The method of obtaining the recursion probability Turbo decoder before

The invention discloses a forward recursion probability acquisition method for a Turbo decoder. The method aims to reduce forward recursion probability storage capacity as well as time overhead. The technical scheme is that: when forward recursion probabilities at each moment are acquired, the forward recursion probability of a 0 state is subtracted from the forward recursion probability of all states at the moment, the forward recursion probabilities of non-zero states at all the moments are ensured to be even numbers, and simultaneously the forward recursion probabilities of all the states at all the moments are ensured not to be overflowed to avoid storage area overhead and logic delay caused by the overflow prevention realized by the subtraction of a maximum value from the forward recursion probability in the conventional method. By the method, the forward recursion probability storage capacity can be reduced to (G-1)*(B-1)*W, the time overhead for acquiring the forward recursion probability of the moment is only Tsub, and a decoding rate is greatly increased; and simultaneously, the bit error rate performance of the method can be ensured to be same as that of the conventionalmethod by experimental analogue simulation.