Insertion of a secondary binary information stream into a main symbol stream of a digital modulation

• US 8,873,670 B2
• Filed: 09/12/2005
• Issued: 10/28/2014
• Est. Priority Date: 09/15/2004
• Status: Active Grant

• Current Assignee: Airbus DS GMBH
• Original Assignee: Cassidian Limited (Airbus SE)
• Inventors: Latouche, Gilles, Rousseau, Frdric
• Primary Examiner(s): Ahn, Sam K
• Assistant Examiner(s): Wong, Linda
• Application Number:
  US11/575,180
• Publication Number:
  US 20080043871A1
• Time in Patent Office: 3,333 Days
• Field of Search: 375/219, 375/222, 375/223, 375/259, 375/261, 375/268, 375/267, 375/271, 375/272, 375/274, 375/275, 375/279, 375/282, 375/283, 375/284, 375/295, 375/300, 375/301, 375/302, 375/303, 375/304, 375/305, 375/316, 375/324, 375/346, 375/348, 375308-309, 375/322, 375/329, 375/332, 375/340, 375/239, 341/50, 341/51, 341/143, 380/217, 380/216, 380/214, 380/210
• US Class Current: 375/295
• CPC Class Codes: G06T 1/0021 Image watermarking
• CPC Class Codes: G06T 1/005 Robust watermarking, e.g. average attack or collusion attack resistant
• CPC Class Codes: G06T 1/0071 using multiple or alternating watermarks
• CPC Class Codes: H04L 27/186 in which the information is carried by both the individual signal points and the subset to which the individual signal points belong, e.g. coset coding or related schemes

Abstract

There is disclosed a method of inserting a secondary stream of binary information into a main symbol stream of at least one standard digital modulation. The stream to be transmitted resulting from the insertion of the secondary stream in the main stream is a symbol stream of a modified digital modulation. The stream to be transmitted has the same symbol rate as the main stream. The sequence of symbols of the stream to be transmitted is encoded according, cumulatively, to a first condition over at least two consecutive symbols of the main stream, on the one hand; and to a second condition on a current bit or a plurality of current bits of the secondary stream, on the other hand.

Claims

1. A method of inserting a secondary stream of information into a main stream of information, the method comprising

inserting the secondary stream of information into the main stream of information to generate a stream to be transmitted;

encoding a sequence of symbols of the stream to be transmitted includes

substituting modified symbols for respective standard symbols when;

a first condition on at least two consecutive symbols of the main stream of information is met; and

a second condition on a current bit or a plurality of current bits of the secondary stream of binary information is met, and

iterating to subsequent standard symbols when the first condition is met,

wherein the main stream of information comprises standard symbols of at least one standard digital modulation, and the secondary stream of information comprises a secondary stream of binary information, and

wherein said stream to be transmitted comprising a stream of modified symbols of a modified digital modulation, and having a same symbol rate as the main stream of information.

2. The method of insertion according to claim 1, wherein said stream of modified symbols are derived from said respective standard symbols by an additional shift in a Fresnel plane.

3. The method of insertion according to claim 2, wherein the additional shift in the Fresnel plane is a phase shift only.

4. The method of insertion according to claim 1, wherein the first condition is satisfied in case of a change in sign of phase transitions respectively associated with each symbol of a pair of consecutive symbols of the main stream of information.

5. The method of insertion according to claim 4, wherein, when the first condition is satisfied and when a current bit of the secondary stream of binary information is in a predefined one of the logical states TRUE or FALSE:

a first modified symbol is substituted for a first standard symbol of the pair of consecutive standard symbols of the main stream of information, said first modified symbol being derived from said first standard symbol by an additional phase shift corresponding to a negative angle −

α

, where α

is less as an absolute value than a minimum phase transition of a digital standard modulation, a negative sign being defined as opposite to the sign of the phase transition associated with said first standard symbol; and

a second modified symbol is substituted for a second standard symbol of said pair of standard symbols, said second modified symbol being derived from said second standard symbol by an additional phase shift of a positive angle +α

, the α

positive sign being defined as identical to the sign of the phase transition associated with said first standard symbol.

6. The method of insertion according to claim 5, wherein α

is close to and within a peak phase error specified for the standard digital modulation.

