Conditions for 90 degrees phase-invariant block-coded QAM
Werner Henkel · IEEE Transactions on Communications · 1993
Based on V.A. Zinoviev's (1981) generalized concatenated codes, conditions for the construction of 90 degrees phase-invariant QAM are derived. Furthermore, a proposal for the necessary differential encoding/decoding is made. The conditions for phase invariance are specialized for the case of Reed-Muller codes as outer codes of the generalized concatenation.>