Method of acquiring a gps signal by iterative decoding

Method of acquiring a satellite signal by a receiver, said signal being spread by a Gold sequence (ci) at a chip frequency, said Gold sequence being obtained as the sum of a first M-sequence (x) generated using a first shift register and a second M-sequence (yi) generated using a second shift register, said second M-sequence identifying one satellite among a plurality of satellites, characterised in that:

• (a) the signal received in base band is sampled (410,510,610,710) at the chip frequency starting from a determined time (q) to provide a sequence of first samples (rq(k), k=0, . . . , M−1);
• (b) the sequence of said first samples is multiplied (420,520,620,720), chip by chip, by said first M-sequence to provide a sequence of second samples ({tilde over (r)}q(k), k=0, . . . , M−1):
• (c) the sequence of second samples is decoded using an iterative message passing decoding (430,530,640,740) to supply an estimate of the content of the second shift register at said determined time;
• (d) the content of the second shift register thus estimated is compared (440, 540, 660, 760) with a plurality of possible contents of the second shift register for the different satellites of said plurality, and if the comparison is successful for an identified satellite (i0), the receiver is synchronised with said identified satellite at the determined time.