Cell Search Synchronization under the Presence of Timing and Frequency Offsets in W-CDMA

Wisam K. HUSSAIN  Loay D. KHALAF  Mohammed HAWA  

IEICE TRANSACTIONS on Communications   Vol.E96-B   No.4   pp.1012-1018
Publication Date: 2013/04/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E96.B.1012
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technologies
cell search,  W-CDMA,  synchronization,  clock drift,  frequency offset estimation,  time offset estimation,  

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Initial cell search in wideband code-division multiple-access (W-CDMA) systems is a challenging process. On the one hand, channel impairments such as multipath fading, Doppler shift, and noise create frequency and time offsets in the received signal. On the other hand, the residual synchronization error of the crystal oscillator at the mobile station also causes time and frequency offsets. Such offsets can affect the ability of a mobile station to perform cell search. Previous work concentrated on cell synchronization algorithms that considered multipath channels and frequency offsets, but ignored clock and timing offsets due to device tolerances. This work discusses a robust initial cell search algorithm, and quantifies its performance in the presence of frequency and time offsets due to two co-existing problems: channel impairments and clock drift at the receiver. Another desired performance enhancement is the reduction of power consumption of the receiver, which is mainly due to the computational complexity of the algorithms. This power reduction can be achieved by reducing the computational complexity by a divide and conquer strategy during the synchronization process.