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Pushing ahead, East, North, West development, facilitating shanty, complete xincheng West Road, stability and reconstruction of the street, Star Ding garden built century Garden District, subject public housing construction, heating the gas expansion accelerated implementation, Jing Rui River and bridge style line solid shaft, further expanded the town development. Beautiful country adhere to the advance and typical for a group to lead. According to \cal lay based, and industry increased income, and live upgrade civilization, and culture rich connotation\caught built beautiful village, and whole village advance, and easily relocation, and \hree built\oject near 30 a; depth into ecological, and industry, and culture, and tourism, elements, high standards caught party original city Liu, and jade are Xia AO, model village, in province City set has benchmark. Four is equal benefits to promote sharing, coordinated development of various social undertakings. In the case of rigid spending slowing revenue growth, increase, financial 75% to the people's livelihood, the masses have more access in the sharing. Cuoban something good and benefit. Adhere to the affordable, best, carefully cuoban village oil, water and heat, cultural, city and County columns practical, developments benefit families, bring more welfare to the masses. Development of social convenience. Acceptance of balanced development of compulsory education through the national assessment, the County vocational education center was named \chool of vocational education in China\hird batch of national reform and development model through provincial ... Five is to deepen reform and innovation to break bottlenecks and endogenous development of effective fire. As an engine of dynamism, adding reform key to adopting reform measures stress energy and break bottlenecks and promoting development. Pay close attention to the key areas of reform. Conscientiously implement the provincial deployment and cancel, adjustment, to undertake the administrative approval items according to Regulation 347 to further improve administrative efficiency continuing deepening reform for poverty alleviation, speeding up rural land right registration certification pilot project, encouraging the orderly transfer of land management, utilize the land resources, in order to promote scale management laid the Foundation. Actively cultivate the market. Firmly establish a market-oriented, nurturing family farms, industrial users, professional cooperation organization new market management main body 456, effectively improve the industry, intensive and marketization of encouraging support social capital into the small micro-credit, urban development, culture and tourism, public services and other areas, easingdevelopment shortfall. To promote mass innovation. To support the rural sector to use new thinking and new ideas, creative work incentives such as actively promoting financial intermediation, bring added 159 in non public enterprises, individually-1540, created a

重庆交通大学信息科学与工程学院

综合性设计性实验报告

专 业： 通信工程专业11级

学 号： 4

姓 名： 黄光莉

实验所属课程： 宽带无线接入技术

实验室(中心)： 软件与通信实验中心

指 导 教 师 ： 吴仕勋

2014年3月

Pushing ahead, East, North, West development, facilitating shanty, complete xincheng West Road, stability and reconstruction of the street, Star Ding garden built century Garden District, subject public housing construction, heating the gas expansion accelerated implementation, Jing Rui River and bridge style line solid shaft, further expanded the town development. Beautiful country adhere to the advance and typical for a group to lead. According to \cal lay based, and industry increased income, and live upgrade civilization, and culture rich connotation\caught built beautiful village, and whole village advance, and easily relocation, and \hree built\oject near 30 a; depth into ecological, and industry, and culture, and tourism, elements, high standards caught party original city Liu, and jade are Xia AO, model village, in province City set has benchmark. Four is equal benefits to promote sharing, coordinated development of various social undertakings. In the case of rigid spending slowing revenue growth, increase, financial 75% to the people's livelihood, the masses have more access in the sharing. Cuoban something good and benefit. Adhere to the affordable, best, carefully cuoban village oil, water and heat, cultural, city and County columns practical, developments benefit families, bring more welfare to the masses. Development of social convenience. Acceptance of balanced development of compulsory education through the national assessment, the County vocational education center was named \chool of vocational education in China\hird batch of national reform and development model through provincial ... Five is to deepen reform and innovation to break bottlenecks and endogenous development of effective fire. As an engine of dynamism, adding reform key to adopting reform measures stress energy and break bottlenecks and promoting development. Pay close attention to the key areas of reform. Conscientiously implement the provincial deployment and cancel, adjustment, to undertake the administrative approval items according to Regulation 347 to further improve administrative efficiency continuing deepening reform for poverty alleviation, speeding up rural land right registration certification pilot project, encouraging the orderly transfer of land management, utilize the land resources, in order to promote scale management laid the Foundation. Actively cultivate the market. Firmly establish a market-oriented, nurturing family farms, industrial users, professional cooperation organization new market management main body 456, effectively improve the industry, intensive and marketization of encouraging support social capital into the small micro-credit, urban development, culture and tourism, public services and other areas, easingdevelopment shortfall. To promote mass innovation. To support the rural sector to use new thinking and new ideas, creative work incentives such as actively promoting financial intermediation, bring added 159 in non public enterprises, individually-1540, created a 教师评阅意见： 签名： 年 月 日 实验成绩：

一、题目

OFDM系统的Matlab仿真

二、仿真要求

要求一：OFDM系统的数据传输

①传输的数据随机产生； ②调制方式采用16QAM； ③必须加信道的衰落 ④必须加高斯白噪声 ⑤接收端要对信道进行均衡。

要求二：要求对BER的性能仿真

设计仿真方案，得到在数据传输过程中不同信噪比的BER性能结论，要求得到的BER曲线较为平滑。

三、仿真方案详细设计

1、实验原理

OFDM即正交频分复用技术，实际上OFDM是多载波调制技术的一种，其基本原理是：把高速的数据流通过串并变换，分配到传输速率相对较低的若干个子信道中进行传输，由于每个子信道中的符号周期会相对增加，因此可以减轻由无线信道的多径时延扩展所产生的时间弥散性对系统造成的影响。并且还可以在OFDM符号之间插入保护间隔，令保护间隔大于无线信道的最大时延扩展，这样就可以最大限度地消除由于多径而带来的符号间干扰（ISI）。而且，一般都采用循环前缀作为保护间隔，从而可以避免由多径带来的子载波间干扰（ICI）。

