System and method for applying frequency domain spreading to multi-carrier communications signals

• US 7,903,749 B2
• Filed: 08/16/2006
• Issued: 03/08/2011
• 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.
• Primary Examiner(s): Liu, Shuwang
• Assistant Examiner(s): Timory, Kabir A
• Application Number:
  US11/464,857
• Publication Number:
  US 20080043859A1
• Time in Patent Office: 1,665 Days
• Field of Search: 375/260, 375/261, 375/268, 375/297, 375/298, 375/300, 375/324, 375/348, 375/349
• US Class Current: 375/260
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

A system and device communicates data. A modulation and mapping circuit modulates and maps data symbols into a plurality of multiple subcarriers that are orthogonal to each other based on a fixed or variable symbol rate. A frequency domain spreader circuit is operatively connected to the modulation and mapping circuit and spreads the multiple subcarriers over the frequency domain.

Claims

1. A device for communicating data, comprising:

a modulation and mapping circuit configured to modulate and map data symbols into a plurality of multiple subcarriers that are orthogonal to each other based on a fixed or variable symbol rate;

a pseudo-random signal generator operative with the modulation and mapping circuit and configured to generate pseudo-random signals to the modulation and mapping circuit using an encryption algorithm, wherein said modulation and mapping circuit, in response to receipt of said pseudo-random signals, is operable to change subcarrier constellation amplitude and phase values using the encryption algorithm and frequency hop each subcarrier and to change subcarrier center frequencies using the same encryption algorithm used to change subcarrier constellation and phase values; and

a frequency domain spreader circuit operatively connected to said modulation and mapping circuit and configured to spread 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 to apply a Walsh Transform to spread said multiple subcarriers over the frequency domain.

3. The device according to claim 2, wherein said Walsh Transform circuit is operative to multiply 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 and apply the Inverse Fast Fourier Transform (IFFT) to modulate multiple subcarriers orthogonal to each other to form an Orthogonal Frequency Division Multiplexed (OFDM) communications signal.

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

6. The device according to claim 1, and further comprising a Forward Error Correction (FEC) coding circuit operable to apply a FEC code.

7. A system for communicating data, comprising:

a transmitter for transmitting a communications signal that carries communications data and comprises a modulation and mapping circuit that is configured to modulate and map data symbols into a plurality of multiple subcarriers that are orthogonal to each other based on a fixed or variable symbol rate and a pseudo-random signal generator operative with the modulation and mapping circuit and configured to generate pseudo-random signals to the modulation and mapping circuit using an encryption algorithm, wherein said modulation and mapping circuit in response to receipt of said pseudo-random signals, is operable to change subcarrier constellation amplitude and phase values using the encryption algorithm and frequency hop each subcarrier and to change subcarrier center frequencies using the same encryption algorithm used to change subcarrier constellation and phase values, and a frequency domain spreader circuit operatively connected to said modulation and mapping circuit and configured to spread the multiple subcarriers over the frequency domain; and

a receiver configured to receive the communications signal, and including a demapping and demodulation circuit and despreading circuit configured to process the communications signal to obtain the communications data.

8. The system according to claim 7, wherein said transmitter is operative to modulate a main carrier signal.

9. The system according to claim 7, wherein said frequency domain spreader circuit comprises a Walsh Transform circuit that is operative to apply a Walsh Transform to spread said multiple subcarriers over the frequency domain.

10. The system according to claim 9, wherein said Walsh Transform circuit is operative to multiply an input vector of a symbol by the Walsh Transform.

11. The system according to claim 7, wherein said transmitter further comprises an Inverse Fast Fourier Transform (IFFT) circuit positioned to receive signals from said frequency domain spreader circuit and to apply the Inverse Fast Fourier Transform and configured to modulate multiple subcarriers orthogonal to each other to form an Orthogonal Frequency Division Multiplexed (OFDM) communications signal.

12. The system according to claim 7, wherein said transmitter further comprises a modulator configured to map communications data into modulated symbols based on a specific mapping algorithm.

13. The system according to claim 7, wherein said transmitter further comprises a Forward Error Correction (FEC) coding circuit configured to apply a FEC code.

14. A method for communicating data, which comprises:

distributing communications data within a modulation and mapping circuit over multiple subcarriers that are orthogonal to each other based on a fixed or variable symbol rate;

generating pseudo-random signals to the modulation and mapping circuit using an encryption algorithm for changing subcarrier constellation amplitude and phase values and frequency hopping each subcarrier and changing subcarrier center frequencies using the same encryption algorithm used to change subcarrier constellation and phase values;

applying a frequency domain spreading function to spread the subcarriers over the frequency domain; and

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

15. The method according to claim 14, which further comprises modulating a main carrier signal on which the multiple subcarrier frequencies are transmitted.

16. The method according to claim 14, which further comprises generating pseudo random noise codes to said subcarriers for spreading said subcarriers over the frequency domain as a Walsh transform.

17. The method according to claim 16, which further comprises multiplying an input vector of a symbol by the Walsh transform.

18. The method according to claim 14, which further comprises forming the communications signal as an Orthogonal Frequency Division Multiplexed (OFDM) communications signal.

19. The method according to claim 14, which further comprises applying the encryption algorithm to a mapping circuit that maps subcarriers to an Inverse Fast Fourier Transform (IFFT).

20. The method according to claim 14, which further comprise applying a Forward Error Correction (FEC) code.

21. The method according to claim 14, which further comprises mapping communications data into modulated symbols based on a specific mapping algorithm.