Distributed sample acquisition-based fast cell search in inter-cell asynchronous DS/CDMA systems

In this paper, we introduce a fast cell-search scheme based on the distribu ted sample acquisition (DSA) technique for inter-cell asynchronous DS/CDMA systems. The proposed DSA scheme enables the long-code acquisition extremel y fast even without employing any passive matched filter which used to domi nate synchronization circuit complexity in asynchronous DS/CDMA systems. In the DSA-based asynchronous DS/CDMA system, each base station spreads its D QPSK-modulated long-code generator information with an assigned short-perio d igniter sequence, and broadcasts it as a common pilot signal. A mobile st ation first identifies and acquires the igniter sequence of the cell group currently located, then detects the conveyed long-code generator informatio n by despreading the acquired igniter sequence, thereby identifying and syn chronizing the long-code of the current cell. The mean acquisition time of this proposed DSA-based inter-cell asynchronous DS/CDMA system, evaluated u nder the assumption that each of 512 cell-specific long-codes is a 10-ms se gment (38 400-chips for the chip rates 3.84 Mchips/s) of complex Gold codes of period 2(18) - 1 and the igniter sequence (or, group code) set is compo sed of 7 complex orthogonal Gold codes of period 256, turned out even short er than that of the inter-cell synchronous DS/CDMA systems employing the co nventional serial search method. Furthermore, simulation results showed tha t the DSA scheme employing a passive matched filter is much superior, in te rms of acquisition time and robustness, to the 3GPP W-CDMA synchronization scheme having comparable complexity.