EP0629059B1 - Spread spectrum digital transmission system with low frequency pseudorandom coding of the useful information and method for spectrum spreading and compressing used in such a system - Google Patents
Spread spectrum digital transmission system with low frequency pseudorandom coding of the useful information and method for spectrum spreading and compressing used in such a system Download PDFInfo
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- EP0629059B1 EP0629059B1 EP94401282A EP94401282A EP0629059B1 EP 0629059 B1 EP0629059 B1 EP 0629059B1 EP 94401282 A EP94401282 A EP 94401282A EP 94401282 A EP94401282 A EP 94401282A EP 0629059 B1 EP0629059 B1 EP 0629059B1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
- H04K1/00—Secret communication
- H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible
Definitions
- the field of the invention is that of modem transmission of digital signals and in particular that of spread spectrum modems. More specifically, the The present invention relates to a transmission system with spread of spectrum between a transmitter and a receiver digital signals where spread spectrum is obtained by pseudo-random coding of information useful to transmit.
- the invention is particularly applicable in wireless telecommunications in the military field.
- ECCM Electronic Counter-CounterMeasures
- code or sequence spreading the signal useful to transmit by a code, called code or sequence spreading, from a pseudo-random generator whose clock signal frequency is much higher than the maximum frequency of the wanted signal. Number of bits of useful information transmitted by Hz is therefore very low.
- Figure 1 shows a timing diagram for understand the principle of spectrum spreading by a spreading sequence.
- a useful SAT signal to be transmitted here coded in two +1 and -1 levels following NRZ coding, is multiplied by a SE cyclic spreading sequence, also coded on two levels.
- the signal resulting from the multiplication is the ST signal transmitted from the transmitter to a receiver after modulation.
- the modulated ST signal transmission medium generally consists of a radio link.
- signal multiplication received ST with the same spreading sequence SE (same phase and same frequency) makes it possible to reconstitute the useful signal SAT.
- Sequence spread spectrum transmission direct is usually used to give the signal transmitted better discretion, resistance to ECM (Electronic CounterMeasures) interference and a resistance to selective fading.
- ECM Electronic CounterMeasures
- the ratio between the chip time and bit time, the chip time corresponding to the duration of a bit of the spreading sequence and the time bit to that of the wanted signal is greater than this spreading gain higher, the more the transmitted signal is able to be transmitted discreetly and therefore resist ECM devices intended to detect it and, possibly, to jam it.
- An essential step in ECM analysis is to determine the spreading hazard of the signal received because this step allows you to penetrate the information content of the signal received, ie to reconstitute the useful signal.
- sequence generator direct must operate at the transmission frequency of chips, or at a frequency of the order of several MHz. he it is therefore necessary to install this generator in an ASIC, which increases the hardware complexity and the cost of hardware development.
- the present invention aims in particular to overcome this drawback.
- one of the objectives of the invention is to provide a signal transmission system digital, where spread spectrum is implemented, this system that does not require a hazard generator operating at the chip frequency. It is therefore more simple to make and less expensive, while allowing large spread of the useful signal spectrum intended for resist ECM devices.
- Another object of the invention is to provide a such a system where spectrum spreading is carried out from orthogonal sequences, for example using M-type sequences (also known as maximum length or Hadamard), well known in the art field of digital signal transmission.
- M-type sequences also known as maximum length or Hadamard
- An additional objective is to provide a process transmission of spread digital signals spectrum where the spreading is carried out at the bit frequency and not at the chip frequency.
- the M sequences of q integers are preferably made up of Hadamard sequences.
- the digital signal to be transmitted SN is applied, here via a serial access, to coding means 21 which supply, for each block of k bits of the signal SN, a coded sample E c taking an integer value included in the set ⁇ 0, ..., N-1 ⁇ , each integer value being representative of the k bits of the corresponding block.
- the coding means 21 can for example be constituted by a simple binary-decimal converter and the bit rate leaving the coding means is then k times lower than the bit rate entering.
- the coding means 21 can optionally also interleave the bits of the SN signal.
- the coded samples E c are applied to means 22 for combining these samples with samples E a originating from a pseudo-random generator 23, which will subsequently be called phase random generator.
- the combination means 22 comprise a transformation algorithm which transforms each coded sample E c into an integer s included in the set ⁇ 0, ..., M-1 ⁇ , with M integer greater than N.
- s f (E vs , E at ) where f is any function taking its values in ⁇ 0, ..., M-1 ⁇ and E has a sample of phase randomness.
- This modulo M addition apart from the fact that it can be implemented by a very simple algorithm to implant, provides optimal resistance performance at ECM interference.
- Each integer is then supplied to means 24 of generation of signals providing, for each integer s, a corresponding SQ sequence of q samples, each sample q being an integer.
- 24 generation means of signals transform each integer s into a SQ sequence, this transformation being bi-unequivocal, that is to say that a given integer s corresponds to a single sequence SQ and reciprocally.
- the signal generator can for example be consisting of a transcoding table.
- a transcoding table We will refer usefully to French patent n ° 2,337,465 in the name of COMPAGNIE IBM FRANCE TM which describes sequences called CAZAC which are periodic pseudo-random sequences of complex numbers that have an autocorrelation function periodic whose only the first coefficient is not zero and of which all complex numbers have an amplitude constant.
- CAZAC periodic pseudo-random sequences of complex numbers that have an autocorrelation function periodic whose only the first coefficient is not zero and of which all complex numbers have an amplitude constant.
- the generation of such sequences can be generalized to obtain sequences made up of whole numbers, these sequences being orthogonal between them, that is to say having properties optimal autocorrelation.
- Gold sequences which are quasi-orthogonal, like those of Kasami, or those called polyphases.
- the means 24 generate sequences SQ which are substantially orthogonal to one another.
- the signal generation means 24 can transform each integer s into a sequence SQ of q bits (samples each taking a value in ⁇ 0,1 ⁇ ) according to table 1 below.
- Input value s SQ Suite generated 0 0000000 1 1110100 2 0111010 3 0011101 4 1001110 5 0100111 6 1010011 7 1101001
- Each suite of q bits is produced by circular shifts of a sequence of maximum length of length 7, excluding the first suite always consisting of zeros.
- These suites have quasi-orthogonality properties, say that for two different and arbitrary sequences, the sum of the EXCLUSIVE OUs of each term is equal to 4.
- each block of k bits of signal SN has been transformed into a sequence Corresponding SQ, each SQ suite comprising a pseudo-random component.
- Useful information is coded in this SQ suite and the different suites are orthogonal or quasi-orthogonal to each other. Since then that M and q are large before k or before N, we understand that this coding operation consisted in increasing by importantly the number of samples to be transmitted and that we have therefore spread the signal spectrum useful SN using hazards provided at low frequency.