7. The method of insertion according to claim 4, wherein the first condition is satisfied when, at one and the same time, the phase transitions associated with the pair of consecutive standard symbols have opposite signs, and are not equal to the maximum phase transition of the standard digital modulation.

8. The method of insertion according to claim 7, wherein, when the first condition is satisfied:

a first modified symbol is substituted for a first standard symbol of the pair of consecutive standard symbols of the main stream of information, said first modified symbol being derived from said first standard symbol by a first additional phase shift corresponding to a negative angle −

α

/2 if a current bit of the secondary stream of binary information is in one of a predetermined logical states TRUE or FALSE, or to a positive angle +α

/2 if the current bit of the secondary stream of binary information is in another of said logical states, where α

is less as an absolute value than the a minimum phase transition of the standard digital modulation, a negative sign and a positive sign being defined respectively as opposite and identical to a sign of the phase transition associated with said first standard symbol; and

a second modified symbol is substituted for a second standard symbol of said pair of standard symbols, said second modified symbol being derived from said second standard symbol by a second additional phase shift, modulus of said second additional phase shift being identical to modulus of said first additional phase shift, and a sign of said modulus of said second additional phase shift being opposite to a sign of said modulus that of said first additional phase shift.

9. Method of insertion according to claim 8, wherein a is close to and within the a peak phase error specified for the standard digital modulation.

10. The method of insertion according to claim 4, wherein the first condition is satisfied for a pair of standard symbols only if a phase turn-around concerning said pair of standard symbols involves a non-minimum amplitude.

11. The method of insertion according to claim 4, wherein the first condition is assessed successively on non-overlapping pairs of consecutive symbols of the main stream of information.

12. The method of insertion according to claim 1, wherein the first condition is satisfied for a pair of standard symbols only if a cumulative phase state prior to pairing said pair of standard symbols is one of a zero cumulative phase state or an initial cumulative phase state.

13. The method of insertion according to claim 1, wherein the first condition is satisfied for a pair of standard symbols only if a phase transition associated with a first symbol of said pair of standard symbols has a predetermined sign, positive or negative.

14. The method of insertion according to claim 1, wherein the first condition is satisfied for a pair of standard symbols only if these standard symbols belong to certain parts of one burst only, defined by distinguishing the training sequences from the payload sequences.

15. The method of insertion according to claim 1, wherein the method of insertion is implemented only intermittently.

16. A method for insertion and extraction, the method comprising

inserting a secondary stream of information into a main stream of information to generate a stream to be transmitted,

wherein the main stream of information comprises standard symbols of at least one standard digital modulation, and the secondary stream of information comprises a secondary stream of binary information;

encoding a sequence of symbols of the stream to be transmitted includes

substituting modified symbols for respective standard symbols when;

a first condition on at least two consecutive symbols of the main stream of information is met; and

a second condition on a current bit or a plurality of current bits of the secondary stream of binary information is met, and

iterating to subsequent standard symbols when the first condition is met,

wherein said stream to be transmitted comprising a stream of modified symbols of a modified digital modulation, and having a same symbol rate as the main stream of information;

transmitting the stream to be transmitted in radio frequency;

extracting a stream of symbols from the transmitted stream by

detecting a presence of said secondary stream of binary information; and

observing a satisfying of the first condition and deducting from the stream of symbols transmitted in radio frequency form at least one current bit of the secondary stream of binary information.

17. The method of extraction according to claim 16, further including observing phase turnarounds, followed by statistically estimating phase states of standard symbols concerning these said phase turnarounds, then detecting the a presence of modified symbols in case of detection of significant phase shifts relative to said phase states.

18. The method of extraction according to claim 16, in which, for a demodulation of the main stream of information, said modified symbols, substituted in place of said respective standard symbols, are compared to the a standard symbol of a twin star.

