Communication system with concatenated matched filter and doppler-tolerant polyphase codes

A method of low data rate communications, comprising:

• encoding a low data rate information-bearing digital signal with a direct sequence spread spectrum code, forming a DSSS signal;
• modulating said DSSS signal with a Doppler tolerant polyphase code, forming a pilot signal;
• and
• transmitting said pilot signal to a cooperating receiver.

A method of low data rate item location, comprising:

• forming a pilot signal at one of a plurality of stations that enables rapid synchronization on receipt;
• encoding an information-bearing signal with a direct sequence spread spectrum code, forming a DSSS signal;
• modulating said DSSS signal with a Doppler tolerant polyphase code, forming a concatenated DTPC pilot signal;
• transmitting said pilot signal to a cooperating receiver;
• receiving at said plurality of stations a responsive signal from said cooperating receiver;
• and
• identifying and locating said cooperating receiver based on said receiving.

A method of communicating, comprising:

• transmitting a signal comprising a pilot signal, wherein said pilot signal is used to acquire one or more parameters of frequency difference and timing;
• receiving said signal in a cooperating device;
• using said acquired parameters in said cooperating device, transmitting a second signal to a plurality of stations, said second signal having corrected frequency and timing;
• receiving at one or more of said stations said second signal.

A communications system, comprising:

• a transmitter comprising:
• means for forming a plurality of direct sequence spread spectrum (DSSS) signals, wherein one or more of said signals are modulated with low data rate information;
• means for forming one or more of said DSSS signals into pilot signals;
• and
• means for transmitting said DSSS signals and said pilot signals;
• and
• a cooperating receiver adapted to receive said transmitted signals, comprising
• means for demodulating said low data rate information from said DSSS signals using said pilot signals.

A computer system for use in low data rate communications, comprising computer instructions for:

• encoding a low data rate information-bearing digital signal with a direct sequence spread spectrum code, forming a DSSS signal;
• modulating said DSSS signal with a Doppler tolerant polyphase code, forming a pilot signal;
• and
• transmitting said pilot signal to a cooperating receiver.

A computer-readable medium storing a computer program executable by a plurality of computers, the computer program comprising computer instructions for:

• encoding a low data rate information-bearing digital signal with a direct sequence spread spectrum code, forming a DSSS signal;
• modulating said DSSS signal with a Doppler tolerant polyphase code, forming a pilot signal;
• and
• transmitting said pilot signal to a cooperating receiver.

A computer data signal embodied in a carrier wave, comprising computer instructions for:

• encoding a low data rate information-bearing digital signal with a direct sequence spread spectrum code, forming a DSSS signal;
• modulating said DSSS signal with a Doppler tolerant polyphase code, forming a pilot signal;
• and
• transmitting said pilot signal to a cooperating receiver.