Initial acquisition performance of biorthogonal modulation systems using differential detector

A frame synchronization system for biorthogonal modulation systems is treated. Biorthogonal modulation systems use several orthogonal sequences and their inverses for data transmission. Because of these several sequences, the bit error rate performance improves. However, in biorthogonal modulation systems, it is more difficult to acquire frame timing than in systems, such as conventional direct sequence spread spectrum systems, which use only one sequence for data transmission. We analyze a frame timing acquisition system based on a method which uses a differential detector. By use of the differential detector, the receiver obtains the frame timing information regardless of the transmitted sequence. We analyze the initial acquisition time which takes the probability of false alarm into account. It is found that the rapid increase of the initial acquisition time can be reduced by increasing the number of verifications and by raising the threshold level.