Channel equalization for multiuser chaotic communications systems
高并发限流参数
高并发限流参数
在处理高并发场景时，为了防止系统因过多请求而崩溃，常常需要设置限流参数。
以下是一些常见的限流参数：
1. QPS（Queries Per Second）限制：限制单位时间内服务的请求数量。
例如，可以设置为每秒最多处理100个请求。
2. 并发连接数限制：限制同时连接服务的客户端数量。
例如，可以设置为最大并发连接数为100。
3. 令牌桶算法：通过令牌桶算法控制请求的速率。
令牌桶中包含一定数量的令牌，每个令牌代表一个请求。
令牌以固定的速率添加到桶中，当有新的请求到达时，会尝试从桶中获取一个令牌。
如果桶中没有令牌，则拒绝或限制请求的速率。
4. 滑动窗口算法：通过记录请求的时间戳和计数器来控制请求的速率。
当计数器达到一定阈值时，会拒绝或限制请求的速率。
5. 漏桶算法：与令牌桶算法类似，漏桶算法也有一个固定水位的桶来存储请求。
但是，与令牌桶算法不同的是，漏桶算法会按照一定的速率均匀地处理请求，而不管桶中的请求数量。
这些参数通常需要根据实际情况进行调整和配置，以达到最佳的性能和可靠性。
利用过采样技术提高ADC测量微弱信号时的分辨率
利用过采样技术提高ADC 测量微弱信号时的分辨率 1. 引言 随着科学技术的发展，人们对宏观和微观世界逐步了解，越来越多领域（物理学、化学、天文学、军事雷达、地震学、生物医学等）的微弱信号需要被检测，例如：弱磁、弱光、微震动、小位移、心电、脑电等[1～3]。
测控技术发展到现在，微弱信号检测技术已经相对成熟，基本上采用以下两种方法来实现：一种是先将信号放大滤波，再用低或中分辨率的ADC 进行采样，转化为数字信号后，再做信号处理，另一种是使用高分辨率ADC ，对微弱信号直接采样，再进行数字信号处理。
两种方法各有千秋，也都有自己的缺点。
前一种方法，ADC 要求不高，特别是现在大部分微处理器都集成有低或中分辨率的ADC ，大大节省了开支，但是增加了繁琐的模拟电路。
后一种方法省去了模拟电路，但是对ADC 性能要求高，虽然∑-△ADC 发展很快，已经可以做到24位分辨率，价格也相对低廉，但是它是用速度和芯片面积换取的高精度[4]，导致采样率做不高，特别是用于多通道采样时，由于建立时间长，采样率还会显著降低，因此，它一般用于低频信号的单通道测量，满足大多数的应用场合。
而本文提出的方案，可以绕过上述两种方法的缺点，利用两者的优点实现微弱信号的高精度测量。
过采样技术是提高测控系统分辨率的常用方法，已经被广泛应用于各个领域。
例如，过采样成功抑制了多用户CDMA 系统中相互正交用户码接收机(A Mutually Orthogonal Usercode-Receiver ，AMOUR )的噪声[5～6],提高了光流估计（optical flow estimation ，OFE ）的精度[7]，改善了正交频分复用（OFDM ）信号的峰-均比[8]等。
但是，这些过采样技术应用的前提是采样前的信号幅值能与ADC 的输入范围相当。
而用ADC 采集微弱信号时，直接使用过采样技术提高不了精度，而且由于信号幅值远小于ADC 的输入范围，它的有效位数还会减小，使精度随之下降。
OFDM系统中基于MMSE-DFE的干扰消除算法
OFDM系统中基于MMSE-DFE的干扰消除算法茅红伟;董淑冷;朱品昌;倪继锋【摘要】OFDM系统中,为去除码元间干扰(ISI)和载波间干扰(ICI)的影响,必须加足够长度的循环前缀(CP),导致带宽效率降低.建立了OFDM系统模型并对ISI和ICI 进行了分析,在此基础上提出了一种基于最小均方误差(MSE)准则的判决反馈均衡(DFE)算法,可有效消除ISI和ICI的影响.分析和仿真结果表明:所提出的算法无论在带宽效率还是在误码率方面都要优于传统的OFDM系统.【期刊名称】《上海师范大学学报（自然科学版）》【年(卷),期】2008(037)003【总页数】5页(P270-274)【关键词】OFDM;判决反馈均衡器;串行干扰消除【作者】茅红伟;董淑冷;朱品昌;倪继锋【作者单位】上海师范大学机械与电子工程学院,上海,200234;上海师范大学机械与电子工程学院,上海,200234;上海师范大学机械与电子工程学院,上海,200234;上海师范大学机械与电子工程学院,上海,200234【正文语种】中文【中图分类】TN914.31 系统模型及干扰分析在OFDM系统的发送端，串行数据序列先映射成QAM数据流，经串/并变换后形成数据块：s(k) = ，其中N表示DFT的长度，sk,i 表示第k个码元、第i个子信道上调制的信号.采用IDFT作为多载波调制的快速实现方式，把频域信号转换成离散时域信号：x(k) = .再将x(k)的最后m个数据复制到其前端作为循环前缀(CP)，与x(k)一起构成OFDM码元.OFDM码元通过多径衰落信道进行传输，并受到加性高斯白噪声(AWGN)的干扰.用h = 来表示信道冲激响应, L是信道冲激响应的长度.用v(k)表示引入的加性高斯白噪声.做如下假设：信号和噪声序列相互独立，信号x(k)是均值为0的高斯过程，其方差归一化为1；噪声序列v(k)方差为σ2，则σ2 = 1 / SNR.接收端在收到数据后，将循环前缀的m个数据去除，后N个数据用r(k) = 表示.r(k)经DFT运算后得到其输出u(k) = .如果假设 N>>L, 这也是与实际情况相符合的, 则对当前码元产生的ISI可以看作只是来自于前一码元.将信道冲激响应表示为矩阵的形式，经推导存在如下关系[2]：r(k) = (H0 -H1 )x(k) + H2x(k-1) +v(k)，(1)其中：(2)用Q表示 DFT矩阵，则Q*为IDFT矩阵，其中 * 为共轭转置，则：x(k) =Q*s(k)， u(k) =Qr(k).(3)对具有循环前缀的OFDM系统来说, 当循环前缀的长度大于信道冲激响应长度时,H1和H2都为0，利用式(1)和(3)可知 :u(k) =QH0Q*s(k) + v(k),(4)其中v(k) 是噪声 v(k)的傅立叶变换.因 H0为循环矩阵, 则Λ =QH0 Q* 是一个N× N 对角矩阵.u(k) =Λ s(k) +v(k).(5)式(5) 表明：OFDM 系统中的均衡处理只需要为每一个子载波加一个单一的复数增益来实现信道补偿，这常常称为单一抽头的频域均衡器.对具有足够长度CP的OFDM系统来说，均衡可以非常简单地实现.但这一简单性是以系统带宽的浪费为代价，此时系统带宽效率为：对时延比较大的信道来说，需要加大循环前缀来保证H1和H2为0，从而导致带宽效率大大降低.为了提高频带利用率，考虑没有循环前缀的OFDM系统. 在这种情况下，H1和H2都不为0，这时接收到的信号受到ICI和 ISI 的干扰.经FFT解调后，接收到的信号可表示为[2]：u(k) =QH0 x(k) -QH1x(k) +QH2x(k-1) +v(k) =Λ s(k) -QH1Q×s(k) +QH2Q*s(k-1) + v(k).(6)式(6)中右边的第二和第三部分分别为产生的ICI和ISI,最后一部分为噪声产生的影响.2 MMSE判决反馈检测算法通过上面的分析，对于没有循环前缀的OFDM系统来说，ISI和ICI 将同时发生. 在这一部分里，提出一种多载波的检测算法来消除ISI和ICI的影响.公式(1)可以写为：r(k) = (H0 -H1 )x(k) + H2x(k-1) +v(k) =(H0 -H1 )Q*s(k) +H2Q*s(k-1) +v(k) =P0s(k) +P1s(k-1) +v(k) ,(7)其中：P0 = (H0 -H1 )Q* ， P1 =H1Q*.(8)基于公式(7), 可以先消除来自前一码元的码间串扰，接下来对由当前码元产生的ICI进行补偿.假设前一码元的判决是正确的，则从接收信号中减去其反馈可以得到无码元间干扰的信号：(9)从(9)可以看出，来自于前一码元的ISI从r(k)中得以消除，但y(k)中仍然含有ICI 和噪声的成分.线性MMSE均衡方法同时检测出所有子载波上的数据，但它只能在消除ICI和噪声之间做一权衡.本研究中提出了一种非线性的基于判决反馈的多载波的检测方法，这种方法类似于DS-CDMA系统中多用户检测中常用的方法：串行干扰消除法(SIC).不同于同时检测出所有子载波上的数据，所提出的方法对数据进行逐一检测，已经判决得到的数据作为反馈从原来信号中减掉，从而减小对接下来要检测信号的干扰.串行检测算法通过判决反馈均衡器(DFE)来实现[3].图 1 DFE结构框图用W来表示前向滤波器，用B来表示反馈滤波器.通过图1可以得到：z(i) =Wy(i) =WP0s(i) +Wv(i),(10)(11)(12)这里Q(·)为判决器.假设判决的顺序为从子载波N-1到子载波0.对于第i个OFDM码元来说，其检测的过程为：第N-1个子载波上的数据首先被检测出，其检测值通过B的最后一列进行加权，然后从z(i)中减去，这样第N-1个子载波对其他子载波所产生的ICI可以去除.接下来对N-2个子载波上的数据进行检测，其检测值通过B的倒数第二列进行加权后从z(i)中减去.这一过程持续至所有子载波上的数据都被检测出[4,5].通过以上对检测过程的分析，可以推出：假设检测的顺序为从子载波N-1到子载波0，则反馈矩阵B应该具有上三角矩阵的结构，这样才能保证串行干扰消除法的实现.在假设前一码元的判决是正确的前提下，得到误差函数：(13)目标是基于MMSE准则来得到前向滤波器矩阵W 和后向反馈矩阵B，也就是说，选择合适的W 和B来最小化均方误差值首先假设B已知的前提下来获得使最小的矩阵W.根据正交准则，误差函数e(i)应与y(i)正交，即[6]：Ee(i)yH(i) =0N× N ⟹WEy(i)yH(i) = (B +IN× N )E s(i)yH(i) .(14)根据式(9)及加性噪声和发送数据序列相互独立的假设，可以得到：(15)(16)把式(5)和 (6)代入式(14),可以得到:(17)通过式(13)和式(17), e(i)可以写为：e(i) = (B +IN× N )φ (i),(18)其中：(19)定义[6]：(20)通过矩阵求逆公式:(A -CB-1D)-1 =A-1 +A-1C(B -DA-1C)-1DA-1.(21)式(20)可以表示为：(22)e(i)的方差可写为[6]：(23)因求e(i)的最小均方误差问题等同于：在B +IN× N 为上三角矩阵且其对角元素为单位值的约束条件下，求取trRee 的最小值.对进行Cholesky分解[6]：(24)U为上三角矩阵且其对角元素为单位值.令：B =U -IN× N ,(25)则 Ree =D-1.因 D 为对角阵，此时具有最小值.通过式 (26)，得到了最佳反馈矩阵B.把B代入式 (17),可得到前向滤波器系数W.3 仿真与结果分析在802.11a的环境中对所提出的方法进行仿真. 所用的调制方式为16-QAM，每个OFDM符号包括64个子载波，其中的52个用于数据传输.系统占用5GHz频带中的20 MHz 的带宽，因此子载波间的频带间隔为0.315MHz. IFFT/FFT 周期为3.2 μs.假设信道已知，总共 5000个 OFDM符号用来仿真.仿真中采用了SUI (Stanford University Interim) -1 信道模型[7]. SUI信道模型已被IEEE 802.16a 小组采用为 2-11G 频段中宽带无线传输的信道. SUI信道根据不同的应用环境分为6种，在此选用了SUI-1, 这一信道模型包含3个抽头,每个抽头为独立的瑞利衰落. 图 2 误码率性能比较在上述环境中对所提出方法做了性能仿真，并与具有足够长度CP的OFDM系统及采用线性MMSE均衡的OFDM系统进行了比较.图2 给出了三者在不同的信噪比情况下所达到的误码率的比较.由仿真结果可以看出：与其他两种方法相比，本研究提出的基于MMSE-DFE的串行干扰消除算法可以达到更低的误码率.其原因为：基于MMSE-DFE的串行干扰消除算法每次检测出具有最大SINR的子载波上的信号后将其减掉，这样就去除了其对其他子载波的干扰，提高了信号检测的可靠性.同时，因为这一方法可以去除循环前缀，因此可大大提高系统频带利用率.4 结论本研究提出了OFDM系统中一种干扰消除算法，可在无循环前缀的条件下有效地消除因多径信道而引起的ISI和ICI.这种算法在去除ISI后，借鉴DS-CDMA中常用的多用户检测的算法——串行干扰消除算法，基于MMSE-DFE来消除ICI.经推导，MMSE-DFE的系数可通过矩阵的Cholesky分解来获得.仿真结果表明：提出的基于MMSE-DFE的串行干扰消除法, 无论在系统的频带利用率还是在系统所获得的误码率方面都要优于常规OFDM及采用线性MMSE均衡的OFDM系统.参考文献:[1] NEE R V, PRASAD R. OFDM for wireless multimedia communications[M]. London: Artech House, 2000.[2] ZHU J, SER W, NEHORAI A. Channel equalization for DMT with insufficient cyclic prefix [C]. Thirty-Fourth Asilomar Conference on Signals, Systems and Computers. Pacific Grove, USA, 2000： 951-955.[3] VERDU S. Multiuser detection [M]. Cambridge, U.K: Cambridge University Press,1998.[4] DEBBAH M, MUQUET B. A MMSE successive interference cancellation scheme for a new adjustable hybrid spread OFDM system[C]. IEEE VTC 2000 , Tokyo, 2000: 745-749.[5] YANG-SEOK C, VOLTZ P J, CASSARA F A. On channel estimation and detection for multicarrier signals in fast and selective Rayleigh fadingchannels[J]. IEEE Trans on Commun, 2001, 49: 1375 -1387.[6] STAMOULIS A, GIANNAKIS G B, SCAGLIONE A. Block FIR Decision-Feedback Equalizers for Filterbank Precoded Transmissions with Blind Channel Estimation Capabilities[J]. IEEE Trans. Comm, 2001, 49(1): 69-83.[7] HARI S. Channel models for fixed wireless applications. IEEE 802.16a standards document [S]. 2001.。
博士英文简历Resume
Zukang ShenHome Address: Work: 214-480-3198 707 Kindred Lane Cell: 512-619-7927 Richardson, TX 75080 Email: zukang.shen@ Education: The University of Texas, Austin, TX, USA Jun. 2003 – May 2006Ph.D., Electrical Engineering.Dissertation Title: “Multiuser Resource Allocation in Multichannel Wireless CommunicationSystems,” Co-advised by Prof. Brian L. Evans and Prof. Jeffrey G. AndrewsThe University of Texas, Austin, TX, USA Aug. 2001 – May 2003Master of Science, Electrical Engineering.Tsinghua University, Beijing, China. Aug. 1997 – Jun. 2001Major: Bachelor of Science, Electronics Engineering,EnglishMinor:Academic Work Experience:Sep. 2004 – Jan. 2006: Graduate Research Assistant, Dept. of ECE, UT-Austin, Austin, TX.I am conducting research in the area of downlink multiuser MIMO channel capacity withapplications to Wireless LAN and Fixed Wireless Systems.Sep. 2003 – Dec. 2003: Teaching Assistant, Dept. of ECE, UT-Austin, Austin, TX.Advanced Wireless: Modulation and Multiple Access, in which I delivered two lectures onequalization and multiuser OFDM, respectively. Other duties included office hours, homeworkgrading, and course website maintenance.Jun. 2003 – Aug. 2003: Graduate Research Assistant, Dept. of ECE, UT-Austin, Austin, TX.I did research in the area of resource allocation in multiuser OFDM systems, which led to twoconference papers and one journal paper.Jun. 2002 – Aug. 2002: Graduate Research Assistant, Dept. of ECE, UT-Austin, Austin, TX.I researched the area of equalization techniques for channel shortening in xDSL systems, andcontributed to the software “UT Austin Multicarrier Equalizer Design Toolbox for Matlab”.Sep. 2001 – May 2003: Teaching Assistant,Dept. of ECE, UT-Austin, Austin, TX.Real-time Digital Signal Processing Laboratory, in which students designed, implemented, andtested a voiceband data modem. Students implemented the modem on TI TMS320C30 (2001-2002) and TMS320C6701 (2002-2003) digital signal processors by programming in C andassembly using Code Composer.Industrial Work Experience:•Feb. 2006 – present: System Engineering, Wireless Infrastructure Group, Texas Instruments, Dallas, TX.I have been with Texas Instruments full-time since Feb. 2006.•May 2005 – Aug. 2005: Summer Co-op, Wireless Infrastructure Group, Texas Instruments, Dallas, TX.I worked on a system level simulator for 3GPP HSUPA, and compared different schedulingalgorithms (proportional fairness, round-robin, etc) in terms of system throughput, fairness,and link reliability.•Jan. 2004 – Aug. 2004: Co-op/Intern,NCSD Baseband Systems and Software Group, Motorola/Freescale Inc. Austin, TX.I participated in a 3GPP TDD (TD-SCDMA) project, and developed a symbol rateprocessing library on the MSC8201ADS board.Current Research Interests:•Multicarrier communication systems•Resource allocation in multiuser OFDM systems.