Receiver Operating Characteristics of GNSS Coarse/Acquisition Signals With Short Codes
Reliable signal acquisition with low computational complexity is an important design objective for the evolution of global navigation satellite systems (GNSS).
Most GNSS signals consist of long pseudorandom noise (PRN) codes whose acquisition is expensive in terms of memory, computation time, and energy. As these resources are particularly scarce in the emerging mass-market user segment, dedicated coarse/acquisition (C/A) signals with short codes are being designed to keep the number of acquisition search bins low.
However, reducing the code length degrades the receiver operating characteristic (ROC), as multiple access interference (MAI) from other C/A signals increases the probability of false alarm.
MAI complicates the C/A signal design process considerably, because (quite different from stationary noise) it does not affect each bin of the search space in the same way.
Taking into account the cyclostationarity of C/A signals, we propose a new randomized version of the spectral separation coefficient (SSC) as a simple yet accurate interference measure, which can be used for ROC performance evaluation and optimization.
Accounting for MAI and other random degradation effects (e.g. data symbol transitions or finite search resolution), we establish a new methodology to assess the ROC for shorter and shorter PRN codes. Ultimately, our approach enables the C/A signal designer to minimize the PRN code length while ensuring a given target ROC performance.