Research On Fast Adaptive Modulation And Slow Adaptive Modulation System

Adaptive modulation technique is an effective solution to the scarcity of spectral efficiency (SE) in mobile communication systems. The key ideas of adaptive modulation technique are as follows:the receiver estimates channel state information (CSI) and sends the estimated CSI back to the sender, then the sender adjusts the modulation mode based on the decision criterion so that we can tradeoff spectral efficiency and communication reliability. Adaptive modulation technique mainly contains two methods:Fast Adaptive Modulation (FAM) and Slow Adaptive Modulation (SAM).In this thesis, we first introduce the basic theories of the adaptive modulation, including the basic model of adaptive modulation, the modulation mode and error coding methods, frame structure, fading types of the wireless channel, as well as concept of FAM and SAM system. Then using MQAM modulation mode, we build the diversity adaptive modulation system model based on the SNR threshold method, mainly compare FAM and SAM system performances, and put forward the concept of redundancy SE probability which can measure efficiency of SE. Then, the thesis does research on the bit-error-rate-decision method with FAM system and SAM system separately, including the theory of bit-error-rate-decision method and the practical system model, and then makes comparison between the effect of different coding methods on the channel estimation and the influence on system performance of fading factor’s amplitude and phase. Finally, this thesis compares the system performance based on different decision rules, and puts forward adaptive modulation system combining two kinds of judgment criterion.Simulation results demonstrate that the SAM technology can better improve the spectral efficiency and reduce complexity; the SNR threshold method is better than error-rate-decision method, and the combined modulation system with relationship of "and" is better than system with relationship of‘’or"...