Ultra wide bandwidth spread-spectrum communications systems
View Patent ↗An ultra wide bandwidth, high speed, spread spectrum communications system uses short wavelets of electromagnetic energy to transmit information through objects such as walls or earth. The communication system uses baseband codes formed from time shifted and inverted wavelets to encode data on a RF signal. Typical wavelet pulse durations are on the order of 100 to 1000 picoseconds with a bandwidth of approximately 8 GHz to 1 GHz, respectively. The combination of short duration wavelets and encoding techniques are used to spread the signal energy over an ultra wide frequency band such that the energy is not concentrated in any particular narrow band (e.g. VHF: 30-300 MHz or UHF: 300-1000 MHz) and is not detected by conventional narrow band receivers so it does not interfere with those communication systems. The use of pulse codes composed of time shifted and inverted wavelets gives the system according to the present invention has a spatial resolution on the order of 1 foot which is sufficient to minimize the negative effects of multipath interference and permit time domain rake processing.
1. A data communications method, comprising:
receiving an input of high-speed digital data for communication;
repetitively generating a codeword to produce a digital code signal;
modulating the digital code signal in accord with the high-speed digital data, to generate a modulated code signal;
generating a modulated ultrawideband impulse signal in response to the modulated code signal, wherein:
(a) the modulated ultrawideband impulse signal comprises a sequence of short impulse wavelets, and
(b) the sequence of short impulse wavelets is modulated in accord with bits of the modulated code signal; and
outputting the modulated ultrawideband impulse signal.
2. The data communication method as in claim 1 , wherein the digital code signal comprises a cyclical stream of pseudo-random bits representing a digital chip code.
3. The data communication method as in claim 1 , further comprising processing the high-speed digital data, wherein the step of modulating the digital code signal in accord with the high-speed digital data comprises modulating the processed high-speed digital data onto the digital code signal to form the modulated code signal.
4. The data communication method as in claim 3 , wherein the step of processing the high-speed digital data comprises:
encoding the high-speed digital data for forward error correction (FEC); and
differentially encoding the FEC encoded data.
5. The data communication method as in claim 2 , wherein the step of modulating the digital code signal comprises modulating each instance of the digital chip code in accord with the value of a bit of the processed high-speed digital data.
6. The data communication method as in claim 2 , wherein the step of modulating the digital code signal comprises:
producing an instance of the digital chip code in the modulated code signal, in response to each 1-bit of the processed high-speed digital data; and
producing an inverse of the digital chip code in the modulated code signal, in response to each 0-bit of the processed high-speed digital data.
7. The data communication method as in claim 1 , wherein the sequence of short impulse wavelets is shape modulated in accord with bits of the modulated code signal.
8. The data communication method as in claim 1 , wherein the sequence of short impulse wavelets is bi-phase modulated in accord with bits of the modulated code signal.
9. The data communication method as in claim 1 , wherein the step of generating the modulated ultrawideband impulse signal comprises:
generating first short impulse wavelets of a first predetermined shape;
generating second short impulse wavelets having a second predetermined shape; and
selecting between one or more of the first short impulse wavelets and one or more of the second short impulse wavelets, in response to the value of each bit of the modulated code signal.
10. The data communication method as in claim 1 , wherein the step of outputting comprises:
analog modulating each impulse wavelet in the modulated sequence of impulse wavelets in accord with a code; and
transmitting the analog modulated wavelets.
11. The data communication method as in claim 1 , wherein responsive to each respective short impulse wavelet of the modulated sequence, the step of outputting comprises:
generating a plurality of time offset replicas of the respective short impulse wavelet;
combining the time offset replicas, in accord with a code, to form a coded group of impulse wavelets derived from the respective short impulse wavelet; and
transmitting the coded group of impulse wavelets.
12. The data communication method as in claim 1 , wherein the step of outputting comprises transmitting the modulated ultrawideband impulse signal as a carrierless baseband signal.
13. The data communication method as in claim 1 , further comprising:
receiving the modulated ultrawideband impulse signal;
demodulating the modulated sequence of short impulse wavelets to recover the modulated code signal; and
demodulating the modulated code signal to recover the high-speed digital data.
14. A data communications method, comprising:
receiving an input of high-speed digital data for communication;
processing the high-speed digital data;
generating a code modulated digital signal responsive to the processed high speed data;
generating a sequence of short impulse wavelets;
processing the sequence of short impulse wavelets in response to the processed high speed data so as to produce a modulated ultrawideband impulse signal, wherein the sequence of short impulse wavelets in the modulated ulrawideband signal is modulated in accord with bits of the code modulated digital signal; and
transmitting the modulated ultrawideband impulse signal.