•Multi-antenna wireless systems•Adaptive modulation•Equalization in OFDM/xDSL systemsPublications:Refereed Journal Articles:•Z. Shen, R. Chen, J. G. Andrews, R. W. Heath, Jr., and B. L. Evans, “Sum Capacity of Multiuser MIMO Broadcast Channels with Block Diagonalization,” submitted to IEEETransactions on Wireless Communications, Oct. 2005, under revision.•Z. Shen, J. G. Andrews, and B. L. Evans, “Sum Capacity of MIMO Gaussian Broadcast Channels with Channel Frobenius Norm Constraints,” to appear in IEEE CommunicationsLetters, 2006.•Z. Shen, R. W. Heath, Jr., J. G. Andrews, and B. L. Evans, “Space-Time Water-filling for Composite MIMO Fading Channels,” to appear in EURASIP Journal on WirelessCommunications and Networking, special issue on Radio Resource Management in 3G+Systems, 2006.•Z. Shen, R. Chen, J. G. Andrews, R. W. Heath, Jr., and B. L. Evans, “Low Complexity User Selection Algorithms for Multiuser MIMO Systems with Block Diagonalization,” toappear in IEEE Transactions on Signal Processing, 2006.•Z. Shen, J. G. Andrews, and B. L. Evans, “Adaptive Resource Allocation in Multiuser OFDM Systems with Proportional Rate Constraints,” IEEE Transactions on WirelessCommunications, vol. 4, no. 6, pp. 2726 – 2737, Nov. 2005.Refereed Conference Papers:•Z. Shen, R. Chen, J. G. Andrews, R. W. Heath, Jr., and B. L. Evans, “Sum Capacity of Multiuser MIMO Broadcast Channels with Block Diagonalization,” submitted to IEEE Int.Symposium on Information Theory, July 9-14, 2006, Seattle, WA, USA.•Z. Shen, J. G. Andrews, and B. L. Evans, “Upper Bounds on MIMO Channel Capacity with Channel Frobenius Norm Constraints,” in Proc. IEEE Int. Global CommunicationsConf., vol. 3, pp. 1505 – 1509, Nov. 28-Dec. 2, 2005, St. Louis, MO, USA.•Z. Shen, R. Chen, J. G. Andrews, R. W. Heath, Jr., and B. L. Evans, “Low Complexity User Selection Algorithms for Multiuser MIMO Systems with Block Diagonalization,” inProc. IEEE Asilomar Conf. on Signals, Systems, and Computers, pp. 628 – 632, Oct. 30-Nov. 2, 2005, Pacific Grove, CA, USA.•Z. Shen, R. W. Heath, Jr., J. G. Andrews, and B. L. Evans, “Comparison of Space-Time Water-filling and Spatial Water-filling for MIMO Fading Channels,” in Proc. IEEE Int.Global Communications Conf., vol. 1, pp. 431 – 435,Nov. 29-Dec. 3, 2004, Dallas, TX,USA.•M. Ding, Z. Shen, and B. L. Evans, “An Achievable Performance Upper Bound for Discrete Multitone Equalization,” in Proc. IEEE Int. Global Communications Conf., vol. 4,pp. 2297 – 2301, Nov. 29-Dec. 3, 2004, Dallas, TX, USA.•I. C. Wong, Z. Shen, J. G. Andrews, and B. L. Evans, “A Low Complexity Algorithm for Proportional Resource Allocation in OFDMA Systems,” in Proc. IEEE Int. Work. SignalProcessing Systems, pp. 1-6, Oct. 13-15, 2004, Austin, TX, USA.•Z. Shen, J. G. Andrews and B. L. Evans, “Optimal Power Allocation in Multiuser OFDM Systems,” in Proc. IEEE Global Comm. Conference, vol. 1, pp. 337-341, Dec. 1-5, 2003,San Francisco, CA, USA.•Z. Shen, J. G. Andrews, and B. L. Evans, “Short Range Wireless Channel Prediction Using Local Information,” in Proc. IEEE Asilomar Conf. on Signals, Systems, and Computers,vol. 1, pp. 1147-1151, Nov. 9-12, 2003, Pacific Grove, CA, USA.Patents:•Z. Shen and T. Muharemovic, “User Scheduling for High Speed Uplink Packet Access Systems,” under Texas Instruments internal review, Sep. 2005.Presentations:•Jan. 19, 2006, “Multiuser Resource Allocation in Multichannel Wireless Communication Systems,” Ph.D. defense, The University of Texas at Austin, Austin, TX.•Nov. 30, 2005, “Upper Bounds on MIMO Channel Capacity with Channel Frobenius Norm Constraints,” lecture at Globecom’05, St. Louis, MO.•Nov. 1, 2005, “Low Complexity User Selection Algorithms for Multiuser MIMO Systems with Block Diagonalization,” lecture at Asilomar’05, Pacific Grove, CA.•Oct. 28, 2005, “User Selection Algorithms for Multiuser MIMO Systems,” lecture at 2005 Texas Wireless Symposium, Austin, TX.•Aug. 18, 2005, “User Scheduling for High Speed Uplink Packet Access Systems,”internship end-of-term presentation at Texas Instruments, Dallas, TX.•May 26, 2005, “Throughput and Fairness in Multi-Antenna Wideband WirelessCommunication Systems,” lecture delivered to Texas Instruments, Dallas, TX.•Feb. 16, 2005, “Increasing Connections Speeds for Next-Generation Wireless LANs Using Multiuser OFDM,” poster presentation at TI Development Conference’05, Houston, TX.•Dec. 2, 2004, “Comparison of Space-Time Water-filling and Spatial Water-filling for MIMO Fading Channels,” lecture at Globecom’04, Dallas, TX.•Oct. 22, 2004, “Multiuser OFDM with Variable Rate Constraints,” lecture at the Second Annual WNCG Wireless Networking Symposium, Austin, TX.•Sep. 30, 2004, “Equalization,” guest lecture for EE 381V: Advanced Wireless – Modulation and Multiple Access, The University of Texas at Austin, Austin, TX.•Jan. 28, 2004, “Multiuser Orthogonal Frequency Division Multiplexing for High-Speed Wireless Communication Systems,” Ph.D. qualifying presentation, The University of Texasat Austin, Austin, TX.•Nov. 11, 2003, “Short Range Wireless Channel Prediction Using Local Information,”poster presentation at 37th Asilomar Conference, Pacific Grove, CA.•Oct. 22, 2003, “Dynamic Resource Allocation in Multiuser OFDM Systems,” poster presentation at the First Annual WNCG Wireless Networking Symposium, Austin, TX.Design Experience:•Wireless Spread Spectrum Multiple Access System (IEEE 802.11b), Jan. 2001-Jun. 2001, Microwave and Digital Communications Lab, Tsinghua University, Beijing, China •VLSI projects: Adder design; Wishbone SoC Interconnection Interface and Synchronous Serial Port, Dept. of ECE, UT Austin•Embedded software system: VDSL system simulation using Agilent Advanced Design System (ADS), Dept. of ECE, UT Austin•FM system design: transmitter and receiver, EE Dept, Tsinghua UniversitySoftware:•G. Arslan, M. Ding, B. Lu, M. Milosevic, Z. Shen, and B. L. Evans, “UT AustinMulticarrier Equalizer Design Toolbox for Matlab,” Version 3.1, Embedded SignalProcessing Laboratory, The University of Texas at Austin, May 10, 2003.Skills:•Hardware description languages: VHDL, Verilog•Hardware design automation tools: Xilinx FPGA Foundation Series, Active-HDL, Max, Sue, Primetime, VCS, Versim, Synopsis Design Analyzer, Spice, Protel•Assembly languages: TI TMS320C30 DSP, TI TMSC6701 DSP, Intel 8086•High-level languages: C, C++, Java•Algorithm development environments: Matlab, Mathematica•Software development tools: Code Composer, CodeWarriorHonors:•David Bruton, Jr. Graduate Fellowship, 2004 – 2005, awarded by Office of Graduate Studies, The University of Texas at Austin•TxTEC fellowship, 2003 – 2004, Dept. of ECE, UT Austin•TxTEC fellowship, 2001 – 2002, Dept. of ECE, UT Austin•‘Kodak’ scholarship, Nov. 2000, Tsinghua University•‘Baogang’ scholarship, Nov. 1999, Tsinghua University•‘Dongfang Communications’ scholarship, Nov. 1998, Tsinghua University•Freshman scholarship, Nov. 1997, Tsinghua UniversityProfessional Activities:•IEEE student member since 2001•Session chair, “WNCG Track,” Texas Wireless Symposium, Oct. 2005, Austin, TX•Session co-chair, “Cellular Systems,” the Second Annual WNCG Wireless Networking Symposium, Oct. 2004, Austin, TX.•Reviewer for the following journalso IEEE Transactions on Signal Processing (2005 – present)o IEEE Transactions on Communications (2005 – present)o IEEE Journal on Selected Areas in Communications (2005 – present)o IEEE Transactions on Wireless Communications (2004 – present)o IEEE Transactions on Vehicular Technology (2004 – present)o IEEE Communications Letters (2004, 2006 – present)o IEEE Signal Processing Letters (2004)o EURASIP Journal on Wireless Communications and Networking (2005 – present)o Journal of Circuits, Systems and Signal Processing (2004)•Reviewer for the following conferenceso2006-Fall IEEE Vehicular Technology Conferenceo2006 IEEE International Conference on Communicationso2006 IEEE Wireless Communications and Networking Conferenceo2005 IEEE International Conference on Communicationso2005 IEEE Global Telecommunications Conferenceo2005 IEEE International Conference on Acoustics, Speech, and Signal Processingo2005-Fall IEEE Vehicular Technology Conferenceo2005-Spring IEEE Vehicular Technology Conferenceo2004 IEEE International Conference on Communicationso2004 IEEE Global Telecommunications Conferenceo2004 IEEE Radio and Wireless ConferenceVisa: F-1 with OPT, citizen of P. R. China.。
Infoprint 250 導入と計画の手引き 第 7 章ホスト
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多发射天线STBC-SCFDE系统的性能研究
多发射天线STBC-SCFDE系统的性能研究叶卓映;顾跃宗;吴江;耿国桐【摘要】针对频率选择性衰落下2根以上发射天线的空时分组码一单载波频域均衡系统(STBC-SCFDE),提出了编码方案和检测方案的一般过程,并分别以3根及4根发射天线为例给出了具体的发射方案和接收方案.仿真结果表明,该方案下的多发射天线STBC SCFDE,在最大时延达到数10个符号周期的情况下仍然具有优良的性能,因而在高速无线通信中具有广阔的应用前景.%Space-time block coding combined with single carrier frequency domain equalization is an attractive technique to combat inter-symbol interference caused by frequency selective fading.In this paper, we firstly investigate the performance of the Alamouti code combined with single carrier frequency domain equalization, then the coding scheme and the corresponding detecting scheme in the receiver when the number of transmitting antennas are more than 2 are designed.Simulation results show that the space-time block coded single carrier frequency domain equalization system exhibits good performance, even when the maximum time delay is up to tens of symbol period.Therefore, this technique is likely to have broad prospect in high-speed wireless transmission.【期刊名称】《电信科学》【年(卷),期】2012(028)012【总页数】6页(P59-64)【关键词】空时分组码;单载波频域均衡;频率选择性衰落信道【作者】叶卓映;顾跃宗;吴江;耿国桐【作者单位】中国国防科技信息中心北京100036【正文语种】中文1 引言未来无线通信系统是一个高速率、大容量系统，如何在无线衰落信道下可靠地传输高速业务，对无线传输链路技术提出了很大的挑战，这种挑战使得人们努力开发高效的编码调制以及信号处理技术来提高无线频率的使用效率。
