Methods of constructing Z-complementary sequence sets are described. Different from those constructions using complementary sequences as a kernel, the proposed constructions are based on sequences with periodic and aperiodic zero-correlation zone (PAZCZ). These PAZCZ sequences are unitary sequences, not complementary sequences. By means of interleaving iteration and orthogonal matrix expansion of PAZCZ sequences, desirable bivalued zero cross-correlation zone (ZCCZ) characteristics can be obtained. Compared with Z-complementary sequence sets with single value ZCCZ which is generally equal to the length of an element sequence, the proposed Z-complementary sequence sets with bivalued ZCCZ have larger set size and then can support more users.

A method for constructing sets of sequences with zero-correlation zone (ZCZ sequences) and sequence sets with low cross correlation is proposed. The method is to use families of short sequences and complete orthogonal sequence sets to derive families of long sequences with desired correlation properties. It is a unification of works of Matsufuji and Torii et al., and there are more choices of parameters of sets for our method. In particular, ZCZ sequence sets generated by the method can achieve a related ZCZ bound. Furthermore, the proposed method can be utilized to derive new ZCZ sets with both longer ZCZ and larger set size from known ZCZ sets. These sequence sets are applicable in broadband satellite IP networks. Index Terms zero-correlation zone (ZCZ), low correlation, perfect sequence, orthogonal sequence, broadband satellite IP networks.

In Code Division Multiple Access (CDMA) systems, the traditional method for selecting spreading codes in order to reduce multiple-access interference (MAI) is to compare the maximum absolute value of the periodic (even) Cross-Correlation Function (CCF) for different code-sets. In many cases this method fails to introduce the best code-set. In this paper we propose a new criterion which is based on the Bit Error Rate (BER) performance of one set of CDMA codes. Through the development of this method, we can also compare and select the best code-set for our application. Also, our method gives us this possibility to consider the channel noise together with the inter-user interference. Using the proposed method, we analyzed the performance of some wellknown Direct Sequence (DS) CDMA spreading codes. While the traditional method to calculate the BER is based on the approximation of the MAI using central-limit theorem, our approach is applicable even when the number of codes is too small to use this theorem. Finally we have analyzed the performance of a family of ternary codes. 1.