Two constellation algorithms for discrete multi-tone

Two new constellations, non-rectangular QAM (NQAM) and snail shift keying are introduced to replace the rectangular QAM constellation for discrete multi-tone modulation. The major property of these schemes is their non-symmetric configurations where demands of subscribers can be prioritised conveniently. These constellation algorithms, compared to well-known QAM modulation especially NQAM with the same implementation complexity, have improved bit error rate performance.