1. Department of Computer Science and Industrial Engineering, University of Lleida, Jaume II 69, 25001 Lleida, Spain
2. Signal and Information Processing for Sensing Systems, Institute for Bioengineering of Catalonia, Baldiri Reixac 10-12, 08028 Barcelona, Spain
3. Department of Electronics, University of Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain