Interference-robust coded-modulation scheme for optical communications and method for modulating illumination for optical communications

• US 20020071161A1
• Filed: 12/08/2000
• Published: 06/13/2002
• Est. Priority Date: 12/08/2000
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Perkins, Matthew R., Stengel, Robert E., Allen, Vernon A.
• Granted Patent: US 6,542,270 B2
• Time in Patent Office: Days
• US Class Current: 398/118
• CPC Class Codes: G01S 1/7038 Signal details
• CPC Class Codes: G01S 2201/02 Indoor positioning, e.g. in covered car-parks, mining facilities, warehouses
• CPC Class Codes: H04B 10/114 Indoor or close-range type systems
• CPC Class Codes: H04B 10/116 Visible light communication
• CPC Class Codes: H05B 47/195 the transmission using visible or infrared light

Abstract

An interference-robust coded-modulation scheme for optical communications and a method for modulating illumination for optical communications include optical signal transmitters connected to signal multipliers. The signal to be transmitted is multiplied by a pseudo-random noise code and transmitted within the transmitter emissions. A receiver converts the received modulated light and correlates the received signal. An estimate of the signal to be transmitted is made by multiplying the received signal by the noise code and correlating such multiplication over the length of the code. A threshold switch outputs the correlation result to a bit estimator approximately when a deterministic peak of the output signal exceeds a threshold.

Claims

1. A method for communicating an optical signal, which comprises:

providing at least one optical transmitter for generating an illumination state based upon at least one input signal;

changing the illumination state by generating the at least one input signal from a supplied signal multiplied by a given code having a length; and

correlating at least one received illumination state in an optical receiver by;

multiplying the at least one received illumination state by the given code to generate at least one multiplied state signal;

summing the at least one multiplied state signal over the length of the code to generate an output signal; and

outputting the output signal from a bit estimator through a threshold switch approximately when a deterministic peak of the output signal exceeds a threshold.

2. The method according to claim 1, wherein the at least one optical transmitter is a light in a lighting infrastructure.

3. The method according to claim 1, wherein the at least one optical transmitter transmits at least one optical emission selected from the group consisting of visible, infrared, and ultraviolet.

4. The method according to claim 1, which further comprises performing the changing step by modulating the illumination state.

5. The method according to claim 1, wherein the supplied signal is a digital data stream.

6. The method according to claim 1, which further comprises selecting the given code such that when the given code is correlated with itself a strong deterministic peak results.

7. The method according to claim 6, wherein the given code is one of a plurality of given codes, and selecting a given code such that when the given code is cross-correlated with any other of the plurality of given codes a result is less than the deterministic peak of the autocorrelation.

8. The method according to claim 7, wherein the result is substantially equal to zero.

9. The method according to claim 1, which further comprises performing the correlating and outputting steps at a rate at least equal to a rate of change of the at least one changed illumination state.

10. The method according to claim 9, wherein the given code has n chips and the rate is n-times faster than the rate of change of the at least one changed illumination state.

11. The method according to claim 9, wherein the given code has n chips and the rate is n-times faster than the rate of change of the at least one changed illumination state during a synchronization stage.

12. The method according to claim 1, which further comprises:

performing the correlating and outputting steps in synchronization with a rate of change of the at least one changed illumination state; and

synchronously sampling an output of the at least one signal correlator with a threshold switch to create an output signal.

13. The method according to claim 1, wherein the given code is one of a plurality of given codes, and performing the correlating step by correlating with one of a number of signal correlators, the number being at most equal to a number of respective different given codes.

14. The method according to claim 1, which further comprises repeating the correlating and outputting steps for each chip of the at least one input signal.

15. The method according to claim 1, wherein the threshold is at most equal to the length of the given code.

16. The method according to claim 1, which further comprises performing the outputting step by converting, with the bit estimator, the output signal into an estimated output signal estimating the at least one received illumination state received by the optical receiver from the at least one optical transmitter.

17. The method according to claim 1, which further comprises supplying the output signal from the bit estimator to a processor for determining a location of the receiver with respect to the at least one optical transmitter.

18. The method according to claim 1, wherein the threshold switch is a sampler.

19. The method according to claim 1, wherein the given code is one of a plurality of given codes, the at least one optical transmitter is one of a plurality of optical transmitters, and selecting a given code of a particular optical transmitter to be different from given codes of optical transmitters adjacent to the particular optical transmitter.

