COMMUNICATION SYSTEM EMPLOYING CHAOTIC SEQUENCE BASED FREQUENCY SHIFT KEYING SPREADING SIGNALS

• US 20180309477A1
• Filed: 04/24/2018
• Published: 10/25/2018
• Est. Priority Date: 04/24/2017
• Status: Active Grant

• Current Assignee: Chaos Prime, Inc.
• Original Assignee: Chaos Prime, Inc.
• Inventors: Michaels, Alan
• Granted Patent: US 10,447,339 B2
• Time in Patent Office: Days
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/70754 Setting of search window, i.e. range of code offsets to be searched H04B1/70758 takes precedence
• CPC Class Codes: H04B 2001/70724 featuring pilot assisted reception
• CPC Class Codes: H04B 2201/7073 Direct sequence modulation synchronisation
• CPC Class Codes: H04L 27/122 using digital generation of carrier signals digital function generators G06F1/02, H04L17/10; generating pulses having stepped portions using digital techniques H03K4/026
• CPC Class Codes: H04L 27/20 Modulator circuits; Transmitter circuits
• CPC Class Codes: H04L 27/2028 in which the phase changes are non-linear
• CPC Class Codes: H04L 27/2035 using a single or unspecified number of carriers
• CPC Class Codes: H04L 27/2092 with digital generation of the modulated carrier (does not include the modulation of a digitally generated carrier)

Abstract

A candidate arbitrary-phase spread spectrum modulation technique that offers similar performance to spread continuous phase modulation (CPM) waveforms and additional capabilities for programming a chosen frequency domain spectra into the resulting spread spectrum signal. The proposed chaotic-FSK waveform is derived from high-order sequence-based spread spectrum signals, with multi-bit resolution chaos-based sequences defining incremental phase words, enabling real-time efficient generation of practically non-repeating waveforms. A result of the C-FSK formulation is a parameterized hybrid modulation capable of acting like a traditional sequence-based spread spectrum signal or a traditional frequency shift keying signal depending on chosen parameters. As such, adaptation in this modulation may be easily implemented as a time-varying evolution, increasing the security of the waveform while retaining many efficiently implementable receiver design characteristics of traditional PSK modulations.

Claims

1. An apparatus for generating a communications signal, the apparatus comprising:

a pseudorandom number generator for providing a sequence of pseudorandom phase words;

a mapping module including a color mapping table containing phase value information, the mapping module being configured to provide an output phase word sequence by phase mapping the sequence of pseudorandom phase words in accordance with the phase value information; and

a modulator operative to generate the communications signal using the output phase word sequence wherein a frequency domain spectra of the communications signal is determined in accordance with the phase value information.

2. The apparatus of claim 1 wherein the mapping module includes a color mapper unit followed by an accumulator.

3. The apparatus of claim 1 wherein the mapping module includes an accumulator followed by a color mapper unit.

4. The apparatus of claim 1 wherein the sequence of pseudorandom phase words includes a sequence of k-bit phase words uniformly distributed as values on GF(2^k), the mapping module being configured to surjectively map the sequence of k-bit phase words onto a subset of GF(2^k).

5. The apparatus of claim 4 wherein the color mapping table includes 2^k memory entries and wherein each of the 2^k memory entries stores a uniform phase value.

6. The apparatus of claim 4 wherein the color mapping table includes 2^k memory entries and wherein the 2^k memory entries are subdivided into a discrete number of M allowable phases, thereby establishing a discrete number of phase steps.

7. The apparatus of claim 4 wherein the color mapping table includes 2^k memory entries and wherein the 2^k memory entries store non-uniform phase values.

8. The apparatus of claim 4 wherein the color mapping table includes 2^k memory entries and wherein the 2^k memory entries store a time-varying programmable set of phase values.

9. The apparatus of claim 4 wherein the color mapping table includes parallel, instantiated tables of phase words, the mapping module being configured to select one of the parallel, instantiated tables of phase words in response to a table selection signal.

10. The apparatus of claim 9 wherein the table selection is based upon at least some portion of the k-bit phase words.

11. The apparatus of claim 1 wherein the sequence of pseudorandom phase words represent a sequence of phase difference values and wherein the phase value information corresponds to phase difference values, the mapping module further including an integrator configured to synthesize ones of the phase difference values into a stream of phase values provided to the modulator wherein the stream of phase values affects a rate of change of phase of the communications signal.

