Nonlinear Turbo Codes for Higher-Order Modulations

— In 1982 Ungerboeck presented a set-partitioning design technique for trellis coded modulation (TCM). Although this technique directly assigns constellation points to the branches of the trellis, it has been shown that the same optimal code can be accomplished by a convolutional code with a mapper that assigns a series of coded bits to a constellation point. This notion has remained with the appearance of turbo codes. Therefore, parallel concatenated trellis coded modulation (PC-TCM) has been traditionally designed using parallel concatenated convolutional codes with a bits-to-symbol mapper. This paper shows that for higher-order modulations using linear codes is too restrictive. Parallel Concatenated Nonlinear Trellis Coded Modulation (PC-NLTCM) which directly assigns constellation points as output-labels to the branches of the trellis can outperform PC-TCM. Simulation results are shown for a 2 bits/s/Hz 16-state nonlinear turbo code with 8PSK. This code is less than 0.5 dB away fr...

• Type: Conference
• Year: 2008
• Where: ICC
• Authors: Miguel Griot, Andres I. Vila Casado, Richard D. Wesel
• Keywords: Communications, Constellation Point, Convolutional Codes, ICC 2008, Trellis Coded Modulation