180 degrees Rotationally Invariant Repeat-Accumulate Codes

Abstract

In digital communication systems employing binary phase-shift keying and non-data-aided carrier phase recovery. a 180 degrees carrier phase ambiguity is inevitable. Here, we propose a simple modification to the standard regular repeat-accumulate (RA) code structure by exploiting the differential encoding inherent to the inner encoder of RA codes resulting in codes that are 180 degrees rotationally invariant. The proposed code structure exhibit performance virtually identical to that of standard regular RA codes with zero carrier phase offset under both zero and 180 degrees carrier phase offsets with negligible additional hardware complexity.