A MUSIC-based algorithm for spreading sequence discovery in multiuser DS-CDMA

A blind scheme based on a multiple signal classification (MUSIC) algorithm for user identification in a synchronous multiuser code division multiplex access (CDMA) system is suggested. The scheme is blind in the sense that it does not require prior knowledge of the spreading codes. Eigenvalue decomposition (EVD) is performed on the received signal, and then all the valid possible signature sequences are projected onto the subspaces. However, as a result of this process, some false answers are also produced and the ambiguity seems un-resolvable. Our approach is to apply a transformation derived from the results of the subspace decomposition on the received signal, and then inspect the statistics of the outcome. It is shown the second order statistics of the transformed signal provides a reliable means for removing the false answers.