Two-stage synchronization of spread-spectrum signals

• US 6,393,049 B1
• Filed: 10/29/1998
• Issued: 05/21/2002
• Est. Priority Date: 05/25/1995
• Status: Expired due to Term

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Golden Bridge Technology Incorporated
• Inventors: Kanterakis, Emmanuel, Davidovici, Sorin
• Primary Examiner(s): VO, DON NGUYEN
• Application Number:
  US09/182,054
• Time in Patent Office: 1,300 Days
• Field of Search: 375/141, 375/142, 375/143, 375/144, 375/145, 375/148-153
• US Class Current: 375/142
• CPC Class Codes: H04B 1/708 Parallel implementation
• CPC Class Codes: H04B 1/7093 Matched filter type
• CPC Class Codes: H04W 52/221 using past power control commands
• CPC Class Codes: H04W 52/226 using past references to control power, e.g. look-up-table
• CPC Class Codes: H04W 52/228 using past power values or information
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters

Abstract

A spread-spectrum-matched-filter apparatus including a code generator, an in-phase-symbol-matched filter, a quadrature-phase-symbol-matched filter, an in-phase-frame-matched filter, a quadrature-phase-frame-matched filter, and a controller. The code generator generates replicas of a chip-sequence signal, which are used to set the symbol-impulse responses of the in-phase-symbol-matched filter and the quadrature-phase-symbol-matched filter. The in-phase-frame-matched filter and the quadrature-phase-frame-matched filter detect a despread-header-symbol-sequence signal and generate a maximum output signal which may be used as a data-start signal or for synchronizing the timing of the controller as to when to trigger sampling of the A/D converter, the output of the symbol-matched filters, detection of the data-symbol-sequence signal and other time-dependent processes.

Claims

1. A spread-spectrum-matched-filter apparatus, for use as part of a spread-spectrum receiver on a received-spread-spectrum signal having a plurality of packets, with each packet of said plurality of packets generated from spread-spectrum processing a header-symbol-sequence signal with a chip-sequence signal and from spread-spectrum processing a data-symbol-sequence signal with the chip-sequence signal, comprising:

code means for generating a replica of the chip-sequence signal;

symbol-matched means, responsive to having a symbol-impulse response set from the replica of the chip-sequence signal, for filtering from the received-spread-spectrum signal, a header portion of the packet, to output a despread-header-symbol-sequence signal and, for filtering from the received-spread-spectrum signal, a data portion of the packet to output a despread-data-symbol-sequence signal;

frame-matched means having a frame-impulse response matched to the header-symbol-sequence signal for filtering the despread-header-symbol-sequence signal and for generating a start-data signal in response to the despread-header-symbol-sequence signal matching the frame-impulse response; and

control means, coupled to said symbol-matched means and said code means, responsive to the start-data signal, for setting said symbol-matched means with a replica of a data-chip-sequence signal for matching said symbol-matched means to the data-chip-sequence signal.

2. The spread-spectrum-matched-filter apparatus as set forth in claim 1 wherein said symbol-matched means includes:

in-phase-symbol-matched means, coupled to said code means, responsive to having an in-phase-symbol-impulse response set from a replica of the header-symbol-sequence signal generated by said code means, for despreading from the received-spread-spectrum signal, an in-phase component of a packet as a despread-in-phase component of the header-symbol-sequence signal, and responsive to having the in-phase-symbol-impulse response set from the replica of the chip-sequence signal generated by said code means, for despreading from the received-spread-spectrum signal, an in-phase component of the packet as a despread-in-phase component of the despread-data-symbol-sequence signal; and

quadrature-phase-symbol-matched means, coupled to said code means, responsive to having a quadrature-symbol-impulse response set from the replica of the chip-sequence signal generated by said code means, for despreading from the received-spread-spectrum signal, a quadrature-phase component of the packet as a despread-quadrature-phase component of the header-symbol-sequence signal, and responsive to having the quadrature-symbol-impulse response set from the replica of the data-chip-sequence signal generated by said code means, for despreading from the received-spread-spectrum signal, a quadrature-phase component of the packet as a despread-quadrature-phase component of the despread-data-symbol-sequence signal.

