Performance Of Coded Modulation Systems In High Mobility Wireless Channels

Channel coding is an essential technology for reliable communication over noisy channel. It serves as an important role in communication systems. As the growing popularity of high-speed train today, relevant research on the high reliability, high spectral efficiency communication technology in high mobility environment will contribute to providing a better quality of service to the passengers on high-speed train. Based on the high-speed mobile communication channel model, this article mainly research on the performance of the coded modulation system under high mobile environment.Under Gaussian channel, Turbo code, binary/non-binary LDPC codes present a very excellent performance. To resist the influence caused by the multipath fading to the communication system, OFDM technology is being introduced. But for the high mobile environment, it is vital to find a channel coding techniques which has good performance under the rapidly changing channel based on OFDM transmission.Firstly, we present the simulation results and analysis to the statistical properties of a non-stationary channel based on the geometry statistic model. Then, we study the channel estimation and channel equalization techniques, which is suitable for rapidly changing channel in OFDM system. Their characteristics, computational complexity, etc. are described in details. On this basis, this paper presents the block diagram and simulation flowchart of a coded modulation system based on OFDM technology. We mainly focus on the performance of the coded modulation systems, which are combined Turbo bode, binary LDPC code or non-binary LDPC code with QPSK, 16 QAM or 64 QAM, under the fast changing channel. The actual results show that for the moving speed of 360 km / h and above, the high-order modulation 64 QAM is no longer suitable because of the limitation of the equalization ability. In various encoding methods, compared to Turbo codes and binary LDPC codes, non-binary LDPC codes have an obvious preponderance under the channel state when the train moving at a high speed. Therefore, non-binary LDPC code is an powerful alternative encoding scheme in high mobile communication system for 5G.