  In this article, we design a new time-of-arrival (TOA) system for
simultaneous user device (UD) localization and synchronization with a periodic
asymmetric ranging network, namely PARN. The PARN includes one primary anchor
node (PAN) transmitting and receiving signals, and many secondary ANs (SAN)
only receiving signals. All the UDs can transmit and receive signals. The PAN
periodically transmits sync signal and the UD transmits response signal after
reception of the sync signal. Using TOA measurements from the periodic sync
signal at SANs, we develop a Kalman filtering method to virtually synchronize
ANs with high accuracy estimation of clock parameters. Employing the virtual
synchronization, and TOA measurements from the response signal and sync signal,
we then develop a maximum likelihood (ML) approach, namely ML-LAS, to
simultaneously localize and synchronize a moving UD. We analyze the UD
localization and synchronization error, and derive the Cramer-Rao lower bound
(CRLB). Different from existing asymmetric ranging network-based TOA systems,
the new PARN i) uses the periodic sync signals at the SAN to exploit the
temporal correlated clock information for high accuracy virtual
synchronization, and ii) compensates the UD movement and clock drift using
various TOA measurements to achieve consistent and simultaneous localization
and synchronization performance. Numerical results verify the theoretical
analysis that the new system has high accuracy in AN clock offset estimation
and simultaneous localization and synchronization for a moving UD. We implement
a prototype hardware system and demonstrate the feasibility and superiority of
the PARN in real-world applications by experiments.