- the main advantage of the invention lies precisely in this coding which is carried out at the bit frequency and not not at the chip frequency (where the spectrum spread is performed by direct sequence).
- the working frequency of means described so far can be very weak, around 16 Kbits, compare with 10 Mchips in the case spread spectrum by direct sequence.
- samples may take larger values, depending on the modulation used in transmission means 25 to which SQ suites are provided.
- These transmission means 25 supply a signal STR transmitted to the attention of the receiver. They can be from any type, analog or digital.
- the means 25 are digital and have a phase shift modulator 28.
- This modulator 28 is by example of type MPSK (Multiple Phase Shift Keying) where M corresponds here to the number of possible values of samples q of the sequences SQ and therefore the number of states of phase of the modulated signal STR. It is for example possible to perform a BPSK modulation if the SQ suites are exclusively made up of bits, QPSK modulation if the integers of the SQ suites are each included in the set ⁇ 0, 1, 2, 3 ⁇ , and a 64-PSK modulation if the whole SQ suites are each included in the set ⁇ 0, 1, ..., 63 ⁇ .
- the phase shift modulator 28 can also be of the QAM type. It provides a modulated signal noted SM.
- the transmission means 25 may also include means 26 for spreading spectrum by spreading sequence.
- the spreading sequence SE is generated by a spreading sequence generator 27.
- the bits of the sequences SQ take their values in ⁇ 0,1 ⁇ and that the chips of the sequence d spreading SE also take their values in ⁇ 0,1 ⁇ .
- Each sample bs / i produced by the signal generation means 24 is added modulo L to G hazards e s belonging to the set ⁇ 0, 1, ..., L-1 ⁇ and coming from the generator 27, where G represents the spread gain by direct sequence.
- G represents the spread gain by direct sequence.
- the increase in bit rate caused by this processing is equal to G.
- SQE the output signal of the means 26, denoted SQE, which is applied to the modulator 28.
- Each sample a i of an SQE sequence takes its value in ⁇ 0, 1, ..., L-1 ⁇ .
- mapping function g of the modulator must respect the relationship: when a spread by direct sequence is implemented (G> 1).
- the impulse response h e of the emission filter is assumed such that:
- the means 26 of spectrum spreading by sequence direct are of course optional in the invention and are therefore shown in broken lines.
- the transmission means 25 can also include frequency escape means 29, 30, also optional and therefore shown in broken lines, suitable to modify the carrier frequency of the signal transmitted to the receiver.
- the frequency escape is to change frequently of carrier frequency in order to further broaden the spectrum of the signal transmitted to the receiver.
- the modulated signal SM in baseband or in intermediate frequency, is applied to a multiplier 29 receiving a signal from carrier frequency of a generator 30.
- phase 23 generator allows low-frequency coding of the signal to be transmitted and allows to modify in a pseudo-random way the phase of the signal transmitted when the modulation is of MPSK type.
- generator 23 and the means of combination 22 provide a phase escape function performed at low frequency. Amplitude modulation, also pseudo-random, the signal to be transmitted comes combine with this phase escape when the modulation is of the QAM type (modification of the phase and the amplitude of the transmitted signal). This is how the system transmission of the invention provides a high resistance to ECM interference.
- the output signal STR of the transmission means 28 is transmitted over the air to receiver 31 whose diagram synoptic is given in figure 3.
- the receiver 31 receives a corresponding signal STRr to the STR signal noisy by the transmission medium. he includes reception means generally referenced by 40 restoring the sequences SQ of q whole numbers, noted SQr at the receiver.
- Means of reception 40 here include means 32 for removing the carrier frequency controlled by a local oscillator 33.
- the means 32 conventionally comprise two mixers controlled by quadrature clock signals and we obtains at the output of these means two quadrature signals.
- the local oscillator 33 operates in synchronism with that of the transmitter, referenced 30. This synchronization can be obtained by known means.
- the output signal of the means 32 is noted SMr and corresponds to the transmitter SM signal.
- the signal SMr is applied to means 34 of spectrum compression to suppress spreading by direct sequence possibly performed at the transmitter 20.
- Spectrum compression means are notably described in "Digital Communications" by J.G. PROAKIS, McGraw-Hill TM, Chapter 8.
- Those depicted in the Figure 3 include a sampler 35 controlled at the frequency chip Fc followed by a module 36 for compression of spectrum.
- Module 36 includes a complex multiplier 37 followed by a summator 38.
- the multiplier 37 receives a direct sequence SE of a generator 39, this sequence direct SE being identical to that generated by the generator 27 of the transmitter 20.
- the phase timing of these two direct sequences is obtained by known means.
- the summator 38 calculates, for each block of G consecutive samples r k from the multiplier 37, the following sum: where e sk is the value of the chip at time k of the direct sequence SE and * denotes the conjugate complex. This summation eliminates spectral spreading by direct sequence.
- Each sum U k therefore corresponds to a sample ⁇ i of the signal STR transmitted to the receiver.
- modules SQr identical to the suites SQ originating from the means 24 for generating signals from the transmitter 20.
- SQr suites are applied to means 45 for processing that have the function of performing a demodulation of the received signal and removing the random phase E is introduced at the transmitter 20 by the generator 23 hazards.
- the correlation means 41 therefore receive a SR reference signal consisting of the different sequences SQ can be generated at transmitter 20, this is to say those for example represented in tables 1 or 2.
- the advantage of generating orthogonal sequences or quasi-orthogonal using the generator 24 of Figure 2 (and not any sequences) is that it is easy to detect a correlation of these signals.
- the calculated correlations provide sums C 0 to C M-1 which each correspond to one of the integers from the combining means 22 of the transmitter 20. These sums are applied to a demultiplexer 42 receiving from a generator 43 a signal E a identical to that generated by the generator 23 of the transmitter, and in phase with it.
- the demultiplexer 42 selects N sums C S from M as a function of the value of the hazard E a .
- the demultiplexer 42 performs an inverse function f -1 to remove the phase hazard introduced at low frequency on transmission.
- the demultiplexer 42 thus selects the samples C s as a function of the hazard E a .
- Each sample d i therefore corresponds to a sample E c of the emitter.
- These samples d i are then applied to decoding means 44 performing an inverse operation to that of the coding means 21 of the transmitter 20. They can also carry out a deinterlacing of the decoded samples if the coding means perform an interleaving of the samples coded.
- the output signal SNr of the decoding means 44 then corresponds to the digital signal SN of the transmitter.
- the processing means 45 then only comprise correlation means such as 41, receiving the signal E a .
- the present invention applies for example to transmission systems where error correcting codes are used and where an alphabet of orthogonal signals of very large size, larger than the alphabet used by the error correction code is available.
- the elements of the alphabet not used by the code can be used for low-frequency pseudo-random coding of signal to be transmitted, thereby improving low cost the robustness of the system with regard to interception.
