1. CSI 5169 --- Wireless Networks and Mobile Computing
Indoor Localization
Zhang Zhang

2. Outline Introduction Definition Important parameters
Indoor Localization Methods
Proximity Detection
Triangulation
Scene Analysis
Indoor Localization Systems
Proximity Based
RF Based
Cameras Based
Comparison of Common Indoor Localization Systems

3. Introduction - Defination
Def. Wirelessly locate objects or people inside a building in real time.
Indoor Positioning Systems (IPS)
Real-time Locating Systems (RTLS)

4. Introduction - Important Parameters
Accuracy
Coverage
Availability
Update Rate
Line of Sight (LoS) and Non Line of Sight (NLoS)
Costs and System Complexity

5. Introduction - LoS / NLoS
Line of Sight (LoS) and Non Line of Sight (NLoS)

6. Indoor Localization Methods / Algorithm

7. Methods / Algorithm - Proximity / Cell of Origan
Proximity Detection: Sensors detect and measure reflected Infrared or
visiable light or RF wave to detect the presence of
an object or person in certain areas.
Highest Received Signal Strength = Highest Probability

8. Methods / Algorithm - Proximity / Cell of Origan
Advantages
No complicated algorithms
Easy to implement
Low cost
Disadvantages
Low accuracy - room level
Identification problem

9. Methods / Algorithm - Time based
ToA: Time of Arrival
The precise measurement of the arrival time of a signal transmitted
from a mobile device to several receiving sensors.
The distance between the mobile device and each receiving sensor
can be determined.

10. Methods / Algorithm - Time based - ToA
Advantages
High Accuracy
2D / 3D
Disadvantages
Precise time synchronization (1 micro-second, 300m error)
Solutions are typically challenged in environments where a
large amount of multipath or interference may exist.

11. Methods / Algorithm - Time based - TDoA
TDoA: Time Difference of Arrival
Using relative Arrival time measurements at each receiving sensor
The synchronization between tag and each sensor is not necessary
Example:
TXC - TXA = 10-8s
TDoAC_A
TXB - TXA = 10-7s
TDoAB_A

12. Methods / Algorithm - Angle based - AoA
AoA/DoA: Angle of Arrival / Direction of Arrival (DoA)
Determining the angle of incidence at which signals arrive at the receiving sensor.

13. Methods / Algorithm - Angle based - AoA
More sensors = Higher accuracy

14. Methods / Algorithm - Angle based - AoA
Advantages
No synchronization requirement
Works well in situations with direct line of sight
Disadvantages
Susceptibility to multipath interference

15. Methods / Algorithm - Signal Property Based
Signal attenuation can be exploited for distance estimation.

16. Methods / Algorithm - Signal Property Based
RSS: Based on the attenuation model, the Received Signal Strength can be used to estimate the distanced of a person or a mobile object.
PR: Received signal strength at the receiver
PT: Transmitted power strength at the emitter
GT GR: Antenna gains of transmitter and receiver
d: Distance
P: The path loss factor

17. Methods / Algorithm - Signal Property Based
The path loss factor (P) is related to the environmental conditions
P = 2 for free space
P > 2 for environments with NLoS multipath
P ≈ (4 - 6) for typical indoor environments
In real world application, interference, multipath propagation and presence of obstacles and people leads to a complex spatial distribution of RSS.
RSS Indicator (RSSI): averaged PR over a certain sampling period

18. Methods / Algorithm - Fingerprinting
Off-Line

19. Methods / Algorithm - Fingerprinting
M(-35, -50, -48, -60, -58,-24) vs. Database

20. Methods / Algorithm - Fingerprinting
Advantages
High accuracy
NLoS
Disadvantages
Complicated algorithms
Not easy to implement
High cost

21. Indoor Localization Systems

22. RSSI Fingerprinting , TDoA
Indoor Localization Systems - WIFI
WIFI: (a superset of IEEE standard) can be used to estimate
the location of a mobile device within this network.
WIFI
Range
50-100m
Accuracy 1m
Method
RSSI Fingerprinting , TDoA
NLOS/LOS
NLOS
Application
Office Space,
Person, Objects

23. RSSI Fingerprinting, TDoA
Indoor Localization Systems - RFID
RFID (Radio Frequency IDentification) system consists of readers with antennas which interrogates nearby active transceivers or passive tags.
RFID
Active
Passive
Range
10-100m
1-5m
Accuracy 1m
0.2m
Method
RSSI Fingerprinting, TDoA
AoA, TDoA
NLOS/LOS
NLOS
LOS
Application
Moving Objects
Assembly Industry

