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Weyl Spreading Sequence Optimizing CDMA Hirofumi TSUDA Ken UMENO Publication IEICE TRANSACTIONS on Communications Vol.E101-B No.3 pp.897-908 Publication Date: 2018/03/01 Publicized: 2017/09/11 Online ISSN: 1745-1345 DOI: 10.1587/transcom.2017EBP3139 Type of Manuscript: PAPER Category: Wireless Communication Technologies Keyword: asynchronous CDMA, nonlinear programming, spreading sequence, signal to interference plus noise ratio, bit error rate, Full Text: PDF(1MB)>>
Summary: This paper shows an optimal spreading sequence in the Weyl sequence class, which is similar to the set of the Oppermann sequences for asynchronous CDMA systems. Sequences in Weyl sequence class have the desired property that the order of cross-correlation is low. Therefore, sequences in the Weyl sequence class are expected to minimize the inter-symbol interference. We evaluate the upper bound of cross-correlation and odd cross-correlation of spreading sequences in the Weyl sequence class and construct the optimization problem: minimize the upper bound of the absolute values of cross-correlation and odd cross-correlation. Since our optimization problem is convex, we can derive the optimal spreading sequences as the global solution of the problem. We show their signal to interference plus noise ratio (SINR) in a special case. From this result, we propose how the initial elements are assigned, that is, how spreading sequences are assigned to each users. In an asynchronous CDMA system, we also numerically compare our spreading sequences with other ones, the Gold codes, the Oppermann sequences, the optimal Chebyshev spreading sequences and the SP sequences in Bit Error Rate. Our spreading sequence, which yields the global solution, has the highest performance among the other spreading sequences tested. | |||||
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