# US 8,570,221 B2 · Wireless localization techniques in lighting systems

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- Number: US 8,570,221 B2
- Document ID: US8570221B2
- Status: Granted
- Kind: B2
- Application number: 13/132,340
- Filed: 2009-11-16
- Published: 2012-01-19
- Granted: 2013-10-29
- Earliest claimed: 2008-12-05
- Assignees: Koninklijke Philips N.V.
- Applicants: Xingkai Bao; Sushanta Das; Monisha Ghosh
- Inventors: Xingkai Bao; Sushanta Das; Monisha Ghosh
- Web page: https://patentgrep.com/patent/US8570221B2

## CPC

- G01S 5/0263: {by combining or switching between positions derived from two or more separate positioning systems}
- H05B 47/19: via wireless transmission
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL

## Abstract

The invention relates to a system and method for localization positioning in lighting systems. At least two of a Time Difference of Arrival (TDOA), Angle of Arrival (AOA), Received Signal Strength Index (RSSI) and a Position Estimation Algorithm with unified TDOA and RSSI are used to obtain localization positioning. The schemes introduce a maximum-likelihood estimation strategy incorporating a partial derivative matrix for each lighting unit using at least two reference nodes in order to achieve higher accuracy.

## Claims

### Claim 1

A method for determining a location of at least one lighting unit in a lighting system, comprising:
transmitting a signal from the at least one lighting unit;
estimating the location of the at least one lighting unit using at least two localization protocols and a position estimation method;
recording at least one of a plurality of reference nodes a time-of-arrival signal from each of the at least one lighting units;
communicating the recording from the at least one of a plurality of reference nodes to each of the other reference nodes;
calculating at each of the reference nodes the distance-difference; and
providing the at least two localization protocols into a derivative matrix.

### Claim 2 (depends on 1)

The method of claim 1, wherein the partial derivative matrix comprises at least two sub-matrices,
a first sub-matrix including partial derivatives of a measured angle-of-arrival at the reference nodes of each of the at least one lighting units with respect to x and y location, and
a second sub-matrix including a partial derivative of a measured distance-difference at one of the reference nodes of a corresponding one of the at least one lighting units with respect to x and y location.

### Claim 3 (depends on 1)

The method of claim 1, wherein the partial derivate matrix is defined as:
G
=
(
A
B
)
.

### Claim 4 (depends on 3)

The method of claim 3, wherein the position estimation of each of the at least one lighting units is defined as:
(x,y)=(x*,y*)+(GTN−1G)−1GTN−1(r(x*,y*)).

### Claim 5 (depends on 1)

The method of claim 1, the reference nodes are located in a position elevated from ground level to provide an improved line-of-sight.

### Claim 6 (depends on 1)

The method of claim 1, wherein the position estimation algorithm is a maximum-likelihood position estimation algorithm.

### Claim 7 (depends on 1)

The method of claim 1, further comprising:
transmitting a data packet from the at least one lighting unit; and
estimating a signal strength of the data packet transmit by the at least one lighting unit and by each of the other at least one lighting units at a plurality of reference nodes.

### Claim 8 (depends on 7)

The method of claim 7, further comprising:
embedding the estimated signal strength into the data packet stored by the other at least one lighting units in proximity to the transmitting lighting unit;
estimating the time-of-arrival at the reference nodes and decoding the data packet to obtain information about each of the at least one lighting units;
sending the time-of-arrival and signal strength from the proximal at least one lighting unit to the reference nodes; and
calculating a position estimation for each of the at least one lighting units.

### Claim 9 (depends on 8)

The method of claim 8, further comprising:
recording at each of the reference nodes a time-of-arrival signal from each of the at least one lighting units;
communicating the recording at one of the reference nodes to each of the other reference nodes; and
calculating at each of the reference nodes the distance-difference.

### Claim 10 (depends on 9)

The method of claim 9, further comprising providing the at least two localization protocols into a partial derivative matrix.

