METHODS AND APPARATUS FOR MULTIPHASE SAMPLING OF MODULATED LIGHT

• US 20140093234A1
• Filed: 09/28/2012
• Published: 04/03/2014
• Est. Priority Date: 09/28/2012
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Roberts, Richard D., Walma, Mathys C., Gopalakrishnan, Praveen
• Granted Patent: US 9,203,541 B2
• Time in Patent Office: Days
• US Class Current: 398/25
• CPC Class Codes: H04B 10/116 Visible light communication
• CPC Class Codes: H04B 10/564 Power control
• CPC Class Codes: H04B 10/60 Receivers
• CPC Class Codes: H04B 10/616 Details of the electronic signal processing in coherent optical receivers
• CPC Class Codes: H04J 14/00 Optical multiplex systems

Abstract

A light transmitter transmits multiple light packets, each formatted to include a same message comprising a series of bits, each bit represented as light that is intensity modulated over a bit period at a frequency indicative of the bit. The light packets are transmitted at different start-times to establish different phases, one for each of the light packets, to permit a light receiver to sample each message at a different phase of a fixed sample timeline that is asynchronous to the bit period and the frequency. The light receiver samples the multiple light packets based on the sample timeline, to sample each received message at one of the different sample phases, then constructs a best series of bits based on the multiple demodulated messages.

Claims

1. A non-transitory computer readable medium encoded with a computer program, including instructions to cause a processor to:

cause one or more lights of a light transmitter to transmit multiple light packets each formatted to include a same message comprising a series of bits, each bit represented as light that is intensity modulated over a bit period at a frequency indicative of the bit; and

vary transmit start-times of the multiple messages relative to each other to permit a light receiver to sample each message at a different phase of a fixed sample timeline that is asynchronous to the bit period and the frequency.

2. The computer readable medium of claim 1, further including instructions to cause the processor to:

cause a light imager configured to receive the transmitted multiple light packets to sample the received multiple light packets based on the asynchronous sample timeline, to produce samples for each received message that coincide in time with a corresponding one of the different phases;

demodulate each of the sampled messages, to produce multiple demodulated messages; and

construct a series of data bits representative of the same message based on the multiple demodulated messages.

4. The computer readable medium of claim 1, wherein:

the instruction to cause one or more lights of a transmitter to transmit further include instructions to cause the processor to cause multiple, spatially separated lights each to transmit a respective one of the multiple light packets so that all of the light packets partially overlap in time; and

the instructions to cause the processor to vary further include instructions to cause the processor to vary start-times of the multiple light packets and, as a result, the start-times of their respective messages, so that the messages have successive start-times to establish the different phases as successive sample phases.

5. The computer readable medium of claim 1, wherein:

each of the multiple light packets includes sequential fields including a delimiter having a variable time duration followed by the same message;

the instruction to cause one or more lights of a transmitter to transmit further include instructions to cause the processor to cause a light to transmit the multiple light packets as successive contiguous light packets; and

the instructions to cause the processor to vary further include instructions to cause the processor to vary the time durations of the successive delimiters with respect to each other to establish the different phases.

6. The computer readable medium of claim 1, wherein the different phases include a first phase followed by remaining successive phases, and phase differences between the first phase and each of the remaining successive phases increase monotonically.

7. The computer readable medium of claim 1, wherein the different phases are all separated from each other by a time offset that is less than 1/frequency.

8. The computer readable medium of claim 1, wherein each of the multiple light packets is further formatted to include sequential light intensity modulated fields, including a delimiter followed by the same message,

each bit in the message being represented as light that is intensity modulated, for the bit period, at one of first and second frequencies indicative of one of first and second bit values, respectively, and

the delimiter being represented as light that is intensity modulated, for a delimiter period, at a third frequency that is greater than each of the first and second frequencies.

3. The computer readable medium of claim 3, wherein:

the sample timeline includes consecutive sample times spaced apart so as to produce at least two samples per bit period;

the instruction to cause the light imager to sample further include instructions to cause the light imager to sample the received light packets for a sample integration time to produce each of the samples; and

adjacent ones of the different phases are separated by at least twice the integration time.

