Fourdimensional modulation and coding: An alternate to frequencyreuse
Abstract
Four dimensional modulation as a means of improving communication efficiency on the bandlimited Gaussian channel, with the four dimensions of signal space constituted by phase orthogonal carriers (cos omega sub c t and sin omega sub c t) simultaneously on space orthogonal electromagnetic waves are discussed. "Frequency reuse' techniques use such polarization orthogonality to reuse the same frequency slot, but the modulation is not treated as four dimensional, rather a product of twod modulations, e.g., QPSK. It is well known that, higher dimensionality signalling affords possible improvements in the power bandwidth sense. FourD modulations based upon subsets of latticepackings in fourD, which afford simplification of encoding and decoding are described. Sets of up to 1024 signals are constructed in fourD, providing a (Nyquist) spectral efficiency of up to 10 bps/Hz. Energy gains over the reuse technique are in the one to three dB range t equal bandwidth.
 Publication:

NASA STI/Recon Technical Report N
 Pub Date:
 September 1983
 Bibcode:
 1983STIN...8336300W
 Keywords:

 Communication Satellites;
 Frequency Modulation;
 Frequency Reuse;
 Signal Transmission;
 Decoding;
 Lattices (Mathematics);
 Orthogonal Multiplexing Theory;
 Communications and Radar