### Claim 11 (depends on 10)

The method of claim 10, wherein the partial derivative matrix comprises at least three sub-matrices,
a first sub-matrix comprising partial derivatives of a measured distance-difference at each of the reference nodes with respect to x and y locations of a corresponding one of the at least one lighting units,
a second sub-matrix comprising partial derivatives of a measured signal strength between two of the at least one lighting units with respect to x and y location, and
a third sub-matrix comprising the signal strength between each of the at least one lighting units to each of the reference nodes.

### Claim 12 (depends on 10)

The method of claim 10, wherein the partial derivative is defined as:
G
=
(
A
B
C
)
.

### Claim 13 (depends on 12)

The method of claim 12, wherein the position estimation of each at least one lighting units is defined as:
(x,y)=(x*,y*)+(GTN−1G)−1GTN−1(r(x*,y*)).

### Claim 14 (depends on 9)

The method of claim 9, wherein the reference nodes are located in a position elevated from ground level to provide an improved line-of-sight.

### Claim 15 (depends on 1)

The method of claim 1, wherein the position estimation comprises:
estimating the location of each of the at least one lighting units using TDOA information; and
refining the location of each of the at least one lighting units using RSSI information from other of the at least one lighting units in proximity thereto.

### Claim 16 (depends on 15)

The method of claim 15, wherein the position estimation further comprises:
transmitting a signal including the signal strength and the RSSI information from each of the at least one lighting units;
recording the transmit time-of-arrival signal at each of the reference nodes from each of the at least one lighting units, and providing the recorded transmit time-of-arrival signal to each of the other reference nodes; and
estimating the position of each of the at least one lightings unit using the time-difference-of-arrival.

### Claim 17 (depends on 16)

The method of claim 16, wherein the position estimation further comprises:
producing a representative network connectivity graph and tanner graph, and message-passing, wherein information being message-passed in the tanner graph includes the location information with difference variance; and
computing the location of each of the at least one lighting unit connected to the reference nodes.

### Claim 18 (depends on 17)

The method of claim 17, further comprising providing the at least two localization protocols into a partial derivative matrix.

### Claim 19 (depends on 18)

The method of claim 18, wherein the refined position estimation is defined as:
(x,y)=(x*,y*)+(GiTN−1Gi)−1GiTN−1(r(x*,y*)),
wherein
(x,y) are the positions of node to be calculated;
(x*,y*) are the initial TDOA position estimates of nodes; and
‘G’ is the partial derivative matrix.

### Claim 20 (depends on 8)

The method of claim 8, wherein the position estimation algorithm is the maximum-likelihood estimation algorithm or the MMSE estimation algorithm.

### Claim 21

A lighting system for determining a location of at least one lighting unit, comprising:
at least one reference node estimating the location of the at least one lighting unit using at least two localization protocols and a position estimation method, wherein the at least one reference node:
records a time-of-arrival signal from each of the at least one lighting units;
communicates the recording from one of the at least one reference nodes to each of the other at least one reference nodes; and
calculates the distance-difference;
and wherein the at least two localization protocols are provided into a partial derivative matrix comprising at least two sub-matrices, a first sub-matrix including partial derivatives of a measured angle-of-arrival at the at least one reference node of each of the at least one lighting units with respect to x and y location, and a second sub-matrix including a partial derivative of a measured distance-difference at one of the at least one reference nodes of a corresponding one of the at least one lighting units with respect to x and y location.

### Claim 22 (depends on 21)

The system of claim 21, wherein the partial derivate matrix is defined as:
G
=
(
A
B
)
.

### Claim 23 (depends on 22)

The system of claim 22, wherein the position estimation of each of the at least one lighting units is defined as:
(x,y)=(x*,y*)+(GTN−1G)−1GTN−1(r(x*,y*)).

### Claim 24 (depends on 21)

The system of claim 21, wherein the at least one reference node is located in a position elevated from ground level to provide an improved line-of-sight.

