基于OFDM的认知无线电技术的研究
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摘要
近年来随着无线通信技术的飞速发展,人们对无线通信数据传输速率的要求越来越高。根据香农信息论原理,通信系统对无线频谱资源的需求也相应增长,这导致频谱资源变得越来越紧张,从而成为制约无线通信发展的重大瓶颈。另一方面,已经分配给现有很多无线通信系统的频谱资源却在时间和空间上存在着不同程度的闲置。1999年,Joe Mitola博士提出了认知无线电(Cognitive Radio)这一全新的概念,这种“智能的无线电”结合了认知科学和软件无线电(Software Defined Radio)技术,旨在对空、时、频等各域上的空闲资源(亦称为“频谱空洞”或“白色空间”)进行有效的感知探测和合理的再利用,认知无线电技术也随之成为了当前无线通信研究和开发的新热点。
目前,以正交频分复用(OFDM)为代表的多载波调制(MCM)技术已被多种无线通信系统和标准所采用。非连续载波NC-OFDM技术具有灵活的频率选择和功率控制特性,这些特性使之较其他物理层接入技术更加适合用于认知无线电系统中。与此同时,OFDM多载波关键技术自身的一些缺点也成为了其在认知无线电系统中应用的障碍,必须加以克服。在这些缺点中,除了传统的高频偏敏感性、高峰均信噪比等之外,由于旁瓣能量泄漏而带来的带外辐射干扰问题被公认为是将OFDM技术应用于认知无线电系统中的典型难题。
本论文针对基于OFDM的认知无线电系统中的带外干扰抑制技术展开讨论,旨在寻求合理高效的方案来解决这一技术难题。论文的基本工作概括如下:
1.从建立非连续载波NC-OFDM系统带外辐射干扰的基本数学模型入手,阐述高带外辐射能量在主次用户共存的认知无线电系统中的危害,从而说明了解决该技术难题的紧迫性。
2.将奈奎斯特和非奈奎斯特加窗技术应用在基于NC-OFDM的认知无线电系统中,结合上述的数学模型分析和仿真来衡量有效频带之外的辐射干扰水平的高低。同时,利用凸函数优化理论来求取适用于认知无线电频谱池中的最优参数的二次连续多项式(SOCW)窗函数。
3.采用对有效频带内不同子载波进行功率控制的措施来达到在给定带外辐射水平的情况下,最大化系统容量,即信息传输速率的问题。论文该部分将针对两种不同的干扰模型(两种不同的场景),提出了区别于传统OFDM注水功率分配的优化模型,同时给出低复杂度的启发式算法。同时,将干扰自适应功率控制算法应用于上述提出的加窗OFDM系统,进一步提高了系统容量。
With the great improvements of the wireless communication techniques, much higher data transmitting rates are needed by peoples. Based on Shannon's Information Theory, the resources of the wireless communication are much more required correspondingly. Currently, The scarcity of frequency resources has become one of the biggest obstacles in wireless communication. On the other hand, large amounts of the wireless resources that have been regulated by many wireless Standards are partly idle on the dimensions of time and frequency. In the year 1999, Dr. Joe Mitola proposed the concept of cognitive radio. Connecting the cognitive science with the software defined radio, this type of agile radio could detect the idle resources in the dimensions of time, frequency or space, and reuse them in high efficiency. As a result, cognitive radio techniques have been becoming the new hot points in both the research and the developing fileds in wireless communication.
At present, multicarrier modulation techniques ,such as OFDM, have been adopted by many wireless protocols. Non-Contiguous OFDM(NC-OFDM),with the characteristics of flexible frequency selection and adaptive power loading, is more appropriate for cognitive radio systems as the physical layer access technique. Meanwhile, many shortcomings of OFDM, such as high Carrier frequency offset sensitivity and Peak-to-Average Power Ratio (PAPR), are also some obstacles in OFDM based cognitive radios. Besides, the out-of-band radiation derived from the side-lobe leakage is considered as the one of the biggest difficulties in OFDM based cognitive radios.