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Description
Le domaine de l'invention est celui des modems de transmission de signaux numériques et notamment celui des modems à étalement de spectre. Plus précisément, la présente invention concerne un système de transmission à étalement de spectre entre un émetteur et un récepteur de signaux numériques où l'étalement de spectre est obtenu par codage pseudo-aléatoire de l'information utile à transmettre. L'invention s'applique notamment dans les télécommunications hertziennes dans le domaine militaire.The field of the invention is that of modem transmission of digital signals and in particular that of spread spectrum modems. More specifically, the The present invention relates to a transmission system with spread of spectrum between a transmitter and a receiver digital signals where spread spectrum is obtained by pseudo-random coding of information useful to transmit. The invention is particularly applicable in wireless telecommunications in the military field.
Dans le domaine militaire, une opération d'étalement de spectre est généralement utilisée en ECCM (Electronic Counter-CounterMeasures) et consiste à multiplier le signal utile à transmettre par un code, appelé code ou séquence d'étalement, issu d'un générateur pseudo-aléatoire dont la fréquence du signal d'horloge est beaucoup plus importante que la fréquence maximale du signal utile. Le nombre de bits d'information utile transmis par Hz est donc très faible.In the military field, a spreading operation is generally used in ECCM (Electronic Counter-CounterMeasures) and consists of multiplying the signal useful to transmit by a code, called code or sequence spreading, from a pseudo-random generator whose clock signal frequency is much higher than the maximum frequency of the wanted signal. Number of bits of useful information transmitted by Hz is therefore very low.
La figure 1 représente un chronogramme permettant de comprendre le principe de l'étalement de spectre par une séquence d'étalement.Figure 1 shows a timing diagram for understand the principle of spectrum spreading by a spreading sequence.
Un signal utile SAT à transmettre, ici codé sur deux niveaux +1 et -1 suivant un codage NRZ, est multiplié par une séquence d'étalement cyclique SE, également codée sur deux niveaux. Le signal résultant de la multiplication est le signal ST transmis de l'émetteur vers un récepteur après modulation. Le support de transmission du signal ST modulé est généralement constitué par une liaison hertzienne. A la réception, après démodulation, la multiplication du signal reçu ST avec la même séquence d'étalement SE (même phase et même fréquence) permet de reconstituer le signal utile SAT.A useful SAT signal to be transmitted, here coded in two +1 and -1 levels following NRZ coding, is multiplied by a SE cyclic spreading sequence, also coded on two levels. The signal resulting from the multiplication is the ST signal transmitted from the transmitter to a receiver after modulation. The modulated ST signal transmission medium generally consists of a radio link. To the reception, after demodulation, signal multiplication received ST with the same spreading sequence SE (same phase and same frequency) makes it possible to reconstitute the useful signal SAT.
La transmission à étalement de spectre par séquence directe est habituellement utilisée pour conférer au signal transmis une meilleure discrétion, une résistance aux brouillages ECM (Electronic CounterMeasures) et une résistance aux évanouissements sélectifs (fading).Sequence spread spectrum transmission direct is usually used to give the signal transmitted better discretion, resistance to ECM (Electronic CounterMeasures) interference and a resistance to selective fading.
On définit par gain d'étalement le rapport entre le temps chip et le temps bit, le temps chip correspondant à la durée d'un bit de la séquence d'étalement et le temps bit à celui du signal utile. Plus ce gain d'étalement est élevé, plus le signal transmis est apte à être transmis discrètement et donc à résister aux dispositifs ECM destinés à le détecter et, éventuellement, à le brouiller. Une étape essentielle de l'analyse ECM consiste à déterminer l'aléa d'étalement du signal capté car cette étape permet de pénétrer le contenu informationnel du signal capté, c'est à dire de reconstituer le signal utile.The ratio between the chip time and bit time, the chip time corresponding to the duration of a bit of the spreading sequence and the time bit to that of the wanted signal. The greater this spreading gain higher, the more the transmitted signal is able to be transmitted discreetly and therefore resist ECM devices intended to detect it and, possibly, to jam it. An essential step in ECM analysis is to determine the spreading hazard of the signal received because this step allows you to penetrate the information content of the signal received, ie to reconstitute the useful signal.
Le principal inconvénient de l'étalement de spectre par séquence directe est que le générateur de la séquence directe doit fonctionner à la fréquence d'émission de chips, soit à une fréquence de l'ordre de plusieurs MHz. Il est donc nécessaire d'implanter ce générateur dans un ASIC, ce qui augmente la complexité hardware et le coût du développement du matériel.The main disadvantage of spread spectrum by direct sequence is that the sequence generator direct must operate at the transmission frequency of chips, or at a frequency of the order of several MHz. he it is therefore necessary to install this generator in an ASIC, which increases the hardware complexity and the cost of hardware development.
La présente invention a notamment pour objectif de pallier cet inconvénient.The present invention aims in particular to overcome this drawback.
Plus précisément, un des objectifs de l'invention est de fournir un système de transmission d'un signal numérique, où un étalement de spectre est mis en oeuvre, ce système ne nécessitant pas de générateur d'aléa fonctionnant à la fréquence chip. Il est dès lors plus simple à réaliser et moins coûteux, tout en permettant un important étalement du spectre du signal utile destiné à résister aux dispositifs ECM.More specifically, one of the objectives of the invention is to provide a signal transmission system digital, where spread spectrum is implemented, this system that does not require a hazard generator operating at the chip frequency. It is therefore more simple to make and less expensive, while allowing large spread of the useful signal spectrum intended for resist ECM devices.
Un autre objectif de l'invention est de fournir un tel système où l'étalement de spectre est réalisé à partir de séquences orthogonales, par exemple à l'aide de séquences de type M-séquences (aussi appelées séquences de longueur maximale ou de Hadamard), bien connues dans le domaine de la transmission de signaux numériques. Another object of the invention is to provide a such a system where spectrum spreading is carried out from orthogonal sequences, for example using M-type sequences (also known as maximum length or Hadamard), well known in the art field of digital signal transmission.
Un objectif complémentaire est de fournir un procédé de transmission de signaux numériques à étalement de spectre où l'étalement est réalisé à la fréquence bit et non pas à la fréquence chip.An additional objective is to provide a process transmission of spread digital signals spectrum where the spreading is carried out at the bit frequency and not at the chip frequency.
