then we carried on the theory operation to the BER of OCDMA system with Matlab , The results show that the proximity degree of the BER derived by the two ways relate with the decision threshold, and with the increasing in the number of users ,the BER get closer.

Thus,we get the decision threshold.

The relative decision threshold was gained through selecting the suitable false alarm probability and missing detection probability,which ensures the validity of the algorithm.

Target echo signal was detected via computing after the peak value was found applying the judge threshold value to part matching filter result.

In this paper, we put forward a new method of Low SNR moving small target detection based on multi-level threshold decision-making and sliding trajectory confidence test technology.

An optimization design for symbol synchronization based on S&C algorithm was proposed,exactly through add a default information on the system because of the inconsistency between threshold and time-varying channels in OFDM communication system.

A new selection method of Fisher linear discriminate threshold is proposed , its error probability is much less than that of traditional identification threshold.