Patent ID: 6434111
Filing Date: 2002-08-13
Classification: H04B,H04J

Abstract:
A process for the demodulation of signals representative of sequences (SE1 to SEN) transmitted in a communications system, each transmitted sequence (SE1 to SEN) being the result of a bi-orthogonal modulation which associates to a symbol (p) either an orthogonal function (S1 to Sn) if said symbol (p) has its last element (uk) which is in a first state, or the logical complement of said orthogonal function (S1 to Sn), if said symbol (p) has its last element (uk) which is in a second state, said process being provided in order to determine each of a plurality of soft decision values (C1 to Ck) to be attributed to each element of the demodulated symbol, with a view to subsequent decoding of a maximum probability type, characterised in that it comprisesdetermining a correlation value (a1to an) between each orthogonal function (S1 to Sn) that could have been used during the modulation process, and the signals to be demodulated; deducting from said correlation values (a1 to an) a confidence value (w1 to wN) attributed to each sequence (SE1 to SEN) that could have been transmitted, said confidence value (w1 to wN) being calculated in the following manner: if the symbol (p) associated with said sequence (SEp) has its last element (Uk) which is in a first state, said value (wp) is either equal to the square of the correlation value (aq) between signal to be demodulated and the function (Sq) used for said sequence (SEp) if said correlation value (aq) is positive, or zero if said correlation value (aq) is negative; if the symbol (p) associated with said sequence (SEp) has its last element (uk) which is in a second state, said value (wp) is either zero if the correlation value (aq) between the signal to be demodulated and the function (Sq) used for said sequence (SEp) is positive, or equal to the square of the correlation value (aq) if said correlation value (aq) is positive; deducting from said confidence values (w1 to wN) said soft decision values (C1 to Ck) to be attributed to each element of the demodulated symbol.