Method and Apparatus for Increasing the Capacity of A Data Communication Channel

System for efficiently increasing the capacity of a data channel being capable of operating in a given data rate B between a transmission end and a receiving end, comprising

• a) a transmitter at said transmission end, for simultaneously transmitting N modulated data streams, each of which having a bit rate of B/N and a bit-time of N/B, to a receiving end of said channel, consisting of:
• a.1) a plurality of signal sources for generating said N modulated data streams;
• a.2) means for generating a shift of 1/B*N between the first modulated data stream and each of its N−1 subsequent modulated data streams;
• a.3) a combiner for combining said first modulated data stream and its shifted subsequent modulated data streams into a reduced bandwidth signal having up to N levels,
• b) a receiver a receiving end, for receiving said reduced bandwidth signal, that consists of:
• b.1) circuitry for sampling said reduced bandwidth signal N times during each bit-time and for obtaining a vector having N elements at each time, such that each element has N+1 possible values;
• and
• b.2) a processor for performing vectorial MLSE for each element by calculating the joint conditional PDF and for reconstructing each of said N modulated data streams.