Multiplex communications – Low speed asynchronous data system
Reexamination Certificate
1998-06-12
2002-08-20
Vu, Huy D. (Department: 2665)
Multiplex communications
Low speed asynchronous data system
C370S203000, C370S524000, C370S538000, C375S222000, C375S262000, C375S265000, C375S295000, C714S755000, C714S762000, C714S789000
Reexamination Certificate
active
06438112
ABSTRACT:
The present invention relates to a device and a method for coding information and to a device and a method for decoding coded information.
It applies in particular to the transmission of information by quadrature amplitude modulation, on any transmission channel using this modulation.
Quadrature amplitude modulation of signals is well known in the communications field. According to this modulation technique, information to be transmitted has associated with it a signal of constant frequency but whose amplitude and phase represent the said information.
However, on reception, these signals may sometimes be difficult to identify when the signal has been distorted or affected by noise during transmission.
In addition, the spectrum of these signals can be relatively narrow compared with the spectrum available for transmission. This gives rise to known drawbacks. By way of example, two of these drawbacks are mentioned below:
when the energy of the signals is concentrated in a spectrum which is too narrow, these signals are easily disturbed by noise or detected and interfered with by any enemies;
for certain applications, regulations make it necessary to distribute the energy of the signals sufficiently over the entire frequency band available.
The invention intends to remedy these drawbacks by proposing a method and a device for coding information having the following advantages:
the signals are more difficult to detect and interfere with;
distribution of the energy over the available frequency band is improved;
resistance of the signals to unintentional noise is increased.
Known labeling methods associate, with the 2
d
points of a constellation representing the amplitude pairs used, polynomials of degree d−1 in B, all the coefficients of which are binary, allowing the use of polynomial calculations. These methods have the drawback that the proximity between the points of the constellation, a proximity which relates to the risks of error between these points, is not well taken into account. In addition, the correction of errors in transmitting the information represented by these signals is not facilitated by these labeling methods.
The present invention intends to remedy these drawbacks.
For this purpose, according to a first aspect, the present invention relates to a device for coding information, characterized in that it has:
a first labeling means adapted to associate. with the information to be coded, K initial first degree polynomials, each of these two coefficients of the said initial polynomials being an integer number between 0 and Q−1 inclusive.
a coding means which performs a polynomial calculation:
to form K coded sequences of a number P greater than or equal to K of coded polynomials, the first coded polynomial of each of these K sequences being equal to one of the K initial polynomials and each of the other coded polynomials of the said sequence being equal to the product of the polynomial preceding it in the sequence and a predetermined polynomial, the coefficients of the coded polynomials being calculated modulo Q and the coded polynomial being calculated modulo an irreducible second degree polynomial, and
to form a resultant sequence of P resultant polynomials respectively equal to the modulo Q sums of the coded polynomials of same rank of the K coded sequences,
a second one-to-one labeling means adapted to label the Q
2
pairs of numbers representing the co-ordinates of the Q
2
points of a Q
2
-point quadrature amplitude modulation signal constellation, with the Q
2
resultant polynomials, in such a way that, if two points of the constellation have one identical co-ordinate and the other co-ordinate as close as possible, then the polynomials labeling them will have one identical coefficient and the other coefficient differing only by 1 modulo Q, and
a modulator adapted to convert each of the P resultant polynomials into a quadrature amplitude modulated signal, the amplitude pair of which is labeled by the said polynomial.
By virtue of these provisions, each of the polynomials in the sequence is associated with a pair of quadrature amplitudes, which makes it possible for the proximity between two of the pairs to correspond to a relationship between the polynomials which correspond to them.
In addition, the spectrum used for the transmission of the information is thus more spread out than the spectrum of a simple modulation of a signal.
According to a particular characteristic, the number Q is a power of a prime number.
By virtue of this provision, a decoding of the coded information can be performed using inverses of sub-matrices of the matrix used by the coding means.
According to other particular characteristics, the coding means uses a matrix having:
K lines of a number P greater than or equal to K, of elements representing polynomials in the finite ring of first degree polynomials with an integer coefficient taken modulo Q, and
at least one sub-matrix of dimensions K×K adapted to be inverted.
By virtue of these provisions, a large number of sub-matrices have an odd determinant. Each of these odd determinants enables a decoding device to determine an estimation of the polynomials supplied by the first labeling means. The multiplication of the number of estimations which can thus be used allows a statistical decoding processing.
When the channel transmitting the coded data is subject to noise, the estimation of the representative polynomials is, thus more reliable than a simple method of statistical approximation on each demodulated polynomial.
According to other particular characteristics:
the decoding means performs the polynomial calculation by using a recursion
the first labeling means is adapted to associate with the information to be coded, K previous polynomials and then to multiply a matrix formed by these K previous polynomials by an invertible matrix of dimensions K×K in order to produce the K initial polynomials.
By virtue of these provisions, a systematic coding can be performed, that is to say a coding in which the first resultant polynomials each represent one and only one initial polynomial.
According to a second aspect, the present invention relates to a method of coding information, characterized in that it includes:
a first labeling operation, during which K initial first degree polynomials are associated with the information to be coded, each of the two coefficients of the said initial polynomials being an integer number between 0 and Q−1, inclusive,
a coding operation which performs a polynomial calculation:
to form K coded sequences of a number P greater than or equal to K of coded polynomials, the first coded polynomial of each of these K sequences being equal to one of the K initial polynomials and each of the other coded polynomials of the said sequence being equal to the product of the polynomial preceding it in the sequence and a predetermined polynomial, the coefficients of the coded polynomial being calculated modulo Q and the coded polynomial being calculated modulo an irreducible second degree polynomial, and
to form a resultant sequence of P resultant polynomials respectively equal to the modulo Q sums of the coded polynomials of same rank of the K coded sequences.
a second operation of one-to-one labeling of Q
2
pairs of amplitudes by means of the Q
2
resulting polynomials able to be formed during the coding operation, any incrementation or decrementation of one of the components, by a predetermined value, when the other remains fixed, corresponding to the incrementation by one, modulo Q, of only one of the coefficients of the resulting polynomial, the other coefficient remaining fixed,
a modulation operation, during which each of the P resulting polynomials is converted into a quadrature amplitude modulation signal where the pair of amplitudes is labeled by the said polynomial.
The invention also intends to propose a method and a device for decoding coded information which has a resistance to added noise.
To this end, according to a third aspect, the present invention relates to a device for decod
Le Dantec Claude
Piret Philippe
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Phan M.
Vu Huy D.
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