This thesis will talk about the out-of-band radiation problem in OFDM based cognitive radio systems, and try to find out some feasible methods to overcome this shortage. The main work includes:
1. Set up the mathematical model of the out-of-band radiation problem in OFDM based cognitive radios, and explain why the larger side-lobes will increase the inference from the secondary users to the primary users.
2. Based on the model proposed afore, the out-of-band radiation power will be evaluated by both theory deduction and computer simulation. Meanwhile, the optimal parameter of the SOCW window in the spectrum pooling system will also be worked out.
3. Perform the adaptive power control method to find out the maximal channel capacity of the OFDM based cognitive radio system under the interference restriction of the primary users. In this part, based on the traditional water-filling power loading theory. We will propose several optimal and sub-optimal algorithms under the two different interference scenarios in spectrum pooling. Whereafter, we combine the optimal SOCW window and the adaptive power control algorithms and demonstrate that these two methods will restrain effectively the out-of-band interference from the secondary users to the primary users in OFDM based cognitive radio systems.
目前,以正交频分复用(OFDM)为代表的多载波调制(MCM)技术已被多种无线通信系统和标准所采用。非连续载波NC-OFDM技术具有灵活的频率选择和功率控制特性,这些特性使之较其他物理层接入技术更加适合用于认知无线电系统中。与此同时,OFDM多载波关键技术自身的一些缺点也成为了其在认知无线电系统中应用的障碍,必须加以克服。在这些缺点中,除了传统的高频偏敏感性、高峰均信噪比等之外,由于旁瓣能量泄漏而带来的带外辐射干扰问题被公认为是将OFDM技术应用于认知无线电系统中的典型难题。
本论文针对基于OFDM的认知无线电系统中的带外干扰抑制技术展开讨论,旨在寻求合理高效的方案来解决这一技术难题。论文的基本工作概括如下:
1.从建立非连续载波NC-OFDM系统带外辐射干扰的基本数学模型入手,阐述高带外辐射能量在主次用户共存的认知无线电系统中的危害,从而说明了解决该技术难题的紧迫性。
2.将奈奎斯特和非奈奎斯特加窗技术应用在基于NC-OFDM的认知无线电系统中,结合上述的数学模型分析和仿真来衡量有效频带之外的辐射干扰水平的高低。同时,利用凸函数优化理论来求取适用于认知无线电频谱池中的最优参数的二次连续多项式(SOCW)窗函数。
3.采用对有效频带内不同子载波进行功率控制的措施来达到在给定带外辐射水平的情况下,最大化系统容量,即信息传输速率的问题。论文该部分将针对两种不同的干扰模型(两种不同的场景),提出了区别于传统OFDM注水功率分配的优化模型,同时给出低复杂度的启发式算法。同时,将干扰自适应功率控制算法应用于上述提出的加窗OFDM系统,进一步提高了系统容量。
With the great improvements of the wireless communication techniques, much higher data transmitting rates are needed by peoples. Based on Shannon's Information Theory, the resources of the wireless communication are much more required correspondingly. Currently, The scarcity of frequency resources has become one of the biggest obstacles in wireless communication. On the other hand, large amounts of the wireless resources that have been regulated by many wireless Standards are partly idle on the dimensions of time and frequency. In the year 1999, Dr. Joe Mitola proposed the concept of cognitive radio. Connecting the cognitive science with the software defined radio, this type of agile radio could detect the idle resources in the dimensions of time, frequency or space, and reuse them in high efficiency. As a result, cognitive radio techniques have been becoming the new hot points in both the research and the developing fileds in wireless communication.
At present, multicarrier modulation techniques ,such as OFDM, have been adopted by many wireless protocols. Non-Contiguous OFDM(NC-OFDM),with the characteristics of flexible frequency selection and adaptive power loading, is more appropriate for cognitive radio systems as the physical layer access technique. Meanwhile, many shortcomings of OFDM, such as high Carrier frequency offset sensitivity and Peak-to-Average Power Ratio (PAPR), are also some obstacles in OFDM based cognitive radios. Besides, the out-of-band radiation derived from the side-lobe leakage is considered as the one of the biggest difficulties in OFDM based cognitive radios.
