Research On TCM And BICM Schemes Of The Coded Modulation Technology

Coded modulation (CM) has been a hot research topic for a long time, with the emergence of high-speed and broadband mobile communications, CM technology, with a character without expanding frequency coding, attracts more and more attentions of the researchers. However, a large number results have showed that: as a typical CM programme, trellis-coded modulation (TCM) is the best option in the AWGN channel, and it has the best coding and decoding methods, the best mapping rules. But in the fading channel, the result is not ideal, losing out a lot of coding gain. Therefore, the discussion of the application performance of various CM programmes in the fading channel has become the hot point of the CM study.In this paper, several CM programmes are discussed in detail, including Ungerboeck TCM, BICM, BICM-ID and Turbo TCM. Their main parts and principles are analysed, and their performance in the AWGN channel and the Rayleigh channel is simulated. Also the principle of set partitioning is given as a main part, and the physical meaning of TCM is explained from the perspective of Shannon channel coding theories.The simulations in this paper focus on the combinations of the best convolutional coding in various constraint lengths and 8PSK modulation. The results show that, in the AWGN channel, the TCM programme can get the best performance. When BER is limited to be 10e-5, a 8PSK-TCM programme of 4 states and 2/3 coding rate can achieve a gain of 2.5dB compared to uncoded QPSK, and the performance of BICM is much worse than TCM relatively, while the performance of BICM-ID is close to TCM after the third round decoding. In the Rayleigh fading channel, the performance of TCM is the worst and the BICM programme can get the best performance of coded modulation, while the BICM-ID programme after the third round decoding can get a gain of 1dB compared to BICM. With the increase in the number of iterative decoding, the system performance of BICM-ID programme improves constantly, but the rate of improve is decreasing as the increase of the iterative number, and the performance of BICM-ID is better than BICM after the second round decoding. In the end, this paper analyses the system design of Turbo TCM, and gives out the performance curves in the Rayleigh fading channel. The results show that, UP set partitioning is the most suitable set partitioning method for Turbo TCM programme, and compared to 8 state 2/3 coding rate 8PSK BICM programme Turbo TCM programme has a gain of 4dB, when BER is limited to be 10e-5.