Multi-channel spread spectrum system

• US 6,324,209 B1
• Filed: 05/12/2000
• Issued: 11/27/2001
• Est. Priority Date: 02/28/2000
• Status: Expired due to Fees

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Golden Bridge Technology Incorporated
• Inventors: Yang, Gang, Li, Don
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Fan, Chieh M.
• Application Number:
  US09/570,393
• Time in Patent Office: 564 Days
• Field of Search: 375/130, 375/133, 375/140, 375/141, 375/146, 375/260, 375/295, 375/308, 375/279, 375/280, 370/208, 370/320, 370/321, 370/335, 370/336, 370/342, 370/345, 370/347, 370/441, 370/442
• US Class Current: 375/146
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04J 13/004 Orthogonal

Abstract

A multi-channel spread-spectrum system separates a data stream, for example from a convolutional encoder and an interleaver, into sub-channel data-sequence signals. For each sub-channel data-sequence signal, m bits are translated to one code of a unique set of orthogonal chip-sequence signals. The other k bits of the same sub-channel data-sequence signal are translated to a distinct phasor. Each phasor is used to modulate the respective chip-sequence signal. A complex-signal combiner combines the real and imaginary components of all the phase-modulated chip-sequence signals into in-phase (I) and quadrature (Q) spread-spectrum multi-channel signals, which are spread by a cell-site specific signature-sequence. The receiver decorrelates the received spread-spectrum signal, preferably with a bank of matched filter (MF) joint-detectors, to recover the bits from all the spread-spectrum sub-channel signals for remultiplexing into the transmitted data stream. The multi-channel spread-spectrum system supports constant data rate throughout the cell by maintaining a large processing gain, at the demultiplexed sub-channel data sequency level, thus a code-reuse-one type spread-spectrum system can be deployed with the aid of power control.

Claims

1. A multi-channel spread-spectrum modulator subsystem, comprising:

a demultiplexer for demultiplexing a representation of an input data stream into a plurality of sub-channel data-sequence signals;

a plurality of mapping circuits, one of which is coupled to receive each respective sub-channel data-sequence signal from the demultiplexer, wherein each mapping circuit is for mapping predetermined-length segments of the respective sub-channel data-sequence signal to generate a respective phase modulated spread-spectrum sub-channel signal,

each phase modulated spread-spectrum sub-channel signal comprising orthogonal spreading-codes selected in response to mapping of first predetermined bits of the segments of the respective sub-channel data-sequence signal, the selected orthogonal spreading-codes being modulated with phasors selected in response to mapping of second predetermined bits of the segments of the respective sub-channel data-sequence signal; and

a signal combiner for receiving the respective spread-spectrum sub-channel signals from the mapping circuits for transmission.

3. A multi-channel spread-spectrum modulator subsystem as in claim 1, wherein the signal combiner comprises a complex signal combiner for algebraically combining the plurality of spread-spectrum sub-channel signals as an in-phase multi-channel spread-spectrum signal and a quadrature multi-channel spread-spectrum signal for transmission.

2. A multi-channel spread-spectrum modulator subsystem, comprising:

a demultiplexer for demultiplexing a representation of an input data stream into a plurality of sub-channel data-sequence signals;

a plurality of mapping circuits, one of which is coupled to receive each respective sub-channel data-sequence signal from the demultiplexer, wherein each mapping circuit is for mapping predetermined-length segments of the respective sub-channel data-sequence signal to generate a respective phase modulated spread-spectrum sub-channel signal, each of the mapping circuits comprising;

(a) a code-mapping circuit for mapping a predetermined m-bits of each segment of the respective sub-channel data sequence signal to a selected one of a unique plurality of orthogonal spreading-codes;

(b) a phase-mapping circuit for mapping a remaining k-bits of each segment of the respective sub-channel data-sequence signal to a selected one of a plurality of distinct phasor signals; and

(c) a product device for modulating each selected code sequence from the code-mapping circuit with a corresponding selected phasor signal from the phase-mapping circuit, to generate the respective spread-spectrum sub-channel signal; and

a signal combiner for receiving the respective spread-spectrum sub-channel signals from the mapping circuits for transmission.