15. The data communication method as in claim 14 , wherein the code modulated digital signal comprises a modulated pseudo-random chip code.
16. The data communication method as in claim 14 , wherein the step of processing the high-speed digital data comprises:
encoding the high-speed digital data for forward error correction (FEC); and
differentially encoding the FEC encoded data.
17. The data communication method as in claim 14 , wherein the step of generating a code modulated digital signal comprises modulating successive instances of a repeating codeword in accord with values of successive bits of the processed high-speed digital data.
18. The data communication method as in claim 17 , wherein the step of modulating successive instances of the repeating codeword comprises:
producing an instance of the codeword in the code modulated digital signal, in response to each 1-bit of the processed high-speed digital data; and
producing an inverse of the codeword in the code modulated digital signal, in response to each 0-bit of the processed high-speed data.
19. The data communication method as in claim 14 , wherein the sequence of short impulse wavelets is shape modulated in accord with bits of the code modulated digital signal.
20. The data communication method as in claim 14 , wherein the sequence of short impulse wavelets is bi-phase modulated in accord with bits of the code modulated digital signal.
21. The data communication method as in claim 14 , wherein:
the step of generating the sequence of short impulse wavelets comprises generating first short impulse wavelets of a first predetermined shape, and generating second short impulse wavelets having a second predetermined shape; and
the step of processing the sequence of short impulse wavelets comprises selecting between one or more of the first short impulse wavelets and one or more of the second
short impulse wavelets, in response to the value of each successive bit of the code modulated digital signal.
22. The data communication method as in claim 14 , wherein the step of transmitting comprises:
analog modulating each impulse wavelet in the modulated sequence of short impulse wavelets in accord with a code; and
transmitting the analog modulated signal.
23. The data communication method as in claim 14 , wherein responsive to each respective short impulse wavelet of the modulated sequence, the step of transmitting comprises:
generating a plurality of time offset replicas of the respective short impulse wavelet;
combining the time offset replicas, in accord with a code, to form a coded group of impulse wavelets derived from the respective short impulse wavelet; and
transmitting the group of impulse wavelets.
24. The data communication method as in claim 14 , wherein the step of transmitting comprises transmitting the modulated ultrawideband impulse signal a carrierless baseband signal.
25. The data communication method as in claim 14 , further comprising:
receiving the modulated ultrawideband impulse signal;
demodulating the modulated sequence of short impulse wavelets to recover the modulated code signal; and
demodulating the modulated code signal to recover the high-speed digital data.
26. An ultrawideband impulse transmitter, for transmitting high-speed digital data for communication, comprising:
an input for receiving the high-speed digital data for communication;
a code generator for generating a digital code signal, the digital code signal comprising a repetitive codeword;
a gate responsive to a stream of bits obtained in response to the high-speed digital data and coupled to the code generator, for modulating the digital code signal in accord with the stream of bits;
at least one impulse generator, for generating short impulse wavelets; and
a selector responsive to the modulated digital code signal and coupled to the at least one impulse generator, wherein the at least one impulse generator and the selector produce a modulated ultrawideband impulse signal comprising a sequence of the short impulse wavelets modulated in accord with the modulated digital code signal.
27. The ultrawideband impulse transmitter as in claim 26 , wherein the code generator generates a cyclical stream of pseudo-random bits representing the digital chip code.
28. The ultrawideband impulse transmitter as in claim 26 , wherein the gate comprises an exclusive OR gate coupled to receive the stream of bits obtained in response to the high-speed digital data and to receive the digital code signal from the code generator, and the exclusive OR gate outputs the modulated digital code signal to the selector.
29. The ultrawideband impulse transmitter as in claim 28 , wherein:
the at least one impulse generator generates short impulse wavelets of a first shape and short impulse wavelets of a second shape; and
the selector comprises a switch controlled in response to the modulated digital code signal and coupled to the at least one impulse generator, for selectively outputting impulse wavelets of the first shape or impulse wavelets of the second shape, in response to the modulated digital code signal from the exclusive OR gate.
30. The ultrawideband impulse transmitter as in claim 26 , wherein the at least one impulse generator comprises a wavelet generator for generating first short impulse wavelets with first shapes selectable from among two or more shapes corresponding substantially to two or more derivatives of a Gaussian waveform.
31. The ultrawideband impulse transmitter as in claim 30 , wherein:
the at least one impulse generator further comprises a second wavelet generator for generating second short impulse wavelets with second shapes selectable from among two or more shapes corresponding substantially to two or more inverses of derivatives of a Gaussian waveform; and
the selector selects between at least one first short impulse wavelet having a selected one of the first shapes from the first wavelet generator and at least one second short impulse wavelet having a selected one of the second shapes from the second wavelet generator, for inclusion in the modulated ultrawideband impulse signal, in response to each successive bit of the modulated digital code signal.
