1. Department of Control and Computer Engineering, Politecnico di Torino, 10129 Turin, Italy
2. Interuniversity Department of Regional and Urban Studies and Planning, Politecnico di Torino, 10129 Turin, Italy
3. Department of Electrical, Electronic and Information Engineering, University of Bologna, 40136 Bologna, Italy
4. Department of Information Technology and Electrical Engineering, ETH Zurich, 8092 Zurich, Switzerland