Three-step fast cell search algorithm utilizing common pilot channel for OFCDM broadband packet wireless access

This paper proposes a three-step cell search algorithm that utilizes only the common pilot channel (CPICH) for the forward link orthogonal frequency and code division multiplexing (OFCDM) broadband packet wireless access, assuming two-layered spreading code assignment with a cell-specific scrambling code (CSSC) and a channel-specific orthogonal code (CSOC). The proposed cell search algorithm is performed in the following three steps: OFCDM symbol timing detection utilizing the guard interval timing in the first step; successive simultaneous frame timing and CSSC group detection in the second step by taking the correlation of the CPICH based on the property yielded by shifting the CSSC phase in the frequency domain; and CSSC identification within the group based on the correlation detection with CPICH in the third step. The most prominent feature of the proposed cell search algorithm is that it does not employ the conventional synchronization channel (SCH), which is exclusively used for the cell search. Computer simulation results elucidate that when the transmission power ratio of the CPICH to one code channel of the traffic channel (TCH) is more than 9 dB, the proposed cell search method achieves faster cell search time performance compared to the conventional method using the SCH with the transmission power ratio of the SCH to one code channel of the TCH of 3 dB. Furthermore, the results show that it can accomplish the cell search within 1.7 msec at 95% of the locations in a 12-path Rayleigh fading channel with the maximum Doppler frequency of 80 Hz and the r.m.s. delay spread of 0.32 μsec.