A fast time acquisition method for PSK-2DSS systems

A fast time acquisition method for PSK-2DSS systems is presented in this paper. By analyzing the structure characteristics of the two dimensional spread spectrum sequence, the redundant operations hidden in traditional time correlation method were found. Then, a novel two-stage acquisition method is proposed, aiming mainly at removing the reduplicate multiply operations in the correlation processing. In this two-stage method, the former stage performs some data rearranging operations, on the basis of the estimate values of the initial phases of the two spreading codes. Then in the latter stage, the rearranged data is time correlated with the local version of the first code, and the result is used to verify whether the estimate is right. The data rearranging breaks through the coherent integration length limit in the serial search acquisition. So the proposed method can achieve much higher acquisition sensitivity than the serial search based and is more suitable for weak signals acquisition. Actually, since the data rearranging only adjusts the computation flow and no information will be lost, the proposed method has the same performance as the traditional time correlation. Benefited from the data rearranging, however, many multiply operations in the correlation processing can be combined. Then the computational complexity is reduced dramatically, and the acquisition can be accomplished very efficiently. At the end of this paper, numerical examples confirm the effectiveness of the proposed method.