Ces objectifs, ainsi que d'autres qui apparaítront par la suite, sont atteints grâce à un système de transmission d'un signal numérique entre un émetteur et un récepteur, caractérisé en ce que :
- l'émetteur comporte successivement :
- des moyens de codage recevant ce signal numérique et fournissant, pour chaque bloc de k bits du signal numérique, un échantillon codé prenant une valeur entière comprise dans l'intervalle [0, N-1], chaque valeur entière étant représentative des k bits du bloc dont elle est issue ;
- des moyens de combinaison des échantillons codés avec des échantillons issus d'un générateur d'aléas de phase pseudo-aléatoire, les moyens de combinaison fournissant un entier compris dans l'intervalle [0, M-1] pour chaque combinaison d'un échantillon codé et d'un échantillon d'aléa de phase issu du générateur d'aléas de phase, M étant supérieur à N ;
- des moyens de génération de signaux fournissant, pour chaque entier compris dans l'intervalle [0, M-1], une suite de q nombres entiers correspondant à cet entier, les différentes suites étant orthogonales ou quasi-orthogonales entre elles ;
- des moyens d'émission des suites de q nombres entiers à l'attention du récepteur, les moyens d'émission comprenant un modulateur à décalage de phase dont le nombre d'états est égal à M ;
- le récepteur comporte successivement :
- des moyens de réception restituant les suites de q nombres entiers ;
- des moyens de traitement recevant d'une part les suites de q nombres entiers des moyens de réception et d'autre part des échantillons d'aléas de phase issus d'un générateur d'aléa de phase synchronisé avec le générateur d'aléas de phase de l'émetteur, les moyens de traitement assurant une démodulation des suites de q nombres entiers et effectuant une opération inverse de celle des moyens de combinaison pour restituer les échantillons codés ;
- des moyens de décodage restituant le signal numérique à partir des échantillons fournis par les moyens de traitement.
- the transmitter successively comprises:
- coding means receiving this digital signal and providing, for each block of k bits of the digital signal, a coded sample taking an integer value included in the interval [0, N-1], each integer value being representative of the k bits of the block from which it came;
- means for combining the coded samples with samples from a pseudo-random phase generator, the combining means providing an integer in the interval [0, M-1] for each combination of a sample coded and of a phase random sample from the phase random generator, M being greater than N;
- means for generating signals providing, for each integer included in the interval [0, M-1], a sequence of q integers corresponding to this integer, the different sequences being orthogonal or quasi-orthogonal to each other;
- means for transmitting sequences of q whole numbers for the attention of the receiver, the transmission means comprising a phase shift modulator whose number of states is equal to M;
- the receiver successively comprises:
- reception means restoring the sequences of q whole numbers;
- processing means receiving on the one hand the sequences of q whole numbers of the reception means and on the other hand samples of phase hazards originating from a phase hazard generator synchronized with the phase hazard generator of the transmitter, the processing means ensuring a demodulation of the sequences of q whole numbers and performing an inverse operation to that of the combination means for restoring the coded samples;
- decoding means restoring the digital signal from the samples supplied by the processing means.
Les M suites de q nombres entiers sont préférentiellement constituées de séquences de Hadamard.The M sequences of q integers are preferably made up of Hadamard sequences.
D'autres caractéristiques et avantages de l'invention apparaítront à la lecture de la description suivante d'un mode de réalisation préférentiel, donné à titre illustratif et non limitatif, et des dessins annexés dans lesquels :
- la figure 1 représente un chronogramme permettant de comprendre le principe de l'étalement de spectre par une séquence d'étalement ;
- la figure 2 est un schéma synoptique d'un émetteur du système de transmission de la présente invention ;
- la figure 3 est un schéma synoptique d'un récepteur des signaux numériques transmis par l'émetteur de la figure 2.
- FIG. 1 represents a timing diagram making it possible to understand the principle of spectrum spreading by a spreading sequence;
- Figure 2 is a block diagram of a transmitter of the transmission system of the present invention;
- FIG. 3 is a block diagram of a receiver of the digital signals transmitted by the transmitter of FIG. 2.
La figure 1 a été décrite précédemment en référence à l'état de la technique.Figure 1 has been described previously with reference to the state of the art.
En se référant à la figure 2, le signal numérique à transmettre SN est appliqué, ici par l'intermédiaire d'un accès série, à des moyens de codage 21 qui fournissent, pour chaque bloc de k bits du signal SN, un échantillon codé Ec prenant une valeur entière comprise dans l'ensemble {0,..., N-1}, chaque valeur entière étant représentative des k bits du bloc correspondant. Les moyens de codage 21 peuvent par exemple être constitués par un simple convertisseur binaire-décimal et le débit sortant des moyens de codage est alors k fois plus faible que le débit entrant.Referring to FIG. 2, the digital signal to be transmitted SN is applied, here via a serial access, to coding means 21 which supply, for each block of k bits of the signal SN, a coded sample E c taking an integer value included in the set {0, ..., N-1}, each integer value being representative of the k bits of the corresponding block. The coding means 21 can for example be constituted by a simple binary-decimal converter and the bit rate leaving the coding means is then k times lower than the bit rate entering.
Les moyens de codage 21 peuvent éventuellement également effectuer un entrelacement des bits du signal SN. The coding means 21 can optionally also interleave the bits of the SN signal.
Les échantillons codés Ec sont appliqués à des moyens
de combinaison 22 de ces échantillons avec des échantillons
Ea issus d'un générateur 23 pseudo-aléatoire, qui sera par
la suite appelé générateur d'aléas de phase. De façon
générale, les moyens de combinaison 22 comprennent un
algorithme de transformation qui transforme chaque
échantillon codé Ec en un entier s compris dans l'ensemble
{0,..., M-1}, avec M entier supérieur à N. On a :
Les moyens de combinaison 22 peuvent par exemple être
constitués par un simple additionneur modulo M, tel que
représenté et fournissant:
où désigne l'addition modulo M pouvant aussi s'écrire :
Cette addition modulo M, mise à part le fait qu'elle peut être mise en oeuvre par un algorithme très simple à implanter, procure des performances optimales de résistance au brouillage ECM.This modulo M addition, apart from the fact that it can be implemented by a very simple algorithm to implant, provides optimal resistance performance at ECM interference.
Chaque entier s est ensuite fourni à des moyens 24 de génération de signaux fournissant, pour chaque entier s, une suite SQ de q échantillons correspondante, chaque échantillon q étant un entier. Les moyens 24 de génération de signaux transforment chaque entier s en une suite SQ, cette transformation étant bi-univoque, c'est à dire qu'à un entier s donné correspond une seule suite SQ et réciproquement.Each integer is then supplied to means 24 of generation of signals providing, for each integer s, a corresponding SQ sequence of q samples, each sample q being an integer. 24 generation means of signals transform each integer s into a SQ sequence, this transformation being bi-unequivocal, that is to say that a given integer s corresponds to a single sequence SQ and reciprocally.
