@conference {, title = {Reduction of Ultrasonic Indoor Localization Infrastructure based on the use of Graph Information}, booktitle = { 2016 International Conference on Indoor Positioning and Indoor Navigation (IPIN-2016).}, year = {2016}, month = {10/2016}, pages = {1-10}, publisher = {IEEE}, organization = {IEEE}, address = {Alcala de Henares, Espa{\~n}a }, isbn = {978-1-5090-2424-7}, author = {Gualda, D and Ure{\~n}a, J. and JC.Garcia and JM. Alcal{\'a} and A. Noburo} }