基于OFDM技术的认知无线电研究
摘要
目前,国际上通用的频谱分配政策是固定分配频谱,也就是根据用户是否享有授权将这些有限的频谱资源划分为授权用户使用的频段和非授权用户使用的频段。这些频谱资源的绝大部分是处于需要授权才能使用的频段,如电视广播频段。而那些不需要授权的频段是相当之少,况且许多新兴的无线通信技术大多使用非授权频段。目前基于固定频谱分配的频谱资源利用率是很低的。这就造成了频谱资源的有限性与频谱资源利用率的低效性之间的矛盾,因此迫切需要一种无线通信新技术缓解这一状况。认知无线电技术就应运而生。
正交频分复用技术拥有灵活控制频谱的能力,这就为认知无线电系统提供了一个良好的频谱管理平台。OFDM技术实现的基本原理就是：发送端将高速串行数据流转换为并行低速数据流,这些低速的并行数据经过IFFT变换实现OFDM调制,而后经串并转换后,再通过高频载波调制,通过天线发射；接收端将接受到的解调后信号,经串并转换,FFT变换,并串转换后实现OFDM解调。由于OFDM技术可以灵活地进行频率选择,方便地实现频谱资源管理,因此它就必然成为认知无线电的首选技术。
本论文就一种采用了OFDM技术来控制频谱算法的认知无线电系统进行Matlab仿真,仿真结果显示该种算法OFDM数据符号的频谱能量可以进一步衰减。在那些授权用户正在使用的频段和频点,利用OFDM技术灵活控制频谱的特点,通过关闭相关频段或者频点OFDM数据符号的子载波来消除对授权用户的干扰。为了进一步减低对授权用户的干扰,该算法就是对OFDM数据符号傅里叶变换后的数学关系式,针对授权用户使用的频段,通过求取子载波数据符号在频带内的频谱能量和其子载波数据符号之间的函数关系,通过对其求导,得出了频谱的极值。最后还在QuartusⅡ8.0的FPGA开发软件上搭建了OFDM调制解调系统,并详细地介绍了组成OFDM调制解调系统的FPGA实现的各个子模块的功能和端口信号说明,测试模块的FPGA实现和整个OFDM调制解调系统FPGA实现的仿真结果。
Currently, the internationally accepted policy is a fixed allocation of spectrum, which is based on whether the user is entitled to authorize the limited spectrum resource is divided into frequency bands used by authorized users and unauthorized users of the band. Most of these spectrum resources are need authorization, such as the television broadcast band. And those who do not need the authorization of the band is quite little, and many of the emerging wireless communications technology is mostly used non-licensed bands. The current spectrum allocation of spectrum based on fixed resource utilization is very low. This has resulted in the conflict between the limited spectrum resources and the inefficient utilization of spectrum resources, there is an urgent need for a wireless communication technology to alleviate this situation. Cognitive radio technology came into being.
OFDM has the ability to flexibly control the spectrum, which provides a good spectrum management platform for cognitive radio system. The basic principle of OFDM technology is:the sending high-speed serial data stream into parallel low-speed data streams, these low-speed parallel data through the IFFT transform OFDM modulation; receiver will receive the demodulated signal, and converted by the string, FFT transform, and the converted string to achieve OFDM demodulation. OFDM technology have the flexibility to choose the frequency to facilitate the realization of the spectrum resource management, so it is bound to become the first choice of cognitive radio technology.
This paper uses OFDM technology for a spectral algorithm to control the cognitive radio system, Matlab simulation results show that the algorithms the energy spectrum of OFDM data symbols can be further attenuated. Authorized users are using those frequency bands and frequencies, the use of OFDM technology features flexible control of the spectrum, by closing the relevant frequency band or sub-carrier OFDM data symbol to eliminate interference to authorized users. To further reduce the interference to authorized users, the algorithm is the Fourier transform of the OFDM data symbol after the mathematical relationship, for authorized users to use the band to strike a sub-carrier data symbols through the band of spectrum in the energy and its sub-carrier the functional relationship between the data symbols, through its derivative spectrum obtained extreme. Finally, the FPGA also QuartusⅡ8.0 software development built on the OFDM modulation and demodulation system, and detailed description of OFDM modulation and demodulation system composed of FPGA implementation of the function of each module and the port signal shows the FPGA implementation and test module the OFDM modulation and demodulation system FPGA implementation of the simulation results.