On peut écrire :
Le générateur de signaux peut par exemple être constitué par une table de transcodage. On se reportera utilement au brevet français n°2.337.465 au nom de COMPAGNIE IBM FRANCE ™ qui décrit des séquences dites CAZAC qui sont des séquences pseudo-aléatoires périodiques de nombres complexes qui ont une fonction d'autocorrélation périodique dont seul le premier coefficient est non nul et dont tous les nombres complexes ont une amplitude constante. La génération de telles séquences peut être généralisée pour obtenir des séquences constituées de nombres entiers, ces séquences étant orthogonales entre elles, c'est à dire présentant des propriétés d'autocorrélation optimales. On peut également mentionner les séquences de Gold qui sont quasi-orthogonales, comme celles de Kasami, ou celles appelées polyphases.The signal generator can for example be consisting of a transcoding table. We will refer usefully to French patent n ° 2,337,465 in the name of COMPAGNIE IBM FRANCE ™ which describes sequences called CAZAC which are periodic pseudo-random sequences of complex numbers that have an autocorrelation function periodic whose only the first coefficient is not zero and of which all complex numbers have an amplitude constant. The generation of such sequences can be generalized to obtain sequences made up of whole numbers, these sequences being orthogonal between them, that is to say having properties optimal autocorrelation. We can also mention Gold sequences which are quasi-orthogonal, like those of Kasami, or those called polyphases.
Dans un mode de réalisation préférentiel, les moyens
24 génèrent des suites SQ sensiblement orthogonales entre
elles. A titre d'exemple, les moyens 24 de génération de
signaux peuvent transformer chaque entier s en une suite SQ
de q bits (échantillons prenant chacun une valeur dans
{0,1}) selon le tableau 1 ci-dessous.
Dans cette configuration, M=8 et q=7. Chaque suite de q bits est issue par décalages circulaires d'une séquence de longueur maximale de longueur 7, à l'exclusion de la première suite toujours constituée de zéros. Ces suites présentent des propriétés de quasi-orthogonalité, c'est à dire que pour deux suites différentes et quelconques, la somme des OU-EXCLUSIF de chaque terme est égale à 4.In this configuration, M = 8 and q = 7. Each suite of q bits is produced by circular shifts of a sequence of maximum length of length 7, excluding the first suite always consisting of zeros. These suites have quasi-orthogonality properties, say that for two different and arbitrary sequences, the sum of the EXCLUSIVE OUs of each term is equal to 4.
Il est possible de généraliser ce principe de génération de signaux SQ quasi-orthogonaux pour tout M puissance de 2. Pour cela, après avoir déterminé une séquence de longueur maximale de période M-1 (par une des méthodes bien connues dans le domaine du traitement numérique de signaux), les M suites de M-1 bits sont obtenues par décalages circulaires de la séquence initiale, à l'exception de la première toujours constituée de zéros.It is possible to generalize this principle of generation of quasi-orthogonal SQ signals for all M power of 2. For this, after determining a sequence of maximum length of period M-1 (by one of the well-known methods in the field of treatment signals), the M sequences of M-1 bits are obtained by circular shifts of the initial sequence, with the exception of the first always consisting of zeros.
Une autre classe de suites utilisables, parfaitement
orthogonales, est celle constituée par des séquences de
Hadamard. Un exemple de telles séquences est illustré dans
le tableau 2, pour des échantillons également constitués
par des bits.
La longueur de ces suites ou séquences est de 8.The length of these sequences or sequences is 8.
La description précédente fait apparaítre que chaque bloc de k bits du signal SN a été transformé en une suite SQ correspondante, chaque suite SQ comportant une composante pseudo-aléatoire. L'information utile est codée dans cette suite SQ et les différentes suites sont orthogonales ou quasi-orthogonales entre elles. Dès lors que M et q sont grands devant k ou devant N, on comprend que cette opération de codage a consisté à augmenter de façon importante le nombre d'échantillons à transmettre et qu'on a donc réalisé un étalement du spectre du signal utile SN à l'aide d'aléas fournis à basse fréquence.The preceding description shows that each block of k bits of signal SN has been transformed into a sequence Corresponding SQ, each SQ suite comprising a pseudo-random component. Useful information is coded in this SQ suite and the different suites are orthogonal or quasi-orthogonal to each other. Since then that M and q are large before k or before N, we understand that this coding operation consisted in increasing by importantly the number of samples to be transmitted and that we have therefore spread the signal spectrum useful SN using hazards provided at low frequency.
Le principal avantage de l'invention réside justement dans ce codage qui est réalisé à la fréquence bit et non pas à la fréquence chip (où l'étalement de spectre est réalisé par séquence directe). La fréquence de travail des moyens décrits jusqu'ici peut ainsi être très faible, de l'ordre de 16 Kbits, à comparer avec 10 Mchips dans le cas d'un étalement de spectre par séquence directe.The main advantage of the invention lies precisely in this coding which is carried out at the bit frequency and not not at the chip frequency (where the spectrum spread is performed by direct sequence). The working frequency of means described so far can be very weak, around 16 Kbits, compare with 10 Mchips in the case spread spectrum by direct sequence.
Il est à signaler que les échantillons peuvent prendre des valeurs plus importantes, en fonction de la modulation utilisée dans des moyens d'émission 25 auxquels sont fournis les suites SQ.It should be noted that the samples may take larger values, depending on the modulation used in transmission means 25 to which SQ suites are provided.
Ces moyens d'émission 25 fournissent un signal STR transmis à l'attention du récepteur. Ils peuvent être de type quelconque, analogique ou numérique.These transmission means 25 supply a signal STR transmitted to the attention of the receiver. They can be from any type, analog or digital.
Dans le mode de réalisation représenté, les moyens
d'émission 25 sont de type numérique et comportent un
modulateur à décalage de phase 28. Ce modulateur 28 est par
exemple de type MPSK (Multiple Phase Shift Keying) où M
correspond ici au nombre de valeurs possibles des
échantillons q des suites SQ et donc au nombre d'états de
phase du signal modulé STR. Il est par exemple possible
d'effectuer une modulation BPSK si les suites SQ sont
exclusivement constituées de bits, une modulation QPSK si
les entiers des suites SQ sont chacun compris dans
l'ensemble {0, 1, 2, 3}, et une modulation 64-PSK si les
entiers des suites SQ sont chacun compris dans l'ensemble
{0, 1, ..., 63}. Le modulateur 28 à décalage de phase peut
également être de type QAM. Il fournit un signal modulé
noté SM.In the embodiment shown, the
Les moyens d'émission 25 peuvent également comporter
des moyens 26 d'étalement de spectre par séquence
d'étalement. La séquence d'étalement SE est générée par un
générateur de séquence d'étalement 27. Dans le mode de
réalisation représenté, on suppose que les bits des suites
SQ prennent leurs valeurs dans {0,1} et que les chips de la
séquence d'étalement SE prennent également leurs valeurs
dans {0,1}. Chaque échantillon b s / i produit par les moyens 24
de génération de signaux est additionné modulo L à G aléas
es appartenant à l'ensemble {0, 1, ..., L-1} et issus du
générateur 27, où G représente le gain d'étalement par
séquence directe. L'augmentation de débit occasionné par ce
traitement est égal à G. Dans le cas d'un étalement de
spectre par séquence directe, c'est donc le signal de
sortie des moyens 26, noté SQE, qui est appliqué au
modulateur 28.The transmission means 25 may also include means 26 for spreading spectrum by spreading sequence. The spreading sequence SE is generated by a spreading
Chaque échantillon ai d'une suite SQE prend sa valeur dans {0, 1, ..., L-1}. Dans le cas où aucun étalement par séquence directe est mis en oeuvre, G = 1 et es = 0, c'est à dire que cet opérateur est transparent.Each sample a i of an SQE sequence takes its value in {0, 1, ..., L-1}. In the case where no spreading by direct sequence is implemented, G = 1 and e s = 0, that is to say that this operator is transparent.
