Channel measurements and performance of indoor time-of-arrival localization at 5GHz

We perform a novel indoor channel measurement campaign to characterize the channel impairments for time-of-arrival (ToA) localization. We use precisely calibrated and time-synchronized RF equipment for transmitting and receiving 10 MHz and 100 MHz bandwidth waveforms over the 5.5 GHz DFS band in line-of-sight (LOS) and non-LOS environments. We collect ToA bias statistics with respect to a direct LOS path, where the bias is caused by multipath and NLOS reflections. Indoor wall reflections create significant ToA bias error of up to a couple hundred nanoseconds, corresponding to a positive ranging error of several tens of meters. We show how the WINNER II channel model, commonly used for communications simulations, is not suitable for ToA localization due to the improperly modeled signal timing and unrealistically low bias. The bias statistics based on our measurements are used for simulations of a ToA localization system using conventional and probabilistic multilateration algorithms. We present numerical results which provide insights for system design and performance-cost tradeoffs with regard to infrastructure density and signal bandwidth.