Design of Almost Perfect Complementary Sequence Pairs

Sequences with very low out-of-phase auto-correlation and cross-correlation function are widely used for synchronization in mobile communication and multimedia systems where reliable data transmissions are required. For optimum detection, synchronization sequences usually have out-of-phase correlation values that are very low or zero. However sequences with ideal correlation function are very rare. Thus, this paper presents a new algorithm to generate almost perfect complementary sequence pairs with ideal bipolar correlation. Using the auto-correlation properties of these synchronization sequences, we can obtain a correlation circuit whose output contains two peak values equal in magnitude and opposite in polarity at zero and middle shifts. This correlation circuit can be used to double-check the synchronization timing and thus reduce the synchronization search time