### Claim 25 (depends on 21)

The system of claim 21, wherein the position estimation algorithm is a maximum-likelihood position estimation algorithm.

### Claim 26 (depends on 21)

The system of claim 21, wherein
the at least one lighting unit transmits a data packet, and
the at least one reference node estimates a signal strength of the data packet transmit by the at least one lighting unit and by each of the other at least one lighting units.

### Claim 27 (depends on 26)

The system of claim 26, wherein
the at least one lighting unit that is transmitting embeds the estimated signal strength into the data packet of the other at least one lighting units in proximity thereto,
the at least one reference node estimates the time-of-arrival and decodes the data packet to obtain information about each of the at least one lighting units,
the proximal at least one lighting unit sends the time-of-arrival and signal strength to the at least one reference node, and
the at least one reference node calculates a position estimation for each of the at least one lighting unit.

### Claim 28 (depends on 27)

The system of claim 27, wherein
the at least one reference node records a time-of-arrival signal from each of the at least one lighting units,
the at least one reference node communicates the recording to each of the other a least one reference nodes, and
the at least one reference node calculates the distance-difference.

### Claim 29 (depends on 28)

The system of claim 28, wherein the at least two localization protocols are provided into a partial derivative matrix comprising at least three sub-matrices,
a first sub-matrix comprising partial derivatives of a measured distance-difference at each of the at least one reference nodes with respect to x and y locations of a corresponding at least one lighting unit,
a second sub-matrix comprising partial derivatives of a measured signal strength between two of the at least one lighting units with respect to x and y location, and
a third sub-matrix comprising the signal strength between each of the at least one lighting units to each of the at least one reference nodes.

### Claim 30 (depends on 29)

The system of claim 29, wherein the partial derivative is defined as:
G
=
(
A
B
C
)
.

### Claim 31 (depends on 29)

The system of claim 29, wherein the position estimation of each at least one lighting unit is defined as
(x,y)=(x*,y*)+(GTN−1G)−1GTN−1(r(x*,y*)).

### Claim 32 (depends on 21)

The system of claim 21, wherein the at least one reference node is located in a position elevated from ground level to provide an improved line-of-sight.

### Claim 33 (depends on 21)

The system of claim 21, wherein the position estimation is calculated at the at least one reference node and comprises:
estimating the location of each of the at least one lighting units using TDOA information; and
refining the location of each of the at least one lighting units using RSSI information from other of the at least one lighting units in proximity thereto.

### Claim 34 (depends on 33)

The system of claim 33, wherein the position estimation calculation further comprises:
the at least one lighting unit transmitting a signal including the signal strength and the RSSI information;
the at least one reference node recording the transmit time-of-arrival signal from each of the at least one lighting units, and providing the recorded transmit time-of-arrival signal to each of the other reference nodes; and
the at least one reference node estimating the position of each of the at least one lighting units using the time-difference-of-arrival.

### Claim 35 (depends on 34)

The system of claim 34, wherein the position estimation calculated at the at least one reference node further comprises:
producing a representative topology graph and tanner graph, and message-passing, wherein information being message-passed in the tanner graph includes the location information with difference variance; and
computing the location of each of the at least one lighting unit connected to the at least one reference node.

### Claim 36 (depends on 35)

The system of claim 35, wherein the at least two localization protocols is provided into a partial derivative matrix.

### Claim 37 (depends on 36)

The system of claim 36, wherein the refined position estimation is defined as:
(x,y)=(x*,y*)+(GiTN−1Gi)−1GiTN−1(r(x*,y*)),
wherein
(x,y) are the positions of node to be calculated;
(x*,y*) are the initial TDOA position estimates of nodes; and
‘G’ is the partial derivative matrix.

### Claim 38 (depends on 21)

The system of claim 21, wherein the position estimation algorithm is the maximum-likelihood estimation algorithm or the MMSE estimation algorithm.