Signal Transmission In The Wireless Channel Adaptive Modulation Technique

Adaptive modulation has become the subject of intensive study in recent years. This paper focus on the variable rate QAM for Mobile Radio. Firstly we introduce mobile radio fading channel variations, Shadow fading. Slow fading. Rapid fading and so on. Then we introduce the QAM schemes of modulation about the design of parameters and constellations of QAM and show the result of 8QAM and 16QAM. Afterward we switch to the study of adaptive project, above all, we find that we can alter the parameter of Nakagami fading channels to other fadings, and then we study three different adaptive projects. We then present numerical results showing that rate adaptation is the key to achieving high link spectral efficiency. Based on these advantages we analyze the performance of constant-power variable-rate M-QAM schemes for spectrally efficient data transmission over NMF channels. By introducing the adaptive modulation approach , we gain two things: 1) the error rate is kept at a constant level. 2) the achievable spectral efficiency comes within 5 dB of the Shannon capacity limit.At the last chapter , the presentation of a single base station and a single mobile scenario proved the feasibility of adaptive schemes.