Carrier and subcarrier hopping for optical OFDM security
View Patent ↗Methods and systems for secure communication include assigning data streams to respective orthogonal sub-carriers according to random number information at a transmitter. The data streams are modulated onto the respective orthogonal sub-carriers before the orthogonal sub-carriers are transmitted. The random number information is transmitted on a second medium, separate from the transmission medium. The orthogonal sub-carriers are received from the transmission medium at a receiver, while the random number information is received from the second medium at the receiver. The orthogonal sub-carriers are associated with data streams using the random number information and demodulated to produce data for the associated data stream.
1. A method for secure communication, the method comprising:
assigning a plurality of data streams to respective orthogonal frequency division multiplexing (OFDM) sub-carriers according to random number information at a transmitter;
modulating the data streams onto the respective OFDM sub-carriers;
transmitting the OFDM sub-carriers on a transmission medium;
transmitting the random number information on a second medium, separate from the transmission medium;
receiving the OFDM sub-carriers from the transmission medium at a receiver;
receiving the random number information from the second medium at the receiver;
associating the OFDM sub-carriers with data streams using the random number information; and
demodulating each OFDM sub-carrier to produce data for the associated data stream.
2. The method of claim 1 , wherein said transmitting and receiving the OFDM sub-carriers is performed using a channel frequency determined by the random number information.
3. The method of claim 1 , further comprising periodically changing the channel frequency according to the random number information.
4. The method of claim 1 , further comprising periodically reassigning the plurality of data streams to different respective OFDM sub-carriers according to the random number information.
5. The method of claim 1 , wherein the transmission medium is an optical fiber.
6. The method of claim 1 , wherein the random number information is a one-time pad.
7. The method of claim 1 , wherein the random number information is a seed for a pseudo-random number generating function.
8. The method of claim 1 , further comprising combining the data streams into an output data stream.
9. A receiver, comprising:
a first reception unit configured to receive a plurality of OFDM sub-carriers from a transmission medium;
a second reception unit configured to receive random number information from a second medium;
a processor configured to associate the plurality of received OFDM sub-carriers with respective data streams according to the received random number information; and
a demodulator configured to extract data from each OFDM sub-carrier and further configured to add said data to the respective data stream.
10. The receiver of claim 9 , further comprising a local oscillator configured to enable reception of a signal comprising the received OFDM sub-carriers, wherein the local oscillator is configured to receive the signal using a frequency determined by the random number information.
11. The receiver of claim 10 , wherein the local oscillator is configured to periodically change the frequency according to the random number information.
12. The receiver of claim 9 , wherein the processor is further configured to periodically change the association between the OFDM sub-carriers and the data streams according to the random number information.
13. The receiver of claim 9 , wherein the random number information is a one-time pad.
14. The receiver of claim 9 , wherein the random number information is a seed for a pseudo-random number generating function.
15. A transmitter, comprising:
a random number generator configured to provide random number information;
a processor configured to assign a plurality of data streams to respective OFDM sub-carriers according to random number information;
a modulator configured to modulate each data stream onto the respective OFDM sub-carrier;
a first transmission unit configured to transmit the modulated OFDM sub-carriers on a transmission medium; and
a second transmission unit configured to transmit the random number information on a second medium.
16. The transmitter of claim 15 , wherein the first transmission unit is configured to change a frequency of transmission according to the random number information.
17. The transmitter of claim 16 , wherein the first transmission unit is configured to periodically change the frequency of transmission.
18. The transmitter of claim 15 , wherein the processor is further configured to periodically change the assignment of the plurality of data streams to the OFDM sub-carriers.
19. The transmitter of claim 15 , wherein the random number information is split into packets that include information pertaining to a type of assignment and information establishing a correspondence between random number information in the packet and particular transmitted symbols.
20. The transmitter of claim 15 , wherein the random number information is a seed for a pseudo-random number generating function.