Analysis Of Performance On Low States Turbo Trellis-coded Modulation And FPGA Design

As a new bandwidth-efficient coded modulation scheme, turbo trellis-coded-modulation (TTCM) has recently received much attention in channel coding of digital communication systems due to its near capacity performance and high bandwidth-efficiency. It has an overall structure similar to binary turbo codes, but employs trellis-coded modulation (TCM) codes (including multidimensional codes) as component codes. The combination of turbo codes with powerful bandwidth-efficient component codes leads to a straightforward encoder structure, and allows iterative decoding in analogy to the binary turbo decoder. However, certain special conditions may need to be met at the encoder, and the iterative decoder needs to be adapted to the decoding of the component TCM codes. A soft-in soft-out component decoder can be implemented using the maximum a posteriori (MAP) or the maximum likelihood (ML) decoding algorithm. While the MAP algorithm offers better performance than the ML algorithm, the computation is complex and not suitable for hardware implementation. The log-MAP algorithm we derived, which performs necessary computations in the logarithm domain, greatly reduces hardware complexity. Simulation results are presented and compare the scheme with traditional TCM. The results show that the novel scheme is very powerful, yet of modest complexity since simple component codes are used.With the proliferation of the battery powered devices, power dissipation, along with speed and area, is a major concern in VLSI design. In this thesis, we investigated a low-power design of a turbo TCM decoder based on the log-MAP algorithm. Our turbo TCM decoder has two component log-MAP decoders, which perform the decoding process alternatively. The encoder and decoder were described in VHDL under the Quartus.