RF Replay System for Narrowband GNSS IF Signals

Although global navigation satellite systems (GNSS) radio frequency (RF) signal simulators have long possessed the capability to generate scenarios, they are, for example, not yet able to model a specific realistic scenario with complex multipath. Software-defined receivers bridge the gap between simulated and real data to the extent that they may offer a replay capability, where a data set is first recorded to disk and later can be processed several times. Unfortunately the recorded data generally cannot be used by hardware-based GNSS receivers, making receiver-to-receiver comparisons difficult and time consuming. A system capable of replaying recorded IF data into any narrow bandwidth L1 (the frequency band of the traditional civilian GPS signal) GNSS receiver is described here, including an evaluation of the difference (position, timing, and signal-to-noise ratio (SNR)) between live and replayed data using a high sensitivity, consumer-grade receiver. The performance of the replayed data set was, with regards to the position and timing, found to match that of the live data.