About the Authors

Shao-Meng Qin

Affiliation Aalto University, Department of Applied Physics, Espoo, Finland

Hannu Verkasalo

Affiliations WR WIRELESS RESEARCH Ltd, Espoo, Finland, Zokem Ltd, Espoo, Finland

Mikael Mohtaschemi

Affiliation Aalto University, Department of Applied Physics, Espoo, Finland

Tuomo Hartonen

Affiliation Aalto University, Department of Applied Physics, Espoo, Finland

Mikko Alava

mikko.alava@aalto.fi

Affiliation Aalto University, Department of Applied Physics, Espoo, Finland

Competing Interests

The authors have the following interests. Author H.Verkasalo was affiliated with WR WIRELESS RESEARCH Ltd, but is now affiliated to Zokem Ltd (since acquired by Arbitron Inc.). There are no patents, products in development or marketed products to declare. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials, as detailed online in the guide for authors.

Author Contributions

Conceived and designed the experiments: SQ HV MM TH MA. Performed the experiments: SQ HV MM TH MA. Analyzed the data: SQ MM TH MA. Contributed reagents/materials/analysis tools: SQ HV MM TH MA. Wrote the paper: SQ MM TH MA.