32. The ultrawideband impulse transmitter as in claim 26 , further comprising:
a forward error correction (FEC) encoder, for FEC encoding of the high-speed data; and
a differential encoder coupled to the FEC encoder for differentially encoding the FEC encoded data and coupled to the gate to supply the differentially encoded data to the gate as the stream of bits.
33. The ultrawideband impulse transmitter as in claim 26 , further comprising an impulse code modulator coupled to receive the modulated ultrawideband impulse signal, for generating a coded group of time offset replicas of each respective short impulse wavelet contained in the modulated ultrawideband impulse signal.
34. The ultrawideband impulse transmitter as in claim 26 , further comprising:
a power amplifier for amplifying the modulated ultrawideband impulse signal; and
an antenna coupled to an output of the amplifier for transmitting the amplified signal over a wireless link.
35. A method of receiving high-speed data via ultrawideband impulse communication, comprising:
receiving a modulated ultrawideband impulse signal transmitted from a remote location, wherein the received modulated ultrawideband impulse signal comprises a sequence of short impulse wavelets modulated in accord with a code signal, the code signal being digitally modulated with the bits obtained from the high-speed data;
generating a local code signal comprising a repeating codeword;
generating a local modulated ultrawideband impulse signal in response to the local code signal, wherein the local modulated impulse signal comprises a local sequence of short impulse wavelets, and the local sequence of short impulse wavelets is modulated in accord with bits of the local code signal;
locking timing of the local modulated ultrawideband impulse signal to the received modulated ultrawideband impulse signal; and
correlating the locked local modulated ultrawideband impulse signal to the received modulated ultrawideband impulse signal to detect the bits obtained from the high-speed data in the received modulated ultrawideband impulse signal.
36. The method of claim 35 , wherein the locking step comprises delay-locking the local modulated ultrawideband impulse signal to the received modulated ultrawideband impulse signal.
37. The method of claim 35 , wherein the step of generating the local modulated ultrawideband impulse signal comprises:
generating first short impulse wavelets of a first predetermined shape;
generating second short impulse wavelets having a second predetermined shape; and
selecting between one or more of the first short impulse wavelets and one or more of the second short impulse wavelets, in response to the value of each bit of the local code signal.
38. The method of claim 35 , wherein for each respective selected short impulse wavelet contained in the local modulated ultrawideband impulse signal, the step of generating the local modulated ultrawideband impulse signal further comprises:
generating a plurality of time offset replicas of the respective selected short impulse wavelet; and
combining the time offset replicas, in accord with a code, to form a coded group of impulse wavelets derived from the respective impulse wavelet.
39. The method of claim 35 , wherein the receiving step comprises applying an analog code for compressive matched filtering of the received modulated ultrawideband impulse signal.
40. The method of claim 35 , wherein a shape of a short impulse wavelet contained in the local modulated ultrawideband impulse signal is a derivative or a Hilbert transform of a shape of a short impulse wavelet expected to be in the received modulated ultrawideband impulse signal.
41. An ultrawideband impulse receiver, for receiving high-speed digital data, comprising:
a receiver from end for receiving a modulated ultrawideband impulse signal transmitted from a remote location, wherein the received modulated ultrawideband impulse signal comprises a sequence of short impulse wavelets modulated in accord with a code signal, the code signal being digitally modulated with bits corresponding to the high-speed data; and
means for demodulating the received modulated ultrawideband impulse signal to recover bits corresponding to the high-speed digital data,
wherein the means for demodulating comprises:
means for generating a local ultrawideband impulse signal; and
a delay lock loop for locking timing of the local ultrawideband impulse signal to timing of the received modulated ultrawideband impulse signal, and for using the locked local ultrawideband impulse signal to recover the bits corresponding to the high-speed digital data from the received modulated ultrawideband impulse signal.
42. A data communications method, comprising:
a step for receiving an input of high-speed digital data for communication;
a step for repetitively generating a codeword to produce a digital code signal;
a step for modulating the digital code signal in accord with the high-speed digital data, to generate a modulated code signal;
a step for generating a modulated ultrawideband impulse signal in response to the modulated code signal, wherein;
(a) the modulated ultrawideband impulse signal comprises a sequence of short impulse wavelets, and
(b) the sequence of short impulse wavelets is modulated in accord with bits of the modulated code signal; and
a step for outputting the modulated ultrawideband impulse signal.