9. A non-transitory computer readable medium encoded with a computer program, including instructions to cause a processor to:

cause a light detector array including spatially-successive lines of light detectors to sample light energy impinging thereon when exposed, the light energy conveying a bit value as light that is intensity modulated to multiple intensity levels at a frequency indicating a bit value;

sequentially expose the spatially-successive lines of light detectors to the light energy impinging thereon at a line exposure rate that is greater than the frequency, to produce a group of sequential lines of sampled light energy; and

determine an intensity level of the light energy, among the multiple intensity levels, based on the group of sequential lines of sampled light energy.

10. The computer readable medium of claim 9, further including instructions to cause the processor to:

expose the spatially-successive lines of light detectors at the line exposure rate at multiple spaced-apart times per bit period, to produce multiple, time-spaced groups of sequential lines of sampled light energy per bit period,

wherein the instructions to cause the processor to determine further include instruction to cause the processor to;

determine an intensity level based on each of the multiple time-spaced groups of sequential lines of the light energy, to produce multiple time-spaced determined intensity levels per bit period; and

determine the frequency, and thereby the bit value, based on the multiple time-spaced determined intensity levels.

11. The computer readable medium of claim 9, wherein the line exposure rate is asynchronous to both the frequency and a bit rate equal to an inverse of the bit period.

12. The computer readable medium of claim 10, wherein:

the light energy conveys one of first and second bit values as light that is intensity modulated to the multiple intensity levels at one of first and second frequencies, respectively; and

the instructions to cause the processor to determine the frequency further include instructions to cause the processor to determine

the first frequency, and thereby the first bit value, if consecutive ones of the time-spaced determined intensity levels are the same, and

the second frequency, and thereby the second bit value, if consecutive ones of the time-spaced determined intensity levels are different.

13. The computer readable medium of claim 9, wherein:

the group of sequential lines of sampled light energy includes past, present, and future lines of sampled light energy indicating respective past, present, and future sampled light intensity levels; and

the instruction to cause the processor to determine further include instructions to cause the processor to determine the intensity level of the light based on a comparison between the past, present, and future sampled light intensity levels.

14. An apparatus, comprising:

a light transmitter including;

one or more lights to transmit multiple light packets each formatted to include a same message comprising a series of bits, each bit represented as light that is intensity modulated over a bit period at a frequency indicative of the bit; and

a controller to vary transmit start-times of the multiple messages relative to each other to permit a light receiver to sample each message at a different phase of a fixed sample timeline that is asynchronous to the bit period and the frequency.

15. The apparatus of claim 14, further comprising a light receiver to receive the multiple transmitted light packets, the light receiver including:

a light imager to sample the multiple received light packets based on the asynchronous sample timeline, to produce samples for each received message that coincide in time with a corresponding one of the different phases;

a detector to demodulate each of the sampled messages, to produce multiple demodulated messages; and

a message constructor to construct a series of data bits representative of the same message based on the multiple demodulated messages.

16. The apparatus of claim 15, wherein:

the sample timeline includes consecutive sample times spaced apart so as to produce at least two samples per bit period;

the light imager is configured to sample the received light packets for a sample integration time to produce each of the samples; and

adjacent ones of the different phases are separated by at least twice the integration time.

17. The apparatus of claim 14, wherein:

the one or more lights include multiple, spatially separated lights each to transmit a respective one of the multiple light packets so that all of the light packets are spatially-separated and partially overlap in time; and

the controller is configured to vary start-times of the multiple light packets and, as a result, the start-times of their respective messages, so that the messages have successive start-times to establish the different phases as successive phases.

18. The apparatus of claim 17, further comprising a light receiver to receive the multiple spatially-separated transmitted light packets, the light receiver including:

a light imager to sample the multiple spatially-separated received light packets based on the asynchronous sample timeline, to produce samples for each received message that coincide in time with a corresponding one of the different phases;

a detector to demodulate each of the sampled messages, to produce multiple demodulated messages; and

a message constructor to construct a series of data bits representative of the same message based on the multiple demodulated messages.

