EP0629059B1 - Digitales Spreizspektrumübertragungssystem mit Niederfrequenz-Pseudozufallkodierung von Nutzinformation und Verfahren zur Spektrumsspreizung und Spektrumskomprimierung zur Verwendung in einem solchen System - Google Patents

Digitales Spreizspektrumübertragungssystem mit Niederfrequenz-Pseudozufallkodierung von Nutzinformation und Verfahren zur Spektrumsspreizung und Spektrumskomprimierung zur Verwendung in einem solchen System Download PDF

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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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Prior art keywords
integer
sequences
transmitter
random phase
integers
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French (fr)
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EP0629059A1 (de
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Philippe Sehier
Dominique Deprey
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Alcatel Lucent SAS
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Alcatel CIT SA
Alcatel SA
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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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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)

Claims (8)

  1. System zur Übertragung eines Digitalsignals (SN) zwischen einem Sender (20) und einem Empfänger (31), dadurch gekennzeichnet, dass:
    der Sender (20) aufeinanderfolgend aufweist:
    Codiermittel (21), die das Digitalsignal (SN) empfangen und für jeden Block mit k Bits des Digitalsignals (SN) eine codierte Probe (Ec) liefern, die einen ganzzahligen Wert im Intervall [0, N-1] annimmt, wobei jeder ganzzahlige Wert (Ec) die k Bits des Blocks, von dem er stammt, darstellt;
    Mittel (22) zum Kombinieren der codierten Proben (Ec) mit Proben (Ea), die von einem Zufallsgenerator (23) mit pseudo-stochastischer Phase stammen, wobei die Kombinationsmittel (22) für jede Kombination einer codierten Probe (Ec) und einer Phasenzufallsprobe (Ea), die vom Phasenzufallsgenerator (23) stammt, eine ganze Zahl (s) im Intervall [0, M-1] liefert, wobei M größer als N ist;
    Mittel (24) zur Erzeugung von Signalen, die für jede ganze Zahl (s) im Intervall [0, M-1] eine Folge (SQ) von q ganzen Zahlen liefern, die dieser ganzen Zahl (s) entspricht, wobei die verschiedenen Folgen (SQ) zueinander orthogonal oder quasi-orthogonal sind;
    Mittel (25) zum Senden der Folgen (SQ) von q ganzen Zahlen an den Empfänger (31), wobei die Sendemittel (25) einen Modulator mit Phasenverschiebung umfasst, dessen Anzahl von Zuständen gleich M ist;
    der Empfänger (31) aufeinanderfolgend aufweist:
    Empfangsmittel (40), die die Folgen (SQr) von q ganzen Zahlen wiederherstellen;
    Verarbeitungsmittel (45), die einerseits die Folgen (SQr) von q ganzen Zahlen von den Empfangsmitteln (40) und andererseits Phasenzufallsproben (Ea) empfangen, die von einem Phasenzufallsgenerator (43) stammen, der mit dem Phasenzufallsgenerator (23) des Sender (20) synchronisiert ist, wobei die Verarbeitungsmittel (45) eine Demodulation der Folgen (SQr) von q ganzen Zahlen sicherstellen und eine Umkehroperation zu derjenigen der Kombinationsmittel (22) ausführen, um die codierten Proben (di) wiederherzustellen;
    Decodiermittel (44), die das Digitalsignal (SNr) ausgehend von den von den Verarbeitungsmitteln (45) gelieferten Proben wiederherstellen.
  2. System nach Anspruch 1, dadurch gekennzeichnet, dass die M Folgen (SQ) von q ganzen Zahlen Hadamard-Folgen sind.
  3. System nach einem der Ansprüche 1 und 2, dadurch gekennzeichnet, dass die Sendemittel (25) Mittel (26, 27) zur Spektrenverbreiterung durch eine Verbreiterungsfolge (SE) umfassen, und dass die Empfangsmittel (40) Mittel (34) zur Spektrenkompression umfassen, die mit den Mitteln (26, 27) zur Spektrenverbreiterung der Sendemittel (25) synchron arbeiten.
  4. System nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die Sendemittel (25) Mittel (29, 30) zur Frequenzausweitung (d'évasion de fréquence) umfassen, die fähig sind die Trägerfrequenz des zum Empfänger (30) übertragenen Signals zu modifizieren, und dass die Empfangsmittel (40) Mittel (32, 33) umfassen, die eine zu derjenigen der Mittel (29, 30) zur Frequenzausweitung umgekehrte Funktion sicherstellen und fähig sind die beim Sender (20) eingeführte Frequenzausweitung aufzuheben.
  5. System nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Codiermittel (21) auch eine Verschachtelung der Bits des Digitalsignals (SN) durchführen und dass die Decodiermittel (44) auch eine Aufhebung der Verschachtelung der decodierten Proben (di) ausführt.
  6. System nach einem der Ansprüche 1 bis 5, dadurch gekennzeichnet, dass die Kombinationsmittel (22) des Senders (20) für jede codierte Probe (Ec) eine ganze Zahl (s) gleich:
    Figure 00220001
    liefern, worin:-s die von den Kombinationsmitteln (22) gelieferte ganze Zahl ist;
    Ec die codierte Probe ist;
    Ea eine Phasenzufallsprobe ist, die vom Phasenzufallsgenerator (23) des Senders (20) stammt;
    Figure 00220002
    die Addition modulo M bezeichnet, wobei M eine ganze Zahl ist;
    und dass die Mittel zur Aufhebung des Phasenzufalls des Empfängers (30) für jede Folge (SQe) von q Bits, die von den Verarbeitungsmitteln stammt, eine ganze Zahl (di) gleich
    Figure 00230001
    liefert, worin Ea eine Phasenzufallsprobe ist, die vom Phasenzufallsgenerator (43) des Senders (31) stammt.
  7. Verfahren zur Übertragung mit Spektrenverbreiterung eines Digitalsignals zwischen einem Sender (20) und einem Empfänger (30), dadurch gekennzeichnet, dass es darin besteht:
    beim Sender (20) :
    für jeden Block mit k Bits des Digitalsignals eine codierte Probe (Ec) zu erzeugen, die einen ganzzahligen Wert im Intervall [0, N-1] annimmt, wobei jeder ganzzahlige Wert die k Bits des entsprechenden Blocks darstellt;
    die codierten Proben (Ec) mit Phasenzufallsproben (Ea) zu kombinieren, um für jede Kombination einer codierten Probe (Ec) und einer Phasenzufallsprobe (Ea) eine ganze Zahl (S) im Intervall [0, M-1] zu erzeugen, wobei M größer als N ist;
    für jede ganze Zahl (s) im Intervall [0, M-1] entsprechend einer eindeutigen Transformation eine Folge (SQ) von q entsprechenden ganzen Zahlen zu erzeugen, wobei die verschiedenen Folgen (SQ) zueinander orthogonal oder quasi-orthogonal sind;
    die Folgen (SQ) von q ganzen Zahlen zum Empfänger (30) zu übertragen;
    beim Empfänger (30):
    die Folgen (SQr) von q ganzen Zahlen ausgehend vom empfangenen Signal vom Sender (20) wiederherzustellen und für jede wiederhergestellte Folge (SQr) von q ganzen Zahlen entsprechend einer Transformation, die zu der beim Sender (20) ausgeführten umgekehrt ist, eine ganze Zahl zu erzeugen;
    jede erzeugte ganze Zahl mit einer Phasenzufallsprobe (Ea), die mit der identisch ist, die beim Sender (20) gestattete diese ganze Zahl zu erhalten, so zu kombinieren, dass die entsprechende codierte Probe (di) wiederhergestellt wird, wobei die Kombination so den Phasenzufall (Ea) wieder aufhebt;
    jede codierte Probe (di) so zu decodieren, dass das Digitalsignal (SNr) wiederhergestellt wird.
  8. Verfahren nach Anspruch 7, dadurch gekennzeichnet, dass die Folgen (SQ) von q ganzen Zahlen Hadamard-Folgen sind.
EP94401282A 1993-06-09 1994-06-08 Digitales Spreizspektrumübertragungssystem mit Niederfrequenz-Pseudozufallkodierung von Nutzinformation und Verfahren zur Spektrumsspreizung und Spektrumskomprimierung zur Verwendung in einem solchen System Expired - Lifetime EP0629059B1 (de)