This thesis will talk about the out-of-band radiation problem in OFDM based cognitive radio systems, and try to find out some feasible methods to overcome this shortage. The main work includes:
1. Set up the mathematical model of the out-of-band radiation problem in OFDM based cognitive radios, and explain why the larger side-lobes will increase the inference from the secondary users to the primary users.
2. Based on the model proposed afore, the out-of-band radiation power will be evaluated by both theory deduction and computer simulation. Meanwhile, the optimal parameter of the SOCW window in the spectrum pooling system will also be worked out.
3. Perform the adaptive power control method to find out the maximal channel capacity of the OFDM based cognitive radio system under the interference restriction of the primary users. In this part, based on the traditional water-filling power loading theory. We will propose several optimal and sub-optimal algorithms under the two different interference scenarios in spectrum pooling. Whereafter, we combine the optimal SOCW window and the adaptive power control algorithms and demonstrate that these two methods will restrain effectively the out-of-band interference from the secondary users to the primary users in OFDM based cognitive radio systems.
引文
[1]Mitola,J.,Ⅲ;"Cognitive radio for flexible mobile multimedia communications",1999 IEEE International Workshop on Mobile Multimedia Communications,pp:3 - 10,15-17 Nov.1999
[2]Mitola,J.,Ⅲ;Maguire,G.Q.,Jr.;"Cognitive radio:making software radios more personal",IEEE Personal Communications,pp:13 - 18,Vol:6,Aug.1999
[3]Svensson,C.;"Software Defined Radio - Vision or Reality",24th Norchip Conference,pp:149- 149,Nov.2006
[4]Haykin,S.;"Cognitive radio:brain-empowered wireless communications",IEEE Journal on Selected Areas in Communications,Vol:23,pp:201 - 220,Feb 2005
[5]Weiss,T.A.;Jondral,F.K.,"Spectrum pooling:an innovative strategy for the enhancement of spectrum efficiency," Communications Magazine,IEEE,Vol42,pp:8-14,March,2004
[6]Muschallik,C.;"Improving an OFDM reception using an adaptive Nyquist windowing",IEEE Transactions on Consumer Electronics,Vo1:42,Aug.1996,pp:259 - 269
[7]Qing Zhao;Sadler,B.M.;"A Survey of Dynamic Spectrum Access",IEEE Signal Processing Magazine,Vol:24,pp:79 - 89,May 2007
[8]ETSI,Radio broadcasting systems:digital audio broadcasting to mobile,portable and fixed receivers,European Telecommunication Standard,ETS 300-401,Feb.1995
[9]ETSI,Digital video broadcasting:framing structure,channel coding and modulation for digital terrestrial television,European Telecommunication Standard,EN 300-744,Aug.1997
[10]Part 11:Wireless LAN Medium Access Control(MAC) and Physical Layer(PHY)Specifications:High-Speed Physical Layer in the 5GHz Band,IEEE Standard 802.11 a-1999
[11]Local and Metroplitan Area Networks-Part 16,Air Interface for Fixed Broadband Wireless Access Systems,IEEE Standard 802.16a
[12]Do-Sik Yoo;Stark,W.E.;"Characterization of WSSUS channels:normalized mean square covariance",IEEE Transactions on Wireless Communications,Vol:4,pp:1575 - 1584,July 2005
