Experiments on three-step fast cell search algorithm employing common pilot channel for OFCDM broadband packet wireless access in forward link

This paper presents laboratory and field experimental results on a three-step cell search algorithm employing the time-multiplexed common pilot channel (CPICH) for orthogonal frequency and code division multiplexing (OFCDM) broadband wireless access with a 100-MHz bandwidth. In the proposed three-step cell search method using a two-dimensional cell-specific scrambling code, the OFCDM symbol timing, packet frame timing and scrambling code group, and the scrambling code within the group are detected by taking advantage of the CPICH in the first, second, and third step, respectively (note that the packet data channel (PDCH) is also used in the first step). The laboratory experimental results using a multipath fading simulator show that the cell detection probability of 90% is achieved within approximately 4 and 26 msec when the average received signal energy per symbol-to-background noise power spectrum density ratio (E_b/N₀) of the PDCH is -2 and -5 dB, respectively, where the maximum Doppler frequency is 20 to 400 Hz and the root mean squared delay spread is 0.1 to 0.6 μsec. Furthermore, field experimental results with the carrier frequency of 4.635 GHz show that the cell search time at the detection probability of 90% is approximately 10 msec in a course that is 800 to 1000 meters away from the cell site, even with the transmission power of the time-multiplexed CPICH (PDCH) of 0.06 W (0.13 W).