Ultra wide bandwidth spread-spectrum communications system

• US 20030053554A1
• Filed: 09/30/2002
• Published: 03/20/2003
• Est. Priority Date: 12/12/1997
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Xtremespectrum Incorporated
• Inventors: McCrokle, John W., Rofheart, Martin
• Granted Patent: US 6,901,112 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H04B 1/71632 Signal aspects H04B1/7172 and H04B1/7176 take precedence
• CPC Class Codes: H04B 1/7172 Pulse shape in general H04L25/03834
• CPC Class Codes: H04B 1/7174 Pulse generation in general H04L25/03834
• CPC Class Codes: H04B 1/7176 Data mapping, e.g. modulation
• CPC Class Codes: H04B 1/7183 Synchronisation
• CPC Class Codes: H04B 1/719 Interference-related aspects
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation
• CPC Class Codes: H04L 27/0004 using wavelets

Abstract

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.

Claims

1. A data communications method, comprising:

producing a bit stream in response to high-speed digital data for communication;

in response to the bit stream, generating a sequence of short impulse wavelets, wherein the sequence of short impulse wavelets is modulated in accord with bits of the bit stream;

responsive to each respective short impulse wavelet of the modulated sequence,

(a) generating a plurality of time offset replicas of the respective short impulse wavelet, and

(b) 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

outputting the coded groups of impulse wavelets in sequence, as a modulated ultrawideband impulse signal.

2. The data communication method as in claim 1, wherein the code comprises a Barker code.

3. The data communication method as in claim 1, wherein the step of combining comprises:

adding any of the time offset replicas at an offset corresponding to a location in the code having a first value; and

subtracting any of the time offset replicas at an offset corresponding to a location in the code having a second value.

4. The data communication method as in claim 1, wherein the step of generating a plurality of time offset replicas comprises:

splitting the respective short impulse wavelet into a number of signal replicas, the number of signal replicas corresponding to a number n of bits of the code, each signal replica corresponding to a bit position of the code; and

delaying each of the signal replicas by a time offset equal to the corresponding bit position of the code multiplied by a time delay factor T_d, to form the time offset replicas.

5. The data communication method as in claim 4, wherein the code consists of a predetermined binary code, and the step of combining comprises:

adding any of the time offset replicas corresponding to a bit position of the predetermined binary code having a first binary value; and

subtracting any of the time offset replicas corresponding to a bit position of the predetermined binary code having a second binary value.

6. The data communication method as in claim 1, wherein the step of producing the bit stream comprises:

receiving an input of the high-speed digital data for communication; and

processing the high-speed digital data to produce the bit stream.

7. The data communication method as in claim 6, wherein the step of processing the high-speed digital data comprises one or more of:

forward error correction (FEC) encoding;

differential encoding; and

modulating a code signal comprising a repeating codeword.

8. The data communication method as in claim 1, wherein the sequence of short impulse wavelets is shape modulated in accord with values of the bits of the bit stream.

9. The data communication method as in claim 1, wherein the sequence of short impulse wavelets is bi-phase modulated in accord with values of the bits of the bit stream.

10. The data communication method as in claim 1, wherein the step of generating the sequence of short impulse wavelets 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 bit stream.

11. 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.

12. The data communication method as in claim 1, further comprising:

receiving the modulated ultrawideband impulse signal;

compressing coded groups of impulse wavelets in the received modulated ultrawideband impulse signal, to form a received modulated sequence of short impulse wavelets; and

demodulating the received modulated sequence of short impulse wavelets to recover the bit stream.

13. A data communications method, comprising:

receiving an input of high-speed digital data for communication;

processing the high-speed digital data;

generating a sequence of short impulse wavelets;

modulating the sequence of short impulse wavelets in response to the processed high speed data so as to produce a modulated sequence of short impulse wavelets;

responsive to each respective short impulse wavelet of the modulated sequence,

(a) generating a plurality of time offset replicas of the respective short impulse wavelet; and

(b) adding and subtracting the time offset replicas, in accord with a predetermined binary code, to form a code modulated group of impulse wavelets derived from the respective short impulse wavelet;

transmitting the code modulated groups of impulse wavelets in sequence, as a modulated ultrawideband impulse signal.

14. The data communication method as in claim 13, wherein the predetermined binary code comprises a Barker code.

15. The data communication method as in claim 13, wherein:

the step of generating the time offset replicas produces a replica of the respective short impulse wavelet at a time offset corresponding to each of a plurality of bit positions of the predetermined binary code; and

the step of adding and subtracting the time offset replicas comprises;

(a) adding the replica of the respective short impulse wavelet at each time offset corresponding to a bit position of the predetermined binary code having a first value; and

(b) subtracting the replica of the respective short impulse wavelet at each time offset corresponding to a bit position of the predetermined binary code having a second value.