24. Indoor Localization Systems - ZigBee
ZigBee is a wireless technology particularly designed for applications which demand low power consumption and low data transmission.
ZigBee
Range
20-30m
Accuracy 2m
Method
RSSI
NLOS/LOS
NLOS
Application
Warehouse management

25. Indoor Localization Systems - Cameras
Images → Cameras
Cameras → Database
Database → Virtual Map

26. Systems
Accuracy
Coverage
Methods
NLoS/Los
Power Consume
Cost
Remarks
GPS
10-50m
Poor Indoor
ToA
NLoS
High
Unstable
Proximity
3-5m
Room level
LoS
Low
ID?
Cameras Networks
0.5m
Building level
Scene Analysis
WIFI 1m
RSSI Fingerprinting
/TDoA
WIFI Covered
RFID
(Active)
Med
Long 
Distance
(Passive)
0.2m
TDoA/ AoA
No Data Exchange
Bluetooth
1-2m
High Data
Rate
ZigBee 2m
Low Data Rate

27. References
[1] Z. Farid, R. Nordin, and M. Ismail, "Recent Advances in Wireless Indoor Localization Techniques and Systems," Journal of Computer Networks and Communications, vol. 2013, 2013.
[2] R. Mautz, "Indoor positioning technologies," Habilitation Thesis, Department of Civil, Environmental and Geomatic Engineering, Institute of Geodesy and Photogrammetry, Habil. ETH Zürich, Zurich, 2012.
[3] H. Koyuncu and S. H. Yang, "A survey of indoor positioning and object locating systems," IJCSNS International Journal of Computer Science and Network Security, vol. 10, pp , 2010.
[4] A. Aboodi andW. Tat-Chee, “Evaluation ofWiFi-based indoor (WBI) positioning algorithm,” in Proceedings of the 3rd FTRA International Conference on Mobile, Ubiquitous, and Intelligent Computing (MUSIC ’12), pp. 260–264, June 2012.
[5] S. Chan and G. Sohn, ¡°Indoor localization using Wi-Fi based fingerprinting and trilateration techiques for LBS applications,¡± in Proceedings of the 7th International Conference on 3D Geoinformation, Quebec, Canada, May 2012.

28. Question 1 5 2 1 3 4 The RSSI pattern is shown below. 3 Wifi routers
9 refernces points
Q: Where is M(1.2, 2.6, 4.5) in this pattern? 5 2 1 3 4

29. Question 1 5 2 1 3 4 Q: Where is M(1.2, 2.6, 4.5) in this pattern?
A: Measured RSSI of Wifi one is 1.2.
Red zone (referenced RSSI of Wifi one is 1) are possible locations. 5 2 1 3 4

30. Question 1 5 2 1 3 4 Q: Where is M(1.2, 2.6, 4.5) in this pattern?
A: Measured RSSI of Wifi two is 2.6.
Green zone (referenced RSSI of Wifi two is 3) are possible locations. 5 2 1 3 4

31. Question 1 The intersection of three zones is the location of M. 5 2 1
Q: Where is M(1.2, 2.6, 4.5) in this pattern?
A: Measured RSSI of Wifi three is 4.5.
Blue zone (referenced RSSI of Wifi two is 5) are possible locations.
The intersection of three zones is the location of M. 5 2 1 3 4

32. Question 2 5 2 1 3 4 The RSSI pattern is shown above. 3 Wifi routers
9 refernces points
Q: Where is M(5, 2, 1) in this pattern?
Is there any methods to increase the acceracy by optimizeing the system? 5 2 1 3 4

33. Question 2
Q: Is there any methods to increase the acceracy of this system?
A: More Wifi routers, more reference points. 1 2 4 3

34. Question 3 A company with 3 buildings.
Building A: Working Office (Wifi coverd)
Building B: Assembly lines
Building C: Warehouse
Q: Building A: Locating persons + high rate data transmission
Building B: Accurate positioning products + no data transmission
Building C: Locating forklifts + low rate data transmission
Which indoor localization system will you choose for Building A, Building B,
Building C, respectively? why?

35. Question 3 A company with 3 buildings.
Building A: Working Office (Wifi coverd)
Building B: Assembly lines
Building C: Warehouse
Q: Building A: Locating persons + high rate data transmission
Building B: Accurate positioning products + no data transmission
Building C: Locating forklifts + low rate data transmission
Which indoor localization system will you choose for Building A, Building B,
Building C, respectively? why?
Answers:
A: WIFI. Wife covered, high data rate, mobile phone.
B: RFID(Passive). Small tag size, high acceracy, low cost.
C: ZigBee. Low power consumption, low cost, low data rate

36. Thank you!