Time-of-arrival estimation algorithm for positioning in NB-IoT physical layer

In this study, the authors propose a new time-of-arrival (ToA) algorithm for positioning in the physical layer of narrowband Internet-of-Things (NB-IoT) technology. This algorithm estimates the ToA of transmitted narrowband positioning reference signals (NPRSs) by detecting the first valid tap of estimated power delay profile (PDP). They estimate the PDP as well as the noise power in the time domain via inverse Fast Fourier transformation of received frequency-domain NPRSs. The accuracy of the estimated noise power is crucial in the ToA estimation since the SNR is extremely low in typical NB-IoT scenarios. The simulations show that the proposed ToA estimation method outperforms the conventional method and performs well in various scenarios.