19. The apparatus of claim 14, wherein:

each of the multiple light packets includes sequential fields including a delimiter having a variable time duration followed by the same message;

the one or more lights includes a light to transmit the multiple light packets as successive contiguous light packets; and

the controller is configured to vary the time durations of the successive delimiters with respect to each other to establish the different phases.

20. The apparatus of claim 14, wherein the different phases include a first phase followed by remaining successive phases, and phase differences between the first phase and each of the remaining successive phases increase monotonically.

21. The apparatus of claim 14, wherein the different phases are all separated from each other by a time offset that is less than 1/frequency.

22. The apparatus of claim 14, wherein each of the multiple light packets is further formatted to include sequential light intensity modulated fields, including a delimiter followed by the same message,

each bit in the message being represented as light that is intensity modulated, for the bit period, at one of first and second frequencies indicative of one of first and second bit values, respectively, and

the delimiter being represented as light that is intensity modulated, for a delimiter period, at a third frequency that is greater than each of the first and second frequencies.

23. The apparatus of claim 14, further comprising:

a communication system to communicate with a network;

a processor to interface between the communication system and a user interface system; and

a housing,

wherein the processor, the communication system, and the light transmitter are positioned within the housing.

24. The apparatus of claim 23, wherein:

the communication system includes a wireless communication system; and

the housing includes a mobile hand-held housing to house the communication system, the processor, the user interface system, and a battery.

25. An apparatus, comprising:

a light detector array including spatially-successive lines of light detectors to sample light energy impinging thereon when exposed, the light energy conveying a bit value as light that is intensity modulated to multiple intensity levels at a frequency indicating a bit value;

an exposure controller to sequentially expose the spatially-successive lines of light detectors to the light energy impinging thereon at a line exposure rate that is greater than the frequency, to produce a group of sequential lines of sampled light energy; and

a detector to determine an intensity level of the light energy, among the multiple intensity levels, based on the group of sequential lines of sampled light energy.

26. The apparatus of claim 25, wherein:

the exposure controller is configured to expose the spatially-successive lines of light detectors at the line exposure rate at multiple spaced-apart times per bit period, to produce multiple, time-spaced groups of sequential lines of sampled light energy per bit period; and

the detector is configured to;

determine an intensity level based on each of the multiple time-spaced groups of sequential lines of the light energy, to produce multiple time-spaced determined intensity levels per bit period; and

determine the frequency, and thereby the bit value, based on the multiple time-spaced determined intensity levels.

27. The apparatus of claim 25, wherein the line exposure rate is asynchronous to both the frequency and a bit rate equal to an inverse of the bit period.

28. The apparatus of claim 26, wherein:

the light energy conveys one of first and second bit values as light that is intensity modulated to the multiple intensity levels at one of first and second frequencies, respectively; and

the detector is configured to determine

the first frequency, and thereby the first bit value, if consecutive ones of the time-spaced determined intensity levels are the same; and

the second frequency, and thereby the second bit value, if consecutive ones of the time-spaced determined intensity levels are different.

29. The apparatus of claim 25, wherein:

the group of sequential lines of sampled light energy includes past, present, and future lines of sampled light energy indicating respective past, present, and future sampled light intensity levels; and

the detector determines the intensity level of the light based on a comparison between the past, present, and future sampled light intensity levels.

30. The apparatus of claim 25, further comprising:

a communication system to communicate with a network;

a processor to interface between the communication system and a user interface system; and

a housing,

wherein the processor, the communication system, imaging array, the exposure controller, and the detector are positioned within the housing.

31. The apparatus of claim 30, wherein:

the communication system includes a wireless communication system; and

the housing includes a mobile hand-held housing to house the communication system, the processor, the user interface system, and a battery.

