Synchronous spread-spectrum communications system and method

• US 5,420,896 A
• Filed: 06/11/1993
• Issued: 05/30/1995
• Est. Priority Date: 12/14/1990
• Status: Expired due to Term

• Current Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Original Assignee: Interdigital Technology Corporation (InterDigital, Inc.)
• Inventors: Schilling, Donald L.
• Primary Examiner(s): Swann, Tod R.
• Application Number:
  US08/075,114
• Time in Patent Office: 718 Days
• Field of Search: 375/1, 375/38, 375/48, 375/66, 375/89, 455/59, 455/103, 455/209, 455/216, 455/303, 380/34
• US Class Current: 370/479
• CPC Class Codes: G01S 13/82 wherein continuous-type signals are transmitted
• CPC Class Codes: G01S 5/0036 of measured values, i.e. measurement on mobile and position calculation on base station
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 7/18547 for geolocalisation of a station position fixing by direction or distance determination G01S5/00
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04W 52/343 taking into account loading or congestion level
• CPC Class Codes: H04W 52/346 distributing total power among users or channels

Abstract

A spread spectrum communications system for use over a communications channel, including a transmitter-generic-chip-code generator, a transmitter-message-chip-code generator, an EXCLUSIVE-OR gate, a combiner, a transmitter, a receiver-generic-chip-code generator, a receiver-generic mixer, a generic-bandpass filter, a receiver-message-chip-code generator, a receiver-message mixer, a message-bandpass filter, and a synchronous detector. The transmitter-generic-chip-code generator generates a generic-chip-code signal and the transmitter-message-chip-code generator generates a message-chip-code signal. The 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 with the spread-spectrum signal. The transmitter transmits the combined generic-chip-code signal and spread-spectrum signal, on a carrier signal over the communications channel as a spread-spectrum-communications signal. The receiver-generic-chip-code generator generates a replica of the generic-chip-code signal. The generic mixer recovers the carrier signal from the spread-spectrum-communications signal. The receiver-message-chip-code generator generates a replica of the message-chip-code signal. The receiver-message mixer despreads the spread-spectrum-communications signal as a modulated-data signal. The tracking and acquisition circuit uses the recovered carrier signal for synchronizing the replicas of the generic-chip-code signal to the recovered carrier signal. The synchronous detector synchronously demodulates the modulated-data signal as received data.

Claims

1. A spread-spectrum communications system for communicating message data comprising:

first generic means for generating a generic-chip-code signal;

spreading means for spread-spectrum processing the message data, synchronized with the generic chip-code signal, as spread-spectrum-processed-message data;

combiner means for combining the generic-chip-code signal with the spread-spectrum-processed-message data, thereby generating a base code-division-multiplex (CDM) signal;

transmitter means for transmitting, using radio waves traversing free space, the CDM signal over a communications channel;

detection means, coupled to said communications channel, for detecting the generic-chip-code signal embedded in the CDM signal, said detection means including,

receiving means for receiving the CDM signal;

second generic means, coupled to said receiving means, for detecting the generic-chip-code signal embedded in the CDM signal and for generating a replica of the first generic-chip-code signal;

despreading means, synchronized with the replica of the first generic-chip-code signal, for despreading the spread-spectrum-processed-message data as a despread signal; and

data detection means, synchronized with the replica of the first generic-chip-code signal, for detecting message data in the despread signal.

2. The spread-spectrum communications system as set forth in claim 1 wherein said despreading means includes,

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

a product detector for mixing the message-chip-code signal with a received CDM signal to generate a detected spread-spectrum signal; and

a bandpass filter for filtering the detected spread-spectrum signal; and

said data detection means includes a data detector, synchronized with the replica of the generic-chip-code signal, for detecting message data in the detected spread-spectrum signal.

3. A spread-spectrum communications system for communicating message data comprising:

a generic-chip-code generator for generating a generic-chip-code signal;

a spread-spectrum modulator for spread-spectrum processing the message data, synchronized with the generic-chip-code signal, as spread-spectrum-processed-message data;

a combiner for combining the generic-chip-code signal with the spread-spectrum-processed-message data, thereby generating a code-division-multiplexed (CDM) signal;

a transmitter for transmitting, using radio waves traversing free space, the CDM signal over a communications channel;

a detector, coupled to said communications channel, for detecting the generic-chip-code signal embedded in the CDM signal, said detector including,

a receiver-generic-chip-code generator, synchronized to the detected-generic-chip-code signal, for generating a replica of the generic-chip-code signal;

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

a product detector for mixing the message-chip-code signal with a received CDM signal to generate a detected spread-spectrum signal;

a bandpass filter for filtering the detected spread-spectrum signal; and

a data detector, synchronized with the replica of the generic-chip-code signal, for detecting message data in the detected spread-spectrum signal.

4. A spread-spectrum communications method for communicating message data, comprising the steps of:

generating a generic-chip-code signal;

synchronizing the message data with the generic-chip-code signal;

spread-spectrum processing the message data as a spread-spectrum-processed-message data;

combining the generic-chip-code signal with the spread-spectrum-processed-message data, thereby generating a code-division-multiplexed (CDM) signal;

transmitting, using radio waves traversing free space, the CDM signal over a communications channel;

detecting, from the communications channel, the generic-chip-code signal embedded in the CDM signal;

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

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

mixing the message-chip-code signal with a received CDM signal to generate a detected spread-spectrum signal;

filtering the detected spread-spectrum signal; and

detecting, synchronized to the replica of the generic-chip-code signal, message data in the detected spread-spectrum signal.