[13]陆大絟等,随机过程及其应用,清华大学出版社
[14]W.C.Jakes,Ed.,Microwave Mobile Communications.New York:Wiley,1974
[15]Yunxin Li,Xiaojing Huang,"The Generation of Independent Rayleigh Faders",IEEE ICC'2000,Vol.2,pp:41-45
[16]佟学俭,罗涛,OFDM移动通信技术原理与应用,人民邮电出版社2003
[17]江裕民,OFDM关键技术与应用,机械工业出版社,2006
[18]Rajbanshi,Rakesh;Wyglinski,Alexander M.;Minden,Gary J.;" An Efficient Implementation of NC-OFDM Transceivers for Cognitive Radios",1st International Conference on Cognitive Radio Oriented Wireless Networks and Communications,pp:1 - 5June 2006
[19]Rajbanshi,R.;Wyglinski,A.M.;Minden,G.J.;"Peak-to-Average Power Ratio Analysis for NC-OFDM Transmissions",IEEE 66th Vehicular Technology Conference,2007.pp:1351-1355,Sept.30 2007-Oct.3 2007
[20]Tu,S;Chen,K;Prasad,R;"Spectrum Sensing of OFDMA Systems for Cognitive Radio Networks",IEEE Transactions on Vehicular Technology,Vol:PP,,pp:1-1,Forthcoming,2003
[21]郑君里,信号与系统,人民教育出版社,1981
[22]Liu,C.;Li,F.;"Spectrum modelling of OFDM signals for WLAN",Electronics Letters,IEEE,Vol40,pp:1431-1432,Oct.2004
[23]Sungkeun Cha;Myonghee Park;Sungenn Lee;Keuk-Joon Bang;Daesik Hong;"A new PAPR reduction technique for OFDM systems using advanced peak windowing method"IEEE Transactions on Consumer Electronics,Vol 54,pp:405-410,May.2008
[24]Mauritz,O.;Popovic,B.M.;"Optimum Family of Spectrum-Shaping Functions for PAPR Reduction of DFT-Spread OFDM Signals" IEEE 64th Vehicular Technology Conference.pp:1-5,Sept.2006
[25]Chin-Liang Wang;Yu-Chih Huang;Po-Chung Shen;"An Intercarrier Interference Suppression Technique Using Time-Domain Windowing for OFDM Systems" IEEE 63rd Vehicular Technology Conference,2006.Vol 5,pp:2518 - 2522,May 2006
[26]Maham,B.;Nader-Esfahani,S.;"Joint ICI and Noise Reduction in OFDM Using a New Windowing Scheme",2006.International Conference on Wireless Communications Networking and Mobile Computing,pp:1-4,Sept.2006
[27]Beaulieu,N.C.;Peng Tan;"Receiver windowing for reduction of ICI in OFDM systems with carrier frequency offset",IEEE Global Telecommunications Conference,Volume 5,pp:2680 -2684,Dec.2005
[28]Beaulieu,N.C.;Tan,P.;"Effect of transmitter Nyquist shaping on ICI reduction in OFDM systems with cartier frequency offset",Electronics Letters,Vol:41,pp:746 - 748,June 2005
[29]Weiss,T.;Hillenbrand,J.;Krohn,A.;Jondral,F.K.,"Mutual interference in OFDM-based spectrum pooling systems",2004 IEEE 59th Vehicular Technology Conference,Vol 4,pp:1873-1877,May 2004
[30]Redfern,A.J.;"Receiver window design for multicarrier communication systems",IEEE Journal on Selected Areas in Communications,,Vol 20,pp:1029-1036,June 2002
[31]Muschallik,C;"Improving an OFDM reception using an adaptive Nyquist windowing",IEEE Transactions on Consumer Electronics,Vol 42,pp:259 - 269,Issue 3,Aug.1996
[32]张贤达、保铮,通信信号处理,国防工业出版社,2000
[33]Weiss,T.;Hillenbrand,J.;Krohn,A.;Jondral,F.K.,"Mutual interference in OFDM-based spectrum pooling systems",2004 IEEE 59th Vehicular Technology Conference,Vol 4,pp:1873-1877,May 2004
[34]飞思科技产品研发中心,Matlab7辅助信号处理技术与应用,电子工业出版社,2005
[35]Rongfang Song;Shu-Huang Leung;"A novel OFDM receiver with second order polynomial Nyquist window function" IEEE Communications Letters,Vol 9,pp:391 - 393,May 2005