5G通信系统中massiveMIMO-FBMC技术地结合概述
massive MIMO-FBMC技术综述摘要为了应对第五代移动通信（5G）中更高数据率和更低时延的需求，大规模MIMO（massive multiple-input multiple-output）技术已经被提出并被广泛研究。
大规模MIMO技术能大幅度地提升多用户网络的容量。
而在5G中的带宽研究方面，特别是针对碎片频谱和频谱灵活性问题，现有的正交频分多址（Orthogonal Frequency Division Multiplexing, OFDM）技术不可能应对未来的挑战，新的波形方案需要被设计出来。
基于此，FBMC（filter bank multicarrier）技术由于具有比OFDM低得多的带外频谱泄露而被受到重视，并已被标准推进组IMT-2020列为5G物理层的主要备选方案之一。
本文首先回顾了5G中波形设计方案（主要是FBMC调制）和大规模多天线系统（即massive MIMO）的现有工作和主要挑战。
然后，简要介绍了基于Massive MIMO的FBMC系统中的自均衡性质，该性质可以用于减少系统所需的子载波数目。
同时，FBMC中的盲信道跟踪性质可以用于消除massive MIMO系统中的导频污染问题。
尽管如此，如何将FBMC技术应用于massive MIMO系统中的误码率、计算复杂度、线性需求等方面仍然不明确，未来更多的研究工作需要在massive MIMO-FBMC方面展开来。
关键词：大规模MIMO；FBMC；自均衡；导频污染；盲均衡AbstractIn order to address the requirements of higher data rates and lower latency in the fifth generation mobile communication systems (5G), massive multiple-input multiple-output (MIMO) has been proposed and is currently an active area of research. This is due to the fact that they can greatly increase the capacity of multiuser networks. In the quest for bandwidth, particular challenges that need to be addressed in the context of 5G are fragmented spectrum and spectrum agility. It is unlikely that these challenges can be satisfied using Orthogonal Frequency Division Multiplexing (OFDM), and new waveforms are required. The filter bank multicarrier (FBMC) technique has been listed by IMT-2020 as one of the key physical layer candidates in 5G, since the FBMC has much lower out-of-band radiation than the OFDM.This article reviews existing related work and identifies the main challenges in the key 5G area at the intersection of waveform design (especially for FBMC) and large-scale multiple antenna systems, also known as Massive MIMO. The property of self-equalization is then introduced for FBMC-based Massive MIMO, which can reduce the number of subcarriers required by the system. It is also shown that the blind channel tracking property of FBMC can be used to address pilot contamination - one of the main limiting factors of Massive MIMO systems. Nevertheless, the implications of FBMC on error-rate performance, computational complexity, and linearity requirements in large-scale MIMO systems with potentially hundreds of antennas at the base station are still unclear. More research works correspond to the massive MIMO-FBMC system are needed in the future.Key Words:massive MIMO; FBMC; self-equalization; pilot contamination; blind equalization目录摘要 (I)Abstract (II)1 引言 (1)2 技术背景简介 (3)2.1 massive MIMO技术 (3)2.1.1 Massive MIMO的引入 (3)2.1.2 点对点MIMO (4)2.1.3 多用户MIMO(MU-MIMO) (6)2.2 FBMC技术 (7)3 massive MIMO-FBMC的结合问题 (10)3.1 信道均衡问题 (10)3.2 导频污染问题 (11)4 结语 (13)参考文献 (14)1 引言Massive MIMO（又称large scale MIMO）技术，是指基站端采用大规模天线阵列，天线数超过十根甚至上百根，并且在同一时频资源内服务多个用户的多天线技术，该技术由贝尔实验室的Marzetta于2010年首次提出，目前已成为5G无线通信领域最具潜力的研究方向之一[1,2]。
channelinitializer 里的方法调用过程
channelinitializer 里的方法调用过程ChannelInitializer是Netty中用于初始化Channel的抽象类，它通常用来配置ChannelPipeline，对Channel进行一些初始化操作。
在ChannelInitializer中，有一个抽象方法initChannel()，开发者需要重写这个方法来配置ChannelPipeline。
在Netty中，当一个Channel被创建时，会通过ChannelInitializer的initChannel()方法来对这个Channel进行初始化。
具体的调用过程如下：1. 当一个Channel被创建时，会先创建一个ChannelPipeline对象，用来管理Channel中的Handler。
2. 创建一个ChannelInitializer实例，并将其添加到ChannelPipeline的最后一个位置。
3. 调用ChannelInitializer的initChannel()方法，传入当前的Channel作为参数。
4. 在initChannel()方法中，开发者可以通过ChannelPipeline添加自定义的Handler，来处理Channel中的数据流。
5. 在initChannel()方法执行完毕后，ChannelPipeline会被激活，开始处理Channel中的数据。
总结来说，ChannelInitializer的方法调用过程主要包括创建ChannelPipeline、调用initChannel()方法、配置ChannelPipeline和激活ChannelPipeline。
通过重写ChannelInitializer的initChannel()方法，开发者可以自定义Channel的初始化过程，添加自定义的Handler来处理Channel中的数据。
数字通信中的多抽样率信号处理中英文翻译（部分）
数字通信中的多抽样率信号处理中英⽂翻译（部分）Multirate Signal Processing Concepts in Digital CommunicationsBojan VrceljIn Partial Fulfillment of the Requirementsfor the Degree ofDoctor of PhilosophyCalifornia Institute of TechnologyPasadena, California2004 (Submitted June 2, 2003)AbstractMultirate systems are building blocks commonly used in digital signal processing (DSP). Their function is to alter the rate of the discrete-time signals, which is achieved by adding or deleting a portion of the signal samples. Multirate systems play a central role in many areas of signal processing, such as filter bank theory and multiresolution theory. They are essential in various standard signal processing techniques such as signal analysis, denoising, compression and so forth. During the last decade, however, they have increasingly found applications in new and emerging areas of signal processing, as well as in several neighboring disciplines such as digital communications.The main contribution of this thesis is aimed towards better understanding of multirate systems and their use in modern communication systems. To this end, we first study a property of linear systems appearing in certain multirate structures. This property is called biorthogonal partnership and represents a terminology introduced recently to address a need for a descriptive term for such class of filters. In the thesis we especially focus on the extensions of this simple idea to the case of vector signals (MIMO biorthogonal partners) and to accommodate for nonintegral decimation ratios (fractional biorthogonal partners).Some of the main results developed here pertain to a better understanding of the biorthogonal partner relationship. These include the conditions for the existence of stable and of finite impulse response (FIR) biorthogonal partners. A major result that we establish states that under some generally mild conditions, MIMO and fractional biorthogonal partners exist. Moreover, when they exist, FIR solutions are not unique. We develop the parameterization of FIR solutions, which makes the search for the best partner in a given application analytically tractable. This proves very useful in the central application of biorthogonal partners, namely, channel equalization in digital communications with signal oversampling at the receiver. Sampling the received signal at a rate higher than that defined by the transmitter provides some flexibility in the design of the equalizer. A good channel equalizer in this context is one that helps neutralize the distortion on the signal introduced by the channel propagation but not at the expense of amplifying the channel noise. This presents the rationale behind the partner design problem which is formulated and solved. Theperformance of such equalizers is then compared to several other equalization methods by computer simulations. These findings point to the conclusion that the communication system performance can be improved at the expense of an increased implementational cost of the receiver.While the multirate DSP in the aforementioned communication systems serves to provide additional degrees of freedom in the design of the receiver, another important class of multirate structures is used at the transmitter side in order to introduce the redundancy in the data stream. This redundancy generally serves to facilitate the equalization process by forcing certain structure on the transmitted signal. If the channel is unknown, this procedure helps to identify it; if the channel is ill-conditioned, additional redundancy helpsVavoid severe noise amplification at the receiver, and so forth. In the second part of the thesis, we focus on this second group of multirate systems, derive some of their properties and introduce certain improvements of the communication systems in question.We first consider the transmission systems that introduce the redundancy in the form of a cyclic prefix. The examples of such systems include the discrete multitone (DMT) and the orthogonal frequency division multiplexing (OFDM) systems. The cyclic prefix insertion helps to effectively divide the channel in a certain number of nonoverlaping frequency bands. We study the problem of signal precoding in such systems that serves to adjust the signal properties in order to fully take advantage of the channel and noise properties across different bands. Our ultimate goal is to improve the overall system performance by minimizing the noise power at the receiver. The special case of our general solution corresponds to the white channel noise and the best precoder under these circumstances simply performs the optimal power allocation.Finally, we study a different class of communication systems with induced signal redundancy, namely, the multiuser systems based on code division multiple access (CDMA). We specifically focus on the special class of CDMA systems called `a mutually orthogonal usercode receiver' (AMOUR). These systems use the transmission redundancy to facilitate the user separation at the receiver regardless of the (different) communication channels. While the method also guarantees the existence of the zero-forcing equalizers irrespective of the channel zero locations, the performance of these equalizers can be further improved by exploiting the inherent flexibility in their design. Weshow how to find the best equalizer from the class of zero-forcing solutions and then increase the size of this class by employing alternative sampling strategies at the receiver. Our method retains the separability properties of AMOUR systems while improving their robustness in the noisy environment.Chapter 1 IntroductionThe theory of multirate digital signal processing (DSP) has traditionally been applied to the contexts of filter banks [61], [13], [50] and wavelets [31], [72]. These play a very important role in signal