RAKE, EP, MLSE, etc.), particularly in single-user radiocommunication link applications; multiple duplex links (several users transmit and receive) with multiple FOPs associated with specific parameters and demodulation and decoding processes (RAKE, EP, MLSE, Join Detection, etc.).) particularly in Multi-User Radio Communications Network applications - CDMA Networks.

[0119] The invention can be implemented in a SIMO receiver in which the channel h(t) and its matched filter h*(-t) are replaced by the vectors with N being the number of receiving antennas.

Claims

DEMANDS 1. A method for transmitting wireless communication, said method being implemented in a wireless telecommunications transmitting device (10) receiving as input a signal to be transmitted, said method comprising the following steps implemented by the transmitting device: application of channel coding, including error-correcting coding and / or interleaving, to the signal to be transmitted, followed by digital modulation of said coded signal to obtain symbols; said method being characterized in that it further comprises the following steps implemented by the transmitting device: DSSS-type spreading of each symbol obtained by a TDSSS period-spreading code applied with a spreading factor SF, the SF chips spreading a symbol being specific to the instant of the symbol's transmission; and obtaining, from each symbol, a set of spread SF chips as a function of the symbol's value, these chips being separated by a period Te;implementation on the chips obtained after spreading a treatment including: compression of the period between the chips by a compression ratio; strictly less than 1, the period between the chips after said compression being equal to; filtering by a formatting filter v e (t): Nyquist root with period of orthogonality T c ; or of a useful strip of finite length B = 1 / T C .

2. A method for transmitting wireless communication, according to claim 1, wherein the signal s e (t) at the end of the filtering is defined by the following equation: with : - : the compression ratio, between 0 and 1; - : the chips made from the displayed symbols; o in the case of a single-code spread: O in the case of a two-code spread: - T c : the time separating the uncompressed chips; - SF: the spreading factor; - v e (t): the impulse response of the shaping filter. - a n ; the symbol to be transmitted (output of the channel coding and digital modulation) with R e (has n ) the real part of the symbol and the imaginary part of the symbol; - or and: the single-code or double-code spreading used.

3. A method for receiving wireless communication implemented in a wireless telecommunications receiving device (20) comprising at least one receiving antenna receiving a transmitted signal as input, said method comprising the following steps implemented by the receiving device on a signal obtained via the receiving antenna: application of digital demodulation and channel decoding to the signal; said method being characterized in that it further comprises the following steps implemented by the receiving device: implementation of signal processing comprising filtering by a filter and to the channel such that the filter is adapted to a shaping filter v e (t) in Nyquist root of orthogonality period T c or of a useful strip of finite length B = 1 / T C ; period sampling of the signal from the filter adapted to the overall channel where is strictly less than 1; despreading of the sampled signal according to the spreading code taken over a length equal to the spreading factor SF, the series of SF chips corresponding to the spreading code on a symbol being specific to the instant of reception of said symbol, the SF chips being separated by a period; and obtaining symbols of duration 4. A method for receiving wireless communication according to the preceding claim in a SIMO receiver wherein the channel h(t) and its matching filter are replaced by the vectors and with N the number of antennas in reception.

5. A method for receiving a wireless communication according to claim 3 or 4, comprising, after despacing, at least one of the following steps: - an equalization of the spread symbols implemented by an equalizer block (28) of the receiving device; - a selection of an element from a constellation of elements, based on the unspread symbols, by the implementation of a Viterbi algorithm by a decision block of said receiving device.

6. Computer program, intended to be stored in the memory of a wireless telecommunications transmitting device (10) further comprising a microcomputer, said computer program comprising instructions which, when executed on the microcomputer, implement the steps of a method according to any one of claims 1-2.

7. Computer program, intended to be stored in the memory of a wireless telecommunications receiving device (20) further comprising a microcomputer, said computer program comprising instructions which, when executed on the microcomputer, implement the steps of a method according to any one of claims 3-5.

8. A wireless communication transmitting device (10), adapted to receive as input a signal to be transmitted, the transmitting device being adapted to apply channel coding, including error-correcting coding and / or interleaving, to the signal to be transmitted, and then digitally modulate said coded signal to obtain symbols; said transmitting device characterized in that it is adapted to perform DSSS-type spreading of each symbol obtained by a spreading code of period T DSSS applied with a spreading factor SF, the SF chips spreading a symbol being specific to the instant of the symbol's emission, and to obtain, from each symbol, a set of spread SF chips as a function of the symbol's value, these chips being separated by a period Tc; said emission device being adapted to implement on the chips obtained after spreading, a treatment comprising: - the compression of the period between the chips by a compression ratio strictly less than 1, the period between the chips after said compression being equal to ; - filtering by a formatting filter v e (t): - in Nyquist root of period of orthogonality T c ; Or - of a useful strip of finite length B = 1 / T C .

9. Wireless communication transmission device (10) according to claim 8, wherein the signal s e(t) obtained after filtering is defined by the following equation: with : - : the compression ratio, between 0 and 1; - : the chips made from the displayed symbols; O in the case of a single-code spread: O in the case of a two-code spread: - T c : the time separating the uncompressed chips; - SF: the spreading factor; - v e (t): the impulse response of the shaping filter. - a n ; the symbol to be transmitted (output of the channel coding and digital modulation) with R e (has n ) the real part of the symbol and the imaginary part of the symbol; - or and: the single-code or two-code spreading used.

10. Wireless communication receiving device (20), adapted to receive a transmitted signal as input via a receiving antenna, said receiving device being adapted to apply digital demodulation and channel decoding to the signal obtained via the receiving antenna; said device being characterized in that it is adapted to implement signal processing comprising filtering by a filter and to the channel such as the filter is suitable for a formatting filter v e (t) in Nyquist root of period of orthogonality T c or of a useful strip of finite length B = 1 / T C said device is adapted to perform period sampling of the signal from the filter adapted to the overall channel where is strictly less than 1; said device is adapted to perform a despreading of the sampled signal according to the spreading code taken over a length equal to the spreading factor SF, the series of SF chips corresponding to the spreading code on a symbol being specific to the instant of reception of said symbol, the SF chips being separated by a period; and to obtain duration symbols

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