Implementation Of TCM Design Based On FPGA

Trellis-coded Modulation (TCM) is always used in bandlimited communication systems. TCM effectively improves coding gain by combining modulation with forward error correction coding in one process. Because it can increase the constellation with double points without changing symbol rate and power spectrum. So it is a high efficiency coding manner.In the dissertation, a TCM encoder/decoder implementation based on FPGA is presented. It is not only increases decoding speed but also reduces complexity of hardware. The design of the algorithm is based on a 16-state convolutional code which is always used in standard 256-QAM wireless systems. In the design, a Hamming distance is used as a cost function. The least of the Hamming distance will determine survival path and the survival path which will decide the path state. Using the relationship between the delay states and the path state in the Trellis tree, the pre-calculated Hamming distances are stored in a look-up table which make the calculation more easy. At the same time, an output look-up-table is used to generate the decoder output. This table is established by the two relative delay states in the code. The dissertation introduces details of the algorithm and structure of TCM. Besides; using parallel processing and pipelining technical also make the decoding run more fast. The language in the program of the design is VHDL. The code has been passed the time simulation and downloaded in the detail chip to validate. The result turns out that this design is feasible.