decomposition, analysis, modeling and reconstruction. Many areas of signal processing would be hard to envision without the use of digital filter banks. This is especially true for audio, video and image compression, digital audio processing, signal denoising, adaptive and statistical signal processing. However, multirate DSP has recently found increasing application in digital communications as well. Multirate building blocks are the crucial ingredient in many modern communication systems, for example, the discrete multitone (DMT), digital subscriber line (DSL) and the orthogonal frequency division multiplexing (OFDM) systems as well as general filter bank precoders, just to name a few. The interested reader is referred to numerous references on these subjects, such as [7]-[9], [17]-[18], [27], [30], [49], [64], [89], etc.This thesis presents a contribution to further understanding of multirate systems and their significance in digital communications. To that end, we introduce some new signal processing concepts and investigate their properties. We also consider some important problems in communications especially those that can be formulated using the multirate methodology. In this introductory chapter, we give a brief overview of the multirate systems and introduce some identities, notations and terminology that will prove useful in the rest of the thesis. Every attempt is made to make the present text as self-contained as possible and the introduction is meant to primarily serve this purpose. While some parts of the thesis, especially those that cover the theory of biorthogonal partners and their extensions provide a rather extensive treatment of the concepts, the material regarding the applications of the multirate theory in communication systems should be viewed as a contribution to a better understanding and by no means the exhaustive treatment of such systems. For a more comprehensive coverage the reader is referred to a range of extensive texts on the subject, for example, [71], [18], [19], [39], [38], [53], etc.1.1 Multirate systems 1.1.1 Basic building blocks The signals of interest in digital signal processing are discrete sequences of real or complex numbers denoted by x(n), y(n), etc. The sequence x(n) is often obtained by sampling a continuous-time signal x c(t). The majority of natural signals (like the audio signal reaching our ears or the optical signal reaching our eyes) are continuous-time. However, in order to facilitate their processing using DSP techniques, they need to be sampled and converted to digital signals. This conversion also includes signal quantization, i.e.,discretization in amplitude, however in practice it is safe to assume that the amplitude of x(n) can be any real or complexSignal processing analysis is often simplified by considering the frequency domain representation of signals and systems. Commonly used alternative representations of x(n) are its z-transform X (z) and the discrete-time Fourier transform X (O'). The z-transform is defined as X(z) = E _.x(n)z-"', and X (e j") is nothing but X(z) evaluated on the unit circle z = e3".Multirate DSP systems are usually composed of three basic building blocks, operating on a discrete-time signal x(n). Those are the linear time invariant (LTI) filter, the decimator and the expander. An LTI filter, like the one shown in Fig.1.1, is characterized by its impulse response h(n), or equivalently by its z-transform (also called the transfer function) H(z). Examples of the M-fold decimator and expander for M = 2 are shown in Fig.1.2. The rate of the signal at the output of an expander is M times higher than the rate at its input, while the converse is true for decimators. That is why the systems containing expanders and decimators are called `multirate' systems. Fig.1.2 demonstrates the behavior of the decimator andthe expander in both the time and the frequency domains.XE(z) = [X (z)]IM XD(z) = [X (z)]iM = X(z M)1 M-1 1 j2 k =M E X(z e n a)k=0for M-fold expander, and (1.1)for M-fold decimator. (1.2)The systems shown in Figs.1.1 and 1.2 operate on scalar signals and thus are called single input-single output (SISO) systems. The extensions to the case of vector signals are ratherstraightforward: the decimation and the expansion are performed on each element separately. The corresponding vector sequence decimators/expanders are denoted within square boxes in block diagrams. In Fig.1.3 this is demonstrated for vector expanders. The LTI systems operating on vector signals are called multiple input-multiple output (MIMO) systems and they are characterized by a (possibly rectangular) matrix transfer function H(z).1.1.2 Some multirate definitions and identitiesThe vector signals are sometimes obtained from the corresponding scalar signals by blocking. Conversely, the scalar signals can be recovered from the vector signals by unblocking. The blocking/unblocking operations can be defined using the delay or the advance chains [61], thus leading to two similar definitions. One way of defining these operations is shown in Fig.1.4, while the other is obtained trivially by switching the delay and the advance operators. Instead of drawing the complete delay/advance chain structure, we often use the simplified block notation as in Fig.1.4. It is usually clear from the context which of the two definitions数字通信中的多抽样率信号处理Bojan Vrcelj博⼠学位论⽂加州技术学会Pasadena, 加州2004 (委托于2003.6.2)摘要多抽样率系统普遍是被运⽤在处理数字信号⽅⾯。
equalizer apo copy channel -回复
equalizer apo copy channel -回复Equalizer 是一种音频处理设备，也是一种音频软件应用程序，被广泛应用于音乐产业、电影制作和音频爱好者中。
Equalizer的主要功能是调节音频频率响应，使得音频信号在不同频段之间达到均衡。
Equalizer APO 是Equalizer的一个开源项目，是一个在Windows系统中运行的系统级均衡器。
它可以用于改善音频质量，调节各种音频设备的音频输出，以及为不同型号的耳机或音响设备进行定制。
这篇文章将为读者提供关于Equalizer APO的详细介绍，并提供一步一步的操作指南，以便他们能够正确使用该软件。
第一步：下载和安装Equalizer APO首先，读者可以在官方网站或其他可靠的下载网站上找到Equalizer APO 的最新版本。
选择与您的操作系统兼容的版本，并下载安装程序。
一旦下载完成，双击运行安装程序并按照提示进行安装。
第二步：选择音频设备安装完成后，启动Equalizer APO并选择要设置的音频设备。
这可以是你的耳机、扬声器或其他外部音频设备。
确保正确选择设备，并继续下一步。
第三步：配置均衡器设置在Equalizer APO中，均衡器设置是通过编辑一个名为“config.txt”的文本文件来完成的。
这个文件控制了音频信号的处理方式和频率响应。
找到并打开“config.txt”文件，然后根据自己的喜好，调整各频段的增益。
相对较低的增益表示减小该频段的响应，而较高的增益则表示增加该频段的响应。
通过不断尝试和调整，找到最适合自己喜好和音频设备的均衡器设置。
第四步：保存和应用更改在调整完均衡器设置后，记得保存更改并关闭“config.txt”文件。
然后，重新启动音频设备，以使更改生效。
这可以通过禁用并重新启用该设备，或重新插拔外部设备来完成。
第五步：测试和优化完成以上步骤后，测试音频设备以确保均衡器设置符合期望。
在播放各种音频内容时，注意清晰度、音域和平衡性是否得到改善。
通信名词中英对照
名词委编号词条英文01.001通信communication01.002电信telecommunication01.003信息information01.004信息技术information technology IT01.005吉普曲线Jipp curve01.006模拟通信analog communication01.007数字通信digital communication01.008有线通信wire communication01.009无线通信wireless communication01.010无线电通信radio communication01.011电话通信telephone communication01.012数据通信data communication01.013图像通信image communication01.014静止图像通信still image communication static image communication 01.015全活动视频full-motion video01.016传真通信fax communication facsimile communication 01.017传真存储转发facsimile storage and forwarding01.018视像通信video communication01.019多媒体通信multimedia communication01.020自适应（的）adaptive01.021自适应通信adaptive communication01.022网（络）network01.023分级网（络）hierarchical network01.024对等网络peer-to-peer network01.025有源网络active network01.026无源网络passive network01.027网络拓扑network topology01.028星状网star network01.029树状网tree network01.030网状网mesh network01.031环状网ring network01.032重叠网overlay network01.033通信系统communication system01.034时变系统time-varying system01.035信源source01.036信宿sink01.037信道channel01.038通道path01.039波道channel01.040物理信道physical channel01.041逻辑信道logical channel01.042承载信道bearer channel01.043对称信道symmetrical channel01.044不对称信道asymmetrical channel01.045多用户信道multiuser channel01.046正向信道forward channel01.047反向信道backward channel01.048同信道co-channel01.049邻信道adjacent channel01.050信道间隔channel spacing01.051信道容量channel capacity01.052信号signal01.053模拟信号analog signal01.054数字信号digital signal01.055n值信号n-ary signal01.056随机信号stochastic signal01.057伪随机信号pseudo-random signal01.058对称信号symmetrical signal01.059突发信号burst01.060正交信号orthogonal signal01.061双极性信号bipolar signal01.062单极性信号unipolar signal01.063有用信号desired signal wanted signal 01.064无用信号undesired signal unwanted signal 01.065信号带宽signal bandwidth01.066波形waveform01.067载波carrier01.068副载波subcarrier01.069谐波harmonic01.070行波traveling wave01.071发送transmit send01.072接收receive01.073传送transport01.074传输transmit transmission 01.075传播propagation01.076传播常数propagation constant01.077传播媒介propagation medium01.078传播时延propagation delay01.079传播速度propagation velocity01.080传递函数transfer function01.081传递特性transfer characteristic01.082传输媒体transmission medium01.083传输控制transmission control01.084传输损耗transmission loss01.085传输因数transmission factor01.086传输线路transmission line01.087传输性能transmission performance01.088数据传输data transmission01.089突发传输burst transmission01.090并行传输parallel transmission01.091串行传输serial transmission01.092带间传输interband transmission01.093带内传输intraband transmission01.094基带传输baseband transmission01.095基带baseband01.096基带信号baseband signal01.097基带处理baseband processing01.098参考模型reference model01.099参考系统reference system01.100单工simplex01.101双工duplex01.102半双工half duplex01.103频分双工frequency-division duplex FDD01.104时分双工time-division duplex TDD01.105白噪声white noise01.106背景噪声background noise01.107大气噪声atmosphere noise01.108高斯噪声Gaussian noise01.109高斯白噪声white Gaussian noise WGN01.110加性高斯白噪声additive white Gaussian noise AWGN01.111互调噪声intermodulation noise01.112参考噪声reference noise01.113加权噪声weighted noise01.114量化噪声quantization noise01.115热噪声thermal noise01.116散粒噪声shot noise01.117闪烁噪声flicker noise01.118随机噪声random noiseSNR01.119信噪比signal-to-noise ratio signal to noi01.120噪声带宽noise