Study Of Trellis Coded Modulation And Application Of TCM Based On OFDM System

Modern communication services require communication systems can provide high date rate with favorable communication quality. But this is a challenge for limited bandwidth channel with inter-symbol interference. In order to solve this problem, this thesis studied on Trellis Coded Modulation (TCM). In TCM, coded and modulation have been considered as one part. TCM has recently received much attention in channel coding of digital communication systems due to its performance and high bandwidth-efficiency. Its basic idea is to partition the constellation optimally by coding, so that the maximal distance between the modulated signal vectors can be obtained.This thesis introduced the concept of TCM, the principle of set partitioning and the method of computing coding gains. Soft decision Viterbi decoding is discussed and the performances of TCM and TCM-OFDM are analyzed by computer simulation. This paper discussed the application of TCM in real modulation systems, proposed the schemes of eight states TCM-8PSK and TCM-16QAM. According to the parameters of these two systems, the means to design encoder and decoder of TCM in FPGA are introduced. The encoder and decoder were described in Verilog HDL under the QuartusⅡ6.0.Due to its high spectrum efficiency and anti-multipath traits, OFDM technology is widely used in high data rate communication field. However, because of the predetermined modulation and demodulation of each sub-carrier, the bandwidth resource is not effectively utilized. Based on accurate estimation of channel, OFDM adaptive modulation and demodulation can fully utilize the frequency resource and greatly improve system performance by allocating bits and power dynamically. This thesis introduces the basic principle and key technologies of adaptive TCM based on OFDM system.