Multicarrier DS-SS for GPS pseudolites: code-acquisition performance in the presence of data modulation

We analyze the code acquisition performance of a multicarrier direct-sequence spread spectrum (DS-SS) system in the presence of data modulation (i.e., no pilot) on multipath Rayleigh fading channels. The motivation of this analysis arises from the possibility of beneficially using multicarrier DS-SS in Global Positioning System (GPS) pseudolites, where an unmodulated pilot is not available. Pseudolites are small, ground-based transmitters that emulate the signal structure of the GPS satellite transmitters, with the intention of augmenting the system performance. We consider equal gain combining (EGC) and selection combining (SC) of subcarrier correlator outputs for each timing hypothesis. We evaluate the probability of incorrect decision and mean acquisition time performance of the multicarrier DS-SS code acquisition scheme. We show that significant reduction in the mean acquisition time (MAT) can be achieved using the multicarrier DS-SS approach for GPS pseudolites.