Impact of Hardware Synchronization Impairments on 5G Uplink Time-of-Flight Measurements using OpenAirInterface

This study examines the impact of User Equipment (UE)-to-Next Generation Node Base (gNB) synchronization on Time of Flight (ToF)-based localization in 5th generation (5G) networks. First, a method for measuring the UE-to-gNB overall ToF delay is introduced, leveraging the Timing Advance (TA) command and Sounding Reference Signals (SRSs). The impact of key synchronization factors, such as clock drift and reception/transmission (RX/TX) timing delays, on ToF measurements and positioning accuracy is thoroughly analyzed. To quantify the effect of these localization impairments on 3GPP-compliant devices, an experimental campaign was conducted using the OpenAirInterface (OAI) platform. Field data were collected to assess errors in UE-to-gNB distance estimation. The results show that after estimating and compensating for RX/TX timing delays, the distance error remains within 3.8m in 95% of cases in a line-of-sight (LoS) urban scenario.