正交频分复用技术拥有灵活控制频谱的能力,这就为认知无线电系统提供了一个良好的频谱管理平台。OFDM技术实现的基本原理就是：发送端将高速串行数据流转换为并行低速数据流,这些低速的并行数据经过IFFT变换实现OFDM调制,而后经串并转换后,再通过高频载波调制,通过天线发射；接收端将接受到的解调后信号,经串并转换,FFT变换,并串转换后实现OFDM解调。由于OFDM技术可以灵活地进行频率选择,方便地实现频谱资源管理,因此它就必然成为认知无线电的首选技术。
本论文就一种采用了OFDM技术来控制频谱算法的认知无线电系统进行Matlab仿真,仿真结果显示该种算法OFDM数据符号的频谱能量可以进一步衰减。在那些授权用户正在使用的频段和频点,利用OFDM技术灵活控制频谱的特点,通过关闭相关频段或者频点OFDM数据符号的子载波来消除对授权用户的干扰。为了进一步减低对授权用户的干扰,该算法就是对OFDM数据符号傅里叶变换后的数学关系式,针对授权用户使用的频段,通过求取子载波数据符号在频带内的频谱能量和其子载波数据符号之间的函数关系,通过对其求导,得出了频谱的极值。最后还在QuartusⅡ8.0的FPGA开发软件上搭建了OFDM调制解调系统,并详细地介绍了组成OFDM调制解调系统的FPGA实现的各个子模块的功能和端口信号说明,测试模块的FPGA实现和整个OFDM调制解调系统FPGA实现的仿真结果。
Currently, the internationally accepted policy is a fixed allocation of spectrum, which is based on whether the user is entitled to authorize the limited spectrum resource is divided into frequency bands used by authorized users and unauthorized users of the band. Most of these spectrum resources are need authorization, such as the television broadcast band. And those who do not need the authorization of the band is quite little, and many of the emerging wireless communications technology is mostly used non-licensed bands. The current spectrum allocation of spectrum based on fixed resource utilization is very low. This has resulted in the conflict between the limited spectrum resources and the inefficient utilization of spectrum resources, there is an urgent need for a wireless communication technology to alleviate this situation. Cognitive radio technology came into being.
OFDM has the ability to flexibly control the spectrum, which provides a good spectrum management platform for cognitive radio system. The basic principle of OFDM technology is:the sending high-speed serial data stream into parallel low-speed data streams, these low-speed parallel data through the IFFT transform OFDM modulation; receiver will receive the demodulated signal, and converted by the string, FFT transform, and the converted string to achieve OFDM demodulation. OFDM technology have the flexibility to choose the frequency to facilitate the realization of the spectrum resource management, so it is bound to become the first choice of cognitive radio technology.
This paper uses OFDM technology for a spectral algorithm to control the cognitive radio system, Matlab simulation results show that the algorithms the energy spectrum of OFDM data symbols can be further attenuated. Authorized users are using those frequency bands and frequencies, the use of OFDM technology features flexible control of the spectrum, by closing the relevant frequency band or sub-carrier OFDM data symbol to eliminate interference to authorized users. To further reduce the interference to authorized users, the algorithm is the Fourier transform of the OFDM data symbol after the mathematical relationship, for authorized users to use the band to strike a sub-carrier data symbols through the band of spectrum in the energy and its sub-carrier the functional relationship between the data symbols, through its derivative spectrum obtained extreme. Finally, the FPGA also QuartusⅡ8.0 software development built on the OFDM modulation and demodulation system, and detailed description of OFDM modulation and demodulation system composed of FPGA implementation of the function of each module and the port signal shows the FPGA implementation and test module the OFDM modulation and demodulation system FPGA implementation of the simulation results.