3. The spread-spectrum-matched-filter apparatus as set forth in claim 2 wherein said frame-matched means includes:

in-phase-frame-matched means having an in-phase-frame-impulse response matched to an in-phase component of the header-symbol-sequence signal for generating an in-phase-time-reference signal for use for in a signal in response to the in-phase component of the despread-header-symbol-sequence signal matching the in-phase-frame-impulse response; and

quadrature-phase-frame-matched means having a quadrature-phase-frame-impulse response matched to a quadrature-phase component of the header-symbol-sequence signal for generating a quadrature-phase-time-reference signal for use in a signal in response to the quadrature-phase component of the despread-header-symbol-sequence signal matching the quadrature-phase-frame-impulse response.

4. The spread-spectrum-matched-filter apparatus as set forth in claim 1, further including demodulator means, coupled to said symbol-matched means, for demodulating the despread-data-symbol-sequence signal as a received data-symbol-sequence signal.

5. The spread-spectrum-matched-filter apparatus as set forth in claim 2 or 3 further including demodulator means, coupled to said in-phase-symbol-matched means and to said quadrature-phase-symbol-matched means, for demodulating the despread-in-phase component of the despread-data-symbol-sequence signal and the despread-quadrature-phase component of the despread-data-symbol-sequence signal, as a received-data-symbol-sequence signal.

6. The spread-spectrum-matched-filter apparatus as set forth in claim 1 or 4 wherein:

said symbol-matched means includes a symbol-digital-matched filter having the symbol-impulse response set by the replica of the chip-sequence signal; and

said frame-matched means includes a frame-digital-matched filter having the frame-impulse response matched to the header-symbol-sequence signal.

7. The spread-spectrum-matched-filter apparatus as set forth in claim 2 wherein:

said in-phase-symbol-matched means includes an in-phase-symbol-programmable-digital-matched filter having the in-phase-symbol-impulse response set by the replica of the chip-sequence signal; and

said quadrature-phase-symbol-matched means includes a quadrature-phase-programmable-digital-matched filter having the quadrature-phase-impulse response set by the replica of the chip-sequence signal.

8. The spread-spectrum-matched-filter apparatus as set forth in claim 3 wherein:

said in-phase-frame-matched means includes an in-phase-frame-digital-matched filter having the in-phase-frame-impulse response matched to the in-phase component of the header-symbol-sequence signal; and

said quadrature-phase-frame-matched means includes a quadrature-phase-frame-digital-matched filter having the quadrature-phase-impulse response matched to the quadrature-phase component of the header-symbol-sequence signal.

9. A method for achieving code phase synchronization comprising the steps of:

loading the spread-spectrum signal samples into the programmable-matched filter;

correlating the spread-spectrum signal samples against the local sequence symbols;

generating, responsive to alignment of the spread-spectrum signal samples with the local sequence symbols, a large information-bearing output at a second clock cycle, the second clock cycle being later in time than the first clock cycle;

loading, at a third clock cycle, the programmable-matched filter with a next group of local sequence symbols, the third clock cycle being later in time than the second clock cycle;

receiving a next group of spread spectrum signal samples;

correlating the next group of local sequence symbols against the next group of spread spectrum signal samples; and

generating, responsive to alignment of the next group of spread spectrum signal samples with the next group of local sequence symbols, a large information-bearing output at a fourth clock cycle, the fourth clock cycle being later in time than the third clock cycle.

10. The method as set forth in claim 9, further including the steps of:

loading the programmable-matched filter with a next group of local sequence symbols;

receiving a next group of spread-spectrum signal samples; and

correlating the next group of local sequence symbols against the next group of spread-spectrum signal samples;

loading, at a fifth clock cycle, the programmable-matched filter with a third group of local sequence symbols, the fifth clock cycle being later in time than the fourth clock cycle;

receiving a third group of spread spectrum signal samples;

correlating the third group of local sequence symbols against the third group of spread spectrum signal samples; and

generating, responsive to alignment of the third group of spread spectrum signal samples with the third group of local sequence symbols, a large information-bearing output at a sixth clock cycle, the sixth clock cycle being later in time than the fifth clock cycle.