[36]Cosovic,I.;Brandes,S.;Schnell,M.;"Subcarrier weighting:a method for sidelobe suppression in OFDM systems" IEEE Communications Letters,Vol:10,pp:444- 446,June 2006
[37]Brandes,S.;Cosovic,I.;Schnell,M.;"Reduction of out-of-band radiation in OFDM systems by insertion of cancellation carriers",IEEE Communications Letters,Vol:10,pp:420 -422,June 2006
[38]Pagadarai,S.;Wyglinski,A.M.;Rajbanshi,R.;"A Novel Sidelobe Suppression Technique for OFDM-Based Cognitive Radio Transmission",3rd IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks.,pp:1 - 7,Oct.2008
[39]Farhang-Boroujeny,B.;Kempter,R.;"Multicarrier communication techniques for spectrum sensing and communication in cognitive radios",IEEE Communications Magazine,Vol 46,pp:80 - 85,April 2008
[40]Sigen Ye;Blum,R.S.;Cimini,L.J.;"Adaptive OFDM Systems With Imperfect Channel State Information",IEEE Transactions on Wireless Communications,Vol:5,pp:3255 -3265,November 2006
[41]Peng Wang;Ming Zhao;Limin Xiao;Shidong Zhou;Jing Wang;"Power Allocation in OFDM-Based Cognitive Radio Systems",IEEE Global Telecommunications Conference,.pp:4061 - 4065 Nov.2007
[42]郭梯云,邬国扬,李建东,移动通信,西安电子科技大学出版社2005
[43]S.Boyd and L.Vandenberghe,"Convex Optimization",Cambridge UniversityPress,2004.
[44]Chengshi Zhao;Mingrui Zou;Bin Shen;Kyungsup Kwak;"Power Allocation in OFDM-Based Cognitive Networks with Interference",Third International Conference on Convergence and Hybrid Information Technology,Vol:1,pp:797 - 800,Nov.2008
[45]Bansal,G.;Hossain,M.J.;Bhargava,V.K.;"Adaptive Power Loading for OFDM-Based Cognitive Radio Systems",IEEE International Conference on Communications,pp:5137 -5142,June 2007
[46]Seyedi,A.;"Windowed OFDM for Spectrum Agile Radios" IEEE Global Telecommunications Conference,2006.pp:1 - 5,Nov.27-Dec.1 2006
[47] Farhang-Boroujeny, B.; Kempter, R.;"Multicarrier communication techniques for spectrum sensing and communication in cognitive radios",IEEE Communications Magazine, Vol: 46,pp:80 - 85,April 2008
[48] Borna, B.; Davidson, T.N.; "Efficient filter bank design for filtered multitone modulation"IEEE International Conference on Communications ,pp:38 - 42,Vol: 1,20-24 June 2004
[49] Benvenuto, N.; Tomasin, S.; Tomba, L; "Equalization methods in OFDM and FMT systems for broadband wireless communications",IEEE Transactions on Communications,pp:1413 -1418,Vol:50,Sept.2002
[50] Rajbanshi, R.; Wyglinski, A.M.; Minden, G.J.; "Adaptive-Mode Peak-to-Average Power Ratio Reduction Algorithm for OFDM-Based Cognitive Radi"o, IEEE 64th Vehicular Technology Conference,. pp:l - 5,25-28 Sept, 2006
[51] Cheng, P.; Zhang, Z.; Chen, H.-H.; Qiu, P.;, "Optimal distributed joint frequency, rate and power allocation in cognitive OFDMA systems", IET Communications, Vol:2, pp:815 - 826,July 2008
[52] Dong Li; Xianhua Dai; Han Zhang; "Cross-Layer Scheduling and Power Control in Cognitive Radio Networks", 4th International Conference onWireless Communications Networking and Mobile Computing, pp:1-3 ,Oct. 2008
[2]Mitola,J.,Ⅲ;Maguire,G.Q.,Jr.;"Cognitive radio:making software radios more personal",IEEE Personal Communications,pp:13 - 18,Vol:6,Aug.1999