20. A method for communicating an optical signal, which comprises:

multiplying at least one input signal by a respective code to generate at least one multiplied signal;

changing a transmitted illumination state of at least one optical transmitter based upon the at least one multiplied signal;

receiving the transmitted illumination state of the at least one optical transmitter with an optical receiver and converting the received transmitted illumination state into at least one received signal;

supplying the at least one received signal to at least one signal correlator having a received signal multiplier and a received signal integrator;

multiplying the at least one received signal by a respective code with the received signal multiplier to generate at least one second multiplied signal;

summing each chip of the at least one second multiplied signal over a length of the respective code with the received signal integrator of the at least one signal correlator;

outputting an output signal of the signal integrator to a bit estimator through a threshold switch approximately when a deterministic peak exceeds a threshold of the switch; and

converting the output signal of the signal integrator to a demodulated output signal with the bit estimator.

21. The method according to claim 20, which further comprises performing the converting, supplying, multiplying, summing, outputting, and converting steps at a rate at least equal to a rate of change of the transmitted illumination state of the at least one optical transmitter.

22. The method according to claim 20, which further comprises:

performing the converting, supplying, multiplying, summing, outputting, and converting steps in synchronization with a rate of change of the transmitted illumination state of the at least one optical transmitter; and

synchronously sampling an output of the at least one signal correlator with a threshold switch to create a demodulated output signal.

23. The method according to claim 20, which further comprises performing the converting, supplying, multiplying, summing, outputting, and converting steps simultaneously in parallel for each received transmitted illumination state received by the receiver.

24. The method according to claim 20, which further comprises repeating the converting, supplying, multiplying, summing, outputting, and converting steps for each chip of each received transmitted illumination state.

25. The method according to claim 20, which further comprises performing the summing step by summing the product of each respective code and the at least one received signal for generating an output having peaks occurring in a deterministic fashion.

26. The method according to claim 20, which further comprises performing the converting step by converting, with the bit estimator, the output signal of the signal integrator into an estimated output signal estimating the received transmitted illumination state received by the optical receiver from at least one optical transmitter.

27. The method according to claim 20, which further comprises supplying the output signal from the bit estimator to a processor for determining a location of the receiver with respect to the at least one optical transmitter.

28. The method according to claim 20, wherein the at least one optical transmitter is one of a plurality of optical transmitters, the respective code is one of a plurality of respective pseudo-random noise codes, and wherein the method further comprises the step of selecting a pseudo-random noise code of a particular optical transmitter to be different from pseudo-random noise codes of optical transmitters adjacent to the particular optical transmitter.

29. The method according to claim 20, wherein the at least one optical transmitter is one of a plurality of optical transmitters, the respective code is one of a plurality of respective pseudo-random noise codes, the at least one input signal is one of a plurality of input signals, the at least one signal correlator is one of a plurality of signal correlators each having a received signal multiplier and a received signal integrator, the threshold switch is one of plurality of threshold switches, and the bit estimator is one of a plurality of bit estimators.

30. A method for communicating input signals through illumination of lights in a lighting infrastructure of a structure, which comprises:

multiplying each input signal by a respective different pseudo-random noise code to generate a corresponding plurality of multiplied signals;

changing a transmitted illumination state of lights based upon a respective one of the plurality of multiplied signals;

receiving transmitted illumination states of some of the lights with an optical receiver and converting the received transmitted illumination states into a received signal;

supplying the received signal to signal correlators, each of the signal correlators having a received signal multiplier and a received signal integrator;

multiplying the received signal by one pseudo-random noise code with each received signal multiplier in each signal correlator and outputting a second multiplied signal from each received signal multiplier;

summing each chip of the second multiplied signal in each signal correlator over a length of the one pseudo-random noise code with each received signal integrator;

outputting an output signal of each signal integrator to a bit estimator through a threshold switch approximately when a deterministic peak exceeds a threshold value of each threshold switch;

converting an output signal of each signal integrator into a demodulated output signal with each bit estimator; and

repeating the steps of receiving, converting, supplying, multiplying, summing, outputting, and converting until each input signal is estimated.

31. An optical communication device, comprising:

at least one optical transmitter for transmitting optical signals;

at least one signal multiplier for multiplying a supplied signal by at least one code, said at least one signal multiplier having a multiplier output connected to said at least one optical transmitter for outputting a multiplied signal;

said at least one optical transmitter configured to modulate the optical signals based upon the multiplied signal;

a receiver for receiving modulated optical signals output by said at least one optical transmitter, said receiver having a converter for converting received modulated light into a received signal and at least one signal correlator for correlating the received signal, said at least one signal correlator having a correlator output;

at least one switch connected to said correlator output and having a switch output for outputting a correlated signal exceeding a given threshold; and

at least one bit estimator connected to said switch output, said at least one bit estimator configured to output an estimation of the supplied signal.