11. The method as set forth in claim 9 or 10 with the step of despreading the data portion of the packet further including the steps of:

despreading, from the received-spread-spectrum signal, an in-phase component of the data portion of the packet as a despread-in-phase component of the despread-data-symbol-sequence signal; and

despreading, from the received-spread-spectrum signal, a quadrature-phase component of the data portion of the packet as a despread-quadrature-phase component of the despread-data-symbol-sequence signal.

12. The method as set forth in claim 10 with the step of filtering the despread header-symbol-sequence signal further including the steps of:

generating an in-phase-data-start signal in response to the despread-in-phase component of the despread-header-symbol-sequence signal matching an in-phase-frame-impulse response; and

generating a quadrature-phase-data-start signal in response to the despread-quadrature-phase component of the despread-header-symbol sequence signal matching a quadrature-phase-frame-impulse response.

13. The method as set forth in claim 9, further including the step of demodulating the despread-data-symbol-sequence signal as a received data-symbol-sequence signal.

14. The method as set forth in claim 10 further including the step of demodulating an in-phase component of the despread-data-symbol-sequence signal and a quadrature-phase component of the despread-data-symbol-sequence signal, as a received-data-symbol-sequence signal.

15. A method, using a symbol-matched filter and a frame-matched filter as part of a spread-spectrum receiver on a received-spread-spectrum signal having a plurality of packets, with each packet of said plurality of packets generated from spread-spectrum processing a header-symbol-sequence signal with a chip-sequence signal and from spread-spectrum processing a data-symbol-sequence signal with the chip-sequence signal, comprising the steps of:

generating a replica of the chip-sequence signal;

filtering, with a symbol-matched filter having a symbol-impulse response set from the replica of the chip-sequence signal, from the received-spread-spectrum signal, a header portion of the packet, to output a despread-header-symbol-sequence signal;

filtering, from the received-spread-spectrum signal, a data portion of the packet to output a despread-data-symbol-sequence signal;

filtering, with a frame-matched filter having a frame-impulse response matched to the header-symbol-sequence signal, the despread-header-symbol-sequence signal;

generating a start-data signal in response to the despread-header-symbol-sequence signal matching the frame-impulse response; and

setting said symbol-matched filter with a replica of a data-chip-sequence signal for matching said symbol-matched filter to the data-chip-sequence signal.

16. A method, using a programmable-matched filter with a spread-spectrum receiver on a received-spread-spectrum signal, the received-spread-spectrum signal having a plurality of packets, with each packet generated from spread-spectrum processing a header-symbol-sequence signal with a header-chip-sequence signal and from spread-spectrum processing a data-symbol-sequence signal with a data-chip-sequence signal, for synchronization comprising the steps of:

generating a replica of the header-chip-sequence signal;

loading said programmable-matched filter with the replica of the header-chip-sequence signal, to set said programmable-matched filter with a programmable-impulse response matched to the header-chip-sequence signal;

despreading, with the programmable-matched filter matched to the header-chip-sequence signal, a header portion of the packet from the received-spread-spectrum signal as a despread-header-symbol-sequence signal;

correlating, with a replica of the header-symbol-sequence signal, the despread-header-symbol-sequence signal to generate a peak-correlation signal;

loading, responsive to timing from the peak-correlation signal, said programmable-matched filter with a replica of the data-chip-sequence signal to set said programmable-matched filter with the programmable-impulse response matched to the data-chip-sequence signal; and

despreading, responsive to timing from the peak-correlation signal, with the programmable-matched filter matched to the data-sequence signal, a data portion of the packet from the received-spread-spectrum signal as a despread-data-symbol-sequence signal.

17. A method, using a processor, for acquiring synchronization to a spread-spectrum signal having a plurality of symbols, with each symbol of the plurality of symbols spread-spectrum processed by a plurality of chips, with the plurality of chips occurring at a plurality of chip times, respectively, comprising the steps of:

filtering, a plurality of symbol-duration segments, with a filter having an impulse response matched to the plurality of chips for each symbol-duration segment, the spread-spectrum signal, to generate, within each symbol-duration segment of the plurality of symbol-duration segments, a plurality of sample values occurring at a plurality of sample times, respectively;

detecting, for each symbol-duration segment from the plurality of sample values, a largest value, thereby generating a plurality of largest values corresponding to the plurality of symbol-duration segments, respectively;

determining, from the plurality of largest values, a plurality of time instants, respectively, within each symbol-duration segment, corresponding to the plurality of largest values, with each time instant occurring at one of the plurality of sample times within the symbol-duration segment;

determining, from the plurality of time instances, a synchronization time; and

verifying the synchronization time.

