Rotate and Guide: Accurate and Lightweight Indoor Direction Finding Using Smartphones.

Today's localization technologies are multitudinous. Resear chers solve the indoor localization problems using diverse methods and equipments. Nowadays, we are still seeking the solutions to the indoor localization problems which have to be precise, efficient and lightweight. Unlike most localization techniques that require either specialized devices or extensive preparations, we propose a novel scheme to find the direction of target anchor points using common smartphones. Ourmethod is derived from a key insight: by moving a smartphone in regular patterns, we can effectively emulate the sensitivity and functionality of an Uniform Circular Array to estimate angle of arrival of target signal. In other words, a user only needs to hold his/her smartphone still in front of him/her, and rotate his/her body around 360. duration with the smartphone. Then our system will provide accurate directional guidance and leads the user to their destinations (normal loudspeakers we preset in the indoor environment transmitting the high frequency acoustic signals) after a few measurements. Major challenges in implementing our system are not only imitating a virtual antenna array by ordinary smartphone but also overcoming the complex indoor environment. We propose rigorous algorithms to address these challenges, and then design and deploy our system in an underground parking lot and a shopping mall. Extensive comparative experiments show that our system is efficient and accurate under various circumstances.