32. The communication device according to claim 31, wherein said at least one optical transmitter is a light in a lighting infrastructure.

33. The communication device according to claim 32, wherein the communication device is part of said light.

34. The communication device according to claim 31, wherein said at least one optical transmitter transmits at least one optical emission selected from the group consisting of visible, infrared, and ultraviolet.

35. The communication device according to claim 31, wherein said at least one optical transmitter is one of a group consisting of incandescent bulbs, fluorescent lamps, halogen bulbs, light emitting diodes, and laser diodes.

36. The communication device according to claim 31, wherein the supplied signal is a digital data stream.

37. The communication device according to claim 31, wherein said receiver, said at least one switch, and said at least one bit estimator operate at a rate at least equal to a modulation rate of said at least one optical transmitter.

38. The communication device according to claim 38, wherein the at least one code has n chips and said rate is n-times faster than said modulation rate.

39. The communication device according to claim 38, wherein said receiver, said switches, and said bit estimators operate simultaneously in parallel.

40. The communication device according to claim 31, wherein said at least one signal correlator has a received signal multiplier and a received signal integrator

41. The communication device according to claim 41, wherein said received signal multiplier is configured to multiply the received signal by the at least one code

42. The communication device according to claim 41, wherein the at least one code has a length and said received signal integrator is configured to sum each chip of the received signal over the length.

43. The communication device according to claim 31, wherein said at least one switch has a threshold value at most equal to said given threshold and said switch output is configured to output a correlated signal exceeding a given threshold approximately when a deterministic peak exceeds said threshold value.

44. The communication device according to claim 31, including:

a signal generator for generating the supplied signal; and

a code generator for generating the at least one code.

45. In a lighting infrastructure having lights configured to optically communicate information from a supplied signal with illuminated light through a transmitted signal, an optical communication device, comprising:

signal multipliers for multiplying a respective given signal by one of different pseudo-random noise codes, each of said signal multipliers having a multiplier output for outputting a multiplied signal, said multiplier output connected to one of the lights;

a receiver for receiving modulated optical signals output by at least one of the lights, said receiver having a converter for converting received modulated light into a received signal and signal correlators for correlating the received signal, each of said signal correlators having a correlator output;

switches, a switch of said switches connected to said correlator output, each of said switches having a switch output for outputting a correlated signal exceeding a given threshold; and

bit estimators, a bit estimator of said bit estimators connected to said switch output, said bit estimators each configured to output an estimation of said respective given signal for each of the optical signals received by said receiver.

46. An optical communication device, comprising:

means for multiplying a plurality of input signals each by a respective different pseudo-random noise code to generate a corresponding plurality of multiplied signals;

means for changing a transmitted illumination state of each of a plurality of optical transmitters based upon a respective one of the plurality of multiplied signals;

means for receiving transmitted illumination states of some of the plurality of optical transmitters with an optical receiver and converting the received transmitted illumination states into a received signal;

means for supplying the received signal to a number of signal correlators, each signal correlator having a received signal multiplier and a received signal integrator;

means for multiplying the received signal by one pseudo-random noise code with each received signal multiplier in each signal correlator and outputting a second multiplied signal from each received signal multiplier;

means for summing each chip of the second multiplied signal in each signal correlator over a length of the one pseudo-random noise code with each received signal integrator;

means for outputting an output signal of each signal integrator to a bit estimator through a threshold switch approximately when a deterministic peak exceeds a threshold value of each threshold switch; and

means for converting an output signal of each signal integrator into a demodulated output signal with each bit estimator.

47. An optical communication device, comprising:

at least one optical transmitter for transmitting optical signals; and

at least one signal multiplier for multiplying a supplied signal by at least one code, said at least one signal multiplier having a multiplier output connected to said at least one optical transmitter for outputting a multiplied signal, said at least one optical transmitter configured to modulate the optical signals based upon the multiplied signal.

48. An optical communication device, comprising:

a receiver for receiving modulated optical signals, said receiver having a converter for converting received modulated optical signals into a received signal and at least one signal correlator for correlating the received signal, said at least one signal correlator having a correlator output;

at least one switch connected to said correlator output and having a switch output for outputting a correlated signal exceeding a given threshold; and

at least one bit estimator connected to said switch output, said at least one bit estimator configured to output an estimation of the modulated optical signals.