ICUFN-TDoA Based Indor Visible Light Positioning System

8/12/2019 ICUFN-TDoA Based Indor Visible Light Positioning System

http://slidepdf.com/reader/full/icufn-tdoa-based-indor-visible-light-positioning-system 1/19



Current approaches for indoor positioning

There is no standard technique for indoor positioning

Problem with current techniques

Availability

Security

Safety

Cost

Using visible light can overcome these limitations

1

ULTRA SOUND



Basis concept of indoor visible light positioning systemMobile node uses received signals from multiple transmitters to locate its own position

Pilot signals are visible light

Transmitters are LED lamps installed on the ceiling

Mobile node uses photo diode or image sensor to receive light

2



Advantage of using visible light for indoor positioningAlways available

Visible light is free

Lighting systems are installed in every building

High secure

The visible light cannot go beyond the roomSafe

Safe for using in hospital, airplanes or hazardous environments

Low cost

LED chips are inexpensive and has long lifetime

The system undertakes both function of positioning and illuminating

3



Candidate for indoor visible light positioning techniqueReceived signal strength (RSS)

Low accuracy due to complicated effects of reflections in the room

Time of arrival (TOA)

Require the synchronization between transmitter and receiver (difficult)

Angle of arrival (AOA)Can achieve high accuracy

But require deploying an array of image sensors (expensive)

Time difference of arrival (TDOA)

Only synchronization between transmitters is required (easy)

Just require to use a single photo diode at receiver (inexpensive)

Reflected light has small impact on the accuracy

4



TDOA positioning in 2DMathematical background

A hyperbola is a locus of pointswhere the absolute value of thedifference of the 2D-distancesto the two foci is a constant.

Positioning from TDOA

3 anchors with knows positions

(at least) are required to find a2D-position from a couple ofTDOAs

5

r1

Anchor 2

Anchor 3

Anchor 1

r2

r3

r3-r1

r3-r2



TDOA positioning in 3DMathematical background

A hyperboloid is a locus of pointswhere the absolute value of thedifference of the 3D-distances tothe two foci is a constant.

Positioning from TDOAs

4 anchors with knows positions (at

least) are required to find a3D-position from a couple ofTDOAs

6



Lighting placement

7



Pilot signal generation schemeEach LED panel transmits a single square pulse of signal after aguard time period

All signals have the same pulse width

All signals have the same guard time period

8



Detection methodReceived signal is a series of pilot signals

Cross-correlation is used to detect each single signal in this series

9



Estimate receiver’s position with known signal IDTime differences of arrival is obtained by using cross-correlation

Distance difference from receiver to two transmitters specifies aunique hyperboloid that the receiver lies in

These hyperboloids intersect with the Z-plane of receiver height

and creates a unique conic in 2-D plane containing the receiver

10



Estimate receiver’s position without knowing signal ID When a series of signals is received, the possible ID combinations of these signals can be guessed

There is only N possible combinations of signal ID if N LED panelsare used

With K received pilot signals, there are K-1 time differencesK-1 conics that the receiver lies in are found

There are up to intersections can be found

If combination of signal ID is correct, these intersection are converged

Otherwise, these intersections are diverged

11

1

2

K



Estimate receiver’s position without knowing signal ID

12



Simulation environment

13



Simulation results

At most region in the room, the estimation error is less than 10cm

The average distance error is 3.6cm

14



Observation through the simulationThe error is greater when the signal is weaker

This is because the stronger pulse can be detected with less error

The error is greater at the corner than that at the center

This is because the conics specified by TDOA is more curve at the

corner than at the center

15

Stronger pulses can be detected with less errorThe conic get curved when the receiver moves

away from the bisector of two transmitters.



Solution to reduce estimation errorOnly use strongest signals

Move transmitter nearer to the corner

16



17



ICUFN-TDoA Based Indor Visible Light Positioning System

Documents