Le signal STR émis à l'attention du récepteur est de la forme: où g est la fonction de mapping réalisée par le modulateur 28, Ts le temps symbole et he(t-iTs) le filtrage émission. A titre d'exemple:
- en modulation BPSK, L = 2 et on a g(0) = -1 et g(1) = 1
- in BPSK modulation, L = 2 and we ag (0) = -1 and g (1) = 1
Dans ce cas la relation 1 s'écrit: avec αi = 0 ou 1
- en modulation QPSK, L = 4 et g(0) = 1, g(1) = j,
g(2) = -1 et g(3) = -j - en modulation 8PSK, L = 8 et g(k) = e2jkπ/8
- in QPSK modulation, L = 4 and g (0) = 1, g (1) = j,
g (2) = -1 and g (3) = -j - in 8PSK modulation, L = 8 and g (k) = e 2jkπ / 8
De façon générale, en modulation MPSK, L=M et g(k)=2jkπ/M.Generally, in MPSK modulation, L = M and g (k) = 2 jkπ / M.
On notera que la fonction de mapping g du modulateur doit respecter la relation: lorsqu'un étalement par séquence directe est mis en oeuvre (G > 1).Note that the mapping function g of the modulator must respect the relationship: when a spread by direct sequence is implemented (G> 1).
La réponse impulsionnelle he du filtre émission est supposée telle que: et The impulse response h e of the emission filter is assumed such that: and
Les moyens 26 d'étalement de spectre par séquence directe sont bien entendu optionnels dans l'invention et sont pour cela représentés en traits discontinus.The means 26 of spectrum spreading by sequence direct are of course optional in the invention and are therefore shown in broken lines.
Les moyens d'émission 25 peuvent également comprendre
des moyens 29, 30 d'évasion de fréquence, également
optionnels et donc représentés en traits discontinus, aptes
à modifier la fréquence porteuse du signal transmis au
récepteur. L'évasion de fréquence consiste à changer
fréquemment de fréquence porteuse afin d'élargir encore le
spectre du signal transmis au récepteur. Le signal modulé
SM, en bande de base ou en fréquence intermédiaire, est
appliqué à un multiplieur 29 recevant un signal de
fréquence porteuse d'un générateur 30.The transmission means 25 can also include
frequency escape means 29, 30, also
optional and therefore shown in broken lines, suitable
to modify the carrier frequency of the signal transmitted to the
receiver. The frequency escape is to change
frequently of carrier frequency in order to further broaden the
spectrum of the signal transmitted to the receiver. The modulated signal
SM, in baseband or in intermediate frequency, is
applied to a
On constate que le générateur d'aléas de phase 23
permet un codage basse-fréquence du signal à transmettre et
permet de modifier de manière pseudo-aléatoire la phase du
signal transmis lorsque la modulation est de type MPSK. On
peut ainsi considérer que le générateur 23 et les moyens de
combinaison 22 assurent une fonction d'évasion de phase
réalisée en basse-fréquence. Une modulation d'amplitude,
également pseudo-aléatoire, du signal à transmettre vient
se combiner avec cette évasion de phase lorsque la
modulation est de type QAM (modification de la phase et de
l'amplitude du signal transmis). C'est ainsi que le système
de transmission de l'invention permet d'obtenir une
résistance importante aux brouillages ECM.We can see that the
Le signal de sortie STR des moyens d'émission 28 est
transmis par voie hertzienne au récepteur 31 dont le schéma
synoptique est donné à la figure 3.The output signal STR of the transmission means 28 is
transmitted over the air to
Le récepteur 31 reçoit un signal STRr correspondant
au signal STR bruité par le milieu de transmission. Il
comporte des moyens de réception généralement référencés
par 40 restituant les suites SQ de q nombres entiers,
notées SQr au niveau du récepteur. Les moyens de réception
40 comprennent ici des moyens 32 de suppression de la
fréquence porteuse pilotés par un oscillateur local 33. Les
moyens 32 comprennent classiquement deux mélangeurs
commandés par des signaux d'horloge en quadrature et on
obtient en sortie de ces moyens deux signaux en quadrature.
Lorsqu'une évasion de fréquence est utilisée au niveau de
l'émetteur 20, l'oscillateur local 33 fonctionne en
synchronisme avec celui de l'émetteur, référencé 30. Cette
synchronisation peut être obtenue par des moyens connus. Le
signal de sortie des moyens 32 est noté SMr et correspond
au signal SM de l'émetteur.The
Le signal SMr est appliqué à des moyens 34 de
compression de spectre destinés à supprimer l'étalement par
séquence directe éventuellement effectué au niveau de
l'émetteur 20. Des moyens de compression de spectre sont
notamment décrits dans "Digital Communications" de J.G.
PROAKIS, McGraw-Hill ™, chapitre 8. Ceux représentés à la
figure 3 comprennent un échantillonneur 35 commandé à la
fréquence chip Fc suivi d'un module 36 de compression de
spectre. Le module 36 comporte un multiplieur complexe 37
suivi d'un sommateur 38. Le multiplieur 37 reçoit une
séquence directe SE d'un générateur 39, cette séquence
directe SE étant identique à celle générée par le
générateur 27 de l'émetteur 20. Le calage de phase de ces
deux séquences directes est obtenu par des moyens connus.The signal SMr is applied to means 34 of
spectrum compression to suppress spreading by
direct sequence possibly performed at
the
Le sommateur 38 calcule, pour chaque bloc de G
échantillons rk consécutifs issus du multiplieur 37, la
somme suivante:
où esk est la valeur du chip à l'instant k de la séquence
directe SE et * désigne le complexe conjugué. Cette
sommation permet de supprimer l'étalement spectral par
séquence directe. The
Chaque somme Uk correspond donc à un échantillon αi
du signal STR transmis au récepteur. En sortie du module
36, on dispose donc de suites SQr identiques aux suites SQ
issues des moyens 24 de génération de signaux de l'émetteur
20.Each sum U k therefore corresponds to a sample α i of the signal STR transmitted to the receiver. At the output of
Ces suites SQr sont appliquées à des moyens 45 de
traitement qui ont pour fonction de réaliser une
démodulation du signal reçu et de supprimer l'aléa de phase
Ea introduit au niveau de l'émetteur 20 par le générateur
d'aléas 23.These SQr suites are applied to means 45 for processing that have the function of performing a demodulation of the received signal and removing the random phase E is introduced at the
Dans le mode de réalisation représenté, les moyens 45 de traitement comprennent des moyens 41 de corrélation qui calculent, pour chaque bloc de Q sommes U successives, la valeur suivante: pour s = 0 à M-1.In the embodiment shown, the processing means 45 comprise correlation means 41 which calculate, for each block of Q successive sums U, the following value: for s = 0 to M-1.
