Radio communication system using spread spectrum techniques

• US 5,077,753 A
• Filed: 04/09/1990
• Issued: 12/31/1991
• Est. Priority Date: 04/09/1990
• Status: Expired due to Term

• Current Assignee: Proxim Wireless Corporation
• Original Assignee: Proxim Inc. (Proxim Corp.)
• Inventors: Messenger, Brian S., Grau, Juan Jr.
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US07/506,476
• Time in Patent Office: 631 Days
• Field of Search: 375/121, 375/1, 380/34, 380/38, 380/39, 380/46
• US Class Current: 375/141
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

A spread spectrum radio communication system includes a generator for generating a pseudo-random chipping sequence, a frequency spreader for combining digital data with the pseudo-random chipping sequence to produce a spread spectrum signal, a modulator for modulating the spread spectrum signal for broadcasting over a predefined frequency band, a demodulator for demodulating broadcast spread spectrum signals, a de-spreader that employs single bit quantization and oversampling for digitally correlating the output of the demodulator means with a pseudo-random chipping sequence, and an extractor for extracting clock and data signals from the output of the de-spreader. The chipping sequence is normally selected from a set of codes including an eleven-bit Barker code, its inverse and reversals of the inverse and non-inverse code.

Claims

1. A transmitter system for use with a spread spectrum radio communication system, comprising:

generator means for generating a pseudo-random chipping sequence;

frequency spreader means for combining digital data with the pseudo-random chipping sequence to produce a spread spectrum signal; and

,

modulator means for modulating the spread spectrum signal over a predefined frequency band.

2. A system according to claim 1 wherein the pseudo-random chipping sequence is an eleven-bit Barker code.

3. A system according to claim 2 wherein the modulator means is of the frequency shift keying type and is driven by the spread spectrum signals to produce a radio-frequency output for broadcasting.

4. A system according to claim 2 wherein the frequency spreader means includes an exclusive-OR gate means for receiving the scrambled data from the scrambler means and the pseudo-random code signals from the generator means, and for providing the input to the modulator means.

5. A system according to claim 1 further including scrambler means for scrambling the digital data prior to the data being operated upon by the frequency spreader means.

6. A system according to claim 5 wherein the pseudo-random chipping sequence is an eleven-bit Barker code.

7. A transmitter system for use with a spread spectrum radio communication system, comprising:

generator means for generating a pseudo-random chipping sequence;

frequency spreader means for combining digital data with the pseudo-random chipping sequence to produce a spread spectrum signal; and

,

modulator means for modulating the spread spectrum signal over a predefined frequency band wherein the pseudo-random chipping sequence is one of a set of codes including non-inverse eleven-bit Barker code, an inverse of the Barker code and a reversed sequence of the inverse or non-inverse Barker code.

8. A system according to claim 7 wherein the eleven-bit Barker code has the non-inverse binary bit sequence 10110111000, the inverse sequence 01001000111, and the reversed sequences of the inverse and non-inverse code are 11100010010 and 00011101101, respectively.

9. A system for receiving spread spectrum radio communication signals, including digital data signals, comprising:

demodulator means for demodulating broadcast spread spectrum signals;

de-spreader means employing single bit quantization and oversampling for digitally correlating the output of the demodulator means with a pseudo-random chipping sequence; and

extractor means for extracting clock and data signals from the output of the de-spreader means.

10. A system according to claim 9 further including de-scrambler means for de-scrambling the extracted data to recover the digital data in a spread spectrum broadcast.

11. A system for receiving spread spectrum radio communication signals, including digital data signals, comprising:

demodulator means for demodulating broadcast spread spectrum signals;

de-spreader means employing single bit quantization and oversampling for digitally correlating the output of the demodulator means with a pseudo-random chipping sequence; and

extractor means for extracting clock and data signals from the output of the de-spreader means wherein the chipping sequence used by the de-spreader is the eleven-bit Barker code, an inverse of the eleven-bit Barker code, and reverse sequences of the inverse and non-inverse Barker code.

12. A system for receiving spread spectrum radio communication signals, including digital data signals, comprising:

demodulator means for demodulating broadcast spread spectrum signals;

de-spreader means employing single bit quantization and oversampling for digitally correlating the output of the demodulator means with a pseudo-random chipping sequence; and

extractor means for extracting clock and data signals from the output of the de-spreader means, wherein the de-spreader means further includes;

means for digitally over-sampling and delaying a demodulated signal to create blocks of over-sampled data for each binary data bit of the demodulated signal;

means for digitally multiplying the blocks over-sampled data with the pseudo-random chipping sequence;

means for digitally summing the blocks of multiplied, over-sampled data into a summation value; and

,

means for digitally comparing the summation value with predetermined thresholds.

13. A system according to claim 12 wherein the chipping sequence used by the de-spreader is the non-inverse eleven-bit Barker code, an inverse of the eleven-bit Barker code, and reversed sequences of the inverse and non-inverse Barker code.

14. A system according to claim 13 wherein the delay means includes a shift register for storing the oversampled demodulated signal.

15. A system according to claim 12, wherein the comparing means includes:

a first digital comparator for producing an output signal indicative of whether the summation value is outside a window defined by a predetermined upper and lower threshold value; and

,

a second digital comparator for producing an output signal indicative of whether the summation value is lesser or greater than a predetermined midpoint threshold value.

16. A system according to claim 15 wherein the extractor means operates to produce a binary data signal from the second digital comparator output if the first digital comparator output signal indicates that the summation value is outside the predetermined thresholds.

17. A system according to claim 16 wherein the extractor means further operates to produce a binary data signal from the second digital comparator output even if the first digital comparator output indicates that the summation value is not outside the predetermined thresholds.

18. A system according to claim 17 further including a carrier detect means that uses the output of the first digital comparator for detecting the presence of a valid received signal.

19. A spread spectrum radio communication system, comprising:

generator means for generating a pseudo-random chipping sequence;

frequency spreader means for combining digital data with the pseudo-random chipping sequence to produce a spread spectrum signal;

modulator means for modulating the spread spectrum signal for broadcasting over a predefined frequency band;

demodulator means for demodulating broadcast spread spectrum signals;

de-spreader means employing single bit quantization and oversampling for digitally correlating the output of the demodulator means with a pseudo-random chipping sequence; and

extractor means for extracting clock and data signals from the output of the de-spreader means.

20. A spread spectrum radio communication system, comprising:

generator means for generating a pseudo-random chipping sequence;

frequency spreader means for combining digital data with the pseudo-random chipping sequence to produce a spread spectrum signal;

modulator means for modulating the spread spectrum signal for broadcasting over a predefined frequency band;

demodulator means for demodulating broadcast spread spectrum signals;

de-spreader means employing single bit quantization and oversampling for digitally correlating the output of the demodulator means with a pseudo-random chipping sequence; and

extractor means for extracting clock and data signals from the output of the de-spreader means, wherein the pseudo-random chipping sequence is selected from a set of codes including a non-inverse eleven-bit Barker code, an inverse of the eleven-bit Barker code and reversed sequences of the inverse and non-inverse Barker code.

21. A system according to claim 20 further including de-scrambler means for de-scrambling the extracted data to recover the digital data in a spread spectrum broadcast.