32. A method, comprising:

transmitting multiple light packets each formatted to include a same message comprising a series of bits, each bit represented as light that is intensity modulated over a bit period at a frequency indicative of the bit; and

varying transmit start-times of the multiple messages relative to each other to permit a light receiver to sample each message at a different phase of a fixed sample timeline that is asynchronous to the bit period and the frequency.

33. The method of claim 32, further comprising:

receiving the multiple transmitted light packets;

sampling the received multiple light packets based on the asynchronous sample timeline, to produce samples for each received message that coincide in time with a corresponding one of the different phases;

demodulating each of the sampled messages, to produce multiple demodulated messages; and

constructing a series of data bits representative of the same message based on the multiple demodulated messages.

34. The method of claim 33, wherein:

the sample timeline includes consecutive sample times spaced apart so as to produce at least two samples per bit period;

the sampling includes sampling the received light packets for a sample integration time to produce each of the samples; and

adjacent ones of the different phases are separated by at least twice the integration time.

35. The method of claim 32, wherein:

the transmitting includes transmitting the multiple light packets as multiple, spatially separated light packets so that all of the light packets partially overlap in time; and

the varying includes varying the start-times of the multiple light packets and, as a result, the start-times of their respective messages, so that the messages have successive start-times to establish the different phases as successive phases.

36. The method of claim 32, wherein:

each of the multiple light packets includes sequential fields including a delimiter having a variable time duration followed by the same message;

the transmitting includes transmitting the multiple light packets as successive contiguous light packets; and

the varying includes varying the time durations of the successive delimiters with respect to each other to establish the different phases.

37. The method of claim 32, wherein the different phases include a first phase followed by remaining successive phases, and phase differences between the first phase and each of the remaining successive phases increase monotonically.

38. The method of claim 32, wherein the different phases are all separated from each other by a time offset that is less than 1/frequency.

39. The method of claim 32, wherein each of the multiple light packets is further formatted to include sequential light intensity modulated fields, including a delimiter followed by the same message,

each bit in the message being represented as light that is intensity modulated, for the bit period, at one of first and second frequencies indicative of one of first and second bit values, respectively, and

the delimiter being represented as light that is intensity modulated, for a delimiter period, at a third frequency that is greater than each of the first and second frequencies.

40. A method, comprising:

receiving light energy on spatially-successive lines of light detectors, the spatially-successive lines of light detectors to sample the light energy impinging thereon when exposed, the light energy conveying a bit value as light that is intensity modulated to multiple intensity levels at a frequency indicating a bit value;

sequentially exposing the spatially-successive lines of light detectors to the light energy impinging thereon at a line exposure rate that is greater than the frequency, to produce a group of sequential lines of sampled light energy; and

determining an intensity level of the light energy, among the multiple intensity levels, based on the group of sequential lines of sampled light energy.

41. The method of claim 40, further comprising:

repeating the sequentially exposing at multiple spaced-apart times per bit period, to produce multiple, time-spaced groups of sequential lines of sampled light energy per bit period,

wherein the determining includes determining

an intensity level based on each of the multiple time-spaced groups of sequential lines of the light energy, to produce multiple time-spaced determined intensity levels per bit period, and

the frequency, and thereby the bit value, based on the multiple time-spaced determined intensity levels.

42. The method of claim 40, wherein the line exposure rate is asynchronous to both the frequency and a bit rate equal to an inverse of the bit period.

43. The method of claim 41, wherein:

the light energy conveys one of first and second bit values as light that is intensity modulated to the multiple intensity levels at one of first and second frequencies, respectively; and

the determining the frequency further includes determining

the first frequency, and thereby the first bit value, if consecutive ones of the time-spaced determined intensity levels are the same, and

the second frequency, and thereby the second bit value, if consecutive ones of the time-spaced determined intensity levels are different.

44. The method of claim 40, wherein:

the group of sequential lines of sampled light energy includes past, present, and future lines of sampled light energy indicating respective past, present, and future sampled light intensity levels; and

the determining includes determining the intensity level of the light based on a comparison between the past, present, and future sampled light intensity levels.