bandwidth01.121干扰interference01.122干扰信号interfering signal01.123干涉图样interference pattern01.124同信道干扰co-channel interference01.125邻信道干扰adjacent channel interference01.126信道间干扰interchannel interference01.127符号间干扰intersymbol interference ISI01.128多址干扰multi-site interference01.129电磁干扰electromagnetic interference EMI01.130电磁兼容性electromagnetic compatibility EMC01.131抗干扰性immunity01.132载波干扰比carrier-to-interference ratio C/I01.133信号干扰比signal to interference ratio01.134率失真理论rate distortion theory01.135失真distortion01.136线性失真linear distortion01.137非线性失真nonlinear distortion01.138量化失真quantization distortion quantizing distortion 01.139过负荷失真overload distortion01.140互调失真intermodulation distortion01.141互调产物intermodulation product01.142不规则畸变fortuitous distortion01.143串扰crosstalk01.144信串比signal-to-crosstalk ratio01.145衰减串话比attenuation-to-crosstalk ratio ACR 01.146侧音sidetone01.147插入损耗insertion loss01.148回波echo01.149回波损耗return loss01.150时延delay01.151群时延group delay01.152包络时延envelop delay01.153窄带narrowband01.154阔带wideband01.155宽带broadband01.156子带subband01.157边带sideband01.158单边带single sideband SSB 01.159双边带double sideband DSB 01.160残留边带vestigial sideband VSB 01.161保护（频）带guard band01.162带内（的）in band01.163带外（的）out of band01.164数字化digitization01.165香农定律Shannon law01.166奈奎斯特定理Nyquist theorem01.167二进制（的）binary01.168二进制数字binary digit bit01.169二进制信道binary channel01.170八比特组octet01.171八进制（的）octal01.172波特baud01.173比特流bit stream01.174比特率bit rate01.175等效比特率equivalent bit rate01.176符号率symbol rate01.177比特差错bit error01.178比特差错率bit error ratio01.179块差错概率block error probability01.180比特滑动bit slip01.181比特间隔bit interval01.182比特交织bit interleaving01.183比特劫取bit robbing01.184比特填充bit stuffing01.185比特同步bit synchronization01.186比特图案bit pattern01.187同步（的）synchronous01.188不同步（的）non-synchronous01.189数字差错digital error01.190差错比特error bit01.191突发差错burst error01.192超时time-out01.193样值sample01.194抽样sampling01.195抽样时间sampling time01.196抽样率sampling rate01.197定时timing01.198定时抽取timing extraction01.199定时恢复timing recovery01.200定时信号timing signal01.201定时信息timing information01.202抖动jitter01.203抖动积累jitter accumulation01.204抖动限值jitter limit01.205量化quantization01.206均匀量化uniform quantization01.207非均匀量化non-uniform quantization non-uniform quantizing 01.208量化误差quantization error01.209开销overhead01.210内务信息housekeeping information01.211时域time domain01.212时隙time-slot TS01.213时基time base01.214时钟恢复clock recovery01.215时钟提取clock extraction01.216帧frame01.217帧结构frame structure01.218帧定位frame alignment01.219帧格式frame format01.220帧滑动frame slip01.221帧同步frame synchronization01.222帧失步out-of-frame OOF01.223帧丢失loss-of-frame01.224复帧multiframe01.225超帧superframe01.226成帧framing01.227成帧图案framing pattern01.228IP技术IP technology01.229分组packet01.230分组拆卸packet disassembly01.231分组装配packet assembly01.232异步转移模式asynchronous transfer mode ATM01.233同步转移模式synchronous transfer mode STMdynamic synchronous transfer mode DTM 01.234动态同步转移模式01.235对等操作peering01.236跳时time hopping01.237跳频frequency hopping FH 01.238扩频frequency spread01.239变频frequency conversion01.240上变频up conversion01.241下变频down conversion01.242并串转换parallel-to-serial conversioserializationdeserialization 01.243串并转换serial-to-parallel conversio01.244模数转换analog-to-digital conversion01.245数模转换digital-to-analog conversion01.246倒谱cepstrum01.247倒相phase inversion01.248极化polarization01.249加扰scrambling01.250解扰descrambling01.251检测detection01.252检错error detection01.253纠错error correcting01.254压缩compression01.255压扩companding01.256扩充expansion01.257压缩比compression ratio01.258数字线对增益digital pair gain DPG 01.259交织interleaving01.260聚合带宽aggregate bandwidth01.261均衡equalization01.262码速调整justification01.263脉冲整形pulse shaping01.264脉冲再生pulse shaping01.265奇偶检验parity check01.266滤波filtering01.267限带滤波band-limiting filtering01.268限幅limiting01.269信号变换signal conversion01.270信号再生signal regeneration01.271预加重pre-emphasis01.272预均衡pre-equalization01.273预校正pre-correction01.274模mode01.275TEM模TEM mode01.276TE模TE mode01.277TM模TM mode01.278相位phase01.279频段frequency band01.280频率frequency01.281高频high frequency HF 01.282甚高频very high frequency VHF 01.283特高频ultrahigh frequency UHF 01.284超高频super high frequency SHF 01.285音频audio frequency AF 01.286射频radio frequency01.287视频video01.288频率响应frequency response01.289频谱frequency spectrum01.290复频谱complex spectrum01.291频域frequency domain01.292谱宽spectral width01.293功率谱power spectrum01.294功率谱密度power spectrum density01.295半功率点half-power point01.296波段band01.297波长wavelength01.298长波long wave LW 01.299中波medium wave MW 01.300短波shortwave SW 01.301超短波ultrashort wave USW 01.302微波microwave MW 01.303导频信号pilot signal01.304参考导频reference pilot01.305单音tone01.306可靠性reliability01.307可用性availability01.308可用时间up time01.309可用状态up state01.310不可用性unavailability01.311不可用时间unavailability time01.312不可用状态down state01.313不能工作状态disabled state01.314冲激impulse01.315冲激响应impulse response01.316带宽距离积bandwidth-distance product01.317增益带宽积gain-bandwidth product01.318增益gain01.319自动增益控制automatic gain control AGC 01.320电平level01.321分贝decibel dB 01.322毫瓦分贝dBm01.323发射emission01.324辐射radiation01.325前馈feedforward01.326反馈feedback01.327正反馈positive feedback01.328负反馈negative feedback01.329反射波reflected wave01.330反射系数reflection coefficient01.331线性linearity01.332非线性nonlinearity01.333载波恢复carrier recovery01.334频偏frequency deviation01.335带宽bandwidth BW 01.336按需分配带宽bandwidth on demand01.337负荷load01.338净荷payload01.339接收机灵敏度receiver sensitivity01.340眼图eye diagram eye pattern 01.341容错fault tolerance01.342透明性transparencyconnectivity transparency01.343连通（性）透明性01.344业务透明性service transparency01.345应用透明性application transparency01.346过冲overshoot01.347过载点overload point01.348钳位clamping01.349门限threshold01.350耦合coupling01.351衰减attenuation01.352衰减系数attenuation coefficient01.353锁相phase locking01.354相干coherence01.355选通gating01.356选择性selectivity01.357争用contention01.358业务属性service attribute01.359连接connection01.360无连接connectionless01.361面向连接connection-oriented01.362多点到多点连接multipoint-to-multipoint connection 01.363多点到点连接multipoint-to-point connection01.364点到多点连接point-to-multipoint connection01.365点到点连接point-to-point connection01.366回程backhaul01.367接入access01.368交叉连接cross-connect01.369级联cascading01.370桥接bridging01.371互连interconnection01.372互联interconnection01.373互通interworking01.374互操作性interoperability01.375呼叫call01.376呼叫建立call set-up01.377主叫方calling party01.378被叫方called party01.379最终用户end user01.380编号numbering01.381寻址addressing01.382选路routing01.383动态选路dynamic routing01.384拥塞控制congestion control01.385链路link01.386上行链路uplink01.387下行链路downlink01.388长途线路long distance line01.389线路段line section01.390支路tributary01.391话路voice channel01.392节点node01.393端口port01.394接口interface01.395物理接口physical interface01.396接口速率interface rate01.397二端网络two-terminal network01.398四端网络four-terminal network01.399流stream01.400流量控制flow control01.401业务量控制traffic control01.402实时控制real-time control01.403调解功能mediation function01.404端到端性能end-to-end performance01.405端到端通信end-to-end communication01.406单方向unidirectional01.407双方向bidirectional01.408单向式one-way01.409双向式two-way01.410话音voice01.411语音speech01.412备用冗余standby redundancy01.413热备用hot standby01.414远程供电remote power-feeding01.415多址接入multiple access01.416频分多址frequency-division multiple access FDMA 01.417时分多址time-division multiple access TDMA 01.418空分多址space-division multiple access SDMA 01.419码分多址code-division multiple access CDMA 01.420时分码分多址time-division CDMA TD-CDMA 01.421波分多址wavelength-division multiple access WDMA01.422复用multiplexing01.423分用demultiplexing01.424频分复用frequency-division multiplexing FDM 01.425时分复用time-division multiplexing01.426码分复用code-division multiplexing01.427波分复用wavelength-division multiplexing01.428异类复用heterogeneous multiplex01.429统计复用statistical multiplexing01.430时分语音插空time-division speech interpolation01.431数字语音内插digital-speech interpolation DSI 01.432逆复用inverse multiplexing01.433数字复用体系digital multiplex hierarchy01.434代码code01.435码字code word01.436码块block01.437归零return to zero RZ 01.438不归零non-return to zero NRZ 01.439传号mark01.440空号space01.441编码coding encoding01.442解码decoding01.443编码率encoding law01.444 A 律A-law01.445μ 律μ-law01.446编码变换transcoding coding transform 01.447编码增益coding gain01.448信源编码source coding01.449信道编码channel coding01.450相关编码correlative coding01.451图像编码image coding01.452游程长度编码run-length coding RLC01.453差错控制编码error control coding ECC01.454差分编码differential encoding01.455均匀编码uniform encoding01.456非均匀编码non-uniform encoding01.457赫夫曼编码Huffman coding01.458群编码group coding01.459极性码polar code01.460双极性码bipolar coding01.461双相编码biphase coding01.462通用编码universal coding01.463预测编码predictive coding01.464线性预测编码linear prediction coding LPC 01.465BCH码BCH code01.466n元码n-ary code01.467部分响应编码partial response coding01.468成对不等性码paired-disparity code01.469定比码constant ratio code01.470二进制码binary codebinary coded decimal BCD 01.471二进制编码的十进01.472双二进码duobinary code01.473汉明码Hamming code01.474曼彻斯特码Manchester code01.475交织码interleaved code01.476检错码error-detection code01.477防错码error-protection code01.478纠错码error-correcting code01.479块码block code01.480平衡码balanced code01.481扰码scramble01.482冗余码redundant code01.483循环码cyclic code01.484调制modulation01.485解调demodulation01.486调制因数modulation factor01.487调制速率modulation rate01.488调制指数modulation index01.489调频frequency modulation FM01.490调幅amplitude modulation AM01.491调相phase modulation PM01.492鉴相phase discrimination01.493数字调制digital modulation01.494幅移调制amplitude-shift modulation01.495脉冲编码调制pulse-code modulation PCM 01.496差分调制differential modulation01.497差分脉码调制differential pulse-code modulation DPCMadaptive differential pulse-code modul ADPCM 01.498自适应差分脉码调01.499无载波幅相调制carrierless amplitude-and-phase modula CAPM 01.500网格编码调制trellis-coded modulation