PN Sequence Preestimator Scheme for DS-SS Signal Acquisition Using Block Sequence Estimation

An m-sequence (PN sequence) preestimator scheme for direct-sequence spread spectrum (DS-SS) signal acquisition by using block sequence estimation (BSE) is proposed and analyzed. The proposed scheme consists of an estimator and a verifier which work according to the PN sequence chip clock, and provides not only the enhanced chip estimates with a threshold decision logic and one-chip error correction among the first m received chips, but also the reliability check of the estimates with additional decision logic. The probabilities of the estimator and verifier operations are calculated. With these results, the detection, the false alarm, and the missing probabilities of the proposed scheme are derived. In addition, using a signal flow graph, the average acquisition time is calculated. The proposed scheme can be used as a preestimator and easily implemented by changing the internal signal path of a generally used digital matched filter (DMF) correlator or any other correlator that has a lot of sampling data memories for sampled PN sequence. The numerical results show rapid acquisition performance in a relatively good CNR