M-link multiplexing over the quadrature communications channel

The possibility of multiplexing more than two independent, unsynchronized data streams on a quadrature carrier channel is investigated theoretically. It is found that by using linear (or near linear) combinations of basis carriers, no increase in overall bandwidth occurs as more channels are added, increasing the overall system throughput. Symbol decoding with banks of independent bit integrators after phase coherent demodulation was investigated, and degradation and bit error probabilities were computed. The results indicate that significant degradations occur even with relatively few added channels, but bandwidth savings and the simple encoder and decoder circuitry may prove a cost-efficient tradeoff in bandwidth restricted systems.