Investigation and Demonstration of Local Positioning System Using Ultrasonic Sensors for Wide Indoor Areas. - Takashi Hada; Hikaru Sunaga; Masaki Akiyama; Shigenori Ioroi; Hiroshi Tanaka (AmI, 2010)

Discrimination of Multiple Objects and Expanding Positioning Area for Indoor Positioning Systems Using Ultrasonic Sensors. - Hikaru Sunaga; Takashi Hada; Masaki Akiyama; Shigenori Ioroi; Hiroshi Tanaka (AmI, 2011)