18. The method as set forth in claim 17, with the step of determining the correct sample time at which the spread spectrum signal is correctly despread, including the step of determining, from the plurality of time instances, using any of a predetermined number of coincidences of largest values OR a maximum number of occurrences of largest values, the correct sample time at which the spread spectrum signal is correctly despread.

19. The method as set forth in claim 17 or 18, further comprising the step of despreading, using the correct sample time at which the spread spectrum signal is correctly despread, a multiplicity of data symbols.

20. A method, using a processor, for acquiring synchronization to a spread-spectrum signal having a plurality of symbols, with each symbol of the plurality of symbols spread-spectrum processed by a plurality of chips, with the plurality of chips occurring at a plurality of chip times, respectively, comprising the steps of:

filtering, during a plurality of symbol-duration segments, with a filter having an impulse response matched to the plurality of chips for each symbol duration segment, the spread-spectrum signal, to generate, within each symbol-duration segment of the plurality of symbol-duration segments, a plurality of sample values occurring at a plurality of sample times, respectively;

detecting, for each symbol-duration segment, from the plurality of sample values, a set of largest values, thereby generating a plurality of sets of largest values corresponding to the plurality of symbol-duration segments, respectively;

determining, from the set of largest values, a set of time instants, respectively, within each symbol-duration segment, corresponding to the set of largest values, with each time instant occurring at one of the plurality of sample times within the symbol-duration segment;

determining, from the plurality of time instances, a synchronization time; and

verifying the synchronization time.

21. The method as set forth in claim 20, with the step of determining the synchronization times including the step of determining, from the plurality of time instances, using any of a predetermined number of coincidences of largest values OR a maximum number of occurrences of largest values, the synchronization times.

22. The method as set forth in claim 20 or 21, further comprising the step of despreading, using the synchronization times, a multiplicity of symbols.

23. The method as set forth in claim 20, with the step of detecting, further including the step of detecting, for each symbol-duration segment, from the plurality of sample values, at least four largest values, thereby generating a plurality of largest values corresponding to the plurality of symbol-duration segments.

24. A method, using a processor, for acquiring synchronization to a spread-spectrum signal having a plurality of symbols, with each symbol of the plurality of symbols spread-spectrum processed by a plurality of chips, with the plurality of chips occurring at a plurality of chip times, respectively, comprising the steps of:

correlating, during a plurality of symbol-duration segments, the spread-spectrum signal with reference signals, to generate, within each symbol-duration segment of the plurality of symbol-duration segments, a plurality of sample values;

detecting, for each symbol-duration segment, from the plurality of sample values, a largest value, thereby generating a plurality of largest values corresponding to the plurality of symbol-duration segments, respectively;

determining, from the plurality of largest values, synchronization time; and

verifying synchronization time.

25. The method as set forth in claim 24, with the step of determining the synchronization time including the step of determining, from the plurality of largest values, using any of a predetermined number of coincidences of largest values OR a maximum number of occurrences of largest values, the synchronization time.

26. The method as set forth in claim 24 or 25, further comprising the step of despreading, using the synchronization time, a multiplicity of symbols.

27. A method, using a processor, for acquiring synchronization to a spread-spectrum signal having a plurality of symbols, with each symbol of the plurality of symbols spread-spectrum processed by a plurality of chips, with the plurality of chips occurring at a plurality of chip times, respectively, comprising the steps of:

correlating, during a plurality of symbol-duration segments, the spread-spectrum signal with reference signals, to generate, within each symbol-duration segment of the plurality of symbol-duration segments, a plurality of sample values;

detecting, for each symbol-duration segment, from the plurality of sample values, a set of largest values, thereby generating a plurality of largest values corresponding to the plurality of symbol-duration segments;

determining, from the plurality of largest values, synchronization time; and

verifying synchronization time.

