System and Method for Communicating Data Using Symbol-Based Randomized Orthogonal Frequency Division Multiplexing (OFDM) With Applied Frequency Domain Spreading

• US 20080043812A1
• Filed: 08/16/2006
• Published: 02/21/2008
• Est. Priority Date: 08/16/2006
• Status: Active Grant

• Current Assignee: Smartsky Networks Llc
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Moffatt, Christopher D.
• Granted Patent: US 7,649,951 B2
• Time in Patent Office: Days
• US Class Current: 375/133
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 27/2628 Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators H04L27/2634 takes precedence
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

A device and system communicates data and includes a modulation and mapping circuit that modulates and maps data symbols into a plurality of multiple subcarrier frequencies that are orthogonal to each other to form an Orthogonal Frequency Division Multiplexed (OFDM) communications signal based on a fixed or variable OFDM symbol rate. A pseudo-random signal generator operative with the modulation and mapping circuit generates pseudo-random signals to the modulation and mapping circuit based on an encryption algorithm for frequency hopping each subcarrier at an OFDM symbol rate to lower any probability of interception and detection, reduce power per frequency (dB/Hz/sec), and lower any required transmission power while maintaining an instantaneous signal-to-noise ratio A frequency domain spreader circuit is operatively connected to the modulation and mapping circuit for spreading the multiple subcarriers over the frequency domain.

Claims

1. A device for communicating data, comprising:

a modulation and mapping circuit that modulates and maps data symbols into a plurality of multiple subcarrier frequencies that are orthogonal to each other to form an Orthogonal Frequency Division Multiplexed (OFDM) communications signal based on a fixed or variable OFDM symbol rate;

a pseudo-random signal generator operative with the modulation and mapping circuit for generating pseudo-random signals to the modulation and mapping circuit based on an encryption algorithm for frequency hopping each subcarrier at an OFDM symbol rate to lower any probability of interception and detection, reduce power per frequency (dB/Hz/sec), and lower any required transmission power while maintaining an instantaneous signal-to-noise ratio; and

a frequency domain spreader circuit operatively connected to said modulation and mapping circuit for spreading the multiple subcarriers over the frequency domain.

2. The device according to claim 1, wherein said frequency domain spreader circuit comprises a Walsh Transform circuit that is operative for applying a Walsh Transform and spreading said multiple subcarriers over the frequency domain.

3. The device according to claim 2, wherein said Walsh Transform circuit is operative for multiplying an input vector of a symbol by the Walsh Transform.

4. The device according to claim 1, and further comprising an Inverse Fast Fourier Transform (IFFT) circuit positioned to receive signals from said frequency domain spreader circuit.

5. The device according to claim 1, wherein said pseudo-random signal generator is operative for generating a pseudo-random signal based on said encryption algorithm such that consecutive OFDM symbols do not transmit subcarriers on the same frequency.

6. The device according to claim 1, wherein said pseudo-random signal generator is operative for generating a pseudo-random signal based on said encryption algorithm such that OFDM symbols do not transmit subcarriers on adjacent frequencies for reduced Inter-Carrier Interference (ICI).

7. The device according to claim 1, wherein said pseudo-random signal generator is operative for generating a pseudo-random signal based on said encryption algorithm such that a Guard Interval is reduced or eliminated.

8. The device according to claim 1, wherein said modulation and mapping circuit is operative for inserting signals for reducing peak-to-average-power ratio (PAPR).

9. The device according to claim 1, and further comprising a modulator for mapping communications data into modulated symbols based on a specific mapping algorithm.

10. The device according to claim 1, wherein said pseudo-random signal generator is operatively connected to said modulator for varying amplitude and phase values using an encryption algorithm.

