Application of correlation-aided DSA(CDSA) technique to fast cell search in IMT-2000 W-CDMA systems

In this paper, we introduce the correlation-aided distributed sample acquis ition (CDSA) scheme for fast cell search in IMT-2000 W-CDMA cellular system s. The proposed scheme incorporates the state symbol correlation process in to the comparison-correction based synchronization process of the original DSA scheme to enable fast acquisition even under very poor channel environm ent. For its realization, each mobile station (MS) has to store in its memo ry a set of state sample sequences, which are determined by the long-period scrambling sequences used in the system and the sampling interval of the s tate samples. CDSA based cell search is carried out in two stages: First, t he MS first acquires the slot timing by using the primary synch code (PSC) and then identifies the igniter code which conveys the state samples of the current cell. Secondly, the MS identifies the scrambling code and frame ti ming by taking the comparison-correction based synchronization approach and , if the identification is not done satisfactorily within preset time, it i nitiates the state symbol correlation process which correlates the received symbol sequence with the pre-stored state sample sequences for a successfu l identification. As the state symbol SNR is relatively high, the state sym bol correlation process enables reliable synchronization even in very low c hip-SNR environment. Simulation results show that the proposed CDSA scheme outperforms the 3GPP 3-step approach, requiring the signal power of about 7 dB less for achieving the same acquisition time performance in low-SNR env ironment. Furthermore, it turns out very robust in the typical synchronizat ion environment where large frequency offset exists.