Modulation for coded light transmission
First Claim
1. A light driver (18) for driving at least one light source arranged to emit coded light based on a control signal, the light driver comprising:
- a receiver arranged to receive a sequence u=[u1, . . . , uk, . . . uK] of source symbols uk representing an information sequence of an information source;
a processing unit arranged to determine, from the sequence of source symbols, a sequence z=[z1, . . . , zk, . . . , zK] of channel symbols zk forming the control signal;
a transmitter arranged to provide the at least one light source with the control signal thereby driving the at least one light source;
wherein the processing unit is arranged to determine the sequence of channel symbols z by mapping each source symbol uk at time k to a composite channel symbol zk=(zk,1, zk,2) comprising at least one first channel symbol zk,1, one of which is identical to uk, and at least one second channel symbol zk,2 having a value chosen from a set M, wherein the value of zk,2 is determined according to a weighting function having the source symbol uk and at least one future and/or past source symbol ui, i≠
k as input arguments, the weighting function comprising at least two non-zero weighting factors, the mapping resulting in that the power spectral density at frequency zero of the sequence z of channel symbols is equal to zero, and whereinthe control signal thereby enables no visible flicker to be present in coded light emitted by the at least one light source.
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Accused Products
Abstract
Coded light has been proposed to enable advanced control of light sources and transmit information using light sources. Sequences of channel symbols to drive the light source are determined from sequences of source symbols such that no visible flicker is present in coded light emitted by the light sources. Each source symbol is mapped to a composite channel symbol comprising at least one first channel symbol which may be identical to the current source symbol and at least one second channel symbol which may be a function of the current source symbol and at least one future and/or past source symbol.
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Citations
18 Claims
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1. A light driver (18) for driving at least one light source arranged to emit coded light based on a control signal, the light driver comprising:
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a receiver arranged to receive a sequence u=[u1, . . . , uk, . . . uK] of source symbols uk representing an information sequence of an information source; a processing unit arranged to determine, from the sequence of source symbols, a sequence z=[z1, . . . , zk, . . . , zK] of channel symbols zk forming the control signal; a transmitter arranged to provide the at least one light source with the control signal thereby driving the at least one light source; wherein the processing unit is arranged to determine the sequence of channel symbols z by mapping each source symbol uk at time k to a composite channel symbol zk=(zk,1, zk,2) comprising at least one first channel symbol zk,1, one of which is identical to uk, and at least one second channel symbol zk,2 having a value chosen from a set M, wherein the value of zk,2 is determined according to a weighting function having the source symbol uk and at least one future and/or past source symbol ui, i≠
k as input arguments, the weighting function comprising at least two non-zero weighting factors, the mapping resulting in that the power spectral density at frequency zero of the sequence z of channel symbols is equal to zero, and whereinthe control signal thereby enables no visible flicker to be present in coded light emitted by the at least one light source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18)
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11. A method for driving at least one light source arranged to emit coded light based on a control signal, the method comprising:
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receiving a sequence u=[u1, . . . , uk, . . . , uK] of source symbols uk representing an information sequence of an information source; determining a sequence z=[z1, . . . , zk, . . . , zK] of channel symbols zk forming the control signal from the sequence of source symbols; providing the at least one light source with the control signal, thereby driving the at least one light source; wherein the sequence of channel symbols z is determined by mapping each source symbol uk at time k to a composite channel symbol zk=(zk,1, zk,2) comprising at least one first channel symbol zk,1, one of which is identical to uk, and at least one second channel symbol zk,2 having a value chosen from a set M, wherein the value of zk,2 is determined according to a weighting function having the source symbol uk and at least one future and/or past source symbol ui, i≠
k as input arguments, the weighting function comprising at least two non-zero weighting factors, the mapping resulting in that the power spectral density at frequency zero of the sequence z of channel symbols is equal to zero, and whereinthe control signal thereby enables no visible flicker to be present in coded light emitted by the at least one light source,
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Specification