11. The device according to claim 1, and further comprising a Forward Error Correction circuit for adding a FEC code.

12. A system for communicating data, comprising:

a transmitter for transmitting a communication signal that carries communications data and comprises a modulation and mapping circuit that maps data symbols into a plurality of multiple subcarrier frequencies that are orthogonal to each other to form an Orthogonal Frequency Division Multiplexed (OFDM) communications signal based on a fixed or variable OFDM symbol rate, and a pseudo-random signal generator operative with the modulation and mapping circuit for generating pseudo-random signals to the modulation and mapping circuit based on an encryption algorithm for frequency hopping each subcarrier at an OFDM symbol rate to lower any probability of interception and detection, reduce power per frequency (dB/Hz/sec), and lower any required transmission power while maintaining an instantaneous signal-to-noise ratio, and a frequency domain spreader circuit operatively connected to said modulation and mapping circuit for spreading the multiple subcarriers over the frequency domain; and

a receiver for receiving the communications signal and including a demapping and demodulation circuit and frequency domain despreading circuit for processing the communications signal to obtain the communications data.

13. A system according to claim 12, wherein said transmitter is operative for modulating a main carrier signal.

14. The system according to claim 12, wherein said frequency domain spreader circuit comprises a Walsh Transform circuit that is operative for applying a Walsh Transform for spreading said multiple subcarriers over the frequency domain.

15. The system according to claim 14, wherein said Walsh Transform circuit is operative for multiplying an input vector of a symbol by the Walsh Transform.

16. The system according to claim 12, and further comprising an Inverse Fast Fourier Transform (IFFT) circuit positioned to receive signals from said frequency domain spreader circuit.

17. The system according to claim 12, wherein said pseudo-random signal generator is operative for generating a pseudo-random signal based on said encryption algorithm such that consecutive OFDM symbols do not transmit subcarriers on the same frequency.

18. The system according to claim 12, wherein said pseudo-random signal generator is operative for generating a pseudo-random signal based on said encryption algorithm such that OFDM symbols do not transmit subcarriers on adjacent frequencies for reduced Inter-Carrier Interference (ICI).

19. The system according to claim 12, wherein said pseudo-random signal generator is operative for generating a pseudo-random signal based on said encryption algorithm such that a Guard Interval is reduced or eliminated.

20. The system according to claim 12, wherein said pseudo-random signal generator is operatively connected to said modulator for varying amplitude and phase values using an encryption algorithm.

21. The system according to claim 12, wherein said transmitter further comprises a circuit for inserting signals for reducing peak-to-average-power ratio (PAPR).

22. The system according to claim 12, wherein said transmitter is operative for adding a Forward Error Correction (FEC) code.

23. A method for communicating data, which comprises:

distributing communications data over multiple subcarriers that are orthogonal to each other to form an Orthogonal Frequency Division Multiplexed (OFDM) communications signal based on fixed or variable OFDM symbol rate;

frequency hopping each subcarrier at an OFDM symbol rate to lower any probability of interception and detection, reduce power per frequency (dB/Hz/sec), and lower any required transmission power while maintaining an instantaneous signal-to-noise ratio;

spreading the multiple subcarriers over the frequency domain; and

transmitting the communications data over a communications signal that includes the frequency hopping subcarriers.

24. The method according to claim 23, which further comprises applying a Walsh Transform for spreading the multiple subcarriers over the frequency domain.

25. The method according to claim 24, which further comprises multiplying an input vector of a symbol by a Walsh Transform.

26. The method according to claim 23, which further comprises applying a frequency spreading function before an Inverse Fast Fourier Transform (IFFT).

27. The method according to claim 23, which further comprises generating a pseudo-random signal based on an encryption algorithm such that consecutive OFDM symbols do not transmit subcarriers on the same frequency.

28. The method according to claim 23, which further comprises generating a pseudo-random signal based on an encryption algorithm such that OFDM symbols do not transmit subcarriers on adjacent frequencies.

29. The method according to claim 23, which further comprises generating a pseudo-random signal based on said encryption algorithm such that a Guard Interval is reduced or eliminated.

30. The method according to claim 23, which further comprises inserting signals for reducing peak-to-average-power ratio (PAPR).

31. The method according to claim 23, which further comprises modulating a main carrier signal on which the multiple subcarrier frequencies are transmitted.

32. The method according to claim 23, which further comprises varying pseudo-randomly a subcarrier constellation amplitude and phase value.

33. The method according to claim 23, which further comprises adding a Forward Error Correction code.