APPARATUS AND METHOD FOR INCREASED DATA RATES IN UNDERWATER COMMUNICATIONS USING ORBITAL ANGULAR MOMENTUM

• US 20170187442A1
• Filed: 03/15/2016
• Published: 06/29/2017
• Est. Priority Date: 03/16/2015
• Status: Active Grant

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: LUDDY, Michael J., WINTERS, Jack H.
• Granted Patent: US 10,103,799 B2
• Time in Patent Office: Days
• CPC Class Codes: H04B 10/0773 Network aspects, e.g. central monitoring of transmission parameters
• CPC Class Codes: H04B 10/0775 Performance monitoring and measurement of transmission parameters
• CPC Class Codes: H04B 10/0795 Performance monitoring; Measurement of transmission parameters
• CPC Class Codes: H04B 10/548 Phase or frequency modulation
• CPC Class Codes: H04B 13/02 Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04J 11/00 Orthogonal multiplex systems, e.g. using WALSH codesH04J13/00 takes precedence
• CPC Class Codes: H04J 14/00 Optical multiplex systems
• CPC Class Codes: H04J 14/007 Orthogonal Optical Code Multiplex
• CPC Class Codes: H04J 14/07 Orbital angular momentum [OAM] multiplex systems
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 25/03898 codebook-based design selection of codebook or precoding matrix for MIMO diversity systems H04B7/0456
• CPC Class Codes: H04L 27/2096 Arrangements for directly or externally modulating an optical carrier optical modulation H04B10/503
• CPC Class Codes: H04L 27/2697 in combination with other modulation techniques
• CPC Class Codes: H04L 5/0046 Determination of how many bits are transmitted on different sub-channels

Abstract

A system for providing underwater communication using orbital angular momentum (OAM) includes a transmitter that processes input data to be transmitted using pre-coding information based on current transmission channel conditions to maximize data rate based on channel conditions. A receiver receives a transmitted multiplexed OAM optical signal and analyzes the received signal for channel state information. The channel state information is used to determine a set of pre-coding values that allow the transmitter to pre-code the input data to maximize the data rate based on current channel conditions. The pre-coding values are mapped to a codebook entry which identifies the pre-coding values. The codebook entry is transmitted from the receiver to the transmitter. The transmitter uses the received codebook entry to identify pre-coding values used to process subsequent input data to be transmitted in order to enhance data rate across the transmit channel.

Claims

1. An underwater optical communications system including a transmitter and a receiver;

the transmitter receiving input data and generating a plurality of orbital angular momentum optical signals based on the input data, the plurality of orbital angular momentum optical signals are transmitted by the transmitter into a water medium; and

the receiver receives the plurality of orbital angular momentum optical signals and generates output data from the received plurality of orbital angular momentum optical signals.

2. The system of claim 1, wherein the transmitter performs orthogonal frequency division multiplexing on the input data to split the input data into a plurality of subcarriers.

3. The system of claim 1, wherein the receiver analyzes the received plurality of orbital angular momentum optical signals and/or an optical pilot beam transmitted by the transmitter and received by the receiver for channel performance;

and further comprising a feedback channel from the receiver to the transmitter, the feedback channel provides channel state information from the receiver to the transmitter.

4. The system of claim 3, wherein the transmitter separates the input data into multiple data streams that are used to form the plurality of orbital angular momentum signals, and the transmitter precodes the multiple data streams based on feedback from the feedback channel.

5. The system of claim 4, wherein the transmitter adjusts a gain of each of the plurality of orbital angular momentum optical signals.

6. The system of claim 4, wherein the transmitter adjusts a gain of each of the data streams.

7. An underwater optical communications system transmitter, comprising:

a module that receives input data and separates the input data into multiple data streams;

orbital angular momentum optical signal generators connected to the module, the orbital angular momentum optical signal generators generating a plurality of orbital angular momentum optical signals based on the multiple data streams; and

a multiplexor connected to the orbital angular momentum optical signal generators, the multiplexor receiving the plurality of orbital angular momentum optical signals and generating a multiplexed orbital angular momentum optical signal that is transmitted into a water medium.

8. The underwater optical communications system transmitter of claim 7, wherein the module performs orthogonal frequency division multiplexing on the input data to split the input data into a plurality of subcarriers.

