Performance simulations and comparisons of modulation and mapping based on the bit interleaved system

Abstract

Bit-Interleaved Coded Modulation with iterative decoding (BICM-ID) is a technique with combination of coding and high-order modulation. Its many outstanding merits such as it can advance the coding gain, suit the fading channel and separately design the encoding part and the modulation part, make it a very competitive technology in the new generation wireless transmission system. This paper analyzed and compared the different performance that the BICM-ID system presented in different modulation and mapping modes. The main component of the study is when the other conditions kept fixed, through the simulation experiments, we got the bit error rate (BER) curves of the system which were corresponding to three different modulation modes (QPSK, 8PSK, 16QAM) under the SP mapping mode, and the BER curves which were corresponding to four different mapping modes (Gray, SP, SSP, MSEW) under the 8PSK and 16QAM modulation modes separately. Then we analyzed the results and found out the best modulation and mapping mode that can make the BICM-ID system present the best BER property in certain signal noise ratio (SNR) range. Considering the constellation mapping and the design of interleaver are inseparable, we also studied the effects of interleaving depth on the performance of the system. In the simulation experiments we used the 8PSK modulation and SP mapping as examples, designed four kinds of interleaving depth (5114, 2048, 1024, 500), and obtained the corresponding four BER curves in Rayleigh channel.