Les moyens 41 de corrélation reçoivent pour cela un
signal de référence SR constitué par les différentes suites
SQ pouvant être générées au niveau de l'émetteur 20, c'est
à dire celles par exemple représentées dans les tableaux 1
ou 2. L'intérêt de générer des séquences orthogonales ou
quasi-orthogonales à l'aide du générateur 24 de la figure 2
(et non pas des séquences quelconques) est qu'il est aisé
de détecter une corrélation de ces signaux.The correlation means 41 therefore receive a
SR reference signal consisting of the different sequences
SQ can be generated at
Les corrélations calculées fournissent des sommes C0
à CM-1 qui correspondent chacune à un des entiers issus des
moyens de combinaison 22 de l'émetteur 20. Ces sommes sont
appliquées à un démultiplexeur 42 recevant d'un générateur
43 un signal Ea identique à celui généré par le générateur
23 de l'émetteur, et en phase avec celui-ci.The calculated correlations provide sums C 0 to C M-1 which each correspond to one of the integers from the combining means 22 of the
Le démultiplexeur 42 sélectionne N sommes CS parmi M en fonction de la valeur de l'aléa Ea. De façon générale, le démultiplexeur 42 assure une fonction inverse f-1 pour supprimer l'aléa de phase introduit en basse fréquence à l'émission. The demultiplexer 42 selects N sums C S from M as a function of the value of the hazard E a . In general, the demultiplexer 42 performs an inverse function f -1 to remove the phase hazard introduced at low frequency on transmission.
A titre d'exemple, si les moyens de combinaison 22 produisent: le démultiplexeur 42 fournit en sortie les signaux: pour i = 0 à N-1 et Ea appartenant à l'ensemble {0, 1, ..., M-1}. Le démultiplexeur 42 sélectionne ainsi les échantillons Cs en fonction de l'aléa Ea.By way of example, if the combining means 22 produce: the demultiplexer 42 outputs the signals: for i = 0 to N-1 and E a belonging to the set {0, 1, ..., M-1}. The demultiplexer 42 thus selects the samples C s as a function of the hazard E a .
Chaque échantillon di correspond donc à un
échantillon Ec de l'émetteur. Ces échantillons di sont
ensuite appliqués à des moyens 44 de décodage effectuant
une opération inverse de celle des moyens de codage 21 de
l'émetteur 20. Ils peuvent en outre réaliser un
désentrelacement des échantillons décodés si les moyens de
codage réalisent un entrelacement des échantillons codés.
Le signal de sortie SNr des moyens de décodage 44
correspond alors au signal numérique SN de l'émetteur.Each sample d i therefore corresponds to a sample E c of the emitter. These samples d i are then applied to decoding means 44 performing an inverse operation to that of the coding means 21 of the
Bien entendu, d'autres modes de réalisation des moyens 45 de traitement sont envisageables. Il est par exemple possible de ne calculer que les échantillons di selon la relation: Of course, other embodiments of the processing means 45 can be envisaged. It is for example possible to calculate only the samples d i according to the relation:
Ce calcul direct permet de ne pas utiliser d'algorithme de corrélation rapide et donc de simplifier la réalisation pratique du récepteur. Seules les corrélations utiles sont alors calculées. Les moyens de traitement 45 comprennent alors uniquement des moyens de corrélation tels que 41, recevant le signal Ea.This direct calculation makes it possible not to use a fast correlation algorithm and therefore to simplify the practical implementation of the receiver. Only the useful correlations are then calculated. The processing means 45 then only comprise correlation means such as 41, receiving the signal E a .
La présente invention s'applique par exemple aux systèmes de transmission où des codes correcteurs d'erreur sont utilisés et où un alphabet de signaux orthogonaux de taille très importante, supérieure à l'alphabet utilisé par le code correcteur d'erreurs, est disponible. Les éléments de l'alphabet non utilisés par le code peuvent être utilisés pour le codage pseudo-aléatoire basse-fréquence du signal à transmettre, permettant ainsi d'améliorer à faible coût la robustesse du système vis à vis de l'interception.The present invention applies for example to transmission systems where error correcting codes are used and where an alphabet of orthogonal signals of very large size, larger than the alphabet used by the error correction code is available. The elements of the alphabet not used by the code can be used for low-frequency pseudo-random coding of signal to be transmitted, thereby improving low cost the robustness of the system with regard to interception.
Claims (8)
- System for transmitting a digital signal (SN) between a transmitter (20) and a receiver (31), characterized in that:said transmitter (20) includes in succession:coding means (21) receiving said digital signal (SN) and supplying, for each block of k bits of said digital signal (SN), a coded sample (Ec) taking an integer value in the range [0, N-1], each integer value (Ec) being representative of the k bits of the block from which it is obtained;combining means (22) for combining said coded samples (Ec) with samples (Ea) from a pseudorandom random phase generator (23), said combining means (22) supplying an integer (s) in the range [0, M-1] for each combination of a coded sample (Ec) and a random phase sample (Ea) from said random phase generator (23), M being greater than N;signal generator means (24) supplying, for each integer (s) in the range [0, M-1], a sequence (SQ) of q integers corresponding to said integer (s), the various sequences (SQ) being orthogonal or quasi-orthogonal;transmit means (25) for transmitting said sequences (SQ) of q integers to said receiver (31), said transmit means (25) comprising a phase shift modulator using M states;said receiver (31) includes in succession:receive means (40) recovering said sequences (SQr) of q integers;processing means (45) receiving said sequences (SQr) of q integers from said receive means (40) and random phase samples (Ea) from a random phase generator (43) synchronized with said random phase generator (23) of said transmitter (20), said processing means (45) demodulating said sequences (SQr) of q integers and implementing an operation which is the inverse of that implemented by said combining means (22) to recover said coded samples (di);decoding means (44) for recovering said digital signal (SNr) from said samples supplied by said processing means (45).
- System according to claim 1 characterized in that said M sequences (SQ) of q integers are Hadamard sequences.
