Performance of DS code acquisition in static and fading multipath channels

The author introduces analytical results of a direct sequence (DS) spread spectrum code acquisition, which is performed using a matched filter in a multipath channel. The performance measure is the mean acquisition time, T_MA. Equations for the mean acquisition times as a function of the number of propagation paths and the number of uncertainty cells are derived for a static channel. A novel approach to apply the equations to a slowly, Rayleigh fading channel is presented. Constant false alarm rate (CFAR) criteria are used as the threshold setting rule. Two cases are investigated: the effect of power difference of the multipaths and the effect of the number of multipaths. The results indicate that the worst performance in a static channel is obtained when the paths have equal power. The acquisition performance decreases as the number of paths increases. Also, the sensitivity to the threshold value is larger in the multipath case. In a slowly fading channel, the mean acquisition time in the multipath channel is shorter than in the one-path channel. The case of equal average power of the paths leads to the best result as opposite to a static channel. The advantage of selection diversity is therefore obtained in a frequency-selective fading channel