引文
[1]尹长川,罗涛,乐光新.多载波宽带无线通信技术.北京：北京邮电大学出版社,2004
[2]张强.认知无线电网络中频谱探测的研究：[硕士学位论文].南京：南京邮电大学,2007
[3]王金龙.认知无线电专题讲座：认知无线电,2007
[4]罗凡.基于认知无线电频谱感知技术的研究：[硕士学位论文].成都：成都理工大学,2009
[5]陈文峰.认知无线电自适应调制技术：[硕士学位论文].大连：大连海事大学,2009
[6]邓丽粼.认知无线电中的频谱感知技术研究：[硕士学位论文].成都：西南交通大学,2010
[7]李丹.认知无线电网络随机路由研究：[硕士学位论文].北京：北京科技大学,2009
[8]徐伟伟.认知无线电网络中的频谱检测技术研究：[硕士学位论文].南京：南京邮电大学,2010
[9]赵铁军.OFDM信道估计及自适应资源分配算法研究：[硕士学位论文].重庆：重庆大学,2007
[10]苗英蕊.OFDM系统增强型信道估计技术算法研究：[硕士学位论文].西安：西安电子科技大学,2010
[11]韩诚.OFDM系统帧同步算法的研究：[硕士学位论文].哈尔滨：哈尔滨工程大学,2008
[12]赤伟.认知无线电学习决策方法研究：[硕士学位论文].重庆：重庆大学,2010
[13]王俭.认知无线电中基于博弈论的功率控制算法：[硕士学位论文].哈尔滨：哈尔滨工业大学,2009
[14]白敏丹.基于认知无线电的无线通信研究现状.通信技术,2010
[15]张强.认知无线电网络中频谱探测的研究：[硕士学位论文].南京：南京邮电大学,2007
[16]李红宁.认知无线电安全性研究：[硕士学位论文].西安：西安电子科技大 学,2010
[17]伍坚.基于数字中频技术的OFDM收发信机研究与实现：[硕士学位论文].北京：北京交通大学,2006
[18]何卫东.MIMO-OFDM系统中自适应功率和比特分配算法的研究：[硕士学位论文].苏州：苏州大学,2010
[19]朱晓明.超宽带通信系统中信道估计方法的研究：[硕士学位论文].哈尔滨：哈尔滨工程大学,2008
[20]佟学俭.正交频分复用通信系统若干关键技术的研究.北京：北京邮电大学出版社,2001
[21]周贤伟,王建萍,王春江.认知无线电.北京：国防工业出版社,2008
[22]张平,冯志勇.认知无线网络.北京：科学出版社,2010
[23]Kwang-Cheng Chen(中国),Ramjee Prasad(丹麦)著,许方敏,李虎生译.认知无线网络.北京：机械工业出版社,2010
[24]王庭昌.软件无线电技术的回顾与展望.[J].现代军事通信,2007：54-59
[25]王立宁,乐光新,詹菲. MATLAB与通信仿真.北京：人民邮电出版社,2000
[26]程佩清.数字信号处理教程.北京：清华大学出版社,1995
[27]吴兵伟,李争平,牛长流.OFDM调制解调算法分析.北京：第十四届全国青年通信学术会议论文集,2009.769 773
[28]Zhigang Xu, Cheng Yang, Mingyan Kou, Zheng Zhou. The relationships among data symbols satisfied for sidelobe suppression in MB-OFDM cognitive radios.
[2]张强.认知无线电网络中频谱探测的研究：[硕士学位论文].南京：南京邮电大学,2007
[3]王金龙.认知无线电专题讲座：认知无线电,2007
[4]罗凡.基于认知无线电频谱感知技术的研究：[硕士学位论文].成都：成都理工大学,2009
[5]陈文峰.认知无线电自适应调制技术：[硕士学位论文].大连：大连海事大学,2009
[6]邓丽粼.认知无线电中的频谱感知技术研究：[硕士学位论文].成都：西南交通大学,2010
[7]李丹.认知无线电网络随机路由研究：[硕士学位论文].北京：北京科技大学,2009
[8]徐伟伟.认知无线电网络中的频谱检测技术研究：[硕士学位论文].南京：南京邮电大学,2010
[9]赵铁军.OFDM信道估计及自适应资源分配算法研究：[硕士学位论文].重庆：重庆大学,2007
[10]苗英蕊.OFDM系统增强型信道估计技术算法研究：[硕士学位论文].西安：西安电子科技大学,2010
[11]韩诚.OFDM系统帧同步算法的研究：[硕士学位论文].哈尔滨：哈尔滨工程大学,2008
[12]赤伟.认知无线电学习决策方法研究：[硕士学位论文].重庆：重庆大学,2010
[13]王俭.认知无线电中基于博弈论的功率控制算法：[硕士学位论文].哈尔滨：哈尔滨工业大学,2009
[14]白敏丹.基于认知无线电的无线通信研究现状.通信技术,2010
[15]张强.认知无线电网络中频谱探测的研究：[硕士学位论文].南京：南京邮电大学,2007
[16]李红宁.认知无线电安全性研究：[硕士学位论文].西安：西安电子科技大 学,2010
[17]伍坚.基于数字中频技术的OFDM收发信机研究与实现：[硕士学位论文].北京：北京交通大学,2006
[18]何卫东.MIMO-OFDM系统中自适应功率和比特分配算法的研究：[硕士学位论文].苏州：苏州大学,2010
[19]朱晓明.超宽带通信系统中信道估计方法的研究：[硕士学位论文].哈尔滨：哈尔滨工程大学,2008
[20]佟学俭.正交频分复用通信系统若干关键技术的研究.北京：北京邮电大学出版社,2001
[21]周贤伟,王建萍,王春江.认知无线电.北京：国防工业出版社,2008
[22]张平,冯志勇.认知无线网络.北京：科学出版社,2010
[23]Kwang-Cheng Chen(中国),Ramjee Prasad(丹麦)著,许方敏,李虎生译.认知无线网络.北京：机械工业出版社,2010
[24]王庭昌.软件无线电技术的回顾与展望.[J].现代军事通信,2007：54-59
[25]王立宁,乐光新,詹菲. MATLAB与通信仿真.北京：人民邮电出版社,2000
[26]程佩清.数字信号处理教程.北京：清华大学出版社,1995
[27]吴兵伟,李争平,牛长流.OFDM调制解调算法分析.北京：第十四届全国青年通信学术会议论文集,2009.769 773
[28]Zhigang Xu, Cheng Yang, Mingyan Kou, Zheng Zhou. The relationships among data symbols satisfied for sidelobe suppression in MB-OFDM cognitive radios.