CDMA subtractive demodulation

A multiple access, spread spectrum communications system for communicating information signals between plural stations using code division spread spectrum communications signals, each station comprising:

• a transmitter including:
• means for spreading an information signal with a corresponding, spreading code;
• a scrambling means for adding a scrambling bit sequence to said spread information;
• and
• means for transmitting said scrambled, spread-coded information signal;
• and
• receiving means for receiving a composite signal of overlapping, transmitted signals including:
• descrambling means for descrambling said composite signal using a scrambling bit sequence;
• and
• decoding means for recursively decoding said composite signal by correlating spreading codes to generate a series of decoded signals.

A multiple access, spread spectrum communications system for communicating information signals between plural stations using code division spread spectrum communications signals, each station comprising:

• a transmitter including:
• coding means for coding blocks of bit sequences of an information signal, and
• means for transmitting said block-coded information signal;
• and
• receiving means for receiving a composite signal of overlapping, transmitted signals, including:
• correlation means for recursively correlating said composite signal with block codes corresponding to said information signals;
• comparison means for determining a block code that generates a greatest correlation and for producing a correlated signal;
• signal removal means for successively removing said correlated signal from said composite signal;
• and
• inverse correlation means for recoding a residual portion of said correlated, composite signal using said corresponding block codes to generate a series of recoded signals.

In a multiple access, spread spectrum communications system for communicating information signals between plural stations using code division spread spectrum communications signals, a method comprising:

• spreading individual information signals from said stations using a corresponding, pseudo-random spreading code, wherein different information signals from different stations may have a same spreading code;
• scrambling each said spread-coded information signal using a unique, selected scrambling bit sequence corresponding to one of said stations;
• transmitting said scrambled, spread-coded signals from each station;
• receiving a composite signal of overlapping, transmitted signals;
• descrambling said composite signal using one of said unique scrambling bit sequences to distinguish spread-coded information signals from a selected station from other signals in said composite signal;
• and
• recursively decoding said composite signals by correlating selected spreading codes to generate a series of decoded signals.