4. A multi-channel spread-spectrum modulator subsystem, comprising:

a demultiplexer for demultiplexing a representation of an input data stream into a plurality of sub-channel data-sequence signals and supplying each respective sub-channel data-sequence signal to a respective output of the demultiplexer;

code-mapping circuits, wherein a respective code-mapping circuit is coupled to each respective output of the demultiplexer, each code-mapping circuit for mapping predetermined m-bit segments of the respective sub-channel data-sequence signal to a plurality of orthogonal spreading-codes;

phase-mapping circuits, wherein a respective phase-mapping circuit is coupled to each respective output of the demultiplexer, each phase-mapping circuit for mapping predetermined k-bit segments of the respective sub-channel data-sequence signal to a plurality of distinct phasor signals;

product devices, wherein a respective product device is for modulating each code sequence output of a respective code-mapping circuit with a corresponding phasor signal output from a respective phase-mapping circuit to generate a spread-spectrum sub-channel signal;

a complex signal combiner, receiving the spread-spectrum sub-channel signals from the product devices, for algebraically combining the plurality of spread-spectrum sub-channel signals to form an in-phase multi-channel spread-spectrum signal and a quadrature multi-channel spread-spectrum signal for transmission.

5. A multi-channel spread-spectrum modulator subsystem as in claim 4, further comprising:

an encoder for receiving and encoding input digital information;

an interleaver, coupled to the encoder and the demultiplexer, for receiving and interleaving the encoded digital information to form the representation of the input data stream for input to the demultiplexer.

6. A multi-channel spread-spectrum modulator subsystem as claim 4, wherein each respective code-mapping circuit maps m-bit segments to a distinct set of orthogonal spreading-codes.

7. A multi-channel spread-spectrum modulator subsystem as in claim 6, wherein:

for n sub-channels, each distinct set of orthogonal spreading-codes comprises 2^m orthogonal spreading-code sequences of n2^m chip-length.

8. A multi-channel spread-spectrum modulator subsystem as in claim 6, wherein each respective phase-mapping circuit maps k-bit segments to a distinct set of phasors.

9. A multi-channel spread-spectrum modulator subsystem as in claim 4, wherein each respective phase mapping circuit maps k-bit segments to a distinct set of phasors.

10. A multi-channel spread-spectrum modulator subsystem as in claim 9, wherein for n respective sub-channel data-sequence signals, each phase mapping circuit for a respective sub-channel data-sequence signal maps k-bit segments to a phase angle set of 2^k distinct phasors, each phasor of which is offset by a phase angle φ

from a corresponding phasor of the phase angle set used by another of the phase mapping circuits.

11. A multi-channel spread-spectrum modulator subsystem as in claim 4, further comprising a transmitter coupled to the complex signal combiner, for transmission of the in-phase multi-channel spread-spectrum signal and the quadrature multi-channel spread-spectrum signal over a channel.

12. A multi-channel spread-spectrum modulator subsystem as in claim 11, wherein the transmitter comprises:

a first spread-spectrum modulator for modulating the in-phase multi-channel spread-spectrum signal with a cell-site specific orthogonal cover code; and

a second spread-spectrum modulator for modulating the quadrature multi-channel spread-spectrum signal with the orthogonal cover code.

13. A multi-channel spread-spectrum modulator subsystem as in claim 12, wherein the transmitter further comprises:

a first multiplier for multiplying an output signal from the first spread-spectrum modulator by a carrier wave of a predetermined frequency and having a first phase; and

a second multiplier for multiplying an output signal from the second spread-spectrum modulator by a carrier wave of the predetermined frequency and having a second phase different from the first phase.