TCM 01.501波长调制wavelength modulation WM01.502换频调制frequency-exchange modulation01.503相干调制coherent modulation01.504增量调制delta modulation DM01.505倒相调制phase-inversion modulation01.506正交调制quadrature modulation01.507正交调幅quadrature amplitude modulation QAM 01.508正交频分复用orthogonal frequency-division multiple OFDM 01.509脉冲调制pulse modulation PM01.510脉幅调制pulse-amplitude modulation PAMPDM,PWM 01.511脉宽调制pulse-duration modulation pulse-width m01.512脉冲位置调制pulse-position modulation PPM 01.513脉冲相位调制pulse-phase modulation PPM 01.514频移键控frequency-shift keying FSK 01.515幅移键控amplitude-shift keying ASK01.516相移键控phase-shift keying PSK 01.517四相移相键控quaternary PSK QPSKminimum frequency-shift keying MSK 01.518最小相位频移键控01.519高斯频移键控Gaussian FSK GFSKGaussian MSK GMSK 01.520高斯最小频移键控01.521欠调制under modulation01.522过调制over modulation01.523互调intermodulation IM 01.524交叉调制cross modulation01.525相干解调coherent demodulation01.526包络解调envelop demodulation01.527包络检波envelop detection01.528平方律检波square-law detection01.529发送机transmitter01.530接收机receiver01.531调制器modulator01.532解调器demodulator01.533倍频器frequency multiplier01.534分频器frequency divider01.535放大器amplifier01.536参量放大器parametric amplifier01.537低噪声放大器low-noise amplifier01.538功率放大器power amplifier01.539选频放大器frequency-selective amplifier01.540带通滤波器bandpass filter01.541带阻滤波器bandstop filter01.542高通滤波器high-pass filter01.543低通滤波器low-pass filter01.544数字滤波器digital filter01.545电路circuit01.546二线电路two-wire circuit01.547四线电路four-wire circuit01.548汇接电路tandem circuit01.549触发电路trigger circuit01.550单稳态电路monostable circuit01.551判决电路decision circuit01.552时序电路sequential circuit01.553平衡电路balanced circuit01.554数字电路倍增digital circuit multiplication DCM 01.555多谐振荡器multivibrator01.556振荡器oscillator01.557缓冲存储器buffer memory01.558弹性缓冲器elastic buffer01.559高速缓冲存储器cache01.560回波抵消器echo canceller01.561回波抑制器echo suppressor01.562混合耦合器hybrid coupler01.563混合线圈hybrid transformer hybrid coil01.564混合网络hybrid network01.565混频器mixer converter01.566检波器detector01.567鉴幅器amplitude discriminator01.568鉴频器frequency discriminator01.569检相器phase detector01.570复用器multiplexer MUX 01.571异步复用器asynchronous multiplexer01.572分用器demultiplexer deMUX 01.573复用分用器muldex01.574编码器coder encoder01.575解码器decoder01.576编解码器codec01.577解扰码器descrambler01.578声码器voice coder vocoder01.579均衡器equalizer01.580耦合器coupler01.581环行器circulator01.582数字配线架digital distribution frame DDF 01.583衰减器attenuator01.584背板backplate01.585波导waveguide01.586带状线strip line01.587散射scattering01.588瑞利散射Rayleigh scattering01.589射束beam01.590分集diversity01.591主瓣main lobe01.592旁瓣side lobe01.593天线antenna01.594天馈线antenna feeder01.595天线方向图antenna pattern01.596天线合路器antenna combiner ACOM 01.597无源天线passive antenna01.598有源天线active antenna01.599捕获acquisition01.600有效辐射功率effective radiated power02.001电信网telecommunication network02.002信息网information network02.003信息基础设施information infrastructure02.004信息高速公路information superhighway02.005业务网service network02.006传输网transmission network02.007城市传输网metropolitan transmission network02.008电视传输网television transmission network02.009宽带网boradband network02.010城市宽带网metropolitan broadband network02.011传送网transport network02.012光同步传送网optical synchronous transport network 02.013中继网trunk network02.014转接网transmit network02.015终接网terminating network02.016核心网core network02.017主干网backbone network02.018分配网distribution network02.019公用网public network02.020专用网private network02.021虚拟专用网virtual private network VPN 02.022企业网enterprise network02.023电路交换网circuit-switched network02.024分组交换网packet-switched network02.025分级选路网hierarchical routing network02.026无级选路网nonhierarchical routing network02.027下一代网络next-generation network NGN 02.028电话网telephone network02.029本地电话网local telephone network02.030市内电话网urban telephone network02.031长途电话网toll telephone network02.032农村电话网rural telephone network02.033公用电话交换网public switched telephone network PSTN 02.034专用电话网private telephone network02.035移动电话网mobile telephone network02.036电话交换局telephone exchange02.037本地电话交换局local telephone exchange02.038长途电话交换局toll telephone exchange02.039汇接局tandem office02.040端局end office02.041电话网编号计划telephone network numbering plan02.042数据网data network02.043公用数据网public data network02.044专用数据网private data network02.045电路交换数据网circuit-switched data network CSDN02.046分组交换数据网packet-switched data network PSDNX.25 packet-switched data network02.047X.25分组交换数据02.048虚电路virtual circuit02.049永久虚电路permanent virtual circuit PVC02.050交换虚电路switched virtual circuit SVC02.051数据站data stationdata circuit terminal equipment DCE02.052数据电路终端设备02.053吞吐量throughput02.054数字数据网digital data network DDN02.055数据业务单元data service unit02.056帧中继网frame relay network02.057介入速率access rate AR02.058承诺信息速率committed information rate CIR02.059承诺突发量committed burst size BC02.060超额突发量excess burst size02.061计算机通信网computer communication network02.062人体域网body area network02.063个人域网personal area network02.064特别联网ad hoc networking02.065局域网local area network LAN02.066城域网metropolitan area network MAN02.067广域网wide area network WAN02.068存储（器）域网storage area network SAN02.069互联网internet02.070IP 网IP network02.071因特网Internet02.072内联网Intranet02.073外联网extranet02.074万维网world wide web WWW02.075泛在网ubiquitous network02.076以太网Ethernet02.077吉比特以太网gigabit Ethernet02.078面向连接网connection-oriented network CO network 02.079无连接网connectionless network CL network 02.080网络服务接入点network service access point NSAP02.081网间互通internetworkingdistributed queue dual bus DQDB02.082分布队列双重总线02.083弹性分组环resilient packet ring RPR02.084光纤分布式数据接fiber-distributed data interface FDDI02.085网桥bridge02.086网关gateway GW02.087核心路由器core router02.088边缘路由器edge router02.089边界路由器border router02.090网守gatekeeper GK02.091多点控制单元multipoint control unit MCU02.092网络运行中心network operation center NOC02.093网络信息中心network information center NIC02.094下一代因特网next-generation Internet NGI02.095网格grid02.096域domain02.097域名系统domain-name system DNS02.098自治系统autonomous system AS02.099因特网接入点point of presence POP02.100网络接入点network access point NAP02.101镜像站点mirror site02.102计算机电话集成computer telephony integration CTI02.103综合数字业务网integrated services digital network ISDN02.104综合数字网integrated digital network IDN02.105用户-网络接口user-network interface UNI02.106参考点reference point02.107参考配置reference configuration02.108基本速率接口basic rate interface BRI02.109基群速率接口primary rate interface PRI02.110 B 信道B-channel02.111 D 信道D-channelbroadband ISDN B-ISDN02.112宽带综合业务数字02.113异步转移模式网asynchronous transfer mode network ATM network02.114同步转移模式网synchronous transfer mode network02.115ATM 信元ATM cell02.116ATM 适配层ATM adaption layer AAL02.117虚信道virtual channel VC02.118虚通道virtual path VP02.119数据交换接口data exchange interface DXI02.120局域网仿真LAN emulation LANE02.121仿真局域网emulated LAN ELAN02.122专用的网间接口private network-to-network interface PNNI02.123有线电视网cable television network CATV network02.124头端head-end02.125用户驻地网customer premise network CPN02.126用户驻地设备customer premise equipment CPE02.127家庭网home network02.128家庭联网home networking02.129接入网access network AN02.130光纤接入网fiber-access network02.131混合光纤同轴电缆hybrid fiber/coax access network HFC access network 02.132无线接入网wireless access network02.133业务节点service node SN 02.134用户节点user node02.135业务节点接口service node interface SNI 02.136业务端口service port02.137用户端口user port02.138用户配线网subscriber distribution network02.139业务接入复用器service access multiplexer02.140远端机remote terminal RT 02.141局端机central office terminal02.142远程接入remote access02.143综合接入设备integrated access device IAD 02.144全业务网full-service network FSN 02.145网络适配器network adapter NA 02.146智能网intelligent network IN 02.147高级智能网advanced intelligent network AIN 02.148业务特征service feature SF 02.149能力集capability set CS 02.150业务逻辑service logic SL 02.151业务交换点service-switching point SSP 02.152业务控制点service-control point SCP 02.153业务数据点service data point SDP 02.154业务管理点service management point SMP 02.155业务管理接入点service management access point SMAP 02.156业务生成环境点service-creation environment point SCEP 02.157智能外设intelligent peripheral IP02.158功能实体functional entity FE03.001支撑网support network03.002信令signaling03.003信令网signaling network03.004信令系统signaling system03.005七号信令系统signaling system No.7SS7 03.006随路信令channel-associated signaling CAS 03.007共路信令common channel signaling CCS 03.008直联信令（方式）associated signalingnon-associated signaling03.009非直联信令（方式quasi-associated signaling03.010准直联信令（方式03.011信令点signaling point03.012信令转接点signaling transfer point03.013信令点编码signaling point coding03.014信令路由signaling route03.015信令链路signaling link03.016信令信息signaling information03.017同步网synchronization network synchronized network,synchronous network 03.018准同步网plesiochronous network03.019混合同步网hybrid synchronization network03.020非同步网non-synchronized network non-synchronous network03.021互同步网mutually synchronized network03.022主从同步master-slave03.023单端同步single-ended synchronization03.024时钟clock CK03.025基准时钟reference clock03.026主时钟master clock03.027本地时钟local clockbuilding-integrated timing supply BITS03.028大楼综合定时供给03.029时钟控制信号clock control signal03.030时钟频率clock frequency03.031世界时universal time UT03.032世界协调时universal tie coordinated UTC03.033同步信息synchronization information03.034同步节点synchronization node03.035同步链路synchronization link03.036网络管理network management03.037电信管理网telecommunication management network TMN03.038网元管理network element management03.039用户网络管理customer network management CNM03.040业务管理service management03.041事务管理business management03.042管理树management tree03.043管理对象managed object MO03.044管理应用功能management application function MAFtelecommunication information network TINA03.045电信信息网络体系common object request broker architect CORBA03.046公共对象请求代理03.047Q3协议Q3 Protocol04.001交换switching04.002模拟交换analog switching04.003数字交换digital