Spread spectrum conference calling system and method

• US 5,179,572 A
• Filed: 06/17/1991
• Issued: 01/12/1993
• Est. Priority Date: 06/17/1991
• Status: Expired due to Term

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: SCS Mobilecom, Inc (InterDigital, Inc.)
• Inventors: Schilling, Donald L.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US07/715,835
• Time in Patent Office: 575 Days
• Field of Search: 375/1
• US Class Current: 375/145
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/10 Code generation
• CPC Class Codes: H04L 7/0332 with an integrator-detector

Abstract

A spread-spectrum-conference-calling receiver, for use over a communications channel. At each of a plurality of spread-spectrum transmitters, a transmitter-generic-chip-code generator generates a generic-chip-code signal and a transmitter-message-chip-code generator generates a message-chip-code signal. An EXCLUSIVE-OR gate spread-spectrum processes message data with the message-chip-code signal to generate a spread-spectrum signal. The combiner combines the generic-chip-code signal and the spread-spectrum-processed signal. A plurality of receiver-generic-chip-code generators generate a plurality of replicas of the generic-chip-code signal. Each receiver-generic mixer recovers a carrier signal from one of the plurality of received spread-spectrum-communications signals. A plurality of receiver-message-chip-code generators generate a plurality of replica of the message-chip-code signals. A plurality of receiver-message mixers despread one of the plurality of received spread-spectrum-communications signal as a modulated-data signal. Tracking and acquistion circuits use the recovered carrier signal for synchronizing the replicas of the generic-chip-code signals to the recovered carrier signals, respectively. An envelope detector demodulates the modulated-data signal as a demodulated signal.

Claims

1. A spread-spectrum-conference-calling receiver for simultaneously listening to a plurality of spread-spectrum channels of a plurality of received spread-spectrum-communications signals comprising:

combiner means;

a plurality of spread-spectrum receivers, each of said spread-spectrum receivers including,

generic-spread-spectrum-processing means for generating a replica of a generic-chip-code signal for recovering a carrier signal for a respective spread-spectrum channel, from the plurality of received spread-spectrum-communications signals;

acquisition and tracking means responsive to acquiring and tracking the recovered carrier signal for synchronizing said generic-spread-spectrum-processing means to the recovered carrier signal;

message-spread-spectrum-processing means for despreading the spread-spectrum-communications signal as a modulated-data signal; and

demodulation means for demodulating the modulated-data signal as a demodulated signal; and

wherein said combiner means combines each of the plurality of demodulated signals from said plurality of spread-spectrum receivers.

2. The spread-spectrum-conference-calling receiver as set forth in claim 1 wherein:

each of said generic-spread-spectrum-processing means includes a generic mixer for recovering the carrier signal for the respective spread-spectrum channel, from the plurality of received spread-spectrum-communications signals;

each of said message-spread-spectrum-processing means includes a message mixer for despreading the respective spread-spectrum channel from the plurality of received spread-spectrum-communications signals, as the modulated-data signal; and

each of said demodulation means includes an envelope detector for detecting the respective modulated-data signal as the respective demodulated signal. PG,40

3. The spread-spectrum conference-calling receiver as set forth in claim I wherein:

each of said generic-spread-spectrum-processing means includes a generic mixer for recovering the carrier signal for the respective spread-spectrum channel, from the plurality of received spread-spectrum-communications signals;

each of said message-spread-spectrum-processing means includes a message mixer for despreading the respective spread-spectrum channel from the plurality of received spread-spectrum-communications signals, as the modulated-data signal; and

demodulation means includes a synchronous detector responsive to the recovered-carrier signal for converting the respective modulated-data signal to the respective demodulated signal.

4. A spread-spectrum-conference-calling receiver for simultaneously listening to a plurality of spread-spectrum channels of a plurality of received spread-spectrum-communications signals comprising:

a plurality of spread-spectrum receivers, each of said spread-spectrum receivers including generic-spread-spectrum-processing means for generating a replica of a generic-chip-code signal for recovering a carrier signal for a respective spread-spectrum channel from the plurality of received spread-spectrum-communications signals, acquisition and tracking means responsive to acquiring and tracking the recovered carrier signal for synchronizing said generic-spread-spectrum-processing means to the recovered carrier signal, and message-spread-spectrum-processing means for despreading a respective spread-spectrum channel of the plurality of received spread-spectrum-communications signals as a modulated-data signal;

demodulation means for demodulating the modulated-data signal as a demodulated signal;

combiner means having a plurality of inputs for combining a plurality of demodulated signals; and

switching means coupled between an input of said demodulation means and each of said message-spread-spectrum-processing means and between an output of said demodulation means and the plurality of inputs of said combiner means, for switching said demodulation means between each of said message-spread-spectrum-processing means and each input of said combiner means, respectively.

5. The spread-spectrum-conference-calling receiver as set forth in claim 4 wherein:

each of said generic-spread-spectrum processing means includes a generic mixer for recovering the carrier signal for the respective spread-spectrum channel, from the plurality of received spread-spectrum-communications signals;

each of said message-spread-spectrum-processing means includes a message mixer for despreading the respective spread-spectrum channel from the plurality of received spread-spectrum-communications signals, as the modulated-data signal; and

said demodulation means includes an envelope detector for detecting the respective modulated-data signal as the respective demodulated signal.

