Adaptive modulation can also control quality of service according to transmitted information type and greatly increase capacity of system . the data frames in adaptive modulation communication system must be redesigned . because the sender must tell the receiver the current modulation mode by some bits in the data frame and the receiver must gain the current channel condition from the data frame in order to control its modulation mode and symbol rate 因为发送方须通过数据帧中的某些比特来通知接收方当前的调制方式和符号速率；同样，接收方也须从数据帧中某个域的比特流来获得当前的信道条件信息，从而去控制其调制方式及符号速率。
Adaptive modulation mainly include several problem for example signal shape , channel estimation , all digital receiver and so on . since the channel referring to adaptive modulation is very hostile in wireless transmission channel , its algorithms and architectures used for the modulation and demodulation should be carefully devised and considered . designing appropriate algorithms and architectures of the adaptive modulation are main research goal of this paper to meet the need of flat fading channel and selective fading channel 自适应调制技术主要包括信号成形、信道估计和检测、全数字接收等方面的问题，由于自适应调制所涉及的信道是非常恶劣的无线传输信道，其调制与解调的算法和结构必须加以精心的设计和考虑，针对具体所假设的平衰落和选择性衰落的无线信道情况来设计自适应调制系统的算法和结构是本文研究的主要方向。
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 然后作者的精力转入信道的自适应方案的研究中，首先通过研究发现nakagami衰落因子的适当调整可以近似于常见的瑞利衰落和莱斯衰落，接着研究在无线信道中采用三种不同自适应方案时的信道容量，研究表明速率的调整是增加信道容量的关键，在此基础上，着重研究了离散变速率qam的情况，表明这种调制方案无论在频带利用率还是在系统平均误码率比其它情况提高很多。
Orthogonal frequency division multiplexing ( ofdm ) techniques and multiple input and multiple output ( mimo ) techniques have gained more and more interest in the last a few years . but there are still many key problems to be solved in ofdm and mimo , including synchronization , channel estimation and adaptive modulation . these are the research targets in this paper 正交频分复用( ofdm )技术和多输入多输出( mimo )技术已经或者即将应用于各种高速宽带无线通信系统中，但是一些关键技术，包括ofdm系统的同步算法和mimo - ofdm系统的同步算法、信道估计和跟踪算法和自适应调制方案等等，仍待解决和完善。
In the code division multiple access ( cdma ) system , the multiple access interference ( mai ) mitigation capability as well as system capacity are determined , to a great extent , by the correlation properties of spreading sequences ; while adaptive modulation and coding ( amc ) with high spectral efficiency is the key technique to obtain high speed and low symbol error rate ( ser ) performance in mobile data transmission 在码分多址( cdma )系统中，扩频序列的特性在很大程度上决定了抗多址干扰( mai )能力和系统容量，而高频谱效率的自适应调制编码( amc )技术则是获得高速率和低误码率( ser )移动数据传输性能的关键因素。
After introducing the ideals of the slow adaptive modulation and fast adaptive modulation , we demonstrated the need applying adaptive modulation from the aspects of broadband wireless multimedia communications . we have introduced the practice application of the adaptive modulation technology in many protocols nowadays . and we have briefly showed research background and developing trend of the adaptive modulation technology 在引入了慢速自适应调制和快速自适应调制的思想后，从宽带无线多媒体通信的需求角度论述了采用自适应调制的必要性，介绍了自适应调制技术在当前众多标准中的实际应用，并对自适应调制技术的研究背景和发展趋势作了一些扼要的介绍。
And considering the practical adaptive modulation , when the value of pilot symbol message length is more than twenty symbol message length , map channel estimation is obviously superior to ml channel estimation . facing the qam constellation controllable adaptive modulation system , we go deep into the models , frame architecture , the constellation select for star qam and square qam , architecture implementation and so on . we elaborate on the slice decision of the square qam 针对qam星座可调的自适应调制系统，深入研究了系统的模型、帧结构、星型qam星座和方型qam星座的选择、实现的结构等，分析了方型星座下的判决门限，并给出了判决门限的仿真结果。
Based on the existent theory and the engineering application , the thesis study the good performance by combined the adaptive modulation technology and the multilevel modulation technology on the simulink model . experiment results show that this combination bring on the high data transmittable efficiency and the well transmission quality . this chapter is a base of next chapter 根据已提出的基本理论，论文基于工程应用，在仿真模型上对自适应调制和多元调制方式的结合所产生的优良的性能进行了探讨，仿真显示出这种结合带来的高数据传输效率和大的传输质量改善，本章是第三章的基础。
Throughputs of adaptive modu - lation , adaptive coding , and joint adaptation schemes are analyzed , and optimal switch - ing threshold of snr is obtained . in comparison with non - adaptive harq , adaptive schemes can get much higher throughput in the given cell . among the three adaptive schemes , adaptive modulation is t 分析了自适应调制、自适应编码和联合自适应方案在小区中的流量特性，得到了最优的切换门限，比较了自适应与非自适应harq的流量，以及三种自适应方案的优劣，其中自适应harq流量特性明显好于非自适应harq 。
