The Research On Transformation Of Spreading Sequence

As technology advances, People need higher and higher quality information transmission. Code-division multiple-access(CDMA) technology enables the development of spread spectrum communication has become one of the most important communication transmission. Spreading sequences play an important role in the spread spectrum communication system. The correlation function of the spreading sequences which are employed in CDMA communication systems play a critical role on the capability of reducing multiple access interference, the multipath interference, and adjacent cell interference, therefore directly influence the performance and capacity of the systems. Existing research on spreading sequences mainly focuses on three aspects, i.e. the theoretic sequence bounds, the sequence design and the sequence applications respectively. But there are a few research results on transformation of spreading sequence. In this thesis, equivalent transformation of directly spreading sequence are investigated concretely, that is,(1) equivalent transformations on single spreading sequence,(2) equivalent transformation pairs of a q-ary sequence and its complex polyphase form,(3) other spreading sequence derived from binary sequence. The results of the studies are listed as follows:(1) An equivalent transformation of q-ary sequence and two equivalent transformation of complex sequence are are put forward, and proved. And there are examples to explain them.(2) Two theorems on equivalent transformation pairs of a q-ary sequence and its complex polyphase form are proposed, and proved. Constructions of aperiodic Z-complementary pairs are proposed by using the two theorems.(3) A method of quadriphase sequence derived from binary sequence is given, and a construction of aperiodic quadriphase complementary sets is proposed. Four similar methods of aperiodic quadriphase or four-level complementary pairs derived from binary complementary pairs are found.