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FR9306936 1993-06-09
FR9306936A FR2706704B1 (fr) 1993-06-09 1993-06-09 Système de transmission numérique à étalement de spectre obtenu par codage pseudo-aléatoire basse fréquence de l'information utile et procédé d'étalement et de compression de spectre utilisé dans un tel système.

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EP0629059B1 true EP0629059B1 (de) 2001-09-05

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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 (ko) * 1997-09-09 2003-04-11 삼성전자 주식회사 이동통신시스템의쿼시직교부호생성및쿼시직교부호를이용한대역확산장치및방법
DE69832589T2 (de) 1998-05-15 2006-08-10 Sony Deutschland Gmbh Sender und Übertragungsverfahren, die die Flexibilität der Zuordnung von Koden erhöhen
KR100318959B1 (ko) * 1998-07-07 2002-04-22 윤종용 부호분할다중접속통신시스템의서로다른부호간의간섭을제거하는장치및방법
RU2200366C2 (ru) 1998-07-20 2003-03-10 Самсунг Электроникс Ко., Лтд. Устройство для генерирования маски квазиортогонального кода в системе мобильной связи
JP3815440B2 (ja) * 2003-02-03 2006-08-30 ソニー株式会社 送信方法及び送信装置
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 (ko) * 2006-08-08 2013-08-09 엘지전자 주식회사 랜덤 액세스 프리앰블 전송 방법
US11095391B2 (en) * 2018-12-19 2021-08-17 Nxp Usa, Inc. Secure WiFi communication

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US5546423A (en) 1996-08-13
ES2162846T3 (es) 2002-01-16
FR2706704A1 (fr) 1994-12-23
FR2706704B1 (fr) 1995-07-13
EP0629059A1 (de) 1994-12-14
DE69428155D1 (de) 2001-10-11
CA2125444A1 (fr) 1994-12-10

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