Orthogonal frequency division multiplexing (OFDM) communications device and method that incorporates low PAPR preamble and frequency hopping

1. A communications device, comprising:

a source of communications data and a training sequence corresponding to a preamble;

a modulation and mapping circuit that modulates the communications data and training sequence into a plurality of multiple subcarriers that are orthogonal to each other to form an Orthogonal Frequency Division Multiplexing (OFDM) communications signal having modulated subcarriers carrying the communications data forming a data payload and modulated subcarriers forming the preamble;

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 based on an encryption algorithm to frequency hop each subcarrier at an OFDM symbol rate and turn ON and OFF selected subcarriers; and

wherein said modulation and mapping circuit is configured to apply a quadratic modulation to each of the subcarriers carrying the training sequences and apply a specific phase angle to each sinusoid forming the modulated subcarrier carrying the training sequence to produce a low peak-to-average power ratio (PAPR) preamble.

2. The communications device according to claim 1 , and further comprising a circuit for spreading the selected ON subcarriers over the frequency domain to reduce average power for enhanced Low Probability of Interception/Low Probability of Detection (LPI/LPD) to allow for more transmit power within a spectral mask and reduce adverse effects of Frequency Selective Fading.

3. The communications device according to claim 2 , and further comprising a circuit for reducing the number of subcarriers as compared to an IFFT size and a spreading sequence length for increased processing gain and reduced average power per frequency bin.

4. The communications device according to claim 1 , wherein said modulation and mapping circuit is operative for independently amplitude modulating each subcarrier carrying the data sequences.

5. The communications device according to claim 1 , wherein the low PAPR preamble is independent of the number of subcarriers forming the OFDM communications signal.

6. The communications device according to claim 1 , wherein the preamble includes a long sync sequence for acquisition, detection, frequency and channel estimation having a guard interval (GI).

7. The communications device according to claim 1 , wherein said modulation and mapping circuit is operative for forming each of the subcarriers that carries the training sequences of the OFDM communications signal to have equal amplitude.

8. A method of communicating data, comprising:

receiving communications data to be transmitted and a training sequence corresponding to a preamble;

generating an Orthogonal Frequency Division Multiplexing (OFDM) communications signal having modulated subcarriers carrying the communications data forming a data payload and subcarriers carrying the training sequences forming the preamble;

generating pseudo-random signals to a modulation and mapping circuit based on an encryption algorithm and frequency hopping each subcarrier at an OFDM symbol rate and turning ON and OFF selected subcarriers;

applying quadratic phase modulation to each of the subcarriers carrying the training sequences at a specific phase angle to each sinusoid forming the modulated subcarriers carrying the training sequence to produce a low peak-to-average power ratio (PAPR) preamble; and

transmitting the OFDM communications signal along a communications channel to a receiver.

9. The method according to claim 8 , which further comprises spreading the selected ON subcarriers over the frequency domain to reduce average power for enhanced Low Probability of Interception/Low Probability of Detection (LPI/LPD) to allow for more transmit power within a spectral mask and reduce adverse effects of Frequency Selective Fading.

10. The method according to claim 9 , which further comprises reducing the number of subcarriers as compared to an IFFT size and a spreading sequence length for increased processing gain and reduced average power per frequency bin.

11. The method according to claim 8 , which further comprises equally spacing in frequency each of the subcarriers carrying the training sequences.

12. The method according to claim 8 , which further comprises forming each of the subcarriers carrying the training sequences to have equal amplitude.

13. The method according to claim 8 , which further comprises independently amplitude modulating each subcarrier carrying the data sequences.

14. The method according to claim 8 , which further comprises measuring fluctuations within a flat-topped spectrum of the OFDM communications signal corresponding to the preamble to reflect the frequency response of the communications channel.