28. The method as set forth in claim 27, with the step of determining the synchronization time including the step of determining, from the plurality of largest values, using any of a predetermined number of coincidences of largest values OR a maximum number of occurrences of largest values, the synchronization time.

29. The method as set forth in claim 27 or 28, further comprising the step of despreading, using the synchronization time, a multiplicity of symbols.

30. The method as set forth in claim 27, with the step of detecting further including the step of detecting, for each symbol-duration segment, from the plurality of sample values, at least four largest values, thereby generating a plurality of largest values corresponding to the plurality of symbol-duration segments.

31. A method, using a programmable-matched filter with a spread-spectrum receiver on a received-spread-spectrum signal, the received-spread-spectrum signal having a plurality of packets, with each packet generated from spread-spectrum processing a header-symbol-sequence signal with a header-chip-sequence signal and from spread-spectrum processing a data-symbol-sequence signal with a data-chip-sequence signal, for synchronization comprising the steps of:

generating a replica of the header-chip-sequence signal;

loading said programmable-matched filter with the replica of the header-chip-sequence signal, to set said programmable-matched filter with a programmable-impulse response matched to the header-chip-sequence signal;

despreading, with the programmable-matched filter matched to the header-chip-sequence signal, a header portion of the packet from the received-spread-spectrum signal as a despread-header-symbol-sequence signal;

correlating, with a replica of the header-symbol-sequence signal, the despread-header-symbol-sequence signal to generate a peak-correlation signal; and

despreading, responsive to timing from the peak-correlation signal, a data portion of the packet from the received-spread-spectrum signal as a despread-data-symbol-sequence signal.

32. A method, using a programmable-matched filter with a spread-spectrum receiver on a received-spread-spectrum signal, the received-spread-spectrum signal having a plurality of packets, with each packet generated from spread-spectrum processing a header-symbol-sequence signal with a header-chip-sequence signal and from spread-spectrum processing a data-symbol-sequence signal with a data-chip-sequence signal, for synchronization comprising the steps of:

generating a replica of the header-chip-sequence signal;

correlating, with the replica of the header-chip-sequence signal, the header-chip-sequence signal embedded is the received-spread-spectrum signal;

despreading, with the replica of the header-chip-sequence signal synchronized to the header-chip-sequence signal, a header portion of the packet from the received-spread-spectrum signal as a despread-header-symbol-sequence signal;

correlating, with the programmable-matched filter matched to the header-symbol-sequence signal, the despread-header-symbol-sequence signal to generate a peak-correlation signal; and

despreading, responsive to timing from the peak-correlation signal, a data portion of the packet from the received-spread-spectrum signal as a despread-data-symbol-sequence signal.

33. A method, using a programmable-matched filter with a spread-spectrum receiver on a received-spread-spectrum signal, the received-spread-spectrum signal having a plurality of packets, with each packet generated from spread-spectrum processing a header-symbol-sequence signal with a header-chip-sequence signal and from spread-spectrum processing a data-symbol-sequence signal with a data-chip-sequence signal, for synchronization comprising the steps of:

generating a replica of the header-chip-sequence signal;

loading said programmable-matched filter with the replica of the header-chip-sequence signal, to set said programmable-matched filter with a programmable-impulse response matched to the header-chip-sequence signal;

despreading, with the programmable-matched filter matched to the header-chip-sequence signal, a header portion of the packet from the received-spread-spectrum signal as a despread-header-symbol-sequence signal;

despreading, with a frame matched filter having an impulse response matched to the header-symbol-sequence signal, the despread-header-symbol-sequence signal to generate a peak-correlation signal; and

despreading, responsive to timing from the peak-correlation signal, a data portion of the packet from the received-spread-spectrum signal as a despread-data-symbol-sequence signal.