16. The data communication method as in claim 15, wherein the step of generating the time offset replicas comprises:

splitting the respective short impulse wavelet into a number of signal replicas, the number of signal replicas corresponding to a number n of bits of the predetermined binary code, each signal replica corresponding to a bit position of the predetermined binary code; and

delaying each of the signal replicas by a time offset equal to the corresponding bit position of the predetermined binary code multiplied by a time delay factor Td, to form the time offset replicas.

17. The data communication method as in claim 13, wherein the step of processing the high-speed digital data comprises one or more of:

forward error correction (FEC) encoding;

differential encoding; and

modulating a chip code signal.

18. The data communication method as in claim 13, wherein the sequence of short impulse wavelets is shape modulated in accord with values of bits of the processed high speed data.

19. The data communication method as in claim 13, wherein the sequence of short impulse wavelets is bi-phase modulated in accord with values of bits of the processed high speed data.

20. The data communication method as in claim 13, wherein:

the step of generating the sequence of short impulse wavelets comprises generating first short impulse wavelets of a first shape, and generating second short impulse wavelets of a second shape; and

the step of modulating 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 bit of the processed high speed data.

21. The data communication method as in claim 13, wherein the step of transmitting comprises transmitting the modulated ultrawideband impulse signal as a carrierless baseband signal.

22. The data communication method as in claim 13, further comprising:

receiving the modulated ultrawideband impulse signal;

compressing code modulated groups of impulse wavelets in the received modulated ultrawideband impulse signal, to form a received modulated sequence of short impulse wavelets; and

demodulating the received modulated sequence of short impulse wavelets, to recover the processed high-speed data.

23. 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 digital impulse modulator responsive to a stream of bits obtained in response to the high-speed digital data for generating a modulated sequence of short impulse wavelets, the sequence being modulated in accord with the stream of bits;

a code modulator, concatenated with the digital impulse modulator, for converting each respective short impulse wavelet in the modulated sequence into a respective group of short impulse wavelets and thereby forming a modulated ultrawideband impulse signal for transmission, the respective group of short impulse wavelets being modulated in accord with a code.

24. The ultrawideband impulse transmitter as in claim 23, wherein the code modulator comprises means responsive to each respective short impulse wavelet of the modulated sequence for generating a plurality of time offset replicas of the respective short impulse wavelet and combining the time offset replicas, in accord with the code.

25. The ultrawideband impulse transmitter as in claim 24, wherein the means for generating comprises:

a delay system for producing a number of signal replicas in response to each respective short impulse wavelet in the modulated sequence, the number of signal replicas corresponding to a number n of bits of the code, each signal replica corresponding to a bit position of the code, and for delaying each signal replica by a time offset equal to the corresponding bit position of the code multiplied by a time delay factor Td; and

a combiner system for forming each respective group of short impulse wavelets by combining any time offset replica corresponding to a bit position of the code having a first value with an inverse of any time offset replica corresponding to a bit position of the code having a second value.

26. The ultrawideband impulse transmitter as in claim 25, wherein the delay system comprises:

a splitter coupled to receive the modulated sequence from the digital impulse modulator for producing the signal replicas; and

a plurality of delay lines of different lengths for processing the signal replicas from the splitter.

27. The ultrawideband impulse transmitter as in claim 24, wherein the means for generating is programmable for utilizing different values for the code.

28. The ultrawideband impulse transmitter as in claim 27, wherein the means for generating comprises a programmable coupler and lattice structure.

29. The ultrawideband impulse transmitter as in claim 23, wherein the digital impulse modulator comprises:

at least one impulse generator for generating short impulse wavelets of a first shape and short impulse wavelets of a second shape; and

a selector controlled in response to the modulated digital code signal and coupled to the at least one impulse generator, for selectively causing an output of impulse wavelets of the first shape or impulse wavelets of the second shape, in response to the stream of bits.

30. The ultrawideband impulse transmitter as in claim 29, 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 stream of bits.

32. The ultrawideband impulse transmitter as in claim 23, 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.

33. The ultrawideband impulse transmitter as in claim 32, further comprising a digital code modulator for modulating the differentially encoded FEC encoded data onto a digital chip code signal, to produce a digitally modulated code signal for input to the digital impulse modulator as the stream of bits obtained in response to the high-speed digital data.

