Quantification of timing uncertainty in a correlation based channel sounder

Abstract

Untethered radio channel sounders use stable frequency standards to synchronize physically separated transmitters and receivers, allowing for practical propagation measurements in complex environments such as cities, factories, and offices. In this paper, measurements of the timing-uncertainty of an untethered, correlation-based channel sounder are presented. Timing results are characterized using both deterministic predictions of timing-drift, as well as analysis of timing-noise using the modified Allan deviation. The 1-6 GHz, correlation-based channel sounder used in this experiment uses a pair of rubidium clocks to provide synchronization between the transmitter and receiver. Measurements of up to 7 days in length were made to determine the long-term behavior of the timing system. We show that the use of rubidium clocks, common to many channel sounders, introduces both deterministic drift as well as several forms of timing noise into channel sounding measurements. This work extends upon existing literature by providing measurements of both timing drift and timing noise, using multiple system configurations, over long test durations.