15. A method of communicating data, comprising:

receiving communications data to be transmitted and a training sequence corresponding to a preamble;

generating an Orthogonal Frequency Division Multiplexing (OFDM) communications signal having modulated subcarriers carrying the communications data forming a data payload and subcarriers carrying training sequences forming the preamble, wherein the preamble includes a long sync sequence for acquisition, detection, frequency and channel estimation having a guard interval (GI);

generating pseudo-random signals to a modulation and mapping circuit based on an encryption algorithm and frequency hopping each subcarrier at an OFDM symbol rate and turning ON and OFF selected subcarriers;

applying a quadratic phase modulation to each of the subcarriers carrying the training sequences at a specific phase angle to each sinusoid forming the modulated subcarrier carrying the training sequence to produce a low peak-to-average power ratio (PAPR) preamble with about a PAPR value of 2.6 decibels (dB); and

splitting the guard interval from the long sync sequence and processing into values that represent the inverse low PAPR preamble as plus or minus one (+/−1) values in a real or imaginary component as adds and subtracts for channel estimation.

16. The method according to claim 15 , which further comprises spreading the selected ON subcarriers over the frequency domain to reduce average power for enhanced Low Probability of Interception/Low Probability of Detection (LPI/LPD) to allow for more transmit power within a spectral mask and reduce adverse effects of Frequency Selective Fading.

17. The method according to claim 16 , which further comprises reducing the number of subcarriers as compared to an IFFT size and a spreading sequence length for increased processing gain and reduced average power per frequency bin.

18. The method according to claim 15 , which further comprises using the “n” samples of the guard interval as a normal guard interval and portions of the long sync sequence for Fast Fourier Transform (FFT) processing for channel estimation.

19. The communications device according to claim 1 , wherein the PAPR preamble has a PAPR value of about 2.6 dB.

20. The method according to claim 8 , wherein the PAPR preamble has a PAPR value of about 2.6 dB.

21. The method according to claim 15 , wherein the PAPR preamble has a PAPR value of about 2.6 dB.

22. A communications device, comprising:

a source of communications data and a training sequence corresponding to a preamble;

a modulation and mapping circuit that modulates the communications data and training sequence into a plurality of multiple subcarriers that are orthogonal to each other to form an Orthogonal Frequency Division Multiplexing (OFDM) communications signal having modulated subcarriers carrying the communications data forming a data payload and modulated subcarriers forming the preamble;

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;

a circuit for spreading the selected ON subcarriers over the frequency domain to reduce average power for enhanced Low Probability of Interception/Low Probability of Detection (LPI/LPD) to allow for more transmit power within a spectral mask and reduce adverse effects of Frequency Selective Fading;

a circuit for reducing the number of subcarriers as compared to an IFFT size and a spreading sequence length for increased processing gain and reduced average power per frequency bin; and

wherein said modulation and mapping circuit is configured to apply a quadratic modulation to each of the subcarriers carrying the training sequences and apply a specific phase angle to each of the sinusoids forming the modulated subcarrier carrying the training sequence to produce a low peak-to-average power ratio (PAPR) preamble.

23. A method of communicating data, comprising:

receiving communications data to be transmitted and a training sequence corresponding to a preamble;

generating an Orthogonal Frequency Division Multiplexing (OFDM) communications signal having modulated subcarriers carrying the communications data forming a data payload and subcarriers carrying training sequences forming the preamble, wherein the preamble includes a long sync sequence for acquisition, detection, frequency and channel estimation having a guard interval (GI);

generating pseudo-random signals to a modulation and mapping circuit based on an encryption algorithm and frequency hopping each subcarrier at an OFDM symbol rate;

applying a quadratic phase modulation to subcarriers carrying the training sequences to produce a low peak-to-average power ratio (PAPR) preamble;

spreading any selected ON subcarriers over the frequency domain to reduce average power for enhanced Low Probability of Interception/Low Probability of Detection (LPI/LPD) to allow for more transmit power within a spectral mask and reduce adverse effects of Frequency Selective Fading;

reducing the number of subcarriers as compared to an IFFT size and a spreading sequence length for increased processing gain and reduced average power per frequency bin; and

splitting the guard interval from the long sync sequence and processing into values that represent the inverse low PAPR preamble as plus or minus one (+/−1) values in a real or imaginary component as adds and subtracts for channel estimation.