@inproceedings{liu2015footstep,
  title={FootStep-Tracker: An Anchor-Free Indoor Localization System via Sensing the Foot Steps},
  author={Chang Liu and Lei Xie and Chuyu Wang and Jie Wu and Sanglu Lu},
  booktitle={Proceedings of ACM international conference on Ubiquitous computing},
  year={2015},
  publisher={ACM}
}