16QAM Pushing ahead, East, North, West development, facilitating shanty, complete xincheng West Road, stability and reconstruction of the street, Star Ding garden built century Garden District, subject public housing construction, heating the gas expansion accelerated implementation, Jing Rui River and bridge style line solid shaft, further expanded the town development. Beautiful country adhere to the advance and typical for a group to lead. According to \cal lay based, and industry increased income, and live upgrade civilization, and culture rich connotation\caught built beautiful village, and whole village advance, and easily relocation, and \hree built\oject near 30 a; depth into ecological, and industry, and culture, and tourism, elements, high standards caught party original city Liu, and jade are Xia AO, model village, in province City set has benchmark. Four is equal benefits to promote sharing, coordinated development of various social undertakings. In the case of rigid spending slowing revenue growth, increase, financial 75% to the people's livelihood, the masses have more access in the sharing. Cuoban something good and benefit. Adhere to the affordable, best, carefully cuoban village oil, water and heat, cultural, city and County columns practical, developments benefit families, bring more welfare to the masses. Development of social convenience. Acceptance of balanced development of compulsory education through the national assessment, the County vocational education center was named \chool of vocational education in China\hird batch of national reform and development model through provincial ... Five is to deepen reform and innovation to break bottlenecks and endogenous development of effective fire. As an engine of dynamism, adding reform key to adopting reform measures stress energy and break bottlenecks and promoting development. Pay close attention to the key areas of reform. Conscientiously implement the provincial deployment and cancel, adjustment, to undertake the administrative approval items according to Regulation 347 to further improve administrative efficiency continuing deepening reform for poverty alleviation, speeding up rural land right registration certification pilot project, encouraging the orderly transfer of land management, utilize the land resources, in order to promote scale management laid the Foundation. Actively cultivate the market. Firmly establish a market-oriented, nurturing family farms, industrial users, professional cooperation organization new market management main body 456, effectively improve the industry, intensive and marketization of encouraging support social capital into the small micro-credit, urban development, culture and tourism, public services and other areas, easingdevelopment shortfall. To promote mass innovation. To support the rural sector to use new thinking and new ideas, creative work incentives such as actively promoting financial intermediation, bring added 159 in non public enterprises, individually-1540, created a发 信源 信宿 串/并 IFFT 加循环前缀CP 并/串 发送滤波器 信道 收 并/串 FFT 去除循环前缀CP 串/并 接收滤波器 1）使用函数randint()产生二进制随机序列进行传输，首先进行串/并变换，将一路高速串行的数据流转化为N路低速并行数据，以增加码元周期，其中N表示子信道的个数，经过基带调制后（这里我们采用16QAM）映射为N个QAM符号。

2）调制后的信号经IFFT（离散反傅里叶）变换，将频域信号转换到时域，输出时域的样点。在实际运用中，信号的产生和解调都是采用数字信号处理的方法来实现的，此时要对信号进行抽样，形成离散时间信号。IDFT可以采用快速反傅立叶变换(IFFT)来实现得到更快的处理速度。

3）在输出的样点前插入循环前缀就形成循环扩展的OFDM信元，加入循环前缀也就是加入保护间隔，由IFFT运算后的每个符号的同相分量和正交分量分别转换为串行数据，并将符号尾部G长度的数据加到头部，构成循环前缀，如果加入空的间隔，在多径传播的影响下，会造成载波干扰ICI，保护间隔的长度G应该大于多径时的扩张的最大值。

4）循环扩展的OFDM信元经并/串变换和脉冲成型（D/A及低通滤波器）输出基带信号，最后经过上变频输出OFDM信号。信道分为多径时延信道和高斯白噪声信道。多径时延信道直射波和延迟波对于标准时间按照固定比率递减，因此多径时延信道参数为比率和最大延迟时间。信道的衰落是二径的瑞利衰落。 5）按要求，利用函数直接加入高斯白噪声，接收端收到的信号是时域信号，经串/并转换后去掉循环前缀CP，如果Cp长度大于信道记忆长度，码间干扰（ISI）仅仅影响CP，而不影响有用数据，去掉CP也就除去了ISI的影响（根据接收到的信号，分别给每个符号的相同分量和正交分量开头的保护间隔去掉。） 然后进行FFT变换并经并串变化就可恢复出信息序列。 6）对信道进行均衡，统计误比特率。

四、仿真结果及结论

结论：根据OFDM的基本原理，利用Matlab编写的系统仿真程序，仿真参数设置为：每信噪比条件

下传输1 000个OFDM符号，共有64个子波，FFT／IFKT点数为64，循环前缀长度为3μs，基带调制模块选择为MPSK或者MQAM方式，多普勒频移为200 Hz，通过小尺度衰落信道模型进行仿真。由仿真所得的误码率曲线图可以看出，在相同信噪比条件下，采用BPSK和QPSK调制方式比采用16QAM和32QAM调制方式的误码率要小，但是当M比较大时，性能不如QAM调制方法的好。每个子信道可采用不同的调制方式，选择时要兼顾数据速率、频谱效率以及传输的可靠性，以频谱利用率和误码率之间的最佳平衡为原则，采用