Sam . . wideband air interface - scalable adaptive modulation physical layer specification - public safety wideband data standards project - digital radio technical standards 宽带空中接口.可扩缩自适应调制
This paper , special research object is the qam constellation controllable adaptive modulation system , symbol rate and modulation level controllable adaptive modulation system 本文以qam星座可调的自适应调制系统、符号率及调制电平可控的自适应调制系统为具体的研究对象。
Some new technologies are introduced in hsdpa , including a shorter transimission time interval ( tti ) 、 adaptive modulation and coding ( amc ) scheme and a fast physical layer hybrid arq mechanism 在该系统中采用了以下技术:更短的传输时间间隔,物理层的混合自动重传,自适应编码调制等。
Afterwards we theoretically analyze and conclude the model of the adaptive modulation system . we find out three kinds of channel model appropriated for actual cannels and draw out pulse response matrix equations 然后，从理论上分析和推导了自适应调制系统的模型，给出了适合实际信道的三种信道模型结构并推导了脉冲响应矩阵方程。
Next , based on the throughput performance of fixed modulation schemes in packet transmission , adaptive modulation with throughput maximization under fading channel is investigated and significant throughput improvement is obtained 接着，基于固定调制方案的分组传输吞吐量性能，本文研究了衰落信道中吞吐量最大化自适应调制技术，该方法可以取得显著的吞吐量性能增益。
Following the third - generation mobile communication , it is a high wireless multimedia communication network . it has extensively application foreground . adaptive modulation technology is one of the key techniques that must be deal with 目前，无线局域网和城域网是美国、欧洲和日本在无线通信领域研究的重点，它是继第三代移动通信后的高速无线多媒体通信网，具有广阔的应用前景，自适应调制技术就是其中要解决的核心技术之一。
Combined with the adaptive modulation and coding technology , this algorithm reallocates the residual power by effectively utilizing the discrete modulation orders according to the different priorities of sub - channels under the limitation of quality of service over the block fading channel 在满足服务质量要求的前提下充分利用星座图尺寸的离散性，将残余功率按照各子信道的不同优先级进行二次分配，并结合自适应调制编码技术改善低信噪比时的系统吞吐量。
Adaptive modulation technology is based on the rapidly development of computer technology and digital signal processing technology . studying algorithm and implementation of the adaptive modulation technology have a signification for studying personal communications , satellite communications , multimedia communications , high wireless local area network and metro area network . at the present , wireless lan and wireless man is the most of the wireless communications field in america , europe and japan 自适应调制技术是以当今计算机技术和数字信号处理技术高度发展为前提的，对自适应调制技术的算法和实现进行研究将对个人通信、卫星通信、多媒体无线通信、高速无线局域网和城域网的研究具有重要意义。
Its ideal is that modulation mode can be adaptively adjusted by estimating such wireless parameters as fading degree , channel traffic and etc . channel capacity will achieve a maximum and system performance will be best anytime . by this way , although mobile wireless channel broadband is more and more congesting today , adaptive modulation can be provided preferable spectral efficiency and can be increased the information transmission rate . so the transmission system broadband will be effectively improved 它的主要思想是通过研究无线信道的衰落程度、信道流量等参数动态地改变调制方式，在任何时刻都使信道容量达到最大或者使系统性能达到最佳，从而使移动无线信道频带日益拥挤的今天能得到较高的频谱利用率，有效地提高信息传输速率、从而提高传输系统的带宽。
And then facing the problem of the channel estimation of the adaptive modulation system , we conclude out the channel estimation algorithms on maximum likelihood ( ml ) estimation and maximum a posteriori ( map ) estimation under the condition of flat fading channel and selective fading channel in detail . to meet flat fading channel , we simulate the relationship of the ratio between the error covariance in map estimation and ml estimation and pilot symbol message length . the conclusion can be drawn from these results 接着，对自适应调制系统中的信道估计问题难点，详细推导了平衰落信道条件下和选择性衰落信道条件下最大似然( ml )估计和最大后验概率( map )估计算法，针对平衰落信道，我们仿真了map估计和ml估计的方差与导频符号长度的关系，仿真结果表明，错误方差受多谱勒频率的变化影响最大，并且对实际的自适应调制系统，导频符号长度的取值超过20个符号长度时， map信道估计明显优于ml信道估计。
