High capacity spread spectrum channel

Abstract

A high-capacity-spread-spectrum transmitter and receiver, for use over a communications channel. A demultiplexer demultiplexes message data into a plurality of demultiplexed-data signals. A transmitter-generic-chip-code generator generates a generic-chip-code signal and a plurality of transmitter-message-chip-code generators generate a plurality of message-chip-code signals which are "near-orthogonal" over a demultiplexed data bit. A plurality of EXCLUSIVE-OR gates, spread-spectrum processes the plurality of demultiplexed-data signals with the plurality of message-chip-code signals to generate a plurality of spread-spectrum signals. A combiner combines the generic-chip-code signal and the plurality of spread-spectrum-processed signals. A receiver-generic-chip-code generator generates a replica of the generic-chip-code signal. A generic mixer recovers the carrier signal from the spread-spectrum-communications signal. A plurality of receiver-message-chip-code generators generate a plurality of replicas of the message-chip-code signals. A plurality of message mixers despreads the spread-spectrum-communications signal as a plurality of modulated-data signals. Tracking and acquisition circuits use the recovered carrier signal for synchronizing the replicas of the generic-chip-code signal to the recovered carrier signal. A plurality of envelope detectors demodulates the modulated-data signal as a plurality of received-demultiplexed data. A multiplexer multiplexes the plurality of received-multiplexed data as received data.

Description

BACKGROUND OF THE INVENTIONThis invention relates to spread-spectrum communications and more particularly to a system and method for a high capacity spread-spectrum communications channel.DESCRIPTION OF THE PRIOR ARTReferring to FIG. 1, message data, d(t), are processed by spread-spectrum data modulator 51, using a message-chip-code signal, g.sub.1 (t), to generate a spread-spectrum data signal. The data spread-spectrum signal is processed by transmitter 52 using a carrier signal at a carrier frequency, f.sub.o, and transmitted over communications channel 53.At a receiver, a spread-spectrum demodulator 54 despreads the received spread-spectrum signal, and the message data are recovered by synchronous data demodulator 60 as received data. The synchronous data demodulator 60 uses a reference signal for synchronously demodulating the despread spread-spectrum signal. The square-law device 55, bandpass filter 56 and frequency divider 57 are well known in the art for generating a referenc...

AI Technical Summary

Benefits of technology

The present invention provides a high-capacity spread-spectrum communications system that can communicate information at a high rate through a shared spectrum with other users. The system includes a transmitter and a receiver. The transmitter demultiplexes the message data signals and generates a generic-chip-code signal. The receiver includes acquisition and tracking means, multiplexer means, and a plurality of spread-spectrum receivers. The system can synchronize the carrier signal and recover the original chip-code signal. The receiver also includes detection means and bit-synchronization means for detecting and synchronizing the modulated-data signals. The technical effect of the invention is a high-capacity, spread-spectrum communication system with efficient data transmission and processing capabilities.

Problems solved by technology

Thus, the sum of voltage levels need not be an exact linear sum, with only a little loss in performance.

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