6. The spread-spectrum-conference-calling receiver as set forth in claim 4 wherein:

each of said generic-spread-spectrum-processing means includes a generic mixer for recovering the carrier signal for the respective spread-spectrum channel, from the plurality of received spread-spectrum-communications signals;

each of said message-spread-spectrum-processing means includes a message mixer for despreading the respective spread-spectrum channel from the plurality of received spread-spectrum-communications signals, as the modulated-data signal; and

said demodulation means includes a synchronous detector responsive to the recovered-carrier signal for converting the respective modulated-data signal to the respective demodulated signal.

7. A spread-spectrum-conference-calling receiver for simultaneously listening to a plurality of spread-spectrum channels of a plurality of received spread-spectrum-communications signals comprising:

a combiner;

a plurality of spread-spectrum receivers, each of said spread-spectrum receivers including,

a receiver generic-chip-code generator for generating a replica of a generic-chip-code signal;

a generic mixer coupled to said generic-chip-code generator and responsive to the replica of the generic-chip-code signal for recovering a carrier signal from a respective spread-spectrum channel, from the plurality of received spread-spectrum-communications signals;

an acquisition and tracking circuit coupled to said generic mixer and responsive to acquiring and tracking the recovered carrier signal, for synchronizing said generic-chip-code generator to the recovered carrier signal;

a receiver-message-chip-code generator for generating a message-chip-code signal;

a message mixer coupled to said message-chip-code generator and responsive to the message-chip-code signal for despreading a respective spread-spectrum channel of the plurality of received spread-spectrum-communications signals as a modulated-data signal;

demodulation means for demodulating the modulated-data signal as a demodulated signal; and

wherein said combiner combines each of the plurality of demodulated signals from said plurality of spread-spectrum receivers.

8. The spread-spectrum-conference-calling receiver as set forth in claim 7 wherein each of said demodulation means includes an envelope detector for detecting the respective modulated-data signal as the respective demodulated signal.

9. The spread-spectrum-conference-calling receiver as set forth in claim 7 wherein demodulation means includes a synchronous detector responsive to the recovered-carrier signal for converting the respective modulated-data signal to the respective demodulated signal.

10. A spread-spectrum-conference-calling receiver for simultaneously listening to a plurality of spread-spectrum channels of a plurality of received spread-spectrum-communications signals comprising:

a plurality of spread-spectrum receivers, each of said spread-spectrum receivers including,

a receiver-generic-chip-code generator for generating a replica of a generic-chip-code signal;

a generic mixer coupled to said generic-chip-code generator and responsive to the generic-chip-code signal for recovering a carrier signal for a respective spread-spectrum channel from the spread-spectrum-communications signal;

an acquisition and tracking circuit responsive to acquiring and tracking the recovered carrier signal for synchronizing said generic-chip-code generator means to the recovered carrier signal; and

a receiver-message-chip-code generator for generating a message-chip-code signal;

a message mixer coupled to said message-chip-code generator and responsive to the message-chip-code signal for despreading the spread-spectrum-communications signal as a modulated-data signal;

demodulation means for demodulating the modulated-data signal as a demodulated signal;

a receiver-combiner having a plurality of inputs for combining a plurality of the demodulated signals; and

a switching circuit coupled between an input of said demodulation means and each of said message mixers of said plurality of spread-spectrum receivers, and between an output of said demodulation means and the plurality of inputs of said combiner, for switching said demodulation means between each of said message mixers and each input of said combiner, respectively.

11. The spread-spectrum-conference-calling receiver as set forth in claim 10 wherein said demodulation means includes an envelope detector for detecting the respective modulated-data signal as the respective demodulated signal.

12. The spread-spectrum-conference-calling receiver as set forth in claim 10 wherein said demodulation means includes a synchronous detector responsive to the recovered-carrier signal for converting the respective modulated-data signal to the respective demodulated signal.

13. A method for simultaneously listening to a plurality of spread-spectrum channels of a plurality of received spread-spectrum communications signals, comprising the steps for each spread-spectrum channel of:

generating a replica of a generic-chip-code signal for a respective spread-spectrum channel;

recovering, using the replica of the respective generic-chip-code signal, a respective carrier signal from the plurality of received spread-spectrum-communications signals;

acquiring and tracking the recovered-carrier signal and synchronizing the replica of the generic-chip-code signal to the recovered-carrier signal;

generating a replica of the message-chip-code signal synchronized to the replica of the generic-chip-code signal;

despreading, using the replica of the message-chip-code signal, the spread-spectrum channel of the spread-spectrum-communications signal as a modulated-data signal; and

demodulating the modulated-data signal as a demodulated signal.

14. The method as set forth in claim 13 wherein the demodulating step includes synchronously demodulating, using the recovered-carrier signal, the respective modulated-data signal as a respective demodulated signal.

15. The spread spectrum communications system as set forth in claim 13 wherein the demodulating step includes demodulating, using an envelope detector, the respective modulated-data signal as the respective demodulated signal.