Single-Anchor Two-Way Localization Bounds for 5G mmWave Systems: Two Protocols
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Recently, mmWave 5G localization has been shown to be a promising technology to achieve centimetre-level accuracy. This generates more opportunities for location-aware communication applications. One assumption usually made in the investigation of localization methods is that the user equipment (UE) and the base station (BS) are synchronized. However, in reality, communications systems are not finely synchronized to a level useful for localization. Therefore, in this paper, we investigate two-way localization protocols that avoid the prerequisite of tight time synchronization. Namely, we consider a distributed localization protocol (DLP), whereby the BS and UE exchange signals in two rounds of transmission and then localization is achieved using the signal received in the second round. On the other hand, we also consider a centralized localization protocol (CLP), whereby localization is achieved using the signals received in the two rounds. We derive the position (PEB) and orientation error bounds (OEB) applying beamforming at both ends and compare them to the traditional one-way localization. Our results obtained using realistic system parameters show that mmWave localization is mainly limited by angular rather than temporal estimation and that CLP significantly outperforms DLP. Our simulations also show that it is more beneficial to have more antennas at the BS than at the UE.
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