Optimal search resolution for single dwell serial-search code phase acquisition in DS-SpSp
Jacob Scheim · 2005
We address the problem of optimal search granularity for a code phase acquisition system in direct-sequence spread-spectrum communication (DS-SpSp). We do this by testing the acquisition systems' performance in terms of the mean acquisition time and variance as a function of the search step size. Apparently, the following tradeoff exists: in a code sequence of length N chips, chip duration, T/sub c/, and search step size, /spl Delta/T, reducing /spl Delta/T usually improves the detector performance, while delaying the whole search process (acquisition time), due to the higher number of hypotheses (m=/spl lceil/N//spl Delta/T/spl rceil/) to be tested, and the processing time required for each hypothesis. This tradeoff points towards the existence of an optimal setting of /spl Delta/T that minimizes the mean acquisition time. An analytical derivation of the mean acquisition time and variance as a function of /spl Delta/T for a coherent acquisition system is carried out. It is shown that, in contrast to some conventional approaches that choose /spl Delta/T=T/sub c//2/sup k/, k=1,2,3... to increase the search granularity, the optimal /spl Delta/T that minimizes the acquisition time is /spl sim/T/sub c/. Furthermore, choosing /spl Delta/T=T/sub c//2/sup k/, k = 1,2,3.... might severely degrade the mean acquisition time and variance by up to a factor of three.