System and Method for Applying Frequency Domain Spreading to Multi-Carrier Communications Signals

• US 20080043859A1
• 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 7,903,749 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 5/0044 allocation of payload

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 that 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; 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 for 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 and applying the Inverse Fast Fourier Transform (IFFT) for modulating 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 for mapping 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 applying 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 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 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 despreading circuit for processing the communications signal to obtain the communications data.

8. The system according to claim 7, wherein said transmitter is operative for modulating 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 for applying a Walsh Transform for spreading said multiple subcarriers over the frequency domain.

10. The system according to claim 9, wherein said Walsh Transform circuit is operative for multiplying 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 applying the Inverse Fast Fourier Transform for modulating 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 for mapping 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 for applying a FEC code.

14. A method for communicating data, which comprises:

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

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.