Performance evaluation of frequency and time domain correlators for spread spectrum receivers.

摘要

Software radios perform all digital signal processing via a programmable microprocessor or digital signal processor (DSP) as opposed to using application-specific integrated circuits (ASIC). Software implementations are becoming more and more attractive due to their flexibility to adapt to system and signal modernizations. The emphasis of this thesis is on studying correlators for software spread spectrum receivers. Correlators synchronize locally generated code replicas with the received signals. The correlation is a signal comparison tool and once receiver generates a local signal which is close enough to the incoming signal, it identifies the received code and received signal's misalignment, i.e., code phase.; In this thesis, we are studying several classes of frequency and time domain correlators. We analyze conventional frequency domain correlators and more advanced techniques such as shifting replica, reduced shifting replica and joint code-frequency methods. In time domain we study conventional matched filters (MF), "recursive MF"s and "Fast and Parallel MF"s (FPMF).; The performance of the correlators is evaluated by determining the execution time taken for correlation using the call graph collector of INTEL VTune performance analyzer. While time domain approaches are expected to perform very well on fixed-point computing platforms the frequency domain methods are mostly outperform them on floating-point processors. Frequency domain correlators perform better for complete code phases search scenario and time domain correlators perform better than frequency domain for limited code phases search for strong signals. For weak signals, joint code frequency approach is the best solution.