Combined Scheme for Fast PN Code Acquisition

In direct-sequence wideband (DS-WB) systems, long spreading sequences are used to span multiple symbol intervals in order to remove spectral lines and to mitigate multiple access interference. The usage of long spreading sequences will result in a large search space during acquisition stage. As a result, the DS-WB systems will need a lot of time to achieve acquisition state. This paper proposes a combined acquisition scheme, known as Fast Serial Search Sequential Estimation (FSSSE), which could be applied to the direct sequence spread spectrum systems with long PN sequences. The proposed scheme is a combination of two acquisition schemes which are the serial search acquisition scheme and the rapid acquisition by sequential estimation (RASE) scheme. The proposed scheme gets the advantages of both schemes while overcome their drawbacks. The mean acquisition time of the proposed scheme is reduced 100 times compared to the conventional serial search scheme for PN sequence with a period of 2-1.