[3]Svensson,C.;"Software Defined Radio - Vision or Reality",24th Norchip Conference,pp:149- 149,Nov.2006
[4]Haykin,S.;"Cognitive radio:brain-empowered wireless communications",IEEE Journal on Selected Areas in Communications,Vol:23,pp:201 - 220,Feb 2005
[5]Weiss,T.A.;Jondral,F.K.,"Spectrum pooling:an innovative strategy for the enhancement of spectrum efficiency," Communications Magazine,IEEE,Vol42,pp:8-14,March,2004
[6]Muschallik,C.;"Improving an OFDM reception using an adaptive Nyquist windowing",IEEE Transactions on Consumer Electronics,Vo1:42,Aug.1996,pp:259 - 269
[7]Qing Zhao;Sadler,B.M.;"A Survey of Dynamic Spectrum Access",IEEE Signal Processing Magazine,Vol:24,pp:79 - 89,May 2007
[8]ETSI,Radio broadcasting systems:digital audio broadcasting to mobile,portable and fixed receivers,European Telecommunication Standard,ETS 300-401,Feb.1995
[9]ETSI,Digital video broadcasting:framing structure,channel coding and modulation for digital terrestrial television,European Telecommunication Standard,EN 300-744,Aug.1997
[10]Part 11:Wireless LAN Medium Access Control(MAC) and Physical Layer(PHY)Specifications:High-Speed Physical Layer in the 5GHz Band,IEEE Standard 802.11 a-1999
[11]Local and Metroplitan Area Networks-Part 16,Air Interface for Fixed Broadband Wireless Access Systems,IEEE Standard 802.16a
[12]Do-Sik Yoo;Stark,W.E.;"Characterization of WSSUS channels:normalized mean square covariance",IEEE Transactions on Wireless Communications,Vol:4,pp:1575 - 1584,July 2005
[13]陆大絟等,随机过程及其应用,清华大学出版社
[14]W.C.Jakes,Ed.,Microwave Mobile Communications.New York:Wiley,1974
[15]Yunxin Li,Xiaojing Huang,"The Generation of Independent Rayleigh Faders",IEEE ICC'2000,Vol.2,pp:41-45
[16]佟学俭,罗涛,OFDM移动通信技术原理与应用,人民邮电出版社2003
[17]江裕民,OFDM关键技术与应用,机械工业出版社,2006
[18]Rajbanshi,Rakesh;Wyglinski,Alexander M.;Minden,Gary J.;" An Efficient Implementation of NC-OFDM Transceivers for Cognitive Radios",1st International Conference on Cognitive Radio Oriented Wireless Networks and Communications,pp:1 - 5June 2006
[19]Rajbanshi,R.;Wyglinski,A.M.;Minden,G.J.;"Peak-to-Average Power Ratio Analysis for NC-OFDM Transmissions",IEEE 66th Vehicular Technology Conference,2007.pp:1351-1355,Sept.30 2007-Oct.3 2007
[20]Tu,S;Chen,K;Prasad,R;"Spectrum Sensing of OFDMA Systems for Cognitive Radio Networks",IEEE Transactions on Vehicular Technology,Vol:PP,,pp:1-1,Forthcoming,2003
[21]郑君里,信号与系统,人民教育出版社,1981
[22]Liu,C.;Li,F.;"Spectrum modelling of OFDM signals for WLAN",Electronics Letters,IEEE,Vol40,pp:1431-1432,Oct.2004
[23]Sungkeun Cha;Myonghee Park;Sungenn Lee;Keuk-Joon Bang;Daesik Hong;"A new PAPR reduction technique for OFDM systems using advanced peak windowing method"IEEE Transactions on Consumer Electronics,Vol 54,pp:405-410,May.2008
[24]Mauritz,O.;Popovic,B.M.;"Optimum Family of Spectrum-Shaping Functions for PAPR Reduction of DFT-Spread OFDM Signals" IEEE 64th Vehicular Technology Conference.pp:1-5,Sept.2006
[25]Chin-Liang Wang;Yu-Chih Huang;Po-Chung Shen;"An Intercarrier Interference Suppression Technique Using Time-Domain Windowing for OFDM Systems" IEEE 63rd Vehicular Technology Conference,2006.Vol 5,pp:2518 - 2522,May 2006