34. The ultrawideband impulse transmitter as in claim 23, 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 groups of code modulated short impulse wavelets;

compressing the code modulated groups of short impulse wavelets in the received modulated ultrawideband impulse signal to recover a sequence of impulse wavelets modulated with bits obtained from the high-speed data from the received modulated ultrawideband impulse signal;

generating a local ultrawideband impulse signal comprising a local sequence of short impulse wavelets;

locking timing of the local modulated ultrawideband impulse signal to the recovered sequence of impulse wavelets; and

correlating the locked local modulated ultrawideband impulse signal to the recovered sequence of impulse wavelets to detect the bits obtained from the high-speed data.

36. The method of claim 35, wherein the step of compressing the code modulated groups of short impulse wavelets comprises compressive matched filtering of the received modulated ultrawideband impulse signal.

37. The method of claim 35, wherein the locking step comprises delay-locking the local modulated ultrawideband impulse signal to the recovered sequence of impulse wavelets.

38. 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 groups of code modulated short impulse wavelets;

generating a local sequence of short impulse wavelets;

for each respective short impulse wavelet contained in the local sequence, generating a plurality of time offset replicas of the respective short impulse wavelet modulated in accord with a code, and thereby forming a local ultrawideband impulse 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 bits obtained from the high-speed data.

39. The method of claim 38, wherein the step of generating a plurality of time offset replicas comprises:

generating a plurality of time offset replicas of the respective selected short impulse wavelet; and

combining the time offset replicas to a group of wavelets, in accord with the code.

40. The method of claim 38, wherein the locking step comprises delay-locking the local modulated ultrawideband impulse signal to form the received modulated ultrawideband impulse signal.

41. An ultrawideband impulse receiver, for receiving high-speed digital data, comprising:

a receiver front end for receiving a modulated ultrawideband impulse signal transmitted from a remote location, wherein the received modulated ultrawideband impulse signal comprises groups of short impulse wavelets modulated in accord with a code;

a matched filter for applying the code to the groups of short impulse wavelets to compress the groups of short impulse wavelets so as to form a sequence of individual short impulse wavelets; and

a correlator for demodulating the sequence of individual short impulse wavelets to recover bits corresponding to the high-speed digital data.

42. The receiver of claim 41, wherein the correlator comprises a sliding correlator.

43. The receiver of claim 41, wherein the correlator comprises:

means for generating a local ultrawideband impulse signal; and

a delay lock loop for locking timing of the local modulated ultrawideband impulse signal to timing of the received modulated ultrawideband impulse signal, and for using the locked local modulated ultrawideband impulse signal to recover the bits corresponding to the high-speed digital data from the received modulated ultrawideband impulse signal.

44. The receiver of claim 43, wherein the delay lock loop comprises:

a mixer for mixing the locked local modulated ultrawideband impulse signal with the received modulated ultrawideband impulse signal; and

an integrator for cyclically integrating a result of the mixing over a bit time interval, to recover the bits corresponding to the high-speed digital data.

45. An ultrawideband impulse receiver, for receiving high-speed digital data, comprising:

a receiver front end for receiving a modulated ultrawideband impulse signal transmitted from a remote location, wherein the received modulated ultrawideband impulse signal comprises groups of short impulse wavelets modulated in accord with a code; and

an impulse generator for generating a local sequence of short impulse wavelets;

a code modulator, concatenated with the impulse generator, for converting each respective short impulse wavelet in the local modulated sequence into a respective group of short impulse wavelets and thereby forming a local modulated ultrawideband impulse signal, each respective group of short impulse wavelets being modulated in accord with the code; and

a delay lock loop for locking timing of the local modulated ultrawideband impulse signal to timing of the received modulated ultrawideband impulse signal, and for using the locked local modulated ultrawideband impulse signal to recover bits corresponding to the high-speed digital data from the received modulated ultrawideband impulse signal.

46. The receiver of claim 45, wherein the delay lock loop comprises a sliding correlator for locking the timing of the local modulated ultrawideband impulse signal to timing of the received modulated ultrawideband impulse signal.

47. The receiver of claim 45, wherein the delay lock loop comprises:

a mixer for mixing the locked local modulated ultrawideband impulse signal with the received modulated ultrawideband impulse signal; and

an integrator for cyclically integrating a result of the mixing over a bit time interval, to recover the bits corresponding to the high-speed digital data.

48. A data communications method, comprising:

a step for producing a bit stream in response to high-speed digital data for communication;

a step, responsive to the bit stream, for generating a sequence of short impulse wavelets, wherein the sequence of short impulse wavelets is modulated in accord with bits of the bit stream;

responsive to each respective short impulse wavelet of the modulated sequence,

(a) a step for generating a plurality of time offset replicas of the respective short impulse wavelet, and

(b) a step for 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

a step for outputting the coded groups of impulse wavelets in sequence, as a modulated ultrawideband impulse signal.