System and method for communicating data using constant radius orthogonal walsh modulation

• US 8,059,693 B2
• Filed: 07/18/2008
• Issued: 11/15/2011
• Est. Priority Date: 07/18/2008
• Status: Active Grant

• Current Assignee: Harris Global Communications, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Nieto, John W., Furman, William N.
• Primary Examiner(s): Payne; David C.
• Assistant Examiner(s): Nguyen; Leon-Viet
• Application Number:
  US12/175,508
• Publication Number:
  US 20100014558A1
• Time in Patent Office: 1,215 Days
• Field of Search: 375/130, 375/260, 375/144, 375/340, 375/229
• US Class Current: 375/130
• CPC Class Codes: H04B 14/023 using pulse amplitude modulation
• CPC Class Codes: H04B 2201/70706 with means for reducing the peak-to-average power ratio
• CPC Class Codes: H04J 13/0048 Walsh
• CPC Class Codes: H04L 27/2614 Peak power aspects

Abstract

A radio device includes a transmitter having a modulator for generating M-PAM communications symbols containing communications data. A Fast Walsh Transform circuit orthogonally encodes and band-spreads the communications symbols using the Fast Walsh Transform. A frequency modulation circuit frequency modulates the communications symbols wherein a constant radius orthogonal Walsh modulated communications signal containing the communications data is generated.

Claims

1. A radio device, comprising:

a transmitter unit comprising

a modulator configured to generate M-PAM (M-Pulse Amplitude Modulation) communications symbols containing communications data;

a Fast Walsh Transform (FWT) circuit connected to the modulator and configured to receive the communications symbols from the modulator and orthogonally encode and band-spread the communications symbols using the Fast Walsh Transform;

a guard time circuit connected to the FWT circuit and configured to cyclically extend the output of Fast Walsh Transform circuit by a guard time; and

a frequency modulation circuit connected to the guard time circuit and configured to frequency modulate the communications symbols wherein a constant radius orthogonal Walsh modulated communications signal containing the communications data is generated.

2. The radio device according to claim 1, and further comprising at least one of a square root raised cosine filter operative before the frequency modulation circuit for band-limiting a signal containing the communications symbols and a clipping device for reducing the peak to average power ratio of signal input to frequency modulation circuit.

3. The radio device according to claim 1, wherein said modulator comprises a circuit for generating binary or multilevel M-PAM communications symbols.

4. The radio device according to claim 1, and further comprising an up-sampling circuit that receives the signal from the FWT circuit for increasing the sampling rate on the signal containing the communications symbols.

5. The radio device according to claim 1, and further comprising a receiver unit that receives a constant radius orthogonal Walsh modulated communications signal having communications symbols containing communications data and comprising at least one of a phase demodulator circuit for phase demodulating the received signal, a phase unwrapper circuit for phase unwrapping the output of phase demodulator and a FWT circuit for performing a Fast Walsh Transform as a demodulator matched filter to obtain the communications data.

6. The radio device according to claim 5, wherein said receiver unit further comprises a multi-user detection circuit for applying standard or iterative multi-user detection algorithms to the received signal.

7. The radio device according to claim 6, wherein said receiver unit further comprises a feedback loop from the multi-user detection circuit for iterative processing.

8. The radio device according to claim 5, wherein said receiver unit further comprises a frequency domain equalizer circuit.

9. The radio device according to claim 5, wherein said receiver unit further comprises a circuit for increasing the sampling rate of the received signal.

10. A system for communicating data, comprising:

a transmitter comprising;

a modulator configured to generate M-PAM (M-Pulse Amplitude Modulation) communications symbols containing communications data;

a Fast Walsh Transform (FWT) circuit connected to the modulator and configured to receive the communications symbols from the modulator and orthogonally encode and band-spread the communications symbols using the Fast Walsh Transform;

a guard time circuit connected to the FWT circuit and configured to cyclically extend the output of the Fast Walsh Transform by a guard time;

a frequency modulation circuit connected to the guard time circuit and configured to frequency modulate the communications symbols wherein a constant radius orthogonal Walsh modulated communications signal containing the communications data is generated;

an antenna through which the communications signal is transmitted; and

a receiver remote from the transmitter that receives the constant radius orthogonal Walsh modulated communications signal and comprising at least one of a phase demodulator circuit configured to phase demodulate the received signal, a phase unwrapper circuit configured to phase unwrap the output of phase demodulator circuit and a FWT circuit configured to perform a Fast Walsh Transform as a demodulator matched filter to obtain any communications data that had been transmitted from the transmitter.

11. The system according to claim 10, wherein said transmitter further comprises at least one of a square root raised cosine filter operative before the frequency modulation circuit for band-limiting a signal containing the communications symbols and a clipping device operative before the frequency modulation circuit for reducing the peak to average power ratio of signal.

12. The system according to claim 10, wherein said modulator of said transmitter further comprises a circuit for generating binary or multilevel M-PAM communications symbols.

13. The system according to claim 10, wherein said transmitter further comprises an up-sampling circuit that receives the signal from the FWT circuit for increasing the sampling rate on the signal containing the communications symbols.

14. The system according to claim 10, wherein said receiver further comprises a multi-user detection circuit for applying standard or iterative multi-user detection algorithms to the received communications signal.

15. The system according to claim 14, wherein said receiver further comprises a feedback loop from the multi-user detection circuit for iterative processing.

16. A method of communicating data, comprising:

generating M-PAM (M-Pulse Amplitude Modulation) communications symbols containing communications data;

receiving the modulated communications symbols and orthogonally encoding and band-spreading the communications symbols using a Fast Walsh Transform;

cyclically extending the Fast Walsh Transform output by a guard time;

frequency modulating the communications symbols generate a constant radius orthogonal Walsh modulated communications signal containing the communications data; and

transmitting the constant radius orthogonal Walsh modulated communications signal to at least one receiver.

17. The method according to claim 16, which further comprises at least one of a band-limiting circuit and a clipping circuit applied to signal containing the communications symbols before frequency modulating the signal.

18. The method according to claim 17, which further comprises band-limiting the signal by filtering the signal within a square root raised cosine filter.

19. The method according to claim 16, which further comprises increasing the sampling rate in the signal containing the communications symbols after orthogonally encoding and band-spreading the communications symbols.

20. The method according to claim 16, which further comprises generating binary or multilevel M-PAM communications symbols.

21. The method according to claim 16, which further comprises receiving the constant radius orthogonal Walsh modulated communications signal within at least one receiver and phase demodulating and performing a Fast Walsh Transform as a demodulator matched filter to obtain any communications data.

22. The method according to claim 21, which further comprises processing the received communications signal at the receiver using standard or iterative multi-user detection (MUD) algorithms.

23. The method according to claim 22, which further comprises iteratively processing from a standard or iterative multi-user detection circuit back to a Fast Walsh Transform circuit or Frequency Domain Equalizer circuit.

24. The method according to claim 21, which further comprises oversampling the received communications signal at the receiver.

25. The method according to claim 21, which further comprises frequency domain equalizing at the receiver.