Opportunistic indoor localization and navigation using wireless LAN (802.11 a/g) signals

The Global Positioning System (GPS) has been the main method for wireless localization and navigation. However, its application is constrained when the GPS signals is unavailable in indoor, metropolitan and heavy-foliage scenarios. Therefore, we need to exploit the terrestrial wireless signal for positioning and navigation. In Hhis paper, we apply the wireless local area network (WLAN) IEEE 802.11a/g signals for time-difference-of-arrival (TDoA) based ranging and localization. We propose a simple model-based time-of-arrival (ToA) estimation approach. In this approach, the channel impulse response (CIR) is recovered with a simple equally-spaced model. Then, the delay of channel path is estimated by minimizing the energy leakage from the first path. Compared with the widely adopted space alternating generalized expectation maximization (SAGE) algorithm, the model-based approach has the advantage of lower complexity. Simulation results show that the model-based approach can achieve similar performance as the SAGE algorithm. Based on this ToA estimator, we realize the TDoA-based and TDoA-Doppler hybrid localization algorithms. Simulations are also carried out to corroborate our theoretical analysis.