14. A method of transmitting an information data stream comprising:

separating the information data stream into a plurality of respective sub-channel data streams;

code-mapping predetermined m-bit segments of each respective sub-channel data-sequence signal to a plurality of orthogonal spreading-codes;

phase-mapping k-bit segments of each respective sub-channel data-sequence signal to a plurality of distinct phasor signals;

for each of the sub-channels, multiplying respective orthogonal spreading-codes with corresponding phasor signals to form a respective sub-channel spread-spectrum signal;

combining all of the sub-channel spread-spectrum signals to form at least one combined signal;

modulating the at least one combined signal with a cell-site specific cover code to form a spread-spectrum channel signal; and

transmitting the spread-spectrum channel signal over a wireless air-link.

15. A method as in claim 14, wherein the code-mapping step comprises mapping segments of each respective sub-channel data-sequence signal to a different plurality of the orthogonal spreading-codes.

16. A method as in claim 15, wherein if there are n sub-channels, each different plurality of the orthogonal spreading-codes comprises 2_m orthogonal spreading-code sequences of n2^m chip-length.

17. A method as in claim 14, wherein the phase-mapping step comprises mapping segments of each respective sub-channel data-sequence signal to a different plurality of the distinct phasor signals.

18. A method as in claim 17, wherein if there are n sub-channels, each different plurality of the distinct phasor signals comprises a phase angle set of 2^k distinct phasors, each phasor of which is rotated by a phase angle φ

from a phasor of an adjacent phase angle set used for another sub-channel.

19. A method as in claim 14, further comprising:

encoding input digital information for forward error correction; and

interleaving the encoded digital information to form the information data stream.

20. A communication system, comprising:

a transmitter system, comprising;

1) a demultiplexer for demultiplexing a representation of an input data stream into a plurality of sub-channel data-sequence signals and supplying each respective sub-channel data-sequence signal to a respective output of the demultiplexer;

2) code-mapping circuits, wherein a respective code-mapping circuit is coupled to each respective output of the demultiplexer, each code-mapping circuit for mapping predetermined m-bit segments of the respective sub-channel data-sequence signal to a plurality of orthogonal spreading-codes;

3) phase-mapping circuits, wherein a respective phase-mapping circuit is coupled to each respective output of the demultiplexer, each phase-mapping circuit for mapping predetermined k-bit segments of the respective sub-channel data-sequence signal to a plurality of distinct phasor signals;

4) product devices, wherein a respective product device is for modulating each code sequence output from a respective code-mapping circuit with a corresponding phasor signal output from a respective phase-mapping circuit to generate a spread-spectrum channel signal;

5) a complex signal combiner, receiving the spread-spectrum channel signals from the product devices, for algebraically combining the plurality of spread-spectrum channels to form an in-phase multi-channel spread-spectrum signal and a quadrature multi-channel spread-spectrum signal; and

6) a modulator for modulating the in-phase multi-channel spread-spectrum signal and a quadrature multi-channel spread-spectrum signal and transmitting the modulated signals over a wireless air-link; and

a receiver system, for receiving and processing the modulated signals over the wireless air-link to recover the input data stream.

21. A communication system as in claim 20, wherein the transmitter system further comprises:

an encoder for receiving and encoding input digital information;

an interleaver, coupled to the encoder and the demultiplexer, for receiving and interleaving encoded digital information to form the representation of an input data stream for input to the demultiplexer.

22. A communication system as in claim 20, wherein the modulator comprises:

a first spread-spectrum modulator for modulating the in-phase multi-channel spread-spectrum signal with a cell-site specific orthogonal cover code; and

a second spread-spectrum modulator for modulating the quadrature multi-channel spread-spectrum signal with the orthogonal cover code.

23. A communication system as in claim 22, wherein the modulator further comprises:

a first multiplier for multiplying an output signal from the first spread-spectrum modulator by a carrier wave of a predetermined frequency and having a first phase; and

a second multiplier for multiplying an output signal from the second spread-spectrum modulator by a carrier wave of the predetermined frequency and having a second phase different from the first phase.