Fast acquisition method for DS-CDMA systems employing asynchronous base stations

There has been significant interest in cellular systems employing direct sequence CDMA, with no synchronization requirement between base-stations (BS), especially in the context of the so-called third generation wireless systems. In this case, since neighboring BS use different spreading sequences, the mobile must first determine the spreading sequence being used by the base station(s) from which the mobile receives sufficiently strong signals. To facilitate acquisition, the total set of spreading sequences is divided into groups, and the group identification is transmitted over a synchronization channel. This paper describes a novel mechanism for transmitting the group ID using cyclically permutable (CP) codes; this scheme results in significant reduction in the search space, allowing for rapid acquisition. The technique described is currently a component of the ARIB and ETSI proposals to the ITU, for third generation wireless systems (IMT-2000)