19. A method of insertion a secondary stream of information into a main stream of information and extraction of a secondary information bit from a stream of symbols transmitted in radio frequency form, the method comprising

inserting the secondary stream of information into the main stream of information to generate a stream to be transmitted;

encoding a sequence of symbols of the stream to be transmitted includes

substituting modified symbols for respective standard symbols when;

a first condition on at least two consecutive symbols of the main stream of information is met; and

a second condition on a current bit or a plurality of current bits of the secondary stream of binary information is met, and

iterating to subsequent standard symbols when the first condition is met,

wherein the main stream of information comprises standard symbols of at least one standard digital modulation, and the secondary stream of information comprises a secondary stream of binary information, and

wherein said stream to be transmitted comprising a stream of modified symbols of a modified digital modulation, and having a same symbol rate as the main stream of information,

wherein the first condition is satisfied in case of a change in sign of the phase transitions respectively associated with each symbol of a pair of consecutive symbols of the main stream of information,

wherein, when the first condition is satisfied and when a current bit of the secondary stream of binary information is in a predefined one of the logical states TRUE or FALSE;

a first modified symbol is substituted for a first standard symbol of the pair of consecutive standard symbols of the main stream of information, said first modified symbol being derived from said first standard symbol by an additional phase shift corresponding to a negative angle −

α

, where α

is less as an absolute value than a minimum phase transition of a digital standard modulation, a negative sign being defined as opposite to the sign of the phase transition associated with said first standard symbol; and

a second modified symbol is substituted for a second standard symbol of said pair of standard symbols, said second modified symbol being derived from said second standard symbol by an additional phase shift of a positive angle +α

, the α

positive sign being defined as identical to the sign of the phase transition associated with said first standard symbol;

extracting of a secondary information bit from the stream of symbols by

detecting a presence of said secondary stream of binary information, observing phase turnarounds, followed by statistically estimating the phase states of standard symbols concerning these phase turnarounds, then detecting a presence of modified symbols in case of detection of significant phase shifts relative to said phase states; and

observing a satisfying of the first condition and deducting from the stream of symbols transmitted in radio frequency form at least one current bit of the secondary stream of binary information, wherein said bit is set to said predefined logical state in case of detection of the presence of modified symbols if and only if, there is a change of the a sign of the phase transitions respectively associated with a pair of successive modified symbols of said stream of symbols transmitted in radio frequency form.

20. A method of insertion and extraction of a secondary information bit from a stream of symbols transmitted in radio frequency form, the method comprising

inserting a secondary stream of information into a main stream of information to generate a stream to be transmitted;

encoding a sequence of symbols of the stream to be transmitted includes

substituting modified symbols for respective standard symbols when;

a first condition on at least two consecutive symbols of the main stream of information is met; and

a second condition on a current bit or a plurality of current bits of the secondary stream of binary information is met, and

iterating to subsequent standard symbols when the first condition is met,

wherein the main stream of information comprises standard symbols of at least one standard digital modulation, and the secondary stream of information comprises a secondary stream of binary information,

wherein said stream to be transmitted comprising a stream of modified symbols of a modified digital modulation, and having a same symbol rate as the main stream of information,

wherein the first condition is satisfied in case of a change in sign of the phase transitions respectively associated with each symbol of a pair of consecutive symbols of the main stream of information,

wherein the first condition is satisfied when, at one and the same time, the phase transitions associated with the pair of consecutive standard symbols have opposite signs, and are not equal to the maximum phase transition of the standard digital modulation,

when the first condition is satisfied;

a first modified symbol is substituted for a first standard symbol of the pair of consecutive standard symbols of the main stream of information, said first modified symbol being derived from said first standard symbol by a first additional phase shift corresponding to a negative angle −

α

/2 if a current bit of the secondary stream of binary information is in one of a predetermined logical states TRUE or FALSE, or to a positive angle +α

/2 if the current bit of the secondary stream of binary information is in another of said logical states, where α

is less as an absolute value than the a minimum phase transition of the standard digital modulation, a negative sign and a positive sign being defined respectively as opposite and identical to a sign of the phase transition associated with said first standard symbol; and

a second modified symbol is substituted for a second standard symbol of said pair of standard symbols, said second modified symbol being derived from said second standard symbol by a second additional phase shift, modulus of said second additional phase shift being identical to modulus of said first additional phase shift, and a sign of said modulus of said second additional phase shift being opposite to a sign of said modulus that of said first additional phase shift;

transmitting a stream of symbols in radio frequency form based on the stream to be transmitted;

extracting of a secondary information bit from the stream of symbols by

detecting a presence of said secondary stream of binary information, observing phase turnarounds, followed by statistically estimating the phase states of standard symbols concerning these said phase turnarounds, then detecting a presence of modified symbols in case of detection of significant phase shifts relative to said phase states; and

observing a satisfying of the first condition and deducting from the stream of symbols transmitted in radio frequency form at least one current bit of the secondary stream of binary information, wherein said bit is set to a predefined one of said logical states in case of detection of a presence of modified symbols of a secondary information bit, according to a sign of the phase shifts detected.