12. The apparatus of claim 1 wherein the communications signal is a chaotic signal.

13. A transmitter, comprising:

an encoder for generating encoded data symbols based upon input data provided by a data source;

a communications signal generator including;

a pseudorandom random number generator for providing a sequence of pseudorandom phase words;

a mapping module including a color mapping table containing phase value information, the mapping module being configured to provide an output phase word sequence by phase mapping the sequence of pseudorandom phase words in accordance with the phase value information;

a modulator operative to generate a spreading sequence using the output phase word sequence wherein a frequency domain spectra of the spreading sequence is determined in accordance with the phase value information; and

a transmit signal generator for generating a transmit signal by spreading the encoded data symbols using the spreading sequence.

14. The transmitter of claim 13 wherein the phase value information includes at least one phase value or at least one phase difference value.

15. A transceiver apparatus, comprising:

a receiver including a channel state information module configured to provide channel state information based upon a received signal;

a color mapping table storing phase value information wherein the phase value information is determined based at least in part upon the channel state information; and

a communications signal generator configured to generate a communications waveform, the communications signal generator including a mapping module operative to introduce a selected frequency domain spectra into the communications waveform in accordance with the phase value information.

16. The transceiver apparatus of claim 15 wherein the phase value information includes at least one phase value or at least one phase difference value.

17. A method for generating a communications signal, the method comprising:

providing a sequence of pseudorandom phase words;

generating a color mapping table containing phase value information;

providing an output phase word sequence by phase mapping the sequence of pseudorandom phase words in accordance with the phase value information; and

generating the communications signal using the output phase word sequence wherein a frequency domain spectra of the communications signal is determined in accordance with the phase value information.

18. The method of claim 17 wherein the sequence of pseudorandom phase words includes a sequence of k-bit phase words uniformly distributed as values on GF(2^k), the method further including surjectively mapping the sequence of k-bit phase words onto a subset of GF(2^k).

19. The method of claim 18 wherein the color mapping table includes 2^k memory entries and wherein each of the 2^k memory entries stores a uniform phase value.

20. The method of claim 18 wherein the color mapping table includes 2^k memory entries and wherein the 2^k memory entries are subdivided into a discrete number of M allowable phases, thereby establishing a discrete number of phase steps.

21. The method of claim 18 wherein the color mapping table includes 2^k memory entries and wherein the 2^k memory entries store non-uniform phase values.

22. The method of claim 18 wherein the color mapping table includes 2^k memory entries and wherein the 2^k memory entries store a time-varying programmable set of phase values.

23. The method of claim 18 wherein the color mapping table includes parallel, instantiated tables of phase words, the method further including selecting one of the parallel, instantiated tables of phase words in response to a table selection signal.

24. The method of claim 23 wherein the table selection is based upon at least some portion of the k-bit phase words.

25. The method of claim 17 wherein the sequence of pseudorandom phase words represent a sequence of phase difference values and wherein the phase value information corresponds to phase difference values, the method further including synthesizing a stream of phase values by integrating ones of the phase difference values wherein the stream of phase values affects a rate of change of phase of the communications signal.

26. The method of claim 17 wherein the communications signal is a chaotic signal.

27. A method, comprising:

generating encoded data symbols based upon input data provided by a data source;

providing a sequence of pseudorandom phase words;

generating a color mapping table containing phase value information;

providing an output phase word sequence by phase mapping the sequence of pseudorandom phase words in accordance with the phase value information;

generate a spreading sequence using the output phase word sequence wherein a frequency domain spectra of the spreading sequence is determined in accordance with the phase value information; and

generating a transmit signal by spreading the encoded data symbols using the spreading sequence.

28. The method of claim 27 wherein the phase value information includes at least one phase value or at least one phase difference value.

29. A method, comprising:

providing channel state information based upon a received signal;

storing phase value information wherein the phase value information is determined based at least in part upon the channel state information; and

generating, in accordance with the phase value information, a communications waveform having a selected frequency domain spectra determined by the phase value information.

30. The method of claim 29 wherein the phase value information includes at least one phase value or at least one phase difference value.