A Rapid Code Acquisition Scheme for DS/SS Systems

In this paper, we propose a rapid code acquisition scheme for direct-sequence spread-spectrum (DS/SS) system basing on the improved seed accumulation of sequential estimation (ISASE). This method solves the problem that SASE scheme cannot work in the presence of carrier-frequency offset. The mean acquisition time of the ISASE scheme is derived by the generating function flow graph technique, and the tolerance of carrier-frequency offset is obtained in a closed-form expression. The performance of the proposed acquisition scheme is analytically evaluated in terms of the mean acquisition time. Analysis in theory and numerical results show that the proposed scheme yields improvement of the mean acquisition time over the RASE scheme by a factor of 2–15 times for the PN} period more than 255 in normal operating condition. For the important parameter-accumulating number m, we recommend to choose from 5 to 20 through the tradeoff of the tolerance of carrier-frequency offset and acquisition speed.