9. The underwater optical communications system transmitter of claim 7, wherein the transmitter precodes the multiple data streams.

10. An underwater optical communications system receiver, comprising:

a demultiplexor that receives a multiplexed orbital angular momentum optical signal transmitted through a water medium and that demultiplexes the multiplexed orbital angular momentum optical signal into a plurality of orbital angular momentum optical signals; and

a module connected to the multiplexor that receives the plurality of orbital angular momentum optical signals and that generates output data therefrom.

11. The underwater optical communications system receiver of claim 10, wherein the module includes an equalizer that reduces crosstalk between a plurality of data streams on the plurality of orbital angular momentum optical signals, multiplexes the plurality of data streams to form the output data, and analyzes the plurality of orbital angular momentum optical signals and/or a transmitted optical pilot beam received by the receiver for channel performance;

and further comprising a feedback channel from the receiver to a transmitter, the feedback channel providing channel state information from the receiver to the transmitter.

12. A method of underwater optical communications using a transmitter and a receiver, comprising:

the transmitter receiving input data and generating a plurality of orbital angular momentum optical signals based on the input data;

the transmitter transmitting the plurality of orbital angular momentum optical signals into a water medium;

the receiver receiving the plurality of transmitted orbital angular momentum optical signals transmitted through the water medium; and

the receiver generating output data from the received plurality of orbital angular momentum optical signals.

13. The method of claim 12, wherein the transmitter multiplexes the plurality of orbital angular momentum signals into a single multiplexed optical signal and transmits the plurality of orbital angular momentum optical signals into the water medium by transmitting the single multiplexed optical signal into the water medium.

14. The method of claim 12, further comprising the transmitter performing orthogonal frequency division multiplexing based on the input data to split the input data into a plurality of subcarriers.

15. The method of claim 12, further comprising the receiver analyzing the received plurality of orbital angular momentum optical signals and/or an optical pilot beam transmitted by the transmitter and received by the receiver for channel performance;

and further comprising the receiver sending channel state information back to the transmitter.

16. The method of claim 13, further comprising:

processing in the transmitter the input data using a channel state information parameter;

producing at the transmitter a plurality of radio frequency (RF) signals based on the input data;

modulating the plurality of RF signals onto an optical signal produced by a laser corresponding to each RF signal;

converting each modulated optical signal to a respective one of the orbital angular momentum optical signals;

multiplexing each of the orbital angular momentum optical signals into a single multiplexed orbital angular momentum optical signal; and

transmitting the multiplexed orbital angular momentum optical signal into the water medium.

17. The method of claim 16, further comprising:

receiving the multiplexed orbital angular momentum optical signal at the receiver;

analyzing the received multiplexed orbital angular momentum optical signal and/or an optical pilot beam transmitted by the transmitter and received by the receiver for channel performance to identify channel state information;

defining a plurality of pre-coding values based on the channel state information;

mapping the plurality of pre-coding values to an entry in a codebook, the entry identifying the plurality of pre-coding values;

transmitting the codebook entry from the receiver to the transmitter;

at the transmitter, identifying a plurality of pre-coding values from the received codebook entry; and

at the transmitter, processing a next portion of input data for transmission using the pre-coding values.

18. The method of claim 17, wherein the plurality of pre-coding values includes a power allocation for each of a plurality of orbital angular momentum modes in the multiplexed orbital angular momentum optical signal.

19. The method of claim 17, wherein the plurality of pre-coding values includes a bit loading scheme for each of the plurality of RF signals.

20. The method of claim 17, wherein the plurality of pre-coding values includes a value of orthogonal frequency division multiplexing sub-carrier spacing for each of the plurality of RF signals.

21. The method of claim 18, wherein the plurality of pre-coding values includes a phase adjustment for at least one of the orbital angular momentum modes in the multiplexed orbital angular momentum optical signal, the phase adjustment configured to mitigate turbidity in a communication channel affecting at least one of the orbital angular momentum modes.

22. The method of claim 18, further comprising:

at the receiver, analyzing the channel state information and performing a maximizing function to determine optimal pre-coding values for each orbital angular momentum mode based on the channel state information.