CDSA: A fast and robust PN code acquisition scheme for inter-cell synchronous and asynchronous DS/CDMA applications

In this paper, we introduce the correlation-aided distributed sample acquis ition (CDSA) scheme to enhance the robustness of the previously proposed di stributed sample acquisition (DSA) schemes [1, 2, 3, 4] in the inter-cell s ynchronous and asynchronous environments. The proposed scheme incorporates the state symbol correlation process in the existing DSA process to maintai n the fast PN code acquisition performance even under very poor channel env ironment. In the first stage of the synchronization procedure, each mobile station attempts to acquire the PN code by taking the comparison-correction based synchronization approach of the original DSA scheme. However, if it cannot acquire the synchronization until it collects a pro-determined numbe r of state symbols, the MS stops the comparison-correction process and dete rmines the PN code timing by correlating the received symbol sequence with each shift of the pre-stored state symbol sequences, As the state symbol-SN R is relatively high due to high processing gain, the state symbol correlat ion process enables reliable synchronization even in very low chip-SNR envi ronment. Computer simulation reveals that the CDSA outperforms the DSA or 3 GPP acquisition schemes and the performance is robust to channel condition variations both for the inter-cell synchronous and asynchronous application s.