21. A modulator for constructing a symbol stream to be transmitted from a main stream of information and a secondary stream of information, the modulator comprising

means for inserting said secondary stream of information into said main stream of information;

an encoder to encode a sequence of symbols of the symbol stream to be transmitted includes substituting modified symbols for respective standard symbols when;

a first condition on at least two consecutive symbols of the main stream of information is met; and

a second condition on a current bit or a plurality of current bits of the secondary stream of binary information is met, and

iterating to subsequent standard symbols when the first condition is met,

wherein said main stream of information comprises standard symbols of standard digital modulation, and the secondary stream of information comprises the secondary stream of binary information,

wherein said symbol stream to be transmitted results from the means for inserting the secondary stream of binary information into the main stream of information, and

wherein said stream to be transmitted comprising a stream of modified symbols of a modified digital modulation, and having a same symbol rate as the main stream of information.

22. A system comprising

a modulator constructing a symbol stream to be transmitted from a main stream of information and a secondary stream of information, the modulator comprising

means for inserting said secondary stream of information into said main stream of information, wherein the main stream of information comprises standard symbols of at least one standard digital modulation, and the secondary stream of information comprises a secondary stream of binary information;

an encoder encoding a sequence of symbols of the stream to be transmitted includes substituting modified symbols for respective standard symbols when;

a first condition on at least two consecutive symbols of the main stream of information is met; and

a second condition on a current bit or a plurality of current bits of the secondary stream of binary information is met, and

iterating to subsequent standard symbols when the first condition is met,

wherein said stream to be transmitted comprising a stream of modified symbols of a modified digital modulation, and having a same symbol rate as the main stream of information;

a transmitter transmitting the stream to be transmitted in radio frequency;

a demodulator to extract a secondary stream of binary information from a symbol stream of the transmitted stream, comprising

means for extracting a stream of symbols from a transmitted stream by

detecting a presence of said secondary stream of binary information; and

observing a satisfying of the first condition and deducting from the stream of symbols transmitted in radio frequency form at least one current bit of the secondary stream of binary information.

23. A transmission device comprising:

a modulator for constructing a symbol stream to be transmitted from a main stream of information and a secondary stream of information,

where the modulator comprising means for inserting said secondary stream of information into said main stream of information,

wherein said main stream of information comprises standard symbols of standard digital modulation, and the secondary stream of information comprises a secondary stream of binary information;

an encoder encoding of a sequence of symbols of the stream to be transmitted includes substituting modified symbols for respective standard symbols when;

a first condition on at least two consecutive symbols of the main stream of information is met; and

a second condition on a current bit or a plurality of current bits of the secondary stream of binary information is met, and

iterating to subsequent standard symbols when the first condition is met,

wherein said stream to be transmitted results from the insertion of the secondary stream of binary information in the main stream of information, said stream to be transmitted comprising a stream of modified symbols of a modified digital modulation, and having a same symbol rate as the main stream of information.

24. A communication device comprising

a modulator constructing a symbol stream to be transmitted from a main stream of information and a secondary stream of information, the modulator comprising

means for inserting said secondary stream of information into said main stream of information, wherein the main stream of information comprises standard symbols of at least one standard digital modulation, and the secondary stream of information comprises a secondary stream of binary information;

an encoder encoding a sequence of symbols of the stream to be transmitted includes substituting modified symbols for respective standard symbols when;

a first condition on at least two consecutive symbols of the main stream of information is met; and

a second condition on a current bit or a plurality of current bits of the secondary stream of binary information is met, and

iterating to subsequent standard symbols when the first condition is met,

wherein said stream to be transmitted comprising a stream of modified symbols of a modified digital modulation, and having a same symbol rate as the main stream of information;

a transmitter transmitting the stream to be transmitted in radio frequency;

a demodulator to extract a secondary stream of binary information from a symbol stream of the transmitted stream, comprising

means for extracting a stream of symbols from a transmitted stream by

detecting a presence of said secondary stream of binary information; and

observing a satisfying of the first condition and deducting from the stream of symbols transmitted in radio frequency form at least one current bit of the secondary stream of binary information.