switching04.004电路交换circuit switching04.005分组交换packet switching04.006报文交换message switching04.007空分交换space-division switching04.008时分交换time-division switching04.009频分交换frequency-division switching04.010时隙交换time-slot interchange TSI04.011波长交换wavelength switching04.012光交换photonic switching04.013软交换softswitching04.014光分组交换optical packet switching OPS 04.015光突发交换optical burst switching04.016异步数据交换机asynchronous data switch04.017多协议标签交换multi-protocol label switching MPLSgeneral multi-protocol label switching GMPLS 04.018通用多协议标签交04.019虚信道交换单元VC switch04.020虚通道交换单元VP switch04.021数字视频交互digital video interactive DVI 04.022帧中继frame relay04.023集中控制centralized control04.024分布（式）控制distributed control04.025存储程序控制stored-program control SPC 04.026分组装拆器packet assembler/disassembler PAD 04.027聚合器aggregatordigital crossconnected system DCS 04.028数字交叉连接系统04.029交换机switch04.030自动交换设备automatic switching equipment04.031专用小交换机private branch exchange PBX 04.032数字交换机digital exchange digital switch 04.033程控数字交换机SPC digital switch04.034汇接交换机tandem switch04.035局域网交换机LAN switch04.036路由器router04.037网桥路由器brouter04.038主干路由器backbone router04.039远端用户模块remote subscriber module04.040交换网（络）switching network04.041交换局exchange switching office 04.042交换中心switching center04.043数字交换局digital exchange04.044本地交换局local exchange local centralLE, LCO 04.045交换矩阵switching matrix04.046中央处理机central processor04.047交换级switching stage04.048集中器concentrator04.049集线器hub04.050信令网关signaling gateway04.051媒体网关media gateway04.052媒体网关控制器media gateway controller04.053总配线架main distribution frame04.054路由route04.055直达路由direct route04.056溢呼路由overflow route04.057逐段路由hop-by-hop route04.058选路策略routing policy04.059迂回路由alternative routing04.060多点接入multipoint access04.061半永久连接semi-permanent connection04.062交换连接switched connection04.063对称连接symmetric connection04.064信元cell04.065信元交换cell switching04.066业务量描述语traffic descriptor04.067峰值信元速率peak cell rate04.068持续信元速率sustained cell rate SRC 04.069允许信元速率allowed cell rate ACR 04.070恒定比特率constant bit rate CBR 04.071可变比特率variable bit rate VBR 04.072可用比特率available bit rate ABR 04.073未定比特率unspecified bit rate UBR 04.074信元时延变化cell delay variation CDV 04.075信元差错比cell error ratio CER 04.076信元丢失比cell loss ratio CLR 04.077信元误插率cell misinsertion rate CMR 04.078信元头cell header04.079逻辑数据链路logical data link04.080逻辑节点logical node04.081用户线（路）subscriber's line04.082用户引入线subscriber's drop line04.083本地环路local loop04.084呼叫跟踪call tracing04.085呼叫单音calling tone04.086拨号dialing04.087拨号连接dial-up connection04.088拨号因特网接入dial-up Internet access04.089国际前缀international prefix04.090国际号码international number04.091个人号码personal number04.092地址address04.093双音多频dual-tone multifrequency DTMF 04.094占线occupation04.095接入时延access delay04.096接入争用access contention04.097试呼call attempt04.098忙时busy hour04.099忙时试呼busy hour call attempts BHCA 04.100业务电路traffic circuit04.101出（局）outgoing04.102入（局）incoming04.103始发originating04.104终接terminating04.105转接transit。
基于MATLAB的OFMD仿真实验-OFDM基础1
Frequency Selective Fading
Delay spread Tm is much larger than symbol duration T
Inter-symbol interference (ISI)
同一个信息的信号由于到达目的地的路径不同，导致了到达 时间不同。也就是接收端在时间1收到第一条路径发来的该信 息，可能在时间4收到2条路径发来的该信息。假设这个信息有 这两条到达路径，那么接收端本来应该在时间1接收完所有关 于该信息的信号，结果却在时间4之后才全部收完。
Multipath channel
In wireless telecommunications, multipath is the propagation phenomenon that result in radio signals reaching the receiving antenna by two or more paths.
相干时间和相干带宽都是描述信道特性的参数，当两个发射 信号的频率间隔小于信道的相干带宽，那么这两个经过信道后 的，受到的信道传输函数是相似的，由于通常的发射信号不是 单一频率的，即一路信号也是占有一定带宽的，如果，这路信 号的带宽小于相干带宽，那么它整个信号受到信道的传输函数 是相似的，即信道对信号而言是平坦特性的，非频率选择性衰 落的。
(TM / max：最大(多径)时延扩展)
BC 1 TM
信道扩展主要可以分为三方面：多径(时延)扩展(delay spread)； 多普勒扩展；角度扩展。
相干带宽(coherence bandwidth) 是描述时延扩展的：相干带宽是 表征多径信道特性的一个重要参数，它指某一特定的频率范围，在 该频率范围内任意两个频率分量都具有很强的幅度相关性。即: 在 相干带宽范围内，多径信道具有恒定的增益和线性相位。通常， 相干带宽Bc近似等于最大多径s), is roughly inversely
IEEE802系列宽带无线接入标准简介
图1 IEEE802系列宽带无线接入标准1 短距无线通信IEEE802.15准确的说，I E E E802.15致力于个人区域网络（PAN）的标准化，其目的是使人们的便携装置随时接入网络。
802.15协议下面分为5个标准：802.15.1是蓝牙标准；802.15.2解决了蓝牙与Wi Fi共存于2.4G频段的互干扰问题；802.15.3是超宽带（UWB）标准；802.15.4是特3 无线城域网IEEE802.16IEEE 802.16标准定义了适用于IEEE Wireless MAN从表3我们可以看出，IEEE802系列宽带无线接入标准在不同的覆盖范围内发挥着不同的作用。
WLAN的应用目前较多，也比较成熟，如公司、校园基本上都有WLAN 的覆盖，正朝着更高速率的方向迈进。
WPAN以低功率、低成本可以内嵌入到很多的终端设备中，组建家庭网络，WLAN的有效补充。
而随着WLAN热点的快速增加，用户通常希望在离开热点区后延伸服务连接，802.16e的出现就是解决这类用户的需求，使其离开家中或办公场所热点地区后仍可以保持与无线ISP网络的连接，甚至可以方便的接入另一个城市的另一家无线ISP。
而与802.16e虽然都是具有移动性的宽带无线接入，有其相似性，但是802.20能达到更高的移动速率，能提供比802.16e更好的接入功能。
6 总结宽带无线接入将成为近一段时间乃至未来一段时间的研究热点。
除开上面讨论的基于IEEE802准的宽带无线接入技术，还有诸如多路微波分配系统（MMDS）、本地多点分配系统（LMDS）、无线光接入（FSO）、卫星接入等。
可以预见的是，随着IP技术的进一步推广、固定网络分组化进程的推动、固定网络和无线网络升级换代需求的增加，各个标准宽带无线接入技术将演进并相互渗透和，逐渐实现接入网的融合。
但在各个网络融合之前，必将经历网络异构的过程，IEEE802.21（下转第图3 MMSE在不同噪声功率下的性能比较（下行）HA A中弱信道冲激响应用户所对应的非对角线元素值可能比对角线元素值还大，这样弱信道冲激响应用户信息是不可靠的，所以MMSE-BLE法的性能仍然会下降。
Spread Spectrum Communications and CDMA说明书
Spread Spectrum Communications and CDMADr. Kwang-Cheng Chen, ProfessorGraduate Institute of Communications EngineeringCollege of Electrical EngineeringNational Taiwan UniversityFAX:02-23683824E-Mail:************.tw NTU EE Mobile CommunicationsKC Chen, NTU GICE 1Why Spread Spectrum?q❑ a nti-jammingq❑ l ow probability of interceptionq❑ l ow interferenceq❑ s ystem capacity and flexibilityq❑ a nti-interferenceq❑ a nti-multipath fadingq❑ r angingNTU EE Mobile CommunicationsKC Chen, NTU GICE 2Anti-Jamming/Interferencenarrowbandsignalnarrowbandsignal jamming or interference wideband spreading signaljamming/interference as a wideband noisespreadingtransmitterchannel receiver despreadingKC Chen, NTU GICE 3NTU EE Mobile CommunicationsFirst Spread Spectrum CommunicationFrom WikipediaGPS: Spread Spectrum Ranging q❑ 24 satellites in orbitsq❑ u p to 6 satellites observable everywhere on earthq❑ s ignals from 4 satellites for locating (3-dim and time)q❑ u sing Gold codesq❑ C/A code: 1.023 MHzq❑ P code: 10.23 MHzNTU EE Mobile CommunicationsKC Chen, NTU GICE 5Forms of Spread Spectrumq❑ D irect Sequence (DS)q❑ F requency Hopped (or Hopping) (FH)q❑ h ybrid DS+FHNTU EE Mobile CommunicationsKC Chen, NTU GICE 7Desired Spreading Waveformq❑ a verage close to zeroq❑ a uto-correlation function close to a delta function, i.e., close to a white noiseq❑ c ross-correlation close to a delta function so that simultaneous transmission over the same frequency spectrum possible, to reduce MAI.q❑ s pectrum expansion factor known as processing gain (processing gain should be large)NTU EE Mobile CommunicationsKC Chen, NTU GICE 11Processing Gainq F CC defines processing gain based on signal bandwidth measurement after spreading and original narrowband signal bandwidth measurement.NTU EE Mobile CommunicationsKC Chen, NTU GICE 12Maximal Length Codesq❑ A cyclic code with length q❑ (L+1)/2 1s and (L-1)/2 0sq❑ A uto-correlationL n =−21ϕτττ(),,==−≠⎧ ⎨ ⎩ L 010KC Chen, NTU GICE 13NTU EE Mobile CommunicationsMaximal Length Codesq❑ A ny circular shift of an m-sequence is another m-sequence.q❑ A ny modulo-2 addition of two m-sequences is another m-sequence.q❑ m-sequence is thus appropriate only for synchronous CDMA.q❑ S preading codes for asynchronous CDMA is thus needed.NTU EE Mobile CommunicationsKC Chen, NTU GICE 19Generation of m-Sequence+ +generating polynomial = 1 + x + x 4m-sequence can be easily generated by shift-register. It is the longest code sequence that can be generated by a given number of stages of delays. This is why called maximal length codes.NTU EE Mobile CommunicationsKC Chen, NTU GICE 20Gold Codes SRG #1SRG #2 +clock maximal length code 1maximal length code 2output codeauto-correaltion and cross-correlation side lobes bounded by(n+1)/22 +1 n odd(n+2)/22 -1 n evenKC Chen, NTU GICE 21 NTU EE Mobile CommunicationsWalsh-Hadamard Codes NTU EE Mobile Communications KC Chen, NTU GICE 22 SRG #2+clockmaximal length code 2output code(a)(b)+ +-++ +-++ +-++ +-+--+ -+ +-++ +-++ +-+--+ -+ +-++ +-++ +-+--+ -+ +-++ +-++ +-+--+ ---+ ---+ ---+ -+ +-+-1-1duplicate duplicateg.10.10(a)Gold codes generation;(b)Walsh codes generation for codelength 2,4,Summary of Part 15q❑ I SM: industrial, scientific, medicalq❑ 902-928 MHz; 2.4-2.4835 GHz; 5.725-5.85 GHz, 24G Hz, 60G Hzq❑ R F output power less than 1 W to antenna q❑ a ntenna gain less than 6 dBi; if higher, must be reduced by the same amountq❑ e ffective EIRP less than 36 dBmNTU EE Mobile CommunicationsKC Chen, NTU GICE 23Part 15 DS-SSq❑ M inimum 6 dB bandwidth is 500 KHz at 900-MHz and 1 MHz at 2.4-GHz.q❑ P ower density in any 3-KHz must be less than 8 dBm in average over 1 sec.q❑ P rocessing gain must be at least 10 dB.q❑ F or hybrid systems, the processing gain must be at least 17 dB.NTU EE Mobile CommunicationsKC Chen, NTU GICE 24Part 15 FH-SSq❑ M inimum channel separation is 25 KHz.q❑ M aximum 20 dB bandwidth is 500 KHz at 900-MHz and 1 MHz at 2.4-GHz.ü✓ T hat is, more than 99% power within 1M Hz at2.4G Hz ISM band.q❑ N umber of frequency channels is at least 50 at 900-MHz and 75 at 2.4-GHz.q❑ A verage occupied time is less than 0.4 sec in 20 sec at 900-MHz and 0.4 sec in 30 sec at 2.4-GHz, at least 2.5 hops/sec.NTU EE Mobile CommunicationsKC Chen, NTU GICE 25DS vs. FHDirect Sequence Frequency Hoppedmore noise-like operable below ambient noise near-far problemless co-channel interferenceinstaneous narrowbandmust have positive SNR usually FEC requiredmore robust in nonlinearenvironmentseasy to synchronize andimplementKC Chen, NTU GICE 26NTU EE Mobile CommunicationsInformation SourceChannelCoding &InterleavingSourceCodingModulation& FilteringRF &Antenna ChannelRF & Antenna NoiseFadingDistortionImpairments Equalization DemodulationChannel Estimation SynchronizationChannelDecoding &De-interleavingSourceDecodingDestinationNarrow-Band Digital Communication SystemKC Chen, NTU GICE 27 NTU EE Mobile CommunicationsSpread Spectrum Systems (Wideband Communications)Information SourceModulatorRF⊗Information destinationDemodulatorRF⊗Synchronization+Code generatorC(t)C(t)KC Chen, NTU GICE28NTU EE Mobile CommunicationsSpread Spectrum Synchronization q❑ A cquisition (coarse synchronization) ü✓ S ingle dwellü✓ M ulti-dwellü✓ S erial searchü✓ P arallel searchü✓ S equential searchq❑ T racking (fine synchronization)ü✓ D elay-Locked Loop (DLL)ü✓ T au-Dither Loop (TDL)NTU EE Mobile CommunicationsKC Chen, NTU GICE 29Single-Dwell Code AcquisitionNTU EE Mobile CommunicationsKC Chen, NTU GICE30with parallel search (timing candidates).