Patent ID: 7227884

Claim:
A communications system for receiving a plurality of messages from a plurality of transmitters that each use a common spreading code, comprising: a receiver that is configured to receive a composite signal that comprises the plurality of messages from the plurality of transmitters, each message having a transmitter code-phase relative to a code-phase of the receiver, each transmitter code-phase being independent of the code-phase of the receiver, and a message discriminator that is configured to: discriminate at least one message from the plurality of messages based on the transmitter code-phase corresponding to the at least one message, and search each frequency of a plurality of frequencies for energy content at each code-phase of a plurality of code-phases to discriminate the at least one message at the transmitter code-phase, wherein: the message discriminator comprises: a detector that is configured to determine a measure of the energy content at each code-phase at a given frequency of the plurality of frequencies, and to identify one or more code-phases at the given frequency, based on the measure of the energy content, a demodulator, operably coupled to the detector, that is configured to demodulate an input signal corresponding to the composite signal, based on at least one of the identified one or more code-phases at the given frequency, the receiver is configured to provide a downconverted composite signal at a baseband frequency of the plurality of messages, and the detector determines the measure of the energy content at each code-phase based on a Fourier Transform that is applied to the downconverted composite signal at one or more given frequencies.