[26]Maham,B.;Nader-Esfahani,S.;"Joint ICI and Noise Reduction in OFDM Using a New Windowing Scheme",2006.International Conference on Wireless Communications Networking and Mobile Computing,pp:1-4,Sept.2006
[27]Beaulieu,N.C.;Peng Tan;"Receiver windowing for reduction of ICI in OFDM systems with carrier frequency offset",IEEE Global Telecommunications Conference,Volume 5,pp:2680 -2684,Dec.2005
[28]Beaulieu,N.C.;Tan,P.;"Effect of transmitter Nyquist shaping on ICI reduction in OFDM systems with cartier frequency offset",Electronics Letters,Vol:41,pp:746 - 748,June 2005
[29]Weiss,T.;Hillenbrand,J.;Krohn,A.;Jondral,F.K.,"Mutual interference in OFDM-based spectrum pooling systems",2004 IEEE 59th Vehicular Technology Conference,Vol 4,pp:1873-1877,May 2004
[30]Redfern,A.J.;"Receiver window design for multicarrier communication systems",IEEE Journal on Selected Areas in Communications,,Vol 20,pp:1029-1036,June 2002
[31]Muschallik,C;"Improving an OFDM reception using an adaptive Nyquist windowing",IEEE Transactions on Consumer Electronics,Vol 42,pp:259 - 269,Issue 3,Aug.1996
[32]张贤达、保铮,通信信号处理,国防工业出版社,2000
[33]Weiss,T.;Hillenbrand,J.;Krohn,A.;Jondral,F.K.,"Mutual interference in OFDM-based spectrum pooling systems",2004 IEEE 59th Vehicular Technology Conference,Vol 4,pp:1873-1877,May 2004
[34]飞思科技产品研发中心,Matlab7辅助信号处理技术与应用,电子工业出版社,2005
[35]Rongfang Song;Shu-Huang Leung;"A novel OFDM receiver with second order polynomial Nyquist window function" IEEE Communications Letters,Vol 9,pp:391 - 393,May 2005
[36]Cosovic,I.;Brandes,S.;Schnell,M.;"Subcarrier weighting:a method for sidelobe suppression in OFDM systems" IEEE Communications Letters,Vol:10,pp:444- 446,June 2006
[37]Brandes,S.;Cosovic,I.;Schnell,M.;"Reduction of out-of-band radiation in OFDM systems by insertion of cancellation carriers",IEEE Communications Letters,Vol:10,pp:420 -422,June 2006
[38]Pagadarai,S.;Wyglinski,A.M.;Rajbanshi,R.;"A Novel Sidelobe Suppression Technique for OFDM-Based Cognitive Radio Transmission",3rd IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks.,pp:1 - 7,Oct.2008
[39]Farhang-Boroujeny,B.;Kempter,R.;"Multicarrier communication techniques for spectrum sensing and communication in cognitive radios",IEEE Communications Magazine,Vol 46,pp:80 - 85,April 2008
[40]Sigen Ye;Blum,R.S.;Cimini,L.J.;"Adaptive OFDM Systems With Imperfect Channel State Information",IEEE Transactions on Wireless Communications,Vol:5,pp:3255 -3265,November 2006
[41]Peng Wang;Ming Zhao;Limin Xiao;Shidong Zhou;Jing Wang;"Power Allocation in OFDM-Based Cognitive Radio Systems",IEEE Global Telecommunications Conference,.pp:4061 - 4065 Nov.2007
[42]郭梯云,邬国扬,李建东,移动通信,西安电子科技大学出版社2005
[43]S.Boyd and L.Vandenberghe,"Convex Optimization",Cambridge UniversityPress,2004.
[44]Chengshi Zhao;Mingrui Zou;Bin Shen;Kyungsup Kwak;"Power Allocation in OFDM-Based Cognitive Networks with Interference",Third International Conference on Convergence and Hybrid Information Technology,Vol:1,pp:797 - 800,Nov.2008
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