Table 9.

Main features of state-of-the-art indoor positioning systems.

System	Scenario	Technology	Accuracy (Average Error)
LIPS [62]	Buildings	Wi-Fi	∼0.76 m
SDM [63]	Small building (598 m${}^2$)	Wi-Fi	∼3 m
OIL [64]	Area with four rooms	Wi-Fi	Order of meters
EZ [65]	Small (486 m${}^2$) and big buildings (12,600 m${}^2$)	Wi-Fi	∼2 m (small) and 7 m (big)
WiGEM [66]	Small (600 m${}^2$) and medium (3,250 m${}^2$) buildings	Wi-Fi	<8 m
WILL [67]	Medium academic buildings (1,600 m${}^2$)	Wi-Fi	86% room level accuracy
UnLoc [68]	Different setups (largest 4,000 m${}^2$)	Wi-Fi and inertial sensors	∼1.69 m
Zee [69]	Medium sized building (2,275 m${}^2$)	Wi-Fi	∼3 m together with EZ or Horus.
LiFS [70]	Medium sized building (1,600 m${}^2$)	Wi-Fi	89% room level accuracy
Walkie-Markie [71]	Medium size office (3,600 m${}^2$) and shopping mall	Wi-Fi	∼1.65 m
RADAR [72]	Area 975 m${}^2$, more than 50 rooms	Wi-Fi	∼3–5 m
Horus [73]	4th floor of the Computer Science building	Wi-Fi	∼3–5 m
AiRISTA Flow [74]	Asset tracking	Wi-Fi	∼1 m
IZat [75]	Automotive	Wi-Fi, GPS, 4G	∼5 m
Ubisense [76]	Smart factory	UWB	∼15 cm
Dart [77]	Manufacturing	UWB	∼30 cm
3D-LOCUS [78]	Laboratory	Ultrasound	∼8 mm
Elpas [79]	Healthcare and commercial	IR, UHF and LF RFID	∼1 m
SpotON [80]	Laboratory	Active RFID	∼3 m
Topaz [81]	Areas of ∼1000 m${}^2$	Bluetooth+IR	2–3 m
Landmarc [82]	Laboratory	Active RFID	<2 m
Sparse distribution [83]	Not specified	Passive RFID	<10 cm
GPs [84]	Area of 1600 m${}^2$ (55 rooms)	Active RFID	∼1.5 m
Robotics-based [85]	3rd floor of Duncan Hall at Rice University	Wi-Fi	∼1.5 m
MultiLoc [86]	4th floor (more than 10 rooms)	Wi-Fi	∼2.7 m
Zigbee IPS [87]	Engineering building 7.26 × 16.5 m${}^2$	Zigbee	∼3.01 m
TIX [88]	Office (1020 m${}^2$)	Wi-Fi	∼5.4 m
BLE fingerprinting [89]	Office (600 m${}^2$)	BLE	<2.6 m, high beacon density
GSM fingerprinting [90]	Large multi-floor buildings	GSM	∼5 m
NDI [91]	Industry and healthcare	Infrared (3D)	0.1 mm
IRIS_LPS [92]	Lecture hall (100 m${}^2$)	Infrared + stereo camara	<16 cm
Bat [93]	Building (1000 m${}^2$), three floors	Ultrasound	3 cm
Cricket [94]	Different rooms	RF + Ultrasound	10 cm, orientation accuracy 3${}^{\circ }$
Sonitor [95]	Healthcare	Ultrasound, Wi-Fi and LF	Room level accuracy
COMPASS [96]	Office building (312 m${}^2$)	Wi-Fi, no real-time tracking	∼1.65 m
OPT [97]	Context aware app in personal network	IEEE 802.15.4	1.5–3.8 m
Easy Living [98]	In-home and in-offices	Multiple tech	Accuracy non guaranteed
Beep [99]	Room 20 × 9 m${}^2$: users can use their own devices	Sound source location	0.4 cm