34. A spread-spectrum-matched-filter apparatus, for use with a spread-spectrum receiver on a received spread-spectrum signal having a pilot-spread-spectrum channel generated from spread-spectrum processing a pilot-bit-sequence signal with a pilot-chip-sequence signal and a data spread-spectrum channel generated from spread-spectrum processing a data-bit-sequence signal with a data-chip-sequence signal, the pilot-chip-sequence signal and the data-chip-sequence signal being different from each other, comprising:

a code generator for generating a replica of the pilot chip-sequence signal and a replica of the data-chip-sequence signal;

programmable-matched means loaded with local sequence symbols, for correlating an incoming received spread-spectrum signal against the local sequence symbols and, responsive to having a programmable-impulse response set from the replica of the pilot-chip-sequence, for filtering from the received spread-spectrum signal, at a local sequence symbol rate, the pilot-spread-spectrum channel, to output a despread-pilot-bit-sequence signal with each bit of the despread-pilot-bit-sequence signal representing local sequence symbols and, responsive to having the programmable-impulse response set from the replica of the data-chip-sequence signal, for filtering from the received spread-spectrum signal, the data-spread-spectrum channel to output a despread-data-bit-sequence signal;

a frame-matched filter having a frame-impulse response matched to the pilot-bit-sequence signal for filtering, at a bit rate, the bits of the despread-pilot-bit-sequence signal and generating a peak-pilot-correlation signal in response to the despread-pilot-bit-sequence signal matching the frame-impulse response; and

a controller, coupled to said programmable-matched means and said code generator, responsive to the peak-pilot-correlation signal, for setting, from said code generator, said programmable-matched means with the replica of the pilot-chip-sequence signal for matching said programmable-matched means to the pilot-chip-sequence signal and, responsive to the peak-pilot-correlation signal, for setting at a time delay from the peak-pilot-correlation signal from said code generator, said programmable-matched means with the replica of the data-chip-sequence signal for matching said programmable-matched means to the data-chip-sequence signal.

35. The spread-spectrum-matched-filter apparatus as set forth in claim 34 with said programmable-matched means further including:

an in-phase-programmable-digital-matched filter, coupled to said code generator, responsive to the replica of the pilot-chip-sequence signal generated by said code generator for despreading from the received spread-spectrum signal, an in-phase component of the pilot-spread-spectrum channel as a despread in-phase component of the pilot-bit-sequence signal, and responsive to the replica of the data-chip-sequence signal generated by said code generator for despreading from the received spread-spectrum signal, an in-phase component of the data-spread-spectrum channel as a despread-in-phase component one the despread-data-bit-sequence signal; and

a quadrature-phase-programmable-digital-matched filter, coupled to said code generator, responsive to the replica of the pilot-chip-sequence signal generated by said code generator for despreading from the received spread-spectrum signal, a quadrature-phase component of the pilot-spread-spectrum channel as a despread quadrature-phase component of the pilot-bit-sequence signal, and responsive to the replica of the data-chip-sequence signal generated by said code generator for despreading from the received spread-spectrum signal, a quadrature-phase component of the data-spread-spectrum channel as a despread-quadrature-phase component of the despread-data-bit-sequence signal.

36. The spread-spectrum-matched-filter apparatus as set forth in claim 34 wherein said frame-matched filter includes:

an in-phase-frame-digital-matched filter having an in-phase impulse response matched to an in-phase component of the pilot-bit-sequence signal for generating an in-phase peak-pilot-correlation signal in response to the in-phase component of the despread-pilot-bit sequence signal matching the in-phase impulse response; and

a quadrature-phase-frame-digital-matched filter having a quadrature-phase impulse response matched to a quadrature-phase component of the pilot-bit-sequence signal for generating a quadrature-phase peak-pilot-correlation signal in response to the quadrature-phase component of the despread-pilot-bit sequence signal matching the quadrature-phase impulse response.

37. The spread-spectrum-matched-filter apparatus as set forth in claim 35 or 36 further including a demodulator, coupled to said in-phase-programmable-digital-matched filter and to said quadrature-phase-programmable-digital-matched filter, for demodulating the despread-in-phase component of the despread-data-bit-sequence signal and the despread-quadrature-phase component of the despread-data-bit-sequence signal as a received-data-bit-sequence signal.

38. The spread-spectrum-matched-filter apparatus as set forth in claim 34, further including a demodulator, coupled to said programmable-matched means, for demodulating the despread-data-bit-sequence signal as a received data-bit-sequence signal.