US 4,358,844 AGranted

Method of and means for spread-spectrum transmission

AssigneeCSELT - Centro Studi e Laboratori Telecomunicazioni S.p.A.

InventorGiancarlo Pirani

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Abstract

An analog signal sent from one telephone subscriber to another is differentiated at a transmitting terminal and the resulting derivative is distorted by mixing with a random or pseudorandom sequence of bipolar binary pulses before being conveyed, e.g. by frequency modulation, to a receiving terminal where it is mixed with a like pulse sequence to re-establish the undistorted derivative signal with substantial suppression of interferences from other users of the same signal link. The re-established signal is integrated over intervals equal to a basic pulse period of the binary sequence and each signal sample thus obtained is additively combined with the sample from the immediately preceding period to restore the original analog signal. The signal link utilized may be an emergency channel made available, e.g. for communication with a mobile station, when regular channels are busy.

Claims7

Dependent claims

A method of sending signals from a plurality of transmitting stations to respective receiving stations over a common channel, comprising the steps of:

(a) differentiating an outgoing analog signal at a given transmitting station to produce a time derivative thereof;
(b) multiplying said time derivative at the given transmitting station with a sequence of bipolar binary pulses individual thereto and essentially uncorrelated with pulse sequences employed at other transmitting stations using said common channel, said individual sequence having a basic pulse period not exceeding the reciprocal of twice the bandwidth of said outgoing signal, to produce a distorted signal;
(c) conveying said distorted signal via said common channel to the associated receiving station;
(d) multiplying the incoming distorted signal at the associated receiving station with a synchronized replica of said individual sequence to re-establish the time derivative of step (b) possibly encumbered by interfering signals from other users of said common channel;
(e) integrating the re-established time derivative over intervals equaling said basic pulse period to produce a succession of signal samples of uniform width;
(f) combining said signal samples into a continuous wave substantially purged of interfering signals and with a low-frequency component conforming to said outgoing analog signal;
and
(g) isolating said low-frequency component.

5 more elements

In a telecommunication system wherein a plurality of transmitting stations and a plurality of receiving stations are provided with a common channel for the conveyance of analog signals from a given transmitting station to an associated receiving station, each transmitting station comprising a first generator of an individual sequence of binary pulses essentially uncorrelated with pulse sequences emitted by corresponding generators at all other transmitting stations, each transmitting station further comprising first arithmetic means for multiplying an outgoing signal with said individual sequence, each receiving station comprising a second generator synchronized with said first generator of the associated transmitting station for emitting a replica of said individual sequence, each receiving station further comprising second arithmetic means for multiplying an incoming signal with said replica and circuitry including integrating means connected to said second arithmetic means for substantially reconstituting said outgoing signal,

the improvement wherein at least one of said transmitting stations and an associated receiving station further comprise:
differentiation means upstream of said first arithmetic means for converting an outgoing analog signal into a time derivative thereof giving rise to a distorted signal in the output of said first arithmetic means, said distorted signal being reconverted by said second arithmetic means into the original time derivative possibly encumbered by interfering signals from other transmitting stations using said common channel, said interfering signals being substantially suppressed by said integrating means operating with integration periods equal to a basic pulse period of said individual sequence;
signal-restoring means in said circuitry connected to said integrating means for receiving therefrom integrated samples of the reconstituted original time derivative substantially purged of interfering signals and combining the integrated samples into a continuous wave with a low-frequency component conforming to said outgoing analog signal;
and
filter means connected to said signal-restoring means for extracting said low-frequency component from said continuous wave.

2 more elements

Dependencies are inferred from the claim text.