•Tracking (fine synchronization):After initial acquisition,we adopt a code tracking mechanism to lock the fine timing,XBPF/LPF(.)2∫−+⋅timedwell T ττ)(If > threshold, start tracking If < threshold, update a new for a new searchReference Waveform Generation Received Waveform To TrackingFig.10.6Single-dwell code acquisition.Multi-dwell AcquisitionZ 1Z 2Z NDetectorr(t)⊗PN generator1BPF ( )22BPF( )2NBPF( )2τ1∫τ2Nτ1∫τ2N τ1∫τ2N KC Chen, NTU GICE31NTU EE Mobile CommunicationsDelay-Lock DiscriminatorXXr(t)y 1(t))T 2T ˆ-C(t K c d 1Δ++ PN code Generator+_Loop Filtery 2(t))T 2T ˆ-C(t K c d 1Δ−VCOWantcd d T T ˆT −=δ∈Baseband Full Time Early-Late TrackingLoop KC Chen, NTU GICE32NTU EE Mobile CommunicationsTwo difficulties to use coherent loops: (1) recovering carrier before code tracking (2) coherence reference at low SNRsNoncoherent Full Time Early-Late TrackingLoop KC Chen, NTU GICE 33NTU EE Mobile CommunicationsCommunication and Code Division Multiple AccessLock DiscriminatorXy 1(t))T T ˆ-C(t K c d1∆++_Loop∈S-Curver (t)XXXBPFy1(t)y2(t)a1a2SpreadingwaveformXlocalosc.b(t)( )2z1(t)LPFBPF ( )2 LPF+∈loopfilterVCOz2(t) +_∨Power dividerKC Chen, NTU GICE 34NTU EE Mobile CommunicationsTau-Dither Noncoherent LoopBig problems for DLLs:(1) Early and late IF channels must be precisely amplitudebalanced.Otherwise, the discriminator characteristic is offset and does not reach zero output when tracking perfectly.(2) Cost for two arms.NTU EE Mobile CommunicationsKC Chen, NTU GICE 35⊗r(t) y(t)BPF( )2 z(t)LPF⊗Loop Filter),(δt ∈-q(t)-1q(t) ⊗a(t) Local osc.. b(t)q (t)Spreading waveformVCO)2ˆ(c d T T t C Δ−−)2ˆ(c d T T t C Δ+−[])()(cos )(2)(t n T t t W T t C P t r d d o d ++−+−=ϕθKC Chen, NTU GICE36NTU EE Mobile CommunicationsFrequency Hopping Spread SpectrumCommunication SystemsNTU EE Mobile Communications KC Chen, NTU GICE 37Spread Spectrum Communication and Code Division Multiple AccessTimeFrequencyNarrowband ModulatorFrequency SynthesizerSignalX PN Hopping CodeRFRF Frequency Synthesizer XPN Hopping CodeNarrowband DemodulatorSignal DestinationFH-SS TransmitterFH-SS Receiver(a)Frequency-Time Space Illustration of FH Signal(b) Block Diagram of FH-SS SystemFig.10.9FH-SS Communications:(a)frequency-time domain illustration of a signal;(b)block diagram of a transmitter and a receiver.Hopping Codes for FHSSq❑ M ultiple access for FH-SS is possible ü✓ E ach user-pair adopts a hopping sequence • Typically orthogonal• Non-coherent wayü✓ P erformance measure is probability of hit.q❑ H opping code designü✓ M inimizing probability of direct hits (i.e.hopping into the same frequency band at thesame time)ü✓ M inimizing adjacent channel interferenceNTU EE Mobile Communications KC Chen, NTU GICE 38ally for military applications. Array•tog.10.140 Origin of Multiuser Detection[Verdu and Poor]X∫0Ty(t)s(t)Conventional optimal receiver (correlation/matched filter) considers one tx-rx pair detection and is MAI (multiple access interference) limited in performance.However, CDMA tx-rx pairs simultaneously transmit over the same spectrum. Optimal detection shall consider all users’ signal, b =(b 1 ….. b K ). Unfortunately, such an optimal receiver generally has NP hard complexity .b iKC Chen, NTU GICE40NTU EE Mobile CommunicationsMultiuser DetectionTechniquesq❑ D e-correlating Receiver, R-1y = Ab• R: cross-correlation matrix• can be polynomial complexity in many cases• worst case NP hardq❑ M MSE receiverq❑ L MMSE receiverq❑ I C (interference cancellation)• based on conventional structure• detecting the strongest user first, then 2nd, ...KC Chen, NTU GICE 41 NTU EE Mobile Communications41。
equalizer apo copy channel -回复
equalizer apo copy channel -回复Title: Equalizer App Copy Channel: Enhancing Audio ExperienceIntroduction:In today's rapidly evolving digital era, a multitude of platforms and devices incorporate audio content as an integral part of our daily lives. From music streaming services to videos and podcasts, the demand for optimal audio quality is on the rise. Audio equalizers, in particular, play a significant role in enhancing the audio experience by providing the ability to customize and fine-tune the sound to individual preferences. This article will explore the functionalities and benefits of an equalizer app copy channel.1. Understanding Equalizers:An equalizer is an audio processing tool that allows users to adjust frequency-specific ranges of sound. In simple terms, it enables users to enhance or attenuate specific frequencies to suit their listening preferences. By modifying the EQ settings, users can manipulate bass, treble, and mid ranges, resulting in a tailored sound output that improves clarity, depth, and balance.2. Why Equalizer Apps?Equalizer apps have gained popularity due to their ability to provide audio enhancement on various devices. These apps offer portability, allowing users to achieve optimum sound quality on their smartphones, tablets, and even laptops. Additionally, equalizer apps often come with a user-friendly interface and customizable presets, making it easier for users to fine-tune their audio settings without any technical expertise.3. Features and Functionalities:Equalizer apps typically offer a range of features to cater to different audio preferences and genres. Some essential functionalities include:a. Predefined Presets: These presets come with predefined equalizer settings for different music genres such as rock, jazz, classical, or pop. Users can select a preset to immediately optimize the sound quality according to the specific genre.b. Custom Equalizers: These apps provide manual control options to adjust individual frequency bands. Users can modify the bass, mid, and treble levels to create their personalized sound signature.c. Visualizers: Many equalizer apps include real-time visualizers, displaying graphical representations of the audio spectrum. Visualizations help users identify peaks and dips in different frequency ranges, allowing them to fine-tune accordingly.d. Bass Boost and Virtual Surround: Equalizer apps often offer options to enhance bass frequencies and simulate virtual surround sound effects. These features create a more immersive and dynamic audio experience.4. Benefits and Applications:The use of an equalizer app copy channel has numerous benefits across various scenarios:a. Music Enthusiasts: Audiophiles and music enthusiasts can use equalizer apps to elevate their listening experience. By adjusting the frequencies to match personal preferences, the app allows for more detailed and immersive audio playback.b. Video and Gaming: Equalizer apps are equally useful for video playback and gaming. Users can enhance dialogue clarity, optimize sound effects, and maintain a balanced audio experienceregardless of the content genre.c. Hearing Impairment: For individuals with hearing impairments, equalizer apps can be a valuable tool. They can emphasize specific frequencies to compensate for hearing deficiencies, ensuring an improved audio experience.d. Audio Professionals: Equalizer apps also find applications in audio production and engineering. Professionals can use these apps to analyze and fine-tune audio tracks during the mixing and mastering process, ensuring optimal sound quality.Conclusion:Equalizer apps have become indispensable tools for audio enthusiasts, providing the ability to customize and enhance sound quality across various devices and platforms. With theiruser-friendly interfaces and customizable presets, these apps empower users to create a personalized audio experience and improve overall satisfaction. Whether for music, gaming, or corrective purposes, equalizer apps continue to revolutionize theway we perceive and enjoy sound.。
聚合网口业务均衡
1 概述在存储产品中提供了多种网口聚合模式，实现存储网络链路冗余和负载均衡。
存储端多个业务口聚合（默认Balance-xor2聚合模式），交换机端也相应聚合，但流量始终上不去，用命令sar -n DEV 3查看，流量全在一个业务口或2个业务口上，其他聚合的业务口没有流量。
此时可以通过修改客户端网口mac地址，达到存储业务口流量均衡。
2 校验xor值2.1 2个口聚合，检验xor值2个口聚合，最少2台客户端打流量，编辑脚本检查校验值，校验值0,1说明：0x48EA63018E51为存储端bond口mac地址（ifconifg bond0查看）后面2个mac地址分别是2个服务器的mac地址（ipconfig -all）如果值不是0,1，需要修改mac地址方法见第三章节。
2.2 3个口聚合，检验xor值3个口聚合，最少3台客户端打流量，编辑脚本检查校验值，校验值0,1,2说明：0x48EA63018E51为存储端bond口mac地址（ifconifg bond0查看）后面3个mac地址分别是3个服务器得mac地址（ipconfig -all）如果值不是0,1,2需要修改mac地址，方法见第3章节。
需保证校验值不一样。
2.3 4个口聚合，检验xor值4个口聚合，最少4台客户端打流量，编辑脚本$1 是传递给该shell脚本的第一个参数$2 是传递给该shell脚本的第二个参数$1^$2 异或xor$value1%4 取模检查校验值，校验值0,1,2,3说明：0x48EA63018E51为存储端bond口mac地址（ifconifg bond0查看）后面4个mac地址分别是4个服务器得mac地址（ipconfig -all）如果值不是0,1,2,3需要修改mac地址，方法见第3章节。
需保证校验值不一样。
2.4 查询存储端网口流量分布情况修改完后，用命令观察一下，流量是否均衡3 修改MAC地址3.1 Linux下修改MAC地址方法一（临时生效）：1. 关闭网卡设备ifconfig eth0 down2. 修改MAC地址ifconfig eth0 hw ether MAC地址3. 重启网卡ifconfig eth0 up方法二（永久生效）：在./etc/sysconfig/network-scripts/ifcfg-eth0中加入下面一句话：例如：MACADDR=00:AA:BB:CC:DD:EE3.2 Windows下修改MAC地址1.选择跑业务的网卡，点击属性，从弹出的属性设置框中选择配置，进行配置设置框。