System and method for communicating digital data while resolving phase ambiguities

摘要

A communication system (10) includes a rotationally invariant pragmatic trellis coded modulation (PTCM) encoder (18) and decoder (34). The PTCM encoder (18) partitions information bits (20) into primary (42) and secondary (44) data streams. A pilot bit (56) is inserted into the secondary data stream (44) during each frame (46). The secondary stream (44) then receives rate +E,fra 1/2+EE convolutional encoding (60) that is punctured to a rate of +E,fra 9/16+EE . The primary data stream (42) is differentially encoded (50). The encoded primary and secondary streams are concurrently phase mapped (70) using an 8-PSK constellation so that an effective code rate of +E,fra 5/6+EE results. The PTCM decoder (34) convolutionally decodes (84) the secondary stream, then re-encodes secondary stream estimates using a systematic, transparent convolutional encoder (88). The pilot bit is evaluated (92) in the re-encoded symbol estimates (90) to detect and correct any secondary stream inversion that may have occurred due to phase ambiguity. After this correction, the secondary modulation is removed (98) from phase value estimates, and the primary stream is decoded.