- System according to claim 1 or claim 2 characterized in that said transmit means (25) comprise spectrum spreading means (26, 27) using a spreading sequence (SE) and in that said receive means (40) comprise spectrum compression means (34) operating in synchronism with said spectrum spreading means (26, 27) of said transmit means (25).
- System according to any one of claims 1 to 3 characterized in that said transmit means (25) comprise frequency evasion means (29, 30) adapted to modify the carrier frequency of said signal transmitted to said receiver (30) and in that said receive means (40) comprise means (32, 33) implementing a function which is the inverse of that of said frequency evasion means (29, 30), adapted to eliminate said frequency evasion introduced at said transmitter (20).
- System according to any one of claims 1 to 4 characterized in that said coding means (21) also interleave the bits of said digital signal (SN) and in that said decoding means (44) also disinterleave the decoded samples (di).
- System according to any one of claims 1 to 5 characterized in that said combining means (22) of said transmitter (20) supply, for each coded sample (Ec), an integer (s) equal to: where:s is said integer supplied by said combining means (22);Ec is said coded sample;Ea is a random phase sample from said random phase generator (23) of said transmitter (20);
- Spread spectrum method of transmitting a digital signal between a transmitter (20) and a receiver (30) characterized in that it consists in:at said transmitter (20):generating, for each block of k bits of said digital signal, a coded sample (Ec) taking an integer value in the range [0, N-1], each integer value being representative of the k bits of the respective block;combining said coded samples (Ec) with random phase samples (Ea) to generate an integer (S) in the range [0, M-1] for each combination of a coded sample (Ec) and a random phase sample (Ea), M being greater than N;generating for each integer (s) in the range [0, M-1] a corresponding sequence (SQ) of q integers, by means of a one-to-one conversion process, the various sequences (SQ) being orthogonal or quasi-orthogonal;transmitting said sequences (SQ) of q integers to said receiver (30);at said receiver (30):recovering said sequences (SQr) of q integers from the signal received from said transmitter (20) and, for each sequence (SQr) of q integers recovered, generating an integer by means of a conversion which is the inverse of that carried out at said transmitter (20);combining each integer generated with a random phase sample (Ea) identical to that used to obtain said integer at said transmitter (20), so as to recover the corresponding coded sample (di), said combination thus eliminating said random phase (Ea);decoding each coded sample (di) to recover said digital signal (SNr).
- Method according to claim 7 characterized in that said sequences (SQ) of q integers are Hadamard sequences.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR9306936 | 1993-06-09 | ||
FR9306936A FR2706704B1 (en) | 1993-06-09 | 1993-06-09 | Spread spectrum digital transmission system obtained by low frequency pseudo-random coding of useful information and spread spectrum compression method used in such a system. |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0629059A1 EP0629059A1 (en) | 1994-12-14 |
EP0629059B1 true EP0629059B1 (en) | 2001-09-05 |
Family
ID=9447937
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP94401282A Expired - Lifetime EP0629059B1 (en) | 1993-06-09 | 1994-06-08 | Spread spectrum digital transmission system with low frequency pseudorandom coding of the useful information and method for spectrum spreading and compressing used in such a system |
Country Status (6)
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---|---|
US (1) | US5546423A (en) |
EP (1) | EP0629059B1 (en) |
CA (1) | CA2125444A1 (en) |
DE (1) | DE69428155D1 (en) |
ES (1) | ES2162846T3 (en) |
FR (1) | FR2706704B1 (en) |
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TW330358B (en) * | 1996-02-28 | 1998-04-21 | Toshiba Kk | Correlator and synchronous tracking apparatus of spectrum expansion receiver thereof |
KR100365346B1 (en) * | 1997-09-09 | 2003-04-11 | 삼성전자 주식회사 | Apparatus and method for generating quasi-orthogonal code of mobile communication system and diffusing band by using quasi-orthogonal code |
DE69832589T2 (en) | 1998-05-15 | 2006-08-10 | Sony Deutschland Gmbh | Transmitters and transmission methods that increase the flexibility of assigning codes |
KR100318959B1 (en) * | 1998-07-07 | 2002-04-22 | 윤종용 | Apparatus and method for eliminating interference between different codes in a CDMA communication system |
WO2000005779A2 (en) * | 1998-07-20 | 2000-02-03 | Samsung Electronics Co., Ltd. | Quasi-orthogonal code mask generating device in mobile communication system |
JP3815440B2 (en) * | 2003-02-03 | 2006-08-30 | ソニー株式会社 | Transmission method and transmission apparatus |
US8102802B2 (en) * | 2006-05-08 | 2012-01-24 | Motorola Mobility, Inc. | Method and apparatus for providing downlink acknowledgments and transmit indicators in an orthogonal frequency division multiplexing communication system |
KR101294781B1 (en) * | 2006-08-08 | 2013-08-09 | 엘지전자 주식회사 | Method for Transmitting Random Access Preamble |
US11095391B2 (en) * | 2018-12-19 | 2021-08-17 | Nxp Usa, Inc. | Secure WiFi communication |
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DE2110468C1 (en) * | 1971-03-05 | 1978-04-27 | Siemens Ag | Procedure for the transfer of information |
US4685132A (en) * | 1985-07-30 | 1987-08-04 | Sperry Corporation | Bent sequence code generator |
US4972474A (en) * | 1989-05-01 | 1990-11-20 | Cylink Corporation | Integer encryptor |
GB2233860B (en) * | 1989-07-13 | 1993-10-27 | Stc Plc | Communications systems |
US5153598A (en) * | 1991-09-26 | 1992-10-06 | Alves Jr Daniel F | Global Positioning System telecommand link |
US5276705A (en) * | 1993-01-06 | 1994-01-04 | The Boeing Company | CCD demodulator/correlator |
US5341396A (en) * | 1993-03-02 | 1994-08-23 | The Boeing Company | Multi-rate spread system |
US5377226A (en) * | 1993-10-19 | 1994-12-27 | Hughes Aircraft Company | Fractionally-spaced equalizer for a DS-CDMA system |
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1993
- 1993-06-09 FR FR9306936A patent/FR2706704B1/en not_active Expired - Lifetime
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1994
- 1994-06-08 US US08/257,057 patent/US5546423A/en not_active Expired - Fee Related
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- 1994-06-08 ES ES94401282T patent/ES2162846T3/en not_active Expired - Lifetime
- 1994-06-08 CA CA002125444A patent/CA2125444A1/en not_active Abandoned
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ES2162846T3 (en) | 2002-01-16 |
FR2706704B1 (en) | 1995-07-13 |
US5546423A (en) | 1996-08-13 |
FR2706704A1 (en) | 1994-12-23 |
EP0629059A1 (en) | 1994-12-14 |
CA2125444A1 (en) | 1994-12-10 |
DE69428155D1 (en) | 2001-10-11 |
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