Signal map 

@article{mostofi2011compressive,
  title={Compressive cooperative sensing and mapping in mobile networks},
  author={Mostofi, Yasamin},
  journal={Mobile Computing, IEEE Transactions on},
  volume={10},
  number={12},
  pages={1769--1784},
  year={2011},
  publisher={IEEE}
}


Signal map (probably not used as related just source)

Estimate and update location

@article{yin2008learning,
  title={Learning adaptive temporal radio maps for signal-strength-based location estimation},
  author={Yin, Jie and Yang, Qiang and Ni, Lionel M},
  journal={Mobile Computing, IEEE Transactions on},
  volume={7},
  number={7},
  pages={869--883},
  year={2008},
  publisher={IEEE}
}